JP7128776B2 - Water-based fluorescent ink for inkjet - Google Patents

Description

TECHNICAL FIELD 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 with excellent resolution by depositing droplets on a substrate surface by an inkjet method.

In recent years, advances in inkjet recording technology have made it possible to obtain high-definition and high-saturation images. As a result, inkjet recording has come to be widely used for a wide variety of colorful printed materials such as posters, magazines, and packages. On the other hand, the use of fluorescent color ink is an effective method for expressing more vivid images.

In contrast, fluorescent coloring materials have conventionally been used in line marker pens and the like. Recently, inks using fluorescent pigments have also appeared in order to improve the durability of handwriting (printing) over time. For example, proposals have been made to provide fluorescent pigment inks for writing instruments using fluorescent pigments (see Patent Documents 1 and 2).

Examples of fluorescent colorants include inorganic or organic fluorescent pigments and fluorescent dyes. Fluorescent dyes have the problem that sufficient printing density cannot be obtained because the ink permeates the printing base material at the molecular level and migrates inside the base material. Moreover, fluorescent dyes also have a problem that the fastness of the formed image is insufficient. Fluorescent pigments, on the other hand, are superior to fluorescent dyes in terms of fastness, discoloration, and fading. However, since inorganic fluorescent pigments have large particle diameters, there is another problem that it is difficult to eject them from nozzles of inkjet printers. On the other hand, as organic fluorescent pigments, pigments obtained by dyeing resin particles with a fluorescent dye, and fluorescent pigments encapsulated in resin particles have been proposed. It can be used as a coloring agent (see Patent Documents 3 to 5).

JP-A-6-346013 JP-A-5-239395 JP-A-2003-26964 Japanese Patent Application Laid-Open No. 2004-189900 JP 2009-161688 A

However, according to the study of the present inventors, it is difficult to say that the conventional technique has been established as a technique because it may not be possible to obtain a stable fluorescence hue and fluorescence intensity in the formed image. . Furthermore, in ink jet recording, in which recording is performed by ejecting ink from nozzles, it is necessary to perform stable ink ejection as a basic performance of the ink, but this point has not yet been sufficient.

Accordingly, an object of the present invention is to provide a water-based fluorescent ink that has good ink storage stability, forms a stable fluorescent color in an image, and achieves excellent ink jettability when used in inkjet recording. to provide. A further object of the present invention is to provide a water-based fluorescent ink for inkjet that is capable of stably obtaining high-quality image quality by inkjet recording due to its excellent ink ejection properties.

The above objects are achieved by the present invention described below.
[1] A fluorescent colored resin emulsion having a resin colored with a fluorescent dye, containing a low acid value polymer emulsion having an acid value of 10 mgKOH/g or less as a binder resin component, a surfactant and a water-soluble organic solvent. , the fluorescent colored resin emulsion and the low acid value polymer emulsion have an average particle size of 300 nm or less, and the water-soluble organic solvent contains at least one water-soluble organic solvent having a boiling point of 200° C. or higher; , and pH adjusted to 7-9.

Preferred embodiments of the water-based fluorescent ink for inkjet include those having the following constitution.
[2] The aqueous fluorescent ink for inkjet according to the above [1], wherein the fluorescent dye is an acidic fluorescent dye.
[3] The aqueous fluorescent ink for 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] containing the water-soluble organic solvent having a boiling point of 200° C. or higher in a 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. 3. The water-based fluorescent ink for inkjet according to any one of .
[5] The aqueous fluorescent ink for inkjet according to any one of [1] to [4] above, wherein the surfactant is a nonionic surfactant.

According to the present invention, there is provided a water-based fluorescent ink that has good ink storage stability, forms a stable fluorescent color, and achieves excellent ink jettability when used in inkjet recording. be. Furthermore, since excellent ink jettability can be achieved, high-quality image quality can be stably obtained according to the water-based fluorescent ink for inkjet of the present invention.

FIG. 2 is a view of 5-point characters printed by an inkjet method using the ink of Example 1 and observed with a desk microscope. FIG. 10 is a view of 5-point characters printed by an inkjet method using the ink of Comparative Example 3, observed with a desk microscope.

