JPH10130558A - Water-based pigment-based ink and ink-jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject ink capable of always carrying out the stable discharge without causing clogging, etc., in an ink-jet printer by including at least water, a pigment, a dispersing agent and a fluorescent pigment so as to satisfy specific conditions. SOLUTION: This ink comprises at least (A) water, (B) a pigment, (C) a dispersing agent and (D) a fluorescent pigment and has <=0.1μm average particle diameter of particles of the component B. The weight ratio of the component C to the component B is 1.2-5 times and the component D is added in an amount of 0.1-3wt.% based on the amount of the ink. Polybutyl butyral resin, a cellulosic derivative, etc., are preferably cited as the component C. A water-soluble organic solvent (preferably a polyhydric alcohol) at 1-20% ratio expressed in terms of weight ratio is further preferably contained in the ink. Thereby, the ink having a good color tone, reduced bleeding properties, etc., be obtained even by compounding the pigment ink with the fluorescent ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous pigment ink which can be suitably used in an ink jet recording apparatus and an ink jet printer for multicolor printing using the aqueous pigment ink.

[0002]

2. Description of the Related Art Conventionally, an ink jet printer which performs printing by ejecting ink from a nozzle having a small diameter has been widely used. This recording method forms characters, images, and the like by ejecting liquid ink from a nozzle (orifice) having a small diameter as flying particles toward a recording medium so that the flying particles of the ink adhere to the recording medium. is there.

In this type of ink jet printer, conventionally, a dye-based ink in which various dyes are dissolved in water or an organic solvent has been generally used. However, dye-based inks are inferior in light resistance and water resistance,
It is not preferable when light resistance and water resistance are required for the recorded image. Therefore, in recent years, it has been proposed to use pigment-based ink instead of dye-based ink. When a pigment-based ink is used in an inkjet printer, it has been proposed to include a specific additive in the pigment-based ink or to improve the dispersion stability by making the pigment-based ink have a specific composition. ing. In other words, in pigment-based inks, the pigment is inherently inferior in affinity with water, so that the pigment component is condensed or sedimented in the ink liquid. Thus, condensation and sedimentation can be suppressed.

Japanese Patent Application Laid-Open No. 7-292302 discloses a recording liquid used in an apparatus for performing non-contact non-impact recording by ejecting ink containing pigment particles. In this publication, a difference C in the weight ratio between the nonvolatile component (A) and the color material component (B) at 25 ° C. in the recording liquid is described.
It is disclosed that (= AB) preferably satisfies 0.01 ≦ 10. Furthermore, it discloses that a plurality of color inks including a black ink is used, and the ratio of the non-volatile component (A) to the color material component (B) at 25 ° C. in each recording liquid (= B / A). Is 0.5 or less.

[0005] Also, republished patent WO95 / 21897 discloses an aqueous ink composition comprising a water-insoluble coloring material, a water-soluble organic solvent, and water, which contains substantially no dispersant. The water-insoluble colorant has a solubility in water of 1% by weight or less at 20 ° C. and is soluble in the water-soluble organic solvent, and the water-insoluble colorant is in a dispersed state in the ink composition. Ink compositions have been proposed.

As described above, for a pigment-based ink, the ratio of an additive as a dispersant can be set under specific conditions,
Alternatively, it has been conventionally proposed to constitute an ink composition by defining the solubility within a specific range without substantially containing a dispersant.

[0007]

As described above, conventionally, dyes or pigments are dissolved and decomposed with a high boiling point solvent and water and used. However, in the case of dyes, there are problems in light resistance and water resistance. In the case of pigments, there were problems such as aggregation and sedimentation. As described above, pigment-based inks are superior to dye-based inks in terms of light resistance and water resistance, but have poor affinity for water, so that aggregation and sedimentation of pigment components in the ink liquid are reduced. Therefore, when the conventional pigment-based ink is used as it is in an ink-jet printer, there is a problem that the stability of ejection from a nozzle (orifice) of the ink-jet head is significantly impaired, resulting in poor printing. This tendency is due to the fact that ink residue is generated around the orifice to prevent stable ejection regardless of the type using thermal energy or the type using pulse pressure.

