JP2008194827A - Inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording method which is excellent in ejection stability, bleeding resistance of a secondary color and weathering resistance, and also excellent in gradient. <P>SOLUTION: In the inkjet recording method of recording to a recording medium by ejecting an inkjet ink from an inkjet recording head, the inkjet ink contains at least a color material, a photoreactive resin and water. After the inkjet ink is ejected to the recording medium, before the process of irradiating it with an active energy ray, a volatile component contained in the inkjet ink is condensed by a drying means or permeation into the recording medium. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording method.

  The ink jet recording method is capable of high-definition image recording with a relatively simple device, and has been rapidly developed in various fields. In addition, there are various uses of the ink jet recording method, and a recording medium or ink jet ink suitable for each purpose is used.

  In particular, in recent years, high speed and high image quality of the ink jet recording method have attracted much attention, and the recording width of the ink jet recording head has been increased from the viewpoint of increasing the number of nozzles of the ink jet recording head. Such an ink jet recording head is referred to as a line head (see Patent Document 1). By adopting such a line head type ink jet recording head, the recording speed has been greatly improved, and an ink jet printer having performance capable of withstanding light printing applications has been developed. However, with normal water-based inkjet ink, printing paper with low ink absorption such as art paper and coated paper, which is mainly used as recording paper for offset printing and gravure printing, plastic film with no ink absorption, etc. In recording, there is a problem such as so-called color bleeding in which ink liquids having different hues are mixed on a recording medium and cause color turbidity.

  In response to the above problems, a hot-melt ink composition comprising a solid wax or the like as a constituent material at room temperature is liquefied by heating or the like, applied with appropriate energy, ejected, adhered onto a recording medium, and simultaneously cooled. There has been proposed a hot-melt type ink jet recording method that solidifies to form dots (see Patent Documents 2 and 3). Since this hot melt ink is solid at room temperature, it does not get dirty during handling, and since there is substantially no ink evaporation at the time of melting, the hot melt ink has the characteristics that nozzle clogging does not occur. Furthermore, it is said to be an ink composition that solidifies immediately after adhering, has little color bleeding, and provides good print quality regardless of the material of the paper. However, an image recorded by such a method has problems such as deterioration of quality due to the rising of the dots and lack of abrasion resistance because the ink dots are in the form of soft wax. is there.

  On the other hand, an inkjet recording ink that is cured by irradiation with active energy rays has been disclosed (see Patent Document 4). In addition, a so-called non-aqueous ink jet ink containing a pigment as a coloring material, a triacrylate or higher polyacrylate as a polymerizable material, and a ketone or alcohol as a main solvent has been proposed (see Patent Document 5). ). An aqueous active energy ray-curable ink jet recording ink composition comprising a polyurethane compound containing a group having an active energy ray-curable unsaturated double bond, a basic compound, a colorant, a water-soluble organic solvent, and water The thing is proposed (refer patent document 6). Furthermore, a water-based active energy ray curing comprising a self-dispersing pigment having one or more hydrophilic groups bonded to the surface of pigment particles, an ultraviolet curable monomer made of a vinyl compound, a photopolymerization initiator, and water. A type inkjet ink has been proposed (see Patent Document 7).

However, the water-based active energy ray-curable inkjet ink described in each of the above-mentioned patent documents has a new color bleed that deteriorates when an image with a large amount of shot such as a secondary color or a tertiary color is printed. There was a serious problem.
JP-A-6-183029 U.S. Pat. No. 4,390,369 U.S. Pat. No. 4,484,948 U.S. Pat. No. 4,228,438 Japanese Patent Publication No. 5-64667 JP 2002-80767 A JP 2002-275404 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to provide an ink jet recording method that is excellent in emission stability, secondary color bleeding resistance, and feathering resistance, and also in excellent gradation. is there.

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

  1. In an inkjet recording method for recording an inkjet ink from an inkjet recording head to record on a recording medium, the inkjet ink contains at least a coloring material, a photoreactive resin, and water, and after ejecting the inkjet ink to a recording medium, An ink jet recording method comprising: concentrating a volatile component contained in the ink jet ink by permeation into a drying means or a recording medium before the step of irradiating active energy rays.

  2. The concentration ratio B / A is 0.8 or less, where A is the ink volume when the ink jet ink is landed on the recording medium and B is the ink volume immediately before irradiation with the active energy ray. 2. The inkjet recording method according to 1 above.

  3. 3. The ink jet recording method according to 1 or 2, wherein the ink jet recording head is a line head system.

  4). The drying means is a means for heating the recording medium with a heat roller, a means for heating the recording medium with a flat panel heater, a means for drying the ink-jet ink using hot air, and the ink-jet ink using a heat source. 4. The ink jet recording method according to any one of items 1 to 3, which is at least one selected from means for drying.

  5. A step of concentrating the ink-jet ink at a time from when the first ink-jet dot hits the recording medium from the ink-jet recording head to when the dot hits a position adjacent to the first shot. 5. The ink jet recording method according to any one of 1 to 4 above.

  6). 6. The inkjet recording method according to any one of 1 to 5, wherein the inkjet ink contains a water-soluble photopolymerization initiator.

  7. 7. The ink jet recording method according to any one of 1 to 6, wherein the image recording is performed using an ink jet ink set including two or more kinds of inks having different color materials and including at least one ink jet ink. .

  8). 8. The inkjet recording method according to 7, wherein at least one of the inkjet inks included in the inkjet ink set has the lowest active energy ray transmittance among the inkjet inks included in the inkjet ink set. .

  9. 9. The ink jet recording method according to any one of 1 to 8, wherein the image forming method is performed twice or more and eight times or less.

  10. 10. The ink jet recording method according to any one of 1 to 9, wherein the recording medium is a low-absorbing recording medium or a non-absorbing recording medium.

  11. 10. The ink jet recording method according to any one of 1 to 9, wherein the recording medium is plain paper.

  12 The photoreactive resin contained in the inkjet ink is a polymer compound having a plurality of side chains with respect to the hydrophilic main chain and capable of crosslinking between the side chains by irradiating active energy rays. The inkjet recording method according to any one of 1 to 11 above.

  13. 13. The ink jet recording as described in 12 above, wherein the polymer compound is a saponified product having a hydrophilic main chain of polyvinyl acetate, a saponification degree of 77 to 99%, and a polymerization degree of 200 to 500. Method.

  14 14. The inkjet recording method according to item 12 or 13, wherein the polymer compound has a side chain modification rate of 0.8 mol% or more and 5 mol% or less with respect to the hydrophilic main chain.

  According to the present invention, it is possible to provide an ink jet recording method which is excellent in emission stability, secondary color bleeding resistance, and feathering resistance, and further has excellent gradation.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventors have found that in an inkjet recording method of ejecting inkjet ink from an inkjet recording head and recording on a recording medium, the inkjet ink includes at least a colorant, a photoreactive resin, and Containing water and condensing the volatile components contained in the ink-jet ink by osmosis into the drying means or the recording medium before the step of irradiating active energy rays after the ink-jet ink is discharged onto the recording medium. With the ink jet recording method that is characterized, even when a line head type ink jet recording head is used, it is possible to realize an ink jet recording method that is excellent in emission stability, secondary color bleeding resistance, feathering resistance, and excellent gradation. As a result, the present invention has been achieved.

