Patent Publication Number: US-2023146297-A1

Title: Liquid discharge head, liquid discharge device, and liquid discharge apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This patent application is based on and claims priority pursuant to 35 U.S.C. §119(a) to Japanese Patent Application No. 2021-182690, filed on Nov. 9, 2021, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein. 
     BACKGROUND 
     Technical Field 
     The present embodiment relates to a liquid discharge head, a liquid discharge device, and a liquid discharge apparatus. 
     Related Art 
     There is a technique in which a piezoelectric member is applied as a drive source for an actuator in a liquid discharge head. 
     Such a liquid discharge head includes a nozzle plate, a chamber substrate having an individual chamber and a liquid supply chamber, a diaphragm, and a piezoelectric member. The individual chamber has a width wider in the vicinity of a region of a nozzle than other regions. A reinforcement including at least an insulating film is formed on the piezoelectric member corresponding to the vicinity of the region of the nozzle. Thus, a stable and uniform liquid droplet can be discharged. 
     An individual chamber and a piezoelectric member are often formed in a rectangular shape in plan view. In this case, due to stress to the diaphragm in long term driving, the diaphragm is likely to be broken. 
     SUMMARY 
     A liquid discharge head includes: a chamber substrate; a diaphragm on the chamber substrate; a lower electrode on the diaphragm; a piezoelectric member on the lower electrode; an upper electrode on the piezoelectric member; wiring electrically connected to the upper electrode to transmit driving signal to the piezoelectric member; and a nozzle substrate having a nozzle. The chamber substrate includes an individual chamber facing the diaphragm, the individual chamber has polygonal shape having four or more sides, the piezoelectric member has polygonal shape having four or more sides, the wiring covers a middle point of a first side of the four or more sides of the individual chamber, and a distance A is smaller than a distance B, where the distance A is between a first end portion of the individual chamber and a second end portion of the piezoelectric member in a second side of the four or more sides in which a distance L is the largest, and a distance B is between a third end portion of the individual chamber and a fourth end portion of the piezoelectric member in a third side of the four or more sides in which the distance L is the smallest, and the distance L is a distance from the middle point of the first side to each of middle points of the four or more sides other than the first side. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein: 
         FIG.  1    is a schematic cross-sectional view in the liquid-chamber lateral direction of an example of a liquid discharge head according to the present embodiment; 
         FIG.  2    is a schematic cross-sectional view in the liquid-chamber longitudinal direction of the example of the liquid discharge head according to the present embodiment; 
         FIG.  3 A  is a schematic plan view of the example of the liquid discharge head according to the present embodiment; 
         FIG.  3 B  is another schematic plan view of the example of the liquid discharge head according to the present embodiment; 
         FIG.  4    is an enlarged view of a part surrounded by a broken line “a” in  FIG.  3 A ; 
         FIG.  5    is an explanatory graph of exemplary displacement of a diaphragm as a function of distance from the center of a liquid chamber in the longitudinal direction of the liquid chamber; 
         FIG.  6    is an explanatory graph of an exemplary amount of a discharge droplet as a function of distance between the end portion of a piezoelectric member and the end portion of the liquid chamber in the lateral direction of the liquid chamber; 
         FIG.  7    is an enlarged view of a part surrounded by a broken line “b” in  FIG.  3 A ; 
         FIG.  8    is a schematic plan view of an example of a connection; 
         FIG.  9 A  is a schematic plan view of another example of the liquid discharge head according to the present embodiment; 
         FIG.  9 B  is a schematic plan view of another example of the connection; 
         FIG.  10 A  is a schematic plan view of still another example of the liquid discharge head according to the present embodiment; 
         FIG.  10 B  is a schematic plan view of still another example of the connection; 
         FIG.  11    is a schematic perspective view of an example of a liquid discharge apparatus according to the present embodiment; 
         FIG.  12    is a schematic side view of the example of the liquid discharge apparatus according to the present embodiment; 
         FIG.  13    is a schematic view of another example of the liquid discharge apparatus according to the present embodiment; 
         FIG.  14    is a schematic view of the another example of the liquid discharge apparatus according to the present embodiment; 
         FIG.  15    is a schematic view of an example of a liquid discharge device; and 
         FIG.  16    is a schematic view of another example of the liquid discharge device. 
     
    
    
     DETAILED DESCRIPTION 
     The accompanying drawings are intended to depict embodiments of the present invention and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views. 
     In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result. 
     Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     A liquid discharge head, a liquid discharge device, and a liquid discharge apparatus according to the present embodiment will be described below with reference to the drawings. Note that the present embodiment is not limited to the following embodiments and thus other embodiments, additions, modifications, and deletions can be made within the scope conceivable by those skilled in the art. Any aspects that achieve the function and effect of the present embodiment are to be included in the scope of the present embodiment. 
     Liquid Discharge Head 
     A liquid discharge head according to the present embodiment includes: a chamber substrate; a diaphragm on the chamber substrate; a lower electrode on the diaphragm; a piezoelectric member on the lower electrode; an upper electrode on the piezoelectric member; wiring for driving the piezoelectric member; and a nozzle substrate having a nozzle, in which the chamber substrate has an individual chamber opposite the piezoelectric member through the diaphragm, the individual chamber and the piezoelectric member are each polygonal with four sides or more in plan view, the wiring overlaps part of the individual chamber and overlaps at least a middle point of one side of a plurality of sides of the individual chamber in plan view, and when the middle point is defined as a base point, a distance from the base point to a middle point of another side of the individual chamber in plan view is defined as a distance L, a distance between an end portion of the individual chamber and an end portion of the piezoelectric member based on a side of which the distance L is largest is defined as A, and a distance between an end portion of the individual chamber and an end portion of the piezoelectric member based on a side of which the distance L is smallest is defined as B, an expression: A &lt; B is satisfied. 
     In a case where a plurality of the sides of which the distance L is largest is present, the expression is satisfied regarding all corresponding sides, and in a case where a plurality of the sides of which the distance L is smallest is present, the expression is satisfied regarding all corresponding sides. 
     An example of the liquid discharge head according to the present embodiment will be described. Herein, given will be a case where an individual chamber and a piezoelectric member are each rectangular in shape in plan view. 
       FIG.  1    is a schematic cross-sectional view of the example of the liquid discharge head according to the present embodiment, along the lateral direction of an individual chamber (Y direction). 
       FIG.  2    is a schematic cross-sectional view of the example of the liquid discharge head according to the present embodiment, along the longitudinal direction of the individual chamber (X direction). 
     A liquid discharge head  1  according to the present embodiment includes an actuator substrate  100  (chamber substrate), a diaphragm  13  on the chamber substrate, a lower electrode  10  on the diaphragm  13 , a piezoelectric member  20  on the lower electrode  10 , an upper electrode  11  on the piezoelectric member  20 , wiring  42  for driving the piezoelectric member  20 , and a nozzle substrate  300  having a nozzle  16 . 
     The actuator substrate  100  has an individual chamber  15  (also referred to as a pressurization chamber or liquid chamber) opposite the piezoelectric member  20  through the diaphragm  13 . 
     The individual chamber  15  is in communication with the nozzle  16 , and such individual chambers  15  are provided. The individual chambers  15  each are separated by a partition  14 . 
     The piezoelectric member  20  and the electrodes are also referred to as a piezoelectric element  12 . 
     As the piezoelectric member  20 , for example, lead zirconate titanate (PZT) can be used, and thus the piezoelectric member  20  is also referred to as a PZT film or PZT. The piezoelectric member  20  is sandwiched between the lower electrode  10  and the upper electrode  11 . The lower electrode  10  may be a common electrode or the upper electrode  11  may be a common electrode. Applied voltage through the wiring  42  causes the piezoelectric element  12  to generate liquid discharge energy. 
     In the present embodiment, the actuator substrate  100  and the nozzle substrate  300  are joined together, so that the actuator substrate  100  and the nozzle substrate  300  form the individual chamber  15 . In order to join such substrates together, for example, adhesive  49  can be used. 
     A support substrate  200  is joined with the actuator substrate  100 . The support substrate  200  has a liquid supply port  66 . Liquid (e.g., recording liquid or ink) is supplied from outside through the liquid supply port  66 . Then, the liquid passes through a common liquid supply path  19  and a common chamber  18  and then is supplied to the individual chamber  15  through a fluid resistant portion  17 . 
