Abstract: An inkjet ink contains a quinacridone pigment, a resin, and an aqueous medium. A 50-fold dilution of a supernatant obtained by centrifugating the inkjet ink at 1,050,000 G for 3 hours has a phosphorous concentration of at least 1.0 ppm and no greater than 6.0 ppm. On an ultraviolet-visible absorption spectrum of the supernatant, a first peak appears at a first absorbance of at least 0.16 and no greater than 0.40. The first peak is a maximum peak in a wavelength range of the ultraviolet-visible absorption spectrum of at least 300 nm and no greater than 340 nm. On the ultraviolet-visible absorption spectrum of the supernatant, a second peak appears at a second absorbance of at least 0.15 and no greater than 0.80. The second peak is a maximum peak in a wavelength range of the ultraviolet-visible absorption spectrum of at least 400 nm and no greater than 490 nm.

Abstract: An ink set includes an inkjet ink and a recording head filling liquid. The inkjet ink includes a pigment, a pigment coating resin, a first alkali metal ion, and water. The recording head filling liquid includes polyethylene glycol, a second alkali metal ion, a surfactant, and water. The polyethylene glycol has a mass average molecular weight of at least 180 and no greater than 800. A content ratio of the surfactant in the recording head filling liquid is greater than 0.00% by mass and no greater than 0.10% by mass. The first and second alkali metal ions each contain at least one of Li+, Na+, and K+.

Abstract: An inkjet recording apparatus includes memory, a processor, an image forming section, and a bending mechanism. The memory stores therein bending information in which a plurality of bending amounts corresponding to respective ejection amounts of an ink ejected from the image forming section are defined. The processor sets a bending amount of a sheet to be conveyed. The bending mechanism includes a roller and a belt that hold the sheet therebetween, and bends the sheet by moving a position of a center of the roller toward the belt based on the set bending amount. The processor calculates for each of areas of the sheet an amount of the ink ejected to the area, and sets the bending amount of the sheet based on the bending amounts corresponding to the calculated amounts of the ink ejected to the respective areas in the bending information.

Abstract: An ink set includes an inkjet ink and a recording head filling liquid. The inkjet ink contains a pigment, a pigment covering resin, and water. The recording head filling liquid contains polyethylene glycol, a nonionic surfactant, and water. The recording head filling liquid has a viscosity of at least 3 mPa·s and no greater than 10 mPa·s. The polyethylene glycol has a mass average molecular weight of at least 170 and no greater than 300. A percentage content of the polyethylene glycol in the recording head filling liquid is at least 7.0% by mass and no greater than 55.0% by mass. The pigment covering resin includes a styrene-acrylic resin.

Abstract: An ink set includes an inkjet ink and a recording head filling liquid. The inkjet ink includes a pigment, a pigment coating resin, a first alkali metal ion, and water. The recording head filling liquid includes polyethylene glycol, a second alkali metal ion, a surfactant, and water. The polyethylene glycol has a mass average molecular weight of at least 180 and no greater than 800. A content ratio of the surfactant in the recording head filling liquid is greater than 0.00% by mass and no greater than 0.10% by mass. The first and second alkali metal ions each contain at least one of Li+, Na+, and K+.

Abstract: An inkjet recording apparatus includes three or more recording heads. The recording heads contain different inks and eject the different inks sequentially on a recording medium. The different inks each contain a pigment and a polyhydric alcohol monobutyl ether. Of the different inks, an ink to be ejected first has the lowest pigment content ratio. Of the different inks, an ink to be ejected third and an ink to be subsequently ejected each have a pigment content ratio equal to or higher than that of a corresponding one of inks to be precedently ejected. Of the different inks, an ink to be ejected second and an ink to be subsequently ejected each have a polyhydric alcohol monobutyl ether content ratio higher than that of a corresponding one of inks to be precedently ejected.

