CN101463207A - Ink composition for ink jet recording - Google Patents

Abstract

The present invention provides an ink composition capable of realizing a high-quality image without white streaks or roughness even at a low resolution when printing on art paper or the like. The ink composition for inkjet recording of the present invention contains a coloring material, water, an alcohol solvent, and a surfactant, wherein the alcohol solvent contains a poorly water-soluble alkanediol, a water-soluble 1,2-alkanediol and Water-soluble 1,3-alkanediol.

Description

Ink composition for inkjet recording

technical field

The present invention relates to an inkjet recording ink composition capable of obtaining high-quality recorded matter without printing unevenness even on various recording media, especially synthetic paper, printing paper, resin film and other recording media with low water absorption .

Background technique

The inkjet recording method is a printing method in which small droplets of ink are splashed and adhered to a recording medium such as paper to print. Due to the innovation and progress of inkjet recording technology in recent years, the inkjet recording method is currently used in the field of high-definition printing that can be realized only by silver halide photography or offset printing. Subsequently, the development of a high-gloss recording medium that is not inferior to printing paper or art paper, which was first used in the field of silver salt photographs or offset printing, so-called special paper for inkjet recording, can achieve the same effect as silver salt photographs. Ink for recording on inkjet media with equivalent glossy images. We are also developing inkjet recording inks that can achieve the same image quality as silver halide photographs even when plain paper is used.

In recent years, with the popularization of image forming technology derived from digital data, especially in the printing field, the demand for digital color proof (DTP) has been increasing, and the inkjet recording method has also begun to be applied to DTP. Since the color reproduction and stability reproduction of the printed matter are required in DTP, special paper for inkjet recording is usually used when making a glue sample by inkjet recording.

However, in color correction applications, there is a need to perform inkjet recording on printed paper rather than special paper, and it is also possible to consider a sample obtained by directly performing inkjet recording on printed paper without using special paper. As the final calibration sample, the cost required for calibration can be greatly reduced. In addition, synthetic paper obtained by mixing inorganic fillers with polyethylene resin or polyester resin and forming a film widely used in the printing field has excellent recyclability, and has attracted attention as an environmentally friendly material in recent years.

Printed paper is coated paper provided with a coating layer for receiving oil-based ink on its surface, but the coating layer has a characteristic of insufficient ink absorption capacity. Therefore, when water-based pigment inks generally used for inkjet recording are used, ink permeability to recording media (printed paper) is low, and leaks or aggregation unevenness may occur on images.

In view of the above problems, for example, Japanese Patent Application Publication No. 2005-194500 (Patent Document 1) discloses a pigment-based ink, which uses a polysiloxane compound as a surfactant and adds 1,2- Alkanediols such as hexanediol are used as co-solvents, which can improve leakage and have excellent gloss for special paper. In addition, Japanese Patent Application Laid-Open No. 2003-213179 (Patent Document 2) proposes to suppress the permeability of the ink in the recording medium by adding a water-soluble organic solvent such as glycerol or 1,3-butanediol, so that high-quality ink can be obtained. Image.

[Patent Document 1] JP-A-2005-194500 Gazette

[Patent Document 2] JP-A-2003-213179

Contents of the invention

In the previous patent application (Japanese Patent Application No. 2007-241158), the present inventors added surfactants such as polysiloxane and two kinds of alkane diols and alkane triols as alcohol solvents to the ink, even if Even when printing at a low resolution on a recording medium with low liquid absorption such as printing paper, high-quality images without white streaks or roughness can be realized.

This time, by using specific alkanediols instead of alkanetriols, the inventors of the present invention came to the realization that not only printed paper but also recording media with no liquid absorption such as resin films can High-quality images free from white streaks and roughness can be realized. The present invention has been achieved in view of the above knowledge.

Therefore, an object of the present invention is to provide an ink capable of realizing a high-quality image without white streaks or roughness even when printing on a low-liquid-absorbing recording medium such as printing paper or a resin film at a low resolution. liquid composition.

Also, the inkjet recording ink composition of the present invention is an inkjet recording ink composition containing at least a coloring material, water, an alcohol solvent, and a surfactant, wherein,

The alcohol solvent contains poorly water-soluble alkanediol, water-soluble 1,2-alkanediol and water-soluble 1,3-alkanediol.

According to the present invention, it is possible to realize a high-quality image free from white streaks and roughness even when printing is performed at a low resolution on a low liquid-absorbing recording medium such as printing paper or a resin film.

Detailed ways

The inkjet recording ink composition of the present invention is an inkjet recording ink composition containing at least a coloring material, water, an alcohol solvent, and a surfactant, wherein,

The alcohol solvent contains poorly water-soluble alkanediol, water-soluble 1,2-alkanediol and water-soluble 1,3-alkanediol. Hereinafter, each component is demonstrated.

<definition>

In the present specification, the alkanediol may be any of linear or branched alkanediols.

In addition, the so-called water solubility means that the solubility in water (the amount of solute relative to 100 g of water) is 10.0 g or more, and the so-called poor water solubility means that the solubility in water (the amount of solute relative to 100 g of water) is less than 1.0 g.

<Alcohol solvent>

The alcohol solvent used in the ink composition for inkjet recording of the present invention contains at least three organic solvents. By containing the above-mentioned three kinds of alcohol solvents as essential components, it can be used on printing paper, especially art paper with relatively high ink absorption ability, POD use paper (such as (Ricoh Co., Ltd. (Ricoh Co., Ltd.) 100, etc.), Ink aggregation is suppressed in laser printing paper (such as Seiko Epson Co., Ltd., LPCCTA4, etc.), and high-quality images without white streaks and roughness can be realized even when printing at low resolutions. Not only that, but even when printing is performed on a recording medium such as a resin film that has little ink absorption ability, high-quality images without white streaks and roughness can be realized.

It should be noted that, in this specification, the so-called agglomeration refers to the local concentration unevenness of the same color system that occurs when printing on a surface (for example, when printing on a 6-inch square with a single color (not the number of colors of ink)), and does not mean It does not mean that a portion of the surface of the recording medium that is not covered with ink remains. In addition, the so-called white streaks indicate the following phenomenon: when printing on the surface (for example, when printing on a 6-inch square with a single color), there is no local uneven color density of the same color system, and it remains in the form of stripes in the driving direction of the recording head. There is a part of the surface of the recording medium that is not covered with ink. In addition, the so-called roughness or poor ink placement means the following phenomenon: when printing on the surface as above, there is no local uneven color density of the same color system, and there is a part of the surface of the recording medium that is not covered with ink. The surface of the recording medium is rough and grainy.

As described above, by adding water-soluble 1,3-alkanediol as an essential component in addition to water-slightly soluble alkanediol and water-soluble 1,2-alkanediol, whitening-free The cause of the high-quality image with graininess and roughness is not yet determined, but it is considered as follows.

