JP2014091760A - Aqueous ink for ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide aqueous ink for an ink jet printer capable of printing without deteriorating printing quality even at almost the same printing speed as a general-purpose printing method such as gravure printing regardless of the type of paper such as wood-free paper, medium quality paper and coated paper.SOLUTION: There is provided aqueous ink for an ink jet printer which comprises: a self-dispersible pigment; 2-ethyl-1,3-hexanediol; 1,6-hexanediol; stearyl methacrylate; methyl metacrylate; acrylic acid and a copolymer with α-methyl styrene.

Description

  The present invention relates to an aqueous inkjet printer ink.

  In recent years, inkjet recording systems have been rapidly spreading due to the advantages of a small body, low price, low running cost, and low noise. Inkjet printers capable of printing on various non-coated plain papers such as electrophotographic transfer paper, printing paper, typewriter paper, wire dot printer paper, word processor paper, letter paper, and report paper are also on the market. In these ink jet printers, various proposals have been made with improved ink absorptivity so that a higher quality image can be obtained.

  Patent Document 1 discloses a technique for improving the drying property by increasing the penetrability of ink. However, since the amount of the surfactant used is large, it is noticeably blurred depending on the type of paper.

  Patent Document 2 discloses a water-based ink containing a colorant that is dispersed or dissolved in water, water and a wetting agent, and further containing 2-ethyl-1,3-hexanediol. According to the present invention, it is possible to provide a water-based ink recording composition that satisfies various properties as an ink, is excellent in permeability and drying properties, and has improved image quality degradation.

  Patent Document 3 contains a coloring material, at least one polyol having a solubility in water at 20 ° C. of 0.2 wt% or more and less than 4.5 wt%, and at least one selected from 11 types of compounds An aqueous recording liquid is disclosed. In this situation, due to the rapid progress in recent technology, the output speed of inkjet printers has been increasing, and even when printing at higher speeds, the ink does not cause color bleeding, and even after rubbing after output, the fingers are soiled. It is required to dry immediately, but the highly dry ink improves the permeability to paper, while the colorant penetrates in the thickness direction of the paper, resulting in a decrease in image density and through-through. In the situation where double-sided printing is indispensable from the viewpoint of paper consumption, there is a need for a water-based ink that is highly dry and that allows double-sided printing with little show-through.

  Patent Document 4 includes at least water, a colorant that dissolves or disperses in water, 2,4-diethyl-1,5-pentanediol, a diol derivative having 4 or less carbon atoms, and a water-soluble organic solvent. An aqueous recording liquid characterized by containing as an ink composition is disclosed, and it has practically sufficient drying properties without using a special drying device in an ink jet printer capable of high-speed printing, and the back of the image. Alternatively, an aqueous recording liquid free from image deterioration such as bleeding and a recording method using the same can be provided.

  Patent Document 5 discloses an organic polymer compound (A) which is “a copolymer of methyl methacrylate or ethyl methacrylate, acrylic acid and styrene” and “stearyl methacrylate, methyl methacrylate, and acrylic acid. And an organic polymer compound (B) which is a “copolymer of α-methylstyrene” and a method for producing an aqueous composition for inkjet having excellent storage stability.

JP 55-29546 A JP-A-6-157959 JP 2001-254037 A JP 2004-182889 A JP 2003-292838 A

At present, there is a demand for ink for inkjet printers that can meet the demand for higher-speed printing. For example, if you print high-speed prints with gravure and then print additional information with an inkjet printer, or overcoat immediately after printing with an inkjet printer, maintain print quality from the viewpoint of productivity. In addition, there is a need for ink for inkjet printers that can cope with printing speeds comparable to gravure printing speeds.
In addition, a coated paper such as a label paper, a photographic paper, and a photographic paper has good solvent permeability but poor water permeability. Therefore, it is necessary to use a large amount of solvent in the ink for an ink jet printer used for the printing in order to improve the permeation drying property. However, on the other hand, there is a demand for water-based ink in consideration of environmental influences.
From such a demand, there is a demand for water-based ink jet printer ink that can be printed at high speed and has little environmental impact.

  Therefore, the present invention is a water-based inkjet that can be printed without degrading the print quality at a printing speed comparable to that of a general-purpose printing method such as gravure printing, regardless of the type of paper such as fine paper, medium paper, and coated paper. It is an object to provide ink for a printer.

