JPH08157760A - Water-base ink, ink jet recording using the same and apparatus therefor - Google Patents

Abstract

PURPOSE: To eliminate the color bleeding on a plain paper print and enable prints with sharper edges to be obtd. without lowering the color development of recording dots by incorporating an oil-film-forming component into an ink. CONSTITUTION: An oil-film-forming component which floats on the surface of water (the main liq. medium component of an ink), is incompatible with water, and is colorless without contg. a colorant is given by the balance of surface energy between the component and water. When oil drops 1 are placed on the surface of water 2, the following conditions satisfied: when rw >ro +rwo (wherein rw is the surface tension of water; ro is that of the oil; and rwo is that between water and the oil), an oil drop floats in the shape of a lens, keeping the balance expressed by the equation: rw =ro cosθ1 +rwo cosθ2 (wherein θ1 and θ2 are each a contact angle). The oil-film-forming component is a compd. selected from among an 8-20C unsatd. hydrocarbon having a water solubility of 2.0wt.% or lower at 20 deg.C, a glyceride, a higher fatty acid, etc., and is incorporated in an amt. of 0.1-15wt.% into an ink.

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. With regard to the ink, in particular, a water-based ink capable of substantially eliminating color bleeding in plain paper recording, without lowering the coloring property of recording dots, and capable of recording with sharper edges.
The present invention relates to an inkjet recording method using the ink and a device 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.

The following methods are known as means for suppressing bleeding. First, as a first example, US 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. Thus, when two color ink droplets come into contact with each other on the paper surface, a 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 each color ink by adding a metal salt as a precipitant to the yellow ink in addition to the cationic dye, because the color bleeding is noticeable especially between black and yellow. . Further, as a third example, US Pat.
No. 11747 discloses a water- or alcohol-soluble desizing agent (polyoxyalkylene derivative, hydrophilic polydimethylsiloxane, aliphatic imidazoline derivative, etc.) in ink as a means for preventing high-speed fixing, feathering and bleeding. It is disclosed that the addition of the ink allows the ink to permeate the paper at high speed to solve the above problems. 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. or,
As a fifth example, US Pat. No. 5,226,957 discloses a microemulsion ink for thermal ink jet recording comprising a high molecular weight colloid, two kinds of surfactants, a water insoluble dye and an oil. According to the above, effects such as prevention of bleeding, printing of sharp characters, and improvement of water resistance of printed matter can be obtained.

[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 the problem that the color developability is poor. In the fifth example, since an oil-in-water type emulsion ink is used, the water resistance of the coloring material is excellent, but a large amount of a surfactant is used to disperse the emulsion. There is a problem that the permeation amount of the ink becomes too large and the color developability deteriorates. Therefore, an object of the present invention is to substantially eliminate color bleeding in plain paper recording, to reduce the color development of recording dots, and to perform recording with a sharper edge of a printed matter. An object of the present invention is to provide a water-based ink, an inkjet recording method using the same, and a device using the ink.

[0007]

The above object can be achieved by the present invention described below. That is, the present invention relates to an ink composed of a liquid composition containing a coloring material and a liquid medium, wherein the water-based ink is characterized by containing an oil film-forming component, an ink jet recording method using the same, and such an ink. It was the equipment that was used.

[0008]

