JP5810673B2 - Liquid ejection head and image forming apparatus - Google Patents

Description

The present invention relates to an image forming apparatus using the liquid ejection heads及 beauty liquid discharge head.

An inkjet head used in an inkjet recording apparatus used as an image recording apparatus (image forming apparatus) such as a printer, a facsimile, a copying apparatus, or a plotter has a nozzle for ejecting ink droplets and a liquid chamber (pressurization chamber, Discharge chamber, pressure chamber, pressurized liquid chamber, etc.) and pressure generating means (driving means or energy generating means) for pressurizing ink in the liquid chamber, and by driving the pressure generating means, The ink is pressurized and ink droplets are ejected from the nozzles.
Conventionally, as an ink jet head, a diaphragm that forms a wall surface of a liquid chamber is deformed using a piezoelectric element to discharge ink droplets (see Patent Document 1), and ink is generated in a liquid chamber using a heating resistor. Ink droplets are ejected at a pressure generated by generating bubbles by heating bubbles (see Patent Document 2), and a diaphragm and an electrode forming a wall surface of a liquid chamber are arranged in parallel, and the diaphragm and the electrode There are known ones in which ink droplets are ejected by deforming a diaphragm by an electrostatic force generated between them (see Patent Document 3, etc.).

By the way, the ink jet head has a liquid chamber, a fluid resistance portion for supplying ink to the liquid chamber, a common ink liquid chamber for supplying the liquid chamber via the fluid resistance portion, a nozzle hole or a nozzle for discharging ink droplets. Various flow paths such as grooves need to be formed. For example, a head is formed by joining a flow path substrate (liquid chamber substrate) for forming a flow path such as a liquid chamber and a member such as a nozzle plate having nozzles. Is done.
Conventionally, the members constituting the inkjet head are generally joined using a wet adhesive or a film adhesive, but in addition to this, a silicon substrate is used as a liquid chamber substrate or a nozzle plate For example, direct bonding, eutectic bonding via a metal material, and anodic bonding when a metal material is used are also performed.

In the ink jet head, the end portion of the bonded portion is exposed to ink, and ink discharge pressure is applied between the members. These discharge cycles are several kHz and are subject to high-frequency pressure fluctuations, so that the deterioration of the bonded portion is likely to proceed. Therefore, liquid resistance is required rather than general adhesion.
By the way, when joining two members generally, there exists a request | requirement that components precision must be maintained and highly reliable joining must be implement | achieved. However, in ink jet heads, there are many parts that are in contact with ink, and this contact with ink deteriorates the bonding agent itself or permeates the bonding interface and causes peeling. Will cause major problems.
For this reason, it is desired that the adhesive be resistant to ink and have sufficient bonding strength with minimal penetration permeation to the bonding interface. However, there is no effective adhesive for all inks. In addition, it was extremely difficult to select a low-degradation adhesive for a specific ink.

In recent years, household ink jet printers and industrial ink jet plotters have become widespread, and the opportunity to eject water-based inks and oil-based inks has increased. Adhesives corresponding to these inks have also been found.
Recently, however, inks for curling in printing on paper media and inks for printing on non-absorbent film media have been developed, and have different characteristics from conventional water-based inks and oil-based inks. That is, as shown in Patent Document 4, the curl suppression ink has a composition in which the moisture in the ink is suppressed and the solvent is increased, and the water characteristic is not as strong as the conventional water-based ink, but the water-soluble organic matter. The ink has a stronger solvent characteristic. Further, the printing ink on the non-absorbing film medium as shown in Patent Document 5 is an ink using a highly soluble solvent such as methyl pyrrolidone, and is more organic. Aggressiveness is high.
Although these inks are inks with water, the characteristics of the organic solvent are strong, so that the penetrability into the organic structure is increased as compared with the conventional water-based inks. For this reason, if the adhesive used for water-based ink is used, the ink can easily penetrate into the adhesive, and the moisture permeates into the interface, so that the adhesive surface is hydrophilic like metal or oxide film. However, there is a problem that the adhesive strength is significantly reduced.

The present invention is resistant to a liquid such as an ink using a water-soluble organic solvent including an amide-based water-soluble organic solvent, and does not cause a problem such as a decrease in adhesive strength in joining the nozzle plate and the flow path plate. liquid ejecting heads, and to provide an image forming apparatus having a liquid discharge head and an object.

（上記式中、Ｒは炭素数１〜４のアルキル基を表す。）

３） １）又は２）に記載の液体吐出ヘッドを備えたことを特徴とする画像形成装置。 The above-described problems are solved by the following inventions 1) to 3 ).
1) A liquid discharge head in which a nozzle plate on which a discharge port for discharging droplets is formed is joined to a flow path plate on which a liquid chamber communicated with the discharge port is formed, wherein the nozzle plate and the flow path plate are Bonded with a fluorine-based epoxy adhesive, and a cured product of the fluorine-based epoxy adhesive and an ink containing 20 to 60% by weight of an amide-based water-soluble organic solvent, water, a colorant, and a surfactant A liquid discharge head having a contact angle of 60 ° or more.
2) The amide water-soluble organic solvent is at least one selected from N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and a compound represented by the following general formula (1). The liquid discharge head according to 1), wherein

(In the above formula, R represents an alkyl group having 1 to 4 carbon atoms.)

3 ) An image forming apparatus comprising the liquid discharge head according to 1) or 2).

According to the present invention, it is resistant to liquids such as ink using a water-soluble organic solvent including an amide-based water-soluble organic solvent, and there is a problem such as a decrease in adhesive strength in joining the nozzle plate and the channel plate. It caused no liquid discharge heads, and can provide an image forming apparatus having a liquid ejection head.

FIG. 3 is a partial cross-sectional view in the liquid chamber longitudinal direction showing an example of the configuration of the liquid discharge head. FIG. 6 is a partial cross-sectional view in the liquid chamber short direction (nozzle arrangement direction) showing an example of the configuration of the liquid discharge head. FIG. 3 is an explanatory perspective view illustrating an example of an image forming apparatus (inkjet recording apparatus) on which a liquid discharge head is mounted. Side surface explanatory drawing of the mechanism part of an image forming apparatus (inkjet recording device).

Hereinafter, the present invention will be described in detail.
<About adhesives>
The hydrophilic organic solvent and moisture, which are ink components, penetrate into the adhesive and the bonding interface, thereby promoting peeling and reducing the adhesive strength. Therefore, it is important to suppress ink penetration into the adhesive. In order to suppress ink penetration, it is necessary to suppress the swelling of the adhesive by increasing the density of the adhesive from the structural surface after curing, and from a chemical aspect, the material composition is difficult to cross ink and prevents penetration. It will be necessary.
The epoxy adhesive is characterized in that a plurality of epoxy groups are bonded by performing three-dimensional crosslinking, so that the crosslinking density is higher than other adhesives and is difficult to swell. Therefore, it is an effective adhesive for conventional water-based inks. However, inks with a large amount of hydrophilic organic solvent such as curling suppression ink and non-absorbing film medium ink cannot suppress a decrease in adhesive strength only with a conventional epoxy adhesive.
However, when a fluorine-based component is added to the epoxy adhesive, it is possible to suppress the penetration of the ink into the adhesive, and it is possible to prevent the adhesive from swelling. Therefore, since it is possible to suppress a decrease in adhesive strength, it is possible to produce an adhesive having resistance to an ink with a large amount of a hydrophilic organic solvent and an ink to which a highly soluble solvent that has not been conventionally used can be added.

In the present invention, when a liquid discharge head is manufactured by bonding a nozzle plate having a discharge port for discharging droplets to a flow path plate having a liquid chamber communicating with the discharge port, a fluorine-based material used for bonding is used. Fluorine epoxy adhesive having a contact angle of 60 ° or more between a cured product of the epoxy adhesive and an ink containing 20 to 60% by weight of an amide water-soluble organic solvent, water, a colorant, and a surfactant. An agent is selected and used. It should be noted that since the fluorine-based epoxy adhesive is not good in applicability, it seems that it has not actually been used in the production of a liquid discharge head, but in the present invention, it is an optimal adhesive in relation to ink.
If the contact angle with the ink having the above composition is 60 ° or more, problems such as a decrease in adhesive strength do not occur at the joint between the nozzle plate and the flow path plate. The penetration of the ink component into the adhesive can be suppressed by reducing the affinity between the ink and the adhesive. When the affinity is high, the contact angle between the ink and the adhesive is low, and when the affinity is low, the contact angle is high. If the contact angle is less than 60 °, the affinity between the ink and the adhesive becomes too high, the ink component penetrates into the adhesive, and the adhesive resin portion is softened, so that the adhesive strength cannot be maintained. Further, the penetrated ink corrodes the interface between the adhesive and the substrate, and the strength cannot be maintained. Therefore, the contact angle needs to be 60 ° or more so that the ink does not penetrate into the adhesive.

