JP5343366B2 - Water-based inkjet recording ink - Google Patents

Description

  The present invention relates to a novel aqueous water-based ink jet recording ink having printing suitability for printing on a non-absorbing or low-absorbing recording medium containing a resin component such as vinyl chloride.

  In recent years, inks that can be directly printed on non-absorbent recording media such as vinyl chloride sheets have been developed as inkjet inks for industrial use. For example, a solvent-based inkjet ink using an organic solvent as a vehicle and an ultraviolet curable inkjet ink mainly containing a polymerizable monomer can be used. The solvent-based inkjet ink is not perfect from the viewpoint of environmental load because the solvent is dried and evaporated in the atmosphere. On the other hand, ultraviolet curable ink-jet inks are cured immediately after printing, so there are few evaporation components, but some monomers may have skin sensitization, and it is necessary to incorporate an expensive UV irradiation light source into the printer. There is also a limited field of application. Further, when printing is performed on a highly glossy recording medium, the glossiness is deteriorated.

  In such a background, a non-absorbent recording medium directly using a water-based ink-jet recording ink that has a small environmental load and has been widely used in home-use ink-jet recording methods. Ink-jet inks that can be printed on are also being developed.

  For example, Patent Document 1 proposes an aqueous ink-jet ink containing glycol and a solvent compatible with water selected from the group excluding glycol ether, and further, a hydrophobic main chain, Ink jet inks have been proposed that contain graft copolymer binders that have ionic and hydrophilic side chains and are soluble in aqueous vehicles but insoluble in water. However, this does not disclose the use of a polymer compound having a structure having an acidic group such as a carboxyl group as a binder to be applied. Further, in the study by the present inventors, the technique disclosed in Patent Document 1 is insufficient as the image quality formed on the non-absorbent recording medium, and the durability of the obtained image is also insufficient. It is.

  On the other hand, Patent Document 2 discloses a liquid medium, a water-insoluble colorant, a polymer binder, and the like for printing on an untreated vinyl sheet or a vinyl-coated base with a piezo-type printing system having at least one heating device. A printing ink comprising a drying inhibitor and other additives, and wherein the liquid medium is composed of water and a water-miscible drying inhibitor, the liquid medium containing at least 80% by mass of water; The ink containing the drying inhibitor is composed of butyl diglycol and 1-methoxypropanol-2, and the ink has a pH value greater than 8.5, and the binder is present in a dissolved state in the liquid inkjet ink. Ink jet inks have been proposed. However, as a result of studies by the present inventors, it has been found that the technique disclosed in Patent Document 2 still has problems such as image quality and drying properties, as in the technique described in Patent Document 1.

Patent Documents 3 to 6 propose water-based inkjet inks in which resin fine particles that are not soluble in inkjet inks are added as binder resins, and the injection is relatively stable, but is formed on a non-absorbent recording medium. Image quality has been found to be inadequate.
JP 2000-44858 A JP 2005-113147 A JP 2004-114692 A JP 2005-220352 A JP 2006-22328 A JP 2006-282822 A

  The present invention has been made in view of the above problems, and its purpose is to be able to record on a non-absorbing or low-absorbing recording medium with high image quality, excellent durability of the obtained image, and on a non-absorbing recording medium. It is an object of the present invention to provide a water-based inkjet recording ink that is quick to dry and has excellent ejection stability.

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

1. A pigment dispersed with a styrene-acrylic acid copolymer , a silicon-based surfactant or an acetylene-based surfactant, the following solvents A and B as water-soluble organic solvents, water-dispersed polymer fine particles, and at least carboxyl A water-soluble copolymer obtained by neutralizing and dissolving a copolymer obtained by polymerizing an unsaturated vinyl having a group or a sulfonic acid group as a monomer component with an amine,
The water-soluble copolymer is contained in an amount of 1.0% by mass to 10% by mass with respect to the total mass of the ink , and the acid value of the water-soluble copolymer is 80 mgKOH / g or more and less than 300 mgKOH / g, A water-based inkjet recording ink which is used for a non-water-absorbing recording medium made of a vinyl chloride resin.
Solvent A: glycol ethers or 1,2-alkanediols
B solvent: sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, 1,1,3,3-tetramethylurea, hexamethyl Two or more solvents selected from the group consisting of phosphoric acid triamide, N, N-dimethylformamide

2. 2. The aqueous inkjet according to 1 above, wherein the content of the solvent A (glycol ethers or 1,2-alkanediols) is 2.0% by mass or more and 20% by mass or less based on the total mass of the ink. Recording ink.

3 . 2. The water -based inkjet recording ink as described in 1 above, wherein the acid value of the water - soluble copolymer is 90 mgKOH / g or more and less than 250 mgKOH / g.

4 . 2. The water-based inkjet recording ink as described in 1 above, wherein the acid value of the water-based dispersed polymer fine particles is 44 mgKOH / g or more and less than 110 mgKOH / g.

5 . 2. The water-based inkjet recording ink as described in 1 above, wherein the content of the water-based dispersed polymer fine particles is 1 to 3%.

  According to the present invention, high-quality images can be recorded on a non-absorbing or low-absorbing recording medium, the resulting image has excellent durability, fast drying on the non-absorbing recording medium, and excellent injection stability. A water-based inkjet recording ink can be provided.

