Inkjet recording method and inkjet recording apparatus

Abstract

To provide an inkjet recording method which is excellent in deformation recovery performance of a tube and can record an image having excellent light resistance despite having a tube crushing mechanism.SOLUTION: An inkjet recording device includes: an aqueous ink containing a first pigment and a second pigment; an ink storage part which stores the aqueous ink; a recording head formed with a discharge port for discharging the aqueous ink; a tube which supplies the aqueous ink from the ink storage part to the recording head; and a choke suction mechanism which can suction air from the discharge port to turn an interior of the ink storage part into a decompression state. An inkjet recording method has a step in which images are recorded by using the inkjet recording device. The choke suction mechanism has a mechanism which performs choke suctioning while crushing the tube. The first pigment is a quinacridone pigment and the second pigment is an azo pigment.SELECTED DRAWING: None

Description

[Technical field]

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

[0002] In recent years, inkjet recording methods have been used when printing business documents including characters and charts on recording media such as plain paper. In addition, due to an increase in the number of home workers and SOHOs, there is also a demand for compact devices that can record documents faster than before. With the increase in frequency of use for such business purposes, there is a strong demand from the market for ink storage units with larger capacities in order to record larger volumes of documents. For example, an inkjet recording device equipped with an ink storage unit capable of storing a large amount of ink has been proposed (Patent Document 1).

[0003] The following configurations can be given as examples of ink supply means in a recording device equipped with a large-capacity ink storage unit. That is, a means is known in which an ink supply tube connects a recording head on a carriage to an ink storage unit installed in a location separate from the carriage, and ink is supplied from the ink storage unit to the recording head through the tube. By employing such a supply means, the capacity of the ink storage unit can be easily increased.

[0004] In the conventional ink filling and recovery method for a recording head using the above-mentioned tube system, a valve unit (hereinafter, also referred to as a "choke valve") that closes and opens the ink supply tube between the ink cartridge and the recording head is used. Specifically, the choke valve provided in the middle of the ink supply tube is closed to temporarily block the ink, and the pressure on the recording head side is reduced from the valve of the ink supply tube, creating a negative pressure in the internal space of the ink storage section and the capping means. Then, a method (hereinafter, "choke suction") has been proposed in which the valve is opened in this state to supply ink to the recording head (Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-001391 A [Patent Document 2] JP 2001-113726 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors have studied the configuration of an inkjet recording device necessary for increasing productivity with a compact size, and an inkjet recording method using the same. Specifically, they have studied the provision of a mechanism for crushing a tube (hereinafter, also referred to as a "crushing mechanism") instead of a conventional choke valve. As a result, they have found that by providing this crushing mechanism, it is possible to reduce the installation space for the choke valve and perform the same operation as when a choke valve is used.

[0007] By providing a squeezing mechanism in the middle of the ink supply tube, it is possible to temporarily block the ink. With the ink temporarily blocked, the pressure is reduced from the recording head side, creating a negative pressure in the internal space of the ink storage section and the capping means, and then the tube is released, allowing for choke suction. Furthermore, it was found that the adoption of the squeezing mechanism makes it possible to quickly recover to a state where ink can be ejected, thereby improving productivity.

[0008] However, it was found that the tubes supplying magenta ink are less likely to recover from a deformed state to their original shape even when the pressure is released, compared to tubes supplying inks of colors other than magenta. Furthermore, it was found that this causes a new problem in that normal ejection becomes difficult after choking. Pigments such as quinacridone, quinacridone solid solution, diketopyrrolopyrrole, and dioxazine are commonly used as colorants for water-based magenta inks used in inkjet recording methods. Images recorded with inks containing these pigments have a magenta hue and good lightfastness. For this reason, even when a mechanism for crushing the tube is provided, there is a demand not to significantly impair the lightfastness of images recorded with magenta ink, and it is difficult to replace these pigments. In particular, in recent years, there has been a demand for good lightfastness of images recorded on recording media (such as plain paper) that are frequently used for recording business documents and the like in recording devices equipped with large-capacity ink storage units.

[0009] Therefore, an object of the present invention is to provide an ink-jet recording method which, even when provided with a mechanism for crushing the tube, has excellent deformation recovery properties for the tube and can stably record images with excellent light resistance. Another object of the present invention is to provide an ink-jet recording apparatus used in the ink-jet recording method. [Means for solving the problem]

[0010] That is, according to the present invention, there is provided an inkjet recording method comprising a step of applying the aqueous ink ejected from the ejection port to a recording medium to record an image using an inkjet recording device including: an aqueous ink containing a first pigment and a second pigment; an ink storage unit that stores the aqueous ink; a recording head that is connected to the ink storage unit and has an ejection port formed therein for ejecting the aqueous ink supplied from the ink storage unit; a capping mechanism that caps the ejection port; a tube that supplies the aqueous ink from the ink storage unit to the recording head; and a choke suction mechanism that can suction from the ejection port to create a reduced pressure inside the ink storage unit; Effect of the Invention

[0011] According to the present invention, it is possible to provide an inkjet recording method that is excellent in deformation recovery of the tube even when a mechanism for crushing the tube is provided, and is capable of recording an image with excellent light resistance. Also, according to the present invention, it is possible to provide an inkjet recording apparatus used in the inkjet recording method. [Brief description of the drawings]

[0012] [Figure 1] 1 is a perspective view illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 2] FIG. 2 is a schematic diagram illustrating an example of an ink supply system. [Diagram 3] 2 is a block diagram showing an example of a control configuration of the inkjet recording apparatus shown in FIG. [Figure 4] FIG. 4 is a schematic diagram showing an example of a recording procedure. [Diagram 5]FIG. 4 is a schematic diagram showing an example of a tube crushing mechanism. [Figure 6] FIG. 13 is a schematic diagram showing an example of a state in which the tube crushing mechanism is activated. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will be described in more detail below with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is dissociated into ions in the ink, but for convenience, it is expressed as "containing salt". In addition, the aqueous ink for inkjet printing may be simply referred to as "ink". Unless otherwise specified, the physical property values ​​are values ​​at room temperature (25°C) and room humidity (relative humidity 50%). Supply of ink through a tube may be simply referred to as "tube supply". The method of temporarily blocking the ink and reducing the pressure from the recording head side, creating a negative pressure in the internal space of the ink storage section and the capping means, and then releasing the pressure all at once to eliminate the negative pressure, and allowing the ink to flow to the recording head and supplying the ink, may also be simply referred to as "choke suction".

