JPH08253717A - Water-base ink set, ink jet recording method using the same, and apparatus using the same - Google Patents

Abstract

PURPOSE: To obtain a water-base ink set which does not cause color bleeding on a plain paper record and can give a high-quality image record without detriment to recording characteristics such as color development of recording dots and to obtain an ink jet recording method and an apparatus using the same. CONSTITUTION: The water-base ink set comprises at least two inks which have different colors and each of which is a liq. compsn. contg. a colorant and a liq. medium. At least one ink of the set contains polyacrylic or polymethacrylic acid, and the other contains a high-molecular material capable of forming a gel when mixed with polyacrylic or polymethacrylic acid. An ink jet recording method and an apparatus using the same are also provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based ink jet recording method in which ink is ejected and ejected as small droplets from an ejection port (orifice), and the small droplets are adhered to the surface of a recording material for recording. More particularly, the present invention relates to an excellent water-based ink set that substantially eliminates color bleeding, an inkjet recording method using the same, and an apparatus using the ink.

[0002]

2. Description of the Related Art Conventionally, water-based inks have been mainly used as ink jet recording inks from the viewpoint of safety and odor. As ink jet inks, various water-soluble dyes or pigments are mixed with water or water and water. There is known an ink in which a humectant, a dye dissolution aid, a fungicide, etc. are added after being dissolved or dispersed in a volatile organic solvent. or,
Inkjet recording is capable of ejecting several thousand or more drops of ink per second, which facilitates high-speed recording, low noise, easy colorization, and high resolution. It has many advantages such as the fact that it can record on plain paper, and has been remarkably popular for several years. Furthermore, due to the recent trend of lower prices, higher performance of personal computers, and standardization of GUI environment, the demand for high color development, high quality, high robustness, high resolution recording and high speed recording has also increased in image recording of printers, etc. Sharpen the edges,
In particular, technical means for reducing bleeding of mixed colors is being proposed.

As a conventionally known means for suppressing bleeding, there are the following various methods. First,
As a first example, U.S. Pat. No. 5,181,045 discloses a method of preventing bleeding by mixing dyes at the boundary between two colors to precipitate a dye by an acid-alkali reaction. Specifically, a dye having different solubilities depending on pH is used for one color material of the ink, for example, this is made alkaline, and the other one is made to have an acidic pH so that the dye is precipitated. By 2 on paper
When the color ink droplets come into contact with each other, the dye is deposited at the boundary between these inks, and bleeding is suppressed.

Also, as a second example, US Pat.
No. 23 discloses a method of precipitating a black anionic dye ink and a yellow cationic dye ink with a metal salt such as calcium chloride. This is a method of reducing the bleeding at the boundary of the ink by adding a metal salt as a precipitant in addition to the cationic dye to the yellow ink, because the color bleeding is noticeable especially between black and yellow. . Further, as a third example, US Pat. No. 5,211,747 discloses a water- or alcohol-soluble desizing agent (polyoxyalkylene derivative, hydrophilic polydimethylsiloxane and hydrophilic polydimethylsiloxane) as a means for preventing high-speed fixing, feathering and bleeding. It is disclosed that the above problem is solved by allowing the ink to permeate into the paper at high speed by adding an aliphatic imidazoline derivative or the like) to the ink. Here, it is said that the desizing agent has a function of reducing the size of the paper.

On the other hand, as a fourth example, Japanese Patent Laid-Open No. 5-194
Japanese Patent No. 884 discloses that a polymer colloid and a surfactant having a CMC (critical micelle concentration) or higher are contained, and the adsorption action of the dye to the micelle formed by the addition of the surfactant having a CMC or higher and the association of the polymer colloid. Due to the adsorption effect of dye molecules,
It is disclosed to suppress bleeding.

