JP4270149B2 - Aqueous ink set for inkjet recording and inkjet recording method - Google Patents

Description

  The present invention relates to a water-based ink set for ink jet recording and an ink jet recording method.

  The ink jet recording method is widely used for color printing of digital color image data. An aqueous ink set for ink jet recording comprising a yellow ink, a magenta ink, and a cyan ink in which a water-soluble dye is dissolved in water and a water-soluble organic solvent is used. It's being used. Further, in order to print texts such as alphabet data and kanji data, a dye-based black ink is added to an aqueous ink set for ink jet recording.

  Furthermore, in order to realize vivid color developability, it has been proposed to form an ink set with a total of seven water-soluble dye-based inks of yellow, magenta, cyan, red, green, blue, and black (Patent Document 1). ). However, according to such an ink set, the number of nozzles of the inkjet head has to be increased, and there is a problem that the cost increases.

  In addition, when an ink set is composed of only dye-based ink, there is a problem that feathering is conspicuous in text. Note that feathering is fine bleeding caused by the presence of fibers and voids in the recording material when the ink lands on and penetrates the recording material such as recording paper.

  On the other hand, in recent years, in addition to vivid color development, sharp text printing quality with minimal blurring such as feathering and printing quality equivalent to photographic image quality with good light and ozone resistance are desired. It is rare.

  Therefore, in order to achieve sharp text printing, all six colors of ink are added as pigmented water-based ink sets for inkjet recording, including three primary colors of yellow, magenta, and cyan, plus black, red, and green. It is proposed that the ink is composed of a system ink (Patent Document 2). Thereby, an inkjet image is excellent in light resistance and ozone resistance, and also in the sharpness of a text.

  However, when all ink sets are composed of pigment-based inks, the color developability of the color is greater than when composed of dye-based three primary color inks, despite the use of additional black, red, and green inks. It was not enough.

  For this reason, as a composition of an ink set that achieves both print quality without feathering in text and vivid color development similar to silver salt photographs in color images, black ink, which emphasizes text print quality, has a pigment as a colorant. As color inks that are used and color development is important, that is, yellow ink, magenta ink, and cyan ink, those using a water-soluble dye as a colorant are commercially available.

  However, when text is printed using an ink set having such an ink configuration, in addition to black in actual text, blue is also frequently used for emphasis, correction, etc., which causes a problem in printing blue text. It was.

  In other words, since blue is expressed by superimposing dye-based magenta ink and dye-based cyan ink, the blue text is misaligned due to the impact error of overstrike. The ink used for blue expression is two types of dye-based inks, and the amount of ink used is about twice that of black text printed with pigment ink, so feathering is likely to occur. There was a problem.

  Further, the blue text has a problem that water resistance, light resistance and ozone resistance are inferior. More specifically, regarding water resistance, for example, a text document output in an office is low in water resistance of ink, so that it is likely to cause bleeding due to moisture such as sweat of human hands, water drops of drinks, etc. (Breaking due to moisture) is also likely to occur.

  Regarding light resistance, blue text posted for a long time faded by exposure to illumination light and sunlight, and the long-term storage stability of the text was poor.

  Moreover, regarding the long-term storage stability of inkjet images, fading due to the influence of various gases present in the air, particularly ozone, has recently attracted attention, and ozone resistance is required. However, cyan ink used for blue expression has lower ozone resistance than yellow ink, magenta ink, and black ink. For this reason, the color balance after fading is lost due to a change over time, and the image changes to a weak blue. For example, since green is formed of yellow ink and cyan ink, after cyan fades due to changes over time, only yellow remains on the recording material, and yellow changes to a strong color. Such a loss of color balance after fading due to a change over time gives an unnatural impression, which is a big problem for improving print quality.

Japanese Patent Laid-Open No. 2002-241661 JP 2001-354886 A

  The present invention has been made in order to solve the above-described problems, and suppresses feathering of black and blue text in a water-based ink set used for ink-jet recording, and has water resistance, light resistance, and ozone resistance. Providing an ink-jet recording method that effectively uses such an ink set, and provides a color developing property that is excellent in color development and excellent in color balance over time. With the goal.

  The inventors of the present invention have excellent color developability by using three primary colors of yellow, magenta, and cyan dye-based inks and black and blue pigment-based inks as the ink constituting the water-based ink set for inkjet recording. In addition, black and blue text feathering can be suppressed to sharpen the print, and cyan ink alone or cyan ink recorded with cyan ink and other color inks can be used. It has been found that by using a pigment-based blue ink in combination with the recording portion, the ozone resistance of those portions can be improved, and the decrease in color balance caused by the fading over time can be suppressed, and the present invention has been completed.