[0014] The present inventors first studied a configuration that allows choke suction without increasing the size of the recording device. As a result, they found that it is effective to reduce the number of choke valves equipped with valve units that require space. In the case of an inkjet recording device equipped with a choke suction mechanism having a conventional choke valve, a choke valve is provided in each tube flow path of each color. Furthermore, a valve unit, which is a separate unit, is connected midway through the tube, so space is required. For this reason, a choke suction mechanism having a choke valve has generally been used in a large inkjet recording device in which a certain amount of space can be secured.

[0015] To operate a conventional choke suction mechanism, first, the ink supply tube is closed by shrinking the space in the choke valve provided upstream of the recording head (on the ink storage side), and the ink supply path is temporarily narrowed and the pressure is reduced from the recording head side. This makes it possible to increase the negative pressure in the internal space of the capping means. Next, the space in the choke valve is expanded to eliminate the negative pressure in the internal space of the capping means, and ink is forced to flow into the recording head. This allows ink with increased viscosity near the ejection port to be expelled, and the ejection properties of the ink can be restored. The choke valve also has the function of maintaining the negative pressure in the internal space of the capping means by closing the valve, and preventing ink leakage from the ejection port.

[0016] The present inventors further studied a means for creating a negative pressure in the internal space of the capping means, which is different from the conventional choke valve and can be applied even when the recording device is small. As a result, they found that by adopting a mechanism (crushing mechanism) for crushing the tube by spring pressure using a cam instead of the choke valve, it is possible to perform an operation equivalent to choke suction by the choke valve. By crushing the tube, the ink supply tube can be temporarily narrowed. In this state, the pressure is reduced from the recording head side, and the negative pressure in the internal space of the ink storage section and the capping means is increased. As a result, the negative pressure in the area from the position where the tube is crushed to the ejection port is increased. After that, when the tube is released from the crushing, the tube expands, so that the ink flows vigorously to the recording head, and the ink can be efficiently filled into the ink storage section and the recording head, and the ink ejection performance can be restored. In this method, the degree of negative pressure can be adjusted by the time for which the pressure is reduced from the recording head side while the tube is crushed. On the other hand, in order to generate a high negative pressure, it is required that the tube easily recovers from the deformed state even after being crushed for a long time. The above-mentioned squeezing mechanism not only functions as a choke valve, but also has the function of maintaining negative pressure in the internal space of the ink storage section and the capping means by squeezing the tube, thereby preventing ink leakage from the ejection port.

[0017] However, it was found that when an image is recorded after the above-mentioned squeezing mechanism is operated to suck the choke, the ink may not be ejected. When the cause of this was examined, it was found that, specific to the use of magenta ink containing a certain pigment, the deformation of the tube does not recover even if the squeezing is released after the choke, and the ink may not reach the ejection port of the recording head. Furthermore, it was also found that such a phenomenon occurs specifically with quinacridone, quinacridone solid solution, diketopyrrolopyrrole, and dioxazine (hereinafter, these pigments are also referred to as "first pigments"), which are pigments that have a magenta hue and good light resistance. That is, when a magenta ink containing a first pigment is used, the recovery of the original shape of the tube through which the ink flows (hereinafter, also referred to as "tube shape recovery") is slow. For this reason, it was found that even if an attempt is made to eject the ink after the choke, the ink is not normally supplied to the recording head, making ejection difficult.

[0018] It is believed that if the deformation recovery of the magenta ink tube is improved, the problem of difficulty in ejection will not occur. The following phenomenon is believed to be the cause of the magenta ink tube's difficulty in recovering from deformation. By performing choke suction while squashing the tube, the ink flowing inside the tube stops and pressure is also applied to the pigment in the ink, causing aggregation of the first pigment and aggregation of the pigment due to the planar structure of the first pigment. Furthermore, since the pigment aggregated due to the planar structure has a hydrophobic surface, it is likely to interact with the inner surface of the tube. As a result, it is believed that the tube's deformation becomes difficult to recover from.

[0019] The first pigment, such as quinacridone, is necessary to improve the lightfastness of the recorded image. Therefore, the present inventors have investigated a recording method that suppresses the problems caused by the difficulty in recovering from the deformation of the magenta ink tube as described above, and improves productivity without impairing lightfastness. As a result, they have found that an azo pigment (hereinafter also referred to as "second pigment"), which is a pigment with lower planarity compared to the first pigment, can be used together with a first pigment having a planar structure such as quinacridone.

[0020] The first pigment has a tendency to aggregate. Since the first pigment has a planar structure, it is easy for molecules to attract each other. Furthermore, since the first pigment has an amide group or a morpholine ring in the molecule, it forms strong hydrogen bonds between molecules. Therefore, when the ink is retained in the tube and pressure is applied, it is considered that the pigments tend to gather in layers and tend to aggregate into flat plates. In addition, since the pigments having a planar structure have a large contact area with the inner surface of the tube, they tend to adhere to the inner surface of the tube. For this reason, it is assumed that the expansion of the tube after choking is easily hindered, making it difficult for the tube to recover from its deformation.

[0021] In the case of an ink containing only a pigment having a planar structure such as the first pigment, the pigment adheres to the inner surface of the tube in layers and aggregates into a plate shape. In contrast, when a pigment having a structure (azo bond) that can rotate three-dimensionally such as the second pigment coexists with the first pigment, the aggregation of the first pigment having a planar structure on the plate is easily hindered. As a result, in the case of an ink containing the first and second pigments, the contact area of ​​the first pigment with the inner surface of the tube is reduced compared to an ink containing only the first pigment. In addition, the molecules of the second pigment can freely rotate around the azo bond as the axis of rotation. In other words, since the molecules of the azo pigment are unlikely to form a planar structure, the pigments do not stack strongly and the aggregation of the pigments is easily broken. As a result, it is considered that the expansion of the tube after choke suction is not easily hindered, the deformation of the tube is quickly restored, and the ink is normally ejected even after choke suction.