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

As a result of intensive studies in view of the above problems, the present inventor has found that at least 1) a pigment,
2) Silicone surfactant or acetylene surfactant,
3) As a water-soluble organic solvent, A solvent (glycol ethers or 1,2-alkanediols) and B solvent (two or more organic solvents that dissolve, soften or swell vinyl chloride resin) are contained,
Furthermore,
4) A water-soluble copolymer obtained by neutralizing and dissolving a copolymer obtained by polymerizing an unsaturated vinyl having at least a carboxyl group or a sulfonic acid group as a monomer component with an amine is 1.0% by mass or more based on the total mass of the ink. A high-quality image can be recorded on a non-absorbing or low-absorbing recording medium with the water-based inkjet recording ink characterized by containing no more than mass%. The obtained image has high durability and is non-absorbing. It has been found that a water-based inkjet recording ink having a fast drying property on an adhesive recording medium or the like and excellent in ejection stability can be obtained, and as a result, the present invention has been achieved.

  Hereinafter, the present invention will be described in detail.

  In the water-based inkjet recording ink of the present invention, a water-soluble copolymer obtained by neutralizing and dissolving a copolymer obtained by polymerizing an unsaturated vinyl having a carboxyl group or a sulfonic acid group as a monomer component with an amine is 1 with respect to the total mass of the ink. It is 1st characteristic to contain 0.0 mass% or more and 10 mass% or less.

  The water-based inkjet recording ink of the present invention exhibits the effect of the present invention that an image having high image quality and excellent scratch resistance can be formed particularly when recording on a non-absorbing or low-absorbing recording medium. . That is, the water-soluble copolymer according to the present invention rapidly increases in viscosity in the drying process after ink landing, forms a high-quality image with suppressed color bleeding, and the coloring material is non-absorbing such as vinyl chloride resin. It has a function of fixing on the surface of a recording medium or the like.

  The present inventors estimate this phenomenon as follows.

That is, in the water-based inkjet ink of the present invention, the carboxyl group in the copolymer is neutralized by the amine and stably exists as a water-soluble copolymer . Then , by landing on the recording medium and drying, the concentration of the water-soluble copolymer increases due to evaporation of moisture. At the same time, the amine used for neutralization at the time of drying also volatilizes, so that the water-soluble copolymer becomes a copolymer, thereby increasing the concentration of the copolymer. As a result, it is possible to obtain a high-quality recorded image in which the viscosity of the ink is increased and the occurrence of color mixing is suppressed.

Furthermore, amines neutralizing agent because after drying is volatilized, even moisture in the recorded image again is granted, the copolymer solidifies without re-dissolved in water, the pigment is fixed Thus, the effect of excellent scratch resistance and water resistance is recognized.

As the copolymer, a hydrophilic component is a carboxyl group, is used to design those having a hydrophobic component with an appropriate balance. At this time, a water-soluble copolymer can be obtained by neutralizing the carboxyl group with a volatile base component to impart water solubility. Water-soluble copolymer according to the present invention is to sufficiently exhibit the above-mentioned function. Examples of such water-soluble copolymers include acrylic resins, styrene-acrylic resins, acrylonitrile-acrylic resins, vinyl acetate-acrylic resins, polyurethane resins, and polyester resins.

Examples of the hydrophobic monomer constituting the copolymer include acrylic acid esters (for example, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, etc.), and methacrylic acid esters (for example, ethyl methacrylate). Butyl methacrylate, glycidyl methacrylate, etc.), styrene and the like.

Examples of the hydrophilic monomer that constitutes the copolymer include acrylic acid, methacrylic acid, and acrylamide.

Carboxyl group which copolymer has needs to be neutralized partially or completely amines. Examples of amines include ammonia, triethylamine, 2-dimethylaminoethanol, 2-di-n-butylaminoethanol, methyldiethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, triethanolamine, 2- Methylaminoethanol or the like can be preferably used.

  In particular, neutralization with amines having a boiling point of less than 200 ° C. is more preferable because amines are likely to volatilize during drying, and the hydrophobicity is increased rapidly to contribute to improvement in image durability.

  When the water-soluble copolymer according to the present invention is contained in an amount of 1.0% by mass or more and 10% by mass or less based on the total mass of the ink, the effect of the present invention is remarkably exhibited.

  About this, this inventor guesses as follows.

  If the content of the water-soluble copolymer is 1.0% by mass or more with respect to the total mass of the ink, the degree of thickening at the time of drying is sufficient, and color bleeding is prevented and a high-quality image is obtained. Can do. If the amount is 10% by mass or less, the storage stability of the ink is high, and the ink can be stably ejected, and a print can be obtained stably over a long period of time.

Further, the acid value of the copolymer is more preferably 80 mgKOH / g or more and less than 300 mgKOH / g . By applying a water-soluble copolymer obtained from a copolymer having an acid value in the range specified above, the viscosity increase during drying becomes remarkable, and the pigment solidifies firmly after drying. The effect of the present invention that the property is improved is remarkably recognized. A more preferred acid value is about 90 to 250 mg KOH / g. The polymerization method is preferably solution polymerization. The acid value defined in the present invention can be measured according to JIS K0070.

  As a molecular weight of the water-soluble copolymer according to the present invention, an average molecular weight of 3000 to 30000 can be preferably used, and more preferably 7000 to 20000.

  The Tg of the water-soluble copolymer according to the present invention is preferably about -30 ° C to 100 ° C, more preferably -10 ° C to 80 ° C.

  The water-based inkjet recording ink of the present invention is characterized in that glycol ethers or 1,2-alkanediols are used as the A solvent. As described above, by using the water-soluble copolymer according to the present invention, it is considered that ink mixing can be prevented due to an increase in ink viscosity in the drying process after ink landing, and color bleeding can be suppressed. In addition, glycol ethers and 1,2-alkanediols reduce water content particularly during the drying process after ink landing due to hydrophobic interaction with the pigment dispersion and the water-soluble copolymer. As the density of the ink increases, the ink acts to increase the viscosity by acting more strongly. Therefore, it is considered that the color bleed prevention effect is remarkably exhibited by using the water-soluble polymer and glycol ethers in combination.

