JP7243246B2 - Ink set, liquid ejection unit, liquid ejection device, printing method, and printing apparatus - Google Patents

Description

The present invention relates to an ink set, a liquid ejection unit, a liquid ejection device, a printing method, and a printing apparatus.

Conventionally, in the field of sign graphics such as advertisements displayed indoors and outdoors, cyan (C), magenta (M), yellow (Y), and black (K) are used to form diverse and high-quality images. 2. Description of the Related Art Inkjet liquid ejection apparatuses are used that are loaded with process color image forming ink and auxiliary ink of a color different from the process color, such as white ink (white ink) or metallic ink.

High productivity is required in industrial printing such as in the field of sign graphics.
2. Description of the Related Art In the field of sign graphics such as advertisements displayed indoors and outdoors, wide-area inkjet printers are on the market, but there is a high demand for improved productivity. A wide-width inkjet device generally employs a multi-pass method in which the head scans in the media width direction (main scanning direction) and the media is conveyed perpendicularly (sub-scanning direction) to the head scanning direction.

Further, when forming an image on a transparent base material, an image with a white background may be formed by overlapping printing of white ink and colored ink such as process color. In such a case, colored inks such as process colors are printed only where the image is formed, but the white ink used as the background is printed over a range larger than the area where the image is formed. need to be printed. As such, productivity can be a particular challenge.

For example, by having a nozzle row in which a plurality of nozzle holes for ejecting process color liquids are arranged in the sub-scanning direction, and having a nozzle row in which a plurality of nozzle holes for ejecting liquids other than process colors are arranged in the sub-scanning direction, 2. Description of the Related Art A liquid ejection unit capable of speeding up image formation has been proposed (see, for example, Japanese Unexamined Patent Application Publication No. 2002-100001).

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid ejection unit capable of achieving both high productivity and image quality free from color unevenness.

A liquid ejection unit of the present invention as a means for solving the above-mentioned problems is a nozzle having a plurality of nozzle holes for ejecting at least one process color liquid for image formation provided in a sub-scanning direction perpendicular to the main scanning direction. and a plurality of nozzle rows each having a plurality of nozzle holes in the sub-scanning direction for ejecting at least one process color liquid, wherein the process color liquids are cyan ink and magenta ink. An ink set containing one type each of ink, yellow ink, and black ink, wherein the pigment content of each color of the ink set is 2.9% by mass or less, and each of the nozzle groups includes at least one type of the process Three or more nozzle rows for ejecting liquid of a color different from the color are arranged in the sub-scanning direction.

According to the present invention, it is possible to provide a liquid ejection unit capable of achieving both high productivity and image quality free from color unevenness.

FIG. 1 is a schematic diagram showing an example of the inkjet recording apparatus of the present invention. FIG. 2 is a block diagram showing an example of the control configuration of the inkjet printing apparatus. FIG. 3 is a plan view showing an example of the nozzle configuration of the recording head. FIG. 4 is a schematic diagram simply showing an example of the colors of each nozzle row.

(Liquid discharge unit)
A liquid ejection unit according to the present invention comprises a nozzle array having a plurality of nozzle holes for ejecting liquid of at least one type of image forming process color in a sub-scanning direction perpendicular to the main scanning direction, and at least one type of process color. and a plurality of nozzle rows in which a plurality of nozzle holes for ejecting liquids of different colors are arranged in the sub-scanning direction. In the ink set containing each type, the pigment content of each color in the ink set is 2.9% by mass or less, and each nozzle group ejects at least one liquid of a color different from the process color. Three or more nozzle rows are arranged in the sub-scanning direction, and other members are provided as necessary.

In the prior art, the pigment content of each color in an ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink is as high as 3 mass %. For this reason, in a multi-pass type wide-width inkjet recording device that uses an ink set with a high pigment concentration, the ink droplet landing position shift occurs due to head vibration, head straddling, etc., and color unevenness (density unevenness) occurs. I have a problem.

Accordingly, the liquid ejection unit of the present invention includes a nozzle array having a plurality of nozzle holes for ejecting at least one type of image forming process color liquid in the sub-scanning direction orthogonal to the main scanning direction, and at least one type of process color. and a plurality of nozzle groups each having a plurality of nozzle rows in the sub-scanning direction for ejecting liquids of colors different from the colors, and the liquids of the process colors are cyan ink, magenta ink, yellow ink, and black ink. wherein each color of the ink set has a pigment content of 2.9% by mass or less, and each of the nozzle groups uses at least one liquid of a color different from the process color. Since three or more ejection nozzle rows are arranged in the sub-scanning direction, it is possible to achieve both high productivity and image quality free from color unevenness.
From the standpoint of high productivity, it is preferable that each of the nozzle groups includes four or more nozzle rows in the sub-scanning direction that eject at least one type of liquid different from the process color.

The process color liquid used in the liquid ejection unit of the present invention is an ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink from the viewpoint of suppressing the occurrence of color unevenness, and contains pigments of each color. The amount must be 2.9 mass % or less, preferably 1.0 mass % or more and 2.9 mass % or less.
In the ink set, the pigment content of the cyan ink is preferably 0.8% by mass or more and 1.5% by mass or less. When the pigment content of the cyan ink is 0.8% by mass or more and 1.5% by mass or less, color unevenness can be further suppressed.
By setting the pigment content to a certain value or less, the occurrence of color unevenness can be suppressed, and the pigment content of cyan ink, in which color unevenness is particularly noticeable, is set to 0.8% by mass or more and 1.5% by mass or less. Thus, a good image without color unevenness can be obtained.

In the ink set, it is preferable to satisfy magenta ink > cyan ink and yellow ink > cyan ink in terms of pigment content from the viewpoint of ensuring suppression of color unevenness. Since color unevenness is particularly noticeable in cyan, it is possible to effectively suppress color unevenness by lowering the density of one cyan dot. By using ink, it is possible to reproduce a color range such as Japan color.

