JP7180476B2 - ink - Google Patents

Description

The present invention relates to ink.

Compared to other recording methods, the inkjet recording method has a simpler process and can easily produce full-color images. , is expanding into the fields of commercial and industrial printing. In the field of commercial printing, in addition to plain paper, coated paper such as coated paper and art paper, and polymeric films for flexible packaging such as PET and (OPP) polypropylene are used as recording media. Since printed matter is handled as merchandise such as postcards and packages, images with high scratch resistance are required. In addition, high productivity by reducing printing downtime and ejection stability in the ink jet recording method are required. However, the ink having abrasion resistance tends to cause ink sticking in the recording head portion, and it has been difficult to achieve both abrasion resistance and ejection stability.
Therefore, a water-insoluble colorant, resin particles, a silicone-based surfactant, an acetylene glycol-based surfactant, a pyrrolidone derivative, a 1,2-alkyldiol, a polyhydric alcohol, and water are contained, and the resin particles are a resin An inkjet recording method using an aqueous ink composition containing fixing particles and wax particles has been proposed (see, for example, Patent Document 1).
Further, it contains acrylic resin particles and urethane resin particles, and the mass ratio of the content (% by mass) of the urethane resin particles to the content (% by mass) of the acrylic resin particles (urethane resin particles/acrylic resin particles) By specifying the , an ink has been proposed that aims to improve scratch resistance and achieve ejection stability and storage stability (see, for example, Patent Document 2).

An object of the present invention is to provide an ink which is excellent in abrasion resistance of an image formed on a polymer film for flexible packaging, and excellent in ejection stability and stability during decap.

The ink of the present invention as a means for solving the above problems is an ink containing water, a coloring material, an organic solvent, acrylic resin particles, and polycarbonate-based urethane resin particles, wherein the organic solvent is 3-methoxy -at least one of 3-methyl-1-butanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol, propylene glycol monomethyl ether, 1-methoxy-2-propyl acetate, and butyl propylene glycol The breaking strength of the polycarbonate-based urethane resin particles is 30 MPa or more, the glass transition point (Tg) of the acrylic resin particles is 40° C. or higher, and the mass of the polycarbonate-based urethane resin particles and the acrylic resin particles The ratio (polycarbonate-based urethane resin particles/acrylic resin particles) is 25/75 to 75/25, and the content of the acrylic resin particles is 4.5% by mass or less with respect to the total amount of the ink.

According to the present invention, it is possible to provide an ink which is excellent in abrasion resistance of an image formed on a polymer film for flexible packaging, excellent in ejection stability, and excellent in stability during decap.

FIG. 1 is a perspective explanatory view showing an example of the inkjet printing apparatus of the present invention. FIG. 2 is a perspective explanatory view showing an example of the main tank in the inkjet printer of the present invention.

(ink)
The ink of the present invention contains water, a coloring material, an organic solvent, acrylic resin particles, and polycarbonate-based urethane resin particles, wherein the organic solvent comprises 3-methoxy-3-methyl-1-butanol, 3 -Methoxy-1-butanol, 1-methoxy-2-propanol, propylene glycol monomethyl ether, 1-methoxy-2-propyl acetate, and at least one of butyl propylene glycol, and breaking of the polycarbonate-based urethane resin particles The strength is 30 MPa or more, the glass transition point (Tg) of the acrylic resin particles is 40 ° C. or more, and the mass ratio of the polycarbonate-based urethane resin particles to the acrylic resin particles (polycarbonate-based urethane resin particles/acrylic resin particles) is 25/75 to 75/25, the content of the acrylic resin particles is 4.5% by mass or less with respect to the total amount of the ink, and other components are further included as necessary.

The inventors of the present invention have studied an ink that is excellent in abrasion resistance of an image formed on a polymer film for flexible packaging, and excellent in ejection stability and decap stability, and obtained the following findings.
Conventional inks do not have sufficient scratch resistance when forming images on polymeric films for flexible packaging.
Also, the scratch resistance was not sufficient when a white pigment was used. White pigments are especially used in polymer films for flexible packaging, but if you want to increase the degree of concealment, you need to increase the amount of pigment added, which increases the non-volatile components in the ink and increases the viscosity of the ink. There is a problem that the stability and the storage stability at the time of decapping are lowered.
In order to obtain sufficient scratch resistance in the formed image, there is a method of increasing the content of resin particles contained in the ink. As a result, there is a problem that ejection stability and storage stability during decapping are lowered.

Therefore, the present inventors found that in an ink containing water, an organic solvent, acrylic resin particles, and polycarbonate-based urethane resin particles, the specific organic solvent, the breaking strength of the polycarbonate-based urethane resin particles, the acrylic resin By specifying the glass transition point (Tg) of the particles, the mass ratio of the polycarbonate-based urethane resin particles and the acrylic resin particles, and the content of the acrylic resin particles, the image formed on the polymer film can be rapidly reproduced. It has been found that the resin particles can be fused together to form a good coating with high film uniformity. In addition, since these organic solvents have high moisture retention properties, they have found that they can prevent drying of the ink in the vicinity of the nozzles, and can improve ejection stability and decap storage stability. In addition, the inventors have found that since the viscosity of the organic solvent itself is low, the viscosity of the ink as a whole can be suppressed, and the ejection stability can be improved.

-Organic solvent-
Examples of the organic solvent include 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol, propylene glycol monomethyl ether, 1-methoxy-2-propyl acetate, and at least one of butyl propylene glycol. These may be used individually by 1 type, and may use 2 or more types together. In particular, when the organic solvent is 3-methoxy-3-methyl-1-butanol, it is suitable for achieving both high ejection stability and storage stability during decap. In addition, it is possible to improve the drying property when an image is formed on a polymer film for flexible packaging.
The organic solvent may further contain an organic solvent other than the above.

