JP2014224248A - Aqueous ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aqueous inkjet ink which has excellent printability to not only hardly permeable base materials having high hydrophobicity, such as coat paper, art paper, a polyvinyl chloride sheet and the like but also to highly permeable paper surface, fiber materials and the like, and which is excellent in discharge stability from an inkjet nozzle, coating film durability, and drawing performance during high speed printing.SOLUTION: The aqueous inkjet ink includes at least water, a color material, an organic solvent and a cross-linkage type polymer having an acid value of 200 KOH mg/g or more as a shear-viscosity reduction imparting agent. When the ink viscosity is defined as V1, the ink viscosity satisfies 4 mPa s<V1<20 mPa s, and when the dynamic surface tension is measured, the value at the time of 10 mS is 35 mN/m or less.

Description

  The present invention is excellent in printability not only for highly hydrophobic and poorly permeable substrates such as coated paper, art paper and polyvinyl chloride sheet, but also for highly permeable paper surfaces, fiber materials, etc. The present invention relates to a water-based ink having excellent ejection stability, coating film resistance, and drawing performance during high-speed printing.

  Inkjet printing has been developed and commercialized in a wide range of fields, and improvement in inkjet technology is expected to be used as an output device for digital printing, and inkjet printers are being put to practical use in various applications.

  Conventionally, in order to form an image on a poorly permeable substrate using an ink jet printer, an ink having good drying property has been demanded. In particular, coated paper and polyvinyl chloride sheets, which are printing base materials used for industrial purposes, are difficult to wet or absorb ink on the base material. Is very difficult. However, there is a background that the above-mentioned base material is used and high-speed productivity is required from the market, and solvent inks and UV-curable inks that are easily wetted and have quick-drying properties are currently used. However, solvent inks are concerned that the odor and harmfulness of solvents that volatilize during drying may affect the environment, and many UV inks have strong irritating properties or odors depending on the monomers used. There was a problem for the workers who handle ink.

  Since it is highly safe for workers and has a low environmental impact, water-based inks are expected to be used for all indoor and outdoor purposes, and development has been promoted in recent years. In addition, for paper substrates that easily absorb ink, such as plain paper and special paper, many system integrators use water-based ink-jet inks used for consumer use to promote the development of industrial printers. Especially in the European and American markets, the printer has been introduced, and the use of newspapers, wallpaper for building materials, cardboard, etc. is limited, and the shift from existing printing to digital printing has begun.

  Considering further conversion to digital printing and market expansion, not only paper base materials that easily absorb ink such as plain paper and special paper, but also textile materials such as cloth used in the textile market, inks, etc. Development of water-based inkjet ink that can form images by direct drawing on various printing substrates such as coated paper, art paper, polyvinyl chloride sheet, etc. It has become.

  However, in order to respond to higher speeds and higher image quality by improving the printer device, as ink droplets become smaller and the discharge frequency from inkjet heads increases, sharpness, color, etc., especially in pigment inks In order to improve quality such as density, pigment particles in the ink are being refined. As a result, a color reproduction area comparable to that of dye ink is secured, and improvement in image quality with respect to inkjet processed paper (especially photographic paper) has been observed. However, for non-processed plain paper and fiber materials, ink droplets are likely to penetrate into the fiber of the paper, resulting in color depth (color development) of the printed matter and image bleeding. As a result, the quality of the printed matter is significantly reduced.

  In addition, it has been confirmed from general literature and published patents that wettability to a substrate is the key to printing on a hardly absorbent substrate such as coated paper or polyvinyl chloride sheet, and hydrophobic Fields that require high-speed productivity, such as the print-on-demand market, which replaces existing printing and powder toner printing, although it is known that reactive solvents and surfactants are added to the formulation Then, it is known from the inventors that the print image quality cannot meet the market demand.

  Water-based inks for inkjet use, as disclosed in Patent Documents 1 to 4, use saccharides, natural polymers, and water-soluble resins as thickeners, and use a non-processed absorbent base as a printing target to improve color development and bleeding. Ink has been developed for a long time. However, it has been found by the inventors that even if an ink having improved color developability and image bleeding is used as a printed matter, the ejection stability deteriorates when the ink after storage with time is used. The cause is that saccharides and natural polymers are likely to be put on by microorganisms due to storage over time, and decay proceeds. As for water-soluble resins, the pH in the ink decreases due to storage over time. This is considered to be the cause of the decrease in ink viscosity and deviating from the appropriate viscosity region of the inkjet head.

  Moreover, although the particulate crosslinked N-vinylcarboxylic acid resin described in Patent Document 5 is used, the ejection stability is lowered by increasing the driving frequency of the inkjet head, and the printed matter productivity of the printer is increased. It is known from the inventors' investigation that this is not possible.

JP-A-62-283174 Japanese Patent No. 4450305 JP-A-8-41394 JP 10-46077 A Japanese Patent No. 2738273

  The object of the present invention is excellent in printability not only on highly hydrophobic and poorly permeable substrates such as coated paper, art paper and polyvinyl chloride sheet, but also on highly permeable paper surfaces, fiber materials, etc. An object of the present invention is to provide a water-based ink excellent in ejection stability from a nozzle, coating film resistance, and drawing performance during high-speed printing.

The above object of the present invention is achieved by the following configurations.
That is, the present invention is an ink containing at least water, a coloring material, an organic solvent, and a vinyl polymer having an acid value of 200 KOHmg / g or more,
The viscosity (V1) of the ink at 25 ° C. is 4 mPa · s <V1 <20 mPa · s, and the value at 10 mS when the dynamic surface tension is measured at 25 ° C. is 35 mN / m or less. It relates to the water-based ink.

  Further, according to the present invention, the viscosity (V2) of the ink when the amount of the organic solvent in the ink is reduced to 50% by weight of the initial total solvent amount (total amount of water and organic solvent) is 8 <V2 / V1 <. It is related with the said water-based ink characterized by being 80.

  Further, according to the present invention, the weight change width when 5 g of ink is heated for 30 minutes using a hot plate at 50 ° C. in an environment where the temperature is 20 ° C. and the humidity is 30% is 0.75 g or more and 1.50 g or less. The present invention relates to the above water-based ink.

  Furthermore, the present invention provides an organic solvent having a boiling point of 150 ° C. or more and 280 ° C. or less, a surface tension of 20 mN / m or more and 35 mN / m or less, and an organic solvent content of 10% by weight or more and 30% by weight or less of the whole ink. It is related with the said water-based ink characterized by the above-mentioned.

  Furthermore, the present invention relates to the above water-based ink, wherein the alkanediol having 4 or more carbon atoms, which is an organic solvent, is contained in an amount of 10% by weight to 25% by weight based on the whole ink.

  Furthermore, the present invention relates to the above water-based ink, wherein 1,2-hexanediol as an organic solvent is contained in an amount of 10% by weight to 20% by weight based on the whole ink.

Furthermore, the present invention provides the water-based ink described above, which contains a water-soluble resin having an acid value of 300 KOH mg / g or less and a weight average molecular weight of less than 30000, and an alkali agent.

  Furthermore, this invention relates to the said water-based ink characterized by including surfactant.

Furthermore, the present invention is an ink set containing the water-based ink,
The present invention relates to an ink set including cyan ink, magenta ink, yellow ink, and black ink.

Furthermore, the present invention relates to an ink jet recording method for performing printing by discharging droplets of the water-based ink and depositing the droplets on a printing substrate.

Furthermore, this invention relates to the printed matter formed by printing with the said water-based ink.

  According to the present invention, it is excellent in printability not only for highly hydrophobic and poorly permeable substrates such as coated paper, art paper, and polyvinyl chloride sheets, but also on highly permeable paper surfaces, fiber materials, etc. It is possible to provide a water-based ink excellent in ejection stability from a nozzle, coating film resistance, and drawing performance during high-speed printing.

  The water-based ink of the present invention will be described below with reference to preferred embodiments.

