JP2008001003A - Inkjet image recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet image recording method which has moderate wettability for many kinds of media, ensures sufficient wettability for the flow passage inner wall of a head or an ink supply system as well, assures exhaustibility of air bubbles and supply of ink, ensures the stability of ink discharge even in high-speed outputting, suppresses occurrence of satellites in discharge and thus can prevent deterioration of an image. <P>SOLUTION: In the inkjet image recording method wherein ink liquid droplets are discharged from nozzles of a recording head and an image pattern is formed on the opposite surface of a recording medium, the static surface tension of the ink discharged is 25-35 mN/m and the dynamic surface tension of the ink at the time of formation of the ink liquid droplet by the discharge is higher by 10 mN/m or above than the static surface tension, while the amount of re-extrusion of a meniscus at the time of discharge of the ink is equal to or smaller than the radius of the nozzle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet image recording method capable of obtaining high image quality in which a wide range of recording media has good ink wetting and spreading after landing (and repelling, etc.), low satellites and high-speed ink ejection.

  As the trend toward higher image quality and faster output in image formation on a drop-on-demand basis using inkjet technology is increasing, there is a great demand for forming high-quality images on various media (recording media).

  As one of them, there is a demand for image formation that moderately wets and spreads even on non-absorbing media and low surface energy media and does not bleed between different color inks.

  On the other hand, in order to form a high quality image, it is necessary to improve the ejection stability of the head.

  In order to obtain high image quality with high-speed output, it is necessary to increase the droplet velocity and increase the landing accuracy. However, when the droplet velocity is increased, there is a problem that a large amount of satellites are generated and the image quality is deteriorated. In addition, it is necessary to increase the discharge frequency and stably inject for high-speed output, but if the discharge frequency is increased, the meniscus extrusion amount during driving increases, discharge stability decreases, and satellites are likely to be generated. There's a problem.

  Techniques for adjusting ink permeability and bleeding and obtaining ejection reliability have been known so far.

  For example, Patent Document 1 and Patent Document 2 disclose techniques for improving ejection stability and ink bleeding by adjusting the surface tension of ink.

However, in a wide range of recording media including non-absorbing recording media and low surface energy recording media, wetting and spreading (and repelling) of ink after landing are improved, and ink ejection stability at higher speed is ensured. A method that satisfies these requirements simultaneously is desired.
Japanese Patent Laid-Open No. 2003-231838 JP 2004-168793 A

  The present invention has moderate wettability with respect to various media, ensures sufficient wettability with respect to the inner wall of the flow path of the head and the ink supply system, ensures bubble discharge and ink supply, Another object of the present invention is to provide an ink jet image recording method that can ensure ink ejection stability even at high-speed output, suppress satellite generation during ejection, and prevent image deterioration.

  The above object of the present invention is achieved by the following means.

  1. In an inkjet image recording method in which an ink droplet is ejected from a nozzle of a recording head to form an image pattern on the opposing recording medium surface, the static surface tension of the ejected ink is 25 mN / m or more and 35 mN / m or less. In addition, the dynamic surface tension of the ink when ink droplets are formed by ejection is 10 mN / m or more higher than the static surface tension, and the meniscus re-extrusion amount during ink ejection is less than the radius of the nozzle. An inkjet image recording method.

  2. 2. The inkjet image recording method according to 1 above, wherein the viscosity of the ejected ink is 5 mPa · sec or more and 15 mPa · sec or less at the ejection temperature.

  3. 3. The ink jet image recording method according to 1 or 2 above, wherein the ejected ink contains a solvent having a static surface tension of 40 mN / m or more and an additive having a surface active function.

  4). 4. In the inkjet image recording method according to any one of 1 to 3, the ejected ink has at least a coloring material, water, and a plurality of side chains in a hydrophilic main chain, and is irradiated with active energy rays. An ink jet image recording method comprising: an ink containing a high molecular compound capable of crosslinking between side chains.

  5. The pressure generating means for ejecting ink of the recording head is formed of a piezoelectric material that forms at least a part of a partition between adjacent ink channels and is deformed in a shear mode by applying a voltage. 5. The inkjet image recording method according to any one of 1 to 4 above.

  The present invention provides an inkjet image recording method capable of forming a high-quality image free from bleeding or the like on various media, having high ejection stability during high-frequency driving, and generating less satellites during ink ejection. .

  The best mode for carrying out the present invention will be described below.

  The present invention is an ink jet recording method in which an ink droplet is ejected from a nozzle of a recording head to form an image pattern on the opposing recording medium surface, and the static surface tension of the ejected ink is 25 mN / m or more and 35 mN. The dynamic surface tension of the ink when forming ink droplets by ejection is 10 mN / m or more higher than the static surface tension, and the meniscus re-extrusion amount (length) during ink ejection is The radius of the nozzle of the recording head is equal to or smaller than the radius.

The dynamic surface tension of ink at the time of droplet formation by ejection is a transient surface tension at 10 ⁴ to 10 ⁶ Hz corresponding to the vibration frequency of the nozzle meniscus at the time of ejection and the droplet formation time. Although a method for measuring the surface tension in a high-speed, high-frequency operation state in which droplets are ejected by a method is proposed (Ind. Eng. Chem. Prod. Res. Dev. 1981, 20, 680-684), it is simple. It is difficult to measure. Therefore, in general, when the dynamic surface tension changes depending on the frequency, it increases and decreases monotonously with respect to the frequency as shown in FIG. 4, so in the present invention, it is close to the measurement limit by the relatively simple maximum bubble pressure method. The dynamic surface tension near the bubble frequency of 100 Hz (10 ms) is obtained and used as the surface tension of the ink when forming droplets by ejection.

  The dynamic surface tension is the surface tension in a very short time, and the measurement method is generally known such as vibration jet method, meniscus method, dropping method, γ / A curve method, maximum bubble pressure method, curtain coater method, etc. Although measurement is possible by the measurement method currently used, in this invention, it measures by the maximum bubble pressure method which can be measured for a shorter time.

  The static surface tension can be measured by a generally known measurement method such as a drop weight method, a capillary rise method, a ring method, or a flat plate method. It is defined as the surface tension at 0.1 Hz (10 sec). The measurement temperature should be a value at the temperature at which droplets are actually ejected. However, since the temperature change of the surface tension is relatively small, the value is 25 ° C.

  The normal surface tension (static surface tension) measures the surface tension in a relatively long time of 1 to 10 seconds or more, and does not express the surface tension in a minute time. Ink absorption is considered to be performed on the order of milliseconds, and the surface tension at that time is related to the permeability and blurring of the recording medium, and droplet formation by ink ejection is on the order of microseconds. It is considered that the surface tension at that time is involved in the ejection stability of the ink, the generation of satellites, mist, and the like.

  Measurement of dynamic surface tension by the maximum bubble pressure method is performed by inserting a capillary into the liquid to be measured, flowing an inert gas through the capillary to generate bubbles at the tip of the capillary, and measuring the change in internal pressure of the bubbles. The surface tension γ is determined from P by the following equation.

γ = 1 / 2R {P− (h + 2 / 3R) ρg}
Here, R is the radius of the capillary inner diameter, h is the depth of the capillary tip from the liquid surface, ρ is the density of the liquid, and g is the acceleration of gravity.

  By changing the gas flow rate, the bubble generation rate changes, and the dynamic surface tension corresponding to the bubble generation time can be obtained.

  If measurement at a bubble frequency of 100 Hz is difficult due to ink, it is obtained by extrapolation from the measured value on the low frequency side.

  In the present invention, the ink is not particularly limited, but a preferred ink according to the present invention has at least a coloring material, water, and a plurality of side chains in the hydrophilic main chain, and is irradiated with active energy rays to thereby form side chains. It is a so-called actinic ray curable water-based ink containing a polymer compound that can be crosslinked between the two.

  In order to perform high-quality recording on various recording media at high speed, various factors must be considered. For example, ink smearability on the inner wall of the head related to the generation and discharge of bubbles in the ink, ink ejection stability, meniscus recovery after droplet ejection, satellite generation, etc., and ink on the recording medium There are wet spread.

  The preferred ink according to the present invention is a stable ink which does not generate satellites or mists even when printing on various recording media, particularly non-absorbing recording media, or recording media with low surface energy at high speed. The ink must be able to ensure ejection and spread appropriately on the low energy medium after landing on the recording medium.

  In order to exhibit such performance on various media, it is necessary to keep the surface tension of the ink particularly appropriate.

  For this reason, the ink according to the present invention has a static surface tension of 25 mN / m or more and 35 mN / m or less in the above definition. In addition, the ink according to the present invention needs to have a dynamic surface tension at the time of droplet formation by ejection or a dynamic surface tension at a bubble frequency of 100 Hz (10 ms) greater than the static surface tension by 10 mN / m or more. It is said.

