Patent Publication Number: US-2011069121-A1

Title: Inkjet printhead and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2009-0089648, filed on Sep. 22, 2009, in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety for all purposes. 
     TECHNICAL FIELD 
     The present disclosure relates to an inkjet printhead and method of manufacturing the same. 
     BACKGROUND OF RELATED ART 
     Inkjet printheads are devices for printing images on a printing medium by ejecting droplets of ink onto the desired regions of the printing medium. Inkjet printheads can be classified broadly into two different types depending on the mechanism, of ejecting ink droplets: piezoelectric inkjet printheads and thermal inkjet printheads. For piezoelectric inkjet printheads, a piezoelectric crystal may be deformed and the pressure due to the deformation of the piezoelectric crystal causes ink droplets to be ejected from the printhead. In contrast, in thermal inkjet printheads, ink may be heated to form ink bubbles and the expansive force of the bubbles causes ink droplets to be ejected from the printhead nozzles. 
     Thermal inkjet printheads typically contain a chamber layer and a nozzle layer that may be sequentially stacked together. In this regard, a plurality of ink chambers, which are filled with ink to be ejected, are formed in the chamber layer, and a plurality of nozzles through which ink may be ejected are formed in the nozzle layer. 
     SUMMARY OF THE DISCLOSURE 
     Aspects of the present disclosure provides an inkjet printhead and method for manufacturing the inkjet printhead. 
     In one aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the oxetane resin may be represented by Formula 1: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20; and R 1  through R 52  are each independently a halogen atom, a carboxyl group, an amino group, a nitro group, a cyano group, a substituted or unsubstituted C 1 -C 20  alkyl group, a substituted or unsubstituted C 1 -C 20  alkoxy group, a substituted or unsubstituted C 2 -C 20  alkenyl group, a substituted or unsubstituted C 2 -C 20  alkynyl group, a substituted or unsubstituted C 1 -C 20  heteroalkyl group, a substituted or unsubstituted C 6 -C 30  aryl group, a substituted or unsubstituted C 7 -C 30  arylalkyl group, a substituted or unsubstituted C 5 -C 30  heteroaryl group, or a substituted or unsubstituted C 3 -C 30  heteroarylalkyl group. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the oxetane resin of Formula 1 may be a compound represented by Formula 2: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the cationic photoinitiator includes an aromatic halonium salt or an aromatic sulfonium salt. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the solvent may be α-butyrolactone, γ-butyrolactone, propylene glycol methyl ethyl acetate, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, or xylene. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be tilled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the adhesion improving agent includes a polyhydric alcoholic compound or a silane-based compound. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the adhesion improving agent includes a polyhydric alcoholic compound or a silane-based compound, and wherein the polyhydric alcoholic compound may be trimethylolethane, trimethylolpropane, 2-methylpropanetriol, glycerol, a glycerol derivative, 1,2,5-pentanetriol, 1,2,4-butanetriol, pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol, 2-hydroxymethylpropane-1,3-diol, 2-methyl-1,2,4-butanetriol, 1,3,5-trihydroxymethylbenzene, 1,2,3,6-hexanetetrol, or 1,4-sorbitan, wherein the glycerol derivative includes a compound represented by Formula 3: 
     
       
         
         
             
             
         
       
     
     where p, q, and r are each independently an integer from 1 to 20. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the adhesion improving agent includes a polyhydric alcoholic compound or a silane-based compound, and wherein the silane-based compound includes a compound represented by Formula 4: 
     
       
         
         
             
             
         
       
     
     where R 61 , R 62 , R 63  and R 64  are each independently hydrogen, a halogen atom, a carboxyl group, an amino group, a nitro group, a cyano group, a substituted or unsubstituted C 1 -C 20  alkyl group, a substituted or unsubstituted C 1 -C 20  alkoxy group, a substituted or unsubstituted C 2 -C 20  alkenyl group, a substituted or unsubstituted C 2 -C 20  alkynyl group, a substituted or unsubstituted C 1 -C 20  heteroalkyl group, a substituted or unsubstituted C 6 -C 30  aryl group, a substituted or unsubstituted C 7 -C 30  arylalkyl group, a substituted or unsubstituted C 5 -C 30  heteroaryl group, or a substituted or unsubstituted C 3 -C 30  heteroarylalkyl group. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the adhesion improving agent includes a polyhydric alcoholic compound or a silane-based compound, and wherein the silane-based compound may be glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropyldimethylethoxysilane, mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethdxysilane, or N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the oxetane resin composition includes about 1 to about 20 parts by weight of a cationic photoinitiator, about 30 to about 300 parts by weight of a solvent and about 1 to about 20 parts by weight of an adhesion improving agent, based on 100 parts by weight of the oxetane resin. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the chamber layer and the nozzle layer includes cured products of a first photosensitive polymer composition and a second photosensitive polymer composition, respectively, and each of the first photosensitive polymer composition and the second photosensitive polymer composition includes a prepolymer, a cationic photoinitiator, and a solvent. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the chamber layer and the nozzle layer includes cured products of a first photosensitive polymer composition and a second photosensitive polymer composition, respectively, and each of the first photosensitive polymer composition and the second photosensitive polymer composition includes a prepolymer, a cationic photoinitiator, and a solvent, and wherein the prepolymer may be a glycidyl ether functional group, a ring-opened glycidyl ether functional group, or an oxetane functional group in a monomer repeating unit. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the chamber layer and the nozzle layer includes cured products of a first photosensitive polymer composition and a second photosensitive polymer composition, respectively, and each of the first photosensitive polymer composition and the second photosensitive polymer composition includes a prepolymer, a cationic photoinitiator, and a solvent, wherein the prepolymer may be a glycidyl ether functional group, a ring-opened glycidyl ether functional group, or an oxetane functional group in a monomer repeating unit, and wherein the prepolymer has a phenol novolac resin-based backbone, a bisphenol-A-based backbone, a bisphenol-F-based backbone, or an alicyclic backbone. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the chamber layer and the nozzle layer includes cured products of a first photosensitive polymer composition and a second photosensitive polymer composition, respectively, and each of the first photosensitive polymer composition and the second photosensitive polymer composition includes a prepolymer, a cationic photoinitiator, and a solvent, and wherein the prepolymer may be a compound of Formulae 5 through 13: 
     
       
         
         
             
             
         
       
       
         
         
             
             
         
       
       
         
         
             
             
         