The fluorine-based compound that can be used in the epoxy adhesive satisfying the above physical properties preferably has a functional group involved in the reaction in the curing reaction of the epoxy adhesive, and more preferably the following epoxy group Fluorine compounds having
1,2-epoxy-1H, 1H, 2H, 3H, 3H-heptadecafluoroundecane, hexafluoroepoxypropane, 3-perfluorobutyl-1,2-epoxypropane, 3-perfluorohexyl-1,2-epoxy Propane, 3- (2,2,3,3-tetrafluoroepoxy) -1,2-epoxypropane, 3- (1H, 1H, 5H-octafluoropentyloxy) -1,2-epoxypropane, 3- ( 1H, 1H, 7H-dodecafluoroheptyloxy) -1,2-epoxypropane, 1,4-bis (2 ′, 3′-epoxypropyl) -perfluoro-n-butane, 1,6-bis (2 ', 3'-epoxypropyl) -perfluoro-n-hexane, bisphenol hexafluoroacetone diglycidyl ether, 1,3-bis (he Such Safuruoro -2-hydroxy-2-propyl) benzene diglycidyl ether.

In addition, it is possible to derive a compound having an epoxy group from a fluorine compound having active hydrogen even if it is not provided with an epoxy group. For example, a reaction between a fluorine compound having a hydroxyl group or an amino group and epichlorohydrin. Things. When equimolar epichlorohydrin is reacted with a hydroxyl group, a monomolecular epoxy group-containing compound is obtained as a main product, and when it is less than equimolar, intermolecular crosslinking proceeds and an oligomer or polymer is obtained.
As fluorine compounds used in these reactions, those having a plurality of hydroxyl groups and amino groups tend to have a large molecular weight when used as an epoxy resin, become harder due to three-dimensional crosslinking, and are swollen by a solvent. This makes it an adhesive with high ink resistance.

Next, specific examples of the fluorine compound having a hydroxyl group or an amino group are shown, but the invention is not limited thereto.
<One with one hydroxyl group)
1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,2-trifluoroethanol, 4,4,4-trifluoro-1-butanol, 4,4,5,5,5 -Pentafluoro-1-pentanol, 2- (perfluorohexyl) ethanol, 3- (2-perfluorohexylethoxy) -1,2-dihydroxypropane, 2,2,3,3,4,4,5,5 , 6,6,7,7,8,8,8-pentadecafluoro-1-octanol, 2,2-bis (trifluoromethyl) propanol, 1H, 1H, 3H-hexafluorobutanol, 2H-hexafluoro- 2-propanol, 1H, 1H, 7H-dodecafluorohexanol, 1H, 1H, 3H-tetrafluoropropanol, 6- (perfluoro-1-methoxyethyl) hexano 1H, 1H-2,5-di (trifluoromethyl) -3,6-dioxaundecafluorononanol, 6- (perfluorohexyl) hexanol, 3- (perfluorohexyl) propanol, 2- ( Perfluorohexyl) ethanol, 2-perfluoropropoxy-2,3,3,3-tetrafluoropropanol, 6- (perfluorobutyl) hexanol, 3- (perfluorobutyl) propanol, 2- (perfluorobutyl) ethanol 1H, 1H-heptafluorobutanol, 6- (perfluoroethyl) hexanol, 1H, 1H-pentafluoropropanol, 1H, 1H-trifluoroethanol and the like.

<Three hydroxyl groups: diol>
2-hydroxy-2-phenyl-hexafluoropropane, 1,3-bis (hexafluoro-2-hydroxy-2-propyl) benzene, 1,4-bis (hexafluoro-2-hydroxy-2-propyl) benzene, 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoro-1,8-octanediol, 2,2,3,3,4,4,5,5- Octafluoro-1,6-hexanediol and the like.

<Those with one amino group)
p-fluoroaniline, 3,4-difluoroaniline, 1H, 1H-heptafluorobutylamine, 1H, 1H-tridecafluoroheptylamine and the like.

<Multifunctional>
5-trifluoromethyluracil, 2,2-bis (3,4-dimethylphenyl) hexafluoropropane, 2,2-bis (4-hydroxyphenyl) hexafluoropropane, 2,2-bis [4- (4- Aminophenoxy) phenyl] hexafluoropropane, 2,2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 2,2 -Bis (4-aminophenyl) hexafluoropropane, 2,2'-bis (trifluoromethyl) benzidine and the like.
Moreover, it is also possible to use the fluororesin oligomer which has a functional group, and it can introduce and use an epoxy group using the same reaction. Examples of such oligomers include Polyfox PF-636, PF-6320, PF-656, and PF-6520 manufactured by OMNOVA.

The above fluorine compounds can be purchased from Dupont, Daikin, Asahi Glass, Central Glass, OMNOVA, Tosoh F-Tech, Unimatec, and Mitsubishi Materials Electronic Chemicals.
Among the above fluorine compounds, bisphenol hexafluoroacetone diglycidyl ether is desirable because it is excellent in the miscibility of the epoxy adhesive and exhibits an effect without impairing the function as an adhesive.
The addition amount of the fluorine compound is preferably 18 to 50% by weight, more preferably 20 to 40% by weight, based on the epoxy adhesive cured product. If the fluorine atom exceeds 50% by weight, the fluorine atom is oriented at the adhesion interface, so that the adhesive strength of the adhesive to the adhesion interface is reduced and the adhesion strength is reduced. Therefore, a large amount of coupling agent is required to increase the interfacial strength. On the other hand, if the amount is less than 18% by weight, the ink repellency of the adhesive is lowered, ink penetration into the adhesive occurs, and the adhesive strength is lowered.

In order to increase the adhesive strength, it is effective to cause the anchor agent to act on the adhesive interface and firmly fix the adhesive and the member by ionic bond or covalent bond. When the adhesive member is a metal, the oil-based ink is firmly fixed by hydrogen bonding, but in the case of the water-based ink, the hydrogen bond is cut by water that has penetrated the bonding interface, so that the adhesive strength is significantly reduced. Therefore, it is desirable to have a covalent bond between the adhesive and the member.
In order to bond a metal and an epoxy adhesive by a covalent bond, it is effective to use a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent. As the method, the surface of the metal member to be bonded may be directly treated with a coupling agent, or after the surface treatment for improving the binding property with the coupling agent is performed, the coupling agent treatment may be performed. Thus, a strong bond can be obtained.
As the surface treatment to be performed before the coupling treatment, SiO ₂ or SiC sputtering treatment is very effective for the silane coupling agent, and the TiO ₂ or TiN treatment is not only a titanate coupling agent. It is also effective for silane coupling agents. Since these pretreatments are thick, the strength of the treatment layer affects the adhesive strength.

Examples of coupling agents used for these treatments are shown below.
Silane coupling agent 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane N-2-aminoethyl-3-aminopropylmethyldimethoxysilane, N-2-aminoethyl-3-aminopropylmethyldiethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, N-2 -Aminoethyl-3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, (1,3-dimethylbutylidene) propylamine, N-phenyl-3-aminopropyltrimethoxy Silane, N, N-bis (3- (to Limethoxysilylpropyl) ethylenediamine, N- (1,3-dimethylbutylidene) -3-triethoxysilyl-1-propanamine, 3-phenylaminopropyltrimethoxysilane, aminoethyl-3-aminopropyltrimethoxysilane Hydrochloride, hydrochloride of N- (2-vinylbenzidineaminoethyl) -3-aminopropyltrimethoxysilane, 1,2-ethanediamine, N- (3-trimethoxysilylpropyl) -N- (ethenylphenylmethyl) ) Derivatives / hydrochlorides, 3-chloropropyltrimethoxysilane, 3-mercaptopropylmethyldimethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, bis (triethoxysilylpropyl) tetrasulfide, 3- Isocyanate Such as pills triethoxysilane.
Regarding the organic group of the silane coupling agent, those having a functional group that reacts with the epoxy resin are preferable, and the above-mentioned coupling agent is an example. These can be purchased from Shin-Etsu Chemical, Toray Dow Corning, Chisso and others.

-Titanate coupling agent, aluminate coupling agent tetra-i-propoxy titanium, tetra-n-butoxy titanium, tetrakis (2-ethylhexyloxy) titanium, titanium-i-propoxyoctylene glycolate, di-i- Propoxy bis (acetylacetonato) titanium, poly (di-i-propoxy oxytitanium), poly (di-n-butoxy oxytitanium), di-n-butoxy bis (triethanolaminato) titanium, di Isopropoxy bis (triethanolamine) titanium, isopropyl tri (N-amidoethylaminoethyl) titanate, acetoalkoxyaluminum diisopropylate and the like.
Titanate and aluminate coupling agents improve the adhesive strength by improving the wettability of the adhesive by forming a polymer organic coating on the inorganic surface. The above is an example, and the present invention is not limited thereto. These coupling agents can be purchased from Mitsubishi Gas Chemical, Nippon Soda and Ajinomoto Fine Techno.
Among the above coupling agents, a coupling agent having an epoxy group or an amino group is preferable. In order to exert the effect by adding the coupling agent to the epoxy adhesive, the reaction proceeds at the effective period of the adhesive and at room temperature. In view of this, an epoxy group coupling agent is desirable.