  As a result of diligent examination, the present inventors have found out a water-based ink jet printer ink that can be printed at high speed without any deterioration in print quality, excellent in drying properties, regardless of the type of paper, The present invention has been completed.

That is, the present invention
(1) A self-dispersing pigment, a copolymer of 2-ethyl-1,3-hexanediol, 1,6-hexanediol and stearyl methacrylate, methyl methacrylate, acrylic acid, and α-methylstyrene. An ink for a water-based inkjet printer, comprising:
(2) Printed matter printed on the base paper using the aqueous inkjet printer ink according to (1),
It is.

  Here, 2-ethyl-1,3-hexanediol contributes to improving the dryness of the surface of the printed material by improving the permeability to the printing paper, and 1,6-hexanediol is effective in improving the compatibility of the ink components. There is. A copolymer of stearyl methacrylate, methyl methacrylate, acrylic acid, and α-methylstyrene corresponds to the organic polymer compound (B) of Patent Document 5, but is an aqueous inkjet printer. This has the effect of providing fixing stability and water resistance to the ink for use.

The water-based ink jet printer ink of the present invention is excellent in drying property and fixing stability, so that the print quality can be reduced without degrading the print quality regardless of the type of paper such as high-quality paper, medium-quality paper, and coated paper. Without printing.
Therefore, the ink for the water-based inkjet printer is suitable for gravure printing or overcoating, for example, when a printed matter is printed at a high speed by gravure printing, then additional information is printed by the ink jet printer, or is overcoated immediately after printing by the ink jet printer. It is possible to print at a printing speed comparable to that of the printing speed. Further, the obtained printed matter is an excellent printed matter having no blur or blur even when printed at high speed.

  Hereinafter, embodiments for carrying out the present invention will be described in detail. Note that this embodiment is merely an embodiment for carrying out the present invention, and the present invention is not limited by this embodiment, and various modified embodiments can be made without departing from the gist of the present invention. Is possible.

  The ink for an aqueous inkjet printer of the present invention comprises a self-dispersing pigment, 2-ethyl-1,3-hexanediol, 1,6-hexanediol and stearyl methacrylate, methyl methacrylate, acrylic acid, and α-methyl. It contains a copolymer with styrene.

The colorant used in the present invention is preferably a self-dispersing pigment in which at least one hydrophilic group is bonded to the pigment surface directly or via another atomic group.
When an ink containing a dispersant is used for ink jet recording, if the resin forming the dispersant adheres to the orifice of the recording head or the like, the recording head has problems such as clogging or non-ejection of ink. Since it may occur, it is not preferable.
In addition, water-soluble dyes are not suitable as the colorant used in the present invention in consideration of fastness such as water resistance and light resistance.

  Examples of the self-dispersing pigment used in the present invention include carbon black, azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments) whose surface has been subjected to hydrophilic treatment, polycyclic pigments (for example, Phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc., dye chelates (for example, basic dye chelates, acidic dye chelates) ), Nitro pigments, nitroso pigments, aniline black, and the like.

As examples of the hydrophilic group obtained by the hydrophilic treatment, which is bonded to the anionically charged pigment surface, —COOM, —SO ₃ M, —PO ₃ HM, —PO ₃ M ₂ , —SO ₂ NH ₂ , -SO ₃ NHCOR, and the like. In the formula, M represents a hydrogen atom, an alkali metal, ammonium or organic ammonium, and R may have an alkyl group having 1 to 12 carbon atoms, a phenyl group which may have a substituent, or a substituent. Represents a good naphthyl group.

Among these, those having —COOM or —SO ₃ M as a hydrophilic group are preferably used. M in the hydrophilic group includes, for example, lithium, sodium, potassium and the like as the alkali metal, and examples of the organic ammonium include mono to trimethyl ammonium, mono to triethyl ammonium, and mono to trimethanol ammonium. Further, as the cationic hydrophilic group, for example, a quaternary ammonium group is preferably used.

  These self-dispersing pigments are usually available as aqueous dispersions, and the amount used depends on the required printing density, but is 0.1 to 5.0% by weight of the ink as a solid. If it exceeds 5.0% by weight, there may be a problem in the storage stability of the ink.

