JP2021147419A - Ink set and inkjet printing apparatus - Google Patents

Abstract

To provide an ink set including dark and light inks, the ink set capable of simultaneously realizing productivity and image quality.SOLUTION: An ink set includes a standard ink and a light ink. The standard ink includes a cyan ink, a magenta ink and a yellow ink. The light ink includes one of a gray ink, a light cyan ink, a light magenta ink and a light yellow ink. The cyan ink has a pigment concentration of 0.75 to 1.8 mass%. The magenta ink and the yellow ink have a pigment concentration of 1.0 to 4.0 times (mass standard) the concentration of the cyan ink.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ink set and an inkjet printing device.

Compared to other recording methods, the inkjet recording method has a simple process, is easy to make into full color, and can obtain high-resolution images even with a device with a simple configuration, so it can be used for personal and office applications. , Is expanding into the field of industrial printing.

In the field of industrial printing, high productivity is required. In the field of sign graphics such as advertisements posted indoors and outdoors, wide inkjet printing equipment is on the market, but there is a high demand for improving productivity. In a wide-width inkjet device, a multi-pass method is generally used in which the head scans in the media width direction (main scanning direction) and the media is conveyed perpendicular to the head scanning direction (sub-scanning direction). In order to improve productivity in the multi-pass method, it is effective to arrange multiple heads in the media transport direction in order to increase the printing area in one pass, but ink droplets are likely to be misaligned. There is a side effect of becoming, and it is an issue to achieve both productivity and image quality.

Patent Document 1 discloses a technique for adjusting the type of ink ejected from a nozzle opening included in a nozzle row of a printer head, with an object of eliminating uneven gloss due to landing deviation in the reciprocating of the head.
Patent Document 2 discloses a method of arranging a plurality of heads and forming an image with light and shade ink.

With the technique disclosed in Patent Document 1, it is not possible to suppress the landing variation between the heads when printing with a plurality of heads.
Further, the technique disclosed in Patent Document 2 is effective in improving image quality, but it is difficult to achieve both in terms of productivity.

An object of the present invention is to provide an ink set that can achieve both productivity and image quality in an ink set containing light and shade ink.

The above problem is solved by the following configuration 1).
1) In an ink set having standard ink and light ink
The standard inks include cyan inks, magenta inks and yellow inks.
The light ink contains any of gray ink, light cyan ink, light magenta ink, and light yellow ink.
An ink set characterized in that the pigment concentration of the cyan ink is 0.75 to 1.8% by mass, and the pigment concentration of the magenta ink and the yellow ink is 1.0 to 4.0 times (mass basis) that of the cyan ink.

According to the present invention, it is possible to provide an ink set that can achieve both productivity and image quality in an ink set containing light and shade ink.

FIG. 1 is a schematic view showing the configuration of an inkjet recording device. FIG. 2 is a block diagram showing a control configuration of the inkjet recording device. FIG. 3 is a plan view showing a nozzle configuration of a recording head.

The ink set of the present invention includes standard ink and light ink, the standard ink includes cyan ink, magenta ink and yellow ink, and the light ink includes gray ink, light cyan ink, light magenta ink and light yellow. It is characterized in that it contains any of the inks, the pigment concentration of the cyan ink is 0.75 to 1.8% by mass, and the pigment concentration of the magenta ink and the yellow ink is 1.0 to 4.0 times (mass basis) of the cyan ink. do.

In the above-mentioned conventional technique, when a wide-width inkjet device in which a plurality of heads are arranged in the sub-scanning direction is used in order to improve productivity, landing deviation occurs between the heads. Color unevenness can be suppressed while maintaining gradation even when printing a large number of drops, and by including light and shade ink, color reproducibility is improved compared to the basic four colors of black ink, cyan ink, magenta ink, and yellow ink only. It turned out to improve.
Since color unevenness is particularly easy to recognize in cyan color, the effect of suppressing color unevenness is high by lowering the density of one dot of cyan ink as described in the above configuration 1). Further, by setting the pigment concentration of magenta ink and yellow ink to 1.0 times or more (mass standard) with respect to cyan ink, it is possible to cover the color reproduction range such as Japan color, and it is possible to achieve both color reproducibility. Further, by setting the pigment concentration of the magenta ink and the yellow ink to 4 times or less (mass standard) with respect to the cyan ink, color unevenness can be suppressed and the image quality can be improved.

Further, in order to further enhance the effect of the present invention, the pigment concentration of cyan ink is 1.0 to 1.4% by mass, and the pigment concentration of magenta ink and yellow ink is 1.5 to 3.0 times (mass basis) the pigment concentration of cyan ink. It is preferable to have.
The pigment concentration of the cyan ink is more preferably 1.2 to 1.4% by mass.
The pigment concentration of the magenta ink and the yellow ink is more preferably 2.0 to 3.0 times (mass basis) the pigment concentration of the cyan ink.