The cause of ink aggregation during recording on printed paper is considered to be that the surface tension of ink dots is high, and the contact angle between the printed paper surface and ink droplets is high, so the printed paper ejects ink. Even when white streaks or poor ink placement occur during low-resolution recording, ink aggregation can be suppressed by lowering the surface tension of the ink adhering to the surface of the printing paper.

In addition, it is considered that the cause of white streaks or poor ink placement in low-resolution recording is that the ink dots adhering to the surface of the printing paper contact the adjacent ink dots, wet and spread each other, and the undried inks flow into each other. It is considered that the mutual ink flow occurs due to the difference in the drying time of the ink dots due to the difference in attachment time between adjacent ink dots or the size of the droplets at the time of attachment. Therefore, it is considered that in order to suppress the aggregation of ink and realize a high-quality image without white streaks and roughness even when printing at a low resolution, it is considered that it is preferable to adhere an ink with low surface tension and low fluidity to the printed surface. on this paper.

However, it is considered that when a penetrating lubricant is not used in order to reduce the fluidity of the ink, the ink dots attached to the surface of the printing paper dry faster, and the absorption of the ink is also accelerated, so the gap between the attached ink dots is lost. The time for wetting spreads, resulting in white streaks or poor ink placement in low-resolution recordings.

The water-soluble 1,3-alkanediol used in the present invention is a viscous substance such as glycerol. In addition, water-soluble 1,3-alkanediols are penetrating lubricants that exhibit lower surface tensions than glycerol. For example, the surface tension of 1,3-butanediol when made into a 10% aqueous solution is 55mN/m, and the surface tension of 3-methyl-1,3-butanediol when made into a 10% aqueous solution is 53mN /m.

In addition, when using a combination of a poorly water-soluble alkanediol and the above-mentioned two types of water-soluble alkanediols as an alcohol solvent, compared with the case of using a poorly water-soluble and water-soluble alkanediol and alkanetriol, the ink The drying property of the liquid is more excellent, so it can realize high-quality images not only on recording media with low liquid absorption such as printing paper, but also on recording media with no liquid absorption at all, such as resin films.

In the present invention, the poorly water-soluble alkanediol is preferably an alkanediol having 7 or more carbon atoms, for example, 1,2-heptanediol, 1,2-octanediol, 5-methano Base-1,2-hexanediol, 4-methyl-1,2-hexanediol, 4,4-dimethyl-1,2-pentanediol, etc. Among the above-mentioned poorly water-soluble alkanediols, 1,2-octanediol is more preferable.

In addition, as the water-soluble 1,2-alkanediol, an alkanediol having 6 or less carbon atoms is preferable, for example, 1,2-hexanediol, 1,2-pentanediol, 1,2- -Butanediol, 4-methyl-1,2-pentanediol, 3,3-dimethyl-1,2-butanediol, etc. Among the above-mentioned water-soluble alkanediols, the surface tension when more preferably made into 15% aqueous solution is water-soluble alkanediols below 28mN/m, particularly preferably 1,2-hexanediol (surface tension: 26.7mN/m ), 4-methyl-1,2-pentanediol (surface tension: 25.4 mN/m), 3,3-dimethyl-1,2-butanediol (surface tension: 26.1 mN/m). From the viewpoint of odor during printing, 1,2-hexanediol is preferable.

As the water-soluble 1,3-alkanediol, an alkanediol having 4 or more carbon atoms in the main chain is preferable, for example, 1,3-butanediol or 3-methyl-1,3-butane diol.

Among the above three alcohol solvents, the content ratio of the poorly water-soluble alkanediol to the water-soluble 1,2-alkanediol is preferably 6:1-1:3, more preferably 6:1-1:1. By setting it within this range, the poorly water-soluble alkanediol can be stably dissolved in the ink, thereby improving discharge stability. On the other hand, when the ratio of the water-soluble 1,2-alkanediol is larger than the above-mentioned range, it is difficult to simultaneously reduce the initial viscosity of the ink and reduce uneven aggregation. In addition, when the ratio of the water-soluble 1,2-alkanediol is less than the above range, it is difficult to stably dissolve the poorly water-soluble alkanediol in the ink, and it is difficult to suppress the change in viscosity over time or maintain storage stability. .

In addition, the content of the poorly water-soluble alkanediol and the water-soluble 1,3-alkanediol is preferably 1:1 to 1:18, more preferably 1:1 to 1:6. By setting it within this range, the initial viscosity of the ink can be lowered, and good clogging recovery properties can be realized. On the other hand, when the ratio of the water-soluble 1,3-alkanediol is larger than the above-mentioned range, the viscosity of the ink initial viscosity increases, and the drying property decreases. In addition, when the ratio of the water-soluble 1,3-alkanediol is less than the above range, the clogging recovery property deteriorates and the dryness increases, so it is difficult to ensure the wetting and spreading time of the ink, so it is difficult for the ink to cover the recording medium, and it is easy to generate White stripes.

In addition, the content ratio of water-soluble 1,2-alkanediol and water-soluble 1,3-alkanediol is preferably 1:1-1:36, more preferably 1:1-1:18. By setting it within this range, white streaks and roughness can be further suppressed when printing on printing paper with a low resolution. On the other hand, when the ratio of the water-soluble 1,2-alkanediol is larger than the above-mentioned range, the initial viscosity of the ink increases and the drying property decreases. In addition, when the proportion of water-soluble 1,3-alkanediol is less than the above range, the clogging recovery property will be deteriorated, and due to the increased dryness, it will be difficult to ensure the wetting and spreading time of the ink, so it is difficult for the ink to cover the recording medium, and it is easy to Produce white streaks.

The content of the poorly water-soluble alkanediol is preferably 1 to 3% by weight, more preferably 1.5 to 2.5% by weight, based on the entire ink composition. When it is less than 1% by weight, printing unevenness may occur on a recording medium with low ink absorption, such as printing paper. On the other hand, when it exceeds 3% by weight, it may not be completely dissolved in the ink.

It preferably contains 0.5 to 6% by weight of water-soluble 1,2-alkanediol, more preferably 0.5 to 3.0% by weight. When it is less than 0.5% by weight, it may not be possible to dissolve the poorly water-soluble alkanediol in the ink. On the other hand, when it exceeds 6% by weight, the initial viscosity of the ink may increase, which is not preferable.

The water-soluble 1,3-alkanediol is preferably contained in an amount of 3 to 18% by weight, more preferably 5 to 8% by weight, based on the entire ink composition. When it is less than 3% by weight, white streaks and a rough feeling may occur when printing on printing paper with a low resolution. On the other hand, when it exceeds 18 weight%, the drying property of the printed matter immediately after printing may be inferior.

