JP2017213798A - Inkjet recording method and inkjet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording method which exhibits high recovery properties and has excellent ink filling ability when using a recording apparatus having a line head to be placed under a high temperature.SOLUTION: An image is recorded by discharging ink to a recording medium 47 using an inkjet recording apparatus M4000 which comprises an ink accommodation part, a line head H1000 for discharging ink and means for adjusting the temperature of the ink in the line head. The ink contains a coloring material, a water-soluble organic solvent and an ionic surfactant and the Krafft point KP(°C) of the ionic surfactant, the temperature Tt(°C) of the ink in the ink accommodation part and the temperature Th(°C) of the ink in the line head satisfy the relations of the following expressions (1) and (2): KP-Tt≥5 (1) and Th-KP≥5 (2).SELECTED DRAWING: Figure 2

Description

  The present invention relates to an inkjet recording method and an inkjet recording apparatus used therefor.

  In recent years, inkjet recording apparatuses have been increasingly used in offices, taking advantage of low power, low cost, and space saving. As a scanning method of the recording head employed in the ink jet recording apparatus, a serial method can be cited. In the serial method, an image is recorded by repeatedly moving the recording head in a direction (sub-scanning direction) orthogonal to the paper feed direction (main scanning direction). Since the serial recording head is relatively small, the recording apparatus main body can be downsized. In recent years, in order to further improve the recording speed (throughput), a recording head that employs a recording head in which the array width of the ejection openings is extended to the maximum width of the paper, that is, a line head has been developed.

  Unlike the serial method, the line head method does not move the recording head, but only transports the paper, so the recording speed is improved in the recording apparatus employing the line head. On the other hand, the line head system has problems with respect to recoverability and ink filling properties. The recoverability means the recovery from the sticking of the ink at the discharge port of the line head or the sag of the surface (discharge port surface) on which the discharge port is formed. Further, the ink filling property means suppression of bubble retention in the ink supply path. Since the line head is long, it takes time to perform a recovery operation per time. For this reason, in order not to reduce the recording speed, it is required to simplify the recovery operation and reduce the number of times.

  In addition, since the line head is long, the ink flow path is complicated, and there are many opportunities to print a large amount at high speed. For this reason, it is necessary to install a large-capacity ink container (ink tank) at a position away from the line head and to supply ink from the ink container to the line head by a separately provided ink supply means. For this reason, the bubbles are more likely to stay in the ink supply path including the ink flow, but in order not to reduce the recording speed, it is required to simplify the operation such as bubble removal and reduce the number of times.

  Under such circumstances, for example, a recording apparatus having a wiping unit having a moving direction different from the arrangement direction of the ejection port arrays of the recording head and a cleaning unit by suction has been proposed (Patent Document 1). In addition, a recording apparatus that has a negative pressure generation mechanism and a positive pressure generation mechanism that facilitates bubble removal in the ink supply path has been proposed (Patent Document 2).

  In addition, a maintenance liquid excellent in detergency in the vicinity of the nozzle tip has been proposed, which contains a poorly water-soluble organic solvent and a nonionic or anionic surfactant for solubilizing or emulsifying the organic solvent in water (patent) Reference 3). Furthermore, there has been proposed an ink containing a specific fluorosurfactant that suppresses the bubbling of ink and improves the ink filling property to the head (Patent Document 4). In addition, an ink containing a specific acetylenic diol-based surfactant and an antifoaming agent that suppresses foaming even when stored for a long time in a high-temperature environment has been proposed (Patent Document 5).

  Furthermore, there has been proposed a recording apparatus that is provided with a long recording head and that uses ink containing an antifoaming agent and that effectively suppresses ink filling defects (Patent Document 6). In addition, an ink composition for inkjet that contains an aqueous carrier medium, a pigment, a binder, and a nonionic, cationic, or anionic surfactant that is a component that suppresses ejection speed reduction has been proposed (Patent Document 7). .

JP 2012-166374 A JP 2007-301799 A JP 2010-137458 A JP 2009-155425 A JP 2007-297558 A JP 2005-305780 A JP 2003-192968 A

  It is assumed that the line head is placed in a heating (temperature adjustment) state from the viewpoint of ink ejection stability. Further, there is a demand for sufficiently recovering such severe sticking and swelling promoted at such high temperatures while still in a high temperature state. As a result of the inventor's investigation, it is difficult to achieve both recoverability and ink filling properties of a line head that is placed at a high temperature, even when any of the techniques proposed in the above patent documents is used. It has been found. For example, in the recording apparatus proposed in Patent Documents 1 and 2, it is possible to avoid complication of the control mechanism and an increase in cost, such as a combination of the wiping means and the suction means, and the combined use of the negative pressure generation mechanism and the positive pressure generation mechanism. I can't. Further, Patent Document 3 does not mention the recoverability of the line head placed at a high temperature. Further, the maintenance liquid proposed in Patent Document 3 cannot naturally improve the ink filling property.

