JP4981261B2 - Ink jet ink, ink jet recording method, ink cartridge, and ink jet recording apparatus - Google Patents

Description

  The present invention relates to an inkjet ink, an inkjet recording method, an ink cartridge, and an inkjet recording apparatus.

  The ink jet recording method is a method for recording images, characters, and the like by ejecting micro droplets of ink by various operating principles and attaching them to a recording medium (paper, etc.). It has features such as easy recording pattern flexibility, no need for development and fixing, and is rapidly spreading in various applications. Furthermore, in recent years, full-color inkjet recording system technology has been developed, and it is possible to form multicolor images that are comparable to multicolor printing by plate making and color photographic printing, and the number of copies is small. In some cases, printed matter can be obtained at a lower cost than ordinary multicolor printing or printing. Against this background, ink jet recording apparatuses and recording methods have been improved along with demands for improving recording characteristics such as higher recording speed, higher definition, and full color. Since an image forming apparatus such as a printer using an ink jet recording system is used in various usage environments, recording stability is also important, and improvement in image durability is also required as ink characteristics.

  Various recording media such as plain paper, coated paper, glossy paper, OHP sheet, and back print film are commercially available, but low-priced plain paper is used for business applications in general offices. There are many cases. However, when plain paper is used as the recording medium, it is necessary to mitigate and suppress the curl (paper warping or curling) phenomenon that occurs when a large amount of ink is applied to the recording medium while satisfying the above-described characteristics. Arise. This curling phenomenon is largely attributed to the application of moisture. That is, it has been found that the curling phenomenon occurs remarkably when the area to which moisture is applied is wide or when the applied amount is large. When inkjet recording is performed on plain paper, it is important not only to curl during printing, but also to mitigate and suppress curling (curling after printing) caused by moisture drying and evaporation after printing.

  Printed matter (print) printed by inkjet is used for various purposes, but curled paper cannot maintain flatness, and causes various problems such as stacking and curling when filing. Also, trial printing of slides, OHP, and other presentations may be done using low-priced plain paper. At that time, if you print figures, photos, and backgrounds in secondary colors (blue, etc.) The paper warps and is often difficult to handle.

Several methods have been proposed in the past as methods for reducing and suppressing curling. For example, an ink-jet ink has been proposed that contains a solid substance that has four or more hydroxyl groups in the molecular structure and is soluble in water or an aqueous organic solvent (see, for example, Patent Document 1). Further, inks containing saccharides, sugar alcohols, and specific amide compounds as anti-curl agents have been proposed (see, for example, Patent Documents 2 to 5). An ink containing a combination of a specific polyhydric alcohol and glycerin has been proposed (see, for example, Patent Document 6). In addition, an ink containing a solvent, a polymer binder, a mordant, a water-soluble anti-curl compound, a water-soluble desizing compound, a light-resistant compound, an antifoaming agent, and the like has been proposed (see, for example, Patent Document 7).
JP-A-4-332775 JP-A-6-157955 JP-A-6-240189 JP-A-9-165539 JP 9-176538 A JP-A-10-130550 JP 2000-198267 A

  Curling can be suppressed to some extent by including a conventional curling-preventing compound in the ink. However, in inkjet recording, the speed is further increased, and ejection stability and reliability at high speed printing are important. Therefore, after obtaining various physical properties such as stability, penetrability and viscosity of the ink itself, further basic characteristics as ink for ink jet recording, particularly ink jet ejection stability, more specifically, ink jet recording head. Curling is alleviated and suppressed while maintaining a high level of clogging resistance and start-up properties (nozzle ink ejection from a nozzle that has been temporarily suspended (stopped or stopped)). It has become important.

  Therefore, the object of the present invention is to ensure the ejection stability after leaving the head required for conventional ink-jet inks and the ejection stability (start-up property) such that there is no disturbance or blurring of the print start portion at the start of printing. An object of the present invention is to provide an ink jet ink, an ink jet recording method, an ink cartridge, and an ink jet recording apparatus that can alleviate and suppress curling.

  Another object of the present invention is to sufficiently relieve and suppress curling, and to make it easy to handle a printed material produced using plain paper.

  The above object is achieved by the present invention described below.

That is, the inkjet ink of the present invention contains at least water, a colorant, seen containing a water-soluble organic compound 1 and the water-soluble organic compound 2, a viscosity at 25 ° C., an inkjet ink is 1～5Cps,
The content X (% by mass) of the water-soluble organic compound 1 is 10% by mass or more and 18.0% by mass or less with respect to the total mass of the inkjet ink,
The content Y (% by mass) of the water-soluble organic compound 2 is less than 15% by mass with respect to the total mass of the inkjet ink,
The water content (% by mass) is 77% by mass or less based on the total mass of the inkjet ink,
The content X (mass%) of the water-soluble organic compound 1 and the content Y (mass%) of the water-soluble organic compound 2 with respect to the total mass of the ink jet ink are represented by the following formulas (I) and (II). It is characterized by satisfying the relationship.
(I) 0.15 ≦ Y / X ≦ 0.9
(II) X + Y ≧ 25 % by mass
Water-soluble organic compound 1: water-retaining water solution having a difference of 36% or less in water holding power in an environment of temperature 23 ° C. and humidity 45% and water holding power in environment of temperature 30 ° C. and humidity 80% Organic compounds.
Water-soluble organic compound 2: Water-soluble organic compound other than coloring agent and water-soluble organic compound 1.

In particular, the difference in water retention between the water- soluble organic compounds 2 is preferably 40% or more.

Another embodiment of the ink-jet ink of the present invention is an ink-jet ink containing at least water and a colorant, and further includes a water-soluble organic compound 1-1, a water-soluble organic compound 1-2, and a water-soluble ink. Content X ₁ (% by mass) of the water-soluble organic compound 1-1 with respect to the total mass of the inkjet ink, including the organic compound 2-1, and content of the water-soluble organic compound 1-2 with respect to the total mass of the inkjet ink The amount X ₂ (% by mass) and the content Y ₁ (% by mass) of the water-soluble organic compound 2 with respect to the total mass of the ink jet ink satisfy the relationships of the following formulas (1) to (3).
(1) 0.1 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 2.5
(2) X ₁ + X ₂ ≧ 10% by mass
(3) X ₂ + Y ₁ ≧ 3% by mass
Water-soluble organic compound 1-1: The difference between the moisture retention in an environment of temperature 23 ° C. and humidity 45% and the moisture retention in an environment of temperature 30 ° C. and humidity 80% is 36% or less, and the molecular weight Mw Is a water-soluble polyhydric alcohol or water-soluble amide compound in the range of 100 ≦ Mw ≦ 1000.
Water-soluble organic compound 1-2: The difference between the water retention capacity in an environment at a temperature of 23 ° C. and a humidity of 45% and the water retention capacity in an environment of a temperature of 30 ° C. and a humidity of 80% is 36% or less, and the molecular weight Mw Is a water-soluble alkanediol having a range of 100 ≦ Mw ≦ 150 and further having —OH groups at both ends of the main chain.
Water-soluble organic compounds 2-1: water-soluble organic compounds other than the colorant, the water-soluble organic solvent 1-1, and the water-soluble organic solvent 1-2.

In particular, it is preferable that the content Y ₁ (% by mass) of the water-soluble organic compound 2-1 is Y ₁ <15% by mass, and the difference in water retention is 40% or more.

The inkjet recording method of the present invention is characterized in that the inkjet ink is applied to a recording medium by an inkjet recording head to form an image.

  In addition, an ink cartridge according to the present invention includes the ink-jet ink.