Further, when using an epoxy adhesive, an adhesive capable of taking a semi-cured state (B stage state) is desirable because it can be adhered after finely adjusting the member adhesion. The “B stage state” is an intermediate stage of the reaction between the epoxy resin and the curing agent, and is a state in which the reactivity is still maintained during the curing, and an initial state of a solution suitable for coating. Compared to the above, it indicates a state in which the fluidity of the epoxy resin is remarkably lowered due to the scattering of the solvent component or the primary reaction resulting in gel to solid.
In order to obtain this B stage state, it is necessary to raise the curing temperature of the epoxy adhesive to a high temperature, which can be selected depending on the type of the curing agent. Such a curing agent is sometimes called a thermal latent curing catalyst or a thermal latent curing accelerator, and the type thereof is not particularly limited, and when mixed, has a low ability to polymerize epoxy groups at room temperature. Any compound that exhibits the ability to polymerize groups may be used.

Specifically, curing agents such as primary, secondary amines, acid anhydrides, carboxylic acids, phenols, mercaptans, isocyanates such as aliphatic polyamines, alicyclic polyamines, aromatic polyamines, polyaminoamides, Anionic polymerization catalysts such as tertiary amines and imidazoles, cationic polymerization catalysts such as Lewis acids, dicyandiamide, organic acid dihydrazides, N, N-dimethylurea derivatives, amine adducts, melamines, amine imides, boron halide complexes , Block carboxylic acids, and modified products thereof, adducts thereof, microencapsulates thereof, and the like, but are not limited thereto. These thermal latent curing agents can be used alone or in admixture of two or more.
Among these, dicyandiamide, N, N-dimethylurea derivative, imidazole solid at room temperature, solid dispersion type amine adduct-based latent curing agent, reaction product of amine compound and epoxy compound (amine-epoxy adduct) System), a reaction product of an amine compound and an isocyanate compound or a urea compound (urea type adduct system).
These latent curing accelerators can be purchased from companies such as Mitsubishi Chemical, Shikoku Kasei Kogyo, Ajinomoto Fine Techno, Adeka, Asahi Kasei Chemicals, and Fuji Kasei Kogyo.

About the epoxy resin which comprises an epoxy adhesive, the hardened | cured material bridge | crosslinked three-dimensionally is obtained by using the polyfunctional compound which has an epoxy group. Epoxy resins can be classified into glycidyl ethers, glycidyl esters, glycidylamines, etc., depending on the glycidyl group binding site, and a wide range of compounds are obtained depending on the compound serving as the binding matrix. The type of epoxy resin used for the adhesive is not particularly limited, and an optimal one can be selected according to the properties of the bonding material and the ink.
In order to suppress the permeability to the ink and eliminate the swelling, it is necessary to reduce the hydrophilicity of the epoxy resin and increase the three-dimensional crosslinking. Therefore, a polyfunctional epoxy resin such as a glycidylamine type or a novolak resin glycidyl ether compound is preferable for swelling. However, it is necessary to consider the wettability and adsorbability to the member, and a plurality of mixtures may be used. In addition, glycidyl ether of bisphenol A is preferable from the viewpoint of hydrogen bonding to metal, and the resin structure may be more elastic as the molecular weight increases. However, since there are swelling with respect to ink and cleavage of hydrogen bonds, it is necessary to mix them appropriately. preferable.
These epoxy resins are sold by a number of companies including Mitsubishi Chemical, Shikoku Kasei Kogyo, Adeka, and DIC, and can be purchased from any of them.

The epoxy adhesive may be solventless, but can be diluted with a solvent so as to have an appropriate viscosity. As a diluting solvent, a solvent without active hydrogen is more preferable than a solvent having active hydrogen reactive with an epoxy group from the viewpoint of storage stability of the adhesive, but the wettability to members, drying speed, viscosity, etc. It is possible to select freely from the surface, and even if it is not completely dissolved but dispersed, it can be used without any problem if the adhesive layer is formed upon drying.
Regarding the drying of the solvent, it may be performed at room temperature, but may be heated as long as it does not react. Further, drying under reduced pressure is possible, and even if a solvent having a high boiling point is used by drying under reduced pressure, the epoxy resin can be dried without reacting.
The solvent to be used can be freely selected according to the epoxy resin, the curing agent, and other additives, but a solvent in which impurities are controlled is desirable in order to stably advance the curing reaction.
In addition to the epoxy resin, the curing agent, the solvent, and the coupling agent, the epoxy adhesive may contain a filler, other binder resin, a viscosity modifier, and the like. The filler may be inorganic particles such as silica and alumina, or resin fine particles such as melamine resin and acrylic resin. It is also possible to add a higher fatty acid amide or the like as a viscosity adjusting agent to adjust the viscosity to be suitable for adhesive coating. Further, a foam suppressor or an antifoaming agent may be added so that coating spots due to foam do not occur in the coating film.

<Ink>
The ink (inkjet ink) that adversely affects the adhesive and adhesive strength between the nozzle plate and the flow path plate related to the problem to be solved by the present invention is at least an amide water-soluble organic solvent, water, a colorant, and an interface. It contains an activator, and further contains other components as necessary. The amide-based water-soluble organic solvent is used as a part of the water-soluble organic solvent, and the proportion thereof is 20 to 60% by weight of the whole water-soluble organic solvent.

・ Water-soluble organic solvent (wetting agent)
Examples of the amide-based water-soluble organic solvent include water-soluble amide compounds. The water-soluble amide compound is generally a polar solvent capable of dissolving many organic compounds and inorganic salts, and can be mixed with a wide range of solvents from water to organic solvents. Therefore, the effect of improving the wettability and solubility with respect to the recording medium and the mixing stability of other components can be obtained.
Examples of such water-soluble amide compounds include 2-pyrrolidone (bp 250 ° C.), N-methyl-2-pyrrolidone (bp 202 ° C.), 1,3-dimethyl-2-imidazolidinone (bp 226) as cyclic amide compounds. C), ε-caprolactam (bp 270 ° C.), γ-butyrolactone (bp 204-205 ° C.), etc., as acyclic amide compounds, formamide (bp 210 ° C.), N-methylformamide (bp 199-201 ° C.), N, N-dimethyl Examples include formamide (bp 153 ° C.), N, N-diethylformamide (bp 176 to 177 ° C.), N, N-dimethylacetamide (bp 165 ° C.) and the like.

（上記式中、Ｒは炭素数１〜４のアルキル基を表す。）
Moreover, the amide compound shown by following General formula (1) which is 1 type of an acyclic amide compound is also contained.

(In the above formula, R represents an alkyl group having 1 to 4 carbon atoms.)

The water-soluble amide compound represented by the above general formula has different hydrophilicity depending on the length of the alkyl group, and has different miscibility with water or an organic solvent. When the alkyl group is a methyl group, the boiling point is as high as 216 ° C., the equilibrium moisture content in the environment of 23 ° C. and 80% relative humidity is also 39.2% by weight, and the liquid viscosity is 1.48 mPa · s in an environment of 25 ° C. s and very low. Furthermore, since it is very easy to dissolve in other water-soluble organic solvents and water, it is possible to reduce the viscosity of the ink, which is very preferable as a water-soluble organic solvent used in the ink. The ink containing the water-soluble amide compound has good storage stability and ejection stability, and is an ink that is gentle to the maintenance device of the ink ejection device.
If the alkyl group is a butyl group, it dissolves freely in water, has solubility in liquid paraffin and n-hexane, has a high boiling point of 252 ° C., and should be added as an ink penetration enhancer or solubilizer. Can do.

Both the cyclic and non-cyclic amide compounds have high solubility, and high solubility in conventional adhesives, making it difficult to increase the amount added to the ink. Therefore, in an inkjet head using an adhesive such as a laminated head, the amount of amide compound added to the ink used is 10% by weight or less. There was a problem that the strength was reduced.
In contrast, in the case of the liquid discharge head of the present invention, it is possible to add 20% by weight or more of a water-soluble amide compound in the ink. The addition amount of the water-soluble amide compound in the ink is preferably 20% by weight or more from the viewpoint of solid uniformity of the printed image. However, if it exceeds 60% by weight, the dryness on the paper surface is inferior and the character quality on plain paper is further reduced. Is not preferred because it may decrease.

