JP2007144931A - Ink jet recording method and ink jet printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording method exhibiting excellent character quality, strike through resistance, curl resistance, continuous ejection properties and intermittent ejection properties even in printing on a plain paper. <P>SOLUTION: In the ink jet recording method for ejecting an ink drop from a nozzle by expanding/contracting an ink chamber, the ink contains water, a water soluble organic solvent, and a pigment wherein the water soluble organic solvent is 50-90 mass% of all ink, and the water soluble organic solvent having SP value of 16.5-24.6 is 30 mass% or more of all ink. The ink jet recording method comprises a first expansion step, a first contraction step for contracting the ink chamber to eject ink, a second expansion step of larger volume variation than that of the first expansion step, and a second contraction step of smaller volume variation than that of the first contraction step and not ejecting ink. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet recording method and an inkjet printer. Furthermore, the present invention relates to an ink jet recording method and an ink jet printer that can obtain high image quality in plain paper printing.

  In recent years, the ink jet recording system can create images easily and inexpensively, and thus has been applied to various printing fields such as photographs, various printing, marking, and special printing such as color filters. In particular, ink jet recording devices that emit and control fine dots, ink with improved color reproduction gamut, durability, and emission suitability, ink absorbency, coloring material color development, surface gloss, etc. are dramatically improved. It is also possible to obtain image quality comparable to silver halide photography using special paper.

  However, in an inkjet image recording system that requires dedicated paper, there are problems in that the recording media that can be used are limited and the cost of the recording media is increased.

  On the other hand, in the office, there is an increasing need for a system that can perform full-color printing at high speed without being restricted by a recording medium (for example, plain paper, coated paper, art paper).

  In particular, it is desired to perform high-quality printing at high speed on plain paper (for example, PPC paper, non-coated paper for printing, etc.) that is inexpensive and easily available. When aqueous ink is used, there are problems such as character image quality, image bleeding, low reflection density, curling after printing, cockling, and the like. When oil-based ink is used, there is no problem with curling and cockling, but there are problems such as character image quality inferior to aqueous ink, intense bleeding, and low reflection density. In addition, when performing double-sided printing, back-through (print-through) is also a major problem. In order to solve the problem of printing on plain paper, various studies have been conducted including the composition of ink.

  As one of the improvement methods for water-based inks, a technique for improving image bleeding and ink back-through during printing on plain paper by using an ink containing a vinylpyrrolidone and an acrylic acid copolymer having a molecular weight of 80,000 to 250,000 is disclosed. (For example, refer to Patent Document 1). However, in this method, when the ink attached to the nozzle plate is wiped off by the wiping operation, the wiping residue is likely to occur (because the added ultra-high molecular weight polymer is likely to stick to the nozzle plate), and the liquid caused by this There has been a problem that image deterioration is likely to occur due to a deviation in the landing positions of the droplets.

  As another method, a technique for reducing feathering, bleeding, and back-through during printing on plain paper using an ink containing alginic acid or alginate is disclosed (for example, see Patent Document 2). In this method, the alginic acid or alginate contained in the ink reacts with a polyvalent metal cation such as calcium or aluminum contained in the plain paper to cause gelation and thickening, thereby improving feathering, bleeding and strike-through. However, polyvalent metal ions such as calcium and aluminum in plain paper are not essential components, but are contained as impurities. The content varies depending on the brand of the paper, and some of the plain paper has extremely low content. Exists. Therefore, the magnitude of these effects depends on the brand of paper to be printed, and there is a problem that a sufficient effect cannot be obtained depending on the brand of paper.

  Further disclosed is a technique for reducing color bleed in plain paper printing by discharging a colorless liquid composition containing a cationic polymer having an average molecular weight of 400 to 1400 and a colored ink on separate papers and combining them on paper. (For example, see Patent Document 3). However, this method requires a head for discharging colorless liquid. Further, there is a problem that paper cockling and curling are likely to occur due to an increase in the total amount of liquid recorded on the paper by the amount of the colorless liquid composition.

  On the other hand, in an oil-based ink composition with almost no curling or cockling, it contains 10% or more of a solvent (nonpolar solvent) having a 50% distillation point of 280 ° C. or lower, and a solvent (polar solvent, ester) of 300 ° C. or higher. A technique for improving bleeding after recording by containing 20% or more of a (system solvent) is disclosed (for example, see Patent Document 4). However, even with this method, the reflection density, behind-the-scenes, and character reproducibility are not necessarily at sufficient levels.

From the above, as for the problem of plain paper recording, there is no disclosure of a technique that balances the problem of image quality such as character image quality, blurring, reflection density, and back-through and the problem of curling and cockling.
Japanese Patent Laid-Open No. 10-1629 JP 2003-176432 A JP-A-10-95107 Japanese Patent Laid-Open No. 2004-2666

  The present invention has been made in view of the above-mentioned problems, and its purpose is excellent in reflection density when printed on plain paper, character quality (character image quality and blurring, etc.), resistance to back-through, curl, cockling and continuous. The present invention provides an ink jet recording method and an ink jet printer excellent in emission (discharge) properties and intermittent emission properties.

  The above object of the present invention has been achieved by the following.

  1. In an inkjet recording method using an inkjet head in which an ink chamber is expanded and contracted by a piezoelectric element and ink droplets are ejected from a nozzle opening, the ink contains at least water, a water-soluble organic solvent, and a pigment, and the water-soluble organic solvent Is a water-soluble organic solvent having a total content of 50% by mass or more and less than 90% by mass of the total ink, and a water-soluble organic solvent having a SP value of 16.5 or more and less than 24.6. In addition, the first expansion step of expanding the ink chamber, the first contraction step of contracting the ink chamber so that the ink droplets are ejected from the nozzle openings, and the first expansion step A second expansion step of expanding larger than the volume change of the first volume and a second contraction step of contracting smaller than the volume change in the first contraction step and not discharging ink droplets. An ink jet recording method according to symptoms.

