JP6528537B2 - White ink, ink set, ink cartridge, ink jet recording apparatus, and recording method - Google Patents

Description

  The present invention relates to a white ink, an ink set, an ink cartridge, an inkjet recording apparatus, and a recording method.

  Conventionally, when expressing a white color on a transparent recording medium or coloring a colored recording medium with a color ink, in order to improve the transparency of the transparent recording medium or the coloring property of the color ink, coloring of the colored recording medium itself is used. Sufficiently concealing with a white ink containing hollow resin particles which has a low specific gravity and is difficult to settle is performed.

However, the hollow resin particles may be softened or disintegrated by the application of heat, and once disintegrated, there is a problem that good whiteness can not be obtained.
Therefore, it contains hollow microspheres as a white colorant for hiding the transparent color of the transparent recording medium and the coloring of the colored recording medium, and the shell of the hollow microspheres is crosslinked with a polymer to achieve high heat resistance. A heat-resistant non-coloring ink which is obtained is proposed (see, for example, Patent Document 1).

  However, since the heat-resistant non-colored ink crosslinks the shell of the hollow microsphere particles with a polymer, light scattering hardly occurs and the whiteness decreases, and as a result, the whiteness of the image after drying is increased. There is a problem of falling.

  An object of the present invention is to provide a white ink capable of suppressing a decrease in whiteness of a white image even if the white image formed on a recording medium is rapidly heated and dried.

  The white ink of the present invention as a means for solving the above problems contains water, a water-soluble organic solvent, and a colorant containing hollow resin particles, and the water-soluble organic solvent has a boiling point of 240 ° C. or less At least one selected from a monohydric alcohol having a boiling point of 240 ° C. or less and a diol having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the end of an alkane chain; The content of at least one selected from the monohydric alcohol and the diol is 75.0% by mass or more based on the total amount of the water-soluble organic solvent.

  According to the present invention, it is possible to provide a white ink capable of suppressing a decrease in whiteness of a white image even if the white image formed on a recording medium is rapidly heated and dried.

FIG. 1 is a schematic view showing an example of the ink cartridge of the present invention. FIG. 2 is a schematic view including the case of the ink jet cartridge of FIG. FIG. 3 is an explanatory view of the side surface of the main part of the ink jet recording apparatus. FIG. 4 is an explanatory view of the bottom of the main part when the image forming unit of FIG. 3 is viewed from the bottom side. FIG. 5 is an explanatory view of the bottom of the main part when the carriage of FIG. 3 is viewed from the bottom side. FIG. 6 is a block diagram of a control unit of the inkjet recording apparatus. FIG. 7 is an explanatory view of an ink jet recording method in which images are overlapped and recorded.

(White ink)
The white ink of the present invention contains water, a water-soluble organic solvent, and a colorant, and further contains other components as necessary.

<Water-soluble organic solvent>
Examples of the water-soluble organic solvent include those having a boiling point of 240 ° C. or less.

  The boiling point of the water-soluble organic solvent having a boiling point of 240 ° C. or less is 240 ° C. or less, preferably 205 ° C. or less, and more preferably 70 ° C. or more and 205 ° C. or less. When the boiling point is 240 ° C. or less, the drying property of the white ink is good and a coating film can be formed with low energy. In addition, since it is easy to dry, the water-soluble organic solvent is unlikely to remain in the hollow portion of the hollow resin particles, and it tends to be hollow in the state of a coated film, so that white can be developed.

  The water-soluble organic solvent having a boiling point of 240 ° C. or less includes, for example, a monohydric alcohol having a boiling point of 240 ° C. or less; a boiling point of 240 ° C. or less, and at least one hydroxyl group is bonded to other than the end of alkane chain It is preferable to contain other solvent components, if necessary, in the form of diol having 4 to 6 carbon atoms. These may be used alone or in combination of two or more. Among these, diols having a boiling point of 240 ° C. or less and at least one hydroxyl group bonded to other than the end of the alkane chain are preferable to be diols having 4 to 6 carbon atoms.

  The monohydric alcohol having a boiling point of 240 ° C. or less includes, for example, methanol (boiling point: 65 ° C.), ethanol (boiling point: 78 ° C.), 1-propanol (boiling point: 97 ° C.), 2-propanol (boiling point: 83 ° C.) 1-Butanol (boiling point: 118 ° C.), 2-butanol (boiling point: 99 ° C.), tert-butanol (boiling point: 82 ° C.), 3-methoxy-1-butanol (boiling point: 158 ° C.), tert-pentanol (Boiling point: 102 ° C.) and the like. These may be used alone or in combination of two or more. Among these, ethanol and 2-propanol are preferable from the viewpoint of the whiteness of the recorded image.

  The carbon number of the diol having 4 to 6 carbon atoms, which has a boiling point of 240 ° C. or less and at least one hydroxyl group is bonded to other than the terminal of the alkane chain, is 4 to 6 and 4 to 5 Is preferred. When the carbon number is 4 or more and 6 or less, suppression of softening of the hollow resin particle and drying property of the white ink after image formation can be improved.

  As the diol having 4 to 6 carbon atoms which has a boiling point of 240 ° C. or less and at least one hydroxyl group is bonded to other than the end of the alkane chain, at least one alcoholic hydroxyl group is other than the end of the alkane chain It is connected. The whiteness of the white image can be improved by bonding the at least one hydroxyl group to other than the end of the alkane chain.

  The diol having 4 to 6 carbon atoms having a boiling point of 240 ° C. or less and at least one hydroxyl group bonded to other than the end of the alkane chain is, for example, 1,2-butanediol (boiling point: 194 ° C.) 1,3-butanediol (boiling point: 203 ° C.), 2,3-butanediol (boiling point: 183 ° C.), 1,2-propanediol (boiling point: 188 ° C.), 3-methyl-1,3-butanediol (Boiling point: 203 ° C.), 2-methyl-2,4-pentanediol (boiling point: 197 ° C.) and the like. These may be used alone or in combination of two or more. Among these, 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, 2-methyl-2 from the point of whiteness of a white image. And 4-pentanediol are preferable, and 3-methyl-1,3-butanediol and 2-methyl-2,4-pentanediol are more preferable.

  The other solvent components are, for example, from the viewpoint of adjusting discharge stability by moisturizing property, drying property of white ink after image formation, miscibility with other components, fixing property to recording medium, etc. Polyhydric alcohol compounds other than diols having a boiling point of 240 ° C. or less and at least one hydroxyl group bonded to other than the end of an alkane chain and having a boiling point of 240 ° C. or less having 4 to 6 carbon atoms; Ether compounds; polyhydric alcohol aryl ether compounds; cyclic ether compounds; nitrogen-containing heterocyclic compounds; amine compounds; amide compounds; sulfur-containing compounds; propylene carbonate; These may be used alone or in combination of two or more.

  Examples of polyhydric alcohol compounds other than diols having a boiling point of 240 ° C. or less having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the terminal of an alkane chain include, for example, ethylene glycol, polyethylene glycol, propylene glycol And dipropylene glycol, tripropylene glycol, polypropylene glycol, glycerin, 1,2,6-hexanetriol, trimethylolethane, trimethylolpropane, propylpropylene diglycol and the like. These may be used alone or in combination of two or more. Among these, glycerin is preferable in terms of discharge stability due to moisture retention and miscibility with other components.

  Examples of the polyhydric alcohol alkyl ether compound include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (boiling point: 231 ° C.), ethylene glycol mono-2-ethylhexyl ether , Propylene glycol monoethyl ether, triethylene glycol dimethyl ether and the like. These may be used alone or in combination of two or more.

  Examples of the polyhydric alcohol aryl ether compounds include ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether. These may be used alone or in combination of two or more.

  Examples of the cyclic ether compound include epoxy compounds, oxetane compounds, tetrahydrofuran compounds, tetrahydropyran compounds, crown ethers and the like. These may be used alone or in combination of two or more. Among these, from the viewpoint of water solubility, oxetane compounds and tetrahydrofuran compounds are preferable, and oxetane compounds are more preferable.

  As the nitrogen-containing heterocyclic compound, for example, N-methyl-2-pyrrolidone (boiling point: 202 ° C.), N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone (boiling point: 245 ° C.), 1,3-dimethylimidazo Lidinone, ε-caprolactam, γ-butyrolactone and the like can be mentioned. These may be used alone or in combination of two or more.

  Examples of the amine compound include monoethanolamine, diethanolamine, triethanolamine, N, N-dimethylmonoethanolamine, N-methyldiethanolamine, N-methylethanolamine, N-phenylethanolamine, 3-aminopropyldiethylamine and the like. Can be mentioned. These may be used alone or in combination of two or more.

  Examples of the amide compound include formamide, N-methylformamide, N, N-dimethylformamide, β-methoxy-N, N-dimethylpropionamide, β-butoxy-N, N-dimethylpropionamide and the like. These may be used alone or in combination of two or more.

  Examples of the sulfur-containing compounds include dimethyl sulfoxide, sulfolane, thiodiglycol and the like. These may be used alone or in combination of two or more.

  As the measurement of the monohydric alcohol and the diol in the water-soluble organic solvent, for example, a differential thermal balance-photoionization mass spectrometry simultaneous measurement system (trade name: Thermo Mass Photo, manufactured by Rigaku Corporation), a differential thermal balance -Gas chromatography mass spectrometry simultaneous measurement apparatus (trade name: TG-DTA / GC-MS, manufactured by Rigaku Corporation) or the like can be used.

  The content of at least one selected from the monohydric alcohol and the diol is 75.0% by mass or more, and preferably 80% by mass to 95% by mass, based on the total amount of the water-soluble organic solvent. . If the content is 75.0% by mass or more, the hollow portion of the hollow resin particles is likely to be in a hollow state even if the water-soluble organic solvent having a boiling point exceeding 240 ° C. remains due to heating and drying of the ink. It can be expressed.

  As content of the water-soluble organic solvent whose boiling point exceeds 240 degreeC, it is 13 mass% or less with respect to the water-soluble organic solvent whole quantity, and 0 mass% or more and 10.0 mass% or less are preferable. If the content is 13% by mass or less, the hollow portion of the hollow resin particles is likely to be hollow and develop white color even if the water-soluble organic solvent having a boiling point exceeding 240 ° C. remains due to heating and drying of the ink. be able to.

  The content of the other solvent component is preferably less than 25% by mass, more preferably 0% by mass to less than 25% by mass, and particularly preferably 0% by mass to 15% by mass, with respect to the total amount of the water-soluble organic solvent. When the content is less than 25% by mass, whiteness can be maintained without breaking the form of the hollow resin particles by heating during drying.

<Colorant>
The colorant contains hollow resin particles, and further contains other coloring components as required.

-Hollow resin particles-
There is no restriction | limiting in particular as said hollow resin particle, According to the objective, it can select suitably, What makes a resin a shell and contains gas, such as air, is preferable.
The hollow means a structure in which the inside of the object is empty, and specifically, it has at least one of a space capable of containing a gas such as air and a hole through which a gas such as air can always pass. I say the structure. The hollow resin particles exhibit whiteness and excellent opacity due to light scattering due to the difference in refractive index between the air layer inside the particles after drying and the polymer layer of the shell.

  As the hollow resin particles, it is desirable not to precipitate or float and separate in a white ink, and therefore, those having a specific gravity substantially equivalent to the specific gravity of the water-soluble organic solvent are preferable. The hollow resin particle is filled with a vehicle component mainly composed of water and the water-soluble organic solvent, in the white ink, the hollow part at the time of drying is filled with the vehicle component. And the sedimentation of the hollow resin particles in the white ink can be suppressed. Although solid resin particles having no hollow structure can also be used, it is necessary to adjust the specific gravity of the solid resin particles to the vehicle component in order to suppress sedimentation in a white ink. In this case, it is necessary to comprehensively consider the resin composition of the solid resin particles, control of the polymerization (crosslinking) reaction, and control of the particle diameter, and thus the technical barrier becomes high. In the present invention, a monohydric alcohol having a boiling point of 240 ° C. or less, and a diol having 4 to 6 carbon atoms having a boiling point of 240 ° C. or less and at least one hydroxyl group is bonded to other than the terminal of an alkane chain. The content of at least one selected from the above is 75.0% by mass or more based on the total amount of the water-soluble organic solvent, so that the hollow portion of the hollow resin particle is filled with the vehicle component, It can suppress that the hollow resin particles swell due to the vehicle component and the resin of the hollow resin particles is softened, and the whiteness can be improved.

  There is no restriction | limiting in particular as a volume average particle diameter (particle outer diameter) of the said hollow resin particle, Although it can select suitably according to the objective, 0.2 micrometer or more and 1 micrometer or less are preferable, 0.3 micrometer or more and 0.8 micrometer The following are more preferable, and 0.3 to 0.5 μm are particularly preferable. When the volume average particle diameter is 0.2 μm or more and 1 μm or less, the whiteness of a white image and the occurrence of clogging in the ink flow path or the ink jet head in the ink jet recording apparatus can be suppressed. In addition, as a measurement of the said volume average particle diameter, the method using the particle size measuring apparatus of laser scattering / diffraction type, etc. are mentioned, for example.

There is no restriction | limiting in particular as a hollow rate of the said hollow resin particle, Although it can select suitably according to the objective, 20 to 80% is preferable, and 35 to 70% is more preferable. When the hollowness ratio is 20% or more, the whiteness of the printed image can be improved, and by being 80% or less, the particle diameter of the hollow resin particles can be kept small, and thus the white ink It is possible to suppress sedimentation in the inside.
Examples of the measurement of the hollowness include a method using a scanning electron microscope (SEM). The hollow ratio is the ratio of the volume of the hollow resin particle when approximated as a sphere from the outer diameter and the inner diameter (diameter of the hollow portion) of the hollow resin particle, and can be represented by the following formula (1).
Hollowness ratio (%) = (internal volume of hollow resin particles / volume of hollow resin particles) × 100 (1)
Internal volume of hollow resin particles = 4/3 × (inner diameter of hollow resin particles) ³
Hollow resin particle volume = 4/3 × (outside diameter of hollow resin particle) ³

  Examples of the resin composition of the hollow resin particles include acrylic resins such as acrylic resins, styrene-acrylic resins, and cross-linked styrene-acrylic resins; urethane resins; and maleic resins. These may be used alone or in combination of two or more.

