JP2016124229A - Inkjet recording device and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet recording device that has constitution dispensing with suction members such as a suction cap and a suction pump, and nonetheless is excellent in sticking-restoration property and can record an image having excellent optical density.SOLUTION: There is provided the inkjet recording device that comprises: a recording unit; an aqueous ink; a protection unit having a covering member covering an ejection port surface of a recording head; a restoring unit having no member suctioning the ink from the ejection port; and a wiping unit wiping the ejection port surface of the recording head. The aqueous ink contains a self-dispersing pigment having an anionic-group-containing functional group linked to the particle surface, and a compound represented by following formula (1) ((l+n) indicates 3 or more and 27 or less; and m indicates 16 or more and 36 or less), and has a viscosity of 2.7 mPa s or less.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an ink jet recording apparatus and an ink jet recording method.

  Inkjet recording apparatuses are widely used because they are low in printing cost and advantageous in terms of power consumption compared to electrophotographic recording apparatuses. In an inkjet recording apparatus, an image is recorded by ejecting ink onto a recording medium from an ejection port of a recording head. However, when ink is clogged at the ejection port or the viscosity of the ink is increased in the flow path due to evaporation of the liquid component, normal ejection of the ink may be difficult. When the normal ejection of ink becomes difficult, a recovery operation is performed to recover the ejection performance of the recording head. This recovery operation is performed at regular intervals or before or after the start of the recording operation.

  Conventionally, a recovery operation has been performed by preliminarily discharging ink that is not used for image recording into a cap disposed at a position facing a surface (discharge port surface) on which a discharge port of the recording head is formed. Also, the recovery operation may be performed by causing the suction cap to contact the discharge port surface, generating a negative pressure by operating the suction pump connected to the suction cap, and forcibly discharging the ink from the recording head. there were. However, when performing these recovery operations, it is necessary to provide a suction member such as a suction cap or a suction pump having a certain weight in the ink jet recording apparatus. In addition, since a space for installing these suction members is required, the size of the recording apparatus tends to increase.

  In recent years, there has been a demand for weight reduction and miniaturization of an ink jet recording apparatus due to an increase in awareness of resource saving and the like. is there. In order to improve the recoverability of the recording apparatus having such a configuration in which the suction member is omitted, the recording head is wetted when the discharge port surface is wiped after preliminary ink ejection for recovering the ejection performance of the recording head. A wet wiping method for discharging ink has been proposed (Patent Document 1).

  Further, in the ink jet recording method, images can be recorded on various recording media. Various inks have been proposed according to the purpose, such as ink suitable for recording a photographic image on glossy paper or the like, or ink suitable for recording a document on plain paper or the like. In recent years, when business sentences including characters and diagrams are recorded on a recording medium such as plain paper, the frequency of using the ink jet recording method has increased remarkably. In such applications, an improvement in the optical density of the image is required. Among recording media for recording images, there are various types of plain paper having different ink permeability. The difference in ink permeability of the recording medium affects the characteristics of the recorded image. For example, the optical density of an image recorded on plain paper with high ink permeability tends to decrease. In recent years, when ink jet recording methods have become widespread, it has been demanded that images having a high optical density can be recorded regardless of the type of recording medium.

  From the viewpoint of improving the optical density of an image, it is advantageous to use a self-dispersing pigment as a coloring material for ink. For example, an ink containing self-dispersing carbon black obtained by ozone-oxidizing carbon black having a predetermined BET specific surface area and adjusting the volatile content has been proposed (Patent Document 2). In order to improve ejection stability, inks containing a self-dispersing pigment to which a block polymer of ethylene oxide and isopropylene oxide is added have been proposed (Patent Documents 3 and 4). Furthermore, an ink containing a resin having a predetermined oxidation and a surfactant having a structure in which an ethylene oxide group block is bonded to both ends of a propylene oxide group block has been proposed (Patent Document 4).

Japanese Patent Application Laid-Open No. 07-276655 JP 2013-060563 A JP 2004-359803 A JP 2013-047322 A

  However, if an inkjet recording apparatus having a configuration without a suction member is left for a certain period of time without discharging ink, moisture in the ink may evaporate from the discharge port, and normal ink discharge may not be performed. there were. In addition, after the ink adhering to the ejection port surface after preliminary ejection is wiped (wiped) by the wiping unit, the remaining ink wiping residue may adhere to the ejection port surface. For this reason, a new problem such as insufficient fixing recovery such as occurrence of ejection deviation has occurred.

  Further, the inventors of the present invention have found that the ink proposed in Patent Document 2 is remarkably easily thickened by moisture evaporation and has insufficient fixing recovery properties. On the other hand, even when the block polymer proposed in Patent Document 3 was added to the ink containing the self-dispersing pigment, the fixing recovery property was insufficient. This is presumed to be because a surfactant such as a block polymer could not sufficiently hydrophilize the thickened ink, resulting in unwiped residue. Furthermore, even when the surfactant and the resin proposed in Patent Document 4 are added to the ink containing the self-dispersing pigment, the ejection stability is insufficient. This is because the viscosity of the ink is high and the viscosity of the ink is significantly increased during the period in which the recording head is left without capping, and the amount of the thickened ink attached to the discharge port surface is increased. Guessed. In addition, since the configuration of the recording apparatus that employs the wet wiping method proposed in Patent Document 1 is complicated, it may hinder cost reduction.

