Inkjet recording method and inkjet recording device

Abstract

To provide an inkjet recording method that can reduce the amount of waste ink generated by a recovery operation while using a downsized inkjet recording device.SOLUTION: Provided is an inkjet recording method that records images by using an inkjet recording device that comprises: aqueous ink that include a resin dispersant for dispersing pigment, the dispersant having an anionic group; an ink housing part that houses the aqueous inks; a recording head having a discharge port face having a plurality of rows of discharge ports arranged on the same recording element board; a cap that covers the plurality of rows of discharge ports; and a sucking means that sucks the aqueous inks through the cap. The aqueous inks comprise a nonionic surfactant respectively, where the content of the nonionic surfactant in the magenta ink is less than the amount of nonionic surfactant in any of other inks, and the HLB value of the nonionic surfactant contained in the magenta ink is less than the HLB value of the nonionic surfactant in any of other inks.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an inkjet recording method and an inkjet recording apparatus. [Background technology]

[0002] In recent years, the demand for home inkjet recording devices has increased due to an increase in remote work from home. In addition, there is a demand for inkjet recording devices to be further miniaturized for home use. In order to miniaturize inkjet recording devices, miniaturization of the recording head and ink storage unit is essential. For example, an inkjet recording device has been proposed that is equipped with a miniaturized recording unit that integrates the ink storage unit and the recording head (Patent Document 1).

[0003] The inkjet recording device proposed in Patent Document 1 employs a recording head that ejects ink by the action of thermal energy, from the viewpoint of enabling a more compact design. Also, the recording head is made smaller by providing ejection port rows that eject ink of multiple colors on the same recording element substrate. Furthermore, the recording unit is made smaller by bonding the recording head to the ink storage section without using other members such as a heat sink. The ink storage section is made of thermoplastic resin to reduce the weight of the recording unit and to reduce the rigidity required for the carriage section, thereby making the device smaller.

[0004] The output of business documents is increasing as a home use of a miniaturized inkjet recording device. An inkjet recording device used for such purposes is required to be able to record images with excellent fastness for each color ink. For this reason, pigment inks using pigments as coloring materials are being used instead of dye inks as described in Patent Document 1. From the viewpoint of color development of the recorded image, color inks often use phthalocyanine pigments for cyan inks, quinacridone pigments for magenta inks, and azo pigments for yellow inks. In addition, when recording is continuously performed on a recording medium with low ink permeability, the image recorded on the recording medium may be transferred to the back side of the next recording medium, which is called offset. In order to suppress such offset, inks containing a nonionic surfactant to reduce the surface tension are used.

[0005] The main dispersion methods of pigments include resin-dispersed pigments using a resin (resin dispersant) having hydrophilic groups such as anionic groups, and self-dispersed pigments in which hydrophilic groups such as anionic groups are bonded to the particle surface directly or via atomic groups. Resin-dispersed pigments are often used from the viewpoint of improving the abrasion resistance of images recorded on recording media such as glossy paper. If a recording head that ejects pigment ink is left unused for a long period of time, the ink may become stuck at the ejection port and may not be ejected normally. For this reason, inkjet recording devices are used that are equipped with a means (recovery means) for recovering the stuck state by sucking the ejection port array in a capped state. Compared to dye ink, pigment ink is more likely to stick, and a strong recovery operation is required. It is effective for miniaturizing the device to use a mode in which multiple ejection port arrays provided on the same recording element substrate are capped and sucked together with the same cap, rather than a mode in which ejection port arrays corresponding to inks of each color are capped and sucked separately. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2017-081152 A Summary of the Invention [Problem to be solved by the invention]

[0007] The inventors used an inkjet recording device adapted for miniaturization having the above-mentioned configuration to evaluate adhesion recovery properties by fixing and then sucking up a plurality of inks in which pigments of each color, cyan, magenta, and yellow, are dispersed with a resin dispersant. As a result, it was found that while the adhesion of cyan ink and yellow ink was easily resolved, the adhesion of magenta ink may be difficult to resolve. As described above, in the recovery operation, a plurality of ejection port rows corresponding to each ink are capped with the same cap at once and sucked up. For this reason, it was found that repeated suction in an attempt to resolve the adhesion of magenta ink would result in a problem of an increase in the amount of waste ink of cyan ink and magenta ink.

[0008] It is therefore an object of the present invention to provide an inkjet recording method that can reduce the amount of waste ink generated by a recovery operation while using a compact inkjet recording apparatus. It is also an object of the present invention to provide an inkjet recording apparatus used in the inkjet recording method. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided an inkjet recording apparatus including: a cyan ink containing a phthalocyanine pigment, a magenta ink containing a quinacridone pigment, and a yellow ink containing an azo pigment, each of which contains a resin dispersant having an anionic group for dispersing the pigment; an ink storage section for storing each of the water-based inks; a recording head having an ejection port surface in which a plurality of ejection ports for ejecting the water-based ink supplied from the ink storage section by the action of thermal energy and a plurality of ejection port arrays composed of the plurality of ejection ports are arranged on the same recording element substrate; a cap that comes into contact with an area including the ejection port surface to cover the plurality of ejection port arrays; and suction means that sucks the water-based ink from the plurality of ejection ports through the cap, thereby recording an image; and sucking the aqueous ink from the plurality of ejection ports through a nozzle, wherein the ink storage section is a housing made of a thermoplastic resin, and the recording head is attached to the ink storage section without any other intervening member, and the aqueous inks each further contain a nonionic surfactant, and the content (mass %) of the nonionic surfactant in the magenta ink is smaller than both the content (mass %) of the nonionic surfactant in the cyan ink and the content (mass %) of the nonionic surfactant in the yellow ink, and the HLB value of the nonionic surfactant in the magenta ink is smaller than both the HLB value of the nonionic surfactant in the cyan ink and the HLB value of the nonionic surfactant in the yellow ink. Effect of the Invention

[0010] According to the present invention, it is possible to provide an inkjet recording method that can reduce the amount of waste ink generated by a recovery operation while using a compact inkjet recording device. Also, according to the present invention, it is possible to provide an inkjet recording device used in the inkjet recording method. [Brief description of the drawings]

[0011] [Figure 1] 1A and 1B are diagrams illustrating an ink jet recording apparatus according to an embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a perspective view with a cover member open. [Diagram 2] 1 is a perspective view showing a schematic internal structure of an inkjet recording apparatus according to an embodiment of the present invention; [Diagram 3] 1A and 1B are diagrams illustrating an example of a recording unit, in which FIG. 1A is a perspective view and FIG. 1B is a perspective view in an exploded state. [Figure 4] FIG. 2 is a schematic diagram showing an example of a suction unit. [Diagram 5] 5A and 5B are schematic diagrams showing examples of a connection state between an ink containing section and a recording head. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is present in the ink in the form of dissociation into ions, but for convenience, it is expressed as "containing a salt." In addition, water-based ink for inkjet printing may be simply referred to as "ink." Physical property values ​​are values ​​at room temperature (25°C) unless otherwise specified.

