JP3055654B2 - Ink jet recording ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink for ink jet recording, and more particularly, to a printing ink having sufficient print density, fixability, abrasion resistance and mark resistance even when the pigment of the ink is carbon black. The present invention relates to an aqueous ink jet recording ink which is excellent in pen properties and does not lower print quality.

[0002]

2. Description of the Related Art Conventionally, ink jet recording has been performed with low noise,
Due to the excellent features of high resolution and high speed printing, it has rapidly become popular. In such an ink jet recording system, an ink in which a water-soluble dye is dissolved in an aqueous medium is generally used. In consideration of the fastness of the printed matter such as water fastness and light fastness, a pigment is more advantageous than a dye as a colorant of the ink, but the pigment is dissolved in the ink medium like a dye. However, since they are merely dispersed, there is a problem of clogging the tip of a small-diameter ink jet nozzle, and it has been difficult to use ink containing carbon black in an ink jet recording system.

On the other hand, in the case of inks used in writing instruments such as felt-tip pens, felt-tip pens and ball-point pens, dyes have been used as coloring agents due to the problem of clogging of the pen tip. By using a polymer comprising a hydrophilic part and a hydrophobic part disclosed in the gazette as a dispersant, the pigment is finely dispersed and stabilized in the ink, and a specific nonvolatile water-soluble organic solvent is used in the ink medium. By doing so, a method for solving the problem of pen tip drying (problem of clogging) was proposed, and thereby, a water-based pigment ink was put to practical use.

For ink jet recording, JP-A-56-147863 and JP-A-56-14786 are known.
No. 5, JP-A-2-276874 and the like disclose an ink and a recording method. Further, various aqueous pigment inks using a polymer as a pigment dispersant have been proposed.

However, the aqueous pigment ink using such a polymer as a pigment dispersant has a problem that ink droplets are difficult to fix on a recording medium. In addition, even if fixing of the printed matter occurs, the pigment in the ink does not absorb into the recording medium and remains on the surface of the recording medium, and when the surface of the printed matter is rubbed with a finger or traced on the printed surface with a mark pen. ,
There are problems such as abrasion resistance such as generation of printing stains and mark pen resistance.

From such a viewpoint, in order to promote fixation of a printed matter on a recording medium, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, isopropanol are used in an ink medium. There have been proposed methods of using a water-soluble organic solvent such as acetylene glycol or adding a surfactant such as acetylene glycol.However, if these methods are used to improve the fixability of printed matter, ink droplets penetrate into a recording medium. And the print density is reduced, or significant blurring occurs,
The print quality deteriorates. That is, it has been difficult to simultaneously satisfy the fixability, the density, and the print quality of a printed matter with an aqueous ink using a pigment as a colorant.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sufficient print density, excellent fixability, abrasion resistance and mark pen resistance, and do not degrade print quality.
An object of the present invention is to provide a pigment ink for aqueous ink jet recording using carbon black as a colorant.

[0008]

The above objects are achieved by the present invention described below. That is, the present invention provides a carbon black,
An ink jet recording ink comprising a dispersant and an aqueous medium, wherein the dispersant is a polymer having both a hydrophilic portion and a lipophilic portion (provided that the polymer and the sulfonic acid
Or an aromatic anionic dispersant having a salt group thereof or
When the aqueous medium is a non-volatile hydrophilic organic solvent (however, a low molecular weight having a number average molecular weight of 200 to 1500)
(Excluding polyethylene glycol) , and the organic solvent contains at least tetrahydrothiophene-1,1-dioxide.

[0009]

According to the present invention, tetrahydrothiophene-1,1 is used as at least a part of the liquid medium component of the ink for ink jet recording.
-By using a dioxide, a water-based ink jet recording that provides a sufficient print density even when the pigment is carbon black, has excellent fixability, abrasion resistance and mark pen resistance, and does not deteriorate print quality. Pigment ink can be provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail with reference to preferred embodiments. The ink for ink jet recording of the present invention comprises a liquid medium containing carbon black, a polymer dispersant, and at least tetrahydrothiophene-1,1-dioxide. That is, the main feature of the present invention is that carbon black and tetrahydrothiophene-
In combination with 1,1-dioxide.

