JP5636951B2 - Pigment ink, ink jet recording apparatus, and ink jet recording method - Google Patents

Description

  The present invention relates to a pigment ink, an ink jet recording apparatus, and an ink jet recording method.

  2. Description of the Related Art Conventionally, ink for ink jet recording has been strongly demanded to increase the speed and quality of image formation.

  For example, Patent Document 1 discloses a static surface tension of ejected ink for the purpose of ensuring ink ejection stability even at high-speed output and suppressing the occurrence of satellites during ink ejection to prevent image degradation. And an ink jet image recording method in which the dynamic surface tension (surface tension in a minute time) of ink at the time of ink droplet formation by ejection is set within a predetermined range.

JP 2008-1003 A

  However, when the recording method disclosed in Patent Document 1 is implemented, there arises a problem that the generation of satellites may not be suppressed yet. Therefore, there is still a need for an ink, an ink jet recording apparatus, and an ink jet recording method that can stably achieve high speed and high quality image formation.

  Accordingly, an object of the present invention is to provide a pigment ink capable of suppressing the generation of satellites and forming a high-quality image at high speed, and an ink jet recording apparatus and an ink jet recording method using the same.

  In order to solve the above problems, the present inventors first examined in detail the mechanism by which satellites are generated.

  A soap bubble dissolves a surfactant in water to reduce the surface tension of the water, so that the water easily becomes a film, and as a result, a large soap bubble is easily formed. It is presumed that the tailing (threading) of the ink ejected by the ink jet method is the same mechanism. When the surface tension of the ink is low, the tail of the ejected ink becomes long, and this long tail is separated into two or more droplets composed of a main droplet and a satellite droplet during the flight of the ink. Then, as a result of these adhering to a recording medium such as paper, the image is disturbed. Thus, the present inventors have found that there is a relationship that satellites are easily generated when the surface tension of the ink is low.

  Subsequently, the present inventors examined factors that cause satellites in the recording method disclosed in Patent Document 1.

  In this recording method, the surface tension of the ink is increased in order to suppress the generation of satellites. This itself is one means for suppressing the generation of satellites as described above. However, when the surface tension of the ink is increased, the permeability of the ink into the recording medium is deteriorated. If the penetrability deteriorates, the ink is kept wet on the recording medium, so that the ink adheres to the medium conveying roller (paper conveying roller) of the recording apparatus, and image defects such as bleeding (bleeding) occur. Or the recorded matter is likely to adhere to the hand.

  As described above, the recording method disclosed in Patent Document 1 simply employs a means for simply increasing the surface tension of the ink with the intention of suppressing satellites, and accompanying the adoption of that means. It has been found that no solution is shown for newly occurring problems.

  Subsequently, the present inventors examined factors that cause satellites in addition to the surface tension of the ink.

  For example, the viscosity of the ink can be cited as a factor for generating satellites. When sugar is added to the soap liquid to increase the liquid viscosity (film strength), large soap bubbles can be formed. In addition, a liquid having a high viscosity such as honey or an adhesive is inferior in fluidity of the liquid, and will elongate for a long time. It is presumed that the trailing mechanism of ink ejected by the ink jet method is the same mechanism. When the viscosity of the ink is high, as in the case where the surface tension of the ink is low, the long tail of the ink droplet separates into two or more droplets during the flight of the ink, resulting in a distorted image.

  Thus, the present inventors have found that satellites are easily generated even when the viscosity of the ink is high.

  In view of the above findings, it is conceivable to reduce the viscosity of the ink. However, it is more difficult to reduce the viscosity of the ink in order to suppress the generation of satellites because the ink having an excellent function contains a large amount of various additives. In particular, if the water content is relatively low as a result of increasing the colorant concentration in order to reduce the ink droplets for the purpose of improving the image quality, the water content is relatively decreased, or the water content is used for the purpose of improving the quick drying property or suppressing the curling. When the amount is suppressed, the viscosity of the ink increases.

  As described above, the inventors simply added various additives to increase the viscosity of the ink when trying to impart an excellent function to the ink, thereby causing satellites to be generated. It has been found that it is difficult to suppress the occurrence of.

  Moreover, high-speed recording can be cited as a factor in which satellites are easily generated. High-speed recording refers to recording (relative speed of 0.5 m / s or more) with a high relative speed of movement when ink is ejected onto the recording medium while at least one of the inkjet head and the recording medium is moving. means. When satellites are generated in the ejected ink during high-speed recording, the deviation of the landing (adhesion) position between the main droplets and the satellite droplets increases, and the satellites stand out in the recorded matter. In recording at low speed, that is, recording with a small relative speed of movement (relative speed less than 0.5 m / s), the landing positions of the main droplet and the satellite droplet are hardly shifted even if satellites are generated. For this reason, satellites are not particularly problematic in recording at low speed (the influence of satellites is not noticeable in recorded matter). However, a decrease in the landing accuracy of ejected ink in high-speed recording, particularly the generation of satellites, is a serious problem because it is very conspicuous in the recorded matter.

  As described above, the present inventors have found that when conventional ink is used, satellites are likely to be generated particularly in high-speed recording, so that the landing accuracy is lowered and deterioration in image quality is unavoidable.

  Based on the above knowledge, as a result of further studies by the present inventors, it has been found that the above problems can be solved by the pigment ink containing a predetermined component as a surfactant and a pH adjuster, The present invention has been completed.