  That is, the present invention is a water-based ink set for inkjet recording composed of a yellow ink, a magenta ink, a cyan ink, a black ink and a blue ink containing at least a colorant, water and a water-soluble organic solvent. An aqueous ink set for ink-jet recording is provided, wherein the colorant of the ink and cyan ink is a water-soluble dye, and the colorant of black ink and blue ink is a pigment.

  The present invention also provides a yellow ink containing a water-soluble dye as a colorant, a magenta ink containing a water-soluble dye as a colorant, a cyan ink containing a water-soluble dye as a colorant, and a black ink containing a pigment as a colorant. An ink jet recording method for performing ink jet recording by ejecting and adhering the ink constituting an aqueous ink set for ink jet recording containing an ink and a blue ink containing a pigment as a coloring agent from an ink jet head to a recording material. Provided is an ink jet recording method comprising using cyan ink together with cyan ink in a cyan ink recording portion on a recording material.

  In the water-based ink set for ink-jet recording and the ink-jet recording method of the present invention, dye-based inks are used as the three primary colors of yellow, magenta and cyan constituting the water-based ink set for ink-jet recording. The color developability is improved. In addition, since pigment-based black ink and blue ink are added to the ink set, feathering of black and blue text can be suppressed and sharp printing can be performed. Further, by using a cyan blue ink in combination with a cyan ink alone or a cyan ink recording portion recorded with cyan ink and other color inks, the ozone resistance of that portion can be improved, and the time-lapse can be improved. A decrease in color balance caused by fading can be suppressed.

Hereinafter, the present invention will be described in detail.
The aqueous ink set for inkjet recording of the present invention is composed of a yellow ink, a magenta ink and a cyan ink, each containing a water-soluble dye as a colorant, and a black ink and a blue ink, each containing a pigment as a colorant. Each ink contains water and a water-soluble organic solvent.

  The ink jet recording method of the present invention is a method for performing ink jet recording by using the above-described aqueous ink set for ink jet recording and ejecting each ink from an ink jet head onto a recording material and depositing the ink on the recording material. This is used together with the cyan ink recording portion.

  Here, “combined use” means that the pigment-based blue ink is attached to the portion of the recording material, such as recording paper, to which the cyan ink is attached before, after, or simultaneously with the cyan ink. Further, the dye-based cyan ink and the pigment-based blue ink may overlap each other on the recording material, or may be adjacent to each other.

In the present invention, blue means a color in the L ^* a ^* b ^* color system and the hue angle is in the range of 265 ° to 320 °, and the blue ink represents blue alone. The ink that can be used. The pigment used in the blue ink is not limited to one type as long as the hue angle can be adjusted within the range of 265 ° to 320 °, and two or more types of pigments may be used.

  Examples of the pigment used as a colorant for the black ink include carbon black such as MA8, MA100 (manufactured by Mitsubishi Chemical Corporation), and color black FW200 (manufactured by Degussa). Further, as the carbon black, a self-dispersing pigment that can be dispersed in water without using a dispersant may be used. Here, the self-dispersing pigment can be obtained by surface treatment so that at least one hydrophilic group such as a carbonyl group, a carboxyl group, a hydroxyl group or a sulfone group or a salt thereof is bonded to the pigment surface. Examples thereof include self-dispersed pigments surface-treated by the methods described in JP-A-8-3498 and JP-T 2000-513396. Examples of the pigment dispersion containing a self-dispersing black pigment include CAB-O-JET (registered trademark) 200, 300 (manufactured by Cabot Corporation) and Bonjet (registered trademark) CW1 (manufactured by Orient Chemical Industry Co., Ltd.). It is possible to use commercially available products such as

  Examples of the pigment used as a colorant for the blue ink include C.I. I. Pigment Blue 15: 1, 15: 3, 15: 6, and 60. Among them, C.I. I. It is preferred to use either pigment blue 15: 3 or 60 or both.

  The blue ink may be mixed with a magenta pigment to express blue. In this case, examples of the magenta pigment include C.I. I. And CI Pigment Red 5, 48, 112, 122, 202 and 207. In addition, these are description of an example of the pigment suitable for this invention, and this invention is not limited by these.

