JP6070609B2 - Aqueous black ink and ink cartridge for ink jet recording - Google Patents

Description

  The present invention relates to an aqueous black ink for ink jet recording and an ink cartridge.

  For the purpose of improving optical density (OD value) and saturation, it has been proposed that a water-dispersible polymer is contained in an aqueous pigment ink (see, for example, Patent Documents 1 and 2).

JP 2006-2141 A JP 2012-87309 A

  However, water pigment inks are required to further improve optical density (OD value).

  Accordingly, an object of the present invention is to provide an aqueous black ink for ink jet recording using a self-dispersing black pigment capable of further improving the optical density (OD value).

In order to achieve the above object, the aqueous black ink for ink-jet recording of the present invention comprises:
A water-based ink for inkjet recording comprising a colorant, water and a water-soluble polymer,
The colorant includes a self-dispersing black pigment modified with a phosphate group,
The water-soluble polymer contains at least one of pullulan and a derivative thereof.

  The water-based black ink for ink-jet recording of the present invention uses a self-dispersed black pigment modified with a phosphoric acid group, and blends at least one of pullulan and a derivative thereof to obtain an optical density (OD value). ) Can be further improved.

FIG. 1 is a schematic perspective view showing an example of the configuration of the ink jet recording apparatus of the present invention.

  In the present invention, “black” means an achromatic color excluding white and includes black (black) and gray (gray).

  In the present invention, “at least one of pullulan and its derivatives” means that pullulan alone, pullulan derivatives alone, or a mixture of pullulan and pullulan derivatives may be used. .

  The aqueous black ink for ink-jet recording of the present invention (hereinafter sometimes referred to as “aqueous black ink” or “black ink”) will be described. The aqueous black ink of the present invention contains a colorant, water and a water-soluble polymer. As described above, the colorant includes a self-dispersing black pigment modified with a phosphoric acid group (hereinafter sometimes referred to as “phosphoric acid group-modified self-dispersing black pigment”). Examples of the phosphoric acid group-modified self-dispersing black pigment include, for example, JP-T 2009-515007, JP-T 2011-515535, JP-A 2006-1999968, JP-T 2009-515802, JP-T 2011. It can be prepared by the method described in JP-A-510155. For example, a commercially available product may be used as the phosphoric acid group-modified self-dispersing black pigment. Since the water-based black ink of the present invention uses a self-dispersing black pigment, there is no problem of viscosity increase due to the polymer pigment dispersant, and the handleability is excellent.

  Examples of the black pigment that can be used as a raw material for the self-dispersing black pigment include carbon black, inorganic pigments, and organic pigments. Examples of the carbon black include furnace black, lamp black, acetylene black, and channel black. Examples of the inorganic pigment include carbon black inorganic pigments. Examples of the organic pigment include aniline black daylight fluorescent pigment. Examples of pigments other than these include C.I. I. Pigment black 1, 6 etc. are also mentioned. In particular, examples of pigments suitable for modification with the phosphate group include carbon blacks such as “MA8” and “MA100” manufactured by Mitsubishi Chemical Corporation and “Color Black FW200” manufactured by Degussa. It is done.

  The solid content (pigment solid content) of the phosphoric acid group-modified self-dispersing black pigment with respect to the total amount of the water-based black ink is not particularly limited, and can be appropriately determined according to, for example, a desired optical density. The pigment solid content is, for example, 0.1% by weight to 20% by weight, preferably 1% by weight to 10% by weight, and more preferably 2% by weight to 8% by weight.

  In addition to the phosphoric acid group-modified self-dispersing black pigment, the colorant may further contain other pigments and dyes, but is preferably composed only of the phosphoric acid group-modified self-dispersing pigment. .

  The water is preferably ion exchange water or pure water. The blending amount (water ratio) of the water with respect to the total amount of the aqueous black ink is, for example, 10% to 90% by weight, and preferably 40% to 80% by weight. The said water ratio is good also as the remainder of another component, for example.

  As described above, the water-soluble polymer includes at least one of pullulan and a derivative thereof (hereinafter sometimes referred to as “pullulan or the like”). Examples of the pullulan derivative include: carboxymethyl pullulan; phosphorylated pullulan; pullulan ether such as pullulan methyl ether, pullulan ethyl ether, and pullulan propyl ether; pullulan ester such as pullulan acetate and pullulan butyrate; silicone-modified pullulan; cyanoethylated pullulan Cyanoethylated hydroxyalkyl pullulan such as cyanoethylated hydroxyethyl pullulan and cyanoethylated hydroxypropyl pullulan; cholesterol pullulan; and the like.