There is no restriction | limiting in particular as said hollow resin particle, What was synthesize | combined suitably may be used and you may use a commercial item.
As the commercial product, for example, in the case of styrene-acrylic resin, trade name: LOPEK OP-62 (average particle size: 450 nm, hollow ratio: 33%), trade name: LOPEK OP-84 J (average particle size: 550 nm, hollow) Rate: 20%), trade name: low-peak OP-91, trade name: low-peak HP-1055 (average particle size: 1000 nm, hollow percentage: 55%), brand name: low-peak HP-91 (average particle size: 1000 nm, hollow) Rate: 50%), trade name: LOPEK ULTRA (average particle diameter: 380 nm, hollow percentage: 45%) (all, manufactured by Rohm and Haas Co., Ltd.); Cross-linked styrene-acrylic resin, trade name: SX-863 (A ), Trade name: SX-864 (B), trade name: SX-866 (A), trade name: SX-866 (B) (average particle diameter: 300 nm, hollow ratio: 30%), quotient Name: SX-868 (average particle size: 500 nm) (all, manufactured by JSR Corporation), trade name: Low-peak ULTRA E (average particle size: 380 nm, hollow percentage: 45%), trade name: Low-peak ULTRA DUAL (average grain) Diameter: 380 nm, hollow ratio: 45% (all, manufactured by Rohm and Haas Co., Ltd.); In the case of modified styrene-acrylic resin, trade name: Nipol MH5055 (average particle diameter: 500 nm), trade name: Nipol MH8101 (average particle diameter: 1 μm) (all manufactured by Nippon Zeon Co., Ltd.) and the like. These may be used alone or in combination of two or more.

  As the glass transition temperature of the hollow resin particles, the hollow resin particles dried by raising the temperature from ordinary temperature in a nitrogen atmosphere and dried at 200 ° C. for 30 minutes are cooled, and from a normal temperature to 200 using a differential scanning calorimeter (DSC) The temperature can be measured by raising the temperature to 5 ° C./min.

  As content of the said hollow resin particle, 1 mass% or more and 20 mass% or less are preferable with respect to white ink whole quantity, and 5 mass% or more and 15 mass% or less are more preferable. The whiteness of a white image can be improved as the said content is 1 mass% or more and 20 mass% or less.

-Other coloring components-
The white ink is mainly white, but the color can be adjusted by adding the other coloring components.
There is no restriction | limiting in particular as a color of said other coloring component, According to the objective, it can select suitably, For example, black, a color, white etc. are mentioned. These may be used alone or in combination of two or more. Among these, in the ink jet recording method, it is difficult to thicken the coating film by recording, and whiteness tends to increase because it is necessary to obtain sufficient whiteness with a thin coating film formed of a small amount of white ink. It is preferable to use one.

  As a material of the said other coloring component, a pigment, a dye, etc. are mentioned, for example. These may be used alone or in combination of two or more. Among these, pigments are preferable in terms of weatherability. In addition, when using the said pigment and the said dye together from the point of color tone adjustment, it is preferable to use the said dye within the range which does not deteriorate a weather resistance.

--Pigment--
Examples of the pigment include inorganic pigments and organic pigments. These may be used alone or in combination of two or more.

  As a method of dispersing the pigment, for example, a method of dispersing using a pigment having a self-dispersing property (self-dispersion type pigment); a pigment dispersant, a polymer dispersion stabilizer, a polymer dispersion stabilizer, etc. And a method of using a pigment dispersion in which the pigment is dispersed.

  Examples of the self-dispersible pigment include those in which at least one hydrophilic group is surface-modified such that it is bonded to the surface of the pigment directly or through another atomic group.

  A method of chemically bonding a specific functional group (functional group such as a sulfone group or a carboxyl group) to the surface of the pigment as a method of producing the self-dispersion pigment; hypohalous acid, hypohalite, etc. And a method of wet oxidation treatment using

  Since the white ink using the self-dispersion pigment is excellent in redispersion after drying, printing is paused for a long period of time, causing clogging even if the water in the white ink near the nozzle of the inkjet head evaporates. By performing a simple cleaning operation, good recording can be easily performed.

When a surfactant and a penetrant to be described later are combined as the self-dispersion pigment, it is possible to obtain a high quality image having a particularly high synergetic effect and higher reliability.
The self-dispersible pigment can be further used as a polymer emulsion in which the self-dispersible pigment is suspended in polymer fine particles. The polymer emulsion refers to one in which a pigment is enclosed in polymer particles or one in which a pigment is adsorbed on the surface of polymer particles.

As the polymer emulsion, it is not necessary for all the pigments to be enclosed and adsorbed, and the self-dispersible pigment may be dispersed in the emulsion as long as the effects of the present invention are not impaired.
Examples of the polymer that forms the polymer emulsion include vinyl polymers, polyester polymers, polyurethane polymers and the like. These may be used alone or in combination of two or more. Among these, vinyl polymers and polyester polymers are preferable, and polymers disclosed in Japanese Patent Application Laid-Open Nos. 2000-53897 and 2001-139849 are more preferable.

The HLB value of the pigment dispersant is preferably 10 or more and 20 or less.
Examples of the pigment dispersant include nonionic surfactants.
Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene polycyclic phenyl ether, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl phenyl ether, poly Examples include oxyethylene alkylamine, polyoxyethylene alkylamide, acetylene glycol and the like. These may be used alone or in combination of two or more. Among these, polyoxyethylene lauryl ether, polyoxyethylene-β-naphthyl ether, polyoxyethylene sorbitan monooleate, and polyoxyethylene styrene phenyl ether are preferable.

  Examples of the polymer dispersion stabilizer include an α-olefin-maleic anhydride copolymer, a styrene- (meth) acrylic copolymer, a water-soluble polyurethane resin, and a water-soluble polyester resin.

--Inorganic pigment---
Examples of the inorganic pigment include titanium dioxide, copper oxide, iron oxide (CI pigment black 11), calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chromium yellow, titanium yellow, carbon black Etc. These may be used alone or in combination of two or more. Among these, titanium dioxide and carbon black are preferable, and titanium dioxide is more preferable by adjusting the sedimentation.

  Examples of crystal forms of the titanium dioxide include tetragonal rutile type, tetragonal anatase type, and orthorhombic brookite type. Among these, rutile type is preferable in terms of high refractive index and easy increase in whiteness.

  The number average primary particle diameter of the titanium dioxide is preferably 100 nm or more and 400 nm or less, and more preferably 200 nm or more and 300 nm or less. Whiteness is high as the said number average primary particle size is 100 nm or more and 400 nm or less, and the scattering characteristic of visible light can be improved. In addition, since the specific gravity of the titanium dioxide is high and it is easy to settle, it is desirable to select the number average primary particle size from the viewpoint of settling property and whiteness.

  There is no restriction | limiting in particular as a manufacturing method of the said titanium dioxide, According to the objective, it can select suitably, For example, the sulfuric acid method, the chlorine method, etc. are mentioned.

  There is no restriction | limiting in particular as surface treatment of the particle | grains of the said titanium dioxide, According to the objective, it can select suitably, For example, resin coat, an alumina coat, etc. are mentioned. Among these, alumina coating is preferable in terms of suppressing the catalytic activity of the titanium dioxide.

  There is no restriction | limiting in particular as said titanium dioxide, What was synthesize | combined suitably may be used and a commercial item may be used. Examples of the commercially available products include Ishihara Sangyo Co., Ltd., Sakai Chemical Industry Co., Ltd., Taika Co., Ltd., Teika Co., Ltd., Titanium Industry Co., Ltd., Fuji Titanium Industry Co., Ltd., Fujikawa Chemicals Co., Ltd., DuPont Co. Tronox Co., Ltd., Kronos Co., Ltd., Millennium Inorganic Chemicals Co., Ltd., etc. may be mentioned.

  Examples of the carbon black include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black and channel black. These may be used alone or in combination of two or more.

  Examples of the method for producing the carbon black include known methods such as a contact method, a furnace method, and a thermal method.

  There is no restriction | limiting in particular as said carbon black, What was synthesize | combined suitably may be used, and a commercial item may be used. Examples of the commercially available product include: trade name: Regal (registered trademark), trade name: Black Pearls (registered trademark), trade name: Elftex (registered trademark), trade name: Monarch (registered trademark), trade name: Mogul ( Trademarks, trade name: Vulcan (registered trademark), and the like (all manufactured by Cabot Corporation).

--Organic pigment---
Examples of the organic pigment include alkylene bismelamine pigments, azo pigments, polycyclic pigments, lake pigments, nitro pigments, nitroso pigments, and aniline black. These may be used alone or in combination of two or more. Among these, azo pigments, polycyclic pigments and the like are preferable.

（ただし、一般式（Ｉ）中、Ｒは水素原子、或いは炭素数１以上４以下のアルキル基若しくは炭素数５以上７以下の飽和又は不飽和の脂環式基を表す。Ｒ_１〜Ｒ_４は同一又は異なる水素原子、或いは炭素数１以上４以下の低級アルキル基を表し、Ｒ_１及びＲ_２、又はＲ_３及びＲ_４が窒素原子と共に複素環式基を形成してもよい。Ｘは、炭素数２以上３以下のアルキレン基を表す。） As said alkylene bis melamine type pigment, the compound etc. which are shown by the following general formula (I) which is an organic white pigment are mentioned, for example.

(Wherein, in the general formula (I), R represents a hydrogen atom, or an alkyl group having 1 to 4 carbon atoms, or a saturated or unsaturated alicyclic group having 5 to 7 carbon atoms. R _{1 to} R ₄ Is the same or different hydrogen atom, or a lower alkyl group having 1 to 4 carbon atoms, and R ₁ and R ₂ , or R ₃ and R ₄ may form a heterocyclic group together with a nitrogen atom. And an alkylene group having 2 or more and 3 or less carbon atoms)

Examples of R in the general formula (I) include a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and a saturated or unsaturated alicyclic group having 5 to 7 carbon atoms.
As said alkyl group, a methyl group, an ethyl group, a propyl group, a butyl group etc. are mentioned, for example.
As said alicyclic group, a cyclohexyl group etc. are mentioned, for example.
Examples of R ₁ , R ₂ , R ₃ and R ₄ include a hydrogen atom, a methyl group, an ethyl group, a propyl group and a butyl group. The R ₁ and the R ₂ , or the R ₃ and the R ₄ may form a heterocyclic group together with a nitrogen atom.
As said heterocyclic group, a piperidyl group, morpholino group, etc. are mentioned, for example.
As said X, an ethylene group, a propylene group, etc. are mentioned, for example.

As the compound represented by the general formula (I), in the following structural formula (II) in which the R, the R ₁ , the R ₂ , the R ₃ and the R ₄ are a hydrogen atom and the X is an ethylene group The compounds shown are preferred. There is no restriction | limiting in particular as a compound shown by said general formula (I), A commercial item can also be used, For example, a brand name: Shigenox OWP (made by Hakkol Chemical Co., Ltd.) etc. are mentioned as said commercial item Be

  As a volume average particle diameter of the said alkylene bis melamine type pigment, 0.01 micrometer or more and 0.3 micrometer or less are preferable. When the volume average particle size is 0.01 μm or more, the particle size does not approach the dye, the light resistance and feathering are not deteriorated, and the eye size of the discharge port is 0.3 μm or less Clogging and clogging of the filter in the printer do not occur, and discharge stability can be obtained.

Examples of the azo pigment include an azo lake pigment, a poorly soluble azo pigment, a condensed azo pigment, and a chelate azo pigment. These may be used alone or in combination of two or more.
Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofarone pigments and the like. These may be used alone or in combination of two or more.

  Examples of the organic pigment include C.I. I. Pigment black 1 (aniline black); C.I. I. Pigment yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 109, 110, 117, 120, 128, 138, 150, 151, 153, 155, 183, 213, 408; I. Pigment orange 5, 13, 16, 17, 36, 43, 51; C.I. I. Pigment red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2 (permanent tread 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (bengal), 104, 105, 106, 108 ( Cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219; I. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 38; I. Pigment blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3 (phthalocyanine blue), 15: 4 (phthalocyanine blue), 16, 17: 1, 56, 60, 63; I. Pigment greens 1, 4, 7, 8, 10, 17, 18, 36 and the like. These may be used alone or in combination of two or more.

--Dye--
Examples of the dye include acid dyes, food dyes, direct dyes, basic dyes, reactive dyes, disperse dyes, and dye chelates. These may be used alone or in combination of two or more. Among these, acid dyes, food dyes and direct dyes are preferable, and acid dyes and direct dyes are more preferable, from the viewpoint of water solubility and color developability.

Examples of the acid dye and the food dye include
C. I. Acid Yellow 17, 23, 42, 44, 79, 142;
C. I. Acid Red 1, 8, 13, 14, 18, 26, 27, 35, 37, 42, 52, 82, 87, 89, 92, 97, 106, 111, 114, 115, 134, 186, 249, 254 289;
C. I. Acid Blue 9, 29, 45, 92, 249;
C. I. Acid Black 1, 2, 7, 24, 26, 94;
C. I. Food yellow 2, 3, 4;
C. I. Food red 7, 9, 14;
C. I. Food black 1 and 2
Etc. These may be used alone or in combination of two or more.

Examples of the direct dyes include
C. I. Direct Yellow 1, 12, 24, 26, 33, 44, 50, 120, 132, 142, 144, 86;
C. I. Direct Red 1, 4, 9, 13, 17, 20, 28, 31, 39, 80, 81, 83, 89, 225, 227;
C. I. Direct Orange 26, 29, 62, 102;
C. I. Direct Blue 1, 2, 6, 15, 22, 25, 71, 76, 79, 86, 87, 90, 98, 163, 165, 199, 202;
C. I. Direct Black 19, 22, 32, 38, 51, 56, 71, 74, 75, 77, 154, 168, 171
Etc. These may be used alone or in combination of two or more.

Examples of the basic dye include
C. I. Basic yellow 1, 2, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 40, 41, 45, 49, 51, 53, 63, 465, 67 , 70, 73, 77, 87, 91;
C. I. Basic red 2, 12, 13, 14, 15, 18, 22, 23, 24, 27, 29, 35, 36, 38, 39, 46, 49, 51, 52, 54, 59, 68, 69, 70 , 73, 78, 82, 102, 104, 109, 112;
C. I. Basic Blue 1, 3, 5, 7, 9, 21, 22, 22, 35, 41, 45, 47, 54, 62, 65, 66, 67, 69, 75, 77, 78, 89, 92, 93 105, 117, 120, 122, 124, 129, 137, 141, 147, 155;
C. I. Basic black 2, 8
Etc. These may be used alone or in combination of two or more.

Examples of the reactive dye include
C. I. Reactive Black 3, 4, 7, 11, 12, 17;
C. I. Reactive yellow 1, 5, 11, 13, 14, 20, 21, 22, 25, 40, 47, 51, 55, 65, 67;
C. I. Reactive red 1, 14, 17, 25, 25, 26, 32, 37, 44, 46, 55, 60, 66, 74, 79, 96, 97;
C. I. Reactive Blue 1, 2, 7, 14, 15, 23, 32, 35, 38, 41, 63, 80, 95;
Etc. These may be used alone or in combination of two or more.

