JP2018069652A - Ink jet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording method capable of recording an image excellent in bleeding resistance by using an ink jet recording apparatus equipped with a line head.SOLUTION: There is provided an ink jet recording method for recording an image on a recording medium by discharging a first ink and a second ink having mutually different hues from a line head. The first ink contains a pigment and a fluorine-based surfactant, the difference between the dynamic surface tension of the first ink at a lifetime of 10 milliseconds and the dynamic surface tension of the second ink at a lifetime of 10 milliseconds is within 2 mN/m, the dynamic surface tensions of the first ink and the second ink at a lifetime of 10 milliseconds are 40 mN/m or less respectively, and an image is recorded on a recording medium by discharging the first ink and the second ink in this order.SELECTED DRAWING: None

Description

  The present invention relates to an ink jet recording method.

  In recent years, inkjet recording apparatuses have been increasingly used in offices, taking advantage of low power, low cost, and space saving. There is also a movement to improve recording speed (throughput) with the aim of further expanding usage in offices. For example, instead of a conventional serial recording head, a recording apparatus has been developed that employs a long recording head (line head) in which the array width of the ejection ports is extended to the maximum width of the paper (Patent Document 1). .

  However, when performing high-speed recording using an inkjet recording apparatus equipped with a line head, the recording medium is likely to be discharged through a discharge roller before the ink penetrates into the recording medium such as plain paper. For this reason, ink may adhere (offset) to the discharge roller, and image defects are likely to occur. In order to suppress the occurrence of such an offset, for example, an ink containing 1,2-octanediol as a high penetrant has been proposed (Patent Document 2).

  In addition, an ink set in which dynamic surface tension is controlled has been proposed in order to suppress bleeding (bleeding) at a boundary portion between an image recorded with black ink and an image recorded with color ink (Patent Document 3). Furthermore, there has been proposed an ink set including a black ink containing a self-dispersing pigment and a color ink, and these inks containing fluorinated surfactants having different structures (Patent Document 4).

JP 2010-143147 A JP 2013-124335 A JP 2007-217532 A JP 2010-070620 A

  When using an inkjet recording apparatus equipped with a line head, in order to cope with high-speed recording, the unit area of the recording medium passes only under the recording head only once, that is, an image is recorded in “one pass”. The inventors of the present invention studied pigment recording with reference to the prior art and recording an image with improved bleeding resistance using an inkjet recording apparatus equipped with a line head. As a result, it was found that by using the highly penetrable ink proposed in Patent Document 2, an offset is suppressed and an image with a certain quality can be recorded. However, when an image is recorded on a recording medium such as plain paper using the ink or ink set proposed in Patent Documents 2 to 4 using an ink jet recording apparatus equipped with a line head, bleeding resistance is insufficient. I understood it.

  Accordingly, an object of the present invention is to provide an ink jet recording method capable of recording an image having excellent bleeding resistance using an ink jet recording apparatus having a line head.

  The above object is achieved by the present invention described below. That is, according to the present invention, there is provided an inkjet recording method for recording an image on a recording medium by ejecting a first ink and a second ink having different hues from a line head, wherein the first ink comprises a pigment and a fluorine-based ink A surfactant is contained, and the difference between the dynamic surface tension of the first ink at a lifetime of 10 milliseconds and the dynamic surface tension of the second ink at a lifetime of 10 milliseconds is within 2 mN / m. The dynamic surface tension of the first ink and the second ink at a lifetime of 10 milliseconds is 40 mN / m or less, respectively, and the first ink and the second ink are ejected in this order to record the recording medium. An ink jet recording method is provided which records the image.

  ADVANTAGE OF THE INVENTION According to this invention, the inkjet recording method which can record the image excellent in bleeding resistance using the inkjet recording device provided with the line head can be provided.

