JP2021105082A - Ink jet ink and recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet ink having excellent drying and cohesive resistance, stackability of a obtained recorded matter, and curl resistance. An inkjet ink containing an inorganic oxide colloid, a compound A containing a phosphate ion or a phosphate group, betaines, and water. [Selection diagram] None

Description

The present invention relates to inkjet inks and recording devices.

The inkjet recording method is a relatively simple device that can record high-definition images, and is rapidly developing in various fields. Among them, various studies have been made on discharge stability and the like. For example, Patent Document 1 describes an inkjet that contains at least a pigment, an inorganic oxide colloid, an alkali metal hydroxide, and an aqueous solvent for the purpose of improving ejection stability and scratch resistance of the obtained recorded material. The recording ink composition is disclosed.

Japanese Unexamined Patent Publication No. 11-012516

However, when an ink containing an inorganic oxide colloid as in Patent Document 1 is used, there is a problem that the inorganic oxide colloid is easily aggregated and the nozzle is easily clogged. Further, the ink of Patent Document 1 does not have both stackability and curl resistance of the obtained recorded matter.

The inkjet ink of the present invention contains an inorganic oxide colloid, a compound A containing a phosphate ion or a phosphate group, betaines, and water.

Further, the recording apparatus of the present invention includes an inkjet head having a nozzle for ejecting the inkjet ink to the recording medium, and a conveying means for conveying the recording medium.

The schematic cross-sectional view which shows the recording apparatus which concerns on this embodiment.

Hereinafter, embodiments of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings as necessary, but the present invention is not limited thereto, and a gist thereof. Various deformations are possible within the range that does not deviate from. In the drawings, the same elements are designated by the same reference numerals, and duplicate description will be omitted. In addition, the positional relationship such as up, down, left, and right shall be based on the positional relationship shown in the drawings unless otherwise specified. Furthermore, the dimensional ratios in the drawings are not limited to the ratios shown.

1. 1. Inkjet Ink The inkjet ink according to the present embodiment (hereinafter, also simply referred to as “ink”) contains an inorganic oxide colloid, a compound A containing a phosphate ion or a phosphate group, betaines, and water. ..

In recent years, as the speed of inkjet printers has increased, the problem of not being able to stack excellent recording media like laser printers has become remarkable. Such a problem becomes particularly remarkable when the recording medium is conveyed at high speed in the 100 ppm class such as a line type inkjet printer. It is considered that this is because in high-speed printing in which the recording media overlap before the ink dries, the wet friction resistance of the printing surface of the inkjet ink is large, so that the recording media sticks without slipping.

Further, in an inkjet printer, since the print surface of the recording medium is expanded by the ink, there is also a problem that curl occurs in which the print surface becomes convex immediately after printing.

Therefore, from the viewpoint of improving the stackability of the obtained recorded material, it is conceivable to use an ink containing an inorganic oxide colloid, and from the viewpoint of suppressing curling, it is conceivable to use betaines. Betaines also have the effect of improving the dispersion stability of inorganic oxide colloids. However, when such an ink dries in the vicinity of the nozzle and the inorganic oxide colloid precipitates as an agglomerate, nozzle clogging may occur even if betaines are contained.

Therefore, in the present embodiment, compound A further containing a phosphate ion or a phosphate group is used. By using the compound A, the inorganic oxide colloid is less likely to aggregate, and the formation of aggregates can be prevented. That is, by using compound A and betaines in combination, the solidification of the inorganic oxide colloid is carried out by the effect of hindering the formation of aggregates of the compound A and the effect of improving the dispersion stability of the inorganic oxide colloid of the betaines. It can be further suppressed. As a result, the drying cohesiveness resistance is excellent, and the stacking property and the curl resistance can be further improved.

Hereinafter, the components, physical properties, and manufacturing method that can be contained in the inkjet ink according to the present embodiment will be described.

1.1. Ink oxide colloid The inorganic oxide colloid refers to a state in which fine particles such as SiO ₂ and Al ₂ O ₃ are dispersed in a dispersion medium, and in the present embodiment, the ink containing the inorganic oxide colloid means a solvent constituting the ink. Is a dispersion medium in which the inorganic oxide fine particles are dispersed.

