JP2005263967A - Ink composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an ink composition that actualizes excellent printing qualities on plain paper in an inkjet recording method, especially secures high print density and edge sharpness and has discharge stability and extremely slight printing unevenness. <P>SOLUTION: Inkjet recording is carried out by using an ink composition comprising at lesat self-dispersion type black pigment, a compound represented by formula (1) (EO is an ethyleneoxy group; PO is a propyleneoxy group; m is an integer of ≤3; n is an integer of ≤2) and a compound represented by formula (2) (EO is an ethyleneoxy group; PO is a propyleneoxy group; m is an integer of ≥4; n is an integer of ≥3). Preferably the ink composition further comprises 1,2-hexanediol. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides good print quality on plain paper, especially high O.D. D. The present invention relates to a black pigment ink composition suitable for ink jet recording which realizes an (optical density) value and edge sharpness, has very little printing unevenness, and further ensures ejection stability.

  Inkjet recording is a method of recording characters and figures on the surface of a recording medium by ejecting ink as small droplets from fine nozzles. Further, there is still a demand for realizing high print quality on plain paper that is inexpensive and widely spread.

  In general, inks in which various water-soluble dyes are dissolved in an aqueous medium are used. It has been generally pointed out that an image formed with an ink containing such a water-soluble dye is inferior in water resistance and light resistance. An ink in which a pigment is dispersed in an aqueous medium is also provided. A pigment-based ink in which a pigment is dispersed in an aqueous medium has a feature of being excellent in water resistance and light resistance as compared with a water-soluble dye. For example, an aqueous pigment ink in which carbon black is dispersed with a surfactant or a polymer dispersant has been proposed. However, in these inks, when the ink content of the colorant is increased in order to increase the print density of the recorded matter, the ink viscosity may increase abruptly with the increase. In addition, in order to stably disperse carbon black in the ink, an excessive surfactant or polymer dispersant is required, which may cause deterioration in printing stability due to foaming or defoaming deterioration. there were. In order to solve these problems, a certain amount or more of surface active hydrogen or a salt thereof is introduced to the surface of carbon black, and carbon black alone is an aqueous solvent without a dispersant such as a surfactant or a polymer dispersant. Disclosed are surface-modified carbon black dispersions that can be dispersed in water and methods for introducing sulfonic acid groups into the carbon black surface (see, for example, Patent Documents 1 to 3). Furthermore, an inkjet ink containing the above-described surface-modified carbon black and glycol ethers has been proposed (see, for example, Patent Document 4). A so-called self-dispersing pigment that does not require a dispersant as described above is used in an ink as a colorant. D. Various developments have been made due to features such as a high (optical density) value and easy adjustment of the viscosity in the ink to an appropriate range. A hydrophilic functional group such as a carbonyl group, a carboxyl group, a hydroxyl group, a sulfone group, or an ammonium group is bonded to the surface directly or indirectly through an alkyl group, an aryl group, or the like.

  However, since self-dispersing pigments have a functional group exposed on the surface, the print quality, particularly O.D. D. The (optical density) value and edge sharpness are easily affected by additives such as surfactants and solvents. In particular, when a self-dispersing pigment is used, the line width is difficult to increase in print quality, and an image with a noticeable streak is likely to occur. D. The (optical density) value decreases, and the edge sharpness is often noticeable. In addition, when the concentration of the pigment contained in the ink is high, the influence is still great, including reliability aspects such as ejection stability.

  Thus, silicon-based and acetylene glycol-based surfactants, glycol ethers, and diol-based solvents are known as additives. Several ink compositions containing these additives are also known. For example, an ink composition for inkjet recording comprising a modified polysiloxane having a specific structure (for example, see Patent Documents 5 and 6), and a dye-based ink composition comprising a diol solvent (for example, see Patent Document 7) It has been known.

  However, not all compounds of the same system are effective, and they are greatly affected by the compatibility with pigment dispersions, especially self-dispersing types, and are effective including reliability such as print quality and ejection stability. It was difficult to select and combine certain additives. In particular, the above-mentioned various surfactants have been studied to widen the line width in terms of print quality. However, effective substances are generally not soluble in aqueous systems, and therefore there are significant problems in terms of reliability such as ejection stability. It was difficult to use.

JP-A-8-3498 JP-A-10-120958 Japanese Patent Laid-Open No. 10-110127 Japanese Patent Laid-Open No. 10-95941 JP-A-5-169790 Japanese Patent Laid-Open No. 10-310732 Japanese Patent Laid-Open No. 10-279871

  The present invention has been made in view of the above problems, and in the ink jet recording method, it is possible to realize good print quality on plain paper, particularly high O.D. D. An object of the present invention is to provide a black pigment ink composition suitable for ink jet recording which realizes a high value and edge sharpness, has very little printing unevenness, and further ensures reliability such as ejection stability.