  The pigment content to be included in each of these black ink and blue ink varies depending on the intended printing density and color, but if it is too small, the coloring on the paper surface is insufficient, and if it is too large, the content of the nozzles of the inkjet head is insufficient. Since clogging is likely to occur, it is preferably 1 to 10% by weight, more preferably 1 to 7% by weight, based on the total amount of each ink.

  A pigment dispersant may be added to each of the black ink and the blue ink in order to maintain their dispersion stability. Examples of the pigment dispersant include a polymer dispersant and a surfactant. Polymeric dispersants include proteins such as gelatin and albumin; natural rubbers such as gum arabic and tragacanth; glucosides such as saponin; cellulose derivatives such as methylcellulose, carboxycellulose and hydroxymethylcellulose; lignin sulfonate, shellac and the like Natural polymer: polyacrylate, salt of styrene-acrylic acid copolymer, salt of vinyl naphthalene-acrylic acid copolymer, salt of styrene-maleic acid copolymer, salt of vinyl naphthalene-maleic acid copolymer And anionic polymers such as sodium salt and phosphate of β-naphthalene sulfonic acid polymarin condensate; nonionic polymers such as polyvinyl alcohol, polyvinyl pyrrolidone and polyethylene glycol. Surfactants include anionic surfactants such as higher alcohol sulfates, liquid fatty oil sulfates, alkyl allyl sulfonates; polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters, sorbitan alkyl esters, polyoxy Nonionic surfactants such as ethylene sorbitan alkyl esters are listed. One or more dispersants can be appropriately selected and used.

  These dispersants are appropriately determined in an appropriate amount to function as a dispersant depending on the type of pigment and the type of dispersant. However, if the amount is too small, the dispersion stability of the pigment is insufficient. Since the viscosity increases and it becomes difficult to discharge from the inkjet head, it is preferably 5 to 50% by weight, more preferably 10 to 40% by weight, based on the amount of the pigment.

  As a method for dispersing the pigment in the black ink or the blue ink, it is preferable to disperse the pigment using a dispersing device. The dispersing device used for dispersing the pigment is not particularly limited as long as it is a general dispersing machine, and examples thereof include a ball mill, a roll mill, and a sand mill. Among these, a high-speed sand mill is preferable.

  On the other hand, a water-soluble dye is used as a colorant in the yellow ink, magenta ink, and cyan ink constituting the water-based ink set for inkjet recording of the present invention. As the water-soluble dye used in yellow ink, magenta ink, and cyan ink, those satisfying the sharpness, water solubility, stability, light resistance and other required performances can be used. For example, direct dyes, acid dyes, Basic dyes and reactive dyes are used. In addition, if classified by the structure of the dye, azo dye, metal complex dye, naphthol dye, anthraquinone dye, indigo dye, carbonium dye, quinoneimine dye, xanthene dye, aniline dye, quinoline dye, nitro dye, nitroso dye, benzoquinone dye, Naphthoquinone dyes, phthalocyanine dyes, metal phthalocyanine dyes and the like can be preferably used.

  Specific examples of direct dyes include C.I. I. Direct yellow 12, 24, 26, 27, 28, 33, 39, 58, 86, 98, 100, 132 and 142, C.I. I. Direct Red 4, 17, 28, 37, 63, 75, 79, 80, 83, 99, 220, 224 and 227, C.I. I. Direct violet 47, 48, 51, 90 and 94, C.I. I. Direct Blue 1, 6, 8, 15, 25, 22, 25, 71, 76, 80, 86, 90, 106, 108, 123, 163, 165, 199 and 226, etc. Specific examples of acid dyes include C . I. Acid Yellow 3, 11, 17, 19, 23, 25, 29, 38, 42, 49, 59, 61, 71 and 72, C.I. I. Acid Red 1,6,8,17,18,32,35,37,42,51,52,57,80,85,87,92,94,115,119,131,133,134,154,181, 186, 249, 254, 256, 289, 315, 317 and 407, C.I. I. Acid Violet 10, 34, 49 and 75, C.I. I. Acid Blue 9, 22, 29, 40, 59, 62, 93, 102, 104, 113, 117, 120, 167, 175, 183, 229 and 234, etc. Specific examples of basic dyes include C.I. I. Basic Yellow 40, C.I. I. Basic Red 1, 2, 9, 12, 13, 14, and 37, C.I. I. Basic Violet 7, 14, and 27, C.I. I. Basic blue 1,3,5,7,9,24,25,26,28 and 29, etc. Specific examples of reactive dyes include C.I. I. Reactive yellow 2, 3, 13 and 15, C.I. I. Reactive Red 4, 23, 24, 31, 56 and 180, C.I. I. Reactive blue 7, 13, 21 etc. are mentioned.