Abstract: An inkjet recording apparatus includes an image forming section, a heater, a first calculation section, storage, and a second calculation section. The image forming section ejects ink onto a sheet in which first to M-th regions are defined (M is an integer of at least 2). The heater heats an n-th region of the sheet using an n-th heat source (n is an integer of at least 1 and no greater than M). The storage stores therein temperature information indicating a first heating temperature for the n-th region. The second calculation section calculates a second heating temperature for the n-th region based on the temperature information and the ink ejection amount to the n-th region calculated by the first calculation section.

Abstract: An inkjet recording apparatus includes memory, a processor, an image forming section, and a bending mechanism. The memory stores therein bending information in which a plurality of bending amounts corresponding to respective ejection amounts of an ink ejected from the image forming section are defined. The processor sets a bending amount of a sheet to be conveyed. The bending mechanism includes a roller and a belt that hold the sheet therebetween, and bends the sheet by moving a position of a center of the roller toward the belt based on the set bending amount. The processor calculates for each of areas of the sheet an amount of the ink ejected to the area, and sets the bending amount of the sheet based on the bending amounts corresponding to the calculated amounts of the ink ejected to the respective areas in the bending information.

Abstract: A de-curling device de-curls a sheet and includes an endless belt, a de-curling roller, a nip width adjusting mechanism, and a belt tension adjusting mechanism. The endless belt is looped around a pair of supporting rollers. The de-curling roller is provided between the pair of supporting rollers and has a first outer circumferential surface pressed against a second outer circumferential surface of the endless belt to form a nip portion at which the endless belt curves along the first outer circumferential surface, the de-curling roller being configured to de-curl the sheet passing through the nip portion. The nip width adjusting mechanism adjusts the nip width by moving the de-curling roller in a direction intersecting the second outer circumferential surface of the endless belt. The belt tension adjusting mechanism adjusts the tension of the endless belt according to the nip width adjusted by the nip width adjusting mechanism.

Abstract: An inkjet recording apparatus (1) includes an image forming section (40), a decurler (20), a changing section (50), a first calculating section (72), storage (60), a second calculating section (73), and a controller (75). The image forming section (40) ejects ink onto a sheet (S). The decurler (20) bends the sheet (S). The changing section (50) changes a bending amount of the sheet (S). The first calculating section (72) calculates an ink ejection rate (?) to the sheet (S) for each of areas of the sheet (S). The storage (60) stores therein first bending information (62) indicating a first target bending amount (?) of a specific area of the sheet (S) corresponding to the ink ejection rate (?) to the specific area. The second calculating section (73) calculates a second target bending amount of each of the areas. The controller (75) controls the changing section (50) based on the second target bending amounts.

Abstract: A controller checks ink quantity to be ejected to a specific area on a first side (specific area ink quantity) and determines an ink quantity ratio. The specific area is a strip-shaped area including a side edge on upstream side in a conveying direction of a paper sheet on the first side. When the ink quantity ratio is larger than a reference ink quantity ratio, the controller performs a black conversion process on pixels in a conversion target range. The conversion target range is a range corresponding to the specific area in the image data of the first side. The black conversion process is a process of converting a pixel to which three color inks, i.e. cyan, magenta, and yellow inks are to be ejected into a pixel to which only black ink is to be ejected.

Abstract: An inkjet recording apparatus includes an image forming section, a roller, a heat source, a calculator, a determination section, and a controller. The determination section determines to activate the heat source when an ink ejection amount calculated by the calculator is larger than a specific reference amount. When the determination section determines to activate the heat source, the controller activates the heat source. When temperature of the roller is equal to or higher than a specific temperature, the controller controls the image forming section to form the image on the sheet.