The present invention will be described in more detail with reference to preferred embodiments. As a result of intensive studies on the above-described problems of the prior art, the inventors of the present invention have found that the difference in the binder component constituting the water-based fluorescent ink, the average particle size of the emulsion, the type of water-soluble organic solvent, etc. In that case, if the pH of the ink is high, the fluorescent density of the formed image will be inferior, and the image will not be formed after the ink is stored. In this case, the inventors have found that the printed color difference between before and after the storage of the ink becomes large, and it is impossible to form an image with stable quality, leading to the present invention.

The water-based fluorescent ink for inkjet of the present invention comprises 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 binder resin component, a surfactant and and a water-soluble organic solvent having a boiling point of 200° C. or higher, and the pH of the ink is adjusted to 7-9. Each component constituting the water-based fluorescent ink for inkjet of the present invention will be described below.

[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 water-based fluorescent ink of the present invention. Dyed emulsions (hereinafter referred to as "acrylic resin-based polymer emulsions") can be mentioned. The fluorescent dye used in this case is preferably an acidic fluorescent dye.

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

A method for producing an acrylic resin polymer emulsion comprises polymerizing or copolymerizing one or more of the above monomers in a solvent such as water. The method of polymerization or copolymerization is not particularly limited, but synthesis by emulsion polymerization is preferred.

The method of dyeing an acrylic resin polymer emulsion with a dye can be applied without any particular limitation as long as it can dye the polymer compound. , a method of reacting a dye during polymerization, or a method of reacting or dyeing after synthesis.

The content of the dye in the colored resin varies depending on the type of dye, etc., so it cannot be determined unconditionally, but the content of the dye 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 concentration quenching of fluorescence may occur due to a high concentration of the dye. I don't like it.

Since the water-based fluorescent ink of the present invention is for inkjet use, the constituting acrylic resin polymer emulsion has an average particle size of 300 nm or less, preferably 50 to 200 nm. If the average particle diameter exceeds 300 nm, the ink jettability tends to deteriorate. In addition, 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 analyzer.

Fluorescent colored resin emulsions that can be suitably used as coloring materials in the present invention are commercially available. Specifically, for example, SF-3000N series, SF-5000 series (manufactured by Shinroihi Co., Ltd.), LUMIKOL NKW-3200 series (manufactured by Nihon Shokuryo Kagaku Co., Ltd.) and the like can be mentioned.

The content of the acrylic resin-based polymer emulsion as the fluorescent colored resin emulsion that constitutes the aqueous fluorescent ink of the present invention is determined by the dye concentration in the resin, and is preferably 1 to 50% by mass, more preferably 1 to 50% by mass in the ink. 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 of the present invention.

The low acid value polymer emulsion constituting the present invention requires that the solid content has an acid value of 10 mgKOH/g or less. The acid value of such 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 polymers. Among them, an acrylic polymer is preferable from the viewpoint of excellent adhesion to the substrate 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. Examples thereof include homopolymers of (meth)acrylic acid ester-based monomers, and copolymers of (meth)acrylic acid ester-based monomers as the main component and other monomers. Preferably, it is an acrylic polymer emulsion obtained by copolymerizing a (meth)acrylic acid ester monomer and other monomers. Styrene may be used as a monomer for obtaining the copolymer. In any case, in the present invention, when selecting and blending the monomers, it is required that the solid content of the resulting polymer emulsion has an acid value of 10 mgKOH/g or less.

A method for producing a low acid value polymer emulsion comprises polymerizing or copolymerizing one or more of the above 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 non-volatile components of the polymer emulsion. Examples of the measuring method include a method using JIS K-0070 acid value measurement, hydrolysis acid value measurement (total acid value measurement), and the like. In many cases, the information is provided by the manufacturing company as the acid value of the product. At that time, it is indicated as an acid value in 1 g of the product, and when volatile components such as solvents are contained in the polymer emulsion product, it should be converted to 100% non-volatile components.

