JP5782758B2 - Ink composition - Google Patents

Description

Background of the Invention

The present invention relates to an ink composition capable of obtaining a high-quality recorded matter even on various recording media, particularly non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper.

BACKGROUND ART An ink jet recording method is a printing method in which printing is performed by causing ink droplets to fly and adhere to a recording medium such as paper. Due to recent advances in inkjet recording technology, inkjet recording methods have been used in the field of high-definition printing that has been realized by silver salt photography and offset printing. Along with that, high gloss recording media comparable to photographic paper and art paper used in the field of silver salt photography and offset printing, so-called special paper, is used for inkjet recording, and glossiness equivalent to silver salt photography. Ink for ink jet recording that can realize an image having the above has been developed. Ink-jet recording inks have been developed that can achieve image quality comparable to that of silver halide photographs even when plain paper is used.

  By the way, with recent spread of image forming technology from digital data, desktop publishing (DTP) is becoming widespread, especially in the printing field. Even when printing is performed by DTP, a color proofing proof is produced in advance in order to confirm glossiness and color feeling with an actual printed matter. An inkjet recording method is applied to the output of this proof, and DTP requires a high color reproducibility of printed matter and a high color stability. Dedicated paper for inkjet recording is used.

  Proof paper, which is a dedicated paper for ink jet recording, is produced so that the gloss and color feel are the same as the output actually printed on the main printing paper. As described above, the material of the special paper is appropriately adjusted according to the type of the printing paper, but producing the special paper corresponding to all of the various printing papers causes an increase in manufacturing cost. Therefore, in color proofing applications, there is a demand from a technical viewpoint that it is desired to perform ink jet recording on printing paper rather than dedicated paper. In addition, there is a demand from an economical viewpoint that if the final calibration sample can be obtained by performing ink jet recording on a directly printed main paper without using dedicated paper, the cost for calibration can be greatly reduced. Synthetic paper, which is widely used in the printing field and is formed into a film by mixing an inorganic filler or the like with polyethylene resin, polypropylene resin, or polyester resin, has recently attracted attention as an environment-friendly material that is excellent in recyclability. There is a demand from an environmental point of view to record on such synthetic paper.

  The main printing paper is a coated paper having a coating layer for receiving oil-based ink on its surface, but has a feature of poor water absorption. For this reason, when water-based pigment ink generally used for ink jet recording is used, the penetrability of the ink into the recording medium (printing paper) is low, and bleeding or aggregation spots may occur in the image.

  In response to the above problem, for example, in Japanese Patent Application Laid-Open No. 2005-194500 (Patent Document 1), a polysiloxane compound is used as a surfactant, and alkanediol such as 1,2-hexanediol is added as a dissolution aid. Thus, a pigment-based ink is disclosed that has improved bleeding and excellent gloss for special paper. Japanese Patent Application Laid-Open No. 2003-213179 (Patent Document 2), Japanese Patent Application Laid-Open No. 2003-253167 (Patent Document 3), or Japanese Patent Application Laid-Open No. 2006-249429 (Patent Document 4) includes glycerin and 1,3- It has been proposed that by adding a diol such as butanediol or a triol alcohol solvent such as pentanetriol into the ink, the penetrability of the ink into the recording medium can be controlled and a high-quality image can be obtained. However, it can be said that there is still a demand for an ink composition capable of obtaining a higher quality image.

  On the other hand, JP-A-2005-226073 (Patent Document 5) discloses a 1,2-alkyldiol and a hydantoin derivative which are stable at a high injection frequency and show a short drying time when attached to a printing medium. An ink composition containing the ink composition is disclosed, but the ink composition is completely different from the ink composition of the present invention.

JP 2005-194500 A JP 2003-213179 A JP 2003-253167 A JP 2006-249429 A Japanese Patent Laying-Open No. 2005-226073

  Inventors of the present invention now include various recording media, especially synthetic paper and printing, by including an ink composition containing a slightly water-soluble alkanediol having 7 to 10 carbon atoms, cyclodextrins, and hydantoin or a derivative thereof. High-quality images with reduced bleeding and beading can be achieved even on non-water-absorbing or low-water-absorbing recording media such as this paper, and ink storage stability, clogging recovery, and ink re-dissolvability can be achieved. It was also found to be excellent.

  Therefore, the object of the present invention is to realize high-quality images in which bleeding and beading are suppressed even in various recording media, particularly non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper. An object of the present invention is to provide an ink composition that is excellent in storage stability, clogging recovery property, and ink re-dissolvability.

  The ink composition according to the present invention is an ink composition comprising a slightly water-soluble alkanediol having 7 to 10 carbon atoms, cyclodextrins, and hydantoin or a derivative thereof.

  According to the ink composition of the present invention, it is possible to realize a high-quality image in which bleeding and beading are suppressed even in various recording media, particularly non-water-absorbing or low-water-absorbing recording media such as synthetic paper and printing paper. It is possible to provide an ink composition having excellent ink storage stability, clogging recovery ability, and ink re-dissolvability.

Detailed description of the invention

<Definition>
In the present specification, the hydrocarbon group portion of the alkanediol may be either a straight chain or a branched chain.

  In the present specification, “poorly water-soluble” means that the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is less than 1.0 g. In this specification, “miscibility” means that when the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is 10.0 g, it is uniformly dispersed or dissolved without aggregation or phase separation. Means the nature of

In the present specification, the “non-water-absorbing or low water-absorbing recording medium” refers to a recording medium that does not have a water-based ink receiving layer or has a poor water-based ink receiving layer. More quantitatively, a non-water-absorbing or low water-absorbing recording medium is a recording medium whose recording surface has a water absorption amount of 10 mL / m ² or less from the start of contact to 30 msec 1/2 in the Bristow method. Indicates. This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPAN TAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method".

<Ink composition>
The ink composition according to the present invention comprises a sparingly water-soluble alkanediol having 7 to 10 carbon atoms, cyclodextrins, and hydantoin or a derivative thereof. In various recording media, particularly non-water-absorbing or low-water-absorbing recording media, an ink composition containing a slightly water-soluble alkanediol having 7 to 10 carbon atoms, cyclodextrins, and hydantoin or a derivative thereof is used. As a result, a high-definition and high-quality image can be realized.

  In the present specification, beading means a single color when printed in a single color (for example, a single color on a 6 inch square (meaning that the printed color is single as a result, and an ink composition that realizes the color) The number may be plural)), and it means that the density of the local color is the same, and does not mean that the portion of the surface of the recording medium not covered with ink remains. . Color material bleeding is a phenomenon in which mixed colors are generated in the vicinity of a boundary line when each single color is printed as an adjacent surface (for example, when each single color is printed as an adjacent surface in 3 inches square). means. In addition, solvent bleeding refers to the movement of coloring material due to solvent bleed in the vicinity of the boundary line when each single color is printed as an adjacent surface (for example, when each single color is printed as an adjacent surface in 3 inches square). Means a phenomenon in which the coating state changes and density spots of similar colors occur.

In the present invention, in the above recording medium, when a printing paper having a basis weight of 73.3 to 209.2 g / m ² is used, the basis weight is particularly 73.3 to 104.7 g / m. ^{Even in} the case of using ² thin printing paper, it is possible to suppress the occurrence of so-called curling, in which the printing surface is warped inward.

  As described above, high-quality images in which bleeding and beading are suppressed can be realized by containing a sparingly water-soluble alkanediol having 7 to 10 carbon atoms, cyclodextrins, and hydantoin or a derivative thereof. The reason is not clear, but it is thought as follows.

  Ink beading that occurs when recording on a recording medium is caused by, for example, ink droplets adhering to the recording medium flowing when ink having a surface tension higher than 24 mN / m is used. Conceivable. That is, it is considered that the contact angle of the ink droplet with respect to the recording medium is increased and the ink droplet is repelled. Therefore, it is necessary to reduce the surface tension of the ink in order to suppress beading. However, when recording on a non-water-absorbing or low-water-absorbing recording medium, it is difficult to absorb water contained in the ink. For example, even an ink having a surface tension of 20 to 24 mN / m is used. Drops may flow.

  In addition, the surface tension in this specification means the value calculated | required using the Wilhelmy method. The surface tension by the Wilhelmy method can be measured by, for example, a fully automatic surface tension meter CBVP-Z (manufactured by Kyowa Interface Science Co., Ltd.).

  Therefore, in order to suppress ink beading in a non-water-absorbing or low-water-absorbing recording medium, it is preferable not only to reduce the surface tension of the ink but also to suppress the fluidity after adhering to the recording medium. it is conceivable that.

  It is known that when ink adheres to a recording medium, the ink penetrates into the recording medium after the ink has wetted and spread on the recording medium. Then, the bleeding of ink that occurs when recording on a recording medium is caused by the fact that ink droplets attached to the recording medium flow when using ink having a surface tension higher than 24 mN / m, for example. it is conceivable that. That is, it is considered that the solvent contained in the ink does not immediately penetrate into the recording medium because the wettability of the ink with respect to the recording medium is low. Therefore, it is necessary to reduce the surface tension of the ink in order to suppress bleeding. However, when recording on a non-water-absorbing or low-water-absorbing recording medium, it is difficult for water contained in the ink to permeate. For example, even an ink having a surface tension of 20 to 24 mN / m may be used. Drops may flow.

  Therefore, in order to suppress the bleeding of ink in a non-water-absorbing or low-water-absorbing recording medium, not only the surface tension of the ink is reduced but also the fluidity of the ink after adhering to the recording medium is suppressed. Is considered preferable.

  In the ink composition according to the present invention, it is considered that an ink having a low surface tension and a suppressed fluidity of ink droplets after adhering to a recording medium could be realized. As a result, bleeding and beading were achieved. Is considered to be effectively suppressed.

