JP2002226750A - Water-based ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-based ink for inkjet recording capable of swiftly penetrating into the recording medium without reduction in printed image definition or in dye solubility or destabilization of pigment-based ink dispersion. SOLUTION: The ink is characterized in that it contains water, a coloring agent, a first alcohol of saturated 2-6C aliphatic monohydric alcohol and a second alcohol expressed by formula (I) (where R1 and R2 are each a 1-3C alkyl group; X1 is -OH or -CH2OH; X2 is -CH3, -C2H5, or -CH2OH).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an aqueous ink for ink-jet recording. More specifically, the present invention relates to a co-solvent that provides rapid penetration into a recording medium without losing the sharpness of an image, and particularly when a pigment is used as a colorant, without causing aggregation of the pigment. The present invention relates to an aqueous ink jet recording ink containing an alcohol mixture.

[0002]

2. Description of the Related Art The ink jet recording system is a printing system in which small droplets of an ink composition are made to fly and adhere to a recording medium to perform printing. This method has a feature that a high-resolution and high-quality image can be printed at a high speed with a relatively inexpensive device. Usually, as the ink used in the ink jet recording system, an odor, an aqueous ink is dominant in terms of safety, etc., and various water-soluble dyes or pigments are mixed with water or a water-soluble organic solvent as a colorant. Solution inks are used.

[0003] The characteristics required of the ink for ink jet recording include print quality, print dryness, print water resistance, storage stability, and the ability not to damage members such as a head. However, these characteristics are often in conflict with each other, so that it is very difficult to satisfy the characteristics at the same time in a well-balanced manner. For example, in order to prevent clogging, a wetting agent is used, but if too much is added, poor print drying properties will result. For this reason, inks satisfying the above-mentioned various properties at the same time have been intensively studied. Further, in recent years, the printing speed has been remarkably improved by the improvement of the ink jet recording apparatus, and particularly, the improvement of the drying speed of the ink has been strongly demanded.

[0004] Drying of the ink results from both evaporation and penetration effects. Evaporation is determined by the vapor pressure of the solvent, while penetration is determined by the interfacial energy between the ink and the paper and the porosity of the print medium, and as a means of increasing the rate of penetration of the ink, the penetration of the ink into the recording medium. The addition of penetrants to promote the penetration is conventionally known. For example, as an ink containing a penetrant, a pigment ink to which a mixture of isopropyl alcohol and another lower alcohol is added (Japanese Unexamined Patent Application Publication No.
09051), acetylene glycol and polyhydric alcohol and 1
Black ink containing polyhydric alcohol (JP-A-5-29397)
6), and a dye ink containing a polyhydric alcohol and a monohydric alcohol at a specific ratio (Japanese Patent Publication No. 7-15754).

However, in these inks, the effect cannot be sufficiently obtained unless the amount of the penetrant added is increased. On the other hand, if the addition amount is simply increased, the permeability and the drying property are improved, but at the same time, the optical density is also reduced, which leads to blurred images and feathering. In addition, these penetrants often cause aggregation or deteriorate dispersibility when a pigment is used as a colorant.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and does not reduce the print characteristics due to feathering or the like, and does not make the pigment-based ink unstable. It is an object of the present invention to provide a water-based ink containing a penetrating agent for improving the drying property of the ink.

[0007]

Thus, according to the present invention, water, a colorant, a first aliphatic compound having 2 to 6 carbon atoms and being saturated aliphatic monovalent.
Alcohols of the general formula (I):

Embedded image

Wherein R 1 and R 2 are alkyl having 1 to 3 carbon atoms
Group; X1 is -OH or -CH_TwoOH; X2 is -CH _Three, -C_TwoH_FiveOr
-CH_TwoOH].
An ink is provided. With the first alcohol
The combined use of a second alcohol deteriorates the print quality.
Without increasing the fast drying of the ink.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ink of the present invention is prepared by adding an ink comprising at least water and a colorant to a saturated aliphatic hydrocarbon having 2 to 6 carbon atoms.
A first alcohol having a valency, and te represented by the general formula (I).
A predetermined amount of a monohydric or dihydric saturated aliphatic primary alcohol (second alcohol) having an rt-butyl skeleton is added to each of them, and the combination of these alcohols allows the ink to rapidly evaporate and penetrate. Have.

