JP2005162899A - Ink for inkjet recording and recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for inkjet recording, improved in marker resistance and scratch resistance without damaging the merit of a pigment-based ink providing an image having excellent image density and water resistance; and to provide a recording method by using the ink. <P>SOLUTION: The ink for the inkjet recording contains at least water, a pigment and a cationic polymer and has ≥33 and ≤39 mN/m surface tension. The recording method uses the ink. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ink jet recording ink suitable for ink jet recording and capable of giving a high image density even to plain paper, and more specifically, for ink jet recording excellent in water resistance, feathering characteristics and marker resistance characteristics. The present invention relates to an ink and a recording method using the ink.

  The ink jet recording method performs recording by ejecting ink and attaching the ink to a recording medium such as paper. In other words, according to the ink jet recording method in which an electrothermal transducer is used as an ejection energy supply means and ink is ejected by applying thermal energy to the ink to generate bubbles, the recording head can be easily formed into a high density multi-orifice. It can be realized, can record high-resolution and high-quality images at high speed, and has become one of the main forces of inkjet recording methods that are currently in practical use (for example, Patent Document 1, Patent Document 2, And Patent Document 3).

  By the way, as a coloring material in the ink used in such an ink jet recording method, for example, a water-soluble dye is used. However, a recorded image using such an ink has more water resistance and marker resistance on plain paper. Improvement is demanded.

  A number of means for improving the density and water resistance of the recorded image, particularly such a problem, have been proposed so far, and one of them is a technique of using a pigment as a coloring material and dispersing it in water to make ink. . For example, an ink using carbon black as a coloring material can give a recorded image having a high image density and excellent water resistance. However, such a recorded image still has room for improvement in terms of scratch resistance and marker resistance, particularly on plain paper.

In order to solve the above-mentioned problems, a technique for improving the fixability of an image by adding a resin to the ink is known. The ink contains a cationic emulsion in which resin particles are dispersed as a fixing agent. A technique for improving the fixability of an ink containing a dye or pigment as a coloring material on a recording medium is disclosed (for example, see Patent Document 4). In addition, an aqueous pigment composition for inkjet which contains a pigment, a colored resin and a humectant as essential components is disclosed, whereby it is disclosed that a print having excellent color developability and excellent water resistance can be obtained (for example, , See Patent Document 5).
Japanese Patent Publication No. 61-59911 Japanese Patent Publication No. 61-59912 Japanese Examined Patent Publication No. 61-59914 JP-A-3-172362 JP-A-8-239610

  However, according to the description, the colored resin described in Patent Document 5 described above is a dispersion of a resin dyed with a dye. It is manufactured by adding a dye to this emulsion polymer, heating to about 80 ° C. and then cooling.

  However, in the left column, lines 38 to 41 of page 4 of the said patent, “In order to make the dye sufficiently incorporated into the resin, 10 parts or less (100% of the dye) per 100 parts of the resin, especially 8 In the method for producing a dyeing resin of Production Examples 8 to 13 in the publication, the mixing ratio of the dye to the amount of resin solids in the emulsion polymer is about 10: 1 to 12 in all cases. : 1 (resin: dye).

  However, according to the study of the present inventor, when a dyeing resin is used, the resin is used in the ink for the purpose of improving the fixability of the pigment ink to the recording medium at the ratio of the dye to the resin described in the publication. It was concluded that it may not be sufficient to compensate for the decrease in image density caused by the decrease in the amount of colorant that can be contained in the ink due to the addition.

  Furthermore, if the colored resin is added to such an extent that a sufficient image density can be obtained, it is necessary to add an amount of the colored resin that deviates from the range in which the inkjet ink can be accurately discharged by the ink jet recording method. It is speculated that there is. As described above, the inventor of the present invention, based on the examination of the prior art, needs to develop a new technology that is completely different from the past in order to further improve the image density and image fixability in the pigment-based ink. This is the conclusion.

  Thus, as a result of repeated studies, the present inventor used an ink containing at least water, a colorant, and a cationic polymer and having a surface tension of 33 mN / m or more and 39 mN / m or less, whereby image density, feathering, It was found that a recorded image having good scratch resistance and marker resistance can be obtained.

