JP2013087207A - Ink for inkjet and inkjet recording method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink which causes little uneven agglomeration and streaks and exhibits an excellent fixation.SOLUTION: The ink for inkjet includes a carboxylate ester containing a hydroxy group having not greater than six carbons expressed by general formula (1), an surfactant, and water. The formula (1) is expressed by HO-CH-COO-CH(in the formula, m is a natural number of 2 or 3; n is a natural number of 1-3; and m+n≤5).

Description

  The present invention relates to an inkjet ink and an inkjet recording method using the same.

  The inkjet recording method is a recording method in which recording 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.

  Incidentally, in recent years, with the spread of image forming technology from digital data, desktop publishing (hereinafter referred to as “DTP”) is becoming widespread, particularly in the printing field. Even in the case of recording by DTP, a color proofing proof is produced in advance in order to confirm glossiness and color feeling with an actual recorded matter. An inkjet recording method is applied to the output of this proof, and DTP requires a high color reproducibility and a high color stability of the recorded matter. In addition, special paper for inkjet recording is used.

  Proof paper, which is a dedicated paper for ink jet recording, is manufactured so that the gloss and color feel are the same as the output actually recorded on the 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 or polyester resin, has recently attracted attention as an environmentally friendly material that is excellent in recyclability. There is a demand from an environmental point of view to record on such synthetic paper. In addition, there is a demand from an environmental viewpoint that it is desired to perform recording with a water-based ink on a polyvinyl chloride resin sheet or the like that is widely used in outdoor advertising or the like.

  The main printing paper is a coated paper provided with a coating layer for receiving oil-based ink on the surface thereof, but has a feature that the ink absorption ability of the coating layer with respect to water-based ink is poor. For this reason, when water-based pigment ink generally used for ink jet recording is used, the permeability of the ink to the recording medium (printing paper) is low, and blurring occurs in the image, unevenness of the aggregation, unevenness of the stripes, etc. Sometimes. For such a problem, for example, Patent Documents 1 to 4 disclose that various components are added to the ink.

  A vinyl chloride resin sheet or the like is a plastic film sheet that does not absorb water and has high water repellency. Therefore, when a water-based pigment ink generally used for ink jet recording is used, the ink permeability is low, and the image In some cases, bleeding may occur, or unevenness of aggregation or unevenness of muscle may occur. For such problems, for example, Patent Documents 5 to 6 have the ability to swell or dissolve a recording medium (vinyl chloride resin sheet or the like) (hereinafter referred to as “swellability”). Non-aqueous inks containing a solvent (hereinafter referred to as “swelling solvent”) are disclosed.

  On the other hand, Patent Document 7 discloses that ink can permeate a recording medium by recording with a characteristic water-based ink containing a swelling solvent on a vinyl chloride resin sheet or the like, and fixability can be obtained.

JP 2005-194500 A JP 2003-213179 A JP 2003-253167 A JP 2006-249429 A Japanese Patent No. 4337425 Japanese Patent No. 4177709 JP 2007-262272 A

  However, when the aqueous ink described in the above-mentioned patent document is used to record an image on a recording medium having a low water-absorbing property such as printing paper, it cannot be said that the ink is sufficiently dry. Since the surface tension is not sufficiently low, uneven image aggregation, uneven stripes, and the like may occur. In particular, for non-absorbent recording media (for example, plastic films such as vinyl chloride sheets), which are inferior in water-based ink absorbability to printing paper, an ink composition containing a swelling solvent with high surface tension is used. For this reason, not only the above-mentioned problem is remarkably caused, but also the fixing property of the image may not be sufficient.

  One of the objects according to some aspects of the present invention is to provide an ink jet ink that has excellent ink drying properties, suppresses the occurrence of uneven aggregation or streak unevenness, and has good image fixability.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
One aspect of the inkjet ink according to the present invention is:
An inkjet ink containing a hydroxycarboxylic acid ester having 6 or less carbon atoms, a surfactant, and water represented by the following general formula (1).
_{HO-C m H 2m -COO-} C n H 2n + 1 ... (1)
(In the formula, m represents a natural number of 2 or 3, n represents a natural number of 1 to 3, and m + n ≦ 5.)

  The ink-jet ink described in Application Example 1 is excellent in drying property, can suppress the occurrence of uneven aggregation or streak, and can provide an image with good fixability.

[Application Example 2]
Furthermore, the ink for inkjets of the application example 1 containing the oxazoline group containing resin whose weight average molecular weight is 2-120000, and carboxyl group-containing resin.

  The ink-jet ink described in Application Example 2 is further excellent in water resistance.

[Application Example 3]
The ratio (MA / MB) of the number of moles of oxazoline groups (MA) in the total mass of the oxazoline group-containing resin to the number of moles of carboxyl groups (MB) in the total mass of the carboxyl group-containing resin is 10 The inkjet ink according to Application Example 2, which is 40 or more.

  The inkjet ink described in Application Example 3 is more preferable from the viewpoint of water resistance.

[Application Example 4]
The inkjet ink according to any one of Application Examples 1 to 3, wherein the hydroxycarboxylic acid ester is methyl 2-hydroxyisobutanoate or methyl 2-hydroxybutanoate.

  The inkjet ink described in Application Example 4 is more preferable from the viewpoint of swelling.

[Application Example 5]
Furthermore, the inkjet ink as described in any one of the application examples 1-4 containing a pigment.

  The inkjet ink described in Application Example 5 is preferable because it can form an image with excellent color developability.

[Application Example 6]
Furthermore, the inkjet ink as described in any one of the application examples 1-5 containing polyoxyalkylene glycol.

  The ink-jet ink described in Application Example 6 is further excellent in clogging recovery.

[Application Example 7]
Furthermore, the ink for inkjets as described in any one of the application examples 1-6 containing a C1-C8 or 1,2-alkanediol.

  The ink for inkjet recording described in Application Example 7 can further suppress the occurrence of uneven aggregation or streaks.

[Application Example 8]
The 1,2-alkanediol having 7 or 8 carbon atoms is 1,2-heptanediol, 1,2-octanediol, 4,4-dimethyl-1,2-pentanediol, 5-methyl-1,2- The inkjet ink according to Application Example 7, which is at least one selected from the group consisting of hexanediol and 4-methyl-1,2-hexanediol.

  The ink-jet ink described in Application Example 8 is more preferable because it can suppress the occurrence of uneven aggregation or unevenness.

[Application Example 9]
The ink-jet ink according to any one of Application Examples 1 to 8, wherein the surfactant is a polyorganosiloxane-based surfactant.

  The ink-jet ink described in Application Example 9 is more preferable because it can further suppress the occurrence of uneven aggregation or unevenness.

[Application Example 10]
An inkjet recording method using an inkjet recording apparatus having a head,
The head includes a nozzle row including a plurality of nozzle holes, and discharges ink droplets of the inkjet ink according to any one of Application Examples 1 to 9 from the nozzle holes;
A dot forming step of attaching the droplets to a recording medium to form dots composed of the droplets;
An inkjet recording method for forming an image on the recording medium by repeating the ejection step and the dot formation step a plurality of times.

  According to the ink jet recording method described in Application Example 10, it is possible to provide an image with excellent drying properties, suppressed generation of aggregation unevenness or stripe unevenness, and excellent fixability.

[Application Example 11]
A plurality of the nozzle rows are arranged,
The image formed by the image forming step has a dot interval of an image resolution of 300 dpi or more in the arrangement direction of the nozzle rows,
The mass of the droplets ejected in the ejection step is 1 to 15 ng.
The diameter of the dot formed in the said dot formation process is an inkjet recording method of the application example 10 which is larger than the said dot space | interval.

  According to the ink jet recording method described in Application Example 11, it is possible to provide an image having excellent drying properties, suppressing occurrence of unevenness of aggregation or unevenness, and excellent fixability.

[Application Example 12]
Furthermore, the inkjet recording method of the application example 10 or 11 including the drying process which dries the said recording medium.

  According to the ink jet recording method described in Application Example 12, it is possible to provide an image having excellent dryability, suppressing occurrence of aggregation unevenness or stripe unevenness, and excellent fixability.

[Application Example 13]
The inkjet recording method according to any one of Application Examples 10 to 12, wherein the recording medium is a low-absorbing or non-absorbing recording medium.

  According to the ink jet recording method described in Application Example 13, it is possible to provide an image having excellent drying properties, suppressing occurrence of aggregation unevenness or stripe unevenness, and excellent fixability.

1 is a block diagram showing a recording system having a recording apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing the configuration of the recording apparatus according to the embodiment of the invention. Schematic which shows the lower surface of the head which concerns on embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described. The embodiment described below describes an example of the present invention. In addition, the present invention is not limited to the following embodiments, and includes various modifications that are implemented within a range that does not change the gist of the present invention.

1. Inkjet ink The inkjet ink according to one embodiment of the present invention contains a hydroxycarboxylic acid ester having 6 or less carbon atoms, a surfactant, and water.

  The inkjet ink according to the present embodiment (hereinafter, also simply referred to as “ink”) forms an image to be described later by adhering onto a recording medium. Hereinafter, components contained in the ink will be described in detail.

1.1. Hydroxycarboxylic acid esters having 6 or less carbon atoms The ink according to the present embodiment includes hydroxycarboxylic acid esters having 6 or less carbon atoms represented by the following general formula (1).
_{HO-C m H 2m -COO-} C n H 2n + 1 ... (1)
(In the formula, m represents a natural number of 2 or 3, n represents a natural number of 1 to 3, and m + n ≦ 5.)
Accordingly, since the ink has excellent swelling and drying properties, an image having excellent fixability and suppressing aggregation unevenness or stripe unevenness can be obtained.