It is a schematic diagram which shows an example of an inkjet recording device. FIG. 6 is a perspective view showing a discharge port surface of the head cartridge. FIG. 3 is a partially broken perspective view schematically showing a structure near a discharge port of a recording element substrate. It is a schematic diagram which shows an example of the supply mechanism which supplies ink to a line head.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. In the present invention, when the compound is a salt, the salt is dissociated into ions in the ink, but is expressed as “contains a salt” for convenience. Ink jet ink may be simply referred to as “ink”. Further, the physical property values are values at normal temperature (25 ° C.) unless otherwise specified.

<Inkjet recording method>
The ink jet recording method of the present invention is an ink jet recording method in which an image is recorded on a recording medium by discharging a first ink and a second ink having different hues from a line head. The first ink contains a pigment and a fluorosurfactant. The difference between the dynamic surface tension of the first ink at a lifetime of 10 milliseconds and the dynamic surface tension of the second ink at a lifetime of 10 milliseconds is within 2 mN / m, and the first ink and the second ink The dynamic surface tension at a lifetime of 10 milliseconds is 40 mN / m or less, respectively. The first ink and the second ink are ejected in this order to record an image on a recording medium.

In order to improve the recording speed, the present inventors employ a line-type recording head (line head) in which ejection openings for ejecting ink are arranged over the entire width of the recording medium in the conveyance direction (maximum paper width). A method for recording an image using the recording apparatus was examined. More specifically, a recording method in which even when ink is ejected from a line head, a reduction in image quality due to offset is less likely to occur. As a result, it has been found that if an ink having high permeability to a recording medium is used, an offset hardly occurs even when ejected from a line head, and a high-quality image can be recorded. However, when an image is recorded using a plurality of inks having different hues, the boundary between the image recorded with the first ink and the image recorded with the second ink, even if the dynamic surface tensions of the inks are made uniform. It turned out that bleeding tends to occur in the part. As a result of further studies, the present inventors satisfy the following requirements (1) and (2) even when a plurality of highly penetrating inks having different hues are ejected from the line head: It has been found that an image excellent in bleeding resistance can be recorded.
(1) The first ink contains a pigment and a fluorine-based surfactant.
(2) The first ink and the second ink are ejected in this order and applied to the recording medium.

  By satisfying the above requirements (1) and (2), an image having excellent bleeding resistance can be recorded even when a plurality of highly penetrable inks having different hues are ejected from the line head. About the reason, the present inventors presume as follows. When the first ink is applied to the recording medium, the moisture in the first ink gradually evaporates and the first ink penetrates into the recording medium. Furthermore, water molecules hydrated to the hydrophilic portion of the fluorosurfactant of the first ink are also hydrated with respect to calcium ions, magnesium ions, etc. present in the recording medium. For this reason, it is considered that the fluorosurfactant in the first ink is easily oriented so that a perfluoroalkyl group having very high hydrophobicity is located on the surface side of the recording medium. In other words, the area to which the first ink is applied has a water repellency due to the influence of the perfluoroalkyl group of the fluorosurfactant while being in a wet state. Then, when the second ink is applied so as to be adjacent to the region to which the first ink is applied, the second ink is likely to be repelled, and the occurrence of bleeding is considered to be suppressed.

(Inkjet recording device)
An ink jet recording apparatus used in the ink jet recording method of the present invention includes, for example, an ink storage unit that stores ink, and a line head that records an image by ejecting the ink stored in the ink storage unit onto a recording medium by an inkjet method. Prepare. And the ink accommodated in this ink accommodating part contains the 1st ink and 2nd ink from which a hue differs. Details of the ink jet recording apparatus will be described below with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating an example of an ink jet recording apparatus. The ink jet recording apparatus shown in FIG. 1 employs an ink jet printing system that records an image by ejecting ink from a line head group 101g composed of a plurality of line heads arranged along the conveyance direction (arrow A direction) of the recording medium. It has been adopted. The line head group 101g includes a black head 101Bk, a cyan head 101C, a magenta head 101M, and a yellow head 101Y. In each line head, for example, about 14,000 nozzles (discharge ports) are arranged in the paper width direction of the recording medium 103 (direction perpendicular to the conveyance direction of the recording medium 103) at a density of 1200 dpi.

