JP2006037062A - Ink jet ink and recording method, recording unit, ink cartridge, and recording apparatus using the same - Google Patents

Abstract

（但し、一般式（１）中、Ｘは、カルボキシル基又はスルホン酸基を表す。Ｙは、水素原子、カルボキシル基及びスルホン酸基の何れかを表す。ｎは、０又は１の整数を表し、ｍは０乃至２の何れかの整数を表す。）
【選択図】 なし
PROBLEM TO BE SOLVED: To provide an ink that is excellent in printing durability as an ink-jet ink and maintains the pH of the ink constant even after a printing durability test, an ink jet recording method, a recording unit, an ink cartridge, and a recording apparatus.
SOLUTION: The coloring material contains 3% by weight or more of a coloring material used for a thermal ink jet printer provided with a recording head having a heat generating part wetted surface made of at least one of a metal or a metal oxide compound. An ink-jet ink used at a pH of the buffer region, comprising a colorant having a buffer region and a pH buffer region expansion aid represented by the following general formula (1).
General formula (1)
[Chemical 1]

(However, in general formula (1), X represents a carboxyl group or a sulfonic acid group. Y represents one of a hydrogen atom, a carboxyl group, and a sulfonic acid group. N represents an integer of 0 or 1. M represents an integer of 0 to 2.)
[Selection figure] None

Description

  The present invention relates to an ink for inkjet that has excellent printing durability, a recording method using the ink, a recording unit, an ink cartridge, and a recording apparatus.

  The ink jet recording method is a recording method in which ink droplets are ejected onto plain paper and a dedicated glossy medium to form an image. The ink jet recording method is rapidly spreading due to its low cost and high printing speed. Further, in addition to the progress of higher image quality of recorded images, with the rapid spread of digital cameras, it has become widespread as a method for outputting photographic images comparable to silver salt photographs.

  In recent years, higher image quality has been promoted, such as miniaturization of flying ink droplets and improvement of the color gamut accompanying the introduction of multicolor ink.

  However, on the other hand, the load associated with the color material or ink becomes larger, and more stringent characteristics are required for the improvement of color development, reliability such as fixing property and ejection stability.

  On the other hand, as a problem of the ink jet recording method when compared with a silver salt photograph, there is an image storability of the recorded matter. Inkjet recordings generally have lower image storability than silver salt photographs, and the recorded matter is exposed to light, humidity, heat, environmental gases present in the air for a long time. There is a problem that the upper coloring material is deteriorated and the color tone of the image is likely to change or fading, and many technical improvements have been made for the improvement.

  For example, as a means for improving fastness, a coloring material having an anthrapyridone structure has been conventionally disclosed. Among them, by using an anthrapyridone-based coloring material having a specific structure, the fastness of the ink is improved. Have been disclosed (see Patent Documents 1 and 2), and these have very excellent fastness properties.

On the other hand, a method for extending the life of the recording head of an ink jet printer by adding an additive to the ink is known. That is, this method is a method of extending the life of the recording head by containing an additive in the ink (see Patent Document 3 and Patent Document 4).
JP 2002-332419 A JP 2003-192930 A JP 2002-12805 A JP 2002-137399 A

  However, when these color materials having excellent fastness properties are used as ink-jet inks, it may be difficult to ensure the reliability of ink-jet recording, and in particular, recording is performed by applying thermal energy to the ink. When ink jet recording for recording on a medium is performed, the heat generating part of the ink jet head (the heat generating part in the case where the heat generating part is in direct contact with the liquid, or the surface of the heat generating part has one or more protective layers) When the protective layer is burnt or when continuous printing is performed for a long period of time, the heat generating part may be deteriorated, and further, disconnection may be caused.

  As a result of examining the cause of the occurrence of these phenomena using the ink containing the color material having excellent fastness, the present inventors have found that the cause of this phenomenon is a specific part of the color material contained in the ink. It turned out to be dependent on specific ions in the ink. For example, the specific site is a substituent that easily releases hydrogen ions, such as a hydroxyl group on a triazine ring, and the specific ion is a hydroxide ion.

  When the coloring material having a substituent that easily releases hydrogen ions is made into an aqueous solution (ink), the ink may have this buffer region (region where the hydrogen ion concentration is kept constant).

  The fact that the ink has this buffering area is welcomed as the ink alone. For example, even if the ink is left in various environments at the time of distribution, there is an advantage that the pH of the ink is kept constant by the buffering action of the ink and the decomposition of the coloring material is suppressed.

  However, in a thermal ink jet printer having a heat generating portion composed of at least one of metal and metal oxide, when ink having a buffer region is used and continuous printing is performed for a long period of time, each time ejection (heat energy is applied), There is also a disadvantage in that the heat generating part reacts with hydroxide ions, and the heat generating part is deteriorated and further disconnected.

  As a method for making full use of the color material having the above-mentioned problems, it is possible to lower the dye concentration to be used. However, if the dye concentration is lowered, it becomes impossible to obtain a high-density printed matter.

  The method for extending the life of an ink jet printer recording head by adding an additive to the ink is that depending on the type of the additive, the ink can be added to the ink to increase the ink hydrogen ion concentration (hereinafter abbreviated as pH). For a color material that may rise (or fall) and is sensitive to changes in pH, the inclusion of the additive in the ink can increase the life of the recording head and cause adverse effects. This is also a concern. The expected adverse effect is that the ink pH is increased (or decreased) by adding the additive to the ink, so that the absorption spectrum of the ink changes, and as a result, the color of the printed matter changes. Or the liquid contact property with the recording head deteriorates (when the ink and the material of the recording head come into contact with each other, a part of the material is eluted in the ink) (as a result, the recording head Narrow the options of members that can be used).

  In order to solve the above problems, the inventors of the present invention have been studying additives and hardly affect the pH of the ink, and the ink pH is within a desired range (preferably almost constant). ), An additive that can be maintained for a long time (hereinafter referred to as expansion of the pH buffer region) was discovered. In the present invention, the additive is referred to as a pH buffer region expansion aid. By containing a pH buffering area expansion aid in the ink, deterioration of the heat generating part can be suppressed, the pH of the ink can be maintained within a desired range (preferably substantially constant), and the pH buffering area of the ink can be maintained. Found to expand. The present invention has been made based on this finding.

