Inkjet recording method, and inkjet recording device

Abstract

To provide an inkjet recording method that uses a miniaturized recording device mounted with a recording unit in which a recording head for discharging ink by heat energy is assembled in an ink storage part, prevents lowering of discharge characteristics while maintaining strength of the recording unit, even in a case of using aqueous ink containing a pigment, and enables recording an image excellent in color developability.SOLUTION: An inkjet recording method records an image using an inkjet recording device which includes aqueous ink, an ink storage part formed of a thermoplastic resin composition containing a filler material, and a recording head for discharging the aqueous ink. The ink storage part has three or more storage parts which are each independently divided, where the storage parts are arrayed in a predetermined one direction, and yellow ink containing C.I. pigment yellow 74 is stored in the storage part arranged inside.SELECTED DRAWING: Figure 4

Description

[Technical field]

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

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

[0003] Some of these inkjet recording devices employ a recording head that ejects ink by the action of thermal energy, from the viewpoint of enabling a more compact design. Also, efforts have been made to miniaturize the recording head by providing ejection port rows that eject ink of multiple colors on the same recording element substrate. Still other inkjet recording devices have a recording unit that is miniaturized by bonding the recording head to the ink storage section without using any other members. The ink storage section is made of a thermoplastic resin to reduce the weight of the recording unit and to reduce the rigidity required for the carriage section, thereby miniaturizing the device.

[0004] However, ink storage parts made only of thermoplastic resins have problems in that they are easily deformed and easily cracked due to external pressure such as impact from being dropped. To solve these problems, an ink storage container has been proposed that is made of a material in which a filler such as a glass filler is added to a thermoplastic resin, thereby reducing the linear expansion coefficient (Patent Document 1). In the case of inkjet recording devices for business use such as remote work at home, a high level of robustness is required even for color images, and thus pigment inks using pigments as color materials are becoming more and more preferred. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-142935 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present inventors have studied the ink storage section formed of a thermoplastic resin composition containing a filler material proposed in Patent Document 1. Specifically, an inkjet recording device was prepared that was equipped with a recording unit (hereinafter, also simply referred to as a "recording unit") formed by bonding a recording head that ejects ink by the action of thermal energy to the above-mentioned ink storage section. Then, an image was recorded using the above-mentioned inkjet recording device in which an aqueous ink containing a pigment was stored in an ink storage section. As a result, it was found that the ejection accuracy of the yellow ink containing CI Pigment Yellow 74 decreased with an increase in the cumulative number of ejections, and ejection irregularities and deformation of the dot shape were likely to occur. In particular, it was found that the ejection accuracy decreased significantly when the recording head was driven at a high frequency. When ejection irregularities and deformation of the dot shape occurred and the ejection accuracy decreased, phenomena such as the ink application position being shifted from the intended position on the recording medium and the dots not being circular occurred, and the image quality decreased.

[0007] Further investigation revealed that when dye ink containing a dye as a coloring material was used, no decrease in ejection accuracy was observed. In addition, an ink storage section formed of a thermoplastic resin containing no filler material was prepared. Then, when an inkjet recording device equipped with a recording unit in which a recording head was bonded to this ink storage section was used, no decrease in ejection accuracy was observed. Furthermore, a recording unit was prepared in which a recording head that ejects ink by the action of mechanical energy using a piezoelectric element was bonded to an ink storage section formed of a thermoplastic resin composition containing a filler material. Then, when an inkjet recording device equipped with this recording unit was used, no decrease in ejection accuracy was observed.

[0008] Therefore, an object of the present invention is to solve the problems that arise when using a recording device equipped with a recording unit in which a recording head is incorporated in an ink storage section formed of a thermoplastic resin composition containing a filler material, and using an aqueous ink containing a pigment. That is, an object of the present invention is to provide an inkjet recording method that uses such a miniaturized recording device and, when discharging an aqueous ink by the action of thermal energy, can record an image with excellent color development while maintaining the strength of the recording unit and preventing a decrease in discharge characteristics. Another object of the present invention is to provide an inkjet recording device used in this inkjet recording method. [Means for solving the problem]

[0009] That is, according to the present invention, there is provided 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 aqueous ink containing a pigment; an ink storage section formed of a thermoplastic resin composition containing a filler material and containing the water-based ink; and a recording head attached to the ink storage section and formed with an ejection port for ejecting the water-based ink supplied from the ink storage section by the action of thermal energy, wherein the ink storage section has three or more storage sections which are divided independently of one another, the storage sections are arranged in a predetermined direction, the water-based ink includes a yellow ink containing CI Pigment Yellow 74, and the yellow ink is contained in the storage section arranged on the inside. Effect of the Invention

[0010] According to the present invention, a recording device equipped with a recording unit in which a recording head is incorporated in an ink storage section formed of a thermoplastic resin composition containing a filler material can be used to solve problems that arise when using aqueous ink containing a pigment. That is, an inkjet recording method can be provided that uses such a miniaturized recording device and ejects aqueous ink by the action of thermal energy, while maintaining the strength of the recording unit, is less likely to deteriorate in ejection characteristics, and can record images with excellent color development. Furthermore, according to the present invention, an inkjet recording device for use in this inkjet recording method can be provided. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view illustrating an embodiment of an inkjet recording apparatus of the present invention. [Diagram 2] 1 is a perspective view showing a schematic internal structure of an inkjet recording apparatus according to an embodiment of the present invention; [Diagram 3] 1A and 1B are diagrams illustrating an example of a recording unit, in which FIG. 1A is a perspective view and FIG. 1B is a perspective view in an exploded state. [Figure 4] 1A and 1B are diagrams showing an example of a recording unit, in which (a) is a diagram seen from above with a tank lid removed, and (b) is a diagram seen from below. [Diagram 5] 11A and 11B are diagrams showing another example of a recording unit, in which (a) is a diagram seen from above with a tank lid removed, and (b) is a diagram seen from below. [Figure 6] FIG. 2 is a schematic diagram showing an example of a suction unit. [Figure 7A] FIG. 4 is a schematic diagram showing an example of an arrangement mode of the storage parts. [Figure 7B] 13 is a schematic diagram showing another example of an arrangement mode of the storage parts. FIG. [Figure 7C] 13 is a schematic diagram showing another example of an arrangement mode of the storage parts. FIG. [Figure 7D] 13 is a schematic diagram showing another example of an arrangement mode of the storage parts. FIG. [Figure 7E] 13 is a schematic diagram showing another example of an arrangement mode of the storage parts. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0013] The present inventors have prepared an inkjet recording device equipped with a recording unit incorporating a recording head that ejects ink by the action of thermal energy in an ink storage section formed of a thermoplastic resin composition containing a filler material, and have investigated the cause of the deterioration of the ejection characteristics of a yellow ink containing CI Pigment Yellow 74 when the recording head is driven at high frequency as the cumulative number of ejections increases when using this inkjet recording device.

