JP2019005987A - Ink jet recording device, and ink jet recording method - Google Patents

Abstract

To achieve down-sizing of an ink jet recording device which is excellent in ink ejection performance.SOLUTION: An ink nozzle 41 is provided on a nozzle head 4, and is opened in a first region R1 of an underside of the nozzle head 4. An aqueous ink is ejected and discharged from the ink nozzle 41. A cleaning fluid nozzle 141 is provided on the nozzle head 4, and is opened in a second region R2 of the underside of the nozzle head 4. An aqueous cleaning fluid is supplied to the second region R2 from the cleaning fluid nozzle 141, and cleans the first region R1. A cleaning member 6 moves along the underside of the nozzle head 4 from a position at which the member faces the second region R2 to a position at which the member faces the first region R1 while contacting the underside of the nozzle head 4. A surface tension of the aqueous ink is 30 mN/m or more and 37 mN/m or less. A surface tension of the aqueous cleaning fluid is 26 mN/m or more and 32 mN/m or less. A ratio of the surface tension of the aqueous ink to the surface tension of the aqueous cleaning fluid is 1.10 or more and 1.40 or less.SELECTED DRAWING: Figure 2

Description

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

  When recording on a recording medium using an inkjet recording apparatus, first, ink is ejected from the ejection surface of the recording head. Next, maintenance of the recording head is performed. Specifically, first, the ink is discharged from the ejection surface (purge process). Further, the cleaning liquid is supplied to the discharge surface. As the cleaning liquid, for example, a maintenance liquid described in Patent Document 1 below is known. Thereafter, the ejection surface is wiped using, for example, a blade (wiping process). By performing maintenance of the recording head, it is possible to prevent a decrease in ink ejection performance.

JP2013-146965A

  Various methods are known for supplying the cleaning liquid to the ejection surface. For example, a sponge impregnated with the cleaning liquid may be pressed against the discharge surface. The cleaning liquid may be applied to the discharge surface using a roller impregnated with the cleaning liquid. You may spray a washing | cleaning liquid on a discharge surface using a sprayer. However, regardless of which method is used, the ink jet recording apparatus becomes large.

  The present invention has been made in view of such circumstances, and an object thereof is to reduce the size of an ink jet recording apparatus that is excellent in ink ejection performance. Another object of the present invention is to provide an ink jet recording method using such an ink jet recording apparatus.

  The ink jet recording apparatus according to the present invention performs recording on a recording medium. Specifically, the ink jet recording apparatus according to the present invention is ejected and discharged from a nozzle head, an ink nozzle provided in the nozzle head and opening in a first region on the lower surface of the nozzle head, and the ink nozzle. A water-based ink, an aqueous cleaning liquid for cleaning the first region, and a cleaning member that moves along the lower surface of the nozzle head while contacting the lower surface of the nozzle head. The nozzle head is further provided with a cleaning liquid nozzle that opens in a second region of the lower surface of the nozzle head excluding the first region. The aqueous cleaning liquid is supplied from the cleaning liquid nozzle to the second region. The cleaning member moves from a position facing the second area to a position facing the first area. The surface tension of the water-based ink is 30 mN / m or more and 37 mN / m or less. The aqueous cleaning liquid has a surface tension of 26 mN / m or more and 32 mN / m or less. The ratio of the surface tension of the aqueous ink to the surface tension of the aqueous cleaning liquid is 1.10 or more and 1.40 or less.

  In the ink jet recording method according to the present invention, recording is performed on a recording medium using the ink jet recording apparatus having the above-described configuration. Specifically, the inkjet recording method according to the present invention includes a discharge step in which the water-based ink is discharged from the ink nozzle to the recording medium, a purge step in which the water-based ink is discharged from the ink nozzle, and the water-based ink A supplying step in which a cleaning liquid is supplied from the cleaning liquid nozzle to the second area; and a position where the cleaning member faces the second area along the lower surface of the nozzle head while contacting the lower surface of the nozzle head. A wiping step of moving to a position facing the first region. The purge process and the supply process are each performed after the discharge process and before the wipe process. In the supplying step, the aqueous cleaning liquid is held in a state of droplets protruding downward in the vertical direction from the opening of the cleaning liquid nozzle.

  According to the present invention, it is possible to reduce the size of an ink jet recording apparatus excellent in ink ejection performance.

It is a figure which shows an example of the inkjet recording device which concerns on this invention. It is a figure which shows an example of the cross-sectional structure of the nozzle head contained in the inkjet recording device which concerns on this invention. It is a figure which shows 1 process of the inkjet recording method which concerns on this invention. It is a figure which shows 1 process of the inkjet recording method which concerns on this invention.

  Hereinafter, the ink jet recording apparatus according to the present embodiment and the ink jet recording method according to the present embodiment will be described in order with reference to FIGS. In the drawings, the same reference numerals represent the same or corresponding parts. The dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships. Moreover, the X axis, the Y axis, and the Z axis shown in FIGS. 1 to 4 are orthogonal to each other. 1 to 4, Z1 represents the upper side in the vertical direction, and Z2 represents the lower side in the vertical direction.

[Inkjet recording apparatus]
FIG. 1 is a diagram showing an ink jet recording apparatus according to this embodiment. The ink jet recording apparatus 10 performs recording on the recording medium S. Specifically, the ink jet recording apparatus 10 includes a cartridge 2, a nozzle head 4, a cleaning member 6, a control unit 8, a paper feed cassette 91, a manual feed tray 93, a first transport unit 95, and a second transport unit. 97 and a discharge tray 99. Hereinafter, the configuration of the inkjet recording apparatus 10 will be specifically described.

  A plurality of recording media S are stored in the paper feed cassette 91 in a stacked state. A plurality of recording media S are set on the manual feed tray 93 in a stacked state. The first transport unit 95 transports the recording medium S supplied from the paper feed cassette 91 or the manual feed tray 93 along the transport direction M1 while adsorbing the recording medium S. The second transport unit 97 transports the recording medium S transported from the first transport unit 95 along the transport direction M2 while adsorbing the recording medium S. The recording medium S conveyed from the second conveyance unit 97 is discharged to the discharge tray 99. As the recording medium S, for example, plain paper, copy paper, recycled paper, thin paper, thick paper, glossy paper, or OHP paper can be used.

  The cartridge 2 is detachably attached to the ink jet recording apparatus 10. The cartridge 2 includes an aqueous ink, an aqueous cleaning liquid, a first tank 21, and a second tank 23. The first tank 21 stores aqueous ink. The second tank 23 contains an aqueous cleaning liquid.

  The nozzle head 4 discharges and discharges aqueous ink. In addition, the nozzle head 4 supplies an aqueous cleaning liquid. The cleaning member 6 wipes the lower surface of the nozzle head 4. The control unit 8 controls the ink jet recording apparatus 10 to execute recording on the recording medium S. Hereinafter, physical properties of each of the water-based ink and the water-based cleaning liquid, the configuration of the nozzle head 4, and the configuration of the cleaning member 6 will be described in order.

<Physical properties of water-based ink and water-based cleaning liquid>
The surface tension of the water-based ink is 30 mN / m or more and 37 mN / m or less. The surface tension of the aqueous cleaning liquid is 26 mN / m or more and 32 mN / m or less. The ratio of the surface tension of the aqueous ink to the surface tension of the aqueous cleaning liquid (hereinafter referred to as “surface tension ratio”) is 1.10 or more and 1.40 or less.

  If the surface tension of the water-based ink is 30 mN / m or more, the ratio of the surface tension tends to be 1.10 or more. If the surface tension of the water-based ink is 37 mN / m or less, the ratio of the surface tension tends to be 1.40 or less. If the surface tension of the aqueous cleaning liquid is 26 mN / m or more, the ratio of the surface tension tends to be 1.40 or less. If the surface tension of the aqueous cleaning liquid is 32 mN / m or less, the ratio of the surface tension tends to be 1.10 or more.