Further, in order to further enhance the effect of the present invention, the pigment concentration of the light ink is preferably 0.2 to 1.0 times (mass standard), and 0.2 to 0.8 times (mass standard) the pigment concentration of the standard ink. Is even more preferable.
The pigment concentration of the light ink is preferably 0.8 to 1.0% by mass.

When the pigment concentration of cyan ink is less than 0.75% by mass, the pigment stays on the surface of the media for non-penetrating media such as PVC and PET and has good color development. Because it is easy, the color development property deteriorates. If the pigment concentration of cyan ink exceeds 1.8% by mass, problems such as color unevenness occur.
Further, in order to suppress color unevenness, it is necessary to set the pigment densities of the magenta ink and the yellow ink with respect to the cyan ink as described above.

Further, in order to further enhance the effect of the present invention, it is preferable that each ink contained in the ink set of the present invention is a water-based ink containing water, and further, each ink contained in the ink set of the present invention is an ejection head. The receding contact angle with respect to the nozzle plate is preferably 30 ° or less. By setting the receding contact angle in this way, it becomes difficult for the ink-repellent film of the nozzle plate to get wet, ejection stability can be ensured, and ink droplet landing accuracy is improved, so that color unevenness can be suppressed.

As described above, the ink set of the present invention has a standard ink and a light ink, and the pigment concentration of the cyan ink contained in the standard ink is 0.75 to 1.8% by mass.
Further, the pigment concentration of the ink other than the cyan ink is preferably 0.75 to 1.8% by mass. Inks other than cyan inks are typically magenta inks and / or yellow inks for standard inks and gray inks, light cyan inks, light magenta inks and / or light yellow inks for light inks. ..

Next, the components of each ink contained in the ink set of the present invention will be described.

<Ink>
Hereinafter, the organic solvent, water, coloring material, resin, additive, etc. used for the ink will be described.

<Organic solvent>
The organic solvent used in the present invention is not particularly limited, and a water-soluble organic solvent can be used. Examples thereof include ethers such as polyhydric alcohols, polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines and sulfur-containing compounds.
Specific examples of the water-soluble organic solvent include, for example, ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, and 1,4-butane. Diore, 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- Polyhydric alcohols such as 1,3-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 Polyhydric alcohol alkyl ethers such as 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. , 1,3-Dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone and other nitrogen-containing heterocyclic compounds, formamide, N-methylformamide, N, N-dimethylformamide, 3-methoxy-N, N- Amidos such as dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide, amines such as monoethanolamine, diethanolamine and triethylamine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate and ethylene carbonate. And so on.
It is preferable to use an organic solvent having a boiling point of 250 ° C. or lower because it not only functions as a wetting agent but also has good drying properties.

Polyol compounds having 8 or more carbon atoms and glycol ether compounds are also preferably used. Specific examples of the polyol compound 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 and ethylene glycol monobenzyl ether can be mentioned.

<Water>
The content of water in the ink is not particularly limited and may be appropriately selected depending on the intended purpose, but from the viewpoint of ink drying property and ejection reliability, it is preferably 10% by mass or more and 90% by mass or less, and 20% by mass. % To 60% by mass is more preferable.

<Color material>
As the pigment, an inorganic pigment or an organic pigment can be used. These may be used alone or in combination of two or more. Moreover, you may use a mixed crystal.
As the pigment, for example, black pigment, yellow pigment, magenta pigment, cyan pigment, white pigment, green pigment, orange pigment, glossy color pigment such as gold or silver, metallic pigment and the like can be used.
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, and thermal method. Can be used.
Examples of organic pigments include azo pigments and polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.). , Dye chelate (for example, basic dye type chelate, acidic dye type chelate, etc.), nitro pigment, nitroso pigment, aniline black and the like can be used. Among these pigments, those having a good affinity with a solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.
As a specific example of the pigment, for black, carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper, iron (CI pigment black 11) , Metals such as titanium oxide, and organic pigments such as aniline black (CI 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 Carmin 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 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 Greens 1, 4, 7, 8, 10, 17, 18, 36, etc.

