Patent Publication Number: US-2023157067-A1

Title: Display device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation application of U.S. application Ser. No. 17/376,173, filed on Jul. 15, 2021, which is a continuation application of U.S. application Ser. No. 17/000,373, filed on Aug. 24, 2020, which is a continuation application of U.S. application Ser. No. 16/019,494, filed on Jun. 26, 2018. The contents of these applications are incorporated herein by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The present disclosure relates to a display device, and more particularly, to a flexible display device with bending sensor units. 
     2. Description of the Prior Art 
     In recent years, flexible electronic devices have become one of the focuses of the new generation electronic technology. The demand of the display device that can be integrated in the flexible electronic device is therefore increased. A flexible display device means the device can be curved, folded, stretched, flexed, bended, or the like. In order to improve the function and performance of the flexible display device, it is in need of detecting the bending status of the flexible display device so as to display corresponding images and providing corresponding control signals, which is still an important issue for the manufacturers. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosures provides a display device that includes a flexible substrate, a display layer disposed on the flexible substrate and including a first light emitting unit, a first conductive layer disposed on the display layer, and a second conductive layer disposed on the first conductive layer, comprising a plurality of second conductive lines, wherein one of the second conductive lines comprises an opening. The first light emitting unit has a round shape and is disposed in a position corresponding to the opening. 
     The present disclosures further provides a display device that includes a flexible substrate, a display layer disposed on the flexible substrate, first conductive layer disposed on the display layer, and a second conductive layer disposed on the first conductive layer. The display layer includes a plurality of first light emitting units each configured to emit a blue light, a plurality of second light emitting units configured to emit a green light, and a plurality of third light emitting units each configured to emit a red light. The first conductive layer includes a plurality of first conductive lines. The second conductive layer includes a plurality of second conductive lines. In a cross-sectional view of the display device along a direction passing through the first light emitting units and the third light emitting units alternately, a distance between two first conductive lines of the plurality of first conductive lines is greater than a distance between two second conductive lines of the plurality of second conductive lines. 
     The present disclosure provides a display device that includes a flexible substrate, a display layer disposed on the flexible substrate and including a plurality of light emitting units, a first conductive layer disposed on the display layer, including a plurality of first conductive lines, and a second conductive layer disposed on the first conductive layer, including a plurality of second conductive lines. Wherein, a portion of the second conductive lines intersects the plurality of first conductive lines to form a plurality of capacitors, and another portion of the second conductive lines forms a plurality of touch units. At least one of the plurality of capacitors does not overlap the plurality of light emitting units in a top view of the display device. 
     These and other objectives of the present disclosure will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the embodiment that is illustrated in the various figures and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of a top view of a display device according to a first embodiment of the present disclosure. 
         FIG.  2    is a partial-enlargement schematic diagram of a top view of the display region of the display device shown in  FIG.  1   . 
         FIG.  3    is a schematic diagram illustrating a cross-sectional view along line A-B of the display device shown in  FIG.  2   . 
         FIG.  4    is a partial-enlargement schematic diagram of a cross-sectional view illustrating a bending state of the display device shown in  FIG.  3   . 
         FIG.  5    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a first variant embodiment of the first embodiment of the present disclosure. 
         FIG.  6    is a partial-enlargement schematic diagram illustrating the conductive lines according to other variant embodiments of the first embodiment of the present disclosure. 
         FIG.  7    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a second variant embodiment of the first embodiment. 
         FIG.  8    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a second embodiment of the present disclosure. 
         FIG.  9    is a schematic diagram illustrating a cross-section view along line A-B of the display device shown in  FIG.  8   . 
         FIG.  10    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a third embodiment of the present disclosure. 
         FIG.  11    is a schematic diagram illustrating a cross-sectional view along line A-B of the display device shown in  FIG.  10   . 
         FIG.  12    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a fourth embodiment of the present disclosure. 
         FIG.  13    is a cross-sectional schematic diagram of a cross-sectional view of a display device according to another embodiment. 
         FIG.  14    is a partial-enlargement schematic diagram illustrating a cross-sectional view of a display device according to a fifth embodiment of the present disclosure. 
         FIG.  15    is a partial-enlargement schematic diagram illustrating a cross-sectional view of a display device according to a sixth embodiment of the present disclosure. 
         FIG.  16    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a seventh embodiment of the present disclosure. 
         FIG.  17    is a schematic diagram illustrating a cross-sectional view of a display device according to another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure may be understood by reference to the following detailed description, taken in conjunction with the drawings as described below. It is noted that, for purposes of illustrative clarity and being easily understood by the readers, various drawings of this disclosure show a portion of the display device, and certain elements in various drawings may not be drawn to scale. In addition, the number and dimension of each device shown in drawings are only illustrative and are not intended to limit the scope of the present disclosure. 
     Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will understand, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include”, “comprise” and “have” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”. 