  Further, when used in combination with the silicon-based surfactant or acetylene-based surfactant according to the present invention, this effect is remarkably exhibited and sufficient for a non-absorbing recording medium such as a vinyl chloride resin. It has wettability and does not cause image quality defects such as repellency. Examples of glycol ethers include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, propylene glycol monopropyl ether, dipropylene glycol monomethyl ether, and tripropylene glycol monomethyl ether. . Examples of the 1,2-alkanediols include 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol, 1,2-heptanediol, and the like.

  The glycol ether or 1,2-alkanediol organic solvent according to the present invention is particularly preferably contained in an amount of 2 to 20% by mass with respect to the total mass of the ink from the viewpoint that the effects of the present invention are remarkably exhibited.

  Furthermore, the ink of the present invention is characterized in that two or more organic solvents that dissolve the vinyl chloride resin are used as the B solvent. It has been found that when the water-based inkjet recording ink of the present invention is used for recording on the surface of a non-absorbable recording medium such as a vinyl chloride resin, the durability of the ink differs for each color material. For example, inks using magenta pigment bodies tend to have poor durability such as scratching properties compared to inks containing other color materials, but this is difficult to dissolve a resin such as vinyl chloride as a recording medium. It is estimated that this is because the material is difficult to be embedded in the recording medium.

  When preparing a pigment dispersion, various types and amounts of a dispersant and a dispersion solvent to be used are selected and adjusted mainly in order to satisfy storage stability. Therefore, in order to balance the fixability of the ink containing the pigment dispersion of each color prepared as described above to the recording medium, various kinds and amounts of the vinyl chloride dissolving solvent used in preparing the ink are devised. There is a need. At this time, the preparation with two or more solvents having different vinyl chloride solubility increases the degree of freedom and the desired ink characteristics can be easily obtained rather than the preparation with a single vinyl chloride dissolving solvent.

  The two or more kinds of organic solvents that dissolve the vinyl chloride resin contained in the ink of the present invention mean two or more kinds of organic solvents having different degrees of dissolving the vinyl chloride resin. Specifically, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, 1,1,3,3-tetramethylurea Two or more solvents selected from hexamethylphosphoric triamide and N, N-dimethylformamide are preferred.

  Among these, the combinations that remarkably exhibit the effects of the present invention include hexamethyl phosphate triamide and N-methyl-2-pyrrolidone, dimethyl sulfoxide and N-methyl-2-pyrrolidone, 1,1,3, Combination of 3-tetramethylurea and N-methyl-2-pyrrolidone, combination of 1,3-dimethyl-2-imidazolidinone and N-methyl-2-pyrrolidone, N, N-dimethylformamide and N-methyl-2 The combination of -pyrrolidone is particularly preferred.

Accordingly, the ink jet recording ink of the present invention is characterized in that the above feature 1) a water-soluble copolymer obtained by neutralizing and dissolving a copolymer obtained by polymerizing unsaturated vinyl having a carboxyl group or a sulfonic acid group as a monomer component with an amine, Containing 1.0% by mass or more and 10% by mass or less based on the total mass;
Feature 2) Use of glycol ethers or 1,2-alkanediols as the solvent A,
Feature 3) Use of two or more organic solvents that dissolve vinyl chloride resin as solvent B,
By combining these, the effects of the present invention can be remarkably exhibited.

  Next, the pigment according to the present invention will be described.

  The pigment applicable to the present invention is not particularly limited as long as it can be stably dispersed in an aqueous system. A pigment dispersion dispersed with a polymer resin, a capsule pigment coated with a water-insoluble resin, a dispersion resin modified with a pigment surface is used. It is possible to select from self-dispersing pigments that can be dispersed without such. When emphasis is particularly placed on the storage stability of the ink, it is preferable to select a capsule pigment coated with a water-insoluble resin.

  When a pigment dispersion dispersed with a polymer resin is used, a water-soluble one can be used as the polymer resin. As the water-soluble resin, styrene-acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid copolymer, styrene-maleic acid copolymer, styrene-maleic acid-acrylic acid alkyl ester copolymer are preferably used. 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 It is a water-soluble resin such as.

  Various methods such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used as a pigment dispersion method.

  In order to prepare the pigment dispersion according to the present invention, it is preferable to use a centrifugal separator or a filter for the purpose of removing coarse particles of the pigment dispersion.

  In the case of using capsule pigments coated with a water-insoluble resin, the water-insoluble resin is a resin that is insoluble in weakly acidic or weakly basic water, and preferably has a solubility in an aqueous solution of pH 4 to 10. The resin is less than mass%.

  Such resins include acrylic, styrene-acrylic, acrylonitrile-acrylic, vinyl acetate, vinyl acetate-acrylic, vinyl acetate-vinyl chloride, polyurethane, silicon-acrylic, acrylic silicon, polyester Examples thereof include epoxy resins and epoxy resins.

  In the present invention, a resin prepared using a hydrophobic monomer and a hydrophilic monomer as constituent components can be used as the resin used to disperse the pigment.

  Examples of hydrophobic monomers include acrylic acid esters (such as n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate), methacrylic acid esters (such as ethyl methacrylate, butyl methacrylate, glycidyl methacrylate), and styrene. Etc.

  Examples of the hydrophilic monomer include acrylic acid, methacrylic acid, acrylamide and the like, and those having an acidic group such as acrylic acid can preferably be those neutralized with a base after polymerization.

  As molecular weight of resin, the thing of 3000-500000 can be used with the weight average molecular weight Mw. Preferably, the thing of 7000-200000 can be used.

  Resin having a Tg of about −30 to 100 ° C. can be used. Preferably about -10-80 degreeC can be used.

  As the polymerization method, solution polymerization or emulsion polymerization can be used. The polymerization may be performed separately from the pigment in advance, or may be performed by supplying a monomer into the system in which the pigment is dispersed.