  Further, hydroxycarboxylic acid esters having 6 or less carbon atoms are preferable from the viewpoint of the storage stability of the ink because alkanediols having 7 or more carbon atoms described later can be stably dissolved uniformly in water.

  Further, since the surface tension of the hydroxycarboxylic acid ester having 6 or less carbon atoms is 30 mN / m or less, it becomes an ink having a low surface tension, which is preferable from the viewpoint of suppressing the occurrence of uneven aggregation and uneven stripes. Since the surface tension of lactam solvents and lactone solvents such as N-methyl-2-pyrrolidone and γ-butyrolactone exceeds 40 mN / m, unevenness of aggregation and unevenness of muscles may occur, which is not preferable.

  Specific examples of hydroxycarboxylic acid esters having 6 or less carbon atoms include methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, propyl 2-hydroxypropionate, methyl 3-hydroxypropionate, and ethyl 3-hydroxypropionate. Hydroxypropionate such as propyl 3-hydroxypropionate, methyl 2-hydroxyisobutanoate, methyl 2-hydroxybutanoate, ethyl 2-hydroxyisobutanoate, ethyl 2-hydroxybutanoate, methyl 3-hydroxyisobutanoate, 3 -Hydroxybutanoic acid ester, such as methyl-hydroxybutanoate, ethyl 3-hydroxyisobutanoate, and ethyl 3-hydroxybutanoate, is mentioned, It can use as these 1 type, or 2 or more types of mixtures.

  Among the hydroxycarboxylic acid esters having 6 or less carbon atoms, methyl 2-hydroxyisobutanoate and methyl 2-hydroxybutanoate are preferable from the viewpoint of fixability and drying property.

  Methyl 2-hydroxyisobutanoate is more preferable from the viewpoint of swelling.

  The amount of the hydroxycarboxylic acid ester having 6 or less carbon atoms may be appropriately determined, but is preferably about 3.0 to 24.0% by mass, more preferably about 6.0 to 16.0% by mass. . By setting it as the above range, not only is drying property excellent, but separation of components contained in the ink can be suppressed.

  In addition, since the hydroxycarboxylic acid alkyl esters having 6 or less carbon atoms can dissolve the polymer material formed by the ink, it is possible to improve the problem of solid ink deposits around the cleaning cap and the flushing box. There are also advantages.

1.2. Oxazoline group-containing resin The ink according to this embodiment may contain an oxazoline group-containing resin. As a function of the oxazoline group-containing resin, the water resistance of an image formed by ink can be improved.

  The oxazoline group-containing resin is excellent in ink acceptability. Therefore, the ink according to the present embodiment having excellent drying properties may be used as a coating liquid by containing an oxazoline group-containing resin. Examples of the coating liquid include a clear ink substantially free of a colorant and a base ink containing a pigment used as a base layer. Examples of the pigment used as the underlayer include a white pigment. According to the said aspect, the acceptability of the ink discharged on a coating layer is improved, and the water resistance of the image formed with the ink discharged on a coating layer is mentioned.

  In particular, the oxazoline group in the oxazoline group-containing resin tends to react with a carboxyl group to form a crosslinked structure. Therefore, for example, if a component having a carboxyl group (for example, a resin dispersant having a carboxyl group in its structure) is added to the ink, the water resistance of the image is further improved.

  Examples of the oxazoline group-containing resin include those having an acryl skeleton or a styrene-acryl skeleton as a main chain and an oxazoline group in a side chain of the main chain. Among these, an oxazoline group-containing acrylic resin having an acrylic skeleton as a main chain and an oxazoline group as a side chain is preferable. The oxazoline group-containing resin may be used alone or in combination of two or more.

  Examples of the oxazoline group include a 2-oxazoline group, a 3-oxazoline group, and a 4-oxazoline group. Among these, a 2-oxazoline group is preferable. The 2-oxazoline group is represented by the following general formula (2).

（一般式（２）中、Ｒ¹¹、Ｒ¹²、Ｒ¹³およびＲ¹⁴は、それぞれ独立に、水素原子、ハロゲン原子、アルキル基、アラルキル基、フェニル基または置換フェニル基を示す。）

(In general formula (2), R ¹¹ , R ¹² , R ¹³ and R ¹⁴ each independently represent a hydrogen atom, a halogen atom, an alkyl group, an aralkyl group, a phenyl group or a substituted phenyl group.)

  The weight average molecular weight of the oxazoline group-containing resin is preferably 20,000 or more and 120,000 or less, and more preferably 20,000 or more and 80,000 or less. When the weight average molecular weight of the oxazoline group-containing resin is in the above range, it is easily dissolved in the solvent (water) in the ink, particularly when the upper limit is not exceeded. Thereby, the surface of a coat layer can be smoothed and a coat layer with favorable glossiness can be obtained. The weight average molecular weight of the oxazoline group-containing resin can be determined by, for example, a polystyrene-equivalent molecular weight measured by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

  The oxazoline group-containing resin can be used as an emulsion type that is emulsified and dispersed in water or an aqueous solution type that is dissolved in water. Among these, it is preferable to use an aqueous solution type as the oxazoline-containing resin. The aqueous solution type oxazoline group-containing resin has a smaller weight average molecular weight than the emulsion type oxazoline group-containing resin. Therefore, the surface of the image can be smoothed and a coat layer with good gloss can be obtained.

  A commercially available product can be used as the oxazoline group-containing resin. Specifically, as a water-soluble type, Epocros WS-300 [main chain: acrylic, weight average molecular weight: 120,000, oxazoline group amount: 7.7 mmol] / G (solid content conversion), solid content: 10%], Epocross WS-500 [main chain: acrylic, weight average molecular weight: 70,000, oxazoline group content: 4.5 mmol / g (solid content conversion), solid content : 39%], Epocross WS-700 [main chain: acrylic, weight average molecular weight: 40,000, oxazoline group amount: 4.5 mmol / g (solid content conversion), solid content 25%], etc. Is mentioned. As emulsion types, Epocros K-2010E [main chain: styrene-acryl, oxazoline group content: 1.8 mmol / g (solid content conversion), solid content: 40%], Epocros K-2020E [main chain: styrene- Acrylic, oxazoline group amount: 1.8 mmol / g (solid content conversion), solid content: 40%], Epocross K-2030E [main chain: styrene-acrylic, oxazoline group content: 1.8 mmol / g (solid content conversion) , An oxazoline group-containing styrene-acrylic resin such as solid content: 40%].

  The content of the oxazoline group-containing resin is preferably 1% by mass or more and 4% by mass or less, and preferably 1.6% by mass or more and 3.6% by mass or less in terms of solid content with respect to the total mass of the ink. More preferably. When the content of the oxazoline group-containing resin is in the above range, the action of receiving the ink in the coat layer may be further improved.

1.3. Carboxyl group-containing resin The ink according to this embodiment may contain a carboxyl group-containing resin. The carboxyl group-containing resin refers to a compound having a carboxyl group in the structural skeleton.

  The carboxyl group-containing resin can undergo a crosslinking reaction (formation of an amide ester bond) with the oxazoline group in the oxazoline group-containing resin. Thereby, the water resistance of the image can be remarkably improved.

  In the ink according to the present embodiment, the ratio (MA) of the number of moles of oxazoline groups (MA) in the total mass of the oxazoline group-containing resin to the number of moles (MB) of carboxy groups in the total mass of the carboxyl group-containing resin. / MB) is preferably 10 or more and 40 or less, and more preferably 15 or more and 30 or less. When the ratio (MA / MB) is within the above range, the water resistance of the image may be further improved.

  Here, the number of moles (MA) of oxazoline groups in the total mass of the oxazoline group-containing resin added to the ink can be calculated by the following formula (3).

  MA = [Oxazoline group amount (g / g) per 1 g of oxazoline group-containing resin (solid content conversion)] × [Solid content conversion amount (g) of oxazoline group-containing resin in ink] (3)

  Further, the number of moles (MB) of carboxyl groups in the total mass of the carboxyl group-containing resin added to the ink can be calculated by the following formula (4).

MB = [{acid value of carboxyl group-containing resin / KOH neutralized acid value} (mmol / g)] × [solid content conversion amount of carboxyl group-containing resin in ink (g)] (4)
In addition, in Formula (4), the value of KOH neutralization acid value is 56.1.

  The carboxyl group-containing resin is not particularly limited as long as it has a carboxyl group in the structural skeleton. For example, among the urethane resin and the fluorene skeleton-containing resin exemplified by the dispersant described later, a compound having a carboxyl group is used. Can be mentioned. Among these, a fluorene skeleton-containing resin having a carboxyl group can be preferably used from the viewpoint of suppressing separation of an alkanediol having 7 or more carbon atoms in the ink.

  The carboxyl group in the carboxyl group-containing resin may be neutralized from the viewpoint of the storage stability of the ink. The neutralization of the carboxyl group can be performed using a neutralizing agent (for example, organic amines). The organic amine used as the neutralizing agent is preferably a tertiary monoamine having 3 or more carbon atoms, more preferably a tertiary monoamine having 3 to 12 carbon atoms. Specific examples of organic amines include aliphatic tertiary amines such as trimethylamine, triethylamine, triethanolamine, N-methyldiethanolamine, and N, N-dimethylethanolamine.