     In the liquid discharge head  1  according to the present embodiment, for example, with each individual chamber  15  filled with liquid (recording liquid or ink), based on image data, a pulse voltage is applied to the upper electrode  11  corresponding to any nozzle  16  through which the ink is to be discharged. As the pulse voltage, for example, a pulse voltage of 20 V can be selected. For example, an oscillating circuit applies such a pulse voltage. The wiring  42  is in connection with the upper electrode  11  through a connection hole that an inter-layer insulating film  45  has. The pulse voltage is applied to the upper electrode  11  through the wiring  42 . 
     Due to electrostrictive effect based on the applied pulse voltage, the piezoelectric member  20  contracts parallel to the diaphragm  13 . Thus, the diaphragm  13  bends toward the individual chamber  15 . Thus, the internal pressure of the individual chamber  15  rises rapidly, so that the ink is discharged through the nozzle  16  in communication with the individual chamber  15 . 
     After the application of the pulse voltage, the piezoelectric member  20  having contracted returns to the original state, so that the diaphragm  13  having bent returns to the original position. Thus, the inside of the individual chamber  15  is lower in pressure than the inside of the common chamber  18 , so that ink is supplied from the common chamber  18  to the individual chamber  15  through the fluid resistant portion  17 . Ink is supplied to the common chamber  18  after passing the common liquid supply path  19  from outside through the liquid supply port  66 . 
     Repetition of the above enables continuous discharging of liquid droplets, leading to formation of an image on a recording medium disposed opposite the liquid discharge head. Such a recording medium is also referred to as a medium on which recording is to be made or medium. For example, plain paper or a non-permeative recording medium can be used. 
     Example 1 
     Next, the example of the liquid discharge head according to the present embodiment will be further described with plan views. 
       FIG.  3 A  is a schematic plan view of a main part of the example of the liquid discharge head according to the present embodiment, namely, an explanatory view of the configuration of the main part in the stack direction of the layers of the piezoelectric element  12 . 
     As illustrated in  FIG.  3 A , the individual chamber  15  in the present embodiment is rectangular in shape in plan view and has two mutually opposite shorter sides and two mutually opposite longer sides. In the figure, the center of the individual chamber  15  is denoted with O. The longitudinal direction and lateral direction of the individual chamber  15  correspond, respectively, to the X axis and the Y axis. 
       FIG.  1    is a schematic cross-sectional view along the lateral direction of the individual chamber  15  (Y-axis direction). 
       FIG.  2    is a schematic cross-sectional view along the longitudinal direction of the individual chamber  15  (X-axis direction). 
     Note that the shape of the individual chamber  15  in plan view is not necessarily rectangular and may be polygonal. As an advantage, a rectangular individual chamber  15  is easy to form. 
     The mutually opposite shorter sides of the individual chamber  15  illustrated in  FIG.  3 A  are indicated as sides  15 - 1  and  15 - 2 . The mutually opposite longer sides are indicated as sides  15 - 3  and  15 - 4 . In the present embodiment, the wiring  42  is formed on the side of location of one of the two shorter sides of the individual chamber  15  (side of location of the side  15 - 2 ) (also refer to  FIG.  2   ). The side of location of the side  15 - 2  is also referred to as the side of location of one of the shorter sides, and the side of location of the side  15 - 1  is also referred to as the side of location of the other shorter side. 
     Note that, referring to  FIG.  3 A , the wiring  42  is schematically illustrated with a broken line. Thus, for example, the shape of the wiring  42  is not limited to the illustration. 
     In the present embodiment, the region of the individual chamber  15  is larger than the region of the piezoelectric member  20 . Such a relationship is illustrated in  FIGS.  1  and  2   . 
     The wiring  42  overlaps part of the individual chamber  15 . The wiring  42  overlaps at least the middle point of one side of the plurality of sides of the individual chamber  15  in plan view, and the middle point is defined as a base point “bp”. In the figure, the middle points of the other three sides of the individual chamber  15  (sides except the side having the base point bp) are denoted with “mp1”, “mp3”, and “mp4”. Note that “mp” represents middle point and mp2 corresponds to bp. 
       FIG.  3 B  is a schematic plan view for describing the distance L from the base point bp to the middle point mp of a side of the individual chamber  15 . In the present embodiment, the distance from the base point bp to the middle point of another side of the individual chamber  15  in plan view is defined as the distance L. The another side of the individual chamber  15  is different from the side having the base point bp. As illustrated in  FIG.  3 B , the distance L from the base point bp to the middle point mp1 of the side  15 - 1  is denoted with L1. The distance L from the base point bp to the middle point mp3 of the side  15 - 3  is denoted with L3. The distance L from the base point bp to the middle point mp4 of the side  15 - 4  is denoted with L4. 
     In the present embodiment, a side of which the distance L is largest and a side of which the distance L is smallest are found. Then, the respective distances between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side of which the distance L is largest and the side of which the distance L is smallest are required to satisfy a predetermined relationship. 
     In the present embodiment, the distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side of which the distance L is largest is defined as A, and the distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side of which the distance L is smallest is defined as B. In the present example, the side of which the distance L is largest corresponds to the side  15 - 1  that is one of the two shorter sides of the individual chamber  15 . In the present example, the side of which the distance L is smallest corresponds to the sides  15 - 3  and  15 - 4  that are the longer sides of the individual chamber  15 . 
     In the present example, the wiring  42  overlaps the shorter side  15 - 2  of the individual chamber  15 , but this is not limiting. Thus, the wiring  42  may overlap the longer side  15 - 3  or  15 - 4  of the individual chamber  15 . In this case, the middle point mp3 of the side  15 - 3  or the middle point mp4 of the side  15 - 4  serves as the base point bp. Thus, the distance L from the base point bp to the middle point of another side of the individual chamber  15  is examined. 
       FIG.  4    is an enlarged view of a part surrounded by a broken line “a” in  FIG.  3 A . As illustrated in  FIG.  4   , the end portion  20   a  of the piezoelectric member  20  is denoted with reference sign “ 20   a ” and the end portion  15   a  of the individual chamber  15  is denoted with reference sign “ 15   a ”. 
     As illustrated in  FIG.  4   , the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber on the side of location of the other of the two shorter sides of the individual chamber  15  (side of location of the side  15 - 1 ) is defined as A. The distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber on the side of location of one of the two longer sides of the individual chamber  15  (side of location of the side  15 - 3 ) is defined as B 1 . The distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber on the side of location of the other longer side (side of location of the side  15 - 4 ) is defined as B 2 . 
     Note that, in a case where the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber based on one side of the individual chamber  15  varies in value depending on places, the numerical values at a plurality of places may be averaged to find a mean value. The mean value may be used as the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber. In other words, A and B may be each a mean value. 
     The relationship between A and B in the present embodiment satisfies the following: 
     A &lt; B. Satisfaction of such a relationship enables an enhancement in reliability without application of tensile stress to the piezoelectric member  20 . Furthermore, an increase can be made in the size of a discharge droplet. 
     In the present embodiment, a plurality of sides of which the distance L is smallest may be provided like the present example. In the present example, the sides  15 - 3  and  15 - 4  each correspond to a side of which the distance L is smallest. In this case, the above expression is satisfied regarding all corresponding sides. That is, the followings are all satisfied: 
     A&lt;B1 andA&lt;B2. 
     Note that a plurality of sides of which the distance L is largest may be provided. In this case, the following: A &lt; B is satisfied regarding all corresponding sides. 
     According to the exceptional examination of the inventor, satisfaction of the above relationship between A and B enables acquisition of the above effect, leading to the present embodiment. This will be described below. 
     In the present example, the individual chamber is rectangular in shape in plan view, and the wiring is formed on the side of location of one of the two shorter sides. In this case, a displacement distribution indicating the displacement of the diaphragm in the longitudinal direction (X-axis direction) is asymmetric. The displacement distribution depends on not only the presence or absence of wiring but also the distance between the end portion of the piezoelectric member and the end portion of the individual chamber. A larger region of the diaphragm in which no piezoelectric member is present with the individual chamber open causes a larger displacement of the diaphragm. 
       FIG.  5    is a graph of exemplary displacement distributions of the diaphragm with a voltage input. The horizontal axis represents the distance [µm] from the center O of the individual chamber in the longitudinal direction of the individual chamber (X-axis direction). The vertical axis represents the displacement [µm] of the diaphragm. As illustrated in  FIG.  5   , the displacement distribution of the diaphragm is asymmetric. This is because the wiring is formed on the side of location of one of the shorter sides of the individual chamber. 