In a multi-color printing ink jet printer, a plurality of color inks including a black ink is used. That is, black, yellow, magenta, and cyan inks are used. Recently, carbon black, which has excellent light resistance and water resistance, has begun to be used as a pigment for black ink. However, when carbon black is used in an ink jet printer, in the case of color display in which black is included in other colors, the black appears somewhat reddish and the quality of multicolor display deteriorates.

SUMMARY OF THE INVENTION An object of the present invention is to provide an aqueous pigment ink and an ink jet printer which can always perform stable discharge without clogging even when the driving conditions of the ink jet printer fluctuate or when the ink jet printer is used for a long time. is there. Another object of the present invention is to have a good color tone in terms of brightness and clarity, to be excellent in light resistance and water resistance, and to prevent bleeding.
An object of the present invention is to provide an aqueous pigment-based ink and an ink jet printer that do not enter a boundary between other colors.

[0010]

In an attempt to improve the affinity for water in a pigment-containing ink, a dispersant is generally added. As the dispersant, a polymer is preferable, and the polymer is used in an amount of 1.2 to the pigment.
It is desirable to have a weight ratio of up to 5 times. Also,
In order to suppress the condensation and the sedimentation of the pigment particles in the ink liquid, it is desirable that the maximum particle size of the pigment particles be 0.1 μm or less.

Therefore, in the present invention, at least water, a pigment, a dispersant and a fluorescent pigment are contained, the average particle size of the pigment particles is 0.1 μm or less, and the weight ratio of the dispersant to the pigment is 1.2 to 5%. Twice the amount of the fluorescent pigment with respect to the ink amount.
An aqueous pigment-based ink characterized by being added in an amount of 1% by weight to 3% by weight is provided. When a pigment is used as a coloring material, the pigment does not transmit light as compared with a dye, so that the pigment does not generally look vivid. % By weight to 3
Since the amount is added by weight, the saturation is increased to the same level as that of the dye-based ink, and the printing quality can be improved. Therefore, it is excellent in color tone and lighting, and has a saturation of about 5%.
To some extent. In addition, when a pigment-based ink having such a composition is used in an inkjet printer,
Printing excellent in light fastness and water fastness is obtained, and by suppressing the condensation and sedimentation of pigment particles, it is possible to discharge ink droplets stably when ejected.

When the average particle size of the pigment particles is 0.1 μm or less, almost no clogging occurs. In order to obtain a more stable recording liquid, the average particle diameter of the pigment particles is desirably 50 nm or less. When the ratio of the pigment to the dispersant in the aqueous ink composition is equal or the ratio of the pigment exceeds the dispersant, sedimentation occurs in about one week. On the other hand, if the ratio of the dispersant exceeds 5 times, the viscosity of the ink rapidly increases, and the ink cannot be used as an inkjet ink. Therefore, the polymer as a dispersant is 1.2 to 5 with respect to the pigment.
It was defined as having twice the weight ratio.

The polymer as a dispersant added to the ink is, for example, a polybutyl butyral resin, a cellulose derivative, a styrene-acrylic copolymer resin, a maleic acid.
It is characterized by comprising one or more selected from the group consisting of a styrene copolymer, a block polymer of a hydrophobic polymer having a basic amino group and a hydrophilic polymer having an acidic functional group.

The aqueous pigment-based ink has a weight ratio of 1%.
It can contain up to 20% of a water-soluble organic solvent. Preferably, the water-soluble organic solvent is a single solvent or a mixed solvent of a polyhydric alcohol such as diethylene glycol. Further, the ink jet printer according to the present invention includes a plurality of ink tanks, a print head having a nozzle for ejecting a plurality of colors of ink, each ink tank contains at least water, a pigment and a dispersant, An aqueous pigment-based ink in which the average particle diameter of the pigment particles is 0.1 μm or less and the weight ratio of the dispersant to the pigment is 1.2 to 5 times, and the nozzle diameter of the print head nozzle is the color of the pigment According to 2
It is characterized in that it is changed within a range of 0 μm to 50 μm.

