JP5900566B2 - Ink composition and recording method - Google Patents

Description

  The present invention relates to an ink composition, a recorded matter using the same, a recording method, and a recording apparatus.

  Conventionally, a white ink composition containing hollow polymer fine particles as a white color material is known (see, for example, Patent Document 1). The hollow polymer fine particles have cavities therein, and the outer shell is formed of a liquid-permeable resin. With such a structure, in the ink composition, the hollow cavity of the hollow resin particles is filled with the solvent, and the specific gravity of the hollow resin particles and the specific gravity of the ink composition are substantially the same. It can be stably dispersed in the composition. When an image is formed on a recording medium using this ink composition, the hollow resin particles are refracted by light between the outer shell and the cavity because the internal space of the hollow resin particles is replaced with air during drying. The hiding effect is exhibited by light scattering caused by the difference in rate (ie, white color is exhibited). In general, the hollow resin particles themselves are formed of a transparent resin such as acrylic. On the other hand, a white ink composition containing a metal oxide or the like as a white color material is also known.

  However, the white ink composition is not excellent in fixability on a recording medium and has insufficient abrasion resistance.

  Further, for example, Patent Documents 2 to 4 disclose techniques for improving the jetting stability and storage stability of a white ink composition or a colored ink composition. However, all of these techniques have room for improvement in rubbing resistance and printing characteristics.

US Pat. No. 4,880,465 JP 2000-103995 A JP 2000-239585 A JP 2006-56990 A

  An object of the present invention is to provide an ink composition which is excellent in abrasion resistance and particularly suitable for an ink jet recording system.

The present invention is as follows.
(1) An ink composition comprising at least one colorant selected from metal compounds and hollow resin particles, and a polyurethane resin, wherein the polyurethane resin is a polycarbonate-based or polyether-based anionic polyurethane resin An ink composition.
(2) The ink composition according to (1), wherein the colorant includes hollow resin particles.
(3) The ink composition according to (1) or (2), wherein the polyurethane resin is dispersed as particles in a solvent.
(4) The ink composition according to any one of (1) to (3), wherein the polyurethane resin is a self-emulsifying dispersion.
(5) The ink composition according to any one of (1) to (4), wherein the content of the polyurethane resin is 0.5 to 10% by mass.
(6) The ink composition according to any one of (1) to (5), wherein the hollow resin particles have an average particle diameter of 0.2 to 1.0 μm.
(7) The ink composition according to any one of (1) to (6), wherein the content of the hollow resin particles is 5 to 20% by mass.
(8) The ink composition according to any one of (1) to (7), which contains at least one selected from alkanediols and glycol ethers.
(9) The ink composition according to any one of (1) to (8) above, which contains an acetylene glycol surfactant or a polysiloxane surfactant.
(10) The ink composition according to any one of (1) to (9), which is applied to an inkjet recording method.
(11) A recorded matter on which an image is formed by the ink composition according to any one of (1) to (10).
(12) A recording method for recording an image using the ink composition according to any one of (1) to (10) above.
(13) A recording apparatus for recording an image by the recording method according to (12).

  The ink composition of the present invention contains a metal compound or hollow resin particles as a coloring material. In particular, the hollow resin fine particles as the color material have a larger particle size and a hollow structure than metal compounds such as metal oxides as other color materials, and thus are difficult to fix on a recording medium and are resistant. It is known to be inferior in rubbing. On the other hand, in the present invention, an ink composition capable of forming an image excellent in abrasion resistance can be provided by using a polyurethane resin having a specific structure as a resin for fixing the coloring material.

  Furthermore, the ink composition of the present invention is excellent in image storage stability. That is, in the case of forming an image by combining an ink composition containing hollow resin particles and another ink composition containing a humectant, for example, the white ink composition of the present invention containing a hollow resin particle and a humectant In the case of forming an image in combination with a color ink composition other than white containing, the obtained recorded matter does not cause the hollow resin particles to be transparent even when stored for a long time or in a high humidity environment, It is possible to maintain a high-quality image over a long period of time.

  Hereinafter, the ink composition of the present invention will be described in detail. The ink composition of the present invention can be preferably applied to a white ink composition containing a metal compound or hollow resin particles as a white color material, but the metal compound or hollow resin particles may exhibit a color other than white, or By using another color material together with the metal compound and / or the hollow resin particles as the white color material, the ink composition itself can have a color other than white.

[Ink composition]
The ink composition of the present invention is an ink composition containing at least one color material selected from a metal compound and hollow resin particles, and a polyurethane resin, wherein the polyurethane resin is a polycarbonate-based or polyether-based ink composition. It is characterized by being an anionic polyurethane resin.

