Patent Publication Number: US-11027547-B2

Title: Liquid ejection head

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present disclosure relates to a liquid ejection head. 
     Description of the Related Art 
     There is known a liquid ejection head that ejects a liquid such as an ink from an ejection orifice to record an image on a recording medium. One of features for reliability required for the liquid ejection head is to suppress an entry of dust and foreign matter into the ejection orifice. The problem is that the liquid supplied to the liquid ejection head contains the dust or the foreign matter. In order to suppress such entry of the dust or the foreign matter in the liquid and improve the reliability of the liquid ejection head, a technique of providing a filter in the liquid ejection head is known. Japanese Patent Application Laid-Open No. 2005-178364 describes a liquid ejection head in which a membrane filter structure is formed in an opening portion of a liquid supply path that penetrates a substrate. 
     SUMMARY OF THE INVENTION 
     A liquid ejection head of the present disclosure includes a substrate, an ejection orifice forming member having a plurality of ejection orifices for ejecting a liquid, and an intermediate layer provided between the substrate and the ejection orifice forming member, in which the substrate has a supply path for supplying the liquid to the plurality of ejection orifices, the ejection orifice forming member has a common liquid chamber communicating with the plurality of ejection orifices, the supply path and the common liquid chamber communicate with each other via a filter portion including a plurality of holes formed in the intermediate layer, the ejection orifice forming member has a wall portion that protrudes into the common liquid chamber at a position opposed to the filter portion, and the wall portion extends along a direction intersecting an arrangement direction of the plurality of ejection orifices. 
     Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  are perspective views of a liquid ejection head according to an embodiment. 
         FIGS. 2A, 2B and 2C  are a perspective plan view and cross-sectional views of the liquid ejection head according to the embodiment. 
         FIG. 3  is an enlarged view of a region surrounded by a circle C in  FIG. 2A . 
         FIGS. 4A and 4B  are perspective plan views illustrating a state where air bubbles staying in a common liquid chamber are combined. 
         FIGS. 5A and 5B  are perspective plan views illustrating a modification example of the liquid ejection head according to the embodiment. 
         FIGS. 6A and 6B  are perspective plan views illustrating a modification example of the liquid ejection head according to the embodiment. 
         FIGS. 7A, 7B and 7C  are cross-sectional views illustrating a method of manufacturing the liquid ejection head according to the embodiment. 
         FIGS. 8A, 8B and 8C  are cross-sectional views illustrating a method of manufacturing the liquid ejection head according to the embodiment. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     When a strong impact or vibration occurs in a liquid ejection head, an air bubble may be introduced into a liquid through an ejection orifice and entrained in the liquid. When the air bubble is entrained in this manner, the air bubble stays in a common liquid chamber communicating with a plurality of ejection orifices and causes an ejection failure. Therefore, it is necessary to suck the air bubble through the ejection orifices. However, in a liquid ejection head described in Japanese Patent Application Laid-Open No. 2005-178364, since a filter is formed at an opening portion of a liquid supply path, the entrained air bubbles may be combined and enlarged in the common liquid chamber on the filter, and so-called “bubble staying” may occur during suction. When the bubble staying occurs, liquid ejection failure occurs, causing a reduction in image quality. Although occurrence of the bubble staying is able to be suppressed by increasing the liquid suction amount, in that case, the amount of waste liquid due to suction increases. Therefore, an aspect of the present disclosure is to provide a liquid ejection head that achieves high reliability while suppressing wasteful liquid consumption due to suction. 
     Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following description, components having the same function may be given the same reference numerals in the drawings, and the description thereof may be omitted. 
       FIG. 1A  is a perspective view of a liquid ejection head according to an embodiment of the present disclosure.  FIG. 1B  is a perspective view of a recording element substrate forming the liquid ejection head of the present embodiment. A liquid ejection head  1  is a head that ejects a liquid such as an ink to record an image on a recording medium, and includes a recording element substrate  2 , an electrical wiring substrate  3 , and a support member  4 . The recording element substrate  2  and the electrical wiring substrate  3  are bonded to the support member  4  so that the recording element substrate  2  is located in the opening portion (not illustrated in  FIGS. 1A and 1B ) formed in the electrical wiring substrate  3 . In a case where the support member  4  is provided with a flow path (not illustrated) for supplying the liquid to the recording element substrate  2 , and two or more types of liquids are supplied, it is preferable that a dividing wall is formed in the flow path so that these liquids are not mixed. 