For example, when the particle diameter of the pigment of the ink is as small as 20 nm, such as yellow, the nozzle diameter of the ink jet head is reduced to about 20 μm. Further, as in cyan and magenta, the particle size of the pigment of the ink is 35 to
For those as large as 36 nm, the nozzle diameter of the head is 50 μm
Increase to about. This makes it possible to keep the droplet diameter (volume of the droplet) of the ink ejected from the nozzle substantially constant irrespective of whether the pigment particle size is large or small.

In this case, the fluorescent pigment is further added in an amount of 0.1% by weight to 3% by weight based on the ink amount. The nozzle diameters of the nozzles are substantially the same for the yellow and black pigments, substantially the same for the magenta and cyan pigments, and are different for the yellow and black groups and the magenta and cyan groups. Have been. Further, the inkjet printer according to the present invention includes a plurality of color ink tanks, a print head having nozzles for ejecting a plurality of color inks, each ink tank includes at least water, a pigment and a dispersant, Including an aqueous pigment-based ink in which the average particle size of the pigment particles is 0.1 μm or less, the weight ratio of the dispersant to the pigment is 1.2 to 5 times, and the size of the ink droplet ejected from the nozzle In at least three stages.

Preferably, the means for changing the size of the ink droplet ejected from the nozzle includes a height of a pulse voltage, a width of the pulse voltage, and a pulse of the pulse voltage applied to eject the ink droplet. Means for changing at least one of the rise times. Furthermore, the ink jet printer according to the present invention includes an ink tank of a plurality of colors including black, and a print head having nozzles for ejecting inks of a plurality of colors, and each ink tank has at least water, a pigment, and a dispersant. And the average particle size of the pigment particles is 0.1 μm
The weight ratio of the dispersant to the pigment is 1.2 to
The ink includes an aqueous pigment-based ink that is five times as large, and the black ink includes carbon black and a cyan-based pigment. Also in this case, the dispersant is a polybutyl butyral resin, a cellulose derivative, styrene-
It consists of one or more selected from the group of acrylic copolymer resin, maleic acid-styrene copolymer, hydrophobic polymer having a basic amino group and hydrophilic polymer having an acidic functional group. preferable. Further, the composition further contains a water-soluble organic solvent in a weight ratio of 1 to 20%. The water-soluble organic solvent is a polyhydric alcohol single solvent or a mixed solvent. Further, the black ink was adjusted to the center of the hue balance of the color ink.

Further, there is provided a black ink for an ink jet printer, wherein the black ink contains carbon black and a cyan pigment.

[0019]

1 and 2 are perspective views showing a print head 10 of an ink jet printer for multicolor printing according to an embodiment of the present invention. The print head 10 includes a black nozzle 12B, a cyan nozzle 12C, a magenta nozzle 12M, a yellow nozzle 12Y, and ink tanks 16B, 16C, 16M, and 16Y. These nozzles can be formed as nozzle plates. The print head 10 is supported by a carrier (not shown) and is movable in the direction of arrow P.
2B, 12C, 12M, and 12Y are arranged in rows in a direction perpendicular to the movement direction P.

The print head 10 has an ink chamber 46 formed between the nozzle body wall 42 and the flexible wall 44, and a piezoelectric actuator 48 mounted on the flexible wall 44.
By expanding and contracting the ink chamber 46 by
The ink is ejected from the nozzles 12 toward the printing paper 50 as ink droplets 49. Ink droplets adhering to the printing paper 50 are indicated by 52. Ink droplet 4 in flight
The size of 9 is indicated by D, and the size of the ink droplet 49 attached to the printing paper 50 is indicated by d.

The four color (black, cyan, magenta, and yellow) inks are stored in the respective ink tanks 16B and 16B.
C, 16M, 16Y, and ink tank 1
6B, 16C, 16M, and 16Y are the respective supply passages 1
The print head 10 communicates with the print head 10 via the print head 8. The nozzle diameters of the nozzles 12B, 12C, 12M, and 12Y for each color are changed in the range of 20 μm to 50 μm according to the color of the pigment.