As the carbon black used as a colorant for the ink of the present invention, any carbon black which has been conventionally used in water-based printing inks and water-based paints can be used. Specifically, for example, Mitsubishi Carbon Black #
1000, # 970, MA100, MA8 (Mitsubishi Carbon), Raven # 5000, # 3500, # 1
100 (all made of Columbia Carbon), Legal 40
0, Monarch 120 (above, made by Cabot), Special Black 4A (made by Degussa) and the like. The content of these carbon blacks is an amount occupying 2 to 30% by weight of the whole ink.

The polymer serving as the carbon black dispersant is mainly a polymer of a monomer having an addition-polymerizable vinyl group, and has both a hydrophilic portion and a lipophilic portion. The hydrophilic portion of the dispersant is a hydrophilic group such as a carboxylic acid group or a sulfonic acid group, and the hydrophilic group is used in preparing a polymer in a predetermined amount of acrylic acid, methacrylic acid, crotonic acid, It is introduced using α, β-unsaturated acid monomers such as itaconic acid, itaconic acid monoester, maleic acid, maleic acid monoester, fumaric acid, vinylsulfonic acid and the like.

The lipophilic monomer units of the dispersant include styrene, styrene derivatives, vinylnaphthalene,
Preferred are vinyl naphthalene derivatives and C ₃ -C ₁₈ aliphatic alcohol esters of α, β-ethylenic carboxylic acids.

Further, in addition to the above monomers, acrylonitrile, other α, β-ethylenic carboxylic acid esters, vinyl acetate, acrylamide, methacrylamide, hydroxyethyl methacrylate, hydroxypropyl methacrylate, N-methylol acrylamide,
N, N-dimethylaminoethyl methacrylate or N, N-diethylaminoethyl methacrylate can be used as a comonomer. The range of the molecular weight of these dispersants is preferably about 5,000 to 100,000. If the molecular weight of the polymer is too low, the effect as a dispersant will be reduced, and if the molecular weight is too high, it will be difficult to lower the viscosity of the ink, which is not preferable.

In order to solubilize or disperse the dispersant in an aqueous medium in a colloidal manner, the dispersant must be converted to a salt. Representative examples of the alkali metal forming a salt with the dispersant include sodium and potassium, and examples of the amine include mono-, di- or tri-methylamine, mono-, di- or tri-ethylamine such as aliphatic Mono-, di- or tri-ethanolamine, mono-, di- or tri-propanolamine, methylethanolamine, alcoholamines such as dimethylethanolamine; and other morpholines and N-methylmorpholine. Representative. The above dispersant can be produced according to a conventionally known method, and its use amount is about 5 to 300 parts by weight, preferably about 10 to 1 part by weight, per 100 parts by weight of the pigment.
50 parts by weight.

The aqueous medium constituting the ink of the present invention is composed of water and a non-volatile hydrophilic organic solvent (provided that the number average molecular weight is
200 to 1500 low molecular weight polyethylene glycol
The present invention is characterized in that tetrahydrothiophen-1,1-dioxide is used as at least a part of the organic solvent. The above-mentioned tetrahydrothiophene-1,1-dioxide is an aprotic polar solvent usually used as a reaction solvent for various chemical reactions, and is sold, for example, by Sumitomo Seika under the trade name of “sulfolane”. The solvent has low odor and toxicity, has a high flash point, and is excellent in safety.

In the ink of the present invention, the above-mentioned tetrahydrothiophene-1,1-dioxide is excellent in fixability, density, abrasion resistance and mark pen resistance of printed matter when printed on a recording medium such as paper. And provides printing quality. The amount of the tetrahydrothiophene-1,1-dioxide used in the ink is 5 to 40% by weight, preferably 5 to 30% by weight of the whole ink. If the content of tetrahydrothiophene-1,1-dioxide in the ink is too small, the effect of the present invention becomes insufficient such that the fixability and the print density do not increase. Conversely, if the content is too large, the ink may be dried at the tip of the nozzle. This is not preferable because it easily occurs.