  According to the inventor's study, (image density, feathering characteristics) and (scratch resistance, marker resistance characteristics) are in a trade-off relationship, and a recorded image with high image density and less feathering is scratch resistant. Marker resistance deteriorates. Conversely, a recorded image having good scratch resistance and marker resistance tends to have low print density and large feathering. Therefore, it has been difficult to realize an ink having all of image density, feathering, scratch resistance, and marker resistance.

  According to the inventor's study, by setting the surface tension to 39 mN / m or less, the permeability of the ink to the paper is improved, the amount of the pigment remaining on the paper is reduced, and the scratch resistance and the marker resistance are improved. Become. In addition, the crosslinking between the cationic polymer and the anionic pigment also improves the scratch resistance and marker resistance, and at the same time, suppresses ink penetration and improves image density and feathering characteristics. As a result, it is possible to give a high image density to the plain paper of the present invention, and an ink for ink jet recording excellent in water resistance, feathering characteristics and marker resistance characteristics has been realized.

  According to the present invention, it is possible to obtain an excellent ink in which marker resistance and scratch resistance are further improved without impairing the merits of a pigment-based ink that gives an image excellent in image density and water resistance. Further, in addition to high image density and excellent water resistance, it is possible to form an image excellent in feathering characteristics, marker resistance characteristics, and scratch resistance.

  An ink according to an embodiment of the present invention capable of achieving the above object is characterized in that it contains at least water, a pigment, and a cationic polymer, and has a surface tension of 33 mN / m or more and 39 mN / m or less. It is.

(1) Pigment Conventionally known pigments such as carbon black and organic pigments can be used without any problem. When preparing the Bk ink, it is preferable to use a self-dispersing carbon black in which at least one hydrophilic group is bonded to the surface of the carbon black directly or through other atomic groups. That is, when self-dispersing carbon black is used, a dispersant for dispersing the pigment in the ink is not added, or the amount added can be greatly reduced. A conventionally known water-soluble polymer or the like is used as the dispersant. However, such a polymer may be deposited on the ink discharge surface of the ink jet recording head and may deteriorate the ink discharge stability.

  However, by using the self-dispersing carbon black as described above as a pigment, the content of such a polymer in the ink can be reduced to zero or greatly reduced. As a result, the ejection stability during ink jet recording can be reduced. It can be further improved.

  Next, the self-dispersing carbon black will be described in detail. The self-dispersing carbon black is preferably ionic, and for example, anionically charged carbon black can be suitably used.

  Examples of the anionically charged carbon black include those in which a hydrophilic group as shown below is bonded to the surface of the carbon black.

_{-COO (M2), - SO 3} (M2), - PO 3 H (M2) and _-PO 3 _{(M2) 2}
In the above formula, M2 represents a hydrogen atom, an alkali metal, ammonium or organic ammonium. Among these, carbon black obtained by bonding —COO (M2) or —SO ₃ (M2) to the surface of carbon black to be anionic is particularly suitable for this embodiment because of its excellent dispersibility in the ink. It can be used. By the way, among those expressed as “M2” in the hydrophilic group, specific examples of the alkali metal include Li, Na, K, Rb and Cs, and specific examples of the organic ammonium include, for example, methylammonium, dimethyl Examples include ammonium, trimethylammonium, ethylammonium, diethylammonium, triethylammonium, methanolammonium, dimethanolammonium, and trimethanolammonium. An example of a method for producing an anionically charged self-dispersing carbon black is a method in which carbon black is oxidized with sodium hypochlorite. By this method, a —COONa group is chemically bonded to the carbon black surface. be able to.

  A plurality of types of pigments can be mixed and used. The ratio of the pigment to the total mass of the ink may be appropriately determined, but is preferably in the range of 0.5 to 20% by mass, and more preferably in the range of 1.0 to 10% by mass.

(2) Cationic polymer The cationic polymer used in the present invention may be water-soluble. Examples of the cationic polymer include polyallylamine, polyethyleneimine, polyvinylamine, polyvinylpyridine, polyethyleneimine-epichlorohydrin reaction product, polyamide-polyamine resin, polyamide-epichlorohydrin resin, cationic starch, or acid neutralized product thereof. However, it is not limited to these.

  The weight average molecular weight (Mw) of the cationic polymer is preferably about 200 to 100,000, more preferably about 500 to 5,000. Cationic polymers can be used alone or in combination. Although the addition amount of the cationic polymer may be appropriately determined, it is preferably added in the range of 0.05 to 20% by mass, more preferably in the range of 0.1 to 10% by mass with respect to the total amount of the ink composition. Is more preferable. If the addition amount of the cationic polymer is too small, the effect becomes small, and if it is too large, the dispersion stability of the pigment becomes poor.