  If the water-based ink contains 0.6% by mass or more and 1.5% by mass or less of an acetylene type surfactant, the surface tension of the water-based ink tends to be 30 mN / m or more and 37 mN / m or less. As the content of the acetylene type surfactant in the water-based ink increases, the surface tension of the water-based ink tends to decrease. The surface tension of the water-based ink tends to increase as the content of the acetylene surfactant in the water-based ink decreases. As the acetylene type surfactant, for example, “Olfin (registered trademark) E1010” manufactured by Nissin Chemical Industry Co., Ltd. can be used. “Orphine E1010” includes an ethylene oxide adduct of acetylenic diol.

  If the aqueous cleaning liquid contains 1.0% by mass or more and 2.0% by mass or less of polyoxyalkylene alkylamine, the surface tension of the aqueous cleaning liquid tends to be 26 mN / m or more and 32 mN / m or less. As the polyoxyalkylene alkylamine content in the aqueous cleaning liquid increases, the surface tension of the aqueous cleaning liquid tends to decrease. The surface tension of the aqueous cleaning liquid tends to increase as the content of polyoxyalkylene alkylamine in the aqueous cleaning liquid decreases.

  The polyoxyalkylene alkylamine preferably has a structure represented by the following formula (1-1). As a polyoxyalkylene alkylamine having a structure represented by the following formula (1-1) (hereinafter referred to as “amine-type surfactant (1-1)”), for example, “Amate ( (Registered trademark) 105A "," Amate 320 "manufactured by Kao Corporation, or" Puamyl (registered trademark) EP-300S "manufactured by Sanyo Chemical Industries, Ltd. can be used.

In the above formula (1-1), R ¹ represents a hydrocarbon group having 1 to 24 carbon atoms. Preferably, R ¹ represents an alkyl group or an alkenyl group having 1 to 24 carbon atoms. A ¹ O and A ² O each independently represent at least one of an oxyethylene group and an oxypropylene group. m1 and n1 each represents an integer of 0 or more, and represents an integer satisfying 1 ≦ (m1 + n1) ≦ 100. Preferably, m1 and n1 each represents an integer of 0 or more, and represents an integer satisfying 1 ≦ (m1 + n1) ≦ 40.

  The surface tension of the water-based ink means the surface tension of the water-based ink measured at 25 ° C. The surface tension of the water-based ink is measured according to, for example, the Wilhelmy method (plate method). Similarly, the surface tension of the aqueous cleaning liquid means the surface tension of the aqueous cleaning liquid measured at 25 ° C. The surface tension of the aqueous cleaning liquid is measured, for example, according to the Wilhelmy method (plate method). In the measurement of the surface tension by the Wilhelmy method, for example, an “automatic surface tension meter DY-300” manufactured by Kyowa Interface Science Co., Ltd. can be used as the surface tension meter.

<Nozzle head>
The nozzle head 4 will be described with reference to FIGS. 1 and 2. FIG. 2 is a view showing a cross-sectional structure of the nozzle head 4.

  As described above, the nozzle head 4 discharges and discharges the aqueous ink and supplies the aqueous cleaning liquid. Therefore, on the lower surface of the nozzle head 4, there are a region (first region R1) where water-based ink is discharged and discharged and a region (second region R2) where aqueous cleaning liquid is supplied. More specifically, the nozzle head 4 includes a recording head 41 and a cleaning liquid supply unit 141. The recording head 41 is connected to the first tank 21 by an ink flow path, and discharges and discharges water-based ink supplied from the first tank 21. The cleaning liquid supply unit 141 is connected to the second tank 23 by a cleaning liquid channel, and supplies the aqueous cleaning liquid supplied from the second tank 23. Accordingly, the first region R1 is located on the lower surface 42 of the recording head 41, and the second region R2 is located on the lower surface 142 of the cleaning liquid supply unit 141. Hereinafter, the recording head 41 and the cleaning liquid supply unit 141 will be described in order.

(Recording head)
The recording head 41 is a line head and extends in a direction perpendicular to the conveyance direction M1 of the recording medium S. Therefore, the longitudinal direction of the recording head 41 is parallel to the X-axis direction.

  The recording head 41 is provided with a plurality of ink nozzles 47. Each of the ink nozzles 47 opens in the central region of the lower surface 42 of the recording head 41. Each of the ink nozzles 47 discharges and discharges water-based ink (for example, water-based ink supplied from the first tank 21) from the opening 48 of the ink nozzle 47 to the lower side Z2 in the vertical direction.

  Note that the recording head 41 may be a serial head. At least the lower surface 42 of the recording head 41 is preferably made of stainless steel (SUS). The number, size, outer shape, and arrangement of the openings 48 of the ink nozzles 47 on the lower surface 42 of the recording head 41 are not particularly limited. The water-based ink ejection method may be a piezo method or a thermal method.

(Cleaning liquid supply unit)
The cleaning liquid supply unit 141 is fixed to one end of the recording head 41 in the longitudinal direction. The cleaning liquid supply unit 141 includes a housing 143 and a plate-like lid 145. The cleaning liquid supply unit 141 is provided with at least one cleaning liquid nozzle 147.

  The housing 143 accommodates the aqueous cleaning liquid supplied from the second tank 23. Specifically, the housing 143 includes a head side wall 143A, an opposite side wall 143B, and a first inclined portion 143C. Of the side walls constituting the housing 143, the side wall that contacts the head end surface of the recording head 41 corresponds to the head side side wall 143A, and the side wall located on the opposite side of the head side side wall 143A corresponds to the opposite side wall 143B. The first inclined portion 143C is connected to the lower end of the opposite side wall 143B. The first inclined portion 143C is inclined so as to approach the head side wall 143A as it proceeds from the vertical upper side Z1 to the vertical lower side Z2, but does not contact the head side side wall 143A.

  The lid 145 is located on the lower side Z2 in the vertical direction than the housing 143. The lid body 145 has a bent portion, and further includes a second inclined portion 145A and a horizontal portion 145B across the bent portion. The second inclined portion 145A is in contact with the lower surface of the first inclined portion 143C. The horizontal portion 145B is located on the lower side Z2 in the vertical direction than the second inclined portion 145A. The horizontal portion 145 </ b> B extends in the horizontal direction toward the peripheral area of the lower surface 42 of the recording head 41 and is fixed to the peripheral area of the lower surface 42 of the recording head 41. Therefore, the lower surface 142 of the cleaning liquid supply unit 141 is positioned on the lower side Z2 in the vertical direction than the lower surface 42 of the recording head 41.

  The cleaning liquid nozzle 147 opens at the lower surface 142 of the cleaning liquid supply unit 141, and more specifically, opens at the lower surface of the horizontal portion 145B. Each of the cleaning liquid nozzles 147 supplies an aqueous cleaning liquid (for example, the aqueous cleaning liquid supplied from the second tank 23) to the second region R2 from the opening 148 of the cleaning liquid nozzle 147. Here, the surface tension of the aqueous cleaning liquid is 26 mN / m or more and 32 mN / m or less. Therefore, the aqueous cleaning liquid is applied to the lower surface 142 of the cleaning liquid supply unit 141 in the form of liquid droplets protruding from the opening 148 of the cleaning liquid nozzle 147 to the lower side Z2 in the vertical direction (hereinafter referred to as “hemispherical liquid droplets”). Easy to be supplied. If the surface tension of the aqueous cleaning liquid is too small, it is difficult to hold the aqueous cleaning liquid in the form of hemispherical droplets. If the surface tension of the aqueous cleaning liquid is too large, the aqueous cleaning liquid is difficult to flow in the cleaning liquid nozzle, so that the aqueous cleaning liquid is difficult to be supplied to the second region.