  2. In an inkjet recording method using an inkjet head in which an ink chamber is expanded and contracted by a piezoelectric element and ink droplets are ejected from a nozzle opening, the ink contains at least water, a water-soluble organic solvent, and a pigment, and the water-soluble organic solvent Is a water-soluble organic solvent having a total content of 50% by mass or more and less than 90% by mass of the total ink, and a water-soluble organic solvent having a SP value of 16.5 or more and less than 24.6. In addition, the first expansion step of expanding the ink chamber, the first contraction step of contracting the ink chamber so that the ink droplets are ejected from the nozzle openings, and the first expansion step A second expansion step of expanding larger than the volume change of the second, a second contraction step of contracting as much as the volume change in the first contraction step but not discharging ink droplets, And a third expansion step for expanding the same volume as the volume change in the expansion step, and a third contraction step for contracting smaller than the volume change in the second contraction step so as not to eject ink droplets. Inkjet recording method.

  3. In an ink jet printer having an ink jet head in which an ink chamber is expanded and contracted by a piezoelectric element to eject ink droplets from a nozzle opening, the nozzle opening diameter of the ink jet head is 25 μm or less, and the ejected ink is at least Water, a water-soluble organic solvent and a pigment are contained, and the water-soluble organic solvent has a total content of 50% by mass or more and less than 90% by mass of the total ink, and the SP value of the water-soluble organic solvent is 16.5. An ink jet printer comprising 30% by mass or more of a water-soluble organic solvent having a value of less than 24.6.

  According to the present invention, an inkjet recording method excellent in reflection density when printed on plain paper, character quality (character image quality and blurring, etc.), resistance to back-through, curling and cockling, and excellent in continuous emission and intermittent emission, and An ink jet printer can be provided.

  Details of the present invention will be described below.

  The ink used in the recording method of the present invention is a water-based ink. However, when such an ink is used, the emission stability from the head is often unstable. In the recording head driving method described below, the stability of continuous emission was ensured, but the stability of intermittent emission was not sufficient. The present inventor As a result of studying the drive method of the recording head as well as the device for the composition, this problem could be achieved. In other words, this is a problem related to two problems that the intermittent emission property is caused by the increase in the viscosity of the ink due to evaporation from the head diameter and the ejection condition (head driving condition) after the pause. This can be achieved by optimizing the head driving conditions.

  Further, according to the present invention, not only ink ejection (ejection) stability (ejection / non-ejection) but also ink droplets after ejection are not formed with chitin, no ink splattering, character quality after landing, etc. The effect of improving is also obtained.

  In the description of the present invention, first, the ink jet recording apparatus used in the present invention will be described with reference to the drawings.

  1 is an exploded perspective view having a partially broken surface of an ink jet head portion of an ink jet recording apparatus used in the present invention, FIG. 2 is a schematic cross sectional view of the ink jet head, and FIG. 3 is a driving state of an ink chamber. FIG.

  In the figure, 1 is a piezoelectric element, 2 is a groove, 3 is an electrode film, 4 is a partition, 5 is a common ink chamber, 7 is a lead portion, 8 is a lid, 9 is an ink chamber, 9 'is a dummy groove, and 10 is a nozzle. A plate, 11 is a nozzle opening, 12 is a communication hole, 14 is an upper plate, 15 is an ink supply port, 16 is a heater, 17 is a heater power source, and 18 is a heat transfer member.

  Further, a piezoelectric element 1 is formed by laminating a lower substrate 1b and an upper substrate 1a made of piezoelectric material lead zirconate titanate (PZT), and the lower substrate 1b and the upper substrate 1a are as shown by arrows in FIG. Polarized in the opposite direction. A plurality of elongated grooves 2 are formed across the upper substrate and the lower substrate. Thereby, a plurality of parallel partition walls 4 and grooves 2 are formed.

  An electrode film 3 is provided by vapor deposition on the inner surfaces of the plurality of grooves, and an insulating film 6 is coated on the surface of the electrode film 3. A lid 8 is bonded to the upper portion of the partition wall 4, and a stepped portion 35 is formed by stepping a part of the end portion of the substrate 1, and a sealing groove 25 is attached to the end portion of the partition wall 4. The lead portion 7 connected to the electrode film 3 is exposed.

  A nozzle plate 10 having a nozzle opening 11 is provided on the other end face where the groove 2 is opened, an ink chamber 9 is formed in every other groove 2, and a nozzle opening is provided corresponding to each ink chamber. Yes. An upper portion of the lid 8 has a common ink chamber 5, and a communication hole 12 for communicating with each ink chamber is provided. Every other groove 2 has a nozzle opening 11 and a communication hole 12, and an upper plate 14 having an ink supply port 15 covers the common ink chamber 5 above the lid 8.

  A heater 16 is provided on the top of the lid 8 via a heat transfer member 18, and a heater power source 17 is connected thereto. The heat transfer member 18 is provided around the nozzle surface. The heat transfer member 18 efficiently transfers heat from the heater 16 to the ink flow path, and carries heat from the heater 16 to the vicinity of the nozzle surface. The purpose is to warm nearby air. Therefore, a material having a good thermal conductivity is used for the heat transfer member 18, and for example, a metal such as aluminum, iron, nickel, copper, and stainless steel, or a ceramic such as SiC, BeO, and AlN is preferable.

  FIG. 3 is a partially enlarged view of the ink chamber. The ink supplied from the common ink chamber 5 fills the ink chambers 9 formed every other groove 2 in parallel. The adjacent grooves are dummy grooves 9 'and no ink is supplied.

  As shown in FIG. 3A, the ink jet head configured as described above has a driving voltage between the electrode film of the ink chamber 9 communicating with the nozzle opening to which ink droplets are to be ejected and the electrode films of the dummy grooves on both sides thereof. , The partition walls on both sides of the ink chamber 9 are deformed outward, the ink chamber expands, and the ink is sucked into the ink chamber. Subsequently, as shown in FIG. 3B, by applying a reverse driving voltage between the ink chamber electrode film and the electrode films of the dummy grooves on both sides thereof, the ink chamber contracts and ink droplets are formed from the nozzle openings. Discharged.