  In the conventional method, the water-based active energy ray-curable inkjet ink has a small ratio of the photocurable resin contained in the ink, so when printing an image with a large amount of shots such as a secondary color and a tertiary color, It was a problem that mixing between dots of different colors occurred and color bleeding deteriorated. Increasing the ratio of the photo-curing resin contained in the ink causes clogging of the nozzles of the head, resulting in severe emission characteristics, and there is a problem in coexistence between color bleeding and emission stability of an image with a large amount of shots.

  In the line head method, where the time until the adjacent dots land is very short, there is a problem that aggregation occurs between adjacent dots before irradiation with active energy rays, so secondary color bleed and emission stability The balance was more severe.

  The present invention is characterized by having a concentration step of concentrating the inkjet ink before irradiating the active energy ray for curing the inkjet ink, whereby the dots are once fixed on the recording medium with a weak force. Further, by firmly fixing on the recording medium at the time of irradiation with active energy rays, the bleed generated between the secondary colors was improved.

  On the other hand, when an ink jet ink containing a photoreactive resin is hit from a line head type ink jet recording head, whose required performance with respect to light emission is stricter than that of the shuttle type, an image is being formed in the vicinity of a nozzle portion not used for image formation or a recording medium In some cases, the nozzle portion may become clogged during printing suspension due to a change in the number of times, and stable emission may be difficult. By having the concentration step, the ratio of the photoreactive resin contained in the ink can be reduced, and this has been solved.

  This problem was remarkable when an active energy ray crosslinkable polymer was used. This is because the ink-jet ink containing the active energy ray-crosslinkable polymer has a large variation in the viscosity of the ink with respect to the drying rate of the dry component in the ink.

  However, by providing the concentration step characterized by the present invention, the ratio of active energy ray crosslinkable polymer in the dot in the ink is increased, so that the thickening effect at the time of irradiation with the active energy ray becomes very high. An effect was also obtained. This is because the active energy ray crosslinkable polymer has high sensitivity, so even if the amount contained in the ink is very small, it can exert a large thickening effect during light irradiation, and the effect of concentrating the ink. Because it is big.

  As a result, it was possible to adjust the amount of addition of the active energy ray polymer contained in the ink at the time of ejection, the degree of polymerization, the modification rate, etc., and it was found that the emission stability can be maintained well even in the line head system. It is.

  In the present invention, from the amount of ink dried and the amount of penetrating into the recording medium that occurs during the time from landing on the recording medium to irradiation with the active energy ray, the polymer concentration having good fixability upon light irradiation is obtained. It is also possible to stably design the type and amount of the photocurable resin contained in the ink at the time of ejection. Thereby, it is possible to give high recording medium suitability.

  Further, in the ink jet recording method of the present invention, by having a concentration step of concentrating the ink between the dot landing and the adjacent dot landing, each dot is recorded on the recording medium or the already printed dots. Since the image is fixed, the gradation of the image is further improved. Here, the adjacent dots are defined as two dots in contact with the transport direction, two dots in contact with the transport direction perpendicularly, or four dots combining them.

  Details of the present invention will be described below.

<Inkjet recording method>
The inkjet recording method using the inkjet ink of the present invention (hereinafter also simply referred to as ink) is an inkjet recording method in which an inkjet ink containing at least a coloring material, a photoreactive resin, and water is ejected from an inkjet recording head, It has a concentration step of concentrating volatile components contained in the ink by permeation into the drying means or the recording medium before the step of irradiating the ink with active energy rays after discharging the ink onto the recording medium. An ink jet recording method is characterized in that after ink is ejected, the recording medium is irradiated with active energy rays to cure the ink, thereby forming an image.

(inkjet printer)
An ink jet printer applicable to the ink jet recording method of the present invention is mainly an ink jet recording head in which an image forming unit is disposed horizontally with respect to a recording medium and ejects ink jet ink from a nozzle outlet toward the recording medium. (When a plurality of inkjet inks are used, a plurality of inkjet recording heads are used) and a light source that irradiates active energy rays.

  In the ink jet recording method of the present invention, before the step of discharging onto the recording medium and irradiating the ink jet ink with active energy rays, the drying means or the recording is performed for the purpose of removing water, water-soluble organic solvent, and the like as volatile components. It has a concentration step of concentrating by permeation into the medium, but it is more preferable to apply a drying means as the concentration means, and further, the drying means heats the recording medium with a heat roller. And at least one selected from means for heating the recording medium with a flat panel heater, means for drying the inkjet ink using hot air, and means for drying the inkjet ink using a thermal light source. preferable. In addition, as a method for concentrating by infiltration of the ink component into the recording medium, an ink jet recording medium having an ink absorbing layer having ink absorbing ability is applied as the recording medium to be applied, and the ink absorbing ability of the recording medium is appropriately set. By adjusting, it is possible to control to a desired ink concentration rate.

  In the ink jet recording method of the present invention, the concentration step as described above, in particular, by providing a drying means, the ink is once fixed on the recording medium with a weak force, and is firmly attached to the recording medium when irradiated with active energy rays. It is possible to improve the bleeding between the inks of two colors.

  In addition, by having a concentration step of drying volatile components in the ink, the ink is concentrated before irradiation with active energy rays, and both emission stability and sufficient fixability during light irradiation can be achieved. .

  Hereinafter, the configuration of the ink jet printer according to the present invention will be described with reference to the drawings.

  In the ink jet recording method of the present invention, it is preferable to use an ink jet printer having a line head type ink jet recording head. The recording medium includes a step of discharging ink onto a recording medium, a concentration step of drying and concentrating ink droplets that have landed on the recording medium, and an active energy ray irradiation step of irradiating the ink with active energy rays to cure the ink. Are preferably arranged in this order from the upstream side in the transport direction. In addition, it includes a transport unit that transports the recording medium, a platen that holds the recording medium, a control unit that controls the ejection of ink, and the like.

  FIG. 1 is a top view illustrating an example of an ink jet printer including a line head type ink jet recording head and an ink concentration step.

  The ink jet printer 1 shown in FIG. 1 shows an example in which a flat panel heater is used as a concentrating means. The flat panel heater 3 is placed on the platen 2 holding the recording medium P upstream of the conveyance section of the recording medium P. It is installed between the side and the active energy ray irradiation unit 5. As shown in FIG. 1, after heating the back surface of the recording medium P conveyed by the flat panel heater 3 to bring the recording medium P to a predetermined temperature, the recording medium P is covered so as to cover the entire width of the recording medium P. The ink is ejected onto a recording medium P heated to a predetermined temperature from a line head type inkjet recording head 4 arranged at a horizontal position with respect to the transport direction. Next, the recording medium P conveyed over a certain time is irradiated with active energy rays (for example, ultraviolet rays) from the active energy ray irradiating unit 5 located on the downstream side to cure the ink.

