JP5697625B2 - Radiation curable inkjet ink set and inkjet recording method - Google Patents

Description

  The present invention relates to a radiation curable inkjet ink set and an inkjet recording method.

  An ink jet system that ejects an ink composition as droplets from an ink ejection port is small and inexpensive, and is used in many printers because it can form an image without contact with a recording medium. Among these ink jet methods, the piezoelectric ink jet method that ejects ink using deformation of a piezoelectric element, and the thermal ink jet method that ejects ink composition droplets by utilizing the boiling phenomenon of the ink composition due to thermal energy are high. It has the characteristics of excellent resolution and high-speed printability.

In recent years, not only photo printing and document printing for home use or office use, but also commercial printing and industrial printing using an ink jet printer have been developed. In particular, the demand for wide-format inkjet printers suitable for printing large format advertisements attached to walls such as show windows and buildings has grown rapidly. Large format advertisements are often used outdoors, and long-term weather resistance is required. As a base material, such as polyvinyl chloride, and pigments have excellent weather resistance (light, rain, wind). In addition, azo skeleton pigments (mainly for yellow), quinacridone pigments (mainly for magenta), copper phthalocyanine pigments (mainly for cyan), and carbon black (mainly for black) are widely used.
In addition, for full-color printing, an ink jet ink set is used that combines four colors including the three primary colors of yellow, magenta, and cyan, and the black ink.

Examples of conventional ink compositions include Patent Documents 1 to 3.
Patent Document 1 discloses C.I. I. An aqueous magenta ink composition containing a solid solution of PV19 and PR202 is disclosed. Patent Document 2 discloses a disazo pigment, and PR48: 4 is included in many organic red pigments described. U.S. Patent No. 6,057,017 discloses a number of organic pigments including PR48: 4 and PR122.

JP 2009-197093 A Special table 2007-514804 gazette JP 2008-208189 A

In recent years, inkjet printing has come to be used not only for outdoor use, but also for indoor printed materials that are installed in stores, station buildings, etc., and are mainly used indoors.
The present inventor has found that ink sets used for indoor printing are required to have characteristics different from outdoor advertisements. In other words, radiation curable inkjet ink sets used mainly for printed materials used indoors have a wider color reproduction range and graininess than conventional products because the observation distance between the observer and the printed material is close indoors. No high image quality is required.

  The problem to be solved by the present invention is a radiation curable inkjet ink set that has a sufficiently wide color reproduction range, in particular, a wide color reproduction range of pink and red, and can reproduce a high-quality color image without graininess, and An ink jet recording method using the ink set is provided.

Said subject was achieved by the means as described in <1> or <11> below. They are listed below together with <2> to <10> which are preferred embodiments.
<1> a first magenta ink containing P1 (mass%) of a radiation curable compound and a first red pigment that is a mixed crystal pigment of PR122 and / or PV19 and PR202; and , A radiation curable compound, and a second magenta ink containing P2 (mass%) of a second red pigment that is PR48: 4 and / or PV19, and P1 and P2 are the following: A radiation curable inkjet ink set, characterized by satisfying the relational expression (1):
20 ≧ (P1 / P2) ≧ 1.2 (1)
<2> The radiation curable inkjet ink set according to <1>, wherein the first red pigment is a mixed crystal pigment of PV19 and PR202.
<3> The radiation curable inkjet ink set according to <1> or <2>, wherein the second red pigment is PR48: 4.
<4> The first magenta ink contains a polymer dispersant, the polymer dispersant has a molecular weight of 20,000 to 80,000, and an amine value of 10 to 30 mgKOH / g. <1> to the radiation curable inkjet ink set according to any one of <3>,
<5> The second magenta ink contains a polymer dispersant, the polymer dispersant has a molecular weight of 20,000 to 80,000, and an amine value of 35 to 45 mgKOH / g. <1> to the radiation curable inkjet ink set according to any one of <4>,
<6> Any one of <1> to <5>, further containing a yellow ink, wherein the yellow ink contains a polymer dispersant, and the glass transition temperature Tg of the polymer dispersant is 25 ° C. or lower. Radiation curable inkjet ink set according to
<7> In the first magenta ink, the concentration D1 (mass%) of the polymer dispersant and the concentration P1 (mass%) of the first red pigment satisfy the following relational expression (2): 4>, a radiation curable inkjet ink set,
0.6 ≧ (D1 / P1) ≧ 0.4 (2)
<8> In the second magenta ink, the concentration D2 (% by mass) of the polymer dispersant and the concentration P2 (% by mass) of the second red pigment satisfy the following relational expression (3): 5>, a radiation curable inkjet ink set,
0.7 ≧ (D2 / P2) ≧ 0.4 (3)
<9> The first magenta ink and the second magenta ink both contain the bifunctional monomer in an amount of 40% by mass or more based on the total amount of each ink, according to any one of <1> to <8>. Radiation curable inkjet ink set,
<10> Both the first magenta ink and the second magenta ink contain 6 to 25% by mass of phenoxyethyl acrylate and / or cyclic trimethylolpropane formal acrylate (CTFA) based on the total amount of each ink. <1> to <9>, the radiation curable inkjet ink set according to any one of
<11> The first magenta ink and / or the second magenta ink contained in the radiation curable inkjet ink set described in any one of <1> to <10> is recorded on the recording medium from the inkjet recording head. And a curing step of curing the first magenta ink and / or the second magenta ink by irradiating the discharged first and / or second magenta ink with active radiation. An ink jet recording method.
The above-mentioned “PR122” is C.I. I. Pigment Red 122, “PV19” is C.I. I. This means the pigment bailet 19, and so on.

In the present invention, embodiments described in the following <12> to <17> are also preferable.
<12> The radiation according to any one of <1> to <10>, wherein the first magenta ink contains 3 to 6% by mass of a mixed crystal pigment of PR122 and / or PV19 and PR202. Curable inkjet ink set,
<13> The first magenta ink and the second magenta ink are both 1,6-hexanediol diacrylate (HDDA), 1,9-nonanediol diacrylate (NDDA), dipropylene glycol diacrylate (DPGDA), Contains one or more bifunctional monomers selected from the group consisting of neopentyl glycol diacrylate (NPGPODA) and tripropylene glycol diacrylate (TPGDA), and the total of the bifunctional monomers is 40 mass with respect to the total amount of each color ink. % Or more of the radiation curable inkjet ink set according to any one of <1> to <8>, <12>,
<14> Both the first magenta ink and the second magenta ink are from phenoxyethyl acrylate (PEA), octadecyl acrylate (ODA), isodecyl acrylate (IDA), and cyclic trimethylolpropane formal acrylate (CTFA). <1> to <8> containing at least one monofunctional monomer selected from the group consisting of 5 to 30% by mass based on the total of the bifunctional monomers in each color ink. <12>, <13> The radiation curable inkjet ink set according to any one of <13>,
<15> The radiation-curable inkjet ink set according to <13> or <14>, containing DPGDA and / or TPGDA as a bifunctional monomer, and further containing PEA and / or CTFA as a monofunctional monomer,
<16> The first magenta ink and the second magenta ink each further contain 0.1 to 3% by mass of a polysiloxane surfactant, <1> to <10>, <12> to <15 > The radiation curable inkjet ink set according to any one of
<17> The radiation curable inkjet ink set according to <1> to <10>, <12> to <16>, further comprising at least one cyan ink and at least one gray or black ink.
<18> The ink set according to any one of <1> to <10> and <12> to <17>, which is for corrugated board printing.
<19> The inkjet recording method according to <11>, wherein the recording medium is cardboard.

  According to the present invention, it is possible to provide a radiation curable ink jet ink set and an ink jet recording method that can record a high-quality color image having excellent saturation and a wide color reproduction range and no graininess.

Hereinafter, the present invention will be described in detail.
In the specification, the description of “lower limit to upper limit” represents “more than the lower limit and less than the upper limit”, and the description of “upper limit to lower limit” represents “the upper limit and less than the lower limit”. That is, it represents a numerical range including an upper limit and a lower limit.
Further, “parts by mass” and “% by mass” are synonymous with “parts by weight” and “% by weight”, respectively.

The radiation curable inkjet ink set of the present invention contains P1 (mass%) of a radiation curable compound and a first red pigment that is a mixed crystal pigment of PR122 and / or PV19 and PR202. A first magenta ink, a radiation curable compound, and a second magenta ink containing P2 (mass%) of a second red pigment that is PR48: 4 and / or PV19, And P1 and P2 satisfy the following relational expression (1).
20 ≧ (P1 / P2) ≧ 1.2 (1)
Hereinafter, for the sake of convenience, the “radiation curable inkjet ink set” is also simply referred to as “ink set”.

(1) Radiation curable inkjet ink set In the present invention, “ink” means “ink composition”, which contains a radiation curable compound as an essential component in addition to a color pigment, The first magenta ink contains PR122, which is a red pigment, and / or a mixed crystal pigment of PV19 and PR202, and the second magenta ink is PR48: 4, which is also a red pigment, and / or Contains PV19.
The ink set of the present invention may contain other primary color inks of a subtractive color method of yellow and cyan, and may further contain an achromatic black ink. Furthermore, a so-called special color ink such as green can be included as an optional component.
In the ink set of the present invention, the first and second magenta inks have radiation curability and are suitably used as an ink composition for ink jet recording.

In the ink set of the present invention, the first and second magenta inks are radiation-curable ink compositions that can be cured by radiation, and are oil-based ink compositions.
The term “radiation” as used in the present invention is not particularly limited as long as it is an actinic radiation that can impart energy capable of generating a starting species in the ink by the irradiation, and widely includes α rays, γ rays, X Among them, ultraviolet rays and electron beams are preferable, and ultraviolet rays and electron beams are more preferable, and ultraviolet rays are more preferable. Therefore, each color ink in the ink set of the present invention is preferably an ink composition that can be cured by irradiating ultraviolet rays as radiation.
In the present invention, the term “(meth) acrylate” is used when referring to both “acrylate” and “methacrylate”, and the term “(meth) acrylate” is used when referring to both “acrylic” and “methacrylic”. Also described as “meth) acryl”.