Other organic solvents are not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include water-soluble organic solvents.
Examples of the water-soluble organic solvent include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds. mentioned. Examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2 ,4-pentanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1, Polyhydric alcohols such as 3-pentanediol and petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, etc. polyhydric alcohol alkyl ethers, ethylene glycol monophenyl ether, polyhydric alcohol aryl ethers such as ethylene glycol monobenzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1 Nitrogen-containing heterocyclic compounds such as ,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone, formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropion amides such as amides, 3-butoxy-N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine and triethylamine; sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol; mentioned. It is preferable to use an organic solvent having a boiling point of 250° C. or less because it not only functions as a wetting agent but also provides good drying properties.
Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol. Specific examples of glycol ether compounds include polyhydric alcohol alkyls such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether. Ethers; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, and the like.
A polyol compound having 8 or more carbon atoms and a glycol ether compound can improve ink permeability when paper is used as a recording medium.

The content of the organic solvent in the ink is not particularly limited and can be appropriately selected according to the purpose, but from the viewpoint of the drying property and ejection reliability of the ink, it is preferably 10% by mass or more and 60% by mass or less. , more preferably 20% by mass or more and 60% by mass or less.

-Acrylic resin particles-
The acrylic resin particles are not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include acrylic silicone resin particles and styrene-acrylic resin particles. These may be used individually by 1 type, and may use 2 or more types together. Among these, styrene-acrylic resin particles are preferred. When the acrylic resin particles are styrene-acrylic resin particles, an image having excellent scratch resistance can be formed.
Examples of the styrene-acrylic resin particles include styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, and styrene-α-methylstyrene-acrylic acid copolymer. coalescence, styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, and the like. Among these, styrene-acrylic acid copolymers are particularly preferred.
The form of the copolymer is not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include random copolymers, block copolymers, alternating copolymers and graft copolymers. be done. These may be used individually by 1 type, and may use 2 or more types together.
Further, the styrene-acrylic resin may contain components derived from monomers other than styrene-acrylic acid and methacrylic acid. Examples of such monomers include α-methylstyrene, styrene derivatives such as vinyltoluene, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n- Butyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate and the like can be mentioned. One or more of these monomers can be added to the above styrene and acrylic acid or methacrylic acid monomer component.

The acrylic resin particles preferably have a glass transition point (Tg) of 40° C. or higher, more preferably 50° C. or higher, and most preferably 60° C. or higher. When the glass transition point (Tg) is 50° C. or higher, the stress can be increased against the pressure applied to the image surface to be formed, so the abrasion resistance can be improved.
As the glass transition point (Tg), a theoretical Tg obtained from a monomer may be used.

The acrylic resin particles are not particularly limited and can be appropriately selected according to the intended purpose. Appropriately synthesized particles may be used, or commercially available products may be used. Examples of the commercially available products include acrylic resin particles under the trade name of Cymac (manufactured by Toagosei Co., Ltd.), trade names of Boncoat (manufactured by DIC Corporation) and Aquabrid (manufactured by Daicel Corporation); and urethane resin particles under the trade name of: Ukote (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), trade name: Takelac (manufactured by Mitsui Chemicals, Inc.), and the like. These may be used individually by 1 type, and may use 2 or more types together.

The volume average particle diameter of the acrylic resin particles is not particularly limited and can be appropriately selected depending on the intended purpose. , more preferably 10 nm or more and 200 nm or less, and particularly preferably 10 nm or more and 100 nm or less. The volume average particle diameter can be measured, for example, using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

The content of the acrylic resin particles should be 4.5% by mass or less with respect to the total amount of the ink in order to obtain good ejection stability and decapping properties. Furthermore, from the point of improving scratch resistance, it is preferably 1.8% by mass or more and 4.2% by mass or less.
Further, the content of the acrylic resin particles is preferably 0.7% by mass or less, 0.3% by mass or more and 0.7% by mass or less, 0.5% by mass or more and 0.7% by mass or less, based on the content of the coloring material. 0.7% by mass or less is more preferable.

The form of the acrylic resin particles is not particularly limited and can be appropriately selected depending on the intended purpose. For example, it is preferably a water-dispersible dispersion.

-Polycarbonate Urethane Resin Particles-
The polycarbonate-based urethane resin particles are particles formed of a polycarbonate-based urethane resin. The polycarbonate-based urethane resin is a urethane resin having a polycarbonate structure in its molecule. The polycarbonate-based urethane resin particles preferably have a breaking elongation of 300% or more and 900% or less, more preferably 350% or more and 850% or less, and even more preferably 400% or more and 800% or less. When the breaking elongation of the polycarbonate-based urethane resin particles is 300% or more, the scratch resistance of the formed image can be improved. Since the film strength of the resin film formed when the ink begins to dry is low, when ink ejection starts, the resin film is destroyed by the pressure at which the ink is ejected. It is possible to suppress film formation and improve ejection stability.

Further, the polycarbonate-based urethane resin particles preferably have a breaking strength of 30 MPa or more. When the elongation at break is 30 MPa or more, an image having high scratch resistance can be formed.

The breaking elongation and breaking strength of the polycarbonate-based urethane resin particles can be measured by the following methods.
Using the polycarbonate-based urethane resin particles, a film of 1 cm square and an average thickness of 1 μm was prepared, and the tensile speed was measured using a breaking elongation and breaking strength measuring device (manufactured by Shimadzu Corporation, product name Autograph AGS-5kNX). : It can be measured as elongation at break and strength at break when the film is stretched at 50 mm/min.

The polycarbonate-based urethane resin particles are not particularly limited as long as they satisfy the properties described above, and can be appropriately selected according to the purpose. may Examples of the commercially available products include trade name: Takelac W-4000, trade name: Takelac W-6010, trade name: Takelac W-6110 (manufactured by Mitsui Chemicals, Inc.). These may be used individually by 1 type, and may use 2 or more types together.

The volume average particle diameter of the polycarbonate-based urethane resin particles is not particularly limited and can be appropriately selected according to the intended purpose. is preferred, 10 nm or more and 200 nm or less is more preferred, and 10 nm or more and 100 nm or less is particularly preferred. The volume average particle diameter can be measured, for example, using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).
The particle size of the solid content in the ink is not particularly limited and can be appropriately selected according to the purpose. is preferably 20 nm or more and 1000 nm or less, more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, and the like. The particle size can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

The content of the polycarbonate-based urethane resin particles is preferably 1% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 4% by mass or less, relative to the total amount of the ink.