  FIG. 4 shows the surface tension-bubble frequency profile of the ink of the present invention (ink example of Example 1). When ink is ejected or at a high frequency of 100 Hz (10 ms), the surface tension is high, and at a static surface tension, that is, at a low frequency of 0.1 Hz (10 s), this greatly decreases, and the ink has a difference of 10 mN / m or more. .

In the ink jet image recording method according to the present invention, the meniscus re-extrusion amount at the time of ink ejection is less than or equal to the radius of the nozzle of the recording head.

  The ink meniscus vibrates in conjunction with the drive cycle of ink discharge. In the present invention, the meniscus re-extrusion amount means that the ink column extends from the meniscus in the nozzle and the tail of the ink column narrows at the time of ink discharge. This is the meniscus extrusion amount when the meniscus extrusion amount is pushed out again in the state before the ink droplets are separated (that is, immediately before the droplet separation).

  The meniscus re-extrusion amount during ink ejection will be described.

  FIG. 6 shows a case where a drive signal shown in FIG. 5 is applied to perform continuous ejection driving using the share mode type recording head shown in FIGS. 2 and 3 (described later) used in the embodiment. It is a conceptual diagram of the mode of the ink discharge from a nozzle, and the change of an ink meniscus.

  Here, 23 is a nozzle, 10 is an ink main droplet, and 10b is a tail portion (ink column) extending from the ink main droplet. The meniscus re-extrusion amount in the present invention is the maximum meniscus extrusion amount when the meniscus (FIG. 6 (4)) once drawn immediately after the liquid column is discharged returns to the nozzle surface and is further extruded (FIG. 6 (6)). It is just now. The re-extrusion of the meniscus is caused by the meniscus rebounding before the tail of the ejected liquid column is separated from the meniscus as a reaction of the meniscus vibration drawn after the liquid column discharge or as a reaction during the droplet discharge operation of the adjacent channel. It will be pushed out. The meniscus push-out amount is the amount of protrusion of the ink meniscus from the nozzle tip (discharge height = length) when the ink droplet is discharged at a predetermined speed of 6 m / s. Measure in a direction substantially perpendicular to the forming member. FIG. 7 shows the relationship between the main ink droplet, ink column, and meniscus push-out amount during ink ejection (definition of meniscus push-out amount during ink ejection).

  Hereinafter, it will be described that the meniscus re-extrusion amount is equal to or less than the radius of the nozzle (defined as the radius of a perfect circle having the same area when the nozzle shape is not a perfect circle).

  When the radius of curvature of the meniscus when pushed out from the nozzle is r and the surface tension is γ, the pressure difference between the inside and outside of the meniscus is expressed by ΔP = 2γ / r according to Laplace's law.

  When the meniscus is pushed out by the same length as the radius of the nozzle, ΔP becomes maximum, and when pushed out beyond this, ΔP becomes small and the position of the meniscus becomes difficult to return to the original position.

  When the meniscus vibrates and is pushed out from the nozzle, if the pushing amount (long) is equal to or less than the radius (r ′) of the nozzle, the pushed meniscus is uniformly applied with an internal pressure, and the meniscus is changed according to the change in the nozzle internal pressure. Vibrates and is drawn back into the nozzle.

  However, when extruded beyond the nozzle radius (r ′), the shape of the ink column changes, and this ink column is formed from a spherical portion at the tip and a straight column portion. For example, if the radius of curvature of the spherical portion is r, the side surface of the column is straight and the radius of curvature is infinite.

  According to Laplace's law, the meniscus holding force is inversely proportional to the radius of curvature r, so the meniscus holding force of the portion of the extruded ink column forming the arc is high, but the column portion is low.

  Then, even if a negative pressure is applied to the ink chamber to return the meniscus, the internal pressure is not evenly applied to the ink column, and the straight portion of the ink column having a low meniscus holding force is drawn, and the tip of the meniscus cannot be pulled back. In this state, the tails of the ejected droplets cannot be effectively cut off in a short time, and the ejection tails extend long and a large number of satellites are generated.

  The amount of meniscus re-extrusion during ink droplet ejection can be adjusted by adjusting the drive pulse, that is, the intensity and timing of the expansion pulse and contraction pulse for ink ejection. For example, when the two-row head shown in FIGS. 2 and 3 (nozzle pitch: 360 dpi (number of dots per inch (2.54 cm)), number of nozzles: 512) is driven by the drive signal shown in FIG. For example, the maximum extrusion amount of the meniscus can be changed by setting the drive signal as the drive voltage Voff = 0 and using only the signal Von.

  Since the surface tension of the ink of the present invention increases during ejection, the meniscus is not pushed out excessively. That is, when pressure is applied to ink during ejection, the meniscus moves within the nozzle. For example, when pressure is applied and ink is pushed out of the nozzle to generate a new ink surface, the newly generated ink surface Has a high surface tension since the surfactant is not oriented. Therefore, the expansion of the meniscus is suppressed.

  In addition, since the dynamic surface tension is high, the return force of the ink meniscus to the steady position in the nozzle after droplet ejection is improved, so the meniscus can settle quickly, the drive frequency can be increased, and ink ejection By controlling the meniscus re-extrusion amount from the nozzle immediately after it to the nozzle radius (r ') or less, the generation of satellites and mist can be suppressed, and the number of satellites and the amount of satellite separation (distance between main droplets and satellites) can be reduced. And tail separation is improved.

  Furthermore, since the static surface tension is low with respect to the inside of the head and the inner wall of the ink flow path, sufficient wettability is ensured, and even if bubbles are generated, the discharge is good, and the ink is discharged and supplied reliably. Discharge stability is improved.

  In addition, after landing on the recording medium, immediately after ink landing on the medium (between 0 and 10 ms), the surface tension of the ink is high, so that bleeding does not easily occur on the recording medium. Further, since the surface tension is lowered with the passage of time (100 to 1000 ms) after the new interface is formed, the permeation is promoted and the drying time is shortened. In particular, even on a low energy medium, the ink spreads moderately, and the ink is free from repellency and vice versa.

  In the case of crosslinkable (curing) ink, repellency or satellites adhere to the vicinity of the nozzles, etc., and then are irradiated with ultraviolet leakage light. The effect is great.

  The water-based crosslinkable ink having the above-mentioned relationship between the dynamic surface tension and the static surface tension according to the present invention can be printed at a high speed, particularly on a non-absorbing recording medium having a low surface energy. At the same time, the ink spreads without getting wet, and at the same time, when printing at high speed as described above, it is an ink that can ensure stable ink ejection without generation of satellites or mist.

  In order to suppress the occurrence of satellites or mists and to suppress the occurrence of satellites or mist, and to appropriately spread and spread on the landing medium, that is, the recording medium, the share mode type recording shown in FIGS. In the case of the head, the viscosity of the ink at the ejection temperature is preferably 5 mPa · s or more and 15 mPa · s or less.

  In addition, the ink according to the present invention preferably has an ink viscosity at a discharge temperature of 5 mPa · s or more and 15 mPa · s or less in order to appropriately wet and spread on the landing medium, that is, a recording medium.

Here, the viscosity of the ink should be defined by the dynamic viscosity in a state where a large share is applied in a state where droplets are actually ejected, but since it is difficult to actually measure, a general-purpose viscoelasticity measuring device The viscosity at a shear rate of about 1000 s ⁻¹ measured with a (rheometer) is substituted. For example, the measurement is performed using a rheometer MCR300 manufactured by Pyhsica.

  Further, when the head and ink are heated and used, the viscosity is defined by the viscosity at the discharge temperature.

  When the pressure is 15 mPa · s or more, the energy required for ejecting the ink becomes large and the ejection becomes difficult and more satellites are likely to be generated. In addition, the wet spread on the recording medium is small and the dots may not cover the pixels. In particular, it is difficult for the medium having a small surface energy. Also, at 5 mPa · s or less, ejection at a high frequency tends to be unstable, the spread of dots becomes too large, and color mixing tends to occur between colors. In particular, color mixing and bleeding progress on a recording medium with relatively high permeability, and repelling, beading, and the like are likely to occur on a medium with low surface energy.

  As described above, the ink of the present invention has a static surface tension of 40 mN / m (25 ° C.) or more in order to increase the dynamic surface tension as compared with the static surface tension. It is preferable to include an additive having a main solvent and a surface active function. The main solvent is a solvent most frequently used in ink. Moreover, it is also preferable to use the liquid which consists of the molecule | numerator which has orientation at an interface as a solvent.

  Examples of the solvent having a static surface tension of 40 mN / m (25 ° C.) or higher include water (72.0 mN / m 25 ° C.), and water-soluble organic solvents such as ethylene glycol (50.21 mN / m), diethylene glycol, Polyhydric alcohols such as triethylene glycol, glycerin (63.4 mN / m), 1,5-pentanediol, 1,2,4-butanetriol, N-methyl-2-pyrrolidone, formamide, N-methylformamide Amides such as N, N-dimethylformamide, monoethanolamine, diethanolamine, and triethanolamine.