That is, the present invention is as follows.
[1]
A pigment ink comprising 2-ethyl-1,3-hexanediol, an unsaturated fatty acid, an amino acid, an alkali metal hydroxide, and an amine.
[2]
The pigment ink according to [1], wherein the unsaturated fatty acid includes oleic acid.
[3]
The pigment ink according to [1] or [2], wherein the amino acid contains at least one of trimethylglycine and dimethylglycine.
[4]
The pigment ink according to any one of [1] to [3], wherein the alkali metal hydroxide includes one or more selected from the group consisting of potassium hydroxide, sodium hydroxide, and lithium hydroxide.
[5]
The pigment ink according to any one of [1] to [4], wherein the amine contains at least one of triethanolamine and tripropanolamine.
[6]
The pigment according to any one of [1] to [5], comprising an acid alkali salt consisting of at least one of the unsaturated fatty acid and the amino acid, and at least one of the alkali metal hydroxide and the amine. ink.
[7]
The pigment ink according to [6], wherein the acid alkali salt is at least one selected from the group consisting of potassium oleate, tripropanolamine oleate, triethanolamine oleate, and amino acid potassium.
[8]
An inkjet recording apparatus comprising an inkjet head that ejects the pigment ink according to any one of [1] to [7] while moving at a relative speed of 0.5 m / s or more with respect to a recording medium.
[9]
An inkjet recording method comprising an ejection step of ejecting the pigment ink according to any one of [1] to [7] from an inkjet head that moves at a relative speed of 0.5 m / s or more with respect to a recording medium.

1 is a perspective view illustrating a configuration of a printer according to an embodiment of the present invention. It is the schematic which shows the arrangement | sequence of the nozzle provided in the inkjet head in embodiment of this invention. It is a fragmentary sectional view showing an internal configuration of an ink jet head in an embodiment of the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. In addition, this invention is not restrict | limited to the following embodiment, A various deformation | transformation can be implemented within the range of the summary.

  In this specification, “ejection stability” refers to the property of ejecting ink droplets from nozzles that are always stable without clogging of the nozzles. “Attack” refers to a phenomenon in which a material constituting a recording head, an ink flow path, or the like in a recording apparatus is dissolved, expanded, cracked, or roughened.

[Pigment ink]
The pigment ink according to an embodiment of the present invention includes 2-ethyl-1,3-hexanediol and an unsaturated fatty acid, and includes an amino acid, an amine, and an alkali metal hydroxide.

  As described above, the significance of the pigment ink of the present embodiment including the above five types of components as essential components will be described below.

  2-Ethyl-1,3-hexanediol is a surfactant excellent in ink permeability to a recording medium (for example, paper), ink drying properties, and ink ejection properties. On the other hand, even when 2-ethyl-1,3-hexanediol is used, there is a problem that the tailing of the ejected ink does not become so short that no satellite is generated.

  First, unsaturated fatty acids are used for the purpose of eliminating the above-mentioned problems in 2-ethyl-1,3-hexanediol. Unsaturated fatty acids are significantly different from 2-ethyl-1,3-hexanediol in molecular structure. When 2-ethyl-1,3-hexanediol and an unsaturated fatty acid are used in combination as a surfactant, the arrangement between the surfactant molecules is disturbed on the surface of the ejected ink due to steric hindrance caused by a significant structural difference. Therefore, it is estimated that the film strength of the ink is lowered. Since the ink tailing is generated due to the high film strength, it is presumed that, as a result, the stringing of the ejected ink is shortened and the satellite can be significantly suppressed.

  Secondly, unsaturated fatty acids are used for pH adjustment purposes with amino acids, amines, and alkali metal hydroxides. Unsaturated fatty acids are oxidizable and unstable components. Therefore, by using this unstable unsaturated fatty acid by utilizing the pH buffering effect of four kinds of acid alkalis including the unsaturated fatty acid itself, it is possible to suppress the generation of satellites over a long period of time. Make long-term stability good.

  As described above, the amino acid, amine, and alkali metal hydroxide are components that exhibit a pH buffering effect as an acid alkali together with the unsaturated fatty acid described above.

  Hereinafter, components that are or can be included in the pigment ink will be described.

[Pigment]
The pigment ink of this embodiment contains a pigment as a color material. Examples of the pigment include, but are not limited to, C.I. I. Pigment Yellow 1,3,12,13,14,17,24,34,35,37,42,53,55,74,81,83,95,97,98,100,101,104,108,109, 110, 117, 120, 128, 138, 150, 153, 155, 174, 180, 198, C.I. I. Pigment Red 1,3,5,8,9,16,17,19,22,38,57: 1,90,112,122,123,127,146,184,202,209, C.I. I. Pigment violet 1,3,5: 1,16,19,23,38, C.I. I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, C.I. I. Pigment Black 1, 7, etc. can be used.

  In these pigments, a dispersibility-imparting group (at least one of a hydrophilic functional group and a salt thereof) is bonded to the pigment surface directly or indirectly through an alkyl group, an alkyl ether group, an aryl group, or the like. As a pigment dispersion that is processed as a self-dispersing pigment that is dispersed or dissolved in an aqueous medium without a dispersant and dispersed in an aqueous medium, or as a pigment dispersion that is dispersed in an aqueous medium by a dispersant. The pigment ink is preferably blended. Examples of the dispersant include a styrene-acrylic acid copolymer resin, and those having a molecular weight of about 10,000 to 150,000 are preferable from the viewpoint of stably dispersing the pigment.