(First and second magenta inks; first and second red pigments)
The radiation curable inkjet ink set according to the present invention contains a first magenta ink and a second magenta ink. Here, the first magenta ink is a normal ink having a normal pigment concentration, in other words, a dark color ink. In the embodiment, it is also simply referred to as “magenta ink”.
The second magenta ink is a light-colored ink having a pigment concentration lower than that of the first magenta ink, and is also referred to as “light magenta” in the embodiments.
The first magenta ink is C.I. I. Pigment Red 122 (PR122) and / or a mixed crystal of PV19 and PR202 is contained as a color pigment. The total content in the ink is a density necessary for full color reproduction.
The second magenta ink that is a light color ink contains PR48: 4 and / or a second red pigment that is PV19 as a color pigment. The total content in the ink is sufficient to reproduce an intermediate density of red.

By using an ink set in which specific dark and light magenta inks are combined as described above, printing excellent in color reproduction from the red to purple region can be performed. In particular, it has been difficult to achieve with conventional techniques, and it is possible to achieve both clear and light pink (L value around 60, hue angle around 45 degrees) and vivid dark red purple (L value around 40, hue angle around 340 degrees). It becomes possible.
The first red pigment is selected from PR122, or a mixed crystal pigment of PV19 and PR202, and the latter is particularly preferable for realizing a bright dark reddish purple.
The second red pigment is selected from PR48: 4 or PV19, but the former is preferable because a wider color gamut can be realized.
In the ink set of the present invention, a combination in which the magenta ink color pigment is a mixed crystal of PV19 and PR202 and the light magenta color pigment is PR48: 4 is preferable because a wider color reproduction range can be realized.

  In the present invention, “mixed crystal of PV19 and PR202” means a minimum unit molecule constituting PV19 (left; quinacridone (trans)) and a minimum unit molecule constituting PV202 crystal (right; 2, 9 -A crystal of a pigment constituting a crystal lattice with both molecules of (dichloroquinacridone).

When the content of the first red pigment in the first magenta ink is P1 (mass%) and the content of the second red pigment in the second magenta ink is P1 (mass%), The following relational expression holds.
20 ≧ (P1 / P2) ≧ 1.2 (1)
(P1 / P2) is preferably in the relationship (1 ′).
15 ≧ (P1 / P2) ≧ 5 (1 ′)

  The relationship P1 / P2 between the concentration P1 of the first red pigment in the first magenta ink containing the first red pigment and the concentration P2 of the second red pigment in the second magenta ink is 20 Exceeding this makes it difficult to achieve a sufficient color reproduction range expansion effect. The effect of expanding the color gamut increases as the value decreases from P1 / P2 of 20 or less. However, when P1 / P2 is less than 1.2, the effect is saturated, and conversely, the graininess tends to deteriorate. . In view of the above, 15 ≧ (P1 / P2) ≧ 5 is preferable, 15 ≧ (P1 / P2) ≧ 5.3 is more preferable, and 10 ≧ (P1 / P2) ≧ 6 is particularly preferable.

The first magenta ink, which is a normal ink, preferably contains a mixed crystal of PR122 and / or PV19 and PR202, which is a total amount of 3 to 5% by mass of the first red pigment in the ink. It is more preferable to contain 0.0-5.0 mass%.
The second magenta ink, which is a light color ink, preferably has a total content of PR48: 4 and / or PV19 in the ink of preferably 0.2 to 4 mass%, more preferably 0.4 to 1.0 mass%. contains.

The first magenta ink contains PR122 which is the first red pigment (dark red pigment) and / or a mixed crystal of PV19 and PR202 of 80% by mass or more of the total amount of the first red pigment. Is preferable, it is more preferable to contain 90 mass% or more, and it is especially preferable to contain 99 mass% or more.
The second magenta ink may contain PR48: 4 and / or PV19, which is the second red pigment (light red pigment), of 80% by mass or more of the total amount of red pigment in the second magenta ink. The content is preferably 90% by mass or more, and more preferably 99% by mass or more.

The red pigment used as an essential pigment for the first and second magenta inks has a particle size distribution in which _DV90 measured by a laser diffraction method is 0.1 μm or more and 0.35 μm or less as a particle size after dispersion. Varieties from which a dispersion can be obtained can be suitably used. With this particle size distribution, the ink jet discharge stability is excellent, and the fluidity is good within the above pigment concentration range.
Here, the dispersion is due to medium dispersion using zirconia beads described in the Examples, and the laser diffraction method follows a conventional method.

An example of a commercial product of PR122 is CROMOPHTAL PINK PT (CI Pigment Red 122, PR122, manufactured by BASF).
An example of a mixed crystal of PV19 and PR202 is CINQUASIA RT355D (a mixed crystal of CI Pigment Violet 19 and CI Pigment Red 202, PV19 / PR202, manufactured by BASF).
As commercial products of PR48: 4, Irgalite Red FBL (manufactured by BASF), Novoperm Red 5BLS (manufactured by Clariant), and Novoperm Red BLS 02 (manufactured by Clariant) can be preferably used.
As a commercially available product of PV19, HOSTAPER INKJET E5B02 (CI Pigment Violet 19, PV19, manufactured by Clariant) can be exemplified.

PR122, a mixed crystal of PV19 and PR202, PR48: 4, or PV19 is dispersion D _V90 which were all measured by the laser diffraction method as the particle size has a 0.35μm following particle size distribution than 0.15μm is obtained The variety which can be used can be used suitably. With this particle size distribution, the ink jet discharge stability is excellent, and the fluidity is good within the above pigment concentration range.

  Examples of the red or magenta pigment that may be used as a minor component in the first or second magenta ink used in the present invention include the following pigments. In the present invention, the content of these combined red pigments is preferably less than 20% by mass, more preferably less than 10% by mass, still more preferably less than 1% by mass, and no content at all. Is particularly preferred.

C. As a thing which exhibits red or magenta color, C.I. I. Monoazo pigments such as CI Pigment Red 3 (Toluidine Red, etc.); I. Disazo pigments such as C.I. Pigment Red 38 (Pyrazolone Red B, etc.); I. Pigment Red 53: 1 (Lake Red C, etc.) and C.I. I. Azo lake pigments such as C.I. Pigment Red 57: 1 (Brilliant Carmine 6B); I. Condensed azo pigments such as C.I. Pigment Red 144 (condensed azo red BR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Red 174 (Phloxine B Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Red 81 (Rhodamine 6G ′ Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Red 177 (eg, dianthraquinonyl red); I. Thioindigo pigments such as C.I. Pigment Red 88 (Thioindigo Bordeaux, etc.); I. Perinone pigments such as C.I. Pigment Red 194 (perinone red, etc.); I. Perylene pigments such as C.I. Pigment Red 149 (perylene scarlet, etc.); I. Pigment violet 19 (unsubstituted quinacridone), C.I. I. Quinacridone pigments such as CI Pigment Red 122 (quinacridone magenta, etc.); I. Isoindolinone pigments such as CI Pigment Red 180 (isoindolinone red 2BLT, etc.); I. And alizarin lake pigments such as CI Pigment Red 83 (Mada Lake, etc.).
In the present invention, when these other pigments are used in addition to the essential red pigment, the content thereof is preferably less than 20% by mass, more preferably less than 10% by mass, and more preferably 1% by mass. % Is more preferable, and it is particularly preferable not to contain at all.

(Ink of other hues used in the ink set)
Specific examples of organic pigments and inorganic pigments having hues other than magenta in the present invention will be described.

  When the ink set of the present invention is used for full-color printing, it is preferable to use a yellow ink, a cyan ink, and a black ink in addition to the first magenta ink and the second magenta ink. For the cyan ink and black ink, the pigments exemplified below can be used.

(Yellow pigment)
As a pigment exhibiting a yellow color, C.I. I. Pigment yellow 185, C.I. I. Pigment Yellow 1 (Fast Yellow G etc.), C.I. I. A monoazo pigment such as C.I. Pigment Yellow 74; I. Pigment Yellow 12 (disaji yellow AAA, etc.), C.I. I. Disazo pigments such as C.I. Pigment Yellow 17; I. Non-benzidine type azo pigments such as CI Pigment Yellow 180; I. Azo lake pigments such as C.I. Pigment Yellow 100 (eg Tartrazine Yellow Lake); I. Condensed azo pigments such as CI Pigment Yellow 95 (Condensed Azo Yellow GR, etc.); I. Acidic dye lake pigments such as C.I. Pigment Yellow 115 (such as quinoline yellow lake); I. Basic dye lake pigments such as CI Pigment Yellow 18 (Thioflavin Lake, etc.), anthraquinone pigments such as Flavantron Yellow (Y-24), isoindolinone pigments such as Isoindolinone Yellow 3RLT (Y-110), and quinophthalone yellow Quinophthalone pigments such as (Y-138), isoindoline pigments such as isoindoline yellow (Y-139), C.I. I. Nitroso pigments such as C.I. Pigment Yellow 153 (nickel nitroso yellow, etc.); I. Examples thereof include metal complex azomethine pigments such as CI Pigment Yellow 117 (copper azomethine yellow and the like).

(Cyan pigment)
As a pigment exhibiting blue or cyan, C.I. I. Disazo pigments such as C.I. Pigment Blue 25 (Dianisidine Blue, etc.); I. Pigment blue 15 or C.I. I. Phthalocyanine pigments such as C.I. Pigment Blue 15: 4 (phthalocyanine blue, etc.); I. Acidic dye lake pigments such as C.I. Pigment Blue 24 (Peacock Blue Lake, etc.); I. Basic dye lake pigments such as C.I. Pigment Blue 1 (Viclotia Pure Blue BO Lake, etc.); I. Anthraquinone pigments such as C.I. Pigment Blue 60 (Indantron Blue, etc.); I. And alkali blue pigments such as CI Pigment Blue 18 (Alkali Blue V-5: 1).