  If the content of the water-soluble dye contained in these yellow ink, magenta ink and cyan ink is too small, the color on the paper surface is insufficient, and if it is too large, the nozzles of the inkjet head are likely to be clogged. Preferably it is 0.1 to 10 weight% with respect to the total amount of each ink, More preferably, it is 0.3 to 10 weight%, Especially preferably, it is the range of 0.5 to 7 weight%.

  In the water-based ink set for ink-jet recording of the present invention, it is preferable to use deionized water as water used for each ink, including the black ink and the blue ink described above, instead of general water containing ions. The water content is determined in a wide range depending on the type and composition of the water-soluble organic solvent used together or the desired ink characteristics. However, if the amount is too small, the ink viscosity increases and it is difficult to eject from the inkjet head. If the amount is too large, the evaporation of water causes colorant precipitation, aggregation and the like, and the nozzles of the inkjet head are likely to be clogged. Therefore, it is preferably 10 to 95% by weight, more preferably 10 to 10% by weight based on the total amount of each ink. It is in the range of 80% by weight, particularly preferably 20 to 80% by weight.

  In the water-based ink set for inkjet recording of the present invention, the water-soluble organic solvent used for each ink is roughly classified into a wetting agent and a penetrating agent. The water-soluble organic solvent used as the wetting agent is added to the ink to prevent clogging of the nozzles of the inkjet head. The water-soluble organic solvent used as the penetrating agent is used when the ink is printed. Is added to the ink so as to quickly penetrate into the recording material.

  Specific examples of the wetting agent include glycerin, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, and the like. Of water-soluble glycol.

  If the content of the water-soluble organic solvent as the wetting agent is too small, it is insufficient to prevent clogging of the nozzles of the inkjet head, and if it is too much, the viscosity of the ink increases and it is difficult to eject from the inkjet head. Therefore, it is preferably in the range of 5 to 50% by weight, more preferably 10 to 40% by weight, and particularly preferably 15 to 35% by weight with respect to the total amount of each ink.

  On the other hand, specific examples of the penetrant include glycol ethers typified by ethylene glycol and propylene glycol alkyl ethers. Specific examples of the ethylene glycol alkyl ether include ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, ethylene glycol-n-butyl ether, ethylene glycol isobutyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol. -N-propyl ether, diethylene glycol-n-butyl ether, diethylene glycol isobutyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol-n-propyl ether, triethylene glycol-n-butyl ether, triethylene glycol isobutyl ether Etc. Specific examples of the glycol-based alkyl ether include propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol-n-propyl ether, propylene glycol-n-butyl ether, dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene Examples include glycol-n-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol methyl ether, tripropylene glycol ethyl ether, tripropylene glycol-n-propyl ether, and tripropylene glycol-n-butyl ether.

  If the content of the water-soluble organic solvent as the penetrating agent is too small, the penetrability is insufficient, and if it is too large, bleeding such as feathering is likely to occur due to excessive penetrability. Is in the range of 1-10 wt%, more preferably 1-7 wt%.

  In addition to the wetting agent and penetrating agent, each ink constituting the aqueous ink set for inkjet recording of the present invention prevents the ink from drying at the tip of the inkjet head, increases the print density, and realizes vivid color development. For the purpose of, for example, another water-soluble organic solvent may be included. Specific examples of such water-soluble organic solvents include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol and other lower alcohols; dimethylformamide, dimethyl Amides such as acetamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Glycerin; Pyrrolidones such as 2-pyrrolidone and N-methyl-2-pyrrolidone; 1,3-dimethyl-2- Examples include imidazolidinone.

  In the water base ink set for ink jet recording of the present invention, the basic composition of black ink, blue ink, yellow ink, magenta ink and cyan ink is as described above. Each ink includes a conventionally known surfactant; polyvinyl alcohol. Viscosity modifiers such as cellulose; surface tension modifiers; antifungal agents; rust inhibitors and the like can be added as necessary.