       
     
     where m may be an integer from 1 to 20, and n may be an integer from 1 to 20. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, further including an insulating layer disposed on the substrate; a plurality of heaters and a plurality of electrodes sequentially disposed on the insulating layer; and a passivation layer disposed to cover the plurality of heaters and the plurality of electrodes. 
     In another aspect, the disclosure provides an inkjet printhead including a substrate having an ink feed hole; a chamber layer disposed on the substrate, the chamber layer having a plurality of ink chambers that may be filled with ink supplied through the ink feed hole; a nozzle layer disposed on the chamber layer, the nozzle layer having a plurality of nozzles through which ink may be ejected; and a glue layer disposed between the substrate and the chamber layer, wherein the glue layer includes a cured product of an oxetane resin composition, further including an insulating layer disposed on the substrate; a plurality of heaters and a plurality of electrodes sequentially disposed on the insulating layer; and a passivation layer disposed to cover the plurality of heaters and the plurality of electrodes, and further including an anti-cavitation layer disposed on the passivation layer. 
     In another aspect, the disclosure provides a method of manufacturing an inkjet printhead by forming a glue layer on a substrate; forming a chamber layer on the glue layer; forming a nozzle layer including a plurality of nozzles on the chamber layer; forming an ink feed hole from a bottom surface to a top surface of the substrate to penetrate the substrate; and forming an ink chamber and a restrictor through the ink feed hole, wherein the glue layer includes a cured product of an oxetane resin composition. 
     In another aspect, the disclosure provides a method of manufacturing an inkjet printhead by forming a glue layer on a substrate; forming a chamber layer on the glue layer; forming a nozzle layer including a plurality of nozzles on the chamber layer; forming an ink feed hole from a bottom surface to a top surface of the substrate to penetrate the substrate; and forming an ink chamber and a restrictor through the ink feed hole, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent. 
     In another aspect, the disclosure provides a method of manufacturing an inkjet printhead by forming a glue layer on a substrate; forming a chamber layer on the glue layer; forming a nozzle layer including a plurality of nozzles on the chamber layer; forming an ink feed hole from a bottom surface to a top surface of the substrate to penetrate the substrate; and forming an ink chamber and a restrictor through the ink feed hole, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the oxetane resin may be represented by Formula 1, wherein n, and R 1  through R 52  are as described herein. 
     In another aspect, the disclosure provides a method of manufacturing an inkjet printhead by forming a glue layer on a substrate; forming a chamber layer on the glue layer; forming a nozzle layer including a plurality of nozzles on the chamber layer; forming an ink feed hole from a bottom surface to a top surface of the substrate to penetrate the substrate; and forming an ink chamber and a restrictor through the ink feed hole, wherein the glue layer includes a cured product of an oxetane resin composition, and wherein the oxetane resin composition includes an oxetane resin, a cationic photoinitiator, a solvent, and an adhesion improving agent, and wherein the adhesion improving agent includes a polyhydric alcoholic compound or a silane-based compound. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various features and advantages of the present disclosure will become more apparent by describing in detail several embodiments thereof with reference to the attached drawings, in which: 
         FIG. 1  is a schematic plan view of an inkjet printhead according to an embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view taken along a line II-II′ of  FIG. 1 . 
         FIGS. 3 through 14  are various cross-sectional views illustrative of a method of manufacturing an inkjet printhead according to an embodiment of the present disclosure. 
         FIG. 15  is a scanning electron microscopic (SEM) image of a pattern A formed using the glue layer forming composition obtained in Example 3; 
         FIG. 16  is a SEM image of a pattern B formed using the glue layer forming composition obtained in Example 4; 
         FIG. 17  is a SEM image of the surface of heaters of an inkjet printhead manufactured using a photosensitive glue layer forming composition according to an embodiment of the present disclosure; and 
         FIG. 18  is a SEM image of the surface of heaters of an inkjet printhead manufactured using a conventional non-photosensitive glue layer forming composition. 
     
    
    
     DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS 
     Aspects of the present disclosure will now be described more fully with reference to the accompanying drawings, in which several embodiments of the present disclosure are shown. In the drawings, like reference numerals denote like elements, and the size or the thickness of each element may be exaggerated for clarity. It will also be understood that when a layer is referred to as being on another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. 
     DEFINITIONS 
     The term alkyl group used for a substituent used in the present disclosure may refer to a linear or branched C 1 -C 20  alkyl group, a linear or branched C 1 -C 12  alkyl group, or a linear or branched C 1 -C 6  alkyl group. Examples of the unsubstituted alkyl group include but are not limited to methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, t-butyl, pentyl, iso-amyl, hexyl, and the like. At least one hydrogen atom in the alkyl group may be substituted with a halogen atom, a hydroxyl group, a —SH group, a nitro group, a cyano group, a substituted or unsubstituted amino group (—NH 2 , —NH(R), —N(R′)(R″) wherein R′ and R″ are each independently a C 1 -C 20  alkyl group), an amidino group, hydrazine, hydrazone, a carboxyl group, a sulfonic acid group, a phosphoric acid, a C 1 -C 20  alkyl group, a halogenated C 1 -C 20  alkyl group, a C 1 -C 20  alkenyl group, a C 1 -C 20  alkynyl group, a C 1 -C 20  heteroalkyl group, a C 6 -C 20  aryl group, a C 6 -C 20  arylalkyl group, a C 6 -C 20  heteroaryl group, or a C 6 -C 20  heteroarylalkyl group. 
     The term cycloalkyl group used in the present disclosure refers to a monovalent monocyclic system of 3-20 carbon atoms, 3-10 carbon atoms, or 3-6 carbon atoms. In the cycloalkyl group, at least one hydrogen atom may be substituted with the substituents described in connection with the alkyl group. 
     The term heterocycloalkyl group used in the present disclosure refers to a monovalent monocyclic system of 3-20 carbon atoms, 3-10 carbon atoms, or 3-6 carbon atoms, containing one, two, or three heteroatoms selected from nitrogen (N), oxygen (O), phosphorus (P), and sulfur (S). Optionally, one or more hydrogen atoms in the heterocycloalkyl group may be substituted with any of the substituents described in connection with the alkyl group. 
     The term alkoxy group used for a substituent in the present disclosure may refer to an oxygen-containing linear or branched alkoxy group having a C 1 -C 20  alkyl moiety. The alkoxy group may have 1-60 carbon atoms or 1-3 carbon atoms. Examples of such alkoxy group include but are not limited to methoxy, ethoxy, propoxy, butoxy, t-butoxy, and the like. The alkoxy group may be a haloalkoxy group substituted further with one or more halogen atoms. Examples of the haloalkoxy group include but are not limited to fluoromethoxy, chloromethoxy, trifluoromethoxy, trifluoroethoxy, fluoroethoxy, fluoropropoxy, and the like. Optionally, one or more hydrogen atoms in the alkoxy group may be substituted with the substituents described in connection with the alkyl group. 
     The term alkenyl group used for a substituent in the present disclosure refers to a linear or branched C 1 -C 20  aliphatic hydrocarbon group. The alkenyl group may have 2-12 carbon atoms or 2-6 carbon atoms. The branched C 2 -C 20  aliphatic hydrocarbon refers to a linear alkenyl chain to which at least one low alkyl or low alkenyl group may be attached. Such an alkenyl group may be unsubstituted or may be independently substituted with one or more halo, carboxy, hydroxy, formyl, sulfur, sulfino, carbamoyl, amino or imino groups. However, the substituents of the alkenyl group may not be limited to these groups. Examples of such alkenyl groups include but are not limited to ethenyl, prophenyl, carboxyethenyl, carboxyprophenyl, sulfinoethenyl, sulfonoethenyl, and the like. Optionally, one or more hydrogen atoms in the alkenyl group may be substituted with the substituents described in connection with the alkyl group. 
     The term alkynyl group used for a substituent in the present disclosure refers to a straight or branched C 2 -C 20  aliphatic hydrocarbon group including a carbon-carbon triple bond. Examples of such an alkenyl group include alkenyl groups containing 2-12 carbon atoms or 2-6 carbon atoms. The branched C 2 -C 20  aliphatic hydrocarbon group having a C—C triple bond may refer to a linear alkynyl chain to which at least one low alkyl or low alkynyl group may be attached. Such an alkenyl group may not be substituted, or may be independently substituted with one or more halo, carboxy, hydroxy, formyl, sulfur, sulfino, carbamoyl, amino or imino groups. However, the substituent of the alkenyl group may not be limited to these groups. Optionally, one or more hydrogen atoms in the alkynyl group may be substituted with the substituents described in connection with the alkyl group. 
     The term heteroalkyl group used for a substituent in the present disclosure refers to an alkyl group in which a linear chain of 1-20 carbons, 1-12 carbons, or 1-6 carbons includes a hetero atom, such as nitrogen (N), oxygen (O), phosphorus (P), or sulfur (S). Optionally, one or more hydrogen atoms in the heteroalkyl group may be substituted with the substituents described in connection with the alkyl group. 
     The term aryl group used for a substituent in the present disclosure refers to a C 6-30  carbocyclic aromatic system, which may be used exclusively or in combination, including at least one ring that may be attached to each other using a pendent method or may be fused together. The term aryl group refers to a group including but not limited to an aromatic radical, such as phenyl, naphthyl, tetrahydronaphthyl, indan, biphenyl, and the like. For example, the aryl group may include phenyl. Optionally, one or more hydrogen atoms in the aryl group may be substituted with the substituents described in connection with the alkyl group. 
     The term arylalkyl group used for a substituent in the present disclosure refers to an alkyl group including at least one hydrogen atom substituted with an aryl group. 
     The term heteroaryl group used for a substituent in the present disclosure refers to a C 5 -C 30  monovalent monocyclic or non-cyclic aromatic radical including one, two, or three heteroatoms selected from N, O, and S. In addition, the heteroaryl group may refer to a monovalent monocyclic or bicyclic aromatic radical group in which a hetero atom in the chain of the radical group may be oxidized or quanternized to form, for example, an N-oxide or a quaternary salt. Examples of the heteroaryl group include but are not limited to thienyl, benzothienyl, pyridyl, pyrazinyl, pyrimidinyl, pyridazinyl, quinolinyl, quinoxalinyl, imidazolyl, puranyl, benzopuranyl, thiazolyl, isoxazoline, benzisoxazoline, benzimidazolyl, triazolyl, pyrazolyl, pyrrolyl, indolyl, 2-pyridonyl, N-alkyl-2-pyridonyl, pyrazinonyl, pyridazinonyl, pyrimidinonyl, oxazolonyl, an N-oxide thereof, such as pyridyl N-oxide or quinolinyl N-oxide, a quaternary salt thereof, and the like. Optionally, one or more hydrogen atoms in the heteroaryl group may be substituted with the substituents described in connection with the alkyl group. 
     The term heteroarylalkyl group used for a substituent in the present disclosure refers to a C 3 -C 30  carbocyclic aromatic system in which at least one hydrogen atom in such an alkyl group as defined above may be substituted with such a heteroaryl group as defined above. Optionally, one or more hydrogen atoms in the heteroarylalkyl group may be substituted with the substituents described in connection with the alkyl group. 
     Thermal Inkjet Printhead 