[0013] The inventors used an inkjet recording device having the following configurations (i) to (iv) to record 10 solid images in cyan, magenta, and yellow inks in succession, and then left the ejection port arrays uncapped for 10 days. The size of the solid images was 6.0 inches by 9.0 inches. (i) Ink storage sections for storing a plurality of types of ink (ii) a printhead having a plurality of ejection ports that eject ink supplied from an ink container by the action of thermal energy, and an ejection port surface in which a plurality of ejection port arrays each composed of the plurality of ejection ports are arranged on the same print element substrate; (iii) a cap that comes into contact with an area including the ejection port surface and covers the multiple ejection port rows; (iv) A suction means for sucking ink from the multiple ejection ports through the cap

[0014] The cyan ink, magenta ink, and yellow ink used contained phthalocyanine pigment, quinacridone pigment, and azo pigment, respectively. The pigments used in each ink were all resin-dispersed pigments dispersed with a resin dispersant having an anionic group. In addition, a nonionic surfactant (product name "Acetylenol E100", manufactured by Kawaken Fine Chemicals) was added to each ink to a concentration of 0.6 mass %, and the dynamic surface tension at 25°C and a life time of 10 ms measured by the maximum bubble pressure method was adjusted to 42 N / m.

[0015] After leaving it for 10 days, water in the ink in the ink flow path of the recording head evaporated from the nozzles, causing the ink to solidify near the nozzles, reducing the ink ejection performance. After that, the nozzle row was covered with a cap, and a suction operation was performed to suck ink from the multiple nozzles through the cap in an attempt to recover from the solidification. As a result, it was found that the solidification of the cyan ink and yellow ink was resolved, but the solidification of the magenta ink was not resolved. When the suction operation was performed again, the solidification of the magenta ink was resolved, but by that time the cyan ink and yellow ink had also been sucked in, and the amount of waste ink increased. In other words, the amount of waste ink increased due to the difference in the fixation recovery properties between the magenta ink and the cyan ink and yellow ink.

[0016] The recording unit used in the inkjet recording device described above is configured by attaching a recording head to an ink storage section, which is a housing made of thermoplastic resin, without any other members such as a heat sink, in order to accommodate the miniaturization of the device. When a situation in which ink is repeatedly discharged continues, such as when a solid image is continuously recorded using a recording head that discharges ink by the action of thermal energy, the recording head heats up and the temperature of the ink in the discharge port also rises. In addition, as described above, since the recording head is directly attached to the ink storage section made of thermoplastic resin, heat is easily trapped, and once the temperature rises, the high temperature state of about 50°C continues for a while.

[0017] When an ink containing both a resin-dispersed pigment and a nonionic surfactant is left at a high temperature, the nonionic surfactant acts on the adsorption portion of the pigment and the resin dispersant, and the resin dispersant is easily peeled off from the pigment, and the amount of pigment without the resin dispersant adsorbed increases. The compound (quinacridone skeleton) constituting the quinacridone pigment has a planar structure, so the area of ​​attraction between the planar surfaces is large. Furthermore, since it has multiple amide groups, it exhibits strong hydrogen bonding properties, so it stacks strongly, and the binding force between the quinacridone compounds constituting the pigment is strong. Thus, the quinacridone pigment has a stronger binding force between pigments than the phthalocyanine pigment and the azo pigment. For this reason, when the water in the ink containing the pigment from which the resin dispersant has peeled off evaporates, it is considered that the magenta ink containing the quinacridone pigment will be more firmly fixed than the cyan ink and the yellow ink containing the phthalocyanine pigment and the azo pigment, respectively.

[0018] This phenomenon is considered to occur particularly conspicuously when a recording head that is prone to heat buildup is used. However, when a heat sink is provided in the recording unit, the recording unit becomes larger and its mass increases, so that the rigidity of the carriage that moves the recording unit must be increased, and the device becomes larger. For this reason, it has been difficult to simultaneously reduce the size of the inkjet recording device and reduce the amount of waste ink. In addition, when an ink containing a self-dispersing pigment in which an anionic group is bonded to the pigment particle surface directly or via an atomic group is used, the resin dispersant is not peeled off from the pigment by the nonionic surfactant, and differences in adhesion recovery between inks are unlikely to occur.

[0019] The present inventors further investigated whether the adhesion recovery of magenta ink can be improved by reducing the content of nonionic surfactant in magenta ink compared to the content of nonionic surfactant in cyan ink and yellow ink. Specifically, the above-mentioned nonionic surfactant (Acetylenol E100) was added to cyan ink and yellow ink at 0.6% by mass, and to magenta ink at 0.3% by mass. As a result, it was found that the difference in adhesion recovery between the inks was reduced and the amount of waste ink was significantly reduced. However, it was found that bleeding, in which the boundary between the area recorded with magenta ink and the area recorded with cyan ink and yellow ink, occurs significantly. The dynamic surface tensions of the cyan ink and yellow ink at a life time of 10 ms measured by the maximum bubble pressure method were both 42 mN / m, while the dynamic surface tension of the magenta ink was 48 mN / m. When two liquids with different surface tensions are adjacent to each other, Marangoni convection occurs, in which the liquid flows from the one with lower surface tension to the one with higher surface tension. It is known that the greater the difference in surface tension, the more pronounced the Marangoni convection becomes. In other words, it is believed that bleeding occurred because the difference between the surface tension of the magenta ink and that of the cyan ink and yellow ink was too large.

[0020] Next, the inventors of the present invention investigated the possibility of making the HLB value of the nonionic surfactant added to the magenta ink smaller than the HLB values ​​of the nonionic surfactant added to the cyan ink and the yellow ink. The value obtained by the Griffin method was considered as the HLB value. Usually, a surfactant with a smaller HLB value has a greater effect of lowering the surface tension. Therefore, when adjusting the surface tension of the ink to a certain value, the amount of the surfactant added can be reduced by using a surfactant with a smaller HLB value. Specifically, the content of the nonionic surfactant required to prepare an ink having a dynamic surface tension of 42 mN / m at a life time of 10 ms was investigated. As a result, it was found that the content of the nonionic surfactant with an HLB value of 13.2 was 0.6% by mass, while the content of the nonionic surfactant with an HLB value of 10.7 was 0.3% by mass. In other words, by using a nonionic surfactant with a smaller HLB value, the content of the nonionic surfactant can be reduced, and the phenomenon of the resin dispersant peeling off from the pigment can be suppressed.

[0021] The present inventors further prepared ink A containing 0.6% by mass of a nonionic surfactant with an HLB value of 13.2, and ink B containing 0.3% by mass of a nonionic surfactant with an HLB value of 10.7. Then, these prepared inks were placed in a sealed container and left overnight at 80°C. The inks after being left were centrifuged at 80,000 rpm for 5 hours, and the resin dispersant content in the supernatant was measured. The resin dispersant in the supernatant corresponds to the amount of resin dispersant that was peeled off and released from the pigment. As a result, it was found that the amount of resin dispersant in the supernatant of ink A was greater than the amount of resin dispersant in the supernatant of ink B. In other words, it was found that the resin dispersant in ink A was peeled off more from the pigment than the resin dispersant in ink B.

[0022] From the above results, the inventors discovered that a nonionic surfactant with a relatively small HLB value is contained in the magenta ink, and a nonionic surfactant with a relatively large HLB value is contained in the cyan ink and the yellow ink, and thus arrived at the present invention. By using nonionic surfactants with different HLB values ​​according to the ink, it is possible to reduce the difference in adhesion recovery between inks, and reduce the amount of waste ink while also responding to the miniaturization of the device.