  As commercial products of black self-dispersing pigments, for example, they are sold as two different products from Cabot. CAB-O-JET200 (sulfonated carbon black), CAB-O-JET300 (carboxylated carbon black) (trade name, manufactured by Cabot Corporation), Bonjet Black CW-1 (ORIENT CHEMICAL INDUSTRIES CO., LTD.) Trade name).

These pigments preferably have an average particle size in the range of 50 to 250 nm in order to improve the storage stability of the ink and to effectively prevent nozzle clogging. Here, in this specification, the average particle diameter means a sphere-converted 50% average particle diameter (d50) by a dynamic light scattering method, and is a value obtained as follows.
The particles in the dispersion medium are irradiated with light, and the generated diffracted scattered light is measured by detectors arranged in front, side, and rear of the dispersion medium. Using the measured values obtained, assuming that particles that are originally indefinite are spherical, a cumulative curve is obtained with the total volume of the particle population converted to a sphere equal to the volume of the particles as 100%. The point at which the cumulative value at that time is 50% is defined as “sphere-converted 50% average particle diameter (d50) by dynamic light scattering method”. Examples of the diffraction scattered light measuring apparatus include a laser diffraction scattering type particle size distribution measuring device LMS-2000e (trade name, manufactured by SEISHIN ENTERPRISE Co., Ltd.).

  Furthermore, these pigments are preferably contained in the range of 2 to 15% by mass with respect to the total mass (100% by mass) of the pigment ink of the present embodiment. When the content is 2% by mass or more, the print density becomes sufficient and the color developability is excellent. Further, when the content is 15% by mass or less, the nozzle is not clogged and the discharge stability is excellent.

[2-ethyl-1,3-hexanediol]
The pigment ink of this embodiment contains 2-ethyl-1,3-hexanediol. 2-Ethyl-1,3-hexanediol is a nonionic surfactant having a structure in which a diol group is located almost in the center, and is known as a wetting agent that hardly foams. 2-Ethyl-1,3-hexanediol has a small molecular weight and a very stable molecular structure, and has the effect of lowering the surface tension of water. It can be controlled moderately.

  The content of 2-ethyl-1,3-hexanediol is preferably 0.3 to 8% by mass and more preferably 1 to 5% by mass with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, the permeability is excellent and bleeding can be effectively prevented.

[Unsaturated fatty acid]
The pigment ink of this embodiment contains an unsaturated fatty acid. Hereinafter, the point that the unsaturated fatty acid has a plurality of functions will be described.

  First, in the pigment ink of this embodiment, it discovered that the following effects were acquired by using together the said 2-ethyl- 1, 3- hexanediol and unsaturated fatty acid. This embodiment contains both 2-ethyl-1,3-hexanediol and an unsaturated fatty acid surfactant. 2-Ethyl-1,3-hexanediol is a low molecular weight surfactant having a three-dimensional structure. Therefore, it is a surfactant that hardly generates foam and has excellent wettability. On the other hand, unsaturated fatty acids such as oleic acid are surfactants that have a straight-chain structure and are prone to foaming used in soaps and the like. However, it has been found that, when these two are combined, foaming is much less likely to occur than each single substance.

  For this reason, the tail of the ejected ink is shortened, and the satellite is reduced. The reason for this is that the surface of the ink that is ejected is obtained by combining 2-ethyl-1,3-hexanediol with an unsaturated fatty acid surfactant having a structure significantly different from that of 2-ethyl-1,3-hexanediol. It is presumed that the surfactant molecules are disturbed by steric hindrance and the film strength is lowered.

  Next, the pigment ink according to the present embodiment includes the unsaturated fatty acid and four types of acid alkalis such as an amino acid, an alkali metal hydroxide, and an amine described later as a pH adjuster. In general, when two kinds of acids and alkalis are included, many are known to have a pH buffer effect, but in this embodiment, four kinds of pH adjusters each having a function other than the pH buffer function. including. The pH adjustment range is preferably in the range of 6 to 10 in order to effectively suppress ink attack on the constituent materials of the ink jet recording apparatus and to ensure clogging recovery.

  The unsaturated fatty acid also has a function as a lubricant and a penetrating agent in addition to the above functions.

  It has been found that when the four types of pH adjusters in the present embodiment are combined, the above functions other than the above can be sufficiently exhibited and a synergistic effect can be exhibited while having a pH buffer function having long-term stability.

Among unsaturated fatty acids, unsaturated fatty acids having one carbon double bond are preferred. Examples of monounsaturated fatty acids include crotonic acid, myristoleic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, gadoleic acid, eicosenoic acid, erucic acid, and nervonic acid. This is because when there are two or more carbon double bonds, unstable methylene hydrogen sandwiched between the carbon double bonds is extracted and easily oxidized. In this case, linoleic acid and linolenic acid are applicable. An unsaturated fatty acid having one carbon double bond is advantageous in that it is difficult to oxidize because there is no unstable methylene hydrogen.
The unsaturated fatty acid contained in the pigment ink is preferably liquid at normal temperature. Furthermore, many saturated fatty acids that are stable against oxidation are solid at room temperature, and many are not suitable for addition to ink. Oleic acid is mentioned as one that satisfies all of these characteristics.
From the above, the unsaturated fatty acid is preferably oleic acid.