       FIG. 1  provides a schematic view of a thermal inkjet printhead according to an embodiment of the present disclosure.  FIG. 2  is a cross-sectional view taken along a line II-II′ of  FIG. 1 . Referring to  FIGS. 1 and 2 , a thermal inkjet printhead according to an embodiment may comprise a glue layer  121 , a chamber layer  120  and a nozzle layer  130  sequentially formed on a substrate  110  on which various material layers are formed. The substrate  110  may be formed of, for example, silicon. An ink feed hole  111  for supplying ink may be formed through the substrate  110 . An insulating layer  112  may be formed on the substrate  110  in order to thermally and electrically insulate from one another the substrate  110  and a heater  114 , which will be described later. To that end, the insulating layer  112  may be formed of, for example, silicon oxide. The heater  114  for heating ink contained in an ink chamber  122  to generate ink bubbles may be formed on the insulating layer  112 . In this regard, the heater  114  may be formed underneath the ink chamber  122 . The heater  114  may be formed of a heating resistor material including, but not limited to, a tantalum-aluminum alloy, a tantalum nitride, a titanium nitride, or a tungsten silicide, and the like. An electrode  116  may be formed on the top surface of the heater  114 . The electrode  116  may be formed of a material having good to excellent electrical conductivity in order to supply current to the heater  114 . The electrode  116  may be formed of conducting metals including, but not limited to, aluminum (Al), an aluminum alloy, gold (Au), silver (Ag), and the like. A passivation layer  118  may be formed on the heater  114  and the electrode  116 . In this regard, the passivation layer  118  may be formed in order to prevent oxidization and corrosion of the heater  114  and the electrode  116  caused by the ink. The passivation layer  118  may be formed of a silicon nitride or a silicon oxide. An anti-cavitation layer  119  may further be formed on a surface region of the passivation layer  118  corresponding to the heater  114 . In this regard, the anti-cavitation layer  119  may be formed in order to protect the heater  114  from a cavitation force generated when bubbles are burst. The anti-cavitation layer  119  may be formed of for example, tantalum (Ta). 
     The glue layer  121  stably binds the chamber layer  120  to the substrate  110 . Alternatively, the glue layer  121  stably binds the chamber layer  120  to the passivation layer  118  when the substrate  110  includes the insulating layer  112 , the heater  114 , the electrode  116 , and the passivation layer  118  sequentially formed thereon. The glue layer  121  may include a cured product of an oxetane resin composition. For example, the glue layer  121  may be formed by coating the substrate  110  with an oxetane resin composition, and by patterning the resultant coated composition into a predetermined pattern by using a photolithography process. The oxetane resin composition may include an oxetane resin, a cationic photoinitiator, a solvent and an adhesion improving agent. The oxetane resin may be represented by Formula (1) below: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20, and where R 1  through R 52  are each independently a halogen atom, a carboxyl group, an amino group, a nitro group, a cyano group, a substituted or unsubstituted C 1 -C 20  alkyl group, a substituted or unsubstituted C 1 -C 20  alkoxy group, a substituted or unsubstituted C 2 -C 20  alkenyl group, a substituted or unsubstituted C 2 -C 20  alkynyl group, a substituted or unsubstituted C 1 -C 20  heteroalkyl group, a substituted or unsubstituted C 6 -C 30  aryl group, a substituted or unsubstituted C 7 -C 30  arylalkyl group, a substituted or unsubstituted C 5 -C 30  heteroaryl group, or a substituted or unsubstituted C 3 -C 30  heteroarylalkyl group. 
     The oxetane resin of Formula (1) may be a compound represented by Formula 2: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 6. 
     The oxetane resin may exhibit excellent photo-curable characteristics. When an oxetane resin composition containing the oxetane resin is used, the glue layer  121  may be formed in an appropriate location. The oxetane resin coated in regions other than the glue layer region and not exposed to light irradiation, may be completely removed through a developing process so that oxetane resin remaining in the inkjet printhead does not cause any failures of the printhead. 
     The cationic photoinitiator in the oxetane resin composition may generate an ion or a free radical that initiates polymerization when exposed to light. Examples of such a cationic photoinitiator include, but are not limited to, an aromatic halonium salt and a sulfonium salt of Group VA and VI elements, and the like. For example, the cationic photoinitiator may be UVI-6974 (available from Union Carbide Co.) or SP-172 (available from Asahi Denka Co., Ltd). Examples of the aromatic sulfonium salt include but are not limited to triphenylsulfonium tetrafluoroborate, triphenylsulfonium hexafluoroantimonate (UVI-6974), phenylmethylbenzylsulfonium hexafluoroantimonate, phenylmethylbenzylsulfonium hexafluorophosphate, triphenylsulfonium hexafluorophosphate, methyl diphenylsulfonium tetrafluoroborate, and dimethyl phenylsulfonium hexafluorophosphate, and the like. Examples of the aromatic halonium salt include but are not limited to an aromatic iodonium salt. Examples of the aromatic iodonium salt include but are not limited to diphenyliodonium tetrafluoroborate, diphenyliodonium hexafluoroantimonate, butylphenyliodonium hexafluoroantimonate, (SP-172), and the like. 
     In one embodiment, the amount of the cationic photoinitiator may be in the range of about 1 to about 20 parts by weight, based on 100 parts by weight of the oxetane resin. In another embodiment, the amount of the cationic photoinitiator may be in the range of about 1.5 to about 15 parts by weight, based on 100 parts by weight of the oxetane resin. In yet another embodiment, the amount of the cationic photoinitiator may be in the range of about 3 to about 10 parts by weight, based on 100 parts by weight of the oxetane resin. When the amount of the cationic photoinitiator is within these ranges, sufficient crosslinking reaction may take place, and photoenergy may not be excessively consumed to form a glue layer having an appropriate thickness so that the crosslinking rate may be increased. 
     The solvent may include, but are not limited to, α-butyrolactone, γ-butyrolactone, propylene glycol methyl ethyl acetate, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, xylene, and the like. In one embodiment, the amount of the solvent may be in the range of about 30 to about 300 parts by weight, based on 100 parts by weight of the oxetane resin. In another embodiment, the amount of the solvent may be in the range of about 50 to about 250 parts by weight, based on 100 parts by weight of the oxetane resin. In yet another embodiment, the amount of the solvent may be in the range of about 70 to about 200 parts by weight, based on 100 parts by weight of the oxetane resin. When the amount of the solvent is within these ranges, the oxetane resin composition may have an appropriate viscosity, and thus have improved workability. As a result, a glue layer pattern may be easily formed. 
     The adhesion improving agent may be any material that intensifies the adhesion of the oxetane resin in the oxetane resin composition to the substrate  110 , which may be formed of an inorganic material, the passivation layer  118 , or to the chamber layer  120 , which may be formed of an organic material. Examples of the adhesion improving agent may include, but are not limited to, polyhydric alcoholic compounds, silane-based compounds, and the like. Polyhydric alcoholic compounds have several hydrophilic hydroxyl groups and hydrophobic aliphatic groups, and thus can effectively bind to both the substrate  110 , which has hydrophilic surface characteristics, and the chamber layer  120 , which may be formed of a hydrophobic organic material. In addition, silane-based compounds include side chains that are liable to be separated from a core element, silicon (Si), and thus, may form a strong bond with the substrate  110  and the chamber layer  120 . The silane-based compounds may provide excellent characteristics for the glue layer  121 . 
     Polyhydric alcoholic compounds include but are not limited to trimethyl-olethane, trimethylolpropane, 2-methylpropanetriol, glycerol, a glycerol derivative, 1,2,5-pentanetriol, 1,2,4-butanetriol, pentaerythritol, dipentaerythritol, tripentaerythritol, sorbitol, 2-hydroxymethylpropane-1,3-diol, 2-methyl-1,2,4-butanetriol, 1,3,5-trihydroxymethylbenzene, 1,2,3,6-hexanetetrol, 1,4-sorbitan, and the like. A glycol derivative may be a compound represented by Formula (3) below: 
     
