JP2021014517A - Aqueous fluorescent ink for inkjet - Google Patents

Abstract

To provide an aqueous fluorescent ink which has good ink storage stability, forms images which develop stable fluorescent colors, and can realize an excellent ink discharge property when used for inkjet recording.SOLUTION: Provided is an aqueous fluorescent ink for inkjet, comprising: a fluorescent colored resin emulsion having a resin colored with a fluorescent dye; an emulsion of low acid value polymer having an acid value of 10 mg KOH/g or less as a resin component for a binder, a surfactant, and a water-soluble organic solvent. An average particle diameter of the fluorescent colored resin emulsion and the emulsion of low acid value polymer is 300 nm or less, the water-soluble organic solvent contains one or more water-soluble organic solvents having boiling points of at least 200°C or higher, and the aqueous fluorescent ink has a pH adjusted between 7 to 9.SELECTED DRAWING: None

Description

The present invention relates to a water-based fluorescent ink for inkjet, and more particularly to a technique for providing a water-based fluorescent ink suitable for forming an image having excellent resolution by attaching droplets to the surface of a substrate by an inkjet method.

In recent years, advances in inkjet recording technology have made it possible to obtain high-definition, high-saturation images. As a result, inkjet recording has come to be widely used in various printed matter with rich colors such as posters, magazines, and packaging. On the other hand, as an effective method for expressing a more vivid image, there is an example of using fluorescent color ink.

On the other hand, conventionally, highlighters have been used for line marker pens and the like. Recently, inks using fluorescent pigments have also appeared in order to improve the fastness of handwriting (printing) over time. For example, it has been proposed to provide a fluorescent pigment ink for writing instruments using a fluorescent pigment (see Patent Documents 1 and 2).

Examples of the fluorescent colorant include inorganic or organic fluorescent pigments and fluorescent dyes. The fluorescent dye has a problem that a sufficient printing density cannot be obtained because the ink permeates the printing base material at the molecular level and migrates to the inside of the base material. Further, the fluorescent dye has a problem that the fastness of the formed image is insufficient. On the other hand, fluorescent pigments are superior to fluorescent dyes in terms of fastness, discoloration, and fading. However, since the inorganic fluorescent pigment has a large particle size, there is another problem that it is difficult to eject it from the nozzle of an inkjet printer. On the other hand, as organic fluorescent pigments, those obtained by dyeing resin particles with a fluorescent dye to make pigments, those in which fluorescent pigments are encapsulated in resin particles, and the like have been proposed, and are used for water-based inkjet inks. It can be used as a colorant (see Patent Documents 3 to 5).

Japanese Unexamined Patent Publication No. 6-346013 Japanese Unexamined Patent Publication No. 5-239395 Japanese Unexamined Patent Publication No. 2003-26964 Japanese Unexamined Patent Publication No. 2004-189900 JP-A-2009-161688

However, according to the studies by the present inventors, it may not be possible to obtain a stable fluorescence hue and fluorescence intensity in the formed image by the above-mentioned conventional technique, and it cannot be said that the technique has been established yet. .. Further, in the inkjet recording in which ink is ejected from a nozzle for recording, it is necessary to perform stable ink ejection as the basic performance of ink, but this point is still not sufficient.

Therefore, an object of the present invention is to provide an aqueous fluorescent ink having good storage stability of the ink, producing a stable fluorescent color in the formed image, and realizing excellent ink ejection property when used for inkjet recording. Is to provide. Furthermore, an object of the present invention is to provide a water-based fluorescent ink for an inkjet that can stably obtain high-quality image quality by inkjet recording due to its excellent ink ejection property.

The above object is achieved by the following invention.
[1] A fluorescent colored resin emulsion having a resin colored with a fluorescent dye, a low acid value polymer emulsion having an acid value of 10 mgKOH / g or less, a surfactant and a water-soluble organic solvent as resin components for a binder. The average particle size of the fluorescent colored resin emulsion and the low acid value polymer emulsion is 300 nm or less, and the water-soluble organic solvent contains at least one water-soluble organic solvent having a boiling point of at least 200 ° C. or higher. , A water-based fluorescent ink for inkjet, characterized in that the pH is adjusted to 7-9.

Preferred forms of the above-mentioned aqueous fluorescent ink for inkjet include those having the following configurations.
[2] The aqueous fluorescent ink for an inkjet according to the above [1], wherein the fluorescent dye is an acidic fluorescent dye.
[3] The aqueous fluorescent ink for an inkjet according to the above [1] or [2], wherein the low acid value polymer emulsion is an acrylic polymer emulsion.
[4] The above [1] to [3], wherein the water-soluble organic solvent having a boiling point of 200 ° C. or higher is contained in the range of 1% by mass or more and 50% by mass or less with respect to the total amount of the water-soluble organic solvent. The water-based fluorescent ink for inkjet according to any one of.
[5] The aqueous fluorescent ink for an inkjet according to any one of the above [1] to [4], wherein the surfactant is a nonionic surfactant.

According to the present invention, there is provided an aqueous fluorescent ink having good storage stability of the ink, the formed image developing a stable fluorescent color, and excellent ink ejection property when used for inkjet recording. To. Further, since excellent ink ejection property can be realized, high quality image quality can be stably obtained according to the water-based fluorescent ink for inkjet of the present invention.

It is a figure which observed the character of 5 points printed by the inkjet method using the ink of Example 1 with a desktop microscope. It is a figure which observed the character of 5 points printed by the inkjet method using the ink of the comparative example 3 with a desktop microscope.

