JP2000086948A - Pigment ink for inkjet recording - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be used for an ink jet recording method using an ink jet recording head having a nozzle plate of a specific structure, to realize reliable ejection of ink droplets without flying deflection, and to correspond to a higher response frequency. Providing a possible ink composition. SOLUTION: An ink composition containing at least a pigment as a colorant and a phosphoric acid ester-based surfactant has a volume in a nozzle from the surface of a nozzle plate to a meniscus forming surface which is 0% with respect to the amount of ink to be ejected. An ink jet recording head comprising a nozzle plate, wherein a part of the ink-repellent coating layer covering the surface of the nozzle plate is inserted into the inner surface of the nozzle so as to be in the range of 0.05 to 0.50. Used in the ink jet recording method using

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink composition used in an ink jet recording method using an ink jet head having a nozzle plate having been subjected to an ink repellency treatment.

2. Description of the Related Art An ink jet recording method is a printing method in which small droplets of an ink composition fly and adhere to a recording medium such as paper to perform printing. This method has a feature that high-resolution and high-quality images can be printed at a high speed with a relatively inexpensive device. In general, an ink composition used for ink jet recording contains water as a main component, and further contains a coloring component and a wetting agent such as glycerin for the purpose of preventing clogging.

Further, a surfactant may be added to the ink composition for ink-jet recording in order to promote or suppress penetration into a recording medium and to realize a good image without bleeding or the like. Prior arts that have proposed the use of a phosphate ester surfactant as a surfactant include, for example, Japanese Patent Application Laid-Open No. 5-59314 discloses an aqueous liquid vehicle,
An ink composition having a short drying time in which a colorant and a phosphate are combined is proposed. In addition, Japanese Unexamined Patent Publication No.
107971 is a water-soluble solution, a pigment, a water-soluble resin, a surfactant containing water and a phosphate ester, a surfactant containing fluorine, a surfactant containing boron, or a polyoxyethylene alkyl ether or polyoxyethylene. We have proposed an aqueous pigment ink that satisfies printing quality by using a recording liquid containing a kenyl ether-based surfactant and does not cause liquid pooling around the ejection port.

On the other hand, the ink composition for ink jet recording has a property of realizing a good image without bleeding on a recording medium, and also ensures that the ink composition does not deviate from a predetermined flight direction from a nozzle of an ink jet recording head. Discharge is required. Ink is not ejected, or ink droplets are ejected with a deviation from a predetermined flight direction (hereinafter, such deviation of the ink droplets from a predetermined flight direction may be referred to as a flight deflection of the ink droplet).
In such a case, missing dots and a decrease in the sharpness of an image occur. In order to prevent such ink ejection failure and flight bending, various proposals have been made to adjust the types and amounts of the additional components of the ink composition. Further, some configurations of an ink jet recording head which is less likely to cause flight bending have also been proposed. Regarding the latter, for example, a proposal has been made to impart a property (ink repellency) that makes the nozzle plate hard to wet with ink, and to guarantee the ejection of the ink droplets reliably and without bending. For example, Japanese Unexamined Patent Publication No.
No. 107848 proposes that an ink-repellent film such as a fluororesin is uniformly formed on the inner surface of the nozzle and the surface of the nozzle plate by sputtering to suppress leakage of ink around the nozzle. Further, Japanese Unexamined Patent Application Publication No. 7-12
Japanese Patent Application Laid-Open No. 5220 proposes that an ink-repellent coating be provided on the inner surface of a nozzle in a predetermined amount in association with the ink amount of ink droplets.

[0005]

SUMMARY OF THE INVENTION The present inventors have recently disclosed in Japanese Patent Laid-Open No. 7-125.
By combining the nozzle plate described in Japanese Patent Publication No. 220 and a pigment-based ink composition containing at least a phosphate ester-based surfactant, poor ejection of ink droplets and flight bends are greatly suppressed, and a higher response frequency is achieved. We learned that we can respond. The present invention is based on this finding.

Accordingly, the present invention is used in an ink jet recording method using an ink jet recording head having a nozzle plate of a specific structure, realizes reliable ejection of ink droplets without flying deflection, and supports a high response frequency. The purpose is to provide an ink composition that can be used.