       
         
         
             
             
         
       
     
     where p, q, and r are each independently an integer from 1 to 20. 
     The silane-based compound may include, but is not limited to, glycidoxypropyl-trimethoxysilane, glycidoxypropylmethyldimethoxysilane, glycidoxypropyldimethyl-ethoxysilane, mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and the like. An example of such a silane-based compound may include a compound represented by Formula (4) below: 
     
       
         
         
             
             
         
       
     
     where R 61 , R 62 , R 63  and R 64  are each independently hydrogen, a halogen atom, a carboxyl group, an amino group, a nitro group, a cyano group, a substituted or unsubstituted C 1 -C 20  alkyl group, a substituted or unsubstituted C 1 -C 20  alkoxy group, a substituted or unsubstituted C 2 -C 20  alkenyl group, a substituted or unsubstituted C 2 -C 20  alkynyl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted C 6 -C 30  aryl group, a substituted or unsubstituted C 7 -C 30  arylalkyl group, a substituted or unsubstituted C 5 -C 30  heteroaryl group, or a substituted or unsubstituted C 3 -C 30  heteroarylalkyl group. 
     In one embodiment, the amount of the adhesion improving agent may be in the range of about 1 to 20 parts by weight, based on 100 parts by weight of the oxetane resin. In another embodiment, the amount of the adhesion improving agent may be in the range of about 1.5 to about 15 parts by weight, based on 100 parts by weight of the oxetane resin. In yet another embodiment, the amount of the adhesion improving agent may be in the range of about 3 to about 10 parts by weight, based on 100 parts by weight of the oxetane resin. When the amount of the adhesion improving agent is within these ranges, the glue layer  121  may have enhanced adhesiveness without any effect on the photocuring reaction in the oxetane resin. 
     The chamber layer  120 , which may be formed of a first photosensitive polymer composition, may be disposed on the glue layer  121 . The chamber layer  120  has a plurality of ink chambers  122  that may be filled with ink supplied through the ink feed hole  111 . The chamber layer  120  may further include a plurality of restrictors  124 , which are paths connecting the ink feed hole  111  and the ink chambers  122 . The chamber layer  120  may be formed by forming a chamber material layer ( 120 ′ of  FIG. 4 ), which includes the first photosensitive polymer composition, on the glue layer  121 , and by patterning the chamber material layer  120 ′ by using a photolithography process. 
     The first photosensitive polymer composition may include a negative-type photosensitive polymer. In this regard, a plurality of ink chambers  122  and restrictors  124  may be formed as unexposed regions of the first photosensitive polymer composition, which may be removed by a developing solution that will be described later. Exposed regions of the first photosensitive polymer composition form the chamber layer  120  having a cross-linked structure through a post-exposure bake (PEB) process. 
     A nozzle layer  130 , which may be formed of a second photosensitive polymer composition, may be formed above the chamber layer  120 . The nozzle layer  130  may have a plurality of nozzles  132  through which ink may be ejected. The nozzle layer  130  may be formed by forming a nozzle material layer  130 ′ (see  FIG. 8 ) including the second photosensitive polymer composition on the chamber layer  120 , and by patterning the nozzle material layer  130 ′ by using a photolithography process. 
     The second photosensitive polymer composition may include a negative-type photosensitive polymer. In this regard, a plurality of nozzles  132  may be formed as unexposed regions of the second photosensitive polymer composition, which are removed by a developing solution that will be described layer. Exposed regions of the second photosensitive polymer composition may form the nozzle layer  130  having a cross-linked structure through a FEB process. The chamber layer  120  and the nozzle layer  13  may alternatively be formed of photosensitive dry films, instead of the first and second photosensitive polymer compositions. The photosensitive dry films may be the same as the first and second photosensitive polymer compositions in terms of composition and curing method, except that the photosensitive dry films are obtained by previously removing a solvent from the first and second photosensitive polymer compositions. When such photosensitive dry films containing no flowable solvent are used, the ink feed hole  111  may be formed before the formation of the chamber layer  120  and the nozzle layer  130  since the solvent does not run. The formation of the chamber layer  120  and the nozzle layer  130  will be described later in more detail with reference to a method of manufacturing an inkjet printhead. 
     Each of the first and second negative photosensitive compositions used in the manufacturing methods described above may include a prepolymer, a cationic photoinitiator, and a solvent. The prepolymer may contain a glycidyl ether functional group, a ring-opened glycidyl ether functional group, or an oxetane functional group in each monomer repeat unit, including, but not limited to, a phenol Novolac resin-based backbone, a bisphenol-A-based backbone, a bisphenol-F-based backbone, an alicyclic backbone, and the like. However, the composition of the first and second photosensitive polymer compositions is not limited to the above, and any material for improving the characteristics of the first and second photosensitive polymer compositions may be further added. The first and second photosensitive polymer compositions may have the same composition or different compositions with respect to each other. 
     Epoxy-based materials may also be used for the prepolymer, but the present disclosure is not limited thereto. Any material suitable for forming a chamber layer or a nozzle layer of inkjet printheads may be used. For example, a prepolymer may include either a glycidyl ether functional group, a ring-opened glycidyl ether functional group, or an oxetane functional group in a monomer repeating unit, and having either a phenol novolac resin-based backbone, a bisphenol-A-based backbone, a bisphenol-F-based backbone, or an alicyclic backbone may be used. 
     The prepolymer in the first and second photosensitive photoresist compositions may form a crosslinked polymer by being exposed to actinic radiation. The prepolymer may include a backbone monomer including but not limited to phenol, o-cresol, p-cresol, bisphenol-A, an alicyclic compound, and the like, or a mixture thereof. Examples of prepolymers having a glycidyl ether functional group include but are not limited to a prepolymer including a bi-functional glycidyl ether group and a prepolymer including a multifunctional glycidyl ether group, and the like. 
     In particular, a prepolymer including a bi-functional glycidyl ether functional group may be a compound represented by Formula (5): 
     