The present invention will be described in more detail with reference to preferred embodiments. As a result of diligent studies on the above-mentioned problems of the prior art, the present inventors have recorded the differences in the binder components constituting the water-based fluorescent ink, the average particle size of the emulsion, the type of the water-soluble organic solvent, and the like. It affects the ejection stability of the ink and the storage stability of the ink, which are the basic performances of the ink. In that case, when the pH of the ink is high, the fluorescence density of the formed image is inferior, and the image is formed after the ink is stored. In this case, the present invention has been made by finding that the print color difference between before and after the ink is stored becomes large and stable quality image formation cannot be performed.

The aqueous fluorescent ink for inkjet of the present invention includes a fluorescent colored resin emulsion having a resin colored with a fluorescent dye, a low acid value polymer emulsion having an acid value of 10 mgKOH / g or less as a resin component for a binder, a surfactant and a surfactant. It contains a water-soluble organic solvent having a boiling point of 200 ° C. or higher, and the pH of the ink is adjusted to 7 to 9. Hereinafter, each component constituting the water-based fluorescent ink for inkjet of the present invention will be described.

[Fluorescent colored resin emulsion]
The fluorescent colored resin emulsion having a resin colored with a fluorescent dye used in the present invention is a component as a coloring material in the aqueous fluorescent ink of the present invention. For example, an acrylic resin-based polymer compound is used as a fluorescent dye. Emulsions of dyed products (hereinafter referred to as "acrylic resin-based polymer emulsions") can be mentioned. The fluorescent dye used at this time is preferably an acidic fluorescent dye.

Examples of the monomers constituting the acrylic resin-based polymer emulsion include acrylic acid and methacrylic acid, styrene and vinyl chloride, acrylates of acrylic acid or methacrylic acid, maleic acid, fumaric acid and its esters, and vinyl monomers such as acrylonitrile. In addition, urethane-based monomers and the like can be used, but the present invention is not limited to these.

In the method for producing an acrylic resin-based polymer emulsion, one or more of the above-mentioned monomers are polymerized or copolymerized in a solvent such as water. The method of polymerization or copolymerization is not particularly limited, but it is preferably synthesized by emulsion polymerization.

The method of dyeing an acrylic resin-based polymer emulsion with a dye can be applied without particular limitation as long as it can dye the polymer compound, and the dye may be reacted with the monomer before synthesizing the polymer compound. , A method of reacting a dye during polymerization, or reacting or dyeing after synthesis can be mentioned.

The content of the dye in the colored resin cannot be unconditionally determined because it varies depending on the type of dye and the like, but the dye content in the colored resin is preferably 1% by mass or more and 10% by mass or less. If it is less than 1% by mass, it may not be sufficient in terms of color development, and if it exceeds 10% by mass, water resistance may be insufficient or fluorescence concentration quenching may occur due to high dye concentration. Not preferable.

Since the water-based fluorescent ink of the present invention is for inkjet use, the acrylic resin-based polymer emulsion to be composed preferably has an average particle size of 300 nm or less, and more preferably an average particle size of 50 to 200 nm. If the average particle size exceeds 300 nm, the ink ejection property tends to deteriorate. The average particle size of the emulsion in this case is a value obtained by measuring the particle size distribution with a dynamic light scattering DLS particle size distribution measuring device.

In the present invention, a fluorescent colored resin emulsion that can be suitably used as a coloring material is available on the market. Specific examples thereof include the SF-3000N series, the SF-5000 series (manufactured by Shinroihi), and the LUMIKOL NKW-3200 series (manufactured by Nippon Fluorescent Chemicals).

The content of the acrylic resin-based polymer emulsion as the fluorescent colored resin emulsion constituting the aqueous fluorescent ink of the present invention is determined by the dye concentration in the resin, but is preferably 1 to 50% by mass in the ink, more preferably. Is used in the range of 1 to 30% by mass.

[Low acid value polymer emulsion]
The low acid value polymer emulsion constituting the water-based fluorescent ink of the present invention is a component as a binder in the water-based fluorescent ink according to the present invention.

The low acid value polymer emulsion constituting the present invention requires that the acid value of the solid content is 10 mgKOH / g or less. The acid value of the solid content is preferably 5 mgKOH / g or less. The lower limit of the acid value is preferably 0 mgKOH / g.

As the low acid value polymer emulsion, a known general resin may be used, and examples thereof include acrylic and styrene-based polymers. Among them, an acrylic polymer is preferable because it is excellent in adhesion to a base material when an image is formed.

The acrylic low acid value polymer emulsion may be obtained by polymerizing a monomer component containing a (meth) acrylic acid ester-based monomer as a main component. For example, a homopolymer of a (meth) acrylic acid ester-based monomer, a copolymer of a (meth) acrylic acid ester-based monomer as a main component, and other monomers can be mentioned. Preferably, it is an acrylic polymer emulsion obtained by copolymerizing a (meth) acrylic acid ester-based monomer and other monomers. Styrene may be used as the monomer used when obtaining the copolymer. In any case, in the present invention, when the monomer is selected and blended, it is necessary to make the acid value of the solid content of the obtained polymer emulsion 10 mgKOH / g or less.

The method for producing a low acid value polymer emulsion is to polymerize or copolymerize one or more of the above-mentioned monomers in a solvent such as water. The method of polymerization or copolymerization can be obtained by a conventionally known polymerization method, and is not particularly limited, but is usually synthesized by emulsion polymerization.

The acid value in the present invention refers to the number of milligrams of potassium hydroxide required to neutralize the acid contained in 1 g of the non-volatile component of the polymer emulsion. As an example of the measuring method, a method using JIS K-0070 acid value measurement, hydrolyzed acid value measurement (total acid value measurement), or the like can be mentioned as an example. In addition, information is often provided by the manufacturing company as the acid value of the product. At that time, it is shown as the acid value in 1 g of the product, and if the polymer emulsion product contains a volatile component such as a solvent, it is converted to 100% of the non-volatile component.