<coloring material>

As the coloring material used in the ink composition for inkjet recording of the present invention, any of dyes and pigments can be used, but pigments can be preferably used from the viewpoint of light resistance or water resistance.

As the pigment, inorganic pigments and organic pigments can be used, and they can be used alone or in combination. As the inorganic pigment, for example, carbon black prepared by a known method such as a contact method, a furnace method, or a thermal method can be used in addition to titanium oxide and iron oxide. In addition, as the organic pigment, azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelated azo pigments, etc.), polycyclic pigments (such as phthalocyanine pigments, perylene pigments, etc.) can be used. Pigments, perionone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone (kinoflaron) pigments, etc.), dye chelates (such as alkali Sexual dye type chelates, acid dye type chelates, etc.), nitro pigments, nitroso pigments, nigrosine, etc.

Specific examples of pigments can be appropriately listed according to the type (color) of the ink composition to be obtained. For example, examples of pigments for yellow ink compositions include C.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, etc., one or two or more of the above pigments can be used. Among the above pigments, one or more selected from the group consisting of C.I. Pigment Yellow 74, 110, 128, and 147 are particularly preferably used. In addition, examples of pigments for the magenta ink composition include C.I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57:1, 112, 122, 123 , 168, 184, 202, 209; C.I. Pigment Violet 19, etc., one or two or more of the above pigments can be used. Among the above pigments, it is particularly preferable to use one or two or more selected from the group consisting of C.I. Pigment Red 122, 202, and 209 and C.I. Pigment Violet 19. In addition, examples of pigments for the cyan ink composition include C.I. Pigment Blue 1, 2, 3, 15:3, 15:4, 15:34, 16, 22, 60; C.I. Vat Blue 4, 60, etc. , one or more of the above-mentioned pigments can be used. Among the above-mentioned pigments, it is particularly preferable to use C.I. Pigment Blue 15:3 and/or 15:4, and it is especially preferable to use C.I. Pigment Blue 15:3.

In addition, examples of pigments for the black ink composition include carbon blacks (C.I. Pigment Black 7) such as furnace black, lamp black, acetylene black, and channel black; inorganic pigments such as iron oxide pigments; aniline Organic pigments such as black (C.I. Pigment Black 1), etc., but in the present invention, carbon black can be preferably used. Specific examples of carbon black include #2650, #2600, #2300, #2200, #1000, #980, #970, #966, #960, #950, #900, #850, MCF-88, #55 , #52, #47, #45, #45L, #44, #33, #32, #30 (manufactured by Mitsubishi Chemical Corporation), Special Blaek 4A, 550, Printex 95, 90, 85, 80, 75, 45, 40 (made by Degussa Corporation above), Regal660, RmogulL, monarch1400, 1300, 1100, 800, 900 (made by Cabot Corporation above), Raven7000, 5750, 5250, 3500, 3500, 2500ULTRA, 2000, 1500, 1255, 1200, 1190ULTRA, 1170, 1100ULTRA, Raven5000UIII, (above, manufactured by Columbian), etc.

The concentration of the pigment may be adjusted to an appropriate concentration (content) of the pigment when preparing the ink composition, so it is not particularly limited, but it is usually 5 to 20% by weight.

From the viewpoint of simultaneously obtaining the glossiness of the image, anti-tarnishing bronze color (browns) and the storage stability of the ink composition, and at the same time being able to form a color image with more excellent glossiness, it is preferable that the pigment is mixed with the following dispersant The pigment obtained by kneading treatment.

<Dispersant>

The ink composition of the present invention preferably contains at least one resin selected from styrene-acrylic copolymer resins, polyurethane resins, and fluorene resins as a dispersant for dispersing the coloring material. The above-mentioned copolymer resin is adsorbed on the pigment to improve the dispersibility.

Specific examples of the hydrophobic monomer of the copolymer resin include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, acrylic acid Isopropyl, isopropyl 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, isooctyl acrylate, isooctyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, acrylic acid Decyl ester, decyl methacrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, 2-hydroxyethyl acrylate, methyl 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate, 2-dimethylaminoethyl methacrylate, 2-diethyl acrylate Aminoethyl methacrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, methyl Cyclohexyl acrylate, phenyl acrylate, phenyl methacrylate, nonylphenyl acrylate, nonylphenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, methacrylic acid Dicyclopentenyl ester, bornyl acrylate, bornyl methacrylate, 1,3-butylene glycol diacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene diacrylate Glycol ester, 1,4-butylene glycol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, three Ethylene Glycol Diacrylate, Triethylene Glycol Dimethacrylate, Tetraethylene Glycol Diacrylate, Tetraethylene Glycol Dimethacrylate, Polyethylene Glycol Diacrylate, Polyethylene Glycol Dimethacrylate Acrylates, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate , trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, glycerol acrylate, glycerol methacrylate, styrene, methyl styrene, vinyl toluene, etc. These monomers may be used alone or in combination of two or more.

As a specific example of a hydrophilic monomer, acrylic acid, methacrylic acid, maleic acid, itaconic acid etc. are mentioned, for example.

From the viewpoint of obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition at the same time, and at the same time being able to form a color image with better glossiness, the combination of the hydrophobic monomer and the hydrophilic monomer The copolymer resin is preferably styrene-(meth)acrylic acid copolymer resin, styrene-methylstyrene-(meth)acrylic acid copolymer resin or styrene-maleic acid copolymer resin, (meth)acrylic acid-(meth) At least one of acrylate copolymer resin or styrene-(meth)acrylic acid-(meth)acrylate copolymer resin.

The copolymer resin may be a resin containing a polymer obtained by reacting styrene and acrylic acid or an ester of acrylic acid (styrene-acrylic resin). Alternatively, the copolymer resin may be an acrylic water-soluble resin. Alternatively, salts of sodium, potassium, ammonium, or the like of the above substances may be used.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and simultaneously being able to form a color image with better glossiness, the content of the above-mentioned copolymer resin is relative to 100 parts by weight of the pigment , preferably 10 to 50 parts by weight, more preferably 10 to 35 parts by weight.

In addition, in the present invention, by using the polyurethane resin as the pigment dispersant, the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition can be obtained at the same time, and a color image with better glossiness can be formed at the same time. The polyurethane resin is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound. In the present invention, it is preferably a resin having a urea bond and/or an amide bond and an acidic group.

Examples of diisocyanate compounds include araliphatic diisocyanate compounds such as 1,6-hexamethylene diisocyanate and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate, toluene diisocyanate, and phenylmethane diisocyanate. and other aromatic diisocyanate compounds and their modified products.

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

The polyurethane resin preferably has a carboxyl group.

