JPH07331148A - Ink - Google Patents

Abstract

PURPOSE:To obtain an ink which is excellent in stability of delivery, has high viscosity giving a high-quality print with little blur, very quickly fixes on printing paper, and exhibits no overlap of color even in color printing. CONSTITUTION:This ink contains a colorant for developing color, a wetting agent for preventing a nozzle tip from drying, a resistivity-adjusting agent for imparting conductivity to the ink, a solvent, and a salt of an acrylic acid- maleic acid copolymer represented by the formula: H-(CHCOOM- CHCOOM)a-(CH2CHCOOM)b-(CHCOOM-CHCOOM)c-H (wherein M is H and/or an alkali metal and/or NH4; and a, b, and c are integers satisfying the relations: 0<a+c<=78 and (0<=b<=15).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink used in various recording tools such as writing tools and printers, and more particularly, an ink used in an ink jet recording system in which droplets are ejected from an orifice of a recording head to perform recording. It is about.

[0002]

2. Description of the Related Art In recent years, demands for printers have been increasing more rapidly, noises have been reduced, and colors have been increasing.

As conventional inks, inks to which a surface active agent having a polyoxyethylene chain is added, inks to which an anionic surface active agent is added, and the like are used, and they have characteristics such as apparently quick-drying property. is there.

Generally, the principle of ink ejection from an ink jet head of an ink jet printer is based on an electric heating type,
There are piezo elements and electrostatic systems.

A conventional energized heat generation type ink jet head will be described below. FIG. 2 is a sectional view of a conventional energization type inkjet head. In FIG. 2, reference numeral 2 is ink, 1a and 1b are electrodes for energization and heat generation for passing a current through the ink 2, 3 is a printer control circuit connected to the electrodes for energization and heat generation 1a and 1b through lead wires, and 4 is a width. , Both height 30
Ink flow path through which ink 2 flows, 5 is a nozzle hole through which ink 2 flies, and 6 is 1 mm in front of nozzle hole 5
The printing paper is a printing paper on which the ink 2 arranged at a certain position penetrates and is printed. The electrodes 1a and 1b for heating by electric current are generally Au, which has an appropriate oxygen overvoltage and is excellent in corrosion resistance,
Pt, Ni, Pb, Ti, etc. are formed by plating or vacuum evaporation. Among them, Ti is preferably used because it has the highest corrosion resistance. The thickness of the electrodes 1a and 1b for heat generation by energization is 10 μm, and the dimensions of the electrodes are 20 μm in width and 40 μm in width.

The operation of the electric heating type ink jet head configured as described above will be described below with reference to FIG. FIG. 3 is an operation diagram of a conventional energization heat generation type inkjet head. 3 (a) is an operation diagram in which electricity is applied through the energization / heating electrodes 1a, 1b, FIG. 3 (b) is an operation diagram in which a bubble 7 is generated, and FIG. 3 (c) is an operation diagram in which an ink droplet 8 is ejected. FIG. 3D is an operation diagram in which the bubble 7 contracts, and FIG. 3E is an operation diagram in which the ink flow path is filled with ink. First, according to a print signal, the printer control circuit 3 causes the frequency 1 to be applied between the electrodes 1a and 1b for energization and heat generation in the ink flow path 4.
An AC signal of 00K to 10 MHz and a voltage of 10 to 50 V is applied, and a current is passed through the ink 2. At this time, the current value is 10m
About A flows. When this is performed by AC driving at 2 MHz, one cycle is performed at 500 nsec. By performing this continuously for 5 to 10 μsec, the ink 2 is w = V ² / (R ×) due to the specific resistance R of the ink 2 itself.
and the temperature of the ink 2 is 150
~ 200 ° C rises. Then, as shown in FIG. 3B, the ink 2 is heated and boiled to generate bubbles 7. Further, as shown in FIG. 3C, the bubble 7 grows and the ink droplet 8 is ejected from the nozzle hole 5 by the boiling pressure. At the same time as the ink droplet 8 is ejected and the application of the AC signal voltage is stopped, as shown in FIG. 3D, the bubble 7 rapidly cools, shrinks and disappears. Finally, as shown in FIG. 3E, the ink 2 is filled in the ink flow path 4, and the ink ejection operation is completed.