[0006]

However, in the first example described above, since the bleeding is suppressed by the precipitation of the dye, the precipitation floats in the ink droplets,
The effect of suppressing bleeding is small. Also, in the second example,
Since the ink contains a metal salt such as calcium chloride, the thermal inkjet recording method has a problem that kogation is generated on the surface of the heat generating portion and the recording characteristics are deteriorated. The third example is to reduce the size of the paper,
Since this method is a method of suppressing high-speed fixing, feathering, and bleeding, there is a problem that the penetration of ink droplets into the paper is excessive and the color developability is poor. Further, in the fourth example, CM
Since a surfactant of C or higher is used, the fixing time can be shortened, but as in the third example, the amount of ink penetrating into the paper becomes large, and there is a problem that the color developability is poor.

Therefore, an object of the present invention is to solve the color bleeding in plain paper recording without deteriorating the recording characteristics such as the color development of recording dots, and to obtain a high quality recorded image. An object of the present invention is to provide an inkjet recording method using the same and devices using such ink.

[0008]

The above objects can be achieved by the present invention described below. That is, the present invention provides a water-based ink set containing at least two kinds of inks having different hues, each of which is composed of a liquid composition containing a coloring material and a liquid medium, and contains polyacrylic acid or polymethacrylic acid in at least one color ink. And a water-based ink set characterized in that a polymer material capable of forming a gel when mixed with the polyacrylic acid or polymethacrylic acid is contained in the ink of another color, and an ink jet recording method using the same And equipment.

[0009]

[Function] Polyacrylic acid or polymethacrylic acid used in the present invention (hereinafter abbreviated as poly (meth) acrylic acid)
Is a water-soluble polymer containing a weakly dissociative anionic group, carboxylic acid, and these polymer materials react with other water-soluble polymer materials to form a gel. Since the reaction in this case is a reaction between polymers which are polyfunctional compounds, there is a feature that a substance to be produced is accompanied by crosslinking of polymer chains. In some cases, the obtained crosslinked product becomes gel or extremely thickens. As a result of intensive studies to solve the problems of the prior art, the present inventors have found that the above reaction is extremely effective as a means for preventing ink bleeding, and completed the present invention.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to preferred embodiments of the present invention. The water-based ink set of the present invention is a water-based ink set for color printing, which contains at least two kinds of inks having different hues, each of which is composed of a liquid composition containing a coloring material and a liquid medium. It is characterized in that it contains a polymethacrylic acid and a polymeric material that is mixed with the polyacrylic acid or polymethacrylic acid in an ink of another color to form a gel.

The polymer material used in the present invention which is mixed with poly (meth) acrylic acid to form a gel has a hydrophilic hydroxyl group, ether oxygen, amide group, ester group or the like in the molecular structure. It is possible to use the material extensively. As such a polymer material, in particular, polyethylene oxide, polypropylene oxide, polyethylene oxide-polypropylene oxide copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide copolymer, polyacrylamide, poly-N-alkylacrylamide, polyvinylpyrrolidone, Polyvinyl methyl ether, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, methyl cellulose, hydroxyalkyl cellulose, etc.
It is preferably used in the present invention.

The prevention of bleeding when the water-based ink set of the present invention is used will be described below.
First, a black ink B in which polyethylene oxide having a molecular weight of 20,000 is dissolved by 10% and a molecular weight of 60,0
A yellow ink color A in which 10% of polymethacrylic acid of 100 was dissolved in a typical inkjet color printer (BJC-600 manufactured by Canon Inc.), and a bleeding test pattern as shown in FIG.
Record on paper. As shown by the dotted line in the figure, the bleeding level is divided into 5 levels, and the two-color boundary (arrow line)
To which line position the mixed color bleeding occurs from
This was evaluated as a bleeding level and evaluated in 5 levels.
As an evaluation criterion, the case where the bleeding is stopped within 1 dot line from the boundary line is set to 5, and 4 or 3, depending on which line below the bleeding occurs.
It is evaluated as 2, 1.

As a result, when an image recorded using the ink of the present invention was evaluated, it was ranked 4 to 5, and it was difficult to visually confirm bleeding. Further, when the boundary portion between the two colors was enlarged and observed, a fibrous gel was produced due to the reaction between the polymer materials, and bleeding was suppressed. Further, even if the recording speed is further increased, it is clear that the bleeding is sufficiently suppressed by the thickening effect due to the apparent increase in the molecular weight of the whole polymer even if it is a partial reaction, because it is a reaction between the polymer materials. did.