Examples of the disperse dye include
C. I. Disperse Yellow 3, 5, 7, 33, 42, 54, 64, 79, 82, 83, 93, 99, 100, 119, 122, 124, 126, 160, 199, 204, 237;
C. I. Disperse Orange 3, 13, 29, 30, 54, 55, 66, 73, 118;
C. I. Disoerse Red 1, 17, 50, 54, 56, 60, 65, 72, 73, 88, 91, 92, 93, 110, 126, 127, 135, 143, 145, 154, 156, 154, 167, 177 207, 258, 283, 311, 323, 348;
C. I. Disperse Violet 1, 4, 26, 28, 35, 38, 43, 77;
C. I. Disperse Blue 3, 7, 56, 60, 73, 79, 81, 91, 94, 96, 102, 106, 128, 139, 146, 148, 149, 165, 183, 186, 187, 201, 205, 207 214, 257, 266, 268, 291, 341, 354, 358;
C. I. Disperse Brown 1;
C. I. Disperse black 1
Etc. These may be used alone or in combination of two or more.

  Examples of the dye chelates include basic dye chelates and acid dye chelates. These may be used alone or in combination of two or more.

  The volume average particle diameter (D50) of the colorant is preferably 300 nm or more and 1 μm or less, and more preferably 300 nm or more and 500 nm or less. When the volume average particle diameter is 300 nm or more and 1 μm or less, the ejection stability can be improved, and the accuracy of the impact position of the dots can also be improved. The volume average particle diameter can be measured using a particle size distribution measuring apparatus (trade name: Microtrac UPA, manufactured by Nikkiso Co., Ltd.) or the like.

  The content of the colorant is preferably 1% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less based on the total amount of the white ink, from the viewpoint of whiteness of the white image. When the content is 1% by mass or more, the whiteness of the white image is good, and the white ink can develop color without losing the color of the recording medium, and when it is 20% by mass or less, the white ink It is possible to suppress the thickening of the ink, to improve the dischargeability, and also to be economically preferable.

  Examples of the other coloring components include those described in The Color Index, Third Edition (The Society of Dyers and Colourists, 1982).

<Water>
There is no restriction | limiting in particular as said water, According to the objective, it can select suitably, For example, pure waters, such as ion-exchange water, ultrafiltration water, reverse osmosis water, distilled water; ultrapure water, etc. are mentioned . These may be used alone or in combination of two or more.

<Other ingredients>
The white ink of the present invention can contain, in addition to the water, the water-soluble organic solvent, and the colorant, other components used in ordinary inks.
There is no restriction | limiting in particular as said other component, According to the objective, it can select suitably, For example, surfactant, film-forming resin, antiseptic and antifungal agent, rust inhibitor, pH adjuster etc. are mentioned. . These may be used alone or in combination of two or more.

-Surfactant-
Examples of the surfactant include anionic surfactants, nonionic surfactants for purposes other than the purpose of dispersing the pigment, amphoteric surfactants, acetylene glycol surfactants, fluorine surfactants, and silicone surfactants. Surfactant etc. are mentioned. These may be used alone or in combination of two or more. Even when it is not easily dissolved alone in a white ink, it may be solubilized and used stably in combination by using two or more kinds. Further, it is preferable to select a surfactant which does not impair the dispersion stability depending on the combination of the type of colorant, the wetting agent and the water-soluble organic solvent.

  Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, borate ester sulfonate, laurate, polyoxyethylene alkyl ether sulfate and the like. These may be used alone or in combination of two or more.

  Examples of the nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene polyoxypropylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, and polyoxy ethylene Ethylene alkyl phenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide and the like can be mentioned. These may be used alone or in combination of two or more.

  Examples of the amphoteric surfactant include alkyldimethylamine oxide, dihydroxyethylalkylamine oxide, polyoxyethylene alkyldimethylamine oxide, laurylaminopropionate, dimethylalkyl (coco) betaine, lauryldimethylbetaine and stearyldimethylbetaine. Examples include lauryl dihydroxyethyl betaine and the like. These may be used alone or in combination of two or more. Among these, lauryl dimethyl amine oxide, myristyl dimethyl amine oxide, stearyl dimethyl amine oxide, dihydroxyethyl lauryl amine oxide, polyoxyethylene coconut oil alkyl dimethyl amine oxide, dimethyl alkyl (co) betaine, lauryl dimethyl betaine and the like can be mentioned. These may be used alone or in combination of two or more.

Examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octin-3,6-diol, and the like. And 5-dimethyl-1-hexyne-3-ol and the like. These may be used alone or in combination of two or more.
There is no restriction | limiting in particular as said acetylene glycol type-surfactant, A commercial item can be used, As said commercial item, brand name: Surfynol 104, 82, 465, 485, TG (above, Air Products, Inc. And the like. These may be used alone or in combination of two or more.

Examples of the fluorine-based surfactant include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines and perfluoroalkylamine oxides. Examples thereof include a compound, a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in a side chain, a sulfuric acid ester salt thereof, and a fluorine-based aliphatic polymer ester. These may be used alone or in combination of two or more.
There is no restriction | limiting in particular as said fluorine-type surfactant, A commercial item can also be used. Examples of the commercially available products include trade names: Surfron S-111, S-112, S-113, S121, S131, S132, S-141, and S-145 (manufactured by Asahi Glass Co., Ltd.); 93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431, FC-4430 (all manufactured by 3M Japan Co., Ltd.); trade name: FT-110, 250, 251, 400S (all manufactured by Neos Co., Ltd.); trade name: Zonyl FS-62, FSA, FSE, FSJ, FSP, TBS, UR, FSO, FSO-100, FSN N, FSN-100, FS-300 , FSK (manufactured by DuPont Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N (manufactured by OMNOVA, Inc.) And the like. These may be used alone or in combination of two or more.

The silicone surfactant is not particularly limited and may be appropriately selected depending on the purpose. It is preferably one that does not decompose even at high pH, such as side chain modified polydimethylsiloxane and both terminal modified polydimethylsiloxane, One end modified polydimethylsiloxane, side chain both ends modified polydimethylsiloxane etc. are mentioned. These may be used alone or in combination of two or more. Among them, polyether modified silicone surfactants having a polyoxyethylene group and a polyoxyethylene polyoxypropylene group as a modifying group are preferable from the viewpoint of exhibiting good properties as an aqueous surfactant.
There is no restriction | limiting in particular as said polyether modified silicone surfactant, According to the objective, it can select suitably, For example, the Si part side chain of dimethylpolysiloxane is represented by the following structural formula. And the like, and the like.
There is no restriction | limiting in particular as said polyether modified silicone surfactant, A commercial item can be used. As said commercial item, brand name: KF-618, KF-642, KF-643 (above, Shin-Etsu Chemical Co., Ltd. make) etc. are mentioned, for example. These may be used alone or in combination of two or more.

  The content of the surfactant is preferably 0.01% by mass or more and 5% by mass or less based on the total amount of the white ink, from the viewpoint of exhibiting the effect of permeability, and corresponds to many commercially available media. From the point of view, 0.5% by mass or more and 2% by mass or less is more preferable. When the content is 0.01% by mass or more, the effect of permeability can be improved, and when the content is 5% by mass or less, the wettability to the recording medium can be suppressed from being increased. Problems such as a decrease in discharge stability and the occurrence of beading can be prevented.

-Film forming resin-
The film-forming resin is contained in order to improve high image density (high color-forming ability), having excellent film-forming property (image-forming ability) and having high water repellency, high water resistance, and high weatherability. Ru.

  The volume average particle diameter of the film-forming resin is preferably 10 nm or more and 1,000 nm or less, more preferably 10 nm or more and 200 nm or less, and particularly preferably 10 nm or more and 50 nm or less. When the volume average particle size is 10 nm or more and 1,000 nm or less, it can be used in the ink jet recording apparatus without any problem. Further, when the volume average particle diameter is 10 nm or more and 50 nm or less, the film forming property is enhanced and a continuous film of a tough film-forming resin is formed, so that a printed product with high strength can be obtained. The volume average particle diameter of the film-forming resin can be measured, for example, using a particle size analyzer (trade name: Microtrac MODEL UPA 9340, manufactured by Nikkiso Co., Ltd.).

  Examples of the film-forming resin include condensation synthetic resins, addition synthetic resins, and natural polymer compounds. These may be used alone or in combination of two or more. Among these, condensation synthetic resins are preferable.

Examples of the condensation synthetic resin include polyester resin, polyurethane resin, polyepoxy resin, polyamide resin, polyether resin, poly (meth) acrylic resin, acrylic-silicone resin, and fluorine-based resin. These may be used alone or in combination of two or more. Among these, polyurethane resin, acryl-silicone resin, and fluorine resin are preferable.
Examples of the addition synthetic resin include polyolefin resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl ester resin, polyacrylic acid resin, unsaturated carboxylic acid resin and the like. These may be used alone or in combination of two or more.
Examples of the natural polymer compound include cellulose compounds, rosin compounds, natural rubber and the like. These may be used alone or in combination of two or more.

  The film-forming resin may be used as a homopolymer, or may be used as a composite resin such as a copolymer, and any one of a single-phase structure type, a core-shell type, and a power feed type emulsion It can be used.

  As the film-forming resin, one appropriately synthesized may be used, or a commercially available product may be used. Examples of the commercially available product include: trade name: Microgel E-1002, E-5002 (component name: styrene-acrylic resin particles, above, manufactured by Nippon Paint Co., Ltd.), trade name: Bon coat 4001 (component name: acrylic) -Based resin particles, manufactured by DIC Corporation, trade name: Bon coat 5454 (component name: styrene-acrylic resin particles, manufactured by DIC Corporation), trade name: SAE-1014 (styrene-acrylic resin particles, Nippon Zeon Co., Ltd.) Product name: Sybinol SK-200 (acrylic resin particles, manufactured by Ciden Chemical Co., Ltd.), trade name: Primal AC-22, AC-61 (acrylic resin particles, manufactured by Rohm and Haas), products Name: NANOKRYL SBC X-2821, 3689 (acrylic silicone resin particles, manufactured by Toyo Ink Co., Ltd.), commerce Name: # 3070 (methyl methacrylate polymer resin particles, manufactured by Mikuni Color Ltd.). These may be used alone or in combination of two or more. Among these, acrylic resins and urethane resins are preferable from the viewpoint of fixability and ink stability.

  As the film-forming resin, when the white ink is used for outdoor applications such as posters and signboards, it is necessary to be able to form a coating film excellent in long-term weather resistance, and from the viewpoint of coating film strength Polyurethane resin particles are preferred, and polycarbonate-based urethane resins are more preferred from the viewpoint of water resistance, heat resistance, abrasion resistance and weather resistance.

The polyurethane resin particles can be synthesized by reacting an isocyanate compound with a diol.
As the isocyanate compound, from the viewpoint of improving the weather resistance, for example, aliphatic diisocyanates and alicyclic diisocyanates are preferable, and alicyclic diisocyanates are more preferable.
Examples of the alicyclic diisocyanate include isophorone diisocyanate, dicyclohexylmethane diisocyanate and the like.
As content of the said alicyclic diisocyanate, 60 mass% or more is preferable with respect to the isocyanate compound whole quantity.

The polycarbonate-based urethane resin particles can be added in the form of a resin emulsion dispersed in an aqueous medium.
As resin solid content in the said resin emulsion, 20 mass% or more is preferable. If the resin solid content is 20% by mass or more, no problem occurs in formulation design when white ink is formed.
The volume average particle diameter of the urethane resin particles is preferably 10 nm or more and 350 nm or less from the viewpoint of liquid storage stability at the time of white ink formation and ejection stability. The volume average particle diameter can be measured using a particle size distribution measuring apparatus (trade name: Microtrac UPA, manufactured by Nikkiso Co., Ltd.) or the like.

  As the urethane resin particles, in the case of dispersing in an aqueous medium, it is also possible to use a forced emulsification type resin emulsion using a dispersing agent. However, since a dispersant may remain in the coating film and the strength of the coating film may be reduced, a self-emulsifying resin emulsion having an anionic group in the molecular structure of the urethane resin particles is preferable.

  The acid value of the self-emulsifying resin is preferably 5 mg KOH / g to 100 mg KOH / g, more preferably 20 mg KOH / g to 100 mg KOH / g, and more preferably 20 mg KOH / g to 50 mg KOH / g from the viewpoint of water dispersibility. Is particularly preferred. Abrasion resistance and chemical resistance can be provided as the said acid value is 5 mgKOH / g or more and 100 mgKOH / g or less. The measurement of the acid value of the said resin can be measured according to JIS K-0070. The film-forming resin is preferably modified with an anionic group from the viewpoint of water dispersibility.

  As said anionic group, a carboxyl group, a sulfonic acid group, etc. are mentioned, for example. Examples of the method of modifying the anionic group on the film-forming resin include reaction with a monomer having the anionic group.

There is no restriction | limiting in particular as a manufacturing method of the said urethane resin particle, It can obtain by a conventionally well-known manufacturing method.
By containing polycarbonate-based urethane resin particles as the film-forming resin from the viewpoint of having high heat resistance, residual solvent can be reduced by heating and drying after recording, and adhesiveness can be improved.
The minimum film-forming temperature of the polycarbonate-based urethane resin particles may not be room temperature or lower, but when heated and dried, it is preferably at least the heating temperature or lower, and more preferably 5 ° C. or more lower than the heating temperature preferable. For example, when the heating temperature is 60 ° C., the minimum film-forming temperature of the resin is preferably 0 ° C. or more and 55 ° C. or less, more preferably 25 ° C. or more and 55 ° C. or less. As the minimum film-forming temperature, lower one is excellent in film-forming property, and when the minimum film-forming temperature is higher than the glass transition temperature of the film-forming resin, sufficient coating film strength can be obtained.
The polycarbonate-based urethane resin particles preferably have a surface hardness of 100 N / mm ² or more when a coating film is formed. When the surface hardness is 100 N / mm ² or more, the ink forms a tough coating film, and stronger scratch resistance can be obtained.

  As content of the said polycarbonate-type urethane resin particle, 0.5 mass% or more and 10 mass% or less are preferable in conversion of solid content with respect to white ink whole quantity, 1 mass% or more and 8 mass% or less are more preferable, and 3 mass % Or more and 8% by mass or less is particularly preferable. When the content is 0.5% by mass or more, a coating film is sufficiently formed on the coloring agent to obtain the required image fastness. When the content is 10% by mass or less, the viscosity is increased Can be suppressed and easily discharged.

  The content of the film-forming resin is preferably 1% by mass or more and 10% by mass or less based on the total amount of the white ink, and the smoothness of the coating film, high glossiness, fixability to the substrate, and dischargeability From the point of view, 5% by mass or more and 10% by mass or less is more preferable. When the content is 1% by mass or more and 10% by mass or less, the fixability and the stability of the white ink can be improved.