Further, when color printing is performed in the energization type ink jet system, when an ink of a certain color is ejected onto a printing paper and another ink of another color is ejected adjacently before the ink is dried, Color bleeding occurs on the printing paper. In order to eliminate this color bleeding, a surfactant having a micelle concentration or more is added to the ink as described in JP-A-55-29546,
There is a method of adjusting the surface tension to a constant value. According to this method, since the ink instantly penetrates between the fibers of the printing paper, it is possible to obtain an apparent quick-drying property and suppress color bleeding.

[0008]

However, in the conventional ink, since the surface tension of the ink is low and the contact angle with the printing paper is small, the printing dots spread and the bleeding is large when the ink penetrates into the printing paper. However, there is a problem in that printing paper for inkjet printers must be used, ordinary printing paper cannot be used, and high printing quality cannot be expected.

The present invention solves the above-mentioned problems of the prior art, has little bleeding when the ink penetrates into the printing paper, can print sufficiently high quality even on plain paper, and does not cause mixed color bleeding during color printing. It is an object of the present invention to provide an ink that has a high penetration rate into the printing paper, takes a long time to be fixed on the printing paper, and can obtain high printing quality.

[0010]

In order to achieve this object, the ink according to claim 1 of the present invention comprises a dye which is a color former, a wetting agent for preventing the nozzle tip from drying, and a conductive ink. And a solvent, and a salt of a copolymer of acrylic acid and maleic acid represented by the following general formula (Formula 2).

[0011]

[Chemical 2]

An ink according to a second aspect is the ink according to the first aspect, wherein the salt of the copolymer of acrylic acid and maleic acid is a = 14, b = 8 in the general formula (Formula 2).
c = 2 or a = 6, b = 4, c = 2 or a = 2
0, b = 12, c = 4, or a = 39, b = 8, c =
2 has a structure having a chemical formula shown in FIG. The ink according to claim 3 is the ink according to claim 1, wherein the salt of the copolymer of acrylic acid and maleic acid is 0.001 to 20 parts by weight, preferably 0.04 to 10 parts by weight, per 100 parts by weight of the ink. It has the composition contained. The ink according to claim 4 is the ink according to claim 1, wherein when the total amount of the solvent and the wetting agent is 100 parts by weight, the amount of the solvent is 10
~ 70 parts by weight, preferably 20-65 parts by weight of water,
And, the wetting agent is 15 to 50 parts by weight, preferably 20 to
It has a composition of 45 parts by weight of a polyhydric alcohol.
The ink according to claim 5 has the viscosity according to claim 1 of 10 cp or less, preferably 8 cp or less, and / or a surface tension of 28 to 65 dyne / cm, preferably 30 to 60 dyne / cm. It has a certain configuration. The ink according to claim 6 is the ink according to claim 1, wherein the specific resistance of the ink is 1 to 100 Ωcm, and preferably 10 to
It has a configuration of 30 Ωcm.

The salt of the copolymer of acrylic acid and maleic acid used in the present invention comprises a block copolymer of maleic acid and acrylic acid.
The method of quasi-polymerizing the monomer by the living polymer method, the method of first synthesizing a polymer having an active group at the terminal and then polymerizing another monomer from the terminal, the method of connecting different polymers, etc. is there.

Salts of copolymers of acrylic acid and maleic acid have a = 14, b = 8, c = 2, or a = 6, b =
4, c = 2, or a = 20, b = 12, c = 4, or a = 39, b = 8, c = 2,
This is because it has advantages in synthesis and stability.
The content of the salt of the copolymer of acrylic acid and maleic acid is
When the amount is less than 0.04 parts by weight, the effect is insufficient, and 1
If it exceeds 0 parts by weight, viscosity increase or nozzle clogging may occur, which is not preferable.

Here, as the pigment, a conventionally used dye or pigment can be used. For example, various dyes such as direct dyes, basic dyes, acid dyes, disperse dyes, reactive dyes, spirit dyes, and carbon black,
Various pigments such as phthalocyanine blue, dioxane yellow and quinacridone red can be mentioned. The content of the dye is preferably 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight.