The form of the polycarbonate-based urethane resin particles is not particularly limited and can be appropriately selected according to the intended purpose. For example, it is preferably a water-dispersible dispersion.

Here, the ink containing the acrylic resin particles or the ink containing the urethane resin particles will be examined.
The ink containing the acrylic resin particles is excellent in ejection stability, but the hardness of the acrylic resin particles is high and the elasticity is low, so the resulting image tends to have low scratch resistance.
On the other hand, in the ink containing the urethane resin particles, since the urethane resin particles are lower in hardness and higher in elasticity than the acrylic resin particles, the resulting image tends to have high abrasion resistance. However, since the ink containing the urethane resin particles has a strong hydrogen bonding force, it tends to form a film, tends to generate sticking matter in the recording head, and tends to lower the ejection stability of the ink. When the ink containing the urethane resin particles is used, the content of the urethane resin particles cannot be increased in order to prevent the generation of sticking matter on the recording head, and an image sufficiently satisfying the abrasion resistance is produced. The problem is that you can't get
It is also known that the ink containing the urethane resin particles can improve the mechanical strength of the image, but increases the coefficient of dynamic friction of the image.

Therefore, by containing the acrylic resin particles and the urethane resin particles in a predetermined mass ratio and limiting the mechanical strength of the urethane resin to a specific region, the ejection stability is ensured and the quality of the obtained image is improved. It was found that an ink capable of improving scratch resistance can be provided.
The mass ratio of the polycarbonate-based urethane resin particles to the acrylic resin particles (the polycarbonate-based urethane resin particles/the acrylic resin particles) is 25/75 to 75/25 (0.3 or more and 3 or less). Preferably, 30/70 to 70/30 (0.4 or more and 2.5 or less) is more preferable, and 50/50 (1) is even more preferable. When the mass ratio of the polycarbonate-based urethane resin particles and the acrylic resin particles (the polycarbonate-based urethane resin particles/the acrylic resin particles) is 25/75 to 75/25 (0.3 or more and 3 or less), It is possible to obtain an ink that forms an image with excellent rubbing resistance, and it is possible to obtain an ink that is excellent in ejection stability. The mixing ratio of the resin particles can be appropriately selected according to the recording medium to be used and the conditions under which the product is handled. When rubbing is repeated, it is preferable to increase the urethane resin ratio to 50/50 (1) or more.

In addition, the ratio of the total amount of the acrylic resin particles and the polycarbonate-based urethane resin particles to the content of the coloring material described later is [(total amount of acrylic resin particles and polycarbonate-based urethane resin particles) / (coloring content)] is preferably 0.20 or more and 2.00 or less, more preferably 0.20 or more and 1.40 or less, and 1.00 or more and 1.00 or more, from the viewpoint of enhancing ejection stability and scratch resistance. 03 or less is more preferable.

In the ink of the present invention, it is particularly preferable to use a white pigment as a coloring material, which will be described later. White pigments are generally made by dispersing inorganic pigments such as titanium oxide and silica with dispersants. need to increase the quantity. In order to obtain scratch resistance when the amount of pigment added is large, it is necessary to increase the content of resin particles in the ink. However, with the composition of the ink of the present invention, it is possible to obtain an ink capable of forming an image having a desired scratch resistance with a relatively small content of resin particles as compared with the prior art.

The ink of the present invention may further contain resin particles other than the acrylic resin particles and the polycarbonate-based urethane resin particles described above.

The other resin particles are not particularly limited and can be appropriately selected depending on the intended purpose. Examples thereof include polyester urethane resin particles and polyether urethane resin particles.

The total amount (content) of all resin particles contained in the ink of the present invention is preferably 1% by mass or more and 30% by mass or less, more preferably 5% by mass or more and 25% by mass or less, relative to the total amount of the ink.

-coloring material-
The coloring material is not particularly limited and can be appropriately selected depending on the intended purpose. For example, pigments and dyes can be used. An inorganic pigment or an organic pigment can be used as the pigment. These may be used individually by 1 type, and may use 2 or more types together. Mixed crystals may also be used.

Examples of the pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy color pigments such as gold and silver, and metallic pigments.

As the inorganic pigment, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, carbon produced by a known method such as a contact method, a furnace method, a thermal method, etc. Black can be used.

Examples of the organic pigment include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinoflurone pigments, etc.), Dye chelates (eg, basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black and the like can be used. Among these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.

Specific examples of the pigments for black include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black and channel black, or copper and iron (C.I. Pigment Black 11). ), metals such as titanium oxide, and organic pigments such as aniline black (C.I. Pigment Black 1).
Further, for color, 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 , 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. 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 Red 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 (red red), 104, 105, 106, 108 ( cadmium red), 112, 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 184, 185, 190, 193, 202, 207, 208, 209, 213, 219, 224, 254, 264, C.I. I. Pigment Violet 1 (rhodamine lake), 3, 5:1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15:1, 15:2, 15:3, 15:4 (phthalocyanine blue), 16, 17:1, 56, 60, 63, C.I. I. Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.

The dyes are not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and may be used singly or in combination of two or more. .

Examples of the dye include C.I. I. Acid Yellow 17, 23, 42, 44, 79, 142, C.I. I. Acid Red 52, 80, 82, 249, 254, 289, C.I. I. Acid Blue 9,45,249, C.I. I. Acid Black 1, 2, 24, 94, C.I. I. Food Black 1, 2, C.I. I. Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, 144, 173, C.I. I. Direct Red 1, 4, 9, 80, 81, 225, 227, C.I. I. Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, C.I. I. Directed Black 19, 38, 51, 71, 154, 168, 171, 195, C.I. I. Reactive Red 14, 32, 55, 79, 249, C.I. I. Reactive Black 3, 4, 35 can be mentioned.

The content of the coloring material in the ink is preferably 0.1% by mass or more and 15% by mass or less, more preferably 1% by mass or more and 10% by mass, from the viewpoints of improving image density, good fixability, and ejection stability. It is below.

