Image forming apparatus and ink set

Abstract

To provide an image forming apparatus capable of achieving both high productivity and discharge stability in an inkjet system by an intermediate transfer system and outputting an image having high fastness, and an ink set.SOLUTION: According to an aspect of the present disclosure, an ink jet recording apparatus includes an ejection head including a nozzle configured to eject an ink composition containing at least a solvent, a resin, and a coloring material and having a total non-volatile solid content in the ink composition of 20% or more and 30% or less. A circulation path through which the ink composition circulates from a first ink tank serving as a supply source through the individual liquid chamber to return to a second ink tank from the discharge port is formed, and an ink pressure of the ink composition in the circulation path is 2 kPa or more and 7 kPa or less between the first ink tank and the ejection head, and a pressure of the ink composition between the second ink tank and the ejection head is -7 kPa or more and -2 kPa or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and an ink set. [Background technology]

[0002] 2. Description of the Related Art Inkjet printers (an example of an image forming apparatus) have advantages such as low noise, low running costs, and ease of color printing, and are widely used as output devices for digital signals.

[0003] Widely used inks for such inkjet printers include, for example, solvent-based inks using organic solvents as solvents and ultraviolet-curable inks containing polymerizable monomers as their main components. However, with solvent-based inks, concerns exist regarding the environmental impact of evaporation of the organic solvent. Furthermore, with ultraviolet-curable inks, the selection of polymerizable monomers used is limited due to safety concerns. Therefore, ink sets including aqueous inks, which have a low environmental impact, have been proposed.

[0004] However, when the above ink is printed directly onto plain paper from the ejection device of an inkjet printer, the ink penetrates into the paper layer, making it difficult to satisfy all of the characteristics required for image density, image clarity, image drying, image bleeding, image show-through, etc. Therefore, a method has been devised to solve the above problems by using an inkjet recording method in which ink is ejected onto an intermediate transfer body, and then the ink held on the intermediate transfer body is transferred to a recording medium to obtain a recorded image.

[0005] Patent documents 1 and 2 disclose that ink ejected from an inkjet head is deposited on an intermediate transfer body, the water content in the ink is evaporated and concentrated by a heating element, and then the intermediate transfer body is pressed against a recording medium, the ink on the intermediate transfer body is transferred to the recording medium, and the recorded image is fixed; this makes it possible to suppress the penetration of the ink into the paper layer, and solves problems such as image drying, image bleeding, and image show-through.

[0006] However, there is an issue that productivity is low because a process of drying the ink deposited on the intermediate transfer body is required, and to solve this issue, a high-drying ink that has improved drying efficiency on the intermediate transfer body is required.

[0007] Generally, to improve the drying efficiency of ink, it is considered to use a low-boiling-point solvent for the ink or to add a non-volatile component to the ink. In particular, adding a resin as a non-volatile component is expected to improve the robustness of the formed image. However, when using a low-boiling-point solvent or a non-volatile component, the ink inside the ejection nozzle of the inkjet head tends to dry out easily, which can cause ejection defects such as non-ejection or deflection.

[0008] As a means of achieving both the use of fast-drying ink and ejection stability, a circulation-type inkjet head is known, which has a supply path leading from the ink supply port of the inkjet head to an individual liquid chamber, and an exhaust path leading from the individual liquid chamber to the ink exhaust port of the head.

[0009] Patent Documents 3 and 4 disclose that by using a circulation-type inkjet head to circulate ink in the flow paths within the head and expel air bubbles in the flow paths within the head, ejection defects can be improved and delicate images can be output. Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in view of the above, and has an object to provide an image forming apparatus and an ink set that can achieve both high productivity and ejection stability in an inkjet system using an intermediate transfer method and output images with high robustness. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems and achieve the object, the present invention provides an ejection head having a nozzle that ejects an ink composition that contains at least a solvent, a resin, and a colorant, and wherein the total amount of non-volatile solids in the ink composition is 20% or more and 30% or less, wherein an individual liquid chamber within the ejection head has both a supply port and a discharge port for the ink composition, and a circulation path is formed through which the ink composition circulates from a first ink tank that is a supply source, through the individual liquid chambers, and back to a second ink tank via the discharge port, and the ink pressure of the ink composition within the circulation path is 2 kPa or more and 7 kPa or less between the first ink tank and the ejection head, and -7 kPa or more and -2 kPa or less between the second ink tank and the ejection head. [Effects of the Invention]

[0012] According to the present invention, it is possible to achieve both high productivity and ejection stability in an inkjet method using an intermediate transfer method, and to output an image with high robustness. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram for explaining an example of an image printing device according to the present embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of a circulation type inkjet head included in the image printing device according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus and an image printing apparatus to which an ink set is applied will be described in detail below with reference to the accompanying drawings.

[0015] The image printing device according to this embodiment solves the problem by using the configuration shown in (1). (1) A printing method comprising: providing an ejection head having a nozzle for ejecting an ink composition containing at least a solvent, a resin, and a colorant, the ink composition having a total non-volatile solid content of 20% or more and 30% or less; The ejection head has an individual liquid chamber in the ejection head that has both a supply port and a discharge port for the ink composition, and a circulation path is formed through which the ink composition circulates from a first ink tank that is a supply source, through the individual liquid chamber, and back to the second ink tank via the discharge port; An image printing device, wherein the ink pressure of the ink composition in the circulation path between the first ink tank and the ejection head is 2 kPa or more and 7 kPa or less, and the pressure of the ink composition between the second ink tank and the ejection head is -7 kPa or more and -2 kPa or less.

