JP2006063322A - Water-based ink set for ink-jet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based ink set for ink-jet recording effective for decreasing the bleeding between a black (Bk) ink and a yellow (Y) ink and decreasing the color shading of a color-mixed part in the case of using color inks. <P>SOLUTION: The water-based ink set for ink-jet recording is composed at least of a Bk ink, a Y ink, a magenta (M) ink and a cyan (C) ink. The dynamic surface tension is measured on each ink by a maximum bubble pressure method at 25°C and the same life time between 30 ms and 1,000 ms. The surface tension of the Y ink is not smaller than Bk ink and the difference is ≤5 mN/m, the difference between Y ink and M ink and the difference between Y ink and C ink are each ≥3 mN/m and the surface tension values of the M ink and the C ink are smaller than that of the Bk ink. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a water-based ink for ink jet recording for reducing bleeding between a black ink (hereinafter referred to as Bk ink) and a yellow ink (hereinafter referred to as Y ink) and also reducing color unevenness in a mixed color portion of the color ink. Regarding the set.

  Examples of the ink jet recording method include an electrostatic suction method, a method of applying mechanical vibration or displacement to the ink using a piezoelectric element, a method of generating bubbles by heating the ink, and utilizing a pressure generated at that time. Ink droplets are formed by this ink ejection method, and a part or all of them are attached to a recording material such as paper to perform recording.

  As an ink for ink jet recording used in such an ink jet recording method, one obtained by dissolving or dispersing a pigment or dye in a liquid medium composed of water and a water-soluble organic solvent is known.

  The ink for ink jet recording is required to have an optimum performance for use in the ink jet recording method. Specifically, for example, when an image is formed on the recording paper, the ink is irregular along the fibers of the recording paper. There is no ink flow or irregular ink permeation between fibers (hereinafter referred to as bleeding), high image quality with sharp image contours, fast drying when recording on recording paper, and abrasion resistance It is required that the resin material and metal material used in the ink jet head are not corroded, the nozzle is not clogged, and stable ink ejection is possible over a long period of time. Improvements have been made. Further, in recent years, the demand for recording on plain paper rather than ink jet dedicated paper has increased due to cost and environmental considerations.

  However, when recording on plain paper with conventional ink, there is a problem in that different colors are mixed at the adjacent boundary portions (hereinafter referred to as bleeding), resulting in a deterioration in print quality. This bleeding is a particularly serious problem because the difference between brightness and darkness is so conspicuous that the Bk ink and the Y ink are easily noticeable.

  As a means for solving such a problem, there is known a method (Patent Document 1) in which a compound that enhances permeability such as a surfactant is added to ink. According to this method, bleeding between Bk ink and Y ink is known. However, when using color ink, the color unevenness of the mixed color portion deteriorates. On the other hand, a polyhydric alcohol alkyl ether such as diethylene glycol butyl ether is used as a penetrant to improve color unevenness in the mixed color portion when using color ink, as is also applied to commercially available color ink jet recording inks. When a large amount is added to the ink, the bleeding between the Bk ink and the Y ink becomes remarkable. Therefore, in the conventional method, it is extremely difficult to achieve both the reduction of bleeding between the Bk ink and the Y ink and the reduction of color unevenness in the mixed color portion of the color ink.

JP 55-65269 A

  The ink set for ink-jet recording of the present invention is made to solve the above-mentioned problems, and achieves both reduction of bleeding between the Bk ink and Y ink and reduction of color unevenness in the mixed portion of the color ink. With the goal.

The present invention has been made to solve such problems, and the gist of the present invention is at least Bk ink, Y ink, magenta ink (hereinafter referred to as M ink), and cyan ink (hereinafter referred to as C ink). In a water-based ink set for ink jet recording consisting of ink), the dynamic dynamic surface tension of each ink at the same lifetime within a measurement temperature of 25 ° C. and a lifetime of 30 ms to 1000 ms by the maximum bubble pressure method,
(1) Y ink is Bk ink or more,
(2) The difference between Y ink and Bk ink is 5 mN / m or less,
(3) The difference between Y ink and M ink and the difference between Y ink and C ink are both 3 mN / m or more,
(4) A water-based ink set for ink-jet recording, wherein M ink and C ink are lower than Bk ink.

