JP2005193658A - Ink jet recording method, ink for ink jet, ink cartridge, recording unit and ink jet recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make compatible the performance of having a high fixing speed and causing no bleeding with the performance of enabling attainment of a sufficient image density and having high image clearness, for a recording medium, principally for plain paper. <P>SOLUTION: In an ink jet recording method wherein ink is made to stick on the recording medium to form the image, the ink containing at least water, a color material and a surfactant is used. The content of the surfactant is equal to or more than the critical micelle concentration of the surfactant and the surface tension of the ink is equal to or lower than the critical surface tension of the recording medium. The ink is made to stick to the recording medium and, after the contact with the recording medium, the surface tension of the ink is changed to be higher than the critical surface tension of the recording medium. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to ink jet recording, and more particularly to an ink jet recording method capable of obtaining a high quality image on a recording medium centering on plain paper and an ink jet ink (hereinafter referred to as “ink”) used therein. Furthermore, the present invention relates to an ink cartridge for ink jet recording, an ink jet recording unit, and an ink jet recording apparatus.

  In the ink jet recording method, recording is performed by applying energy to ink to cause ink droplets to fly and adhere to a recording medium such as paper. In particular, according to the method of using the electrothermal converter as the ejection energy supply means disclosed by the present applicant and ejecting droplets by generating bubbles by applying thermal energy to the ink, the high-density multi-orifice of the recording head Can be easily realized, and high-resolution and high-quality images can be recorded at high speed (see, for example, Patent Documents 1 to 3).

  However, inks used in conventional ink jet recording generally contain water as a main component, and generally contain water-soluble high-boiling solvents such as glycols for the purpose of preventing drying and clogging. When recording on plain paper using ink, the ink penetrates the inside of the recording paper, and sufficient image density cannot be obtained, or the recording paper surface filler and sizing agent are unevenly distributed. Possible uneven image density. In particular, when trying to obtain a color image, the inks of a plurality of colors are stacked one after another before fixing, so that the color is blurred or mixed unevenly at the boundary portion of the different color image. As a result, satisfactory images were not obtained (hereinafter referred to as bleeding).

  As means for solving the above-mentioned problem, for example, it is disclosed that a compound that enhances permeability such as glycol ether or a surfactant is added to the ink and an ink having a critical surface tension or less of the recording medium is used ( For example, see Patent Documents 4 and 5). However, this method improves the permeability of ink to the recording paper (recording medium), and although bleeding can be suppressed to some extent, the ink penetrates deep into the recording paper together with the color material. There are disadvantages such as a decrease in density and a decrease in image sharpness. Further, the wettability with respect to the surface of the recording paper is improved, so that the ink easily spreads, the resolution is lowered, and bleeding occurs, which is not preferable. This problem is particularly noticeable when expressing black characters.

  On the other hand, when the surface tension of the ink is set higher than the critical surface tension of the recording medium, the above-mentioned image density and sharpness deterioration and black character quality problems do not occur, but the fixing speed is slow and the bleeding performance is There is a problem that it becomes inferior.

Japanese Patent Publication No. 61-59911 Japanese Patent Publication No. 61-59912 Japanese Examined Patent Publication No. 61-59914 Japanese Patent Publication No. 60-34992 Japanese Examined Patent Publication No. 62-28828

  The present invention has been made in view of the above circumstances, and an object of the present invention is to have a performance that a fixing speed is fast and bleeding does not occur on a recording medium centering on plain paper, and sufficient image quality. It is an object to provide an ink jet recording method and an ink jet recording ink cartridge, an ink jet recording ink cartridge, an ink jet recording unit, and an ink jet recording apparatus used in the ink jet recording method, which are compatible with the performance of obtaining a high density and high image clarity.

  The above object is achieved by the present invention described below. That is, the ink jet recording method according to the present invention is an ink jet recording method in which an image is formed by adhering ink on a recording medium, and contains at least water, a coloring material, and a surfactant, and the content of the surfactant Is used, wherein the ink has a critical micelle concentration equal to or higher than the critical micelle concentration of the surfactant and the surface tension is equal to or lower than the critical surface tension of the recording medium, and the ink is adhered to the recording medium, After the contact with the recording medium, the surface tension of the ink is changed to a surface tension higher than the critical surface tension of the recording medium.

  In the recording method of the present invention, the recording medium is plain paper; the color material contained in the ink is a pigment, and the surfactant is an anionic surfactant; The critical micelle concentration is 0.0005 mol / l or less; the change in the surface tension of the ink after contact with the recording medium is due to the deactivation of the surface activation ability of the surfactant caused by the pH change of the ink, The effect of the invention is more conspicuous when the surfactant is deactivated due to the reaction between the surfactant in the ink and the polyvalent metal ion.

  In addition, an embodiment of the ink according to the present invention is an ink-jet ink containing at least water, a coloring material, and a surfactant having a critical micelle concentration or more. The ink is characterized in that the ink has a surface tension that is equal to or lower than the surface tension and changes to a surface tension higher than the critical surface tension of the recording medium after contact with the recording medium.

  The ink of the present invention has a pH of 6.5 or more, and the surfactant is an anionic surfactant; the anionic surfactant has a cyclic peptide in its molecular structure and a critical micelle concentration Is 0.0005 mol / l or less; and the effect of the invention is more remarkable when the pH is 6.5 or more and less than 7.5.

  In addition, an embodiment of the ink cartridge for ink jet recording according to the present invention is characterized by including a storage portion that stores any one of the above-described forms of ink.

  In addition, an embodiment of the ink jet recording unit according to the present invention is characterized in that the ink jet recording unit includes an accommodating portion for accommodating any one of the above-described forms and a head portion for ejecting the ink.

  Another embodiment of the ink jet recording apparatus according to the present invention comprises the above ink jet recording ink cartridge.

  An embodiment of the ink jet recording apparatus according to the present invention includes the above ink jet recording unit.

  According to the present invention, for a recording medium centering on plain paper, which has been a problem for many years in ink jet recording, the performance of fast fixing, no bleeding, and sufficient image density can be obtained. Ink jet recording that achieves both high performance and high sharpness can be performed.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. The present inventors have concluded that it is important to control the state of ink permeation with respect to the recording medium (mainly plain paper) in order to achieve the above-described object. First, in order to fix on a recording medium centering on plain paper at a high speed and record without causing bleeding, the super-penetrating ink, that is, the recording medium It was considered essential to use ink with a critical surface tension or less. However, in the next stage where ink penetrates into the recording medium, if super-penetrating ink is used, the color material in the ink penetrates into the interior, resulting in a drop in density. From the point of view, it is inappropriate. In view of these facts, in order to prevent bleeding and to prevent a decrease in image density, the inventors of the present invention have a surface tension of ink that functions as a super-penetrating ink when attached to a recording medium. Suppresses ink penetration by rapidly increasing the surface tension of the ink to be higher than the critical surface tension of the recording medium after it is below the critical surface tension of the recording medium and after adhering to the recording medium. It was concluded that this is effective in solving the above problems.