In addition, in the present invention, a fluorene-based resin can also be used as the pigment dispersant.

The weight ratio of the copolymer resin to the polyurethane resin (the former/the latter) is preferably 1/2 to 2/1, but at the same time, the glossiness of the color image, the bronze color of anti-tarnishment and the storage stability of the ink composition are obtained. From the viewpoint of being able to form a color image with more excellent glossiness and at the same time, it is more preferably 1/1.5 to 1.5/1.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time forming a color image with better glossiness, the solid content of the pigment and the solid content of the pigment other than the pigment The weight ratio (the former/the latter) is preferably 100/20 to 100/80.

From the point of view of simultaneously obtaining the glossiness of the color image, the bronze color of anti-tarnishment and the storage stability of the ink composition, and at the same time being able to form a color image with better glossiness, the content of the copolymer resin is relative to 100 parts by weight of the above-mentioned The pigment is preferably 10 to 50 parts by weight, more preferably 10 to 35 parts by weight.

From the point of view of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time being able to form a color image with better glossiness, the content of the polyurethane resin is relative to 100 parts by weight of the above-mentioned The pigment is preferably 10 to 40 parts by weight, more preferably 10 to 35 parts by weight.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time being able to form a color image with better glossiness, the content of the fluorene-based resin is relative to 100 parts by weight. The pigment is preferably 20-200 parts by weight, more preferably 10-80 parts by weight.

From the viewpoint of obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition at the same time, and at the same time forming a color image with better glossiness, the total amount of the copolymer resin and the polyurethane resin is preferably 90 parts by weight or less (more preferably 70 parts by weight or less) is used relative to 100 parts by weight of the pigment.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the bronze color of anti-tarnishment and the storage stability of the ink composition, and at the same time being able to form a more excellent glossiness, the acid value of the copolymer resin is preferably 50 to 320, more preferably 100-250.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time being able to form a more excellent glossiness, the acid value of the polyurethane resin is preferably 10 to 300, more preferably 20 to 100. In addition, the acid value is the mg amount of KOH required for 1 g of resins in total.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time being able to form a more excellent glossiness, the weight average molecular weight (Mw) of the copolymer resin is preferably 2,000 to 3 Ten thousand, more preferably 2,000 to 20,000.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time being able to form a more excellent glossiness, the weight average molecular weight (Mw) of the polyurethane resin before crosslinking is preferably It is 1 million to 200,000, more preferably 1,000 to 50,000. Mw is determined, for example, by GPC (Gel Permeation Chromatography).

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time being able to form a more excellent glossiness, the glass transition temperature (Tg; measured according to JISK6900) of the copolymer resin is preferably It is 30°C or higher, more preferably 50 to 130°C.

From the viewpoint of simultaneously obtaining the glossiness of the color image, the anti-bronze color and the storage stability of the ink composition, and at the same time being able to form a more excellent glossiness, the glass transition temperature (Tg; measured according to JISK6900) of the polyurethane resin is preferably -50 to 200°C, more preferably -50 to 100°C.

The copolymerized resin has the situation of being adsorbed in the pigment and the situation of being free in the pigment dispersion liquid, so as to simultaneously obtain the glossiness of the color image, the anti-change bronze color and the storage stability of the ink composition, and at the same time, it can form a more glossy color image. From the standpoint of excellence, the copolymer resin preferably has a maximum particle size of 0.3 μm or less, more preferably an average particle size of 0.2 μm or less (more preferably 0.1 μm or less). It should be noted that the average particle diameter is the average of the dispersion diameters (cumulative 50% diameter) of the particles actually formed by the pigment in the dispersion liquid, and can be measured, for example, using Microtrac UPA (Microtrac Inc.).

In addition, the said fluorene resin will not be limited at all as long as it is resin which has a fluorene skeleton, For example, it can obtain by copolymerizing the following monomer unit.

Cyclohexane, 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethyl (CASNo.4098-71-9)

Ethanol, 2,2'-[9H-fluorene-9-indene bis(4,1-phenyleneoxy)]bis (CAS No.117344-32-8)

Propionic acid, 3-hydroxy-2-(hydroxymethyl)-2-methyl (CAS No.4767-03-7)

Ethylamine, N, N-diethyl-(CAS No.121-44-8)

In addition, a surfactant can be used as a dispersant. Examples of the surfactant include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, polycondensates of higher fatty acids and amino acids, sulfosuccinates, Anionic surfactants such as naphthenates, liquid fatty oil sulfates, alkyl allyl sulfonates, etc.; cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts, phosphonium, etc.; polyoxygen Nonionic surfactants such as ethylene alkyl ethers, polyoxyethylene alkyl esters, sorbic acid alkyl esters, polyoxyethylene sorbic acid alkyl esters, and the like. Of course, the function as a surfactant can be realized by adding the above-mentioned surfactant to the ink composition.

<Surfactant>

The ink composition for inkjet recording of the present invention contains a surfactant as an essential component. As a recording medium, the recording medium coated with an ink-accepting resin on its surface can realize an image with excellent gloss even on a recording medium such as photographic paper where glossiness is more important, by using a surfactant. Especially in the case of using a recording medium such as printed paper, which is provided with a coating layer for accepting oily ink on the surface receiving layer, it is also possible to prevent leakage (diffusion) between colors, and at the same time prevent the ink from accompanying ink. Whitening caused by reflected light of light that occurs due to increased liquid adhesion.

As the surfactant used in the present invention, organopolysiloxane-based surfactants can be preferably used, which can improve the wettability on the surface of the recording medium and improve the ink permeability when forming a recorded image. When organopolysiloxane surfactants are used, since the above three types of alcohol solvents are contained, the solubility of the surfactant in the ink can be improved, and the generation of insoluble matter can be suppressed, thereby achieving better ejection stability. ink composition.

Above-mentioned surfactant can use commercially available surfactant, for example can use Olfine PD-501 (manufactured by Nissin Chemical Industry Co., Ltd.), Olfine PD-502 (manufactured by Nissin Chemical Industry Co., Ltd.), Olfine PD-570 (manufactured by Nissin Chemical Industry Co., Ltd.) Shin Chemical Industry Co., Ltd.), etc.

In addition, as an organopolysiloxane-based surfactant, one or more compounds represented by the following formula (I) may be more preferably contained, or in the compound of the above formula (I), R is a hydrogen atom or a 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 5 or two or more compounds. In addition, it is more preferred that in the compound of the above formula (I), R is a hydrogen atom or a methyl group, a is an integer of 2-13, m is an integer of 2-50, and n is an integer of 1-8 or both above compounds. Or it is more preferable to contain one or two or more compounds in which R is a methyl group, a is an integer of 6-18, m is 0, and n is 1 among the compounds of the above formula (I). By using the above-mentioned specific organopolysiloxane-based surfactant, even when printing on printed paper as a recording medium, uneven aggregation of ink can be further improved.