[0022] <Inkjet recording method and inkjet recording apparatus> The inkjet recording method of the present invention uses an inkjet recording device that includes an aqueous ink, an ink storage section, a recording head formed with an outlet for discharging the aqueous ink, a capping mechanism for capping the outlet, a tube, and a choke suction mechanism. The aqueous ink contains a first pigment and a second pigment. The ink storage section is a section that stores the aqueous ink. The recording head is connected to the ink storage section. The tube is a member that connects the recording head and the ink storage section and supplies the aqueous ink from the ink storage section to the recording head. The choke suction mechanism is a mechanism that can suction from the outlet and reduce the pressure inside the ink storage section. The inkjet recording method of the present invention includes a step of recording an image by applying the aqueous ink discharged from the outlet of the recording head to a recording medium. The inkjet recording device of the present invention includes an aqueous ink, an ink storage section, a recording head formed with an outlet for discharging the aqueous ink, a capping mechanism for capping the outlet, a tube, and a choke suction mechanism. The choke suction mechanism of the inkjet recording device includes a mechanism that performs choke suction while crushing the tube.

[0023] (Inkjet recording device) FIG. 1 is a perspective view showing a schematic diagram of an embodiment of an inkjet recording apparatus of the present invention. The inkjet recording apparatus of this embodiment is a so-called serial type inkjet recording apparatus that performs a recording operation by reciprocating a recording head in an X direction (main scanning direction). A recording medium 101 is intermittently transported in a Y direction (sub-scanning direction) by a transport roller 107. A recording unit 102 mounted on a carriage 103 is reciprocally scanned in an X direction (main scanning direction) that is a direction perpendicular to the Y direction that is the transport direction of the recording medium 101. A recording operation is performed by transporting the recording medium 101 in the Y direction and reciprocating scanning of the recording unit 102 in the X direction. The recording unit 102 is composed of an inkjet type recording head 203 (FIG. 2) that ejects ink from a plurality of ejection ports, and a subtank 202 (FIG. 2) as a second ink storage section, and is mounted on the carriage 103. The carriage 103 is supported so as to be movable along a guide rail 105 arranged along the X direction, and is fixed to an endless belt 106 that moves in parallel with the guide rail 105. The endless belt 106 reciprocates due to the driving force of a motor, thereby causing the carriage 103 to scan back and forth in the X direction.

[0024] A main tank 201 (FIG. 2) serving as a first ink storage section is stored inside the main tank storage section 108. The main tank 201 stored in the main tank storage section 108 and a sub-tank 202 of the recording unit 102 are connected by an ink supply tube 104. Ink is supplied from the main tank 201 to the sub-tank 202 (FIG. 2) via the ink supply tube 104, and then ejected from the ejection opening of the recording head 203. The main tank 201, ink supply tube 104, and sub-tank 202 can each be provided in numbers corresponding to the type of ink. It is preferable that the main tank 201 and the sub-tank 202 are connected by the ink supply tube 104 without going through another ink storage section.

[0025] The main tank housing section 108 is provided with an ink inlet 216 for injecting ink into the main tank 201 from outside the inkjet recording device. When using the inkjet recording device for the first time, or when the amount of ink has decreased, ink is injected from an ink bottle into the main tank placed inside the inkjet recording device. The user can open the ink inlet 216 and inject ink into the ink tank 201. In other words, the main tank is left inside the inkjet recording device and is not replaced itself.

[0026] 2 is a schematic diagram showing an example of an ink supply system. Ink (shown by hatching) stored in a main tank 201 is supplied to a sub tank 202 via an ink supply tube 104, and then passes through a filter 215 before being supplied to a print head 203. A gas introduction tube 204 is connected to the main tank 201 as an air communication section. When printing is performed and ink is consumed, ink is supplied from the main tank 201 to the sub tank 202, and the ink in the main tank 201 decreases. Then, air is introduced into the main tank 201 from the gas introduction tube 204, one end of which is open to the atmosphere, so that the internal negative pressure for holding the ink is kept substantially constant in the ink supply system.

[0027] In order to increase the number of recordable sheets and thereby realize high productivity, it is preferable that the main tank 201 has a large maximum ink capacity V1 (mL). Specifically, the maximum ink capacity V1 (mL) of the main tank 201 is preferably 60 mL or more and 300 mL or less, and more preferably 100 mL or more and 250 mL or less. In addition, it is preferable that the initial ink filling amount of the main tank 201 is about 95% based on the maximum ink capacity.

[0028] It is also preferable that the subtank 202 has a large maximum ink capacity V2 (mL) in order to reduce the frequency of ink supply from the main tank 201 and to stably supply ink to the recording head 203. However, for example, assuming a serial system as shown in FIG. 1 in which the subtank 202 is mounted on the carriage 103, it is preferable that the maximum ink capacity V2 (mL) of the subtank 202 is not too large. In other words, if too much ink is stored in the subtank 202, the recording unit 102 becomes large, the moving speed of the carriage 103 decreases, and it becomes necessary to increase the strength of the endless belt 106 and the motor that move the carriage 103. Therefore, it is preferable that the maximum ink capacity V2 (mL) of the subtank 202 is 1 mL or more and 20 mL or less, and more preferably 2 mL or more and 10 mL or less.

[0029] The housings of the main tank 201 and the sub tank 202 are formed of thermoplastic resins such as polyester, polycarbonate, polyethylene, polypropylene, polystyrene, polyphenylene ether, and mixtures or modified products thereof. An ink absorber that generates negative pressure to hold the ink may be disposed inside the housing. The ink absorber is preferably made of compressed fibers such as polypropylene or urethane. Alternatively, the ink may be directly stored inside the housing without disposing the ink absorber. From the viewpoint of realizing high-speed recording, it is preferable that the sub tank 202 does not have an absorber for impregnating and storing the ink, and the ink is directly stored inside the housing constituting the sub tank 202.