The water-soluble organic solvent used by mixing with the water-soluble amide compound includes at least one polyhydric alcohol having an equilibrium water content of 30% by weight or more in an environment at a temperature of 23 ° C. and a relative humidity of 80%, Wetting agent A having a fairly high equilibrium water content and boiling point (having a temperature of 23 ° C. and a relative humidity of 80%, an equilibrium water content of 30% by weight or more, preferably 40% by weight or more, and a boiling point of 250 ° C. or more), and Contains wetting agent B (high equilibrium water content but relatively low boiling point, with equilibrium water content of 30% by weight or more at a temperature of 23 ° C. and a relative humidity of 80% and a boiling point of 140 ° C. or more and less than 250 ° C.) Is preferred.
In the polyhydric alcohol, the wetting agent A having a boiling point exceeding 250 ° C. at normal pressure includes 1,2,3-butanetriol (bp 175 ° C./33 hPa, 38 wt%), 1,2,4-butanetriol (bp 190 to 191 ° C./24 hPa, 41 wt%), glycerin (bp 290 ° C., 49 wt%), diglycerin (bp 270 ° C./20 hPa, 38 wt%), triethylene glycol (bp 285 ° C., 39 wt%), tetraethylene glycol (bp 324) The wetting agent B having a boiling point of 140 ° C. or higher and lower than 250 ° C. includes diethylene glycol (bp 245 ° C., 43 wt%), 1,3-butanediol (bp 203-204 ° C., 35 Weight%) and the like. Of these, glycerin and 1,3-butanediol are preferred.

These wetting agent A and wetting agent B are both highly hygroscopic materials having an equilibrium moisture content of 30% by weight or more in an environment at a temperature of 23 ° C. and a relative humidity of 80%. Is relatively highly evaporable.
The weight ratio B / A of both when wetting agent A and wetting agent B are used in combination depends on the type and amount of other additives, so it cannot be generally stated, but 10/90 to 90 / A range of 10 is preferred.
The above equilibrium water content is maintained in a desiccator using a saturated aqueous solution of potassium chloride / sodium chloride at a temperature of 23 ± 1 ° C. and a relative humidity of 80 ± 3%, and a petri dish in which 1 g of each water-soluble organic solvent is weighed. Is stored, and the amount of water saturated is determined by the following equation.
Saturated water content (%) = [Moisture absorbed by organic solvent / (Amount of organic solvent + Absorbed by organic solvent]
Water amount)] × 100
Use of the polyhydric alcohol in an amount of 50% by weight or more based on the total amount of the water-soluble organic solvent is preferable because it is excellent in securing ejection stability and preventing waste ink sticking in a maintenance device of the ink ejection device.

In addition to the above-mentioned wetting agents A and B, other water-soluble organic solvents (wetting agents) may be used in the ink in place of the wetting agents A and B as necessary or in addition to the wetting agents A and B. ) Can be used in combination.
Water-soluble organic solvents (wetting agents) that can be used in combination include polyhydric alcohols, polyhydric alcohol alkyl ethers, polyhydric alcohol aryl ethers, amines, sulfur-containing compounds, propylene carbonate, ethylene carbonate, and other water-soluble substances. Organic solvent (wetting agent) is included.
Examples of the polyhydric alcohols include dipropylene glycol (bp 232 ° C), 1,5-pentanediol (bp 242 ° C), 3-methyl-1,3-butanediol (bp 203 ° C), and propylene glycol (bp 187 ° C). 2-methyl-2,4-pentanediol (bp 197 ° C.), ethylene glycol (bp 196-198 ° C.), tripropylene glycol (bp 267 ° C.), hexylene glycol (bp 197 ° C.), polyethylene glycol (viscous liquid 0 solid) , Polypropylene glycol (bp 187 ° C.), 1,6-hexanediol (bp 253 to 260 ° C.), 1,2,6-hexane triol (bp 178 ° C.), trimethylol ethane (solid, mp 199 to 201 ° C.), trimethylol propane ( Solid, mp61 ° C) And so on.

Examples of the polyhydric alcohol alkyl ethers include ethylene glycol monoethyl ether (bp 135 ° C.), ethylene glycol monobutyl ether (bp 171 ° C.), diethylene glycol monomethyl ether (bp 194 ° C.), diethylene glycol monoethyl ether (bp 197 ° C.), and diethylene glycol monoethyl ether. Examples include butyl ether (bp 231 ° C.), ethylene glycol mono-2-ethylhexyl ether (bp 229 ° C.), propylene glycol monoethyl ether (bp 132 ° C.), and the like.
Examples of the polyhydric alcohol aryl ethers include ethylene glycol monophenyl ether (bp 237 ° C.) and ethylene glycol monobenzyl ether.
Examples of the amines include monoethanolamine (bp 170 ° C), diethanolamine (bp268 ° C), triethanolamine (bp360 ° C), N, N-dimethylmonoethanolamine (bp139 ° C), N-methyldiethanolamine (bp243 ° C). ), N-methylethanolamine (bp 159 ° C.), N-phenylethanolamine (bp 282 to 287 ° C.), 3-aminopropyldiethylamine (bp 169 ° C.) and the like.
Examples of the sulfur-containing compounds include dimethyl sulfoxide (bp 139 ° C.), sulfolane (bp 285 ° C.), thiodiglycol (bp 282 ° C.), and the like.

Other solid wetting agents are preferably sugars.
Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), polysaccharides, and the like. Specific examples include glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, and the like.
Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature such as α-cyclodextrin and cellulose.
The derivatives of these saccharides are represented by the reducing sugars of the saccharides described above {for example, sugar alcohol [general formula: HOCH ₂ (CHOH) _n CH ₂ OH, where n is an integer of 2 to 5]). }, Oxidized sugar (eg, aldonic acid, uronic acid, etc.), amino acid, thioic acid and the like. Among these, sugar alcohols are preferable, and specific examples include maltitol and sorbit.

-Colorant As for the colorant, a pigment is mainly used from the viewpoint of weather resistance, but a dye may be used in combination for color tone adjustment within a range not deteriorating the weather resistance. Preferred dyes are acid dyes and direct dyes.
Inorganic pigments were manufactured by known methods such as contact method, furnace method, thermal method, in addition to titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, and chromium yellow. Carbon black can be used.
Organic pigments include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (eg, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazines). Pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye type chelates, acidic dye type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used. Among these pigments, those having particularly good affinity with water are preferably used.

The pigment is preferably a self-dispersing pigment whose surface is modified so that at least one hydrophilic group is bonded directly or via another atomic group. In order to obtain this pigment, a specific functional group (functional group such as sulfonic acid group or carboxyl group) is chemically bonded to the surface of the pigment, or hypohalous acid and / or a salt thereof is used. A method such as wet oxidation is used. Among these, a form in which carboxyl groups are bonded to the surface of the pigment and dispersed in water is preferable. In this case, the carboxyl group bonded to the surface of the pigment improves the dispersion stability, obtains high-quality print quality, and further improves the water resistance of the recording medium after printing.
In addition, since this form of ink has excellent redispersibility after drying, printing is suspended for a long period of time, and clogging does not occur even when the water content of the ink near the nozzles of the inkjet head evaporates, making it easy with a simple cleaning operation. Can be printed well. In addition, this self-dispersing pigment has a particularly large synergistic effect when combined with a surfactant and a penetrating agent, which will be described later, and it is possible to obtain a more reliable and high-quality image.

It is also possible to use a polymer emulsion in which a pigment is contained in fine polymer particles in addition to the pigment in the above form. The polymer emulsion containing a pigment is one in which a pigment is encapsulated in polymer fine particles and / or a pigment adsorbed on the surface of the polymer fine particles. In this case, it is not necessary for all the pigments to be encapsulated and / or adsorbed, and a part of the pigments may be dispersed in the emulsion.
Examples of the polymer that forms the polymer emulsion include vinyl polymers, polyester polymers, polyurethane polymers, and the like. Particularly preferred are vinyl polymers and polyester polymers, and examples thereof include JP-A-2000-53897. , 2001-139849, and polymers disclosed therein.
The amount of the colorant added to the ink is preferably about 1 to 15% by weight, more preferably about 3 to 12% by weight.

-Surfactant An anionic surfactant, a nonionic surfactant, an amphoteric surfactant, and a fluorochemical surfactant are used as the surfactant. A surfactant that does not impair the dispersion stability is selected depending on the combination of the color material, the wetting agent, and the water-soluble organic solvent.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecyl benzene sulfonate, oxalate sulfonate, laurate, polyoxyethylene alkyl ether sulfate salt, and the like.
Nonionic surfactants include, for example, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene polyoxypropylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene Examples thereof include alkylphenyl ether, polyoxyethylene alkylamine, and polyoxyethylene alkylamide.
Examples of amphoteric surfactants include lauryl aminopropionate, lauryl dimethyl betaine, stearyl dimethyl betaine, and lauryl dihydroxyethyl betaine. Specific examples below are preferably used, but are not limited thereto. Examples include lauryl dimethylamine oxide, myristyl dimethylamine oxide, stearyl dimethylamine oxide, dihydroxyethyl lauryl amine oxide, polyoxyethylene coconut oil alkyl dimethyl amine oxide, dimethyl alkyl (coconut) betaine, and dimethyl lauryl betaine.
Such surfactants are readily available from surfactant manufacturers such as Nikko Chemicals, Nippon Emulsion, Nippon Shokubai, Toho Chemical, Kao, Adeka, Lion, Aoki Oil, Sanyo Kasei.