[0023] <Inkjet recording method and inkjet recording apparatus> The inkjet recording method of the present invention is a recording method using an inkjet recording device including ink, an ink storage section, a recording head, a cap, and a suction means for sucking ink from a plurality of ejection ports through the cap. The ink includes a cyan ink containing a phthalocyanine pigment, a magenta ink containing a quinacridone pigment, and a yellow ink containing an azo pigment, and each of the inks contains a resin dispersant having an anionic group for dispersing the pigment. The ink storage section is a portion for storing each color ink, and is a housing formed of a thermoplastic resin, to which the recording head is attached without any other member being interposed. The recording head has an ejection port surface on which a plurality of ejection ports that eject ink supplied from the ink storage section by the action of thermal energy, and a plurality of ejection port arrays composed of the plurality of ejection ports are arranged on the same recording element substrate. The cap is a member that abuts against an area including the ejection port surface of the recording head and covers the plurality of ejection port arrays. The inkjet recording method of the present invention includes a step of applying ink ejected from the plurality of ejection ports to a recording medium to record an image, and a step of sucking ink from the plurality of ejection ports through the cap. The inks each further contain a nonionic surfactant. The content (mass %) of the nonionic surfactant in the magenta ink is smaller than the content (mass %) of the nonionic surfactant in the cyan ink and the content (mass %) of the nonionic surfactant in the yellow ink. The HLB value of the nonionic surfactant in the magenta ink is smaller than the HLB value of the nonionic surfactant in the cyan ink and the HLB value of the nonionic surfactant in the yellow ink.

[0024] The inkjet recording device of the present invention includes ink, an ink storage section, a recording head, a cap, and a suction means for sucking ink from a plurality of ejection ports through the cap. The ink includes a cyan ink containing a phthalocyanine pigment, a magenta ink containing a quinacridone pigment, and a yellow ink containing an azo pigment, and each of the inks contains a resin dispersant having an anionic group for dispersing the pigment. The ink storage section is a section for storing each of the inks of each color, and is a housing formed of a thermoplastic resin, to which the recording head is attached without any other member being interposed. The recording head has an ejection port surface on which a plurality of ejection ports for ejecting ink supplied from the ink storage section by the action of thermal energy, and a plurality of ejection port rows composed of the plurality of ejection ports are arranged on the same recording element substrate. The cap is a member that comes into contact with an area including the ejection port surface of the recording head and covers the plurality of ejection port rows. Each of the inks further contains a nonionic surfactant. The content (mass %) of the nonionic surfactant in the magenta ink is smaller than the content (mass %) of the nonionic surfactant in the cyan ink and the content (mass %) of the nonionic surfactant in the yellow ink, and the HLB value of the nonionic surfactant in the magenta ink is smaller than the HLB value of the nonionic surfactant in the cyan ink and the HLB value of the nonionic surfactant in the yellow ink.

[0025] (Inkjet recording device) 1 is a drawing that shows a schematic diagram of an embodiment of an inkjet recording device of the present invention, where (a) is a perspective view and (b) is a perspective view with a cover member open. As shown in FIG. 1, the inkjet recording device 1 of this embodiment has an exterior 2 and a cover member 3 provided on the upper surface of the exterior 2. The cover member 3 is a member that can be opened and closed in the vertical direction, and by opening it in the upward direction, the inside of the inkjet recording device 1 can be seen. The shape of the inkjet recording device 1 is a substantially rectangular parallelepiped.

[0026] FIG. 2 is a perspective view showing a schematic internal structure of an embodiment of an inkjet recording device of the present invention. The inkjet recording device 1 of the embodiment shown in FIG. 2 includes a paper feed tray 4 on the rear side of the exterior. A recording medium such as paper is placed in the paper feed tray 4. A recording unit 8 is placed inside the inkjet recording device 1. A recording head is provided under the recording unit 8. The recording unit 8 ejects ink from ejection ports formed in the recording head while moving back and forth in the y direction in FIG. 2. The recording medium placed on the paper feed tray 4 is sent forward in the x direction by the paper feed roller 5 and the transport roller 6, and reaches and is supported by the platen 7. The recording medium supported by the platen 7 is placed at a position facing the surface (ejection port surface) of the recording head on which the ejection ports are formed, and in this state, ink is ejected from the recording head onto the recording medium. The ejected ink adheres to the recording medium, and an image is recorded on the recording medium. The inkjet recording device 1 further includes a cap 9 at a home position that abuts against an area including the ejection port surface of the recording head and covers a plurality of ejection port rows composed of a plurality of ejection ports.

[0027] FIG. 3 is a diagram showing an example of a recording unit, where (a) is a perspective view and (b) is a perspective view in an exploded state. The recording unit 8 shown in FIG. 3 has an ink storage section 10, which is a housing made of a thermoplastic resin, and a recording head 11. The recording head 11 is attached to the ink storage section 10 without any other member such as a heat sink. The ink storage section 10 is lightweight because it is a housing made of a thermoplastic resin. Furthermore, the recording head 11 is attached to the ink storage section 10 without any other member such as a heat sink, so the entire recording unit 8 is small and lightweight. By using such a recording unit 8, the inkjet recording device can be made small and lightweight. The heat sink can be made of a material such as a metal oxide such as alumina.

[0028] The recording head 11 is provided with a plurality of ejection ports for ejecting ink, energy generating elements for generating thermal energy for ejecting ink, and the like. The energy generating elements can be driven, for example, by power supplied through an electric wiring member 14. The energy generating elements are elements that generate thermal energy, and the ink can be ejected from the ejection ports by the action of the generated thermal energy.

[0029] The recording head 11 has an ejection port surface in which multiple ejection port arrays each consisting of multiple ejection ports are arranged on the same recording element substrate. By arranging multiple ejection port arrays on the same recording element substrate, it is possible to eject multiple inks with one recording unit, and the entire inkjet recording device can be made smaller. It is preferable that the multiple ejection port arrays are arranged in a direction (sub-scanning direction) perpendicular to the reciprocating movement direction (main scanning direction) of the recording unit. Furthermore, by configuring the ejection port array with multiple ejection ports, the area that can be printed when the recording unit moves becomes wider, and therefore the printing speed can be increased.

[0030] Sponge-like ink absorbers 12a to 12c are stored in the ink storage section 10. Filters 13a to 13c are disposed below the ink storage section 10 in the direction of gravity. By utilizing the capillary force of the sponge-like ink absorbers 12a to 12c to generate negative pressure, it is possible to prevent ink from leaking from the ejection orifices. Furthermore, by disposing the filters 13a to 13c, it is possible to prevent fine foreign matter such as dust from entering the ejection orifices.

[0031] Fig. 4 is a schematic diagram showing an example of a suction means. As shown in Fig. 4, the inkjet recording device includes a cap 9 that abuts against an area including the discharge port surface of the recording head 11 and covers a plurality of discharge port rows. A tube 17 that functions as an air communication section and a waste ink tube 18 that discharges waste ink that is accumulated in the cap 9 and is not used for recording are connected to the cap 9. An air communication valve 16 is provided in the middle of the tube 17. Waste ink discharged from the discharge ports of the recording head 11 is stored in a waste ink storage section 19. A suction valve 20 is provided in the middle of the waste ink tube 18, and a suction operation is performed to discharge unnecessary waste ink using a pump 21.