  Accordingly, a first object of the present invention is to provide a color material having a buffer region and a pH buffer region expansion aid having the structure of the following general formula (1) in an inkjet ink used at the pH of the buffer region of the color material. When using the contained ink, when continuous printing is performed for a long period of time, the deterioration of the heat generating part, and further the disconnection of the wiring for applying a voltage to the heat generating part is suppressed, and the pH of the ink is desired. (Preferably almost constant).

Although the problem of deterioration of the heat generating part and further disconnection of the wiring for applying voltage to the heat generating part can be solved by the above contents, the compound of the general formula (1) and the coloring material shown in the first object of the present invention As a result of further study on the ink containing the above, it was found that when the acidity constant of the coloring material is pKa ₁ and the acidity constant of the pH buffering region expansion aid is pKa ₂ , pKa ₁ <pKa ₂ In this case, or even if pKa ₁ ≧ pKa ₂ , if the difference between pKa ₁ and pKa ₂ is larger than 1, a new fact has been discovered that the coloring material tends to precipitate. Therefore, in order to solve this new problem, the second object of the present invention is to determine the acidity constant (pKa) of the coloring material and the acidity constant of the pH buffer region expansion aid having the structure of the following general formula (1). When the difference from (pKa) is 0 or more and 1 or less, in addition to the first purpose, it is to suppress the precipitation of the coloring material.

  On the other hand, similarly to the first purpose, when looking at the factors of pH change, the pH of the ink may change due to exposure to various physical distribution environments. If the pH of the ink is too low, the coloring material or the like tends to precipitate. If the pH of the ink is too high, the heat generating portion may be deteriorated and disconnected. Therefore, a third object of the present invention is that when a color material having a buffer region has a structure of the following general formula (2) and an ink containing the color material and the following general formula (1) is used, It is also possible to cope with the environment, and to extend the period of maintaining the pH of the ink within a desired range (preferably substantially constant) (expanding the pH buffer region).

  Further, from another viewpoint, it has become possible to provide a high-quality image comparable to a silver salt photograph, and therefore, there is a demand for ink that does not fade the printed matter even if it is left for a long time after printing. It became so. Accordingly, a fourth object of the present invention is to have the structure of the following general formula (4), and in addition to the first to third objects when continuous printing is performed using an ink containing the coloring material. And providing an ink having excellent fastness.

  In order to overcome the first problem of deterioration of the heat generating part and further disconnection of wiring for applying a voltage to the heat generating part, the compound represented by the general formula (1) shown for the first to fourth purposes of the present invention When the ink containing the color material was studied, there was no problem with normal ejection, but from the viewpoint of continuous printing, there was a case where some long-term continuous printing characteristics deteriorated. Accordingly, a fifth object of the present invention is to use an inkjet ink in which the compound having the structure of the general formula (1) is taurine (2-aminoethanesulfonic acid) and perform continuous printing. An object of the present invention is to provide an ink that is more effective in suppressing deterioration and further disconnection of a wiring or the like for applying a voltage to a heat generating portion, maintaining a constant pH of the ink, and having excellent robustness.

  As a result of intensive studies to solve the above problems, the present inventors have reached the present invention.

  Means for achieving the first object of the present invention is to provide 3% of a color material used in a thermal ink jet printer including a recording head having a heat generating part wetted surface made of at least one compound of metal or metal oxide. An ink jet ink that contains at least a weight and is used at a pH of a buffer region of a color material, the ink containing a color material having a buffer region and a pH buffer region expansion aid having a structure of the following general formula (1) Ink.

  General formula (1)

(However, in general formula (1), X represents a carboxyl group or a sulfonic acid group. Y represents one of a hydrogen atom, a carboxyl group, and a sulfonic acid group. N represents an integer of 0 or 1. M represents an integer of 0 to 2.)

The means for achieving the second object of the present invention is the means for achieving the first object of the present invention, wherein the color material having the buffer region has an acidity constant of pKa ₁ and the pH buffer region expansion aid. when formed into a pKa ₂ acidity constant, and the difference between the pKa ₁ and pKa ₂ is 0 or more and 1 or less, and, the buffer region colorant acidity constants with (pKa ₁₎ and expanding said pH buffering region The ink for inkjet is a relationship of the following formula (A) with the acidity constant (pKa ₂ ) of the auxiliary agent.
Formula (A)
pKa ₁ ≧ pKa ₂

  Means for achieving the third object of the present invention is an ink jet ink that uses a colorant having a structure represented by the following general formula (2).

  General formula (2)

(In the general formula (2), Ar ¹ represents an unsubstituted or substituted benzene ring, an unsubstituted or substituted naphthyl ring, or a substituent represented by the following general formula (3). And Ar ² represents a benzene ring which may be unsubstituted or substituted, or a naphthyl ring which may be unsubstituted or substituted.
General formula (3)

(In General Formula (3), R ¹ represents a hydrogen atom, an alkoxycarbonyl group, or an unsubstituted or substituted benzoyl group, and R ² represents a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, A mono or dialkylaminoalkyl group and a cyano lower alkyl group are represented, X represents a carboxylic acid group, a sulfonic acid group, or a salt thereof, and l represents 1 or 2.)

  The means for achieving the fourth object of the present invention is an ink-jet ink that uses a color material in which the color material is an anthrapyridone compound having a structure represented by the following general formula (4) or a salt thereof.

  General formula (4)

(In General Formula (4), R ³ is a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, a mono- or dialkylaminoalkyl group, a cyano lower alkyl group, R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ is independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a carboxyl group (except when R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are all hydrogen atoms. .).)

  Means for achieving the fifth object of the present invention is an inkjet ink in which the compound having the structure of the general formula (1) is taurine (2-aminoethanesulfonic acid) and taurine is contained in the ink.

  The effect of the first means of the present invention is that the coloring material contains 3% by weight or more of the coloring material used in the thermal ink jet printer having the recording head having the liquid contact surface of the heat generating portion, and the buffering region of the coloring material. Ink-jet ink used at pH, and containing a coloring material having a buffer region and a pH buffer region expansion aid represented by the following general formula (1) in the ink-jet ink, Ink-jet ink that can obtain a high-quality printed matter even when a printing durability test) is performed and can maintain the pH of the ink within a desired range (preferably substantially constant), and an ink set using the ink Another object of the present invention is to provide a recording method, a recording unit, an ink tank, and a recording apparatus.