  The ink jet recording apparatus of the present invention is characterized in that the ink jet ink is mounted.

  According to the present invention, curling can be sufficiently suppressed with respect to an ink jet recording method for plain paper, and in particular, printed matter of plain paper can be easily handled. Another object of the present invention is to provide an ink capable of obtaining ink ejection stability and a recording method using the same in ink jet recording. Furthermore, an ink capable of obtaining good image characteristics and a recording method using the same are provided.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments.

[Mechanism of curling]
The present invention has been made for the purpose of suppressing curling of a recording medium after ink jet ink (hereinafter referred to as “ink”) is applied to the recording medium by an ink jet recording method.

  The mechanism by which curling occurs after printing on a recording medium is as follows. Cellulose fibers are made by a paper machine so that they are aligned in the direction in which the paper flows (in other words, they are forcibly oriented). Cellulose fibers differ greatly in the degree of expansion due to moisture in the longitudinal direction and in the lateral direction, and therefore the paper size change that occurs when moisture is applied differs between the horizontal and vertical eyes of the paper. Therefore, when moisture is added to the paper, the lateral direction of the cellulose fibers of the paper swells, and the direction perpendicular to the machine flow direction (often the vertical direction of the paper) when the paper is made (the horizontal direction of the paper) The length of the paper increases. For this reason, if the ink application amount at the time of printing, that is, the water application amount is large, curling to the opposite side of the surface to which water has been applied, that is, negative curling occurs. However, once the moisture absorbed in the cellulose fibers is gradually evaporated, the reshrinking of the cellulose fibers starts and the paper shrinks again. Along with this, the paper becomes shorter than the length before moisture is applied. Accordingly, the paper gradually curls, i.e., positively curls, on the surface to which moisture has been applied. This is because the moisture applied by printing once enters between the hydrogen bonds between the fibers, and the tension applied initially loosens as the moisture moves due to evaporation, etc. It is thought that it occurs by doing. This plus curl becomes a problem when ink jet recording is performed on a recording medium such as plain paper.

  The present inventors have observed in detail the plus curl phenomenon that occurs when printing is performed by the ink jet recording method. As a result, it has been discovered that when ink jet ink is applied to paper, the plus curl phenomenon proceeds continuously for a long period of time, unlike when water is simply applied to paper.

  Currently, organic compounds such as glycerin and urea contained in many ink jet inks greatly contribute to reliability as ink jet inks, particularly ejection stability. On the other hand, it is considered that these organic compounds are factors that cause the positive curl phenomenon to proceed continuously.

[Water-soluble organic compound with water retention]
Since the curl after the liquid medium containing water is applied to the paper is considered to have some correlation with the evaporation of moisture applied to the paper, the present inventors have proposed a water-soluble solution commonly used in ink jet inks. The following detailed study was conducted on the water retention of organic compounds.

  First, 20% by mass aqueous solutions of various water-soluble organic compounds were prepared, 10 g each was precisely weighed into a glass petri dish, and left in an environment at a temperature of 23 ° C. and a humidity of 45%. At the same time, pure water containing no water-soluble organic compound was also allowed to stand. As the water evaporates, the amount of solution in the petri dish decreases and the mass becomes constant over time. At the same time, the pure water-only petri dish that was allowed to stand at the same time has evaporated all the pure water. Therefore, the remaining water in the petri dish containing the water-soluble organic compound is retained by the water-soluble organic compound and the substance. The water retention of each water-soluble organic compound was calculated by the following formula.

  Next, the petri dish was moved to an environment with a temperature of 30 ° C. and a humidity of 80%. Similarly, after waiting for the equilibrium to be reached, the remaining weight under this environment was measured, and the moisture retention was determined according to the above formula. . Furthermore, the same petri dish was moved again to an environment of a temperature of 23 ° C. and a humidity of 45%, the remaining weight was measured, and the water retention capacity was similarly determined. The obtained results are shown in FIG. Further, FIG. 2 shows the difference in water retention between the two environments.

  The present inventors considered that there is some correlation between the difference in moisture retention force under the above-described environment and the occurrence of curling of plain paper. Then, when the aqueous solution containing the water-soluble organic compound examined above was applied to plain paper and the occurrence of curling was examined, the moisture retention in an environment of temperature 23 ° C. and humidity 45%, temperature 30 ° C., humidity 80 It was found that the water-soluble organic compound 1 having a difference in water retention capacity of 36% or less in an environment of 50% markedly suppresses curling. Therefore, an ink containing a coloring material, an additive, and these water-soluble organic compounds was further prepared and subjected to ink jet recording, and the occurrence of curling was observed. As a result, it was confirmed that no curling occurred even after several days at room temperature after printing.

  In the present invention, the water-soluble organic compound having water retention is a water-soluble organic compound having a moisture retention of 5% or more in an environment of a temperature of 23 ° C. and a humidity of 45%.

  However, when an ink composed of a water-soluble organic compound of only the water-soluble organic compound 1 is mounted on an ink jet recording apparatus mounted on an ink jet recording head that discharges droplets from the nozzle and left for a long time, the nozzle is clogged. As a result, there were new problems such as deterioration of ejection stability due to the above, and disorder of the writing portion at the start of printing in a low temperature and low humidity environment.

Therefore, the present inventors have made further studies with the aim of ensuring the same level of ejection stability as that of conventional ink-jet inks while suppressing curling to a certain extent. As a result, in addition to the water-soluble organic compound 1, water-soluble organic compounds other than the water-soluble organic compound 1, more specifically, water retention in an environment of a temperature of 23 ° C. and a humidity of 45% are added to the inkjet ink. And a water-soluble organic compound 2 having a water retention capacity difference of 36% or more in an environment of a temperature of 30 ° C. and a humidity of 80% in a ratio satisfying the following formulas (I) and (II): Thus, it has been found that the above problems can be solved.
(I) 0 <Y / X ≦ 0.9
(II) X + Y ≧ 15% by mass
(X: content (% by mass) of water-soluble organic compound 1 with respect to the total mass of the ink-jet ink, Y: content (% by mass) of water-soluble organic compound 2 with respect to the total mass of the ink-jet ink)
Furthermore, according to the study of the present invention, in addition to the above conditions, the content of the water-soluble organic compound 1 when the amount of applied ink is large, specifically, when the amount is larger than 3.0 g / m ^2. It has been found that X (mass%) needs to be 10 mass% or more with respect to the total mass of the inkjet ink.

  The water-soluble organic compound 1 is preferably a polyhydric alcohol having an amide bond or a polyhydric alcohol having a sulfone group.

  The water-soluble organic compound usually used in the inkjet ink corresponds to the water-soluble organic compound 2 in the present invention. The water-soluble organic compound 2 has a large difference in water retention, and in the process of drying the recording medium to which moisture has been applied, the water-soluble organic compound 2 tends to release moisture and increases the shrinkage of cellulose fibers. The water-soluble organic compound 2 has many molecular weights as small as 100 or less and easily moves with moisture in the recording medium, so that it is difficult to stay on the cellulose fiber. For this reason, the water-soluble organic compound 2 gradually migrates in the recording medium and causes curling to proceed. Therefore, the curl is considerably increased when a large amount of ink containing the water-soluble organic compound 2 which is a water-soluble organic compound usually used in ink jet inks is applied to plain paper.

  As a result of the study by the present inventors, even when the ink-jet ink contains the water-soluble organic compound 2 having the property of advancing curling, the ink-jet ink further contains the water-soluble organic compound 1, and the water-soluble organic compound Curling can be effectively suppressed by setting the ratio Y / X of the content of 1 and the water-soluble organic compound 2 to 0 <Y / X ≦ 0.9, as shown by the formula (I). It was found that the discharge stability was also improved.

