JP2007144682A - Ink for inkjet and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet which exhibits enough curing properties by irradiating with a low energy active energy beam after inkjet recording, has a high resolution of an image formed, has good gloss, and exhibits less bleeding between colors, and to provide an inkjet recording method using it. <P>SOLUTION: A method for recording the ink for inkjet which comprises water and at least a polymer compound having a plurality of side chains on a hydrophilic main chain and is crosslinkable between the side chains by irradiating with an active energy beam, is provided. After at least three color inks 3a are delivered on a recording medium 2 to be printed, it is irradiated with the active energy beam. In an inkjet recording method in which after at least three color inks are delivered on an intermediate transferring medium, and the inks existing in an image-like manner on the intermediate transferring medium are transferred on the recording medium to be printed, they are irradiated with the active energy beam, a first color and a second color injected ink colors are black color, cyan color or blue color. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet ink containing an active energy ray reactive compound and an ink jet recording method using the same.

  As for the active energy ray-curable ink jet ink, the ink jet recording method and the apparatus, conventionally, many disclosures have been made on the ejected image forming technique using three or more colors of ink.

  When three or more colors of ink are used, as a matter of course, an ink image in which multiple colors are overlapped is formed. However, for the curability of this overlapping portion, conventionally, active energy rays (ultraviolet rays, electron beams, and other high colors) are used. Energy beam irradiation) has been supported with high output, but the curability is insufficient, high resolution is difficult to obtain, physical and chemical resistance is insufficient, and bleeding between colors There are problems such as being likely to occur and difficult to obtain high quality images. In addition, when a high-power active energy line is used, there are problems such as an increase in power consumption and device cost.

  In view of the above, in recent years, there has been a market for ink image formation that has sufficient curability by irradiating active energy rays with low energy onto images ejected using inks of three or more colors, and at the same time exhibits high resolution. It is requested from.

  In response to such a demand, for example, water-based ultraviolet curable ink-jet ink is used to print on a recording material that does not absorb ink, and then is irradiated with ultraviolet rays, an ink-jet recording method using the same, and ink-jet recording A recording apparatus is disclosed, and for ink color ejection and ultraviolet irradiation, for example, yellow, magenta, cyan, and black are ejected in this order, and ultraviolet irradiation is performed after each color ejection (Patent Document 1). .

  However, this method requires high exposure energy to collectively cure ultraviolet rays after the injection of multicolor inks such as three colors or four colors, and in addition, there are problems such as high power consumption, recording speed, and apparatus cost. There was a point.

  Also disclosed is an inkjet ink and an inkjet recording apparatus which are irradiated with ultraviolet rays after printing on plain paper and various printing papers using ultraviolet curable heat-meltable inkjet ink made of wax or the like (see Patent Document 2). An inkjet recording method and an inkjet recording apparatus are disclosed in which an ultraviolet curable ink is used to cure an ultraviolet ray on an intermediate transfer medium to produce a primary image and then transferred to a recording medium to produce a secondary image. However, in these techniques, even when high energy is applied during ink image formation, problems such as scratch resistance, solvent resistance (water resistance, alcohol resistance), resolution, bleeding between colors, and the like. The solution was insufficient.

In addition, since these proposed active energy ray reactive inks are cured by a curing component, it is possible to record on a non-absorbent recording medium. This results in an unnatural and uncomfortable image quality due to the difference in glossiness from the white background portion, and as a result, the image uniformity is impaired. Furthermore, it has been found that some of the images formed with these proposed active energy ray reactive inks cause a reduction in image water resistance and color bleeding, and an immediate improvement is required.
JP-A-8-2180817 JP-A-6-200204 Japanese Patent Laid-Open No. 10-250052

  The present invention has been made in view of the above problems, and an object of the present invention is to exhibit sufficient curability by irradiation with low energy active energy rays after inkjet recording, and the resolution of the formed image is high and the gloss is good. In addition, the present invention provides an ink-jet ink having less bleeding between colors and an ink-jet recording method using the same.

  The above object of the present invention can be achieved by the following constitution.

1. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
After ejecting at least three colors of ink onto the printing medium, irradiate with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium, print the ink present on the intermediate transfer medium like an image In the inkjet recording method of irradiating active energy rays after being transferred to a medium,
An inkjet recording method, wherein the first and second ejection ink colors are black, cyan, or blue.

2. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
After ejecting at least three colors of ink onto the printing medium, irradiate with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium, print the ink present on the intermediate transfer medium like an image In the inkjet recording method of irradiating active energy rays after being transferred to a medium,
2. An ink jet recording method, wherein the second and subsequent ejection ink colors are yellow, orange, red, magenta, green, or light ink.

3. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
After ejecting at least four colors of ink onto the printing medium, irradiate active energy rays, or after ejecting at least four colors of ink onto the intermediate transfer medium, cover the ink that exists like an image on the intermediate transfer medium. In the inkjet recording method of irradiating active energy rays after being transferred to a print medium,
An ink jet recording method, wherein the ejection ink colors are in the order of black, cyan, yellow, and magenta.

4). 4. The ink jet recording method according to any one of 1 to 3, wherein the amount of energy applied by the active energy ray is 400 mJ / cm ² or less.

5. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
In an ink jet recording method for ejecting at least three colors of ink onto an intermediate transfer medium, irradiating the intermediate transfer medium with active energy rays, and then transferring the ink to a print medium.
An ink jet recording method, wherein the first or second ejection ink color is yellow, orange, red, magenta, green, or light ink.

6). An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
In an ink jet recording method for ejecting at least three colors of ink onto an intermediate transfer medium, irradiating the intermediate transfer medium with active energy rays, and then transferring the ink to a print medium.
2. An ink jet recording method, wherein the second and subsequent colors are black, cyan, or blue.

7). An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
In an ink jet recording method for ejecting at least four colors of ink onto an intermediate transfer medium, irradiating active energy rays on the intermediate transfer medium, and then transferring the ink to a printing medium.
An ink jet recording method, wherein the ejection ink colors are in the order of magenta, yellow, cyan, and black.

8). The ink recording method according to any one of 5 to 7, wherein the amount of energy applied by the active energy ray is 400 mJ / cm ² or less.

9. After ejecting at least three colors of ink onto the printing medium and irradiating with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium and irradiating the formed ink image with active energy rays, In an inkjet ink used for inkjet recording to be transferred to a printing medium,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. An ink jet ink, wherein the concentration of the polymerization initiator contained in the ink ejected earlier is higher than the concentration of the polymerization initiator contained in the ink ejected later.

  An ink jet recording method comprising using the ink jet ink described in 10.9.

11. After ejecting at least three colors of ink onto the printing medium and irradiating with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium and irradiating the formed ink image with active energy rays, In an inkjet ink used for inkjet recording to be transferred to a printing medium,
The ink has water and a plurality of side chains in the hydrophilic main chain, and contains at least a polymer compound that can be cross-linked between the side chains by irradiating active energy rays. An ink jet ink, wherein the ratio of the crosslinkable polymer compound contained in the ink is higher than the ratio of the crosslinkable polymer compound contained in the ink ejected later.

  12. An ink jet recording method using the ink for ink jet recording according to 12.11.

13. After ejecting at least three colors of ink onto the printing medium and irradiating with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium and irradiating the formed ink image with active energy rays, In an inkjet ink used for inkjet recording to be transferred to a printing medium,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. The overlap of the absorption spectrum of the polymerization initiator contained in the previously ejected ink and the emission spectrum of the active energy ray is the overlap of the absorption spectrum of the polymerization initiator contained in the ink ejected later and the emission spectrum of the active energy ray. An ink-jet ink characterized by being larger.

  14. An ink jet recording method comprising using the ink jet ink described in 14.13.

15. Used in an ink jet recording method in which at least three colors of ink jet ink are ejected onto an intermediate transfer medium, an ink image formed on the intermediate transfer medium is transferred to a print medium, and then the transferred ink image is irradiated with active energy rays. Ink jet ink,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. An ink-jet ink, wherein the concentration of the polymerization initiator contained in the ink ejected earlier is lower than the concentration of the polymerization initiator contained in the ink ejected later.