  Accordingly, an object of the present invention is an ink jet recording which is excellent in fixing recovery property and capable of recording an image having an excellent optical density even though the suction member such as a suction cap and a suction pump is omitted. An apparatus and an ink jet recording method are provided.

  The above object is achieved by the present invention described below. That is, according to the present invention, a recording unit having a recording head provided with an ejection port; an aqueous ink ejected from the ejection port and recording an image on a recording medium; a surface of the recording head provided with the ejection port A protection unit having a cover member covering the ink; having an ink receiving member provided separately from the cover member for receiving waste ink discharged from the discharge port based on preliminary discharge data without passing through another member An ink jet recording apparatus comprising: a recovery unit that does not include a member that sucks ink from the ejection port; and a wiping unit that wipes a surface of the recording head provided with the ejection port. Contains a self-dispersing pigment in which a functional group containing an anionic group is bonded to the particle surface, and a compound represented by the following formula (1), and has a viscosity of 2.7 mPa · s or less. An ink jet recording apparatus is provided, characterized in that it.

（前記式（１）中、ｌ＋ｎは３以上２７以下であり、ｍは１６以上３６以下である）

(In the formula (1), l + n is 3 or more and 27 or less, and m is 16 or more and 36 or less)

  According to the present invention, there is provided an ink jet recording apparatus capable of recording an image excellent in fixing recovery and having an excellent optical density while having a configuration in which a suction member such as a suction cap and a suction pump is omitted. An ink jet recording method can be provided.

1 is a perspective view schematically showing an embodiment of an ink jet recording apparatus of the present invention. FIG. 3 is a partial perspective view schematically illustrating an example of a recording unit. It is a fragmentary perspective view showing an example of a recovery unit typically.

  Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. Hereinafter, the water-based ink may be simply referred to as “ink”. In the present invention, various physical property values are values at 25 ° C. unless otherwise specified.

  As a result of investigations, the present inventors have found that the above-described problems can be solved by using an ink containing a self-dispersing pigment and a compound represented by the formula (1) described later. That is, the present invention has been completed by finding that it is possible to record an image having excellent fixing recovery and excellent optical density while omitting a suction member such as a suction cap and a suction pump. It came. About the mechanism in which the above effects are acquired, the present inventors presume as follows.

  If the ink jet recording apparatus is left in a state where the ink containing the self-dispersing pigment is not ejected for a certain period of time, moisture in the ink evaporates from the ejection port and the viscosity of the ink increases. When preliminary ink discharge is performed in this state, the concentrated and thickened ink is not properly discharged from the discharge port, and a part of the thickened ink adheres to the periphery of the discharge port. Wiping the discharge port surface to which the thickened ink has adhered causes wiping residue, and the thickened ink is stretched by the discharge port surface. Further, it is considered that the ink is not normally ejected by the thickened ink that is attached and stretched around the ejection port, so that the ejection deviation is generated. Further, when the viscosity of the ink exceeded 2.7 mPa · s, the increase in viscosity due to water evaporation became remarkable, and the ejection deviation was remarkably generated. Note that the above phenomenon does not occur if a recovery operation for forcibly discharging the thickened ink from the ejection port using a suction member such as a suction cap or a suction pump is performed.

  If the compound represented by the formula (1) is added to the ink containing the self-dispersing pigment and the viscosity of the ink is 2.7 mPa · s or less, no wiping residue due to wiping is generated, and the ink is properly It can be discharged. The inventors presume the reason as follows. The compound represented by the formula (1) is composed of a hydrophobic propylene oxide group and a hydrophilic ethylene oxide group, and has a structure in which an ethylene oxide group is bonded to both ends of the propylene oxide group. When examined in detail, it was found that the compound represented by the formula (1) has lower surface active ability than a general surfactant. That is, in the ink, the compound represented by the formula (1) has low orientation and adsorption on the particle surface (hydrophobic surface) of the pigment. However, in the process where the ink is concentrated by water evaporation, it is considered that the compound represented by the formula (1) is adsorbed on the hydrophobic surface of the pigment and exists on the surface of the thickened ink. As a result, hydrophilicity is imparted to the thickened ink, and it is considered that no thickened ink remains after wiping.

  Furthermore, it has been found that by limiting the structural unit of the compound represented by the formula (1), it is possible to record an image having excellent optical density while improving the fixing recovery property. That is, in the present invention, in formula (1), “l and n” representing the number of repeating hydrophilic units is 3 or more and 27 or less, and “m” representing the number of repeating hydrophobic units is 16 or more and 36 or less. Is used.

