JP2002226751A - Ink for inkjet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink satisfying in all respects of quick drying, print quality, and print fluorescence intensity, for an inkjet printer ink containing a fluorescent compound, capable of presenting reflected colors under visible light and emitting fluorescence under ultraviolet rays, a surfactant, and water. SOLUTION: The surfactant is a mixture of a 1st compound described by formula (1) wherein R is an isobutyl group and a 2nd compound described by formula (1) wherein R is an ethyl group. The mixture is so prepared that, when the content by percentage of the 1st compound is A wt.% and that of the 2nd compound is B wt.%, both A and B are more than zero and that the relationship between A and B satisfies 5.0<=16A+B<=6.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink for an ink jet printer containing a fluorescent compound which gives a reflected color under visible light and emits fluorescence by irradiation with ultraviolet rays.

[0002]

2. Description of the Related Art Ink-jet printing is to directly print characters, figures, and images on a recording medium by discharging ink as droplets from fine nozzles. As a method of inkjet printing, a drop-on-demand method and a continuous method are known.

The drop-on-demand system is a system in which ink is ejected as needed, and an ink jet printer of this system is used as a printer for a personal computer or the like. The continuous method is a method in which continuously ejected ink particles are charged according to an electric signal, and only necessary ink is ejected from the ink onto paper, and is a method excellent in high-speed printing.

[0004] In a conventional ink for an ink jet printer, a colorant which absorbs a part of the visible light to give a reflection color under a visible light is contained at a density at which the color of the printed matter is visible to the naked eye. I have. On the other hand, Japanese Patent Application Laid-Open No. Sho 58-4
No. 9765 discloses a fluorescent compound which gives a reflected color under visible light and emits fluorescent light by ultraviolet irradiation so that the recording density on a recording paper becomes 0.1 or less in optical density (that is, printing density). Inks for ink jet printers are described in which the color is contained at a content which is normally invisible to the naked eye under light.

If such ink and ink for an ordinary ink jet printer are ejected from a plurality of nozzles of an ink jet head, for example, a character to be seen by a human and a character to be read by a machine without being seen by a human are simultaneously printed. Can be easily done. Here, the printing method is a drop-on-demand method, and the following characteristics are required for a fluorescent ink used in a machine-readable inkjet printer.

(1) A high quality image can be obtained on plain paper. (2) The ink is fixed quickly and high-speed printing is possible. (3) Stable discharge without discharge bends (ink is discharged obliquely instead of directly below) and missing dots without clogging nozzles. (4) A fluorescence intensity that can be read by a machine with an appropriate light source should be obtained.

Hitherto, for the purpose of (2), many inks have been proposed in which an organic solvent or a surfactant called a penetrant is added to the ink. Among them, when an acetylene glycol (acetylene diol) -based surfactant is used, it is possible to obtain printing without bleeding while securing the printing speed by penetrating the ink deeply in the thickness direction of the paper. It has been known. This is described in Japanese Patent Application Laid-Open No.
No. 59071, for example.

For the purpose of (4), for example, an ink composition using transparent solid fine particles having a particle size of 1 μm or less is disclosed in
No. 78022. In this publication, it is described that by adding fine particles, the fine particles adhere to the surface of the paper, and the fluorescent dye is adsorbed on the surface of the paper, thereby increasing the fluorescent dye concentration and increasing the emission intensity upon irradiation with ultraviolet light. . Therefore, in this case, if an acetylenic diol-based surfactant is used for the purpose of (2), it is considered that the fluorescent compound of the fluorescent ink permeates deep into the paper, and a sufficient fluorescence emission intensity cannot be obtained. .

[0009]

As described above, in the ink for a drop-on-demand type ink-jet printer containing the above-mentioned fluorescent compound, the quick-drying property of the ink after printing, the printing quality, and the fluorescent emission of the printing are as follows. Although there is a demand for a product that is satisfactory in all aspects of strength, there is still room for further improvement in the inks described in the above publications.

