WO2012070243A1 - Ink jet ink and method for ink jet recording - Google Patents

Abstract

The purpose of the present invention is to provide an ink jet ink and a method for ink jet recording which are capable of obtaining images with excellent image uniformity, dropout resistance, gloss and scratch resistance. The present invention: comprises water, an organic solvent, a pigment and resin; contains 1.0 mass% or more of β-alkoxy propionamides represented by general formula (1), and 0.001-0.20 mass% of a surfactant (A) which is capable of making the surface tension of a 30 mass% aqueous solution of β-alkoxy propionamides to 25.0 mN/m or less when 1.0 mass% thereof is added to the 30 mass% aqueous solution of β-alkoxy propionamides; and has a viscosity of 50.0 mPa or less, and a surface tension of 25.0 mN/m-35.0 mN/m.

Description

Ink jet ink and ink jet recording method

The present invention relates to a water-based ink-jet ink and an ink-jet recording method using the same, and more particularly to an ink-jet ink that can be recorded on a recording medium having poor ink absorbability and an ink-jet recording method using the same.

As an inkjet ink for industrial use, in addition to paper and cloth, recording media with poor water absorption, such as coated paper for printing with the surface of the paper coated with resin or clay, etc. Ink-jet inks that can be directly printed on a recording medium that is configured or has almost no ink absorption ability, such as a resin film itself, have been developed.

Examples of these ink-jet inks include solvent ink-jet inks using an organic solvent as a vehicle and UV-curable ink-jet inks mainly composed of a photopolymerizable monomer. When the solvent inkjet ink is dried, the solvent contained in the ink is scattered in the atmosphere. That is, solvent inkjet has a problem that it contains a lot of VOC, which has become a social problem in recent years, and is scattered in the atmosphere. Also, there are concerns about odors and safety effects on workers, and it is necessary to take measures such as providing facilities that can be sufficiently ventilated during use.

On the other hand, ultraviolet curable ink-jet inks are cured immediately after printing, so the VOC problem is close to zero, but some monomers used in the ink have skin sensitization properties. In addition, there is a limit to the fields that can be used due to the restriction of incorporating an expensive ultraviolet irradiation light source into an ink jet printer. Furthermore, when printing on a glossy sheet or the like with an ultraviolet curable ink jet ink, there is a problem that the glossiness of the portion to which the ink has adhered is significantly impaired and a high-quality image cannot be obtained.

Against this backdrop, the use of water-based ink-jet inks mainly composed of water, which has been used widely in household specifications, has a low environmental impact, and has recording properties such as cloth and paper. Attempts have also been made to print on recording media with poor ink absorbability. In addition, ink-jet inks applicable to such applications have been actively developed. However, many recording media with poor ink absorbability, such as coated paper and resin film, have low surface energy and do not absorb normal aqueous inkjet ink. For this reason, a phenomenon that ink droplets landed on the recording medium are repelled, so-called repellency occurs, and the image tends to be deteriorated such as whitening of the image or mottled solid portions. Further, since the recording medium does not have the ability to absorb inkjet ink, there is a problem that it takes time to dry. Furthermore, since the color material is not absorbed into the recording medium, there is a problem that the image durability such as abrasion resistance is low.

As a means for preventing repellency of inkjet ink, a method of adding a surfactant or a water-soluble organic solvent having a low surface tension to the ink can be mentioned. According to this method, ink wettability with respect to a recording medium having poor ink absorbability can be improved, so that the occurrence of repelling is improved to some extent. However, if the surfactant is added excessively, it concentrates and precipitates when the ink dries, causing problems such as reducing the glossiness of the image. Further, the surfactant is oriented at the interface between the recording medium and the ink to suppress repellency, but the integrity between the inkjet ink film and the recording medium is lowered by the surfactant. Thereby, the adhesiveness of the inkjet ink film with respect to a recording medium falls, and image durability falls.

On the other hand, when an organic solvent having a low surface tension is added to the ink, the above precipitation does not occur, but there is no effect of improving the abrasion resistance, and the image durability is still insufficient. Further, since many organic solvents having a low surface tension have a high boiling point, there is a problem that the drying property of the ink-jet ink is further deteriorated.

As a method for solving these problems, a method is disclosed in which a solvent having permeability to a resin such as polyvinyl chloride is added to inkjet ink to improve the abrasion resistance (for example, Patent Document 1). . Examples of the solvent include β-alkoxypropionamides. Ink-jet inks containing the β-alkoxypropionamides are excellent in gloss and abrasion resistance, and also improved against the above repellency. It is said to have an effect. However, in the invention described in Patent Document 1, although a certain degree of improvement effect is seen against weak repellency, strong repellency and whiteout failures still occur, and the viewpoint of improving image quality degradation (such as mottled or missing). Then it was still insufficient.

Furthermore, in order to improve repelling, a method of improving the image quality by adding a silicone surfactant or a fluorosurfactant as a surfactant is disclosed (for example, see Patent Documents 2 and 3).

JP 2010-168433 A JP 2010-89370 A JP 2009-226764 A

However, in order to improve the wettability of the inkjet ink with respect to the ink non-absorbing recording medium (especially polyvinyl chloride) and to improve the image quality, the ink containing the aforementioned β-alkoxypropionamides is disclosed in Patent Document 2 or 3. When the described surfactants were added, the wettability of the ink to the recording medium was improved, but the effect of improving the image quality, in particular, the effect of improving the mottle or white spots of the solid portion was insufficient. In addition, with the addition of the surfactant, there may be a further deterioration in image quality.

For this reason, it is a big problem to completely prevent image deterioration of inkjet inks containing β-alkoxypropionamides and surfactants.

The present invention has been made in view of the above-described problems, and provides an inkjet ink that can be printed on a wide variety of recording media with little environmental load during image formation. In the present invention, by adding β-alkoxypropionamides to the ink jet ink, the gloss and scratch resistance of the printed image are improved. In the present invention, while maintaining these effects, the image quality when printed on a non-ink-absorbing recording medium is improved, and in particular, mottle and white spots on the solid portion are suppressed.

That is, an object of the present invention is to provide a water-based inkjet ink capable of obtaining an image having no white spots and excellent in image uniformity, glossiness, and abrasion resistance, and an inkjet recording method using the same. It is in.

The above object of the present invention is achieved by the following configuration.

1. In an inkjet ink containing water, an organic solvent, a pigment, and a resin, 1.0% by mass or more of β-alkoxypropionamide represented by the following general formula (1), and a surfactant A having the following characteristics: 0.001% by mass or more and 0.20% by mass or less, the viscosity is 50.0 mPa or less, and the surface tension is 25.0 mN / m or more and 35.0 mN / m or less. Inkjet ink.

[Wherein, R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₂ and R ₃ are each a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms. R ₂ and R ₃ may be the same or different. ]
Surfactant A: When 1.0% by mass is added to a 30% by mass aqueous solution of the β-alkoxypropionamides, the surface tension of the 30% by mass aqueous β-alkoxypropionamides is 25.0 mN / m. Surfactant that can be:

2. 2. The ink-jet ink as described in 1 above, wherein the surfactant A is a fluorine-based surfactant or a silicone-based polymer surfactant.

3. The total amount of β-alkoxypropionamides represented by the general formula (1) and the organic solvent is 10.0% by mass or more and 40.0% by mass or less, according to 1 or 2 above. Inkjet ink.