  The unsaturated fatty acid may be purified, or may be a vegetable oil such as olive oil based on oleic acid.

  An unsaturated fatty acid may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the unsaturated fatty acid is preferably 0.05 to 3% by mass and more preferably 0.1 to 1% by mass with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, the two functional balances of an excellent surfactant and a pH adjuster (acid side) are excellent.

〔amino acid〕
The pigment ink of this embodiment contains an amino acid as described above.

  The amino acid, which is one of the above four pH adjusters, has a function as a moisturizer and a curling inhibitor for recording media in addition to an excellent pH adjusting function having both amino and carboxyl functional groups. .

  The amino acid is preferably a chemically stable tertiary amino acid or quaternary amino acid. Among them, at least one of dimethylglycine and trimethylglycine is preferable because of its low molecular weight.

  An amino acid may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of the amino acid is preferably 1 to 30% by mass and more preferably 4 to 20% by mass with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, it has a function as a moisturizing agent and a curling inhibitor for a recording medium, and also has an excellent pH adjusting function as an amphoteric electrolyte of acid and alkali.

[Amine]
The pigment ink of this embodiment contains an amine as described above.

  An amine that is one of the above four types of pH adjusters has a function as a weak alkali adjuster that is easy for the human body, such as shampoos and cosmetics. Also, since the amine is amphiphilic and excellent in long-term stability of the ink, alkanolamine is preferable among the above amines. Furthermore, since clogging can be prevented by using an alkanolamine having a high boiling point, trialkanolamine is more preferable, and at least one of tripropanolamine and triethanolamine is more preferable.

  In addition, an amine has a fault which is easy to form a precipitate with an unsaturated fatty acid, and when it is one kind of amine as an alkali, it is inferior to stability. Therefore, as the alkali, an alkali metal hydroxide described later is included in addition to the amine.

  An amine may be used individually by 1 type and may be used in combination of 2 or more type.

  The amine content is preferably 0.05 to 2 mass%, more preferably 0.1 to 1 mass%, based on the total mass (100 mass%) of the pigment ink. An amine and an alkali metal hydroxide are excellent in the synergistic effect as an alkali component as it exists in the range of the said content.

[Alkali metal hydroxide]
The pigment ink of this embodiment contains an alkali metal hydroxide as described above.

  Alkali metal hydroxide, which is one of the above four kinds of pH adjusters, is an excellent alkali, but metal ions are easily trapped in a complex like an organic solvent or pigment, and have poor long-term stability. Alkali metal ions are less likely to precipitate with unsaturated fatty acids than amines. Therefore, by using an amine and an alkali metal hydroxide in combination as an alkali, both defects can be compensated for and only the features can be exhibited.

  The alkali metal hydroxide is preferably one or more selected from the group consisting of sodium hydroxide (NaOH), potassium hydroxide (KOH), and lithium hydroxide (LiOH), and at least one of NaOH and KOH More preferred.

  An alkali metal hydroxide may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the alkali metal hydroxide is preferably 0.01 to 1% by mass and more preferably 0.03 to 0.5% by mass with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, the synergistic effect as an alkali component of the amine and the alkali metal hydroxide is excellent.

  Here, the unsaturated fatty acid, the amino acid, the alkali metal hydroxide, and the amine may be contained in the ink as a single substance or may be contained as an acid alkali salt. In particular, when the pigment ink contains an acid-alkali salt composed of at least one of an unsaturated fatty acid and an amino acid and at least one of an alkali metal hydroxide and an amine, the pH buffering effect is further exhibited, It can be said that it is preferable. Examples of the acid alkali salt include, but are not limited to, potassium oleate, sodium oleate, lithium oleate, tripropanolamine oleate, triethanolamine oleate, potassium amino acid, amino acid sodium, and lithium amino acid. It is done.

  Among them, potassium oleate, tripropanolamine oleate, triethanolamine oleate, and amino acid potassium are superior in solubility in ink and pH adjustment function and do not adversely affect pigments and other ink materials. One or more selected from the group consisting of

[Other additives]
The pigment ink of this embodiment may contain additives other than the above-mentioned additives. Examples of such additives are shown below.

(Wetting agent)
For the purpose of preventing clogging in the vicinity of the nozzles of the inkjet head, it is preferable to add a water-soluble organic solvent having a wetting effect as a wetting agent to the pigment ink of this embodiment.

  As the wetting agent, for example, glycerin, 1,2,6-hexanetriol, trimethylolpropane, pentamethylene glycol, trimethylene glycol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, number Polyethylene glycol having an average molecular weight of 2000 or less, dipropylene glycol, tripropylene glycol, isobutylene glycol, acetylene glycol, 2-butene-1,4-diol, 2-methyl-2,4-pentanediol, mesoerythritol, pentaerythritol, etc. Polyhydric alcohols, as well as glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucose Sugars such as tall (sorbite), maltose, cellobiose, lactose, sucrose, trehalose, and maltotriose, so-called solid wetting agents such as sugar alcohols, hyaluronic acids, and ureas, and ethanol, methanol, butanol, propanol, and C1-C4 alkyl alcohols such as isopropanol, and 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, formamide, acetamide, dimethyl sulfoxide, sorbit, sorbitan, acetin, Examples include diacetin, triacetin, and sulfolane.

