Water-based ink, ink discharge apparatus, image recording apparatus, and printing method

Abstract

Provided is a water-based ink in which the discharge properties, roughness, and uncovering properties of the ink are ensured without being in contact with the VOC limit reference. The water-based ink contains water, a solvent group A, a thickening agent and a binder polymer, and when 1.5 + / -0.1 g of the solvent group A is placed in an aluminum foil box of 40 mm * 40 mm * 10 mm which is open upwards in a room with the room temperature of 25 DEG C and the humidity of 65% and heated for 30 minutes at the temperature of 100 + / -5 DEG C, the weight change amount of the solvent group A exceeds 0.01 g of the thickening agent and the binder polymer. The weight% of the solvent group A relative to the total amount of the water-based ink is 25.0-30.0 wt%. The weight% of the thickener relative to the total amount of the water-based ink is 10.1% or more. And the viscosity of the water-based ink is 10 to 14 mPa.s.

Description

TECHNICAL FIELD

[0001] The present application relates to an aqueous ink for an inkjet recording device, an ink ejection device, an image recording device, and a printing method. BACKGROUND

[0002] As an aqueous ink used in an inkjet recording device, an aqueous ink for inkjet recording of Patent Literature 1 is known. The aqueous ink for inkjet recording of Patent Literature 1 contains water, a water-soluble organic solvent, a pH adjuster, a viscosity adjuster, a surface tension adjuster, a mildew preventive agent, and the like. In Patent Literature 1, the viscosity of the ink is adjusted to be low viscosity so that the ink is easily ejected from the nozzles of the head.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Laid-Open No. 2020-196779 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] In the above-described aqueous ink for inkjet recording, although the ejection property of the ink is excellent, since the viscosity of the ink is low, it is difficult to obtain clear quality. That is, the raggedness is low. Therefore, in order to improve the raggedness, it is considered to make the viscosity of the above-described aqueous ink high viscosity. However, in this case, not only the ejection property of the ink deteriorates, but also since a large amount of solvent is used, depending on the kind of the solvent or the solvent ratio, there is a risk of conflicting with the VOC limit standard, or a problem of deterioration of so-called decap in which the ink adhering to the nozzle dries quickly and clogging easily occurs in the nozzle.

[0008] An object of the present application is to provide an aqueous ink, an ink ejection device, an image recording device, and a printing method which do not conflict with the VOC limit standard and can ensure the ejection property, the raggedness, and the decap of the ink.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] (1) The aqueous ink according to the present application contains water, a solvent group A, a thickening agent, and a binder polymer, the solvent group A having a weight change amount exceeding 0.01 g when 1.5 ± 0.1 g is put in an aluminum foil case of 40 mm x 40 mm x 10 mm opened upward in a room at room temperature 25°C and humidity 65% and heated at a temperature of 100 ± 5°C for 30 minutes. The weight % of the above-described solvent group A with respect to the total amount of the aqueous ink is 25.0 to 30.0% by weight. The weight % of the above-described thickening agent with respect to the total amount of the aqueous ink is 10.1% or more. The viscosity is 10 to 14 mPa-s.

[0011] Since the weight % of the solvent group A with respect to the total amount of the water-based ink is 30.0 wt% or less, the water-based ink does not conflict with the VOC limit standard. Since the weight % of the solvent group A with respect to the total amount of the water-based ink is 25.0 wt% or more, the weight % of water which evaporates easily compared to the solvent group A becomes small. Therefore, the case where the water-based ink adhering to the nozzle dries quickly is suppressed, and thus the water-based ink is difficult to solidify. Therefore, the case where clogging occurs on the nozzle due to the solidified ink is suppressed. That is, the uncapping property can be ensured. Since the viscosity of the water-based ink is adjusted to 10 mPa-s or more by the thickening agent, the image formed by the ink is difficult to become unsharp. Therefore, the tightness can be ensured. Since the viscosity of the water-based ink is adjusted to 14 mPa-s or less by the thickening agent, the case where the ink is difficult to be ejected from the nozzle is suppressed. Thus, the ejection property of the ink can be ensured.

[0012] (2) The above thickening agent can contain a solvent group B which has a weight change amount of 0.01 g or less when 1.5 ± 0.1 g is heated at a temperature of 100 ± 5 °C for 30 minutes. The weight % of the above solvent group B with respect to the total amount of the water-based ink can be 25.0 wt% or less.

[0013] Since the weight % of the solvent group B which evaporates more difficultly compared to the solvent group A is limited to 25.0 wt% or less, the drying property of the water-based ink is improved.

[0014] (3) The weight % of the above solvent group B with respect to the total amount of the water-based ink can be 5.0 wt% or less.

[0015] The drying property of the water-based ink is further improved.

[0016] (4) The above binder polymer can also be a substance which has a viscosity of less than 10 to 100 mPa-s when added to a low-viscosity binder polymer dispersion medium so as to be 38.0 wt%.

[0017] The scratch resistance of the film formed by the binder polymer is improved.

[0018] (5) The weight % of the above binder polymer with respect to the total amount of the water-based ink can be 5.0 wt% or less.

[0019] When the water-based ink dries, since the case where the film is formed on the nozzle face or inside the nozzle is suppressed, the ejection failure of the water-based ink is suppressed.

[0020] (6) The weight % of the above binder polymer with respect to the total amount of the water-based ink can be 3.0 wt% or less.

[0021] When the aqueous ink dries, since the membrane formation in the nozzle face or inside the nozzle is inhibited, the ejection failure of the aqueous ink is further inhibited.

[0022] (7) The above-mentioned adhesive polymer can be an acrylic polymer.

[0023] The rub resistance and stability of the film formed by the adhesive polymer are further improved.

[0024] (8) The above-mentioned thickening agent can contain a high-viscosity adhesive polymer dispersion liquid in which the above-mentioned adhesive polymer is dispersed. The above-mentioned high-viscosity adhesive polymer dispersion liquid can be a substance whose viscosity is 100 mPa-s or more and less than 5000 mPa-s when the above-mentioned adhesive polymer is added to a high-viscosity adhesive polymer dispersion medium at 38.0% by weight.

[0025] The rub resistance of the film formed by the adhesive polymer is further improved.

[0026] (9) The weight % of the above-mentioned thickening agent with respect to the total amount of the aqueous ink can be 28.0% by weight or less.

[0027] (10) The evaporation rate after 5 g of the above-mentioned aqueous ink is added to a container of 60 mm in diameter which is open upward in a room at room temperature of 25°C and humidity of 65% and heated at 100°C for 4 hours can be 70% or more.

[0028] The aqueous ink has high drying properties.

[0029] (11) The ink ejection device of the present application has a nozzle which ejects the above-mentioned aqueous ink and a heater which heats at least one of the above-mentioned non-absorbing medium ejected from the above-mentioned nozzle and the above-mentioned aqueous ink adhered to the above-mentioned non-absorbing medium.

[0030] The aqueous ink adhered to the non-absorbing medium becomes easy to dry.

[0031] (12) The heating temperature of the above-mentioned heater can be 60°C or more.

[0032] The aqueous ink ejected to the non-absorbing medium becomes more easy to dry.

[0033] (13) The above-mentioned nozzle can also eject the above-mentioned ink in the vertical direction.

[0034] Since the viscosity of the water-based ink is increased in order to ensure the roughness of the water-based ink, even if the distance between the nozzle and the non-absorbing medium is enlarged, the water-based ink is difficult to spread in the non-absorbing medium, and thus the image formed by the water-based ink is difficult to become unsharp. Therefore, by enlarging the distance between the nozzle and the non-absorbing medium, the size restriction of the print object is easily relaxed.

[0035] (14) The nozzle can also eject the ink in the horizontal direction.

[0036] Since the viscosity of the water-based ink is increased in order to ensure the roughness of the water-based ink, even if the water-based ink is ejected in the horizontal direction, the liquid drops of the water-based ink adhered to the non-absorbing medium can be suppressed.

[0037] (15) The ink ejection device can further include a cover that abuts against the nozzle and covers the nozzle, a suction pump that suctions the ink in the cover, and a controller. In the image recording process of ejecting the ink to the non-absorbing medium, the controller can periodically perform a cleaning process of driving the suction pump in a state where the cover covers the nozzle.

[0038] The clogging of the nozzle due to foreign matter is more reliably prevented.

[0039] (16) The image recording device according to the present application includes the ink ejection device and a conveyance device that conveys the non-absorbing medium in a conveyance direction.

[0040] The image is suitably recorded on the non-absorbing medium.

[0041] (17) The printing method according to the present application includes a first step of ejecting the water-based ink from the nozzle, and a second step of heating at least one of the non-absorbing medium to which the water-based ink ejected from the nozzle is adhered and the water-based ink adhered to the non-absorbing medium by a heater.

[0042] The water-based ink adhered to the non-absorbing medium becomes easier to dry.

[0043] (18) In the second step, the temperature at which the heater heats at least one of the non-absorbing medium and the water-based ink can be 60°C or higher.

