JP2002179968A - Fluorescent ink for ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluorescent ink for an ink jet printer that is so excellent in reliability such as printing stability, storage stability or the like as to be suitably applicable to an on-demand ink jet printer and that can sufficiently satisfy durability of a printed matter. SOLUTION: The fluorescent ink for an ink jet printer comprises an organic fluorescent dye that is substantially invisible in a visible light region and emits the light in a visible light region when excited by ultraviolet rays, a resin, a water-soluble organic solvent having a boiling point of not lower than 110 deg.C and water, wherein a weight ratio of the organic fluorescent dye the resin (the weight of the organic fluorescent dye/the weight of the resin) is 1/1-1/50 and a pH is in a range of 5-8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent ink for an ink-jet printer containing an organic fluorescent dye which is substantially invisible in the visible light region and emits light in the visible light region when excited by ultraviolet rays, and more particularly to an on-demand type ink. The present invention relates to a fluorescent ink for an inkjet printer suitable for an inkjet printer.

[0002]

2. Description of the Related Art In recent years, information such as a manufacturer and a product name of an article is displayed as a bar code or certain characters, numbers, and symbols, and the pattern and information are displayed using a bar code reader or an OCR (Opti).
It is often used for reading by optical detection methods such as cal Character Reader) and used for total sales of products and analysis of distribution. Recently, not only products using such barcode systems and OCR systems have been found, but also applications to file management have been made. For example, in the automatic sorting of mail, a system for distributing articles by code management is used, and in banks, a system for printing character and numerical information on forms and using the information to sort and manage the information is introduced.

Conventionally, in a barcode system, a method of printing a barcode such as black on a white background using a printing method such as an ink jet printer, an impact printer, a thermal transfer printer, offset printing, gravure printing, and screen printing. It's being used. However, since this method reads information using the difference in reflectance between the barcode and the base, the base color of the article is limited to a light color, and the base color of the rule is black, such as ruled lines, characters, and numbers. An article having a symbol has a disadvantage that a barcode cannot be printed. In addition, since reflected light in the visible light region is used, there is a disadvantage that the appearance of the article is necessarily impaired. The OCR system also has the same problem because information such as characters, numbers, and symbols is printed in blue or black.

[0004] In such a bar code system or OCR system, in order to solve the problem that the base color of the article is limited or the appearance of the article is impaired, the bar code system or the OCR system is substantially invisible in the visible light region and is exposed to ultraviolet light. A method using an ink containing a fluorescent dye that emits light in the visible light region when excited has been used or proposed. When a printed material is prepared using this fluorescent ink, the printed material is read using the emission of the fluorescent dye, so that the background color is not limited to a light color. There is an advantage that even if the code is printed, it can be read by a machine. Further, there is an advantage that printing can be performed without impairing the appearance of the article, and attention has been paid as an alternative to a bar code such as black and white.

[0005] As a printing method of the fluorescent ink, an ink jet printer has been proposed because of the advantage that it is possible to perform non-contact and high-speed printing on an article. As an inkjet printer, a continuous method in which ink droplets are continuously discharged from nozzles and the flight direction of the droplets is controlled by charge control, or a continuous method in which printing is performed on an article by applying pressure only when printing on an article is optional. An on-demand method in which ink droplets are ejected from a nozzle may be used. As a fluorescent ink for an ink jet printer containing a fluorescent dye which is substantially invisible in the visible light region and emits light in the visible light region when excited by ultraviolet light, Japanese Patent Publication No. Sho 54-2
No. 2336, No. 4-64517, No. 11-5
No. 10213 and other publications.

[0006] The above-described on-demand type ink jet printer has advantages such as high definition and good image quality, a simple machine structure and low cost as compared with a continuous type ink jet printer. In addition to barcode systems and OCR systems that require printed materials, they are being put to practical use in the design and graphic fields such as signboards, posters, and wallpapers. Conventionally, colored inks have been exclusively used, but in recent years, there has been a movement to use fluorescent inks having the above advantages for the above-described on-demand type inkjet printer.

However, the on-demand type ink jet printer has the following differences as compared with the conventional continuous type ink jet printer, so that the conventionally proposed fluorescent ink cannot be used as it is.

[0008]

As described above, the use of the on-demand type ink jet printer is significantly different from that of the conventional continuous type ink jet printer. The use of a compound is inferior in reliability such as printing stability and storage stability, and insufficient in durability of printed matter. For example, with a fluorescent ink using a low-boiling lower alcohol or a mixture of the same and water as a solvent, the ink dries too quickly at the nozzles, causing clogging, and defective ejection. Further, in a fluorescent ink adjusted to an alkaline region (pH 8 or more) to stably dissolve the fluorescent dye, the fluorescent dye is easily decomposed by long-term storage, and the emission intensity is reduced. Furthermore, with a fluorescent ink that does not use a resin component at all or uses a small proportion of the resin component with respect to the organic fluorescent dye, the printing layer has low adhesion strength to a printing material having poor ink permeability, such as coated paper, so that sufficient printing can be performed. There are problems such as not being able to do.

[0009] In particular, in the on-demand method, 600 to
The nozzle diameter is extremely small because a resolution of about 2,400 dpi, which is about 10 times higher than that of the continuous method, is required. In this case, if the fluorescent ink proposed in the conventional continuous method is used, the fluorescent ink in which a fluorescent dye is dispersed in a solvent and formed into a granular material has a particle diameter that is too large and nozzle clogging is likely to occur. . Further, in the case of a fluorescent ink in which a fluorescent dye is dissolved in a solvent, if the solvent evaporates in a portion of the nozzle portion that comes into contact with the outside air, the nozzle diameter is small, so that even if a small amount of nozzle clogging occurs, ejection failure is likely to occur. For this reason, in the on-demand method, development of a fluorescent ink having higher reliability than before has been demanded.