FIG. 1 shows an example in which four line head type ink jet recording heads 4 are arranged. For example, yellow ink, magenta ink, cyan ink, black ink, and the like are discharged from each ink jet recording head 4. Perform image formation. At this time, the selection of the respective ink types to be filled in the ink jet recording head 4 installed at a position where the distance from the active energy ray irradiation unit 5 is different, that is, the concentration time in the concentration process is different is arbitrary. It is preferable to fill the respective ink jet recording heads 4 with the optimum ink. In addition, when performing image formation in the image recording using the ink jet printer shown in FIG. It is preferable to have a step of concentrating the ink-jet ink during the time from when the first dot of the ink jet hits until the dot hits a position adjacent to the first shot.

  Further, when forming an image, it is preferable to form the image with the number of scans of 2 times or more and 8 times or less. That is, 1) ink ejection onto a recording medium (image recording process), 2) landing ink drying (concentration process), and 3) ink curing (curing process) by irradiation with active energy rays. By forming the image by dividing it into a plurality of times, in particular, the heat generated when irradiating the active energy ray from the active energy ray irradiating part can contribute to the drying in the subsequent scanning step. By forming an image with the number of passes, it is possible to dry each dot. As means for changing the scanning man-hours, there are means for passing a recording medium a plurality of times in a line head type ink jet printer, and means for forming an image with a plurality of times of scanning in a shuttle type ink jet printer.

  FIG. 2 is a schematic diagram illustrating an example of each dot arrangement when performing image formation with a plurality of passes.

  For example, when printing in four passes, it is preferable to print in the first, second, third, and fourth passes with the dot arrangement of 1, 2, 3, and 4 shown in FIG. In this case, in order to form secondary color and tertiary color images, it is preferable to increase the number of ink droplets in one pass to two to three times. As a result, it is possible to perform the concentration process before the landing of adjacent dots, and it is possible to fix each dot, and as a result, it is possible to obtain an image with excellent gradation. Therefore, as the number of passes is increased, the gradation is further improved, but from the viewpoint of image formation efficiency, the upper limit of the number of passes is preferably eight.

  FIG. 3 is a top view showing another example of an ink jet printer including a line head type ink jet recording head and an ink concentration step.

In FIG. 1, one active energy ray irradiation unit 5 is provided on the downstream side of a group of ink jet recording heads 4 (four), and each ink discharged from each ink jet recording head 4 and subjected to a concentration process. In the inkjet printer 1 shown in FIG. 3, a pair of active energy ray irradiation units 5 </ b> Y is provided on the downstream side of each inkjet recording head 4 </ b> Y, 4 </ b> M, 4 </ b> C, 4 </ b> K. 5M, 5C, and 5K are arranged. In the line head type ink jet printer having such a configuration, the ink jet recording heads 4Y, 4M, 4C, and 4K for each color ink are arranged in an ink jet order that ejects ink containing a pigment having a high active energy ray shielding property. It is preferable to arrange the set of the recording head and the active energy ray irradiating unit on the more upstream side. With this configuration, the number of times the active energy ray is irradiated to the ink containing the pigment having a high active energy ray shielding property is increased. As a result, it is possible to concentrate to a desired concentration rate immediately before the irradiation unit 5 located on the most downstream side, and it is possible to firmly fix the recording medium by the light irradiation of the irradiation unit 5 located on the most downstream side. It becomes. Therefore, as shown in FIG. 3, the inkjet recording head 4K for black ink, the inkjet recording head 4C for cyan ink, the inkjet recording head 4M for magenta ink are arranged from the upstream side, and the inkjet recording head 4Y for yellow ink is arranged on the most downstream side. It is preferable. It is preferable that the viscosity when the inkjet ink adjusted to a desired concentration rate is irradiated with ultraviolet rays of 200 mJ / cm ² is 200 mPa · s or more. Thereby, the fixability to the recording medium is further improved.

  1 and 3 show an example in which a flat panel heater is used as the concentrating means, but other concentrating means include a method of heating the back surface of the recording medium using a heating roller, on the recording medium. A method of drying and concentrating by blowing warm air etc. on the ink droplets landed on the ink, a method of drying and concentrating the ink droplets landed on the recording medium by radiant heat of a heat source having a wavelength that does not cure the ink droplets, Examples thereof include a method for removing volatile components by a reduced pressure treatment, a method for drying and concentrating with an electromagnetic wave such as microwave drying, and the like.

  FIG. 4 is a cross-sectional view illustrating an example of an ink jet printer including a line head type ink jet recording head and an ink concentration step.

  FIG. 4A is a cross-sectional view of an ink jet printer using the flat panel heater 3 described above. For example, the support roller 7 and the transport roller 6 transport the recording medium P while niping it. In this method, the back surface of the recording medium P being conveyed is heated by the flat panel heater 3. In FIG. 4a), the position landed on the recording medium P from the ink jet recording head 4M is the image recording process unit, and the active energy ray irradiation unit 5M and the active energy beam irradiation unit 5M The concentration process zone L is between the curing process and the irradiation process.

  FIG. 4 b) shows a method of heating the recording medium P using a heating roller 8 instead of a flat panel heater. The heating roller 8 and the conveying roller 6 are opposed to each other on the upstream side of the ink jet recording head. In this method, the recording medium P is nipped by these two rollers and conveyed while being heated.

  FIG. 4 c) shows an example of a configuration in which the ink concentration means 9 that has landed on the surface of the recording medium is provided between each inkjet recording head 4 and the active energy ray irradiation unit 5. The ink is landed on the recording medium P from the ink jet recording head 4M, and immediately after that, a method of concentrating the ink by blowing dry air adjusted in temperature and humidity from the ink concentrating means 9M, or a heat source that generates radiant heat. It is a method of obtaining a desired concentration ratio in the concentration step zone L by a method of concentrating ink by scattering volatile components in the ink by radiant heat.

  In the ink jet recording method of the present invention, when the ink is concentrated in the concentration step zone, the concentration rate is not particularly limited, but the efficiency in the curing step by irradiation with active energy rays to be performed thereafter and the concentration in a short time. In view of the effect of the concentration, when the ink volume when landing on the recording medium of the ink-jet ink is A, and the ink volume immediately before the irradiation with the active energy ray through the concentration process zone is B, the concentration ratio B / A is 0.8 or less, that is, it is preferable to volatilize or penetrate 20% or more of the volatile components of the ink in the concentration step, and more preferably, the concentration ratio B / A is 0.4 or more and 0.7. It is as follows. The concentration ratio defined above can be achieved by appropriately selecting the concentration means to be applied and its conditions (heating temperature, hot air temperature, etc., recording medium conveyance speed, etc.).

  In the present invention, in order to cure the ink, the active energy ray irradiated from the active energy ray irradiation unit includes, for example, an electron beam, an ultraviolet ray, an α ray, a β ray, a γ ray, an X ray, etc. Dangerous, easy to handle, and electron beams and ultraviolet rays that are widely used industrially are preferred. In particular, ultraviolet rays are preferably used in the present invention.

  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 recording medium or the like may be deteriorated.