To disperse the pigment in the ink, a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersing pigment, a method of coating the surface of the pigment with a resin to disperse it, and a method of dispersing it using a dispersant. , and so on.

As a method of making a self-dispersing pigment by introducing a hydrophilic functional group into the pigment, for example, a pigment (for example, carbon) is added with a functional group such as a sulfone group or a carboxyl group to make it dispersible in water. Pigments and the like can be used.
As a method of coating the surface of the pigment with a resin and dispersing the pigment, a method that encloses the pigment in microcapsules and can be dispersed in water can be used. This can be rephrased as a resin-coated pigment. In this case, all the pigments mixed in the ink need not be coated with a resin, and uncoated pigments or partially coated pigments may be dispersed in the ink as long as the effects of the present invention are not impaired. may be
Examples of the method of dispersing using the dispersant include a method of dispersing using a known low-molecular-weight dispersant and high-molecular-weight dispersant typified by surfactants.
As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, etc. can be used depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used as a dispersant.
The dispersant may be used singly or in combination of two or more.

Examples of the white pigment include, but are not limited to, white inorganic pigments such as titanium oxide, zinc oxide, zinc sulfide, antimony oxide, and zirconium oxide. Besides the white inorganic pigment, white organic pigments such as white hollow resin particles and polymer particles can also be used.

The color index (C.I.) of the white pigment is not limited to the following, but includes, for example, C.I. I. Pigment White 1 (basic lead carbonate), 4 (zinc oxide), 5 (mixture of zinc sulfide and barium sulfate), 6 (titanium oxide), 6:1 (titanium oxide containing other metal oxides), 7 ( zinc sulfide), 18 (calcium carbonate), 19 (clay), 20 (titanium mica), 21 (barium sulfate), 22 (natural barium sulfate), 23 (gloss white), 24 (alumina white), 25 (gypsum) , 26 (magnesium oxide/silicon oxide), 27 (silica), and 28 (anhydrous calcium silicate). Among these, titanium oxide is preferable because it is excellent in color developability, hiding property and dispersed particle size, and good visibility (brightness) can be obtained.
Among the above titanium oxides, rutile-type titanium oxide, which is commonly used as a white pigment, is preferable. The rutile-type titanium oxide may be one produced by oneself or one commercially available. Industrial production methods for producing rutile-type titanium oxide (powder) include the conventionally known sulfuric acid method and chlorine method. Commercial products of rutile type titanium oxide include, for example, Tipaque (registered trademark) CR-60-2, CR-67, R-980, R-780, R-850, R-980, R-630, R- Rutile types such as 670 and PF-736 (the above are trade names of ISHIHARA SANGYO KAIS HA, LTD.).

--Pigment Dispersion--
Inks can be obtained by mixing materials such as water and organic solvents with the pigments. Ink can also be produced by mixing a pigment, water, a dispersant, and the like to form a pigment dispersion, and then mixing materials such as water and an organic solvent.

The pigment dispersion is obtained by dispersing water, a pigment, a pigment dispersant, and optionally other components, and adjusting the particle size. Dispersion should be carried out using a disperser. The particle size of the pigment in the pigment dispersion is not particularly limited, but the dispersion stability of the pigment is improved, and the image quality such as ejection stability and image density is improved. 500 nm or less is preferable, and 20 nm or more and 150 nm or less is more preferable.
However, the white pigment preferably has a 50% average particle diameter (hereinafter also referred to as “D ₅₀ ”) of 50 nm or more and 500 nm or less, more preferably 150 nm or more and 350 nm or less. When _D50 is within the above range, the abrasion resistance of the printed image and the visibility of the image are excellent, so that a high-quality image can be formed. Here, the “50% average particle size of titanium oxide” in this specification means the _D50 of titanium oxide present in the ink composition, not the _D50 of titanium oxide before preparation of the ink composition. . In addition, the "50% average particle size" in this specification means the 50% average particle size in terms of spheres by the dynamic light scattering method, and a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd. ) can be measured using

The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected according to the purpose. % or more and 50 mass % or less is preferable, and 0.1 mass % or more and 30 mass % or less is more preferable. The pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator, or the like, if necessary.

-water-
The content of water in the ink is not particularly limited and can be appropriately selected according to the purpose. % to 60% by mass is more preferable.
The water is not particularly limited and can be appropriately selected depending on the purpose. Examples include pure water such as ion-exchanged water, ultrafiltrated water, reverse osmosis water, and distilled water; ultrapure water. . These may be used individually by 1 type, and may use 2 or more types together.

-Other ingredients-
As the other components, waxes, surfactants, antifoaming agents, antiseptic and antifungal agents, antirust agents, pH adjusters and the like may be added.

--wax--
The wax can reduce the dynamic friction coefficient of the surface of the image (ink film), and in particular, when combined with urethane resin particles, the abrasion resistance of the image can be dramatically improved.
This can suppress an increase in the coefficient of dynamic friction due to the urethane resin particles contained to improve the scratch resistance of the image, reduce the force applied to the image, and sufficiently increase the mechanical strength of the urethane resin particles. Since it is exhibited, it is presumed that the abrasion resistance can be dramatically improved.
As the wax, a water-dispersible wax emulsion is preferable.
Examples of the wax include polyethylene wax and paraffin wax. These may be used individually by 1 type, and may use 2 or more types together. Among these, polyethylene wax is preferable from the viewpoint of storage stability.
As the wax, a commercially available product can be used. Examples of the commercially available product include HYTEC E-8237 (polyethylene wax, melting point: 106°C, average particle size: 80 nm, manufactured by Toho Chemical Industry Co., Ltd.). , Trade name: AQUACER531 (polyethylene wax, melting point: 130°C, manufactured by BYK-Chemie), trade name: AQUACER515 (polyethylene wax, melting point: 135°C, manufactured by BYK-Chemie), trade name: AQUACER537 (paraffin, melting point: 110°C, manufactured by BYK-Chemie) company) and the like. These may be used individually by 1 type, and may use 2 or more types together.
The melting point of the wax is preferably 70° C. or higher and 170° C. or lower, more preferably 100° C. or higher and 140° C. or lower. When the melting point is 70° C. or higher, the image does not become sticky, and image transfer does not occur even when the images are superimposed. Because of this, the abrasion resistance is improved.
The volume average particle size of the wax is preferably 200 nm or less, more preferably 20 nm or more and 150 nm or less. When the volume average particle diameter is 200 nm or less, the particles are not caught on the nozzle or the filter in the head, and good ejection stability can be obtained.
The volume average particle diameter can be measured, for example, using a particle size analyzer (Microtrac MODEL UPA 9340, manufactured by Nikkiso Co., Ltd.).
The content of the wax is preferably 0.09% by mass or more and 0.5% by mass or less in solid content with respect to the total amount of the ink. When the solid content concentration is 0.09% by mass or more and 0.5% by mass or less, it is sufficiently effective in reducing the coefficient of dynamic friction on the surface of the resulting image (ink film), and the storage stability of the ink is improved. Ejection stability is also less likely to be adversely affected.