-Antiseptic and fungicide-
As the antiseptic and fungicide, for example, 1,2-benzisothiazolin-3-one, sodium benzoate, sodium dehydroacetate, sodium sorbate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide and the like It can be mentioned.

-Rust inhibitor-
Examples of the antirust agent include acid sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropyl ammonium nitrate, pentaerythritol tetranitrate, dicyclohexyl ammonium nitrite and the like.

-PH adjuster-
The pH adjuster is not particularly limited as long as it can adjust the pH to a desired value without adversely affecting the prepared ink, and can be appropriately selected according to the purpose. Examples of the pH adjuster include hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide; carbonates of alkali metals such as lithium carbonate, sodium carbonate and potassium carbonate; quaternary ammonium Hydroxides; amines such as diethanolamine and triethanolamine; ammonium hydroxide; quaternary phosphonium hydroxides and the like.

-Method of producing white ink-
As a method for producing the white ink, for example, a colorant, a water-soluble organic solvent, a surfactant, a penetrant, water, and, if necessary, other components are dispersed or dissolved in an aqueous medium, and appropriately mixed by stirring Can be manufactured. As the stirring and mixing, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, a stirrer using a common stirring blade, a magnetic stirrer, a high-speed disperser and the like can be used.

-Physical properties of white ink-
There is no restriction | limiting in particular as a physical property of the said white ink, Although it can select suitably according to the objective, It is preferable that a viscosity and static surface tension are the following ranges.

--Viscosity--
The viscosity of the white ink is preferably 2 mPa · s or more and 20 mPa · s or less, and more preferably 3 mPa · s or more and 15 mPa · s or less at the time of ejection at 25 ° C. When the viscosity is 2 mPa · s or more, residual vibration during discharge of the white ink is less likely to occur, and it is easy to suppress vibration after discharge by the drive waveform, and the next discharge can be performed in a short time, suitable for high speed printing It can be used to Moreover, discharge property can be improved as it is 20 mPa * s or less. In addition, since a viscosity changes according to use environment temperature, it is preferable that the said viscosity satisfy | fills the said range in use environment temperature. Viscosity can be measured, for example, using a viscometer (trade name: RE-550L, manufactured by Toki Sangyo Co., Ltd.).

-Static surface tension-
The static surface tension is preferably 20 mN / m to 40 mN / m at 25 ° C., and more preferably 20 mN / m to 35 mN / m. When the static surface tension is 20 mN / m or more and 40 mN / m or less, the wettability is increased, bleeding on the recording medium can be reduced, and dots are expanded on the surface of the recording medium. It is possible to improve the quality. Further, if it is 20 mN / m or more, the nozzle plate of the ink jet head is not excessively wetted, and expelling of the white ink around the nozzle holes and non-uniformity of wettability due to wiping spots due to maintenance, and discharge bending, And it can prevent causing a non-discharge state.

  As a method of ejecting the white ink, for example, a piezoelectric element is used as a pressure generating unit for pressurizing the white ink in the ink channel, and the diaphragm forming the wall surface of the ink channel is deformed to form the ink channel volume So-called piezo method (see, for example, Japanese Examined Patent Publication No. 2-51734); and heat generation of ink in the ink flow path using a heating resistor to generate air bubbles, so-called thermal method. (See, for example, Japanese Examined Patent Publication No. 61-59911): A diaphragm and an electrode forming a wall surface of an ink flow path are disposed opposite to each other, and the diaphragm is formed by the electrostatic force generated between the diaphragm and the electrode. An electrostatic method (see, for example, Japanese Patent Application Laid-Open No. 6-71882) in which the ink flow path inner volume is changed and the ink droplet is discharged by being deformed is mentioned.

The white ink may be used, for example, in a printer having a function of promoting recording and fixing by heating the recording medium and the white ink at 50 ° C. or more and 200 ° C. or less at the time of recording or before and after recording.
The white ink is, for example, preferably for inkjet, and more preferably for heat drying.
Examples of other coating methods include blade coating, bar coating, and roll coating.

(Ink set)
Examples of the ink set of the present invention include an ink set comprising a white ink and an ink not containing hollow resin particles.

-Ink set comprising white ink and ink not containing hollow resin particles-
The ink set comprising a white ink and an ink not containing hollow resin particles contains a white ink and an ink not containing hollow resin particles, and optionally contains other inks.
After applying the white ink using the white ink and the other ink, the image is fixed by heat recording, and when the other ink is applied on the coating film of the white ink, the hollow resin particles in the white ink are Under the influence of the solvent in the other ink, the glass transition temperature of the hollow resin particles is lowered, which tends to cause the transparency. When the amount of light reflected from the coating film by the white ink is reduced due to the transparency, the coloring of the other ink formed on the coating film can not utilize the reflected light, so that the coloring of the other ink is insufficient. There is a problem that
Therefore, by using an ink set comprising a white ink and an ink not containing hollow resin particles, even if the ink containing no hollow resin particles is coated on the white ink, It has been found that it is possible to prevent the decrease in whiteness and to suppress the decrease in color development of the ink not containing the hollow resin particles.

As the white ink, the same one as the white ink of the present invention can be used.
The ink containing no hollow resin particles contains water and a water-soluble organic solvent, contains other components as necessary, and does not contain hollow resin particles.
As said water, the thing similar to the water used for the white ink of this invention can be used.

As the water-soluble organic solvent, the same water-soluble organic solvent as used in the white ink of the present invention can be used, which has a boiling point of 240 ° C. or less and at least one hydroxyl group is other than the alkane chain terminal It is preferable to include a bonded diol having 4 or more and 6 or less carbon atoms.
The diol having 4 to 6 carbon atoms which has a boiling point of 240 ° C. or less and at least one hydroxyl group is bonded to other than the end of the alkane chain has a boiling point of 240 ° C. or less used in white ink The same diol as that having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the end of the alkane chain can be used.

  The content of the diol having 4 to 6 carbon atoms having a boiling point of 240 ° C. or lower and at least one hydroxyl group bonded to other than the end of the alkane chain is based on the total amount of ink containing no hollow resin particles. 80 mass% or more is preferable.

Examples of the other components include a colorant, a surfactant, a film-forming resin, a preservative / antifungal agent, a rust inhibitor, and a pH adjuster.
As said coloring agent, the same thing as the other coloring component in the white ink of this invention can be used.
As the surfactant, the film-forming resin, the antiseptic agent, the antirust agent, and the pH adjuster, a surfactant, a film-forming resin, an antiseptic agent used for the white ink of the present invention The same agent as the agent, the rust inhibitor, and the pH adjuster can be used.

(ink cartridge)
The ink cartridge of the present invention contains the white ink in a container, and further includes other members appropriately selected as necessary.

  The container is not particularly limited, and the shape, structure, size, material, and the like can be appropriately selected according to the purpose. For example, an ink bag formed of an aluminum laminate film, a resin film, etc. Those having at least one can be mentioned.

Next, the ink cartridge will be described with reference to FIGS. 1 and 2.
Here, FIG. 1 is a schematic view showing the ink cartridge, and FIG. 2 is a schematic view including the case 200 of the ink jet cartridge of FIG.
As shown in FIG. 1, after the white ink is filled in the ink bag 241 from the ink inlet 242 and exhausted, the ink inlet 242 is closed by fusion.
At the time of use, a needle of an ink jet recording apparatus main body 101 of the present invention described later is pierced through an ink discharge port 243 made of a rubber member, and the white ink is supplied to the ink jet recording apparatus main body 101. The ink bag 241 is formed of a packaging member such as an aluminum laminate film having low air permeability. As shown in FIG. 2, the ink bag 241 is usually housed in a plastic cartridge case 244, and is detachably mounted to various ink jet recording apparatuses. The ink cartridge 201 can accommodate the white ink and can be detachably mounted to various ink jet recording apparatuses, and can be detachably mounted to the ink jet recording apparatus 101 of the present invention described later. preferable.

(Ink jet recording method and ink jet recording apparatus)
The inkjet recording method includes at least an ink applying step of flying white ink and applying it to a recording medium, and a heating step of heating and drying the recording medium having an image recorded thereon, the heating step heating the recording medium; It is preferable to include at least the second heat treatment of applying warm air to the recording medium, and further include other appropriately selected steps, for example, a stimulus generation step, a control step, etc., as necessary.
The inkjet recording apparatus includes at least an ink applying unit for flying white ink to apply the ink to a recording medium, and a heating unit for heating and drying the recording medium having an image recorded thereon, the heating unit heating the recording medium; And at least a second heat treatment for applying warm air to the recording medium, and further comprising other means appropriately selected as necessary, such as a stimulation means, a control means, etc. .

  The ink jet recording method can be suitably carried out by the ink jet recording apparatus, and the ink applying step can be suitably carried out by an ink applying means. Further, the first heat treatment in the heating step can be suitably performed by the first heat treatment in the heating means, and the second heat treatment in the heating step can be suitably performed by the second heat treatment in the heating means. The other steps can be suitably performed by other means.

<Ink application process and ink application means>
The ink application step is a step of applying a stimulus (energy) to the white ink to fly the white ink to form an image on a recording medium.
The ink application unit is a unit that applies a stimulus (energy) to the white ink to fly the white ink to form an image on a recording medium.
There is no restriction | limiting in particular as said ink provision means, For example, the various nozzles for ink discharge etc. are mentioned.
The stimulation (energy) can be generated, for example, by the stimulation generation unit. There is no restriction | limiting in particular as said stimulation, According to the objective, it can select suitably, Heat (temperature), a pressure, a vibration, light, etc. are mentioned. These may be used alone or in combination of two or more. Among these, heat and pressure are preferable.
Examples of the stimulation generating means include a heating device, a pressurizing device, a piezoelectric element, a vibration generating device, an ultrasonic oscillator, a light, etc. For example, a piezoelectric actuator such as a piezoelectric element; electrothermal conversion such as a heating resistor The thermal actuator which utilizes the phase change by film boiling of a liquid using an element; The shape memory alloy actuator which uses the metal phase change by temperature change; The electrostatic actuator etc. which use electrostatic force are mentioned.
In the case of using the ink set comprising the white ink and the ink containing no hollow resin particles, which is the ink set of the present invention, the white ink is applied by the white ink applying step of applying the white ink to a recording medium It is preferable to have the process of apply | coating the ink which does not contain a hollow resin particle on the said coating film after forming a film | membrane. The application amount of the white ink is preferably larger than the application amount of the ink not containing the hollow resin particles, and more preferably 10 g / m ² or more and 100 g / m ² or less. The application amount of the ink containing no organic hollow particles means the total application amount of all the colors of the ink.
The size of the droplets of the white ink applied to the recording medium is, for example, preferably 3 × 10 ^-15 m ³ or more and 40 × 10 ^-15 m ³ or less ( ³ pL or more and 40 pL or less).
The speed of ejection and ejection of the white ink applied to the recording medium is preferably 5 m / s or more and 20 m / s or less.
The driving frequency of the white ink applied to the recording medium is preferably 1 kHz or more.
The resolution of the image obtained by the white ink applied to the recording medium is preferably 60 dpi or more, more preferably 150 dpi or more.
Examples of the ink application unit include an inkjet head. The ink jet head is formed of, for example, a material including at least one of stainless steel (SUS), silicon, and nickel in at least a part of a liquid chamber, a fluid resistance unit, a diaphragm, and a nozzle member. Etc.
The stainless steel is compatible with a wide range of liquid inks and has a high thermal conductivity, so the ink jet head made of a stainless steel member can improve temperature controllability.
The silicon can be processed using semiconductor technology and micro electro mechanical system (MEMS) technology, so that very fine and high-precision processing can be performed.
As the nickel, since a metal thin film can be manufactured using an electroforming technique, a highly accurate shape can be manufactured.
The nickel tends to be easily dissolved by the acidification, so the ink adaptability tends to be low, but it has high durability and excellent processability by electroforming with an alloy such as palladium. Thin metal film parts can be manufactured.
The nozzle diameter of the nozzle of the inkjet head is preferably 50 μm or less, and more preferably 10 μm to 30 μm.

<Heating process and heating means>
The inkjet recording method preferably includes a heating step of heating and drying the recording medium to which the white ink is applied.
The inkjet recording apparatus preferably has a heating unit that heats and dries the recording medium to which the white ink is applied.
The heating step of the inkjet recording method preferably includes a first heat treatment, and more preferably includes a second heat treatment after the first heat treatment.
The heating unit of the inkjet recording apparatus preferably has a first heating member, and further preferably has a second heating member in addition to the first heating member.

<< First heat treatment in the heating step and first heating member in the heating means >>
As the inkjet recording method, the first heat treatment can be provided in the heating step in order to accelerate the fixing and drying of the white ink on the recording medium to which the white ink is applied by flying.
Further, even in an ink set comprising a white ink and an ink not containing hollow resin particles, the first heat treatment is provided in the heating step in order to accelerate the fixing and drying of the white ink, in order to accelerate the fixing and drying of the white ink be able to.
Examples of the first heating member in the heating means include an infrared drying device, a microwave drying device, a roll heater, a drum heater and the like.
By providing the first heating member in the first heat treatment and heating means in the heating step, drying and fixing immediately after the white ink is adhered to the recording medium is promoted, and the movement of the white ink on the coated surface is suppressed. be able to. By this, it is possible to suppress beading and bleeding, to improve the printability on the recording medium and the image quality, and by promoting the drying, the resin component in the component of the white ink tends to form a film, and recording Fixability immediately after can be improved.

  In order to accelerate the drying and fixing during the recording, it is necessary to heat the recording medium before printing or during the printing. The heating temperature is preferably 40 ° C. or more and 70 ° C. or less under the ink ejection head. When the heating temperature is 40 ° C. or more, evaporation of the white ink on the recording medium can be promoted to suppress beading, and when the heating temperature is 70 ° C. or less, the ink jet head warms up and the discharge nozzle It is possible to suppress the occurrence of non-ejection by drying. In addition, the hollow resin particles have a softening temperature lower than the glass transition temperature due to the influence of components in the white ink, and if the heating temperature is 70 ° C. or less, they are damaged and lose the hollow shape. It can be prevented. In addition, when the heating temperature is in the above range, a good image without color bleeding or dot fusion can be obtained, and the shape of the hollow resin particles can be maintained to form a good image showing white. it can.

  The heating time in the first heat treatment in the heating step is preferably 10 seconds to 600 seconds.

  Further, the heating temperature in the vicinity of the ink discharge head is more preferably 40 ° C. or more and 60 ° C. or less under the ink jet head from the viewpoint of drying the meniscus of the head nozzle portion and deteriorating the discharge performance. The heating can be performed in the first heat treatment in the heating step. As the first heat treatment in the heating step, it is preferable to change the heating state under the printing conditions, and it is more preferable to use a capacitor in combination also in order to cover the power used for rapid heating.

