JP2002256186A - Water-based ink composition for ink jet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ink composition which gives a printed matter having improved storage stability and exhibits high delivering stability and storage stability as an ink for ink jet recording. SOLUTION: The water-based ink composition for ink jet recording comprises a coloring agent, an organic solvent and a surfactant. When an image is formed by means of an ink jet recording method so that a liquid drop, the amount of one liquid drop being set to 20 picolitter, is arranged to all pixels under a condition of resolution of 720 dpi, the optical density (OD(A)) of an image obtained using the water-based ink composition to which no NaOH is added and the optical density (OD(B)) of an image obtained using the water-based ink composition having 0.1-5 pts.wt., based on 100 pts.wt. of the water-based ink composition, of NaOH incorporated thereinto satisfy the relation: OD(A)/ OD(B)<=1.05.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink used for an ink jet recording apparatus.

[0002]

2. Description of the Related Art Inkjet printers (IJ printers) do not require processes such as development and fixing.
Since colorization is very easy and printing on plain paper is possible, it has been dramatically spread. In particular, recently, high-definition color printers and the like corresponding to photographic images are commercially available, and this type of printer is becoming the mainstream of inkjet printers. Therefore, recent inkjet printers are required to handle photographic images.
Printed materials produced by IJ printers are required to have image quality and storage stability as well as stability equivalent to silver halide photographs. For this reason, in order to improve the storage stability of the printed matter, high stability performance is desired for the IJ ink used in the IJ printer.

In general, IJ inks are roughly classified into dye inks using an aqueous dye as a coloring agent and pigment inks dispersing a pigment in water as a coloring agent.

[0004] Japanese Patent Application Laid-Open No. 56-14763 discloses I
Pigment inks for J printers have been proposed. The image printed with this ink has good stability, and the printed image is excellent in water resistance and light resistance. However, the dispersion stability of the IJ ink is poor, and the ink may be clogged when ejected. Had a point.

To improve the ejection stability of the pigment ink, a pigment ink to which a special water-soluble resin has been added is disclosed in JP-A-6-100810 and JP-A-6-1810.
No. 22846 has proposed this. However, these pigment inks also did not satisfy the ejection characteristics required for photographic image printers that eject minute droplets.

As described above, it is difficult to use pigment inks as inks for photographic image printers, and at present color printers mainly use dye inks. However, while the dye ink can provide a clear image, the problems are that water resistance and light resistance are poor, and furthermore, when left for a long period of time, the decomposition of the dye occurs and the color tone changes significantly. Have been. Since the dye is inherently inferior in chemical structure, it is considered that a substituent or a bonding group in the molecular structure is cleaved by contact with light or water.

Therefore, as a technique for improving the stability of the dye ink, an aqueous ink to which a specific resin is added has been proposed in JP-A-11-323230. However, this ink has not yet attained the required stability, and sufficient long-term storage stability cannot be ensured. In addition, printed matter printed with this ink is required in terms of water resistance and light resistance. Has not reached the standard.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an aqueous ink for inkjet recording which has high ejection stability and very excellent storage stability as an IJ ink. An object of the present invention is to provide an ink jet recording method and an ink jet recording apparatus using the same.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have made an aqueous ink composition for ink jet recording containing a colorant, an organic solvent and a surfactant, wherein the amount of one droplet is 20. When an image was formed using an inkjet recording method so that liquid droplets were arranged in all pixels under the condition of a picoliter and a resolution of 720 dpi, NaOH was used.
Optical density (OD (A)) of an image of the aqueous ink composition without addition, and an image of the aqueous ink composition with 0.1 to 5 parts by weight of NaOH added to 100 parts by weight of the aqueous ink composition Has an optical density (OD (B)) of
It has been found that the aqueous ink composition for inkjet recording satisfying the relationship of OD (A) / OD (B) ≦ 1.05 has excellent ejection stability and storage stability despite less bleeding. The present invention has been completed.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The aqueous ink composition of the present invention contains a colorant, an organic solvent, and a surfactant, which are at least dispersed or dissolved in an aqueous medium. The aqueous ink composition of the present invention comprises the ink composition itself as ink A, the ink composition 10 as ink A,
When a composition obtained by adding 0.1 to 5 parts by weight of NaOH per 0 parts by weight was used as ink B and an image was formed using these inks by a specific inkjet recording method, the optical density of the image using ink A was Assuming that the value is OD (A) and the optical density value of the image using ink B is OD (B),
It is characterized by satisfying a relationship of OD (A) / OD (B) ≦ 1.05, thereby realizing high ejection stability and storage stability.