  Among these, water is preferable.

  In addition, in order to prevent the ink from drying, the organic solvent is used alone or in combination with water. The main solvent having a static surface tension of 40 mN / m (25 ° C.) or more constitutes 50% by volume or more, preferably 70% by volume or more of the entire solvent. Of the above, the solvents preferably used include diethylene glycol, triethylene glycol, glycerol, 1,2,6-hexanetriol, 1,2,4-butanetriol, petriol, 1,5-pentadiol, N-methyl. -2-pyrrolidone, N-hydroxyethylpyrrolidone and the like.

  Further, the use of these has an effect of preventing the ink from drying.

  In the present invention, an additive having a surface active function is contained in addition to the main solvent. An additive having a surface active function is a penetrating agent for adjusting surface tension, such as diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol mono Examples thereof include alkyl and aryl ethers of polyhydric alcohols such as butyl ether and tetraethylene glycol chlorophenyl ether, higher alcohols, surfactants (anionic, cationic, nonionic or amphoteric).

  Among the above, surfactants include anionic properties such as alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, fatty acid salts, etc. Nonionic surfactants such as surfactants, polyoxyethylene alkyl ethers, polyoxyalkylene alkyl phenyl ethers, acetylene glycols, polyoxyethylene-polyoxypropylene block copolymers, glycerin esters, sorbitan esters, polyoxyethylene Activating agents such as fatty acid amides and amine oxides, and cationic surfactants such as alkylamine salts and quaternary ammonium salts.

  The surfactant stabilizes the interface by forming micelles, but it is preferable to select a surfactant having a large dynamic and static surface tension difference.

  The surfactant can also be used as a pigment dispersant, and in particular, anionic and nonionic surfactants can be preferably used.

  In particular, Olfin E1010 manufactured by Nissin Chemical, which is an acetylene glycol nonionic activator, is effective for adjusting the surface tension of the ink because it has low foaming properties and strong surface activity.

  In addition, a polymer having a hydrophobic part (—OAc) and a hydrophilic part (—OH), such as a polymer such as polyvinyl alcohol and vinyl acetate, is also preferable. Among the penetrants, diethylene glycol monobutyl ether is preferable.

  By adjusting the additive amount of these surface active functions, particularly surfactants, and alkyl and aryl ethers of polyhydric alcohols and higher alcohols, the static surface tension according to the present invention, It is possible to adjust ink having a large difference in dynamic surface tension during ink ejection.

  In hydrophobic solvent inks, for example, acrylates of glycols such as dipropylene glycol diacrylate and tripropylene glycol diacrylate, acrylates of higher alcohols such as lauryl acrylate, surfactants and the like are surface-active. As an additive having a function.

  The ink-jet ink preferably used in the present invention is a water-based ink that crosslinks and cures when irradiated with actinic rays after landing on a recording medium, and includes at least a colorant, water, and a hydrophilic main chain. It contains a polymer compound having side chains and capable of crosslinking between side chains by irradiation with actinic rays.

<Active energy ray crosslinkable polymer compound>
The polymer compound having a plurality of side chains in the hydrophilic main chain according to the present invention and capable of cross-linking between side chains by irradiating with actinic rays is a saponified product of polyvinyl acetate, polyvinyl acetal, polyethylene oxide , Polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, or a derivative of the hydrophilic resin, and at least one hydrophilic resin selected from the group consisting of these copolymers On the other hand, modified groups such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, and a photodepolymerization type are introduced into the side chain. Among these, a photopolymerizable crosslinkable group is desirable from the viewpoint of sensitivity and performance of the generated image.

  Further, from the viewpoint of reactivity with the color material to be combined, the side chain is preferably nonionic, anionic, or amphoteric (betaine compound). In particular, when the color material is combined with an anionic dye or an anionic pigment, The chain is preferably nonionic or anionic, particularly preferably nonionic.

  In the hydrophilic main chain, a saponified product of polyvinyl acetate is preferable from the viewpoint of ease of introduction of side chains and handling, and the degree of polymerization is preferably 200 or more and 2000 or less, and more preferably 200 or more and 500 or less. When the degree of polymerization is less than 200, the viscosity increase during the crosslinking reaction is insufficient, and color bleeding and beading may not be sufficiently prevented. On the other hand, if the degree of polymerization exceeds 2000, the viscosity when added to the ink is increased, which may impair the emission stability.

  The modification rate of the side chain with respect to the main chain is preferably 0.3 mol% or more and 4 mol% or less, and more preferably 0.8 mol% or more and 4 mol% or less from the viewpoint of reactivity. If it is less than 0.3 mol%, the crosslinkability is insufficient and the effect of the present invention is reduced. If it is more than 4 mol%, the crosslink density is increased and the film is hard and brittle, and the strength of the film is lowered.

  As the photodimerization-type modifying group, those having a diazo group, a cinnamoyl group, a stilbazolium group, a styrylquinolium group or the like are preferably used. For example, a photosensitive resin described in JP-A-60-129742 (Composition).

  The photosensitive resin described in JP-A-60-129742 is a compound represented by the following general formula (1) in which a stilbazolium group is introduced into a polyvinyl alcohol structure.

In the formula, R ₁ represents an alkyl group having 1 to 4 carbon atoms, and A ⁻ represents a counter anion.

  The photosensitive resin described in JP-A-56-67309 includes a 2-azido-5-nitrophenylcarbonyloxyethylene structure represented by the following general formula (2) in the polyvinyl alcohol structure, or the following general formula. This is a resin composition represented by (3) and having a 4-azido-3-nitrophenylcarbonyloxyethylene structure.

  Further, a modifying group represented by the following general formula (4) is also preferably used.

  In the formula, R represents an alkylene group or an aromatic ring. A benzene ring is preferred.

  As the photopolymerization type modifying group, for example, a resin represented by the following general formula (5) shown in JP-A Nos. 2000-181062 and 2004-189841 is preferable from the viewpoint of reactivity.

In the formula, R ₂ represents a methyl group or a hydrogen atom, n represents 1 or 2, X represents — (CH ₂ ) _m —COO— or —O—, and Y represents an aromatic ring or a single bond. And m represents an integer from 0 to 6.

  Moreover, it is also preferable to use the photopolymerization type | mold modified group represented by following General formula (6) described in Unexamined-Japanese-Patent No. 2004-161942 for a conventionally well-known water-soluble resin.

In the formula, R ₃ represents a methyl group or a hydrogen atom, and R ₄ represents a linear or branched alkylene group having 2 to 10 carbon atoms.

  Such an active energy ray-crosslinking resin is preferably contained in an amount of 0.8% by mass to 5.0% by mass with respect to the total mass of the ink. The presence of 0.8% by mass or more improves cross-linking efficiency, and beading and color bleeding are more preferable due to a rapid increase in ink viscosity after cross-linking. In the case of 5.0% by mass or less, it is difficult to adversely affect the ink physical properties and the state of the ink in the recording head.

  In the active energy ray cross-linking resin used in the ink according to the present invention, the main chain having a certain degree of polymerization is cross-linked through a cross-linking bond between side chains. The effect of increasing the molecular weight per photon is remarkably large with respect to an active energy ray-curable resin that polymerizes via a photon. On the other hand, in the conventionally known active energy ray curable resins, the number of crosslinking points cannot be controlled, so the physical properties of the cured film cannot be controlled, and the film tends to be hard and brittle.

  In the resin used in the ink according to the present invention, the number of crosslinking points can be completely controlled by the length of the hydrophilic main chain and the amount of side chains introduced, and the physical properties of the ink film can be controlled according to the purpose.

  Furthermore, almost all of the conventionally known active energy ray-curable inks other than the colorant are curable, so that the dots after curing are raised and inferior in image quality typified by gloss, are used in the present invention. The resin requires only a small amount, and since there are many dry components, the image quality after drying is improved and the fixing property is also good.

(Photopolymerization initiator, sensitizer)
In the ink according to the present invention, it is preferable to add a photopolymerization initiator or a sensitizer. These compounds may be dissolved or dispersed in a solvent, or may be chemically bonded to the photosensitive resin.

  There is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A conventionally well-known thing can be used.

  Although there is no restriction | limiting in particular about the photoinitiator and photosensitizer which are applied, A water-soluble thing is preferable from a viewpoint of mixability and reaction efficiency. In particular, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (HMPK), thioxanthone ammonium salt (QTX), and benzophenone ammonium salt (ABQ) are preferable from the viewpoint of miscibility with an aqueous solvent.

  Furthermore, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (n = 1, HMPK) represented by the following general formula (7) from the viewpoint of compatibility with the resin, The ethylene oxide adduct (n = 2 to 5) is more preferable.

  In the formula, n represents an integer of 1 to 5.