1. Metal compound, hollow resin particles The ink composition of the present invention contains at least one selected from a metal compound and hollow resin particles as a coloring material.
The metal compound in the present invention is not particularly limited as long as it is a metal atom-containing compound that can be used as a pigment, and is preferably a metal oxide, barium sulfate or calcium carbonate conventionally used as a white pigment. is there. Although it does not restrict | limit especially as a metal oxide, For example, titanium dioxide, a zinc oxide, a silica, an alumina, magnesium oxide etc. are mentioned. As the metal compound in the present invention, titanium dioxide and alumina are preferable.
The content of the metal compound is preferably 1.0 to 20.0% by mass and more preferably 5.0 to 10.0% by mass with respect to the total mass of the ink composition. When the content of the metal oxide exceeds 20.0% by mass, reliability such as clogging of the ink jet recording head may be impaired. On the other hand, if it is less than 1.0% by mass, the color density such as whiteness tends to be insufficient.

  The average particle diameter (outer diameter) of the metal compound is preferably 30 to 600 nm, more preferably 200 to 400 nm. When the outer diameter exceeds 600 nm, the particles may settle and the dispersion stability may be impaired, and the reliability such as clogging of the ink jet recording head may be impaired. On the other hand, when the outer diameter is less than 30 nm, the color density such as whiteness tends to be insufficient.

  The average particle diameter of the metal compound can be measured by a particle size distribution measuring apparatus using a laser diffraction scattering method as a measurement principle. As the laser diffraction type particle size distribution measuring device, for example, a particle size distribution meter (for example, “Microtrack UPA” manufactured by Nikkiso Co., Ltd.) having a dynamic light scattering method as a measurement principle can be used.

  The hollow resin particles in the present invention preferably have a cavity in the inside thereof and the outer shell is formed of a resin having liquid permeability. With such a configuration, when hollow resin particles are present in the aqueous ink composition, the internal cavity is filled with the aqueous medium. Since the particles filled with the aqueous medium have a specific gravity almost equal to that of the external aqueous medium, the dispersion stability can be maintained without settling in the aqueous ink composition. Thereby, the storage stability and ejection stability of the ink composition can be enhanced.

  Further, when the ink composition of the present invention is ejected onto a paper or other recording medium, the aqueous medium inside the particles escapes during drying to form a cavity. When the particles contain air inside, the particles form a resin layer and an air layer having different refractive indexes, and effectively scatter incident light, so that white can be exhibited. In addition, it is also possible to exhibit colors other than white by coloring the resin layer which forms a hollow resin particle in the state which left light transmittance.

  The hollow resin particles used in the present invention are not particularly limited, and known ones can be used. For example, hollow resin particles described in specifications such as US Pat. No. 4,880,465 and Japanese Patent No. 3,562,754 can be preferably used.

  The average particle diameter (outer diameter) of the hollow resin particles is preferably 0.2 to 1.0 μm, and more preferably 0.4 to 0.8 μm. When the outer diameter exceeds 1.0 μm, the particles may settle and the dispersion stability may be impaired, and the reliability such as clogging of the ink jet recording head may be impaired. On the other hand, when the outer diameter is less than 0.2 μm, the color density such as whiteness tends to be insufficient. The inner diameter is suitably about 0.1 to 0.8 μm.

  The average particle diameter of the hollow resin particles can be measured by a particle size distribution measuring apparatus using a laser diffraction scattering method as a measurement principle. As the laser diffraction type particle size distribution measuring device, for example, a particle size distribution meter (for example, “Microtrack UPA” manufactured by Nikkiso Co., Ltd.) having a dynamic light scattering method as a measurement principle can be used.

  The content (solid content) of the hollow resin particles is preferably 5 to 20% by mass and more preferably 8 to 15% by mass with respect to the total mass of the ink composition. When the content (solid content) of the hollow resin particles exceeds 20% by mass, reliability such as clogging of the ink jet recording head may be impaired. On the other hand, when it is less than 5% by mass, the color density such as whiteness tends to be insufficient.

  The method for preparing the hollow resin particles is not particularly limited, and a known method can be applied. As a method for preparing the hollow resin particles, for example, a so-called emulsion polymerization method in which a hollow resin particle emulsion is formed by stirring a vinyl monomer, a surfactant, a polymerization initiator, and an aqueous dispersion medium while heating in a nitrogen atmosphere. Can be applied.

  Examples of vinyl monomers include nonionic monoethylenically unsaturated monomers such as styrene, vinyl toluene, ethylene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, (meth) acrylamide, (meth) acrylic acid esters, and the like. Can be mentioned. As (meth) acrylic acid ester, methyl acrylate, methyl methacrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-hydroxyethyl methacrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, lauryl (Meth) acrylate, oleyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate and the like can be mentioned.