[0044] The water-based ink adhered to the non-absorbing medium becomes more easily dried.

[0045] (19) In the first step, the nozzle can also eject the water-based ink in the vertical direction.

[0046] Since the viscosity of the water-based ink is increased in order to ensure the roughness of the water-based ink, even if the distance between the nozzle and the non-absorbing medium is enlarged, the image formed by the water-based ink is difficult to become unsharp. Therefore, by enlarging the distance between the nozzle and the non-absorbing medium, the size restriction of the printed object is easily relaxed.

[0047] (20) In the above-mentioned first step, the above-mentioned nozzle can also eject the above-mentioned water-based ink in the horizontal direction.

[0048] Since the viscosity of the water-based ink is increased in order to ensure the roughness of the water-based ink, even if the water-based ink is ejected in the horizontal direction, the liquid drop of the water-based ink attached to the non-absorbing medium is inhibited.

[0049] (21) The above-mentioned printing method can further have a third step of: when the image recording process of ejecting the above-mentioned water-based ink from the above-mentioned nozzle to record the image on the non-absorbing medium, the controller periodically performs the cleaning process of driving the suction pump that suctions the ink in the cap in the state that the cap covers the above-mentioned nozzle.

[0050] The clogging of the nozzle due to foreign matter is more reliably prevented.

[0051] (22) The above-mentioned printing method can further have a fourth step before the above-mentioned first step: the conveying device transports the above-mentioned non-absorbing medium to the position opposite to the nozzle.

[0052] The image is suitably recorded on the non-absorbing medium.

[0053] Effects of the Invention

[0054] According to the present application, the ejection property, the roughness, and the cap opening property of the ink can be ensured without conflicting with the VOC limit standard. BRIEF DESCRIPTION OF DRAWINGS

[0055] [ Figure 1 ] Figure 1 is an appearance perspective view of an image recording apparatus 100 according to an embodiment of the present application.

[0056] [ Figure 2 ] Figure 2 is a cross-sectional view showing a II-II cross section of Figure 1 .

[0057] [ Figure 3 ] Figure 3 is a schematic view showing an ink circuit 113.

[0058] [ Figure 4 ] Figure 4 is a block diagram showing a controller 130.

[0059] Reference Signs

[0060] 36 convey roller group (conveying device)

[0061] 38 nozzle

[0062] 38A nozzle

[0063] 39 heater

[0064] 62 cover

[0065] 74 suction pump

[0066] 100 image recording device (ink jetting device)

[0067] 130 controller

[0068] S sheet (non-absorbing medium) DETAILED DESCRIPTION

[0069] A preferred embodiment of the present application will be described below. In addition, the present embodiment is merely one embodiment of the present application, and the embodiment can be changed within the scope of the gist of the present application. In addition, in the following description, the advancement from the start point to the end point of an arrow is expressed as a direction, and the to-and-fro on the line connecting the start point and the end point of the arrow is expressed as a direction. In addition, in the following description, the up-and-down direction 7 is defined with the state in which the image recording device 100 is set to be usable (the state of Figure 1 ) as a reference, the front-and-back direction 8 is defined with the side on which the discharge port 33 is provided as a front side (front face), and the left-and-right direction 9 is defined with the image recording device 100 viewed from the front side (front face).

[0070] [Appearance configuration of image recording device 100]

[0071] Figure 1 The image recording device 100 (an example of an ink jetting device) illustrated in the drawing records an image on a sheet S constituting a roller body 37 (refer to Figure 2 ) by an ink jet recording method.

[0072] As illustrated in Figure 1 , the image recording device 100 is provided with a housing 30. The housing 30 is generally in a rectangular parallelepiped shape as a whole. In addition, a frame for supporting each component can be appropriately provided inside the housing 30.

[0073] A discharge port 33 in the form of a slit longer in the left-and-right direction 9 is formed in the front face 30F of the housing 30. The sheet S on which an image has been recorded (refer to Figure 2 ) is discharged from the discharge port 33. An operation panel 44 is provided on the front face 30F. A user performs input on the operation panel 44 for causing the image recording device 100 to act or determining various settings.

[0074] The right cover 35A is located at the right surface 30R of the housing 30. By opening and closing the right cover 35A, the bracket 35 and the like located in the sheet accommodating space 32C can be exposed or shielded (refer to Figure 2 ).

[0075] The front cover 29 is located at the front face 30F of the housing 30. The front cover 29 is capable of opening by tilting the upper end side toward the front, about a rotation shaft (not shown) extending in the left-right direction 9 near the lower end. By opening and closing the front cover 29, the ink cartridge mounting portion 110 and the like located in the internal space 31 of the housing 30 can be exposed or shielded (refer to Figure 2 ).

[0076] [Internal configuration of the image recording apparatus 100]

[0077] As shown in Figure 2 , the bracket 35, the tensioner 45, the conveyance roller set 36, the conveyance roller set 40, the nozzle 38, the platen 51, the heater 39, the CIS 25, the cutter unit 26, the ink cartridge mounting portion 110, and the like are disposed in the internal space 31 of the housing 30. In addition, although not shown in Figure 2 , a fixing unit, an image sensor, a maintenance unit, and the like can also be located in the internal space 31.

[0078] The internal space 31 is provided with a partition wall 41. The partition wall 41 partitions the lower rear portion of the internal space 31, dividing the sheet accommodating space 32C. The sheet accommodating space 32C is a space surrounded by the partition wall 41 and the lower housing 32, and is isolated from the nozzle 38 and the like.

[0079] The roller body 37 is accommodated in the sheet accommodating space 32C. The roller body 37 has a core tube and a long sheet S. The sheet S is wound around the core tube in a circumferential direction of the axis of the core tube and is in a roll shape. The sheet S is a non-absorbing medium having a low water absorption surface. Specifically, the sheet S refers to a sheet in which the water absorption amount from the start of contact to 30 msec1 / 2 is 10 mL / m2 or less in the Bristow method. In addition, the so-called "non-absorbing" can also refer to a case in which the water absorption rate for 24 hours is less than 0.5% according to ASTM D570. More specifically, the "non-absorbing" can also refer to a case in which the water absorption rate is less than 0.2%. In addition, the unit "%" of the water absorption rate is a mass basis. As the material of the sheet S, for example, plastics (for example, polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride resin, polycarbonate, and the like) and the like can be cited.

[0080] The tensioner 45 is located above the partition wall 41 in the rear portion of the internal space 31. The tensioner 45 has an outer peripheral surface 45A facing outward from the lower housing 32. The outer peripheral surface 45A has a size in the left-right direction 9 that is larger than the maximum width of the sheet S and has a shape that is symmetrical with respect to the center of the sheet feed (the center of the sheet S in the left-right direction 9). The upper end of the outer peripheral surface 45A is located in a vertical position approximately the same as the nip position of the conveyor roller group 36 in the vertical direction 7.

[0081] The sheet S pulled from the roller body 37 is hooked onto and abuts the outer peripheral surface 45A. The sheet S bends forward along the outer peripheral surface 45A, extends in the conveying direction 8A, and is guided to the conveying roller group 36. The conveying direction 8A is a forward direction along the front-to-back direction 8. The tensioner 45 applies tension to the sheet S using a known method.

[0082] The conveying roller group 36 is located in front of the tensioner 45. The conveying roller group 36 includes a conveying roller 36A and a pinch roller 36B. The conveying roller 36A and the pinch roller 36B abut against each other at approximately the same upper and lower positions as the upper end of the outer peripheral surface 45A. The conveying roller group 36 is an example of a conveying device.

[0083] The conveying roller group 40 is located in front of the conveying roller group 36. The conveying roller group 40 includes a conveying roller 40A and a pinch roller 40B. The conveying roller 40A and the pinch roller 40B abut at substantially the same upper and lower positions as the upper end of the outer peripheral surface 45A.

[0084] The conveyor rollers 36A and 40A rotate by a driving force transmitted by a motor (not shown). The conveyor roller group 36 rotates while gripping the sheet S extending from the tensioner 45 in the conveying direction 8A, thereby feeding the sheet S in the conveying direction 8A along the conveying surface 43A. The conveyor roller group 40 rotates while gripping the sheet S fed from the conveyor roller group 36, thereby feeding the sheet S in the conveying direction 8A. Furthermore, the rotation of the conveyor roller groups 36 and 40 pulls the sheet S from the sheet storage space 32C through the slit 42 and toward the tensioner 45.

[0085] like Figure 2 As shown, a conveying path 43 is formed in the internal space 31 from the upper end of the outer peripheral surface 45A to the discharge port 33. The conveying path 43 extends substantially straight along the conveying direction 8A and is a space through which the sheet S can pass. Figure 2 In FIG, the conveying surface 43A is indicated by a two-dot chain line showing the conveying path 43. The conveying path 43 is divided by a guide member (not shown) located away from the vertical direction 7, the nozzle head 38, the platen 51, and the like.