  Other examples include benzophenones such as benzophenone, hydroxybenzophenone, bis-N, N-dimethylaminobenzophenone, bis-N, N-diethylaminobenzophenone, 4-methoxy-4'-dimethylaminobenzophenone. Thioxanthones such as thioxatone, 2,4-diethylthioxanthone, isopropylthioxanthone, chlorothioxanthone, and isopropoxychlorothioxanthone. Anthraquinones such as ethyl anthraquinone, benzanthraquinone, aminoanthraquinone and chloroanthraquinone. Acetophenones. Benzoin ethers such as benzoin methyl ether. 2,4,6-trihalomethyltriazines, 1-hydroxycyclohexyl phenyl ketone, 2- (o-chlorophenyl) -4,5-diphenylimidazole dimer, 2- (o-chlorophenyl) -4,5-di ( m-methoxyphenyl) imidazole dimer, 2- (o-fluorophenyl) -4,5-phenylimidazole dimer, 2- (o-methoxyphenyl) -4,5-phenylimidazole dimer, 2- (P-methoxyphenyl) -4,5-diphenylimidazole dimer, 2, -di (p-methoxyphenyl) -5-phenylimidazole dimer, 2- (2,4-dimethoxyphenyl) -4,5 -2,4,5-triarylimidazole dimer of diphenylimidazole dimer, benzyldimethyl ketal, 2-benzyl-2-dimethyl Amino-1- (4-morpholinophenyl) butan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-1-propanone, 2-hydroxy-2-methyl-1-phenyl -Propan-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propan-1-one, phenanthrenequinone, 9,10-phenanthrenequinone, Benzoins such as methylbenzoin and ethylbenzoin, 9-phenylacridine, acridine derivatives such as 1,7-bis (9,9'-acridinyl) heptane, bisacylphosphine oxide, and mixtures thereof are preferably used. May be used alone or in combination.

  In addition to these photopolymerization initiators, accelerators and the like can also be added. Examples of these include ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, triethanolamine and the like.

  Even if these photoinitiators are grafted to the side chain with respect to the hydrophilic main chain.

[Colorant]
As the color material used in the ink jet ink according to the present invention, a dye or a pigment is preferably used.

(dye)
The dye that can be used in the inkjet ink according to the present invention is not particularly limited, and examples thereof include water-soluble dyes such as acid dyes, direct dyes, and reactive dyes, and disperse dyes.

  Specific examples of dyes applicable to the ink jet ink of the present invention are listed below, but the present invention is not limited to these exemplified dyes.

[Water-soluble dye]
Examples of water-soluble dyes that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, and diphenylmethane dyes.

<C. I. Acid Yellow>
1, 3, 11, 17, 18, 19, 23, 25, 36, 38, 40, 42, 44, 49, 59, 61, 65, 67, 72, 73, 79, 99, 104, 110, 114, 116, 118, 121, 127, 129, 135, 137, 141, 143, 151, 155, 158, 159, 169, 176, 184, 193, 200, 204, 207, 215, 219, 220, 230, 232, 235, 241, 242, 246,
<C. I. Acid Orange>
3, 7, 8, 10, 19, 24, 51, 56, 67, 74, 80, 86, 87, 88, 89, 94, 95, 107, 108, 116, 122, 127, 140, 142, 144, 149, 152, 156, 162, 166, 168,
<C. I. Acid Red>
88, 97, 106, 111, 114, 118, 119, 127, 131, 138, 143, 145, 151, 183, 195, 198, 211, 215, 217, 225, 226, 249, 251, 254, 256, 257, 260, 261, 265, 266, 274, 276, 277, 289, 296, 299, 315, 318, 336, 337, 37, 359, 361, 362, 364, 366, 399, 407, 415,
<C. I. Acid Violet>
17, 19, 21, 42, 43, 47, 48, 49, 54, 66, 78, 90, 97, 102, 109, 126,
<C. I. Acid Blue>
1, 7, 9, 15, 23, 25, 40, 62, 72, 74, 80, 83, 90, 92, 103, 104, 112, 113, 114, 120, 127, 128, 129, 138, 140, 142, 156, 158, 171, 182, 185, 193, 199, 201, 203, 204, 205, 207, 209, 220, 221, 224, 225, 229, 230, 239, 249, 258, 260, 264, 278, 279, 280, 284, 290, 296, 298, 300, 317, 324, 333, 335, 338, 342, 350,
<C. I. Acid Green>
9, 12, 16, 19, 20, 25, 27, 28, 40, 43, 56, 73, 81, 84, 104, 108, 109,
<C. I. Acid Brown>
2, 4, 13, 14, 19, 28, 44, 123, 224, 226, 227, 248, 282, 283, 289, 294, 297, 298, 301, 355, 357, 413,
<C. I. Acid Black>
1, 2, 3, 24, 26, 31, 50, 52, 58, 60, 63, 107, 109, 112, 119, 132, 140, 155, 172, 187, 188, 194, 207, 222,
<C. I. Direct yellow>
8, 9, 10, 11, 12, 22, 27, 28, 39, 44, 50, 58, 79, 86, 87, 98, 105, 106, 130, 132, 137, 142, 147, 153,
<C. I. Direct orange>
6, 26, 27, 34, 39, 40, 46, 102, 105, 107, 118,
<C. I. Direct Red>
2, 4, 9, 23, 24, 31, 54, 62, 69, 79, 80, 81, 83, 84, 89, 95, 212, 224, 225, 226, 227, 239, 242, 243, 254,
<C. I. Direct Violet>
9, 35, 51, 66, 94, 95,
<C. I. Direct Blue>
1, 15, 71, 76, 77, 78, 80, 86, 87, 90, 98, 106, 108, 160, 168, 189, 192, 193, 199, 200, 201, 202, 203, 218, 225, 229, 237, 244, 248, 251, 270, 273, 274, 290, 291,
<C. I. Direct Green>
26, 28, 59, 80, 85,
<C. I. Direct Brown>
44, 106, 115, 195, 209, 210, 222, 223,
<C. I. Direct Black>
17, 19, 22, 32, 51, 62, 108, 112, 113, 117, 118, 132, 146, 154, 159, 169,
<C. I. Basic Yellow>
1, 2, 11, 13, 15, 19, 21, 28, 29, 32, 36, 40, 41, 45, 51, 63, 67, 70, 73, 91,
<C. I. Basic Orange>
2, 21, 22,
<C. I. Basic Red>
1, 2, 12, 13, 14, 15, 18, 23, 24, 27, 29, 35, 36, 39, 46, 51, 52, 69, 70, 73, 82, 109,
<C. I. Basic Violet>
1, 3, 7, 10, 11, 15, 16, 21, 27, 39,
<C. I. Basic Blue>
1, 3, 7, 9, 21, 22, 26, 41, 45, 47, 52, 54, 65, 69, 75, 77, 92, 100, 105, 117, 124, 129, 147, 151,
<C. I. Basic Green>
1, 4,
<C. I. Basic Brown>
1,
<C. I. Reactive Yellow>
2, 3, 7, 15, 17, 18, 22, 23, 24, 25, 27, 37, 39, 42, 57, 69, 76, 81, 84, 85, 86, 87, 92, 95, 102, 105, 111, 125, 135, 136, 137, 142, 143, 145, 151, 160, 161, 165, 167, 168, 175, 176,
<C. I. Reactive Orange>
1, 4, 5, 7, 11, 12, 13, 15, 16, 20, 30, 35, 56, 64, 67, 69, 70, 72, 74, 82, 84, 86, 87, 91, 92, 93, 95, 107,
<C. I. Reactive Red>
2, 3, 5, 8, 11, 21, 22, 23, 24, 28, 29, 31, 33, 35, 43, 45, 49, 55, 56, 58, 65, 66, 78, 83, 84, 106, 111, 112, 113, 114, 116, 120, 123, 124, 128, 130, 136, 141, 147, 158, 159, 171, 174, 180, 183, 184, 187, 190, 193, 194, 195, 198, 218, 220, 222, 223, 228, 235,
<C. I. Reactive Violet>
1, 2, 4, 5, 6, 22, 23, 33, 36, 38,
<C. I. Reactive Blue>
2, 3, 4, 5, 7, 13, 14, 15, 19, 21, 25, 27, 28, 29, 38, 39, 41, 49, 50, 52, 63, 69, 71, 72, 77, 79, 89, 104, 109, 112, 113, 114, 116, 119, 120, 122, 137, 140, 143, 147, 160, 161, 162, 163, 168, 171, 176, 182, 184, 191, 194, 195, 198, 203, 204, 207, 209, 211, 214, 220, 221, 222, 231, 235, 236,
<C. I. Reactive Green>
8, 12, 15, 19, 21,
<C. I. Reactive Brown>
2, 7, 9, 10, 11, 17, 18, 19, 21, 23, 31, 37, 43, 46,
<C. I. Reactive Black>
5, 8, 13, 14, 31, 34, 39,
<C. I. Food Black>
1, 2,
Etc.

  Furthermore, examples of the dye include a compound represented by the following general formula (8) or a compound represented by the general formula (9).