  Moreover, a bifunctional vinyl monomer can also be used as a vinyl monomer. Examples of the bifunctional vinyl monomer include divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, 1,3-butane-diol dimethacrylate, diethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, and the like. By hollowly copolymerizing the above monofunctional vinyl monomer and the above bifunctional vinyl monomer and highly crosslinked, not only light scattering properties but also hollow properties with heat resistance, solvent resistance, solvent dispersibility, etc. Resin particles can be obtained.

  The surfactant is not particularly limited as long as it forms a molecular aggregate such as micelles in water, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants. Can be mentioned.

  As the polymerization initiator, a known compound soluble in water can be used, and examples thereof include hydrogen peroxide and potassium persulfate.

  Examples of the aqueous dispersion medium include water and water containing a hydrophilic organic solvent.

2. Polyurethane Resin In the present invention, a polycarbonate-based or polyether-based anionic polyurethane resin is used as the polyurethane resin.
A known method can be applied to the synthesis of the polyurethane resin having such a structure. For example, it can be obtained by reacting a compound having two or more isocyanate groups with a compound having two or more active hydrogen groups. Can do. The compound having two or more active hydrogen groups is a polyether polyol or a polycarbonate polyol.

  The compound having two or more isocyanate groups is not particularly limited, and examples thereof include chain aliphatic isocyanates such as tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, 1,3-cyclohexylene diisocyanate, 1,4-cyclohexylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 3,3'-dimethyl-4,4'-dicyclohexylmethane diisocyanate, etc. Aliphatic isocyanate having a cyclic structure of 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene dii Cyanate, p-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, 3,3 ' -Dimethoxy-4,4'-biphenylene diisocyanate, 3,3'-dichloro-4,4'-biphenylene diisocyanate, 1,5-naphthalene diisocyanate, 1,5-tetrahydronaphthalene diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate Aromatic isocyanates such as One of these may be used alone, or two or more thereof may be used in combination.

  As the polyether polyol, a cyclic ether compound such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, or epichlorohydrin may be used alone or 2 by using a compound having an active hydrogen atom as a catalyst. A polymer obtained by, for example, mixing ring-opening polymerization by mixing more than one species. Specific examples include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. These may be used alone or in combination of two or more.

  Examples of the polycarbonate polyol include 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, or diols such as polytetramethylene glycol, phosgene, Examples thereof include a reaction product with a dialkyl carbonate such as dimethyl carbonate or a cyclic carbonate such as ethylene carbonate. These may be used alone or in combination of two or more.

  In order to make the polyurethane resin anionic, for example, a monomer having a carboxyl group or a sulfone group may be introduced. Examples of such monomers include monohydroxycarboxylic acids such as lactic acid; dihydroxycarboxylic acids such as α, α-dimethylolacetic acid, α, α-dimethylolpropionic acid, α, α-dimethylolbutyric acid, and 3,4-diaminobutanesulfone. Examples include acids and diaminosulfonic acids such as 3,6-diamino-2-toluenesulfonic acid.

  Generally, as a property of the polyurethane resin, the main chains of the polyurethane resin are loosely bonded by hydrogen bonds, so that a flexible and tough film structure can be formed. By using the polyurethane resin, in order to form a flexible film structure while spreading on the recording medium while maintaining fluidity at a temperature (10 ° C. to 40 ° C.) at which normal inkjet printing is performed, Friction improves. In addition, since a medium generally used for printing (for example, an inkjet recording sheet “OHP sheet” manufactured by Seiko Epson Corporation) is often positively charged, anionic urethane is used as an ink fixing resin. Thus, adhesion is improved by electrostatic interaction. In addition, since the polyether-based or polycarbonate-based polyurethane resin easily forms a highly flexible film as compared with a polyester-based polyurethane resin or the like, the abrasion resistance is improved. In addition, polyether-based or polycarbonate-based polyurethane resins are preferable for use in water-based inks because they have the property of not easily deteriorating against water.

  The glass transition temperature (Tg) of the polyurethane resin is preferably 50 ° C. or lower, more preferably 0 ° C. or lower, and particularly preferably −10 ° C. or lower. Although the detailed reason is not clear, in order to form an image while a polyurethane resin having a glass transition temperature of 50 ° C. or less spreads on the recording medium, a metal compound or a hollow resin particle that is a coloring material is formed on the recording medium. It can be firmly fixed. Thereby, an image having excellent abrasion resistance can be obtained. In particular, by setting the glass transition temperature of the polyurethane resin to 0 ° C. or less, intermittent printing characteristics can be remarkably improved and nozzle omission during ink jet recording can be suppressed.