<Slightly water-soluble alkanediol>
The ink composition of the present invention contains a poorly water-soluble alkanediol having 7 to 10 carbon atoms (hereinafter, the slightly water-soluble alkanediol having 7 to 10 carbon atoms is simply referred to as “slightly water-soluble alkanediol”). In some cases).

  According to a preferred embodiment of the present invention, the slightly water-soluble alkanediol having 7 to 10 carbon atoms is a one-terminal alkanediol. According to a preferred embodiment of the present invention, the sparingly water-soluble alkanediol having 7 to 10 carbon atoms is sparingly water-soluble 1,2-alkanediol and can more effectively suppress beading. Examples of the slightly water-soluble 1,2-alkanediol include 1,2-heptanediol, 1,2-octanediol, 5-methyl-1,2-hexanediol, and 4-methyl-1,2-hexanediol. Or 4,4-dimethyl-1,2-pentanediol. Among these, 1,2-octanediol is more preferable.

  According to a preferred embodiment of the present invention, the content of the poorly water-soluble alkanediol having 7 to 10 carbon atoms is as long as high quality images can be realized as long as ink bleeding and beading ink can be efficiently suppressed. Although it may determine suitably, 1.0-4.0 mass% is preferable with respect to the whole composition, More preferably, it is 1.5-3.0 mass%. The amount of the sparingly water-soluble alkanediol having 7 to 10 carbon atoms is within the above range, and particularly within the lower limit, thereby suppressing ink bleeding and beading and realizing a high-quality image. Can do. In addition, since the amount of the slightly water-soluble alkanediol having 7 to 10 carbon atoms is in the above range, the initial viscosity of the ink does not become too high because the upper limit is not exceeded, and in a normal ink storage state, Separation of the oil layer can be effectively prevented, which is preferable from the viewpoint of ink storage stability.

According to a preferred aspect of the present invention, the poorly water-soluble alkanediol is 1,2-octanediol, and the poorly water-soluble alkanediol is used with respect to the ink composition.
An ink composition containing 1.5 to 3.0% by mass. By preventing the content of the hardly water-soluble alkanediol from falling below the lower limit, ink bleeding and beading ink can be suppressed, and by not exceeding the upper limit, the viscosity of the ink can be kept low. Can do.

<Cyclodextrins>
The ink composition according to the present invention comprises cyclodextrins. The cyclodextrins of the present invention are cyclic oligosaccharides, and preferably a kind of compound having an inclusion ability. Cyclodextrins have a basic skeleton formed by binding of glucose molecules with α-1,4 glucoside bonds. Depending on the number of glucose molecules, α-cyclodextrin (6), β-cyclodextrin (7 ), Γ-cyclodextrin (8), and δ-cyclodextrin (9) (in parentheses indicate the number of glucose molecules, respectively).

  Cyclodextrins generally have a specific structure in which the outside of the cyclic structure is hydrophilic and the inside of the cyclic structure is hydrophobic (lipophilic). Due to the specific structure described above, cyclodextrins are often able to entrap and complex so as to enclose lipophilic molecules smaller than the inner diameter of the cyclic structure. Even if the molecule is larger than the inner diameter of the cyclic structure, if there is a lipophilic part smaller than the inner diameter of the cyclic structure, the part is often incorporated into the cyclodextrins and complexed. The internal diameter of cyclodextrins is, for example, 4.7 to 5.3 mm for α-cyclodextrin, 6.0 to 6.5 mm for β-cyclodextrin, and 7.5 to 8.3 mm for γ-cyclodextrin. is there.

  Although it does not specifically limit as cyclodextrins used by this invention, For example, 1 type, or 2 or more types selected from the group which consists of (alpha) -cyclodextrin, (beta) -cyclodextrin, (gamma) -cyclodextrin, and (delta) -cyclodextrin Can be used and preferably has one or more substituents. As an example of the substituent which cyclodextrins have, an acyl group, a hydroxylalkyl group, an alkyl group, a glucosyl group, an amino group, and a carboxymethyl group are mentioned. Further, it may be a cyclodextrin polymer crosslinked with a crosslinking agent such as epichlorohydrin or polyvalent glycidyl ether, a branched cyclodextrin having a branched side chain such as glucose or malnose, or a highly branched cyclic dextrin.

  One or more of the above cyclodextrins can be used. As a preferable substituent, an alkyl group is preferable, and a methyl group is more preferable. In particular, methyl-β-cyclodextrin is more preferable from the viewpoint of high solubility in water (30% by mass or more at 25 ° C.) and high miscibility with a slightly water-soluble alkanediol.

Although it does not specifically limit as a manufacturing method of cyclodextrins, It selects suitably from viewpoints, such as the ease of manufacture, cost, and the structure of the cyclodextrin obtained. As a method for producing cyclodextrins having no substituent, for example, a method in which an enzyme derived from Bacillus macerans is allowed to act on starch can be used. As a method for producing a cyclodextrin having a substituent, for example, a production method in which cyclodextrin in which a part of the hydroxyl group of cyclodextrin is deprotonated or a derivative thereof is reacted as a reaction intermediate can be used. It is. As the cyclodextrins, commercially available products may be used, and examples include CAVASOL and CAVAWAX (both manufactured by Wacker).

  According to a preferred embodiment of the present invention, the cyclodextrins may be appropriately determined as long as the above effects are exhibited, but are contained in an amount of 4.5 to 18.0% by mass with respect to the entire ink composition. Is more preferable, and 4.5 to 9.0% by mass is more preferable. By making the quantity of cyclodextrins into the said range, it is preferable from a viewpoint of the fixability to a film especially that it is not less than a minimum. In addition, by setting the amount of cyclodextrins within the above range, the viscosity of the ink can be kept low by not exceeding the upper limit, and the precipitation of cyclodextrins in a low temperature environment can be suppressed. Is preferable. More preferably, the cyclodextrin is a methylated β-cyclodextrin, and the cyclodextrin contains 4.5 to 9.0% by mass with respect to the ink composition.

  Moreover, according to the preferable aspect of this invention, although content ratio of the said slightly water-soluble alkanediol and the said cyclodextrins is not specifically limited, It is preferable that it is 1: 3 to 1: 6. By setting it as the above range, the stickiness of the ink is reduced, the storage stability of the ink is improved, and the re-dissolvability of the ink is improved.

<Hydantoin and hydantoin derivatives>
The ink composition according to the present invention comprises hydantoin or a derivative thereof. The hydantoin derivative used in the ink composition of the present invention is preferably a solid even when left for 24 hours in an environment of 20 ° C./60% RH, and preferably has a melting point higher than the boiling point of water. Further, the hydantoin derivative preferably has a solubility in 100 g of water at 20 ° C. of 10.0% by mass or more and less than 30% by mass.

  Hydantoin or a derivative thereof is not particularly limited as long as the effects of the present invention are exhibited. For example, hydantoin, allantoin, 5-hydantoin acetic acid, 1-methylhydantoin, 1-hydroxymethylhydantoin, 1-ethylhydantoin, 1-propylhydantoin 1-isopropylhydantoin, 1-butylhydantoin, 3-methylhydantoin, 3-ethylhydantoin, 3-propylhydantoin, 3-butylhydantoin, 5-methylhydantoin, 5-ethylhydantoin, 5-propylhydantoin, 5-butylhydantoin 1,3-dimethylhydantoin, 1,5-dimethylhydantoin, 3,5-dimethylhydantoin, 1,3-diethylhydantoin, 1,5-diethylhydantoin, 3,5-diethylhydantoin Tontoin, 5,5-dimethylhydantoin, 1-hydroxymethyl-5,5-dimethylhydantoin, 1,3-bis (hydroxymethyl) -5,5-dimethylhydantoin, 1,3-bis (2-hydroxyethyl)- 5,5-dimethylhydantoin, 1,3,5-trimethylhydantoin, 1,3,5-triethylhydantoin, 1-allylhydantoin, 1-phenylhydantoin, 3-phenylhydantoin, 5-phenylhydantoin, 1- (4- Methylphenyl) hydantoin, 3- (4-methylphenyl) hydantoin, 1- (1-naphthyl) hydantoin, 1- (2-naphthyl) hydantoin, 3- (1-naphthyl) hydantoin, 3- (2-naphthyl) hydantoin 1-benzylhydantoin, 3-benzylhydantoin Benzylhydantoin of 5-benzyl hydantoin and the like. In particular, 5,5-dimethylhydantoin and 1-hydroxymethyl-5,5-dimethylhydantoin are preferable from the viewpoints of water solubility and melting point.

  In addition, the ink composition containing hydantoin or a derivative thereof improves both clogging recovery under a capping environment and clogging recovery under a high temperature and low humidity environment. The reason is not clear, but hydantoin or its derivative has high crystallinity and excellent solubility of the resin contained in the ink, so that it is locally solidified without being taken in during the dry film formation of the resin. I think it can be done. Even after the resin contained in the ink is dry-formed, when the ink adheres again to this dried product, the hydantoin or its derivative that has been dried and solidified locally re-dissolves and becomes clogged. It is thought that it has been solved.

  The hydantoin or a derivative thereof having a high melting point and poor water solubility is more preferable because it solidifies prior to evaporation of water and resin dry film formation (MFT), and is easily dried and solidified locally. In particular, 5,5-dimethylhydantoin and 1-hydroxymethyl-5,5-dimethylhydantoin are preferable from the viewpoint of clogging recovery and re-dissolvability.