       FIG.  5    illustrates displacement distributions responsive to changes in the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber on the side of location of the other of the shorter sides of the individual chamber  15  (side of location of the side  15 - 1 ), namely, changes in A. Herein, the displacement distributions correspond to an A of 1.5 µm, an A of 4.5 µm, and an A of 9.5 µm. A larger value of A causes a larger displacement of the diaphragm in the range of from -50 to -120 µm. That is, between the three examples, the displacement of the vibration is largest when A is 9.5 µm. 
     This may be because a longer distance between the end portion of the piezoelectric member and the end portion of the individual chamber causes less stress in the longitudinal direction to the diaphragm, leading to a larger displacement of the diaphragm. However, a larger displacement of the diaphragm causes a larger tensile stress to the piezoelectric member, leading to less improvement in the durability of the piezoelectric member. No improvement in the durability of the piezoelectric member results in no enhancement in the reliability of the liquid discharge head. Thus, the value of A is required to be brought to a certain extent. 
     Meanwhile, a larger amount of a discharge droplet is preferable to an improvement in the print area to drive time. A larger amount of a discharge droplet enables an improvement in discharge characteristics. The distance between the end portion of the piezoelectric member and the end portion of the individual chamber affects the amount of a discharge droplet. A longer distance between the end portion of the piezoelectric member and the end portion of the individual chamber causes a larger displacement of the diaphragm, leading to a larger amount of a discharge droplet. Thus, from the viewpoint of the amount of a discharge droplet, the distance between the end portion of the piezoelectric member and the end portion of the individual chamber is required to be selected appropriately. 
     However, as described above, the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber on the side of location of the other of the shorter sides of the individual chamber  15  (side of location of the side  15 - 1 ), namely, A is preferably not excessively large from the viewpoint of suppression of tensile stress. In other words, the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the longitudinal direction (X-axis direction) is preferably not excessively large. 
     Referring to  FIG.  5   , a smaller value of A causes the maximum point in displacement closer to the center (X = 0) in the longitudinal direction, resulting in a reduction in asymmetry. For example, the maximum point in displacement when A is 1.5 µm is at approximately -50 µm, resulting in a displacement distribution having similarity between the left side and right side with respect to the maximum point in displacement. 
     In contrast to this, the maximum point in displacement when A is 9.5 µm is at approximately -80 µm, resulting in a displacement distribution larger in difference between the left side and right side with respect to the maximum point in displacement than the displacement distribution when A is 1.5 µm. Thus, the asymmetry is lower when A is 1.5 µm than when A is 9.5 µm. An increase in asymmetry leads a discharge droplet into a bend. From the viewpoint of the above, the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the longitudinal direction (X-axis direction) is preferably not excessively large. 
     Thus, instead of an increase in the distance between the end portion of the piezoelectric member and the end portion of the individual chamber in the longitudinal direction for the purpose of attainment of an amount of discharge droplet, preferably, the above purpose is achieved with a different configuration. Thus, examined has been adjustment of the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction (Y-axis direction). The distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction (Y-axis direction) has less influence on the displacement of the diaphragm in the longitudinal direction. Thus, it can be thought that the value of the distance can be adjusted in order to attain an amount of discharge droplet. 
     The inventor performed measurements and examinations with various samples. 
       FIG.  6    is a graph of an exemplary relationship between the amount of a discharge droplet and the distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction (Y-axis direction). The horizontal axis represents the distance [µm] between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction. The vertical axis represents the relative difference of the amount of a discharge droplet to 100% that is the amount of a discharge droplet based on a distance of 6.5 µm between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction. 
     Note that the horizontal axis in  FIG.  6    corresponds to B 1  or B 2  in  FIG.  4   . The graph of  FIG.  6    indicates a result of measurement with B 1  and B 2  equal to each other. 
     As illustrated in  FIG.  6   , a larger distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction causes a larger amount of a discharge droplet. This may be because a larger distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction causes a larger displacement of the diaphragm in the lateral direction, leading to a larger amount of a discharge droplet (larger size of a discharge droplet). The inventor further examined what distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber in the lateral direction enables acquisition of a satisfied amount of discharge droplet. 
     The distance between the end portion  20   a  of the piezoelectric member and the end portion  15   a  of the individual chamber was examined in consideration of specific numerical values. As a result, it is found that the relationship between A and B satisfying the following: A &lt; B as described above enables acquisition of an expected effect. It is found that satisfaction of the above relationship enables no application of tensile stress to the piezoelectric member  20  or a reduction in tensile stress, leading to an enhancement in the durability of the piezoelectric member  20  and an enhancement in reliability. 
     Furthermore, it is found that satisfaction of the above relationship enables a larger amount of a discharge droplet, leading to an improvement in discharge characteristics. According to the present embodiment, the diaphragm can be inhibited from being broken and a larger amount of a discharge droplet can be obtained, so that an improvement in reliability and an improvement in discharge characteristics can be simultaneously achieved. In addition, because a reduction can be made in the asymmetry of a displacement distribution in the longitudinal direction, a reduction can be made in discharge bending. Thus, from this viewpoint, an improvement can be made in discharge characteristics. 
     The following: A≥ B causes a larger tensile stress to the piezoelectric member. Thus, no favorable reliability is acquired, and no increase can be made in the amount of a discharge droplet. In a case where two sides of which the distance L is smallest are present like the present example, the following: A≥ B 1  or A≥ B 2  leads to no acquisition of a favorable result. Thus, B 1  and B 2  are required to satisfy the following relationship: A &lt; B. 
     In the present embodiment, for example, the lower limit of A is preferably, but is not particularly limited to, 1 µm or more in consideration of misalignment at the time of patterning of each layer. 
     In this case, prevented can be a deterioration in reliability due to stress to the piezoelectric member, which is a brittle material, due to overlap between the piezoelectric member and the individual chamber. 
     In the present embodiment, for example, the upper limit of B is preferably, but is not particularly limited to, 20 µm or less. In this case, prevented can be a deterioration in pressure generation force due to a reduction in the area of the piezoelectric member. 
     In a case where a plurality of sides of which the distance L is smallest is present, the respective values of Bs are preferably the same or substantially the same. In the above example, the respective values of B 1  and B 2  are preferably the same or substantially the same. This case enables symmetry of the displacement distribution of the diaphragm in the lateral direction, so that variations can be suppressed in stress in the lateral direction to the piezoelectric member. Thus, a further improvement can be made in reliability. 
     Note that, in a case where a plurality of sides of which the distance L is largest is present, the respective values of As are preferably the same or substantially the same. For example, in a case where A1 and A2 are given, the respective values of A1 and A2 are preferably the same or substantially the same. This case enables suppression of variations in pressure to the piezoelectric member, so that a further improvement can be made in reliability. 
     In the present embodiment, in plan view (e.g.,  FIGS.  3 A and  3 B ), the individual chamber  15  and the piezoelectric member  20  each have corner portions preferably curved in shape. The corner portion is also referred to as a “curved corner”. Such curved corner portions of each of the individual chamber  15  and the piezoelectric member  20  enable stress dispersion, leading to an improvement in reliability. Note that a corner portion corresponds to a portion connecting two sides. 
     The mean value of distance between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape based on one of the corner portions of the individual chamber  15  is defined as C. 
     In a case where a corner portion connecting the side having A and the side having B is present, preferably, the corner portion satisfies the following: 
     A &lt; C &lt; B. Thus, stress load can be softened at the corner portion of the piezoelectric member, so that an improvement can be made in reliability at the time of long term driving. 
     In the present example, as illustrated in  FIG.  3 A , the side having A corresponds to the side  15 - 1  (second side), and the side having B corresponds to the sides  15 - 3  and  15 - 4  (third side). The side  15 - 1  is also referred to as a “second side”, the side  15 - 2  is also referred to as a “first side”, and the sides  15 - 3  and  15 - 4  are referred to as a “third side”. 
     Thus, preferably, both the corner portion connecting the sides  15 - 1  and  15 - 3  and the corner portion connecting the sides  15 - 1  and  15 - 4  satisfy the following: A &lt; C &lt; B. 