  The water-soluble polymer may further contain other water-soluble polymers in addition to the pullulan and the like.

  The molecular weight of the pullulan or the like is preferably 1000 to 1000000.

  The amount of pullulan or the like (ratio of pullulan or the like) with respect to the total amount of the aqueous black ink is, for example, 0.5% by weight to 10% by weight, and preferably 0.8% by weight to 5% by weight. By setting the proportion of pullulan or the like to 0.8% by weight or more, an aqueous black ink having a higher optical density can be obtained. Further, when the proportion of pullulan or the like is set to 5% by weight or less, an aqueous black ink having more excellent storage stability can be obtained.

  The weight ratio of the pigment solid content (X) to the pullulan or the like (Y) in the total amount of the water-based ink is, for example, X: Y = 1: 0.07 to 2, preferably 1: 0.11. ~ 1.25. By setting X: Y to be 0.11 or more, an aqueous black ink having a higher optical density (OD value) can be obtained. Further, when X: Y is set to 1: 1.25 or less, an aqueous black ink having more excellent storage stability can be obtained.

  Although the mechanism is unknown, as shown in the examples described later, the water-based black ink of the present invention uses a self-dispersed black pigment modified with a phosphoric acid group and is blended with pullulan or the like. Thus, the optical density (OD value) can be further improved.

  The aqueous black ink of the present invention preferably further contains a water-soluble organic solvent. Examples of the water-soluble organic solvent include a wetting agent that prevents drying of the aqueous black ink at the nozzle tip of the ink jet head and a penetrating agent that adjusts the drying speed on the recording medium.

  The wetting agent is not particularly limited, and examples thereof include lower alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol; dimethylformamide, dimethylacetamide Amides such as acetone; Ketones such as acetone; Keto alcohols such as diacetone alcohol; Ethers such as tetrahydrofuran and dioxane; Polyethers such as polyalkylene glycol; Polyhydric alcohols such as alkylene glycol, glycerin, trimethylolpropane, and trimethylolethane; 2-pyrrolidone; N-methyl-2-pyrrolidone; 1,3-dimethyl-2-imidazolidinone and the like. Examples of the polyalkylene glycol include polyethylene glycol and polypropylene glycol. Examples of the alkylene glycol include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, thiodiglycol, and hexylene glycol. These wetting agents may be used alone or in combination of two or more. Among these, polyhydric alcohols such as alkylene glycol and glycerin are preferable.

  The blending amount of the wetting agent with respect to the total amount of the water-based black ink is, for example, 0% by weight to 95% by weight, preferably 5% by weight to 80% by weight, and more preferably 5% by weight to 50% by weight. %.

  Examples of the penetrant include glycol ether. Examples of the glycol ether include ethylene glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol-n-propyl ether, diethylene glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol-n-propyl ether, diethylene glycol-n-butyl ether, diethylene glycol-n-. Hexyl ether, triethylene glycol methyl ether, triethylene glycol ethyl ether, triethylene glycol-n-propyl ether, triethylene glycol-n-butyl ether, propylene glycol methyl ether, propylene glycol ethyl ether, propylene glycol-n-propyl ether, Propylene glycol-n-butyl ether , Dipropylene glycol methyl ether, dipropylene glycol ethyl ether, dipropylene glycol-n-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol methyl ether, tripropylene glycol ethyl ether, tripropylene glycol-n-propyl ether And tripropylene glycol-n-butyl ether. The said penetrant may be used individually by 1 type, and may use 2 or more types together.

  The blending amount of the penetrant with respect to the total amount of the aqueous black ink is, for example, 0% by weight to 20% by weight, preferably 0.1% by weight to 15% by weight, and more preferably 0.5% by weight. % To 10% by weight.

  The water-based black ink may further contain a conventionally known additive as required. Examples of the additive include a surfactant, a pH adjuster, a viscosity adjuster, a surface tension adjuster, and an antifungal agent. Examples of the viscosity modifier include polyvinyl alcohol, cellulose, and a water-soluble resin.

  In the water-based black ink, for example, a colorant, water, a water-soluble polymer, and other additive components as necessary are uniformly mixed by a conventionally known method, and an insoluble matter is removed by a filter or the like. Can be prepared.

  Next, the ink cartridge of the present invention is an ink cartridge containing a water-based black ink for ink-jet recording, wherein the water-based black ink is the water-based black ink for ink-jet recording of the present invention. As the main body of the ink cartridge, for example, a conventionally known one can be used.

  Next, the ink jet recording apparatus and the ink jet recording method of the present invention will be described.

