JP2018114669A - Liquid discharge device, ink jet recording method, and ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both of discharge stability and improvement of image quality even if ink having low defoaming property is used.SOLUTION: A liquid discharge device 1 includes ink and a liquid discharge section 2 which has a nozzle 3 for discharging the ink. The liquid discharge section 2 has a liquid chamber communicating with the nozzle 3, and a first supply port 5 and a second supply port 6 for making the ink flow into/out of the liquid chamber, and is provided with circulation means which makes the ink flowing out of one supply port of the first supply port 5 and the second supply port 6 flow into the other supply port through a circulation path 120. The ink has foam stability of 150 mm or more five minutes after a measurement according to Ross-Miles method (JISK3362).SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid ejection apparatus, an inkjet recording method, and ink.

  There is known an ink jet recording method in which ink droplets are ejected from very fine nozzles, and ink droplets are deposited on a recording medium to form characters and images. The ink jet recording method has been widely used in recent years because it has the advantage of being able to achieve full color compared to other recording methods and also capable of obtaining a high-resolution image even with an apparatus having a simple configuration.

  A pigment-based ink is known as an ink used in the ink jet recording system. Since pigments are superior to dyes in terms of water resistance and weather resistance, in recent years, inks using pigments as colorants have been mainly used.

  In pigment-based inks, it is difficult to achieve a level equivalent to that of dye inks in terms of uniformity of solid image portions and color development of color images by adding ordinary hydrocarbon surfactants to the ink. . For this reason, it is already known that the use of a fluorosurfactant having a higher ability to lower the surface tension of the ink can improve the uniformity of the solid image portion and improve the color development.

  In addition, the ink used in the ink jet recording system is required to have various characteristics in addition to the image quality. In particular, the ejection stability when ejecting ink from the head is important because it affects the image quality.

  Ink bubbling greatly affects the ink supply path and the ejection stability at the head. The cause of foaming is usually a surfactant / penetrating agent added to the ink. In particular, a fluorosurfactant is widely used because an image with a high image density and a low bleeding can be obtained, but it is a material that easily causes foaming.

  Therefore, an antifoaming agent is added to the ink. However, in general ink production, a mixed solution in which a solvent, a colorant, an antifoaming agent, and the like are mixed is prepared, and then impurities are filtered in a filtering step (see, for example, Patent Documents 1 and 2). In this filtration step, the antifoaming agent is trapped by the filtration filter, so the amount of antifoaming agent in the ink is reduced and the antifoaming effect is deteriorated.

  On the other hand, considering the amount of the antifoaming agent trapped in the filtration step, it is conceivable to increase the amount of the antifoaming agent added to the ink. However, in this case, since the life of the filter is shortened, the manufacturing cost of the ink is increased. In addition, the amount of the defoaming agent component contained in the initial distillation and the final distillation of the ink that has passed through the filtration process is likely to be different, and it is difficult to ensure stable ink quality.

  Therefore, the present invention improves the ejection stability and image quality even when using low-foaming ink that may cause nozzle omission or adversely affect the ink supply unit due to bubbles generated in the ink, thereby impairing the image quality. It is an object of the present invention to provide a liquid ejection device that can achieve both of the above.

  In order to achieve this object, a liquid discharge apparatus according to the present invention is a liquid discharge apparatus including ink and a liquid discharge unit having a nozzle for discharging the ink, wherein the liquid discharge unit includes the nozzle A first supply port and a second supply port for allowing the ink to flow into or out of the liquid chamber, and the first supply port and the second supply port. A circulation means for allowing the ink flowing out from one of the supply ports to flow into the other supply port via a circulation path, and the ink is stable in bubbles after 5 minutes measured according to the Ross Miles method (JIS K3362). The property is 150 mm or more.

  According to the present invention, it is possible to achieve both ejection stability and improved image quality even when ink having low defoaming properties is used.

1 is a schematic diagram illustrating a configuration of an example of a liquid ejection apparatus. It is a perspective explanatory view of an ink jet recording apparatus using a liquid ejection apparatus. It is a side explanatory view of a mechanism part of an ink jet recording apparatus using a liquid ejecting apparatus.

  First, an outline of an embodiment of a liquid ejection apparatus according to the present invention will be described. The liquid ejection apparatus according to the present embodiment is a liquid ejection apparatus (liquid ejection apparatus 1) including ink and a liquid ejection section (head, liquid ejection section 2) having a nozzle (nozzle 3) that ejects ink. The liquid ejecting unit includes a liquid chamber communicating with the nozzle, and a first supply port (first supply port 5) and a second supply port (second supply port) for allowing ink to flow into or out of the liquid chamber. Circulation that has a supply port 6) and causes ink flowing out from one of the first supply port and the second supply port to flow into the other supply port via the circulation path (circulation path 120) The ink is one having a foam stability of 150 mm or more after 5 minutes measured according to the Ross Miles method (JIS K3362). In addition, the code | symbol in embodiment and the example of application are shown in a parenthesis.

  The above-mentioned bubbles generated in the ink can cause nozzle omission and adversely affect the ink supply unit, and can achieve both ejection stability and improved image quality even with low-foaming ink that may impair image quality. For this reason, the inventors of the present application have made extensive studies. As a result, it has been found that the above-described problems can be solved without causing bubbles to enter the discharge section by discharging the generated bubbles from the liquid chamber by circulating ink in the head.

  The ink used in the liquid ejection apparatus according to the present embodiment has a foam stability of 150 mm or more after 5 minutes as measured according to the Ross Miles method (JIS K3362). The Ross Miles method is a method in which 200 ml of a sample solution is dropped from a height of 90 cm in a tube containing 50 ml of a sample solution such as ink or an antifoaming solution in 30 seconds. And it is the method of measuring the height of the bubble which produced at this time as foaming force, and measuring the height of the foam after 5 minutes as defoaming property (foam stability). Note that the lower the foam height, the lower the foaming power and the higher the defoaming property.

  Also, evaluate the amount of foam generated when the sample solution is placed in a container such as a glass sample tube and shaken a specified number of times as foaming power, and evaluate the time until the generated foam disappears as defoaming ability. You can also. That is, the smaller the amount of bubbles generated, the lower the bubble force, and the faster the time until the bubbles disappear, the higher the defoaming property of the sample solution. A sample solution having a lower foaming power and a higher defoaming property is an excellent defoaming effect.

  Further, according to the JIS-specified loss miles method, it is specified that the temperature is a constant temperature. In this embodiment, it is measured as 25 ° C.

  By the way, from the viewpoint of ejection stability, there is a possibility that white streaks may occur due to nozzle omission due to the bubbles entering the ejection section when bubbles are present. Desired.

  However, if an antifoaming agent or the like is added to impart high defoaming properties to the ink, as described above, there is a risk of adversely affecting the problems associated with the filtration process, the storage stability of the ink, and the like.

  Therefore, as in the liquid ejection device according to the present embodiment, the liquid ejection unit having the first supply port and the second supply port for allowing the ink to flow in or out, the first supply port, and the second supply By using a liquid ejection device that has a circulation means that allows ink flowing out from one supply port to flow into the other supply port via a circulation path, no defoaming agent is added or the amount added is reduced. Ink can be used, and the above-mentioned problems can be solved.