  When ultraviolet rays are used, the light source is, for example, 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 having an operating pressure of several hundred Pa to 1 MPa. A conventionally well-known thing, such as LED, is used.

  The irradiation conditions of the active energy ray are not particularly limited as long as a desired concentration ratio can be achieved by the concentration step according to the present invention. It is preferable that the active energy ray is irradiated during 01 to 1.0 seconds, and more preferably 0.01 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.

In the inkjet recording method of the present invention, as a method for controlling the time from when an ink droplet has landed on a recording medium until the active energy ray is irradiated by the active energy ray irradiation light source, The present invention can be achieved by appropriately adjusting the distance between the nozzle of the ink jet recording head and the recording speed. The present invention may include a drying step after irradiation with active energy rays. The drying means provided after irradiation with active energy rays is not particularly limited, but the same method as used in the above-described concentration step can be applied.

(Inkjet printer member)
In the ink jet printer used in the ink jet recording method of the present invention, as a printer member to be used, in order to prevent irradiation of the head surface due to active reflection of an active energy ray, for example, ultraviolet rays, the transmittance or reflectivity for the active energy ray is Low ones are preferred.

  For the active energy ray irradiation unit, a method in which a shutter is mounted is preferable. For example, when ultraviolet rays are used, the ratio of illuminance when opening and closing the shutter is preferably shutter open / shutter close = 10 or more. 100 or more are more preferable, and 10,000 or more are still more preferable.

(Inkjet recording head)
In the inkjet recording method of the present invention, it is preferable to form an image by ejecting the inkjet ink according to the present invention onto a recording medium using a line head type inkjet recording head. The ink jet recording head used in the ink jet recording method of the present invention may be an on-demand system or a continuous system. As the discharge method, an electro-mechanical conversion method (for example, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), electro-thermal conversion method (for example, thermal ink jet) Specific examples include a mold, a bubble jet (registered trademark) type, an electrostatic attraction method (for example, an electric field control type, a slit jet type, etc.), and a discharge method (for example, a spark jet type). However, any discharge method may be used.

(Line-type inkjet recording head)
In the ink jet recording method of the present invention, it is preferable to use a line head type ink jet recording head which has a severe demand for clogging as a printing method. A line head type ink jet recording head is a long ink jet recording head having a width equal to or larger than the width of the recording medium. Even a long head having a large number of nozzles, a plurality of ink jet recording heads can be unitized and long. Even a scaled head can be preferably used. By using a line head type ink jet recording head, a carriage equipped with the ink jet recording head scans in a direction perpendicular to the direction in which the recording medium is transported in a shorter time than a serial head that forms an image. Many image recordings can be performed, and productivity is dramatically improved.

<Inkjet ink>
Next, the inkjet ink according to the present invention will be described.

  The inkjet ink according to the present invention includes at least a color material, a photoreactive resin, and water.

[Photoreactive resin]
As the photoreactive resin applicable to the inkjet ink according to the present invention, a polymerizable or crosslinkable compound that undergoes radical polymerization by active energy rays is preferable.

  The polymerizable compound that can be used in the present invention is preferably water-soluble, and has, for example, an acidic group and a (meth) acryloyl group or a vinyl group in the molecule. Examples thereof include esters with 2-hydroxyethyl (meth) acrylate, esters of orthophthalic anhydride and 2-hydroxyethyl (meth) acrylate, vinyl naphthalenesulfonic acid, and the like.

  As an industrially produced compound that is soluble in water and has two or more polymerizable functional groups in one molecule, a polymerizable compound imparted with hydrophilicity by a polyethylene oxide chain is known. Examples of such include (meth) acrylic acid esters of polyhydric alcohols such as diethylene glycol di (meth) acrylate and tetraethylene glycol di (meth) acrylate.

  In the present invention, as a photoreactive resin, a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays (hereinafter referred to as active energy ray cross-linking). It is particularly preferable to use an organic polymer).

  Hereinafter, the active energy ray crosslinkable polymer will be described.

  Examples of the polymer compound having a plurality of side chains in the hydrophilic main chain according to the present invention and capable of crosslinking between the side chains by irradiating active energy rays include, for example, saponified 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 selected from the group consisting of these copolymers In the hydrophilic resin, 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.

  The side chain is preferably nonionic, anionic, or amphoteric (betaine compound), and particularly when combined with an anionic pigment as a colorant, it is preferably nonionic or anionic from the viewpoint of ink storage stability. Preferably it is 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 saponification is preferably 77% or more and 99% or less. Further, the average degree of polymerization is preferably 200 or more and 4000 or less, more preferably 200 or more and 1800 or less from the viewpoint of handling, and the effect of the present invention can be more preferably exhibited at 200 or more and 500 or less. If the average degree of polymerization is 200 or more, the effect of thickening by drying is moderate, and the secondary color bleed when using a line head type ink jet recording head is good. Further, when the average degree of polymerization is 500 or less, the discharge stability after stopping the discharge for a certain time, that is, the so-called intermittent discharge stability is good. The average degree of polymerization can be calculated according to Japanese Industrial Standard K 6726.

  The addition amount of the active energy ray crosslinkable polymer according to the present invention is preferably 1% by mass or more and 10% by mass or less based on the total amount of the ink. If the addition amount is 1% by mass or more, the ink can be increased to a sufficient viscosity at the time of irradiation with active energy rays, good bleeding resistance can be obtained, and if the addition amount is 10% by mass or less, the ink jet recording head It is possible to adjust the ink viscosity to suit the suitability, and the speed drop of the first ink droplet immediately after the ejection is stopped for a certain time is small.

  The modification rate of the side chain with respect to the hydrophilic main chain is preferably 0.8 mol% or more and 5.0 mol% or less, and is preferably 1.0 mol% or more and 3.5 mol% or less. From the viewpoint of If it is 0.8 mol% or more, it has sufficient crosslinkability and good beading resistance, and if it is 5.0 mol% or less, the storage stability is good.

  In the present invention, since the ink can be concentrated in the ink concentration step according to the present invention, the type of the photoreactive resin and the active energy ray crosslinkable polymer are adjusted in accordance with the ink concentration rate at the time of active energy ray irradiation. It is possible to select the polymerization degree, main chain structure, side chain structure, addition amount and the like. For this reason, it became possible to achieve both good emission stability and sufficient curability after light irradiation.

  As the photodimerization-type modifying group, those in which a diazo group, a cinnamoyl group, a stilbazolium group, a stilquinolium group or the like is introduced are preferable. (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. It 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—, —CH ₂ —COO— or —O—, and Y represents an aromatic ring. Or a single bond and m represent the integer of 0-6.

  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.

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

  The water-soluble photopolymerization initiator to be applied is not particularly limited, but 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (HMPK) is particularly preferable from the viewpoint of mixing property and reaction efficiency. ), Thioxanthone ammonium salt (QTX), and benzophenone ammonium salt (ABQ) are preferable from the viewpoint of miscibility with an aqueous solvent.

