Patent Publication Number: US-9833992-B2

Title: Recording-element substrate, recording head, and recording apparatus

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The aspect of the embodiments relates to a recording-element substrate that is to be mounted on a liquid discharge head, a recording head, and a recording apparatus. 
     Description of the Related Art 
     An example of an information-output apparatus that records information regarding a desired letter, image, or the like onto a recording medium, such as a sheet or a film, is a recording apparatus that performs recording by discharging a liquid. The recording apparatus performs recording by causing liquid droplets discharged from a liquid discharge head to land on a recording medium. There are various methods by which such a liquid discharge head discharges a liquid. A thermal method is a well-known example of a liquid discharging method. The thermal method is a liquid discharging method in which liquid droplets are discharged by using foaming of a liquid such as an ink that is induced by thermal energy generated by passing a current through a heater, which is brought into contact with the liquid, for about a few μs. In general, a liquid discharge head that is used in the thermal method is provided with a recording-element substrate that includes a heater (hereinafter also referred to as heating element), which serves as a recording element. 
     The recording-element substrate includes a substrate on which the heater has been formed, a flow-path-forming member, and a discharge-port-forming member. An example of the configuration of the heater is one in which a portion of a heater electrode provided on the substrate is removed, and a heater layer positioned between portions of the heater electrode functions as the heater. The heater is coated with a cavitation resistant layer that protects the heater against heat and physical and chemical impacts generated at the time of foaming and defoaming of a liquid. In addition, an insulating layer is disposed between the heater and the heater electrode and the cavitation resistant layer. 
     An example of a process for manufacturing a liquid discharge head will now be described. First, a heater and the like are formed on a substrate in a wafer state, after which a dry film is attached to the substrate. Then, a flow-path-forming member and a discharge-port-forming member are formed by using a resist coating or the like. Next, the substrate in a wafer state is attached to a dicing tape and cut by using a diamond saw or the like. The recording-element substrate that has been cut into individual substrates is cleaned in order to remove swarf and the like while being attached to the dicing tape. After that, the recording-element substrate is separated from the dicing tape, and each of the individual substrates is incorporated into a liquid discharge head. 
     Issues may sometimes occur in a recording-element substrate due to electrostatic discharge (hereinafter referred to as ESD) during, for example, the above-described process for manufacturing a recording-element substrate and during a recording operation performed by a liquid discharge head. U.S. Pat. No. 7,267,430 describes a phenomenon in which, in a recording-element substrate that includes an insulating layer having a film thickness of about 200 nm, electrical breakdown occurs in the insulating layer, which is positioned between a cavitation resistant layer and a heater electrode, due to ESD. In addition, U.S. Pat. No. 7,267,430 describes a configuration in which the cavitation resistant layer is connected to a grounded-gate metal oxide semiconductor (MOS) in order to prevent the phenomenon from occurring. Furthermore, U.S. Pat. No. 7,267,430 describes an advantageous effect in which, by employing the above configuration, a current that has been generated by ESD and that has flowed in the cavitation resistant layer can escape to a substrate, and thus, electrical breakdown can be prevented from occurring in the insulating layer positioned between the cavitation resistant layer and the heater electrode. 
     SUMMARY OF THE INVENTION 
     A recording-element substrate according to an aspect of the embodiments includes a substrate that includes a base member, a pair of electrodes, a heating element formed of a thermal resistor layer, which is positioned between the pair of electrodes, a surface on which an electroconductive film coating the heating element has been formed, and an insulating film positioned between the heating element and the electroconductive film and a flow-path-forming member that is disposed on a side of the surface of the substrate and that includes walls for forming a flow path through which a liquid flows to the heating element. The substrate includes an electric connecting portion that is in contact with the electroconductive film and that connects the electroconductive film and the base member to each other, and the shortest distance between the electric connecting portion and a portion where an angle formed by the walls is not more than 120 degrees when viewed from a direction orthogonal to the surface is smaller than the shortest distance between a boundary between the pair of electrodes and the heating element and the portion. 
     Further features of the aspect of the embodiments will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view illustrating a portion of a recording-element substrate according to an embodiment of the disclosure. 
         FIG. 2  is an enlarged view of the peripheral portion of a heater illustrated in  FIG. 1 . 
         FIG. 3  is a sectional view taken along line III-III of  FIG. 2 . 
         FIG. 4  is a perspective view of the recording-element substrate. 
         FIGS. 5A to 5D  are plan views each illustrating another embodiment. 