In the present invention, an aqueous ink composition containing a colorant, an organic solvent and a surfactant is used as the ink A, and 1 to 5 parts by weight of the ink A is used as the ink B based on the total weight of the ink. The addition amount of NaOH is used, but the addition amount of NaOH in the ink B is preferably 3 to 5 parts by weight, more preferably 5 parts by weight.

Hereinafter, an image forming method and an optical density measuring method essential for specifying the ink composition of the present invention will be described in detail.

The image sample has an ink droplet amount of 2
It is manufactured by printing an aqueous ink on plain paper with a piezo-type inkjet printer adjusted to be 0 picoliter under a condition of a resolution of 720 dpi so that droplets are arranged on all pixels. The plain paper is not particularly limited as long as it is a commercially available plain paper.
ox L is used.

The optical density measurement was performed using RD918 manufactured by Macbeth.
This is performed using an optical densitometer. It is preferable that a filter for the ink be used for the color ink, a cyan filter be used for the cyan ink, a magenta filter be used for the magenta ink, and a yellow filter be used for the yellow ink.

In the present invention, the coloring material is a dye or a pigment, and is not particularly limited as long as it contributes to coloring in the ink, but it is preferable to use a water-soluble dye.
Examples of the water-soluble dye include acid dyes, basic dyes, direct dyes, food dyes, and the like. Specific examples include direct black 19, direct black 32, direct black 38, direct black 51, direct black 62, and direct black. 71, Direct Black 105, Direct Black 108, Direct Black 112, Direct Black 154, Direct Black 168, Direct Black 171, Acid Black 24, Acid Black 31, Acid Black 52, Acid Black 94, Food Black 1, Food Black 2, Direct Yellow 23, Direct Yellow 50, Direct Yellow 86, Direct Yellow 100, Direct Yellow 132, Direct Yellow 142, Die ECTS Yellow 157, Acid Yellow 23, Acid Yellow 42, Direct Red 83, Direct Red 227, Acid Red 35,
Acid Red 40, Acid Red 52, Acid Red 87, Acid Red 186, Acid Red 25
4, Acid Red 289, Reactive Red 24,
Reactive Red 120, Reactive Red 18
0, direct blue 76, direct blue 86, direct blue 108, direct blue 199, direct blue 236, acid blue 9, acid blue 78, acid blue 82, acid blue 86, acid blue 234, and the like. Without limitation, any water-soluble dye can be used. The amount of the dye is 1 to 10 with respect to the total weight of the ink composition.
% By weight is preferred. When the dye is added in an amount of 10% by weight or more, the stability as an ink is deteriorated, clogging is likely to occur in a head discharge portion of an ink jet printer or the like, and the viscosity is greatly increased. On the other hand, when the amount of the dye is less than 1% by weight, there is a problem that a good printed image cannot be obtained because the dye concentration is low.

In the aqueous ink of the present invention, it is preferable to use water as an aqueous medium for dissolving or dispersing a colorant, particularly a dye. As the water, ion-exchanged water is preferable from the viewpoint of dye stability, but commercially available distilled water may be used.

The organic solvent used in the aqueous ink of the present invention is not particularly limited. Examples thereof include ethylene glycol, diethylene glycol, propylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol MW200, polyethylene glycol MW300, and polyethylene glycol. MW600,
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, methyl carbitol, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, diethyl carbitol, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, Examples include triethylene glycol monobutyl ether, glycerin, triethanolamine, formamide, dimethylformamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidine and the like. Among these organic solvents, at least one organic solvent selected from the group consisting of diethylene glycol, propylene glycol, polyethylene glycol, glycerin, triethylene glycol monobutyl ether and diethylene glycol monobutyl ether has ink storage stability and printing paper. It is suitably used from the viewpoint of permeability to water.

