JPH05320549A - Method for degassing ink for ink-jet recording and in for ink-jet recording - Google Patents

Abstract

PURPOSE:To carry out degassing of the subject ink and to stably deliver the ink by changing air to a gas having lower solubility in ink than air as a gas to come into contact with ink to reduce the gas dissolved in the ink. CONSTITUTION:A gas (preferably nitrogen or helium) having a lower solubility in ink than air is brought into contact with ink for ink-jet recording comprising a colorant and a vehicle as main components free from a disoxidant under lower than 1 atmospheric pressure to carry out the objective degassing free from oxygen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink degassing method and ink composition used for ink jet recording, and more particularly to an ink degassing method and ink composition used for an on-demand type ink jet printer.

[0002]

2. Description of the Related Art In an on-demand type ink jet printer, an image is formed by applying pressure to ink in an ink chamber in response to an image signal and causing the ink to fly from a nozzle. As a method for applying pressure to the ink in the ink chamber, a method using an electrostrictive element such as PZT,
A method of vaporizing ink by a heating element to form bubbles, a method of applying a constant pressure to the ink with a pump and controlling it with a valve, and the like have been put into practical use.

In any of these methods of applying pressure to the ink, when bubbles are generated in the ink chamber, the bubbles absorb the pressure applied to the ink, so that a normal ejection state cannot be obtained. Will end up. It is conventionally known that it is effective to use an ink from which gas dissolved in the ink is removed by heating the ink or by reducing the pressure in order to prevent gas from being generated in the ink chamber. .. Further, a method has also been proposed in which a deoxidizer such as sodium sulfite or sodium hydrogen sulfite is added to the ink to keep the amount of oxygen in the ink at a low level (JP-A-52-74406).

How much the amount of the gas component dissolved in the ink should be suppressed depends on the structure of the head to be used, how long the printer is left unused, and what environmental conditions. Although it varies depending on the usage conditions such as whether or not it is used, the smaller the dissolved amount, the better. When removing the gas dissolved in the ink by adding the oxygen absorber, not only the oxygen in the ink can be removed but the gas removal effect is not sufficient, and the dye is stored because the oxygen absorber is a reducing agent. If the salt is added, the solubility of the dye is lowered, or the solubility of the oxygen scavenger itself in the wetting agent is low, so that the nozzle is likely to be clogged.

In the method of removing the gas dissolved in the ink simply by reducing the pressure, it is preferable to lower the pressure of the air in contact with the ink as much as possible because the gas removal rate is large, but the pressure is lower than the vapor pressure of the material forming the ink. If set to, the amount of evaporation of ink will increase and the ink will boil,
A device that recirculates the evaporated ink component is required, which complicates the device. Further, in the method of heating the ink to remove the dissolved gas, in order to bring the dissolved gas to a sufficiently low level, it must be heated to near the boiling point. There is a problem that the ink components such as are decomposed.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, that is, to have a sufficient gas removing effect and to sufficiently suppress the decomposition of dye and the occurrence of nozzle clogging. SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for degassing an inkjet recording ink that does not complicate the apparatus, and to provide an ink that is degassed by the method and has excellent ejection characteristics.

[0007]

According to the present invention, the amount of gas dissolved in ink is changed by substituting air for gas contacting ink with gas having a lower solubility in ink than air. A method for degassing an inkjet recording ink is provided.

Further, according to the present invention, there is provided an ink jet recording ink containing a colorant and a vehicle as main components, containing no oxygen absorber and containing substantially no oxygen.

That is, the degassing method of the present invention is configured to degas the ink by replacing the gas contacting with the ink with a gas having a lower solubility in the ink than the air. Therefore, according to the present invention, the amount of gas dissolved in the ink is sufficiently reduced (in particular, the amount of dissolved oxygen is substantially zero), and when bubbles are generated in the liquid chamber of the print head, The size of the bubbles is relatively small and stable ejection is possible. In addition, the ink of the present invention has a composition that does not contain an oxygen scavenger and substantially does not contain oxygen (typically, ink degassed by the method of the present invention), and thus has stable ejection characteristics. At the same time as it is obtained, the change of the ink component during storage can be sufficiently suppressed.