       
         
         
             
             
         
       
     
     where m may be an integer from 1 to 20. 
     The prepolymer including the bi-functional glycidyl ether functional group may form a film having a relatively low degree of crosslinking. Examples of such a prepolymer having a bi-functional glycidyl ether functional group may include, but are not limited to, EPON 828, EPON 1004, EPON 1001F, and EPON 1010, which are available from Shell Chemical Company, DER-332, DER-331, and DER-164, which are available from Dow Chemical Company, and ERL-4201 and ERL-4289, which are available from Union Carbide Corporation, and the like. In addition, examples of prepolymers including a multi-functional glycidyl ether functional group may include, but are not limited to, EPON SU-8 and EPON DPS-16, which are available from Shell Chemical Company, DEN-431 and DEN-439, which are available from Dow Chemical Company, and EHPE-3150, which is available from Daicel Chemical Industries. Ltd., and the like. 
     Examples of prepolymers having a glycidyl ether functional group in a monomer repeating unit and a phenol novolac resin-based backbone may include, but are not limited to, a compound represented by Formula (6) below: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20, for example, from 1 to 10. 
     Examples of prepolymers having a glycidyl ether functional group in a monomer repeating unit and a phenol novolac resin-based backbone may also include, but are not limited to, compounds including o-cresol or p-cresol, instead of phenol, as represented by Formulae (7) and (8) below: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20, for example, from 1 to 10. 
     Examples of prepolymers having a glycidyl ether functional group in a monomer repeating unit and a bisphenol-A-based backbone may include, but are not limited to, compounds represented by Formulae (9) and (10) below: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20, for example, from 1 to 10. 
     Examples of prepolymers having a glycidyl ether functional group in a monomer repeating unit and an alicyclic backbone include but are not limited to a compound represented by Formula (11) below, and in particular, additional products of 1,2-epoxy-4(2-oxiranyl)-cyclohexane of 2,2-bis(hydroxy methyl)-1-butanol, which can be purchased as EHPH-3150. 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20, for example, from 1 to 10. 
     Examples of prepolymers having a glycidyl ether functional group in a monomer repeating unit and a bisphenol-F-based backbone may include, but are not limited to, a compound represented by Formula (12) below: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20, for example, from 1 to 10. 
     Examples of prepolymers having an oxetane functional group in a monomer repeating unit and a bisphenol-A-based backbone may include, but are not limited to, a compound represented by Formula (13) below: 
     
       
         
         
             
             
         
       
     