  The inventors recorded images using inks containing various compounds represented by the formula (1) having different numbers of repeating hydrophobic units and hydrophilic units, and evaluated the optical density. Further, after the ink jet recording apparatus was allowed to stand for a certain period of time without discharging ink, a recovery operation was performed to evaluate the fixing recovery property. As a result, the ink containing the compound represented by the formula (1) having a smaller number of repeating hydrophobic units is the ink containing the compound represented by the formula (1) having a larger number of repeating hydrophobic units. In comparison, the optical density of the obtained image was found to be high. Specifically, when m representing the number of repeating hydrophobic units is 36 or less, the optical density of the obtained image is improved. This is presumably because the ink aggregation speed on the recording medium exceeded the ink permeation speed on the recording medium.

  In addition, the ink containing the compound represented by the formula (1) having a small number of repeating hydrophilic units is compared with the ink containing the compound represented by the formula (1) having a large number of repeating hydrophilic units. Thus, it was found that the adhesion recovery was good. Specifically, when l + m representing the number of repeating hydrophilic units is 27 or less, the fixing recovery property is improved. This is because the compound represented by the formula (1) is gradually oriented and adsorbed on the hydrophobic surface of the pigment in the process of concentration of the ink and is uniformly present on the surface of the thickened ink. it is conceivable that.

<Inkjet recording apparatus and inkjet recording method>
An ink jet recording apparatus of the present invention includes a recording unit having a recording head, a water-based ink, a protection unit having a cover member, and an ink receiving member that receives waste ink discharged from the ejection port without passing through other members. Having a recovery unit. Furthermore, the ink jet recording apparatus of the present invention includes a wiping unit for wiping the surface of the recording head on which the discharge port is provided. Hereinafter, the configuration of the ink jet recording apparatus and details of the ink jet recording method of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view schematically showing an embodiment of the ink jet recording apparatus of the present invention. The ink jet recording apparatus according to this embodiment includes a paper feed unit 101, a transport unit 102, a recording unit 103, a protection unit 104, and a recovery unit 105. The paper supply unit 101 supplies a recording medium to the inside of the recording apparatus. The transport unit 102 transports the recording medium supplied by the paper feed unit 101.

  FIG. 2 is a partial perspective view schematically showing an example of the recording unit. As shown in FIG. 2, the recording unit 103 records an image on a recording medium transported by the transport unit 102 (FIG. 1) based on the image data. The recording unit 103 includes an ink cartridge 31 mounted on a carriage that reciprocates in the main scanning direction. A recording head 32 is provided on the bottom surface of the ink cartridge 31. An image is recorded on the recording medium by repeating the recording operation by the recording head performed in synchronization with the movement of the carriage (main scanning) and the conveyance (sub-scanning) of the recording medium at a predetermined pitch. Examples of the method for ejecting ink include a method for imparting mechanical energy to the ink and a method for imparting thermal energy to the ink. In the present invention, it is preferable to employ a method using thermal energy.

  As shown in FIGS. 1 and 2, the protection unit 104 is provided with an ejection port of the recording head when recording is not performed in order to prevent clogging of the ejection ports 33 provided in a row on the recording head 32. The formed surface (discharge port surface 34) is covered. The protection unit 104 includes a cap 41 so as to correspond to the recording head 32. When recording is not performed, the ink cartridge 31 is moved to a position corresponding to the cap 41 by the carriage, and the cap 41 is brought into contact with the ejection port surface 34 to form a sealed space (capping). Thereby, evaporation of the liquid component in the ink is suppressed.

  FIG. 3 is a perspective view schematically showing an example of the recovery unit. As shown in FIGS. 1 to 3, the recovery unit 105 is used to maintain the ejection performance of the recording head 32 in a normal state. The recovery unit 105 includes an ink receiving member 51 that receives waste ink discharged from the discharge port 33 of the recording head 32 based on preliminary discharge data. The ink receiving member 51 is provided so as to correspond to the ejection port 33 of the recording head 32, and the upper surface thereof has a shape with a part opened. Further, the ink receiving member 51 may be configured by using a plurality of members (components) as the wall surface or the bottom surface of the ink receiving member 51.

  If there is a period when ink is not ejected when the ejection port surface is not capped by the cap, the ink is clogged at the ejection port, or the ink thickens in the flow path due to evaporation of the liquid component, There are cases where normal ejection of ink becomes difficult. When these phenomena occur, so-called preliminary ejection, in which ink is ejected from the ejection port of the recording head based on preliminary ejection data, is performed so that the ejection performance of the recording head can be recovered and ink can be ejected normally. Done. This preliminary ejection is performed at regular time intervals or before or after the start of the recording operation, and the carriage on which the recording head is mounted is moved to a position corresponding to the ink receiving member so that the ink receiving member is opened. To be done.

  However, there is a case where ink adheres to the periphery of the ejection port due to the preliminary ejection, and ejection deviation occurs. For this reason, so-called wiping is performed in which ink adhering to the ejection port surface after preliminary ejection is wiped by the wiping unit 53 (FIG. 3). That is, the recording head repeatedly moves the carriage in the recovery unit 105, so that the ink attached to the ejection port surface can be wiped off.