  According to a preferred aspect of the present invention, the hydantoin or a derivative thereof may be appropriately determined as long as the above effect is obtained, but is contained in an amount of 4.5 to 9.0% by mass with respect to the entire ink composition. Preferably it is. By setting the amount of the hydantoins having a high melting point within the above range, the clogging recovery property under the environment where the head is capped and the clogging recovery property under a high temperature and low humidity environment can be obtained, particularly without lowering the lower limit. It is preferable because both are improved. In addition, it is preferable to set the amount of the hydantoin or a derivative thereof within the above range, particularly because the lowering of gloss can be suppressed by not exceeding the upper limit.

  According to a further preferred aspect of the present invention, the content ratio of the poorly water-soluble alkanediol and the hydantoin or a derivative thereof is not particularly limited, but is preferably 1: 3 to 1: 6. By setting it as this content ratio, beading and bleeding can be ensured while improving open system clogging recovery and closed system clogging recovery.

<Solid wetting agent>
The ink composition according to the present invention is preferably a solid wetting agent (hereinafter simply referred to as “ It may also be referred to as a “solid wetting agent”. As what is contained in this solid wetting agent, the 1st saccharide and the 2nd saccharide are mentioned. Moreover, it is preferable that a solid wetting agent contains 1 or more types chosen from the group which consists of a 1st saccharide | sugar and a 2nd saccharide | sugar. The first carbohydrate and the second carbohydrate are described in detail below.

First carbohydrate The first carbohydrate that can be suitably used in the present invention is a sugar, and it is preferable that the first carbohydrate is a solid even if it is allowed to stand for 24 hours in an environment of 20 ° C./60% RH. Moreover, it is preferable that the moisture absorption rate from 20 degreeC / 60% RH to 20 degreeC / 80% RH is 0 mass% or more and less than 10 mass%. The first carbohydrate preferably has a solubility in 100 g of water at 20 ° C. of 30% by mass or more.

In this specification, for example, “RH moisture absorption rate from A ° C./X% RH to B ° C./Y%” is a value represented by the following formula.
(Hygroscopic rate (mass%)) = 100 × (MB ₋ M− _A−X ) / M _A−X
M _A-X is the mass after being allowed to stand for 24 hours in an environment of A ° C. and relative humidity X%.
M _B-Y is the mass after standing for 24 hours in an environment of B ° C. and relative humidity Y%.

  The first saccharide is not particularly limited as long as the effect of the present invention is exhibited, but one or more selected from the group consisting of trehalose, isotrehalose, neotrehalose, and mannitol are preferable. Further, it may be a trisaccharide or more containing a carbohydrate selected from the group consisting of trehalose, isotrehalose, and neotrehalose, and examples thereof include maltosyl trehalose consisting of trehalose and maltose. Among these, trehalose is more preferable as the first carbohydrate.

  Trehalose is a non-reducing disaccharide in which the first positions of glucose form a glucoside bond. Since it is a non-reducing sugar, brown color change due to the Maillard reaction does not occur, which is preferable from the viewpoint of storage stability of the ink. In addition, it has high water solubility and water retention, and extremely low hygroscopicity. Specifically, high-purity trehalose anhydride has very high solubility in water (69 g / 100 g (20 ° C.)), but does not exhibit hygroscopicity at a humidity of 95% or less. Therefore, when trehalose comes into contact with water, it absorbs water and becomes a gel, but in a normal environment (20 ° C., humidity is about 45%), it does not exhibit hygroscopicity and can exist stably.

  Isotrehalose and neotrehalose are non-reducing disaccharides having a glucoside bond. Since it is a non-reducing sugar, brown color change due to the Maillard reaction does not occur, which is preferable from the viewpoint of storage stability of the ink.

  Examples of the first commercially available saccharide include Treharose fine powder (manufactured by Hayashibara Shoji Co., Ltd.), a commercial product of trehalose, and D-mannitol (manufactured by Kao Chemical Co., Ltd.) which is a commercial product of mannitol. .

  Furthermore, the first carbohydrate is produced from starch sugar by a conventional method such as a fermentation method, a hydrolysis method, a sugar transfer reaction method, a sugar condensation reaction method, an epimerase (isomerization) method, a polymerization method, or a chemical crosslinking method. Is possible. Solidification can also be produced by a conventional method. In other words, a method of spray-drying a mass kit, which is a solution containing carbohydrates, a method of crystallizing and solidifying into a block shape by naturally drying the moisture of the mass kit, and recrystallization using a seed crystal from a molten mass kit It is possible to use the method of doing. In addition, the mass kit to be used may be a saccharide capable of obtaining the first saccharide having the above-described low hygroscopicity, and may contain two or more types of saccharides.

  When such an ink composition containing the first carbohydrate is used, it is possible to suppress beading caused by flow spots generated particularly when high-speed printing is performed. The reason is not clear, but it can be considered as follows, for example. The first saccharide contained in the ink composition deposited on the recording medium has high solubility in water and high water retention, so that after the deposition, the first sugar is gelled (or solidified) by incorporating the water contained in the ink composition. )can do. Then, it is considered that the fluidity (flow spots) of the ink droplets that have gelled (or solidified) is suppressed. Moreover, it is considered that the osmotic pressure was increased and the permeation rate was improved by adding a large amount of water-soluble sugar in accordance with the Vanthoff's law. Regardless of the above-described inference, high-speed printing is possible by suppressing beading, and the color reproduction region of the printed matter is improved because the duty limit value of the ink deposited on the recording medium is increased.

  Further, a recorded matter obtained using such an ink composition containing the first carbohydrate can improve the condensation resistance in a humid environment at 20 ° C. and a humidity of about 60%.

  Further, such an ink composition containing the first carbohydrate can improve the clogging recovery property particularly in an environment (sealed system) in which the head is capped. The reason is not clear, but since the hygroscopic property is low, the ink composition staying in the cap does not take away moisture from the ink composition filled in the head, so the state is sealed with the cap. It is thought that it is excellent in clogging recovery performance.

  Furthermore, since the ink composition containing such a first carbohydrate prevents the growth of ice crystals, the low-temperature storage stability of the ink is improved.

According to a preferred aspect of the present invention, the first carbohydrate may be appropriately determined as long as the first effect is exhibited, but is contained in an amount of 3.0 to 9.0% by mass with respect to the entire ink composition. It is preferable. By setting the amount of the crystalline saccharide within the above range, it is preferable that the amount is not lower than the lower limit, in order to improve the clogging recovery property in the above-mentioned environment, and also from the viewpoint of gloss. In addition, by setting the amount of the first carbohydrate within the above range, the initial viscosity of the ink does not become excessively high and the freezing temperature is lowered because the upper limit is not exceeded. It is preferable from the viewpoint. Further, even when thin printing paper or PPC paper (plain paper) having a basis weight of 73.3 g / m ² or less is used, the occurrence of so-called curling, in which the printing surface is warped inward, can be remarkably suppressed. The reason is not clear, but it is thought as follows. Cellulose is a long chain saccharide in which monosaccharides are linked (polymerized). Curl occurs when hydrogen bonds between celluloses are cleaved by water molecules, and when water evaporates and drys, hydrogen bonds between celluloses are regenerated at a site different from the hydrogen bond sites between cleaved celluloses. . Therefore, in order to suppress curling, it is only necessary to inhibit the regeneration of hydrogen bonds between celluloses as quickly as possible after water has evaporated and dried. A substance effective as an inhibitor is a crystalline saccharide having a molecular structure similar to that of cellulose, and more preferably trehalose, isotrehalose and neotrehalose which are excellent in drying and recrystallization properties.

Second carbohydrate The second carbohydrate that can be suitably used in the present invention is a sugar, and it is preferable that the second carbohydrate is a solid even when it is allowed to stand for 24 hours in an environment of 20 ° C./60% RH. Moreover, it is preferable that the moisture absorption rate from 20 degreeC / 60% RH to 20 degreeC / 80% RH is 10 mass% or more and 30 mass% or less. The second carbohydrate preferably has a solubility in 100 g of water at 20 ° C. of 30% by mass or more.

  The second saccharide is not particularly limited as long as the effects of the present invention are exhibited, but in the case of a linear malto-oligosaccharide having only α-1,4 bonds, maltose, maltotriose, maltotetraose, maltopentaose, maltohexa There are ose, maltohebutaose, maltooctaose, malt nonaose, malto dekaose. Examples of branched maltooligosaccharides having α-1,6 bonds in the molecule obtained from the branched portion of amylopectin include isomaltose, panose (glucosyl-maltose), glucosyl-maltotriose, and the like. There are also maltitol, sorbitol, xylitol, erythritol, and sucrose. Among these, one or more selected from the group consisting of maltotriose, maltotetraose, and maltopentaose are preferable because of their excellent hygroscopicity, and maltotriose is particularly preferable. These reducing sugars may also be used.

  Commercially available products of the second carbohydrate include, for example, oligotoose (manufactured by Sanwa Starch Kogyo Co., Ltd.), a commercial product of maltotriose, sun malt (manufactured by Hayashibara Shoji Co., Ltd.), maltitol, Examples of commercially available products include Mabit (manufactured by Hayashibara Shoji Co., Ltd.) and Crystal Mabit (manufactured by Hayashibara Shoji Co., Ltd.), and commercial products of crystalline erythritol include Nikken Chemical Co., Ltd., Mitsubishi Chemical Foods Co., Ltd. Company, Selestar, and Cargill products are available.

  The second saccharide can be produced by a conventional method in the same manner as the first saccharide described above.

  Further, such an ink composition containing the second carbohydrate can improve clogging recovery in a low humidity environment (open system). The reason is not clear, but it is considered to be excellent in clogging recovery ability by taking in moisture in the atmosphere even in a low humidity environment because of its high hygroscopicity. Therefore, for example, stable recording can be performed over a long period of time without performing capping of the head.