The average particle size of the low acid value polymer emulsion constituting the present invention is 300 nm or less, preferably 30 to 160 nm, and more preferably 40 to 120 nm. If the average particle size is too large, the glossiness of the ink coating film tends to decrease and ejection tends to be difficult.

The content of the low acid value acrylic polymer emulsion is preferably 1% by mass or more and 15% by mass or less in terms of solid content with respect to the total mass of the ink.

[PH adjustment]
The water-based fluorescent ink for inkjet of the present invention requires that the pH be adjusted to 7-9. When the pH of the ink is made strongly alkaline over 9, fluorescent dye discoloration and fluorescence quenching occur, and stable fluorescent hue and intensity cannot be obtained. On the other hand, if the ink is acidic with a pH of less than 7, there is a risk of corroding the nozzles of the printer head, and when wiping the head surface during printing, other colors of alkaline ink placed on other channels of the same head. There is a risk that the pigment will aggregate on the head surface and wiper when mixed with the ink, causing nozzle clogging.

The pH adjusting agent used for adjusting the pH of the aqueous fluorescent ink for inkjet of the present invention is not particularly limited, and any pH adjusting agent can be used as long as it can adjust the pH without adversely affecting the ink. For example, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide; carbonates of alkali metals such as lithium carbonate, sodium carbonate and potassium carbonate; quaternary ammonium hydroxides; diethanolamine and tri. Amines such as ethanolamine; neutralizers such as ammonium hydroxide can be mentioned.

[Surfactant]
The aqueous fluorescent ink for inkjet of the present invention contains a surfactant in addition to the above components. The surfactant that can be used at this time can be used without particular limitation as long as the object of the present invention is not impaired. For example, a nonionic surfactant or the like is suitable.

Examples of the nonionic surfactant include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, and poly. Examples thereof include those having 25 or more ethylene oxide chains such as oxyethylene stearylamine and polyoxyethylene. The present invention is not limited thereto. In the water-based fluorescent ink for inkjet of the present invention, it is preferable that the surface tension of the ink is adjusted to 35 mN / m or less by using a surfactant.

The surfactant as described above is preferably configured to contain 0.1 to 5% by mass with respect to the total mass of the ink. When the content is 0.1% by mass or more, the wettability to the base material can be ensured when the image is formed, so that the image quality can be improved. Further, if it is used in the range of 5% by mass or less, the ink is less likely to foam and excellent ejection stability can be obtained.

[Water-soluble organic solvent]
The water-soluble organic solvent constituting the water-based fluorescent ink for inkjet of the present invention will be described. The aqueous fluorescent ink for an inkjet of the present invention comprises a fluorescent colored resin emulsion, a low acidity polymer emulsion which is a binder component, a surfactant, and an aqueous liquid medium like a normal inkjet ink. The aqueous liquid medium constituting the present invention is a mixed solvent of water and a water-soluble organic solvent, and as water, ion-exchanged water (deionized water) is used instead of general water containing various ions. Is preferable.

Since the water-based fluorescent ink for inkjet of the present invention uses a low acid value polymer emulsion as a binder component, it is dissolved and removed or physically rubbed when the nozzle portion of the inkjet printer head is dried. It becomes necessary to remove the dried binder component due to such factors. At that time, in order to suppress the occurrence of being unable to be removed, the aqueous fluorescent ink of the present invention contains a water-soluble organic solvent containing at least one water-soluble organic solvent having a boiling point of at least 200 ° C. or higher. It is necessary to make a configuration.

The water-soluble organic solvent used by mixing with water is not particularly limited and may be appropriately selected depending on the intended purpose. For example, polyhydric alcohol compounds, polyhydric alcohol alkyl ether compounds, polyhydric alcohol aryl ether compounds, nitrogen-containing heterocyclic compounds, propylene carbonate (propylene carbonate) (boiling point: 240 ° C.), ethylene carbonate (boiling point: 261 ° C.), etc. Can be mentioned. It is preferable to use two or more of these in combination. According to the studies by the present inventors, in order to achieve the object of the present invention, it is possible to prepare an ink having a structure containing at least one water-soluble organic solvent having a boiling point of 200 ° C. or higher. is necessary.

Examples of the polyhydric alcohol compound include ethylene glycol (boiling point: 196 ° C.), diethylene glycol (boiling point: 244 ° C.), triethylene glycol (boiling point: 287 ° C.), and propylene glycol (1,2-propanediol) (boiling point: 188 ° C), dipropylene glycol (boiling point: 231 ° C), tripropylene glycol (boiling point: 273 ° C), 1,3-propanediol (boiling point: 214 ° C), 1,2-butanediol (boiling point: 194 ° C), 1,3-Butanediol (boiling point: 208 ° C), 2,3-butanediol (boiling point: 183 ° C), 1,4-butanediol (boiling point: 230 ° C), 1,2-pentanediol (boiling point: 206 ° C) ), 2,4-Pentanediol (boiling point: 201 ° C.), 2-methyl-1,3-butanediol (boiling point: 203 ° C.), 3-methyl-1,3-butanediol (boiling point: 203 ° C.), 1 , 5-Pentanediol (boiling point: 242 ° C), 2,2-dimethyl-1,3-propanediol (boiling point: 208 ° C), 2-methyl-1,3-propanediol (boiling point: 124 ° C), 2- Methyl-2,4-pentanediol (boiling point: 198 ° C), 1,2-hexanediol (boiling point: 223 ° C), 1,6-hexanediol (boiling point: 250 ° C), 2,5-hexanediol (boiling point: 223 ° C) 217 ° C.), 2-ethyl-1,3-hexanediol (boiling point: 243 ° C.), tetraethylene glycol (boiling point: 314 ° C.), glycerin (boiling point: 290 ° C.), 1,2,6-hexanetriol (boiling point: 234 ° C.) 178 ° C.), 1,2,4-butanetriol (boiling point: 170 ° C.), 1,2,3-butanetriol (boiling point: 175 ° C.), and the like.