(Black pigment)
Examples of the pigment exhibiting black (black) include carbon black, titanium black, and aniline black, and carbon black is preferable.

  The ink set of the present invention can be used by selecting inks of other hues from the following groups according to the purpose of use. That is, the inks of other hues are preferably composed of two types of magenta ink, yellow ink, cyan ink, and black ink, and may be five types with white ink added. . Further, the cyan ink may be a combination of normal and dark cyan inks. A combination of dark and light inks in which light gray is added to black may be used.

  In addition, in the ink set of the present invention, so-called special color inks of green, violet, and orange may be used as the colored ink, in addition to the three primary color inks based on the color reduction methods of yellow, magenta, and cyan, as necessary.

As a pigment exhibiting a green color, C.I. I. Pigment green 7 (phthalocyanine green), C.I. I. Phthalocyanine pigments such as C.I. Pigment Green 36 (phthalocyanine green); I. And azo metal complex pigments such as CI Pigment Green 8 (Nitroso Green).
As a pigment exhibiting violet, C.I. I. And CI Pigment Violet 19 (unsubstituted quinacridone).
As a pigment exhibiting an orange color, C.I. I. An isoindoline pigment such as C.I. Pigment Orange 66 (isoindoline orange); I. And anthraquinone pigments such as CI Pigment Orange 51 (dichloropyrantron orange).

<Polymer dispersant>
(First magenta ink)
In the ink set of the present invention, it is preferable that the first magenta ink and the second magenta ink each further contain a polymer dispersant. These polymer dispersants will be described below.
Here, the polymer dispersant refers to a polymer having a weight average molecular weight of 1,000 or more, a basic group, and a red pigment dispersion aid.
Examples of the polymer include a random copolymer, a block copolymer, and a graft copolymer. Examples of the basic group include amino groups, imino groups, amide groups, imide groups, and nitrogen-containing heterocyclic groups. The polymer dispersant may have the basic group in the main chain in the polymer dispersant, in the side chain, or in both of them.
The amine value of the polymer dispersant is measured by the following procedure. The dispersant was dissolved in methyl isobutyl ketone, potentiometric titration was performed with a 0.01 mol / L methyl isobutyl ketone perchlorate solution, and the value converted to mg KOH / g was used as the amine value. The potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.

(First magenta ink polymer dispersant)
The first magenta ink preferably further contains a polymer dispersant having a molecular weight of 20,000 to 80,000 and an amine value of 10 to 30 mgKOH / g.
By using a dispersant having the above physical properties, good fluidity during and after pigment dispersion and excellent long-term ink storage stability can be obtained.
In order to maintain fluidity during dispersion, the concentration D1 of the polymer dispersant and the concentration P1 of the first red pigment in the first magenta ink are 0.6 ≧ (D1 / P1) ≧ 0. .4 is preferable.

  In order to obtain a wide color reproduction range, the glass transition temperature of the dispersant is preferably 25 ° C. or lower, and particularly preferably the melting point of the dispersant is 25 ° C. or lower. The effect of the glass transition temperature / melting point of the dispersant on the color reproducibility is estimated as follows. In order to obtain a wider color gamut, it is preferable that the ejected ink droplet spread as much as possible on the already deposited / cured ink film. A high concentration of dispersant is concentrated on the surface of the ink droplet that has been deposited / cured (based on cutting TOFSIMS analysis), and the dispersant at room temperature (around 25 ° C.) has fluidity (glass transition temperature). Is 25 ° C. or lower), it is estimated that the ink droplet spreads more widely.

  In addition, a glass transition temperature (Tg) can be calculated | required from the main body maximum peak measured using the differential scanning calorimeter (Perkin-Elmer company make: DSC-7) based on ASTMD3418-8. The temperature correction of the detection part of this apparatus (DSC-7) uses the melting point of indium and zinc, and the correction of heat quantity uses the heat of fusion of indium. The sample used was an aluminum pan, and an empty pan was set as a control. The temperature was raised at a rate of 10 ° C / min, held at 150 ° C for 5 minutes, cooled from 150 ° C to 0 ° C at -10 ° C / min using liquid nitrogen, held at 0 ° C for 5 minutes, and again 0 It is obtained based on the onset temperature analyzed from the endothermic curve at the second temperature increase obtained by increasing the temperature from 10 ° C. to 150 ° C. at 10 ° C./min.

Dispersants having the physical properties as described above are commercially available products, such as Ajinomoto Fine Techno Co., Ltd. (Ajisper series), Evonik (TEGODispers series), BYK (DISPERBYK series, BYK series), BASF (EFKA series), It can be obtained from Lubrizol (Solsperse series). Since the amine value may vary depending on the pigment production lot, it is preferable to use it after confirming that the amine value is in the desired range.
The basic polymer dispersant is synthesized by a method known to those skilled in the art, in addition to being obtained as a commercial product.

  Commercially available products that can be used as a polymer dispersant for the first magenta ink, in particular, as a polymer dispersant for PV19 / PR202, EFKA7731 (amine value 25.1 mgKOH / g, Tg of 25 ° C. or less) manufactured by BASF, Lubrizol SOLSPERSE 32000 (amine value 10.3 mgKOH / g) manufactured by KK and Ajisper PB-821 (amine value 10.3 mgKOH / g) manufactured by Ajinomoto Fine Techno Co. can be preferably exemplified.

(Secondary magenta ink polymer dispersant)
In the present invention, a polymer dispersant that can be preferably used for dispersing the second red pigment will be described. When PR48: 4 is used as the second red pigment, the fluidity of the pigment dispersion (mill base) may be deteriorated. To prevent this, the amine value of the polymer dispersant is 35 to 45 mgKOH. / G is preferable. Moreover, it is preferable that molecular weight is 20,000-80,000 from the same viewpoint. In order to maintain fluidity during dispersion, it is preferable that the concentration D2 of the polymer dispersant and the total amount concentration P2 of the second red pigment are 0.7 ≧ D2 / P2 ≧ 0.4.
In order to obtain a wider color gamut, the glass transition temperature of the dispersant is preferably 25 ° C. or lower, and particularly preferably the melting point of the dispersant is 25 ° C. or lower. The effect of the glass transition temperature / melting point of the dispersant on the color reproducibility is estimated as follows. In order to obtain a wider color gamut, it is preferable that the ejected ink droplet spread as much as possible on the already deposited / cured ink film. The surface layer of the droplet ejection / cured ink film is concentrated with a high concentration of dispersant (based on cutting TOFSIMS analysis), and has fluidity of the dispersant at room temperature (around 25 ° C.) (glass transition temperature). Is 25 ° C. or lower), the ink droplets are further spread.

The basic polymer dispersant is preferably an acrylic polymer, more preferably a random copolymer, and still more preferably an acrylic graft copolymer.
The above basic polymer dispersant can also be synthesized by methods known to those skilled in the art.

Dispersants having the physical properties described above are commercially available from Ajinomoto Fine Techno Co., Ltd., Evonik (TEGODispers series), BYK (DISPERBYK series, BYK series), BASF (EFKA series), Lubrizol (Solsperse series). ) Etc. Since the amine value may vary depending on the pigment production lot, it is preferably used after confirming that the amine value is in the desired range.
In the second magenta ink, commercially available polymer dispersants that are preferably used particularly for PR48: 4 are exemplified below.
This polymer dispersant includes EFKA7701 manufactured by BASF (amine value 40.0 mgKOH / g, Tg25 ° C. or lower), TEGODISPER685 (amine value 37.4 mgKOH / g, Tg25 ° C or lower) manufactured by Evonik, and BYK manufactured by BYK. DISPERBYK168 (amine value 33.2 mgKOH / g, Tg25 ° C. or higher) is included.

(Radiation curable compounds)
Both the first and second magenta inks included in the ink set of the present invention are radiation curable. Both inks contain a radiation curable compound in order to have radiation curable properties. Even when yellow ink, cyan ink and / or black ink are used in combination with both inks, these inks preferably have radiation curability.
Both the first and second magenta inks can contain cationically polymerizable cyclic ethers (epoxy compounds, oxetane compounds, etc.) as radiation curable compounds, preferably radically polymerizable ethylenically unsaturated compounds. Containing. As the ethylenically unsaturated compound, it is preferable to use a monofunctional monomer having only one ethylenically unsaturated group in the molecule and a bifunctional monomer having two ethylenically unsaturated groups in the molecule. In addition, a polyfunctional monomer containing three or more ethylenically unsaturated groups in the molecule may be used in combination as appropriate.

<Bifunctional monomer>
The inventor has found that the first and second magenta inks included in the ink set of the present invention contain a predetermined amount of a bifunctional monomer selected from a specific compound group. It has been found preferable to obtain ink jet suitability and excellent cured film strength.
In indoor printing in which the ink set of the present invention can be suitably used, it is preferable that the cured film has little odor. One of the causes of odor is a monomer remaining in the cured film. Therefore, it is preferable to select from the above-mentioned specific polymerizable monomer group having low residual monomer volatility and high molecular weight.
That is, both the first and second magenta inks were 1,6-hexanediol diacrylate (HDDA), 1,9-nonanediol diacrylate (NDDA), dipropylene glycol diacrylate (DPGDA), neopentyl glycol diester. Contains at least one bifunctional monomer selected from the group consisting of acrylate (NPGPODA) and tripropylene glycol diacrylate (TPGDA), and the total of the bifunctional monomers is 40% by mass or more based on the total amount of each color ink. It is preferably 40 to 80% by mass, particularly preferably 45 to 70% by mass.
The bifunctional monomers contained in the first and second magenta inks may be the same or different, but are preferably the same.
In the ink set of the present invention, it is preferable that both the first and second magenta inks are substantially free of a bifunctional monomer other than the specific bifunctional monomer. Here, “substantially” means 10% by mass or less of the total bifunctional monomer, and preferably 1% by mass or less.