  FIG. 4 shows a drive voltage pattern for ejecting ink droplets used in the present invention. 4A shows (a) a first expansion step (voltage V1) for expanding the ink chamber, (b) a hold step for adjusting the timing of ink droplet discharge, and (c) for discharging the ink droplet. A first contraction step for contracting the ink chamber to a second hold voltage (voltage V1 ′), (d) a hold step for adjusting a meniscus generated after ink droplet ejection, and (e) a volume change in the first expansion step. A second expansion step in which the ejection of ink droplets is stopped by causing the ink droplets to expand to a greater extent, (f) a hold step in which vibration of the meniscus is leveled, and (g) a volume in the first contraction step without ejecting ink droplets. And a second contraction process for setting the piezoelectric element to an initial voltage by contracting smaller than the change.

  That is, after the volume change (first expansion step) by applying V1 once, after the hold step, the second hold voltage (V1 ′) is applied to discharge the ink droplets, and the ink chamber is opened. Since the first ink chamber volume is contracted larger than the initial ink chamber volume (first contraction step), the second expansion step after the first contraction step again starts from the volume of the ink chamber contracted by the application of V1. The ink expands greatly to the ink chamber volume in the first expansion step, and becomes a larger expansion step than the first expansion step. The second contraction process is a process in which the ink chamber returns to the initial volume value from the hold process, and the volume change is smaller than that in the first contraction process for ejecting ink.

  In the second contraction step, there is a fluctuation (vibration) of the ink meniscus, so that no ink is ejected here even though the application of the pulse potential V1 is released. For example, in a recording head using PZT which is a commonly used piezoelectric material, the potential applied to the ink chamber is a pulse of 10 to 20 V at V1, and is an absolute value of 1/2 × V1 <V1 ′. <2 × V1 range.

  Thus, by changing V1 and V1 ′, the dot diameter of the ejected ink droplet can be controlled.

  In the present invention, the same effect can be obtained with the drive waveform shown in FIG.

  Steps (a) to (f) are the same as those in FIG. 4A, and (g) a second contraction step for contracting the same volume change as in the first contraction step without ejecting ink droplets. , (H) a holding step for leveling the meniscus vibration, (i) a third expansion step for expanding as much as the volume change in the second expansion step, and (j) a holding step for leveling the meniscus vibration. And (k) a third contraction step in which the piezoelectric vibrator is set to an initial voltage by contracting smaller than the volume change in the second contraction step.

  Note that FIG. 4C shows a comparative drive voltage that is normally used, and the steps (a) and (b) are the same as those in FIG. 4 (A). 4A and 4B used in the present invention, the ink droplets can be cut well when a relatively high viscosity ink is used. By doing so, there was no clogging and high print quality could be obtained.

As described above, having the steps after the first expansion stroke according to the present invention, that is, having the driving method of the present invention, achieved the object of the present invention and solved the problems. That is, as one factor that exerts the effect of the present invention,
1) A first expansion process for expanding the ink chamber, a first contraction process for contracting the ink chamber so that ink droplets are ejected from the nozzle openings, and a volume expansion larger than the volume change in the first expansion process. A second expansion step, a second expansion step that contracts smaller than the volume change in the first contraction step and does not discharge ink droplets, and 2) a first expansion step that expands the ink chamber; A first contraction process for contracting the ink chamber so that ink droplets are ejected from the nozzle openings, a second expansion process for expanding larger than the volume change in the first expansion process, and a first contraction process. A second contraction process in which the ink droplets are contracted as much as the volume change but ink droplets are not ejected, a third expansion process in which the same volume expansion is performed as in the second expansion process, and a volume in the second contraction process Shrink smaller than the change It can be said that the effect of the present invention can be achieved by including the third contraction step in which the ink droplets are not ejected.

  Next, the ink used in the present invention will be described.

  The ink according to the present invention contains at least water, a water-soluble organic solvent, and a pigment. The water-soluble organic solvent has a total content of 50% by mass or more and less than 90% by mass of the total ink, and the water-soluble organic solvent. 30% by mass or more of a water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6 is included among the solvents. With this ink and the ink jet head driving method of the present invention, it is possible to realize a water-based ink that has high reflection density when printed on plain paper, little show-through, excellent character image quality, and low curling and cockling. It is up to the present invention.

  When ink having a high water content ratio in ink such as a general water-based ink is recorded on plain paper, the permeation into the paper is not so large, and a reasonable character image quality and not very high level of penetration are obtained.

  However, the curl is very large. This is because the water in the ink is coordinated with the cellulose constituting the plain paper, so that the penetration is small, and for curls, a force in the shrinking direction works by evaporating and drying the water. It is considered that curling occurs as a result of insufficient force for suppressing drying shrinkage due to separation of bonds between celluloses by coordinating to cellulose.

  On the other hand, when water-free, for example, oil-based ink is recorded on plain paper, the penetration of the ink into the plain paper is large, and the surface image density is lowered and the ink see-through is increased.

  This is thought to be because the interaction between the oily solvent and cellulose is small, and the oily solvent easily diffuses through the gaps between the cellulose, so that the penetration increases, the image density decreases, and the showthrough increases. On the other hand, since the coordination to cellulose is small and the bond between celluloses is not broken, the paper structure before recording is maintained, and it is considered that curling is difficult.

  In the water-based ink of the present invention, the total content of the water-soluble organic solvent in the ink is 50% by mass or more and less than 90% by mass, and the SP value of the water-soluble organic solvent in the ink is 16.5 or more and 24.6. One feature is that it contains a water-soluble organic solvent having a value of less than 30% by mass or more of the total ink. With this feature, even when recorded on plain paper, it is possible to obtain a print with excellent character image quality, small show-through, and almost no curling, which is one of the factors that exhibit the effects of the present invention. be able to. Furthermore, the effect of achieving both character image quality, back-through and curl suppression is completely deviated from the trend of characteristics of conventional water-based ink and oil-based ink.

