JP2003096370A - Ink composition for ink jet printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a new ink composition which can be stably used by selecting a specified combination of three essential constituents comprising pigment species, a dispersion medium and a dispersant in an organic solvent based pigment ink composition for ink jet printing. SOLUTION: The new organic solvent based pigment ink composition for ink jet printing, which suffers neither the thickening of an ink nor the agglomeration of a pigment during storage and can be stably used, is realized by selecting a combination of three essential constituents comprising the specified pigment species, a specified glycol ether ester serving as the dispersion medium, and an acrylic living copolymer serving as the dispersant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous organic solvent-based pigment ink composition which can be stably used in an ink composition for inkjet printing, in which the viscosity of the ink and the aggregation of the pigment are prevented during storage. It is a thing.

[0002]

2. Description of the Related Art Various organic solvent-based pigment ink compositions have been proposed as ink compositions for ink jet printing. Compared to conventional organic solvent-based dye inks, water-based dye inks, or water-based pigment inks, organic solvent-based pigment inks use an organic solvent as a medium to make paper, metal, plastics, etc. It is characterized in that it can be printed without being selected and that it has excellent water resistance and light resistance of the printed matter in combination with the characteristics of the pigment. However, if the combination of the three essential components, pigment, non-aqueous organic solvent-based medium, and dispersant is not appropriate, the viscosity of the ink will increase and the pigment will agglomerate during storage. There are many. Such a situation should not occur when the ink is stored in a closed container or set in an ink jet printer. According to a study by the present inventors, the ink for ink-jet printing may be stored in a closed container for one year, or may be thickened or agglomerated with the pigment for one week even when the ink is set in the ink-jet printing machine. The ink viscosity and the particle size distribution of the pigment in the ink remain unchanged within the experimental error before and after the accelerated test of constant temperature storage at 60 ° C for 1 month. It is necessary to be. To our knowledge, no such stable ink jet printing ink has been found. This difficulty is due to the fact that the prior art focused on one or two components of the above three components and did not reach an appropriate composition selection for all three components.

In order to achieve fine printing, there are nozzle holes and nozzle holes in the ink flow path of an ink jet printer, and the pigment must be dispersed in fine particles. Since the finer the pigment particles are, the more easily they aggregate, the ink for inkjet printing uses a larger amount of a dispersant than those of other pigment inks and paints to stabilize the dispersion. This is because if the pigment agglomerates further, the ink flow path is blocked and printing cannot be continued. In addition, the aggregation of the pigment causes a change in the ink viscosity, which causes a change in the ink ejection amount and a change in the print tone. When the volatility of the dispersion medium is high, the ink on the nozzle surface is dried and solidified when the printing is interrupted, and the nozzle hole is clogged, so that the printing cannot be resumed as it is. Inappropriate combination of the characteristics of the pigment, the dispersion medium, and the dispersant causes the above-mentioned difficulties. Therefore, the present inventors decided to work on the development of a novel organic solvent-based pigment ink composition for inkjet printing, which can be stably used, while searching for the presence or absence of appropriate blending of the above three essential components.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel organic solvent-based pigment ink composition for inkjet printing, which can be stably used without thickening of ink or aggregation of pigment during storage. is there.

[0005]

[Means for Solving the Problems] The object is achieved by selecting the composition of the ink.

[0006] The present inventors have found that glycol ether esters are non-soluble in ink-jet printing organic solvent-based pigment ink compositions because of their low viscosity, low toxicity, low odor, wide range of boiling point selection, and good affinity with print targets. Since I knew experientially that it was excellent as an aqueous organic solvent-based medium, I examined the ink composition to make use of this suitability.