[0086] The nozzle head 38 is located on the upper side of the conveyance path 43, downstream of the conveyance roller set 36, closer to the conveyance direction 8A. The nozzle head 38 includes a frame 48 and a spray module 49 having a plurality of nozzles 38A. The spray module 49 is supported by the frame 48. The spray module 49 has an inflow port 22 and an outflow port 23. The inflow port 22 and the outflow port 23 are connected to the manifold 24, respectively. The manifold 24 is connected to the plurality of nozzles 38A (refer to Figure 3 ). The plurality of nozzles 38A spray the water-based ink supplied from the sub-ink cartridge 181 (refer to Figure 3 ) toward the sheet S supported by the conveyance belt 101 and downward. Thereby, the image is recorded on the sheet S.

[0087] The platen 51 is located on the lower side of the conveyance path 43, downstream of the conveyance roller set 36, closer to the conveyance direction 8A. The platen 51 is located on the lower side of the nozzle head 38, opposite the nozzle head 38. The platen 51 has the conveyance belt 101 and a support portion 104. The conveyance belt 101 supports the sheet S conveyed by the conveyance roller set 36 in the conveyance direction 8A and located directly below the nozzle head 38. The conveyance belt 101 conveys the sheet S supported thereby in the conveyance direction 8A.

[0088] The heater 39 is located in the lower side of the conveyance path 43, downstream of the nozzle head 38, closer to the conveyance direction 8A, and upstream of the conveyance roller set 40, closer to the conveyance direction 8A. The heater 39 heats the sheet S conveyed in the conveyance path 43. The heater 39 is an example of a heater.

[0089] The CIS 25 is located in the upper side of the conveyance path 43, downstream of the conveyance roller set 40, closer to the conveyance direction 8A. The CIS 25 reads the image of the printed surface of the sheet.

[0090] The cutter unit 26 is located in the upper side of the conveyance path 43, downstream of the CIS 25, closer to the conveyance direction 8A. The cutter unit 26 is a unit in which the cutter 28 is mounted on the cutter disc 27. The sheet S located in the conveyance path 43 is cut along the left-right direction 9 by the movement of the cutter 28.

[0091] The ink cartridge mounting portion 110 is located near the front end and the lower end of the housing 30, is a box shape open toward the front. The ink cartridge 34 is inserted into the ink cartridge mounting portion 110 rearward. The ink needle 112 extending forward is located on the rear end surface 111 of the ink cartridge mounting portion 110. The ink needle 112 communicates with the sub-ink cartridge 181 through the flow path 182 (refer to Figure 3 ).

[0092] The contact 114 is located on the end surface 111. When the ink cartridge 34 is installed in the ink cartridge installation portion 110, the contact 114 is electrically connected to the IC substrate 70 included in the ink cartridge 34. The controller 130 can access the storage area of ​​the IC substrate 70 through the contact 114. In addition, when the preservative solution cartridge 11 is installed in the ink cartridge installation portion 110, the contact 114 is electrically connected to the IC substrate 12 included in the preservative solution cartridge 11 (see Figure 3 ). The controller 130 can access the storage area of ​​the IC substrate 12 through the contact 114.

[0093] The ink cartridge 34 stores aqueous ink. When the aqueous ink is consumed, the ink cartridge 34 is removed from the ink cartridge mounting portion 110 and replaced with a new ink cartridge 34 containing aqueous ink. The IC substrate 70 is located behind the ink cartridge 34. The IC substrate 70 stores identification information for the ink cartridge 34 in a storage area.

[0094] The preservative solution cartridge 11 (second liquid cartridge) is inserted into the cartridge mounting portion 110 in place of the ink cartridge 34. The preservative solution cartridge 11 stores a preservative solution. When the image recording device 100 is not in use and is stored for an extended period, the preservative solution cartridge 11 is installed in the cartridge mounting portion 110 in place of the ink cartridge 34. The IC substrate 12 is located behind the preservative solution cartridge 11. The IC substrate 12 stores identification information indicating the preservative solution cartridge 11 in its storage area.

[0095] [Ink circuit 113]

[0096] like Figure 3 As shown, the ink cartridge installation unit 110 and the ejection module 49 of the printhead 38 are connected via an ink circuit 113. The ink circuit 113 includes a sub-cartridge 181, flow paths 182, 183, and 184, an air flow path 185, a replenishing valve 187, a purge valve 190, a positive pressure pump 191, and a liquid level sensor 192.

[0097] The sub-cartridge 181 is located above the ink cartridge mount 110 within the interior space 31 of the housing 30. Aqueous ink is stored within the interior space of the sub-cartridge 181. The interior space of the sub-cartridge 181 communicates with the ink needle 112 of the ink cartridge mount 110 via a flow path 182. When the ink cartridge 34 is installed in the ink cartridge mount 110, the ink stored in the ink cartridge 34 can flow into the sub-cartridge 181 through the flow path 182. Furthermore, when the preservative solution cartridge 11 is installed in the ink cartridge mount 110, the preservative solution stored in the preservative solution cartridge 11 can flow into the sub-cartridge 181 through the flow path 182. A replenishing valve 187 is located on the flow path 182. The replenishing valve 187 is controlled by the controller 130 to open and close the flow path 182.

[0098] The internal space of the sub-cartridge 181 is connected to the ejection module 49 via flow paths 183 and 184. Flow path 183 is connected to the inlet port 22 of the ejection module 49. Flow path 184 is connected to the outlet port 23 of the ejection module 49. The aqueous ink or preservative liquid stored in the internal space of the sub-cartridge 181 can be supplied to the ejection module 49 via flow path 183. A positive pressure pump 191 is located on flow path 183. The positive pressure pump 191 is controlled by the pump motor 138 (see FIG. 1 ) via the controller 130. Figure 4 ) is driven to operate. The cleaning stop valve 188 is located on the flow path 184. The cleaning stop valve 188 is controlled by the controller 130 to open and close the flow path 184.

[0099] A bypass flow path 186 connects the positive pressure pump 191 and the inlet port 22 on the flow path 183, and the purge shutoff valve 188 and the ink sub-cartridge 181 on the flow path 184. A bypass valve 189 is located on the bypass flow path 186. The bypass valve 189 is controlled by the controller 130 to open and close the bypass flow path 186.

[0100] The interior space of the sub-ink cartridge 181 and the outside are connected via an air flow path 185. A purge valve 190 is located on the air flow path 185. The purge valve 190 is controlled by the controller 130 to open and close the air flow path 185.

[0101] Liquid level sensor 192 is located in sub-cartridge 181. Liquid level sensor 192 detects the presence of aqueous ink at the replenishment level within the sub-cartridge 181. Liquid level sensor 192 outputs a detection signal to controller 130. Liquid level sensor 192 outputs an ON signal as a detection signal when aqueous ink is detected and an OFF signal as a detection signal when no aqueous ink is detected. Based on the detection signal output by liquid level sensor 192, controller 130 determines whether the liquid level within the sub-cartridge 181 has reached the replenishment level.

[0102] A decompression pump 193 is connected to the sub-cartridge 181. The decompression pump 193 decompresses the internal space of the sub-cartridge 181 by discharging the gas in the internal space of the sub-cartridge 181 to the outside.

[0103] like Figure 3 As shown, the cover 62 is located below each ejection module 49. Figure 3 Only one ejection module 49 is shown. The cover 62 is made of an elastic body such as rubber or silicone. The cover 62 is a box-shaped body that opens upward. The cover 62 has an outlet port 21 for discharging water-based ink or the like from the internal space 67 of the cover 62. The outlet port 21 is connected to the waste liquid tank 77 via a flow path 178. A suction pump 74 is provided on the flow path 178. The suction pump 74 is driven by a suction pump motor 58 (see FIG. 1 ). Figure 4 )drive.

[0104] [Controller 130]

[0105] like Figure 4 As shown, the controller 130 includes a CPU 131, a ROM 132, a RAM 133, an EEPROM 134, and an ASIC 135, which are connected by an internal bus 137. The ROM 132 stores programs for controlling the various operations of the CPU 131. The RAM 133 is used as a storage area for temporarily recording data and signals used by the CPU 131 when executing the programs, or as an operation area for data processing. The EEPROM 134 stores settings and flags that should be maintained even after power is turned off, the water-based ink supply time, and the number of supply and discharge times corresponding to the elapsed time. The supply and discharge times are preset, for example, so that the supply and discharge times increase in units of hours as the elapsed time increases.

[0106] The ASIC 135 is connected to the conveying motor 53, the suction pump motor 58, and the pump motors 138 and 139. Furthermore, the ASIC 135 is connected to the supply valve 187, the purge stop valve 188, and the purge valve 190. Each valve is connected to the ASIC 135 via a drive circuit for driving the valve.

