JPH07310038A - Ink for ink-jet printer - Google Patents

Abstract

PURPOSE:To produce an ink for color ink-jet printer, effective for suppressing the bleeding of ink in the printing of letter, etc., and having high dispersion stability and weather resistance by using a specific organic pigment in combination with a water-soluble binder resin and water. CONSTITUTION:This ink for ink-jet printer contains (A) an organic pigment having particle diameter of <=5mum in combination with (B) a water-soluble binder resin and (C) water and preferably has a viscosity of 2-25 cps, a surface tension of 23-40dyne/cm, a specific resistance of 2,0OOOMEGAcm and pH of 4.5-10. Preferably, the amount of the component A is 3-45wt.%, an organometallic compound such as an organic fluorescent material emitting infrared rays is used as the component A and the ink further contains (D) a water-soluble organic solvent having low boiling point, (E) a dye, (F) an electrolyte and (G) a stabilizing agent selected from alkyl phthalate, aryl phthalate and glycol (ester).

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, and more specifically, an organic pigment is used to suppress the exudation of the ink during printing and improve the dispersion stability and weather resistance. The present invention relates to various colors of ink for inkjet printers.

[0002]

2. Description of the Related Art Generally, an ink for an ink jet printer is composed of a water-soluble dye and an aqueous solution of a wetting agent,
A usual water-soluble dye is used for coloring, but in recent years, a water-soluble fluorescent organic dye which is invisible to the naked eye has also been used. (Japanese Patent Publication No. 51-40484, Japanese Patent Publication No. 62-24024, Japanese Patent Publication No. 6-50090)

Ink for ink jet printers using pigments instead of water-soluble dyes is also used. For example, inorganic pigments such as titanium oxide are mixed with acrylic resin,
Ink for inkjet printers prepared by mixing and dispersing with water and an alcohol solvent is used. (U.S. Pat. No. 4365035)

[0004]

However, the ink for an ink jet printer using a water-soluble dye has a drawback that bleeding is likely to occur during printing such as printing, and has poor chemical stability and poor weather resistance. Further, inks for inkjet printers using an inorganic pigment such as titanium oxide have a problem that the pigment is deposited due to poor dispersion stability, and no one other than titanium oxide has been used yet.

The present invention has been made in view of the above circumstances, and by using an organic pigment, the bleeding of ink during printing such as printing is suppressed, and various colors having excellent dispersion stability and weather resistance are obtained. The purpose of the present invention is to obtain an ink for an inkjet printer.

[0006]

The present invention has a particle size of 5
An ink for an inkjet printer is obtained by incorporating an organic pigment having a size of not more than μm together with a water-soluble binder resin and water.

The ink for an ink jet printer has a viscosity of 2 to 25 cps and a surface tension of 23 to 40 dyn.
e / cm, specific resistance 2000 Ωcm or less, pH
It is set to 4.5-10.

The content of the organic pigment is 3 to 45% by weight.
The organic metal compound is used as the organic pigment, the organic metal compound is an organic phosphor, the infrared emitting organic phosphor is used as the organic phosphor, and a coloring pigment is contained.

Further, a water-soluble low-boiling organic solvent, a dye, an electrolyte, a stabilizer and the like are further contained.

[0010]

The ink for an ink jet printer of the present invention uses the organic pigment as described above, and the viscosity, the surface tension, the specific resistance, the pH, the content of the organic pigment, the content ratio of the water-soluble binder resin to the organic pigment, etc. Since it is adjusted and a water-soluble low-boiling organic solvent, a dye, an electrolyte, a stabilizer, etc. are used in combination, ink bleeding during printing such as printing is favorably suppressed, and dispersion stability and Ink for inkjet printers of various colors having excellent weather resistance can be obtained.

When an infrared-emitting organic fluorescent substance is used as the organic pigment, a print or a pattern that is invisible to the naked eye can be displayed, and when a color pigment is used in combination, the print and the print which are excellent in forgery prevention can be obtained. An ink for an inkjet printer capable of displaying a pattern is obtained.

