JP2015212319A - Water-based ink, ink cartridge, recording unit, inkjet recording device and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ink containing resin particles and free from the generation of printing torsion.SOLUTION: Provided is an aqueous ink comprising: (A) resin particles dispersed with a surfactant including ethylene oxide chains; (B) a water-soluble resin having anionic charges; and (C) at least one kind of water-soluble organic solvent selected from the group consisting of 1,6-hexanediol, 1,5-pentanediol and 1,4-butanediol.

Description

  The present invention relates to an aqueous ink, an ink cartridge, a recording unit, an ink jet recording apparatus, and an ink jet recording method.

  In recent years, a recording head has a large number of nozzles arranged at high density in order to obtain a high-resolution image. In addition, the ink ejection frequency is improved to improve the printing speed. Such higher functionality creates new challenges. Specifically, the energy applied for ink ejection is lost as heat in addition to being used for ink ejection. A part of the generated heat is radiated by the ejected ink droplets, but not all of the heat is radiated, and the temperature of the recording head easily rises due to continuous ejection of ink. In this case, since the temperature of the ink in the recording head also rises, there may be a problem in ink ejection stability.

  On the other hand, as a water-based ink for inkjet recording, an ink to which resin particles are added has been developed in order to have excellent scratch resistance and image quality. Patent Document 1 proposes an ink containing resin particles and a water-soluble resin. Thereby, an ink jet recording method having high image quality and good scratch resistance can be proposed.

JP-A-6-171072

  The ink added with the resin particles sometimes has a phenomenon that the image quality of “printing quality” is lowered. This printing is a phenomenon in which the straightness of ink droplets is hindered when ink is ejected and the landing position of the ink is shifted, thereby degrading the image quality. In particular, such a phenomenon occurred remarkably when the temperature of the recording head rose.

  Thus, as a result of investigations by the present inventors, it has been found that the above-mentioned problems can be solved by adding specific components to the aqueous ink containing resin particles. That is, an object of the present invention is to provide a water-based ink that contains resin particles and does not cause printing distortion.

One embodiment is:
(A) resin particles dispersed by a surfactant containing an ethylene oxide chain;
(B) a water-soluble resin having an anionic charge;
(C) at least one water-soluble organic solvent selected from the group consisting of 1,6-hexanediol, 1,5-pentanediol, and 1,4-butanediol;
It relates to the water-based ink characterized by containing.

  A water-based ink that contains resin particles and does not cause printing distortion can be provided.

FIG. 2 is a longitudinal sectional view of a recording head. It is a cross-sectional view of the recording head. FIG. 2 is a perspective view of a recording head in which the recording head shown in FIG. It is a perspective view which shows an example of an inkjet recording device. It is a longitudinal cross-sectional view of an ink cartridge. It is a perspective view which shows an example of a recording unit. FIG. 3 is a schematic diagram illustrating an example of a configuration of a recording head.

  The water-based ink of this embodiment contains (A) resin particles dispersed by a surfactant containing an ethylene oxide chain, (B) a water-soluble resin having an anionic charge, and (C) a water-soluble organic solvent. (C) The water-soluble organic solvent contains at least one selected from the group consisting of 1,6-hexanediol, 1,5-pentanediol, and 1,4-butanediol.

Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. However, the embodiments described below are merely examples, and the scope of the present invention is not limited to the following embodiments.
According to this embodiment, it is possible to provide a water-based ink that contains (A) resin particles and does not cause printing distortion even when the temperature of the recording head rises. The case where the temperature of the recording head rises indicates, for example, a state where the temperature of the aqueous ink in the recording head is 45 ° C. or higher.

The present inventor presumes the reason why printing distortion does not occur even when the temperature of the recording head rises by using the water-based ink having the above-described configuration.
First, (A) a water-based ink containing resin particles dispersed by a surfactant containing an ethylene oxide chain is obtained. This surfactant obtains hydrophilicity by forming hydrogen bonds with oxygen atoms in the ethylene oxide chain and hydrogen atoms in water in the water-based ink, and the surface active ability is obtained by adsorbing the hydrophobic molecular chains to the resin particles. Is demonstrating.