  Furthermore, from the viewpoint of compatibility with the resin, 4- (2-hydroxyethoxy) phenyl- (2-hydroxy-2-propyl) ketone (n = 1, HMPK) represented by the following general formula (7), 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 and 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 water-soluble photopolymerization initiators, accelerators and the like can also be added. Examples of these include, for example, ethyl p-dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, ethanolamine, diethanolamine, and triethanolamine.

  These water-soluble photopolymerization initiators are preferable even if they are grafted to the side chain with respect to the hydrophilic main chain.

  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 the side chains by irradiating active energy rays is the main chain side having a certain degree of polymerization. Since cross-linking is performed between the chains via a cross-linking bond, the effect of increasing the molecular weight per photon is significantly greater than that of an ultraviolet ray curable resin that is polymerized via a general chain reaction. As a result, a very high curing sensitivity was realized.

  In the active energy ray crosslinkable polymer used in 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. It is.

[Color material]
As the coloring material used in the ink jet ink according to the present invention, various dyes or pigments known in ink jetting can be used.

(dye)
There is no restriction | limiting in particular as dye which can be used by this invention, Water-soluble dyes, such as an acid dye, a direct dye, and a reactive dye, a disperse dye, etc. are mentioned, It is an anionic dye.

<Water-soluble dye>
Examples of the anionic water-soluble dye that can be used in the present invention include azo dyes, methine dyes, azomethine dyes, xanthene dyes, quinone dyes, phthalocyanine dyes, triphenylmethane dyes, diphenylmethane dyes, and the like. The specific compound is shown below. However, it is not limited to these exemplified compounds.

<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, 357, 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. 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.

(Pigment)
As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used, and anionic pigments are preferred. 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.

  In the ink according to the present invention, an anionic self-dispersing pigment is preferably used. The anion-modified self-dispersing pigment preferably used in the present invention refers to a pigment having an anionic group on the surface and capable of being dispersed without a dispersant. An anionic self-dispersing pigment refers to a pigment in which an acidic group is modified and neutralized with a basic compound, thereby making the anionic group dispersible in water without a dispersant.

  The pigment particle having an acidic group on the surface means a pigment directly modified with an acidic group on the surface of the pigment particle, or an organic substance having an organic pigment mother nucleus and having an acidic group bonded directly or through a joint. .

  Examples of the acidic group (also referred to as polar group) include a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a boric acid group, and a hydroxyl group, preferably a sulfonic acid group and a carboxylic acid group, and more preferably a carboxylic acid group. It is an acid group.

  Acid group modifiers include sulfuric acid, fuming sulfuric acid, sulfur trioxide, chlorosulfuric acid, fluorosulfuric acid, amidosulfuric acid, sulfonated pyridine salt, sulfamic acid and other treatments containing sulfur atoms, and the pigment particle surface is oxidized. Carboxylating agents such as sodium hypochlorite and potassium hypochlorite that introduce carboxylic acid groups can be mentioned. Among them, a sulfonating agent such as sulfur trioxide, sulfonated pyridine salt or sulfamic acid, or a carboxylating agent is preferable. Examples of basic compounds that neutralize acidic groups include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amines such as ammonia, alkylamines, and alkanolamines. In the present invention, amines are used. Is particularly preferred.

  Examples of a method for obtaining pigment particles having a polar group on the surface include, for example, WO97 / 48769 pamphlet, JP-A-10-110129, JP-A-11-246807, JP-A-11-57458, and 11-189739. In other words, the surface of the pigment particles described in JP-A-11, JP-A-11-323232, JP-A-2000-265094, etc. is oxidized with an appropriate oxidizing agent, so that at least a part of the pigment surface has a sulfonic acid group or a salt thereof. The method of introduce | transducing such polar groups is mentioned. Specifically, it is prepared by oxidizing carbon black with concentrated nitric acid, or in the case of color pigments by oxidizing with sulfamic acid, sulfonated pyridine salt, amide sulfuric acid, etc. in sulfolane or N-methyl-2-pyrrolidone. can do. In these reactions, the pigment dispersion can be obtained by removing and purifying the substance that has been excessively oxidized and becomes water-soluble. Moreover, when a sulfonic acid group is introduced onto the surface by oxidation, the acidic group may be neutralized with a basic compound as necessary.

  Other methods include a method of adsorbing the pigment derivatives described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. on the surface of pigment particles by a treatment such as milling, and the like. Examples include a method of dissolving the pigment described in 2002-179777, 2002-201401 and the like together with a pigment derivative in a solvent and then crystallization in a poor solvent. Pigment particles having a polar group can be obtained.

  In the present invention, the polar group may be free or in a salt state, or may have a counter salt. Examples of the counter salt include inorganic salts (eg, lithium, sodium, potassium, magnesium, calcium, aluminum, nickel, ammonium) and organic salts (eg, triethylammonium, diethylammonium, pyridinium, triethanolammonium, etc.). A counter salt having a monovalent valence is preferable.

  The average particle diameter 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. If 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.

  The content of the colorant that can be dispersed or dissolved in water used in the inkjet ink according to the present invention is preferably 1 to 10% by mass relative to the total mass of the ink.

[Dispersant]
As the water-soluble polymer dispersant for stably dispersing the pigment in the ink, the following water-soluble resin can be used, which is preferable from the viewpoint of ejection stability.

  As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer are preferably used. Styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer It is a water-soluble resin such as.

  The content of the water-soluble resin with respect to the total amount of the ink is preferably 0.1 to 10% by mass, and more preferably 0.3 to 5% by mass.

  Two or more of these water-soluble resins can be used in combination.

(Water-soluble solvent)
As the solvent applicable to the ink according to the present invention, an aqueous liquid medium is preferably used, and as the aqueous liquid medium, a mixed solvent such as water and a water-soluble organic solvent is more preferably used. Examples of water-soluble organic solvents that are preferably used include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol). , Triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (eg, ethylene glycol monomethyl ether) , Ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol Monomethyl ether, diethylene glycol monoethyl 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 monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylene) Tolamine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), 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, etc.), sulfoxides (for example, dimethyl sulfoxide, etc.) and the like.

[Surfactant]
Surfactants preferably used in the ink according to the present invention include alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, polyoxyalkylene alkyl ether phosphates, Anionic surfactants such as fatty acid salts, nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyalkylene alkyl phenyl ethers, acetylene glycols, polyoxyethylene-polyoxypropylene block copolymers, glycerin esters, Activators such as sorbitan esters, polyoxyethylene fatty acid amides, amine oxides, cationic surfactants such as alkylamine salts and quaternary ammonium salts, silicone surfactants, fluorosurfactants And the like. These surfactants can also be used as pigment dispersants, and anionic surfactants can be particularly preferably used.

[Various additives]
The ink according to the present invention may contain other conventionally known additives. For example, fluorescent brighteners, antifoaming agents, lubricants, preservatives, thickeners, antistatic agents, matting agents, water-soluble polyvalent metal salts, acid bases, pH adjusters such as buffers, antioxidants, surfaces These are tension adjusters, specific resistance adjusters, rust inhibitors, inorganic pigments 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 viscosity modifier, specific resistance modifier, film forming agent, ultraviolet absorber, antioxidant, fading inhibitor, antifungal agent, rust inhibitor, 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, JP-A-57-87988, and JP-A-62-261476, 57-74192, 57-87989, 60-72785, 61-146591, JP-A-1-95091 and 3-13376, etc. Anti-fading agents, fluorescent whitening agents described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871, and JP-A-4-219266. be able to.