  As a mechanism for manifesting this effect, the total amount of the water-soluble organic solvent is 50% by mass or more and less than 90% by mass of the total ink, and the SP value of the water-soluble organic solvent has a value of 16.5 or more and less than 24.6. The water-soluble organic solvent is contained in an amount of 30% by mass or more of the total ink, and further contains at least water, thereby reducing the interaction between the ink and cellulose, and the amount of cellulose necessary to resist drying shrinkage even after recording. Curling is suppressed by leaving the bond remaining, and it has a portion that interacts with cellulose by containing an appropriate amount of water, so that it is considered that character image quality and show-through are good. . More preferably, the water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6 is contained in an amount of 50% by mass or more of the total ink.

  Furthermore, the ink of the present invention preferably has a total amount of alkali metals (lithium, sodium, potassium) in the ink of less than 500 ppm. By making the total amount of alkali metals in the ink less than 500 ppm, the total amount of the water-soluble organic solvent is 50% by mass or more of the total ink, and the SP value of the water-soluble organic solvent is 16.5 or more and less than 24.6. The water-soluble organic solvent having a value is contained in an amount of 30% by mass or more of the total ink, and the pigment dispersion can be more stably present even in a solvent composition containing at least water.

  In order to obtain such an ink, it is preferable to use a combination of a surfactant for dispersing a pigment, a method of adding a dispersant as a salt of an organic base, and the like.

  As described above, the composition of the solvent of the ink of the present invention includes at least water, and the total amount of the water-soluble organic solvent is 50% by mass or more and less than 90% by mass of the total ink. A water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6 is contained by 30% by mass or more of the total ink. Furthermore, it is preferable that the total amount of the water-soluble organic solvent having an SP value of 16.5 or more and less than 22.5 is 30% by mass or more of the ink. This is presumed to be one of the reasons for improving the intermittent emission characteristics due to the suppression of evaporation and viscosity from the head aperture and the influence of liquid physical properties, in addition to the curl and penetration characteristics described above. In addition, when the ink having such a composition range is combined with the driving method of the present invention, the ejected ink droplets are extremely stable and splatter is reduced, so that the character quality on plain paper is very high. I think that it will improve.

The solubility parameter (SP value) of the solvent referred to in the present invention is a value represented by the square root of the molecular aggregation energy, and is described in Polymer Handbook (Second Edition) Chapter IV Solubility Parameter Values. The unit is (J / cm ³ ) ^1/2 or (MPa) ^1/2 and refers to the value at 25 ° C. In addition, about what does not have description of data, it can calculate by calculating | requiring evaporation heat from a boiling point.

  As this calculation method, R.I. F. The method described in Fedors, Polymer Engineering Science, 14, p147 (1974) can be used.

  Hereinafter, examples of water-soluble organic solvents having an SP value of 16.5 or more and less than 24.6 are shown together with the SP value. Needless to say, the present invention is not limited to this.

Ethylene glycol monomethyl ether (24.5)
Ethylene glycol monoethyl ether (23.5)
Ethylene glycol monobutyl ether (22.1)
Ethylene glycol monoisopropyl ether (22.3)
Ethylene glycol monomethyl ether (23.0)
Diethylene glycol monoethyl ether (22.4)
Diethylene glycol monobutyl ether (21.5)
Diethylene glycol diethyl ether (16.8)
Triethylene glycol monomethyl ether (22.1)
Triethylene glycol monoethyl ether (21.7)
Triethylene glycol monobutyl ether (21.1)
Propylene glycol monomethyl ether (23.0)
Propylene glycol monophenyl ether (24.2)
Dipropylene glycol monomethyl ether (21.3)
Tripropylene glycol monomethyl ether (20.4)
1,3-dimethyl-2-imidazolidinone (21.8)
The ink of the present invention contains 30% by mass or more of a water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6. When this addition amount is less than 30% by mass, curling and cockling during recording on plain paper become extremely large.

  If the SP value of the organic solvent is also less than 16.5, the compatibility with water is deteriorated and separation occurs. Conversely, an organic solvent having an SP value of 24.6 or more has an insufficient curl suppressing effect.

  The range of the SP value of the water-soluble organic solvent of the present invention is more preferably 20.0 or more and less than 22.5.

  In the present invention, in addition to the water-soluble organic solvent having an SP value of 16.5 or more and less than 24.6, various water-soluble organic solvents are used in combination, and the total amount of the water-soluble organic solvent is 50% by mass or more of the total ink. It can be less than mass%. Examples of water-soluble organic solvents are shown below.

  Examples of water-soluble organic solvents preferably used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), Polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, 1,3 -Propanediol, 1,4-butanediol, 1,5-pentanediol, 1,2-pentanediol 1,2-hexanediol, 1,2,6-hexanetriol, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine) , Diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), Heterocycles (eg, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfo Kishido compound (such as dimethyl sulfoxide, etc.), sulfones (e.g., sulfolane), urea, acetonitrile, and acetone.

  Moreover, it is preferable that water is 10-45 mass% in all the inks. The presence of 10% by mass or more of water is preferable for the penetration property, and the presence of 45% by mass or less of water is preferable from the viewpoint of curling suppression.

  The ink according to the present invention preferably contains an alkali metal (lithium, sodium, potassium), and the total amount of the alkali metal in this case is preferably less than 500 ppm. If it is 500 ppm or more, the ink storage stability may be deteriorated such as aggregation of the pigment or metal oxide colloid or increase in ink viscosity during storage, and the above range is preferable.