  The heating temperature can be changed according to the type and amount of the water-soluble organic solvent contained in the white ink, and the minimum film forming temperature of the water-dispersed resin to be added, and further according to the type of recording medium to be printed. You can even change it. The heating temperature is preferably high from the viewpoint of the drying property and the film-forming temperature of the water-dispersed resin.

  As a result of intensive investigations, in order to prevent damage to the hollow resin particles, it is necessary to heat the hollow resin particles so that the temperature is lower by 30 ° C. or more than the glass transition temperature of the hollow resin particles. I found out. By setting the heating temperature equal to or lower than the above temperature, the hollow resin particles are prevented from being softened, and the shape of the hollow resin particles is rapidly destroyed in the second heat treatment in the heating step, resulting in a film without hollow. Therefore, it can be prevented that it does not show a white color. In addition, in the case of an ink set containing neither white ink nor hollow resin particles, the heating temperature in the first heat treatment after white ink application is lower by at least 30 ° C. than the glass transition temperature of hollow resin particles. Is preferred.

  In the first heat treatment in the heating step, when the heating temperature is 70 ° C. or less, damage to the recording medium can be suppressed, and the heat dispersion also differs depending on the water dispersion resin, but in particular In the case of a vinyl chloride film or the like, when the heating temperature is high, thermal contraction occurs, and it is possible to suppress the occurrence of abnormality in the shape of the recording medium as well as the image.

  In addition, after the recording, a drying step of heating by the second heat treatment in the heating unit may be accompanied, and the drying of the coating film can be promoted to accelerate the fixation of the white ink. Also in heating after recording, it is preferable to carry out heating so that the temperature is 30 ° C. or more lower than the glass transition temperature of the hollow resin particles, because the hollow resin particles are not damaged by the heating.

<< Second heat treatment in the heating step and second heating member in the heating means >>
In the inkjet recording method, the second heat treatment in the heating step can be provided in order to accelerate the fixing and drying of the white ink of the recording medium after the first heat treatment in the heating step.
Further, even in the ink set including the white ink and the ink containing no hollow resin particles, the second heating in the heating process is performed to promote the fixing and drying of the white ink of the recording medium after the first heating process in the heating process. A treatment can be provided.
As a second heating member in the heating means of the second heat treatment in the heating step, for example, a heat generation source for heating air is a resistance heating system such as a heating wire, an induction heating system such as an IH heater, a high frequency A dielectric heating method such as induction heating, a microwave heating method such as a microwave oven, an infrared heating method such as a halogen heater, and the like can be mentioned. Examples of the infrared heating method include various heat sources such as a nichrome wire heating element, a halogen lamp, a halogen heater, and a ceramic heater, and can have a complicated shape.

The warm air is blown by the blower constituted by the motor and the fan to warm the air warmed by the heat source, thereby promoting the drying and fixing of the white ink on the recording medium being dried in the first heat treatment in the heating step. Can be completely fixed.
By drying the white ink with the hot air, it is possible to remove the water, water-soluble organic solvent, and other vapors contained in the white ink from the surface of the recording medium, and it is possible to dry more effectively by heating without wind. it can. In the second heat treatment in the heating step, the resin component in the white ink component tends to form a film, promotes the drying of the solvent component in the hollow resin particles, and improves the fixability and the white expression. Can.

  The temperature of the warm air is not particularly limited as long as evaporation of the solvent in the white ink by air blowing is promoted, but the temperature of the coating film is easily lowered due to the heat of vaporization of water or the like, and the temperature of the coating film is lowered. It is preferable to apply warm air at a temperature equal to or higher than the heating temperature of the first heat treatment in the heating step, more preferably 40 ° C. or more and 100 ° C. or less, and particularly preferably 50 ° C. or more and 80 ° C. or less. Drying property can be improved as it is the said temperature, and the shape of a hollow resin particle can be maintained.

  The heating time in the second heat treatment in the heating step is preferably 60 seconds or more and 1,800 seconds or less.

  As a result of earnestly examining in using the said 2nd heating member in a heating means, in the said 1st heat processing in a heating process, as content of the water-soluble organic solvent in white ink, it will be 20 mass% or less It turned out that it can dry and maintain the shape of the said hollow resin particle in the said 2nd heat processing in a heating process by drying. Softening of the said hollow resin particle by the influence of the said water-soluble resin particle is suppressed as the said content is 20 mass% or less, and the shape of the hollow resin particle can be maintained also with the heat of warm air.

As a method of analyzing the content of the water-soluble organic solvent in the white ink, for example, a method of calculating from weight loss by thermogravimetric analysis, quantitative analysis of volatile components by gas chromatography, quantitative analysis of dissolved components by liquid chromatography , Quantitative analysis of infrared absorption spectrum from functional groups by ATR method, quantitative analysis of structure from ¹ H and ¹³ C by NMR, and the like.

  As the second heating member in the heating means, a heating member from the back surface of the recording medium may be used in combination. By providing the heating member from the back surface of the recording medium, the drying property is improved, and the temperature of the warm air can be lowered.

  The control means is not particularly limited as long as it can control the movement of each means, and can be appropriately selected according to the purpose. Examples thereof include devices such as sequencers and computers.

-Ink jet recording apparatus-
Hereinafter, the ink jet recording apparatus of the present invention will be described with reference to the drawings.
First, an inkjet recording apparatus according to the present invention will be described with reference to FIGS. 3, 4 and 5. FIG. 3 is an explanatory view of the side surface of the main part of the ink jet recording apparatus, FIG. 4 is an explanatory view of the bottom surface of the main part when the image forming unit 2 of FIG. It is explanatory drawing of the principal part bottom which looked at the carriage 23 of 3 from the bottom face side.

  The ink jet recording apparatus is a serial type ink jet recording apparatus, and as shown in FIG. 3, has an image forming unit 2, a transport mechanism unit 5, an ink cartridge 30, an ink jet recording head 24, etc. inside the ink jet recording apparatus main body. The recording medium 10 is delivered from the delivery unit 4 on the side of the inkjet recording apparatus main body, and while the recording medium 10 is intermittently transported horizontally by the transport mechanism unit 5, the liquid is directed downward in the vertical direction by the image forming unit 2. After recording a required image by discharging droplets, the direction of the recording medium is changed by the delivery roller 62, and the recording medium 10 is taken up by the take-up unit 7 which delivers the recording medium 10 having the image recorded thereon. to recover.

  Here, as shown in FIG. 4, the image forming unit 2 can slide the carriage 23 on which the ink jet head 24 is mounted with the main guide member 21 and the sub guide member 22 which are horizontally extended between the left and right side plates 11L and 11R. The main scanning motor 25 moves and scans in the main scanning direction via the timing belt 28 passed between the drive pulley 26 and the driven pulley 27.

  On the carriage 23, ink jet heads 24a, 24b, which are liquid ejection heads for ejecting ink droplets of respective colors of yellow (Y), magenta (M), cyan (C), black (K) and white (W) 24c, 24d, 24e (if not distinguished from each other, referred to as "inkjet recording head 24" as described above), a nozzle row consisting of a plurality of nozzles is arranged in the sub scanning direction orthogonal to the main scanning direction, and the droplet discharge direction is vertical It is wearing facing downward.

As a liquid discharge head constituting the ink jet head 24, a piezoelectric actuator such as a piezoelectric element; a thermal actuator utilizing a phase change due to film boiling of the liquid using an electrothermal conversion element such as a heating resistor; A shape memory alloy actuator using phase change; an electrostatic actuator using electrostatic force or the like can be used as a pressure generating means for generating pressure for discharging a droplet.
The carriage 23 can also be provided with a liquid discharge head or the like that discharges a fixing liquid that improves the fixability of the ink by reacting with the ink.

Further, a head tank 29 for supplying ink of each color corresponding to each nozzle row of the ink jet recording head 24 is mounted on the carriage 23, and the head tank 29 is detachably mounted on the apparatus main body. Ink is supplied from the ink cartridge 30 (main tank) of each color.
Since the ink jet recording head 24 has the droplet discharge direction in the vertical direction downward, it is necessary to form a negative pressure in order to prevent dripping, and the head tank 29 has a negative pressure maintaining function as well as a buffer tank function. Have.

  Further, an encoder scale 121 having a predetermined pattern formed thereon is stretched between the side plates 11L and 11R along the main scanning direction of the carriage 23, and the carriage 23 is formed of a transmissive photo sensor for reading the pattern of the encoder scale 121. An encoder sensor (not shown) is provided, and a linear encoder (main scan encoder) 123 configured to detect the movement of the carriage 23 by the encoder scale 121 and the encoder sensor is configured.

Further, a maintenance recovery mechanism 9 for maintaining and recovering the state of the nozzles of the inkjet head 24 is disposed in the non-printing area on one side in the scanning direction of the carriage 23.
The maintenance recovery mechanism 9 wipes the nozzle surface with the caps 92a, 92b, 92c, 92d, 92e (referred to as "cap 92" if not distinguished) for capping the nozzle surfaces of the inkjet head 24. A wiper member (wiper blade) 93, and an idle discharge receptacle 94 for receiving a droplet when performing idle discharge for discharging a droplet that does not contribute to recording in order to discharge thickened recording liquid are provided.

  The recording medium 10 for recording is taken up by the delivery paper tube 41 of the delivery unit 4 and sent to the first platen 53 after being fed between the upper and lower feed roller pairs 51 and 52 of the transport mechanism unit 5. Along the line, the sheet is wound by the feed roller 62 and fixed to the winding paper pipe 71 of the winding unit 7, and the winding paper pipe 71 is wound by being rotated by a motor.

  A code wheel 154 is attached to the shaft 52a of the feed roller 52, and an encoder sensor 155 consisting of a transmission type photo sensor for detecting a pattern formed on the code wheel 154 is provided, and the code wheel 154 and the encoder sensor 155 A rotary encoder (feed encoder) 156 is configured to detect the amount of rotation and the rotation angle of the feed roller.

  Similarly, a code wheel 157 is attached to the shaft 62 a of the delivery roller 62, and an encoder sensor 158 consisting of a transmission type photo sensor for detecting a pattern formed on the code wheel 157 is provided. These code wheel 157 and encoder sensor 158 A rotary encoder (delivery encoder) 159 is configured to detect the rotation amount and the rotation angle of the delivery roller.

The rotation amount of the feed roller 51 and the winding unit 7 is controlled to be the same or the winding unit is slightly increased, and tension is applied to the recording medium 10 on the first platen 53 in the conveyance direction, The floating of the recording medium 10 is prevented.
In the ink jet recording apparatus configured as described above, the recording medium 10 is fed out from the delivery unit 4 in the horizontal direction with the transport amount corresponding to one scan. A first platen 53 is disposed corresponding to the recording area by the ink jet head 24, and a heater is incorporated in the first platen 53 so that the recording medium 10 can be heated from the back of the recording surface. The first platen 53 heats the recording medium 10.

  Therefore, by driving the inkjet head 24 according to the recording signal while moving the carriage 23, ink droplets are discharged downward from above onto the stopped recording medium 10 to record one line After transporting the recording medium 10 by a predetermined amount, the next line is recorded, and the recording medium 10 for which the recording is completed is discharged from the recording area. The discharged recording medium 10 is heated by applying warm air to the recording surface by a warm air unit 8 including a blower fan 82 and a heater 81. Further, a second platen 83 is installed facing the blower fan 82 so that the recording medium 10 is not bent by the warm air. A heater is also incorporated in the second platen 83 and heats from the back surface of the recorded recording medium 10 to accelerate the drying of the recording medium 10. The recording medium 10 is dried in a noncontact manner on the recording surface so as not to contact the warm air portion 8, and is wound by the winding portion 7.

  Then, when the remaining amount near the end of the ink jet recording ink in the head tank 29 is detected, the ink tank 30 is replenished with the required amount of ink for ink jet recording. When maintenance and recovery of the nozzles of the inkjet head 24 is performed, the carriage 23 is moved to a position opposite to the maintenance and recovery mechanism 9 which is the home position, capping by the cap 92 is performed, and suction and discharge of nozzles are performed. By performing maintenance and recovery operations such as idle discharge that discharges droplets that do not contribute to formation, image formation by stable droplet discharge can be performed.

Next, the outline of the control unit of the inkjet recording apparatus will be described with reference to the block diagram of FIG.
The control unit 500 is a CPU 501 that controls the entire inkjet recording apparatus, various programs including a program that causes the CPU 501 to execute control (processing) according to the present invention, a ROM 502 that stores other fixed data, print data , Etc., a rewritable non-volatile memory 504 for holding data even while the power supply of the ink jet printing apparatus is shut off, and image processing for performing various signal processing, sorting, etc. on print data And an ASIC 505 that processes input and output signals for controlling the entire inkjet recording apparatus.

Further, a data transfer unit for driving and controlling the inkjet head 24, an inkjet head drive control unit 508 including a driving signal generating unit, and an inkjet head driver for driving the inkjet head 24 provided on the carriage 23 (inkjet head IC ) 509).
A carriage unit movement motor drive control unit 510 is provided to drive and control the main scanning motor 25 for moving and scanning the carriage 23.

Furthermore, a delivery unit motor 523 for delivering the recording medium 10 by rotating the delivery paper tube 41 for taking up the recording medium 10 before recording, and a position for rotating the delivery roller 51 for feeding the recording medium 10 to the recording unit The feed motor 522 for holding the sheet, the feed motor 521 for holding the position by rotating the feed roller 62 for sending the recording medium from the recording unit, and the winding unit motor for rotating the winding paper tube 71 for winding the fed recording medium 524, a medium transport motor drive control unit 520 which drives and controls these motors.
Further, the control unit 500 is connected to an operation panel 514 for inputting and displaying information necessary for the ink jet printing apparatus.

  The control unit 500 includes a host I / F 506 for transmitting and receiving data and signals with the host side, and an image processing apparatus such as an information processing apparatus such as a personal computer, an image reading apparatus such as an image scanner, and a digital camera. The host I / F 506 receives data from the host 600 such as a device via a cable or a network.

  Then, the CPU 501 of the control unit 500 reads out and analyzes the recording data in the receiving buffer included in the host I / F 506, performs necessary image processing, data rearrangement processing and the like by the ASIC 505, and The ink is transferred from the ink jet head drive control unit 508 to the ink jet head IC 509. The printer driver 601 on the host 600 side prepares dot pattern data for outputting an image.