In view of such circumstances, the present invention provides an ink jet printer which has excellent reliability such as printing stability and storage stability which can be applied to an on-demand type ink jet printer, and which can sufficiently satisfy the durability of printed matter. It is an object of the present invention to provide a fluorescent ink so that anyone can easily produce a printed matter which is substantially invisible in a visible light region and which can be viewed by emitting ultraviolet light.

[0011]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and as a result, the fluorescent ink for an on-demand type inkjet printer is substantially invisible in the visible light region, And an organic fluorescent dye that emits in the visible light region when excited by ultraviolet light, a resin, a water-soluble organic solvent having a boiling point of 110 ° C. or higher, and water, and a weight ratio of the organic fluorescent dye to the resin (organic fluorescent dye Weight / resin weight) is 1/1 to 1/50, and the pH is in the range of 5 to 8. According to the fluorescent ink for an inkjet printer, continuous printing stability and long-term printer You can print immediately without using,
In addition, it was found that the reliability was excellent such that the decrease in luminescence intensity over time was small, and it was found that the printed matter obtained by printing this on an article had improved durability,
The present invention has been completed.

[0012]

DETAILED DESCRIPTION OF THE INVENTION The organic fluorescent dye used in the present invention is:
A dye substantially invisible in the visible light region (wavelength 400 to 700 nm) and excited by ultraviolet light (wavelength less than 400 nm) to be in the visible light region (wavelength 400 to 700 nm).
Is a dye having an emission center wavelength. Although the emission color is not particularly limited, it is red (preferably at a wavelength of 615 ± 20).
nm) are preferred because they emit visible light with excellent detectability.

The reason why organic fluorescent dyes emitting red light are excellent is that an inexpensive and easily available silicone photodiode can be used for detecting light emission. In other words, this diode has a higher light-receiving sensitivity for visible light on a longer wavelength side than on a shorter wavelength side, and thus has higher detection sensitivity for long-wavelength red visible light. In addition, generally used white paper contains a fluorescent whitening agent, and may emit blue light when irradiated with ultraviolet light. In the case of using an organic fluorescent dye that emits red light, since the emission wavelength of red is separated from the emission wavelength of blue from the optical brightener, even when printed on white paper to which an optical brightener has been added. The luminescence of the dye can be detected with high sensitivity.

As described above, the organic fluorescent dye of the present invention is a red-emitting organic fluorescent dye which has no absorption in the visible light region and which has an emission center wavelength in a long wavelength region around 600 nm when excited by ultraviolet light. Although it is preferably used, a typical example thereof is a metal complex having a rare earth element such as europium or samarium as a light emission center and a ligand having a large number of π electrons as a counter ion. Among these, a europium compound having a large emission intensity is particularly preferred.

Specifically, it has no absorption in the visible light region of 400 to 700 nm, and is therefore substantially invisible in the visible light region and 615 ±
Including europium having an emission center wavelength at 20 nm,
This includes tenoyl trifluoroacetone, naphthoyl trifluoroacetone, benzoyl trifluoroacetone,
Methylbenzoyltrifluoroacetone, furoyltrifluoroacetone, pivaloyltrifluoroacetone,
Metal complexes having hexafluoroacetylacetone, trifluoroacetylacetone, fluoroacetylacetone, heptafluorobutanoylpivaloylmethane and the like as ligands are exemplified. Among these, a europium compound having a ligand of tenoyl trifluoroacetone, naphthoyl trifluoroacetone or methylbenzoyl trifluoroacetone having high emission intensity is most preferable.

Further, for the purpose of improving the emission intensity of the printed matter and the storage stability of the ink, a phosphorus-based organic compound can be used as a part of the ligand of the europium compound. For example, triethylphosphine oxide,
Tri-n-propylphosphine oxide, tri-n-
Phosphine oxide compounds such as butylphosphine oxide, tri-n-hexylphosphine oxide, tri-n-octylphosphine oxide, triphenylphosphine oxide, tris (3-hydroxymethyl) phosphine oxide, and tris (3-hydroxypropyl) phosphine oxide; Phosphine sulfide compounds such as tri-n-butylphosphine sulfide, triethylphosphine, tri-n-propylphosphine, tri-n-butylphosphine, tri-n-hexylphosphine, tri-n-octylphosphine, triphenylphosphine, tris ( And phosphine compounds such as (3-hydroxypropyl) phosphine.

Such organic fluorescent dyes include, for example,
J. Am. Chem. Soc. Volume 186, 5117
Page, 1964 (Melby etc.) and Tokuhei 6-1526
No. 9 can be synthesized. Also,
Commercially available products of such organic fluorescent dyes include, for example,
"Rumilux CD33" manufactured by Riedel de Haen
5, "CD331", "CD332", "ER-120", "ER-122" manufactured by Mitsui Chemicals, Inc., and the like.