  A wetting agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the wetting agent is preferably 10 to 50% by mass with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, it is possible to ensure appropriate physical property values (such as viscosity) of the pigment ink and to ensure recording quality and reliability.

(water)
The pigment ink of this embodiment preferably contains water as a main solvent, and it is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide in order to prevent the generation of mold and bacteria and enable long-term storage of the pigment ink.

(Antioxidant)
Examples of the antioxidant (ultraviolet absorber) that can be contained in the pigment ink of the present embodiment include allohanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret, and tetramethylbiuret, and L-ascorbine. Examples thereof include acids and salts thereof, and lanthanide oxides. As these commercial items, for example, Tinuvin 328, 900, 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035 manufactured by Novartis International AG MD1024 or the like is used.

  An antioxidant may be used individually by 1 type and may be used in combination of 2 or more type.

  The content of the antioxidant is preferably 0.5% by mass or less with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, oxidation can be effectively prevented without deteriorating ink characteristics.

(Preservatives / antifungal agents)
Examples of the antiseptic / antifungal agent that can be included in the pigment ink of the present embodiment include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1, 2-dibenzisothiazolin-3-one, dichlorophen, hexachlorophene, p-hydroxybenzoate, ethylenediaminetetraacetic acid (EDTA), sodium dehydroacetate, 3,4-isothiazolin-3-one, and 4,4- Examples include dimethyl oxazolidine. Examples of these commercially available products include Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2 (1,2-benchazolin-3-one), Proxel TN (all are trade names manufactured by Avecia) and the like. .

  An antiseptic | preservative and an antifungal agent may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the antiseptic / antifungal agent is preferably 0.5% by mass or less with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, the antiseptic and antifungal effects can be improved without deteriorating the ink characteristics.

(Penetration enhancer)
For the purpose of accelerating the penetration of the aqueous solvent (water or water-based organic solvent) into the recording medium, it is preferable that the pigment ink of this embodiment further contains a penetration accelerator. As the aqueous solvent quickly permeates the recording medium, a recorded matter with less image blur can be obtained.

  As such a penetration enhancer, at least one of alkyl ethers of polyhydric alcohols (also referred to as glycol ethers) and 1,2-alkyldiols is preferably used. Examples of the alkyl ether of polyhydric alcohol include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol mono Isopropyl ether, diethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, 1-methyl-1-methoxybutanol, Lopylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether , Dipropylene glycol monoisopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monobutyl ether, and the like. Examples of the 1,2-alkyldiol include 1,2-pentanediol and 1,2-hexanediol. In addition to these, straight-line such as 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, and 1,8-octanediol. There may be mentioned diols of chain hydrocarbons.

  A penetration enhancer may be used individually by 1 type, and may be used in combination of 2 or more type.

  The content of the penetration accelerator is preferably 3 to 20% by mass with respect to the total mass (100% by mass) of the pigment ink. When the content is within the above range, the permeability of the pigment ink into the recording medium can be improved, bleeding can be prevented from occurring in an image recorded using the pigment ink, and the pigment ink can be prevented. It is possible to prevent the viscosity of the resin from becoming too high.

  Thus, according to this embodiment, it is possible to provide a pigment ink that can suppress the generation of satellites and can form a high-quality image at high speed. Specifically, according to the present embodiment, 2-ethyl-1,3-hexanediol and an unsaturated fatty acid are combined as a surfactant, and as a pH adjuster in order to eliminate problems when these are used. Pigment ink with excellent long-term stability that can suppress the generation of satellites even during high-speed recording with an ink composition that combines the unsaturated fatty acid itself, amino acid, amine, and alkali metal hydroxide. Can be provided.

[Inkjet recording apparatus]
Hereinafter, an ink jet recording apparatus according to an embodiment of the present invention will be described with reference to the drawings. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size. In the present embodiment, an inkjet printer (hereinafter simply referred to as “printer”) is illustrated as an inkjet recording apparatus according to the present invention.

FIG. 1 is a perspective view illustrating a configuration of a printer 1 according to the present embodiment. The printer 1 represents a serial printer.
As shown in FIG. 1, a printer 1 includes an inkjet head 2 and a carriage 4 on which an ink cartridge 3 is detachably mounted, and a platen 5 disposed below the inkjet head 2 and to which a recording medium 6 is conveyed. And a carriage moving mechanism 7 for moving the carriage 4 in the medium width direction of the recording medium 6 and a medium feeding mechanism 8 for conveying the recording medium 6 in the medium feeding direction. In addition, the printer 1 includes a control device CONT that controls the operation of the entire printer 1. The medium width direction is the main scanning direction (head scanning direction). The medium feeding direction is a sub-scanning direction (a direction orthogonal to the main scanning direction).

  The ink cartridge 3 is not limited to the one mounted on the carriage 4 as in the present embodiment, but instead, for example, a type that is mounted on the housing side of the printer 1 and is supplied to the inkjet head 2 via the ink supply tube. It may be. The ink cartridge 3 contains the pigment ink according to the above-described embodiment having different colors such as yellow (Y), magenta (M), cyan (C), and black (Bk).