  In a conventional ink jet recording apparatus, a recovery operation is performed by forcibly discharging ink from a recording head by bringing a cap into contact with an ejection port surface and operating a suction pump connected to the cap. However, when the suction member is provided, the weight of the suction member increases, and the recording apparatus increases in size. The ink jet recording apparatus of the present invention has a configuration in which a suction pump is omitted for weight reduction and size reduction. In this case, it is necessary to recover only by preliminary ink ejection and wiping into a cap disposed at a position facing the surface (ejection port surface) on which the ejection port of the recording head is formed. For this reason, the inkjet recording apparatus of this invention comprises the specific water-based ink mentioned later excellent in the wiping off property by wiping.

  The inkjet recording method of the present invention uses the above-described inkjet recording apparatus of the present invention. That is, the inkjet recording method of the present invention includes a recording process, a protection process, a preliminary ejection process, and a wiping process. In the recording process, an aqueous ink is discharged from the discharge port of the recording head to record an image on a recording medium. In the protection step, the surface of the recording head on which the discharge port is provided is covered with a covering member. In the preliminary ejection step, the waste ink discharged from the ejection port based on the preliminary ejection data is received by an ink receiving member provided separately from the cover member without passing through another member. In the wiping process, the surface (discharge port surface) on which the discharge port of the recording head is provided is wiped, and the ink attached to the discharge port surface is wiped off. Furthermore, the ink jet recording method of the present invention does not have a step of sucking ink from the ejection port. And in the inkjet recording method of this invention, the self-dispersion pigment which the functional group containing an anionic group has couple | bonded with the particle | grain surface, and the compound represented by following formula (1) are contained, and a viscosity is 2.7 mPa *. Water-based ink that is s or less is used. The steps other than those described above in the ink jet recording method of the present invention may be the same as those of a known ink jet recording method.

（前記式（１）中、ｌ＋ｎは３以上２７以下であり、ｍは１６以上３６以下である）

(In the formula (1), l + n is 3 or more and 27 or less, and m is 16 or more and 36 or less)

<Water-based ink>
The ink used in the ink jet recording apparatus and the ink jet recording method of the present invention is a water-based ink containing a self-dispersing pigment in which a functional group containing an anionic group is bonded to the particle surface, and a compound represented by the above formula (1) It is. Hereinafter, the components constituting the ink used in the ink jet recording apparatus and the ink jet recording method of the present invention and the physical properties of the ink will be described in detail.

(Self-dispersing pigment)
The ink used in the present invention contains a self-dispersing pigment in which a functional group containing an anionic group is bonded to the particle surface as a coloring material. By using such a self-dispersing pigment as a coloring material, it is not necessary to add a dispersant for dispersing the pigment in the ink, or the amount of the dispersant added can be reduced.

  Examples of the types of pigments include organic pigments and inorganic pigments such as carbon black, and any of those usable for ink jet inks can be used. In addition, for purposes such as toning, a dye or the like may be used in combination. In the present invention, a black ink using carbon black as a pigment is preferable. The content (mass%) of the pigment in the ink is preferably 0.10 mass% or more and 15.00 mass% or less, based on the total mass of the ink, and is 1.00 mass% or more and 10.00 mass% or less. More preferably.

  In the self-dispersing pigment, a functional group containing an anionic group is bonded to the particle surface of the pigment particle surface. The self-dispersing pigment is preferably one in which an anionic group is chemically bonded directly to the particle surface. The anionic group is preferably a carboxylic acid group. When using a self-dispersing pigment in which the carboxylic acid group is directly bonded to the surface of the pigment particle, the ink is used in comparison with the case of using a self-dispersing pigment in which the carboxylic acid group is bonded to the pigment particle surface through another atomic group. The optical density of an image recorded on plain paper having high penetrability can be increased. Self-dispersed pigments in which carboxylic acid groups are bonded to the pigment particle surface via other atomic groups tend to have low acid dissociation constants (higher ionicity) of anionic groups, so ink is recorded. Immediately after adhering to the medium, the pigment particles tend to repel each other and maintain a dispersed state. Therefore, when recording is performed on plain paper having high ink permeability, it is considered that the influence of the permeability to plain paper becomes larger than the cohesiveness on plain paper, and the optical density of the image is likely to be lowered.

  Examples of the method for directly bonding the anionic group to the pigment particle surface include an oxidation treatment method using ozone and an oxidation treatment method using an oxidizing agent such as potassium hypochlorite. The counter ion of the anionic group is preferably a hydrogen atom, alkali metal, ammonium, organic ammonium or the like.

(Compound represented by Formula (1))
The ink used in the present invention contains a compound represented by the following formula (1). The compound represented by the following formula (1) is composed of a hydrophobic propylene oxide group and a hydrophilic ethylene oxide group, and has a structure in which ethylene oxide groups are bonded to both ends of the propylene oxide group. In the following formula (1), l, m and n represent the number of repetitions of each constituent unit. l and n show the repeating number of ethylene oxide groups. m shows the repeating number of a propylene oxide group. In the following formula (1), l + n is 3 or more and 27 or less, and m is 16 or more and 36 or less.