  The water-based ink of the present invention is an ink containing at least water, a coloring material, an organic solvent, and a vinyl polymer having an acid value of 200 KOH mg / g or more, and the viscosity (V1) of the ink at 25 ° C. is 4 mPa · s < V1 <20 mPa · s, and when dynamic surface tension is measured at 25 ° C., the value at 10 mS is 35 mN / m or less. First, the vinyl polymer that characterizes the present invention will be described.

  In general, non-processed plain paper or fiber base material that easily penetrates ink causes ink droplets to permeate into the fiber of the base material when printed, resulting in a decrease in print density (color development) and image bleeding. Occurs and the quality of the printed matter is significantly reduced. On the other hand, the characteristics of the ink side are that, in particular, in pigment ink, in order to improve the sharpness, color density, etc., the finer pigment particles in the ink are progressing. The ink has become more easily penetrated. Therefore, in order to create an excellent printed matter that can be drawn directly on any printing substrate, pigment particles, which are coloring components, are coated when the ink ejected from the inkjet head is fixed on the recording medium. It is desirable that the surface of the recording material is fixed without agglomeration.

  As a result of intensive studies by the present inventors, when a vinyl polymer having a specific acid value is used as a shear thinning agent in the ink composition of the present invention, it is more permeable than unprocessed plain paper or plain paper. It was possible to draw directly even on a fiber substrate such as a strong cloth, and a marked improvement in color development and bleeding was confirmed, confirming an improvement in printed matter quality. In addition, when printed with a high-speed printer, which is commonly used in the print-on-demand market, not only absorbent substrates such as surface-treated inkjet paper, but also coated paper and art paper Even with such difficult-to-absorbent substrates, the density and color developability were excellent, and image bleeding was remarkably improved even at high-speed printing settings, and it was confirmed that the quality of printed matter was improved.

  The reason why a vinyl polymer other than the above-mentioned specific acid value cannot be used as the shear thinning agent will be described below. Polysaccharides such as pentose, hexose, heptose, octose, etc., gums such as xanthan gum, carrageenan gum, locust bin gum, and natural polymers such as hydroxyethyl cellulose are susceptible to microorganisms when stored over time, resulting in a decrease in viscosity. However, it cannot be used due to problems such as significantly deteriorated ejection stability and deteriorated coating film resistance. In addition, a water-soluble resin that is not a vinyl polymer having a specific acid value has no problem with stability over time, but the printing density (coloring property) is reduced and image blur occurs on plain paper, and the quality of the printed matter is significantly reduced. In addition, when a water-soluble resin is added until the quality of printed matter on plain paper or a fiber base material is improved, the discharge stability is lowered, so that it cannot be used.

  The reason why printing is possible even on a non-processed penetrating substrate by using a vinyl polymer having a specific acid value as the shear thinning agent is considered as follows.

  A three-dimensional network structure formed by adsorbing carboxylic acid groups incorporated in the resin structure of a vinyl polymer having a specific acid value onto pigment particles or water-dispersible resin particles while hydrating with water molecules Since structural viscosity is imparted (cross-linked) by the body even with a small addition amount, it is stably ejected from the inkjet head. In addition, by adding a shear thinning agent, the ink solvent that has landed on the recording medium volatilizes, and the viscosity of the recording body surface increases rapidly without agglomeration of the ink. Since it adheres, it is possible to produce printed matter that is excellent in color developability on any recording medium and does not have bleeding. Moreover, the reason why the number of non-processable penetrating base materials that can be printed increases as the acid value increases is because the physical crosslinking point with the hydration part, pigment dispersion, and resin fine particles increases. This is because the ink viscosity rapidly increases on the surface of the recording medium.

  Inkjet printing is a system that generates pressure waves by bubbles generated by vibrating a piezoelectric element or boiling ink, and then ejects ink droplets to record them. It can be stably ejected from an inkjet head. Essential performance. The vinyl polymer used as the shear thinning agent this time can be expected to improve the quality of printed matter by adding a smaller amount as the acid value is higher as shown above. Therefore, the three-dimensional network structure formed with water, pigment particles, and water-dispersible resin fine particles is easily broken even by a small pressure wave, and can be easily formed into fine droplets and ejected stably. From these backgrounds, there is no problem with the ejection stability from the inkjet head.

  The material names corresponding to the vinyl polymer used as the shear thinning agent in the present invention are exemplified below. These are vinyl polymerization polymers obtained by polymerizing vinyl monomers.

(Crosslinked acrylic resin)
Carbopol 934, 940, 941, 1341, EZ-1, ET2020, Pemulen TR-1, TR-2, Nippon Kayaku Co., Ltd. Junron PW110, PW111, PW115, BF Goodrich , Rheological 250H, 252L, 305L, 306L, 830L, 830L, 835H, Leonate 101 manufactured by Elementis Japan, Hibiswako 103, 104, 105, 204, 304 manufactured by Wako Pure Chemical Industries, Ltd. Synthetic Aron A20L, A7100, A10H, A30, A93, A93, A7255, A7185, A7195, Sumitomo Seika Co., Ltd. Akpek HV-501, HV-504, HV-505, Sanyo Chemical Sacris A-1, Co., Ltd. C-1, L-1, N-1, Rohm & Haas Primal G111, RM5, TT935, Claviant Polymer Lebios CR, CRX, DP60-3902

(Cross-linked acrylic resin emulsion type)
Rohm & Haas Primal ASE 60, TT 615, Elementis Japan Leonate 1, 430, 450, Clariant Polymer Viscalex HV-30, VG-2, AT-55, AT-77, Dai-ichi Kogyo Seiyaku Co., Ltd. Superflex VF, VM, BASF Coracral P, D, Toagosei Aron B300K, B500, A7075, 7055, San Nopco SN thickener 613, 615, 618, 630, 632, 633, 634, 634, 635, 636, 650, A813, A815, A818, A850

  Among them, an acid value of 200 KOH mg / g or more is preferable, and a resin having a large resin molecular weight is preferable. The vinyl polymer is preferably an emulsion type rather than an aqueous resin solution because it has a large resin molecular weight, can be added in a small amount, and can prevent deterioration in ejection stability. The addition amount is preferably 0.01% by weight or more and 0.50% by weight or less, and more preferably 0.05% by weight or more and 0.20% by weight or less, based on the total amount of ink as solid content weight. If it is less than 0.01% by weight, the color developability and image bleeding may occur on the non-processed printing substrate, which may be undesirable because the quality of the printed matter is significantly reduced. On the other hand, if it exceeds 0.50% by weight, the ejection stability at a high frequency in the inkjet head, which is necessary for improving the printed matter production performance of the printer, is deteriorated, so that the printing reliability for high-speed printing is deteriorated. Sometimes.

  Furthermore, as water contained in the water-based inkjet ink used in the present invention, it is preferable to use ion-exchanged water (deionized water) instead of general water containing various ions.

  The water content that can be used in the present invention is in the range of 20 to 80% by weight based on the total amount of ink.

  The color material used in the present invention is not particularly limited and can be a dye or a pigment. However, although pigments lack color developability compared to dyes, they are excellent in weather resistance and can be applied to printed materials for outdoor use, so that it is particularly preferable to use pigments in terms of increased versatility.

  As the pigment, inorganic pigments and organic pigments can be used, and each can be used alone or in combination. As the inorganic pigment, for example, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black and the like can be used. Specifically, as described below, a desired pigment is used in accordance with each color ink. The pigment is not limited to the following examples.

  Examples of pigments that can be used in the present invention include cyan pigments. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 16, 22, C.I. I. Vat Blue 4, 6 etc. are mentioned.

  Examples of magenta pigments that can be used in the present invention include C.I. I. Pigment Red 5, 7, 12, 22, 23, 31, 48 (Ca), 48 (Mn), 49, 52, 53, 57 (Ca), 57: 1, 112, 122; quinacridone solid solution, 146, 147, 150 238, 269, C.I. I. Pigment Violet 19 etc. are mentioned.