  That is, the ink used in the liquid ejection apparatus according to the present embodiment has a foam stability of 150 mm or more after 5 minutes measured according to the Ross Miles method (JIS K3362), but the liquid ejection having the above circulation means. By combining with the configuration of the apparatus, it is possible to improve the adverse effects caused by bubbles.

  The foam stability at this time can be arbitrarily controlled by the type and amount of the antifoaming agent and the type and amount of the surfactant. In addition, when a very small amount of antifoaming agent is used or when it is not used completely, the stability of the foam after 5 minutes of ink evaluated by the Ross Miles method may be 200 mm or more. The effect of the device appears more prominently. The upper limit of the stability of the bubbles after 5 minutes of ink is 500 mm.

  In addition, the ink in which the stability of the foam after 5 minutes is 150 mm or more like the ink used in the liquid ejection apparatus according to the present embodiment has a circulation means capable of discharging the foam as in the present invention. It is difficult to adopt in a normal liquid ejection device that is not present. That is, if the stability of the foam after 5 minutes is 150 mm or more, it is a fairly strong foam. Therefore, when mixed in the liquid chamber, there is a possibility of clogging the discharge hole, and it is considered difficult to recover by a refresh operation or the like. . For this reason, when an ink is used that does not have a circulation means capable of discharging bubbles as in the present invention and the stability of the bubbles after 5 minutes is 150 mm or more, the discharge holes will be reduced. It can be said that there is a great risk of being stuck.

  As described above, according to the liquid ejection apparatus according to the present embodiment, the low defoaming ink that may cause nozzle omission or adversely affect the ink supply unit due to bubbles generated in the ink, which may impair image quality. Even if the ink is used or an ink having a low defoaming property is used, both the discharge stability and the improvement of the image quality can be achieved.

  In addition, since it is possible to use a low level of defoaming ink, which is difficult to use with a normal liquid ejecting apparatus that does not have a circulation means that can discharge bubbles, it is possible to produce ink with less defoaming agent. It can be stabilized and a high image can be obtained even in a low temperature and low humidity environment.

  In a low-temperature and low-humidity environment, the liquid discharge apparatus according to the present embodiment can be used to discharge, for example, at 5 ° C. or more and 12 ° C. or less, 10% RH or more and 20% RH or less. Generally, in a low-temperature and low-humidity environment, the surface tension is increased and the viscosity is increased, so that foaming properties are improved and defoaming properties are decreased. However, according to the liquid ejection device according to the present embodiment, it is possible to expel bubbles generated by the circulation means regardless of the ink state, and therefore, stable ejection can be performed without problems even in a low temperature and low humidity environment. Become.

  Furthermore, ink with low defoaming properties is not limited to the fact that no defoaming agent is used or that the amount of defoaming agent used is reduced. It is preferably realized by using an active agent having high foaming property represented by an agent. Surfactants typified by fluorosurfactants can greatly reduce the surface tension with a small amount, so they are very easy to use for controlling the surface tension, but they are highly foamable and can discharge bubbles. It is difficult to use without a defoaming agent in a normal liquid ejecting apparatus that does not have a circulation means. On the other hand, according to the liquid ejecting apparatus according to the present embodiment, it is possible to use an activator having high foaming property represented by a fluorine-based surfactant.

  The dynamic surface tension of the ink at 25 ° C. and a surface life of 15 ms according to the maximum bubble pressure method is preferably 20.0 mN / m or more and 60.0 mN / m or less, preferably 30.0 mN / m or more and 40.0 mN / m. It is more preferable that it is m or less. If it is 20.0 mN / m or less, it becomes difficult to stretch the meniscus at the discharge portion, and there is a concern that non-discharge may occur. On the other hand, if it is 60.0 mN / m or more, wetting and spreading are less likely to occur on the print medium, and the image density may decrease.

  Hereinafter, the ink of the present invention, the liquid ejection apparatus using the ink, and the image forming apparatus will be described in detail.

[ink]
Hereinafter, the organic solvent, water, color material, resin, additive, and the like 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. Diol, 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-he Polyhydric alcohols such as sundiol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl-1,3-pentanediol, petriol, ethylene glycol mono Polyhydric alcohol alkyl ethers such as ethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol mono Polyhydric alcohol aryl ethers such as benzyl ether, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl- -N-containing heterocyclic compounds such as pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, γ-butyrolactone, formamide, N-methylformamide, N, N-dimethylformamide, 3-methoxy-N, Amides such as N-dimethylpropionamide and 3-butoxy-N, N-dimethylpropionamide, amines such as monoethanolamine, diethanolamine and triethylamine, sulfur-containing compounds such as dimethylsulfoxide, sulfolane and thiodiethanol, propylene carbonate, Examples thereof include ethylene carbonate.

  In addition to functioning as a wetting agent, it is preferable to use an organic solvent having a boiling point of 250 ° C. or lower because good drying properties can be obtained.

  A polyol compound having 8 or more carbon atoms and a glycol ether compound are also preferably used. Specific examples of the polyol compound having 8 or more carbon atoms include 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl-1,3-pentanediol, and the like.

  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. Examples of ethers include polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

  A polyol compound having 8 or more carbon atoms and a glycol ether compound can improve ink permeability when paper is used as a recording medium.

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

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

<Color material>
The color material is not particularly limited, and pigments and dyes can be used.

  An inorganic pigment or an organic pigment can be used as the pigment. These may be used alone or in combination of two or more. A mixed crystal may be used. As the pigment, for example, a black pigment, a yellow pigment, a magenta pigment, a cyan pigment, a white pigment, a green pigment, an orange pigment, a glossy pigment such as gold or silver, a metallic pigment, or the like can be used.

  Carbon black produced by known methods such as contact method, furnace method, thermal method in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow as inorganic pigments Can be used.

  Organic pigments include azo pigments, polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.) Dye chelates (for example, basic dye type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used. Of these pigments, those having good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.

  Specific examples of pigments include black for carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper, iron (CI pigment black 11). And metal pigments such as titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1).

  Further, for color use, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 108, 109, 110, 117, 120, 138, 150, 153, 155, 180, 185, 213, C.I. I. Pigment orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1, 57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (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 Green 1, 4, 7, 8, 10, 17, 18, 36, etc.

  The dye is not particularly limited, and an acid dye, a direct dye, a reactive dye, and a basic dye can be used. One kind may be used alone, or two or more kinds may be used in combination.

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

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

  In order to disperse the pigment in the ink, a method of introducing a hydrophilic functional group into the pigment to form a self-dispersing pigment, a method of dispersing the pigment surface by coating with a resin, a method of dispersing using a dispersant, Etc.

  Examples of a method for introducing a hydrophilic functional group into a pigment to form a self-dispersing pigment include a self-dispersing pigment that can be dispersed in water by adding a functional group such as a sulfone group or a carboxyl group to the pigment (for example, carbon). Can be used.

  As a method for coating the surface of the pigment with a resin and dispersing it, a method in which the pigment is included in microcapsules and can be dispersed in water can be used. This can be paraphrased as a resin-coated pigment. In this case, it is not necessary that all pigments blended in the ink are coated with a resin, and within a range where the effects of the present invention are not impaired, uncoated pigments and partially coated pigments are dispersed in the ink. It may be.

  Examples of the method of dispersing using a dispersant include a method of dispersing using a known low-molecular type dispersant or high-molecular type dispersant represented by a surfactant.