M in the formula (1) is preferably 16 or more and 30 or less. When m is 30 or less,
The cohesiveness of the ink on the recording medium is superior to the ink permeability to the recording medium. For this reason, the optical density of the obtained image is further improved.

  L + n in the formula (1) is preferably 6 or more and 27 or less. When l + n is less than 6 or more, the compound represented by the formula (1) is easily oriented on the surface of the pigment particles during the concentration of the ink. For this reason, it becomes difficult for the compound represented by the formula (1) to be present evenly on the surface of the thickened ink, and sufficient hydrophilicity cannot be imparted to the thickened ink, so that the fixing recoverability is improved. May decrease.

The content (mass%) of the compound represented by the formula (1) in the ink is a mass ratio with respect to the content (mass%) of the self-dispersing pigment, and is 0.02 times or more and 0.05 times or less. preferable.
When the mass ratio is less than 0.02 times, it is difficult to make the compound represented by the formula (1) uniformly exist on the surface of the thickened ink after concentration. For this reason, sufficient hydrophilicity cannot be imparted to the thickened ink, and the fixing recovery property may deteriorate. On the other hand, if the above mass ratio exceeds 0.05 times, the ink permeability is too high, and the influence of the permeability to the recording medium becomes larger than the aggregation property on the recording medium. For this reason, the optical density of the recorded image may decrease.

(Aqueous medium)
The ink used in the ink jet recording apparatus and the ink jet recording method of the present invention is an aqueous ink containing water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent. It is preferable to use deionized water as water. The content (% by mass) of water in the ink is preferably 50.00% by mass or more and 95.00% 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 3.00% by mass or more and 50.00% by mass or less based on the total mass of the ink. As the water-soluble organic solvent, any of those usable for ink-jet inks such as alcohols, glycols, glycol ethers and nitrogen-containing compounds can be used. In the present invention, it is preferable to use at least a polyhydric alcohol such as glycerin, a nitrogen-containing compound such as 2-pyrrolidone, and an alkylene glycol such as triethylene glycol. These water-soluble organic solvents can be used alone or in combination of two or more.

(Other additives)
In addition to the above components, the ink used in the inkjet recording apparatus and inkjet recording method of the present invention may contain a water-soluble organic compound that is solid at room temperature, such as urea and its derivatives, trimethylolpropane, and trimethylolethane. . In the present invention, it is preferable to use at least trimethylolpropane. The content (% by mass) of the water-soluble organic compound that is solid at room temperature in the ink is preferably 0.10% by mass or more and 20.00% by mass or less based on the total mass of the ink, and 3.00% by mass. More preferably, it is 10.00 mass% or less. If necessary, it contains various additives such as surfactants, resins, pH adjusters, antifoaming agents, rust preventives, antiseptics, antifungal agents, antioxidants, anti-reducing agents, chelating agents, etc. You may let them. As the surfactant, it is preferable to use a nonionic surfactant. As the nonionic surfactant, acetylene glycol surfactants and polyoxyethylene alkyl ethers are preferable.

(Ink physical properties)
The ink used in the inkjet recording apparatus and the inkjet recording method of the present invention has a viscosity at 25 ° C. of 2.7 mPa · s or less. By using an ink having a viscosity at 25 ° C. of 2.7 mPa · s or less, it is possible to more effectively reduce the thickening of the ink after moisture evaporation. The viscosity of the ink is mainly correlated with the contents of solid components, surfactants, and water-soluble organic solvents in the ink, and the viscosity tends to decrease by reducing these components. The viscosity of the ink at 25 ° C. is preferably 1.0 mPa · s or more and 2.4 mPa · s or less. Further, the static surface tension at 25 ° C. of the ink is preferably 28 mN / m or more and 45 mN / m or less. The pH of the ink at 25 ° C. is preferably 5 or more and 9 or less.

  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>
(Amount of pigment functional group introduced)
A potentiometric automatic titration apparatus (trade name “AT-510”, manufactured by Kyoto Electronics Industry) equipped with a streaming potential titration unit (trade name “PCD-500”, manufactured by Kyoto Electronics Industry Co., Ltd.) was prepared. Using this potentiometric automatic titration apparatus, the amount of functional groups bonded to the pigment particle surface (functional group introduction amount) was measured by potentiometric titration using methyl glycol chitosan as a titration reagent.