Therefore, the present inventors have conducted various studies on a water-soluble polymer that gels when mixed with poly (meth) acrylic acid in addition to the above-mentioned polyethylene oxide. As a result, polypropylene oxide, polyethylene oxide-polypropylene oxide copolymer, polyethylene oxide-polypropylene oxide polyethylene oxide copolymer, polyacrylamide, poly-N
It has been found that many polymeric materials like alkyl acrylamide, polyvinyl pyrrolidone, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, polyvinyl amine, methyl cellulose, hydroxyalkyl cellulose also gel.

The effect of any of these water-soluble polymers having a relatively large molecular weight is high in order to prevent bleeding. On the other hand, in the ink for inkjet recording, the viscosity of the ink is limited, and it is desirable that the viscosity is 20 mPa · s or less. Therefore, the addition amount of the above-mentioned polymer material naturally has an upper limit. That is, the water-soluble polymer used in the present invention preferably has a molecular weight of 2,000 or more, more preferably 20,000 or more. The addition amount is 0.01 to 20 wt.
% Is preferable. The effects of the various polymer materials as described above are the same whether they are used alone or in combination. The molecular weight of the poly (meth) acrylic acid used in the ink of the present invention is preferably 30 times or less the molecular weight of the water-soluble polymer when combined in an equimolar mixture.

As the coloring material that can be used as a constituent of the water-based ink of the present invention, a dye forming an anionic dye ion is preferable, and for example, a direct dye, an acid dye and a reactive dye are preferable. . Specifically, CI
Direct Black 17, CIDirect Black 19, CIDire
ct Black 62, CIDirect Black 154, IJA26
0, IJA286, CIFood Black 2, CIReactive
Black 5, black dyes such as those described in USP-5,053,495, CIAcid Yellow 17, CIAcid Ye
llow 23, CIDirect Yellow 11, CIDirect Yell
ow 44, CIDirect Yellow 86, CIDirect Yellow
142, yellow dyes such as CI Reactive Yellow 2,
CIDirect Red 227, CIDirect Red 52, IJR
-016, CI 45100 and other magenta dyes and CIAc
id Blue 15, CIDirect Blue199, CI4209
Cyan dyes such as 0, CI Acid Blue 9, and CI Reactive Blue 5 can be mentioned. Other than these dyes,
Reduced solubilizing groups to increase water resistance, solubility at pH
Any of the special grades that are sensitive to changes in the above can be used in the present invention.

Pigments can also be used as they do not affect the effect of the present invention. That is, carbon black (Mitsubishi Kasei's No. 2300, No. 900, MCF88, No. 33, N
o.40, No.45, No.52, MA7, MA8, # 220
OB, MA-100, Raven made by Colombia Carbon
1255, Raven 1060, Rega 13 made by Cabot
30R, Rega1 660R, Mogul L, DEGUSSA Color Black FW18, Printex 35, Printex U
Etc.), carbon black surface treated by oxidation or plasma treatment, insoluble azo pigment, soluble azo pigment, phthalocyanine pigment, isoindolinone higher pigment, quinacridone higher pigment, dioxane violet, perinone / perylene higher pigment And the like, and inorganic pigments such as ultramarine (ultramarine), navy blue (Prussian blue), titanium yellow, molybdenum red and the like can be used. Further, a so-called dyeing lake, in which a dye, which is a coloring material classified into the above pigments, is dyed with an extender pigment, can be used as a coloring material constituting the water-based ink of the present invention.

In order to impart more excellent ink jet recording suitability such as reliability and storage stability to the water-based ink of the present invention having the above-mentioned constitution, the following moisturizing agents,
Alternatively, a dissolution aid may be contained. As such materials, alkylene glycols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, thiodiglycol, 1,2,6-hexanetriol and propylene glycol, monoethanolamine, diethanolamine, triethanolamine, etc. Aprotic polar solvents such as alcohol amines, dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, triethylene glycol monomethyl ether, triethylene glycol monomethyl ether, Lower alkyl ethers of polyhydric alcohols such as ethylene glycol monoethyl ether Ethers, glycerol, formamide, 2-pyrrolidone, N- methyl-2-pyrrolidone, sorbitol, sorbitol, urea, beta-hydroxyethyl urea, and the like.