[0107] ASIC 135 generates a drive signal for rotating each motor and controls each motor based on the drive signal. Each motor rotates forward or reverse according to the drive signal from ASIC 135. Controller 130 controls the drive of conveyor motor 53 to rotate carriage 35, conveyor roller 36A, and conveyor roller 40A. Controller 130 controls the drive of suction pump motor 58 to drive suction pump 74. Controller 130 controls the drive of pump motor 138 to drive positive-pressure pump 191. Controller 130 controls the drive of pump motor 139 to drive pressure-reducing pump 193.

[0108] The ASIC 35 is connected to an operation panel 44, a display unit 44A, a contact 114, a liquid level sensor 192, and a piezoelectric element (not shown). The operation panel 44 outputs an operation signal corresponding to the user's operation to the controller 130. The operation panel 44 may have, for example, a button or a touch sensor overlapping with the display. The controller 130 reads or writes to the storage area of ​​the IC substrate 70 of the ink cartridge 34 or the IC substrate 12 of the storage liquid cartridge 11 through the contact 114. The controller 130 receives a detection signal from the liquid level sensor 192. The piezoelectric element is powered by the controller 130 via a drive circuit not shown in the figure to operate. The controller 130 controls the power supply to the piezoelectric element to selectively eject ink droplets from a plurality of nozzles 38A.

[0109] [Water-based ink]

[0110] The aqueous ink is described below in detail. The aqueous ink contains water, solvent group A, a binder polymer, a thickener, a colorant, and a surfactant. The aqueous ink is an ink in which the solvent group A, the binder polymer, the thickener, the colorant, and the surfactant are dissolved or dispersed in water. The aqueous ink is a substance having a viscosity in the range of 10 to 14 mPa-s. 10 mPa-s and 14 mPa-s are included in the above range. In addition, a viscosity of less than 10 mPa-s is not included in the above range. A viscosity of more than 14 mPa-s is not included in the above range. The viscosity of the aqueous ink can be measured by, for example, a cone-plate type rotational viscometer. The aqueous ink is preferably such that, in a room at a room temperature of 25°C and a humidity of 65%, 5 g of the above aqueous ink is added to a container of 60 mm in diameter that is open upward, and the evaporation rate after heating at 100°C for 4 hours is 70% or more. The above container is placed on the heater 39, and the above container is heated by the heater 39 so that the temperature in the above container reaches 100°C.

[0111] The water is preferably ion exchange water or pure water. The weight % of the water with respect to the total amount of the ink is in the range of 35.0 to 62.0 weight %. In addition, the weight % of the water may, for example, also be the remaining portion of the other components. 35.0 weight % and 62.0 weight % are included in the above range. In addition, a weight % of less than 35.0 weight % is not included in the above range. A weight % of more than 62.0 weight % is not included in the above range.

[0112] The solvent group A is added in order to adjust the unclogging property and the drying property of the aqueous ink. The unclogging property refers to the property that it is difficult to clog the nozzle due to the aqueous ink adhering to the nozzle. The drying property refers to the ease of drying of the aqueous ink. The solvent group A is a solvent for which the result obtained by testing according to the test method described in the Chinese government published method for measuring the content of volatile organic compounds (VOCs) of an ink (standard number: GB / T 38608-2020) satisfies the prescribed condition. Specifically, the solvent group A is a solvent for which the weight change amount of the solvent over 30 minutes exceeds 0.01 g when 1.5 ± 0.1 g of the solvent is added to an aluminum foil box of 40 mm x 40 mm x 10 mm that is open upward in a room at a room temperature of 25°C and a humidity of 65% and heated at 100 ± 5°C. The above aluminum foil box is placed on the heater 39, and the above aluminum foil box is heated by the heater 39 so that the temperature in the above aluminum foil box reaches 100 ± 5°C.

[0113] As the solvent group A, for example, tripropylene glycol (TPG) (vapor pressure: 0.7 Pa), propylene glycol (PG) (vapor pressure: 10.6 Pa), 1,5-pentanediol (vapor pressure: 0.52 Pa), 1,3-propanediol (4.5 Pa), 1,2-butanediol (vapor pressure: 10.0 Pa), 1,3-butanediol (vapor pressure: 8.0 Pa), 1,4-butanediol (vapor pressure: 1.0 Pa), 3-methyl-1,5-pentanediol (MPD) (vapor pressure: 0.072 Pa) can be given. The solvent group A is a concept of a solvent including one or more (for example, two) of these solvents. The weight% of the solvent group A with respect to the total amount of the water-based ink is in the range of 25.0 to 30.0% by weight. 25.0% by weight and 30.0% by weight are included in the above range. The reason why the solvent group A is limited to 30.0% by weight or less is to satisfy the VOC limit standard. In addition, the weight% of less than 25.0% by weight is not included in the above range. The weight% of more than 30.0% by weight is not included in the above range.

[0114] The binder polymer is a polymer that forms a film on the sheet S when the water-based ink is dried. As the binder polymer, for example, an acrylic resin, a maleate resin, a vinyl acetate resin, a carbonate resin, a polycarbonate resin, a styrene resin, an ethylene resin, a polyethylene resin, a propylene resin, a polypropylene resin, a urethane resin, a polyurethane resin, a polyester resin, and a copolymer resin thereof, and the like can be given, and an acrylic resin is preferable. In the present embodiment, the binder polymer is an acrylic polymer containing acrylic acid as a monomer.

[0115] The acrylic polymer can be obtained from, for example, a low-viscosity binder polymer dispersion liquid (manufactured by Japan Coating Resin Co., Ltd., Mowinyl 6969D) or a high-viscosity binder polymer dispersion liquid (Mowinyl 6775, Mowinyl 6960, Mowinyl 6899D, RA-071B1, RA-071B2 manufactured by Japan Coating Resin Co., Ltd.). The low-viscosity binder polymer dispersion liquid is a substance having a viscosity of 10 mPa-s or more and less than 100 mPa-s when the acrylic polymer is added to a low-viscosity binder polymer dispersion medium so that the acrylic polymer becomes 38.0% by weight in the low-viscosity binder polymer dispersion liquid. In addition, hereinafter, for convenience, the acrylic polymer added to the low-viscosity binder polymer dispersion medium is sometimes referred to as a low-viscosity acrylic polymer. The weight% of the low-viscosity acrylic polymer with respect to the total amount of the water-based ink is preferably 5.0% by weight or less. More preferably, the weight% of the low-viscosity acrylic polymer with respect to the total amount of the water-based ink is 3.0% by weight or less.

[0116] The high-viscosity adhesive polymer dispersion liquid is a substance whose viscosity at 25°C is 100 mPa-s or more and less than 5000 mPa-s when an acrylic polymer is added to a high-viscosity adhesive polymer dispersion medium so as to be 38.0% by mass. Preferably, the viscosity of the high-viscosity adhesive polymer dispersion liquid is in the range of 2000 to 5000 mPa-s. 2000 mPa-s and 5000 mPa-s are included in the above range. In addition, a viscosity of less than 2000 mPa-s is included in the above range. A viscosity of more than 5000 mPa-s is not included in the above range. In addition, the acrylic polymer added to the high-viscosity adhesive polymer dispersion medium is sometimes referred to as a high-viscosity acrylic polymer for convenience below. The high-viscosity acrylic polymer is the same as the low-viscosity acrylic polymer. The high-viscosity acrylic polymer also has the function of a thickening agent described later. A low-viscosity acrylic polymer is used in the present embodiment.

[0117] The thickening agent is added in order to increase the viscosity of the water-based ink. The thickening agent refers to a liquid whose viscosity is 44 mPa-s or more when mixed at 80.0% by mass in water. The thickening agent includes the high-viscosity adhesive polymer dispersion liquid and the solvent group B. The high-viscosity adhesive polymer dispersion liquid also has the function of an adhesive polymer because it contains an acrylic polymer. On the other hand, the low-viscosity acrylic polymer dispersion liquid does not function as a thickening agent.

[0118] The solvent group B is a solvent whose result obtained by testing according to the test method described in the Chinese government published method for determination of volatile organic compounds (VOCs) content of inks (standard number: GB / T 38608-2020) satisfies the prescribed condition. Specifically, the solvent group B is a solvent whose weight change amount of the solvent is 0.01 g or less within 30 minutes when 1.5 ± 0.1 g of the solvent is added to an upwardly open 40 mm x 40 mm x 10 mm aluminum foil box in a room at room temperature 25°C, humidity 65%, and heated at 100 ± 5°C. In other words, the solvent group B is more difficult to evaporate than the solvent group A. The heating is performed by placing the above aluminum foil box on the heater 39 and heating the above aluminum foil box with the heater 39 so that the temperature in the above aluminum foil box reaches 100 ± 5°C. As the solvent group B, for example, glycerin (vapor pressure: 0.01 Pa), diglycerin (vapor pressure: less than 0.01 Pa) can be cited. The solvent group B is a concept of a solvent containing one or more (for example, one or two) of these solvents. The weight % of the thickening agent with respect to the total amount of the water-based ink is 10.1% by mass or more. The weight % of the thickening agent with respect to the total amount of the water-based ink is preferably 28.0% by mass or less. The weight % of the solvent group B with respect to the total amount of the water-based ink is preferably 25.0% by mass or less. It is more preferable that the weight % of the solvent group B with respect to the total amount of the water-based ink be 5.0% by mass or less.