[0032] In cases where ink dries and solidifies in flow paths connected to the ejection ports, making normal ejection difficult, the state where normal ejection is difficult can be resolved by circulating new ink from the ink storage unit 10 through a suction operation. Normally, when multiple ejection port arrays are arranged on the same recording element substrate, the suction operation is performed using the same cap. For example, when ejection port arrays that eject cyan ink, magenta ink, and yellow ink are arranged on the same recording element substrate, these inks are sucked together using the same cap. Generally, when inks that are easy to remove from the solidification and inks that are difficult to remove from the solidification are mixed, it is necessary to continue the suction operation for the inks that are difficult to remove from the solidification, even though the solidification of the ejection ports that eject the inks that are easy to remove from the solidification has been removed, which increases the amount of waste ink.

[0033] The recording head has an ejection port surface in which a plurality of ejection port arrays corresponding to each of the cyan ink, magenta ink, and yellow ink are arranged on the same recording element substrate. The ejection port array consisting of the ejection port for ejecting the magenta ink is preferably arranged at a position sandwiched between the ejection port array consisting of the ejection port for ejecting the cyan ink and the ejection port array consisting of the ejection port for ejecting the yellow ink. That is, it is preferable that the ejection port array consisting of the ejection port for ejecting the magenta ink is arranged at the center. When the ejection port arrays are covered with the same cap and a suction operation is performed, the negative pressure in the center is higher than that at the end. That is, the ejection port array arranged at the center is sucked most efficiently. For this reason, by arranging the ejection port array consisting of the ejection port for ejecting the magenta ink, which has poor adhesion recovery, at the center, it is possible to further improve adhesion recovery. Each of the plurality of ejection port arrays is preferably arranged along a predetermined direction of the recording element substrate, and it is more preferable that the plurality of ejection port arrays are arranged parallel to each other.

[0034] FIG. 5 is a schematic diagram showing an example of the connection state of the ink storage section and the recording head. FIG. 5 shows a recording unit 28 as a part corresponding to the ink of 1, and includes a liquid chamber 22 communicating with the ejection port of the recording head 11, a filter 13 disposed between the ink storage section 10 and the liquid chamber 22, and an ink flow path 23 through which ink flows between the filter 13 and the liquid chamber 22. The ink flow path corresponding to the magenta ink is preferably shorter than both the ink flow path corresponding to the cyan ink and the ink flow path corresponding to the yellow ink. When the rows of ejection ports are covered with a cap and suction is applied, the ink flows from the ink storage section to the recording head, passing through the filter, the ink flow path, and the liquid chamber in sequence. If the ink flow path is short, pressure loss is unlikely to occur, and a strong negative pressure is applied to the corresponding ejection port, so that the efficiency of adhesion recovery is good. By making the ink flow path through which the magenta ink, which has poor adhesion recovery properties, flows shorter than both the ink flow paths corresponding to the cyan ink and the yellow ink, the difference in adhesion recovery properties between the inks can be reduced.

[0035] The inkjet recording device preferably further includes a second ink storage unit such as a main tank having a larger capacity than the ink storage unit (first ink storage unit) such as a subtank, and a tube through which ink flows between the second ink storage unit and the ink storage unit. Considering the usage mode in remote work at home, it is important to reduce the frequency of replacing the ink cartridge as well as to reduce the size of the device. For this reason, by further providing a second ink storage unit such as a main tank, it is possible to reduce the frequency of ink replacement while avoiding an increase in the size of the device body. Hereinafter, an inkjet recording device in which only a first ink storage unit such as a subtank bonded to a recording head is provided as an ink storage unit is also referred to as a "first device configuration". In addition, an inkjet recording device in which a second ink storage unit such as a main tank having a larger capacity than the subtank is further provided as an ink storage unit is also referred to as a "second device configuration".

[0036] In the case of the second device configuration, the frequency of ink replacement is reduced compared to the first device configuration, so the period during which the ink is held in a stationary state in the main tank is longer. In addition, in the case of pigment ink, the pigment is more likely to settle if the period during which the ink is held in a stationary state is longer. The decrease in ejection performance due to ink adhesion occurs due to the ink drying in the flow path and the pigment coagulating, so the greater the pigment content of the ink used, the more pronounced the ink is. Depending on the usage conditions, the adhesion recovery of the second device configuration is often inferior to that of the first device configuration. Furthermore, if there is a difference in adhesion recovery between inks, the difference becomes greater. For this reason, generally, the second device configuration is prone to problems such as an even greater amount of waste ink compared to the first device configuration. In contrast, in the inkjet recording method of the present invention, the difference in adhesion recovery between the inks used is small, so it is possible to reduce the amount of waste ink even when the second device configuration is used, and it is possible to achieve both a reduction in the frequency of ink replacement and a reduction in the amount of waste ink.

[0037] (Water-based ink) The inkjet recording method of the present invention uses inks including cyan ink, magenta ink, and yellow ink, each of which contains a resin dispersant having an anionic group for dispersing a pigment. The method includes a step of applying the inks ejected from a plurality of ejection openings of a recording head to a recording medium to record an image. All of the inks are pigment inks containing a pigment as a coloring material. The components constituting the inks are described below.

[0038] [Colorant] As the coloring material of the ink, a resin-dispersed pigment using a resin dispersant that disperses the pigment in the aqueous ink is used. By using the resin-dispersed pigment, the fastness and abrasion resistance of the recorded image can be improved. In addition, from the viewpoint of color development, a phthalocyanine pigment is used for the cyan ink, a quinacridone pigment is used for the magenta ink, and an azo pigment is used for the yellow ink. Examples of the phthalocyanine pigment used for the cyan ink include CI Pigment Blue 15, CI Pigment Blue 15:3, and CI Pigment Blue 15:4. Examples of the quinacridone pigment used for the magenta ink include CI Pigment Red 122, CI Pigment Red 202, and CI Pigment Violet 19. The magenta ink can further contain a diketopyrrolopyrrole pigment such as CI Pigment Red 254; or an azo pigment such as CI Pigment Red 150; in order to adjust the color tone. Examples of azo pigments used in yellow ink include CI Pigment Yellow 74, CI Pigment Yellow 128, and CI Pigment Yellow 155.

[0039] The pigment content (mass %) in the ink is preferably from 0.1 to 15.0% by mass, and more preferably from 1.0 to 10.0% by mass, based on the total mass of the ink.

[0040] The content (mass%) of the quinacridone pigment in the magenta ink is preferably smaller than both the content (mass%) of the phthalocyanine pigment in the cyan ink and the content (mass%) of the azo pigment in the yellow ink. By making the content of the quinacridone pigment in the magenta ink the smallest among the multiple inks, the adhesion recovery of the magenta ink is further improved, so that the difference between the adhesion recovery of the cyan ink and the yellow ink can be further reduced. Here, a case is assumed in which the magenta ink further contains a diketopyrrolopyrrole pigment or an azo pigment. Even in such a case, the content (mass%) of the quinacridone pigment in the magenta ink is preferably smaller than both the content (mass%) of the phthalocyanine pigment in the cyan ink and the content (mass%) of the azo pigment in the yellow ink. Even if the resin dispersant attached to the diketopyrrolopyrrole pigment or the azo pigment is peeled off, these pigments are not easily strongly bonded to each other between the compounds constituting the pigment, unlike the quinacridone pigment.

[0041] [Resin dispersant] The resin dispersant used to disperse the pigment in the ink is a resin dispersant having an anionic group. Examples of the anionic group include a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group. The resin dispersant preferably has a hydrophobic portion that adsorbs to the pigment in addition to the anionic group that disperses the pigment.

