EP3037265A1

EP3037265A1 - Inkjet dyeing method

Info

Publication number: EP3037265A1
Application number: EP14837343.4A
Authority: EP
Inventors: Hitoshi Morimoto; Ryohei Kobayashi
Original assignee: Konica Minolta Inc
Current assignee: Konica Minolta Inc
Priority date: 2013-08-22
Filing date: 2014-08-22
Publication date: 2016-06-29
Anticipated expiration: 2034-08-22
Also published as: CN105473339B; CN105473339A; WO2015025524A1; EP3037265A4; EP3037265B1; JP6341206B2; JPWO2015025524A1

Abstract

Provided is an inkjet dyeing method for recording on fiber by ejecting an ink containing a disperse dye from an inkjet head. The inkjet head has two or more rows in which are aligned pressure chambers for generating pressure to discharge internal ink from a nozzle using a pressure applying means operated by the imparting of a drive signal. The pressure chambers are connected to each other through a shared ink chamber. The rows in which the pressure chambers are arranged are divided into N drive groups (where N is an integer of 2 or greater), and a phase difference of nAL+t is applied to drive signals applied to the pressure applying means of the pressure chambers in each drive group. n represents an integer of 1 or greater, AL represents 1/2 of an acoustic resonance period of a pressure wave in a pressure chamber, t represents a pressure wave transmission time period determined by dividing the distance between nozzles in a drive group by the speed at which sound propagates through the ink.

Description

Technical Field

The present invention relates to an inkjet dyeing method.

Background Art

An inkjet head that generates pressure in a pressure chamber by the operation of a pressure-imparting means to discharge an ink inside the pressure chamber from a nozzle is required to perform faster and higher-definition recording, and thus the number of nozzles and the number of nozzle rows have tended to be more and more increased. In association with the tendency, there has been a problem of the increase of crosstalk where a pressure wave generated in a pressure chamber during discharge is propagated to other pressure chambers to destabilize droplet velocity (droplet volume).
The destabilization of the droplet velocity due the crosstalk occurs as a result of the following process: the pressure wave generated in the pressure chamber during discharge is propagated to a common ink chamber through the inlet side of the pressure chamber to affect other pressure chambers via the common ink chamber. In particular, in the case of an inkjet head which has two or more pressure chamber rows and in which pressure chambers of each pressure chamber row are in fluid communication with each other via a common ink chamber, the pressure wave is also propagated to pressure chambers of other pressure chamber rows via the common ink chamber, and therefore it is important to suppress the crosstalk between the pressure chamber rows.
As for the crosstalk problem, Patent Literature (hereinafter, referred to as "PTL") 1 discloses that a common ink chamber is halved by a separation wall between and along pressure chamber rows to prevent the propagation of a pressure wave from one pressure chamber row to the other pressure chamber row. In addition, PTL 2 discloses that the wall surface of a common ink chamber facing the inlet of a pressure chamber is specified to have a predetermined value or lower of volume elasticity to thereby attenuate a pressure wave propagated into the common ink chamber, thus reducing crosstalk.

Citation List

Patent Literature

PTL 1 Japanese Patent Application Laid-Open No. 2003-11368
PTL 2 Japanese Patent Application Laid-Open No. 2007-168185

Summary of Invention

Technical Problem

There is also a problem of satellites being likely to be generated for ink droplets discharged from an inkjet head when crosstalk occurs in the inkjet head. When satellites are generated in the case of printing an image at high ejection frequency (such as a solid image), it is highly probable that the generated satellites are adhered to a nozzle surface of the inkjet head. When the satellites are adhered to the vicinity of a nozzle on a nozzle surface, the volume of a droplet ejected from the nozzle may differ from a set volume; the discharging direction of the droplets may differ from a set direction; or, in addition, droplets may fail to be ejected from the nozzle. As a result, defect occurs in a printed image.
There is also a problem in which, when the ink to be applied by an inkjet head is an ink containing a disperse dye having many coarse particles or an ink having a high thixotropic index, satellites are likely to be generated. Although the mechanism by which the satellites are generated is not particularly limited, it is considered that satellites are likely to be generated, due to the inhibition of predetermined droplet formation by coarse particles, or due to high thixotropic index during high-speed continuous driving and low-speed intermittent driving causing applied voltage to be out of a proper range.
The present invention provides a means for enhancing the ejection stability of an inkjet head in an inkjet dyeing method with an ink containing a disperse dye. In particular, specifically, the present invention reduces the frequency of occurrence of nozzle omission in inkjet dyeing with high ejection frequency.

Solution to Problem

The present invention relates to an inkjet dyeing method as set forth below:

[1] An inkjet dyeing method for ejecting an ink from an inkjet head for recording on a fiber, the ink containing at least a disperse dye, a dispersant, water and a water-soluble organic solvent, wherein
a ratio of the number of disperse dye particles having a particle diameter of 5 µm or more to the total number of disperse dye particles contained in the ink is 5% or less,
the inkjet head has two or more rows in which pressure chambers generating pressure for discharging an ink inside the pressure chambers from a nozzle with a pressure-imparting means operable by application of a drive signal are arranged, with the pressure chambers being in fluid communication with each other via a common ink chamber, and
a row in which the pressure chambers are arranged is divided into N (N is an integer of 2 or more) drive groups, and for each of the drive groups a phase difference of nAL + t (with the proviso that n is an integer of 1 or more, AL is 1/2 of acoustic resonance period of a pressure wave in a pressure chamber, and t is a pressure wave transmission time determined by "inter-nozzle distance between drive groups"/"speed at which sound is transmitted in the ink") is imparted to the drive signal to be applied to the pressure-imparting means of the pressure chamber.
[2] The inkjet dyeing method according to [1], in which adjacent rows of the pressure chambers are set as drive groups different from each other.
[3] The inkjet dyeing method according to [1] or [2], in which a thixotropic index of the ink is 1.2 or less.

Advantageous Effects of Invention

According to the inkjet dyeing method of the present invention, it is possible to suppress the generation of satellites and the occurrence of nozzle omission (phenomenon in which ink droplets fail to be discharged from a nozzle) leading to the enhancement of ejection stability. Therefore, it is possible to achieve a high-quality image at high ejection frequency (such as a solid image).

Brief Description of Drawings

FIG. 1 illustrates a schematic configuration of an inkjet recording apparatus;
FIG. 2 is a broken perspective view illustrating a schematic configuration of an inkjet head;
FIG. 3 is a partial rear view of a head chip illustrated in FIG. 2;
FIG. 4 is a partial sectional view of the head chip;
FIG. 5 illustrates an example of a drive signal used in the present invention;
FIGS. 6A and 6B are explanatory drawings of a deformation operation of a partition wall by the drive signal illustrated in FIG. 5;
FIG. 7 is a front view of a head chip illustrating a mode in which drive groups are divided into two channel rows;
FIG. 8 is a timing chart of a drive signal applied to each of the drive groups illustrated in FIG. 7;
FIG. 9 is an explanatory graph of a relationship between droplet velocity fluctuation and Delay [AL];
FIG. 10 is an explanatory drawing of a drive timing between a plurality of channel rows;
FIG. 11 is a front view of a head chip illustrating a mode in which drive groups are divided into four channel rows;
FIG. 12 is a timing chart of a drive signal applied to each of the drive groups illustrated in FIG. 11;
FIG. 13 is a front view of a head chip illustrating a mode in which drive groups are divided into six channel rows;
FIG. 14 is a timing chart of a drive signal applied to each of the drive groups illustrated in FIG. 13; and
FIG. 15 is an explanatory drawing of a mode in which a plurality of channel rows are driven by a plurality of drive circuits.

Description of Embodiments

In the inkjet dyeing method of the present invention, an inkjet ink containing at least a disperse dye, a dispersant, water and a water-soluble organic solvent is ejected from an inkjet head to dye a fiber.

1. Inkjet Ink

An ink used in the inkjet dyeing method of the present invention contains at least a disperse dye, a dispersant, water and a water-soluble organic solvent.