On the other hand, the present inventors are a case where an image is formed by combining an ink composition containing hollow resin particles and another ink composition containing a humectant, for example, a white ink composition containing hollow resin particles. When an image is formed by combining a non-white color ink composition containing a moisturizing agent, the resulting recorded matter may be deteriorated in color tone or color image when stored for a long time or in a high humidity environment. It has been found that phenomena such as transparency of the boundary between the image and the white image may occur. This is because when the recorded material is stored for a long time or in a high humidity environment, the humectant remaining in the color ink composition absorbs moisture in the air and oozes out into a white image, or moisture. This is considered to be caused by entering into the hollow of the hollow resin particles constituting the white image by moving into the white image while maintaining the color. That is, the hollow resin particles exhibit a concealing effect by light scattering due to the difference in the refractive index of light between the outer shell and the cavity, and exhibit a white color due to the concealing effect when a moisturizing agent holding moisture enters the cavity. It is because it cannot be done.
The ink composition of the present invention using a polycarbonate-based or polyether-based anionic polyurethane resin as the polyurethane resin is formed into a film on the surface upon drying, and has a higher flexibility than a polyester-based urethane resin. Therefore, the penetration of the humectant into the white image in the color ink composition can be prevented at the boundary between the color image and the white image, and the transparency of the hollow resin particles can be suppressed. It turns out that it is possible.

  As the polyurethane resin in the present invention, any of an emulsion type dispersed in a solvent and a solution type existing in a dissolved state in the solvent may be used. The emulsion type can be classified into a forced emulsification type and a self-emulsification type according to the emulsification method, and any type can be used in the present invention, but the self-emulsification type is preferred. The self-emulsification type dispersion is superior to the forced emulsification type in terms of film-forming property and water resistance, so a water-resistant film is formed on the surface, and moisture from the color ink image to the white image formed by the hollow resin particles is reduced. Intrusion of moisturizing agents can be prevented.

  Examples of the polyurethane resin used in the present invention include forced emulsification type polyurethane emulsions such as “Takelac (registered trademark) W-6061” (manufactured by Mitsui Chemicals), and “Takelac (registered trademark) W-6021” (Mitsui Chemicals). And a self-emulsifying polyurethane emulsion such as “WBR-016U” (manufactured by Taisei Fine Chemical Co., Ltd., polyether, Tg = 20 ° C.).

  When the above emulsion type is applied as the polyurethane resin, the average particle size of the polyurethane resin is preferably 50 to 200 nm, more preferably 60 to 200 nm. When the average particle diameter of the polyurethane resin is within the above range, the polyurethane resin particles can be uniformly dispersed in the ink composition.

  The content (solid content) of the polyurethane resin is preferably 0.5 to 10% by mass and more preferably 0.5 to 5% by mass with respect to the total mass of the ink composition. If the content of the polyurethane resin exceeds 10% by mass, ink reliability (clogging, ejection stability, etc.) may be impaired, and appropriate physical properties (viscosity, etc.) may not be obtained. On the other hand, if it is less than 0.5% by mass, the ink fixing property on the recording medium is not excellent, and an image having excellent abrasion resistance cannot be formed.

3. Penetration Organic Solvent The ink composition of the present invention preferably contains at least one selected from alkanediols and glycol ethers. Alkanediols and glycol ethers can enhance the wettability of a recording surface such as a recording medium and improve the ink permeability.

  Examples of the alkanediol include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, 1,2-octanediol, 2-Alkanediol is preferred. Of these, 1,2-hexanediol, 1,2-heptanediol, and 1,2-octanediol having 6 to 8 carbon atoms are more preferred because of their particularly high permeability to recording media.

  As glycol ethers, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, triethylene glycol Mention may be made of lower alkyl ethers of polyhydric alcohols such as monomethyl ether, triethylene glycol monobutyl ether and tripropylene glycol monomethyl ether. Among these, when triethylene glycol monobutyl ether is used, good recording quality can be obtained.

  The content of at least one selected from these alkanediols and glycol ethers is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, based on the total mass of the ink composition.

4). Surfactant The ink composition of the present invention preferably contains an acetylene glycol surfactant or a polysiloxane surfactant. Acetylene glycol surfactants or polysiloxane surfactants can increase the wettability of a recording surface such as a recording medium to increase the ink permeability.

  Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3, 5-dimethyl-1-hexyn-3-ol, 2,4-dimethyl-5-hexyn-3-ol and the like can be mentioned. Moreover, a commercial item can also be utilized for acetylene glycol type-surfactant, for example, Orphine E1010, STG, Y (above, Nissin Chemical Co., Ltd.), Surfinol 104, 82, 465, 485, TG (above , Air Products and Chemicals Inc.).

  Commercially available products can be used as the polysiloxane surfactant, and examples thereof include BYK-347, BYK-348 (manufactured by BYK Japan).

  Furthermore, the ink composition of the present invention can also contain other surfactants such as an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant.

  The content of the surfactant is preferably 0.01 to 5% by mass and more preferably 0.1 to 0.5% by mass with respect to the total mass of the ink composition.

5. Polyhydric alcohol The ink composition of the present invention preferably contains a polyhydric alcohol. When the ink composition of the present invention is applied to an ink jet recording apparatus, the polyhydric alcohol can suppress ink drying and prevent ink clogging in the ink jet recording head portion.

  Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, and trimethylolethane. And trimethylolpropane.

  The content of the polyhydric alcohol is preferably 0.1 to 30% by mass and more preferably 0.5 to 20% by mass with respect to the total mass of the ink composition.

6). Tertiary amine The ink composition of the invention preferably contains a tertiary amine. The tertiary amine has a function as a pH adjusting agent and can easily adjust the pH of the ink composition.

  Examples of the tertiary amine include triethanolamine.

  The content of the tertiary amine is preferably 0.01 to 10% by mass and more preferably 0.1 to 2% by mass with respect to the total mass of the ink composition.

7). Solvent and Additive The ink composition of the present invention usually contains water as a solvent. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltered water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be suppressed over a long period of time.

  If necessary, the ink composition of the present invention comprises a fixing agent such as a water-soluble rosin, an antifungal agent / preservative such as sodium benzoate, an antioxidant / ultraviolet absorber such as an allophanate, a chelating agent, an oxygen absorbing agent. Additives such as agents can be included. These additives can be used alone or in combination of two or more.

  The ink composition of the present invention may contain other color materials in addition to the metal compound and the hollow resin particles. As other colorants, general-purpose pigments and dyes can be used.

8). Adjustment Method The ink composition of the present invention can be prepared in the same manner as a conventional pigment ink using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, a roll mill, or the like. In the preparation, it is preferable to remove coarse particles using a membrane filter or a mesh filter.

  The ink composition of the present invention can form an image by applying it to various recording media. Examples of the recording medium include paper, cardboard, textiles, sheets or films, plastic, glass, ceramics, and the like.

  The use of the ink composition of the present invention is not particularly limited, but it can be applied to various ink jet recording systems. Examples of the ink jet recording method include thermal jet ink jet, piezo ink jet, continuous ink jet, roller application, and spray application.

[Recordings]
The present invention can also provide a recorded matter in which an image having excellent abrasion resistance is formed by the ink composition described above. In particular, in the recorded matter of the present invention in which an image is formed using an ink composition containing hollow resin particles as a coloring material, the hollow resin particles become transparent even when stored for a long time or in a high humidity environment. In addition, a high-quality image can be maintained over a long period of time.

[Recording method, recording apparatus]
The present invention can also provide a recording method for recording an image on a recording medium using the ink composition described above.
The recording method is not particularly limited, and includes a relief printing method, an intaglio printing method, a lithographic printing method, a stencil printing method, an electrophotographic recording method, a thermal transfer recording method, an inkjet recording method, and the like, and particularly preferably an inkjet recording method. It is a recording method.
As the ink jet recording method, any of the conventionally known methods can be used, and in particular, a method of ejecting droplets using vibration of a piezoelectric element (using an ink jet head that forms ink droplets by mechanical deformation of an electrostrictive element). Recording method) and a method using thermal energy, it is possible to perform excellent image recording.

  The present invention can also provide a recording apparatus for recording an image by the above-described recording method of the present invention.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited at all by these.

1. Preparation of white ink composition In the blending amounts shown in Table 1, metal oxide, hollow resin particles, resin, organic solvent, polyhydric alcohol, tertiary amine, surfactant, and ion-exchanged water were mixed and stirred to obtain a pore size. The ink compositions of Examples 1 to 6 and Comparative Examples 1 to 6 were obtained by filtration with a 5 μm metal filter and deaeration treatment using a vacuum pump. In addition, the unit of the numerical value described in Examples 1 to 6 and Comparative Examples 1 to 6 in Table 1 is mass%, and all of metal oxides, hollow resin fine particles, and polyurethane resin particles are converted into solid content. It is.

  As the metal oxide, a commercially available product “NanoTek (R) Slurry” described in Table 1 (manufactured by CI Kasei Co., Ltd.) was used. NanoTek (R) Slurry is a slurry containing titanium dioxide having an average particle diameter of 36 nm as a solid content at a ratio of 15%.