  The aqueous test ink containing the component (A) and not containing the components (B) and (C) caused printing distortion when the temperature of the recording head increased. The reason for this is considered to be that when the ink temperature is increased, the molecular motion of water and the surfactant becomes intense, the hydrogen bond between the two is broken, and the hydrophilicity of the surfactant is lowered. For this reason, it is considered that the surface active ability of the surfactant was lowered and the dispersion of the resin particles became unstable. In addition to this, it is considered that the water in the ink evaporates in the vicinity of the nozzle outlet due to the temperature rise of the recording head, and the resin particles tend to aggregate.

  Next, (B) a water-soluble resin having an anionic charge was added to the test water-based ink. By adding this (B) water-soluble resin, the dispersibility of (A) resin particles can be improved even when the temperature of the recording head rises. The reason for this is considered to be that (B) the water-soluble resin is adsorbed to the resin particles together with the surfactant, and (A) has a function of assisting the dispersion of the resin particles. Therefore, even when the temperature of the recording head rises, even when the hydrogen bond is broken and the surface active ability of the surfactant is lowered, the water-soluble resin having an anionic charge does not deteriorate the surface active ability. Dispersion of particles can be assisted.

  However, even with the test aqueous ink containing the above components (A) to (B), when the temperature of the recording head rises, the effect of preventing printing distortion is insufficient. The reason for this is that when the ink temperature rises, (B) the amount of water-soluble resin adsorbed on (A) resin particles is small, and the surfactant and component (B) alone are not sufficient for the dispersion stability of the resin particles. This is probably because of this.

  Accordingly, the present inventor has further found that the water-based ink further comprises at least one water-soluble organic material selected from the group consisting of (C) 1,6-hexanediol, 1,5-pentanediol, and 1,4-butanediol. The inclusion of a solvent was studied. As a result, it has been found that even when the temperature of the recording head rises, printing distortion can be prevented. In this water-based ink, resin particles are dispersed by a surfactant and a part of the adsorbed (B) water-soluble resin. Furthermore, the hydrophobicity of the ink solvent is increased by the addition of the water-soluble organic solvent (C) as a solvent. Along with this, the water-soluble resin (B) whose solubility in the ink solvent has been reduced tends to exist in a more stable state in the ink. It is thought that it adsorbs stably. For this reason, in the water-based ink of the present embodiment, it is considered that (A) the dispersion stability of the resin particles is further improved, and printing does not occur even when the temperature of the recording head rises.

1. Below, each component used in water-based ink is demonstrated.

(Surfactant containing ethylene oxide chain)
The surfactant contains at least an ethylene oxide chain (—CH ₂ CH ₂ O—) in the molecular structure. The resin particles are dispersed in the ink by the surfactant. The number of ethylene oxide moieties (—CH ₂ CH ₂ O—) in one molecule of the surfactant is not particularly limited. The surfactant is not particularly limited as long as it is a compound having at least an ethylene oxide chain as a hydrophilic group and further having a hydrophobic molecular chain, and a known nonionic surfactant can be used. . Furthermore, two or more kinds of surfactants can be mixed and used. Specific examples of the nonionic surfactant include polyoxyethylene cetyl ether (Nikko Chemical BC-20, BC-15 manufactured by Nikko Chemicals). Moreover, polyoxyethylene oleyl ether (Nikko Chemicals NIKKOL BO-15V) can be mentioned.

  Further, as the surfactant, a polymerizable surfactant which is a compound composed of a polymerizable group, at least a hydrophilic group having an ethylene oxide chain, and a hydrophobic molecular chain may be used. Specifically, examples of the polymerizable surfactant include ADEKA rear soap SR-10S, ADEKA rear soap SR-30 (above, manufactured by ADEKA), and ANTOX LMA-20 (above, made by Nippon Emulsifier). Further, latemul PD-105, latemul PD-430 (manufactured by Kao) can be mentioned. These two or more kinds of polymerizable surfactants can be used as a mixture, or can be used as a mixture with a surfactant having no polymerizable group.

  The content of the surfactant in the water-based ink is preferably from 0.1% by mass to 20% by mass. When the content of the surfactant is within these ranges, the dispersibility of the resin particles in the aqueous ink can be effectively improved. As a result, printing distortion can be effectively prevented.