--Surfactant--
Any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants, and anionic surfactants can be used as surfactants.
The silicone-based surfactant is not particularly limited and can be appropriately selected depending on the purpose. Among them, those that do not decompose even at high pH are preferable. Those having an oxyethylene group or a polyoxyethylene polyoxypropylene group are particularly preferred because they exhibit good properties as water-based surfactants. As the silicone-based surfactant, a polyether-modified silicone-based surfactant can also be used, and examples thereof include compounds in which a polyalkylene oxide structure is introduced into the side chain of the Si portion of dimethylsiloxane.
Examples of fluorine-based surfactants include perfluoroalkylsulfonic acid compounds, perfluoroalkylcarboxylic acid compounds, perfluoroalkylphosphoric acid ester compounds, perfluoroalkylethylene oxide adducts, and perfluoroalkyl ether groups in side chains. Polyoxyalkylene ether polymer compounds are particularly preferred due to their low foaming properties. Examples of the perfluoroalkylsulfonic acid compound include perfluoroalkylsulfonic acid and perfluoroalkylsulfonate. Examples of the perfluoroalkylcarboxylic acid compounds include perfluoroalkylcarboxylic acids and perfluoroalkylcarboxylic acid salts. As the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain, a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in a side chain, and a perfluoroalkyl ether group in a side chain Examples thereof include salts of polyoxyalkylene ether polymers. Counter ions of salts in these fluorosurfactants include Li, Na, K, NH4, NH3CH2CH2OH, NH2(CH2CH2OH)2, NH(CH2CH2OH)3 and the like.
Examples of amphoteric surfactants include laurylaminopropionate, lauryldimethylbetaine, stearyldimethylbetaine, lauryldihydroxyethylbetaine and the like.
Nonionic surfactants include, for example, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan Examples include fatty acid esters and ethylene oxide adducts of acetylene alcohol.
Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzene sulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates.
These may be used individually by 1 type, or may use 2 or more types together.
The silicone-based surfactant is not particularly limited and can be appropriately selected depending on the intended purpose. Examples include polydimethylsiloxane modified at both chain ends, and polyether-modified silicone-based surfactants having polyoxyethylene groups or polyoxyethylene-polyoxypropylene groups as modifying groups exhibit excellent properties as water-based surfactants. preferable.
As such a surfactant, an appropriately synthesized one may be used, or a commercially available product may be used. Commercially available products are available from, for example, BYK Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nihon Emulsion Co., Ltd., Kyoeisha Chemical Co., Ltd., and the like.
The content of the surfactant in the ink is not particularly limited and can be appropriately selected according to the purpose. % or more and 5 mass % or less is preferable, and 0.05 mass % or more and 5 mass % or less is more preferable.

-- Defoamer --
The antifoaming agent is not particularly limited, and examples thereof include silicone antifoaming agents, polyether antifoaming agents, and fatty acid ester antifoaming agents. These may be used individually by 1 type, or may use 2 or more types together. Among these, silicone-based antifoaming agents are preferred because of their excellent foam breaking effect.

-- Antiseptic and antifungal agents --
The antiseptic and antifungal agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one.

--anti-rust--
The rust inhibitor is not particularly limited, and examples thereof include acidic sulfites and sodium thiosulfate.

--pH adjuster--
The pH adjuster is not particularly limited as long as it can adjust the pH to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

The physical properties of the ink are not particularly limited and can be appropriately selected depending on the intended purpose. For example, viscosity, surface tension, pH and the like are preferably within the following ranges.
The viscosity of the ink at 25° C. is preferably 5 mPa·s or more and 30 mPa·s or less, more preferably 5 mPa·s or more and 25 mPa·s or less, from the viewpoint of improving the print density and character quality and obtaining good ejection properties. more preferred. Here, the viscosity can be measured using, for example, a rotational viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.). Measurement conditions are 25° C., standard cone rotor (1°34′×R24), sample liquid volume 1.2 mL, rotation speed 50 rpm, 3 minutes.
The surface tension of the ink is preferably 35 mN/m or less, more preferably 32 mN/m or less at 25° C., from the viewpoint that the ink is appropriately leveled on the recording medium and the drying time of the ink is shortened.
The pH of the ink is preferably from 7 to 12, more preferably from 8 to 11, from the viewpoint of preventing corrosion of metal members in contact with the liquid.

The particle size of the solid content in the ink is not particularly limited and can be appropriately selected according to the purpose. However, it is preferably 20 nm or more and 1000 nm or less, more preferably 20 nm or more and 150 nm or less. The solid content includes resin particles, pigment particles, and the like. The particle size can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

The ink can be suitably used for inkjet printing.