         FIG. 6  is a sectional view illustrating a path of an ESD current. 
         FIG. 7  is a plan view illustrating a path of an ESD current. 
         FIG. 8  is a perspective view of a recording head. 
         FIG. 9  is a perspective view of a recording apparatus. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     An ESD current is likely to concentrate at some locations in a recording-element substrate, and there is a possibility of electrical breakdown occurring in an insulating layer due to the ESD current. This matter will now be described with reference to  FIG. 6  and  FIG. 7 .  FIG. 6  is a sectional view of a recording-element substrate illustrating one of heaters  101 , a corresponding one of discharge ports  201 , and the peripheral portions, and  FIG. 7  is an enlarged plan view of the peripheral portion of the heater  101 . Note that, some components are illustrated in a see-through manner in  FIG. 7  in order to illustrate the position of the heater  101 . 
     One of insulating layers  131  is provided above the heater  101 , a corresponding one of heater electrodes  150   a , and a corresponding one of heater electrodes  150   b . In addition, one of cavitation resistant layers  130  is provided above the insulating layer  131 . An ESD current  1003  that has flowed in the vicinity of the discharge port  201  from the outside flows along a creepage surface of a discharge-port-forming member  200   a  and a creepage surface of a flow-path-forming member  200   b . In addition, the ESD current  1003  flows in a direction in which the electric potential thereof is more stable, that is, flows toward a region in the discharge-port-forming member  200   a  and a region in the flow-path-forming member  200   b  that the ESD current  1003  has not yet reached in such a manner as to be diffused in all directions. The ESD current  1003 , which has been diffused, reaches the cavitation resistant layer  130  that is made of a metal material or the like and that has a conductivity higher than that of the discharge-port-forming member  200   a , which is made of a resin, and that of the flow-path-forming member  200   b , which is made of a resin. 
     The ESD current  1003  is likely to concentrate at some locations through a process in which the ESD current  1003  is diffused depending on the shape of a member  200 , which forms a corresponding one of foaming chambers  202  and a corresponding one of flow paths  203 . In other words, the ESD current  1003  is likely to concentrate at a corner portion of the flow-path-forming member  200   b , the corner portion having a small angle when viewed from a direction orthogonal to a surface of a substrate  100  on which the heater  101  has been formed. In  FIG. 7 , corner portions  1002  of the flow-path-forming member  200   b  that allow the flow path  203  and the foaming chamber  202  to communicate with each other are located close to the discharge port  201 , and the corner portions  1002  each have an angle smaller than that of a portion of the flow-path-forming member  200   b  in the vicinity of the corner portions  1002 . Consequently, the ESD current  1003  is likely to concentrate at the corner portions  1002  and the cavitation resistant layer  130 , which is located in the vicinity of the corner portions  1002 . The voltage in the cavitation resistant layer  130  is partially high at a location at which the ESD current  1003  has concentrated, and thus, if a portion where the insulating property of the insulating layer  131  is low, examples of the portion being steps  1017  ( FIG. 6 ) formed of the heater electrodes  150   a  and  150   b , is present in the vicinity of the location at which the voltage is high, there is a possibility of electrical breakdown occurring. 
     In particular, in the case of a substrate that is long, if the configuration described in U.S. Pat. No. 7,267,430 is employed, the distance between a grounded-gate MOS and a heater increases, and accordingly, the distance between a cavitation resistant layer provided on the heater and the grounded-gate MOS increases. As a result, the distance between a location in the cavitation resistant layer where a current has flowed in due to ESD and the grounded-gate MOS increases, and electrical breakdown is likely to occur due to ESD at a location that is between the location where the current has flowed in and the grounded-gate MOS and at which the insulating property of an insulating film is low. 
     Accordingly, the aspect of the embodiments is directed at reducing the probability of electrical breakdown occurring in an insulating film due to an ESD current. 
     Embodiment 
       FIG. 4  is a perspective view illustrating an example of a recording-element substrate  1000  to which the aspect of the embodiments can be applied.  FIG. 8  is a perspective view illustrating an example of a recording head  103  on which the recording-element substrate  1000  has been mounted, and  FIG. 9  is a perspective view illustrating an example of a recording apparatus  104  on which the recording head  103  has been mounted. 
     The recording head  103  on which the recording-element substrate  1000  is mounted includes a housing  105  for mounting a liquid container  108  in which a liquid to be discharged from the recording-element substrate  1000  is contained. The recording head  103  further includes an electrical wiring board  107 , which includes a terminal for being electrically connected to the outside, and an electrical wiring member  106  that connects the electrical wiring board  107  and the recording-element substrate  1000  to each other. 