1-1. Disperse Dye

The ink used in the inkjet dyeing method of the present invention contains a disperse dye as a colorant. The disperse dye is a non-ionic dye not having an ionic water-soluble group such as a sulfonic acid or carboxy group, and is less soluble to water. Therefore, the disperse dye is in a fine powdery shape, and is typically dispersed in water by a dispersant to be blended in the ink. Unlike a pigment, the disperse dye is soluble in an organic solvent such as acetone or dimethylformamide. Further, the disperse dye can be diffused in a molecular state in a synthetic fiber for coloring. An ink containing the disperse dye is used, for example, for dyeing a synthetic fiber.
Specific compounds of preferred disperse dyes is listed below, but not limited to the exemplified compounds.
[C.I. Disperse Yellow] 3, 4, 5, 7, 9, 13, 23, 24, 30, 33, 34, 42, 44, 49, 50, 51, 54, 56, 58, 60, 63, 64, 66, 68, 71, 74, 76, 79, 82, 83, 85, 86, 88, 90, 91, 93, 98, 99, 100, 104, 108, 114, 116, 118, 119, 122, 124, 126, 135, 140, 141, 149, 160, 162, 163, 164, 165, 179, 180, 182, 183, 184, 186, 192, 198, 199, 202, 204, 210, 211, 215, 216, 218, 224, 227, 231, 232
[C.I. Disperse Orange] 1, 3, 5, 7, 11, 13, 17, 20, 21, 25, 29, 30, 31, 32, 33, 37, 38, 42, 43, 44, 45, 46, 47, 48, 49, 50, 53, 54, 55, 56, 57, 58, 59, 61, 66, 71, 73, 76, 78, 80, 89, 90, 91, 93, 96, 97, 119, 127, 130, 139, 142
[C.I. Disperse Red] 1, 4, 5, 7, 11, 12, 13, 15, 17, 27, 43, 44, 50, 52, 53, 54, 55, 56, 58, 59, 60, 65, 72, 73, 74, 75, 76, 78, 81, 82, 86, 88, 90, 91, 92, 93, 96, 103, 105, 106, 107, 108, 110, 111, 113, 117, 118, 121, 122, 126, 127, 128, 131, 132, 134, 135, 137, 143, 145, 146, 151, 152, 153, 154, 157, 159, 164, 167, 169, 177, 179, 181, 183, 184, 185, 188, 189, 190, 191, 192, 200, 201, 202, 203, 205, 206, 207, 210, 221, 224, 225, 227, 229, 239, 240, 257, 258, 277, 278, 279, 281, 288, 298, 302, 303, 310, 311, 312, 320, 324, 328
[C.I. Disperse Violet] 1, 4, 8, 23, 26, 27, 28, 31, 33, 35, 36, 38, 40, 43, 46, 48, 50, 51, 52, 56, 57, 59, 61, 63, 69, 77

[C.I. Disperse Green] 9

[C.I. Disperse Brown] 1, 2, 4, 9, 13, 19

[C.I. Disperse Blue] 3, 7, 9, 14, 16, 19, 20, 26, 27, 35, 43, 44, 54, 55, 56, 58, 60, 62, 64, 71, 72, 73, 75, 79, 81, 82, 83, 87, 91, 93, 94, 95, 96, 102, 106, 108, 112, 113, 115, 118, 120, 122, 125, 128, 130, 139, 141, 142, 143, 146, 148, 149, 153, 154, 158, 165, 167, 171, 173, 174, 176, 181, 183, 185, 186, 187, 189, 197, 198, 200, 201, 205, 207, 211, 214, 224, 225, 257, 259, 267, 268, 270, 284, 285, 287, 288, 291, 293, 295, 297, 301, 315, 330, 333,373

[C.I. Disperse Black] 1, 3, 10, 24

When a dye is allowed to develop color with a high temperature treatment in a dyeing process, it is preferable to select a disperse dye with good sublimation fastness, in order not to cause a stain due to the sublimation of the dye at the white ground of a cloth or a machine.
The disperse dye content in the ink is preferably 0.1 to 20 mass%, and more preferably 0.2 to 13 mass%. As the disperse dye, a commercially available product may be used as it is, but it is preferable to perform a refining treatment. Examples of possible refining methods include a known recrystallization method and washing. Preferably, a refining method and an organic solvent used for the refining treatment are selected appropriately depending on the type of dyes.
As for the particle diameter of the disperse dye, it is preferable that the volume average particle diameter is 300 nm or less, and that the maximum particle diameter is 900 nm or less. When the volume average particle diameter and the maximum particle diameter exceed the above-mentioned ranges, nozzle clogging is likely to occur, making it difficult to perform stable ejection in an inkjet printing method in which an ink is ejected from fine nozzles. It is noted that the volume average particle diameter can be determined by means of a commercially available particle size analyzer using light scattering method, electrophoresis method, laser Doppler method, or the like, and specific examples of the particle size analyzer include Zetasizer 1000, manufactured by Malvern Instruments Ltd.
The ratio of the number of disperse dye particles having a particle diameter of 5 µm or more to the total number of the disperse dye particles contained in the ink is preferably 5% or less, and more preferably 1% or less. Further, the ratio of the number of disperse dye particles having a particle diameter of 2 µm or more to the total number of the disperse dye particles contained in the ink is preferably 5% or less, and more preferably 1 % or less.
The ratio of the number of disperse dye particles having a particle diameter of 5 µm or more can be determined by actually measuring the total number of the disperse dye particles and the number of disperse dye particles having a particle diameter of 5 µm or more using a liquid particle counter (e.g., HIAC-8000A manufactured by Hach Company) and by obtaining the ratio therebetween.

1-2. Dispersant

The dispersant contained in the ink used in the inkjet dyeing method of the present invention is preferably a polymer dispersant, a low-molecular surfactant, or the like. Examples of the polymer dispersant include natural rubbers such as gum arabic and gum tragacanth, glucosides such as saponin, cellulose derivatives such as methyl cellulose, carboxy cellulose and hydroxymethyl cellulose, natural polymers such as lignosulfonate and shellac, anionic polymers such as polyacrylate, salt of styrene-acrylic acid copolymer, salt of vinylnaphthalene-maleic acid copolymer, sodium salt of β-naphthalenesulfonic acid-formalin condensate and phosphonate, and non-ionic polymers such as polyvinyl alcohol, polyvinylpyrrolidone and polyethylene glycol.
The dispersant is preferably a dispersant having a carboxyl group, and such a dispersant is available as a commercially available product; examples thereof include polymer dispersants such as lignosulfonate (e.g., Vanillex RN manufactured by Nippon Paper Industries Co., Ltd.), copolymer of α-olefin and maleic anhydride (e.g., Flowlen G-700 manufactured by Kyoeisha Chemical Co., Ltd.), and San X (manufactured by Nippon Paper Industries Co., Ltd.).
The content of the dispersant such as a polymer dispersant is preferably 20 to 200 mass% to the mass of the disperse dye. When there is less dispersant, the micronizing capacity and dispersion stability of the disperse dye become insufficient, whereas when there is more dispersant content, the micronization and dispersion stability are deteriorated, causing ink viscosity to be undesirably increased. These dispersants may be used either singly or in combination.
As for the dispersant, the ratio of the molar number of carboxyl groups to the molar number of the total acidic dissociable groups of the dispersant is preferably 50% by mol or more, more preferably 80% by mol or more, and even more preferably 80% by mol or more and 100% by mol or less. By using the dispersant having the above-specified molar number ratio of carboxyl groups, the effects of the present invention including discharge stability are demonstrated more effectively.
The term acidic dissociable group of the dispersant as used herein is also referred to as a proton dissociable group, and examples thereof include carboxyl group, sulfo group, sulfato group, phosphono group, alkylsulfonylcarbamoyl group, acylcarbamoyl group, acylsulfamoyl group, and alkylsulfonylsulfamoyl group.
Examples of the low-molecular surfactant as the dispersant include anionic surfactants such as fatty acid salts, higher alcohol sulfuric acid ester salts, liquid fatty acid sulfuric acid ester salts and alkylallylsulfonic acid salts, and non-ionic surfactants such as polyoxyethylene alkyl ethers, sorbitan alkyl esters and polyoxyethylene sorbitan alkyl esters. Either a single of these compounds or two or more thereof can be appropriately selected for using. The content of the low-molecular surfactant as the dispersant is preferably in a range of from 1 to 20 mass% to the total mass of the ink.