  According to the ink composition comprising at least two types of silicon surfactants having a specific structure for the self-dispersing pigment ink composition, the present inventor achieves good print quality in ink jet recording, that is, high O . D. The value (optical density) and edge sharpness were realized, printing unevenness was extremely small, and high reliability was ensured for printing stability.

  The ink composition according to the present invention comprises a self-dispersing black pigment and at least a compound represented by the following formula (1) and the following formula (2).

  The ink composition of the present invention further comprises 1,2-hexanediol.

  According to the present invention, good print quality, particularly high O.D. D. Value and edge sharpness are obtained, reliability such as ejection stability is ensured, and a suitable black pigment ink composition with very little printing unevenness is obtained.

  The ink composition according to the present invention is used in a recording system using the ink composition.

  In particular, the ink composition according to the present invention is preferably used in an ink jet recording method.

  The aqueous ink composition of the present invention comprises at least an aqueous medium, a self-dispersing pigment that can be dispersed and / or dissolved in water without a dispersant, a compound represented by formula (1), and formula (2). The compound represented by these.

  The ink composition of the present invention further comprises 1,2-hexanediol.

  Hereinafter, each component will be described in detail.

  The ink composition according to the present invention comprises a self-dispersing pigment that can be dispersed and / or dissolved in water without a dispersant.

  The self-dispersing pigment that can be dispersed and / or dissolved in water without a dispersant in the present invention is contained in the aqueous ink composition as a colorant, and has a large number of hydrophilic functional groups and / or on the pigment surface. Or a salt thereof (hereinafter also referred to as “dispersibility-imparting group”) directly or indirectly bonded through an alkyl group, an alkyl ether group, an aryl group, or the like, and an aqueous medium without a dispersant. A pigment that can be dispersed and / or dissolved therein. Here, “dispersed and / or dissolved in an aqueous medium without a dispersant” means that the pigment is stably present at the minimum particle size that can be dispersed in an aqueous medium without using a dispersant as described above. State. Here, the “minimum particle size that can be dispersed” refers to the particle size of the pigment that does not become smaller even if the dispersion time is increased.

The ink containing the self-dispersing pigment as a coloring material does not need to contain the above-described dispersant to be contained in order to disperse a normal pigment. It is easy to adjust ink that has almost no discharge stability. Further, since a significant increase in viscosity due to the dispersant can be suppressed, it is possible to contain more pigment, and the printing density can be sufficiently increased.
Examples of the dispersibility-imparting group bonded to the surface of the self-dispersing pigment include a carboxyl group, a carbonyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, a quaternary ammonium, and salts thereof. Carbon black can be used as a pigment as a raw material for the self-dispersing pigment.

  The self-dispersing pigment is obtained by, for example, bonding (grafting) the dispersibility-imparting group or the active species having the dispersibility-imparting group to the surface of the pigment by performing physical treatment or chemical treatment on the pigment. Manufactured. Examples of the physical treatment include vacuum plasma treatment. Examples of the chemical treatment include a wet oxidation method in which the pigment surface is oxidized with an oxidizing agent in water, and a method in which a carboxyl group is bonded via a phenyl group by bonding p-aminobenzoic acid to the pigment surface. It can be illustrated.

Commercially available products can also be used as the self-dispersing pigment, such as Microjet CW-1 (trade name; manufactured by Orient Chemical Industry Co., Ltd.), CAB-O-JET200, CAB-O-JET300 (and above). (Trade name; manufactured by Cabot Corporation).
The self-dispersing pigment preferably has an average particle size in the range of 1 to 300 nm, more preferably in the range of 10 to 200 nm, from the viewpoints of ink storage stability and prevention of nozzle clogging. .

  The self-dispersing pigment is preferably contained in the ink of the present invention in the range of about 1 to 30% by weight, more preferably in the range of about 1 to 15% by weight. If the content is less than 1% by weight, the print density may be insufficient, and if it is more than 30% by weight, the ink viscosity may increase, and problems such as nozzle clogging may occur.

  The ink composition according to the present invention comprises the compound of the above formula (1).

  In the formula (1), EO represents an ethyleneoxy group, PO represents a propyleneoxy group, m represents an integer of 3 or less, and n represents an integer of 2 or less. Preferably m + n is 1-4.