     Satisfaction of the following: A &lt; C &lt; B will be supplementarily described. Regarding a corner portion connecting the side having A and the side having B, A and B are required to satisfy the following: A &lt; C &lt; B. In other words, for example, regarding a corner portion different from the corner portion, A and B based on the two sides of the different corner portion do not necessarily satisfy the above expression. This will be described with  FIG.  4   . C based on the corner portion connecting the sides  15 - 1  and  15 - 3  is defined as C 11 . The following: A &lt; C 11  &lt; B 1  enables acquisition of the above expected effect. At this time, further preferably, the following is satisfied: A &lt; C 11  &lt; B 2 . However, even in a case where the following is not satisfied: A &lt; C 11  &lt; B 2 , the above effect is acquired. Similarly, regarding the corner portion connecting the sides  15 - 1  and  15 - 4 , the following: A &lt; C 12  &lt; B 2  enables acquisition of the above expected effect. Further preferably, the following is satisfied: A &lt; C 12  &lt; B 1 . 
     Note that, as described below, in a case where no corner portion connecting the side having A and the side having B is present, preferably, the corner portions of the individual chamber  15 , excluding any corner portion having the side having the base point bp as one side, all satisfy the following: A &lt; C &lt; B. 
     C described above will be described with  FIG.  7   . 
       FIG.  7    is an enlarged view of a part surrounded by a broken line b in  FIG.  3 A , namely, an enlarged schematic view of one corner portion. As illustrated in  FIG.  7   , an end portion  20   a  of the piezoelectric member  20  is denoted with reference sign “ 20   a ”. An end portion  15   a  of the individual chamber  15  is denoted with reference sign “ 15   a ”. The portion curved in shape based on the corner portion is denoted with reference sign W. 
     In the present embodiment, since the following is satisfied: A &lt; B, the distance between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape is expected to vary depending on places. Referring to  FIG.  7   , changes in the distance between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape are indicated with C 1 , C 2 , and C 3 . In this example, the distance reduces from B 1  toward A, namely, in the order of C 1 , C 2 , and C 3 . In the present example, for example, C 1 , C 2 , and C 3  are averaged to find a mean value. Then, the mean value is defined as C (particularly, C 11 ) and is compared with A, B 1 , or B 2 . Note that the number of measurement places for finding a mean value of distance between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  can be appropriately changed. 
     As above, in a case where the distance between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape varies depending on places, preferably, a mean value is found and then is compared with A, B 1 , or B 2 . 
     In the present embodiment, the individual chamber  15  has a connection with a channel in communication with the common chamber  18 . For disposition of the connection, a favorable place is present. That is, preferably, a connection  15   b  is formed at the central portion of one of the sides opposite the side having the base point bp in the individual chamber  15  or at the corner portion connecting two sides opposite the side having the base point bp in the individual chamber  15 . In this case, applied stress to the diaphragm  13  can be dispersed at any side opposite the side having the base point bp in the individual chamber  15 , so that damage can be inhibited from occurring. 
     This will be described with  FIG.  8   . 
       FIG.  8    is a schematic plan view similar to the schematic plan view of  FIG.  3 A . In the figure, the wiring  42  is formed on the side of location of one of the two shorter sides of the individual chamber  15  (side of location of the side  15 - 2 ), and the side  15 - 2  has the base point bp. In the present example, the central portion of the side  15 - 1  opposite the side  15 - 2  having the base point bp in the individual chamber  15  has the connection  15   b  with a channel  68  in communication with the common chamber  18 . The connection  15   b  is formed, for example, by providing an opening to the partition of the individual chamber  15 . 
     Note that, in the present example, the channel  68  corresponds to the position of the fluid resistant portion  17 . At the central portion, the distance between the upper end portion of the connection  15   b  in the Y-axis direction and the X axis passing through the center O of the individual chamber  15  and the distance between the lower end portion of the connection  15   b  in the Y-axis direction and the X axis are equal. 
     Favorable places for formation of the connection  15   b  are as follows. 
     The individual chamber  15  is defined as being N-gonal in shape (N is an integer of 4 or more) in plan view. In a case where N is even, preferably, the central portion of the side opposite the side having the base point bp in the individual chamber  15  has the connection with the channel  68  in communication with the common chamber  18 . 
     In a case where N is odd, preferably, the corner portion connecting two sides of the sides opposite the side having the base point bp in the individual chamber  15  has the connection with the channel  68  in communication with the common chamber  18 . 
     In a case where the individual chamber  15  is rectangular in shape in plan view like the present example, the number of sides opposite the side having the base point bp is one. 
     In a case where the individual chamber  15  is polygonal in shape, the number of sides opposite the side having the base point bp is not necessarily one. Thus, the expression “one of the sides opposite” is used. 
     Exemplary Production of Liquid Discharge Head 
     Next, exemplary production of the liquid discharge head according to the present embodiment will be described. 
     (a) The diaphragm  13  is formed on a silicon single crystal substrate with the plane orientation (110) (e.g., a thickness of 400 µm) as the actuator substrate  100 . 
     For example, preferably, the diaphragm  13  has a structure in which three layers of a silicon dioxide film, a silicon nitride film, and an amorphous layer are stacked. In this case, the silicon dioxide film corresponds to compressive stress, and the silicon nitride film corresponds to tensile stress. 
     As a method for producing the diaphragm  13 , for example, a low pressure chemical vapor deposition (LP-CVD) method can be used. 
     The thickness of the diaphragm  13  can be appropriately selected to obtain a desired value of stress. 
     As the amorphous layer, preferably, for example, a silicon dioxide film or alumina is used. In these cases, Pb included in an upper formed film of PZT is easily trapped. From the viewpoint of reliable prevention of Pb dispersion, the thickness of the amorphous layer is preferably 40 nm or more. 
     Next, for example, a film of TiO 2  having a thickness of 20 nm and a film of Pt having a thickness of 160 nm are formed by sputtering as the lower electrode  10  on the diaphragm  13 . 
     (b) Next, a film of PZT having a thickness of 2 µm is formed as the piezoelectric member  20  on the lower electrode  10 , for example, by a plurality of times of spin coating. Next, a film of SRO having a thickness of 40 nm and a film of Pt having a thickness of 100 nm are formed by sputtering as the upper electrode  11 . 
     A method for forming the piezoelectric member  20  is not limited to a sol-gel method with spin coating and thus may be, for example, a sputtering method, an ion plating method, an aerosol method, or an inkjet method. 
     Herein, exemplary film formation with a sol-gel method will be given. 
     First, as a seed layer for controlling the orientation of PZT, a film of PbTiO 3  is formed by spin coating. Furthermore, a PZT precursor is formed by spin coating. At this time, the PZT precursor has a drying temperature of 120° C., a calcination temperature of 380° C., and a sintering temperature of 700° C. These temperatures can be appropriately changed. 
     Then, with a litho-etch method, the piezoelectric element  12  and the upper electrode  11  are formed positionally corresponding to the individual chamber  15  to be formed. The piezoelectric element  12  is formed positionally corresponding to a junction  48 . 
     (c) Next, the inter-layer insulating film  45  is formed in order to insulate the lower electrode  10  and the piezoelectric member  20  against the lead wiring  42  to be formed. 
     As the inter-layer insulating film  45 , for example, an SiO 2  film having a thickness of 1000 nm is formed with a plasma chemical vapor deposition (CVD) method. The inter-layer insulating film is not necessarily such an SiO 2  film and thus may be any film, having no influence on the piezoelectric element  12  and electrode materials and having insulation, with a plasma CVD method. 
     Next, a connection hole for connection of the upper electrode  11  and the lead wiring  42  is formed with a litho-etch method. For connection of the lower electrode  10  to the lead wiring  42 , similarly, a connection hole is formed. 
     (d) Next, as the wiring  42 , for example, a film of TiN having a thickness of 30 nm and a film of A1 having a thickness of 3 µm are formed by sputtering. Pt, as a material of the upper electrode  11  or the lower electrode  10 , connected directly with A1 as a material of the lead wiring  42  at the bottom of the connection hole is alloyed due to heat history in a post-process. Thus, in order to prevent film detachment due to stress based on a change in volume, TiN serves as a barrier layer that prevents alloying. 
     The wiring  42  is also formed at a place for the junction  48  with the support substrate  200 . 
     (e) Next, as a passivation film  50 , for example, a silicon nitride film having a thickness of 1000 nm is formed with a plasma CVD method. 