Furthermore, the present inventors have found that the total X + Y (mass%) of the contents of the water-soluble organic compound 1 and the water-soluble organic compound 2 needs to be X + Y ≧ 15 mass%. The reason for this is that when ink is applied to the paper, in order to suppress the paper shrinkage caused by short-term moisture evaporation and migration, the relative content is increased by increasing the total content of water-soluble organic compounds in the ink-jet ink. This is because it is necessary to reduce the amount of water. In addition to this, in order to prevent evaporation of the ink applied to the paper, it is assumed that the water-soluble organic compound having water retention, that is, the total amount of the water-soluble organic compound 1 and the water-soluble organic compound 2 is required to be 15% by mass or more. Yes.

The X + Y further preferably satisfies the relationship of X + Y ≧ 20% by mass, and more preferably satisfies the relationship of X + Y ≧ 25% by mass. Therefore, in the present invention, X + Y ≧ 25 mass%. The inventors of the present invention prepared an ink having an increased total content X + Y (mass%) of the water-soluble organic compound 1 and the water-soluble organic compound 2 and observed the curled state. It has been found that curling that occurs within a short period of time can be effectively suppressed. In particular, when X + Y is X + Y ≧ 25% by mass, curling that occurs within a short time after printing is very effectively improved.

Furthermore, the water content is 77% by mass or less, more preferably 71% by mass or less , based on the total mass of the ink jet ink.

The content Y (% by mass) in the water-soluble organic compound 2 with respect to the total mass of the ink jet ink is set to Y <15% by mass. The reason is presumed as follows. As described above, since the water-soluble organic compound 2 has a property of causing curling, curling tends to occur as the content in the ink increases. For this reason, even if the inkjet ink contains a large amount of the water-soluble organic compound 1, the water-soluble organic compound 2 migrates the water-soluble organic compound 1, thereby reducing the curl suppressing effect of the water-soluble organic compound 1. It is because it ends. Furthermore, it is preferable that the difference in water retention of the water-soluble organic compound 2 is 40% or more.

  By the way, according to another embodiment of the present invention described below, good ejection stability can be achieved while effectively suppressing curling after printing on a recording medium, particularly plain paper.

The present inventors have further investigated using the water-soluble organic compound 1 and the water-soluble organic compound 2. As a result, the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2, which are specific water-soluble organic compounds among the water-soluble organic compounds 1, are each contained in one or more ink-jet inks. We found that the problem can be solved effectively. That is, each of the water-soluble organic compound 1-1, the water-soluble organic compound 1-2, and the water-soluble organic compound 2-1, and the content X ₁ (mass%) of the water-soluble organic compound with respect to the total mass of the inkjet ink. ), X ₂ (mass%), and Y ₁ (mass%) were found to be able to solve the above problems by containing them at a ratio that satisfies the following conditions.
(1) 0.1 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 2.5
(2) 10% by mass ≦ X ₁ + X ₂
(3) 3% by mass ≦ X ₂ + Y ₁
(X ₁ : content (mass%) of water-soluble organic compound 1-1 relative to the total mass of ink-jet ink, X ₂ : content (mass%) of water-soluble organic compound 1-2 relative to the total mass of ink-jet ink, Y ₁ : Content (% by mass) of the water-soluble organic compound 2-1 with respect to the total mass of the inkjet ink
The action of the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2 in this embodiment will be described below.

  The water-soluble organic compound 1-1 has a molecular weight difference of 36% or less between the moisture retention ability in an environment of a temperature of 23 ° C. and a humidity of 45% and the moisture retention ability in an environment of a temperature of 30 ° C. and a humidity of 80%. It is a water-soluble polyhydric alcohol or a water-soluble amide compound in which Mw is in the range of 100 ≦ Mw ≦ 1000.

  Since the water-soluble organic compound 1-1 has a large molecular size, it is difficult to enter between the cellulose fibers and has little effect on curling that occurs in a relatively short time after printing. Difficult to cause migration. This is because it has an appropriate water retention capacity, it is difficult to hold water more than necessary, and there are a plurality of at least three or more sites where hydrogen bonding is likely to occur in the molecule, and it has a high affinity for cellulose fibers. Conceivable.

  For example, 3 or more —OH groups such as triols, 2 or more —OH groups and carbonyl groups such as saccharides, and 2 such as N, N′-bis- (2-hydroxyethyl) -urea The above -OH group and amide bond, two or more -OH groups and sulfone groups such as bishydroxyethyl sulfone, two or more -OH groups and at least three ether bond groups such as tetraethylene glycol. have. Furthermore, it is considered that a plurality of factors such as a large molecular size and difficulty in migration with water act effectively.

  On the other hand, for example, diethylene glycol has a molecular weight of 100 or more, has two —OH groups at both ends of the molecule, and one ether bond in the molecule, but its curl-inhibiting effect is small. This is probably because one ether bond is less hydrophilic (hydrogen bond) than one -OH group, and in an aqueous solution, the molecule is bent due to the interaction between the ether bond and water. Is considered to be smaller. Therefore, it is considered that at least three ether bonds are required in order to exert a curl suppressing effect with a diol having an ether bond in the molecule.

  The water-soluble organic compound 1-2 has a molecular weight difference of 36% or less between the moisture retention ability in an environment of a temperature of 23 ° C. and a humidity of 45% and the moisture retention ability in an environment of a temperature of 30 ° C. and a humidity of 80%. It is a water-soluble alkanediol having Mw in the range of 100 ≦ Mw ≦ 150 and further having —OH groups at both ends of the main chain.

  The action of the water-soluble organic compound 1-2 suppresses curling that occurs in a relatively short time after printing (several hours after printing). However, although the water-soluble organic compound 1-2 effectively suppresses the curling phenomenon that occurs in a relatively short time after printing, it does not cause curling that occurs in a longer time range (5, 6 hours to several weeks). The effect is small. This is because the water-soluble organic compound 1-2 is an alkanediol having a molecular weight of 100 to 150 and having —OH groups at both ends of the main chain, so that the molecule does not have a hydrophilic bond such as an ether bond, and the molecule is bent. This is probably because the molecular size is relatively large. In addition, it is considered that the internal structure of the molecule is lipophilic and the molecular end is hydrophilic, so that it has surface-active properties and is easily wetted with cellulose fibers. Moreover, since it has an appropriate molecular size, it can easily enter between cellulose fibers, and curling that occurs in a short time can be suppressed. However, since there are few -OH groups with affinity with a cellulose fiber, it is considered that migration may occur in a long time.

  The inventors of the present invention used the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2 in combination, so that curling can be started from a short time after printing rather than containing these water-soluble organic compounds alone. It has been found that there is an effect of suppressing for a long time. This is because the structures of the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2 are similar, so that the water-soluble organic compound 1-1 is effective together with the water-soluble organic compound 1-2. It is thought that curling can be suppressed from a short time after printing to a long time since it enters the cellulose fiber.

  The inventors of the present invention particularly when the total content in the case of using a combination of the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2 is less than 25% by mass with respect to the total mass of the inkjet ink, or water It has been found that curling can be effectively improved in a short time even when the content is more than 71 mass% with respect to the total mass of the ink jet ink. In particular, the difference between the curling phenomenon that occurs in a relatively short time after printing appears remarkably between the ink containing the water-soluble organic compound 1-2 and the ink not containing it under the above conditions.

  As described above, the ink-jet ink containing the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2 can effectively suppress curling. However, in order to satisfy the ejection stability as an inkjet ink, it is necessary to use the water-soluble organic compound 2-1 in combination.