4. 4. The inkjet ink according to any one of items 1 to 3, wherein the total amount of the pigment and the resin is 8.0% by mass or more.

5. 5. An inkjet recording method comprising forming an image on a recording medium using the inkjet ink according to any one of 1 to 4 above.

6. 6. The ink jet recording method as described in 5 above, wherein the recording medium is an ink non-absorbing recording medium.

7. 7. The ink jet recording method as described in 6 above, wherein the non-ink-absorbing recording medium is polyvinyl chloride.

8. 6. The inkjet recording method according to item 5, wherein the recording medium is heated to 45 ° C. or higher and 90 ° C. or lower to form an image.

According to the present invention, it is possible to provide a water-based inkjet ink capable of obtaining an image having no white spots and excellent in image uniformity, glossiness, and abrasion resistance, and an inkjet recording method using the same.

Hereinafter, embodiments for carrying out the present invention will be described in detail.

The present inventor has obtained, in an inkjet ink containing water, an organic solvent, a pigment and a resin, (1) 1.0 mass% or more of β-alkoxypropionamide represented by the general formula (1) and (2 ) The above problem was solved by adding a specific surfactant A in an amount of 0.001% by mass to 0.20% by mass. When 1.0% by mass of the surfactant A is added to a 30% by mass aqueous solution of the β-alkoxypropionamides, the surface tension of the 30% by mass aqueous solution of the β-alkoxypropionamides is 25.0 mN / m or less. And, by setting the viscosity of the inkjet ink to 50.0 mPa or less and the surface tension to 25.0 mN / m or more and 35.0 mN / m or less, white spots do not occur, image uniformity, glossiness, and abrasion resistance. A water-based inkjet ink containing β-alkoxypropionamides capable of obtaining an image having excellent properties was realized.

The reason why the above-described effect can be obtained by the inkjet ink having the above-described configuration defined in the present invention is presumed as follows.

In view of the “repellency phenomenon” in inkjet inks containing β-alkoxypropionamides, the present inventors have proceeded with studies on the image quality degradation mechanism (a phenomenon in which the effect of adding a surfactant cannot be obtained). The repellency phenomenon is particularly prominent when a recording medium having poor ink absorption capability is used. As a result, it was inferred that there was a problem that the surface tension of the ink increased in the process of evaporating water in the ink jet ink droplets landed on the recording medium.

That is, as the water content in the ink droplets evaporates, the surface tension increases, so it is considered that the image quality is deteriorated.

When image printing is performed by the inkjet recording method, for example, ink is ejected so that ink droplets ejected in the first scan and ink droplets ejected in the second and subsequent scans partially overlap. The A portion of the ink droplets ejected in the first scan is dried (mainly water that is easily evaporated) until the carriage returns in the next scan. When the ink droplet ejected in the first scan comes into contact with the ink droplet in the second scan that is subsequently ejected, the surface tension of the ink droplet in the first scan is high, Ink droplets ejected in the second scan with relatively low surface tension flow onto the first ink droplet and merge. As a result, it is considered that a white portion or a spotted failure occurs in the solid portion due to white spots in a portion printed in the second and subsequent scans or a lighter color.

The phenomenon that the surface tension of the droplets increases as the water evaporates is mainly due to the property that β-alkoxypropionamides easily dissolve the surfactant. That is, when ink droplets are concentrated by evaporation of water or the like, the relative ratio of β-alkoxypropionamides in the ink increases in the process. As a result, the surfactant is not oriented on the surface of the droplet but is dissolved in the ink droplet, so that the effect is not sufficiently exhibited, and the surface tension of the ink is estimated to increase.

Based on this inference, an ink-jet ink containing a β-alkoxypropionamide and having the characteristic that the surface tension is lowered upon drying was prepared, and the same image formation was performed. As a result, white spots and mottled failures have been dramatically reduced.

This is because the surface tension of the ink droplets printed later is relatively higher than the ink droplets printed earlier in the case of the ink jet ink having the characteristic that the surface tension decreases during drying. Therefore, the ink droplet printed first flows into the ink droplet side to be printed later. However, since the ink droplet printed earlier has already spread on the recording medium, it does not easily flow into the ink droplet printed later. In addition, the ink droplets printed earlier are more difficult to flow in because the viscosity has increased due to the evaporation of water. Accordingly, it is considered that the ink droplets printed earlier and the ink droplets printed later are prevented from being merged, and white spots and mottled portions in the solid portion are less likely to occur.

In order to realize an ink-jet ink having a characteristic that the surface tension decreases as the ink dries, the inventors of the present invention select 1) a specific surfactant and 2) add a very small amount of the surfactant. Designed. With this design, the surface tension does not increase even with an inkjet ink containing β-alkoxypropionamides. That is, 1) By selecting a specific surfactant, even if β-alkoxypropionamides are present, the surface tension does not change or decreases. 2) By making the addition amount of the surfactant extremely small, the increase in the surface tension of the droplet accompanying drying is canceled, that is, the surfactant dissolves in the ink droplet along with drying. Even in this case, the amount of change of the surfactant present on the ink surface is small, and the change of the surface tension can be small.

Therefore, according to the present invention, it is possible to achieve both the image quality improvement effect of β-alkoxypropionamides themselves and the repellency prevention effect of surfactants, and a high-quality image free from whitening failure and mottled failure. Can be obtained.

Hereinafter, details of the ink-jet ink of the present invention will be described.

<Inkjet ink>
The inkjet ink of the present invention (hereinafter also simply referred to as ink) is a water-based inkjet ink containing water, an organic solvent, a pigment and a resin, and the β-alkoxy represented by the general formula (1) is used as the organic solvent. Propionamides are contained in an amount of 1.0% by mass or more based on the total mass of the ink. Further, the specific surfactant A is contained in a trace amount range of 0.001% by mass to 0.20% by mass with respect to the total mass of the ink. By containing β-alkoxypropionamides and surfactant A in the amounts described above, not only recording media having ink absorptivity such as paper and fabric, but also ink such as coated paper and resin recording media. An image having high durability such as abrasion resistance can be formed even on a recording medium having poor absorption and low surface energy.

[Water content]
The ink of the present invention is a water-based inkjet ink and contains water. Usually, water is preferably contained in an amount of 30% by mass or more, more preferably 50% by mass or more of the total mass of the ink.

[Β-alkoxypropionamides represented by the general formula (1)]
The β-alkoxypropionamides represented by the general formula (1) contained in the ink of the present invention will be described.

The above-mentioned β-alkoxypropionamides exhibit an effect in an ink jet recording method using various recording media. Above all, the effect is exhibited in forming an ink jet image on a recording medium having a resin component. β-alkoxypropionamides have a high ability to dissolve the resin component. Therefore, when printing is performed on a recording medium containing a resin component, the landed ink droplets penetrate into the recording medium. In addition, while β-alkoxypropionamides dissolve or swell the resin component that constitutes the recording medium, the color material in the ink and other ink solvents enter the resin component, so that the color material and the like are recorded. Integrate with media. Thereby, the adhesiveness of the formed image is increased and the image durability is improved.

The above effect is particularly easily obtained when an image is formed on a recording medium in which ink repellency easily occurs, that is, a recording medium having a surface energy of 30 mN / m or more and less than 40 mN / m, or a recording medium having a resin surface. The surface energy of the recording medium can be calculated by measuring the contact angle using two or more types of liquids with known surface tension.