Moreover, there is an acetylene glycol surfactant as a nonionic surfactant other than the above. Examples thereof include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5-dimethyl-1- Hexin-3-ol and the like are listed, and there are commercially available products such as Surfynol 104, 82, 465, 485, and TG from Air Products (USA). Surfhinol 465, 104, and TG in particular have good print quality. Show.
Fluorosurfactants include perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkyl phosphate ester, perfluoroalkyl ethylene oxide adduct, perfluoroalkyl betaine, perfluoroalkylamine oxide compounds, Examples thereof include polyoxyalkylene ether polymers having a fluoroalkyl ether group in the side chain, sulfate salts thereof, and fluorine-based aliphatic polymer esters. Commercially available products include Surflon S-111, S-112, S-113, S121, S131, S132, S-141, S-145 (manufactured by Asahi Glass Co., Ltd.), Fullrad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431, FC-4430 (manufactured by Sumitomo 3M), FT-110, 250, 251, 400S (manufactured by Neos), Zonyl FS-62, FSA, FSE, FSJ, FSP, TBS, UR, FSO, FSO-100, FSN N, FSN-100, FS-300, FSK (manufactured by Dupont), Polyfox PF-136A, PF-156A, PF-151N ( OMNOVA) and can be easily obtained from the manufacturer.

The surfactant is not limited to these, and may be used alone or in combination. Even if it is not easily dissolved by itself in the recording liquid, it can be solubilized by mixing and exist stably.
In order to exert a penetrating effect as the total amount of the surfactant, it is desirable that the ink is contained in an amount of 0.01 to 5.0% by weight. If the total amount of the surfactant is less than 0.01% by weight, there is no effect of addition, and if it is more than 5.0% by weight, the permeability to the recording medium becomes unnecessarily high, and the image density decreases and the occurrence of show-through occurs. Will occur. Furthermore, 0.5 to 2.0% by weight is more preferable in order to cope with plain paper having many physical properties.

-Other ingredients-
The other components are not particularly limited and may be appropriately selected as necessary. For example, a penetrant, a water-dispersible resin, a pH adjuster, an antiseptic / antifungal agent, a chelating agent, an antirust agent, an oxidation agent Examples thereof include an inhibitor, an ultraviolet absorber, an oxygen absorber, a light stabilizer, and an antifoaming agent.

-Penetration agent As a penetration agent, it is desirable to contain at least 1 sort (s) of the polyol whose solubility with respect to 20 degreeC water is 0.2 to 5.0 weight%.
Among such polyols, aliphatic diols include 2-ethyl-2-methyl-1,3-propanediol, 3,3-dimethyl-1,2-butanediol, and 2,2-diethyl-1,3. -Propanediol, 2-methyl-2-propyl-1,3-propanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1 , 2-diol, 2-ethyl-1,3-hexanediol, and the like. Of these, 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol are the most desirable.
Other penetrants that can be used in combination include polyhydric alcohols such as diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, diethylene glycol monobutyl ether, propylene glycol monobutyl ether, and tetraethylene glycol chlorophenyl ether. Alkyl and aryl ethers, lower alcohols such as ethanol, and the like, but are not limited thereto as long as they can be dissolved in ink and adjusted to desired physical properties.

Even if the solubility in water is low, it can be used as a penetrant as long as it is solubilized by the above-mentioned water-soluble amide compound and does not precipitate from the ink.
In conventional inks, the amount of water-soluble amide compound added was small, so the effect of solubilization was small. However, in the ink of the present invention, since a large amount of water-soluble amide compound can be added, it is also necessary to add poorly soluble organic substances that could not be used conventionally. Can do. For this reason, it is possible to penetrate into coated paper for printing which has been difficult to penetrate.
The amount of penetrant added is preferably in the range of 0.1 to 4.0% by weight of the total ink. When the amount of penetrant added is less than 0.1% by weight, quick drying cannot be obtained and a blurred image is obtained. On the other hand, if the added amount is more than 4.0% by weight, the dispersion stability of the colorant is impaired, the nozzle is likely to be clogged, the permeability to the recording medium becomes higher than necessary, and the image density is reduced. Problems such as reduction and occurrence of strikethrough occur.

・ Water-dispersible resins Water-dispersible resins include condensation-type synthetic resins (polyester resin, polyurethane resin, polyepoxy resin, polyamide resin, polyether resin, silicon resin, etc.) and addition-type synthetic resins (polyolefin resin, polystyrene type). Resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, unsaturated carboxylic acid resins, etc.) and natural polymers (celluloses, rosins, natural rubber, etc.) can be used.
These resins may be homopolymers or copolymers, and any of single phase structure type, core shell type, and power feed type emulsions can be used.
As the water-dispersible resin, a resin itself having a hydrophilic group and having a self-dispersibility, or a resin itself having no dispersibility and imparted with a surfactant or a resin having a hydrophilic group is used. In particular, an emulsion of resin particles obtained by emulsification and suspension polymerization of an ionomer or an unsaturated monomer of a polyester resin or a polyurethane resin is optimal.

In the case of emulsion polymerization of unsaturated monomers, in order to obtain a resin emulsion by performing a reaction in water to which an unsaturated monomer, a polymerization initiator, a surfactant, a chain transfer agent, a chelating agent, a pH adjusting agent, etc. are added. Thus, a water-dispersible resin can be easily obtained, and the desired properties can be easily produced because the resin configuration can be easily changed.
Usable unsaturated monomers include unsaturated carboxylic acids, (meth) acrylic acid ester monomers, (meth) acrylic acid amide monomers, aromatic vinyl monomers, vinyl cyanide compounds A monomer, a vinyl monomer, an allyl compound monomer, an olefin monomer, a diene monomer, an oligomer having an unsaturated carbon, and the like can be used alone or in combination. The properties can be flexibly modified by combining these monomers, and the properties of the resin can also be modified by performing a polymerization reaction or a graft reaction using an oligomer type polymerization initiator.

It is possible to flexibly modify the properties of the water-dispersible resin by using an unsaturated monomer alone or in combination, and converting it into a resin using a polymerization initiator. Further, such a water-dispersible resin has a strong alkalinity and a strong acidity, and thus the molecular chain is broken such as dispersion breakage and hydrolysis. Therefore, the pH is preferably 4 to 12. In particular, the pH is preferably 6 to 11 and more preferably 7 to 9 from the viewpoint of miscibility with the water-dispersible colorant.
The particle size of the water-dispersible resin is related to the viscosity of the dispersion. When the composition is the same, the viscosity at the same solid content increases as the particle size decreases. The average particle size of the water-dispersible resin is desirably 50 nm or more so that the viscosity does not become excessively high when the ink is formed. If the particle size is several tens of μm, it becomes larger than the nozzle opening of the ink jet head and cannot be used. It is known that the presence of particles having a large particle diameter in the ink, even if smaller than the nozzle opening, deteriorates the discharge performance. In order not to impair the ink discharge performance, the average particle diameter is preferably 500 nm or less, more preferably 150 nm or less. preferable.
The water-dispersible resin has a function of fixing the water-dispersible colorant on the paper surface, and it is desired to form a film at room temperature to improve the fixability of the colorant. For this purpose, it is desirable that the minimum film-forming temperature (MFT) is normal temperature or lower, particularly 20 ° C. or lower. However, when the glass transition temperature is −40 ° C. or lower, the resin film becomes more viscous and the printed matter is tacky. Therefore, a water dispersible resin having a glass transition temperature of −30 ° C. or higher is desirable.

PH adjuster The pH adjuster is not particularly limited as long as it can adjust the pH to 7 to 11 without adversely affecting the ink, and can be appropriately selected according to the purpose. And alkali metal element hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like.
When the pH is less than 7 or more than 11, the amount of the ink jet head or the ink supply unit that melts is large, and problems such as ink deterioration, leakage, and ejection failure may occur.
Examples of the alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide.
Examples of the phosphonium hydroxide include quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.

-Antiseptic / antifungal agent Examples of the antiseptic / antifungal agent include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, and sodium pentachlorophenol.
Chelating agent Examples of the chelating agent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.
-Rust preventive agent Examples of the rust preventive agent include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

-Antioxidants Examples of antioxidants include phenolic antioxidants (including hindered phenolic antioxidants), amine antioxidants, sulfur antioxidants, and phosphorus antioxidants. .
UV absorbers Examples of UV absorbers include benzophenone UV absorbers, benzotriazole UV absorbers, salicylate UV absorbers, cyanoacrylate UV absorbers, and nickel complex UV absorbers.
-Antifoaming agent Examples of antifoaming agents include silicone antifoaming agents, polyether antifoaming agents, and fatty acid ester antifoaming agents. In addition, when a general antifoaming agent is used in combination and an ink containing a large amount of inorganic fine particles is used in order to enhance the bubble breaking effect, coarse particles having a particle diameter of 0.5 μm or more in the ink using the antifoaming agent are used. The content of the particles is 3.0 × 10 ⁷ (pieces / 5 μL) or less, and the amount of particles having a particle size of 1 to 5 μm in the coarse particles needs to be 1% by number or less. There is a need to.