  As the hollow resin particles, commercially available products “SX8782 (D)” (manufactured by JSR Corporation) shown in Table 1 were used. SX8782 (D) is an aqueous dispersion type having an outer diameter of 1.0 μm and an inner diameter of 0.8 μm, and has a solid content concentration of 20.5%.

  The following polyurethane resin was used as the fixing resin.

  U-1: Polycarbonate anionic polyurethane resin, Tg = −70 ° C., average particle size = 130 μm, self-emulsifying dispersion

(Synthesis of U-1)
Dissolve 1 mol of polycarbonate (number average molecular weight 2000) and 0.7 mol of 1,6-hexanediol in a solvent (DMF) in a reaction vessel equipped with a heating device, stirrer, thermometer, cooler, and dripping device. Was adjusted to 30%. Subsequently, 1.7 mol (NCO / OH = 1.0) of 4,4′-diphenylmethane diisocyanate was added and reacted at 100 ° C. until no absorption due to free isocyanate groups of 2270 cm ⁻¹ was observed in the infrared absorption spectrum. Reaction was performed to obtain a polyurethane resin solution. Furthermore, it was dispersed in water by a known method to obtain a polyurethane water dispersion U-1 (solid content 40%) having a viscosity of 20 to 800 (mPa · s / 25 ° C.).

  U-2: “Rezamin D2020” (a polyether anionic polyurethane resin manufactured by Dainichi Seika Kogyo Co., Ltd., Tg = −30 ° C., average particle size = 100 μm, self-emulsifying dispersion)

  U-3: “WS-5000” (Mitsui Chemicals Polyurethane Polyester Anionic Polyurethane Resin, Tg = 65 ° C., average particle size = 70 μm)

  U-4: “W-635” (a polycarbonate nonionic polyurethane resin manufactured by Mitsui Chemicals Polyurethanes, Tg = 70 ° C., average particle size = 150 μm)

  U-5: “WBR-601U” (Taisei Fine Chemical Co., Ltd. polyester anionic polyurethane resin, Tg = −30 ° C.)

  U-6: “W-512A6” (polyether-based nonionic polyurethane resin manufactured by Mitsui Chemicals Polyurethanes Co., Ltd., Tg = 2 ° C., average particle size => 1000 μm)

  U-7: “Rezamin D-4200” (a polyether anionic polyurethane resin, self-emulsifying dispersion manufactured by Dainichi Seika Co., Ltd.)

  U-8: “Rezamin W-100” (a polyether anionic polyurethane resin, forced emulsification type emulsion, manufactured by Dainichi Seika Co., Ltd.)

  A-1: “UC-3510” (manufactured by Toa Gosei Co., Ltd., anionic acrylic resin, Tg = −50 ° C.)

  SA-1: “UF-5022” (manufactured by Toa Gosei Co., Ltd., anionic styrene acrylic resin, Tg = 75 ° C.)

  “BYK-348” (manufactured by Big Chemie Japan Co., Ltd.) is a polysiloxane surfactant.

2. Evaluation method 2-1. Evaluation of abrasion resistance Each white ink composition shown in Table 1 was filled in a black ink chamber of a dedicated cartridge of an inkjet printer ("PX-G930" manufactured by Seiko Epson Corporation). The ink cartridge thus produced was mounted on a printer and a printing test was performed. Commercially available ink cartridges other than black were installed. This is used as a dummy and is not used in the evaluation of the present embodiment, so it is not involved in the effect.

  Next, the output was performed at a resolution of 720 × 720 dpi on an inkjet recording sheet (“OHP sheet” manufactured by Seiko Epson Corporation). The printing pattern was a 100% duty solid pattern.

In this specification, “duty” is a value calculated by the following equation.
duty (%) = number of actual printing dots / (vertical resolution × horizontal resolution) × 100
(Where “number of actual print dots” is the number of actual print dots per unit area, and “vertical resolution” and “horizontal resolution” are resolutions per unit area. 100% duty is a single color for a pixel. Means the maximum ink mass.)

The OHP sheet printed with the white ink composition was then dried for 1 hour at room temperature. After drying, two kinds of tests, “rubbing test with nail” and “rubbing test with non-woven fabric”, were conducted by the person in charge of the test. The nail rubbing test is a test method for rubbing the printed surface with a nail so that it is repelled a few times. The rubbing test with a non-woven fabric is a test method for rubbing the printed surface in a state where a load equivalent to 200 g is applied to the non-woven fabric (Bencot Lab (Asahi Kasei Fibers)). The evaluation criteria are as follows.
<Abrasion test with nails>
A: No change is observed on the printed surface.
B: Traces of rubbing on the printed surface are observed, but do not come off.
C: The printed surface is peeled off.
D: The printed surface is peeled off only by lightly touching.
<Abrasion test with non-woven fabric>
A: No change is observed on the printed surface.
B: Traces of rubbing on the printed surface are observed, but do not come off.
C: The printed surface is peeled off.
D: The printed surface is peeled off only by lightly touching.

