JP2002146258A - Water-based ink composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-based ink composition less hazardous, friendly to the global environment and excellent in solubility and printing stability. SOLUTION: In the water-based ink composition comprising as solvents an alcohol and water, the content of ingredients other than the alcohol and water is at least 5 wt.% but less than 10 wt.% based on the water-based ink composition, and the viscosity of the water-based ink composition is at least 1 cP but less than 8 cP.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink composition having excellent printing stability and being friendly to the global environment. More specifically, the present invention relates to an aqueous ink composition used for an inkjet printer.

[0002]

2. Description of the Related Art In recent years, various kinds of cards, such as security cards utilizing the properties of fluorescent materials, factory automation, and various kinds of cards used for managing substances, have been actively developed. There is also an example in which a barcode is printed with ink using a fluorescent material, and a system for distributing articles by code management is used for mail or the like.

As a luminescent material used for these, a fluorescent complex in which a low-molecular ligand is coordinated to a rare earth element as a luminescent center has been used and conventionally made into an ink. For example,
These are described in JP-B-54-22336, JP-A-9-188835, JP-A-8-239609, and JP-T-11-510213. These fluorescent complexes are uniformly dissolved as a dye in a liquid such as water or a solvent, or uniformly dispersed as a pigment to form an ink.

Since these inks mainly use an organic solvent as a solvent, they have problems such as pollution such as air pollution, occupational safety and health such as poisoning of organic solvents, and danger of ignition explosion. As one means for solving these problems, there has been proposed an aqueous ink using water and an aqueous solvent as a solvent. However, these aqueous inks have the drawbacks that their solubility is not sufficient, and that head clogging tends to occur during printing, resulting in poor printing stability.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a water-based ink composition which has low danger and is environmentally friendly and has excellent solubility and printing stability.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and have found that the content of components other than alcohol or water in an aqueous ink composition using alcohol and water as a solvent. Found an aqueous ink composition in which the content of the aqueous ink composition was 5 wt% or more and less than 10 wt%, and the viscosity of the aqueous ink composition was 1 cp or more and less than 8 cp, and completed the invention.

[0007] The aqueous ink composition of the present invention is characterized by using alcohol and water as main solvents. The use of alcohol and water does not use organic solvents having a low flash point such as acetone, methyl ethyl ketone, and ethyl acetate as solvents. Components other than the solvent consisting of alcohol and water in the aqueous ink composition mainly include additives such as resins, dyes, and binders.

It is essential that the content of components other than the solvent in the aqueous ink composition of the present invention is 5% or more and less than 10%. If it is less than 5%, the amount of the dye or resin must be reduced, which is not preferable. For example, if the amount of the dye is small, sufficient visibility of the printed matter cannot be obtained. On the other hand, if the amount of the resin is small, the solubility of the dye and the fixability of the printed matter on the film are insufficient. On the other hand, if the content is 10% or more, the solid content of the resin and the dye is too large, so that clogging of the head and the like are easily caused, and the printing stability is not good.

It is essential that the viscosity of the ink composition is 1 cp or more and less than 8 cp. Outside of the above range, head contamination during continuous printing is severe, and printing stability is poor. It is preferably 1.5 cp or more and less than 5 cp.

[0010] The alcohol content in the aqueous ink composition of the present invention is preferably 1% by weight or more and less than 60% by weight.
0 wt% or more and less than 50 wt% are more preferable. Further, the alcohol is preferably a saturated monohydric alcohol having 1 to 3 carbon atoms or a denatured alcohol.

The flash point is preferably 23 ° C. or higher.
If the alcohol content is 60 wt% or more, the flash point is 23 ° C. or less, and the flammability is high, and the danger increases. 1wt
% Or less is not preferable because the dye and the like do not dissolve. Further, the ink drying property is extremely slow, which is not preferable.