  Here, the water-soluble organic compound 2-1 is a water-soluble organic compound other than the colorant, the water-soluble organic solvent 1-1, and the water-soluble organic solvent 1-2. More specifically, it is a water-soluble organic compound having a difference between the water retention capacity in an environment of a temperature of 23 ° C. and a humidity of 45% and the water retention capacity in an environment of a temperature of 30 ° C. and a humidity of 80% of more than 36%.

  The reason is presumed as follows. Since the water-soluble organic compound 1-2 has surface-active properties as described above, and further has low miscibility with the colorant, the water-soluble organic compound 1-2 has a higher concentration than other components in the inkjet nozzle. It exists in the vicinity. For this reason, moisture evaporation near the nozzle can be suppressed. By using this in combination with the water-soluble organic compound 2-1, which has good miscibility with the colorant and has a high water retention ability, an increase in the viscosity inside the nozzle can be suppressed and the ejection stability can be improved.

As a result of the study by the present inventors, even when the ink-jet ink contains the water-soluble organic compound 2-1 having the property of advancing curling, the water-soluble organic compound 1-1 and the water-soluble organic compound 1 are further included. -2 and the ratio (X ₂ + Y ₁ ) / X ₁ of the content of the water-soluble organic compound 1-1, the water-soluble organic compound 1-2, and the water-soluble organic compound 2 in the formula (1) As shown in the drawing, 0.1 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 2.5, curling can be continuously suppressed from a short time to a long time after printing, and ejection stability is further improved. Was also found to be good.

Further, according to the study of the present invention, in order to suppress curling when the amount of applied ink is large, specifically when it is larger than 3.0 g / ^{m 2} , in addition to the above conditions, water-soluble It has been found that the total content X ₁ + X ₂ (mass) of the organic compound 1-1 and the water-soluble organic compound 1-2 needs to be X ₁ + X ₂ ≧ 10 mass%.

Further, according to the study of the present inventors, in order to improve the ejection stability, in addition to the above conditions, the total content X ₂ + Y of the water-soluble organic compound 1-2 and the water-soluble organic compound 2-1. ₁ were found to X ₂ + Y ₁ ≧ 3% by weight, needs to be.

  Furthermore, the water content is preferably 77% by mass or less, more preferably 71% by mass or less, based on the total mass of the inkjet ink.

The content Y ₁ (% by weight) of the water-soluble organic compound 2-1 for ink jet ink total mass, Y ₁ <is preferably 15% by mass. The reason is presumed as follows. As described above, since the water-soluble organic compound 2-1 has a property of causing curling, curling tends to occur as the content in the ink increases. For this reason, even if the inkjet ink contains a large amount of the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2, the water-soluble organic compound 2-1 is the water-soluble organic compound 1-1 and the water-soluble organic compound. This is because 1-2 is migrated and the curl suppressing effect of the water-soluble organic compound 1-1 and the water-soluble organic compound 1-2 is reduced. Furthermore, the difference in water retention between the water-soluble organic compounds 2-1 is preferably 40% or more.

Furthermore, it is preferable that one or more selected from the following conditions (A) to (F) is satisfied in addition to the above formulas (1) to (3).
(A) X ₁ , X ₂ and Y ₁ further satisfy the following formula.
0.2 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 2.0, X ₁ + X ₂ ≧ 13 mass%, and X ₁ + X ₂ + Y ₁ ≧ 15 mass%
(B) X ₁ , X ₂ and Y ₁ further satisfy the following formula.
0.2 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 1.5
(C) X ₁ , X ₂ and Y ₁ further satisfy the following formula.
0.2 ≦ (X ₂ + Y ₁ ) /X1≦1.5, 0% by mass <Y ₁ ≦ 11% by mass, and X ₁ + X ₂ + Y ₁ ≧ 20% by mass
(D) X ₁ , X ₂ and Y ₁ further satisfy the following formula.
0.2 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 1.5 and X ₁ + X ₂ + Y ₁ ≧ 25% by mass
(E) X ₁ , X ₂ and Y ₁ further satisfy the following formula.
0.2 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 1.0, X ₁ + X ₂ ≧ 13 mass%, and X ₁ + X ₂ + Y ₁ ≧ 20 mass%
(F) X ₁ , X ₂ and Y ₁ further satisfy the following formula.
0 <Y ₁ / (X ₁ + X ₂ ) ≦ 0.9
[Inkjet ink]
The components constituting the ink jet ink according to the present invention will be described in detail.

(Water-soluble organic compounds with water retention)
Specific examples of the water-soluble organic compound 1 or the water-soluble organic compound 1-1, the water-soluble organic compound 1-2, the water-soluble organic compound 2 or the water-soluble organic compound 2-1 are shown below.

-Specific example of water-soluble organic compound 1 Ethylene oxide modified (ethylene oxide addition number 6-30) glycerol triacrylic acid ester, dipentaerythritol. Modification with ethylene oxide (8 to 40 ethylene oxide additions)
Water-soluble organic compound having a polyethylene glycol skeleton such as acrylic ester and other hydrophilic bonding groups other than -OH group-Specific examples of water-soluble organic compound 1 or water-soluble organic compound 1-1 Average molecular weight 200 (mainly Polyethylene glycol such as component tetraethylene glycol), 300 (main component hexaethylene glycol), 400 (main component nonaethylene glycol), 600 (main component tridecaethylene glycol), 1000 (main component docosaethylene glycol), 1, 2 , 6-hexanetriol, trimethylolpropane, trimethylolethane, pentaerythritol, diglycerin and other polyhydric alcohol compounds, glucose, sorbitol, bishydroxyethylsulfone, N, N′-bis- (2-hydroxy Ethyl) -ure , Tetra - (2-hydroxyethyl) - carbonyl group, such as phenyl diamide, sulfone group, a polyhydric alcohol compound having a group having a hydrogen bonding such as an amide group. Of these, polyethylene glycol having an average molecular weight of 200, 1,2,6-hexanetriol, trimethylolpropane, bishydroxyethylsulfone, and N, N′-bis- (2-hydroxyethyl) -urea are particularly preferable.

Specific examples of water-soluble organic compound 1 or water-soluble organic compound 1-2 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3-methyl-1,5-pentanediol, 2- Alkanes having —OH groups at both ends of the carbon main chain which may have substituents such as amino-2-methyl-1,3-propanediol and 2-amino-2-ethyl-1,3-propanediol Diol. Of these, 1,6-hexanediol is particularly preferable.
Specific examples of water-soluble organic compound 2 or water-soluble organic compound 2-1 Water-soluble organic compounds having a hydrophilic group with a small number of carbon atoms, such as urea, ethylene glycol, 2-pyrrolidone, ethylene urea, glycerin, diethylene glycol, and the like. Of these, urea, 2-pyrrolidone, ethylene urea, and glycerin are particularly preferable.

  In the present invention, it is preferable that at least one of the water-soluble organic compound 1 and the water-soluble organic compound 1-1 is a water-soluble organic compound having an amide bond in the molecule. Of these, N, N'-bis- (2-hydroxyethyl) -urea is most preferable. The reason for this is that N, N′-bis- (2-hydroxyethyl) -urea has the ability to prevent molecular association, and therefore it is essential to use it in combination with other water-soluble organic compounds in the present invention. Prevent association of each water-soluble organic compound. In particular, in the case of the ink used in the ink jet recording method, it is easier to draw out performances such as clogging prevention and dye solubility, and further curling can be effectively suppressed, and ejection stability and reliability can be greatly improved. In particular, when N, N′-bis- (2-hydroxyethyl) -urea or bishydroxyethylsulfone is used as the water-soluble organic compound 1 or the water-soluble organic compound 1-1, the number of carbon atoms is 5. It is preferable to use a combination of the above diols or triols. Among diols or triols having 5 or more carbon atoms, 1,6-hexanediol and 1,2,6-hexanetriol are preferable. When these are used in combination, the above-described performance for preventing the association of molecules can be exhibited more efficiently, and a particularly excellent curl suppressing effect and ejection stability can be obtained.