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, 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 become 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 relative to the total mass of the ink.

[pH adjustment]
The aqueous fluorescent ink for inkjet of the present invention needs to be adjusted to pH 7-9. If the ink has a pH of more than 9 and is strongly alkaline, fluorescent dye discoloration and fluorescence quenching occur, and stable fluorescent hue and intensity cannot be obtained. On the other hand, if the ink is made 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, alkaline inks of other colors placed on other channels of the same head may be used. There is a risk of nozzle clogging by mixing with ink and agglomeration of pigment on the head surface and wiper.

The pH adjuster used for adjusting the pH of the water-based fluorescent ink for inkjet of the present invention is not particularly limited, and any agent can be used as long as the pH can be adjusted 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; amines such as ethanolamine; and neutralizing agents such as ammonium hydroxide.

[Surfactant]
The water-based fluorescent ink for inkjet of the present invention contains a surfactant in addition to the above components. Surfactants that can be used at this time are not particularly limited as long as they do not impair the object of the present invention. For example, nonionic surfactants are suitable.

Examples of nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, poly Those having 25 or more ethylene oxide chains such as oxyethylene stearylamine and polyoxyethylene can be mentioned. The present invention is not limited to these. The water-based fluorescent ink for inkjet of the present invention preferably has a surface tension adjusted to 35 mN/m or less by using a surfactant.

It is preferable that the surfactant as described above is contained in an amount of 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 substrate can be ensured when an image is formed, so that the image quality can be improved. In addition, when used in the range of 5% by mass or less, the ink is less likely to bubble, 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 water-based fluorescent ink for inkjet of the present invention comprises a fluorescent colored resin emulsion, a low acid value polymer emulsion as a binder component, a surfactant, and an aqueous liquid medium similar to the usual inkjet ink. The aqueous liquid medium constituting the present invention is a mixed solvent of water and a water-soluble organic solvent, and as the water, ion-exchanged water (deionized water) is used instead of general water containing various ions. is preferred.

Since the water-based fluorescent ink for inkjet of the present invention uses a low acid value polymer emulsion as a binder component, when drying occurs in the nozzle part of the inkjet printer head, it can be removed by dissolution or physical rubbing operation. It becomes necessary to remove the dried binder component. At that time, in order to suppress the occurrence of being unable to be removed, the aqueous fluorescent ink of the present invention contains at least one water-soluble organic solvent having a boiling point of 200° C. or higher. configuration.

The water-soluble organic solvent used by mixing with water is not particularly limited and can be appropriately selected depending on the 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. mentioned. These are preferably used in combination of two or more. According to studies by the present inventors, in order to achieve the object of the present invention, it is preferable to use an ink containing one or more water-soluble organic solvents 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.), 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: 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: 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), diethylene glycol monoethyl ether ( 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: 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: 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.

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), 1,3-dimethylimidazolidinone (boiling point: 220°C), ε-caprolactam (boiling point: 137°C), N-methylpyrrolidinone (boiling point: 202°C) and the like.

Examples of water-soluble organic solvents 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 Glycol methyl 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, 3-dimethylimidazolidinone (boiling point: 220°C), N-methylpyrrolidinone (boiling point: 202°C), and the like. At least one selected from these is used in the aqueous fluorescent ink of the present invention.

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

Also, 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 the content is 60% by mass or less, the viscosity of the ink can be kept low, so the ejection stability can be improved.

[Other ingredients]
The water-based fluorescent ink for inkjet of the present invention may contain the following components in addition to the above components. Other components are not particularly limited and can be appropriately selected depending on the intended purpose. These may be used individually by 1 type, and may use 2 or more types together.

Examples of the antiseptic and antifungal agents include 1,2-benzisothiazolin-3-one, sodium benzoate, sodium dehydroacetate, sodium sorbate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, and the like. mentioned. Examples of the antirust agent include acid sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

[Ink manufacturing method]
As a method for producing the water-based fluorescent ink for 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 acid value polymer emulsion as a binder, a surfactant, and, if necessary, other It can be produced by dispersing or dissolving the components in an aqueous medium and stirring and mixing appropriately. For the stirring and mixing, for example, a sand mill, homogenizer, ball mill, paint shaker, ultrasonic disperser, stirrer using ordinary stirring blades, magnetic stirrer, high-speed disperser, or the like can be used.

