JPH04332774A - Ink for ink jet recording - Google Patents

Abstract

PURPOSE:To obtain an ink for recording, containing a pigment and a resin emulsion, having the average particle diameter of a coloring component within a prescribed range and capable of providing high printing quality on normal commercially available plain paper without causing bleeding in printing due to compatibility therewith. CONSTITUTION:An ink for ink jet recording, containing (A) a pigment such as carbon black or an azo lake pigment and (B) a resin emulsion such as an acrylic-styrene-based resin emulsion and having 0.3-1.2mu average particle diameter of the coloring component contained in the ink. Furthermore, the weight ratio of the aforementioned components (A) to (B) is preferably within the range of (1:0.1)-(1:1).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pigment-dispersed ink for ink-jet recording, and more particularly to an ink for ink-jet recording that does not cause bleeding and provides high print quality on plain paper commonly used in offices.

0002

[Prior Art] Since the inkjet recording method prints by ejecting liquid dye ink, large smearing occurs when recording on plain paper commonly used in offices, such as copy paper or bond paper. However, there was a problem in that the contours and edges of the dots were not sharp, making it impossible to obtain high-quality recordings.

0003

SUMMARY OF THE INVENTION The present invention is intended to solve this problem, and an object of the present invention is to provide an inkjet recording device that records characters and images using liquid ink. An object of the present invention is to provide an inkjet recording ink that uses a pigment as a coloring agent and achieves high print quality without causing bleeding.

0004

[Means for Solving the Problems] The inkjet recording ink of the present invention contains at least a pigment and a resin emulsion, and the average particle size of the coloring component contained in the ink is 0.3.
~1.2 μm, and furthermore, the weight ratio of the solid content of the pigment and the resin emulsion is 1:0.1 to 1:1.
It is characterized by a range of .

That is, the inventors of the present invention have repeatedly studied inks that achieve high print quality for many types of plain paper, and have found that the ink contains at least a pigment and a resin emulsion, and the average particle size of the coloring component is It has been discovered that by using ink having a diameter of 0.3 to 1.2 μm, high quality printing can be achieved on many types of plain paper. Furthermore, it has been found that the above ink can be realized by an ink in which the weight ratio of the solid content of the pigment to the resin emulsion is in the range of 1:0.1 to 1:1. The present invention will be explained in detail.

[0006] The pigment used as a coloring agent in the present invention is:
In addition to carbon black, organic pigments described in generally accepted literature can be used. for example,
Azo pigments such as azo lake pigments, insoluble azo pigments, condensed azo pigments, and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, atraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and polycyclic pigments such as quinophthalone pigments. Examples include dye lakes such as basic dye lakes and acid dye lakes; organic pigments such as nitro pigments, nitroso pigments, aniline black, and daylight fluorescent pigments; and inorganic pigments such as titanium oxide and iron oxide. Furthermore, any pigment other than those mentioned above that can be dispersed in the aqueous phase can be used in the present invention.

[0007]Furthermore, pigments surface-treated with surfactants, polymeric dispersants, etc., such as grafted carbon, can also be used.

These pigments are suitable for the ink of the present invention.
In a proportion of 0.5 to 20% by weight, more preferably 3 to 15%
It is used in a range of % by weight. If the pigment content is less than 0.5% by weight, the desired color tone and density cannot be obtained, and if it exceeds 20% by weight, the nozzle portion of the inkjet recording head will be clogged and the storage stability of the ink will be affected.

The resin emulsions used in the present invention include vinyl acetate, vinyl acetate-acrylic, vinyl acetate-ethylene, acrylic, and acrylic-styrene. As mentioned above, these resin emulsions have a solid content ratio of pigment to resin emulsion of 1:0.1 to 1:1.
Used within the range of If the ratio of the resin emulsion exceeds this range, the average particle size of the coloring component will be smaller than 0.3 μm, making it impossible to obtain high-quality printing. Furthermore, if the ratio of the resin emulsion is less than this range, the average particle size of the coloring component will be larger than 1.2 μm, which will clog the minute nozzles of the inkjet head.

To prepare the ink of the present invention, the pigment is preferably dispersed together with a suitable dispersant, solvent, pure water and, if necessary, other additives by a conventionally known method.