(3) Surface tension A surfactant is preferably used for adjusting the surface tension of the ink according to this embodiment. The surfactant used in the present invention is not particularly limited, and examples thereof include various anionic surfactants, nonionic surfactants, cationic surfactants, and amphoteric surfactants.

  Anionic surfactants include fatty acid salts, alkyl sulfate esters, alkyl benzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfosuccinates, alkyl diphenyl ether disulfonates, alkyl phosphates, polyoxyethylene alkyl sulfates Salts, polyoxyethylene alkylaryl sulfates, alkane sulfonates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphates, N-methyl-N-oleoyl taurate, α-olefin sulfonic acid Examples include salts.

  Although it does not restrict | limit especially as a nonionic surfactant, From the point of storage stability and printing density, what has an ethylene oxide structure or a propylene oxide structure is preferable, Among these, HLB is 9-17, Especially 10-16. More preferred.

  Specific examples of the nonionic surfactant include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene lauryl ether, polyoxyethylene oleyl ether, polyoxyethylene tridecyl ether. , Polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene alkylamine, aminopolyoxyethylene, sorbitan fatty acid ester, polyoxyethylene sorbitan laurate, polyoxyethylene sorbitan palmitate, polyoxyethylene sorbitan stearate, poly Oxyethylene sorbitan oleate, naphthol ethylene oxide adduct, acetylene glycol ethylene oxide addition Bisphenol A ethylene oxide adduct, oxyethylene oxypropylene block polymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester, polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, etc. It is done.

  On the other hand, examples of the cationic surfactant and the amphoteric surfactant include alkylamine salts, quaternary ammonium salts, alkylbetaines, and aminoxides.

  The addition amount of the above-described surfactant is not particularly limited, but the surface tension is preferably 33 mN / m or more and 39 mN / m or less, more preferably 34 mN / m or more and 38 mN / m or less. If the surface tension is greater than 39 mN / m, the ink penetrates slowly into the paper, and many pigments remain on the paper surface, resulting in poor scratch resistance and marker resistance. On the other hand, if the surface tension is less than 33 mN / m, the ink permeates faster and the feathering becomes worse.

(4) Aqueous medium, other additives, etc. The above-described pigment is held in a dispersed state in an aqueous medium to constitute an ink. The constituent component of the aqueous medium is basically water, and the ratio of water to the total mass of the ink is preferably 20 to 95% by mass, and more preferably 60 to 95% by mass.

  In addition, the ink for ink jet recording of the present invention contains a water-soluble organic solvent as described below in order to impart more ink jet recording suitability such as reliability, storage stability, or ink permeability control. Also good. Examples of the water-soluble organic solvent preferably used include alkyl alcohols having 1 to 4 carbon atoms (for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert- Butyl alcohol etc.), ketones or keto alcohols (eg amides such as dimethylformamide and dimethylacetamide, acetone, diacetone alcohol etc.), ethers (eg tetrahydrofuran, dioxane etc.), polyalkylene glycols (eg polyethylene glycol, polypropylene) Glycol), alkylene glycols in which the alkylene group contains 2 to 6 carbon atoms (for example, ethylene glycol, propylene glycol, butylene glycol, triethylene) Recall, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol, diethylene glycol, etc.), alkyl ethers such as polyhydric alcohols (eg ethylene glycol methyl ether, ethylene glycol ethyl ether, triethylene monomethyl ether, triethylene) Glycol monoethyl ether and the like) and N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, glycerin and the like. The total amount of the water-soluble organic solvent in the ink is 2 to 60% by mass, and more preferably 5 to 25% by mass with respect to the total amount of the ink.

  The ink according to this aspect is suitably used in an ink jet recording method in which an image is recorded by ejecting ink from a recording head by thermal energy or mechanical energy and attaching the ink to a recording medium. When the ink according to this embodiment is particularly suitable for ink jet recording applications, it is preferable that the viscosity at the ink 25 ° C. is 15 cP or less, particularly 10 cP or less, and further 5 cP or less.

  Specific ink compositions that can achieve such characteristics include, for example, various inks used in Examples described later.