  The inkjet head drive control unit 508 transfers the above-described print data as serial data, and outputs a transfer clock, a latch signal, a control signal, etc. necessary for transferring the print data and determining the transfer to the inkjet head IC 509. In addition to this, it also includes a D / A converter for D / A converting the pattern data of the drive pulse stored in the ROM, and a drive signal generation unit composed of a voltage amplifier, a current amplifier, etc. A drive signal composed of a plurality of drive pulses is output to the inkjet head IC 509.

The inkjet head IC 509 selectively selects drive pulses of the inkjet head 24 which form drive signals supplied from the inkjet head drive control unit 508 based on print data corresponding to one line of the inkjet head 24 input serially. The ink jet head 24 is driven by applying to a drive element (for example, a piezoelectric element) that generates energy for discharging a droplet.
At this time, by selecting the drive pulse that constitutes the drive signal, it is possible to eject droplets having different droplet amounts, such as large droplets, medium droplets, small droplets, and the like, to separately eject dots having different sizes.

  The I / O 513 acquires information from the main scanning encoder 123, the feed encoder 156, the delivery encoder 159, and various sensors 515 mounted on the inkjet recording apparatus, extracts information necessary for controlling the printer, and the inkjet head It is used to control the drive control unit 508, the carriage unit movement motor drive control unit 510, the medium conveyance motor drive control unit 520, the maintenance and recovery unit drive control unit 534, the ink supply unit drive control unit 535, and the heating unit control unit 540.

  The sensor 515 detects an opening and closing of an optical sensor (medium sensor) 160 provided on a carriage 23 for detecting the position of the recording medium 10, a thermistor for monitoring the temperature and humidity inside the machine, and opening and closing of each machine body cover. And the I / O 513 can process various sensor information.

  For example, the CPU 501 detects a speed detection value and a position detection value obtained by sampling detection pulses from an encoder sensor (not shown) constituting the main scanning encoder 123, and a speed target obtained from a speed / position profile stored in advance. A drive output value (control value) for the main scanning motor 25 is calculated based on the value and the position target value, and the carriage unit moving motor 25 is driven via the carriage unit moving motor drive control unit 510.

  Similarly, a speed detection value and a position detection value obtained by sampling a detection pulse from an encoder sensor 155 constituting the feeding encoder 156, and a speed target value and a position target value obtained from a speed / position profile stored in advance The drive output value (control value) for the feed motor 522 is calculated based on the above, and the feed motor 522 is driven via the medium conveyance motor drive control unit 520. Similarly, based on the detection pulse from the delivery encoder 159, the delivery motor 521 is driven via the medium transport motor drive control unit 520.

Further, the control unit 500 drives the maintenance motor 91 via the maintenance and recovery unit drive unit 534 to move the cap 92 of the maintenance and recovery mechanism 9 back and forth with respect to the nozzle surface of the ink jet head 24, and the wiper member 93. To move the suction pump.
In addition, the supply motor 31 is driven via the ink supply unit drive control unit 535 to operate the supply pump, thereby transferring ink from the ink tank 30 to the head tank 29 or from the head tank 29 to the ink tank 30. Send back the ink.

  The heating unit controls the platen heater 541 according to the information of the sensor 515 from the I / O 513 to adjust the temperature of the first platen 53. Similarly, the temperature and air volume of the warm air drying unit are detected by the sensor 515, and the heater 542 for warm air is controlled to change the temperature of the heater 81, and the fan motor 543 for warm air is controlled. Rotate 82 to generate wind.

When an abnormality is detected in the encoder sensor or the medium conveyance motor drive control unit 520, the heating unit control unit 540 stops the heating by weakening or stopping the output of the platen heater 541 or the warm air heater 542. The heat accumulation on the recording medium 10 is suppressed. Further, by driving the hot air fan motor 543, the blower fan 82 is rotated, and the cooling of the warm air heater 542 and the cooling of the recording medium are advanced to stop the operation safely.
In the ink jet recording apparatus, when the ink for ink jet recording in the ink cartridge 201 is used up, the housing of the ink cartridge 201 can be disassembled to replace only the ink bag 241 inside.

  Although the example applied to a serial type (shuttle type) ink jet recording apparatus in which the carriage 23 scans is described, the present invention can be similarly applied to a line type ink jet recording apparatus provided with a line type head. In the case of a line type ink jet recording apparatus, the same effect as the multi-pass recording of the serial type ink jet recording apparatus can be obtained by arranging a plurality of ink jet heads of the same color in the recording path instead of multipass printing. To improve the image quality of a recorded matter by lowering the surface temperature as the line head of the same color increases, instead of lowering the surface temperature of the non-porous substrate according to the increase in the number of image recording scans. Can.

  FIG. 7 is an explanatory view of an ink jet recording method in which images are overlapped and recorded. As shown in FIG. 7, first, the lower half nozzle of the ink jet head 701 in the longitudinal direction is used to apply ink to the recording medium 700, and after the recording image 702 is recorded, the length of the ink jet head 701 in the longitudinal direction is half The recording medium 700 is fed by a length, ink is applied to the recording medium 700 in the same manner as described above using the lower half nozzle of the ink jet head 701 in the longitudinal direction, and the recording image 704 is recorded. The other ink is applied onto the recording image 702 by the nozzle in the upper half of the longitudinal direction 701 to record the recording image 703 with the other ink. A superimposed image 705 can be suitably formed by repeating this operation.

  The ink jet recording apparatus and the ink jet recording method of the present invention can be applied to various recordings by the ink jet recording method, and for example, particularly suitable for an ink jet recording printer, a facsimile machine, a copying machine, a printer / fax / copier complex machine, etc. It can be applied to

<Ink jet recordings>
The ink jet recorded matter has an image formed using the white ink of the present invention on a recording medium.
The recording medium is not particularly limited, and examples thereof include plain paper, glossy paper, special paper, cloth and the like. When applied to a transparent film or a colored recording medium, the white ink of the present invention can provide an image with particularly good color development.
Examples of the transparent film include those made of plastic materials such as polyvinyl chloride film, polyethylene terephthalate (PET) film, polycarbonate film, acrylic film, polypropylene film, polyimide film, polystyrene film and the like.
Examples of the colored recording medium include colored paper, the colored transparent film, fabric, clothes, ceramic and the like. In addition, by printing with the white ink before the ink at the time of color printing, the color of the recording medium can be made white and the color development of the ink can be improved.

  EXAMPLES The present invention will be described below by way of Examples and Comparative Examples, but the present invention is not limited to these Examples. Moreover, unless otherwise indicated, "part" shown in an Example and a comparative example shows a "mass part." The total amount of the water-soluble organic solvent is meant to include the water-soluble organic solvent component introduced from the other components.

<Production example of white ink>
-Preparation of titanium dioxide aqueous dispersion-
In a dispersion container, 30.8 g of high pure water and 1.2 g of a dispersant (trade name: DISPERBYK-190, manufactured by BIC-Chemie Japan Co., Ltd.) are put and lightly stirred to be uniform, and then titanium dioxide (trade name: GTR-100) Add 12.0 g of primary particle size: 260 nm, crystalline form: rutile type, organic processed product for aqueous dispersion), made by Sakai Chemical Industry Co., Ltd., and while cooling with water, use an ultrasonic homogenizer (trade name: US-300T, Japan Co., Ltd.) Treated with Seiki Seisakusho Co., Ltd., chip: φ26) for 1 hour at 200 μA, filter with a cellulose acetate membrane filter (trade name: Minizart 17594K, manufactured by Sartorius) with an average pore diameter of 5 μm, and disperse in titanium dioxide with solid content of 30% I got a body. The volume average particle size (D50) was 352 nm. The volume average particle diameter (D50) was measured using a particle size distribution measuring apparatus (trade name: Microtrac UPA, manufactured by Nikkiso Co., Ltd.).

-Preparation of urethane resin particles-
-Preparation of urethane resin particles 1--
Polycarbonate diol 1,500 g, 2,2-dimethylol propionic acid which is a reaction product obtained by reacting 1,6-hexanediol and dimethyl carbonate in a reaction vessel into which a stirrer, a reflux condenser, and a thermometer are inserted. 220 g of (DMPA) and 1,347 g of N-methylpyrrolidone (NMP) were charged under a nitrogen stream, and heated to 60 ° C. to dissolve 2,2-dimethylol propionic acid.
Next, 1,445 g of 4,4'-dicyclohexylmethane diisocyanate and 2.6 g of dibutyltin dilaurate (catalyst) are added, and the mixture is heated to 90 ° C. for urethane reaction over 5 hours to obtain an isocyanate-terminated urethane prepolymer solution. I got one.
Then, the isocyanate-terminated urethane prepolymer solution 1 is cooled to 80 ° C., 149 g of triethylamine is added, and 4,340 g is extracted from the mixed mixture, and mixed with 5,400 g of water and 15 g of triethylamine while vigorously stirring It was added into the solution.
Next, 1,500 g of ice is added, and 626 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine is added to carry out a chain extension reaction, and the solvent is distilled off so that the solid concentration becomes 30% by mass. Thus, a urethane resin particle dispersion A was obtained.

-Preparation of urethane resin particles 2-
A polycarbonate diol, a reaction product obtained by reacting 1,6-hexanediol and dimethyl carbonate in a reaction vessel into which a stirrer, a reflux condenser and a thermometer are inserted, 1,500 g of a polyoxyethylene chain-containing diol Name: DHD 1000 S (manufactured by Mitsui Chemicals, Inc.) 254 g and acetone 600 g were charged under a nitrogen stream, mixed and dissolved.
Next, 390 g of 4,4'-dicyclohexylmethane diisocyanate and 0.7 g of stannous octoate (catalyst) are added, and the mixture is heated to 55 ° C. for urethane reaction over 5 hours to obtain an isocyanate-terminated urethane prepolymer solution 2 I got
Next, 860 g of acetone was added to the isocyanate-terminated urethane prepolymer solution 2, mixed, and cooled to 30 ° C.
Then, 4,000 g of ion exchange water was slowly added to obtain an aqueous dispersion of prepolymer.
Subsequently, 148 g of a 35% by mass aqueous solution of 2-methyl-1,5-pentanediamine was added to carry out a chain extension reaction of the prepolymer. Thereafter, by adjusting the amount of water, acetone was distilled off so that the solid content concentration was 30% by mass, and a urethane resin particle dispersion liquid B was obtained.

Example 1
-Preparation of white ink-
29% by mass of 3-methyl-1,3-butanediol (boiling point: 203 ° C.), 1% by mass of 2-pyrrolidone (boiling point: 245 ° C.), 1% by mass of diethylene glycol n-butyl ether (boiling point: 231 ° C.), fluorine system Surfactant (trade name: FS-300, manufactured by DuPont, active ingredient 40% by mass) 0.25% by mass, antifoaming agent (trade name: Envirogem AD01, manufactured by Air Products) 0.5% by mass, antibacterial Agent (component name: 1,2-benzothiazolin-3-one, trade name: PROXEL GXL, manufactured by Arch Chemicals Japan Ltd.) 0.05% by mass, ion-exchanged water (remaining amount) is added to beaker, and a stirrer The mixture was stirred for 15 minutes and uniformly mixed to obtain a mixed solution. Next, 33% by mass of the urethane resin particle dispersion A (solids concentration: 30% by mass, N-methyl-2-pyrrolidone (boiling point 202 ° C) 11% by mass) is added to the mixed solution, and after stirring for 15 minutes 30% by mass of a crosslinkable styrene-acrylic resin A (trade name: manufactured by LUPEK ULTRA E, manufactured by Rohm and Haas Co., active ingredient: 30% by mass) as hollow resin particles was added and stirred for 30 minutes. Thereafter, pressure filtration was performed with a cellulose acetate membrane filter (trade name: Minizart 17594K, manufactured by Sartorius) with a pore size of 5 μm to remove coarse particles. From the above, the white ink of Example 1 was produced. In addition, the glass transition temperature of the hollow resin particles is such that the hollow resin particles dried by raising the temperature from ordinary temperature in a nitrogen atmosphere and dried at 200 ° C. for 30 minutes are cooled, and from a normal temperature with a differential scanning calorimeter (DSC) The temperature was measured by raising the temperature to 200 ° C. at 5 ° C./min.

(Examples 2 to 12 and Comparative Examples 1 to 6)
White ink was produced like Example 1 except having changed into the composition of Table 1-Table 3, and content about Examples 2-12 and Comparative Examples 1-6. The composition and content of Examples 1 to 12 and Comparative Examples 1 to 6 are shown in Tables 1 to 3.

In Tables 1 to 3, abbreviations and the like indicate the following contents.
* 1: Product name: Low-peak ULTRA E (manufactured by Rohm and Haas, active ingredient: 30% by mass)
* 2: Product name: Low-peak ULTRA DUAL (manufactured by Rohm and Haas, active ingredient: 30% by mass)
* 3: Product name: SX868B (manufactured by JSR Corporation, active ingredient: 20.3% by mass)
* 4: Brand name: Nipol MH8101 (manufactured by Nippon Zeon Co., Ltd., active ingredient: 26.5 mass%)
* 5: Brand name: FS-300 (manufactured by DuPont)
* 6: Product name: Envirogem AD 01 (manufactured by Air Products)
* 7: Product name: Proxel GXL (manufactured by Arch Chemicals Japan Co., Ltd.)

  Next, the following evaluation was performed using produced white ink 1-18.

(Examples 13 to 39 and Comparative Examples 7 to 21)
-Whiteness of white image-
The white inks 1 to 9 and the white inks 13 to 17 were formed on transparent polyethylene terephthalate (PET) film using a doctor blade (manufactured by Toyo Seiki Seisakusho, Ltd., wet film thickness: 25 μm). After heating at a heating temperature for 600 seconds, the ink is dried at a drying temperature shown in Table 4 for 1,800 seconds using a natural convection mode of a drier (trade name: Multi-oven MOV-300S, manufactured by As One Corporation) to apply white ink I got a membrane.
Thereafter, the heating temperature and the drying temperature shown in Table 4 with respect to the whiteness (brightness: L ₁ *) of a white image which was formed into a film at room temperature (25 ° C.) and sufficiently dried at room temperature (25 ° C.) for 4 days Difference in whiteness (brightness: L ₂ *) of white image in dried coating film (ΔL * = (brightness after room temperature film formation and drying at room temperature: L ₁ *)-(brightness after heat drying shown in Table 4) The whiteness of the white image was evaluated based on the following evaluation criteria from L ₂ :)). The results are shown in Table 4. The lightness is measured by using a spectrophotometric densitometer (trade name: X-Rite 939, manufactured by X-Rite Co., Ltd.) with a printed black paper laid under the recorded PET film and using the printed part. did.
[Evaluation criteria]
A: ΔL * is less than 5 B: ΔL * is 5 or more and less than 10 C: ΔL * is 10 or more

  When the white ink of the present invention of Examples 13 to 39 is dried at the heating and drying temperature shown in Table 4, the hollow resin particles, which are colorants, are prevented from lowering the whiteness of the white image even if they are dried by heating. I understand that It is found that the whiteness of the white images of Comparative Examples 7 to 21 is such that the decrease in whiteness due to heating at the time of film formation and drying is larger than the decrease in whiteness of the white images of Examples 13 to 39. It is considered that this is because the hollow resin particles are softened by the water-soluble organic solvent and crushed without being able to maintain the hollow form, and light scattering is less likely to occur.