The inorganic oxide colloid is not particularly limited, and examples thereof include colloidal silica and alumina colloid. Of these, colloidal silica is preferred. By using such an inorganic oxide colloid, the stackability of the obtained recorded material is further improved, which enables high-speed transfer of the recording medium. Further, colloidal silica tends to suppress sedimentation and further improve dispersion stability as compared with dry silica such as fumed silica, and even if it is contained, the viscosity of the inkjet ink does not easily increase, so that the ejection stability is improved. Also tends to be excellent. In addition to this, when such an inorganic oxide colloid is used in combination with betaines and compound A, the drying aggregation resistance tends to be further improved. The inorganic oxide colloid may be used alone or in combination of two or more.

The particles of the inorganic oxide colloid may be surface-treated. For example, colloidal silica may be surface-treated with alumina. As a result, the range of pH at which the colloid can be stably dispersed is expanded, and the dispersion stability tends to be further improved.

Commercially available products can be used as the colloidal silica as described above. For example, Snowtex 20, Snowtex 30, Snowtex 40, Snowtex O, Snowtex N, and Snowtex C (all of the above are "Nissan Chemical Industries, Ltd." Co., Ltd.).

The average particle size of the inorganic oxide colloid is preferably 5 to 100 nm, more preferably 5 to 80 nm, and even more preferably 10 to 70 nm. When the average particle size is 100 nm or less, sedimentation is suppressed and the dispersion stability tends to be further improved. Further, when the average particle size is 5 nm or more, the sliding friction of the printed surface tends to be further improved.

The average particle size of colloidal silica can be measured by a particle size distribution measuring device based on a dynamic light scattering method. Examples of such a particle size distribution measuring device include "Zeta potential / particle size / molecular weight measuring system ELSZ2000ZS" (trade name) manufactured by Otsuka Electronics Co., Ltd., which employs a homodyne optical system as a frequency analysis method. In the present specification, the "average particle size" refers to the average particle size based on the number of particles, unless otherwise specified.

The content of the inorganic oxide colloid as a solid content is preferably 1.0 to 15% by mass, more preferably 3.0 to 10% by mass, and further preferably 4. It is 0 to 9.0% by mass. When the content of the inorganic oxide colloid is 3.0% by mass or more, the stackability of the obtained recorded material is further improved, and thus the paper transport speed can be further improved. Further, when the content of the inorganic oxide colloid is 15% by mass or less, the drying and cohesive resistance tends to be further improved.

The solid content of the inorganic oxide colloid is preferably higher than the content of compound A on a mass basis. Specifically, the solid content of the inorganic oxide colloid is preferably 5 to 150 times, more preferably 10 to 100 times, based on the mass, with respect to the content of compound A, and further. It is preferably 20 to 50 times. When the content of the inorganic oxide colloid is within the above range, the stackability of the obtained recorded material tends to be further improved, and the drying and cohesiveness resistance tends to be further improved.

When the organic amine described later is contained, the solid content of the inorganic oxide colloid is preferably equal to or higher than the content of the organic amine on a mass basis. Specifically, the solid content of the inorganic oxide colloid is preferably 2.0 to 20 times, more preferably 3.0 to 17 times, based on the mass, with respect to the content of the organic amine. It is more preferably 4.0 to 15 times. When the content of the inorganic oxide colloid is within the above range, the stackability of the obtained recorded material tends to be further improved, and the drying and cohesiveness resistance tends to be further improved.

1.2. Compound A
Compound A is a compound containing a phosphate ion or a phosphate group. By using such a compound A in combination with betaines, the drying aggregation resistance is further improved. The compound A is not particularly limited, and examples thereof include phosphoric acid or phosphate; a phosphoric acid monoester compound, a phosphoric acid diester compound, a phosphoric acid triester compound, or a salt thereof. Among these, phosphoric acid or phosphoric acid monoester compound is preferable, and phosphoric acid, alkyl phosphoric acid monoester, polyoxyalkylene glycol alkyl ether phosphoric acid monoester, monoglycerite phosphoric acid ester, or salts thereof are more preferable. Phosphoric acid or lauryl phosphate monoester is more preferred. By using such a compound A, the drying aggregation resistance tends to be further improved.

The content of compound A is preferably 0.05 to 3.0% by mass, more preferably 0.05 to 2.0% by mass, still more preferably 0.1 to 0% by mass, based on the total amount of the ink. It is 1.5% by mass. When the content of the compound A is within the above range, the drying agglomeration resistance tends to be further improved.