1-3. Water-Soluble Organic Solvent

Examples of the water-soluble organic solvent contained in the ink used in the inkjet dyeing method of the present invention include polyhydric alcohols (such as ethylene glycol, glycerol, 2-ethyl-2-(hydroxymethyl)-1,3-propanediol, tetraethylene glycol, triethylene glycol, tripropylene glycol, 1,2,4-butanetriol, diethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, 1,6-hexanediol, 1,2-hexanediol, 1,5-pentanediol, 1,2-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,5-pentanediol, 3-methyl-1,3-butanediol, and 2-methyl-1,3-propanediol), amines (such as ethanol amine and 2-(dimethylamino)ethanol), monohydric alcohols (such as methanol, ethanol, and butanol), polyhydric alcohol alkyl ethers (such as diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, and dipropylene glycol monomethyl ether), 2,2'-thiodiethanol, amides (such as N,N-dimethylformamide), heterocycles (such as 2-pyrrolidone), and acetonitrile. The amount of the water-soluble organic solvent to the total mass of the ink is preferably 10 to 60 mass%.

1-4. Water

Water contained in the ink used in the inkjet dyeing method of the present invention may be ion-exchanged water. The amount of the water to the total mass of the ink is typically 20 mass% or more and less than 60 mass%, but is not particularly limited thereto.

1-5. Other Components

The ink used in the inkjet dyeing method of the present invention may contain other arbitrary components such as a surfactant, an inorganic salt, an antiseptic, a fungicide, and a dye auxiliary.
Any of cationic, anionic, amphoteric, and non-ionic surfactants can be used. Examples of the cationic surfactant include aliphatic amine salt, aliphatic quaternary ammonium salt, benzalkonium salt, benzethonium chloride, pyridinium salt, and imidazolidinium salt. Examples of the anionic surfactants include fatty acid soap, N-acyl-N-methyl glycine salt, N-acyl-N-methyl-β-alanine salt, N-acylglutamate, alkyl ether carboxylate, acylated peptide, alkylsulfonate, alkylbenzenesulfonate, alkynaphthalenesulfonate, dialkylsulfo succinic acid ester salt, alkylsulfo acetate, α-olefin sulfonate, N-acyl-methyl taurine, sulfated oil, higher alcohol sulfuric acid ester salt, secondary higher alcohol sulfuric acid ester salt, alkyl ether sulfate, secondary higher alcohol ethoxysulfate, polyoxyethylene alkylphenyl ether sulfate, monoglysulfate, fatty acid alkylol amide sulfuric acid ester salt, alkyl ether phosphoric acid ester salt, and alkyl phosphoric acid ester salt. Examples of the amphoteric surfactant include a carboxybetaine type, a sulfobetaine type, aminocarboxylate, and imidazolinium betaine. Examples of the non-ionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether (e.g., Emulgen 911), polyoxyethylene sterol ether, polyoxyethylenelanolin derivative, polyoxyethylene polyoxypropylene alkyl ether (e.g., Newpol PE-62), polyoxyethylene glycerol fatty acid ester, polyoxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerol fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alkanol amide, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetylene glycol, and acetylene alcohol. In the present invention, the surfactants are not limited to those mentioned above.
These surfactants can be used either singly or as a mixture of two or more thereof, and are added in a range of from 0.001 to 3.0 mass% to the total amount of the ink.
In the present invention, non-ionic surfactants or anionic surfactants are preferred, and dodecylbenzene sulfonic acid soda, 2-ethylhexylsulfosuccinic acid soda, alkylnaphthalenesulfonic acid soda, an ethylene oxide adduct of phenol, and an ethylene oxide adduct of acetylene diol are particularly preferred.
In order to maintain the viscosity of and a dye in an ink, or to enhance the color development, an inorganic salt may be added into the ink. Examples of the inorganic salt include sodium chloride, sodium sulfate, magnesium chloride, and magnesium sulfide. When the present invention is carried out, the inorganic salts are not limited to those mentioned above.
In order to maintain the long-term storage stability of the ink, an antiseptic or fungicide may be added into the ink. Examples of the antiseptic or fungicide include aromatic halogen compounds (e.g., Preventol CMK), methylene dithiocyanate, halogen-containing nitrogen sulfur compounds, and 1,2-benzisothiazolin-3-one (e.g., PROXEL GXL). In the present invention, the antiseptic or fungicide is not limited to those mentioned above.

1-6. Thixotropic Index of Ink

The thixotropic index of the ink used in the inkjet dyeing method of the present invention is preferably 1.2 or less, and more preferably 1.1 or less. The term thixotropic index means the ratio between viscosity value A and viscosity value B ("viscosity value A / viscosity value B") when the viscosity at a shearing rate of 100/sec is set as viscosity value A, and the viscosity at a shearing rate of 1,000/sec is set as viscosity value B. The viscosity value A and viscosity value B can be measured using a rotary rheometer (e.g., MCR-300 manufactured by Anton Paar GmbH).