     The recording apparatus  104  includes a conveying unit  102  that conveys a recording medium P and a carriage  109  that causes the recording head  103  to scan while holding the recording head  103  therein. The recording head  103  performs recording by discharging liquid droplets while being scanned and by causing the liquid droplets to land on desired locations on the recording medium P. After the recording head  103  has completed a scanning operation, the recording medium P is conveyed by the conveying unit  102  in a direction perpendicular to a scanning direction in which the recording head  103  performs the scanning operation. By repeating these operations, recording performed on the recording medium P is completed. 
     As illustrated in  FIG. 4 , the recording-element substrate  1000  includes a substrate  100  on which a plurality of heaters  101  (heating elements) serving as recording elements are disposed, a discharge-port-forming member  200   a , and a flow-path-forming member  200   b . The substrate  100  includes a supply port  110  used for supplying the liquid, which is to be discharged from the recording-element substrate  1000 . The flow-path-forming member  200   b  forms a plurality of foaming chambers  202  in each of which a corresponding one of the heaters  101  is disposed, flow paths  203  (flow-path portions) each of which is connected to a corresponding one of the foaming chambers  202 , and a liquid chamber  204  that allows the flow paths  203  and the supply port  110  to communicate with each other. The discharge-port-forming member  200   a  forms a plurality of discharge ports  201  each of which corresponds to one of the heaters  101 . Note that a configuration in which the discharge-port-forming member  200   a  and the flow-path-forming member  200   b  are integrally formed may be employed. The plurality of heaters  101  are arranged so as to form heater arrays, and the plurality of discharge ports  201  and the plurality of foaming chambers  202  are each arranged so as to correspond to one of the heaters  101 . The substrate  100  includes a plurality of terminals  170  used for supplying a voltage and a signal from the outside to the substrate  100 . 
       FIG. 1  is a plan view illustrating the heater arrays and the supply port  110  of the recording-element substrate  1000  according to an embodiment to which the disclosure can be applied and illustrating the peripheral portions of the heater arrays and the supply port  110 .  FIG. 2  is an enlarged view of the peripheral portion (portion indicated by frame II in  FIG. 1 ) of one of the heaters  101 . Note that, in  FIG. 1  and  FIG. 2 , some components are illustrated in a see-through manner in order to describe the layouts of the heaters  101 , ESD inductive wiring lines  1001  (described later), ESD inductive connecting portions  1050  (described later), and the like. Similarly, some components are illustrated in a see-through manner in the other plan views, which will be described later. 
     Since the plurality of heaters  101  have the same configuration, the configuration of the peripheral portion of one of the heaters  101  illustrated in  FIG. 3  will be described below as a representative example.  FIG. 3  is a sectional view taken along line III-III of  FIG. 2 . A thermal oxide film  120  and a gate oxide film  121  are formed on a silicon base member  10 . A first heat-storage layer  122  is formed on the thermal oxide film  120 . A first switching-element electrode  123  is formed on the first heat-storage layer  122 . The first switching-element electrode  123  is connected to the base member  10  by a via  122   b  formed in the first heat-storage layer  122 . An impurity-diffusion region is formed in a connection region in which the first switching-element electrode  123  and the base member  10  are connected to each other. 
     A second heat-storage layer  132  is formed on the first switching-element electrode  123 . A heater layer  151  serving as a thermal resistor layer is formed on the second heat-storage layer  132 . A heater-electrode layer  150  ( FIG. 2 ) is formed on the heater layer  151 , and a common heater electrode  150   a  and an individual heater electrode  150   b  serving as a pair of electrodes are formed by the heater-electrode layer  150 . The heater  101  is formed of the heater layer  151 , which is formed between the common heater electrode  150   a  and the individual heater electrode  150   b . The heater  101  is connected to the first switching-element electrode  123  by a via formed in the second heat-storage layer  132 . 
     An insulating layer  131  made of SiC, SiN, SiCN, or the like is formed on the common heater electrode  150   a  and the individual heater electrode  150   b . A cavitation resistant layer  130  made of a material such as Ta or Ir is formed on the insulating layer  131 . The heater  101  is coated with the cavitation resistant layer  130  functioning as an electroconductive film. The cavitation resistant layer  130  is a protective layer that protects the heater  101  against heat and physical and chemical impacts generated at the time of foaming and defoaming of a liquid. 