The content of these additives in the ink is preferably in the range of 1-40% of the total weight of the ink. Further, when the ink of the present invention is used for ink jet recording, it is more effective if it contains an alkyl alcohol such as methanol, ethanol, propanol or butanol to improve the ejection property. These alcohols are
It is preferably contained in the range of 1 to 30% of the total weight of the ink. In the present invention, the ink may further contain additives such as a surfactant, a pH adjuster, a rust preventive, a fungicide and an antioxidant, if necessary.

As described above, the ink of the present invention exhibits excellent effects when used in ink jet recording. The inkjet recording method used in the present invention may be any method as long as the intended purpose can be achieved. For example, a recording method in which mechanical energy is applied to ink to eject droplets, and thermal recording to ink are performed. There are recording methods in which energy is applied to eject droplets by foaming the ink, and it is particularly preferable to use the ink of the present invention in these inkjet recording methods.

Of the above recording methods, first, FIGS. 1 to 3 show an example of the structure of a head which is a main part of an ink jet recording apparatus utilizing thermal energy. Figure 2
It is a cross-sectional view of the head along the ink flow path, which will be described below. The head 1 is obtained by bonding a glass, ceramic, silicon or plastic plate or the like having a flow path (nozzle) 2 for passing ink and the heating element substrate 3 to each other. The heating element substrate 3 includes a protective layer 4 made of silicon oxide, silicon nitride, silicon carbide, etc., an electrode 5 made of aluminum, gold, aluminum-copper alloy, etc., and a high melting point of HfB ₂ , TaN, TaAl, etc. A heat generating resistor layer 6 made of a material, a heat storage layer 7 made of thermally oxidized silicon or aluminum oxide, etc., and a substrate 8 made of a material having good heat dissipation such as silicon, aluminum or aluminum nitride. ing.

The electrode 5 of the head 1 having the above structure
When a pulsed electric signal is applied to the heating element substrate 3
However, since the area indicated by h rapidly generates heat, bubbles are generated in the ink in contact with this surface, and the meniscus 10 is projected by the generated pressure, and the ink is ejected from the nozzle 2 of the head 1.
The droplets are ejected through the orifices 11 to form spherical recording liquid droplets 12 and fly toward the recording material 13. FIG.
FIG. 1 shows an external view of a multi-head in which many heads shown in FIG. 1 are arranged. 1 is a sectional view of the head along the ink flow path, and FIG. 2 is a sectional view taken along line XY of FIG.

FIG. 4 shows an example of an ink jet recording apparatus incorporating the above head. In FIG. 4, reference numeral 61 denotes a blade as a wiping member, one end of which is held by a blade holding member to become a fixed end, which is in the form of a cantilever. The blade 61 has a recording head 65.
It is arranged at a position adjacent to the recording area by and is held in a protruding form in the movement path of the recording head 65. Also, 6
Reference numeral 2 denotes a cap of the ejection port surface of the recording head 65, which is arranged at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, contacts the ink ejection port surface, and caps. Is provided.
Further, 63 is an ink absorber provided adjacent to the blade 61, and like the blade 61, is held in a form protruding in the movement path of the recording head 65.

The blade 61, the cap 62, and the ink absorber 63 constitute an ejection recovery unit 64, and the blade 61 and the ink absorber 63 remove water and dust from the ink ejection port surface. Reference numeral 65 denotes a recording head which has an ejection energy generating means and ejects ink onto a recording material facing the ejection port surface where the ejection ports are arranged to perform recording.
Reference numeral 6 denotes a carriage on which the recording head 65 is mounted and which is moved. The carriage 66 slidably engages with a guide shaft 67, and a part of the carriage 66 is connected (not shown) to a belt 69 driven by a motor 68.
As a result, the carriage 66 can move along the guide shaft 67, and the recording head 65 can move the recording area and its adjacent area.