[0014] A recording unit in which a recording head is incorporated in an ink reservoir formed of a thermoplastic resin composition containing a filler material is usually stored with the ink reservoir filled with ink, and is set in an inkjet recording device when the device is first used. As a result of the investigation, it was found that inorganic metals such as calcium (Ca), magnesium (Mg), iron (Fe), and aluminum (Al) are eluted from the filler material during storage and are easily dissolved in the ink. When inorganic metals are dissolved in the ink, the dispersion state of the pigment becomes unstable. In addition, in the case of a recording head that ejects ink by the action of thermal energy, the ink becomes hot when foaming, so that the dispersion state of the pigment becomes even more unstable and the pigment is easily aggregated. Here, when dye ink was used, no deterioration in ejection characteristics was confirmed. This is thought to be because dye ink is not easily destabilized even when inorganic metals are dissolved in it.

[0015] The gas barrier properties of the ink storage portion formed of the thermoplastic resin composition containing the filler material are not necessarily high, and therefore, the liquid components such as water in the ink stored in the ink storage portion gradually evaporate, causing the pigment concentration in the ink to relatively increase, destabilizing the pigment dispersion state, and promoting the sedimentation of the pigment, which are thought to be factors in the deterioration of the ejection characteristics.

[0016] Since CI Pigment Yellow 74 has low heat resistance, it may partially melt due to the action of heat generated by the heater to eject the ink, and then cool down, crystallize, and precipitate. The pigment precipitates thus generated are the starting point for the generation of aggregates, which gradually adhere to the ink flow path. As a result, the flow path width becomes narrower, and the ink supply cannot keep up, especially during high-frequency driving, causing ejection irregularities and deformation of the dot shape, and decreasing the ejection accuracy. Further investigation revealed that the above-mentioned decrease in ejection accuracy occurs significantly as the evaporation of liquid components such as water in the ink progresses. It is believed that the relative increase in the pigment content of the ink due to the evaporation of liquid components such as water causes an increase in the amount of attached matter, resulting in a significant decrease in ejection accuracy.

[0017] As a result of the study, the inventors produced an ink storage unit having three or more storage parts that are divided independently from each other and arranged in a predetermined direction. Then, cyan ink, magenta ink, and yellow ink were respectively stored in the storage parts arranged in a row, and the inks were left under conditions that make it easy for the inks to evaporate. After that, the ejection characteristics were evaluated. As a result of these studies, it was found that the occurrence of a decrease in ejection accuracy can be suppressed by storing a yellow ink containing CI Pigment Yellow 74 in a storage part arranged on the inside, and the present invention was achieved. When three or more storage parts are arranged in one direction, water moves from the storage parts arranged on both sides to the storage part arranged on the inside, and the water content of the ink stored in the storage part arranged on the inside increases slightly (humidification). Furthermore, since the storage part arranged on the inside has a relatively small contact area with the outside air, the water stored in the ink is less likely to evaporate compared to the storage parts arranged on both sides. And, it is considered that the decrease in ejection accuracy can be suppressed by storing a yellow ink containing CI Pigment Yellow 74, which is easy to aggregate due to the evaporation of liquid components such as water, in a storage part arranged on the inside.

[0018] <Inkjet recording method and inkjet recording apparatus> The inkjet recording method of the present invention is a recording method using an inkjet recording device including an ink containing a pigment, an ink storage section that stores the ink, and a recording head that is bonded to the ink storage section. The ink storage section is formed of a thermoplastic resin composition that contains a filler material. The recording head is formed with an ejection port that ejects the ink supplied from the ink storage section by the action of thermal energy. The inkjet recording method of the present invention includes a step of applying the ink ejected from the ejection port to a recording medium to record an image. The ink storage section has three or more storage sections that are divided independently of each other, and these storage sections are arranged in a predetermined direction. The ink includes a yellow ink containing CI Pigment Yellow 74, and this yellow ink is stored in the storage section arranged on the inside.

[0019] The inkjet recording device of the present invention is an inkjet recording device including an ink containing a pigment, an ink storage section that stores the ink, and a recording head that is bonded to the ink storage section. The ink storage section is formed of a thermoplastic resin composition that contains a filler material. The recording head is formed with an ejection port that ejects the ink supplied from the ink storage section by the action of thermal energy. The ink storage section has three or more storage sections that are divided independently of each other, and these storage sections are arranged in a predetermined direction. The ink includes a yellow ink that contains CI Pigment Yellow 74, and this yellow ink is stored in the storage section that is arranged on the inside.

[0020] (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. As shown in Fig. 1, an inkjet recording apparatus 70 of this embodiment has an exterior 71 and a cover member 72 provided on the upper surface of the exterior 71. The cover member 72 is a member that can be opened and closed in the vertical direction, and by opening it in the upward direction, the inside of the inkjet recording apparatus 70, which has a substantially rectangular parallelepiped shape, can be seen.

[0021] FIG. 2 is a perspective view showing a schematic internal structure of an embodiment of an inkjet recording device of the present invention. A recording unit 30 in which a recording head and an ink storage unit are integrally formed is configured to be mountable on a carriage (support member) 81, and is mounted on the carriage by connecting to a joint (not shown) provided on the upper part of the carriage 81. The recording unit 30 is connected to a tube 82 which is a flexible member, and the other end of the tube 82 is connected to a main tank (second ink storage unit) 73 which is a second ink storage unit. When the recording unit 30 is mounted on the carriage 81, the recording head 36 (FIG. 3) communicates with the main tank 73 via the joint and the tube 82. The inkjet recording device 70 of this embodiment is a serial scan type recording device, and the carriage 81 is guided by a guide shaft so as to be freely movable in the main scanning direction. The carriage 81 reciprocates in the main scanning direction by a driving force transmission mechanism such as a carriage motor and a belt which transmits the driving force of the carriage motor (both not shown).

[0022] The recording medium is transported in a sub-scanning direction perpendicular to the main scanning direction of the carriage 81 by the transport roller. The inkjet recording device 70 moves the recording head 36 (FIG. 3) in the main scanning direction while repeatedly performing a recording operation in which ink is ejected toward a recording area of ​​the recording medium on the platen, and a transport operation in which the recording medium is transported in the sub-scanning direction by a distance corresponding to the recording width. In this way, images are sequentially recorded on the recording medium.

[0023] FIG. 3 is a drawing showing an example of a recording unit, where (a) is a perspective view and (b) is a perspective view in an exploded state. The recording unit shown in FIG. 3 has an ink storage section 37, which is a housing formed of a thermoplastic resin composition containing a filler material, and a recording head 36. Examples of the thermoplastic resin composition include polyester, polycarbonate, polypropylene, polyethylene, polystyrene, polyphenylene ether, and mixtures or modified products thereof. Examples of the filler material include flake fillers such as mica and fibrous fillers such as glass fiber. Glass fiber is a material called E-glass (alkali-free glass), and is generally cut to a predetermined length (chopped strands). It is preferable that the recording head 36 is bonded to the ink storage section 37 without any other members. The ink storage section 37 is lightweight because it is a housing formed of a thermoplastic resin composition. By bonding the recording head 36 to the ink storage section 37 without any other members such as a heat sink, the entire recording unit is made smaller and lighter. By using such a recording unit, the inkjet recording device as a whole can be made smaller and lighter. The heat sink can be made of a material such as a metal oxide, such as alumina. In addition, the ink storage section 37 made of a thermoplastic resin composition containing a filler has a lower linear expansion coefficient than one made of a thermoplastic resin that does not contain a filler. This prevents the housing from being deformed and also prevents cracks caused by external pressure, such as when the housing is dropped.