1.3. Betaines The betaines in the present embodiment refer to compounds having positive and negative charges that are not adjacent to each other in the same molecule and have no charge as a whole molecule. The positive charge site is preferably a quaternary ammonium cation. Such betaines are not particularly limited, and examples thereof include trimethylglycine, γ-butyrobetaine, homarin, trigonelline, carnitine, homoserine betaine, valine betaine, lysine betaine, ornithine betaine, alanine betaine, stachidrine, and glutamate betaine. Can be mentioned. Of these, trimethylglycine, γ-butyrobetaine and carnitine are preferable, and trimethylglycine is more preferable. By using such betaines, the curl of the obtained recorded material tends to be further suppressed, and the drying and cohesiveness resistance tends to be further improved. The betaines may be used alone or in combination of two or more.

The number of carbon atoms constituting the betaines is preferably 4 to 12, more preferably 4 to 7, and even more preferably 4 to 6. When the carbon number of betaines is within the above range, the stability against disturbances such as the mixing of charged foreign substances tends to be further improved.

The content of betaines is preferably 2.0 to 20% by mass, more preferably 3.0 to 15% by mass, and further preferably 4.0 to 10% by mass with respect to the total amount of the ink. be. When the content of betaines is within the above range, the curl of the obtained recorded material tends to be further suppressed. In addition, the formation of hard aggregates when the inorganic oxide colloids agglomerate due to drying is suppressed, and the dispersion stability of the inorganic oxide colloids is improved, so that the drying agglomeration resistance tends to be further improved.

The content of betaines is preferably equal to or higher than the solid content of the inorganic oxide colloid on a mass basis. Specifically, the content of betaines is preferably 1.0 to 5.0 times, more preferably 1.0 to 5.0 times the content of the solid content of the inorganic oxide colloid on a mass basis. It is 3.0 times, more preferably 1.1 to 2.0 times. When the content of betaines is within the above range, the curl of the obtained recorded material is more suppressed, and the drying and cohesiveness resistance tends to be further improved.

1.4. Water The water content is preferably 40 to 80% by mass, more preferably 50 to 80% by mass, still more preferably 55 to 75% by mass, and particularly preferably 60% by mass, based on the total amount of ink. ~ 70% by mass. When the water content is 50% by mass or more, the increase in the viscosity of the ink is suppressed even when a part of the water evaporates, and the ejection stability tends to be further improved. Further, when the water content is 80% by mass or less, curling and cockling of the obtained recorded matter tend to be further suppressed.

1.5. Organic Amine The inkjet ink of this embodiment may further contain an organic amine. The organic amine is not particularly limited, and examples thereof include triethanolamine, diethanolamine, monoethanolamine, tripropanolamine, and triisopropanolamine. Of these, triethanolamine or triisopropanolamine is preferable. These organic amines can function as a buffer to improve the stability of the inorganic oxide colloid. Therefore, by using such an organic amine, the drying and cohesive resistance tends to be further improved. In particular, by using a bulky compound such as triethanolamine or triisopropanolamine, the dispersion stability of the inorganic oxide colloid tends to be further improved, and the drying aggregation resistance tends to be further improved.

The content of the organic amine is preferably 0.1 to 5.0% by mass, more preferably 0.3 to 4.0% by mass, and further preferably 0.5 to 4.0% by mass with respect to the total amount of the ink. It is 3.0% by mass. When the content of the organic amine is within the above range, the dispersion stability of the inorganic oxide colloid is further improved, so that the drying and cohesive resistance tends to be further improved.

1.6. Inorganic base The inkjet ink of the present embodiment may further contain an inorganic base. The inorganic base is not particularly limited, and examples thereof include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like.

The content of the inorganic base is preferably 0.05 to 0.50% by mass, more preferably 0.10 to 0.30% by mass, based on the total amount of the ink. The inkjet ink of the present embodiment includes a mode in which the inorganic base is intentionally added within the above range and a mode in which the inorganic base is not intentionally added, but a mode in which the inorganic base is not intentionally added is preferable. In the case of the mode in which the ink is not intentionally added, the inorganic base contained in the inkjet ink is unavoidably added to the ink together with the pigment and the inorganic oxide colloid, and the total amount thereof is about 1000 ppm or less.

1.7. Pigment The inkjet ink of the present embodiment may contain a pigment as a coloring material. The pigment is not particularly limited, and is, for example, an azo pigment (including, for example, azo lake, insoluble azo pigment, condensed azo pigment, chelate azo pigment, etc.), polycyclic pigment (for example, phthalocyanine pigment, perylene pigment, perinone pigment, anthraquinone). Organic pigments such as pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, nitro pigments, nitroso pigments, aniline blacks; carbon blacks (eg furnace blacks, thermal lamp blacks, acetylene blacks, channels) Inorganic pigments such as black, etc.), metal oxides, metal sulfides, metal chlorides; extender pigments such as calcium carbonate, talc, etc. can be used.