  As a method for coating the pigment with the resin, various known methods can be used. Preferably, in addition to the phase-emulsification method and the acid precipitation method, the pigment is dispersed using a polymerizable surfactant. It is good to select from the method of supplying a monomer there and coat | covering, superposing | polymerizing.

  As a more preferable method, a water-insoluble resin is dissolved in an organic solvent such as methyl ethyl ketone, and after partially or completely neutralizing an acidic group in the resin with a base, a pigment and ion-exchanged water are added and dispersed. A production method in which an organic solvent is removed and water is added as necessary is preferable.

  The mass ratio of the pigment and the resin can be selected from 100/40 to 100/150 as a pigment / resin ratio. Particularly, 100/60 to 100/110 have good image durability, injection stability, and ink storage stability.

  The average particle size of the pigment particles coated with the water-insoluble resin is preferably about 80 to 150 nm from the viewpoint of ink storage stability and color development.

  The average particle diameter can be determined by a commercially available particle size measuring instrument using a light scattering method, an electrophoresis method, a laser Doppler method, or the like. It is also possible to obtain a particle image with a transmission electron microscope on at least 100 particles and perform statistical processing on the image using image analysis software such as Image-Pro (manufactured by Media Cybernetics). Is possible.

  In addition, as the self-dispersing pigment, commercially available products that have been surface-treated can be used, and examples thereof include CABO-JET200, CABO-JET300 (manufactured by Cabot), and Bonjet CW1 (manufactured by Orient Chemical Industries). .

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

  Specific organic pigments are exemplified below.

  Examples of pigments for magenta or red 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 15, C.I. I. Pigment red 16, 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 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the orange or yellow pigment include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, 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 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. And CI Pigment Yellow 138.

  Examples of pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  Next, the surfactant according to the present invention will be described.

  In the present invention, one of the characteristics is that a silicon-based surfactant or an acetylene-based surfactant is used. Even when the solvent A used in the present invention (glycol ethers or 1,2-alkanediols) is added in an amount of 50% by mass or more, the wettability to a recording medium such as vinyl chloride can be satisfied. Other performances such as image quality, ink storage stability, ejection stability, etc. cannot be ensured. Therefore, as specified in the present invention, for example, by using a silicon surfactant or an acetylene surfactant together with an appropriate amount of A solvent such as 20% by mass or less, a recording medium such as vinyl chloride can be used. The wettability can also be satisfied.

  The silicon surfactant according to the present invention is preferably a dimethylpolysiloxane whose side chain or terminal is polyether-modified (polyether-modified polysiloxane compound). For example, KF-351A, KF- manufactured by Shin-Etsu Chemical Co., Ltd. 642, BigKemi's BYK347, BYK348 and the like.

  As the acetylene surfactant according to the present invention, an acetylene glycol surfactant is particularly preferable, which has a triple bond in the molecule, a hydroxyl group and an alkyl group on the adjacent carbon atom, and a triple bond. What is a left-right symmetric structure is preferable. The acetylene glycol compound and acetylene alcohol compound used in the present invention can be obtained as commercial products, and examples thereof include Surfinol and Olphine manufactured by Nissin Chemical Industry Co., Ltd. and acetylenol manufactured by Kawaken Fine Chemical Co., Ltd.

  The water-based inkjet recording ink of the present invention preferably further contains water-based dispersed polymer fine particles. In the present invention, by using a water-soluble copolymer, the ink thickens upon drying after ink landing and promotes fixing of the coloring material on the recording medium. On the other hand, immediately after ink landing and before drying thickening When the droplets are appropriately leveled, unevenness on the image surface can be prevented and image clarity can be kept good. At this time, if it is attempted to control the degree of dry thickening by reducing the amount of the water-soluble copolymer, it is not easy to balance leveling and bleeding, but the water-based dispersion polymer according to the present invention is not dissolved in the water-soluble copolymer. It has been found that by using together with a polymer, it is possible to easily control to increase the viscosity increasing rate in the subsequent drying process by suppressing the viscosity increasing rate immediately after landing of the ink and leveling the ink.

  Further, the Tg of the water-dispersible polymer fine particles is preferably 35 ° C. or more, more particularly from the viewpoint of exhibiting an image scratch resistance effect, and more preferably 49 ° C. or more. The upper limit of Tg is not particularly limited, but is preferably about 100 ° C. or less because a flexible ink film can be obtained and cracking of an image due to bending of a printed matter can be suppressed.

  The acid value of the aqueous dispersion type polymer fine particles is preferably 44 mgKOH / g or more, and more preferably 60 mgKOH / g or more. The upper limit of the acid value is not particularly limited, but is preferably less than 110 mgKOH / g from the viewpoint of more easily obtaining a dispersion.

  The average particle size of the water-dispersible polymer fine particles is preferably 300 nm or less, more preferably 130 nm or less, from the viewpoint that there is no clogging in the nozzle of the ink jet recording head and a good gloss feeling is obtained. The lower limit of the average particle diameter is preferably 30 nm from the viewpoint of production stability of fine particles. The average particle diameter of the water-dispersed polymer fine particles can be easily measured by using a commercially available measuring apparatus using a light scattering method or a laser Doppler method. Alternatively, the dispersion of the aqueous dispersion polymer fine particles can be freeze-dried, and the average particle diameter can be converted from the particles observed with a transmission microscope.

  The content of the water-based dispersed polymer fine particles is preferably 0.7% to 6%, and it is easy to obtain good fixability (abrasion resistance, alcohol resistance) and long-term storage stability of the ink. Particularly preferably, it is 1 to 3%.