These organic solvents are used as penetrants and dye dissolution aids, and their amounts are preferably not more than 50% by weight based on the total weight of the ink composition. If the compounding amount of the organic solvent exceeds 50% by weight, the drying property on the recording paper is deteriorated, and a good printed image may not be obtained.

The surfactant contained in the ink composition of the present invention is not particularly limited, but it is preferable to use a nonionic surfactant. Examples of the nonionic surfactant include an acetylene glycol-based compound and a propylene oxide-ethylene oxide copolymer, but are not particularly limited thereto. The amount of the surfactant is 0.1% based on the total weight of the ink composition.
It is preferably from 01% to 10% by weight. 0.01% by weight
If the compounding amount is less than the above, the amount is too small, so that a sufficient surface tension adjusting effect cannot be obtained. On the other hand, when the content is 10% by weight or more, the viscosity of the ink is greatly increased because the amount is too large.

The ink composition of the present invention comprises a pH adjuster,
Conventionally known additives such as an antifungal agent and a chelating agent can be mixed. Examples of the pH adjuster include potassium carbonate, sodium carbonate, and triethanolamine. Examples of the fungicide include sodium benzoate. Examples of the chelating agent include sodium diethylenetriaminepentaacetate.

The surface tension of the ink composition of the present invention is 25
It is preferably 20 to 50 dyne / cm at ° C.
The surface tension in the present invention is a static surface tension when the liquid surface is at rest, and can be measured by a Wilhelmy plate hanging method or the like. Static surface tension is 50 dyne
If the aqueous ink is more than / dyne / cm or less than 20 dyne / cm, the permeability and the drying property are deteriorated at the time of image formation, and a good printed image may not be obtained.

The viscosity of the ink composition of the present invention is preferably adjusted to a range of 1 to 5 cps at 25 ° C.
In the case of an aqueous ink having a viscosity of more than 5 cps or less than 1 cps, the ink ejection stability of the head is deteriorated, and a good printed image may not be obtained.

The pH of the ink composition of the present invention is 2
Preferably, the temperature is adjusted to 6.5 to 11.5 at 5 ° C. By adjusting the pH of the aqueous ink to 6.5 to 11.5, long-term storage stability of the ink is improved, changes in various physical properties such as surface tension and viscosity are reduced, and stable ink ejection over a long period of time is possible. Become.

When a water-soluble dye is used in the ink composition of the present invention, a printed matter having particularly high ejection stability and excellent sharpness can be obtained.

Although the use of the ink composition of the present invention is not particularly limited, it can be used in an ink jet recording method and apparatus in which ink droplets are ejected from minute orifices by the action of a piezo element to perform recording. preferable.

The ink composition of the present invention is used by being incorporated in an ink container. The ink container has a storage chamber for storing the ink composition of the present invention, and at least a portion of the storage chamber that contacts the ink may be made of a material that is inert to the ink composition of the present invention. preferable. The material inert to the ink composition of the present invention is a material that is at least insoluble in the ink composition of the present invention and a material that does not adversely affect the ink composition of the present invention during storage, such as deterioration. For example, a resin such as polypropylene, a metal such as aluminum, or a ceramic.

The ink jet recording apparatus of the present invention has an ink discharge port for discharging the ink composition of the present invention, and can record an image or the like on a recording medium such as paper using the ink of the present invention. . As described above, the ink composition of the present invention is used for an ink jet recording apparatus that performs recording by discharging ink droplets, but its use is not particularly limited.

Such an ink jet recording apparatus and ink jet recording method have excellent ejection stability because the aqueous ink composition of the present invention is used. Also,
Since the ink composition of the present invention does not decompose the dye even under strong alkaline conditions, the ink composition has excellent light stability and liquid contact stability with water, and has extremely high storage stability. .

[0029]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

In this embodiment, an aqueous ink composition containing a colorant, an organic solvent, and a surfactant is used as the ink A.
As the ink B, an ink A obtained by adding 5 parts by weight of NaOH to the total weight of the ink was used.