The 2-ethyl-1,3-hexanediol used in the present invention is added to stabilize the ink ejection, but the wettability to the thermal element is improved, and the ejection stability and frequency stability are improved even with a small amount of addition. In addition to achieving the properties, it has the effect of increasing the osmotic drying property to the printed paper. Accordingly, the coated paper having a large coating amount has good permeability, and as a result, the print surface is dried to prevent color transfer.
The amount of 2-ethyl-1,3-hexanediol added is 1 to 10% by weight of the ink. If it is less than 1%, the ink permeability is insufficient, and if it exceeds 10%, the stability of the ink is deteriorated.

  In the inkjet ink of the present invention, a low-volatile water-soluble organic solvent is used as a wetting agent. Low volatile water-soluble organic solvents include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol, 1,3-butanediol, 2,3 -Butanediol, 1,4-butanediol, 1,5-pentanediol, 2-methyl-2,4-pentanediol, 1,6-hexanediol, glycerin, 1,2,6-hexanetriol, 1,2 Polyhydric alcohols such as 1,4-butanetriol, 1,2,3-butanetriol, and petriol; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, die Glycol ethers such as lenglycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monobenzyl ether; 2-pyrrolidone, N- Nitrogen-containing heterocyclic compounds such as methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; formamide, N-methylformamide, N, N -Amides such as dimethylformamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triamine Amines such as ethylamine; dimethyl sulfoxide, sulfolane, thiodiethanol, sulfur-containing compounds such as thiodiglycol; propylene carbonate, ethylene carbonate. These solvents are used alone or in combination with water.

  Among these, 1,6-hexanediol also functions as a compatibilizing agent, and can improve the storage stability and ejection stability of the ink. The amount used is 2 to 15% by weight with respect to the ink. If it is less than 2%, the compatibility of the ink is insufficient, and if it exceeds 15%, the drying property becomes insufficient.

  In addition, at least one selected from glycerin and glycol ethers such as diethylene glycol monobutyl ether and diethylene glycol monobenzyl ether is preferably used as the wetting agent. These play an auxiliary role in the penetrability and compatibility of the ink for an ink jet printer, but are added by appropriately adjusting the addition amount in order to bring the viscosity into a desired range.

  Furthermore, the ink-jet ink of the present invention is a copolymer of stearyl methacrylate, methyl methacrylate, acrylic acid, and α-methylstyrene (copolymer) in order to impart fixing stability and water resistance to the printed ink. Contains polymer A).

  The copolymer A preferably has a weight average molecular weight in the range of 10,000 to 300,000, more preferably in the range of 20,000 to 100,000. If the weight average molecular weight is less than 10,000, the stability over time is poor when an ink for an ink jet printer is produced. On the other hand, if the weight average molecular weight is more than 300,000, the solubility in water becomes poor and This is not preferable because the viscosity increases and the ink for an ink jet printer causes ejection failure. Here, the weight average molecular weight is a value measured by the GPC method (polystyrene conversion).

  The copolymer A has an acid value of preferably 50 to 200 KOHmg / g, and more preferably 80 to 150 KOHmg / g. When the acid value is less than 50, the hydrophobicity becomes strong, so the solubility in water is low. On the other hand, when the acid value is more than 200, the hydrophilicity becomes strong and the water resistance of the coating film is remarkably lowered. Absent.

  Moreover, it is preferable that the copolymer A has a glass transition point measured by DSC method higher than 50 degreeC. Blocking tends to occur at 50 ° C. or lower due to stickiness.

  The amount of copolymer A used is 0.2 to 1% by weight based on the ink. If it is less than 0.2%, the fixing stability and water resistance of the print are inferior. If it exceeds 1%, the viscosity of the ink increases, which is not preferable.

  The copolymer A is finely pulverized, added to water in which a neutral amount of a basic compound such as potassium hydroxide, ammonia, triethanolamine, etc. is dissolved, and heated to 60 to 100 ° C. with stirring and mixing. It is preferable to use it as a dissolved varnish. In order to impart storage stability to the varnish, alcohols such as ethanol, ethylene glycol monoethyl ether, diethylene glycol monoethyl ether and the like may be appropriately added.

  The ink for inkjet printers of the present invention is produced by mixing the components described above and water (preferably pure water). If they are mixed according to the above description, they become uniform, and no separation or precipitation occurs. In addition, additives such as an antifoaming agent, a rust preventive agent, and an antifungal agent may be appropriately added as long as the physical properties of the ink are not impaired.