In the general formula (8), R ₁ represents a hydrogen atom or a substitutable substituent, and is preferably a hydrogen atom or a phenylcarbonyl group. R ₂ may be different and represents a hydrogen atom or a substitutable substituent, and is preferably a hydrogen atom. R ₃ represents a hydrogen atom or a substitutable substituent, and is preferably a hydrogen atom or an alkyl group. R ₄ represents a hydrogen atom or a substitutable substituent, preferably a hydrogen atom or an aryloxy group. R ₅ may be different and represents a hydrogen atom or a substitutable substituent, and is preferably a sulfonic acid group. n represents an integer of 1 to 4, and m represents an integer of 1 to 5.

In the general formula (9), X represents a phenyl group or a naphthyl group, may be substituted with a substitutable substituent, and is preferably substituted with a sulfonic acid group or a carboxyl group. Y represents hydrogen ion, sodium ion, potassium ion, lithium ion, ammonium ion or alkylammonium ion. R ₆ may be different and represents a hydrogen atom or a substituent that can be substituted on the naphthalene ring. q represents 1 or 2. p represents an integer of 1 to 4. However, q + p = 5. Z represents a substitutable substituent, and represents a carbonyl group, a sulfonyl group or a group represented by the following general formula (10), and particularly preferably a group represented by the following general formula (10).

In the general formula (10), W ₁ and W ₂ each independently represent a halogen atom, amino group, hydroxyl group, alkylamino group or arylamino group, preferably a halogen atom, hydroxyl group or alkylamino group.

[Disperse dye]
As the disperse dye, various disperse dyes such as azo disperse dyes, quinone disperse dyes, anthraquinone disperse dyes, quinophthalone disperse dyes can be used, and specific compounds thereof are listed below.

<C. I. Disperse Yellow>
3, 4, 5, 7, 9, 13, 23, 24, 30, 33, 34, 42, 44, 49, 50, 51, 54, 56, 58, 60, 63, 64, 66, 68, 71, 74, 76, 79, 82, 83, 85, 86, 88, 90, 91, 93, 98, 99, 100, 104, 108, 114, 116, 118, 119, 122, 124, 126, 135, 140, 141, 149, 160, 162, 163, 164, 165, 179, 180, 182, 183, 184, 186, 192, 198, 199, 202, 204, 210, 211, 215, 216, 218, 224, 227, 231, 232,
<C. I. Disperse Orange>
1, 3, 5, 7, 11, 13, 17, 20, 21, 25, 29, 30, 31, 32, 33, 37, 38, 42, 43, 44, 45, 47, 48, 49, 50, 53, 54, 55, 56, 57, 58, 59, 61, 66, 71, 73, 76, 78, 80, 89, 90, 91, 93, 96, 97, 119, 127, 130, 139, 142,
<C. I. Disperse Red>
1, 4, 5, 7, 11, 12, 13, 15, 17, 27, 43, 44, 50, 52, 53, 54, 55, 56, 58, 59, 60, 65, 72, 73, 74, 75, 76, 78, 81, 82, 86, 88, 90, 91, 92, 93, 96, 103, 105, 106, 107, 108, 110, 111, 113, 117, 118, 121, 122, 126, 127, 128, 131, 132, 134, 135, 137, 143, 145, 146, 151, 152, 153, 154, 157, 159, 164, 167, 169, 177, 179, 181, 183, 184, 185, 188, 189, 190, 191, 192, 200, 201, 202, 203, 205, 206, 207, 210, 221, 224, 225, 227, 229, 23 , 240,257,258,277,278,279,281,288,298,302,303,310,311,312,320,324,328,
<C. I. Disperse Violet>
1, 4, 8, 23, 26, 27, 28, 31, 33, 35, 36, 38, 40, 43, 46, 48, 50, 51, 52, 56, 57, 59, 61, 63, 69, 77,
<C. I. Disperse Green>
9,
<C. I. Disperse Brown>
1, 2, 4, 9, 13, 19,
<C. I. Disperse Blue>
3, 7, 9, 14, 16, 19, 20, 26, 27, 35, 43, 44, 54, 55, 56, 58, 60, 62, 64, 71, 72, 73, 75, 79, 81, 82, 83, 87, 91, 93, 94, 95, 96, 102, 106, 108, 112, 113, 115, 118, 120, 122, 125, 128, 130, 139, 141, 142, 143, 146, 148, 149, 153, 154, 158, 165, 167, 171, 173, 174, 176, 181, 183, 185, 186, 187, 189, 197, 198, 200, 201, 205, 207, 211, 214, 224, 225, 257, 259, 267, 268, 270, 284, 285, 287, 288, 291, 293, 295, 297, 301, 315, 3 0,333,
<C. I. Disperse Black>
1, 3, 10, 24
Etc.

<Pigment>
As the pigment that can be used in the ink according to the present invention, conventionally known organic and inorganic pigments can be used, and are anionic pigments. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Examples include cyclic pigments, dye lakes such as acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as carbon black.

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red 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 orange or yellow pigment 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 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. And CI Pigment Yellow 138.

  Examples of pigments 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.

  As a method for dispersing the pigment, for example, various dispersing machines such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

  In the ink according to the present invention, a self-dispersed pigment in which polar groups such as sulfonic acid and carboxylic acid are pendant on the pigment surface, or a pigment dispersed using a polymer dispersant is preferable.

  The polymer dispersant according to the present invention is not particularly limited, and a water-soluble resin or a water-insoluble resin is used. Examples of these polymers include styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, methacrylic acid, methacrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid. Examples thereof include a polymer composed of a single monomer selected from acid derivatives, a copolymer composed of two or more monomers, and salts thereof. Water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, cellulose derivatives, gelatin, and polyethylene glycol can also be used.

  The content of these water-soluble resins with respect to the total amount of ink is preferably 0.1 to 10% by mass, and more preferably 0.3 to 5% by mass. These water-soluble resins can be used in combination of two or more.

  The average particle size of the pigment dispersion used in the inkjet ink according to the present invention is preferably 500 nm or less, more preferably 200 nm or less, preferably 10 nm or more and 200 nm or less, and more preferably 10 nm or more and 150 nm or less. When the average particle size of the pigment dispersion exceeds 500 nm, the dispersion becomes unstable. In addition, even when the average particle size of the pigment dispersion is less than 10 nm, 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 device using a light scattering method, an electrophoresis method, a laser Doppler method or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

  Various methods such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used as a method for dispersing the pigment.

<Water-soluble solvent>
As described above, an aqueous liquid medium is preferably used as the solvent used in the ink according to the present invention. In the present invention, the static surface tension of the main solvent is 40 mN at 25 ° C. as described above. Preferably, water or an organic solvent having a static surface tension of 40 mN / m or more is used as the main solvent. In addition to these, the following water-soluble organic solvents may be mixed. it can.

  Alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene) Glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl) Ether, diethylene glycol monoe Ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol mono Phenyl ether), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethylene I , Pentamethyldiethylenetriamine, tetramethylpropylenediamine), amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocyclics (eg, 2-pyrrolidone, N-methyl-2) -Pyrrolidone, cyclohexyl pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone), sulfoxides (for example, dimethyl sulfoxide) and the like.

<Various additives>
The ink according to the present invention may contain a conventionally known additive in addition to the additive having the surface activity. For example, optical brighteners, antifoaming agents, lubricants, preservatives, thickeners, antistatic agents, matting agents, water-soluble polyvalent metal salts, acid bases, pH adjusting agents such as buffer solutions, antioxidants, conductivity They are regulators, surface tension modifiers, rust inhibitors, inorganic pigments, and the like.

  In the inkjet image recording method of the present invention, the active energy ray-curable ink is fixed on the recording medium by being irradiated with active energy rays such as ultraviolet rays, and then crosslinked and cured.

(Active energy rays, irradiation method)
The active energy ray as used in the present invention includes, for example, electron beam, ultraviolet ray, α ray, β ray, γ ray, X ray and the like. However, it is dangerous to human body, easy to handle, and industrially used. Electron beams and ultraviolet rays are widely used.

  When using an electron beam, the amount of the electron beam to be irradiated is preferably in the range of 0.1 to 30 Mrad. If it is less than 0.1 Mrad, a sufficient irradiation effect cannot be obtained, and if it exceeds 30 Mrad, the support or the like may be deteriorated.

  When using ultraviolet rays, the light source is a low pressure, medium pressure, high pressure mercury lamp, metal halide lamp, xenon lamp having a light emission wavelength in the ultraviolet region, cold cathode tube, hot cathode tube, for example, having an operating pressure of 0.1 kPa to 1 MPa. A conventionally well-known thing, such as LED, is used.

(Light irradiation conditions after ink landing)
As the irradiation condition of the active energy ray, it is preferable that the active energy ray is irradiated within 0.001 to 1.0 seconds after ink landing, and more preferably 0.001 to 0.5 seconds. In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible.