  In particular, in this water-based ink set for inkjet recording, the difference between Y ink and M ink and the difference between Y ink and C ink are both 3 mN / m to 15 mN / m, and the difference between Y ink and Bk ink is An embodiment in which the difference between Y ink and M ink and the difference between Y ink and C ink are both 3.5 mN / m to 12 mN / m, and the dynamic surface of Y ink It is related with the aspect whose tension is 38 mN / m-52 mN / m.

  According to the water base ink set for ink jet recording of the present invention, it is possible to achieve both reduction of bleeding between Bk ink and Y ink and reduction of color unevenness in a mixed color portion of color ink.

  The water base ink set for ink jet recording in the present invention comprises at least Bk ink, Y ink, M ink, and C ink.

  The aqueous ink set for ink-jet recording of the present invention has the following (1) and (2) for the dynamic surface tension of each ink at the same lifetime within a measurement temperature of 25 ° C. by a maximum bubble pressure method and a lifetime of 30 ms to 1000 ms. ), (3) and (4) are all satisfied.

(1) Y ink is Bk ink or more (2) Difference between Y ink and Bk ink is 5 mN / m or less, preferably 0 mN / m to 4.5 mN / m (3) Y ink The difference between the M ink and the difference between the Y ink and the C ink are both 3 mN / m or more, preferably 3 mN / m to 15 mN / m, more preferably 3.5 mN / m to 12 mN / m. ) M ink and C ink are lower than Bk ink

  Regarding (1), when the dynamic surface tension of the Y ink is equal to or greater than the dynamic surface tension of the Bk ink, the penetrating power of these Y and Bk inks into the recording material becomes approximately the same. Alternatively, the penetrating power of Y ink is lower than that of Bk ink. For this reason, the penetration of the Y ink is pulled by the penetration of the Bk ink, and the Y ink is mixed in the Bk ink recording portion side, so that bleeding is not noticeable. On the other hand, if the dynamic surface tension of the Y ink is less than the dynamic surface tension of the Bk ink, the penetrating power of the Bk ink is lower than that of the Y ink at the contact surface between the Y ink and the Bk ink, and the Y ink recording is performed. This is not preferable because Bk ink is mixed on the partial side and bleeding becomes conspicuous.

  Regarding (2), if the value obtained by subtracting the dynamic surface tension of the Bk ink from the dynamic surface tension of the Y ink exceeds 5 mN / m, the penetration of the Y ink is excessively pulled by the penetration of the Bk ink. Bleeding with Y ink tends to be noticeable, which is not preferable. However, when it is 5 mN / m or less, it is difficult to stand out, which is preferable. In order to make the bleeding of Y ink and Bk ink less noticeable, the value obtained by subtracting the dynamic surface tension of Bk ink from the dynamic surface tension of Y ink is preferably set to 0 mN / m to 4.5 mN / m. .

  Regarding (3), the value obtained by subtracting the dynamic surface tension of the M ink from the dynamic surface tension of the Y ink and the value obtained by subtracting the dynamic surface tension of the C ink from the dynamic surface tension of the Y ink are 3 mN / m or more. When Y ink alone has low penetrating power, it is preferable because the ink penetrating power as a whole increases and color unevenness hardly occurs in the mixed color portion of Y ink and M ink or Y ink and C ink. However, if this value is less than 3 mN / m, the dynamic surface tension of M ink and C ink is as high as that of Y ink, so that sufficient ink permeation cannot be obtained as a whole of the mixed color portion, resulting in uneven color. Is liable to occur. In order to further reduce the color unevenness, it is preferable that the value of the dynamic surface tension is 3.5 mN / m or more.

  On the other hand, in order to sufficiently reduce bleeding of Y ink and M ink, Y ink and C ink, Bk ink and M ink, and Bk ink and C ink, the dynamic surface tension of M ink is determined from the dynamic surface tension of Y ink. The value obtained by subtracting the tension and the value obtained by subtracting the dynamic surface tension of the M ink from the dynamic surface tension of the Y ink is preferably 15 mN / m or less, and more preferably 12 mN / m or less.