(Examples 40 to 48 and Comparative Examples 22 to 26)
-Whiteness of white image by inkjet recording method-
The cleaning solution is washed by passing pure water through the ink supply path including the ink jet head of an ink jet printer (trade name: IPSiO GXe 3300, manufactured by Ricoh Co., Ltd.) with the exterior removed and the rear multi-manual feeder attached. The solution was sufficiently passed until the color did not change. Next, the cleaning liquid was discharged from the apparatus to obtain an inkjet recording apparatus for evaluation. Moreover, the gas in white ink was deaerated by stirring white ink 1-9 and white ink 13-17 for 30 minutes on pressure reduction conditions of 5 Pa or more and 10 Pa or less. Thereafter, the ink cartridge was filled and used as an evaluation ink cartridge. The ink jet printer was caused to perform a filling operation, and it was confirmed that all the nozzles were filled with the white ink and no abnormal image appeared. The setting of the ink jet printer was such that the color matching off was set as the printing mode in the user setting after selecting the glossy paper cleaning mode with the driver attached to the printer. The discharge amount was adjusted by changing the driving voltage of the ink jet head such that the white ink adhesion amount of the solid image on the recording medium in the printing mode was 20 g / m ² .

  A transparent PET film (trade name: Ester film E5100, manufactured by Toyobo Co., Ltd.) fixed on double-sided tape on PPC plain paper (trade name: My Paper, manufactured by Ricoh Co., Ltd.) is fed from a back side multi manual feeder, Microsoft Word 2003 The solid image of 50 mm × 50 mm prepared in the above was inkjet-recorded on the transparent PET film.

Thereafter, printing is performed at room temperature (25 ° C.), and the whiteness (brightness: L ₁ *) of a white image in a coating film sufficiently dried at room temperature (25 ° C.) for four days as it is The difference in whiteness (brightness: L ₂ *) of a white image in a heat-dried coated film placed in a bath for 30 minutes (ΔL * = (room temperature film formation and room temperature drying L ₁ *)-(heating shown in Table 5) The whiteness of the white image was evaluated based on the following evaluation criteria from L ₂ *)) after drying. The lightness is measured by using a spectrophotometric densitometer (trade name: X-Rite 939, manufactured by X-Rite Co., Ltd.) with a printed black paper laid under a printed PET film, and using the printed part did. The evaluation results are shown in Table 5.
[Evaluation criteria]
A: ΔL * value is less than 5 B: ΔL * value is 5 or more and less than 10 C: ΔL * value is 10 or more

--Drying property of white ink--
The peel-off state was confirmed by rubbing the coated film surface after the drying with a finger, and the drying property of the white ink was evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: The coating does not peel off B: A part of the coating peels off, and the white ink is transferred to the finger C: The coating comes off and disappears

-Discharge stability--
After confirming the discharge state, the head nozzle surface was protected by a cap and left for 2 weeks. After leaving for 2 weeks, the discharge operation was performed, the discharge state was confirmed, and the discharge stability of the white ink was evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: Discharge from all nozzles without problems B: There are nozzles that do not discharge, but recovery is possible when performing maintenance and recovery operation C: There are nozzles that do not discharge, and recovery does not occur even if maintenance and recovery operations are performed

  From the results in Table 5 above, it was found that the white ink of the present invention also has the whiteness equivalent to room temperature drying even when heat-dried after ink jet recording, even in the whiteness of white images by the inkjet recording method.

<Production example of ink set>
-Preparation of pigment dispersion-
—Preparation Example of Cyan Pigment Dispersion 1—
Cyan pigment (Pigment Blue 15: 3, trade name: LIONOL BLUE FG-7351, manufactured by Toyo Ink Co., Ltd.) 15 parts, anionic surfactant (trade name: Pionin A-51-B, manufactured by Takemoto Yushi Co., Ltd.) 2 Parts and 83 parts of ion-exchanged water, and then circularly dispersed for 7 hours with a disk type bead mill (KDL type, manufactured by Shinmaru Enterprises Co., Ltd., media: diameter 0.3 mm zirconia balls) to obtain cyan pigment A dispersion (total solids: 17% by mass, pigment solids: 15% by mass) was obtained.

-Preparation Example of Magenta Pigment Dispersion Liquid 2-
Magenta pigment dispersion (total solid) in the same manner as in Preparation Example 1 for cyan pigment dispersion except that the cyan pigment was changed to magenta pigment (Pigment Red 122, trade name: toner magenta EO02, manufactured by Clariant Japan Ltd. Min: 17% by mass, pigment solid content: 15% by mass).

-Preparation Example of Yellow Pigment Dispersion 3-
A yellow pigment dispersion (in the same manner as in Preparation Example 1 for cyan pigment dispersion) except that the cyan pigment was changed to yellow pigment (Pigment Yellow 74, trade name: Fast Yellow 531, manufactured by Dainichi Seika Kogyo Co., Ltd.) Total solid content: 17% by mass, pigment solid content: 15% by mass).

-Preparation Example of Black Pigment Dispersion 4-
A black pigment dispersion (total solids content: 17) in the same manner as in Preparation Example 1 of the cyan pigment dispersion except that the cyan pigment is changed to a black pigment (carbon black, trade name: Black Pearls 1000, manufactured by Cabot Corporation). Mass%, pigment solid content: 15 mass%) was obtained.

-Preparation of color ink and ink not containing hollow resin particles-
—Preparation Example of Cyan Ink (Cy-1) 1—
20 parts of cyan pigment dispersion, aqueous polyurethane resin particle dispersion (solid content: 25% by mass) 24 parts of Hydran HW-340 (average particle size: 35 nm, manufactured by DIC Corporation), fluorinated surfactant (trade name: FS -300, manufactured by DuPont Co., Ltd. 2 parts, 1,4-butanediol 12 parts, 1,2-propanediol 10 parts, diethylene glycol n-butyl ether 10 parts, glycerin 8 parts, Envirogem AD 01 (manufactured by Air Products) .5 parts of ion-exchange water (remaining amount) and 0.1 parts of Proxel GXL (manufactured by Arch Chemicals Japan Co., Ltd.) were mixed and stirred, and then filtered through a 0.2 μm polypropylene filter to obtain a cyan ink.

-Cyan ink (Cy-1 and Cy-2), magenta ink (Ma-1, Ma-2, Ma-3 and Ma-4), yellow ink (Ye-1, Ye-2 and Ye-3) ), And Preparation Examples 2 to 11 of Black Inks (Bk-1, Bk-2 and Bk-3)
Cyan ink (Cy-1 and Cy-2), magenta ink in the same manner as in Preparation Example 1 of cyan ink (Cy-1) except that the composition and content described in Table 7 and Table 8 were changed (Ma-1, Ma-2, Ma-3, and Ma-4), yellow inks (Ye-1, Ye-2, and Ye-3), and black inks (Bk-1, Bk-2, and Bk -3) was obtained. Tables 7 and 8 show cyan ink (Cy-1 and Cy-2), magenta ink (Ma-1, Ma-2, Ma-3 and Ma-4), yellow ink (Ye-1, Ye-2) And Ye-3) and preparation examples 2 to 11 of black inks (Bk-1 and Bk-2) are shown.

In Tables 6 and 7, abbreviations and the like indicate the following contents.
* 5: Brand name: FS-300 (manufactured by DuPont)
* 6: Product name: Envirogem AD 01 (manufactured by Air Products)
* 7: Product name: Proxel GXL (manufactured by Arch Chemicals Japan Co., Ltd.)
* 8: Product name: Hydran HW-340 (manufactured by DIC Corporation)

-Ink set consisting of white ink and color ink-
(Example 49)
An ink set having the white ink 1 obtained in Example 1 and the cyan ink (Cy-1) obtained in Preparation Example 1 was produced.

(Examples 50 to 84 and Comparative Examples 27 to 50)
An ink set was produced in the same manner as in Example 49 except that the white ink 1 and the cyan ink (Cy-1) were changed to the white ink described in Tables 8 to 14 and the color ink. Tables 8-14 show ink sets of Examples 49-84 and Comparative Examples 27-50.

  Next, the following evaluation was performed using the ink set of produced Examples 49-84 and Comparative Examples 27-50.

--Whiteness of white image--
The cleaning solution is washed by passing pure water through the ink supply path including the ink jet head of an ink jet printer (trade name: IPSiO GXe 3300, manufactured by Ricoh Co., Ltd.) with the exterior removed and the rear multi-manual feeder attached. The solution was sufficiently passed until the color did not change. Next, the cleaning liquid was discharged from the apparatus to obtain an inkjet recording apparatus for evaluation. Moreover, the gas in each ink was deaerated by stirring the ink of each ink set for 30 minutes on pressure reduction conditions of 5 Pa or more and 10 Pa or less. Thereafter, the ink cartridge was filled and used as an evaluation ink cartridge. The ink jet printer was caused to perform a filling operation, and it was confirmed that all the nozzles were filled with the ink and no abnormal image appeared. The setting of the ink jet printer was such that the color matching off was set as the printing mode in the user setting after selecting the glossy paper cleaning mode with the driver attached to the printer. The ejection amount was adjusted by changing the driving voltage of the inkjet head so that the amount of the solid image attached to the recording medium in the printing mode was 20 g / m ² .

  A transparent PET film (trade name: Ester film E5100, manufactured by Toyobo Co., Ltd.) fixed on double-sided tape on PPC plain paper (trade name: My Paper, manufactured by Ricoh Co., Ltd.) is fed from a back side multi manual feeder, Microsoft Word 2003 The solid image of 50 mm × 50 mm color ink single color produced in the above was inkjet-recorded on the transparent PET film.

Then, after drying in a thermostat at 70 ° C. for 30 minutes, a solid image of white ink of 50 mm × 50 mm was recorded on the solid image of the color ink single color, and dried in a thermostat at 70 ° C. for 30 minutes . Commercially available black paper or white paper is placed on the solid image recording side of the transparent PET film on which the solid image is recorded, and the hue of the recording portion is measured using a spectrophotometric densitometer (trade name: X-Rite 939, manufactured by X-Rite Inc. Was measured from the PET film side, the hue difference (ΔE) was calculated when the background was black paper and white paper, and the whiteness was evaluated based on the following evaluation criteria. The results are shown in Tables 8-14.
-Evaluation criteria-
A: ΔE is less than 5 B: ΔE is 5 or more and less than 10 C: ΔE is 10 or more

  From the results in Tables 8 to 14, in the ink set of the present invention, when a white ink is used, the hollow resin particles, which are colorants, maintain the form even after the heating and drying process after recording, and the whiteness of the white image It was found that the change in hue of the recorded portion due to the difference in background color was not affected.

-Ink set comprising white ink and ink not containing hollow resin particles-
(Example 85)
An ink set having the white ink 10 obtained in Example 10 and the cyan ink (Cy-2) not containing the hollow resin particles obtained in Preparation Example 5 was produced.

(Examples 86 to 89 and Comparative Examples 51 to 55)
An ink set was prepared in the same manner as in Example 85, except that the white ink 10 and the cyan ink (Cy-2) were changed to the white ink described in Tables 15 and 16 and the ink not containing hollow resin particles. Made. Tables 15 and 16 show the ink sets of Examples 85-89 and Comparative Examples 51-55.

  Next, the following evaluation was performed using the ink set of produced Examples 85-89 and Comparative Examples 51-55.

-Drying and degree of coloration--
Evaluation was performed using the apparatus of the structure of FIG. 3 provided with the inkjet head (brand name: MH5440, Ricoh Co., Ltd. make). When a solid image is recorded on an inkjet mat-coated paper at a resolution of 1,200 dpi × 1,200 dpi, the coating amount of white ink on the inkjet mat-coated paper is 30 g / m ² , and the coating amount of ink not containing hollow resin particles The discharge amount was adjusted by changing the drive voltage of the head such that the value of 15 g / m ² . The evaluation was performed by increasing the adhesion amount to 400% by superimposing the recorded images, with the adhesion amount to the solid image at this time being 100%. Also, as a recording medium to be recorded, a transparent PET film (trade name: ester film E5100, manufactured by Toyobo Co., Ltd.) fixed on double-sided tape on PPC plain paper (trade name: My Paper, manufactured by Ricoh Co., Ltd.) is used. The recording speed was adjusted by changing the driving frequency of the ink jet head so that the image was 1,200 dpi × 1,200 dpi and the printing speed was 0.15 mm / sec.

Using the ink jet recording method shown in FIG. 7, a 50 mm × 50 mm solid image is recorded with white ink using the nozzles in the lower half of the recording head in the longitudinal direction, and after recording, the half length of the inkjet head in the longitudinal direction I just sent out the recording medium. Next, a solid image is recorded in the same manner as above using white ink using the lower half of the ink jet head, and at the same time the solid image formed of white ink using the nozzles of the upper half of the ink jet head in the longitudinal direction A solid image of 50 mm × 50 mm was recorded on the top of the ink not containing hollow resin particles. At this time, recording was performed so that the white ink containing hollow resin particles and the ink not containing hollow resin particles do not land on the same portion and adjacent portions in the same scan.
Next, warm air temperature 70 ° C., warm air flow rate 10 m ³ / m ² / sec, heat drying time during recording is 15 minutes, and heat drying is performed, “drying”, based on the following evaluation criteria, And the "coloration degree" was evaluated. In addition, the temperature of heat drying set the temperature of the film surface as setting temperature, made the Toa Electric device mold type surface sensor MF-O-K contact, and measured it. Similarly, the temperature of the air at the hot air outlet was measured.

---Drying---
With respect to the obtained image, the peeling state was confirmed by lightly rubbing the image surface with the belly of the forefinger, and the "dryness" of the image was evaluated. The results are shown in Tables 16 and 17.
---Evaluation criteria---
A: The image is not peeled off B: A part of the image is peeled off, and the ink is transferred to the index finger C: The image is peeled off and disappears

--Degree of color---
Commercially available black paper or white paper is placed on the solid image recording side of the transparent PET film on which the solid image is recorded, and the hue of the recording portion is measured using a spectrophotometric densitometer (trade name: X-Rite 939, manufactured by X-Rite Inc.) Was measured from the PET film side, the hue difference (.DELTA.E) was calculated when the background was black paper and white paper, and the degree of coloring was evaluated based on the following evaluation criteria. The results are shown in Tables 16 and 17.
---Evaluation criteria---
A: ΔE is less than 10 B: ΔE is 10 or more and less than 20 C: ΔE is 20 or more and less than 30 D: ΔE is 30 or more

  From the results of Tables 15 and 16, it was found that even when using a white ink and an ink not containing hollow resin particles, the color development of the ink not containing hollow resin particles can be improved.