The operation of the above-described ink of the present invention will be described in detail below. FIG. 1 shows a schematic diagram of the behavior of the ink when the water-based ink of the present invention is adhered to the surface of a recording material such as paper by an inkjet recording method. In a non-contact type recording method such as ink jet recording, the small droplets flying from the recording head have a spherical shape in the space between the recording head and the recording material. Therefore, the oil film layer formed by the oil film forming component that is a constituent of the ink of the present invention is in a state of covering the surface of the spherical droplet, and as shown in FIG. Spherical droplets of the ink droplets land on a recording material such as paper. After landing, the permeation speed onto the recording material such as paper is much faster for the oil film forming component than for water, and it exists on the surface where the ink droplets contact the paper and the outline of the droplets. The oil film-forming component first penetrates into the paper prior to water, which is a component that occupies most of the ink. After the permeation of the oil film forming component, the liquid medium containing water mainly containing the colorant component permeates the paper isotropically after a delay. As a result, as the behavior of water permeating into the recording material such as paper, the outline of the recording dot is (parallel to) the paper surface.
The permeation of water or the like in the direction is blocked by the wall of the oil film forming component that has permeated the paper first, so that it does not spread beyond the dot diameter when the ink droplets land on the recording material. For that reason,
The edges of the recording dots are held in a circular shape, so-called feathering is suppressed, and as a result, the edges of the recording dots are sharpened. Further, as shown in FIG. 1, the permeation of the coloring material mainly composed of water into the paper in the direction perpendicular to the surface of the paper also causes the formation of the oil film layer of ink droplets to permeate into the direction of the sphere in the direction as shown in FIG. Therefore, the penetration into the deeper layer than the penetration of the oil film forming component is suppressed. As a result, the coloring material remains closer to the surface of the paper, so that the coloring property is improved. On the other hand, even in the case of color printing, between dots of different colors recorded adjacently,
Since the oil film forming component has already penetrated into the paper, the coloring material component mainly composed of water on the paper surface cannot be mixed with the dots. As a result, almost no color mixture bleeding occurs on the printed matter.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to preferred embodiments. The oil film that characterizes the water-based ink of the present invention is present in a thin film state by floating on the surface of water, which is the main liquid medium component that constitutes the ink, and hardly dissolves with water, and contains a coloring material component. It consists of a colorless component. Next, materials suitable as the oil film forming component as described above will be described. The conditions required for the oil film-forming component are determined by the balance of the surface energies of the two types of liquids that do not dissolve each other. Now liquid 1 is water and liquid 2 is oil,
When an oil drop is placed on the water surface, the oil drop is subjected to three tensions. γ _w is the surface tension of water, γ _o is the surface tension of oil, γ _wo
Is the interfacial tension between water and oil, and when γ _w > γ _o + γ _wo ,
The oil droplet floats like a lens, and γ _w = γ _o cos θ ₁ + γ _wo
A balance of cos θ ₂ (θ ₁ and θ ₂ are contact angles) is maintained. Therefore, the oil film of the present invention means one that satisfies the condition of γ _w > γ _o + γ _wo .

Further, those having a solubility in water at 20 ° C. of not more than 2.0 wt% and being substantially insoluble in water or insoluble in water are preferably used as the oil film-forming component. As the material having such physical properties, specifically, the below-mentioned organic solvent selected from organic compounds is suitable. The content of the above oil film-forming components in the ink is 0.1
It is preferably set to ˜15 wt%. If it is less than 0.1 wt%, the thickness of the oil film layer is too thin to obtain a sufficient effect,
If it is more than 15 wt%, odor, flammability, adverse effects on the human body, and adverse effects on constituent members of the recording apparatus are not preferable.

Next, specific examples of suitable materials as the oil film-forming component used in the present invention will be given. First of all, hydrocarbons are preferable, and among them, those having a relatively high boiling point and being liquid at room temperature are preferable. For example, octane, nonane, decane, which are saturated hydrocarbons having 8 or more and 20 or less carbon atoms,
Undecane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, heptadecane, octadecane, nonadecane and icosane can be used. These may be linear or branched isomers, and may be a mixture thereof.

Further, glycerides which are fatty acid esters can also be preferably used, and in particular, compounds having an iodine value of 130 or less are preferably used. When the iodine value is more than 130, it belongs to a dry oil and forms a film when left in the air, which causes clogging of the nozzle of the recording head, so that the reliability of the apparatus cannot be obtained. As those that meet the above requirements, specifically, cottonseed oil, soybean oil, coconut oil, rapeseed oil, castor oil, squalane, and the like, some of which are edible oils and fats, safety Is a high compound.