     The recording element substrate  2  includes a substrate  11  and an ejection orifice forming member  16  provided on the substrate  11 . The ejection orifice forming member  16  is formed with a plurality of ejection orifices  19  for ejecting a liquid, a plurality of flow paths  17  each communicating with the ejection orifices  19 , and a common liquid chamber  15  communicating with the plurality of flow paths  17 . The plurality of ejection orifices  19  are arranged at a predetermined pitch along a longitudinal direction of the ejection orifice forming member  16  to form two parallel ejection orifice rows. The common liquid chamber  15  is disposed between these two ejection orifice rows. An arrangement direction of the plurality of ejection orifices  19  is along the longitudinal direction of the opening of the common liquid chamber  15 . In  FIGS. 1A and 1B , the arrangement direction of the plurality of ejection orifices  19  is parallel to the longitudinal direction of the opening of the common liquid chamber  15 . The substrate  11  is provided with an energy generating element  12 , which is a heating element generating energy used for ejecting the liquid, at a position opposed to the ejection orifice  19 . With this thermal energy, the liquid in the flow path  17  is able to be foamed and ejected from the ejection orifice  19 . As the energy generating element  12 , a piezoelectric element (piezo element) that generates a pressure by deforming a wall of the flow path  17  and ejects the liquid is able to be used in addition to a heating element (heater). In addition, a supply path  18  that penetrates the substrate  11  and communicates with the flow path of the support member  4  is formed in the substrate  11 . The supply path  18  is a path for supplying the liquid to the plurality of ejection orifices  19 , and includes an opening portion  18   a  that opens along an arrangement direction (hereinafter, referred to as “arrangement direction of ejection orifices”) X of the ejection orifice  19  on a surface of the substrate  11  opposed to the ejection orifice forming member  16 . Although a plurality of energy generating elements  12  form two element rows corresponding to the two ejection orifice rows including the plurality of ejection orifices  19 , the opening portion  18   a  of the supply path  18  is located between these two element rows. A connection terminal group  20  for supplying a drive signal and drive power to the energy generating element  12  is also formed at an end portion of the substrate  11  in the longitudinal direction. 
       FIG. 2A  is an enlarged perspective plan view illustrating a vicinity of the ejection orifice of the liquid ejection head of the present embodiment.  FIG. 2B  is a cross-sectional view taken along line A-A in  FIG. 2A , and  FIG. 2C  is a cross-sectional view taken along line B-B in  FIG. 2A .  FIG. 3  is an enlarged view of a region surrounded by a circle C in  FIG. 2A . The liquid ejection head  1  includes an adhesion layer  13  as an intermediate layer between the substrate  11  and the ejection orifice forming member  16 . The adhesion layer  13  has a function of improving adhesion between the substrate  11  and the ejection orifice forming member  16 . Therefore, for example, in a case where the substrate  11  is formed of silicon and the ejection orifice forming member  16  is formed of an epoxy resin, the adhesion layer  13  preferably is formed of a polyether amide resin. The adhesion layer  13  includes a filter portion  14  in a region opposed to the supply path  18  and the common liquid chamber  15 . In other words, the supply path  18  and the common liquid chamber  15  communicate with each other through the filter portion  14  of the adhesion layer  13 . The filter portion  14  includes a plurality of holes  14   a  and has a function of removing dust and foreign matter contained in the liquid supplied from the supply path  18  to the common liquid chamber  15  and suppressing the dust and the foreign matter from entering the ejection orifice  19 . From this viewpoint, each hole  14   a  preferably satisfies a relationship of D&gt;E, where D is a diameter of the ejection orifice  19  and E is a diameter of the hole  14   a.    
     Furthermore, in order to improve the performance of the filter portion  14 , it is preferable that the diameter of the hole  14   a  is made as small as possible and an interval between the adjacent holes  14   a  is made as narrow as possible. However, when the plurality of holes  14   a  are configured in this manner, a pressure loss (flow resistance) increases and the flow of the liquid degrades, and a liquid ejection speed is affected. Therefore, it is not preferable to unnecessarily reduce the diameter or the interval of the holes  14   a . That is, since a trade-off relationship is established between the performance of the filter portion  14  including the plurality of holes  14   a  and the pressure loss (flow resistance), the diameter or the interval of the holes  14   a  is preferably determined in consideration of a balance between a filter performance and a liquid supply performance. From such a viewpoint, it is preferable that the relationship of L&gt;E/2 is satisfied, where E is the diameter of the hole  14   a  and L is the interval between the two adjacent holes  14   a . In addition, the plurality of holes  14   a  are preferably disposed in a triangular lattice shape so that the centers of the three adjacent holes  14   a  are located at apexes of an equilateral triangle. As a result, the filter performance and the liquid supply performance are able to be made compatible. 