Examples of the polyhydric alcohol alkyl ether compound include ethylene glycol monoethyl ether (boiling point: 135 ° C.), ethylene glycol monobutyl ether (boiling point: 171 ° C.), diethylene glycol methyl ether (boiling point: 194 ° C.), and diethylene glycol monoethyl ether (boiling point: 194 ° C.). Boiling point: 202 ° C.), Triethylene glycol methyl ether (boiling point: 249 ° C.), Triethylene glycol ethyl ether (boiling point: 256 ° C.), Diethylene glycol-n-hexyl ether (boiling point: 259 ° C.), Ethylene glycol phenyl ether (boiling point: 259 ° C.) 237 ° C.), ethylene glycol-n-propyl ether (boiling point: 150 ° C.), diethylene glycol-n-butyl ether (boiling point: 171 ° C.), tetraethylene glycol monomethyl ether (boiling point: 159 ° C.), dipropylene glycol monomethyl ether (boiling point: 159 ° C.) 188 ° C), propylene glycol monoethyl ether (boiling point: 133 ° C), propylene glycol-n-butyl ether (boiling point: 171 ° C), propylene glycol-t-butyl ether (boiling point: 153 ° C), dipropylene glycol-n-propyl ether (Boiling point: 213 ° C.), tripropylene glycol methyl ether (boiling point: 243 ° C.), tripropylene glycol-n-propyl ether (boiling point: 261 ° C.), propylene glycol phenyl ether (boiling point: 243 ° C.) and the like can be mentioned.

Examples of the polyhydric alcohol aryl ether compound include ethylene glycol monophenyl ether (boiling point: 237 ° C.) and ethylene glycol monobenzyl ether (boiling point: 256 ° C.).

Examples of the nitrogen-containing heterocyclic compound include N-methyl-2-pyrrolidone (boiling point: 204 ° C.), N-hydroxyethyl-2-pyrrolidone (boiling point: 309 ° C.), 2-pyrrolidone (boiling point: 245 ° C.). Examples thereof include 1,3-dimethylimidazolidinone (boiling point: 220 ° C.), ε-caprolactam (boiling point: 137 ° C.), and N-methylpyrrolidinone (boiling point: 202 ° C.).

Examples of the water-soluble organic solvent having a boiling point of 200 ° C. or higher that can be used in the present invention include diethylene glycol monoethyl ether (boiling point: 202 ° C.), triethylene glycol methyl ether (boiling point: 249 ° C.), and triethylene glycol. Ethyl ether (boiling point: 256 ° C), diethylene glycol-n-hexyl ether (boiling point: 259 ° C), ethylene glycol phenyl ether (boiling point: 237 ° C), dipropylene glycol-n-propyl ether (boiling point: 213 ° C), tripropylene Glycolmethyl ether (boiling point: 243 ° C), tripropylene glycol-n-propyl ether (boiling point: 261 ° C), propylene glycol phenyl ether (boiling point: 243 ° C), ethylene glycol monophenyl ether (boiling point: 237 ° C), ethylene glycol mono Benzyl ether (boiling point: 256 ° C), N-methyl-2-pyrrolidone (boiling point: 204 ° C), N-hydroxyethyl-2-pyrrolidone (boiling point: 309 ° C), 2-pyrrolidone (boiling point: 245 ° C), 1, Examples thereof include 3-dimethylimidazolidinone (boiling point: 220 ° C.) and N-methylpyrrolidinone (boiling point: 202 ° C.). In the water-based fluorescent ink of the present invention, at least one selected from these is used.

The aqueous fluorescent ink for inkjet of the present invention contains at least one water-soluble organic solvent having a boiling point of at least 200 ° C. or higher, and the content of the water-soluble organic solvent having a boiling point of 200 ° C. or higher is water-soluble in the ink. It is preferably 1% by mass or more and 50% by mass or less with respect to the total amount of the organic solvent. When the content is 50% by mass or less, when inkjet recording is performed, the ink does not dry at the nozzle portion of the inkjet printer head, and good maintenance suitability can be imparted. On the other hand, if the content exceeds 50% by mass, the ink evaporation rate is slow and the printing may not dry on the non-absorbent substrate, which is not preferable.

The content of the water-soluble organic solvent is preferably 15% by mass or more and 60% by mass or less with respect to the total amount of the ink. More preferably, it is 20% by mass or more and 40% by mass or less. When the content is 15% by mass or more, the ink can obtain sufficient ejection stability. Further, when it is 60% by mass or less, the viscosity of the ink is suppressed to be low, so that the ejection stability can be improved.

[Other ingredients]
The aqueous fluorescent ink for an inkjet of the present invention may contain the following components in addition to the components listed above. The other components are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include antiseptic and antifungal agents and anticorrosive agents. These may be used alone or in combination of two or more.

Examples of the antiseptic and antifungal agent include 1,2-benzisothiazolin-3-one, sodium benzoate, sodium dehydroacetate, sodium sorbate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide and the like. Can be mentioned. Examples of the rust preventive include acidic sulfites, sodium thiosulfate, ammon thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite and the like.