Further, as described above, the β-alkoxypropionamides have an effect as an organic solvent having a low surface tension, and lower the surface tension of the ink-jet ink so that whitening caused by weak repellency generated during printing can be achieved. It is also effective for prevention.

However, the addition of the above β-alkoxypropionamides is not sufficient to completely suppress strong repelling or white spot failure. Furthermore, when a normal amount of a general surfactant is added to the ink containing the β-alkoxypropionamide, the expected image improvement effect may be poor or may deteriorate. . Therefore, in the present invention, in order to obtain a sufficient image quality improvement effect, a very small amount of a surfactant A described later is added.

The β-alkoxypropionamides are represented by the following general formula (1).

In the general formula (1), R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms, and R ₂ and R ₃ are each a hydrogen atom, or a straight chain having 1 to 4 carbon atoms or It represents a branched alkyl group, and R ₂ and R ₃ may be the same or different.

By selecting each group defined above as R ₁ , R ₂ , and R ₃ , the solubility and penetration ability of the resin component of β-alkoxypropionamides is maintained and the compatibility with water is increased. be able to.

R ₁ is preferably a methyl group, an ethyl group or an n-butyl group, and preferred R ₂ and R ₃ are a methyl group or an ethyl group, respectively.

Specific examples of β-alkoxypropionamides represented by the general formula (1) are shown below, but the present invention is not limited to these exemplified compounds.

1) 3-methoxy-N, N-dimethylpropionamide 2) 3-ethoxy-N, N-dimethylpropionamide 3) 3-propyloxy-N, N-dimethylpropionamide 4) 3-butoxy-N, N- Dimethylpropionamide 5) 3-Pentyloxy-N, N-dimethylpropionamide 6) 3-Hexyloxy-N, N-dimethylpropionamide 7) 3-methoxy-N, N-diethylpropionamide 8) 3-methoxy- N, N-dipropylpropionamide 9) 3-methoxy-N, N-dibutylpropionamide 10) 3-ethoxy-N, N-diethylpropionamide 11) 3-ethoxy-N, N-dipropylpropionamide 12) 3-Ethoxy-N, N-dibutylpropionamide 13) 3-Propyloxy-N, -Diethylpropionamide 14) 3-Propyloxy-N, N-dipropylpropionamide 15) 3-Propyloxy-N, N-dibutylpropionamide 16) 3-Butoxy-N, N-diethylpropionamide 17) 3- Butoxy-N, N-dipropylpropionamide 18) 3-Butoxy-N, N-dibutylpropionamide 19) 3-Pentyloxy-N, N-diethylpropionamide 20) 3-Pentyloxy-N, N-dipropyl Propionamide 21) 3-Pentyloxy-N, N-dibutylpropionamide 22) 3-Hexyloxy-N, N-diethylpropionamide 23) 3-Hexyloxy-N, N-dipropylpropionamide 24) 3-Hexyl Oxy-N, N-dibutylpropionamide

The amount of β-alkoxypropionamide represented by the general formula (1) added to the ink is preferably 1.0% by mass or more and less than 40.0% by mass of the total mass of the ink. In particular, 3 mass% or more and 10 mass% or less are preferable.

Next, an example of a method for synthesizing β-alkoxypropionamides represented by the general formula (1) will be shown.

(Synthesis of β-alkoxypropionamides 1)
N, N-dimethylacrylamide (19.828 g) and 1-hexanol (20.434 g) were placed in a 300 ml separable flask equipped with a stirrer, a thermocouple, and a nitrogen gas inlet tube, and stirred while introducing nitrogen gas. Next, 0.338 g of sodium-t-butoxide was added, and the reaction was performed at 35 ° C. for 4 hours. After completion of heating, 150 mg of phosphoric acid was added to make the solution uniform, and the mixture was allowed to stand for 3 hours. The solution was filtered to remove precipitates, and unreacted substances were removed by an evaporator to obtain β-alkoxypropionamides 1 (3-hexyloxy-N, N-dimethylpropionamide).

(Synthesis of β-alkoxypropionamides 2)
N, N-dimethylacrylamide (19.828 g) and 1-butanol (14.824 g) were placed in a 300 ml separable flask equipped with a stirrer, a thermocouple, and a nitrogen gas inlet tube, and stirred while introducing nitrogen gas. Next, 0.338 g of sodium-t-butoxide was added, and the reaction was performed at 35 ° C. for 4 hours. After completion of heating, 150 mg of phosphoric acid was added to make the solution uniform, and the mixture was allowed to stand for 3 hours. The solution was filtered to remove precipitates, and unreacted substances were removed by an evaporator to obtain β-alkoxypropionamides 2 (3-butoxy-N, N-dimethylpropionamide).

(Synthesis of β-alkoxypropionamides 3)
In a 300 ml separable flask equipped with a stirrer, a thermocouple, and a nitrogen gas introduction tube, 19.828 g of N, N-dimethylacrylamide and 26.046 g of 2-ethylhexanol were added and stirred while introducing nitrogen gas. Next, 0.338 g of sodium-t-butoxide was added, and the reaction was performed at 35 ° C. for 4 hours. After completion of heating, 150 mg of phosphoric acid was added to make the solution uniform, and the mixture was allowed to stand for 3 hours. The solution was filtered to remove precipitates, and unreacted substances were removed by an evaporator to obtain β-alkoxypropionamides 3 (3- (2-ethylhexyloxy) -N, N-dimethylpropionamide).

(Synthesis of β-alkoxypropionamides 4)
In a 300 ml separable flask equipped with a stirrer, a thermocouple, and a nitrogen gas inlet tube, 19.828 g of N, N-dimethylacrylamide and 26.046 g of n-octanol were placed, and stirred while introducing nitrogen gas. Next, 0.338 g of sodium-t-butoxide was added, and the reaction was performed at 35 ° C. for 4 hours. After completion of heating, 150 mg of phosphoric acid was added to make the solution uniform, and the mixture was allowed to stand for 3 hours. The solution was filtered to remove precipitates, and unreacted substances were removed by an evaporator to obtain β-alkoxypropionamides 4 (3-octyloxy-N, N-dimethylpropionamide).

The specific method for producing β-alkoxypropionamides represented by the general formula (1) is not limited to the above, and is described in, for example, JP2009-185079A and WO2008 / 102615. It can be done. Further, β-alkoxypropionamides represented by the general formula (1) are commercially available from Idemitsu Kosan Co., Ltd. under the trade name of echamide.

[Surfactant A]
In the present invention, when the surfactant A according to the present invention is added in an amount of 1.0% by mass to a 30% by mass aqueous solution of β-alkoxypropionamides used in the ink, the surface tension of the aqueous solution is 25 mN / m. It is defined as a surfactant that can be: This means that the surfactant A can exhibit a sufficient effect even when water in the ink-jet ink evaporates and the content ratio of β-alkoxypropionamides in the ink increases. Further, when the surfactant A is added in an amount of 1.0% by mass to a 30% by mass aqueous solution of β-alkoxypropionamides, the surface tension of the aqueous solution can be set to 17 mN / m or more. preferable.

The surface tension value of the liquid defined in the present invention is obtained as a surface tension value (mN / m) at a temperature of 25 ° C. by a platinum plate method using a surface tension meter (for example, CBVP-Z, manufactured by Kyowa Interface Science). Can do.