     In addition, the liquid ejection head  1  includes a columnar protrusion  101  and a beam-shaped protrusion  102  as two types of protrusions that are formed on the ejection orifice forming member  16  and protrude into the common liquid chamber  15 . The columnar protrusion  101  is provided at a position facing an inlet of the flow path  17 . The columnar protrusion  101  functions as a filter that removes the dust or the foreign matter in the liquid supplied to the ejection orifice  19  through the flow path  17 . In addition, the beam-shaped protrusion  102  is provided along an arrangement direction of the ejection orifices X at a position opposed to the filter portion  14  of the adhesion layer  13 . The beam-shaped protrusion  102  is disposed on a center line of the common liquid chamber  15  along the arrangement direction of the ejection orifices X. It is preferable that the beam-shaped protrusion  102  abuts on the filter portion  14  at a tip end in a protruding direction, thereby the filter portion  14  formed between the supply path  18  and the common liquid chamber  15  is able to be held and the strength thereof is able to be improved. 
     Furthermore, the ejection orifice forming member  16  is formed with a dividing wall (wall portion)  103  protruding into the common liquid chamber  15 . The dividing wall  103  is provided on both sides of the beam-shaped protrusion  102  and extends along a direction intersecting the arrangement direction of the ejection orifices X (longitudinal direction of the opening of the common liquid chamber  15 ). The fact that the dividing wall  103  extends along the direction intersecting the arrangement direction of the ejection orifices X means that the dividing wall  103  extends within an inclination range of 20 degrees or less with respect to a direction perpendicular to the arrangement direction of the ejection orifices X. Preferably, the dividing wall  103  extends along a direction perpendicular to the arrangement direction of the ejection orifices X (parallel to the perpendicular direction). The dividing wall  103  preferably abuts on the filter portion  14 , similarly to the beam-shaped protrusion  102 ; thereby the filter portion  14  formed between the supply path  18  and the common liquid chamber  15  is able to be held and the strength thereof is able to be improved. In addition, the dividing wall  103  is disposed at a position corresponding to the flow path  17  in the arrangement direction of the ejection orifices X, and includes an end portion facing the flow path  17 . Therefore, similarly to the columnar protrusion  101 , the dividing wall  103  also functions as a filter for removing the dust or the foreign matter in the liquid. In addition, in a case where the air bubble is embraced in the liquid through the ejection orifice  19 , the dividing wall  103  also has a function of suppressing such an air bubble from being combined and enlarged in the arrangement direction of the ejection orifices X, in addition to the functions described above. Hereinafter, this function will be described with reference to  FIGS. 4A and 4B .  FIG. 4A  is a perspective plan view illustrating a state where air bubbles staying in the common liquid chamber are combined in the liquid ejection head not provided with the dividing wall.  FIG. 4B  is a perspective plan view illustrating a state where air bubbles staying in the common liquid chamber are combined in the liquid ejection head of the present embodiment provided with the dividing wall. 
     As illustrated in  FIG. 4A , in the liquid ejection head  201  not provided with the dividing wall  103 , there is no structure that divides the common liquid chamber  15  in the arrangement direction of the ejection orifices X. Therefore, in a case where air bubbles  104  entrained in the liquid through the ejection orifice  19  stay on the filter portion  14  in the common liquid chamber  15 , the air bubbles are combined in the arrangement direction of the ejection orifices X and enlarged, and a liquid ejection failure may occur. In order to suppress the liquid ejection failure, it is conceivable to suck the air bubble  104  through the ejection orifice  19 , and due to the enlarged air bubble  104 , there is a possibility that the bubble staying may occur during suction. Although occurrence of the bubble staying is able to be suppressed by increasing the liquid suction amount, in that case, the amount of waste liquid due to suction increases. On the other hand, as illustrated in  FIG. 4B , in the liquid ejection head  1  of the present embodiment, the dividing wall  103  that divides the common liquid chamber  15  in the arrangement direction of the ejection orifices X is provided. As a result, even in a case where the air bubbles  104  entrained in the liquid through the ejection orifice  19  stay on the filter portion  14  in the common liquid chamber  15 , it is possible to suppress the air bubbles from being combined and enlarged in the arrangement direction of the ejection orifices X. As a result, the filter portion  14  is provided between the supply path  18  and the common liquid chamber  15 . Therefore, it is possible to suppress an enlargement of air bubbles in the common liquid chamber  15  and to suppress wasteful liquid consumption due to suction, while securing high reliability. 