Reference numeral 51 designates a paper feeding section for inserting a recording material, and 5
A paper feed roller 2 is driven by a motor (not shown). With these configurations, the recording material is fed to the position facing the ejection port surface of the recording head 65, and is ejected to the ejection section provided with the ejection roller 53 as the recording progresses.

In the above structure, when the recording head 65 returns to the home position after the recording is completed, the cap 62 of the ejection recovery unit 64 is retracted from the movement path of the recording head 65, but the blade 61 is projected in the movement path. There is. As a result, the ejection port surface of the recording head 65 is wiped.
When the cap 62 comes into contact with the ejection surface of the recording head 65 to perform capping, the cap 62 moves so as to project into the movement path of the recording head.

When the recording head 65 moves from the home position to the recording start position, the cap 62 and the blade 61 are in the same position as the above-mentioned position during wiping. As a result, the ejection opening surface of the recording head 65 is wiped even during this movement. The above-described movement of the recording head 65 to the home position is performed not only at the end of recording or at the time of ejection recovery, but also at the home position adjacent to the recording area at a predetermined interval while the recording head 65 moves in the recording area for recording. And the wiping is performed in accordance with this movement.

FIG. 5 is a diagram showing an example of an ink cartridge 45 in which ink is supplied to the head through an ink supply member, for example, a tube. Where 4
Reference numeral 0 is an ink containing portion containing the supply ink, for example, an ink bag, and a rubber stopper 42 is provided at the tip thereof. By inserting a needle (not shown) into this stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives the waste ink.
It is preferable for the present invention that the ink containing portion has a liquid contact surface with ink formed of polyolefin, particularly polyethylene.

The ink jet recording apparatus used in the present invention is not limited to the one in which the head and the ink cartridge are separately provided as described above, but is also suitable for the one in which they are integrated as shown in FIG. Used. In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink containing portion containing ink, for example, an ink absorber is contained, and the ink in the ink absorber has a head portion having a plurality of orifices. The ink is ejected from 71 as an ink droplet.

Polyurethane is preferably used for the present invention as the material of the ink absorber. Further, the structure may be such that the ink containing portion is an ink bag having a spring or the like provided therein, without using the ink absorber. Reference numeral 72 denotes an atmosphere communication port for communicating the inside of the recording unit with the atmosphere. The recording unit 70 is used in place of the recording head shown in FIG. 4, and is detachable from the carriage 66.

Next, as a second type of the ink jet recording apparatus used in the present invention, a nozzle forming substrate having a plurality of nozzles, a pressure generation composed of a piezoelectric material and a conductive material arranged facing the nozzles. Examples of the apparatus include an on-demand inkjet recording head that includes an element and ink that fills the circumference of the pressure generating element, and that displaces the pressure generating element by an applied voltage to eject small ink droplets from a nozzle. I can.

FIG. 7 shows a structural example of a recording head which is a main part of the recording apparatus as described above. The head has an ink flow path 80 communicating with an ink chamber (not shown) and an ink of a desired volume. An orifice plate 81 for ejecting droplets, a vibrating plate 82 for directly applying pressure to ink, and the vibrating plate 8
A piezoelectric element 83 which is joined to 2 and is displaced by an electric signal;
The piezoelectric element 83, the orifice plate 81, the vibrating plate 82, and the like, and a substrate 84 for fixing and supporting the same. In FIG. 7, the ink flow path 80 is formed of a photosensitive resin or the like, the orifice plate 81 is made of stainless steel,
A discharge port 85 is formed in a metal such as nickel by electroforming or punching by press working.
Is formed of a metal film such as stainless steel, nickel and titanium, or a high elastic resin film, and the piezoelectric element 83 is formed of a dielectric material such as barium titanate or PZT.

In the recording head having the above-described structure, a pulse voltage is applied to the piezoelectric element 83 to generate strain stress, and the energy deforms the vibration plate 82 bonded to the piezoelectric element to cause the inside of the ink flow path. The ink is pressurized vertically, and the ink droplets are ejected from the ejection port 85 of the orifice plate to perform recording. Such a recording head is used by incorporating it in a recording device similar to that shown in FIG. or,
The detailed operation of the recording apparatus can be performed in the same manner as described above.