The organic pigment used in the present invention has a particle size of 5 μm or less because the nozzle of an ink jet is clogged if the particle size is larger than 5 μm, and an organic metal compound having a particle size of 5 μm or less is used. Is used.

Examples of the organic metal compound include phthalocyanine blue, liquid C, and fast yellow.
G, quinophthalone yellow, dianidin orange, para red, etc., infrared emitting phosphors such as neodymium cinnamate, neodymium cinnamate / ytterbium complex salt, neodymium naphthoate, neodymium naphthoate / ytterbium complex, europium cinnamate. Organic phosphors such as visible light emitting phosphors are also used.

The ink for an ink jet printer of the present invention using such an organic pigment has a viscosity of 2 to 25c.
It is preferably in the range of ps, and if it is made lower than 2 cps, the pigment content must be remarkably lowered, and it is difficult to obtain excellent color. If it is higher than 25 cps, it becomes difficult to print with an inkjet printer.

The surface tension is 23-40 dyne / c.
It is preferably within the range of m, and outside the range, the required uniform droplets are difficult to be generated.

Further, the specific resistance is preferably 2000 Ωcm or less, and when it is higher than 2000 Ωcm, it becomes difficult to control the charge of the liquid droplets, and the printing may be chipped or bent, which makes it difficult to perform good printing.

If the pH is less than 4.5 or more than 10, the pigment in the ink aggregates and the dispersion stability is slightly inferior, so the pH is preferably in the range of 4.5 to 10.
Is more preferably in the range of 5 to 7.

As described above, the ink for an ink jet printer of the present invention has a viscosity of 2 to 25 cps, a surface tension of 23 to 40 dyne / cm, a specific resistance of 2000 Ωcm or less, and a pH of 4.5 to 10 at the time of printing such as printing. The bleeding is effectively suppressed, and the dispersion stability and weather resistance are sufficiently improved.

When the amount of the organic pigment used in the ink for an ink jet printer is less than 3% by weight, it is difficult to obtain a sufficient color, and when it exceeds 45% by weight, it becomes difficult to form an ink. It is preferable to use it within the range of 45 wt%.

Such an organic pigment may be used alone or in combination with a dye. As the dye to be used in combination, any dye generally used in inks for ink jet printers may be used. Black G
W, Capamin Black ESA, Rhodamin B, Rhodamin 7G, Methylene Blue, Direct Fast Orange, Planning Lean G, Milling Yellow
O and Cation Pink FG are preferably used together.

As the water-soluble binder resin, an acrylic resin and an acrylic resin containing an ester group or a polyether in the side chain are used. In addition to this, polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose are used. -, Starch, formalin condensate of naphthalene sulfonate, polystyrene sulfonate and the like are also used.

Further, water is used as a solvent, and in addition to water alone, a low-boiling organic solvent such as ethanol, methyl ethyl ketone, tetrahydrofuran, isopropyl alcohol, and acetone, which is soluble in water, is used in combination. You may. Further, an electrolyte may be additionally used, for example, LiNO ₃ , LiCl, KCl, NaCl, KNO.
Electrolytes such as ₃ are preferably used together.

Such inks for ink jet printers are further preferably used in combination with a stabilizer, a defoaming agent, etc. As the stabilizer, alkyl phthalate, allyl phthalate, glycol, glycol ester, etc. are used alone. Or they are mixed and used together.

As the alkyl phthalate as a stabilizer,
Examples thereof include dioctyl phthalate and dibutyl phthalate, and allyl phthalate and the like can also be used.
Examples of the glycol include ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol and the like, and glycol ester and the like are also used.

As the defoaming agent, for example, silicone type, silica / silicon type, metal soap type, amide type,
A defoaming agent such as a polyether type is preferably used in combination, and specific examples of commercially available products include, for example, San Nopco Ltd .; Nopco 8034, SN Deformer-381, SN Deformer-485, SN Deformer. 154, manufactured by BYK Chemie; BYK025, BYK024 and the like.