[Ink analysis method]
By analyzing the ink, the elongation at break of the polycarbonate-based urethane resin particles, the glass transition point (Tg) of the acrylic resin particles, the mass ratio of the polycarbonate-based urethane resin particles to the acrylic resin particles, the acrylic resin particles and the polycarbonate-based urethane. As a method for analyzing the total amount of resin particles, for example, it can be carried out as follows. The ink is centrifuged to isolate polycarbonate-based urethane resin particles and acrylic resin particles. Identification of polycarbonate-based urethane resin particles and acrylic resin particles is performed by NMR, IR, or the like. Using the isolated polycarbonate-based urethane resin particles and acrylic resin particles, the breaking elongation of the polycarbonate-based urethane resin particles, the glass transition point (Tg) of the acrylic resin particles, and the mass of the polycarbonate-based urethane resin particles and the acrylic resin particles ratio, the total amount of the acrylic resin particles and the polycarbonate-based urethane resin particles is measured and calculated.

The recording medium for recording the ink of the present invention is not particularly limited and can be appropriately selected according to the purpose. can be done.
Examples of the impermeable base material include polypropylene film, polyethylene terephthalate film, and nylon film.
Examples of the polypropylene film include P-2002, P-2161 and P-4166 manufactured by Toyobo, PA-20, PA-30 and PA-20W manufactured by SUNTOX, and FOA, FOS and FOR manufactured by Futamura Chemical.
Examples of the polyethylene terephthalate film include E-5100 and E-5102 manufactured by Toyobo, P60 and P375 manufactured by Toray, and G2, G2P2, K and SL manufactured by Teijin DuPont Films.
Examples of the nylon film include Harden film N-1100, N-1102 and N-1200 manufactured by Toyobo, and ON, NX, MS and NK manufactured by Unitika.

(recorded matter)
The ink recorded matter of the present invention has an image formed on a recording medium using the ink of the present invention.

-recoding media-
Examples of the recording medium include, but are not limited to, plain paper, glossy paper, special paper, cloth, film, OHP sheet, and general-purpose printing paper.

The recording medium is not particularly limited and can be appropriately selected according to the purpose, but it is possible to form an image having particularly good adhesion to the impermeable substrate.
Examples of the impermeable base material include polypropylene film, polyethylene terephthalate film, and nylon film.
Examples of the polypropylene film include P-2002, P-2161 and P-4166 manufactured by Toyobo, PA-20, PA-30 and PA-20W manufactured by SUNTOX, and FOA, FOS and FOR manufactured by Futamura Chemical.
Examples of the polyethylene terephthalate film include E-5100 and E-5102 manufactured by Toyobo, P60 and P375 manufactured by Toray, and G2, G2P2, K and SL manufactured by Teijin DuPont Films.
Examples of the nylon film include Harden film N-1100, N-1102 and N-1200 manufactured by Toyobo, and ON, NX, MS and NK manufactured by Unitika.

<Recording device, recording method>
The ink of the present invention can be suitably used for various inkjet recording apparatuses, such as printers, facsimile machines, copiers, printer/facsimile/copier complex machines, stereolithography machines, and the like.
In the present invention, a recording apparatus and a recording method refer to an apparatus capable of ejecting ink, various treatment liquids, and the like onto a recording medium, and a method of performing recording using the apparatus. A recording medium means a medium to which ink or various processing liquids can adhere even temporarily.
This recording apparatus can include not only a head portion for ejecting ink, but also means for feeding, conveying, and discharging a recording medium, and other devices called pre-processing devices and post-processing devices. .
The recording apparatus and recording method may have heating means used in the heating process and drying means used in the drying process. The heating means and drying means include, for example, means for heating and drying the printing surface and the back surface of the recording medium. The heating means and drying means are not particularly limited, but for example, hot air heaters and infrared heaters can be used. Heating and drying can be performed before, during, or after printing.
Also, the recording apparatus and recording method are not limited to those that visualize significant images such as characters and graphics with ink. For example, it includes those that form patterns such as geometric patterns, and those that form three-dimensional images.
In addition, unless otherwise specified, the recording apparatus includes both a serial type apparatus in which the ejection head is moved and a line type apparatus in which the ejection head is not moved.
Furthermore, this recording device can be used not only as a desktop type, but also as a wide recording device that can print on A0 size recording media, and for example, can use continuous paper wound into a roll as a recording medium. A continuous feed printer is also included.
An example of a recording apparatus will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a perspective explanatory view of the device. FIG. 2 is a perspective explanatory view of the main tank. An image forming apparatus 400 as an example of a recording apparatus is a serial image forming apparatus. A mechanical unit 420 is provided inside the exterior 401 of the image forming apparatus 400 . Each ink container 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is packed with, for example, an aluminum laminated film. It is made up of members. The ink containing portion 411 is housed, for example, in a container case 414 made of plastic. Thus, the main tank 410 is used as an ink cartridge for each color.
On the other hand, a cartridge holder 404 is provided on the far side of the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404 . As a result, each ink discharge port 413 of the main tank 410 communicates with the ejection head 434 for each color via the supply tube 436 for each color, and ink can be ejected from the ejection head 434 onto the printing medium.

This recording apparatus can include not only a portion that ejects ink, but also devices called pre-processing devices and post-processing devices.
As an aspect of the pre-treatment device and the post-treatment device, it has a pre-treatment liquid and a post-treatment liquid in the same manner as in the case of inks such as black (K), cyan (C), magenta (M), and yellow (Y). There is a mode in which a liquid container and a liquid ejection head are added, and the pretreatment liquid and the posttreatment liquid are ejected by an inkjet recording method.
As another aspect of the pre-treatment device and the post-treatment device, there is an aspect in which a pre-treatment device and a post-treatment device using a method other than the inkjet recording method, such as a blade coating method, a roll coating method, and a spray coating method, are provided.

It should be noted that the method of using the ink is not limited to the ink jet recording method, and can be widely used. In addition to the inkjet recording method, for example, a blade coating method, a gravure coating method, a bar coating method, a roll coating method, a dip coating method, a curtain coating method, a slide coating method, a die coating method and a spray coating method can be used.

In the present invention, the terms image formation, recording, printing, and printing are all synonymous.

The terms recording medium, medium, and printed material are all synonymous.

