JP2010095628A - Ink for inkjet recording and method for inkjet recording - Google Patents

Abstract

An ink for ink jet recording and an ink jet recording method using the ink that can improve the ejection reliability of an ink jet printer without performing the operation of a reliability maintenance mechanism such as wiping or capping of the ejection nozzle surface as much as possible. Provided.
[MEANS FOR SOLVING PROBLEMS] (1) Water, a colorant, an acidic compound, a volatile alkali compound, and a water-solubility that is reduced in viscosity by the acidic compound and is increased in viscosity by the volatile alkali compound Ink for inkjet recording containing resin.
(2) The ink for inkjet recording according to (1), wherein the acidic compound is an organic acid.
(3) The ink for inkjet recording according to (1) or (2), wherein the volatile alkali compound is an alkylamine having an alkyl group having 1 to 2 carbon atoms.
(4) The ink for inkjet recording according to any one of (1) to (3), wherein the water-soluble resin is a water-soluble resin having a carboxyl group.
[Selection] Figure 1

Description

  The present invention relates to an ink for ink jet recording and an ink jet recording method.

It is difficult to satisfy the ejection reliability peculiar to an ink jet printer while maintaining the image quality. In particular, water-based ink for ink jet recording has a problem that, when moisture evaporates, the ink solid content concentration increases and the ink viscosity increases, which causes nozzle clogging of the ink jet head. For example, Patent Document 1 discloses that a specific amine is added to the ink, and Patent Document 2 discloses that 2-oxazolidone that generates monoethanolamine by hydrolysis is added to the ink. This method is not a fundamental measure against an increase in ink viscosity (increased ink) due to evaporation of water in a state where the discharge nozzle portion, that is, the ink is open to the outside air.
On the other hand, there is an idea of obtaining ejection reliability by a reliability maintenance mechanism such as wiping of the ejection nozzle surface or capping for suppressing moisture evaporation. However, the phenomenon and mechanism around the discharge nozzle are complex, and the head surface and nozzle holes may be damaged or contaminated by wiping or capping, which may cause nozzle clogging or ejection variation.
In addition, high-speed inkjet printers equipped with line heads have a large reduction in print productivity due to the large amount of printing per unit time when ejection failures occur or when frequent maintenance operations are introduced, compared to serial printers. Therefore, further improvement in ejection reliability is desired.

JP-A-6-166840 JP-A-6-228476

  SUMMARY OF THE INVENTION An object of the present invention is to provide an ink for ink jet recording and an ink jet recording method using the ink, which can be satisfactorily discharged without causing a viscosity to increase so much even when moisture evaporates.

The above problems are solved by the following inventions 1) to 8).
1) Containing water, a coloring material, an acidic compound, a volatile alkali compound, and a water-soluble resin that is reduced in viscosity by the acidic compound and increased in viscosity by the volatile alkali compound. An ink for ink jet recording characterized by the above.
2) The ink for inkjet recording according to 1), wherein the acidic compound is an organic acid.
3) The ink for inkjet recording according to 2), wherein the organic acid is a hydroxy fatty acid having 2 to 6 carbon atoms.
4) The ink for ink jet recording according to any one of 1) to 3), wherein the volatile alkali compound is an alkylamine having only an alkyl group having 1 to 2 carbon atoms.
5) The ink for inkjet recording according to any one of 1) to 4), wherein the water-soluble resin is a water-soluble resin having a carboxyl group.
6) The ink for inkjet recording according to 5), wherein the water-soluble resin having a carboxyl group is a styrene- (meth) acrylic acid copolymer.
7) A water-soluble organic solvent is further included, and the water-soluble organic solvent contains a polyoxypropylene diglyceryl ether of the following formula (1) and an alkylalkanediol, 2. Ink for ink jet recording described in 1.
(In the formula, m, n, o, and p are each an integer of 0 to 24 that satisfies 4 ≦ m + n + o + p ≦ 24.)
8) Ink jet recording using a line head, the ink for ink jet recording according to any one of 1) to 7) is used.