In order to disperse the pigment to obtain an ink, a method of introducing a hydrophilic functional group into the pigment to obtain a self-dispersing pigment, a method of coating the surface of the pigment with a resin and dispersing it, and a method of dispersing using a dispersant are used. The method, etc. can be mentioned.
As a method of introducing a hydrophilic functional group into a pigment to obtain a self-dispersing pigment, for example, a method of adding a functional group such as a sulfone group or a carboxyl group to a pigment (for example, carbon) so that the pigment can be dispersed in water. Can be mentioned.
Examples of the method of coating the surface of the pigment with a resin and dispersing the pigment include a method of encapsulating the pigment in microcapsules so that the pigment can be dispersed in water. This can be rephrased as a resin coating pigment. In this case, it is not necessary that all the pigments blended in the ink are coated with the resin, and the uncoated pigments and the partially coated pigments are 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 represented by a surfactant.
As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant and the like can be used depending on the pigment.
RT-100 (nonionic surfactant) manufactured by Takemoto Oil & Fat Co., Ltd. and a naphthalene sulfonate Na formalin condensate can also be suitably used as a dispersant.
The dispersant may be used alone or in combination of two or more.

<Pigment dispersion>
It is possible to obtain an ink by mixing a material such as water or an organic solvent with a pigment. It is also possible to produce an ink by mixing a material such as water or an organic solvent with a pigment dispersion obtained by mixing a pigment and other water or a dispersant.
The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and other components as necessary, and adjusting the particle size. It is preferable to use a disperser for dispersion.
The particle size of the pigment in the pigment dispersion is not particularly limited, but the maximum frequency is 20 nm or more in terms of the maximum number because the dispersion stability of the pigment is good and the image quality such as ejection stability and image density is also high. It is preferably 500 nm or less, more preferably 20 nm or more and 150 nm or less. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).
The content of the pigment in the pigment dispersion is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of obtaining good ejection stability and increasing the image density, 0.1 mass is used. % Or more and 50% by mass or less are preferable, and 0.1% by mass or more and 30% by mass or less are more preferable.
If necessary, the pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifuge, or the like.

<Resin>
The type of resin contained in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, etc. Examples thereof include resins, styrene-butadiene resins, vinyl chloride resins, acrylic styrene resins, and acrylic silicone resins.
Resin particles made of these resins may be used. It is possible to obtain ink by mixing resin particles with a material such as a coloring material or an organic solvent in the state of a resin emulsion in which water is dispersed as a dispersion medium. As the resin particles, those synthesized as appropriate may be used, or commercially available products may be used. Further, these may be used alone or in combination of two or more kinds of resin particles.

The volume average particle diameter of the resin particles is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of obtaining good fixability and high image hardness, 10 nm or more and 1,000 nm or less are preferable. More than 200 nm is more preferable, and 10 nm or more and 100 nm or less is particularly preferable.
The volume average particle size can be measured using, for example, a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

The content of the resin is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of fixability and storage stability of the ink, 1% by mass or more and 30% by mass or less with respect to 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, but from the viewpoint of improving image quality such as ejection stability and image density, the maximum frequency in terms of the maximum number of inks. Is preferably 20 nm or more and 1000 nm or less, and 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.).

<Additives>
If necessary, a surfactant, a defoaming agent, an antiseptic / antifungal agent, a rust preventive, a pH adjuster, or the like may be added to the ink.

<Surfactant>
As the surfactant, any of a silicone-based surfactant, a fluorine-based surfactant, an amphoteric surfactant, a nonionic surfactant, and an anionic surfactant can be used.
The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. Among them, those that do not decompose even at high pH are preferable, and examples thereof include side chain modified polydimethylsiloxane, double-ended modified polydimethylsiloxane, single-ended modified polydimethylsiloxane, side chain double-ended modified polydimethylsiloxane, and the like. Those having an oxyethylene group and a polyoxyethylene polyoxypropylene group are particularly preferable because they exhibit good properties as an aqueous surfactant. Further, as the silicone-based surfactant, a polyether-modified silicone-based surfactant can also be used, and examples thereof include a compound in which a polyalkylene oxide structure is introduced into the Si side chain of dimethylsiloxane.
Examples of the fluorine-based surfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate ester compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group in the side chain. A polyoxyalkylene ether polymer compound is particularly preferable because it has a low foaming property. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonic acid salt. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylic acid salt. The polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain includes a sulfate ester salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain and a perfluoroalkyl ether group in the side chain. Examples thereof include salts of polyoxyalkylene ether polymers. The counter ions of the salts in these fluorine-based surfactants are Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH). _3rd grade can be mentioned.
Examples of amphoteric surfactants include laurylaminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.
Examples of the nonionic surfactant include polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkyl amine, polyoxyethylene alkyl amide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, and polyoxyethylene sorbitan. Examples thereof include a fatty acid ester and an ethylene oxide adduct of acetylene alcohol.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, salt of polyoxyethylene alkyl ether sulfate, and the like.
These may be used alone or in combination of two or more.

The content of the surfactant in the ink is not particularly limited and may be appropriately selected depending on the intended purpose. However, 0.001 mass is obtained from the viewpoint of excellent wettability and ejection stability and improvement in image quality. % Or more and 5% by mass or less are preferable, and 0.05% by mass or more and 5% by mass or less are more preferable.