  In general, those classified as water-soluble organic compounds 1 often have high viscosity when added to ink, and curling improves when the amount added is increased. There was a thing. In order to improve this problem, it is preferable that at least one of the water-soluble organic compound 1 and the water-soluble organic compound 1-1 is a water-soluble organic compound having a sulfone bond in the molecule. Of these, bishydroxyethyl sulfone is most preferable. This is because bishydroxyethyl sulfone, when used in combination with other components, makes it difficult to cause solvation between these other components and water, and reduces the viscosity. In particular, in the case of ink used in the ink jet recording method, it is effective for improving start-up property among ejection stability.

  Also, water-soluble organic compounds such as urea and ethylene urea are preferable because they have a low molecular weight and are difficult to increase in viscosity even when the addition amount is increased. A water-soluble organic compound such as urea or ethylene urea can be used as a water-soluble organic compound having water retention in the present invention by using it in combination with a water-soluble organic solvent or a compound showing water solubility such as a dye. In addition, the measurement result (difference by an environment) of the water retention power of ethylene urea in FIG. 1 is data at the time of measuring using it with a dye.

In addition, the molecular weight of the water-soluble organic compound having a molecular weight distribution such as the polyhydric alcohol and polyethylene glycol having the amide bond was an average molecular weight determined by any of the following.
(1) According to JIS handbook chemical analysis K0118 and K0123, mass spectrometry, gas chromatography mass spectrometry (GC-MS) method, and liquid chromatography mass spectrometry (LC-MS method) were performed to measure the molecular weight.
(2) For polyethylene glycol having a molecular weight distribution, the average molecular weight was determined from the size exclusion chromatography method (GPC method) in accordance with JIS Handbook Chemical Analysis K0124, and was used as the molecular weight. Furthermore, the water-soluble organic compound having a molecular weight distribution other than polyethylene glycol was determined as a molecular weight by obtaining a weight average molecular weight in terms of polyethylene glycol.
(3) The structure of the water-soluble organic compound was identified from the NMR method, infrared analysis method, elemental analysis method, etc., and the molecular weight was determined.

(Coloring agent)
Examples of the colorant used in the inkjet ink of the present invention include water-soluble dyes and pigments. A coloring agent can be used 1 type or in combination of 2 or more types.

(dye)
Examples of the dye used in the present invention include an anionic water-soluble dye having a hue such as black, cyan, magenta, and yellow. The anionic water-soluble dye is not particularly limited as long as it is an acid dye, a direct dye, or a reactive dye described in the color index (COOLUR INDEX). Moreover, even if it is a dye which is not described in a color index, there will be no restriction | limiting in particular if it has an anionic group, for example, a sulfone group. These dyes are used in the range of 1 to 10% by mass, preferably 1 to 5% by mass, based on the total mass of the ink jet ink. In addition, dyes other than those described above can also be used. Specific examples include dyes having a carboxyl group as a solubilizing group. Among these, dyes that exhibit solubility dependency on pH are preferable. These dyes can be used in the ink in an amount of 1 to 10% by mass, preferably 1 to 7% by mass.

When the dye is indicated by a color index (CI) number, the following can be exemplified. Of course, it is not limited to the following.
C. I. Direct yellow: 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85, 86, 87, 88, 98, 100, 110
C. I. Direct Red: 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75, 79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226 227, 228, 230
C. I. Direct blue: 1, 15, 22, 25, 41, 76, 77, 80, 86, 90, 98, 106, 108, 120, 158, 163, 168, 199, 226
C. I. Acid Yellow: 1, 3, 7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99
C. I. Acid Red: 6, 8, 9, 13, 14, 18, 26, 27, 32, 35, 42, 51, 52, 80, 83, 87, 89, 92, 94, 106, 114, 115, 133, 134 145, 158, 198, 249, 265, 289
C. I. Acid Blue: 1, 7, 9, 15, 22, 23, 25, 29, 40, 43, 59, 62, 74, 78, 80, 90, 100, 102, 104, 117, 127, 138, 158, 161
C. I. Direct black: 17, 19, 22, 31, 32, 51, 62, 71, 74, 112, 113, 154, 168
C. I. Acid Black: 2, 48, 51, 52, 110, 115, 156
C. I. Reactive black: 1, 8, 12, 13
C. I. Food black: 1, 2
(Pigment)
Next, examples of the pigment used in the present invention include carbon black and organic pigments. These pigments are used in the range of 1 to 20% by mass, preferably 2 to 12% by mass, based on the total mass of the inkjet ink.

Carbon black Specific examples of carbon black are carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. For example, Raven 7000, Rayvan 5750, Rayvan 5250, Rayvan 5000, Rayvan 3500, Rayvan 2000 , Ray Van 1500, Ray Van 1250, Ray Van 1200, Ray Van 1190 ULTRA-II, Ray Van 1170, Ray Van 1255 (manufactured by Columbia), Black Pearls L, Legal 400R, Legal 330R, Legal 660R, Moguul ) L, Monarch 700, Monak 800, Monak 880, Monak 900, Mon 1000, Monak 1100, Monak 1300, Monak 1400, Valcan XC-72R (manufactured by Cabot), Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Printex 140V, Special Black 6, Special Black 5, Special Black 4A , Special Black 4 (Degussa) 25, no. 33, no. 40, no. 47, no. 52, no. 900, no. 2300, MCF-88, MA600, MA7, MA8, MA100 (manufactured by Mitsubishi Chemical Corporation) and the like can be used. Of course, it is not limited to these, and conventionally known carbon black can be used. Further, magnetic fine particles such as magnetite and ferrite, titanium black and the like may be used as the black pigment.

Organic pigments Specific examples of organic pigments include insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, pyrazolone red, soluble azo pigments such as ritole red, heliobordeaux, pigment scarlet, permanent red 2B, alizarin, Derivatives from vat dyes such as indanthrone and thioindigo maroon, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, quinacridone pigments such as quinacridone red and quinacridone magenta, perylene pigments such as perylene red and perylene scarlet, isoindo Isoindolinone pigments such as linone yellow and isoindolinone orange, imidazolones such as benzimidazolone yellow, benzimidazolone orange and benzimidazolone red Pigments, pyranthrone pigments such as pyranthrone red, pyranthrone orange, thioindigo pigments, condensed azo pigments, thioindigo pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone Other pigments such as orange, anthrone orange, dianthraquinonyl red, and dioxazine violet can be exemplified.

Moreover, the following can be illustrated when an organic pigment is shown by a color index (CI) number. Of course, conventionally known organic pigments can be used other than the following.
C. I. Pigment Yellow: 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 109, 110, 117, 120, 125, 128, 137, 138, 147, 148, 151, 153, 154, 166 168
C. I. Pigment Orange: 16, 36, 43, 51, 55, 59, 61
C. I. Pigment Red: 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 215, 216, 217, 220, 223, 224, 226, 227 228, 238, 240
C. I. Pigment Violet: 19, 23, 29, 30, 37, 40, 50
C. I. Pigment Blue: 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64
C. I. Pigment Green: 7, 36
C. I. Pigment Brown: 23, 25, 26
-Dispersant When using the above-described carbon black or organic pigment, it is preferable to use a dispersant in combination. As the dispersant, a dispersant that can stably disperse the above pigment in an aqueous medium by the action of an anionic group is suitably used. Specific examples of the dispersant include, for example, a styrene-acrylic acid copolymer, a styrene-acrylic acid-alkyl acrylate copolymer, a styrene-maleic acid copolymer, and a styrene-maleic acid-alkyl acrylate copolymer. Styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, A styrene-maleic anhydride-maleic acid half ester copolymer or a salt thereof is included. These dispersants preferably have a weight average molecular weight in the range of 1,000 to 30,000, particularly preferably in the range of 3,000 to 15,000.