The above pigment can be used as a pigment dispersion liquid obtained by dispersing in water with a dispersant, or by dispersing a self-dispersing surface-treated pigment in which a hydrophilic group is introduced on the surface of pigment particles by utilizing a chemical reaction. It is preferably added to the ink as a pigment dispersion obtained by dispersing the obtained or polymer-coated pigment in water.

The pigment and the dispersant constituting the pigment dispersion liquid may be used individually by 1 type, or may be used in combination of 2 or more types.

The content of the pigment is preferably 1.0 to 12% by mass, more preferably 2.0 to 10% by mass, and further preferably 3.0 to 7 as a solid content with respect to the total amount of the ink. It is 5.5% by mass.

1.8. Surfactant The inkjet ink of this embodiment may contain a surfactant. The surfactant is not particularly limited, and examples thereof include an acetylene glycol-based surfactant, a fluorine-based surfactant, and a silicone-based surfactant. Among these, an acetylene glycol-based surfactant is preferable from the viewpoint of drying and cohesive resistance.

The acetylene glycol-based surfactant is not particularly limited, and is, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol and 2,4,7,9-tetramethyl-5. Selected from alkylene oxide adducts of decin-4,7-diol and alkylene oxide adducts of 2,4-dimethyl-5-decyne-4-ol and 2,4-dimethyl-5-decyne-4-ol. One or more is preferable. Commercially available products of acetylene glycol-based surfactants are not particularly limited, but for example, E series such as Orfin 104 series and Orfin E1010 (trade name manufactured by Air Products & Chemicals), Surfinol 61, 104, 465 (Nisshin Kagaku Kogyo). Company-made product name) and the like. The acetylene glycol-based surfactant may be used alone or in combination of two or more.

The fluorine-based surfactant is not particularly limited, and is, for example, perfluoroalkyl sulfonate, perfluoroalkyl carboxylic acid salt, perfluoroalkyl phosphate, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, and per. Fluoroalkylamine oxide compounds can be mentioned. The commercially available fluorosurfactant is not particularly limited, but for example, S-144, S-145 (manufactured by Asahi Glass Co., Ltd.); FC-170C, FC-430, Florard-FC4430 (manufactured by Sumitomo 3M Ltd.). FSO, FSO-100, FSN, FSN-100, FS-300 (manufactured by DuPont); FT-250, 251 (manufactured by Neos Co., Ltd.) and the like. The fluorine-based surfactant may be used alone or in combination of two or more.

Examples of the silicone-based surfactant include polysiloxane-based compounds and polyether-modified organosiloxanes. The commercially available silicone-based surfactant is not particularly limited, but specifically, BYK-306, BYK-307, BYK-333, BYK-341, BYK-345, BYK-346, BYK-347, BYK. -348, BYK-349 (trade name, manufactured by Big Chemie Japan Co., Ltd.), KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-640 , KF-642, KF-643, KF-6020, X-22-4515, KF-6011, KF-6012, KF-6015, KF-6017 (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) and the like.

The content of the surfactant is preferably 0.1 to 5.0% by mass, more preferably 0.1 to 3.0% by mass, based on the total mass of the ink. When the content of the surfactant is within the above range, the drying and cohesive resistance tends to be further improved.

1.9. Water-soluble organic solvent The inkjet ink of the present embodiment may contain a water-soluble organic solvent as a component other than the above. The water-soluble organic solvent is not particularly limited, and for example, a nitrogen-containing solvent such as glycerin; 2-pyrrolidone, N-methylpyrrolidone; ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, etc. Glycols of propanediol, butanediol, pentanediol and hexylene glycol; glycol monoalkyl ethers such as ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether and triethylene glycol monobutyl ether can be mentioned. Of these, glycerin, 2-pyrrolidone, and triethylene glycol monobutyl ether are preferable. By using such a water-soluble organic solvent, the drying and cohesive resistance tends to be further improved.

The content of the water-soluble organic solvent is preferably 5 to 25% by mass, more preferably 10 to 20% by mass, and further preferably 12 to 16% by mass with respect to the total amount of the ink.