The effect of the second means of the present invention is that, in the means for achieving the first object of the present invention, the acidity constant of the coloring material is pKa, and the acidity constant of the pH buffer region expansion aid is pKa. The difference between pKa ₁ and pKa ₂ is 0 or more and 1 or less, and the acidity constant (pKa ₁ ) of the colorant having the buffer region and the acidity constant (pKa of the pH buffer region expansion aid) ₂ ) By using the inkjet ink having the relationship of the above formula (A), a high-quality printed matter can be obtained even if continuous printing is performed for a long period of time (print durability test), and It is an object of the present invention to provide an inkjet ink capable of maintaining the pH of the ink within a desired range (preferably substantially constant), an ink set using the ink, a recording method, a recording unit, an ink tank, and a recording apparatus.

  The effect of the third means of the present invention is that continuous printing is performed for a long period of time (print durability test) by using an inkjet ink containing the color material represented by the following general formula (2). However, it is possible to obtain a high-quality printed matter and to maintain the pH of the ink within a desired range (preferably substantially constant), an ink set using the ink, a recording method, and recording. To provide a unit, an ink tank, and a recording apparatus.

  The effect of the fourth means of the present invention is that continuous printing is performed for a long period of time (print durability test) by using an ink jet ink containing the color material represented by the following general formula (4). However, it is possible to obtain a high-quality printed matter and to maintain the pH of the ink within a desired range (preferably substantially constant), an ink set using the ink, a recording method, and recording. To provide a unit, an ink tank, and a recording apparatus.

  The effect of the fifth means of the present invention is to use an inkjet ink in which the compound represented by the general formula (1) is taurine (2-aminoethanesulfonic acid) and taurine is contained in the ink. Therefore, even if continuous printing is performed for a long period (print durability test), a high-quality printed matter can be obtained, and the pH of the ink can be kept within a desired range (preferably substantially constant). To provide ink, an ink set using the ink, a recording method, a recording unit, an ink tank, and a recording apparatus.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  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.

  In the present invention, the coloring material contains 3% or more of a coloring material used for a thermal ink jet printer including a recording head having a heat generating portion wetted surface made of at least one of a metal or a metal oxide, and An ink-jet ink for use at a pH in a buffer region, comprising a coloring material having a buffer region and a pH buffer region expansion aid represented by the following general formula (1).

  General formula (1)

(However, in general formula (1), X represents a carboxyl group or a sulfonic acid group. Y represents one of a hydrogen atom, a carboxyl group, and a sulfonic acid group. N represents an integer of 0 or 1. , M represents an integer of 0 to 2.)

  Here, the mechanism in which the ink containing no pH buffer region expansion aid in the ink and containing the color material having the buffer region in pH deteriorates the heat generating portion of the recording head of the ink jet printer, and is further disconnected. Although not clear, the present inventors presume as follows. In the description here, the color material having the structure of the general formula (2) will be described as an example of the color material having a buffer region in pH. However, the color material having the buffer region is limited to this. is not.

  Hydroxide ions present in the ink are adsorbed on the wetted surface of either the metal or the metal oxide, and the hydroxide ion concentration in the ink decreases. As shown in the following formula (I), when a color material having a buffer region in pH is present in the ink, the hydroxide ion concentration increases to maintain a constant hydroxide ion concentration. Oxide ions are adsorbed on the wetted surface of the heat generating part. When the heat generating part is heated (during discharge), the hydroxide ions adsorbed in large amounts on the heat generating part liquid contact surface react with the heat generating part liquid contact surface and further dissolve (shave). Since the above reaction is repeated each time the heat generating portion is heated (discharged), if a color material having a buffer region within the ink use range is present in the ink, the heat generating portion of the ink jet printer recording head deteriorates (the heat generated). Dissolution of the part wetted surface) and further disconnection.

  By containing the coloring material having a buffer region and the pH buffer region expansion aid of the general formula (1) in the ink, the deterioration of the heat generating portion of the ink jet printer is inhibited and the pH buffer region of the ink is expanded. Although the mechanism is not clear, the present inventors presume as follows.

  In the present invention, the pH buffer region expansion aid represented by the general formula (1) is an acid having an amino group, and therefore exists in an aqueous solution as an amphoteric ion such as the following (A). Here, the case where the X position of the structure of the general formula (1) is a sulfonic acid group will be described as an example, but the same applies to the case where the X position is a carboxyl group.

(However, Y in the above formula (A) represents a hydrogen atom, a carboxyl group, or a sulfonic acid group, n represents an integer of 0 or 1, and m represents an integer of 0 to 2.)

The coloring material represented by the general formula (2) has a buffering region in pH, and exists in the buffering region with anions as shown on the left side of the following formula (I), and water (H ₂ O in the ink) ) To generate hydroxide ions (OH ⁻ ). The hydroxide ion reacts with the hydrogen ion on the nitrogen atom of the acid having an amino group described above, and returns to water. As described above with respect to the deterioration of the heat generating portion of the recording head of the ink jet printer and the mechanism of the subsequent disconnection, the causative substance causing the disconnection of the heat generating portion is hydroxide ions. It is considered that hydroxide ions are neutralized by the reactions of the following formulas (I) and (II), and deterioration of the exothermic part and subsequent disconnection are inhibited.

  Furthermore, the mechanism by which the pH buffer region as the ink is presumed to be expanded by adding the pH buffer region expansion aid represented by the general formula (1) to the ink will be described.

  In the following formula (II), the pH buffer region expansion aid that has reacted with hydroxide ions and has lost the hydrogen ions, as shown in the following formula (III), removes hydrogen ions from a colorant having a buffer region in pH. Supplied and becomes zwitterion again.

  The rest is the repetition of the following formulas (I) to (III). It is considered that this series of reactions inhibits the deterioration of the heat generating portion of the recording head and expands the pH buffer region of the ink.

(In the above formula (I) or (III), Ar ¹ is an unsubstituted or substituted benzene ring, an unsubstituted or substituted naphthyl ring, or the following general formula (3). In the formula (II) or (III), Ar ² represents a benzene ring which may be unsubstituted or substituted, or a naphthyl ring which may be unsubstituted or substituted. Y represents a hydrogen atom, a carboxyl group, or a sulfonic acid group, n represents an integer of 0 or 1, and m represents an integer of 0 to 2.)

