Patent Publication Number: US-8991975-B2

Title: Liquid ejection head having structural modifications to film layers and method of manufacturing the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid ejection head that ejects liquid such as ink on a recording material to perform recording, and a method of manufacturing the liquid ejection head. 
     2. Description of the Related Art 
     In an ink jet printer that ejects liquid such as ink, ink is supplied from an ink tank to a liquid ejection head including a silicon substrate having energy generating elements provided on a surface thereof, and ink ejection operation is performed to record an image. 
     An ink ejection structural portion of the liquid ejection head is formed with use of a semiconductor manufacturing technology in order to reduce the size and increase the density. 
     In the following, with reference to the drawings, the structure of a conventional liquid ejection head is described. 
       FIG. 4A  is a plan view of an ejection orifice forming surface of the conventional liquid ejection head. 
       FIGS. 4B to 4D  are sectional views taken along the line C-C of  FIG. 4A  in the conventional liquid ejection head.  FIGS. 4B to 4D  illustrate the internal structure. 
     On a silicon substrate  104 , multiple energy generating elements  711  for generating energy to eject ink are provided. The energy generating elements  711  are arranged at positions corresponding to ejection orifices, respectively. 
     When viewed from a bubble generating chamber side, on an ink supply path side, round-shaped nozzle filters  101  for capturing foreign matters such as dust mixed inside the ink are provided. The round-shaped nozzle filters  101  are each formed of a photosensitive resin film  102 . The round-shaped nozzle filter  101  prevents occurrence of non-ejection of ink caused by clogging of dust inside the nozzle. 
     The liquid ejection head having such a configuration is disclosed in, for example, Japanese Patent Application Laid-Open No. 2005-161763. The above-mentioned configuration of the liquid ejection head has generally been put into practical use. 
     As illustrated in  FIGS. 4B to 4D , hitherto, there has been adopted a configuration in which a resin film  105  is formed so as to be prevented from protruding from an upper opening edge of a supply port  106  in the silicon substrate  104  to the inner side of the supply port  106 . The reason is as follows. In the region in which the resin film  105  is formed, the thickness of the photosensitive resin film  102  is reduced by the thickness of the resin film  105  (about 2 μm). In order to avoid reduction in degree of freedom of nozzle formation, a region that has no need to form the resin film  105  is reduced as much as possible. 
     However, in the above-mentioned configuration, in the vicinity of the nozzle filter  101 , the photosensitive resin film  102  and a silicon nitride film  103  are directly bonded to each other. Therefore, vibrations to be applied during the manufacturing steps (for example, ultrasonic vibrations used when a flow path pattern member (mold) for forming a bubble generating chamber and a flow path pattern forming a flow path is removed) are directly transmitted to the silicon nitride film  103 . Therefore, when the supply port  106  is formed by etching, there is a fear that an end portion (remainder portion)  107  of the silicon nitride film  103 , which is generated in an exposed manner at the upper opening edge, is damaged to be chipped. The remainder portion  107  damaged as described above may remain inside the ink flow path, and hence there is a fear that nozzle clogging occurs in the ejection orifice. 
     When the nozzle is clogged, ejection failure and non-ejection may occur, resulting in a risk of deterioration in recording image quality. 
     SUMMARY OF THE INVENTION 
     According to one embodiment of the present invention, there is provided a liquid ejection head, including: a substrate including: a supply port that is a through hole for supplying liquid; an energy generating element for generating energy to be used for ejecting the liquid; a first film that covers the energy generating element; and a second film formed on the first film; and a flow path forming member bonded to the substrate, for forming a flow path for supplying the liquid supplied from the supply port to an ejection orifice, in which, when viewed from a direction perpendicular to the substrate, an end portion of the first film extends inwardly from an opening edge of the supply port, and an end portion of the second film is located between the opening edge of the supply port and the end portion of the first film. 
     Further, according to one embodiment of the present invention, there is provided a method of manufacturing a liquid ejection head, the method including: preparing a substrate including a supply port that is a through hole for supplying liquid, an energy generating element for generating energy to be used for ejecting the liquid, a first film that covers the energy generating element, and a second film formed on the first film; providing, on the substrate, a mold for forming a flow path; and removing the mold, in which the removing of the mold includes, when viewed from a direction perpendicular to the substrate, extending an end portion of the first film inwardly from an opening edge of the supply port, and locating an end portion of the second film between the opening edge of the supply port and the end portion of the first film. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a plan view illustrating an ejection orifice forming surface of a liquid ejection head according to a first embodiment of the present invention. 
         FIGS. 1B ,  1 C, and  1 D are sectional views taken along the line A-A of  FIG. 1A . 
         FIG. 2A  is a plan view of an ejection orifice forming surface of a liquid ejection head according to a second embodiment of the present invention. 
         FIGS. 2B ,  2 C, and  2 D are sectional views taken along the line B-B of  FIG. 2A . 