The specific surfactant A satisfying such performance is not particularly limited, but among them, a silicone-based polymer surfactant or a fluorine-based polymer surfactant is preferable.

The polymer type surfactant referred to in the present invention means a surfactant having an average molecular weight of 1000 or more, and even if it is in an emulsion state in ink, it does not matter if it satisfies the above requirements. .

The silicone-based polymer surfactant is preferably a polyether-modified polysiloxane compound, such as KF-905 manufactured by Shin-Etsu Chemical, BYK375 manufactured by Big Chemie, TSF4440, TSF4445 manufactured by Momentive Performance Materials, TSF4446 etc. are mentioned.

Fluorine-based polymer surfactant means a compound in which a part or all of the hydrogen atom bonded to the carbon of the hydrophobic group of a normal surfactant is substituted with a fluorine atom. Of these, those having a perfluoroalkyl group in the molecule are preferred.

Examples of the fluorine-based polymer surfactant include Megafac F manufactured by DIC, Surflon manufactured by Asahi Glass, Novec manufactured by 3M, and EI Dupont Nemeras and Company. Zonyls (Zonyls) made by a company etc. are mentioned.

The present invention is also characterized in that the surfactant A is contained in an amount of 0.001% by mass to 0.20% by mass with respect to the total mass of the ink.
Usually, the surface tension decreases as the addition amount of the surfactant increases. However, in the present invention, the point that the surface tension stops decreasing with a certain amount of addition (critical micelle concentration, CMC) is used. For example, in a surfactant aqueous solution, when the liquid volume is halved due to evaporation of moisture, the concentration of the surfactant is doubled. Assuming that the decrease in surface tension due to the addition of the surfactant is about 0.4% by mass, the concentration of the surfactant is doubled when the surfactant concentration in the ink is 0.2% by mass or less. Thus, the effect of lowering the surface tension can be obtained. On the other hand, when the surfactant concentration is 0.2% by mass or more, even if the surfactant concentration doubles, the surface tension reducing effect of the surfactant has stopped decreasing, and accompanying the evaporation of moisture The effect of lowering the surface tension is small.

In the present invention, in consideration of the lowering stop and the concentration of the surfactant due to the evaporation of moisture in the ink, a sufficient surface tension lowering effect is obtained by adding the minimum necessary surfactant. In addition, in the present invention, the effect of improving the image quality is obtained by the reverse means of reducing the surfactant further to the problem that the effect of the surfactant cannot be sufficiently obtained and the image quality is lowered. .

Normal ink jet ink is affected by drying and the like, and the composition of the ink near the nozzle changes depending on, for example, time, environment, and printing conditions. From the viewpoint of robustness during production, a sufficient amount of surfactant is added so that the physical properties do not fluctuate with respect to the change in the content of the surfactant. However, in the ink of the present invention, if the amount of the surfactant exceeds 0.20% by mass, the image quality may be deteriorated such as white spots or mottle, which is not preferable.

On the contrary, when the addition amount of the surfactant is less than 0.001% by mass, the effect of the surfactant itself is too small, which is the same as the case where the surfactant is not added.

In addition, in the case of fluorine-based surfactants, the surface tension often stops decreasing when the amount of the surfactant in the ink is about 0.2% by mass. Therefore, when the surfactant A is a fluoropolymer type surfactant, the amount of the surfactant A in the ink is more preferably 0.1% by mass or less.

〔Organic solvent〕
Next, water-soluble organic solvents other than the β-alkoxypropionamides applicable to the ink of the present invention will be described.

In the ink of the present invention, a water-soluble organic solvent having a low surface tension can be further added as necessary. By adding a low surface tension water-soluble organic solvent, the effect of β-alkoxypropionamides is assisted, and recording media made of various hydrophobic resins such as soft polyvinyl chloride sheets, printing paper, etc. Even on a paper support that absorbs slowly, ink mixing can be further suppressed and printing can be performed with good image quality.

In the ink of the present invention, it is particularly preferable to add glycol ethers or 1,2-alkanediols as organic solvents. Specifically, the following low surface tension glycol ethers or 1,2-alkanediols are preferably added.

Examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl. Examples include ether.

Examples of 1,2-alkanediols include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and the like.

It is also preferable to add a solvent that can dissolve, soften, or swell a recording medium such as polyvinyl chloride from the viewpoint of further improving the adhesion and abrasion resistance of the printed image.

Examples of such solvents include cyclic solvents containing nitrogen or sulfur atoms, cyclic ester solvents, lactic acid esters, alkylene glycol diethers, alkylene glycol monoether monoesters, and dimethyl sulfoxide.

Preferable specific examples of the cyclic solvent containing a nitrogen atom include 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, ε-caprolactam, And cyclic amide compounds such as methylcaprolactam and 2-azacyclooctanone.

As a preferable specific example of the cyclic solvent containing a sulfur atom, a compound having a cyclic 5- to 7-membered ring is preferable, and examples thereof include sulfolane.

Preferable specific examples of the cyclic ester solvent include γ-butyrolactone and ε-caprolactone. Preferable specific examples of the lactic acid ester include butyl lactate and ethyl lactate.

Preferable specific examples of the alkylene glycol diether include diethylene glycol diethyl ether.
Preferable specific examples of the alkylene glycol monoether monoester include diethylene glycol monoethyl monoacetate.

In addition to the above solvents, other solvents may be added. Other solvents include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol); polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol) , Propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol); amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N -Ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, di Tylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine; amides (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.) It is done.

When the total amount of the organic solvent exceeds 40.0% by mass with respect to the total mass of the ink, the organic solvent may be excessive depending on the type of the organic solvent in a secondary color solid image having a large amount of applied ink. If the organic solvent is excessive, the ink flow may not stop and density unevenness may occur due to repelling. Therefore, the addition amount of the organic solvent with respect to the total mass of the ink is preferably 40.0% by mass or less including the β-alkoxypropionamides.

Further, from the viewpoints of addition amount of the above-mentioned β-alkoxypropionamides, ejection performance, control of wettability to the ink non-absorbing medium, etc., 3.0% by mass or more of β-alkoxypropionamide with respect to the total mass of the ink And a water-soluble organic solvent having a low surface tension of the same amount or about three times as much. As a result, the solvent content is preferably 10.0% by mass or more based on the total mass of the ink.

〔resin〕
In the present invention, as described above, it is preferable from the viewpoint of suppressing the coalescence of the liquid droplets that the surface tension does not increase until the ink is dried after the ink is dripped. However, in the present invention, how much water is evaporated from the ink and “the ink is dried” depends on the ink. That is, how much the surface tension of the ink needs to be kept until the water is evaporated is determined by how much the ink stops flowing when the water is evaporated.

The ink flow stop time is affected by the solid content of the ink and the amount of organic solvent. Considering that the amount of organic solvent is determined from the viewpoints of color tone, pigment concentration, ink ejection properties, and other performances, the flow of ink droplets can be accelerated by incorporating resin into the ink and increasing the solid content. It is preferable to stop.

The resin used for such purpose is not particularly limited as long as it can be dissolved or dispersed in water. However, in general, it is particularly preferable to use the same resin as that added to the ink in order to increase the abrasion resistance of the printed matter.