     where n may be an integer from 1 to 20, for example, from 1 to 10. 
     As described above, the prepolymer included in the first and second photosensitive polymer compositions may include, but are not limited to, the compounds represented by Formulae (5) through (13) above. 
     The cationic photoinitiator in the first and second photosensitive polymer compositions may generate an ion or a free radical that initiates polymerization when exposed to light. Examples of the cationic photoinitiator may include, but are not limited to, an aromatic halonium salt or a sulfonium salt of Group VA or VI elements, such as UVI-6974 available from Union Carbide Co., SP-172 available from Asahi denka, and Cyracure 6974 available from Dow Chemical, and the like. 
     In one embodiment, the amount of the cationic photoinitiator may be in the range of about 1 to about 10 parts by weight, based on 100 parts by weight of the prepolymer. In another embodiment, the amount of the cationic photoinitiator may be in the range of about 1.5 to about 7 parts by weight, based on 100 parts by weight of the prepolymer. In yet another embodiment, the amount of the cationic photoinitiator may be in the range of about 3 to about 5 parts by weight, based on 100 parts by weight of the prepolymer. When the amount of the cationic photoinitiator is within these ranges, sufficient crosslinking reaction may take place using an appropriate amount of photoenergy, and the crosslinking rate may be increased so that the overall processing time may be reduced. The resulting photocured product may have excellent mechanical characteristics. 
     All the above-description of the cationic photoinitiator used in the oxetane resin composition may be applied to the cationic photoinitiator used in the first and second photosensitive polymer compositions. 
     Examples of the solvent used in the first and second photosensitive polymer compositions may include, but are not limited to, α-butyrolactone, γ-butyrolactone, propylene glycol methyl ethyl acetate, tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, xylene, and the like, or mixtures thereof. 
     In one embodiment, the amount of the solvent may be in the range of about 30 to about 300 parts by weight, based on 100 parts by weight of the prepolymer. In another embodiment, the amount of the solvent may be in the range of about 50 to about 250 parts by weight or about 70 to about 200 parts by weight, based on 100 parts by weight of the prepolymer. When the amount of the solvent is within these ranges, the first and second photosensitive polymer compositions may have an appropriate viscosity, and thus have improved workability. As a result, patterns of the chamber layer and the nozzle layer may be easily formed. In addition, it may be also easy to control the shape and size of ink flow paths to be more uniform. 
     Each of the first and second photosensitive polymer compositions may further include one or more plasticizers. In this regard, the plasticizer may prevent or substantially reduce cracks from being generated in the nozzle layer after nozzles are developed in the nozzle layer and a sacrificial layer may be eliminated to form the nozzles. In addition, the plasticizer may also reduce variations of nozzle chamber angles, and thus reduce image defects caused due to Y spacing, since the plasticizer having a high melting point functions as a lubricant among the crosslinked polymers to reduce stress in the nozzle layer. The plasticizer may simplify the entire process of manufacturing the inkjet printhead, since an additional baking process may not be required. 
     The plasticizer may include, but is not limited to, a phthalate-based compound, a trimellitate-based compound, a phosphate-based compound, and the like. Examples of the phthalate-based plasticizer may include, but are not limited to, dioctyl phthalate (DOP) and diglycidyl hexahydro phthalate (DGHP), and the like. An example of the trimellitate-based plasticizer may include, but is not limited to, triethylhexyl trimellitate. An example of the phosphate-based plasticizer may include, but is not limited to, tricresyl phosphate. The plasticizer may be used exclusively or included in a combination of at least two of the above listed compounds. In one embodiment, the amount of the plasticizer may be in the range of about 1 to 15 parts by weight, based on 100 parts by weight of the prepolymer. In another embodiment the amount of the plasticizer may be in the range of about 5 to about 10 parts by weight, based on 100 parts by weight of the prepolymer. When the amount of the plasticizer is within these ranges, the plasticizer may effectively work without affecting the degree of crosslinking of the prepolymer. 
     Each of the first and second photosensitive polymer compositions may further include one or more additives including, but not limited to, a photosensitizer silane coupling agent, a filler, a viscosity modifier, and the like. The photosensitizer absorbs light energy and facilitates transfer of the energy to another compound to generate a radical or ionic initiator. Mostly, the photosensitizer widens an energy wavelength range effective for light exposure. The photosensitizer may be typically an aromatic light-absorbing chromophore. In addition, the photosensitizer may induce generation of a radical or ionic photoinitiator. Each of the first and second photosensitive polymer compositions may further include an additive other than the above-listed additives. 
       FIGS. 3 through 12  are cross-sectional views of an inkjet printhead according to an embodiment of the present disclosure illustrative of the method according to an embodiment of manufacturing the inkjet printhead. Referring to  FIG. 3 , a substrate  110  may be prepared, and an insulating layer  112  may be formed on a surface of the substrate  110 . The substrate  110  may be a silicon substrate. The insulating layer  112 , which insulates from one another the substrate  110  and heaters  114 , which will be described later, may be formed of, for example, silicon oxide. The heaters  114  for heating ink to generate ink bubbles are formed on the insulating layer  112 . The heaters  114  may be formed by depositing a heating resistive material, such as a tantalum-aluminum alloy, a tantalum nitride, a titanium nitride, or a tungsten silicide, on the insulating layer  112 , and by patterning the heating resistive material. A plurality of electrodes  116  for supplying current to the heaters  114  are formed on the heaters  114 . The electrodes  116  may be formed by depositing a metal having excellent electrical conductivity, such as aluminum (Al), an Al alloy, gold (Au), or silver (Ag), on the heaters  114 , and then patterning the metal. A passivation layer  118  may be formed on the insulating layer  112  so as to cover the heaters  114  and the electrodes  116 . The passivation layer  118  prevents the heaters  114  and the electrodes  116  from being oxidized or corroded by ink contacting the same. The passivation layer  118  may be formed of a silicon nitride or a silicon oxide. A glue layer  121  as described above may be formed on the passivation layer  118  in order to increase an adhesion force between a chamber material layer  120 ′ and the passivation layer  118 . An anti-cavitation layer  119  may further be formed on a surface region of the passivation layer  118  corresponding to the heaters  114 . The anti-cavitation layer  119  protects the heaters  114  from a cavitation force generated when bubbles are burst. The anti-cavitation layer  119  may be formed of tantalum (Ta). 
     Referring to  FIG. 4 , the chamber material layer  120 ′ may be formed on the passivation layer  118 . The chamber material layer  120 ′ may include a first photoresist polymer composition. The chamber material layer  120 ′ may be formed by laminating a dry film including a photosensitive resin, a photo acid generator (PAG), a cationic photoinitiator, or the like, on the passivation layer  118 . The photosensitive resin in the chamber material layer  120 ′ may be a negative-type photosensitive polymer, for example, a prepolymer included in the first photosensitive polymer composition described above. The chamber material layer  120 ′ may be subjected to a light exposure process and a PEB process. In particular, the chamber material layer  120 ′ may be s exposed to light by using a photomask (not shown) having an ink chamber pattern and a restrictor pattern. In this regard, when the chamber material layer  120 ′ includes the first photosensitive polymer composition, ions or free radicals that initiate polymerization are generated in exposed regions  120 ′ a  of the chamber material layer  120 ′ by the cationic photoinitiator as a result of the exposure process. Alternatively, when the chamber material layer  120 ′ includes a negative-type photosensitive polymer, acid may be generated in the exposed regions  120 ′ a  of the chamber material layer  120 ′ by, for example, a photoacid generator (PAG), as a result of the exposure process. The exposed chamber material layer  120 ′ may be subjected to the PEB process. The PEB process may be performed, for example, at a temperature ranging from about 90 to about 120° C. for about 3 to 5 minutes. In the PEB process, a cross-linking reaction occurs in the exposed regions  120 ′ a  of the chamber material layer  120 ′ so that a cross-linked product of the first photosensitive polymer composition may be formed. 
     Referring to  FIG. 5 , the chamber material layer  120 ′ which has undergone the light exposure process and the PEB process may be subjected to a development process in order to form a chamber layer  120 . Unexposed regions (not shown) of the chamber material layer  120 ′ are removed by a developing solution during the development process. In this regard, since the first photosensitive polymer composition in the exposed regions  120 ′ a  of the chamber material layer  120 ′ has a cross-linked structure formed through the PEB process, the exposed regions  120 ′ a  of the chamber material layer  120 ′ are not removed by the development process and form the chamber layer  120 . 
     Referring to  FIG. 6 , after the chamber layer  120  may be formed and before a nozzle layer may be formed, the passivation layer  118 , the insulating layer  112  and the substrate  110  are partially etched. This partial etching process may be effective to define the location of an ink feed hole to be formed later to pass through the substrate  110 . 
     Referring to  FIG. 7 , a sacrificial layer S may be formed on the chamber layer  120  which has undergone the light exposure process and the PEB process. The sacrificial layer S may be formed to cover the chamber layer  120 . The sacrificial layer S may be formed by coating a positive photoresist polymer or a non-photosensitive soluble polymer on the substrate  110  to a predetermined thickness by using a spin coating process, for example. In this regard, the positive photoresist polymer may be an imide-based positive photoresist polymer. When the sacrificial layer S is formed of an imide-based positive photoresist polymer, the effect of a solvent on the sacrificial layer S may be insignificant and the sacrificial layer S may not generate nitrogen gas when exposed to light. To this end, the imide-based positive photoresist polymer should be hard-baked at about 140° C. Alternatively, the sacrificial layer S may be formed by spin coating a liquid photosensitive soluble polymer on the substrate  110  to a predetermined thickness, and then by baking the resultant structure. In this regard, the liquid non-sensitized soluble polymer may include, but are not limited to, a phenol resin, a polyurethane resin, an epoxy resin, a polyimide resin, an acryl resin, a polyamide resin, an urea resin, a melamine resin, a silicon resin, and the like. 
     As illustrated in  FIG. 8 , the top surfaces of the chamber layer  120  and the sacrificial layer S may be planarized by using a chemical mechanical polishing (CMP) process. In particular, the top surfaces of the sacrificial layer S and the chamber layer  120  may be polished using CMP to a desired height of the ink passage, so that the top surfaces of the chamber layer  120  and the sacrificial layer S have the same level. 
     Referring to  FIG. 9 , a nozzle material layer  130 ′ may be formed on the chamber layer  120  and the sacrificial layer S. The nozzle material layer  130 ′ may include a second photosensitive polymer composition or the like. The nozzle material layer  130 ′ may be formed by laminating a dry film including a photosensitive resin, a photoacid generator (PAG), or the like, on the chamber layer  120 . The photosensitive region in the nozzle material layer  130 ′ may be a negative-type photosensitive polymer. 
     A process of forming a nozzle layer and the nozzles will now be described with reference to  FIGS. 10 and 11 . Initially, the nozzle material layer  130 ′ may be subjected to an exposure process. In particular, the nozzle material layer  130 ′ may be exposed to light by using a photomask (not shown) having the nozzle pattern. In this regard, when the nozzle material layer  130 ′ includes the second photosensitive polymer composition, ions or free radicals that initiate polymerization are generated in exposed regions  130 ′ a  of the nozzle material layer  130 ′ by the cationic photoinitiator as a result of the exposure process. Alternatively, when the nozzle material layer  130 ′ includes a negative-type photosensitive polymer, acid may be generated in the exposed regions  130 ′ a  of the nozzle material layer  130 ′ by, for example, a photoacid generator (PAG), as a result of the exposure process. In  FIG. 10 , reference numeral  130 ′ b indicates unexposed regions of the nozzle material layer  130 ′. 
     Referring to  FIG. 11 , the nozzle material layer  130 ′ which has undergone the exposure process may be subjected to a PEB process and a development process to form a nozzle layer  130 . In particular, the nozzle material layer  130 ′ may be subjected to a PEB process. The PEB process may be performed, for example, a temperature ranging from about 90 to about 120° C. for about 3 to 5 minutes, but the present disclosure is not limited to these ranges. The second photosensitive polymer composition may be cross-linked in the exposed regions  130 ′ a  of the nozzle material layer  130 ′ due to the PEB process. The nozzle material layer  130 ′ may be subjected to a development process. The unexposed regions  130 ′ b of the nozzle material layer  130 ′ are removed by a predetermined developing solution through the development process, and thus a plurality of nozzles  132  are formed. In this regard, since the second photosensitive polymer composition in the exposed regions  130 ′ a  of the nozzle material layer  130 ′ has a cross-linked structure through the PEB process, the exposed regions  130 ′ a  of the nozzle material layer  130 ′ are not removed by the development process, and thus form the nozzle layer  130 . 
     A process of forming an ink feed hole will be described with reference to  FIGS. 12 through 14 . Referring to  FIG. 12 , an etch mask  140  for forming an ink feed hole  111  (see  FIG. 14 ) may be provided on the bottom surface of the substrate  110 . The etching mask  140  may be formed, for example, by coating a positive or negative photoresist on the bottom surface of the substrate  110  and then patterning the coated photoresist. 
     As illustrated in  FIG. 13 , the ink feed hole  111  may be formed by etching a bottom surface region of the substrate  110  exposed by the etching mask  140  to penetrate the substrate  110 . The etching mask  140  may then be removed as illustrated in  FIG. 14 . The bottom surface of the substrate  110  may be etched using a dry etching method, for example, using plasma. Alternatively, the bottom surface of the substrate  110  may be etched using a wet etching method, for example, by using tetra-methyl ammonium hydroxide (TMAH) or potassium hydroxide (KOH) as an etchant. Alternatively, the ink feed hole  111  may be formed by laser processing or various other processes. Finally, the sacrificial layer S may be removed by using a solvent to form an ink chamber  122  and a restrictor  124 , which are surrounded by the chamber layer  120 . Through the above-described process, an inkjet printhead according to an embodiment as illustrated in  FIG. 14  may be manufactured. 
     The present disclosure will now be described in further detail with reference to the following examples. These examples are for illustrative purposes only and are not intended to limit the scope of the disclosure. 
     Example 1 
     Synthesis of Toluene-4-Sulfonic Acid 3-Methyl-oxetane-3-yl Methyl Ester 
     Toluene-4-sulfonic acid 3-methyl-oxetan-3-yl methyl ester represented by Formula 16 below may be synthesized according to Scheme 1. 
     