[0026]

EXAMPLES Next, examples of the present invention will be described. Example 1 Neodymium cinnamate / ytterbium complex salt (particle size 4 μm) 80 parts by weight Phthalocyanine Nile-1 〃 Cationic acrylic resin 20 〃 Polyethylene glycol 1 〃 Dioctyl phthalate 0.5 〃 KCl 0.5 〃 Defoamer 0.4 〃 Water 100 〃 Ethanol 20 〃 The above composition was mixed and dispersed in a sand mill for 1 hour to prepare an ink for an inkjet printer. Then, the obtained ink for inkjet printer was used to print on paper by an inkjet printer.

When the printing on the paper was observed, no ink bleeding was observed, and highly accurate blue printing was recognized.
In addition, the wavelength of 97
Excitation is performed by an excitation light source with central emission in the vicinity of 0 nm, the emitted light is received by a silicon photodiode detector, and a reading test is performed at a reading speed of 4 m / sec.
When it was performed 100 times, it could be detected 100 times.

Example 2 An ink for inkjet printer was prepared in the same manner as in Example 1 except that the phthalocyanine blue was omitted from the composition of the ink for inkjet printer in Example 1. Then, the obtained ink for inkjet printer was used to print on paper by an inkjet printer.

Wavelength 970n for detecting print on paper
It is excited by radiating with an exciting light source that radiates in the vicinity of m.
Emission was received by a silicon photo diode detector, and a reading test was performed 100 times at a reading speed of 4 m / sec. It was possible to detect 100 times. Also,
When the printing was observed, no ink bleeding was observed and high-precision printing was recognized.

Example 3 Neodymium cinnamate-ytterbium cinnamate complex salt was omitted from the composition of the ink for an ink jet printer in Example 1, and the amount of phthalocyanine blue used was from 1 part by weight to 1 part by weight.
An ink for inkjet printer was prepared in the same manner as in Example 1 except that the amount was changed to 5 parts by weight. Then, the obtained ink for inkjet printer was used to print on paper by an inkjet printer.

When the printing on the paper was observed, no ink bleeding was observed, and highly accurate blue printing was recognized.

Example 4 An ink for an ink jet printer was prepared in the same manner as in Example 2 except that polyethylene glycol and dioctyl phthalate were omitted from the composition of the ink for an ink jet printer in Example 2. Then, the obtained ink for inkjet printer was used to print on paper by an inkjet printer.

When the printing on the paper was observed, no ink bleeding was observed. Further, in order to detect printing of infrared light emission on paper, the silicon photodiode is excited by being radiated and excited by an exciting light source radiating in the vicinity of a wavelength of 970 nm.
Light emission is received by the detector and the reading speed is 4m / sec.
When the reading test was conducted 100 times, the detection could be performed 100 times.

Example 5 An ink for inkjet printer was prepared in the same manner as in Example 4 except that LiNO ₃ was omitted from the composition of the ink for inkjet printer in Example 4.
Then, the obtained ink for inkjet printer was used to print on paper by an inkjet printer.

When the print on the paper was observed, no ink bleeding was observed. Further, in order to detect printing of infrared light emission on paper, the silicon photodiode is excited by being radiated and excited by an exciting light source radiating in the vicinity of a wavelength of 970 nm.
Light emission is received by the detector and the reading speed is 4m / sec.
When the reading test was conducted 100 times, the detection could be performed 100 times.

Example 6 Ink composition similar to that of Example 2 except that ethanol was omitted and the amount of water used was changed from 100 parts by weight to 120 parts by weight in the composition of the ink for an ink jet printer in Example 2. A printer ink was prepared.
Then, the obtained ink for inkjet printer was used to print on paper by an inkjet printer.

When the printing on the paper was observed, no ink bleeding was observed. Further, in order to detect printing of infrared light emission on paper, the silicon photodiode is excited by being radiated and excited by an exciting light source radiating in the vicinity of a wavelength of 970 nm.
Light emission is received by the detector and the reading speed is 4m / sec.
When the reading test was conducted 100 times, the detection could be performed 100 times.