The ink composition for ink-jet recording according to the present invention is a pigment-based ink composition for ink-jet recording containing a pigment as a colorant, and comprises at least a phosphate-based surfactant. The void volume in the nozzle from the surface of the surface to the meniscus formation surface is 0.05 to 0.5 with respect to the amount of ink to be ejected.
Ink jet recording using an ink jet recording head having a nozzle plate, wherein a part of the ink-repellent coating layer covering the surface of the nozzle plate is inserted into the inner surface of the nozzle so as to fall within a range of 0. It is used for the method.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Nozzle plate The ink composition according to the present invention is disclosed in JP-A-7-125220.
JP-A No. 11-204,197, which is used for an ink-jet recording method using an ink-jet recording head provided with a nozzle plate. Its basic structure is as shown in FIG. The nozzle plate 1 has a substrate 2 on which a nozzle 3 is provided, and an ink-repellent coating layer 4 provided on an inner surface of the substrate 1 and the nozzle 3. The ink-repellent coating layer 4 is configured to penetrate to the position 5 on the inner surface of the nozzle 3. FIG. 2 is an enlarged view near the nozzle 3. When the ink composition is filled in the ink jet recording head provided with the nozzle plate having such a structure, the vibration surface of the meniscus of the ink composition causes the lower edge 5 of the ink-repellent coating layer 5 in the nozzle 3 of the ink-repellent coating layer 4 to move. It is formed in a tied form. The vibration center position A is as shown in FIG. Further, when the ink composition is ejected, the ink droplet is ejected in a form as shown by B in FIG. 2 and separates from the nozzle. After the ink ejection, the ink composition was changed to C in FIG.
Is temporarily retracted to the position indicated by, but will soon return to the meniscus vibration position A. In the plate described in this publication, the gap volume in the nozzle from the surface of the nozzle plate 1 to the vibration center A of the meniscus is Vm, and the volume from the surface 2 of the nozzle 4 to the front surface B of the ink immediately before ejection, that is, the ink droplet to be ejected The lower edge 5 of the ink-repellent coating layer is set so that the amount of
Is determined. According to a preferred embodiment, the ink-repellent coating layer is immersed in an electrolyte in which nickel ions and particles of a water-repellent polymer resin such as polytetrafluoroethylene are dispersed by electric charge, and the nozzle plate is stirred while the liquid is stirred. It is preferably formed by a method of forming a eutectoid plating layer on the surface of the first electrode. As the fluorine-based polymer material used in the eutectoid plating treatment, a resin such as polytetrafluoroethylene, polybarfluoroalkoxybutadiene, polyvinylidene, polyfluorovinyl, or polydiperfluoroalkyl fumarate alone or mixed. Things.

Ink Composition The ink composition according to the present invention contains at least a phosphate-based surfactant. By using an ink composition containing a phosphate ester-based surfactant in combination with an ink jet recording head having the above-described nozzle plate, it is possible to significantly suppress ink droplet ejection failure and flight bend, and in particular, The advantage is that the ejection stability under a high response frequency is excellent. This advantage is more remarkable when the composition contains substantially only a phosphate-based surfactant. According to a preferred embodiment of the present invention, the surface tension of the ink composition is 30 to 40 mN /.
m. The reason why the above advantages can be obtained by the present invention is not clear, but is considered as follows. In the aqueous pigment-dispersed ink composition,
Since the ink composition has thixotropic properties, ejection tends to be unstable. However, according to the ink composition containing the phosphate-based surfactant according to the present invention,
It is considered that the degree of vibration of the meniscus starting from the lower edge 5 inside the nozzle 3 in FIG. 2 becomes uniform, and stable ink ejection becomes possible. However, this is only an assumption, and the present invention is not limited to these.

According to a preferred embodiment of the present invention, preferred examples of the phosphate ester-based surfactant include the following formula (I)
Are represented.

[0011]

Embedded image (Wherein R ¹ , R ² and R ³ may be the same or different, and may be a hydroxyl group or a group RO- (CH ₂ CH ₂ O) n-
(Where R represents an alkyl group or an alkyl-substituted phenyl group), provided that all R ¹ , R ² and R ³ do not represent a hydroxyl group.

According to a preferred embodiment of the present invention, R is preferably a linear or branched C _8-30 alkyl group or a linear or branched C _8-30 alkyl-substituted phenyl group. More preferably, it is a branched C _8-30 alkyl group. According to another preferred embodiment of the present invention, R ¹ ,
It is preferable to use phosphate esters in which at least one or two of R ² and R ³ represent a hydroxyl group, that is, monoesters and diesters. However, the ink composition according to the present invention not only contains one kind of the compound of the formula (I) alone as a phosphate ester-based surfactant, but also contains a mixture of a plurality of the compounds represented by the formula (I). It can be.