Examples of such resins include water-soluble resins such as polyacrylic resins, polystyrene-acrylic, polyacrylonitrile-acrylic, vinyl acetate-acrylic, polyurethane resins, polyamide resins, polyester resins, polyolefin resins, and water-dispersed polymers. Fine particles are mentioned. In particular, it is preferable to add a water-soluble resin or water-dispersed polymer fine particles made of an acrylic copolymer resin or polyurethane resin.

As is well known, acrylic copolymer resins are preferable because they can be freely selected and designed from a wide variety of monomers, are easily polymerized, and can be produced at low cost. In particular, as described above, an acrylic copolymer resin having a high degree of design freedom is suitable for responding to a large number of requirements required when added to ink.

Polyurethane resin is particularly preferred because it is easy to produce water-based dispersed polymer fine particles, and MFT (minimum film-forming temperature) is easily controlled.

The resin may be one obtained by neutralizing all or part of the acid component contained in the copolymer component with a base. As the neutralizing base, an alkali metal-containing base (for example, NaOH, KOH, etc.), an amine (for example, alkanolamine, alkylamine, etc.) or ammonia can be used.

The amount of neutralizing base added depends on the amount of acid monomer contained in the resin, but if it is too small, the effect of neutralization of the copolymer component cannot be obtained, and if it is too large, the water resistance and discoloration of the image, There are issues such as odor. Therefore, it is preferable to add the neutralizing base so that the amount of the neutralizing base is 0.2% by mass or more and 2.0% by mass or less of the total mass of the ink.

The amount of resin added is preferably 1.0% by mass or more and 15.0% by mass or less with respect to the total mass of the ink. More preferably, it is 3.0 mass% or more and 10.0 mass% or less.

Further, from the viewpoint of fluidity of ink droplets, the total amount of the resin and the pigment of the resin described below is preferably 7.0% by mass or more, and 8.0% by mass or more with respect to the total mass of the ink. Is more preferable.

The glass transition temperature (Tg) of the resin is preferably 0 ° C. or higher and 100 ° C. or lower. If Tg is 0 ° C. or higher, the printed image has sufficient abrasion resistance, and the occurrence of blocking can also be suppressed. If Tg is 100 ° C. or lower, desired abrasion resistance can be obtained. Further, by setting Tg to 100 ° C. or less, it is possible to prevent the film after drying the ink from becoming too hard and brittle.

[Pigment]
Next, the pigment that is the color material contained in the ink of the present invention will be described. The pigment has high image durability and is suitable as a color material.

As the pigment that can be used in the present invention, conventionally known organic and inorganic pigments can be used. For example, azo pigments such as azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments, phthalocyanine pigments, perylene and perylene pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments, etc. Examples include polycyclic pigments, dye lakes such as basic dye lakes, and acid dye lakes, organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments, and inorganic pigments such as carbon black.

Specific pigments are exemplified below.
Examples of pigments for magenta or red and violet include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 8, C.I. I. Pigment red 12, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 17, C.I. I. Pigment red 22, C.I. I. Pigment red 23, C.I. I. Pigment red 41, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 112, C.I. I. Pigment red 114, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 146, C.I. I. Pigment red 148, C.I. I. Pigment red 149, C.I. I. Pigment red 150, C.I. I. Pigment red 166, C.I. I. Pigment red 170, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 220, C.I. I. Pigment red 202, C.I. I. Pigment red 222, C.I. I. Pigment red 238, C.I. I. Pigment red 245, C.I. I. Pigment red 258, C.I. I. Pigment red 282, C.I. I. Pigment violet 19, C.I. I. And CI Pigment Violet 23.

¡As pigments for orange or yellow and brown, C.I. I. Pigment orange 13, C.I. I. Pigment orange 16, C.I. I. Pigment orange 31, C.I. I. Pigment orange 34, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 1, C.I. I. Pigment yellow 3, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 16, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 43, C.I. I. Pigment yellow 55, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 81, C.I. I. Pigment yellow 83, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 109, C.I. I. Pigment yellow 110, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 129, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 139, C.I. I. Pigment yellow 147, C.I. I. Pigment yellow 150, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 153, C.I. I. Pigment yellow 154, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 175, C.I. I. Pigment yellow 180, C.I. I. Pigment yellow 181, C.I. I. Pigment yellow 185, C.I. I. Pigment yellow 194, C.I. I. Pigment yellow 199, C.I. I. Pigment yellow 213, C.I. I. Pigment Brown 22 and the like.

¡As pigments for green or cyan, C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 1, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 15: 5, C.I. I. Pigment blue 16, C.I. I. Pigment blue 29, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

¡In addition to carbon black, C.I. I. Pigment black 5, C.I. I. Pigment black 7 and the like.

¡In addition to titanium oxide, white pigments include C.I. I. Pigment white 6 and the like. The present invention is not limited to these. The pigments may be used alone or in combination of two or more.

In order to maintain a stable dispersion state of the pigment in water-based ink, it is preferable that the pigment is subjected to various kinds of processing or a pigment dispersion.

Various processing methods and pigment dispersion methods are not particularly limited as long as they can disperse pigments stably in an aqueous system. For example, a pigment dispersion in which a pigment is dispersed in a polymer dispersion resin, a capsule pigment in which the pigment is coated with a water-insoluble resin, a self-dispersion pigment that modifies the pigment surface and can be dispersed without using a dispersion resin, and the like can do.

When the pigment is a pigment dispersion in which the pigment is dispersed in a polymer dispersion resin, the dispersion resin is preferably a water-soluble resin. Preferred examples of water-soluble resins include styrene-acrylic acid-acrylic acid alkyl ester copolymers, styrene-acrylic acid copolymers, styrene-maleic acid copolymers, and styrene-maleic acid-acrylic acid alkyl ester copolymers. Styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid alkyl ester copolymer, styrene-maleic acid half ester copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene-maleic acid copolymer, etc. Is mentioned. As the dispersion resin, the water-soluble resin described in the above-mentioned resin section can also be used.

The molecular weight of the dispersion resin is preferably an average molecular weight of 3000 to 500,000, and more preferably 7000 to 200,000. The Tg of the dispersion resin is preferably about −30 ° C. to 100 ° C., more preferably about −10 ° C. to 80 ° C.

The pigment can be dispersed by, for example, a ball mill, sand mill, attritor, roll mill, agitator, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, wet jet mill, paint shaker, or the like.

When preparing the pigment dispersion, it is preferable to use a centrifugal separator or a filter from the viewpoint of removing coarse particles of the pigment dispersion and uniforming the particle size distribution of the pigment particles.

In addition, when the pigment is used as a capsule pigment coated with a water-insoluble resin, the water-insoluble resin is a resin that is insoluble in water in a weakly acidic to weakly basic range, and preferably has a pH of 4 to 10. Is a resin having a solubility in an aqueous solution of 2% by mass or less.

The water-insoluble resin is preferably acrylic, styrene-acrylic, acrylonitrile-acrylic, vinyl acetate, vinyl acetate-acrylic, vinyl acetate-vinyl chloride, polyurethane, silicone-acrylic, acrylic silicone, Listed are polyester resins and epoxy resins.

The molecular weight of the water-insoluble resin is preferably 3,000 to 500,000, more preferably 7,000 to 200,000. The Tg of the water-insoluble resin is preferably about −30 ° C. to 100 ° C., more preferably about −10 ° C. to 80 ° C.

The average particle size of the capsule pigment is preferably about 80 to 200 nm from the viewpoint of ink storage stability and color developability.