The recording method using the ink of the present invention can record an image with high image quality on a non-permeable substrate. It is preferable to heat the substrate during printing in order to be able to cope with the above. It is also preferable to heat and dry the substrate after printing.
The heating device used to heat the substrate can be one or more of many known heating devices. For example, devices for forced air heating, radiant heating, conductive heating, high frequency drying, and microwave drying, which can be used singly or in combination of two or more. Such a heating device may be one built into an existing inkjet printer or one externally attached to an existing inkjet printer.
It is preferable that the heating temperature of the base material is high in consideration of the drying property. However, if the heating temperature is too high, the base material may be damaged, the ink head may warm up, causing non-ejection, and the formation of a uniform ink film may be hindered. Generally, it is preferable to heat in the range of 30° C. or higher and 60° C. or lower during printing. Moreover, it is preferable to control the drying temperature after printing at 110° C. or less.

Examples of the present invention will be described below, but the present invention is not limited to these examples. In addition, "%" described in the examples means "% by mass" except for the description in the evaluation criteria.

[Preparation of Coloring Material: Preparation of Dispersant-Dispersed White Pigment Dispersion W]
250 g of titanium oxide "R62N" (manufactured by Sakai Chemical Industry Co., Ltd.) as a white pigment, 10 g of "Demoll EP" (manufactured by Kao Corporation) as a pigment dispersant (2.5 g of active ingredients), and 740 g of ion-exchanged water and, using a bead mill (DYNO-MILL KDL A type, manufactured by Shinmaru Enterprises Co., Ltd.), 0.5 mmΦ zirconia beads were dispersed at a filling rate of 80% and a residence time of 2 minutes, dispersing agent dispersion type A white pigment dispersion W was obtained.

[Preparation of Coloring Material: Preparation of Self-dispersing Black Pigment Dispersion A]
100 g of carbon black (Black Pearl 1000) manufactured by Cabot Corporation is added to 3000 mL of 2.5 N (regulation) sodium hypochlorite solution, stirred at a temperature of 60 ° C. and a speed of 300 rpm, and reacted for 10 hours to oxidize. After treatment, a reaction liquid containing a pigment having a carboxylic acid group attached to the surface of carbon black was obtained. This reaction liquid was filtered, and the filtered carbon black was neutralized with a sodium hydroxide solution and subjected to ultrafiltration to obtain a pigment dispersion. Next, the pigment dispersion and ion-exchanged water were subjected to ultrafiltration with a dialysis membrane, and then ultrasonic dispersion. After that, the water content was adjusted so that the solid content concentration was 20%, and a self-dispersion type black pigment dispersion A having a solid content concentration of 20% was obtained.

[Preparation of color material: preparation of dispersant-dispersed black pigment dispersion B]
After premixing a mixture of 100 g of carbon black (Black Pearl 1000) manufactured by Cabot Corporation, 15 g of sodium naphthalenesulfonate formalin condensate (Pionin A-45-PN) manufactured by Takemoto Oil Co., Ltd., and 280 g of ion-exchanged water , using zirconia beads with a diameter of 0.3 mm in a Dyno Mill (manufactured by Shinmaru Enterprises Co., Ltd.) at a rotational speed of 10 m/sec and a liquid temperature of 10°C for 30 minutes to obtain a pigment dispersion. The resulting pigment dispersion and zirconia beads were then separated and filtered through a 0.8 μm membrane filter (cellulose acetate type). Thereafter, the water content was adjusted so that the solid content concentration was 20%, and a dispersant-dispersed black pigment dispersion B having a solid content concentration of 20% was obtained.

[Preparation of acrylic resin particle dispersion Ac-1]
Acrylic acid 5.0 parts by mass, Sila Ace 210 (vinyltrimethoxysilane, manufactured by Chisso Corporation) 6 parts by mass, 2-ethylhexyl methacrylate 6.0 parts by mass, 2-ethylhexyl acrylate 22.0 parts by mass, methacrylic acid A mixture of 5.0 parts by weight of cyclohexyl, 22.0 parts by weight of styrene, 1.5 parts by weight of Aqualon KH-20 (reactive emulsifier manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as an emulsifier, and 53.1 parts by weight of ion-exchanged water was emulsified with a batch-type homomixer to prepare an acrylic resin particle dispersion Ac-1, which was placed in a dropping tank.
The cumulative 50% particle diameter (D ₅₀ ) of the obtained acrylic resin particle dispersion Ac-1 was measured by a dynamic light scattering method and found to be 80 nm. The theoretical Tg obtained from monomers other than vinyltrimethoxysilane was 30°C. Moreover, solid content concentration was 39.4 mass %.

[Preparation of acrylic resin particle dispersion Ac-2]
An acrylic resin particle dispersion Ac-2 was prepared in the same manner as the acrylic resin particle dispersion Ac-1, except that the following composition was used in the preparation of the acrylic resin particle dispersion Ac-1.

[composition]
・Methacrylic acid: 3.0 parts by mass ・Butyl acrylate: 25.0 parts by mass ・Acrylamide: 1.0 parts by mass ・Styrene: 29.0 parts by mass ・Sila Ace 210 ^*1 : 6 parts by mass *1: Sila Ace 210 ( Vinyltrimethoxysilane, manufactured by Chisso Corporation)

The cumulative 50% particle size (D ₅₀ ) of the obtained acrylic resin particle dispersion Ac-2 was measured by a dynamic light scattering method and found to be 80 nm. The theoretical Tg obtained from monomers other than vinyltrimethoxysilane was 45°C. Moreover, solid content concentration was 39.5 mass %.

[Preparation of acrylic resin particle dispersion Ac-3]
An acrylic resin particle dispersion Ac-3 was prepared in the same manner as the acrylic resin particle dispersion Ac-1, except that the following composition was used in the preparation of the acrylic resin particle dispersion Ac-1.

[composition]
・Methacrylic acid: 3.0 parts by mass ・Butyl acrylate: 20.0 parts by mass ・Acrylamide: 1.0 parts by mass ・Styrene: 34.0 parts by mass ・Sila Ace 210 ^*1 : 6 parts by mass *1: Sila Ace 210 ( Vinyltrimethoxysilane, manufactured by Chisso Corporation)

The cumulative 50% particle diameter (D ₅₀ ) of the obtained acrylic resin particle dispersion Ac-3 was measured by a dynamic light scattering method and found to be 90 nm. The theoretical Tg obtained from monomers other than vinyltrimethoxysilane was 70°C. Moreover, solid content concentration was 39.7 mass %.