[Inkjet ink set]
In the ink jet recording method of the present invention, it is preferable to record an image using an ink jet ink set composed of two or more kinds of inks having different color materials. At that time, at least one kind of each color ink constituting the ink jet ink set is The inkjet ink containing at least the coloring material, photoreactive resin, and water according to the present invention described above is preferable, and particularly preferably, all the inks constituting the inkjet ink set include at least the colors according to the present invention. An ink-jet ink containing a material, a photoreactive resin, and water.

"recoding media"
As a recording medium that can be applied in the ink jet recording method of the present invention using the ink jet ink according to the present invention, an absorbent support such as plain paper or fine paper, or a low absorbent recording medium such as art paper or coated paper, or A non-absorbing medium such as a film and an ink jet recording medium can be widely used. However, in the ink jet recording method of the present invention, a low-absorbing recording medium or a non-absorbing recording medium is used as one combination. It is preferable to apply the concentration means according to the invention from the viewpoint that the effects of the present invention can be exhibited.

  On the other hand, in the ink jet recording method of the present invention, an ink absorbing recording medium is also expected to have a concentration effect due to ink absorption into the recording medium. The amount and type of the photoreactive resin can be changed in accordance with the ink absorbing ability of the recording medium to be used, and suitability for the recording medium can be imparted.

  The ink concentration rate corresponding to the recording medium type can be estimated as follows.

  The amount of absorption in the recording medium that occurs in the time from the ink landing on the recording medium to the irradiation of the active energy ray is determined by the Bristow method or the like. The Bristow method is a method for measuring the liquid absorption behavior on paper or a slightly absorbent recording medium in a short time. By this method, the amount of ink dried and the amount of ink dried in the time from ink landing to irradiation are obtained.

The amount of ink dried can be determined according to the following method. For example, when a solid image having an arbitrary resolution and area is printed from an inkjet recording head, the dry amount of ink is the mass of the recording medium before printing (g / m ² ) + the amount of ink applied (g / m ² ). It can be calculated by the mass (g / m ² ) of the recording medium containing the image after printing. As a method for measuring the ink ejection amount (g / m ² ), ink droplets are ejected from an ink jet recording head in an environment of 25 ° C. and 80% RH, and the ink mass (g) per dot is obtained. The amount of ink dried (g / m ² ) can be determined from the image area and resolution. The dry amount (g / m ² ) of the ink can be converted into (ml / m ² ) by the method described in JIS K0061. Ink concentration rate (%) = (Absorption amount to recording medium (ml / m ² ) + Ink dry amount (ml / m ² )) / Ink placement amount (ml / m ² ) Can do. The ink concentration rate is preferably 20% or more and 80% or less. If it is 20% or more, nozzle clogging at the time of ejection is very good. If it is 20% or more, the abrasion resistance of the formed image is good. If it is 80% or less, the effect of the thickening by active energy ray irradiation will fully be acquired.

The paper, coated paper, there is a non-coated paper, as the coated paper, the coating amount per 1m ² is one side 20g before and after of art paper, 1m ² per coated amount on one side 10g before and after the coated paper Examples include a light coated paper having a coating amount per 1 m ^{2 of} about 5 g on one side, a fine coated paper, a mat coated paper with a matte finish, a dull coated paper with a dull finish, and a newspaper. 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. More details are described in detail in “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, Uto + 9 Lilo 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 NIP (above, made by Daio Paper), Sun Ring, Moon Ring, Unzen, Galaxy, Baiyun, Weiss, Moon Ring Ace, Baiyun Ace, Unzen Ace (above, Nippon Paper Industries), Taiou, Bright Foam, 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 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, Chi Such as Jerry IV Super (manufactured by Marusumi Paper), SHF (manufactured by Toyo Pulp), and TRP (manufactured by Tokai Pulp).

  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.

  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.

  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.

Example 1
《Synthesis of active energy ray crosslinkable polymer compound》
(Synthesis of active energy ray crosslinkable polymer compound 1)
Active energy ray crosslinkable polymer compound 1 was synthesized by the following method.

  Glycidyl methacrylate (58 g), p-hydroxybenzaldehyde (42 g), pyridine (3 g), and N-nitroso-phenylhydroxyamine ammonium salt (1 g) were placed in a reaction vessel and stirred in a water bath at 80 degrees for 8 hours.

  Subsequently, 45 g of polyvinyl acetate saponified product having an average degree of polymerization of 330 and a saponification rate of 98% was dispersed in 225 g of ion-exchanged water, and then 4.5 g of phosphoric acid was added to this solution and p- (3- Methacryloxy-2-hydroxypropyloxy) benzaldehyde was added so that the modification rate was 3.0 mol% with respect to polyvinyl alcohol, 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 2 hours. Thereafter, the ion exchange resin was filtered, and Irgacure 2959 (manufactured by Ciba Specialty Chemicals) as a photopolymerization initiator was mixed at a rate of 0.5 g with respect to 100 g of a 15% aqueous solution, and then diluted with ion exchange water. As a result, an aqueous solution of 10% active energy ray-crosslinkable polymer compound 1 was obtained.

<Preparation of ink set>
Ink sets 1 to 3 were prepared according to the following method.

(Preparation of pigment dispersion)
<Preparation of magenta pigment dispersion>
The following additives were mixed and dispersed using a sand grinder filled with 50% by volume of 0.6 mm zirconia beads to prepare a magenta pigment dispersion having a magenta pigment content of 15%. The average particle diameter of the magenta pigment particles contained in this magenta pigment dispersion was 120 nm. The particle size was measured with a Zetasizer 1000HS manufactured by Malvern.

C. I Pigment Red 122 15 parts Jonkrill 61 (styrene acrylic resin dispersant, manufactured by Johnson, solid content 30%) 10 parts Glycerin 15 parts Ion-exchanged water 67 parts <Preparation of black pigment dispersion>
Carbon black self-dispersion cabojet 300 manufactured by Cabot was diluted with ion-exchanged water to prepare a black pigment dispersion having a carbon black content of 15%. The average particle size of the carbon black particles contained in this black pigment dispersion was 130 nm. The particle size was measured with a Zetasizer 1000HS manufactured by Malvern.

<Preparation of yellow pigment dispersion>
The following additives were mixed and dispersed using a sand grinder filled with 0.6 mm zirconia beads at a volume ratio of 50% to prepare a yellow pigment dispersion having a yellow pigment content of 15%. The average particle size of the magenta pigment particles contained in this yellow pigment dispersion was 110 nm. The particle size was measured with a Zetasizer 1000HS manufactured by Malvern.