Further, higher fatty acids can be similarly used, and examples thereof include decanoic acid, undecanoic acid, dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid) and hexadecanoic acid (palmitic acid). Furthermore, 1-hexanol, 2-methyl-1-pentanol, 4-methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol having 6 or more carbon atoms, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1-nonaol, 3,5,5-trimethyl-1-hexanol, 1-
Water-insoluble aliphatic alcohols (including isomers) such as decanol, 1-undecanol and 1-dodecanol.
Can also be used. In addition, methyl isobutyl ketone (MIBK), 2-hexanone, 2-heptanone, 4-
Ketones having 6 or more carbon atoms such as heptanone, 2,6-dimethyl-4-heptanone, phorone, isophorone, and acetophenone can also be used because the oil film to be formed satisfies the above-mentioned physical property conditions.

Further, fatty acid ester having 6 or more carbon atoms; butyl acetate, isobutyl acetate, sec-butyl acetate, pentyl acetate, isopentyl acetate, sec-hexyl acetate,
2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, butyl propionate, isopentyl propionate, methyl butyrate, ethyl butyrate, butyl butyrate, isopentyl butyrate, isobutyric acid ester, isovaleric acid ester, stearic acid ester, myristin In addition to the acid isotridecyl, tributyl borate, tripentyl borate, tributyl phosphate, dioctyl phthalate and the like can also be used. It is also possible to use aromatic hydrocarbons such as toluene and xylene. The compounds described above may be used alone or in a mixed form without affecting the effect. Needless to say, an oil film formed of a compound other than the above compounds can be used as long as it satisfies the above-mentioned physical property conditions.

The water-based ink of the present invention depends on the oil film forming ability of the oil film forming component. Therefore, in the case of an oil film forming component having a relatively high surface tension, the interface between the oil film and the liquid medium such as water described above is used. Lowering the tension is more preferable because the effect is further enhanced. Therefore, for that purpose, it is effective to add a surfactant to the various oil film-forming components as described above, and at that time, various surfactants can be used. Specifically, as anionic surfactants, carboxylates, sulfonates, sulfates, phosphates, etc., as cationic surfactants, aliphatic amine salts, aliphatic quaternary ammonium salts, etc., As nonionic surfactants, ether type such as alkyl and alkylallyl polyoxyethylene ethers, ether ester type such as polyoxyethylene ethers of glycerin ester, ester type such as polyethylene glycol fatty acid ester, and aliphatic alkanolamides, amphoteric Examples of the surfactant include carboxybetaine type, aminocarboxylic acid salts, imidazolium betaine, and the like. Also, the amount of the surfactant used should be below the critical micelle concentration (CMC). This is because when the concentration of the surfactant is increased, the surfactant molecules associate with each other in the vicinity of the CMC to form an aggregate called micelle with the hydrophilic group on the outside. When the amount is larger than CMC, micelles having an oil film forming component as a nucleus are generated inside the liquid, and the oil film forming component existing on the surface of the base medium is taken in, and the effect of the oil film in the ink is reduced. Is.

Surfactants other than those mentioned above include
Fluorine-based surfactants that are effective in reducing the interfacial tension with a small amount of addition are effective. In many cases, a sufficient effect can be obtained by adding about several hundreds of ppm, which is particularly preferable.
Another characteristic of the fluorine-based surfactant is that it has extremely high chemical resistance and heat resistance.

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, CIDirect Yellow 11, CIDirect
Yellow 44, CIDirect Yellow 86, CIDirect Y
yellow dyes such as ellow 142, CI Reactive Yellow 2, CIDirect Red 227, CIDirect Red 52, I
Magenta dyes such as JR-016 and CI45100 and C.I.
I.DirectBlue 15, CIDirect Blue 199, CI4
Examples include cyan dyes such as 2090, CIAcid Blue 9, and CI Reactive Blue 5. Other than these dyes, those having reduced water-solubilizing groups to enhance water resistance, special grades having pH-sensitive solubility, and the like can be used in the present invention.