  As the dispersant, for example, an anionic surfactant, a cationic surfactant, an amphoteric surfactant, a nonionic surfactant, or the like can be used depending on the pigment. RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and naphthalenesulfonic acid Na formalin condensate can also be suitably used as a dispersant. A dispersing agent may be used individually by 1 type, or may use 2 or more types together.

<Pigment dispersion>
An ink can be obtained by mixing a material such as water or an organic solvent with a pigment. Further, it is also possible to produce an ink by mixing a pigment, other water, a dispersant, and the like into a pigment dispersion and mixing a material such as water or an organic solvent.

  The pigment dispersion is obtained by dispersing water, a pigment, a pigment dispersant, and other components as required, and adjusting the particle size. For dispersion, a disperser is preferably used.

  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 maximum number because the pigment dispersion stability is good and the image quality such as ejection stability and image density is also high. 500 nm or less is preferable and 20 nm or more and 150 nm or less are more preferable. The particle size of the pigment can be measured using a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack 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% by mass. % To 50% by mass is preferable, and 0.1% to 30% by mass is more preferable.

  The pigment dispersion is preferably degassed by filtering coarse particles with a filter, a centrifugal separator or the like, if necessary.

<Resin>
The type of resin contained in the ink is not particularly limited and can be appropriately selected according to the purpose. For example, urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene type 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. An ink can be obtained by mixing resin particles with a material such as a colorant or an organic solvent in a resin emulsion state in which water is dispersed as a dispersion medium. As said resin particle, what was synthesize | combined suitably may be used and a commercial item may be used. Moreover, these may be used individually by 1 type, or may be used in combination of 2 or more types of resin particles.

  The volume average particle diameter of the resin particles is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 10 nm or more and 1,000 nm or less from the viewpoint of obtaining good fixability and high image hardness. It is more preferably 200 nm or less and particularly preferably 10 nm or more and 100 nm or less.

  The volume average particle diameter can be measured using, for example, a particle size analyzer (Nanotrack Wave-UT151, manufactured by Microtrack Bell Co., Ltd.).

  The resin content is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of fixability and ink storage stability, 0.5% by mass to 30% by mass with respect to the total amount of the ink. % Or less is preferable, and 5 mass% or more and 20 mass% or less are 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. From the viewpoint of improving the image quality such as ejection stability and image density, the maximum frequency in terms of the maximum number Is preferably 20 nm to 1000 nm, and more preferably 20 nm to 150 nm. 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, an antifoaming agent, an antiseptic / antifungal agent, a rust inhibitor, a pH adjuster, and the like may be added to the ink.

<Surfactant>
As the surfactant, any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants and anionic surfactants can be used.

  There is no restriction | limiting in particular in silicone type surfactant, According to the objective, it can select suitably. Among them, those that do not decompose even at high pH are preferable, and examples thereof include side chain modified polydimethylsiloxane, both terminal modified polydimethylsiloxane, one terminal modified polydimethylsiloxane, and side chain both terminal modified polydimethylsiloxane. Those having an oxyethylene group or a polyoxyethylene polyoxypropylene group are particularly preferred because they exhibit good properties as an aqueous surfactant. In addition, as the silicone surfactant, a polyether-modified silicone surfactant can be used, and examples thereof include a compound in which a polyalkylene oxide structure is introduced into the side chain of the Si portion of dimethylsiloxane.

Examples of the fluorosurfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate compound, a perfluoroalkyl ethylene oxide adduct, and a perfluoroalkyl ether group in the side chain. Polyoxyalkylene ether polymer compounds are particularly preferred because of their low foaming properties. Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid, perfluoroalkyl sulfonate, and the like. Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylate. Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain include 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. As counter ions of salts in these fluorosurfactants, 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) ₃ etc. are mentioned.

  Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine.

  Nonionic surfactants include, for example, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ester, polyoxyethylene alkylamine, polyoxyethylene alkylamide, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan Examples include fatty acid esters and ethylene oxide adducts of acetylene alcohol.

  Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate salt, and the like.

  These may be used alone or in combination of two or more.

  The silicone surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. For example, side chain modified polydimethylsiloxane, both terminal modified polydimethylsiloxane, one terminal modified polydimethylsiloxane, side Since both ends of the chain are modified with polydimethylsiloxane, a polyether-modified silicone surfactant having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group exhibits good properties as an aqueous surfactant. preferable.

  As such a surfactant, an appropriately synthesized product or a commercially available product may be used. Commercially available products can be obtained from, for example, Big Chemie Co., Ltd., Shin-Etsu Chemical Co., Ltd., Toray Dow Corning Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.

  There is no restriction | limiting in particular as said polyether modified silicone surfactant, According to the objective, it can select suitably, For example, the polyalkylene oxide structure represented by a general formula (S-1) type | formula is dimethylpolyethylene. Examples thereof include those introduced into the side chain of Si part of siloxane.

Formula (S-1)
(In the general formula (S-1), m, n, a, and b represent integers. R and R ′ represent an alkyl group and an alkylene group.)

  A commercial item can be used as said polyether modified silicone type surfactant, For example, KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS- 1906EX (Japan Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Toray Dow Corning Silicone Co., Ltd.), BYK-33, BYK-387 (Bic Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicon Co., Ltd.), etc. are mentioned.

  As the fluorine-based surfactant, a fluorine-substituted compound having 2 to 16 carbon atoms is preferable, and a fluorine-substituted compound having 4 to 16 carbon atoms is more preferable.

  Examples of the fluorosurfactant include perfluoroalkyl phosphate compounds, perfluoroalkylethylene oxide adducts, and polyoxyalkylene ether polymer compounds having a perfluoroalkyl ether group in the side chain. Among these, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain is preferable because of its low foaming property, and in particular, fluorine-based compounds represented by the general formulas (F-1) and (F-2) A surfactant is preferred.

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

Formula (F-2)
_{C n F 2n + 1- CH 2} CH (OH) CH 2 -O- (CH 2 CH 2 O) a -Y

In the compound represented by the general formula (F-2), Y is H, or CnF _{2n + 1} , n is an integer of 1 to 6, or CH ₂ CH (OH) CH ₂ —CnF _{2n + 1,} where n is 4 to 6. An integer, or CpH _{2p + 1} , p is an integer of 1-19. a is an integer of 4-14.

  A commercial item may be used as said fluorosurfactant. As this commercial item, for example, Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullrad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M Limited); Megafac F-470, F -1405, F-474 (all manufactured by Dainippon Ink & Chemicals, Inc.); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all are corporations) (Manufactured by Male), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (Omnova), Unidyne DSN-403N (produced by Daikin Industries, Ltd.), and the like. Among these, FS-300 manufactured by Du Pont, FT-110, FT-250 manufactured by Neos Co., Ltd., and the like, have excellent print quality, particularly color developability, paper permeability, wettability, and leveling. FT-251, FT-400S, FT-150, FT-400SW, Polyfox PF-151N manufactured by Omninova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferable.

  There is no restriction | limiting in particular as content of surfactant in an ink, Although it can select suitably according to the objective, From the point which is excellent in wettability and discharge stability, and image quality improves, it is 0.001 mass. % To 5% by mass is preferable, and 0.05% to 5% by mass is more preferable.

  Any of the above surfactants can be used in the present invention. However, it is preferable to use a fluorosurfactant from the viewpoints of high foaming properties and low defoaming properties. It is preferable to use a fluorine-based surfactant of 05% by mass or more.