[0030] The recording unit 102 is composed of a recording head 203 and a subtank 202. The subtank 202 may be attached to the recording unit 102, which is a head cartridge in which the recording head 203 is built, and the recording unit 102 with the subtank 202 attached may be attached to the carriage 103. Furthermore, the recording unit 102, which is integrally configured with the subtank 202 and the recording head 203, may be attached to the carriage 103. Among these, it is preferable to adopt a configuration in which the recording unit with the subtank 202 attached is set on the carriage 103 as shown in Figures 1 and 2.

[0031] The ink ejection method of the recording head 203 may be a method of applying mechanical energy to the ink or a method of applying thermal energy to the ink. Among these, it is preferable to adopt a method of ejecting ink by applying thermal energy to the ink.

[0032] When not printing, an area including the ejection ports of the print head 203 is covered with a cap 205 to suppress evaporation of ink from the ejection ports. A tube 207 as an atmosphere communication section provided with an atmosphere communication valve 206, and a waste ink tube 208 for discharging waste ink that is accumulated in the cap 205 and is not used for printing are connected to the cap 205. The waste ink discharged from the ejection ports of the print head 203 is stored in a waste ink storage section 209. A suction valve 210 is provided in the waste ink tube 208, and ink is sucked in by using a pump 211.

[0033] Depending on the purpose, the location from which ink is sucked and the amount of ink to be sucked can be set appropriately. In either case, the pump 211 is operated to suck ink while the atmosphere communication valve 206 is closed.

[0034] When performing a normal "recovery operation" that is not charge suction, the pump 211 is operated with the suction valve 210 open and the tube crushing mechanism 212 released. This allows ink to be sucked in with a relatively weak suction pressure. On the other hand, when performing so-called charge suction, such as for initial filling or when an abnormality occurs, the pump 211 is operated with the tube crushing mechanism 212 released and the suction valve 210 closed, increasing the negative pressure in the waste ink tube 208. By subsequently opening the suction valve 210, ink is sucked in with a relatively strong suction pressure, allowing ink to be filled or discharged all at once.

[0035] When performing choke suction, the pump 211 is operated with the tube crushing mechanism 212 closed and the suction valve 210 open, increasing the overall negative pressure between the tube crushing mechanism 212 and the pump 211. By subsequently releasing the tube crushing mechanism 212, it is possible to rapidly discharge a larger amount of ink. In other words, when comparing the suction methods, the order of suction pressure is as follows: choke suction is strongest, charge suction is medium strength, and normal suction recovery operation is weakest.

[0036] (Control Configuration) FIG. 3 is a block diagram showing an example of the control configuration of the inkjet recording apparatus shown in FIG. 2. The controller 800 is a main control unit, and executes the procedure shown in FIG. 4. The controller 800 has, for example, a CPU 801 in the form of a microcomputer, a ROM 803 storing a program corresponding to the procedure and other fixed data, and a RAM 805 having an area for developing image data and an area for working. The controller 800 further has a timer 807 and a counter 809 used for performing a recovery operation under a predetermined condition. The host device 810 is a supply source of image data, and may be a computer that generates and processes image data related to recording, or may be a reader unit for reading images. Image data, other commands, status signals, etc. are transmitted to and received from the controller 800 via an interface (I / F) 812.

[0037] The operation unit 820 is composed of switches that receive instructions input by an operator, such as a power switch 822, a copy switch 824 for instructing the start of recording or copying, and a recovery switch 826 for instructing the start of a recovery operation. The sensor group 830 is composed of sensors for detecting the state of the recording apparatus, such as a pump position sensor 834 for detecting the position of the pump 211 (FIG. 2). The head driver 840 drives the heater 421 for ejecting ink in the recording head 1, and the sub-heater 429 for adjusting the ink temperature. The transport motor 850 is a motor for transporting the recording medium, and is driven by a motor driver 852.

[0038] FIG. 5 is a schematic diagram showing an example of a tube crushing mechanism. FIG. 6 is a schematic diagram showing an example of a state in which the tube crushing mechanism is operated. As shown in FIGS. 5 and 6, the tube crushing mechanism 212 includes an ink supply tube 104 through which ink flows, a pressing member 504 that directly applies pressure to the ink supply tube 104 to press it, and a cam 500 that is connected to the pressing member 504 via a spring 502. When performing choke suction, the cam 500 is rotated to compress the spring 502. The pressure generated by the compression of the spring 502 is transmitted to the pressing member 504 and applied to the ink supply tube 104. This makes it possible to directly crush the ink supply tube 104, and to temporarily narrow the ink flow path. The degree to which the ink supply tube 104 is crushed by the pressing member 504 can be adjusted by providing a stopper 506 that can control the moving distance of the pressing member 504. The ink supply tube 104 is crushed, and the ink flow path is temporarily narrowed (closed), and then the recording head 203 is capped with the cap 205 and the pump 211 is operated (FIG. 2). This creates a negative pressure in the area from the position where the ink supply tube 104 is crushed to the ejection port of the recording head 203. Thereafter, the cam 500 (FIGS. 5 and 6) is driven to rotate and release the spring 502. This causes the ink supply tube 104 that was crushed to return to its original shape, and the ink flows again, flowing vigorously into the recording head 203 and being ejected from the ejection port, thereby restoring the ink ejection properties.

[0039] The ink supply tube 104 is connected to a sub-tank 202 constituting the recording unit 102 mounted on the carriage 103. Therefore, the ink supply tube 104 is routed around inside the device following the reciprocating scanning of the carriage 103. Therefore, it is preferable to select a material constituting the ink supply tube 104 that has flexibility that can withstand the frequent reciprocating scanning of the carriage 103. The durometer hardness (A50 / 15 / S) of the tube at 25°C is preferably 35 or more and 45 or less. By using a tube whose durometer hardness is within the above range, it is possible to further improve the deformation recovery property of the tube when released from crushing. If the durometer hardness of the tube is less than 35, the tube tends to be too soft, and therefore the deformation recovery property of the tube when released from crushing may be reduced. On the other hand, if the durometer hardness of the tube exceeds 45, the tube tends to be too hard, making it difficult for the tube to close when crushed, or even if it does close, it is difficult for it to recover, which may reduce the deformation recovery of the tube.

