JP2007063390A - Water-based pigment ink for inkjet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a water-based pigment ink for inkjet, capable of providing a recorded image having high image quality and excellent rub resistance. <P>SOLUTION: The water-based pigment ink for inkjet containing at least a pigment, a hydrophilic solvent and water contains diamond particles. The diamond particle is preferably the one of a synthetic diamond produced by an impact method, and has preferably a spherical shape. The content of the diamond particles is preferably 2-50 wt.% based on the amount of the pigment. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a water-based pigment ink suitable for an ink jet recording system, and more particularly to a water-based pigment ink having excellent rub resistance of a recorded image.

  The ink jet recording method is a printing method in which recording is performed by ejecting ink droplets and attaching them to a recording medium such as paper. Conventionally, dye inks using dyes as colorants have been the mainstream as inks for ink jet recording, but recently, they have better fastness (light resistance, gas resistance, water resistance) to ink jet recording images. Etc.), and a pigment ink using a pigment having excellent image fastness as a colorant compared to a dye has been used as an ink that can meet such a demand.

  A problem when using pigment ink is the abrasion resistance (hardness of scratches) of the recorded image. Since the recorded image produced using the pigment ink is formed by fixing the pigment particles as the colorant on the surface of the recording medium, the pigment particles are likely to fall off from the surface, and the recorded image is damaged. There is a problem that is easily attached. In particular, when the recording medium used for recording is a recording medium having high surface glossiness (surface smoothness) such as glossy paper, the pigment particles are likely to fall off.

  As a method for improving the abrasion resistance of a recorded image, for example, Patent Documents 1 and 2 disclose a method of incorporating a latex into a pigment ink. However, in this method, when an amount of latex that exhibits sufficient abrasion resistance is added to the ink even in a recording medium with high surface glossiness, the storage stability of the ink is reduced and the nozzle of the recording head is clogged. There was a problem that ejection failure was likely to occur.

  In Patent Documents 3 and 4, colorless ink containing a cationic compound is mixed with an ink containing an anionic coloring material on a recorded image to improve the abrasion resistance of the recorded image. A method is disclosed. However, this method has a problem that at least one series of dedicated nozzles is required to discharge colorless ink, and a plurality of recording head cleaning mechanisms are required, which makes the apparatus complicated and large.

Japanese Patent Publication No. 60-32663 JP-A-4-18462 JP-A-6-99576 JP-A-8-20159

  Accordingly, an object of the present invention is to provide an aqueous pigment ink for inkjet that can provide a recorded image with high image quality and excellent abrasion resistance.

  The present invention achieves the above-mentioned object by providing an aqueous inkjet pigment ink containing diamond particles in an inkjet aqueous pigment ink containing at least a pigment, a hydrophilic solvent, and water. It is.

  Since the aqueous pigment ink for ink-jet recording of the present invention contains diamond particles, it can record an image having excellent abrasion resistance and being hardly scratched. That is, when the ink-jet aqueous pigment ink of the present invention is attached to a recording medium, the innumerable diamond particles contained in the ink are fixed to the recording medium in a state of protruding outward from the pigment particles. Functions as a protective member. The fixed portion (recorded image) of the pigment particles and diamond particles has a higher hardness and higher wear resistance than recording medium forming materials such as silica and alumina even when the surface is rubbed with a finger or other recording medium. Since the particles stably prevent the pigment particles from coming into contact with other objects, the pigment particles do not easily fall off and are not easily damaged.

  In addition, the recorded image produced using the aqueous pigment ink for inkjet of the present invention is excellent not only in abrasion resistance but also in color development, and has high quality and high image quality comparable to a silver salt photograph. . Further, even if the water-based pigment ink for inkjet of the present invention contains diamond particles, since the diamond particles are fine particles, they are less likely to cause ejection failure and have excellent ejection stability and can be used with confidence in inkjet recording. can do.

  The aqueous pigment ink of the present invention contains diamond particles as an essential component. As the diamond particles, either natural diamond or synthetic diamond can be used. In particular, synthetic diamond is preferable, and above all, by a diamond synthesis method using an explosive impact of several hundred thousand atmospheres by an explosive, called an impact method. Manufactured synthetic diamond is preferred.