The degassing method and ink composition of the present invention will be described in detail below. The method for degassing an ink jet recording ink of the present invention, the gas contacting the ink,
The amount of gas dissolved in ink is reduced by replacing air with gas having a lower solubility in ink than air. The solubility in ink here means the value at 20 ° C. means.

Generally, an ink jet recording ink is composed of a colorant, a vehicle, an additive and the like. As the vehicle, in the case of an aqueous ink, a combination of water and an organic solvent is used, and in the case of an oil ink. Are organic solvents or waxes that are solid at room temperature.
The most widely used is water-based ink, but the base material in that case is water. Therefore, in the present invention, in the case of a water-based ink, it is degassed by replacing it with a gas having a low solubility in water.

In the method of the present invention, the gas to be replaced is required to have not only lower solubility in ink than air, but also low reactivity and gas remaining in the ink having no adverse effect during storage. Therefore, preferable examples of the gas used in the present invention include nitrogen, helium, neon, CF ₄ , C ₃ F _{6 and the} like.

In the method of the present invention, the amount of gas dissolved in the ink is reduced only by replacing the gas in contact with the ink with air from the above gas, but it is dissolved in the ink in order to obtain stable ejection characteristics. It is preferable to further reduce the gas, and it is preferable to reduce the pressure or heat while replacing the gas in contact with the ink with a gas having a low solubility. In this method, the amount of gas dissolved in the ink is sufficiently reduced without lowering the pressure to the extent that the solvent forming the ink boils. In order to prevent the evaporation of the ink constituents, it is necessary to quickly equilibrate the gas with which the ink comes into contact with the ink, and a method of maintaining a reduced pressure while bubbling the replacement gas in the ink is particularly preferable in that respect.

As described above, the ink degassed in the atmosphere in which the gas has a low solubility in ink and is chemically stable is not only stable in ejection but also does not contain oxygen, so that the ink is not discharged. It also has an effect of sufficiently suppressing the deterioration of ink constituents such as dyes during storage.

As the ink material used in the present invention, all known materials are used. For example, a water-based ink can be obtained with a composition including a vehicle in which a colorant, water, an organic solvent and the like are combined, and an additive. In this case, specific examples of the colorant include the following aqueous dyes.

C. I. Acid. Yellow 17,23,42,4
4,79,142 C.I. I. Acid. Red 1,13,14,18,26,27,35,37,4
2,52,82,87,89,92,97,111,114,115,134,186,249,254,28
9 C. I. Acid. Blue 9,29,45,89,92,249 C.I. I. Acid. Black 1,2,7,24,26,94 C.I. I. hood. Yellow 3,4 C.I. I. hood. Red 7,9,14 C.I. I. hood. Black 2 C. I. direct. Yellow 1,12,26,33,44,50,86,
120,132,142,144 C.I. I. direct. Red 1,9,13,17,20,28,31,39,
80,81,83,89,225,227 C.I. I. direct. Orange 26,29,62,102 C.I. I. direct. Blue 1,2,15,22,25,71,76,79,
86,87,98,163,165,202 C.I. I. direct. Black 19,22,32,38,51,56,7
4,75,77,154,168 etc.

Specific examples of the organic solvent include monohydric alcohols such as ethanol, methanol and propanol, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol and glycerin. Polyhydric alcohols; ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol Monoethyl ether, tetrae Ethers of polyhydric alcohols such as lenglycol monoethyl ether and propylene glycol monoethyl ether; heterocyclic compounds such as N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone and ε-caprolactam, monoethanolamine And amines such as diethanolamine and triethanolamine.

In the case of oil-based ink, a coloring agent,
It can be obtained with a composition comprising an organic solvent or a vehicle which is solid at room temperature and wax, and additives. In this case, specific examples of the colorant include the following oil-soluble dyes.

C. I. Solvent. Yellow 1,2,3,
4,5,6,7,8,9,10,11,12,14,16,17,26,27,29,30,39,40,4
6,49,50,51,56,61,80,86,87,89,96 C.I. I. Solvent. Orange 12,23,31,43,51,61 C.I. I. Solvent. Red 1,2,3,16,17,18,19,20,2
2,24,25,26,40,52,59,60,63,67,68,121 C.I. I. Solvent. Violet 7,16,17 C.I. I. Solvent. Blue 2,6,11,15,20,30,31,32,
35,36,55,58,71,72 C.I. I. Solvent. Brown 2,10,15,21,22 C.I. I. Solvent. Black 3,10,11,12,13 etc.