  In the present invention, the first and second magenta inks more preferably contain DPGDA and / or TPGDA as a bifunctional monomer, and particularly preferably contain DPGDA and TPGDA.

<Monofunctional monomer>
The present inventor obtains the storage stability of the cured ink that the first and second magenta inks included in the ink set of the present invention contain a predetermined amount of a monofunctional monomer selected from a specific compound group. The present inventor has found that this is preferable. That is, both the first and second magenta inks are selected from the group consisting of phenoxyethyl acrylate (PEA), octadecyl acrylate (ODA), isodecyl acrylate (IDA), and cyclic trimethylolpropane formal acrylate (CTFA). It is preferable that at least one monofunctional monomer is contained, and the total of the monofunctional monomers is 5 to 30% by mass with respect to the total of the bifunctional monomers in each color ink. The content of the monofunctional monomer is preferably 6 to 25% by mass and more preferably 10 to 20% by mass with respect to the total amount of the ink composition.
As a monofunctional monomer, it is more preferable to contain PEA and / or CTFA, and it is still more preferable to contain PEA and CTFA.
In addition, since PEA has a low viscosity, it is preferably used as a dispersion medium when dispersing the pigment.
Each color ink used in the ink set of the present invention is preferably a solventless ink that does not contain a volatile solvent.
In the ink set of the present invention, it is preferable that both the first magenta ink and the second magenta ink are substantially free of monofunctional monomers other than the above-described four specific monofunctional monomers. Here, “substantially free” means 10% by mass or less of the total monofunctional monomer, and preferably 1% by mass or less.

In the ink composition included in the ink set of the present invention, the difunctional monomer preferably contains dipropylene glycol diacrylate (DPGDA) and / or tripropylene glycol diacrylate (TPGDA).
More preferably, DPGDA and / or TPGDA are contained as the bifunctional monomer, and PEA and / or CTFA are further contained as the monofunctional monomer. It is particularly preferable that DPGDA and TPGDA are contained as the bifunctional monomer, and that PEA and CTFA are further contained as the monofunctional monomer.

  In the following description, when referring to “acrylate” and / or “methacrylate”, “(meth) acrylate” and when referring to “acryloxy” and / or “methacryloxy”, “(meth) acryloxy” , Respectively.

  In the present invention, monofunctional ethylenically unsaturated compounds that can be used in combination include 2- (2-ethoxyethoxy) ethyl (meth) acrylate, norbornyl (meth) acrylate, and isobornyl (meth) acrylate as monofunctional (meth) acrylate compounds. ) Acrylate, isophoryl (meth) acrylate, 3,3,5-trimethylcyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, carbitol (meth) ) Acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, benzyl (meth) acrylate, methyl (meth) acrylate, n-butyl (meth) acrylate, decyl (meth) acrylate Lauryl (meth) acrylate, allyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminomethyl (meth) acrylate, and the like.

  In the present invention, polyfunctional ethylenically unsaturated compounds that can be used in combination include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate. , Polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tetrapropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol (meth) acrylate , Ethoxylated neopentyl glycol diacrylate, propoxylated neopentyl glycol diacrylate, pentaerythritol tri (meth) acrylate Pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, trimethylolethane tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, bis (4- (meta ) Acryloxypolyethoxyphenyl) propane, oligoester (meth) acrylate, 2,2-bis (4- (meth) acryloxypolyethoxyphenyl) propane can be preferably exemplified.

More specifically, Shinzo Yamashita “Cross-linking agent handbook” (1981, Taiseisha); Kato Kiyosumi “UV / EB curing handbook (raw material)” (1985, Polymer publication society); Ed. “Application and Market of UV / EB Curing Technology” on page 79 (1989, CMC Publishing Co., Ltd.); “Polyester Resin Handbook” by Eiichiro Takiyama (1988, Nikkan Kogyo Shimbun) Radical polymerizable or crosslinkable monomers, oligomers and polymers known in the industry can be used.
The molecular weight of the ethylenically unsaturated compound is preferably 80 to 2,000, more preferably 80 to 1,000, and still more preferably 80 to 800.

The ink composition of the present invention preferably contains an oligomer having an ethylenically unsaturated group. The ethylenically unsaturated group is preferably a radically polymerizable ethylenically unsaturated group, and more preferably a (meth) acryloxy group.
Examples of the oligomer having an ethylenically unsaturated group include a radical polymerizable group, an olefin type (ethylene oligomer, propylene oligomer butene oligomer, etc.), a vinyl type (styrene oligomer, vinyl alcohol oligomer, vinyl pyrrolidone oligomer acrylate oligomer, Methacrylate oligomers, etc.), diene systems (butadiene oligomers, chloroprene rubber, pentadiene oligomers, etc.), ring-opening polymerization systems (di-, tri-, tetraethylene glycol, polyethylene glycol, polyethylimine, etc.), polyaddition systems (oligoester acrylate) , Polyamide oligomers, polyisocyanate oligomers), addition condensation oligomers (phenol resins, amino resins, xylene resins, ketone resins, etc.). In this, oligoester (meth) acrylate is preferable, in which urethane (meth) acrylate, polyester (meth) acrylate, and epoxy (meth) acrylate are more preferable, and urethane (meth) acrylate is still more preferable.
Preferred examples of the urethane (meth) acrylate include aliphatic urethane (meth) acrylates and aromatic urethane (meth) acrylates, and more preferred are aliphatic urethane (meth) acrylates.
The urethane (meth) acrylate is preferably a tetrafunctional or lower urethane (meth) acrylate, and more preferably a bifunctional or lower urethane (meth) acrylate.
By containing urethane (meth) acrylate, an ink composition having excellent adhesion to the substrate and excellent curability can be obtained.
Regarding the oligomer, the oligomer handbook (supervised by Junji Furukawa, Chemical Industry Daily Co., Ltd.) can also be referred to.

Moreover, what is shown below can be illustrated as a commercial item of an oligomer.
Examples of the urethane (meth) acrylate include R1204, R1211, R1213, R1217, R1218, R1301, R1302, R1303, R1304, R1306, R1308, R1901, and R1150 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. EBECRYL series (for example, EBECRYL230, 270, 4858, 8402, 8804, 8807, 8803, 9260, 1290, 1290K, 5129, 4842, 8210, 210, 4827, 6700, 4450, 220) manufactured by Co., Ltd. NK oligo U-4HA, U-6HA, U-15HA, U-108A, U200AX, etc. manufactured by Kogyo Co., Ltd., Aronix M-1100, M-1200, M-1210, M-1310 manufactured by Toagosei Co., Ltd. M-1600, M-1960, and the like.
Examples of the polyester (meth) acrylate include EBECRYL series (for example, EBECRYL770, IRR467, 81, 84, 83, 80, 675, 800, 810, 812, 1657, 1810, IRR302, 450, manufactured by Daicel Cytec Co., Ltd. 670, 830, 870, 1830, 1870, 2870, IRR267, 813, IRR483, 811, etc.), Aronix M-6100, M-6200, M-6250, M-6500, M-7100, manufactured by Toagosei Co., Ltd. , M-8030, M-8060, M-8100, M-8530, M-8560, M-9050 and the like.
Moreover, as an epoxy (meth) acrylate, for example, EBECRYL series (for example, EBECRYL600, 860, 2958, 3411, 3600, 3605, 3700, 3701, 3703, 3702, 3708, RDX63182, 6040, manufactured by Daicel Cytec Co., Ltd. Etc.).

The oligomer which has an ethylenically unsaturated group may be used individually by 1 type, or may use 2 or more types together.
As content of the oligomer which has an ethylenically unsaturated group in the ink composition of this invention, it is preferable that it is 0.1-50 mass% with respect to the total mass of an ink composition, and 0.5-20 mass %, More preferably 1 to 10% by mass.

  In the present invention, the total amount of the ethylenically unsaturated compound in the entire ink composition is preferably 50 to 95% by mass, and preferably 60 to 90% by mass, from the viewpoint of curability and adhesion. More preferably, it is more preferably 70 to 90% by mass.

(Polymerization initiator)
The first and second magenta inks included in the ink set of the present invention preferably contain a polymerization initiator.
A known polymerization initiator can be used as the polymerization initiator that can be used in the present invention.
The polymerization initiator that can be used in the present invention may be used alone or in combination of two or more. Moreover, although a cationic polymerization initiator and a radical polymerization initiator may be used together, it is preferable to contain at least a radical polymerization initiator.
The polymerization initiator that can be used in the present invention is a compound that absorbs external energy and generates a polymerization initiating species. External energy used for initiating polymerization is roughly divided into heat and actinic radiation, and a thermal polymerization initiator and a photopolymerization initiator are used, respectively. Examples of the active radiation include γ rays, β rays, electron beams, ultraviolet rays, visible rays, and infrared rays.

<Radical polymerization initiator>
There is no restriction | limiting in particular as a radical polymerization initiator which can be used by this invention, A well-known radical polymerization initiator can be used.
The radical polymerization initiator that can be used in the present invention includes (a) aromatic ketones, (b) acylphosphine compounds, (c) aromatic onium salt compounds, (d) organic peroxides, and (e) thio compounds. (F) hexaarylbiimidazole compound, (g) ketoxime ester compound, (h) borate compound, (i) azinium compound, (j) metallocene compound, (k) active ester compound, (l) carbon halogen bond And (m) an alkylamine compound. These radical polymerization initiators may use the above compounds (a) to (m) alone or in combination.
Among these, it is preferable to use (a) aromatic ketones and (b) acylphosphine compounds.