<Defoamer>
The defoaming agent is not particularly limited, and examples thereof include a silicone-based defoaming agent, a polyether-based defoaming agent, and a fatty acid ester-based defoaming agent. These may be used alone or in combination of two or more. Among these, a silicone-based defoaming agent is preferable because it has an excellent defoaming effect.

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

<Rust inhibitor>
The rust preventive is not particularly limited, and examples thereof include acidic sulfites and sodium thiosulfate.

<pH adjuster>
The pH adjusting agent is not particularly limited as long as the pH can be adjusted to 7 or more, and examples thereof include amines such as diethanolamine and triethanolamine.

The physical characteristics of the ink are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the viscosity, surface tension, pH and the like are preferably in the following ranges.
The viscosity of the ink at 25 ° C. is preferably 5 mPa · s or more and 30 mPa · s or less, 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 the viscosity, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. As the measurement conditions, it is possible to measure at 25 ° C. with a standard cone rotor (1 ° 34'x R24), a sample liquid volume of 1.2 mL, a rotation speed of 50 rpm, and 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 preferably leveled on the recording medium and the drying time of the ink is shortened.
The pH of the ink is preferably 7 to 12, more preferably 8 to 11, from the viewpoint of preventing corrosion of the metal member in contact with the liquid.

<Recording medium>
The recording medium is not particularly limited, and plain paper, glossy paper, special paper, cloth, or the like can be used, but good image formation can be achieved even if a non-permeable base material is used.
The non-permeable base material is a base material having a surface having low water permeability and low absorbability, and includes a material that does not open to the outside even if there are many cavities inside, and more quantitatively. , A base material having a water absorption amount of 10 mL / m ² or less from the start of contact to 30 msec ^{1/2 in the Bristow method.}
As the non-permeable base material, for example, a plastic film such as a vinyl chloride resin film, a polyethylene terephthalate (PET) film, polypropylene, polyethylene, or a polycarbonate film can be preferably used.

<Recorded material>
The ink recording material of the present invention comprises an image formed by using the ink of the present invention on a recording medium.
It can be recorded by an inkjet recording device and an inkjet recording method to obtain a recorded material.

The use of the ink of the present invention is not particularly limited and can be appropriately selected depending on the intended purpose, and can be applied to, for example, printed matter, paint, coating material, base material and the like. Further, it can be used not only as an ink to form two-dimensional characters and images, but also as a three-dimensional modeling material for forming a three-dimensional three-dimensional image (three-dimensional model).
A known three-dimensional modeling device can be used for modeling the three-dimensional object, and the device is not particularly limited, but for example, an device provided with ink accommodating means, supply means, ejection means, drying means, and the like is used. be able to. The three-dimensional model includes a three-dimensional model obtained by overcoating with ink. In addition, a molded product obtained by processing a structure in which ink is applied on a base material such as a recording medium is also included. The molded product is, for example, a recorded material or structure formed in a sheet shape or a film shape, which has been subjected to molding processing such as heat stretching or punching, and is, for example, an automobile, OA equipment, or electricity. -Suitably used for molding after decorating the surface of electronic devices, meters of cameras, panels of operation parts, etc.

In addition, image formation, recording, printing, printing, etc. in the terms of the present invention are all synonymous.
Recording media, media, and printed matter are all synonymous.

<Inkjet recording device>
FIG. 1 is a schematic view showing the configuration of the inkjet recording device 1. The inkjet recording device 1 which is a liquid ejection device is a serial type inkjet recording device. As shown in FIG. 1, the inkjet recording device 1 includes an image forming unit 2 for printing a required image, a drying device 3, a roll media storage unit 4, and a conveying mechanism 5. The roll media storage unit 4 stores the roll media (recording media) 40. 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-penetrating medium such as PVC (vinyl chloride) or PET (polyethylene terephthalate) film, or a penetrating 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 the transport path 54 of the recording medium 40. The nip roller 51 is provided on the front side (upstream side in the transport direction A) of the image forming portion 2. The nip roller 51 rotates with the drive of the motor M (see FIG. 2) to convey the sandwiched recording medium 40 toward the image forming unit 2. Further, the take-up roller 53 winds up the printing media 40 after printing by rotating with the drive of the motor M. The driven roller 52 rotates following the transportation of the recording medium 40.

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

That is, the recording media 40 stored in the roll media storage unit 4 is conveyed to the image forming unit 2 by the rotation of the nip roller 51 via the driven roller 52. The recording medium 40 that has reached the image forming unit 2 is printed with a required image by the image forming unit 2. Then, the recording medium 40 after printing is taken up by the rotation of the take-up roller 53.