  In the aqueous ink set for inkjet recording of the present invention, the black ink and the blue ink preferably have a dynamic surface tension at a lifetime of 100 ms, measured by a maximum bubble pressure method (bubble pressure method) at 25 ° C. It is preferable that they are 40 mN / m or more and 45 mN / m or less. As a result, it is possible to perform text printing with less feathering and good dryness on the recording material. On the other hand, when the dynamic surface tension is less than 40 mN / m, the feathering tends to be conspicuous, and when it exceeds 45 mN / m, the drying property of the ink on the recording material tends to deteriorate.

  It is known that the dynamic surface tension of a liquid such as ink is generally measured by a vibration jet method, a meniscus method, a maximum bubble pressure method, etc., but the value of the dynamic surface tension defined in the present invention is: It is based on the maximum bubble pressure method (bubble pressure method) and can be measured using, for example, an automatic dynamic surface tension meter BP-D4 manufactured by Kyowa Interface Science Co., Ltd.

  In dynamic surface tension measurement by the maximum bubble pressure method, gas is sent from a gas supply source to the probe, and bubbles are generated from the tip of the probe immersed in ink. By changing the gas flow rate at this time, the gas generation speed is changed, and the surface tension is measured by the pressure applied to the bubbles from the ink that changes accordingly. When the bubble radius becomes equal to the radius of the probe tip, the maximum pressure (maximum bubble pressure) is indicated. The surface tension σ of the ink at this time is

（式中、ｒはプローブ先端部分の半径、
ΔＰは気泡にかかる圧力の最大値と最小値との差である。）
で表される。

(Where r is the radius of the probe tip,
ΔP is the difference between the maximum value and the minimum value of the pressure applied to the bubbles. )
It is represented by

  The term “lifetime” as used herein refers to the time from when the bubble leaves the probe after the maximum bubble pressure until the next maximum bubble pressure is reached after a new surface is formed.

  In black ink and blue ink, the reason why the dynamic surface tension is preferably in the above-mentioned range is as follows. Unlike the static surface tension, the dynamic surface tension of a liquid such as ink is a surface tension in the order of a lifetime of several to several thousand ms, and the ink permeates into the recording material when adhered (landing). There seems to be a big impact. When the dynamic surface tension is high, since the permeability of the ink to the recording material is low, the feathering is good, but the drying property of the ink to the recording material is lowered. On the other hand, if the dynamic surface tension is low, the permeability of the ink to the recording material is high and the feathering is deteriorated, but the drying property of the ink to the recording material is improved. In a general ink jet recording method, the penetration phenomenon of the ink jet ink into the recording material when the ink jet ink lands on the recording material is on the order of several tens of ms. Therefore, in the present invention, the dynamic surface tension value at a lifetime of 100 ms is adopted in consideration of errors of the dynamic surface tension measuring device and the like, in which the measurement accuracy is stable.

  The ink jet recording method of the present invention performs ink jet recording using the aqueous ink set for ink jet recording of the present invention, and as the recording material and the ink jet head, those used in conventional ink jet recording are appropriately used. can do.

  In the ink jet recording method of the present invention, when using the aqueous ink set for ink jet recording of the present invention, the color image data includes dye-based yellow ink, magenta ink and cyan ink, and if necessary, pigment-based black ink and Blue ink is used. In particular, blue ink is used together with cyan ink in a cyan ink recording portion. As a result, the light resistance and ozone resistance of the cyan ink recording portion can be improved, the color fading can be improved, and the change in color balance over time can be suppressed.

  If the amount of blue ink used in the cyan ink recording portion is too small, the combined effect of blue ink will not appear, and if it is too large, it will be difficult to reproduce the desired color. It is preferable to set it to 20 vol% or less.

  In the ink jet recording method of the present invention, if necessary, the pigment-based blue ink is toned to a strong reddish blue, and the blue ink is used in the cyan ink recording portion as described above. You may use together with a magenta ink in a recording part. As a result, the light fastness and ozone resistance of the magenta ink recording portion can be improved, and the color fading can be improved.

  On the other hand, black and blue text data are reproduced using pigment-based black ink and blue ink, respectively.

  The ink-jet image reproduced in this way is excellent in color balance over time due to color development, light resistance, and ozone resistance, and is a sharp representation of not only black but also blue text. Become.

  The present invention will be specifically described below with reference to examples and comparative examples.