     (f) Next, with a litho-etch method, openings are made for a lead wiring pad  41  of the lead wiring  42 , an actuator, and the common liquid supply path  19 . 
     (g) Next, with a litho-etch method, the diaphragm  13  at places for the common liquid supply path  19  and the common chamber  18  is removed. 
     (h) Next, with a litho-etch method, a spot facing  67  is provided positionally corresponding to the actuator, resulting in formation of a mainstream liquid chamber and a sub-stream liquid chamber. Then, the support substrate  200  is produced. At this time, for example, Si is subjected to dry etching. 
     Next, the support substrate  200  and the actuator substrate  100  are joined with the adhesive  49  through the junction  48 . The adhesive having a thickness of approximately 1 µm is coated on the support substrate  200  by a typical thin-film transfer apparatus. 
     Next, for formation of the individual chamber  15 , the common chamber  18 , and the fluid resistant portion  17 , the actuator substrate  100  is polished by a publicly known technique so as to have a desired thickness t (e.g., a thickness of 80 µm). The actuator substrate  100  may be etched instead of being polished. 
     (i) Next, a partition portion not corresponding to the individual chamber  15 , the common chamber  18 , and the fluid resistant portion  17  is covered with resist by lithography. Next, the individual chamber  15 , the common chamber  18 , and the fluid resistant portion  17  are formed by dry etching with an inductively coupled plasma (ICP) etcher. The lead wiring  42  for supplying a voltage to the upper electrode  11  is formed on the side of location of one of the end portions in the longitudinal direction (side of location of the side  15 - 2 ). 
     In the above, for example, as illustrated in  FIG.  4   , the individual chamber  15  and the piezoelectric member  20  are formed such that the followings are satisfied: A &lt; B 1  and A &lt; B 2 . As an exemplary configuration in the present embodiment, preferably, the individual chamber  15  is formed so as to have four corner portions curved in shape and the piezoelectric member  20  is formed so as to have four corner portions curved in shape corresponding one-to-one to the corner portions of the individual chamber  15 . 
     (j) Next, the nozzle substrate  300  is joined such that nozzles  16  positionally correspond one-to-one to individual chambers  15  formed separately. In this manner, the liquid discharge head  1  can be produced. 
     Example 2 
     Next, another example of the present embodiment will be described. The duplicate descriptions to the above embodiment will be omitted. 
     In the above embodiment, the individual chamber  15  and the piezoelectric member  20  are each rectangular in shape in plan view, but the present embodiment is not limited to this. An individual chamber  15  and a piezoelectric member  20  are each polygonal with four sides or more in plan view. 
       FIG.  9 A  exemplifies the individual chamber  15  and the piezoelectric member  20  each pentagonal in plan view. As illustrated in  FIG.  9 A , the individual chamber  15  in the present example has sides  15 - 11  to  15 - 15  as five sides. The side  15 - 15  has a base point bp at its middle point, and the other sides have middle points mp11 to mp14. The respective distances (distances L) from the base point bp to the middle points of the other sides of the individual chamber  15  are denoted with L 11  to L 14 . 
     In the present example, the side of which the distance L is largest corresponds to the sides  15 - 11  and  15 - 12 , and the side of which the distance L is smallest corresponds to the sides  15 - 13  and  15 - 14 . In the present example, the distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side  15 - 11  is defined as A 11 , and the distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side  15 - 12  is defined as A 12 . The distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side  15 - 13  is defined as B 13 , and the distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side  15 - 14  is defined as B 14 . 
     In the present example, regarding all corresponding sides, the relationship between A and B satisfies the following: A &lt; B. 
     That is, the followings are all satisfied:
     A 11  &lt; B 13 ,   A 11  &lt; B 14 ,   A 12  &lt; B 13 , and   A 12  &lt; B 14 .   

     In this case, such an expected effect as described in the above embodiment is acquired. 
     In the present example, the number of sides of which the distance L is largest may be one or the number of sides of which the distance L is smallest may be one. For example, in a case where the following is satisfied: L 11  &gt; L 12 , the side of which the distance L is largest corresponds to only the side  15 - 1 . In a case where the following is satisfied: L 13  &gt; L 14 , the side of which the distance L is smallest corresponds to only the side  15 - 4 . In a case where the followings are satisfied: L 11  &gt; L 12  and L 13  &gt; L 14 , the following is required to be satisfied: A 11  &lt; B 14 . Conversely, in a case where the followings are satisfied: L 11  &lt; L 12  and L 13  &lt; L 14 , the following is required to be satisfied: A 12  &lt; B 13 . Note that, in a case where the shape of the individual chamber  15  is a regular pentagon, a plurality of As and a plurality of Bs are present. 
     Similarly to the above example, in the present example, preferably, the individual chamber  15  and the piezoelectric member  20  each have corner portions curved in shape. In the present example, preferably, the mean value of distance C between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape satisfies the following: A &lt; C &lt; B. 
     In the present example, a corner portion connecting the side having A and the side having B is present. In this case, preferably, the corner portion satisfies the following: A &lt; C &lt; B. That is, preferably, the mean value of distance C 13  between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape based on the corner portion connecting the side  15 - 11  having A 11  and the side  15 - 13  having B 13  satisfies the following: A 11  &lt; C 13  &lt; B 13 . 
     Preferably, the mean value of distance C 14  between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape based on the corner portion connecting the side  15 - 12  having A 12  and the side  15 - 14  having B 14  satisfies the following: A 12  &lt; C 14  &lt; B 14 . 
     Satisfaction of the following: A 11  &lt; C 13  &lt; B 13  regarding the corner portion connecting the side  15 - 11  having A 11  and the side  15 - 13  having B 13  enables acquisition of the above expected effect. Further preferably, the following is satisfied: A 11  &lt; C 13  &lt; B 14  or A 12  &lt; C 13  &lt; B 13 . However, the expressions are not necessarily satisfied in configuration. 
     In the present example, in a case where a connection  15   b  with a channel  68  in communication with a common chamber  18  is formed at the individual chamber  15 , preferably, the connection  15   b  is formed at the corner portion connecting two sides (sides  15 - 11  and  15 - 12 ) of the sides opposite the side  15 - 15  having the base point bp in the individual chamber  15 .  FIG.  9 B  is a schematic plan view for describing an exemplary case where the connection  15   b  is formed in the present example. As illustrated in  FIG.  9 B , the connection  15   b  is formed at the corner portion connecting two sides (corner portion connecting the sides  15 - 11  and  15 - 12 ) of the sides opposite the side  15 - 15  having the base point bp in the individual chamber  15 . 
     Example 3 
     Next, still another example of the present embodiment will be described. 
       FIG.  10 A  exemplifies an individual chamber  15  and a piezoelectric member  20  each hexagonal in plan view. As illustrated in  FIG.  10 A , the individual chamber  15  in the present example has sides  15 - 21  to  15 - 26  as six sides. The side  15 - 26  has a base point bp at its middle point, and the other sides have middle points mp21 to mp25. The respective distances (distances L) from the base point bp to the middle points of the other sides of the individual chamber  15  are denoted with L 21  to L 25 . 
     In the present example, the side of which the distance L is largest corresponds to the side  15 - 21 , and the side of which the distance L is smallest corresponds to the sides  15 - 24  and  15 - 25 . In the present example, the distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side  15 - 21  is defined as A 21 . The distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side  15 - 24  is defined as B 24 . The distance between the end portion of the individual chamber  15  and the end portion of the piezoelectric member  20  based on the side  15 - 25  is defined as B 25 . 
     In the present example, regarding all corresponding sides, the relationship between A and B satisfies the following: A &lt; B. 
     That is, the followings are all satisfied: 
     A 21  &lt; B 24 , and 
     A 21  &lt; B 25 . In this case, such an expected effect as described in the above embodiment is acquired. 
     In the present example, the number of sides of which the distance L is largest may be one or the number of sides of which the distance L is smallest may be one. 
     Similarly to the above embodiment, in the present example, preferably, the individual chamber  15  and the piezoelectric member  20  each have corner portions curved in shape. In the present example, preferably, the mean value of distance C between the end portion of the piezoelectric member  20  and the end portion of the individual chamber  15  at the portion curved in shape satisfies the following: A &lt; C &lt; B. 