  Preferable examples of (a) aromatic ketones, (b) acylphosphine compounds, and (e) thio compounds are “RADIATION CURING IN POLYMER SCIENCE AND TECHNOLOGY”, J. P. FOUASSIER, J.F. Examples include compounds having a benzophenone skeleton or a thioxanthone skeleton described in 77-117. More preferable examples include α-thiobenzophenone compounds described in JP-B-47-6416, benzoin ether compounds described in JP-B-47-3981, α-substituted benzoin compounds described in JP-B-47-22326, Benzoin derivatives described in JP-B-47-23664, aroylphosphonic acid esters described in JP-A-57-30704, dialkoxybenzophenones described in JP-B-60-26483, JP-B-60-26403, JP-A Benzoin ethers described in JP-A-62-81345, JP-B-1-34242, US Pat. No. 4,318,791, α-aminobenzophenones described in European Patent 0284561A1, JP-A-2-21152 P-Di (dimethylaminobenzoyl) benze Thio-substituted aromatic ketones described in JP-A-61-194062, acylphosphine sulfides described in JP-B-2-9597, acylphosphines described in JP-B-2-9596, and JP-B-63-61950 Thioxanthones, and coumarins described in JP-B-59-42864.

  The ink contained in the ink set of the present invention preferably uses an acylphosphine compound and α-hydroxyacetophenone as radical polymerization initiators, and more preferably uses benzophenone together.

(Polysiloxane surfactant)
In the ink set of the present invention, it is preferable that the first magenta ink and the second magenta ink further contain a polysiloxane surfactant in an amount of 0.1% by mass to 3% by mass with respect to the total amount of the ink. . By using the above surfactants together, the surface tension of the ink is adjusted to provide appropriate wetting and overlapping of inks with different hues to the ink droplets deposited on the substrate used for printing. can do.
When the ink set of the present invention is used for indoor printing, particularly when a corrugated board is used as a base material, the surface of the corrugated cardboard is relatively poor in smoothness (there is unevenness), and the surface tension. Is low. Therefore, in order to obtain a uniform cured film, in addition to the first magenta ink and the second magenta ink, 0.1% by mass of a polysiloxane surfactant is further added to the yellow ink, the cyan ink, and the black ink. The content is preferably 3% by mass or less. Especially preferably, they are 1 mass% or more and 2 mass% or less.

The ink set of the present invention is preferably used for printing applications mainly used indoors, and is preferably used for printing on a corrugated board.
When printing on corrugated cardboard, flexibility (no cracking when bent) is required as a performance required for ink film physical properties. From the viewpoint of preventing cracking when the substrate is bent, the monofunctional monomer contains at least one monomer selected from the group consisting of PEA and CTFA, and the sum of the monomers is the sum of the bifunctional monomers. It is preferable that they are 5 mass% or more and 30 mass% or less.

(Inert methyl methacrylate homopolymer and / or copolymer)
The first magenta ink and the second magenta ink included in the ink set of the present invention preferably contain an inert methyl methacrylate homopolymer and / or copolymer. “Inert” means having no reactive ethylenically unsaturated group or the like.
When inks of other hues such as cyan ink and black ink are used in combination, these inks preferably also contain this inactive homopolymer and / or copolymer. By using this polymer in combination, the scratch resistance of the ink can be improved, and an ink excellent in ejection stability can be obtained.
The inert homopolymer and / or copolymer preferably has a weight average molecular weight of 4,000 to 120,000, and more preferably 8,000 to 80,000.
As a preferred homopolymer, a methyl methacrylate homopolymer (polymethyl methacrylate PMMA) can be exemplified.
Preferred examples of the copolymer include ELVACITE 2013: methyl methacrylate / n-butyl methacrylate copolymer (mass ratio 36/64, Mw: 37,000, manufactured by Lucite International).
The inert polymer is preferably added in a total amount of 0.3 to 4.0% by mass based on the total mass of the ink.

(Other ingredients)
The first magenta ink and the second magenta ink contained in the ink set of the present invention may include other surfactants, co-sensitizers, ultraviolet absorbers, and antioxidants as necessary, in addition to the above components. Agents, anti-fading agents, conductive salts, solvents, polymer compounds, basic compounds and the like. These are described in, for example, Japanese Patent Application Laid-Open No. 2009-22214 and can be used in the present invention.

Moreover, the ink composition in the ink set of the present invention preferably contains a polymerization inhibitor from the viewpoints of storage stability and suppression of head clogging.
The polymerization inhibitor is preferably added in an amount of 200 to 20,000 ppm based on the total amount of the ink composition.
Examples of the polymerization inhibitor include nitroso polymerization inhibitors, hindered amine polymerization inhibitors, hydroquinone, benzoquinone, p-methoxyphenol, TEMPO, TEMPOL, and cuperon Al.

(Ink properties)
In the first and second magenta inks contained in the ink set of the present invention, their viscosity and surface tension are preferably in a range suitable for ejection with an inkjet head mounted on the printer to be used. Assuming that it is used in a piezo-type inkjet head that is generally widely used, the viscosity is preferably 6 to 30 mPa · s (25 ° C.), and particularly preferably 15 to 25 mPa · s.
Moreover, it is preferable that the viscosity in discharge temperature (Preferably 25-80 degreeC, More preferably, 25-50 degreeC) is 3-15 mPa * s, and it is more preferable that it is 3-13 mPa * s. It is preferable that the composition ratio of the ink composition of the present invention is appropriately adjusted so that the viscosity is in the above range. By setting the viscosity at room temperature high, even when a porous recording medium (support) is used, the penetration of the ink composition into the recording medium can be avoided, and uncured monomers can be reduced. Become. Furthermore, ink bleeding at the time of landing of the ink composition droplets can be suppressed, and as a result, the image quality is improved, which is preferable.

  On the other hand, the surface tension at 25 ° C. is preferably 20 to 40 mN / m, and particularly preferably 28 to 38 mN / m. When recording on various recording media such as polyolefin, polyethylene terephthalate (PET), coated paper, and non-coated paper, 20 mN / m or more is preferable from the viewpoint of bleeding and penetration, and 40 mN / m or less is preferable in terms of wettability. preferable.

(Ink storage container (ink pack))
As the storage state of the first and second magenta inks in the ink set of the present invention, it is preferable that the contact with air is kept to a minimum and the light is kept in a light-shielding state during storage. The reason for keeping the light-shielded state is to prevent gelation due to a photopolymerization reaction during storage.

As a container that can be preferably used, an aluminum vapor-deposited plastic pouch is particularly preferable. For the inner wall of the aluminum vapor-deposited plastic pouch (the surface in contact with the ink), a material having excellent solvent resistance such as polypropylene (PP), polyethylene (PE), and polytetrafluoroethylene (PTFE) is preferably used.
For example, as a commercially available ink pack, BiLL PAK series (San-A Chemical Co., Ltd.), flow pack series UV (manufactured by Fujimori Kogyo Co., Ltd.) and the like can be mentioned. Aluminum vapor deposition pouches can also be obtained from SJ-D5 and Showa Marutsutsu Co., Ltd.

  That is, the ink pack of the present invention is preferably stored in an aluminum vapor-deposited plastic pouch and has no air bubbles inside the pouch. The presence or absence of internal bubbles can be confirmed by an inspection using a syringe. It is preferable that no air bubbles are visible when the ink is extracted with a syringe.

(Low molecular pigment dispersant)
When the first and second red pigments are dispersed, a low molecular pigment dispersant may be used in combination with the polymer dispersant as necessary when preparing the pigment particles.
Examples of the low molecular weight pigment dispersant that can be used in the present invention include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates, naphthalene sulfonates, and alkyl phosphates. , Active agents such as polyoxyalkylene alkyl ether phosphates, polyoxyalkylene alkyl phenyl ethers, polyoxyethylene polyoxypropylene glycols, glycerin esters, sorbitan esters, polyoxyethylene fatty acid amides, amine oxides and their salts Can do.

The method for dispersing the pigment is not particularly limited, and various methods known to those skilled in the art can be employed. As one method, after preliminary dispersion with a mixer, final dispersion can be performed to fine pigment particles by so-called medium dispersion (ball mill, sand mill, bead mill, circulating bead mill, etc.). Among these, a bead mill dispersing device is preferable because of its excellent dispersibility.
The beads used when performing bead mill dispersion preferably have a volume average particle diameter of 0.01 to 3.0 mm, more preferably 0.05 to 1.5 mm, and still more preferably 0.1 to 1.0 mm. By using this, a pigment dispersion having excellent stability can be obtained.
It is also preferable to use a filter for the purpose of removing coarse particles of the pigment dispersion after dispersing the pigment.

(Inkjet recording method)
The inkjet recording method of the present invention includes a recording step of discharging the first magenta ink and / or the second magenta ink contained in the radiation curable inkjet ink set from the inkjet recording head onto a recording medium; and A step of irradiating the ejected first and / or second magenta ink with actinic radiation to cure the first and / or second magenta ink. As the recording medium, a corrugated board base material is preferable.
For full-color printing, in addition to the first and second magenta inks, it is preferable to use a yellow ink and a cyan ink, more preferably a black ink, more preferably a black ink and a white ink. It is particularly preferable to do this.
The ink jet recording method of the present invention includes the recording step and the curing step described above, whereby a cured image of the colored ink containing the first and second magenta inks is formed on the recording medium (base material).
Further, a printed matter containing magenta ink cured on a substrate can be obtained by the ink jet recording method of the present invention.

  For the recording step in the ink jet recording method of the present invention, an ink jet recording apparatus described in detail below can be used.

(Inkjet recording device)
There is no restriction | limiting in particular as an inkjet recording device which can be used for the inkjet recording method of this invention, The well-known inkjet recording device which can achieve the target resolution can be selected arbitrarily and can be used. That is, any known inkjet recording apparatus including a commercially available product can discharge both magenta inks onto a recording medium in the inkjet recording method of the present invention.