Various known methods can be used as a method of coating the pigment with the water-insoluble resin. Preferably, the water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and the acidic group in the resin is partially or completely neutralized with a base component. Thereafter, the pigment and ion-exchanged water are added and dispersed, then the organic solvent is removed, and water is added if necessary. Also preferred is a method in which a pigment is dispersed using a polymerizable surfactant, a monomer is supplied thereto, and coating is performed while polymerizing.

In the pigment dispersion or capsule pigment, the mass ratio of the pigment and the dispersion resin or the pigment and the water-insoluble resin is preferably selected in the range of 100/150 or more and 100/30 or less in the pigment / resin ratio. it can. In particular, in order to improve the image durability, the ink ejection stability, and the ink storage stability, it is preferably in the range of 100/100 or more and 100/40 or less.

Further, as the self-dispersing pigment, a surface-treated commercial product can be used, and preferable self-dispersing pigments include, for example, CABO-JET200, CABO-JET300 (manufactured by Cabot), Bonjet CW1 (Orient Chemical Co., Ltd.) )) And the like.

[Surfactants other than Surfactant A]
In the ink of the present invention, in addition to the surfactant A described above, other surfactants can be used as long as the effects of the present invention are not impaired. By adding other surfactants, ink ejection stability and image quality can be improved.

Other surfactants that can be used in the ink of the present invention include anionic surfactants such as dialkylsulfosuccinates, alkylnaphthalenesulfonates, and fatty acid salts; polyoxyethylene alkyl ethers, polyoxyethylene alkyl Nonionic surfactants such as allyl ethers, acetylene glycols, polyoxyethylene / polyoxypropylene block copolymers: cationic surfactants such as alkylamine salts and quaternary ammonium salts; silicone-based and fluorine-based surfactants Surfactant is mentioned.

By selecting such a surfactant, it is possible to improve the ink dischargeability or improve the wettability without hindering the effect of the present invention (that is, without hindering the design of the surface tension fluctuation due to drying). Furthermore, the dot diameter can be increased. The addition amount of the other surfactant is preferably 0.5% by mass or more and less than 2.0% by mass with respect to the total mass of the ink.

[Other ingredients]
In addition to the above-mentioned components, the ink of the present invention contains urea, thiourea, antifungal agent, rust inhibitor, antifoaming agent, viscosity modifier, penetrating agent, pH adjuster, and nozzle drying inhibitor as necessary. Ethylene urea or the like can be added.

<Physical properties of inkjet ink>
The viscosity of the inkjet ink of the present invention is 50.0 mPa or less, preferably 0.5 mPa · s or more and less than 50 mPa · s. Within this range, droplets can be ejected using a thermal or piezo inkjet head.

The surface tension of the inkjet ink of the present invention is 25.0 mN / m or more and 35.0 mN / m or less. When the surface tension of the ink is less than 25 mN / m depending on the solvent, other surfactant, or the type of the surfactant, the difference in decrease in the surface tension due to the concentration of the surfactant is reduced. It is difficult to obtain an effect, and furthermore, it becomes difficult to eject ink by an ink jet method. On the other hand, it is preferably 35 mN / m or less from the viewpoint of ink ejection stability and wettability.

<< Method for producing inkjet ink >>
There is no restriction | limiting in particular in the manufacturing method of the inkjet ink of this invention, It can be made to be the same as that of a well-known method. For example, it can be produced by mixing the aforementioned β-alkoxypropionamide, surfactant A, water, organic solvent, pigment, resin and the like.

The mixing order of β-alkoxypropionamide, surfactant A, water, organic solvent, pigment, resin, etc. is not particularly limited. However, the resin is preferably mixed after the pigment dispersion treatment from the viewpoint of pigment dispersibility.

<Inkjet recording method>
In the ink jet recording method of the present invention, the ink jet ink of the present invention is used to form an image on a recording medium, and the recording medium is preferably an ink non-absorbing recording medium having low ink absorbability. Furthermore, it is preferable that the non-absorbing recording medium is polyvinyl chloride.

In the inkjet recording method of the present invention, it is preferable to form an image by heating the recording medium. By heating the recording medium, the drying and thickening speed of the ink is remarkably improved, and high image quality can be obtained. Also, the durability of the image is improved.

It is preferable to adjust the recording surface temperature of the recording medium to 45 ° C. or more and 90 ° C. or less, more preferably 45 ° C. or more and 60 ° C. or less by heating. From the viewpoint of obtaining sufficient image quality and sufficient image durability, from the viewpoint of enabling drying after ink ejection to be processed in a short time, and from the viewpoint of stable printing.

As the heating method, a method of heating a contact heater from the bottom of the recording medium by incorporating a heater in the media transport system or the platen member, or a method of heating non-contact from below or above by a lamp or the like can be selected.

Further, the method of the ink jet head used for image formation is not particularly limited, and for example, an on-demand method or a continuous method can be used. Also, the discharge method is not particularly limited. For example, electro-mechanical conversion method (for example, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), electro-thermal conversion method Any discharge method such as a thermal ink jet type or a bubble jet (registered trademark) type can be used.

(recoding media)
As described above, the recording medium applicable to the ink jet recording method using the water-based ink-jet ink of the present invention includes, for example, a surface having a resin in addition to a recording medium having a high ink absorbing ability such as plain paper, ink jet exclusive paper, and cloth. Examples thereof include non-ink-absorbing recording media having low or no ink absorbing ability, such as manufactured recording media. In particular, the present invention exhibits an excellent effect during ink jet recording on a non-ink-absorbing recording medium.

<Non-ink-absorbing recording medium>
An ink non-absorbing recording medium applicable to the present invention will be described.

The non-ink-absorbing recording medium refers to a recording medium in which the surface of the surface on which recording is performed by the ink jet method is difficult to penetrate water. In particular, it refers to a medium having an ink absorption rate of 0 to 0.05 cc / m ² · ms ^1/2 or less in the Bristow test. The effect of the present invention is particularly high for media having a hydrophobic or polar surface with a surface energy of about 0.02 to 0.05 J · cm ⁻² .
Examples of non-ink-absorbing recording media include resin plates such as polystyrene and acrylonitrile-butadiene-styrene copolymer (ABS resin); plastic films such as vinyl chloride and polyethylene terephthalate (PET), or these plastic films as paper Affixed to the surface of the substrate; soft polyvinyl chloride, hard polyvinyl chloride, acrylic board, polyolefin board, etc .; glass; tile; rubber; synthetic paper; coated paper.

These non-ink-absorbing recording media have poor ink absorbability, and since the surface energy of the recording medium is low, ink absorption does not occur even when printing with a water-based inkjet ink, and drying properties are poor. Further, since the image is disturbed by repelling the ink or the adhesiveness of the ink is low, the image forming property and the image durability are poor. Therefore, by applying the inkjet ink of the present invention, even with these recording media, white spots do not occur, and an image excellent in image uniformity, glossiness, abrasion resistance, and the like can be obtained.