Here, the wetting agent has a boiling point higher than that of water and is used to prevent the nozzle tip from drying.
A polyhydric alcohol is used as the wetting agent. Specifically, alkylene glycols such as polyethylene glycol, polypropylene glycol, butylene glycol, hexylene glycol containing 2 to 6 carbon atoms, for example ethylene glycol ethyl ether,
Examples thereof include lower alkyl ethers of diethylene glycol such as diethylene glycol methyl ether and diethylene glycol ethyl ether, and glycerin. When the content of the wetting agent is less than 20 parts by weight, the wetting effect is insufficient, and when it exceeds 45 parts by weight, thickening and deterioration of print quality may occur, which are not preferable.

Here, the resistivity adjusting agent is necessary in order to make the ink conductive in the ink jet printer. Specific resistance adjusting agents include ammonium chloride, ammonium acetate, sodium chloride, potassium chloride, lithium chloride, lithium perchlorate, inorganic salts such as potassium bromide, water-soluble amines such as diethanolamine, triethanolamine and dimethylamine hydrochloride. And quaternary ammonium salts such as tetramethylammonium chloride and tetraethylammonium bromide.

Examples of the solvent include water and an organic solvent that can be mixed with water. Examples of the organic solvent include alkyl alcohol such as methyl alcohol, ethyl alcohol, n-propyl alcohol and isopropyl alcohol, ketone or keto alcohol such as acetone and diacetone alcohol, amides such as dimethylformamide and dimethylacetamide, tetrahydrofuran, dioxane and the like. And ether alcohols such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether. Usually, the amount of the organic solvent mixed with water is preferably 80 parts by weight or less when the solvent is 100 parts by weight. In the ink according to claim 4, when the content of water is less than 10 parts by weight, it is difficult to dissolve the other components, and when it exceeds 70 parts by weight, the effect of the other components is hindered. As it exceeds the range, the effect of other components is hindered, which is not preferable.

In order to adjust the physical properties of the liquid, the ink may further contain a pH adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent and the like.

The pH adjusting agent may be any one as long as it can be adjusted to a desired pH value without adversely affecting the ink to be prepared. Specifically, a lower alkanolamine,
Examples thereof include monovalent hydroxides of alkali metal hydroxides and ammonium hydroxide.

The viscosity modifier is for adjusting the viscosity of the ink, and specifically, polyvinyl alcohol, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose,
Examples include water-soluble acrylic resin, polyvinylpyrrolidone, and gum arabic starch.

The surface tension adjusting agent is for adjusting the surface tension of the ink, and specific examples thereof include anionic, cationic and nonionic surfactants. As the anionic type, polyethylene glycol alkyl ether sulfuric acid, ester salt, higher alcohol sulfate, naphthalenesulfonic acid formalin condensate, etc., and as the cationic type, poly2-vinylpyridine derivative, poly-4-vinylpyridine derivative, etc., nonionic type , Polyoxyethylene alkyl ester, polyoxyethylene sorbitan monoalkyl ester, polyoxyethylene alkylamine and the like. In addition, diethanolamine, propanolamine, amine acids such as morpholine acid, basic substances such as ammonium hydroxide and sodium hydroxide, and substituted pyrrolidones such as N-methyl-2-pyrrolidone are also used.

The addition amount of the surface tension adjusting agent is determined depending on other constitutions and components of the ink and desired recording characteristics, but is usually 0.001 to 10 parts by weight, preferably It is preferably 0.001 to 5 parts by weight.

The ink according to claim 5 has a viscosity of 10c.
The discharge resistance becomes excessive as it exceeds p, and the surface tension becomes less than 28 dyne / cm, and the bleeding is large and the print quality is low. When it exceeds 65 dyne / cm, the penetration into the printing paper is slow and multicolor It is unsuitable for printing and is not preferable.

The ink according to claim 6 has a specific resistance of 10
If it is less than Ωcm, there is a possibility of precipitation or clogging, and if it exceeds 30 Ωcm, the conductivity is insufficient, which is not preferable.

Further, in order to reinforce the strength of the ink coating when it adheres to printing paper, alkyd resin, acrylic resin, acrylamide resin, polyvinyl alcohol,
A resin polymer such as polyvinylpyrrolidone may be added.