[0010] The present invention relates to an ink for an ink jet printer comprising a fluorescent compound which gives a reflected color under visible light and emits fluorescence by emitting ultraviolet light (emits fluorescence to emit color), a surfactant, and water. It is another object of the present invention to provide an ink that can satisfy all of the following requirements in terms of the quick drying property of the ink after printing, the printing quality, and the fluorescent emission intensity of printing.

[0011]

In order to solve the above-mentioned problems, the present invention comprises a fluorescent compound which gives a reflection color under visible light and emits fluorescence by irradiation with ultraviolet light, a surfactant, and water. In the ink for an ink jet printer, the surfactant is an acetylene diol (acetylene glycol) surfactant represented by the following chemical formula (1), wherein R is an isobutyl group (—CH ₂ CH (CH ₃ ) C).
H ₃ ) and R is an ethyl group (—CH ₂ C)
H ₃ ), and when the content of the first compound in the ink is A (% by weight) and the content of the second compound is B (% by weight), A and B Is "0"
Provided is an ink for an ink-jet printer, which is larger and is configured so that the relationship between A and B satisfies the following equation (1).

[0012]

Embedded image

5.0 ≦ 16A + B ≦ 6.5 ‥‥ (1) The surface tension of the first compound is 26 to 38 mN / m, and the surface tension of the second compound is 50 mN / m or more.
According to the present invention, by using a surfactant mixed so that the relationship between the contents A and B of the first compound and the second compound in the ink satisfies the expression (1), the visible light can be reduced. A fluorescent compound that gives a reflected color under, emits fluorescent light by ultraviolet irradiation, a surfactant, and an ink for an inkjet printer containing water, as a quick-drying ink after printing,
An ink that satisfies all aspects of print quality and print fluorescence emission intensity can be obtained.

If the value of "16A + B" is less than 5.0, the effect of improving ink permeability is not sufficient. If the value of "16A + B" exceeds 6.5, bleeding occurs or the ink ejection state is adversely affected, resulting in poor print quality. I do. As the first compound constituting the surfactant used in the present invention, Air Products and Chemical
"Surfinol 104" and "Surfinol TG" manufactured by s.Inc.
G "is commercially available. The second compound is Air Prod
"Surfinol 8" manufactured by ucts and Chemicals. Inc.
2 "is commercially available.

The content of the surfactant in the ink of the present invention is preferably in the range of 0.3% by weight or more and 5.0% by weight or less based on the total amount of the ink. The ratio is appropriately determined according to the required characteristics, but is preferably 0.1% by weight or more and 10.0% by weight or less. For example, when it is desired to make the printed contents invisible under visible light, it is usually required to be 1.0% by weight or less, though it depends on the coloring power of the fluorescent compound. In this case, it is desirable to use, as the fluorescent compound, a fluorescent compound that gives a yellow reflection color with low relative luminous efficiency.
On the other hand, when the content of the fluorescent compound in the ink is less than 0.1% by weight, the emission intensity when irradiated with ultraviolet rays is small, and the visibility is poor.

In the case where fluorescent light is emitted while ensuring the visibility of the print for the purpose of preventing forgery of the printed matter by, for example, color copying, the content of the fluorescent compound in the ink is printed under visible light. The content should be such that the contents can be confirmed. For that purpose, the content of the fluorescent compound in the ink needs to be usually 1.0% by weight or more, although it depends on the coloring power of the fluorescent compound. On the other hand, if the addition amount is more than 10.0% by weight, clogging at the nozzle tip is likely to occur even when a humectant or the like is added, and the printing reliability decreases.

In the conventional ink composition, when the content of the fluorescent compound is large, concentration quenching occurs and the fluorescence emission intensity is greatly reduced, and in some cases, the fluorescence emission intensity sufficient for practical use cannot be obtained. In the ink composition, by specifying the surfactant, the fluorescent compound in the discharged ink penetrates not only on the surface of the paper surface but also inside, and is widely distributed.
If the content of the fluorescent compound in the ink is 10% by weight or less, a significant decrease in fluorescence emission intensity due to concentration quenching does not occur.