(In the formula, 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.)

More preferably use the compound that a is the integer of 2～5 in the compound of above-mentioned formula (I), m is the integer of 20～40, n is the compound of the integer of 2～4; a is the integer of 7～11, m is 30～ A compound that is an integer of 50, and n is an integer of 3 to 5; a compound that is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2; or a is an integer of 6 to 10, m The compound which is an integer of 10-20, and n is an integer of 4-8. By using the above-mentioned compound, the aggregation unevenness of ink can be further improved. For example, the surfactant is 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 (I), and R is a hydrogen atom, a Surfactant obtained from the compound which is an integer of 7-11, m is an integer of 30-50, and n is an integer of 3-5.

In addition, it is more preferred to use compounds of the above formula (I) in which R is a hydrogen atom, a is an integer of 2 to 5, m is an integer of 20 to 40, and n is an integer of 2 to 4; or a is 7 to 11 Compounds in which m is an integer of 30-50 and n is an integer of 3-5. By using the above compound, uneven aggregation and wetting of the ink can be further improved.

In addition, it is further preferred to use compounds 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 compound of the above formula (I); or a is 6 to 2 The compound which is an integer of 10, m is an integer of 10-20, and n is an integer of 4-8. By using the above compound, uneven aggregation and wetting of the ink can be further improved.

Furthermore, it is more preferable to use a compound in which R is a methyl group, a is an integer of 6 to 12, m is 0, and n is 1 among the compounds of the above formula (I). By using the above compound, uneven aggregation and wetting of the ink can be further improved.

In addition, it is most preferable to use a compound in which R is a hydrogen atom, a is an integer of 7 to 11, m is an integer of 30 to 50, n is an integer of 3 to 5, R is a methyl group, and 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, and R is a methyl group, a is an integer of 6 to 10, m is an integer of 10 to 20, and n is 4 A surfactant obtained from a compound of an integer of ∼8. By using the above compound, uneven aggregation and wetting of the ink can be further improved.

Furthermore, it is most preferable to use a compound in which 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 in the above formula (I), R is a methyl group, and a is The surface activity obtained from the compound which is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, and R is a methyl group, a is an integer of 6 to 18, m is 0, and n is 1 agent. By using the above compound, uneven aggregation and wetting of the ink can be further improved.

The ink composition of the present invention preferably contains 0.01 to 1.0% by weight, more preferably 0.05 to 0.50% by weight of the aforementioned surfactant. In addition, it is preferable to use the above-mentioned surfactant in which R is a methyl group and the above-mentioned surfactant in which R is a hydrogen atom in combination, since small characters are not deformed. In particular, from the viewpoint of ink aggregation unevenness, it is preferable to use a larger content when using the above-mentioned surfactant whose R is a methyl group than when using the above-mentioned surfactant whose R is H.

Furthermore, it is more preferable that content of the said surfactant whose R is H is large with respect to the said surfactant whose R is a methyl group. Thereby, it is possible to improve the ink that is easy to bounce off, such as cast-coated paper, and the penetration speed is slow, and the uneven aggregation and leakage of ink in printing paper can be improved.

Other surfactants, specifically acetylene glycol-based surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, etc., may also be added to the ink composition of the present invention.

Among the above-mentioned surfactants, examples of acetylene diol-based surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl - 4-octyne-3,6-diol or 3,5-dimethyl-1-hexyne-3-ol, 2,4-dimethyl-5-hexyne-3-ol, etc. In addition, commercially available products can also be used as the acetylene glycol-based surfactant, for example, Olfine 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 Co., Ltd.).

<water, other ingredients>

The inkjet recording ink composition of the present invention contains the above-mentioned specific alcohol solvent, surfactant, and other various additives, and water as a solvent. As water, it is preferable to use pure water or ultrapure water such as ion-exchanged water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, it is preferable to sterilize the above-mentioned water by ultraviolet irradiation or adding hydrogen peroxide or the like to prevent the generation of mold or bacteria for a long period of time.

In addition, it is preferable that the ink composition of the present invention further contains a penetrating agent in addition to the above components.

As the penetrant, glycol ethers can be preferably used.

Specific examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-isopropyl ether, ethylene glycol mono-n-butyl ether, Alcohol mono-isobutyl ether, ethylene glycol mono-tert-butyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono- n-propyl ether, diethylene glycol mono-isopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-tert-butyl ether, triethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether , propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-isopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-tert-butyl ether, dipropylene glycol monomethyl ether, dipropylene glycol Glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol-isopropyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-tert-butyl ether, 1-Methyl-1-methoxybutanol and the like can be used alone or as a mixture of two or more of the above-mentioned compounds.

Among the above-mentioned glycol ethers, alkyl ethers of polyhydric alcohols are preferred, especially ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether , Diethylene glycol mono-n-butyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether or triethylene glycol mono- n-butyl ether. More preferred is triethylene glycol mono-n-butyl ether.

The amount of the penetrating agent added can be appropriately determined, but is preferably about 0.1 to 30% by weight, and more preferably about 1 to 20% by weight.

In addition, it is preferable that the ink composition of the present invention further contains a recording medium dissolving agent in addition to the above components.

As the recording medium dissolving agent, pyrrolidones such as N-methyl-2-pyrrolidone can be preferably used. The addition amount of the above-mentioned recording medium dissolving agent can be appropriately determined, but it is preferably about 0.1 to 30% by weight, and more preferably about 1 to 20% by weight.

In addition, it is preferable that the ink composition for inkjet recording of the present invention does not substantially contain a wetting agent. Wetting agents have the function of preventing ink from drying and solidifying in inkjet nozzles, etc., so when ink drops onto synthetic paper with low ink absorption performance of the film, the ink will not dry, which may be a problem in high-speed printing. In addition, when ink containing a wetting agent is used, unabsorbed ink exists on the surface of the recording medium, and subsequent ink adheres to the recording medium in this state, which may cause aggregation unevenness.

Therefore, in the present invention, when the above-mentioned recording medium with low ink absorption performance is used, it is preferable to use an ink that does not substantially contain a wetting agent. It should be noted that even when the ink is dried and solidified in the inkjet nozzle, the solidified ink can be redissolved by applying a solution containing a dampening liquid.

Particularly in the present invention, it is preferable not to substantially contain a wetting agent having a vapor pressure of 2 mPa or less at 25°C. The term "substantially not contained" means that the added amount of the above-mentioned wetting agent is less than 1% by weight relative to the ink composition.