(Pigment dispersion 1)
A self-dispersing pigment was prepared by surface oxidation treatment using ozone gas with reference to the description in Example 3 of JP-T-2003-535949. A pigment (carbon black, trade name “FW-18”, manufactured by Orion Engineered Carbon, BET specific surface area 260 m ² / g, DBP oil absorption 140 mL / 100 g) was predispersed in ion-exchanged water and then subjected to ozone treatment for 6 hours. . While adjusting the pH of the mixture to about 7 by adding potassium hydroxide, the mixture was circulated for 3 hours using a liquid-liquid collision type disperser. After purification by ultrafiltration, an appropriate amount of water was added so that the content of the self-dispersing pigment was 10.0%. As a result, a pigment dispersion 1 was obtained in which a self-dispersed pigment in which a carboxylic acid group having a counter ion of potassium was bonded to the pigment particle surface was dispersed in water. The amount of functional group introduced into the self-dispersing pigment was 0.30 mmol / g.

(Pigment dispersion 2)
A self-dispersing pigment was prepared by surface oxidation treatment using an oxidizing agent with reference to the description in Example 1 of WO2000 / 058411. 14.0 parts of pigment (carbon black, trade name “FW-18”, manufactured by Orion Engineered Carbon, BET specific surface area 260 m ² / g, DBP oil absorption 140 mL / 100 g) was dispersed in 65.0 parts of ion-exchanged water. . 21.0 parts of sodium hypochlorite (effective chlorine concentration 4%) was added dropwise and stirred at a temperature of 100 ° C. for 10 hours to obtain a slurry. The obtained slurry was filtered and washed with water, and aqueous ammonia was added to adjust the pH of the liquid to 6.0. An appropriate amount of water was added so that the content of the self-dispersing pigment was 10.0%. As a result, a pigment dispersion 2 was obtained in which a self-dispersing pigment in which a carboxylic acid group whose counter ion is ammonium was bonded to the pigment particle surface was dispersed in water. The introduction amount of the functional group of the self-dispersing pigment was 0.30 mmol / g.

(Pigment dispersion 3)
A solution obtained by dissolving 5 g of concentrated sulfuric acid in 5.5 g of water was cooled to 5 ° C., and 1.55 g of p-aminobenzoic acid was added. The container containing this solution was placed in an ice bath, and the solution obtained by dissolving 1.8 g of potassium nitrite in 9 g of water at 5 ° C. was added while stirring the solution and keeping the temperature at 10 ° C. or lower. After stirring for 15 minutes, 6 g (solid content) of carbon black (with a specific surface area of 220 m ² / g and a DBP oil absorption of 105 mL / 100 g) was added with stirring. After further stirring for 15 minutes, the resulting slurry was filtered with a filter paper (trade name “standard filter paper No. 2”, manufactured by Advantech), and the particles were sufficiently cooled with water and then dried in an oven at 110 ° C. An appropriate amount of water was added so that the content of the self-dispersing pigment was 10.0%. As a result, a pigment dispersion 3 was obtained in which a self-dispersing pigment in which a benzenecarboxylic acid group having a counter ion of potassium was bonded to the particle surface of the pigment was dispersed in water. The amount of functional group introduced into the self-dispersing pigment was 0.28 mmol / g.

(Pigment dispersion 4)
A product obtained by adding water to a trade name “CAB-O-JET200” (manufactured by Cabot) and adjusting the pigment content to 10.0% was used as the pigment dispersion 4. This trade name “CAB-O-JET200” is a pigment dispersion in which a self-dispersed pigment in which a benzenesulfonic acid group whose counter ion is sodium is bonded to the pigment (carbon black) particle surface is dispersed in water. The amount of functional group introduced into the self-dispersing pigment was 0.26 mmol / g.

(Pigment dispersion 5)
Carbon black (20 g), ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid monosodium salt (7 mmol), nitric acid (20 mmol), and pure water (200 mL) were mixed. Carbon black having a specific surface area of 220 m ² / g and DBP oil absorption of 105 mL / 100 g was used. The mixing was performed at 6,000 rpm under a room temperature condition using a Silverson mixer. After 30 minutes, 20 mmol of sodium nitrite dissolved in a small amount of water was slowly added. The temperature of the mixture reached 60 ° C. by mixing, and the mixture was reacted for 1 hour in this state. Thereafter, the pH of the mixture was adjusted to 10 using an aqueous sodium hydroxide solution. After 30 minutes, 20 mL of pure water was added, and diafiltration was performed using a spectrum membrane. After replacing the counter ion from sodium ion to ammonium ion by an ion exchange method, an appropriate amount of water was added so that the content of the self-dispersing pigment was 10.0%. Thereby, the pigment dispersion 5 in which the self-dispersed pigment in which the ((4-aminobenzoylamino) -methane-1,1-diyl) bisphosphonic acid group whose counter ion is ammonium is bonded to the pigment particle surface is dispersed in water is obtained. Obtained. The amount of functional group introduced into the self-dispersing pigment was 0.26 mmol / g.