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

<Rust preventive>
There is no restriction | limiting in particular as a rust preventive agent, For example, acidic sulfite, sodium thiosulfate, etc. are mentioned.

<PH adjuster>
The pH adjuster 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.

  There is no restriction | limiting in particular as a physical property of an ink, According to the objective, it can select suitably, For example, it is preferable that a viscosity, surface tension, pH, etc. are the following ranges.

  The viscosity at 25 ° C. of the ink 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 printing density and character quality and obtaining good discharge properties. More preferred. Here, for the viscosity, for example, a rotary viscometer (RE-80L manufactured by Toki Sangyo Co., Ltd.) can be used. Measurement conditions are 25 ° C., standard cone rotor (1 ° 34 ′ × R24), sample liquid amount 1.2 mL, rotation speed 50 rpm, and measurement is possible for 3 minutes.

  The pH of the ink is preferably 7 to 12 and more preferably 8 to 11 from the viewpoint of preventing corrosion of the metal member in contact with the liquid.

[Liquid ejection device (droplet ejection device)]
FIG. 1 is a schematic diagram showing the configuration of a liquid ejection apparatus 1 (inkjet apparatus) which is an embodiment of the liquid ejection apparatus of the present invention.

  The liquid ejecting apparatus 1 supplies nozzles 3 for ejecting droplets of ink and the like, a head (droplet ejecting unit) 2 having an ejecting mechanism, and liquids (first liquid and second liquid) to the head 2. A first ink supply path (first path) 100 for supplying the liquid and a second ink supply path (second path) 110 for supplying the liquid (first liquid, second liquid) to the head 2. A first liquid supply unit 20 including an ink tank (first liquid storage unit) 21 that supplies ink (first liquid) 22 to the head 2 via the first ink supply path 100; The first ink supply path 100 and the second ink supply path 110 are connected to each other via a valve A (first switching valve 101) and a valve B (second switching valve 111), and bypass the head 2. Circulation path (third path) 120 and circulation path Degassing device 121 (degassing means 121a + vacuum generating device (pump) 121b) and liquid circulating means (pump) 122 arranged on 20 and first ink supply path 100 or second ink supply path 110 A cleaning liquid supply path (fourth path) 130 connected to the head via the valve C (third switching valve 102) and a cleaning liquid for supplying the cleaning liquid 42 (second liquid) to the head via the cleaning liquid supply path 130 In order to flow the liquid in the second liquid supply unit 40 provided with the tank 41 and the first ink supply path 100 or the second ink supply path 110 to the head, the first ink supply path 100 or the second ink supply path 100 is used. And a valve D (path opening / closing means 112) installed on the ink supply path 110.

  The head (droplet discharge unit) 2 includes a plurality of fine nozzles 3 that discharge ink (first liquid) 22 on the tip surface, and a liquid chamber that communicates with the nozzles and holds ink therein. ing. In addition, a first supply port 5 and a second supply port 6 for allowing ink or cleaning liquid to flow into or out of the liquid chamber are disposed at different portions of the head 2, respectively. The first supply port 5 is connected to one end of the first ink supply path 100, and the second supply port 6 is connected to one end of the second ink supply path 110.

  As a method for ejecting ink as droplets from the nozzle 3 (droplet ejection mechanism), a method for extruding the ink by heating, a method for extruding the ink by applying a voltage to the piezo element disposed inside the head and deforming it, etc. Is mentioned.

  Printing can be performed by ejecting ink from the nozzles 3 to the print target. Examples of the print target include sheet-like items such as paper.

  One end of the first ink supply path (first path) 100 is connected to the first supply port 5 of the head, and the other end communicates with the ink 22 in the ink tank 21, and the three flow paths r1 and r2 are connected. , R3.

  The cleaning liquid supply path (fourth path) 130 includes a flow path r4 having one end connected to the valve C and the other end communicating with the cleaning liquid 42 in the cleaning liquid tank 41.

  The valve A (first switching valve 101), the valve B (second switching valve 111), and the valve C (third switching valve 102) are connected in communication with three paths, respectively. It has a function of conducting (communication) any two of them simultaneously.

  That is, the valve A is disposed in the middle of the first ink supply path 100 and is connected to one end of the circulation path 120. The valve B is disposed in the middle of the second ink supply path 110 and is connected to the other end of the circulation path 120. The valve C is disposed in the middle of the first ink supply path 100 closer to the ink tank 21 than the valve A, and is connected to one end (downstream end) of the cleaning liquid supply path 130. The valve D (path opening / closing means 112) is disposed in the middle of the second ink supply path 110 closer to the waste liquid tank 50 than the valve B, and opens and closes the second ink supply path 110 to communicate with the atmosphere. Has a function of connecting and disconnecting (blocking, connecting).

  As a method of switching the connection pattern (opening / closing pattern) between paths by the valve A, the valve B, the valve C, and the valve D, there are a manual method, a pneumatic method, and an electromagnetic method. However, when these are controlled by the control circuit, the electromagnetic type is desirable.

<First liquid supply unit>
Next, the ink tank 21 and its peripheral part (first liquid supply part 20) will be described. The ink tank 21 is a container that stores ink discharged from the nozzles of the head 2. A first pressurization device (first pressurization means) 23 and a decompression device (decompression means) 24 communicate with the gas phase at the upper part in the ink tank. Also, one end (opening) of the first ink supply path 100 enters the ink tank and reaches the lower part thereof, and is arranged to communicate with the ink 22 inside the ink tank.

  The first ink supply path 100 is connected from the ink tank 21 to the first supply port 5 through the valve C and the valve A.

  The first pressurizing device 23 is a pneumatic pressurizing device that sends out compressed air, and is controlled to be driven and stopped arbitrarily in response to a control signal from a control circuit. An example of the first pressurizing device 23 is a configuration in which a compressor and a solenoid valve that opens and closes a path for sending out compressed air generated by the compressor are combined. When the first pressure device 23 is driven, the gas phase in the sealed ink tank is pressurized, and the ink is pushed out in the direction of the first ink supply path 100.

  The decompression device 24 is a device that decompresses air, and is driven, stopped, and controlled in magnitude by the control circuit. The decompression device 24 generates a pressure difference between the first liquid supply unit and the second ink supply path 110 to recover the ink (first liquid) from the head to the first liquid supply unit 20. 1 liquid recovery mechanism. The decompression device 24 may be configured by combining a vacuum pump and an adjustment device that regulates the amount of decompression by limiting the flow rate of air flowing through a path connected to the vacuum pump. When the decompression device 24 is driven to decompress the gas phase in the ink tank, the ink in the first ink supply path 100 is drawn back to the ink tank 21 side.

  In the liquid ejecting apparatus 1, when the ink pressure in the head 2 is larger than the atmospheric pressure, ink leaks unintentionally from the nozzle 3. In order to prevent this, it is effective to drive the decompression device 24. By decompressing the gas phase in the sealed ink tank, the ink in the ink tank 21 is decompressed. Thereby, a negative pressure is supplied into the liquid chamber of the head through the first ink supply path 100, and the ink in the head 2 can be decompressed. For this reason, the pressure of the ink in the head 2 can be maintained at an appropriate negative pressure.

  Further, by increasing the amount of decompression generated by the decompression device 24, the ink in the head 2 can be collected in the ink tank 21 through the first ink supply path 100.