[0011] As the dispersant, polymeric dispersants and surfactants which are generally used for dispersing pigments can be used. Examples of polymeric dispersants include natural gums such as gum arabic and gum tragacanth, proteins such as gelatin, albumin, and casein, glucosides such as saponin, cellulose derivatives such as methylcellulose, carboxycellulose, and hydroxymethylcellulose, lignin sulfonates, and shellac. Natural polymers such as polyacrylates, salts of vinylnaphthalene-acrylic acid copolymers, salts of styrene-maleic acid copolymers, sodium salts of β-naphthalenesulfonic acid formalin condensates, vinylnaphthalene-maleic acid copolymers, etc. Polymer dispersants such as anionic polymers such as salts of polymers and phosphates, nonionic polymers such as polyvinyl alcohol, polyvinylpyrrolidone, and polyethylene glycol, fatty acid salts, and higher alcohol sulfuric esters as surfactants. salts,
There are anionic surfactants such as liquid fatty oil sulfate ester salts and alkylaryl sulfonates, and nonionic surfactants such as polyoxyethylene alkyl ethers and sorbitan alkyl esters. One type or two or more types can be appropriately selected and used. The amount used is preferably 0.1 to 20% by weight based on the total amount of ink.

[0012] As a pigment dispersion method, a fine powder mill/ultrasonic mill such as a ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, pearl mill, jet mill, etc. is used. can.

Examples of the water-soluble organic solvent to be added include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
Alkyl alcohols having 1 to 5 carbon atoms such as sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-amyl alcohol; amides such as dimethylformamide and dimethylacetamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, triethylene glycol,
- Alkylene glycols in which the alkylene group has 2 to 6 carbon atoms such as hexanetriol, thiodiglycol, hexylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monomethyl ether and triethylene glycol monoethyl ether, lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl ether and triethylene glycol diethyl ether, glycerin, sulfolane, N-methyl -2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like.

The amount of the water-soluble organic solvent used is generally 0.1 to 40% by weight, preferably 3 to 30% by weight, based on the total weight of the ink.

In addition to the above-mentioned components, various surfactants, viscosity modifiers, surface tension modifiers, binder resins for improving the fixability of ink on non-recording materials, etc. may be added as necessary. Can be done.

For example, viscosity modifiers or binders such as polyvinyl alcohol, celluloses, water-soluble resins, cationic, anionic, or nonionic surfactants,
Examples include surfactants such as secondary alcohols or their ethylene oxide adducts, surface tension regulators such as diethanolamine and triethanolamine, pH regulators using buffer solutions, and fungicides.

[0017]

[Operation] According to the present invention, the printing quality is better when the particle size of the coloring component of the ink is larger to some extent. This is because when pigment ink adheres to the surface of paper, the pigment remains on the surface,
This is because only the dispersion medium holding the pigment quickly diffuses to the surface and easily penetrates into the interior. This diffusion and permeation of only the dispersion medium is called blurring with respect to the coloring component. Inks that tend to smudge easily will not smudge and dry quickly. It has been found that the inkjet recording ink of the present invention has good printing quality and high quick-drying properties when the average particle diameter of the coloring component in the ink is 0.3 to 1.2 μm. Furthermore, when the ratio of the diameter of the smudge to the overall diameter of the ink permeating and diffusing into the paper is 0.2 or more, no smearing occurs and the print quality is good, and when it is smaller than 0.2, no smearing occurs and no smearing occurs. Put it away. In addition, if the particle size is less than 0.3 μm, the dispersibility as a pigment ink will be good, but bleeding will not occur, and if it exceeds 1.2 μm, bleeding will occur, but the pigment will aggregate and further settle. It becomes impossible to redisperse it, it lacks storage stability as an ink, and the minute nozzles of inkjet printers become clogged.

[0018]

[Examples] The present invention will be specifically explained below by giving examples and comparative examples.

The inks of Examples 1 to 4 and Comparative Examples 1 to 3 were prepared by stirring the following components excluding the pigment at 70°C for 30 minutes, returning the solution to room temperature, adding the pigment, and using a sand mill (Co., Ltd.). (manufactured by Yaskawa Electric Manufacturing Co., Ltd.), and the resulting dispersion was filtered through a 50 μm membrane filter to remove dust and coarse particles, and an ink was obtained.

Example 1 Carbon black #5B (Mitsubishi Chemical Corporation (
Co., Ltd.) 5wt%
glycerin

18wt% Boncoat 5454 (
Acrylic-styrenic resin emulsion, solids content 55
%, manufactured by Tohoku Dick Co., Ltd.) 1.
8wt% polyvinyl alcohol (polymerization degree 500
, degree of saponification 86.5-89 mol%) 0.1wt
% gelatin

1wt% potassium hydroxide

1wt% N-2-hydroxyethyl-p-toluenesulfonamide 1wt%
Pure water

72.1wt% Example 2 Aniline black

10wt% Boncoat 6290 (
Vinyl acetate-acrylic resin emulsion, solid content 5
0%
, manufactured by Dainippon Ink and Chemicals Co., Ltd.) 10wt%
Polyvinylpyrrolidone