1.4. Alkanediol having 7 or more carbon atoms The ink according to this embodiment contains an alkanediol having 7 or more carbon atoms. One of the functions of alkanediol having 7 or more carbon atoms is a surface-active effect. That is, by appropriately reducing the interfacial tension between the inkjet ink and the low-absorbing or non-absorbing recording medium, the contact area between the droplet and the recording medium is increased. Thereby, it is possible to improve the fixability of the droplets on the recording medium. On the other hand, one of the functions of alkanediool having 7 or more carbon atoms is the effect of suppressing the flow of droplets. That is, the alkanediol having 7 or more carbon atoms is a liquid or solid having a high viscosity due to the characteristic of 7 or more carbon atoms. This makes it difficult for the ink droplets to flow after the ink droplets adhere on the recording medium, thereby reducing the occurrence of uneven aggregation and streaks and further improving the fixing property to the recording medium more uniformly. Can be mentioned.

  In this specification, aggregation unevenness means local density spots that occur when a coating layer is formed using ink, and the film thickness of the solid component (resin component, color material component) is not good. This phenomenon is observed by becoming uniform. This does not mean that a portion of the recording medium surface that is not covered with ink remains. Aggregation unevenness occurs when droplets flow on the recording medium and come into contact with other droplets.

  Further, in the present specification, streak unevenness means a phenomenon in which a portion of the surface of a recording medium that is not covered with droplets remains on the streak due to poor filling of ink droplets. The streaks occur because the droplets ejected onto the recording medium (flow from the position to be fixed) or the contact area of the droplets with the recording medium is “repelled”.

  Further, in the present specification, the fixability means a property that a droplet stays at a position to be fixed. When the droplets flow from the position to be fixed (inferior in fixability), the above-mentioned aggregation unevenness and stripe unevenness are likely to occur particularly when the droplets are recorded at a high duty.

  The alkanediol having 7 or more carbon atoms is more preferably 7 or more and 10 or less, and further preferably 1,2-alkanediol having 7 to 10 carbon atoms. In the present invention, the hydrocarbon group portion of the alkanediol may be linear or branched.

  Examples of the alkanediol having 7 or more carbon atoms include 1,2-heptanediol, 1,2-octanediol, 4,4-dimethyl-1,2-pentanediol, 5-methyl-1,2-hexanediol, Examples include 4-methyl-1,2-hexanediol. Among these, 1,2-octanediol is more preferable.

  The content of the alkanediol having 7 or more carbon atoms may be appropriately determined as long as the fixability of the ink droplets can be obtained, but is 1% by mass or more and 5% by mass or less with respect to the total mass of the ink. It is preferably 1% by mass to 4% by mass, more preferably 1% by mass to 3% by mass. When the amount of the alkanediol having 7 or more carbon atoms is within the above range, the fixability of the droplets is improved particularly when the amount is not lower than the lower limit. Further, since the amount of the slightly water-soluble alkanediol is in the above range, the initial viscosity of the ink does not become too high because the upper limit is not exceeded, and the oil layer (for example, carbon (Separation of alkanediol of several 7 or more) can be suppressed, which is preferable from the viewpoint of storage stability of the coating solution.

1.5. Surfactant The ink according to this embodiment contains a surfactant. As a recording medium, it is possible to adjust bleeding by using a surfactant on a surface with a fiber layer that accepts ink, such as plain paper, so that an image expressing excellent fine lines can be realized. Can do. In particular, even when an ink low-absorbing or non-absorbing recording medium is used, the ink droplets are likely to spread on the recording medium and the fixability of the droplets is good. It is possible to reduce the occurrence of aggregation unevenness and the occurrence of muscle unevenness.

  In addition, the surfactant can act synergistically in combination with the above-described alkanediol having 7 or more carbon atoms to further improve the fixability of the droplets, and the unevenness of aggregation and the unevenness of streaks can be achieved. Can be effectively suppressed.

  As the surfactant, a polyorganosiloxane-based surfactant can be suitably used. When an image is formed, the wettability to the surface of the recording medium can be enhanced and the ink permeability can be enhanced.

  Commercially available polyorganosiloxane surfactants may be used, for example, BYK-347 (by Big Chemie), BYK-348 (by Big Chemie), BYK-349 (by Big Chemie). BYK-3550 (manufactured by Big Chemie Co., Ltd.), BYK-UV3510 (manufactured by Big Chemie Co., Ltd.) and the like can be used.

  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 possible to further improve the fixability of the droplets by using a 1Hz dynamic surface tension of the aqueous solution of 26 mN / m or less. Therefore, it is particularly preferable. 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.), etc. Can be used.

  Further, as the polyorganosiloxane surfactant, specifically, one or more compounds represented by the following general formula (5) can be included.

  In the compound of the following general formula (5), R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 11, m represents an integer of 2 to 50, and n represents an integer of 1 to 5. It is preferable to comprise one or more compounds, or in the compound of the following general formula (5), 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 more preferably 1 type or 2 types or more of compounds which are integers of 1 to 5.

  In the compound of the following general formula (5), 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 following formula (5), R is a methyl group, a is an integer of 6 to 18, m is 0 to 4, and n is 1 or 2, It is preferable to include a compound, or R includes a methyl group, a is an integer of 6 to 18, m is 0, and n is 1 or 2 or more. It is more preferable that By using such a specific organopolysiloxane-based surfactant, even when recording on a non-ink-absorbing or low-absorbing recording medium as the recording medium, there is more aggregation unevenness on the recording medium. Improved.

（式中、Ｒは水素原子またはメチル基を表し、ａは２〜１８の整数を表し、ｍは０〜７０の整数を表し、ｎは１〜８の整数を表す。）

(In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 18, m represents an integer of 0 to 70, and n represents an integer of 1 to 8.)

  In the compound of the general formula (5), the aggregation unevenness may be further improved by using a compound in which R is a methyl group. In addition, in the compound of the above formula (5), the unevenness of muscle may be further improved by using a compound in which R is a hydrogen atom.

  In the compound of the above formula (5), a high-quality coat in which aggregation unevenness and stripe unevenness are further improved by appropriately adjusting the blending ratio of the compound in which R is a methyl group and the compound in which R is a hydrogen atom. A layer can be obtained, and it is effective as a regulator when the fluidity varies depending on the amount of resin.

  The polyorganosiloxane surfactant is preferably contained in an amount of 0.01 to 1.0% by mass, more preferably 0.05 to 0.50% by mass, based on the total mass of the ink. In particular, when the surfactant in which R in the formula (5) is a hydrogen group is used, it is contained more than in the case of using the surfactant in which R in the formula (5) is a methyl group. It is preferable to reduce the amount from the viewpoint of uneven aggregation. By containing 0.01 to 0.1% by mass of a surfactant in which R in the formula (5) is a hydrogen group, water repellency is exhibited and bleeding can be adjusted.

  To the ink according to the present embodiment, other surfactants, specifically, acetylene glycol surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like may be further added.

  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.).

  Of these, commercially available products can be used as the fluorosurfactant, and examples thereof include 251 and 208G (manufactured by Neos).

1.6. (Poly) oxyalkylene glycol The ink according to this embodiment may contain (poly) oxyalkylene glycol.

  The (poly) oxyalkylene glycol can be preferably obtained by addition polymerization of ethylene oxide and / or propylene oxide. According to a preferred aspect of the present invention, more preferably, one or more selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol, Preferably, it is one or more selected from the group consisting of triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol. According to a preferred embodiment of the present invention, the (poly) oxyalkylene glycol is more preferably (poly) propylene glycol. The (poly) propylene glycol is not particularly limited, but tripropylene glycol (CAS No. 24800-44-0) is more preferable from the viewpoint of low hygroscopicity.

  The (poly) oxyalkylene glycol may be appropriately determined as long as ink unevenness and streaks can be efficiently suppressed, but is contained in an amount of 1.5 to 18.0% by mass with respect to the total mass of the ink. Is more preferable, and 1.5 to 6.0 mass% is more preferable. By making the amount of (poly) oxyalkylene glycol within the above range, it is preferable that the amount of (poly) oxyalkylene glycol is not lower than the lower limit in particular, because drying of the ink can be suppressed and the fluidity of the waste ink can be maintained. In addition, by setting the amount of (poly) oxyalkylene glycol within the above range, the initial viscosity of the ink does not become excessively high without exceeding the upper limit, and is preferable from the viewpoint of the storage stability of the inkjet ink. This is preferable from the viewpoint of gloss since the hydroxycarboxylic acid ester having a number of 6 or less is prevented from being incompatible with the adhered ink after selectively evaporating early.

  In addition, (poly) oxyalkylene glycol is difficult to dry even when left at high temperature and low humidity, so that it is possible to improve the clogging recovery of the nozzle in an open environment with a relative humidity of 15% RH at 50 ° C. Also have.

1.7. Water The ink according to this embodiment contains water. 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.

1.8. Other Components The ink according to this embodiment may contain components other than those described above. Hereinafter, components that can be added to the ink according to the present embodiment will be described.

  The crystalline carbohydrate is not particularly limited as long as the effect of the present invention is exhibited, but one or two selected from the group consisting of maltitol, sorbitol, xylitol, erythritol, trehalose, isotrehalose, neotrehalose, and sucrose. The above is preferable, and one or more selected from the group consisting of trehalose, isotrehalose, neotrehalose, and sucrose are more preferable. In addition, one or more monosaccharides and disaccharides selected from the group consisting of maltose, maltitol, sorbitol, xylitol, erythritol, trehalose, isotrehalose, neotrehalose, and sucrose, and these sugars, It may be a trisaccharide or more combined with another saccharide.