  Regarding (4), if the dynamic surface tension of the Bk ink is lower than the dynamic surface tension of the M ink and the dynamic surface tension of the C ink, the bleeding of the Bk ink is noticeable or the penetration of the M ink and the C ink Insufficient properties cause color unevenness in the mixed color portion of M ink and C ink, but by making the dynamic surface tension of Bk ink higher than the dynamic surface tension of M ink and the dynamic surface tension of C ink Bk ink bleeding or color unevenness in the mixed color portion of M ink or C ink can be reduced.

  The dynamic surface tension of the M ink and the C ink may be the same or a large one under the same lifetime within a measurement temperature of 25 ° C. and a lifetime of 30 ms to 1000 ms by the maximum bubble pressure method. Good.

  In addition, in each of the Bk ink, the Y ink, the M ink, and the C ink, in an ink set that uses an ink having a different colorant concentration corresponding to each ink, at least one of the ink and the ink having a different color density The above conditions (1), (2), (3) and (4) may be satisfied.

  Here, the above conditions (1), (2), (3) and (4) indicate that the conditions are satisfied in all the same lifetimes within the range of lifetimes 30 ms to 1000 ms.

  Furthermore, in the present invention, the dynamic surface tension of Y ink is preferably 38 mN / m to 52 mN / m at a measurement temperature of 25 ° C. by the maximum bubble pressure method and a dynamic surface tension within a lifetime of 30 ms to 1000 ms. 40 mN / m to 50 mN / m is more preferable. If the dynamic surface tension is less than 38 mN / m, the Bk ink tends to bleed when the dynamic surface tensions of the Y ink and the Bk ink are approximately the same, which is not preferable. On the other hand, if the dynamic surface tension exceeds 52 mN / m, it is not preferable because the ink ejection property is deteriorated and the color unevenness tends to be deteriorated.

で表される。ここで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り、その最大値は気泡の曲率半径がプローブ先端部分の半径と等しい時の最大圧力（最大泡圧）である。 In general, it is known that the dynamic surface tension is 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 a comparison such as ink ejection. This is based on the maximum bubble pressure method suitable for measuring the surface tension of a short life. In the measurement by the maximum bubble pressure method, gas is sent from the 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 bubble generation speed is changed, and the surface tension is measured from the pressure applied to the bubbles from the ink that changes accordingly. When the bubble radius is 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

It is represented by Here, r is the radius of the probe tip, and ΔP is the difference between the maximum value and the minimum value of the pressure applied to the bubble. The maximum value is the maximum pressure (maximum when the radius of curvature of the bubble is equal to the radius of the probe tip. Bubble pressure).

  In addition, the term “lifetime” as used in the present invention refers to the time from when a bubble is separated from the probe after the maximum bubble pressure and a new surface is formed to the next maximum bubble pressure.

  Each ink constituting the aqueous ink set for ink jet recording of the present invention contains at least a colorant such as water, a dye and a pigment, and a penetrant.

  Use high-purity water such as ion-exchanged water, distilled water, and ultrapure water instead of ordinary tap water to prevent clogging of nozzles and filters due to impurities contained in the water. Is preferred. The water content in each ink is 10% to 98% by weight, more preferably 30% to 97% by weight, and more preferably 40% to 95% by weight with respect to the total weight of each ink.

  There is no problem even if the colorant contained in each ink is either a dye or a pigment. However, Bk ink is generally used when printing text data on a recording material, and at that time, it is required to prevent blurring and bleeding to increase the sharpness and contrast of the edge portion of the text, and to increase the visibility of the text. Is strong. In addition, improvement in water resistance and light resistance is also required. Therefore, in order to meet these requirements, it is preferable to use a pigment as the colorant. On the other hand, color inks such as Y ink, M ink, and C ink are often used for printing graphic data and the like. Therefore, it is preferable to use a dye as the colorant so that the color portion is well colored and has a vivid color.