  An explanation will be given of whether the action of expanding the pH buffer region of the ink is important in the present invention.

  The pH of the ink changes due to, for example, being left for a certain period of time under various environments or by evaporation of volatile substances from the ink cartridge. It is generally difficult to maintain the pH of the ink within a desired range (preferably substantially constant).

  However, the inclusion of the pH buffering area expansion aid in the ink expands the pH buffering area of the ink by the mechanism described above. The expansion of the pH buffer region of the ink means that the pH in the ink can be maintained within a desired range (preferably almost constant), and the heat generating portion is deteriorated, disconnected, or broken due to a high pH. , Problems such as precipitation of coloring material due to lowering of pH can be solved. A description will be given of whether or not an inkjet ink in which the difference between the acidity constant of the coloring material (hereinafter abbreviated as pKa) and the pH buffering area expansion aid pKa is 0 or more and 1 or less is particularly effective in the present invention. .

  The pH of the inkjet ink changes due to various factors, and the adverse effects caused by the change are as described above. When the difference between the pKa of the color material and the pKa of the pH buffering area expansion aid exceeds 1, the pH of the ink cannot be maintained within a desired range (preferably almost constant), and the pH becomes too high. A large amount of hydroxide ions are generated, and the wetted surface of the heat generating part is dissolved (shaved) and disconnected.

  In addition, deterioration of the heat generating part and further disconnection can be observed when a printing durability test is performed with an ink in which a color material having a buffer region within the ink use range contains 3% or more in the ink. It is a phenomenon that was issued.

  Here, it will be described whether the coloring material having the structure of the general formula (2) is particularly effective in the present invention.

  General formula (2)

(In the general formula (2), Ar ¹ represents an unsubstituted or substituted benzene ring, an unsubstituted or substituted naphthyl ring, or a substituent represented by the following general formula (3). And Ar ² represents a benzene ring which may be unsubstituted or substituted, or a naphthyl ring which may be unsubstituted or substituted.

  General formula (3)

(In General Formula (3), R ¹ represents a hydrogen atom, an alkoxycarbonyl group, or an unsubstituted or substituted benzoyl group, and R ² represents a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, A mono or dialkylaminoalkyl group and a cyano lower alkyl group are represented, Z represents a carboxylic acid group, a sulfonic acid group, or a salt thereof, and l represents 1 or 2.)
The ink containing the color material having the structure of the general formula (2) has a buffer region between pH 8 and 10. As described above, the ink having a buffer region in pH causes the deterioration of the liquid contact surface of the heat generating portion. By incorporating the compound of the general formula (1) into the ink, it is possible to suppress dissolution (scraping) of the liquid contact surface of the heat generating portion by the mechanism shown in the formulas (I) to (III), and It is assumed that the pH buffer region is expanded.

  In the present invention, it is more desirable to use a colorant which is an anthrapyridone compound having a structure of the general formula (4) or a salt thereof. The reason why it is desirable to use the coloring material having the structure of the general formula (4) is that the image storage stability such as gas resistance can be improved.

  General formula (4)

(In General Formula (4), R ³ is a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, a mono- or dialkylaminoalkyl group, a cyano lower alkyl group, R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ is independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a carboxyl group (except when R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are all hydrogen atoms) .).)

  The following exemplary compounds are preferred exemplary compounds of the compound having the structure of the general formula (4). However, the present invention is not limited to the following.

  The color material concentration is preferably 10% by weight or less. This is because if it exceeds 10.0% by weight, good ink jet properties cannot be obtained, such as failure to obtain fixing recovery.

  Of course, the above exemplified compounds can be used alone, but two or more kinds of compounds can also be used in combination.

  In addition, as a method for verifying the color material used in the present invention, (1) peak retention time by high performance liquid chromatography, (2) maximum absorption wavelength of the peak, and (3) M / Z in the mass spectrum of the peak It can be verified by using (posi, nega).

(1) (2) Analytical conditions for high performance liquid chromatography are as follows.
The ink solution diluted about 1000 times with pure water is analyzed by high performance liquid chromatography under the following conditions, and the retention time of the peak and the maximum absorption wavelength of the peak are measured.
Column: Symmetry C18 2.1 mm x 150 mm
Mobile phase gradient conditions

Flow rate: 0.2 ml / min
Column temperature: 40 ° C
PDA: 200 nm to 700 nm

(3) Mass spectrum analysis conditions are as follows.
With respect to the obtained peak, a mass spectrum is measured under the following conditions, and the most strongly detected M / Z is measured for each of posi and negative.
Ionization method ESI
Capillary voltage 3.5 kV
Desolvent gas 300 ℃
Ion source temperature 120 ° C
Detector posi 40V 200-1500amu / 0.9sec
nega 40V 200-1500amu / 0.9sec
Among the exemplified compounds, the retention time, maximum absorption wavelength, M / Z (posi), and M / Z (negative) values for the exemplified compound (*) are shown below.

  In the present invention, the pH buffer region expansion aid represented by the general formula (1) is preferably taurine (2-aminoethanesulfonic acid) and contained in the ink in an amount of 0.5 wt% to 5.0 wt%. desirable. When taurine is contained in the ink in an amount of less than 0.5% by weight, the role as a pH buffer region expansion aid represented by the general formula (1) may be insufficient. That is, the pH buffer region of the ink cannot be expanded sufficiently, and therefore, the effect of suppressing the dissolution (scraping) of the heat generating portion liquid contact surface is not sufficient, and the heater may be scraped. . When taurine is contained in the ink in an amount of more than 5.0% by weight, when printing is performed with the ink, the print quality of the writing start portion may deteriorate. In the compound of the general formula (1), the pH buffering area expansion aid is preferably taurine, and 0.5 wt% or more and 5.0 wt% or less is contained in the ink, whereby the pH buffer area of the ink is adjusted. In addition, it is possible to enlarge, suppress dissolution (scraping) of the liquid contact surface of the heat generating portion, and obtain a high-quality printed matter.

(Buffer area)
The buffer region is a pH region where the solution tries to maintain a substantially constant pH regardless of the addition or disappearance of a certain amount of acid or alkali. When the results of measuring changes in pH by adding acid or alkali to the solution are shown in the figure (a titration curve: the horizontal axis indicates the amount of acid or alkali added, and the vertical axis indicates pH), in the present invention, buffering is performed. The region is a region before and after a region where the pH change is small (a region between two inflection points of the titration curve).