1.10. Method for Producing Inkjet Ink The method for producing the inkjet ink of the present embodiment is not particularly limited, and includes an inorganic oxide colloid, a compound A containing a phosphate ion or a phosphate group, betaines, water, and if necessary. There is a method of mixing with other components. The inorganic oxide colloid may be mixed in the state of a colloidal solution, or may be mixed in the state of a pigment dispersion liquid when a pigment is used.

2. Inkjet Method The inkjet method according to the present embodiment includes a ejection step of ejecting the inkjet ink and adhering it to a recording medium using a predetermined inkjet head, and a conveying step of conveying the recording medium. The discharge process and the transfer process may be performed at the same time or alternately.

2.1. Discharge process In the discharge process, ink is ejected from the inkjet head and adhered to the recording medium. More specifically, the pressure generating means provided in the inkjet head is driven to eject the ink filled in the pressure generating chamber of the inkjet head from the nozzle. Such a discharge method is also called an inkjet method.

Examples of the inkjet head used in the ejection process include a line head that records by a line method and a serial head that records by a serial method.

In the line method using a line head, for example, an inkjet head having a width equal to or larger than the recording width of the recording medium is fixed to the recording device. Then, the recording medium is moved along the sub-scanning direction (the transport direction of the recording medium), and in conjunction with this movement, ink droplets are ejected from the nozzle of the inkjet head to record an image on the recording medium.

In the serial system using a serial head, for example, the inkjet head is mounted on a carriage that can move in the width direction of the recording medium. Then, the carriage is moved along the main scanning direction (width direction of the recording medium), and in conjunction with this movement, ink droplets are ejected from the nozzle of the head to record an image on the recording medium.

2.2. Conveying process In the transporting process, the recording medium is transported in a predetermined direction in the recording device. More specifically, the recording medium is conveyed from the paper feeding section to the paper ejection section of the recording device by using a transfer roller or a transfer belt provided in the recording device. In the transport process, the ink ejected from the inkjet head adheres to the recording medium to form a recorded object. The transport may be carried out continuously or intermittently.

2.3. Recording medium The recording medium used in the present embodiment is not particularly limited, and examples thereof include an absorbent or non-absorbable recording medium. Among these, since the absorbent recording medium tends to cause problems such as curling, the present invention, which is excellent in drying and cohesive resistance while using an inorganic oxide colloid, is effective.

The absorbent recording medium is not particularly limited, but for example, plain paper such as electrophotographic paper having high ink permeability, inkjet paper (an ink absorbing layer composed of silica particles or alumina particles, or polyvinyl alcohol (PVA)). ) And polyvinyl pyrrolidone (PVP), which is an inkjet paper with an ink absorbing layer composed of a hydrophilic polymer), art paper, coated paper, and cast paper used for general offset printing with relatively low ink permeability. Examples include paper.

The non-absorbable recording medium is not particularly limited, and is, for example, a film or plate of plastics such as polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate (PET), polycarbonate, polystyrene, and polyurethane; iron, silver, copper, and aluminum. Plates of metals such as; or metal plates produced by vapor deposition of various metals, plastic films, alloy plates such as stainless steel and true cast; polyvinyl chloride, polyethylene, polypropylene, polyethylene terephthalate on a paper base material. Examples thereof include a recording medium in which a plastic film such as (PET), polypropylene, polystyrene, or polyurethane is adhered (coated).

3. 3. Recording device The recording device of the present embodiment includes an inkjet head having a nozzle for ejecting inkjet ink onto a recording medium, and a transport means for transporting the recording medium. The inkjet head includes a pressure chamber to which ink is supplied and a nozzle for ejecting ink. Further, the transport means is composed of a transport roller and a transport belt provided in the recording device.

Hereinafter, the recording device according to the present embodiment will be described with reference to FIG. In the XYZ coordinate system shown in FIG. 1, the X direction indicates the length direction of the recording medium, the Y direction indicates the width direction of the recording medium in the transport path in the recording device, and the Z direction indicates the height direction of the device. There is.

As an example, the recording device 10 is a line-type inkjet printer capable of high-speed and high-density printing. The recording device 10 includes a feeding unit 12 for storing a recording medium P such as paper, a transport unit 14, a belt transport unit 16, a recording unit 18, and an Fd (face-down) discharge unit 20 as a “discharge unit”. The Fd (face-down) mounting portion 22 as the "mounting portion", the reversing path portion 24 as the "reversing transport mechanism", the Fu (face-up) discharging portion 26, and the Fu (face-up) mounting. It is provided with a part 28.