     In the present example, no corner portion connecting the side having A and the side having B is present. In this case, preferably, the corner portions of the individual chamber  15 , excluding any corner portion having the side  15 - 26  having the base point bp as one side, all satisfy the following: A &lt; C &lt; B. 
     Note that the corner portion having the side  15 - 26  having the base point bp as one side corresponds to the corner portion connecting the sides  15 - 24  and  15 - 26  (lower left in  FIG.  10 A ) and the corner portion connecting the sides  15 - 25  and  15 - 26  (lower right in  FIG.  10 A ). Preferably, the four corner portions without the two corner portions all satisfy the following: A &lt; C &lt; B. 
     For example, preferably, the followings are all satisfied: A 21  &lt; C 22  &lt; B 24  ... (1), A 21  &lt; C 24  &lt; B 24  ... (2), A 21  &lt; C 23  &lt; B 25  ... (3), and A 21  &lt; C 25  &lt; B 25  ... (4). 
     Note that satisfaction of the following: A &lt; C &lt; B regarding all the corresponding corner portions is not limited to satisfaction of all the above expressions (1) to (4). 
     For example, preferably, the followings are all satisfied: A 21  &lt; C 22  &lt; B 25  ... (5), A 21  &lt; C 24  &lt; B 25  ... (6), A 21  &lt; C 23  &lt; B 24  ... (7), and A 21  &lt; C 25  &lt; B 24  ... (8). 
     If the relationship: A &lt; C &lt; B is satisfied regarding all the corresponding corner portions, an expected effect can be acquired. 
     In a case where a connection  15   b  with a channel  68  in communication with a common chamber  18  is formed at the individual chamber  15 , preferably, the formation of the connection  15   b  is similar to the formation of the connection  15   b  in  FIG.  8   . That is, preferably, the connection  15   b  is formed at the central portion of the side  15 - 21  opposite the side  15 - 26  having the base point bp in the individual chamber  15 . 
       FIG.  10 B  is a schematic plan view for describing an exemplary case where the connection  15   b  is formed in the present example. As illustrated in  FIG.  10 B , the connection  15   b  is formed at the side  15 - 21  opposite the side  15 - 26  having the base point bp in the individual chamber  15 . 
     Liquid Discharge Apparatus and Liquid Discharge Device 
     Next, an inkjet recording apparatus will be described as an example of the liquid discharge apparatus according to the present embodiment. 
       FIGS.  11  and  12    illustrate an inkjet recording apparatus  90  in the present example. 
     The inkjet recording apparatus  90  includes, for example, a carriage  98 , a liquid discharge head  1 , and a print mechanism  91 . The carriage  98  is movable in the scanning direction inside an apparatus body. As the liquid discharge head  1 , the liquid discharge head according to the present embodiment can be used. For example, the liquid discharge head  1  is mounted on the carriage  98 . The print mechanism  91  includes, for example, an ink cartridge  99  that supplies ink to the liquid discharge head  1 . 
     The apparatus body has a lower portion to which a sheet feeding cassette  93  (or a sheet feeding tray), on which a plurality of sheets  92  can be loaded, is detachably attached from the front side. Provided may be a manual sheet feeding tray  94  openable for manual feeding of a sheet  92 . After import of a sheet  92  fed from the sheet feeding cassette  93  or the manual sheet feeding tray  94 , the print mechanism  91  records a required image on the sheet  92 . After that, the sheet  92  is ejected to a sheet ejection tray  95  attached to the back face side. 
     The print mechanism  91  includes a primary guide rod  96  and a secondary guide rod  97  as guide members laterally bridged between a left side plate and a right side plate, and retains the carriage  98  slidably in the main scanning direction. The liquid discharge head  1  that discharges ink droplets of respective colors of yellow (Y), cyan (C), magenta (M), and black (Bk) is attached to the carriage  98  such that a plurality of ink discharge ports (nozzles) is arrayed in a direction intersecting the main scanning direction with a downward direction of discharging of ink droplets. Ink cartridges  99  each for supplying ink for the corresponding color to the liquid discharge head  1  are exchangeably attached to the carriage  98 . 
     The ink cartridges  99  each have an upper portion provided with an air vent in communication with the air and a lower portion provided with a supply port for supplying ink to the liquid discharge head  1 . The ink cartridges  99  each have a porous member filled with ink, inside. Due to the capillary force of the porous member, the ink to be supplied to the liquid discharge head  1  is kept at a slight negative pressure. 
     As the liquid discharge head  1 , provided are liquid discharge heads  1  for the colors. However, provided may be a single liquid discharge head having nozzles for discharging ink droplets of the colors. 
     The carriage  98  has a rear portion (on the downstream side of sheet conveyance) slidably fit to the primary guide rod  96  and a front portion (on the upstream side of sheet conveyance) slidably placed on the secondary guide rod  97 . In order to move the carriage  98  for scanning in the main scanning direction, a timing belt  104  is stretched between a drive pulley  102  that a main scanning motor  101  drives to rotate and a driven pulley  103 . 
     The timing belt  104  is secured to the carriage  98 . Thus, the carriage  98  reciprocates due to forward and reverse rotations of the main scanning motor  101 . 
     For conveyance of a sheet  92  set in the sheet feeding cassette  93  to the lower side of the liquid discharge head  1 , the apparatus in the present example includes a sheet feeding roller  105 , a friction pad  106 , a guide member  107 , a conveying roller  108 , and a leading rolling member  110 . 
     The sheet feeding roller  105  and the friction pad  106  separates and feeds a sheet  92  from the sheet feeding cassette  93 . The guide member  107  guides the sheet  92 . The conveying roller  108  inverts and conveys the fed sheet  92 . The leading rolling member  110  regulates the angle of delivery of the sheet  92  from a conveying rolling member  109  thrust against the circumferential face of the conveying roller  108  and the conveying roller  108 . The conveying roller  108  is driven to rotate by a sub-scanning motor through a gear train. 
     The apparatus in the present example includes a sheet guide member  111 . The sheet guide member  111  guides, on the lower side of the liquid discharge head  1 , the sheet  92  delivered from the conveying roller  108  in accordance with the range of movement of the carriage  98  in the main scanning direction. 
     On the downstream side in the direction of sheet conveyance of the sheet guide member  111 , provided are a conveying rolling member  112  and a spur gear  113  to be driven to rotate to deliver the sheet  92  in the direction of sheet ejection. Furthermore, disposed are a sheet ejection roller  114  and a spur gear  115  that deliver the sheet  92  to the sheet ejection tray  95 , and guide members  118  and  119  forming a sheet ejection path. 
     For recording, while moving the carriage  98 , the inkjet recording apparatus  90  drives the liquid discharge head  1  in accordance with an image signal. For example, ink is discharged to the sheet  92  remaining stopped to perform recording for one line. Then, after a predetermined amount of conveyance of the sheet  92 , recording is performed for the next line. In response to reception of a recording termination signal or a signal indicating that the rear end of the sheet  92  has reached the recording region, the recording operation terminates, leading to ejection of the sheet  92 . 
     A recovery device  117  that recovers the liquid discharge head  1  from discharge trouble is disposed out of the recording region on the right end side in the direction of movement of the carriage  98 . The recovery device  117  includes a cap, a sucker, and a cleaner. The carriage  98  moves to the side of location of the recovery device  117  in order to stand for printing. Then, the liquid discharge head  1  is capped with the cap to keep a discharge port portion in a moist state, leading to prevention of discharge trouble due to ink drying. 
     For example, in the middle of recording, ink discharge not relating to the recording causes the viscosity of ink at all the discharge ports to be constant, leading to maintenance of a stable discharge state. 
     For example, in a case where discharge trouble occurs, the cap seals hermetically the discharge ports (nozzles) of the liquid discharge head  1 . Then, the sucker sucks out, for example, air bubbles together with ink from the discharge ports through a tube. Thus, the cleaner removes, for example, ink or dust having adhered to a discharge port face, resulting in recovery from the discharge trouble. The sucked ink is discharged to a waste ink container provided at the lower portion of the body and then is absorbed and retained by an ink absorber inside the waste ink container. 
     The inkjet recording apparatus  90  including the liquid discharge head  1  according to the present embodiment enables a stable ink discharge characteristics, leading to an improvement in image quality. The inkjet recording apparatus  90  including the liquid discharge head  1  has been described above. However, the liquid discharge head  1  may be applied to an apparatus that discharges non-ink liquid droplets, such as liquid resist for patterning. 