  According to a preferred aspect of the present invention, the second carbohydrate may be appropriately determined as long as the above-described effect is exhibited, but is contained in an amount of 3.0 to 9.0% by mass with respect to the entire ink composition. It is preferable. By making the amount of the second saccharide having high hygroscopicity within the above-mentioned range, it is preferable not to be lower than the lower limit, in order to improve the clogging recovery property in a high-temperature and high-humidity open environment. From the viewpoint of this, it is preferable. In addition, by setting the amount of the second saccharide within the above range, the Tg of the ink film is not excessively high and the flexibility can be imparted by not exceeding the upper limit. It is preferable from the viewpoint. Furthermore, it is preferable because the first carbohydrate having excellent drying properties and recrystallization properties can be prevented from being deposited in the waste liquid portion of the printer.

  According to a preferred aspect of the present invention, the solid wetting agent is preferably contained in an amount of 4.5 to 13.5% by mass with respect to the ink composition.

  According to another preferable aspect of the present invention, the total content of the first and second carbohydrates is preferably 6.0 to 18.0% by mass with respect to the total amount of the ink composition. . The above range is preferable because improvement in clogging recovery can be obtained. Moreover, the content ratio of the first saccharide and the second saccharide is not particularly limited, but is preferably 1: 5 to 5: 1. The above range is preferable because it is possible to improve the clogging recovery property of the closed system and to ensure the fluidity of the ink waste liquid.

  According to a preferred aspect of the present invention, the solid wetting agent comprises one or two selected from the group consisting of a first carbohydrate and a second carbohydrate, and the first carbohydrate. Is one or two selected from the group consisting of trehalose, isotrehalose, neotrehalose, and mannitol, and the second carbohydrate is selected from the group consisting of maltotriose, maltotetraose, and maltopentaose. It is preferable that it is 1 type, or 2 or more types selected. This is a case where the ink composition contains both the first saccharide having low hygroscopicity and the second saccharide having high hygroscopicity as the solid wetting agent, thereby including the second saccharide having high hygroscopicity. Even in the case where the clogging recoverability in the closed system is excellent and the first carbohydrate having a low hygroscopicity is contained, the clogging recovery performance in the open system is excellent. That is, by including both the first saccharide and the second saccharide in the ink composition of the present invention, both effects of the clogging recovery of the open system and the clogging recovery of the closed system can be obtained. Both effects are achieved without harm, and this effect has been found for the first time.

  According to a further preferred embodiment of the present invention, the content ratio of the poorly water-soluble alkanediol and the solid wetting agent is not particularly limited, but is preferably 1: 3 to 1: 9. By setting it as this content ratio, beading and bleeding can be improved, ensuring open system clogging recovery property and closed system clogging recovery property.

<Water-soluble alkanediol>
According to a preferred embodiment of the present invention, the ink composition according to the present invention comprises a water-soluble alkanediol in addition to a slightly water-soluble alkanediol having 7 to 10 carbon atoms, cyclodextrins, and hydantoin or a derivative thereof. Can comprise. This is advantageous in that the occurrence of bleeding of a substance other than the solid content contained in the ink composition, that is, an aqueous solution containing a solvent can be further suppressed.

  According to a preferred embodiment of the present invention, the water-soluble alkanediol is a biterminal or single-terminal alkanediol, and more preferably has a branched chain. The water-soluble alkanediol of the present invention is preferably an alkanediol having 3 or more carbon atoms, more preferably an alkanediol having 3 to 6 carbon atoms. The water-soluble alkanediol contained in the ink composition according to the present invention is preferably 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, 1,5-pentanediol, 1, 2-hexanediol and 1,6-hexanediol are preferable, and water-soluble hexanediol such as 1,2-hexanediol and 1,6-hexanediol is more preferable. Hexanediol is preferred. Further, 1,6-hexanediol may be used from the viewpoint of excellent discharge stability at a high frequency.

<Colorant>
The ink composition according to the present invention may contain a colorant. As the colorant, both dyes and pigments can be used, but pigments can be preferably used from the viewpoint of light resistance and water resistance. Moreover, it is preferable that a coloring agent contains the following dispersing agent which can disperse | distribute the said pigment and the pigment in an ink.

  As the pigment, inorganic pigments and organic pigments can be used, and each can be used alone or in combination. As the inorganic pigment, for example, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments), dye chelates (for example, basic dye type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used.

  Specific examples of the pigment are appropriately given according to the type (color) of the ink composition to be obtained. For example, as a pigment for a yellow ink composition, C.I. I. Pigment Yellow 1, 2, 3, 12, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 139, 147, 150, 151, 154, 155, 180, 185 and the like, and one or more of these are used. Of these, C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Yellow 74, 110, 128, and 129. Examples of the pigment for the magenta ink composition include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209; I. Pigment violet 19 or the like, and one or more of these may be used. Of these, C.I. I. Pigment red 122, 202, 209, and C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Violet 19, and these may be solid solutions. Examples of the pigment for the cyan ink composition include C.I. I. Pigment Blue 1, 2, 3, 15: 2, 15: 3, 15: 4, 15:34, 16, 22, 60; I. Vat Blue 4, 60 and the like are listed, and one or more of these are used. Of these, C.I. I. Pigment Blue 15: 3 and / or 15: 4 are preferably used, especially C.I. I. Pigment Blue 15: 3 is preferably used.

  Examples of the pigment for the black ink composition include lamp black (CI pigment black 6), acetylene black, furnace black (CI pigment black 7), and channel black (CI pigment black). 7), carbons such as carbon black (CI Pigment Black 7), inorganic pigments such as iron oxide pigments, and organic pigments such as aniline black (CI Pigment Black 1). In carbon black, carbon black is preferably used. Specifically, as carbon black, # 2650, # 2600, # 2300, # 2200, # 1000, # 980, # 970, # 966, # 960, # 950, # 900, # 850, MCF-88, # 55, # 52, # 47, # 45, # 45L, # 44, # 33, # 32, # 30 (above, manufactured by Mitsubishi Chemical Corporation), SpecialBlaek4A, 550, Printex95, 90, 85, 80, 75 , 45, 40 (above, manufactured by Degussa), Regal660, RmogulL, monarch1400, 1300, 1100, 800, 900 (above, manufactured by Cabot), Raven7000, 5750, 5250, 3500, 3500, 2500 ULTRA, 2000, 1500, 1255 , 1200, 1190 ULTRA, 1170, 1100 ULTRA, Raven5000UIII (above, Colombian) and the like.

  The concentration of the pigment is not particularly limited because it may be adjusted to an appropriate pigment concentration (content) when the ink composition is prepared. For example, by setting the pigment concentration to 1 to 4% by mass, it is possible to obtain an image in which the granularity is suppressed. On the other hand, by setting the pigment concentration to 4 to 12% by mass, it is possible to obtain an image excellent in color developability.

  In the present invention, it is possible to obtain an image in which bleeding is suppressed by setting the solid content concentration of the pigment to 6 to 12% by mass. When ink droplets adhere on the recording medium, the ink wets and spreads on the surface of the recording medium. However, when the pigment solid concentration is set to 6% by mass or more, the fluidity of the ink after the wet spreading stops is lost early. Therefore, even when printing is performed on a recording medium such as printing paper at a low resolution, bleeding can be further suppressed. That is, by using a combination of the poorly water-soluble alkanediol and the solid wetting agent, the ink spreads even on a recording medium with low ink absorbability, and the initial viscosity is remarkably increased due to the effect of the solid wetting agent. In addition to increasing the solid content without increasing the speed and increasing the drying property, the solid content concentration of the ink is increased with a pigment, thereby reducing the fluidity of the ink on the recording medium and suppressing bleeding. It is considered possible. In particular, beading in the case of a recording time interval between adjacent or overlapping within approximately 2 seconds after the preceding ink droplet has landed and after the subsequent ink droplet is less than 2 seconds. And the bleeding suppression effect is remarkable. The recording time interval refers to two continuous inks when a plurality of different inks are applied to a recording medium and the inks are adjacent or overlapped, and the recording time is divided up to the number of recording pixels. The time interval between recordings.

  The pigment is a pigment that has been kneaded with a dispersant, which will be described later, to achieve both the glossiness of the image, the prevention of bronzing, and the storage stability of the ink composition, and to form a color image that is further excellent in glossiness. From the viewpoint of being able to.

<Dispersant>
In the ink composition according to the present invention, a styrene-acrylic acid copolymer resin (styrene acrylic acid copolymer resin), an oxyethyl acrylate resin (oxyethyl resin), and a urethane resin are used as a dispersant for dispersing the colorant. And at least one resin selected from the group consisting of fluorene resins, more preferably at least one resin selected from the group consisting of oxyethyl acrylate resins and fluorene resins. It becomes. These copolymer resins are adsorbed on the pigment to improve dispersibility.

  Specific examples of the hydrophobic monomer in the copolymer resin include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso- Octyl acrylate, iso-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, Sil acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate, 2 -Dimethylaminoethyl methacrylate, 2-diethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, nonyl phenyl acrylate, noni Phenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butane Diol diacrylate, 1,4-butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetra Ethylene glycol dimethacrylate, polyethylene glycol di Acrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylol Mention may be made of methylolpropane trimethacrylate, glycerol acrylate, glycerol methacrylate, styrene, methylstyrene, vinyltoluene, hydroxyethylated orthophenylphenol acrylate and the like. You may use these individually or in mixture of 2 or more types.

  Specific examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.

  From the viewpoint that the copolymer resin of the hydrophobic monomer and the hydrophilic monomer can form a color image having both glossiness of the color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. , Styrene- (meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin, or styrene-maleic acid copolymer resin, (meth) acrylic acid- (meth) acrylic acid ester copolymer resin Or a styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer resin or a hydroxyethylated orthophenylphenol acrylic acid ester- (meth) acrylic acid copolymer resin.