  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 95 RH% or less. Therefore, when trehalose comes into contact with water, it absorbs water and becomes a gel, but in a normal environment (20 ° C., about 45 RH%), it does not exhibit hygroscopicity and can exist stably. Moreover, it is preferable from a viewpoint which does not react with amino group containing resin.

  Isotrehalose, neotrehalose, and sucrose 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.

  According to a preferred embodiment of the present invention, the crystalline carbohydrate may be appropriately determined as long as the above-described effect is exhibited, but is contained in an amount of 6.0 to 36.0% by mass with respect to the total mass of the ink. It is preferable that it is 6.0-18.0 mass% more preferably.

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

  The ink according to the present embodiment further includes a nozzle clogging preventive agent, an antiseptic / antifungal agent, 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. Can be contained.

  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 hydroxide (tetramethylammonium etc.), carbonates such as potassium carbonate, sodium carbonate, lithium carbonate and other phosphates, or 2-pyrrolidone, urea, thiourea, tetramethyl Examples include ureas such as urea, allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret, and tetramethylbiuret, and L-ascorbic acid and salts thereof.

  Further, the ink according to the present embodiment 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.

  Moreover, the ink according to the present embodiment may include a crosslinking catalyst such as organic titanium or organic zirconium.

  The ink according to the present embodiment may contain a water-soluble alkanediol. In this specification, water-soluble means that the solubility in water (the amount of solute with respect to 100 g of water) at 20 ° C. is 10.0 g or more, and poorly water-soluble means that it is soluble in water. It means that the solubility (the amount of solute with respect to 100 g of water) is less than 1.0 g.

  The water-soluble alkanediol is a bi-terminal or single-terminal alkanediol. The water-soluble alkanediol is preferably an alkanediol having 3 to 6 carbon atoms. The water-soluble alkanediol is preferably a water-soluble hexanediol such as 1,2-hexanediol or 1,6-hexanediol, 2-methyl-1,3-propanediol, or 3-methyl-1,5. -Pentanediol is exemplified, and among these, 1,2-hexanediol or 3-methyl-1,5-pentanediol is preferable. Further, 1,6-hexanediol may be used from the viewpoint of excellent discharge stability at a high frequency. Here, the both-end alkanediol means an alkanediol having a hydroxyl group at both ends of the alkyl chain main chain, and the one-end alkanediol means an alkane having a hydroxyl group at one end of the main chain of the alkyl chain. Means diol. Thus, for example, 1,6-hexanediol and 3-methyl-1,5-pentanediol are both terminal alkanediols and 1,2-hexanediol is a one-terminal alkanediol.

  Furthermore, according to a preferred aspect of the present invention, the content ratio of the alkanediol having 7 or more carbon atoms and the water-soluble alkanediol is preferably 1: 1 to 10: 1, more preferably Each is 2: 1 to 4: 1. By being in this range, it may be possible to suppress the occurrence of uneven aggregation when the droplet landing time interval is short.

  Further, according to a preferred embodiment of the present invention, the amount of water-soluble alkanediol added may be appropriately determined as long as the aggregation unevenness and the stripe unevenness can be efficiently suppressed. 1-4.0 mass% is preferable, More preferably, it is 0.5-3.0 mass%, More preferably, it is 0.5-1.0 mass%. When the amount of the water-soluble alkanediol is in the above range, the occurrence of unevenness in the muscles can be sufficiently suppressed particularly when the amount is not lower than the lower limit. In addition, when the amount of the water-soluble alkanediol is within the above range, the initial viscosity of the ink does not become too high because the upper limit is not exceeded, and separation of the oil layer is effectively performed in a normal ink storage state. This is preferable from the viewpoint of ink storage stability. In addition, by including 1,2-hexanediol, which is a preferred embodiment of the water-soluble alkanediol, in an amount of 0.1 to 4.0% by mass with respect to the entire composition, the quality is further improved without unevenness of muscles and aggregation. An image can be realized, and it is effective as an adjusting agent when the discharge performance varies depending on the pigment type and the resin amount.

  The water-soluble alkanediol can be preferably used because it can swell and dissolve the dispersion resin and adjust the dispersion state when producing a color ink dispersion described later.

2.1. Color ink dispersion Hereinafter, each component of the color ink dispersion contained in the color ink according to the present embodiment will be described.

2.1.1. Colorant As the color ink used together with the above ink, any colorant of dyes and pigments can be used, but pigments can be preferably used from the viewpoint of light resistance and water resistance. The colorant preferably includes the pigment and the following dispersant capable of dispersing the pigment in the ink, and is preferably included in an anionic dispersion.

  As the pigment, inorganic pigments and organic pigments can be used, and each can be used alone or in combination. Organic pigments 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, etc.), dye chelates (eg basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, etc., contact method, furnace method, thermal Carbon black produced by a known method such as a method can be used.

  Specific examples of the pigment are appropriately given according to the type (color) of the color ink to be obtained. For example, as a pigment for yellow ink, 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, 129 and 180. Examples of the pigment for magenta ink 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 pigments for cyan ink 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 black ink 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). 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, manufactured by Columbian) and the like.

  Examples of white pigments for white ink include metal oxides, barium sulfate, and calcium carbonate. Examples of the metal oxide include titanium dioxide, zinc oxide, silica, alumina, and magnesium oxide. The white pigment includes particles having a hollow structure, and the particles having a hollow structure are not particularly limited, and known ones can be used. As the particles having a hollow structure, for example, particles described in specifications such as US Pat. No. 4,880,465 can be preferably used.

  The volume-based 50% cumulative particle size (hereinafter referred to as “average particle size”) of the white pigment is preferably 30 nm or more and 600 nm or less, and more preferably 200 nm or more and 400 nm or less. The average particle diameter of the white pigment can be measured by a particle size distribution measuring apparatus using a laser diffraction scattering method as a measurement principle. Examples of the particle size distribution measuring apparatus include a particle size distribution meter (for example, “Microtrack UPA” manufactured by Nikkiso Co., Ltd.) having a dynamic light scattering method as a measurement principle.

  The concentration of the pigment contained in the color ink is not particularly limited because it may be adjusted to an appropriate pigment concentration (content) when the ink is prepared. For example, the solid content concentration of the pigment is 1.0 to 30.0. It can be made into the mass%.

2.1.2. Resin dispersant The color ink contains at least one resin selected from the group consisting of a copolymer resin containing a hydrophobic monomer and a hydrophilic monomer as constituent monomers, an oxyethyl acrylate resin, a urethane resin, and a fluorene skeleton-containing resin. Preferably, it comprises at least one resin selected from the group consisting of oxyethyl acrylate resins and fluorene skeleton-containing resins. These resin dispersants are adsorbed on the pigment to improve dispersibility.

  Moreover, when the said resin dispersing agent has a carboxyl group, it is easy to carry out a crosslinking reaction (formation of an amide ester bond) with the oxazoline group which exists in the above-mentioned coat layer. Therefore, when the resin dispersant has a carboxyl group, the water resistance of an image formed with the color ink may be remarkably improved.

  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 Decyl 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, Nylphenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4- Butanediol 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, Tetraethylene glycol dimethacrylate, polyethylene glycol Diacrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triacrylate, Mention may be made of trimethylolpropane 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.

  The copolymer resin of the hydrophobic monomer and the hydrophilic monomer is styrene from the viewpoint of achieving both color image glossiness, bronzing prevention, and ink storage stability and forming a color image having further glossiness. -(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 It is preferably at least one of a styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer resin and 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 color image glossiness, bronzing prevention, and ink storage stability while being able to form a color image having further excellent glossiness. More preferably, it is 100-250.

  The weight-average molecular weight (Mw) of the copolymer resin is preferably 2 from the viewpoint of achieving both color image glossiness, bronzing prevention, and ink storage stability while being able to form a color image with even higher glossiness. 3,000 to 30,000, more preferably 2,000 to 20,000.

  The glass transition temperature (Tg; measured in accordance with JISK6900) of the copolymer resin is from the viewpoint of achieving a color image that is excellent in glossiness and bronzing prevention of color images, and storage stability of ink and that is further excellent in glossiness. The temperature is preferably 30 ° C. or higher, and more preferably 50 to 130 ° C.

  The copolymer resin may be adsorbed to the pigment or separated from the pigment in the pigment dispersion, and achieves both glossiness of color images, prevention of bronzing, and storage stability of ink, and further glossiness. From the viewpoint of forming a color image with excellent properties, 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). More preferably it is. 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 compatible with 100 parts by mass of the pigment from the viewpoint of achieving a color image having both glossiness of a color image, prevention of bronzing, and ink storage stability and excellent glossiness. The amount 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 resin 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 clogging recovery.

  Although the said oxyethyl acrylate-type resin will not be specifically limited if it is resin which has an oxyethyl acrylate frame | skeleton, Preferably it is a compound represented by following General formula (6). The compound represented by the following general formula (6) 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. No. 72009-86-0 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%.

（上記式（６）中、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。）

(In the above formula (6), R1 and / or R3 is a hydrogen atom or a methyl group, and R2 is an alkyl group or an aryl group. N is an integer of 1 or more.)

  The compound represented by the above formula (6) is preferably nonylphenoxy polyethylene glycol acrylate or polypropylene glycol # 700 acrylate.

