JPH07118584A - Ink for ink jet recording - Google Patents

Abstract

PURPOSE:To obtain an ink for ink jet recording which neither soil fingers even when the fingers touch printing surface nor cause clogging and printing unevenness by mixing a pigment, a water-soluble resin that is soluble at a high alkalinity, and a sugar in a specific proportion. CONSTITUTION:The ink is prepared by mixing at least a pigment A (e.g. carbon black), 1.5-7wt.% of a water-soluble resin B that is soluble at a pH of 10 or more (e.g. WS-32 (trade name) made by Rhom & Haas Co.) and 0.5-10wt.% of a sugar C (e.g. pentose) so that the ratio of the components A to B may become 1: 0.5-1:2. As an alkali source for controlling the pH of the ink, an inorganic or organic amine or ammonium hydroxide is preferably used. A polymer dispersant, surfactant, etc., can be used as a dispersant for dispersing the pigment. Further, a water-soluble solvent (e.g. urea) may be added to the ink.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aqueous recording ink for use in an ink jet printer that records using liquid ink.

[0002]

2. Description of the Related Art The properties required of ink jet recording inks are that physical properties do not change during long-term storage,
It is required that the fine nozzles are not clogged, that the printed matter has a high density and is clear, and that the printed matter is storable (water resistance, light resistance, etc.). In particular, in the case of a pigment ink, it is required that the storage stability and the nozzle do not clog during printing or during restarting after printing is interrupted. As a pigment-based ink having these characteristics improved, JP-A-56-147 is known.
863, JP-A-62-283174, JP-A-4-1.
8462, JP-A-4-18421, JP-A-3-21
Japanese Patent Laid-Open No. 0373 and Japanese Patent Laid-Open No. 4-83375 have been proposed.

However, in the above-described conventionally known pigment-based ink, both the clogging property of the nozzle and the finger touch property such that the print surface and the finger are contaminated when the print surface is touched by the finger are compatible with each other. Cannot be achieved, and as the fill of the print becomes larger, there arises a new problem that is not seen with the dye ink, that the print becomes shaded during the fill (hereinafter referred to as “print unevenness”). Although the exact cause of this print unevenness is unknown, printing was performed by increasing the pigment concentration or using an excessive amount of ink ejection to improve print unevenness, but it did not improve. It is believed that it depends largely on this. Therefore, the conventional pigment ink composition cannot achieve high-quality recording, which will be required in the future, and this printing unevenness is an important issue for use in applications in which not only simple characters but also large shapes such as figures and graphs become large. Has become.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an ink jet recording ink, which does not have nozzle clogging and can be printed with excellent finger touch. There is.

It is another object of the present invention to provide an ink jet recording ink which does not cause uneven printing.

[0006]

Therefore, according to the present invention, at least a pigment and a water-soluble resin soluble at a pH of 10 or more are used.
The ink for inkjet recording is characterized by containing ˜7 wt% and sugar in an amount of 0.5 to 10 wt%, and further having a pigment / resin ratio of 1: 0.5 to 1: 2. The present invention will be described in detail below.

In order to satisfy the above-mentioned object of obtaining an ink having good touchability without clogging fine nozzles of an ink jet, the inside of the nozzle does not solidify but maintains fluidity, and when it adheres to paper. However, it is necessary to have two contradictory properties of not being redissolved in water or ink. The present inventors have found that the above object can be satisfied by using a resin having a narrow pH range for solubilization, that is, a resin solubilized at a pH of 10 or more in order to obtain a rapid change in PH. . In addition, it is possible to achieve both printing unevenness and ink aggregation due to a sharp decrease in PH.

The resin used in the present invention is PH1.
Any resin that is solubilized at 0 or more can be used. The molecular weight is not particularly specified, but one having a range of about 7,000 to 250,000 can be used, and specific examples thereof include WS-32 manufactured by Rohm and Haas.

In order to solubilize the above resin, the pH of the ink is preferably 10 or more, and the upper limit is preferably 11 or less from the viewpoint of safety and durability of the head member. Examples of the alkali source for adjusting the pH of the ink include inorganic and organic amines, ammonium hydroxide, sodium hydroxide and the like.

As the pigment in the present invention, an inorganic pigment,
Both organic pigments can be used. These pigments are used in a proportion of 0.5 to 25% by weight with respect to the ink of the present invention. It is preferably used in a proportion of 2 to 15% by weight.

As the dispersant for dispersing the pigment, conventionally known polymer dispersants and surfactants can be used. As a pigment dispersion method, a ball mill, a sand mill,
Attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer,
A dispersing machine such as a pearl mill, a jet mill or an ong mill can be used.

The saccharides used in the ink of the present invention include monosaccharides such as diose, triose, tetrose, pentose, hexose, heptose, octose and nonose, disaccharides, trisaccharides, tetrasaccharides, polysaccharides and / or derivatives thereof. Reduced derivatives such as certain sugar alcohols and deoxy sugars, oxidized derivatives such as aldonic acid and uronic acid,
Examples thereof include dehydrated derivatives such as glycoceene, and sugars such as amino sugar and thio sugar. Polysaccharides refers to sugars in a broad sense, and includes substances widely existing in nature such as alginic acid, dextrin, and cellulose.