[0119] The color material is, for example, a pigment capable of being dispersed in water by a pigment dispersing resin (resin dispersant). As the color material, for example, carbon black, inorganic pigments, and organic pigments, and the like can be given. As the carbon black, for example, furnace black, lamp black, acetylene black, channel black, and the like can be given. As the inorganic pigments, for example, titanium oxide, iron oxide-based inorganic pigments, carbon black-based inorganic pigments, and the like can be given. As the organic pigments, for example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, and the like; polycyclic pigments such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, and the like; dye lake pigments such as basic dye-based lake pigments, acid dye-based lake pigments, and the like; nitro pigments; nitroso pigments; aniline black daylight fluorescent pigments; and the like can be given. The resin dispersant can be, for example, a general-purpose high-molecular dispersant (pigment dispersing resin), and can also be adjusted as desired.

[0120] The weight % of the color material in the total amount of the water-based ink is not particularly limited, and can be appropriately determined in accordance with the desired optical density or chroma, and the like. The weight % of the color material is, for example, preferably in the range of 0.1% by weight or more and 20.0% by weight or less, and more preferably in the range of 1.0% by weight or more and 15.0% by weight or less. The weight % of the color material is the weight of the pigment alone, and does not include the weight of the binder polymer. The color material can be used alone in one kind, or two or more kinds can be used in combination.

[0121] The surfactant can also contain a cationic surfactant, an anionic surfactant, or a nonionic surfactant. These surfactants can be, for example, commercially available products. As commercially available products, for example, "OLFINE (registered trademark) E1010", "OLFINE (registered trademark) E1006", "OLFINE (registered trademark) E1004", "SILFACE SAG503A", and "SILFACE SAG002" manufactured by Nippon Shokubai Co., Ltd., and the like can be given. The weight % of the surfactant in the total amount of the water-based ink is, for example, 5.0% by weight or less, 3.0% by weight or less, or 0.1% by weight to 2.0% by weight.

[0122] The water-based ink can also contain, as necessary, additives conventionally known. As the additives, for example, pH adjustors, viscosity adjustors, surface tension adjustors, preservatives, antifungal agents, leveling agents, defoaming agents, light stabilizers, antioxidants, nozzle drying preventing agents, polymer components such as emulsions, dyes, and the like can be given. The viscosity adjustor can be, for example, polyvinyl alcohol, cellulose, water-soluble resins, and the like.

[0123] The aqueous ink can be prepared, for example, by uniformly mixing water, solvent group A, a binder polymer, a thickener, a colorant, a surfactant, and other additives as needed, and removing insoluble matter using a filter or the like.

[0124] A printing method will be described below in which the controller 130 performs a process (image recording process) for recording an image on a sheet S using the image recording apparatus 100 .

[0125] [Image recording processing]

[0126] When the controller 130 receives an instruction to record an image on the sheet S from the outside, such as the operation panel 44 or an information processing device connected to the image recording apparatus 100 via a LAN, the controller 130 performs the image recording process. Specifically, the controller 130 drives the bracket 35, the conveying roller 36A, and the conveying roller 40A by driving the conveying motor 53. As a result, the sheet S is pulled out from the roller body 37 and conveyed in the conveying direction 8A. When the sheet S reaches directly below the nozzle 38, the controller 130 causes the aqueous ink to be ejected from the nozzle 38A (an example of the first step). As a result, the image is recorded on the sheet S. The aqueous ink attached to the sheet S is heated when passing through the heater 39, thereby drying (an example of the second step). As a result, a film is formed by the adhesive polymer, and the aqueous ink is fixed on the sheet S. The sheet S that has passed through the heater 39 is further conveyed along the conveying direction 8A by the conveying roller group 40. The sheet S, which is conveyed in the conveying direction 8A by the conveying roller group 40, is cut into a predetermined size by the cutter unit 26 and discharged after the recorded image is inspected by the CIS 25. After the sheet S is cut, the controller 130 reverses the conveying motor 53 to return the leading end of the sheet S to the position of the conveying roller group 36. The controller 130 repeats the above process until the image to be recorded is recorded on the sheet S.

[0127] [Purification treatment]

[0128] On the other hand, during the image recording process, the controller 130 performs the cleaning process (an example of the third step) at regular intervals (for example, when images have been recorded on 100 sheets S). Figure 3 As shown, with the cap 62 covering the nozzle face 50, the controller 130 opens the purge shutoff valve 188 and bypass valve 189, and closes the replenishment valve 187 and the vent valve 190. The controller 130 then drives the suction pump motor 58 to drive the suction pump 74. This draws the aqueous ink from the nozzle 38A and discharges it from the internal space 67 of the cap 62 through the discharge port 21 and the flow path 178 into the waste liquid tank 77.

[0129] [Effects of the Implementation]

[0130] In the above water-based ink, the weight % of the solvent group A with respect to the total amount of the water-based ink is 30.0 wt% or less, and thus the water-based ink does not conflict with the VOC limit standard. The weight % of the solvent group A with respect to the total amount of the water-based ink is 25.0 wt% or more, and thus the weight % of water, which evaporates easily compared to the solvent group A, is small. Thus, the case where the water-based ink adhering to the nozzle 38A dries quickly is suppressed, and thus the water-based ink is difficult to solidify. Thus, the case where clogging occurs on the nozzle 38A due to the solidified water-based ink is suppressed. That is, the openability is ensured. Since the viscosity of the water-based ink is adjusted to 10 mPa s or more by the thickening agent, the image formed by the water-based ink is difficult to become unsharp. Thus, the stretchability is ensured. Since the viscosity of the water-based ink is adjusted to 14 mPa s or less by the thickening agent, the case where the water-based ink is difficult to be ejected from the nozzle 38A is suppressed. Thus, the ejection property of the water-based ink is ensured.

[0131] In the above water-based ink, the weight % of the solvent group B, which evaporates more difficultly than the solvent group A, is limited to 25.0 wt% or less, and thus the drying property of the water-based ink is high.

[0132] In the above water-based ink, the weight % of the solvent group B with respect to the total amount of the water-based ink is limited to 5.0 wt% or less, and thus the drying property of the water-based ink is high.

[0133] In the above water-based ink, since the binder polymer is a low viscosity acrylic polymer having a viscosity of 10 mPa s or more and less than 100 mPa s when added to the low viscosity binder polymer dispersion medium to be 38.0 wt% in the low viscosity binder polymer dispersion liquid, the film formed by the binder polymer has high scratch resistance.

[0134] In the above water-based ink, the weight % of the low viscosity acrylic polymer with respect to the total amount of the water-based ink is 5.0 wt% or less, and thus the case where the low viscosity acrylic polymer is filmized in the nozzle face 50 or the nozzle 38A when the water-based ink dries is suppressed. Thus, the ejection failure of the water-based ink is suppressed.

[0135] In the above water-based ink, the weight % of the low viscosity acrylic polymer with respect to the total amount of the water-based ink is 3.0 wt% or less, and thus the case where the low viscosity acrylic polymer is filmized in the nozzle face 50 or the nozzle 38A when the water-based ink dries is suppressed. Thus, the ejection failure of the water-based ink is further suppressed.

[0136] In the above water-based ink, since the binder polymer is an acrylic polymer, the film formed by the binder polymer has high scratch resistance and stability.

[0137] Since the above water-based ink is such that the evaporation rate is 70% or more when 5 g of the above water-based ink is put in a container of 60 mm in diameter open upward in a room at room temperature of 25°C and humidity of 65% and heated at 100°C for 4 hours, the drying property is high.

[0138] In the image recording apparatus 100 and the printing method, the water-based ink attached to the sheet S is heated when passing through the heater 39, so the water-based ink attached to the sheet S easily dries.

[0139] In the image recording apparatus 100 and the printing method, since the heating temperature of the heater is 60°C or more, the water-based ink attached to the sheet S easily dries.

[0140] In the image recording apparatus 100 and the printing method, the viscosity of the water-based ink is 10 mPa s or more. Therefore, even if the distance between the nozzle 38 and the sheet S in the up-and-down direction 7 is enlarged, the water-based ink is difficult to spread on the sheet S when the water-based ink is ejected downward from the nozzle 38A, so the image formed by the water-based ink is difficult to become unsharp. Therefore, by enlarging the distance between the nozzle 38 and the sheet S in the up-and-down direction 7, the size restriction of the printed object is easily relaxed.

[0141] In the image recording apparatus 100 and the printing method, the purging process of driving the suction pump 74 is periodically performed in the state where the cover 62 covers the nozzle 38A at the time of the image recording process, so the nozzle 38A is difficult to be clogged by foreign matter.

[0142] In the image recording apparatus 100 and the printing method, the sheet S is conveyed to the position opposite to the nozzle 38 in the up-and-down direction 7 by the conveyance roller group 36, so the image is properly recorded on the sheet S.