  16. An inkjet recording method comprising using the inkjet ink described in 16.15.

17. Used in an ink jet recording method in which at least three colors of ink jet ink are ejected onto an intermediate transfer medium, an ink image formed on the intermediate transfer medium is transferred to a print medium, and then the transferred ink image is irradiated with active energy rays. Ink jet ink,
The ink has water and a plurality of side chains in the hydrophilic main chain, and contains at least a polymer compound that can be cross-linked between the side chains by irradiating active energy rays. An ink-jet ink, wherein the ratio of the crosslinkable polymer compound contained in the ink is lower than the ratio of the crosslinkable polymer compound contained in the ink ejected later.

  18. An ink jet recording method comprising using the ink jet ink described in 18.17.

19. Used in an ink jet recording method in which at least three colors of ink jet ink are ejected onto an intermediate transfer medium, an ink image formed on the intermediate transfer medium is transferred to a print medium, and then the transferred ink image is irradiated with active energy rays. Ink jet ink,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. The overlap of the absorption spectrum of the polymerization initiator contained in the previously ejected ink and the emission spectrum of the active energy ray is the overlap of the absorption spectrum of the polymerization initiator contained in the ink ejected later and the emission spectrum of the active energy ray. Ink-jet ink characterized by being smaller.

  20. An inkjet recording method comprising using the inkjet ink described in 20.19.

In the inkjet recording method according to any one of 21.1 to 8, 10, 12, 14, 16, 18, and 20,
The printing medium or the intermediate transfer body is transparent, and after the ejection ink image is applied on the printing medium or the intermediate transfer body, active energy rays are emitted from the opposite side of the side having the ejection ink image. Irradiating, an inkjet recording method.

  According to the present invention, ink jet ink that exhibits sufficient curability by irradiation with low energy active energy rays after ink jet recording, has high resolution of the formed image, good gloss, and little bleeding between colors. And the inkjet recording method using the same can be provided.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention is not limited to these.

  One form of the apparatus structure preferably used for the inkjet recording method of the present invention will be described with reference to FIGS.

  FIG. 1 is a schematic sectional view showing an example of the configuration of an apparatus for directly ejecting ink onto a printing medium (direct recording method) used in the present invention.

  In FIG. 1, an ink 3 a is ejected from an inkjet recording head 3 onto a printing recording medium 2 conveyed from the original winding roll 1, and an ink image 3 c on the printing recording medium 2 is obtained by an active energy ray irradiation device 5. The active energy ray is irradiated, dried, fixed on the printing recording medium 2, and taken up by the take-up roller 6.

  FIG. 2 shows an ink image formed on an intermediate transfer medium used in the present invention, irradiated with an active energy ray on the ink image on the intermediate transfer member, dried, and then transferred to the print medium (indirect). (Irradiation transfer recording method) FIG.

  In FIG. 2, first, ink 3 a is ejected from the inkjet recording head 3 onto the intermediate transfer roll 8, and an ink image 3 b is formed on the intermediate transfer roll 8. The ink image 3b is irradiated with an active energy ray from the active energy ray irradiating device 5, and after being dried, the ink image 3b is conveyed from the original winding roll 1 while being in close contact with the intermediate transfer roll 8 and the heating and pressing roll 7. An ink image 3c transferred and fixed on the recording medium 2 is formed and taken up on the take-up roll 6 together with the recording medium 2 to be printed.

  FIG. 3 shows an example of the configuration of an apparatus used in the present invention for forming an ink image on an intermediate transfer medium, transferring the image onto a printing medium, and curing the ink image by irradiation with active energy rays (indirect transfer method). It is a schematic sectional drawing which shows.

  In FIG. 3, first, ink 3 a is ejected from the inkjet recording head 3 onto the intermediate transfer roll 8, and an ink image 3 b is formed on the intermediate transfer roll 8.

  Next, the ink image 3b is transferred onto the printing recording medium 2 conveyed from the original winding roll 1 in a state where the ink image 3b is in close contact with the intermediate transfer roll 8 and the heat and pressure roll 7, and a fixed ink image 3c is formed. Next, the active energy ray is irradiated by the active energy ray irradiating device 5 to form a cured image, and then wound around the take-up roll 6.

  In the ink jet recording method of the present invention, a known recording apparatus described in JP-A Nos. 6-200204, 8-2118017 and 10-250052 can be modified and used.

  In the ink jet recording method of the present invention, when three or more colors of ink are used, as described in claims 1 to 3 and claims 5 to 7, a specific ink is used as the ink color to be ejected. The color injection order is set to a specific order, and as shown in claims 9 to 19, the concentration of the polymerization initiator contained in the ink, the ratio of the cross-linkable polymer compound in the ink, the polymerization initiator By adjusting the absorption spectrum and the emission spectrum of the active energy ray, an image in which bleeding between colors is sufficiently prevented can be obtained even by irradiation with a low energy active energy ray.

  In the present invention, the light-color ink refers to a low-density ink in an inkjet ink set composed of at least two same-color inks having different densities. The density ratio of the ink jet ink sets having different densities may be any value. However, in order to achieve smooth gradation reproduction, the ratio of the high density ink to the low density ink (color material density / high density of the low density ink) The color material density of the density ink is preferably between 0.1 and 1.0, more preferably between 0.2 and 0.5, and between 0.25 and 0.4. It is particularly preferred.

  The active energy ray according to the present invention will be described. The active energy ray according to the present invention is not particularly limited as long as it cures the active energy ray-curable ink-jet ink according to the present invention, and specifically includes ultraviolet rays (UV), electron beams, heat, and the like. .

  In ultraviolet irradiation, since heat is likely to be generated and the recording medium may be deformed, it is preferable that a cooling mechanism such as a cold mirror, a cold filter, and a workpiece cooling is provided. Moreover, as a kind of lamp | ramp used for ultraviolet irradiation, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a metal halide etc. are mentioned.

  The ultra-high pressure mercury lamp is a point light source, but the Deep UV type, which has high light utilization efficiency in combination with an optical system, can irradiate in a short wavelength region. Metal halide is effective for colored materials because of its wide wavelength range. Metal halides such as Pb, Sn, and Fe are used and can be selected according to the absorption spectrum of the photoinitiator. Any lamp that is effective for curing can be used without particular limitation.

From the viewpoint of preferably obtaining the effects described in the present invention, low-energy active energy ray irradiation is preferable. Specifically, the amount of energy imparted by active energy ray irradiation is preferably 400 mJ / cm ² or less, more preferably at most 300 mJ / cm ² or less, particularly preferably ^{50mJ / cm 2 ~300mJ / cm 2} .

  In the inkjet recording method of the present invention, the inkjet ink discharged onto the recording medium or the intermediate transfer medium is cured by irradiation with active energy rays, and then dried for the purpose of removing unnecessary water-soluble organic solvents and the like. .

  The ink drying means is not particularly limited, for example, a method for drying the recording medium or the intermediate transfer medium by contacting the back surface with a heating roller or a flat heater, or a means for blowing warm air on the printing surface with a dryer, Alternatively, a method of removing volatile components by a decompression process can be appropriately selected or combined.

  As the recording medium applicable in the ink jet recording method of the present invention, various papers, various films, various cloths, various woods, various ink jet recording media, and the like can be used. The recording medium is preferably a recording medium.

[Coated paper for printing]
Coated paper for printing is coated paper often used in printing. Generally, high-quality paper or medium-quality paper is used as the base paper, and after applying a pigment such as clay on the surface of the paper, smoothness is improved. Therefore, it is produced by applying a calendar process. Such processing improves whiteness, smoothness, print ink acceptability, halftone dot reproducibility, print gloss, print opacity, and the like. The paper is classified into art paper, coated paper, lightweight coated paper, etc., depending on the coating amount, and is classified into glossy, dull, matte, etc., depending on the gloss of the paper.