  The aqueous dispersion type polymer fine particles may be used as it is or after treatment of a dispersion polymerized in an aqueous system, or a dispersion of a polymer polymerized in a solvent system may be used in an acrylic, It can be selected from urethane, styrene, vinyl acetate, vinylidene chloride, vinyl chloride, styrene-butadiene, styrene-acrylonitrile, polybutadiene, polyethylene, polyisobutylene, polyester, and the like.

  In addition, in order to satisfy the ejection stability as the physical properties of the ink, it is preferable that there is no shear dependency on the viscosity. From this viewpoint, the emulsifier such as an activator is made as low as possible or the emulsifier is used as the dispersion form of the polymer fine particles. Soap-free dispersed polymer particles are preferred. Particularly preferred aqueous dispersion polymer fine particles are self-dispersion dispersions of a copolymer obtained by polymerizing unsaturated vinyl having a carboxyl group as a monomer component. For example, acrylic monomers such as ethyl acrylate alone or acrylic Mechanically sheared after a dispersion obtained by emulsion polymerization or suspension polymerization of acrylic acid or maleic acid as a carboxylic acid monomer in a composition comprising an ethylenically unsaturated monomer that can be copolymerized with a monomer is swelled with alkali, and then mechanically sheared. Is an acrylic hydrosol obtained by dividing the particles. Among acrylic hydrosols, it is preferable to contain styrene in the monomer composition from the viewpoint of increasing the refractive index of the resin and obtaining high glossiness.

  Examples of the alkali used above include ammonia, triethylamine, 2-dimethylaminoethanol, 2-di-n-butylaminoethanol, methyldiethanolamine, 2-amino-2-methyl-1-propanol, diethanolamine, triethanolamine, 2- An amine such as methylaminoethanol is preferable, and ammonia, 2-amino-2-methyl-1-propanol, and 2-methylaminoethanol are particularly preferable in terms of dispersion stability of the aqueous dispersion polymer fine particles.

  As the acrylic hydrosol, Jonkrill (trademark) manufactured by Johnson Polymer Co., Ltd. is commercially available.

  The ink of the present invention can contain various compounds other than those described above.

  In addition to the A solvent and B solvent according to the present invention, those used as solvents are preferably aqueous liquid media, and more preferably mixed solvents such as water and water-soluble organic solvents. For example, alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, etc.), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol) , Dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), amines (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyl) Diethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenedi Amine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (for example, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.) and the like. It is done.

  The ink of the present invention exhibits the effects of the present invention remarkably when recording on a non-absorbing recording medium such as a vinyl chloride sheet or a low-absorbing recording medium. In addition, it is suitable for printing on plain paper, coated paper, ink jet dedicated paper, and the like.

  Non-absorbent recording media include polymer sheets, boards (soft vinyl chloride, hard vinyl chloride, acrylic plates, polyolefins, etc.), glass, tile, rubber, synthetic paper, and the like.

  Examples of the low absorption or absorption recording medium include plain paper (copy paper, plain paper for printing), coated paper, art paper, inkjet paper, inkjet glossy paper, cardboard, and wood.

  In particular, it is a recording medium having at least polyvinyl chloride on the recording surface side that exhibits the effects of the present invention remarkably. For example, specific examples of the recording medium having polyvinyl chloride include SOL-371G, SOL-373Mm, SOL-4701 (big technos) and glossy vinyl chloride (manufactured by Stemgraph).

  The ink of the present invention is more preferably printed by heating a recording medium. By heating the recording medium, the drying and thickening speed of the ink is remarkably improved, and high image quality is obtained. Also, the durability of the image is improved. As the heating temperature, it is particularly preferable that the recording surface temperature of the recording medium is 40 to 80 ° C. If it is 40 ° C. or higher, the image quality is sufficient and sufficient image durability is obtained, and the drying time is relatively short. On the other hand, when the temperature is 80 ° C. or lower, it is possible to ensure stable ink ejection and stably print. More preferably, the recording surface temperature of the recording medium is 40 to 60 ° C.

  As a heating method, it is possible to select a method in which a heating heater is incorporated in the recording medium conveyance system or the platen member and heated from the lower side of the recording medium in a contact manner, or a method of heating in a non-contact manner from the lower side or the upper side by a lamp or the like.

  EXAMPLES 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.

<< Preparation of pigment dispersion >>
[Preparation of Pigment Dispersion-C11]
As a pigment dispersant, 3 parts of a styrene-acrylic acid copolymer (John Cryl 678, molecular weight 8500, acid value 215), 1.3 parts of dimethylaminoethanol, and 80.7 parts of ion-exchanged water are stirred and mixed at 70 ° C to dissolve. did.

  Next, C.I. I. After adding 15 parts of Pigment Blue 15: 3 and premixing, the mixture was dispersed using a sand grinder filled with 50% by volume of 0.5 mm zirconia beads, and a pigment dispersion having a cyan pigment content of 15% -C11 was prepared.

[Preparation of Pigment Dispersion-Y11, M11, Bk11]
In the preparation of the pigment dispersion-C11, cyan pigment C.I. I. Instead of CI Pigment Blue 15: 3, C.I. I. Pigment Yellow-74, C.I. I. Pigment Dispersion-Y11, Pigment Dispersion-M11, and Pigment Dispersion-Bk11 were prepared in the same manner except for using Pigment Red 122 and carbon black as the black pigment.

<Synthesis of water-soluble copolymer>
[Synthesis of water-soluble copolymer 1]
50 g of methyl ethyl ketone was added to a flask equipped with a dropping funnel, a nitrogen introducer, a reflux condenser, a thermometer and a stirrer, and heated to 75 ° C. while bubbling nitrogen.