It is preferable to have a white ink as a liquid having a color different from the process color from the viewpoint that an image with a white background can be formed on a transparent base material.

As a method for analyzing each ink in the ink set and measuring the content of pigment contained in each ink, the ink is separated into a supernatant liquid and a sediment by centrifugation, then the sediment is collected, and an organic The pigment is collected by repeating washing with a solvent and filtration. The content can be obtained by weighing the collected pigment. Further, the structure of the pigment can be confirmed by performing data analysis through GC-MS analysis.
[Centrifugation]
・ Apparatus: himac CS150GX manufactured by Hitachi Koki Co., Ltd.
・Rotation speed: 150,000 rpm
・Rotation time: 1 hour
[GC-MS]
・Apparatus: QP5000 manufactured by Shimadzu Corporation
・Column: Ultra ALLOY-5L=30m, ID=0.25mm Film=0.25μm
・Column temperature rise: 50°C to 330°C
・Column flow rate: 1.0 ml/min
・Split: 1:100
・Ionization method: EI method (70 eV)
・Measuring mass range: m/z 33 to 600
・Data analysis, analysis software: GCMSsolution manufactured by Shimadzu Corporation

Hereinafter, each ink in an ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink as the process color liquid used in the liquid ejection unit of the present invention, and liquids of colors different from the process colors White ink as . Note that these inks may be collectively referred to simply as "ink".
As the cyan ink, an ink containing a cyan pigment is used. Cyan inks include inks with varying concentrations of cyan pigment, such as light cyan inks. Similarly, an ink containing a magenta pigment is used as magenta ink, an ink containing yellow pigment is used as yellow ink, an ink containing black pigment is used as black ink, and a white pigment is used as white ink. Use ink that

<Ink>
Organic solvents, water, coloring materials, resins, additives, and the like used in the ink are described below.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited, and any water-soluble organic solvent can be used. Examples thereof 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.
Examples of water-soluble organic solvents 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-1,3 - Polyhydric alcohols such as 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, polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and 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-dimethylpropionamide , 3-butoxy-N, N-dimethylpropionamide and other amides, monoethanolamine, diethanolamine, triethylamine and other amines, dimethylsulfoxide, sulfolane, thiodiethanol and other sulfur-containing compounds, propylene carbonate, ethylene carbonate, and the like. be done.
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.
Examples of glycol ether compounds include polyhydric alcohol alkyl ethers 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. such as polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

The content of the organic solvent in the ink is not particularly limited and can be appropriately selected according to the purpose. 20% by mass or more and 60% by mass or less is more preferable.

Among the above organic solvents, it is preferable to contain at least the compound represented by the general formula (1).
By including the compound represented by the general formula (1), film formation of the resin in the drying process of the ink is promoted, so that the drying property can be improved.

（ただし、前記一般式（１）中、Ｒ^１、Ｒ^２、及びＲ^３は、それぞれ、炭素数１以上５以下のアルキル基を示し、Ｒ^１、Ｒ^２、及びＲ^３は同一であっても、異なっていてもよい）

(wherein R ¹ , R ² and R ³ each represent an alkyl group having 1 to 5 carbon atoms in the general formula (1), and R ¹ , R ² and R ³ are the same may be different)

<Water>
The content of water in the ink is not particularly limited and can be appropriately selected according to the purpose. % or more and 60 mass % or less is more preferable.

<Color material>
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 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 inorganic pigments, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chrome yellow, carbon black produced by known methods such as contact method, furnace method, thermal method, etc. can be used.
Organic pigments 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. 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 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 (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 and the like.

A white colorant is used as the colorant for the white ink used for the auxiliary ink (ink for background or base).
ISO-2469 (JIS-8148) is used as a standard for the whiteness of white ink, and generally when the value is 70 or more, it is used as a white colorant.
Metal oxides used in white ink include, for example, titanium oxide, iron oxide, tin oxide, zirconium oxide, and iron titanate (composite oxide of iron and titanium). Alternatively, hollow particles may be used as a white coloring material. As the hollow particles, resin hollow particles and inorganic hollow particles can be used.

In order 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 and dispersing it, a method of dispersing using a dispersant, etc.
As a method of making a self-dispersing pigment by introducing a hydrophilic functional group into a pigment, for example, a self-dispersing pigment that is dispersible in water by adding a functional group such as a sulfone group or a carboxyl group to a pigment (for example, carbon). etc. can be used.
As a method for dispersing the pigment by coating the surface of the pigment with a resin, a method in which the pigment is encapsulated in microcapsules and dispersible 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 a 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, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Oil & Fat Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used as a dispersant. A dispersing agent may be used individually by 1 type, or may use 2 or more types together.

<Resin>
The type of resin contained in the ink is not particularly limited and can be appropriately selected according to the purpose. resins, styrene-butadiene-based resins, vinyl chloride-based resins, acrylic-styrene-based resins, acrylic-silicone-based resins, and the like.
Resin particles made of these resins may also be used. Ink can be obtained by mixing resin particles in a resin emulsion state in which water is dispersed as a dispersion medium with a material such as a coloring material or an organic solvent. As the resin particles, appropriately synthesized ones may be used, or commercially available products may be used. Moreover, these may be used individually by 1 type, or may be used in combination of 2 or more types of resin particles.

The volume average particle diameter of the resin particles is not particularly limited and can be appropriately selected according to the intended purpose. 200 nm or less is more preferable, and 10 nm or more and 100 nm or less is particularly preferable.
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 resin is not particularly limited and can be appropriately selected according to the purpose. However, from the viewpoint of fixability and storage stability of the ink, the content is 1% by mass or more and 30% by mass or less based on the total amount of the ink. is preferable, and 5% by mass or more and 20% by mass or less is more preferable.

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 1,000 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.).