  Examples of yellow pigments that can be used in the present invention include C.I. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 74, 83, 86, 93, 94, 95, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151 , 154, 155, 166, 168, 180, 185, 213 and the like.

Examples of the black pigment that can be used in the present invention include carbon black, a primary particle diameter of 11 to 40 mμm (nm), a specific surface area by the BET method of 50 to 400 m ² / g, and a volatile content of 0.5. Those having characteristics of 10 to 10% by weight and pH values of 2 to 10 are suitable. The following are mentioned as a commercial item which has such a characteristic. For example,
No. 33, 40, 45, 52, 900, 2200B, 2300, MA7, MA8, MCF88 (manufactured by Mitsubishi Chemical), RAVEN1255 (manufactured by Colombia), REGAL330R, 400R, 660R, MOGUL L (manufactured by Cabot), Nipex 160IQ , Nexex 170IQ, Nipex 75, Printex 85, Printex 95, Printex 90, Printex 35, Printex U (manufactured by Degussa) and the like, and any of them can be preferably used.

  In the present invention, the above color materials can be used as cyan ink, magenta ink, yellow ink, and black ink, and these four color ink sets can also be used. However, the present invention is not limited to the above-described pigments, and can be used as an ink set in which other pigments are combined with special colors such as orange, green, white, and clear not containing pigments.

  As content of the pigment which can be used by this invention, it is the range of 0.1-20 weight% with respect to the ink whole quantity.

The ink of the present invention uses the above-mentioned pigment and may or may not contain a dispersant for dispersing the pigment, but without using a dispersant (0% by weight) Self-dispersing pigments can also be used. The self-dispersing pigment has a functional group (dispersibility-imparting group) such as one or more selected from the group consisting of —COOH, —CHO, —OH, —SO ₃ H and salts thereof on the pigment surface. ), And can be uniformly dispersed in water-based ink without adding a dispersant separately. The term “dispersion” as used herein refers to a state in which a self-dispersion type dispersion is stably present in water without a dispersant, not only in a dispersed state but also in a dissolved state. Include.

  However, as the content of the organic solvent used in the present invention increases, the dispersion state of the pigment is destroyed and the storage stability of the ink is likely to deteriorate. From these backgrounds, as a result of the study by the authors, it was confirmed in this study that the storage stability of the ink was better when the dispersant for dispersing the pigment was contained than the self-dispersed pigment. It was. Therefore, it is more preferable to contain a dispersant.

Examples of the dispersant species used in the present invention include a cationic dispersant, an anionic dispersant, a nonionic dispersant, and a surfactant. Examples of anionic dispersants include polyacrylic acid, polymethacrylic acid, acrylic acid-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, acrylic acid-acrylic acid alkyl ester copolymer, styrene-acrylic acid. Copolymer, styrene-methacrylic acid copolymer, styrene-acrylic acid-alkyl acrylate copolymer, styrene-methacrylic acid-alkyl acrylate copolymer, styrene-α-methylstyrene-acrylic acid copolymer Styrene-α-methylstyrene-acrylic acid-alkyl acrylate copolymer, styrene-maleic acid copolymer, vinyl naphthalene-maleic acid copolymer, vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene Copolymer, vinyl acetate-maleic ester Examples thereof include a copolymer, a vinyl acetate-crotonic acid copolymer, and a vinyl acetate-acrylic acid copolymer.
Examples of anionic surfactants include sodium dodecylbenzenesulfonate, sodium laurate, ammonium salt of polyoxyethylene alkyl ether sulfate, and examples of nonionic surfactants include polyoxyethylene alkyl. Examples include ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylamine, polyoxyethylene alkylamide, and the like, and one or more of these are used.

  The dispersant used in the present invention is preferably a conventionally known alkali-soluble resin used in water-based pigment inks, and is not particularly limited, but the one having both the pigment dispersant and the binder functions. Still preferred. The weight average molecular weight is preferably 50000 or less and more preferably 30000 or less from the viewpoint of ejection stability. The addition amount is preferably 0.30% by weight or more and 2.00% by weight or less based on the total amount of the ink, and there is no problem even if two or more types are used in combination. If it is less than 0.3% by weight, it is difficult to maintain the dispersion stability with respect to the addition of the organic solvent, which is not preferable. On the other hand, if the amount exceeds 2.00% by weight, the ink viscosity will increase abruptly when the ink is dried on the ink jet head nozzle, the ink ejection stability will be deteriorated, and the printing reliability will be lowered. .

  More specifically, styrene, styrene derivatives such as α-methylstyrene, vinyl naphthalene derivatives, aliphatic, alicyclic and aromatic alcohol esters of α, β-ethylenically unsaturated carboxylic acid, (meth) acrylic acid, etc. And a random copolymer comprising two or more monomers selected from (meth) acrylic acid alkyl ester derivatives and the like, a graft copolymer or a block copolymer.

  Here, the (meth) acrylic acid alkyl ester derivative preferably has 10 or more carbon atoms. For example, decyl (meth) acrylate, undecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, Examples include tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, and behenyl (meth) acrylate. Examples of aliphatic, alicyclic and aromatic alcohol esters of α, β-ethylenically unsaturated carboxylic acid include aliphatic and alicyclic unsaturated dibasic acids such as maleic acid, fumaric acid and itaconic acid. , Aromatic alcohol diesters and half esters.

  Furthermore, it is preferable to use an alkali agent in order to solubilize the dispersant. Although it does not specifically limit as an alkali agent kind to be used, For example, from the group which consists of ammonia, a primary, secondary, or tertiary organic amine (a basic nitrogen-containing heterocyclic compound is included) and an alkali metal hydroxide. A compound can be suitably used. Specifically, ammonia water, various organic amines such as dimethylaminoethanol, diethanolamine, and triethanolamine; inorganic alkali agents such as alkali metal hydroxides such as sodium hydroxide, lithium hydroxide, and potassium hydroxide; organic acids And mineral acids. Of these, dimethylaminoethanol is preferred because it is easy to use from the safety and legal regulations.

The meaning, measurement method, and reason of the dynamic surface tension described in the present invention are shown below. The dynamic surface tension indicates the surface tension when a certain time has elapsed after the liquid level is generated. As a measuring method, it is possible to measure by a bubble pressure method or a plate method.
In the present invention, BP100 (bubble pressure dynamic surface tension meter) manufactured by KRUSS was used. The measured time is 10 mS, which is measured after a very long time compared to the dynamic surface tension considered in inkjet ink, but there is little measurement error, and it is necessary to measure a stable value. The method was considered preferred. As the dynamic surface tension value, when the value at 10 ms is 35 mN / m or less, the ink is wetted even on a hardly absorbent substrate such as coated paper or vinyl chloride sheet, and the quality of printed matter is improved. Has been confirmed in this study. This is a surfactant that is commonly used in inkjet inks. Even if the static surface tension value is reduced, wetting to the printing substrate is improved, but there is no improvement in printed quality. Think of it as explaining. That is, it is generally known that a surfactant requires time from the generation of the liquid surface to the surface, and exerts an action after being adsorbed on the liquid surface. However, with ink-jet ink, since the image is formed in a microdroplet state of about 10 pL, the ink is dried and solidified before the surfactant moves to the liquid surface, and the performance of the surfactant cannot be expressed. Since it is the situation, it is estimated that the quality of the printed matter is not improved in the actual printing test.