  In addition, you may add various additives, such as a pH adjuster and an antifungal agent, to the ink concerning this aspect.

  The recording medium used in the recording method using the ink according to the present embodiment is not particularly limited, and is a plain paper such as copy paper or bond paper, coated paper specially prepared for ink jet recording, or gloss. Examples thereof include paper and an OHP film.

  Hereinafter, although it demonstrates more concretely using an Example and a comparative example, this invention is not limited by the following Example, unless the summary is exceeded. In the following description, “part” and “%” are based on mass unless otherwise specified. In the following examples, the average particle diameter is a value measured using a dynamic light scattering method (trade name: ELS-800; manufactured by Otsuka Electronics Co., Ltd.).

(Examples 1-6 and Comparative Examples 1-4)
C-1 and C-2 prepared as follows were prepared as dispersions of carbon black.

(C-1)
First, styrene-ethyl methacrylate acrylate (acid value 350, weight average molecular weight 3000, aqueous solution having a solid content concentration of 20% by mass, neutralizer = potassium hydroxide) was used as a dispersant, and the materials shown below were batch-type sand mills ( Imex Co., Ltd.) was filled with 1 mm diameter glass beads as a medium, and dispersion treatment was performed for 3 hours while cooling with water.

・ Dispersant aqueous solution (20% by mass aqueous solution) 30 parts ・ Carbon black (trade name: Mogul L; manufactured by Cablack) 20 parts ・ Glycerin 10 parts ・ Water 40 parts of the carbon black thus obtained The average particle size of the dispersion was 0.1 micron and pH = 10.0.

(C-2)
As C-2, self-dispersing carbon black CAB-O-JET200 (solid content concentration 20% by mass, having a sulfone group as a surface functional group) manufactured by Cabot Corporation was used. The average particle size was 0.13 microns, pH = 7.

  An ink having the following composition was prepared using C-1 and C-2.

・ C-1 25.0 parts ・ 80% ethoxylated polyethyleneimine (Mw 2,000) 0.5 parts ・ Glycerin 10.0 parts ・ Water 64.5 parts Further, acetylenol EH (acetylene glycol-based surfactant manufactured by Kawaken Fine Chemicals) The surface tension was adjusted to 37.0.

・ C-1 25.0 parts ・ N, N-dimethylallylamine (Mw 1,500) 0.5 parts ・ Glycerin 10.0 parts ・ Water 64.5 parts In addition, acetylenol EH (acetylene glycol-based surfactant manufactured by Kawaken Fine Chemicals) The surface tension was adjusted to 37.0.

・ C-2 25.0 parts ・ 80% ethoxylated polyethyleneimine (Mw 2,000) 1.0 parts ・ Glycerin 10.0 parts ・ Water 64.0 parts Furthermore, acetylenol EH (acetylene glycol-based surfactant manufactured by Kawaken Fine Chemicals) The surface tension was adjusted to 37.0.

・ C-2 25.0 parts ・ N, N-dimethylallylamine (Mw 1,500) 1.5 parts ・ Glycerin 10.0 parts ・ Water 63.5 parts In addition, acetylenol EH (acetylene glycol-based surfactant manufactured by Kawaken Fine Chemicals) The surface tension was adjusted to 37.0.

<Comparative Example 1>
・ C-1 25.0 parts ・ N, N-dimethylallylamine (Mw 1,500) 0.5 parts ・ Glycerin 10.0 parts ・ Water 64.5 parts In addition, acetylenol EH (acetylene glycol-based surfactant manufactured by Kawaken Fine Chemicals) The surface tension was adjusted to 40.0.

<Comparative example 2>
-C-1 25.0 parts-80% ethoxylated polyethyleneimine (Mw 2,000) 1.0 parts-Glycerol 10.0 parts-Water 64.0 parts Furthermore, acetylenol EH (acetylene glycol type surface activity by Kawaken Fine Chemicals) The surface tension was adjusted to 32.0.

<Comparative Example 3>
・ C-2 25.0 parts ・ N, N-dimethylallylamine (Mw 1,500) 1.5 parts ・ Glycerin 10.0 parts ・ Water 63.5 parts In addition, acetylenol EH (acetylene glycol-based surfactant manufactured by Kawaken Fine Chemicals) The surface tension was adjusted to 40.0.