[0042] Examples of the resin dispersant include acrylic resin, polyester resin, urethane resin, urea resin, polysaccharides, and polypeptides. Among them, acrylic resin is preferred from the viewpoint of ejection characteristics from the ejection port of the recording head. In this specification, "acrylic resin" means a resin having at least a unit derived from an acrylic monomer such as (meth)acrylic acid or (meth)acrylate. In the following description, "(meth)acrylic" means "acrylic" and "methacrylic", and "(meth)acrylate" means "acrylate" and "methacrylate". As the acrylic resin, one having a unit (hydrophilic part) having an anionic group and a unit (hydrophobic part) not having an anionic group as a constituent unit is preferred. Examples of the form of the acrylic resin include random copolymer, block copolymer, graft copolymer, and combinations thereof.

[0043] Examples of monomers that become units constituting the acrylic resin upon polymerization include monomers having an anionic group and monomers having no anionic group. Usually, a monomer having an anionic group becomes a hydrophilic unit upon polymerization, and a monomer having no anionic group becomes a hydrophobic unit upon polymerization.

[0044] Examples of the monomer having an anionic group include monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid; anhydrides and salts of these monomers; and examples of the cation constituting the salt of the monomer having an anionic group include lithium cation, sodium cation, potassium cation, ammonium cation, and organic ammonium cation.

[0045] Examples of monomers not having an anionic group include monomers having an aromatic group, such as styrene, α-methylstyrene, benzyl (meth)acrylate, 2-vinylpyridine, 4-vinylpyridine, and 1-vinylimidazole; and (meth)acrylic acid esters, such as ethyl (meth)acrylate, methyl (meth)acrylate, (iso)propyl (meth)acrylate, (n-, iso-, and t-)butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0046] The content (mass %) of the resin dispersant in the ink is preferably from 0.03 to 5.0 mass %, and more preferably from 0.3 to 3.0 mass %, based on the total mass of the ink.

[0047] The mass ratio of the resin dispersant content Rm (mass%) to the quinacridone pigment content Pm (mass%) in the magenta ink is defined as the "mass ratio Rm / Pm". The mass ratio of the resin dispersant content Rc (mass%) to the phthalocyanine pigment content Pc (mass%) in the cyan ink is defined as the "mass ratio Rc / Pc". The mass ratio of the resin dispersant content Ry (mass%) to the azo pigment content Py (mass%) in the yellow ink is defined as the "mass ratio Ry / Py". In this case, it is preferable that the mass ratio Rm / Pm is higher than both the mass ratio Rc / Pc and the mass ratio Ry / Py. The higher the mass ratio of the resin dispersant content (mass%) to the pigment content (mass%), the more resin dispersant is present in the vicinity of the pigment particles. Therefore, even if a nonionic surfactant acts, the remaining amount of resin dispersant attached to the pigment particle surface increases, and the fixation recovery property of the ink is improved. For this reason, by setting the mass ratio Rm / Pm higher than both the mass ratio Rc / Pc and the mass ratio Ry / Py, the difference in adhesion recovery property between the magenta ink and the cyan ink and the yellow ink can be made smaller. The content (mass%) of the resin dispersant in the ink is preferably 0.1 to 1.0 times the mass ratio of the pigment content (mass%).

[0048] [Nonionic surfactants] Each of the aqueous inks including the cyan ink, magenta ink, and yellow ink contains a nonionic surfactant. The HLB value of the nonionic surfactant is a value determined by the Griffin method. The HLB value determined by the Griffin method can be calculated from the following formula (A). The HLB value determined by the Griffin method is a physical property value that indicates the degree of hydrophilicity or lipophilicity of a surfactant, and takes a value between 0.0 and 20.0. The smaller the HLB value, the higher the lipophilicity, and the larger the HLB value, the higher the hydrophilicity. HLB value = 20 × (formula weight of hydrophilic group of surfactant / molecular weight of surfactant) (A)

[0049] From the viewpoint of solubility in aqueous ink, the HLB value of the nonionic surfactant is preferably 6.0 or more. Also, from the viewpoint of appropriately lowering the surface tension, the HLB value of the nonionic surfactant is preferably 17.0 or less. Examples of the nonionic surfactant include hydrocarbon surfactants such as acetylene glycol compounds, ethylene oxide adducts of acetylene glycol, and polyoxyethylene alkyl ethers; fluorine-based surfactants such as perfluoroalkylethylene oxide compounds; and silicone-based surfactants such as polydimethylsiloxane compounds.

[0050] The content (mass %) of the nonionic surfactant in the ink is preferably from 0.1 to 5.0% by mass, more preferably from 0.2 to 2.0% by mass, and particularly preferably from 0.1 to 1.0% by mass, based on the total mass of the ink.

[0051] [Aqueous medium] The ink is an aqueous ink containing at least water as an aqueous medium. The ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. The ink preferably contains a water-soluble organic solvent. As the water, deionized water or ion-exchanged water is preferably used. The content (mass%) of water in the ink is preferably 40.0 mass% or more and 95.0 mass% or less based on the total mass of the ink. As the water-soluble organic solvent, any of those usable for inkjet inks such as alcohols, glycols, glycol ethers, and nitrogen-containing compounds can be used. The water-soluble organic solvent is preferably one whose vapor pressure at 25°C is lower than that of water. The content (mass%) of the water-soluble organic solvent in the ink is preferably 3.0 mass% or more and 50.0 mass% or less based on the total mass of the ink, and more preferably 10.0 mass% or more and 30.0 mass% or less. In particular, it is particularly preferable that it is 15.0 mass% or more and 25.0 mass% or less.

[0052] The mass average value of the dielectric constant of the water-soluble organic solvent in the magenta ink is preferably greater than both the mass average value of the dielectric constant of the water-soluble organic solvent in the cyan ink and the mass average value of the dielectric constant of the water-soluble organic solvent in the yellow ink. A water-soluble organic solvent with a high dielectric constant has high hydrophilicity. For this reason, in an ink containing a water-soluble organic solvent with a high dielectric constant, strong binding between pigments is suppressed even when water in the ink evaporates near the ejection orifice. When the mass average value of the dielectric constant of the water-soluble organic solvent in the magenta ink is greater than both the mass average values ​​of the dielectric constant of the water-soluble organic solvent in the other inks, the difference between the adhesion recovery property of the magenta ink and the adhesion recovery property of the other inks can be further reduced.