  The diamond particles are preferably spherical. Since spherical diamond particles have a smaller contact area with other objects than diamond particles of other shapes, the spherical diamond particles are fixed to the recording medium in a state of protruding outward from the pigment particles. By constructing a recorded image together with the pigment particles, it becomes possible to reduce the contact area of the recorded image with the other object when the surface of the recorded image is rubbed with another object. It becomes possible to further improve the abrasion resistance.

  In addition, the average particle diameter of the diamond particles contained in the aqueous pigment ink is preferably 200 nm or less from the viewpoints of ink ejection stability and color development of recorded images.

  The content of diamond particles is preferably 2 to 50% by weight with respect to the pigment (colorant) contained in the ink. When the content of diamond particles is less than 2% by weight with respect to the pigment, the effect of improving the abrasion resistance of the recorded image is poor. On the other hand, when the content exceeds 50% by weight with respect to the pigment, the surface of the pigment particles fixed on the recording medium is excessively covered with diamond particles, and the color developability of the recorded image may be reduced. In particular, since the synthetic diamond produced by the impact method preferably used in the present invention uses graphite as a raw material, it may contain a small amount of graphite, and diamond particles containing such graphite When a large amount of is contained in the ink, there is a possibility that the saturation is lowered when it is deposited on the recorded image.

  The aqueous pigment ink of the present invention contains, in addition to the above-mentioned diamond particles, pigments (colorants), a hydrophilic solvent, and water (water as a main solvent) as essential components. As water, pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water can be used. In addition, water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because it can prevent generation of mold and bacteria when the ink is stored for a long period of time.

  As the pigment contained in the aqueous pigment ink of the present invention, those usually used for inkjet aqueous pigment inks can be used without particular limitation. For example, azo pigments (for example, azo lakes, insoluble azo pigments, condensed azo pigments) can be used. Pigments, including chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinophthalone pigments), nitro pigments, Organic pigments such as nitroso pigments and aniline black; inorganic pigments such as carbon black (eg furnace black, thermal lamp black, acetylene black, channel black), metal oxides, metal sulfides, metal chlorides; silica, calcium carbonate , Talc, etc. It can be used extender pigments. Specifically, for example, C.I. I. Pigment Yellow 74, 93, 109, 110, 128, 138, 150, 151, 154, 155, 180, 185; I. Pigment red 122, 202, 209; I. Pigment violet 19; C.I. I. Pigment blue 15: 3, 15: 4, 60; C.I. I. Pigment green 7 (phthalocyanine green), 10 (green gold), 36, 37; C.I. I. Pigment brown 3, 5, 25, 26; I. Pigment orange 1, 2, 5, 7, 13, 14, 15, 16, 34, 36, 38 and the like. The content of the pigment is preferably 1 to 30% by weight based on the total weight of the ink from the viewpoint of the balance between the color density of the image and the ejection stability.

  As the hydrophilic solvent contained in the water-based pigment ink of the present invention, those usually used for water-based inks for inkjet can be used without particular limitation, and examples thereof include alcohols (for example, methanol, ethanol, propanol, isopropanol). , Butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl alcohol, etc.), polyhydric alcohols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene) Glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.) Polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl Ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, Reethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amide (For example, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, etc.), heterocycles (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3 -Dimethyl-2-imidazolidinone etc.), sulfoxides (eg dimethyl sulfoxide etc.), sulfones (eg sulfolane etc.), urea, acetonitrile, acetone, 1,2- Examples include alkanediol. The content of the hydrophilic solvent is preferably 3 to 25% by weight with respect to the total weight of the ink from the viewpoint of improving ejection stability and permeability to the recording medium.

  Further, the aqueous pigment ink of the present invention may contain a surfactant as necessary. As the surfactant, amphoteric surfactants and nonionic surfactants are preferably used. Examples of amphoteric surfactants include lauryldimethylaminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, coconut oil fatty acid amidopropyldimethylaminoacetic acid betaine, polyoctylpolyaminoethylglycine and other imidazolines. There are derivatives. Nonionic surfactants include acetylene glycol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene Ethers such as oxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, polyoxyethylene oleic acid, polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, Sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate Ester such as chromatography bets, and the like other fluorine alkyl esters, fluorine-containing surfactants such as perfluoroalkyl carboxylates. One of these surfactants may be used alone, or two or more thereof may be mixed and used. The content of the surfactant is preferably 0.3 to 2% by weight based on the total weight of the ink.