<Comparative example 4>
-C-2 25.0 parts-Glycerin 10.0 parts-Water 65.0 parts Furthermore, acetylenol EH (Acetylene glycol type surfactant made by Kawaken Fine Chemicals) was added, and the surface tension was adjusted to 37.0.

  For the black of the BJ cartridge BC-21 mounted on the color BJ printer (trade name: BJC-420J; manufactured by Canon Inc.) with the 10 ink examples 1 to 6 and Comparative Examples 1 to 4 thus completed. Fill the ink tank, set this cartridge in BJC-420J, and record paper (BJ-electrophotographic co-paper Canon PB paper; manufactured by Canon Inc.) in BJC-420J plain paper, 360 x 360 DPI, HQ mode ) Was printed.

(Evaluation)
Evaluation of printed matter was performed as follows.

(water resistant)
The same solid image for which the image density was evaluated is used and left for 12 hours after printing. Then, the printed matter is allowed to stand in tap water for 3 seconds, the reflection density after the water is dried is measured, and the residual ratio of the reflection density before and after the water resistance test is obtained and used as a measure of water resistance. . The evaluation results were classified as follows.

A: Image density remaining rate is 90% or more B: Image density remaining rate is 70% or more and less than 90% C: Image density remaining rate is less than 70% (image density)
The solid image was allowed to stand for 12 hours after printing, and then measured using a reflection densitometer Macbeth RD-918 (manufactured by Macbeth). The evaluation results were classified as follows.

A: Image density is 1.35 or more B: Image density is 1.2 to 1.34
C: Image density is less than 1.2 (feathering)
Ten minutes after printing the solid pattern, the boundary between the printed portion and the non-printed portion was observed. The evaluation results were classified as follows.

A: Feathering has not occurred B: Some feathering has occurred C: Feathering has occurred and the boundary is uneven (marker resistance)
Using a yellow fluorescent pen spot lighter yellow manufactured by Pilot Corporation, the character part was marked once with a normal writing pressure 1 hour after character printing, and the marker resistance was evaluated according to the following evaluation criteria.

A: No smudges or smudges on the white background are observed on the printed matter, and the pen tip is not smudged. B: Stain on the white background is not recognized on the printed matter, but the pen tip is slightly dirty. C: White on the printed matter. Part is dirty (Abrasion resistance)
After 4 hours from image printing, when the Sylbon paper is placed on the printed paper, and further, a weight of 1 cm on each side is placed on the printed paper, and then the sylbon paper is pulled, the non-printing portion of the recording paper ( It was visually observed whether or not stains were caused by rubbing the printed part on the white background) and the Sylbon paper.

A: No dirt on the white background and the Sylbon paper B: Only the Sylbon paper is dirty C: Both the white background and the Sylbon paper are dirty Evaluation results are shown in Table 1 below.

From Table 1 above, by using the ink according to the present invention, an inkjet ink having a sufficiently high image density on plain paper and sufficiently good water resistance, feathering characteristics, marker resistance characteristics, scratch resistance, and ejection stability can be obtained. I found out that In Comparative Examples 1 and 3 with a surface tension of 40 mN / m, the image density and feathering characteristics were good, but the marker resistance characteristics and scratch resistance were poor. In Comparative Example 2 with a surface tension of 32 mN / m, resistance was good. Although the marker characteristics and scratch resistance were good, the image density was low and the feathering characteristics were poor. In Comparative Example 4 containing no cationic polymer, satisfactory results were not obtained in image density, water resistance, feathering characteristics, marker resistance characteristics, and scratch resistance.

Claims (6)

  An ink for ink jet recording, comprising at least water, a pigment, and a cationic polymer, and having a surface tension of 33 mN / m or more and 39 mN / m or less.   The ink according to claim 1, wherein the pigment is carbon black.   The inkjet according to claim 1, wherein the pigment is a pigment dispersion dispersed with an anionic polymer or an anionic surfactant, or a self-dispersing pigment bonded to the pigment surface through an atomic group having an anionic group. Recording ink.   The ink for inkjet recording according to claim 1, wherein the cationic aqueous polymer has at least one structure selected from the group consisting of ethyleneimine, allylamine, diallylamine, and dimethylallylamine in the molecule.   An ink jet recording method for performing printing by ejecting ink droplets and attaching the droplets to a recording material, wherein the ink for ink jet recording according to claim 1 is used. A recorded matter recorded by the recording method according to claim 5.