2-2. Evaluation of intermittent printing characteristics An intermittent printing test was performed using an inkjet printer PX-20000 (trade name, manufactured by Seiko Epson Corporation). The printer ink cartridges were filled with the white ink compositions of Examples 1 to 6 and Comparative Examples 1 to 6, respectively, and mounted on the printer. All the nozzles were normal in an environment of 32 ° C. and 20% humidity. After confirming that the ink is ejected in a continuous manner, 44-inch wide continuous printing is performed for 30 minutes, and then ejection from all nozzles is performed to evaluate whether or not ink droplets are bent and nozzle missing (dot missing) has occurred. did. The above evaluation was made into one set in 30 minutes, and the evaluation was repeated three times. The evaluation criteria are as follows.
AA: No nozzle omission and flight bend until 30 minutes × 3.
A: No nozzle omission and no flight curve until 30 minutes × 2.
B: No nozzle omission and no flight curve until 30 minutes × 1.
C: Nozzle comes out in 30 minutes or there is a flight curve.

2-3. Evaluation of change in color tone after white + color printing For white printing, the white ink composition shown in Table 1 is applied to the black ink chamber of a special cartridge of an inkjet printer ("PX-G930" manufactured by Seiko Epson Corporation). Each was filled. The ink cartridge thus produced was mounted on a printer and a printing test was performed. For color printing, a commercially available inkjet printer ("PX-G5500" manufactured by Seiko Epson Corporation) and an ink set (EPSON IC9CL3337 Photo Black, Matte Black, Gray, Light Gray, Yellow, Cyan, Light Cyan, Magenta, Light Magenta) Used for printing test.

  Next, the output was performed at a resolution of 720 × 720 dpi on an inkjet recording sheet (“OHP sheet” manufactured by Seiko Epson Corporation). The printing pattern was a 100% duty solid pattern for both white and color.

Printing was performed by forming a color image layer of a color ink composition other than white on a medium and then forming a white image layer on the color image layer using a white ink composition.
The resulting printed matter was evaluated for changes in color tone under high humidity conditions. The evaluation criteria are as follows. The results are shown in Table 1.
The L ^* value was measured using a commercially available colorimeter with black as a substrate, for example, Gretag Macbeth Spectroscan and Spectrolino (manufactured by X-Rite).

A: When kept in an environment of 27 ° C. and 35% for 24 hours and then kept in an environment of 27 ° C. and 65% for 24 hours, the decrease in the L ^* value of the color ink of the white + color portion is less than 5.
B: When kept in an environment of 27 ° C. and 35% for 24 hours and then kept in an environment of 27 ° C. and 65% for 24 hours, the decrease in L ^* value of the color ink of the white + color portion is 5 or more and less than 10.
C: When kept in an environment of 27 ° C. and 35% for 24 hours and then kept in an environment of 27 ° C. and 65% for 24 hours, the decrease in the L ^* value of the color ink of the white + color portion is 10 or more.

2-4. Evaluation of transparency at the boundary of the white image area side after white + color printing For white printing, the white ink composition described in Table 1 was used for an inkjet printer ("PX-G930" manufactured by Seiko Epson Corporation). Each black ink chamber of a dedicated cartridge was filled. The ink cartridge thus produced was mounted on a printer and a printing test was performed. For color printing, a commercially available inkjet printer ("PX-G5500" manufactured by Seiko Epson Corporation) and an ink set (EPSON IC9CL3337 Photo Black, Matte Black, Gray, Light Gray, Yellow, Cyan, Light Cyan, Magenta, Light Magenta) Used for printing test.

  Next, the output was performed at a resolution of 720 × 720 dpi on an inkjet recording sheet (“OHP sheet” manufactured by Seiko Epson Corporation). The printing pattern was a 100% duty solid pattern for both white and color.

As a printing method, a white image area and a color image area are recorded on a medium so that the boundary of each area is in contact, and the transparency at the boundary portion on the white image area side after aging at room temperature is performed. Evaluation was performed. The evaluation criteria are as follows. The results are shown in Table 1.
The printing area for both white and color was 100 mm × 100 mm (horizontal × vertical). In addition, the measurement method of transparency is measured by measuring the L ^* value using a commercially available colorimeter with black as a substrate, for example, Gretag Macbeth Sptroscan and Spectrolino (manufactured by X-Rite), and starting from the initial state. ^* Locations where the value decreased by 30 or more were defined as locations where transparency occurred.