(Installation of lamp)
As a method for irradiating active energy rays, a basic method is disclosed in Japanese Patent Application Laid-Open No. 60-132767. According to this, the light source is provided on both sides of the head unit, and the head and the light source are scanned by the shuttle method. Irradiation is performed after a certain period of time after ink landing. Further, the curing is completed by another light source that is not driven. In US Pat. No. 6,145,979, as an irradiation method, a method using an optical fiber or a method of applying a collimated light source to a mirror surface provided on the side of the head unit and irradiating the recording unit with UV light is disclosed. Yes. Any of these irradiation methods can be used in the image forming method of the present invention.

  Also preferred is a method in which the irradiation of active energy rays is divided into two stages, the active energy rays are first irradiated by the above-described method within 0.001 to 2.0 seconds after ink landing, and further the active energy rays are irradiated. It is one of. By dividing the irradiation of the active energy ray into two stages, it is possible to further suppress the shrinkage of the recording material that occurs during ink curing.

<recoding media>
The ink according to the present invention is applied to a wide range of recording media including the following various recording media, non-absorbing recording media, and low surface energy recording media. In addition, the present invention provides an ink jet recording method that does not generate satellites and has excellent ink ejection stability in high-speed recording. In particular, the non-absorbing recording medium and the low surface energy recording medium exhibit excellent effects.

As a recording medium, firstly, there is a paper medium, the paper, coated paper, there is a non-coated paper, the coated paper, the coated amount per 1 m ² is one side 20g around the art paper, per 1 m ² of the coating amount on one side 10g before and after the coated paper, the coating amount per 1m ² is one side 5g before and after of lightweight coated paper, Binurikoshi, mat coated paper matte finish, Darukoto paper of dull finish, newsprint And so on. Non-coated paper includes printing paper A using 100% chemical pulp, printing paper B using 70% or more chemical pulp, printing paper C using 40% or more and less than 70% chemical pulp, and printing using less than 40% chemical pulp. Examples thereof include paper D, gravure paper containing mechanical pulp and subjected to calendar treatment. 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.

  The plain paper is 80 to 200 μm uncoated paper belonging to a part of uncoated paper, special printing paper and information paper. The plain paper used in the present invention includes, for example, high-grade printing paper, intermediate-grade printing paper, low-grade printing paper, thin-like printing paper, fine-coating printing paper, special printing paper such as fine-quality printing paper, foam paper, PPC paper, and others There are information sheets and the like. Specifically, there are the following sheets and various modified / processed sheets using these sheets, but the present invention is not particularly limited thereto. High quality paper and colored high quality paper, recycled paper, copy paper / colored paper, OCR paper, carbonless paper / colored paper, synthetic paper such as YUPO 60, 80, 110 microns, YUPO COAT 70, 90 microns, etc. Coated paper 90kg, Foam mat paper 70, 90, 110kg, Foamed PET 38 microns, Mitsuori-kun (above, Kobayashi recording paper), OK fine paper, New OK fine paper, Sunflower, Phoenix, OK Royal White, Export fine paper ( NPP, NCP, NWP, Royal White) OK Book Paper, OK Cream Book Paper, Cream Premium Paper, OK Map Paper, OK Ishikari, Cucumber, OK Foam, OKH, NIP-N (above, Shin Oji Paper), Gold Wang, Toko, export quality paper, special demand quality paper, book paper, book paper L, light cream book paper, elementary 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 Foam, NPI Foam DX (Nippon Paper), Pearl, Kinryo, Uscream fine paper, Special Book Paper, Super Book Paper, Book Paper, Diamond Foam, Inkjet Foam (Mitsubishi Paper), Carpet V, carpet SW, white elephant, luxury publication paper, cream carpet, cream white elephant, securities / voucher paper, book paper, map paper, copy paper, HNF (above, Hokuetsu), phone book cover, Book paper, cream shirairai, cream shirairaifu, cream shirairaifu, DSK (above, Daishowa Paper), Sendai MP fine paper, Jiang, Thunderbird fine, hanging paper, colored paper base, dictionary paper, cream book, white book, cream fine paper, map paper, continuous slip paper (above, Chuetsu Pulp), OP gold cherry (Chuetsu), gold sand, reference book paper, Replacement certificate paper (white), form printing paper, KRF, white foam, color foam, (K) NIP, fine PPC, Kishu inkjet paper (above, made by Kishu Paper), Taiou, Bright Foam, Kant, Kant White, Dante , CM paper, Dante Comic, Heine, paperback book 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 Foam, New Bright NI P (above, made by Daio Paper), Sun Ring, Moon Ring, Cloud Pass, Galaxy, Baiyun, Wyeth, Moon Ring Ace, Baiyun Ace, Cloud Pass Ace (above, Nippon Paper Industries), Taiou, Bright Foam, Bright Nip (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 Quality 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), Stalinden (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, Cherry III Super, Cheri -IV Super (above, made by Maruzumi Paper), SHF (above, made by Toyo Pulp), TRP (above, made by Tokai Pulp) and the like.

<Various films>
As the various films, all commonly used films 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>
As the various ink jet recording media, an ink receiving layer is formed on the surface using an absorbent support or a non-absorbent support as a base material. 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.

  As described above in detail, in an inkjet image recording apparatus using an ink that is crosslinked and cured by irradiation with active energy rays according to the present invention, an ink having a large difference in dynamic surface tension and static surface tension should be used. Therefore, in a wide range of recording media, from plain paper to non-absorbing recording media, both high-speed ejection of ink droplets and suppression of satellite generation and suppression of ink bleeding and repellency on the recording medium are compatible. it can. In particular, the inkjet image recording method using the active energy ray-curable ink according to the present invention appropriately spreads the landed ink on a non-ink-absorbing recording medium or a recording medium having a small surface energy, In addition, there is no phenomenon such as dot repelling, and there is little satellite generation when ink droplets are ejected at a high speed, so that the image recording method can obtain high-quality image recording.

  FIG. 1 is a diagram showing a schematic configuration of an apparatus used in an inkjet image recording method according to the present invention. In the recording apparatus 1, the recording medium P is sandwiched between the conveyance roller pair 32 of the conveyance mechanism 3 and further conveyed in the Y direction in the drawing by a conveyance roller 31 that is rotationally driven by a conveyance motor 33.

  The recording head 2 is provided between the conveying roller 31 and the conveying roller pair 32 so as to face the recording surface PS of the recording medium P. The recording head 2 is shown substantially orthogonal to the conveyance direction (sub-scanning direction) of the recording medium P by a driving means (not shown) along the guide rail 4 spanning the width direction of the recording medium P. The flexure cable 6 is mounted on a carriage 5 provided so as to be capable of reciprocating along the XX ′ direction (main scanning direction) so that the nozzle surface side faces the recording surface PS of the recording medium P. Is electrically connected to drive signal generating means 100 (see FIG. 3) provided with a circuit for generating a drive signal. The carriage 5 includes a plurality of recording heads that eject a plurality of inks, and irradiation means (specifically, halogen lamps) of active energy rays (ultraviolet rays) at both ends of the carriage (not shown in the drawing). ), The recording head 2 moves the recording surface PS of the recording medium P in the direction of XX ′ in the drawing along with the movement of the carriage 5, and ejects ink droplets in this movement process to record a desired inkjet image. At the same time, the ink can be cured and fixed to the recording medium by irradiating with active energy rays immediately after ejection.

  In the figure, reference numeral 7 denotes an ink receiver, and the recording head 2 is provided at a standby position such as a home position during non-recording. When the recording head 2 is in this standby position, a small amount of ink droplets are discarded toward the ink receiver 7. When the recording head 2 has stopped operating for a long time at this standby position, although not shown, the nozzle surface of the recording head 2 is covered by a cap. Reference numeral 8 denotes an ink receiver provided at a position opposite to the ink receiver 7 with the recording medium P in between. When recording in both reciprocating directions, the same operation is performed when switching from forward to backward movement. Accept discarded ink drops.

  There are various active energy rays for crosslinking and curing the ink, such as electron beams, alpha rays, ultraviolet rays, and visible light. In the present invention, ultraviolet rays are most preferred.

In the case where ultraviolet rays are used, as a light source, in addition to the above, for example, low pressure, medium pressure, high pressure mercury lamps having an operating pressure of several hundred Pa to 1 MPa, xenon lamps having a light emission wavelength in the ultraviolet region, metal halide lamps, cold cathodes A conventionally well-known thing, such as a pipe | tube, a hot cathode tube, LED, is used. A low-pressure mercury lamp, a hot cathode tube, a cold cathode tube, and a germicidal lamp that emit ultraviolet light having a wavelength of 254 nm are preferable because they can effectively prevent bleeding and control the dot diameter. When performing ultraviolet irradiation, ultraviolet irradiation dose, 100 mJ / cm ² or more, preferably 500 mJ / cm ² or more, also, 10,000 / cm ² or less, preferably performed at 5,000 mJ / cm ² or less in the range . If it is the amount of ultraviolet irradiation within this range, a sufficient curing reaction can be carried out.