  The copolymer resin may be a resin (styrene-acrylic acid resin) containing a polymer obtained by reacting styrene with acrylic acid or an ester of acrylic acid. Alternatively, the copolymer resin may be an acrylic acid-based water-soluble resin. Alternatively, salts thereof such as sodium, potassium, ammonium, triethanolamine, triisopropanolamine, triethylamine, and diethanolamine may be used.

  The acid value of the copolymer resin is preferably 50 to 320 from the viewpoint of achieving both color image glossiness, bronzing prevention, and storage stability of the ink composition, and forming a color image having further excellent glossiness. More preferably, it is 100-250.

  The weight-average molecular weight (Mw) of the copolymer resin is preferable from the viewpoint of achieving a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is from 2,000 to 30,000, more preferably from 2,000 to 20,000.

  The glass transition temperature (Tg; measured in accordance with JISK6900) of the copolymer resin is a viewpoint capable of forming a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Is preferably 30 ° C. or higher, and more preferably 50 to 130 ° C.

  The copolymer resin may be adsorbed to the pigment in the pigment dispersion or may be free, and achieves both glossiness of the color image, prevention of bronzing, and storage stability of the ink composition. From the viewpoint of forming a color image with further excellent gloss, the copolymer resin preferably has a maximum particle size of 0.3 μm or less, and an average particle size of 0.2 μm or less (more preferably 0.1 μm or less). ) Is more preferable. The average particle diameter is an average value of the dispersion diameter (cumulative 50% diameter) as the particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

  The content of the copolymer resin is 100 parts by weight of the pigment from the viewpoint of achieving a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. On the other hand, it is preferably 20 to 50 parts by mass, and more preferably 20 to 40 parts by mass.

  In the present invention, an oxyethyl acrylate resin may be used as the copolymer resin. The use is more preferable because it reduces the initial viscosity of the ink, is excellent in storage stability at high temperatures, and is excellent in clogging recovery.

  The oxyethyl acrylate resin is not particularly limited as long as it is a resin having an oxyethyl acrylate skeleton, but is preferably a compound represented by the following formula (I). The compound represented by the following formula (I) is, for example, CAS No. 7-2009-86-0 ortho-hydroxyethylated phenylphenol acrylate, 45-55%, CAS No. CAS No. 79-10-7 acrylic acid 20-30%. Resins containing 20-30% of 79-41-4 methacrylic acid. These may be used alone or in admixture of two or more. The monomer composition ratio is not particularly limited, but preferably CAS No. 7-2009-86-0 ortho-hydroxyethylated phenylphenol acrylate, CAS No. 79-10-7 acrylic acid is 5 to 15% by mass, CAS No. 79-41-4 methacrylic acid is 10-20 mass%.

（Ｒ１および/またはＲ３は水素原子またはメチル基であって、Ｒ２はアルキル基またはアリール基である。ｎは１以上の整数である。）

(R1 and / or R3 is a hydrogen atom or a methyl group, R2 is an alkyl group or an aryl group. N is an integer of 1 or more.)

  The compound represented by the above formula (I) is preferably nonylphenoxy polyethylene glycol acrylate or polypropylene glycol # 700 acrylate.

  From the viewpoint that the content of the oxyethyl acrylate-based resin is compatible with the initial viscosity of the ink composition and the storage stability of the ink composition, suppresses aggregation spots, and can form a color image having excellent filling properties. Preferably it is 10-40 mass parts with respect to 100 mass parts of said pigments, More preferably, it is 15-25 mass parts.

  The total of the resin composition ratio derived from the monomer having a hydroxyl group selected from the group of acrylic acid and methacrylic acid in the oxyethyl acrylate resin is compatible with the initial viscosity of the ink composition and the storage stability of the ink composition, From the viewpoint of clogging recovery, it is preferably 30 to 70%, more preferably 40 to 60%.

  The number average molecular weight (Mn) before crosslinking of the oxyethyl acrylate resin is preferably 4000 to 9000, more preferably from the viewpoint of achieving both the initial viscosity of the ink composition and the storage stability of the ink composition. 5000 to 8000. Mn is measured by, for example, GPC (gel permeation chromatography).

  The oxyethyl acrylate-based resin may be adsorbed to the pigment in the pigment dispersion or may be liberated, achieving both color image gloss, bronzing prevention, and storage stability of the ink composition. In addition, from the viewpoint of being able to form a color image having further excellent gloss, the maximum particle size of the copolymer resin is preferably 0.3 μm or less, and the average particle size is 0.2 μm or less (more preferably 0.2 μm or less). More preferably, it is 1 μm or less. The average particle diameter is an average value of the dispersion diameter (cumulative 50% diameter) as the particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

  The content of the oxyethyl acrylate resin is such that the pigment 100 is capable of forming a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Preferably it is 20-50 mass parts with respect to a mass part, More preferably, it is 20-40 mass parts.

  In the present invention, by using a urethane-based resin as a fixing pigment dispersant, a color image having excellent glossiness while being compatible with glossiness of a color image, prevention of bronzing, and storage stability of an ink composition. An image can be formed. The urethane resin is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound. In the present invention, the urethane resin is a resin having a urethane bond and / or an amide bond and an acidic group. It is preferable.

  Examples of the diisocyanate compound include aromatic aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products thereof. .

  Examples of the diol compound include polyethers such as polyethylene glycol and polypropylene glycol, polyesters such as polyethylene abido and polybutylene abates, and polycarbonates.

  The acid value of the urethane-based resin is preferably 10 to 300 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image having further excellent glossiness. More preferably, it is 20-100. The acid value is the mg amount of KOH required to neutralize 1 g of resin.

  The weight-average molecular weight (Mw) before crosslinking of the urethane resin is compatible from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and at the same time forming a more glossy color image. , Preferably it is 100-200,000, More preferably, it is 1000-50,000. Mw is measured by GPC (gel permeation chromatography), for example.

  The urethane resin has a glass transition temperature (Tg; measured in accordance with JISK6900) from the viewpoint of achieving a color image having excellent glossiness while maintaining the glossiness of the color image, prevention of bronzing, and storage stability of the ink composition. Is preferably −50 to 200 ° C., and more preferably −50 to 100 ° C.

  The urethane resin preferably has a carboxyl group.

  The content of the urethane-based resin is 100 parts by mass of the pigment from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image with further excellent glossiness. On the other hand, it is preferably 20 to 50 parts by mass, and more preferably 20 to 40 parts by mass.

  Further, in the present invention, a fluorene resin can be used as the fixing pigment dispersant. The use is more preferable because it reduces the initial viscosity of the ink, is excellent in storage stability at high temperatures, and is excellent in fixability to printing paper.

The fluorene-based resin is not limited as long as it has a fluorene skeleton, and can be obtained, for example, by copolymerizing the following monomer units.
5-Isocyanate-1- (isocyanatemethyl) -1,3,3-trimethylcyclohexane (CAS No. 4098-71-9)
2,2 ′-[9H-Fluorene-9-ylidenebis (4,1-phenyleneoxy)] bisethanol (CAS No. 117344-32-8)
3-hydroxy-2- (hydroxymethyl) -2-methylpropionic acid (CAS No. 4767-03-7)
N, N-diethyl-ethanamine (CAS No. 121-44-8)

  As long as the fluorene resin is a resin having a fluorene skeleton, the monomer composition ratio is not particularly limited, but preferably 5-isocyanate-1- (isocyanatomethyl) -1,3,3-trimethylcyclohexane (CAS No. 5). 4098-71-9) is 35 to 45% by mass, and 2,2 ′-[9H-fluorene-9-ylidenebis (4,1-phenyleneoxy)] bisethanol (CAS No. 117344-32-8) is 40 to 40%. 60% by mass, 5-15% by mass of 3-hydroxy-2- (hydroxymethyl) -2-methylpropionic acid (CAS No. 4767-03-7), N, N-diethyl-ethanamine (CAS No. 121-) 44-8) is 5 to 15% by mass.

  The number average molecular weight (Mn) before crosslinking of the fluorene-based resin is preferably 2000 to 5000, and more preferably 3000 to 5000, from the viewpoint of achieving both the initial viscosity of the ink composition and the storage stability of the ink composition. 4000. Mn is measured by, for example, GPC (gel permeation chromatography).

  The fluorene-based resin has a case where it is adsorbed to a pigment in a pigment dispersion and a case where it is liberated, and achieves both glossiness of a color image, prevention of bronzing, and storage stability of an ink composition. In addition, from the viewpoint of forming a color image having further excellent gloss, the copolymer resin preferably has a maximum particle size of 0.3 μm or less, and an average particle size of 0.2 μm or less (more preferably 0.1 μm). The following is more preferable. The average particle diameter is an average value of the dispersion diameter (cumulative 50% diameter) as the particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

  The content of the fluorene-based resin is 100 parts by mass of the pigment from the viewpoint that both color image fixability, bronzing prevention, and storage stability of the ink composition can be achieved and a color image having further excellent fixability can be formed. On the other hand, it is preferably 20 to 50 parts by mass, and more preferably 20 to 40 parts by mass.

  The mass ratio (the former / the latter) of the copolymer resin and the fixing pigment dispersant is preferably 1/2 to 2/1. However, the glossiness of the color image, the prevention of bronzing, and the storage stability of the ink composition are improved. From the standpoint of being able to form a color image that is compatible and more excellent in gloss, it is more preferably 1 / 1.5 to 1.5 / 1.

  The mass ratio of the solid content of the pigment to the solid content of the copolymer resin and the fixing pigment dispersant (the former / the latter) is effective for the glossiness of the color image, the prevention of bronzing, and the storage stability of the ink composition. From the viewpoint of being able to form a color image that is compatible with both glossiness and glossiness, it is preferably 100/40 to 100/100.