     Next, another embodiment of the liquid discharge apparatus according to the present embodiment will be described. A recording apparatus will be described below as an example of the liquid discharge apparatus according to the present embodiment. 
     The liquid discharge head according to the present embodiment can be used in various types of recording apparatuses of an inkjet recording system, such as a printer, a facsimile apparatus, a copying machine, a printer/facsimile/multifunction peripheral, a solid shaping apparatus, and a bioprinter. 
     In the present embodiment, a recording apparatus corresponds to an apparatus capable of discharging ink or various types of treatment liquids to a recording medium, and a recording method corresponds to a method for recording with the apparatus. Such a recording medium denotes an object to which ink or various types of treatment liquids can adhere temporarily. 
     The recording apparatus can include not only a head that discharges ink but also a feeder, a conveyer, and an ejector for recording media, and devices, such as a preprocessing device and postprocessing device. 
     For the recording apparatus and the recording method, provided may be a heater for use in a heat process and a dryer for use in a dry process. For example, the heater heats the printed face or back face of a recording medium. The dryer dries the printed face or back face of a recording medium. Examples of the heater and the dryer that can be used include, but are not particularly limited to, a warm air heater and an infrared heater. Heating and drying can be performed, for example, before printing, during printing, or after printing. 
     The recording apparatus and the recording method are not limited to visualization of a significant image, such as a character or a figure, with ink. For example, the recording apparatus and the recording method may be intended for formation of a pattern, such as a geometric pattern, or shaping of a three-dimensional image. Examples of the recording apparatus include, but are not particularly limited to, a serial type apparatus that moves a liquid discharge head and a line type apparatus that does not move a liquid discharge head. Examples of the recording apparatus further include a desktop recording apparatus, a wide recording apparatus capable of printing to an A0-size recording medium, and a continuous stationery printer for rolled continuous paper as a recording medium. 
     Next, another example of the liquid discharge apparatus according to the present embodiment will be described with reference to  FIGS.  13  and  14   . 
       FIG.  13    is an explanatory plan view of a main part of the apparatus. 
       FIG.  14    is an explanatory side view of the main part of the apparatus. 
     The apparatus serves as a serial type apparatus. Due to a main scanning movement mechanism  493 , a carriage  403  reciprocates in the main scanning direction. The main scanning movement mechanism  493  includes a guide member  401 , a main scanning motor  405 , and a timing belt  408 . The guide member  401  is bridged between a left side plate  491 A and a right side plate  491 B and retains the carriage  403  movably. Then, due to the main scanning motor  405 , the carriage  403  reciprocates in the main scanning direction through the timing belt  408  bridged between a drive pulley  406  and a driven pulley  407 . 
     The carriage  403  is equipped with a liquid discharge device  440  including a liquid discharge head  404  according to the present embodiment and a head tank  441 , integrally. The liquid discharge head  404  of the liquid discharge device  440  discharges liquids of colors, such as yellow (Y), cyan (C), magenta (M), and black (K). The liquid discharge head  404  is attached such that a nozzle array of a plurality of nozzles  16  is disposed in the sub-scanning direction orthogonal to the main scanning direction with a downward direction of discharging. 
     A supply mechanism  494  that supplies the liquid discharge head  404  with liquid stored outside the liquid discharge head  404  supplies the head tank  441  with liquid stored in a liquid cartridge  450 . 
     The supply mechanism  494  includes a cartridge holder  451  as a holder to which the liquid cartridge  450  is attached, a tube  456 , and a liquid feeding unit  452  including a liquid feeding pump. The liquid cartridge  450  is detachably attached to the cartridge holder  451 . The liquid feeding unit  452  feeds the liquid from the liquid cartridge  450  to the head tank  441  through the tube  456 . 
     The apparatus includes a conveyance mechanism  495  that conveys a sheet  410 . The conveyance mechanism  495  includes a conveying belt  412  as a conveyor and a sub-scanning motor  416  that drives the conveying belt  412 . 
     The conveying belt  412  attracts and conveys the sheet  410  such that the sheet  410  faces the liquid discharge head  404 . The conveying belt  412  serves as an endless belt stretched between a conveying roller  413  and a tension roller  414 . Such attraction as above can be achieved by electrostatic attraction or air suction. 
     Then, through a timing belt  417  and a timing pulley  418 , the sub-scanning motor  416  drives the conveying roller  413  to rotate, so that the conveying belt  412  runs circumferentially in the sub-scanning direction. 
     Furthermore, on the lateral side of the conveying belt  412  on one side in the main scanning direction of the carriage  403 , disposed is a maintenance mechanism  420  that maintains the liquid discharge head  404 . 
     The maintenance mechanism  420  includes, for example, a cap member  421  that caps the nozzle face of the liquid discharge head  404  (face on which the nozzles  16  are formed) and a wiper member  422  that wipes the nozzle face. 
     The main scanning movement mechanism  493 , the supply mechanism  494 , the maintenance mechanism  420 , and the conveyance mechanism  495  are attached to a housing including the left side plate  491 A, the right side plate491B, and a rear plate  491 C. 
     In the apparatus having such a configuration as above, the sheet  410  is fed on and attracted to the conveying belt  412 . Then, the sheet  410  is conveyed in the sub-scanning direction due to a circumferential run of the conveying belt  412 . 
     Then, with the carriage  403  moving in the main scanning direction, the liquid discharge head  404  is driven, in accordance with an image signal, to discharge liquid to the sheet  410  remaining stopped, leading to formation of an image. 
     As above, the apparatus including the liquid discharge head according to the present embodiment enables stable formation of a high-quality image. 
     Next, another example of the liquid discharge device according to the present embodiment will be described with reference to  FIG.  15   . 
       FIG.  15    is an explanatory plan view of a main part of the liquid discharge device. 
     The liquid discharge device includes the housing including the left side plate  491 A, the right side plate  491 B, and the rear plate  491 C, the main scanning movement mechanism  493 , the carriage  403 , and the liquid discharge head  404 , from among the constituent members of the liquid discharge apparatus described above. 
     Note that, for example, the liquid discharge device may have the right side plate  491 B to which at least either the maintenance mechanism  420  or supply mechanism  494  described above is attached. 
     Next, still another example of the liquid discharge device according to the present embodiment will be described with reference to  FIG.  16   . 
       FIG.  16    is an explanatory front view of the liquid discharge device. 
     The liquid discharge device includes a liquid discharge head  404  to which a channel component  444  is attached, and a tube  456  connected to the channel component  444 . 
     Note that the channel component  444  is disposed inside a cover  442 . Instead of the channel component  444 , a head tank  441  can be provided. The channel component  444  has an upper portion provided with a connector  443  for electrical connection with the liquid discharge head  404 . 
     In the present specification, the “liquid discharge apparatus” includes a liquid discharge head or a liquid discharge device and drives the liquid discharge head to discharge liquid. Examples of the liquid discharge apparatus include an apparatus capable of discharging liquid to an object to which liquid can adhere and an apparatus that discharges liquid into gas or liquid. 
     The “liquid discharge apparatus” can include a feeder, a conveyer, and an ejector for an object to which liquid can adhere, a preprocessing device, and a postprocessing device. 
     Examples of the “liquid discharge apparatus” include an image forming apparatus that discharges ink to a sheet to form an image on the sheet, and a solid shaping apparatus (three-dimensionally shaping apparatus) that discharges shaping liquid to a powder-conglomeration layer as a layered conglomeration of powder in order to shape a solid shaped object (three-dimensionally shaped object). 
     The “liquid discharge apparatus” is not limited to visualization of a significant image, such as a character or a figure, with discharged liquid. For example, the liquid discharge apparatus may be intended for formation of a meaningless pattern or shaping of a three-dimensional image. 
     The “object to which liquid can adhere” denotes an object to which liquid can adhere at least temporarily, an object on which liquid fastens after adhering to, and an object into which liquid permeates after adhering to. Specific examples of the “object to which liquid can adhere” include a recording medium, such as a sheet, recording paper, a recording sheet, a film, or cloth, an electronic component, such as an electronic circuit board or a piezoelectric element, and a medium, such as a powder-conglomeration layer (powder layer), an organ model, or a testing cell. Unless otherwise particularly limited, the “object to which liquid can adhere” may be any object to which liquid adheres. 