<Additive>
Surfactants, antifoaming agents, antiseptic and antifungal agents, antirust agents, pH adjusters, etc. may be added to the ink, if necessary.

-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 ,} and NH( _CH2CH2OH ). ₃ and the like.
Amphoteric surfactants include, for example, 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 acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate and the like.
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 ends, and polyether-modified silicone surfactants having polyoxyethylene groups or polyoxyethylene polyoxypropylene groups as modifying groups are particularly preferred because they exhibit good properties as water-based surfactants. .
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 above polyether-modified silicone-based surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, a polyalkylene oxide structure represented by the following general formula (S-1) Examples include those introduced into the side chain of the Si portion of dimethylpolysiloxane.

（但し、前記一般式（Ｓ－１）式中、ｍ、ｎ、ａ、及びｂは整数を表す。Ｒ及びＲ’はアルキル基、アルキレン基を表す。）

(However, in the general formula (S-1), m, n, a, and b represent integers. R and R' represent an alkyl group and an alkylene group.)

Commercially available products can be used as the above polyether-modified silicone-based surfactants. -1906EX (manufactured by Nippon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (manufactured by Dow Corning Toray Silicone Co., Ltd.), BYK -33, BYK-387 (manufactured by BYK-Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (manufactured by Toshiba Silicon Co., Ltd.) and the like.

As the fluorosurfactant, a fluorine-substituted compound having 2 to 16 carbon atoms is preferable, and a fluorine-substituted compound having 4 to 16 carbon atoms is more preferable.
Examples of fluorine-based surfactants include perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in side chains. Among these, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in a side chain is preferable because of its low foamability, and a fluorine-based compound represented by the following general formula (F-1) and general formula (F-2) Surfactants are more preferred.

上記一般式（Ｆ－１）で表される化合物において、水溶性を付与するためにｍは０～１０の整数が好ましく、ｎは０～４０の整数が好ましい。 [General formula (F-1)]

In the compound represented by the general formula (F-1), m is preferably an integer of 0 to 10 and n is preferably an integer of 0 to 40 in order to impart water solubility.

[General formula (F-2)]
_{CnF2n +1- CH2CH} (OH)CH2 _- O-( _CH2CH2O ) _{a -} Y
In the compound represented by the general formula (F-2), Y is H, or C _n F _2n+1 where n is an integer of 1 to 6, or CH ₂ CH(OH)CH ₂ —C _n F _2n+1 where n is an integer from 4 to 6, or C _p H _2p+1 where p is an integer from 1 to 19; a is an integer from 4 to 14;

Commercially available products may be used as the fluorosurfactant. Examples of commercially available products include Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fleurard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (both manufactured by Sumitomo 3M); Megafac F-470, F -1405, F-474 (both manufactured by DIC Corporation); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (both manufactured by DuPont) ); FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Co., Ltd.), Polyfox PF-136A, PF-156A, PF-151N, PF -154, PF-159 (manufactured by Omnova), and Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.). Among these, FS-300 manufactured by DuPont, FT-110 and FT- 250, FT-251, FT-400S, FT-150, FT-400SW, Polyfox PF-151N manufactured by Omnova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferable.

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.

<Antifoaming agent>
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.

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

<Antirust agent>
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, for viscosity, for example, a rotational viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. 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.

<Recording medium>
The recording medium is not particularly limited, and plain paper, glossy paper, special paper, cloth, and the like can be used.
The non-permeable substrate is a substrate having a surface with low water permeability and low absorbency, and includes materials that do not open to the outside even if there are many cavities inside. , refers to a substrate having a water absorption of 10 mL/m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method.
As the impermeable substrate, for example, plastic films such as vinyl chloride resin films, polyethylene terephthalate (PET) films, polypropylene, polyethylene and polycarbonate films can be suitably used.

<Records>
An ink recorded matter relating to the present invention has an image formed on a recording medium using the ink of the present invention.
A recorded matter can be obtained by recording with an inkjet recording apparatus and an inkjet recording method.

(liquid ejection device)
The liquid ejection device of the present invention comprises the liquid ejection unit of the present invention,
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. a control unit for controlling the auxiliary layer, which is an auxiliary layer to be printed, so that it can be arranged as one of preprinting, postprinting, and interprinting, and other units as necessary.

(printing method)
A printing method of the present invention comprises a liquid ejection step of ejecting liquid using the liquid ejection unit of the present invention;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. a control step for controlling that the auxiliary layer, which is the auxiliary layer, can be arranged as one of preprinting, postprinting, and interprinting, and other steps as necessary.

A printing apparatus of the present invention comprises a liquid ejecting unit comprising the liquid ejecting unit of the present invention;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. control means for controlling that the auxiliary layer, which is the auxiliary layer, can be arranged as one of preprinting, postprinting, and interprinting, and other means as necessary.

(ink set)
The ink set of the present invention is an ink set used in the printing apparatus of the present invention,
The process color liquid is an ink set containing one each of cyan ink, magenta ink, yellow ink, and black ink, and the pigment content of each color in the ink set is 2.9% by mass or less.
Each ink of the ink set contains water, an organic solvent, a coloring material, resin particles and a siloxane compound, and further contains other components as necessary.
Preferably, the ink set has a white ink as a liquid of a color different from the process color liquid.

<Recording device>
FIG. 1 is a schematic diagram showing the configuration of an inkjet recording apparatus 1. As shown in FIG. An inkjet recording apparatus 1, which is a liquid ejection apparatus, is a serial type inkjet recording apparatus. As shown in FIG. 1 , the inkjet recording apparatus 1 includes an image forming section 2 that prints a desired image, a drying device 3 , a roll media storage section 4 and a transport mechanism 5 . The roll media storage unit 4 stores roll media (recording media) 40 . Note that the roll media storage unit 4 can store recording media 40 having different sizes in the width direction. The recording medium 40 may be a non-permeable medium such as PVC (vinyl chloride) or PET (polyethylene terephthalate) film, or a permeable medium such as cloth or synthetic paper.