2. Inkjet Head and Inkjet Apparatus

The inkjet dyeing method of the present invention is typically performed using an inkjet recording apparatus provided with an inkjet head. FIG. 1 is a schematic configuration illustrating an example of an inkjet recording apparatus provided with an inkjet head.
Inkjet recording apparatus 100 has a pair of conveyance rollers 201 of conveyance mechanism 200, which nips recording medium P. Further, inkjet recording apparatus 100 has conveyance roller 203 which is rotationally driven by conveyance motor 202. Recording medium P is designed to be conveyed in illustrated Y direction (sub-scanning direction) by the pair of conveyance rollers 201 and conveyance roller 203.
Inkjet recording apparatus 100 is provided with inkjet head H arranged so as to face recording surface PS of recording medium P, between conveyance roller 203 and the pair of conveyance rollers 201. Inkjet head H is mounted on carriage 400 such that the nozzle surface side is arranged to face recording surface PS of recording medium P. Carriage 400 is provided reciprocably in illustrated X-X' direction (main scanning direction) approximately orthogonal to the conveyance direction of recording medium P (sub-scanning direction) by a driving means (not illustrated) along guide rail 300 bridged in the width direction of recording medium P. As described in detail hereinafter, inkjet head H is connected electrically to drive apparatus 500 via flexible printed circuit board (FPC) 4.
Inkjet head H moves for scanning over recording surface PS of recording medium P in illustrated direction X-X', in association with the movement of carriage 400 in the main scanning direction. In the course of this movement for scanning, droplets are discharged from nozzles to thereby record a desired image.
FIGS. 2 to 4 illustrate an example of inkjet head H which is preferably used. FIG. 2 is a broken perspective view of the inkjet head, FIG. 3 is a partial rear view of the head chip of the inkjet head, and FIG. 4 is a partial sectional view of the head chip.
Inkjet head H illustrated in FIGS. 2 to 4 has so-called harmonica-shaped head chip 1, nozzle plate 2, wiring circuit board 3, FPC 4 and ink manifold 5.
Head chip 1 is in a hexahedral shape, and has two channel rows (row A and row B) in which a plurality of channels are arranged. In the channel rows of head chip 1, drive channel 11 which is a pressure chamber and from which an ink is discharged, and dummy channel 12 from which the ink is not discharged are arranged alternately. Head chip 1 is an independent drive type head chip which performs recording by discharging an ink only from drive channels 11.
The drive channels arranged in row A of the two channel rows are defined as 11 A, and dummy channels arranged in row A are defined as 12A. Further, the drive channels arranged in row B of the two channel rows are defined as 11B, and dummy channels arranged in row B are defined as 12B.
In each channel row (row A or row B), drive channels (11A, 11B) and dummy channels (12A, 12B) are disposed alternately. Partition walls 13 between drive channels (11A, 11B) and dummy channels (12A, 12B) adjacent to each other function as a pressure-imparting means composed of a piezoelectric element such as PZT. Hereinafter, the partition walls in row A and row B may be sometimes referred to as 13A and 13B, respectively.
Each of the drive channels (11A, 11B) and each of the dummy channels (12A, 12B) opens at both front end surface 1a and rear end surface 1b of head chip 1. In inkjet head H illustrated in FIG. 2, the end surface on the ink-discharging side of head chip 1 is referred to as "front end surface 1a," and the end surface on the opposite side is referred to as "rear end surface 1b."
On the inner surface of each channel (11A, 11B, 12A, 12B), drive electrode 14 is formed closely. An outlet of each channel is provided at front end surface 1a of head chip 1, and an inlet thereof is provided at rear end surface 1b of head chip 1. Each channel is formed straight from the inlet to the outlet.
On rear end surface 1b of head chip 1, connection electrodes (15A, 15B) are formed. One end of each connection electrode (15A, 15B) is conducted to a drive electrode in the corresponding drive channel 11A or 11B or dummy channel 12A or 12B. Further, connection electrode 15A elongates from the inside of each channel 11A or 12A to one end edge 1c of head chip 1. Connection electrode 15B extends toward row A from the inside of each channel 11B or 12B, and elongates to an area before the channel row of row A. Thus, both of connection electrodes 15A and 15B extend in the same direction from each channel (11A, 11B, 12A, 12B).
Nozzle plate 2 is joined to front end surface 1a of head chip 1 with an adhesive. In nozzle plate 2, nozzles 21 open only at positions corresponding to drive channels 11 A and 11B.
Wiring circuit board 3 is a tabular circuit board larger than rear end surface 1b of head chip 1. At an area within a joining area (area indicated by dashed line in FIG. 2) 31 of wiring circuit board 3, to which rear end surface 1b of head chip 1 is joined, through- holes 32A and 32B are provided separately. The positions of through- holes 32A and 32B correspond, respectively, to drive channels 11A and 11B which open at rear end surface 1b of head chip 1. Through through- holes 32A and 32B, the ink is suppled from common ink chamber 51 of ink manifold 5 to the inside of the respective drive channels (11A, 11B).
Common ink chamber 51 is composed of the inner space of box-shaped ink manifold 5 adhered to the rear surface side (opposite to head chip 1) of wiring circuit board 3. The ink inside common ink chamber 51 is supplied to the respective drive channels 11A and 11B through through- holes 32A and 32B. Accordingly, drive channels 11A and 11 B are in fluid communication with each other via this common ink chamber 51. Dummy channels 12A and 12B are sealed with wiring circuit board 3, and are not in fluid communication with common ink chamber 51.
On the surface of wiring circuit board 3, wiring electrodes 33A and 33B are formed, which are electrically connected to the respective connection electrodes 15A and 15B arranged on rear end surface 1b of head chip 1. Wiring electrodes 33A and 33B extend on the surface of wiring circuit board 3 in the direction orthogonal to the channel rows (row A and row B) of head chip 1. Wiring electrodes 33A and 33B are arranged alternately. Further, wiring electrodes 33A and 33B are formed by means of vapor deposition or a sputtering method.
One end of wiring electrode 33A corresponding to connection electrode 15A drawn from each of channels 11A and 12A arranged in row A is positioned in the vicinity corresponding to each of channels 11A and 12A in row A in joining area 31. Further, wiring electrode 33A extends in a direction orthogonal to the channel rows of head chip 1 from joining area 31, and elongates to end portion 3a of wiring circuit board 3.
On the other hand, one end of wiring electrode 33B corresponding to connection electrode 15B drawn from each of channels 11B and 12B arranged in row B is positioned in the vicinity corresponding to each of channels 11B and 12B in row B in joining area 31. Further, wiring electrode 33B extends in the same direction as wiring electrode 33A, and elongates to end portion 3a of wiring circuit board 3 through between adjacent through-holes 32A in row A.
Wiring circuit board 3 is pasted to rear end surface 1b of head chip 1, so that connection electrodes (15A, 15B) of head chip 1 and wiring electrodes (33A, 33B) of wiring circuit board 3 correspondingly connect to each other electrically. Wiring circuit board 3 and head chip 1 are joined together by an adhesive at a predetermined pressing force (e.g., 1 MPa or more). The adhesive to be used may be an anisotropic conductive adhesive containing conductive particles, but is preferably an adhesive not containing conductive particles for enhancing the reliability in preventing short circuit.
Inkjet head H is mounted on carriage 400 of inkjet recording apparatus 100 such that the row direction of the channel rows (row A and row B) is in the same direction as Y direction in FIG. 1. Inkjet head H is electrically connected to drive apparatus 500 via FPC 4 (refer to FIG. 1). When a drive signal corresponding to image data transmitted from a drive circuit in drive apparatus 500 is applied to drive electrode 14 of each of drive channels 11 via FPC 4, partition wall 13 undergoes shear deformation to change the volume of drive channels 11, thus imparting discharging pressure to the ink inside drive channels 11.