The feeding unit 12 is arranged at the lower part of the recording device 10 in the recording device 10. The feeding unit 12 includes a feeding tray 30 for storing the recording medium P, and a feeding roller 32 for sending the recording medium P stored in the feeding tray 30 to the transport path 11.

The recording medium P stored in the feed tray 30 is fed to the transport unit 14 along the transport path 11 by the feed roller 32. The transport unit 14 includes a transport drive roller 34 and a transport driven roller 36. The transport drive roller 34 is rotationally driven by a drive source (not shown). In the transport unit 14, the recording medium P is narrowly held (nipped) between the transport drive roller 34 and the transport driven roller 36 and transported to the belt transport unit 16 located on the downstream side of the transport path 11.

The belt transport unit 16 is endlessly rotatably attached to the first roller 38 located on the upstream side, the second roller 40 located on the downstream side, the first roller 38, and the second roller 40 in the transport path 11. A belt 42 and a support 44 that supports the upper section 42a of the endless belt 42 between the first roller 38 and the second roller 40 are provided.

The endless belt 42 is driven by a first roller 38 or a second roller 40 driven by a drive source (not shown) so as to move from the + X direction to the −X direction in the upper section 42a. Therefore, the recording medium P transported from the transport unit 14 is further transported to the downstream side of the transport path 11 in the belt transport unit 16.

The recording unit 18 includes a line-type inkjet head 48 and a head holder 46 that holds the inkjet head 48. The recording unit 18 may be of a serial type in which an inkjet head is provided on a carriage that reciprocates in the Y-axis direction. The inkjet head 48 is arranged so as to face the upper section 42a of the endless belt 42 supported by the support 44. When the recording medium P is conveyed in the upper section 42a of the endless belt 42, the inkjet head 48 ejects ink toward the recording medium P and executes recording. The recording medium P is transported to the downstream side of the transport path 11 by the belt transport unit 16 while recording.

The "line-type inkjet head" is provided so that a nozzle region formed in a direction intersecting the transport direction of the recording medium P can cover the entire intersecting direction of the recording medium P, and the head or recording. This is a head used in a recording device in which one of the media P is fixed and the other is moved to form an image. It should be noted that the nozzle region in the intersecting direction of the line heads may not be able to cover the entire intersecting direction of all the recording media P supported by the recording device.

Further, a first branch portion 50 is provided on the downstream side of the transport path 11 of the belt transport portion 16. The first branching section 50 has a transport path 11 for transporting the recording medium P to the Fd discharge unit 20 or the Fu discharge unit 26, and an inversion in which the recording surface of the recording medium P is inverted and the recording medium P is conveyed to the recording unit 18 again. It is configured to be switchable to the reverse path 52 of the path unit 24. The recording medium P, which is switched to the reversing path 52 by the first branching portion 50 and is conveyed, has its recording surface inverted in the transfer process in the inversion path 52, and the surface opposite to the first recording surface is the inkjet head 48. It is conveyed again to the recording unit 18 so as to face each other.

A second branch portion 54 is further provided on the downstream side of the first branch portion 50 along the transport path 11. The second branch portion 54 is configured to be able to switch the transport direction of the recording medium P so as to transport the recording medium P toward the Fd discharge unit 20 or the recording medium P toward the Fu discharge unit 26. There is.

The recording medium P conveyed toward the Fd discharge unit 20 in the second branch portion 54 is discharged from the Fd discharge unit 20 and placed on the Fd mounting unit 22. At this time, the recording surface of the recording medium P is placed so as to face the Fd mounting portion 22. Further, the recording medium P conveyed toward the Fu discharge unit 26 at the second branch portion 54 is discharged from the Fu discharge unit 26 and placed on the Fu mounting unit 28. At this time, the recording surface of the recording medium P is placed so as to face the side opposite to the Fu mounting portion 28.

In a recording device using an inkjet method, liquid ink is adhered to a recording medium, so that the recording medium, particularly an absorbent recording medium such as plain paper or inkjet paper, has problems such as curling, or before the ink is dried. Since the recorded materials are discharged and overlapped with each other, there may be a problem that the recorded materials cannot be stacked accurately. In particular, when the recording medium is conveyed at a high speed of 0.5 m / s or more, this problem tends to become remarkable. In addition, if the inkjet printed surface becomes a solid image with a large wet friction resistance, the recorded material will not slip and will be stuck, or even if the recorded material is almost aligned, it will be difficult to align it neatly, and the stapler (stapler) will shift. There will be problems such as printing. Further, in face-down paper ejection in which the printed surface faces downward, it is difficult to dry the ink, which causes a problem that stackability becomes more difficult. In addition, in an absorbent recording medium, when printing is performed, the print surface expands, so that there is also a problem that paper discharge curl (primary curl) in which the print surface becomes convex immediately after printing occurs. Further, as the drying progresses, the printed surface shrinks, so that there is a problem that permanent curl (secondary curl) in which the printed surface becomes concave occurs in a dozen seconds to a few minutes.