(Test Examples 1 to 6)
-Evaluation of influence on temperature of first heat treatment and second heat treatment-
The white ink 11 thus prepared was evaluated using the inkjet recording apparatus shown in FIG. 3 described above using an inkjet head under the trade name: RICOH MH 5440 (manufactured by Ricoh Co., Ltd.) as follows. In addition, a solid image is recorded at a resolution of 1200 dpi x 1200 dpi on inkjet mat coated paper (trade name: Super Fine Paper KA4250SFR, manufactured by Seiko Epson Corporation), and the white ink including overprinting is printed. It adjusted by changing the drive voltage of an inkjet head so that the adhesion amount might be 60 g / m < ² >. Furthermore, a transparent polyethylene terephthalate (PET) film (trade name: ester film E5100, manufactured by Toyobo Co., Ltd.) is used as a recording medium for recording, and the driving frequency of the head is adjusted so that the recording speed is 0.15 mm / sec. It recorded on the temperature conditions in the 1st heat processing shown in Table 6. Thereafter, the white ink was dried by applying warm air at the temperature in the second heat treatment shown in Table 6 to obtain a recorded matter.
In addition, the temperature in each heating process made the temperature of the transparent PET film surface the setting temperature, and made the mold type | mold surface sensor (brand name: MF-OK, the Toa Electric Co., Ltd. make) contact, and measured. Similarly, the temperature of the air at the hot air outlet was measured. Further, the second platen at the time of warm air heating was set to be heated to the same temperature as the warm air temperature. The volume of the warm air was set to 10 m ³ / m ² / sec. The heat drying was performed for 15 minutes including the heating time during recording, and the hot air time was performed for 15 minutes.

--Whiteness of white image--
For the recording material at room temperature was recorded at (25 ° C.), as is 4 days at room temperature (25 ° C.) in the whiteness of white image was sufficiently dried: for (lightness L 1 _*), heated under the conditions shown in Table 6 From the difference in whiteness (brightness: L ₂ *) of the white image of the recorded matter dried (ΔL * = (room temperature film formation and room temperature drying L ₁ *) − (heating time L ₂ *)) The whiteness of the white image was evaluated based on the following evaluation criteria. The lightness is measured by using a spectrophotometric densitometer (trade name: X-Rite 939, manufactured by X-Rite Co., Ltd.) with a printed black paper laid under the recorded PET film and using the printed part. did.
[Evaluation criteria]
A: ΔL * value is 70 or more B: ΔL * value is 60 or more and less than 70 C: ΔL * value is less than 60

-Measurement of the water content in the coating film and the content of the water-soluble organic solvent-
Remove the white ink coating film after the first heat treatment with a spatula, and use a thermogravimetric measurement / differential thermal analyzer (trade name: ThermoPlus, manufactured by Rigaku Corporation) to make water soluble from thermogravimetric change (TG) data The weight of the organic solvent component was calculated and shown as a relative value (%) to the solvent weight of the white ink alone. About 15 mg of white ink was heated up to 300 ° C. at 10 K / min under a nitrogen atmosphere by a thermogravimetric measurement / differential thermal analysis apparatus to obtain TG data. The weight of the water-soluble organic solvent component is a temperature Tw (° C.), To (° C.) showing a decreasing amount consistent with the water content Siw (%) from the TG data of the white ink alone and the total amount Sio (%) of water-soluble organic solvent The weight Wsw (mg) at Tw and the weight Wso (mg) at To are calculated from the TG data of the white ink coating film, and the water content of the white ink coating film and the water-soluble organic solvent content are determined by the following formula The
Water content = Wsw × (100-Siw-Sio) / Wso
Water-soluble organic solvent content = (Wsw-Wso) x (100-Siw-Sio) / Wso

--Drying property of white ink--
The peeled state was confirmed by rubbing the dried white ink coating film surface with a finger pad, and the drying property of the white ink was evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: The coating does not peel off B: A part of the coating peels off, and the white ink is transferred to the finger C: The coating comes off and disappears

-Discharge stability--
After confirming the discharge state, the head nozzle surface was protected by a cap and left for 2 weeks. After leaving for 2 weeks, the discharge operation was performed, the discharge state was confirmed, and the discharge stability of the white ink was evaluated based on the following evaluation criteria.
[Evaluation criteria]
A: Discharge from all nozzles without problems B: There are nozzles that do not discharge, but recovery is possible when performing maintenance and recovery operation C: There are nozzles that do not discharge, and recovery does not occur even if maintenance and recovery operations are performed

  As is clear from Table 17, it can be seen that Test Examples 1 to 4 are excellent in the whiteness of the white image even when dried by heating. In addition, Test Examples 1 to 4 were also favorable for the ejection stability. On the other hand, in Test Examples 5 and 6, the whiteness was inferior.

As an aspect of this invention, it is as follows, for example.
<1> water, a water-soluble organic solvent, and a colorant containing hollow resin particles,
The water-soluble organic solvent is a monohydric alcohol having a boiling point of 240 ° C. or less and a boiling point of 240 ° C. or less, and at least one hydroxyl group is bonded to other than the terminal of an alkane chain And at least one selected from diols,
The white ink is characterized in that the content of at least one selected from the monohydric alcohol and the diol is 75.0% by mass or more based on the total amount of the water-soluble organic solvent.
<2> The white ink according to <1>, which is for inkjet.
<3> The white ink according to any one of <1> to <2>, wherein the content of the water-soluble organic solvent having a boiling point exceeding 240 ° C. is 13% by mass or less based on the total amount of the water-soluble organic solvent. It is.
<4> A diol having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the end of an alkane chain is 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 3 It is a white ink in any one of said <1> to <3> which is at least 1 sort (s) selected from-methyl 1, 3- butanediol, and 2-methyl- 2, 4- pentanediol.
<5> The white ink according to any one of <1> to <4>, wherein the volume average particle diameter of the hollow resin particles is 0.2 μm or more and 1 μm or less.
<6> The white ink according to any one of <1> to <5>, wherein the hollow resin particles have a hollow ratio of 30% to 95%.
<7> The white ink according to any one of <1> to <6>, wherein the hollow resin particles are a styrene-acrylic resin.
It is a white ink in any one of said <1> to <7> whose content of a <8> hollow resin particle is 1 mass% or more and 30 mass% or less.
<9> The white ink according to any one of <1> to <8>, which further contains a film-forming resin.
<10> The white ink according to any one of <1> to <9>, wherein the volume average particle diameter of the film-forming resin is 10 nm or more and 1,000 nm or less.
<11> The white ink according to any one of <1> to <10>, wherein the film-forming resin is a polyurethane resin.
<12> The white ink according to any one of <1> to <11>, wherein a content of the film-forming resin is 1% by mass to 10% by mass.
<13> The white ink according to any one of <1> to <12> for heat drying.
<14> An ink set comprising a white ink containing a colorant containing water, a water-soluble organic solvent, and hollow resin particles, and an ink containing water and a water-soluble organic solvent but not containing hollow resin particles In
The water-soluble organic solvent in the white ink has a boiling point of 240 ° C. or less and contains a diol having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the end of the alkane chain.
The content of the diol in the white ink is 80% by mass or more based on the total amount of the water-soluble organic solvent in the white ink,
The water-soluble organic solvent in the ink not containing hollow resin particles has a boiling point of 240 ° C. or less and contains a diol having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the terminal of the alkane chain
The ink set is characterized in that the content of the diol in the ink containing no hollow resin particles is 80% by mass or more with respect to the total amount of the water-soluble organic solvent in the ink containing no hollow resin particles. It is.
<15> An ink cartridge containing the white ink according to any one of <1> to <13> in a container.
<16> Ink applying means for flying a white ink for inkjet according to any one of <1> to <13> to record an image on a recording medium,
At least a heating unit for heating and drying the recording medium having an image recorded thereon.
<17> A first heating member for heating the recording medium at 40 ° C. or more and 70 ° C. or less,
It is an inkjet recording device as described in said <16> which has a 2nd heating member which applies a warm air to a recording medium in this order.
<18> The inkjet recording apparatus according to <17>, wherein the warm air temperature of the second heating member exceeds the heating temperature of the first heating member.
<19> The inkjet recording apparatus according to any one of <17> to <18>, wherein the heating temperature of the first heating member is lower by 30 ° C. or more than the glass transition temperature of the hollow resin particles.
<20> The inkjet recording apparatus according to any one of <17> to <19>, wherein the content of the water-soluble organic solvent in the white ink after the first heating member is 20% by mass or less.
<21> An ink applying step of flying a white ink for inkjet according to any one of <1> to <13> to record an image on a recording medium,
At least a heating step of heating and drying the recording medium having an image recorded thereon.
<22> A first heat treatment of heating the recording medium at 40 ° C. or more and 70 ° C. or less,
It is an inkjet recording method as described in said <21> including the 2nd heat processing which applies a warm air to the said recording medium in this order.
<23> The inkjet recording method according to <22>, wherein the warm air temperature of the second heat treatment exceeds the heating temperature of the first heat treatment.
<24> The inkjet recording method according to any one of <22> to <23>, wherein the heating temperature of the first heat treatment is lower by 30 ° C. or more than the glass transition temperature of the hollow resin particles.
<25> The inkjet recording method according to any one of <22> to <24>, wherein the content of the water-soluble organic solvent in the white ink after the first heat treatment is 20% by mass or less.
<26> A recording method for recording an image on a recording medium using the ink set according to <14>,
A recording method comprising a first application step of applying a white ink to a recording medium, and a second application step of applying an ink containing no organic hollow particles on a white ink coating film in this order. is there.
<27> The recording method according to <26>, wherein the coating amount of the white ink on the recording medium is larger than the coating amount of the ink containing no organic hollow particles on the recording medium.
<28> A heating step of heating the recording medium to which the white ink is applied, between the first coating step and the second coating step,
The recording method according to any one of <26> to <27>, wherein the heating temperature in the heating step is lower by 30 ° C. or more than the glass transition temperature of the hollow resin particles in the white ink.

The white ink according to any one of <1> to <13>, the ink set according to <14>, the inkjet recording apparatus according to any one of <16> to <20>, or <21> The inkjet recording method according to any one of <25> and the recording method according to any one of <26> to <28> solve the problems in the related art and achieve the following objects. I assume. That is, the white ink, the ink set, the inkjet recording apparatus, the inkjet recording method, and the recording method can suppress the decrease in the whiteness of the white image even if the white image formed on the recording medium is rapidly heated and dried. It is an object of the present invention to provide a white ink, an ink set, an ink jet recording apparatus, an ink jet recording method, and a recording method that can be performed.
The ink cartridge described in the above <15> has an object to solve the above-mentioned various problems in the related art and to achieve the following object. That is, it is an object of the present invention to provide an ink cartridge capable of containing a white ink capable of suppressing a decrease in whiteness of a white image even if the white image formed on the recording medium is rapidly heated and dried. Do.

Patent No. 4015043

30, 201 Ink cartridge 101 Ink jet recording apparatus

Claims (12)

Water, a water-soluble organic solvent, and a colorant containing hollow resin particles,
The water-soluble organic solvent is a monohydric alcohol having a boiling point of 240 ° C. or less and a boiling point of 240 ° C. or less, and at least one hydroxyl group is bonded to other than the terminal of an alkane chain at least one selected from a diol,
A water-soluble organic solvent having a boiling point exceeding 240 ° C .;
A white ink, wherein the content of at least one selected from the monohydric alcohol and the diol is 80% by mass or more and 95% by mass or less with respect to the total amount of the water-soluble organic solvent.   The white ink according to claim 1, wherein the content of the water-soluble organic solvent having a boiling point exceeding 240 ° C is 13% by mass or less based on the total amount of the water-soluble organic solvent.   A diol having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the end of an alkane chain is 1,2-butanediol, 1,3-butanediol, 2,3-butanediol, 3-methyl- The white ink according to any one of claims 1 to 2, which is at least one selected from 1,3-butanediol and 2-methyl-2,4-pentanediol. In an ink set comprising a white ink containing water, a water-soluble organic solvent, and a colorant containing hollow resin particles, and an ink containing water and a water-soluble organic solvent but not containing hollow resin particles,
The water-soluble organic solvent in the white ink has a boiling point of 240 ° C. or less and contains a diol having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the end of the alkane chain.
The content of the diol in the white ink is 80% by mass or more based on the total amount of the water-soluble organic solvent in the white ink,
The water-soluble organic solvent in the ink not containing hollow resin particles has a boiling point of 240 ° C. or less and contains a diol having 4 to 6 carbon atoms in which at least one hydroxyl group is bonded to other than the terminal of the alkane chain
The ink set is characterized in that the content of the diol in the ink containing no hollow resin particles is 80% by mass or more with respect to the total amount of the water-soluble organic solvent in the ink containing no hollow resin particles. .   An ink cartridge containing the white ink according to any one of claims 1 to 3 in a container. An ink applying means for causing the white ink according to any one of claims 1 to 3 to fly and applying it to a recording medium,
An inkjet recording apparatus comprising at least a heating unit for heating and drying the recording medium to which the white ink is applied. A first heating member configured to heat the recording medium at 40 ° C. or more and 70 ° C. or less;
The ink jet recording apparatus according to claim 6, further comprising: a second heating member for applying warm air to the recording medium in this order.   The ink jet recording apparatus according to claim 7, wherein the warm air temperature of the second heating member exceeds the heating temperature of the first heating member. A recording method for recording an image on a recording medium by using the ink set according to claim 4;
A recording method comprising a first application step of applying a white ink to a recording medium, and a second application step of applying an ink containing no organic hollow particles on a white ink coating in this order. . Between the first coating step and the second coating step, a heating step of heating the recording medium to which the white ink is applied,
The recording method according to claim 9, wherein the heating temperature in the heating step is 30 ° C or more lower than the glass transition temperature of the hollow resin particles in the white ink. An ink jet recording apparatus for recording an image on a recording medium by using the ink set according to claim 4;
What is claimed is: 1. An ink jet recording apparatus comprising: a first application means for applying a white ink to a recording medium; and a second application means for applying an ink containing no organic hollow particles on a white ink coating film. Between the first application means and the second application means, there is provided a heating means for heating the recording medium to which the white ink has been applied,
12. The ink jet recording apparatus according to claim 11, wherein the heating temperature in the heating means is lower by 30 [deg.] C. or more than the glass transition temperature of the hollow resin particles in the white ink.

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