     The flow-path-forming member  200   b  is formed on the cavitation resistant layer  130  and the insulating layer  131 , and the discharge-port-forming member  200   a  is formed on the flow-path-forming member  200   b.    
     A configuration for enabling an ESD current  1003  to escape to the base member  10  will now be described. The ESD current  1003  that has flowed in the vicinity of the discharge port  201  from the outside flows into the vicinity of the heater  101  by passing through a wall forming the discharge port  201  and a wall forming the foaming chamber  202  in this order. The ESD current  1003 , which has flowed in, is likely to concentrate at corner portions  1002  ( FIG. 2 ) of the flow-path-forming member  200   b  and the cavitation resistant layer  130  located in the vicinity of the corner portions  1002 . This is because, in the flow-path-forming member  200   b , the corner portions  1002  are located in the vicinity of the discharge port  201  and connect the foaming chamber  202  and the flow path  203  to each other, and each of the corner portions  1002  forming part of the foaming chamber  202  and part of the flow path  203  has an angle smaller than that of the peripheral portion of the corner portion  1002 . 
     The voltage in the cavitation resistant layer  130  is partially high at a location at which the ESD current  1003  has concentrated. Thus, if a portion having a low insulating property due to a low film thickness or a low film quality of the insulating layer  131 , examples of the portion being steps  1017  formed of the heater electrodes  150   a  and  150   b , is present in the vicinity of the location at which the voltage is high, there is a possibility of electrical breakdown occurring at the portion. 
     Accordingly, in the present embodiment, the ESD inductive connecting portion  1050  that induces the ESD current  1003  is disposed in the vicinity of the corner portions  1002  on the side on which the substrate  100  is present. More specifically, the ESD inductive connecting portion  1050  is disposed in such a manner that a shortest distance D 1  between the ESD inductive connecting portion  1050  and one of the corner portions  1002  is smaller than a shortest distance D 2  between the boundary between the heater electrode  150  and the heater  101  and the corner portion  1002 . 
     Note that the term “corner portion” refers to a portion where the angle formed by walls forming a flow path is 120 degrees or smaller when viewed from a direction orthogonal to a surface of the substrate  100  on which the cavitation resistant layer  130  has been formed, and the shape of the corner portion includes a slightly contoured shape. In particular, the above-mentioned concentration of the ESD current  1003  is more likely to occur at the corner portion where the angle is 90 degrees or smaller. 
     The shortest distance D 1  is the shortest distance between the ESD inductive connecting portion  1050  and one of the corner portions  1002  that is closest to the ESD inductive connecting portion  1050 . The shortest distance D 2  is the shortest distance between the corner portion  1002  and the boundary between the heater  101 , which is closest to the corner portion  1002 , and the heater electrode  150  ( 150   a  or  150   b ). Here, the boundary between the heater electrode  150  and the heater  101  is a ridge line where the heater electrode  150  positioned on the two sides of the heater  101  and the heater  101  are in contact with each other and is a portion where the film thickness of the insulating layer  131  is small or the film quality of the insulating layer  131  is low as described above. 
     As illustrated in  FIG. 2 , in the present embodiment, each of the corner portions  1002  is formed of a wall  202   a  that forms the foaming chambers  202  and a wall  203   a  that forms the flow paths  203 . Note that a combination of the foaming chambers  202  and the flow paths  203  will also be referred to herein as a flow path. 
     As illustrated in  FIG. 1  to  FIG. 3 , the ESD inductive connecting portion  1050  is an electric connecting portion that is in contact with the cavitation resistant layer  130 , and the cavitation resistant layer  130  is electrically connected to the base member  10  via the ESD inductive connecting portion  1050 . More specifically, the ESD inductive connecting portion  1050  connects the cavitation resistant layer  130  and the ESD inductive wiring line  1001  by a via  1007  ( FIG. 3 ), which is formed by removing the insulating layer  131 . The ESD inductive connecting portions  1050  are each disposed at a position described above and are each connected to the corresponding ESD inductive wiring line  1001  extending in a direction in which the arrays of the heaters  101  extend ( FIG. 1 ). End portions of the ESD inductive wiring lines  1001  in the direction in which the arrays of the heaters  101  extend are electrically connected to the base member  10  by vias  1012 . Since the ability of the base member  10  to store electric charge is sufficiently large compared with those of the cavitation resistant layer  130  and the ESD inductive wiring lines  1001 , the base member  10  is likely to draw in the ESD current  1003 . 