C. I Pigment Yellow 74 15 parts Jonkrill 61 (styrene acrylic resin dispersant, manufactured by Johnson, solid content 30%) 10 parts Glycerin 15 parts Ion-exchanged water 67 parts <Preparation of cyan pigment dispersion>
The following additives were mixed and dispersed using a sand grinder filled with 50% by volume of 0.6 mm zirconia beads to prepare a cyan pigment dispersion having a cyan pigment content of 15%. The average particle diameter of the cyan pigment particles contained in this cyan pigment dispersion was 130 nm. The particle size was measured with a Zetasizer 1000HS manufactured by Malvern.

C. I Pigment Blue 15 15 parts Jonkrill 61 (styrene acrylic resin dispersant, Johnson, solid content 30%) 10 parts Glycerin 15 parts Ion-exchanged water 67 parts (Preparation of ink set 1)
<Preparation of magenta pigment ink 1>
Magenta pigment dispersion (solid content 15%) 20 parts Active energy ray crosslinkable polymer compound 1 aqueous solution (solid content 10%) 23 parts Propylene glycol 30 parts Ethylene glycol 10 parts Olphine E1010 (manufactured by Nissin Chemical) 1 part Prevention Glaze: Proxel GXL (manufactured by Avicia) 0.3 part Ion exchange water was added to finish to 100 parts.

<Preparation of Black Pigment Ink 1>
A black pigment ink 1 was obtained in the same manner as in the preparation of the magenta pigment ink 1 except that a black pigment dispersion was used instead of the magenta pigment dispersion.

<Preparation of yellow pigment ink 1>
A yellow pigment ink 1 was obtained in the same manner as in the preparation of the magenta pigment ink 1 except that a yellow pigment dispersion was used instead of the magenta pigment dispersion.

<Preparation of cyan pigment ink 1>
Cyan pigment ink 1 was obtained in the same manner as in the preparation of magenta pigment ink 1 except that a cyan pigment dispersion was used instead of the magenta pigment dispersion.

  The prepared magenta pigment ink 1, black pigment ink 1, yellow pigment ink 1, and cyan pigment ink 1 were used as an ink set 1.

(Preparation of ink set 2)
<Preparation of magenta pigment ink 2>
Magenta pigment dispersion (solid content 15%) 20 parts Aqueous UV curable urethane acrylate resin emulsion (solid content 40%, manufactured by Taisei Kako Co., Ltd., trade name: WBR-839) 20 parts 2-pyrrolidinone 15 parts Ethylene glycol 10 parts Orphin E1010 (manufactured by Nissin Chemical Co., Ltd.) 1 part Antifungal agent: Proxel GXL (manufactured by Abyssia) 0.3 part Ion exchange water was added to finish to 100 parts.

<Preparation of black pigment ink 2>
A black pigment ink 2 was obtained in the same manner as in the preparation of the magenta pigment ink 2 except that a black pigment dispersion was used instead of the magenta pigment dispersion.

<Preparation of yellow pigment ink 2>
A yellow pigment ink 2 was obtained in the same manner as in the preparation of the magenta pigment ink 2 except that a yellow pigment dispersion was used instead of the magenta pigment dispersion.

<Preparation of Cyan Pigment Ink 2>
Cyan pigment ink 2 was obtained in the same manner as in the preparation of magenta pigment ink 2 except that a cyan pigment dispersion was used instead of the magenta pigment dispersion.

  The prepared magenta pigment ink 2, black pigment ink 2, yellow pigment ink 2, and cyan pigment ink 2 were used as an ink set 2.

(Preparation of ink set 3)
In the preparation of the magenta pigment ink 1, black pigment ink 1, yellow pigment ink 1, and cyan pigment ink 1 of the ink set 1, the addition amount of the 10% active energy ray-crosslinking polymer compound 1 aqueous solution was changed to 40 parts. Except for the above, magenta pigment ink 3, black pigment ink 3, yellow pigment ink 3, and cyan pigment ink 3 were prepared.

<Recording images>
[Image recording method 1]
Each recording medium was heated to 60 ° C. using a line head type ink jet recording apparatus (concentration means: flat panel heater) having the configuration shown in FIG. The ink jet recording head 4 shown in FIG. 1 has a piezo type having a nozzle diameter of 25 μm, a driving frequency of 20 kHz, a nozzle number of 512, a minimum liquid amount of 12 pl, and a nozzle density of 180 dpi (dpi represents the number of dots per 2.54 cm). The line head type ink jet recording heads were formed by arranging the ink jet recording heads so as to cover the print width perpendicular to the paper conveyance direction. The active energy ray irradiation light source 5 shown in FIG. 1 is composed of a 160 W / cm metal halide lamp (manufactured by Nippon Battery Co., Ltd., MAN200 (N) L) to constitute a line head type active energy ray irradiation means. In this manner, a line head type ink jet recording apparatus having a maximum recording density of 720 × 720 dpi was manufactured.

  The ink set 1 is mounted on each inkjet recording head shown in FIG. 1 in the order of black pigment ink, cyan pigment ink, magenta pigment ink, and yellow pigment ink from the upstream side, and in one pass, a polyethylene terephthalate (PET) film A recorded image was created on top and irradiated from an active energy ray irradiation light source.

[Image recording methods 2 to 8]
In accordance with the conditions described in Table 1, each type of image is recorded using image recording methods 2 to 8 by changing the type of ink set, the type of recording medium, whether the recording medium is heated, the type of ink jet recording apparatus, and the number of passes. Created.

  In the image forming method 3, the apparatus shown in FIG. 1 was used, and the recording medium was not heated by a flat panel heater. In image forming method 3, 1 dot shown in FIG. 2 was printed in the first pass, 2 dots in the second pass, 3 dots in the third pass, 4 dots in the fourth pass, and 4 passes. In image forming method 4, 1 and 2 dots shown in FIG. 2 were printed in the first pass, and 3 and 4 dots were printed in the second pass.

  In the recording media shown in Table 1, the PET film is a non-absorbent recording medium, and the POD gloss coat (Oji Paper, product name: POD gloss coat 128, low-absorbent coated paper) is a low-absorbency recording medium. Plain paper (A4 size First Class paper manufactured by Konica Minolta Business Technologies) is an absorbent recording medium.

[Measurement of ink concentration rate]
In each of the image recording methods 1 to 4 and 6 to 8, the cyan ink is concentrated from immediately after landing the cyan ink mounted second from the upstream to the last active energy ray irradiating unit that irradiates cyan in the image forming process. The rate was measured by the following formula according to the method described above.

When using non-absorbent recording media,
Ink concentration ratio = (mass of recording medium before printing (g / m ² ) + ink ejection amount (g / m ² ) −mass of recording medium including image after printing (g / m ² )) / ink ejection amount (G / m ² )
In addition, when an absorbent recording medium is used,
Ink concentration ratio = (Absorption amount to recording medium (ml / m ² ) + Ink dry amount (ml / m ² )) / Ink placement amount (ml / m ² )
<< Evaluation of output stability and formed image >>
[Evaluation of output stability 1]
Using the inkjet recording head described in each image recording method, each inkjet ink was subjected to an intermittent operation of 30 seconds of continuous discharge → 2 seconds of rest → continuous discharge. At this time, the emission stability 1 was evaluated based on the following criteria by measuring the drop rate of the droplet velocity before and after ejection stepwise.