  Examples of the dye that can be used in each ink include water-soluble dyes represented by direct dyes, acid dyes, basic dyes, and reactive dyes. Among these dyes, those satisfying the performance required for each ink, such as sharpness, water solubility, stability, light resistance, and the like, for example, Color Index (hereinafter referred to as CI) Direct Black 17, 19, 32, 51, 71, 108, 146, 154 and 168, C.I. I. Direct Blue 6, 22, 25, 71, 86, 90, 106 and 199, C.I. I. Direct Red 1, 4, 17, 28, 83 and 227, C.I. I. Direct Yellow 12, 24, 26, 86, 98, 132 and 142, C.I. I. Direct orange 34, 39, 44, 46 and 60, C.I. I. Direct violet 47 and 48, C.I. I. Direct Brown 109, C.I. I. Direct dyes such as Direct Green 59; C.I. I. Acid Black 2, 7, 24, 26, 31, 52, 63, 112 and 118, C.I. I. Acid Blue 9, 22, 40, 59, 93, 102, 104, 113, 117, 120, 167, 229 and 234, C.I. I. Acid Red 1, 6, 32, 37, 51, 52, 80, 85, 87, 92, 94, 115, 181, 256, 289, 315 and 317, C.I. I. Acid Yellow 11, 17, 23, 25, 29, 42, 61 and 71, C.I. I. Acid Orange 7 and 19, C.I. I. Acid dyes such as Acid Violet 49; C.I. I. Basic Black 2, C.I. I. Basic Blue 1, 3, 5, 7, 9, 24, 25, 26, 28 and 29, C.I. I. Basic Red 1, 2, 9, 12, 13, 14 and 37, C.I. I. C. basic dyes such as basic violet 7, 14, and 27; I. Reactive blue 2, 5, 7, 12, 13, 14, 15, 17, 18, 19, 20, 21, 25, 27, 28, 37, 38, 40, 41 and 71, C.I. I. Reactive Red 6, 7, 11, 12, 15, 17, 21, 23, 24, 35, 36, 42, 63, 66 and 180, C.I. I. Reactive yellow 1, 2, 3, 13, 14, 15 and 17, C.I. I. Reactive oranges 2, 5, 7, 16, 20 and 24, C.I. I. Reactive violet 2, 4, 5, 8 and 9, C.I. I. Reactive Brown 1, 7 and 16, C.I. I. Reactive dyes such as Reactive Green 5 and 7; Food Black 1 and 2; and the like can be used, and one or two or more of these can be used to obtain an ink of a desired color.

  As the pigment, carbon black, inorganic pigments and organic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments; polycyclic rings such as phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments Formula pigments; Dye lake pigments such as basic dye type lake pigments and acid dye type lake pigments; Organic pigments such as nitro pigments, nitroso pigments, aniline black daylight fluorescent pigments; titanium oxides, iron oxides, carbon blacks, etc. Inorganic pigments can be mentioned. Also, other pigments can be used as long as they can be dispersed in the aqueous phase. Specific examples of these pigments include C.I. I. Pigment Black 1 and 7; C.I. I. Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 65, 74 and 83; I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 49, 50, 51, 52, 53, 55, 60, 64, 83, 87, 88, 89, 90, 112, 114, 122, 123 and 163; I. Pigment Blue 2, 3, 15, 16, 22 and 25 can be used, and an ink having a desired color can be obtained by using one or two or more of these.

  Furthermore, a self-dispersing pigment obtained by surface-treating a pigment with a surfactant, a polymer dispersant or the like, for example, graft carbon can also be used. Commercially available products can be used as the self-dispersing pigment, such as carbon black, CAB-O-JET (registered trademark) 200, 250, 260, 300 and 700 manufactured by Cabot Specialty Chemicals, Inc. BONJET (registered trademark) BLACK CW-1, CW-2, CW-3, etc. are available.

  The total content of the colorant contained in each ink is 0.1% to 20% by weight, preferably 0.3% to 15% by weight, more preferably 0.5% by weight, based on the total weight of each ink. -10% by weight. If it is less than 0.1% by weight, the color fading speed of the ink on the recording material is rapidly increased, so that the color balance cannot be maintained and a sufficient print density cannot be obtained. On the other hand, if the amount exceeds 20% by weight, the dye may not be sufficiently dissolved in the ink composition and the dye may precipitate, and if it is a pigment, it will be difficult to maintain dispersion stability. Is also not preferred.