(1) Preparation of ink Inks having the compositions shown in Tables 1 and 2 were prepared as follows.
The prepared pigment-based black ink and blue ink were subjected to dynamic surface tension in the range of 25 ° C. and lifetime of 20 to 5000 ms using an automatic dynamic surface tension meter BP-D4 manufactured by Kyowa Interface Science Co., Ltd. Measurements were taken and dynamic surface tension measurements at a lifetime of 100 ms were read. The results are shown in Table 1.

(1-a) Black pigment ink 1
An ink solvent was prepared by mixing 39 parts by weight of ion-exchanged water, 25.5 parts by weight of glycerin, 2 parts by weight of dipropylene glycol-n-propyl ether and 0.5 parts by weight of propylene glycol-n-propyl ether. CAB-O-JET (registered trademark) 300 which is a black pigment dispersion under stirring (carbon black concentration 15%, manufactured by Cabot Corporation) 67 parts by weight of an ink solvent is gradually added to 33 parts by weight, and stirring is continued for 30 minutes. Thereafter, the mixture was filtered through a membrane filter having a pore diameter of 1 μm to prepare an ink.

  The concentration of carbon black relative to the total amount of ink was 5% by weight.

(1-b) Black pigment ink 2-5
It was prepared in the same manner as the black pigment ink 1 except that the ink composition was changed as shown in Table 1.

(1-c) Blue pigment ink 1
C. I. After mixing 4 parts by weight of Pigment Blue 60, 1 part by weight of polyoxyethylene lauryl ether ammonium sulfate (oxyethylene average polymerization degree = 12), 4 parts by weight of glycerin and 16 parts by weight of ion exchange water, zirconia beads having a diameter of 0.3 mm were mixed. Dispersion treatment was performed with a wet sand mill as a medium to obtain a blue pigment dispersion.

  Further, 51 parts by weight of ion-exchanged water, 22 parts by weight of glycerin, and 2 parts by weight of dipropylene glycol-n-propyl ether were mixed to prepare an ink solvent.

  An ink was prepared by gradually adding 75 parts by weight of an ink solvent to 25 parts by weight of the blue pigment dispersion being stirred, and further stirring for 30 minutes, followed by filtration through a membrane filter having a pore size of 1 μm.

(1-d) Blue pigment ink 2
C. I. Pigment Blue 15: 3 2 parts by weight, polyoxyethylene lauryl ether ammonium sulfate (oxyethylene average polymerization degree = 12) 0.5 part by weight, glycerin 2 parts by weight, ion-exchanged water 8 parts by weight are mixed, and the diameter is 0.3 mm. Dispersion treatment was performed in a wet sand mill using zirconia beads as a medium to obtain a cyan pigment dispersion.

  In addition, C.I. I. Pigment Red 122 2 parts by weight, polyoxyethylene lauryl ether ammonium sulfate (oxyethylene average polymerization degree = 12) 0.5 part by weight, glycerin 2 parts by weight, ion-exchanged water 8 parts by weight are mixed, and zirconia beads having a diameter of 0.3 mm A magenta pigment dispersion was obtained by performing a dispersion treatment in a wet sand mill using as a medium.

  Equal amounts of the prepared cyan pigment dispersion and magenta pigment dispersion were mixed and stirred for 10 minutes to obtain a blue pigment dispersion.

  On the other hand, 51 parts by weight of ion-exchanged water, 22 parts by weight of glycerin, and 2 parts by weight of dipropylene glycol-n-propyl ether were mixed to prepare an ink solvent.

  An ink was prepared by gradually adding 75 parts by weight of an ink solvent to 25 parts by weight of the blue pigment dispersion being stirred, and further stirring for 30 minutes, followed by filtration through a membrane filter having a pore size of 1 μm.

(1-e) Blue pigment ink 3-5, yellow pigment ink, magenta pigment ink, cyan pigment ink Prepared in the same manner as blue pigment ink 1 or 2 except that the ink composition was changed as shown in Table 1 or 2. did.

(1-f) Black dye ink 68 parts by weight of ion-exchanged water, 24 parts by weight of glycerin, and 5 parts by weight of dipropylene glycol-n-propyl ether were mixed to prepare an ink solvent.

  A black dye ink was prepared by gradually adding 30 parts by weight of black dye, Food Black 23, to 97 parts by weight of the ink solvent under stirring, and continuing stirring for 30 minutes, followed by filtration through a membrane filter having a pore size of 1 μm. .

(1-g) Blue dye ink, yellow dye ink, magenta dye ink, cyan dye ink Prepared in the same manner as the black dye ink except that the ink composition was changed as shown in Table 1 or 2.