It is also possible to use an organic fluorescent dye which has no absorption in the visible light region and emits visible light other than red, such as blue, green, yellow-green, or yellow, when excited by ultraviolet light, depending on the application. it can. For example, various luminous brighteners such as coumarin-based, stilbene-based, triazine-based, imidazole-based, thiazole-based, oxazole-based, pyrazolone-based, benzoxazine-based, etc. And a metal complex having a ligand having a large number of as a counter ion. Commercially available products include Rimmellx CD301, CD302, CD304, manufactured by Riedel De Haen.
"CD770" and "CD729", Mitsui Chemicals, Inc.
EB-501, EG-302, EG-3
07 "and" Tinopearl SK-B "manufactured by Ciba-Geigy.

In the present invention, the content of such an organic fluorescent dye is preferably 0.1 to 20% by weight based on the total amount of the fluorescent ink. That is, the content is preferably 0.1% by weight or more in order to secure a suitable fluorescence emission intensity, and 20% by weight in order to obtain suitable ink storability.
The content is preferably as follows.

In the present invention, water is used as an essential component as one of the solvents in the ink for an on-demand type ink jet printer. Water is preferably used because it has a low viscosity and a high surface tension, so that it is easy to form ink droplets, and since the evaporation and drying speed is low, nozzles are hardly clogged. The content of water is preferably 50 to 99.5% by weight based on the total amount of the fluorescent ink.

In the present invention, as another solvent, a boiling point (atmospheric pressure: 760) is used in order to obtain good printing stability.
Use a water-soluble organic solvent with a temperature of 110 ° C or more (mmHg).
The boiling point of this water-soluble organic solvent is preferably 110 to 350 ° C, more preferably 125 to 350 ° C, and 200 to 350 ° C.
C is most preferred. If the temperature is lower than 110 ° C, nozzle clogging due to drying is likely to occur.
It takes time to dry the printed matter. Such water-soluble organic solvents include, for example, polyhydric alcohols, pyrrolidones,
Glycol ethers, etc., and γ-butyrolactone (boiling point: 206 ° C., hereinafter the boiling point is shown in parentheses), 1,3-dimethyl-2-imidazolidinone (22
6 ° C.), sulfolane (287 ° C.), trimethylolpropane (295 ° C.), neopentyl glycol, dimethylformamide (153 ° C.), dimethyl sulfoxide (189 ° C.), and the like. These may be used alone or in a combination of two or more.

The above-mentioned polyhydric alcohols include, for example,
Ethylene glycol (198 ° C), diethylene glycol (245 ° C), triethylene glycol (288
° C), tetraethylene glycol (327 ° C), propylene glycol (188 ° C), dipropylene glycol (232 ° C), tripropylene glycol, polyethylene glycol, polypropylene glycol, hexylene glycol (197 ° C), glycerin (290 ° C), And pentaerythritol. Examples of the pyrrolidones include 2-pyrrolidone (245
° C) and N-methyl-2-pyrrolidone (202 ° C).

Further, as the above glycol ethers, for example, ethylene glycol monomethyl ether (125 ° C.), ethylene glycol monoethyl ether (136 ° C.), ethylene glycol monopropyl ether, ethylene glycol isopropyl ether (14
1 ° C), ethylene glycol monobutyl ether (17
0 ° C.), ethylene glycol monoisobutyl ether,
Ethylene glycol monoallyl ether, ethylene glycol monophenyl ether (245 ° C), diethylene glycol monomethyl ether (194 ° C), diethylene glycol monoethyl ether (202 ° C), diethylene glycol monobutyl ether (230 ° C), diethylene glycol monoisobutyl ether, diethylene glycol diethyl ether ( 186 ° C), triethylene glycol monomethyl ether (249 ° C), triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, triethylene glycol dimethyl ether (222 ° C), triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol Diethyl ether, propylene Glycol monomethyl ether (120
° C), propylene glycol monoethyl ether (13
2 ° C.), propylene glycol monobutyl ether, dipropylene glycol monomethyl ether (190
° C), dipropylene glycol monoethyl ether (1
98 ° C), dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether (243 ° C)
And the like.

Among these water-soluble organic solvents, when the organic fluorescent dye is dispersed as a particulate material in the solvent, a water-soluble organic solvent that does not dissolve the dye is used. For example, polyhydric alcohols are preferably used. Can be When the organic fluorescent dye is dissolved in a solvent, a water-soluble organic solvent capable of dissolving the dye is used.For example, glycol ethers and pyrrolidones are preferable in that the solubility and print stability are good. Used.

In the present invention, the above-mentioned water-soluble organic solvent having a boiling point of 110 ° C. or more is used in an amount of 0.1 to 0.5% based on the total amount of the fluorescent ink.
The content is preferably 3 to 49% by weight, and 2 to 30% by weight.
More preferably, the content is by weight. 0.3% by weight
If the value is less than the above range, the ink is likely to dry in the nozzle portion that comes into contact with the outside air, and the printing stability deteriorates due to nozzle clogging. On the other hand, when the content exceeds 49% by weight, the printed matter when printed on an article is difficult to dry. In the present invention, a water-soluble organic solvent having a low boiling point can be used in combination as a solubilizing agent for an organic fluorescent dye, in addition to using water and the above-mentioned water-soluble organic solvent having a high boiling point in combination. However, the amount of the water-soluble organic solvent having a low boiling point needs to be small so as not to adversely affect the printing stability of the ink jet printer.