[0040] The durometer hardness (A50 / 15 / S) of the tube at 25°C is measured using a type A durometer measuring instrument in accordance with the JIS K 6253:1997 hardness test and durometer hardness test standard for vulcanized and thermoplastic rubber. The measurement conditions are 25°C, 50% relative humidity, 50 (points), and 15 seconds later. In addition, JIS K 6253:1997 states that a type AM durometer should be used when the thickness of the test piece is less than 6.0 mm. However, in this specification, the value measured using a type A durometer is used regardless of the thickness of the test piece, since the correlation with performance can be accurately grasped. The durometer hardness of the tube can be adjusted by known methods such as the material (resin material, additives, etc.) constituting the tube, the conditions (temperature, etc.) when manufacturing the tube by extrusion molding, etc., and the size of the tube (diameter, inner diameter, wall thickness, etc.).

[0041] The tube is a member formed by molding a resin material into a tubular shape. The resin material constituting the tube may be a single resin material or a combination of two or more resin materials. It may also be a resin material containing various additives. The structure of the tube may be a single-layer structure or a laminated structure. As the resin material, a thermoplastic elastomer is preferable because it has excellent moldability, rubber elasticity, and flexibility. Examples of the thermoplastic elastomer include olefin-based, urethane-based, ester-based, styrene-based, and vinyl chloride-based resins. Among them, a styrene-based thermoplastic elastomer is preferable because it has particularly excellent flexibility and rubber elasticity. Examples of additives to be mixed into the resin material include softeners, lubricants, surfactants, antioxidants, antiaging agents, adhesion promoters, and pigments.

[0042] The inner diameter and wall thickness of the tube are appropriately set in consideration of productivity such as molding, bending rigidity when routed through a recording device, ink supplyability, gas barrier properties, etc. The inner diameter of the tube is preferably 1 mm or more and 5 mm or less, and more preferably 1 mm or more and 3 mm or less. The wall thickness of the tube is preferably 0.5 mm or more and 5 mm or less, and more preferably 0.5 mm or more and 3 mm or less.

[0043] (Recording process) Next, a specific example of the recording procedure of the inkjet recording method of this embodiment will be described. FIG. 4 is a schematic diagram showing an example of the recording procedure. When a recording command is detected in step S1, a recovery operation is executed in step S3 as necessary. When it is determined that the recovery operation is unnecessary, a preliminary ejection is executed in step S5. This preliminary ejection is a process performed to discharge thickened ink and foreign matter present in the vicinity of the ejection port, and ink is ejected from each ejection port before the recording operation. The ejection of ink as the preliminary ejection is performed based on the preliminary ejection data, regardless of the recording data. After the preliminary ejection is executed in step S5, the recording operation is executed immediately in step S7. After the recording operation is completed, a recovery operation may be executed in step S9 as necessary.

[0044] If an unexpected event occurs, such as ink not being ejected normally, and it is determined that a recovery operation is necessary, the recovery operation is also executed in step S13 when the operator operates the recovery switch in step S11, as shown in FIG. 4. Examples of the recovery operation in step S13 include normal suction, charge suction, and choke suction. If a recording operation or a recovery operation is not executed, it is preferable to cap the ejection port surface with a cap provided in the recording device in step S15. This makes it possible to suppress ink adhesion. When capping the ejection port surface with a cap, it is preferable to wipe the ejection port surface in step S17 to remove ink droplets and the like adhering to the vicinity of the ejection port prior to closing the cap in step S19.

[0045] The inkjet recording method of this embodiment includes a step of recording an image by applying ink ejected from the ejection ports of a recording head to a recording medium. Therefore, in the recording operation of step S7, an image is recorded by applying ink ejected from the ejection ports to the recording medium. It is preferable to record an image by applying ink to a unit area of ​​the recording medium through one relative scan of the recording head and the recording medium. By recording an image through one relative scan, i.e., by setting the number of recording passes to one, recording can be completed in a short time.

[0046] Any recording medium may be used as the target for recording an image. In particular, it is preferable to use a recording medium having ink permeability, such as a recording medium without a coating layer, such as plain paper or uncoated paper, or a recording medium with a coating layer, such as glossy paper or art paper.

[0047] (Water-based ink) The inkjet recording method of the present invention includes a step of applying the aqueous ink ejected from the ejection port of the recording head to a recording medium to record an image. The aqueous ink contains a first pigment and a second pigment. Hereinafter, the first pigment and the second pigment may be collectively referred to as "pigment" without distinction. The aqueous ink is preferably a magenta ink. The magenta ink in the present invention means an ink having a magenta hue when the hue of the ink is classified into black, cyan, magenta, yellow, red, green, blue, and the like. The components constituting the ink will be described below.

[0048] [Colorant] As the coloring material, a pigment is used. The dispersion method of the pigment is not particularly limited. For example, a resin-dispersed pigment dispersed by a resin dispersant, a pigment dispersed by a surfactant, and a microcapsule pigment in which at least a part of the pigment particle surface is covered with a resin or the like can be used. In addition, a self-dispersed pigment in which a functional group containing a hydrophilic group such as an anionic group is bonded to the pigment particle surface, or a pigment in which an organic group containing a polymer is chemically bonded to the pigment particle surface (resin-bonded self-dispersed pigment) can also be used. Pigments with different dispersion methods may be used in combination. Among them, a resin-dispersed pigment dispersed by a resin dispersant is preferred. It is more preferred to use a water-soluble resin as the resin dispersant.

[0049] The first pigment is at least one selected from the group consisting of quinacridone pigments, quinacridone solid solutions formed from two or more of the quinacridone pigments, diketopyrrolopyrrole pigments, and dioxazine pigments. The second pigment is at least one selected from the group consisting of azo pigments. By using these first and second pigments in combination, the deformation of the magenta ink tube can be quickly restored, and the occurrence of non-ejection can be suppressed. In addition, by using these first and second pigments in combination, the hue of magenta can also be expressed.