  The amount of the compound of formula (1) may be appropriately determined, but is preferably in the range of about 0.03 to 1% by weight, more preferably in the range of about 0.05 to 0.5% by weight.

  The compound of formula (1) is commercially available and can be used. For example, a silicon surfactant BYK-347 and the like can be used from Big Chemie Japan Co., Ltd.

  The ink composition according to the present invention comprises the compound of the above formula (2).

  In the formula (2), EO represents an ethyleneoxy group, PO represents a propyleneoxy group, m represents an integer of 4 or more, and n represents an integer of 3 or more. Preferably m + n is 7-15. The amount of the compound of formula (2) may be appropriately determined, but is preferably in the range of about 0.05 to 2% by weight, more preferably in the range of about 0.1 to 1% by weight with respect to the ink composition. is there.

  The compound of formula (2) is commercially available and can be used. For example, silicon surfactants BYK-345, BYK-348, etc. can be used from Big Chemie Japan Co., Ltd.

  According to a preferred embodiment of the present invention, the ink composition according to the present invention preferably further comprises 1,2-hexanediol. The amount of 1,2-hexanediol added may be appropriately determined, but is preferably about 0.5 to 10% by weight, more preferably about 1 to 5% by weight.

  Regarding the compound represented by the additive formula (1), the compound represented by the formula (2), and 1,2-hexanediol, if the addition amount is too small, the improvement effect on the printing quality does not appear, and the amount is too large. Therefore, the addition amount is a preferable addition range.

  In the ink composition of the present invention, the water can be pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water. In addition, the use of water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be prevented when the ink composition is stored for a long period of time.

  The water-soluble organic solvent that can be used in the present invention is preferably a low-boiling organic solvent, and examples thereof include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, and sec-butanol. , Tert-butanol, iso-butanol, n-pentanol and the like. A monohydric alcohol is particularly preferable. The low boiling point organic solvent has an effect of shortening the drying time of the ink. The amount of the low-boiling organic solvent added is preferably in the range of about 5% by weight or less, more preferably in the range of about 2% by weight or less with respect to the ink composition.

  According to a preferred embodiment of the present invention, the ink composition according to the present invention preferably further comprises a wetting agent comprising a high boiling point organic solvent. Preferred examples of the high boiling point organic solvent include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin, triglyceride, And polyhydric alcohols such as methylolethane and trimethylolpropane, urea, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and the like. It can be used as a mixture. Among these, glycerin, 2-pyrrolidone, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, and urea are preferable. These addition amounts are preferably in the range of about 1 to 20% by weight, more preferably in the range of about 5 to 10% by weight with respect to the ink composition.

  According to a preferred embodiment of the present invention, the ink composition according to the present invention comprises a penetrant. Preferable specific examples of the penetrant include glycol ethers.

  Specific examples of glycol ethers used in the present invention include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n- Propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-n-butyl ether, triethylene glycol mono-n- Butyl ether, diethylene glycol mono-t- Chill ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol Mono-n-butyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-iso-propyl ether and the like, It can be used as a mixture of two or more. Among these, triethylene glycol mono-n-butyl ether is particularly preferable. The amount of glycol ether added is preferably in the range of 1 to 20% by weight, more preferably in the range of 2 to 15% by weight, based on the ink composition.

  The ink composition according to the present invention may further contain a nozzle clogging preventive agent, an antiseptic, an antioxidant, a conductivity adjusting agent, a pH adjusting agent, a viscosity adjusting agent, a surface tension adjusting agent, an oxygen absorber, and the like. it can.

  Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzthiazoline-3-one ( ICI's Proxel CRL, Proxel BND, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

  Furthermore, examples of pH adjusters, solubilizers or antioxidants include amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, potassium hydroxide, sodium hydroxide, lithium hydroxide. Inorganic salts such as ammonium hydroxide, quaternary ammonium hydroxide (such as tetramethylammonium), carbonates such as potassium carbonate, sodium carbonate, lithium carbonate, and other phosphates, or N-methyl-2-pyrrolidone, urea, Examples include L-ascorbic acid and salts thereof, such as ureas such as thiourea and tetramethylurea, allophanates such as allophanate and methylallohanate, and biurets such as biuret, dimethylbiuret and tetramethylbiuret.

  In addition, the ink composition according to the present invention may contain an antioxidant and an ultraviolet absorber. 153, Irganox 1010, 1076, 1035, MD1024, lanthanide oxide, and the like.