<Second liquid supply unit>
Next, the configuration of the cleaning liquid tank 41 and its peripheral part (second liquid supply part 40) will be described. The cleaning liquid tank 41 is a sealed container that stores a cleaning liquid 42 for cleaning the head 2 and its peripheral paths 100 and 110. A second pressurizing device (second pressurizing means) 43 communicates with the gas phase at the upper part in the cleaning liquid tank 41. Further, the end (opening) of the cleaning liquid supply path 130 enters the cleaning liquid tank and extends to the lower part thereof, and is arranged to communicate with the cleaning liquid inside the cleaning liquid tank. The cleaning liquid supply path 130 is connected to the valve C from the cleaning liquid tank 41.

  The internal configuration of the second pressure device 43 is the same as that of the first pressure device 23. When the second pressurizing device 43 is driven, the gas phase in the cleaning liquid tank 41 is pressurized, and the cleaning liquid 42 is pushed out in the direction of the cleaning liquid supply path 130.

(Waste liquid tank)
Next, the configuration of the waste liquid tank 50 and its periphery will be described. The waste liquid tank 50 is a container for discharging a part of the cleaning liquid 42 that has cleaned the liquid chamber of the head 2. The liquid discharged from the head 2 to the second ink supply path 110 is received by the waste liquid tank 50.

  The waste liquid in the waste liquid tank 50 is not in contact with the end of the second ink supply path 110, and the end of the second ink supply path 110 on the waste liquid tank side is in contact with the atmosphere. Thereby, when the pressure reducing device 24 on the ink tank 21 side is driven, the air can be sucked from the second ink supply path 110 to the head 2. The waste liquid tank 50 is used for cleaning the head peripheral path in the cleaning process.

<Circulation route>
Next, the circulation path 120 that circulates the liquid through the path avoiding the head will be described. The circulation path 120 has one end connected to the valve A and the other end connected to the valve B. A deaerator 121a, a pump 122, and a filter 123 are disposed on the circulation channel.

  The deaeration device 121a is a device that removes dissolved gas in the ink. The inside of the deaeration device is divided into an ink chamber 121a-1 and a gas chamber 121a-2. The ink chamber and the gas chamber 121a-1 are partitioned by a member 121a-3 that allows gas to pass through without passing through the liquid. When ink is flowed into the ink chamber 121a-1 and the gas chamber 121a-2 is depressurized, the gas dissolved in the ink in the ink chamber moves to the gas chamber via the gas-permeable member 121a-3, and passes through the ink. I can degas. A hollow fiber membrane is mentioned as a member which permeate | transmits gas without letting a liquid pass.

  As the deaeration device 121a, a material having a property of allowing ink to pass therethrough, for example, a hollow fiber bundle made of a Teflon (registered trademark) tube or a silicon tube is disposed in the deaeration chamber, and the periphery thereof is depressurized by a vacuum pump. It is also possible to use a gas treatment that separates and removes the gas dissolved in the ink. Furthermore, various other methods such as an ultrasonic vibration method and a centrifugal separation method can be adopted as the ink degassing method in the degassing device 121a.

  The filter 123 allows the ink flowing through the circulation path 120 to pass therethrough and removes dust, foreign matter, solid matter, and the like mixed in the ink. Examples of the material of the filter 123 include fibrous materials such as glass fiber.

  The pump 122 is a means for circulating the ink in the circulation path 120 and the head 2 at a constant flow rate, and the drive and stop of the pump 122 can be arbitrarily controlled by the control circuit.

  The gas chamber 121a-2 of the deaerator 121a is connected to the vacuum generator 121b through a tube 121c. By depressurizing the gas chamber 121a-2 in the degassing device 121a by driving the vacuum generator 121b, degassing from the ink can be performed. A vacuum pump etc. are mentioned as the vacuum generator 121b. The vacuum generator 121b can be arbitrarily controlled to be driven and stopped by a control circuit. Thereby, the deaeration and stop by the deaeration apparatus 121a can be controlled arbitrarily. In addition, the order which arrange | positions the pump 122, the deaeration apparatus 121a, and the filter 123 in the middle of a circulation path may be out of order.

<Ink filling>
Next, a procedure for filling the circulation path 120 with ink will be described. First, the valve A is operated and set so that the flow paths (r1, r2, r8) from the ink tank 21 to the deaeration device 121a are communicated. On the other hand, the flow path r3 is blocked by the valve A, and the flow path r4 is also blocked by the valve C. Further, the valve B is operated and set so that the pump 122 in the circulation path can communicate with the waste liquid tank 50 (atmosphere).

  Next, the pump 122 is driven to move the ink from the ink tank 21 toward the waste liquid tank 50. In other words, the flow path r5 is blocked by the valve B to connect the flow path r11 (flow paths r10, r9, r8) and the flow path r6, and the valve D is opened to connect the flow paths r6 and r7.

  The pump 122 is driven until the circulation path 120 (r8, r9, r10, r11) from the valve A to the deaerator 121a, the pump 122, and the valve B is filled with ink, and when the circulation path 120 is filled with ink, The pump 122 is stopped. As a result, the ink is filled in the circulation path 120 of the valve A to the deaerator 121 to the pump 122 to the filter 123 to the valve B.

  Next, a method for filling the head 2 with ink will be described. First, the valve A and the valve C are operated to set the flow paths (r1, r2, r3) from the ink tank 21 to the first supply port 5 in a communicating state.

  The valve r is operated to keep the flow path r8 open. Further, the valve C is operated to block the flow path r4. Further, the valve B is operated to connect the flow paths r5, r6, r11 so that the flow path is communicated from the second supply port 6 to the waste liquid tank. At this time, the valve D is operated to open the flow path r7.

  Thereby, the flow paths r1, r2, r3, the liquid chamber in the head, and the flow paths r5, r6, r7 are in communication. The circulation path 120 is also in communication with the first ink supply path 100 and the valve B.

  Next, the inside of the ink tank 21 is pressurized using the first pressure device 23, and the ink 22 is moved into the head 2 through the first ink supply path 100. When the first ink supply path 100, the liquid chamber in the head, and the flow paths r1 to r3, r5, r6 from the second supply port 6 to the valve D are filled with ink, the ink tank 21 is pressurized. Stop. Next, the valve D is closed. As a result, ink is filled in the ink tank 21 to the deaerator 121a to the pump 122 to the filter 123 to the valve B circulation path and the head.

  By driving the head in this state, it is possible to eject ink droplets from the nozzles.

  In addition, by driving the vacuum generator 121b while circulating the ink in the circulation path by the pump 122, deaeration from the ink using the deaerator 121a can be performed.

  Since the pump 122 is used to circulate and deaerate ink in the circulation path, the ink can be deaerated. In addition, the inside of the head can be cleaned by pressurizing the cleaning liquid with air pressure and pushing it out from the nozzle, so that it is possible to simultaneously satisfy two requirements that have been difficult to achieve in the past.

<Ink ejection>
Next, a method for ejecting ink (droplets) from the nozzles of the head will be described. First, the valve A and the valve C are operated so that the first ink supply path 100 from the ink tank 21 to the first supply port 5 is communicated. Further, the valve B is operated to connect the flow paths r5 and r6, the flow path r7 is set from the second supply port 6 to the waste liquid tank (atmosphere), and the valve D is operated to open the flow path r7. Set as follows. At this time, the liquid chamber in the head is filled with ink, and the first ink supply path 100 from the ink tank 21 to the head is opened.