The alcohol is preferably a saturated monohydric alcohol having 1 to 3 carbon atoms or a modified alcohol, and most preferably ethanol having 2 carbon atoms. Alcohols having 3 or more carbon atoms are not preferred because they have low solubility in water. In addition, the drying property is undesirably slow. The ink composition of the present invention may contain a resin. As the resin, polyvinylpyrrolidone, polyacrylic acid, polyacrylate, polyurethane, polyether, polyvinyl alcohol and their copolymers, or derivatives thereof are preferable,
Polyvinylpyrrolidone, polyacrylic acid, polyurethane and their copolymers, or their derivatives are more preferred because of their good solubility and printing stability. Further, ink compositions using these resins are excellent in fixing property of printed matter and weather resistance.

The ink composition of the present invention may contain a resin. As the resin, polyvinylpyrrolidone, polyacrylic acid, polyacrylate, polyurethane, polyether, polyvinyl alcohol and their copolymers or derivatives thereof are preferable, and polyvinylpyrrolidone, polyacrylic acid, polyurethane and their copolymers are preferred. Or their derivatives are more preferred because of their good solubility and printing stability. Further, ink compositions using these resins are excellent in fixing property of printed matter and weather resistance.

The weight average molecular weight of the resin is 500 or more and 500 or more.
Less than 00 is preferable, 800 or more and less than 10,000 is preferable, and 1000
Most preferably, it is less than 5000. If the molecular weight is less than 500,
Insufficient solubility or dispersion stability or weather resistance in aqueous solvent. On the other hand, when the molecular weight is 50,000 or more, the viscosity becomes high, and when applied to an ink composition for inkjet, it causes ejection failure and the like, which is not so preferable.

When the water-based ink composition of the present invention is used as a fluorescent ink, it further contains a fluorescent dye. Examples of the fluorescent dye include a β-diketone compound and a rare earth element.

The β-diketone compound includes tenoyl trifluoroacetone, naphthoyl trifluoroacetone,
Benzoyltrifluoroacetone, methylbenzoyltrifluoroacetone, furoyltrifluoroacetone,
Pivaloyltrifluoroacetone, hexafluoroacetylacetone, trifluoroacetylacetone, fluoroacetylacetone, heptafluorobutanoylpivaloylmethane, 8-hydroquinoline, 8-mercaptoquinoline, tri-n-butyl phosphate, tri-n-butylphosphine Oxides, tri-n-octylphosphine oxide, di-n-butylsulfoxide, pyridine, α-picoline, β-picoline, γ-picoline, piperidine, quinoline and the like. Among these, tenoyl trifluoroacetone, naphthoyl trifluoroacetone, and benzoyl trifluoroacetone are particularly preferred.

Examples of the rare earth element which is the emission center of the fluorescent dye include europium, dysprosium, terbium, neodymium, pseodymium, samarium, saddle, holmium, erbium and thulium. These elements can form a fluorescent dye stably and can obtain a sufficient emission intensity. When considering the application of the fluorescent dye of the present invention to security, FA, various cards, bar code systems, etc., europium is the most preferable among the above rare earths. When europium is used as the emission center, the emission is red at 615 ± 20 nm. Therefore, the printed mark emits the visible light on the longer wavelength side when excited by ultraviolet light, so that it is less affected by the color of the base and can be detected with high sensitivity by a silicon photodiode or the like. Blue or green emission may be poor in detectability. When a mark that emits blue light is formed on white paper impregnated with a fluorescent whitening agent, the base also emits light, so that the difference in the amount of emitted light is substantially small, and detection may not be possible. In addition, upon detecting visible light to be emitted,
If a silicon photodiode, which is generally inexpensive and easily available, is used as a photoelectric conversion element, the light receiving sensitivity of visible light is lower on the short wavelength side than on the long wavelength side, and visible light of a relatively short wavelength of blue or green is used. Light is less than half the sensitivity of visible light on the long wavelength side near 600 nm, and it may be difficult to obtain sufficient detection sensitivity.