  It has been found that even if the inks proposed in Patent Documents 4 and 5 are used, the recoverability of the line head placed at a high temperature is insufficient. Furthermore, it was found that the recording apparatus proposed in Patent Document 6 is still insufficient in the recoverability of the line head placed at a high temperature. Further, Patent Document 7 does not mention anything about the recoverability of the line head and the ink filling property at high temperatures.

  Accordingly, an object of the present invention is to provide an ink jet recording method that exhibits high recoverability and excellent ink filling properties when a recording apparatus having a line head placed at a high temperature is used. Another object of the present invention is to provide an ink jet recording apparatus used in the above ink jet recording method.

The above object is achieved by the present invention described below. That is, according to the present invention, an ink, an ink storage portion in which the ink is stored, a line head that discharges the ink that is filled with the ink in the ink storage portion, and the ink in the line head And an ink jet recording apparatus comprising: means for adjusting the temperature of the ink; and an ink jet recording method for recording an image by ejecting the ink onto a recording medium, wherein the ink comprises a colorant, a water-soluble organic A solvent and an ionic surfactant, the kraft point KP (° C.) of the ionic surfactant, the temperature Tt (° C.) of the ink in the ink container, and the temperature of the ink in the line head There is provided an ink jet recording method characterized in that Th (° C.) satisfies the relationship of the following formulas (1) and (2).
KP-Tt ≧ 5 (1)
Th-KP ≧ 5 (2)

  According to the present invention, it is possible to provide an ink jet recording method that exhibits high recoverability and excellent ink filling properties when a recording apparatus including a line head placed at a high temperature is used. Moreover, according to this invention, the inkjet recording device used for the said inkjet recording method can be provided.

It is an image figure which records an image with a line head. It is a schematic diagram which shows an example of an inkjet recording device. It is a figure which shows an example of a line head typically, (a) is a perspective view, (b) is a disassembled perspective view. It is a figure which shows an example of a recovery mechanism, (a) is a perspective view, (b) is a schematic diagram. 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 a method for recording an image by ejecting ink onto a recording medium using a predetermined ink jet recording apparatus. An ink jet recording apparatus to be used includes an ink, an ink containing portion that contains the ink, a line head that is filled with ink in the ink containing portion, and a means for adjusting the temperature of the ink in the line head. With. Moreover, the ink to be used contains a color material, a water-soluble organic solvent, and an ionic surfactant. The Kraft point KP (° C.) of the ionic surfactant, the temperature Tt (° C.) of the ink in the ink containing portion, and the temperature Th (° C.) of the ink in the line head are expressed by the following formulas (1) and (2). It is characterized by satisfying the relationship.
KP-Tt ≧ 5 (1)
Th-KP ≧ 5 (2)

  As described above, in order to expand the use of an inkjet recording apparatus in an office or the like, an improvement in recording speed (throughput) that can compete with an electrophotographic recording apparatus is strongly demanded. In order to improve the recording speed, it is necessary to improve the moving speed of the recording head in the sub-scanning direction and increase the number of ejections per nozzle (that is, improve the ejection frequency). However, simply increasing the ejection frequency has various limitations such as mechanical limitations and insufficiency of ink supply (refilling), which increases the recording speed of an inkjet recording apparatus equipped with a serial recording head. There are limits.

  In view of such a situation, in recent years, a line-type recording head (hereinafter referred to as “line head”) in which ejection ports (nozzles) that eject ink over the entire width in the conveyance direction of the recording medium (maximum paper width) are arranged. A recording apparatus employing the above has been developed. Since the line head has a number of ejection openings corresponding to the maximum sheet width of the recording medium, there is an advantage that it is not necessary to move the recording head and high-speed recording is possible. That is, in the case of a recording apparatus that employs a line head, it is not necessary to move the recording head in a direction (main scanning direction) orthogonal to the recording medium conveyance direction (sub-scanning direction). Therefore, the unit area of the recording medium passes just under the recording head only once, that is, an image can be recorded in “one pass”, and the time required for recording can be shortened.

  The inventor of the present invention studied an even higher speed recording by combining an ink jet recording apparatus employing a line head with a conventional ink for ink jet. As a result, it was found that when a heated (temperature-controlled) line head was used, the recoverability from a state in which a phenomenon such as sticking or slipping occurred occurred. Since the line head is long, it takes time to perform a recovery operation per time. For this reason, in order not to reduce the recording speed, it is required to simplify the recovery operation and reduce the number of times. Furthermore, it is assumed that the line head is placed in a heating (temperature adjustment) state from the viewpoint of ink ejection stability. In order to improve the recording speed, it is required to sufficiently recover such severe sticking and slipping promoted at such a high temperature without being cooled.