  Next, the head 2 is driven using a head driving circuit, and ink is ejected from the nozzle 3. When the ink in the liquid chamber in the head is consumed by discharging the ink, the ink is supplied from the ink tank 21 to the head 2 by the osmotic pressure.

  Further, by driving the pressure reducing device 24 to adjust the amount of pressure reduction in the ink tank, the ink pressure in the head is maintained at an appropriate negative pressure through the gas phase in the ink tank and the first ink supply path 100. .

  Here, a negative pressure amount for properly maintaining the ink pressure in the head will be described. When the ink tank 21 is installed at a position relatively higher than the head 2 and the head 2 is filled with ink, pressure is applied to the ink in the head according to Bernoulli's theorem.

If the pressure in the gas phase in the ink tank is P1, the ink pressure in the nozzle part in the head is P2, and the height of the bottom surface of the ink tank viewed from the nozzle part is h0, the ink pressure P2 in the nozzle part is Given in 1).
P2 = P1 + ρ × h0 × g (1)
Here, ρ is the density of the ink, and g is the acceleration of gravity.

  If the gas-phase pressure P1 in the ink tank is equal to the atmospheric pressure, the ink pressure P2 in the nozzle portion is higher than the atmospheric pressure according to the equation (1). At this time, since the pressure of the air outside the nozzle is atmospheric pressure, the pressure P2 in the nozzle portion becomes higher than the air outside the nozzle, and a phenomenon occurs in which ink dripping from the nozzle portion to the outside occurs.

  Therefore, in order to prevent ink from dripping from the nozzle portion to the outside, the ink pressure P2 of the nozzle portion needs to be approximately the same as the atmospheric pressure. In order to prevent ink from dripping from the nozzle portion to the outside, it is effective to make the gas phase pressure P1 in the ink tank smaller than the atmospheric pressure from the relationship of the equation (1).

When the pressure of the gas in the gas phase in the ink tank when the ink pressure P2 of the nozzle portion is equal to the atmospheric pressure is P1 ′, P1 ′ is given by the following equation (2) from the equation (1).
P1 ′ = P0−ρ × h0 × g (2)
Here, P0 is atmospheric pressure.

  When ejecting ink from the head 2, the decompression device is driven so that the pressure in the gas phase in the ink tank 21 is approximately the same as P1 'given by the equation (2). Printing can be performed by relatively moving the print target and the head 2 while discharging ink from the head 2.

<Ink circulation / deaeration>
Next, a method for circulating and degassing the ink in the circulation path 120 (circulation and degassing timing, ink flow direction and flow channel) will be described.

  As an example, a degassing method for degassing while circulating ink (second liquid) in the circulation path 120 (third path) in the liquid ejection apparatus 1 will be described.

  In this deaeration method for deaeration while circulating, the valve A (first switching valve 101), the circulation path 120, the valve B (second switching valve 111), and the head 2 (droplet discharge unit) are closed. The ink is circulated by the pump 122 (liquid circulation means) in a state where ink is filled in the route (flow paths r3, r8, r9, r10, r11, r5, head), and the deaerator 121a (degasser) The deaeration is performed from the ink using a gas means.

  That is, circulation and deaeration are performed in a state where ink is filled in the valve A to the first supply port 5 to the head 2 to the second supply port 6 to the valve B and the circulation path 120.

  First, the ink in the closed path of the valve A, the deaerator 121a, the pump 122, the filter 123, the valve B, the second supply port 6, the head 2, the first supply port 5, and the valve A is discharged by the pump 122. Circulate.

  At this time, the valve A is set so that the flow paths r3 and r8 from the first supply port 5 to the deaeration device 121a communicate with each other (the flow path r2 is blocked). The valve B is set so that the flow paths r10, r11, r5 from the pump to the second supply port 6 communicate with each other (the flow path r6 is blocked).

  Next, while the pump 122 is driven to circulate the ink in the path, the ink is deaerated using a deaeration device. That is, the vacuum generator 121b is driven to depressurize the gas chamber 121a-2 inside the deaerator. Thus, the dissolved air in the ink flowing inside the liquid chamber 121a-1 of the deaerator is sucked to the vacuum generator through the deaerator and the ink is deaerated.

  At this time, since the ink passes through the filter 123 in the circulation path, fine particles such as dust mixed in the ink can be removed.

  This ink circulation and deaeration is performed for a predetermined time. After a predetermined time has elapsed since the start of circulation and deaeration, the vacuum generator 121b is stopped to stop the deaeration operation. Next, the pump is stopped to stop the ink circulation. The direction in which the ink is circulated in the closed path by the pump 122 can be circulated and deaerated by any of the clockwise and counterclockwise directions in FIG.

[Image forming apparatus]
The liquid ejection apparatus according to the present invention described above can be applied to an image forming apparatus (inkjet recording apparatus).

  FIG. 2 is a perspective explanatory view of an ink jet recording apparatus using the liquid ejection apparatus according to the present invention, and FIG. 3 is a side explanatory view of a mechanism portion of the recording apparatus.

  The ink jet recording apparatus 200 includes a carriage that is movable in the main scanning direction inside the recording apparatus main body 201, a recording head that is an ink jet head that implements the present invention mounted on the carriage, an ink cartridge that supplies ink to the recording head, and the like. The printing mechanism unit 202 and the like to be stored are accommodated.

  A sheet feeding cassette (or a sheet feeding tray) 204 on which a large number of sheets P can be stacked from the front side can be detachably attached to the lower part of the apparatus main body 201. Further, the manual feed tray 205 for manually feeding the paper P can be opened, the paper P fed from the paper feed cassette 204 or the manual feed tray 205 is taken in, and a required image is displayed by the printing mechanism unit 202. After recording, the paper is discharged to a paper discharge tray 206 mounted on the rear side.

  The printing mechanism unit 202 holds the carriage 209 slidably in the main scanning direction with a main guide rod 207 and a sub guide rod 208 which are guide members horizontally mounted on the left and right side plates. The carriage 209 is provided with a head 210 comprising an ink jet head according to the present invention for ejecting ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Holes) are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward. In addition, each ink cartridge 211 for supplying ink of each color to the head 210 is replaceably mounted on the carriage 209.

  The ink cartridge 211 has an air port that communicates with the atmosphere upward, a supply port that supplies ink to the inkjet head below, and a porous body filled with ink inside, and the capillary force of the porous body Thus, the ink supplied to the inkjet head is maintained at a slight negative pressure. Further, although the heads 210 of the respective colors are used here as the recording heads, a single head having nozzle holes for ejecting ink droplets of the respective colors may be used.

  Here, the carriage 209 is slidably fitted on the main guide rod 207 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 208 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 209 in the main scanning direction, a timing belt 215 is stretched between a driving pulley 213 and a driven pulley 214 that are rotationally driven by a main scanning motor 212. The timing belt 215 is fixed to the carriage 209, and the carriage 209 is driven to reciprocate by forward and reverse rotation of the main scanning motor 212.

  On the other hand, in order to convey the paper P set in the paper cassette 204 to the lower side of the head 210, the paper P is guided to the paper feed roller 216 and the friction pad 217 for separating and feeding the paper P from the paper cassette 204. A guide member 218, a transport roller 219 that reverses and transports the fed paper P, a transport roller 220 that is pressed against the peripheral surface of the transport roller 219, and a leading edge that defines the feed angle of the paper P from the transport roller 219 A roller 221 is provided. The transport roller 219 is rotationally driven by a sub-scanning motor 222 through a gear train.