[0034]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. The ink composition in the table is wt% unless otherwise specified. When a dye is used as the coloring material, a moisturizer and a solubilizing agent are added to the dye aqueous solution, and a polymer material such as poly (meth) acrylic acid is made into an aqueous solution and then added to a predetermined concentration. It is preferable to add an additive such as a surfactant or a pH adjuster, if necessary. When a pigment is used as the coloring material, it is preferable to disperse a predetermined pigment in an appropriate dispersant aqueous solution, add a moisturizer and a solubilizing agent as needed, and then add a polymer aqueous solution such as polyethylene oxide. . Table 1 shows the names / sources and molecular weights of polymer materials that can be used in the ink of the present invention.

Table 1 Polymer materials used in Examples

Examples 1 to 12 and Comparative Examples 1 to 4 Next, using the polymer materials shown in Table 1, various black inks having the compositions shown in Table 2 and yellow inks having the compositions shown in Table 3 were used. To prepare the ink sets of Examples 1 to 12, respectively. Table 2 shows how to make each ink.
Alternatively, each component is mixed so as to have the composition shown in Table 3, stirred for 2 hours, suction-filtered with a 0.45 μm membrane filter, and 1-12 black ink and Y1 and Y
Two yellow inks were prepared respectively. In addition, as comparative examples, inks (Refl, Ref2) having the composition shown in Table 4 containing no specific polymer material constituting the ink of the present invention were prepared,
Ink sets of Comparative Examples 1 to 4 were prepared.

Table 2 Composition of each black ink *: FB2 is C.I. I. Abbreviation for Food Black 2 dye **: Carbon black is MA- manufactured by Mitsubishi Kasei Co., Ltd.
Use 100. ***: Styrene-maleic acid polymer is a pigment dispersant with an acid value of 70 and a molecular weight of 50,000. ****: Acetylenol 100 is a surfactant manufactured by Kawaken Fine Chemicals Co., Ltd.

Table 3 Composition components of the yellow ink used in the examples *: AY17 is CIAcid Yellow 23 **: AY23 is CIAcid Yellow 23

Table 4 Composition components of inks used in Comparative Examples

The ink sets of the examples were prepared using the inks having the compositions shown in Tables 2 and 3 above.
Further, inks of comparative examples were prepared using the inks having the compositions shown in Table 4, and the performance of the inks was evaluated using each ink set.

[0041]

[Evaluation] The inks of Examples 1 to 12 of the present invention having the compositions shown in Tables 2 and 3 and the inks of Comparative Examples 1 and 2 were evaluated for ink performance. . The ink performance evaluation items were bleeding and optical density (OD value). In each evaluation, the evaluation test was conducted in a constant temperature test room at a temperature of 23 ° C. and a humidity of 60%. As the recording device, BJC-600 (resolution 360 dpi) manufactured by Canon Inc. was used. The ink was supplied by using a method of filling the intended ink in each dedicated ink container. Hereinafter, each evaluation method and evaluation criteria will be specifically described.

Bleeding An evaluation pattern as shown in FIG. 8 is prepared, and the level of bleeding is defined as the position of the line where mixed color bleeding occurs from the two-color boundary portion indicated by the arrow line, and the bleeding is performed in five levels evaluated. That is, the case where the bleeding stopped within 1 dot line from the boundary line was set to 5, and the evaluation was set to 4, 3, 2, and 1 depending on which line the bleeding occurred. As shown in FIG. 8, in the evaluation pattern, the part A is a colored background (for example, a yellow background in the examples and comparative examples of the present invention), and the part B is a black pattern, and the boundary between the two colors is indicated by an arrow line, Five lines are recorded with a broken line at an interval of 1 dot line / 1 dot space. At this time, the recording paper is Xerox 4024 paper (LotN).
o. P435-309-T03-AB) and NP-SK paper (Lot No. OKK107) were used.

Optical Density (OD Value) A pattern having 5 square portions of 10 mm square was printed on an A4 size paper, and the optical density of the print sample after 30 minutes or more was measured. The density of 5 solid areas in the print image was measured with a Macbeth reflection densitometer RD914, and the average value was measured.
Value. The paper used at this time is the same as that used for the bleeding of evaluation items. At this time, the recording paper is NP-SK paper (LotNo.OKK1).
07) was used.