  The recording medium 103 is fed by a registration roller 114 driven by a conveyance motor, and is guided by a pair of guide plates 115 and the leading ends thereof are registered, and then conveyed by a conveyance belt 111 that is an endless belt. . The conveyor belt 111 is held by two rollers 112 and 113, and the displacement of the upper portion of the conveyor belt 111 in the vertical direction is defined by the platen 104. The recording medium 103 is attracted to the transport belt 111 by electrostatic attraction, for example. The recording medium 103 on which an image is recorded while being transported by the transport belt 111 by the ink ejected from the line head group 101 g is discharged to the stocker 116 through the discharge roller 105.

  FIG. 2 is a perspective view showing the discharge port surface of the head cartridge. As shown in FIG. 2, the head cartridge H is provided with a plurality of recording element substrates 120 on which nozzles (ejection ports) for ejecting ink in the direction of the arrow are formed. The recording element substrate 120 is electrically connected to a flexible cable 130 that supplies electric power to each recording element substrate 120 and transmits a control signal.

  FIG. 3 is a partially broken perspective view schematically showing the structure near the discharge port of the recording element substrate. A plurality of heaters 121 and sub-heaters (not shown) for heating ink are arranged on the substrate 123. Further, a temperature sensor 128 for detecting the temperature of the line head is disposed on the substrate 123. On the substrate 123, a resin coating layer 127 and a discharge port plate 125 are sequentially laminated. In addition, the resin coating layer 127 is formed with a channel wall 126 that constitutes a channel for supplying ink to each ejection port 122, and the ejection port plate 125 is laminated on the resin coating layer 127. A plurality of nozzles that eject ink are formed. Ink that has flowed out of an ink tank (not shown) is supplied to each nozzle through the ink supply port 124, and then is given thermal energy by the heater 121 and is discharged from the discharge port 122.

  As the temperature sensor 128, for example, a diode having a property that the forward voltage changes according to the temperature can be used. It is not efficient to detect the ink temperature directly. For this reason, the temperature of the substrate 123 detected by the temperature sensor 128 may be adopted as the temperature of the recording head. As the temperature sensor 128 other than the diode, for example, a metal thin film sensor or the like can be used. Further, a thermistor (not shown) is provided on the substrate 123, and the environmental temperature can be read. The ink is filled in the nozzles from the ink supply port 124 to the discharge port 122. The ink can be heated by the heater 121 to cause film boiling in the ink, and the ink in the vicinity of the ejection port 122 can be ejected by the generation pressure of the bubbles.

  In FIG. 1, when recording is not performed (when the recording apparatus is not in operation), each line head is moved upward by a predetermined mechanism (not shown), and then a cap (not shown) is placed below each line head. Slide. Thereafter, the discharge ports 122 can be capped by lowering each line head. By capping the ejection port 122, evaporation of volatile components in the ink in the vicinity of the ejection port 122 can be prevented. Further, a recovery operation such as pressure recovery or suction recovery may be performed in a state where the ejection port 122 is capped at a stage before the start of recording. The pressure recovery is an operation of pressurizing the inside of the line head and discharging the ink in the nozzles from the ejection port 122. The suction recovery is an operation of reducing the pressure in the cap and discharging the ink in the nozzle from the ejection port 122. Both pressure recovery and suction recovery may be performed. Further, after the recovery operation, a wiping operation may be performed in which an adhering matter such as ink remaining on the ejection port surface is wiped with a wiping member.

  FIG. 4 is a schematic diagram illustrating an example of a supply mechanism that supplies ink to the line head. As shown in FIG. 4, ink is supplied from the sub tank T2 to the line head H1000 by the pump P1. The ink overflowing from the line head H1000 is returned to the sub tank T2. The valve V1 is provided for switching to pressurize or release the pressure of the ink liquid chamber inside the line head during the recovery operation. When the pressure is restored, the valve V1 is closed and the pressure is applied by the pump P1, whereby a part of the bubbles in the ink supply path and the ink flow path is removed. The ink liquid level in the sub-tank T2 is configured to maintain the water head difference from the discharge port surface of the line head H1000 within a certain range, and maintain the negative pressure on the discharge port surface of the line head H1000 within an appropriate range. To do. When the ink in the sub tank T2 is insufficient, the ink is sent from the main tank T1 to the sub tank T2 by the pump P2.