[0016] Furthermore, although this embodiment relates to the ink described in (1) above, the following embodiments (2) to (8) are also included, and therefore these embodiments will also be described.

[0017] (2) The image printing device according to (1), wherein the flow rate of the ink composition in the circulation path is 10 mL / min or more and 100 mL / min or less. (3) The image printing device according to (1), having at least a first ink tank and a second ink tank in the circulation path, and having a structure in which the ink composition circulates from the second ink tank to the first ink tank through a liquid feed pump. (4) The image printing device according to (1), wherein the ink pressure of the ink composition in the circulation path is −3 kPa or more and −1 kPa or less on the nozzle surface of the ejection head. (5) The image printing device according to (1), wherein the flow rate of the ink composition in the liquid feed pump that circulates the ink composition from the second ink tank to the first ink tank is 10 mL / min or more and 100 mL / min or less. (6) The image printing device according to (1), wherein the resin contained in the ink composition is an acrylic resin. (7) The image printing device according to (1), wherein the total amount of resin solids contained in the ink composition is 20% or more and 25% or less. (8) The image printing device according to (1), wherein the ejection head has a pressure sensor for detecting the pressure of the ink composition and a pressure control device. (9) An ink jet head having a nozzle for jetting an ink composition containing at least a solvent, a resin, and a colorant, wherein the total amount of non-volatile solids in the ink composition is 20% or more and 30% or less, and the total amount of resin solids contained in the ink composition is 20% or more and 25% or less, The ink set is an ink set in which an individual liquid chamber in the ejection head has both a supply port and an outlet for the ink composition, and a circulation path is formed through which the ink composition circulates from a first ink tank, which is the supply source, through the individual liquid chamber, and back to a second ink tank via the outlet.

[0018] As described above, according to the image printing device of this embodiment, by using an ink composition in which the total amount of non-volatile solids in the ink composition is 20% or more and 30% or less, and the total amount of resin solids contained in the ink composition is 20% or more and 25% or less, high drying properties can be achieved, thereby improving the productivity of the intermediate transfer method and the robustness of the output image. Furthermore, by using an ejection head in which the individual liquid chambers in the ejection head have both a supply port and an outlet port for the ink composition and a circulation path is formed through which the ink composition circulates from the first ink tank, which is the supply source, through the individual liquid chambers in the ejection head, and from the outlet port back to the second ink tank, it is possible to prevent the ink composition from solidifying in the ejection head nozzles, and to achieve both ejection stability and stability.

[0019] Next, an image printing apparatus (an example of an image forming apparatus) according to this embodiment will be described in detail. FIG. 1 is a diagram illustrating an example of an image printing apparatus according to this embodiment. The image printing apparatus (e.g., an inkjet transfer recording apparatus) shown in FIG. 1 is equipped with inkjet recording heads 2, 3, 4, and 5 that eject a first ink (an example of an ink composition) onto an intermediate transfer belt 1, and a recording head 6 that ejects a second ink onto the intermediate transfer belt 1. The image printing apparatus shown in FIG. 1 also includes a transport roller 7 that is rotationally driven by gears, a heater (heating means) 8 that is arranged to heat the intermediate transfer belt 1, and a fixing roller 9 that transfers a recorded image formed on the intermediate transfer belt 1 to a recording medium 10 and fixes the recorded image.

[0020] The intermediate transfer belt 1 transports the first ink and the second ink adhering to its surface to the recording medium 10, and also has the function of evaporating the volatile components in the recorded image by heating with a heater 8, and transferring the dried recorded image between the intermediate transfer belt 1 and the recording medium 10 by the mechanical pressure of a fixing roller 9.

[0021] The surface of the intermediate transfer belt 1 can be formed using rubber materials such as silicone rubber, fluororubber, urethane rubber, NR natural rubber, SBR, NBR, nitrile rubber, CR chloroprene, HR butyl rubber, EPDM ethylene propylene rubber, and Hypalon. EPDM ethylene propylene rubber is particularly preferred because it improves the releasability of the intermediate transfer belt 1 and the recorded image, as well as the image quality on the intermediate transfer belt 1.

[0022] The inkjet recording heads 2 to 5 may be any of a variety of ink ejection heads, including a piezoelectric type that uses a piezoelectric element as a pressure generating means for pressurizing the ink in the ink flow path to deform a vibration plate that forms the wall of the ink flow path, thereby changing the internal volume of the ink flow path and ejecting ink droplets; a thermal type that uses a heating resistor to heat the ink in the ink flow path and generate bubbles; and an electrostatic type that arranges a vibration plate that forms the wall of the ink flow path opposite an electrode, and deforms the vibration plate by electrostatic force generated between the vibration plate and the electrode, thereby changing the internal volume of the ink flow path and ejecting ink droplets.

[0023] In the present embodiment, the inks (first and second inks) may be stored in ink storage containers such as ink cartridges.

[0024] The heater 8 (heating means) is not particularly limited, and heating means such as a halogen lamp or hot air may be used.

[0025] The temperature setting of the heater 8 (heating means) improves the transferability of the recorded image when the heater heats the intermediate transfer belt 1 (intermediate transfer body) and the recorded image to a temperature between 120°C and 160°C. If the temperature setting of the heater 8 is less than 120°C, the recorded image will not dry and solidify sufficiently, reducing the strength of the ink coating, causing the ink coating to break during transfer and reducing the transferability of the recorded image. If the temperature setting of the heater 8 is more than 160°C, the recorded image will dry out too much, causing the ink coating to break during transfer and reducing the image quality of the recorded image.