The image forming unit 2 includes a carriage 21. The carriage 21 is slidably held by a guide rod (guide rail) 22. The carriage 21 moves on the guide rod (guide rail) 22 in a direction (main scanning direction) orthogonal to the transport direction A of the recording medium 40 as the motor M is driven. More specifically, the carriage 21 is located in a recording area that can be printed by the image forming unit 2 on the recording medium 40 conveyed by the conveying mechanism 5 in the main scanning area that is a movable area in the main scanning direction. Move back and forth.

The carriage 21 is equipped with a recording head 20 in which a plurality of nozzle holes, which are discharge ports for discharging droplets, are arranged. The recording head 20 integrally includes a tank for supplying ink to the recording head 20. However, the recording head 20 is not limited to the one provided with the tank integrally, and may be provided with the tank separately. The recording head 20 functions as a liquid ejection unit, and is a process color recording liquid such as black (K), yellow (Y), magenta (M), cyan (C), gray ink (G), and light. Ink droplets of each color of yellow (LY), light magenta (LM), and light cyan (LC) are ejected. Black (K), yellow (Y), magenta (M), cyan (C), gray ink (G), light yellow (LY), light magenta (LM), and light cyan (LC) are inks for image formation. be.

The image forming unit 2 includes a platen 23 that supports the recording medium 40 below the recording head 20 when printing on the recording head 20.

Further, the image forming unit 2 includes an encoder sheet for detecting the main scanning position of the carriage 21 along the main scanning direction of the carriage 21. Further, the carriage 21 includes 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 includes a sensor 24 that optically detects an end portion of the recording medium 40 as the carriage 21 moves. The detection signal by the sensor 24 is used to calculate the position of the end portion 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, for example, electric heaters using ceramic or nichrome wire.

The preheater 30 is provided upstream of the image forming unit 2 in the transport direction A of the recording medium 40. The preheater 30 preheats the recording medium 40 conveyed by the transfer 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 are landed.

The drying heater 32 is provided downstream of the image forming unit 2 in the transport direction A of the recording medium 40. The drying heater 32 continuously heats the recording medium 40 printed by the image forming unit 2 to promote the drying of the landed ink droplets.

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

By mounting such a drying device 3, the inkjet recording device 1 can adopt a non-penetrating medium such as vinyl chloride, PET, or acrylic that does not soak in ink as the recording medium 40.

In the inkjet recording device 1 that ejects ink from the recording head 20 to form an image while the carriage 21 reciprocates to the width of the recording medium 40, ink is ejected only when the carriage operation is the outward path to output an image. There are one-way printing to form and two-way printing in which the carriage operation ejects ink on both the outward and return paths to form an image. In the inkjet recording apparatus 1, bidirectional printing, which is advantageous in terms of printing speed, is mainly used. Here, the operation of ejecting ink from the recording head 20 while the carriage 21 moves in the main scanning direction is defined as one scan.

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

As shown in FIG. 2, the inkjet recording device 1 includes a control unit 10 that controls the entire device. The control unit 10 comprises a CPU (Central Processing Unit) 11 as a control main body, 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. The ROM 12 stores computer programs and other fixed data executed by the CPU 11. The RAM 13 temporarily stores image data and the like. The memory 14 is a rewritable non-volatile memory for holding data even while the power supply of the inkjet recording device 1 is cut off. The ASIC 15 executes image processing for performing various signal processing and sorting on image data, and other input / output signal processing for controlling the entire device.

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

The host I / F 16 transmits and receives image data (print data) and control signals to and from the host side via a cable or a network. Examples of the host connected to the inkjet recording device 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.

The I / O 19 inputs detection pulses from the encoder 26 and the wheel encoder 55. In addition, the I / O 19 connects various sensors 25 such as a humidity sensor, a temperature sensor, and other sensors in addition to the sensor 24. 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 unit 17 transfers the image data as serial data. Further, the head drive control unit 17 generates a transfer clock and a latch signal necessary for transferring image data and confirming the transfer, and a drive waveform used when ejecting droplets 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 unit 18 drives the motor M. 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 the detection pulse from the wheel encoder 55. Then, the motor control unit 18 drives the motor M based on the calculated control value via the internal motor drive circuit.

Further, the control unit 10 includes a heater control unit 8 and a hot air fan control unit 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 are set to the set temperatures. More specifically, when the heater control unit 8 controls the heaters 30, 31, 32, the heater control unit 8 acquires temperature information by the temperature sensors provided in the heaters 30, 31, 32. Then, the heater control unit 8 controls so that the temperature of each of the heaters 30, 31, and 32 becomes the set temperature while monitoring the temperature of each of the heaters 30, 31, and 32. When a heater is provided on the tank of the recording head 20 or the ink path, the heater control unit 8 controls this heater in the same manner.

The hot air fan control unit 9 controls the output of the hot air fan 33 so that air is blown 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 device 1.