In the present invention, the fluorescent compound includes
Dyes called fluorescent dyes, fine particle fluorescent pigments in which fine particles made of synthetic resin are dyed with a fluorescent dye, and pigments called fluorescent pigments can be used. As a commercially available product, "Kayarus Light Ye" manufactured by Nippon Kayaku Colors Co., Ltd.
llow F8G, Kayanol Brilliant Flavine FL
, "Kayaset Flavine F2G", "Kayaset Flavine
FN ”,“ LUMIKOL NKW-3000 ”manufactured by Nippon Fluorescent Chemicals Co., Ltd.
Series "and" Shinloich Color "manufactured by Shinloich Co., Ltd.

Further, the ink of the present invention preferably contains a polyhydric alcohol in order to prevent nozzle clogging. Specific examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol having a molecular weight of 2000 or less,
1,3-propylene glycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, glycerin, thiodiglycol, mesoerythritol And pentaerythritol.

Among them, glycerin, 1,5-pentanediol, diethylene glycol, or thiodiglycol, and a mixture thereof can appropriately control the viscosity of the ink composition and effectively prevent nozzle clogging. Is preferred. The addition amount of these polyhydric alcohols is preferably 3 to less than 40% by weight, more preferably 5 to 30% by weight, based on the ink composition.

[0021]

Embodiments of the present invention will be described below. As a fluorescent compound constituting the ink of the present invention, "LUMIKOL NKW" manufactured by Nippon Fluorescent Chemical Co., Ltd.
-3005 "was prepared. This is a dispersion in which the yellow fine-particle fluorescent pigment is dispersed in water, and has a solid content of 42% by weight.

As the first compound of the surfactant constituting the ink of the present invention, an aqueous solution containing 37.5% by weight of the first compound "Surfinol 104H (Air Products and C)
chemicals. Inc.) "was prepared. As the second compound of the surfactant constituting the ink of the present invention, “Surfinol 82 (Air Products and
Chemicals. Inc.) "was prepared.

Glycerin and n-methyl-2-pyrrolidone were prepared as other additives. These components were mixed with ultrapure water, and the content of each component was adjusted to 6.0% by weight of the fluorescent compound, 8.0% by weight of n-methyl-2-pyrrolidone, and 20.0% by weight of glycerin. %, And a large number of inks were prepared in which the content A of the first compound (% by weight) and the content B of the second compound (% by weight) were changed.

The contents A and B of the first compound and the second compound
Was varied as shown in Table 1 below. Further, the weight of the effect of improving the permeability of the ink with respect to the second compound of the first compound was set to 16 times, and the permeability evaluation value (16A + B) of the surfactant composed of a mixture of both compounds was calculated. A printing test was performed using a large number of the produced inks, and the ink permeability (quick drying), printing quality, and fluorescence intensity of the printing after printing were examined. The printing test was performed on a drop-on-demand type inkjet printer "Epson TM-J8".
000 "was used to print characters for a printing test on a register paper," 45 kg cash register paper "manufactured by Oji Paper Co., Ltd.

The permeability of the ink after printing is evaluated by visually observing the stain on the printed surface after printing the solid image, and “印字” when the printed surface is not stained, and when the printed surface is dirty due to insufficient quick drying. Indicates “×”. The printing quality is 365 nm wavelength on the printing surface.
By irradiating the ultraviolet light to emit fluorescent light, the printed characters were raised, and the characters were enlarged with a stereoscopic microscope, and the print density, dot shape, and dot size were comprehensively determined.

Regarding the fluorescence emission intensity of the printed matter, a hand-held UV lamp SLUV-4 (manufactured by Inuchi Seieido Co., Ltd.) was used to visually illuminate the printed surface with ultraviolet light having a wavelength of 365 nm from 15 cm above the printed matter. Evaluation was made as to whether light emission could be confirmed. A case where a sufficiently large fluorescent light emission was observed was evaluated as “、”, and a case where only a fluorescent light emission that could somehow be confirmed with the naked eye was obtained was evaluated as “x”.

The results are shown in Table 1 below.