(Static surface tension) It was measured using a Wilhelmy surface tensiometer (CBVP-A3, manufactured by Kyowa Interface Chemical Co., Ltd.). The measurement temperature was 25 ° C.

(Viscosity) Automatic Viscometer DVM-EII
(Manufactured by Tokimec). The measurement temperature is 25
° C.

(PH) Personal pH meter PH81
(Manufactured by Yokogawa Electric Corporation). The measurement temperature was 25 ° C.

(Evaluation 1 of Image Stability) The storage stability of the image formed by the ink composition was evaluated. Using a piezo-type inkjet printer adjusted so that the amount of one ink droplet is 20 pl (picoliter), the ink is arranged so that the droplets are arranged on all pixel grids under the condition of a resolution of 720 dpi. A and ink B are printed on a plain paper in a square of 2 cm × 2 cm, and two image samples (A) and (B) corresponding to each ink are printed.
I got Xerox L paper was used as plain paper. The optical densities (OD values) of these image samples (A) and (B) were measured. Each image sample was immersed in water by the water immersion operation described below, and the optical density (OD value (A) value and OD value (B)) of each image sample after the water immersion operation was measured. The optical density is RD9 manufactured by Macbeth.
It measured using the 18 type optical densitometer. As an index for judging the water resistance, the OD value of the image sample (A) before immersion in water was separately measured, and the difference in optical density before and after immersion in water was calculated.
D was calculated.

(Evaluation 2 of Image Stability) The storage stability of an image formed by the ink composition was evaluated by another method. Using a piezo-type inkjet printer adjusted so that the amount of one ink droplet becomes 20 pl (picoliter), the ink is arranged such that the droplets are arranged on all pixel grids under the condition of a resolution of 720 dpi. A was printed on plain paper in a 2 cm × 2 cm square to obtain an image sample (A). Xerox L paper was used as plain paper. The color values (L ^* , a ^* , b ^* ) of the image (solid) portion of the image sample (A) are converted into the L ^* a ^* b ^* color system (CIELA).
B color system). Specifically, the color values (L1 ^* , a1 ^* , b1 ^* ) of the image sample before the water immersion operation described later.
And the color value (L2 ^* , a) of the image sample after the water immersion operation
2 ^* , b2 ^* ) were measured using the L ^* a ^* b ^* color system. As a judgment index of water resistance performance, a water resistance deterioration change rate ΔE was calculated by the following equation (1).

Equation (1) ΔE = ｛(L1 ^* −L2 ^* ) ² + (a1 ^* −a2 ^* ) ² + (b
1 ^* -b2 ^* ) ² ｝ ^1/2 color value was measured using a 938 Spectro-Densitometer (manufactured by X-Rite).

(Water immersion operation) Glass water tank (capacity 10
L) was filled with pure water at 25 ° C., the image portion of the image sample was immersed in water over the entire surface, and left at 25 ° C. for 5 minutes.
The image sample pulled out of the water tank was dried at room temperature for 3 hours. Here, room temperature means 25 ° C.

(Evaluation of Ejection Stability) A printing test was performed on 100 sheets using a piezo-type inkjet printer with a resolution of 720 dpi adjusted so that the amount of one ink droplet was 20 pl (picoliter). Commercially available recycled paper (A4 size) was used as the printing paper.

The sharpness of the image was confirmed for 100 print samples, and the ejection stability was evaluated according to the following evaluation criteria. ：: All are good printed images. Δ: Most of the images were good, but some abnormal images were observed. ×: Many abnormal printed images were observed.

(Evaluation of Storage Stability) The aqueous ink was stored in a polyethylene container at 60 ° C. for one month, examined for changes in surface tension, viscosity and pH, and for the presence or absence of precipitates. The sex was evaluated. ：: There is almost no change in physical properties, and no precipitate is observed. Δ: Physical properties slightly changed, but no precipitate was observed. ×: Physical properties are significantly changed, and precipitates are confirmed.