(2) Structure of ink set The inks shown in Tables 1 and 2 were combined as shown in Table 3 to form water-based ink sets for inkjet recording in Examples 1 to 5 and Comparative Examples 1 to 5. .

(3) Evaluation For each ink set, its constituent ink is filled in a predetermined ink cartridge, and is mounted on a digital multifunction device (MFC-5200J) equipped with an inkjet printer manufactured by Brother Industries, Ltd. Printed the color patch.

  In this case, black and blue text data were printed on plain paper (m-real DATA, COPY paper) using black ink and blue ink, respectively. However, in the case of the ink sets of Comparative Examples 1, 2, and 5 in which the blue ink was not included in the ink set, blue printing was performed using magenta ink and cyan ink.

  The color patches were printed on glossy paper (manufactured by Fuji Film Co., Ltd., Image (registered trademark) photofinishing) with different mixing ratios of yellow, magenta, cyan, and blue inks. At this time, cyan ink and blue ink were used together in the cyan ink recording portion. The ratio of cyan ink and blue ink in the cyan ink recording portion was 15% in terms of the volume ratio of cyan ink to blue ink. However, in the case of the ink sets of Comparative Examples 1, 2, and 5 in which the blue ink was not included in the ink set, this combination was not performed.

  Black and blue text prints were evaluated for (a) feathering, (b) paper surface dryness, (c) water resistance and (d) light resistance as follows. The printed color patches were evaluated for (e) color development and (f) ozone resistance and fading balance as follows. These results are shown in Table 3.

(a) Feathering The following evaluation was made by visual observation.
◎… feathering is not recognized ○… feathering is almost inconspicuous △… feathering is conspicuous, there is a problem in practical use ×… feathering is clearly conspicuous, not suitable for practical use

(b) Paper surface drying property Paper surface drying property is the drying property of the ink on the paper surface after printing. Thus, 15 seconds after printing, the ink was rubbed with a finger, and ink rubbing was evaluated by visual observation as follows.
◎… Ink rubbing is not recognized ○… Ink rubbing is almost inconspicuous △… Ink rubbing is conspicuous and there is a problem in practical use ×… Ink rubbing is conspicuous and is not suitable for practical use

(c) Water resistance After the printed matter was immersed in tap water for 5 minutes, the ink blot on the paper surface was visually observed and evaluated as follows.
◎… Ink bleed is not recognized ○… Ink bleed is hardly noticeable △… Ink bleed is conspicuous and there is a problem in practical use ×… Ink bleed is conspicuous and is not suitable for practical use

(d) Light resistance Using a strong energy xenon weather meter SC750-WN manufactured by Suga Test Instruments Co., Ltd., the printed matter was irradiated with light for 30 hours, and a color difference ΔE before and after irradiation was determined.

In this case, as irradiation conditions, xenon lamp light was used as a light source, room temperature was 25 ° C., humidity was 50% Rh, and irradiance was 100 W / m ² (300 to 400 nm).

Further, the color difference ΔE before and after the irradiation was measured with Spectrolino (light source: D ₆₅ ; field of view: 2 °) manufactured by Gretag Macbeth, and L ^* a ^* b ^* color specification standardized by the CIE (International Commission on Illumination) The color difference ΔE of the system was determined by the following formula.

（式中、ΔＬ^*＝照射前後の明度の差、
Δａ^*＝照射前後の赤緑方向の彩度の差、
Δｂ^*＝照射前後の黄青方向の彩度の差）

(Where, ΔL ^* = difference in brightness before and after irradiation,
Δa ^* = saturation difference in red and green directions before and after irradiation,
Δb ^* = difference in yellow-blue saturation before and after irradiation)

And it evaluated as follows with the magnitude | size of (DELTA) E.
◎… ΔE is less than 5 ○… ΔE is 5 or more and less than 10 △… ΔE is 10 or more and less than 20 ×… ΔE is 20 or more

(e) Color development The printed color patch was visually confirmed and evaluated as follows.
◎… Has vivid color developability ○… No problem in color developability △… Some problems in color developability and practical problems ×… There is a problem in color developability clearly and is not suitable for practical use

(f) Ozone resistance and fading balance For the evaluation of ozone resistance, a color patch printed matter was used with an ozone resistance test (Suga Test Instruments Co., Ltd., Ozone Weather Meter OMS-H). When exposed to an atmosphere with an internal temperature of 24 ° C. and a humidity of 60% Rh for 40 hours, for each patch of yellow, magenta, cyan, red, green, and blue, the color difference ΔE before and after the exposure is as follows: (d) It asked similarly.