[0024] The recording head 36 is provided with a plurality of ejection ports for ejecting ink, thermal energy generating elements for generating thermal energy for ejecting ink, and the like. The thermal energy generating elements can be driven by, for example, power supplied through the electrical wiring member 32. The thermal energy generating elements are elements that generate thermal energy, and can eject ink from the ejection ports by the action of the generated thermal energy. An example of the element that generates thermal energy is an electrothermal converter.

[0025] The recording head 36 has an ejection port surface in which multiple ejection port arrays each consisting of multiple ejection ports are arranged on the same recording element substrate. By arranging multiple ejection port arrays on the same recording element substrate, it is possible to eject multiple inks with one recording unit, and the inkjet recording device can be made smaller. It is preferable that the multiple ejection port arrays are arranged in a direction (sub-scanning direction) perpendicular to the reciprocating movement direction (main scanning direction) of the recording unit in which the recording head is incorporated. In addition, by configuring the ejection port array with multiple ejection ports, the area that can be printed during the reciprocating movement of the recording head is widened, allowing for faster printing.

[0026] Sponge-like ink absorbers 34a to 34c are stored in the ink storage section 37. Filters 35a to 35c are disposed below the ink storage section 37 in the direction of gravity. By using the capillary force of the sponge-like ink absorbers 34a to 34c to generate negative pressure, it is possible to prevent ink from leaking from the ejection openings. Furthermore, by disposing the filters 35a to 35c, it is possible to prevent fine foreign matter such as dust from entering the ejection openings. Furthermore, by providing the tank lid 33 by thermocompression bonding above the ink storage section 37 in the direction of gravity, it is possible to prevent ink from leaking from the ink storage section 37.

[0027] The printhead preferably has a heating means for heating the ink in the printhead. The heating means may be any means capable of heating the ink in the printhead to a temperature higher than the printing environment temperature, such as room temperature (25° C.). Examples of such heating means include a heater for adjusting the ink temperature, which is disposed in contact with the printhead, and a heater for ink ejection. To heat the ink using a heater for ink ejection, for example, a current that is not strong enough to eject the ink may be repeatedly applied.

[0028] The inkjet recording device preferably further includes a second ink storage unit such as a main tank having a larger capacity than the ink storage unit (first ink storage unit) such as a sub-tank, and a tube through which ink flows between the second ink storage unit and the ink storage unit. Considering the usage mode in remote work at home, it is important to reduce the frequency of replacing the ink cartridge as well as to reduce the size of the device. For this reason, by further providing a second ink storage unit such as a main tank, it is possible to reduce the frequency of ink replacement while avoiding an increase in the size of the device body. Hereinafter, an inkjet recording device in which only a first ink storage unit such as a sub-tank bonded to the recording head is provided as an ink storage unit is also referred to as a "first device configuration". In the case of the first device configuration, when the ink stored inside the ink storage unit is consumed, it is replaced with another ink storage unit (ink storage unit filled with ink). Therefore, compared to the second device configuration, the main tank and tube can be omitted, and the weight of the inkjet recording device can be reduced. An inkjet recording device further provided with a second ink containing unit, such as a main tank having a larger capacity than the sub-tank, as an ink containing unit, is also referred to as a "second device configuration." In the case of the second device configuration, for example, by forming a connection part for connecting to a tube on the tank lid 33 shown in FIG. 3, the ink containing unit 37 and the second ink containing unit, such as the main tank, can be connected.

[0029] In the case of the second device configuration, the frequency of ink replacement is reduced compared to the first device configuration, so that the period during which the ink is held in a stationary state in the main tank is longer. In addition, in the case of pigment ink, the pigment is more likely to settle if the period during which the ink is held in a stationary state is longer. The decrease in ejection performance due to adhesion occurs due to the ink drying in the flow path and the pigment coagulating, so it becomes more noticeable when an ink with a higher pigment content is used. Depending on the usage conditions, the ejection characteristics of the second device configuration are more likely to decrease than those of the first device configuration. In particular, when an ink containing CI Pigment Yellow 74 is ejected from a recording head that uses thermal energy, the ejection characteristics are likely to decrease significantly. In contrast, the inkjet recording method of the present invention can achieve both a reduction in the frequency of ink replacement and an improvement in ejection characteristics.

[0030] FIG. 4 is a diagram showing an example of a recording unit, where (a) is a view from above with the tank lid removed, and (b) is a view from below (the recording head side). As shown in FIG. 4, the ink storage section 37 has three or more storage sections 31a to 31c that are divided independently from each other. These storage sections 31a to 31c are divided by a partition section 50 made of the same material as the housing, for example, and can store multiple types of ink individually. In addition, the recording head 36 has an ejection port surface in which multiple ejection port rows 38a to 38c consisting of multiple ejection ports are arranged on the same recording element substrate. These ejection port rows 38a to 38c correspond to the multiple types of ink stored individually in the storage sections 31a to 31c, respectively. The storage sections 31a to 31c are arranged in a predetermined direction, and a yellow ink containing CI Pigment Yellow 74 is stored in the storage section 31b arranged on the inside of the storage sections 31a to 31c. Since the inside storage portion 31b has a relatively small contact area with the outside air, water is less likely to evaporate from the stored yellow ink compared to the storage portions 31a and 31c located on both sides. Furthermore, water moves from the storage portions 31a and 31c located on both sides to the inside storage portion 31b, causing the water content of the yellow ink stored in the storage portion 31b to increase slightly (become humidified). This is thought to suppress the aggregation of CI Pigment Yellow 74 in the yellow ink stored in the storage portion 31b, and to suppress a decrease in the ejection accuracy of the yellow ink.

[0031] FIG. 5 is a drawing showing another example of the recording unit, where (a) is a view from above with the tank lid removed, and (b) is a view from below (the recording head side). The ink storage section 57 shown in FIG. 5 has three or more storage sections 51a to 51c that are divided independently of each other, and these storage sections 51a to 51c are arranged in a predetermined direction. The arrangement direction of the multiple storage sections may be in one predetermined direction. For example, they may be arranged in a direction perpendicular to the main scanning direction of the recording head 36 as shown in FIG. 4, or they may be arranged in a direction parallel to the main scanning direction of the recording head 36 as shown in FIG. From the viewpoint of the strength of the ink storage section, it is particularly preferable that the arrangement direction of the multiple storage sections is arranged in a direction perpendicular to the main scanning direction of the recording head 36.

[0032] The ratio (A / B) of the length A in the longitudinal direction (sub-scanning direction) of the ink storage section to the length B in the lateral direction (main scanning direction) is preferably 2.0 times or more and 4.0 times or less (FIG. 4(a)). By making the A / B ratio 2.0 times or more, the width of the device can be made compact. In order to record an image on the entire surface of a recording medium using a so-called serial type inkjet recording device that records an image while scanning the recording head back and forth in the main scanning direction perpendicular to the conveying direction of the recording medium, it is necessary to move the ejection port array from one end of the recording medium to the other end. If the width of the recording head is wide, the width of the inkjet recording device will inevitably be wide. In addition, if the A / B ratio of the ink storage section is too large, when an external force is applied to the housing, stress is concentrated in the longitudinal direction, and deformation due to insufficient strength of the housing may easily occur. For this reason, the A / B ratio is preferably 4.0 times or less.