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

EXAMPLES 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. "Parts" and "%" in the text are based on mass unless otherwise specified.

[Preparation of polymer emulsion]
<Production of low acid value polymer emulsion 01>
70.0 parts of water and 1.2 parts of a nonionic surfactant were charged into a reaction vessel equipped with a stirrer, a backflow condenser and a thermometer, and heated to 85° C. while bubbling nitrogen gas under reflux. . In addition, separately prepared 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 parts of potassium persulfate are mixed. Of the 146 parts dissolved aqueous solution, 16 parts were added. The remaining 130 parts of the aqueous solution was placed in the dropping funnel, and slowly added dropwise into the reaction vessel over 2 hours and 30 minutes while maintaining the temperature at 80°C to 85°C. After the dropwise addition, the pH was adjusted to 7 using an aqueous ammonia solution, the mixture was 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 measured by titration with a toluene/ethanol=50/50 solution using phenolphthalein as an indicator and a 0.1N KOH ethanol solution as a titrant. The acid value of the low acid value polymer emulsion 01 obtained above was 5.7 mgKOH/g. Also, 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 analyzer (trade name: NICOMP380, manufactured by Nihon Entegris 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>
Polymer emulsion 02 was obtained in the same synthesis method as for low acid value polymer emulsion 01, except that the starting monomers were changed to 70.0 parts of methyl methacrylate, 30.0 parts of butyl acrylate and 5 parts of methacrylic acid. The acid value of polymer emulsion 02 measured by the same method as for low acid value polymer emulsion 01 was 12.3 mgKOH/g. The average particle size of polymer emulsion 02 measured by the same method as described above was 121.4 nm.

<Production of polymer emulsion 03 used in Comparative Example>
Polymer emulsion 03 was obtained in the same synthesis method as for low acid value polymer emulsion 01, except that the starting monomers were changed to 70.0 parts of methyl methacrylate, 30.0 parts of butyl acrylate and 12 parts of methacrylic acid. The acid value of Polymer Emulsion 03 measured by the same method as for Low Acid Value Polymer Emulsion 01 was 51.3 mgKOH/g. The average particle size of polymer emulsion 03 measured by the same method as described above was 126.4 nm.

<Production of low acid value polymer emulsion 04>
Low acid value polymer emulsion 04 was obtained in the same synthesis method as low acid value polymer emulsion 01, except that the raw material monomers were changed to 70.0 parts of methyl methacrylate and 30.0 parts of butyl acrylate. The acid value of the low acid value polymer emulsion 04 measured by the same method as that for 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 method as described above was 109.7 nm.

[Example 1]
The following components were mixed in the proportions indicated below, thoroughly stirred, and filtered under pressure through 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 colored with a fluorescent acid dye (trade name: SF-5017; manufactured by Shinroihi Co., Ltd.) was used. Also, as the binder resin component, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH/g was used. As a surfactant, a nonionic surfactant polyoxyethylene cetyl ether (trade name: BC-40TX; manufactured by Nikko Chemicals Co., Ltd.) was used. Diethanolamine was used as a 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>
A cartridge bottle was filled with the ink described above, and an inkjet recording image was formed using a piezo inkjet printer (trade name: MMP813P, manufactured by Mastermind Co., Ltd.) to evaluate the ink obtained above.

The papers used for the evaluation are Canon PPC paper and PB-paper.

(Ink ejection stability)
Using the inkjet printer, 5-point characters, solid print areas, 1-point ruled lines, etc. were printed, and the state of the printed image was observed to evaluate the ejection stability of the ink from the nozzles of the inkjet printer. . As a result, it was confirmed that the ejection property of the ink of Example 1 was good and that stable prints could be obtained. FIG. 1 shows a 5-point character observed using a desk microscope (trade name: 3R-MSTVUSB273, manufactured by 3R Systems).