  Among the above surfactants, acetylene glycol surfactants are particularly preferable from the viewpoints of image quality and ejection stability, and examples thereof include 2,4,7,9-tetramethyl-5-decyne-4,7- Examples include diol, 3,6-dimethyl-4-octyne-3,6-diol, and 3,5-dimethyl-1-hexyne-3ol. Commercially available acetylene glycol surfactants include Surfinol 82, 104, 440, 465, 485, or TG (all available from Air Products and Chemicals. Inc.), Olphine STG, Olphine E1010 (trade name) ( As described above, Nissin Chemical Co., Ltd.) is preferably used. Silicone surfactants can also be preferably used in the present invention. Examples of commercially available silicone surfactants include BYK347 and 348 (manufactured by Big Chemie Japan).

  In addition to the components described above, the water-based pigment ink of the present invention includes a dispersant for uniformly dispersing the pigment in an aqueous medium as necessary (for example, polyvinyl alcohols, acrylic resins, styrene-acrylic copolymer). Moisturizers (eg, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glycyci, sorbitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose Saccharides, etc.), pH adjusters, antiseptics, fungicides, antifoaming agents, ultraviolet absorbers, antioxidants, water-soluble dyes, and the like.

  The water-based pigment ink of the present invention has a viscosity of 2 to 5 mPa · s at a liquid temperature of 20 ° C. and a surface tension from the viewpoint of stably ejecting from an inkjet nozzle and obtaining a good image quality. It is preferable that it exists in the range of 18-50 mN / m. Such physical property values can be obtained by appropriately adjusting the contents of various components such as a hydrophilic solvent and a surfactant.

  The aqueous pigment ink of the present invention can be used in a known ink jet printer and can be used for various recording media. The present invention is particularly effective for a recording medium having high surface glossiness (surface smoothness), in which pigment particles are likely to fall off with a conventional pigment ink, and the pigment particles fall off on the recording medium. It is possible to output an image that hardly occurs and has excellent abrasion resistance. As a recording medium in which the present invention is particularly effective, for example, glossy paper having a 20 glossiness of 10% or more as defined by JIS-Z8741 on the recording surface can be mentioned. Specific examples of the glossy paper include a void structure containing a porous pigment such as silica or alumina and a binder resin for binding the porous pigment on a support made of paper, film, resin-coated paper, or the like. Glossy inkjet exclusive paper having a configuration in which the ink receiving layer is provided.

  Hereinafter, the present invention will be described more specifically with reference to examples of the present invention and test examples showing the effects of the present invention. However, the present invention is not limited to the examples.

[Example 1]
Synthetic diamond particles (spherical diamond particles produced by impact method, average particle size 110 nm, manufactured by NOF Corporation) 10% by weight, dispersing agent (poise 520, manufactured by Kao) 1% by weight, and the remaining amount of ion-exchanged water are mixed Then, this mixture was dispersed using a high-pressure homogenizer (40 MPa, 2H) to obtain a diamond dispersion. Then, an aqueous pigment ink having the following composition was prepared using this diamond dispersion.

<Composition of pigment ink>
・ Cycnadoline pigment (CI Pigment Red 122) 4.0% by weight
・ Glycerin 10.0% by weight
・ 1,2-propanediol 5.0% by weight
・ Surfactant (BYK348, manufactured by Big Chemie) 0.5% by weight
・ Diamond dispersion 5.0% by weight
(0.5 wt% in terms of solid content, 12.5 wt% with respect to pigment)
・ Ion exchange water remaining
100% by weight

[Example 2]
An aqueous pigment was prepared in the same manner as in Example 1 except that the content of the diamond dispersion was 0.9% by weight (0.09% by weight in terms of solid content and 2.25% by weight with respect to the pigment). An ink was prepared.