  For example, it is considered that the following phenomenon occurs when the ink containing the nonionic surfactant proposed in Patent Documents 4 to 6 is heated on the discharge port surface of the line head. As the ink temperature rises, the molecular motion of the hydrophilic part of the nonionic surfactant becomes active. As a result, water molecules hydrated in the hydrophilic part of the nonionic surfactant are reduced, and the hydrophobic environment is changed. For this reason, at high temperatures, moisture tends to volatilize from adhering substances and adhering substances containing the coloring material and the nonionic surfactant, and the recoverability is impaired due to heavy adhering or swelling on the discharge port surface of the line head. .

  The nonionic surfactant has a hydrophobic portion such as an acetylene glycol skeleton, a polypropylene oxide chain, or a long alkyl chain in its molecule. For this reason, the interaction between the hydrophobic part of the nonionic surfactant and the hydrophobic part of the coloring material is maintained even at high temperatures. However, since the above-mentioned fixed matter formed at a high temperature has low re-dissolvability, even when fresh ink is replenished by pressure recovery or the like, the recoverability remains low.

  In order to solve the above-described problems, the present inventor has further studied. As a result, it was found that it is effective to contain an ionic surfactant in the ink. Unlike nonionic surfactants, ionic surfactants are likely to dissolve in water and form micelles at high temperatures, and easily exhibit surface activity. In order to develop the active ability of the ionic surfactant in the heated line head, it is effective to use an ionic surfactant having a low Kraft point compared to the temperature of the ink in the line head. I understood it. In addition, it is easy to maintain the moisture retention state even if it is a fixed matter or adhering matter containing a coloring material and an ionic surfactant formed at high temperature, so it can be easily wiped off by wiping, It is thought that resilience will increase.

  However, when the ink containing the ionic surfactant and the recording apparatus employing the line head are further studied, bubbles are likely to stay in the ink supply path including the line head, and the ink filling property is reduced. It was found that a new problem arises. Such a decrease in ink filling property is presumed to occur for the following reason.

  As described above, since the line head is long, the ink flow path is complicated, and there are many opportunities to print a large amount at high speed. For this reason, it is necessary to install a large-capacity ink container at a position away from the line head, and to supply ink from the ink container to the line head by a separately provided ink supply means. For this reason, bubbles are more likely to stay in the ink supply path including the ink flow path, but in order not to reduce the recording speed, it is required to simplify the operation such as bubble removal and reduce the number of times. Under such circumstances, it was considered that the ink filling property was lowered because the ink containing the ionic surfactant having higher foaming property than the nonionic surfactant was used.

Under such circumstances, the present inventor has further studied. As a result, the use of an ionic surfactant with a high craft point compared to the temperature of the ink in the ink storage unit improves the ink filling property by deactivating the surface active ability when filling the line head with ink. Turned out to be. Specifically, the Kraft point KP (° C.) of the ionic surfactant contained in the ink and the temperature Tt (° C.) of the ink in the ink containing portion must satisfy the relationship of the following formula (1). It is preferable that the relationship of the following formula (1-1) is satisfied. Furthermore, it is necessary that the Kraft point KP (° C.) of the ionic surfactant contained in the ink and the temperature Th (° C.) of the ink in the line head satisfy the relationship of the following formula (2). It is preferable to satisfy the relationship of the following formula (2-1).
KP-Tt ≧ 5 (1)
KP-Tt ≧ 10 (1-1)
Th-KP ≧ 5 (2)
Th-KP ≧ 10 (2-1)

(Inkjet recording device)
An ink jet recording apparatus used for the ink jet recording method of the present invention includes ink, an ink container, a line head for ejecting ink, and a means for adjusting the temperature of the ink in the line head. Ink is stored inside the ink storage portion. The ink in the ink container is supplied to the line head and filled therein. The ink contains a color material, a water-soluble organic solvent, and an ionic surfactant. The ink jet recording apparatus includes means for controlling the temperature of the ink in the ink container and the temperature of the ink in the line head so as to satisfy the relationship of the following formulas (1) and (2). Hereinafter, the details of the ink jet recording apparatus of the present invention will be described with reference to the drawings.
KP-Tt ≧ 5 (1)
Th-KP ≧ 5 (2)

  FIG. 1 is an image diagram in which an image is recorded by a line head. FIG. 2 is a schematic diagram illustrating an example of an ink jet recording apparatus. In the recording apparatus M4000 shown in FIG. 2, a line head (recording head H1000) is fixed to the recording apparatus main body, and a system is adopted in which the recording medium 47 is conveyed in the direction of the arrow 45 and recorded. The recording apparatus M4000 includes, for example, a recording head H1000Y for yellow ink, a recording head H1000M for magenta ink, a recording head H1000C for cyan ink, and a recording head H1000Bk for black ink (FIG. 1).