  The aqueous ink composition of the present invention can be prepared in the same manner as conventional inks using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, or a roll mill. In the adjustment, it is preferable to remove coarse particles from the viewpoint of preventing nozzle clogging. The coarse particles are removed by, for example, filtering the ink obtained by mixing the above components using a filter such as a membrane filter or a mesh filter, and removing particles of preferably 10 μm or more, more preferably 5 μm or more. Done.

<Example>
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In addition, the numerical value in a table | surface shows weight%.

(1) Preparation of Pigment Dispersion Color Black S170 (trade name: manufactured by Degussa Huls), which is a commercially available acidic carbon black, was mixed with 1 kg of water and pulverized with a ball mill using zirconia beads. 1400 g of sodium hypochlorite (effective chlorine concentration 12%) was added dropwise to this pulverized stock solution, reacted for 5 hours while pulverizing with a ball mill, and further boiled for 4 hours with stirring to perform wet oxidation. The obtained dispersion stock solution was filtered through glass fiber filter paper GA-100 (trade name: manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake was redispersed in 5 kg of water, desalted and purified with a reverse osmosis membrane until the conductivity reached 2 mS / cm, and further concentrated until the pigment concentration became 15% by weight. It was adjusted.

(2) Preparation of ink composition The obtained dispersion and the components shown in Table 1 below were mixed and stirred at 25 ° C for 60 minutes. The mixed solution was filtered through a 5 μm membrane filter to obtain ink compositions of Examples 1 to 4 and Comparative Example 1.

  BYK347 (manufactured by Big Chemie Japan) is a compound included in the formula (1). BYK348 (manufactured by Big Chemie Japan) is a compound included in the formula (2).

  The compositions of Examples 1 to 4 and Comparative Example 1 are summarized in Table 1.

(3) Evaluation test About each ink composition of this invention, it filled in inkjet printer EM930C (made by Seiko Epson Corporation), the following evaluation tests were done, and the result obtained is shown in Table 2.

<Evaluation 1: Printing unevenness>
As a recording medium, characters and solid printing were performed in a plain paper-clean mode on three types of papers of Xerox 4024 (Xerox), Xerox P (Xerox), and Hanmer Mill Copy Plus (Hanmer Mill). The print density of the printed part D. Ten points were randomly measured with a value measuring instrument (SPM-50, manufactured by GRETAG), and the result was determined according to the following criteria.
Determination A: The difference in OD values of 10 points is less than 0.05.
Determination B: The difference in 10-point OD value is 0.05 or more and less than 0.1.

<Evaluation 2: Edge sharpness>
The printed matter obtained in Evaluation 1 was visually observed, and bleeding was evaluated according to the following criteria.
Judgment A: No bleeding occurred on all sheets.
Determination B: Slight bleeding occurred only on at least one type of paper.

<Evaluation 3: Print density (OD value)>
After leaving the three types of printed matter obtained in Evaluation 1 for 1 hour in a general environment, the print density of the solid print portion was determined as O.D. D. It measured with the value measuring device (The product made by GRETAG, SPM-50). The result was determined according to the following criteria.
Determination A: O.I. D. When the value is 1.3 or more Determination B: O.I. D. When the value is 1.2 or more and less than 1.3

<Evaluation 4: Continuous printing stability>
Continuous printing was performed at room temperature (25 ° C.), and the presence or absence of printing defects such as missing dots and ink scattering was observed. The results were evaluated according to the following criteria.
Judgment A: The occurrence of missing dots or ink scattering is 10 times or less after 72 hours.
Determination B: Within 48 to 72 hours, dot missing or ink scattering occurred 10 times.

  The test results of Examples 1 to 4 and Comparative Example 1 are summarized in Table 2.

  As shown in Table 2, the inks of Examples 1 to 6 of the present invention have good print quality on plain paper, particularly high O.D. D. Value and edge sharpness are obtained, and further, it is possible to provide a suitable black pigment ink composition that ensures ejection stability and has very little printing unevenness.

The aqueous ink composition of the present invention has high printing quality and high ejection stability, and is particularly suitable for use as an ink for inkjet recording.

Claims (5)

An ink composition comprising at least a self-dispersing black pigment, a compound represented by the following formula (1), a compound represented by the following formula (2), and water.

  The ink composition according to claim 1, further comprising 1,2-hexanediol.   The ink composition according to claim 1, comprising 0.03 to 1% by weight of the compound of the formula (1).   The ink composition according to any one of claims 1 to 3, comprising 0.05 to 2% by weight of the compound of the formula (2). The ink composition according to any one of claims 2 to 4, comprising 0.5 to 10% by weight of the 1,2-hexanediol.