[0033] FIG. 6 is a schematic diagram showing an example of a suction means. As shown in FIG. 6, the inkjet recording device includes a cap 61 that abuts against an area including the discharge port surface of the recording head 36 and covers a plurality of discharge port rows. A tube 63 that functions as an air communication part and a waste ink tube 66 that discharges waste ink that is accumulated in the cap 61 and is not used for recording are connected to the cap 61. An air communication valve 62 is provided in the middle of the tube 63. Waste ink discharged from the discharge ports of the recording head 36 is stored in a waste ink storage part 67. A suction valve 64 is provided in the middle of the waste ink tube 66, and a suction operation is performed to discharge unnecessary waste ink using a pump 65. In this example, the suction operation using a pump provided downstream of the recording head has been described as an example, but waste ink not used for recording may be discharged from the discharge ports by a pressurizing operation using a pump provided upstream of the recording head.

[0034] In cases where ink dries and solidifies in the flow passages connected to the ejection ports, making it difficult to eject ink normally, the state where it is difficult to eject ink normally can be resolved by circulating new ink from the ink storage section 37 through a suction operation. Normally, when multiple ejection port rows are arranged on the same recording element substrate, the suction operation is performed using the same cap. For example, when ejection port rows for ejecting cyan ink, magenta ink, and yellow ink are arranged on the same recording element substrate, these inks are sucked together using the same cap. Generally, when inks that are easy to remove from the solidification and inks that are difficult to remove from the solidification are mixed, it is necessary to continue the suction operation for the inks that are difficult to remove from the solidification, even though the solidification of the ejection ports ejecting the inks that are easy to remove from the solidification has been removed. In addition, inks with poor ejection characteristics may tend to increase the amount of wasted ink.

[0035] (Water-based ink) The inkjet recording method of the present invention includes a step of recording an image by using an ink containing a pigment and applying the ink ejected from an ejection port to a recording medium. The ink includes a yellow ink. The ink usually further includes an ink of a hue other than yellow. Examples of the ink of a hue other than yellow include magenta ink and yellow ink. The components constituting the ink are described below. When it is not necessary to distinguish between cyan ink, magenta ink, and yellow ink, each ink is collectively referred to as "ink". Within the scope of the preferred embodiments shown below, the inks of each color may have the same composition or different compositions.

[0036] [Colorant] Pigments are used as the coloring material for the ink in order to improve the fastness of images, etc. CI Pigment Yellow 74 must be used for the yellow ink contained in the innermost storage section among three or more storage sections arranged in a predetermined direction.

[0037] Examples of the pigment include organic pigments such as azo pigments, phthalocyanine pigments, quinacridone pigments, isoindolinone pigments, imidazolone pigments, diketopyrrolopyrrole pigments, and dioxazine pigments. The pigment for the yellow ink is CI Pigment Yellow 74, which is an azo pigment. Examples of the pigment for other inks (cyan ink, magenta ink, etc.) that can be used together with the yellow ink include phthalocyanine pigments, dioxazine pigments, quinacridone pigments, azo pigments, and diketopyrrolopyrrole pigments.

[0038] The pigment content (mass %) in the ink is preferably from 0.50 to 10.00 mass %, and more preferably from 1.00 to 8.00 mass %, based on the total mass of the ink.

[0039] The ink includes a yellow ink containing CI Pigment Yellow 74. The content (mass %) of CI Pigment Yellow 74 in the yellow ink is preferably 0.50 mass % or more and 10.00 mass % or less, and more preferably 1.00 mass % or more and 8.00 mass % or less, based on the total mass of the yellow ink.

[0040] Examples of pigment dispersion methods include resin-dispersed pigments that use a resin (resin dispersant) as a dispersant, and self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface. In addition, resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microcapsule pigments in which the pigment particle surface is coated with a resin, etc. can be used. Among these, it is particularly preferable to use a resin-dispersed pigment in which a resin dispersant having a hydrophobic portion and a hydrophilic portion is used, the hydrophobic portion of the resin dispersant is adsorbed to the pigment particle surface, and the pigment is dispersed by the hydrophilic portion.

[0041] As the resin dispersant, it is preferable to use a resin that can disperse the pigment in an aqueous medium by the action of an anionic group. As the resin dispersant, a water-soluble resin described below can be used. When a resin-dispersed pigment is used, the content (mass%) of the pigment in the ink is preferably 0.3 to 10.0 times the content (mass%) of the resin dispersant in terms of mass ratio.

[0042] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0043] [resin] The ink may contain a resin such as a water-soluble resin. The content (mass%) of the resin in the ink is preferably 0.10% by mass or more and 20.00% by mass or less, and more preferably 0.50% by mass or more and 15.00% by mass or less, based on the total mass of the ink. 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. Also, the resin may be added to the ink (ii) to improve various properties of the recorded image. Examples of the form of the resin include block copolymers, random copolymers, graft copolymers, and combinations thereof. The resin may be a water-soluble resin that can be dissolved in an aqueous medium, or may be resin particles that are dispersed in an aqueous medium.

[0044] Examples of the resin include acrylic resin, urethane resin, and olefin resin. Among them, acrylic resin and urethane resin are preferred, and acrylic resin is more preferred. The acrylic resin is preferably one having a hydrophilic unit as a hydrophilic part and a hydrophobic unit as a hydrophobic part as a constituent unit. The hydrophilic unit is a unit having a hydrophilic group such as an anionic group. The hydrophilic unit can be formed, for example, by polymerizing a hydrophilic monomer having a hydrophilic group. Examples of the hydrophilic monomer having a hydrophilic group include acidic monomers having a carboxylic acid group such as (meth)acrylic acid, itaconic acid, maleic acid, and fumaric acid; anionic monomers such as anhydrides and salts of these acidic monomers; and the like. Examples of the cations constituting the salts of the acidic monomers include ions such as lithium, sodium, potassium, ammonium, and organic ammonium. The hydrophobic unit is a unit that does not have a hydrophilic group such as an anionic group. The hydrophobic unit can be formed, for example, by polymerizing a hydrophobic monomer that does not have a hydrophilic group such as an anionic group. Examples of hydrophobic monomers include monomers having an aromatic ring, such as styrene, α-methylstyrene, and benzyl (meth)acrylate; and (meth)acrylic acid ester monomers, such as methyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.

[0045] The yellow ink preferably contains a water-soluble resin having a unit derived from styrene. Since CI Pigment Yellow 74 has a benzene ring, it strongly interacts with the benzene ring derived from styrene in the water-soluble resin. Therefore, the water-soluble resin having a unit derived from styrene is easily adsorbed to the surface of CI Pigment Yellow 74, and can suppress the crystallization of CI Pigment Yellow 74. As a result, it is possible to suppress the generation of adhesion, and the decrease in ejection accuracy can be further suppressed. The content (mass %) of the unit derived from styrene in the water-soluble resin is preferably 10.00 mass % or more, and more preferably 15.00 mass % or more and 30.00 mass % or less, based on the total mass of the water-soluble resin. If the content of the unit derived from styrene is less than 10.00 mass %, the adsorption of the water-soluble resin to CI Pigment Yellow 74 may be weak, and the effect of suppressing the crystallization of CI Pigment Yellow 74 may be slightly reduced.