The above-mentioned ink is further necessary by dispersing or dissolving a colorant, a water-soluble organic solvent (wetting agent), a surfactant, a penetrating agent, a water-dispersible resin, water, and other components as necessary in an aqueous medium. According to the above, the mixture is mixed by stirring.
The dispersion can be performed by, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, etc., and stirring and mixing are performed by a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser, or the like. be able to.

The physical properties of the ink are not particularly limited and can be appropriately selected according to the purpose.
For example, the viscosity of the ink at 25 ° C. is preferably 3 to 20 mPa · s. By setting the viscosity to 3 mPa · s or more, the effect of improving the printing density and the character quality can be obtained. Moreover, discharge property is securable by suppressing a viscosity to 20 mPa * s or less. The viscosity can be measured using, for example, a viscometer (RL-550, manufactured by Toki Sangyo Co., Ltd.).
The surface tension of the ink is preferably 35 mN / m or less, more preferably 32 mN / m or less at 25 ° C. If the surface tension exceeds 35 mN / m, leveling of the ink on the recording medium is difficult to occur and the drying time may be prolonged.
There is no restriction | limiting in particular in the color of an ink, Although it can select suitably according to the objective, For example, yellow, magenta, cyan, black etc. are mentioned.
When recording is performed using an ink set in which two or more inks of various colors are combined, a multicolor image can be formed. When recording is performed using an ink set in which all colors are combined, a full color image is formed. Can be formed.

  The ink uses a piezoelectric element as pressure generating means for pressurizing the ink in the ink flow path, deforms a diaphragm that forms the wall surface of the ink flow path, changes the volume in the ink flow path, and discharges ink droplets. Piezo type (refer to Japanese Patent Laid-Open No. 2-51734), so-called thermal type that generates bubbles by heating ink in an ink flow path using a heating resistor (see Japanese Patent Laid-Open No. 61-59911). ), The diaphragm and the electrode forming the wall surface of the ink flow path are arranged opposite to each other, and the diaphragm is deformed by an electrostatic force generated between the vibration plate and the electrode, thereby changing the volume of the ink flow path to change the ink. It can also be used in a printer equipped with any ink jet head such as an electrostatic type that discharges droplets (see JP-A-6-71882).

<Head configuration>
1 and 2 show a configuration of a liquid discharge head 1 that constitutes a recording unit in an image forming apparatus. FIG. 1 is a partial sectional view along the longitudinal direction of the liquid chamber, and FIG. It is a fragmentary sectional view of (arrangement direction of a nozzle).
The liquid chamber discharge head 1 includes, for example, a flow path plate 11 formed by anisotropic etching of a single crystal silicon substrate, and a vibration plate 12 formed of, for example, a metal material layer and a resin material layer bonded to the lower surface of the flow path plate 11. And a nozzle plate 13 bonded to the upper surface of the flow path plate 11 are bonded and stacked, and thereby, a nozzle communication path 15 that is a flow path through which a nozzle 14 that discharges droplets (ink droplets, etc.) communicates with the liquid. A chamber 16 and an ink supply port 18 communicating with a common liquid chamber 17 for supplying ink to the liquid chamber 16 are formed. The flow path plate 11, the vibration plate 12, and the nozzle plate 13 each have a positioning hole, and after being applied with an adhesive, they are positioned and joined by being inserted into the same positioning pin.
Here, the flow path plate 11 is formed by, for example, subjecting the single crystal silicon substrate having the crystal plane orientation (110) to an anisotropic etching using an alkaline etching solution such as an aqueous potassium hydroxide solution (KOH) and the nozzle communication passage 15 and the liquid plate. Although a recess or a hole serving as the chamber 16 is formed, it is not limited to a single crystal silicon substrate, and other stainless steel substrates, photosensitive resins, and the like can also be used.

The vibration plate 12 is formed from a nickel metal plate, and is produced by, for example, an electroforming method (electroforming method). In addition to this, a metal plate, a joining member between a metal and a resin plate, polycrystalline silicon, or the like. A material obtained by etching a plate can also be used.
The nozzle plate 13 forms nozzles 14 having a diameter of 10 to 30 μm corresponding to the respective liquid chambers 16 and is bonded to the flow path plate 11 with an adhesive. The nozzle plate 13 may be made of a metal such as stainless steel or nickel, a combination of a metal and a resin such as a polyimide resin film, silicon, or a combination thereof.
The nozzle surface of the nozzle plate is subjected to water repellent treatment. By this water repellent treatment, it is possible to prevent discharge defects such as dirt on the nozzle surface, discharge bending, and non-discharge. The means for forming the water repellent film by the water repellent treatment may be vacuum deposition or may be applied after being dissolved in a suitable solvent.
In vacuum deposition, for example, an RF glow discharge is caused in a vacuum atmosphere, and the orifice surface of the liquid discharge head is surface-treated in a plasma atmosphere to form a water repellent film on the nozzle surface. Depending on the material and the degree of vacuum in the vacuum chamber, the water repellent film can also be formed at a low temperature of about room temperature to about 200 ° C.

As for coating, for example, a method of dissolving a water-repellent material in an organic solvent and coating it with a jig such as a wire bar or a doctor blade, a method of spin coating with a spin coater, a method of spray coating, satisfying the coating solution There is a method of dipping in a container.
As the water-repellent material, an organic compound having a fluorine atom, particularly an organic substance having a fluoroalkyl group, an organic silicon compound having a dimethylsiloxane skeleton, or the like can be used. As another water-repellent material, an organic compound having a silicon atom, particularly an organic compound having an alkylsiloxane group can be used.
The thickness of the water repellent film is preferably 5 μm or less, more preferably 2 μm or less. When the film thickness exceeds 5 μm, drying of the coating film is delayed, productivity may be deteriorated or mechanical durability may be impaired, and peeling may occur when wiping is performed.

Further, the liquid discharge head 1 is deformed by the diaphragm 12 to pressurize the liquid in the liquid chamber 16, and two rows as electromechanical conversion elements which are pressure generating means (actuator means) (only one row is shown in FIG. 2). ) And a base substrate 20 to which the piezoelectric element 19 is bonded and fixed. A strut portion 21 is provided between the piezoelectric elements 19. The column portion 21 is a portion formed at the same time as the piezoelectric element 19 by dividing the piezoelectric element member. However, since the drive voltage is not applied, the column portion 21 is a simple column. Further, an FPC cable 22 equipped with a drive circuit (drive IC) (not shown) is connected to the piezoelectric element 19.
The peripheral edge of the diaphragm 12 is joined to the frame member 23, and the frame member 23 serves as a through-hole 24 and a common liquid chamber 17 that accommodates an actuator unit composed of the piezoelectric element 19 and the base substrate 20. A recess and a liquid supply hole 25 for supplying liquid from the outside to the common liquid chamber 17 are formed. The frame member 23 is formed by injection molding with a thermosetting resin such as an epoxy resin or polyphenylene sulfite, for example.
The piezoelectric element 19 is a stacked piezoelectric element (here, PZT) in which piezoelectric materials 26 and internal electrodes 27 are alternately stacked. An individual electrode 28 and a common electrode 29 are connected to each internal electrode 17 drawn out on the alternately different end faces of the piezoelectric element 19. Further, a structure in which one row of piezoelectric elements 19 is provided on one substrate 20 may be employed.

In the liquid ejection head 1, for example, the voltage applied to the piezoelectric element 19 is lowered from the reference potential, the piezoelectric element 19 contracts, and the diaphragm 12 descends to expand the volume of the liquid chamber 16, thereby expanding the liquid chamber 16. Then, the liquid flows in, and then the voltage applied to the piezoelectric element 19 is increased to extend the piezoelectric element 19 in the stacking direction, and the diaphragm 12 is deformed toward the nozzle 14 to contract the volume / volume of the liquid chamber 16. As a result, the ink in the liquid chamber 16 is pressurized, and ink droplets are ejected (jetted) from the nozzle 14. Then, by returning the voltage applied to the piezoelectric element 19 to the reference potential, the diaphragm 12 is restored to the initial position, the liquid chamber 16 expands and a negative pressure is generated, and ink is supplied from the common liquid chamber 18 into the liquid chamber 16. Is filled. Therefore, after the vibration of the meniscus surface of the nozzle 14 is attenuated and stabilized, the operation proceeds to the next droplet discharge.
Note that the driving method of the head is not limited to the above example (drawing-pushing), and striking or pushing can be performed depending on how the drive waveform is given.