     As described above, the dividing wall  103  preferably abuts on the filter portion  14  from the viewpoint of improving the strength of the filter portion  14 . However, the dividing wall  103  may not abut on the filter portion  14 , and there may be a gap of approximately several μm between the dividing wall  103  and the filter portion  14 , from the viewpoint of suppressing the enlargement of air bubbles in the common liquid chamber  15 . In addition, a planar shape and disposition of the dividing wall  103  are not limited to the shape and disposition described above.  FIGS. 5A, 5B, 6A, and 6B  are perspective plan views illustrating modification examples of such a dividing wall. It is preferable that both the dividing wall (wall portion)  103  and the filter portion  14  are formed of organic resins. As illustrated in  FIG. 5A , the liquid ejection head  1  may not be provided with the beam-shaped protrusions  102 , that is, only the dividing wall  103  may be provided. In addition, as illustrated in  FIG. 5B , an end portion of the dividing wall  103  may have a shape (tapered shape) a width of which decreases toward the flow path  17  when viewed from a liquid ejection direction. In order to suitably suppress combining of air bubbles, it is preferable that a plurality of dividing walls  103  extending along the direction intersecting an arrangement direction of the ejection orifices are provided in the arrangement direction of the ejection orifices. That is, it is preferable that the plurality of dividing walls  103  are provided so as not to overlap in the arrangement direction of the ejection orifices. Specifically, it is preferable that three or more dividing walls  103  are provided in the arrangement direction of the ejection orifices. When there are a dividing wall A and a dividing wall B connected via the beam-shaped protrusion  102 , the plurality of dividing walls are provided (that is, the dividing wall A and the dividing wall B are regarded as separate dividing walls). 
     In addition, as illustrated in  FIG. 6A , the plurality of dividing walls  103  may be provided on both sides of the beam-shaped protrusion  102 , respectively. In this case, in order to cause the plurality of dividing walls  103  to abut on the filter portion  14  to improve the strength of the filter portion  14 , it is preferable to narrow the interval between the adjacent dividing walls  103  in the arrangement direction of the ejection orifices X as much as possible. However, when the interval between the dividing walls  103  is too narrow, the pressure loss (flow resistance) increases, the liquid flow degrades, and the liquid ejection speed is affected. That is, a trade-off relationship is established between the strength improvement of the filter portion  14  by the plurality of dividing walls  103  and the pressure loss (flow resistance). Therefore, it is preferable that the interval between the dividing walls  103  is determined in consideration of the balance between the strength improvement of the filter portion  14  and the liquid supply performance. From such a viewpoint, in the arrangement direction of the ejection orifices X, it is preferable that the relationship of G≥2F is satisfied when the interval between the plurality of ejection orifices  19  is F and the interval between the plurality of dividing walls  103  is G. As a result, the strength improvement of the filter portion  14  and liquid supply performance are able to be made compatible. The disposition of the plurality of dividing walls  103  may not be symmetrical with respect to the beam-shaped protrusion  102  as illustrated in  FIG. 6A , and may be asymmetric with respect to the beam-shaped protrusion  102  as illustrated in  FIG. 6B , when viewed from the liquid ejection direction. In this case, the strength of the filter portion  14  is able to be further improved by allowing the plurality of dividing walls  103  to abut on the filter portion  14  as compared with the case where the plurality of dividing walls  103  is disposed symmetrically. 
     Next, with reference to  FIGS. 7A, 7B, 7C, 8A, 8B, and 8C , a method of manufacturing the liquid ejection head according to the present embodiment will be described.  FIGS. 7A, 7B, 7C, 8A, 8B, and 8C  are schematic cross-sectional views of the liquid ejection head in each step of the manufacturing method according to the present embodiment, and are views corresponding to  FIG. 1B . 