  A printing receiving member 223 is provided as a paper guide member for guiding the paper P sent from the transport roller 219 on the lower side of the recording head 210 corresponding to the movement range of the carriage 209 in the main scanning direction. A conveyance roller 224 and a spur 225 that are rotationally driven to send the paper P in the paper discharge direction are provided on the downstream side of the printing receiving member 223 in the paper conveyance direction, and the paper P is further delivered to the paper discharge tray 206. A roller 226 and a spur 227 and guide members 228 and 229 that form a paper discharge path are disposed.

  At the time of recording, the recording head 210 is driven according to the image signal while moving the carriage 209, thereby ejecting ink onto the stopped paper P to record one line. Record the line. Upon receiving a recording end signal or a signal that the trailing edge of the paper P reaches the recording area, the recording operation is terminated and the paper P is discharged.

  Further, a recovery device 230 for recovering the ejection failure of the head 210 is disposed at a position outside the recording area on the right end side in the moving direction of the carriage 209. The recovery device 230 includes a cap unit, a suction unit, and a cleaning unit. The carriage 209 is moved to the recovery device 230 side during printing standby, and the head 210 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

  When ejection failure occurs, etc., the ejection port (nozzle hole) of the head 210 is sealed by the capping unit, and bubbles and the like are sucked out from the ejection port by the suction unit through the tube. Etc. are removed by the cleaning means, and the ejection failure is recovered. The sucked ink is discharged to a waste ink reservoir installed at the lower part of the main body, and is absorbed and held by an ink absorber inside the waste ink reservoir.

<Recording medium>
The recording medium used for recording is not particularly limited, and examples thereof include plain paper, glossy paper, special paper, cloth, film, OHP sheet, and general-purpose printing paper.

<Recorded material>
The ink recorded matter of the present invention has an image formed using the ink of the present invention on a recording medium. Recording can be performed by recording with an inkjet recording apparatus and an inkjet recording method.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples. In the following, “part” means “part by mass” unless otherwise specified. “%” Represents “% by mass” unless otherwise specified.

The components of the surfactant and antifoam used in the inks of Examples and Comparative Examples are as follows (Tables 1 to 3).
Surfactant A-1:
Fluorine-based surfactant (polyoxyalkylene (C2-C3) -2-perfluoroalkyl (C4-C16) ethyl ether)
Surfactant A-2:
Acetylene glycol surfactant (2,4,7,9-tetramethyl-5-decyne-4,7-diol)
-Antifoam B-1
2,4,7,9-tetramethyl-4,7-decanediol

<Preparation of Bk self-dispersing pigment dispersion>
Black Pearls (registered trademark) 1000 manufactured by Cabot Corporation (carbon black having a BET surface area of 343 m ² / g and DBPA 105 mL / 100 g), 100 mmol of sulfanilic acid, and 1 L of ion-exchanged high-purity water were mixed in a Silverson mixer (6000 rpm) at room temperature. If the pH of the resulting slurry is higher than 4, 100 mmol of nitric acid is added. After 30 minutes, sodium nitrite (100 mmol) dissolved in a small amount of ion-exchanged high purity water was slowly added to the above mixture. Furthermore, it heated at 60 degreeC, stirring, and was made to react for 1 hour. A modified pigment with sulfanilic acid added to carbon black was produced.

  Subsequently, the modified pigment dispersion was obtained after 30 minutes by adjusting the pH to 9 with a 10% tetrabutylammonium hydroxide solution (methanol solution). Perform ultrafiltration using a dialysis membrane using a dispersion containing a pigment bound to at least one sulfanilic acid group or sulfanilic acid tetrabutylammonium salt and ion-exchanged high-purity water, and further ultrasonically disperse the pigment solids. Accident-dispersed pigment dispersion liquid 1 having a concentration of 20% was obtained. The surface treatment level was 0.75 mmol / g, and the particle diameter (D50) measured with a particle size distribution analyzer (Nikkiso Co., Ltd., Nanotrac UPA-EX150) was 120 nm.

<Preparation of aqueous dispersion of polyurethane resin 1>
In a simple pressure reactor equipped with a stirrer and a heater, 287.9 parts of crystalline polycarbonate diol of Mn 2,000 [Duranol T6002, manufactured by Asahi Kasei Chemicals Co., Ltd.], 3.6 parts of 1,4 butanediol, DMPA (Dimethylolpropionic acid) 8.9 parts, hydrogenated MDI 98.3 parts and acetone 326.2 parts were charged while introducing nitrogen. Thereafter, the mixture was heated to 90 ° C. and subjected to urethanization reaction for 8 hours to produce a prepolymer.

  After cooling the reaction mixture to 40 ° C., 10.0 parts of triethylamine was added and mixed, and 568.8 parts of water was further added and emulsified with a rotor-stator type mechanical emulsifier to obtain an aqueous dispersion. . 28.1 parts of 10% ethylenediamine aqueous solution was added to the obtained aqueous dispersion with stirring, and the mixture was stirred at 50 ° C. for 5 hours to carry out chain elongation reaction.

  Thereafter, acetone was removed at 65 ° C. under reduced pressure to adjust the water content to obtain an aqueous dispersion of polyurethane resin 1 having a solid content of 40% by mass. The particle size (D50) of the aqueous dispersion of polyurethane resin 1 was 9 nm as measured with a particle size distribution measuring device (Nanotrack UPA-EX150, manufactured by Nikkiso Co., Ltd.).

-Preparation of ink-
The resin particle content shown below is all solid content.

<Ink 1>
In a container equipped with a stirrer, 20.00 parts by mass of propylene glycol, 10.00 parts by mass of 1.3-butanediol, 5.00 parts by mass of 3-methyl-1.3butanediol and 2-ethyl-1. Add 2 parts of 3-hexanediol and 0.50 parts by mass of Capstone FS-300 (manufactured by DuPont) as a surfactant, and stir it for about 30 minutes to make it uniform. Next, 6.0 parts by mass and high-purity water are added to the self-dispersing pigment dispersion 1 in terms of solid content, and the mixture is stirred for about 60 minutes to make it uniform. Further, 4.50 parts by mass of polyurethane resin 1 is added and stirred for 30 minutes to make the ink uniform. This ink was subjected to pressure filtration with a polyvinylidene fluoride membrane filter having an average pore diameter of 1.2 μm to remove coarse particles and dust, thereby preparing the ink of Example 1 (Table 1). High purity water was added so that the total amount would be 100 parts by mass.

<Ink 2-14>
As with Ink 1, the water-soluble organic solvent and the surfactant shown in Tables 1 and 2 below are mixed and stirred, and a water-dispersible colorant (pigment dispersion) and high-pure water are added and mixed and stirred. Mixing and stirring the functional resin to make the ink uniform.

  This ink was filtered under pressure with a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, thereby preparing inks 2 to 14.

<Ink physical properties>
The viscosity and dynamic surface tension of each of the inks 1 to 14 were measured as follows. The results are shown in Tables 3 and 4.

-Viscosity-
The viscosity (mPa · s) of each ink at 25 ° C. was measured at an appropriate rotation speed of 10 to 100 rpm using an R-type viscometer (RC-500, manufactured by Toki Sangyo Co., Ltd.).