(ink)
In the ink jet recording method of the present invention, the first ink and the second ink having different hues are ejected from the line head to record an image on a recording medium. In the present invention, “different hues” means that the first ink and the second ink are classified into different hues within the range of hues classified into black and color. Color hues include cyan, magenta, yellow, red, green, blue, and the like. However, the hue of the first ink is preferably black. That is, it is preferable that the first ink is a black ink and the second ink is a color ink. The first ink and the second ink do not need to cause a reaction or thickening when they are in contact with each other. That is, it is not necessary for each ink to contain a reactive agent or a thickener.

[Pigment]
The first ink contains a pigment as a color material. Further, the color material contained in the second ink is not particularly limited, but it is preferable to use a pigment. Specific examples of the pigment include inorganic pigments such as carbon black; organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, and dioxazine. These pigments can be used alone or in combination of two or more. The pigment content (% by mass) in each ink is preferably 0.10% by mass or more and 15.00% by mass or less based on the total mass of the ink, and is 1.00% by mass or more and 10.00% by mass. More preferably, it is as follows.

  The pigment dispersion method is not particularly limited. For example, a resin-dispersed pigment dispersed with a resin dispersant, a pigment dispersed with a surfactant, a microcapsule pigment in which at least a part of the pigment particle surface is coated with a resin, or the like can be used. In addition, self-dispersed pigments in which a functional group containing a hydrophilic group such as an anionic group is bonded to the pigment particle surface, or a pigment (resin bond) in which an organic group containing a polymer is chemically bonded to the pigment particle surface Type self-dispersing pigments) and the like can also be used. In addition, pigments having different dispersion methods may be used in combination. However, in the case of a pigment of a type dispersed using a resin, the surfactant may be adsorbed on the resin. For this reason, in order to exhibit the effect of the present invention more effectively, at least one of the first ink and the second ink preferably contains a self-dispersing pigment.

[Fluorosurfactant]
The first ink contains a fluorinated surfactant. The fluorosurfactant may be any of anionic, cationic, and nonionic. The fluorosurfactant is preferably a perfluoroalkylethylene oxide adduct having a perfluoroalkyl group having 6 or less carbon atoms for the reasons described below. As the fluorosurfactant, it is preferable to use one that is stably present in the water-based ink. If the perfluoroalkyl group has more than 6 carbon atoms, the hydrophilic group (ethylene oxide group) must be lengthened in consideration of the stability in the ink. If it does so, the effect | action by having increased hydrophilicity will become more dominant, and the effect which further improves bleeding resistance may not be acquired enough.

Commercially available fluorosurfactants have the following trade names: Megafax: F470, F444 (above, manufactured by DIC); Surflon: S-141, S-145 (above, manufactured by Asahi Glass); Zonyl: FSO-100 FS-3100 (manufactured by DuPont). The content of the fluorosurfactant in the first ink is such that the dynamic surface tension γ ₁₀ of the first ink at 25 ° C. and a lifetime of 10 milliseconds is 40 mN / m or less, as measured by the maximum bubble pressure method. May be an amount that is 35 mN / m or less. Specifically, the content (% by mass) of the fluorosurfactant in the first ink is preferably 0.01% by mass or more and 0.20% by mass or less based on the total mass of the first ink. .

[Acetylene glycol surfactant]
The first ink and the second ink preferably each contain an acetylene glycol surfactant. By using the first ink and the second ink containing an acetylene glycol-based surfactant, an image superior in bleeding resistance can be recorded. When the acetylene glycol surfactant is contained in the first ink, the orientation speed of the acetylene glycol surfactant is high, so that the wettability of the first ink with respect to the recording medium is increased, and the penetration start is accelerated. However, when the first ink begins to permeate the recording medium, a fluorine-based surfactant having a low orientation speed but a high orientation power becomes dominant. Furthermore, since the acetylene glycol surfactant deprives water molecules hydrated to the fluorosurfactant, the second ink applied thereafter is more likely to be repelled. As a result, it is considered that an image superior in bleeding resistance can be recorded.