Example 1 Ink Composition A Reactive Yellow 67 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder Ink composition A of Example 1, surface tension γ = 30.4
dyne / cm, viscosity η = 3.0 cps, pH = 9.1
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 1. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In the ink composition B of Example 1, the surface tension γ = 30.4
dyne / cm, viscosity η = 3.2 cps, pH = 11.
It was 8.

Example 2 Ink Composition A Reactive Yellow 67 1 part Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 2, the surface tension γ = 30.2
dyne / cm, viscosity η = 2.8 cps, pH = 8.7
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 2. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Example 2, surface tension γ = 30.3
dyne / cm, viscosity η = 3.0 cps, pH = 11.0.
It was 7.

Example 3 Ink Composition A Reactive Yellow 67 5 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 3, the surface tension γ = 30.7
yne / cm, viscosity η = 3.2 cps, pH = 9.3. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 3. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Example 3, surface tension γ = 30.5
dyne / cm, viscosity η = 3.4 cps, pH = 12.
It was 4.

Example 4 Ink Composition A Reactive Yellow 47 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion exchange water Remainder Ink composition A of Example 4 has a surface tension γ = 30.5
dyne / cm, viscosity η = 3.0 cps, pH = 8.8
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 4. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Example 4, surface tension γ = 30.5
dyne / cm, viscosity η = 3.2 cps, pH = 11.
It was 5.

Example 5 Ink Composition A Reactive Red 14 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 5, the surface tension γ = 30.5
dyne / cm, viscosity η = 3.0 cps, pH = 9.5
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 5. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In the ink composition B of Example 5, the surface tension γ = 30.7
dyne / cm, viscosity η = 3.3 cps, pH = 12.
It was 4.

Example 6 Ink Composition A Reactive Blue 7 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 6, the surface tension γ = 30.8
dyne / cm, viscosity η = 3.0 cps, pH = 9.4
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 6. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Example 6, surface tension γ = 30.9
dyne / cm, viscosity η = 3.3 cps, pH = 12.
It was one.

Example 7 Ink Composition A Direct Blue 71 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 7, the surface tension γ = 30.7
dyne / cm, viscosity η = 3.0 cps, pH = 9.1
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 7. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Example 7, surface tension γ = 31.0
dyne / cm, viscosity η = 3.2 cps, pH = 12.
It was 0.

Example 8 Ink Composition A Direct Blue 199 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 8, the surface tension γ = 30.5
dyne / cm, viscosity η = 3.0 cps, pH = 8.9
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 8. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In the ink composition B of Example 8, the surface tension γ = 30.4
dyne / cm, viscosity η = 3.2 cps, pH = 12.
It was 5.

Example 9 Ink Composition A Reactive Black 11.6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder Ink composition A of Example 9 has a surface tension γ = 30.7
dyne / cm, viscosity η = 3.3 cps, pH = 9.4
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 9. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Example 9, surface tension γ = 30.8
dyne / cm, viscosity η = 3.5 cps, pH = 12.
It was 6.

Example 10 Ink Composition A Direct Black 154 6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 10, the surface tension γ = 30.
8 dyne / cm, viscosity η = 3.7 cps, pH = 9.
It was 2. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Example 10. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In the ink composition B of Example 10, the surface tension γ = 30.
9 dyne / cm, viscosity η = 3.9 cps, pH = 1
2.1.

Example 11 Ink Composition A Direct Black 154 6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder Ink composition A of Example 11, surface tension γ = 30.
8 dyne / cm, viscosity η = 3.7 cps, pH = 9.
It was 2. Ink Composition B Ink Composition B was prepared by adding 3.0 parts by weight of NaOH to Ink Composition A of Example 11. Ink composition A 97.1 parts (100/103 parts) NaOH remaining part (3/103 parts) In the ink composition B of Example 11, the surface tension γ = 30.
9 dyne / cm, viscosity η = 3.9 cps, pH = 1
It was 1.8.