Art paper is coated paper having a coating amount of about 20 g / m ^{2 on} one side, and is generally prepared by applying a pigment to the paper surface and then applying a calendar treatment. There are special art, average art, matte (matte) art, single art (single side coating), double art (double side coating), and more specifically, OK Kanto N, Satin Kanto N, SA Kanou, Ultra Satin Kinto N, OK Ultra Aqua Satin, OK Kanto Single Side, N Art Post, NK Special Side Art, Thunderbird Super Art N, Thunderbird Super Art MN, Thunderbird Art N, Thunderbird Dull Art N, Hi McKinley Art, Hi McKinley Mat, High McKinley Pure Dull Art, Hi McKinley Super Dal, Hi McKinley Mat Elegance, Hi McKinley Deep Mat, etc.

The coated paper is a coated paper having a coating amount of about 10 g / m ^{2 on} one side, and is generally produced by processing with a coating apparatus provided in the middle of the paper machine. The coating amount is smaller than that of art paper, and the smoothness is slightly reduced, but the advantages are low cost and light weight. There is also a type of coated paper with a smaller coating amount, such as a light-weight coat and a finely coated paper. Specific examples of these coated papers include POD gloss coat, OK top coat +, OK top coat S, aurora coat, mu coat, mu white, thunderbird coat N, utrilo coat, pearl coat, white pearl coat, POD mat coat, New Age, New Age W, OK top coat mat N, OK royal coat, OK top coat dull, Z coat, Silver diamond, Ulite, Neptune, Mu mat, White mu mat, Thunderbird mat coat N, Utrilogros mat, New V mat, white new V mat, etc. are mentioned.

[Non-absorbent recording medium]
As the non-absorbable recording medium, all commonly used various 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.

  The ink-jet ink according to the present invention will be described. In the inkjet ink of the present invention (hereinafter, also simply referred to as ink), a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of being cross-linked between the side chains by irradiating with active energy rays (hereinafter referred to as an ink). And a crosslinkable polymer compound).

<Crosslinkable polymer compound>
An image formed by applying a crosslinkable polymer compound according to the present invention (hereinafter also referred to as a crosslinkable polymer compound) to the ink and exhibiting sufficient curability by irradiation with low energy active energy rays. Ink-jet ink with a high resolution, good gloss, and little bleeding between colors can be obtained.

  Next, the crosslinkable polymer compound according to the present invention will be described.

  The hydrophilic main chain of the crosslinkable polymer compound according to the present invention includes saponified polyvinyl acetate, polyvinyl acetal, polyethylene oxide, polyalkylene oxide, polyvinyl pyrrolidone, polyacrylamide, polyacrylic acid, hydroxyethyl cellulose, methyl cellulose, hydroxy And propyl cellulose.

  Among these, when the hydrophilic main chain is a saponified product of polyvinyl acetate, the introduction of the side chain is simplified and the handleability is improved. The degree of polymerization of the main chain is in the range of 200 or more and 2000 or less, but the degree of polymerization is particularly preferably 200 or more and 500 or less from the viewpoint of sufficiently achieving the object effect of the present invention. If the degree of polymerization is 200 or more, a moderate increase in viscosity during the crosslinking reaction can be imparted, and color bleed and beading described later can be sufficiently prevented. If the degree of polymerization is 2000 or less, an increase in viscosity when added to the ink can be suppressed, and good emission stability can be obtained.

  For the side chain, a modifying group such as a photodimerization type, a photodecomposition type, a photopolymerization type, a photomodification type, and a photodepolymerization type can be introduced. From the viewpoint of reactivity with the color material to be combined, the side chain is preferably nonionic, anionic, or amphoteric (betaine compound). Particularly, when the color material is combined with an anionic dye or an anionic pigment, the side chain is It is preferably nonionic or anionic, and particularly preferably nonionic.

  The modification rate of the side chain with respect to the hydrophilic main chain is preferably 0.8 mol% or more and 4.0 mol% or less, and more preferably 1.5 mol% or more and 3.0 mol% or less. More preferable from the viewpoint of reactivity. If the modification rate of the side chain with respect to the hydrophilic main chain is 0.8 mol% or more, it has sufficient crosslinkability, and the object effect of the present invention can be obtained. On the other hand, if it is 4.0 mol% or less, the crosslinking density is appropriate, so that a flexible image film can be easily obtained and the film strength is particularly good.

  As the photodimerization-type modifying group, those in which a diazo group, a cinnamoyl group, a stilbazonium group, a stilquinolium group or the like is introduced are preferable. 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 stilbazonium 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.

  In such an active energy ray-crosslinked polymer compound, the main chain originally having a certain molecular weight is cross-linked between the side chains through a cross-linking bond. The effect of increasing the molecular weight per photon is remarkably large compared to a conventionally known active energy ray-curable resin produced by polymerization.

  Furthermore, ink using a conventionally known active energy ray-curable resin is a component that is involved in almost all of the ink other than the color material, so that the dots after curing rise and the image quality represented by gloss is significantly deteriorated. On the other hand, the polymer compound according to the present invention requires only a small amount of ink used in the ink and, on the other hand, has many dry components, so that the image quality after drying is improved and the fixing property is also good.

  The hydrophilic main chain according to the present invention has a plurality of side chains, and the amount of the polymer compound that can be cross-linked between the side chains by irradiating active energy rays in the ink is 0.8% or more, It is preferably 5.0% or less.

  If the addition amount is within this range, the crosslinking efficiency is improved, and the ink is ejected from the head and adhered to the base material, and then crosslinked, so that the viscosity of the ink after crosslinking is rapidly increased and the beading resistance and color bleed resistance are increased. Will improve. When the addition amount is less than 0.8%, the objective effect of the present invention obtained due to insufficient crosslinkability is reduced, and when it exceeds 5.0%, the ink viscosity increases and affects intermittent emission stability. Sometimes.

  In the case of changing the ratio of the addition amount for each ink color to be ejected, it is preferable that the mass ratio of the crosslinkable polymer compound between colors is different by at least 20%.

  In the inkjet ink of the present invention, when using a polymer compound having a photopolymerizable modifying group, it is preferable to use a known photopolymerization initiator, and it is particularly preferable to use a water-soluble photopolymerization initiator.

  As a water-soluble photopolymerization initiator applicable to the ink jet ink of the present invention, a compound represented by the following general formula (7) is preferable from the viewpoint of compatibility with a polymer compound and sensitivity.

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

  The concentration of the polymerization initiator in the ink composition may be the same or different for each ink color to be used, but a multicolor ink layer is formed on the intermediate transfer medium or the printing medium, When performing energy beam irradiation, when comparing the concentration of the polymerization initiator in the lower ink layer and the upper ink layer adjacent to the lower ink layer, the amount of the polymerization initiator contained in the upper ink layer is The amount is preferably at least 1.2 times the amount of the polymerization initiator contained in the ink layer.

  Here, a multicolor ink layer is formed on the intermediate transfer medium. On the intermediate transfer medium, the active energy ray is irradiated after the ink layer is transferred onto the printing medium without irradiating the active energy ray. In the case of performing, since the structure of the ink layer on the intermediate transfer medium is reversed on the printing medium, the concentration of the polymerization initiator in the lower ink layer of the multicolor ink layer is the upper ink layer adjacent to the lower layer. It is preferable to adjust the concentration to be lower than the polymerization initiator concentration therein.

<< Evaluation of overlap of absorption spectrum of polymerization initiator and emission spectrum of active energy ray >>
The type of the polymerization initiator used in the present invention may be changed for each ink color, or the same compound may be used. In that case, the polymerization initiator is dissolved in a suitable solvent at a constant concentration (molar concentration), the measured absorption spectrum and the emission spectrum of the active energy ray used for curing are overlapped, and the overlapping areas are relatively compared, It is preferable to make a difference of at least 10% or more.

  Here, the above absorption spectrum can be measured using a commercially available ultraviolet / visible spectrophotometer, and the calculation processing of the overlap between the absorption spectrum of the polymerization initiator and the emission spectrum of the active energy ray is a conventionally known processing apparatus. Can be used to calculate.

  Next, other components of the inkjet ink of the present invention will be described.

《Coloring material》
As the color material used in the ink jet ink of the present invention, a dye or a pigment can be used.

  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.