  As the inner diameter of the cleaning liquid nozzle 147 is smaller, the radius of the hemispherical droplet tends to be smaller, so that the aqueous cleaning liquid tends to be held in a hemispherical droplet state. On the other hand, since the radius of the hemispherical droplet tends to increase as the inner diameter of the cleaning liquid nozzle 147 increases, the supply amount of the aqueous cleaning liquid (the amount of the aqueous cleaning liquid retained in the vicinity of the opening 148 of the cleaning liquid nozzle 147) ) Tend to increase. Considering these, it is preferable to determine the inner diameter of the cleaning liquid nozzle 147 in consideration of the surface tension of the aqueous cleaning liquid being 26 mN / m or more and 32 mN / m or less. For example, the inner diameter of the cleaning liquid nozzle 147 is preferably 10 μm or more and 500 μm or less, more preferably 30 μm or more and 400 μm or less, and further preferably 40 μm or more and 200 μm or less. Processing of nozzles having an inner diameter of less than 10 μm can be difficult.

  Note that at least the lower surface 142 of the cleaning liquid supply unit 141 is preferably made of resin. The number, size, external shape, and arrangement of the openings 148 of the cleaning liquid nozzle 147 on the lower surface 142 of the cleaning liquid supply unit 141 are not particularly limited. In addition, a cap member for closing the opening 148 of the cleaning liquid nozzle 147 may be provided. If the cap member is provided, the aqueous cleaning liquid can be prevented from drying in the cleaning liquid nozzle 147.

<Cleaning member>
The cleaning member 6 will be described with reference to FIG. The cleaning member 6 has a blade 61. The blade 61 moves between a position facing the lower surface of the nozzle head 4 and a position facing the second transport unit 97. Further, the blade 61 moves along each direction of the ascending direction D1 and the descending direction D2. “Upward direction D1” means a direction toward the upper side Z1 in the vertical direction along the Z-axis direction. The “downward direction D2” means a direction toward the lower Z2 in the vertical direction along the Z-axis direction.

  Further, the blade 61 moves along a lower surface of the nozzle head 4 from a position facing the lower surface 142 of the cleaning liquid supply unit 141 to a position facing the lower surface 42 of the recording head 41 while contacting the lower surface of the nozzle head 4. “The blade 61 moves along the wiping direction D 3” described later means that the blade 61 faces the lower surface 42 of the recording head 41 from a position facing the lower surface 142 of the cleaning liquid supply unit 141 along the lower surface of the nozzle head 4. It means to move to the position.

[Inkjet recording method]
An ink jet recording method using the ink jet recording apparatus 10 will be described with reference to FIGS. 3 and 4 are diagrams showing one process of the ink jet recording method. In the inkjet recording apparatus 10, recording can be performed on the recording medium S by causing the CPU to execute a predetermined control program stored in the ROM by the control unit 8.

  Specifically, first, the control unit 8 supplies the recording medium S from the paper feed cassette 91 or the manual feed tray 93 into the inkjet recording apparatus 10. Next, the control unit 8 transports the recording medium S (the recording medium S supplied into the inkjet recording apparatus 10) to the first transport unit 95. Subsequently, when the control unit 8 controls the recording head 41, the water-based ink is supplied from the first tank 21 to the recording head 41 and discharged from the opening 48 of the ink nozzle 47 to the lower side Z <b> 2 in the vertical direction. (Discharge process). Subsequently, the control unit 8 transports the recording medium S (the recording medium S on which the water-based ink has been ejected) to the second transport unit 97 and then discharges it to the discharge tray 99. After the discharging process, the control unit 8 further performs the following control.

  First, the control unit 8 supplies water-based ink from the first tank 21 to the recording head 41. Thereafter, the control unit 8 controls the recording head 41, so that the water-based ink is discharged from the opening 48 of the ink nozzle 47 to the lower side Z2 in the vertical direction (purge process). As a result, as shown in FIG. 3, the purge ink 51 is supplied to the lower surface 42 of the recording head 41.

  Next, the control unit 8 supplies the aqueous cleaning liquid from the second tank 23 to the cleaning liquid supply unit 141. Thereafter, the control unit 8 controls the cleaning liquid supply unit 141 so that the aqueous cleaning liquid flows in the cleaning liquid nozzle 147 from the vertical upper side Z1 to the vertical lower side Z2, and is supplied to the lower surface 142 of the cleaning liquid supply unit 141. (Supply process). Here, the surface tension of the aqueous cleaning liquid is 26 mN / m or more and 32 mN / m or less. Therefore, as shown in FIG. 3, the aqueous cleaning liquid is supplied to the lower surface 142 of the cleaning liquid supply unit 141 in a hemispherical droplet 52 state.

  In the ejection step, it is preferable that the control unit 8 controls the cleaning liquid supply unit 141 so that the aqueous cleaning liquid is not supplied to the lower surface 142 of the cleaning liquid supply unit 141. That is, in the discharging step, the aqueous cleaning liquid is preferably held in the cleaning liquid nozzle 147 without protruding from the opening 148 of the cleaning liquid nozzle 147 to the lower side Z2 in the vertical direction. Thereby, it is possible to prevent the aqueous cleaning liquid from adhering to the recording medium S. The supply process may be performed before the purge process or may be performed simultaneously with the purge process.

  Subsequently, the control unit 8 controls the blade 61 so that the blade 61 is disposed closer to the longitudinal direction end of the recording head 41 than the second inclined portion 145A (blade 61 indicated by a broken line in FIG. 4). See). Thereafter, the blade 61 moves along the wiping direction D3 while the upper end of the blade 61 is in contact with the lower surface of the nozzle head 4 (wiping step).

  The upper end of the blade 61 is curved when contacting the lower surface of the second inclined portion 145A (see the blade 61 indicated by a solid line in FIG. 4). Therefore, the blade 61 moves along the wiping direction D3 while contacting the lower surface of the horizontal portion 145B with its upper end curved. Thereby, the blade 61 moves along the wiping direction D3 while pushing the aqueous cleaning liquid constituting the hemispherical droplet 52 (see FIG. 4). Accordingly, the aqueous cleaning liquid is supplied to the lower surface 42 of the recording head 41.

  Thereafter, the blade 61 further moves along the wiping direction D3 while contacting the lower surface 42 of the recording head 41 with its upper end curved. Accordingly, the blade 61 moves along the wiping direction D3 while pushing the aqueous cleaning liquid and the purge ink 51. When the movement of the blade 61 along the wiping direction D3 ends, the control unit 8 controls the blade 61 so that the blade 61 moves along the descending direction D2. In this way, the ink jet recording method using the ink jet recording apparatus 10 is completed.

[Effects of inkjet recording apparatus]
The effects produced by the ink jet recording apparatus 10 will be described. The ink jet recording apparatus 10 can achieve the effects 1 to 3 described later.

<Effect 1>
Effect 1 includes downsizing of the inkjet recording apparatus 10. Hereinafter, after describing the conventional problem, the effect 1 will be described.

  Conventionally, as a method for supplying a cleaning liquid to the lower surface (corresponding to an ejection surface) of a recording head, the following methods are known. For example, a sponge impregnated with the cleaning liquid may be pressed against the discharge surface. The cleaning liquid may be applied to the discharge surface using a roller impregnated with the cleaning liquid. You may spray a washing | cleaning liquid on a discharge surface using a sprayer.

  When the cleaning liquid is supplied to the ejection surface using a sponge or roller (hereinafter referred to as “sponge” or the like), the sponge or the like is pressed against the ejection surface during maintenance of the recording head. Therefore, a sponge or the like faces the discharge surface. However, when water-based ink is discharged, the water-based ink is discharged from the discharge surface to the recording medium. Therefore, the recording medium faces the ejection surface, and the sponge or the like does not face. Thus, during recording on the recording medium, the sponge or the like moves between a position facing the recording medium (opposing position) and a position not facing the recording medium (non-facing position). Therefore, it is necessary to provide a space for moving the sponge or the like in the ink jet recording apparatus. Therefore, it is difficult to reduce the size of the ink jet recording apparatus.