[0046] The urethane resin can be obtained, for example, by reacting a polyisocyanate with a polyol. In addition, a chain extender may be further reacted with the urethane resin. Examples of the olefin resin include polyethylene and polypropylene.

[0047] In this specification, "a resin is water-soluble" means that when the resin is neutralized with an alkali equivalent to the acid value, it exists in an aqueous medium in a state in which it does not form particles whose particle size can be measured by dynamic light scattering. Whether or not a resin is water-soluble can be determined according to the following method. First, a liquid (resin solid content: 10 mass%) containing a resin neutralized with an alkali (sodium hydroxide, potassium hydroxide, etc.) equivalent to the acid value is prepared. Next, the prepared liquid is diluted 10 times (volume basis) with pure water to prepare a sample solution. Then, when the particle size of the resin in the sample solution is measured by dynamic light scattering, if particles having a particle size are not measured, the resin can be determined to be water-soluble. On the other hand, if particles having a particle size are measured, the resin can be determined to be "resin particles" (i.e., "water-dispersible resin"). The measurement conditions at this time can be, for example, as follows. [Measurement conditions] SetZero: 30 seconds Number of measurements: 3 Measurement time: 180 seconds

[0048] As the particle size distribution measuring device, a particle size analyzer using a dynamic light scattering method (for example, the product name "UPA-EX150" manufactured by Nikkiso Co., Ltd.) can be used. Of course, the particle size distribution measuring device and the measurement conditions to be used are not limited to those described above.

[0049] [Aqueous medium] The ink is an aqueous ink containing an aqueous medium that is water or a mixed solvent of water and a water-soluble organic solvent. As the water, deionized water (ion-exchanged water) is preferably used. The content (mass%) of water in the ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of the ink.

[0050] The water-soluble organic solvent may be any of those usable in inkjet inks, such as alcohols, glycols, (poly)alkylene glycols, nitrogen-containing compounds, and sulfur-containing compounds. The content (mass %) of the water-soluble organic solvent in the ink is preferably 3.00% by mass or more and 50.00% by mass or less, based on the total mass of the ink.

[0051] The yellow ink preferably further contains a first water-soluble organic solvent having a relative dielectric constant of 37.0 or more. The content (mass%) of the first water-soluble organic solvent in the yellow ink is preferably 1.2 times or more and 2.0 times or less, more preferably 1.4 times or more and 1.8 times or less, in terms of mass ratio to the content (mass%) of CI Pigment Yellow 74. If the mass ratio is less than 1.2 times, the pigment dispersion state becomes unstable and tends to aggregate, and the effect of suppressing the decrease in ejection accuracy may decrease. On the other hand, if the mass ratio is more than 2.0 times, the amount of the water-soluble organic solvent having a high relative dielectric constant becomes excessive relative to CI Pigment Yellow 74. For this reason, CI Pigment Yellow 74 becomes more soluble, and the amount of deposits that crystallize and precipitate may increase, and the effect of suppressing the decrease in ejection accuracy may decrease.

[0052] The content (mass%) of the first water-soluble organic solvent in the yellow ink is preferably 5.00% by mass or more and 10.00% by mass or less based on the total mass of the yellow ink. Examples of the first water-soluble organic solvent include glycerin (42.3), 2-hydroxyethyl-2-pyrrolidone (37.6), ethylene glycol (40.4), and ethyleneurea (49.7) (the numbers in parentheses are the relative dielectric constants at 25°C). The first water-soluble organic solvent is preferably one that has a lower vapor pressure than water or a relative dielectric constant of 150.0 or less.

[0053] The relative dielectric constant of a water-soluble organic solvent can be measured using a dielectric constant meter (for example, trade name "BI-870" manufactured by BROOKHAVEN INSTRUMENTS CORPORATION) at a frequency of 10 kHz. The relative dielectric constant of a water-soluble organic solvent that is solid at 25°C is a value calculated from the relative dielectric constant of a 50% by mass aqueous solution measured using the following formula (A). Usually, "water-soluble organic solvents" are liquids, but in the present invention, for the sake of convenience, those that are solid at 25°C (room temperature) are also included in the water-soluble organic solvent. ε sol =2ε 50% -ε water (A) ε sol : Dielectric constant of solid water-soluble organic solvent at 25℃ ε 50% : Relative dielectric constant of a 50% by mass aqueous solution of a solid water-soluble organic solvent at 25°C ε water : relative dielectric constant of water

[0054] Examples of water-soluble organic solvents that are generally used in aqueous inks and are solid at 25°C include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, and polyethylene glycol with a number-average molecular weight of 1,000. The reason for determining the relative dielectric constant of a water-soluble organic solvent that is solid at 25°C from the relative dielectric constant of a 50% by mass aqueous solution is as follows. Among water-soluble organic solvents that are solid at 25°C and can be used as components of aqueous inks, it is difficult to prepare a high-concentration aqueous solution of more than 50% by mass. On the other hand, in a low-concentration aqueous solution of 10% by mass or less, the relative dielectric constant of water becomes dominant, and it is not possible to obtain a reliable (effective) relative dielectric constant value of the water-soluble organic solvent. As a result of the inventors' investigation, it was found that the aqueous solution to be measured can be prepared from almost all of the water-soluble organic solvents that are solid at 25°C and can be used in inks, and the relative dielectric constant to be determined is consistent with the effect of the present invention. For these reasons, it was decided to use a 50% by mass aqueous solution. For water-soluble organic solvents that are solid at 25°C and cannot be prepared as a 50% aqueous solution due to their low solubility in water, use an aqueous solution of the saturated concentration and use the above ε solFor convenience, the value of the relative dielectric constant calculated in accordance with the case of determining

[0055] Other water-soluble organic solvents other than the first water-soluble organic solvent having a relative dielectric constant of less than 37.0 include trimethylolpropane (33.7), N-methyl-2-pyrrolidone (32.0), triethanolamine (31.9), diethylene glycol (31.7), 1,4-butanediol (31.1), 1,3-butanediol (30.0), 1,2-propanediol (28.8), 1,2,6-hexanetriol (28.5), 2-methyl- 1,3-propanediol (28.3), 2-pyrrolidone (28.0), 1,5-pentanediol (27.0), 3-methyl-1,3-butanediol (24.0), 3-methyl-1,5-pentanediol (23.9), 1-(hydroxymethyl)-5,5-dimethylhydantoin (23.7), triethylene glycol (22.7), 1,2-butanediol (22.2), tetraethylene glycol (20.8), dipropylene glycol Examples of dielectric constants include propylene glycol (19.7), polyethylene glycol having a number average molecular weight of 200 (18.9), 2-ethyl-1,3-hexanediol (18.5), 1,3-bis(2-hydroxyethyl)-5,5-dimethylhydantoin (16.0), 1,2-hexanediol (14.8), propylene glycol monomethyl ether (12.4), polyethylene glycol having a number average molecular weight of 600 (11.4), diethylene glycol monobutyl ether (11.0), triethylene glycol monobutyl ether (9.8), ethylene glycol monobutyl ether (9.4), tetraethylene glycol monobutyl ether (9.4), tripropylene glycol monomethyl ether (8.5), 1,6-hexanediol (7.1), and polyethylene glycol having a number average molecular weight of 1,000 (4.6) (the numbers in parentheses are the relative dielectric constants at 25°C). As the other water-soluble organic solvent, those having a vapor pressure lower than that of water and a relative dielectric constant of 2.0 or more are preferable.