The transport mechanism 5 constitutes a roll-to-roll transport means. The transport mechanism 5 includes a pair of nip rollers 51 , a pair of driven rollers 52 and a take-up roller 53 on a transport path 54 for the recording medium 40 . The nip roller 51 is provided on the front side of the image forming section 2 (on the upstream side in the transport direction A). The nip rollers 51 convey the nipped recording medium 40 toward the image forming section 2 by rotating with the drive of the motor M (see FIG. 2). The take-up roller 53 rotates as the motor M is driven to take up the recording medium 40 after printing. The driven roller 52 rotates following the conveyance of the recording medium 40 .

The transport mechanism 5 has a wheel encoder 55 (see FIG. 2) for detecting the transport speed. The conveying mechanism 5 controls the conveying speed by controlling the motor M based on the target value and the detected speed value obtained by sampling the detection pulse from the wheel encoder 55 .

That is, the recording medium 40 stored in the roll media storage section 4 is conveyed to the image forming section 2 through the driven roller 52 by the rotation of the nip roller 51 . A desired image is printed by the image forming section 2 on the recording medium 40 that has reached the image forming section 2 . The recording medium 40 after printing is wound up by the rotation of the winding roller 53 .

The image forming section 2 has a carriage 21 . The carriage 21 is slidably held by guide rods (guide rails) 22 . As the motor M is driven, the carriage 21 moves on a guide rod (guide rail) 22 in a direction (main scanning direction) perpendicular to the transport direction A of the recording medium 40 . More specifically, the carriage 21 moves within a recording area in which the image forming section 2 can print on the recording medium 40 conveyed by the conveying mechanism 5 in the main scanning area which is a movable area in the main scanning direction. move back and forth.

A carriage 21 carries a recording head 20 having a plurality of nozzle holes, which are ejection openings for ejecting droplets. Note that the recording head 20 is integrally provided with a tank that supplies ink to the recording head 20 . However, the recording head 20 is not limited to the one integrally provided with the tank, and may be provided with the tank separately. The recording head 20 functions as a liquid ejection unit, and ejects ink droplets of black (K), yellow (Y), magenta (M), and cyan (C), which are process color recording liquids. . Black (K), yellow (Y), magenta (M), and cyan (C) are inks for image formation. In addition, the recording head 20 ejects white (W) ink droplets, which are auxiliary inks (background and base inks).

The image forming section 2 includes a platen 23 that supports the recording medium 40 below the recording head 20 during printing by the recording head 20 .

The image forming section 2 also includes an encoder sheet for detecting the main scanning position of the carriage 21 along the main scanning direction of the carriage 21 . The carriage 21 also has an encoder 26 (see FIG. 2). The image forming unit 2 detects the main scanning position of the carriage 21 by reading the encoder sheet with the encoder 26 of the carriage 21 .

The carriage 21 has a sensor 24 that optically detects the edge of the recording medium 40 as the carriage 21 moves. A detection signal from the sensor 24 is used to calculate the position of the edge of the recording medium 40 in the main scanning direction and the width of the recording medium 40 .

The drying device 3 includes a preheater 30 , a platen heater 31 , a drying heater 32 and a hot air fan 33 . The preheater 30, the platen heater 31, and the drying heater 32 are electric heaters using, for example, ceramic or nichrome wire.

The preheater 30 is provided upstream in the transport direction A of the recording medium 40 with respect to the image forming section 2 . The preheater 30 preliminarily heats the recording medium 40 transported by the transport mechanism 5 .

The platen heater 31 is arranged on the platen 23 . The platen heater 31 heats the recording medium 40 on which the ink droplets ejected from the nozzle holes of the recording head 20 land.

The drying heater 32 is provided downstream of the image forming section 2 in the conveying direction A of the recording medium 40 . The drying heater 32 continues to heat the recording medium 40 printed by the image forming section 2 to promote drying of the ink droplets that have landed.

The hot air fan 33 is provided downstream in the conveying direction A of the recording medium 40 with respect to the drying heater 32 (image forming section 2). The hot air fan 33 blows hot air onto the recording surface of the recording medium 40 on which the ink has landed. The hot air fan 33 blows hot air directly onto the ink on the recording surface of the recording medium 40 to reduce the humidity of the atmosphere around the recording surface of the recording medium 40 and dry it completely.

By installing such a drying device 3, the inkjet recording apparatus 1 adopts non-permeable media such as polyvinyl chloride (PVC), polyethylene terephthalate (PET), and acrylic as the recording media 40. can do.

Note that in the inkjet recording apparatus 1 that forms an image by ejecting ink from the recording head 20 while the carriage 21 reciprocates across the width of the recording medium 40, ink is ejected to form an image only when the carriage is moving forward. There are unidirectional printing that forms an image and bidirectional printing that forms an image by ejecting ink in both forward and backward carriage operations. The inkjet recording apparatus 1 mainly uses bidirectional printing, which is advantageous in terms of printing speed. Here, the operation of ejecting ink from the recording head 20 while the carriage 21 moves in the main scanning direction is assumed to be one scan.

Next, the control configuration of the inkjet recording apparatus 1 will be described. Here, FIG. 2 is a block diagram showing the control configuration of the inkjet recording apparatus 1. As shown in FIG.

As shown in FIG. 2, the inkjet recording apparatus 1 includes a control section 10 that controls the entire apparatus. The control unit 10 includes a CPU (Central Processing Unit) 11 serving as a control subject, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, a memory 14, and an ASIC (Application Specific Integrated Circuit) 15. I have it. The ROM 12 stores computer programs executed by the CPU 11 and other fixed data. The RAM 13 temporarily stores image data and the like. The memory 14 is a rewritable non-volatile memory for retaining data even while the inkjet recording apparatus 1 is powered off. The ASIC 15 executes various signal processing for image data, image processing such as rearrangement, and input/output signal processing for controlling the entire apparatus.