Examples of the ink jet recording apparatus that can be used in the present invention include an apparatus including an ink supply system, a temperature sensor, and an active energy ray source.
The ink supply system includes, for example, an original tank containing the ink composition of the present invention, a supply pipe, an ink supply tank immediately before the inkjet head, a filter, and a piezo-type inkjet head. The piezo-type inkjet head preferably has a multi-size dot of 1 to 100 pl, more preferably 8 to 30 pl, preferably 320 × 320 to 4,000 × 4,000 dpi, more preferably 400 × 400 to 1,600 ×. It can be driven so that it can discharge at a resolution of 1,600 dpi, more preferably 720 × 720 dpi. In the present invention, dpi represents the number of dots per 2.54 cm.

The first and second magenta inks included in the ink set of the present invention (both inks are collectively referred to as “magenta ink composition” in the present invention) may cause the discharged ink composition to have a constant temperature. Therefore, it is preferable that the ink jet recording apparatus includes a means for stabilizing the ink composition temperature. The parts to be kept at a constant temperature are all the piping systems and members from the ink tank (intermediate tank if there is an intermediate tank) to the nozzle ejection surface. That is, heat insulation and heating can be performed from the ink supply tank to the inkjet head portion.
The temperature control method is not particularly limited, but for example, it is preferable to provide a plurality of temperature sensors at each piping site and perform heating control according to the ink flow rate and the environmental temperature. The temperature sensor can be provided near the ink supply tank and the nozzle of the inkjet head. Moreover, it is preferable that the head unit to be heated is thermally shielded or insulated so that the apparatus main body is not affected by the temperature from the outside air. In order to shorten the printer start-up time that requires heating or to reduce the loss of heat energy, it is preferable to insulate from other parts and reduce the heat capacity of the entire heating unit.

In the magenta ink recording process of the present invention using the above-described inkjet recording apparatus, the ink composition is preferably heated to 25 to 80 ° C., more preferably 25 to 50 ° C., and the viscosity of the ink composition is determined. The discharge is preferably performed after the pressure is lowered to 3 to 15 mPa · s, more preferably 3 to 13 mPa · s. In particular, it is preferable to use an ink composition having an ink viscosity at 25 ° C. of 50 mPa · s or less as the ink composition of the present invention, since it can be discharged satisfactorily. By using this method, high ejection stability can be realized.
A radiation curable ink composition for ink jet recording, such as the ink composition of the present invention, generally has a higher viscosity than a water-based ink composition usually used in ink jet recording, and therefore has a large viscosity fluctuation due to temperature fluctuations during ejection. Viscosity fluctuation of the ink composition has a great influence on the change of the droplet size and the change of the droplet discharge speed, thereby causing the deterioration of the image quality. Therefore, it is preferable to keep the temperature of the ink composition during ejection as constant as possible. Therefore, in the present invention, the temperature control range of the ink composition is preferably set to ± 5 ° C. of the set temperature, more preferably ± 2 ° C. of the set temperature, and further preferably set temperature ± 1 ° C. .

Next, a curing process for curing the magenta ink by irradiating the ejected ink composition with active radiation (active energy rays) will be described.
The ink composition ejected on the recording medium is cured by irradiation with actinic radiation. This is because the radical polymerization initiator contained in the ink composition of the present invention is decomposed by irradiation with active energy rays to generate polymerization initiating species such as radicals and acids, and the function of the initiating species is polymerization of a polymerizable compound. This is because the reaction occurs and is accelerated. At this time, if the sensitizer is present together with the polymerization initiator in the ink composition, the sensitizer in the system absorbs the active energy ray to be in an excited state, and the polymerization initiator is decomposed by interaction with the polymerization initiator. It can be accelerated and a more sensitive curing reaction can be achieved.

  Here, α-rays, γ-rays, electron beams, X-rays, ultraviolet rays, visible light, infrared rays, or the like can be used as active energy rays. Although the peak wavelength of the active energy ray depends on the absorption characteristics of the sensitizer, for example, it is preferably 200 to 600 nm, more preferably 300 to 450 nm, still more preferably 320 to 420 nm, The active energy ray is particularly preferably ultraviolet light having a peak wavelength in the range of 340 to 400 nm.

Further, the polymerization initiation system of the ink composition of the present invention has sufficient sensitivity even with a low output active energy ray. Therefore, it is appropriate to cure the exposed surface with an illuminance of 10 to 4,000 mW / cm ² , more preferably 20 to 2,500 mW / cm ² .

Mercury lamps, gas / solid lasers, etc. are mainly used as active energy ray sources, and mercury lamps and metal halide lamps are widely used as light sources for curing UV photocurable ink jet recording ink compositions. Are known. However, from the viewpoint of environmental protection, mercury-free is strongly desired, and replacement with a GaN-based semiconductor ultraviolet light-emitting device is very useful industrially and environmentally. Furthermore, LED (UV-LED) and LD (UV-LD) are small, have a long lifetime, high efficiency, and low cost, and are expected as light sources for photo-curable ink jets.
In addition, a light emitting diode (LED) and a laser diode (LD) can be used as an active energy ray source. In particular, when an ultraviolet light source is required, an ultraviolet LED and an ultraviolet LD can be used. For example, Nichia Corporation has introduced a purple LED whose main emission spectrum has a wavelength between 365 nm and 420 nm. When even shorter wavelengths are required, US Pat. No. 6,084,250 discloses an LED that can emit active energy rays centered between 300 nm and 370 nm. Other ultraviolet LEDs are also available and can emit radiation in different ultraviolet bands. A particularly preferable active energy ray source in the present invention is a UV-LED, and a UV-LED having a peak wavelength at 340 to 400 nm is particularly preferable.
Incidentally, it is preferable that maximum illumination intensity of the LED on a recording medium is 10 to 2,000 mW / cm ^2, more preferably 20 to 1,000 mW / cm ^2, is 50 to 800 mW / cm ² It is particularly preferred.

The ink composition of the present invention is preferably irradiated with such active energy rays for 0.01 to 120 seconds, more preferably for 0.1 to 90 seconds.
The irradiation conditions of active energy rays and the basic irradiation method are disclosed in JP-A-60-132767. Specifically, the light source is provided on both sides of the head unit including the ink composition discharge device, and the head unit and the light source are scanned by a so-called shuttle method. The irradiation with the active energy ray is performed for a certain period of time after the ink composition has landed (preferably 0.01 to 0.5 seconds, more preferably 0.01 to 0.3 seconds, and still more preferably 0.01 to 0.15). Seconds). In this way, by controlling the time from landing to irradiation of the ink composition to an extremely short time, it is possible to prevent the ink composition that has landed on the recording medium from spreading before curing. In addition, since the ink composition can be exposed to a porous recording medium before the ink composition penetrates to a deep part where the light source does not reach, it is preferable because residual unreacted monomers can be suppressed.
Further, the curing may be completed by another light source that is not driven. International Publication No. 99/54415 pamphlet discloses a method using an optical fiber or a method of irradiating a recording unit with UV light by applying a collimated light source to a mirror surface provided on the side of the head unit, as an irradiation method. Such a curing method can also be applied to the ink jet recording method of the present invention.

By adopting the ink jet recording method as described above, the dot diameter of the landed ink composition can be kept constant even on various recording media having different surface wettability, and the image quality is improved. In addition, in order to obtain a color image, it is preferable to superimpose in order from a color with high brightness. By superimposing the ink compositions in order from the lightness, it becomes easy for the irradiation rays to reach the lower ink composition, and good curing sensitivity, reduction of residual monomers, and improvement in adhesion can be expected. In addition, irradiation can be performed by discharging all colors and collectively exposing, but exposure for each color is preferable from the viewpoint of promoting curing.
Thus, the ink composition of the present invention can form an image on the surface of a recording medium by being cured with high sensitivity by irradiation with active energy rays.

The ink set of the present invention is preferably used as an ink set to which yellow, cyan, black, and, if necessary, white ink is added.
In the inkjet recording method of the present invention, the order of the respective colored ink compositions to be ejected is not particularly limited, but it is preferably applied to the recording medium from a colored ink composition having high brightness, yellow, cyan, When magenta and black are used, it is preferable that yellow, cyan, magenta and black are applied on the recording medium in this order. In addition, when white is added to this, it is preferable to apply it on the recording medium in the order of white → yellow → cyan → magenta → black. Further, the present invention is not limited to this, and an ink set including at least a total of seven colors including yellow, light cyan, light magenta, cyan, magenta, black, and white ink compositions can be preferably used. In this case, it is preferable to apply white, light cyan, light magenta, yellow, cyan, magenta, and black on the recording medium in this order.

  In the present invention, the recording medium is not particularly limited, and a known recording medium can be used as a support or a recording material. For example, corrugated cardboard, paper, paper laminated with plastic (eg, polyethylene, polypropylene, polystyrene, etc.), metal plate (eg, aluminum, zinc, copper, etc.), plastic film (eg, cellulose diacetate, cellulose triacetate, propion) Acid cellulose, cellulose butyrate, cellulose acetate butyrate, cellulose nitrate, polyethylene terephthalate, polyethylene, polystyrene, polypropylene, polycarbonate, polyvinyl acetal, etc.), paper or plastic film on which the above-mentioned metal is laminated or vapor-deposited. Further, corrugated cardboard can be suitably used as the recording medium in the present invention.

  Corrugated cardboard refers to a plate-shaped paper product that has been processed so that it can be used for packaging materials, etc., with a multi-layered structure. In addition to corrugated cardboard sheets, reprocessed cardboard boxes and other cardboard products are included. The corrugated cardboard may be a craft-colored corrugated cardboard, which is the color of a normal base paper, but a white white corrugated cardboard with a white liner is preferable because it produces a beautiful print. In the case of craft color cardboard, if necessary, color printing may be performed after solid printing of white ink.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited by these Examples.
In the following description, “part” refers to “part by mass” unless otherwise specified, and “%” refers to “mass%” unless otherwise specified.