[0010] The first alcohol is not particularly limited,
It has a low boiling point of around 100 ° C and / or has a solubility in water of about
10g / 100ml to infinity and high. Such a property promotes evaporation of the ink and avoids problems such as deposition of the colorant. Specifically, 2-butanol,
2-pentanol, 3-methyl-2-butanol, 4-methyl-2-
Pentanol, among which ethanol, 1-
Propanol, 2-propanol, 1-butanol, isobutyl alcohol, tert-butyl alcohol are preferred.
These may be used alone or in combination of two or more.

The second alcohol is represented by the general formula (I)

Embedded image

Wherein R 1 and R 2 are an alkyl group having 1 to 3 carbon atoms, for example, methyl, ethyl, propyl; X 1 is —OH or —CH ₂
OH; X2 may be any compound represented by —CH ₃ , —C ₂ H ₅ or —CH ₂ OH]. However, if the solubility is low, the solubility and dispersibility of the colorant decrease, so that the second alcohol desirably has a solubility in water of 1% by weight or more at 25 ° C. For example, neopentyl alcohol,
tert-pentyl alcohol, neopentyl glycol, 2
-Ethyl-2-methyl-1,3-propanediol and 2,2-diethyl-1,3-propanediol are preferred. These may be used alone or in combination like the first alcohol.

In the alcohol mixture composed of the first and second alcohols, the content of the first alcohol is 1 to 1% of the total weight of the ink in consideration of the permeability to the recording medium, the deterioration of the print quality, and the like. Preferably it is in the range of 15%. In addition, the weight ratio of the content of the first alcohol to the content of the second alcohol is set to 20: 1 to 2:
Desirably 1. As an alcohol mixture satisfying such requirements, for example, based on the total weight of the ink,
A mixture of 4% ethanol and 10: 1 neopentyl alcohol, based on the total weight of the ink
A mixture consisting of 2% 2-propanol and neopentyl alcohol and 2,2-diethyl-1,3-propanediol in a ratio of 20: 1 respectively, 2% tert. A mixture of -butyl alcohol and 2,2-diethyl-1,3-propanediol in a 5: 1 ratio thereto.

The colorant used in the present invention can be selected from known dyes and pigments, and is not particularly limited. Examples of the dye include direct dyes, acid dyes, basic dyes, reactive dyes, disperse dyes, construction dyes, soluble construction dyes, reaction disperse dyes, and oil dyes, and any of them can be used. The content of these dyes depends on the type of liquid medium component, the properties required for the ink, and the like, but is generally desirably 1 to 6% of the total weight of the ink.

As the pigments, inorganic pigments and organic pigments can be used. As the inorganic pigments, yellow pigments (cadmium yellow, chrome yellow, strontium yellow, yellow iron oxide, etc.), and red pigments (Komeitan, Zhu, Bengala, Cuprous oxide), purple pigment (cobalt violet, etc.), blue pigment (prussian blue, etc.), green pigment (emerald green, cobalt green, chromium oxide, etc.), white pigment (titanium oxide, zinc white, lead white, lithobon) Black pigments (self-dispersible carbon black such as carbon black, graphite, or modified carbon black whose surface has been oxidized, or graft carbon whose pigment surface has been treated with a resin, etc.)
Etc. can be used. As the organic pigment, azo, acridine, phthalocyanine, quinacridone, anthraquinone, indanthrene, dioxazine, indigo, thioindigo, perylene, perinone, isoindolenine and the like can be used. The content of the pigment is preferably from 1 to 30% of the total weight of the ink, and more preferably from 3 to 12%. It is preferable to use a pigment composed of particles having a particle diameter of 25 μm or less, more preferably 0.5 μm or less, from the viewpoint of print density, storage stability of ink, ejection stability and the like.

The pigment of the present invention is generally subjected to dispersion treatment with a polymer dispersant or the like and used as a pigment dispersion. A commercially available or synthesized polymer dispersant can be used. Specific types include polyvinyl alcohol, polyvinylpyrrolidone, β-naphthalenesulfonic acid formalin condensate, acrylic acid-acrylate copolymer salt,
Examples include water-soluble resins such as styrene-acrylic acid copolymer salts and maleic anhydride, and hydrophobic resin dispersions of acrylic-urethane copolymers. As the copolymerization form of the polymer dispersant, any of a block copolymer, a graft copolymer, a random copolymer and the like can be used.