[0027]

With this structure, since it has appropriate specific gravity, viscosity and surface tension, it is excellent in ink ejection stability, stability in the ink flow path, and storage stability. Due to bleeding, high-quality printing can be performed without bleeding even on plain paper other than inkjet recording paper that could not be printed with high quality.
By imparting high penetrating power, the penetrating speed into printing paper becomes faster, fixing time on printing paper can be shortened, and bleeding due to overlapping of colors can be controlled even in color printing,
At the same time, since it has a high surface tension, it is possible to realize printing with less spread of printing dots and bleeding.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

(Example 1) Direct Fast Black G (Direct FastBlac) which is a dye
1.5 parts by weight of K G (Dye manufactured by Sumitomo Chemical), H- (CHCO) which is a salt of a copolymer of acrylic acid and maleic acid.
_{ONa-CHCOONa) 14 - (CH} 2 CHCOON
_{a) 8 - (CHCOONa-CHCOONa} ) 0.4 parts by weight of ₂ -H, 17 parts by weight of triethanolamine hydrochloride a resistance adjusting agent ratio, 25 parts by weight of diethylene glycol wetting agents, water as a solvent 56.1 parts by weight are weighed in a beaker, sufficiently stirred and dissolved to form a uniform solution,
Pressure filtration was performed using a 0.5 μm Teflon filter paper to obtain a black ink. The ink was stored in a vacuum drying oven connected to a rotary pump with a thick rubber tube, and degassed for 4 hours.

The above ink was tested by an energization type recording apparatus shown in FIG. The test items are continuous discharge stability due to continuous operation at 5 KHz, intermittent discharge stability when a 5 KHz signal is given at 2 second intervals, storage stability after observing changes in external physical properties after leaving for 3 months, 3 months Storage stability, surface tension, and ejection response observed for the first input signal after leaving
It is a setting property that is the time from when the ink 2 adheres to the printing paper to when the object is rubbed on the printing paper until it becomes dirty.
The test conditions are shown in (Table 1) and the test results are shown in (Table 2).

[0031]

[Table 1]

[0032]

[Table 2]

FIG. 1 shows H- (C in one embodiment of the present invention.
_{HCOONa-CHCOONa) 14 - (CH} 2 CHCO
_{ONa) 8 - (CHCOONa-CHCOONa} ) 2 -
It is a change figure of the amount of addition of H, surface tension, and set time.

As is clear from (Table 2), the ink according to the present example has good ejection stability, storage stability after being left for 3 months, and settability is improved. Excellent effect can be obtained.

As described above, according to this embodiment, H- (C
_{HCOONa-CHCOONa) 14 - (CH} 2 CHCO
_{ONa) 8 - (CHCOONa-CHCOONa} ) 2 -
Since the ink contains 0.4 parts by weight of H, extremely stable ejection characteristics can be obtained, the change over time is small, and the fixing time on the printing paper can be shortened.

(Example 2) Direct Fast Black G (Direct FastBlac) which is a dye
1.3 parts by weight of K G (dye manufactured by Sumitomo Chemical Co., Ltd.), H- (CHCO) which is a salt of a copolymer of acrylic acid and maleic acid.
_{ONa-CHCOONa) 14 - (CH} 2 CHCOON
_{a) 8 - (CHCOONa-CHCOONa} ) 1.3 parts by weight of ₂ -H, 16.3 parts by weight of triethanolamine hydrochloride are specific resistance adjusting agent, 24 parts by weight of diethylene glycol wetting agents, a solvent Using 57 parts by weight of water as a raw material, the following inks were prepared and tested in the same manner as in the examples, and the results are shown in (Table 3).

[0037]

[Table 3]

As is clear from this (Table 3), the ink according to the present embodiment has extremely stable ejection stability both when continuously performed and when a signal is input at 2-second intervals.
The storage stability after leaving for 3 months is also good, and the settability is improved to 20 seconds, and an excellent effect is obtained.