In the present invention, the organic fluorescent dye is used by being dispersed or dissolved in a solvent. In particular, in order to impart good light resistance and weather resistance to a fluorescent ink or a printed matter obtained by printing the fluorescent ink on an article, an organic fluorescent dye is present as a particulate matter having an average particle diameter of 10 to 300 nm in a solvent. It is desirable to make it. This is because even if the dye comes into contact with the outside air, only the surface of the particulate matter is deteriorated, and an active dye is present inside, thereby suppressing a decrease in luminescence output even after long-term storage. If the average particle diameter of the dye is smaller than 10 nm, the emission intensity is liable to be deteriorated with time because it is easily affected by the outside air. If the average particle diameter is larger than 300 nm, problems such as sedimentation of the dye in the ink and clogging of nozzles are caused. Easy to happen.

The organic fluorescent dye composed of the above particulate matter has an average particle diameter of 10 after the dispersion step in the preparation of the ink composition.
It may be in the range of ３００300 nm, and not all of the granules need to have a uniform particle size. The above-mentioned average particle size is defined as that a sample prepared by diluting the ink composition about 1,000 times with the same ratio of solvent is placed in a cell having a diameter of 12 mm, and a dynamic light scattering method is used. This is a value measured using a Ne laser under the conditions of a measurement angle of 90 degrees and an integration count of 100.

Further, in the present invention, although the above-mentioned durability such as light resistance and weather resistance is slightly disadvantageous,
From the viewpoint of printing stability and the like, it is desirable to use the organic fluorescent dye in a form dissolved in a solvent. This is because, when the organic fluorescent dye is dissolved in the solvent, problems such as sedimentation of the organic fluorescent dye particles and clogging of the nozzle due to coarse particles are eliminated, and the design of the ink is simplified.

In the present invention, a resin is used in order to improve the dispersibility or solubility of the organic fluorescent dye in the fluorescent ink and to improve the luminous intensity and durability of the printed matter. This resin includes polyvinyl chloride, polyvinyl acetate,
Polyvinyl resins such as polyvinyl butyral, polyvinyl alcohol, polyvinyl pyrrolidone, and copolymers thereof; polymers and copolymers of acrylic acid, methacrylic acid or their esters; acrylonitrile-acrylic copolymer; styrene-acrylic copolymer There are acrylic resins such as coalescing, polyurethane resins, and other, cellulose resins such as methylcellulose, carboxycellulose, and hydroxymethylcellulose, polyether resins, polyester resins, polyimide resins, polyamide resins, and more. Examples thereof include these copolymer resins, casein, gelatin, starch, dextrin, shellac and the like. One of these resins can be used alone or as a mixture of two or more.

Among the above resins, a polyvinyl resin, an acrylic resin, a polyurethane resin or a copolymer thereof is preferable. In particular, as the dispersant for the europium compound, polyvinyl alcohol, styrene-acrylic copolymer, acryl-urethane graft copolymer, and the like are preferable, and the average particle diameter of the organic fluorescent dye is 10 to 10.
It can be adjusted according to the range of 300 nm. Further, when a polyvinylpyrrolidone, a vinylpyrrolidone-based copolymer such as a vinylpyrrolidone-acrylic copolymer or a vinylpyrrolidone-vinyl acetate copolymer is used as a dissolution stabilizer for a europium compound, the solubility of the organic fluorescent dye is improved. This is preferable because it has the effect of stabilizing and increasing the emission intensity.

In the present invention, the resin preferably contains at least one resin having an oxygen permeability coefficient of 1 × 10 ⁻¹⁹ m ² · S ⁻¹ · Pa ⁻¹ or less. When such a low oxygen-permeable resin is used, the organic fluorescent dye is covered with the resin, and the dye is effectively prevented from being oxidized and deteriorated by oxygen in the air in the print layer. Can be. As the antioxidant, quinones are usually used.However, in the case of a solventless fluorescent composition or printed matter that is constantly exposed to the air, the above-described resin having a low oxygen permeability is used rather than the quinones. It is more effective for preventing oxidation of the organic fluorescent dye. In the present invention, the oxygen permeability coefficient of the resin refers to ASTM-D1434-75.
(Measurement method of gas permeability coefficient in plastic films and sheets).

The oxygen permeability coefficient is 1 × 10 ^-19 m ² · S ^-1 · P
Examples of the resin having a ^-1 or less include polyvinyl alcohol, a vinyl resin such as a vinyl alcohol-vinyl acetate copolymer, a vinyl alcohol-vinyl pyrrolidone copolymer, an acrylic resin, and a cellulose resin. There are polyether-based resins, polyester-based resins, polyimide-based resins, polyamide-based resins and the like, and one or more of them are used. Among these, polyvinyl alcohol resins are preferred. Since the oxygen permeability coefficient depends on the degree of saponification of the polyvinyl alcohol-based resin, by adjusting the degree of saponification, a resin having a desired oxygen permeability coefficient can be easily obtained. Generally, a polyvinyl alcohol-based resin having a degree of saponification of 0.2 or more has an oxygen permeability coefficient of 1 × 10
^-19 m ² · S ^-1 · Pa ^-1 or less, and at the same time, it has extremely good solubility in aqueous solvents, which is desirable when applied to fluorescent ink for ink jet printers.

In the present invention, the content of such a resin is preferably 0.1 to 30% by weight based on the total amount of the fluorescent ink. If the content of the resin is less than 0.1% by weight, the dispersibility or solubility of the organic fluorescent dye, the emission intensity and durability of the printed matter become insufficient, and
If it exceeds 0% by weight, the viscosity of the ink becomes too high,
This is because handling becomes difficult, for example, the nozzle is easily clogged.