  In order to form a high-definition image, it is particularly important that the irradiation timing is as early as possible. Therefore, it is preferable that the irradiation means 3 is equipped with a shutter. For example, when using ultraviolet rays, the ratio of illuminance when opening and closing the shutter is preferably shutter open / shutter close = 10 or more, more preferably 100 or more. More preferably, it is 10,000 or more.

  As the recording head to be used, as an ejection 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 type, bubble jet (registered trademark) type, etc.), electrostatic suction type (for example, electric field control type, slit jet type, etc.) and discharge type (for example, spark jet type, etc.). .

  Any ejection method may be used, but particularly preferably, the pressure generating means for ejecting ink forms at least a part of a partition wall between adjacent ink channels and applies a voltage to perform shearing. The effect is great in the case of a shear mode method constituted by a piezoelectric material that deforms in a mode. In the share mode method, in order to deform and drive the partition wall between adjacent ink channels, the meniscus is pushed out by ejection of the adjacent channel, and the amount of meniscus pushed out from the nozzle surface increases, so the ejection stability is lowered and the satellite is Many are likely to occur. By applying the present invention in this system, it is possible to suppress meniscus extrusion, increase injection stability, and reduce the amount of satellites generated.

  Hereinafter, the present invention will be described by way of examples, but the present invention is not limited thereto.

  The structure of the shear mode (shear mode) type recording head 2 used in the examples is shown in FIGS. 2A is a schematic perspective view, FIG. 2B is a cross-sectional view, and FIG. 3 is a diagram illustrating the operation of the recording head pressure generating chamber during ink ejection. In the figure, 21 is an ink tube, 22 is a nozzle forming member, 23 is a nozzle, 24 is a cover plate, 25 is an ink supply port, 26 is a substrate, and 27 is a partition wall. An ink channel 28 is formed by the partition wall 27, the cover plate 24, and the substrate 26.

  As shown in FIG. 3, the recording head 2 is separated between a cover plate 24 and a substrate 26 by a plurality of partition walls 27A, 27B, 27C, and 27D made of a piezoelectric material such as PZT that is an electromechanical conversion means. This is a shear mode type recording head in which a large number of pressure generating chambers 28 are arranged in parallel. In FIG. 3, three (28A, 28B, 28C) which are a part of many pressure generation chambers 28 are shown. One end (hereinafter sometimes referred to as a nozzle end) of the pressure generating chamber 28 is connected to a nozzle 23 formed on the nozzle forming member 22, and the other end (hereinafter also referred to as a manifold end) is an ink supply port. 25, the ink tube 21 is connected to an ink tank (not shown). Electrodes 29A, 29B, and 29C are formed in close contact with the surface of the partition wall 27 in each pressure generating chamber 28 from above the partition walls 27 to the bottom surface of the substrate 26. The electrodes 29A, 29B, and 29C generate drive signals. Connected to means 100.

  The drive signal generation means 100 includes a drive signal generation circuit that generates a series of drive signals including a plurality of drive pulses for each pixel period, and a drive signal supplied from the drive signal generation circuit for each ink channel. A driving pulse selection circuit that selects a driving pulse according to the data of each pixel and supplies it to each ink channel. The driving pulse for driving the partition wall 27 as an electro-mechanical conversion means according to the data of each pixel. Supply.

  Here, each partition wall 27 of the pressure generating chamber is composed of two piezoelectric materials 27a and 27b having different polarization directions as indicated by arrows in FIG.

PZT (PbZrO ₃ —PbTiO ₃ ) is used as the piezoelectric material.

  When an ejection pulse is applied to the electrodes 29A, 29B, and 29C formed in close contact with the surfaces of the partition walls 27 under the control of the drive signal generator 100, ink droplets are ejected from the nozzles 23 by the operation exemplified below. In FIG. 3, the nozzle is omitted.

  First, when no ejection pulse is applied to any of the electrodes 29A, 29B, and 29C, none of the partition walls 27A, 27B, and 27C is deformed, but the electrodes 29A and 29C are grounded in the state shown in FIG. In addition, when an ejection pulse is applied to the electrode 29B, an electric field in a direction perpendicular to the polarization direction of the piezoelectric material constituting the partition walls 27B and 27C is generated, and both the partition walls 27B and 27C are deformed in the joint surfaces of the partition walls 27a and 27b. As shown in FIG. 3B, the partition walls 27B and 27C are deformed toward the outside, and the volume of the ink channel 28B is enlarged to generate a negative pressure in the ink channel 28B, so that the ink flows (Draw). .

  When the potential is returned to 0 from this state, the partition walls 27B and 27C return from the expanded position shown in FIG. 3B to the neutral position shown in FIG. 3A, and high pressure is applied to the ink in the ink channel 28B. (Release). Next, as shown in FIG. 3C, when the ejection pulse is applied so as to deform the partition walls 27B and 27C in the opposite directions to reduce the volume of the ink channel 28B, a positive pressure is generated in the ink channel 28B. It occurs (Reinforce). As a result, the ink meniscus in the nozzle due to a part of the ink filling the ink channel 28B changes in the direction pushed out from the nozzle. When the positive pressure becomes so large that the ink droplet is ejected from the nozzle, the ink droplet is ejected from the nozzle. Each of the other ink channels operates in the same manner as described above by applying an ejection pulse. Such an ejection method is called a DRR driving method, which is a typical driving method for a share mode type recording head.

  When the recording head 2 having a plurality of ink channels 28 separated by the partition walls 27 at least partially made of a piezoelectric material is driven as described above, when the partition wall of one ink channel performs an ejection operation, the adjacent ink is used. Since the channels are affected, normally, among the plurality of ink channels 28, two or more ink channels 28 that are separated from each other by sandwiching one or more ink channels 28 are combined into one set. It is divided into groups, and the drive control is performed so that the ink ejection operation is sequentially performed in time division for each group. For example, when all the ink channels 28 are driven to output a solid image, a so-called three-cycle ejection method is performed in which the ink channels 28 are selected every two ink channels and ejected in three phases.

  The metal electrode 29 in each pressure generating chamber 28 extends to the rear side surface of the piezoelectric material 27a through the shallow groove portion 28b. The flexible cable 6 is bonded to each metal electrode 29 via an anisotropic conductive film 78 on the rear side surface. By applying a drive signal to each metal electrode 29 from the drive signal generating means 100, the side wall 27 is applied. The ink in the pressure generating chamber 28 is ejected from the nozzles 23 formed on the nozzle plate 22 by the deformation pressure.

Examples 1 to 3, Comparative Examples 1 to 4 (using water-based ink containing a photocrosslinkable polymer compound)
A water-based ink containing a polymer compound having a plurality of side chains in the hydrophilic main chain and crosslinked between the side chains by UV light irradiation was prepared, and the ejection performance and printing performance were evaluated using a shear mode head. . The surface tension of the ink was adjusted by changing the amount of the water-soluble organic solvent diethylene glycol monobutyl ether, which is an additive having a surface active function, and Olphine E1010 (manufactured by Nissin Chemical), which is an acetylene-based surfactant.

<Synthesis of polymer compounds>
56 g of glycidyl methacrylate, 48 g of p-hydroxybenzaldehyde, 2 g of pyridine, and 1 g of N-nitroso-phenylhydroxyamine ammonium salt were put in a reaction vessel and stirred in a hot water bath at 80 ° C. for 8 hours.

  Next, 45 g of a polyvinyl acetate saponified product having a degree of polymerization of 300 and a saponification rate of 88% was dispersed in 225 g of ion-exchanged water, and then 4.5 g of phosphoric acid and p- (3-methacryloxy-) obtained by the above reaction were added to this solution. 2-Hydroxypropyloxy) benzaldehyde was added to PVA so that the modification rate was 3 mol%, and the mixture was stirred at 90 ° C. for 6 hours. After cooling the obtained solution to room temperature, 30 g of basic ion exchange resin was added and stirred for 1 hour. Thereafter, the ion exchange resin was filtered, and Irgacure 2959 (manufactured by Ciba Specialty Chemicals Co., Ltd.) as a photopolymerization initiator was mixed at a rate of 0.1 g with respect to 100 g of 15% aqueous solution, and then diluted with ion exchange water. As a result, a 10% aqueous polymer compound solution was obtained.

(Preparation of ink)
A magenta ink was prepared as follows.
C. I. Acid Red 35 5 parts 10% aqueous polymer compound solution 30 parts glycerin 7 parts diethylene glycol 15 parts diethylene glycol monobutyl ether Orphine e1010 (made by Nissin Chemical Co., Ltd.) changed mainly about 10 parts Then, ion exchange water was added to make the total amount 100 parts, and magenta inks shown in Table 1 were obtained.