[0053] The mass average value of the relative dielectric constant of the water-soluble organic solvent in the ink can be calculated by the following formula (B) for an ink containing, for example, 15.0 mass % of a water-soluble organic solvent with a relative dielectric constant of 40.0 and 10.0 mass % of a water-soluble organic solvent with a relative dielectric constant of 20.0. Note that the relative dielectric constant of water is not taken into consideration when calculating the mass average value of the relative dielectric constant of the water-soluble organic solvent in the ink. This is because the water-soluble organic solvents generally used in aqueous inks used in small inkjet recording devices have a lower vapor pressure than water, and when the ink solidifies near the ejection port, the evaporation of water has progressed sufficiently, and most of the liquid medium is water-soluble organic solvent. (40.0×15.0+20.0×10.0) / (15.0+10.0)=32.0 (B)

[0054] The relative dielectric constant of a water-soluble organic solvent can be measured using a dielectric constant meter (for example, trade name "BI-870" manufactured by BROOKHAVEN INSTRUMENTS CORPORATION) at a frequency of 10 kHz. The relative dielectric constant of a water-soluble organic solvent that is solid at 25°C is a value calculated from the relative dielectric constant of a 50% by mass aqueous solution by the following formula (1). Usually, a "water-soluble organic solvent" is a liquid, but in the present invention, for the sake of convenience, those that are solid at 25°C (room temperature) are also included in the water-soluble organic solvent. ε sol =2ε 50% -ε water (1) ε sol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C ε water : relative dielectric constant of water

[0055] Examples of water-soluble organic solvents that are generally used in aqueous inks and are solid at 25°C include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol with a number-average molecular weight of 1,000. The reason for determining the relative dielectric constant of a water-soluble organic solvent that is solid at 25°C from the relative dielectric constant of a 50% by mass aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25°C and can be used as components of aqueous inks, it is difficult to prepare a high-concentration aqueous solution of more than 50% by mass. On the other hand, in a low-concentration aqueous solution of 10% by mass or less, the relative dielectric constant of water becomes dominant, and it is not possible to obtain a reliable (effective) relative dielectric constant value of the water-soluble organic solvent. As a result of the inventors' investigation, it was found that the aqueous solution to be measured can be prepared from almost all of the water-soluble organic solvents that are solid at 25°C and can be used in inks, and the relative dielectric constant to be determined is consistent with the effect of the present invention. For these reasons, it was decided to use a 50% by mass aqueous solution. For water-soluble organic solvents that are solid at 25°C and cannot be prepared as a 50% aqueous solution due to their low solubility in water, use an aqueous solution of the saturated concentration and use the above ε sol For convenience, the value of the relative dielectric constant calculated in accordance with the case of determining

[0056] Specific examples of water-soluble organic solvents include the following (the numbers in parentheses indicate the relative dielectric constant at 25°C): monohydric alcohols having 1 to 4 carbon atoms, such as methanol (33.1), ethanol (23.8), n-propanol (12.0), isopropanol (18.3), n-butanol, sec-butanol, and tert-butanol. Dihydric alcohols such as 1,2-propanediol (28.8), 1,2-butanediol (22.2), 1,3-butanediol (30.0), 1,4-butanediol (31.1), 1,5-pentanediol (27.0), 1,2-hexanediol (14.8), 1,6-hexanediol (7.1), 2-methyl-1,3-propanediol (28.3), 3-methyl-1,3-butanediol (24.0), 3-methyl-1,5-pentanediol (23.9), 2-ethyl-1,3-hexanediol (18.5), etc. Polyhydric alcohols such as 1,2,6-hexanetriol (28.5), glycerin (42.3), trimethylolpropane (33.7), trimethylolethane, etc. Alkylene glycols such as ethylene glycol (40.4), diethylene glycol (31.7), triethylene glycol (22.7), tetraethylene glycol (20.8), dipropylene glycol (19.7), butylene glycol, hexylene glycol, thiodiglycol, etc. Glycol ethers such as ethylene glycol monobutyl ether (9.4), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether (11.0), triethylene glycol monoethyl ether, triethylene glycol monobutyl ether (9.8), tetraethylene glycol monobutyl ether (9.4), propylene glycol monomethyl ether (12.4), tripropylene glycol monomethyl ether (8.5), etc. Polyalkylene glycols having a number average molecular weight of 200 to 1,000 such as polyethylene glycol having a number average molecular weight of 200 (18.9), polyethylene glycol having a number average molecular weight of 600 (11.5), polyethylene glycol having a number average molecular weight of 1,000 (4.6), polypropylene glycol, etc.Nitrogen-containing compounds such as 2-pyrrolidone (28.0), N-methyl-2-pyrrolidone (32.0), 1-(2-hydroxyethyl)-2-pyrrolidone (37.6), 1,3-dimethyl-2-imidazolidinone, N-methylmorpholine, 1-(hydroxymethyl)-5,5-dimethylhydantoin (23.7), 1,3-bis(2-hydroxyethyl)-5,5-dimethylhydantoin (16.0), urea (110.3), ethyleneurea (49.7), and triethanolamine (31.9). Sulfur-containing compounds such as dimethyl sulfoxide (48.9) and bis(2-hydroxyethylsulfone). As the water-soluble organic solvent to be contained in the ink, it is preferable to use one having a relative dielectric constant of 3.0 or more, 120.0 or less, and a vapor pressure at 25°C lower than that of water.

[0057] [Other ingredients] The ink may further contain various additives, such as antifoaming agents, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors, as necessary. These additives are not included in the calculation of the relative dielectric constant.

[0058] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the static surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0059] As described above, when two liquids with different surface tensions are adjacent to each other, Marangoni convection occurs in which the liquid flows from the one with lower surface tension to the one with higher surface tension. The greater the difference in surface tension, the more pronounced the Marangoni convection occurs. When two inks with a large difference in surface tension come into contact, the ink with lower surface tension flows into the ink with higher surface tension, which makes bleeding more likely to occur. The smaller the difference in surface tension, the less likely bleeding occurs, and conversely, the greater the difference in surface tension, the more likely bleeding occurs. In recording media such as plain paper, ink is usually fixed to the recording media within several tens to several hundreds of milliseconds after it is applied. Therefore, from the viewpoint of suppressing bleeding, it can be said that the dynamic surface tension at a life time of 10 ms is the dominant physical property. In order to effectively suppress bleeding, the difference (maximum difference) in the dynamic surface tension at a life time of 10 ms of each ink is preferably 0 mN / m or more and 5 mN / m or less, and more preferably 0 mN / m or more and 3 mN / m or less. Furthermore, the dynamic surface tension of each ink at a life time of 10 ms is preferably 30 mN / m or more and 50 mN / m or less, and more preferably 35 mN / m or more and 50 mN / m or less. EXAMPLES

[0060] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples without departing from the gist of the invention. "Parts" and "%" used to describe the amounts of components are based on mass unless otherwise specified.

[0061] <Preparation of pigment dispersion> (Pigment dispersion 1) A water-soluble resin, styrene-acrylic acid copolymer (composition (molar) ratio = 33:67), was neutralized with potassium hydroxide in an amount equimolar to the acid value and dissolved in ion-exchanged water to prepare an aqueous solution of resin dispersant with a resin (solid content) content of 20.0%. The weight-average molecular weight of this water-soluble resin is 10,000, and the acid value is 200 mg KOH / g. A mixture of 15.0 parts of pigment (CI Pigment Blue 15:3), 22.5 parts of the aqueous solution of the resin dispersant, and 62.5 parts of water was placed in a sand grinder and dispersed for 1 hour, and then centrifuged to remove coarse particles. After pressure filtration with a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm, an appropriate amount of ion-exchanged water was added to obtain pigment dispersion 1. The pigment content of the obtained pigment dispersion 1 was 10.0%, and the resin dispersant content was 3.0%.

[0062] (Pigment dispersion 2) A water-soluble resin, styrene-acrylic acid copolymer (composition (molar) ratio = 33:67), was neutralized with potassium hydroxide in an amount equimolar to the acid value and dissolved in ion-exchanged water to prepare an aqueous solution of resin dispersant with a resin (solid content) content of 20.0%. The weight-average molecular weight of this water-soluble resin was 10,000, and the acid value was 200 mg KOH / g. A mixture of 15.0 parts of pigment (CI Pigment Blue 15), 30.0 parts of the aqueous solution of the resin dispersant, and 55.0 parts of water was placed in a sand grinder and dispersed for 1 hour, and then centrifuged to remove coarse particles. After pressure filtration with a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm, an appropriate amount of ion-exchanged water was added to obtain pigment dispersion liquid 2. The pigment content of the obtained pigment dispersion liquid 2 was 10.0%, and the resin dispersant content was 4.0%.