Further, in order to prevent drying of the ink at the tip of the nozzle, to prevent aggregation and sedimentation of the dispersed pigment, and to adjust the physical properties of the ink, the ink of the present invention may be other than the above sulfolane. Of a non-volatile hydrophilic organic solvent. Examples of these hydrophilic organic solvents include polyhydric alcohols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and glycerin, and derivatives thereof (however,
Low molecular weight polyethylene glycol having an average molecular weight of 200 to 1500
Recall) or a mixture thereof. Considering the viscosity of the ink, the content of these components is preferably an amount occupying 10 to 70% by weight of the whole ink, and more preferably an amount occupying 10 to 45% by weight.
The water content at this time is an amount occupying 20 to 80% by weight, preferably 40 to 70% by weight of the whole ink.

The ink of the present invention is composed of the above-mentioned constituent components and compounds, and various production methods can be adopted. For example, blending each of the above components, ball mill, homomixer, sand grinder, roll mill,
Alternatively, a method of mixing and grinding carbon black using an ultrasonic disperser or the like is typical. In the above manufacturing method,
The aqueous medium containing tetrahydrothiophene-1,1-dioxide can be added either before or after the pigment is dispersed. Such a dispersion step is carried out in a state where the pigment is as high as possible in consideration of economy, and after the dispersion treatment, an aqueous medium is added to obtain an appropriate viscosity as an ink for ink jet recording, that is, about 1 to 10 cp. It is preferred to reduce the viscosity. In the ink of the present invention, in addition to the above essential components, various conventionally known additives (provided that sulfonic acid or
Aromatic anionic dispersants having a salt group are excluded.
However , for example, a surfactant or a salt may be used in combination.

[0020]

EXAMPLES Next, the present invention will be described more specifically with reference to Reference Examples, Examples and Comparative Examples. In the text, "part" and "%"
All parts are by weight unless otherwise specified. [Reference Example 1 (Preparation of Pigment Dispersion A)] Ethyl acrylate 20 parts Ethyl methacrylate 15 parts Methacrylic acid 10 parts Styrene 5 parts Azobisisobutyronitrile 1 part Ethyl carbitol 50 parts

The above components were mixed and polymerized at about 65 ° C. for 8 hours. To this polymerization solution, 9 parts of dimethylaminoethanol and 16 parts of water were added. To 5 parts of the alkali water-soluble polymer, 10 parts of Raven # 3500 (manufactured by Columbia Carbon), 50 parts of water, 5 parts of ethylene glycol, and 0.1 part of potassium hydroxide were added, and the mixture was dispersed with a Dynomill (manufactured by Shinmaru Enterprises) for 3 hours. . Further, 20 parts of water and 20 parts of diethylene glycol were added to make the pigment concentration 9%, and the mixture was dispersed for 30 minutes. This dispersion was subjected to an ultracentrifuge to remove coarse particles, thereby obtaining a black pigment dispersion A having a pigment content of 8.5%.

Reference Example 2 (Preparation of Pigment Dispersion B) Methyl methacrylate 30 parts Hydroxyethyl methacrylate 20 parts Butyl acrylate 20 parts N, N-dimethylaminoethyl methacrylate 15 parts Methacrylic acid 15 parts Azobisisobutyronitrile 2 Parts butyl carbitol 50 parts ethanol 50 parts

The above components were mixed and polymerized at about 70 ° C. for 8 hours. To this polymerization liquid, 10.5 parts of potassium hydroxide and 39.5 parts of water were added. To 5 parts of the alkali water-soluble polymer, 10 parts of Mitsubishi Carbon Black # 970 (manufactured by Mitsubishi Carbon), 50 parts of water, 5 parts of ethylene glycol, and 0.1 part of potassium hydroxide were added, and the mixture was dispersed with a sand mill (manufactured by Igarashi Kikai) for 3 hours. . Further, 25 parts of water and 15 parts of glycerin were added to make the pigment concentration 9%, and the mixture was dispersed for 30 minutes. The dispersion was subjected to an ultracentrifuge to remove coarse particles, and a black pigment dispersion B having a pigment content of 8.5% was obtained.

Example 1 To 100 parts of the pigment dispersion A obtained in Reference Example 1, 10 parts of water and 30 parts of tetrahydrothiophene-1,1-dioxide were added to obtain an ink for ink jet recording of the present invention.
Using BJ-10V (manufactured by Canon), two kinds of commercially available copy paper (Xerox 4024,
Printing was performed on Canon PB paper), and each evaluation test shown below was performed.