  The values of static surface tension and dynamic surface tension of each ink were changed by changing the addition amount of diethylene glycol monobutyl ether and orphine e1010. The surface tension was measured using a measuring device modified from a commercially available maximum bubble pressure method measuring device (Dynamic Surface Tension Meter BP-D4 type manufactured by Kyowa Interface Science Co., Ltd.), and a static surface tension at a bubble frequency of 0.1 Hz (10 sec). The dynamic surface tension was measured at a bubble frequency of 100 Hz (10 msec) (25 ° C.). The viscosity was measured using a vibration viscometer (Pehsica Rheometer MCR300) at the discharge temperature.

<Evaluation>
For the measurement, the share mode type recording head (nozzle pitch: 180 dpi x 2 rows, number of nozzles: 512, nozzle diameter: 23 μm, AL: 2.4 μs, ink droplet amount: 6 pl) shown in FIG. 2 is prepared. The nozzle rows were bonded to each other so as to be shifted by ½ pitch from each other and arranged in a staggered manner. Thus, it was used as a 360 dpi recording head.

  Channels of each column of the two-row head (nozzle pitch: 360 dpi, number of nozzles: 512) are connected to the drive signal (expansion pulse width: 1 AL, contraction pulse width: 2 AL, drive voltage Von / Voff = 2/1) was applied by three-cycle driving with a cycle of 7 AL / cycle to perform continuous ejection. In Comparative Example 4, the driving signal was set to the driving voltage Voff = 0, and only the signal Von was used, and the maximum meniscus extrusion amount (μm) was changed.

  Here, AL (Acoustic Length) is 1/2 of the acoustic resonance period of the recording head pressure generating chamber. This AL measured the speed of ink droplets discharged by applying a rectangular wave pulse to the partition wall 27 as an electric / mechanical conversion means, and changed the pulse width of the rectangular wave while keeping the voltage value of the rectangular wave constant. Sometimes it is determined as the pulse width that maximizes the flying speed of the ink droplets. The AL of the recording head 2 of this embodiment is 2.4 (μs), and this value is determined depending on the head structure, ink density, and the like.

(Meniscus extrusion amount)
The extrusion amount of the ink meniscus from the nozzle was measured by stroboscopic synchronization using a digital microscope “VH-6300” manufactured by KEYENCE. An outline of the change of the ink meniscus M before and after the droplet discharge is shown in FIG. The meniscus push-out amount measured here is the maximum push-out amount when the meniscus (FIG. 6 (4)) once drawn immediately after droplet discharge is returned to the nozzle surface and further pushed out (FIG. 6 (6)). The amount of meniscus extrusion was determined by measuring the amount of protrusion of the ink meniscus from the nozzle tip at the approximate nozzle center when ejected at a droplet velocity of 6 m / s in a direction substantially perpendicular to the nozzle forming member (FIG. 7).

(Bubble removal)
Ink was introduced into the recording head, the ink was driven to discharge, and the presence or absence of an injection missing nozzle was observed. When there was an injection missing nozzle, cleaning by nozzle sucking (suction) was repeated to remove bubbles in the head, and the bubble removal property was evaluated according to the following criteria from the number of times of sucking that the injection missing nozzle was eliminated.

Number of times of sucking evaluation 1 or less ◎
2 to 3 times ○
4 times or more ×
(Injection stability)
Full-duty driving is performed by changing the driving speed by changing the driving voltage by the above driving method, and the CCD uses the maximum droplet speed at which the droplets are ejected straight and stably without causing ejection failure. The injection stability was evaluated according to the following criteria.

Maximum droplet speed evaluation Over 10m / s ◎
7-10m / s ○
Less than 7m / s ×
(Satellite evaluation)
Flying speed and satellite length measurement: The ink droplet velocity and satellite length (from the main droplet of the droplet to the rear end of the satellite) when the ink droplet flew about 1 mm from the nozzle opening by strobe measurement using a CCD camera. Length) was measured to determine the droplet velocity at which satellites began to occur. The longer the satellite length and the lower the satellite generation speed, the larger the satellite amount. From the satellite generation rate, the amount of satellite was evaluated according to the following criteria.

Satellite generation rate evaluation Over 5m / s ◎
3-5m / s ○
Less than 3m / s ×
(Bleeding)
Using the inkjet recording apparatus of FIG. 1 having a maximum recording density of 720 × 720 dpi, a fine line having a width of 250 μm and a length of 5 cm is printed on high-quality paper (First Class paper manufactured by Konica Minolta Business Technology), and visually observed. The feathering was evaluated according to the following.

  Each ink was continuously ejected, and 0.1 seconds after landing, a 120 W / cm metal halide lamp (MAL 400NL power supply power 3 kW · hr, manufactured by Nippon Batteries Co., Ltd.) was irradiated.

◎: Thin lines are reproduced without blurring due to bleeding ○: Lines are not thickened due to bleeding, but less than 5 spots, ink bleeding along the paper fiber is observed Δ: Lines are thickened due to bleeding No, but ink blots along the paper fibers are observed at less than 10 points. X: Lines are thickened due to blotting, and ink blots along the paper fibers are also observed at 10 or more points.

  The above results are shown in Table 1.

  Examples 1-3 are not repelled on the polymer film because of the low static surface tension (25-34 mN / m). Further, since the dynamic surface tension is 10 mN / m or more higher than the static surface tension (13 to 15 mN / m), when the ink column is cut during ejection, the meniscus is not excessively pushed out and there are few satellites.

  In Comparative Example 1, since the static surface tension is only 3 to 5 mN / m higher than the dynamic surface tension, the meniscus is excessively pushed out during the discharge, resulting in an increase in satellites. Further, since the dynamic surface tensions of Comparative Examples 2 and 3 deviate from the scope of this patent, even if the difference is large, Comparative Example 2 wets the nozzle plate and forms an ink reservoir. In Comparative Example 3, the static surface tension is too large, and bubble removal, bleeding, and the like deteriorate.

  Further, in Comparative Example 4, the static surface tension is also within the present invention, and the dynamic surface tension is 10 mN / m or more higher than this, but the maximum meniscus extrusion amount is larger than the nozzle radius, and there are many satellites and stable injection. The nature is bad.

Example 4 and Comparative Example 5 (using non-aqueous UV curable ink)
Consists of 5% colorant, 10% photoinitiator, 10% acrylate functional oligomer, and acrylic (1,2) functional monomer, and adjusts static and dynamic surface tension by adding acetylenic activator. A similar test was performed and evaluated using a UV curable ink.

  An ink having a large dynamic surface tension compared to a static surface tension has a good satellite amount, and also has good bubble bleeding, ejection stability, and bleeding.

It is a figure which shows schematic structure of the apparatus used for the inkjet image recording method which concerns on this invention. FIG. 2 is a perspective view and a cross-sectional view showing a structure of a shear mode (shear mode) type recording head used in Examples. It is a figure which shows the action | operation of the recording head pressure generation chamber at the time of ink discharge. It is a figure which shows the surface tension-bubble frequency profile of the ink of this invention. It is a figure which shows the drive signal used in the Example. It is a figure which shows the meniscus change in the recording head nozzle at the time of ink ejection. It is a figure which shows the relationship between the ink drop at the time of ink discharge, an ink column, and the meniscus extrusion amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet recording apparatus 2 Recording head 21 Ink tube 22 Nozzle formation member 23 Nozzle 24 Cover plate 25 Ink supply port 26 Substrate 27 Partition 28 Pressure generating chamber 3 Conveying mechanism 31 Conveying roller 32 Conveying roller pair 33 Conveying motor 4 Guide rail 5 Carriage 6 Flexi cable 7, 8 Ink receiver 100 Drive signal generating means P Recording medium PS Recording surface 10 Ink main droplet 10b Ink tail portion M Ink meniscus

Claims (5)

In an inkjet image recording method in which an ink droplet is ejected from a nozzle of a recording head to form an image pattern on the opposing recording medium surface, the static surface tension of the ejected ink is 25 mN / m or more and 35 mN / m or less. In addition, the dynamic surface tension of the ink when ink droplets are formed by ejection is 10 mN / m or more higher than the static surface tension, and the meniscus re-extrusion amount during ink ejection is less than the radius of the nozzle. An inkjet image recording method. The inkjet image recording method according to claim 1, wherein the viscosity of the ejected ink is 5 mPa · sec or more and 15 mPa · sec or less at the ejection temperature. 3. The ink jet image recording method according to claim 1, wherein the ejected ink contains a solvent having a static surface tension of 40 mN / m or more and an additive having a surface active function. The inkjet image recording method according to any one of claims 1 to 3, wherein the ejected ink has at least a coloring material, water, and a plurality of side chains in a hydrophilic main chain, and an active energy ray. An ink jet image recording method comprising: an ink containing a polymer compound capable of crosslinking between side chains by irradiation. The pressure generating means for ejecting ink of the recording head is formed of a piezoelectric material that forms at least a part of a partition between adjacent ink channels and is deformed in a shear mode by applying a voltage. The inkjet image recording method according to any one of claims 1 to 4, wherein

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