Example 12 Ink Composition A Direct Black 154 6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion exchange water Remainder In the ink composition A of Example 12, the surface tension γ = 30.
8 dyne / cm, viscosity η = 3.7 cps, pH = 9.
It was 2. Ink Composition B Ink Composition B was prepared by adding 1.0 part by weight of NaOH to Ink Composition A of Example 12. Ink composition A 99.0 parts (100/101 parts) NaOH remaining part (1/101 parts) In ink composition B of Example 12, the surface tension γ = 30.
9 dyne / cm, viscosity η = 3.9 cps, pH = 1
1.3.

Example 13 Ink Composition A Direct Black 154 6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Example 13, the surface tension γ = 30.
8 dyne / cm, viscosity η = 3.7 cps, pH = 9.
It was 2. Ink Composition B Ink Composition B was prepared by adding 0.5 parts by weight of NaOH to Ink Composition A of Example 13. Ink composition A 99.5 parts (100 / 100.5 parts) NaOH remaining part (0.5 / 101 parts) In the ink composition B of Example 13, the surface tension γ = 30.
9 dyne / cm, viscosity η = 3.9 cps, pH = 9.
Nine.

[Comparative Example 1] Ink Composition A Direct Yellow 12 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water balance The ink composition A of Comparative Example 1 has a surface tension γ = 30.6
dyne / cm, viscosity η = 3.0 cps, pH = 8.8
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Comparative Example 1. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Comparative Example 1, surface tension γ = 30.6
dyne / cm, viscosity η = 3.2 cps, pH = 12.
It was 3.

Comparative Example 2 Ink Composition A Acid Yellow 142 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder Ink composition A of Comparative Example 2 has a surface tension γ = 30.6
dyne / cm, viscosity η = 3.0 cps, pH = 8.9
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Comparative Example 2. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Comparative Example 2, surface tension γ = 30.9
dyne / cm, viscosity η = 3.2 cps, pH = 11.
It was 6.

Comparative Example 3 Ink Composition A Reactive Red 5 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder In the ink composition A of Comparative Example 3, the surface tension γ = 30.3
dyne / cm, viscosity η = 3.0 cps, pH = 9.4
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Comparative Example 3. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Comparative Example 3, surface tension γ = 30.4
dyne / cm, viscosity η = 3.2 cps, pH = 12.
It was 8.

[Comparative Example 4] Ink Composition A Acid Blue 9 3 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water remainder The ink composition A of Comparative Example 4 has a surface tension γ = 30.6
dyne / cm, viscosity η = 3.0 cps, pH = 9.0
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Comparative Example 4. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Comparative Example 4, surface tension γ = 30.8
dyne / cm, viscosity η = 3.2 cps, pH = 12.
It was one.

Comparative Example 5 Ink Composition A Direct Black 31 6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remaining Ink composition A of Comparative Example 5, the surface tension γ = 30.6
dyne / cm, viscosity η = 3.3 cps, pH = 8.9
Met. Ink Composition B Ink Composition B was prepared by adding 5.0 parts by weight of NaOH to Ink Composition A of Comparative Example 5. Ink composition A 95.2 parts (100/105 parts) NaOH remaining part (5/105 parts) In ink composition B of Comparative Example 5, surface tension γ = 30.8
dyne / cm, viscosity η = 3.6 cps, pH = 12.
It was 3.

Comparative Example 6 Ink Composition A Direct Black 31 6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder Ink composition A of Comparative Example 6 has a surface tension γ = 30.6
dyne / cm, viscosity η = 3.3 cps, pH = 8.9
Met. Ink Composition B Ink Composition B was prepared by adding 3.0 parts by weight of NaOH to Ink Composition A of Comparative Example 6. Ink composition A 97.1 parts (100/103 parts) NaOH remaining part (3/105 parts) In ink composition B of Comparative Example 6, surface tension γ = 30.8
dyne / cm, viscosity η = 3.6 cps, pH = 11.
Nine.