[0050] The content (mass%) of the first pigment in the aqueous ink is preferably 0.1% by mass or more and 15.0% by mass or less, more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. Specific examples of the first pigment include quinacridone pigments such as CI Pigment Red: 122, 192, 202, 206, 207, 209, 282, and CI Pigment Violet 19; quinacridone solid solutions formed from two or more of these quinacridone pigments; diketopyrrolopyrrole pigments such as CI Pigment Red: 254, 255, 264, 270, 272, 283, and 291; and dioxazine pigments such as CI Pigment Violet: 23, 34, 35, 37, and 57. Among them, since they can express a suitable color tone as magenta, the first pigment is preferably a quinacridone pigment, a quinacridone solid solution formed from two or more of the quinacridone pigments, etc. Among them, a quinacridone solid solution formed from two or more of the quinacridone pigments having the above CI numbers is particularly preferred since it has excellent saturation.

[0051] The content (mass%) of the second pigment in the aqueous ink is preferably 0.1% by mass or more and 15.0% by mass or less, more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink. Specific examples of the second pigment include CI Pigment Red: 4, 9, 12, 14, 23, 31, 32, 49:1, 49:2, 57, 63:1, 112, 146, 147, 150, 170, 175, 176, 184, 185, 187, 188, 208, 210, 245, 268, and 269. Among them, CI Pigment Red 150 is preferable as the second pigment. These second pigments are not solid solution pigments, that is, the second pigments are non-solid solution pigments.

[0052] In order to more quickly recover from the deformation of the tube, it is preferable that the cumulative 50% particle diameter D1 based on volume of the first pigment and the cumulative 50% particle diameter D2 based on volume of the second pigment are different. Similarly, in order to more quickly recover from the deformation of the tube, it is preferable that the cumulative 50% particle diameter D2 based on volume of the second pigment is larger than the cumulative 50% particle diameter D1 based on volume of the first pigment. Similarly, in order to more quickly recover from the deformation of the tube, it is preferable that the cumulative 50% particle diameter D2 based on volume of the second pigment is 130 nm or more. Also, it is preferable that the cumulative 50% particle diameter D1 based on volume of the first pigment is 110 nm or less. If the particle diameter of the first pigment is too large, the saturation of the recorded image may decrease. If the difference between the particle diameters of the first pigment and the second pigment is large, it is possible to cause irregularity in the aggregation of the pigments due to the crushing of the tube. Therefore, the aggregation of the pigments is more quickly released by choke suction, the deformation of the tube is more quickly recovered, and non-ejection can be more effectively suppressed. The volume-based cumulative 50% particle diameter D2 of the second pigment is preferably 180 nm or less. The volume-based cumulative 50% particle diameter D1 of the first pigment is preferably 80 nm or more. The volume-based cumulative 50% particle diameter (so-called D50) of a pigment can be measured using a particle diameter measuring device that uses dynamic light scattering.

[0053] The content (mass%) of the second pigment in the aqueous ink is preferably 0.20 times or more of the content (mass%) of the first pigment. If the mass ratio is less than 0.20 times, the pigments may not easily disaggregate even with the suction pressure after choke suction, which may slightly affect the degree to which the tube deformation is restored. In addition, the content (mass%) of the second pigment in the aqueous ink is preferably 0.80 times or less of the content (mass%) of the first pigment. If the mass ratio is more than 0.80 times, the lightfastness of the image may be slightly reduced.

[0054] [Surfactants] The ink may contain various surfactants. The content (mass%) of the surfactant in the aqueous ink is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.2% by mass or more and 1.5% by mass or less, based on the total mass of the ink. Examples of the surfactant include a hydrocarbon-based surfactant, a fluorine-based surfactant, and a silicone-based surfactant. These surfactants may be any of a nonionic surfactant, an anionic surfactant, a cationic surfactant, and an amphoteric surfactant.

[0055] In particular, the ink preferably contains a nonionic surfactant. As the nonionic surfactant, a hydrocarbon-based nonionic surfactant is preferable. Examples of the hydrocarbon-based nonionic surfactant include polyoxyethylene alkyl ether, an ethylene oxide adduct of acetylene glycol, and a polyethylene glycol polypropylene glycol block copolymer.

[0056] [resin] The ink may contain a resin. The resin may be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. The resin may also be added to the ink (ii) to improve various properties of the image to be recorded. The state of the resin in the ink may be a state in which it is dissolved in the aqueous medium, or a state in which it is dispersed as resin particles in the aqueous medium. In this specification, "the resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it does not form particles whose particle size can be measured by a measurement method such as a dynamic light scattering method. The content (mass%) of the resin in the aqueous ink is preferably 0.1% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 3.0% by mass or less, based on the total mass of the ink.

[0057] Examples of the resin include acrylic resin, polyester resin, urethane resin, urea resin, polysaccharides, polypeptides, etc. Among them, acrylic resin and urethane resin are preferable from the viewpoint of ejection characteristics from the ejection port of the recording head. However, since resin components such as resin particles tend to easily retain air bubbles, it is preferable not to include too much of them in the ink.

[0058] [Aqueous medium] The ink is an aqueous ink containing at least water as an aqueous medium. The ink can contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As the water-soluble organic solvent, any of those usable for inkjet inks, such as alcohols, (poly)alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds, can be used. The content (mass%) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. As the water, it is preferable to use deionized water or ion-exchanged water. The content (mass%) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink.

[0059] [Other ingredients] The ink may further contain water-soluble organic compounds that are solid at 25° C., such as urea or its derivatives, trimethylolpropane, and trimethylolethane. The content (mass %) of the water-soluble organic compounds in the ink is preferably 0.1 mass % or more and 10.0 mass % or less, based on the total mass of the ink. In addition to the above components, the ink may contain various additives such as antifoaming agents, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and reduction inhibitors, as necessary. EXAMPLES

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

[0061] <Preparation of pigment dispersion> The components (unit: parts) shown in the upper part of Table 1 were mixed to obtain a mixture. In Table 1, "Solid solution pigment" is a solid solution of CI Pigment Red 202 and CI Pigment Violet 19 (product name "Cromophtal Jet Magenta 2BC", manufactured by Ciba). The obtained mixture was dispersed using a sand grinder for 1 hour, and then centrifuged to remove coarse particles. After pressure filtration using a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm, an appropriate amount of ion-exchanged water was added to obtain each pigment dispersion. The lower parts of Tables 2-1 and 2-2 show the contents of pigment and resin (resin dispersant) in the pigment dispersion, and the cumulative 50% particle size (D50) based on volume of the pigment. D50 was measured for a sample prepared by diluting the pigment dispersion with ion-exchanged water using a particle size measuring device that uses dynamic light scattering (product name "UPA-EX150", manufactured by Nikkiso) under the following conditions: SetZero: 30 seconds, number of measurements: 3, measurement time: 180 seconds, refractive index: 1.5.