  The content of the oxyethyl acrylate-based resin is compatible with the initial viscosity of the ink and the storage stability of the ink, suppresses aggregation spots, and forms a color image with excellent filling properties. Preferably it is 10-40 mass parts with respect to a part, 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 and the storage stability of the ink, and is capable of recovering clogging. From this point of view, 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 5000 to 8000 from the viewpoint of achieving both the initial viscosity of the ink and the storage stability of the ink. is there. Mn is measured by, for example, GPC (gel permeation chromatography).

The oxyethyl acrylate-based resin has the maximum particle size of the copolymer resin from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of ink while forming a color image with further excellent glossiness. Is preferably 0.3 μm or less, and the average particle size is more preferably 0.2 μm or less (more preferably 0.1 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-based resin is 100 parts by mass of the pigment from the viewpoint of achieving color image glossiness, bronzing prevention, and ink storage stability while being able to form a color image with even higher glossiness. On the other hand, it is preferably 20 to 50 parts by mass, and more preferably 20 to 40 parts by mass.

  In addition, by using a urethane-based resin as the resin dispersant, the color ink can form a color image having both glossiness of the color image, prevention of bronzing, and storage stability of the ink and excellent glossiness. The urethane-based resin is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound, but in the present invention, it is preferably a resin having an acidic group which is a carboxyl group. 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 while being able to form a color image having further excellent glossiness. More preferably, it is 20-100. The acid value is the mg amount of KOH necessary for neutralizing 1 g of the resin.

  The weight-average molecular weight (Mw) before crosslinking of the urethane resin is preferably from the viewpoint of achieving a color image having excellent glossiness while being compatible with glossiness of color images, prevention of bronzing, and storage stability of ink. Is 100 to 200,000, more preferably 1000 to 50,000. Mw is measured by GPC (gel permeation chromatography), for example.

  The glass transition temperature (Tg; measured in accordance with JISK6900) of the urethane resin is from the viewpoint of achieving a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink and excellent glossiness. Preferably it is -50-200 degreeC, More preferably, it is -50-100 degreeC.

  The urethane resin preferably has a carboxyl group. The carboxyl group easily undergoes a crosslinking reaction (formation of an amide ester bond) with the oxazoline group present in the above-mentioned coat layer. Therefore, if the urethane resin has a carboxyl group, the water resistance of an image formed with the color ink may be remarkably improved.

  The content of the urethane-based resin is 100% by mass with respect to 100 parts by mass 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 ink and excellent glossiness. The amount is preferably 20 to 50 parts by mass, and more preferably 20 to 40 parts by mass.

  Furthermore, in the present invention, a fluorene skeleton-containing resin can also be used as the resin dispersant. Use is more preferable because it reduces the initial viscosity of the ink and is excellent in storage stability at high temperatures.

  The fluorene skeleton-containing resin is obtained by a reaction between a polyol component containing a first diol containing a fluorene skeleton and a second diol having a hydrophilic group, and a polyisocyanate component containing a polyisocyanate compound. Can do.

  The fluorene skeleton-containing resin preferably has a carboxyl group for the same reason as the urethane resin.

  More specifically, as the first diol containing a fluorene skeleton, for example, 9,9-bis (4- (hydroxymethoxy) phenyl) fluorene, 9,9-bis (4- (2-hydroxyethoxy)) Phenyl) fluorene, 9,9-bis (4- (3-hydroxypropoxy) phenyl) fluorene, 9,9-bis (4- (4-hydroxybutoxy) phenyl) fluorene, 9,9-bis (4-hydroxyphenyl) ) Fluorene, 9,9-bis (4-hydroxytoluyl) fluorene, 9,9-bis (hydroxyalkyl) fluorene, and the like. In addition, as said 1st diol, you may use a commercial item, For example, bisphenoxyethanol fluorene, bisphenol fluorene, biscresol fluorene (above, brand name; Osaka Gas Chemical Co., Ltd. make) etc. are mentioned.

  These first diols containing a fluorene skeleton may be used alone or in combination of two or more, and preferably 9,9-bis (4- (2-hydroxyethoxy) phenyl) fluorene.

  Moreover, the 1st diol containing a fluorene skeleton can be mix | blended in the ratio of 40-60 mass% with respect to fluorene skeleton containing resin, for example. When the content of the first diol containing a fluorene skeleton is in the above range, the fixing property and transparency are excellent.

  In the present invention, the second diol can have a hydrophilic group. Examples of the hydrophilic group include nonionic groups such as a polyoxyethylene group and ionic groups such as a carboxyl group, a sulfonyl group, a phosphate group, and a sulfobetaine group.

  More specifically, as the second diol having a carboxyl group, for example, 2,2-dimethylolacetic acid, 2,2-dimethylollactic acid, 2,2-dimethylolpropionic acid (2,2-bis (hydroxymethyl)) Propionic acid), 2,2-dimethylolbutanoic acid, 2,2-dimethylolbutyric acid, dihydroxylcarboxylic acids such as 2,2-dimethylolvaleric acid, and diaminocarboxylic acids such as lysine and arginine.

  Examples of the second diol having a sulfonyl group include N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid, 1,3-phenylenediamine-4,6-disulfonic acid, and diaminobutanesulfone. Examples include acid, 3,6-diamino-2-toluenesulfonic acid, and 2,4-diamino-5-toluenesulfonic acid.

  Examples of the second diol having a phosphate group include 2,3-dihydroxypropylphenyl phosphate.

  Examples of the second diol having a betaine structure-containing group include a sulfobetaine group-containing compound obtained by a reaction between a tertiary amine such as N-methyldiethanolamine and 1,3-propane sultone.

  Furthermore, examples of the second diol include alkylene oxide modified products in which an alkylene oxide such as ethylene oxide or propylene oxide is added to the second diol.

  In addition, these second diols may be used singly or in combination of two or more, preferably, a second diol having a carboxyl group, for example, 2,2-dimethylolpropionic acid.

  Moreover, the 1st diol which has a hydrophilic group can be mix | blended in the ratio of 5-15 mass% with respect to fluorene skeleton containing resin, for example. When the content of the first diol containing a fluorene skeleton is in the above range, the fixing property and transparency are excellent.

  The second diol can be blended so that the acid value of the fluorene skeleton-containing resin is 10 to 130 KOHmg / g, preferably 20 to 60 KOHmg / g. When the acid value of the fluorene skeleton-containing resin is in the above range, the dispersion stability of the pigment is excellent.

  In addition, the fluorene skeleton-containing resin may contain a polyol compound as necessary. The polyol compound is a compound having two or more hydroxyl groups, and examples thereof include a low molecular weight polyol and a high molecular weight polyol.

  The polyisocyanate compound is a compound having two or more isocyanate groups, preferably a compound having two isocyanate groups, for example, aliphatic polyisocyanate, alicyclic polyisocyanate, araliphatic polyisocyanate, aromatic Polyisocyanate etc. are mentioned.

  Examples of the aliphatic polyisocyanate include hexamethylene diisocyanate and tetramethylene diisocyanate.

  Examples of the alicyclic polyisocyanate include isophorone diisocyanate (3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate), 4,4'-, 2,4'- or 2,2'-dicyclohexylmethane diisocyanate. Or the mixture etc. are mentioned.

  Examples of the araliphatic polyisocyanate include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, 1,3- or 1,4-bis (1-isocyanato-1-methylethyl) benzene or a mixture thereof. Etc.

  Aromatic polyisocyanates include, for example, 4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate or mixtures thereof, 2,4- or 2,6-tolylene diisocyanate or mixtures thereof, Examples thereof include 4'-toluidine diisocyanate and 1,5-naphthalene diisocyanate.

  Moreover, as a polyisocyanate compound, the above-mentioned various polyisocyanate compound multimers (for example, dimers, trimers, etc.), for example, the above-mentioned various polyisocyanate compounds or multimers thereof, and reaction with water. The resulting biuret modified product, the allophanate modified product produced by reaction with alcohol or the above low molecular weight polyol, the oxadiazine trione modified product produced by reaction with carbon dioxide gas, and the reaction with the above low molecular weight polyol. Examples thereof include a modified polyol product to be produced.

  These polyisocyanate compounds may be used singly or in combination of two or more, and preferably include alicyclic polyisocyanates, such as isophorone diisocyanate.

  Then, a polyol component (that is, a first diol containing a fluorene skeleton, a second diol having a hydrophilic group, and a polyol compound if necessary) and a polyisocyanate component (that is, a polyisocyanate compound) are reacted. For example, a known method may be used. For example, the equivalent ratio of the isocyanate group of the polyisocyanate component to the hydroxyl group of the polyol component (NCO / hydroxy group) may be blended at a ratio of 0.4 to 1.0, for example. The ratio is preferably 0.8 to 0.95. Therefore, it can mix | blend with the ratio of 30-45 mass% with respect to fluorene frame | skeleton containing resin, for example. When the content of the first diol containing a fluorene skeleton is in the above range, the fixing property and transparency are excellent.

  In this reaction, the reaction temperature is set to, for example, 40 to 100 ° C. under normal pressure and, if necessary, in a nitrogen atmosphere, and the reaction time is set to, for example, 5 to 24 hours. In this reaction, a reaction solvent or a reaction catalyst can be used as necessary.

  The reaction solvent is a low-boiling solvent inert to isocyanate groups, for example, alcohols such as ethanol and isopropanol, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran, methyl cellosolve, Examples include cellosolves such as ethyl cellosolve, carbitols such as methyl carbitol and ethyl carbitol, and nitriles such as acetonitrile. The amount of reaction solvent used is appropriately determined.