Abstract: An inkjet recording apparatus includes three or more recording heads. The recording heads contain different inks and eject the different inks sequentially on a recording medium. The different inks each contain a pigment. Of the different inks, an ink to be ejected first has the lowest pigment content ratio. Of the different inks, an ink to be ejected third and an ink to be subsequently ejected each have a pigment content ratio equal to or higher than that of the pigment contained in a corresponding one of inks to be precedently ejected. Of the different inks, an ink to be ejected second and an ink to be subsequently ejected each have a lower viscosity at 25° C. than a corresponding one of inks to be precedently ejected.

Abstract: An inkjet recording apparatus includes an image forming section, a roller, a heat source, a calculator, a determination section, and a controller. The determination section determines to activate the heat source when an ink ejection amount calculated by the calculator is larger than a specific reference amount. When the determination section determines to activate the heat source, the controller activates the heat source. When temperature of the roller is equal to or higher than a specific temperature, the controller controls the image forming section to form the image on the sheet.

Abstract: An inkjet recording apparatus includes an image forming section, a heater, a first calculation section, storage, and a second calculation section. The image forming section ejects ink onto a sheet in which first to M-th regions are defined (M is an integer of at least 2). The heater heats an n-th region of the sheet using an n-th heat source (n is an integer of at least 1 and no greater than M). The storage stores therein temperature information indicating a first heating temperature for the n-th region. The second calculation section calculates a second heating temperature for the n-th region based on the temperature information and the ink ejection amount to the n-th region calculated by the first calculation section.

Abstract: A controller checks ink quantity to be ejected to a specific area on a first side (specific area ink quantity) and determines an ink quantity ratio. The specific area is a strip-shaped area including a side edge on upstream side in a conveying direction of a paper sheet on the first side. When the ink quantity ratio is larger than a reference ink quantity ratio, the controller performs a black conversion process on pixels in a conversion target range. The conversion target range is a range corresponding to the specific area in the image data of the first side. The black conversion process is a process of converting a pixel to which three color inks, i.e. cyan, magenta, and yellow inks are to be ejected into a pixel to which only black ink is to be ejected.

Abstract: A decurling device includes a decurler. The decurler includes a first dryer roller, a second dryer roller, and a heat source. The heat source is disposed at the first dryer roller to heat the first dryer roller. The first dryer roller and the second dryer roller rotate while holding a sheet therebetween to convey the sheet.

Abstract: An inkjet recording apparatus includes three or more recording heads. The recording heads contain different inks and eject the different inks sequentially on a recording medium. The different inks each contain a pigment. Of the different inks, an ink to be ejected first has the lowest pigment content ratio. Of the different inks, an ink to be ejected third and an ink to be subsequently ejected each have a pigment content ratio equal to or higher than that of the pigment contained in a corresponding one of inks to be precedently ejected. Of the different inks, an ink to be ejected second and an ink to be subsequently ejected each have a lower viscosity at 25° C. than a corresponding one of inks to be precedently ejected.

Abstract: An inkjet recording apparatus includes three or more recording heads. The recording heads contain different inks and eject the different inks sequentially on a recording medium. The different inks each contain a pigment and a polyhydric alcohol monobutyl ether. Of the different inks, an ink to be ejected first has the lowest pigment content ratio. Of the different inks, an ink to be ejected third and an ink to be subsequently ejected each have a pigment content ratio equal to or higher than that of a corresponding one of inks to be precedently ejected. Of the different inks, an ink to be ejected second and an ink to be subsequently ejected each have a polyhydric alcohol monobutyl ether content ratio higher than that of a corresponding one of inks to be precedently ejected.

Abstract: An inkjet recording apparatus includes an image forming section, a heater, a calculation section, storage, and a determination section. The image forming section ejects ink onto a sheet in which first to M-th regions are defined (M is an integer of at least 2). The heater includes first to M-th heat sources and heats an n-th region of the sheet using an n-th heat source (n is an integer of at least 1 and no greater than M). The calculation section calculates an ink ejection rate of ink to be ejected onto the n-th region. The storage stores therein heating information indicating whether it is necessary to heat the n-th region. The determination section determines whether or not to cause the n-th heat source to generate heat.