Also, printing using the ink of the present invention exhibits a particularly excellent effect when an image is formed on a recording medium made of polyvinyl chloride. Specific examples of the recording medium made of polyvinyl chloride include SOL-371G, SOL-373M, SOL-4701 (manufactured by Big Technos Co., Ltd.), glossy polyvinyl chloride (manufactured by System Graphy Co., Ltd.), KSM-VS. , KSM-VST, KSM-VT (above, manufactured by Kimoto Co., Ltd.), J-CAL-HGX, J-CAL-YHG, J-CAL-WWWG (above, manufactured by Kyosho Osaka Co., Ltd.), BUS MARK V400 F vinyl , Litecal V-600F vinyl (above, made by Flexcon), FR2 (made by Hanwha), LLBAU13713 (above, made by Sakurai Co., Ltd.), P-370B, P-400M (above, made by Kambo Plus Co., Ltd.), S02P, S12P, S13P, S14P, S22 , S24P, S34P, S27P (above, manufactured by Grafityp), P-223RW, P-224RW, P-249ZW, P-284ZC (above, manufactured by Lintec Corporation), LKG-19, LPA-70, LPE-248, LPM-45, LTG-11, LTG-21 (above, Shinsei Co., Ltd.), MPI3023 (Toyo Corporation Co., Ltd.), Napoleon Gloss Polyvinyl chloride (Fujiki Electronics Co., Ltd.), JV-610 Y-114 (above, manufactured by ICC Corporation), NIJ-CAPVC, NIJ-SPVCGT (above, manufactured by Nichie Corporation), 3101 / H12 / P4, 3104 / H12 / P4, 3104 / H12 / P4S, 9800 / H12 / P4, 3100 / H12 / R2, 3101 / H12 / 2, 3104 / H12 / R2, 1445 / H14 / P3, 1438 / One Way Vision (manufactured by Inetrcoat, Inc.), JT5129PM, JT5728P, JT5822P, JT5829P, JT5829R, JT5829PM, JT5829RM, JT5929PM (above, Mactac) MPI1005, MPI1900, MPI2000, MPI2001, MPI2002, MPI3000, MPI3021, MPI3500, MPI3501 (above, manufactured by Avery), AM-101G, AM-501G (above, manufactured by Ginichi Co., Ltd.), FR2 (manufactured by Hanwha Japan Co., Ltd.) ), AY-15P, AY-60P, AY-80P, DBSP137GGH, DBSP137GGL (above, manufactured by Insight Inc.) , SJT-V200F, SJT-V400F-1 (above, manufactured by Hiraoka Orizome Co., Ltd.), SPS-98, SPSM-98, SPSH-98, SVGL-137, SVGS-137, MD3-200, MD3-301M, MD5 -100, MD5-101M, MD5-105 (manufactured by Metamark), 640M, 641G, 641M, 3105M, 3105SG, 3162G, 3164G, 3164M, 3164XG, 3164XM, 3165G, 3165SG, 3165M, 3169M, 3451SG, 3551G, 3551M, 3631, 3641M, 3651G, 3651M, 3651SG, 3951G, 3641M (above, manufactured by Orafol), SVTL-HQ130 (manufactured by Lamy Corporation), SP300 GWF, PCLEARAD vinyl (above, manufactured by Catalina), RM-SJR (produced by Ryoyo Corporation), Hi Lucky, New Lucky PVC (above, made by LG), SIY-110, SIY-310, SIY-320 (above, Sekisui Chemical Industry Co., Ltd.), PRINT MI Frontlit, PRINT XL Light weight banner (above, manufactured by Endexex), RIJET 100, RIJET 145, RIJET 165 (above, made by Ritrama), NM-SG, NM-SM Company), LTO3GS (manufactured by Lucio Co., Ltd.), easy print 80, performance print 80 (manufactured by Jetgraph Corporation), DSE 550, DSB 550, DSE 800G, SE 802/137, V250WG, V300WG, V350WG (manufactured by Hexis Ltd.), Digital White 6005PE, 6010PE (or, Multifix Co., Ltd.).

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Preparation of ink>
(Preparation of cyan pigment dispersion)
As a pigment dispersant, 20 parts of Floren TG-750W (solid content 40%, manufactured by Evonik Degussa) and 3 parts of triethylene glycol monobutyl ether were added to 62 parts of ion-exchanged water. To this solution, C.I. I. 15 parts of Pigment Blue 15: 3 was added and premixed, and then dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads to obtain a cyan pigment dispersion having a pigment solid content of 15%. It was.

[Preparation of ink C-1]
β-alkoxypropionamides 3-butoxy-N, N-dimethylpropionamide (abbreviated as BDMPA in Table 1) and 1,2 hexanediol (abbreviated as HDO in Table 1) ) And 10 parts of dipropylene glycol monomethyl ether (abbreviated as DPGME in Table 1), 30 parts of ion-exchanged water were added, and then, as a surfactant A, MegaFac F-477 ( 0.005 part of DIC Corporation (fluorine-based surfactant) is added, and 17 parts of Jonkrill JDX-6500 (BASF Corporation, acrylic resin, solid content 29.7%), which is a water-soluble resin, is added thereto. Was added and stirred, and the total amount was adjusted to 80 parts with ion-exchanged water.

Next, 20 parts of the above-prepared cyan pigment dispersion was added thereto to make the total amount 100 parts, and the mixture was stirred and filtered through a 0.8 μm filter to obtain ink C-1.

[Preparation of inks C-2 to C-20]
In the preparation of the ink C-1, the types and addition amounts of β-alkoxypropionamides, the types and addition amounts of organic solvents, and the types and addition amounts of surfactants were changed to the combinations shown in Table 1. In the same manner, inks C-2 to C-20 were prepared. The remaining amount of water listed in Table 1 is an added amount that makes the total amount of ink 100 parts.

In addition, the detail of each additive described with the abbreviation in Table 1 is as follows.

<Β-alkoxypropionamides>
BDMPA: 3-butoxy-N, N-dimethylpropionamide MDMPA: 3-methoxy-N, N-dimethylpropionamide <Organic solvent>
PDN: 2-pyrrolidinone HDO: 1,2-hexanediol DPGME: Dipropylene glycol monomethyl ether DEGBE: Diethylene glycol monobutyl ether <Resin>
JDX: Jonkrill JDX-6500 (manufactured by BASF, acrylic resin, solid content 29.7%)
<Surfactant A>
MF477: MegaFuck F-477 (manufactured by DIC Corporation, fluorosurfactant)
Novec: Novec 4432 (made by 3M, fluorine-based polymer surfactant)
BYK: BYK340 (manufactured by Big Chemie, fluorosurfactant, solid content 10%)
TSF: TSF4445 (made by Momentive Performance Materials, silicone activator)
<Other surfactants>
E108: Emulgen 108 (manufactured by Kao Corporation, polyoxyethylene alkyl ether surfactant)
F100: Footent 100 (manufactured by Neos, fluorinated surfactant)
DW: BYK DYNWET 800 (by Big Chemie, polyoxyethylene alkyl ether surfactant)

<Measurement of ink characteristic values>
For each of the inks prepared above, the surface tension at 25 ° C. was measured by a platinum plate method using a surface tension meter CBVP-Z manufactured by Kyowa Interface Science.

Further, the surface tension (mN / m) when 1.0% by mass of each surfactant was added to 30% by mass of the β-alkoxypropionamides used for the preparation of each ink was measured in the same manner. The inks (C-8 to C-11) and (C-19, C-20) to which β-alkoxypropionamide was not added were not measured.