―Dynamic surface tension―
The dynamic surface tension was measured by a maximum bubble pressure method using a dynamic surface tension meter SITA DynaTester (manufactured by SITA Messtechnik) in a 25 ° C. environment.

―Measurement of Ross Miles method―
Each ink was stored for 10 days in an environment of 70 ° C., and the foaming power and defoaming power of the ink before and after storage were measured by the above-mentioned Ross Smiles method (JIS K3362). The measured value according to the Ross Miles method (JIS K3362) before storage was defined as the Ross Miles method (initial value), and the measured value after storage was defined as the Ross Miles method (after storage).

  Next, various characteristics were evaluated as follows for each of the produced inks. The results are shown in Tables 3 and 4. Regarding the conditions shown below, when each ink satisfies the condition, it is indicated by “◎, ○, Δ”, and when the condition is not satisfied, it is indicated by “x”.

<Discharge stability>
In an environment adjusted to a temperature of 10 ° C. ± 0.5 ° C. and 15 ± 5% RH, an ink jet recording apparatus incorporating the liquid discharge device having the circulation means shown in FIG. 1 (Ricoh's IPSiO GXe-5500 modified machine) Using Ricoh Co., Ltd., printing was performed on My Paper (manufactured by NBS Ricoh Co., Ltd.). The print pattern was a chart in which each color print area was 5% of the total area of the paper, and each ink of yellow, magenta, cyan, and black was printed at 100% duty. The printing conditions were one-pass printing with a recording density of 600 dpi. After printing and drying, the presence or absence of streaks, white spots, and jet disturbance in the 5% chart solid portion was visually observed and evaluated. As a comparative example, a similar test was performed with a commercially available inkjet recording apparatus (Ricoh, IPSiO GXe-5500, manufactured by Ricoh Co., Ltd.) having no circulation mechanism. The evaluation criteria at this time were as follows, ◎ to Δ were accepted and x was rejected.

〔Evaluation criteria〕
A: There are no streaks, white spots, or jet turbulence observed in the solid part.
○: Some streaks, white spots, and jet turbulence are observed at one place in the solid portion.
Δ: Some streaks, white spots, and jet turbulence are observed in the solid portion within 3 places.
X: Streaks, white spots, and jet turbulence are observed throughout the solid part.

<Storage stability evaluation>
Changes in the values of the Ross Miles method (initial value) and the Ross Miles method (after storage) in the measurement of the Ross Miles method were evaluated according to the following criteria.
○: Decrease in foaming power after storage is less than 30% before storage Δ: Decrease in foaming power after storage is 30% or more and less than 50% before storage ×: Decrease in foaming power after storage More than 50% before storage

<Fixed image abrasion>
(Printing conditions)
Evaluation paper: RJT (Ricoh Co., Ltd.)
Chart: Black monochromatic solid patch Printing mode: Clean mode In the above chart, after 1 minute of printing, the black solid image portion was rubbed with the same evaluation paper under a load of 500 g, and the density of the transferred stain was measured by a reflection spectral densitometer (Xrite). The black density was measured with a Model: 939) manufactured by the company.
◎: Less than 0.1 ○: Less than 0.2 △: Less than 0.3 ×: 0.3 or more

<Image density>
In an environment adjusted to a temperature of 25 ° C. ± 0.5 ° C. and 50 ± 5% RH, printing is performed on My Paper (manufactured by NBS Ricoh Co., Ltd.) using the ink jet printer. The drive voltage of the piezo element was varied so as to make it easier, so that the same amount of ink was attached to the recording medium. Black ink was printed at 100% duty. The printing conditions were one-pass printing with a recording density of 300 dpi.

After the print was dried, measurement was performed with a reflective color spectrophotometric densitometer (manufactured by X-Rite) in a black single-color solid image portion, and the determination was made according to the following criteria.
◎: 1.25 or more ○: 1.20 or more and less than 1.25 Δ: 1.15 or more and less than 1.20 ×: less than 1.15

  The results are shown in Tables 3 and 4 below. Comprehensive judgment made x which has x even in one place in each evaluation.

1 Liquid Discharge Device 2 Head (Droplet Discharge Unit)
3 Nozzle 5 Supply port 6 Supply port 20 First liquid supply unit 21 Ink tank 22 Ink (first liquid)
23 Pressurizing device (pressurizing means)
24 Pressure reducing device (pressure reducing means)
40 Second liquid supply unit 41 Cleaning liquid tank 42 Cleaning liquid (second liquid)
43 Pressurizing device (pressurizing means)
50 Waste liquid tank 100 First ink supply path (first path)
101 First switching valve 102 Third switching valve 110 Second ink supply path (second path)
111 Second switching valve 112 Path opening / closing means 120 Circulation path 121 Deaeration means 121a Deaeration device 121a-1 Liquid chamber 121a-2 Gas chamber 121a-3 Member 121b Vacuum generator 121c Tube 122 Pump (liquid circulation means)
130 Cleaning liquid supply path 200 Inkjet recording apparatus (image forming apparatus)

JP 2007-270143 A JP 2008-63540 A

Claims (10)

A liquid discharge apparatus comprising ink and a liquid discharge unit having a nozzle for discharging the ink,
The liquid ejection unit includes a liquid chamber communicating with the nozzle, and a first supply port and a second supply port for allowing the ink to flow into or out of the liquid chamber,
A circulation means for causing the ink flowing out from one of the first supply port and the second supply port to flow into the other supply port via a circulation path;
The liquid ejecting apparatus according to claim 1, wherein the ink has a foam stability of 150 mm or more after 5 minutes measured according to the Ross Miles method (JIS K3362).   2. The liquid ejection apparatus according to claim 1, wherein the stability of the foam after 5 minutes measured according to the ink Loss-Miles method (JIS K3362) is 200 mm or more.   3. The liquid ejection according to claim 1, wherein the ink has a dynamic surface tension of 20.0 mN / m or more and 60.0 mN / m or less at 25 ° C. and a surface life of 15 ms by a maximum bubble pressure method. apparatus.   The liquid ejecting apparatus according to claim 1, wherein the ink contains a coloring material, an organic solvent, and water.   The liquid ejecting apparatus according to claim 1, wherein the ink contains a fluorinated surfactant.   The liquid ejecting apparatus according to claim 5, wherein the content of the fluorosurfactant contained in the ink is 0.05% by mass or more.   The liquid ejecting apparatus according to claim 1, wherein the ink includes resin particles.   8. The liquid ejection apparatus according to claim 7, wherein the content of the resin particles is 0.5% by mass or more and 30% by mass or less with respect to the total amount of ink.   An ink jet recording method for performing printing by discharging at 5 ° C. or more and 12 ° C. or less, 10% RH or more and 20% RH or less using the liquid discharge apparatus according to claim 1. A liquid discharge section having a nozzle for discharging liquid, a liquid chamber communicating with the nozzle, and a first supply port and a second supply port for allowing the liquid to flow into or out of the liquid chamber;
Ink for a liquid ejection apparatus, comprising: circulation means for causing the liquid flowing out from one of the first supply port and the second supply port to flow into the other supply port via a circulation path Because
An ink characterized by having a foam stability of 150 mm or more after 5 minutes measured according to the Ross Miles method (JIS K3362).

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