In the present invention, it is important that the amount of the resin used is such that the weight ratio of the organic fluorescent dye to the resin (weight of the organic fluorescent dye / weight of the resin) is 1/1 to 1/50. It is. When the amount of the resin used is less than 1 part by weight per 1 part by weight of the organic fluorescent dye, when a printed material is produced using this fluorescent ink, the printed layer is not adhered to the printed material having poor ink permeability such as coated paper. If the strength is reduced, and if it is more than 50 parts by weight, the ratio of the resin is too large, and the luminous intensity of the printed matter becomes weak.

In the fluorescent ink of the present invention, HLB1
It preferably contains two or more water-soluble surfactants such as nonionic surfactants and anionic surfactants.
This is a thermal-type on-demand inkjet printer with a heating element on the head.
This is because the generation of bubbles can be assisted to stabilize the ejection of the ink, and in the piezo type in which the piezoelectric element is provided on the head, the meniscus can be kept stable and the ejection of the ink can be stabilized.

The nonionic surfactant having an HLB of 12 or more includes polyoxyethylene such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, and polyoxyethylene higher alcohol ether. Alkyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene alkyl allyl ether such as polyoxyethylene nonyl phenyl ether, polyoxyethylene derivative, oxyethylene / oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan monolaurate, Polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene Nso ruby tristearate,
Examples include polyoxyethylene sorbitan fatty acid esters such as polyoxyethylene sorbitan monooleate and polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitol fatty acid esters such as polyoxyethylene sorbite tetraoleate, glycerin fatty acid esters, and acetylene glycol. Among these, sorbitan-based surfactants and acetylene glycol-based surfactants with less foaming are preferred.

Examples of the anionic surfactant include fatty acid salts such as sodium stearate soap, sodium oleate soap, semi-hardened tallow fatty acid soda soap, sodium lauryl sulfate,
Alkyl sulfates such as triethanolamine lauryl sulfate and higher alcohol sodium sulfate, alkyl benzene sulfonates such as sodium dodecylbenzene sulfonate, alkyl naphthalene sulfonates such as sodium alkyl naphthalene sulfonate, and alkyl sulfosuccinic acids such as sodium dialkyl sulfosuccinate Salts, alkyl diphenyl ether disulfonates such as sodium alkyl diphenyl ether disulfonate, alkyl phosphates such as potassium alkyl phosphate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene alkyl sulfate salts such as polyoxyethylene alkyl sulfate triethanolamine, Alkyl allyl sulfate such as sodium polyoxyethylene alkyl phenyl ether sulfate Ether salts, polyoxyethylene alkyl phosphate esters, naphthalene sulfonic acid formalin condensate. Among these, alkylsulfosuccinates and sulfonates are preferred for stabilizing the generation of bubbles.

One of the above water-soluble surfactants may be used alone, or two or more thereof may be used in combination. The addition amount of these surfactants is preferably 0.1 to 10 parts by weight, and more preferably 0.15 to 100 parts by weight per 100 parts by weight of the fluorescent ink.
-5 parts by weight is more preferred. If the amount is less than 0.1 part by weight, the ink ejection from the nozzle becomes unstable. If the amount is more than 10 parts by weight, the viscosity becomes too high and printing becomes difficult.

In the present invention, it is important to design the pH of the fluorescent ink for an on-demand type ink jet printer in the range of 5 to 8. pH 5
Deviating from 8, the organic fluorescent dye dispersed or dissolved in the ink after storage for a long period of time will cause decomposition or deterioration, and the printed matter printed using the fluorescent ink after storage will be more fluorescent than the initial one. The emission intensity decreases. Designing the pH of the ink to be in the range of 5 to 8 can avoid all such problems.

In the present invention, the pH of the fluorescent ink is adjusted to 5 to 5.
In order to design in the range of 8, a pH adjuster can be used if necessary. For example, water-soluble inorganic salts such as sodium carbonate, calcium carbonate, and sodium chloride; water-soluble inorganic hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide; monoethanolamine, diethanolamine ,
The pH of the fluorescent ink is determined using at least one selected from amino alcohols such as triethanolamine.
Can be adjusted to fall within the range of 5 to 8.

The fluorescent ink of the present invention comprises, as an essential component,
It contains the above-mentioned organic fluorescent dye, resin, water, and a water-soluble organic solvent having a boiling point of 110 ° C. or higher, and may optionally contain various additives as optional components. For example, luminescence intensity improvers, drying accelerators, surface conditioners, defoamers, dot conditioners, viscosity adjusters, crosslinkers, fungicides, preservatives, humectants, rust inhibitors, antistatic agents, lubricants Various known additives such as UV absorbers, antioxidants, charge control agents, and agents for imparting water resistance to printed matter can be used.

Colored resin particles can be used as a luminous intensity enhancer to reduce the absorption of the emitted ultraviolet light or the fluorescent light emitted from the fluorescent dye into the base. For example, acrylic polymers such as acrylic esters and methacrylic esters, vinyl aromatic hydrocarbon polymers such as polystyrene, styrene- (meth) acrylic acid copolymers, styrene-acrylonitrile copolymers, polyethylene, polypropylene, Ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, vinyl chloride
Resin particles such as a vinyl acetate copolymer, a polyamide, a polyacetal, a benzoguanamine resin, an alkyd resin, a melamine resin, and an aromatic sulfonamide resin.
These may be either hollow particles or solid particles. These may be used alone or as a mixture of two or more.