  The recording heads H1000Y to H1000Bk shown in FIG. 2 are fixed by a recording head holder 42 mounted on the recording apparatus M4000. 1 and 2 show a configuration in which each color of yellow, magenta, cyan, and black, and further a reaction liquid is ejected from separate recording heads. Of course, a configuration may be employed in which an image is recorded by ejecting a plurality of inks and further a reaction liquid from each of a plurality of ejection port arrays provided on one recording element substrate.

  The ink jet recording apparatus may include means for applying a reaction liquid containing a component that aggregates the color material in the ink to the recording medium. Examples of means for applying the reaction liquid to the recording medium include means for applying the reaction liquid to the recording medium by a coating method, means for applying the reaction liquid to the recording medium by a discharge method, and the like. In the means for applying the reaction liquid to the recording medium by the application method, for example, the reaction liquid is applied to the recording medium using a conventionally known application member such as a roller. Further, in the means for applying the reaction liquid to the recording medium by the discharge method, for example, the reaction liquid is applied to the recording medium by using a discharge device such as a reaction liquid line head (recording head H1000R) as shown in FIG. To do. As shown in FIG. 1, when four recording heads are provided corresponding to four colors of ink, a means for applying the reaction liquid to the recording medium can be separately provided.

  The ink jet recording apparatus used in the ink jet recording method of the present invention includes means for controlling the temperature of ink in the line head. The temperature of the ink in the line head can be controlled by means for controlling the temperature of the line head, for example. Examples of the means for controlling the temperature of the line head include a temperature adjusting heater disposed so as to be in contact with the recording head and an ink discharge heater. In order to control (heat or warm) the temperature of the line head by the ink discharge heater, for example, a current that does not discharge ink may be repeatedly applied. The temperature of the line head and the ink in the line head can be read by, for example, a temperature sensor provided in the line head. The temperature of the line head is preferably adjusted to 40 to 70 ° C.

  The paper feed cassette 46 stores therein a recording medium 47 such as plain paper, and is detachably attached to the apparatus main body. The pickup roller 48 is a member that feeds out the uppermost one of the recording media 47 stored in the paper feed cassette 46. The conveyance roller 49 is a member that conveys the recording medium 47 sent out from the pickup roller 48 to the conveyance path 50. The conveyance roller 51 disposed on the exit side of the conveyance path 50 is a member that conveys the recording medium 47 in the direction of the recording head H1000 while being placed on the conveyance belt 44.

  FIG. 3 is a diagram schematically illustrating an example of a line head, where (a) is a perspective view and (b) is an exploded perspective view. As shown in FIG. 3, the line head (recording head H1000) includes a recording element unit H1400 and an ink supply unit H1500 which is a liquid supply unit for supplying ink to the recording element unit H1400. The ink supply unit H1500 includes a connection portion H1700 formed with a connection port H1710 that is connected to the outside in order to supply ink to the ink chamber (not shown) from the outside of the recording apparatus or the like. The recording element unit H1400 includes a recording element substrate H1100, a support substrate H1200, and a wiring member H1300.

  The support substrate H1200 is a member that holds and fixes the recording element substrate H1100 and the wiring member H1300, and an ink supply hole H1210 that supplies ink supplied from the ink supply unit H1500 to the recording element substrate H1100 is formed. The plurality of recording element substrates H1100 are arranged and fixed on the main surface of the support substrate H1200 with a predetermined positional accuracy. The plurality of recording element substrates H1100 are arranged in a staggered manner on the support substrate H1200 so that the ejection ports are continuously arranged along the direction of the ejection port array between the adjacent recording element substrates H1100. . In this way, by disposing the recording element substrate H1100 by overlapping the discharge ports of the adjacent recording element substrates H1100, it is possible to correct the influence on the image due to the positional deviation of the recording element substrate, and the recording width is long. Realizes a full-line type recording head.

  The wiring member H1300 transmits an electrical signal or power for driving the recording element provided on the recording element substrate H1100 from the outside of the recording head H1000 (recording apparatus) to the recording element substrate H1100. And are electrically connected. As the wiring member H1300, a flexible printed wiring board such as a flexible wiring board is used. The flexible wiring member H1300 is bent so as to facilitate electrical connection between the recording element substrate H1100 and the recording apparatus, and is fixed to the ink supply unit H1500.

  FIG. 5 is a schematic diagram illustrating an example of a supply mechanism that supplies ink to the line head. As shown in FIG. 5, 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, thereby eliminating some of the bubbles in the ink supply path and the ink flow path. 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.

  The ink jet recording apparatus used in the ink jet recording method of the present invention includes means for controlling the temperature of ink in the ink containing portion (main tank and sub tank). Examples of the means for controlling the temperature of the ink in the ink storage unit include a temperature adjusting heater arranged so as to come into contact with the ink. The temperature of the ink in the ink container can be read by a temperature sensor provided in the ink container, for example. The temperature of the ink in the ink container depends on the environmental temperature in which the ink jet recording apparatus is installed, but is preferably in the range of 15 to 45 ° C., for example. As in the main tank T1 and the sub tank T2 shown in FIG. 5, the “temperature Tt (° C.) of the ink in the ink containing portion” in the case where there are two or more ink containing portions containing ink is closest to the line head. It means the temperature Tt (° C.) of the ink in the ink container. Of course, the temperature of the ink stored in the ink storage section farther from the line head may or may not be adjusted as in the closest ink storage section.