Self-dispersing pigment As a coloring material, a pigment that can be dispersed in an aqueous medium without a dispersant by bonding an ionic group (anionic group) to the pigment surface, a so-called self-dispersing pigment can also be used. Examples of such pigments include self-dispersing carbon black. Examples of the self-dispersing carbon black include an anionic carbon black in which an anionic group is bonded to the surface of the carbon black.

Anionic carbon black Anionic carbon black has at least one anionic group selected from, for example, —COOM, —SO ₃ M, —PO ₃ HM, and —PO ₃ M ₂ bonded to the surface of carbon black. Things. In the above formula, M represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. Among these, carbon black in which —COOM or —SO ₃ M is bonded to the carbon black surface and charged anionically has good dispersibility in the ink and can be particularly preferably used in the present invention.

  By the way, among those represented as “M” in the hydrophilic group, specific examples of the alkali metal include, for example, Li, Na, K, Rb and Cs, and specific examples of the organic ammonium include, for example, Examples include methylammonium, dimethylammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methanolammonium, dimethanolammonium, and trimethanolammonium.

  The ink of the present invention containing self-dispersing carbon black in which M is ammonium or organic ammonium can further improve the water resistance of a recorded image, and can be particularly preferably used in this respect. This is considered to be due to the fact that when the ink is applied onto the recording medium, ammonium is decomposed and ammonia is evaporated. Here, the self-dispersing carbon black in which M is ammonium is, for example, a method of substituting self-dispersing carbon black in which M is an alkali metal with ammonium using an ion exchange method, or adding an acid to form H-type. And a method of adding M to ammonium by adding ammonium hydroxide.

  Examples of the method for producing anionic carbon black include a method in which carbon black is oxidized with sodium hypochlorite. By this method, a —COONa group can be chemically bonded to the surface of carbon black.

By the way, various hydrophilic groups as described above may be directly bonded to the surface of carbon black. Alternatively, another atomic group may be interposed between the carbon black surface and the hydrophilic group, and the hydrophilic group may be indirectly bonded to the carbon black surface. Specific examples of the other atomic groups include a linear or branched alkylene group having 1 to 12 carbon atoms, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group. Here, examples of the substituent of the phenylene group and the naphthylene group include a linear or branched alkyl group having 1 to 6 carbon atoms. Specific examples of combinations of other atomic groups and hydrophilic groups include, for example, —C ₂ H ₄ COOM, —Ph—SO ₃ M, —Ph—COOM (where Ph represents a phenylene group). It is done.

  By the way, in the present invention, two or more kinds of self-dispersing carbon blacks described above may be used as the ink coloring material appropriately selected. Further, the addition amount of the self-dispersing carbon black in the ink is preferably in the range of 0.1 to 15% by mass, particularly 1 to 10% by mass with respect to the total mass of the ink. By setting this range, the self-dispersing carbon black can maintain a sufficiently dispersed state in the ink. Further, for the purpose of adjusting the color tone of the ink, a dye may be added as a coloring material in addition to the self-dispersing carbon black.

Colored fine particles / microencapsulated pigments In addition to the above-mentioned color materials, pigments microencapsulated with polymers, etc., and colored fine particles in which the periphery of resin particles is coated with a color material can also be used. Originally, microcapsules have dispersibility in an aqueous medium, but in order to improve dispersion stability, a dispersant as described above may further coexist in the ink. Moreover, when using colored fine particles as a coloring material, it is preferable to use the anionic dispersant described above.

(Aqueous medium)
In the present invention, water or a mixed solvent of water and a water-soluble organic solvent can be appropriately used as long as the effects obtained by adding these are obtained and the object effects of the present invention are not impaired. Specific examples of the water-soluble organic solvent include 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; Amides such as formamide and dimethylacetamide; Ketones or ketoalcohols such as acetone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyalkylene glycols such as ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, Alkylene glycols wherein the alkylene group contains 2 to 6 carbon atoms, such as thiodiglycol, hexylene glycol, diethylene glycol; glycerin; ethylene glycol mono Lower alkyl ethers of polyhydric alcohols such as til (or ethyl) ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3 -Dimethyl-2-imidazolidinone and the like. The above water-soluble organic solvents can be used alone or as a mixture. The water is preferably deionized water (ion exchange water).

(Other ingredients)
In addition to the above-described components, the ink-jet ink according to the present invention may be added with a moisturizing agent as necessary, and may also have a desired physical property value, such as a viscosity adjusting agent, a pH adjusting agent, and a surfactant. Antifoaming agents, antiseptics, antifungal agents, antioxidants, and the like may be added as long as the effects of adding these are obtained and the object effects of the present invention are not impaired.

(Physical properties)
Suitable ranges for the physical properties of the inkjet ink according to the present invention are around 25 ° C., pH is 3 to 12, preferably 7 to 10, and surface tension is 10 to 60 dyn / cm, preferably 10 to 40 dyn / cm. The viscosity is 1-5 cps.

[Inkjet recording apparatus]
By using the ink-jet ink of the present invention described above, it is possible to relieve and suppress curling and obtain recording characteristics excellent in ejection stability when performing ink-jet recording on a recording medium. The ink jet recording apparatus of the present invention is provided with an ink containing portion containing the ink, a recording unit provided with a head portion for discharging the ink, and an ink containing portion containing the ink. An ink jet recording apparatus including the ink cartridge.

  A recording apparatus suitable for recording using the ink-jet ink of the present invention provides thermal or mechanical energy corresponding to a recording signal to ink in a recording head having an ink storage portion in which ink is stored. And an apparatus for generating ink droplets by the energy.

  FIG. 3 shows an example of an ink jet recording apparatus incorporating this head. In FIG. 3, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end and form a cantilever. The blade 61 is disposed at a position adjacent to the recording area by the recording head, and in the case of the example shown in FIG. 3, the blade 61 is held in a form protruding in the moving path of the recording head. Reference numeral 62 denotes a cap, which is disposed at a home position adjacent to the blade 61 and moves in a direction perpendicular to the moving direction of the recording head so as to come into contact with the ejection surface and perform capping. Further, reference numeral 63 in FIG. 3 denotes an ink absorber provided adjacent to the blade 61 and, like the blade 61, is held in a form protruding in the moving path of the recording head.

  The blade 61, the cap 62, and the absorber 63 constitute a discharge recovery portion 64, and the blade 61 and the absorber 63 remove moisture, dust, dust, and the like from the ink discharge port surface. Reference numeral 65 denotes a recording head that has discharge energy generating means and performs recording by discharging ink onto a recording material facing the discharge port surface on which the discharge ports are arranged. Reference numeral 66 denotes a recording head 65 having the recording head 65 mounted thereon. It is a carriage for performing the movement. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 driven by a motor 68. Accordingly, the carriage 66 can move along the guide shaft 67, and the recording area by the recording head 65 and its adjacent area can be moved.