(Pigment dispersion 6)
A solution obtained by dissolving 5 g of concentrated sulfuric acid in 5.5 g of water was cooled to 5 ° C., and 2.0 g of 4-aminophthalic acid was added. A container containing this solution was placed in an ice bath, and the solution obtained by dissolving 2.2 g of potassium nitrite in 9 g of water at 5 ° C. was added while stirring the solution and keeping the temperature at 10 ° C. or lower. After stirring for 15 minutes, 6 g (solid content) of carbon black (with a specific surface area of 220 m ² / g and a DBP oil absorption of 105 mL / 100 g) was added with stirring. After further stirring for 15 minutes, the resulting slurry was filtered with a filter paper (trade name “standard filter paper No. 2”, manufactured by Advantech), and the particles were sufficiently cooled with water and then dried in an oven at 110 ° C. After replacing the counter ion from potassium ion to ammonium ion by the ion exchange method, an appropriate amount of water was added so that the content of the self-dispersing pigment was 10.0%. As a result, a pigment dispersion 6 was obtained in which a self-dispersed pigment in which a phthalic acid group whose counter ion is ammonium was bonded to the pigment particle surface was dispersed in water. The amount of functional group introduced into the self-dispersing pigment was 0.44 mmol / g.

(Pigment dispersion 7)
The pigment dispersion 7 was prepared by adding water to the trade name “CAB-O-JET300” (Cabot) and adjusting the pigment content to 10.0%. This trade name “CAB-O-JET300” is a pigment dispersion in which a self-dispersed pigment in which a phthalic acid group whose counter ion is sodium is bonded to the pigment (carbon black) particle surface is dispersed in water. The amount of functional group introduced into the self-dispersing pigment was 0.10 mmol / g.

(Pigment dispersion 8)
A solution obtained by dissolving 5 g of concentrated sulfuric acid in 5.5 g of water was cooled to 5 ° C., and 2.0 g of 4-aminobenzenesulfonic acid was added. A container containing this solution was placed in an ice bath, and a solution obtained by dissolving 2.4 g of sodium nitrite in 9 g of water at 5 ° C. was added while stirring the solution and keeping the temperature at 10 ° C. or lower. After stirring for 15 minutes, C.I. I. 6 g of Pigment Yellow 74 (specific surface area 65.5 m ² / g) was added with stirring. After further stirring for 15 minutes, the resulting slurry was filtered with a filter paper (trade name “standard filter paper No. 2”, manufactured by Advantech), and the particles were sufficiently cooled with water and then dried in an oven at 110 ° C. An appropriate amount of water was added so that the content of the self-dispersing pigment was 10.0%. As a result, a pigment dispersion 8 was obtained in which a self-dispersing pigment in which a benzenesulfonic acid group whose counter ion is sodium was bonded to the pigment particle surface was dispersed in water. The amount of functional group introduced into the self-dispersing pigment was 0.10 mmol / g.

<Compound represented by Formula (1)>
As compounds represented by the formula (1), compounds 1 to 8 shown in Table 1 were prepared. Further, a compound represented by the following formula described in Patent Document 3 was prepared and used as Compound 9.
_{HO- (CH 2 (CH 3)} CHO) k - (CH 2 CH 2 O) m - (CH 2 (CH 3) CHO) n -H (k + n = 30, m = 25)

<Preparation of ink>
After mixing each component (unit:%) shown in the upper part of Tables 2-1 to 2-3 and stirring sufficiently, pressure filtration is performed with a polypropylene filter (made by Pole) having a pore size of 2.5 μm. Each ink was prepared. “Acetyleneol E100” in Tables 2-1 to 2-3 is an ethylene oxide adduct of acetylene glycol manufactured by Kawaken Fine Chemicals, and is a surfactant having 10 addition moles of ethylene oxide groups. “Zonyl FS-300” is a DuPont fluorosurfactant, and “Lumiflon FE4300” is a fluoroethylene / vinyl ether alternating copolymer manufactured by Asahi Glass. As an aqueous solution of acrylic resin, a styrene / butyl acrylate / acrylic acid random copolymer was prepared by neutralizing all acidic groups using 10.0% aqueous sodium hydroxide solution and then adding ion-exchanged water. A thing was used. The acid value of the styrene / butyl acrylate / acrylic acid random copolymer (acrylic resin) was 100 mgKOH / g, and the weight average molecular weight was 10,000. The copolymerization (mass) ratio of styrene / butyl acrylate / acrylic acid random copolymer was 64/20/16. Moreover, content (solid content) of the acrylic resin in aqueous solution was 10.0%. In the lower part of Tables 2-1 to 2-3, the content A (%) of the compound represented by the formula (1), the content B (%) of the self-dispersing pigment, and the value (times) of A / B are shown. Indicated. Further, in the lower part of Tables 2-1 to 2-3, each ink measured using a viscometer (trade name “RE-85L”, manufactured by Toki Sangyo Co., Ltd., rotor used: 1 ° 34 ′ × R24). The viscosity was also shown.