Furthermore, when the ink viscosity described in the present invention is V1, and the ink viscosity when the total amount of solvent in the ink (total amount of water and organic solvent) is 50% by weight is set to V2, the ink is dried. The reason why the viscosity behavior is preferably 8 <V2 / V1 <80 is shown below.
First, since the ink viscosity is measured in a low viscosity range of 20 mPa · s or less, it is detected with a standard solution for calibration of a viscometer defined in JIS Z 8809, and measured at 25 ° C. under normal pressure. is there. The measurement model was a TV-22 viscometer manufactured by Toki Sangyo Co., Ltd. The dry viscosity behavior of the ink was also described in the explanation of the shear thinning agent. However, the ink viscosity is reduced when the ink droplets land on the substrate and the solvent in the ink volatilizes instantaneously. As the ink rapidly rises and adheres to the surface of the base material, the ink does not penetrate into the absorbent base material such as a cloth. Further, since it is not possible to expect the effect of penetrating into a base material such as coated paper or a vinyl chloride sheet, it is very difficult to fix the base material surface at high speed printing. Therefore, as described above, the ink rapidly adheres to the surface of the substrate due to the thickening of the ink on the surface of the substrate. As a result, the quality of the printed matter can be remarkably improved without causing a beading phenomenon in which a feeling of roughness appears in the image or a bleeding phenomenon in which bleeding appears between different colors. Moreover, it is the effect which arises by adding the said shear thinning agent, and since it is not the cohesion fixation generally implemented, it is excellent also in color development. When the dry viscosity behavior is V2 / V1 <8, dot fusion occurs on the base material during high-speed printing, and the quality of printed matter is deteriorated. Further, when V2 / V1> 80, the ink viscosity tends to increase on the inkjet head nozzle, the discharge stability is lowered, and the printing reliability is deteriorated, which is not preferable.

Furthermore, when 5 g of ink is heated on a hot plate at 50 ° C. for 30 minutes in an environment of 20 ° C. and 30% humidity described in the present invention, the weight change width of the ink is 0.75 to 1 The reason why .50 g is preferable is shown below.
First, the weight change width is a value that defines the volatilization rate of the ink. When the drying viscosity behavior and the volatilization rate are within the specified values, the ink will land on the substrate and the ink viscosity will increase on the printing substrate. Since the above ink droplets do not fuse, it is confirmed that the quality of printed matter is further improved. As a method for measuring the change in the weight of the ink, 5 g of ink was charged into a mentum can under an environment where the temperature was 20 ° C. and humidity was 30%, and then left on a 50 ° C. hot plate for 30 minutes and heated. The change in the weight of the ink before and after heating was measured with a balance and defined as a numerical value for the volatilization rate. When the weight change width of the ink is 0.75 g or less, the moisture retention performance of the ink is good. Therefore, a sudden increase in viscosity hardly occurs on the inkjet head, and the ejection stability is improved and the printing reliability is improved. Since the ink viscosity on the printing substrate cannot be rapidly increased due to the slow speed, the quality of the printed matter is deteriorated, which is not preferable. In addition, when the ink weight change width is 1.50 g or more, the ink volatilization rate is fast. Therefore, the ink viscosity on the printing substrate rapidly increases. In this case, a sudden increase in viscosity occurs, the discharge stability is deteriorated, and the printing reliability is lowered.

  The organic solvent used as a humectant in the present invention is a viewpoint of improving wettability on a highly hydrophobic hardly-permeable substrate such as coated paper, art paper, and polyvinyl chloride sheet and moisturizing property on an inkjet nozzle. Therefore, the boiling point is 150 ° C. or more and 280 ° C. or less, the surface tension of the solvent itself is 20 mN / m or more and 35 mN / m or less, and the organic solvent content in the ink is 10% by weight or more and 30% by weight with respect to the total amount of the ink. The following is preferable.

  The reason for using the humectant in the present invention is to prevent ink from being easily dried at the nozzles of an inkjet head, the ink viscosity to rapidly increase, and deterioration of ejection stability to be prevented. In addition, when a water-soluble organic solvent having a boiling point or surface tension value in the above-described preferred range is used, sufficient moisture retention can be ensured, and excellent discharge stability and wettability to hardly absorbable substrates can be dramatically achieved. It is preferable because it can be improved. When an organic solvent having a boiling point higher than the above range is used, the drying property is deteriorated, and although the ejection stability can be ensured, the ink is hard to volatilize. This is not preferable because it does not occur and the print quality is lowered. Moreover, when the surface tension of the organic solvent is higher than the above range, it is not preferable because sufficient wettability cannot be obtained on the hardly absorbent substrate and the quality of the printed matter is deteriorated.

  The total content of the organic solvent used as a humectant in the present invention in the ink is preferably 10% by weight to 30% by weight with respect to the total amount of the ink. If the total content of the water-soluble organic solvent is less than 10% by weight, the moisture retention of the ink is insufficient, and the ejection stability may be impaired. In addition, the wettability on the hardly absorbent substrate may be reduced, and the print quality may be deteriorated. When the total content of the water-soluble organic solvent is more than 30% by weight, the viscosity of the ink becomes high, which may impair the ejection stability. In addition, the storage stability and volatilization speed of the ink are not suitable for practical use, and the print quality may be deteriorated.

  In addition, an organic solvent can be used alone or in combination, as long as it is within a suitable content range that does not reduce the effect of the present invention.

  Specific organic solvents include ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, triethylene glycol. Monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol Monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, 3-methoxy-1-butanol, 3-methoxy-3-methylbutanol, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol Dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, triethylene glycol methyl ethyl ether, tetraethylene glycol methyl ethyl ether, diethylene glycol butyl methyl ether, triethylene glycol butyl methyl ether Ether, tetraethylene glycol butyl ether, propylene glycol dimethyl ether, tripropylene glycol dimethyl ether alkanediols like.

  Further, a water-soluble nitrogen-containing solvent can be added for the purpose of improving the penetration and adhesion to the hardly permeable substrate.

  Examples of the nitrogen-containing solvent include 2-pyrrolidone, N-methylpyrrolidone, N-ethylpyrrolidone, 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-ethoxypropionamide, N, N-dimethyl-β-butoxypropionamide, N, N-dimethyl-β-pentoxypropionamide, N, N-dimethyl-β-hexoxypropionamide, N, N-dimethyl-β-heptoxypropionamide, N, N-dimethyl-β-2-ethylhexoxypropionamide, N, N-dimethyl-β-octoxypropionamide, N, N-diethyl-β- Butoxypropionamide, N, N-diethyl-β-pentoxypropionamide, N, N-diethyl β- hexoxyphenyl propionamide, N, N- diethyl -β- heptene Toki Cipro propionamide, N, etc. N- diethyl -β- octoxynol propionamide and the like.

  Examples of alkanediols having 4 or more carbon atoms used in the present invention include 2-methyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 1,2-butanediol, 1, Examples include 3-butanediol, 3-methyl-1,3-butanediol, 1,2-pentanediol, 2-methyl-2,4-pentanediol, 1,2-hexanediol, and the like. be able to. From the viewpoint of obtaining excellent wettability on a poorly permeable substrate, it is more preferable to use 1,2- (alkanes having 4 to 6 carbon atoms) diols among the alkane diols.

  The content of the alkanediol in the ink is 10% by weight or more and 25% by weight or less based on the total amount of the ink from the viewpoint of ensuring excellent wettability and drying on the poorly permeable substrate. Preferably, it is 10% by weight or more and 20% by weight or less. When the content is less than 10% by weight, the moisture retention on the ink jet nozzle is insufficient, which may impair ejection stability. In addition, the wettability of the ink with respect to the poorly permeable substrate is insufficient, and the white spots of the image are generated. If it exceeds 25% by weight, the volatilization rate of the ink is deteriorated, dots are connected on the poorly permeable substrate, and the quality of the printed matter may be deteriorated such as mixed color bleeding or white spots due to dot fusion.

  Among the above alkanediols, 1,2-hexanediol has a low surface tension of the solvent itself, but has a relatively good stability to the pigment dispersion, and hardly absorbs without deteriorating the storage stability of the ink. It is possible to improve the wettability with respect to the conductive substrate. In addition, it is preferable to use a pigment dispersion because a uniform ink coating can be formed while the pigment dispersion is kept dispersed in the drying process, and a high glossy printed matter quality can be obtained. The content is preferably 10% by weight or more and 20% by weight or less based on the total amount of the ink.