  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.

  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, 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.

  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.

  These dyes listed above are described in “Dyeing Note 21st Edition” (published by Color Dyeing Co., Ltd.) and the like.

  In addition, chelate dyes and azo dyes used for silver dye bleach (silver dye bleaching) photosensitive materials (for example, Cibachrome manufactured by Ciba Geigy) can be used.

  Chelating dyes are described, for example, in British Patent No. 1,077,484. As for azo dyes for silver dye bleaching photosensitive materials, for example, British Patent Nos. 1,039,458, 1,004,957, 1,077,628, U.S. Pat. 612,448.

  Examples of the pigment that can be used in the present invention include conventionally known organic or inorganic pigments. For example, azo pigments such as azo lake pigments, 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. Polycyclic pigments, dye lakes such as basic dye type lakes and acid dye type lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, daylight fluorescent pigments, and inorganic pigments such as carbon black .

  Hereinafter, specific examples of the pigment applicable to the ink-jet ink of the present invention will be listed, but the present invention is not limited only to these exemplified pigments.

  Examples of magenta or red pigments 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 orange or yellow pigments 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. Pigment yellow 138, C.I. I. Pigment yellow 150, pigment yellow 180, and the like.

  Examples of green or cyan pigments 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 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Examples of the pigment for black include carbon black.

(Self-dispersing pigment)
In the inkjet ink of the present invention, a self-dispersing pigment can also be used as the pigment. The self-dispersing pigment refers to a pigment that can be dispersed without a dispersant, and particularly preferably pigment particles having a polar group on the surface.

  Pigment particles having a polar group on the surface are pigments directly modified with a polar group on the surface of the pigment particle, or organic substances having an organic pigment mother nucleus and having a polar group bonded directly or via a joint , Referred to as pigment derivative).

  Examples of the 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 sulfonic acid group.

  Examples of a method for obtaining pigment particles having a polar group on the surface include WO97 / 48769, JP-A-10-110129, JP-A-11-246807, JP-A-11-57458, and 11-189739. By making the surface of pigment particles described in JP-A-11-323232, JP-A-2000-265094, etc. with an appropriate oxidizing agent, polarities such as sulfonic acid groups or salts thereof are formed on at least a part of the pigment surface. The method of introduce | transducing group 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, amidosulfuric 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 derivative described in JP-A-11-49974, JP-A-2000-273383, JP-A-2000-303014, etc. on the pigment particle surface by a treatment such as milling, and the like. Examples include a method of dissolving the pigment described in 2002-179777, 2002-201401, etc. together with a pigment derivative in a solvent and then crystallization in a poor solvent, and any method can easily polarize the surface. Pigment particles having groups can be obtained.

  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.

(Method for producing pigment dispersion)
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.

(Surfactant applicable to pigment dispersion)
In preparing the pigment dispersion, if necessary, a surfactant or a polymer dispersant may be contained as a pigment dispersant. The type of surfactant and polymer dispersant is not particularly limited. Examples of the surfactant include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, and naphthalene sulfonates. , Alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine oxide and the like As the polymer dispersant, a water-soluble resin is preferably used from the viewpoint of ejection stability. For example, styrene, a styrene derivative, a vinyl naphthalene derivative, acrylic acid, an acrylic acid derivative, maleic acid, maleic acid. acid Examples include conductors, itaconic acid, itaconic acid derivatives, fumaric acid, block copolymers composed of two or more monomers selected from fumaric acid derivatives, random copolymers, and salts thereof. Styrene-acrylic acid-alkyl acrylate ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid-alkyl acrylate copolymer, styrene-maleic acid copolymer, styrene-methacrylic acid-acrylic acid Examples thereof include an alkyl ester copolymer, a styrene-methacrylic acid copolymer, a styrene-maleic acid half ester copolymer, a vinyl naphthalene-acrylic acid copolymer, and a vinyl naphthalene-maleic acid copolymer.

  The amount of each polymer dispersant added to the total amount of the ink is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass. Two or more of these polymer dispersants can be used in combination.

(Particle size of pigment particles)
The particle size of the pigment particles includes the particle size (primary particle size) obtained by directly observing the particles with an electron microscope, and the dispersed particle size (secondary particle size) using a particle size measuring device utilizing light scattering. There is a viscosity-converted particle size obtained from the intrinsic viscosity.

  The primary particle diameter of the pigment in the ink of the present invention is preferably 10 nm or more and 1000 nm or less, more preferably 10 nm or more and 70 nm, from the viewpoint of light resistance and dispersion stability. If the thickness is smaller than 10 nm, the light resistance is not deteriorated. If the thickness is larger than 100 nm, the head is clogged due to aggregation. Here, in order to obtain primary particles, the major axis of 1000 pigment particles is measured with a transmission electron microscope, and the average value (number average) can be obtained.

"solvent"
In the inkjet ink of the present invention, it is preferable to use a water-soluble organic solvent. Examples of the water-soluble organic solvent that can be used in the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl). Alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol Etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol) Ether monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl 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, mole) Phosphorus, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N , N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides ( For example, dimethyl sulfoxide etc.), sulfones (for example, sulfolane etc.), urea, acetonitrile, acetone etc. are mentioned. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

  The water-soluble organic solvent may be used alone or in combination. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to 35% by mass.

<Inkjet ink set>
The ink-jet ink set of the present invention is composed of three or four or more ink-jet inks.

  As the ink having different hues constituting the inkjet ink set of the present invention, it is preferable to use an ink set composed of inkjet inks of yellow, magenta, cyan, and black.

  Further, in addition to the four color inks, a light cyan ink, a light magenta ink, a dark yellow ink, and a light black ink (gray ink) may be used. It is also possible to use so-called special color inks such as blue, red, green, orange and violet.

(Dark ink)
In the ink-jet ink set of the present invention, an ink-jet ink set composed of at least two inks of the same color having different densities in at least one color ink may be used. Furthermore, in two or more colors of ink, an ink jet ink set composed of at least two same color inks having different densities may be used. In particular, in three or more color inks, at least two same color inks having different densities. From the viewpoint of gradation, it is preferable to use an ink-jet ink set comprising: In particular, it is preferable to use at least two inks having different densities in magenta ink or cyan ink having high human visibility.

  The density ratio of the ink jet ink sets having different densities may be any value. However, in order to achieve smooth gradation reproduction, the ratio of the high density ink to the low density ink (color material density / high density of the low density ink) The color material density of the density ink is preferably between 0.1 and 1.0, more preferably between 0.2 and 0.5, and between 0.25 and 0.4. It is particularly preferred.

(White ink)
In the inkjet ink set of the present invention, a white ink containing a white pigment may be used in addition to the colored pigment. The white pigment used is not particularly limited as long as it makes the ink-jet ink white, and examples thereof include inorganic white pigments, organic white pigments, and white hollow polymer fine particles.

  Examples of inorganic white pigments include sulfates of alkaline earth metals such as barium sulfate, carbonates of alkaline earth metals such as calcium carbonate, silicas such as fine silicate, synthetic silicate, calcium silicate, alumina , Alumina hydrate, titanium oxide, zinc oxide, talc, clay and the like. In particular, since titanium oxide has a high refractive index, it is fine and has high concealability and colorability, and can be preferably used.

  Examples of the organic white pigment include organic compound salts disclosed in JP-A No. 11-129613 and alkylene bismelamine derivatives disclosed in JP-A Nos. 11-14365 and 2001-234093. Specific examples of the white pigment include Shigenox OWP, Shigenox OWPL, Shigenox FWP, Shigenox FWG, Shigenox UL, and Shigenox U (all trade names manufactured by Hackol Chemical Co., Ltd.).

  Examples of the white hollow polymer fine particles include thermoplastic fine particles substantially made of an organic polymer disclosed in US Pat. No. 4,089,800.

  In the present invention, the white pigment may be used alone or in combination. For the dispersion of the pigment, 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, a paint shaker, or the like can be used. It is also possible to add a dispersant when dispersing the pigment.

  A normal dispersant can be used as the dispersant, but a polymer dispersant is preferably used.