For example, when the pigment particle size of the ink is as small as 20 nm, such as yellow, the yellow nozzle 1
The nozzle diameter of 2Y is made as small as about 20 μm. Since the particle diameter of the black pigment is also about 20 nm, the nozzle diameter of the black nozzle 12B is also about 20 μm. Also,
Ink particles such as cyan and magenta have a particle size of 3
When the diameter is as large as 5 to 36 nm, the nozzle diameter of the cyan or magenta nozzles 12C and 20M is increased to about 50 μm. This makes it possible to keep the droplet diameter (volume of the droplet) of the ink ejected from the nozzle substantially constant irrespective of whether the pigment particle size is large or small.

Next, further examples of the aqueous pigment-based ink will be described. Four types (Comparative Examples 1 to 3 and Example 1) of aqueous pigment-based inks having the compositions shown in Table 1 below were prepared. The chroma and the viscosity of the ink of each of these samples were measured, and the results are shown in Table 1.
In each sample, phthalocyanine blue was used as a pigment, and a polymer (methacrylic acid-b-2-phenylethyl methacrylate) was used as a dispersant.

[0024]

[Table 1]

For all samples, the pigment was 4% by weight, the alcohols were 5% by weight, and the glycol (diethylene glycol) was 10% by weight. Comparative Examples 1 to 3 did not contain a fluorescent pigment, and Examples contained 2% by weight of a fluorescent pigment. Further, the dispersant was prepared in Comparative Example 1 and Example 1
In Comparative Example 2, 20% by weight, and Comparative Example 3 in 22% by weight.

In Comparative Examples 1 to 3, since no fluorescent pigment was contained, the saturation (saturation according to JIS standard color chart) was as low as 71 to 72, and in Example 1, the pigment contained 2% by weight of the fluorescent pigment and had a saturation of 80.
It can be seen that the color saturation is high and good. Examples of usable fluorescent pigments are, for example, as shown in the following chemical formulas and structural formulas.

[0027]

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[0028]

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[0029]

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[0030]

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[0031]

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In Comparative Examples 1 and 2, the dispersant was 6% by weight and 20% by weight, respectively, and was 1.2 times as large as the pigment.
The viscosity (CPS) is within 3.8 and 6.
3, it can be seen that the viscosity is within a range suitable for the ink used in the ink jet printer. However, Comparative Example 3
In this case, the weight ratio of the dispersing agent to the pigment exceeded 22 times the range of 5 times and the viscosity (CPS) was too high at 16, which was unsuitable as an ink for an ink jet printer. On the other hand, in Example 1, the dispersant was 6% by weight, which was in the range of 1.2 to 5 times the pigment, and the viscosity (CPS) was 3.
9, which was within the range of viscosity suitable for ink-jet printing ink.

In the present invention, the aqueous pigment-based ink contains at least water, a pigment, a dispersant, and a fluorescent pigment, has an average pigment particle size of 0.1 μm or less, and has a weight ratio of the dispersant to the pigment of 1%. 0.2 to 5 times. This is a basic configuration. In the above embodiment, a fluorescent pigment is further added to this basic configuration. However, in the following embodiments, another feature is included in this basic configuration. However, it goes without saying that a fluorescent pigment may be added.

Table 2 shows the diameter (volume) of the ink droplets ejected from the nozzles, which is determined by the relationship between the particle diameter of the pigment of the color pigment ink and the nozzle diameter of the nozzle of the ink jet head. In this example, in addition to having the above basic configuration, the pigment ink of each color, yellow (ink particle size 20
nm), magenta (ink diameter 35 nm), cyan (ink diameter 36 nm), black (ink diameter 21 nm)
About, nozzle diameter 15μm, 20μm, 40μm,
It was changed to 50 μm and 60 μm.