[0026] Next, an example of the configuration of the circulating inkjet head (inkjet recording heads 2 to 5) will be described. Fig. 2 is a diagram for explaining an example of the circulating inkjet head provided in the image printing device according to this embodiment.

[0027] The circulation type inkjet head has an ejection head 101 (an example of an ejection head), a supply side ink tank 102, a supply positive pressure air pump 103, a discharge side ink tank 104, a discharge negative pressure air pump 105, a circulation liquid feed pump 106, a supply ink pressure gauge 107, a discharge ink pressure gauge 108, and liquid feed paths 109, 110, and 111.

[0028] Ink liquid and air are introduced into a supply-side ink tank 102 (an example of a first ink tank) and a discharge-side ink tank 104 (an example of a second ink tank). By supplying air to the supply-side ink tank 102 from a supply positive pressure air pump 103, the ink inside is supplied to the ejection head 101 through a liquid feed path 109 (an example of a circulation path). Meanwhile, air is discharged from the discharge-side ink tank 104 through a discharge negative pressure air pump 105 to reduce the pressure, and ink is discharged from the ejection head 101 through a liquid feed path 110 (an example of a circulation path). Ink is also recovered from the discharge-side ink tank 104 to the supply-side ink tank 102 through a circulation liquid feed pump 106 (an example of a liquid feed pump) and a liquid feed path 111 (an example of a circulation path). The ejection head 101 has a structure that circulates ink from the discharge-side ink tank 104 to the supply-side ink tank 102 through the circulation liquid feed pump 106. The ink flow rate in the liquid feed paths 109, 110, and 111 may be 10 mL / min or more and 100 mL / min or less (see Table 2, etc.). Furthermore, the ink flow rate in the circulation liquid feed pump 106 may be 10 mL / min or more and 100 mL / min or less.

[0029] Pressure gauges 107 and 108 are installed in the liquid delivery paths 109 and 110, respectively, to measure the internal ink pressure, and mechanisms for controlling the pressure of the positive supply pressure air pump 103 and the negative discharge pressure air pump 105 are also installed. The method for controlling the pressure of each air pump can be selected as appropriate. That is, the pressure gauges 107 and 108 are an example of a pressure sensor that detects the pressure of the ink. Furthermore, the mechanisms for controlling the pressure of the positive supply pressure air pump 103 and the negative discharge pressure air pump 105 are an example of a device for controlling the pressure of the ink.

[0030] In the image printing device according to this embodiment, from the viewpoint of ink supply amount and ejection stability, it is preferable that the ink pressure P1 in the liquid feed path 109 is 2 kPa or more and 7 kPa or less. If the pressure P1 is less than 2 kPa, the ink supply will be insufficient, resulting in ejection failure. On the other hand, if the pressure P1 is more than 7 kPa, the ink supply will be excessive, causing ink to overflow from the nozzle surface and preventing normal ejection.

[0031] On the other hand, it is preferable that the ink pressure P2 in the liquid delivery path 110 is -7 kPa or more and -2 kPa or less. If the pressure P2 is less than -7 kPa, outside air is taken in from the nozzle surface, causing ejection defects, and if the pressure P2 is more than -2 kPa, the ink flow rate on the discharge side becomes small, causing ink to overflow from the nozzle surface and preventing normal ejection.

[0032] Furthermore, it is preferable that the ink pressure P3 in the ejection head 101 (i.e., the circulation path) be greater than -3 kPa and less than -1 kPa. If the pressure P3 is less than -3 kPa, outside air is taken in from the nozzle surface, causing ejection problems. If the pressure P3 is greater than -1 kPa, the ink flow rate on the discharge side decreases, causing ink to overflow from the nozzle surface and preventing normal ejection.

[0033] Next, the organic solvent (an example of a solvent), water, coloring material, resin, additives, etc. used in the first ink will be described. The first ink is an example of an ink composition containing at least a solvent, a resin, and a coloring material. The total amount of non-volatile solids in the first ink is 20% or more and 30% or less.

[0034] <Organic solvents> The organic solvent used in the present embodiment is not particularly limited, and any water-soluble organic solvent can be used. Examples of the water-soluble organic solvent include polyhydric alcohols, ethers such as polyhydric alcohol alkyl ethers and polyhydric alcohol aryl ethers, nitrogen-containing heterocyclic compounds, amides, amines, and sulfur-containing compounds.

[0035] Specific examples of the water-soluble organic solvent include ethylene glycol, diethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 3-methyl, 1,3-butanediol, triethylene glycol, polyethylene glycol, polypropylene glycol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 1,5-pentanediol, and the like. Polyhydric alcohols such as pentanediol, 1,2-hexanediol, 1,6-hexanediol, 1,3-hexanediol, 2,5-hexanediol, 1,5-hexanediol, glycerin, 1,2,6-hexanetriol, 2-ethyl, 1,3-hexanediol, ethyl, 1,2,4-butanetriol, 1,2,3-butanetriol, 2,2,4-trimethyl, 1,3-pentanediol, and petriol, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether. polyhydric alcohol alkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, N-methyl, 2-pyrrolidone, N-hydroxyethyl, 2-pyrrolidone, 1,3-dimethyl, 2-imidazolidinone, ε-caprolactam, and γ-butyrolactone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, 3-methoxy-N,N-dimethylpropionamide, and 3-butoxy, N,N-dimethylpropionamide; amines such as monoethanolamine, diethanolamine, and triethylamine; sulfur-containing compounds such as dimethyl sulfoxide, sulfolane, and thiodiethanol; propylene carbonate; and ethylene carbonate. The organic solvent not only functions as a wetting agent but also has good drying properties, so it is preferable to use an organic solvent having a boiling point of 250° C. or less.

[0036] As the organic solvent, polyol compounds having 8 or more carbon atoms and glycol ether compounds are also suitably used. Specific examples of polyol compounds having 8 or more carbon atoms include 2-ethyl, 1,3-hexanediol, 2,2,4-trimethyl, and 1,3-pentanediol.

[0037] Specific examples of glycol ether compounds include polyhydric alcohol alkyl ethers such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, and propylene glycol monoethyl ether; and polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether.

[0038] Polyol compounds having 8 or more carbon atoms and glycol ether compounds can improve the permeability of ink when paper is used as the recording medium.

[0039] The content of the organic solvent in the ink is not particularly limited and can be selected appropriately depending on the purpose. From the viewpoint of the drying property and ejection reliability of the ink, however, the content is preferably 3% by mass or more and 30% by mass or less, and more preferably 5% by mass or more and 20% by mass or less.

[0040] <Water> The water content in the ink is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoint of the drying properties and ejection reliability of the ink, it is preferably 10% by mass or more and 90% by mass or less, and more preferably 50% by mass to 80% by mass.

[0041] <Colorant> The coloring material is not particularly limited, and pigments and dyes can be used. As the pigment, inorganic pigments or organic pigments can be used. These can be used alone or in combination of two or more. Mixed crystals can also be used.

[0042] Examples of pigments that can be used include black pigments, yellow pigments, magenta pigments, cyan pigments, white pigments, green pigments, orange pigments, glossy pigments such as gold and silver pigments, and metallic pigments.

[0043] As inorganic pigments, titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, as well as carbon black produced by known methods such as the contact method, furnace method, and thermal method can be used.

[0044] In addition, examples of organic pigments that can be used include azo pigments, polycyclic pigments (e.g., phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc.), dye chelates (e.g., basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, and aniline black. Of these pigments, those with good affinity with the solvent are preferably used. In addition, resin hollow particles and inorganic hollow particles can also be used.

[0045] Specific examples of pigments for black include carbon blacks (CI Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black, metals such as copper, iron (CI Pigment Black 11), and titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1).

[0046] In addition, for color, CI 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, CI Pigment Yellow Ranges 5, 13, 16, 17, 36, 43, 51, CI Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48:2, 48:2 (Permanent Red 2B (Ca)), 48:3, 48:4, 49:1, 52:2, 53:1, 57:1 (Brilliant Carmine 6B), 60:1, 63:1, 63:2, 64:1, 81, 83, 88 , 101 (Red Iron), 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, CI Pigment Violet 1 (Rhodamine Lake), 3, 5:1, 16, 19, 23, 38; CI Pigment Blue 1, 2, 15 (Phthalocyanine Blue), 15:1, 15:2, 15:3, 15:4 (Phthalocyanine Blue), 16, 17:1, 56, 60, 63; CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc.

[0047] The dye is not particularly limited, and acid dyes, direct dyes, reactive dyes, and basic dyes can be used, and one type may be used alone, or two or more types may be used in combination.

[0048] Examples of the dyes include CI Acid Yellow 17, 23, 42, 44, 79, and 142, CI Acid Red 52, 80, 82, 249, 254, and 289, CI Acid Blue 9, 45, and 249, CI Acid Black 1, 2, 24, and 94, CI Food Black 1 and 2, and CI Direct Yellow 1, 12, 24, 33, 50, 55, 58, 86, 132, 142, and 144. ,173, CI Direct Red 1, 4, 9, 80, 81, 225, 227, CI Direct Blue 1, 2, 15, 71, 86, 87, 98, 165, 199, 202, CI Directed Black 19, 38, 51, 71, 154, 168, 171, 195, CI Reactive Red 14, 32, 55, 79, 249, CI Reactive Black 3, 4, 35.

[0049] The content of the coloring material in the ink is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, from the viewpoints of improving image density, good fixability, and ejection stability.

[0050] Methods for dispersing a pigment to obtain an ink include a method of introducing a hydrophilic functional group into the pigment to make it a self-dispersing pigment, a method of dispersing the pigment by coating the surface of the pigment with a resin, and a method of dispersing the pigment using a dispersant.

[0051] As a method for introducing a hydrophilic functional group into a pigment to make it a self-dispersible pigment, for example, a method of adding a functional group such as a sulfone group or a carboxyl group to a pigment (e.g., carbon) to make it dispersible in water can be mentioned.

[0052] One method for dispersing a pigment by coating its surface with a resin is to encapsulate the pigment in microcapsules, making it dispersible in water. This can also be called a resin-coated pigment. In this case, it is not necessary for all of the pigments blended into the ink to be coated with resin; uncoated or partially coated pigments may be dispersed in the ink, as long as the effects of this embodiment are not impaired.

[0053] Examples of the method for dispersing using a dispersant include a method for dispersing using a known low molecular weight dispersant or a high molecular weight dispersant, such as a surfactant.

[0054] As the dispersant, for example, anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, etc. can be used depending on the pigment.

[0055] RT-100 (nonionic surfactant) manufactured by Takemoto Yushi Co., Ltd. and sodium naphthalenesulfonate formalin condensate can also be suitably used as dispersants.

[0056] The dispersants may be used alone or in combination of two or more.

[0057] <Pigment dispersion> Ink can be obtained by mixing a pigment with materials such as water, an organic solvent, etc. Alternatively, ink can be produced by mixing a pigment with other materials such as water and a dispersant to form a pigment dispersion, and then mixing the pigment with materials such as water and an organic solvent.

[0058] The pigment dispersion is obtained by mixing and dispersing water, a pigment, a pigment dispersant, and optionally other components, and adjusting the particle size. Dispersion is preferably performed using a disperser.

[0059] Although there are no particular restrictions on the particle size of the pigment in the pigment dispersion, the maximum frequency, calculated as the maximum number, is preferably 20 nm or more and 500 nm or less, and more preferably 20 nm or more and 150 nm or less, in order to improve the dispersion stability of the pigment and the image quality such as ejection stability and image density. The particle size of the pigment can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0060] The content of the pigment in the pigment dispersion is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of obtaining good ejection stability and increasing image density, the content is preferably 0.1% by mass or more and 50% by mass or less, and more preferably 0.1% by mass or more and 30% by mass or less.

[0061] The pigment dispersion is preferably degassed after filtering coarse particles using a filter, a centrifugal separator, or the like, as needed.

[0062] <Resin> The type of resin contained in the ink is not particularly limited and can be appropriately selected depending on the purpose. Examples include urethane resin, polyester resin, acrylic resin, vinyl acetate resin, styrene resin, butadiene resin, styrene-butadiene resin, vinyl chloride resin, acrylic styrene resin, and acrylic silicone resin. Resin particles made of these resins may also be used. Ink can be obtained by mixing the resin particles in the form of a resin emulsion in which the resin particles are dispersed in water as a dispersion medium with materials such as colorants and organic solvents. The resin particles may be appropriately synthesized or commercially available. These may be used alone or in combination of two or more types of resin particles.

[0063] The volume average particle size of the resin particles is not particularly limited and can be appropriately selected depending on the purpose. However, from the viewpoint of obtaining good fixing properties and high image hardness, the volume average particle size is preferably 10 nm or more and 1,000 nm or less, more preferably 10 nm or more and 200 nm or less, and particularly preferably 10 nm or more and 100 nm or less.

[0064] The volume average particle size can be measured using, for example, a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0065] The resin content is not particularly limited and can be selected appropriately depending on the purpose, but from the viewpoint of fixability and ink storage stability, it is preferably 1% to 30% by mass, and more preferably 20% to 25% by mass, relative to the total amount of ink. In other words, the total amount of resin solids in the ink may be 20% to 25%.

[0066] There are no particular restrictions on the particle size of the solids in the ink and they can be selected appropriately depending on the purpose. However, to improve image quality such as ejection stability and image density, the maximum frequency, calculated as the maximum number, is preferably 20 nm or more and 1000 nm or less, and more preferably 20 nm or more and 150 nm or less. The solids include resin particles, pigment particles, etc. Particle size can be measured using a particle size analyzer (Nanotrac Wave-UT151, manufactured by Microtrac Bell Co., Ltd.).

[0067] <Additives> If necessary, surfactants, antifoaming agents, antiseptic and antifungal agents, antirust agents, pH adjusters, etc. may be added to the ink.

[0068] <Surfactant> As the surfactant, any of silicone surfactants, fluorine surfactants, amphoteric surfactants, nonionic surfactants and anionic surfactants can be used.

[0069] Silicone surfactants are not particularly limited and can be appropriately selected depending on the purpose.Among them, those that do not decompose even at high pH are preferred, such as side-chain modified polydimethylsiloxane, both-end modified polydimethylsiloxane, one-end modified polydimethylsiloxane, and both-end modified polydimethylsiloxane of side chain, and those having a polyoxyethylene group or a polyoxyethylene polyoxypropylene group as a modifying group are particularly preferred because they exhibit good properties as aqueous surfactants.In addition, polyether-modified silicone surfactants can also be used as the silicone surfactant, and examples thereof include compounds in which a polyalkylene oxide structure is introduced into the Si part side chain of dimethylsiloxane.

[0070] As fluorosurfactants, for example, perfluoroalkyl sulfonic acid compounds, perfluoroalkyl carboxylic acid compounds, perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain are particularly preferred due to their low foaming properties. Examples of the perfluoroalkyl sulfonic acid compounds include perfluoroalkyl sulfonic acids and perfluoroalkyl sulfonate salts. Examples of the perfluoroalkyl carboxylic acid compounds include perfluoroalkyl carboxylic acids and perfluoroalkyl carboxylate salts. Examples of the polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chain include sulfate ester salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chain, and salts of polyoxyalkylene ether polymers having perfluoroalkyl ether groups in the side chain. Counterions of the salts in these fluorosurfactants include Li, Na, K, NH, NHCHCHOH, NH(CHCHOH), NH(CHCHOH), and the like.

[0071] Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, lauryl dihydroxyethyl betaine, etc. Examples of nonionic surfactants include polyoxyethylene alkyl phenyl ethers, polyoxyethylene alkyl esters, polyoxyethylene alkylamines, polyoxyethylene alkylamides, polyoxyethylene propylene block polymers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and ethylene oxide adducts of acetylene alcohol.

[0072] Examples of anionic surfactants include polyoxyethylene alkyl ether acetates, dodecylbenzenesulfonates, laurates, and salts of polyoxyethylene alkyl ether sulfates. These may be used alone or in combination of two or more.

[0073] The silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. Examples include side-chain-modified polydimethylsiloxane, both-end-modified polydimethylsiloxane, one-end-modified polydimethylsiloxane, and both-end-modified side-chain polydimethylsiloxane. Polyether-modified silicone surfactants having a polyoxyethylene group or a polyoxyethylene-polyoxypropylene group as the modifying group are particularly preferred because they exhibit good properties as aqueous surfactants.

[0074] Such surfactants may be synthesized appropriately or commercially available products, such as those available from BYK Corporation, Shin-Etsu Chemical Co., Ltd., Dow Corning Toray Silicone Co., Ltd., Nippon Emulsion Co., Ltd., and Kyoeisha Chemical Co., Ltd.

[0075] The polyether-modified silicone surfactant is not particularly limited and can be appropriately selected depending on the purpose. For example, it can be a surfactant represented by the following general formula (S-1), in which a polyalkylene oxide structure is introduced into the Si moiety side chain of dimethylpolysiloxane.

number

[0076] As the polyether-modified silicone surfactant, commercially available products can be used, such as KF-618, KF-642, KF-643 (Shin-Etsu Chemical Co., Ltd.), EMALEX-SS-5602, SS-1906EX (Nihon Emulsion Co., Ltd.), FZ-2105, FZ-2118, FZ-2154, FZ-2161, FZ-2162, FZ-2163, FZ-2164 (Dow Corning Toray Silicone Co., Ltd.), BYK-33, BYK-387 (BYK-Chemie Co., Ltd.), TSF4440, TSF4452, TSF4453 (Toshiba Silicone Co., Ltd.), and the like.

[0077] The fluorine-based surfactant is preferably a compound having 2 to 16 fluorine-substituted carbon atoms, more preferably a compound having 4 to 16 fluorine-substituted carbon atoms.

[0078] Examples of fluorine-based surfactants include perfluoroalkyl phosphate ester compounds, perfluoroalkyl ethylene oxide adducts, and polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains. Among these, polyoxyalkylene ether polymer compounds having perfluoroalkyl ether groups in the side chains are preferred because they have low foaming properties, and fluorine-based surfactants represented by the following general formulas (F-1) and (F-2) are particularly preferred.

number

number

[0079] As the fluorine-based surfactant, commercially available products may be used, such as Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all manufactured by Asahi Glass Co., Ltd.); Fullard FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, and FC-431 (all manufactured by Sumitomo 3M Limited); Megafa F-470, F-1405, F-474 (all manufactured by Dainippon Ink and Chemicals, Inc.); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR, Capstone FS-30, FS-31, FS-3100, FS-34, FS-35 (all manufactured by Chemours); FT-110, FT- 250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos Corporation), Polyfox PF-136A, PF-156A, PF-151N, PF-154, PF-159 (manufactured by Omnova), Unidyne DSN-403N (manufactured by Daikin Industries, Ltd.), and among these, FS-3100, FS-34, FS-300 manufactured by Chemours Corporation, FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW manufactured by Neos Corporation, Polyfox PF-151N manufactured by Omnova, and Unidyne DSN-403N manufactured by Daikin Industries, Ltd. are particularly preferred in terms of achieving good print quality, particularly significant improvements in color development, paper penetration, wettability, and dye leveling.

[0080] The content of the surfactant in the ink is not particularly limited and can be selected appropriately depending on the purpose. However, from the viewpoint of achieving excellent wettability and ejection stability and improving image quality, the content is preferably 0.001% by mass or more and 5% by mass or less, and more preferably 0.05% by mass or more and 5% by mass or less.

[0081] <Antifoaming agent> The defoaming agent is not particularly limited, and examples thereof include silicone-based defoaming agents, polyether-based defoaming agents, fatty acid ester-based defoaming agents, etc. These may be used alone or in combination of two or more. Among these, silicone-based defoaming agents are preferred because of their excellent defoaming effect.

[0082] <Antiseptic and mildew-proof agent> The antiseptic and mildew-proof agent is not particularly limited, and examples thereof include 1,2-benzisothiazolin-3-one, etc.

[0083] <Rust inhibitor> The rust inhibitor is not particularly limited, and examples thereof include acid sulfite, sodium thiosulfate, etc.

[0084] <pH adjuster> The pH adjuster is not particularly limited as long as it can adjust the pH to 7 or higher, and examples thereof include amines such as diethanolamine and triethanolamine.

[0085] (Examples) Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0086] [Preparation of ink] [Preparation of cyan dispersion A] After premixing the materials of the following formulation, it was circulated and dispersed for 7 hours in a disk-type bead mill (KDL type manufactured by Shinmaru Enterprises Co., Ltd., media: zirconia balls with a diameter of 0.3 mm) to obtain a cyan pigment dispersion. · Pigment Blue 15:4 15% by mass · Anionic surfactant (trade name: Pionin A-51-B, manufactured by Takemoto Yushi Co., Ltd.) 2% by mass · Ion-exchanged water 83% by mass

[0087] [Preparation of cyan dispersion B] The materials according to the following formulation were premixed and then circulated and dispersed for 7 hours in a disc-type bead mill (KDL model manufactured by Shinmaru Enterprises, media: zirconia balls with a diameter of 0.3 mm) to obtain a cyan pigment dispersion. Pigment Blue 15:4 23% by weight Anionic surfactant (trade name: Paionin A-51-B, manufactured by Takemoto Oil & Fat Co., Ltd.) 2% by mass Ion-exchanged water 75% by mass

[0088] <Preparation of Acrylic Resin Emulsion A> As the acrylic resin emulsion A, TOCRYL W168 (manufactured by Toyochem) was used.

[0089] <Preparation of Acrylic Resin Emulsion B> As the acrylic resin emulsion B, TOCRYL BCX-8111 (manufactured by Toyochem) was used.

[0090] <Preparation of Acrylic Resin Emulsion C> As the acrylic resin emulsion C, TOCRYL X-4403 (manufactured by Toyochem) was used.

[0091] <Preparation of Urethane Resin Emulsion A> As the urethane resin emulsion A, a product name SF-460 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used.

[0092] <Preparation of Urethane Resin Emulsion B> As the urethane resin emulsion B, a product name SF-820 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used.