  The carriage 4 is attached in a state of being supported by a guide rod 9 which is a support member installed in the main scanning direction. The carriage 4 is moved in the main scanning direction along the guide rod 9 by the carriage moving mechanism 7.

  The linear encoder 10 detects the position of the carriage 4 in the main scanning direction with a signal. This detected signal is transmitted to the control device CONT as position information. The control device CONT recognizes the scanning position of the ink jet head 2 based on the position information from the linear encoder 10 and controls the recording operation (discharge operation) and the like by the ink jet head 2. Further, the control device CONT is configured to be able to variably control the moving speed of the carriage 4.

FIG. 2 is a schematic diagram showing the arrangement of the nozzles 17 provided in the inkjet head 2 in the present embodiment.
As shown in FIG. 2, the inkjet head 2 has a nozzle forming surface 21A provided with a plurality of nozzles 17 for discharging pigment ink. A nozzle row 16 is formed for each of the plurality of nozzles 17 on the nozzle formation surface 21 </ b> A that is also an ink ejection surface. In each nozzle row 16, for example, different color pigment inks can be ejected. In the present embodiment, four rows corresponding to the color of the pigment ink, that is, nozzle row (black) 16 (Bk), nozzle row (magenta) 16 (M), nozzle row (cyan) 16 (C), and nozzle row ( Yellow) 16 (Y) is provided. Each of the nozzle rows 16 is composed of, for example, 180 nozzles 17.

FIG. 3 is a partial cross-sectional view showing the internal configuration of the inkjet head 2 in the present embodiment.
As shown in FIG. 3, the inkjet head 2 includes a head main body 18 and a flow path forming unit 22 connected to the head main body 18. The flow path forming unit 22 includes a vibration plate 19, a flow path substrate 20, and a nozzle substrate 21, and forms a common ink chamber 29, an ink supply port 30, and a pressure chamber 31. Furthermore, the flow path forming unit 22 includes an island portion 32 that functions as a diaphragm portion, and a compliance portion 33 that absorbs pressure fluctuation in the common ink chamber 29. The head main body 18 is formed with an accommodation space 23 for accommodating the drive unit 24 together with the fixing member 26, and an internal flow path 28 for guiding the pigment ink to the flow path forming unit 22.

  According to the above configuration, that is, the piezo-type inkjet head 2, when a drive signal is input to the drive unit 24 via the cable 27, the piezoelectric element 25 expands and contracts. As a result, the diaphragm 19 is deformed (moved) in a direction toward and away from the pressure chamber 31. For this reason, the volume of the pressure chamber 31 changes and the pressure of the pressure chamber 31 containing the pigment ink fluctuates. Pigment ink is ejected from the nozzle 17 due to this pressure fluctuation.

  Returning to FIG. 1, a home position serving as a scanning start point of the inkjet head 2 is set in a region outside the platen 5 in the movement range of the inkjet head 2. A maintenance unit 11 is provided at the home position. The maintenance unit 11 performs a moisturizing operation for suppressing the evaporation of the pigment ink by capping the inkjet head 2 with the cap member 12 other than the printing operation, and pre-discharges the pigment ink from each nozzle 17 of the inkjet head 2 to the cap member 12. To prevent the nozzle 17 from being clogged by the thickened ink, adjust the meniscus of the nozzle 17 to normally discharge the pigment ink from the inkjet head 2, and suction (not shown) after the inkjet head 2 is capped by the cap member 12. A suction operation (head cleaning) for adjusting the meniscus by forcibly sucking the pigment ink or the adhering dust from the nozzles 17 by driving the pump and adjusting the meniscus, and discharging the pigment ink normally from the inkjet head 2; Inkjet head The wiper member 13 wipes the nozzle forming surface 21A (see FIG. 2) 2 to remove the pigment ink adhering to the vicinity of the nozzle 17 or the thickened pigment ink, or destroys the meniscus of the nozzle 17. And a wiping operation for performing a purge process for readjusting the meniscus.

  The printer 1 of this embodiment suppresses the occurrence of satellites by discharging the pigment ink of the above embodiment while the inkjet head 2 moves at a relative speed of 0.5 m / s or more with respect to the recording medium 6. Is. The relative speed corresponds to the moving speed of the carriage 4 in the main scanning direction in the inkjet head 2 of the serial printer.

  Note that the printer 1 of this embodiment may be a line printer with a fixed head instead of the serial printer of this embodiment. In this line printer, the relative speed is recorded in the sub-scanning direction. This corresponds to the moving speed of the medium.

  In the present embodiment, satellites are more likely to be generated at a higher speed, and the greater the effect, the greater the obtained effect. Specifically, when the relative speed is 0.8 m / s or more, the satellite suppressing effect is further increased.

  The ink ejection speed by the ink jet method is preferably 4 to 15 m / s in order to improve the flight stability of the ink droplets. When the ejection speed is 4 m / s or more, it becomes possible to deposit (land) the ink on the recording medium with high accuracy. Moreover, generation | occurrence | production of a satellite drop can be effectively suppressed as discharge speed is 15 m / s or less.

  Here, the influence of the satellite will be described from the viewpoint of the relative speed and the length of the tail. For example, when an ink droplet having a trailing length of 400 μm is ejected at 7 m / s, the landing time difference between the main droplet and the satellite droplet is about 60 μsec. Therefore, in this case, if the relative velocity is 0.5 m / s, the landing position deviation between the main droplet and the satellite droplet is 30 μm based on the landing time difference. Similarly, if the relative velocity is 1.0 m / s, the deviation of the landing position between the main droplet and the satellite droplet is 60 μm.