[0035]

[Table 2]

The preferred amount (volume) of ink droplets is, for example, in the range of 40 pl to 60 pl. Therefore, within the range of selection in Table 2, it is appropriate that yellow has a nozzle diameter of 20 μm or 40 μm, magenta has a nozzle diameter of 50 μm, cyan has a nozzle diameter of 50 μm, and black has a nozzle diameter of 20 μm or 40 μm. In this way, by changing the nozzle diameter for each color ink, the droplet diameter (droplet volume) of the ink jetting ejected from the nozzles
Can be made substantially constant regardless of whether the pigment particle size is large or small.

FIGS. 3 and 4 illustrate a means for changing the size of the ink droplet ejected from the nozzle in at least three stages when the pigment-based ink having the above-described basic structure is used. FIG. FIG. 3 is a diagram showing a pulse voltage (V) applied to the piezoelectric actuator 48 to eject ink droplets from the nozzles. The horizontal axis is time (T). The pulse voltage has a pulse voltage height V ₁ ,
Including factors such as the pulse voltage width T ₁ and the rise time T ₂ , by changing at least one of these factors, the size of the ejected ink droplet can be changed.

FIG. 4 is a diagram showing the relationship between the height V ₁ of the pulse voltage and the diameter of the ejected ink droplet. Thus, by changing the height V ₁ of the pulsed voltage, the nozzle diameter can vary the diameter of the ink droplets ejected be constant. Figure 5 is a diagram illustrating the size of the ink droplet when varying the height V ₁ of the pulsed voltage. As shown in Table 3, by changing the voltage to 60, 70, and 80 V, the amount of ejected ink droplets was 20, 50, 80
pl, and the diameter d (FIG. 2) of the ink droplet 49 attached to the printing paper 50 at this time is 0.03, 0.06, 0.
It became 10 mm. Note that the pulse voltage width T ₁ and the rise time T ₂ can be changed.

[0039]

[Table 3]

As described above, by using the pigment-based ink and changing the size of the ink droplet ejected from the nozzle in at least three stages, a very excellent gradation display can be performed. That is, if a pigment-based ink is used, the ejected ink does not spread or spread on the printing paper 50 when it adheres to the printing paper 50 and after it adheres, and has a predetermined size. The color mixture with the ink of the above color does not change, and excellent gradation display can be performed.

Further, in another example of the present invention, four color inks having the above-mentioned basic structure, namely, yellow, magenta, cyan, and black aqueous pigment inks are used. And a cyan-based pigment. Therefore, samples shown in Table 4 below were prepared and evaluated. In Examples 2 and 3, black ink was obtained using a pigment obtained by combining phthalocyanine blue with carbon black. On the other hand, in Comparative Example 4, only carbon black was used.

[0042]

[Table 4]

As a result, in the second and third embodiments, the hue balance (a
*, B *), the ink was black at the center, and a good color balance could be realized even when mixed with other colors, and the ink had light fastness, water fastness, bleeding and bleeding properties. In Comparative Example 4, the color became reddish black, and when mixed with other colors, it appeared reddish brownish black despite being black, and the color balance was reduced. The evaluation of hue was based on the Lab display system defined by the International Commission on Illumination (CIF).

The embodiments of the present invention have been described above in detail with reference to the accompanying drawings. However, the present invention is not limited to the above-described embodiments, and various forms and modifications are possible within the spirit and scope of the present invention. It should be noted that variations, modifications, etc. are possible.

[0045]

As described above, according to the present invention, by combining a pigment ink and a fluorescent ink, good color tone, light fastness, and water fastness are ensured while ensuring high reliability without clogging. Aqueous pigment ink having water-soluble, bleeding and bleeding properties was obtained. Further, when performing multi-color printing using a color pigment ink, an ink jet head having improved bleeding property and bleeding property between each color could be obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a print head of an inkjet printer for multicolor printing according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a part of a print head.

FIG. 3 is a diagram showing a waveform of a pulse voltage applied to a piezoelectric actuator.

FIG. 4 is a diagram illustrating a relationship between a pulse voltage and a diameter of an ink droplet.

[Explanation of symbols]

 10 Heads 12B, 12C, 12M, 12Y Nozzles 16B, 16C, 16M, 16Y Ink tank 18 Supply path

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kohei Kiyota 1405 Daimaru, Inagi-shi, Tokyo Fujitsu A Isotec Co., Ltd.