  This alkali metal may be brought in as a salt of a surfactant or a pigment dispersant. Therefore, in order to control the alkali metal content, not only ion-exchanged water is used during ink production, but in the case of using other surfactants, nonionic surfactants are used. This is preferably done, so that the amount brought in can be controlled. Further, it is preferable to use a dispersant neutralized with an organic base as a dispersant used for dispersing the pigment.

  The content of the pigment according to the present invention is preferably 0.1% by mass or more and less than 12% by mass with respect to the total ink.

  As the pigment according to the present invention, conventionally known pigments can be used without particular limitation, and any of water-dispersible pigments, solvent-dispersible pigments and the like can be used. For example, organic pigments such as insoluble pigments and lake pigments, and carbon black Inorganic pigments such as can be preferably used. This pigment is preferably present in a dispersed state in the ink (pigment dispersion state), and the dispersion method may be any of self-dispersion, active agent dispersion, polymer dispersion, and microcapsule dispersion. Polymer dispersion and microcapsule dispersion are particularly preferred from the standpoint of fixability.

  In addition, the pigment used in the present invention is preferably dispersed by a disperser and used together with the above-described dispersant and other additives necessary for various desired purposes. As the disperser, a conventionally known ball mill, sand mill, line mill, high-pressure homogenizer, or the like can be used. Among them, the dispersion by sand mill is preferable because the particle size distribution is sharp when the dispersion is aimed at an average particle diameter of around 100 nm. The material of the beads used for sand mill dispersion is preferably zirconia or zircon from the viewpoint of contamination of bead fragments and ionic components. Further, the bead diameter is preferably 0.1 mm or more and 0.5 mm.

  Examples of the polymer dispersant for dispersing the pigment of the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, alkyl phosphates, and polyoxyalkylenes. Activators such as alkyl ether phosphates, polyoxyalkylene alkyl phenyl ethers, polyoxyethylene polyoxypropylene glycols, glycerin esters, sorbitan esters, polyoxyethylene fatty acid amides, amine oxides, or styrene, styrene derivatives, vinyl naphthalene derivatives Block copolymer comprising two or more monomers selected from acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, random Polymers and can be exemplified salts thereof. These can be obtained, for example, such as commercially available EFKA4570, Jonkrill 60, Jonkrill 501, BYK190.

  The neutralizing base of the dispersant is preferably an organic base such as ammonia, monoethanolamine, diethanolamine, triethanolamine, or morpholine rather than a non-periodic base such as lithium hydroxide, sodium hydroxide, or potassium hydroxide. .

  Moreover, in this invention, it is preferable that the addition amount of a pigment dispersant is 10-100 mass% with respect to a pigment.

  The average particle size of the dispersed particles of the pigment dispersion is preferably 50 nm or more and less than 200 nm. When the average particle diameter is less than 50 nm or 200 nm or more, the stability of the pigment dispersion tends to deteriorate, and the storage stability of the ink tends to deteriorate.

  The particle size of the pigment dispersion can be determined by a commercially available particle size measuring instrument using a dynamic light scattering method, an electrophoresis method, or the like. Accurate and often used.

  Further, a surfactant can be used as an additive at the time of dispersion. As the surfactant used in the present invention, any of cationic, anionic, amphoteric and nonionic surfactants can be used, but it is particularly preferable to use a nonionic surfactant from the viewpoint of dispersion stability.

  Nonionic activators include polyoxyethylene secondary alcohol ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sterol ether, polyoxyethylene lanolin derivative polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene glycerin fatty acid ester, Oxyethylene castor oil, hydrogenated castor oil, polyoxyethylene sorbitol fatty acid ester, polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester, sucrose fatty acid ester, fatty acid alkanolamide, polyoxyethylene Fatty acid amide, polyoxyethylene alkylamine, alkylamine oxide, acetate Glycol, acetylene alcohol, and the like.

  The pigment according to the present invention is not particularly limited. , Thiazine, dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Examples of pigments that can be preferably used include the following pigments. Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 15: 3, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138. Commercially available MA7, MA100, M600, etc. are also useful.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  In addition to the above, when red, green, blue and intermediate colors are required, it is preferable to use the following pigments alone or in combination. Examples of the pigment include C.I. I. Pigment Red; 209, 224, 177, 194, C.I. I. Pigment Orange; 43, C.I. I. Vat Violet; 3, C.I. I. Pigment Violet; 19, 23, 37, C.I. I. Pigment Green; 36, 7, C.I. I. Pigment Blue; 15: 6, and the like.

  Examples of black pigments include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  In addition to the above description, the ink according to the present invention is publicly known depending on the purpose of improving the emission stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Various additives such as polysaccharides, viscosity modifiers, specific resistance regulators, film forming agents, ultraviolet absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. For example, oil droplet fine particles such as liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil, ultraviolet absorbers described in JP-A-57-74193, 57-78988 and 62-261476, JP-A-57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-6-2422871, and JP-A-4-219266 Etc.

  In the ink according to the present invention, the surface tension of the ink is preferably 25 to 40 mN / m at 25 ° C., more preferably 25 to 35 mN / m, and still more preferably 30 to 35 mN / m. The ink viscosity is preferably 1 to 40 mPa · s at 25 ° C., more preferably 5 to 40 mPa · s, and still more preferably 5 to 20 mPa · s.

  In addition, the dissolved oxygen concentration in the ink of the present invention is preferably 2 ppm or less at 25 ° C. By setting this dissolved oxygen concentration condition, the formation of bubbles can be suppressed, and the emission stability even in high-speed printing. An ink jet recording method having excellent properties can be realized. As a method for measuring the dissolved oxygen dissolved in the ink, for example, it can be measured using a dissolved oxygen measuring device DO-14P (manufactured by Toa Radio).

  Next, the ink jet recording method according to the present invention will be described.