On the other hand, in the present embodiment, by using the inkjet ink containing the inorganic oxide colloid, it is possible to suppress the curl while reducing the wet frictional resistance of the printed surface, so that the stackability can be improved. In particular, when inkjet recording is performed while transporting the recording medium P at a high speed of 0.5 m / s or more, the effect of improving the stackability becomes remarkable.

Although an example in which a line-type inkjet head is used has been described above, the recording device according to the present embodiment may be a printer (serial printer) that uses a serial-type inkjet head. In a serial printer, printing is performed by moving the inkjet head in a direction intersecting the transport direction while transporting the recording medium in the transport direction. Even with a serial printer, if the relative speed between the head and the recording medium during printing is as high as 0.5 m / s or more, a problem of stackability may occur. Therefore, the stackability is improved by using the above-mentioned ink. The effect is obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited to the following examples.

1. 1. Preparation of Inks Inkjet inks of each example were obtained by putting each component in a tank for mixture, mixing and stirring, and further filtering with a 5 μm membrane filter so as to have the composition shown in Table 1. The numerical value of each component shown in each example in the table represents mass% unless otherwise specified. Further, in the table, the numerical values of the inorganic oxide colloid and the pigment dispersion liquid represent the mass% of the solid content.

The abbreviations and product ingredients used in Table 1 are as follows.

[Pigment dispersion]
Cyan pigment (CI Pigment Blue 15: 4)
Magenta Pigment (CI Pigment Red 122)
Black pigment (carbon black)
[Inorganic oxide colloid]
Colloidal silica (manufactured by Nissan Chemical Industries, Ltd., ST-CM, particle size 20 nm, solid content 30%)
[Compound A]
Phosphoric acid Lauryl phosphate monoester [betaines]
Trimethylglycine (anhydrous betaine, manufactured by Tokyo Chemical Industry Co., Ltd.)
[Organic amine]
Triethanolamine [inorganic base]
Potassium hydroxide (KOH)
[Water-soluble solvent]
Glycerin Triethylene Glycol Monobutyl Ether 2-Pyrrolidone [Surfactant]
Orphine E1010 (trade name manufactured by Nissin Chemical Industry Co., Ltd., acetylene glycol-based surfactant)

2. Evaluation method 2-1. Drying and coagulation resistance EPSON PX-M860F ink cartridge is filled with ink, and the temperature is 40 ° C and the humidity is 20% with respect to the recording medium (Fuji Xerox A4 copy paper, basis weight 64 g / m2, paper thickness 88 μm). In this environment, 5000 sheets of test charts published by the Japan Imaging Society with an image coverage of 5% were printed continuously. Then, it was confirmed whether or not there were white streaks due to nozzle misalignment or nozzle omission in the solid printing portion after printing 5000 sheets. It can be evaluated that the smaller the number of the inks, the more the ink has excellent drying and cohesiveness resistance. When printing with an image coverage of 5%, ink is not ejected to the remaining 95% of the nozzles, so that the nozzles continue to be exposed to an environment of 40 ° C. and 20% humidity, and drying aggregation is likely to proceed even during printing.

2-2. Stackability An EPSON LX-10000F (line inkjet printer) ink cartridge is filled with ink, and the temperature is 25 ° C. for a ^{recording medium (Fuji Xerox A4 copy paper, basis weight 64 g / m 2, paper thickness 88 μm).} In an environment of 50% humidity, 200 solid patterns were printed continuously with a printing duty of 100%. The printing speed was 100 sheets / minute. After printing, the number of sheets of paper that could be stacked without being scattered on the face-down ejection part of the printer was confirmed, and the stackability was evaluated according to the following evaluation criteria.
(Evaluation criteria)
A: 100 or more consecutive cards could be stacked B: 50 or more consecutive sheets could be stacked C: 20 or more consecutive sheets could be stacked D: 3 or more consecutive sheets could be stacked E: 3 or more consecutive sheets could not be stacked