  FIG. 1 shows an acid-alkali titration curve of a 2% aqueous taurine solution. In FIG. 1, the vertical axis represents the pH of the color material aqueous solution. The horizontal axis represents the amount of acid or alkali added, the number greater than 0 represents the amount of sodium hydroxide aqueous solution added, and the number smaller than 0 represents the amount of nitric acid aqueous solution added. The procedure for measuring the titration curve of the aqueous solution is, for example, preparing a 10% aqueous solution of the compound to be titrated and measuring the initial pH. The pH is adjusted to 7 using acid or alkali of the colorant aqueous solution. The acid is added to one color material aqueous solution whose pH is adjusted to 7, and the other alkali is added to the other color material aqueous solution whose pH is adjusted to 7. The pH of the color material aqueous solution is measured respectively. There is a way. From FIG. 1, the range from A to B is the buffer region of taurine, which is pH 6.5 or more and pH 10.8 or less.

  FIG. 2 shows an acid-alkali titration curve of an ink containing 5% by weight of the exemplary compound (*). The view of FIG. 2 is the same as that of FIG. From FIG. 2, the range from C to D is the buffer region of the exemplary compound (*), which is pH 6.8 or more and pH 10.8 or less.

  FIG. 3 shows an acid-alkali titration curve of an ink containing 5% by weight of the exemplary compound (*) and 2% by weight of taurine. The way of viewing FIG. 3 is the same as that of FIG. From FIG. 3, the range from E to F is the buffer region of the comparative example, which is pH 7.3 or more and pH 10.5 or less.

  Comparing FIG. 1, FIG. 2 and FIG. 3, the pH buffer region in the 2 wt% aqueous solution of taurine or the 5 wt% ink of the exemplary compound (*) has an acid-alkali addition amount of 100 mmol / L to 150 mmol / L. On the other hand, in the pH buffer region of the ink containing 2% by weight of taurine and 5% by weight of the exemplary compound (*), the acid / alkali addition amount is 220 mmol / L. By adding taurine to the ink, the pH buffer region of the ink was expanded. The expansion of the pH buffer region of the ink means that the pH can be kept more constant as the pH changes.

(Acidity constant pKa)
The acidity constant (pKa) of the ink is the midpoint of the buffer region.

  From FIG. 1, the pKa of the 2% taurine aqueous solution is 8.7.

From FIG. 2, the pKa of the 5% by weight aqueous solution of the exemplary compound (*) is 8.9. 1, from 2, the acidity constants of the coloring material with the buffer region and pKa _1, when the acidity constants of said pH buffering region expansion aid and pKa _2, the difference between the pKa ₁ and pKa ₂ The relationship between the acidity constant (pKa ₁ ) of the colorant which is 0 or more and 1 or less and has the buffer region and the acidity constant (pKa ₂ ) of the pH buffer region expansion aid is represented by the following formula (A): It can be seen that the relationship is satisfied.
Formula (A)
pKa ₁ ≧ pKa ₂

(PH buffer region expansion aid)
In the present invention, the pH buffering area expansion aid is a compound having the structure of the general formula (1), and the pH buffering area of the ink is expanded by including the pH buffering area expansion aid in the ink. It is a compound. As an example of taurine as a representative example of the general formula (1) and an example compound (*) as a representative example of a coloring material having a buffer region, a titration curve of an aqueous solution containing 2% by weight of taurine is shown in FIG. is there. FIG. 2 is a titration curve of an ink containing 5% by weight of the exemplary compound (*). FIG. 3 is a titration curve of an ink containing 5% by weight of the exemplary compound and 2% by weight of taurine. Comparing FIG. 1 and FIG. 3, the buffer region is wider in FIG. Comparing FIG. 2 and FIG. 3, the buffer region is wider in FIG. From this, it can be seen that the buffer region was expanded by including taurine and the exemplary compound (*) together in the ink.

(Water-soluble organic solvents and additives)
In the ink of the present invention, as long as glycerin and the acetylene glycol compound having the above specific structure are contained, there is no particular limitation as to what other water-soluble organic solvents and additives are contained. Various water-soluble organic solvents can be optionally used. The water-soluble organic solvent is not particularly limited as long as it is water-soluble, and includes alcohol, polyhydric alcohol, polyglycol, glycol ether, nitrogen-containing polar solvent, sulfur-containing polar solvent and the like. Although the water-soluble organic solvent which can be used with the ink of this invention is illustrated below, it is not limited to these water-soluble organic solvents. Specifically, for example, alkyl alcohols having 1 to 4 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; dimethylformamide, dimethyl Amides such as acetamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as polyethylene glycol and polypropylene glycol; Ethylene glycol, propylene glycol, butylene glycol, and triethylene 2 to 6 alkylene groups such as glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and diethylene glycol Alkylene glycols containing carbon atoms; lower alkyl ether acetates such as polyethylene glycol monomethyl ether acetate; multivalents such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether Lower alkyl ethers of alcohols; polyhydric alcohols such as trimethylolpropane and trimethylolethane; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like. The water-soluble organic solvents as described above can be used alone or as a mixture.

  If necessary, surfactants other than the above-mentioned acetylene glycol compounds, pH adjusters, rust inhibitors, antiseptics, antifungal agents, antioxidants, reduction inhibitors, evaporation accelerators, chelating agents Various additives such as an agent and a water-soluble polymer may be contained.

(Ink set)
The ink of the present invention can be preferably used as an ink set used in combination with other inks. There is no particular limitation on other inks that can be combined as an ink set.

(recoding media)
As the recording medium on which an image can be formed using the ink of the present invention, any recording medium can be used as long as it is a recording medium on which ink is attached.

(Inkjet recording method)
An ink jet recording method in which ink is ejected from an orifice in accordance with a recording signal and recording is performed on a recording medium can be preferably used. In particular, recording is performed by applying thermal energy to the ink. An ink jet recording method for recording on a medium can be more preferably used.

(Recording unit)
As a recording unit suitable for performing recording using the ink of the present invention, a recording unit including a recording head having an ink storage unit in which these inks are stored can be cited. There is a recording unit characterized in that thermal energy corresponding to a recording signal is given and ink droplets are generated by the energy.