(fluorescence in image)
The fluorescence density and hue of the solid printed 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 variation in fluorescence intensity due to differences in the type of printed paper or lot was observed.

(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 physical properties of the ink before high temperature storage was good at 10% or less. Further, when ink jet printing was performed with the ink after storage, the printing condition was as good as the ink before storage, and a stable print 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 colored with a fluorescent acid dye (trade name: SF-3017, manufactured by Shinroihi Co., Ltd.) was used as the fluorescent colored resin emulsion. In addition, the previously prepared low acid value polymer emulsion 04 having an acid value of 0 mgKOH/g was used as a binder resin component. Then, the ink of this example was prepared using the same components and method as those used in Example 1, except that the following formulation was used. Diethanolamine was used as a 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 ejection stability of the ink was as good as in Example 1, and stable prints could be obtained. Further, in the fluorescence image, red 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, as in Example 1, the change in physical properties was 10% or less, the printing condition was stable without any change before and after storage, and the print color difference ΔE between the inks before and after storage was 2 or less. there were.

[Example 3]
In this example, an acrylic resin emulsion colored with a fluorescent acid dye (trade name: SF-5014, manufactured by Shinroihi Co., Ltd.) was used as the fluorescent colored resin emulsion. As the binder resin component, the previously prepared low acid value polymer emulsion 04 having an acid value of 0 mgKOH/g was used in the same manner as in Example 2, and the nonionic surfactant polyoxy Ethylene oleyl ether (trade name: BO-50; manufactured by Nikko Chemicals Co., Ltd.) was used. Then, the ink of this example was prepared using the same components and method as those used in Example 1, except that the following formulation was used. Diethanolamine was used as a 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 ejection stability of the ink was as good as in Example 1, and stable prints could be obtained. Further, in the fluorescence 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, as in Example 1, the change in physical properties was 10% or less. The color difference ΔE was 2 or less.

[Comparative Example 1]
Polymer emulsion 03 having a high acid value of 51.3 mgKOH/g, prepared earlier, was used as the binder resin component. As the fluorescent colored resin emulsion, an acrylic resin emulsion colored with the same fluorescent acid dye as used in Example 1 (trade name: SF-5017; manufactured by Shinroihi Co., Ltd.) was used, and as the surfactant, Example 3 The same nonionic surfactant polyoxyethylene oleyl ether as used in . Then, the ink of this example was prepared using the same components and method as those used in Example 1, except that the following formulation was used. Diethanolamine was used as a 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 parts 0 parts 2-pyrrolidone (boiling point: 245 ° C.): 5.0 parts pure water: 42.7 parts

<Evaluation>
An attempt was made to form an inkjet recorded image by loading the ink obtained above into a cartridge bottle. However, the ink gelled and the ink could not be ejected from the inkjet printer head, so that no evaluation could be made.

[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, which is slightly higher than that specified in the present invention, was used, and the composition was the same as in Comparative Example 1, except that the following formulations were used. The inks of this example were prepared with similar ingredients and methods. Diethanolamine was used as a 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 ・Nonionic surfactant (polyoxyethylene oleyl ether): 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: 42.7 parts

<Evaluation>
An attempt was made to form an inkjet recorded image by loading the ink obtained above into a cartridge bottle. However, when the ink was stored at a high temperature of 70° C. for 1 week in the same manner as in Example 1 and the storage stability of the ink was evaluated, the viscosity of the ink after storage increased by 10%, indicating that the ink had poor ejection properties. Confirmed inferior. In addition, the ejection stability of the ink before storage was inferior to that of the inks of Examples.

[Comparative Example 3]
As a binder resin component, as a resin that is not a polymer emulsion, polyvinylpyrrolidone (abbreviated as PVP) using N-vinyl-2-pyrrolidone as a monomer (trade name: Luviscol K30; manufactured by BASF) is used, and the following formulation is used. The ink of this example was prepared with the same ingredients and method as in Comparative Example 1, except that the inks of this example were prepared. Diethanolamine was used as a 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>
An attempt was made to form an inkjet recorded image by loading the ink obtained above into a cartridge bottle. However, the printing was faint and the ejection was unstable. FIG. 2 shows an enlarged view of the obtained characters with a magnifying glass.