  In addition, since the acetylene glycol surfactant has a characteristic “U-shaped” skeleton, it has a high surface activity even though the hydrophobic portion is small. For this reason, when the acetylene glycol surfactant is contained in the second ink, the hydrated water molecules are not easily separated due to the “U-shaped” skeleton. As a result, it is considered that an image superior in bleeding resistance can be recorded.

  As the acetylene glycol surfactant, those represented by the following general formula (1) can be used.

（前記一般式（１）中、ｍ及びｎは、それぞれ独立に、整数を表す）

(In the general formula (1), m and n each independently represents an integer)

  In general formula (1), m is preferably an integer of 1 to 10, and n is preferably an integer of 1 to 10. A mixture of two or more compounds having different values of m and n can also be used.

  Commercially available acetylene glycol surfactants have the following trade names: acetylenol: E00, E13T, E40, E60, E100 (above, manufactured by Kawaken Fine Chemical); Surfynol: 465, 485 (above, Nissin Chemical Industry Manufactured).

  In both the first ink and the second ink, it is preferable to use an acetylene glycol ethylene oxide adduct having an HLB value obtained by the Griffin method of 11 or less as the acetylene glycol surfactant. When the HLB value is more than 11, it is necessary to add more in order to adjust the dynamic surface tension of each ink at a lifetime of 10 milliseconds. However, when the amount of the acetylene glycol surfactant added is increased, the bleeding resistance of the recorded image may be easily lowered. The HLB value is preferably 6 or more.

The HLB value by the Griffin method can be calculated from the following formula (1). The HLB value obtained by the Griffin method is a physical property value representing the degree of hydrophilicity or lipophilicity of the surfactant, and takes a value of 0 to 20. The smaller the HLB value, the higher the lipophilicity, and the higher the HLB value, the higher the hydrophilicity.
HLB value = 20 × formula weight of surfactant ethylene oxide group / molecular weight of surfactant (1)

The content of the acetylene glycol surfactant in each ink is determined by a maximum bubble pressure method. The dynamic surface tension γ ₁₀ of each ink at 25 ° C. and a lifetime of 10 milliseconds is 40 mN / m or less, preferably What is necessary is just the quantity used as 35 mN / m or less. Specifically, the content (% by mass) of the acetylene glycol surfactant in each ink is preferably 0.10% by mass or more and 2.00% by mass or less based on the total mass of each ink.

[Aqueous medium]
Each of the first ink and the second ink can contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. As water, it is preferable to use deionized water (ion exchange water). The content (% by mass) of water in each ink is preferably 50.00% by mass or more and 95.00% by mass or less based on the total mass of each ink. The content (% by mass) of the water-soluble organic solvent in each ink is preferably 3.00% by mass or more and 50.00% by mass or less based on the total mass of each ink. As the water-soluble organic solvent, any of those generally used for inks applied to the ink jet recording method can be used. Examples of the water-soluble organic solvent include alcohols, (poly) alkylene glycols, glycol ethers, nitrogen-containing compounds, and sulfur-containing compounds. These water-soluble organic solvents can be used alone or in combination of two or more.

[Other ingredients]
In addition to the above components, the first ink and the second ink may each contain a water-soluble organic compound that is solid at room temperature, such as urea and its derivatives, trimethylolpropane, and trimethylolethane. The content (% by mass) of the water-soluble organic compound in each ink is preferably 0.10% by mass or more and 10.00% by mass or less based on the total mass of each ink. In addition, in order to obtain an ink having a desired physical property value as necessary, a resin, an antifoaming agent, other surfactant, a pH adjuster, an antiseptic, an antifungal agent, an antioxidant, an anti-reduction agent, etc. Various additives may be contained.