Further, in the ink of the present invention, various water-soluble organic solvents can be used to prevent clogging. Specifically, polyethylene glycol, polyalkylene glycols such as polypropylene glycol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, glycols such as thiodiglycol, glycerin, ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl ( Or ethyl) ether, lower alcohol ethers of polyhydric alcohols such as triethylene glycol monomethyl (or ethyl) ether, DMF, amides such as dimethylacetamide, 2-pyrrolidone, N-methyl-2-
Examples include, but are not limited to, nitrogen-containing heterocyclic ketones such as pyrrolidone and 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, and sulfolane. These water-soluble organic solvents can be contained in an amount that does not deteriorate the effect of the present invention. Desirable solvents include polyethylene glycol, diethylene glycol,
Triethylene glycol, glycerin, N-methyl-2-pyrrolidone, etc., and their content is 10% of the total weight of the ink.
It is desirable to be ~ 30%.

In addition, if necessary, inorganic salts such as potassium hydrogen phosphate and sodium hydrogen phosphate as pH adjusters;
Benzoic acid, dichlorophen, hexachlorophen, sorbic acid, p-hydroxybenzoic acid ester, ethylenediaminetetraacetic acid (EDTA), and the like can be added to the ink for the purpose of preventing mold, preserving, and preventing rust. Further, urea, thiourea, ethylene urea and the like can be added for the purpose of preventing nozzle drying.

It is also possible to add various nonionic, cationic, anionic and amphoteric surfactants and dispersants for the purpose of adjusting the surface tension, improving the fixability, and improving the dispersibility of the pigment. it can. Preferred surfactants are ethylene oxide adducts of alkyl phenyl ethers,
Non-ionic activators such as polyethylene oxide-polypropylene oxide copolymers, ethylene oxide adducts of acetylene glycol, sulfate and sulfonate type anionic activators, quaternary amine salt type cationic activators,
Examples include betaine-type and amino acid-type amphoteric activators, and the addition amount thereof is desirably 0.01 to 10% by weight based on the ink.

In the present invention, the primary alcohol and the secondary alcohol may be mixed in advance before being added to water and the colorant, or may be separately added to the water and the colorant, and then mixed and stirred together with the ink and the ink. can do. Mixing and stirring can be performed using a conventional stirrer, and if necessary, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, a high-speed disperser, an emulsifier, or the like can be used. It is preferable that the mixed ink is sufficiently filtered before or after dilution by centrifugal filtration using a centrifugal separator or a membrane filter having a pore size of 5 μm or less.

As a recording apparatus suitable for performing recording using the ink of the present invention, an on-demand type or continuous type ink jet apparatus which ejects ink to perform printing on a recording medium is exemplified. As a method of ink ejection, thermal energy corresponding to a recording signal is applied to ink in the recording head chamber, and a droplet is generated and ejected by the energy, or a thermal jet method in which ink in the recording head chamber corresponds to the recording signal. Any of a piezoelectric element type in which a pressure is applied by a piezoelectric element to eject the liquid may be used. The recording medium to which the ink of the present invention is attached is not particularly limited, and examples thereof include a paper dedicated to inkjet printing and a PPC paper known in the art.

[0022]

EXAMPLES Examples and comparative examples of the present invention will be described more specifically below, but the present invention is not limited to these examples. Basic solvent composition: A: 10% by weight of diethylene glycol 5% by weight of urea 2% by weight of ethylene glycol monomethyl ether B: 5% by weight of polyethylene glycol (average molecular weight = 400) 5% by weight of N-methyl-2-pyrrolidone 3% by weight of ethylene glycol C : 2-Pyrrolidone 10% by weight Thiodiglycol 5% by weight Surfynol 465 (manufactured by Air Products) 1% by weight

Colorant: Black: Cabojet 300 (carbon black) (Cabot Corporation) 5% by weight Yellow: C.I. Acid Yellow 172 2% by weight Magenta: C.I. Acid Red 52 2.5% by weight Cyan: C.I. Direct Blue 199 2.5% by weight

[Table 1]

The four-color compositions shown in the examples and comparative examples shown in Table 1 were sufficiently stirred, and then filtered under pressure through a membrane filter having a pore size of 0.45 μm to obtain an ink of the present invention. Use this ink with a commercially available inkjet printer DeskJet970
Using Cxi (manufactured by Hewlett Packard), PPC paper (Xerox Corporation registered trademark PPC paper), recycled paper (Honshu Paper registered trademark Yamayuri), bond paper (Mead registered trademark Gilbert Bond 25% cotton paper) The line was printed and the following items (1) to (4) were evaluated.