2.3. Evaluation of curl resistance The ink cartridge of EPSON PX-S840 (serial inkjet printer) is filled with ink, and the ink cartridge is applied to the recording medium (Fuji Xerox A4 copy paper, basis weight 64 g / m ² , paper thickness 88 μm). A solid pattern was printed with a printing duty of 100% in an environment of a temperature of 25 ° C. and a humidity of 50%. Then, the state of the paper was confirmed when it was left face-up for 1 day after printing and then left until 7 days after printing. The evaluation criteria are as follows.
〔Evaluation criteria〕
A: The paper is not curled after being left for 1 day and is not curled even after being left for 7 days. B: The paper is not curled after being left for 1 day and is slightly curled after being left for 7 days. C 1: The paper is slightly curled after being left for 1 day, and is slightly curled after being left for 7 days. D: The paper is slightly curled after being left for 1 day, and is curled into a cylinder after being left for 7 days. E: The paper is curled into a cylinder after being left for 1 day, and is curled into a cylinder even after being left for 7 days.

3. 3. Evaluation Results Table 1 shows the composition of the inks used in each example and the evaluation results. From Table 1, when an ink containing an inorganic oxide colloid, a compound A containing a phosphate ion or a phosphate group, and betaines was used, the ink contained was excellent in drought aggregation resistance, and a stack of obtained records was obtained. It was found that it was also excellent in property and curl resistance.

More specifically, when each Example is compared with Comparative Example 1, it can be seen that the inclusion of the compound A further improves the drying and cohesiveness resistance, and is also excellent in the stacking property and the curl resistance of the obtained recorded material. Further, when each Example is compared with Comparative Example 2, it can be seen that the inclusion of the inorganic oxide colloid is excellent in the stacking property and the curl resistance of the obtained recorded material. Furthermore, when each Example and Comparative Example 3 are compared, it can be seen that the inclusion of betaines further improves the drying and cohesiveness resistance, and is also excellent in the stacking property and curl resistance of the obtained recorded material.

10 recording device, 11 transport path, 12 feed section, 14 transport section, 16 belt transport section, 18 recording section, 20 Fd discharge section, 22 Fd mounting section, 24 reversal path section, 26 Fu discharge section, 28 Fu mounting section, 30 Feed tray, 32 feed roller, 34 transport drive roller, 36 transport driven roller, 38 first roller, 40 second roller, 42 endless belt, 42a endless belt upper section, 44 support, 46 head holder, 48 inkjet Head, 50 1st branch, 52 reversal path, 54 2nd branch, 56 discharge roller pair, 64 discharge drive roller, 68 drive shaft, 76 mounting surface, 78 convex part, 80 1st urging member, 82 Second urging member, 84, 86 support shaft, P recording medium

Claims (15)

Containing inorganic oxide colloid, compound A containing a phosphate ion or a phosphate group, betaines, and water.
Inkjet ink. The inorganic oxide colloid contains colloidal silica.
The inkjet ink according to claim 1. The compound A contains a phosphoric acid monoester compound, a phosphoric acid diester compound, or a phosphoric acid triester compound.
The inkjet ink according to claim 1 or 2. The content of the inorganic oxide colloid is 3.0 to 10% by mass as a solid content with respect to the total amount of the ink.
The inkjet ink according to any one of claims 1 to 3. The inkjet ink according to any one of claims 1 to 4, wherein the content of the compound A is 0.05 to 3.0% by mass with respect to the total amount of the ink. The betaines contain trimethylglycine.
The inkjet ink according to any one of claims 1 to 5. The content of the betaines is 2.0 to 20% by mass with respect to the total amount of the ink.
The inkjet ink according to any one of claims 1 to 6. The solid content of the inorganic oxide colloid is higher than the content of the compound A on a mass basis.
The inkjet ink according to any one of claims 1 to 7. The content of the betaines is higher than the solid content of the inorganic oxide colloid on a mass basis.
The inkjet ink according to any one of claims 1 to 8. Contains organic amines,
The inkjet ink according to any one of claims 1 to 9. The organic amine comprises triethanolamine or triisopropanolamine.
The inkjet ink according to claim 10. The content of the organic amine is 0.1 to 5.0% by mass with respect to the total amount of the ink.
The inkjet ink according to claim 10 or 11. The water content is 50 to 80% by mass with respect to the total amount of ink.
The inkjet ink according to any one of claims 1 to 12. An inkjet head having a nozzle for ejecting the inkjet ink according to any one of claims 1 to 13 onto a recording medium.
A transport means for transporting the recording medium.
Recording device. The inkjet head is a line head.
The recording device according to claim 14.

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