[Ink properties]
The dynamic surface tensions of the first ink and the second ink at a lifetime of 10 milliseconds are each 40 mN / m or less, preferably 35 mN / m or less, and preferably 25 mN / m or more. The difference between the dynamic surface tension of the first ink at a lifetime of 10 milliseconds and the dynamic surface tension of the second ink at a lifetime of 10 milliseconds is within 2 mN / m, preferably within 1 mN / m. It is. By using the first ink and the second ink whose dynamic surface tension is controlled in the above relationship, even when the image is recorded on the recording medium by being ejected from the line head, the offset is unlikely to occur and the high quality is achieved. A good image can be recorded. The reason why the dynamic surface tension at the lifetime of 10 milliseconds is controlled is that it is considered that it is about 10 milliseconds that the ink spreads on the recording medium at a certain speed after the ink adheres to the recording medium. .

  The “dynamic surface tension” of the ink in the present invention is a physical property value measured by a maximum bubble pressure method. The maximum bubble pressure method is a method for measuring the maximum pressure required to release bubbles generated at the tip of a probe (thin tube) immersed in the liquid to be measured, and determining the surface tension of the liquid from this maximum pressure. The maximum pressure is measured while bubbles are continuously generated at the tip of the probe. At this time, the time from when the surface of a new bubble is generated at the tip of the probe until the maximum bubble pressure is reached (when the radius of curvature of the bubble is equal to the radius of the probe tip) is called a lifetime. The dynamic surface tension can be adjusted by, for example, the type and amount of a water-soluble organic solvent or surfactant.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited at all by the following Example, unless the summary is exceeded. In addition, what is described as “parts” and “%” with respect to the component amounts is based on mass unless otherwise specified.

<Preparation of pigment dispersion>
(Pigment dispersion Bk1)
20.0 g of pigment, 7.0 mmol of ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid monosodium salt, 20 mmol of nitric acid, and 200 mL of pure water were mixed for 30 minutes using a Silverson mixer. Stir to give a mixture. The mixing conditions were room temperature and 6,000 rpm. Carbon black (trade name “Black Pearls 880”, manufactured by Cabot) was used as the pigment. To the resulting mixture, 20 mmol of sodium nitrite dissolved in a small amount of water was slowly added and mixed. The temperature of the mixture reached 60 ° C. by mixing sodium nitrite. It was made to react in this state for 1 hour. Thereafter, an aqueous sodium hydroxide solution was added to adjust the pH of the mixture to 10. After 30 minutes, 20 mL of pure water was added, and diafiltration was performed using a spectrum membrane to obtain a self-dispersing pigment. Water was added to the obtained self-dispersed pigment to obtain a pigment dispersion Bk1 having a pigment content of 10.0%.

(Pigment dispersion C1)
The type of pigment is C.I. I. A pigment dispersion C1 having a pigment content of 10.0% was obtained by the same procedure as in the case of the pigment dispersion Bk1 except that Pigment Blue 15: 4 was used.

(Pigment dispersion M1)
The pigment is C.I. I. A pigment dispersion M1 having a pigment content of 10.0% was obtained by the same procedure as in the case of the pigment dispersion Bk1 except that the pigment red 122 was used.

(Pigment dispersion Y1)
The type of pigment is C.I. I. A pigment dispersion Y1 having a pigment content of 10.0% was obtained by the same procedure as in the case of the pigment dispersion Bk1 except that Pigment Yellow 74 was used.

(Pigment dispersion Bk2)
An aqueous solution of a resin dispersant in which a styrene / acrylic acid copolymer, which is a water-soluble resin, is dissolved in ion exchange water by adding sodium hydroxide equivalent to the acid value, and the resin content is 20.0%. Was prepared. The composition ratio (molar ratio) of the styrene / acrylic acid copolymer was styrene: acrylic acid = 33: 67, the weight average molecular weight was 8,000, and the acid value was 120 mgKOH / g. 10.0 parts of a pigment (trade name “Black Pearls 880”, carbon black, manufactured by Cabot), 30.0 parts of an aqueous solution of a resin dispersant, and 60.0 parts of water were placed in a sand grinder and dispersed for 1 hour. Centrifugation was performed to remove coarse particles, followed by pressure filtration using a microfilter having a pore size of 3.0 μm (manufactured by Fuji Film). An appropriate amount of ion-exchanged water was added to obtain a pigment dispersion Bk2 having a pigment content of 10.0% and a resin content of 6.0%.