[0028]

[Table 1]

As can be seen from this table, "16A + B"
Is not less than 5.0 and not more than 6.5, quick drying (permeability),
An ink that satisfies all aspects of printing quality and fluorescence emission intensity can be obtained. If "16A + B" is less than 5.0, the quick-drying property and the printing quality will be poor. When "16A + B" exceeds 6.5, the quick-drying property is excellent, but the printing quality is poor. In addition, No. 1-1, 1-6, 1-7, 1-11, 1
Regarding -12 and 1-16, evaluation of the fluorescence emission intensity was not performed because the printing quality was poor. In addition, all samples do not generate bubbles during ink production,
The ink productivity was good.

Next, using each of the above components, n-methyl-2
-The content of pyrrolidone is 8.0% by weight, the content of glycerin is 20.0% by weight, the content A of the first compound is 0.5% by weight, and the content B of the second compound is 2.5% by weight. A large number of inks were prepared by changing the content of the fluorescent compound as shown in Table 2 below. A printing test was performed using each of the produced inks by the same method as described above, and the fluorescence emission intensity of the printed matter was measured by the same method.

The results are shown in Table 2 below.

[0032]

[Table 2]

Next, "Kayarus LightYellow F8G" manufactured by Nippon Kayaku Colors Co., Ltd. was prepared as a fluorescent compound. Otherwise, each of the above components was used, and n-methyl-2-
Pyrrolidone is 8.0% by weight, glycerin is 20.0% by weight, the content A of the first compound is 0.5% by weight, and the content B of the second compound is 2.5% by weight.
Numerous inks were prepared by changing the content of the fluorescent compound as shown in Table 3 below. A printing test was performed using each of the produced inks by the same method as described above, and the fluorescence emission intensity of the printed matter was measured by the same method.

The results are shown in Table 3 below.

[0035]

[Table 3]

Next, "Kayaset Flavine F2G" manufactured by Nippon Kayaku Colors Co., Ltd. was prepared as a fluorescent compound.
Other than the above, each of the above-mentioned components was used, n-methyl-2-pyrrolidone was 8.0% by weight, glycerin was 20.0% by weight, the content A of the first compound was 0.5% by weight, and the content of the second compound was 0.5% by weight. Rate B was 2.5% by weight, and the content of the fluorescent compound was changed as shown in Table 4 below.
A number of inks were made. A printing test was performed using each of the produced inks by the same method as described above, and the fluorescence emission intensity of the printed matter was measured by the same method.

The results are shown in Table 4 below.

[0038]

[Table 4]

In the ink of the present invention, regarding the surfactant, the relationship between the first compound and the second compound is “5.
In addition to satisfying 0 ≦ 16A + B ≦ 6.5 ”,“ A> 0 ”, and“ B> 0 ”, the concentration of the first and second compounds alone in the ink is“ 0.1 ≦ A ≦ 0.4 "and" 1.0≤B≤4.0 ".
If the content of the first compound is too large, the solubility in water becomes low, so that even if a large amount of the organic solvent is added, the uniformity of the ink is deteriorated. If the content of the second compound is too large, the ink easily follows the fibers of the paper and enters the gaps between the fibers.
The printing quality deteriorates.

[0040]

As described above, according to the present invention,
After printing by specifying the composition of the surfactant to be used in an ink jet printer ink containing a fluorescent compound that gives a reflected color under visible light and emits fluorescence by ultraviolet irradiation, a surfactant, and water, The ink which satisfies all points of quick drying property, printing quality, and fluorescent emission intensity of printing is provided.

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Claims (2)

[Claims] 1. An ink-jet printer ink comprising a fluorescent compound that gives a reflected color under visible light and emits fluorescence by irradiation with ultraviolet light, a surfactant, and water, wherein the surfactant has the following chemical formula ( A first compound in which R is an isobutyl group (—CH ₂ CH (CH ₃ ) CH ₃ ), which is an acetylene diol-based surfactant represented by 1), and R is an ethyl group (—CH ₂ CH ₃ ); When the content of the first compound in the ink is A (% by weight) and the content of the second compound is B (% by weight), A and B are “0”. An ink for an ink jet printer, wherein the relationship between A and B satisfies the following expression (1). Embedded image 5.0 ≦ 16A + B ≦ 6.5 ‥‥ (1) 2. The content of the fluorescent compound is 0.1% by weight.
2. The ink for an ink jet printer according to claim 1, which is at least 10.0% by weight.