3. Drive of Inkjet Head

FIG. 5 illustrates an example of a drive signal given to inkjet head H for discharging the ink from nozzles 21 of inkjet head H. The drive signal is a rectangular wave composed of a positive voltage (+V) with pulse width PW, and generates a negative pressure in the channel.
The ink-discharging operation of inkjet head H by the drive signal is described with reference to FIGS. 6A and 6B. FIGS. 6A and 6B illustrate a single drive channel 11, two dummy channels 12 arranged adjacently on both sides of the signal drive channel 11, and two partition walls 13 therebetween, in a single channel row of inkjet head H.
As illustrated in FIG. 6A, when partition wall 13 between drive channel 11 and dummy channel 12 is in a medium state, a drive signal illustrated in FIG. 5 is applied to drive electrode 14 of drive channel 11. Then, as illustrated in FIG. 6B, an electric field is generated in a direction perpendicular to the polarization direction (indicated by arrows in drawings) of a piezoelectric element forming partition wall 13. As a result, both partition walls 13 undergo shear deformation outwardly from each other in a doglegged shape to expand the volume of drive channel 11. Due to the deformation of partition wall 13, the ink flows into drive channel 11. The deformed state is maintained for the period of predetermined pulse width PW, and then the drive signal returns to 0 potential. Thereupon, pressure is applied to the ink inside drive channel 11 to discharge droplets from nozzles 21.
The variation of ink pressure inside drive channel 11 caused by the deformation of partition wall 13 repeats reversion for every 1 acoustic length (AL) "from negative to positive" and "positive to negative." Therefore, in order to discharge droplets efficiently, it is preferable that pulse width PW which is a duration of positive voltage of the drive signal be approximated to the time difference (1AL) between the timing at which the pressure inside drive channel 11 shifts "from negative to positive" and the timing at which the pressure inside drive channel 11 shifts "from positive to negative," and specifically pulse width PW is preferably set in a range of from 0.8 AL or more to 1.2 AL or less.
AL indicating the duration of the drive signal refers to 1/2 of the acoustic resonance period of a pressure wave in dummy channel 12. AL is determined as a pulse width at which the flying velocity of a droplet is the maximum, when measuring the velocity of a droplet discharged at the time of applying rectangular wave drive signals to drive electrode 14, with pulse width PW of the rectangular wave being varied, and the voltage value of the rectangular wave being constant.
The pulse is a rectangular wave of a constant voltage peak value. Pulse width PW is defined as a time difference between the timing at which the voltage reaches 10% after rising from 0 V and the timing at which the voltage reaches 10% after falling from the peal value, when 0 V is set as 0% and the peak value of the voltage is set as 100%.
The rectangular wave refers to a wave form in which both the time required for the voltage to rise from 10% to 90% and the time required for the voltage to fall from 90% to 10% are within 1/2 of AL, and more preferably within 1/4 of AL.
Next, a method in which drive apparatus 500 applies a drive signal to inkjet head H.
Drive apparatus 500 drives N (N is an integer of 2 or more) drive groups independently into which all the channel rows of inkjet head H are divided.
The drive channels in a channel row belonging to a single drive group receive drive signals applied from drive apparatus 500 at identical timing within drive period T of inkjet head H. A plurality of channel rows may belong to a single drive group. Each drive channel 11 and each dummy channel 12 included in a single channel row are inevitably included in an identical drive group.
For example, inkjet head H illustrated in FIG. 2 has two channel rows. Here, under the condition of N = 2, the channel row of row A is defined as drive group A, and the channel row of row B as drive group B, as illustrated in FIG. 7. That is, all the channel rows of inkjet head H are divided into two drive groups.
In inkjet head H, all drive channels 11 in a channel row belonging to an identical drive group receive applied drive signals simultaneously.
Phase difference "nAL + t" is given to between a drive signal applied to drive electrode 14 of each of drive channels 11 constituting drive group A from drive apparatus 500 and a drive signal applied to drive electrode 14 of each of drive channels 11 constituting drive group B therefrom, as illustrated in the timing chart of FIG. 8. Here, a drive signal is applied to drive period T of drive group A, so that drive group A is driven prior to drive group B. It is noted that n is an integer of 1 or more, and AL is 1/2 of acoustic resonance period of a pressure wave in drive channel 11, as described above. FIG. 8 exemplifies the case of n = 1.
Further, t is a pressure wave transmission time determined by "inter-nozzle distance between drive groups"/"speed at which sound is transmitted in an ink."
The term "between drive groups" in the "inter-nozzle distance between drive groups" represents the meaning of "between two drive groups which are to be driven with a phase difference." When there are two channel rows as illustrated in FIG. 7, "inter-nozzle distance between drive groups" is a distance indicated by D in FIG. 7.
Speed C at which sound is transmitted in an ink can be calculated by the following equation. This speed C is a value intrinsic to an ink. $C = \sqrt{K / ρ}$
where K is bulk modulus, and p is the density of an ink.
Drive channels 11A of drive group A and drive channels 11B of drive group B are in fluid communication with each other via common ink chamber 51. Therefore, when drive signals are applied respectively to drive electrodes 14 of drive channels 11 A of drive group A and drive electrodes 14 of drive channels 11B of drive group B to discharge droplets, the droplets velocity may sometimes fluctuate considerably due to the influence of crosstalk. However, according to the experiments of the present inventors, it has been found that, for example, when inkjet head H is driven such that droplets are discharged from drive channels 11 A of drive group A and then droplets are discharged from drive channels 11 B of drive group B after the elapse of a predetermined Delay time, the velocity of the droplets discharged from drive channels 11 B of drive group B periodically fluctuate depending on the Delay time with respect to the velocity of the droplets discharged from drive channels 11 A of drive group A.
As illustrated in FIG. 9, the velocity of a droplet discharged from drive channels 11 B repeats reversion toward plus or minus for every 1 AL, after "time lag" from the time of discharging droplets from drive group A. At the time of the reversion, the velocity of the droplets from drive channels 11 B of drive group B becomes substantially equal to the velocity of the droplets from drive channels 11 A of drive group A. Further, it has been ascertained that the "time lag" from the time of discharging droplets from drive group A corresponds to the above-mentioned "time t."
That is, it has been found that the velocity of the droplets from drive channels 11B of drive group B after the elapse of nAL + t from the time of discharging droplets from drive channels 11A of drive group A is substantially equal to the velocity of the droplets from drive channels 11 A of drive group A.
Therefore, by imparting phase difference nAL + t to between drive signals applied to drive groups A and drive signals applied to drive groups B, it becomes possible to substantially ignore the influence of crosstalk between drive groups A and B sharing common ink chamber 51 without modifying the head structure of inkjet head H at all. That is, it becomes possible to suppress the fluctuation of ink droplet velocity between channel rows. Moreover, the drive load is also suppressed, because a phase difference is imparted to between the drive signals for drive group A and the drive signals for drive group B.
As illustrated in FIG. 9, the velocity of the droplets from drive channels 11 of drive group B undergoes reversion toward plus or minus for every 1AL after the elapse of time t. Therefore, any integer of 1 or more can be employed for n. However, it is necessary that drive signals for the discharge from a drive group to be driven later should not overlap subsequent drive period T. Further, when n value becomes too large, the differences among timings to drive different drive groups become large, which may cause printing speed to be lowered. Therefore, from the viewpoint of high-speed printing, n is preferably a value as small as possible, and n = 1 is the most preferred.
Typically, an inkjet head having a plurality of channel rows discharges droplets from nozzles at preset different timings, in order to adjust the deviation of landing position due to the differences in the physical nozzle position among channel rows adjacent to each other. For example, in inkjet head H having two channel rows, as illustrated in FIG. 10, at a certain physical position, a first channel row (e.g., drive group A) starts discharging; recording medium P and inkjet head H move relatively to each other; and nozzles 21 of a second channel row (drive group B) reach the above-mentioned physical position. Then, the moment the nozzles 21 of the second channel row (drive group B) reach there, the second channel row starts discharging. Even in this case, the respective drive channels 11 typically perform discharging at the same drive timing, and differ for every channel row only in the starting time and the finishing time.
Thus, the phase difference nAL + t among drive groups in the present invention means a Delay time not including the difference in the starting time and the finishing time caused by the landing position adjustment (time period of landing position adjustment between drive groups) due to the difference in the physical nozzle position among drive groups. That is, as illustrated in FIG. 10, the phase difference nAL + t means a Delay time provided in a time period during which two drive groups to which a phase difference is imparted are driven together. That is, the phase difference nAL + t is imparted between different drive groups A and B at a timing of application of drive signals in the time period during which two drive groups are driven together. Thus, the timings per se at which droplets are discharged are different.
Strictly speaking, there is a problem where imparting the phase difference nAL + t to between drive groups A and B requires the landing position adjustment between drive groups A and B. However, this problem can be solved by adjusting the relative moving speed between recording medium P and inkjet head H.
The above description is an explanation for the case where the inkjet head has two channel rows. In the present invention, any of a plurality of channel rows can be sufficient for the inkjet head. The plurality of channel rows can be divided into N (N is an integer of 2 or more) drive groups to be driven in the same manner as described above.
FIG. 11 illustrates a case where the inkjet head has four channel rows; and four channel rows are divided into 2 drive groups (drive groups A and B). Drive groups A and B are arranged alternately such that channel rows adjacent to each other belong to drive groups different from each other.
In the embodiment illustrated in FIG. 11, D' is preferably substantially as large as D or large enough to attenuate a pressure wave. Among these, D is defined as "inter-nozzle distance between drive groups."
As for the timing of application of drive signals in this case, as illustrated in FIG. 12, phase difference of 1AL + t (in the case of n = 1) is imparted to between drive groups A and B. Thus, it becomes possible to suppress droplet velocity fluctuation between drive groups A and B, and to lower the drive load.
FIG. 13 illustrates a case where the inkjet head has six channel rows; all the six channel rows are divided into three drive groups (drive groups A, B, and C). Drive groups are arranged in the order of A, B, C, A, B, C such that channel rows adjacent to each other belong to drive groups different from each other.
In the embodiment illustrated in FIG. 13, D' is preferably substantially as large as D or large enough to attenuate a pressure wave. Among these, D is defined as "inter-nozzle distance between drive groups."
As for the timing of application of drive signals in this case, as illustrated in FIG. 14, phase difference of 1 AL + t (in the case of n = 1) is imparted to between drive groups A and B adjacent to each other, and to between drive groups B and C adjacent to each other. Thus, it becomes possible to suppress droplet velocity fluctuation among drive groups A, B, and C, and to lower the drive load.
Thus, when the channel rows are divided into three or more drive groups, it is preferable that all n values in the phase difference nAL + t among drive groups be the same values, from the viewpoint of avoiding the lowering of printing speed.
In the case where the number of channel rows is three or more, drive groups in adjacent channel rows are preferably different from each other. When at least one channel row belonging to different drive group is arranged between channel rows belonging to the same drive group, the clearance between the same drive groups is increased, thus lowering the influence of crosstalk between the same drive groups.
All the channel rows of inkjet head H need not be necessarily driven by a common drive circuit inside drive apparatus 500. Drive apparatus 500 may have two or more drive circuits, and may allow the two or more drive circuits to drive channel rows of each drive group. In this case, channel rows driven by a single drive circuit preferably belong to drive groups different from each other.
FIG. 15 illustrates an example in which two of four channel rows of inkjet head H are respectively driven by two drive circuits (drive circuits 501 and 502) inside drive apparatus 500. In this case, two channel rows driven by drive circuit 501 belong to drive groups (A and B) different from each other. Likewise, two channel rows driven by drive circuit 502 belong to drive groups (A and B) different from each other. By configuring in this manner, it becomes possible to reduce the lowering of droplet velocity. The reason for this is because the reduction in the number of drive channels driven simultaneously by a single drive circuit can reduce the load on the drive circuit, thus reducing the waveform rounding of the drive signal.
In the above description, the drive signal of a rectangular wave composed of a positive voltage (+V) with pulse width PW is employed for generating a negative pressure for dummy channels 12, but the drive signal is not limited to such a drive signal. Any drive signal for charging droplets can be employed.
In the above description, so-called "harmonica-shaped head chip" assuming a hexagonal shape with inlets and outlets of channels being disposed on end surfaces opposite to each other is employed as head chip 1 of inkjet head H. In harmonica-shaped head chip 1, the inlets of drive channels 11 of all the channel rows are disposed on rear end surface 1b, and common ink chamber 51 is disposed on the side of the inlets of drive channels 11. Accordingly, the influence of crosstalk is relatively large, and thus droplet velocity fluctuation is likely to occur. Therefore, this head chip structure is a preferred mode, because a remarkable effect is easily obtained from the configuration of the present invention. However, the head chip structure in the present invention is not necessarily limited to such a structure, and any structure in which respective pressure chambers in a plurality of pressure chamber rows are in fluid communication with each other can be sufficient.
Further, the inkjet recording apparatus in the present invention is not limited to the one which discharges droplets for recording in the course of moving inkjet head H for scanning in the width direction (main scanning direction) of recording medium P; it is also possible to employ an inkjet recording apparatus which is configured by a line-shaped inkjet head fixed over recording medium P in the width direction and which discharges droplets from nozzles 21 for recording in the course of moving recording medium P in Y direction in FIG. 1. In this case, the channel rows of inkjet head H are arranged in X-X' direction in FIG. 1.