Hereinafter, the present invention will be described in detail.
The ink for ink jet recording of the present invention contains an acidic compound and a volatile alkali compound, and contains a water-soluble resin that is reduced in viscosity by the acidic compound and increased in viscosity by the volatile alkali compound. In a normal state, the water-soluble resin is in a high viscosity state due to the presence of the volatile alkali compound. However, in an environment where moisture evaporates, the volatile alkali compound also volatilizes, so the water-soluble resin is acidic. Viscosity is reduced by the compound. Since the water-soluble resin is in a low viscosity state, an increase in the viscosity of the ink due to the evaporation of water is offset, so that the increase in the viscosity of the ink when the water is evaporated can be reduced.
For example, in the case of a water-soluble resin having a carboxyl group, it is in a low viscosity state in the presence of an acidic compound, that is, in a low solubility state as shown in FIG. 1 (a), and is neutralized by a volatile alkali compound. And it will be in a highly viscous state, that is, a highly soluble state as shown in FIG. When the volatile alkali compound in the ink is volatilized, the high viscosity state due to neutralization as shown in FIG. 1B is eliminated, and the low viscosity state as shown in FIG. Therefore, even if the water in the ink is evaporated at the ink jet nozzle, the increase in the viscosity of the ink due to the evaporation of the water is offset by the decrease in the viscosity of the water-soluble resin due to the volatilization of the volatile alkali compound. Since the increase does not occur or can be suppressed to a slight increase in viscosity, the discharge stability can be maintained even after being left standing.

  As the acidic compound, an organic acid is preferable, and a hydroxy fatty acid having 2 to 6 carbon atoms is particularly preferable. Specific examples thereof include 2-hydroxyacetic acid (glycolic acid) having 2 carbon atoms, 2-hydroxypropanoic acid (lactic acid), 3-hydroxypropanoic acid (3-hydroxypropionic acid, hydroacrylic acid) having 3 carbon atoms. 2,3-dihydroxypropanoic acid, 4 carbon atoms, 2-hydroxybutanoic acid (2-hydroxybutyric acid), 3-hydroxybutanoic acid (3-hydroxybutyric acid), 4-hydroxybutanoic acid (4-hydroxybutyric acid), 2-hydroxy-2-methylpropanoic acid (methyl lactic acid), 2-hydroxybutanedioic acid (malic acid), 2,3-dihydroxybutanedioic acid (tartaric acid), 3-hydroxy-2-methylpropanoic acid, 2-hydroxy -3-butenoic acid, 5 carbon atoms, itartaric acid, oxymethyl succinic acid (itamalic acid), 2-hydroxypentanoic acid (2-hydro Valeric acid, 2-hydroxyvaleric acid), 2,3-dihydroxypentanoic acid (2,3-dihydroxyvaleric acid, 2,3-dihydroxyvaleric acid), 2-hydroxy-3-methylbutanoic acid, 2-hydroxy-2 -Methylbutanedicarboxylic acid, 6-carbon 2-hydroxypropane-1,2,3-tricarboxylic acid (citric acid), 1-hydroxytricarboxylic acid (1-hydroxypropane-1,2,3-tricarboxylic acid, Acid), galacturonic acid, 2-keto-galactonic acid, 2-hydroxyhexanoic acid (2-hydroxycaproic acid), 2-hydroxy-2-methylglutaric acid and the like.

Among the hydroxy fatty acids, 2-hydroxyacetic acid (glycolic acid) and 2-hydroxypropanoic acid (lactic acid) are particularly preferable from the viewpoint of the effect.
The amount of the hydroxy fatty acid is about 0.5 to 5% by weight of the whole ink. Within this range, after water or volatile alkali compounds have evaporated or volatilized, the pH will change greatly to the acidic side, and the solubility of the water-soluble resin will decrease, thereby suppressing the increase in ink viscosity. The discharge stability can be improved. As an actual operation, the blending amount is adjusted so that the pH before the pH adjustment by the volatile alkali compound performed at the end of the ink blending is 6 or less, and preferably the pH is 5 or less. Good.