(A) Resin Particles As a result of investigations by the inventors, resin particles dispersed with a surfactant containing an ethylene oxide chain in a related technique are liable to cause printing problems. The surfactant containing an ethylene oxide chain has a surface active ability because the ethylene oxide chain exhibits hydrophilicity and has a hydrophobic molecular chain. This hydrophilicity originates from the fact that hydrogen bonds are formed between oxygen atoms in the ethylene oxide chain molecules and hydrogen atoms of water in the ink. However, when the temperature of the recording head rises, both hydrogen bonds are cut and the hydrophilicity is lowered, so that the surface activity of the surfactant is lowered. As a result, it is presumed that when the temperature of the recording head rises, the dispersion of the resin particles becomes unstable and aggregates in the nozzles of the recording head and in the vicinity of the discharge ports.

  In the case where the surfactant is polyoxyethylene alkyl ether, the printing distortion is particularly remarkable when the temperature of the recording head is increased. In this case, the surfactant is in an equilibrium state where the hydrophobic alkyl group repeats the physical adsorption reaction / desorption reaction on the surface of the resin particle. When the temperature of the recording head rises, the hydrophilicity of the ethylene oxide chain decreases and the surface activity of the surfactant decreases, and the equilibrium tends to desorption reaction, which is an endothermic reaction. For this reason, it is presumed that the surfactant for stabilizing the dispersion of the resin particles decreases and the dispersion tends to become unstable.

  In contrast, in the present embodiment, the water-based ink contains (B) a water-soluble resin and (C) a specific water-soluble organic solvent. Thereby, (A) resin particle can be effectively disperse | distributed because a part of (B) water-soluble resin adsorb | sucks to (A) resin particle with surfactant. In addition, the addition of the water-soluble organic solvent (C) increases the hydrophobicity of the ink solvent. Along with this, the water-soluble resin (B) whose solubility in the ink solvent has been lowered becomes a more stable state, and therefore a part of the free (B) water-soluble resin is adsorbed to the (A) resin particles. It is considered a thing. For this reason, with the water-based ink of the present embodiment, it is considered that (A) the dispersion stability of the resin particles is further improved, and that printing can be prevented even when the temperature of the recording head rises.

The resin particles are used for preparing a water-based ink in the form of a dispersion dispersed by a surfactant. (A) There are several methods for obtaining a dispersion of resin particles using a surfactant as described below.
As a first method, a method of mixing resin particles and a surfactant can be mentioned. Specific examples include a dispersion method using ultrasonic waves, various dispersion machines such as a paint shaker, and various stirring machines such as CLEARMIX.
As a second method, a method of obtaining a dispersion of a surfactant and resin particles by mixing a surfactant when polymerizing resin particles from a monomer can be mentioned. Examples of the polymerization method for the resin particles include emulsion polymerization, miniemulsion polymerization, and microemulsion polymerization.
As a third method, after synthesizing the polymer constituting the resin particles, a method of obtaining a dispersion of the surfactant and the resin particles can be mentioned. Examples of the preparation method include a phase inversion emulsification method.

Further, whether or not the surfactant and the resin particles are physically adsorbed can be measured by the following method, but is not limited to the following method.
The dispersion of the surfactant and resin particles is centrifuged, and the supernatant is removed. A solvent in which the surfactant dissolves and the resin particles do not dissolve is added to the remaining precipitate and suspended. Examples of this solvent include methanol and ethanol. Again, centrifuge and remove the supernatant. When the supernatant is dried, if a solid remains, it is considered that the surfactant is physically adsorbed on the resin particles. More specifically, the type and amount of the surfactant can be known by analyzing solids by liquid chromatography (LC), mass spectrometry (MS), or the like.
In addition, the resin particle (A) of this embodiment has a particle size in the aqueous ink. In contrast, (B) the water-soluble resin is dissolved in the ink and does not have a particle size.

  Specific examples of resins used for the resin particles include polyolefin, polystyrene, polyurethane, polyester, polyether, polyurea, polyamide, polyvinyl alcohol, poly (meth) acrylic acid and salts thereof, poly (meth) acrylate alkyl, polydiene and the like. A homopolymer or a copolymer obtained by combining a plurality of these can be given. The weight average molecular weight of the resin used for the resin particles is preferably 5000 or more and 3500000 or less, and more preferably 100000 or more and 1000000 or less. The average particle diameter of the resin particles is preferably in the range of 10 nm to 500 nm, and more preferably in the range of 50 nm to 300 nm. The content of the resin particles in the water-based ink is preferably 1.0% by mass or more and 50.0% by mass or less with respect to the total mass of the ink.