  Further, when the cleaning liquid is supplied to the discharge surface using the sprayer, the sprayer needs to be installed in the ink jet recording apparatus. Even in this case, it is difficult to reduce the size of the ink jet recording apparatus. When the sprayer moves between the facing position and the non-facing position, it is more difficult to reduce the size of the ink jet recording apparatus.

  On the other hand, in the inkjet recording apparatus 10, maintenance of the recording head 41 is performed using the cleaning liquid supply unit 141. Thereby, maintenance of the recording head 41 can be performed without the movement of the cleaning liquid supply unit 141. Therefore, it is not necessary to provide a space in the inkjet recording apparatus 10 for the cleaning liquid supply unit 141 to move. Therefore, it is possible to reduce the size of the inkjet recording apparatus 10.

  If the cleaning liquid supply unit 141 does not move, the control unit 8 does not need to control the movement of the cleaning liquid supply unit 141. Thereby, it can prevent that the control program of the inkjet recording device 10 becomes complicated.

  In the inkjet recording apparatus 10, a cleaning liquid nozzle 147 is provided in a cleaning liquid supply unit 141 that is a separate member from the recording head 41. This eliminates the need to provide a cleaning liquid supply mechanism (for example, the cleaning liquid nozzle 147) in the recording head 41. Therefore, the recording head 41 can be downsized as compared with the case where the cleaning liquid supply mechanism is provided in the recording head. Therefore, the ink jet recording apparatus 10 can be easily downsized.

  If it is not necessary to provide the cleaning liquid supply mechanism in the recording head 41, the configuration of the recording head 41 can be prevented from becoming complicated. Thereby, the processing cost of the recording head 41 can be suppressed. Therefore, the inkjet recording apparatus 10 can be provided at a relatively low cost.

<Effect 2>
Effect 2 includes the fact that the inkjet recording apparatus 10 is excellent in water-based ink ejection performance.
Specifically, the surface tension of the aqueous cleaning liquid is 26 mN / m or more and 32 mN / m or less. Thereby, in the supplying step, the aqueous cleaning liquid is easily held in the state of the hemispherical droplets 52, and therefore it is easy to ensure the supply amount of the aqueous cleaning liquid. Therefore, in the wiping process, the aqueous cleaning liquid easily spreads over the entire lower surface 42 of the recording head 41.

  The ratio of the surface tension is 1.10 or more and 1.40 or less. Here, the supply amount of the aqueous cleaning liquid is larger than the discharge amount of the purge ink 51. Therefore, the physical property of the liquid wiped by the blade 61 in the wiping process is more easily governed by the physical property of the aqueous cleaning liquid than the physical property of the purge ink 51. Therefore, if the ratio of the surface tension is 1.10 or more and 1.40 or less, the surface tension of the liquid wiped by the blade 61 in the wiping process can be prevented from becoming too large. Therefore, in the wiping process, the purge ink 51 and the aqueous cleaning liquid are likely to spread over the entire lower surface 42 of the recording head 41.

  As described above, when recording is performed on the recording medium S using the ink jet recording apparatus 10, the purge ink 51 and the aqueous cleaning liquid easily spread on the entire lower surface 42 of the recording head 41. Therefore, the fixed ink can be removed from the lower surface 42 of the recording head 41 by performing the purge process, the supply process, and the wipe process. Therefore, it is possible to provide the ink jet recording apparatus 10 having excellent discharge performance. The fixed ink will be described later.

  Further, if the purge ink 51 and the aqueous cleaning liquid are easily spread over the entire lower surface 42 of the recording head 41 in the wiping process, it is possible to prevent the number of purge processes and the number of supply processes from becoming excessive. Thereby, it is possible to prevent the consumption of the water-based ink and the consumption of the aqueous cleaning liquid from becoming excessive. Therefore, the cost required for recording on the recording medium S can be suppressed.

  The reason why the fixed ink is removed when recording on the recording medium S using the inkjet recording apparatus 10 is considered as follows. In the following, prior to explaining the reason why the fixed ink is removed, the structure of the water-based ink and the formation process of the fixed ink will be described in order.

(Composition of water-based ink)
The aqueous ink has a pigment dispersion. A pigment dispersion means a composition in which a plurality of pigment particles are dispersed in an aqueous medium. Each of the pigment particles includes a pigment core containing a pigment and a coating resin provided on the surface of the pigment core.

  A resin salt is used as the coating resin. The aqueous ink contains a sufficient amount of an aqueous medium. For these reasons, ionization is likely to occur on the surface of the coating resin. Therefore, an electric double layer is formed on the surface of the coating resin. Thus, the pigment particles are dispersed with each other in the aqueous medium.

(Fixed ink formation process)
When the ejection step is performed, the water-based ink may adhere to the lower surface of the recording head and dry on the lower surface of the recording head. When the water-based ink is dried, since the ionization hardly occurs on the surface of the coating resin, the pigment particles are easily aggregated with each other. When the pigment particles are aggregated with each other, the coating resins existing on the surfaces of the different pigment cores are easily brought into contact with each other to form a film. Thus, when the water-based ink is dried, the aggregate of the pigment core is easily covered with the resin film. In this way, a fixed ink is formed.

(Reason for removal of fixed ink)
As described in the above (fixed ink formation process), the pigment particles aggregate to form a fixed ink. However, the purge ink and the aqueous cleaning liquid are each often supplied to the lower surface of the recording head during the formation of the fixed ink.

  In the present embodiment, the ratio of the surface tension is 1.10 or more and 1.40 or less. As a result, the aqueous cleaning liquid exhibits high affinity for the aqueous ink, and thus easily enters between adjacent pigment particles. Further, since the aqueous cleaning liquid has a high affinity for the aqueous ink, it also has a high affinity for the purge ink 51. For this reason, the purge ink 51 as well as the aqueous cleaning liquid easily enters between adjacent pigment particles. For these reasons, the fixed ink is easily dissolved in the purge ink 51. That is, the fixed ink is easily removed.

  Further, as described above, the surface tension of the aqueous cleaning liquid can be adjusted to 26 mN / m or more and 32 mN / m or less by adjusting the content of the amine type surfactant (1-1) in the aqueous cleaning liquid. Here, the amine type surfactant (1-1) is likely to enter between adjacent pigment particles as compared with the surfactant which is not the amine type surfactant (1-1). Therefore, when the aqueous cleaning liquid contains the amine type surfactant (1-1), the aqueous liquid between the adjacent pigment particles is less than when the aqueous cleaning liquid does not contain the amine type surfactant (1-1). Easy to enter the cleaning solution. Also by this, the fixed ink is easily dissolved in the purge ink 51. That is, the fixed ink is easily removed.

<Effect 3>
The effect 3 includes that the ink jet recording apparatus 10 has excellent water-based ink ejection performance even when it is durable.
Specifically, the lower surface 142 of the cleaning liquid supply unit 141 is located on the lower side Z2 in the vertical direction than the lower surface 42 of the recording head 41. Accordingly, when the blade 61 moves along the wiping direction D3 while the upper end of the blade 61 is in contact with the lower surface 42 of the recording head 41, the blade 61 is in contact with the lower surface 142 of the cleaning liquid supply unit 141. Compared to the case where 61 is moving along the wiping direction D3, the bending state of the upper end of the blade 61 is relaxed. Therefore, compared to the case where the position of the lower surface of the recording head and the position of the lower surface of the cleaning liquid supply unit are the same in the vertical direction, the load acting on the blade 61 in the wiping process is reduced. Therefore, the wiping process can be performed even during durability. Therefore, the ink jet recording apparatus 10 is easily excellent in ink ejection performance even during durability.

  Further, since the lower surface 142 of the cleaning liquid supply unit 141 is positioned on the lower side Z2 in the vertical direction than the lower surface 42 of the recording head 41, the aqueous cleaning liquid enters between the lower surface 42 of the recording head 41 and the lid 145 in the wiping process. Can be prevented. Thereby, it is possible to prevent the lower surface 42 of the recording head 41 from being contaminated by the aqueous cleaning liquid. Even when the wiping process is performed a plurality of times, contamination of the lower surface 42 of the recording head 41 by the aqueous cleaning liquid can be prevented, so that the ink jet recording apparatus 10 is easily excellent in ink ejection performance even during durability.