[Ink manufacturing method]
As a method for producing a water-based fluorescent ink for an inkjet of the present invention, any conventionally known method can be used. For example, water, a fluorescent colored resin emulsion having a resin colored with a fluorescent dye, a water-soluble organic solvent having a boiling point of 200 ° C. or higher, a low acidity polymer emulsion as a binder, a surfactant, and, if necessary, other The components can be dispersed or dissolved in an aqueous medium and appropriately stirred and mixed for production. In the stirring and mixing, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser and the like can be used.

[Ink bottle, etc.]
In order to perform recording using the water-based fluorescent ink for inkjet of the present invention, an ink bottle or container containing ink or an ink cartridge provided with an ink container containing ink is required. The ink bottle and container are not particularly limited, and the shape, structure, size, material, and the like can be appropriately selected according to the purpose. For example, an ink formed of an aluminum laminate film, a resin film, or the like. Examples include those having at least a bag or the like.

Next, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. The terms "part" and "%" in the text are based on mass unless otherwise specified.

[Preparation of polymer emulsion]
<Manufacturing of low acid value polymer emulsion 01>
In a reaction vessel equipped with a stirrer, a backflow condenser, and a thermometer, 70.0 parts of water and 1.2 parts of a nonionic surfactant were charged, and the temperature was raised to 85 ° C by heating and refluxing while bubbling nitrogen gas. .. In addition, 70.0 parts of methyl methacrylate, 30.0 parts of butyl acrylate, 3 parts of methacrylic acid, 40.0 parts of water, 2.5 parts of nonionic surfactant, and 0.2 part of potassium persulfate prepared separately are mixed. Of the 146 parts of the dissolved aqueous solution, 16 parts were added. The remaining 130 parts of the above aqueous solution was placed in a dropping funnel and slowly added dropwise to the reaction vessel under the condition that the temperature was kept at 80 ° C. to 85 ° C. over 2 hours and 30 minutes. After completion of the dropping, the pH was adjusted to 7 using an aqueous ammonia solution, the mixture was further stirred at 85 ° C. for 3 hours, and then cooled to room temperature to obtain a low acid value polymer emulsion 01.

The acid value was titrated with phenolphthalein as an indicator, a 0.1 N KOH ethanol solution as a titration solution, and a toluene / ethanol = 50/50 solution. The acid value of the low acid value polymer emulsion 01 obtained above was 5.7 mgKOH / g. Further, the polymer emulsion was diluted 3000 times with a 0.1% KOH solution, and the particle size distribution was measured with a dynamic light scattering DLS particle size distribution measuring device (trade name: NICOMP380, manufactured by Nippon Integris LLC). As a result, the average particle size of the low acid value polymer emulsion 01 obtained above was 116.2 nm.

<Production of Polymer Emulsion 02 Used in Comparative Example>
The raw material monomer was changed to 70.0 parts of methyl methacrylate, 30.0 parts of butyl acrylate, and 5 parts of methacrylic acid by the same synthesis method as the low acid value polymer emulsion 01 described above to obtain a polymer emulsion 02. The acid value of the polymer emulsion 02 measured by the same measuring method as the low acid value polymer emulsion 01 described above was 12.3 mgKOH / g. The average particle size of the polymer emulsion 02 measured by the same measuring method as described above was 121.4 nm.

<Manufacture of Polymer Emulsion 03 Used in Comparative Example>
The raw material monomer was changed to 70.0 parts of methyl methacrylate, 30.0 parts of butyl acrylate, and 12 parts of methacrylic acid by the same synthesis method as the low acid value polymer emulsion 01 described above to obtain a polymer emulsion 03. The acid value of the polymer emulsion 03 measured by the same measuring method as the low acid value polymer emulsion 01 was 51.3 mgKOH / g. The average particle size of the polymer emulsion 03 measured by the same measuring method as described above was 126.4 nm.

<Manufacturing of low acid value polymer emulsion 04>
The raw material monomer was changed to 70.0 parts of methyl methacrylate and 30.0 parts of butyl acrylate by the same synthesis method as the low acid value polymer emulsion 01 described above to obtain a low acid value polymer emulsion 04. The acid value of the low acid value polymer emulsion 04 measured by the same measuring method as the low acid value polymer emulsion 01 was 0 mgKOH / g. The average particle size of the low acid value polymer emulsion 04 measured by the same measuring method as described above was 109.7 nm.

[Example 1]
The following components were mixed with the following formulations, and after sufficient stirring, pressure filtration was performed with a PTFE filter (manufactured by Merck Millipore) having a pore size of 5 μm to prepare the ink of this example. As the fluorescent colored resin emulsion, an acrylic resin emulsion (trade name: SF-5017; manufactured by Shinroihi) colored with a fluorescent acid dye was used. Further, as the resin component for the binder, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH / g was used. As the surfactant, a nonionic surfactant, polyoxyethylene cetyl ether (trade name: BC-40TX; manufactured by Nikko Chemicals Co., Ltd.) was used. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 8.4.

-Fluorescent colored resin emulsion: 24.0 parts-Low acid value polymer emulsion 01: 10.0 parts-Nonionic surfactant: 2.0 parts-Diethanolamine: 0.3 parts-Propylene glycol (boiling point: 188 ° C) : 20.0 parts, 2-pyrrolidone (boiling point: 245 ° C): 5.0 parts, pure water: 38.7 parts

<Evaluation>
The above ink was loaded into a cartridge bottle, and an inkjet recorded image was formed using a piezo type inkjet printing machine (manufactured by Mastermind, trade name: MMP813P), and the ink obtained above was evaluated.

The paper used for the evaluation is PPC paper and PB-paper manufactured by Canon Inc.