Examples of the antifoaming agent include cationic surfactants such as alkylbenzenesulfonic acid type, alkyl sulfate type, fatty acid salt type and quaternary ammonium salt type, and betaine type surfactant such as alkyl betaine and amine oxide. Agents, organic silicone-based nonionic surfactants such as a methylpolysiloxane copolymer, fatty acid esters such as a sorbitanate ester, polyoxyethylene alkyl ether, and silicone oil.

As the dot adjusting agent, a fluorine-based surfactant which is effective for adjusting the dot diameter when printing on a plastic sheet, bag, bottle or the like is used. The dot diameter when the fluorinated surfactant is added is about 40% smaller than when not added. It is preferable to add 0.05 to 0.5% by weight of a fluorine-based surfactant with respect to the total amount of the fluorescent ink. If it is less than 0.05% by weight, the effect of reducing the dot diameter is small, and if it exceeds 0.5% by weight, the ink composition tends to foam.

The nozzle clogged due to the generation of mold and microorganisms,
A fungicide or a preservative is used to prevent the ink from being disturbed. For example, formalin, sodium dehydroacetate, sodium benzoate, pentachlorophenol sodium salt, 1,2-benzisothiazolin-3-one, 4- (2-nitrobutyl) morpholine,
-(4-thiazolyl) benzimidazole, sodium fluoride, 2-chloroacetamide, α-bromocinnamaldehyde, 2-pyridinethiol-1-oxide sodium salt, triazine compounds and the like.

As the humectant, urea, ethylene urea, thiourea and the like are used. Further, when a metal is used in a portion that comes into contact with the fluorescent ink, benzotriazole, ethylenediaminetetraacetate, or the like is used as a rust inhibitor for preventing metal corrosion. Furthermore, in order to suppress deterioration of the organic fluorescent dye due to long-term storage, a phosphorus-based organic compound or the like can be used separately from the ligand of the organic fluorescent dye.

In the fluorescent ink of the present invention, other water-soluble surfactants other than those described above include alkylamine salts such as coconutamine acetate and stearylamine acetate, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, and alkylbenzyldimethyl. Cationic surfactants such as quaternary ammonium salts such as ammonium chloride; alkyl betaines such as lauryl betaine and stearyl betaine;
Betaine based surfactants such as amine oxides such as lauryl dimethylamine oxide can be used.

The fluorescent ink of the present invention has a viscosity in the range of 1 to 15 mPa · s and a surface tension of 25 to 70 mN · in terms of reliability such as printing stability for an on-demand type ink jet printer. m.

The fluorescent ink of the present invention can be easily prepared according to a conventionally known method using various known stirring devices, dispersers, centrifuges, and filters according to the purpose.
For example, it is manufactured by adding a resin and an organic fluorescent dye to the solvent and dispersing or dissolving the dye. When dispersing the organic fluorescent dye, any commonly used dispersing machine can be used. For example, a medium stirring mill, a high-pressure wet pulverizer, or the like is used.

As an example of dispersing the organic fluorescent dye in a solvent, the resin is dissolved in a solvent of water and a water-soluble organic solvent, and the pH is adjusted to 5 to 8 using an alkali or an acid as appropriate. After adding the organic fluorescent dye to
If necessary, an antifoaming agent, a water-soluble organic solvent, or the like is added, and the mixture is dispersed by a disperser until a desired particle size is obtained. Dispersing media used in the dispersing machine include glass beads, steel beads, ceramic beads and the like.
Ceramic beads of 1 to 1 mm are particularly preferably used. The dispersion conditions in this case are not limited, but it is preferable that the acceleration is 5 to 50 G for a planetary ball mill, the filling rate of ceramic beads is 50 to 90%, and the peripheral speed is 5 to 20 m / s for a sand mill. After the dispersion, if necessary, a surfactant or a water-soluble organic solvent is added to make the mixture uniform, and then the mixture is filtered to produce an ink. A large particle may be removed using a centrifuge instead of the above-mentioned filter.

As one example of dissolving an organic fluorescent dye in a solvent, a resin is added to a solvent of water and a water-soluble organic solvent, and a uniform solution is prepared using a simple stirrer such as a disper. , An organic fluorescent dye is added thereto, and the pH is adjusted to 5 to 8 using an alkali or an acid as appropriate, followed by dissolution. Thereafter, if necessary, a surfactant or a water-soluble organic solvent is added to make the mixture uniform, and then the mixture is filtered to produce an ink. A large particle may be removed using a centrifuge instead of the above-mentioned filter.

The on-demand type ink jet printer to which the fluorescent ink of the present invention is applied includes a piezo type represented by Seiko Epson Corporation and a thermal type represented by Canon Inc. and Hewlett-Packard Japan Limited. and so on. In particular, the above-mentioned piezo type is suitable for a fluorescent ink in which an organic fluorescent dye is dispersed in a solvent as particulate matter having an average particle diameter of 10 to 300 nm,
The above-mentioned thermal type is suitable for a fluorescent ink in which an organic fluorescent dye is dissolved in a solvent.

[0053]

Next, an embodiment of the present invention will be described in more detail. However, the present invention is not limited only to the following examples. In the following, “parts” means “parts by weight”.