3wt% ethylene glycol

15wt% triethylene glycol monomethyl ether
0.3wt% pure water


61.7wt% Example 3 Carbon black #40 (Mitsubishi Chemical Industries (
Co., Ltd.) 6wt%
Boncourt 4001 (acrylic emulsion resin,
Solid content 50%, Dainippon
(manufactured by Ink Kagaku Kogyo Co., Ltd.)
10wt% polyvinyl alcohol
0.1wt%
diethylene glycol

20wt% pure water

63.9wt%
Example 4 Carbon black MA-100 (manufactured by Mitsubishi Chemical Industries, Ltd.) 5wt% Boncoat 2310 (vinyl acetate emulsion resin, solid content 50%, Dainichi)
Manufactured by Hon-ink Kagaku Kogyo Co., Ltd.)
10wt% glycerin

18w
t% gum arabic

3wt% ethanol

3wt% potassium hydroxide

1wt% pure water

60wt% Comparative Example 1 Carbon black #5B (Mitsubishi Chemical Industries (
Co., Ltd.) 5wt%
Boncourt 5454

15wt% glycerin

18wt%
polyvinyl alcohol
0.
1wt% gelatin

1wt% potassium hydroxide

1wt% N-2-hydroxyethyl-
p-Toluenesulfonamide 1w
t% pure water

58.9wt% Comparative example 2 Aniline black

10wt% polyvinylpyrrolidone
3wt%
ethylene glycol

15wt% triethylene glycol monomethyl ether 0.
3wt% pure water

71.7wt% Comparative Example 3 Carbon black MA-100

5wt% Boncourt 2310

0.5wt% glycerin

1
8wt% gum arabic

3wt% ethanol

3wt% potassium hydroxide

1wt%
Pure water

Using ink obtained at 69.5 wt% or more,
The average particle size was measured using a particle size distribution analyzer (manufactured by Horiba, Ltd., ultracentrifugal automatic particle size distribution analyzer CAPA-700). Note that the average particle size is the median value of the particle size distribution.

Average particle size (unit: μm) Measured using the ultracentrifugal automatic particle size distribution measuring device described above, and the median value is taken as the average particle size.

Furthermore, the following evaluations were conducted to examine the printing quality, quick drying properties, and storage stability of the obtained ink.

Wrinkling evaluation: Xe, a typical general-purpose plain paper
1 μl of ink is spotted on roxP (Fuji Xerox trademark), and the diameter of the smearing is calculated from the total diameter of the ink permeating and diffusing into the paper (the coloring component remaining on the paper surface from the total diameter of the ink permeating and diffusing into the paper). (subtracting the diameter). When the ratio is 0.2 or more, uniform spreading is possible ○
If the ratio is less than 0.2, there will be no blurring. ×Storage stability After printing with the ink using the inkjet printer and confirming that all nozzles can eject, stop the printer and leave it at room temperature. . After one month, drive the printer again, check the printing condition, and judge according to the following criteria.

[0024] All nozzles can discharge
○ Discharge from one or more nozzles was not possible due to clogging. ×The above results are shown in Table 1.

[0025]

[Table 1]

D in Table 1 indicates weight ratio of pigment to resin emulsion.As is clear from Table 1, the weight ratio of pigment to resin emulsion is 1:0.1 to 1:1 as in Examples 1 to 4. If so, the average particle size of the coloring component will be 0.3 to 1.2 μm,
Ink in this range has good print quality and good storage stability as it smudges. When the amount of resin emulsion relative to the pigment is large as in Comparative Example 1, the average particle size becomes less than 0.3 μm, and although storage stability is good, smearing does not occur and high-quality printing cannot be obtained. When no resin emulsion is used as in Comparative Example 2, or when the amount of resin emulsion added to the pigment is small as in Comparative Example 3, the average particle size exceeds 1.2 μm, causing smearing, but storage stability is poor. It's bad.

[0027]

Effects of the Invention As explained above, according to the inkjet recording ink of the present invention, in liquid ink using pigment as a coloring agent, bleeding does not occur on commonly available plain paper, and high quality printing can be achieved. is obtained.

Claims (2)

[Claims] 1. An inkjet recording ink containing a pigment and a resin emulsion, characterized in that the average particle size of the coloring component contained in the ink is 0.3 to 1.2 μm. 2. In the ink, the solid content weight ratio of the pigment and the resin emulsion is 1:0.1 to 1:1.
2. The inkjet recording ink according to claim 1, wherein the ink is within a range of 1.