(B) Water-soluble resin having anion charge "Water-soluble resin having anion charge" refers to a resin having an anion charge which is dissolved in water and ionized at least partially in water-based ink. The water-soluble resin containing an anionic charge is not particularly limited. Specifically, a resin having at least one acidic group such as a carboxyl group (—COOH), a sulfonic acid group (—SO ₃ H), and a phosphoric acid group (—PO ₄ H) introduced therein, and these acidic groups as bases For example, a resin neutralized with the above can be used.

Examples of the water-soluble resin having a carboxyl group include polyacrylic acid, acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, and styrene-methacrylic acid-acrylic acid ester copolymer. Examples thereof include styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-maleic acid copolymer, vinyl acetate-acrylic acid copolymer, and salts thereof. As the form of the copolymer, any form of a random copolymer, a block copolymer, an alternating copolymer, and a graft copolymer can be used.
Examples of the water-soluble resin having a sulfonic acid group include polystyrene sulfonic acid, styrene-styrene sulfonic acid copolymer, and salts thereof.
Examples of the water-soluble resin having a phosphoric acid group include styrene-vinylphosphonic acid copolymers and salts thereof.

  Commercially available products can also be used as the water-soluble resin (B) described above. As a specific example, Joncryl 586 (weight average molecular weight: 4,600, acid value: 108) can be mentioned. The water-soluble resin preferably has an acid value of 70 or more and 120 or less and can be stably dissolved in water in which a base is dissolved. The acid value is represented by the number of mg of potassium hydroxide required to neutralize the acidic component in 1 g of resin. The acid value can be calculated from the calculation if the monomer component ratio in the resin is known. Moreover, when it is not known, it can also be obtained from neutralization measurement by the method prescribed in JIS K0070.

The present inventor presumes the reason why the water-soluble resin (B) having an acid value of 70 or more and 120 or less is particularly good as follows.
By using a water-soluble resin having an acid value of 120 or less, the acidic component in 1 g of the resin becomes an appropriate amount, and (B) the water-soluble resin can be made to have an appropriate water solubility. Furthermore, since it has moderate hydrophobicity, it can be adsorbed to (A) resin particles, and (A) printing distortion due to a decrease in dispersibility of resin particles can be effectively suppressed. Moreover, it can prevent that hydrophobicity becomes high by using (B) water-soluble resin whose acid value is 70 or more. As a result, it is possible to effectively suppress (B) the water-soluble resin from being deposited due to evaporation in the vicinity of the nozzle and the occurrence of printing distortion.

  The weight average molecular weight of the water-soluble resin (B) is preferably in the range of 1,000 to 100,000, and more preferably in the range of 2,000 to 20,000. Moreover, it is preferable that mass ratio represented by (A) resin particle / (B) water-soluble resin is 1 / 0.5 or more and 1 / 0.2 or less. By setting it as this range, the quantity of (B) water-soluble resin with respect to another component can be made into a suitable quantity. As a result, (A) the resin particles can be stably dispersed, and (B) the water-soluble resin released in the ink can be effectively prevented from being adsorbed and deposited near the nozzle surface. Therefore, it is possible to effectively prevent printing distortion. In addition, (A) resin particle / (B) water-soluble resin represents the ratio of the mass of resin particles alone (not including the surfactant) and the mass of the water-soluble resin.

(C) Water-soluble organic solvent (C) The water-soluble organic solvent is at least one solvent selected from the group consisting of 1,6-hexanediol, 1,5-pentanediol, and 1,4-butanediol. is there. By using these (C) water-soluble organic solvents in combination with other components (A) to (B), it is possible to effectively prevent printing distortion when the temperature of the recording head rises. Even if the water-soluble organic solvent is a diol, if the number of carbon atoms is 3 or less, the carbon chain is short and the solubility in water is high, so that (B) the effect of adsorbing the water-soluble resin to (A) resin particles is weak it is conceivable that. On the other hand, when the number of carbon atoms is 7 or more, the carbon chain is long and the solubility in water is low. Therefore, the water-soluble organic solvent itself is precipitated when the ink is dried, which may cause nozzle sticking and face wetting.

(D) Water-soluble organic solvent (D) The water-soluble organic solvent is a water-soluble organic solvent other than 1,6-hexanediol, 1,5-pentanediol, and 1,4-butanediol. The water-based ink of this embodiment may contain a water-soluble organic solvent other than (C) the water-soluble organic solvent as long as the effects of the present invention are not impaired. The (D) water-soluble organic solvent is not particularly limited, and any known water-soluble organic solvent can be used. Specific examples of the water-soluble organic solvent include glycerin, polyethylene glycol, and 2-pyrrolidone.