  In the ink of the present invention, a surfactant can be used for the purpose of adjusting the surface tension and ensuring the wettability on the substrate. Various surfactants are known, such as acetylene-based, silicon-based, acrylic-based, and fluorine-based surfactants. However, the surface tension of ink is sufficiently lowered and used for the nozzle surface of inkjet heads. From the viewpoint of maintaining ink repellency and realizing stable ejection with respect to the water-repellent film, it is preferable to use a silicon-based surfactant. As an example of the addition amount of the surfactant, 0.1 to 5% by weight is preferable with respect to the total amount of the ink, and 0.5 to 4% by weight from the viewpoint of the storage stability of the ink. Is preferred.

  In addition to the above-described components, the ink of the present invention can be appropriately added with additives such as an antifoaming agent and an antiseptic agent in order to obtain an ink having desired physical properties as required. As an example of the addition amount of these additives, 0.01 to 10% by weight is preferable with respect to the total weight of the ink.

Furthermore, regarding the binder resin used in the present invention, a binder resin can be used in order to increase the coating film resistance of the printed matter. It is preferable to use water-dispersible resin fine particles as the binder resin. Water-soluble resins and fine resin particles are generally known as binder resins for water-based inks. In general, resin fine particles have a higher molecular weight than water-soluble resins, and can achieve high resistance.
The water-soluble resin preferably has an acid value of 300 KOH mg / g or less and a weight average molecular weight of less than 30000.

In addition, the resin fine particles can reduce the viscosity of the ink and can be blended with a larger amount of resin in the ink, so that it can be said that the resin fine particles are suitable for enhancing the resistance of the ink-jet ink. Examples of the resin fine particles include acrylic, urethane, styrene butadiene, vinyl chloride, and polyolefin.
By increasing the glass transition temperature (Tg) of the water-dispersible resin fine particles, it is possible to improve resistance such as abrasion resistance and chemical resistance, preferably in the range of 50 to 100 ° C., more preferably Is in the range of 75 ° C to 90 ° C. When the temperature is lower than 50 ° C., sufficient resistance cannot be obtained, and printing may be peeled off from the printed matter in practice. When the temperature is higher than 100 ° C., the coating film becomes very hard, and cracking and cracking may occur on the printed surface when the printed material is bent.

  In addition, the water-dispersible resin fine particles not only increase the coating film resistance of the printed matter, but also quickly form a film after the droplets have landed, thereby suppressing the bleeding between dots and being excellent without bleeding between colors. Print quality can be obtained.

The content of the water-dispersible resin fine particles as described above in the ink is preferably in the range of 3 to 20% by weight with respect to the total amount of ink non-volatile content.

<Ink preparation method>
Examples of the method for preparing the ink of the present invention comprising the components described above include the following methods, but the present invention is not limited to these. First, a method for preparing a pigment dispersion using a dispersant will be described below. First, a pigment is added to an aqueous medium in which at least a pigment-dispersed resin and water are mixed, and after mixing and stirring, a dispersion treatment is performed using a dispersion means described later, and a centrifugal separation treatment is performed as necessary. A pigment dispersion is obtained. Next, an ink production method will be described below. First, if necessary, a water-soluble organic solvent or an appropriately selected additive component as listed above is added to the pigment dispersion, and the mixture is stirred and filtered as necessary to obtain the ink of the present invention. To do.

  In the ink preparation method of the present invention, as described above, a pigment dispersion obtained by carrying out a dispersion treatment is used for ink preparation, or a commercially available self-dispersion is used. When preparing a pigment dispersion using a dispersant, it is effective to perform premixing before the dispersion treatment performed when preparing the pigment dispersion. That is, premixing may be performed by adding a pigment to an aqueous medium in which at least a pigment dispersant and water are mixed. Such a premixing operation is preferable because it improves wettability of the pigment surface and promotes adsorption of the dispersant to the pigment surface.

  The disperser used in the above-described pigment dispersion treatment may be any disperser that is generally used, and examples thereof include a ball mill, a roll mill, a sand mill, a bead mill, and a nanomizer. Among these, a bead mill is preferably used. Examples of such include a super mill, a sand grinder, an agitator mill, a glen mill, a dyno mill, a pearl mill, and a cobol mill (all are trade names).

  Further, in the above-described pigment premixing and dispersion treatment, the pigment dispersion resin may be dissolved or dispersed only in water, or may be dissolved or dispersed in a mixed solvent of a water-soluble organic solvent and water. .

  Since the ink of the present invention is for inkjet recording, it is preferable to use a pigment having an optimum particle size distribution. That is, in order to allow ink containing pigment particles to be suitably used in the ink jet recording method, it is preferable to use a pigment having an optimum particle size distribution in view of demands such as nozzle clogging resistance. Examples of a method for obtaining a pigment having a desired particle size distribution include the following methods. Reduce the size of the grinding media of the disperser as mentioned above, increase the filling rate of the grinding media, increase the processing time, classify with a filter or centrifuge after grinding, and these There are methods such as a combination of methods.

<Recording method>
The recording method used in the present invention is an inkjet recording method in which printing is performed by adhering to a printing substrate, and an inkjet recording method using the above-described aqueous inkjet ink is provided.

<Recorded material>
Moreover, according to this invention, the printed matter formed by printing with the above-mentioned water-based inkjet ink is provided.

  Hereinafter, the present invention will be described more specifically with reference to examples. In the examples, “part” represents “part by weight”, and “%” represents “% by weight”. The average primary particle diameter of the pigment, the weight average molecular weight (Mw), and the acid value (KOHmg / g) of the resin are as follows.

  The weight average molecular weight (Mw) of the resin was measured in terms of polystyrene measured using TSKgel column (manufactured by Tosoh Corporation) and GPC (manufactured by Tosoh Corporation, HLC-8120GPC) equipped with an RI detector using THF as a developing solvent. It is a weight average molecular weight (Mw).

  For the resin acid value, an automatic dropping device (manufactured by KEM, AT-610) was used, and the dropping solution was added dropwise with a 0.1 mol / l potassium hydroxide-ethanol solution. The acid value (KOHmg / g) was calculated from the sample amount, sample solid content, titer, and titrant concentration.

<Example of production of alkali-soluble resin 1>
A reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer was charged with 93.4 parts of triethylene glycol monomethyl ether and replaced with nitrogen gas. The inside of the reaction vessel was heated to 110 ° C., and a mixture of 35.0 parts of lauryl methacrylate, 35.0 parts of styrene, 30.0 parts of acrylic acid, and 6.0 parts of V-601 (manufactured by Wako Pure Chemical Industries) was added for 2 hours. Over the course of the polymerization reaction. After completion of the dropwise addition, the mixture was further reacted at 110 ° C. for 3 hours, 0.6 parts of V-601 (manufactured by Wako Pure Chemical Industries) was added, and the reaction was further continued at 110 ° C. for 1 hour to obtain a solution of the alkali-soluble resin 1. Obtained. The weight average molecular weight of the alkali-soluble resin 1 was about 16000.
Further, after cooling to room temperature, 37.1 parts of dimethylaminoethanol was added for neutralization. This is the amount that neutralizes 100% of acrylic acid. Further, 200 parts of water was added to make it aqueous. 1 g of this was sampled, heated and dried at 180 ° C. for 20 minutes to measure the non-volatile content, and water was added so that the non-volatile content of the previously aqueous resin solution was 20%. As a result, an aqueous solution having a non-volatile content of 20% of the alkali-soluble resin 1 was obtained. The actually measured acid value of the alkali-soluble resin 1 is 230 KOH mg / g, and the weight average molecular weight (Mw) is about 16000.