[0056] [Surfactants] The ink preferably further contains a surfactant. Examples of the surfactant include anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants, and other surfactants. Of these, it is preferable to use a nonionic surfactant.

[0057] Examples of anionic surfactants include polyoxyethylene alkyl ether sulfate salts, polyoxyethylene alkyl ether sulfonates, polyoxyethylene alkyl phenyl ether sulfate salts, polyoxyethylene alkyl phenyl ether sulfonates, alpha sulfo fatty acid ester salts, alkyl benzene sulfonates, alkyl phenol sulfonates, alkyl naphthalene sulfonates, alkyl tetralin sulfonates, and dialkyl sulfosuccinates. Examples of cationic surfactants include alkyl trimethyl ammonium salts and dialkyl dimethyl ammonium chlorides.

[0058] Examples of nonionic surfactants include acetylene glycol surfactants, polyoxyethylene alkyl ethers, polyoxyethylene fatty acid esters, polyoxyethylene alkyl phenyl ethers, fatty acid diethanolamides, and polyoxyethylene-polyoxypropylene block copolymers. Examples of amphoteric surfactants include alkyl carboxybetaines. Other examples of surfactants include fluorine-based surfactants, silicon-based surfactants, and the like.

[0059] The content (mass %) of the surfactant in the ink is preferably from 0.10 to 5.00% by mass, and more preferably from 0.10 to 2.00% by mass, based on the total mass of the ink.

[0060] The yellow ink preferably contains an acetylene glycol surfactant. The acetylene glycol surfactant has a good balance between the amount added to the ink and the ability to reduce surface tension, and the amount added suitable for adjusting the surface tension of the ink is an amount that appropriately suppresses the crystallization of CI Pigment Yellow 74, so it is suitable. In the case of a surfactant with too high an ability to reduce surface tension, it may be difficult to add an amount to the ink that suppresses the crystallization of CI Pigment Yellow 74. On the other hand, in the case of a surfactant with too low an ability to reduce surface tension, although it is possible to suppress the crystallization of CI Pigment Yellow 74, the ink may be easily foamed due to the large amount added, which may cause a decrease in ejection accuracy. Since the acetylene glycol surfactant has antifoaming properties, even if the amount added is increased to a certain extent, a decrease in ejection accuracy due to foaming is unlikely to occur.

[0061] The content (mass%) of the acetylene glycol surfactant in the yellow ink is preferably 1.50% by mass or more and 2.50% by mass or less, and more preferably 1.80% by mass or more and 2.20% by mass or less, based on the total mass of the yellow ink. If the content of the acetylene glycol surfactant is less than 1.50% by mass, it may be difficult to act on CI Pigment Yellow 74, and the effect of suppressing crystallization may be reduced. On the other hand, if the content of the acetylene glycol surfactant is more than 2.50% by mass, it may be easy for the ejection accuracy to decrease due to foaming.

[0062] The content (mass %) of the acetylene glycol surfactant in the yellow ink is preferably 0.3 to 0.6 times the content (mass %) of CI Pigment Yellow 74. Of these, 0.4 to 0.5 times is more preferable. If the mass ratio is less than 0.3, the effect of suppressing crystallization may decrease. On the other hand, if the mass ratio is more than 0.6, the pigment dispersion state may become unstable, and the pigment may easily aggregate, which may lead to a decrease in ejection accuracy.

[0063] The yellow ink preferably further contains a compound represented by the following general formula (1). The compound represented by general formula (1) has hydrophobic propylene oxide groups that interact with the pigment and alternates with ethylene oxide groups, so it has many adsorption points to the pigment (CI Pigment Yellow 74) and adsorbs to cover the pigment. For this reason, by including the compound represented by general formula (1) in the yellow ink, it is possible to further suppress crystallization of the pigment.

[0064] TIFF2025024682000002.tif22170 (in the general formula (1), p+r represents a number of 3.0 or more and 27.0 or less, and q represents a number of 16.0 or more and 31.0 or less)

[0065] In the yellow ink, the content (mass%) of the compound represented by general formula (1) is preferably 0.80% by mass or more and 1.20% by mass or less, and more preferably 0.90% by mass or more and 1.10% by mass or less, based on the total mass of the yellow ink. If the content of the compound represented by general formula (1) is less than 0.80% by mass, the amount is too small to act on CI Pigment Yellow 74, and the effect of suppressing crystallization may decrease. On the other hand, if the content of the compound represented by general formula (1) is more than 1.20% by mass, the ejection accuracy may be easily reduced due to foaming.

[0066] The content (mass%) of the compound represented by formula (1) in the yellow ink is preferably 0.1 to 0.3 times the content (mass%) of CI Pigment Yellow 74. If the mass ratio is less than 0.1, the amount of the compound represented by formula (1) is too small, and the effect of suppressing crystallization may decrease. On the other hand, if the mass ratio is more than 0.3, the pigment dispersion state may become unstable, and the pigment may easily aggregate, which may lead to a decrease in ejection accuracy.

[0067] [Other ingredients] 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. These additives are not included in the measurement of the relative dielectric constant.

[0068] [Ink properties] The ink is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the static surface tension of the ink at 25°C is preferably 28 mN / m or more and 45 mN / m or less. Furthermore, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 5.0 mPa·s or less, and more preferably 1.0 mPa·s or more and 3.0 mPa·s or less. The pH of the ink at 25°C is preferably 5.0 or more and 9.5 or less. EXAMPLES

[0069] 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.

[0070] <Preparation of pigment dispersion> (Pigment dispersion 1) A styrene-acrylic acid copolymer with an acid value of 120 mgKOH / g and a weight average molecular weight of 10,000 was neutralized with a 10% potassium hydroxide aqueous solution. 10.0 parts of CI Pigment Yellow 74, 3.0 parts of the neutralized styrene-acrylic acid copolymer (solid content), and 85.0 parts of ion-exchanged water were mixed to obtain a mixture. The mixture obtained was dispersed for 1 hour using a sand grinder, and then centrifuged to remove coarse particles. The mixture was then filtered under pressure using a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to obtain Pigment Dispersion Liquid 1 in which CI Pigment Yellow 74 was dispersed in water by the resin. The pigment content in Pigment Dispersion Liquid 1 was 15.00%, and the resin dispersant content was 4.50%.