◎: Speed reduction rate is less than 20% ○: Speed reduction rate is 20% or more and less than 40% △: Speed reduction rate is 40% or more and less than 60% ×: Speed reduction rate is 60% or more, 80 Less than% XX: Speed reduction rate is 80% or more [Evaluation of Outgoing Stability 2]
Using the inkjet recording head described in each image recording method for each inkjet ink, an intermittent operation of 30 seconds of continuous discharge (100 nozzles) → 30 seconds of pause → continuous discharge was performed. At this time, before and after the discharge pause, the nozzle clogging of intermittent discharge is measured by stepwise evaluating the occurrence rate of defective nozzles such as initial disturbance in the discharge direction, decrease in discharge speed, and missing nozzles. Was evaluated as emission stability 2.

◎: No defective nozzle ○: The defective nozzle rate is 1% or more and less than 20% △: The defective nozzle rate is 20% or more and less than 50% ×: The defective nozzle rate is 50% or more, 80% Xx: defective nozzle rate is 80% or more [Evaluation of Feathering Resistance]
With the image recording method 6 described above, a thin line having a width of 200 μm was printed on plain paper (First Class paper manufactured by Konica Minolta Business Technologies) using cyan ink. The obtained thin line image was visually observed for the presence or absence of bleeding, and the feathering resistance was evaluated according to the following criteria.

◎: Fine lines can be clearly confirmed ○: Slight blurring is confirmed, but the effect on the fine line image is small △: Slight blurring is observed, but it is within a practically acceptable range ×: Smudge is seriously generated , Practical quality is unacceptable. XX: Severe blurring, unclear border of fine lines, unusable for practical use [Evaluation of secondary color bleed resistance]
In accordance with each of the above image recording methods (excluding image recording method 6), the printing point is changed on each recording medium on a red solid image created using a 20 cm × 20 cm magenta pigment ink and a yellow pigment ink. Thus, an image pattern in which blue characters were arranged using magenta pigment ink and cyan pigment ink was output. The formed image was visually observed for color mixing, and the color bleed resistance of the secondary color was evaluated according to the following criteria.

◎: No color mixing at all ○: Color mixing is a little, but 7-point characters can be confirmed △: Color mixing is slightly, but 9-point characters can be confirmed, and is in a practically acceptable range ×: Color Mixing was severe and only 12-point characters could be confirmed. XX: Color mixing was quite severe and even 12-point characters could not be confirmed. [Evaluation of gradation]
According to each image recording method described above (excluding image recording method 6), an S7 color vignette image of JIS X 9204: 2004 high-definition color digital standard image (XYZ / SCID) was output on each recording medium. The continuity of gradations of red, green, and blue formed with secondary colors was visually observed, and the gradation of the image was evaluated according to the following criteria.

A: Gradation is very good. B: Gradation is good. B: Gradation is slightly good, but is in a practically acceptable range. Table 1 shows the results obtained as described above.

  As apparent from the results shown in Table 1, the image recording method of the present invention in which the ink is concentrated by permeation into the drying means or the recording medium defined in the present invention is superior to the comparative example in terms of emission stability, Excellent feathering resistance when using paper, and when using a low-absorbency recording medium or non-absorbing recording medium, it is understood that the secondary color color bleed resistance of the formed image is excellent. .

Example 2
In the image recording methods 1 to 3 described in Example 1, the heating / concentration means is the same except that the configuration described in b) and c) illustrated in FIG. 4 is used instead of the configuration illustrated in FIG. As a result of image formation and evaluation, as in Table 1, it was confirmed that all of the image recording methods of the present invention provided good results.

It is a top view which shows an example of the inkjet printer provided with the inkjet recording head of a line head system, and the ink concentration process. It is a schematic diagram showing an example of each dot arrangement when performing image formation with a plurality of passes. It is a top view which shows another example of the inkjet printer provided with the inkjet recording head of a line head system, and the ink concentration process. It is sectional drawing which shows an example of the inkjet printer provided with the inkjet recording head of a line head system, and the ink concentration process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet printer 2 Platen 3 Flat panel heater 4, 4Y, 4M, 4C, 4K Inkjet recording head 5, 5Y, 5M, 5C, 5K Active energy ray irradiation part 6 Conveyance roller 7 Support roller 8 Heating roller 9, 9Y, 9M, 9C, 9K Ink concentration means P Recording medium

Claims (14)

In an inkjet recording method for recording an inkjet ink from an inkjet recording head to record on a recording medium, the inkjet ink contains at least a coloring material, a photoreactive resin, and water, and after ejecting the inkjet ink to a recording medium, An ink jet recording method comprising: concentrating a volatile component contained in the ink jet ink by permeation into a drying means or a recording medium before the step of irradiating active energy rays. The concentration ratio B / A is 0.8 or less, where A is the ink volume when the ink jet ink is landed on the recording medium and B is the ink volume immediately before irradiation with the active energy ray. The inkjet recording method according to claim 1. The inkjet recording method according to claim 1, wherein the inkjet recording head is a line head type. The drying means is a means for heating the recording medium with a heat roller, a means for heating the recording medium with a flat panel heater, a means for drying the ink-jet ink using hot air, and a means for heating the ink-jet ink using a heat source. The ink jet recording method according to claim 1, wherein the ink jet recording method is at least one selected from means for drying. A step of concentrating the ink-jet ink from the time when the first dot of the ink jet is landed on the recording medium from the ink-jet recording head to the time when the dot is landed at a position adjacent to the first shot. The inkjet recording method according to claim 1, wherein: The inkjet recording method according to claim 1, wherein the inkjet ink contains a water-soluble photopolymerization initiator. The inkjet recording according to any one of claims 1 to 6, wherein the image recording is performed using an inkjet ink set including two or more types of inks having different color materials and including at least one of the inkjet inks. Method. 8. The inkjet recording according to claim 7, wherein at least one of the inkjet inks included in the inkjet ink set has the lowest active energy ray transmittance among the inkjet inks included in the inkjet ink set. Method. The ink jet recording method according to claim 1, wherein the image forming method is performed twice or more and eight times or less. The inkjet recording method according to claim 1, wherein the recording medium is a low-absorbency recording medium or a non-absorbent recording medium. The inkjet recording method according to claim 1, wherein the recording medium is plain paper. The photoreactive resin contained in the inkjet ink has a plurality of side chains with respect to the hydrophilic main chain, and is a polymer compound that can be cross-linked between side chains by irradiating active energy rays. The inkjet recording method according to claim 1, wherein: The inkjet according to claim 12, wherein the polymer compound is a saponified product having a hydrophilic main chain of polyvinyl acetate, a saponification degree of 77 to 99%, and a polymerization degree of 200 to 500. Recording method. The inkjet recording method according to claim 12 or 13, wherein a modification rate of the side chain with respect to the hydrophilic main chain of the polymer compound is 0.8 mol% or more and 5 mol% or less.

Images