         FIG. 3  is an exploded perspective view illustrating a liquid ejection head cartridge of the first embodiment of the present invention. 
         FIG. 4A  is a plan view illustrating an ejection orifice forming surface of a conventional liquid ejection head. 
         FIGS. 4B ,  4 C, and  4 D are sectional views taken along the line C-C of  FIG. 4A . 
         FIG. 5A  is a plan view illustrating an ejection orifice forming surface of another conventional liquid ejection head. 
         FIGS. 5B ,  5 C, and  5 D are sectional views taken along the line D-D of  FIG. 5A . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     In the following, specific embodiments of the present invention are described with reference to the drawings. 
     (First Embodiment) 
       FIG. 3  is an exploded perspective view of an example of a liquid ejection head cartridge of a first embodiment of the present invention. As illustrated in  FIG. 3 , a liquid ejection head cartridge  300  includes an ink tank holding unit  302 , an ink supply unit  303 , and a liquid ejection head  301 . 
     Ink supplied from an ink tank (not shown) is supplied via the ink tank holding unit  302  to the ink supply unit  303 , and is ejected from the liquid ejection head  301  bonded to the ink supply unit  303 , to thereby perform recording operation. 
     The liquid ejection head  301  includes a silicon substrate  104 , and a photosensitive resin film  102  that is arranged on the silicon substrate  104  and has multiple ejection orifices formed therein. 
     Between the silicon substrate  104  and the photosensitive resin film  102 , a silicon oxide film, a silicon nitride film  103 , and a resin film  105  are formed so as to be laminated in the stated order. The silicon oxide film is formed for the purpose of insulating the surface of the silicon substrate  104 . The silicon nitride film  103  is formed as an upper layer of the silicon oxide film, and functions as a protective film for an energy generating element  711 . The resin film  105  is provided between the photosensitive resin film  102  and the silicon nitride film  103 . The resin film  105  has a function as a bonding film for bonding together the silicon substrate  104  and the photosensitive resin film  102 , to thereby improve the adhesion. 
     Further, the ink supplied from the ink cartridge is supplied from a supply port  106  via an ink flow path to the ejection orifice. The ink supplied in the vicinity of the ejection orifice is ejected from the ejection orifice by driving the energy generating element  711  in accordance with an electrical signal to perform ink ejection operation. 
     Next, the steps of manufacturing the liquid ejection head are described. First, the silicon nitride film  103  which is to be a protective film of the energy generating element is applied on the silicon substrate  104  and is patterned into a predetermined shape. Thereafter, the resin film  102  is applied on the silicon nitride film  103  and is patterned into a predetermined shape. At that time, the patterning is conducted such that an end portion of the silicon nitride film  103  and an end portion of the resin film  105  are positioned as shown in  FIG. 2B . Then the photosensitive resin film  102  is applied by well-known method to form the flow path and the like. Subsequently, the silicon substrate  104  is etched, whereby the supply port  106  is formed. 
       FIG. 1A  is a plan view of an ejection orifice forming surface of the liquid ejection head of the first embodiment of the present invention, and  FIGS. 1B to 1D  are sectional views taken along the line A-A of  FIG. 1A . 
     The liquid ejection head  301  of the first embodiment includes the silicon substrate  104 . The silicon substrate  104  has the supply port  106  (liquid supply port) for supplying ink as the liquid, and the energy generating element for applying energy to ink supplied from the supply port  106 . Further, the liquid ejection head  301  includes the photosensitive resin film  102  that is bonded to the silicon substrate  104  and has the multiple ejection orifices for ejecting ink, and the silicon nitride film (first film)  103  formed on the silicon substrate  104  so as to cover the energy generating element. Further, the liquid ejection head  301  includes the resin film (second film)  105  that is provided between the silicon nitride film  103  and the photosensitive resin film (flow path forming member)  102  and bonds together the silicon nitride film  103  and the photosensitive resin film  102 . In this embodiment, the resin film  105  is a film containing poly(etheramide). 
     As illustrated in  FIG. 1A , the liquid ejection head  301  includes round-shaped nozzle filters  101  each formed of the photosensitive resin film  102 . 
     As illustrated in  FIGS. 1A to 1D , the liquid ejection head  301  of this embodiment differs from the conventional configuration illustrated in  FIGS. 4A to 4D  in a region in which the resin film  105  is formed. Other configurations of this embodiment are similar to those of the conventional liquid ejection head illustrated in  FIGS. 4A to 4D , and hence detailed description of the components having the same function as those in the conventional case is omitted. 
     In the following, the action of preventing damage on a remainder portion (end portion) of the silicon nitride film  103  in this embodiment is described. 
     In the configuration of the conventional liquid ejection head illustrated in  FIGS. 4A to 4D , the resin film  105  is not protruded on the inner side of the supply port  106  from the upper opening edge of the supply port  106  in the silicon substrate  104 , the upper opening edge being provided in parallel to the arranging direction of the multiple ejection orifices. Therefore, in the vicinity of the nozzle filter  101 , there is a region in which the photosensitive resin film  102  and the silicon nitride film  103  are brought into direct contact with each other. 