  The mass ratio represented by (C) water-soluble organic solvent / (D) water-soluble organic solvent is preferably 1 / 3.0 or more and 1 / 0.20 or less. When the mass ratio is within these ranges, the hydrophobicity of the ink solvent can be increased moderately, and the effect of assisting the dispersion of (A) resin particles by the (B) water-soluble resin can be effectively increased. Further, (B) molecules of the water-soluble resin can be prevented from aggregating in the nozzles of the recording head and in the vicinity of the discharge ports.

  The total content of the water-soluble organic solvent (C) and (D) in the water-based ink is preferably 10% by mass or more and 50% by mass or less, and 15% by mass or more and 35% by mass or less with respect to the total mass of the ink. More preferred. When the content is 10% by mass or more, it is possible to prevent the water in the ink near the nozzle surface from evaporating and the viscosity of the ink from changing greatly during a printing pause or the like, and to perform stable printing. Further, when the content is 50% by mass or less, it is possible to prevent the ink viscosity from increasing and to perform good ink ejection.

  Further, (D) a water-soluble organic solvent may contain a surfactant. Examples of the surfactant include a cationic surfactant, an anionic surfactant, an amphoteric surfactant, and a nonionic surfactant. In addition to hydrocarbon surfactants, fluorine surfactants, silicone surfactants, and the like can also be used. Specific examples of the surfactant include acetylenol E100 (manufactured by Kawaken Fine Chemical Co., Ltd.).

(E) Coloring material The water-based ink of the present embodiment can use a known dye or pigment as the coloring material. That is, the water-based ink of the present embodiment can be used as a pigment ink, a dye ink, or an ink containing a pigment and a dye. For example, the pigment is not particularly limited, and C.I. I. Carbon black can be suitably used as the pigment represented by the (color index) number and the inorganic pigment. The content ratio of the color material in the water-based ink can be 15% by mass or less, preferably 10% by mass or less. Further, the water-based ink of the present embodiment may be used as a clear ink that does not contain a color material. In this case, since the (A) resin particle exists in the portion to which the ink is applied on the recording medium, the applied portion can be visually recognized. And by using the configuration of the water-based ink of the present embodiment, it is possible to prevent the ink-applied portion from being distorted.

(F) Other components In addition to the above components, the water-based ink according to the present embodiment includes a pH adjuster, a rust inhibitor, an antiseptic, an antifungal agent, an antioxidant, a reduction inhibitor, and a water-soluble resin. You may contain various additives, such as a neutralizing agent and a salt.

(G) Water The water in the water-based ink is preferably deionized water. The water content in the water-based ink can be 30% by mass or more and 95% by mass or less, and preferably 50% by mass or more and 85% by mass or less with respect to the total mass of the ink.

2. Inkjet Recording Apparatus Hereinafter, an example of an inkjet recording apparatus using the water-based ink of the present embodiment will be described. First, FIG. 1 and FIG. 2 show an example of the configuration of a recording head that is a main part of an ink jet recording apparatus using thermal energy. FIG. 1 is a cross-sectional view of the recording head 13 along the ink flow path, and FIG. 2 is a cross-sectional view taken along the line AB of FIG. The recording head 13 includes a member having an ink flow path (nozzle) 14 and a heating element substrate 15. The heating element substrate 15 includes a protective layer 16, electrodes 17-1 and 17-2, a heating resistor layer 18, a heat storage layer 19, and a substrate 20. When a pulsed electric signal is applied to the electrodes 17-1 and 17-2 of the recording head 13, the region indicated by n of the heating element substrate 15 rapidly generates heat, and this embodiment is in contact with this surface. Air bubbles are generated in the water-based ink 21. Then, the meniscus 23 protrudes due to the pressure of the bubbles, and the aqueous ink 21 is ejected as an ink droplet 24 from the ejection port 22 of the nozzle 14 toward the recording medium 25.

FIG. 3 is an external view of an example of a multi-head in which a large number of recording heads shown in FIG. 1 are arranged. The multi-head includes a glass plate 27 having multi-nozzles 26 and a heating element substrate 28 similar to that shown in FIG.
FIG. 4 is a perspective view showing an example of an ink jet recording apparatus incorporating a recording head. The blade 61 is a wiping member, one end of which is held by a blade holding member, and forms a cantilever. The blade 61 is disposed at a position adjacent to the recording area by the recording head 65 and is held in a form protruding in the moving path of the recording head 65.