In the ink of the present invention, it goes without saying that not only the dyes described above but also pigments can be used as the colorant, including the case of the water-based ink.

Organic solvents used as vehicles for oil-based inks include monohydric alcohols such as ethanol, methanol and propanol; ketones such as acetone, methyl ethyl ketone and methyl isopropyl ketone; esters such as ethyl acetate and methyl acetate; ethylene. Glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethyl glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl Ether, propylene glycol diethyl ether, etc. Polyhydric alcohols ethers, ethylene glycol monoacetate, diethylene glycol monoacetate, esters of polyhydric alcohols such as ethylene glycol diacetate; naphthalic acid dioctyl,
Aromatic carvone such as didecyl phthalate, dibutyl phthalate, diethyl phthalate, dinonyl phthalate, diisononyl phthalate, di-2 ethylhexyl phthalate, ditridecyl phthalate, butylbenzyl phthalate, trioctyl trimellitate and tridecyl trimellitate. Acid esters; Aliphatic carboxylic acid esters such as butyl sebacate, butyl oleate, butyl stearate, dibutyl adipate, butylphthalyl ethylene glycolate, methylphthalyl ethylene glycol, methylphthalyl butyl glycolate, monoacetin, diacetin, triacetin, and vegetable oils Unsaturated higher fatty acids such as oleic acid; silicone oils that are modified or unmodified polymethylsiloxanes; dodecane, 2,2,3-trimethylpentane, hexadecane, Loin, refined kerosene and other aliphatic hydrocarbons; alkylnaphthalene, hydrogenated triphenyl, diphenylmethane, monoethyldiphenyl, triethyldiphenyl, diethyldiphenyl, diphenyl, terphenyl, 1,4-diphenylbenzene, phenylxylyl Alkyl-substituted aromatic hydrocarbons such as ethane, toluene and xylene; Alkyl-substituted biphenyls, halogen-substituted aliphatic and aromatic hydrocarbons such as trichloroethylene, tetrachloroethylene and bromonophthalene; anisole, phenetole, methoxytoluene, diphenyl ether , Ethers such as belarol,
And so on.

Further, as a vehicle material for an ink used in a printer which is a solid at room temperature and which melts and ejects ink by heating a head, beeswax, carnauba wax, rice wax, wood wax , Jojoba oil, whale wax, candelilla wax, lanolin, montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, petrolactam, and other natural waxes; polyethylene wax and its derivatives; chlorinated hydrocarbons; olein Acid amide,
Lauric acid amide, stearic acid amide, ricinoleic acid amide, palmitic acid amide, tetrahydrofuranic acid amide, erucic acid amide, myristic acid amide, 12-hydroxystearic acid amide, N-stearyl erucic acid amide, N-oleyl stearic acid amide, N -Oleyl palmitate amide, N-oleyl oleate amide, N-stearyl oleate amide, N-stearyl oleate amide, N, N'-ethylenebislauric acid amide, N, N'-ethylenebisstearate amide, N , N'-ethylenebisoleic acid amide, N,
N'-methylenebisstearic acid amide, N, N'-ethylenebisbehenic acid amide, N, N'-xylylenebisstearic acid amide, N, N'-butylenebisstearic acid amide, N, N'-dioleyl Adipic amide,
N, N'-Distearyl adipic acid amide, N, N'-
Amides such as dioleyl sebacic acid amide, N, N'-distearyl sebacic acid amide, N, N'-distearyl terephthalic acid amide, N, N'-distearyl isophthalic acid amide, phenacetin, toluamide, acetamide; palmitin Organic acids such as acids, stearic acid, behenic acid, tiglic acid, 2-acetonaphthone behenic acid, 12-hydroxystearic acid and dihydroxystearic acid;
Dodecanol, tetradecanol, hexadecanol,
Eicosanol, docosanol, tetracosanol, hexacosanol, octacosanol, 9-dodecene-1
-Ol, myricyl alcohol, 9-tetracene-1-
All, 9-hexadecen-1-ol, 9-eicosen-1-ol, 13-docosen-1-ol, pinene glycol, hinokiol, butynediol, nonanediol, isophthalyl alcohol, messerine, terephthalyl alcohol, hexanediol. , Alcohols such as decanediol, dodecanediol, tetradecanediol, hexadecanediol, docosandiol, tetracosanediol, televisionneol, phenylglycerin, eicosanediol, octanediol, phenylpropylene glycol; benzoylacetone, diacetobenzene, Ketones such as benzophenone, trichosanone, heptacosanone, heptatriacontanone, hentriacontanone, stearone, laurone, dianisole; the above-mentioned acids and groups Serine, diethylene glycol,
Esters with alcohols such as ethylene glycol;
Synthetic waxes such as p-toluenesulfonamide, N-ethyl-p-toluenesulfonamide, ethylbenzenesulfonamide, butylbenzenesulfonamide, and other sulfonamide compounds can be used.