A: Transparency after standing for 1 month occurs at less than 0.5 mm from the boundary.
B: Transparency after standing for 1 month occurs at 0.5 mm or more and less than 5 mm from the boundary.
C: Transparency after standing for 1 month occurs at 5 mm or more from the boundary.

In Examples 1 to 4, since a polycarbonate-based or polyether-based anionic polyurethane resin was used as the fixing resin, the scuff resistance was all evaluated as A, and the glass transition temperature of the urethane resin was 0 ° C. or lower. Therefore, it has excellent intermittent printing characteristics.
Also, a recorded matter obtained by combining the white ink composition of Examples 1 and 2 containing hollow resin particles as a white color material and a color ink composition other than white containing a humectant is stored for a long time or in a high humidity environment. Even when placed underneath, the transparency of the hollow resin particles is substantially suppressed, and it has been found that a high-quality image can be maintained over a long period of time. In particular, when Examples 1, 2, and 5 in which the polyurethane resin as the fixing resin is a self-emulsifying dispersion and Example 6 that is a forced emulsification type dispersion are compared, Example 1 that is a self-emulsifying type dispersion. 2 and 5 were found to suppress the transparency of the hollow resin particles.

  In Comparative Examples 1 and 3 using an anionic polyurethane resin having no polycarbonate-based or polyether structure, the scuff resistance was evaluated as B in both the nail test and the cloth test. Further, in Comparative Example 3, even when the glass transition temperature was 0 ° C. or lower, the intermittent printing characteristics were not improved so much.

  In Comparative Examples 2 and 4 using a nonionic polyurethane resin having a polycarbonate or polyether structure, the scuff resistance is C evaluation in both the nail test and the cloth test, and the results are inferior in intermittent printing characteristics. became.

  In Comparative Examples 5 and 6 using an anionic acrylic resin and an anionic styrene acrylic resin, in Comparative Example 5, the scuff resistance was C evaluation, and in Comparative Example 6, the scuff resistance was D evaluation. It was. Further, in Comparative Examples 5 and 6, even when the glass transition temperature was 0 ° C. or lower, the intermittent printing characteristics were not improved so much.

  Furthermore, a recorded matter obtained by combining the white ink compositions of Comparative Examples 1 to 6 containing hollow resin particles as a white color material and a color ink composition other than white containing a humectant is stored for a long time or in a high humidity environment. Below, changes in color tone due to the transparency of the hollow resin particles and transparency at the boundary portion on the white image area side were observed.

Claims (12)

An ink composition comprising at least one white color material selected from metal compounds that are any of metal oxides, barium sulfate, and calcium carbonate and hollow resin particles, and a polyurethane resin,
The polyurethane resin is a polycarbonate-based or polyether-based anionic polyurethane resin and has a glass transition temperature of 0 ° C. or lower,
1,2-alkanediol having 4 to 8 carbon atoms, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene Containing at least one permeable organic solvent selected from glycol monoethyl ether and tripropylene glycol monomethyl ether ;
A white ink composition containing an acetylene glycol surfactant or a polysiloxane surfactant .   The white ink composition according to claim 1, comprising hollow resin particles as the color material.   The white ink composition according to claim 1 or 2, wherein the polyurethane resin is dispersed as particles in a solvent.   The white ink composition according to any one of claims 1 to 3, wherein the polyurethane resin is a self-emulsifying dispersion.   The white ink composition according to any one of claims 1 to 4, wherein the content of the polyurethane resin is 0.5 to 10% by mass.   The white ink composition according to any one of claims 1 to 5, wherein an average particle diameter of the hollow resin particles is 0.2 to 1.0 µm.   The white ink composition according to any one of claims 1 to 6, wherein the content of the coloring material is 5 to 20% by mass.   The content of the penetrating organic solvent in the ink composition is 10% by mass or less, and further contains 10 to 30% by mass of polyhydric alcohol with respect to the ink composition. The white ink composition described. The white ink composition according to any one of claims 1 to 8 , wherein the content of the surfactant with respect to the total mass of the ink composition is 0.01 to 5 mass% .   The white ink composition according to any one of claims 1 to 9, which is applied to an inkjet recording system.   As polyhydric alcohols, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylol The white ink composition according to any one of claims 1 to 10, comprising at least one of propane.   The recording method which records an image using the white ink composition as described in any one of Claims 1-11.