  Reference numeral 51 denotes a paper feed unit for inserting a recording material, and 52 denotes a paper feed roller driven by a motor (not shown). With these configurations, a recording material is fed to a position facing the ejection port surface of the recording head, and is discharged to a paper discharge unit provided with a paper discharge roller 53 as recording progresses.

  In the above configuration, when the recording head 65 returns to the home position due to the end of recording or the like, the cap 62 of the head recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port surface of the recording head 65 is wiped. When the cap 62 is in contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the moving path of the recording head.

  When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are at the same position as that at the time of wiping described above. As a result, even in this movement, the ejection port surface of the recording head 65 is wiped. The above-mentioned movement of the recording head to the home position is performed not only at the end of recording or at the time of recovery of ejection, but also to the home position adjacent to the recording area at a predetermined interval while the recording head moves the recording area for recording. In accordance with this movement, the wiping is performed.

  FIG. 4 is a cross-sectional view showing an example of an ink cartridge 45 that contains ink supplied to the head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink container, for example, an ink bag, in which supply ink is stored, and a rubber plug 42 is provided at the tip thereof. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives waste ink.

  The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge as described above are separated, and one in which they are integrated as shown in FIG. 5 is also preferably used. In FIG. 5, reference numeral 70 denotes a recording unit, in which an ink containing portion containing ink, for example, an ink absorber is housed, and a head portion in which the ink in the ink absorber has a plurality of orifices. 71 is ejected as ink droplets. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. The recording unit 70 is used in place of the recording head 65 shown in FIG. 3 and is detachable from the carriage 66.

  FIG. 6 shows an example of an ink jet cartridge that can be mounted on the above-described ink jet recording apparatus. The cartridge 1012 in this example is of a serial type, and the main part is composed of an ink jet recording head 100 and a liquid tank 1001 for containing a liquid such as ink. The inkjet recording head 100 is formed with a number of ejection ports 832 for ejecting liquid, and liquid such as ink is supplied from the liquid tank 1001 to a common liquid chamber of the liquid ejection head 100 via a liquid supply passage (not shown). It has come to be guided. A cartridge 1012 shown in FIG. 6 has an ink jet recording head 100 and a liquid tank 1001 integrally formed so that liquid can be supplied into the liquid tank 1001 as necessary. A structure in which a liquid tank 1001 is connected to 100 in a replaceable manner may be adopted.

  Hereinafter, although it demonstrates more concretely using an Example and a comparative example, this invention is not limited at all by the following Example, unless the summary is exceeded. In the following description, parts and% are based on mass unless otherwise specified.

[Examples 1 to 6 , Comparative Examples 1 to 4, Reference Examples 1 to 5 ]
(Preparation of ink)
After mixing each component according to the following Table 1 and stirring sufficiently, pressure filtration was performed with a membrane filter having a pore size of 0.2 μm to prepare inks 1 to 10, comparative inks 1 to 4, and reference ink 1. The reference ink 1 is an ink containing only the water-soluble organic compound 1. Table 2 shows data of X and Y, and X + Y and Y / X.

(Evaluation of curl)
The obtained ink was applied to a recording medium using an inkjet recording apparatus having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to a recording signal to the ink. The ink jet recording apparatus used has the configuration shown in FIG. 3 and has a recording density of 2.8 pL per dot, a recording density of 2400 × 1200 dpi, and a driving condition of a driving frequency of 10 kHz. Using the apparatus, printing was performed so that the printing duty was 100%. The printing was performed by two-pass printing in which the printing area was scanned twice. A4 size PPC paper (manufactured by Canon) was used as the recording medium. These recording conditions are the same throughout the examples, comparative examples, and reference examples.

Curling evaluation method The printed matter was left for 1 hour, 1 day, 4 days, and 7 days in an environment of a temperature of 24 ° C and a humidity of 50%, and then the curl amount was measured over time. When the printed paper was curled in the concave direction, it was defined as + (plus curl), and when it was curled in the convex direction, it was defined as-(minus curl), and the distance from the leading edge of the curled paper to the ground contact surface of the paper was measured with a ruler. . The curl criteria are as follows. The evaluation results are shown in Table 3.
The curl criteria are as follows.

A: Within ± 10 mm A: Greater than ± 10 mm and within ± 25 mm B: Greater than ± 25 mm and within ± 40 mm C: State where the leading edge of the paper is warped inside the paper surface D: State where the leading edge of the paper is curled inside the paper surface (Evaluation of ejection stability)
The obtained ink was applied to a recording medium using an inkjet recording apparatus having an on-demand type multi-recording head that ejects ink by applying thermal energy corresponding to a recording signal to the ink. The ink jet recording apparatus used has the configuration shown in FIG. 3 and has a recording density of 2.8 pL per dot, a recording density of 2400 × 1200 dpi, and a driving condition of a driving frequency of 10 kHz. Using the apparatus, printing was performed so that the printing duty was 100%. The printing was performed by two-pass printing in which the printing area was scanned twice. A4 size PPC paper (manufactured by Canon) was used as the recording medium. These recording conditions are the same throughout the examples, comparative examples, and reference examples.

・ Evaluation method of ejection stability 1 (ejection stability after leaving the head) In order to evaluate the ejection stability of the ink, whether or not problems such as nozzle clogging occur is set on the head and left for one month. After printing, it was confirmed whether the image was disturbed or blurred. The standard of the ejection stability 1 (ejection stability after leaving the head) is as follows. The evaluation results are shown in Table 3.

A: No fading B: Slight fading but virtually no problem C: Faint and image problematic level D: Non-ejection ・ Discharge stability 2 (startup characteristics) evaluation method Ink As an evaluation of ejection stability, it was confirmed in the environment 1: normal temperature and normal humidity, and in the environment 2: temperature 15 ° C. and humidity 10%, whether or not the printed writing portion was disturbed or blurred at the start of printing. The criteria for ejection stability 2 (startup characteristics) are as follows. The evaluation results are shown in Table 3.

A: No fading B: No fading and the image is slightly distorted, but there is virtually no problem level C: The export part is faint and there is a problem with the image D: The export part is faint

[Examples 7 to 15 and Comparative Examples 5 and 6]
(Preparation of ink)
Ingredients were mixed according to the following Table 4 and sufficiently stirred, and then pressure filtered through a membrane filter having a pore size of 0.2 μm to prepare inks 11 to 19 and comparative inks 5 and 5. Table 5 shows data of X ₁ , X ₂ , Y, and X ₁ + X ₂ , X ₂ + Y ₁ , X ₁ + X ₂ + Y ₁ , Y / X, (X ₂ + Y) / X ₁ .

(Evaluation of curl)
The curl evaluation method is the same as described above. The evaluation results are shown in Table 6.

(Evaluation of ejection stability)
The ejection stability 1 (ejection stability after leaving the head) evaluation method and the ejection stability 2 (startup characteristics) evaluation method are the same as described above. The evaluation results are shown in Table 6.

It is a figure which shows the measurement result of the moisture retention of various water-soluble organic compounds. It is a figure which shows the difference of the water | moisture retention power in two specific both environments. It is a perspective view which shows an example of an inkjet recording device. It is a longitudinal cross-sectional view of an ink cartridge. It is a perspective view of a recording unit. It is a schematic perspective view which shows an example of the inkjet cartridge provided with the liquid discharge head.