  The ink jet recording apparatus of the present invention is an ink jet recording apparatus that includes an ink storage portion and an ink discharge means, and discharges ink stored in the ink storage portion by the ink discharge means. The water-based black ink for ink jet recording is accommodated.

  The ink jet recording method of the present invention is an ink jet recording method for recording by ejecting water-based ink onto a recording medium by an ink jet method, wherein the water-based black ink for ink-jet recording of the present invention is used as the water-based ink. To do.

  The ink jet recording method of the present invention can be performed using, for example, the ink jet recording apparatus of the present invention. The recording includes printing, printing, printing, and the like.

  FIG. 1 shows the configuration of an example of the ink jet recording apparatus of the present invention. As shown in the figure, this ink jet recording apparatus 1 includes four ink cartridges 2, an ink discharge means (ink jet head) 3, a head unit 4, a carriage 5, a drive unit 6, a platen roller 7, and a purge device 8. And as a major component.

  The four ink cartridges 2 contain one color each of four colors of water-based inks of yellow, magenta, cyan, and black. For example, the water-based black ink is the water-based black ink for inkjet recording of the present invention. Other water-based inks may be general water-based inks. The ink jet head 3 installed in the head unit 4 performs recording on a recording medium (for example, recording paper) P. Four ink cartridges 2 and a head unit 4 are mounted on the carriage 5. The drive unit 6 reciprocates the carriage 5 in the linear direction. As the drive unit 6, for example, a conventionally known one can be used (for example, see Japanese Patent Laid-Open No. 2008-246821). The platen roller 7 extends in the reciprocating direction of the carriage 5 and is disposed to face the inkjet head 3.

  The purge device 8 sucks out defective ink containing bubbles and the like accumulated in the ink jet head 3. As the purge device 8, for example, a conventionally known device can be used (see, for example, JP-A-2008-246821).

  A wiper member 20 is disposed adjacent to the purge device 8 on the platen roller 7 side of the purge device 8. The wiper member 20 is formed in a spatula shape, and wipes the nozzle formation surface of the inkjet head 3 as the carriage 5 moves. In FIG. 1, a cap 18 covers a plurality of nozzles of the inkjet head 3 that is returned to the reset position when recording is completed in order to prevent the water-based ink from drying.

  In the ink jet recording apparatus 1 of this example, four ink cartridges 2 are mounted on one carriage 5 together with the head unit 4. However, the present invention is not limited to this. In the ink jet recording apparatus 1, each of the four ink cartridges 2 may be mounted on a carriage different from the head unit 4. Further, each of the four ink cartridges 2 may be arranged and fixed in the inkjet recording apparatus 1 without being mounted on the carriage 5. In these aspects, for example, each cartridge of the four ink cartridges 2 and the head unit 4 mounted on the carriage 5 are connected by a tube or the like, and each cartridge of the four ink cartridges 2 is connected to the head unit 4 from the cartridge. Aqueous ink is supplied.

  Ink jet recording using this ink jet recording apparatus 1 is performed as follows, for example. First, the recording paper P is fed from a paper feed cassette (not shown) provided on the side of or below the ink jet recording apparatus 1. The recording paper P is introduced between the inkjet head 3 and the platen roller 7. Predetermined recording is performed on the introduced recording paper P by water-based ink ejected from the inkjet head 3. The recording sheet P after recording is discharged from the inkjet recording apparatus 1. The recorded matter recorded with the aqueous black ink of the present invention has a high optical density (OD value). In FIG. 1, the paper feed mechanism and paper discharge mechanism for the recording paper P are not shown.

  The apparatus shown in FIG. 1 employs a serial type ink jet head, but the present invention is not limited to this. The ink jet recording apparatus may be an apparatus that employs a line type ink jet head.

  Next, examples of the present invention will be described together with comparative examples. In addition, this invention is not limited and restrict | limited by the following Example and comparative example.

[Examples 1 to 9 and Comparative Examples 1 to 5]
In the black ink composition (Table 1), components other than self-dispersing carbon black were uniformly mixed to obtain an ink solvent. Next, the ink solvent was added to the self-dispersing carbon black dispersed in water and mixed uniformly. Thereafter, the obtained mixture was filtered through a cellulose acetate type membrane filter (pore size: 3.00 μm) manufactured by Toyo Roshi Kaisha, Ltd., so that the aqueous black system for inkjet recording of Examples 1 to 9 and Comparative Examples 1 to 5 was used. Ink was obtained.

  For the aqueous black inks of Examples and Comparative Examples, (a) optical density (OD value) evaluation, (b) storage stability evaluation, and (c) comprehensive evaluation were performed by the following methods.