  In the ink jet recording method of the present invention, the above-described driving method of the present invention is used, but the recording paper used in the ink jet recording method according to the present invention can be plain paper, and the plain paper is not particularly limited. As its constitution, those made mainly by chemical pulps represented by LBKP and NBKP, sizing agents and fillers and using other paper making auxiliaries as necessary, and made by a conventional method are preferable. As this pulp material, mechanical pulp or waste paper recycled pulp may be used in combination, and these may be used alone as a main material without any problem.

  Examples of the sizing agent include rosin size, AKD, Alnicel succinic anhydride, petroleum resin-based size, epichlorohydrin, cationic starch, acrylamide, and the like.

  Examples of the filler include finely divided silicic acid, aluminum silicate, diatomaceous earth, kaolin, kaolinite, halloysite, nacrite, dickite, pyrophyllite, sericite, titanium dioxide, bentonite and the like.

  In the ink jet recording method according to the present invention, for example, a method of obtaining an ink jet print by ejecting ink as droplets from an ink jet head based on a digital signal and adhering to plain paper with a printer loaded with ink jet ink is used. .

  When performing the ink jet recording method according to the present invention, the ink jet head to be used may be an on-demand system or a continuous system. Also, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, thermal ink jet) Any ejection method such as a mold, a bubble jet (registered trademark) mold, or the like may be used.

  Among them, in the ink jet recording method of the present invention, the ink of the present invention is ejected from a piezo ink jet recording head having a nozzle diameter of 25 μm or less, recording is performed on plain paper, and the nozzle diameter is 25 μm or less. One characteristic is that recording is performed on plain paper by discharging from a piezo-type ink jet recording head of a line head type. This will be described in more detail below.

<Recording sheet>
Examples of the recording paper used in the ink jet recording method of the present invention include those described above. Examples of the paper include coated paper and non-coated paper, and the coated paper has a coating amount per 1 m ^2. one side 20g before and after of art paper, 1m coating amount per ² is one side 10g before and after the coated paper, lightweight coated paper of the coating amount per 1m ² is one-sided 5g before and after, Binurikoshi, mat coated paper matte finish And dull-coated paper, newsprint, etc. Non-coated paper includes printing paper A using 100% chemical pulp, printing paper B using 70% or more chemical pulp, and chemical pulp 40. %, 70% or less of printing paper C, chemical pulp 40% or less of printing paper D, mechanical gravure paper containing calendered paper, etc. can be used, and these can also be used. Further details are described in detail in the “Latest Paper Processing Handbook” edited by the Paper Processing Handbook Editorial Committee, published by Tech Times, “Printing Engineering Handbook” edited by the Japan Printing Society.

  Moreover, as the above-mentioned plain paper, an uncoated paper of 80 to 200 μm belonging to a part of uncoated paper, special printing paper and information paper can be mentioned. As the plain paper used in the present invention, for example, Advanced printing paper, intermediate printing paper, lower printing paper, thin printing paper, fine-coating printing paper, special printing paper such as fine-quality printing paper, foam paper, PPC paper, other information paper, etc. are preferable, specifically Examples of the paper include various modified / processed papers using these, but the invention is not particularly limited thereto.

  Examples of plain paper include high-quality paper and colored high-quality paper, recycled paper, copy paper / color, OCR paper, carbonless paper / color, YUPO 60, 80, 110 microns, YUPO COAT 70, 90 microns, etc. , Other single-sided art paper 68kg, Coated paper 90kg, Foam mat paper 70, 90, 110kg, Foamed PET 38 microns, Mitsori-kun (Kobayashi recording paper), OK fine paper, New OK fine paper, Sunflower, Phoenix, OK Royal White, Export Quality Paper (NPP, NCP, NWP, Royal White) OK Book Paper, OK Cream Book Paper, Cream Quality Paper, OK Map Paper, OK Ishikari, Cucumber, OK Form, OKH, NIP-N Shin-Oji Paper), Kim Wang, Toko, export quality paper, special demand quality paper, book paper, book paper L, light cream Register paper, elementary school textbook paper, continuous slip paper, high quality NIP paper, silver ring, gold yang, gold yang (W), bridge, capital, silver ring book, harp, harp cream, SK color, securities paper, opera cream, Opera, KYP Medical Record, Silvia HN, Excellent Form, NPI Form DX (above, Nippon Paper Industries), Pearl, Kinryo, Usscream fine paper, Special Book Paper, Super Book Paper, Book Paper, Diamond Form, Inkjet Foam (above, Mitsubishi Paper Industries), Carpet V, Carpet SW, White Elephant, Premium Publishing Paper, Cream Carpet, Cream White Elephant, Securities / Voucher Paper, Book Paper, Map Paper, Copy Paper, HNF (above, Hokuetsu Paper) Rai, phone book cover, book paper, cream shirairai, cream shirairai ruff, cream shirairaifu, DSK (above, Daishowa Paper), Master MP fine paper, Jinjiang, Thunderbird fine paper, hanging paper, colored paper base paper, dictionary paper, cream book, white book, cream fine paper, map paper, continuous slip paper (above, Chuetsu Pulp), OP Kinzakura (Chuetsu), Gold sand, reference book paper, exchange paper (white), form printing paper, KRF, white foam, color foam, (K) NIP, fine PPC, Kishu inkjet paper (made by Kishu Paper), Taiou, Bright foam, Kant, Kant White, Dante, CM Paper, Dante Comic, Heine, Bunko Paper, Heine S, New AD Paper, Utrilo Excel, Excel Super A, Kant Excel, Excel Super B, Dante Excel, Heine Excel, Excel Super C, Excel Super D, AD Excel, Excel Super E, New Bright Form , New Bright NIP (above, made by Daio Paper), Sunflower, Moon Ring, Unzen, Galaxy, Baiyun, Weiss, Moon Ring Ace, Baiyun Ace, Unzen Ace (above, Nippon Paper Industries), Taiou, Bright Form , Brightnip (Nagoya Pulp), Peony A, Golden Pigeon, Special Peony, White Peony A, White Peony C, Silver Pigeon, Super White Peony A, Light Cream White Peony, Special Medium Quality Paper, White Pigeon, Super Medium Paper, Blue Pigeon, Red Pigeon, Gold Pigeon M Snow Vision, Snow Vision, Gold Pigeon Snow Vision, White Pigeon M, Super DX, Hamanasu O, Red Pigeon M, HK Super Printing Paper (above, Honshu Paper), Star Linden (A / AW), Star Elm, Star Maple, Star Laurel, Star Poplar, MOP, Star Cherry I, Cherry I Super, Cherry II Super, Star Cherry III, Star Cherry IV, Cheri -III Super, Cherry IV Super (above, made by Maruzumi Paper), SHF (above, made by Toyo Pulp), TRP (above, made by Tokai Pulp) and the like.