  In the dispersion of the pigment, the average particle diameter is preferably 0.05 to 1.0 μm, more preferably 0.08 to 0.3 μm.

(Colorless ink)
In the inkjet ink set of the present invention, a colorless ink (also referred to as a transparent ink) that does not substantially contain a coloring material can be used in combination.

  In the present invention, the colorless ink containing substantially no color material means a state in which the content of the color material is 0.1% or less with respect to the total ink mass, and preferably contains no color material. is there.

  The component contained in the colorless ink according to the present invention may be either uniformly dissolved or present in a non-uniform dispersion system. Examples of the resin that can be added include a water-based dissolved resin, a water-based dispersed resin, an organic solvent-based dissolved resin, an organic solvent-based dispersed resin, and the like. A resin dispersed in an aqueous system is preferred. Although colorless inks obtained by removing only the color material from the ink-jet ink used can be used, it is preferable to add the following additives in order to add various functions.

  Examples of resins that are dissolved in water include polyvinyl alcohol, gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color ginnan (κ, ι, λ, etc.), agar, pullulan, water-soluble Polyvinyl butyral, hydroxyethyl cellulose, carboxymethyl cellulose and the like can be added.

  As the resin dispersed in an aqueous system, it is particularly preferable to add fine particles of a thermoplastic resin because the glossiness of the image is improved. As the thermoplastic resin fine particles, the thermoplastic resin that can be added to the surface layer of the recording medium or the kind described in the description of the fine particles can be used. In particular, it is preferable to apply those which do not cause thickening or precipitation even when added to the ink. The average particle size of the thermoplastic resin particles is preferably 0.5 μm or less. The fine particles of the thermoplastic resin to be added are preferably those that melt and soften in the range of 0 to 150 ° C.

<< Other Additives for Inkjet Inks >>
In the ink of the present invention, if necessary, various known additives such as ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other performance improvement purposes, for example, , Viscosity modifier, Surface tension modifier, Specific resistance modifier, Film forming agent, Dispersant, Surfactant, Ultraviolet absorber, Antioxidant, Anti-fading agent, Antifungal agent, Rust inhibitor, etc. For example, polystyrene, polyacrylates, polymethacrylates, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine Organic latex such as resin, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil and other oil droplets, ON or nonionic surfactants, UV absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, 60-72785, 61-146591, anti-fading agents described in JP-A-1-95091 and 3-13376, JP-A-59-42993, 59-52689, 62- 280069, 61-242871, and JP-A-4-219266, etc., optical brighteners, pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc. Can be mentioned.

(latex)
In the inkjet ink of the present invention, latex may be added to the ink. Examples thereof include latex such as styrene-butadiene copolymer, polystyrene, acrylonitrile-butadiene copolymer, acrylate copolymer, polyurethane, silicon-acrylic copolymer, and acrylic-modified fluorine-fatting. The latex may be obtained by dispersing polymer particles using an emulsifier, or may be dispersed without using an emulsifier. A surfactant is often used as an emulsifier, but a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a single group having a solubilizing group). It is also preferable to use a polymer obtained from a monomer and a monomer having an insoluble part.

  Moreover, it is particularly preferable to use soap-free latex in the ink jet ink of the present invention. Soap-free latex is a latex that does not use an emulsifier and a polymer having a water-soluble group such as a sulfonic acid group or a carboxylic acid group (for example, a polymer in which a solubilizing group is graft-bonded, a solubilizing group) A polymer obtained from a monomer having an insoluble part and a monomer having an insoluble part).

  In recent years, as latex polymer particles, there are also latexes in which core-shell type polymer particles having different compositions at the center and outer edge of the particles are dispersed in addition to the latex in which the polymer particles are uniform throughout. However, this type of latex can also be preferably used.

  In the inkjet ink of the present invention, the average particle size of the polymer particles in the latex is preferably 10 nm or more and 300 nm or less, and more preferably 10 nm or more and 100 nm or less. When the average particle size of the latex exceeds 300 nm, the glossiness of the image is deteriorated, and when it is less than 10 nm, the water resistance and scratch resistance become insufficient. The average particle size of the polymer particles in the latex can be determined by a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, or a laser Doppler method.

  In the inkjet ink of the present invention, the latex is preferably added so that the solid content is 0.1% by mass or more and 20% by mass or less with respect to the total mass of the ink. It is particularly preferable that the content be 0.5 mass% or more and 10% mass% or less. If the amount of latex solids added is less than 0.1% by mass, it is difficult to exert a sufficient effect on the weather resistance, and if it exceeds 20% by mass, the ink viscosity increases over time and the ink storage stability is increased. There are many problems that arise.

(Outgoing stabilizer for thermal)
The ink jet ink of the present invention may be used in a thermal ink jet printer. At this time, in order to solve the clogging of the head called kogation, (M1) ₂ SO ₄ , CH ₃ COO (M1), Ph-COO (M1), ( A salt selected from M1) NO ₃ , (M1) Cl, (M1) Br, (M1) I, (M1) ₂ SO ₃ and (M1) ₂ CO ₃ may be added. Here, M1 represents an alkali metal, ammonium or organic ammonium, and Ph represents a phenyl group. Examples of the alkali metal include Li, Na, K, Rb, and Cs. Examples of organic ammonium include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, trihydroxymethylamine, dihydroxymethylamine, monohydroxymethylamine, monoethanolammonium, diethanolammonium, and triethanol. Ammonium, N-methylmonoethanolammonium, N-methyldiethanolammonium, monopropanolammonium, dipropanolammonium, tripropanolammonium, etc. are mentioned.

(Crosslinking agent)
The inkjet ink of the present invention may contain a crosslinking agent. Specific examples of the crosslinking agent include, for example, epoxy curing agents (diglycidyl ethyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidyl cyclohexane, N, N-diglycidyl- 4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde curing agents (formaldehyde, glioxal, etc.), active halogen curing agents (2,4-dichloro-4-hydroxy-1,3,5) , -S-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.), aluminum alum, boric acid or a salt thereof.

(Anti-fading agent)
In the ink-jet ink of the present invention, a known anti-fading agent can be used in conventional ink-jet inks. This anti-fading agent suppresses fading caused by light irradiation and fading caused by various oxidizing gases such as ozone, active oxygen, NOx, and SOx. Examples of such anti-fading agents include antioxidants described in JP-A-57-74192, JP-A-57-87989, and JP-A-60-72785, and ultraviolet absorbers described in JP-A-57-74193. Hydrazides described in JP-A-61-154989, hindered amine-based antioxidants described in JP-A-61-146591, nitrogen-containing heterocyclic mercapto-based compounds described in JP-A-61-177279, The thioether antioxidants described in 1-115677 and 1-36479, the hindered phenol antioxidants having a specific structure described in JP-A-1-36480, JP-A-7-195824 and 8-150773. Ascorbic acids described in JP-A-7-149037, zinc sulfate described in JP-A-7-314882, Phosphates such as thiourea derivatives described in JP-A-7-314883, saccharides described in JP-A-7-276790 and 8-108617, and phosphate-based antioxidants described in JP-A-8-118791 Examples of the anti-fading agent include nitrites, sulfites, and thiosulfates described in JP-A-8-300807, and hydroxylamine derivatives described in JP-A-9-267544. Furthermore, polycondensates of dicyandiamide and polyalkylene polyamine described in JP-A No. 2000-266928 and the like are also effective anti-fading agents in inkjet.

(PH buffer)
In the inkjet ink of the present invention, a pH buffer agent may be added to the ink. For example, organic acids and inorganic acids. Examples of the organic acid include nonvolatile phthalic acid, terephthalic acid, salicylic acid, benzoic acid, sebacic acid, lauric acid, palmitic acid, ascorbic acid, citric acid, malic acid, lactic acid, succinic acid, succinic acid, and polyacrylic acid. And various organic acids such as benzylic acid.