     As described above, in the present embodiment, each of the cavitation resistant layers  130  and the base member  10  are electrically connected to each other, and the ESD inductive connecting portions  1050 , which are in contact with the corresponding cavitation resistant layers  130  and which are used for the electric connection, are disposed in the vicinity of the corresponding corner portions  1002 . More specifically, each of the ESD inductive connecting portions  1050  are disposed in such a manner that the shortest distance D 1  between the ESD inductive connecting portion  1050  and the corresponding corner portion  1002  is smaller than the shortest distance D 2  between the boundary between the corresponding heater electrode  150  and the corresponding heater  101  and the corner portion  1002 . As a result, even in the case where the ESD current  1003  flows into the foaming chambers  202  and then flows into the cavitation resistant layers  130 , which are disposed below the corner portions  1002  at which the ESD current  1003  is likely to concentrate, the ESD current  1003  is likely to flow into the base member  10  via the ESD inductive connecting portions  1050 . Therefore, the probability that the insulating layers  131 , which are positioned in the vicinity of the corresponding heaters  101 , will be broken by the ESD current  1003  can be reduced. 
     Regarding each of the locations where the ESD current  1003  is likely to concentrate, the distance between the location and the corresponding heater electrodes  150   a  and  150   b  may be relatively larger than the distance between the location and the corresponding ESD inductive connecting portion  1050 . Accordingly, a direction in which the flow paths  203  extend, that is, a direction in which the liquid flows from the liquid chamber  204  toward the heaters  101  may cross a direction in which each of the common heater electrodes  150   a  and the corresponding individual heater electrode  150   b  face each other. In the present embodiment, the flow paths  203  and the heater electrodes  150   a  and  150   b  are arranged in such a manner that these directions cross at right angles to each other. 
     In addition, the ESD inductive connecting portions  1050  may at least be disposed at the above-mentioned locations. For example, a configuration may be employed in which the insulating layers  131  are not provided on the ESD inductive wiring lines  1001  and in which the ESD inductive wiring lines  1001  and each of the cavitation resistant layers  130  are in contact with each other along the ESD inductive wiring lines  1001 . 
     In the present embodiment, although ends of fuses  1051  are each directly connected to the base member  10  at an end of a corresponding one of the arrays of the heaters  101 , the fuses  1051  and the base member  10  may be connected to each other via a ground layer of a logic circuit or a ground layer of the corresponding heater  101 . 
     As illustrated in  FIG. 1 , the ESD inductive wiring lines  1001  are electrically connected to the base member  10  at the ends of the arrays of the heaters  101  via the fuses  1051  that may be blown by heat generated as a result of a current flowing therethrough. Electric charge supplied by the ESD current  1003  is used by energy that causes blowout of the fuses  1051 , and thus, only a small quantity of electric charge will be stored in the base member  10 . As a result, the probability that electric charge stored in the base member  10  will be discharged to a manufacturing apparatus when manufacturing the recording-element substrate  1000 , which in turn results in ESD breakdown can be reduced. Therefore, the fuses  1051  may be provided as described above. 
     In the case where the recording apparatus is used for long periods of time and where the heaters  101  are repeatedly driven, there is a possibility that breakage of a wire will occur in one of the heaters  101  due to cavitation or the like. In this case, the individual heater electrode  150   b  connected to the heater  101  and the corresponding cavitation resistant layer  130  disposed on the heater  101  may sometimes be electrically connected to each other. If a recording operation is continued in this state, a positive electric potential is applied to the individual heater electrode  150   b , and there is a possibility that the current will flow into the base member  10  via the cavitation resistant layer  130 , the corresponding ESD inductive connecting portion  1050 , the corresponding ESD inductive wiring lines  1001 , and the corresponding fuse  1051 . Consequently, the fuses  1051  may be blown in accordance with the potential differences between the two ends of the heaters  101  when the heaters  101  are driven. As a result, even if breakage of a wire occurs in one of the heaters  101 , which in turn results in the above-described state, when the heaters  101  are driven afterward, the fuses  1051  are blown by a voltage applied to the heaters  101  and are isolated, and accordingly, the flow of current toward the two ends of the fuses  1051  can be blocked. 
     Note that the material of the fuses  1051  may be a conductive material such as polysilicon. Alternatively, the fuses  1051  may be made of a material the same as that of the heater layer  151  or the same as that of the ESD inductive wiring lines  1001  and may be formed so as to be partially thin by using. In this case, a common material may be used to form these members, and accordingly, the manufacturing process may be simplified. 