As the phosphate ester surfactant represented by the formula (I), a commercially available product can be used, and specific examples thereof include Phosphanol series (manufactured by Toho Chemical Industry Co., Ltd.). And phosphanol RS-410, RS-610, RS-71, among others.
Use of 0 is preferred.

The amount of the phosphoric acid ester-based surfactant may be appropriately determined, but is preferably 0.01 to 10% based on the ink composition.
About 0.5% is preferable.

The ink composition according to the present invention comprises a pigment as a colorant. As the pigment, inorganic pigments and organic pigments can be used without any particular limitation. As the inorganic pigment, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, and a thermal method can be used. As the organic pigment, azo pigments (Azo Lake,
Including insoluble azo pigments, condensed azo pigments, chelated azo pigments, etc., polycyclic pigments (for example, phthalocyanine pigments,
Perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinoflurone pigments),
Dye chelates (eg, basic dye chelates, acid dye chelates, etc.), nitro pigments, nitroso pigments, aniline black, and the like can be used.

According to a preferred embodiment of the present invention, these pigments are preferably added to the ink as a pigment dispersion obtained by dispersing in an aqueous medium with a dispersant or a surfactant. As a preferred dispersant, a dispersant commonly used for preparing a pigment dispersion, for example, a polymer dispersant can be used.

The amount of the pigment to be added to the ink is 0.5-2.
It is preferably about 5% by weight, more preferably about 2 to 15% by weight.

Preferred examples of the polymer dispersant include natural polymers, and specific examples thereof include proteins such as glue, gelatin, casein and albumin, natural rubbers such as gum arabic and tragacanth, and savonin. Glucosides, alginic acid and alginic acid propylene glycol ester alginic acid triethanolamine, alginic acid derivatives such as ammonium alginate,
Examples include cellulose derivatives such as methylcellulose, carboxymethylcellulose, hydroxyethylcellulose, and ethylhydroxycellulose. Further, preferred examples of the polymer dispersant include a synthetic polymer,
Polyvinyl alcohols, polyvinylpyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer,
Acrylic resins such as vinyl acetate-acrylate copolymer, acrylic acid-acrylate copolymer,
Styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, styrene-α-methylstyrene-acrylic acid -Styrene-acrylic resin such as acrylate copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinylnaphthalene-acrylic acid copolymer, vinylnaphthalene-maleic acid copolymer, and Vinyl acetate-based copolymers such as vinyl acetate-ethylene copolymer, vinyl acetate-fatty acid vinyl ethylene copolymer, vinyl acetate-maleic acid ester copolymer, vinyl acetate-crotonic acid copolymer, and vinyl acetate-acrylic acid copolymer And copolymers and salts thereof. Among them, a copolymer of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and a polymer composed of a monomer having both a hydrophobic group and a hydrophilic group in a molecular structure are preferable.

The solvent of the ink composition according to the present invention preferably comprises water and a water-soluble organic solvent. The water-soluble organic solvent is preferably a low-boiling organic solvent, and examples thereof include methanol, ethanol, and n- Propyl alcohol, iso-propyl alcohol, n-butanol, s
ec-butanol, tert-butanol, iso-butanol, n-pentanol and the like. Particularly, a monohydric alcohol is preferable. Low-boiling organic solvents have the effect of shortening the drying time of the ink. The amount of the low boiling organic solvent added is preferably 0.5 to 10% by weight of the ink, more preferably 1.5 to 6% by weight.

According to a preferred embodiment of the present invention, the ink composition used in the present invention preferably further comprises a wetting agent comprising a high-boiling organic solvent. Preferred examples of the high-boiling organic solvent include ethylene glycol,
Diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, propylene glycol, butylene glycol, 1,2,6-
Polyhydric alcohols such as hexanetriol, thioglycol, hexylene glycol, glycerin, trimethylolethane, trimethylolpropane, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, Alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, urea, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2 -Imidazolidinones and the like.

The amount of the wetting agent added is 0.5% of the ink.
Preferably, it is in the range of 2 to 20% by weight.