(A) Evaluation of optical density (OD value) Black ink with a resolution of 600 dpi × 300 dpi on plain paper using the aqueous black inks of Examples and Comparative Examples using an inkjet printer DCP-J525N manufactured by Brother Industries, Ltd. An image including the patch was recorded to produce an evaluation sample. The optical density (OD value) at five locations in the evaluation sample was measured with a spectrocolorimeter SpectroEye manufactured by X-Rite, and the average value was obtained and evaluated according to the following evaluation criteria. For the plain paper, Recycled Supreme made by XEROX was used.

Evaluation of optical density (OD value) Evaluation standard A: Optical density (OD value) of Comparative Examples 3 to 5 was the same as that of Comparative Example 3-5 except that pullulan was not blended. 1.19 times or more B: The optical density (OD value) is 1.15 times the optical density (OD value) of the comparative example under the same conditions except that no pullulan is blended among the comparative examples 3 to 5. And less than 1.19 times C: Optical density (OD value) of Comparative Examples 3 to 5 is the same as that of Comparative Example 3-5 except that no pullulan was blended. .15 times or less

(B) Storage Stability Evaluation The aqueous black inks of Examples and Comparative Examples were placed in a sealed container and stored for one day in an environment at a temperature of 40 ° C. The evaluation sample thus prepared was observed with a microscope (200 times magnification) for the presence of aggregates, and the storage stability was evaluated according to the following evaluation criteria.

Evaluation of storage stability Evaluation criteria A: No aggregate B: A trace of aggregate was observed C: A large amount of aggregate was observed

(C) Comprehensive evaluation About each water-based black ink, comprehensive evaluation was performed according to the following evaluation criteria from the results of (a) and (b).

Overall Evaluation Evaluation Criteria G: The evaluation results of (a) and (b) were not C. NG: Either or both of the evaluation results of (a) and (b) were C.

  Table 1 shows the black ink compositions and evaluation results of the aqueous black inks of Examples and Comparative Examples.

  As shown in Table 1, in Examples 1 to 7, the optical density (OD value) was improved to 1.17 times or more that of Comparative Example 3 under the same conditions except that pullulan was not blended. Also in Examples 8 and 9, the optical density (OD value) was improved to 1.20 times and 1.19 times that of Comparative Example 5 under the same conditions except that no pullulan was blended. In particular, the weight ratio (X: Y) of phosphoric acid group-modified self-dispersing black pigment (X) to pullulan (Y) is 1: 0.11 to 1.25 (Y / X is 0.11 to 1. 25), and in Examples 1-5, 7 and 8 in which the blending amount (Y) of pullulan was 0.8 wt% to 5 wt%, the optical density (OD value) was not blended with pullulan. Except for this, it was significantly improved to 1.19 times or more of the comparative example under the same conditions, and the storage stability was also excellent. On the other hand, in Comparative Example 1 using a self-dispersing black pigment modified with a sulfonic acid group in place of the phosphoric acid group-modified self-dispersing black pigment, the optical density (OD value) did not include pullulan. Except for this, it was 1.14 times that of Comparative Example 4 under the same conditions. Furthermore, in Comparative Example 2 using starch instead of pullulan, the optical density (OD value) remained at 1.08 times that of Comparative Example 3 under the same conditions except that no starch was used.

  As described above, the aqueous black ink of the present invention can further improve the optical density (OD value). The use of the aqueous black ink of the present invention is not particularly limited and can be widely applied to various ink jet recordings.

DESCRIPTION OF SYMBOLS 1 Inkjet recording apparatus 2 Ink cartridge 3 Ink discharge means (inkjet head)
4 Head unit 5 Carriage 6 Drive unit 7 Platen roller 8 Purge device

Claims (4)

A water-based ink for inkjet recording comprising a colorant, water and a water-soluble polymer,
The colorant includes a self-dispersing black pigment modified with a phosphate group,
An aqueous black ink for ink-jet recording, wherein the water-soluble polymer contains at least one of pullulan and a derivative thereof. The weight ratio of the self-dispersing black pigment (X) modified with the phosphoric acid group in the water-based black ink to at least one of pullulan and its derivative (Y) is X: Y = 1: 0.11. The aqueous black ink for ink-jet recording according to claim 1, wherein the water-based black ink is for ink jet recording. 3. The aqueous black ink for ink-jet recording according to claim 1, wherein a blending amount of at least one of the pullulan and the derivative thereof is 0.8% by weight to 5% by weight with respect to the total amount of the aqueous black ink. . An ink cartridge comprising a water-based black ink for ink-jet recording, wherein the water-based black ink is the water-based black ink for ink-jet recording according to any one of claims 1 to 3. cartridge.

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