  Examples of the reaction catalyst include known urethanization catalysts such as amine-based, tin-based, and lead-based catalysts. The amount of reaction solvent added is appropriately determined.

  By this reaction, the polyol component and the polyisocyanate component undergo a urethanation reaction, and the fluorene skeleton-containing resin of the present invention can be obtained.

  The fluorene skeleton-containing resin thus obtained has a mass average molecular weight of, for example, a number average molecular weight of 2000 to 40,000 (weight average molecular weight of 3000 to 50,000) as a standard polystyrene conversion value by GPC measurement, and more preferably. Has a number average molecular weight of 2000 to 10,000.

  The fluorene skeleton-containing resin of the present invention is preferably prepared as an aqueous dispersion. For example, when the hydrophilic group of the second diol is an anionic group, the obtained fluorene skeleton-containing resin is The anionic group is neutralized and then dispersed in water.

  Neutralization of an anionic group is, for example, trimethylamine, triethylamine, tri-n-propylamine, tributylamine, triethanolamine, aminomethylpropanol, aminomethylpropanediol, aminoethylpropanediol, trihydroxymethylaminomethane, monoethanol An organic amine such as amine or triisopropanolamine, for example, an inorganic alkali salt such as potassium hydroxide or sodium hydroxide, or a neutralizing agent selected from ammonia or the like is added to the fluorene skeleton-containing resin to form an anion. A salt of a sex group is formed.

  The addition amount of a neutralizing agent can be 0.3-1.0 equivalent per anionic group equivalent, for example.

  Next, in order to disperse the fluorene skeleton-containing resin in water, for example, while stirring the fluorene skeleton-containing resin, water is gradually added thereto, or the water is gradually stirred while being stirred. A fluorene skeleton-containing resin is added. Thereby, an aqueous dispersion of the fluorene skeleton-containing resin is prepared. The stirring is preferably performed using a homomixer or the like so as to impart high shear.

  Although the addition amount of water is suitably determined by the solid content mass of the desired aqueous dispersion of the fluorene skeleton-containing resin, for example, it is 100 to 900 parts by mass, more preferably 200 to 100 parts by mass of the fluorene skeleton-containing resin. It is in the range of ~ 400.

  Thus, an aqueous dispersion of the fluorene skeleton-containing resin in which the fluorene skeleton-containing resin of the present invention is dispersed in water is prepared. The pH of the aqueous dispersion of the fluorene skeleton-containing resin is usually about 7 to 9.

  The aqueous dispersion of the fluorene skeleton-containing resin thus obtained is prepared such that its solid content is, for example, 10 to 50% by mass, preferably 25 to 35% by mass.

  When a reaction solvent is used in the urethanization reaction, after the urethanization reaction is completed or after water dispersion, the reaction solvent is heated at an appropriate temperature, for example, under reduced pressure. Leave.

  The content of the fluorene skeleton-containing resin is 100 parts by mass of the pigment from the viewpoint of achieving both color image fixability, bronzing prevention, and ink storage stability, and a color image that is further excellent in fixability. 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, but it is compatible with glossiness of color images, prevention of bronzing, and storage stability of ink. In addition, from the viewpoint of being able to form a color image having further excellent glossiness, it is more preferably 1 / 1.5 to 1.5 / 1.

  The mass ratio (the former / the latter) of the solid content of the pigment and the solid content of the copolymer resin and the fixing pigment dispersant achieves both color image gloss, bronzing prevention, and ink storage stability. In addition, from the viewpoint of forming a color image having further excellent 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 above-described surfactant is also added to the ink so as to function as a surfactant.

3. Ink Production Method The ink according to the present embodiment can be produced by dispersing and mixing the above components by an appropriate method. After sufficiently stirring each of the above components, the target ink can be obtained by performing filtration in order to remove coarse particles 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.

3.1. Ink physical properties The viscosity of the ink according to this embodiment at 20 ° C. is preferably 3 mPa · s or more and 10 mPa · s or less, and more preferably 3 mPa · s or more and 6 mPa · s or less. If the viscosity at 20 ° C. is within the above range, the ink can be suitably used for an ink jet recording apparatus because it can be discharged in an appropriate amount from the nozzle and can further reduce the occurrence of flight bending or scattering. The viscosity of the ink can be measured by keeping the temperature of the ink at 20 ° C. using a vibration viscometer VM-100AL (manufactured by Yamaichi Electronics Co., Ltd.).

  Further, the surface tension at 20 ° C. of the ink according to the present embodiment is preferably 26 mN / m or less, and more preferably 21 mN / m or more and 26 mN / m or less. If the surface tension at 20 ° C. of the ink for inkjet is within the above range, the ink droplets adhering to the recording medium will have excellent fixability, and therefore effectively suppress the unevenness of aggregation, unevenness of streaks, etc. Can do.

3.2. Ink Set The ink set according to an embodiment of the present invention includes a dispersion containing at least a colorant. Examples of the color ink include yellow ink, magenta ink, cyan ink, black ink, and white ink.

4). Inkjet Recording Method An inkjet recording method according to an embodiment of the present invention is an inkjet recording method using an inkjet recording apparatus having a head, and includes an ejection step of ejecting ink droplets, and the droplets on a recording medium. And a dot forming step of forming dots formed by the droplets, and a step of forming an image on the recording medium by repeating the discharging step and the dot forming step a plurality of times.

  First, an ink jet recording apparatus used in the ink jet recording method according to the present embodiment will be described.

4.1. Inkjet recording apparatus An inkjet recording apparatus according to an embodiment of the present invention includes a head including a nozzle row including a plurality of nozzle holes. The ink jet recording apparatus according to this embodiment will be described with reference to FIGS. In each drawing used for the following description, the scale of each member is appropriately changed to make each member a recognizable size.

  FIG. 1 is a block diagram showing a recording system in which a computer 90 is connected to the inkjet recording apparatus 1.

  FIG. 2 is a schematic perspective view showing the configuration of the inkjet recording apparatus 1.

  The ink jet recording apparatus 1 is an apparatus that records (forms) a recorded matter on a recording medium P by an ink jet method. The controller 10 is a control unit for controlling the ink jet recording apparatus 1. The interface unit 11 (I / F) is for transmitting and receiving data between the computer 90 and the inkjet recording apparatus 1. The CPU 12 is an arithmetic processing device for controlling the entire inkjet recording apparatus 1. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit by the unit control circuit 14. The detector group 60 monitors the situation in the ink jet recording apparatus, and the controller 10 controls each unit based on the detection result.

  The transport unit 20 transports the recording medium from the upstream side to the downstream side in the direction in which the recording medium P continues (transport direction, X direction in the figure). By rotating the transport roller 21 by a motor, the recording medium before recording is supplied to the ink-jet ink application region.

  The carriage unit 30 reciprocates the head in the moving direction (width direction of the recording medium, Y direction in the figure). The carriage unit 30 includes a carriage 31 on which the head 41 is mounted, a carriage moving mechanism 32 for reciprocating the carriage, and an ink cartridge 33.

  The ink cartridge 33 is filled with the above-described ink or color ink. The ink cartridge 33 is not limited to the one mounted on the carriage 4 as in the present embodiment, but instead is one that is mounted on the housing side of the printer 1 and supplied to the head 41 via the liquid supply tube. There may be.

  The head unit 40 has a head 41 provided on the carriage 31. On the lower surface of the head 41, nozzle holes for ejecting ink and color ink are provided. The configuration of the head 41 (arrangement of nozzle rows) will be described later.

  The drying unit 50 is for drying ink and color ink applied to the recording medium. As the drying unit, for example, a platen heater, a warm air heater, an IR heater or the like having a heating function is used. A blower or the like that does not have a heating function is used.

  FIG. 3 is a schematic view showing the lower surface of the head 41. The illustrated configuration is shown for reference, and the head 41 may have a different configuration.

  The head 41 includes a plurality of nozzle rows. In the example of FIG. 3, five nozzle rows are arranged along the conveyance direction of the recording medium P. The five nozzle rows are a black nozzle row (K), a cyan nozzle row (C), a magenta nozzle row (M), a yellow nozzle row (Y), and a white nozzle row (W). The black nozzle row, cyan nozzle row, magenta nozzle row, yellow nozzle row, and white nozzle row are nozzle rows (color nozzle rows) that discharge color ink for recording a color image (colored layer).

  Each nozzle row is formed by arranging a plurality of nozzle holes. In the example of FIG. 3, each nozzle row includes a plurality of nozzle holes arranged along the conveyance direction of the recording medium P. Each nozzle row is composed of 180 nozzle holes. The 180 nozzle holes in each nozzle row are arranged along the transport direction at a nozzle pitch N of 1/180 inch intervals (that is, L in the figure is 1 inch). By intermittently ejecting ink (or ink) from a certain nozzle row, each time the carriage 31 moves once in the movement direction (for each pass), a large number of dot rows are formed at 1/180 inch intervals. Will be recorded. The interval D of dots recorded on the recording medium P may be expressed as “N ÷ k” using the nozzle pitch N and an integer k representing the number of passes. For example, when recording an image with a resolution of 720 dpi, since D is 1/720 inch, k = 4 (four passes).

  The ink jet recording apparatus 1 is a so-called serial type ink jet recording apparatus. A serial type ink jet recording apparatus has a head mounted on a carriage that moves in a predetermined direction, and ejects droplets onto a recording medium when the head moves as the carriage moves.