In addition, a water-soluble solvent may be added to the present invention. Of these, urea is the most preferred,
In addition, glycerin, diethylene glycol, polyethylene glycol, polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, glycerin, trimethylolethane, triglyceride Solvents such as methylolpropane, 2-pyrrolidone, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone can be used. Further, if necessary, methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, te
Add rt-butanol, iso-butanol, n-pentanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, etc. You can

When urea is used as the water-soluble solvent, the ratio of resin to urea is preferably 1: 0.5 to 1:35. If it is out of this range, the clogging property is significantly deteriorated, which is not preferable.

If necessary, additives for controlling the physical properties of the ink, fungicides and preservatives can be added as appropriate.

[0016]

[Examples] The present invention will be specifically described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The numerical values in the present invention are% by weight.

<Example 1> Carbon black MA7 (manufactured by Mitsubishi Kasei Co., Ltd.) 5 Dispersant (ammonia salt of styrene-acrylic copolymer) 1 WS-32 (resin content 22%) 13.6 Sugar 7 Urea 10 NH ₄ water (35%) 1 ion-exchanged water 62.4 The ink was manufactured by the following procedure, but the invention is not limited to this. First, fill carbon beads and dispersant in water in a sand mill (Yasukawa Seisakusho Co., Ltd.) in an amount 1.5 times that of the dispersion solution and stir and mix for 30 minutes or longer to confirm that the particle size is about 1 μm or less. Confirm by microscopic observation,
Add sugar and urea and stir at room temperature for 20 minutes to completely dissolve. Furthermore, after adding NH ₄ water, WS-32 is added to 30
Mix and stir to dissolve completely. Dust and coarse particles were removed by pressure filtration with an 8 μm membrane filter to obtain an aqueous recording ink of PH10. Ink was prepared in the same procedure as described below.

<Example 2> Carbon black MA7 (manufactured by Mitsubishi Kasei Co., Ltd.) 5 Dispersant 0.8 (Ammonia salt of styrene-acrylic copolymer) WS-32 (resin content 22%) 6.8 Sugar 1.4 Urea 10 NH ₄ Water (35%) 1 Ion-exchanged Water 75 <Example 3> KETBLUEEX-15 (manufactured by Dainippon Ink and Chemicals, Inc.) Dispersant 1 (Ammonia salt of styrene-acrylic copolymer) WS-32 (resin content 22%) 13.6 sugar 7 urea 10 NH ₄ water (35%) 1 ion-exchanged water 62.4 <Comparative example 1> carbon black MA7 5 (manufactured by Mitsubishi Kasei Co., Ltd.) dispersant 1 (Ammonia salt of styrene-acrylic copolymer) Sugar 7 Urea 10 NH ₄ Water (35%) 1 Ion-exchanged water 76 The following evaluation was performed using the ink obtained above.

Clogging Characteristic An ink jet printer HG-5130 (manufactured by Seiko Epson Corp.) is filled with a predetermined ink, and after confirming that all the nozzles are free from scratches, omissions, and print bending, the cap and flushing are performed. Printing was performed every 5 seconds in a state where the ink did not enter, and the time at which defective portions such as blurring, omission, and print bending of each nozzle printing occurred was measured.

More than 15 seconds: ○ 5 to 15 seconds: △: within 5 seconds ・ ・ ・ × Touchability 100% dut on Xerox P paper with an inkjet printer HG-5130 (manufactured by Seiko Epson Corp.)
Printing was performed with y, and the printed matter was naturally dried for one day. The printed matter was rubbed with a finger in an environment of 25 ° C. and 70% RH, and the presence or absence of stains on the print was visually observed.

No stains on the prints are observed. ○ Some stains on the prints occur, but the characters can be distinguished.
△ Characters cannot be discerned due to stains on the prints. × Print unevenness Xero Image paper and Dres on the inkjet printer HG-5130 (manufactured by Seiko Epson Corp.)
Printing was performed on her paper, and the printed matter was dried for one day.

Using a Macbeth PCMII, OD values at arbitrary 5 points on the printed portion were measured, and the average value was obtained. This procedure was repeated 5 times, and the difference between the five maximum values and the minimum value was obtained.

OD value difference is less than 0.4. OD value difference is 0.4 or more. The above evaluation results are shown in Table 1.

[0024]

[Table 1]

As is clear from Table 1, an ink jet recording ink having good clogging property, finger touch property and printing unevenness was obtained.

[0026]

As described above, according to the present invention, at least a pigment and a water-soluble resin soluble at a pH of 10 or more are
5-7 wt% and 0.5-10 wt% sugar,
When the ratio of the pigment to the resin is 1: 0.5 to 1: 2, it is possible to obtain an inkjet recording ink that can achieve both clogging, finger touch, and print unevenness.

Claims (3)

[Claims] 1. At least a pigment, 1.5 to 7 wt% of a water-soluble resin soluble at a pH of 10 or more, and 0.5 to 10 wt of sugar.
%, And the ratio of pigment to water-soluble resin is 1: 0.5-
Ink for ink jet recording characterized by being 1: 2. 2. The ink for ink jet recording according to claim 1, which contains at least ammonium hydroxide. 3. The ink for ink jet recording according to claim 1, wherein the water-soluble resin comprises at least a copolymer of acrylic acid ester and methacrylic acid.