  The ink jet recording apparatus 10 and the ink jet recording method have been described above with reference to FIGS. Hereinafter, the material contained in the water-based ink, the preferred method for producing the water-based ink, the material contained in the aqueous cleaning solution, and the preferred method for producing the aqueous cleaning solution will be described in order without using the drawings.

In addition, the evaluation result (a value indicating the shape or physical properties) of the powder is the number average of the values measured for a considerable number of particles unless otherwise specified. The measured value of the volume median diameter (D ₅₀ ) of the powder is a laser diffraction particle size distribution measuring device (“Zetasizer nano-ZS” manufactured by Malvern, Inc.) unless otherwise specified. It is the value measured using.

  In addition, a compound and a derivative thereof may be generically named by adding “system” after the compound name. When the name of a polymer is expressed by adding “system” after the compound name, it means that the repeating unit of the polymer is derived from the compound or a derivative thereof. Acrylic and methacrylic are sometimes collectively referred to as “(meth) acrylic”.

[Materials contained in water-based ink]
The aqueous ink contains a pigment dispersion and an aqueous medium. The aqueous ink preferably further contains an acetylene type surfactant. The water-based ink may further contain at least one of a surfactant that is not an acetylene-type surfactant, a dissolution stabilizer, a humectant, and a penetrating agent. The water-based ink may further contain sorbitol.

<Pigment dispersion>
The pigment dispersion includes a plurality of pigment particles. Each of the pigment particles includes a pigment core and a coating resin.

(Pigment core)
The pigment core contains a pigment. As the pigment, for example, a yellow pigment, an orange pigment, a red pigment, a blue pigment, a purple pigment, or a black pigment can be used. Examples of yellow pigments include C.I. I. Pigment yellow 74, 93, 95, 109, 110, 120, 128, 138, 139, 151, 154, 155, 173, 180, 185, or 193. Examples of the orange pigment include C.I. I. Pigment orange 34, 36, 43, 61, 63, or 71. Examples of red pigments include C.I. I. Pigment red 122 or 202. Examples of blue pigments include C.I. I. Pigment Blue 15 or 15: 3. Examples of purple pigments include C.I. I. And CI Pigment Violet 19, 23, or 33. Examples of black pigments include C.I. I. And CI Pigment Black 7.

  The content of the pigment core in the water-based ink is preferably 4% by mass or more and 8% by mass or less. Thereby, an image having a desired image density is easily obtained. Further, it is easy to ensure the permeability of the water-based ink to the recording medium. If the content of the pigment core is too small, an image having a desired image density may not be obtained. On the other hand, if the content of the pigment core is too large, the permeability of the water-based ink to the recording medium may not be ensured. In addition, since the fluidity of the pigment particles may not be ensured in the water-based ink, an image having a desired image density may not be obtained.

The volume median diameter (D ₅₀ ) of the pigment core is preferably 30 nm or more and 200 nm or less. Thereby, the color density, hue, and stability of the water-based ink are easily improved. More preferably, the volume median diameter (D ₅₀ ) of the pigment core is 70 nm or more and 130 nm or less.

(Coating resin)
The coating resin is provided on the surface of the pigment core. The coating resin preferably has an anionic property, for example, styrene-acrylic acid resin, styrene-maleic acid copolymer, styrene-maleic acid half ester copolymer, vinylnaphthalene-acrylic acid copolymer, and vinyl. It is preferably at least one of naphthalene-maleic acid copolymers. More preferably, the coating resin is a styrene-acrylic acid resin. If the coating resin is a styrene-acrylic acid resin, pigment particles can be easily produced. Further, the dispersibility of the pigment core can be enhanced.

  The styrene-acrylic acid resin is a resin including a unit derived from styrene and a unit derived from acrylic acid, methacrylic acid, an acrylic ester, or a methacrylic ester. Preferably, the styrene-acrylic acid resin is a copolymer of styrene, acrylic acid, and alkyl acrylate, a copolymer of styrene, methacrylic acid, alkyl methacrylate, and alkyl acrylate, styrene and acrylic acid. A copolymer of styrene, maleic acid and alkyl acrylate, a copolymer of styrene and methacrylic acid, and a copolymer of styrene and alkyl methacrylate. is there. More preferably, the styrene-acrylic acid resin is a copolymer of styrene, methacrylic acid, a methacrylic acid alkyl ester, and an acrylic acid alkyl ester. More specifically, the styrene-acrylic acid resin is a copolymer of styrene, methacrylic acid, methyl methacrylate, and n-butyl acrylate.

  The content of the coating resin is preferably 15 parts by mass or more and 100 parts by mass or less with respect to 100 parts by mass of the pigment core. Thereby, it is easy to prevent the occurrence of show-through in the recording medium after recording. Further, it is easy to obtain an image having a desired image density. If the content of the coating resin is too small, the printout after recording may occur. On the other hand, if the content of the coating resin is too large, an image having a desired image density may not be obtained.

<Aqueous medium>
The aqueous medium preferably contains water, more preferably ion-exchanged water. The water content in the water-based ink is preferably 20% by mass or more and 70% by mass or less. Thereby, the water-based ink which has a suitable viscosity can be provided.

  The aqueous medium preferably contains ion-exchanged water, glycerin and / or glycol, and alcohol and / or glycol ether. If the water-based ink contains glycerin and / or glycol, drying of the water-based ink can be prevented. If the water-based ink contains alcohol and / or glycol ether, the permeability of the water-based ink to the recording medium can be improved.

  Examples of the glycol ether include diethylene glycol monoethyl ether, triethylene glycol mononormal butyl ether, triethylene glycol monoisobutyl ether, triethylene glycol monoisopropyl ether, and diethylene glycol mononormal butyl ether.

<Surfactant>
If the water-based ink contains a surfactant, the wettability of the water-based ink with respect to the recording medium is improved. The surfactant that is not an acetylene type surfactant is preferably a nonionic surfactant. The surfactant that is not an acetylene type surfactant is preferably contained in the water-based ink in an amount of 0.05% by mass or more and 2.00% by mass or less. Thereby, the image density is improved while suppressing the offset of the image.

<Dissolution stabilizer>
If the water-based ink contains a dissolution stabilizer, the components contained in the water-based ink are easily compatible, so that the dissolved state of the water-based ink can be stabilized. Examples of the dissolution stabilizer include 2-pyrrolidone, N-methyl-2-pyrrolidone, and γ-butyrolacton. The content of the dissolution stabilizer in the water-based ink is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less.

<Humectant>
If the water-based ink contains a humectant, the volatilization of the liquid component from the water-based ink can be suppressed, so that the viscosity of the water-based ink can be stabilized. Examples of the humectant include polyalkylene glycols and alkylene glycols. The polyalkylene glycol is preferably polyethylene glycol or polypropylene glycol. Alkylene glycols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, dipropylene glycol, trimethylene glycol (1,3-propanediol), triethylene glycol, tripropylene glycol, 1,2,6-hexanetriol, thiol Diglycol, 1,3-butanediol, or 1,5-pentanediol is preferred. The content of the humectant in the water-based ink is preferably 2% by mass or more and 30% by mass or less, and more preferably 10% by mass or more and 25% by mass or less.

<Penetration agent>
If the water-based ink contains a penetrant, the penetrability of the water-based ink into the recording medium is improved. Examples of the penetrant include 1,2-hexylene glycol, 1,2-octanediol, 2,4-diethyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, Examples include diethylene glycol mono-normal butyl ether or triethylene glycol mono-normal butyl ether. The content of the penetrant in the aqueous ink is preferably 0.5% by mass or more and 20.0% by mass or less.