[0062] TIFF0007669220000001.tif77170

[0063] <Ink Preparation> Each component (unit: %) shown in Tables 2-1 and 2-2 was mixed, thoroughly stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantec) with a pore size of 3.0 μm to prepare each ink (magenta ink). In Tables 2-1 and 2-2, "Acetinol E100" is the trade name of a nonionic surfactant (acetylene glycol ethylene oxide adduct) manufactured by Kawaken Fine Chemicals.

[0064] TIFF0007669220000002.tif147170

[0065] TIFF0007669220000003.tif160170

[0066] <Preparing the tube> The types of tubes shown in Table 3 were prepared, each with an inner diameter of 2 mm and an outer diameter of 4 mm. These tubes were made of a resin material that was a mixture of a styrene-based thermoplastic elastomer and additives (lubricant, softener), and the durometer hardness was adjusted by changing the resin material and manufacturing conditions. The durometer hardness (A50 / 15 / S) of the tubes was measured at 25°C, relative humidity of 50%, and for 15 seconds.

[0067] TIFF0007669220000004.tif50170

[0068] <Evaluation> An inkjet recording device was prepared that has the main components shown in Fig. 1 and incorporates an ink supply system with the configuration shown in Fig. 2. This recording device is a serial type recording device in which a recording head 203 is incorporated and a recording unit 102 with a sub-tank 202 attached is mounted on a carriage 103. The tube (ink supply tube 104) that connects the main tank 201 and the sub-tank 202 was one shown in Table 3. The maximum ink capacity V1 of the main tank was 150 mL, and the maximum ink capacity V2 of the sub-tank was 5 mL.

[0069] The prepared ink was poured into the main tank of the inkjet recording device, and the ink was supplied to the sub-tank and the recording head. Table 4 shows the type of ink used and whether or not the mechanism for crushing the tube (crushing mechanism) was activated. In Reference Examples 1 to 3, instead of performing choke suction with the tube crushing mechanism 212 activated, the pump 211 was operated with the suction valve 210 open and the tube crushing mechanism 212 released, and suction recovery was performed for 30 seconds. In this embodiment, the recording duty of a solid image recorded under the condition that two ink droplets with a mass of 5 ng per droplet are applied to a unit area of ​​1 / 600 inch x 1 / 600 inch is defined as 100%. In the present invention, the evaluation criteria for each item shown below are "AAAA", "AAA", "AA", "A", and "B" as acceptable levels, and "C" as unacceptable levels. The evaluation results are shown in Table 4. In addition, in the image evaluation (light resistance, color tone, saturation) of Comparative Example 1, in which the evaluation result of the deformation recovery of the tube was ranked C, some parts of the solid image were blurred, but there were also areas that were not blurred and could be measured in color, so the evaluation was performed using those areas.

[0070] (Tube deformation recovery) Using the inkjet recording device described above, the tube crushing mechanism 212 was operated to perform choke suction while maintaining the tube crushed state for a predetermined period of time. After that, a solid image with a recording duty of 100% was recorded on the entire surface of an A4-sized recording medium (plain paper) using all the nozzles. As the recording medium, a product name "High-quality dedicated paper HR-101S" (manufactured by Canon) was used. The ink ejection state was confirmed by visually checking the fading state of the solid image, and the deformation recovery property of the tube was evaluated according to the evaluation criteria shown below. AAAA: No fading of the solid image occurred after 55 seconds of squashing the tube. AAA: When the tube was crushed for more than 40 seconds but less than 50 seconds, the solid image started to fade. AA: When the tube was crushed for more than 30 seconds but less than 40 seconds, the solid image started to fade. A: When the tube was crushed for more than 20 seconds but less than 30 seconds, the solid image started to fade. B: When the tube was crushed for more than 5 seconds but less than 20 seconds, the solid image started to fade. C: After 5 seconds of squeezing the tube, the solid image started to fade.

[0071] (Lightfastness) Using the inkjet recording device, an image was recorded as follows. The tube crushing mechanism 212 was operated to crush the tube for 10 seconds, while choke suction was performed. Then, 20 types of 1 cm x 1 cm solid images were recorded on a recording medium (plain paper, product name "PB Paper", manufactured by Canon) by changing the recording duty in 5% increments between 5% and 100%. The optical density of the obtained 20 types of solid images was measured using a fluorescent spectrodensitometer (product name "FD-7", manufactured by Konica Minolta), and the solid image with the optical density closest to 1.0 was identified. The optical density of this solid image was defined as the "optical density before lightfastness test". Then, the solid image was placed on a xenon lightfastness tester (product name "Weather-O-Meter Ci4100", manufactured by Atlas). Black panel temperature: 60°C, test chamber temperature: 40°C, relative humidity: 50%, irradiation amount: 550 W / m 2 The total cumulative irradiation dose is 12 kJ / cm 2 The solid image was irradiated with xenon light until the optical density reached 100%. The solid image was then removed and the optical density was measured again (referred to as "optical density after lightfastness test"). The optical density remaining rate was calculated based on the formula: optical density remaining rate (%) = (optical density after lightfastness test / optical density after lightfastness test) x 100%, and the lightfastness was evaluated according to the following evaluation criteria. A: The remaining optical density was 80% or more. B: The remaining optical density was 65% or more and less than 80%. C: The remaining optical density was less than 65%.