[Comparative Example 4]
As the fluorescent colored resin emulsion, the acrylic resin emulsion colored with the same fluorescent acid dye as in Example 1 (trade name: SF-5017; manufactured by Shinroihi Co., Ltd.) was used. Also, as the binder resin component, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH/g was used. As a surfactant, a nonionic surfactant polyoxyethylene cetyl ether (trade name: BC-40TX; manufactured by Nikko Chemicals Co., Ltd.) was used. Diethanolamine was used as a pH adjuster. The pH of the ink of this example is 9.8, which exceeds the range defined by 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 Trimethylolpropane (boiling point: 160°C): 5.0 parts Pure water: 40.0 parts

<Evaluation>
A cartridge bottle was charged with the ink obtained above, an inkjet recorded image was formed, 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 after the storage test and before the storage test was 2 or more, indicating a large variation. Then, when the fluorescence intensity of the formed image was measured, it was confirmed that the fluorescence intensity was lowered even in a portion where the print density and the like appeared to be satisfactory by visual observation.

[Comparative Example 5]
As the fluorescent colored resin emulsion, an acrylic resin emulsion (trade name: SF-8017; manufactured by Shinroihi Co., Ltd.) colored with a fluorescent acid dye having an average particle size of about 400 nm, which has a larger particle size than specified in the present invention, is used. board. Also, as the binder resin component, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH/g was used. As a surfactant, a nonionic surfactant polyoxyethylene cetyl ether (trade name: BC-40TX; manufactured by Nikko Chemicals Co., Ltd.) was used. Diethanolamine was used as a 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>
An attempt was made to form an inkjet recorded image by loading the ink obtained above into a cartridge bottle. However, no ink was ejected from the ink jet printer head, and no evaluation could be made.

[Comparative Example 6]
As the fluorescent colored resin emulsion, the acrylic resin emulsion colored with the same fluorescent acid dye as in Example 1 (trade name: SF-5017; manufactured by Shinroihi Co., Ltd.) was used. Also, as the binder resin component, the previously prepared low acid value polymer emulsion 01 having an acid value of 5.7 mgKOH/g was used. As a surfactant, the same nonionic surfactant polyoxyethylene oleyl ether as used in Example 3 was used. In this example, no water-soluble solvent with a boiling point of 200° C. or higher was used. Diethanolamine was used as a 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>
An attempt was made to form an inkjet recorded image by loading the ink obtained above into a cartridge bottle. As a result, the ejection of ink gradually became impossible during long continuous printing.

Tables 1 and 2 collectively show the results of the above examples and comparative examples.

Description of the evaluation items in Tables 1-3:
(Evaluation criteria for ink ejection stability):
◯: Printable, no lack of nozzle check pattern, no printing failure phenomenon.
Δ: Printing is possible, but the nozzle check pattern is missing (pin missing phenomenon), or there is another printing failure phenomenon.
x: Unable to eject, or poor printing phenomenon is so severe that printing cannot be practically used.

(fluorescence density of image):
<Measurement method>
Make a water dilution of the same concentration of the fluorescent pigment dispersion as used in the ink. Using the obtained water-diluted liquid, printing is performed on the same paper as that on which the ink-jet recording image is formed with each ink described above, by the same printing method. The hue and fluorescence intensity of the solid portion of the obtained printed matter of the water-diluted solution were measured with the same colorimeter (trade name: SPECTRO 2 GUIDE, manufactured by BYK). The obtained measured values and the measured values of the solid print portions formed with the inks of Examples and Comparative Examples were evaluated according to the following criteria.
<Evaluation Criteria>
◯: The fluorescence density of the solid printed portion of the ink is higher than the fluorescence density of the solid portion of the water-diluted liquid, or lower within 5%.
Δ: The fluorescence density of the solid printed portion of the ink is lower than the fluorescence density of the solid portion of the water-diluted solution by more than 5% to within 10%.
x: The fluorescence density of the solid printed portion of the ink is lower than that of the solid portion of the water-diluted liquid by more than 10%.