Further, as shown in FIG. 2, the control section 10 includes a host interface (I/F) 16, a head drive control section 17, a motor control section 18, and an I/O 19. FIG.

The host I/F 16 transmits and receives image data (print data) and control signals to and from the host via a cable or network. Hosts connected to the inkjet recording apparatus 1 include an information processing device such as a personal computer, an image reading device such as an image scanner, and an imaging device such as a digital camera.

I/O 19 receives detection pulses from encoder 26 and wheel encoder 55 . In addition, I/O 19 connects sensor 24 as well as various sensors 25 such as humidity, temperature and other sensors. The I/O 19 inputs detection signals from the sensor 24 and various sensors 25 .

The head drive control unit 17 drives and controls the recording head 20 and includes data transfer means. More specifically, the head drive control section 17 transfers the image data as serial data. The head drive control unit 17 also generates transfer clocks and latch signals necessary for transfer of image data and determination of transfer, and drive waveforms used when droplets are ejected from the recording head 20 . Then, the head drive control unit 17 inputs the generated drive waveform and the like to the drive circuit inside the recording head 20 .

The motor control section 18 drives the motor M. As shown in FIG. More specifically, the motor control unit 18 calculates the control value based on the target value given from the CPU 11 side and the speed detection value obtained by sampling detection pulses from the wheel encoder 55 . Then, the motor control unit 18 drives the motor M based on the calculated control value via an internal motor drive circuit.

The controller 10 also includes a heater controller 8 and a hot air fan controller 9 .

The heater control unit 8 controls the outputs of the preheater 30, the platen heater 31, and the drying heater 32 so that the temperatures of the heaters 30, 31, and 32 become the set temperatures. More specifically, the heater control unit 8 acquires temperature information from temperature sensors provided in the heaters 30 , 31 , 32 when controlling the heaters 30 , 31 , 32 . Then, the heater control unit 8 monitors the temperatures of the heaters 30, 31, and 32 and controls the temperatures of the heaters 30, 31, and 32 to the set temperatures. If a heater is provided in the tank of the print head 20 or on the ink path, the heater control section 8 controls the heater in the same manner.

The warm air fan controller 9 controls the output of the warm air fan 33 so as to blow air at a predetermined temperature and air volume.

In addition, the control unit 10 connects an operation panel 60 for inputting and displaying necessary information to the inkjet recording apparatus 1 .

The control unit 10 develops a computer program read from the ROM 12 (or the memory 14) by the CPU 11 into the RAM 13 and executes the computer program, thereby comprehensively controlling each unit.

The computer program executed by the inkjet recording apparatus 1 of the present embodiment is a file in an installable format or an executable format, and can be stored on a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk). provided by being recorded on a computer-readable recording medium such as

Further, the computer program executed by the inkjet recording apparatus 1 of this embodiment may be stored in a computer connected to a network such as the Internet, and may be provided by being downloaded via the network. Further, the computer program executed by the inkjet recording apparatus 1 of this embodiment may be provided or distributed via a network such as the Internet.

Further, the computer program executed by the inkjet recording apparatus 1 of the present embodiment may be configured so as to be pre-installed in a ROM or the like and provided.

Next, image data transfer print processing executed by the control unit 10 of the inkjet recording apparatus 1 will be briefly described. The CPU 11 of the control unit 10 reads and analyzes the image data (print data) in the reception buffer included in the host I/F 16, and the ASIC 15 performs necessary image processing, data rearrangement processing, and the like. Next, the CPU 11 of the controller 10 transfers the image data (print data) processed by the ASIC 15 from the head drive controller 17 to the recording head 20 .

Note that dot pattern data for image output may be generated by, for example, storing font data in the ROM 12, or by developing the image data into bitmap data using a printer driver on the host side, and printing the data onto the inkjet printing apparatus. 1 may be transferred.

Next, characteristic functions of the inkjet recording apparatus 1 will be described. The inkjet recording apparatus 1 of this embodiment has the following features when performing inkjet printing on the recording medium 40, which is a transparent non-penetrable medium.

In short, the inkjet recording apparatus 1 preprints an auxiliary layer, which is an auxiliary layer with auxiliary ink (for example, white ink), on an image layer, which is an image layer formed with ink for image formation. , post-printing, and inter-printing, and speeding up the formation of the auxiliary layer.

Here, FIG. 3 is a plan view showing the nozzle configuration of the recording head 20, and FIG. 4 is a schematic diagram simply showing the colors of each nozzle row. FIG. 3 transparently shows the nozzle rows of the recording head 20 from above. As shown in FIG. 3, the recording head 20 includes a first nozzle group 20a, a second nozzle group 20b, and a third nozzle group 20c.

As shown in FIG. 3, the nozzle groups 20a, 20b, and 20c are arranged in two rows in the main scanning direction and alternately arranged in a zigzag pattern in the sub-scanning direction. That is, the nozzle groups 20a, 20b, and 20c are configured so that the nozzle rows do not overlap from the upstream side to the downstream side in the conveying direction A of the recording medium 40 so that the third nozzle group 20c, the second nozzle group 20b, the third 1 nozzle group 20a. Further, as shown in FIG. 3, the second nozzle group 20b is arranged in a position shifted in the main scanning direction from the first nozzle group 20a and the third nozzle group 20c.

The first nozzle group 20a and the third nozzle group 20c include one row of nozzles for ejecting ink droplets of auxiliary ink (background ink, base ink) and CMY (process color) inks for image formation. and three rows of nozzles for ejecting droplets. Each nozzle row has a nozzle number No. No. 1 nozzle hole to No. 1 nozzle hole. It has 192 nozzle holes of 192 nozzle holes. In the example shown in FIG. 3, each nozzle hole is numbered from the nozzle hole on the downstream side in the conveying direction A of the recording medium 40 toward the nozzle hole on the upstream side. 1 to nozzle number No. 192. The pitch P between these nozzle holes is 150 dpi (dots per inch).