  The ink jet recording apparatus used in the ink jet recording method of the present invention may further include a recovery mechanism for recovering the sticking of the ink at the discharge port of the line head and the sag of the discharge port surface. FIG. 4 is a diagram illustrating an example of a recovery mechanism, where (a) is a perspective view and (b) is a schematic diagram. As shown in FIG. 4, the wiper W1001 is held by a clip member W1002, and the clip member W1002 is held by a connecting member W1003. The clip member W1002 is attached to a wipe base W1011 that can move the slide rail W1006. The wipe base W1011 can move on the slide rail W1006 by driving the timing belt W1007 through the connecting member W1003. The timing belt W1007 is supported by a driven pulley W1004 and a driving pulley W1005, and a shaft of a driving motor W1010 that drives the timing belt W1007 is coupled to the driving pulley W1005. Further, photosensors W1008 and W1009 are provided at both ends of the slide rail W1006 in order to control the position of the wiper W1001 during the recovery operation. During the recovery operation by wiping, the wiper W1001 is slid and moved by the slide rail W1006, so that the discharge port surface of the recording head H1000 is wiped while the wiper W1001 is bent.

(ink)
The ink used in the inkjet recording method of the present invention contains a color material, a water-soluble organic solvent, and an ionic surfactant.

[Color material]
As the color material, either a dye or a pigment can be used. Examples of the pigment include inorganic pigments and organic pigments. In consideration of printing on plain paper, it is preferable to use a pigment as a coloring material. As the pigment, a resin dispersion type pigment using a resin as a dispersant, a self-dispersion type pigment having a hydrophilic group introduced on the surface of the pigment particle (self-dispersion pigment), or the like can be used. Resin-dispersed pigments include resin-dispersed pigments that use polymer dispersants, microcapsule-type pigments whose surfaces are coated with resin, and organic groups that contain polymers on the surface of pigment particles. Resin-bonded self-dispersing pigments that are bonded together. In addition, pigments having different dispersion methods can be used in combination. The content (% by mass) of the coloring material in the ink is preferably 0.1% by mass or more and 15.0% by mass or less, and 1.0% by mass or more and 10.0% by mass based on the total mass of the ink. More preferably, it is as follows.

[Water-soluble organic solvent]
For the ink, water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent can be used. As water, it is preferable to use deionized water (ion exchange water). The content (% by mass) of water in the ink is preferably 50.0% by mass or more and 95.0% by mass or less based on the total mass of the ink.

  The content (% by mass) of the water-soluble organic solvent in the ink is preferably 3.0% by mass or more and 50.0% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, any of those generally used for inks applied to the ink jet recording method can be used. Specific examples of the water-soluble organic solvent include alkyl alcohols having 1 to 4 carbon atoms, amides, ketones or keto alcohols, ethers, polyalkylene glycols, glycols, and alkylene groups having 2 to 6 carbon atoms. Alkylene glycols, alkyl ether acetates, alkyl ethers of polyhydric alcohols, nitrogen-containing compounds, and the like. These water-soluble organic solvents can be used alone or in combination of two or more. Usually, the “water-soluble organic solvent” means a liquid, but in the present invention, those which are solid at 25 ° C. (room temperature) are also included in the water-soluble organic solvent. Specific examples of water-soluble organic solvents that are general to ink and are solid at 25 ° C. include 1,6-hexanediol, trimethylolpropane, ethylene urea, urea, polyethylene glycol having a number average molecular weight of 1,000, and the like. be able to.

[Ionic surfactant]
As the ionic surfactant, at least one of an anionic surfactant, a cationic surfactant, and an amphoteric surfactant can be used. Examples of the anionic surfactant include alkylbenzene sulfonate, alkylphenyl sulfonate, alkylnaphthalene sulfonate, higher fatty acid salt, sulfate of higher fatty acid ester, sulfonate of higher fatty acid ester, higher alcohol ether. Sulfuric acid ester salts and sulfonates, higher alkyl sulfosuccinates, polyoxyethylene alkyl ether carboxylates, polyoxyethylene alkyl ether sulfates, alkyl phosphates, polyoxyethylene alkyl ether phosphates, etc. it can.

  Examples of the cationic surfactant include alkylamine salts, alkyl and aromatic quaternary ammonium salts. Examples of amphoteric surfactants include betaines, aminocarboxylates, imidazoline derivatives, and the like. Among the ionic surfactants, anionic surfactants are preferable from the viewpoints of stability as a compound and chemical safety.