       
         
         
             
             
         
       
     
     Example 2 
     Synthesis of Oxetane Containing Compound of Formula 2 
     The oxetane containing compound of Formula (2) may be synthesized according to Scheme 2. 
     
       
         
         
             
             
         
       
     
     where n is 2. 
     Example 3 
     Preparation of the Composition for Forming a Glue Layer 
     2 g of PGMEA (available from AZ EM Co.), 5 g of SP-172 (available from Asahi Denka Korea Chemical Co.) and 5 g of glycerol (available from Aldrich) as an adhesion improving agent were placed in a jar and mixed together to prepare a solution. 48 g of the oxetane-containing compound of Formula (2) obtained in Example 2 was added to the jar and mixed with the solution for 24 hours on a roller before being used as a composition for forming a glue layer. The composition for forming a glue layer had a viscosity of about 1,000 cps at 25° C. 
     Example 4 
     Preparation of the Composition for Forming a Glue Layer 
     A composition for forming a glue layer was prepared in the same manner as in Example 3, except that glycerol as an adhesion improving agent was not used. 
     Example 5 
     Preparation of the Photosensitive Polymer Composition 
     30 g of PGMEA (available from AZ EM Co.) and 3 g of SP-172 (available from Asahi Denka Korea Chemical Co.) were placed in a jar and mixed together to prepare a solution. 40 g of the oxetane-containing compound of Formula 2 obtained in Example 2 was added to the jar and mixed with the solution for 24 hours on a roller before being used as a composition for forming a glue layer. The composition for forming a glue layer had a viscosity of about 2,000 cps at 25° C. 
     Example 6 
     Manufacture of an Inkjet Printhead Having the Structure Illustrated in FIG.  14   
     An insulating layer  112  formed of a silicon oxide to a thickness of about 2 μm, a tantalum nitride heater pattern  114  having a thickness of about 500 Å, an electrode pattern formed of an AlSiCu alloy in which the amounts of Si and Cu were respectively 1% by weight or less, to a thickness of about 500 Å, a silicon nitride passivation layer  118  having a thickness of about 3000 Å, and an anti-cavitation layer  119  formed of tantalum to have a thickness of about 3000 Å were sequentially formed on a 6-inch silicon wafer  110  using a sputtering process and photolithography process (refer to  FIG. 3 ). 
     The silicon wafer  110  on which the layers were formed was heat treated at 200° C. for 10 minutes to remove moisture, and treated with hexamethyldisliazane (HMDS) as an adhesion promoter. The composition for forming a glue layer prepared in Example 3 was spin coated on the silicon wafer  110  at 2,000 rpm/40 sec, and soft-baked at 95° C. for 3 minutes. A light exposure process was performed with UV light of about 13 mW/cm 2  for 5 seconds using a negative photomask, and a PEB process was performed at 110° C. for 1 minute to form a pattern. The resultant was developed by using PGMEA as a developer for 30 seconds, rinsed using isopropyl alcohol (IPA), and dried. A post-bake process was conducted at 90° C. for 5 minutes and at 180° C. for 10 minutes, and the resultant was slowly cooled to form a glue layer  121  having a thickness of about 2 μm on the passivation layer  118  (refer to  FIG. 3 ). 
     The photoresist polymer composition prepared in Preparation Example 4 was spin-coated on the glue layer  121  at 2000 rpm for 40 seconds, and baked at 95° C. for 7 minutes to form a first negative photoresist layer, i.e., the chamber material layer  120 ′, having a thickness of about 10 μm (refer to  FIG. 4 ). As illustrated in  FIG. 5 , the first negative photoresist layer was exposed to i-line UV rays by using a first photomask having a predetermined ink chamber pattern and restrictor pattern. In this regard, the amount of exposure light was controlled to 130 mJ/cm 2 . The wafer was baked at 95° C. for 3 minutes, immersed in a PGMEA developer for 1 minute for development, and then rinsed with isopropanol for 20 seconds. Thus, a chamber layer  120  was manufactured (refer to  FIG. 5 ). 
     The passivation layer  118  and the insulating layer  112  were removed from a surface region of the silicon water (substrate)  110  where the ink feed hole was to be formed and from other regions of the substrate  110  (refer to  FIG. 6 ). 
     As illustrated in  FIG. 7 , an imide-based positive photoresist (PW-1270, manufactured by TORAY Industries, Inc.) was spin-coated on the overall surface of the silicon wafer  110 , on which the pattern of the chamber layer  120  was formed, at 1000 rpm for 40 seconds and baked at about 140° C. for 10 minutes to form a sacrificial layer S. The thickness of the sacrificial layer S was controlled so that the sacrificial layer S formed on the pattern of the chamber layer  120  had a thickness of about 5 μm. 
     The top surfaces of the pattern of the chamber layer  120  and the sacrificial layer S were planarized using a chemical mechanical polishing (CMP) process, as illustrated in  FIG. 8 . To this end, the silicon wafer  110  was placed onto a polishing pad such that the sacrificial layer S faced the polishing pad of a polishing plate (Model no.: JSR FP 8000, manufactured by JSR Co., Ltd.). The silicon wafer  110  was pressed by a press head on the polishing pad and a backing pad under a pressure of 10-15 kPa. The press head was rotated with respect to the polishing plate, while polishing slurries (POLIPLA 103, FUJIMI Corporation) were applied to the polishing pad. Each of the press head and the polishing pad was rotated at 40 rpm. The hacking pad was made of a material having a Shore D hardness of 30 to 70. The sacrificial layer S was planarized at an etch rate of 5 to 7 μm until the top surface of the pattern of the chamber layer  120  was removed by a thickness of about 1 μm. 
     A pattern of the nozzle layer  130  was formed on the silicon wafer  110 , on which the pattern of the chamber layer  120  and the sacrificial layer S were formed, under the same conditions as for the formation of the pattern of the chamber layer  120  by using the photosensitive polymer composition prepared in Example 4 and a photomask (refer to  FIGS. 9 ,  10 , and  11 ). 
     As illustrated in  FIGS. 12 and 13 , an etch mask  140  for forming the ink feed hole  111  was formed on the bottom surface of the silicon wafer  110  by using conventional photolithography. A bottom surface region of the silicon wafer  110  exposed through the etch mask  140  was etched using a plasma etching process to form the ink feed hole  111 , and the etch mask  140  was removed. In this regard, the power of a plasma etching device used was 2000 Watts, the etching gas was a mixture of sulfur hexafluoride (SF 6 ) and oxygen (O 2 ) (in a volume ratio of 10:1), and the etching rate was 3.7 μm/min. 
     Finally, the silicon wafer  110  was dipped in a methyl lactate solvent for 2 hours to remove the sacrificial layer S, thereby forming an ink chamber  122  and a restrictor  124  surrounded by the chamber layer  120  in the space formed due to the removal of the sacrificial layer S. The manufacture of an inkjet printhead having a structure illustrated in  FIG. 14  was completed. 
     Comparative Example 
     An inkjet printhead was manufactured in the same manner as in Example 6, except that the glue layer was formed of the composition for forming a glue layer prepared in Example 4. 
     Pattern Evaluation 
     The composition for forming a glue layer obtained in Example 3 was spin-coated on a 6-inch silicon wafer at 300 rpm for 40 seconds and heated at 95° C. for 7 minutes to form a glue layer having a uniform thickness of about 10 μm. The glue layer was exposed to i-line light of about 260 mJ/cm 2  by using a Hg/Xe lamp exposure apparatus and then heated at 95° C. for 3 minutes. The glue layer was developed in PGMEA for 1 minute and then rinsed with isopropyl alcohol (IPA) for 10 seconds to form a pattern A. A scanning electron microscopic (SEM) image of the pattern A is shown in  FIG. 15 . 
     In addition, a pattern B was formed in the same manner as above, except that the composition for forming a glue layer obtained in Example 4 was used. A SEM image of the pattern B is shown in  FIG. 16 . 
     Referring to  FIGS. 15 and 16 , pattern A strongly adhered to the silicon wafer without being separated therefrom since the glue layer forming composition of Example 3 containing glycerol as an adhesion improving agent was used. However, pattern B formed from the glue layer forming composition of Example 4 excluding an adhesion improving agent was separated during the developing process. 
       FIG. 17  is a SEM image from a surface of the heaters of an inkjet printhead manufactured using the disclosed photosensitive glue layer forming composition. In addition, an inkjet printhead may be manufactured by forming a glue layer pattern from a non-photosensitive glue layer forming composition (Himal, available from Hitachi Co., Ltd.), instead of using the photosensitive composition used in the present disclosure, and removing the composition remaining unused for the glue layer pattern by using a dry etching process.  FIG. 18  is a SEM image from a surface of the heaters of the inkjet printhead manufactured using the conventional glue layer forming composition. 
     Referring to  FIG. 17 , the glue layer forming composition may be completely removed from the top surface of the heaters of the inkjet printhead. However, referring to  FIG. 8 , the non-photosensitive glue layer forming composition may remain on the heaters. 
     The glue layer forming composition may be a photocurable resin composition, unlike the conventional composition used to form the inkjet printhead illustrated in  FIG. 18 , so that the glue layer remaining unpatterned may be completely removed through the developing process. However, when the non-photosensitive composition is used, the glue layer remaining unpatterned may not be completely removed using the dry etching process. The unremoved residue of the non-photosensitive composition may contaminate ink or may cause an inkjet ejection failure. As described above, an inkjet printhead having excellent mechanical characteristics and adhesion to a substrate may be manufactured through a simple process. The inkjet printhead may have improved flexibility and may not be susceptible to cracking or failures caused by unnecessary composition residue. 
     While the present disclosure has been particularly shown and described with reference to several embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims and their equivalents.