As shown in FIG. 3, a cyan ink nozzle array NC for ejecting cyan (C) ink droplets and a magenta ink nozzle array for ejecting magenta (M) ink droplets to the first nozzle group 20a and the third nozzle group 20c, respectively. It has a nozzle row NM and a yellow ink nozzle row NY for ejecting yellow (Y) ink droplets.

In the second nozzle group 20b as well, each row has a nozzle number No. 1 in the same manner as in the first nozzle group 20a. 1 to nozzle number No. It has four rows of nozzles each having 192 nozzle holes. The pitch P between the nozzle holes of the second nozzle group 20b is 150 dpi as well as the first nozzle group 20a.

The second nozzle group 20b includes nozzle rows for auxiliary recording. Specifically, the second nozzle group 20b includes one row of nozzles for ejecting ink droplets of auxiliary ink (background ink, base ink) and two rows of nozzles for ejecting ink droplets of special colors for image formation. and one row of nozzles for ejecting ink droplets of K (process color) for image formation.

As shown in FIG. 4, the second nozzle group 20b has a nozzle row NW that ejects white (W) ink droplets as an example of auxiliary ink (background ink, base ink). The second nozzle group 20b has a nozzle row NO for ejecting orange (O) ink droplets and a nozzle row NG for ejecting green (G) ink droplets as an example of a special color ink for image formation. ing. Further, the second nozzle group 20b has a nozzle row NK that ejects black (K) ink droplets.

As described above, the nozzle groups 20a, 20b, and 20c have the same number of nozzle rows and the same number of nozzles. Since it can be reduced, the cost of the device can be reduced.

In this embodiment, as shown in FIG. 3, white ink, orange ink, and green ink are described as liquids other than process colors. However, liquids other than process colors are not limited to these. For example, special color inks such as red and blue, silver inks, gold inks, transparent inks, primers, surface protective agents, etc. are applied as necessary. be able to. These inks are used to enhance image quality and add texture.

For example, when printing on a transparent base material, by printing white ink on the base material and then printing ink with a color such as a process color on top of it, a white background can be used on the transparent base material. image can be formed.
Alternatively, an image with a white background when viewed from the substrate side can be formed by printing an ink having a color such as a process color and then printing a white ink thereon.
In addition, by printing ink with a color such as a process color, printing white ink on it, and printing ink with a color such as a process color again on top of it, the side that sees white as a background different images can be formed.

In this embodiment, the nozzle rows of the nozzle groups 20a, 20b, and 20c are arranged along the conveying direction A of the recording medium 40, but the nozzle rows are arranged obliquely to the conveying direction A. may be set.

Examples of the present invention will be described below, but the present invention is not limited to these examples. Unless otherwise specified, ink preparation and evaluation were performed under the conditions of a room temperature of 25° C. and a relative humidity of 60%.

(Preparation Example 1 of Pigment Dispersion)
<Preparation of cyan pigment dispersion>
Materials with the following formulation were mixed and further circulated and dispersed in a disk-type bead mill (manufactured by Shinmaru Enterprises, Model KDL, media: zirconia balls with a diameter of 0.3 mm) for 7 hours to obtain a pigment dispersion ( Pigment solid content 15% by weight).
[Prescription]
Pigment Blue 15:3 (trade name: LIONOL BLUE FG-7351, manufactured by Toyo Ink Co., Ltd.): 15 parts by mass Anionic surfactant (Pionin A-51-B, manufactured by Takemoto Oil Co., Ltd.): 2 parts by mass・Ion-exchanged water: 83 parts by mass

(Preparation Example 2 of Pigment Dispersion)
<Preparation of Magenta Pigment Dispersion>
In Pigment Dispersion Preparation Example 1, Pigment Blue 15:3 (trade name: LIONOL BLUE FG-7351, manufactured by Toyo Ink Co., Ltd.) was added to Pigment Red 122 (trade name: Toner Magenta EO02, manufactured by Clariant Japan Co., Ltd.). A magenta pigment dispersion was prepared in the same manner as in Pigment Dispersion Preparation Example 1 except for the change (pigment solid content: 15% by mass).

(Preparation Example 3 of pigment dispersion)
<Preparation of yellow pigment dispersion>
In Preparation Example 1 of the pigment dispersion, Pigment Blue 15:3 (trade name: LIONOL BLUE FG-7351, manufactured by Toyo Ink Co., Ltd.) was added to Pigment Yellow 74 (trade name: Fast Yellow 531, manufactured by Dainichi Seika Kogyo Co., Ltd.). ), a magenta pigment dispersion was prepared in the same manner as in Pigment Dispersion Preparation Example 1 (pigment solid content: 15% by mass).

(Preparation Example 4 of Pigment Dispersion)
<Preparation of Black Pigment Dispersion>
In Pigment Dispersion Preparation Example 1, Pigment Blue 15:3 (trade name: LIONOL BLUE FG-7351, manufactured by Toyo Ink Co., Ltd.) was changed to a carbon black pigment (trade name: Monarch 800, manufactured by Cabot). A black pigment dispersion was prepared in the same manner as in Pigment Dispersion Preparation Example 1 (pigment solid content: 15% by mass).

(Preparation Example 5 of pigment dispersion)
<Preparation of white pigment dispersion>
25 parts by mass of titanium oxide (trade name: STR-100W, manufactured by Sakai Chemical Industry Co., Ltd.), 5 parts by mass of a pigment dispersant (trade name: TEGO Dispers 651, manufactured by Evonik), and 70 parts by mass of water are mixed, and a bead mill ( zirconia beads with a diameter of 0.3 mm were dispersed at a filling rate of 60% and 8 m/s for 5 minutes in Research Labo, manufactured by Shinmaru Enterprises Co., Ltd. to obtain a white pigment dispersion (pigment solid min 25% by mass).