  The ionic surfactant forms micelles at a temperature higher than the Kraft point, and the solubility increases rapidly. By forming micelles, surface active ability is exhibited, and actions such as washing and emulsification occur. The Kraft point is measured according to the method described in Kaoru Tsujii, Naoyuki Sato, and Takashi Takeuchi, Journal of Physical Chemistry, 84, 2287 (1980). That is, 1 g of surfactant is added to 100 mL of distilled water to prepare a mixture, and the mixture is cooled in an ice bath. This cooling causes the mixture to become cloudy. The mixture is then slowly heated at a rate of 1 ° C./min and the temperature at which it becomes transparent from a cloudy state is measured.

  The crafting point of the ionic surfactant is 5 ° C. or more higher than the temperature of the ink in the ink container, and 5 ° C. or lower than the temperature of the ink in the line head. For this reason, the crafting point of the ionic surfactant is preferably 35 ° C. or more and 65 ° C. or less from the relationship between the environmental temperature where the ink jet recording apparatus and the ink container are installed, and the adjustment temperature of the line head. Preferable examples of such ionic surfactants include those described in Table 1. Of course, it is not limited to these.

  The content (% by mass) of the ionic surfactant in the ink is preferably 0.01% by mass or more and 2.0% by mass or less, based on the total mass of the ink, and 0.1% by mass or more and 1.% by mass. More preferably, it is 0 mass% or less. If the content of the ionic surfactant is less than 0.01% by mass, the recoverability may be insufficient. On the other hand, when the content of the ionic surfactant is more than 2.0% by mass, the suppression of foaming becomes insufficient and the ink filling property may be insufficient.

[Nonionic surfactant]
The ink used in the ink jet recording method of the present invention preferably further contains a nonionic surfactant. By using an ink further containing a nonionic surfactant, foaming is further suppressed, and ink filling properties can be further improved.

  Specific examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid Esters, polyoxyethylene glycerin fatty acid esters, polyglycerin fatty acid esters, sucrose fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene fatty acid amides, alkyl alkanolamides, acetylene glycol, oxyethylene adducts of acetylene glycol, polyethylene glycol polypropylene glycol Silicone systems such as block copolymers and polysiloxane oxyethylene adducts Surface active agents, and fluorine-based surfactants such as polyoxyethylene perfluoroalkyl ether. Of these, polyoxyethylene alkyl ether, acetylene glycol, oxyethylene adduct of acetylene glycol, and polyethylene glycol polypropylene glycol block copolymer are preferable.

  Said nonionic surfactant can be used individually by 1 type or in combination of 2 or more types. The HLB value of the nonionic surfactant calculated by the Griffin method is preferably in the range of 6 to 20 in view of dissolution stability and the like. In addition, polyoxyethylene type nonionic surfactants tend to break the hydrogen bond between the polyether chain and water when the cloud point is exceeded, so that the solubility is drastically lowered and it becomes impossible to form micelles. Separate and become opaque. For this reason, at the temperature above the cloud point, the surface activity is rapidly lost. Therefore, it is preferable to use a polyoxyethylene nonionic surfactant having a cloud point higher than the temperature range that the ink can take.

  The content (% by mass) of the nonionic surfactant in the ink is preferably 0.5 times or less as a mass ratio with respect to the content (% by mass) of the ionic surfactant. If this mass ratio is more than 0.5 times, the recoverability may be lowered.

[resin]
In addition to the above components, the ink may contain a resin as necessary. Examples of the resin include water-soluble resins such as polystyrene (meth) acrylic acid resin, poly (meth) acrylic acid resin, poly (meth) acrylic acid ester resin, polyurethane resin, polyamide resin, polyester resin, polyvinyl alcohol resin, and polyolefin resin. Resins can be mentioned. These water-soluble resins can be used alone or in combination of two or more. A base may be added to improve the solubility of the water-soluble resin. Examples of the base include inorganic bases such as lithium hydroxide, sodium hydroxide, and potassium hydroxide; organic bases such as dimethylamine, monoethanolamine, diethanolamine, triethanolamine, aminemethylpropanol, N, N-dimethylethanolamine; and Ammonia can be used. These bases can be used individually by 1 type or in combination of 2 or more types.

[Other ingredients]
In addition to the above components, the ink may contain various additives such as a pH adjuster, a rust inhibitor, a preservative, an antifungal agent, an antioxidant, and an anti-reduction agent as necessary. .