Thereto, a mixture composed of 80 g of n-butyl methacrylate, 20 g of acrylic acid, 50 g of methyl ethyl ketone, and 500 mg of a polymerization initiator (AIBN) was added dropwise from a dropping funnel over 3 hours. After the dropwise addition, the mixture was further heated to reflux for 6 hours. After allowing to cool, the mixture was heated under reduced pressure, and methyl ethyl ketone was distilled off to obtain a polymer residue , that is, copolymer 1 (acid value 117 mgKOH / g) .

In 450 ml of ion-exchanged water, dimethylaminoethanol corresponding to 1.05 moles of acrylic acid added as a monomer was dissolved, and the polymer residue was added and dissolved therein. Then, to adjust the concentration of ion-exchanged water, water-soluble copolymer content was obtained a 20% aqueous solution of the water-soluble copolymer 1.

[Synthesis of water-soluble copolymers 2, 3]
In the synthesis of the water-soluble copolymer 1, except that the monomers used were changed to the monomer described in Table 1 in the same manner, the copolymer 2 (acid value 155mgKOH / g), copolymer 3 (acid value 194mgKOH / G) to obtain an aqueous solution of water-soluble copolymers 2, 3 having a water-soluble copolymer content of 20%.

[Synthesis of water-soluble copolymer A for comparison]
50 g of methyl ethyl ketone was added to a flask equipped with a dropping funnel, a nitrogen introducer, a reflux condenser, a thermometer and a stirrer, and heated to 75 ° C. while bubbling nitrogen.

  Thereto, a mixture of 80 g of n-butyl methacrylate, 20 g of acrylic acid, 50 g of methyl ethyl ketone, and 500 mg of a polymerization initiator (AIBN) was dropped from a dropping funnel over 3 hours. It heated and refluxed for 6 hours after dripping. After allowing to cool, the mixture was heated under reduced pressure to distill off methyl ethyl ketone to obtain a polymer residue.

  Sodium hydroxide equivalent to 1.05 moles of acrylic acid added as a monomer was dissolved in 450 ml of ion-exchanged water, and the polymer residue was dissolved therein. The concentration was adjusted with ion-exchanged water to obtain an aqueous solution of water-soluble copolymer A having a solid content of 20%.

<Preparation of ink set>
[Preparation of ink set 11: the present invention]
(Preparation of ink C11)
While stirring 26.7 parts of the pigment dispersion-C1 prepared above, 10 parts of an aqueous solution having a solid content of 20% of the water-soluble copolymer 1 having a hydrophobic monomer as a polymerization component was added. An ink composition was prepared by sequentially adding each of the compounds shown, and filtered through a 0.8 μm filter to obtain ink C11.

Pigment dispersion-C1 26.7 parts Aqueous solution of water-soluble copolymer 1 (solid content 20%) 12.0 parts Aqueous dispersion type polymer fine particles 3.3 parts A solvent: triethylene glycol monobutyl ether 10.0 parts A solvent : 1,2-hexanediol 5.0 parts B solvent: sulfolane 3.0 parts B solvent: N-methyl-2-pyrrolidone 3.0 parts Other solvents: diethylene glycol 11.2 parts Silicone surfactant: KF- 351A (manufactured by Shin-Etsu Chemical Co., Ltd.) 0.6 parts ion exchange water was added to prepare a total amount of 100 parts. The content of the water-soluble copolymer 1 in the ink C11 is 3.3% by mass.

  In addition, PDX-7667 (manufactured by Johnson Polymer Co., Ltd., acid value is 82 mgKOH / g, Tg is 75 ° C., solid content concentration is 45%) was used as the aqueous dispersion polymer fine particles.

(Preparation of inks Y11, M11, Bk11)
Ink Y11 and ink Bk11 were prepared in the same manner as in the preparation of ink C11 except that pigment dispersions -Y1 and Bk1 were used instead of pigment dispersion -C1.

  In addition, in the preparation of the ink C11, the pigment dispersion-M1 was used instead of the pigment dispersion-C1, the addition amount of sulfolane was 2.0 parts, and the addition amount of N-methyl-2-pyrrolidone was 4. Ink M11 was prepared in the same manner except that the content was changed to 0.0 parts.

  The ink C11, the ink Y11, the ink M11, and the ink Bk11 prepared as described above were used as an ink set 11.

[Preparation of ink set 12: the present invention]
In the preparation of the ink set 11 described above, each color ink (ink C12, ink Y12, ink) was used in the same manner except that the water-soluble copolymer 2 was used instead of the water-soluble copolymer 1 used to prepare each color ink. M12 and ink Bk12) were prepared and used as ink set 12.

[Preparation of ink set 13: the present invention]
In the preparation of the ink set 11 described above, each color ink (ink C13, ink Y13, ink) was used in the same manner except that the water-soluble copolymer 3 was used instead of the water-soluble copolymer 1 used for the preparation of each color ink. M13 and ink Bk13) were prepared and used as ink set 13.

[Preparation of ink set 14: the present invention]
In the preparation of the ink set 11, KF-351A (manufactured by Shin-Etsu Chemical Co., Ltd.), which is a silicon-based surfactant used for the preparation of each color ink, was replaced with Surfynol (Nisshin Chemical Industry Co., Ltd.), an acetylene-based surfactant having the same mass. Each color ink (Ink C14, Ink Y14, Ink M14, and Ink Bk14) was prepared in the same manner except that the ink set 14 was used.

[Preparation of ink set 15: comparative example]
In the preparation of the ink set 11 described above, each color ink (ink C15, ink Y15, ink) was similarly obtained except that the water-soluble copolymer A was used instead of the water-soluble copolymer 1 used for the preparation of each color ink. M15 and ink Bk15) were prepared and used as ink set 15.