  A surfactant may be used as the dispersant. Such surfactants include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinate esters, naphthenates, liquid fats. Anionic surfactants such as oil sulfate esters and alkyl allyl sulfonates; Cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts and phosphoniums; polyoxyethylene alkyl ethers and polyoxyethylene alkyls Nonionic surfactants such as esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters and the like can be mentioned. It goes without saying that the surfactant described above also functions as a surfactant by being added to the ink composition.

<Surfactant>
The ink composition according to the present invention may contain a surfactant. Glossy recording media such as photographic paper, where glossiness is more important by using a surfactant, compared to a recording medium coated with a resin for receiving ink on the surface. Can be realized. In particular, even when a recording medium having a coating layer for receiving oil-based ink is provided on the surface receiving layer such as printing paper, bleeding between colors (bleeding) can be prevented. At the same time, it is possible to prevent whitening due to reflected light of light generated with an increase in the amount of ink attached.

  As the surfactant used in the present invention, a polyorganosiloxane-based surfactant can be preferably used, and when forming a recorded image, the wettability to the surface of the recording medium can be improved to increase the ink permeability. it can. When polyorganosiloxane-based surfactants are used, they contain poorly water-soluble alkanediols as described above, so that the solubility of the surfactant in the ink is improved and the generation of insoluble matters can be suppressed. In addition, it is possible to realize an ink composition having more excellent ejection stability.

  The polyorganosiloxane surfactant is not particularly limited, but 20% by mass of glycerin, 10% by mass of 1,2-hexanediol, 0.1% by mass of the polyorganosiloxane surfactant, and water. When an aqueous solution containing 69.9% by mass is used, it is preferable to use an aqueous solution having a 1 Hz dynamic surface tension of 26 mN / m or less. The dynamic surface tension can be measured using, for example, a bubble pressure dynamic surface tension meter BP2 (manufactured by KRUS).

  Commercially available surfactants such as those described above may be used. For example, Olfin PD-501 (manufactured by Nissin Chemical Industry Co., Ltd.), Olphine PD-570 (manufactured by Nissin Chemical Industry Co., Ltd.), BYK. -347 (made by Big Chemie Co., Ltd.), BYK-348 (made by Big Chemie Co., Ltd.), etc. can be used.

（式中、Ｒは水素原子またはメチル基を表し、ａは２〜１３の整数を表し、ｍは２〜７０の整数を表し、ｎは１〜８の整数を表す。）
で表される一種または二種以上の化合物を含んでなるか、または、上記式（II）の化合物において、Ｒは水素原子またはメチル基を表し、ａは２〜１１の整数を表し、ｍは２〜５０の整数を表し、ｎは１〜５の整数である一種または二種以上の化合物を含んでなることが好ましく、または、上記式（II）の化合物において、Ｒが水素原子またはメチル基であり、ａが２〜１３の整数であり、ｍは２〜５０の整数であり、ｎは１〜５の整数である一種または二種以上の化合物を含んでなることがより好ましい。また、上記式（II）の化合物において、Ｒが水素原子またはメチル基であり、ａが２〜１３の整数であり、ｍは２〜５０の整数であり、ｎは１〜８の整数である一種または二種以上の化合物を含んでなることがより好ましい。あるいは、上記式（II）の化合物において、Ｒがメチル基であり、ａが６〜１８の整数であり、ｍが０〜４であり、ｎが１または２である一種または二種以上の化合物を含んでなることが好ましく、または、Ｒがメチル基であり、ａが６〜１８の整数、であり、ｍが０であり、ｎが１である一種または二種以上の化合物を含んでなることがより好ましい。このような特定のオルガノポリシロキサン系界面活性剤を使用することにより、記録媒体として印刷本紙に印刷した場合であっても、インクの凝集むらがより改善される。 Further, as the polyorganosiloxane surfactant, the following formula (II):

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 13, m represents an integer of 2 to 70, and n represents an integer of 1 to 8.)
Or in the compound of the above formula (II), R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 11, and m represents It represents an integer of 2 to 50, and n preferably comprises one or more compounds which are integers of 1 to 5, or, in the compound of the above formula (II), R represents a hydrogen atom or a methyl group More preferably, a is an integer of 2 to 13, m is an integer of 2 to 50, and n is an integer of 1 to 5, or one or more compounds. In the compound of the above formula (II), R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, m is an integer of 2 to 50, and n is an integer of 1 to 8. More preferably, it comprises one or more compounds. Alternatively, in the compound of the above formula (II), R is a methyl group, a is an integer of 6 to 18, m is 0 to 4, and n is 1 or 2, one or two or more compounds Or R is a methyl group, a is an integer of 6 to 18, m is 0, and n is 1 or 2 or more compounds. It is more preferable. By using such a specific organopolysiloxane surfactant, unevenness of ink aggregation is further improved even when printing on a printing paper as a recording medium.

  In the compound of the above formula (II), a is an integer of 2 to 5, m is an integer of 20 to 40, n is an integer of 2 to 4, and a is an integer of 7 to 11. M is an integer of 30 to 50, n is an integer of 3 to 5, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2 It is more preferable to use a certain compound or a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, the unevenness of ink aggregation can be further improved.

  In the compound of the above formula (II), R is a hydrogen atom, a is an integer of 2 to 5, m is an integer of 20 to 40, and n is an integer of 2 to 4, Alternatively, it is more preferable to use a compound in which a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (II), R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2, Alternatively, it is more preferable to use a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Furthermore, in the compound of the above formula (II), it is more preferable to use a compound in which R is a methyl group, a is an integer of 6 to 12, m is 0, and n is 1. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (II), R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5; , R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, R is a methyl group, and a is 6 It is most preferable to use a mixture of a compound having an integer of 10 to 10, m being an integer of 10 to 20, and n being an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Furthermore, in the above formula (II), R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5, A compound in which R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, R is a methyl group, and a is 6 to It is most preferable to use a mixture of a compound having an integer of 18, m is 0, and n is 1. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  The polyorganosiloxane surfactant is not particularly limited, but 20% by mass of glycerin, 10% by mass of 1,2-hexanediol, 0.1% by mass of the polyorganosiloxane surfactant, and water. When the ink composition contains 69.9% by mass, it is preferable to use the ink composition having a dynamic surface tension of 1 Hz of 26 mN / m or less. The dynamic surface tension can be measured using, for example, a bubble pressure dynamic surface tension meter BP2 (manufactured by KRUS).

  The surfactant is preferably contained in the ink composition according to the present invention in an amount of 0.01 to 1.0% by mass, more preferably 0.05 to 0.50% by mass. In particular, when using the surfactant in which R is a hydrogen group, it is preferable from the viewpoint of beading to reduce the content, compared to using the surfactant in which R is a methyl group. By containing 0.01 to 0.1% by mass of a surfactant in which R is a hydrogen group, water repellency is exhibited and bleeding can be adjusted.

  Other surfactants, specifically, acetylene glycol surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants and the like may be further added to the ink composition according to the present invention.

  Among these, acetylene glycol surfactants include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6- Diol, or 3,5-dimethyl-1-hexyn-3ol, 2,4-dimethyl-5-hexyn-3-ol and the like can be mentioned. A commercially available product can also be used as the acetylene glycol surfactant, for example, Olphine E1010, STG, Y (trade name, manufactured by Nissin Chemical Co., Ltd.), Surfynol 61, 104, 82, 465, 485, or TG (trade name, manufactured by Air Products and Chemicals Inc.).

<Water, other ingredients>
The ink composition according to the present invention contains the above-described poorly water-soluble alkanediol and cyclodextrins, and water as a solvent. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria is prevented for a long period of time.

  The ink composition according to the present invention may contain a penetrant in addition to the above components.

  Specific examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert -Butyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-iso-propyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol mono-n-butyl ether, Propylene glycol monomethyl ester Ter, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-tert-butyl ether, dipropylene glycol monomethyl ether, dipropylene Glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol-iso-propyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-tert-butyl ether, 3-methoxy-3-methyl- 1-butanol, 3-methoxy-1-butanol and the like, and these may be used as one kind or a mixture of two or more kinds. Can.

Among the above glycol ethers, polyhydric alcohol alkyl ethers are preferred, and ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether , Propylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol mono-n-butyl ether, or 3-methoxy-1-butanol is preferred.
More preferred is triethylene glycol monomethyl ether, triethylene glycol mono-n-butyl ether, or 3-methoxy-1-butanol.

  The addition amount of the penetrant may be appropriately determined, but is preferably about 0.1 to 30% by mass, more preferably about 1 to 20% by mass.

  The ink composition according to the present invention may contain a recording medium solubilizer in addition to the above components.

  As the recording medium solubilizer, pyrrolidones such as N-methyl-2-pyrrolidone, pyrrolidone carboxylic acid, and alkali metal salts thereof can be suitably used. The addition amount of the recording medium solubilizer may be appropriately determined, but is preferably about 0.1 to 30% by mass, more preferably about 1 to 20% by mass.

  In the ink composition according to the present invention, glycerin and its derivatives, such as 3- (2-hydroxyethoxy) -1,2-propanediol (CAS14641-24-8) and 3- (2-hydroxypropoxy)- It is preferable to include a wetting agent such as 1,2-propanediol. Glycerin and derivatives thereof have a function of preventing ink from drying and solidifying in an inkjet nozzle or the like, and thus are preferable from the viewpoint of improving clogging recovery. In the present invention, these wetting agents may be contained in an amount of 0.1 to 8% by mass or less.