Example 1 83.5 parts of water and 10 parts of glycerin (boiling point: 290 ° C.)
2 parts of an acrylic urethane graft copolymer (“3DR-057” manufactured by Taisei Kako Co., Ltd.) was added, and the mixture was stirred and dissolved to form a resin solution. An organic fluorescent dye [Lumilux CD335 (manufactured by Rieder de Haen) (a europium compound which is substantially invisible in the visible light region and emits red light when excited by ultraviolet light, excitation wavelength 365 nm, emission wavelength] 615 nm)], dispersed by a sand mill for 4 hours, filtered using a 0.5 μm filter, and then treated with polyvinyl alcohol (Kuraray “P”
VA205 ") 3 parts, sorbitan surfactant (" Reodol Super TW-S120 "manufactured by Kao Corporation, HLB1
4.9) By adding 0.5 part, the above-mentioned organic fluorescent dye is present as particulate matter having an average particle diameter of 150 nm,
An ultraviolet excitation type fluorescent ink having H of 7.1 was prepared.

Example 2 82.3 parts of water, ethylene glycol (boiling point: 198 ° C.) 1
To 5 parts, 1.6 parts of a styrene-acrylic copolymer ("Johncryl 62" manufactured by Johnson Polymer Co., Ltd.) was added and dissolved by stirring to obtain a resin solution. To this, an organic fluorescent dye [“Rumilux CD302” manufactured by Rieder de Haen Co., Ltd.]
(A benzoxazine-based derivative that is substantially invisible in the visible light region and emits green light when excited by ultraviolet light, excitation wavelength 365 nm, emission wavelength 515 nm)].
Add 8 parts and disperse for 4 hours with a sand mill.
After filtration using a 0.5 μm filter, 0.3 parts of an alkylsulfosuccinate-based surfactant (“Aerosol OT” manufactured by Wako Pure Chemical Industries, Ltd.) is added, so that the organic fluorescent dye has an average particle size of An ultraviolet-excited fluorescent ink having a pH of 7.7, which was present as 200-nm particulate matter, was prepared.

Example 3 An organic fluorescent dye having an average particle diameter of 150 nm was prepared in the same manner as in Example 1 except that no sorbitan surfactant was added.
A UV-excited fluorescent ink having a pH of 7.1 was prepared.

Example 4 40 parts of water, 12 parts of propylene glycol monomethyl ether (boiling point: 120 ° C.), 2-pyrrolidone (boiling point: 245)
C), 2.2 parts of polyvinylpyrrolidone (weight average molecular weight: 3,000) was added and stirred to dissolve to obtain a resin solution. After adding 1.1 parts of thenoyltrifluoroacetone and stirring and dissolving, an aqueous solution obtained by stirring and dissolving 2 parts of sodium acetate and 0.3 part of europium nitrate hexahydrate in 35.2 parts of water, and dimethylethanol 0.7 part of an amine was added and dissolved by stirring. Furthermore, an alkyl sulfosuccinate surfactant ("Aerosol O" manufactured by Wako Pure Chemical Industries, Ltd.)
T "), 0.3 parts, preservative (" Proxel L "manufactured by Zeneca Corporation)
V ") By adding 0.2 part, the above-mentioned organic fluorescent dye was dissolved in the solvent to prepare a UV-excited fluorescent ink having a pH of 6.5.

Comparative Example 1 Instead of glycerin (10 parts), ethyl alcohol (boiling point 7
8 ° C.) Except that 10 parts were used,
An ultraviolet excitation type fluorescent ink having an organic fluorescent dye as a particulate matter having an average particle diameter of 160 nm and a pH of 7.1 was prepared.

Comparative Example 2 The procedure of Example 1 was repeated, except that an appropriate amount of potassium hydroxide was added to adjust the pH to 8.5, and the organic fluorescent dye was present as particulate matter having an average particle diameter of 150 nm, and the pH was 8.5. Was prepared.

Comparative Example 3 The same procedure as in Example 1 was repeated except that the amount of the acrylic urethane graft copolymer was changed to 0.7 part and 3 parts of polyvinyl alcohol was not added, and the average particle size of the organic fluorescent dye was changed. An ultraviolet-excited fluorescent ink having a pH of 7.0, which was present as 180-nm particulate matter, was prepared.

For each of the fluorescent inks prepared in Examples 1 to 4 and Comparative Examples 1 to 3, printing stability, storage stability, fluorescence emission intensity and durability (abrasion resistance, Light resistance) was evaluated. The results were as shown in Table 1.

<Print stability> A cartridge is filled with a fluorescent ink, and “MJ-5” manufactured by Seiko Epson, which is a piezo-type on-demand ink jet printer.
10C ”on A4 size high quality paper
After printing alphanumeric characters on each sheet, the printed matter was irradiated with black light, the state of the printed matter was observed, and the evaluation was made according to the following criteria. 〇: Normal printing can be performed △: Printing is slightly disturbed, but legible ×: Poor ejection, missing or blurring

<Storage Stability> After the above printing test, the printer was stopped and left at room temperature for one week. After the standing, a printing test was performed again, and whether or not the same printing quality as before the standing was obtained was evaluated by observing the state of the printed matter by the following criteria. 〇: The same print quality as before leaving is obtained. △: Slightly worse than before leaving, but practically acceptable. ×: The same printing quality as before leaving is not obtained.

<Fluorescence emission intensity of printed matter>
It is applied to a high-quality paper using a # 4 bar coater, dried, and then subjected to a fluorescence spectrophotometer [“FP75” manufactured by JASCO Corporation.
0 "] to measure the emission intensity. Further, 50 cc of the fluorescent ink is placed in a glass bottle, and 1
After storing for months, the luminescence intensity was measured in the same manner as described above. The larger the value is, the higher the fluorescence emission intensity is.