(Ink ejection stability)
The inkjet printing machine printed 5-point characters, solid printing parts, 1-point ruled lines, etc., and observed the state of the printed image to evaluate the ink ejection stability from the nozzle of the inkjet printer. .. As a result, it was confirmed that the ink ejection property of Example 1 was good and a stable printed matter could be obtained. FIG. 1 shows a diagram in which 5-point characters are observed using a desktop microscope (trade name: 3R-MSTVUSB273, manufactured by 3R System Co., Ltd.).

(Fluorescence of image)
The fluorescence density and hue of the solid printing portion printed with the ink of Example 1 were measured with a colorimeter (trade name: SPECTRO 2 GUIDE, manufactured by BYK). As a result, red fluorescence was observed, and no change in fluorescence intensity was observed due to differences in the type and lot of printed paper.

(Ink storage stability)
The ink of Example 1 was stored at a high temperature of 70 ° C. for 1 week, and the storage stability of the ink was evaluated. As a result, the change in the physical characteristics of the ink before storage at high temperature was as good as 10% or less. Further, when inkjet printing was performed with the ink after storage, the printing condition was as good as that of the ink before storage, and a stable printed matter could be obtained. Further, when the color of the solid print portion was measured, the print color difference ΔE before and after the storage test was 2 or less.

[Example 2]
In this example, an acrylic resin emulsion (trade name: SF-3017, manufactured by Shinroihi) colored with a fluorescent acid dye was used as the fluorescent colored resin emulsion. Further, as the resin component for the binder, the previously prepared low acid value polymer emulsion 04 having an acid value of 0 mgKOH / g was used. Then, the ink of this example was prepared by the same components and methods as in Example 1 except that the composition was as follows. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 7.8.

-Fluorescent colored resin emulsion: 20.0 parts-Low acid value polymer emulsion 04: 8.0 parts-Nonionic surfactant: 2.0 parts-Diethanolamine: 0.2 parts-Propylene glycol (boiling point: 188 ° C) : 20.0 parts, 2-pyrrolidone (boiling point: 245 ° C): 5.0 parts, pure water: 44.8 parts

<Evaluation>
An inkjet recorded image was formed in the same manner as in Example 1 except that the ink obtained above was loaded into the cartridge bottle, and the ink obtained above was evaluated.

The ink ejection stability was as good as in Example 1, and a printed matter could be obtained stably. Further, in the fluorescence of the image, red fluorescence was observed, and it was confirmed that the fluorescence intensity was stable as in the ink of Example 1. Regarding the storage stability of the ink, as in Example 1, the change in physical properties is 10% or less, the printing condition is stable before and after storage, and the print color difference ΔE of the ink before and after storage is 2 or less. there were.

[Example 3]
In this example, an acrylic resin emulsion (trade name: SF-5014, manufactured by Shinroihi) colored with a fluorescent acid dye was used as the fluorescent colored resin emulsion. Further, as the resin component for the binder, the low acid value polymer emulsion 04 having an acid value of 0 mgKOH / g prepared above was used as in Example 2, and the nonionic surfactant polyoxy was used as the surfactant. Ethylene oleyl ether (trade name: BO-50; manufactured by Nikko Chemicals Co., Ltd.) was used. Then, the ink of this example was prepared by the same components and methods as in Example 1 except that the composition was as follows. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 8.2.

-Fluorescent colored resin emulsion: 30.0 parts-Low acid value polymer emulsion 04: 8.0 parts-Nonionic surfactant: 2.0 parts-Diethanolamine: 0.3 parts-Propylene glycol (boiling point: 188 ° C) : 20.0 parts, 2-pyrrolidone (boiling point: 245 ° C): 5.0 parts, pure water: 34.7 parts

<Evaluation>
An inkjet recorded image was formed in the same manner as in Example 1 except that the ink obtained above was loaded into the cartridge bottle, and the ink obtained above was evaluated. The ink ejection stability was as good as in Example 1, and a printed matter could be obtained stably. Further, in the fluorescence of the image, yellow-green fluorescence was observed, and it was confirmed that the fluorescence intensity was stable as in the ink of Example 1. As for the storage stability of the ink of Example 3, the change in physical properties is 10% or less as in Example 1, and the printing condition is stable before and after storage, and the ink is printed before and after storage. The color difference ΔE was 2 or less.

[Comparative Example 1]
As the resin component for the binder, the polymer emulsion 03 having a high acid value of 51.3 mgKOH / g prepared above was used. As the fluorescent colored resin emulsion, an acrylic resin emulsion (trade name: SF-5017; manufactured by Shinroihi) colored with the same fluorescent acid dye used in Example 1 was used, and Example 3 was used as a surfactant. The same nonionic surfactant polyoxyethylene oleyl ether used in the above was used. Then, the ink of this example was prepared by the same components and methods as in Example 1 except that the composition was as follows. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 8.3.

-Fluorescent colored resin emulsion: 20.0 parts-Polymer emulsion 03: 10.0 parts-Nonionic surfactant: 2.0 parts-Diethanolamine: 0.3 parts-Propylene glycol (boiling point: 188 ° C): 20. 0 part, 2-pyrrolidone (boiling point: 245 ° C): 5.0 part, pure water: 42.7 part

<Evaluation>
The ink obtained above was loaded into a cartridge bottle to attempt to form an inkjet recorded image. However, the ink gelled and the ink was not ejected from the inkjet printer head, so evaluation could not be performed at all.

[Comparative Example 2]
As the resin component for the binder, the previously prepared polymer emulsion 02 having an acid value of 12.3 mgKOH / g and slightly higher than that specified in the present invention was used, and it was carried out in Comparative Example 1 except for the following formulation. The ink of this example was prepared by the same components and methods. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 8.5.