Pigments may 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.52, MA7, MA8, # 2200B, M
Raven 125 made by A-100, Colombia Carbon
5, Raven 1060, Cabot's Rega 1330
R, Rega1660R, Mogul L, made by 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 humectant,
Alternatively, a dissolution aid may be contained. Examples of such materials include 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2, 3-butanediol, 1,5-pentanediol, 1,7-heptanediol, 2-methyl-2,4-
Pentanediol, 2-ethyl-1,3-hexanediol, glycerin, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol 200, dipropylene glycol, 2,2 '
-Alkylene glycols such as thiodiethanol, 1,2,6-hexanetriol, monoethanolamine,
Alcohol amines such as diethanolamine and triethanolamine, dimethylformamide, dimethylacetamide, dimethylsulfoxide, sulfolane, 1,3-
Aprotic polar solvent such as propane sultone, 1,2-
Dimethoxyethane, 1,2-diethoxyethane, 1,2
-Dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 2-methoxyethanol, 2-ethoxyethanol, 2- (methoxymethoxy) ethanol, 2-butoxyethanol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monoethyl ether Butyl ether, triethylene glycol monomethyl ethyl ether, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, dipropylene glycol, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, tripropylene glycol methyl ether, etc. Lower alkyl ethers of polyhydric alcohols, Muamido, 2-pyrrolidone, N- methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, sorbitol, sorbitol, urea, 1,3-bis (beta-hydroxyethyl) urea and the like.

The content of these additives in the ink is preferably in the range of 1 to 30% of the total weight of the ink. Among them, the addition of urea derivatives such as triethanolamine, urea and 1,3-bis (β-hydroxyethyl) urea as the moisturizing component is particularly excellent in terms of effect. Further, when using the ink of the present invention for ink jet recording, methanol, ethanol, propanol,
When an alkyl alcohol such as 2-propanol, 1-butanol or 2-butanol is contained, the dischargeability is improved,
It is even more effective. These alcohols are preferably contained in the range of 1 to 10% of the total weight of the ink.
In the present invention, if necessary, a surfactant, p
It is also possible to add additives such as an H-adjusting agent, a rust preventive, a fungicide and an antioxidant to the ink.

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. 2 and 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
FIG. 3A 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 and aluminum oxide, etc., and a substrate 8 made of a material having good heat dissipation such as silicon, aluminum and 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.
2 shows an external view of a multi-head in which many heads shown in FIG. 2 are arranged.

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
2 is a cap on the ejection port surface of the recording head 65, or is disposed at a home position adjacent to the blade 61, moves in a direction perpendicular to the moving direction of the recording head 65, and contacts the ink ejection port surface, It has a configuration for capping. Further, 63 is an ink absorber provided adjacent to the blade 61, like the blade 61.
5 is retained in a protruding form in the movement path of 5.

The blade 61, the cap 62 and the ink absorber 63 constitute an ejection recovery section 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 denotes 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 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 into 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 wiping position. 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 via 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. 3, and is detachable from the carriage 66.

Next, as the second type of the ink jet recording apparatus used in the present invention, a nozzle forming substrate having a plurality of nozzles, and 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 an example of the structure of the recording head which is the 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 pulsed 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.

[0035]

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. First, production of various water-based inks of the present invention will be described. First, when a dye is used as a coloring material, a moisturizer and a solubilizer are sequentially added to an aqueous dye solution having an appropriate concentration, and a surfactant and a pH are added as necessary.
Add a regulator and the like, filter with a membrane filter 0.45 μm, and then add an appropriate amount of an appropriate oil film forming component,
Shake for 4 hours on a shaker. When a surfactant is added to the oil film forming component, the oil film forming component to which a predetermined amount of the surfactant has been added in advance is added to the filtrate. When a pigment is used as the coloring material, a predetermined pigment is previously dispersed in an appropriate aqueous dispersant solution, and an appropriate amount of this dispersion and, if necessary, a humectant, a dissolution aid, a surfactant and Sequentially add a pH adjuster, etc., and finally add an appropriate amount of oil film forming component,
Shake for 4 hours on a shaker. As in the case of the dye, when a surfactant is added to the oil film forming component, the oil film forming component to which a predetermined amount of the surfactant has been added in advance is added to the dispersion liquid.

Examples 1 to 8 Table 1 shows the compositions of the Bk inks of Examples 1 to 8 of the present invention.