<Image forming apparatus>
Next, an example of an image forming apparatus (inkjet recording apparatus) in which the liquid ejection head according to the present invention is mounted as an inkjet head will be described with reference to FIGS. FIG. 3 is a perspective explanatory view of the recording apparatus, and FIG. 4 is a side explanatory view of a mechanism portion of the recording apparatus.
The ink jet recording apparatus includes a printing mechanism unit including a carriage movable in the main scanning direction inside the recording apparatus main body 111, an ink jet head according to the present invention mounted on the carriage, an ink cartridge for supplying ink to the head, and the like. 112 and the like, and a paper feed cassette (or a paper feed tray) 114 on which a large number of sheets 113 can be stacked from the front side can be detachably attached to the lower part of the apparatus main body 111. The manual feed tray 115 for manually feeding the paper 113 can be opened, the paper 113 fed from the paper feed cassette 114 or the manual feed tray 115 is taken in, and a desired image is recorded by the printing mechanism unit 112. Thereafter, the paper is discharged to a paper discharge tray 116 mounted on the rear side.

The printing mechanism 112 holds a carriage 123 slidably in the main scanning direction by a main guide rod 121 and a sub guide rod 122 which are guide members horizontally mounted on left and right side plates (not shown). A head 124 that ejects ink droplets of each color (Y), cyan (C), magenta (M), and black (Bk) is arranged in a direction crossing a plurality of ink ejection ports with the main scanning direction, and the ink droplet ejection direction. Is attached facing down.
In addition, each ink cartridge 125 for supplying each color ink to the head 124 is replaceably mounted on the carriage 123.
The ink cartridge 125 has an air port that communicates with the atmosphere at the top, a supply port that supplies ink to the ink jet head at the bottom, and a porous body filled with ink inside, and is supplied to the ink jet head by the capillary force of the porous body. The supplied ink is maintained at a slight negative pressure.
Although the heads 124 for each color are used here, a single head having nozzles for ejecting ink droplets for each color may be used.
Here, the carriage 123 is slidably fitted to the main guide rod 121 on the rear side (downstream side in the paper conveyance direction), and is slidably mounted on the sub guide rod 122 on the front side (upstream side in the paper conveyance direction). doing. In order to move and scan the carriage 123 in the main scanning direction, a timing belt 130 is stretched between a driving pulley 128 and a driven pulley 129 that are rotationally driven by a main scanning motor 127. The carriage 123 is reciprocally driven by forward and reverse rotations of the main scanning motor 127.

On the other hand, in order to convey the sheet 113 set in the sheet cassette 114 to the lower side of the head 124, the sheet 113 is guided from the sheet feeding cassette 114 to the sheet feeding roller 131 and the friction pad 132. A guide member 133, a transport roller 134 that reverses and transports the fed paper 113, a transport roller 135 that is pressed against the peripheral surface of the transport roller 134, and a tip that defines the feed angle of the paper 113 from the transport roller 134 A roller 136 is provided.
The transport roller 134 is rotationally driven by a sub-scanning motor 137 through a gear train. A printing receiving member 139 is provided as a paper guide member for guiding the paper 113 fed from the transport roller 134 below the head 124 corresponding to the range of movement of the carriage 123 in the main scanning direction. On the downstream side of the printing receiving member 139 in the sheet conveyance direction, a conveyance roller 141 and a spur 142 that are rotationally driven to send the sheet 113 in the sheet discharge direction are provided, and a sheet discharge roller that further feeds the sheet 113 to the sheet discharge tray 116. 143 and a spur 144, and guide members 145 and 146 forming a paper discharge path are disposed.

At the time of recording, the head 124 is driven according to the image signal while moving the carriage 123, thereby ejecting ink onto the stopped sheet 113 to record one line, and after the sheet 113 is conveyed by a predetermined amount, Records lines. Upon receiving a recording end signal or a signal that the trailing edge of the sheet 113 reaches the recording area, the recording operation is terminated and the sheet 113 is discharged.
A recovery device 147 for recovering defective ejection of the head 124 is disposed at a position outside the recording area on the right end side in the movement direction of the carriage 123. The recovery device 147 includes a cap unit, a suction unit, and a cleaning unit. The carriage 123 is moved to the recovery device 147 side during printing standby, and the head 124 is capped by the capping unit, and the ejection port portion is kept in a wet state to prevent ejection failure due to ink drying. Further, by ejecting ink that is not related to recording during recording or the like, the ink viscosity of all the ejection ports is made constant and stable ejection performance is maintained.

When a discharge failure occurs, the discharge port (nozzle) of the head 124 is sealed by the capping unit, and bubbles and the like are sucked out from the discharge port by the suction unit through the tube. Is removed by the cleaning means to recover the ejection failure. Further, the sucked ink is discharged to a waste ink reservoir (not shown) installed at the lower part of the main body and absorbed and held by an ink absorber inside the waste ink reservoir.
Thus, since this ink jet recording apparatus is equipped with the ink jet head according to the present invention, the cost can be reduced.
In the above embodiment, the liquid discharge head according to the present invention is used as an inkjet head. However, a liquid discharge head that discharges droplets other than ink, for example, a liquid resist for patterning, and a liquid that discharges a gene analysis sample. It can also be applied to a discharge head or the like.
In the above embodiment, a head using an electromechanical transducer having a diaphragm as a driving unit has been described. However, the present invention can also be applied to other electrostatic heads and thermal heads (however, there is no diaphragm). Can do.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited at all by these Examples.

(Preparation example of epoxy resin)
<Fluorinated epoxy resin 1>
2,2-bis (4-hydroxyphenyl) -hexafluoropropane and epichlorohydrin were reacted according to a conventional method to obtain bisphenol hexafluoroacetone diglycidyl ether having an melting point of 75 ° C. and an epoxy equivalent of 232 (g / eq.).

<Fluorinated epoxy resin 2>
1,3-bis (hexafluoro-2-hydroxy-2-propyl) benzene and epichlorohydrin are reacted according to a conventional method, and 1,3-bis (hexafluoro-2-) of liquid epoxy equivalent 271 (g / eq.) Is reacted. Hydroxy-2-propyl) benzenediglycidyl ether was obtained.

(Preparation example of fluorine-based epoxy adhesive)
Using the materials shown in the respective columns of Preparation Examples 1 to 4 in Table 1, fluorine-based epoxy adhesives were prepared by the following procedure. In addition, the numerical value in Table 1 is a weight part.
First, an epoxy resin, a filler, and a solvent were mixed, pre-dispersed with an ultrasonic cleaner for 30 minutes, and then stirred for 1 hour to mix uniformly. A curing agent dissolved in a solvent was added to the mixed solution and stirred for 15 minutes. This dispersion was subjected to pressure filtration through a PTFE membrane filter having a small diameter of 5 μm to remove coarse particles and dust to obtain the fluorine-based epoxy adhesives of Preparation Examples 1 to 4.
The details of the materials in Table 1 are as follows.
-Mitsubishi Chemical Epicoat 828: Bisphenol A type epoxy resin-Mitsubishi Chemical Epicoat 152: phenol novolac type epoxy resin-Mitsubishi Chemical Epicure DICY15: Dicyandiamide-Shikoku Kasei Co., Ltd. Curesol 2Pz: 2-Phenylimidazole Colloidal silica-Shin-Etsu Chemical KBM-403: 3-glycidoxypropyltrimethoxysilane

Table 2 shows the solid content ratio (% by weight) of the epoxy adhesives of Preparation Examples 1 to 4 and the fluorine content (% by weight) in the dry solid content.

(Example of ink preparation)
<Preparation of polymer solution>
After sufficiently replacing nitrogen gas in the 1 L flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube and dropping funnel, 11.2 g of styrene, 2.8 g of acrylic acid, 12.0 g of lauryl methacrylate, Polyethylene glycol methacrylate 4.0 g, styrene macromer 4.0 g and mercaptoethanol 0.4 g were mixed and heated to 65 ° C.
Next, 100.8 g of styrene, 25.2 g of acrylic acid, 108.0 g of lauryl methacrylate, 36.0 g of polyethylene glycol methacrylate, 60.0 g of hydroxylethyl methacrylate, 36.0 g of styrene macromer, 3.6 g of mercaptoethanol, azobismethylvaleronitrile A mixed solution of 2.4 g and methyl ethyl ketone 18 g was dropped into the flask over 2.5 hours. After dropping, a mixed solution of 0.8 g of azobismethylvaleronitrile and 18 g of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 g of azobismethylvaleronitrile was added and further aging was performed for 1 hour. After completion of the reaction, 364 g of methyl ethyl ketone was added to the flask to obtain 800 g of a polymer solution having a concentration of 50% by weight.

<Preparation of pigment-containing polymer fine particle aqueous dispersion>
28 g of the polymer solution and C.I. I. 26 g of CI Pigment Blue 15: 3, 13.6 g of a 1 mol / L aqueous potassium hydroxide solution, 20 g of methyl ethyl ketone and 13.6 g of ion-exchanged water were sufficiently stirred and then kneaded using a roll mill. The obtained paste was put into 200 g of pure water and sufficiently stirred, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain an aqueous dispersion of cyan polymer fine particles having a pigment content of 20% by weight.