     In the case of this configuration, vibrations to be applied during the manufacturing steps (for example, ultrasonic vibrations used when the mold for forming the bubble generating chamber and the flow path pattern forming the flow path is removed) are directly transmitted to the silicon nitride film  103 . Therefore, when the supply port  106  is formed by etching, there is a fear that the remainder portion  107  of the silicon nitride film  103 , which is generated in an exposed manner at the upper opening edge portion, is damaged to be chipped. As a result, the piece of the damaged remainder portion  107  may induce damage on the photosensitive resin film  102 . 
     As a countermeasure, in this embodiment, as illustrated in  FIGS. 1A to 1D , the resin film  105  is formed so as to extend along the photosensitive resin film  102  in the opening plane of the supply port  106  from the opening edge of the supply port  106  toward the inner side of the supply port  106 . 
     Further, the resin film  105  is preferred to be made of a material that has hardness lower than those of the photosensitive resin film  102  and the silicon substrate  104 . In this manner, the effect of preventing damage on the remainder portion  107  can be further improved. 
     In addition, in this embodiment, the end portion of the resin film  105  extending from the opening edge of the supply port  106  toward the inner side of the supply port  106  is located on the opening edge side of the supply port  106  with respect to the remainder portion  107  of the silicon nitride film  103 . With this, the resin film  105  can prevent the remainder portion  107  of the silicon nitride film  103  from being damaged, and the resin film  105  is prevented from being damaged as well. 
     According to the configuration of this embodiment, the liquid ejection head  301  is formed so that, above the inner side of the supply port  106 , the upper surface side of the remainder portion  107  of the silicon nitride film  103  is covered with the resin film  105 . With this, the vibrations applied to the photosensitive resin film  102  when the mold is removed are not directly transmitted to the silicon nitride film  103 , and the resin film  105  exerts the effect of relaxing the stress. Therefore, it is possible to prevent the damage on the remainder portion  107  and prevent the nozzle from clogging. 
     (Second Embodiment) 
       FIG. 2A  is a plan view of an ejection orifice forming surface of a liquid ejection head according to a second embodiment of the present invention, and  FIGS. 2B to 2D  are sectional views taken along the line B-B of  FIG. 2A . 
       FIG. 5A  is a plan view of an ejection orifice forming surface of another conventional liquid ejection head.  FIGS. 5B to 5D  are sectional views of the conventional liquid ejection head taken along the line D-D of  FIG. 5A .  FIGS. 2B to 2D  and  5 B to  5 D illustrate the internal structure. 
     In the above-mentioned first embodiment of the present invention, the liquid ejection head adopting the round-shaped nozzle filter  101  is applied, but also a liquid ejection head adopting a rib-shaped nozzle filter  201  exerts similar effects. 
     Depending on the type of the ink, the photosensitive resin film  102  may swell. In this case, there is a fear that the photosensitive resin film  102  may peel off from the silicon substrate  104 . As a countermeasure, in some cases, as illustrated in  FIG. 5A , the rib-shaped nozzle filter  201  is adopted as the nozzle filter to increase the area in which the photosensitive resin film  102  and the silicon substrate  104  are brought into contact with each other. The rib-shaped nozzle filter  201  is formed of the photosensitive resin film  102  similarly to the round-shaped nozzle filter  101 . 
     By the way, in the case of the configuration in which the rib-shaped nozzle filter  201  is used as described above, as illustrated in  FIGS. 5B to 5D , the area in which the photosensitive resin film  102  and the silicon nitride film  103  are brought into direct contact with each other increases. Therefore, due to the vibrations of the photosensitive resin film  102  generated during the manufacturing steps, the rate of occurrence of damage on the remainder portion  107  of the silicon nitride film  103  increases. 
     As illustrated in  FIGS. 2A to 2D , the liquid ejection head  301  of this embodiment differs from the conventional configuration illustrated in  FIGS. 5A to 5D  in the region in which the resin film  105  is formed. Other configurations are similar to those of the conventional liquid ejection head illustrated in  FIGS. 5A to 5D , and hence detailed description of the components having the same function as those in the conventional case is omitted. 
     Also in the second embodiment of the present invention, as illustrated in  FIGS. 2A to 2D , the photosensitive resin film  102  is formed immediately above the upper opening edge of the supply port  106 , the upper opening edge being provided in parallel to the arranging direction of the multiple ejection orifices. Also with this configuration, the resin film  105  covers the silicon nitride film  103  to exert the effect of relaxing the stress. Therefore, in the second embodiment of the present invention, similarly to the first embodiment of the present invention, the resin film  105  can prevent the remainder portion  107  of the silicon nitride film  103  from being damaged. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2012-169851, filed Jul. 31, 2012, which is hereby incorporated by reference herein in its entirety.