(ink cartridge)
As an ink cartridge suitable for performing recording using the ink of the present invention, an ink cartridge having an ink containing portion for containing these inks may be mentioned.

(Inkjet recording device)
As a recording apparatus suitable for recording using the ink of the present invention, thermal energy corresponding to a recording signal is given to the ink in the chamber of the recording head having an ink storage part in which these inks are stored. An apparatus that generates ink droplets by energy is used.

  Hereinafter, a schematic configuration of the base rear portion of the ink jet recording apparatus used in the present embodiment will be described. The main body of the recording apparatus according to the present embodiment includes a paper feed unit, a paper transport unit, a carriage unit, a paper discharge unit, a cleaning unit, and an exterior unit that protects these parts and has a design from the role of each mechanism. The outline of these will be described below.

  FIG. 2 is a perspective view of a recording apparatus applied in this embodiment. 3 and 4 are diagrams for explaining the internal mechanism of the recording apparatus main body. FIG. 3 is a perspective view from the upper right part, and FIG. 4 is a side sectional view of the recording apparatus main body. is there.

  When paper feeding is performed in the recording apparatus applied in the present embodiment, first, only a predetermined number of recording media in the paper feeding unit including the paper feeding tray M2060 is transferred to the nip part constituted by the paper feeding roller M2080 and the separation roller M2041. Sent. The sent recording medium is separated at the nip portion, and only the uppermost recording medium is conveyed. The recording medium sent to the paper transport unit is guided by the pinch roller holder M3000 and the paper guide flapper M3030, and is sent to the roller pair of the transport roller M3060 and the pinch roller M3070. A roller pair composed of a conveyance roller M3060 and a pinch roller M3070 is rotated by driving of the LF motor E0002, and the recording medium is conveyed on the platen M3040 by this rotation.

  When an image is formed on a recording medium in the carriage unit, the recording head H1001 (FIG. 5) is disposed at a target image forming position, and ink is ejected onto the recording medium in accordance with a signal from the electric substrate E0014. Although the detailed configuration of the recording head H1001 will be described later, in the recording apparatus of the present embodiment, a recording medium is scanned by the carriage M4000 in the column direction while recording is performed by the recording head H1001, and a recording medium is detected by the conveyance roller M3060. An image is formed on the recording medium by alternately repeating the sub-scan transported in the row direction.

  The recording medium on which the image has been finally formed is sandwiched between nips of the first paper discharge roller M3110 and the spur M3120 at the paper discharge unit, conveyed, and discharged to the paper discharge tray M3160.

  For the purpose of cleaning the recording head H1001 before and after image recording in the cleaning unit, if the pump M5000 is operated in a state where the cap M5010 is in close contact with the ink discharge port of the recording head H1001, it is unnecessary from the recording head H1001. Ink or the like is sucked. Further, by sucking the ink remaining in the cap M5010 with the cap M5010 opened, consideration is given to preventing the remaining ink from adhering and the subsequent adverse effects.

(Recording head configuration)
The configuration of the head cartridge H1000 applied in the present embodiment will be described below. The head cartridge H1000 in this embodiment has a recording head H1001, a means for mounting the ink tank H1900, and a means for supplying ink from the ink tank H1900 to the recording head, and is detachable from the carriage M4000. Mounted on.

  FIG. 5 is a diagram illustrating a state in which the ink tank H1900 is attached to the head cartridge H1000 applied in the present embodiment. The recording apparatus of the present embodiment forms an image with yellow, magenta, cyan, black, light magenta, light cyan, and green ink, and therefore, ink tanks H1900 are also prepared for seven colors independently. In the above, the ink according to the present invention is used as at least one kind of ink. As shown in the figure, each is detachable from the head cartridge H1000. The ink tank H1900 can be attached and detached while the head cartridge H1000 is mounted on the carriage M4000.

  FIG. 6 is an exploded perspective view of the head cartridge H1000. In the figure, a head cartridge H1000 includes a first recording element substrate H1100 and a second recording element substrate H1101, a first plate H1200, a second plate H1400, an electric wiring substrate H1300, a tank holder H1500, and a flow path forming member H1600. , Filter H1700, seal rubber H1800, and the like.

  The first recording element substrate H1100 and the second recording element substrate H1101 are Si substrates, and a plurality of recording elements (nozzles) including a heat generating portion having a liquid contact surface in contact with ink for ejecting ink on one side thereof. Is formed by photolithography. Electric wiring such as Al for supplying electric power to each recording element is formed by a film forming technique, and a plurality of ink flow paths corresponding to individual recording elements are also formed by a photolithography technique. Further, an ink supply port for supplying ink to the plurality of ink flow paths is formed to open on the back surface.

  FIG. 7 is an enlarged front view for explaining the configuration of the first recording element substrate H1100 and the second recording element substrate H1101. H2000 to H2600 are printing element rows (hereinafter also referred to as nozzle rows) corresponding to different ink colors, and the first printing element substrate H1100 has a nozzle row H2000 supplied with yellow ink and a supply of magenta ink. The nozzle row for three colors is configured, that is, the nozzle row H2100 to be supplied and the nozzle row H2200 to which cyan ink is supplied. The second recording element substrate H1101 includes a nozzle row H2300 supplied with light cyan ink, a nozzle row H2400 supplied with black ink, a nozzle row H2500 supplied with orange ink, and a nozzle supplied with light magenta ink. Nozzle rows for four colors of the row H2600 are configured.

  Each nozzle row is composed of 768 nozzles arranged at an interval of 1200 dpi (dot / inch; reference value) in the conveyance direction of the recording medium, and ejects approximately 2 picoliters of ink droplets. The opening area at each nozzle outlet is set to about 100 square μm 2. Further, the first recording element substrate H1100 and the second recording element substrate H1101 are bonded and fixed to the first plate H1200. Here, the first recording element substrate H1100 and the second recording element substrate H1101 are attached. An ink supply port H1201 for supplying ink is formed.

  Further, a second plate H1400 having an opening is bonded and fixed to the first plate H1200, and the second plate H1400 includes the electric wiring substrate H1300, the first recording element substrate H1100, and the second recording element substrate H1100. The electric wiring substrate H1300 is held so that the recording element substrate H1101 is electrically connected.