The solvent used in the aqueous ink composition of the present invention may be acetone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, propyl acetate, dioxane, dimethyl sulfoxide, dimethyl imidazo, in addition to water or alcohol, in order to enhance dye solubility. Less than 5 wt% of a water-soluble solvent such as lydinone, methoxyethanol, ethoxyethanol, methoxypropanol, butanol, ethylene glycol and propylene glycol may be added. Addition of 5 wt% or more is not preferable because harmfulness and danger may increase.

The above-mentioned aqueous ink composition contains a binder, a charge-imparting agent, a pH adjuster, a fluorescent sensitizer, a surfactant, an ink defoaming agent, a bactericide, a quick-drying agent, and an oxidizing agent which are usually contained in the ink composition. Various additives such as an inhibitor may be included. As the binder, for example, a polyvinyl resin, a phenol resin, a polyester resin, an acrylic resin,
Cellulose-based resins, polyamides, maleic resins and the like can be mentioned. Examples of the charge control agent include Li salts such as LiNO3, K salts such as KCN and KSCN, and cationic compounds such as tetraphenylphosphonium bromide. Examples of the pH adjuster include amine compounds such as diethanolamine, triethanolamine and triethylenetetramine, as well as amide compounds and carbonates. Examples of the fluorescent sensitizer include phosphine oxide compounds, phosphine sulfide compounds, and phosphorus-based organic compounds such as phosphine compounds.

In the production of the ink composition, a container driving medium mill such as a ball mill, a centrifugal mill, and a planetary ball mill, a high-speed rotation mill such as a sand mill, a medium stirring mill such as a stirring tank mill, and a simple method such as a disperser are used. It can be manufactured using a dispersing machine.

The printed matter of the above ink composition is completely or substantially invisible to the naked eye and cannot be confirmed.
Printed material using rare earth europium etc. as the luminescent center,
When irradiated with ultraviolet light, it is possible to confirm printing only after emitting red light in the visible light region. When neodymium is used as the rare earth element at the emission center, it is excited by infrared light and emits light in the infrared light region, and can be detected only by a dedicated detector. These printed matter of the present invention, which emit visible light and infrared light, are usually invisible.
A, can be applied to various things such as various cards.

When a bar code is printed using the above ink composition, it can be used as an improvement in a black and white bar code.
Conventional black-and-white barcodes have drawbacks such as impairing the appearance of articles, but they can be avoided. Barcode printing using the above ink composition can also be used for postal items to which a system for distributing articles by code management is applied.

The method for producing the printed matter may be any ordinary printing method. For example, inkjet printing, offset printing, gravure printing, thermal transfer printing, and the like. In particular, the ink composition of the present invention is suitable for inkjet printing. Since the ink composition of the present invention is dissolved or stably dispersed in an aqueous solvent, the ink composition can be stably discharged without causing nozzle clogging of an inkjet printer.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION

EXAMPLES Examples of the present invention will be described below in more detail. In the following, “parts” means “parts by weight”.

(Example 1) Tenoyl trifluoroacetone 10.6 parts Ethanol 312.0 parts Europium nitrate hexahydrate 3.0 parts Ion-exchanged water 255.6 parts Hydroxylation while stirring the above components with a magnetic stirrer The pH was adjusted to 6 to 7 by adding 1.8 parts of sodium. Thereafter, 2.3 parts of resin (polyvinylpyrrolidone (weight average molecular weight: 2000)) was added, and the mixture was stirred at 60 ° C. for 3 hours, and then filtered.
I got Further, 0.2 parts of BYK-348 (manufactured by BYK-Chemie) was added to the obtained phosphor liquid A, and the mixture was stirred at 25 ° C. for 1 hour and then filtered to obtain ink composition A.