<Friction Resistance of Printed Material> A fluorescent ink is filled in a cartridge, and alphanumeric characters are printed on A4 size cast-coated paper using the above-mentioned ink jet printer.
After drying for 10 minutes, the printed matter was rubbed back and forth ten times with an eraser. Next, the emission intensity of the printed matter before and after the friction was measured by the above-mentioned fluorescence spectrophotometer, and the maintenance ratio by comparison before and after the friction, that is, [(emission intensity after the friction / emission intensity before the friction) × 100 (%)] Was calculated. The larger the value, the better the friction resistance.

<Light resistance of printed matter> The test sample used in the measurement of the above-mentioned "fluorescence emission intensity of printed matter" was used.
Light fastness tester (“Xenon weatherometer Ci65” manufactured by Atlas Co., Ltd .; irradiance: 0.36 W / at 340 nm
m ² ), the light was irradiated for 1 hour, and the emission intensity was measured with a fluorescence spectrophotometer [“FP750” manufactured by JASCO Corporation]. From the measured values, a maintenance ratio by comparison before and after irradiation, that is, [(emission intensity after irradiation / emission intensity before irradiation) × 100 (%)] was calculated. The larger the value is, the better the light resistance is.

[0067]

As is clear from the results in Table 1, the fluorescent inks of Examples 1 to 4 of the present invention have excellent printing stability and storage stability, and have high emission intensity of the printed matter before and after storage. It can be seen that the durability is excellent. On the other hand, the fluorescent ink of Comparative Example 1 using a water-soluble organic solvent having a low boiling point, the fluorescent ink of Comparative Example 2 in which the pH is in an alkaline region, and the fluorescent ink of Comparative Example 3 in which the amount of resin is reduced. All of the above properties cannot be simultaneously satisfied to a high degree.

[0069]

As described above, the present invention provides an organic fluorescent dye, a resin, and a water-soluble dye having a boiling point of 110 ° C. or more, which are substantially invisible in the visible light range and are excited by ultraviolet rays to emit light in the visible light range. An on-demand type ink jet printer comprising an organic solvent and water, wherein the weight ratio of the dye to the resin is in the range of 1/1 to 1/50 and the pH is in the range of 5 to 8 It is possible to provide a fluorescent ink that has excellent reliability such as printing stability and storage stability that can be applied to inks, and that sufficiently satisfies the durability of the printed matter, so that it is substantially invisible in the visible light region and emits ultraviolet light This provides a special effect that anyone can easily produce a printed material that can be visually recognized by the user.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takahiro Furuya 1-1-88 Ushitora, Ibaraki City, Osaka Prefecture Inside Hitachi Maxell Co., Ltd. (72) Yoshinori Yamamoto 1-188 Ushitora, Ibaraki City, Osaka Hitachi Maxell F term (reference) 2C056 EA13 FC01 2H086 BA52 BA53 BA55 BA59 BA60 4J039 AB01 AB02 AB07 AB09 AD03 AD05 AD06 AD08 AD10 AD11 AE04 BC09 BC10 BC11 BC13 BC14 BC15 BC36 BC53 BE01 BE12 BE22 BE30 CA06 DA02 EA21 EA41 GA44 GA24

Claims (12)

[Claims] An organic fluorescent dye, a resin, a water-soluble organic solvent having a boiling point of 110 ° C. or higher, and water, which are substantially invisible in the visible light region and emit light in the visible light region when excited by ultraviolet light. Wherein the weight ratio of the organic fluorescent dye to the resin (weight of the organic fluorescent dye / weight of the resin) is 1/1 to 1/5.
A fluorescent ink for an ink jet printer, wherein the pH is 0 and the pH is in the range of 5 to 8. 2. The organic fluorescent dye has an average particle diameter of 10 to 300.
2. The fluorescent ink for an ink jet printer according to claim 1, wherein the fluorescent ink is dispersed in a solvent as particles having a particle size of nm. 3. The fluorescent ink according to claim 1, wherein the organic fluorescent dye is substantially dissolved in a solvent. 4. When the organic fluorescent dye is excited by ultraviolet rays,
The fluorescent ink for an inkjet printer according to any one of claims 1 to 3, which is a europium compound having an emission center wavelength of 5 ± 20 nm. 5. The fluorescent ink for an inkjet printer according to claim 1, wherein the europium compound is a complex having a phosphorus-based organic compound as a part of a ligand. 6. The fluorescent ink for an ink jet printer according to claim 1, wherein the resin is at least one selected from a polyvinyl resin, an acrylic resin, a polyurethane resin, and a copolymer thereof. . 7. A resin having an oxygen permeability coefficient of 1 × 10 ^−19.
The fluorescent ink for an inkjet printer according to any one of claims 1 to 6, further comprising at least one resin having m ² · S ^-1 · Pa ^-1 or less. 8. The method according to claim 1, which comprises a water-soluble surfactant.
7. The fluorescent ink for an inkjet printer according to any one of 7. 9. The fluorescent ink according to claim 8, wherein the water-soluble surfactant is a nonionic surfactant having an HLB of 12 or more and / or an anionic surfactant. 10. The fluorescent ink for an inkjet printer according to claim 9, wherein the nonionic surfactant having an HLB of 12 or more is a sorbitan surfactant and / or an acetylene glycol surfactant. 11. The fluorescent ink according to claim 9, wherein the anionic surfactant is a sulfonate. 12. The fluorescent ink for an ink jet printer according to claim 1, which is used for an on-demand type ink jet printer.