  The electrical wiring substrate H1300 applies an electrical signal for ejecting ink from each nozzle formed on the first recording element substrate H1100 and the second recording element substrate H1101, and the first recording element substrate Electrical wiring corresponding to the H1100 and the second recording element substrate H1101, and an external signal input terminal H1301 for receiving an electrical signal from the recording apparatus main body located at the end of the electrical wiring. The external signal input terminal H1301 is positioned and fixed on the back side of the tank holder H1500.

  On the other hand, in a tank holder H1500 that holds the ink tank H1900, a flow path forming member H1600 is fixed by, for example, ultrasonic welding to form an ink flow path H1501 that communicates from the ink tank H1900 to the first plate H1200.

  A filter H1700 is provided at the ink tank side end of the ink flow path H1501 that engages with the ink tank H1900, and can prevent dust from entering from the outside. Further, a seal rubber H1800 is attached to the engaging portion with the ink tank H1900 so that ink can be prevented from evaporating from the engaging portion.

  Further, as described above, the tank holder portion composed of the tank holder H1500, the flow path forming member H1600, the filter H1700, and the seal rubber H1800, the first recording element substrate H1100, the second recording element substrate H1101, and the first plate. The head cartridge H1000 is configured by bonding the recording head unit H1001 including the H1200, the electric wiring substrate H1300, and the second plate H1400 by bonding or the like.

  Here, as an embodiment of the recording head, a bubble jet (registration) that performs recording using an electrothermal transducer (recording element) that generates thermal energy for causing film boiling to the ink in response to an electrical signal. A trademark type recording head has been described with an example.

  About this typical structure and principle, for example, what is performed using the basic principle disclosed in US Pat. Nos. 4,723,129 and 4,740,796 is preferable. . This method can be applied to both the so-called on-demand type and the continuous type. In particular, in the case of the on-demand type, it corresponds to a sheet or liquid flow path in which liquid (ink) is held. By applying at least one drive signal that corresponds to the recorded information and gives a rapid temperature rise exceeding the nucleate boiling to the electrothermal transducer arranged in a manner, heat energy is generated in the electrothermal transducer, This is effective because film boiling occurs on the heat acting surface of the recording head, and as a result, bubbles in the liquid (ink) corresponding to the drive signal on a one-to-one basis can be formed. By the growth and contraction of the bubbles, liquid (ink) is ejected through the ejection opening to form at least one droplet. When this drive signal is in a pulse shape, bubbles are grown and contracted immediately and appropriately, so that it is possible to achieve the discharge of liquid (ink) with particularly excellent responsiveness, which is more preferable.

  Further, as a form of the ink jet recording apparatus using the second mechanical energy, a nozzle forming substrate having a plurality of nozzles, a pressure generating element made of a piezoelectric material and a conductive material disposed opposite to the nozzles, and this pressure An on-demand ink jet recording head that includes ink that fills the periphery of the generating element, displaces the pressure generating element by an applied voltage, and discharges a small droplet of ink from a nozzle can be exemplified.

  Further, the ink jet recording apparatus is not limited to the one in which the head and the ink tank are separated as described above, but may be one in which they are integrated so as not to be separated. The ink tank is integrated with the head so as to be separable or inseparable from the head and mounted on the carriage, and is provided at a fixed portion of the apparatus so that ink is supplied to the recording head via an ink supply member, for example, a tube. The thing of the form to supply may be sufficient. Further, when the ink tank is provided with a configuration for applying a preferable negative pressure to the recording head, a configuration in which an absorber is disposed in the ink storage portion of the ink tank, or a flexible ink storage bag and the same A form having a spring portion that applies a biasing force in the direction of expanding the internal volume can be employed. In addition to the serial recording method as described above, the recording apparatus may take the form of a line printer in which recording elements are aligned over a range corresponding to the entire width of the recording medium.

(PH buffer region expansion aid)
A commercially available product was purchased and used as it was for the pH buffering range expansion aid used in this example. In this embodiment, taurine is used, but it is not limited to taurine.

(Preparation of coloring material)
Exemplary compound 1 is synthesized as follows. The following compound α, sodium carbonate, and ethyl benzoyl acetate were reacted in xylene, and the reaction product was filtered and washed. This was sequentially charged with metaaminoacetanilide, copper acetate and sodium carbonate in N, N-dimethylformamide and reacted, and the reaction product was filtered and washed. Furthermore, it was sulfonated in fuming sulfuric acid, filtered and washed, and this was subjected to a condensation reaction with cyanuric chloride in the presence of sodium hydroxide.

  Anthranilic acid was added to the reaction solution, and a condensation reaction was performed in the presence of sodium hydroxide. This was filtered and washed to obtain Exemplified Compound 1 below.

  Exemplary Compound 1

(Preparation of ink)
Inks were prepared according to the formulations shown in Table 3 below, and each was pressure filtered through a 0.2 μm membrane filter, and inks of Examples and Comparative Examples were obtained. Unless otherwise specified, the ink components in Examples and Comparative Examples mean “parts by mass”.

  In addition, in the ink shown in the Example and the Comparative Example, it was confirmed by measuring the pH of the ink that it was in the buffer region.

(Evaluation of ink)
The following inks were used to evaluate printing durability.

(1) Printing durability The prepared ink was filled in an ink tank, the ink tank was mounted on an ink jet printer (F890; manufactured by Canon), and a printing durability test was performed with a pattern that printed 100% solid on A4 size paper. . Evaluation was performed as follows.
A: No problem even after printing 20000 sheets.
A: There is slight blurring due to minute twisting between 15000 and 20000 printing.
Δ: Slight blurring due to slight twisting between 10000 and 15000 prints.
X: Disappearance caused by fading and disconnection before reaching 10,000 sheets.
◎ and ○ were judged to be acceptable levels, △ was judged to be acceptable without problems in actual use, and × was judged to be unacceptable.

  When a printing durability test was performed using an ink (comparative example) that did not contain a pH buffer region expansion aid in the ink, undischarge occurred due to disconnection of the heat generating portion wetted surface of the heat generating portion of the recording head. . On the other hand, even when the printing durability test was performed using the ink containing the pH buffering area expansion aid (Example) in the ink, the heat generation part liquid contact surface of the heat generation part did not break, Good printing was obtained until the end of the printing durability test. From this, it can be seen that the pH buffer region expansion aid suppresses the deterioration of the wetted surface of the heat generating portion.