The content of the wetting agent whose vapor pressure at 25°C is 2 mPa or less is less than 1% by weight relative to the ink, so that not only printing paper and other recording media with low ink absorption, but also no ink absorption at all Capable metal or plastic can also be printed by inkjet recording. It is clear to those skilled in the art that some of the penetrating solvents also function as wetting agents, but in this specification, the penetrating solvents are not included in the wetting agents. In addition, in this specification, the said alcohol solvent is not included in a wetting agent.

Examples of the wetting agent include those commonly used in inkjet recording inks, specifically glycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, trimethylolpropane, trimethylolpropane, Methylolmethane, Trimethylolethane, etc.

In the ink composition of the present invention, an anti-clogging agent for nozzles, an antiseptic, an antioxidant, a conductivity regulator, a pH regulator, a viscosity regulator, a surface tension regulator, an oxygen absorber, and the like may be added.

Examples of preservatives and antifungal agents include sodium benzoate, sodium pentachlorophenolate, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzothiazoline -3-ketone (Proxel CRL, Proxel BND, Proxel GXL, Proxel XL-2, Proxel TN of ICI Corporation), etc.

Furthermore, examples of pH adjusters, solubilizers, and antioxidants include amines such as diethanolamine, triethanolamine, propanolamine, and morpholine, and their modified products, potassium hydroxide, sodium hydroxide, hydroxide Lithium and other inorganic salts, ammonium hydroxide, quaternary ammonium hydroxide (tetramethylammonium, etc.), potassium carbonate, sodium carbonate, lithium carbonate and other carbonates, other phosphates, etc., or N-methyl-2-pyrrolidone , urea, thiourea, tetramethylurea and other urea, allophanate, methyl allophanate and other allophanate, biuret, dimethylbiuret, tetramethylbiuret, etc. Biurets, etc., L-ascorbic acid and its salts.

In addition, the ink composition of the present invention may contain an antioxidant and an ultraviolet absorber, and examples thereof include Tinuvin 328, 900, 1130, 384, 292, 123, 144, 622, 770, 292 , Irgacor252 153, Irganox1010, 1076, 1035, MD1024, oxides of lanthanides, etc.

The ink composition of the present invention can be prepared by dispersing and mixing the above-mentioned components by an appropriate method. It is preferably prepared as follows: first, the pigment, the polymer dispersant and water are homogenized with a suitable dispersing machine (such as a ball mill, a sand mill, an attritor, a roller mill, a stirring mill, a Henschel mixer, a colloid mill, and an ultrasonic wave). pulp machine, jet mill, Ong mill, etc.) to prepare a uniform pigment dispersion, and then add additionally prepared resin (resin emulsion), water, water-soluble organic solvent, sugar, pH regulator, preservative, anti-fungal agent and so on to make it fully dissolved to prepare an ink solution. After sufficient stirring, filtration is performed to remove coarse particles and foreign substances that cause clogging, and the target ink composition can be obtained.

Inkjet recording method

The inkjet recording method of the present invention is a method of ejecting liquid droplets of the above-mentioned ink composition, attaching the liquid droplets to a recording medium, and printing. In the recording method of the present invention, it is preferable to use synthetic paper or printed paper as the recording medium, especially fine art paper and high-quality paper for POD (Print On Demand) applications with low resolution. Even when printing on paper and special paper for laser printing, high-quality images without white streaks or roughness can be realized. Examples of high-quality paper for POD use include Ricoh business coat gross 100 (manufactured by Ricoh Co., Ltd.). Moreover, as a special paper for laser printing, LPCCTA4 (made by Seiko Epson Corporation) is mentioned, for example.

【Example】

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

<Preparation of ink composition>

Each component was mixed according to the composition in Table 1 below, and filtered through a 10 μm membrane filter to prepare each ink. It should be noted that the styrene-acrylic resin in the table is a copolymer having a molecular weight of 1600 and an acid value of 150. The polyurethane resin is a copolymer with a molecular weight of 6000 and an acid value of 50. In addition, the fluorene resin is a resin containing a monomer having a fluorene skeleton represented by CAS No. 117344-32-8 in a monomer composition ratio of about 50% by weight, and has a molecular weight of 3300. Furthermore, the surfactant used is an organopolysiloxane-based surfactant, which is mixed with the above formula (I) where R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is 1 A surfactant obtained from a compound having an integer of ˜2 and a compound wherein 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.

Table 1 (continued)

Examples 49-60

Ink sets 49 to 60 were prepared in the same manner except that 3-methyl-1,3-butanediol in Examples 1 to 12 was replaced with 1,3-butanediol.

Embodiment 61～120 and comparative example 7～12

In addition, the ink set 61 of the example was prepared in the same manner except that the surfactants of the ink sets of Examples 1 to 60 and the ink sets of Comparative Examples 1 to 6 were replaced with the following surfactants. ～120 and the ink groups 7～12 of the comparative example.

The tensio-active agent that is used for embodiment 61～120 and comparative example 7～12 is that in above-mentioned formula (I), R is methyl, a is the integer of 6～10, m is the integer of 10～20, n is 4～20. A surfactant formed from a compound that is an integer of 8.

Examples 121-180 and Comparative Examples 13-18

Ink sets 121 to 180 of Examples were prepared in the same manner except that the surfactants in the ink sets of Examples 1 to 60 and Comparative Examples 1 to 6 were replaced with the following surfactants. and ink sets 13 to 18 of comparative examples.

The surfactant used in Examples 121-180 and Comparative Examples 13-18 is to mix R in the following formula (I) for a hydrogen atom, a for an integer of 7 to 11, m for an integer of 30 to 50, and n for 3 A compound of an integer of ∼5, a compound in which R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2, and R is a methyl group and a is an integer of 6 to 10 , a surfactant obtained from a compound in which m is an integer of 10 to 20 and n is an integer of 4 to 8.

Examples 181-240 and Comparative Examples 19-24

In addition, the ink set 181 of the example was prepared in the same manner except that the surfactants of the ink sets of Examples 1 to 60 and the ink sets of Comparative Examples 1 to 6 were replaced with the following surfactants. ～240 and the ink groups 19～24 of the comparative example.

The surfactants used in Examples 181 to 240 and Comparative Examples 19 to 24 are surfaces formed by compounds in which R is a methyl group, a is an integer of 6 to 18, m is 0, and n is 1 in the above formula (I). active agent.

Embodiment 241～300 and comparative example 25～30

In addition, the ink set 240 of the example was prepared in the same manner except that the surfactants of the ink sets of Examples 1 to 60 and the ink sets of Comparative Examples 1 to 6 were replaced with the following surfactants. ～300 and the ink group 25～30 of the comparative example.