Evaluation Results Table 5 shows the evaluation results of the bleeding and the optical density of the evaluation items.

Table 5: Evaluation results for ink sets of Examples

Table 6: Evaluation results for ink set of comparative example

From the results shown in Table 5, the inks of the examples of the present invention exhibited an excellent effect of suppressing bleeding, and the boundary between the two colors was at a level at which it was recognized as an extremely sharp image as compared with the conventional case. The optical density measurement results in Table 5 also revealed that the ink of the present invention contains a polymer, so that the ink does not excessively penetrate into the paper and the density tends to be higher than that of the conventional example.

[0048]

As described above, according to the present invention, bleeding can be prevented to a satisfactory level, especially in comparison with the case where a printed matter by ink jet recording is recorded by a laser beam printer or the like. In addition, the color developability is also superior to that of the conventional ink, and in particular, high quality and high resolution recording is achieved by inkjet recording.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a head portion of a thermal ink jet recording apparatus.

FIG. 2 is a cross-sectional view of a head portion of a thermal inkjet recording device.

FIG. 3 is a diagram showing an example of a head having a plurality of nozzles of an inkjet recording apparatus.

FIG. 4 is a perspective view showing an example of an inkjet recording apparatus.

FIG. 5 is a vertical cross-sectional view showing an example of an ink cartridge.

FIG. 6 is a perspective view of a specification in which an inkjet recording head and an ink cartridge are integrated.

FIG. 7 is a vertical sectional view of an inkjet recording head using a piezoelectric element.

FIG. 8 is an image pattern for bleeding evaluation.

[Explanation of symbols]

 14: Bubbles generated in the thermal inkjet recording head 51: Paper feeding section 52: Paper feeding roller 53: Paper ejection roller 61: Wiping member 62: Cap 63: Ink absorber 64: Ejection recovery section 65: Inkjet recording head 66: Carriage 67: Carriage guide shaft 68: Carriage drive unit 69: Drive belt unit

Claims (8)

[Claims] 1. A water-based ink set containing at least two kinds of inks having different hues, each of which is composed of a liquid composition containing a color material and a liquid medium, wherein at least one color ink contains polyacrylic acid or polymethacrylic acid. A water-based ink set, wherein a polymer material that is mixed with the polyacrylic acid or polymethacrylic acid to form a gel is contained in the inks of other colors. 2. The polymer material is polyethylene oxide, polypropylene oxide, polyethylene oxide-polypropylene oxide copolymer, polyethylene oxide-polypropylene oxide-polyethylene oxide copolymer, polyacrylamide, poly-N-.
1 selected from alkyl acrylamide, polyvinyl pyrrolidone, polyvinyl methyl ether, polyvinyl alcohol, polyvinyl acetate, polyvinyl acetal, methyl cellulose and hydroxyalkyl cellulose
The water-based ink set according to claim 1, which is a material containing at least one kind of water-soluble polymer compound. 3. Polyacrylic acid or polymethacrylic acid,
The water-based ink set according to claim 1, wherein the content of the polymer compound that forms a gel and the ink in the ink is 0.01 to 20 wt%. 4. The inkjet recording method according to claim 1, wherein an ink droplet containing a color material and a liquid medium is ejected from an orifice of a recording head according to a recording signal to record on a recording material. An ink jet recording method, wherein recording is performed using the water-based ink set described in 1. 5. The inkjet recording method according to claim 4, wherein recording is performed by causing thermal energy to act on the ink to eject droplets. 6. The ink jet recording method according to claim 4, wherein recording is performed by causing mechanical energy to act on the ink to eject liquid droplets. 7. A recording unit comprising an ink containing portion containing ink and a recording head portion for ejecting the ink as ink droplets, wherein the ink is contained in any one of claims 1 to 3.
A recording unit which is the water-based ink set described in any one of 1. 8. An ink jet recording apparatus comprising an ink containing portion containing ink and a recording unit for ejecting ink as ink droplets, wherein the recording unit according to claim 7 is used. apparatus.