<Preparation of magenta dispersions MM1 to MM4>
Among the compositions shown in Table 1 below, components other than the pigment are stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm), and a uniform transparent liquid (dispersant diluent) Got. A pigment was added to this transparent liquid (dispersant diluent), and further stirred with a mixer (10 to 20 minutes, 2,000 to 3,000 rpm) to obtain a uniform preliminary dispersion. Then, the dispersion process was implemented using the circulation type bead mill apparatus (Laboratory Mini Mill) made from EIGER, and magenta dispersion MM1-MM4 was obtained, respectively. Dispersion conditions were such that 100 parts of zirconia beads having a diameter of 0.65 mm were filled, the peripheral speed was 15 m / s, and the dispersion time was 60 to 120 minutes. In addition, each numerical value of Table 1 shows a mass part.

<Preparation of Cyan, Yellow, and Black Dispersions CM1, YM1, and KM1>
In the composition shown in Table 2 below, components other than the pigment are stirred with a mixer manufactured by SILVERSON (10-15 minutes, 2,000-3,000 rpm), and a uniform transparent liquid (dispersant diluent) Got. A pigment was added to this transparent liquid (dispersant diluent), and further stirred with a mixer (10 to 20 minutes, 2,000 to 3,000 rpm) to obtain a uniform preliminary dispersion. Then, the dispersion process was implemented using the circulation type bead mill apparatus (Laboratory Mini Mill) made from EIGER, and cyan dispersion CM1, yellow dispersion YM1, and black dispersion KM1 were obtained, respectively. Dispersion conditions were such that 100 parts of zirconia beads having a diameter of 0.65 mm were filled, the peripheral speed was 15 m / s, and the dispersion time was 30 to 60 minutes. In addition, each numerical value of Table 2 shows a mass part.

<Preparation of magenta ink MH1 to MH4>
Among the compositions shown in Table 3 below, components other than the pigment dispersion were stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm) to obtain a uniform transparent liquid. To this transparent liquid, the dispersion prepared as described above was added and stirred (10 to 20 minutes, 2,000 to 3,000 revolutions / minute) to obtain magenta inks MH1 to MH4, respectively. In addition, the ink after preparation performed the filtration process with a 1.5 micrometer filter (made by PROFILE STAR PALL). Each numerical value in Table 3 below indicates parts by mass.

<Preparation of light magenta inks ML1 to ML4>
Among the compositions shown in Table 4 below, components other than the pigment dispersion were stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rotations / minute) to obtain a uniform transparent liquid. To this transparent liquid, the dispersion prepared as described above was added and stirred (10 to 20 minutes, 2,000 to 3,000 rpm) to obtain light magenta inks ML1 to ML4. In addition, the ink after preparation performed the filtration process with the 1.5 micrometer filter (made by PROFILE STAR PALL), respectively. Each numerical value in the following Table 4 indicates parts by mass.

<Production of cyan, light cyan, yellow, and black inks CH1, CL1, Y1, and K1>
Among the compositions shown in Table 5 below, components other than the pigment were stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm) to obtain a uniform transparent liquid. To this transparent liquid, the dispersion prepared as described above is added and stirred (10 to 20 minutes, 2,000 to 3,000 rpm), and cyan ink CH1, light cyan ink CL1, yellow ink Y1, and black ink K1. Respectively. In addition, the ink after preparation performed the filtration process with the 1.5 micrometer filter (made by PROFILE STAR PALL), respectively. Each numerical value of the following Table 5 shows a mass part.

(Examples 1-4 and Comparative Examples 1-12)
<Production of printed matter by UV inkjet printer>
The ink prepared above was filled in a commercially available ink jet printer (SP320, manufactured by Inca) with the combinations shown in Table 6 below, and print samples were prepared respectively. The printed matter is 100% yellow, 100% magenta, 100% cyan, 100% black, 100% red, 100% blue, 100% green. The substrate was white cardboard.
Here, 100% means UVjet EI ink series ink series (EI215 (cyan), EI255 (light cyan), EI867 (magenta), EI335 (light magenta), EI052 (yellow), EI004 (black)). , FujiFilmSpecialtyInkSystems Inc.), the maximum ink amount obtained when printing is performed.

<Color gamut evaluation>
The color gamut (L = 40, saturation at L = 60 was calculated) of the printed matter prepared above was measured with a colorimeter (SpectroEye, manufactured by Xrite), and the color gamut was evaluated. . Table 7 shows the evaluation results.
In addition, Table 8 is a score table of evaluation criteria for the color gamut, and a larger score is preferable, and 5 to 3 is a practically preferable range.

<Preparation of magenta dispersions MM5 to MM12>
Among the compositions shown in Table 9 below, components other than the pigment are stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm), and a uniform transparent liquid (dispersant diluent) Got. A pigment was added to this transparent liquid (dispersant diluent), and further stirred with a mixer (10 to 20 minutes, 2,000 to 3,000 rpm) to obtain a uniform preliminary dispersion. Then, the dispersion process was implemented using the circulation type bead mill apparatus (Laboratory Mini Mill) made from EIGER, and magenta dispersion MM5-MM12 was obtained, respectively. Dispersion conditions were such that 100 parts of zirconia beads having a diameter of 0.65 mm were filled, the peripheral speed was 15 m / s, and the dispersion time was 60 to 120 minutes. In addition, each numerical value of Table 9 shows a mass part.

<Preparation of magenta dispersions MM13 to MM20>
In the composition described in Table 10 below, components other than the pigment are stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm), and a uniform transparent liquid (dispersant diluent) Got. A pigment was added to this transparent liquid (dispersant diluent), and further stirred with a mixer (10 to 20 minutes, 2,000 to 3,000 rpm) to obtain a uniform preliminary dispersion. Then, the dispersion process was implemented using the circulation type bead mill apparatus (Laboratory Mini Mill) made from EIGER, and magenta dispersion MM13-MM20 was obtained, respectively. Dispersion conditions were such that 100 parts of zirconia beads having a diameter of 0.65 mm were filled, the peripheral speed was 15 m / s, and the dispersion time was 60 to 120 minutes. In addition, each numerical value of Table 10 shows a mass part.

<Evaluation of handling properties of magenta dispersions MM1, MM4 to MM20>
The handling properties of the produced magenta dispersions MM1, MM4 to MM20 (Table 11) were compared. After production, 30 g of the magenta dispersion was placed in a 30 mL plastic bottle and stored at room temperature (15-30 ° C.) for 2 weeks. Two weeks later, the plastic bottle was gently tilted 135 degrees without stirring, and the time taken to transfer the pigment dispersion to another plastic bottle was measured. Specifically, another plastic bottle was placed on an electronic balance, and the time when it became 25 g was measured. The evaluation results are as shown in Table 11 below.

<Preparation of magenta inks MH5 to MH7>
Among the compositions shown in Table 12 below, components other than the pigment were stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm) to obtain a uniform transparent liquid. To this transparent liquid, the magenta dispersion prepared as described above was added and stirred (10 to 20 minutes, 2,000 to 3,000 revolutions / minute) to obtain magenta inks MH5 to MH7, respectively. In addition, the ink after preparation performed the filtration process with the 1.5 micrometer filter (made by PROFILE STAR PALL), respectively. Each numerical value in the following Table 12 indicates parts by mass.

<Preparation of light magenta ink ML5 to ML7>
Among the compositions shown in Table 13 below, components other than the pigment were stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm) to obtain a uniform transparent liquid. To this transparent liquid, the dispersion prepared as described above was added and stirred (10 to 20 minutes, 2,000 to 3,000 rpm) to obtain light magenta inks ML5 to ML7, respectively. In addition, the ink after preparation performed the filtration process with the 1.5 micrometer filter (made by PROFILE STAR PALL), respectively. Each numerical value in the following Table 13 indicates parts by mass.

(Examples 5-7)
<Production of printed matter by UV inkjet printer>
The ink prepared above was filled in a commercially available ink jet printer (SP320, manufactured by Inca) with the combinations shown in Table 14 below, and print samples were prepared. The printed matter is 100% yellow, 100% magenta, 100% cyan, 100% black, 100% red, 100% blue, 100% green. The substrate was white cardboard.
In this case, 100% means UVjet EI ink series ink series (EI215 (cyan), EI255 (light cyan), EI867 (magenta), EI335 (light magenta), EI052 (yellow)), EI004 (black). , FujiFilmSpecialtyInkSystems Inc.), the maximum ink amount obtained when printing is performed.

<Color gamut evaluation>
The reflection density and saturation (C) of the printed matter prepared above were measured with a colorimeter (SpectroEye, manufactured by Xrite) in the same manner as described above, and the color gamut was evaluated. The evaluation results are shown in Table 15.

<Preparation of light magenta ink ML8 to ML11>
Among the compositions shown in Table 16 below, components other than the pigment were stirred with a mixer manufactured by SILVERSON (10 to 15 minutes, 2,000 to 3,000 rpm) to obtain a uniform transparent liquid. To this transparent liquid, the dispersion prepared as described above was added and stirred (10 to 20 minutes, 2,000 to 3,000 rpm) to obtain light magenta inks ML8 to ML11, respectively. In addition, the ink after preparation performed the filtration process with the 1.5 micrometer filter (made by PROFILE STAR PALL), respectively. Each numerical value in the following Table 16 indicates a part by mass.

(Examples 8 and 9 and Comparative Examples 13 and 14)
<Production of printed matter by UV inkjet printer>
The ink prepared above was filled in a commercially available ink jet printer (SP320, manufactured by Inca) with the combinations shown in Table 17 below, and print samples were prepared. The printed matter is 100% yellow, 100% magenta, 100% cyan, 100% black, 100% red, 100% blue, 100% green. The base material was white corrugated cardboard (trade name: Corrugated Board: manufactured by Robert Horne).
Here, 100% means UVjet EI ink series ink series (EI215 (cyan), EI255 (light cyan), EI867 (magenta), EI335 (light magenta), EI052 (yellow), EI004 (black)). , FujiFilmSpecialtyInkSystems Inc.), the maximum ink amount obtained when printing is performed.
In addition to the above print sample, a print sample of a solid image of 3 color gray (composed of cyan, magenta, and yellow ink) (adhesion amount adjusted so that the L value is 68 to 72 for each ink set) is prepared. did.