Table 1 Ink compositions of Examples 1 to 8 *: FB2 is C.I. I. It is Food Black 2 dye. **: Carbon black is MA-10 manufactured by Mitsubishi Kasei Co., Ltd.
0. ***: Styrene-maleic acid polymer is a pigment dispersant having an acid value of 70 and a molecular weight of 50,000. ****: Acetylenol EH is a surfactant manufactured by Kawaken Fine Chemicals Co., Ltd., and was added to the liquid medium. *****: Nonipol 20 is a surfactant manufactured by Sanyo Kasei Co., Ltd., and was added to the oil film forming component.

Comparative Examples 1 to 5 Next, an ink having the same composition as the composition of the ink of Example 1 in Table 1 except for the oil film forming component and the surfactant (added to the oil film) was prepared. The ink of Comparative Example 1 was the ink of Comparative Example 2 including the same components as those of the ink of Example 3 except for the oil film forming component and the surfactant (added to the oil film). Similarly, the ink corresponding to Example 4 is used as the ink of Comparative Example 3, the ink corresponding to Example 7 is used as the ink of Comparative Example 4, and the ink corresponding to Example 8 is used as the ink of Comparative Example 5. Each was made.
In these comparative examples, a comparative ink was prepared by replacing the components corresponding to the oil film forming component and the surfactant (added to the oil film) with water.

Examples 9 to 11 As examples of the present invention, color inks of Examples 9 to 11 having the compositions shown in Table 2 were prepared.

Table 2 Compositions of color inks of Examples 9 to 11 *: DY86 is CIDirect Yellow 86. **: DR227 is CIDirect Red 227. ***: AB9 is CI Acid Blue 9. ****: SURERON S-141 is a fluorine-based surfactant manufactured by Asahi Glass Co., Ltd., and was added to the oil film forming component.

Comparative Examples 6 to 8 Inks each consisting of the ink compositions of Examples 9, 10 and 11 in Table 2 except for the oil film-forming component and the surfactant (added to the oil film) were removed. The ink was prepared and used as the inks of Comparative Example 6, Comparative Example 7, and Comparative Example 8. In these comparative examples, inks were prepared by replacing the components corresponding to the oil film-forming component and the surfactant (added to the oil film) with water.

[0042]

[Evaluation] Each of the inks of Examples 1 to 11 of the present invention and the inks of Comparative Examples 1 to 8 having the compositions shown in Tables 1 and 2 was evaluated as an ink. . Ink performance evaluation items are bleeding, optical density (OD value), and feathering.
I made it an item. 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 a recording device, a BJC-600 (resolution 360d, manufactured by Canon Inc.) is used.
pi) 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 indicated by the arrow line, and the bleeding is performed in five stages. 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 and the part B is a black pattern,
The boundary between the two colors is indicated by an arrow line, and 5 lines are recorded by a broken line at an interval of 1 dot line / 1 dot space.
At this time, the recording paper is plain paper NP-S for electrophotography.
K paper (Lot No. OKK107) was 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 five solid areas in the printed image was measured with a Macbeth reflection densitometer RD914, and the evaluation value was OD.
Value. The paper used at this time is the same as that used in the bleeding of evaluation items.

Feathering A4 paper (NP-SK paper) was used to record Chinese characters consisting of 36 characters × 30 lines with black ink, and the sharpness of the edge of the recorded document was visually evaluated on a 5-grade scale. The highest rank was set to 5, and for the reference of rank 5, the same typeface as the above-mentioned text for evaluation was recorded on the same paper using a laser beam printer (LBP-A404E manufactured by Canon Inc.). The evaluation was performed by the number of ranks, and when the edge of the recorded character was sharp and could not be discriminated from the one recorded by LBP, it was set to 5, and as the sharpness was deteriorated, 4, 3, 2,
It was evaluated as 1.

Evaluation Results Table 3 shows the evaluation results for the bleeding and optical density of the evaluation items, and Table 4 shows the results for the feathering evaluation items. Table 5 shows the evaluation results of the comparative examples regarding the evaluation items and the optical densities, and the results regarding the feathering of the evaluation items. In Table 3, the bleeding evaluation, which is an evaluation item, is the result of the combination of ink in the vertical columns. For example, the bleeding of the boundary line when the Bk ink of Example 1 and the yellow ink of Example 9 were used was evaluated. Further, the feathering evaluation results of the evaluation items are only for the Bk inks of Examples 1 to 8 and are shown in the bottom row of Table 3.