4. Dyeing Method

Fibers to be dyed by the dyeing method of the present invention are not particularly limited as long as the fibers can be dyed with a disperse dye; above all, fibers such as polyester, acetate, and triacetate are preferred. Among those, polyester fibers are particularly preferred.
Fibers to be dyed may be clothes. Clothes in any form of woven fabric, knit fabric, and nonwoven fabric cloth of fibers can be sufficient. Further, a cloth made of 100% fiber which is dyeable with a disperse dye is suitable, but a blended fabric cloth or blended nonwoven fabric cloth with rayon, cotton, polyurethane, acrylic fiber, nylon, wool, silk, and the like can also be used as a cloth for printing. The thickness of yarn for composing the above-mentioned cloth is preferably in a range of from 10 to 100 d.
A cloth to be dyed by means of high-temperature steaming preferably contains a dye auxiliary. The dye auxiliary produces a eutectic mixture with water condensed on a printed cloth when steaming the cloth, thus restricting the amount of water content which evaporates again to shorten the temperature rising time. Further, this eutectic mixture dissolves a dye on a fabric to accelerate the speed of diffusion of the dye into the fiber.

Examples of the dye auxiliary include urea.

The inkjet dyeing method of the present invention may be printing (inkjet printing).
In the case of the inkjet dyeing method of the present invention, it is desirable to wash natural impurities (such as fat and oil, wax, pectic substance, and natural coloring matter) adhered to a fiber, residual chemical agents (such as sizing agent) used in cloth production processes, and stains, before subjecting the fiber to a pretreatment with a water-soluble polymers to obtain a uniformly dyed product. Examples of a washing agent to be used in washing include alkalis such as sodium hydroxide and sodium carbonate, surfactants such as anionic surfactants and non-ionic surfactants, and enzymes.
In the inkjet dyeing method of the present invention, it is preferable to apply a pretreatment agent by means of padding method, coating method, spray method, and the like for a bleed-preventing effect (pretreatment step). Thereafter, an image is formed on a fiber which is dyeable with a disperse dye in an inkjet recording method using the above-described ink (ink-imparting step), then a cloth to which the ink was imparted is subjected to a thermal treatment (color development step), and further the cloth having been subjected to the thermal treatment is washed (washing step), thereby finishing the printing on the fiber to obtain a dyed product (printed product).
As the pretreatment, a method suitable to a fiber material or an ink can be appropriately selected from known methods such as a method in which a fiber is treated with a water-soluble polymer, and the pretreatment method is not particularly limited. For example, when at least a single material selected from the group consisting of a water-soluble metal salt, a polycation compound, a water-soluble polymer, a surfactant and a water repellant is used so as to be added to the fiber at a ratio of 0.2 to 50 mass%, a high degree of bleeding prevention is possible, which preferably enables a high-definition image to be printed on a cloth.
Examples of the specific water-soluble polymer used in the pretreatment include starches such as corn and wheat, cellulose derivatives such as carboxymethyl cellulose, methyl cellulose and hydroxyethyl cellulose, polysaccharides such as sodium alginate, guar gum, tamarind gum, locust bean gum and gum arabic, and protein substances such as gelatin, casein and keratin, and synthesized water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and acrylic acid-based polymer. Examples of the surfactant used in the pretreatment include anionic, cationic, amphoteric and nonionic surfactants. Typical examples thereof include anionic surfactants such as a higher alcohol sulfuric acid ester salt and a sulfonate of a naphthalene derivative; cationic surfactants such as a quaternary ammonium salt; amphoteric surfactants such as an imidazolidine derivative; and nonionic surfactants such as polyoxyethylene alkyl ether, polyoxyethylene propylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, and an ethylene oxide adduct of acetylene alcohol.
Examples of the water repellent include a silicon-based, fluorine-based, and wax-based water repellents. These water-soluble polymers and surfactants to be added to a cloth in advance are preferably stable to a high-temperature environment, so as not to be a cause of stain by tarring at the time of color development at a high temperature during inkjet printing. Further, these water-soluble polymers and surfactants to be added to a cloth in advance are preferably those which can be easily removed from the cloth with a washing treatment after the color development at a high temperature during inkjet printing.
An inkjet printing method for performing printing on a cloth desirably winds the printed cloth after ink discharge, develops color with heating, and washes and dries the cloth. In the inkjet printing, satisfactory dyeing is not obtained only by performing printing on a cloth with an ink and merely leaving the ink printed on the cloth to stand. Further, for example, when continuing printing on a long cloth for a long period of time, printed cloth continues to be stacked on a floor or the like, and therefore it not only takes up space due to continuous discharge of the cloth, but also is insecure and causes a stain unexpectedly. For these reasons, it becomes necessary to perform a winding operation after printing. During this operation, a medium not involved in printing such as paper, fabric or vinyl, may be interposed between the clothes. However, in the case of cutting a cloth on the way or in the case of a short cloth, winding is not always necessary.
The color development step is a step of developing an original color hue of an ink by allowing a dye in the ink having been only adhered to the surface of a cloth after printing but not having been sufficiently adsorbed or fixed to the cloth, to adsorb and fix to the cloth. As the color development method, steaming with vapor, baking with dry heat, thermosol, and HT steamer with superheated vapor are used. These color development methods are appropriately selected depending on materials, inks, or the like. Further, the printed cloth may be dried and subjected to color development treatment depending on use applications by subjecting the printed cloth to heating treatment either immediately, or after having been left to stand for a while; the present invention may employ either of these methods.
In dyeing using a disperse dye, a carrier may also be used in addition to a method of color development at a high temperature. Compounds to be used as a carrier preferably have features of large dye enhancement, simple usage, stability, less load on human body or environment, easy removal from fiber, and no influence on dye fastness. Examples of the carrier include phenols such as o-phenylphenol, p-phenylphenol, methylnaphthalene, alkyl benzoate, alkyl salicylate, chlorobenzene and diphenyl, ethers, organic acids, and hydrocarbons. These carriers facilitates the swelling and plasticization of a fiber such as a polyester difficult to be dyed at a temperature around 100°C to allow the disperse dye to easily enter the fiber. The carrier may be either adsorbed to fibers of a cloth to be used for inkjet printing in advance, or contained in an inkjet printing ink.
A washing step is necessary after the heating treatment, because the remaining of a dye not having been involved in dyeing deteriorates the stability of color to lower the fastness of the color. Further, it is also necessary to remove a pretreatment substance applied to the cloth. When the pretreatment substance is left as it is, not only the fastness is lowered, but also the cloth undergoes discoloration. Therefore, washing depending on substances to be removed or purposes is essential. The method therefor is selected depending on materials to be printed or inks; for example, a polyester is treated typically with a liquid mixture of caustic soda, a surfactant and hydrosulfite. The method therefor is typically performed using an open soaper in continuous dyeing, or using a jet dyeing machine in batch dyeing; in the present invention, either of the above methods may be used.
Drying is necessary after the washing. The washed cloth is squeezed or dewatered, and subsequently aired or dried using a drying machine, heat roll, iron, or the like.