(Preparation example of urethane resin particle liquid)
<Synthesis of polyester polyol>
While introducing nitrogen into a 0.5 L separable flask, 343 g of BA-2 (ethylene oxide adduct of bisphenol A, manufactured by Nippon Nyukazai Co., Ltd.) and 137 g of dimethyl isophthalate were charged and melted at 130°C. When these melted, 0.14 g of titanium tetraisopropoxide was added, the temperature was raised to 230° C. over 3 to 4 hours while stirring, and the mixture was reacted at 230° C. for 2 to 3 hours. After that, 0.07 g of titanium tetraisopropoxide was added and the mixture was held for 2 hours. Then, introduction of nitrogen was stopped, and reaction was continued under a reduced pressure of 1 kPa for 2 hours to obtain polyester polyol 1. The obtained polyester polyol 1 had a number average molecular weight of 1,646 and a hydroxyl value of 95.6 mgKOH/g.

<Synthesis of urethane resin particle liquid>
In a 0.5 L separable flask equipped with a stirring blade, a thermometer, and a reflux tube, while introducing nitrogen, polyester polyol 1 100 g, 2,2-bis (hydroxymethyl) propionic acid (2,2-dimethylol Propionic acid) 5.4 g, triethylamine 4.1 g, and acetone 78 g were charged and heated to 40° C. to dissolve the raw materials.
Then, 35 g of isophorone diisocyanate and 1 drop of tin (II) 2-ethylhexanoate were added, the temperature was raised to 80° C., and the reaction was allowed to proceed for 4 hours. Thereafter, the temperature was lowered to 40° C., 268 g of water was added to form fine particles, and 2.3 g of diethylenetriamine was further added and reacted for 4 hours. Finally, acetone was removed to obtain a urethane resin emulsion 1 having a solid concentration of 35% by mass.

(Example 1)
<Production of ink set 1>
Ink set 1 was prepared by combining cyan ink, magenta ink, yellow ink, black ink, and white ink prepared as follows.

-Preparation of cyan ink-
Prepared cyan pigment dispersion 11% by mass, prepared urethane resin particle liquid 16% by mass, 1,2-butanediol 20% by mass, 3-methoxy-N,N-dimethylpropionamide 12% by mass, siloxane compound (trade name : FZ2110, manufactured by Dow Toray Co., Ltd., active ingredient concentration 100% by mass) 1% by mass, and the remaining amount of ion-exchanged water is mixed and stirred so that the total is 100% by mass, and filtered through a polypropylene filter with an average pore size of 0.2 μm. By doing so, a cyan ink was prepared. The cyan pigment content in the cyan ink was 1.7% by mass.

- Preparation of magenta ink -
A magenta ink was prepared in the same manner as the cyan ink, except that 11% by weight of the cyan pigment dispersion was changed to 19% by weight of the prepared magenta pigment dispersion.

-Preparation of yellow ink-
A yellow ink was prepared in the same manner as the cyan ink, except that 11% by mass of the cyan pigment dispersion was changed to 19% by mass of the prepared yellow pigment dispersion.

- Preparation of black ink -
A black ink was prepared in the same manner as the cyan ink, except that 11% by mass of the cyan pigment dispersion was changed to 15% by mass of the prepared black pigment dispersion.

-Preparation of white ink-
A white ink was prepared in the same manner as the cyan ink, except that the 11% by mass of the cyan pigment dispersion was changed to 15% by mass of the prepared white pigment dispersion.

(Examples 2-4 and Comparative Examples 1-2)
<Production of ink sets 2 to 6>
In Example 1, the same procedure as in Example 1 was repeated except that the compositions and contents of the cyan ink, magenta ink, yellow ink, black ink, and white ink were changed from Table 2 to the compositions and contents shown in Table 6. , Ink Sets 2-6 of Examples 2-4 and Comparative Examples 1-2 were obtained.

Next, each ink set produced was printed using the inkjet recording apparatus shown in FIG.
Using the inkjet recording device, printing was performed on a polyethylene terephthalate (PET) film (TP-188, manufactured by Kimoto Co., Ltd.).
The liquid ejection unit of the ink jet recording apparatus shown in FIG. 1 has a plurality of nozzle holes for ejecting at least one process color liquid for image formation in the sub-scanning direction perpendicular to the main scanning direction, as shown in FIG. and a plurality of nozzle rows in which a plurality of nozzle holes for ejecting at least one type of liquid different from the process color are arranged in the sub-scanning direction, and each of the nozzle groups includes at least A liquid ejection unit was used in which three or more nozzle rows for ejecting a liquid different from the one process color were arranged in the sub-scanning direction.
"NW", "NC", "NM", and "NY" of the first nozzle group 20a and the third nozzle group 20c use "white ink", "cyan ink", "magenta ink", and "white ink" of each ink set. I used yellow ink.
In the second nozzle group 20b, "NO" is changed to "NW", "NG" is changed to "NK", and "NW" and "NK" use the "white ink" and "black ink" of each ink set. .