In the ink of the present invention, as additives, surfactants, antiseptics, rust preventives, penetrants, thickeners, fixability improvers, ultraviolet absorbers, etc. are added according to the purpose. can do.

By applying the degassing method of the present invention to the ink made of the above materials, the ink for ink jet recording of the present invention containing no oxygen absorber and containing substantially no oxygen can be obtained. ..

[0025]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. All the percentages shown below are based on weight.

Example 1 C. I. Direct Black 154 5.0% Diethylene glycol 8.5% Ion-exchanged water 86.5%

The mixture of the above formulation was dissolved and stirred at 50 ° C. for 2 hours, cooled, and then filtered with a filter having a pore size of 0.1 μm. The pressure in the ink container was maintained at 60 mmHg for 15 minutes while slightly bubbling CF ₄ gas through the ink while keeping the filtered ink at room temperature (22 ° C.). At this time, the amount of water evaporated due to the reduced pressure was 0.1% or less of the entire ink. Further, when the amount of oxygen dissolved in this ink was measured by a diaphragm electrode type oxygen concentration meter, dissolved oxygen was not observed. The dissolved gas amount of this ink was 0.0005 ml / ml or less.

An ink bag is formed by a film composed of three layers of polyethylene / Al vapor deposition film / polyester, and the above degassed ink is filled in this bag, and a known PZT on-demand type ink jet device is used as an electrostrictive element. -When a jet test was conducted with a printer, normal printing was possible.

Comparative Example 1 When the ink before the deaeration operation in Example 1 was used to perform printing in the same manner as in Example 1, 26 out of 48 nozzles were defective in ejection.

Comparative Example 2 Sodium sulfite 2% was added to the ink of the formulation of Example 1, and the ink of the formulation in which the amount of water was reduced was similarly dissolved and filtered, and the deaeration operation of Example 1 was not performed. Then, when the ink bag was directly filled and the same printing was performed, 18 out of 48 nozzles were defective in ejection.

COMPARATIVE EXAMPLE 3 The ink of the formulation of Example 1 was degassed to a level equivalent to that of Example 1 by simply reducing the pressure.
The pressure had to be reduced to 20 mmHg or less, and due to fluctuations in the adjusted pressure, the ink occasionally blew.

Example 2 C. I. Acid Blue 9 2.0% Polyethylene glycol 3.5% Ethylene glycol 4.5% N-Methyl-2-pyrrolidone 4.0% Polyoxyethylene nonylphenyl ether 3.0% Sodium dehydroacetate 0.3% Ion-exchanged water 82.7%

The mixture of the above formulation was dissolved and stirred at 50 ° C. for 2 hours, cooled, and filtered with a filter having a pore size of 0.1 μm. The filtered ink was heated to 40 ° C., and the pressure in the ink container was kept at 80 mmHg for 15 minutes while bubbling a slight amount of He gas through the ink. At this time, the amount of water evaporated due to the reduced pressure is 0.
It was 2% or less. When the amount of oxygen dissolved in this ink was measured in the same manner as in Example 1, dissolved oxygen was not observed. The amount of dissolved gas in this ink is 0.0005 ml
/ Ml or less.

An on-demand type ink-jet which uses a film composed of three layers of polyethylene / Al vapor-deposited film / polyester and is filled with the above degassed ink, and which is a known PZT as an electrostrictive element. -When a jet test was conducted with a printer, normal printing was possible.