(Pigment dispersion Y2)
The type of pigment is C.I. I. A pigment dispersion liquid having a pigment content of 10.0% and a resin content of 6.0% according to the same procedure as in the case of the pigment dispersion liquid Bk2 except that Pigment Yellow 74 was used. Y2 was obtained.

<Preparation of ink>
After mixing each component (unit:%) shown in the upper part of Table 1-1, 1-2, 2-1, and 2-2 and stirring sufficiently, a polypropylene filter having a pore size of 2.5 μm (manufactured by Pall) ) Was subjected to pressure filtration to prepare each ink (first ink and second ink). The dynamic surface tension γ ₁₀ of the prepared ink is shown in the lower part of Tables 1-1, 1-2, 2-1, and 2-2. The dynamic surface tension γ _{10 of the} ink was measured by a maximum bubble pressure method at 25 ° C. using a dynamic surface tension meter (trade name “BUBLE PRESSURE TENSIOMETER BP-2”, manufactured by KRUSS).

Details of the surfactants in Tables 1-1, 1-2, 2-1, and 2-2 are shown below.
・ Zonyl FSO-100 (trade name, manufactured by DuPont): perfluoroalkylethylene oxide adduct having a perfluoroalkyl group of 8 carbon atoms. • Zonyl FSA (trade name, manufactured by DuPont): anionic fluorosurfactant・ Zonyl FS-3100 (trade name, manufactured by DuPont): Perfluoroalkylethylene oxide adduct having 6 carbon atoms in the perfluoroalkyl group. • Polyfox PF-136A (trade name, manufactured by Omninova): anionic fluorine type Surfactant / Polyfox PF-151N (trade name, manufactured by Omnova): Perfluoroalkylethylene oxide adduct having 16 carbon atoms in the perfluoroalkyl group Acetyleneol E40: Acetylene glycol ethylene oxide having an HLB value of 9 Addendum (trade name, Kawaken Made § Inn Chemical)
Acetylenol E60: acetylene glycol ethylene oxide adduct having an HLB value of 11 (trade name, manufactured by Kawaken Fine Chemicals)
Acetylenol E100: acetylene glycol ethylene oxide adduct having an HLB value of 13 (trade name, manufactured by Kawaken Fine Chemicals)
-NIKKOL BL9EX (trade name, manufactured by Nikko Chemicals): polyoxyethylene alkyl ether

<Evaluation (bleeding resistance)>
The prepared ink is set in an ink jet recording apparatus having a line head having the configuration shown in FIGS. 1 to 4, and the first ink is applied to the first drop and the second ink is applied to the second drop. Images were recorded. As the recording medium, plain paper (trade name “HP Bright White Inkjet Paper”, manufactured by Hured Packard) was used. In this inkjet recording apparatus, 1/600 inch × 1/600 inch is defined as one pixel, and the recording duty of an image in which the applied amount of ink per pixel is 18 ng is defined as 100%. In the present invention, according to the following evaluation criteria, “A” and “B” are acceptable levels, and “C” and “D” are unacceptable levels.

(Examples 1-17, Comparative Examples 1-4)
Using the first ink and the second ink in the combinations shown in Table 3, the bleeding resistance of the images recorded by the procedure shown below was evaluated. First, an ink cartridge filled with each ink was set in the ink jet recording apparatus. Then, a solid image (2 cm × 2 cm) of the first ink having a recording duty of 100% and an image adjacent to the solid image (2 cm × 2 cm) of the second ink having a recording duty of 100% are recorded on a recording medium. A record was obtained. The boundary portion of each solid image in the obtained recorded matter was visually confirmed, and bleeding resistance was evaluated according to the following evaluation criteria. The results are shown in Table 3.
A: Bleeding hardly occurred.
B: Slight bleeding occurred.
C: Although bleeding occurred remarkably, the boundary could be discriminated.
D: Bleeding occurred remarkably and the boundary could not be determined.