-Fluorescent colored resin emulsion: 20.0 parts-Polymer emulsion 02: 10.0 parts-Non-ionic surfactant (polyoxyethylene oleyl ether): 2.0 parts-Diethanolamine: 0.3 parts-Poiling point 188 ° C): 20.0 parts, 2-pyrrolidone (boiling point: 245 ° C): 5.0 parts, pure water: 42.7 parts

<Evaluation>
The ink obtained above was loaded into a cartridge bottle to attempt to form an inkjet recorded image. However, as in Example 1, when the ink was stored at a high temperature of 70 ° C. for one week and the storage stability of the ink was evaluated, the viscosity of the ink after storage increased by 10%, and the ejection property was improved. Confirmed to be inferior. In addition, the ejection stability of the ink before storage was also inferior to that of the ink of the example.

[Comparative Example 3]
Polyvinylpyrrolidone (abbreviated as PVP) (trade name: Rubiscol K30; manufactured by BASF) using N-vinyl-2-pyrrolidone as a monomer is used as a resin component for a binder as a resin other than a polymer emulsion, and is formulated as follows. The ink of this example was prepared by the same components and methods as those used in Comparative Example 1. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 8.7.

・ Fluorescent colored resin emulsion: 20.0 parts ・ PVP: 8.0 parts ・ Polyoxyethylene oleyl ether: 2.0 parts ・ Diethanolamine: 0.4 parts ・ Propylene glycol (boiling point: 188 ° C): 15.0 parts ・2-Pyrrolidone (boiling point: 245 ° C): 5.0 parts, pure water: 49.6 parts

<Evaluation>
The ink obtained above was loaded into a cartridge bottle to attempt to form an inkjet recorded image. However, the print was faint and the ejection was unstable. FIG. 2 shows a magnified view of the obtained characters with a magnifying glass.

[Comparative Example 4]
As the fluorescent colored resin emulsion, an acrylic resin emulsion (trade name: SF-5017; manufactured by Shinroihi) colored with the same fluorescent acid dye as in Example 1 was used. Further, as the resin component for the binder, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH / g was used. As the surfactant, a nonionic surfactant, polyoxyethylene cetyl ether (trade name: BC-40TX; manufactured by Nikko Chemicals Co., Ltd.) was used. Diethanolamine was used as the pH adjuster. The pH of the ink of this example is 9.8, which exceeds the range specified in the present invention.

-Fluorescent colored resin emulsion: 24.0 parts-Low acid value polymer emulsion 01: 8.0 parts-Nonionic surfactant: 2.0 parts-Diethanolamine: 1.0 parts-Diethylene glycol (boiling point: 244 ° C): 20.0 parts ・ Trimethylol propane (boiling point: 160 ° C): 5.0 parts ・ Pure water: 40.0 parts

<Evaluation>
The ink obtained above was loaded into a cartridge bottle to form an inkjet recorded image, and the same evaluation as in Example 1 was performed. As a result, when the ink was stored at a high temperature of 70 ° C. for one week, it was confirmed that the print color difference ΔE between the print after the storage test and the print before the storage test was 2 or more, and the fluctuation was large. Then, when the fluorescence intensity of the formed image was measured, it was confirmed that the fluorescence intensity was lowered even in the portion where the print density and the like seemed to have no problem visually.

[Comparative Example 5]
As the fluorescent colored resin emulsion, an acrylic resin emulsion (trade name: SF-8017; manufactured by Shinroihi), which has a larger particle size than specified in the present invention and is colored with a fluorescent acid dye having an average particle size of about 400 nm, is used. There was. Further, as the resin component for the binder, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH / g was used. As the surfactant, a nonionic surfactant, polyoxyethylene cetyl ether (trade name: BC-40TX; manufactured by Nikko Chemicals Co., Ltd.) was used. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 8.2.

-Fluorescent colored resin emulsion (400 nm): 24.0 parts-Low acid value polymer emulsion 01: 8.0 parts-Nonionic surfactant: 2.0 parts-Diethanolamine: 1.0 parts-Propylene glycol (boiling point: 188 ° C): 20.0 parts, 2-pyrrolidone (boiling point: 245 ° C): 5.0 parts, pure water: 40.0 parts

<Evaluation>
The ink obtained above was loaded into a cartridge bottle to attempt to form an inkjet recorded image. However, the ink was not ejected from the inkjet printer head, and evaluation could not be performed at all.

[Comparative Example 6]
As the fluorescent colored resin emulsion, an acrylic resin emulsion (trade name: SF-5017; manufactured by Shinroihi) colored with the same fluorescent acid dye as in Example 1 was used. Further, as the resin component for the binder, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH / g was used. As the surfactant, the same nonionic surfactant polyoxyethylene oleyl ether as used in Example 3 was used. In this example, a water-soluble solvent having a boiling point of 200 ° C. or higher was not used. Diethanolamine was used as the pH adjuster. The pH of the ink of this example was 8.6.

-Fluorescent colored resin emulsion: 24.0 parts-Low acid value polymer emulsion 01: 8.0 parts-Diethanolamine: 1.0 parts-Nonionic surfactant: 2.0 parts-Propylene glycol (boiling point: 188 ° C) 15.0 parts, pure water: 50.0 parts

<Evaluation>
The ink obtained above was loaded into a cartridge bottle to attempt to form an inkjet recorded image. As a result, it became difficult to eject ink during continuous printing for a long time.

The results of the above Examples and Comparative Examples are summarized in Tables 1 and 2.

Explanation of evaluation items in Table 1-3:
(Evaluation criteria for ink ejection stability):
◯: Printing is possible, there is no chipping in the nozzle check pattern, and there is no printing defect phenomenon.
Δ: Printing is possible, but the nozzle check pattern is chipped (pin missing phenomenon), or there is another printing defect phenomenon.
X: Cannot be ejected, or the printing defect phenomenon is so severe that it cannot be practically used as a printed matter.