The ink filled in the above bag was stored in a thermo-hygrostat at 70 ° C. for 1 month, the ink before and after storage was diluted 2000 times, and the absorbance was measured, but no change was observed.

Comparative Example 4 An ink having the same formulation as in Example 2 was similarly dissolved and filtered, and then degassed under the same conditions as in Example 2 except that air was not replaced with He gas. When the obtained ink was subjected to a storage test at 70 ° C. in the same manner as in Example 2, the absorbance was reduced by 2%.

Example 3 C. I. Direct Yellow 86 1.5% Polyethylene glycol 2.5% Thiodiethanol 6.5% Ethanol 4.0% Sodium dehydroacetate 0.3% Ion-exchanged water 82.7%

The mixture having the above formulation was dissolved and stirred at 50 ° C. for 2 hours, cooled, and filtered with a filter having a pore size of 0.1 μm. While bubbling a slight amount of nitrogen gas into the ink while keeping the filtered ink at room temperature (20 ° C.),
The pressure in the ink container was kept at 40 mmHg for 15 minutes.
At this time, the amount of water evaporated due to the reduced pressure was 0.2% or less of the entire ink. When the amount of oxygen dissolved in this ink was measured in the same manner as in Example 1, dissolved oxygen was not observed. The dissolved gas amount of this ink is 0.001
It was 0 ml / ml or less.

In the same manner as in Example 1, when the deaerated ink was filled in the ink bag and printing was performed, normal printing was possible. Further, the ink was filled in this ink printer, and printing was performed after leaving it for 3 months with the printing paused, but stable printing was possible as before the printing.

Comparative Example 5 An ink having the same formulation as in Example 3 was dissolved and filtered in the same manner as in Example 3 except that 2% of sodium sulfite was added and the amount of water was reduced. 40 mmH of this ink at room temperature
It was degassed by reducing the pressure with a pressure of g. When the obtained ink was filled in an ink bag and printed in the same manner as in Example 3, normal printing was possible. However, when the printing pause was performed as in Example 3, 13 nozzles out of 48 nozzles could not be ejected.

Example 4 C. I. Solvent Red 1.5% Methylcellosolve 43.0% Ethanol 40.5% Oleic acid 15.0%

The mixture of the above formulation was dissolved and stirred at 50 ° C. for 2 hours, cooled, and then filtered with a filter having a pore size of 0.1 μm. While bubbling a slight amount of Ne gas into the ink while keeping the filtered ink at room temperature (20 ° C.),
The pressure in the ink container was kept at 40 mmHg for 15 minutes.
At this time, the amount of water evaporated due to the reduced pressure was 0.5% or less of the entire ink.

When the ink bag was filled with the degassed ink and printing was performed in the same manner as in Example 1, normal printing was possible.

[0044]

According to the first aspect of the present invention, there is provided a method for degassing an ink for ink jet recording by degassing the ink by replacing the gas in contact with the ink with a gas having a lower solubility in the ink than the air. According to this method, the amount of gas dissolved in the ink is sufficiently reduced (especially, the amount of dissolved oxygen is substantially zero) and bubbles are generated in the liquid chamber of the print head. Even at this time, the size of the bubble is relatively small, and stable ejection is possible.

According to the second aspect of the present invention, the method of degassing the ink for ink jet recording adds a condition that the ink is brought into contact with a gas having a pressure lower than 1 atm. Therefore, according to this method, the amount of dissolved gas in the ink is further increased. And more stable ejection characteristics can be obtained. Further, as compared with the case where degassing is performed only by decompression, it is possible to suppress evaporation of components in the ink to degas to an equivalent level.

Since the ink-jet recording ink according to claim 3 is configured to contain no oxygen absorber and substantially no oxygen, stable ejection characteristics can be obtained, and at the same time, the ink components of the ink components during storage can be improved. Change can be suppressed sufficiently.

Claims (3)

[Claims] 1. An ink jet recording device, characterized in that the amount of gas dissolved in ink is reduced by replacing the gas in contact with ink with air and substituting gas having a lower solubility in ink than air. Method of degassing ink. 2. The method for degassing an ink jet recording ink according to claim 1, wherein the ink is brought into contact with a gas having a pressure lower than 1 atm. 3. An ink jet recording ink, which comprises a colorant and a vehicle as main components, does not contain an oxygen scavenger, and contains substantially no oxygen.