<Color unevenness of image>
The output image was a 4C composite image in which the gradation was changed from 100% solid chart to 0%. The 4C composite image was visually observed, and color unevenness of the image was evaluated based on the following criteria. Incidentally, △ or more is the practical usable level. The results are shown in Tables 1 to 6.
[Evaluation criteria]
◎: Color unevenness is not recognized at a distance of less than 30 cm from the image ○: Color unevenness is not recognized at a distance of 30 cm or more and less than 1 m from the image △: Color unevenness is not recognized at a distance of 1 m or more and less than 3 m from the image ×: From the image Color unevenness can be recognized at a distance of 3m or more

Embodiments of the present invention are, for example, as follows.
<1> Nozzle rows in which a plurality of nozzle holes for ejecting at least one type of process color liquid for image formation are provided in the sub-scanning direction perpendicular to the main scanning direction, and at least one type of liquid of a color different from the process color. A plurality of nozzle groups having a nozzle row in which a plurality of nozzle holes for ejecting are arranged in the sub-scanning direction,
An ink set in which the process color liquid includes one type each of cyan ink, magenta ink, yellow ink, and black ink,
The pigment content of each color of the ink set is 2.9% by mass or less,
Each of the nozzle groups is a liquid ejection unit, wherein three or more nozzle rows for ejecting liquid of at least one color different from the process color are arranged in the sub-scanning direction.
<2> In the ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink, the pigment content of the cyan ink is 0.8% by mass or more and 1.5% by mass or less. >.
<3> In the ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink,
The liquid ejection unit according to any one of <1> and <2> above, wherein the relationship in pigment content is such that magenta ink > cyan ink and yellow ink > cyan ink.
<4> The liquid ejection unit according to any one of <1> to <3>, including white ink as the liquid having a color different from the process color.
<5> the liquid ejection unit according to any one of <1> to <4>;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. A control unit that controls so that the auxiliary layer, which is an auxiliary layer to be used, can be arranged as one of preprinting, postprinting, and interprinting;
A liquid ejecting apparatus comprising:
<6> A liquid ejection step of ejecting liquid using the liquid ejection unit according to any one of <1> to <4>;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. a control step for controlling the auxiliary layer, which is an auxiliary layer to be applied, so that it can be arranged as one of preprinting, postprinting, and interprinting;
A printing method comprising:
<7> liquid ejection means comprising the liquid ejection unit according to any one of <1> to <4>;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. a control means for controlling so that the auxiliary layer, which is an auxiliary layer to be printed, can be arranged as one of pre-printing, post-printing, and inter-printing;
A printing apparatus comprising:
<8> An ink set for use in the printing apparatus according to <7>,
The process color liquid is an ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink,
The ink set is characterized in that the pigment content of each color of the ink set is 2.9% by mass or less.
<9> In the ink set containing one kind each of cyan ink, magenta ink, yellow ink, and black ink, the pigment content of the cyan ink is 0.8% by mass or more and 1.5% by mass or less. > is an ink set described in .
<10> In the ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink,
The ink set according to any one of <7> to <10>, wherein the relationship in pigment content is magenta ink>yellow ink.
<11> The ink set according to any one of <7> to <10>, including white ink as the liquid having a color different from the process color liquid.
<12> The ink set according to any one of <7> to <11>, wherein each ink of the ink set contains water, an organic solvent, a coloring material, resin particles, and a siloxane compound.

The liquid ejection unit according to any one of <1> to <4>, the liquid ejection device according to <5>, the printing method according to <6>, the printing apparatus according to <7>, and According to the ink set described in any one of <8> to <12>, it is possible to solve the conventional problems and achieve the object of the present invention.

Reference Signs List 1 inkjet recording apparatus 10 control unit 20 recording head 20a, 20b, 20c nozzle group

JP 2017-105193 A

Claims (8)

A nozzle array having a plurality of nozzle holes for ejecting at least one type of image forming process color liquid in a sub-scanning direction perpendicular to the main scanning direction, and ejecting at least one type of process color liquid different from the process color. a plurality of nozzle groups having a nozzle row in which a plurality of nozzle holes are arranged in the sub-scanning direction;
An ink set in which the process color liquid includes one type each of cyan ink, magenta ink, yellow ink, and black ink,
The pigment content of each color of the ink set is 2.9% by mass or less,
The magnitude relationship of the pigment content satisfies magenta ink, yellow ink > black ink > cyan ink ,
the liquid having a color different from the process color is white ink;
A liquid ejection unit, wherein each of the nozzle groups has three or more nozzle rows arranged in the sub-scanning direction for ejecting liquid of at least one color different from the process color. 2. The ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink, wherein the pigment content of each color in the ink set is 1.0% by mass or more and 2.9% by mass or less. A liquid ejection unit as described. 3. The method of claim 1 or 2, wherein in the ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink, the pigment content of the cyan ink is 0.8% by mass or more and 1.5% by mass or less. A liquid ejection unit according to any one of the above. a liquid ejection unit according to any one of claims 1 to 3;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. A control unit that controls so that the auxiliary layer, which is an auxiliary layer to be used, can be arranged as one of preprinting, postprinting, and interprinting;
A liquid ejection device comprising: a liquid ejection step of ejecting liquid using the liquid ejection unit according to any one of claims 1 to 3;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. a control step for controlling the auxiliary layer, which is an auxiliary layer to be applied, so that it can be arranged as one of preprinting, postprinting, and interprinting;
A printing method comprising: a liquid ejection means comprising the liquid ejection unit according to any one of claims 1 to 3;
An image layer, which is an image layer formed by ejecting a process color liquid for image formation to the nozzle arrays of the liquid ejection unit, is formed by ejecting a liquid of a color different from the process color. a control means for controlling so that the auxiliary layer, which is an auxiliary layer to be printed, can be arranged as one of pre-printing, post-printing, and inter-printing;
A printing device comprising: An ink set used in the printing apparatus according to claim 6,
The process color liquid is an ink set containing one type each of cyan ink, magenta ink, yellow ink, and black ink,
The pigment content of each color of the ink set is 2.9% by mass or less,
The magnitude relationship of the pigment content satisfies magenta ink, yellow ink > black ink > cyan ink,
An ink set, wherein the liquid having a color different from the process color is white ink. 8. The ink set according to claim 7, wherein each ink of said ink set contains water, an organic solvent, a coloring material, resin particles and a siloxane compound.

Images