The control unit 10 comprehensively controls each unit by expanding the computer program read from the ROM 12 (or the memory 14) by the CPU 11 into the RAM 13 and executing the computer program. More specifically, the CPU 11 reads the control content set for each print mode from the ROM 12 (or the memory 14) based on the print mode set from the operation panel 60. Then, the CPU 11 controls each unit based on the control content read from the ROM 12 (or the memory 14).

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 is a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk). It is recorded and provided on a computer-readable recording medium such as.

Further, the computer program executed by the inkjet recording device 1 of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading via the network. Further, the computer program executed by the inkjet recording device 1 of the present 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 to be provided by incorporating it into a ROM or the like in advance.

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

Note that the dot pattern data for image output may be generated by storing the font data in the ROM 12, for example, or expanding the image data into bitmap data by the printer driver on the host side and using the inkjet recording device 1 for the generation of the dot pattern data. You may try to transfer it.

Next, the characteristic functions of the inkjet recording device 1 will be described. The inkjet recording device 1 of the present embodiment has the following features when inkjet printing is performed on the recording medium 40, which is a transparent non-penetrating medium.

In short, the inkjet recording apparatus 1 preprints an auxiliary layer, which is an auxiliary layer of an auxiliary ink (for example, white ink), with respect to an image layer, which is an image layer formed of an image forming ink. -It is possible to arrange it as a post-print or an inter-print, and to speed up the formation of an auxiliary layer.

Here, FIG. 3 is a plan view showing a nozzle configuration of the recording head 20. FIG. 3 shows the nozzle row of the recording head 20 transparently from the upper surface. 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 staggered pattern in the sub-scanning direction. That is, the nozzle groups 20a, 20b, and 20c have the third nozzle group 20c, the second nozzle group 20b, and the second nozzle group 20b so that the nozzle rows do not overlap from the upstream side to the downstream side in the transport direction A of the recording medium 40. One nozzle group 20a is arranged in this order. Further, as shown in FIG. 3, the second nozzle group 20b is arranged so as to be displaced from the first nozzle group 20a and the third nozzle group 20c in the main scanning direction.

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

As shown in FIG. 3, the first nozzle group 20a and the third nozzle group 20c have a cyan ink nozzle row NC for ejecting cyan (C) ink droplets and a magenta for ejecting magenta (M) ink droplets, respectively. It has an ink nozzle row NM, a yellow ink nozzle row NY that ejects yellow (Y) ink droplets, and a black ink nozzle row NK that ejects black (K) ink droplets. Further, in the second nozzle group 20b, a gray ink nozzle row G for ejecting gray (G) ink droplets, a light cyan ink nozzle row LC for ejecting light cyan (LC) ink droplets, and a light magenta (LM). It has a light magenta ink nozzle row LM for ejecting ink droplets of the above, and a light yellow ink nozzle row LY for ejecting light yellow (LY) ink droplets.

In the second nozzle group 20b, as in the first nozzle group 20a, each row has a nozzle number No. Nozzle number No. from 1 It has four rows of nozzles with 192 192 nozzle holes. Similarly to the first nozzle group 20a, the pitch P between the nozzle holes of the second nozzle group 20b is 150 dpi.

As described above, since each nozzle group 20a, 20b, 20c has the same number of nozzle rows and the same number of nozzles, each nozzle group 20a, 20b, 20c can be composed of the same parts, so that the component types can be changed. Since the number can be reduced, the cost of the device can be reduced.

In the present embodiment, the nozzle rows of the nozzle groups 20a, 20b, and 20c are arranged along the transport direction A of the recording medium 40, but the nozzle rows are arranged diagonally with respect to the transport direction A. It may be installed.

As described above, the inkjet recording device 1 has a liquid ejection unit including an ejection head for ejecting an ink set containing cyan ink, magenta ink, yellow ink, and light ink, and the liquid ejection unit is a liquid ejection unit of each of the inks. It is provided with a nozzle array in which four or more nozzle holes for discharging each are arranged in the sub-scanning direction orthogonal to the main scanning direction. The light ink can be gray ink, light cyan ink, light magenta ink and / or light yellow ink as described above.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. Unless otherwise specified, Examples (preparation, evaluation, etc.) were carried out under the conditions of room temperature of 25 ° C. and relative humidity of 60%.