  The penetrant contained in each ink is preferably a polyhydric alcohol alkyl ether with low odor and low vapor pressure. Among the polyhydric alcohol alkyl ethers, the ink penetration rate into a recording material such as paper is effective. It is preferable to select and use a material that improves the quick-drying property of the ink on the recording material, prevents bleeding due to the slow-drying property, and does not easily cause bleeding due to permeation. Specific examples of such polyhydric alcohol alkyl ethers include, for example, diethylene glycol methyl ether, diethylene glycol butyl ether, diethylene glycol isobutyl ether, dipropylene glycol methyl ether, dipropylene glycol propyl ether, dipropylene glycol isopropyl ether, dipropylene glycol butyl ether, Examples thereof include triethylene glycol methyl ether, triethylene glycol butyl ether, tripropylene glycol methyl ether, and tripropylene glycol butyl ether. You may use these 1 type or in mixture of 2 or more types.

  The content of penetrant in each ink is 0.05% to 20% by weight, preferably 0.1% to 15% by weight, based on the total weight of each ink. If it is less than 0.05% by weight, the ink penetration rate into the recording material is slow, causing problems in drying time and bleeding, and if it exceeds 20% by weight, the ink excessively penetrates into the recording material. This is not preferable because the ink reaches the back surface of the ink and the bleeding occurs remarkably.

  Furthermore, a wetting agent may be optionally added to each ink in order to prevent the ink from drying at the nozzle of the head of the ink jet recording system printer and to improve the liquid stability of the ink. Specific examples of the wetting agent include, for example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, 1,3-butanediol, 1,5-pentanediol, 1,6- Polyhydric alcohols such as hexanediol, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol; N-methyl-2-pyrrolidone, N-hydroxyethyl Nitrogen-containing heterocyclic compounds such as 2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolidinone, and ε-caprolactam; amides such as formamide, N-methylformamide, N, N-dimethylformamide; ethanolamine, Jietanau Can be exemplified dimethyl sulfoxide, sulfolane, and the like sulfur-containing compounds such as thiodiethanol; amines, triethanolamine, ethylamine, diethylamine, amines such as triethylamine. You may use these 1 type or in mixture of 2 or more types.

  The content of the wetting agent in each ink is determined in a wide range depending on the ink composition or desired ink characteristics, but is usually preferably 0 to 40% by weight, and preferably 0% by weight based on the total weight of each ink. % To 30% by weight is more preferable. Exceeding 40% by weight is not preferable because the ink may thicken more than necessary, which may cause problems such as difficulty in ejection and extremely slow drying on the recording material.

  Further, monovalent alcohols such as ethanol and isopropyl alcohol may be used for the purpose of controlling the penetrability of the ink into the recording material and the drying property.

  In addition to water, a colorant, and a penetrating agent, each ink constituting the aqueous ink set for inkjet recording of the present invention includes, as an optional component, a commonly used dispersion in addition to the wetting agent and monohydric alcohol described above. An agent, a viscosity modifier, a surfactant, a pH adjuster, an antiseptic and antifungal agent and the like may be added as necessary. In addition, when applied to an ink jet system in which ink is ejected by the action of thermal energy, an additive that adjusts thermal physical properties such as specific heat, thermal expansion coefficient, and thermal conductivity may be used.

  Hereinafter, some examples of the present invention will be shown and the present invention will be clarified more specifically, but the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention, in addition to the above specific description. It should be understood that modifications and the like can be made.

(1) Preparation of ink and measurement of dynamic surface tension Each ink used in Examples and Comparative Examples was prepared as follows.

  Bk ink is 35% by weight of CAB-O-JET (registered trademark) 300 (colorant solid content concentration 15%) manufactured by Cabot Specialty Chemicals as a colorant, and 21.5% by weight of glycerin as a wetting agent. As a surfactant, 1.0% by weight of dipropylene glycol propyl ether, 0.1% by weight of Sannol (registered trademark) DL-1430 manufactured by Lion Co., Ltd., and 42.4% by weight of ultrapure water as a surfactant were sufficiently measured. Obtained by stirring and mixing.