(Evaluation 1: Print Density) The density of the obtained printed matter was measured using a Macbeth densitometer (TR918).
Was measured. (Evaluation 2: Scratch resistance, mark resistance pen) After 24 hours have passed since printing, the obtained printed matter was traced with a fluorescent pen (OPTEX: manufactured by Zebra) to trace the printed part.
Stain properties were determined. (Evaluation 3: Fixing Property) After 30 seconds from printing of the obtained printed matter, paper was placed on the printing surface, a weight of 100 g was further placed thereon, pressure was applied thereto, and the paper on the upper surface was pulled to check for the presence of print stains.

Example 2 To 100 parts of the pigment dispersion B obtained in Reference Example 2, 20 parts of water and 20 parts of tetrahydrothiophene-1,1-dioxide were added to obtain an ink for ink jet recording of the present invention.
The same test as in Example 1 was performed on the obtained ink.

Comparative Example 1 To 100 parts of the pigment dispersion A obtained in Reference Example 1, 10 parts of water and 30 parts of ethylene glycol were added to obtain an ink for ink jet recording of a comparative example.
The same test as in Example 1 was performed on the obtained ink.

Comparative Example 2 To 100 parts of the pigment dispersion B obtained in Reference Example 2, 20 parts of water and 20 parts of ethylene glycol were added to obtain an ink for ink jet recording of a comparative example.
The same test as in Example 1 was performed on the obtained ink.

Comparative Example 3 To 100 parts of the pigment dispersion B obtained in Reference Example 2, 20 parts of water, 15 parts of ethylene glycol and 5 parts of isopropanol were added to obtain an ink for ink jet recording of a comparative example.
The same test as in Example 1 was performed on the obtained ink.

Comparative Example 4 To 100 parts of the pigment dispersion B obtained in Reference Example 2, 20 parts of water, 15 parts of ethylene glycol, and 5 parts of N-methyl-2-pyrrolidone were added to prepare an ink for ink jet recording of a comparative example. Obtained.
The same test as in Example 1 was performed on the obtained ink. The above results are shown in Table 1 below.

Table 1: Evaluation results

* [Evaluation 2] Evaluation criteria for scratch resistance, mark pen resistance and [Evaluation 3] fixing property in Table 1 are as follows. ：: No stain on print surface ×: Slight print stain XX: Strong print stain

[0033]

As described above, according to the present invention, the pigment is made of carbon black by using tetrahydrothiophene-1,1-dioxide as at least a part of the liquid medium component of the ink for ink jet recording. Even with this, it is possible to provide a water-based ink jet recording pigment ink that can provide a sufficient print density, is excellent in fixability, abrasion resistance and mark pen resistance, and does not degrade print quality.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akio Yoshida 1-7-6 Nihonbashi Bakurocho, Chuo-ku, Tokyo Inside Dainichi Seika Kogyo Co., Ltd. (72) Inventor Tohru 1-7 Nihonbashi Bakurocho, Chuo-ku, Tokyo No. 6 Inside Dainichi Seika Kogyo Co., Ltd. (56) References JP-A-56-147683 (JP, A) JP-A-56-90865 (JP, A) JP-A-8-333530 (JP, A) 8-3333531 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 11/00-11/20

Claims (5)

(57) [Claims] 1. An ink jet recording ink comprising carbon black, a dispersant and an aqueous medium, wherein the dispersant is a polymer having both a hydrophilic portion and a lipophilic portion (provided that the polymer and the Has a sulfonic acid or salt group
In combination with aromatic anionic dispersants are excluded), the aqueous medium is a non-volatile hydrophilic organic solvent (however, number average
Low molecular weight polyethylene glyco having a molecular weight of 200 to 1500
Lumpur excluded) containing ink-jet recording ink for the organic solvent is characterized in that it comprises at least tetrahydrothiophene 1,1-dioxide. 2. The ink for ink jet recording according to claim 1, wherein the content of tetrahydrothiophene-1,1-dioxide accounts for 5 to 40% by weight of the whole ink. 3. The ink for ink jet recording according to claim 1, wherein the content of carbon black accounts for 2 to 30% by weight of the whole ink. 4. The ink for ink jet recording according to claim 1, wherein the content of the dispersant is 5 to 300 parts by weight per 100 parts by weight of the pigment. 5. A dispersant having a molecular weight of 5,000 to 100,
5. The ink for ink jet recording according to claim 1, which is an acrylic polymer of 000.