[0093] <Preparation method of cyan ink A> The cyan pigment dispersion A and acrylic resin emulsion A obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink was 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 14.3% by mass Acrylic resin emulsion A (resin content: 49.5% by mass) 44.5% by mass Propylene glycol 3.2% by mass Octadiol 0.5% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0% by mass ·Pure water: remainder

[0094] <Preparation method for cyan ink B> The cyan pigment dispersion A and acrylic resin emulsion A obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink was 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 15.4% by mass Acrylic resin emulsion A (resin content: 49.5% by mass) 48.0% by mass Propylene glycol 3.4% by mass Octadiol 0.6% by mass Solfit Fine Grade (Kuraray) 0.6% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.2% by mass ·Pure water: remainder

[0095] <Preparation method for cyan ink C> The cyan pigment dispersion A and acrylic resin emulsion A obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink was 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 66.0% Acrylic resin emulsion A (resin content: 49.5% by mass) 21.4% by mass Propylene glycol 4.3% by mass Octadiol 0.7% by mass Solfit Fine Grade (Kuraray) 0.8% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 2.4% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.8% by mass ·Pure water: remainder

[0096] <Preparation method of cyan ink D> The cyan pigment dispersion B and acrylic resin emulsion B obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink was 100.0% by mass. Cyan pigment dispersion (pigment content: 23.0% by mass) 32.6% Acrylic resin emulsion B (resin content: 50.0% by mass) 28.9% by mass Propylene glycol 4.4% by mass Octadiol 0.7% by mass Solfit Fine Grade (Kuraray) 0.8% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 2.4% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.8% by mass ·Pure water: remainder

[0097] <Preparation method of cyan ink E> The cyan pigment dispersion A and acrylic resin emulsion A obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink was 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 14.3% by mass Acrylic resin emulsion A (resin content: 49.5% by mass) 50.8% by mass Propylene glycol 3.1% by mass Octadiol 0.5% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0% by mass ·Pure water: remainder

[0098] <Preparation method of cyan ink F> The cyan pigment dispersion A and acrylic resin emulsion A obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink was 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 46.67% by mass Acrylic resin emulsion A (resin content: 49.5% by mass) 43.11% by mass Propylene glycol 3.1% by mass Octadiol 0.5% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0% by mass ·Pure water: remainder

[0099] <Preparation method for cyan ink G> The cyan pigment dispersion A and acrylic resin emulsion C obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink is 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 14.3% by mass Acrylic resin emulsion C (resin content: 58.0% by mass) 38.0% by mass Propylene glycol 3.2% by mass Octadiol 0.5% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0% by mass ·Pure water: remainder

[0100] <Preparation method for cyan ink H> The cyan pigment dispersion A and urethane resin emulsion A obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink is 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 14.3% by mass Urethane resin emulsion A (resin content: 30.0% by mass) 73.5% by mass Propylene glycol 3.2% by mass Octadiol 0.5% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0% by mass ·Pure water: remainder

[0101] <Preparation method of cyan ink I> The cyan pigment dispersion A and urethane resin emulsion B obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink is 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 14.3% by mass Urethane resin emulsion B (resin content: 30.2% by mass) 73.0% by mass Propylene glycol 3.2% by mass Octadiol 0.5% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0% by mass ·Pure water: remainder

[0102] <Preparation method of cyan ink J> The cyan pigment dispersion A and acrylic resin emulsion A obtained above were mixed with the following components. Note that the "remainder" of pure water refers to the amount such that the total of all components constituting the ink was 100.0% by mass. Cyan pigment dispersion (pigment content: 15.0% by mass) 14.3% by mass Acrylic resin emulsion A (resin content: 49.5% by mass) 33.0% by mass Propylene glycol 3.2% by mass Octadiol 0.5% by mass Equamide M100 (Idemitsu Kosan Co., Ltd.) 1.8% by mass 2-amino-2-ethyl-1,3-propanediol 0.2% by mass Silface SAG503A (manufactured by Nissin Chemical Industry Co., Ltd.) 2.0% by mass ·Pure water: remainder [Table 1] [Table 2]

[0103] [evaluation] <Discharge stability> The circulation inkjet head shown in Figure 2 was installed in an EV1000 (manufactured by Ricoh Co., Ltd.), and droplets were ejected for 5 minutes while circulating ink at the supply ink pressure and discharge ink pressure described in the examples. After 5 minutes, the percentage of nozzle holes that continued to eject droplets was measured, and the continuous ejection stability was evaluated based on the following evaluation criteria. According to the evaluation criteria, a rating of △ or better was deemed practical. (Evaluation criteria) ○: The percentage of nozzle holes that continue to eject is 100% △: The percentage of nozzle holes that continue to eject is 95% or more but less than 100% ×: The percentage of nozzle holes that continue to eject ink is less than 95%, or ink is overflowing from the nozzle surface.