Further, the fading balance was evaluated as follows by the difference (Δ (ΔE) _max ) between the maximum value and the minimum value of the color difference ΔE of each color.
○ ... Δ (ΔE) _max is less than 10 Δ ... Δ (ΔE) _max is 10 or more and less than 20 × ... Δ (ΔE) _max is 20 or more

  The ink sets of Examples 1 to 5 consist of pigment-based black ink and blue ink, and dye-based yellow ink, magenta ink, and cyan ink, and (a) feathering of text printed matter, (b) paper surface drying property. (C) Water resistance, (d) Light resistance, (e) Color development of color patch prints, (f) Ozone resistance and fading balance were all good.

  In particular, the black pigment ink and the blue pigment ink used in Examples 1 to 3 have a dynamic surface tension of 40 mN / m or more and 45 mN / m or less at 25 ° C. and a lifetime of 100 ms. Both were better than the other examples.

  On the other hand, from Comparative Examples 1 to 4, when text was not printed with pigment-based ink but printed with dye-based ink, feathering, water resistance, and light resistance were inferior. In particular, in Comparative Examples 1 and 2 that do not contain either a blue pigment ink or a blue dye ink, a blue text is expressed using a magenta dye ink and a cyan dye ink, so a dye-based ink is used. In addition to the feathering caused by the two types of ink and the feathering caused by the increase in the ink amount due to the use of two types of ink, a deviation due to landing error occurred, and the sharpness of the blue text printing was remarkably inferior. Further, in Comparative Examples 1 to 3 not including the blue pigment ink, the ozone resistance (ΔE) of the color patch was significantly inferior in the cyan and blue patches.

  In Comparative Example 5 in which the inks constituting the ink set are all pigment-based inks, blue text printing is expressed using magenta pigment ink and cyan pigment ink, so that two types of ink are used. Misalignment due to the effect of feathering due to an increase in the amount of ink and landing errors of the two types of ink was observed. Further, the color developability of the color patch was clearly inferior to that of the example.

  The aqueous ink set for inkjet recording and the inkjet recording method of the present invention are useful when printing a color image and black text or blue text by the inkjet recording method.

Claims (9)

  An aqueous ink set for ink-jet recording composed of yellow ink, magenta ink, cyan ink, black ink and blue ink containing at least a colorant, water and a water-soluble organic solvent, and coloring of yellow ink, magenta ink and cyan ink A water-based ink set for ink-jet recording, wherein the agent is a water-soluble dye, and the colorant for black ink and blue ink is a pigment.   2. The dynamic surface tension of black ink and blue ink at a lifetime of 100 ms measured by a maximum bubble pressure method (bubble pressure method) at 25 ° C. is 40 mN / m or more and 45 mN / m or less, respectively. The water-based ink set for inkjet recording as described.   The blue ink colorant is C.I. I. The water-based ink set for inkjet recording according to claim 1 or 2, comprising at least one of CI Pigment Blue 15: 3 and 60.   The water-based ink set for inkjet recording according to any one of claims 1 to 3, wherein the colorant of the black ink is carbon black.   Yellow ink containing water-soluble dye as colorant, magenta ink containing water-soluble dye as colorant, cyan ink containing water-soluble dye as colorant, black ink containing pigment as colorant, and pigment as colorant An ink jet recording method for performing ink jet recording by ejecting and adhering the ink constituting a water-based ink set for ink jet recording containing a blue ink containing an ink from an ink jet head to a recording material, comprising: a cyan ink on a recording material An ink jet recording method comprising using a blue ink together with a cyan ink in a recording portion.   6. The ink jet recording method according to claim 5, wherein the amount of blue ink adhering to the recording material is 10 vol% or more and 20 vol% or less of the amount of cyan ink adhering to the cyan ink recording portion.   6. The dynamic surface tension of black ink and blue ink at a lifetime of 100 ms measured by a maximum bubble pressure method (bubble pressure method) at 25 ° C. is 40 mN / m or more and 45 mN / m or less, respectively. Or the inkjet recording method of 6.   The blue ink colorant is C.I. I. The inkjet recording method according to claim 5, comprising at least one of CI Pigment Blue 15: 3 and 60. The ink jet recording method according to claim 5, wherein the black ink colorant is carbon black.