The tensio-active agent that is used for embodiment 240～300 and comparative example 25～30 is that R is a hydrogen atom, a is the integer of 7～11, m is the integer of 30～50, n is 3～50 in the above-mentioned formula (I). Compounds with an integer of 5, R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, R is a methyl group, a is an integer of 6 to 18, A surfactant obtained from a compound in which m is 0 and n is 1.

<Evaluation>

Evaluation of initial viscosity of ink

The ink viscosity was evaluated for each of the inks obtained as described above. Using a vibrating viscometer (MV100 model, manufactured by Yamaichi Electric Co., Ltd.), the viscosity of the ink one hour after the preparation of the ink was measured, and evaluated according to the following criteria. In addition, the measurement temperature was 20 degreeC.

S: The viscosity is 4 mPa·s or less.

AA: The viscosity is more than 4 mPa·s and not more than 5 mPa·s.

A: The viscosity is more than 5 mPa·s and not more than 6 mPa·s.

B: The viscosity is more than 6 mPa·s and not more than 7 mPa·s.

C: The viscosity is more than 7 mPa·s and not more than 8 mPa·s.

D: The viscosity is more than 8 mPa·s.

The evaluation results are shown in Table 2 below.

Evaluation of ink viscosity

After leaving the ink prepared as described above in an environment of 70° C. for 3 days, the viscosity of the ink was measured in the same manner as above, and evaluated according to the following criteria.

A: The difference from the initial viscosity is 0.5 mPa·s or less.

B: The difference from the initial viscosity is more than 0.5 mPa·s but not more than 1.0 mPa·s.

C: The difference from the initial viscosity is more than 1.0 mPa·s but not more than 2.0 mPa·s.

D: The difference from the initial viscosity exceeds 2.0 mPa·s.

The evaluation results are shown in Table 2 below.

Evaluation of uneven ink aggregation and ink retentivity other than cast-coated paper

Each of the inks of Y, M, C, and K obtained above was used as an ink set, and placed in an ink cartridge of an inkjet printer (PX-G920, manufactured by Seiko Epson Co., Ltd.), so that it can be scanned at 720dpi in the main scanning (head drive) ) direction, and recording was performed at 360 dpi in the sub-scanning (recording medium transport) direction. Then, adjust the voltage of the printer so that the dot size at the time of landing is about 7ng, and record on OKT+ (manufactured by Oji Paper Co., Ltd.) and LPCCT (manufactured by Seiko Epson Co., Ltd.) of about 128g/square meter with a single drive of 720×360dpi Full image of 720×720dpi. Recording is carried out in two-way and one-way, and it is carried out in a normal temperature and humidity environment. The ink adhesion amount is about 3.6mg/inch square meter.

The obtained images were evaluated according to the following criteria.

A: White streaks due to uneven aggregation and poor ink placement also appeared in bidirectional printing.

B: There is no aggregation unevenness in bidirectional printing, but there are white streaks due to ink failure.

C: There is uneven aggregation in bidirectional printing, and there is no uneven aggregation in unidirectional printing, but white streaks due to poor ink placement occur.

D: There are white streaks due to aggregation unevenness and poor ink placement in unidirectional printing.

The results are shown in Table 2 below.

Evaluation of uneven ink coagulation and ink retentivity of cast-coated paper

Each of the inks of Y, M, C, and K obtained above was used as an ink set, and placed in an ink cartridge of an inkjet printer (PX-G920, manufactured by Seiko Epson Co., Ltd.), so that it can be scanned at 720dpi in the main scanning (head drive) ) direction and recording was performed at 360 dpi in the sub-scanning (recording medium transport) direction. Then, the voltage of the printer was adjusted so that the dot size was about 7ng, and a full image of 720×720dpi was recorded on Mirror Coat Platinum (manufactured by Oji Paper Co., Ltd.) of about 128g/square meter with a single drive of 720×360dpi. Recording is carried out in two-way and one-way, and it is carried out in a normal temperature and humidity environment. The ink adhesion amount is about 3.6mg/inch square meter.

The obtained images were evaluated according to the following criteria.

A: There are also white streaks caused by uneven aggregation and poor ink placement in bidirectional printing.

B: There is no aggregation unevenness in bidirectional printing, but there are white streaks due to ink failure.

C: There is uneven aggregation in bidirectional printing, and there is no uneven aggregation in unidirectional printing, but white streaks due to poor ink placement occur.

D: There are white streaks due to aggregation unevenness and poor ink placement in unidirectional printing.

The results are shown in Table 2 below.

Evaluation of Small Font Deformation

Each of the inks of Y, M, C, and K obtained above was used as an ink set, and placed in an ink cartridge of an inkjet printer (PX-G920, manufactured by Seiko Epson Co., Ltd.), so that it can be scanned at 720dpi in the main scanning (head drive) ) direction and recording was performed at 360 dpi in the sub-scanning (recording medium transport) direction. Next, adjust the voltage of the printer in a normal temperature and humidity environment so that the dot size at landing is about 7ng, and record the full image with a single driver at 720×360dpi and 720×720dpi. The ink adhesion at this time is about 3.6 mg/inch square meter. Under these conditions, the Chinese character "rose" of font 8 and font 12 was printed on OKT+ (manufactured by Oji Paper Co., Ltd.) of about 128 g/square meter in one direction.

The obtained characters were evaluated according to the following criteria.

A: The Chinese character "rose" in font 8 is easy to recognize.

B: Although the Chinese character "rose" in font 12 is easy to recognize, the Chinese character "rose" in font 8 cannot be easily recognized.

C: The Chinese character "rose" in font 12 cannot be easily recognized.

The results are shown in Table 2 below.

dryness evaluation

In addition, printing was performed by the same recording method as above except that a polyethylene terephthalate film (RUMIRER, manufactured by Toray Corporation) was used instead of OKT+ and LPCCT as the recording medium. After the obtained printed matter was dried at 40° C. for 3 minutes under an environment of 15% RH, XeroxP (manufactured by Xerox Corporation) was loaded on the printed surface, and a weight of 500 g/cm ² was applied, and left for 3 minutes. Then, the dryness was evaluated by measuring the OD value of the surface of XeroxP on which the ink was transferred from the printed matter using SPM50 manufactured by Gretag.

The evaluation criteria are as follows.

A: OD value is less than 0.2

B: OD value is 0.2 or more

The results are shown in Table 2 below.

Evaluation of blockage recovery

With the above ink cartridges and inkjet printers, after pressing the ink exchange button, remove the socket. As described above, the printer was left to stand in an environment of 40° C. and 15% RH for 2 days after leaving the inkjet head cap (head cap) off.

After being left to stand, the cleaning operation was repeated until all the nozzles ejected the same amount of ink as at the beginning, and the ease of recovery was evaluated based on the following criteria.

A: The cleaning operation was repeated 3 times, and the blockage recovered.