     First, a substrate  11  formed of single crystal silicon and whose main surface is a (100) surface is prepared. As illustrated in  FIG. 7A , an energy generating element  12  is provided on a surface  11   a  of the substrate  11 . Next, an organic resin such as a polyether amide resin is applied to the surface  11   a  of the substrate  11  and patterned to form an adhesion layer  13  having a filter portion  14  as illustrated in  FIG. 7B . As a method of applying a resin, a spin coating method, a direct coating method, a spray method, or the like is able to be used. In addition, the patterning is performed by applying a resist, performing exposure and development to form a resist pattern, and by etching using the resist pattern as an etching mask. Patterning may be performed directly using a photosensitive resin material, or a desired pattern may be formed by attaching a film. 
     Next, as illustrated in  FIG. 7C , a mold material  21  for forming the common liquid chamber  15  and the flow path  17  is formed in the surface  11   a  of the substrate  11  by patterning. Patterning of the mold material  21  is performed by applying a resist, performing exposure and development to form a resist pattern, and etching using the resist pattern as a mask. Patterning may be performed directly using a photosensitive resin material, or a desired pattern may be formed by attaching a film. Next, an organic resin such as an epoxy resin is applied on the mold material  21  and patterned, thereby forming the ejection orifice forming member  16  having the ejection orifices  19  as illustrated in  FIG. 8A . As a method of applying a resin, a spin coating method, a direct coating method, a spray method, or the like is able to be used. In addition, patterning is performed by removing a portion corresponding to the ejection orifice  19  by exposure and development. A resist pattern may be formed and patterned by etching using the resist pattern as an etching mask, or a desired pattern may be formed by attaching a film. 
     Next, after protecting the surface  11   a  of the substrate  11  with cyclized rubber, tape, or the like, the substrate  11  is etched to form a supply path  18  in the substrate  11  as illustrated in  FIG. 8B . An etching time is able to be shortened by forming a leading hole in advance. Therefore, it is preferable to form an etching mask having an opening by patterning a resin layer in advance on a rear surface  11   b  of the substrate  11 , and to form a leading hole in the substrate  11  through the opening thereof. As a method of forming the leading hole, laser beam irradiation, a drill, or the like is able to be used. Etching of the substrate  11  may be wet etching using a liquid exhibiting a desired alkalinity, or dry etching using a gas having a desired ratio. Thereafter, the cyclized rubber or tape that protects the substrate  11  is removed, and the mold material  21  for forming the common liquid chamber  15  and the flow path  17  is removed. As a result, as illustrated in  FIG. 8C , the common liquid chamber  15  and the flow path  17  are formed in the ejection orifice forming member  16 , and the dividing wall  103  protruding into the common liquid chamber  15  is formed. A recording element substrate  2  is obtained by cutting and separating the substrate  11  with a laser sorter or a dicing sorter. 
     Next, a support member  4  for bonding the recording element substrate  2  is prepared. The support member  4  may be formed by molding a resin material or an alumina material, or may be formed by sintering a powder material. In a case of molding a resin material, a filler formed of glass or the like may be mixed into the resin material in order to improve the shape rigidity. As the material of the support member  4 , a resin material such as modified polyphenylene ether (PPE), a ceramic material typified by Al 2 O 3 , or the like is able to be used widely. Next, the corresponding lead terminal group of the electrical wiring substrate  3  is bonded to a connection terminal group  20  of the recording element substrate  2 . An adhesive is applied to a recessed portion of the support member  4 , and the recording element substrate  2  is bonded to the support member  4  so that the flow path of the support member  4  and the supply path  18  of the recording element substrate  2  communicate with each other. A method of applying the adhesive may be transferred using a transfer pin, or drawing application using a dispenser. As an adhesive used here, in a case where an ink is used as a liquid, an ink having good ink resistance is preferable. For example, a thermosetting adhesive containing an epoxy resin as a main component is able to be used. In this manner, the recording element substrate  2  bonded to the electrical wiring substrate  3  is bonded to the support member  4 , whereby the liquid ejection head  1  illustrated in  FIGS. 1A and 1B  is formed. 
     While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure 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 modification examples and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2019-018017, filed Feb. 4, 2019, and Japanese Patent Application No. 2020-004247, filed Jan. 15, 2020, which are hereby incorporated by reference herein in their entirety.