JP2002249698A - Ink-jet recording ink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare an ink-jet recording ink having an excellent quality grade, resistance to scuffing and quick drying property of printed materials and having an ability of stable spurt after long-term storage and on continuous spurt. SOLUTION: This ink contains pigments, a water soluble organic solvent, a hydrophilic polymer which has a viscosity of 0.1-5 mPa.s of 1 wt.% water solution at ordinary temperature and has at least one or two carboxyl groups in one molecule and water. The hydrophilic polymer is neutralized with an alkanol amine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ink for ink jet recording. More specifically, the present invention relates to an ink jet recording ink characterized by containing a hydrophilic polymer neutralized with an alkanolamine and having excellent print quality, abrasion resistance, quick drying property, ejection stability and the like.

[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 aqueous ink occupies the mainstream in terms of odor, safety, etc., and a solution in which various water-soluble dyes or pigments are mixed with water or a water-soluble organic solvent as a dye. Is used. The characteristics required for the ink jet recording ink include print quality, quick drying, water resistance, abrasion resistance, storage stability, ejection stability, and the ability not to damage members such as a head. However, since these characteristics are often in a mutually contradictory relationship, it is considerably difficult to satisfy the respective characteristics simultaneously with good balance. For example, if a penetrating agent that promotes the penetration of the ink into the recording medium is added to improve the drying property, the ink is likely to bleed, which adversely affects the print quality and the optical density.

In order to improve the abrasion resistance of printed matter, a terpolymer of acrylic acid-styrene-α-methylstyrene (JP-A-8-253716) or diisobutylene-maleic acid is used as a binder. Copolymer (JP-A-8-4139)
It has been studied to add a small amount of 4) to the ink.
However, these resins, while improving the abrasion resistance of the printed matter, reduce the water resistance of the ink, and as a result of evaporating water and highly volatile components from the ink discharge ports, increase the resin concentration and increase the viscosity. There is a problem that nozzle clogging is liable to occur, and further, the film is formed. On the other hand, instead of a water-soluble resin, an ink containing a hydrophobic resin dispersion such as an acryl-urethane copolymer (JP-A-10-60353) or a resin emulsion (JP-A-4-18462) may cause nozzle clogging. Although it is slightly improved, there is a problem that when a pigment is used as a pigment, dispersion stability and storage stability are deteriorated.

Further, according to the findings of the present inventors, an ink containing an acrylic acid-based hydrophilic polymer used as a binder for imparting not only abrasion resistance but also water resistance, and a base for neutralizing a carboxyl group thereof. When the base is a hydroxide of an alkali metal such as lithium, sodium, or potassium, the solubility of the polymer is sufficiently increased due to its high ionic strength, but the ink remains on the recording medium due to ejection during printing. And poor water resistance. In addition, when ammonia or an aliphatic amine is used as a base, the ink is easily volatilized from an orifice in contact with the outside air in the ink cartridge because their vapor pressure is too high,
Clogging occurs frequently due to solidification. As described above, in the case of the aqueous ink which has been conventionally reported, all of the characteristics required for ink jet recording have not yet been satisfied.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides an ink jet recording ink which is excellent in print quality, abrasion resistance, quick drying property and ejection stability. The purpose is to:

[0006]

Thus, according to the present invention, a dye, a water-soluble organic solvent, and a 1% by weight aqueous solution have a viscosity of 0.1 to 5 mPa · s at room temperature, and one or two carboxyls in a molecule. In an ink containing a hydrophilic polymer having a group and water, an ink for inkjet recording is provided, wherein the hydrophilic polymer is neutralized with an alkanolamine.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION A hydrophilic polymer having one or two carboxyl groups in a molecule is 0.1 to 5 mPa in a 1% by weight aqueous solution in consideration of clogging of ink and stable ejection.
S (at room temperature, specifically at 25 to 30 ° C), preferably 0.5
It has a viscosity of ~ 3 mPa · s. Further, the polymer viscosity is within the above range, the weight-average molecular weight M _W is 3,000～15,00
0, preferably 5,000～12,000, and the ratio of the weight-average molecular weight M _W to the number average molecular weight M _N (dispersity M _W / M _N) is 1-2.
5, more preferably 1.2 to 2.0. Examples of the viscosity measuring device include a rotary type, a vibration type, and a viscoelasticity measuring device.
A rotary viscometer or a vibratory viscometer such as (Haake) is suitably used. The weight average molecular weight M _W and the number average molecular weight
_MN is measured by GPC (gel filtration chromatography) or the like.