[Preparation of ink set 16: Comparative example]
In the preparation of the ink set 11, each color ink (ink C16, ink Y16, ink Y16, ink Y16, ink Y16, ink Y16, ink Y16) Ink M16 and ink Bk16) were prepared and used as ink set 16.

[Preparation of ink set 17: the present invention]
In the preparation of the ink set 11, each color ink (ink C17, ink Y17, ink Y17, ink Y17, ink Y17, ink Y17) was prepared in the same manner except that the amount of the water-soluble copolymer 1 used for the preparation of each color ink was 1.2 mass. Ink M17 and ink Bk17) were prepared and used as ink set 17.

[Preparation of ink set 18: the present invention]
In the preparation of the ink set 11 described above, each color ink (ink C18, ink Y18, ink Y18, ink K18, ink Y18, Ink M18 and ink Bk18) were prepared, and this was designated as ink set 18.

[Preparation of ink set 19: comparative example]
In the preparation of the ink set 11, each color ink (ink C19, ink Y19, ink 19) was similarly prepared except that the addition amount of the water-soluble copolymer 1 used for the preparation of each color ink was 11.0 mass. Ink M19 and ink Bk19) were prepared and used as ink set 19.

[Preparation of inkjet set 21: the present invention]
In the preparation of the ink set 11, instead of sulfolane (3.0 parts) and N-methyl-2-pyrrolidone (3.0 parts) used for the preparation of the inks C11, Y11, and Bk11, 1,1, Ink C21, ink Y21 and ink Bk21 were prepared in the same manner except that 10 parts of 3,3-tetramethylurea and 4.0 parts of N-methyl-2-pyrrolidone were used.

  In the preparation of the ink set 11, 1,1,3,3 instead of sulfolane (2.0 parts) and N-methyl-2-pyrrolidone (4.0 parts) used to prepare the ink M11. Ink M21 was prepared in the same manner except that 12 parts of tetramethylurea and 5.0 parts of N-methyl-2-pyrrolidone were used.

  Inks C21, Y21, M21 and Bk21 prepared as described above were used as an ink set 21.

[Preparation of ink set 22: the present invention]
In the preparation of the ink set 11, the ink C22, the ink C22, and the ink C22 were prepared in the same manner except that 5.0 parts of dimethyl sulfoxide was used instead of the sulfolane (3.0 parts) used for the preparation of the inks C11, Y11, and Bk11. Ink Y22 and Ink Bk22 were prepared.

  Further, in the preparation of the ink set 11, an ink M22 was prepared in the same manner except that 7.0 parts of dimethyl sulfoxide was used instead of the sulfolane (2.0 parts) used to prepare the ink M11.

  Inks C22, Y22, M22 and Bk22 prepared as described above were used as an ink set 22.

[Preparation of ink set 23: the present invention]
In the preparation of the ink set 21, the same amount of hexamethylphosphoric triamide was used in place of 1,1,3,3-tetramethylurea (10 parts) used for the preparation of the inks C21, Y21, M21 and Bk21. Ink C23, Ink Y23, Ink M23 and Ink Bk23 were prepared in the same manner except for the above.

  Inks C23, Y23, M23 and Bk23 prepared as described above were used as an ink set 23.

[Preparation of ink set 24: the present invention]
In the preparation of the ink set 11, 3.0 parts of 1,3-dimethyl-2-imidazolidinone was used in place of the sulfolane (3.0 parts) used in preparing the inks C11, Y11, and Bk11. Ink C24, Ink Y24 and Ink Bk24 were prepared in the same manner except for the above.

  Further, in the preparation of the ink set 11, the same procedure except that 2.0 parts of 1,3-dimethyl-2-imidazolidinone was used instead of the sulfolane (2.0 parts) used to prepare the ink M11. Ink M24 was prepared.

  Inks C24, Y24, M24 and Bk24 prepared as described above were used as an ink set 24.

[Preparation of ink set 25: the present invention]
In the preparation of the ink set 11, the same procedure except that 2.0 parts of N, N-dimethylformamide was used in place of the sulfolane (3.0 parts) used in the preparation of the inks C11, Y11 and Bk11. Thus, ink C25, ink Y25 and ink Bk25 were prepared.

  Further, in the preparation of the ink set 11, in the same manner except that 1.0 part of N, N-dimethylformamide was used instead of the sulfolane (2.0 parts) used to prepare the ink M11, Ink M25 was prepared.

  Inks C25, Y25, M25 and Bk25 prepared as described above were used as an ink set 25.

[Preparation of ink set 26: comparative example]
In the preparation of the ink set 11, except for the sulfolane used for the preparation of the inks C11, Y11, M11, and Bk11, the addition amount of N-methyl-2-pyrrolidone was changed to 5.0 parts in the same manner. Thus, ink C26, ink Y26, ink M26, and ink Bk26 were prepared, and this was used as an ink set 26.

"Characteristic value measurement of the copolymer"
(Measurement of acid value)
The acid value of the copolymer was measured based on JIS K0070.

[Measurement of weight average molecular weight Mw]
The weight average molecular weight Mw of the water-soluble copolymer was measured using high performance liquid chromatography.

  The results obtained as described above are shown in Table 1.

<Evaluation of ink>
[Evaluation of output stability]
Each color ink constituting each ink set produced above was filled in a glass bottle and sealed, and then stored at 65 ° C. for 2 weeks. Next, using the strobe light emission type ink flight observation device described in FIG. 2 of Japanese Patent Application Laid-Open No. 2002-363469, the ejection cycle and the light emission cycle are synchronized, and the flying state of each ink that constitutes each ink set by the CCD camera Was monitored.

  As an observation result, it was determined that all nozzles had no emission abnormality, and that some nozzles were obliquely emitted or nozzle clogging occurred, x.

<< Image formation and evaluation >>
(Image formation)
Each color image was formed according to the following method using each prepared ink set.