(1) Evaluation of print quality Observation with a microscope at 100 × and visual observation. ◎: Bleeding, whiskers are not observed with the naked eye.…: Bleeding, whiskers are slightly observed.…: Bleeding, whiskers are large but characters can be recognized. Evaluation of print drying property After printing, the printed area was rubbed with a finger, and the time required for the finger or paper to become clean was measured. (3) Printing stability evaluation Continuous printing was performed, and the time during which printing was stable was measured. ◎… 24 hours or more ○ …… 10 hours or more and less than 24 hours × …… less than 10 hours (4) Ink storage stability evaluation The number of cleanings until printing is completely recovered by leaving the ink in a 60 ° C thermostat for 1 month Measure. ◎ …… Recover completely after cleaning less than 3 times ○ …… Recover completely after cleaning more than 3 times and less than 5 times △ …… Recover completely after cleaning more than 5 times and less than 10 times × …… More than 10 times cleaning But does not return

The results are shown in Table 2 below.

[Table 2]

[0027]

As described above, the ink of the present invention comprises at least water, a dye or pigment as a colorant, a first alcohol having 2 to 6 carbon atoms and a saturated aliphatic monovalent alcohol, and a compound represented by the general formula (1). Since the ink contains the second alcohol represented by I), it is possible to increase the permeation speed of the ink into the recording medium without lowering print characteristics such as feathering on plain paper. Here, when the primary alcohol is one or more selected from the group consisting of ethanol, 1-propanol, 2-propanol, 1-butanol, isobutyl alcohol and tert-butyl alcohol, the ink It promotes evaporation and avoids problems such as colorant deposition. The second alcohol is neopentyl alcohol, ter
t-pentyl alcohol, neopentyl glycol, 2-ethyl-2-methyl-1,3-propanediol and 2,2-diethyl
In the case of one or more selected from the group consisting of -1,3-propanediol, the solubility and dispersibility of the colorant and the like become good. Further, when the content of the first alcohol is 1 to 15% by weight of the total weight of the ink and the weight ratio of the first alcohol to the second alcohol is 20: 1 to 2: 1,
Inkjet recording inks that not only provide excellent drying properties, but also have sufficient permeability to recording media and prevent deterioration of print quality, and have print quality, quick drying, print stability, storage stability, etc. A water-based ink that satisfies all of the properties required for a high level is obtained.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroaki Nakaya 22-22, Nagaikecho, Abeno-ku, Osaka City, Osaka Inside (72) Inventor Ichiro Fujii 22-22, Nagaikecho, Abeno-ku, Osaka City, Osaka (72) Inventor Masaru Nakamura 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 2C056 FC01 2H086 BA52 BA53 BA55 BA60 BA62 4J039 AD03 AD06 AD09 AD10 AD14 AD17 AD23 AE01 AE04 BA03 BA04 BA13 BA31 BA34 BA35 BA36 BA37 BA38 BC07 BC09 BC13 BC36 BC39 BC50 BC51 BC54 BC55 BC60 BE01 BE03 BE04 BE05 BE07 BE08 BE12 BE22 CA03 CA06 EA10 EA15 EA16 EA17 EA19 EA42 EA44 EA47

Claims (8)

[Claims] 1. The following components: (a) water, (b) a colorant,
(c) a first alcohol having 2 to 6 carbon atoms and a saturated aliphatic monovalent
And (d) the following general formula (I):Wherein R1 and R2 are an alkyl group having 1 to 3 carbon atoms; X1 is -OH
Or -CH_TwoOH; X2 is -CH _Three, -C_TwoH_FiveOr -CH_TwoOH]
Characterized in that it contains a second alcohol
Link. 2. The ink according to claim 1, wherein the content of the (c) first alcohol is in the range of 1 to 15% of the total weight of the ink. 3. The weight ratio of the content of the (c) first alcohol to the content of the (d) second alcohol is 20: 1 to 2: 1. The ink according to the above. 4. The ink according to claim 1, wherein the solubility of (d) the second alcohol in water at 25 ° C. is 1% by weight or more. 5. The method according to claim 1, wherein the (c) first alcohol is ethanol, 1-propanol, 2-propanol, 1-butanol,
One or more alcohols selected from the group consisting of isobutyl alcohol and tert-butyl alcohol, wherein the (d) second alcohol is neopentyl alcohol, te
rt-pentyl alcohol, neopentyl glycol, 2-
The alcohol is one or more alcohols selected from the group consisting of ethyl-2-methyl-1,3-propanediol and 2,2-diethyl-1,3-propanediol. The ink according to one of the above. 6. The ink according to claim 1, wherein the colorant (b) is a dye or a pigment. 7. The ink according to claim 6, wherein the colorant (b) is a pigment dispersion that has been subjected to a dispersion treatment with a polymer dispersant. 8. The ink according to claim 1, wherein the ink is used in an ink ejecting apparatus that ejects ink to perform printing on a recording medium.