     The ESD inductive connecting portions  1050  may be disposed at positions that are superposed with the corresponding corner portions  1002 , where the ESD current  1003  is likely to concentrate, when the base member  10  is viewed from the direction orthogonal to the surface on which the cavitation resistant layer  130  has been formed. This configuration enables the ESD current  1003  to be more likely to flow toward the base member  10 . 
     The shape of the above-described substrate  100  may be a parallelogram shape, a triangular shape, or other polygonal shapes, and a heat-storage layer formed on the substrate  100  may be processed so as to be flat. In addition, a plurality of the supply ports  110 , which are open to the substrate  100 , may be formed for each of the arrays of the heaters  101 . 
     Note that there is a case where the influence of the above-mentioned ESD current notably occurs depending on the thickness of a heater electrode and the material of an insulating film. In other words, in the case where the length of a recording-element substrate is increased in order to further improve a recording speed, and where the film thickness of the heater electrode is increased in order to suppress an increase in the resistance of the heater electrode due to the increase in the length of the recording-element substrate, there is a possibility that the insulating property of the insulating film will deteriorate. This is because, for example, in the case where the insulating film is formed by a chemical vapor deposition (CVD) method, a gas, sneaking of a precursor radical, and deposition are likely to deteriorate in the vicinity of a step of the electrode. As a result, the film thickness of the insulating film on a side surface of the heater electrode is likely to be small, and the film quality of the insulating film is likely to deteriorate. 
     In addition, if a liquid containing various pigment-dispersing elements and solvents is used in order to improve image quality and reliability, there is a possibility that the insulating film will dissolve, and studies have been conducted on the use of SiCN instead of SiC or SiN in order to obtain both chemical stability and electrical insulating property. However, since SiCN is a ternary insulating film, it is difficult to control the film quality thereof compared with the case of a binary insulating film, and there is a possibility that the film quality of the insulating film will deteriorate in the vicinity of the step of the heater electrode. 
     The present embodiment is also useful in a recording-element substrate in which the influence of an ESD current is likely to occur as a result of using an insulating layer whose film quality has deteriorated as described above. 
     Other Embodiments 
     Other embodiments to which the disclosure can be applied will now be described with reference to  FIGS. 5A to 5D . In each of the other embodiments, the shape of the flow-path-forming member  200   b  is different from that in the above-described embodiment. Note that the driving configuration of the heaters  101  and the configuration of the ESD inductive connecting portions  1050  in the other embodiments are similar to those in the above-described embodiment. 
     In  FIG. 5A , the cross-sectional area of one of the foaming chambers  202  and the cross-sectional area of the corresponding flow path  203  with respect to the flow direction of the liquid are the same as each other, and an ESD current is likely to concentrate at corner portions  1008 , which are formed of the flow-path-forming member  200   b . Accordingly, the ESD inductive connecting portion  1050  is disposed in the vicinity of the corner portions  1008 . 
     In  FIG. 5B , the flow path  203  has a shape in which the cross-sectional area of the flow path  203  with respect to the flow direction of the liquid gradually changes, and the ESD current is likely to concentrate at corner portions  1010 , which are formed of the flow-path-forming member  200   b . Accordingly, the ESD inductive connecting portion  1050  is disposed in the vicinity of the corner portions  1010 . 
     In  FIG. 5C , the foaming chamber  202  has a cylindrical shape, and the cross-sectional area of the flow path  203  decreases in a direction toward the foaming chamber  202 . In this case, the ESD current is likely to concentrate at a corner portion  1012  that allows the foaming chamber  202  and the flow path  203  to communicate with each other. Accordingly, the ESD inductive connecting portion  1050  is disposed in the vicinity of the corner portion  1013 . 
       FIG. 5D  illustrates a configuration in which a filter  1014  is provided in the flow path  203 . A corner portion  1015  that is a portion of the filter  1014  and that is located on the side on which the foaming chamber  202  is present is a portion having the sharpest angle in the vicinity of a heater, and thus, the ESD current is likely to concentrate at the corner portion  1015 . Accordingly, the ESD inductive connecting portion  1050  is disposed in the vicinity of the corner portion  1015 . 
     Also in these embodiments, the ESD current  1003  flowed in from the discharge ports  201  can escape to the base member  10  via ESD inductive wiring lines, and thus, the probability of electrical breakdown occurring in the recording-element substrate  1000  can be reduced. 
     While the 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 modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2015-249126, filed Dec. 21, 2015, which is hereby incorporated by reference herein in its entirety.