  It is necessary to adjust the viscosity of the ink for an inkjet printer of the present invention to a desired value. In general, the viscosity of the ink is preferably 10 mPa · s or less although it depends on the ejection force of the head. When the pressure is 10 mPa · s or less, sufficient discharge can be performed by ink jetting, and printing becomes favorable.

  As the base material to be printed with the ink for an ink jet printer of the present invention, high quality paper, medium quality paper, coated paper and the like can be suitably used regardless of paper quality. In particular, the print does not blur or bleed even at high speed printing at a printing speed of 170 m / min or more, as well as at low speed.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to these. In addition, the part in an Example and a comparative example means a weight part,% means weight%.

<Production of copolymer A>
A four-necked flask equipped with a stirrer, a reflux cooling device, and a nitrogen gas introduction tube was charged with 400 parts of ethyl acetate, and at 80 ° C., while introducing nitrogen gas, 200 parts of a monomer mixture having a composition ratio shown in Table 1 and polymerization A mixture of 1 to 3 parts of t-butyl peroxide was added dropwise as an initiator over 2 hours. Furthermore, after making it react for 2 hours, keeping at 80 degreeC, ethyl acetate was removed under reduced pressure and copolymer A1-A3 of Table 1 was obtained.
Next, 150 parts of each of the copolymers A1 to A3 was finely pulverized, added to 350 parts of pure water mixed with a neutralizing amount of potassium hydroxide, heated to 80 ° C. with stirring and dissolved, and then dissolved. Pure water was added to obtain a concentration of 10% to obtain varnishes A1 to A3 of copolymers A1 to A3, respectively.

“Examples and Comparative Examples”
Inks of Examples 1 to 5 and Comparative Examples 1 to 5 having the compositions shown in Table 2 were prepared, and the following three evaluation tests for compatibility, viscosity, and storage stability were performed.

<Compatibility>
When the ink components of Examples and Comparative Examples were mixed, a transparent and non-turbid material was evaluated as having compatibility (O). In addition, the other evaluation was stopped because it was not possible to carry out incompatibility and poor storage stability (x).

<Viscosity>
About the ink of an Example and a comparative example, the viscosity in 25 degreeC was measured using cone plate type viscometer TV-22 (made by Toki Sangyo Co., Ltd.), and 3-10 mPa * sec was made into the pass level (circle).

<Storage stability>
The composition described in Table 3 was stored in an oven at 5 ° C. and 45 ° C. for 3 days. If the change in viscosity was less than ± 5% from the initial viscosity and there was no precipitation, sedimentation, etc. It was.

Printing test 1
Using the inks of Examples and Comparative Examples, UF coating (manufactured by Oji Paper Co., Ltd.) was used as a printing substrate, and printing was performed at 170 m / min using a tri-tech Co., Ltd. roll jet printing tester. The printed materials were subjected to evaluation tests for sharpness, dryness (set-off) and scratching.

Printing test 2
Furthermore, using Kinryo (Mitsubishi Paper Co., Ltd.) as a printing substrate, printing was performed at 170 m / min using a roll jet printing tester manufactured by Tritec Co., Ltd., and the resulting printed matter was sharp and dry ( Set-off), fretting property and see-through property evaluation test.

<Clarity>
After printing and drying, the misalignment of the boundary between the two colors, the misery of the image, the color tone, and the density are comprehensively judged visually and by a reflective color spectrophotometric densitometer (manufactured by X-Rite). ○, bad things were evaluated as x.

<Drying (set down)>
Solid printing was carried out at 170 m / min on the printing substrate, and the case where the back side of the wound paper was soiled was judged as x, and the case where it was not soiled was judged as ○.

<Abrasion>
The printed image is rubbed with a finger, cloth, eraser or marking pen 30 seconds after printing, and the appearance after rubbing is visually observed. .

<Betrayal>
The back side of the obtained printed matter was observed, and the case where ink was blotted on the back side was evaluated as x, and the case where the ink was not blotted was evaluated as ◯.

  The above evaluation test results are summarized in Table 3.

Claims (2)

  A self-dispersing pigment, 2-ethyl-1,3-hexanediol, 1,6-hexanediol and stearyl methacrylate, methyl methacrylate, acrylic acid, and a copolymer of α-methylstyrene. Water-based inkjet printer ink characterized by the above.   A printed matter printed on the base paper using the ink for an aqueous inkjet printer according to claim 1.