  Although the serial type ink jet recording apparatus is exemplified as the ink jet recording apparatus according to the present embodiment, the present invention is not limited thereto, and for example, a line type ink jet recording apparatus may be used. A line-type ink jet recording apparatus is a device in which a head is formed wider than the width of a recording medium and droplets are ejected onto the recording medium without moving the head.

  In the line-type ink jet recording apparatus, each nozzle row is arranged along the width direction of the recording medium, and a plurality of nozzle holes constituting the nozzle row are arranged along the width direction of the recording medium. At this time, when each nozzle row is composed of 180 nozzle holes, the nozzle rows are arranged along the width direction of the recording medium at a nozzle pitch of 1/180 inch interval. By ejecting ink (or ink) once from a certain nozzle row, dots are arranged at an interval of 1/180 inch, and an image is recorded with a resolution of 180 dpi. That is, when a line type ink jet recording apparatus is used, the image resolution in the width direction of the recording medium is equal to the number of nozzle holes arranged along the width direction of the recording medium. In the above-described line type ink jet recording apparatus, when an image is recorded with a resolution of 180 dpi or more, for example, when an image is recorded with a resolution of 720 dpi, four nozzle arrays each including 180 nozzle holes are arranged. By using the column, an image of 720 dpi can be recorded. Therefore, the dot interval D can be expressed as “N ÷ l” using the nozzle pitch N and the number of nozzle rows l. In the above example, since N = 1/180 and l = 4, the dot interval D is 1/720.

4.2. Recording Method The ink jet recording method according to the present embodiment is performed using an ink jet recording apparatus, and includes an ejection step of ejecting the ink droplets from the nozzle holes, and attaching the ink droplets to a recording medium. A dot forming step of forming dots made of droplets, and a step of forming a color image on the recording medium by repeating the ejection step and the dot forming step a plurality of times. Hereinafter, an ink jet recording method using the ink jet recording apparatus 1 will be specifically described.

  The ink jet recording apparatus 1 alternately repeats an operation (pass) for moving the carriage 31 in the moving direction and a transport operation. At this time, when performing each pass, the controller 10 controls the carriage unit 30 to move the carriage 31 in the moving direction, and also controls the head unit 40 so that ink is discharged from a predetermined nozzle hole of the head 41. A droplet is ejected, and the droplet is attached to the recording medium P. Further, the controller 10 controls the transport unit 20 to transport the recording medium P in the transport direction by a predetermined transport amount during the transport operation.

  By repeating the pass and the transport operation, the region to which a plurality of droplets (dots) are attached is gradually transported toward the drying unit 50. Then, at a position facing the drying unit 50, the droplets attached to the recording medium are dried to complete the coat layer. Thereafter, the completed recorded matter may be wound up in a roll shape by a winding mechanism (not shown) or conveyed by a flat bed mechanism (not shown).

  The color image drying process by the drying unit is not an essential process, but is effective from the viewpoint of further improving the water resistance of the color image. The timing for performing the drying step is not particularly limited. For example, the drying step may be performed simultaneously with the color image forming step, before, after, or before and after the color image forming step. Moreover, you may perform several drying processes (for example, arbitrary combinations in the said example). When the drying process is performed after the color image forming process, the winding mechanism or the flat bed mechanism described above may be the drying process.

  The means for the drying step is not particularly limited, but it is preferable to dry the droplets by heating. The heating in the drying step includes not only a mode in which the droplets themselves are directly heated by hot air, an IR heater, etc., but also a mode in which the droplets are indirectly heated via a recording medium, such as the drying unit 50 described above. It is.

  When forming a coat layer having a dot interval of 300 dpi or more in the image resolution in the nozzle array arrangement direction (width direction of the recording medium P in the example of FIG. 1) using a serial type ink jet recording apparatus, It is preferable that the diameter of the adhered dots is larger than the dot interval. In addition, when forming a coat layer having a dot interval with an image resolution of 300 dpi or more in the nozzle hole arrangement direction using a line-type ink jet recording apparatus, the diameter of the dots attached to the recording medium must be larger than the dot interval. Is preferred.

  In this way, a sufficiently coated recording medium can be obtained with a smaller number of passes or a smaller number of nozzle rows.

  Furthermore, even when a high-quality coat layer (image resolution of 300 dpi or more) is formed with a larger number of passes or a larger number of nozzle rows, the gap between dots is small and the coat layer is sufficiently covered. A recording medium can be obtained with a uniform film thickness.

  As shown in the experimental results of Examples described later, the ink for ink jet according to the present embodiment has fewer passes if the mass of ink droplets ejected in the ejection process is set to 1 ng to 15 ng per droplet. If the number of or fewer nozzle rows is sufficient and the number of passes is increased or the number of nozzle rows is increased, a well-coated and uniform film can be obtained in a multilayer state. Therefore, it is preferable from the viewpoint that the swelling and dissolution of the ink can be easily maintained constant and the fixing ability can be adjusted uniformly.

  Examples of the recording medium used in the inkjet recording method according to the present embodiment include non-ink-absorbing or low-absorbing recording media.

  Examples of non-ink-absorbing recording media include plastic films that do not have an ink absorbing layer, those that are coated with plastic on a substrate such as paper, and those that have a plastic film adhered thereto. . Examples of the plastic here include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, and polypropylene.

  Examples of the ink-absorbing recording medium include coated paper having a coating layer for receiving oil-based ink on the surface, and examples include printing paper such as art paper, coated paper, and matte paper. .

  In addition to the above recording medium, a non-ink-absorbing or low-absorbing recording medium such as metal or glass may be used.

5. EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these examples.

5.1. Preparation of ink After mixing and stirring each component according to the composition of Tables 1 to 5, ink was prepared by filtering with a 10 μm membrane filter. In addition, each component shown to Tables 1-5 is as follows.
・ 1,2-octanediol (alkanediol having 7 or more carbon atoms)
・ Methyl 2-hydroxyisobutanoate (hydroxycarboxylic acid ester having 6 or less carbon atoms, CAS No. 2110-78-3)
・ Tripropylene glycol (polyoxyalkylene glycol)
Fluorene-based resin (carboxylic acid group-containing resin having a fluorene skeleton, acid value 40, solid content 30%, CAS No. 9111-03-27-0)
WS-700 (trade name “Epocross WS-700”, main chain: acrylic, weight average molecular weight: 40,000, oxazoline group amount: 4.5 mmol / g (solid content conversion), solid content 25%)
WS-500 (trade name “Epocross WS-500”, main chain: acrylic, weight average molecular weight: 70,000, oxazoline group amount: 4.5 mmol / g (solid content conversion), solid content 39%)
・ Triethanolamine (organic amine)
・ Silicon-based Surf. (Polyorganosiloxane-based surfactant. In the above formula (2), 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. And 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, and n is an integer of 1 to 2 in the above formula (2) And a compound in which R is a methyl group is larger than a compound in which R is a hydrogen atom)
・ Ion exchange water

5.2. Preparation of color ink The color ink is prepared by mixing and stirring the components shown in Table 5 and preparing a pigment dispersion by dispersion treatment, and then mixing and stirring the components shown in Tables 1 to 4 to form a 10 μm membrane. It was prepared by filtering through a filter.

  The color ink thus obtained is used as a color ink set including a yellow ink (Y), a magenta ink (M), a cyan ink (C), a black ink (K), and a white ink (W). It was.

In addition, each component shown in Table 5 is as follows.
Pigment Yellow 180 (yellow pigment, volume average particle size 120 nm)
Pigment Magenta 122 (magenta pigment, volume average particle size 120 nm)
Pigment Blue 15: 3 (cyan pigment, volume average particle size 120 nm)
Pigment Black 7 (black pigment, volume average particle size 120 nm)
・ Titanium dioxide (white pigment, volume average particle size 240 nm)
Styrene acrylic acid resin (weight average molecular weight 16500, acid value 240, Tg 100 ° C.)

5.3. Evaluation Test The ink and color ink obtained as described above were filled in an ink cartridge of an ink jet printer (trade name “PX-G5100”, manufactured by Seiko Epson Corporation).

  In conducting the following Evaluation Test 1 to Evaluation Test 5, first, the average ink mass of ink ejected from the nozzle holes of the printer and the droplets ejected with ink (hereinafter also simply referred to as “average ink mass”). .) Was adjusted. Specifically, droplets were ejected from a predetermined nozzle 10 times, and the ink mass was measured with a precision balance. The average ink mass was calculated by dividing the measured value obtained by the total number of ink droplet ejections (the product of the number of ejections per nozzle and the number of nozzles). Based on the obtained value, the ejection waveform (driving voltage, etc.) for ejecting ink droplets was adjusted so that the average ink mass became a desired value.

  Table 6 shows recording conditions in evaluations 1 to 4. In all evaluations, the vertical resolution × horizontal resolution per scan (one pass) was set to 360 × 720 dpi. In addition, the image resolution and duty in Table 8 and Table 9 are expressed by the following formulas (7) and (8), respectively.

Image resolution (dpi) = (vertical resolution per scan × horizontal resolution) × (number of scans) (7)
(In Expression (7), the image resolution is the resolution per unit area.)

  The duty is defined by the following formula (8).

Duty (%) = (actual recording dot number) / (image resolution) × 100 (8)
(In Expression (8), “actual recording dot number” is the actual number of recording dots per unit area.)

Further, the average ink mass in Table 5 was set in advance based on the ejection conditions corresponding to the Duty 100% image having the image resolution shown in Table 5. For example, in the condition 1A, the ejection waveform was adjusted to be 7.26 mg / inch ² (= 1440 × 720 × 7).