The sugars that can be added to the ink composition according to the present invention include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, and the like. Ribose,
Xylose, arabinose, galactose, aldonic acid, glucitol, (sorbitol), maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like. Here, the polysaccharide means a sugar in a broad sense, and is used to include a substance widely existing in nature such as alginic acid, α-cyclodextrin, and cellulose. Derivatives of these saccharides are represented by reducing sugars of the above-mentioned saccharides (for example, sugar alcohols (general formula HOCH ₂ (CHOH) nCH ₂ OH, where n is an integer of 2 to 5). ), Oxidized sugars (eg, aldonic acid, uronic acid, etc.), amino acids, thiosugars, etc. Particularly preferred are sugar alcohols.
Specific examples include maltitol and sorbitol.

The content of these saccharides is 0.1 to 0.1% of the ink.
It is in the range of 40% by weight, more preferably 0.5 to 30% by weight.

The ink composition of the present invention can further contain a surfactant. Examples of surfactants include:
Anionic surfactants (for example, sodium dodecylbenzenesulfonate, sodium laurate, ammonium salts of polyoxyethylene alkyl ether sulfate, etc.), nonionic surfactants (for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl ester) , Polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, polyoxyethylene alkylamines, polyoxyethylene alkylamides, etc.) and acetylene glycols (olefin Y, and Surfynol 82, 104,
440, 465, and 485 (all Air Products
and Chemicals Inc.). These can be used alone or in combination of two or more.

In addition, if necessary, a pH adjuster, a preservative, a fungicide, a phosphorus-based antioxidant, and the like may be added.

The ink composition according to the present invention can be produced by dispersing and mixing the above components by an appropriate method. Preferably, first, the pigment, the polymer dispersant, and water are mixed with an appropriate dispersing machine (for example, a ball mill, a sand mill, an attritor, a roll mill, an agitator mill, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a jet mill, an ang mill). Then, a uniform pigment dispersion is prepared, and then water, a water-soluble organic solvent, sugar, a pH adjuster, a preservative, a fungicide and the like are added and sufficiently dissolved to prepare an ink solution. After sufficient stirring, filtration is performed to remove coarse particles and foreign substances that cause clogging, thereby obtaining a target ink composition.

[0027]

Example Ink 1 Carbon black MA7 3.5 wt% (Mitsubishi Chemical Corporation) Styrene-acrylic copolymer / ammonium salt 1.5 wt% (molecular weight 7000, resin component 38 wt%: dispersant) Liquid medium glycerin 10 wt % Phosphanol RS-610 0.2 wt% (Toho Chemical Industry Co., Ltd.) Proxel XL2 0.3 wt% (Preservative: ZENECA) Ion exchange water Residual ink 2 Carbon black MA7 3.5 wt% Styrene- Acrylic copolymer / ammonium salt 1.5 wt% (molecular weight 7000, resin component 38 wt%: dispersant) Liquid medium glycerin 10 wt% Phosphanol RS-410 0.05% (Toho Chemical Industry Co., Ltd.) Surfynol 465 0.5wt% triethylene glycol monobutyl ether 3wt% Proxel XL2 0.3 wt% (preservative: manufactured by ZENECA) Ion-exchanged water Residual ink 3 carbon black MA7 3.5 wt% (manufactured by Mitsubishi Chemical Corporation) Styrene-acrylic copolymer / ammonium salt 1.5 wt% ( Molecular weight 7000, resin component 38 wt%: dispersant) Liquid medium Glycerin 10 wt% Proxel XL2 0.3 wt% (preservative: manufactured by ZENECA) Ion-exchanged water The surface tension of the ink composition above the remaining amount printing evaluation test is as follows. Met. Surface tension tension (mN / m) Ink 1 33.0 Ink 2 32.0 Ink 3 43.2 Printing evaluation test The following evaluation 1 and evaluation 2 tests were performed by an inkjet printer MJ-930C (manufactured by Seiko Epson Corporation).
Was performed at a resolution of 720 dpi / dot and an ink ejection amount of 25 ng / dot. The nozzle plate of the recording head of this printer has the eutectoid plating layer as the ink-repellent coating layer, and the void volume in the nozzle from the surface of the nozzle plate to the meniscus forming surface is 0.4 with respect to the amount of ink to be ejected. Has a structure in which it enters the inner surface of the nozzle. The following six types of paper were used for evaluation.