As the volatile alkali compound, an alkylamine having only an alkyl group having 1 to 2 carbon atoms or a compound having volatility equivalent to or higher than the alkylamine is preferable. Due to the high volatility, the viscosity of the water-soluble resin is surely lowered due to the volatilization of the alkali compound, so that it is possible to more effectively improve the discharge stability after being left.
However, those that are too volatile, such as ammonia (corresponding to 0 carbon atoms), are not so preferable. When the volatility is too high, the viscosity of the water-soluble resin is rapidly and easily reduced. For this reason, an unnecessary ink viscosity drop is likely to occur during printing, and the continuous ejection stability may deteriorate.
Specific examples of the alkylamine having only the alkyl group having 1 to 2 carbon atoms include monoethylamine, diethylamine, triethylamine, monomethylamine, dimethylamine, and trimethylamine.
The amount of the alkylamine is preferably about 0.3 to 3% by weight of the total ink. Within this range, after moisture or the alkylamine evaporates or volatilizes, the pH greatly changes to the acidic side, and the solubility of the water-soluble resin decreases, thereby suppressing the increase in ink viscosity more effectively. Further, it is possible to further improve the discharge stability after being left. As an actual operation, the pH is adjusted to 8 or more, preferably 9 or more, by adjusting the pH with the alkylamine at the end of the ink formulation.

The water-soluble resin needs to be in a reduced viscosity state by the acidic compound and in a higher viscosity state by the volatile alkali compound.
As such a water-soluble resin, there is a water-soluble resin having a carboxyl group, and specific examples thereof include a styrene- (meth) acrylic acid copolymer. The number average molecular weight (MW) of the styrene- (meth) acrylic acid copolymer is preferably 2000 or less, and in this case, the viscosity increases moderately when dissolved. Moreover, it is preferable that the acid value of a styrene- (meth) acrylic acid copolymer is 200 or more, and in this case, the amount of carboxyl groups for expressing water solubility becomes appropriate.
Examples of such styrene- (meth) acrylic acid copolymers include styrene, (meth) acrylic acid, and (meth) acrylic acid esters of alcohols or phenols having 10 or less carbon atoms as main monomer components. There are polymers and are commercially available. As an example of a commercially available product, Jonkrill 682 (number average molecular weight 1600 / acid value 235) manufactured by Johnson may be mentioned.
The blending amount of the styrene- (meth) acrylic acid copolymer is preferably about 0.1 to 1.0% by weight, more preferably 0.1 to 0.5% by weight of the whole ink. Within this range, when the pH changes greatly to the acidic side after water or volatile alkali compounds have evaporated or volatilized, the copolymer becomes in a low-viscosity state, the ink viscosity also decreases, and ejection stability after standing is left. Can increase the sex.

As the coloring material, for example, a pigment or a dye can be used, but a pigment is preferable.
Examples of pigments include organic pigments and inorganic pigments. For example, for black and white, carbon blacks such as furnace black, lamp black, acetylene black, channel black (CI pigment black 7), copper oxide, iron oxide Organic pigments such as products (CI Pigment Black 11), metals such as titanium oxide, and aniline black (CI Pigment Black 1).
For color, C.I. I. Pigment Yellow 1 (Fast Yellow G), 3, 12 (Disazo Yellow AAA), 13, 14, 17, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55, 81, 83 (Disazo Yellow HR) ), 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 138, 153, C.I. I. Pigment orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 2 [Permanent Red B (Ba)], 48: 2 (Permanent Red 2B (Ca)), 48 : 3 [permanent red 2B (Sr)], 48: 4 [permanent red 2B (Mn)], 49: 1, 52: 2, 53: 1, 57: 1 (brilliant carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G rake), 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (Quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, C CI Pigment Violet 1 (Rhodamine Lake), 3, 5: 1, 16, 19 (Quinacridone Red), 23, 38, CI Pigment Blue 1, 2, 15 (Phthalocyanine Blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 127 (bitumen), 28 (cobalt blue), 29 (ultraviolet), 56, 60, 63, CI Pigment Green 1, 4, 7, 8, 10, 17, 18, 36, etc., but is not limited thereto.