Example 3
In Example 1, the aqueous pigment ink was prepared in the same manner as in Example 1 except that the content of the diamond dispersion was 19.6% by weight (1.96% by weight in terms of solid content and 49% by weight with respect to the pigment). Prepared.

Example 4
Aqueous pigment in the same manner as in Example 1 except that the content of the diamond dispersion in Example 1 was changed to 0.5 wt% (0.05 wt% in terms of solid content and 1.25 wt% with respect to the pigment). An ink was prepared.

Example 5
In Example 1, the aqueous pigment ink was prepared in the same manner as in Example 1 except that the content of the diamond dispersion was 22.0% by weight (2.2% by weight in terms of solid content and 55% by weight with respect to the pigment). Prepared.

[Comparative example]
In Example 1, an aqueous pigment ink was prepared in the same manner as in Example 1 except that the ink did not contain a diamond dispersion.

〔Evaluation test〕
With respect to each of the aqueous pigment inks of the above Examples and Comparative Examples, the image abrasion resistance, color developability, and ejection stability were evaluated by the following evaluation methods. These results are shown in Table 1 below.

(Image scrub resistance evaluation method)
Using an inkjet printer (PX-G900, manufactured by Seiko Epson), recording on glossy inkjet dedicated paper (photographic paper <gloss>, 20 glossiness 15% specified by JIS-Z8741 of recording surface, manufactured by Seiko Epson) The surface was printed with a solid 100% duty with the aqueous pigment ink. Then, according to JIS-K5701, using a Sutherland rubbing resistance tester (NO. 468 manufactured by Toyo Seiki Co., Ltd.), this solid printed part was rubbed back and forth 20 times, and the state of the solid printed part after friction was visually observed, A (Abrasion resistance is good) is shown when the printed part is not damaged, B is shown when a fine flaw is seen in the printed part but there is no practical problem, and C is shown when the printed part is noticeable.

(Evaluation method of color development)
Using an inkjet printer (PX-G900, manufactured by Seiko Epson), recording on glossy inkjet dedicated paper (photographic paper <gloss>, 20 glossiness 15% specified by JIS-Z8741 of recording surface, manufactured by Seiko Epson) The surface was printed with a solid 100% duty with the aqueous pigment ink. And about this solid printing part, the reflection optical density | concentration (OD value) was measured on the conditions with a viewing angle of 2 degree | times, the light source D50, and no filter using Spectrolino SPM-50 made from Gretag Macbeth Co., and OD value is 1. A of 8 or more was designated as A (high image density and good color development), an OD value of more than 1.6 and less than 1.8 was designated as B, and an OD value of 1.6 or less was designated as C.

(Evaluation method of discharge stability)
First, printing was performed using an ink jet printer (PX-G900, manufactured by Seiko Epson) in which the aqueous pigment ink was contained in an ink cartridge, and it was confirmed that the ink was stably ejected. Next, the ink jet printer was left for 4 weeks in an environment of room temperature 50 ° C. and relative humidity 40% with the recording head removed from the home position. Next, the inkjet printer was placed in a normal indoor environment, and when the printer temperature was almost the same as room temperature, the printer was turned on and solid printing was performed on 1000 sheets of recording paper. When the ink ejection became unstable, a predetermined cleaning function provided as a standard in the ink jet printer was used to restore the ejection to a stable state. The above operation was performed and the ejection stability was evaluated according to the following evaluation criteria.
A: No nozzle clogging occurs during printing, and ink is stably ejected. Good discharge stability.
B: Clogging occurs during printing, and two or more cleaning operations are required until ink ejection is stabilized. There is no practical problem.
C: Clogging occurs during printing, and three or more cleaning operations are required until ink ejection is stabilized.

Claims (4)

  An aqueous pigment ink for ink-jet, comprising at least a pigment, a hydrophilic solvent and water, and containing diamond particles.   The water-based pigment ink for inkjet according to claim 1, wherein the diamond particles are synthetic diamond produced by an impact method.   The aqueous pigment ink for inkjet according to claim 1 or 2, wherein the diamond particles have a spherical shape. The water-based pigment ink for inkjet according to any one of claims 1 to 3, wherein the content of the diamond particles is in the range of 2 to 50% by weight with respect to the pigment.