<Example of production of alkali-soluble resin 2>
20 parts of JONCRYL 611 (weight average molecular weight 8100, acid value 55 KOHmg / g), 1.74 parts of dimethylaminoethanol and 78.26 parts of water were added to a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser and a stirrer. And neutralized. This neutralized and made water-soluble acrylic acid 100%. 1 g of this was sampled, heated and dried at 180 ° C. for 20 minutes to measure the non-volatile content, and water was added so that the non-volatile content of the previously aqueous resin solution was 20%. As a result, an aqueous solution having a non-volatile content of 20% of the alkali-soluble resin 2 was obtained.

<Example of production of alkali-soluble resin 3>
In a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser and a stirrer, 20 parts BYK P105 (weight average molecular weight 10000 or less, acid value 360 KOHmg / g), 11.44 parts dimethylaminoethanol and 68.56 parts water Added, neutralized, and water-solubilized. This is the amount that neutralizes 100% of acrylic acid. 1 g of this was sampled, heated and dried at 180 ° C. for 20 minutes to measure the non-volatile content, and water was added so that the non-volatile content of the previously aqueous resin solution was 20%. As a result, an aqueous solution having a non-volatile content of 20% of the alkali-soluble resin 3 was obtained.

<Example of production of water-dispersible resin fine particles 1>
A reaction vessel equipped with a stirrer, a thermometer, a dropping funnel, and a refluxing vessel was charged with 40 parts of ion exchange water and 0.2 part of Aqualon KH-10 (Daiichi Kogyo Seiyaku) as a surfactant. -10 parts of ethylhexyl acrylate, 57 parts of methyl methacrylate, 30 parts of styrene, 2 parts of dimethylacrylamide, 1 part of methacrylic acid, 53 parts of ion-exchanged water and 1.8 parts of Aqualon KH-10 (Daiichi Kogyo Seiyaku) as a surfactant An additional 1% of the pre-emulsion previously mixed with was added. After raising the internal temperature to 60 ° C. and sufficiently purging with nitrogen, 10 parts of a 5% aqueous solution of potassium persulfate and 20 parts of a 1% aqueous solution of anhydrous sodium bisulfite were added to initiate polymerization. After maintaining the reaction system at 60 ° C. for 5 minutes, the remaining pre-emulsion, 5% aqueous solution of potassium persulfate, and 1% aqueous solution of anhydrous sodium bisulfite were maintained for 1.5 hours while maintaining the internal temperature at 60 ° C. The mixture was added dropwise and stirring was continued for 2 hours. After confirming that the conversion rate exceeded 98% by solid content measurement, the temperature was cooled to 30 ° C. Diethylaminoethanol was added to adjust the pH to 8.5, and the non-volatile content was adjusted to 40% with ion exchange water to obtain a resin fine particle water dispersion. The obtained resin fine particle water dispersion was designated as water dispersible resin fine particles 1. The calculated glass transition temperature of the water-dispersible resin fine particles 1 is 80 ° C.

<Aqueous self-dispersing pigment dispersion>
The self-dispersing pigment dispersion used in the examples is shown below.
-Pigment dispersion A: CAB-O-JET 450C manufactured by Cabot
(PB15: 4 cyan pigment dispersion) -Pigment dispersion B: CAB-O-JET 265M manufactured by Cabot
(PR122 magenta pigment dispersion) -pigment dispersion C: CAB-O-JET 470Y manufactured by Cabot
(PY74 yellow pigment dispersion)-Pigment dispersion D: CAB-O-JET 400 manufactured by Cabot Corporation
(Carbon black dispersion) The pigment dispersions A to D are dispersions utilizing a pigment surface modification technique, and are positioned as self-dispersions.

<Production of pigment dispersion containing dispersant>
[Production of cyan pigment dispersion]
Pigment Blue 15: 3 as pigment, 202.9 parts of an aqueous solution of alkali-soluble resin 1 and 37.1 parts of water were charged into a mayonnaise bottle, predispersed with a disper, and then dispersed as zirconia with a diameter of 0.5 mm. This dispersion was carried out for 2 hours using a 0.6 L dyno mill filled with 1800 g of beads to obtain a cyan pigment dispersion. This cyan pigment dispersion was designated as Pigment Dispersion E.

[Production of magenta pigment dispersion]
A magenta pigment dispersion was obtained in the same manner as the cyan pigment dispersion F except that Pigment Red 122 was changed to 20 parts as the pigment. This magenta pigment dispersion was used as a pigment dispersion.

[Production of yellow pigment dispersion]
A yellow pigment dispersion was obtained in the same manner as the cyan pigment dispersion, except that Pigment Yellow 120 was changed to 20 parts as the pigment. This yellow pigment dispersion was designated as Pigment Dispersion G.

[Production of black pigment dispersion]
A black pigment dispersion was obtained in the same manner as the cyan pigment dispersion, except that the carbon black was changed to 20 parts as the pigment. This black pigment dispersion was designated as pigment dispersion H.

It shows below about the water-soluble organic solvent used by an Example and a comparative example.
<Water-soluble organic solvent>
・ PGMME: Propylene glycol monomethyl ether
(Boiling point: 120 ° C., surface tension: 25.4 mN / m) DMTEG: tetraethylene glycol dimethyl ether
(Boiling point: 275 ° C., surface tension: 33.0 mN / m) BDG: diethylene glycol monobutyl ether
(Boiling point: 230 ° C., surface tension: 27.9 mN / m) MMB: 3-methyl-3-methoxybutanol
(Boiling point: 174 ° C., surface tension: 29.7 mN / m) MEG: ethylene glycol monomethyl ether
(Boiling point: 124 ° C., surface tension: 29.9 mN / m) GLY: glycerin (boiling point: 290 ° C., surface tension: 62.0 mN / m)
<Alkanediols>
1,2-PD: 1,2-propanediol
(Boiling point: 187.6 ° C, surface tension: 35.1 mN / m) 1,2-BD: 1,2-butanediol
(Boiling point: 194 ° C., surface tension: 31.6 mN / m), 1,2-HexD: 1,2-hexanediol
(Boiling point: 224 ° C, surface strength: 25.9 mN / m)

<Examples 1-34, Comparative Examples 2-9>
Using the above pigment dispersions A to H, inks as shown in Tables 1, 3, and 4 were prepared. When using a self-dispersion, the pigment dispersions A to D are mixed. When using a resin dispersion, the pigment dispersions E to H and each raw material are mixed while being stirred with a disper. After stirring until sufficiently uniform, the mixture was filtered through 1 μm and 0.45 μm membrane filters to remove coarse particles causing the clogging of the head to prepare an ink. The prepared inks of four colors of cyan, magenta, yellow and black were used as one ink set, and ink sets of Examples 1 to 34 and Comparative Examples 2 to 9 having different compositions shown in Tables 1, 3 and 4 were obtained. . The following evaluation was performed using these ink sets.

  The evaluation method of the prepared ink is shown below.