  Reference numeral 62 denotes a cap on the ejection port surface of the recording head 65, which is disposed at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, abuts on the ink ejection port surface, and performs capping. The structure to perform is provided. An ink absorber 63 provided adjacent to the blade 61 is held in a form protruding in the moving path of the recording head 65, similarly to the blade 61. The ejection recovery unit 64 includes a blade 61, a cap 62, and an ink absorber 63. The blade 61 and the ink absorber 63 remove moisture, dust, and the like from the discharge port surface.

  Reference numeral 65 denotes a recording head which has discharge energy generating means and performs recording by discharging ink onto a recording medium facing the discharge port surface where the discharge port is arranged. Reference numeral 66 denotes a movement of the recording head 65 by mounting the recording head 65. It is a carriage for performing. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 (not shown) driven by a motor 68. As a result, the carriage 66 can move along the guide shaft 67, and the recording area by the recording head 65 and the area adjacent thereto can be moved.

  Reference numeral 51 denotes a paper feeding unit for inserting a recording medium, and 52 denotes a paper feed roller driven by a motor (not shown). With these configurations, the recording medium is fed to a position facing the ejection port surface of the recording head 65 and discharged to a paper discharge unit having a paper discharge roller 53 as recording progresses. When recording by the recording head 65 is completed and the recording head returns to the home position, the cap 62 of the ejection recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. Yes. In this way, the ejection port of the recording head 65 is wiped.

  When the cap 62 is in contact with the ejection port surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the moving path of the recording head. When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are in the same position as in the wiping described above. As a result, the ejection port surface of the recording head 65 is wiped even during this movement. The recording head 65 is moved to the home position adjacent to the recording area at a predetermined interval not only when the recording is finished or when the ejection is recovered, but also while the recording head moves the recording area for recording. It moves, and wiping is performed along with this movement.

  FIG. 5 is a diagram illustrating an example of an ink cartridge 45 that contains ink supplied to the recording head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink container, for example, an ink bag, in which supply ink is stored, and a rubber plug 42 is provided at the tip thereof. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the recording head. An ink absorber 44 receives waste ink.

  The recording head and the ink cartridge are not limited to separate units, and as shown in FIG. 6, a unit in which the recording head and the ink cartridge are integrated can be suitably used. In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage unit that stores ink, for example, an ink absorber is stored, and a recording head unit in which the ink in the ink absorber has a plurality of ejection openings. 71 is ejected as ink droplets. Alternatively, a structure in which the ink container is an ink bag with a spring or the like inside without using an ink absorber may be used. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the cartridge with the atmosphere. The recording unit 70 is used in place of the recording head 65 shown in FIG. 4 and is detachable from the carriage 66.

  Next, an ink jet recording apparatus using mechanical energy will be described. A nozzle forming substrate having a plurality of nozzles, a pressure generating element composed of a piezoelectric material and a conductive material, and ink that fills the surroundings of the pressure generating element are provided. The pressure generating element is displaced by an applied voltage, and ink droplets are ejected from ejection ports. It has a feature of having a recording head. FIG. 7 is a schematic diagram showing an example of the configuration of the recording head. The recording head includes an ink flow path 80 communicating with an ink chamber, an orifice plate 81, a vibration plate 82 that applies pressure to ink, a piezoelectric element 83 that is bonded to the vibration plate 82 and is displaced by an electric signal, the orifice plate 81, and the vibration plate. It is comprised with the board | substrate 84 which supports and fixes 82 etc. The distortion stress generated by applying a pulsed voltage to the piezoelectric element 83 deforms the vibration plate bonded to the piezoelectric element 83 and pressurizes the ink in the ink flow path 80, thereby causing the discharge port of the orifice plate 81 to discharge. Ink droplets are ejected from 85. Such a recording head can be used by being incorporated in an ink jet recording apparatus similar to that shown in FIG.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by the following examples unless it exceeds the gist. In the text, “parts” and “%” are based on mass unless otherwise specified.