  Each ink constituting each ink set was loaded into an ink jet printer equipped with a drop on demand piezo type ink jet head (720 dpi, droplet amount 16 pl). Subsequently, each color solid image of 35 × 35 mm was recorded on the recording medium by one scan.

  Incidentally, for 3 minutes after the start of image formation from the start of printing, the recording medium was heated from the back side with a heater to control the surface temperature of the recording medium at 45 ± 2 ° C. In the present invention, dpi represents the number of dots per 2.54 cm.

  The evaluation conditions are as follows.

-Print resolution: 720 dpi x 720 dpi
・ Head transport speed: 200 mm / sec, bi-directional printing ・ Recording medium: Vinyl chloride resin sheet (Metamark, digitalvinil)
Evaluation environment: 30 ° C, relative humidity 65%
[Evaluation of image quality]
When each ink set was evaluated for the presence or absence of ink repelling by evaluating the character of the cyan ink, all the cyan inks were good.

  In addition, the presence or absence of color bleed was evaluated on an image obtained by drawing magenta fine lines on a cyan image using each ink set. In addition, the black letters of each ink set were used to visually observe the lower case drawing characteristics with letters and white letters, and the image quality was evaluated according to the following criteria.

1: Color bleed is conspicuous and lower-case characters cannot be drawn 2: Color bleed is slightly seen and lower-case characters can be drawn, but slightly unclear 3: Although lower-case characters can be drawn without color bleed, the drawability of white characters is slightly Unclear 4: Draws lower-case letters without color bleed, and draws out white letters clearly [durability evaluation]
A solid image was created for each color of each ink set, and durability was evaluated according to the following criteria. The cloth used was Bencott (Asahi Kasei Co., Ltd.).

1: A magenta image can be removed with a dry cloth, but other colors cannot be wiped with a dry cloth. 2: An image cannot be obtained by wiping with a dry cloth. Can be taken 3: No image can be taken with a dry cloth or cloth soaked in water 4: An image cannot be taken with a dry cloth or cloth soaked in water, but an image can be taken with a mixture of water / alcohol = 1/1. No image can be taken with a dry cloth, a cloth soaked in water, or a mixture of water / alcohol = 1/1. Table 2 shows the evaluation results of image quality and durability obtained as described above.

  As is apparent from the results shown in Table 2, the ink jet set composed of the ink having the structure defined in the present invention is superior to the comparative example in the image quality (color bleed resistance) and durability of the formed image. It can be seen that it has stable emission characteristics.

  That is, even if an aqueous copolymer that has not been subjected to neutralization dissolution treatment with an amine as defined in the present invention or an aqueous copolymer that has been subjected to neutralization dissolution treatment with an amine is used, the amount added is 1.0. If it is less than the mass, the color bleed resistance and durability of the image formed on the vinyl chloride resin sheet as a non-absorbent recording medium cannot be said to be of sufficient quality, but the addition amount is 1.0 mass or more. If it is in the range of 10% by mass, sufficient quality as color bleed resistance and durability can be obtained. Further, when the amount of the aqueous copolymer added is increased and exceeds 10% by mass, the color bleed resistance and durability are surely maintained, but the emission stability is greatly reduced.

  As described above, using the ink of the present invention containing 1.0% by mass or more and 10% by mass of the aqueous copolymer subjected to the neutralization and dissolution treatment with the amine specified in the present invention, a non-absorbent recording medium ( By forming an image on a sheet made of vinyl chloride resin), it was possible to achieve both excellent image quality (color bleed resistance), durability, and emission stability, which could not be achieved by conventional techniques.

[Evaluation of dryness]
After each color solid image was created in the same manner as in the above durability evaluation, heating was continued at 50 ° C. from the bottom of the recording medium, and the solid image portion formed with a cotton swab was rubbed every 30 seconds until the swab no longer colored. When the time was measured, all the inks of the present invention were within 4 minutes and the drying property was good.

  From the above results, it can be seen that the water-based inkjet recording ink of the present invention is excellent in the image quality of the formed image, the durability drying property, and the emission stability.

Claims (5)

A pigment dispersed with a styrene-acrylic acid copolymer , a silicon-based surfactant or an acetylene-based surfactant, the following solvents A and B as water-soluble organic solvents, water-dispersed polymer fine particles, and at least carboxyl A water-soluble copolymer obtained by neutralizing and dissolving a copolymer obtained by polymerizing an unsaturated vinyl having a group or a sulfonic acid group as a monomer component with an amine,
The water-soluble copolymer is contained in an amount of 1.0% by mass to 10% by mass with respect to the total mass of the ink , and the acid value of the water-soluble copolymer is 80 mgKOH / g or more and less than 300 mgKOH / g, A water-based inkjet recording ink which is used for a non-water-absorbing recording medium made of a vinyl chloride resin.
Solvent A: glycol ethers or 1,2-alkanediols
B solvent: sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, 1,1,3,3-tetramethylurea, hexamethyl Two or more solvents selected from the group consisting of phosphoric acid triamide, N, N-dimethylformamide   2. The aqueous solution according to claim 1, wherein the content of the solvent A (glycol ethers or 1,2-alkanediols) is 2.0% by mass or more and 20% by mass or less based on the total mass of the ink. Inkjet recording ink. The water -based inkjet recording ink according to claim 1, wherein an acid value of the water - soluble copolymer is 90 mgKOH / g or more and less than 250 mgKOH / g.   The water-based inkjet recording ink according to claim 1, wherein the acid value of the water-based dispersed polymer fine particles is 44 mgKOH / g or more and less than 110 mgKOH / g.   The water-based inkjet recording ink according to claim 1, wherein the content of the water-based dispersed polymer fine particles is 1 to 3%.