[0071] (Pigment dispersion 2) A styrene / n-butyl acrylate / acrylic acid copolymer with an acid value of 120 mgKOH / g and a weight average molecular weight of 10,000 was neutralized with a 10% potassium hydroxide aqueous solution. 10.0 parts of CI Pigment Yellow 74, 3.0 parts of the neutralized styrene / n-butyl acrylate / acrylic acid copolymer (solid content), and 85.0 parts of ion-exchanged water were mixed to obtain a mixture. The mixture obtained was dispersed for 1 hour using a sand grinder, and then centrifuged to remove coarse particles. Furthermore, the mixture was filtered under pressure with a microfilter (manufactured by Fujifilm) with a pore size of 3.0 μm to obtain a pigment dispersion liquid 2 in which CI Pigment Yellow 74 was dispersed in water by a resin. The pigment content in the pigment dispersion liquid 2 was 15.00%, and the resin dispersant content was 4.50%.

[0072] (Pigment dispersion 3) Pigment Dispersion Liquid 3 was obtained in the same manner as in Pigment Dispersion Liquid 1 described above, except that CI Pigment Yellow 155 was used instead of CI Pigment Yellow 74. The pigment content in Pigment Dispersion Liquid 3 was 15.00%, and the resin dispersant content was 4.50%.

[0073] (Pigment Dispersion 4) Pigment Dispersion Liquid 4 was obtained in the same manner as Pigment Dispersion Liquid 1 described above, except that CI Pigment Blue 15:3 was used instead of CI Pigment Yellow 74. The pigment content in Pigment Dispersion Liquid 4 was 15.00%, and the resin dispersant content was 4.50%.

[0074] (Pigment Dispersion 5) Pigment Dispersion 5 was obtained in the same manner as Pigment Dispersion 1 described above, except that CI Pigment Blue 15:4 was used instead of CI Pigment Yellow 74. The pigment content in Pigment Dispersion 5 was 15.00%, and the resin dispersant content was 4.50%.

[0075] (Pigment Dispersion 6) Pigment Dispersion Liquid 6 was obtained in the same manner as in Pigment Dispersion Liquid 1 described above, except that CI Pigment Red 122 was used instead of CI Pigment Yellow 74. The pigment content in Pigment Dispersion Liquid 6 was 15.00%, and the resin dispersant content was 4.50%.

[0076] (Pigment Dispersion 7) Pigment Dispersion 7 was obtained in the same manner as in Pigment Dispersion 1 described above, except that CI Pigment Violet 19 was used instead of CI Pigment Yellow 74. The pigment content in Pigment Dispersion 7 was 15.00%, and the resin dispersant content was 4.50%.

[0077] (Pigment Dispersion 8) Pigment dispersion 8 was obtained in the same manner as in the above-mentioned Pigment Dispersion 1, except that CI Pigment Red 150 was used instead of CI Pigment Yellow 74. The pigment content in Pigment Dispersion 8 was 15.00%, and the resin dispersant content was 4.50%.

[0078] <Preparation of dye-containing liquid> Dyes 1 to 3 shown below were each dissolved in ion-exchanged water to obtain liquids containing dyes 1 to 3, respectively (dye content: 15.00%). Dye 1: CI Direct Yellow 132 Dye 2: CI Direct Blue 199 Dye 3: CI Acid Red 289

[0079] <Preparation of Water-Soluble Resin> Each component (unit: parts) shown in Table 1 was copolymerized according to a conventional method to obtain water-soluble acrylic resins 1 to 5. The obtained water-soluble acrylic resin was neutralized with potassium hydroxide in an amount equimolar to the acid value, and then an appropriate amount of pure water was added to obtain liquids containing water-soluble acrylic resins 1 to 5, each with an acrylic resin (solid content) content of 20.00%. The meanings of the abbreviations in Table 1 are as follows. St: styrene MMA: Methyl methacrylate ·AA: Acrylic acid

[0080] TIFF2025024682000003.tif60170

[0081] <Ink Preparation> Each ink was prepared by mixing the components (unit: %) shown in the upper part of Tables 2-1 to 2-4, thoroughly stirring, and then filtering under pressure with a polypropylene filter (manufactured by Pall) having a pore size of 2.5 μm. In Tables 2-1 to 2-4, the numerical value attached to the polyethylene glycol is the number average molecular weight. In addition, "Acetylenol E100" and "Acetylenol E60" are both the trade names of acetylene glycol-based nonionic surfactants (manufactured by Kawaken Fine Chemicals). In addition, "Pluronic (registered trademark) L31" is the trade name of a Pluronic (registered trademark)-based surfactant (manufactured by Adeka), and "Zonyl FS3100" is the trade name of a fluorine-based surfactant (manufactured by Chemours). In Tables 2-1 to 2-4, the numerical value in parentheses attached to the water-soluble organic solvent indicates the relative dielectric constant.

[0082] TIFF2025024682000004.tif242170

[0083] TIFF2025024682000005.tif241170

[0084] TIFF2025024682000006.tif241170

[0085] TIFF2025024682000007.tif255157

[0086] <Recording unit configuration> A recording head was prepared that ejects ink by applying thermal energy. A recording element substrate constituting the recording head has an ejection port array in which 384 ejection ports are arranged at an array density of 600 dpi. The mass of an ink droplet ejected from one ejection port is 5.5 ng. A thermoplastic resin composition was molded to obtain recording units 1 to 9 having storage portions arranged in the manner shown in Figs. 7A to 7E. The thermoplastic resin composition used was a mixture of 100 parts of a thermoplastic resin, which is a mixture of a styrene-based resin and polyphenylene ether, to which 25 parts of chopped strands of E glass having a length of 5 mm were added as a filler material. The properties of the obtained recording unit are shown in Table 3.

[0087] In the ink storage section 37 shown in FIG. 7A, three storage parts a to c are arranged in a direction perpendicular to the scanning direction of the recording head. In the ink storage section 77 shown in FIG. 7B, three storage parts a to c are arranged in a direction perpendicular to the scanning direction of the recording head. In the ink storage section 87 shown in FIG. 7C, three storage parts a to c are arranged in a direction perpendicular to the scanning direction of the recording head. In the ink storage section 107 shown in FIG. 7D, three storage parts a to c are arranged in a direction parallel to the scanning direction of the recording head. In the ink storage section 117 shown in FIG. 7E, three storage parts a to c are arranged in a T-shape, not in one direction. The recording units 7 and 8 shown in Table 3 were obtained by molding a thermoplastic resin that is a mixture of a styrene resin and polyphenylene ether, that is, a thermoplastic resin to which no filler material is added. Then, a recording head was attached to the obtained ink storage section without interposing any other member, to manufacture a recording unit.

[0088] TIFF2025024682000008.tif75170

[0089] <Evaluation> (Inkjet recording device) As the device 1, a product name "PIXUS TS5130S" (manufactured by Canon) was prepared as an inkjet recording device of the type in which the ink contained in the ink container (ink cartridge) is replaced with a new ink container filled with ink when the ink is consumed. As the device 2, a product name "G3370" (manufactured by Canon) was prepared as an inkjet recording device of the type in which the ink container (sub tank) on the carriage and the ink container (main tank) placed inside the device are connected by a tube through which the ink flows. These devices were modified so that the recording unit prepared above could be mounted. In this embodiment, the recording duty of a solid image recorded under the condition that two ink droplets with a mass of 5.5 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 were set to "AA", "A", and "B" as acceptable levels and "C" as unacceptable levels. The evaluation results are shown in Tables 4-1 and 4-2. In Tables 4-1 and 4-2, the symbols (a to c) indicating the positions of each color ink correspond to the symbols (a to c) in FIGS. 7A to 7E.