(Preparation of pigment dispersion)
<Preparation of cyan pigment dispersion>
A cyan pigment dispersion was obtained in the same manner as in the method described in − Method A− of [Pigment Surface Modification Treatment] of JP2012-207202A.
Specifically, C.I. I. Pigment Blue 15: 3 (trade name: Chromofine Blue, manufactured by Dainichiseika Kogyo Co., Ltd.), 20 mmol of the compound of the following structural formula (5), and 200 mL of ion-exchanged water under a room temperature environment with a Silverson mixer (6,000 rpm). (0.6% by mass)) to obtain a slurry. If the pH of the resulting slurry is higher than 4, 20 mmol of nitric acid is added. After 30 minutes, sodium nitrite (20 mmol) dissolved in a small amount of ion-exchanged water was slowly added to the slurry. Further, the mixture was heated to 60 ° C. with stirring and reacted for 1 hour. The C.I. I. A modified pigment having the compound of the following structural formula (5) added to the surface of Pigment Blue 15: 3 was obtained. Then, the pH was adjusted to 10 with an aqueous NaOH solution to obtain a modified pigment dispersion after 30 minutes. Ultrafiltration using a dialysis membrane is performed using the modified pigment dispersion and ion-exchanged water, and further ultrasonic dispersion is performed to have a bisphosphonic acid group as a hydrophilic functional group having a pigment concentration of 15% by mass. A cyan pigment dispersion (self-dispersed type) was obtained.
Structural formula (5)

(Preparation of pigment dispersion)
<Preparation of magenta pigment dispersion>
In the preparation of the cyan pigment dispersion, C.I. I. Pigment Blue 15: 3 20g C.I. I. Pigment Red 122 (trade name: Toner Magenta EO02, manufactured by Clariant Japan Co., Ltd.) was changed to 20 g, and a magenta pigment dispersion having a pigment concentration of 15% by mass was prepared in the same manner as in the preparation of the cyan pigment dispersion. ..

(Preparation of pigment dispersion)
<Preparation of yellow pigment dispersion>
In the preparation of the cyan pigment dispersion, C.I. I. Pigment Blue 15: 3 20g C.I. I. Pigment Yellow 74 (trade name: First Yellow 531; manufactured by Dainichiseika Kogyo Co., Ltd.) A yellow pigment dispersion having a pigment concentration of 15% by mass was prepared in the same manner as in the preparation of the cyan pigment dispersion, except that the pigment was changed to 20 g. Made.

<Preparation of black pigment dispersion>
In the preparation of the cyan pigment dispersion, C.I. I. A black pigment dispersion having a pigment concentration of 15% by mass was prepared in the same manner as in the preparation of the cyan pigment dispersion except that 20 g of Pigment Blue 15: 3 was changed to 20 g of carbon black (NIPEX160, manufactured by Degussa).

(Example 1)
Cyan pigment dispersion 7% by mass, 1.3-butanediol (trade name: 1,3-butanediol, manufactured by Daicel Chemical Co., Ltd.) 20% by mass, 3-methoxy-N, N-dimethylpropionamide (trade name:) Equamid M-100, manufactured by Idemitsu Kosan Co., Ltd.) 10% by mass, diethylene glycol diethyl ether (trade name: Highsolve EDE, manufactured by Toho Chemical Industry Co., Ltd.) 5% by mass, triethylene glycol butylmethyl ether (trade name: Highsolve BTM, manufactured by Toho Chemical Industry Co., Ltd.) Polycarbonate urethane resin particle solution (solid content concentration: 30% by mass) containing 5% by mass, siloxane compound (trade name: FZ2110, manufactured by Toray Dow) 1% by mass, and ion-exchanged water. The remaining amount (100% by mass in total) was mixed and stirred, and then filtered through a membrane filter (trade name: DISMIC-25cs, manufactured by Advantech) having an average pore size of 0.8 μm to obtain cyan ink (C).

Black ink (K) was obtained in the same manner as in cyan ink 1 except that 7% by mass of the cyan pigment dispersion was changed to 15% by mass of the black pigment dispersion.

Gray ink (G) was obtained in the same manner as in cyan ink 1 except that 7% by mass of the cyan pigment dispersion was changed to 5% by mass of the black pigment dispersion.

Light cyan ink (LC) was obtained in the same manner as in cyan ink 1 except that 7% by mass of the cyan pigment dispersion was changed to 5% by mass of the cyan pigment dispersion.

Magenta ink (M) was obtained in the same manner as cyan ink 1 except that 7% by mass of the cyan pigment dispersion was changed to 21% by mass of the magenta pigment dispersion.

Light magenta ink (LM) was obtained in the same manner as cyan ink 1 except that 7% by mass of the cyan pigment dispersion was changed to 5% by mass of the magenta pigment dispersion.

A yellow ink (Y) was obtained in the same manner as in cyan ink 1 except that 7% by mass of the cyan pigment dispersion was changed to 15% by mass of the yellow pigment dispersion.

Light yellow ink (LY) was obtained in the same manner as in cyan ink 1 except that 7% by mass of the cyan pigment dispersion was changed to 5% by mass of the yellow pigment dispersion.
In this way, the ink set of Example 1 was obtained.