<Various films>
Further, in the ink jet recording method according to the present invention, various films may be used as recording paper, and any film generally used can be used. For example, there are a polyester film, a polyolefin film, a polyvinyl chloride film, a polyvinylidene chloride film, and the like. Resin-coated paper that is photographic printing paper or YUPO paper that is synthetic paper can also be used.

<Various inkjet recording media>
Further, in the inkjet recording method according to the present invention, various inkjet recording media may be used as recording paper, and as various inkjet recording media, an absorbent support or a non-absorbent support is used as a base material. Examples thereof include those having an ink receiving layer formed on the surface. Examples of the ink receiving layer include a coating layer, a swelling layer, and a fine void layer.

  The swelling layer absorbs ink when the ink receiving layer made of a water-soluble polymer swells. The fine void layer is composed of inorganic or organic fine particles having a secondary particle size of about 20 to 200 nm and a binder, and fine voids of about 100 nm absorb ink.

  In recent years, an inkjet recording medium in which the above-mentioned fine void layer is provided on a base material using RC paper in which both sides of a paper base material are coated with an olefin resin is preferably used in terms of photographic images.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

[Preparation of Pigment Dispersion A to Pigment Dispersion E]
After mixing the colorant, water-soluble organic solvent, dispersant and water in the combinations shown in Table 1, the mixture was sealed in a polypropylene plastic bottle together with 200 g of zirconia beads having a diameter of 0.5 mm, and 5 in a paint shaker. Dispersion was carried out over time to obtain pigment dispersion A to pigment dispersion E having a black pigment concentration of 15%.

[Preparation of ink]
The following pigment dispersion, water-soluble organic solvent and water were added and stirred well. Subsequently, this liquid was filtered through a # 3500 mesh metal filter, and deaerated with a hollow fiber membrane to prepare inks (1 to 10).

Pigment dispersion (described as “dispersion” in Table 2) 26.7% (colorant 4.0%)
Water-soluble organic solvent (described in “Solvent” in Table 2) Addition amount listed in Table 2 Water (described in Table 2) Addition amount listed in Table 2 After mixing each of the above additives, add water to finish to 100% It was.

In Table 2, the “solvent (mass%) of the SP value of the present invention” means the mass% of the water-soluble organic solvent contained in the ink and having an SP value of 16.5 or more and less than 24.6 based on the total ink. Means.
<Water-soluble organic solvent>
DPGME: Dipropylene glycol monomethyl ether TPGME: Tripropylene glycol monomethyl ether TEGME: Triethylene glycol monomethyl ether EG: Ethylene glycol

<Inkjet image recording>
A piezo-type inkjet head having a nozzle diameter of 22 μm, a drive frequency of 12 kHz, a nozzle count of 128, and a nozzle density of 180 dpi is used. The piezo-type inkjet head has drive signals (respectively shown in FIGS. 4A, 4B, and 4C). Waveforms A, B, and C) can be used to emit 2 to 30 pl multi-size dots with a resolution of 1440 × 1440 dpi (dpi represents the number of dots per 2.54 cm).

That is, the applied voltage for driving the piezoelectric element was adjusted so that the ink droplet ejection speed was 5 to 10 m / s using the drive signals (waveforms A, B, and C, respectively) shown in FIG. The drive waveforms used are as shown in Table 3.
(Image printing)
(Evaluation of character quality)
A piezo-type head having the above basic configuration and having a nozzle diameter of 22 μm, a drive frequency of 12 kHz, a number of nozzles of 128, a nozzle density of 180 dpi, and an on-demand type ink jet printer with a maximum recording density of 1440 × 1440 dpi is used. 4 point MS Mincho characters are printed with black ink on Shirahoi paper (64 g / m ² ) manufactured by Daishowa Paper Co., Ltd. under the conditions described above. The character quality was evaluated according to the following evaluation criteria. The results are shown in Table 3.

A: There is no roughness and the dot shape is a perfect circle. O: A slight roughness is observed, but the dot shape is a perfect circle. Δ: A roughness is observed and the dot shape is slightly disturbed, but within the allowable range. Yes x: A level in which roughness is recognized and the dot shape is bad, causing a problem in practical use.

XX: Both rough and dot shape are extremely bad.
(Evaluation of strikethrough resistance)
Using the same ink jet printer and Shirai paper as above, solid images were taken under the conditions of a droplet volume of 8 pl, an ink adhesion amount of 10 ml / m ² , and an image size of 200 × 280 mm, and placed in a room at a temperature of 23 ° C. and 30% RH. The printed surface was laid flat for 1 day and dried to create an image.

  The back side of the sample printed on the plain paper was visually observed and evaluated for through-through resistance according to the following criteria. The results are shown in Table 3.