EXAMPLES

Hereinafter, the present invention will be described in more detail by way of Examples. The scope of the present invention is not construed to be limited by these Examples.

[Example 1]

<<Preparation of Ink>>

[Preparation of Dye Dispersion Liquids A1 to A4, B1 to B4, C1, D1, E1 to E4, F1, and G1]

A liquid mixture obtained by sequentially mixing the following additives was subjected to dispersion treatment using a sand grinder to prepare a dye dispersion liquid. During the dispersion treatment, the amount of coarse particles in a liquid particle counter (HIAC-8000A manufactured by Hach Company) was measured. When a set percentage was obtained, the dispersion treatment was finished.

Dye (Type listed in Table 1)	25 parts
Glycerol	30 parts
Dispersant (Type and amount listed in Table 1)
Ion-exchanged water	amount required to make the total amount 100 parts

[Table 1]

Dispersion Liquid	Dye	Dispersant	Addition Amount of Dispersant	Percentage of Coarse Particles of 5 µm or more	Percentage of Coarse Particles of 2 µm or more
A1	C.I.Disperse Yellow 114		12 parts	6%	-
A2	C.I.Disperse Yellow 114		12 parts	3%	-
A3	C.I.Disperse Yellow 114		12 parts	1%	-
A4	C.I.Disperse Yellow 114		12 parts	0.5 %	-
B1	C.I.Disperse Blue 165		4 parts	6%	-
B2	C.I.Disperse Blue 165		7 parts	3%	-
B3	C.I.Disperse Blue 165		10 parts	1 %	-
B4	C.I.Disperse Blue 165	BYK-190	12 parts	0.5%	-
C1	C.I.Disperse Blue 60	(BYK, Inc.)	12 parts	0.5%	-
D1	C.I.Disperse Red 302		14 parts	less than 5 %	6%
D2	C.I.Disperse Red 302		14 parts	-	3%
D3	C.I.Disperse Red 302		14 parts	-	1 %
D4	C.I.Disperse Red 302		14 parts	-	0.5%
E1	C.I.Disperse Red 92		14 parts	-	0.5%
F1	C.I.Disperse Red 177		14 parts	-	0.5%
G1	C.I.Disperse Violet 57		14 parts	-	0.5%

[Preparation of Inks A1 to A4, B1 to B4, C1, D1, E1 to E4, F1, and G1]

Inks A1 to A4, B1 to B4, C1, D1, E1 to E4, F1, and G1 were prepared in accordance with the following formulation using the above-prepared respective dye dispersion liquids.

Dye Dispersion Liquid	40 parts
Ethylene glycol	15 parts
Glycerol	appropriate amount
Diethylhexyl sodium sulfosuccinate	appropriate amount
PROXEL GXL (Avecia Biotechnology, Inc.)	0.1 part
Ion-exchanged water	amount required to make the total
	amount
100 parts

The amount of glycerol was adjusted such that the viscosity of the ink was 5.7 mPa·s. An appropriate amount of diethylhexyl sodium sulfosuccinate was added to set the surface tension of the ink at 41 mN/m. Thereafter, each ink having been prepared was flowed into a hollow fiber film having gas permeability (manufactured by Mitsubishi Rayon Co., Ltd.), and the outer surface side of the hollow fiber film was depressurized with a water-flow aspirator to thereby remove gas dissolved in the ink. Further, the ink was filled into a vacuum pack after the degassing to prevent air from mixing into the ink.

<<Continuous Ejection Test>>

Continuous ejection test was performed using the prepared inks A1 to A4, B1 to B4, C1, D1, E1 to E4, F1 and G1 and using an inkjet apparatus.
As illustrated in FIG. 11, an inkjet head having four nozzle rows was prepared. All the channel rows were divided into two drive groups A and B such that adjacent channel rows belonged to different drive groups. Each channel row had 256 nozzles, and the inter-nozzle distance D between channel rows belonging to different drive groups was 0.846 mm, with AL = 5.0 µs.
As illustrated in FIG. 15, the four channel rows of this inkjet head were driven by two drive circuits.
As described above, the inks A1 to A4, B1 to B4, C1, D1, E1 to E4, F1 and G1 had a viscosity of 5.7 mPa·s and a surface tension of 41 mN/m, and the speed at which sound is transmitted in the ink was 1,600 m/s. From the above conditions, pressure wave transmission time t determined by "inter-nozzle distance between adjacent pressure chamber rows"/"speed at which sound is transmitted in an ink" was calculated as: 846 (µm) / 1,600 × 10⁶ (µ/s) = 0.53 ×10^-6 (s) = 0.53 (µs). From this calculated value, the approximation: t = 0.5 (µs) was obtained.
As a drive signal applied to each drive channel from a drive apparatus, a rectangular wave composed only of a positive voltage (+V) illustrated in FIG. 5 was employed. Pulse width PW was set at 1AL = 5.0, and drive period T was set at 100 µs. It is noted that drive signals are applied to all the channel rows from a common drive apparatus.
An inkjet head was mounted on a carriage of an inkjet recording apparatus illustrated in FIG. 1. With the phase difference between drive groups A and B: (nAL + t), where n = 1, being set as: 1 × 5.0 + 0.9 = 5.9 µs, the inkjet head was driven so as to apply drive signals first to drive group A for performing inkjet printing.

30-minute or 60-minute continuous ink ejection was performed from all the nozzles of the used head at full duty, and the number of the occurrence of nozzle omission and of the droplets adhered to the surface of nozzles at the time of the continuous ejection to thereby evaluate the continuous ejection test. The results thereof are shown in Table 2.

1: No nozzle omission occurred, with no adherence of droplets
2: No nozzle omission occurred, with adherence of 5 droplets or less
3: No nozzle omission occurred, with adherence of 20 droplets or less
4: Nozzle omission occurred

Droplets discharged from the nozzles of each of drive groups A and B were captured using a camera. The obtained droplet image was subjected to image processing to thereby calculate droplet velocity. From the results, the average velocity of the nozzles for each channel row was determined. From the obtained average velocity, |average velocity of drive group A - average velocity of drive group B| was calculated, from which calculated value, the fluctuation ratio relative to the average velocity of drive group A (= calculated value / average velocity of drive group A × 100: unit (%)) was determined. The influence of crosstalk was evaluated according to the following criteria. The results thereof are shown in Table 2.

1: less than 5%
2: 5% or more and less than 10%
3: 10% or more and less than 15%
4: 15% or more

Drive load at the time of driving an inkjet head was determined as a ratio (%) to a current value set as 100 when driving all the drive channels, with no phase difference being provided with any of all the channel rows, with nAL + t = 0. A smaller drive load value is more preferred. The results thereof are shown in Table 2.

[Table 2]

Ink	Ejection Stability (30 min)	Ejection Stability (60 min)	Crosstalk	Drive Load	TI Value
A1
	4		1	50%	1.0	Comp. Ex.
A2	2		1	50%	1.0	Ex.
A3	1		1	50%	1.0	Ex.
A4	1		1	50%	1.0	Ex.
B1	4		1	50%	1.3	Comp. Ex.
B2	2		1	50%	1.2	Ex.
B3	1		1	50%	1.1	Ex.
B4	1		1	50%	1.0	Ex.
C1		1	1	50%	1.0	Ex.
D1		3	1	50%	1.0	Ex.
D2		2	1	50%	1.0	Ex.
D3		1	1	50%	1.0	Ex.
D4		1	1	50%	1.0	Ex.
E1		1	1	50%	1.0	Ex.
F1		1	1	50%	1.0	Ex.
G1		1	1	50%	1.0	Ex.