When the hydrophilic polymer satisfies the above conditions, not only the ink is easy to handle and the ink ejection is stable, but also the robustness of the printed matter is suitably maintained.
Further, even if the recording medium is a medium having poor fixability such as a transparent film or a resin-coated paper whose surface is polymer-treated,
Dyes can penetrate and fix these media, especially in the case of anionic pigments generally used for ink jet recording, since the anionic charge of the polymer is strong, the electrical repulsion of the pigment and the electric double layer of the hydrophilic polymer To increase the dispersion stability of the pigment.
Further, from the viewpoint of re-dissolvability after solidification of the ink and quick-drying of printed matter, fastness of the hydrophilic polymer, 50-100 ° C.
For example, it preferably has a glass transition temperature Tg in the range of 60 to 90 ° C.

Accordingly, in this specification, “hydrophilic” means that the solubility in normal-temperature water is 20 to 30% or more.
It is selected from the group consisting of monomer units having one or two carboxyl groups in the molecule, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid and their monoesters.
These monomers may be used alone as a homopolymer or as a copolymer composed of a plurality of the above monomers. Further, in addition to the above monomers, a hydrophobic monomer having a high affinity for the pigment, for example, styrene, α
Using methylstyrene, naphthalene, vinyltoluene, vinylnaphthalene (derivative), alkyl (meth) acrylate, aryl (meth) acrylate, alkyl crotonate, dialkyl itaconate, dialkyl maleate, etc. It can be synthesized and used as a copolymer of any form such as a block copolymer, a graft copolymer or a random copolymer.

The polymerization ratio and polymerization form of the copolymer are determined within the proper range of the physical properties such as viscosity and dispersity without deteriorating the required physical properties of the ink, generally, the water solubility of the polymer. , A 2: 1: 1 weight ratio of acrylic acid: styrene: α-methylstyrene or a 1: 1 weight ratio of acrylic acid: methyl acrylate. However, in order to obtain the robustness of the printed matter and the stability of ink ejection, it is preferable that the hydrophilic polymer is contained in an amount of 0.5 to 5% by weight, for example, 1 to 3% by weight based on the total amount of the ink.

The alkanolamines used in the present invention may be those having a moderate volatility having a boiling point of about 140 ° C. to about 340 ° C. and an appropriate ionic strength. Specifically, ethanolamine, diethanolamine, Examples include triethanolamine, propanolamine, methylaminoethanol, dimethylaminomethanol, diethylaminoethanol, and dimethylaminoethanol. Since these have different basicity, vapor pressure, viscosity, solubility in water, etc., one or more are selected and used, and when used for ink jet recording ink, evaporation from the orifice in the cartridge is prevented. The polymer can be kept in a stable dissolved state with little occurrence. In addition, the ink after printing evaporates in a short time due to an increase in the contact surface area with the outside air, and solidifies the polymer according to the evaporation, so that the ink is coated with a hydrophobic film of the polymer, thereby producing a printed matter having sufficient water resistance. be able to. Furthermore, since these alkanolamines are extremely water-soluble and have a high affinity for other water-soluble organic solvents and dyes, the solubility of the dyes is remarkably increased, and a problem such as precipitation of the dyes in aqueous ink may occur. There is no.

The hydrophilic polymer is 50% based on the acid value.
As described above, preferably 70 to 90% is neutralized with the alkanolamine. In the present invention, an excess (1.2 to 2.5 equivalents) of alkanolamines (corresponding to 1 to 2% by weight of the final total ink weight) relative to the acid value of the polymer is added, and pure water is added for 30 minutes to several hours. Was heated at a temperature in the range of 60 to 90 ° C. in the presence of and stirred using a stirrer known in the art. As a result, the pH of the polymer becomes
Adjusted to the range of 7-11 and "neutralized".