◎: No ink bleed or show-through on the back side is observed ○: Ink bleed or show-through on the back side is slightly recognized and acceptable quality △: Ink bleed or show-through is observed on the back side Slightly recognized, but not of concern when printing on the back side ×: Ink bleed and back-through on the back side are quite acceptable, and unacceptable quality for back side printing XX: Clear ink bleed on the back side, back Missing omissions and unsuitable quality for backside printing << Evaluation of curl characteristics (after printing) >>
Use the same inkjet printer and Shirai paper as above,
Under the conditions of 23 ° C. and 30% RH, a solid image was formed under the conditions of a droplet amount of 8 pl, an ink adhesion amount of 10 ml / m ² , and an image size of 200 × 280 mm. The samples were left for a week, and then the heights at the four corners were measured. For the negative curl sample with the central part floating upside down, the sample was allowed to stand for another day after being turned upside down. The raised heights of the four corners were measured as described above, and the curl characteristics were evaluated according to the following criteria. The results are shown in Table 3.

A: Almost flat, even at the most floating part at the four corners, the lifting height is less than 5 mm. O: The lifting height at the most floating part at the four corners is 5 mm or more and less than 10 mm. Δ: Most floating at the four corners. The height of the lifted portion is 10 mm or more and less than 20 mm. X: The height of the lifted portion at the four corners is 20 mm or more and less than 50 mm. XX: The height of the lifted portion of the four corners. Is 50 mm or more, or rounded into a cylindrical shape and cannot be measured (evaluation of continuous emission)
Under the condition of 23 ° C. and 30% RH, each ink set was mounted, and under the condition of discharging 8 pl per drop, the state after discharging continuously for 1 hour without cleaning was visually observed. The ejection stability was evaluated according to the criteria shown below. The results are shown in Table 3.

◎: Normal emission from all nozzles ○: Clogging is observed in 1 to 3 nozzles, but recovered by suction cleaning from the nozzle surface △: Clogging occurs in 4 or more nozzles and cannot be recovered by suction cleaning Clogging occurs in one nozzle, but is in a practically acceptable range. X: Clogging occurs in 7 or more nozzles, and clogging that cannot be recovered by suction cleaning occurs in 2 nozzles. Xx: Clogging in 10 or more nozzles. 3 or more nozzles that could not be recovered by suction cleaning occurred (evaluation of intermittent emission)
In an environment of 23 ° C. and 30% RH, each ink set was mounted, and intermittent operation of continuous discharge for 10 seconds → pause for a fixed time → continuous discharge was performed under the condition of discharging 12 pl per drop. At this time, since whether or not the discharge direction is disturbed at the beginning after the discharge pause is determined by the length of the pause time, the stability of intermittent discharge is measured by changing the length of the discharge pause time stepwise. The evaluation was based on the following criteria. The results are shown in Table 3.

◎: Stable discharge even after 31 to 45 seconds ○: Stable discharge even after 21 to 30 seconds △: Stable discharge even after 11 to 20 seconds ×: Pause for 6 to 10 seconds Even though it was stably discharged XX: Only 5 seconds or less were stably discharged

  From the above evaluation results, it was confirmed that the image recording method using the ink of the present invention is excellent in character quality even in a recording medium having no ink absorption, and good in continuous emission and intermittent emission.

1 is an exploded perspective view having a partially broken surface of an ink jet head portion of an ink jet recording apparatus used in the present invention. It is a schematic sectional drawing of an inkjet head. FIG. 4 is a partially enlarged view showing a driving state of an ink chamber. The pattern of the drive voltage for discharging the ink droplet used for this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Groove 3 Electrode film 4 Partition 5 Common ink chamber 7 Lead part 8 Cover 9 Ink chamber 10 Nozzle plate 11 Nozzle opening 15 Ink supply port 16 Heater 17 Heater power supply 18 Heat transfer member 101 Ultraviolet light source 102 Optical fiber 103 Radiation irradiation part 105 Carriage 106 Ink supply tank 107 Filter 108 Supply piping 109 Heating unit 110 Recording object 116 Post-processing exposure apparatus 4Y, 4M, 4C, 4K Inkjet head

Claims (3)

In an inkjet recording method using an inkjet head in which an ink chamber is expanded and contracted by a piezoelectric element and ink droplets are ejected from a nozzle opening, the ink contains at least water, a water-soluble organic solvent, and a pigment, and the water-soluble organic solvent Is a water-soluble organic solvent having a total content of 50% by mass or more and less than 90% by mass of the total ink, and a water-soluble organic solvent having a SP value of 16.5 or more and less than 24.6. In addition, the first expansion step of expanding the ink chamber, the first contraction step of contracting the ink chamber so that the ink droplets are ejected from the nozzle openings, and the first expansion step A second expansion step of expanding larger than the volume change of the first volume and a second contraction step of contracting smaller than the volume change in the first contraction step and not discharging ink droplets. An ink jet recording method according to symptoms. In an inkjet recording method using an inkjet head in which an ink chamber is expanded and contracted by a piezoelectric element and ink droplets are ejected from a nozzle opening, the ink contains at least water, a water-soluble organic solvent, and a pigment, and the water-soluble organic solvent Is a water-soluble organic solvent having a total content of 50% by mass or more and less than 90% by mass of the total ink, and a water-soluble organic solvent having a SP value of 16.5 or more and less than 24.6. In addition, the first expansion step of expanding the ink chamber, the first contraction step of contracting the ink chamber so that the ink droplets are ejected from the nozzle openings, and the first expansion step A second expansion step of expanding larger than the volume change of the second, a second contraction step of contracting as much as the volume change in the first contraction step but not discharging ink droplets, And a third expansion step for expanding the same volume as the volume change in the expansion step, and a third contraction step for contracting smaller than the volume change in the second contraction step so as not to eject ink droplets. Inkjet recording method. In an ink jet printer having an ink jet head in which an ink chamber is expanded and contracted by a piezoelectric element to eject ink droplets from a nozzle opening, the nozzle opening diameter of the ink jet head is 25 μm or less, and the ejected ink is at least Water, a water-soluble organic solvent and a pigment are contained, and the water-soluble organic solvent has a total content of 50% by mass or more and less than 90% by mass of the total ink, and the SP value of the water-soluble organic solvent is 16.5. An ink jet printer comprising 30% by mass or more of a water-soluble organic solvent having a value of less than 24.6.

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