Example 7 In the ink composition for ink jet printers in Example 1, various kinds of inks for ink jet printers having different viscosities were prepared by changing the amount of cationic acrylic resin used. Then, the relationship between the viscosities of various types of inkjet printer inks having different viscosities and the fluctuation rates of the relative output and the droplet size was investigated.

FIG. 1 is a graph showing the relationship between the viscosity of such an ink for an ink jet printer and the variation rate of relative output and droplet size. The ink for inkjet printers using the organic pigment described in 1) provides sufficient output when the viscosity is in the range of 2 to 25 cps, and the droplet size variation rate is 10% or less to obtain uniform droplets. It is understood that good printing can be obtained.

Example 8 In the ink composition for ink jet printers in Example 1, various kinds of ink for ink jet printers having different surface tensions were prepared by changing the amount of ethanol used. Then, the relationship between the surface tension of various types of inkjet printer inks having different surface tensions and the variation rate of the droplet size was investigated.

FIG. 2 is a graph showing the relationship between the surface tension of such an ink for an ink jet printer and the variation rate of the droplet size. As is apparent from this graph, the organic pigment of the present invention is shown. When the surface tension is within a range of 23 to 40 dyne / cm, the ink for an inkjet printer using is capable of obtaining uniform droplets with a variation rate of the droplet size of 10% or less, and good printing is obtained. You can see that

Example 9 In the ink composition for ink jet printer of Example 1, various kinds of inks for ink jet printer were prepared by changing the amount of the electrolyte used variously. Then, the relationship between the specific resistance of various types of inks for inkjet printers having different specific resistances and the variation rate of the droplet size was investigated.

FIG. 3 is a graph showing the relationship between the specific resistance of such an ink for ink jet printers and the variation rate of the droplet size. As is apparent from this graph, the organic pigment of the present invention is shown. It can be seen that when the specific resistance is 2000 Ωcm or less, the variation in the size of the droplets is 10% or less, and uniform droplets are obtained in the ink for an inkjet printer using the above method, and good printing is obtained.

Example 10 In the composition of the ink for an ink jet printer of Example 1, KCl and KOH were added in various addition amounts,
Various types of inks for inkjet printers having various pH values were prepared. Then, the relationship between the pH and the dispersion stability of various types of inkjet printer inks having different pHs was investigated. The dispersion stability was represented by the ratio of the supernatant formation after the obtained ink for inkjet printers was allowed to stand for one week to the whole.

FIG. 4 is a graph showing the relationship between the pH and the dispersion stability of such an ink for an ink jet printer. When the dispersion stability is 80% or more, the dispersion stability is optimum and the dispersion stability is high. When the stability is 60 to 80%, the dispersion stability is good, and when the stability is less than 60%, the dispersion stability is slightly inferior. As is clear from this graph, the ink for an ink jet printer using the organic pigment of the present invention has good ink dispersion stability when the pH is in the range of 4.5 to 10, and has a pH of 5 to 7. It can be seen that the dispersion stability of the ink is optimum.

Comparative Example 1 Direct Black GW (dye) 1.5 parts by weight Polyethylene glycol resin (molecular weight 200) 4.5 〃 ethoxy glycol 4.5 〃 dioxine 0.1 〃 water 89.4 〃 The above composition was mixed and dispersed in a sand mill for 0.5 hours. An ink for inkjet printer was prepared. Then, the obtained ink for inkjet printer was used to print on paper by an inkjet printer.

When the printing on the paper was observed, bleeding of the ink was observed, and highly accurate black printing was not recognized.

Comparative Example 2 In the composition of the ink for an ink jet printer in Example 1, the same amount of neodymium cinnamate / ytterbium cinnamate having a particle diameter of 6 μm was used instead of neodymium cinnamate / ytterbium cinnamate salt having a particle diameter of 4 μm. An ink for inkjet printer was prepared in the same manner as in Example 1 except for the above.