[Preferred production method of water-based ink]
First, a coating resin is synthesized. Specifically, a monomer or prepolymer capable of synthesizing a coating resin by polymerization and a polymerization initiator are added to a predetermined solvent, and the mixture is heated to reflux at a predetermined temperature. In this way, the coating resin is synthesized. More specifically, styrene, (meth) acrylic acid, (meth) acrylic acid alkyl ester, and a polymerization initiator are added to a mixed solution of isopropyl alcohol and methyl ethyl ketone, and the mixture is heated to reflux at 70 ° C. Thereby, a styrene-acrylic acid resin is synthesized.

  Next, the synthesized resin, the pigment core, and the aqueous medium are kneaded using a media-type disperser. In this way, a pigment dispersion containing a large number of pigment particles is obtained. By changing the particle diameter (for example, bead diameter) of the media used in the media type disperser, the degree of dispersion of the pigment particles, the amount of resin released to the pigment dispersion, or the particle diameter of the pigment particles can be adjusted. For example, the smaller the particle diameter of the media, the smaller the particle diameter of the pigment particles.

  The obtained pigment dispersion is mixed with other ink components. It is preferable to mix the pigment dispersion and other ink components using a stirrer (for example, “Three-One Motor (registered trademark) BL-600” manufactured by Shinto Kagaku Co., Ltd.). The other ink component preferably contains an acetylene type surfactant. The other ink component may further include at least one of a surfactant that is not an acetylene surfactant, a dissolution stabilizer, a humectant, and a penetrating agent. After mixing the pigment dispersion and the other ink components, filtration is performed as necessary. In this way, an aqueous ink is obtained.

[Materials contained in aqueous cleaning solution]
The aqueous cleaning liquid contains an aqueous medium and a surfactant. The surfactant may be composed of an amine-type surfactant (1-1) or may further contain a surfactant that is not an amine-type surfactant (1-1). The aqueous cleaning liquid may further contain at least one of a dissolution stabilizer, a humectant, a penetrating agent, and a pH adjusting agent. The aqueous cleaning liquid may further contain sorbitol.

  The amine type surfactant (1-1) is a nonionic surfactant. Therefore, if the amine type surfactant (1-1) is used as the surfactant, the following two effects can be obtained in addition to the above effects. Specifically, the foaming property of the aqueous cleaning liquid can be suppressed. In addition, an aqueous cleaning liquid that is less harmful to the human body can be provided. In order to effectively obtain these two effects, the surfactant that is not the amine surfactant (1-1) is preferably a nonionic surfactant.

  As the aqueous medium, it is preferable to use the material described in the above <Aqueous medium>. As the dissolution stabilizer, it is preferable to use the materials described in <Dissolution Stabilizer>. As the humectant, it is preferable to use the material described in <Moisturizer>. As the penetrant, it is preferable to use the material described in <Penetration Agent>. For these reasons, the aqueous cleaning liquid tends to show affinity for the aqueous ink and also easily shows affinity for the purge ink.

  If the aqueous cleaning liquid contains a pH adjuster, the pH of the aqueous cleaning liquid can be adjusted so that the pH of the aqueous cleaning liquid is close to the pH of the aqueous ink. Also by this, the aqueous cleaning liquid tends to show affinity for the aqueous ink and easily shows affinity for the purge ink.

  Considering that the water-based ink tends to exhibit basicity, the pH adjuster is preferably an alkali metal salt. More specifically, the alkali metal salt is preferably an alkali metal hydroxide. More preferably, the alkali metal salt comprises at least one of lithium hydroxide, sodium hydroxide, potassium hydroxide, and cesium hydroxide.

[Preferred production method of aqueous cleaning liquid]
A preferable method for producing the aqueous cleaning liquid includes a step of uniformly mixing the materials in a predetermined blending amount. It is preferable to mix the materials using a stirrer (for example, “Three-One Motor BL-600” manufactured by Shinto Kagaku Co., Ltd.).

  Examples of the present invention will be described. Note that the evaluation result (a value indicating the shape or physical properties) of the powder containing a plurality of particles is the number average of the values measured for a considerable number of particles unless otherwise specified. In the evaluation in which an error occurs, a considerable number of measurement values with which the error is sufficiently small are obtained, and the arithmetic average of the obtained measurement values is used as the evaluation value.

  Inkjet recording apparatuses according to Examples and Comparative Examples (more specifically, each of apparatuses A-1 to A-10) were prepared by the method described below. Next, the wiping performance and the landing accuracy were evaluated using the devices A-1 to A-10. Hereinafter, a manufacturing method, an evaluation method, and an evaluation result of apparatuses A-1 to A-10 will be described in order.

[Inkjet recording apparatus manufacturing method]
Table 1 shows the configurations of the devices A-1 to A-10. Table 2 shows the configurations of the water-based inks B-1 to B-6. In Table 2, “surfactant” means “Olfin E1010” manufactured by Nissin Chemical Industry Co., Ltd. “BTG” means triethylene glycol mono-normal butyl ether. “1,3-PG” means 1,3-propanediol. “Pigment dispersion L” is as shown in Table 3. In Table 3, “resin A-Na” means a resin obtained by neutralizing resin A with an aqueous sodium hydroxide (NaOH) solution. “Pigment” means any one of a cyan pigment, a yellow pigment, a magenta pigment, and a black pigment. Table 4 shows the configurations of the aqueous cleaning liquids C-1 to C-5. In Table 4, “surfactant” means “Puamyl EP-300S” manufactured by Sanyo Chemical Industries. “1,3-PG” means 1,3-propanediol. “NaOH aqueous solution” means an aqueous NaOH solution having a concentration of 0.1N. “BTG” means triethylene glycol mono-normal butyl ether.

<Manufacture of water-based ink>
The water-based inks in Examples and Comparative Examples (more specifically, water-based inks B-1 to B-6) are both water-based ink containing cyan pigment (cyan ink) and water-based ink containing yellow pigment ( Yellow ink), an aqueous ink containing a magenta pigment (magenta ink), and an aqueous ink containing a black pigment (black ink). Hereinafter, a method for producing cyan ink will be mainly described. When there is no need to indicate the color of the water-based ink, it is described as “water-based ink”.

(Synthesis of Resin A)
First, resin A was synthesized. Specifically, a stirrer, a nitrogen introduction tube, a condenser (stirrer), and a dropping funnel were set in a four-necked flask (volume: 1000 mL). The flask was then charged with 100 g isopropyl alcohol and 300 g methyl ethyl ketone. The flask was heated to reflux at 70 ° C. while bubbling nitrogen through the contents of the flask.

  Also 40.0 g styrene, 10.0 g methacrylic acid, 40.0 g methyl methacrylate, 10.0 g n-butyl acrylate, 0.4 g azobisisobutyronitrile (AIBN, And a polymerization initiator) to obtain a monomer solution. While heating and refluxing at 70 ° C., the monomer solution was dropped into the flask over about 2 hours. After the dropwise addition, the mixture was further refluxed at 70 ° C. for 6 hours.

  A methyl ethyl ketone solution containing 0.2 g of AIBN was added dropwise to the flask over 15 minutes. After the dropwise addition, the mixture was further refluxed at 70 ° C. for 5 hours. Thus, Resin A (styrene-acrylic acid resin) was obtained. In the obtained resin A, the mass average molecular weight (Mw) was 20000, and the acid value was 100 mgKOH / g.

The mass average molecular weight of Resin A was measured under the following conditions using gel filtration chromatography (“HLC-8020GPC” manufactured by Tosoh Corporation).
Column: “TSKgel SuperMultipore HZ-H” manufactured by Tosoh Corporation (semi-micro column of 4.6 mm ID × 15 cm)
Number of columns: 3 Eluent: Tetrahydrofuran Flow rate: 0.35 mL / min Sample injection volume: 10 μL
Measurement temperature: 40 ° C
Detector: IR detector In addition, a calibration curve is F-40, F-20, F-4, F-1, A-5000, A-2500, and A-1000 from TSKgel standard polystyrene made from Tosoh Corporation. 7 types and n-propylbenzene were selected.