[0143] [Modified Example]

[0144] In the above water-based ink, an acrylic polymer having a viscosity of 10 mPa s or more and less than 100 mPa s when added to a low-viscosity adhesive polymer dispersion medium to reach 38.0% by weight in a low-viscosity adhesive polymer dispersion liquid is used, but an acrylic polymer having a viscosity of 100 to 5000 mPa s when added to a high-viscosity adhesive polymer dispersion medium to reach 38.0% by weight in a high-viscosity adhesive polymer dispersion liquid can also be used. In this way, the scratch resistance of the film formed by the adhesive polymer is higher.

[0145] In the image recording apparatus 100 and the printing method, the water-based ink is ejected downward from the nozzle 38A, but can also be ejected horizontally from the nozzle 38A. In this case, the head 38 is disposed so that the nozzle face 50 becomes a direction orthogonal to the horizontal direction. Even if the water-based ink is ejected horizontally from the nozzle 38A, since the viscosity of the water-based ink is as high as 10 mPa-s or more, it is difficult for the water-based ink adhering to the sheet S to generate droplets.

[0146] In the image recording apparatus 100, the sheet S is a non-absorbing medium having a low water-absorbing surface, but can also be an absorbing medium having a high water-absorbing surface. As the absorbing medium, for example, ordinary paper, glossy paper, matte paper, and the like can be cited.

[0147] In the image recording apparatus 100, the cleaning processing is periodically performed at the time of the image recording processing, but can also not be performed.

[0148] In the image recording apparatus 100, the ink cartridge 34 is different from the liquid holding cartridge 11, and is replaced at the ink cartridge mounting portion 110, but the ink cartridge 34 and the liquid holding cartridge 11 can also be integrated and mounted at the ink cartridge mounting portion 110.

[0149] Embodiment

[0150] An embodiment of the present application is shown below.

[0151] (Embodiment 1)

[0152] As the water-based ink, a water-based ink liquid containing 39.1% by weight of pure water as water, 3.7% by weight of carbon black as a color material, 3.0% by weight of tripropylene glycol and 25.0% by weight of propylene glycol as a solvent group A, 5.0% by weight of a low viscosity acrylic polymer as a binder polymer, 21.5% by weight of glycerin as a solvent group B, 1.4% by weight of Olefin (registered trademark) E1004 (manufactured by Nippon Shokubai Co., Ltd.) as a surfactant, and 1.2% by weight of a pigment dispersant as another additive was used. The viscosity of the water-based ink was 12.7 mPa-s at 25°C. The low viscosity acrylic polymer was obtained from a low viscosity acrylic polymer dispersion liquid (manufactured by Nippon Paint Resin Co., Ltd., Mowinyl 6969D).

[0153] (Embodiment 2)

[0154] The composition was set to be the same as in Example 1 except that 53.8% by weight of pure water was used as water, 4.5% by weight of high viscosity acrylic polymer was used as a binder polymer, 11.9% by weight of high viscosity binder polymer dispersion liquid (Mowinyl 6775 by Nippon Paint Resin Co., Ltd.) was used as a thickening agent, and solvent group B was omitted. The viscosity of the water-based ink was 11.6 mPa-s at 25°C. In addition, the % by weight of the high viscosity binder polymer dispersion liquid was a value obtained by adding 4.5% by weight of the high viscosity acrylic polymer and 7.4% by weight of the high viscosity acrylic polymer dispersion medium. In Table 1, the % by weight of the high viscosity acrylic polymer dispersion medium is shown in order to easily understand that the total is 100% by weight.

[0155] (Example 3)

[0156] The composition was set to be the same as in Example 1 except that 51.2% by weight of pure water was used as water and 9.5% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 11.1 mPa-s at 25°C.

[0157] (Example 4)

[0158] The composition was set to be the same as in Example 1 except that 40.6% by weight of pure water was used as water and 20.0% by weight of diglycerin was used as solvent group B. The viscosity of the water-based ink was 14.0 mPa-s at 25°C.

[0159] (Example 5)

[0160] The composition was set to be the same as in Example 1 except that 44.4% by weight of pure water was used as water, 30.0% by weight of propylene glycol was used as solvent group A, and 14.3% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 13.6 mPa-s at 25°C.

[0161] (Example 6)

[0162] The composition was set to be the same as in Example 1 except that 36.6% by weight of pure water was used as water, 30.0% by weight of propylene glycol was used as solvent group A, and 22.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 13.7 mPa-s at 25°C.

[0163] (Example 7)

[0164] The composition was set to be the same as in Example 1 except that 49.5% by weight of pure water was used as water, 30.0% by weight of 1,5-pentanediol was used as solvent group A, and 9.1% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 13.2 mPa-s at 25°C.

[0165] (Example 8)

[0166] The composition was set to be the same as Example 1 except that 43.4% by weight of pure water was used as water, 25.0% by weight of tripropylene glycol was used as solvent group A, and 20.3% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 13.4 mPa-s at 25°C.

[0167] (Example 9)

[0168] The composition was set to be the same as Example 1 except that 39.9% by weight of pure water was used as water, 25.0% by weight of propylene glycol was used as solvent group A, and 23.7% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 11.5 mPa-s at 25°C.

[0169] (Example 10)

[0170] The composition was set to be the same as Example 1 except that 41.6% by weight of pure water was used as water, 25.0% by weight of 1,5-pentanediol was used as solvent group A, and 22.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 12.3 mPa-s at 25°C.

[0171] (Example 11)

[0172] The composition was set to be the same as Example 1 except that 38.6% by weight of pure water was used as water, 5.0% by weight of polyethylene was used as binder polymer, 28.0% by weight of propylene glycol was used as solvent group A, and 22.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 11.1 mPa-s at 25°C.

[0173] (Example 12)

[0174] The composition was set to be the same as Example 1 except that 36.6% by weight of pure water was used as water, 30.0% by weight of 1,3-propanediol was used as solvent group A, and 22.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 12.2 mPa-s at 25°C.

[0175] (Example 13)

[0176] The composition was set to be the same as Example 1 except that 43.6% by weight of pure water was used as water, 25.0% by weight of 1,2-butanediol was used as solvent group A, and 20.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 10.6 mPa-s at 25°C.

[0177] (Example 14)

[0178] The composition was set to be the same as in Example 1 except that 45.6% by weight of pure water was used as water, 25.0% by weight of 1,3-butanediol was used as solvent group A, and 18.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 10.0 mPa-s at 25°C.

[0179] (Example 15)

[0180] The composition was set to be the same as in Example 1 except that 43.6% by weight of pure water was used as water, 25.0% by weight of 1,4-butanediol was used as solvent group A, and 20.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 10.1 mPa-s at 25°C.

[0181] (Example 16)

[0182] The composition was set to be the same as in Example 1 except that 46.6% by weight of pure water was used as water, 25.0% by weight of 3-methyl-1,5-pentanediol was used as solvent group A, and 17.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 10.1 mPa-s at 25°C.

[0183] (Example 17)

[0184] The composition was set to be the same as in Example 1 except that 55.6% by weight of pure water was contained as water, 3.8% by weight of a high-viscosity acrylic polymer was contained as a binder polymer, 10.1% by weight of a high-viscosity binder polymer dispersion liquid was contained as a thickening agent, and solvent group B was omitted. The viscosity of the water-based ink was 10.1 mPa-s at 25°C. The % by weight of the high-viscosity binder polymer dispersion liquid is a value obtained by adding 3.8% by weight of the high-viscosity acrylic polymer and 6.3% by weight of a high-viscosity acrylic polymer dispersion medium.

[0185] (Example 18)

[0186] The composition was set to be the same as in Example 1 except that 36.3% by weight of pure water was used as water, 25.0% by weight of propylene glycol was used as solvent group A, and 27.3% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 14.0 mPa-s at 25°C.

[0187] (Example 19)

[0188] The composition was set to be the same as in Example 1 except that 37.4% by weight of pure water was used as water and 23.2% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 13.9 mPa-s at 25°C.

[0189] (Example 20)

[0190] The composition was set to be the same as in Example 1 except that 44.2% by weight of pure water was used as water, 24.0% by weight of tripropylene glycol was used as solvent group A, and 20.4% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 12.8 mPa-s at 25°C.

[0191] (Example 21)

[0192] The composition was set to be the same as in Example 1 except that 51.5% by weight of pure water was used as water, 3.0% by weight of a low-viscosity acrylic polymer was used as a binder polymer, 30.0% by weight of 1,5-pentanediol was used as solvent group A, and 9.1% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 11.5 mPa-s at 25°C.

[0193] (Example 22)

[0194] The composition was set to be the same as in Example 1 except that 50.2% by weight of pure water was used as water, 6.0% by weight of a low-viscosity acrylic polymer was used as a binder polymer, and 9.5% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 12.1 mPa-s at 25°C.