The glycol ether ester in the present invention is a substance represented by the general formula 1. Depending on the type and combination of pigments and dispersants used in combination, R
When R ′ and R ′ exceed the above range of carbon number, the ink thickens or finely dispersed pigments aggregate during long-term storage to form coarse particles, which makes it unusable as an ink for inkjet printing. When the value of n exceeds the above range, the initial viscosity of the ink becomes high, and thus it is possible to prepare an ink having an appropriate viscosity by reducing the blending ratio, but similarly to the above, thickening during storage for a long period of time and aggregation of pigment may occur. It happens and becomes unusable as an ink jet printing ink. After all, in the present invention, the object can be achieved only by selecting the combination with the pigment or the dispersant and further selecting the dispersing medium in this way. In the present invention, suitable glycol ether esters are ethylene glycol ethyl ether acetate, ethylene glycol-n-butyl ether acetate, ethylene glycol-n-butyl ether propionate, diethylene glycol-n-propyl ether acetate, diethylene glycol-n-butyl ether acetate, triethylene glycol. Ethylene glycol ethyl ether acetate, triethylene glycol-n-butyl ether acetate, triethylene glycol-n
-Butyl ether propionate and the like, and particularly preferable are ethylene glycol-n-butyl ether acetate, diethylene glycol-n-propyl ether acetate, triethylene glycol-n-butyl ether propionate and the like.

The glycol ether ester in the present invention is a single substance or a mixture of two or more of the above substances.
It is added to the ink composition. In the preparation of ink compositions, the addition of water should be avoided in order to reach the object of the invention. However, it is acceptable for the ink composition to contain water that has naturally absorbed from the atmosphere when the ink is used. The content of the medium in the ink composition of the present invention is in the range of 55 to 95%, preferably 60 to 90% based on the weight of the essential components of the ink.

The pigment in the present invention means CI Pigment Blue 15: 3, CI Pigment Blue 15: 4, CI
Pigment Yellow 138, CI Pigment Yellow 15
0, CI Pigment Red 122 treated with acidic substance, C.I.
I. Pigment Green 7, CI Pigment Green 3
At least one pigment selected from the group consisting of 6 and carbon black. The acidic substance-treated product is a pigment in which a substance in which a carboxylate or a sulfonate is introduced is added to a part of the pigment skeleton. In the present invention, the object can be achieved only by selecting the combination of the dispersion medium and the dispersant and further selecting the pigment in this way. There are various kinds of pigments, and many pigments other than the above were investigated, but they were unsuitable as pigments for ink jet printing inks due to aggregation due to long-term storage.

The blending ratio of the pigment in the ink composition of the present invention may be in a range useful as an ink in which a drawn image can be visually recognized, and it varies depending on the kind and the purity of the pigment.
Generally, it is 0.5% by weight or more and 15% by weight or less in the essential components of the ink. If it is blended in excess, the optical density of the image will be saturated and wasteful, and the viscosity of the ink will be high, which will hinder the use, so 2% by weight or more and 10% by weight or less is preferable. Finer pigment particles in the ink are preferable because a finer image can be formed, but in order to ensure dispersion stability of the pigment particles in the ink, the average particle diameter is 0.01 μm or more and 0.5 μm or more.
It is desirable to be in the range of μm or less. Particularly, it is preferable that the average particle diameter is in the range of 0.05 μm or more and 0.3 μm or less.

The dispersant in the present invention is a living copolymer acrylic polymer as an effective main component. Specifically, the one commercially available as BYK-2001 from BYK Chemie can be preferably used. Copolymerized acrylic polymer prepared by a method other than living polymerization, even if the copolymer composition is the same, such as BYK-
In 2000, it is possible to prepare an ink for inkjet printing, but it is not suitable because pigment agglomeration occurs after long-term storage. Possibly the difference in the molecular weight homogeneity of the dispersant polymer is causing such a situation. When the polymer compositions are different, for example, the acrylic dispersant polymer and the polyurethane dispersant polymer, etc. were also examined, but it is possible to prepare an ink for inkjet printing in the same manner as in the above case,
The pigment was agglomerated during long-term storage and was unsuitable. Even if the combination of the pigment and the dispersion medium was changed for these dispersants, good results were not obtained.

The blending ratio of the dispersant varies depending on the kind of the pigment used, but generally speaking, it is in the range of 30% by weight or more and 200% by weight or less in terms of the pure content of the dispersing agent with respect to the pigment. If the blending ratio is too small, long-term dispersion stability of the pigment cannot be ensured, and if it is too large, the viscosity of the ink becomes high, which is unsuitable as an ink for inkjet printing. A more preferable blending ratio is in the range of 35% by weight or more and 150% by weight or less. In the ink composition of the present invention, the object could be achieved by selecting a dispersant and further increasing the compounding amount thereof. According to the studies by the present inventors, the blending ratio of the dispersant to the pigment is 45% by weight when the pigment is carbon black, 70% by weight when the pigment is yellow, 100% by weight when the pigment is red, and when the pigment is blue or pigment green. 90% by weight was a suitable example. This value may be appropriately optimized according to the composition history of the pigment and the mechanism of the inkjet printing machine, and can be easily determined from printing experiments and storage stability tests.