  The acid value of the resin A is described in “JIS (Japanese Industrial Standard) K0070-1992 (acid acid value, saponification value, ester value, iodine value, hydroxyl value, and unsaponified test method for chemical products)”. Required in accordance with the method.

(Preparation of pigment dispersion L)
Using the resin A, a pigment dispersion L having the configuration shown in Table 3 was prepared. Specifically, 6.0% by mass of Resin A and 15.0% by mass of a vessel (capacity: 0.6 L) of a media-type disperser (“Dynomill” manufactured by Willy et Bacofen (WAB)) Phthalocyanine Blue 15: 3 (cyan pigment, “Lionol (registered trademark) Blue FG-7330” manufactured by Toyo Ink Co., Ltd.), 0.5% by mass of 1,2-octanediol, and ion-exchanged water (remaining amount) Put.

  Further, an aqueous NaOH solution in an amount necessary for neutralizing the resin A was added to the vessel. Here, an aqueous NaOH solution was added to the vessel so that the pH of the vessel contents was 8. More specifically, an aqueous NaOH solution having a mass 1.1 times the neutralization equivalent was added to the vessel. In addition, when determining the compounding quantity of the material which comprises the pigment dispersion liquid L, the sum total of the mass of Resin A and the mass of Na which should be added to a vessel was considered as the mass of Resin A. Further, the total of the mass of ion-exchanged water, the mass of water contained in the NaOH aqueous solution, and the mass of water generated by the neutralization reaction was regarded as the mass of ion-exchanged water.

The vessel was filled with media (zirconia beads having a diameter of 0.5 mm) so that the filling amount was 70% by volume with respect to the vessel capacity. The media-type disperser is adjusted so that the volume median diameter (D ₅₀ ) of the pigment particles falls within the range of 70 nm or more and 130 nm or less while water-cooling the vessel under conditions where the temperature is 10 ° C. and the peripheral speed is 8 m / sec. The contents of the vessel were kneaded. In this way, a pigment dispersion L was obtained.

(Mixing of pigment dispersion L and other ink components)
The pigment dispersion L and other ink components were mixed. Specifically, the materials described in Table 2 were put in a beaker with the blending amounts described in Table 2. Using a stirrer (“Three-One Motor BL-600” manufactured by Shinto Kagaku Co., Ltd.), the contents of the beaker were stirred at a rotation speed of 400 rpm to uniformly mix the contents of the beaker. The mixed solution was filtered using a filter (pore size: 5 μm) to remove foreign substances and coarse particles contained in the mixed solution. In this way, a cyan ink was obtained.

  As a pigment, C.I. I. Yellow ink was obtained using Pigment Yellow 74. A magenta ink was obtained using quinacridone / magenta (PR122) as a pigment. Moreover, black ink was obtained using carbon black as a pigment. In this manner, water-based inks (more specifically, each of water-based inks B-1 to B-6) in Examples and Comparative Examples were obtained.

  Based on the Wilhelmy method (plate method), the surface tension of the water-based ink at 25 ° C. was measured using a surface tension meter (“Automatic surface tension meter DY-300” manufactured by Kyowa Interface Science Co., Ltd.). The results are shown in Table 2.

<Manufacture of aqueous cleaning liquid>
The materials described in Table 4 were put in a beaker with the blending amounts described in Table 4. Using a stirrer (“Three-One Motor (registered trademark) BL-600” manufactured by Shinto Kagaku Co., Ltd.), the contents of the beaker were stirred at a rotational speed of 400 rpm to uniformly mix the contents of the beaker. The liquid mixture obtained using a filter (pore size 5 μm) was filtered to remove foreign substances and coarse particles contained in the liquid mixture. In this way, aqueous cleaning liquids (more specifically, each of the aqueous cleaning liquids C-1 to C-5) in Examples and Comparative Examples were obtained.

  Based on the Wilhelmy method (plate method), the surface tension of the aqueous cleaning liquid at 25 ° C. was measured using a surface tension meter (“Automatic surface tension meter DY-300” manufactured by Kyowa Interface Science Co., Ltd.). The results are shown in Table 4.

<Preparation of prototype>
The ink jet recording apparatus shown in FIG. 1 was prepared as a prototype. Specifically, the prototype includes four first tanks, one second tank, four nozzle heads, and four blades. Each nozzle head had a recording head and a cleaning liquid supply unit. Different first tanks were connected to the recording head. Further, each of the recording heads is provided with a plurality of ink nozzles, and each of the ink nozzles is opened on the lower surface of the recording head. Each of the recording heads has a resolution of 360 dpi (= 180 dpi × 2 rows), 512 nozzles (= 256 × 2 rows), a droplet amount of 14 pL, and a driving frequency of 12.8 kHz (manufactured by Konica Minolta Co., Ltd.). )Met. The recording heads were arranged at an interval of 20 mm so that the longitudinal direction thereof was orthogonal to the paper transport direction. The lower surface of the recording head was all washed and was not contaminated with water-based ink.

  Each of the cleaning liquid supply units was fixed to one end in the longitudinal direction of the recording head. Each of the cleaning liquid supply units is provided with a plurality of cleaning liquid nozzles, and each of the cleaning liquid nozzles is open on the lower surface of the cleaning liquid supply unit. The lower surface of the cleaning liquid supply unit was positioned on the lower side in the vertical direction than the lower surface of the recording head.

  The blade moved from the position facing the lower surface of the cleaning liquid supply unit to the position facing the lower surface of the recording head along the lower surface of the nozzle head while the upper end of the blade was in contact with the lower surface of the nozzle head. In such a prototype, it is possible to perform recording on a recording sheet by executing a predetermined control program stored in the ROM by the control unit using the CPU.

<Filling liquid>
The first tank contained water-based inks having different colors (each of water-based inks B-1 to B-6 in Examples and Comparative Examples). The second tank contained an aqueous cleaning liquid (each of the aqueous cleaning liquids C-1 to C-5 in Examples and Comparative Examples). After that, the installation operation was performed. In this manner, ink jet recording apparatuses (more specifically, each of apparatuses A-1 to A-10) according to Examples and Comparative Examples were obtained.

[Evaluation method]
<Evaluation of wiping performance>
First, in a temperature 25 ° C. and humidity 60% RH environment, a printing durability test was performed using the ink jet recording apparatuses according to Examples and Comparative Examples (more specifically, each of apparatuses A-1 to A-10). went. In the printing durability test, a solid image (size 10 cm × 10 cm, printing rate 100%) with a conveyance speed of 350 mm / second and 5000 recording sheets (Fuji Xerox Co., Ltd. “C ² ”, A4 size ordinary Paper). In addition, the solid images were recorded so that the solid images with different colors overlapped on the recording sheet.

  After the printing durability test, the recording head was maintained. Specifically, first, the control unit of the inkjet recording apparatus according to the example and the comparative example supplies water-based ink (more specifically, each of water-based inks B-1 to B-6) from the first tank to the recording head. did. In addition, the control unit supplied the aqueous cleaning liquid (more specifically, each of the aqueous cleaning liquids C-1 to C-5) from the second tank to the cleaning liquid supply unit. Next, the control unit controlled each of the recording heads, so that the water-based ink was discharged downward in the vertical direction from the opening of the ink nozzle. The control unit controls the cleaning liquid supply unit, so that the aqueous cleaning liquid flows in the cleaning liquid nozzle from the upper side in the vertical direction to the lower side in the vertical direction and is supplied to the lower surface of the cleaning liquid supply unit. Subsequently, the control unit controlled the blade, so that the blade was disposed closer to the end in the longitudinal direction of the recording head than the second inclined portion of the cleaning liquid supply unit. Thereafter, the blade moved along the wiping direction while the upper end of the blade was in contact with the lower surface of the nozzle head.