Evaluation paper Xerox P (manufactured by Xerox Co., Ltd.) Riccopy 6200 (manufactured by Ricoh Co., Ltd.) Xerox 4024 3R 721 (manufactured by Xerox Co., Ltd.) Neenah Bond (manufactured by Kimberly-Clark Co., Ltd.) )) Yamayuri (manufactured by Honshu Paper Co., Ltd.) Evaluation 1: Print quality The above-mentioned recording paper was printed in alphabetical letters, and the presence or absence of print bleeding and whiskers was visually observed.
The results were evaluated according to the following criteria. A: Bleeding was observed on all papers, and hardly any beard was observed. B: Bleeding and beard were slightly recognized on some papers. C: Depending on the paper, bleeding and beard were observed. D: Bleeding and whiskers were observed on all papers. Evaluation 2: OD value Graphic printing was performed on all the recording papers described above, the optical density (OD value) of the solid portion was measured, and the average value of the OD values of the six papers was evaluated according to the following criteria. In addition, in the OD value measurement,
The reflection density was measured using Macbeth TR-927 manufactured by Macbeth. A: The average OD value is 1.20 or more. B: The average OD value is 1.10 or more and less than 1.20. C: Average OD value is 1.00 or more and less than 1.10. D: Average OD value is less than 1.00.

Evaluation 3: A nozzle plate having a frequency responsive plate thickness of 80 μm and a penetration amount of eutectoid plating into the inside of the nozzle of 5 μm was prepared, and these were mounted on an on-demand type ink jet printer employing a piezo drive system. 25 ng / d from a 30 μm diameter nozzle
An experiment in which ot ink droplets were fully discharged for 30 seconds at a response frequency of 15 kHz or 20 kHz was performed 100 times, and discharge failures and the like at that time were counted. The results were evaluated according to the following criteria. A: The number of ejection failure occurrences is less than 5 times. B: The number of ejection failure occurrences is 5 or more and less than 20 times. C: The number of ejection failure occurrences is 20 or more. The above results were as shown in the following table.

[0030] Evaluation 1 Evaluation 2 Evaluation 3 15 kHz 20 kHz Ink 1 A A A A Ink 2 A A A B Ink 3 A A B C

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a nozzle plate of an ink jet recording head using an ink composition according to the present invention.

FIG. 2 is an enlarged view of the nozzle plate of FIG.

[Description of Signs] 1 Nozzle plate 2 Substrate 3 Nozzle 4 Ink repellent coating layer 5 Lower edge of ink repellent coating layer in nozzle 3 A Ink meniscus vibration position surface

Claims (12)

[Claims] 1. A pigment-based ink jet recording ink composition comprising a pigment as a colorant, comprising at least a phosphoric acid ester-based surfactant, and a gap in a nozzle from a surface of a nozzle plate to a meniscus forming surface. A part of the ink-repellent coating layer covering the surface of the nozzle plate is inserted into the inner surface of the nozzle so that the volume is in the range of 0.05 to 0.50 with respect to the amount of ink to be ejected. An ink composition used in an ink-jet recording method using an ink-jet recording head having a nozzle plate. 2. The ink composition according to claim 1, wherein the phosphate ester-based surfactant is represented by the following formula (I). Embedded image (Wherein R ¹ , R ² and R ³ may be the same or different and each represents a hydroxyl group or a group RO- (CH ₂ CH ₂ O) n
-Where R represents an alkyl group or an alkyl-substituted phenyl group, provided that all R ¹ , R ² and R ³
Does not represent a hydroxyl group) 3. The ink composition according to claim 2, wherein R represents a linear or branched C _8-30 alkyl group or a linear or branched C _8-30 alkyl-substituted phenyl. 4. The ink composition according to claim 3, wherein R is a branched C _8-30 alkyl group. 5. The ink composition according to claim 2, wherein one or two of R ¹ , R ² , and R ³ represent a hydroxyl group. 6. The ink composition according to claim 2, wherein a plurality of the compounds represented by the formula (I) are mixed and contained as the phosphate-based surfactant. 7. The ink composition according to claim 1, comprising substantially only a phosphate ester surfactant as the surfactant. 8. The ink composition according to claim 1, wherein the surface tension is 30 to 40 mN / m. 9. The method according to claim 1, wherein the phosphate ester-based surfactant is used in an amount of 0.01%.
The ink composition according to any one of claims 1 to 8, comprising from 0.5 to 0.5%. 10. The ink composition according to claim 1, wherein said ink-repellent coating layer is formed by eutectoid plating. 11. An ink jet recording method in which droplets of an ink composition are ejected, and the droplets are attached to a recording medium to perform printing, wherein the ink composition is any one of claims 1 to 10. A method comprising using an ink-jet head provided with a nozzle plate having been subjected to an ink-repellent treatment using the ink composition as described above. 12. A recorded matter recorded by the recording method according to claim 11.