(image rub fastness):
A Gakushin type friction tester was used. The mass of the friction element used was 200 g, the number of frictions was 20, and the colored state of the friction paper after friction was relatively compared and judged in five stages.
◯: The coloring state of the friction paper is 4 or more and 5.
Δ: The coloring state of the friction paper is 3 or more and less than 4.
x: The coloring state of the friction paper is less than 3.

(Ink properties for storage stability):
The ink was stored at a high temperature of 70°C for one week. Then, the fluctuation rate of the pH value, viscosity and average particle size of the ink after the storage test and the ink before the storage test were calculated and evaluated according to the following criteria.
◯: The rate of change before and after the storage test is within 5%.
Δ: Variation rate before and after the storage test is more than 5% and less than 10%.
x: The rate of change before and after the storage test is 10% or more.

(Printing color difference of storage stability):
The ink was stored at a high temperature of 70°C for one week. A solid printed portion obtained with the ink after the storage test and a solid printed portion 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 the use of a binder component with a significantly high acid value caused the ink to gel and become unusable, making subsequent evaluation tests impossible. From the results of Comparative Example 2, it was found that the use of a binder component having an acid value higher than that specified in the present invention results in poor ejection stability of the ink and poor storage stability. 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 printed was faint and the ejection stability was lowered. These facts mean that the inks having the configurations of Comparative Examples 1 and 3, in particular, cannot achieve the basic performance of inkjet inks. Furthermore, according to the results of Comparative Example 4, when the pH value of the ink exceeds 9, the fluorescent density of the formed ink image decreases, the storage stability of the ink deteriorates, and the printed matter after the storage test and storage The color difference ΔE from the printed matter before the test was as large as 2 or more, and it was found that image formation with stable quality could not be performed.

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, according to the results of Comparative Example 6, unless a high boiling point water-soluble organic solvent having a boiling point of 200° C. or higher is used in the formulation of the ink, the ink can be ejected at the beginning of the recording, but can be gradually ejected during continuous printing. It was found that nozzle clogging occurred and ejection stability decreased.

From the results of Examples 1 to 3 in Table 1, for the inks of the above-described comparative examples, a low acid value polymer emulsion having a low acid value defined in the present invention was used as a binder, and a surfactant and a temperature of 200 ° C. or higher were used. The aqueous fluorescent ink defined in the present invention, which has a configuration in which a water-soluble organic solvent having a boiling point of It was found that the properties are good and the fluorescent density of the printed matter can be improved.

Claims (6)

A fluorescent colored resin emulsion having a resin colored with a fluorescent dye, containing a low acid value polymer emulsion having an acid value of 10 mgKOH/g or less as a binder resin component, a surfactant and a water-soluble organic solvent (provided that (Except when pigment dispersion resin is included) ,
The fluorescent colored resin emulsion and the low acid value polymer emulsion have an average particle size of 300 nm or less, and the water-soluble organic solvent contains at least one water-soluble organic solvent having a boiling point of 200° C. or higher, and
A water-based fluorescent ink for inkjet, wherein the pH is adjusted to 7-9. 2. The aqueous fluorescent ink for inkjet according to claim 1, wherein the fluorescent dye is an acidic fluorescent dye. 3. The aqueous fluorescent ink for inkjet according to claim 1 or 2, wherein the low acid value polymer emulsion is an acrylic polymer emulsion. The water-based fluorescent ink for inkjet according to any one of claims 1 to 3, wherein the content of the low acid value polymer emulsion is 1% by mass or more and 15% by mass or less in terms of solid content relative to the total mass of the ink. 5. The method according to any one of claims 1 to 4 , wherein the water-soluble organic solvent having a boiling point of 200°C or higher is contained in a 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. A water-based fluorescent ink for inkjet as described. The water-based fluorescent ink for inkjet according to any one of claims 1 to 5 , wherein the surfactant is a nonionic surfactant.

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