In the present invention, the water-soluble organic solvent has a high boiling point, low volatility and extremely high hygroscopicity, and has a high effect of preventing drying of the nozzle. Therefore, the polyalkylene of polyethylene glycol or polypropylene glycol having a molecular weight of 200 to 600 is used. It is preferred to select from glycols. These solvents have a high affinity for the hydrophilic polymer and have a large effect of preventing nozzle clogging by the polymer.

In addition to the above polyalkylene glycol,
For the purpose of preventing clogging, adjusting permeability, adjusting viscosity, etc.
Glycerin, esters, amides, carboxylic acids, ethers, alcohols, organic sulfides, organic sulfoxides,
One or more water-soluble organic solvents selected from the group consisting of sulfonic acids and ketones can also be used. Specifically, ethylene glycol, propylene glycol,
Glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, 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-pyrrolidone, 1,3
-Dimethyl-2-imidazolidinone and the like nitrogen-containing heterocyclic ketones, dimethyl sulfoxide, sulfolane and the like, among which diethylene glycol, triethylene glycol, glycerin, 2-pyrrolidone and N-methyl-2-pyrrolidone preferable. The content of these solvents is 3 to 30% by weight of the total weight of the ink, but is more preferably 5 to 20% by weight from the viewpoints of ejection stability and surface tension.

The dye used in the present invention can be selected from known dyes and pigments, and is desirably contained in the range of 1 to 10% by weight based on the total weight of the ink. Examples of the dye include a direct dye, an acid dye, a reactive dye, a disperse dye, a construction dye, a soluble construction dye, a reactive disperse dye, and an oil dye, and any of them can be used. The content of these dyes depends on the type of liquid medium component, the characteristics required for the ink, and the like. As the pigments, inorganic pigments and organic pigments can be used. As the inorganic pigments, yellow pigments (cadmium yellow, chromium yellow, strontium yellow, yellow iron oxide, etc.) and red pigments (Koumeitan, vermilion, red iron oxide, Copper pigments), purple pigments (cobalt violet, etc.), blue pigments (Prussian blue, etc.), green pigments (emerald green, cobalt green, chromium oxide, etc.), white pigments (titanium oxide, zinc white, lead white, lithobon, etc.), Black pigments (e.g., carbon black, graphite, modified carbon black whose surface is oxidized, and self-dispersed carbon black such as graft carbon whose pigment surface is treated with a resin or the like) can be used.

The organic pigments include azo, acridine, phthalocyanine, quinacridone, anthraquinone, indanthrene, dioxazine, indigo, thioindigo, perylene, perinone, and isoindolenine. Can be used. Pigments are generally polyvinyl alcohol, polyvinylpyrrolidone, styrene-
It may be used as a pigment dispersion by performing a dispersion treatment with a commercially available or synthesized polymer dispersant such as an acrylic acid copolymer salt or the like, and a pigment having a particle diameter of 25 μm or less, or even 0.5 μm or less. It is preferable to use them from the viewpoint of print density, storage stability of ink, ejection stability, and the like.

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. Further, various nonionic or anionic surfactants and dispersants can be added for the purpose of adjusting the surface tension, improving the fixing property, and improving the dispersibility of the pigment. Preferred surfactants include non-ionic surfactants such as alkylphenyl ether ethylene oxide adducts, polyethylene oxide-polypropylene oxide copolymers, and acetylene glycol ethylene oxide adducts, and sulfate and sulfonate type anionic surfactants. And the amount of addition is
0.01 to 10% by weight is preferred.