In the ink for inkjet recording, a water-soluble organic solvent is usually added.
Preferable water-soluble organic solvents include polyoxypropylene diglyceryl ether (POP-DG) and alkylalkanediol (AAD) represented by the following formula (1).
(In the formula, m, n, o, and p are each an integer of 0 to 24 that satisfies 4 ≦ m + n + o + p ≦ 24.)
AAD includes a main chain of alkanediol having 3 to 6 carbon atoms and a branched chain of alkyl group having 1 to 2 carbon atoms, such as 2-methyl-1,3-propanediol, 3-methyl-1, Examples include 3-butanediol, 3-methyl-1,5-pentanediol, and 2-ethyl-1,3-hexanediol. A plurality of these may be used in combination.
The POP-DG and AAD have a low ability to dissolve a water-soluble resin in which a volatile alkali compound has been volatilized to a low viscosity state, so that the viscosity of the ink is greatly reduced and the ejection stability after being left is high. . In addition, since it is difficult to break hydrogen bonds between cellulose molecules even if they penetrate between cellulose molecules, an ink with high image quality and high ejection reliability can be obtained.
The total blending amount of the POP-DG and AAD may be appropriately set in consideration of the solubility of the water-soluble resin. For example, in the case of the water-soluble resin having the carboxyl group, 10 to 50 of the entire ink. % By weight is preferred, more preferably 20 to 50% by weight, still more preferably 40 to 50% by weight. If it is the said range, since the solubility of the water-soluble resin which has a carboxyl group is low, the discharge stability after leaving to stand can be improved.

  Examples of water-soluble organic solvents other than the above include glycerin, 1,3-butanediol, triethylene glycol, 1,6-hexanediol, propylene glycol, 1,5-pentanediol, diethylene glycol, dipropylene glycol, trimethylolpropane, Trimethylolethane, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,2, Hydroxy compounds such as 6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, thiodiglycol, pentaerythritol; ethylene glycol monoethyl ether Polyhydric alcohol alkyl ethers such as ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether; ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, etc. Polyhydric alcohol aryl ethers; nitrogen-containing compounds such as 2-pyrrolide, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, and γ-butyrolactone Heterocyclic compounds (lactams); amides such as formamide, N-methylformamide, N, N-dimethylformamide; Methyl sulfoxide, sulfolane, sulfur-containing compounds such as thiodiethanol; propylene carbonate, ethylene carbonate and the like, may be used these multiple combination.

In the present invention, if necessary, resin emulsions, surfactants, antiseptic / antifungal agents, rust preventives, metal ion sealants, water-soluble UV absorbers, water Various materials such as a radiant infrared absorber can be included.
The resin emulsion is an emulsion in which the continuous phase is water and the dispersed phase is a resin component, has the property of thickening and aggregating, suppressing the penetration of colored components, and further promoting the fixing to the recording material. Has an effect. Further, depending on the type of resin emulsion, a film is formed on the recording material, and the printed material has an effect of improving the abrasion resistance.
Examples of the resin component in the dispersed phase include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, and styrene resins. As the resin, a polymer having both a hydrophilic part and a hydrophobic part is preferable. The particle size of these resin components is not particularly limited as long as an emulsion is formed, but is preferably about 150 nm or less, more preferably about 5 to 100 nm.

These resin emulsions can be obtained by mixing resin particles in water together with a surfactant as necessary. For example, an acrylic resin or styrene-acrylic resin emulsion can be obtained by adding (meth) acrylic acid ester or styrene, (meth) acrylic acid ester, and optionally (meth) acrylic acid ester, and a surfactant to water. It can be obtained by mixing.
The mixing ratio of the resin component and the surfactant is usually preferably about 10: 1 to 5: 1. If the amount of the surfactant used is less than the above range, it is difficult to form an emulsion, and if it exceeds the above range, the water resistance of the ink tends to be lowered or the penetrability tends to deteriorate.
The ratio of the resin and the water in the resin emulsion is suitably in the range of 60 to 400 parts by weight, preferably 100 to 200 parts by weight, with respect to 100 parts by weight of the resin.
Examples of commercially available resin emulsions include Microgel E-1002, E-5002 (styrene-acrylic resin emulsion, manufactured by Nippon Paint Co., Ltd.), Boncoat 4001 (acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), Boncoat 5454 ( Styrene-acrylic resin emulsion, manufactured by Dainippon Ink & Chemicals, Inc.), SAE-1014 (styrene-acrylic resin emulsion, manufactured by Nippon Zeon), Cybinol SK-200 (acrylic resin emulsion, manufactured by Seiden Chemical), etc. Can be mentioned.