(Defoamer)
In the inkjet ink of the present invention, an antifoaming agent can be added, and a commercially available product can be used without particular limitation as the antifoaming agent. Examples of such commercially available products include KF96, 66, 69, KS68, 604, 607A, 602, 603, KM73, 73A, 73E, 72, 72A, 72C, 72F, 82F, 70, 71 manufactured by Shin-Etsu Silicone. 75, 80, 83A, 85, 89, 90, 68-1F, 68-2F (trade name), and the like. Although there is no restriction | limiting in particular in the compounding quantity of these compounds, It is preferable to mix | blend 0.001-2 mass% in the ink of this invention. If the compounding amount of the compound is less than 0.001% by mass, bubbles are likely to be generated at the time of preparing the ink, and it is difficult to remove small bubbles in the ink. During printing, repellency may occur in the ink and the print quality may be deteriorated.

(Surfactant)
Surfactants preferably used in the inkjet ink of the present invention include alkyl sulfates, alkyl ester sulfates, dialkyl sulfosuccinates, alkyl naphthalene sulfonates, alkyl phosphates, and 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 , Surfactants such as sorbitan esters, polyoxyethylene fatty acid amides and amine oxides, and cationic surfactants such as alkylamine salts and quaternary ammonium salts.

<Preparation of ink>
There is no particular limitation on the preparation of the ink-jet ink of the present invention. However, when an ink containing a dispersion such as a pigment, a disperse dye, inorganic fine particles, or resin fine particles is prepared, no aggregation or sedimentation occurs in the preparation process. Thus, it is preferable to prepare the ink. If necessary, a preparation method such as adjusting the order of addition of the dispersion, solvent, water, photosensitive resin and other additives, and the addition rate can be taken. In addition, for the purpose of stabilizing the dispersion and redispersing the agglomeration generated during the blending of the ink during or after the blending, a dispersion process using a bead mill or ultrasonic waves, a heating process, or the like may be performed.

《Ink physical properties》
(viscosity)
The viscosity of the inkjet ink of the present invention is not particularly limited, but the viscosity at 25 ° C. is preferably 2 mPa · s or more and 10 mPa · s or less. Moreover, it is preferable that the viscosity of the inkjet ink of the present invention has no speed dependency.

  The ink viscosity (mPa · s) in the present invention is not particularly limited as long as it is tested with a standard solution for calibration of a viscometer specified in JIS Z 8809, and is measured at 25 ° C. according to a known method. As the viscosity measuring device, a rotary, vibration or capillary type viscometer can be used, for example, a Saybolt viscometer, a Redwood viscometer, etc., for example, a cone plate type manufactured by Tokimec E type viscometer, Toki Sangyo E Type Viscometer (rotary viscometer), Tokyo Keiki B type viscometer BL, Yamaichi Denki FVM-80A, Nametor Kogyo Viscoliner VISCO MATE MODEL VM-1A, DD-1 manufactured by Denki Co., Ltd. can be exemplified.

(surface tension)
Moreover, in the ink for inkjet of this invention, it is preferable that surface tension is 40 mN / m or less, More preferably, it is 25-35 mN / m.

  The surface tension (mN / m) of the ink as used in the present invention is a value measured by a surface tension measured at 50 ° C., and its measuring method is described in general interface chemistry, colloid chemistry reference books, etc. For example, New Experimental Chemistry Course Volume 18 (Interface and Colloid), The Chemical Society of Japan, published by Maruzen Co., Ltd. 68-117 can be referred to. Specifically, it can be determined using a ring method (Dunoi method) or a platinum plate method (Wilhelmy method), but in the present invention, it is represented by a surface tension value (mPa · s) measured by the platinum plate method. For example, it can be measured using a surface tension meter CBVP-Z manufactured by Kyowa Interface Science.

(Electrical conductivity)
In the inkjet ink of the present invention, from the viewpoint of ink storage stability, the electrical conductivity is preferably 1 mS / m or more and 500 mS / m or less, more preferably 1 mS / m or more and 200 mS / m or less. More preferably, it is 10 mS / m or more and 100 mS / m or less. When the electric conductivity of the ink exceeds 500 mS / m, an emission defect due to deposition of a coloring material occurs. Moreover, if it is 1 ms / m or less, sufficient electrostatic repulsion for allowing the dispersion to exist stably cannot be obtained, and it will also aggregate. Therefore, the dispersion can be stably present by setting the electric conductivity to 1 mS / m or more and 500 mS / m.

  In the ink according to the present invention, there is no particular limitation as a means for achieving a desired electric conductivity. In the present invention, a pigment is used as a coloring material, and a polymer compound (polymer dispersing agent) is used as a pigment dispersant. The method used or a method using an electrical conductivity modifier, for example, an inorganic salt such as potassium chloride, ammonium chloride, sodium sulfate, sodium nitrate, or sodium chloride, or an aqueous amine such as triethanolamine is appropriately selected or combined. Can be achieved.

  The measurement of the electrical conductivity of the ink in the present invention should be easily performed according to the method described in JIS K 0400-13-10 (1999) or the method disclosed in JP-A-61-61164. Can do.

(Ion concentration adjustment)
In preparing the inkjet ink of the present invention, it is preferable to adjust the ion concentration as appropriate.

  An aqueous dye solution having a predetermined concentration is measured by ICP-AES, and the ion concentration of the ink state is calculated in terms of the dye concentration used in the ink. By using distilled water or ion-exchanged water, the ion concentration at the time of ink formation can be estimated.

  Next, other additives are added to prepare an ink, and the ion concentration in the ink is measured by ICPAES. When the target ion concentration is exceeded, the ion concentration can be lowered by passing the aqueous dye solution through an ion exchange resin. Ion exchange can be performed a plurality of times to further reduce the ion concentration. If the desired ion concentration is not reached, the additives other than the dye are also subjected to treatment such as ion exchange. Moreover, you may add processes, such as filtration by an activated carbon process or an ultrafiltration membrane, as needed.

(Deaeration treatment)
The dissolved oxygen concentration in the inkjet ink of the present invention is preferably 2 ppm or less, more preferably 1 ppm or less. If the dissolved oxygen concentration in the ink-jet ink exceeds 2 ppm, cavitation occurs when ink is ejected, and emission defects are likely to occur.

  The method for adjusting the dissolved oxygen concentration is not particularly limited. However, as described in JP-A-11-209670, a method for degassing an inkjet ink under reduced pressure, a method for degassing by irradiating ultrasonic waves, and a method for degassing. Examples include a degassing method using a hollow fiber membrane. In particular, degassing with a degassing hollow fiber membrane is preferred.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “part” or “%” in the examples represents “part by mass” or “mass%”.

Example 1
<< Preparation of crosslinkable polymer compound >>
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, respectively, and stirred in a hot water bath at 80 ° C. for 8 hours.

  Next, 45 g of polyvinyl acetate saponified product having a degree of polymerization of 300 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 to obtain p- (3 -Methacryloxy-2-hydroxypropyloxy) benzaldehyde was added to polyvinyl alcohol so that the modification rate was 2.5 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. The ion exchange resin was filtered and then diluted with pure water to obtain a 15% by mass aqueous solution of the crosslinkable polymer compound. A crosslinkable polymer compound is a polymer compound that has a plurality of side chains in a saponified polyvinyl acetate that is a hydrophilic main chain, and can be crosslinked between side chains by irradiating active energy rays. is there.

<Preparation of ink set>
[Preparation of ink set 1]
Ink set 1 composed of yellow ink 1, magenta ink 1, cyan ink 1 and black ink 1 was prepared according to the following method.

(Preparation of yellow ink 1)
The following compositions were sequentially mixed, dispersed using a bead mill, and then filtered through a # 3000 metal mesh filter to prepare yellow ink 1.

Crosslinkable polymer compound 2 parts as solid content Ethylene glycol 20 parts 2-pyrrolidinone 15 parts Activator: Olphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part Polymerization initiator: Irgacure 2959 0.5 parts Pigment: Cab-O- Jet270 (Yellow self-dispersing pigment manufactured by Cabot)
3 parts as solid content Antifungal agent: Proxel GXL (manufactured by Avicia) 0.2 parts Ion exchange water was added to each of the above compositions to finish 100 parts.