[0090] (Strength of ink storage section) To promote thermal deformation of the ink storage part (housing), the recording unit was stored in an environment at a temperature of 60°C for one month. With the top surface of the ink storage part facing downward in the direction of gravity and the ejection port surface of the recording head facing upward, the recording unit was dropped twice onto lauan wood from a height of 80 cm. After the drop, the ink storage part of the recording unit was visually observed and the strength of the ink storage part was evaluated according to the evaluation criteria shown below. A: No cracks or chips occurred in the ink storage area. B: Cracks and chips were found in the ink storage area, but no ink leakage was observed. C: Cracks or chips were found in the ink storage area, and ink leakage was confirmed.

[0091] (Discharge characteristics) After applying a predetermined number of electric pulses to the heater of the recording head of the above inkjet recording device, a nozzle check pattern was recorded on the "Pixus TS5130S" or "G3370" using magenta ink and yellow ink at a driving frequency of 24 kHz. The state of ejection irregularities and dot deformation that occurred in the recorded nozzle check pattern was visually observed, and the ejection characteristics during high-frequency driving were evaluated according to the evaluation criteria shown below. AA:2.0×10 8 When electric pulses were applied more than once, the difference in the number of ejection ports where ejection irregularities and dot deformation occurred was less than 10 for magenta ink and yellow ink. A: 1.5×10 8 More than 2.0×10 times 8 When an electric pulse of less than 10 times was applied, the difference in the number of ejection ports where ejection irregularities and dot deformation occurred was 10 or more for the magenta ink and the yellow ink. B: 1.0×10 8 More than 1.5×10 times 8 When an electric pulse of less than 10 times was applied, the difference in the number of ejection ports where ejection irregularities and dot deformation occurred was 10 or more for the magenta ink and the yellow ink. C:1.0×10 8 When an electric pulse was applied less than once, the difference in the number of ejection ports where ejection irregularities or dot deformation occurred was 10 or more for the yellow ink compared to the magenta ink.

[0092] (Image color development) Using the above inkjet recording device, a 2 cm x 2 cm solid image with a recording duty of 100% was recorded on a recording medium (PPC paper, product name "CS-680", manufactured by Canon) with yellow ink. The recording environment was a temperature of 25°C and a relative humidity of 50%. Using a spectrophotometer (product name "Spectorolino", manufactured by Gretag Macbeth), the optical density of the recorded solid image was measured under conditions of light source: D50, field of view: 2°, and the color development of the image was evaluated according to the evaluation criteria shown below. A: The optical density was 0.90 or higher. C: The optical density was less than 0.90.

[0093] (Device size) Device 1 or 2 was modified so that a recording unit could be installed. The size of the device before and after the modification was compared, and the device size was evaluated according to the evaluation criteria shown below. A: We were able to modify it and make it smaller. B: It has been modified to the same size. C: It was modified and enlarged.

[0094] TIFF2025024682000009.tif203170

[0095] TIFF2025024682000010.tif197170

[0096] The discharge characteristics of Example 43 were relatively poor compared to the other Examples which were ranked B.

Claims

1. an inkjet recording device is used, the inkjet recording device comprising: an aqueous ink containing a pigment; an ink storage section for storing the aqueous ink and formed of a thermoplastic resin composition containing a filler material; and a recording head attached to the ink storage section and having an ejection port for ejecting the aqueous ink supplied from the ink storage section by the action of thermal energy; An inkjet recording method comprising a step of applying the water-based ink ejected from the ejection orifice to a recording medium to record an image, the ink storage section has three or more storage sections that are divided independently from one another, and the storage sections are arranged in one predetermined direction; The water-based ink comprises a yellow ink containing C.I. Pigment Yellow 74, The ink-jet recording method according to claim 1, wherein the yellow ink is contained in the containing portion disposed on the inside.

2. the yellow ink further contains a first water-soluble organic solvent having a relative dielectric constant of 37.0 or more; 2. The inkjet recording method according to claim 1, wherein the content (mass%) of the first water-soluble organic solvent in the yellow ink is 1.2 times or more and 2.0 times or less in mass ratio to the content (mass%) of the C. I. Pigment Yellow 74.

3. The ink jet recording method according to claim 1, wherein the yellow ink further contains a water-soluble resin having a unit derived from styrene.

4. The inkjet recording method according to claim 3, wherein the content (mass %) of the unit derived from styrene in the water-soluble resin is 10.00 mass % or more based on the total mass of the water-soluble resin.

5. the yellow ink further contains an acetylene glycol surfactant, 5. The inkjet recording method according to claim 1, wherein the content (mass %) of the acetylene glycol surfactant in the yellow ink is 1.50 mass % or more and 2.50 mass % or less based on the total mass of the yellow ink.

6. 6. The inkjet recording method according to claim 5, wherein the content (mass%) of the acetylene glycol surfactant in the yellow ink is 0.3 to 0.6 times the content (mass%) of the C. I. Pigment Yellow 74 in terms of mass ratio.

7. The yellow ink further contains a compound represented by the following general formula (1):

5. The inkjet recording method according to claim 1, wherein the content (mass %) of the compound represented by the following general formula (1) in the yellow ink is 0.80 mass % or more and 1.20 mass % or less based on the total mass of the yellow ink: (In the general formula (1), p+r represents a number of 3.0 or more and 27.0 or less, and q represents a number of 16.0 or more and 31.0 or less.)

8. 8. The inkjet recording method according to claim 7, wherein the content (mass%) of the compound represented by the general formula (1) in the yellow ink is 0.1 to 0.3 times the content (mass%) of the C. I. Pigment Yellow 74 in terms of mass ratio.

9. a discharge port array is formed in the recording head, the discharge port array being arranged parallel to a longitudinal direction of the ink storage section; 5. The ink jet recording method according to claim 1, wherein a ratio (A / B) of a length A in a longitudinal direction of the ink storage section to a length B in a lateral direction perpendicular to the longitudinal direction is 2.0 times or more and 4.0 times or less.

10. 5. The ink jet recording method according to claim 1, wherein the ink containing unit is replaced with another ink containing unit after the water-based ink contained therein is consumed.

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

12. An inkjet recording device comprising: an aqueous ink containing a pigment; an ink storage section for storing the aqueous ink and formed of a thermoplastic resin composition containing a filler material; and a recording head bonded to the ink storage section and having an ejection port for ejecting the aqueous ink supplied from the ink storage section by the action of thermal energy, the ink storage section has three or more storage sections that are divided independently from one another, and the storage sections are arranged in a predetermined direction; The water-based ink comprises a yellow ink containing C.I. Pigment Yellow 74, an ink jet recording apparatus, characterized in that the yellow ink is contained in the containing portion disposed on the inside;

Images