  The change in surface tension of the ink must be rapid. This is because super penetrating ink has a very short time to fixing, and in most cases, fixing itself is completed before the change in surface tension. In order to cope with this response speed, the present inventors diligently studied a technique in which the surface tension rapidly increases after the ink adheres to the recording medium. As a result, it has been found that a remarkably good result is recognized in the method utilizing the deactivation of the surface activating ability of the surfactant contained in the ink, and the present invention has been achieved.

  In the image forming method utilizing the deactivation of the surface activation ability of the surfactant contained in the ink, the reason why remarkably good results have been obtained for achieving both prevention of bleeding and prevention of decrease in image density is as follows. I think so. When the surfactant is gradually added to the ink, the surface tension of the ink is drastically decreased until the critical micelle concentration is reached, but when the critical micelle concentration is exceeded, the surface tension of the ink is exceeded. Has a property that it is substantially a steady value. Therefore, the large change in the surface tension of the ink before and after adhering to the recording medium, which is expected by the present invention, is possible only in the density region below the critical micelle density. From this, the critical surface tension value of the recording medium to which the ink is to be adhered exists in the range of the surface tension that changes in the concentration region below the critical micelle concentration of the surfactant contained in the ink. In this case, the present invention is a target system. For example, the ink formulation to be combined with the recording medium having such a critical surface tension value is precisely controlled so that the surface activation ability of the surfactant in the ink is invalidated when it is attached to the recording medium. Thus, the problem in the present invention can be solved. In addition, the surface activation ability in this invention is the effect that surface tension falls by presence of surfactant.

  That is, the ink according to the present invention utilizes a phenomenon in which a surfactant whose initial concentration is higher than the critical micelle concentration changes to less than the critical micelle concentration due to the deactivation of the surface activation ability after adhering to the recording medium. The effect of the present invention can be obtained only when the critical surface tension of the target recording medium exists between the changed surface tension values. Hereinafter, a specific method for deactivating the surface activation ability of the surfactant will be described. First, it is preferable that the concentration of the surfactant in the ink is a value that exceeds the critical micelle concentration. In this case, it is advantageous to use a surfactant having a low critical micelle concentration itself in order to increase the change in surface tension even if the amount of expired is small. For this purpose, it is particularly preferable to use a surfactant having a critical micelle concentration as low as 0.0005 mol / l or less.

  The following is an example of a specific method for changing the concentration below the critical micelle concentration by the deactivation of the surface activation ability of the surfactant using the ink in which the concentration of the surfactant is set as described above. explain.

  As the first method, after the ink adheres to the recording medium, an adsorption reaction of the surfactant in the ink with respect to the hydrophobic substance in the recording medium can be used. In this case, due to the adsorption of the surfactant, the concentration of the surfactant in the ink is lowered to be lower than the critical micelle concentration, and the surface tension of the ink is increased.

  Examples of the second method include a decrease in pH of the anionic surfactant into the acidic region and a deactivation of the surface activation ability due to the formation of an insoluble salt with the polyvalent metal ion. In either case, the anionic group in the surfactant becomes an acid form or an insoluble salt due to a chemical reaction and is insolubilized in the ink, so that the function as the surfactant is lost. More specifically, this method can be achieved by using acidic paper as a recording medium or applying an acidic substance to paper in advance when pH reduction is used. In the case of salt formation with polyvalent metal ions, the polyvalent metal substance is added to the paper in advance from the paper making stage during the production of the recording medium, or the polyvalent metal substance is added before printing when the recording medium is used. This can be achieved by coating. In the case of such a method in which a substance that reacts with an anionic surfactant is applied in advance to a recording medium, it is preferable to apply more reactive substances than the number of water-soluble groups in the surfactant. .

  Any of the reactions used above has a high reaction rate and is suitable for solving the problems. These means are not particularly limited, but among them, a method using the pH change of the anionic surfactant and a method using the insolubilization phenomenon of the hydrophilic portion by the polyvalent metal ion of the anionic surfactant are preferable. It is.

<Recording medium>
Next, a recording medium used in the present invention will be described. There are various recording media for inkjet recording. A so-called inkjet paper that is generally used for output of a label printer or a digital camera is a paper having an ink receiving layer. The ink receiving layer has a void structure composed of an inorganic filler such as silica or alumina and a water-soluble resin, or is a swelling type composed of a water-soluble resin such as gelatin. Inkjet paper with these ink-receptive layers ensures that even the highest surface tension inks, for example, inks that only have a water-soluble dye dissolved in 100% water, are wetted with a critical surface tension. In most cases exceeds 70 mN / m. In the present invention, since the surface tension of the ink is made higher than the critical surface tension of the recording medium after contact with the recording medium, the inkjet dedicated paper having such a general ink receiving layer is out of the object.

  Therefore, the present invention is aimed at so-called plain paper mainly composed of cellulose and added with a sizing agent, and even if there is an ink receiving layer, it is lightweight, and its critical surface tension is 26 to 44 mN / m, preferably 27 to 40 mN / m, more preferably 28 to 36 mN / m. Within this range, it is possible to realize a change in the surface tension of the ink accompanying the expiration of the surface activation ability of the surfactant by precise control of the ink formulation.

  As a method for measuring the critical surface tension of the recording medium, there is a general method proposed by Zisman. Usually, the contact angle θ of the recording medium is measured for a series of saturated hydrocarbon liquids having different surface tensions γ, and these In the plot of (COSθ−γ) of the measured values, γ of the value extrapolated to COSθ = 1 is the critical surface tension of the recording medium. However, in the recording medium centering on plain paper which is the subject of the present invention, the critical surface tension value is high, and the range of measurement values is shifted in the measurement method using the saturated hydrocarbon liquid as described above. Therefore, in the present invention, the point at which COSθ = 1 is obtained using solutions of various mixing ratios of water-ethanol, and the surface tension of the mixed solution at that time is defined as the critical surface tension of the recording medium. .

  Next, a method for measuring the surface tension of the ink after the ink contacts the recording medium will be described. The actual ink droplet is very small, and it is difficult to collect the ink after contact and measure the surface tension. Further, after contact, there is an influence such as evaporation of moisture in the ink, and it is difficult to obtain an accurate value. Therefore, the value of the following method was used for the change in the surface tension of the ink according to the present invention.

  The contact volume between the ink in the recording medium and the recording medium before the ink droplet collides with the recording medium and the deactivation reaction of the surface active ability of the surfactant contained in the ink occurs is important. is there. As a premise of the calculation, the final ink fixing state is that the perfect spherical ink droplet has a blurring rate of 2 with respect to the surface of the recording medium, and the distribution due to the penetration of the ink is hemispherical To fix. Furthermore, it was assumed that the ink was distributed up to 1/4 of the final distribution volume immediately after contact. The specific gravity of the paper was 0.8 in terms of ink ratio. Based on this concept, the ink and the target recording medium are mixed at a mass% ratio of ink / recording medium = 1 / 0.8, the ink is quickly recovered, the surface tension is measured, and this value is calculated. The surface tension of the ink after contact with the recording medium was defined.

  Actually, since the initial surface tension of the ink is equal to or lower than the critical surface tension of the recording medium, according to the study by the present inventors, the bleeding rate is not 2, and even if other setting conditions are taken into consideration, The conditions reliably estimate the contact volume to be small, and in an actual system, the contact volume is even larger. On the other hand, since the deactivation reaction of the surfactant is proportional to the contact volume, the accompanying change in the surface tension of the ink is even greater. Therefore, discussing the surface tension value in the measurement based on this assumption has no problem in showing the properties of the ink according to the present invention.

  In addition, when a recording agent containing an acidic substance or a polyvalent metal ion is previously applied to a recording medium and the ink is adhered, the surface activation ability of the surfactant in the ink is invalidated. It is preferable to apply the corresponding substance at a molar ratio of at least the number of anionic groups in the anionic surfactant present in the ink.

<Ink>
Next, the ink according to the present invention will be described. The ink according to the present invention contains at least water, a coloring material, and a surfactant, the content of the surfactant is not less than the critical micelle concentration, and the surface tension of the recording medium described above. It is characterized by being below the critical surface tension. These components are described below.

(Aqueous medium)
First, although the ink according to the present invention contains water as an essential component, the content of water in the ink is preferably 30% by mass or more and 95% by mass or less with respect to the total mass of the ink. Preferably there is.

  In many cases, an aqueous medium in which water and a water-soluble solvent and substance are used in combination is used. Examples of the constituent material used in combination with water include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, n-pentanol and the like. Alkyl alcohols of 5 to 5; amides such as dimethylformamide and dimethylacetamide; ketones or ketoalcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene Oxyethylene or oxypropylene polymers such as glycol, tripropylene glycol, polyethylene glycol, polypropylene glycol; ethylene glycol, propylene Alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms, such as recall, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol; 1,2,6-hexanetriol, glycerin, trimethylol Triols such as propane; lower alkyl ethers of glycols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl, butyl) ether; triethylene glycol dimethyl (or ethyl) ) Lower dialkyl ethers of polyhydric alcohols such as ether and tetraethylene glycol dimethyl (or ethyl) ether; Al such as monoethanolamine, diethanolamine and triethanolamine Noruamin like; sulfolane, N- methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, urea, ethylene urea, and a bis-hydroxyethyl sulfone and the like.

  Among them, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol (average molecular weight 200 to 1,000), 2-pyrrolidone, glycerin, 1,2,6-hexanetriol, ethylene urea, trimethylolpropane are used. In particular, glycerin is most preferred. In the ink according to the present invention, the type and content of the water-soluble solvent used in combination with water are not particularly limited, but are preferably 3% by mass or more and 60% by mass or less, for example, based on the total amount of the ink. It is preferable that

(Surfactant)
The ink according to the present invention must contain an anionic surfactant having a critical micelle concentration or higher. The surfactant that can be used in the present invention will be described. Surfactants include anionic surfactants such as fatty acid salts, higher alcohol sulfates, alkylbenzene sulfonates, higher alcohol phosphates, carboxylates of cyclic peptides, aliphatic amine salts, quaternary ammonium Cationic surfactant such as salts, higher alcohol ethylene oxide adduct, alkylphenol ethylene oxide adduct, aliphatic ethylene oxide adduct, polyhydric alcohol fatty acid ester ethylene oxide adduct, higher alkylamine ethylene oxide adduct, fatty acid amide ethylene oxide Nonionic surfactants such as adducts, polypropylene glycol ethylene oxide adducts, fatty acid esters of polyhydric alcohols, fatty acid amides of alkanolamines, amino acid type, betaine type amphoteric interfaces Sex, or the like are used. These surfactants are used alone or in combination.

  The surfactant that can be used in the present invention is not particularly limited, but it is essential to use at least an anionic surfactant. Among the anionic surfactants, those having a cyclic peptide in the molecular structure and a critical micelle concentration of 0.0005 mol / l or less are more preferable.

  Specific examples of amino acids contained in the cyclic peptide structure include glycine, alanine, valine, norvaline, leucine, norleucine, isoleucine, phenylalanine, tyrosine, diiodotyrosine, sulinamine, threonine, serine, proline, and hydroxyproline. , Tryptophan, thyroxine, methionine, cystine, cysteine, α-aminobutyric acid, aspartic acid, glutamic acid, asparagine, glutamine, lysine, hydroxylysine, arginine, histidine and the like.

  The amino acid contained in the surfactant having a cyclic peptide structure is not particularly limited as long as the critical micelle concentration as an anionic surfactant is in the range of 0.0005 mol / l or less. A structure comprising a hydrophilic moiety comprising a cyclic peptide containing a group, and a hydrophobic moiety comprising a long-chain alkyl and / or a long-chain alkylphenyl having a main chain carbon number of 8 or more, which may have a branched structure. Preferably there is. As the water-soluble group, a carboxyl group and a salt thereof are preferable.

  Anionic surfactants having a structure as listed above with a critical micelle concentration of 0.0005 mol / l or less can be synthesized in various ways by conventional methods. For example, those having the structures listed below can be used. preferable.

上記式中のＲ₁はアミノ酸残基であって、ＣＨ(ＣＨ₃)₂、ＣＨ₂ＣＨ(ＣＨ₃)₂、ＣＨ(ＣＨ₃)ＣＨ₂ＣＨ₃の何れかであり、Ｒ₂は長鎖アルキル鎖であって、(ＣＨ₂)₆ＣＨ(ＣＨ₃)₂、(ＣＨ₂)₉ＣＨ(ＣＨ₃)₂、(ＣＨ₂)₁₁ＣＨ₃の何れかである。

R ₁ in the above formula is an amino acid residue and is any _one of CH (CH ₃ ) ₂ , CH ₂ CH (CH ₃ ) ₂ , CH (CH ₃ ) CH ₂ CH ₃ , and R ₂ is a long chain It is an alkyl chain, and is any one of (CH ₂ ) ₆ CH (CH ₃ ) ₂ , (CH ₂ ) ₉ CH (CH ₃ ) ₂ , (CH ₂ ) ₁₁ CH ₃ .

Aminofect (trade name: manufactured by Showa Denko, critical micelle concentration: 0.000003 mol / l, amino acid residue number 7, carboxyl group number 2, alkyl chain carbon number 12) corresponds to the substance having the above-mentioned structure on the market. . The aminofect contains, for example, a substance having a structure in which R ₁ is CH ₂ CH (CH ₃ ) ₂ and R ₂ is (CH ₂ ) ₉ CH (CH ₃ ) ₂ .

  The content of the specific anionic surfactant having the above-described structure and having an extremely low critical micelle concentration used in the present invention is 0.00001 to 3% by mass, preferably 0.00005 in the total amount of the ink. To 2.5% by mass, more preferably 0.0001 to 2% by mass.

  Furthermore, in order to obtain a more balanced ejection stability and printing durability, it is preferable to use a nonionic surfactant in combination with the anionic surfactants listed above. Among these, for example, it is preferable to use a nonionic surfactant such as polyoxyethylene alkyl ether or an acetylene glycol ethylene oxide adduct in combination. The HLB of these nonionic surfactants is 10 or more, preferably 13 or more, more preferably 15 or more. When these nonionic surfactants are used in combination, the content of the nonionic surfactant in the ink is 0.01 to 3% by mass, preferably 0.05 to 2.5% by mass, and more preferably 0.00. 1-2% by mass.

  The initial surface tension of the ink according to the present invention must be set to a surface tension equal to or lower than the critical surface tension of the target recording medium, but the smaller the lower, the better from the viewpoint of reaction speed. Basically, the surface tension of the ink is adjusted by the surfactant as mentioned above, but the range of the lower limit is, for example, 0 to 10 mN / m with respect to the critical surface tension of the recording medium. Preferably it is 0-8 mN / m, More preferably, it is 0-5 mN / m.

(Color material)
Next, the color material contained in the ink according to the present invention will be described. As the coloring material used in the present invention, both dyes and pigments can be used. The amount added to the ink is not limited to this range, but is preferably in the range of 0.1 to 15% by mass, more preferably 0.2 to 12% by mass, and still more preferably 0.3 to 10% by mass.

  As the dye used in the ink, for example, almost all of the water-soluble acidic dye, direct dye, basic dye and reactive dye described in the COLOR INDEX can be used. Even those not described in the color index can be used as long as they are water-soluble dyes. However, it is more preferable to use a pigment in order to obtain an ink that clearly exhibits the effects of the present invention described above.

Examples of the pigment that can be used in the present invention will be described. Carbon black is suitable as the pigment used in the black ink. Specifically, for example, carbon black pigments such as furnace black, lamp black, acetylene black and channel black, the primary particle diameter of which is 15 to 40 nm, the specific surface area by the BET method is 50 to 300 m ² / g, and DBP oil absorption Those having the characteristics of an amount of 40 to 150 ml / 100 g and a volatile content of 0.5 to 10% are preferably used.

  As the pigment used in the color ink, organic pigments as listed below are preferably used. Specifically, insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow and pyrazolone red, soluble azo pigments such as ritole red, helio bordeaux, pigment scarlet, and permanent red 2B, alizarin, indanthrone, thio Derivatives from vat dyes such as indigo maroon, phthalocyanine pigments such as phthalocyanine blue and phthalocyanine green, quinacridone pigments such as quinacridone red and quinacridone magenta, perylene pigments such as perylene red and perylene scarlet, isoindolinone yellow, iso Isoindolinone pigments such as indolinone orange, imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange and benzimidazolone red, Pylanthrone pigments such as Throne Red, Pyranthrone Orange, thioindigo pigments, condensed azo pigments, thioindigo pigments, diketopyrrolopyrrole pigments, flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, Examples thereof include pigments such as perinone orange, anthrone orange, dianthraquinonyl red, and dioxazine violet.

  Further, when the organic pigment is represented by a color index (CI) number, C.I. I. Pigment Yellow 12, 13, 14, 17, 20, 24, 55, 74, 83, 86, 93, 97, 98, 109, 110, 117, 120, 125, 128, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185; I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71; C.I. I. Pigment Red 9, 48, 49, 52, 53, 57, 97, 122, 123, 149, 168, 175, 176, 177, 180, 192, 202, 209, 215, 216, 217, 220, 223, 224, 226, 227, 228, 238, 240, 254, 255, 272; I. Pigment violet 19, 23, 29, 30, 37, 40, 50; C.I. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64; C.I. I. Pigment green 7, 36; I. Examples thereof include CI Pigment Brown 23, 25, 26, and the like. Although pigments other than those described above can be used, in particular, among these pigments, C.I. I. Pigment Yellow 13, 17, 55, 74, 93, 97, 98, 110, 128, 139, 147, 150, 151, 154, 155, 180, 185; I. Pigment red 122, 202, 209; I. Pigment Blue 15: 3 and 15: 4 are more preferable.

(Dispersant)
When the pigments listed above are used, it is preferable to include a dispersant for dispersing the pigments listed below in the ink. The dispersant used in this case is not particularly limited as long as it is water-soluble. Specifically, styrene, a styrene derivative, vinyl naphthalene, a vinyl naphthalene derivative, an α, β-ethylenically unsaturated carboxylic acid fat. At least selected from acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, vinyl acetate, vinylpyrrolidone, acrylamide, and derivatives thereof, etc. Examples thereof include a block copolymer composed of two or more monomers (of which at least one is a hydrophilic monomer), a random copolymer, a graft copolymer, or a salt thereof. Among these, a block copolymer is a particularly preferable dispersant for carrying out the present invention.

  The block copolymer has a structure represented by AB, BAB, ABC type or the like. Block copolymers having a hydrophobic block and a hydrophilic block and having a balanced block size that contributes to dispersion stability are particularly advantageous in the practice of this invention. That is, such block copolymers can incorporate functional groups into hydrophobic blocks (blocks to which the colorant binds), thereby improving the dispersion stability between the dispersant and the colorant. Specific interaction is further enhanced. Furthermore, the ink jet recording method using thermal energy, particularly, an ink jet recording head compatible with small droplets (0.1 to 20 pl, more preferably 0.1 to 15 pl, still more preferably 0.1 to 10 pl) was used. In some cases, it is more preferable due to its rheological suitability. The amount of polymer in the ink depends on the structure, molecular weight, and other properties of the polymer, as well as other components of the ink composition. The weight average molecular weight of the polymer selected in practicing the present invention is less than 30,000, preferably less than 20,000, more preferably in the range of 2,000 to 10,000.

  The production method and the pigment dispersion method for these polymers are described in JP-A Nos. 05-179183, 06-136411, 07-053841, and 10-87768. The details are disclosed in Japanese Laid-Open Patent Publication No. 11-043639, Japanese Laid-Open Patent Publication No. 11-236502, Japanese Laid-Open Patent Publication No. 11-269418.

  Typical hydrophobic monomers that can be used in the block copolymer include the following monomers, but the present invention is not limited thereto. For example, benzyl acrylate, benzyl methacrylate, methyl methacrylate (MMA), ethyl methacrylate (EMA), propyl methacrylate, n-butyl methacrylate (BMA or NBMA), hexyl methacrylate, 2-ethylhexyl methacrylate (EHMA), octyl methacrylate, lauryl methacrylate ( LMA), stearyl methacrylate, phenyl methacrylate, hydroxyethyl methacrylate (HEMA), hydroxypropyl methacrylate, 2-ethoxyethyl methacrylate, methacrylonitrile, 2-trimethylsiloxyethyl methacrylate, glycidyl methacrylate (GMA), p-tolyl methacrylate, sorbyl Methacrylate, methyl acrylate, ethyl acrylate Propyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, phenyl acrylate, 2-phenylethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, acrylonitrile, 2-trimethylsiloxyethyl acrylate, Such as glycidyl acrylate, p-tolyl acrylate and sorbyl acrylate. Preferred hydrophobic monomers are benzyl acrylate, benzyl methacrylate, 2-phenylethyl methacrylate, methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, and homopolymers and copolymers prepared therefrom, such as methyl methacrylate and butyl methacrylate. It is preferable to produce a block copolymer using a copolymer.

  Examples of typical hydrophilic monomers that can be used in the block copolymer include the following monomers, but the present invention is not limited to these. For example, methacrylic acid (MAA), acrylic acid, dimethylaminoethyl methacrylate (DMAEMA), diethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, dimethylaminopropyl methacrylamide, methacrylamide, acrylamide And dimethylacrylamide. It is preferable to produce a block copolymer using a homopolymer or copolymer of methacrylic acid, acrylic acid or dimethylaminoethyl methacrylate.

  Acid-containing polymers are made directly or from blocked monomers with blocking groups that are removed after polymerization. Examples of blocked monomers that yield acrylic acid or methacrylic acid after removal of blocking groups include trimethylsilyl methacrylate (TMS-MA), trimethylsilyl acrylate, 1-butoxyethyl methacrylate, 1-ethoxyethyl methacrylate, 1-butoxyethyl acrylate 1-ethoxyethyl acrylate, 2-tetrahydropyranyl acrylate and 2-tetrahydropyranyl methacrylate.

  In particular, when an ink jet recording head using thermal energy is driven at a high frequency, for example, 5 kHz or more, the ink according to the present invention contains the block copolymer as described above, so that the ink The effect of improving the discharge property becomes more remarkable.

  Further, the content of the dispersant as described above in the ink is in the range of 0.5 to 10% by mass, preferably 0.8 to 8% by mass, and more preferably 1 to 6% by mass. If the content of the pigment dispersant in the ink is higher than this range, it becomes difficult to maintain a desired ink viscosity.

  The above is the description of the components constituting the ink according to the present invention. The average particle diameter of the pigment dispersion that is the ink according to the present invention is preferably in the range of 50 to 200 nm. As a method for measuring the average particle size in this case, for example, ELS-8000 (manufactured by Otsuka Electronics Co., Ltd.), Microtrac UPA 150 (manufactured by Nikkiso Co., Ltd.) using laser light scattering can be used.

(Additive)
In addition, the ink according to the present invention may be used as an additive other than the above-described components, for example, a pH adjuster, a viscosity adjuster, an antifoaming agent, in order to obtain an ink having a desired physical property value. Preservatives, fungicides, antioxidants and the like can be added. The pH is preferably 6.5 or more, and more preferably less than 7.5.

<Inkjet recording method, recording apparatus, etc.>
Next, an ink jet recording method and recording apparatus according to the present invention using the ink according to the present invention configured as described above will be described. In the case of using acid paper or added paper to which polyvalent metal ions are added at the paper making stage as a recording medium, the configuration of the apparatus described below is not necessary. On the other hand, for example, when a liquid containing an acidic substance or a polyvalent metal substance (hereinafter referred to as a first liquid) is applied in advance to a recording medium such as recording paper before printing, the following are listed. It is necessary to configure the apparatus. That is, the first liquid containing a reactive substance such as an acidic substance or a polyvalent metal substance and the ink according to the present invention are used. First, the first liquid is attached to the recording paper prior to the ink. The recording image is obtained by attaching the ink according to the present invention to the portion to which the first liquid is adhered without heating the recording paper or forcibly drying the recording paper. In some cases, after the first liquid is attached to the recording paper, forced drying such as heat drying may be performed.

  As a method of adhering the first liquid to the recording medium, a method of adhering the first liquid to the entire surface of the recording paper with a spray, a roller, or the like is conceivable, but the first liquid is adhering to the ink after that. More preferably, it is performed by an ink jet system that allows selective adhesion only to the portion to be applied and uniform adhesion. When the first liquid is attached by the inkjet method, it is necessary to attach the first liquid in advance to at least a portion to which the ink is attached. However, there is no particular limitation on the size of one drop of the first liquid and the ink or the dot diameter formed on the recording paper, but the larger the dot diameter of the first liquid is larger than the dot diameter of the recording ink. The desired effect is obtained.

  Next, the recording apparatus used in the present invention will be described. In the present invention, an ink jet method is preferably used in which a recording signal is given to ink of a recording head and droplets are ejected by generated thermal energy. The configuration of the recording head which is the main part of the apparatus is shown in FIGS.

  The head 13 is a heating head 15 having a heating resistor used for thermal recording (glass, ceramic, plastic, or the like in which the ink flow path 14 is formed (the head is shown in the figure, but is not limited thereto). It is obtained by bonding The heating head 15 includes a protective film 16 formed of silicon oxide or the like, aluminum electrodes 17-1 and 17-2, a heating resistor layer 18 formed of nichrome or the like, a heat storage layer 19, and a substrate 20 having good heat dissipation such as alumina. It has become more.

  The ink 21 reaches the ejection orifice 22 and forms a meniscus 23 by pressure. Here, when an electrical signal is applied to the electrodes 17-1 and 17-2, the region indicated by n of the heat generating head 15 rapidly generates heat, bubbles are generated in the ink 21 in contact therewith, and the meniscus is generated by the pressure. Is generated, becomes a recording droplet 24 from the orifice 22, and flies toward the recording medium 25. FIG. 3 is a schematic view of a recording head in which a large number of nozzles shown in FIG. 1 are arranged. The recording head is made by closely contacting a glass plate 27 having a multi-nozzle 26 and a heating head 28 similar to that described in FIG. 1 is a cross-sectional view of the head 13 along the ink flow path, and FIG. 2 is a cross-sectional view taken along the line AB of FIG.

  FIG. 4 shows an example of an ink jet recording apparatus incorporating the 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, and forms a cantilever. The blade 61 is disposed at a position adjacent to a recording area by the recording head, and has a configuration in which the blade 61 moves in a direction perpendicular to the moving direction of the recording head to contact the ejection port surface and capping. Further, reference numeral 63 denotes an ink absorber provided adjacent to the blade 61 and, like the blade 61, is held in a form protruding in the moving path of the recording head. The blade 61, the cap 62, and the absorber 63 constitute a discharge recovery portion 64, and the blade 61 and the absorber 63 remove moisture, dust, and the like from the ink discharge port surface.

  Reference numeral 65 denotes a recording head which has discharge energy generating means and performs recording by discharging ink onto a recording medium facing the discharge port surface on which the discharge port is arranged. Reference numeral 66 denotes a movement of the recording head 65 by mounting the recording head 65. It is a carriage for performing. The carriage 66 is slidably engaged with the guide shaft 67, and a part of the carriage 66 is connected to a belt 69 driven by a motor 68 (not shown). As a result, the carriage 66 can move along the guide shaft 67, and the recording area and its adjacent area can be moved by the recording head 65.

  51 is a paper feeding unit for inserting a recording medium, and 52 is a paper feed roller driven by a motor (not shown). With these configurations, the recording medium is fed to a position facing the ejection port surface of the recording head, and is discharged to a paper discharge unit provided with a paper discharge roller 53 as recording progresses.

  In the above configuration, when the recording head 65 returns to the home position due to the end of recording or the like, the cap 62 of the ejection recovery unit 64 is retracted from the moving path of the recording head 65, but the blade 61 protrudes into the moving path. As a result, the ejection port surface of the recording head 65 is wiped. When the cap 62 is in contact with the ejection port surface of the recording head 65 to perform capping, the cap 62 moves so as to protrude into the moving 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 at the same position as that at the time of wiping. As a result, the ejection port surface of the recording head 65 is wiped even during this movement.

  The recording head moves to the home position adjacent to the recording area at a predetermined interval while the recording head moves the recording area for recording as well as at the end of recording or at the time of ejection recovery. Then, the wiping is performed with this movement.

  FIG. 5 is a diagram showing an example of an ink cartridge 45 that contains ink supplied to the head via an ink supply member, for example, a tube. Here, reference numeral 40 denotes an ink container, for example, an ink bag, which contains supply ink, and a rubber plug 42 is provided at the tip thereof. By inserting a needle (not shown) into the stopper 42, the ink in the ink bag 40 can be supplied to the head. An ink absorber 44 receives waste ink. As the ink storage portion, a liquid contact surface with ink is preferably 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 separated as described above, but the one in which they are integrated as shown in FIG. 6 is also preferably used.

  In FIG. 6, reference numeral 70 denotes a recording unit, in which an ink storage portion that stores ink, for example, an ink absorber, is stored. The ink in the ink absorber is transferred from a head portion 71 having a plurality of orifices. It is configured to be ejected as ink droplets. As a material for the ink absorber, for example, polyurethane can be used. 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. In the recording apparatus used in the present invention, an ink jet recording apparatus that discharges ink droplets by applying thermal energy to the ink has been described as an example. However, the present invention also includes a piezo method that uses a piezoelectric element. Other ink jet recording apparatuses can be used similarly.

  When the color recording method is carried out in the present invention, for example, a recording apparatus in which the recording heads shown in FIG. 3 are arranged on five carriages is used. FIG. 7 shows an example. Reference numerals 81, 82, 83, and 84 denote recording heads for ejecting yellow, magenta, cyan, and black inks, respectively. Reference numeral 85 denotes a head for discharging the first liquid. The head is disposed in the above-described recording apparatus and ejects recording ink of each color according to a recording signal. Prior to that, the first liquid is previously deposited on the portion where at least the recording ink of each color adheres to the recording paper. FIG. 7 shows an example in which five recording heads are used. However, the present invention is not limited to this, and as shown in FIG. 8, yellow, magenta, cyan, black, and the first liquid are supplied by one recording head. A case where the liquid flow path is divided is also preferable.

  When the first liquid is not used, for example, a recording apparatus in which four recording heads shown in FIG. 3 are arranged on a carriage is used. FIG. 9 shows an example. Reference numerals 81, 82, 83, and 84 denote recording heads for ejecting recording inks of yellow, magenta, cyan, and black, respectively. The head is disposed in the above-described recording apparatus and ejects recording ink of each color according to a recording signal. FIG. 9 shows an example in which four recording heads are used. However, the present invention is not limited to this. As shown in FIG. 10, one recording head uses yellow, magenta, cyan, and black liquid flow paths. It is also preferable to carry out separately.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. In the text, “part” or “%” is based on mass unless otherwise specified. First, inks 1 to 8 were prepared as follows.

<Preparation of ink 1>
(Preparation of pigment dispersion 1)
First, using benzyl methacrylate and methacrylic acid as raw materials, an AB type block polymer having an acid value of 250 and a weight average molecular weight of 3,000 is prepared by a conventional method, further neutralized with an aqueous potassium hydroxide solution, and diluted with ion-exchanged water. A homogeneous 50% aqueous polymer solution was prepared. 180 g of the obtained aqueous polymer solution, C.I. I. 100 g of Pigment Blue 15: 3 and 220 g of ion-exchanged water were mixed and mechanically stirred for 0.5 hour. The mixture was then processed using a microfluidizer by passing the mixture through the interaction chamber five times under a liquid pressure of about 10,000 psi (about 70 MPa). Further, the dispersion obtained above was centrifuged (12,000 rpm, 20 minutes) to remove the non-dispersion containing coarse particles, thereby preparing a cyan pigment dispersion 1. The obtained pigment dispersion 1 had a pigment concentration of 10% and a dispersant concentration of 10%.

(Preparation of ink 1)
The ink 1 was prepared using the cyan pigment dispersion 1 obtained above, and the following components were added thereto to obtain a predetermined concentration (adjusted with ion-exchanged water so that the total would be 100 parts). After sufficiently mixing and stirring the above components, pressure filtration was performed with a microfilter (manufactured by Fuji Film) having a pore size of 2.5 μm to prepare ink 1 having a pigment concentration of 2% and a dispersant concentration of 2%. As shown below, aminofect (trade name: manufactured by Showa Denko, critical micelle concentration: 0.000003 mol / l, molecular weight: 1036), which is an anionic surfactant having a cyclic peptide structure, was added to ink 1. In combination with this, polyoxyethylene cetyl ether, which is a nonionic surfactant, and an ethylene oxide adduct of acetylene glycol were used.

-20 parts of the above pigment dispersion-7 parts of glycerin-4 parts of trimethylolpropane-4 parts of ethylene urea-1 part of polyoxyethylene cetyl ether (ethylene oxide addition number = 20, HLB17)-Anionic surfactant with cyclic peptide structure 0.01 parts-Ethylene oxide adduct of acetylene glycol (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals) 0.5 parts-balance of ion-exchanged water

<Preparation of ink 2>
Ink 2 was prepared in the same manner as in ink 1 except that the content of the cyclic peptide structure anionic surfactant was 0.1 part in the composition of ink 1.

<Preparation of ink 3>
Ink 3 was prepared in the same manner as ink 1 except that the content of the cyclic peptide structure anionic surfactant was 0.001 part in the composition of ink 1.

<Preparation of ink 4>
(Preparation of pigment dispersion 2)
100 g of a polymer solution similar to that used in the preparation of Pigment Dispersion Liquid 1, C.I. I. 100 g of Pigment Red 122 and 300 g of ion-exchanged water were mixed and mechanically stirred for 0.5 hour. The mixture was then processed using a microfluidizer by passing the mixture through the interaction chamber five times under a liquid pressure of about 10,000 psi (about 70 MPa). Further, the dispersion obtained above was centrifuged (12,000 rpm, 20 minutes) to remove the non-dispersion containing coarse particles, thereby obtaining a magenta pigment dispersion 2. The obtained pigment dispersion 2 had a pigment concentration of 10% and a dispersant concentration of 5%.

(Preparation of ink 4)
The ink 4 is prepared by using the magenta pigment dispersion 2 and adding the following components to a predetermined concentration (adjusted with ion-exchanged water so that the total amount becomes 100 parts). After sufficiently mixing and stirring, pressure filtration was performed with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm to prepare ink 4 having a pigment concentration of 4% and a dispersant concentration of 2%. As shown below, aminofect (trade name: manufactured by Showa Denko, critical micelle concentration: 0.000003 mol / l, molecular weight: 1036), which is an anionic surfactant having a cyclic peptide structure, was added to ink 4. In combination with this, polyoxyethylene cetyl ether, which is a nonionic surfactant, and an ethylene oxide adduct of acetylene glycol were used.

-40 parts of the above pigment dispersion 2-7 parts of glycerin-2 parts of ethylene urea-5 parts of 1,2,6-hexanetriol-0.5 part of polyoxyethylene cetyl ether (ethylene oxide addition number = 20, HLB17)-cyclic Peptide structure anionic surfactant 0.1 part ・ Acetylene glycol ethylene oxide adduct (trade name: Acetylenol EH, manufactured by Kawaken Fine Chemical Co., Ltd.) 0.2 part ・ Ion-exchanged water remainder

<Preparation of ink 5>
(Preparation of pigment dispersion 3)
First, using benzyl acrylate and methacrylic acid as raw materials, an AB type block polymer having an acid value of 300 and a weight average molecular weight of 4,000 is prepared by a conventional method, further neutralized with an aqueous potassium hydroxide solution, and diluted with ion-exchanged water. A homogeneous 50% aqueous polymer solution was prepared. 110 g of the above polymer solution, C.I. I. 100 g of Pigment Yellow 128 and 290 g of ion-exchanged water were mixed and mechanically stirred for 0.5 hour. The mixture was then processed using a microfluidizer by passing the mixture through the interaction chamber five times under a liquid pressure of about 10,000 psi (about 70 MPa). Further, the yellow pigment dispersion 3 obtained above was centrifuged (12,000 rpm, 20 minutes) to remove the non-dispersed material containing coarse particles, thereby obtaining a pigment dispersion 3. The obtained pigment dispersion 3 had a pigment concentration of 10% and a dispersant concentration of 6%.

(Preparation of ink 5)
The ink 5 is prepared by using the above-mentioned yellow pigment dispersion 3 and adding the following components to a predetermined concentration (adjusted with ion-exchanged water so that the total is 100 parts). After sufficiently mixing and stirring, pressure filtration was performed with a microfilter (manufactured by Fuji Film) having a pore size of 2.5 μm to prepare ink 5 having a pigment concentration of 5% and a dispersant concentration of 3%. As shown below, the anionic surfactant monosodium lauroyl glutamate (critical micelle concentration 0.0003 mol / l, molecular weight 351) was added to the ink 5. In combination with this, polyoxyethylene cetyl ether, which is a nonionic surfactant, and an ethylene oxide adduct of acetylene glycol were used.

・ Pigment dispersion 3 50 parts ・ Glycerin 7 parts ・ Diethylene glycol 4 parts ・ Ethylene glycol 5 parts ・ Polyoxyethylene cetyl ether (ethylene oxide addition number = 20, HLB17) 0.5 part ・ Lauroyl monosodium glutamate 0.05 part・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemical Co., Ltd.) 0.3 part ・ Balance of ion-exchanged water

<Preparation of ink 6>
(Preparation of pigment dispersion 4)
First, using benzyl methacrylate, methacrylic acid and 2-ethoxyethyl methacrylate as raw materials, an ABC type block polymer having an acid value of 350 and a weight average molecular weight of 5,000 is prepared by a conventional method, and further neutralized with an aqueous potassium hydroxide solution. Diluted with ion-exchanged water to make a homogeneous 50% polymer aqueous solution. 60 g of the above polymer solution, 100 g of carbon black, and 340 g of ion exchange water were mixed and mechanically stirred for 0.5 hour. The mixture was then processed using a microfluidizer by passing the mixture through the interaction chamber five times under a liquid pressure of about 10,000 psi (about 70 MPa). Further, the dispersion obtained above was centrifuged (12,000 rpm, 20 minutes) to remove the non-dispersion containing coarse particles, whereby a black pigment dispersion 4 was obtained. The obtained pigment dispersion 4 had a pigment concentration of 10% and a dispersant concentration of 3.5%.

(Preparation of ink 6)
The ink 6 is prepared by using the black pigment dispersion 4 and adding the following components to a predetermined concentration (adjusted with ion-exchanged water so that the total amount becomes 100 parts). After mixing and stirring, pressure filtration was performed with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm to prepare ink 6 having a pigment concentration of 3% and a dispersant concentration of 1.05%. As shown below, Aminofect (trade name: manufactured by Showa Denko, critical micelle concentration: 0.000003 mol / l, molecular weight: 1036), which is a cyclic peptide structure anionic surfactant, was added to ink 6. In combination with this, an ethylene oxide adduct of acetylene glycol, which is a nonionic surfactant, was used.

-Pigment dispersion 4 30 parts-Glycerol 7 parts-Ethylene urea 5 parts-Ethylene glycol 5 parts-Cyclic peptide structure anionic surfactant 0.02 parts-Ethylene oxide adduct of acetylene glycol (trade name: acetylenol EH, Made by Kawaken Fine Chemicals) 0.1 part, balance of ion-exchanged water

<Preparation of ink 7>
Ink 7 was prepared in the same manner as in ink 6 except that the content of the anionic surfactant having a cyclic peptide structure in the composition of ink 6 was 0.001 part.

<Preparation of ink 8>
The following components were added to a predetermined concentration (adjusted with ion-exchanged water so that the total would be 100 parts), and after these components were sufficiently mixed and stirred, a microfilter (made by Fuji Film) with a pore size of 0.45 μm was added. And pressure-filtered to prepare ink 8 having a dye concentration of 2%. As shown below, aminofect (trade name: manufactured by Showa Denko, critical micelle concentration: 0.000003 mol / l, molecular weight: 1036), which is an anionic surfactant having a cyclic peptide structure, was added to ink 8.

・ C. I. Direct Yellow 86 2 parts ・ Glycerin 7 parts ・ Ethanol 3 parts ・ Ethyleneurea 5 parts ・ Polyoxyethyleneoxypropylene block polymer (molecular weight 1,700, ethylene oxide ratio 40%) 0.05 part ・ Cyclic peptide structure anionic surfactant 0.03 parts of agent and the balance of ion-exchanged water

The surface tension and pH of the inks 1 to 8 prepared above are shown in Table 1 below.

<Preparation of first liquid I for reaction>
The following components were added to a predetermined concentration (adjusted with ion-exchanged water so that the total would be 100 parts), and after these components were sufficiently mixed and stirred, a microfilter (made by Fuji Film) with a pore size of 0.45 μm was added. And filtered under pressure to prepare a first liquid I. The pH of the liquid I was 2.5.

・ 0.5 parts of citric acid ・ 15 parts of diethylene glycol ・ 2.5 parts of isopropyl alcohol ・ 5 parts of ethylene urea ・ Ethylene oxide adduct of acetylene glycol (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals) 1 part

<Preparation of first liquid II for reaction>
A first liquid II was prepared in the same manner as in the first liquid I except that 0.5 part of citric acid in the first liquid I was changed to 0.5 part of calcium chloride.

<Preparation of reference ink for recording density evaluation>
Except for adding each composition of inks 1 to 8 so that the content of ethylene oxide adduct of acetylene glycol was 1.5 parts, the same operation as inks 1 to 8 was performed to evaluate the recording density of each ink. A reference ink was prepared (adjusted with ion-exchanged water so that the total would be 100 parts). In any of these inks, no change in surface tension was observed before and after contact with the recording medium.

<Preparation of reference ink for bleed evaluation>
0.5 parts of citric acid in the first liquid I prepared above was added to the acid dye C.I. I. A reference red dye ink for bleed evaluation was prepared in the same manner as in the first liquid I except that 0.5 part of Acid Red 35 was used.

<Evaluation of Examples 1-12 and Comparative Examples 1-12>
Next, using the inks 1 to 8 obtained above, recording was performed on commercially available copy paper, bond paper, and lightweight coated paper having the characteristics shown in Table 2 below. Table 2 shows the critical surface tension of each recording medium.

  For image formation, an ink jet recording apparatus similar to that shown in FIG. 4 was used, and a color image was formed using the five recording heads shown in FIG. As the recording head, the same recording head as that used in an inkjet printer (trade name: BJC820; manufactured by Canon Inc.) was used. The recording head drive conditions, that is, the energization conditions for the heater, were set to an applied voltage of 28 V, a pulse width of 3.2 μsec, and a drive frequency of 5 kHz.

  Image formation was performed with each combination shown in Table 3 selected from inks 1 to 8 and papers A to F, and evaluation was performed according to the following evaluation methods and evaluation criteria.

(Recording density)
Using each of the inks 1 to 8 to be evaluated and each ink prepared for recording density criteria, a solid portion was recorded on each paper shown in Table 3, and then left for 1 hour. It was measured with Macbeth RD915 (manufactured by Macbeth). Then, the ratio of the evaluation ink recording density / reference ink recording density was determined, and the evaluation was performed according to the following criteria using the value. The results are shown in Table 3.
A: The recording density ratio was 1.10 or more.
Δ: The recording density ratio was 1.04 or more and less than 1.10.
X: The recording density ratio was less than 1.04.

(Bleeding)
Using each of the inks 1 to 8 to be evaluated and the red dye reference ink prepared for bleeding evaluation, a solid portion was recorded adjacent to each paper shown in Table 3, and the obtained image was bordered. It was observed whether the color was blurred or unevenly mixed in the part. And it evaluated on the following references | standards and the result was shown in Table 3.
◯: There was no part in which the color was blurred or mixed unevenly.
Δ: There were some portions where the color was blurred or mixed unevenly.
X: The color was blurred or mixed unevenly.

<Example 13>
In the combination of the ink 1 and the paper C of Comparative Example 3, the step of recording the entire surface of the first liquid I for reaction prepared previously on the paper C in advance by another recording head mounted on the apparatus. In addition, image formation was performed. And it evaluated by the method similar to the comparative example 3. Table 4 shows the results obtained.

<Example 14>
In the combination of the ink 5 and the paper E of Comparative Example 9, the step of recording the entire surface of the first liquid II for the reaction prepared previously on the paper E in advance with a separate recording head mounted on the apparatus. In addition, image formation was performed. And it evaluated by the method similar to the comparative example 9. Table 4 shows the results obtained.

  As described above, as shown in the examples, in the image forming method according to the present invention, the surface tension of the ink was changed from low to high across the critical surface tension of the recording medium before and after contact. Therefore, when the ink penetrates into the recording medium in the second stage, the ink penetrating power decreases rapidly, so that the ink is in the upper layer portion of the recording medium. The recording density became high. As a result, it was possible to achieve both the performance of preventing bleeding and high recording density, which was difficult to achieve in the past.

It is a longitudinal cross-sectional view of the head part of an inkjet recording device. It is a cross-sectional view of the head part of an inkjet recording device. FIG. 2 is an external perspective view of a head in which the head shown in FIG. It is a perspective view which shows an example of an inkjet recording device. It is a longitudinal cross-sectional view of an ink cartridge. It is a perspective view of a recording unit. FIG. 6 is a perspective view illustrating a recording unit in which a plurality of recording heads are arranged. It is a perspective view of another recording head used for the present invention. FIG. 6 is a perspective view illustrating a recording unit in which a plurality of recording heads are arranged. It is a perspective view of another recording head used for the present invention.

Explanation of symbols

13: Head 14: Ink channel 15: Heat generating head 16: Protective film 17-1, 17-2: Aluminum electrode 18: Heat generating resistor layer 19: Heat storage layer 20: Substrate 21: Ink 22: Discharge orifice (micropore)
23: Meniscus 24: Recording droplet 25: Recording medium 26: Multi-nozzle 27: Glass plate 28: Heat generating head 40: Ink bag 42: Plug 44: Ink absorber 45: Ink cartridge 51: Paper feed unit 52: Paper feed Roller 53: Paper discharge roller 61: Blade 62: Cap 63: Ink absorber 64: Discharge recovery unit 65: Recording head 66: Carriage 67: Guide shaft 68: Motor 69: Belt 70: Recording unit 71: Head unit 72: Air Communication port 81: Yellow ink recording head 82: Magenta ink recording head 83: Cyan ink recording head 84: Black ink recording head 85: Recording head for discharging the first liquid

Claims (14)

  In an inkjet recording method for forming an image by depositing ink on a recording medium, at least water, a coloring material, and a surfactant are contained, and the content of the surfactant is not less than the critical micelle concentration of the surfactant. And an ink having a surface tension equal to or lower than a critical surface tension of the recording medium, the ink is adhered to the recording medium, and the surface tension of the ink is adjusted after the contact with the recording medium. An ink jet recording method, wherein the surface tension is changed to a surface tension higher than the critical surface tension of the recording medium.   The inkjet recording method according to claim 1, wherein the recording medium is plain paper.   The inkjet recording method according to claim 1, wherein the colorant is a pigment and the surfactant is an anionic surfactant.   The inkjet recording method according to claim 3, wherein the critical micelle concentration of the anionic surfactant is 0.0005 mol / l or less.   The change in the surface tension of the ink after contact with the recording medium is due to the expiration of the surface activation ability of the surfactant caused by a change in the pH of the ink. Inkjet recording method.   The change in the surface tension of the ink after contact with the recording medium is due to the expiration of the surface activation ability due to the reaction between the surfactant contained in the ink and a polyvalent metal ion. The inkjet recording method according to any one of the above.   In an inkjet ink containing at least water, a coloring material, and a surfactant having a critical micelle concentration or higher, the surface tension is equal to or lower than the critical surface tension of a recording medium to which the ink is attached, and the recording target An ink-jet ink characterized by changing to a surface tension higher than a critical surface tension of a recording medium after contact with the medium.   The inkjet ink according to claim 7, wherein pH is 6.5 or more, and the surfactant is an anionic surfactant.   The inkjet ink according to claim 8, wherein the pH is less than 7.5.   The inkjet ink according to claim 8, wherein the anionic surfactant has a cyclic peptide in a molecular structure and has a critical micelle concentration of 0.0005 mol / l or less.   An ink cartridge for ink-jet recording, comprising an accommodating portion for accommodating the ink-jet ink according to any one of claims 7 to 10.   11. An ink jet comprising: a storage unit that stores the ink for ink jet according to claim 7; and a head unit for discharging the ink for ink jet stored in the storage unit. Recording unit.   An ink jet recording apparatus comprising the ink cartridge for ink jet recording according to claim 11.   An inkjet recording apparatus comprising the inkjet recording unit according to claim 12.

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