<Evaluation 1: Discharge stability test>
For the inks obtained in Examples 1 to 34 and Comparative Examples 1 to 9, One Pass manufactured by Tritech Co., Ltd., which is an inkjet printer equipped with an inkjet head manufactured by Kyocera having a piezo element in an environment of 25 ° C. Injected into the JET with a syringe. Leave the inkjet head nozzle part at room temperature for a few minutes without sealing it with a cap. Thereafter, without performing cleaning or the like of the ink jet head nozzles, a nozzle check pattern was printed, and the presence or absence of nozzle missing was confirmed and evaluated. The evaluation criteria are as follows.
1: Ink cannot be ejected from the inkjet head when left at room temperature for 5 minutes or less.
2: Ink cannot be ejected from the inkjet head when left at room temperature for 5 to 10 minutes or less.
3: Ink cannot be ejected from the inkjet head when left at room temperature for 10 to 20 minutes or less.
4: Ink cannot be ejected from the inkjet head when left at room temperature 20-30 minutes or less.
5: The ink can be stably ejected from the inkjet head even when left at room temperature for 30 minutes or more.
<Evaluation 2: Evaluation of coating film resistance>
About the inks obtained in Examples 1 to 34 and Comparative Examples 1 to 9, the ink jet printer (Effects of Mutoh Industries, Ltd. Inkjet Printer VJ-1608HSJ) equipped with an Epson inkjet head having a piezo element in an environment of 25 ° C. Filled and solid-printed at a printing rate of 100% while heating to 60 ° C. After printing using Metamark MD-5 which is a polyvinyl chloride sheet (PVC) as a printing substrate, the printed matter is dried by heating at 70 ° C. for 3 minutes. Using the Gakushin type friction fastness tester AB-301 (manufactured by Tester Sangyo Co., Ltd.), the obtained printed matter is a friction with a white cotton cloth for friction (Kanakin No. 3) attached under conditions of a load of 500 g and a friction count of 100 times. The child and the print sample were rubbed together, and the surface state of the image was visually observed. The evaluation criteria are as follows. When the evaluation is 4 or 5, it can be determined that an image having excellent abrasion resistance is formed.
1: When the number of friction is less than 20 times, the ink coating can be removed as the printing substrate is seen 2: When the number of frictions is 20 or more and less than 50 times, the ink coating can be removed as the printing substrate is seen 3: The number of frictions is 50 or more Less than 100 times, the ink coating can be removed so that the printing substrate can be seen 4: Ink adhesion is slightly on the canakin, but the printing substrate is not visible 5: There is no ink adhesion on the kanakin

<Evaluation 3: Print quality confirmation test on cloth base material using sign graphic printer>
About the inks obtained in Examples 1 to 34 and Comparative Examples 1 to 9, the ink jet printer (Effects of Mutoh Industries, Ltd. Inkjet Printer VJ-1608HSJ) equipped with an Epson inkjet head having a piezo element in an environment of 25 ° C. Filling and solid printing with a printing rate of 100% was performed in the G1 mode (resolution: 720 × 1080 dpi—printed product production speed: 8 m ² / h) while heating the following substrate to 60 ° C. Visual confirmation of the degree of white spots on the printed material and confirmation by measuring the density (OD value) at a printing rate of 100% with a colorimeter (eye-one pro manufactured by X-rite). The evaluation criteria are as follows.
1: Since the ink wettability varies depending on the base material, there is a printed matter in which white spots in the printed portion exist due to dot fusion or penetration into the printing base material.
The difference in OD value at 0% is ± 1.50 or more.
2: Since the ink wettability varies depending on the base material, there is a printed matter in which white spots are present in the printed portion due to dot fusion or penetration into the print base material, and the print ratio is 10 for different print base materials.
The difference in OD value at 0% is ± 0.75 or more and less than ± 1.50.
3: Regardless of the base material, the ink spreads sufficiently and there is no white spot visually, but the OD with a printing rate of 100%
The value difference is ± 0.5 or more and less than ± 0.75.
4: Regardless of the base material, the ink spreads sufficiently and no white spots are visually observed, but an OD with a printing rate of 100%.
The value difference is less than ± 0.5.
5: Regardless of the base material, the ink spreads sufficiently and there is no white spot visually, but the OD with a printing rate of 100%
The value difference is less than ± 0.3.
(Evaluation substrate)
-Polyvinyl chloride sheet (PVC): MD-5 manufactured by Metamark
・ Coated paper: OK Top Coat made by Oji Paper Co., Ltd. +
・ Cloth base material: TYVEK1082D manufactured by DuPont

<Evaluation 4: Confirmation of print image quality at high-speed printing with a 1-pass printer>
For the inks obtained in Examples 1 to 34 and Comparative Examples 1 to 9, One Pass manufactured by Tritech Co., Ltd., which is an inkjet printer equipped with an inkjet head manufactured by Kyocera having a piezo element in an environment of 25 ° C. Injected into the JET with a syringe. Solid printing was performed at a printing rate of 100% under two conditions of a printing substrate conveyance speed of 50 m / min and 25 m / min, and the image quality was evaluated. The evaluation base material used was OK Top Coat + (coated paper) manufactured by Oji Paper Co., Ltd.
At both 1:25 m / min and 50 m / min, a large number of streaks and blurs occur in the solid printed image.
At 2:25 m / min, several streaks occur in the solid print image, and at 50 m / min, a large number of streaks and blurs occur.
3: For both 25 m / min and 50 m / min, several streaks occur in the solid print image.
At 4:25 m / min, the solid print image is completely filled, but at 50 m / min, several streaks are generated.
5: The solid print image is completely filled at both 25 m / min and 50 m / min.

Table 1 lists the ink formulations of Examples 1-15. Table 2 shows the viscosity of each ink, the dynamic surface tension value at 10 mS, or the above four evaluation results.

Table 1

Table 2

  Examples 1 to 15 are inks containing a vinyl polymer having an acid value of 200 KOHmg / g or more as water, a coloring material, an organic solvent, and a shear thinning agent within the scope of the claims, and the ink viscosity is set as V1. The ink viscosity is 4 mPa · s <V1 <20 mPa · s, and when the dynamic surface tension is measured, the value at 10 mS is 35 mN / m or less, and printing is performed with an ink jet printer. This makes it possible to provide excellent printed materials not only for difficult-to-absorbable substrates even at high-speed printing, but also for permeable substrates such as unprocessed plain paper and cloth substrates, and from inkjet nozzles. A water-based inkjet ink excellent in ejection stability and coating film resistance has been obtained.

  In Examples 1 to 5, the tendency to improve the coating film resistance and the quality of the printed material with respect to multiple substrates was confirmed by changing the type and amount of the shear thinning agent and water-soluble resin. However, from Examples 6 to 10, the change from the self-dispersion to the resin dispersion, the type of shear thinning agent and the increase / decrease in the amount added, confirmed the deterioration of the discharge stability and the deterioration of the print quality with respect to multiple substrates. . Moreover, in the prescription of Examples 1-10, the tendency for the printed matter quality at the time of the high-speed printing used for evaluation 4 to become favorable is not seen. On the other hand, in Examples 11 to 15, by changing the solvent type used in the ink, not only in the coating film resistance and the printed material quality with multiple substrates, but also in the discharge stability and the printed material quality during high-speed printing. Good results are obtained. From these results, the authors use a cross-linked polymer with an acid value of 200 KOHmg / g or more as the shear thinning agent, and not only adjust the ink viscosity and dynamic surface tension, but also control other parameters. We estimate that good results can be obtained for all evaluation items. Continuous evaluation was carried out in Examples 16 to 34.

  Inks were prepared according to the formulations shown in Tables 3 and 4 for Examples 16 to 34 and Comparative Examples 1 to 9. In addition to ink viscosity and dynamic surface tension at 10 mS, parameters such as ink viscosity behavior by drying and ink volatilization rate by heating at 50 ° C. for 30 minutes were newly measured, and the same as in Examples 1 to 15 Evaluation was performed. Tables 5 and 6 show the results.

  In Comparative Example 1, evaluation was carried out using Eco-Sol Max ink (solvent inkjet ink) mounted on a sign graphic inkjet printer.

Table 3

Table 4

Table 5

Table 6

  In Examples 17-21, the improvement tendency of discharge stability was confirmed by shaking the kind and addition amount of a shear thinning property imparting agent. Also, in Examples 21 and 23, a dramatic improvement in ejection stability was confirmed by changing the pigment dispersion from self-dispersion to resin dispersion and changing the binder resin from alkali-soluble resin 1 to water-dispersible resin fine particles 1. . In addition to the above combinations, the aqueous ink-jet ink excellent in ejection stability in Examples 28 to 34 by controlling the ink weight change width at 50 ° C. for 30 minutes by changing the kind and amount of the additive solvent Is obtained.