[0104] <Decap resistance> A nozzle check pattern was printed on a recording substrate (plain paper, manufactured by Canon) to confirm the number of ejecting nozzles. The ink was then circulated for one hour at the supply-side pressure (supply-side ink pressure) and discharge-side pressure (discharge-side ink pressure) described in the examples, and a nozzle check pattern was printed again on the recording substrate. The number of ejecting nozzles in the pattern printed before circulation was taken as 100%, and the percentage of ejecting nozzles in the pattern printed after circulation was calculated and evaluated based on the following evaluation criteria. A rating of ◯ or △ indicates practical use. (Evaluation criteria) ○: Number of normal discharge nozzles is 95% or more △: Number of normal discharge nozzles is 90% or more but less than 95% ×: Number of normal discharge nozzles is less than 90%

[0105] <Drying> Ink was printed on the surface of the intermediate transfer member (intermediate transfer belt 1) using the supply-side pressure (supply-side ink pressure) and discharge-side pressure (discharge-side ink pressure) described in the examples, and then heated and dried at the drying temperature listed in the table to form an image. The formed image and recording substrate (plain paper, manufactured by Canon) were pressed together with a roller and heated to 120°C, thereby transferring the image to the recording substrate. The transferred image was cut into strips, and the printed image faces were overlapped and left overnight in a 25°C, 50% humidity environment under a load of 0.5 kg / cm^2. After overnight, the load was removed, and the overlapping recording substrates were peeled off. The image was evaluated based on the following criteria. A rating of ◯ indicates practical use. (Evaluation criteria) ○: When observing the adhesive surface from a distance of 300 mm, no peeling of the image is visible △: When observing the adhesive surface from a distance of 300 mm, peeling of the image is visible ×: When observing the adhesive surface from a distance of 1000 mm, peeling of the image is visible

[0106] <Image fixation> Ink was printed on the surface of the intermediate transfer member using the supply-side pressure and discharge-side pressure (discharge-side ink pressure) described in the examples, and then heated and dried at the drying temperature listed in the table to form an image. The formed image and a recording substrate (plain paper, manufactured by Canon) were pressed together with a roller and heated at 120°C to transfer the image to the recording substrate. The transferred image was rubbed with a metal brush using a Gakushin tester (device name: dyed material rub fastness tester, manufactured by Intec) under conditions of a load of 200 gf and 25 rubs. The image density (OD) of the image transferred to the metal brush was measured using an xRite (manufactured by Pantone), and fixability was evaluated based on the following evaluation criteria: A rating of △ or better was deemed practical. (Evaluation criteria) ○: Less than 0.15 △: 0.15 or more and less than 0.28 ×:0.28 or more [Table 3]

[0107] As described above, the image printing apparatus according to this embodiment achieves both high productivity and ejection stability using an inkjet method with an intermediate transfer system, and can output images with high robustness.

[0108] In the above embodiment, the image printing device of the present invention is described as being applied to a multifunction device having at least two of the functions of a copy function, a printer function, a scanner function, and a facsimile function, but it can be applied to any image forming device such as a copier, printer, scanner device, or facsimile device. [Explanation of symbols]

[0109] 1 Intermediate transfer belt 2, 3, 4, 5 Inkjet recording head 6. Second ink jet recording head 7 Conveyor roller 8 Heater 9 Fuser roller 10 Recording media 101 Discharge head 102 Supply ink tank 103 Supply positive pressure air pump 104 Ejection side ink tank 105 Discharge negative pressure air pump 106 Circulation pump 107 Ink supply pressure gauge 108 Discharge Ink Pressure Gauge 109,110,111 Fluid delivery path [Prior art documents] [Patent documents]

[0110] [Patent Document 1] Japanese Patent Application Publication No. 62-92849 [Patent Document 2] Japanese Patent Application Publication No. 1-226336 [Patent Document 3] Japanese Patent Application Publication No. 2023-53764 [Patent Document 4] Japanese Patent Publication No. 2022-51512

Claims

1. an ejection head having a nozzle for ejecting an ink composition containing at least a solvent, a resin, and a colorant, the ink composition having a total non-volatile solid content of 20% or more and 30% or less; the ejection head has an individual liquid chamber in the ejection head that has both a supply port and a discharge port for the ink composition, and a circulation path is formed through which the ink composition circulates from a first ink tank that is a supply source, through the individual liquid chamber, and back to a second ink tank via the discharge port; an ink pressure of the ink composition in the circulation path between the first ink tank and the ejection head is 2 kPa or more and 7 kPa or less, and an ink pressure of the ink composition between the second ink tank and the ejection head is -7 kPa or more and -2 kPa or less.

2. 2. The image forming apparatus according to claim 1, wherein a flow rate of the ink composition in the circulation path is 10 mL / min or more and 100 mL / min or less.

3. 2. The image forming apparatus according to claim 1, wherein the circulation path includes at least the first ink tank and the second ink tank, and the ink composition is circulated from the second ink tank to the first ink tank via a liquid feed pump.

4. 2. The image forming apparatus according to claim 1, wherein the ink pressure of the ink composition in the circulation path is −3 kPa or more and −1 kPa or less on the nozzle surface of the ejection head.

5. 2. The image forming apparatus according to claim 1, wherein a flow rate of the ink composition in a liquid feed pump that circulates the ink composition from the second ink tank to the first ink tank is 10 mL / min or more and 100 mL / min or less.

6. The image forming apparatus according to claim 1 , wherein the resin contained in the ink composition is an acrylic resin.

7. 2. The image forming apparatus according to claim 1, wherein the total amount of resin solids contained in the ink composition is 20% or more and 25% or less.

8. 2. The image forming apparatus according to claim 1, wherein the ejection head comprises a pressure sensor for detecting the pressure of the ink composition and a device for controlling the pressure.

9. an ejection head having a nozzle for ejecting an ink composition containing at least a solvent, a resin, and a colorant, the ink composition having a total non-volatile solid content of 20% or more and 30% or less, and a total resin solid content of 20% or more and 25% or less; The ink set is such that the individual liquid chambers in the ejection head have both a supply port and an outlet for the ink composition, and a circulation path is formed through which the ink composition circulates from a first ink tank, which is a supply source, through the individual liquid chambers, and back to a second ink tank via the outlet.

Images