(Fluorescence density of image):
<Measurement method>
Make an aqueous diluent of the same concentration as the fluorescent pigment dispersion used in the ink. Using the obtained water diluent, printing is performed on the same paper on which the inkjet recorded image is formed with each of the inks described above by the same printing method. A colorimeter (trade name: SPECTRO 2) similar to that used in the measurement of the solid print portion formed with the inks of Examples and Comparative Examples by measuring the hue and fluorescence intensity of the solid portion of the obtained printed matter of the water diluent. Measure using GUIDE, manufactured by BYK. The obtained measured values and the measured values of the solid printing portion formed with the inks of Examples and Comparative Examples were evaluated according to the following criteria.
<Evaluation criteria>
◯: The fluorescence concentration of the solid printing portion of the ink is higher than the fluorescence concentration of the solid portion of the water-diluted solution, or is low within 5%.
Δ: The fluorescence concentration of the solid printing portion of the ink is lower than the fluorescence concentration of the solid portion of the aqueous diluent within 5% to 10%.
X: The fluorescence concentration of the solid printing area of the ink is more than 10% lower than the fluorescence concentration of the solid area of the water diluted solution.

(Friction fastness of image):
A Gakushin type friction tester was used. The mass of the friction element used was 200 g, the number of times of friction was 20 times, and a comparative judgment was made in 5 steps based on the colored state of the friction paper after friction.
◯: The colored state of the friction paper is 4 or more and 5.
Δ: The colored state of the friction paper is 3 or more and less than 4.
X: The colored state of the friction paper is less than 3.

(Ink physical characteristics of storage stability):
The ink was stored at a high temperature of 70 ° C. for 1 week. Then, the volatility of the numerical values of the pH value, the viscosity and the average particle size in the ink after the storage test and the ink before the storage test was calculated and evaluated according to the following criteria.
◯: The volatility before and after the storage test is within 5%.
Δ: The volatility before and after the storage test is more than 5% and less than 10%.
X: The volatility before and after the storage test is 10% or more.

(Print color difference for storage stability):
The ink was stored at a high temperature of 70 ° C. for 1 week. Then, the solid printing part obtained with the ink after the storage test and the solid printing part obtained with the ink before the storage test were measured with a colorimeter and evaluated according to the following criteria.
◯: Color difference ΔE is 2 or less.
X: The color difference ΔE is more than 2.

From the results of Comparative Example 1 in Table 2, it was found that by using the binder component having a remarkably high acid value, the ink gelled and became unable to be ejected, and the subsequent evaluation test could not be performed. From the results of Comparative Example 2, it was found that when a binder component having an acid value higher than that specified in the present invention was used, the ejection stability of the ink was inferior and the storage stability was poor. Further, from the results of Comparative Example 3, it was found that when PVP was used as the binder component instead of the polymer emulsion, the ink was faintly printed and the ejection stability was lowered. These facts mean that the basic performance of the inkjet ink cannot be obtained with the inks having the configurations of Comparative Example 1 and Comparative Example 3. Further, from the result of Comparative Example 4, when the pH value of the ink exceeds 9, the fluorescence density of the formed ink image is lowered, the storage stability of the ink is also deteriorated, and the printed matter and the printed matter after the storage test are stored. It was found that the color difference ΔE from the printed matter before the test was as large as 2 or more, and it was not possible to form an image with stable quality.

From the results of Comparative Example 5, it was found that an ink using a fluorescent pigment dispersion having an average particle size larger than that specified in the present invention could not be ejected, and subsequent evaluation tests could not be performed. Further, from the result of Comparative Example 6, if a water-soluble organic solvent having a boiling point of 200 ° C. or higher is not used for the ink compounding, the ink can be ejected at the initial stage when recording is started, but it can be ejected gradually in continuous printing. It was found that the ink disappeared, the nozzle was clogged, and the ejection stability was lowered.

Based on the results of Examples 1 to 3 in Table 1, for the inks of the above comparative examples, a low acid value polymer emulsion having a low acid value specified in the present invention is used as a binder, and a surfactant and 200 ° C. or higher are used. The water-based fluorescent ink specified in the present invention, which has a structure in which the pH value of the ink is adjusted to 7 to 9 by using a water-soluble organic solvent having a boiling point of, is stable in ink ejection and storage when applied to inkjet printing. It was found that the properties were good and the fluorescence density of the printed matter could be improved.

Claims (5)

A fluorescent colored resin emulsion having a resin colored with a fluorescent dye, a low acid value polymer emulsion having an acid value of 10 mgKOH / g or less, a surfactant and a water-soluble organic solvent as a resin component for a binder.
The average particle size of the fluorescent colored resin emulsion and the low acid value polymer emulsion is 300 nm or less, and the water-soluble organic solvent contains at least one water-soluble organic solvent having a boiling point of at least 200 ° C. or more, and
A water-based fluorescent ink for inkjet, characterized in that the pH is adjusted to 7-9. The aqueous fluorescent ink for an inkjet according to claim 1, wherein the fluorescent dye is an acidic fluorescent dye. The aqueous fluorescent ink for an inkjet according to claim 1 or 2, wherein the low acid value polymer emulsion is an acrylic polymer emulsion. According to any one of claims 1 to 3, the water-soluble organic solvent having a boiling point of 200 ° C. or higher is contained in the range of 1% by mass or more and 50% by mass or less with respect to the total amount of the water-soluble organic solvent. The water-based fluorescent ink for inkjet described. The aqueous fluorescent ink for an inkjet according to any one of claims 1 to 4, wherein the surfactant is a nonionic surfactant.