(Examples 1 to 14 and Comparative Examples 1 to 11)
Based on the compositions shown in Tables 2 to 7, each material was mixed, thoroughly stirred with a disperser, and then filtered through a 0.8 μm membrane filter (cellulose acetate type) to prepare Inks 1-23. In the table, Surfynol 440 (Nissin Chemical Industry Co., Ltd.) is a nonionic surfactant.
The polycarbonate-based urethane resin particles used in the ink were commercially available products listed in Table 1 below.

Next, the prepared inks were evaluated for "scratch resistance", "ejection stability" and "decapping properties" as follows. Tables 2 to 7 show the results.

<Scratch resistance>
The prepared ink was filled into an inkjet printer (IPSiO GXe5500 manufactured by Ricoh Co., Ltd.), and PP (Pylen P2102 manufactured by Toyobo), PET (Spet E5100 manufactured by Toyobo), and NY (Harden N1100 manufactured by Toyobo) were used as recording media. A solid image was printed and dried at 80° C. for 5 minutes.
The solid image was a 50 mm×50 mm solid image created with Microsoft Word.
Each film was fixed on MyPaper (PPC plain paper manufactured by Ricoh Co., Ltd.) with a double-faced tape, and the film was fed from the rear multi-manual feeder and printed on the film surface.
The solid image was rubbed with a dry cotton cloth (Kanakin No. 3) with a weight of 400 g, and the image density was measured using X-Rite eXact (manufactured by X-Rite). Scratch resistance" was evaluated. In the following evaluation criteria, "image density is reduced" means that the rate of change in image density before and after the printed image is rubbed is 80% or more. When white ink was used, black paper having a black density of 1.2 or more was placed on the back side of the paper on which the image to be measured was printed, and the image density was measured.

[Evaluation criteria]
A: The image does not change even after rubbing 50 times or more.
B: Some scratches remain after rubbing 50 times, but the image density is not affected and there is no problem in actual use.
C: The image density decreases while rubbing 20 times or more and less than 50 times.
D: The image density is lowered by rubbing less than 20 times.

<Ejection stability>
With an inkjet printer (IPSiO GXe5500 manufactured by Ricoh Co., Ltd.), 100 sheets of A4 size solid images were continuously printed in glossy paper clean mode, and the printed images were visually observed. gender” was determined.

[Evaluation criteria]
A: The image does not change until after the completion of 100 sheets.
B: Streaks and unevenness occur in the image after 50 sheets to 100 sheets.
C: Streaks and unevenness occur in the image before the completion of 50 sheets.

<Decapability>
With an inkjet printer (IPSiO GXe5500 manufactured by Ricoh Co., Ltd.), the power supply was cut off during printing, left at room temperature of 23° C. and humidity of 50% for 72 hours, and printing was performed after power was supplied again. "Decap property" was determined based on the following evaluation criteria.

[Evaluation criteria]
A: No abnormalities such as density unevenness, faintness, or omissions occur in the normal initialization operation.
B: Abnormalities such as density unevenness, faintness, and blanking occur in the normal initialization operation, but are recovered by refreshing.
C: Recovery does not occur unless refreshing is performed 5 or more times in addition to the normal initialization operation.
Also, "refreshing" is an operation of discarding a large amount of ink from an inkjet nozzle at once, and is a function installed in the printer.

Embodiments of the present invention are, for example, as follows.
<1> An ink containing water, a coloring material, an organic solvent, acrylic resin particles, and polycarbonate-based urethane resin particles,
the organic solvent is 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol, propylene glycol monomethyl ether, 1-methoxy-2-propyl acetate, and at least one of butyl propylene glycol,
The breaking strength of the polycarbonate-based urethane resin particles is 30 MPa or more,
The acrylic resin particles have a glass transition point (Tg) of 40° C. or higher,
The mass ratio of the polycarbonate-based urethane resin particles to the acrylic resin particles (polycarbonate-based urethane resin particles/acrylic resin particles) is from 25/75 to 75/25,
The content of the acrylic resin particles is 4.5% by mass or less with respect to the total amount of the ink.
The ink is characterized by:
<2> The ink according to <1>, wherein the coloring material is a white pigment.
<3> The ink according to any one of <1> and <2>, wherein the content of 3-methoxy-3-methyl-1-butanol is 5.0% by mass or more and 20.0% by mass or less. be.
<4> An ink cartridge containing the ink according to any one of <1> to <3>.
<5> An inkjet recording apparatus comprising the ink cartridge according to <4>.

According to the ink described in any one of <1> to <3>, the ink cartridge described in <4>, and the inkjet recording apparatus described in <5>, various problems in the related art are solved, and the present invention can achieve the purpose of

400 Image forming apparatus 401 Exterior 401c Cover 404 Cartridge holder 410, 410k, 410c, 410m, 410y Main tank 411 Ink storage unit 413 Ink discharge port 414 Storage container case 420 Mechanism unit 436 Supply tube 434 Ejection head

JP 2010-90266 A JP 2017-88846 A

Claims (3)

An ink containing water, a coloring material, an organic solvent, acrylic resin particles, and polycarbonate-based urethane resin particles,
the organic solvent is 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol, propylene glycol monomethyl ether, 1-methoxy-2-propyl acetate, and at least one of butyl propylene glycol,
The breaking strength of the polycarbonate-based urethane resin particles is 30 MPa or more,
The acrylic resin particles have a glass transition point (Tg) of 40° C. or higher,
The mass ratio of the polycarbonate-based urethane resin particles to the acrylic resin particles (polycarbonate-based urethane resin particles/acrylic resin particles) is from 25/75 to 75/25,
The content of the acrylic resin particles is 4.5% by mass or less with respect to the total amount of the ink.
An ink characterized by: The ink according to claim 1, wherein the coloring material is a white pigment. 3. The ink according to any one of claims 1 and 2, wherein the content of 3-methoxy-3-methyl-1-butanol is 5.0% by mass or more and 20.0% by mass or less.

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