<Evaluation>
Using the inks obtained above, the following items were evaluated. For the evaluation, an ink jet recording apparatus (trade name “PIXUS iP2700”, manufactured by Canon Inc.) equipped with a recording head for discharging ink by thermal energy was used. The resolution of this ink jet recording apparatus is 600 dpi × 600 dpi. Further, “recording duty is 100%” is defined as follows. For black ink, the condition for applying one drop of ink having a mass per drop of 25 ng ± 10% to a unit area of 1/600 inch × 1/600 inch is defined as “recording duty is 100%”. To do. For color ink, the condition for applying two ink droplets having a mass per droplet of 5.7 ng ± 10% to a unit area of 1/600 inch × 1/600 inch is “recording duty is 100%”. Is defined as Each evaluation result is shown in Table 3. In the present invention, “A” and “B” are acceptable levels and “C” is an unacceptable level in the evaluation criteria for the following items.

(Optical density)
Each ink was filled in an ink cartridge and set in the ink jet recording apparatus. A solid image (2 cm × 2 cm / 1 line) having a recording duty of 100% was recorded on the following four types of recording media (plain paper). One day after recording, the optical density of the solid image was measured using a reflection densitometer (trade name “Macbeth RD-918”, manufactured by Macbeth), and the average value was calculated. According to the evaluation criteria shown below The optical density of the image was evaluated.
[recoding media]
・ Product name “PB PAPER” (Canon)
・ Product name "Super White Paper SW-101" (manufactured by Canon)
・ Product name "Bright White Inkjet Paper" (manufactured by Hewlett-Packard)
・ Product name "Xerox 4200" (manufactured by Xerox)
[Evaluation criteria]
A: Optical density was 1.40 or more B: Optical density was 1.35 or more and less than 1.40 C: Optical density was less than 1.35

(Adhesive recovery)
Each ink was put into an open container to prepare a liquid (concentrated ink) evaporated by 35%. The ink cartridge 31 filled with the prepared concentrated ink was set in the above-described protection unit and recovery unit of the ink jet recording apparatus modified to the protection unit 104 and the recovery unit 105 configured as shown in FIGS. In this apparatus, the recovery unit 105 is supported by a support member, and the bottom portion of the ink receiving member 51 is provided at a position away from the bottom surface inside the recording apparatus main body. In addition, the bottom surface of the ink receiving member 51 is configured to double as an exterior cover of the recording apparatus main body. This ink jet recording apparatus was placed in an environment of a temperature of 30 ° C. and a relative humidity of 10% for 7 days, and then a nozzle check pattern was recorded. The obtained nozzle check pattern is visually confirmed, and for the ink that could not be recorded normally, recovery operation (preliminary ejection and wiping) is performed until normal recording can be performed, and fixing recovery is performed according to the following evaluation criteria. Sex was evaluated. The reason why the concentrated ink is used is to confirm that the fixing recovery property is excellent even under more severe conditions.
[Evaluation criteria]
A: Recording could be performed normally by zero or one recovery operation.
B: Recording was successfully performed by two recovery operations.
C: Three or more recovery operations were required before normal recording could be performed.

Claims (6)

A recording unit having a recording head provided with a discharge port;
A water-based ink that is ejected from the ejection port and records an image on a recording medium;
A protection unit having a cover member that covers a surface of the recording head on which the discharge port is provided;
An ink receiving member provided separately from the cover member for receiving waste ink discharged from the discharge port based on preliminary discharge data without passing through another member; and ink from the discharge port A recovery unit without a suction member;
An ink jet recording apparatus comprising: a wiping unit for wiping the surface of the recording head provided with the discharge port;
The water-based ink contains a self-dispersing pigment in which a functional group containing an anionic group is bonded to the particle surface, and a compound represented by the following formula (1):
An ink jet recording apparatus having a viscosity of 2.7 mPa · s or less.

(In the formula (1), l + n is 3 or more and 27 or less, and m is 16 or more and 36 or less)   2. The content (mass%) of the compound represented by the formula (1) is 0.02 times or more and 0.05 times or less as a mass ratio with respect to the content (mass%) of the self-dispersing pigment. 2. An ink jet recording apparatus according to 1.   The ink jet recording apparatus according to claim 1, wherein the self-dispersing pigment has an anionic group directly bonded to the particle surface.   The inkjet recording apparatus according to any one of claims 1 to 3, wherein m in the formula (1) is 16 or more and 30 or less.   5. The inkjet recording apparatus according to claim 1, wherein l + n in the formula (1) is 6 or more and 27 or less. A recording step of recording an image on a recording medium by discharging water-based ink from the discharge port of the recording head;
A protection step of covering the surface of the recording head provided with the discharge port with a covering member;
A preliminary ejection step of receiving waste ink discharged from the ejection port based on preliminary ejection data in an ink receiving member provided separately from the cover member without passing through another member;
A wiping step of wiping the surface of the recording head on which the discharge port is provided; and
An inkjet recording method that does not include a step of sucking ink from the ejection port,
The water-based ink contains a self-dispersing pigment in which a functional group containing an anionic group is bonded to the particle surface, and a compound represented by the following formula (1):
An ink jet recording method having a viscosity of 2.7 mPa · s or less.

(In the formula (1), l + n is 3 or more and 27 or less, and m is 16 or more and 36 or less)

Images