[0063] (Pigment dispersion 3) Pigment dispersion 3 having a pigment content of 10.0% and a resin dispersant content of 4.0% was obtained in the same manner as in the above-mentioned Pigment Dispersion 2, except that CI Pigment Violet 19 was used instead of CI Pigment Blue 15.

[0064] (Pigment Dispersion 4) Pigment dispersion 4 having a pigment content of 10.0% and a resin dispersant content of 4.0% was obtained in the same manner as in the above-mentioned pigment dispersion 2, except that CI Pigment Red 202 was used instead of CI Pigment Blue 15.

[0065] (Pigment Dispersion 5) Pigment dispersion 5 having a pigment content of 10.0% and a resin dispersant content of 4.0% was obtained in the same manner as in the above-mentioned Pigment Dispersion 2, except that CI Pigment Red 150 was used instead of CI Pigment Blue 15.

[0066] (Pigment Dispersion 6) Pigment dispersion 6 having a pigment content of 10.0% and a resin dispersant content of 3.0% was obtained in the same manner as in the above-mentioned Pigment Dispersion 1, except that CI Pigment Violet 19 was used instead of CI Pigment Blue 15:3.

[0067] (Pigment Dispersion 7) Pigment dispersion 7 having a pigment content of 10.0% and a resin dispersant content of 3.0% was obtained in the same manner as in the above-mentioned Pigment Dispersion 1, except that CI Pigment Yellow 74 was used instead of CI Pigment Blue 15:3.

[0068] (Pigment Dispersion 8) Pigment dispersion 8 having a pigment content of 10.0% and a resin dispersant content of 3.0% was obtained in the same manner as in the above-mentioned pigment dispersion 1, except that CI Pigment Yellow 128 was used instead of CI Pigment Blue 15:3.

[0069] (Pigment Dispersion 9) Pigment dispersion 9 having a pigment content of 10.0% and a resin dispersant content of 4.0% was obtained in the same manner as in the above-mentioned Pigment Dispersion 2, except that CI Pigment Yellow 74 was used instead of CI Pigment Blue 15.

[0070] (Pigment Dispersion 10) With reference to the description in JP 2013-253230 A, 0.10 mmol / g of "phosphonic acid group" derived from ((4-aminobenzoylamino)-methane-1,1-diyl)bisphosphonic acid was introduced into a pigment (CI Pigment Blue 15:4). Furthermore, 0.15 mmol / g of "sulfonic acid group" derived from p-aminobenzenesulfonic acid was introduced to prepare a self-dispersing pigment. Then, an aqueous potassium hydroxide solution and water were added to obtain pigment dispersion 10 having a pigment content of 10.0% and a pH of 10.

[0071] (Pigment Dispersion 11) Pigment Dispersion 11 having a pigment content of 10.0% and a pH of 10 was obtained in the same manner as in the case of Pigment Dispersion 10 described above, except that CI Pigment Violet 19 was used instead of CI Pigment Blue 15:4.

[0072] (Pigment Dispersion 12) Pigment Dispersion 12 having a pigment content of 10.0% and a pH of 10 was obtained in the same manner as in the case of Pigment Dispersion 10 described above, except that CI Pigment Yellow 74 was used instead of CI Pigment Blue 15:4.

[0073] <Ink Preparation> Each component (unit: %) shown in Tables 1-1 to 1-4 was mixed, thoroughly stirred, and then pressure filtered through a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to prepare each ink. In Tables 1-1 to 1-4, "Acetylenol E100" and "Acetylenol E60" are both trade names of nonionic surfactants manufactured by Kawaken Fine Chemicals. In addition, in Tables 1-1 to 1-4, "Surfynol 440" and "Surfynol 465" are both trade names of nonionic surfactants manufactured by Nissin Chemical Industry. In addition, in Tables 1-1 to 1-4, "Emulgen 709" and "Emulgen 103" are both trade names of nonionic surfactants manufactured by Kao. In Tables 1-1 to 1-4, the numbers in parentheses attached to the nonionic surfactants indicate HLB values, and the numbers in parentheses attached to the water-soluble organic solvents indicate relative dielectric constants. The dynamic surface tension (γc, γm, and γy) of each ink at a lifetime of 10 ms was measured at 25° C. using a dynamic surface tensiometer based on the maximum bubble pressure method (product name "BUBLE PRESSURE TENSIOMETER BP-2", manufactured by KRUSS).

[0074] TIFF2024174832000001.tif187170

[0075] TIFF2024174832000002.tif175170

[0076] TIFF2024174832000003.tif186170

[0077] TIFF2024174832000004.tif176170

[0078] <Inkjet recording device> As an inkjet recording device, a product name "PIXUS TS5330" (manufactured by Canon) was prepared. In addition, recording heads 1 to 5 shown in Table 2 were prepared. Using these, an inkjet recording device for the following evaluations was prepared. The ink used to evaluate device configuration 2 was made to have a composition simulating a situation in which the solid content (pigment and resin dispersant) was concentrated by 30 mass % compared to the ink used to evaluate device configuration 1, assuming a situation in which the ink in a stationary state was held in the main tank for a long period of time. In other words, the solid content was set high in advance. · Device configuration 1 (first device configuration): The above recording device (PIXUS TS5330) is equipped with the recording heads shown in Tables 3-1 and 3-2. This device does not have a second ink storage section (main tank). Device configuration 2 (second device configuration): The above recording device (PIXUS TS5330) is equipped with a recording head of the type shown in Tables 3-1 and 3-2 as a second ink storage section (main tank) and a first ink storage section (sub tank).

[0079] TIFF2024174832000005.tif55170

[0080] <Evaluation> In the present invention, in the evaluation criteria for each item shown below, "AA", "A", and "B" were considered acceptable levels, and "C" and "D" were considered unacceptable levels. The evaluation results are shown in Tables 3-1 and 3-2.

[0081] (waste ink volume) The ink storage section was filled with cyan ink, magenta ink, and yellow ink of the types shown in Tables 3-1 and 3-2, and the ink was filled up to the recording head. In this embodiment, the recording duty of an image recorded under the condition that four ink droplets are applied to a unit area of ​​1 / 600 inch x 1 / 600 inch is defined as 100%. As the ink application amount that results in 100% duty for each ink, a 6.0 inch x 9.0 inch solid image was continuously recorded on 10 recording media, and the recording head was left uncapped for 10 days. Plain paper (product name "CS-068", manufactured by Canon) was used as the recording medium. After leaving it for 10 days, the mass of the recording head removed from the inkjet recording device was measured. After the recording head was attached to the inkjet recording device, it was capped and then a fixing recovery operation was performed. The suction condition during the fixing recovery operation was set to a condition that the suction amount for each ink was 0.1 g. After the adhesion recovery operation, a nozzle check pattern was recorded to determine whether there was any non-ejection, and if there was an ejection port with a deteriorated ejection performance, the adhesion recovery operation was performed again, and was repeated until ink ejection from all ejection ports was confirmed. After that, the mass of the recording head removed from the inkjet recording device was measured, and the difference from the mass before the adhesion recovery operation was calculated as the amount of waste ink. The amount of waste ink was then evaluated according to the evaluation criteria shown below. AA: The amount of waste ink was 0.3 g or less. A: The amount of waste ink was more than 0.3g but not more than 0.6g. B: The amount of waste ink was more than 0.6 g and 0.9 g or less. C: The amount of waste ink was more than 0.9 g and was 1.2 g or less. D: The amount of waste ink exceeded 1.2 g.