Explanation of symbols

40: ink container 42: plug 45: ink cartridge 44: ink absorber 51: paper feed unit 52: paper feed roller 53: paper discharge roller 61: blade 62: cap 63: ink absorber 64: discharge recovery unit 65: Discharge energy generating means 66: carriage 67: guide shaft 68: motor 69: belt 70: recording unit 71: head unit 72: atmosphere communication port 100: inkjet recording head 832: discharge port 1001: liquid tank 1012: cartridge

Claims (23)

At least water, a colorant, seen containing a water-soluble organic compound 1 and the water-soluble organic compound 2, a viscosity at 25 ° C., an inkjet ink is 1～5Cps,
The content X (% by mass) of the water-soluble organic compound 1 is 10% by mass or more and 18.0% by mass or less with respect to the total mass of the inkjet ink,
The content Y (% by mass) of the water-soluble organic compound 2 is less than 15% by mass with respect to the total mass of the inkjet ink,
The water content (% by mass) is 77% by mass or less based on the total mass of the inkjet ink,
The content X (mass%) of the water-soluble organic compound 1 and the content Y (mass%) of the water-soluble organic compound 2 with respect to the total mass of the ink jet ink are represented by the following formulas (I) and (II). An inkjet ink characterized by satisfying the relationship.
(I) 0.15 ≦ Y / X ≦ 0.9
(II) X + Y ≧ 25 % by mass
Water-soluble organic compound 1: water-retaining water solution having a difference of 36% or less in water holding power in an environment of temperature 23 ° C. and humidity 45% and water holding power in environment of temperature 30 ° C. and humidity 80% Organic compounds.
Water-soluble organic compound 2: Water-soluble organic compound other than coloring agent and water-soluble organic compound 1.   The inkjet ink according to claim 1, wherein the water-soluble organic compound 1 is a polyhydric alcohol having an amide bond.   The inkjet ink according to claim 1, wherein the water-soluble organic compound 1 is a polyhydric alcohol having a sulfone group. The content of the water (mass%) The inkjet ink according to any one of claim 1 to 3 or less 71% by mass. The ink for ink jet according to any one of claims 1 to 4 , wherein a difference in water retention of the water-soluble organic compound 2 is 40% or more. The water-soluble organic compound 1 has an average molecular weight of 200, 300, 400, 600, and 1000, polyethylene glycol, 1,2,6-hexanetriol, trimethylolpropane, trimethylolethane, pentaerythritol, diglycerin, glucose, sorbitol Bishydroxyethylsulfone, N, N′-bis- (2-hydroxyethyl) -urea, tetra- (2-hydroxyethyl) -phenyldiamide, 1,5-pentanediol, 1,6-hexanediol, 1, Selected from the group consisting of 7-heptanediol, 3-methyl-1,5-pentanediol, 2-amino-2-methyl-1,3 - propanediol, 2-amino-2-ethyl-1,3-pentanediol at least one compound is any one of claims 1 to 5 is 1 The inkjet ink according to. Wherein the water-soluble organic compound 2, urea, ethylene glycol, 2-pyrrolidone, ethylene urea, glycerin, according to any one of claim 1 to 6, and at least one compound selected from the group consisting of diethylene glycol Ink for inkjet. The ink-jet ink according to any one of claims 1 to 7 , wherein the water-soluble organic compound 2 contains at least glycerin. An ink-jet ink containing at least water and a colorant, further comprising a water-soluble organic compound 1-1, a water-soluble organic compound 1-2, and a water-soluble organic compound 2-1, and the water-soluble organic compound content relative to the ink jet ink total mass of 1-1 X ₁ (wt%), the content relative to the ink jet ink total mass of the water-soluble organic compound 1-2 X ₂ (wt%), and water-soluble organic compound 2 An inkjet ink, wherein the content Y ₁ (% by mass) with respect to the total mass of the inkjet ink satisfies the relationships of the following formulas (1) to (3).
(1) 0.1 ≦ (X ₂ + Y ₁ ) / X ₁ ≦ 2.5
(2) X ₁ + X ₂ ≧ 10% by mass
(3) X ₂ + Y ₁ ≧ 3% by mass
Water-soluble organic compound 1-1: The difference between the moisture retention in an environment of temperature 23 ° C. and humidity 45% and the moisture retention in an environment of temperature 30 ° C. and humidity 80% is 36% or less, and the molecular weight Mw Is a water-soluble polyhydric alcohol or water-soluble amide compound in the range of 100 ≦ Mw ≦ 1000.
Water-soluble organic compound 1-2: The difference between the water retention capacity in an environment at a temperature of 23 ° C. and a humidity of 45% and the water retention capacity in an environment of a temperature of 30 ° C. and a humidity of 80% is 36% or less, and the molecular weight Mw Is a water-soluble alkanediol having a range of 100 ≦ Mw ≦ 150 and further having —OH groups at both ends of the main chain.
Water-soluble organic compounds 2-1: water-soluble organic compounds other than the colorant, the water-soluble organic solvent 1-1, and the water-soluble organic solvent 1-2. The inkjet ink according to claim 9 , wherein the water-soluble organic compound 1-1 is a polyhydric alcohol having an amide bond. The inkjet ink according to claim 9 or 10 , wherein the water-soluble organic compound 1-1 is a polyhydric alcohol having a sulfone group. The total content X ₁ + X ₂ + Y ₁ of the water-soluble organic compound 1-1, the water-soluble organic compound 1-2, and the water-soluble organic compound 2-1 with respect to the total mass of the inkjet ink is X ₁ + X. The inkjet ink according to claim 9 , wherein ₂ + Y ₁ ≧ 20% by mass. The inkjet ink according to claim 12 , wherein the X ₁ + X ₂ + Y ₁ is X ₁ + X ₂ + Y ₁ ≧ 25% by mass. The content of the water-soluble organic compound 1-1 X ₁ (wt%), the content of the water-soluble organic compound 1-2 X ₂ (wt%), and the content of the water-soluble organic compound 2 Y ₁ (wt% The inkjet ink according to any one of claims 9 to 13 , further satisfying a relationship of the following formula (4).
(4) 0 <Y ₁ / (X ₁ + X ₂ ) ≦ 0.9 The ink for ink jet according to any one of claims 9 to 14 , wherein the water content (% by mass) is 77% by mass or less based on the total mass of the ink jet ink. The inkjet ink according to claim 15 , wherein the water content (% by mass) is 71% by mass or less. The content Y ₁ (% by mass) of the water-soluble organic compound 2-1 is Y ₁ <15% by mass, and the difference in water retention between the water-soluble organic compound 2-1 is 40% or more. The inkjet ink according to any one of claims 9 to 16 . The water-soluble organic compound 1-1 is polyethylene glycol having an average molecular weight of 200, 300, 400, 600 and 1000, 1,2,6-hexanetriol, trimethylolpropane, trimethylolethane, pentaerythritol, diglycerin, glucose And at least one compound selected from the group consisting of sorbitol, bishydroxyethylsulfone, N, N′-bis- (2-hydroxyethyl) -urea, and tetra- (2-hydroxyethyl) -phenyldiamide. The ink for inkjet of any one of 9-17 . The water-soluble organic compound 1-2 is 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 3-methyl-1,5-pentanediol, 2-amino-2-methyl- The inkjet ink according to any one of claims 9 to 18 , which is at least one compound selected from the group consisting of 1,3 - propanediol and 2-amino-2-ethyl-1,3-pentanediol. .   The water-soluble organic compound 2-1 is at least one compound selected from the group consisting of urea, ethylene glycol, 2-pyrrolidone, ethylene urea, glycerin, and diethylene glycol. The ink for inkjet described. The inkjet ink according to any one of claim 1 to 20 an ink jet recording method characterized by forming an image by applying a recording medium by an ink jet recording head. An ink cartridge comprising the ink according to any one of claims 1 to 20 . An ink jet recording apparatus characterized by an ink-jet ink according is mounted to any one of claims 1 to 20.

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