  Y-1 to Y-6 ink, M-1 to M-2 ink, and C-1 to C-2 ink were prepared in the same manner as the Bk ink according to the composition shown in Table 1.

In addition, the dynamic surface tension of each ink was measured using an automatic dynamic surface tension meter BP-D4 manufactured by Kyowa Interface Science Co., Ltd. at a measurement temperature of 25 ° C. under measurement conditions of a lifetime of 20 ms to 5000 ms. Table 1 shows values of time 30 ms and 1000 ms.

(2) Examples 1-2 and Comparative Examples 1-5: Structure of Ink Set In Examples 1-2 and Comparative Examples 1-5, Bk ink, Y ink, M ink, and C ink prepared by the above method were used. The ink set was configured by combining as shown in Table 2.

  The dynamic surface tension measured in (1) for each ink set is shown in FIGS. 1 to 6 as a relationship diagram with the lifetime.

(3) Evaluation:
An ink tank is filled with the ink of each ink set of Examples 1-2 and Comparative Examples 1-5, and a predetermined pattern sample is printed using MFC-3100C manufactured by Brother Industries, Ltd. (a) Bleeding evaluation (B) Bleeding evaluation of black part and yellow part, (c) Color unevenness evaluation of mixed color part (red part) of Y ink and M ink and mixed color part (green part) of Y ink and C ink, d) Comprehensive judgment was performed as follows.

(a) Bleeding evaluation Evaluation As a pattern sample, black characters were printed without a background, and line disturbance due to ink bleeding and character readability were evaluated according to the following criteria. In this case, the font size was set to 11 and plain paper (Fuji Xerox Office Supply Co., Ltd., 4200DP PAPER 20LB) was used.
○… There is almost no bleeding and the characters are clear. ×… Bleeding is clearly occurring, but the characters can be read.

(b) Bleeding evaluation As an evaluation pattern sample, an image in which black and yellow are combined with the text color and background color is printed, and as a control pattern sample, black and yellow text is printed without a background. did. In this case, the font was set to a font size of 11 and plain paper (Fuji Xerox Office Supply Co., Ltd., 4200DP PAPER 20LB) was used as the recording paper.

The evaluation was performed according to the following criteria based on the degree of bleeding at the boundary surface where the colors are mixed and the readability of the characters by comparing the characters with background and characters without background by visual observation.
◎… There is almost no bleeding and the same level of clarity compared to characters with no background. ○… Slight bleeding occurs compared to characters with no background. … Obtaining bleeding clearly compared to characters without background, making it difficult to interpret the characters

(c) Color unevenness evaluation As a pattern sample for color unevenness evaluation, a pattern in which each ink blending ratio is 1: 1 and the size of the mixed color portion is 3 cm in length and 3 cm in width is a plain paper (Fuji Xerox Office Supply Co., Ltd.). 4200DP PAPER 20LB), and visually observe the mixed color part (red part) of Y ink and M ink and the mixed color part (green part) of Y ink and C ink from a place about 30 cm away from each other. Uniformity was evaluated. The evaluation criteria are as follows.
○: Color unevenness is hardly noticeable in the mixed color part ×: Clear color unevenness is generated in the mixed color part

(d) Comprehensive judgment Comprehensive judgment was performed according to the following criteria.
○: Each evaluation of bleeding, bleeding, and color unevenness is ◎ or ○ ×: There is at least one × in each evaluation of bleeding, bleeding, and color unevenness Table 2 shows the evaluation results.

  From the above, in the water-based ink sets for ink jet recording of Examples 1 and 2, black bleeding, black and yellow bleeding, a mixed color portion of Y ink and M ink (red portion), and a mixed portion of Y ink and C ink An ink set having favorable color unevenness in the (green part) could be obtained. On the other hand, in the water base ink set for ink jet recording of Comparative Examples 3 to 4, the dynamic surface tension of Y ink is smaller than the dynamic surface tension of Bk ink in the entire region of lifetime 30 ms to 1000 ms. Since the dynamic surface tension of the Y ink is smaller than the dynamic surface tension of the Bk ink in almost the entire region of 30 ms to 1000 ms, bleeding between black and yellow occurs, and sufficient print quality cannot be obtained.