<Preparation of pigment resin dispersion>
7.7 g of Joncryl 679 (manufactured by BASF, molecular weight 7000, acid value 200), 22.5 g of triethanolamine, 0.8 g of 2-propanol and 331 g of water were mixed and stirred to obtain a uniform state. There, C.I. I. Pigment Blue 15: 3 was mixed while being stirred, and the pigment was dispersed by a bead mill for 2 hours. 483 g of pure water was added, and coarse particles were removed with an ultracentrifuge to obtain a cyan pigment resin dispersion having a pigment content of 15.5% by weight.

<Preparation of ink>
Using the materials shown in the respective columns of Preparation Examples 5 to 13 in Table 3, inks were prepared according to the following procedure.
First, a wetting agent, a penetrating agent, a surfactant, and water were mixed and stirred for 1 hour to mix uniformly. A colorant was added to the mixture and stirred for 1 hour. This dispersion was subjected to pressure filtration through a 0.8 μm cellulose acetate membrane filter to remove coarse particles and dust to obtain inks of Preparation Examples 5 to 13. The numerical values in Table 3 are parts by weight.
The details of the materials in Table 3 are as follows.
・ Emulgen LS-106 manufactured by Kao Chemicals: Polyoxyalkylene alkyl alcohol ether (nonionic surfactant)
BYK-348 manufactured by Big Chemie: Polyether-modified siloxane (nonionic surfactant)

(Evaluation of epoxy adhesive)
The epoxy adhesives of Preparation Examples 1 to 4 and the inks of Preparation Examples 5 to 13 were combined as shown in Table 4, and the properties of each epoxy adhesive were evaluated.

(I) Ink Swellability An epoxy adhesive was poured into a mold so as to have a thickness of 1 mm, and dried at 23 ° C. under reduced pressure (1000 Pa) for 1 hour. After the process of pouring and drying was repeated 4 times, it was dried at 80 ° C. under reduced pressure (1000 Pa) for 24 hours. Thereafter, the pressure was returned to atmospheric pressure, and reaction curing was performed at 180 ° C. for 5 hours to prepare an adhesive block. The block removed from the mold was immersed in ink, accelerated and deteriorated by ultrasonic irradiation at 50 ° C. for 40 hours, and evaluated according to the following criteria based on the block swelling rate.
〔Evaluation criteria〕
○: Swelling rate is 5% or less ×: Swelling rate exceeds 5%

(Ii) Contact angle 3 μL of ink was dropped on a flat plate made of a cured epoxy adhesive, and the contact angle formed by the ink and the epoxy adhesive was measured with an automatic contact angle measuring device (OCA200H manufactured by Data Physics).

(Iii) B-stage property The adhesive was put in a pan for measurement, and the epoxy cured heat generation up to 200 ° C of the dried product after drying was measured and evaluated. The calorific value by DSC of the drying condition A [23 ° C., reduced pressure (1000 Pa), 1 hour] and the drying condition B (50 ° C., atmospheric pressure, 1 hour) was measured, and the unreacted rate was calculated by the following formula. . The evaluation criteria are as follows.
Unreacted rate (%)
= (Calorific value of drying condition A-calorific value of drying condition B) / calorific value of drying condition A x 100
〔Evaluation criteria〕
○: Unreacted rate is 90% or more ×: Unreacted rate is less than 90%

(Iv) Initial adhesiveness The following peel strength test was conducted.
A rolled SUS304 flat plate having a width of 19 mm and a thickness of 40 μm formed by forming slits having a width of 140 μm and a length of 2000 μm at a pitch of 150 dpi, the slit groups being arranged in four rows, and the slit positions being shifted by 42.3 μm. The epoxy adhesive was applied to the adhesive surface with a rate of 64.7% so that the dry film thickness was 0.5 μm, and the solvent was evaporated and dried at 100 ° C. for 3 minutes. Subsequently, it was superposed on a rolled SUS304 flat plate having a width of 19 mm and a thickness of 50 μm, heated while being pressurized at 240 cN · m, and adhesively cured at 180 ° C. for 5 hours.
For the adhered sample, the average peel strength when peeled 5 mm at a rate of 90 mm direction peel strength measurement 20 mm / min with a desktop material testing machine (Orientec Corp., Tensilon STA-1150) was measured, and the following standard It was evaluated with.
〔Evaluation criteria〕
○: 1N or more △: 0.5N or more, less than 1N ×: Less than 0.5N

(V) Adhesion reliability After curing adhesion in the peel strength test, the sample was immersed in ink at 50 ° C. for 1 month. Next, a peel test was performed and evaluated according to the following criteria.
〔Evaluation criteria〕
○: 1N or more △: 0.5N or more, less than 1N ×: Less than 0.5N

(Inkjet head ejection evaluation)
The adhesives of Preparation Examples 1 to 4 were applied to the flow path plate of the liquid discharge head having the structure shown in FIGS. 1 and 2, and then dried to obtain a semi-cured state (B stage state). Next, the flow path plate and the nozzle plate are aligned and joined, and heated while being pressurized from both sides of the nozzle plate side and the flow path plate side with a SUS jig so that the alignment is not shifted. An ink jet head was prepared.
With respect to these ink jet heads, the ink filling properties and the ink resistance reliability were evaluated by the combinations of adhesives and inks shown in Table 4 as follows.

(A) Ink filling property Piping was performed so that ink could be supplied to the ink-jet head. After suction from the nozzle surface at 50 kPa for 1 minute, the head surface was maintained and an appropriate negative pressure was formed and discharged. The discharge rate (number of discharge nozzles / total number of nozzles × 100) was evaluated according to the following criteria.
〔Evaluation criteria〕
○: Discharge rate of 98% or more Δ: Discharge rate of 90% or more and less than 98% ×: Discharge rate of less than 90%

(B) Ink resistance reliability The ink jet head filled with ink was left at 60 ° C. for 3 months, and the state of the discharge speed after being left was evaluated according to the following criteria.
〔Evaluation criteria〕
○: When the discharge speed of all nozzles is less than ± 10% of the average before leaving ×: When the discharge speed of all nozzles is ± 10% or more of the average before leaving

(Curl evaluation)
When the above-mentioned head is attached to the printing device, a solid chart set to the limit of the printing range for A4 paper is ejected onto the recording medium, and recording is performed when the printing surface is placed on a flat surface with the printing surface facing down within 5 seconds after printing. The height from the flat surfaces at the four corners of the medium was measured and judged according to the following evaluation criteria. As a recording medium, a recycled PPC made by Daio Paper Co., Ltd. was used, and the evaluation was performed three times.
〔Evaluation criteria〕
○: Less than 20 mm Δ: 20 mm or more, less than 40 mm ×: 40 mm or more

DESCRIPTION OF SYMBOLS 1 Liquid chamber discharge head 11 Flow path plate 12 Vibrating plate 13 Nozzle plate 14 Nozzle 15 Nozzle communication path 16 Liquid chamber 17 Common liquid chamber 18 Ink supply port 19 Piezoelectric element 20 Base substrate 21 Strut portion 22 FPC cable 23 Frame member 24 Through portion 25 Liquid supply hole 26 Piezoelectric material 27 Internal electrode 28 Individual electrode 29 Common electrode 31 Metal layer 32 Resin layer 33 Diaphragm part 34 Positioning pin hole 35 Liquid supply hole 111 Image forming apparatus main body 112 Printing mechanism part 113 Paper 114 Paper feed cassette 115 Manual feed Tray 116 Paper discharge tray 121 Main guide rod 122 Subordinate guide rod 123 Carriage 124 Head 125 Ink cartridge 127 Main scanning motor 128 Drive pulley 129 Driven pulley 130 Timing belt 131 Feed roller 132 Flick Yonpaddo 133 guide member 134 conveying rollers 135 transport roller 136 distal roller 137 sub-scanning motor 139 marked copy receiving member 141 conveying roller 142 spur 143 paper discharge roller 144 spur 145 guide members 146 guide member 147 recovery device

Japanese Patent Laid-Open No. 2-51734 JP-A-61-59911 Japanese Patent Laid-Open No. 6-71882 JP 2005-220296 A Japanese Patent No. 4277898

Claims (3)

  A liquid discharge head in which a nozzle plate on which a discharge port for discharging droplets is formed is joined to a flow path plate on which a liquid chamber communicated with the discharge port is formed, wherein the nozzle plate and the flow path plate are fluorine-based Contact angle between a cured product of the fluorine-based epoxy adhesive and an ink containing 20 to 60% by weight of an amide-based water-soluble organic solvent, water, a colorant, and a surfactant, which are bonded with an epoxy adhesive Is a liquid discharge head characterized by being 60 ° or more. The amide water-soluble organic solvent is at least one selected from N-methyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, and a compound represented by the following general formula (1). The liquid discharge head according to claim 1, wherein the liquid discharge head is provided.

(In the above formula, R represents an alkyl group having 1 to 4 carbon atoms.)
  An image forming apparatus comprising the liquid discharge head according to claim 1.

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