  Regarding Example 17, the improvement in coating film resistance was confirmed by using alkali-soluble resin 1 as the binder resin. In addition, the coating film resistance was improved by changing the dispersion to resin dispersion and the binder resin to water-dispersible resin fine particles 1 in Examples 21 to 23. In particular, aqueous ink-jet inks having remarkably improved coating film resistance were obtained in Examples 22 to 23 in which the binder resin was changed.

  Regarding Examples 16, 21, 22, 24, and 26, when the ink was heated at 50 ° C. for 30 minutes, the ink weight change width was 1.3 g or more, so that the ink was landed on the printing substrate, and then shear thinning was performed. Due to the effect of the imparting agent, the viscosity rapidly increases, it becomes difficult to penetrate the base material, and by forming a coating film on the surface of the base material, the image quality is good in any of the poorly absorbable base material or the absorbent base material, And the water-based inkjet ink which can produce printed matter with favorable coloring property irrespective of the kind of base material is obtained. Further, in Examples 27 to 30, in the presence of a shear thinning agent, 1,2-alkanediol is used as the organic solvent, and the water-dispersible resin fine particles 1 are used as the binder resin, whereby the ink is 50 ° C.-30. Although the ink weight change width when heated for 1 minute is 1.3 g or less, a water-based inkjet ink capable of producing a printed matter having good color developability regardless of the type of substrate has been obtained. The reason is that 1,2-alkanediol, which is used as an ink raw material, is a solvent that easily breaks the dispersed state of the water-dispersible resin fine particles 1, and after the ink has landed on the substrate surface, the water in the ink And 1,2-alkanediol destroys the dispersed state of the water-dispersible resin fine particles 1 and dissolves the resin, whereby the ink viscosity increases rapidly and forms a coating film. In spite of the slow volatilization rate of the ink, it was possible to control the drying viscosity behavior of the ink. A water-based inkjet ink capable of achieving both excellent printed matter production has been obtained.

  Regarding Examples 21, 22, 24 and 26, V2 / V1> 30, which is the drying viscosity behavior of the ink, and the ink weight change width when the ink is heated at 50 ° C. for 30 minutes is 1.3 g or more. As a result, a water-based inkjet ink is obtained that is unlikely to lose or bleed even under high-speed printing conditions and can obtain a printed matter with good image quality. In Examples 29, 31, 32, and 34, 1,2-hexanediol is used in a certain amount or more, and the ink is heated at 50 ° C. for 30 minutes by setting the dynamic surface tension of the ink to 32 mN / m or less. Although the ink weight change width at the time of printing is 1.3 g or less, a water-based inkjet ink capable of obtaining a printed matter with good image quality even under high-speed printing conditions has been obtained. The reason is that the ink surface wettability is further improved by decreasing the dynamic surface tension of the ink, and the diameter of dots formed by one ink drop is increased. In addition, the presence of a shear thinning agent in the ink and the dissolution of the water-dispersible resin fine particles 1 by 1,2-hexanediol cause a rapid increase in ink viscosity on the printing substrate. Due to these combined actions, even if the first ink droplet lands on the printing substrate and the next ink droplet lands next to the first ink dot within a short time, the ink droplets are fused. This prevents the occurrence of beading that causes the image to appear uneven and the bleeding phenomenon that causes bleeding between different colors. It becomes possible to obtain. Despite the slowing down of the ink volatilization rate in this way, we were able to control the wetting of the printing substrate by adjusting the dynamic surface tension of the ink and the drying viscosity behavior of the ink. A water-based inkjet ink capable of achieving both excellent quality printed matter production under high-speed printing conditions has been obtained.

  On the other hand, in the comparative example which is out of the scope of the present invention, it is shown that all the evaluation items are satisfied and it is not possible to obtain a practical quality ink. In Comparative Example 1 using a solvent ink, although the dynamic surface tension is low, the drying viscosity behavior and the ink weight change width when the ink is heated at 50 ° C. for 30 minutes are small, and the volatilization rate of the ink is slow. Further, it was confirmed that the color developability was lowered in the permeable base material such as the cloth base material, and the deterioration of the image quality was remarkable. In addition, the printed matter drawing performance under high-speed printing conditions is extremely bad. Although it is the water-based ink of Comparative Example 2 in which the dynamic surface tension of the ink is 35 mN / m or more, since the wetness to the printing substrate is poor, beading or bleeding phenomenon occurs in any printing substrate, and the printed matter The quality is extremely bad. In Comparative Examples 3 and 4, the ink composition excluding the shear thinning agent is studied, but the discharge stability is deteriorated because the ink viscosity V1 is 4 mPa · s or less. Moreover, in order to make the ink viscosity 4 mPa · s or more, by increasing the amount of added solvent in the ink, the ink weight change width when the ink is heated at 50 ° C. for 30 minutes becomes 0.75 g or less, As a result, the increase in viscosity on the substrate is delayed, resulting in a decrease in the quality of the obtained printed matter. In Comparative Example 5, even when the shear thinning agent is added, the ink viscosity V1 becomes 20 mPa · s or more because the amount of addition is not controlled, and the discharge stability may deteriorate. It has been confirmed.

  Regarding Comparative Examples 6 and 7 using a cross-linked polymer having an acid value of 200 KOHmg / g or less as a shear thinning agent, the pigment dispersion, the water-dispersible resin fine particles and the three-dimensional network structure are formed due to the small acid value. Because there are few adsorption points to form, when ink lands on the printing substrate, the ink viscosity does not increase suddenly. Due to the occurrence of dot fusion, the quality of the printed matter has deteriorated. Moreover, regarding Comparative Examples 8 and 9, from the point of being easily soluble in water, having a large molecular weight, etc., by using, as a shear thinning agent, maltose which is a polysaccharide and Kelzan AR (xanthan gum) which is a natural polymer. In addition, it has been confirmed that discharge stability and coating film resistance are lowered.

Claims (11)

An ink containing at least water, a coloring material, an organic solvent, and a vinyl polymer having an acid value of 200 KOHmg / g or more,
The viscosity (V1) of the ink at 25 ° C. is 4 mPa · s <V1 <20 mPa · s, and the value at 10 mS when the dynamic surface tension is measured at 25 ° C. is 35 mN / m or less. Water-based ink.   Furthermore, the viscosity (V2) of the ink when the amount of the organic solvent in the ink is reduced to 50% by weight of the initial total solvent amount (total amount of water and organic solvent) is 8 <V2 / V1 <80. The water-based ink according to claim 1, wherein   Further, the weight change width when 5 g of ink is heated for 30 minutes using a hot plate at 50 ° C. in an environment where the temperature is 20 ° C. and the humidity is 30% is 0.75 g or more and 1.50 g or less. The water-based ink according to claim 1 or 2.   The organic solvent has a boiling point of 150 ° C. or more and 280 ° C. or less, a surface tension of 20 mN / m or more and 35 mN / m or less, and an organic solvent content based on the whole ink of 10% by weight or more and 30% by weight or less. The water-based ink according to any one of claims 1 to 3.   The water-based ink according to any one of claims 1 to 4, wherein the alkanediol having 4 or more carbon atoms, which is an organic solvent, is contained in an amount of 10 wt% to 25 wt% with respect to the whole ink.   6. The water-based ink according to claim 1, wherein 1,2-hexanediol, which is an organic solvent, is contained in an amount of 10% by weight to 20% by weight based on the whole ink.   The water-based ink according to any one of claims 1 to 6, further comprising a water-soluble resin having an acid value of 300 KOHmg / g or less and a weight average molecular weight of less than 30000, and an alkali agent.   Furthermore, surfactant is included, The water-based ink in any one of Claims 1-7 characterized by the above-mentioned. An ink set comprising the water-based ink according to claim 1,
Ink set including cyan ink, magenta ink, yellow ink, and black ink.   An ink jet recording method for performing printing by discharging a droplet of the water-based ink according to any one of claims 1 to 8 and depositing the droplet on a printing substrate.   The printed matter formed by printing with the water-based ink in any one of Claims 1-8.