<(A) Preparation of dispersion of resin particles 1>
2 parts of n-hexadecane, 20 parts of methyl methacrylate and 2 parts of 2,2′-azobis- (2-methylbutyronitrile) were mixed and stirred for 0.5 hour. This mixture was dropped into 76 parts of a 5% NIKKOL BC15 (Nikko Chemicals) aqueous solution and stirred for 0.5 hour. Next, the ultrasonic wave was irradiated to the mixture for 3 hours using the ultrasonic irradiation machine. Subsequently, a polymerization reaction was performed in a nitrogen atmosphere at 80 ° C. for 4 hours to obtain a dispersion of (A) resin particles 1. The particle diameter of the obtained (A) resin particle 1 was 121 nm. The above-mentioned NIKKOL BC15 corresponds to a surfactant containing an ethylene oxide chain.

<Preparation of (B) water-soluble resin>
((B) Preparation of water-soluble resin 1)
By neutralizing a styrene-ethyl acrylate-acrylic acid copolymer having a weight average molecular weight of 9000 and an acid value of 120 with a 10% aqueous potassium hydroxide solution, (B) water-soluble resin 1 was obtained.
((B) Preparation of water-soluble resin 2)
A water-soluble resin (B) was obtained by neutralizing a styrene-ethyl acrylate-acrylic acid copolymer having a weight average molecular weight of 12,000 and an acid value of 50 with a 10% aqueous potassium hydroxide solution.
((B) Preparation of water-soluble resin 3)
A water-soluble resin (B) was obtained by neutralizing a styrene-ethyl acrylate-acrylic acid copolymer having a weight average molecular weight of 9000 and an acid value of 70 with a 10% aqueous potassium hydroxide solution.
((B) Preparation of water-soluble resin 4)
A styrene-ethyl acrylate-acrylic acid copolymer having a weight average molecular weight of 7000 and an acid value of 160 was neutralized with a 10% aqueous potassium hydroxide solution to obtain (B) water-soluble resin 4.
(Preparation of (B) water-soluble resin 5)
A water-soluble resin (B) was obtained by dissolving a styrene-sodium styrenesulfonate copolymer having a weight average molecular weight of 7000 and an acid value of 100 in water.
(Preparation of (B) water-soluble resin 6)
By dissolving polyvinylpyrrolidone having a weight average molecular weight of 10,000 in water, (B) water-soluble resin 6 was obtained.

<Preparation of (E) Pigment Dispersion>
(Preparation of black pigment dispersion 1)
10 parts of carbon black (Printex80, manufactured by Evonik), aqueous resin solution (styrene-ethyl acrylate-acrylic acid copolymer, acid value 150, weight average molecular weight 8,000, solid content 20% aqueous solution, neutralizing agent: hydroxylation 15 parts of potassium) and 75 parts of pure water were mixed. This mixed solution was charged into a batch type vertical sand mill (manufactured by Imex), charged with 200 parts of 0.3 mm-diameter zirconia beads, and dispersed for 5 hours while cooling with water. This dispersion was centrifuged to remove coarse particles, and a black pigment dispersion 1 having a pigment concentration of 10% was obtained.

<Preparation of ink>
Inks having the compositions shown in Tables 1 to 3 below were prepared. Specifically, various components described in the following Tables 1 to 3 were mixed so as to have the composition in the table, and sufficiently stirred. Thereafter, each ink was prepared by pressure filtration with a micro filter (manufactured by Fuji Film Co., Ltd.) having a pore size of 3 μm. The resin particles 1 were prepared so that the solid content thereof was a value shown in the table (excluding the content of the resin particles and the content of the surfactant). Moreover, (B) water-soluble resin was also prepared so that the solid content might become the value of a table | surface. Although not explicitly shown in Tables 1 to 3, the dispersion of the resin particles 1 contains NIKKOL BC15 as a surfactant containing an ethylene oxide chain. For this reason, all of the inks 1 to 27 contain a surfactant containing an ethylene oxide chain.

<Inks used in Examples and Comparative Examples>
In Tables 4 to 6 below, the types of inks used in each example and comparative example, (B) acid value of water-soluble resin, (A) resin particles / (B) water-soluble resin mass ratio, and (C The mass ratio of water-soluble organic solvent / (D) water-soluble organic solvent is shown. The mass ratio of (A) resin particles / (B) water-soluble resin represents the ratio of the mass of resin particles alone (not including the surfactant) and the mass of the water-soluble resin.