  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 liquid containing coloring material>
(Pigment dispersion 1)
A water-soluble resin (resin dispersant) was dissolved in ion-exchanged water using sodium hydroxide having a neutralization equivalent of 1, to prepare an aqueous solution of a resin dispersant having a water-soluble resin content of 20.0%. As the water-soluble resin, a styrene / acrylic acid copolymer (styrene: acrylic acid (molar ratio) = 33: 67, weight average molecular weight 10,000, acid value 200 mgKOH / g) was used. 15.0 parts of pigment (carbon black), 30.0 parts of an aqueous resin dispersant solution, and 55.0 parts of water were placed in a sand grinder and dispersed for 1 hour. After removing coarse particles by centrifugation, pressure filtration was performed with a micro filter (manufactured by Fuji Film) having a pore size of 3.0 μm, and an appropriate amount of ion-exchanged water was added to obtain a pigment dispersion 1. The pigment dispersion 1 obtained had a pigment content of 15.0% and a water-soluble resin (resin dispersant) content of 6.0%.

(Pigment dispersion 2)
90 g of carbon black having a CTAB specific surface area of 150 m ² / g and a DBP oil absorption of 100 ml / 100 g was added to 3,000 mL of 2.5N sodium sulfate solution. Oxidation was performed by stirring at 60 ° C. and a speed of 300 rpm for 10 hours. The carbon black obtained by filtration was neutralized with a sodium hydroxide solution and subjected to ultrafiltration. After washing and drying, pigment dispersion 2 was obtained by dispersing in ion exchange water. The content of pigment in the obtained pigment dispersion 2 was 15.0%.

(Pigment dispersion 3)
A water-soluble resin (resin dispersant) was dissolved in ion-exchanged water using sodium hydroxide having a neutralization equivalent of 1, to prepare an aqueous solution of a resin dispersant having a water-soluble resin content of 20.0%. As the water-soluble resin, trade name “Joncrill 67” (manufactured by BASF, weight average molecular weight 12,500, acid value 215 mgKOH / g) was used. 15.0 parts of pigment (CI Pigment Blue 15: 3), 30.0 parts of an aqueous resin dispersant solution and 55.0 parts of water were placed in a bead mill filled with zirconia beads and dispersed for 1 hour. After removing coarse particles by centrifugation, pressure filtration was performed with a microfilter (manufactured by Fuji Film) having a pore size of 3.0 μm, and an appropriate amount of ion-exchanged water was added to obtain a pigment dispersion 3. In the obtained pigment dispersion 3, the content of the pigment was 15.0%, and the content of the water-soluble resin (resin dispersant) was 6.0%.

(Dye aqueous solution)
C. I. A 15.0% aqueous solution of Direct Black 195 was prepared. This aqueous solution was designated as “dye aqueous solution”.

<Preparation of surfactant>
Surfactants 1 to 8 shown in Table 2 were prepared.

<Preparation of ink>
(Ink 1-12)
Each component (unit:%) shown in Table 3 was mixed and sufficiently stirred, and then pressure filtered through a cellulose acetate filter having a pore size of 1.20 μm (manufactured by Advantech) to prepare inks 1 to 12.

(Ink 13)
The components shown below were mixed and sufficiently stirred, and then pressure filtered through a cellulose acetate filter having a pore size of 1.20 μm (manufactured by Advantech) to prepare ink 13.
-Pigment dispersion 2: 20.0%
2-pyrrolidone: 6.0%
1,6-hexanediol: 3.0%
-Product name "Liponic EG-1" (manufactured by Lipochemicals, wetting agent): 1.5%
Surfactant 4 (anionic surfactant): 2%
-Product name "Surfinol CT-111" (manufactured by Air Products, nonionic surfactant, cloud point less than 50 ° C): 0.7%
-Product name "Silwet L-77" (manufactured by GE Toshiba Silicone, nonionic surfactant, cloud point less than 10 ° C): 0.3%
・ Product name "Johncrill 67" (BASF, water-soluble resin): 3.0%
・ Ion exchange water: 63.5%

(Ink 14)
Each component shown below was mixed and sufficiently stirred, and then pressure filtered through a cellulose acetate filter having a pore size of 1.20 μm (manufactured by Advantech) to prepare ink 14.
-Pigment dispersion 3: 20.0%
・ 2-Pyrrolidone: 7.0%
1,6-hexanediol: 3.0%
Tetraethylene glycol: 6.0%
1-hydroxyethyl-2-pyrrolidone: 9.0%
-Product name "Liponic EG-1" (manufactured by Lipochemicals, wetting agent): 1.0%
Surfactant 4 (anionic surfactant): 1.0%
・ Product name "Surfinol 420" (manufactured by Air Products, nonionic surfactant, cloud point less than 0 ° C): 0.5%
・ Ion exchange water: 52.5%

(Ink 15)
The following components were mixed and sufficiently stirred, and then pressure filtered through a cellulose acetate filter (manufactured by Advantech) having a pore size of 1.20 μm to prepare ink 15.
-Pigment dispersion 2: 20.0%
・ Glycerin: 10.0%
・ Diethylene glycol: 10.0%
・ Product name "Star Factor 20" (manufactured by Cognis, antifoaming agent): 0.002%
Surfactant 6 (nonionic surfactant): 0.5%
・ Ion exchange water: 59.498%