As shown in Table 2, it was found that, in inks A1 and B1 in which the percentage of coarse particles of 5 µm or more was 6%, nozzle omission occurred, so that stable ejection was not possible. In contrast, in all the inks in which the percentage of coarse particles of 5 µm or more was 3% or less, nozzle omission did not occur. However, in inks A2 and B2 in which the percentage of coarse particles of 5 µm or more was 3%, or ink C1 or C2 in which the percentage of coarse particles of 2 µm or more was 6% or 3%, nozzle omission did not occur, but droplets were adhered to the surface of nozzles.

[Example 2]

[Preparation of Dye Dispersion Liquids H1 and H2]

After the following additives were mixed sequentially, the mixture was subjected to dispersion treatment using a sand grinder to prepare a dye dispersion liquid. At that time, in the same manner as Example 1, a liquid particle counter was used during the dispersion treatment to measure the amount of coarse particles, and the dispersion treatment was finished when a set percentage was obtained.

Disperse dye (type listed in Table 3)	25 parts
Glycerol	30 parts
Dispersant (Type and amount listed in Table 1)
Ion-exchanged water	amount required to make the total amount
	100 parts

[Table 3]

Dispersion Liquid	Dye	Dispersant	Addition Amount of Dispersant	Percentage of Coarse Particles of 2 µm or more
H1	C.I.Disperse Red 343	BYK-190 (BYK, Inc.)	12 parts	0.5%
H2	C.I.Disperse Red 145	BYK-190 (BYK, Inc.)	12 parts	0.5%

[Preparation of Inks H1 and H2]

Using the above-prepared dye dispersion liquids H1 and H2, inks H1 and H2 were prepared in accordance with the following formulation.

Dye Dispersion Liquid	40 parts
Ethylene glycol	20 parts
Glycerol	appropriate amount
Diethylhexyl sodium sulfosuccinate	appropriate amount
PROXEL GXL (Avecia Biotechnology, Inc.)	0.1 part
Ion-exchanged water	amount required to make the total
	amount
100 parts

The amount of glycerol was adjusted such that the viscosity of the ink was 10.0 mPa·s. The appropriate amount of diethylhexyl sodium sulfosuccinate was added such that the surface tension of the ink was 32 mN/m. Thereafter, each ink having been prepared was flowed into a hollow fiber film having gas permeability (manufactured by Mitsubishi Rayon Co., Ltd.), and the outer surface side of the hollow fiber film was depressurized with a water-flow aspirator to thereby remove gas dissolved in the ink. Further, the ink was filled into a vacuum pack after the degassing to prevent air from mixing into the ink.

<<Continuous Ejection Test>>

Continuous ejection test was performed using the prepared inks H1 and H2 and using an inkjet apparatus.
An inkjet head having two channel rows with the same structure as that of the inkjet head illustrated in FIG. 2 was prepared. One channel row was defined as drive group A, and the other channel row as drive group B. Each channel row had 256 nozzles, and the inter-nozzle distance D between channel rows was 1.128 mm, with AL = 5.0 µs. The two channel rows of this inkjet head were driven by the same drive circuit.
As described above, the inks H1 and H2 had a viscosity of 10 mPa·s and a surface tension of 32 mN/m, and the speed at which sound is transmitted in the ink was 1,300 m/s. From the above conditions, pressure wave transmission time t determined by "inter-nozzle distance between drive groups"/"speed at which sound is transmitted in an ink" was calculated as: 1,128 (µm) / 1,300 × 10⁶ (µ/s) = 0.87 ×10^-6 (s) = 0.87 (µs). From this calculated value, the approximation: t = 0.9 (µs) was obtained.
As a drive signal applied to each drive channel from a drive apparatus, a rectangular wave composed only of a positive voltage (+V) illustrated in FIG. 5 was used. Pulse width PW was set at 1AL = 5.0, and drive period T was set at 100 µs. It is noted that drive signals are applied to all the channel rows from a common drive apparatus.

The inkjet head was mounted on a carriage of an inkjet recording apparatus illustrated in FIG. 1. With the phase difference between drive groups A and B: (nAL + t), where n = 1, being set as: 1 × 5.0 + 0.9 = 5.9 µs, the inkjet head was driven so as to apply drive signals first to drive group A.

In the same inkjet head as that in Drive Condition 1, a phase difference between drive groups A and B was not provided at all, with nAL + t = 0, to evaluate ejection stability, crosstalk, and drive load in the same manner. The results thereof are shown in Table 4.

In the same inkjet head as that in Drive Condition 1, the same conditions as in Example 1 were followed except that the phase difference (nAL + t), where n = 0.5 and t = 0, was set as: 0.5 × 5.0 = 2.5 µs, to evaluate ejection stability, crosstalk, and drive load. The results thereof are shown in Table 4.

The evaluations of ejection stability (continuous ejection time was set to 120 minutes), crosstalk, and drive load were performed in the same manner as Example 1.

[Table 4]

Drive Condition and Ink		Ejection Stability (120 min)	Crosstalk	Load Value	TI Value
Drive Condition
Drive Condition	1	H1		1	50%	1.0
H2	1	1	1	50%	1.0
Drive Condition 2	H1	1	3	100%	1.0
Drive Condition 2	H2	1	3	100%	1.0
Drive Condition 3	H1	1	4	100%	1.0
Drive Condition 3	H2	1	4	50%	1.0

As shown in Table 4, in drive condition 1, ejection was stable, with no generation of crosstalk, and drive load was also suppressed. On the other hand, in drive condition 2, no phase difference was provided between drive groups A and B, and thus crosstalk was generated. Furthermore, in drive condition 3, the phase difference between drive groups A and B was inappropriate, and thus crosstalk was generated.

Industrial Applicability

The inkjet dyeing method of the present invention is capable of enhancing the ejection stability of an ink from an inkjet head, and accordingly can make it possible to obtain a high-quality inkjet dyed product.

Reference Signs List

H:: Inkjet head
1:: Head chip
1a:: Front end surface
1b:: Rear end surface
1 c:: End edge
11, 11 A, 11B:: Drive channel (pressure chamber)
12, 12A, 12B:: Dummy channel
13, 13A, 13B:: Partition wall (pressure-imparting means)
14:: Drive electrode
15A, 15B:: Connection electrode
2:: Nozzle plate
21:: Nozzle
3:: Wiring circuit board
3a: End portion
31: Joining area
32A, 32B: Through-hole
33A, 33B: Wiring electrode
4: FPC
5: Ink manifold
51: Common ink chamber
100: Inkjet recording apparatus
200: Conveyance mechanism
201: A pair of conveyance rollers
202: Conveyance motor
203: Conveyance roller
300: Guide rail
400: Carriage
500: Drive apparatus
501, 502: Drive circuit

Claims

An inkjet dyeing method for ejecting an ink from an inkjet head for recording on a fiber, the ink containing at least a disperse dye, a dispersant, water and a water-soluble organic solvent, wherein
a ratio of the number of disperse dye particles having a particle diameter of 5 µm or more to the total number of disperse dye particles contained in the ink is 5% or less,
the inkjet head has two or more rows in which pressure chambers generating pressure for discharging an ink inside the pressure chambers from a nozzle with a pressure-imparting means operable by application of a drive signal are arranged, with the pressure chambers being in fluid communication with each other via a common ink chamber, and
a row in which the pressure chambers are arranged is divided into N (N is an integer of 2 or more) drive groups, and for each of the drive groups a phase difference of nAL + t (with the proviso that n is an integer of 1 or more, AL is 1/2 of acoustic resonance period of a pressure wave in a pressure chamber, and t is a pressure wave transmission time determined by "inter-nozzle distance between drive groups"/"speed at which sound is transmitted in the ink") is imparted to the drive signal to be applied to the pressure-imparting means of the pressure chamber.
The inkjet dyeing method according to claim 1, wherein adjacent rows of the pressure chambers are set as drive groups different from each other.
The inkjet dyeing method according to claim 1 or 2, wherein a thixotropic index of the ink is 1.2 or less.