《Image formation》
Four rows of piezo heads having a nozzle diameter of 28 μm, a driving frequency of 10 kHz, a nozzle number of 512, a minimum droplet amount of 14 pl, and a nozzle density of 360 dpi (dpi in the present invention represents the number of dots per 2.54 cm) are mounted. Each cyan ink was loaded into one of the inkjet heads of an on-demand inkjet printer.

Also, in the inkjet printer, the recording medium can be arbitrarily heated from the back surface (the surface opposite to the surface facing the head) by a contact heater. In addition, an ink emptying position and a blade wipe type maintenance unit are provided at the head storage position so that the head can be cleaned at an arbitrary frequency.

Next, a solid image with a printing resolution of 720 dpi × 720 dpi and a 10% × 10 cm 100% duty is recorded by unidirectional 4-pass printing on MD5 (manufactured by Metamark), which is a soft vinyl chloride sheet for solvent inkjet printers, as a recording medium. Images were taken (in this case, the Pass time interval was about 8 s). Further, during printing on the recording medium, the recording medium was heated from the back side and controlled with a heater so that the surface temperature of the recording medium during image recording was 50 ° C. The surface temperature of the recording medium was measured using a non-contact thermometer (IT-530N type, manufactured by HORIBA, Ltd.). Also, immediately after recording, the recording medium was left on a hot plate at 60 ° C. to dry the image.

<Evaluation of recorded images>
(Evaluation of mottle resistance)
For the 100% duty solid image portion of the recorded image, the uniformity of the printed surface (darkness unevenness of the ink application portion) was visually observed, and the mottle resistance was evaluated according to the following criteria.

◎: Solid image is uniform and no unevenness is observed. ○: Density unevenness in the solid image is inconspicuous, but there are scattered areas with extremely weak shading at the boundary between the solid image and the unprinted portion. : Shading unevenness is observed in the solid image portion, and it is not recognized as a uniform solid image. ×: Occurrence of repellency and mottle is observed in the entire image by visual observation, and a large number of shadings in the size of mm are generated. In the above-mentioned evaluation rank, which is unacceptable for practical use, ◎ and ○ were judged to be practically preferable.

(Evaluation of whiteout failure tolerance)
About the 100% Duty solid image portion of the recorded image, the degree of embedding of the print surface was determined by visual observation, and white spots were evaluated according to the following criteria.

◎: The whole solid image is uniformly filled, and no white spots are observed. ○: Slightly unprinted areas (white areas) are observed in the solid image, but the whole image is uniform. △: White spots connected in a streaky pattern occur in the solid image, streak in the scanning direction is recognized even when separated by 50 cm or more, and a decrease in density is recognized. ×: Depending on the portion that was not buried by visual observation. A large white spot was generated, and the image was recognized as a white streak and the image quality was not practical. In the above evaluation rank, お よ び and ○ were judged to be practically preferable.

(Evaluation of abrasion resistance)
The 100% duty solid image portion of the recorded image was rubbed 30 times with a dry cotton (Kanakin No. 3) with a weight of 200 g, and the rub resistance was evaluated according to the following criteria.

○: No change in image was observed. ×: White line-shaped scratches or image peeling was observed. In the above evaluation rank, ○ was determined to be practically preferable.

(Evaluation of gloss)
For the 100% duty solid image portion of the recorded image, the gloss was visually observed, and the gloss was evaluated according to the following criteria.

○: An image having glossiness.
×: No glossiness or white image as a film is stretched on the surface. −: Severe repellency and gloss was difficult to discriminate. did.

Table 2 shows the results obtained as described above.

As is clear from the results shown in Table 2, the ink of the present invention containing the specified amounts of β-alkoxypropionamides and surfactant A is excellent in gloss and scratch resistance, and has a solid image area with mottle resistance and whiteness. It can be seen that the fault tolerance is improved.

In particular, Comparative Example Ink C-7 contains β-alkoxypropionamides but does not contain Surfactant A, and therefore has insufficient mottle resistance and white spot failure resistance. This is contrary to the general phenomenon that in inks C-9 to 11 which do not contain β-alkoxypropionamides, the more the surfactant is contained, the more the mottle resistance and white spot failure resistance are slightly improved. Similarly, the ink of the present invention has improved mottledness and whiteout failure resistance compared to ink C-11 whose image quality has been improved by using only a surfactant, and has no problem with gloss or abrasion resistance. I understand.

As described above, 1) containing β-alkoxypropionamides, and 2) as surfactant A, the surface tension of a 30% by weight aqueous solution of β-alkoxypropionamides can be 25.0 mN / m or less. 3) In general, an ink containing a very small amount of an agent (silicone-based polymer type surfactant or fluorine-based polymer type surfactant) is generally improved in mottle resistance and white spot failure resistance, and is resistant to rubbing. A printed matter with no problem in properties and gloss could be obtained.

Example 2
In the ink preparation of Example 1, C.I. I. Instead of Pigment Blue 15: 3, Pigment Black 7 (Mitsubishi Chemical Corporation, # 52) as a black pigment, Pigment Yellow 150 (LANXESS, E4GN-GT CH20015) as a yellow pigment, Pigment Red 122 (Large) as a magenta pigment A black ink, a yellow ink, and a magenta ink were prepared in the same manner except that Nissei Kasei Co., Ltd. CFR-321) was used, and the same evaluation as in Example 1 was performed. The same effect as the result described in Table 2 of Example 1 could be obtained.

The ink-jet ink of the present invention does not have white spots even when an image is formed on a recording medium with poor ink absorbability, and can provide an image excellent in image uniformity, glossiness, and abrasion resistance. Therefore, it is possible to form an image on a wide variety of recording media that hardly penetrate water, such as polyvinyl chloride, and can be applied to printing in various fields.

Claims (8)

1. In the inkjet ink containing water, organic solvent, pigment and resin,
   1.0 mass% or more of β-alkoxypropionamides represented by the following general formula (1):
   Containing 0.001% by mass or more and 0.20% by mass or less of surfactant A having the following characteristics;
   An inkjet ink having a viscosity of 50.0 mPa or less and a surface tension of 25.0 mN / m or more and 35.0 mN / m or less.
   

   

   [Wherein R ₁ represents a linear or branched alkyl group having 1 to 6 carbon atoms,
   R ₂ and R ₃ each represent a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ may be the same or different. ]
   Surfactant A: When 1.0% by mass is added to a 30% by mass aqueous solution of the β-alkoxypropionamides, the surface tension of the 30% by mass aqueous β-alkoxypropionamides is 25.0 mN / m. Surfactant that can be:
2. 2. The inkjet ink according to claim 1, wherein the surfactant A is a fluorine-based surfactant or a silicone-based polymer surfactant.
3. 3. The total amount of β-alkoxypropionamides represented by the general formula (1) and the organic solvent is 10.0% by mass or more and 40.0% by mass or less, according to claim 1 or 2. The inkjet ink as described.
4. The inkjet ink according to any one of claims 1 to 3, wherein the total amount of the pigment and the resin is 8.0% by mass or more.
5. An ink jet recording method comprising forming an image on a recording medium using the ink jet ink according to any one of claims 1 to 4.
6. 6. The ink jet recording method according to claim 5, wherein the recording medium is a non-ink-absorbing recording medium.
7. The ink jet recording method according to claim 6, wherein the non-ink-absorbing recording medium is polyvinyl chloride.
8. The inkjet recording method according to claim 5, wherein the recording medium is heated to 45 ° C. or higher and 90 ° C. or lower to form an image.