In the present invention, the ink can be produced by mixing and stirring the neutralized solution of the polymer produced in advance as described above with a dye, a water-soluble organic agent and water. Mixing and stirring can be performed using a conventional stirrer, and if necessary, a sand mill, a homogenizer, a ball mill, an ultrasonic disperser, a high-speed disperser, an emulsifier, or the like can be used. The mixed ink can be used as needed
It is preferable to sufficiently filter by centrifugal filtration with a centrifuge and a membrane filter with 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 can be cited. As a method of ink ejection, thermal energy corresponding to a recording signal is given to ink in a recording head chamber, and a droplet is generated by the energy.
Either a thermal jet method of ejecting ink or a piezoelectric element method of ejecting ink by pressurizing ink in a print head chamber by a piezoelectric element corresponding to a recording signal 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 that are known in the art.

[0020]

EXAMPLES Examples and comparative examples of the present invention will be described below in more detail, but the present invention is not limited to these examples. Basic solvent composition: A: polyethylene glycol (average molecular weight = 400) 10% by weight urea 5% by weight ethylene glycol monomethyl ether 2% by weight B: polyethylene glycol (average molecular weight = 600) 6% by weight N-methyl-2-pyrrolidone 5% by weight % C: 2-pyrrolidone 15% by weight Thiodiglycol 5% by weight Surfynol 465 (manufactured by Air Products) 1% by weight

Pigment: 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

According to a known method for synthesizing an acrylic polymer (see “Synthesis and Reaction of Polymer (1) (2)”, Kyoritsu Shuppan), a polymer having a monomer composition (% by weight) shown in Table 1 below was synthesized, 1 wt% viscosity of the aqueous solution in (mPa · s), the molecular weight M _W and polydispersity (M _W / M _N) was measured (Table 1). The viscosity was measured by a vibration viscometer (VM-1A-L manufactured by Yamaichi Denki Kogyo), and the molecular weight was measured by GPC (Waters 600E system).

[Table 1]

After adding pure water and a base shown in Table 2 in a water bath, the above synthesized product was heated and stirred at 70 ° C. for 1.5 hours to be completely dissolved. This solution, a dye, an organic solvent, and pure water were mixed and sufficiently stirred. Further, the ink was filtered under reduced pressure through a 1.2 μm membrane filter to remove dust and coarse particles to prepare an ink. Comparative Example 1 is the molecular weight M _W of 3,000 smaller ink Examples of the polymer; Comparative Example 2 has a molecular weight M _W 15,000 greater than ink Examples of the polymer; Comparative Example 3 viscosity of 5 mPa · s greater than ink Examples of polymers Comparative Example 4 is an ink composition example in which the polymer does not contain a hydrophilic monomer unit; Comparative Example 5 is an ink composition example in which the amount of the polymer added is more than 5% by weight; Comparative Example 6 is an ink composition example in which the polymer is neutralized with ammonia Comparative Example 7 is an example of an ink composition obtained by neutralizing a polymer with NaOH; Comparative Example 8 is an example of an ink composition containing no polyalkylene glycol.

[Table 2]

Inkjet printer DeskJet 970Cx
An i (manufactured by Hewlett-Packard) cartridge was filled with ink, and English characters, lines and images were printed, and the following items (1) to (5) were evaluated. (1) Evaluation of clogging resistance After cleaning the cartridge head and performing predetermined printing, the state of the nozzle was observed with a microscope (顕 微鏡: no clogging, x: clogging was present). (2) Evaluation of print drying property After printing, the printed portion was rubbed with a finger, and the time (second) until the finger or paper was not stained was measured ((: less than 60 seconds, ×: 60 seconds or more). (3) Water resistance evaluation Printed on commercially available PPC paper (MultiACE AK-701 manufactured by Nippon Paper Industries Co., Ltd.), left for 6 hours, immersed in tap water for 5 minutes, measured the optical density value before and after the test, and measured the residual ratio (% (○: survival rate 9)
0% or more, ×: residual rate less than 90%). (4) Evaluation of fixability
The change of the printed portion when rubbing was evaluated visually (○:
No rubbing, ×: There was rubbing). (5) Print quality Printed on commercially available PPC paper (MultiACE AK-701, manufactured by Nippon Paper Industries), and evaluated visually (目: good, ×: bad). Table 3 shows the results.