(Preparation of magenta ink 1, cyan ink 1, black ink 1)
In the preparation of the yellow ink 1, the pigment was replaced with Cab-O-Jet 270, Cab-O-Jet 260 (magenta self-dispersing pigment manufactured by Cabot), Cab-O-Jet 250 (cyan self-dispersing pigment manufactured by Cabot), respectively. Magenta ink 1, cyan ink 1, and black ink 1 were prepared in the same manner except that Cab-O-Jet 300 (black self-dispersing pigment manufactured by Cabot) was used.

[Preparation of ink set 2]
In the preparation of ink set 1, the content of Irgacure 2959 is 1.2 parts for yellow ink 1, 0.9 parts for magenta ink 1, 0.7 parts for cyan ink 1, and 0 parts for black ink 1. An ink set 2 comprising yellow ink 2, magenta ink 2, cyan ink 2 and black ink 2 was prepared by the same preparation method except that the amount was .5 parts.

[Preparation of ink set 3]
In the preparation of ink set 1, Irgacure 2959 was changed to 2-chlorothioxanthone for yellow ink 1, Irgacure 3907 for magenta ink 1, Irgacure 184 for cyan ink 1, and Irgacure 651 for black ink 1. An ink set 3 composed of yellow ink 3, magenta ink 3, cyan ink 3 and black ink 3 was prepared in the same manner except that. The overlap between the ultraviolet emission spectrum of the active energy ray irradiation apparatus described later and the absorption spectrum of the polymerization initiator in each ink is 91% for yellow ink 3, 80% for magenta ink 3, 61% for cyan ink 3, and black ink. 3 was 70%.

[Preparation of ink set 4]
Ink set 4 (comparative example) composed of yellow ink 4, magenta ink 4, cyan ink 4 and black ink 4 was prepared according to the following method.

(Preparation of yellow ink 4)
The following compositions were sequentially mixed and dispersed using a bead mill, and then pre-dispersed for 1 hour using a dissolver. Further, the mixture was kneaded using a bead mill and filtered through a # 3000 metal mesh filter to prepare yellow ink 4.

Active energy ray reactive compound: A-TMPT-3EO 5 parts Propylene glycol 15 parts Diethylene glycol 10 parts Activator: Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1 part Polymerization initiator: Irgacure 2959 0.5 parts Pigment: C.I. I. Pigment Yellow 74 3 parts Pigment dispersant: Solsperse 20000 (manufactured by Avicia) 1 part Antifungal agent: Proxel GXL (manufactured by Abyssia) 0.2 part Ion-exchanged water was added to each of the above compositions to finish 100 parts. In the preparation of the yellow ink 4, the pigment is C.I. I. In place of Pigment Yellow 74, C.I. I. Pigment red 122, C.I. I. Magenta ink 4, cyan ink 4 and black ink 4 were prepared in the same manner except that CI pigment blue 15: 3 and carbon black were used.

[Preparation of ink set 5]
Ink set 5 (comparative example) composed of yellow ink 5, magenta ink 5, cyan ink 5 and black ink 5 was prepared according to the following method.

(Preparation of yellow ink 5)
The following compositions were sequentially mixed and dispersed using a bead mill, and then pre-dispersed for 1 hour using a dissolver. Further, the mixture was kneaded using a bead mill and filtered through a # 3000 metal mesh filter to prepare yellow ink 5.

C. I. Pigment Yellow 74 10 parts Azisper PB821 (manufactured by Ajinomoto Fine Techno) 5 parts Aronix M5700 (manufactured by Toagosei) 10 parts Ethylene oxide added 1,6 hexanediol acrylate 60 parts 3-methoxybutyl acrylate 10 parts Irgacure 369 5 parts Yellow ink 5 In the preparation of C.I. I. In place of Pigment Yellow 74, C.I. I. Pigment red 122, C.I. I. Magenta ink 5, cyan ink 5, and black ink 5 were prepared in the same manner except that CI pigment blue 15: 3 and carbon black were used.

  About the ink-jet ink sets 1 to 5 obtained above, as shown below, an ink type and a commercially available ink-jet printer were combined to form an image, and as shown in Table 1, samples 1 to 10 were each Produced.

  An ink jet printer PX9000 (manufactured by EPSON) was modified for ink sets 1 to 4, and an ink jet printer UJF-605R (manufactured by MIMAKI) was remodeled for ink set 5 to form an image.

  When preparing a sample, the ink is directly ejected onto the printing medium as shown in FIG. 1 (direct recording method), or once ejected onto the intermediate medium as shown in FIG. 3 and transferred to the printing medium (indirect). After the transfer recording method, the ink image was irradiated with active energy rays to fix the image.

  As another ink jet recording method, as shown in FIG. 3, after ejecting ink onto the intermediate medium, the ink image on the intermediate medium is irradiated with active energy rays, and then the image is transferred to the printing medium again ( Indirect irradiation transfer recording method).

<< Preparation of Sample 1 >>
Using the apparatus shown in FIG. 1 and the ink set 1 for inkjet, NK special art paper was ejected in the order of black, yellow, magenta, and cyan, and then exposed using an ultraviolet irradiation device (mercury lamp, 1.5 kW). .

<< Preparation of Sample 2 >>
The procedure was the same as that for Sample 1 except that the color order of ink ejection was changed to black, cyan, yellow, and magenta.

<< Preparation of Sample 3 >>
Using the apparatus configuration shown in FIG. 2, magenta, yellow, black, and cyan colors are ejected in the order of ink set 1 onto the intermediate transfer drum, and then OK Kanto is used as a printing medium under heat and pressure (55 The ink image was transferred at a temperature of 50 N / cm. Finally, an active energy ray was irradiated to the image on OK Kanto using an ultraviolet irradiation device (mercury lamp, 1.5 kW).

<< Preparation of Sample 4 >>
Similar to the preparation of Sample 3, except that the apparatus configuration shown in FIG. 2 was used, the order of ink ejection was changed to magenta, yellow, cyan, and black, and the printing medium was changed from OK Kanto to polyethylene terephthalate film. And an ink-fixed image was obtained on the film.

<< Preparation of Sample 5 >>
Sample 5 was prepared in the same manner as Sample 1 except that yellow, magenta, cyan, and black were emitted in this order using the apparatus shown in FIG. 1 and inkjet ink set 2.

<< Preparation of Sample 6 >>
Sample 6 was prepared in the same manner as Sample 1 except that yellow, magenta, cyan, and black were emitted in this order using the apparatus shown in FIG. 1 and inkjet ink 3.

<< Preparation of Sample 7 >>
Sample 7 was prepared in the same manner as Sample 3 except that the apparatus shown in FIG. 2 and ink-jet ink set 2 were used to emit in the order of cyan, black, magenta, and yellow.

<< Preparation of Sample 8 >>
Surface-treated polypropylene film having a thickness of 75 μm using the apparatus shown in FIG. 1 (where the active energy ray irradiation apparatus is installed on the back side of the printing medium on which the ink image is formed) and the ink set 1 for inkjet. Ink is ejected in the order of magenta, yellow, cyan, and black, and an ultraviolet irradiation device (mercury lamp, 1.5 kW) is applied to the ink ejected on the film from the film surface opposite to the ink ejection surface of the polypropylene film. The active energy ray was irradiated using.

<< Preparation of Sample 9 (Comparative Example) >>
Sample 9 (Comparative Example) was prepared in the same manner as Sample 1 except that the apparatus shown in FIG. 1 and the ink-jet ink set 4 were used and the inks were ejected in the order of black, yellow, magenta, and cyan. Produced.

<< Preparation of Sample 10 (Comparative Example) >>
Sample 10 (Comparative Example) was prepared in the same manner as Sample 1 except that the apparatus shown in FIG. 1 and inkjet ink set 5 were used, and the inks were ejected in the order of black, yellow, magenta, and cyan. Produced.

  The samples 1 to 10 obtained above were evaluated for image gloss, bleeding between colors, and the like.