(2) Print quality Next, the print quality was evaluated. The contents of the evaluation were such that the prepared ink was filled in an ink tank, the ink tank was mounted on an ink jet printer (F890; manufactured by Canon Inc.), and a printing durability test was performed with a pattern that printed 100% solid on A4 paper. During the endurance test, when a twist occurred, the endurance test was terminated, and the nozzle was observed with an optical microscope to confirm the presence of precipitates. Evaluation was performed as follows.
A: Printing deviation does not occur even when printing 20000 sheets.
○: At the time of printing 20000 sheets, although there is a slight deviation in printing, no precipitate was confirmed.
(Triangle | delta): The printing twist generate | occur | produced at the time of printing 20000 sheets, and the deposit was also confirmed by some nozzles.
X: At the time of printing 20000 sheets, noticeable printing deviation occurred, and deposits were confirmed at all nozzles.

As can be seen from Example 3, when the pH buffer region expansion aid pKa ₂ satisfies the formula (A), printing deviation, precipitates, and the like were not observed even when printing 20000 sheets. On the other hand, when the pKa _{2 of} the pH buffer region expansion aid does not satisfy the formula (A), comparatively noticeable deviation occurred when 20000 sheets were printed. When the recording head subjected to the printing test was observed using an optical microscope, precipitates were attached to almost all the nozzles.

  From the above, the pH buffer region expansion aid satisfies the formula (A), so that even when printing 20000 sheets, the heat generating portion is not deteriorated, no deposit is adhered, and high A high quality printed matter can be obtained.

It is a titration curve of 2% aqueous taurine solution. It is a titration curve of an Example. Comparative example titration curve 1 is a perspective view of a recording apparatus according to an embodiment of the present invention. FIG. 3 is a perspective view of a mechanism unit of the recording apparatus according to the embodiment of the invention. 1 is a cross-sectional view of a recording apparatus in an embodiment of the present invention. FIG. 5 is a perspective view showing a state where an ink tank is mounted on the head cartridge applied in the embodiment of the present invention. It is a disassembled perspective view of the head cartridge applied in the embodiment of the present invention. FIG. 3 is a front view showing a recording element substrate in a head cartridge applied in an embodiment of the present invention.

Explanation of symbols

M2041 Separation roller M2060 Paper feed tray M2080 Paper feed roller M3000 Pinch roller holder M3030 Paper guide flapper M3040 Platen M3060 Transport roller M3070 Pinch roller M3110 Paper discharge roller M3120 Spur M3160 Paper discharge tray M4000F Carriage M5000 Pump M500P Head cartridge H1001 Recording head H1100 First recording element substrate H1101 Second recording element substrate H1200 First plate H1201 Ink supply port H1300 Electrical wiring substrate H1301 External signal input terminal H1400 Second plate H1500 Tank holder H1501 Ink channel H1600 Flow path forming member H1700 Luther H1800 seal rubber H1900 ink tank H2000 yellow nozzle row H2100 magenta nozzle row H2200 cyan nozzle row H2300 light cyan nozzle row H2400 black nozzle row H2500 green nozzle row H2600 light magenta nozzle row

Claims (9)

3% by weight or more of a color material used for a thermal ink jet printer including a recording head having a heat generating part wetted surface made of at least one of a metal or a metal oxide compound, and a buffer region of the color material An ink-jet ink for use at a pH, comprising a colorant having a buffer region and a pH buffer region expansion aid represented by the following general formula (1).
General formula (1)

(However, in general formula (1), X represents a carboxyl group or a sulfonic acid group. Y represents one of a hydrogen atom, a carboxyl group, and a sulfonic acid group. N represents an integer of 0 or 1. M represents an integer of 0 to 2.) The acidity constant of the coloring material with the buffer region and pKa _1, when the acidity constants of said pH buffering region expansion aid and pKa _2, the difference between the pKa ₁ and pKa ₂ is 0 or more than 1, and, the relationship between the acidity constants of the coloring material with the buffer area (pKa ₁₎ and the acidity constant of said pH buffering region expansion aid (pKa ₂₎ is, according to claim 1 which is the relationship of the formula (a) The ink for inkjet described.
Formula (A)
pKa ₁ ≧ pKa ₂ The inkjet ink according to claim 1, wherein the coloring material has a structure represented by the following general formula (2).
General formula (2)

(In the general formula (2), Ar ¹ represents an unsubstituted or substituted benzene ring, an unsubstituted or substituted naphthyl ring, or a substituent represented by the following general formula (3). And Ar ² represents a benzene ring which may be unsubstituted or substituted, or a naphthyl ring which may be unsubstituted or substituted.
General formula (3)

(In General Formula (3), R ¹ represents a hydrogen atom, an alkoxycarbonyl group, or an unsubstituted or substituted benzoyl group, and R ² represents a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, A mono or dialkylaminoalkyl group and a cyano lower alkyl group are represented, X represents a carboxylic acid group, a sulfonic acid group, or a salt thereof, and l represents 1 or 2.) The inkjet ink according to any one of claims 1 to 3, wherein the coloring material is an anthrapyridone compound represented by the following general formula (4) or a salt thereof.
General formula (4)

(In General Formula (4), R ³ is a hydrogen atom, an alkyl group, a hydroxy lower alkyl group, a cyclohexyl group, a mono- or dialkylaminoalkyl group, a cyano lower alkyl group, R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ is independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or a carboxyl group (except when R ⁴ , R ⁵ , R ⁶ , R ⁷ , and R ⁸ are all hydrogen atoms) .).)   The inkjet ink according to any one of claims 1 to 4, wherein the compound represented by the general formula (1) is taurine (2-aminoethanesulfonic acid) and taurine is contained in the ink.   6. An ink jet recording method in which ink is ejected from an orifice in accordance with a recording signal and recording is performed on a recording medium, wherein the ink is the ink according to any one of claims 1 to 5.   7. A recording unit comprising an ink containing portion containing ink and a recording head for discharging the ink, wherein the ink is the ink according to any one of claims 1 to 6.   An ink cartridge comprising an ink containing portion containing ink, wherein the ink is the ink according to any one of claims 1 to 6. 7. An ink jet recording apparatus comprising a recording unit having an ink containing portion containing ink and a head portion for ejecting the ink, wherein the ink is an ink according to any one of claims 1 to 6. Recording device.

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