[Table 3]

[0025]

As described above, the ink of the present invention has a viscosity of 0.1 to 5 mPa · s at room temperature in a dye, a water-soluble organic solvent, and a 1% by weight aqueous solution, and has one or two In an ink containing a hydrophilic polymer having a carboxyl group and water, the hydrophilic polymer is neutralized with an alkanolamine, and has excellent print quality, sufficient abrasion resistance, quick drying property, and water resistance. In addition, it is possible to give the ink a property that enables stable ejection even after long-term storage or during continuous ejection. The alkanolamine is one or two selected from the group consisting of ethanolamine, diethanolamine, triethanolamine, propanolamine, methylaminoethanol, dimethylaminomethanol, diethylaminoethanol, and dimethylaminoethanol.
When the number of seeds is more than one, clogging of nozzles can be avoided and a printed matter having high water resistance can be produced. Further, a hydrophilic polymer is a polymer having a weight average molecular weight M _{W of} 3,000 to 15,000 and a dispersity of M _W / M _{N of} 1 to 2.5, particularly (meth) acrylic acid,
Crotonic acid, itaconic acid, (anhydride) maleic acid, a polymer having one or more monomer units selected from the group consisting of fumaric acid and monoesters thereof as a component, 0.5 to the total amount of the ink By containing 5% by weight, good balance characteristics such as abrasion resistance and ejection stability can be obtained. Furthermore, as a water-soluble organic solvent, a molecular weight of 200
By using polyethylene glycol or polypropylene glycol of ~ 600, drying of the nozzle is prevented. Further, glycerin, esters, amides, carboxylic acids, ethers, alcohols, organic sulfides, organic sulfoxides, sulfonic acids, and at least one compound selected from the group consisting of ketones are included to prevent nozzle clogging, and inkjet A water-based ink that satisfies all the properties required for a recording ink can be obtained.

Continued on the front page (72) Inventor Hiroaki Nakaya 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Ichiro Fujii 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Sharp (72) Inventor Masaru Nakamura 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka F-term (reference) 2C056 EA13 FC01 FC02 2H086 BA52 BA53 BA55 BA59 4J039 AD02 AD03 AD09 AD10 AD13 AD14 AD17 BA04 BA13 BA31 BA35 BA36 BA37 BA38 BC09 BC12 BC39 BC60 BE01 BE03 BE04 BE07 BE08 BE12 CA06 EA10 EA15 EA16 EA17 EA19 EA20 EA36 EA41 EA42 EA44 GA24

Claims (7)

[Claims] 1. The following components: (a) a dye, (b) a water-soluble organic solvent, (c) a 1% by weight aqueous solution having a viscosity of 0.1 to 5 mPa · s at room temperature, and one or two (D) an ink containing water, wherein the hydrophilic polymer is neutralized with an alkanolamine. 2. The alkanolamine is ethanolamine, diethanolamine, triethanolamine,
The ink according to claim 1, wherein the ink is at least one selected from the group consisting of propanolamine, methylaminoethanol, dimethylaminomethanol, diethylaminoethanol, and dimethylaminoethanol. The weight average molecular weight M _W of claim 3 wherein said (c) a hydrophilic polymer is 3,000 to 15,000, according to claim 1 or 2 dispersity M _W / M _N is characterized in that 1 to 2.5 Ink. 4. The (c) hydrophilic polymer is (meth) acrylic acid, crotonic acid, itaconic acid, (anhydride) maleic acid,
The ink according to any one of claims 1 to 3, wherein one or more monomer units selected from the group consisting of fumaric acid and their monoesters are used as constituent elements. 5. The ink according to claim 1, wherein the hydrophilic polymer (c) is contained in an amount of 0.5 to 5% by weight based on the total weight of the ink. 6. The method according to claim 6, wherein (c) the hydrophilic polymer is acrylic acid: styrene: α-methylstyrene in a weight ratio of 2: 1: 1, or
The ink according to any one of claims 1 to 5, comprising acrylic acid: methyl acrylate in a weight ratio of 1: 1. 7. The (b) water-soluble organic solvent has a molecular weight of 200 to 200.
The ink according to any one of claims 1 to 6, wherein the ink is 600 polyethylene glycol or polypropylene glycol.