(Example 2) Tenoyl trifluoroacetone 10.6 parts Ethanol 312.0 parts Europium nitrate hexahydrate 3.0 parts Ion-exchanged water 255.6 parts Hydroxylation while stirring the above components with a magnetic stirrer The pH was adjusted to 6 to 7 by adding 1.8 parts of sodium. Thereafter, 33.5 parts of resin: polyvinylpyrrolidone (weight average molecular weight: 2,000) was added, and the mixture was stirred at 60 ° C. for 3 hours, and then filtered.
I got Further, 0.2 parts of BYK-348 (manufactured by BYK-Chemie) was added to the obtained phosphor liquid B, and the mixture was stirred at 25 ° C. for 1 hour, followed by filtration to obtain an ink composition B.

(Example 3) Tenoyl trifluoroacetone 7.1 parts Ethanol 312.0 parts Dimethylimidazolidinone 12.6 parts Europium nitrate hexahydrate 3.0 parts Ion-exchanged water 255.6 parts While stirring with a tick stirrer, 1.1 parts of sodium hydroxide was added to adjust the pH to 6 to 7. Thereafter, 18.0 parts of a resin: polyvinylpyrrolidone (Wako Pure Chemical Industries, average molecular weight 25,000) was added, and the mixture was stirred at 60 ° C. for 3 hours, filtered, and then subjected to filtration.
I got Further, to the obtained phosphor liquid C, a leveling agent: 0.2 part of BYK-348 manufactured by BYK-Chemie was added, and the mixture was stirred at 25 ° C. for 1 hour and then filtered to obtain an ink composition C.

Example 4 "Europime nitrate" of Example 1
Ink composition D was obtained in the same manner as above except that “hexahydrate” was changed to “neodymium nitrate hexahydrate”.

(Comparative Example 1) Tenoyl trifluoroacetone 10.6 parts Ethanol 312.0 parts Europium nitrate hexahydrate 3.0 parts Ion-exchanged water 255.6 parts Hydroxylation while stirring the above components with a magnetic stirrer The pH was adjusted to 6 to 7 by adding 1.8 parts of sodium. Thereafter, 12.0 parts of resin: polyvinylpyrrolidone (weight average molecular weight: 2,000) was added, and the mixture was stirred at 60 ° C. for 3 hours, and then filtered.
I got Further, a leveling agent: 0.2 part of BYK-348, manufactured by BYK-Chemie, was added to the obtained phosphor liquid E, and the mixture was stirred at 25 ° C. for 1 hour, followed by filtration to obtain an ink composition E.

(Comparative Example 2) Tenoyl trifluoroacetone 10.6 parts Ethanol 312.0 parts Europium nitrate hexahydrate 3.0 parts Ion-exchanged water 255.6 parts Hydroxylation while stirring the above components with a magnetic stirrer The pH was adjusted to 6 to 7 by adding 1.8 parts of sodium. Thereafter, 48.0 parts of resin: polyvinylpyrrolidone (weight average molecular weight: 2000) was added, and the mixture was stirred at 60 ° C. for 3 hours, and then filtered.
I got Further, 0.2 parts of BYK-34 (manufactured by BYK-Chemie) was added to the obtained phosphor liquid F, and the mixture was stirred at 25 ° C. for 1 hour, followed by filtration to obtain an ink composition F.

[0031]

[Table 1]

(Comparative Example 3) Tenoyl trifluoroacetone 4.2 parts Ethanol 312.0 parts Europium nitrate hexahydrate 1.2 parts Ion-exchanged water 255.6 parts Hydroxylation while stirring the above components with a magnetic stirrer The pH was adjusted to 6 to 7 by adding 0.9 parts of sodium. Thereafter, 22.3 parts of resin: polyvinylpyrrolidone (weight average molecular weight: 2,000) was added, and the mixture was stirred at 60 ° C. for 3 hours, and then filtered.
I got Further, 0.2 parts of BYK-348 (manufactured by BYK-Chemie) was added to the obtained phosphor liquid G, and the mixture was stirred at 25 ° C. for 1 hour, followed by filtration to obtain an ink composition G.