(Examples 2 to 8 and Comparative Examples 1 to 4)
In Example 1, the same as in Example 1 except that the compositions and contents of the cyan, light cyan, magenta, light magenta, yellow, and light yellow inks were changed as shown in Tables 1 to 5. , Examples 2 to 8 and Comparative Examples 1 to 4 were obtained.

Next, printing was performed using the ink sets shown in each table and the inkjet recording apparatus 1 of FIG. The inkjet recording device 1 is equipped with the recording head shown in FIG.
The recording medium was PVC (trade name: GIY-11Z5, manufactured by Lintec Corporation) or cloth (trade name: SS8000, manufactured by Seiren Co., Ltd.). The printing speed is 25 m ² / h (the printing speed is listed in the productivity column in each table).
In the prepared image, "color unevenness of the image", "gamut volume", and "backward contact angle" were evaluated. The results are shown in Tables 1-5.

<Image color unevenness>
Black ink, cyan ink, magenta ink and yellow ink were used as standard inks, and gray ink, light cyan, light yellow and light magenta inks were used as light inks to form a composite image. The output image changed the gradation from 100% solid chart to 0%. The evaluation was performed visually and judged according to the following criteria.
⊚: Color unevenness is not recognized when visually observed at a distance of 30 cm from the image.
〇 ... Color unevenness is not recognized when visually viewed at a distance of 1 m from the image, but color unevenness is recognized when approaching a distance of 30 cm from the image.
Δ: Color unevenness is not recognized when visually viewed at a distance of 3 m from the image, but color unevenness is recognized when approaching a distance of 1 m from the image.
X ... Color unevenness is recognized when visually observed at a distance of 3 m from the image.
◎, ○, △ Evaluation is passed.

<Gamut volume>
An evaluation chart was output and evaluation was performed using I-One Isis 2 (manufactured by XRITE). The larger the value of the gamut volume, the better the color reproducibility.

<Backward contact angle>
On the surface of the nozzle plate taken out from the image forming apparatus (IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.), 2 inks shown in Tables 1 to 5 were applied from a syringe equipped with a syringe needle having an inner diameter of 0.37 μm in an environment of 25 ° C. The receding contact angle (°) at 25 ° C. was measured by an automatic contact angle measuring device (DSA25, manufactured by KRUSS) by an extrusion and contraction method of .5 μL.

From the results in each table, it was found that the ink sets of each example were excellent in color unevenness and color reproducibility without impairing productivity.

1 Inkjet recording device 2 Image forming unit 3 Drying device 4 Roll media storage unit 5 Conveying mechanism 8 Heater control unit 9 Warm air fan control unit 10 Control unit 11 CPU
12 ROM
13 RAM
14 memory 15 ASIC
16 Host interface 17 Head drive control unit 18 Motor control unit 19 I / O
20 Recording head 20a, 20b, 20c Nozzle group 21 Carriage 22 Guide rod 23 Platen 24 Sensor 25 Sensor 26 Encoder 30 Preheater 31 Platen heater 32 Drying heater 33 Warm air fan 40 Recording media 51 Nip roller 52 Driven roller 53 Winding roller 54 Conveyance Path 55 Wheel encoder 60 Operation panel

Japanese Unexamined Patent Publication No. 2004-314352 Japanese Patent No. 4222325

Claims (6)

In an ink set with standard ink and light ink,
The standard inks include cyan inks, magenta inks and yellow inks.
The light ink contains any of gray ink, light cyan ink, light magenta ink, and light yellow ink.
An ink set characterized in that the pigment concentration of the cyan ink is 0.75 to 1.8% by mass, and the pigment concentration of the magenta ink and the yellow ink is 1.0 to 4.0 times (mass basis) that of the cyan ink. The ink according to claim 1, wherein the cyan ink has a pigment concentration of 1.0 to 1.4% by mass, and the magenta ink and the yellow ink have a pigment concentration of 1.5 to 3.0 times (mass basis) the pigment concentration of the cyan ink. set. The ink set according to claim 1, wherein the pigment concentration of the light ink is 0.2 to 1.0 times (mass basis) the pigment concentration of the standard ink. The ink set according to any one of claims 1 to 3, which contains water in the ink. The ink set according to claim 1, wherein the back contact angle of the ink with respect to the nozzle plate is 30 ° or more. In an inkjet printing apparatus having a liquid ejection unit having an ejection head for ejecting an ink set containing cyan ink, magenta ink, yellow ink, and light ink.
The liquid ejection unit includes a nozzle array in which four or more nozzle holes for ejecting each of the inks are arranged in the sub-scanning direction orthogonal to the main scanning direction.
An inkjet printing apparatus in which the ink set is the ink set according to any one of claims 1 to 5.

Images