Then, it was attempted to print on the paper with an ink jet printer using the obtained ink for an ink jet printer, but the nozzle of the ink jet printer was clogged and printing could not be performed.

Comparative Example 3 An ink for inkjet printer was prepared in the same manner as in Example 3 except that 10 parts by weight of titanium oxide was used in place of phthalocyanine blue in the composition of the ink for inkjet printer in Example 3. However, the resulting ink for inkjet printers could not be printed on paper by the inkjet printer because the pigment settled quickly.

The ink jet printer inks obtained in Examples 1-6 and Comparative Examples 1-2 were tested for dispersion stability and weather resistance by the following methods.

<Dispersion Stability> The appearance of the supernatant after the obtained ink for inkjet printers was allowed to stand for one week was shown as a ratio to the whole.

<Weather resistance> A change in color after leaving for 8 hours with a weather maker manufactured by Atlas Electric was shown. Table 1 below shows the results.

[0054]

[0055]

As is apparent from Table 1 above, Example 1
The inks for inkjet printers of the present invention obtained in Nos. 6 to 6 have better dispersion stability and weather resistance than the inks for inkjet printers obtained in Comparative Examples 1 and 2.

As is clear from each of the examples and the comparative examples, when the ink for the ink jet printer of Comparative Example 1 was printed, the ink bleeding was observed. However, the ink for the ink jet printer of the present invention was used. When printed with no bleeding, high-precision color printing was recognized.

From the above, it can be seen that the ink for ink jet printers obtained by the present invention has good dispersion stability, excellent weather resistance, no bleeding during printing, and highly accurate color printing. .

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the viscosity of ink for an inkjet printer according to the present invention and the variation rate of relative output and droplet size.

FIG. 2 is a diagram showing the relationship between the surface tension of ink for an inkjet printer and the variation rate of the size of a droplet in the present invention.

FIG. 3 is a diagram showing the relationship between the specific resistance of the ink for an inkjet printer and the variation rate of the droplet size in the present invention.

FIG. 4 is a relationship diagram between pH and dispersion stability of the ink for an inkjet printer according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsunemi Oiwa 1-88, Tora-Tora, Ibaraki-shi, Osaka, Hitachi Hitachi Maxel Co., Ltd. Maxel Co., Ltd.

Claims (15)

[Claims] 1. An ink for an ink jet printer, comprising an organic pigment having a particle diameter of 5 μm or less, together with a water-soluble binder resin and water. 2. The ink for an ink jet printer according to claim 1, which has a viscosity of 2 to 25 cps. 3. The ink for an ink jet printer according to claim 1, which has a surface tension of 23 to 40 dyne / cm. 4. The ink for an ink jet printer according to claim 1, which has a specific resistance of 2000 Ωcm or less. 5. The ink for an ink jet printer according to claim 1, which has a pH of 4.5 to 10. 6. The ink for an ink jet printer according to claim 1, wherein the content of the organic pigment is in the range of 3 to 45% by weight. 7. The ink for an inkjet printer according to claim 1, wherein the organic pigment is an organometallic compound. 8. The ink for an ink jet printer according to claim 8, wherein the organometallic compound is an organic phosphor. 9. The ink for an ink jet printer according to claim 8, wherein an organic phosphor is used and a coloring pigment is further contained. 10. The ink for an ink jet printer according to claim 8, wherein the organic phosphor is an infrared-emitting organic phosphor. 11. The ink for an ink jet printer according to claim 1, further comprising a low boiling point organic solvent soluble in water. 12. The ink for an inkjet printer according to claim 1, further comprising a dye. 13. The ink for an ink jet printer according to claim 1, further comprising an electrolyte. 14. The method according to claim 1, further comprising a stabilizer.
Ink for inkjet printers described 15. The ink according to claim 14, wherein the stabilizer is at least one selected from alkyl phthalate, allyl phthalate, glycol and glycol ester.