Claims (15)

[Claims] 1. An ink composition comprising at least water, a pigment, a dispersant, and a fluorescent pigment, wherein the average particle size of the pigment particles is 0.1 μm or less, the weight ratio of the dispersant to the pigment is 1.2 to 5 times, 0.1% to 3% by weight of fluorescent pigment based on ink amount
An aqueous pigment-based ink characterized by being added. 2. The dispersant includes a polybutyl butyral resin, a cellulose derivative, a styrene-acrylic copolymer resin, a maleic acid / styrene copolymer, a hydrophobic polymer having a basic amino group and a hydrophilic polymer having an acidic functional group. The water-based pigment-based ink according to claim 1, comprising one or more selected from the group consisting of a block polymer of a hydrophilic polymer. 3. The aqueous pigment-based ink according to claim 2, further comprising 1 to 20% by weight of a water-soluble organic solvent. 4. The aqueous pigment-based ink according to claim 3, wherein the water-soluble organic solvent is a single solvent or a mixed solvent of a polyhydric alcohol. 5. A printing apparatus comprising: a plurality of ink tanks; and a print head having nozzles for ejecting a plurality of color inks.
Each of the ink tanks contains at least water, a pigment, and a dispersant, an aqueous pigment-based ink in which the average particle size of the pigment particles is 0.1 μm or less, and the weight ratio of the dispersant to the pigment is 1.2 to 5 times. Wherein the nozzle diameter of the nozzle of the print head is changed within a range of 20 μm to 50 μm according to the color of the pigment. 6. The method according to claim 1, wherein the amount of the fluorescent pigment is 0.1 to the amount of the ink.
The ink jet printer according to claim 5, wherein 1% by weight to 3% by weight is added. 7. The nozzle diameters of the nozzles are substantially the same for the yellow and black pigments, substantially the same for the magenta and cyan pigments, and for the yellow and black groups and the magenta and cyan groups. 6. The ink jet printer according to claim 5, wherein: 8. A print head having a plurality of color ink tanks and a nozzle for ejecting a plurality of color inks,
Each of the ink tanks contains at least water, a pigment, and a dispersant, an aqueous pigment-based ink in which the average particle size of the pigment particles is 0.1 μm or less, and the weight ratio of the dispersant to the pigment is 1.2 to 5 times. And a means for changing the size of the ink droplet ejected from the nozzle in at least three stages. 9. The means for changing the size of the ink droplet ejected from the nozzle includes a height of a pulse voltage, a width of the pulse voltage, and a pulse of the pulse voltage applied to eject the ink droplet. 9. The ink jet printer according to claim 8, further comprising means for changing at least one of the rise times. 10. An ink tank having a plurality of colors including black, and a print head having nozzles for ejecting a plurality of colors of ink, wherein each ink tank contains at least water, a pigment and a dispersant, The average particle size of the particles is 0.1 μm or less, and the weight ratio of the dispersant to the pigment is 1.2 to 5
An ink-jet printer comprising an aqueous pigment-based ink which is twice as large, and wherein the black ink comprises carbon black and a cyan-based pigment. 11. The dispersant includes a polybutyl butyral resin, a cellulose derivative, a styrene-acrylic copolymer resin, a maleic acid / styrene copolymer, a hydrophobic polymer having a basic amino group and a hydrophilic polymer having an acidic functional group. The inkjet printer according to claim 10, comprising one or more selected from the group consisting of a block polymer of a hydrophilic polymer. 12. The ink-jet printer according to claim 11, further comprising a water-soluble organic solvent in a weight ratio of 1 to 20%. 13. The method according to claim 1, wherein the water-soluble organic solvent is a single solvent or a mixed solvent of a polyhydric alcohol.
3. The inkjet printer according to 2. 14. The ink jet printer according to claim 10, wherein the black ink is adjusted to the center of the hue balance of the color ink. 15. A black ink for an ink jet printer, wherein the black ink contains carbon black and a cyan pigment.