Examples of the surfactant include anionic, cationic, fluorine, acetylene glycol, and the like, and these can be used alone or in admixture of two or more.
Fluorosurfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, perfluoroalkylamine oxide compounds, etc. Can be mentioned.
Examples of commercially available fluorine-based compounds include Surflon S-111, S-112, S-113, S121, S131, S132, S-141, and S-145 (manufactured by Asahi Glass Co., Ltd.), Fullrad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (manufactured by Sumitomo 3M) and the like can be easily obtained and used in the present invention. When FT-110, 250, 251, 400S manufactured by Neos Co., Ltd. is used, good print quality is obtained and the color developability is remarkably improved.
Examples of acetylene glycol surfactants include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5- Examples include dimethyl-1-hexyn-3-ol.
As for acetylene glycol surfactants, commercially available products such as Surfynol 104, 82, 465, 485 or TG from Air Products (USA) can be easily obtained and used in the present invention. In particular, when Surfynol 465 is used, good print quality is obtained, and the permeability of the vehicle to paper is significantly improved.

Examples of the antiseptic / antifungal agent include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, 1,2-benzisothiazolin-3-one, and the like.
Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and benzotriazole.
The ink for inkjet recording of the present invention is suitably used for inkjet recording with a line head. Line head inkjet printers are required to have higher printing productivity than so-called serial inkjet printers. In particular, a maintenance operation that stops printing, for example, a reliability maintaining operation such as idle ejection, wiping of the ejection nozzle surface, and capping must be avoided as much as possible. If the ink for ink jet recording of the present invention is used, the ejection reliability is improved, and therefore the frequency of the reliability maintaining operation can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, even if a water | moisture content evaporates, the viscosity does not rise so much and can provide the ink for inkjet recording which can discharge favorably, and the inkjet recording method using this ink.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these Examples. The pigment in the ink formulation (self-dispersing system) is a pigment having a hydrophilic group on the surface and dispersible in water without a dispersant.

Examples 1-7, Comparative Examples 01-02
Inkjet recording inks of Examples and Comparative Examples were prepared and evaluated as follows. The ink formulations are the following (i) to (ix), and the blending ratio (% by weight) of each component is as shown in Tables 1 to 3.
(I) Pigment (self-dispersing system)
(Ii) Surfactant (iii) Water-soluble organic solvent (iv) Acidic compound (v) Water-soluble resin (vi) Volatile alkali compound (vii) Water (viii) Preservative (ix) Rust inhibitor

<Ink preparation method>
First, the water-soluble organic solvent, water-soluble resin, water, preservative, and rust inhibitor were dispersed and stirred with a dissolver (DISPERMAT-FE) to prepare a water-soluble resin dispersion.
Next, a pigment and a surfactant were added to this water-soluble resin dispersion, and dispersed and stirred with a dissolver (DISPERMAT-FE) to prepare a pigment dispersion.
Next, an acidic compound was added to the pigment dispersion to adjust the pH to around 5, thereby preparing an acidic pigment dispersion.
Next, a volatile alkaline compound was added to the acidic pigment dispersion, and the mixture was dispersed and stirred with a dissolver (DISPERMAT-FE) to prepare an alkaline pigment dispersion, followed by filtration with a 3 μm filter to obtain an ink for inkjet recording. .

The ink jet recording ink was evaluated for the viscosity, the viscosity after standing, the image density, the continuous ejection property, and the ejection property after standing by the following methods.
<Viscosity evaluation method>
Evaluation was performed by the following apparatus and conditions.
Viscometer: manufactured by A & D, tuning fork type vibration viscometer SV-10
-Measurement conditions: 23 ° C
<Method for evaluating viscosity after standing>
2 g of ink was put into a glass bottle with an inner diameter of 20 mm, dried without a lid and dried at 24 ° C. and 20% RH for 24 hours, and then evaluated with the same apparatus and conditions as in the case of the viscosity.