  The deviation of the landing position affects the image quality of the obtained recorded material. Furthermore, the sensitivity of the human eye to the recorded material is such that it is easy to detect a deviation of 60 μm or more when the distance between the paper and the eyes is 30 cm. Therefore, the deviation of the landing position between the main droplet and the satellite droplet is preferably within 60 μm, more preferably within 30 μm.

  Further, when the relative speed is constant, the length of the tail affects the deviation of the landing positions of the main droplet and the satellite droplet. Therefore, an ink having a tail length of less than 400 μm is preferable. In addition, by using an ink having a tail length of less than 400 μm, the generation of satellite droplets can be effectively suppressed.

  In addition, since the printer 1 of the present embodiment uses a pigment ink containing an unsaturated fatty acid as described above, it is preferable to use a piezo-type inkjet head that is less susceptible to oxidation of the unsaturated fatty acid by heat. When the amount of unsaturated fatty acid added is small, a thermal ink jet head may be used, but a piezo type with less concern about nozzle clogging due to oxidation of unsaturated fatty acid is more preferable.

  Thus, according to the present embodiment, it is possible to provide an ink jet recording apparatus that can suppress the generation of satellites and can form a high-quality image at high speed.

[Inkjet recording method]
As described in the section of the ink jet recording apparatus of the above embodiment, the ink jet recording method according to one embodiment of the present invention is an ink jet head 2 that moves relative to the recording medium 6 at a relative speed of 0.5 m / s or more. A discharge step of discharging the pigment ink of the above embodiment.

  Thus, according to the present embodiment, it is possible to provide an ink jet recording method capable of suppressing the generation of satellites and forming a high-quality image at high speed.

  Hereinafter, the embodiments of the present invention will be described more specifically by way of examples. However, the embodiments are not limited to these examples.

[Materials used]
(Pigment dispersion)
・ CAB-O-JET300 (trade name, solid content 15%, manufactured by Cabot)
・ BONJET BLACK CW-1 (trade name, 20% pigment content, manufactured by Orient Chemical Industries)
[Surfactant]
2-ethyl-1,3-hexanediol Triton X-100 (Roche Applied Science, trade name, C ₁₄ H ₂₂ O (C ₂ H ₄ O) _n , linear nonionic surfactant )
[Surfactant and pH adjuster]
・ Oleic acid (manufactured by Tokyo Chemical Industry Co., Ltd., monounsaturated fatty acid)
・ Linolic acid (manufactured by Tokyo Chemical Industry Co., Ltd., diunsaturated fatty acid)
・ Stearic acid (manufactured by Tokyo Chemical Industry Co., Ltd., saturated fatty acid)
[PH adjuster]
・ Trimethylglycine (anhydrous betaine, manufactured by Tokyo Chemical Industry Co., Ltd.)
・ Dimethylglycine (N, N-dimethylglycine, manufactured by Tokyo Chemical Industry Co., Ltd.)
・ Tripropanolamine (Triisopropanolamine, manufactured by Tokyo Chemical Industry Co., Ltd.)
・ Triethanolamine (Tokyo Chemical Industry Co., Ltd.)
・ Potassium hydroxide (KANTO CHEMICAL CO., INC)
・ Sodium hydroxide (manufactured by Kanto Chemical)
[Penetration enhancer]
・ 1,2-Hexanediol ・ Triethylene glycol monobutyl ether (abbreviated as “TEGmBE” in Table 1)
[Wetting agent]
・ Glycerin ・ Trimethylolpropane (preservative / antifungal agent)
・ Ethylenediaminetetraacetic acid disodium (EDTA)
・ Proxel XL-2

[Examples 1 to 5, Comparative Examples 1 to 10]
[Preparation of pigment ink]
Each component was mixed with the content shown in Table 1, stirred for 2 hours at room temperature, and then filtered through a membrane filter having a pore size of 5 μm to prepare each aqueous pigment ink of Examples 1 to 5 and Comparative Examples 1 to 10. did.
In addition, the unit of content shown in Table 1 is the mass%, and in Table 1, the pigment dispersion is represented by solid content concentration (equivalent to pigment content). Moreover, a blank part represents that it is no addition. The “remaining amount” of ion-exchanged water means that ion-exchanged water is added so that the total amount of ink becomes 100% by mass.

  Each of the pigment inks shown in Table 1 was evaluated as follows.

[Evaluation of tail length]
Ink jet printer PX-500 (trade name, manufactured by Seiko Epson Corporation) is filled with pigment ink, and ink ejected by an inkjet discharge observation device Dot View (trade name, manufactured by Tritek). The length of the tail was observed. The evaluation criteria are as follows. The results are shown in Table 2.
○: The length of the tail is less than 400 μm,
X: The length of the tail is 400 μm or more.

[Ink bubbling evaluation]
A cylindrical glass container having a diameter of 2 cm and a height of 10 cm was charged with 10 g of pigment ink and shaken 50 times, and the height (H) from the interface between the bubbles (bubbles) and the liquid to the maximum height of the bubbles was measured. The evaluation criteria are as follows. The results are shown in Table 2.
○: less than 5 cm,
Δ: 5 cm or more and less than 8 cm,
X: 8 cm or more.