<Color gamut evaluation>
The reflection density and saturation (C) of the printed matter prepared above were measured with a colorimeter (SpectroEye, manufactured by Xrite) in the same manner as described above, and the color gamut was evaluated. The evaluation results are shown in Table 17.
Moreover, the granularity of the printed matter (3 color gray) produced above was evaluated by the following evaluation criteria by five evaluators.
(Evaluation criteria: Sensory evaluation for standard samples)
5 points 4 people judged that there was no big deterioration compared to the standard sample 4 points 3 people judged that there was no big deterioration compared to the standard sample 3 points 2 people judged that there was no big deterioration compared to the standard sample 2 points 1 person Judgment that there is no significant deterioration with respect to the standard sample 1 point Everyone determines that there is a large deterioration with respect to the standard sample. In this evaluation standard, it is preferably 2 points or more, particularly preferably 5 points.
The standard sample is a solid image of 3 color gray (L value is 68 to 72) produced by a commercially available inkjet printer (SP320, manufactured by Inca) using only the same standard ink.

  Below, the detail of each component used in the present Example and the comparative example is shown.

<Pigment>
The list of pigments used is as follows.
-CINQUASIA RT355D (mixed crystal of CI Pigment Violet 19 and CI Pigment Red 202, PV19 / PR202, manufactured by BASF)
・ CROMOPHTAL PINK PT (CI Pigment Red 122, PR122, manufactured by BASF)
・ HOSTAPERM INKJET E5B02 (CI Pigment Violet 19, PV19, manufactured by Clariant)
・ IRGALITE RED FBL (CI Pigment Red 48: 4, PR48: 4, manufactured by BASF)
・ IRGALITE BLUE GLVO (Cyan Pigment, CI Pigment Blue 15: 4, PB15: 4, manufactured by BASF)
-PALIOTOL YELLOW D1155 (yellow pigment, CI Pigment Yellow 185, PY185, manufactured by BASF)
・ MOGUL E (black pigment, CI Pigment Black 7, CB, carbon black, manufactured by Cabot)

<Dispersant>
Table 18 shows a list of polymer dispersants used.
・ EFKA7701 (polymer dispersant, manufactured by BASF)
・ EFKA7731 (polymer dispersant, manufactured by BASF)
-TEGODISPER 685 (polymer dispersant, manufactured by Evonik)
BYK168 (DISPERBYK168, polymer dispersant, manufactured by BYK)
SOLPERSE 32000 (polymer dispersant, manufactured by Lubrizol)
・ PB-821 (Ajisper PB-821, polymer dispersant, manufactured by Ajinomoto Fine Techno Co., Ltd.)

The synthetic dispersant (1) was synthesized by the following procedure.
A monomer mixture of amine monomer 1 (8.0 parts), oligomer 1 (16.0 parts), and methyl ethyl ketone (30.0 parts) was introduced into a nitrogen-substituted three-necked flask and stirred with a stirrer. The mixture was heated to 65 ° C. while flowing nitrogen into the flask.
First stage: 0.060 part of V-65 was added to the above mixture and stirred at 65 ° C. for 1 hour.
Second stage: 0.060 part of V-65 was added, and the mixture was further heated and stirred at 65 ° C. for 1 hour.
The resultant reaction liquid was poured into 659 parts of hexane with stirring, and the resulting precipitate was heated and dried to obtain a synthetic dispersant (1).
Amine monomer 1: 3-dimethylaminopropylacrylamide (manufactured by Kojin Co., Ltd.)
Oligomer 1: Poly (methyl methacrylate) macromonomer having a methacryloyl group at the end, trade name: AA-6 (manufactured by Toagosei Co., Ltd.)
V-65: 2,2′-azobis (2,4-dimethylvaleronitrile) (manufactured by Wako Pure Chemical Industries, Ltd.)

For the synthetic dispersant (2) and the synthetic dispersant (3), the molecular weight is changed by appropriately changing the amount of V-65 to be added and the heating time in the same procedure as the synthesis of the synthetic dispersant (1). Different dispersants were prepared.
The weight average molecular weight (in terms of polystyrene) of each dispersant was measured by gel permeation chromatography (GPC), and as shown in Table 18.

In addition, the measurement of the weight average molecular weight (polystyrene conversion) by GPC was performed on condition of the following.
1) Equipment: HLC-8220GPC manufactured by Tosoh Corporation
2) Column: Particle gel based on hydrophilic vinyl polymer 3) Solvent: N-methylpyrrolidone (10 mM LiBr)
4) Flow rate: 0.5 mL / min
5) Sample concentration: 0.1% by mass
6) Injection volume: 60 μL
7) Temperature: 40 ° C
8) Detector: Differential refractometer (RI)

The amine value was measured according to the following procedure.
The dispersant was dissolved in methyl isobutyl ketone, potentiometric titration was performed with a 0.01 mol / L methyl isobutyl ketone perchlorate solution, and the value converted to mg KOH / g was used as the amine value. The potentiometric titration was measured using an automatic titrator COM-1500 manufactured by Hiranuma Sangyo Co., Ltd.
Moreover, the glass transition temperature (Tg) was calculated | required from the measured main body maximum peak using the differential scanning calorimeter (The Perkin-Elmer company make: DSC-7) based on ASTMD3418-8. The temperature correction of the detection part of this apparatus (DSC-7) uses the melting point of indium and zinc, and the correction of heat quantity uses the heat of fusion of indium. The sample used was an aluminum pan, and an empty pan was set as a control. The temperature was raised at a rate of 10 ° C / min, held at 150 ° C for 5 minutes, cooled from 150 ° C to 0 ° C at -10 ° C / min using liquid nitrogen, held at 0 ° C for 5 minutes, and again 0 It calculated | required based on the onset temperature analyzed from the endothermic curve at the time of the 2nd temperature increase obtained by heating up from 10 degreeC to 150 degreeC at 10 degree-C / min.

<Monomer (radiation curable compound), polymerization initiator, other additives>
PEA: SR339C, phenoxyethyl acrylate (manufactured by Sartomer)
UV12: FLORSTAB UV12, polymerization inhibitor (manufactured by Kromachem)
DPGDA: SR508, dipropylene glycol diacrylate (manufactured by Sartomer)
-TPGDA: SR306, tripropylene glycol diacrylate (manufactured by Sartomer)
CTFA: SR531, cyclic trimethylolpropane formal acrylate (manufactured by Sartomer)
ELVACITE 2013: acrylic resin (Lucite)
-PARALOID DM-55: Acrylic resin (Dow)
IRGACURE 184: polymerization initiator, 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF)
TPO: DAROCUR TPO, polymerization initiator, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by BASF)
・ Benzophenone: Benzophenone (manufactured by LAMBSON)
-BYK 307: Surfactant (by Big Chemie)

Claims (9)

Radiation-curable compound, and, P1 (mass%) of the first red pigment is a mixed crystal pigment of the PV19 and PR202 in the ink first magenta ink containing and,
A radiation curable compound and a second magenta ink containing P2 (mass%) of a second red pigment that is PR48: 4 and / or PV19 in the ink;
P1 and P2 satisfy the following relational expression (1):
Radiation curable inkjet ink set.
20 ≧ (P1 / P2) ≧ 1.2 (1)   A first magenta ink containing a radiation curable compound and P1 (mass%) of a first red pigment which is a mixed crystal pigment of PR122 and / or PV19 and PR202; and
  A radiation curable compound, and a second magenta ink containing P2 (mass%) of a second red pigment that is PR48: 4 in the ink,
  P1 and P2 satisfy the following relational expression (1):
  Radiation curable inkjet ink set.
    20 ≧ (P1 / P2) ≧ 1.2 (1) The radiation-curable inkjet ink set according to claim 1, comprising a radiation-curable compound and a second magenta ink containing P2 (mass%) of a second red pigment that is PR48: 4 in the ink. Further contains a yellow ink, the yellow ink contains a polymer dispersant, the glass transition temperature Tg of the polymer dispersant is 25 ° C. or less, the radiation according to any one of claims 1 to 3 A curable inkjet ink set. The first magenta ink contains a polymer dispersant, and the concentration D1 (mass%) of the polymer dispersant and the concentration P1 (mass%) of the first red pigment are expressed by the following relational expression (2). The radiation-curable inkjet ink set according to claim 1, wherein
0.6 ≧ (D1 / P1) ≧ 0.4 (2) The second magenta ink contains a polymer dispersant, and the concentration D2 (mass%) of the polymer dispersant and the concentration P2 (mass%) of the second red pigment are expressed by the following relational expression (3). The radiation curable inkjet ink set according to claim 1, wherein
0.7 ≧ (D2 / P2) ≧ 0.4 (3) The radiation curable inkjet according to any one of claims 1 to 6 , wherein both the first magenta ink and the second magenta ink contain 40% by mass or more of a bifunctional monomer based on the total amount of each ink. Ink set. The first magenta ink and the second magenta ink each contain 6 to 25% by mass of phenoxyethyl acrylate and / or cyclic trimethylolpropane formal acrylate (CTFA) based on the total amount of each ink. The radiation curable inkjet ink set according to any one of 1 to 7 . Recording step of discharging onto a recording medium a first magenta ink and / or the second magenta ink contained in the radiation-curable ink jet ink set according to any one of claims 1-8 from an ink jet recording head ,as well as,
A curing step of curing the first magenta ink and / or the second magenta ink by irradiating the ejected first and / or second magenta ink with actinic radiation. .