<Image density evaluation method>
The image density after monochrome solid printing was evaluated by the following apparatus and conditions.
・ Printer name: Prototype line head printer (see Fig. 2)
・ Media name: TYPE6200 PPC paper manufactured by Ricoh Co., Ltd. ・ Printing conditions: recording density 300 × 600 dpi, 100% duty, Mj21pl,
23 ° C 65% RH
Concentration measuring device: manufactured by X-Rite, portable spectral density X-Rite 939

<Evaluation method of continuous discharge>
The dot diameter change rate (%) after printing 1000 sheets was evaluated by the following apparatus and conditions.
・ Printer name: Prototype line head printer (see Fig. 2)
・ Media name: TYPE6200 PPC paper manufactured by Ricoh Co., Ltd. ・ Printing conditions: recording density 300 × 600 dpi, 100% duty, Mj21pl,
23 ° C 65% RH
The evaluation criteria were as follows.
5: Less than 5%
4: 5% or more and less than 10%
3: 10% or more and less than 15%
2: 15% or more and less than 20%
1: 20% or more

<Evaluation method of ejectability after leaving>
The dot diameter change rate (%) was evaluated when reprinting was performed after the inkjet head was left open for 30 minutes under the following apparatus and conditions.
・ Printer name: Prototype line head printer (see Fig. 2)
・ Media name: TYPE6200 PPC paper manufactured by Ricoh Co., Ltd. ・ Printing conditions: recording density 300 × 600 dpi, 100% duty, Mj21pl,
23 ° C 65% RH
The evaluation criteria were as follows.
5: Less than 5%
4: 5% or more and less than 10%
3: 10% or more and less than 15%
2: 15% or more and less than 20%
1: 20% or more

Here, the apparatus of FIG. 2 will be described.
FIG. 2 is a schematic diagram showing the internal structure of the prototype line head printer used for the evaluation.
In the image recording apparatus A, the paper feed tray 1 has a configuration in which a pressure plate 2 and a paper feed rotating body 4 for feeding recording paper 3 are attached to a base 5. The pressure plate 2 can rotate around a rotation axis a attached to the base 5, and is urged by the pressure plate spring 6 to the sheet feeding rotator 4.
A separation pad (not shown) made of a material having a large friction coefficient, such as an artificial skin, is provided at a portion of the pressure plate 2 facing the sheet feeding rotator 4 in order to prevent double feeding of the recording paper 3. . Further, a release cam (not shown) for releasing the contact between the pressure plate 2 and the sheet feeding rotating body 4 is provided.
In the above configuration, the release cam pushes the pressure plate 2 down to a predetermined position in the standby state. As a result, the contact between the pressure plate 2 and the sheet feeding rotating body 4 is released. In this state, when the driving force from the transport roller 7 is transmitted to the sheet feeding rotator 4 and the release cam by a gear or the like, the release cam moves away from the pressure plate 2 and the pressure plate 2 rises, and the sheet feeding rotator 4 and the recording are recorded. The paper 3 comes into contact.
Then, the recording paper 3 is picked up and started to be fed along with the rotation of the paper feed rotating body 4 and separated one by one by a separation claw (not shown). The sheet feeding rotator 4 rotates to feed the recording sheet 3 to the platen 10 via the conveyance guides 8 and 9.
The recording paper 3 passes between the conveyance guides 8 and 9 and is guided to the conveyance roller 7, and is conveyed to the platen 10 by the conveyance roller 7 and the pinch roller 11. After that, the contact state between the recording paper 3 and the paper feed rotating body 4 is released again, and the driving force from the transport roller 7 is cut off.
The paper feed rotator 12 for manual paper feed feeds the recording paper 3 mounted on the manual feed tray 13 in accordance with the recording command signal of the computer and transports it to the transport roller 7.
The recording paper 3 conveyed to the platen 10 passes under the line head 14. Here, the recording paper conveyance speed and the droplet discharge timing are adjusted based on a signal controlled by an electric circuit (not shown), thereby forming a desired image.