As described above, according to this embodiment, H- (C
_{HCOONa-CHCOONa) 14 - (CH} 2 CHCO
_{ONa) 8 - (CHCOONa-CHCOONa} ) 2 -
Since the ink contains 1.3 parts by weight of H, the ejection stability is excellent, the change over time is small, and the fixing time on the printing paper can be shortened.

(Example 3) Direct Fast Black G (Direct FastBlac) which is a dye
1.3 parts by weight of K G (dye manufactured by Sumitomo Chemical Co., Ltd.), H- (CHCO) which is a salt of a copolymer of acrylic acid and maleic acid.
_{ONa-CHCOONa) 14 - (CH} 2 CHCOON
_{a) 8 - (CHCOONa-CHCOONa} ) 2 -H 3.1 parts by weight, 15 parts by weight of triethanolamine hydrochloride a resistance adjusting agent ratio, 22.1 parts by weight of diethylene glycol wetting agents, a solvent Using 58.5 parts by weight of water as a raw material, the following inks were prepared and tested in the same manner as in the examples, and the results are shown in (Table 4).

[0041]

[Table 4]

As is clear from (Table 4), the ink according to the present example has good ejection stability, storage stability of 3 months, and fixing time on printing paper. Certain set characteristics have also been improved.

As described above, according to this embodiment, H- (C
_{HCOONa-CHCOONa) 14 - (CH} 2 CHCO
_{ONa) 8 - (CHCOONa-CHCOONa} ) 2 -
Since the ink contains 3.1 parts by weight of H, both ejection stability and storage stability are extremely stable, and the fixing speed on printing paper is also greatly improved.

(Example 4) Direct Fast Black G (Direct FastBlac) which is a dye
1.1 parts by weight of K G (dye manufactured by Sumitomo Chemical Co., Ltd.), H- (CHCO) which is a salt of a copolymer of acrylic acid and maleic acid.
_{ONa-CHCOONa) 14 - (CH} 2 CHCOON
_{a) 8 - (CHCOONa-CHCOONa} ) 2 6.2 parts by weight of -H, 12.9 parts by weight of triethanolamine hydrochloride are specific resistance adjusting agent, 18.9 parts by weight of diethylene glycol wetting agents, solvents Using 60.9 parts by weight of water as a raw material, the following inks were prepared and tested in the same manner as in the examples, and the results are shown in (Table 5).

[0045]

[Table 5]

As is clear from (Table 5), the ink according to the present embodiment stably ejected liquid droplets having uniform ejection stability for a long time, and the storage stability after being left for 3 months did not change at all. It was good, and the fixing time on the printing paper was very fast.

As described above, according to this embodiment, H- (C
_{HCOONa-CHCOONa) 14 - (CH} 2 CHCO
_{ONa) 8 - (CHCOONa-CHCOONa} ) 2 -
Since the ink contains 6.2 parts by weight of H, the ejection stability is excellent, the storage stability is also extremely stable, and the fixing speed on the printing paper is sufficiently high.

(Example 5) Direct Fast Black G (Direct FastBlac) which is a dye
1.1 parts by weight of K G (dye manufactured by Sumitomo Chemical Co., Ltd.), H- (CHCO) which is a salt of a copolymer of acrylic acid and maleic acid.
_{OK-CHCOOK) 14 - (CH} 2 CHCOOK) 8 -
6.2 parts by weight of (CHCOOK-CHCOOK) ₂ -H, 12.9 parts by weight of triethanolamine hydrochloride which is a specific resistance adjusting agent, 18.9 parts by weight of diethylene glycol which is a wetting agent, and water which is a solvent. Using 60.9 parts by weight as a raw material, the following inks were prepared and tested in the same manner as in the examples, and the results are shown in (Table 6).

[0049]

[Table 6]

As is clear from this (Table 6), the ink according to this example was extremely stable in both ejection stability and storage stability, and the setting property was sufficiently fast.

As described above, according to this embodiment, H- (C
_{HCOOK-CHCOOK) 14 - (CH} 2 CHCOO
_{K) 8 - (CHCOOK-CHCOOK} ) the ₂ -H 6.
Since the ink contains 2 parts by weight, the ejection stability is excellent, the storage stability is sufficiently stable, and the fixing speed on the printing paper is fast.