<Evaluation of ink>
Each ink used in each of the examples and comparative examples obtained above was mounted on an inkjet printer PIXUS Pro 9500 (manufactured by Canon Inc.). As the recording medium, glossy paper (PR-201; manufactured by Canon Inc.) was used.
Printing at room temperature (25 ° C.) was performed as follows. First, after performing a predetermined recovery operation as initial printing, a pattern for printing check was printed. Thereafter, one A4 100% Duty image was printed. Thereafter, a print check pattern was printed again, and it was examined whether there was any printing error with respect to the initial print.
Printing at 50 ° C. was performed as follows. First, after performing a predetermined recovery operation as initial printing, a pattern for printing check was printed. Thereafter, 100 sheets of A4 100% Duty images were continuously printed, and the head temperature was raised to 50 ° C. ± 3 ° C. Thereafter, a print check pattern was printed again, and it was examined whether there was any printing error with respect to the initial print.
The evaluation of printing shading was performed according to the following criteria.
A: No print distortion relative to the initial print.
B: There is slight printing distortion relative to the initial printing.
C: Print distortion occurs with respect to initial printing.
The evaluation results of Examples and Comparative Examples are shown in Table 7-9.

From the results of Examples 1 to 18 and Comparative Examples 1 to 10, it was found that the water-based ink of the present invention is effective in improving printing distortion even when the temperature of the recording head is increased.
From the results of Example 1, Examples 3 to 7, and Examples 2 and 8, the mass ratio of (C) the water-soluble organic solvent and (D) the water-soluble organic solvent was 1 / 3.0 or more and 1 / 0.0. It was found that by setting it to 20 or less, it is further effective in improving printing distortion.
From the results of Examples 1 and 10 and Examples 9 and 11, (B) a water-soluble resin having an anionic charge is a water-soluble resin having a carboxyl group, and the acid value is set to 70 to 120, thereby further printing. From the results of Examples 1, 14, and 15 and Examples 13 and 16 that were found to be effective in improving the twist, the mass ratio of (A) resin particles and (B) water-soluble resin having an anionic charge was determined. It was found that by setting it to 1 / 0.5 or more and 1 / 0.2 or less, it is further effective in improving the printing distortion.
From the results of Examples 17 and 18, the water-based ink of the present invention was effective in improving printing even when the dye / pigment was added or when the temperature of the recording head increased.

40: Ink bag 42: Plug 44: Ink absorber 45: Ink cartridge 51: Paper feed unit 52: Paper feed roller 53: Paper discharge roller 61: Blade 62: Cap 63: Ink absorber 64: Ejection recovery unit 65: Recording Head 66: Carriage 67: Guide shaft 68: Motor 69: Belt 70: Recording unit 71: Recording head 72: Air communication port

Claims (10)

(A) resin particles dispersed by a surfactant containing an ethylene oxide chain;
(B) a water-soluble resin having an anionic charge;
(C) at least one water-soluble organic solvent selected from the group consisting of 1,6-hexanediol, 1,5-pentanediol, and 1,4-butanediol;
A water-based ink comprising: The water-based ink further contains (D) a water-soluble organic solvent other than 1,6-hexanediol, 1,5-pentanediol, and 1,4-butanediol as a water-soluble organic solvent,
The aqueous ratio according to claim 1, wherein a mass ratio represented by (C) water-soluble organic solvent / (D) water-soluble organic solvent is 1 / 3.0 or more and 1 / 0.20 or less. ink.   The water-based ink according to claim 1, wherein the (B) water-soluble resin contains a carboxyl group.   The water-based ink according to any one of claims 1 to 3, wherein the water-soluble resin (B) has an acid value of 70 or more and 120 or less.   5. The mass ratio represented by (A) resin particles / (B) water-soluble resin is 1 / 0.5 or more and 1 / 0.2 or less, 5. The water-based ink described in 1.   The water-based ink according to claim 1, wherein the surfactant is polyoxyethylene alkyl ether.   An ink cartridge comprising an ink storage unit that stores the water-based ink according to claim 1. An ink containing portion for containing the water-based ink according to any one of claims 1 to 6;
A recording head for discharging the water-based ink;
A recording unit comprising: An ink containing portion for containing the water-based ink according to any one of claims 1 to 6;
A recording head for discharging the water-based ink;
An ink jet recording apparatus comprising:   An ink jet recording method comprising discharging the water-based ink according to any one of claims 1 to 6 by an ink jet method.

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