  The ink composition according to the present invention may further contain a nozzle clogging preventive agent, an antiseptic, an antioxidant, a conductivity adjusting agent, a pH adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent, an oxygen absorber, and the like. it can.

  Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzthiazoline-3-one ( ICI's Proxel CRL, Proxel BND, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

  Further, examples of pH adjusters, solubilizers, or antioxidants include amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, potassium hydroxide, sodium hydroxide, lithium hydroxide, etc. Inorganic salts, ammonium hydroxide, quaternary ammonium hydroxides (tetramethylammonium, etc.), carbonates such as potassium carbonate, sodium carbonate, lithium carbonate and other phosphates, or N-methyl-2-pyrrolidone, urea, thio Examples include ureas such as urea and tetramethylurea, allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, and L-ascorbic acid and salts thereof.

  In addition, the ink composition according to the present invention may contain an antioxidant and an ultraviolet absorber. Examples thereof include Tinuvin 328, 900, 1130, 384, 292, 123, and 144 manufactured by Ciba Specialty Chemicals. 622, 770, 292, Irgacor 252 153, Irganox 1010, 1076, 1035, MD1024, lanthanide oxide, and the like.

  The ink composition according to the present invention can be produced by dispersing and mixing each of the above components by an appropriate method. Preferably, the pigment, polymer dispersant, and water are first used in a suitable dispersing machine (for example, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, jet mill, ang mill, etc.). Mix to prepare a uniform pigment dispersion, then add separately prepared resin (resin emulsion), water, water-soluble organic solvent, sugar, pH adjuster, preservative, fungicide, etc. An ink solution is prepared. After sufficiently stirring, the target ink composition can be obtained by performing filtration in order to remove the coarse particle diameter and foreign matters that cause clogging. The filtration may be preferably performed using a glass fiber filter as a filter medium. The glass fiber is preferably a resin-impregnated glass fiber from the viewpoint of the electrostatic adsorption function. The pore diameter of the glass fiber filter is preferably 1 to 40 microns, and more preferably 1 to 10 microns, from the viewpoint of productivity and adsorption removal of charged free resin and the like. By sufficiently removing and adsorbing the charged free resin and the like, the discharge stability can be improved. An example of the filter is Ultipore GF Plus manufactured by Nippon Pole.

  The ink composition according to the present invention is preferably used for inkjet recording.

<Inkjet recording method>
An ink jet recording method using an ink composition according to the present invention performs printing by discharging droplets of the ink composition described above and attaching the droplets to a recording medium. In the recording method according to the present invention, the recording medium to be recorded is not particularly limited. For example, the recording medium is a non-water-absorbing or low-water-absorbing recording medium in addition to a recording medium having a receiving layer of plain paper or water-based ink. However, it can be preferably used.

<Non-water-absorbing or low-water-absorbing recording medium>
Examples of the non-water-absorbing recording medium include a plastic film coated on a substrate such as a plastic film or paper that is not surface-treated for ink jet recording (that is, does not have an ink receiving layer). And those having a plastic film adhered thereto. Examples of the plastic here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene.

  Examples of the low water-absorbing recording medium include coated paper, and recording paper (printing paper) such as finely coated paper, art paper, coated paper, matte paper, and cast paper.

  Coated paper is paper whose surface is coated with a paint to enhance aesthetics and smoothness. The paint can be prepared by mixing pigments such as talc, pyrophyllite, clay (kaolin), titanium oxide, magnesium carbonate, and calcium carbonate and an adhesive such as starch and polyvinyl alcohol. The paint is applied using a machine called a coater in the paper manufacturing process. There are two types of coater: an on-machine type in which papermaking and coating are performed as a single step by being directly connected to a paper machine, and an off-machine type in which the papermaking and coating are performed separately. It is mainly used for recording and is classified as coated paper for printing in the “Production Dynamic Statistics Classification” of the Ministry of Economy, Trade and Industry.

The finely coated paper refers to a recording paper having a coating amount of paint of 12 g / m ² or less. Art paper refers to recording paper obtained by applying a coating of about 40 g / m ^{2 to} high-grade recording paper (quality paper, paper with a chemical pulp usage rate of 100%). The coated paper refers to a recording paper coated with a paint of about 20 g / m ² to 40 g / m ² . The cast paper refers to a recording paper obtained by finishing art paper or coated paper by applying pressure to the surface with a machine called a cast drum so that the gloss and the recording effect are further enhanced.

  Synthetic paper or printing paper (OKT +: manufactured by Oji Paper Co., Ltd.) is preferably used as a non-water-absorbing or low-water-absorbing recording medium, but in particular, high-quality paper used for art paper and POD (print on demand) applications. In particular, even when printing at a low resolution on a dedicated paper for a laser printer, it is possible to realize a high-quality image with suppressed bleeding and beading. Examples of the high-quality paper for POD use include Ricoh Business Coat Gloss 100 (manufactured by Ricoh Co., Ltd.). Examples of the dedicated paper for the laser printer include LPCCTA4 (manufactured by Seiko Epson Corporation). Examples of water-resistant paper include KALEKA (manufactured by Mitsubishi Chemical Media Co., Ltd.) and laser peach (manufactured by Nisshinbo Postal Chemical Co., Ltd.).

<Nis coat>
The recorded matter using the ink composition according to the present invention may be overcoated with offset varnish or gravure varnish by a varnish coater used for commercial printing or the like. Variable printing with good image can be realized by inkjet recording method, and it can be used for low-volume printing of various products. Overcoat with offset varnish or gravure varnish can realize good water resistance and solvent resistance. It is.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by these Examples.

<Preparation of ink composition>
Each ink was prepared by mixing each component according to the composition of the following Table 1 and Table 2, and filtering with a 10 μm membrane filter. The numerical values in Table 1 and Table 2 below represent the content (% by mass) in the ink. Moreover, resin represents content (mass%) of solid content. In addition, trehalose in the following Table 1 and Table 2 is a treha fine powder manufactured by Hayashibara Shoji Co., Ltd., and the surfactant used in Examples and Comparative Examples is a polyorganosiloxane surfactant, In the formula (II), R is a methyl group, a is an integer of 6 to 18, m is an integer of 0, and n is an integer of 1 (surfactant 1 in which R is methyl) In the above formula (II), R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5 (R is hydrogen) In the formula (II) above, R is a methyl group, a is an integer from 9 to 13, m is an integer from 2 to 4, and n is an integer from 1 to 2 A surfactant comprising the compound (R is methyl surfactant 2). When the surfactant is an aqueous solution containing 20% by mass of glycerin, 10% by mass of 1,2-hexanediol, 0.1% by mass of the surfactant, and 69.9% by mass of water, The dynamic surface tension of 1 Hz of the aqueous solution was 26 mN / m or less. Specifically, when a dynamic surface tension of 1 Hz (= one bubble / 1 second) was measured using a bubble pressure dynamic surface tension meter BP2 (manufactured by KRUS), a 1 Hz dynamic surface of the aqueous solution was measured. The tension was 24.6 mN / m.

  In Tables 1 and 2, “Y” contained in the following ink set represents C.I. I. Pigment Yellow 74, “M” is C.I. I. Pigment Violet 19 and “C” is C.I. I. Pigment Blue 15: 3 and “K” is C.I. I. Pigment Black 7 is included.

“Duty” used below is a value calculated by the following equation.
Duty (%) = actual recording dot number / (vertical resolution × horizontal resolution) × 100 (where “actual recording dot number” is the actual recording dot number per unit area, and “vertical resolution” and “horizontal resolution”) Is the resolution per unit area.)

<Evaluation>
Evaluation of curling property Each ink of Y, M, C, and K obtained above was filled into an ink cartridge of an ink jet printer (PXG930, manufactured by Seiko Epson Corporation) as an ink set. The mounting order was YYMMCCCK in the order from the cap. After that, using a printer driver, the printer head was filled with ink, and it was confirmed that normal recording was possible. The recording method was such that recording was possible at 720 dpi in the main scanning (head drive) direction and 360 dpi in the sub-scanning (recording medium conveyance) direction. Next, the voltage applied to the piezo element of the printer head is adjusted so that the dot size upon landing is 3 ng. One drive is 720 × 360 dpi, and the OKT + (Oji Paper Co., Ltd.) is approximately 73.3 g / m ^2. 720 × 720 dpi image was recorded in a single direction. The recorded material is a solid image with a margin of about 6 mm in the periphery. The recording was performed in a normal temperature and normal humidity (25 ° C., 45% humidity) environment. At this time, the ink adhesion amount of a single color duty of 100% was approximately 1.6 mg / inch ² . The recording surface of the obtained recorded matter was placed on a flat desk in a normal temperature and normal humidity (25 ° C., 45% humidity) environment for 3 days. The recorded image is a monochrome image. The media temperature during recording was about 20 ° C.
The distance between the recording paper and the recording head was 1 mm.

The obtained image was evaluated according to the following criteria.
A: The average value of warping from the desk to the four corner tips of the paper is less than 20 mm.
B: The average value of the warp from the desk to the four corners of the paper is 20 mm or more.
The results were as described in Table 1 and Table 2 above.

Clogging recovery of high temperature and low humidity open system (open system clogging recovery)
The Y, M, C, and K inks obtained above were filled into an ink cartridge of an ink jet printer (PXG930, manufactured by Seiko Epson Corporation) as an ink set. The mounting order was YYMMCCCK in the order from the cap. After that, using a printer driver, the printer head was filled with ink, and it was confirmed that normal recording was possible. Further, after moving the carriage to the ink cartridge replacement position, the outlet was disconnected, the ink cartridge was removed, and then the head was removed. Thus, after the ink cartridge and the head cap were removed, the head was left in an environment of 40 ° C./humidity 20% for 3 days.