An outline of the method for producing the ink composition of the present invention will be described. A dispersant is uniformly dissolved in glycol ether ester as a dispersion medium, a pigment is added thereto, and the pigment is dispersed with a disperser such as a bead mill until the pigment particles have a predetermined average particle diameter. In order to carry out the dispersion efficiently, the amount of the dispersion medium is used in an amount smaller than a predetermined amount to prepare a concentrated dispersion liquid of the pigment. If coarse particles are present, they are removed by filtration or centrifugation, and a dispersion medium is added to obtain an ink for inkjet printing having a predetermined concentration. The medium in the ink composition of the present invention is basically only glycol ether ester, but it is possible to select a useful substance from various conventionally known compounds as an additive of the ink and add an appropriate amount thereof. As an additive, for accelerating the drying and solidification of the ink after image formation, for example, a drying accelerator such as ethanol or isopropanol, and a dispersion when the dispersant is dissolved in advance as a solution for the convenience of measuring and handling the dispersant. Solvents compatible with the medium, for example, solvents such as alkoxypropyl acetate, propylene glycol monomethyl ether, butyl cellosolve and the like can be mentioned. These various additives may be added either before the dispersion step or before or after the final concentration adjustment step.

As described above, in the present invention, by selecting the combination of the essential components, the ink viscosity and the particle size distribution of the pigment in the ink are within the experimental error before and after the test of promoting the constant temperature storage of the ink at 60 ° C. for one month. Inkjet that is stable and can be used stably for 1 year when stored in an airtight container, and for 1 week when set in an inkjet printing machine without ink thickening or pigment aggregation. A printing ink composition can now be provided. The ink composition of the present invention is particularly suitable for piezo element type inkjet printing due to the characteristics of the dispersion medium.

[0015]

EXAMPLES The present invention will be described below with reference to examples. Parts in the examples are parts by weight. The particle size of the pigment was measured with a laser diffraction type particle size distribution analyzer, and the viscosity was measured with a B-type viscometer. In the stability acceleration test, the ink is stored at 60 ° C for a month at a constant temperature, and before and after that, the viscosity of the ink and the particle size distribution of the pigment in the ink are measured, and the pigment in the ink is observed with an ultramicroscope. The presence or absence of aggregation of

Example 1 In a container, ethylene glycol ethyl ether acetate as a dispersion medium and a living copolymer acrylic polymer solution (BYK Che as a dispersant) were used.
Mie BYK-2001, net content 46%), and then CI Pigment Blue 15: 4 (Rionol Blue FG7400G manufactured by Toyo Ink Mfg. Co., Ltd.), which is a pigment, was weighed in a predetermined amount, and zircon beads were added to the beads mill ( Set in Red Devil paint conditioner) 2
The pigment was dispersed by shaking for a period of time. Coarse particles of the pigment are removed by centrifugation, ethylene glycol ethyl ether acetate is added, and the pigment concentration is 12.0% by weight, the dispersant concentration (net content) is 11.0% by weight, and the ethylene glycol ethyl ether acetate is 64.0%. An ink having a weight% of 13.0% by weight of a mixed solvent which is a glycol ether or its ester as a solvent of a dispersant, a viscosity of 11.3 mPa · s, and an average particle diameter of a pigment of 0.12 μm was prepared. As a result of the stability acceleration test, the viscosity and the average particle diameter of the pigment were not changed, and the aggregation of the pigment was not recognized. The prepared ink is an ink jet printer Xaarjet XJ manufactured by Saar.
It was loaded in 128/360/55 and subjected to an intermittent printing test in which 1 hour of printing and 15 hours of interruption were repeated for 5 cycles, but smooth printing was possible without trouble. Then, the same intermittent printing test was performed using the ink after the stability promotion test, and smooth printing could be performed.