The evaluation results are summarized in Tables 1 to 3. The meanings of the abbreviations in the table are as follows.
C = cyan, m = magenta, y = yellow, k = black. PB15: 4 = C. I. Pigment Blue 15: 4 (Cabot, CAB-O-JET250, volume average particle size: 0.091 μm)
DQ122 = C. I. Pigment Red 122 (Cabot, CAB-O-JET260, volume average particle size: 0.105 μm)
MA74 = C. I. Pigment Yellow 74 (manufactured by Cabot, CAB-O-JET270, volume average particle size: 0.137 μm)
Acid CB = acid carbon black (Cabot, CAB-O-JET300, volume average particle size: 0.130 μm)
FSAA: Fluorosurfactant (FT-110 manufactured by Neos Co., Ltd.)
AG: Acetylene glycol surfactant (Surfinol 465 manufactured by Air Products)
1,3-BD = 1,3-butanediolPOP-DG (9): polyoxypropylene diglyceryl ether
(M + n + o + p = 9)
MBD: 3-methyl-1,3-butanediol glycol: 2-hydroxyacetic acid (glycolic acid)
・ Lact: 2-hydroxypropanoic acid (lactic acid)
Citr: 2-hydroxypropane-1,2,3-tricarboxylic acid (citric acid)
1600/235: Styrene- (meth) acrylic acid copolymer
(Number average molecular weight 1600, acid value 235)
MM: monomethylamine TE: triethylamine BIT: 1,2-benzisothiazolin-3-one BTA: benzotriazole In addition, as PB15: 4, CAB-O-JET250: manufactured by Cabot, average particle diameter: 0 091 μm self-dispersing pigment, CAQ-O-JET260: manufactured by Cabot as DQ122, self-dispersing pigment having an average particle size of 0.105 μm, CAB-O-JET270: manufactured by Cabot as MA74 The self-dispersing pigment having an average particle size of 0.137 μm was used as the acidic CB, and CAB-O-JET300: manufactured by Cabot Corporation, and the self-dispersing pigment having an average particle size of 0.130 μm was used.

As can be seen from Table 2 above, in Comparative Example 01 which does not contain an acidic compound, the evaluation of the ejection property after being left was “2”.
Further, in Comparative Example 02 containing no volatile alkali compound, although the viscosity after standing is not so much increased, the evaluation of continuous dischargeability is “3” or “2”, and the evaluation of dischargeability after leaving is “2”. Or "1". The cause of this is not clear, but if it does not contain a volatile alkali compound, the water-soluble resin curls in an insoluble state (see FIG. 1 (a)), which has an adverse effect on ejection and is left as it is. If it is lost, the water-soluble resin is further insolubilized, which seems to cause discharge failure.
Further, in Example 2 using POP-DG and MBD as water-soluble organic solvents, the evaluation of ejection property after standing was “4”, but glycerin and 1,3-BD were used as water-soluble organic solvents. In Example 7, the evaluation of the ejection property after being left was “3”, and it was found that the combination of POP-DG and MBD was superior.

The schematic diagram which shows the low viscosity state and high viscosity state of water-soluble resin which has a carboxyl group. (A) Low viscosity state, ie, low solubility state, (b) High viscosity state, ie, high solubility state. The figure which shows the prototype line head printer used for the continuous discharge property evaluation of this invention.

Explanation of symbols

A Image recording apparatus a Rotating shaft 1 Paper feed tray 2 Pressure plate 3 Recording paper 4 Paper feed rotator 5 Base 6 Pressure plate spring 7 Transport roller 8 Transport guide 9 Transport guide 10 Platen 11 Pinch roller 12 Paper feed rotator for manual feed 13 Bypass tray 14 Line head

Claims (8)

  It includes water, a coloring material, an acidic compound, a volatile alkali compound, and a water-soluble resin that is reduced in viscosity by the acidic compound and is increased in viscosity by the volatile alkali compound. An inkjet recording ink.   2. The ink for ink jet recording according to claim 1, wherein the acidic compound is an organic acid.   3. The ink for ink jet recording according to claim 2, wherein the organic acid is a hydroxy fatty acid having 2 to 6 carbon atoms.   The ink for inkjet recording according to any one of claims 1 to 3, wherein the volatile alkali compound is an alkylamine having only an alkyl group having 1 to 2 carbon atoms.   The ink for inkjet recording according to any one of claims 1 to 4, wherein the water-soluble resin is a water-soluble resin having a carboxyl group.   6. The ink for inkjet recording according to claim 5, wherein the water-soluble resin having a carboxyl group is a styrene- (meth) acrylic acid copolymer. It further contains a water-soluble organic solvent, and the water-soluble organic solvent contains a polyoxypropylene diglyceryl ether of the following formula (1) and an alkylalkanediol. Ink jet recording ink.
(In the formula, m, n, o, and p are each an integer of 0 to 24 that satisfies 4 ≦ m + n + o + p ≦ 24.)   An inkjet recording method using the inkjet recording ink according to any one of claims 1 to 7 in inkjet recording by a line head.