(Comparative Example 4) Tenoyl trifluoroacetone 10.6 parts Ethanol 510.8 parts Europium nitrate hexahydrate 3.0 parts Ion-exchanged water 56.8 parts Hydrolysis while stirring the above components with a magnetic stirrer The pH was adjusted to 6 to 7 by adding 1.8 parts of sodium. Thereafter, 22.3 parts of resin: polyvinylpyrrolidone (weight average molecular weight: 2,000) was added, and the mixture was stirred at 60 ° C. for 3 hours, and then filtered.
I got Further, 0.2 parts of BYK-348 (manufactured by BYK-Chemie) was added to the obtained phosphor liquid H, and the mixture was stirred at 25 ° C. for 1 hour, followed by filtration to obtain an ink composition H. (Flash Point of Ink Composition) The flash point was measured in accordance with the closed-tag method. (Viscosity of ink composition) The viscosity at 25 ° C was measured using an E-type viscometer. (Solubility of Ink Composition) The sample dissolved at 25 ° C. was evaluated as “○”, and the sample not dissolved was evaluated as “X”. (Printing stability) Domino inkjet printer
Using CB3, continuous printing was performed, and those that can be printed neatly even after 8 hours were rated as ○, and those that were dirty (such as prints applied) were rated as x. (Emission intensity of printed matter) The emission intensity of the printed matter was measured by a fluorescence spectrophotometer ("FP750", manufactured by JASCO Corporation).
The emission intensity of the printed matter was evaluated by printing the ink composition on plain paper (XEROX) using a Domino inkjet printer CB3. The emission intensity was compared with the ink composition A of Comparative Example 1 as 100. Except for the printed matter using the ink composition D, the excitation light of 365 nm was irradiated, and the emission peak intensity at 615 nm was obtained.
m of excitation light, and the emission peak intensity at 1065 nm was used for comparison.

From the above results, the aqueous ink compositions A to D of the present invention had a low danger of a flash point of 23 ° C. or more, a low viscosity of 1 cp to less than 8 cp, and good solubility. In addition, the printed matter stability and the printed matter emission intensity were also excellent.
Conventionally, the ink composition E was insufficient in solubility and printing stability. Ink composition F had a high viscosity and printing stability was insufficient. The ink composition G had insufficient light emission intensity on printed matter. Ink composition H had a low flash point and a high danger.

[0035]

According to the present invention, an aqueous ink composition which is environmentally friendly with little harmfulness and danger, and has excellent solubility and printing stability can be obtained.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2C056 EA19 FC01 2H086 BA52 BA53 BA55 BA59 BA60 BA62 4J039 AD06 AD09 AD10 AD20 AE04 AE07 BC07 BC10 BC18 BC50 BC72 CA06 DA05 EA19 EA28 EA44 EA45 EA46 GA03 GA06 GA24

Claims (7)

[Claims] In an aqueous ink composition using alcohol and water as a solvent, the content of components other than alcohol or water is 5% by weight or more and less than 10% by weight with respect to the aqueous ink composition, and the viscosity of the aqueous ink composition is reduced. An aqueous ink composition having a content of 1 cp or more and less than 8 cp. 2. The method according to claim 1, wherein the content of the alcohol is 1% by weight or more and less than 60% by weight with respect to the aqueous ink composition, and the alcohol is a saturated monohydric alcohol having 1 to 3 carbon atoms or a denatured alcohol. The aqueous ink composition as described in the above. 3. The aqueous ink composition according to claim 1, wherein the flash point is 23 ° C. or higher. 4. The composition further comprises a resin, wherein the resin is polyvinylpyrrolidone, polyacrylic acid, polyacrylate,
The aqueous ink composition according to claim 1, comprising at least one of polyurethane, polyether, polyvinyl alcohol, a copolymer thereof, and a derivative thereof. 5. The aqueous ink composition according to claim 4, wherein the resin has a weight average molecular weight of 500 or more and less than 50,000. 6. The aqueous fluorescent ink composition according to claim 1, further comprising a fluorescent dye. 7. The aqueous fluorescent ink composition according to claim 6, wherein the fluorescent dye comprises a β-diketone compound and a rare earth element.