[0195] (Example 23)

[0196] The composition was set to be the same as in Example 1 except that 41.6% by weight of pure water was used as water, 5.0% by weight of a polyurethane was used as a binder polymer, 25.0% by weight of propylene glycol was used as solvent group A, and 22.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 11.1 mPa-s at 25°C.

[0197] (Example 24)

[0198] The composition was set to be the same as in Example 1 except that 42.6% by weight of pure water was used as water, 5.0% by weight of a polyurethane was used as a binder polymer, 25.0% by weight of propylene glycol was used as solvent group A, 20.0% by weight of glycerin and 1.0% by weight of diglycerin were used as solvent group B. The viscosity of the water-based ink was 11.0 mPa-s at 25°C.

[0199] (Comparative Example 1)

[0200] The composition was set to be the same as in Example 1 except that 36.6% by weight of pure water was used as water and 24.1% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 14.6 mPa-s at 25°C.

[0201] (Comparative Example 2)

[0202] The composition was set to be the same as Comparative Example 1 except that 39.1% by weight of pure water was used as water and 21.5% by weight of diglycerol was used as solvent group B. The viscosity of the water-based ink was 15.4 mPa-s at 25°C.

[0203] (Comparative Example 3)

[0204] The composition was set to be the same as Comparative Example 1 except that 39.1% by weight of pure water was used as water, 24.0% by weight of propylene glycol was used as solvent group A, and 25.6% by weight of glycerol was used as solvent group B. The viscosity of the water-based ink was 12.3 mPa-s at 25°C.

[0205] (Comparative Example 4)

[0206] The composition was set to be the same as Comparative Example 1 except that 52.0% by weight of pure water was used as water, 2.5% by weight of a low-viscosity acrylic polymer and 2.6% by weight of a high-viscosity acrylic polymer were used as binder polymers, 6.9% by weight of a high-viscosity binder polymer dispersion liquid was used as a thickening agent, and 4.3% by weight of glycerol was used as solvent group B. The viscosity of the water-based ink was 12.0 mPa-s at 25°C. The % by weight of the high-viscosity binder polymer dispersion liquid is a value obtained by adding 2.6% by weight of the high-viscosity acrylic polymer and 4.3% by weight of a high-viscosity acrylic polymer dispersion medium.

[0207] (Comparative Example 5)

[0208] The composition was set to be the same as Comparative Example 1 except that 39.1% by weight of pure water was contained as water and 3.0% by weight of tripropylene glycol, 25.0% by weight of propylene glycol, and 21.5% by weight of 1,5-pentanediol were contained as solvent group A, and solvent group B was omitted. The viscosity of the water-based ink was 13.2 mPa-s at 25°C.

[0209] (Comparative Example 6)

[0210] The composition was set to be the same as Comparative Example 1 except that 37.6% by weight of pure water was contained as water and 48.0% by weight of propylene glycol was contained as solvent group A, and solvent group B was omitted. The viscosity of the water-based ink was 12.2 mPa-s at 25°C.

[0211] (Comparative Example 7)

[0212] The composition was set to be the same as Comparative Example 1 except that 40.6% by weight of pure water was contained as water and 45.0% by weight of propylene glycol was contained as solvent group A, and solvent group B was omitted. The viscosity of the water-based ink was 10.8 mPa-s at 25°C.

[0213] (Comparative Example 8)

[0214] The composition was set to be the same as that of Comparative Example 1 except that 45.8% by weight of pure water was used as water, 31.0% by weight of tripropylene glycol was used as solvent group A, and 11.8% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 12.7 mPa-s at 25°C.

[0215] (Comparative Example 9)

[0216] The composition was set to be the same as that of Comparative Example 1 except that 38.1% by weight of pure water was used as water, 31.0% by weight of propylene glycol was used as solvent group A, and 19.6% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 12.6 mPa-s at 25°C.

[0217] (Comparative Example 10)

[0218] The composition was set to be the same as that of Comparative Example 1 except that 54.6% by weight of pure water was used as water, 25.0% by weight of propylene glycol was used as solvent group A, and 9.0% by weight of glycerin was used as solvent group B. The viscosity of the water-based ink was 9.5 mPa-s at 25°C.

[0219] [Uncovering test]

[0220] After the nozzle face 50 was left uncovered by the cover 62, the water-based ink ejected from the nozzle 38A was visually judged as to whether it could be printed on the sheet S or not after the printhead 38 was left for 30 minutes. As the sheet S, a resin film formed of a non-absorbing medium, such as polypropylene, was used.

[0221] A: No missing needles and misalignments were at all visible

[0222] B: A few missing needles and misalignments were visible

[0223] C: Missing needles and misalignments were visible

[0224] D: Many missing needles and misalignments were visible

[0225] [Coarseness test]

[0226] The water-based ink was ejected from the nozzle 38A to record an image on the sheet S, and the image quality was visually judged in accordance with the following evaluation criteria. As the sheet S, a resin film formed of a non-absorbing medium, such as polypropylene, was used.

[0227] A: The image was clear

[0228] B: Some of the image was blurred

[0229] C: The entire image was blurred

[0230] [1st ejection test]

[0231] The water-based ink was ejected from the nozzle 38A to record an image on 100 sheets S, and the quality of the image was visually judged according to the following evaluation criteria. As the sheets S, a resin film formed of a non-absorbing medium such as polypropylene was used.

[0232] A: No missing nozzles and misregistration were observed at all

[0233] B: A few missing nozzles and misregistration were observed

[0234] C: Many missing nozzles and misregistration were observed

[0235] [Drying test]

[0236] After the water-based ink was ejected from the nozzle 38A to adhere to the sheets S at a resolution of 600 x 600 dpi and a droplet volume of about 17 pL, and the sheets S were heated at about 60°C for 10 minutes with an infrared heater, visual judgment was made according to the following evaluation criteria. As the sheets S, a resin film formed of a non-absorbing medium such as polypropylene was used.

[0237] A: The coating film was not disturbed when rubbed with a finger

[0238] B: The coating film did not feel sticky when touched with a finger

[0239] C: The coating film felt sticky when touched with a finger

[0240] D: The coating film was disturbed when touched with a finger

[0241] [Scrubbability test]

[0242] After the water-based ink was ejected from the nozzle 38A to adhere to the sheets S, the water-based ink was heated at a temperature of 60°C for 10 minutes with the heater 39, thereby forming a film formed of a binder polymer on the sheets S. The film was wiped with a cotton swab, and visual judgment was made according to the following evaluation criteria.

[0243] A: No peeling of the film occurred at all

[0244] B: The film was slightly peeled

[0245] C: The film was peeled

[0246] [2nd ejection test]

[0247] After the water-based ink was ejected from the nozzle 38A, the head 38 was left for 30 minutes in a state where the nozzle face 50 was not covered with the cover 62, and then the water-based ink was ejected from the nozzle 38A to record an image on the sheets S, and the quality of the image was visually judged according to the following evaluation criteria.

[0248] A: No missing nozzles and misregistration were observed at all

[0249] B: Several needle missing and offset can be seen

[0250] C: Needle missing and offset can be seen

[0251] D: Many needle missing and offset can be seen

[0252] [Decap test results]

[0253] As shown in Tables 1 to 6, the decap property of Examples 2, 17 and above is evaluated as C, and the decap property of Examples 2, 17 and below is evaluated as D, and it is found that the decap property of Examples 2, 17 and below is excellent. The weight % of solvent group A in Examples 2, 17 and the weight % of solvent group A in Examples 2, 17 and below are approximately the same, but in Examples 2, 17, since solvent group B which is more difficult to evaporate than solvent group A is not contained, it is considered that the decap property is deteriorated. On the other hand, in Examples 2, 17 and below, since solvent group B which is more difficult to evaporate than solvent group A is contained, it is considered that the decap property can be ensured.

[0254] In addition, the decap property of Examples 1, 4 to 6, 8 to 16, 18 to 20, 23, and 24 and above is evaluated as B, and the decap property of Examples 3, 7, 21, and 22 and below is evaluated as C, and it is found that the decap property of Examples 1, 4 to 6, 8 to 16, 18 to 20, 23, and 24 is excellent. In Examples 1, 4 to 6, 8 to 16, 18 to 20, and 23, since solvent group B which is more difficult to evaporate than solvent group A is contained in an amount of 10.0 wt% or more, it is considered that the decap property can be further ensured. On the other hand, in Examples 3, 7, 21, and 22, solvent group B which is more difficult to evaporate than solvent group A is less than 10.0 wt%, and thus it is considered that the weight % of pure water which is more easily evaporated than solvent group A becomes large.

[0255] [Coarseness test results]

[0256] As shown in Tables 1 to 6, the coarseness of Examples 1 to 24 and above is evaluated as B, and the coarseness of Comparative Example 10 and below is evaluated as C, and it is found that the coarseness of Examples 1 to 24 is excellent. In Examples 1 to 23, since the viscosity of the water-based ink is as high as 10.0 mPa-s or more, it is considered that a substantially clear image is obtained. On the other hand, in Comparative Example 10, since the viscosity of the water-based ink is as low as 9.5 mPa-s, it is considered that the image as a whole is blurred.