  In Comparative Example 2, there was a portion where the difference in the dynamic surface tension between the Y ink and the Bk ink exceeded 5 mN / m, so that black and yellow bleeding occurred. Furthermore, in Comparative Example 2, since there is a portion where the dynamic surface tension of Y ink exceeds 52 mN / m, the difference in dynamic surface tension between Y ink and M ink and the dynamic surface tension between Y ink and C ink are present. Even if the difference is 3 mN / m or more, the penetrability of the ink as a whole decreases in the mixed portion (red portion) of Y ink and M ink and the mixed portion (green portion) of Y ink and C ink. Color unevenness occurred and sufficient print quality could not be obtained.

  In Comparative Example 5, since the difference in dynamic surface tension between Y ink and M ink and the difference in dynamic surface tension between Y ink and C ink are less than 3 mN / m, color mixing between Y ink and M ink Color unevenness occurred in the portion (red portion) and the Y ink and C ink mixed portion (green portion), and sufficient print quality could not be obtained.

  The water-based ink set for ink-jet recording of the present invention is useful for printing clear text data with Bk ink with an ink-jet recording printer and printing a high-quality image with reduced color unevenness in the color portion.

3 is a graph showing measurement results of dynamic surface tension of each ink in Example 1. 6 is a graph showing measurement results of dynamic surface tension of each ink in Example 2. 6 is a graph showing measurement results of dynamic surface tension of each ink in Comparative Example 1. 6 is a graph showing measurement results of dynamic surface tension of each ink in Comparative Example 2. 10 is a graph showing measurement results of dynamic surface tension of each ink in Comparative Example 3. 10 is a graph showing measurement results of dynamic surface tension of each ink in Comparative Example 4. 14 is a graph showing measurement results of dynamic surface tension of each ink in Comparative Example 5.

Claims (6)

In a water-based ink set for ink-jet recording composed of at least black ink, yellow ink, magenta ink, and cyan ink, the dynamics of each ink in the same lifetime within a measurement temperature of 25 ° C. and a lifetime of 30 ms to 1000 ms by the maximum bubble pressure method For surface tension,
(1) Yellow ink is more than black ink,
(2) The difference between yellow ink and black ink is 5 mN / m or less,
(3) The difference between yellow ink and magenta ink and the difference between yellow ink and cyan ink are both 3 mN / m or more,
(4) A water-based ink set for ink-jet recording, wherein magenta ink and cyan ink are lower than black ink.   The difference between yellow ink and magenta ink and the difference between yellow ink and cyan ink are the dynamic surface tension of each ink within the range of measurement temperature 25 ° C. and lifetime 30 ms to 1000 ms by the maximum bubble pressure method. The water-based ink set for inkjet recording according to claim 1, wherein both are 3 mN / m to 15 mN / m.   The difference between the yellow ink and the black ink is 0 mN / m to 4.5 mN / m with respect to the dynamic surface tension of each ink in the same lifetime within the measurement temperature of 25 ° C. by the maximum bubble pressure method and the lifetime of 30 ms to 1000 ms. The aqueous ink set for inkjet recording according to claim 1, wherein the difference between the yellow ink and the magenta ink and the difference between the yellow ink and the cyan ink are 3.5 mN / m to 12 mN / m.   4. The ink jet recording according to claim 1, wherein the dynamic surface tension of the yellow ink is 38 mN / m to 52 mN / m within a measurement temperature of 25 ° C. by a maximum bubble pressure method and a lifetime of 30 ms to 1000 ms. Water-based ink set.   The aqueous ink set for inkjet recording according to any one of claims 1 to 4, wherein each of the black ink, yellow ink, magenta ink, and cyan ink comprises at least water, a colorant, and a penetrating agent.   The aqueous ink set for inkjet recording according to any one of claims 1 to 5, wherein the colorant contained in the black ink is a pigment, and the colorant contained in the yellow ink, magenta ink and cyan ink is a dye.

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