When the maintenance of the recording head was completed, the lower surface of the recording head was observed using an optical microscope, and the presence or absence of ink stains on the lower surface of the recording head was confirmed. The evaluation criteria are shown below. The evaluation results are shown in Table 5.
Excellent (◎): No ink stain was observed on the lower surface of the recording head.
Good (O): Ink smear was confirmed on the lower surface of the recording head. The confirmed ink stain was within an acceptable range.
Defect (x): Ink smear was confirmed on the lower surface of the recording head. The confirmed ink stain was beyond the allowable range.

<Evaluation of landing accuracy>
First, initial landing accuracy (3σ value) was obtained.
Next, according to the method described in <Evaluation of wiping performance> described above, a printing durability test and recording head maintenance were performed. Over a week, the ink jet recording apparatuses according to Examples and Comparative Examples (more specifically, each of the apparatuses A-1 to A-10) were allowed to stand. Thereafter, the landing accuracy (3σ value) was determined. In this way, the landing accuracy (3σ value) after standing was determined. The evaluation criteria are shown below. The evaluation results are shown in Table 5.
Good (◯): The difference between the initial landing accuracy (3σ value) and the landing accuracy after standing (3σ value) was less than 3.
Defect (x): The difference between the initial landing accuracy (3σ value) and the landing accuracy after standing (3σ value) was 3 or more.

  The landing accuracy (3σ value) was determined by the following method. Specifically, one dot was ejected from all nozzles of the four recording heads on the recording sheet in a state where the recording sheet was not conveyed (stamp type). Next, for each dot on the recording sheet, the landing accuracy 3σ was measured using a general-purpose image processing system (“DA-6000” manufactured by Oji Scientific Instruments). The arithmetic average value of the obtained measurement data (landing accuracy of each dot 3σ) was defined as the landing accuracy (3σ value).

The landing accuracy 3σ means the landing accuracy represented by the expression “3σ = 3√ (σ _x ² + σ _y ² )”. In the equation, σ _x means a standard deviation of the positional deviation amount in the X direction from the nozzle design position. Σ _y means a standard deviation of the amount of positional deviation in the Y direction from the nozzle design position.

[Evaluation results]
Table 5 shows the evaluation results of the devices A-1 to A-10. In Table 5, “Ratio” indicates the ratio of the surface tension of the aqueous ink to the surface tension of the aqueous cleaning liquid. “Evaluation A” describes the evaluation result of the wiping performance of the fixed ink on the lower surface of the recording head. “Evaluation B” describes the evaluation result of the landing accuracy of the water-based ink after standing for one week.

[Discussion]
Inkjet recording apparatuses according to Examples 1 to 4 (more specifically, apparatuses A-1 to A-4) each had the basic configuration shown below. More specifically, the ink jet recording apparatuses according to Examples 1 to 4 were provided with a nozzle head, an ink nozzle, a cleaning liquid nozzle, an aqueous ink, an aqueous cleaning liquid, and a cleaning member. The ink nozzle was provided in the nozzle head and opened in the first region R1 on the lower surface of the nozzle head. The water-based ink was discharged and discharged from the ink nozzle. The cleaning liquid nozzle was provided in the nozzle head and opened in the second region on the lower surface of the nozzle head. The aqueous cleaning liquid was supplied from the cleaning liquid nozzle to the second area, and the first area was cleaned. The cleaning member moved from the position facing the second area along the lower surface of the nozzle head to the position facing the first area while contacting the lower surface of the nozzle head. The surface tension of the water-based ink was 30 mN / m or more and 37 mN / m or less. The surface tension of the aqueous cleaning liquid was 26 mN / m or more and 32 mN / m or less. The ratio of surface tension was 1.10 or more and 1.40 or less.

  Each of the inkjet recording apparatuses according to Examples 1 to 4 was excellent in the wiping performance of the fixed ink on the lower surface of the recording head. In the inkjet recording apparatuses according to Examples 1 to 4, the landing accuracy of the water-based ink was maintained even after one week had elapsed since the water-based cleaning liquid was supplied. The present inventors considered as follows about the evaluation result of the inkjet recording device which concerns on Examples 1-4. The ink jet recording apparatuses according to Examples 1 to 4 had the basic configuration described above. Therefore, during the maintenance of the recording head, the aqueous cleaning liquid is easily supplied to the lower surface of the cleaning liquid supply unit in the form of hemispherical droplets. Therefore, the wiping performance was excellent and the landing accuracy of the water-based ink was maintained.

  The ink jet recording apparatus according to the present invention can be used as a color printer, for example.

4 Nozzle head 6 Cleaning member 10 Inkjet recording apparatus 41 Recording head 42 Lower surface 47 of recording head Ink nozzle 48 Ink nozzle opening 52 Hemispherical droplet 141 Cleaning liquid supply part 142 Lower surface of cleaning liquid supply part 147 Cleaning liquid nozzle 148 Cleaning liquid Nozzle opening R1 first region R2 second region S recording medium

Claims (5)

An inkjet recording apparatus for recording on a recording medium,
A nozzle head;
An ink nozzle provided in the nozzle head and opening in a first region on a lower surface of the nozzle head;
Water-based ink discharged and discharged from the ink nozzle;
An aqueous cleaning solution for cleaning the first region;
A cleaning member that moves along the lower surface of the nozzle head while contacting the lower surface of the nozzle head;
With
The nozzle head is further provided with a cleaning liquid nozzle that opens in a second region excluding the first region of the lower surface of the nozzle head,
The aqueous cleaning liquid is supplied from the cleaning liquid nozzle to the second region,
The cleaning member moves from a position facing the second region to a position facing the first region;
The surface tension of the water-based ink is 30 mN / m or more and 37 mN / m or less,
The surface tension of the aqueous cleaning liquid is 26 mN / m or more and 32 mN / m or less,
The inkjet recording apparatus, wherein a ratio of a surface tension of the aqueous ink to a surface tension of the aqueous cleaning liquid is 1.10 or more and 1.40 or less. The water-based ink contains an acetylene type surfactant in an amount of 0.6% by mass to 1.5% by mass,
The aqueous cleaning liquid contains 1.0% by mass or more and 2.0% by mass or less of polyoxyalkylene alkylamine,
The inkjet recording apparatus according to claim 1, wherein the polyoxyalkylene alkylamine has a structure represented by the following formula (1-1).

In the above formula (1-1), R ¹ represents a hydrocarbon group having 1 to 24 carbon atoms. A ¹ O and A ² O each independently represent at least one of an oxyethylene group and an oxypropylene group. m1 and n1 each represents an integer of 0 or more, and represents an integer satisfying 1 ≦ (m1 + n1) ≦ 100. The nozzle head includes a recording head and a cleaning liquid supply unit.
The recording head is provided with the ink nozzle,
The ink nozzle opens on the lower surface of the recording head;
The cleaning liquid supply unit is provided with the cleaning liquid nozzle,
The inkjet recording apparatus according to claim 1, wherein the cleaning liquid nozzle opens at a lower surface of the cleaning liquid supply unit.   The ink jet recording apparatus according to claim 3, wherein a lower surface of the cleaning liquid supply unit is positioned on a lower side in a vertical direction than a lower surface of the recording head. An inkjet recording method for recording on a recording medium using the inkjet recording apparatus according to any one of claims 1 to 4,
An ejection step in which the water-based ink is ejected from the ink nozzle to the recording medium;
A purge step in which the water-based ink is discharged from the ink nozzle;
A supplying step in which the aqueous cleaning liquid is supplied from the cleaning liquid nozzle to the second region;
A wiping step in which the cleaning member moves from a position facing the second region along the lower surface of the nozzle head to a position facing the first region while contacting the lower surface of the nozzle head;
Including
The purge step and the supply step are each performed after the discharge step and before the wipe step,
In the ink jet recording method, in the supplying step, the aqueous cleaning liquid is held in a state of liquid droplets protruding downward in the vertical direction from the opening of the cleaning liquid nozzle.

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