(Example 6) Direct Fast Black G (Direct FastBlac) which is a dye
1.1 parts by weight of K G (dye manufactured by Sumitomo Chemical Co., Ltd.), H- (CHCO) which is a salt of a copolymer of acrylic acid and maleic acid.
_{ONH 4 -CHCOONH 4) 14 - (} CH 2 CHCOO
_{NH 4) 8 - (CHCOONH 4} -CHCOONH 4)
6.2 parts by weight of _2- H, 12.9 parts by weight of triethanolamine hydrochloride which is a resistivity adjusting agent, 18.9 parts by weight of diethylene glycol which is a wetting agent, and 6 parts of water which is a solvent.
Using 0.9 parts by weight as a raw material, the following inks were prepared and tested in the same manner as in the examples, and the results are shown in (Table 7).

[0053]

[Table 7]

As is clear from this (Table 7), the ink according to this embodiment is extremely stable in both continuous ejection stability and ejection stability in which a signal is input every 2 seconds, and after being left for 3 months. The storage stability was not deteriorated at all, and the setting property, which is the fixing speed on the printing paper, was sufficiently improved.

As described above, according to this embodiment, H-
(CHCOONH_Four -CHCOONH _Four )₁₄-(CH₂ 
CHCOONH_Four )₈ -(CHCOONH_Four -CHCO
ONH _Four )₂ It is an ink containing 6.2 parts by weight of -H.
Therefore, the ejection stability is very stable and the storage stability is also
Sufficiently stable and extremely fast on the printing paper
Is getting worse.

[0056]

As described above, since the present invention is an ink containing a salt of a copolymer of acrylic acid and maleic acid appropriately, it has sufficiently stable ejection characteristics and little deterioration over time. Fixing time on printing paper is extremely short,
Very little character bleeding during printing, high quality printing with no bleeding on regular printing paper as well as printing paper exclusively for inkjet printers, and excellent printing quality even when color printing Ink can be realized.

[Brief description of drawings]

FIG. 1 shows an H- (CHCOON according to an embodiment of the present invention.
_{a-CHCOONa) 14 - (CH} 2 CHCOONa) 8
-(CHCOONa-CHCOONa) _2- H addition amount, surface tension and set time change chart

FIG. 2 is a cross-sectional view of a conventional electric heating type inkjet head.

FIG. 3 is an operation diagram of a conventional energization heat generation type inkjet head.

[Explanation of symbols]

 1a, 1b Electric heating electrodes 2 Ink 3 Printer control circuit 4 Ink flow path 5 Nozzle hole 6 Printing paper 7 Bubble 8 Ink drop 9 Ink flow direction

Claims (6)

[Claims] 1. A coloring agent, a coloring agent, a wetting agent for preventing the nozzle tip from drying, a resistivity adjusting agent for making the ink conductive, a solvent, and a general formula (Formula 1) below. An ink comprising: a salt of a copolymer of acrylic acid and maleic acid represented. [Chemical 1] 2. The salt of the copolymer of acrylic acid and maleic acid has the formula (1) wherein a = 14 and b =
8, c = 2 or a = 6, b = 4, c = 2 or a
= 20, b = 12, c = 4, or a = 39, b = 8,
The ink according to claim 1, having a chemical formula represented by c = 2. 3. 100 parts by weight of the ink contains 0.001 to 20 parts by weight, preferably 0.04 to 10 parts by weight of the salt of the copolymer of acrylic acid and maleic acid. The ink according to claim 1 or 2. 4. The solvent has a total solvent and wetting agent of 100.
When the amount is 10 parts by weight, the solvent is 10 to 70 parts by weight, preferably 20 to 65 parts by weight of water, and the wetting agent is 15 to 50 parts by weight, preferably 20 to 45 parts by weight. It is a polyhydric alcohol, It is characterized by the above-mentioned.
The ink according to item 1. 5. The ink has a viscosity of 10 cp or less, preferably 8 cp or less, and / or a surface tension of 28 to 65 d.
The ink according to claim 1, wherein the ink has a yne / cm, preferably 30 to 60 dyne / cm. 6. The specific resistance of the ink is 1 to 100 Ωcm,
The ink according to claim 1 is preferably 10 to 30 Ωcm.