Comparative Example 1 Dispersant BY in Example 1
BY Chem-made BYK-2001 is the same as BYK-2
The procedure of Example 1 was repeated with the exception of 000. As a result of a stability acceleration test, this ink showed a viscosity increase of 18% and a slight increase in the average particle diameter of the pigment, but the activity of the Brownian motion of the pigment was reduced by an ultramicroscope, and aggregation of the pigment particles was observed. . In the same intermittent printing test as in Example 1, the prepared ink did not eject at the beginning of the third cycle, and the ink after the stability promotion test did not eject at a part of the nozzles 35 minutes after the start of the first printing. .

(Example 2) Ethylene glycol-n-butyl ether acetate as a dispersion medium and a living copolymer acrylic polymer solution (BYK Che as a dispersant).
BYK-2001 manufactured by Mie, 46% pure), carbon black as a pigment (Special Black 4 manufactured by Degussa)
A predetermined amount of A) was weighed out, and in the same procedure as in Example 1, the composition of the essential components was such that the pigment concentration was 15.0% by weight, the dispersant concentration (purity) was 7.0% by weight, and the dispersion medium 78. An ink having 0% by weight, a viscosity of 6.1 mPa · s, and an average particle diameter of the pigment of 0.15 μm was prepared. As a result of the stability acceleration test, the viscosity and the average particle diameter of the pigment were not changed, and the aggregation of the pigment was not recognized. The ink after the preparation and after the stability accelerating test could be successfully printed by the same inkjet printing test as in Example 1.

Comparative Example 2 Dispersant BY in Example 2
BY Chem-made BYK-2001 is the same as BYK-2
The procedure of Example 1 was repeated with the exception of 000. As a result of a stability acceleration test, this ink showed a 23% increase in viscosity and a slight increase in the average particle size of the pigment, but the activity of the Brownian motion of the pigment was reduced by an ultramicroscope, and aggregation of the pigment particles was observed. . In the same intermittent printing test as in Example 1, the prepared ink did not eject at the beginning of the third cycle, and the ink after the stability promotion test did not eject at a part of the nozzles 30 minutes after the start of the first printing. .

Comparative Example 3 Dispersant BY in Example 2
The method of Example 2 was repeated except that BYK-2001 manufactured by K Chemie was replaced with BYK-161, a dispersant of a copolymer polyurethane type. As a result of a stability acceleration test, this ink was found to be unsuitable as an organic solvent-based pigment ink composition for inkjet printing, as an increase in viscosity of 30% and aggregation of pigment were observed.

Example 3 Diethylene glycol-n-propyl ether acetate was used as the dispersion medium, and a living copolymer acrylic polymer solution (BYK C) was used as the dispersant.
hemie BYK-2001, pure content 46%), and a predetermined amount of CI Pigment Yellow 150 (Bayplast Yellow 5GN01 manufactured by Bayer Co., Ltd.) as a pigment is weighed and the composition of the essential components is determined by the same procedure as in Example 1. , Pigment concentration 12.
An ink having 0% by weight, a dispersant concentration (pure content) of 8.0% by weight, a dispersion medium of 80.0% by weight, a viscosity of 13.1 mPa · s, and an average particle diameter of the pigment of 0.21 μm was prepared. The result of the stability promotion test is that the viscosity and the average particle size of the pigment do not change,
No pigment agglomeration was observed. The ink after the preparation and after the stability accelerating test could be successfully printed by the same inkjet printing test as in Example 1.

Comparative Example 4 Dispersant BY in Example 3
K-2001 was mixed with an acrylic dispersant (EFKA-4400 manufactured by EFKA ADDITIVES, pure content 40).
% / Solvent: butyl acetate, butanol) and the method of Example 3 was repeated. As a result of a stability acceleration test, the obtained ink was found to be unsuitable as an organic solvent-based pigment ink composition for inkjet printing, as viscosity was increased by 35% and pigment aggregation was observed.

Example 4 Triethylene glycol-n-butyl ether acetate was used as a dispersion medium, and a living copolymer acrylic polymer solution (BYK C was used as a dispersant).
Hemie BYK-2001, net content 46%), CI pigment red 122 as a pigment treated with an acidic substance (Dainippon Ink and Chemicals, Inc. Fastgen Super Magenta RG) was weighed in a predetermined amount, and Example 1 In the same procedure as described above, the composition of the essential component is 12.0% by weight in pigment concentration,
Dispersant concentration (purity) 12.0% by weight, dispersion medium 76.0
An ink having a weight%, a viscosity of 30.4 mPa · s, and an average particle diameter of the pigment of 0.28 μm was prepared. As a result of the stability acceleration test, the viscosity and the average particle diameter of the pigment were not changed, and the aggregation of the pigment was not recognized. The ink after the preparation and after the stability accelerating test could be successfully printed by the same inkjet printing test as in Example 1.