5.3.1. Image evaluation test (1) Evaluation 1 <Agglomeration and filling>
Using the printer, a solid image of 100% duty was recorded on a recording medium MACtac vinyl chloride sheet JT5829R) under the recording conditions of Condition 1A and Condition 1B in an environment of 20 ° C. Thus, about the obtained solid image (coat layer), the generation | occurrence | production of the nonuniformity of the aggregation and the stripe unevenness was evaluated. The evaluation criteria are as follows, and the evaluation results are shown in Tables 1 to 4.
A: No streak is generated due to aggregation and poor filling.
B: Generation of streaks due to aggregation and poor filling.

(2) Evaluation 2 <Fixability of image>
Using the printer, a solid image with a duty of 100% was recorded on a recording medium MACtac vinyl chloride sheet JT5829R) under a recording condition of Condition 3 in an environment of 20 ° C. The recorded matter thus obtained was placed on a hot plate at 100 ° C. and heated for 15 minutes to obtain an evaluation sample. Then, using a Gakushin type friction fastness tester (AB-301 COLOR FASTNESS RUBING TESTER, TESTER SANGYO, LTD) The fixability was evaluated. The evaluation criteria are as follows, and the evaluation results are shown in Tables 1 to 4.
A: Even after 20 times, the recorded image is not peeled off.
B: The recorded image is not peeled after 10 times, but the printed image is peeled after 20 times.
C: The recorded image is peeled after 10 times.

(3) Evaluation 3 <Clogging recovery property>
Using the printer, it was confirmed that all nozzles were ejecting normally. Then, the nozzle face was opened from the cleaning cap by moving the head to the ink replacement position. The printer body in this state was left in a 40 ° C. environment for 12 hours. After leaving, the cleaning was repeated by pressing the cleaning button on the printer body, and the clogging recovery property was evaluated.
A: Clogging recovered within 10 times.
B: The clogging did not recover within 10 times.

(4) Evaluation 4 <Water resistance of image>
Using the printer, a solid image (coat layer) of 100% Duty was recorded in an environment of 20 ° C. on a recording medium MACtac vinyl chloride sheet JT5829R) under the recording condition of Condition 3. The recorded matter thus obtained was placed on a hot plate at 100 ° C. and heated for 15 minutes to obtain an evaluation sample. Then, using a Gakushin type friction fastness tester (AB-301 COLOR FASTNESS RUBING TESTER, made by TESTER SANGYO, LTD.), A weight of 500 g was applied to the cloth soaked with water (gold width) 20 times. The water resistance was evaluated by rubbing. The evaluation criteria are as follows, and the evaluation results are shown in Tables 1 to 3.
A: Even after 20 times, the recorded image is not peeled off.
B: Peeling of the recorded image is observed after 20 times.

(5) Evaluation 5 <Average dot diameter>
An image (coat layer) of 1% Duty was recorded on the recording medium MACtac (vinyl chloride sheet JT5829R) using the above printer under the recording condition of Condition 4. Ten dots in the obtained recorded matter were photographed with an optical microscope, and an average value of ten dot areas was calculated from the obtained photographed image. The diameter of a circle having the same area as the calculated average value was taken as the average dot diameter. The evaluation criteria are as follows. The evaluation results are shown in Table 7.

5.3.1. Evaluation Results As shown in Tables 1 to 4, it was shown that the ink according to the example can form a good image with little aggregation unevenness and stripe unevenness and is excellent in fixability.

  Moreover, as shown in Table 7, according to the ink according to the example, a high correlation was recognized between the average ink mass and the dot diameter. From this, it can be said that when the ink according to the embodiment is used, the recording medium can be satisfactorily covered by increasing the average ink mass even with a small number of passes, and the recording medium can be uniformly swelled and dissolved.

  Furthermore, as shown in Tables 1 to 4, it was shown that the ink according to the example was excellent in water resistance by containing the oxazoline group-containing resin and the carboxylic acid group-containing resin at the same time. Moreover, it was shown that it is excellent in clogging recoverability by containing oxyglycols.

  In the ink compositions of Examples 4 to 6, those in which 1,2-octanediol was changed to 1,2-heptanediol were designated as Examples 7 to 9. When the above evaluations 1 to 5 were performed, the same results as in Examples 4 to 6 were obtained.

  Comparative Examples 13-18 were obtained by changing the ink composition of Comparative Examples 3, 4, 7, 8, 11, and 12 to 1,2-heptanediol instead of 1,2-octanediol. When the above evaluations 1 to 5 were performed, the same results as in Comparative Examples 3, 4, 7, 8, 11, and 12 were obtained.

  Moreover, what changed the dispersion liquid 5 into the pure water in the composition of the ink of Example 3 and 6 was set as Example 10 and 11. When the above evaluations 1 to 5 were performed, the same results as in Examples 3, 4, 7, 8, 11, and 12 were obtained.

  Moreover, what changed the dispersion 5 into the dispersion 1 in the composition of the ink of Examples 1-6 was set as Examples 12-17. When the above evaluations 1 to 5 were performed, the same results as in Examples 1 to 6 were obtained.

  Moreover, what changed the dispersion 5 into the dispersion 2 in the composition of the ink of Examples 1-6 was set as Examples 18-23. When the above evaluations 1 to 5 were performed, the same results as in Examples 1 to 6 were obtained.

  Moreover, what changed the dispersion 5 into the dispersion 3 in the composition of the ink of Examples 1-6 was set as Examples 24-29. When the above evaluations 1 to 5 were performed, the same results as in Examples 1 to 6 were obtained.

  Moreover, what changed the dispersion liquid 5 into the dispersion liquid 4 in the composition of the ink of Examples 1-6 was set as Examples 30-35. When the above evaluations 1 to 5 were performed, the same results as in Examples 1 to 6 were obtained.

  Of the inks of the comparative examples, those that did not contain a hydroxycarboxylic acid ester having 6 or less carbon atoms were shown to have a tendency to lower the fixability.

  Further, among the inks of the comparative examples, those containing N-methyl-2-pyrrolidone or γ-butyrolactone instead of the hydroxycarboxylic acid ester having 6 or less carbon atoms have a tendency to decrease cohesion. It has been shown.

  The present invention is not limited to the embodiments described above, and various modifications are possible. For example, the present invention includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect) as the configuration described in the embodiment. In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that achieves the same effect as the configuration described in the embodiment or a configuration that can achieve the same object. In addition, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Recording device, 10 ... Controller, 11 ... Interface part, 12 ... CPU, 13 ... Memory, 14 ... Unit control circuit, 20 ... Conveyance unit, 21 ... Conveyance roller, 30 ... Carriage unit, 31 ... Carriage, 32 ... Carriage Movement mechanism, 33 ... ink cartridge, 40 ... head unit, 41 ... head, 50 ... drying unit, 60 ... detector group, 90 ... computer.

Claims (13)

An inkjet ink containing a hydroxy group-containing carboxylic acid ester having 6 or less carbon atoms, a surfactant, and water represented by the following general formula (1).
_{HO-C m H 2m -COO-} C n H2 n + 1 ... (1)
(In the formula, m represents a natural number of 2 or 3, n represents a natural number of 1 to 3, and m + n ≦ 5.)   The inkjet ink according to claim 1, further comprising an oxazoline group-containing resin having a weight average molecular weight of 2 to 120,000 and a carboxyl group-containing resin.   The ratio (MA / MB) of the number of moles of oxazoline groups (MA) in the total mass of the oxazoline group-containing resin to the number of moles of carboxyl groups (MB) in the total mass of the carboxyl group-containing resin is 10 The inkjet ink according to claim 2, which is 40 or more.   The inkjet ink according to any one of claims 1 to 3, wherein the hydroxycarboxylic acid ester is methyl 2-hydroxyisobutanoate or methyl 2-hydroxybutanoate.   Furthermore, the ink for inkjets as described in any one of Claims 1-4 containing a pigment.   Furthermore, the inkjet ink as described in any one of Claims 1-5 containing polyoxyalkylene glycol.   Furthermore, the ink for inkjets as described in any one of Claims 1-6 containing a C1-C8 or 1,2-alkanediol.   The 1,2-alkanediol having 7 or 8 carbon atoms is 1,2-heptanediol, 1,2-octanediol, 4,4-dimethyl-1,2-pentanediol, 5-methyl-1,2- The inkjet ink according to claim 7, which is at least one selected from the group consisting of hexanediol and 4-methyl-1,2-hexanediol.   The inkjet ink according to claim 1, wherein the surfactant is a polyorganosiloxane surfactant. An inkjet recording method using an inkjet recording apparatus having a head,
The head includes a nozzle row including a plurality of nozzle holes, and a discharge step for discharging the ink-jet ink droplets according to any one of claims 1 to 9 from the nozzle holes;
A dot forming step of attaching the droplets to a recording medium to form dots composed of the droplets;
An inkjet recording method for forming an image on the recording medium by repeating the ejection step and the dot formation step a plurality of times. A plurality of the nozzle rows are arranged,
The image formed by the image forming step has a dot interval of an image resolution of 300 dpi or more in the arrangement direction of the nozzle rows,
The mass of the droplets ejected in the ejection step is 1 to 15 ng.
The inkjet recording method according to claim 10, wherein a diameter of dots formed in the dot forming step is larger than the dot interval.   The inkjet recording method according to claim 10, further comprising a drying step of drying the recording medium.   The inkjet recording method according to claim 10, wherein the recording medium is an ink low-absorbing or non-absorbing recording medium.

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