(Examples 18 and 19, Comparative Examples 5 to 8)
An ink cartridge filled with four colors of ink was set in the ink jet recording apparatus so that recording was performed in the order of Bk → C → M → Y. Then, solid images (2 cm × 2 cm) of each ink having a recording duty of 100% were recorded on a recording medium to obtain a recorded matter. The boundary portion of each solid image in the obtained recorded matter was visually confirmed, and bleeding resistance was evaluated according to the following evaluation criteria. The results are shown in Table 4.
A: Bleeding hardly occurred.
B: Slight bleeding occurred.
C: Although bleeding occurred remarkably, the boundary could be discriminated.
D: Bleeding occurred remarkably and the boundary could not be determined.

(Reference Examples 1-4)
Using the first ink and the second ink in the combinations shown in Table 5, the bleeding resistance of the images recorded by the procedure shown below was evaluated. First, an ink cartridge filled with each ink is set to a modified ink jet recording device (trade name “PIXUS Pro 9500”, manufactured by Canon) equipped with a recording head (serial head) that ejects ink by the action of thermal energy. did. In the above-described ink jet recording apparatus, the recording duty is 100% under the condition that one ink droplet having a mass per droplet of 3.5 ng is applied to a unit area of 1/1200 inch × 1/1200 inch. Define. As the recording medium, plain paper (trade name “HP Bright White Inkjet Paper, manufactured by Hewlett Packard”) was used.In the forward direction, the first ink applied to the recording medium was the first ink, and the second applied ink was the second. In addition, in the backward direction, the ink applied first to the recording medium is the second ink, and the ink applied later is the first ink in the backward direction, and in the forward direction and the backward direction. Then, a solid image (2 cm × 2 cm) of the first ink having a recording duty of 100% and a solid image (2 cm × 2 cm) of the second ink having a recording duty of 100% were recorded. The recorded image was visually checked for the boundary portion of each solid image, and the bleeding resistance was evaluated according to the following evaluation criteria. The results are shown in Table 5.
A: Bleeding hardly occurred.
B: Slight bleeding occurred.
C: Although bleeding occurred remarkably, the boundary could be discriminated.
D: Bleeding occurred remarkably and the boundary could not be determined.

Claims (8)

An inkjet recording method for recording an image on a recording medium by discharging a first ink and a second ink having different hues from a line head,
The first ink contains a pigment and a fluorosurfactant,
The difference between the dynamic surface tension of the first ink at a lifetime of 10 milliseconds and the dynamic surface tension of the second ink at a lifetime of 10 milliseconds is within 2 mN / m,
The dynamic surface tension of each of the first ink and the second ink at a lifetime of 10 milliseconds is 40 mN / m or less,
An ink jet recording method comprising: recording the image on the recording medium by ejecting the first ink and the second ink in this order.   The inkjet recording method according to claim 1, wherein the first ink contains an acetylene glycol surfactant.   The inkjet recording method according to claim 1, wherein the second ink contains an acetylene glycol surfactant.   The inkjet recording method according to claim 3, wherein the HLB value of the acetylene glycol surfactant in the first ink and the second ink is 11 or less.   The inkjet recording method according to any one of claims 1 to 4, wherein the fluorosurfactant is a perfluoroalkylethylene oxide adduct having 6 or less carbon atoms in a perfluoroalkyl group.   6. The ink jet recording method according to claim 1, wherein dynamic surface tensions of the first ink and the second ink at a lifetime of 10 milliseconds are each 35 mN / m or less.   The ink jet recording method according to claim 1, wherein at least one of the first ink and the second ink contains a self-dispersing pigment.   The inkjet recording method according to claim 1, wherein the hue of the first ink is black.

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