(Comparative Example 5) The pigment in Example 4 was mixed with CI.
Pigment Red 122 (Fastgen Super Magenta RE03 manufactured by Dainippon Ink and Chemicals, Inc.) was repeated, and the method of Example 4 was repeated. As a result of the stability acceleration test, the obtained ink was found to be unsuitable as an organic solvent-based pigment ink composition for inkjet printing, as viscosity increased and pigment aggregation was observed.

Example 5 Ethylene glycol-n-propyl ether propionate as a dispersion medium and a living copolymer acrylic polymer solution (BYK) as a dispersant.
Chemie Co. BYK-2001, pure content 46%), CI pigment green 7 (Dainippon Ink and Chemicals, Inc. Fastgen Green S) as a pigment were weighed in a predetermined amount, and the same procedure as in Example 1 was performed. The composition of the essential components is as follows: pigment concentration 18.0% by weight, dispersant concentration (pure content) 16.0% by weight, dispersion medium 66.0% by weight, viscosity 11.5 mPa.
s, an ink having an average particle size of the pigment of 0.25 μm was prepared. As a result of the stability acceleration test, the viscosity and the average particle diameter of the pigment were not changed, and the aggregation of the pigment was not recognized. The ink after the preparation and after the stability accelerating test could be successfully printed by the same inkjet printing test as in Example 1.

Comparative Example 6 The dispersant in Example 5 was replaced with a polyurethane dispersant (EFKA-4050 manufactured by EFKAADDITIVES, pure content 45% / solvent: butyl acetate, butanol, methoxypropyl acetate). The method was repeated. As a result of the stability acceleration test, the obtained ink was found to be unsuitable as an organic solvent-based pigment ink composition for inkjet printing, as viscosity increased and pigment aggregation was observed.

[0027]

EFFECTS OF THE INVENTION The present invention has made it possible to provide a novel organic solvent-based pigment ink composition for ink jet printing, which can be stably used without thickening of ink or aggregation of pigment during storage.

Claims (3)

[Claims] 1. An ink composition for inkjet printing, which comprises a pigment, a non-aqueous organic solvent medium and a dispersant as essential components, wherein the pigment is CI Pigment Blue 15: 3,
At least one pigment selected from the group consisting of CI Pigment Blue 15: 4, CI Pigment Yellow 138, CI Pigment Yellow 150, CI Pigment Red 122 treated with an acidic substance, CI Pigment Green 7, CI Pigment Green 36, and carbon black. And
The dispersant is a living copolymer acrylic polymer as an effective main component, and the non-aqueous organic solvent-based medium is at least one selected from the group consisting of glycol ether esters represented by the following general formula 1. An ink composition for inkjet printing, which is Embedded image R (OA) nOC (O) R ′ (wherein R in Chemical formula 1 is an alkyl group having 1 to 4 carbon atoms, A is an alkylene group having 2 or 3 carbon atoms, and R ′ is 1 or more carbon atoms). An alkyl group of 3 or less, and n is an integer of 1 or more and 3 or less that represents the chain length of oxyalkylene.) 2. The composition ratio of the essential components is 0.5% by weight of pigment.
15% by weight or more, 55% by weight of non-aqueous organic solvent medium
More than 95% by weight, the dispersant is 30% in pure content with respect to the pigment
2. The weight ratio is in the range of 200% by weight or more and 200% by weight or less, and the total of these is 100% by weight.
The ink composition for inkjet printing according to item 4. 3. The composition ratio of the essential components is 2% by weight or more and 10% by weight or less of the pigment, 60% by weight or more and 90% by weight or less of the non-aqueous organic solvent medium, and the dispersant is 35% by weight as a pure component with respect to the pigment. % Or more and 150% by weight or less, and the total of these is 100% by weight, and the ink composition for inkjet printing according to claim 1.