[0072] (color tone) Using the above inkjet recording device, an image was recorded as follows. The tube crushing mechanism 212 was operated to crush the tube for 10 seconds while performing choke suction, and then a solid image with a recording duty of 100% was recorded. Glossy paper (product name "Canon Photo Paper Glossy Gold GL-101", manufactured by Canon) was used as the recording medium. The chromaticity (a * and b * ) was measured, the hue angle H° was calculated based on the following formula, and the color tone of the image was evaluated according to the following evaluation criteria. [Calculation of hue angle H°] a * ≧0, b * ≧0 (first quadrant), H°=tan -1 (b * / a * ) a * ≦0, b * ≧0 (second quadrant), H°=180+tan -1 (b * / a * ) a * ≦0, b * ≦0 (third quadrant), H°=180+tan -1 (b * / a * ) a * ≧0, b * ≦0 (fourth quadrant), H°=360+tan -1 (b * / a * ) [Evaluation Criteria] A: H° was 0° or more and less than 18°, or 335° or more and less than 360°. B: H° was greater than or equal to 18° and less than 335°.

[0073] (Saturation) Using the above-mentioned inkjet recording device, an image was recorded as follows. After choke suction was performed while the tube was kept in a crushed state for 10 seconds by operating the tube crushing mechanism 212, a solid image with a recording duty of 100% was recorded. Glossy paper (product name "Canon Photo Paper Glossy Gold GL-101", manufactured by Canon) was used as the recording medium. The obtained solid image was measured for chroma C in the Lab color system using a fluorescence spectrodensitometer (product name "FD-7", manufactured by Konica Minolta). * The color saturation of the image was evaluated according to the following evaluation criteria. A:C * The value was 78 or higher. B:C * The value was less than 78.

[0074] TIFF0007669220000005.tif223170

Claims

1. an inkjet recording method comprising: a step of applying the water-based ink ejected from the ejection port to a recording medium to record an image using an inkjet recording device including: an ink containing a first pigment and a second pigment; an ink storage unit that stores the water-based ink; a recording head that is connected to the ink storage unit and has an ejection port formed therein for ejecting the water-based ink supplied from the ink storage unit; a capping mechanism that caps the ejection port; a tube that supplies the water-based ink from the ink storage unit to the recording head; and a choke suction mechanism that can suck from the ejection port to reduce pressure inside the ink storage unit, The choke suction mechanism has a mechanism for performing choke suction while crushing the tube, the first pigment is at least one selected from the group consisting of a quinacridone pigment, a quinacridone solid solution formed from two or more of the quinacridone pigments, a diketopyrrolopyrrole pigment, and a dioxazine pigment; The ink-jet recording method according to claim 1, wherein the second pigment is at least one selected from the group consisting of azo pigments.

2. 2. The ink jet recording method according to claim 1, wherein the first pigment is at least one selected from the group consisting of quinacridone pigments and quinacridone solid solutions.

3. 2. The ink jet recording method according to claim 1, wherein the first pigment is a quinacridone solid solution.

4. 4. The ink-jet recording method according to claim 1, wherein the azo pigment is a non-solid solution pigment.

5. 2. The ink-jet recording method according to claim 1, wherein the first pigment is a quinacridone solid solution and the second pigment is C. I. Pigment Red 150.

6. 6. The ink-jet recording method according to claim 1, wherein the durometer hardness of the tube is 35 or more and 45 or less.

7. An inkjet recording method described in any one of claims 1 to 6, wherein the inner diameter of the tube is 1 mm or more and 5 mm or less.

8. The volume-based cumulative 50% particle diameter D of the first pigment １ and the volume-based cumulative 50% particle diameter D of the second pigment. ２ The ink-jet recording method according to claim 1 , wherein

9. The volume-based cumulative 50% particle diameter D of the second pigment ２ is the volume-based cumulative 50% particle diameter D of the first pigment １ The ink jet recording method according to claim 1 , wherein the ink jet recording capacity is greater than or equal to 1000 m / s.

10. The volume-based cumulative 50% particle diameter D of the second pigment ２ The ink-jet recording method according to any one of claims 1 to 9, wherein the thickness of the ink-jet recording layer is 130 nm or more.

11. The inkjet recording method according to claim 1, wherein the second pigment has a volume-based cumulative 50% particle diameter D 2 of 180 nm or less.

12. The volume-based cumulative 50% particle diameter D of the first pigment １ The ink-jet recording method according to any one of claims 1 to 11, wherein the average particle diameter is 110 nm or less.

13. The inkjet recording method according to claim 1, wherein the first pigment has a volume-based cumulative 50% particle diameter D 1 of 80 nm or more.

14. 14. The inkjet recording method according to claim 1, wherein the content (mass %) of the second pigment in the aqueous ink is 0.20 times or more the content (mass %) of the first pigment in the aqueous ink.

15. 15. The inkjet recording method according to claim 1, wherein the content (mass %) of the second pigment in the aqueous ink is 0.80 times or less in mass ratio to the content (mass %) of the first pigment.

16. 16. The inkjet recording method according to claim 1, wherein a content (mass %) of the first pigment in the aqueous ink is from 0.1 mass % to 15.0 mass % based on the total mass of the ink.

17. The inkjet recording method according to claim 1 , wherein the content (mass %) of the second pigment in the aqueous ink is from 0.1 mass % to 15.0 mass % based on the total mass of the ink.

18. The inkjet recording method according to claim 1 , wherein the water-based ink contains a water-soluble resin dispersant for dispersing each of the first pigment and the second pigment.

19. 19. The ink-jet recording method according to any one of claims 1 to 18, wherein the water-based ink is a magenta ink.

20. 20. The inkjet recording method according to claim 1, wherein the recording medium is a recording medium having permeability for the water-based ink.

21. an inkjet recording device comprising: an aqueous ink containing a first pigment and a second pigment; an ink storage section for storing the aqueous ink; a recording head connected to the ink storage section and having an ejection port formed therein for ejecting the aqueous ink supplied from the ink storage section; a capping mechanism for capping the ejection port; a tube for supplying the aqueous ink from the ink storage section to the recording head; and a choke suction mechanism capable of suctioning from the ejection port to reduce pressure inside the ink storage section, The choke suction mechanism has a mechanism for performing choke suction while crushing the tube, the first pigment is at least one selected from the group consisting of a quinacridone pigment, a quinacridone solid solution formed from two or more of the quinacridone pigments, a diketopyrrolopyrrole pigment, and a dioxazine pigment; The ink-jet recording apparatus according to claim 1, wherein the second pigment is at least one selected from the group consisting of azo pigments.

Images