[0082] Tables 3-1 and 3-2 also show the number of recovery operations "Ncy (times)" required to recover cyan ink and yellow ink, and the number of recovery operations "Nm (times)" and "Nm-Ncy (times)" required to recover magenta ink. When a fixation recovery operation is performed, the amount of waste ink is 0 because ink is not discharged until the fixed ink is removed. For this reason, the amount of waste ink when recovery is performed with one fixation recovery operation is almost the same as the amount of waste ink when recovery is performed with two fixation recovery operations. The reason the amount of waste ink increases is not the number of fixation recovery operations itself, but the fact that cyan ink and yellow ink are recovered but magenta ink is not recovered, so cyan ink and yellow ink are sucked in excess.

[0083] (Bleeding resistance) A pattern in which solid images of cyan ink, magenta ink, and yellow ink were adjacent to each other was printed on a printing medium (plain paper, product name "CS-068", manufactured by Canon) in one pass printing. The printing duty of each solid image was 100%, and the size was 1.0 inch x 1.0 inch. The boundaries of the solid images of each color in the printed pattern were visually observed, and the bleeding resistance of the images was evaluated according to the following evaluation criteria. A: There was no bleeding at any of the boundaries. C: There was bleeding at least at one of the boundaries.

[0084] TIFF2024174832000006.tif206170

[0085] TIFF2024174832000007.tif141170

[0086] (Device size) Reference Examples 1 to 3 are examples using a recording head having a heat sink. In the combination of Reference Example 2 and Comparative Example 1, and the combination of Reference Example 2 and Comparative Example 4, the same type of ink was used. From Tables 3-1 and 3-2, the amount of waste ink in Reference Examples 2 and 3 was smaller than that in Comparative Examples 1 and 4. The amount of waste ink in Reference Examples 2 and 3 was ranked at the same level as Reference Example 1, which used the same type of ink as Example 1, and therefore it is shown that providing a heat sink in the recording head does not increase the amount of waste ink. However, in Reference Examples 1 to 3, since a recording head having a heat sink was used, the recording unit became larger, and the inkjet recording device became larger because a carriage having a rigidity capable of supporting the mass was used.

Claims

1. a water-based ink, each of which contains a resin dispersant having an anionic group for dispersing a pigment, the water-based ink including a cyan ink containing a phthalocyanine pigment, a magenta ink containing a quinacridone pigment, and a yellow ink containing an azo pigment; an ink container for containing the water-based ink; a print head having a plurality of ejection ports for ejecting the water-based ink supplied from the ink storage unit by the action of thermal energy, and an ejection port surface in which a plurality of ejection port arrays each composed of the plurality of ejection ports are arranged on a same printing element substrate; a cap that comes into contact with an area including the ejection port surface and covers the plurality of ejection port arrays; a suction unit that sucks the water-based ink from the plurality of ejection ports through the cap; An inkjet recording apparatus comprising: a step of applying the water-based ink ejected from the plurality of ejection ports onto a recording medium to record an image; sucking the water-based ink from the plurality of ejection ports through the cap; An inkjet recording method comprising the steps of: the ink container is a housing made of a thermoplastic resin, and the recording head is bonded to the ink container without any other member therebetween; The aqueous ink further contains a nonionic surfactant, the content (% by mass) of the nonionic surfactant in the magenta ink is smaller than both the content (% by mass) of the nonionic surfactant in the cyan ink and the content (% by mass) of the nonionic surfactant in the yellow ink; an HLB value of the nonionic surfactant in the magenta ink is smaller than both an HLB value of the nonionic surfactant in the cyan ink and an HLB value of the nonionic surfactant in the yellow ink.

2. The water-based ink further contains a water-soluble organic solvent, 2. The inkjet recording method according to claim 1, wherein the mass average value of the relative dielectric constant of the water-soluble organic solvent in the magenta ink is greater than both the mass average value of the relative dielectric constant of the water-soluble organic solvent in the cyan ink and the mass average value of the relative dielectric constant of the water-soluble organic solvent in the yellow ink.

3. 2. The inkjet recording method according to claim 1, wherein a mass ratio of a content (mass%) of the resin dispersant to a content (mass%) of the quinacridone pigment in the magenta ink is higher than any of a mass ratio of a content (mass%) of the resin dispersant to a content (mass%) of the phthalocyanine pigment in the cyan ink and a mass ratio of a content (mass%) of the resin dispersant to a content (mass%) of the azo pigment in the yellow ink.

4. 2. The inkjet recording method according to claim 1, wherein a content (% by mass) of the quinacridone pigment in the magenta ink is smaller than a content (% by mass) of the phthalocyanine pigment in the cyan ink and a content (% by mass) of the azo pigment in the yellow ink.

5. 5. The inkjet recording method according to claim 1, wherein the nozzle array composed of the nozzles ejecting the magenta ink is arranged at a position sandwiched between the nozzle array composed of the nozzles ejecting the cyan ink and the nozzle array composed of the nozzles ejecting the yellow ink.

6. the ink jet recording apparatus further comprises a liquid chamber communicating with the ejection port, a filter disposed between the ink storage section and the liquid chamber, and an ink flow path through which the water-based ink flows between the filter and the liquid chamber, 5. The ink jet recording method according to claim 1, wherein the ink flow path corresponding to the magenta ink is shorter than both the ink flow path corresponding to the cyan ink and the ink flow path corresponding to the yellow ink.

7. 5. The inkjet recording method according to claim 1, further comprising: a second ink containing section having a larger capacity than the ink containing section; and a tube through which the water-based ink circulates between the second ink containing section and the ink containing section.

8. a water-based ink including a cyan ink containing a phthalocyanine pigment, a magenta ink containing a quinacridone pigment, and a yellow ink containing an azo pigment; an ink container for containing the water-based ink; a print head having a plurality of ejection ports for ejecting the water-based ink supplied from the ink storage unit by the action of thermal energy, and an ejection port surface in which a plurality of ejection port arrays each composed of the plurality of ejection ports are arranged on a same printing element substrate; a cap that comes into contact with an area including the ejection port surface and covers the plurality of ejection port arrays; a suction unit that sucks the water-based ink from the plurality of ejection ports through the cap; An inkjet recording apparatus comprising: the ink container is a housing made of a thermoplastic resin, and the recording head is bonded to the ink container without any other member therebetween; The water-based ink further contains a resin dispersant and a nonionic surfactant for dispersing the pigment, each of which has an anionic group; the content (% by mass) of the nonionic surfactant in the magenta ink is smaller than both the content (% by mass) of the nonionic surfactant in the cyan ink and the content (% by mass) of the nonionic surfactant in the yellow ink; an HLB value of the nonionic surfactant in the magenta ink is smaller than both of an HLB value of the nonionic surfactant in the cyan ink and an HLB value of the nonionic surfactant in the yellow ink.

Images