From the results shown in Table 3, the inks of the examples of the present invention showed 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. This is a result of the oil film forming component suppressing the mutual diffusion of the color material components at the boundary between the two color inks. The optical density measurement results in Table 3 also show that the ink of the present invention has a relatively slow penetration of the liquid medium containing the coloring material.
It was found that the ink did not excessively penetrate into the paper and the density tended to be higher than that of the conventional example. Further, in the feathering evaluation results (Table 4), the high speed penetration of the oil film forming component at the recording dot edge and the permeation of the coloring material component beyond the dot edge are suppressed due to the suppression of permeation in the paper surface. In comparison, it was several steps higher than conventional ink.

Table 3 Evaluation results of Examples

Table 4 Evaluation results of comparative examples

[0050]

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 coloring property is superior to that of the conventional ink, and the sharpness of the recorded image is brought about, and the high quality and high resolution recording by the ink jet recording is realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram illustrating a state in which a water-based ink of the present invention penetrates into paper.

FIG. 2 is a vertical 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]

 51: Paper Feeding Section 52: Paper Feeding Roller 53: Paper Ejecting 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 Section 69: Driving belt

Claims (20)

[Claims] 1. An aqueous ink comprising a liquid composition containing a coloring material and a liquid medium, wherein an oil film forming component is contained. 2. A solution the surface tension of the medium gamma _w, the surface tension of the oil film forming component gamma _o, when the interfacial tension gamma _wo of the liquid medium and the oil film forming _{component, γ w> γ o + γ} wo relationship The water-based ink according to claim 1, which satisfies: 3. The water-based ink according to claim 1, wherein the oil film-forming component is an organic compound having a solubility in water at 20 ° C. of 2.0 wt% or less. 4. An ink film-forming component is added to the ink in an amount of 0.1 to 15
The water-based ink according to claim 1, which comprises wt%. 5. The water-based ink according to claim 4, wherein the oil film forming component contains a surfactant in an amount equal to or lower than the critical micelle concentration. 6. The water-based ink according to claim 1, wherein the oil film forming component is a saturated hydrocarbon and / or glyceride. 7. The water-based ink according to claim 6, wherein the oil film-forming component is a saturated hydrocarbon having 8 to 20 carbon atoms. 8. The aqueous ink according to claim 6, wherein the oil film-forming component is a glyceride having an iodine value of 130 or less. 9. The water-based ink according to claim 8, wherein the glyceride is an edible oil or fat. 10. The water-based ink according to claim 1, wherein the oil film-forming component is an aliphatic alcohol having 6 or more carbon atoms. 11. The water-based ink according to claim 1, wherein the oil film-forming component is an aliphatic ketone having 6 or more carbon atoms. 12. The oil film-forming component is selected from the group consisting of an aliphatic ester having 6 or more carbon atoms and / or tributyl borate, tripentyl borate, tributyl phosphate and dioctyl phthalate. Water-based ink. 13. The water-based ink according to claim 1, wherein the liquid medium is a mixture of water and a water-soluble organic solvent. 14. The aqueous ink according to claim 1, wherein the liquid medium contains urea and / or a urea derivative. 15. The water-based ink according to claim 1, wherein the coloring material is a dye and / or a pigment. 16. The ink jet recording method according to claim 1, wherein ink droplets containing a color material and a liquid medium are ejected from an orifice of a recording head in response to a recording signal to perform recording on a recording material. An ink jet recording method, wherein recording is performed by using the water-based ink. 17. The ink jet recording method according to claim 16, wherein recording is performed by causing thermal energy to act on the ink to eject droplets. 18. The ink jet recording method according to claim 16, wherein recording is performed by causing mechanical energy to act on the ink to eject liquid droplets. 19. A water-based ink according to any one of claims 1 to 5, wherein the ink is a recording unit including an ink containing portion containing ink and a recording head portion for ejecting the ink as ink droplets. Is a recording unit. 20. 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 19 is used. apparatus.