Comparative Example 7 Ink Composition A Direct Black 31 6 parts Polyethylene glycol # 200 15 parts Glycerin 10 parts Nonionic surfactant 1 part Ion-exchanged water Remainder Ink composition A of Comparative Example 7 has a surface tension γ = 30.6
dyne / cm, viscosity η = 3.3 cps, pH = 8.9
Met. Ink Composition B Ink Composition B was prepared by adding 1.0 part by weight of NaOH to Ink Composition A of Comparative Example 7. Ink composition A 99.0 parts (100/101 parts) NaOH remaining part (1/105 parts) In ink composition B of Comparative Example 7, surface tension γ = 30.8
dyne / cm, viscosity η = 3.6 cps, pH = 11.
It was 0.

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

As described above, the aqueous ink composition for ink jet recording of the present invention has a droplet volume of 20 droplets.
When an image was formed using an inkjet recording method so that liquid droplets were arranged in all pixels under the condition of picoliter and a resolution of 720 dpi, the optical density of the image by the aqueous ink composition without NaOH was added. (OD
(A)) and the aqueous ink composition 10
The optical density (OD (B)) of an image by the aqueous ink composition added in an amount of 0.1 to 5 parts by weight per 0 parts by weight is OD
Since this satisfies the relationship of (A) / OD (B) ≦ 1.05, the ink has high ejection stability and extremely excellent storage stability. Further, the storage stability of the printed matter using the aqueous ink is also improved.

In the ink jet recording method and apparatus of the present invention, recording is performed by discharging an ink liquid from micropores according to a recording signal. The aqueous ink composition of the present invention is used as the ink. Therefore, a printed material having excellent ejection stability and very excellent storage stability can be obtained.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Hiroyuki Ueki 5-7-1, Shiba, Minato-ku, Tokyo F-term in NEC Corporation (reference) 2C056 EA13 FA04 FC01 FC02 2H086 BA01 BA03 BA53 BA59 BA60 BA61 BA62 4J039 AE07 BC07 BC09 BC10 BC11 BC13 BC15 BE01 BE03 BE04 BE05 BE06 BE12 BE22 BE28 BE30 CA03 CA06 EA44 EA48 GA24

Claims (14)

[Claims] 1. A water-based ink composition for ink-jet recording comprising a colorant, an organic solvent and a surfactant, wherein the droplet volume is 20 picoliters and the resolution is 720d.
When an image is formed using an inkjet recording method so that droplets are arranged in all the pixels under the condition of pi, the optical density (OD (A)) of the image by the aqueous ink composition containing no NaOH is added. ) And the optical density (OD) of an image obtained by adding 0.1 to 5 parts by weight of NaOH to 100 parts by weight of the aqueous ink composition.
(B)) satisfying the following relationship: OD (A) / OD (B) ≦ 1.05. 2. The ink composition according to claim 1, wherein the ink jet recording method includes a step of forming the ink composition into droplets using a piezoelectric vibrator. 3. The ink composition according to claim 1, wherein the coloring material is a water-soluble dye. 4. The ink composition according to claim 3, wherein the dye is contained in an amount of 1 to 10% by weight based on the total weight of the ink composition. 5. The method according to claim 1, wherein the organic solvent is ethylene glycol,
The method according to any one of claims 1 to 4, wherein the compound is one or more selected from the group consisting of diethylene glycol, propylene glycol, polyethylene glycol, glycerin, triethylene glycol monobutyl ether and diethylene glycol monobutyl ether. Ink composition. 6. The ink composition according to claim 1, wherein the organic solvent is contained in an amount of 1 to 50% by weight based on the total weight of the ink composition. 7. The ink composition according to claim 1, wherein the surfactant is a nonionic surfactant. 8. The ink composition according to claim 1, wherein the surfactant is contained in an amount of 0.01 to 10% by weight based on the total weight of the ink composition. 9. A static surface tension at 25 ° C. of 20 to 5
The ink composition according to any one of claims 1 to 8, wherein 0 dyne / cm. 10. The ink composition according to claim 1, wherein the pH at 25 ° C. is 6.5 to 11. 11. The ink composition according to claim 1, wherein the viscosity at 25 ° C. is 1 to 5 cps. 12. An ink container comprising the ink composition according to claim 1 incorporated therein. 13. An ink jet recording method using the ink composition according to claim 1. 14. An ink jet recording apparatus using the ink composition according to claim 1. Description: