JP2010084066A - Ink for inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet recording suitable to inkjet recording processes, including a plurality of pigments in one kind of ink, excellent in print qualities of records, particularly in glossiness in glossy paper and image fastness such as scratch resistance and marker resistance to general recording media, good in storage stability, and maintaining good and stable response even when ejected at wide range of driving frequency. <P>SOLUTION: This ink for inkjet recording comprises pigments as a core, and microcapsuled color materials containing a resin having dispersing functions to aqueous media as a shell, where the pigments as the core are a pigment mixture including a plurality of kinds of organic pigment. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is suitable for an ink jet recording method, and relates to an ink for ink jet recording (hereinafter sometimes referred to as “ink”) having a plurality of types of pigment in one ink and having the following characteristics. That is, the present invention relates to an ink excellent in print quality of a recorded matter, in particular, glossiness when printed on glossy paper, and image fastness such as scratch resistance and marker resistance with respect to general recording media. Furthermore, the present invention relates to an ink that has good ink storage stability and can maintain good and stable response even when ejected at a wide range of driving frequencies.

  The ink jet recording method performs recording by causing ink droplets to fly and adhere to a recording medium such as paper. Among the ink jet recording methods, there is a thermal method in which an electrothermal converter is used as a discharge energy supply unit, and droplets are discharged by generating bubbles by applying heat energy to ink. According to this thermal method, it is possible to easily realize a high-density multi-nozzle of the recording head, and it is possible to record a high-resolution and high-quality image at a high speed (see Patent Document 1).

  In recent years, further improvement in the fastness of ink-jet recorded images has been desired, and accordingly, the study of adopting a pigment as a coloring material in ink has become active. When a pigment is used as a coloring material for an aqueous inkjet ink, it is important to stably disperse the pigment in an aqueous medium. In general, in order to uniformly disperse a pigment in an aqueous medium, the pigment is physically adsorbed on a dispersant, for example, a hydrophilic group for stably dispersing the pigment in the aqueous medium and a hydrophobic pigment surface. There is a method of using a resin dispersant having a hydrophobic part (see Patent Document 2).

  When the pigment ink obtained by the method using the resin dispersant is used, an image having relatively good scratch resistance and glossiness may be obtained when the ink shot is small. However, when the secondary colors red, green, and blue are expressed by three types of inks of yellow, magenta, and cyan, it is difficult to sufficiently achieve these performances. In relation to this, there is also a proposal for a vermilion ink in which a plurality of pigments are contained in one ink (see Patent Document 3), but good ink storage stability and ink ejection stability. It was difficult to secure.

  The present inventors have energetically studied the following objectives with respect to the problems against the background of future technological trends as described above. Specifically, in a configuration in which a plurality of types of pigments are contained in one ink, the print quality of the recorded matter, in particular, glossy paper is printed while ensuring the dispersion stability and ejection stability of the pigment ink. The ink which can make the glossiness excellent in the case was examined. Furthermore, an ink that can form an image excellent in image fastness such as scratch resistance and marker resistance was examined on all recording media. The outline of each problem mentioned above is shown below.

1. Scratch resistance / marker resistance When an ink is printed on a recording medium and the obtained recorded matter is traced with a marker such as a fluorescent pen or a finger, the recorded matter may be stained. This is not a problem with inks of a type that has a strong penetrating power and the colorant in the ink is absorbed in a recording medium such as a dye, but has a weak penetrating power to paper and the like, and the colorant Is often a problem with inks that remain on the recording medium, such as pigments. In particular, in the case of an ink using a self-dispersing pigment that does not use a dispersing resin or the like, these phenomena are remarkable. Further, even in the case of ink using a dispersion resin, it is a major technical problem in expressing secondary colors red, green, and blue by the subtractive color mixing method.

2. Glossiness To express photographic image quality at a high level by the inkjet method, glossy paper is used instead of plain paper. At this time, the glossiness of the image is a very important required performance, and is an indispensable performance when a silver salt photograph-like image is desired. When dye ink is used, relatively good gloss can be obtained. On the other hand, when pigment ink is used, the surface of the glossy paper becomes very dense and the pigment remains on the surface of the paper. The uneven state of the surface greatly determines the glossiness. For this reason, the glossiness of the image is inferior. This problem is particularly noticeable when a secondary color obtained by the subtractive color mixing method is expressed using two inks. For this reason, a method of using a single ink as a special color, that is, an ink in which a plurality of types of pigments are contained in one ink, may be employed for expressing the secondary color.

3. Discharge stability When the pigment ink is used in an ink jet recording apparatus in which recording is performed by ejecting ink from fine holes (orifices) of the recording head by an energy action, there are the following problems. That is, when an ink having poor dispersion stability is used, there is a drawback in that the ink ejection stability is remarkably hindered and printing defects are generated. In particular, when a conventional water-based pigment ink is used for recording by discharging droplets by the thermal method, when a pulse is applied to the ink, the heat is applied to the thin film resistor by a certain driving voltage. There was sometimes a deposit. In this case, the ink is not completely foamed, and the ejection of the droplet cannot respond to the applied pulse, resulting in non-ejection. In particular, such a problem often occurs in the type of ink in which a plurality of types of pigments are individually dispersed to obtain a pigment dispersion and then these are mixed in the ink.

Japanese Patent Publication No. 61-59911 Japanese Patent Laid-Open No. 9-241564 JP 2000-44856 A

  Accordingly, an object of the present invention is to provide an ink for ink jet recording having the following characteristics, which is suitable for an ink jet recording method and is an ink having a form containing a plurality of types of pigments in one ink. That is, the present invention provides an ink for inkjet recording that is excellent in print quality of recorded matter, in particular, glossiness when printed on glossy paper, and image fastness such as scratch resistance and marker resistance against general recording media. There is. Furthermore, in addition to the characteristics as described above, the ink storage stability is also good, and an ink for ink jet recording that can maintain good and stable responsiveness even when ejected at a wide range of driving frequencies is provided. is there.

  The above object is achieved by the present invention described below. That is, the present invention provides an inkjet recording ink having a pigment as a core and a microcapsule coloring material having a resin having a dispersion function with respect to an aqueous medium as a shell. Provided is an ink for ink jet recording, which is a pigment mixture containing a pigment.

  Since the ink of the present invention is obtained by microencapsulating a pigment mixture composed of a plurality of types of organic pigments using a resin having a dispersion function, the plurality of types of organic pigments contained therein are individually contained in the ink. Compared with the conventional ink dispersed in the ink, it has the following excellent characteristics. That is, according to the present invention, it is suitable for the ink jet recording method, the print quality of the recorded matter, in particular, the gloss when printed on glossy paper, and the scratch resistance and marker resistance against the recording medium in general. An ink for ink jet recording excellent in image fastness can be provided. Furthermore, ink storage stability is good, and an ink for ink jet recording that can maintain good and stable responsiveness even when ejected at a wide range of driving frequencies can be provided.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. The ink of the present invention is an inkjet recording ink containing a microcapsule coloring material having a pigment as a core and a resin having a dispersion function with respect to an aqueous medium as a shell. It is a pigment mixture containing a pigment. First, each component constituting the ink of the present invention will be described.

(Pigment)
It is essential that the pigment forming the core contained in the ink of the present invention is a pigment mixture in which a plurality of types of organic pigments are mixed. The kind of each pigment constituting the pigment mixture is not particularly limited, and examples thereof include the following, and those obtained by mixing two or more of these in advance can be used as the pigment mixture. .

First, carbon black is preferably used as the black pigment. Examples thereof include carbon black pigments such as furnace black, lamp black, acetylene black, and channel black. In particular, the primary particle diameter is 15 nm to 40 nm, the specific surface area according to the BET method is 50 m ² / g to 300 m ² / g, the DBP oil absorption is 40 ml / 100 g to 150 ml / 100 g, and the volatile content is 0.5% by mass or more. Those having characteristics of 10% by mass or less are preferably used.

  Next, organic pigments are preferably used as pigments mainly used in color inks. Specifically, insoluble azo pigments such as toluidine red, toluidine maroon, Hansa yellow, benzidine yellow, and pyrazolone red. Water-soluble azo pigments such as Ritolol Red, Helio Bordeaux, Pigment Scarlet, and Permanent Red 2B. Derivatives from vat dyes such as alizarin, indanthrone and thioindigo maroon, and 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 pigments such as isoindolinone yellow and isoindolinone orange. Imidazolone pigments such as benzimidazolone yellow, benzimidazolone orange, and benzimidazolone red. Pilanthrone pigments such as pyranthrone red and pyranthrone orange. Thioindigo pigment. Condensed azo pigment. Thioindigo pigment. Diketopyrrolopyrrole pigment. Examples include pigments such as flavanthrone yellow, acylamide yellow, quinophthalone yellow, nickel azo yellow, copper azomethine yellow, perinone orange, anthrone orange, dianthraquinonyl red, and dioxazine violet.

  Moreover, when an organic pigment is shown by a color index (CI) number, the following can be illustrated. C. 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. C. I. Pigment Orange 16, 36, 43, 51, 55, 59, 61, 71. C. 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. C. I. Pigment violet 19, 23, 29, 30, 37, 40, 50. C. I. Pigment Blue 15, 15: 1, 15: 3, 15: 4, 15: 6, 22, 60, 64. C. I. Pigment Green 7, 36. C. I. Pigment brown 23, 25, 26, and the like.

  As an example of a combination in which the above pigments are mixed, there is an example for the purpose of expressing a secondary color by a subtractive color mixing method. In this case, cyan and yellow pigments are used for green ink, cyan and magenta pigments are used for blue ink, and magenta and yellow pigments are used for red ink. It is preferable to mix in the range of 5. Suitable individual pigments used in this case include, but are not limited to, the following. Examples of yellow pigments include C.I. I. Pigment Yellow 13, 17, 55, 74, 93, 97, 98, 110, 128, 139, 147, 150, 151, 154, 155, 180, 185. Examples of cyan pigments include C.I. I. Pigment Blue 15: 3, 15: 4. Examples of magenta pigments include C.I. I. Pigment red 122, 202, 209, C.I. I. Pigment violet 19.

  Examples of combinations in which pigments are mixed for other purposes include color tone adjustment of black ink. That is, it is difficult to obtain a pure black color tone with an ink using carbon black alone, and it often shifts slightly to a blue and red color tone. This is particularly problematic when the density of the black ink is low. For this reason, in order to obtain a pure black color tone, the black ink is mixed with a color pigment mainly composed of carbon black. For example, it is preferable to mix these so that the ratio of carbon black to color pigment is in the range of 100/1 to 2/1.

  In addition, a combination in which pigments of the same color having different functions are mixed is also effective. For example, when there is no pigment having both excellent color developability and light resistance, a pigment having excellent color developability and a pigment having excellent light resistance can be mixed and used.

  In the present invention, the content of the pigment in the ink is not limited to this range, but the total amount of the pigment mixture with respect to the total amount of the ink may be 0.1% by mass or more and 15% by mass or less. preferable. More preferably, they are 0.2 mass% or more and 12 mass% or less, More preferably, they are 0.3 mass% or more and 10 mass% or less.

(Resin having a dispersion function for aqueous media)
As the resin forming the shell, any resin can be used as long as it has a dispersion function with respect to the aqueous medium. Suitable resins include polymers having a block structure formed by polymerizing at least three components of a hydrophobic monomer, a nonionic hydrophilic monomer, and an ionic hydrophilic monomer. The block structure in this case refers to a structure in which at least one of the three components forms a block structure. Furthermore, in the present invention, it is particularly preferable that the polymer has a polyvinyl ether structure as a repeating unit. Moreover, the following method is mentioned as a concrete synthesis method preferably used in order to polymerize a monomer and to obtain a polymer. That is, the method of cationic living polymerization by Aoshima et al. Described in Polymer Bulletin Vol. 15 (1986, page 417), Japanese Patent Application Laid-Open No. 11-322942, Japanese Patent Application Laid-Open No. 11-322866, and the like.

  In the above polymer, which is a resin used in the present invention, the repeating unit derived from the ionic hydrophilic monomer forming the block structure is not limited to these, but is represented by the following general formula (1). Preferred is a repeating unit.

（上記式（１）中、Ｒ₀は−Ｘ−（ＣＯＯＨ）_r、−Ｘ−（ＣＯＯ−Ｍ）_rを表す。Ｘは炭素数１から２０までの直鎖状、分岐状又は環状のアルキレン基。又は−（ＣＨ（Ｒ₅）−ＣＨ（Ｒ₆）−Ｏ）_p−（ＣＨ₂）_m−ＣＨ_3-r−若しくは−（ＣＨ₂）_m−（Ｏ）_n−（ＣＨ₂）_q−ＣＨ_3-r−。又は、それらのメチレン基の少なくとも１つがカルボニル基又は芳香族基で置換された構造を表す。ｒは１又は２を表す。ｐは１から１８までの整数を表す。ｍは０から３５までの整数を表す。ｎは１又は０を表す。ｑは０から１７の整数を表す。Ｍは１価又は多価のカチオンを表す。Ｒ₅、Ｒ₆はアルキル基を表す。また、Ｒ₅、Ｒ₆は同じでも異なっていてもよい。）

(In the above formula (1), R ₀ represents —X— (COOH) _r , —X— (COO—M) _r , where X is a linear, branched or cyclic alkylene having 1 to 20 carbon atoms. . group or _{- (CH (R 5) -CH} (R 6) -O) p - (CH 2) m -CH 3-r - or _{- (CH 2) m - (} O) n - (CH 2) q -CH3 _-r-, or a structure in which at least one of these methylene groups is substituted with a carbonyl group or an aromatic group, r represents 1 or 2, and p represents an integer of 1 to 18. m represents an integer of 0 to 35. n represents 1 or 0. q represents an integer of 0 to 17. M represents a monovalent or polyvalent cation. R ₅ and R ₆ represent an alkyl group. R ₅ and R ₆ may be the same or different.)

  The specific structure of the preferable repeating unit represented by the general formula (1) is given below.

（Ｍ₁は水素、リチウム、ナトリウム又はカリウムを表し、Ｐｈはフェニレン基を表す。）

(M ₁ represents hydrogen, lithium, sodium or potassium, and Ph represents a phenylene group.)

  In the above-mentioned polymer, which is a resin used in the present invention, a repeating unit derived from a hydrophobic monomer or a nonionic hydrophilic monomer that forms a block structure is not limited to these, but the following general The repeating unit represented by formula (2) is preferred.

（上記式（２）中、Ｒ₁は炭素数１から１８までの直鎖状、分岐状又は環状のアルキル基、−Ｐｈ、−Ｐｙｒ、−Ｐｈ−Ｐｈ、−Ｐｈ−Ｐｙｒ、−（ＣＨ（Ｒ₅）−ＣＨ（Ｒ₆）−Ｏ）_p−Ｒ₇及び−（ＣＨ₂）_m−（Ｏ）_n−Ｒ₇から選ばれるいずれかの基である。また、これらの基の、芳香環中の水素原子は炭素数１から４の直鎖状又は分岐状のアルキル基と、芳香環中の炭素原子は窒素原子とそれぞれ置換していてもよい。ｐは１から１８の整数、ｍは１から３６の整数、ｎは０又は１である。Ｒ₅、Ｒ₆はそれぞれ独立に水素原子若しくは−ＣＨ₃である。Ｒ₇は水素原子、炭素数１から１８までの直鎖状、分岐状又は環状のアルキル基、−Ｐｈ、−Ｐｙｒ、−Ｐｈ−Ｐｈ、−Ｐｈ−Ｐｙｒ、−ＣＨＯ、−ＣＨ₂ＣＨＯ、−ＣＯ−ＣＨ＝ＣＨ₂、−ＣＯ−Ｃ（ＣＨ₃）＝ＣＨ₂又は−ＣＨ₂ＣＯＯＲ₈である。また、Ｒ₇が水素原子以外である場合、Ｒ₇中の炭素原子に結合している水素原子は炭素数１から４の直鎖状又は分岐状のアルキル基又は−Ｆ、−Ｃｌ、−Ｂｒと、また、芳香環中の炭素原子は窒素原子とそれぞれ置換することができる。Ｒ₈は水素原子又は炭素数１から５のアルキル基である。Ｐｈはフェニル基、Ｐｙｒはピリジル基を表わす。）

(In the above formula (2), R ₁ is a linear, branched or cyclic alkyl group having 1 to 18 carbon atoms, -Ph, -Pyr, -Ph-Ph, -Ph-Pyr,-(CH ( R ₅ ) —CH (R ₆ ) —O) _p —R ₇ and — (CH ₂ ) _m — (O) _n —R ₇ , and the aromatic ring of these groups The hydrogen atom in the ring may be substituted with a linear or branched alkyl group having 1 to 4 carbon atoms, and the carbon atom in the aromatic ring may be substituted with a nitrogen atom, p is an integer of 1 to 18, and m is An integer from 1 to 36, n is 0 or 1. R ₅ and R ₆ are each independently a hydrogen atom or —CH ₃ , R ₇ is a hydrogen atom, a straight chain having 1 to 18 carbon atoms, branched Jo or cyclic alkyl group, -Ph, -Pyr, -Ph-Ph , -Ph-Pyr, -CHO, -CH 2 CHO, -CO-CH = _{H 2, -CO-C (CH} 3) = CH ₂ or -CH ₂ COOR _8. Also, when R ₇ is other than hydrogen atom, the hydrogen atoms attached to the carbon atoms in R ₇ carbon A linear or branched alkyl group of 1 to 4 or —F, —Cl, —Br, and a carbon atom in the aromatic ring can be substituted with a nitrogen atom, and R ₈ is a hydrogen atom or (It is an alkyl group having 1 to 5 carbon atoms. Ph represents a phenyl group, and Pyr represents a pyridyl group.)

  As the specific structure of the repeating unit derived from the hydrophobic monomer represented by the general formula (2), those described below are preferable.

（Ｐｈはフェニレン基、Ｃ₁₀Ｈ₈はナフタレン基を表す。）

(Ph represents a phenylene group, and C ₁₀ H ₈ represents a naphthalene group.)

  As the specific structure of the repeating unit derived from the nonionic hydrophilic monomer represented by the general formula (2), those described below are preferable.

  In the present invention, the content of the resin having the dispersing function in the ink is preferably in the range of 0.1% by mass or more and 15% by mass or less, more preferably 0.3% by mass with respect to the total amount of the ink. % Or more and 10 mass% or less. When the content of the resin having the dispersing function is higher than this range, it may be difficult to maintain a desired ink viscosity. In the present invention, the content ratio of the pigment mixture and the resin having a dispersion function in the ink is preferably 1: 5 to 10: 1. On the other hand, if the content ratio is out of this range, the ink ejection properties, particularly the thermal ink ejection properties, may deteriorate, or the image marker resistance and scratch resistance may deteriorate.

(Microcapsule coloring material)
The particle diameter of the microcapsule coloring material obtained by encapsulating the pigment mixture in a resin having a function of dispersing the pigment in an aqueous medium is preferably 200 nm or less in terms of average particle diameter. Is 150 nm or less. On the other hand, when the average particle size of the microcapsule color material exceeds 200 nm, the color material tends to settle, and glossiness may be poor in the formed image. As a method for measuring the average particle size, 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.

  As a method for forming the above-described microcapsule coloring material constituting the ink of the present invention, any means can be used as long as it can obtain a core-shell microcapsule structure, but a particularly preferable method is a phase inversion method. Can be mentioned. Among them, there is a method in which a mixture containing the pigment mixture and the resin having a dispersion function is used as an organic solvent phase and water is injected into the organic medium phase, or a method in which the organic medium phase is injected into water. It is extremely effective as a method for obtaining the microcapsule coloring material used in the present invention.

(Aqueous medium)
The ink according to the present invention contains water as an essential component, but 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. Is preferred. An aqueous medium in which water and a water-soluble solvent are used in combination can also be used. Examples of the water-soluble solvent used in combination with water include the following. Alkyl alcohols having 1 to 5 carbon atoms such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, and n-pentanol; Amides such as dimethylformamide and dimethylacetamide. Ketones or ketoalcohols such as acetone and diacetone alcohol. Ethers such as tetrahydrofuran and dioxane. Oxyethylene or oxypropylene polymers such as diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, and polypropylene glycol. Alkylene glycols in which an alkylene group contains 2 to 6 carbon atoms, such as ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, 1,5-pentanediol; Triols such as 1,2,6-hexanetriol, glycerin and trimethylolpropane. 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. Lower dialkyl ethers of polyhydric alcohols such as triethylene glycol dimethyl (or ethyl) ether and tetraethylene glycol dimethyl (or ethyl) ether. Alkanolamines such as monoethanolamine, diethanolamine, and triethanolamine. Examples include, but are not limited to, sulfolane, N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, urea, ethylene urea, bishydroxyethyl sulfone, diglycerin, and triglycerin. It is not something. Particularly preferred are ethylene glycol, glycerin, diglycerin, polyethylene glycol, ethylene urea, and trimethylolpropane. The content of the water-soluble solvent used in combination with water is not particularly limited, but is preferably 3% by mass or more, and preferably 60% by mass or less, based on the total amount of the ink.

(Surfactant)
In the ink according to the present invention, in order to obtain a more balanced ejection stability, it is preferable to include a surfactant in the ink. Among these, it is preferable to contain a nonionic surfactant. Among the nonionic surfactants, polyoxyethylene alkyl ethers and ethylene oxide adducts of acetylene glycol are particularly preferable. These nonionic surfactants have an HLB (Hydrophile-Lipophile Balance) value of 10 or more. In the present invention, the content of the surfactant is 0.01% by mass or more and 5% by mass or less, preferably 0.05% by mass or more and 4% by mass or less, more preferably 0.1% by mass with respect to the total amount of the ink. The content is 3% by mass or less.

(Other additives)
In addition to the above-described components, the ink according to the present invention includes, as necessary, a viscosity modifier, an antifoaming agent, an antiseptic, and an antifungal agent in order to obtain an ink having a desired physical property value. Antioxidants and the like can be added. The additive is preferably selected so that the surface tension of the ink is 25 mN / m or more, preferably 28 mN / m or more.

(Inkjet recording device)
Next, an ink jet printer will be described as an example of an ink jet recording apparatus used when an image is formed using the ink of the present invention. The ink jet printer described in this specific example is a thermal printer, but the ink of the present invention is more effective as an ink used in a thermal printer. In the case of the thermal method, an insoluble matter resulting from the ink components may accumulate on the heat generating heater as a driving source, causing non-ejection of ink. Even if such a phenomenon does not occur in an ink containing individual color materials alone, a problem occurs only when these color materials are mixed into an ink containing a plurality of types of color materials. There is. In addition, such a phenomenon is a phenomenon that does not occur so much in the case of dye ink, but often becomes a problem in the case of pigment ink. On the other hand, the ink of the present invention uses a core-shell color material in which a pigment for forming a core is a mixture in which a plurality of pigments are gathered in advance and these are encapsulated in a resin layer. For this reason, it seems that the phenomenon that different pigments act on each other and insoluble matters are likely to be deposited on the heater surface hardly occurs.

  Hereinafter, an outline of an ink jet printer that is suitably used will be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view showing a main part of an example of a liquid discharge head as a liquid discharge head of a discharge method that communicates bubbles with the atmosphere during discharge and an ink jet printer that is a liquid discharge apparatus using the head. In FIG. 1, the ink jet printer includes a conveyance device 1030, a recording unit 1010, and a movement drive unit 1006. The conveying device 1030 intermittently conveys a sheet 1028 as a recording medium provided in the casing 1008 along the longitudinal direction in the direction indicated by an arrow P shown in the drawing. The recording unit 1010 is reciprocated substantially in parallel with the guide shaft 1014 in an arrow S direction substantially orthogonal to the conveyance direction P of the paper 1028 by the conveyance device 1030. The movement drive unit 1006 is a drive unit that reciprocates the recording unit 1010.

  In addition, the transport device 1030 includes a pair of roller units 1022a and 1022b, a pair of roller units 1024a and 1024b, and a driving unit 1020 for driving the roller units. I have. With this configuration, when the driving unit 1020 of the transport device 1030 is activated, the paper 1028 is sandwiched between the roller units 1022a and 1022b and the roller units 1024a and 1024b, and is intermittently fed in the direction of the arrow P. It will be transported. The movement drive unit 1006 includes a pulley 1026a and a belt 1016 wound around a pulley 1026a and a pulley 1026b that are arranged to face each other with a predetermined interval. Further, the movement drive unit 1006 includes a roller unit 1022a and a motor 1018 that is arranged substantially parallel to the roller unit 1022b and drives the belt 1016 connected to the carriage member 1010a of the recording unit 1010 in the forward and reverse directions. It is configured.

  When the motor 1018 is activated and the belt 1016 rotates in the arrow R direction, the carriage member 1010a of the recording unit 1010 is moved in the arrow S direction by a predetermined movement amount. When the motor 1018 is activated and the belt 1016 rotates in the direction opposite to the arrow R direction shown in FIG. 1, the carriage member 1010a of the recording unit 1010 has a predetermined direction in the direction opposite to the arrow S direction. It will be moved by the amount of movement. Further, a recovery unit 1026 for performing an ejection recovery process of the recording unit 1010 is opposed to the ink ejection port array of the recording unit 1010 at one end of the movement driving unit 1006 at a position that is the home position of the carriage member 1010a. Is provided. The recording unit 1010 includes ink jet cartridges 1012Y, 1012M, 1012C, and 1012B that are detachably attached to the carriage member 1010a for each color, for example, yellow, magenta, cyan, and black. Hereinafter, the “inkjet cartridge” may be simply referred to as “cartridge”.

  FIG. 2 shows an example of an ink jet cartridge that can be mounted on the above-described ink jet recording apparatus. The cartridge 1012 in the example shown in FIG. 2 is of a serial type, and the main part is composed of the ink jet recording head 100 and an ink tank 1001 for containing ink.

  The ink jet recording head 100 is formed with a number of ejection ports 832 for ejecting ink, and the ink is supplied from the ink tank 1001 through an ink supply passage (not shown) to a common liquid chamber (not shown) of the liquid ejection head 100. ). In the cartridge 1012 shown in FIG. 2, the ink jet recording head 100 and the ink tank 1001 are integrally formed so that liquid can be supplied into the ink tank 1001 as necessary. In addition to this, a structure in which the ink tank 1001 is connected to the inkjet recording head 100 in a replaceable manner may be adopted. An ink jet cartridge 1012 provided with the ink jet recording head 100 is a recording unit.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. In the following description, “parts” and “%” are based on mass unless otherwise specified.

<Preparation of Resin 1>
First, polymerization ratios (A: A, B, and C shown in Table 1 below are used as raw materials by a cation living polymerization method (described in JP-A Nos. 11-322942 and 11-322866). An ABC type block polymer of B: C) = 40: 20: 10 was produced. The number average molecular weight (Mn) of the obtained block polymer was 13,600, and the ratio of the number average molecular weight to the weight average molecular weight (Mn / Mw) was 1.1. Next, the obtained block polymer was neutralized with an aqueous potassium hydroxide solution and further diluted with ion-exchanged water to obtain a homogeneous aqueous polymer solution. Next, the obtained polymer aqueous solution was neutralized with hydrochloric acid to obtain a resin 1 which is a triblock polymer in which the C component is a free carboxylic acid. In addition, NMR and GPC were used for the identification of the compound.

<Preparation of resin 2>
Similarly to the preparation of the resin 1, an AC type block polymer having a polymerization ratio A: C = 40: 20 was prepared by a cation living polymerization method using the monomers A and C shown in Table 1 below as raw materials. The number average molecular weight (Mn) of the obtained block polymer was 11,000, and the ratio of the number average molecular weight to the weight average molecular weight (Mn / Mw) was 1.1. Next, the obtained block polymer was neutralized with an aqueous potassium hydroxide solution and further diluted with ion-exchanged water to obtain a homogeneous aqueous polymer solution. Next, the obtained polymer aqueous solution was neutralized with hydrochloric acid to obtain a resin 2 which is a diblock polymer in which the C component is a free carboxylic acid. In addition, NMR and GPC were used for the identification of the compound.

<Preparation of pigment dispersions 1 to 10 by phase inversion method>
In the composition shown in Table 2 below, a resin and one or a mixture of two pigments are co-dissolved in 250 g of tetrahydrofuran (THF), and further converted into an aqueous phase using 500 g of distilled water. Was removed. Next, the concentration is adjusted by removing moisture from each of the obtained pigment dispersions, and the pigment concentration is 6%, which contains a colorant having a core-shell structure in which the pigment is encapsulated by the resin. Pigment dispersions 1 to 10 were obtained. The pigment dispersions 1 to 5 include a color material having a core-shell structure in which a pigment mixture obtained by mixing two kinds of pigments with a resin is included. The pigment dispersions 6 to 10 are made of a resin. It includes a color material having a core-shell structure in which one kind of pigment is included.

<Preparation of inks of Examples 1 to 5>
The inks of Examples 1 to 5 were prepared by using the pigment dispersions 1 to 5 obtained above, and further adding each component according to the following formulation to a predetermined concentration (100 parts in total). . Specifically, each component is sufficiently mixed and stirred according to the following formulation, and after adjusting the pH to 9.0 with potassium hydroxide, pressure filtration is performed with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm. I got it.

[Ink of Example 1]
・ Pigment dispersion 1 60 parts ・ Diglycerin 15 parts ・ Diethylene glycol 5 parts ・ Ethylene urea 4 parts ・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Example 2]
・ Pigment dispersion 2 60 parts ・ Glycerin 15 parts ・ Ethylene glycol 10 parts ・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Example 3]
・ Pigment dispersion 3 60 parts ・ Polyethylene glycol (average molecular weight 300) 10 parts ・ Glycerin 10 parts ・ Acetylene glycol ethylene oxide adduct (trade name: Acetyleneol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Example 4]
-Pigment dispersion 4 60 parts-Trimethylolpropane 8 parts-Ethylene glycol 5 parts-Diethylene glycol 5 parts-Polyoxyethylene cetyl ether (ethylene oxide addition number 20, HLB 17.5) 0.5 parts-Acetylene glycol ethylene oxide adduct (Product name: Acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Example 5]
-Pigment dispersion 5 60 parts-Diglycerin 15 parts-Diethylene glycol 5 parts-Ethylene urea 4 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

<Preparation of inks of Comparative Examples 1-5>
The inks 1 to 5 of the comparative examples were prepared by using the pigment dispersions 6 to 10 obtained above, and further adding each component according to the following formulation to a predetermined concentration (100 parts in total). . Specifically, each component is sufficiently mixed and stirred according to the following formulation, and after adjusting the pH to 9.0 with potassium hydroxide, pressure filtration is performed with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm. I got it.

[Ink of Comparative Example 1]
-Pigment dispersion 6 30 parts-Pigment dispersion 8 30 parts-Diglycerin 15 parts-Diethylene glycol 5 parts-Ethylene urea 4 parts-Acetylene glycol ethylene oxide adduct (trade name: Acetyleneol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Comparative Example 2]
・ Pigment dispersion 8 30 parts ・ Pigment dispersion 9 30 parts ・ Glycerin 15 parts ・ Ethylene glycol 10 parts ・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Comparative Example 3]
-Pigment dispersion 6 30 parts-Pigment dispersion 9 30 parts-Polyethylene glycol (average molecular weight 300) 10 parts-Glycerin 10 parts-Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Comparative Example 4]
-Pigment dispersion 6 30 parts-Pigment dispersion 7 30 parts-Trimethylolpropane 8 parts-Ethylene glycol 5 parts-Diethylene glycol 5 parts-Polyoxyethylene cetyl ether (ethylene oxide addition number 20, HLB 17.5) 0.5 parts・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Comparative Example 5]
-Pigment dispersion 9 6 parts-Pigment dispersion 10 54 parts-Diglycerin 15 parts-Diethylene glycol 5 parts-Ethylene urea 4 parts-Acetylene glycol ethylene oxide adduct (trade name: Acetyleneol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

<Preparation of inks of Reference Examples 1 and 2>
The inks of Reference Examples 1 and 2 were prepared by using the pigment dispersions 8 and 9 obtained above and further adding each component according to the following formulation to a predetermined concentration (100 parts in total). . Specifically, each component is sufficiently mixed and stirred according to the following formulation, and after adjusting the pH to 9.0 with potassium hydroxide, pressure filtration is performed with a micro filter (manufactured by Fuji Film) having a pore size of 2.5 μm. I got it. The inks of Reference Examples 1 and 2 are inks containing one type of pigment unlike the inks of Examples 1 to 5 and Comparative Examples 1 to 5 containing two types of pigments.

[Ink of Reference Example 1]
・ Pigment dispersion 8 60 parts ・ Glycerin 15 parts ・ Ethylene glycol 10 parts ・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

[Ink of Reference Example 2]
・ Pigment dispersion 9 60 parts ・ Glycerin 15 parts ・ Ethylene glycol 10 parts ・ Acetylene glycol ethylene oxide adduct (trade name: acetylenol EH, manufactured by Kawaken Fine Chemicals)
0.5 part, remaining water

<Evaluation>
The obtained inks of Examples 1 to 5, Comparative Examples 1 to 5, and Reference Examples 1 and 2 were evaluated as follows.

[Evaluation item]
(1) Ink Storage Stability / Inkjet Discharge Stability Each of the inks of Examples, Comparative Examples, and Reference Examples was placed in a Teflon (registered trademark) container, sealed, and stored at 60 ° C. for 1 month. Each ink after storage thus obtained and each ink before storage were separately filled in an ink jet recording apparatus equipped with an ink jet recording head equipped with Canon BJF900. Next, after ejecting each ink filled at a driving frequency of 0.1 kHz, the frequency was gradually increased, and the frequency was measured when the ejection shape became unstable ejection with no main droplets. The evaluation criteria are as follows. The evaluation results are shown in Table 3 below.
A: Both inks before and after storage are 10 kHz or more B: Either ink before and after storage is less than 10 kHz C: Both inks before and after storage are less than 10 kHz

(2) Marker resistance of printed matter The inks of Examples and Comparative Examples were each filled into an ink jet printer (trade name: BJF900) manufactured by Canon Inc. Next, in a plain paper mode, a character pattern was printed on PPC paper NSK manufactured by Canon Inc., and each printed portion was traced with a line marker after 1 minute and 1 hour from the printing. The evaluation criteria are as follows. The evaluation results are shown in Table 3 below.
A: No ink tailing is observed in the printed part after 1 minute and 1 hour B: Ink trailing is seen in the printed part after 1 minute, but not observed after 1 hour C: 1 minute After and after 1 hour, there is ink tailing in the print area

(3) Scratch resistance of printed matter The inks of Examples and Comparative Examples were respectively filled into an ink jet printer manufactured by Canon Inc. (trade name: BJF900). Next, in the plain paper mode, a character pattern was printed on PPC paper NSK manufactured by Canon Inc., and each printed part was traced with a finger 1 minute and 1 hour after printing. The evaluation criteria are as follows. The evaluation results are shown in Table 3 below.
A: No ink tailing is observed in the printed part after 1 minute and 1 hour B: Ink trailing is seen in the printed part after 1 minute, but not observed after 1 hour C: 1 minute After and after 1 hour, there is ink tailing in the print area

(4) Glossiness The ink of Example 2 and the ink of Comparative Example 2 having the same content and ratio of cyan pigment and magenta pigment were respectively filled into an ink jet printer manufactured by Canon Inc. (trade name: BJF900). . Next, a 200% solid pattern was printed on a professional photo paper manufactured by Canon Inc. in the corresponding printing mode, and the obtained printed matter was allowed to stand for 3 days, and the glossiness of each printing portion was measured with a gloss meter GMX- 203 (Murakami Color Research Laboratory) was used. In addition, using the same printer as described above for each of the inks of Reference Examples 1 and 2, 100% solid patterns were applied to the same place, and the ink of Example 2, the ink of Comparative Example 2, the cyan pigment, and the magenta pigment were used. Printing was performed so that the total applied amount was the same. The obtained printed matter was allowed to stand for 3 days in the same manner as described above, and then the 20 ° glossiness of the printed portion was measured using a gloss meter GMX-203 (manufactured by Murakami Color Research Laboratory). When the measured glossiness was compared and evaluated, the glossiness was the best when the ink of Example 2 was used. When the ink of Comparative Example 2 was used, the glossiness was slightly inferior compared with the case of using the ink of Example 2. Further, in the printing method using Reference Examples 1 and 2, the glossiness was clearly inferior as compared with the case of using the ink of Example 2 and the ink of Comparative Example 2.

  From the evaluation results of the evaluation items (1) to (3) shown in Table 3 above, all of the inks of Examples 1 to 5 which are the inks of the present invention have good ink storage stability, inkjet ejection stability, It was confirmed that the film had scratch resistance and marker resistance. Further, from the evaluation result of the evaluation item (4), in the image formation with the ink using a plurality of kinds of pigments, particularly when the image is formed using the ink of the present invention, the glossiness of the image is excellent. It was confirmed.

It is a schematic perspective view which shows the principal part of an example of the inkjet printer which can mount a liquid discharge head. It is a schematic perspective view showing an example of an ink jet cartridge provided with a liquid discharge head.

Claims (8)

  Ink jet recording ink having a pigment as a core and a microcapsule coloring material having a resin having a dispersion function with respect to an aqueous medium as a shell, wherein the pigment as the core contains a plurality of types of organic pigments An ink for ink jet recording characterized by the above.   The ink for inkjet recording according to claim 1, wherein the average particle diameter of the microcapsule coloring material is 200 nm or less.   3. The ink jet recording according to claim 1, wherein the resin as the shell is a polymer having a block structure formed by polymerizing at least three components of a hydrophobic monomer, a nonionic hydrophilic monomer, and an ionic hydrophilic monomer. ink.   The ink for inkjet recording according to any one of claims 1 to 3, wherein the resin as the shell has a polyvinyl ether structure as a repeating unit.   The ink for inkjet recording according to any one of claims 1 to 4, wherein the pigment constituting the pigment mixture includes a cyan pigment and a yellow pigment.   The ink for inkjet recording according to any one of claims 1 to 4, wherein the pigment constituting the pigment mixture includes a cyan pigment and a magenta pigment.   The ink for inkjet recording according to any one of claims 1 to 4, wherein the pigment constituting the pigment mixture includes a magenta pigment and a yellow pigment.   The ink for inkjet recording according to any one of claims 1 to 4, wherein the pigment constituting the pigment mixture contains carbon black.

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