[0257] [1st ejection test results]

[0258] As shown in Tables 1 to 6, the first ejection property of Examples 1 to 24 was evaluated as A or B, and the first ejection property of Comparative Examples 1 and 2 was evaluated as C, and it was found that the first ejection property of Examples 1 to 24 was excellent. In Examples 1 to 23, the viscosity of the water-based ink was as low as 14.0 mPa-s or less, and it was considered that the water-based ink was smoothly ejected from the nozzle 38A. On the other hand, in Comparative Examples 1 and 2, the viscosity of the water-based ink was more than 14.0 mPa-s, and it was considered that the water-based ink was not smoothly ejected from the nozzle 38A, and a prescribed amount of the water-based ink was not adhered to the sheet S.

[0259] [Results of the drying property test]

[0260] As shown in Tables 1 to 6, the drying property of Examples other than Example 18 was evaluated as A or B, and the drying property of Example 18 and Comparative Example 3 was evaluated as C, and it was found that the drying property of Examples other than Example 18 was excellent. In Examples other than Example 18, it was considered that the weight % of the solvent group B which was more difficult to evaporate than the solvent group A was limited to 25.0 wt% or less. On the other hand, in Example 18 and Comparative Example 3, it was considered that the weight % of the solvent group B which was more difficult to evaporate than the solvent group A was more than 25.0 wt%.

[0261] In addition, the drying property of Examples 2, 7, 17, 21, and 22 was evaluated as A or B, and the drying property of Examples 1, 4 to 6, 8 to 16, 18 to 20, 23, and 24 was evaluated as C or D, and it was found that the drying property of Examples 2, 7, 17, 21, and 22 was excellent. In Examples 2, 7, 17, 21, and 22, it was considered that the weight % of the solvent group B which was more difficult to evaporate than the solvent group A was limited to 10.0 wt% or less. On the other hand, in Examples 1, 4 to 6, 8 to 16, 18 to 20, and 23, it was considered that the weight % of the solvent group B which was more difficult to evaporate than the solvent group A was more than 10.0 wt%.

[0262] In addition, Examples 2, 17, and Comparative Example 4 were evaluated as A. In Examples 2, 17, and Comparative Example 4, it was considered that the weight % of the solvent group B which was more difficult to evaporate than the solvent group A was limited to 5.0 wt% or less.

[0263] [Resistance to abrasion test]

[0264] As shown in Tables 1 to 6, the resistance to abrasion of Examples 2 and 17 was evaluated as A, and the resistance to abrasion of Examples other than Examples 2 and 17 was evaluated as B, and it was found that the resistance to abrasion of Examples 2 and 17 was excellent. In Examples 2 and 17, a high viscosity acrylic polymer was used as the binder polymer, and in contrast, in Examples other than Examples 2 and 17, it was considered that a low viscosity acrylic polymer was used as the binder polymer.

[0265] [Second ejection property test]

[0266] As shown in Tables 1 to 6, the 2nd ejection of the examples other than Example 22 was excellent, which was evaluated as B or more, relative to Example 22 which was evaluated as C. In the examples other than Example 22, the weight % of the binder polymer was limited to 5.0% or less, and thus it is considered that the film formation caused by the binder polymer in the nozzle face 50 or the nozzle 38A was suppressed when the water-based ink was dried. On the other hand, the weight % of the binder polymer in Example 22 exceeded 5.0%, and thus it is considered that the film formation caused by the binder polymer in the nozzle face 50 or the nozzle 38A was easily caused when the water-based ink was dried.

[0267] In addition, Example 21 was evaluated as A. In Example 21, the weight % of the binder polymer was limited to 3.0% or less, and thus it is considered that the film formation caused by the binder polymer in the nozzle face 50 or the nozzle 38A was further suppressed when the water-based ink was dried.

[0268] [Table 1]

[0269]

[0270] [Table 2]

[0271]

[0272] [Table 3]

[0273]

[0274] [Table 4]

[0275]

[0276] [Table 5]

[0277]

[0278] [Table 6]

[0279]

Claims

1. A water-based ink, characterized in that: contain: water, When 1.5±0.1g of solvent group A is placed in a 40mm×40mm×10mm aluminum foil box with an upward opening at a room temperature of 25℃ and a humidity of 65%, and heated at a temperature of 100±5℃ for 30 minutes, the weight change exceeds 0.01g. thickener, and Binder polymers, The weight percentage of the solvent group A relative to the total weight of the aqueous ink is 25.0-30.0% by weight. The weight percentage of the thickener relative to the total weight of the aqueous ink is 10.1 weight % or more, The viscosity of the water-based ink is 10-14 mPa·s.

2. The water-based ink according to claim 1, wherein The thickener contains a solvent group B, wherein the solvent group B is a substance whose weight change is 0.01 g or less when 1.5 ± 0.1 g of the solvent is placed in a 40 mm × 40 mm × 10 mm aluminum foil box open upward and heated at 100 ± 5 ° C for 30 minutes in a room at room temperature of 25 ° C and humidity of 65%. The weight percentage of the solvent group B relative to the total weight of the aqueous ink is 25.0 weight % or less.

3. The water-based ink according to claim 2, wherein: The weight percentage of the solvent group B relative to the total weight of the aqueous ink is 5.0 weight % or less.

4. The water-based ink according to claim 1, wherein The binder polymer has a viscosity of 10 mPa·s or more and less than 100 mPa·s when added to a low-viscosity binder polymer dispersion medium so as to provide 38.0 wt % in the low-viscosity binder polymer dispersion. 5 . The water-based ink according to claim 4 , wherein the weight % of the binder polymer relative to the total weight of the water-based ink is 5.0 weight % or less.

6. The water-based ink according to claim 5, wherein The weight % of the binder polymer relative to the total weight of the aqueous ink is 3.0 weight % or less.

7. The water-based ink according to claim 6, wherein The binder polymer is an acrylic polymer.

8. The aqueous ink according to claim 1, wherein the thickener comprises a high-viscosity binder polymer dispersion in which the binder polymer is dispersed. The high-viscosity binder polymer dispersion has a viscosity of 100 mPa·s or more and less than 5000 mPa·s when added to a high-viscosity binder polymer dispersion medium so that the binder polymer in the high-viscosity binder polymer dispersion is 38.0 wt %.

9. The water-based ink according to claim 1, wherein The weight percentage of the thickener relative to the total weight of the aqueous ink is 28.0 weight % or less.

10. The water-based ink according to claim 3, wherein: 5 g of the aqueous ink was placed in a container with a diameter of 60 mm and open upward in a room at a room temperature of 25° C. and a humidity of 65%. After heating at 100° C. for 4 hours, the evaporation rate was 70% or more.

11. An ink ejection device, characterized in that: Equipped with nozzle and heater, The nozzle has a nozzle for ejecting the aqueous ink according to any one of claims 1 to 10. The heater heats at least one of the non-absorbing medium to which the aqueous ink ejected from the nozzle adheres and the aqueous ink adhered to the non-absorbing medium.

12. The ink ejection device according to claim 11, wherein: The heating temperature of the heater is 60° C. or higher.

13. The ink ejection device according to claim 11, wherein: The nozzle ejects the aqueous ink in a vertical direction.

14. The ink ejection device according to claim 11, wherein The nozzle sprays the aqueous ink in a horizontal direction.

15. The ink ejection device according to claim 11, wherein Also has: a cover abutting against the nozzle and covering the nozzle; a suction pump for sucking ink from the cap, and controller, During an image recording process in which the aqueous ink is ejected onto a non-absorbent medium, the controller periodically executes a cleaning process in which the suction pump is driven while the cap covers the nozzle.

16. An image recording device, characterized in that: An ink ejection device according to any one of claims 11 to 15, and A conveyor device that conveys non-absorbent media in a conveying direction.

17. A printing method, characterized in that: include: Step 1: ejecting the aqueous ink according to any one of claims 1 to 10 from a nozzle, The second step is to heat at least one of the non-absorbing medium to which the aqueous ink ejected from the nozzle adheres and the aqueous ink adhered to the non-absorbing medium using a heater.

18. The printing method according to claim 17, wherein: In the second step, the heater heats at least one of the non-absorbing medium and the aqueous ink to a temperature of 60° C. or higher.

19. The printing method according to claim 18, wherein In the first step, the nozzle ejects the aqueous ink in a vertical direction.

20. The printing method according to claim 18, wherein In the first step, the nozzle ejects the aqueous ink in a horizontal direction.

21. The printing method according to claim 17, wherein The method further includes a third step of periodically executing a cleaning process in which a controller drives a suction pump to suck ink from the cap while the cap covers the nozzle during image recording processing in which the aqueous ink is ejected from the nozzle to record an image on a non-absorbent medium.

22. The printing method according to claim 21, wherein The method further comprises a fourth step: before the first step, a conveying device conveys the non-absorbent medium to a position opposite to the nozzle.

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