(Ink 16)
The following components were mixed and sufficiently stirred, and then pressure filtered through a cellulose acetate filter having a pore size of 1.20 μm (manufactured by Advantech) to prepare ink 16.
-Pigment dispersion 2: 20.0%
・ Glycerin: 10.0%
1,3-butanediol: 15.0%
2-ethyl-1,3-hexanediol: 2.0%
2-pyrrolidone: 2.0%
Surfactant 8 (nonionic surfactant): 1.0%
-Product name "KS508" (manufactured by Shin-Etsu Chemical, silicone antifoaming agent): 0.1%
・ Ion exchange water: 49.9%

<Evaluation>
(Recovery)
An inkjet recording apparatus having the configuration shown in FIG. 2 and further having a recovery mechanism shown in FIG. 4 and a supply mechanism shown in FIG. 5 was prepared. The prepared ink was filled in the main tank of the ink jet recording apparatus. Then, the ink was sent to the sub tank by the pump, and the temperature Tt (° C.) of the ink in the main tank and the temperature Tt (° C.) of the ink in the sub tank were set to the temperatures shown in Table 4. Next, ink was sent from the sub tank to the line head, and the temperature Th (° C.) of the ink in the line head was set to the temperature shown in Table 4. After performing a pressure recovery operation with the recovery mechanism and supply mechanism and confirming that the nozzle check pattern is normally recorded, 30 continuous A4 size solid images giving 20 ng of ink per 1/600 inch square are continuously displayed. Recorded and left for 30 minutes. Thereafter, the recovery operation (no pressurization) was performed until the nozzle check pattern was normally recorded, the number of times was measured, and the recoverability was evaluated according to the following evaluation criteria. The results are shown in Table 4. In the evaluation criteria shown below, “AA”, “A”, and “B” are acceptable levels, and “C” is an unacceptable level.
AA: Normal recording was recovered by one recovery operation.
A: Normal recording was recovered by two recovery operations.
B: Normal recording was recovered by three recovery operations.
C: Normal recording was recovered by four or more recovery operations.

(Ink filling property)
An inkjet recording apparatus having the configuration shown in FIG. 2 and further having a recovery mechanism shown in FIG. 4 and a supply mechanism shown in FIG. 5 was prepared. The prepared ink was filled in the main tank of the ink jet recording apparatus. Then, the ink was sent to the sub tank by the pump, and the temperature Tt (° C.) of the ink in the main tank and the temperature Tt (° C.) of the ink in the sub tank were set to the temperatures shown in Table 4. Next, ink was sent from the sub tank to the line head, and the temperature Th (° C.) of the ink in the line head was set to the temperature shown in Table 4. Thereafter, the pressure recovery operation was performed until the nozzle check pattern was normally recorded, the number of times was measured, and the ink filling property was evaluated according to the following evaluation criteria. The results are shown in Table 4. In the evaluation criteria shown below, “AA”, “A”, and “B” are acceptable levels, and “C” is an unacceptable level.
AA: Recorded normally without pressure recovery operation.
A: Normal recording was recovered by one pressure recovery operation.
B: Normal recording was recovered by two pressure recovery operations.
C: Normal recording was recovered by three or more pressure recovery operations.

Claims (5)

Ink, an ink containing portion containing the ink, a line head for discharging the ink filled with the ink in the ink containing portion, and a means for adjusting the temperature of the ink in the line head; Inkjet recording method for recording an image by ejecting the ink onto a recording medium using an inkjet recording apparatus comprising:
The ink contains a coloring material, a water-soluble organic solvent, and an ionic surfactant;
The craft surfactant point KP (° C.) of the ionic surfactant, the temperature Tt (° C.) of the ink in the ink container, and the temperature Th (° C.) of the ink in the line head are expressed by the following formula (1) and An inkjet recording method characterized by satisfying the relationship (2).
KP-Tt ≧ 5 (1)
Th-KP ≧ 5 (2)   The inkjet recording method according to claim 1, wherein the color material is a pigment.   The inkjet recording method according to claim 1, wherein the ionic surfactant is an anionic surfactant.   The inkjet recording method according to claim 1, wherein the ink further contains a nonionic surfactant. Ink, an ink containing portion containing the ink, a line head for discharging the ink filled with the ink in the ink containing portion, and a means for adjusting the temperature of the ink in the line head; An inkjet recording apparatus comprising:
The ink contains a coloring material, a water-soluble organic solvent, and an ionic surfactant;
The craft surfactant point KP (° C.) of the ionic surfactant, the temperature Tt (° C.) of the ink in the ink container, and the temperature Th (° C.) of the ink in the line head are expressed by the following formula (1) and An ink jet recording apparatus, further comprising means for controlling the temperature of the ink in the ink container and the temperature of the ink in the line head so as to satisfy the relationship (2).
KP-Tt ≧ 5 (1)
Th-KP ≧ 5 (2)

Images