B: The cleaning operation was repeated 6 times, and the clogging recovered.

C: The cleaning operation was repeated 12 times, and the clogging was recovered.

D: Even if the cleaning operation was repeated 12 times, the clogging did not recover.

The results are shown in Table 2 below.

When the same evaluation as above was performed on Examples 61 to 120 and Comparative Examples 7 to 12, a one-level improvement was observed in the evaluation of uneven ink aggregation and ink retentivity of cast-coated paper. However, in the evaluation of small font deformation, two levels of deterioration were observed. Additional Examples 1 to 60 and Comparative Examples 1 to 6 have the same evaluation results.

In addition, when the same evaluation as above was performed on Examples 121 to 180 and Comparative Examples 13 to 18, one level of improvement was observed in the evaluation of uneven ink aggregation and ink retentivity of cast-coated paper. However, in the evaluation of small font deformation, one level of deterioration was observed. Examples 1-72 and Comparative Examples 1-6 are the same evaluation results.

In addition, when the same evaluation as above was performed on Examples 181 to 240 and Comparative Examples 19 to 24, one rank improvement was observed in the evaluation of uneven ink aggregation and ink retentivity of cast-coated paper. However, one grade of deterioration was observed in the evaluation of small font deformation. Examples 1-72 and Comparative Examples 1-6 are the same evaluation results.

In addition, when the same evaluation as above was performed on Examples 241 to 300 and Comparative Examples 25 to 30, one rank improvement was observed in the evaluation of uneven ink aggregation and ink retentivity of cast-coated paper. However, in the evaluation of small font deformation, one level of deterioration was observed. Examples 1-60 and Comparative Examples 1-6 are the same evaluation results.

Claims (27)

1. An ink composition for inkjet recording, which is an ink composition for inkjet recording containing at least a coloring material, water, an alcohol solvent, and a surfactant, wherein, The alcohol solvent contains poorly water-soluble alkanediol, water-soluble 1,2-alkanediol and water-soluble 1,3-alkanediol. 2. The ink composition for inkjet recording according to claim 1, wherein the poorly water-soluble alkanediol is an alkanediol having 7 or more carbon atoms. 3. The ink composition for inkjet recording according to claim 1 or 2, wherein the water-soluble 1,2-alkanediol is an alkanediol having 6 or less carbon atoms. 4. The ink composition for inkjet recording according to any one of claims 1 to 3, wherein the water-soluble 1,3-alkanediol is an alkane diol having 4 or more carbon atoms. alcohol. 5. The ink composition for inkjet recording according to any one of claims 1 to 4, wherein the mixture of the poorly water-soluble alkanediol and the water-soluble 1,2-alkanediol The content ratio is 6:1～1:3. 6. The ink composition for inkjet recording according to any one of claims 1 to 5, wherein the combination of the poorly water-soluble alkanediol and the water-soluble 1,3-alkanediol The content ratio is 1:1～1:18. 7. The ink composition for inkjet recording according to any one of claims 1 to 6, wherein the combination of the poorly water-soluble alkanediol and the water-soluble 1,2-alkanediol The sum of the contents is 6% by weight or less with respect to the ink composition. 8. The ink composition for inkjet recording according to any one of claims 1 to 7, wherein the mixture of the poorly water-soluble alkanediol and the water-soluble 1,3-alkanediol is The sum of the contents is 21% by weight or less based on the ink composition. 9. The inkjet recording ink composition according to any one of claims 1 to 8, wherein the poorly water-soluble alkanediol is contained in an amount of 1 to 3% by weight relative to the ink composition. 10. The inkjet recording ink composition according to any one of claims 1 to 9, wherein the water-soluble 1,2-alkane is contained in an amount of 0.5 to 3.0% by weight relative to the ink composition diol. 11. The ink composition for inkjet recording according to any one of claims 1 to 10, wherein the water-soluble 1,3-alkane is contained in an amount of 3 to 18% by weight relative to the ink composition diol. 12. The inkjet recording ink composition according to any one of claims 1 to 11, wherein the poorly water-soluble alkanediol is 1,2-octanediol. 13. The ink composition for inkjet recording according to any one of claims 1 to 12, wherein the water-soluble 1,2-alkanediol is selected from 1,2-hexanediol, One or more selected from the group consisting of 4-methyl-1,2-pentanediol and 3,3-dimethyl-1,2-butanediol. 14. The inkjet recording ink composition according to any one of claims 1 to 13, wherein the water-soluble 1,3-alkanediol is 1,3-butanediol and/or 3-methyl-1,3-butanediol. 15. The inkjet recording ink composition according to any one of claims 1 to 14, wherein the surfactant is contained in an amount of 0.01 to 1.0% by weight relative to the ink composition. 16. The ink composition for inkjet recording according to claim 15, wherein the surfactant is a polyorganosiloxane-based surfactant. 17. The ink composition for inkjet recording according to claim 16, wherein the polyorganosiloxane contains one or two or more compounds represented by the following formula,

In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2-11, m represents an integer of 2-50, and n represents an integer of 1-5. 18. The ink composition for inkjet recording according to claim 16, wherein the polyorganosiloxane contains one or two or more compounds represented by the following formula,

In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2-13, m represents an integer of 2-50, and n represents an integer of 1-5. 19. The ink composition for inkjet recording according to claim 16, wherein the polyorganosiloxane contains one or two or more compounds represented by the following formula, In the formula, R represents a hydrogen atom or a methyl group, a represents an integer of 2-13, m represents an integer of 2-50, and n represents an integer of 1-8. 20. The ink composition for inkjet recording according to claim 16, wherein the polyorganosiloxane contains one or two or more compounds represented by the following formula,

In the formula, R represents a methyl group, a represents an integer of 6-18, m is 0, and n is 1. 21. The inkjet recording ink composition according to any one of claims 1 to 20, wherein the coloring material contains a pigment and a dispersant capable of dispersing the pigment in the ink. 22. The ink composition for inkjet recording according to claim 21, wherein the dispersant contains at least one resin selected from the group consisting of styrene-acrylic copolymer resins, polyurethane resins and fluorene resins. 23. The ink composition for inkjet recording according to claim 22, wherein the dispersant is contained in an amount of 1.0 to 6.0% by weight relative to the ink composition. 24. An inkjet recording method, which is an inkjet recording method in which droplets of an ink composition are ejected and the droplets are attached to a recording medium for printing, wherein any one of claims 1 to 23 is used The ink composition for inkjet recording. 25. The method according to claim 24, wherein the recording medium is a recording medium selected from the group consisting of synthetic paper mainly made of synthetic resin, printed paper, and resin film. 26. The method of claim 25, wherein the recording medium is a resin film. 27. A recorded matter recorded by the inkjet recording method according to any one of claims 24 to 26.