     Examples of the material of the “object to which liquid can adhere” include paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramic, building materials, such as wallpaper and flooring, and a textile for clothing that enable temporary adhesion of liquid. 
     Examples of the “liquid” include ink, treatment liquid, a deoxyribonucleic acid (DNA) sample, resist, pattern material, a binder, shaping liquid, and a solution or dispersion liquid containing an amino acid, protein, or calcium. 
     The “liquid discharge apparatus” may be, but is not limited to, an apparatus that moves relatively a liquid discharge head and an object to which liquid can adhere. Specific examples of the “liquid discharge apparatus” include a serial type apparatus that moves a liquid discharge head and a line type apparatus that does not move a liquid discharge head. 
     Examples of the “liquid discharge apparatus” further include a treatment-liquid coating apparatus that discharges, for the purpose of reforming the surface of a sheet, treatment liquid to the sheet to coat the treatment liquid on the surface of the sheet, and a jet granulation apparatus that jets a composition liquid including row material dispersed in a solution, through a nozzle to granulate fine particles of the row material. 
     The “liquid discharge device” corresponds to an integration of a liquid discharge head and a functional component or mechanism, namely, an assembly of components relating to liquid discharge. Examples of the “liquid discharge device” include a combination of a liquid discharge head with at least one of a head tank, a carriage, a supply mechanism, a maintenance mechanism, or a main scanning movement mechanism. 
     Examples of such an integration as above include a combination of a liquid discharge head and a functional component or mechanism secured together, for example, by fastening, bonding, or engaging, and a combination of a liquid discharge head and a functional component or mechanism, in which one of the liquid discharge head and the functional component or mechanism is retained movably to the other. A liquid discharge head and a functional component or mechanism may be detachably attachable to each other. 
     Like the liquid discharge device  440  illustrated in  FIG.  14   , for example, a liquid discharge head and a head tank are integrated together as a liquid discharge device. For example, a liquid discharge head and a head tank mutually connected through a tube are integrated together as a liquid discharge device. Such a liquid discharge device can have a unit including a filter between the head tank and the liquid discharge head. 
     For example, a liquid discharge head and a carriage are integrated together as a liquid discharge device. 
     For example, a liquid discharge head and a main scanning movement mechanism are integrated together as a liquid discharge device, with the liquid discharge head retained movably by a guide member as part of the main scanning movement mechanism. For example, as such a liquid discharge device as illustrated in  FIG.  15   , a liquid discharge head, a carriage, and a main scanning movement mechanism are integrated together. 
     For example, a liquid discharge head, a carriage, and a maintenance mechanism are integrated together as a liquid discharge device, in which a cap member as part of the maintenance mechanism is secured to the carriage to which the liquid discharge head is attached. 
     For example, as such a liquid discharge device as illustrated in  FIG.  16   , a liquid discharge head and a supply mechanism are integrated together, with a tube connected to the liquid discharge head to which a head tank or a channel component is attached. 
     Such a main scanning movement mechanism as above includes a guide member as a single item. Such a supply mechanism as above includes a tube as a single item and a holder as a single item. 
     The “liquid discharge head” is not limited in terms of a pressure generator to be used. For example, instead of such a piezoelectric actuator as described in the above embodiment (or a multilayered piezoelectric element), used may be a thermal actuator employing a thermoelectric conversion element, such as a heat-generating resistor, or an electrostatic actuator including a diaphragm and opposed electrodes. 
     In the present specification, the terms “image forming”, “recording”, “printing”, “image printing”, “print”, and “shaping” are synonymous. 
     The liquid discharge head according to the present embodiment can improve reliability while reducing tensile stress generated in the piezoelectric member. The liquid discharge head can increase a discharge droplet and improve discharge characteristic. 
     Aspect 1 
     A liquid discharge head ( 1 ) includes: a chamber substrate ( 100 ) ; a diaphragm ( 13 ) on the chamber substrate; a lower electrode ( 10 ) on the diaphragm ( 13 ); a piezoelectric member ( 20 ) on the lower electrode ( 10 ); an upper electrode ( 11 ) on the piezoelectric member ( 20 ); wiring ( 42 ) electrically connected to the upper electrode to transmit driving signal to the piezoelectric member ( 20 ); and a nozzle substrate ( 300 ) having a nozzle ( 16 ). 
     The chamber substrate ( 100 ) includes an individual chamber ( 15 ) facing the diaphragm ( 13 ), the individual chamber ( 15 ) has polygonal shape having four or more sides, the piezoelectric member ( 20 ) has polygonal shape having four or more sides, the wiring ( 42 ) covers a middle point (bp) of a first side ( 15 - 2 ) of the four or more sides of the individual chamber ( 15 ), and a distance A is smaller than a distance B, where the distance A is between a first end portion ( 15   a ) of the individual chamber ( 15 ) and a second end portion ( 20   a ) of the piezoelectric member ( 20 ) in a second side ( 15 - 1 ) of the four or more sides in which a distance L is the largest, and a distance B is between a third end portion ( 15   a ) of the individual chamber ( 15 ) and a fourth end portion ( 20   b ) of the piezoelectric member ( 20 ) in a third side ( 15 - 3 ,  15 - 4 ) of the four or more sides in which the distance L is the smallest, and the distance L is a distance from the middle point (bp) of the first side ( 15 - 2 ) to each of middle points (mp) of the four or more sides other than the first side ( 15 - 2 ). 
     Aspect 2 
     In the liquid discharge head according to Aspect 1, multiple sides in the four or more sides have the largest distance L. 
     Aspect 3 
     In the liquid discharge head according to Aspect 1, multiple sides in the four or more sides have the smallest distance L. 
     Aspect 4 
     In the liquid discharge head according to Aspect 1, each of the individual chamber ( 15 ) and the piezoelectric member ( 20 ) has a curved corner between the second side and the third side. 
     Aspect 5 
     In the liquid discharge head according to Aspect 3, wherein the curved corner has distance C between a fifth end portion of the individual chamber ( 15 ) and a sixth end portion of the piezoelectric member ( 20 ), and the distance C is larger than the distance A and smaller than the distance B. 
     Aspect 6 
     In the liquid discharge head according to Aspect 1, further includes a channel ( 68 ) communicating with a common chamber ( 18 ); and a connection ( 15   b ) connecting the channel ( 68 ) and the individual chamber ( 15 ). The connection ( 15   b ) covers another middle point of the second side ( 15 - 1 ) opposite to the first side ( 15 - 2 ). 
     Aspect 7 
     In the liquid discharge head according to Aspect 2, further includes a channel ( 68 ) communicating with a common chamber ( 18 ); and a connection ( 15   b ) connecting the channel ( 68 ) and the individual chamber ( 15 ). The connection ( 15   b ) covers the curved corner opposite to the first side ( 15 - 2 ). 
     Aspect 8 
     In the liquid discharge head according to Aspect 1, the individual chamber ( 15 ) has a rectangular shape. 
     Aspect 9 
     In a liquid discharge device includes the liquid discharge head according to Aspect 1. 
     Aspect 10 
     In the liquid discharge device according to Aspect 8, further includes at least one of: a head tank storing liquid to be supplied to the liquid discharge head; a carriage on which the liquid discharge head is mounted; a supply mechanism configured to supply the liquid to the liquid discharge head; a maintenance mechanism configured to maintain the liquid discharge head; or a main scanning movement mechanism configured to move the liquid discharge head in a main scanning direction, combined together with the liquid discharge head to form a single body. 
     Aspect 11 
     In a liquid discharge apparatus includes the liquid discharge device according to Aspect 9. 
     The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention. 
     Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above. 
     The functionality of the elements disclosed herein may be implemented using circuitry or processing circuitry which includes general purpose processors, special purpose processors, integrated circuits, application specific integrated circuits (ASICs), digital signal processors (DSPs), field programmable gate arrays (FPGAs), conventional circuitry and/or combinations thereof which are configured or programmed to perform the disclosed functionality. 
     Processors are considered processing circuitry or circuitry as they include transistors and other circuitry therein. In the disclosure, the circuitry, units, or means are hardware that carry out or are programmed to perform the recited functionality. The hardware may be any hardware disclosed herein or otherwise known which is programmed or configured to carry out the recited functionality. When the hardware is a processor which may be considered a type of circuitry, the circuitry, means, or units are a combination of hardware and software, the software being used to configure the hardware and/or processor.