[Confirmation evaluation of satellite]
The produced ink was put into an ink cartridge of a printer PX-B500 (trade name, manufactured by Seiko Epson Corporation) to be ready for printing. Since the printer PX-B500 is a printer having a head carriage speed of 1.1 m / sec, the printer PX-B500 was modified so that the carriage speed could be varied from 0.3 to 1.1 m / sec. Then, the maximum carriage speed was set in four stages of 0.3, 0.5, 0.7, and 0.9 m / sec, and the relationship between the printing speed and the satellite at each maximum carriage speed was examined. Regarding the satellite, the recorded matter printed on the super fine paper manufactured by Seiko Epson Corporation was observed with an optical microscope to confirm whether or not the satellite was present.
Ideally, there are no satellites, but it is difficult to have no satellites in any situation because there is a problem of probability as to whether the ejected ink droplets are split in the air. Therefore, even if the satellite is generated, it is not necessary to observe the satellite on the recorded matter. That is, the distance between the main droplet and the satellite droplet of the recorded material may be less than 60 μm. Furthermore, the sensitivity of the human eye to the recorded material is supposed to easily detect a deviation of 60 μm or more when the distance between the paper and the eye is 30 cm.
From the above, in this specification, the presence or absence of satellites is determined more practically as follows, and the evaluation criteria are also the same. The results are shown in Table 2.
A: There was no satellite. Specifically, the interval between the main droplet and the satellite droplet of the recorded material was 0 μm.
○: There was no satellite (there was a suppression effect). Specifically, the distance between the main droplet and the satellite droplet of the recorded material was less than 60 μm.
X: There was a satellite. Specifically, the interval between the main droplet and the satellite droplet of the recorded material was 60 μm or more.

[Ink long-term stability evaluation]
The recorded matter printed at a carriage speed of 0.9 m / sec in the satellite confirmation evaluation was placed in the ink cartridge of the printer PX-B500 (trade name, manufactured by Seiko Epson), and left for 1 month, 6 months, and 1 year. The satellite changes were observed. The evaluation criteria are the same as those for the satellite confirmation evaluation. The results are shown in Table 2.

  From Table 2, it was found that the inks to which 2-ethyl-1,3-hexanediol and unsaturated fatty acid were added suppressed the generation of satellite as in Examples 1 to 5 and Comparative Examples 5 to 10. . Moreover, when it included four types, unsaturated fatty acid, an amino acid, an alkali metal hydroxide, and an amine, it turned out that generation | occurrence | production of a satellite can be stably suppressed over a long term like Examples 1-5.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Inkjet head, 3 ... Ink cartridge, 4 ... Carriage, 5 ... Platen, 6 ... Recording medium, 7 ... Carriage moving mechanism, 8 ... Medium feed mechanism, 9 ... Guide rod, 10 ... Linear encoder, DESCRIPTION OF SYMBOLS 11 ... Maintenance unit, 12 ... Cap member, 13 ... Wipe member, 16 ... Nozzle row, 16 (Bk) ... Nozzle row (black), 16 (M) ... Nozzle row (magenta), 16 (C) ... Nozzle row ( Cyan), 16 (Y) ... Nozzle row (yellow), 17 ... Nozzle, 18 ... Head body, 19 ... Vibration plate, 20 ... Channel substrate, 21 ... Nozzle substrate, 21A ... Nozzle formation surface, 22 ... Channel formation Unit: 23 ... Accommodating space, 24 ... Drive unit, 25 ... Piezoelectric element, 26 ... Fixing member, 27 ... Cable, 28 ... Internal channel, 29 ... Common ink chamber, 30 ... Ink supply ports, 31 ... pressure chamber, 32 ... islands, 33 ... compliance portion, CONT ... controller, Y ... yellow, M ... magenta, C ... cyan, Bk ... black.

Claims (9)

  A pigment ink comprising 2-ethyl-1,3-hexanediol, an unsaturated fatty acid, an amino acid, an alkali metal hydroxide, and an amine.   The pigment ink according to claim 1, wherein the unsaturated fatty acid comprises oleic acid.   The pigment ink according to claim 1 or 2, wherein the amino acid contains at least one of trimethylglycine and dimethylglycine.   The pigment ink according to any one of claims 1 to 3, wherein the alkali metal hydroxide includes one or more selected from the group consisting of potassium hydroxide, sodium hydroxide, and lithium hydroxide.   The pigment ink according to any one of claims 1 to 4, wherein the amine contains at least one of triethanolamine and tripropanolamine.   The pigment according to any one of claims 1 to 5, comprising an acid alkali salt comprising at least one of the unsaturated fatty acid and the amino acid, and at least one of the alkali metal hydroxide and the amine. ink.   The pigment ink according to claim 6, wherein the acid alkali salt is at least one selected from the group consisting of potassium oleate, tripropanolamine oleate, triethanolamine oleate, and potassium amino acid.   An ink jet recording apparatus comprising: an ink jet head that discharges the pigment ink according to claim 1 while moving at a relative speed of 0.5 m / s or more with respect to a recording medium.   An ink jet recording method comprising a discharge step of discharging the pigment ink according to claim 1 from an ink jet head that moves at a relative speed of 0.5 m / s or more with respect to a recording medium.

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