《Image gloss》
The obtained image was visually evaluated according to the following criteria, and ○ was regarded as a problem-free level.
◯: Glossy feeling between the image part and the non-image part is an image having a texture close to printing. Δ: Glossy feeling is felt between the image part and the non-image part. Gloss is very deteriorated, so the image quality is greatly impaired.
An image portion in which colors having greatly different color tones are adjacent to each other was evaluated according to the following criteria, and a level of ◯ or higher was regarded as a problem-free level.
◎: Bleeding between colors is not observed even in an image area with a large amount of ink applied ○: Bleeding between colors is slightly observed in an image area with a large amount of ink applied, but the color of the entire image is felt No: Bleeding between colors is observed in an image area with a large amount of ink shot, and depending on the image pattern, the bleeding between colors is worrisome ×: Bleeding between colors occurs in the entire image Table 1 shows the results .

  From Table 1, it is clear that the sample of the present invention can obtain an image having excellent gloss and less blur between colors even if the amount of energy applied by irradiation with active energy rays is low as compared with the comparative example.

  INDUSTRIAL APPLICABILITY According to the present invention, an inkjet ink that exhibits sufficient curability by irradiation with a low energy active energy ray, has high resolution of the formed image, has good gloss, and has less bleeding between colors, and the same are used. An ink jet recording method could be provided.

It is a schematic sectional drawing which shows an example of an apparatus structure used for this invention which injects ink directly to a to-be-printed medium (direct recording method). An apparatus configuration used in the present invention to form an ink image on an intermediate transfer medium, irradiate the ink image on the intermediate transfer body with active energy rays, and then transfer the image onto a printing medium (indirect irradiation transfer recording method). It is a schematic sectional drawing which shows an example. 1 is a schematic cross-sectional view showing an example of the configuration of an apparatus for irradiating an active energy ray after forming an ink image on an intermediate transfer medium, transferring an image on a printing medium, and irradiating active energy rays (indirect transfer method). It is a figure which shows the overlap with the emission spectrum of a photoinitiator (2-chlorothioxanthone), a photoinitiator (Irgacure 184), and a high pressure mercury lamp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Original winding roll 2 Printed recording medium 3 Inkjet recording head 3a Ink 3b, 3c Ink image 5 Active energy ray irradiation apparatus 6 Take-up roll 7 Heating and pressing roll 8 Intermediate transfer roll

Claims (21)

An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
After ejecting at least three colors of ink onto the printing medium, irradiate with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium, print the ink present on the intermediate transfer medium like an image In the inkjet recording method of irradiating active energy rays after being transferred to a medium,
An inkjet recording method, wherein the first and second ejection ink colors are black, cyan, or blue. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
After ejecting at least three colors of ink onto the printing medium, irradiate with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium, print the ink present on the intermediate transfer medium like an image In the inkjet recording method of irradiating active energy rays after being transferred to a medium,
2. An ink jet recording method, wherein the second and subsequent ejection ink colors are yellow, orange, red, magenta, green, or light ink. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
After ejecting at least four colors of ink onto the printing medium, irradiate active energy rays, or after ejecting at least four colors of ink onto the intermediate transfer medium, cover the ink that exists like an image on the intermediate transfer medium. In the inkjet recording method of irradiating active energy rays after being transferred to a print medium,
An ink jet recording method, wherein the ejection ink colors are in the order of black, cyan, yellow, and magenta. The ink recording method according to any one of claims 1 to 3, wherein the amount of energy applied by the active energy ray is 400 mJ / cm ² or less. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
In an ink jet recording method for ejecting at least three colors of ink onto an intermediate transfer medium, irradiating the intermediate transfer medium with active energy rays, and then transferring the ink to a print medium.
An ink jet recording method, wherein the first or second ejection ink color is yellow, orange, red, magenta, green, or light ink. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
In an ink jet recording method for ejecting at least three colors of ink onto an intermediate transfer medium, irradiating the intermediate transfer medium with active energy rays, and then transferring the ink to a print medium.
2. An ink jet recording method, wherein the second and subsequent colors are black, cyan, or blue. An inkjet ink recording method comprising at least a polymer compound having water and a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiation with active energy rays,
In an ink jet recording method for ejecting at least four colors of ink onto an intermediate transfer medium, irradiating active energy rays on the intermediate transfer medium, and then transferring the ink to a printing medium.
An ink jet recording method, wherein the ejection ink colors are in the order of magenta, yellow, cyan, and black. The ink jet recording method according to any one of claims 5 to 7, wherein the amount of energy applied by the active energy ray is 400 mJ / cm ² or less. After ejecting at least three colors of ink onto the printing medium and irradiating with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium and irradiating the formed ink image with active energy rays, In an inkjet ink used for inkjet recording to be transferred to a printing medium,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. An ink jet ink, wherein the concentration of the polymerization initiator contained in the ink ejected earlier is higher than the concentration of the polymerization initiator contained in the ink ejected later. An inkjet recording method using the inkjet ink according to claim 9. After ejecting at least three colors of ink onto the printing medium and irradiating with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium and irradiating the formed ink image with active energy rays, In an inkjet ink used for inkjet recording to be transferred to a printing medium,
The ink has water and a plurality of side chains in the hydrophilic main chain, and contains at least a polymer compound that can be cross-linked between the side chains by irradiating active energy rays. An ink jet ink, wherein the ratio of the crosslinkable polymer compound contained in the ink is higher than the ratio of the crosslinkable polymer compound contained in the ink ejected later. An inkjet recording method using the inkjet ink according to claim 11. After ejecting at least three colors of ink onto the printing medium and irradiating with active energy rays, or after ejecting at least three colors of ink onto the intermediate transfer medium and irradiating the formed ink image with active energy rays, In an inkjet ink used for inkjet recording to be transferred to a printing medium,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. The overlap of the absorption spectrum of the polymerization initiator contained in the previously ejected ink and the emission spectrum of the active energy ray is the overlap of the absorption spectrum of the polymerization initiator contained in the ink ejected later and the emission spectrum of the active energy ray. An ink-jet ink characterized by being larger. An ink jet recording method using the ink jet ink according to claim 13. Used in an ink jet recording method in which at least three colors of ink jet ink are ejected onto an intermediate transfer medium, an ink image formed on the intermediate transfer medium is transferred to a print medium, and then the transferred ink image is irradiated with active energy rays. Ink jet ink,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. An ink-jet ink, wherein the concentration of the polymerization initiator contained in the ink ejected earlier is lower than the concentration of the polymerization initiator contained in the ink ejected later. An inkjet recording method using the inkjet ink according to claim 15. Used in an ink jet recording method in which at least three colors of ink jet ink are ejected onto an intermediate transfer medium, an ink image formed on the intermediate transfer medium is transferred to a print medium, and then the transferred ink image is irradiated with active energy rays. Ink jet ink,
The ink has water and a plurality of side chains in the hydrophilic main chain, and contains at least a polymer compound that can be cross-linked between the side chains by irradiating active energy rays. An ink-jet ink, wherein the ratio of the crosslinkable polymer compound contained in the ink is lower than the ratio of the crosslinkable polymer compound contained in the ink ejected later. An inkjet recording method using the inkjet ink according to claim 17. Used in an ink jet recording method in which at least three colors of ink jet ink are ejected onto an intermediate transfer medium, an ink image formed on the intermediate transfer medium is transferred to a print medium, and then the transferred ink image is irradiated with active energy rays. Ink jet ink,
The ink contains water, a polymerization initiator, and a polymer compound having a plurality of side chains in the hydrophilic main chain and capable of crosslinking between the side chains by irradiation with active energy rays. The overlap of the absorption spectrum of the polymerization initiator contained in the previously ejected ink and the emission spectrum of the active energy ray is the overlap of the absorption spectrum of the polymerization initiator contained in the ink ejected later and the emission spectrum of the active energy ray. Ink-jet ink characterized by being smaller. An ink jet recording method using the ink jet ink according to claim 19. The inkjet recording method according to any one of claims 1 to 8, 10, 12, 14, 16, 18, and 20.
The printing medium or the intermediate transfer body is transparent, and after the ejection ink image is applied on the printing medium or the intermediate transfer body, active energy rays are emitted from the opposite side of the side having the ejection ink image. Irradiating, an inkjet recording method.

Images