After leaving, install the head left on the carriage as it was, then install the ink cartridge that was left in the room temperature and humidity environment, and repeat the cleaning operation until all nozzles ejected to the same level as the initial stage. The ease of recovery was evaluated according to the following criteria.
AA: The clogging is recovered within 6 times by repeating the cleaning operation.
A: The clogging is recovered within 12 times by repeating the cleaning operation.
B: The clogging does not recover within 12 times after repeating the cleaning operation. The results were as described in Table 1 and Table 2 above.

Clogging recovery of high-temperature, normal-humidity sealed systems (sealed system clogging recovery)
The Y, M, C, and K inks obtained above were filled into an ink cartridge of an ink jet printer (PXG930, manufactured by Seiko Epson Corporation) as an ink set. The mounting order was YYMMCCCK in the order from the cap. After that, using a printer driver, the printer head was filled with ink, and it was confirmed that normal recording was possible. Then, according to a normal use procedure, the switch was pressed to turn off the power, and the outlet was disconnected. In this manner, the printer was left in an environment of 40 ° C./humidity 45% for 7 days in a normal state where the ink cartridge and the head cap were not removed.

After being left, the printer was energized and the cleaning operation was repeated until all nozzles ejected at the same level as the initial stage. The ease of recovery was evaluated according to the following criteria.
A: The clogging is recovered within 12 times by repeating the cleaning operation.
B: The clogging does not recover within 12 times after repeating the cleaning operation.
The results were as described in Table 1 and Table 2 above.

Evaluation of Storage Stability (Ink) The viscosity at 20 ° C. of each of the Y, M, C, and K inks obtained above was measured as the initial viscosity. Thereafter, 100 g of each ink was injected into a 110 ml Laboran sample tube (manufactured by ASONE) and capped. This was left to stand at 70 ° C. for 1 week and then allowed to cool to 20 ° C. The viscosity of the ink after standing at 20 ° C. was measured.
A: Viscosity change is less than 0.4 mPas.
B: The viscosity change is 0.4 mPas or more and less than 0.8 mPas.
The results were as described in Table 1 and Table 2 above.

Evaluation of Film Line Width Each of the Y, M, C, and K inks obtained above was filled as an ink set into an ink cartridge of an ink jet printer (PXG930, manufactured by Seiko Epson Corporation). The mounting order was YYMMCCCK in the order from the cap. After that, using a printer driver, the printer head was filled with ink, and it was confirmed that normal recording was possible.
The recording method was such that recording was possible at 720 dpi in the main scanning (head drive) direction and 360 dpi in the sub-scanning (recording medium conveyance) direction. Next, the voltage applied to the piezo element of the printer head is adjusted so that the dot size upon landing is 3 ng. One drive is 720 × 360 dpi, and 720 is applied to Lumirror S10 (100 micron thickness) (made by Toray Industries, Inc.). A ruled line image in the main scanning direction of × 180 dpi was recorded in a single direction. The medium temperature during recording was about 37 ° C. The distance between the recording paper and the recording head was 1 mm.

The obtained ruled lines were evaluated according to the following criteria.
A: The line width is 60 microns or more and less than 70 microns.
B: The line width is 70 microns or more.
The results were as described in Table 1 and Table 2 above.

Evaluation of resolubility 100 g of each of the Y, M, C, and K inks obtained above was injected into a glass beaker with a capacity of 200 mm and a diameter of 65 mm. This was left in an environment of a temperature of 40 ° C. and a humidity of 20% for 3 days. After that, the glass beaker was taken out and allowed to cool in an environment of 20 ° C. and 50% humidity for 3 hours. The solidified ink adhered to the side wall of the glass beaker. The glass beaker was tilted 45 °, waited for 10 seconds, and then returned to the flat state. By such an experiment, re-dissolvability was evaluated by repeating the contact of the ink at 20 ° C. remaining on the bottom of the glass beaker with the solidified ink adhered to the side wall of the glass beaker for 10 seconds.
AA: At the first time (after 10 seconds), the solidified ink was redissolved, and the solidified ink adhered was lost.
A: In the second time (after 20 seconds), the solidified ink was re-dissolved, and the solidified ink adhered was lost.
B: The solidified ink adhered after the second time (after 20 seconds), but after the third time (after 30 seconds), the solidified ink adhered to the side wall was re-dissolved, and the adhered solid ink disappeared.
C: The solidified ink is adhered even after the third time (after 30 seconds).
The results were as described in Table 1 and Table 2 above.

Evaluation of ink beading (image quality) on film (beading property)
The Y, M, C, and K inks obtained above were filled into an ink cartridge of an ink jet printer (PXG930, manufactured by Seiko Epson Corporation) as an ink set. The mounting order was YYMMCCCK in the order from the cap. After that, using a printer driver, the printer head was filled with ink, and it was confirmed that normal recording was possible.
The recording method was such that recording was possible at 720 dpi in the main scanning (head drive) direction and 360 dpi in the sub-scanning (recording medium conveyance) direction. Next, the voltage applied to the piezo element of the printer head is adjusted so that the dot size upon landing is 3 ng. One drive is 720 × 360 dpi, and the Lumirror S10 (100 micron thickness) (made by Toray Industries, Inc.) A x720 dpi image was recorded in a single direction. In this case, for example, the ink deposition amount of a single color duty 100% was 3.1 mg / inch ² . The medium temperature during recording was about 37 ° C.
The distance between the recording paper and the recording head was 1 mm.
The recorded image is a secondary color image obtained by mixing single colors having the same duty.

The obtained image was evaluated according to the following criteria.
A: Up to 160% of the secondary color Duty of each single color Duty 80% can be reproduced without beading.
B: Up to secondary color Duty of 120% for each single color Duty can be reproduced without beading, but secondary color Duty of 160% for each single color Duty cannot be reproduced by beading.
C: Up to a secondary color Duty of 80% for each single color Duty can be reproduced without beading, but a secondary color Duty of 120% for each single color Duty cannot be reproduced by beading.
The results were as described in Table 1 and Table 2 above.

Evaluation of ink bleeding (image quality) on film (bleedability)
The Y, M, C, and K inks obtained above were filled into an ink cartridge of an ink jet printer (PXG930, manufactured by Seiko Epson Corporation) as an ink set. The mounting order was YYMMCCCK in the order from the cap. After that, using a printer driver, the printer head was filled with ink, and it was confirmed that normal recording was possible.
The recording method was such that recording was possible at 720 dpi in the main scanning (head drive) direction and 360 dpi in the sub-scanning (recording medium conveyance) direction. Next, the voltage applied to the piezo element of the printer head is adjusted so that the dot size upon landing is 3 ng. One drive is 720 × 360 dpi, and the Lumirror S10 (100 micron thickness) (made by Toray Industries, Inc.) A x720 dpi image was recorded in a single direction. In this case, for example, the ink deposition amount of a single color duty 100% was 3.1 mg / inch ² . The medium temperature during recording was about 37 ° C.
The distance between the recording paper and the recording head was 1 mm.
The recorded image is an image in which 2 to 8 pixel ruled lines of the primary color of 80% duty are brought into contact with the secondary color of 160% duty of 80% duty.

The obtained image was evaluated according to the following criteria.
A: A 6/720 inch ruled line can be reproduced without bleeding, but a 2/720 inch ruled line cannot be reproduced due to bleeding.
B: The 10/720 inch ruled line is reproduced without bleeding, but the 6/720 inch ruled line is bleeding and cannot be reproduced.
C: A ruled line cannot be obtained due to ejection failure.
The results were as described in Table 1 and Table 2 above.

  Ink compositions and ink sets of Examples were obtained in the same manner except that 1,6-hexanediol of the resin solubilizer contained in the dispersion was changed to 1,2-hexanediol. In the same manner as described above, the curling property, open system clogging recovery property, closed system clogging recovery property, storage stability (ink), film line width, re-dissolution property, beading property, and bleeding property are evaluated. Carried out. The same evaluation result was obtained even when 1,6-hexanediol was changed to 1,2-hexanediol.

  Ink compositions and ink sets of Examples were obtained in the same manner except that the styrene acrylic acid copolymer of the dispersion resin contained during the production of the dispersion was changed to an oxyethyl resin. In the same manner as described above, the curling property, open system clogging recovery property, closed system clogging recovery property, storage stability (ink), film line width, re-dissolution property, beading property, and bleeding property are evaluated. Carried out. Even when the styrene acrylic acid copolymer was changed to an oxyethyl resin, the same evaluation result was obtained.

Claims (5)

An ink composition comprising a slightly water-soluble alkanediol having 7 to 10 carbon atoms, a cyclodextrin, hydantoin or a derivative thereof, and water .   The ink composition according to claim 1, wherein the hydantoin derivative is 5,5-dimethylhydantoin or 1-hydroxymethyl-5,5-dimethylhydantoin.   The ink composition according to claim 1 or 2, wherein the content ratio of the slightly water-soluble alkanediol having 7 to 10 carbon atoms and the cyclodextrins is 1: 3 to 1: 6. The ink composition according to any one of claims 1 to 3, further comprising a solid wetting agent that is solid at 20 ° C and a relative humidity of 60% .
The solid wetting agent comprises one or two selected from the group consisting of a first carbohydrate and a second carbohydrate; and
The first carbohydrate is one or more selected from the group consisting of trehalose, isotrehalose, neotrehalose, and mannitol;
The second carbohydrate is one or more selected from the group consisting of maltotriose, maltotetraose, and maltopentaose.
Ink composition. Furthermore, the ink composition as described in any one of Claims 1-4 which comprises 1 type, or 2 or more types of polyorganosiloxane surface activity represented by a following formula:

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 13, m represents an integer of 2 to 70, and n represents an integer of 1 to 8).