     It will be understood that when an element or layer is referred to as being “on” or “connected to” another element or layer, it can be directly on or directly connected to the other element or layer, or intervening elements or layers maybe presented. In contrast, when an element is referred to as being “directly on” or “directly connected to” another element or layer, there are no intervening elements or layers presented. 
     It should be noted that the technical features in different embodiments described in the following can be replaced, recombined, or mixed with one another to constitute another embodiment without departing from the spirit of the present disclosure. 
     Referring to  FIG.  1    to  FIG.  3   ,  FIG.  1    is a schematic diagram of a top view of a display device according to a first embodiment of the present disclosure,  FIG.  2    is a partial-enlargement schematic diagram of a top view of a display region of the display device shown in  FIG.  1   , and  FIG.  3    is a schematic diagram illustrating a cross-sectional view along line A-B of the display device shown in  FIG.  2   . A display device  100  is provided in this embodiment. The display device  100  can be a flexible display device and can be capable of being repeatedly bended along at least a bending axis AX for example. The terms “bended” in the present disclosure means curved, bended, folded, rolled, stretched, flexed, or the like (generally referred to as “bended” or “flexible” hereinafter). In this embodiment, the display device  100  includes a substrate structure  102 . For example, the substrate structure  102  may include a flexible substrate  1021 . The substrate structure  102  has a first portion R 1  which is a bendable region, and the first portion R 1  of the substrate structure  102  can be repeatedly bended as mentioned above. The substrate structure  102  may further include a second portion R 2  positioned adjacent to the first portion R 1 . The second portion R 2  may be a main portion for displaying image and may be a non-bendable region, but not limited thereto. In this embodiment, the display device  100  includes two second portions R 2  for instance, and the first portion R 1  is disposed adjacent to and between the two second portions R 2  in a first direction D 1 . The bending axis AX extends along a second direction D 2 . The second direction D 2  is different from the first direction D 1 . In other words, the second direction D 2  crosses the first direction D 1 . In this embodiment, the second direction D 2  is perpendicular to the first direction D 1  for example, but not limited thereto. 
     In addition, a peripheral region Ra and a display region Rb are defined on the substrate structure  102 . The peripheral region Ra can be disposed at a side of the display region Rb. In this embodiment, the peripheral region Ra may surround the display region Rb, and one or more peripheral wires and elements may be disposed in the peripheral region Ra. For example, one or more control units  104  or integrated circuits (ICs) may be electrically connected to the wirings (not shown) on the substrate structure  102 . Referring to  FIG.  1   , in some embodiments, the control unit  104  can be disposed in the peripheral region Ra and bent to a rear surface  102 B of the substrate structure  102  ( FIG.  1    shows the state of not bending to the rear surface  102 B). In this way, the control unit  104  does not occupy the front surface  102 A of the substrate structure  102 . Accordingly, the area of the peripheral region Ra may be reduced. Or, alternatively, in some embodiments, the control unit  104  can be disposed on a flexible printed circuit board (not shown) and electrically connected to the wirings (not shown) on the substrate structure  102  by a chip on film (COF) technique. The flexible printed circuit board can also be bent to the rear surface  102 B of the substrate structure  102 . Thus, the control unit  104  does not occupy the front surface  102 A of the substrate structure  102 , and the area of the peripheral region Ra may be reduced. 
     Referring to  FIG.  2    and  FIG.  3   , the display device  100  further includes a display layer  106  and a bending sensor layer  108 . The display layer  106  is disposed on the front surface  102 A of the substrate  102 . The bending sensor layer  108  is disposed on the display layer  106  and includes a plurality of bending sensor units BS. The bending sensor units BS are disposed in the display region Rb. In this embodiment, since the first portion R 1  is the bendable region of the display device  100 , the bending sensor units BS are disposed within the first portion R 1 , but not limited thereto. In some embodiments, the bending sensor units BS may be disposed both in the first portion R 1  and the second portions R 2  or arranged in the whole display region Rb for instance. In some embodiments, a density of the bending sensor units BS in the first portion R 1  is greater than a density of the bending sensor units BS in the second portions R 2 , but not limited thereto. 
     As shown in  FIG.  2    and  FIG.  3   , the display layer  106  may include a plurality of light emitting units LE in the display region Rb of the display device  100 . In this embodiment, the display layer  106  includes three kinds of light emitting units LE, such as a plurality of first light emitting units LE 1 , a plurality of second light emitting units LE 2 , and a plurality of third light emitting units LE 3 . For example, the first light emitting units LE 1  can emit blue light, the second light emitting units LE 2  can emit green light, and the third light emitting units LE 3  can emit red light, but not limited thereto. The first light emitting units LE 1 , the second light emitting units LE 2 , and the third light emitting units LE 3  may be arranged in an array alternately and repeatedly. The numbers of the first light emitting units LE 1 , the second light emitting units LE 2 , and the third light emitting units LE 3  in the display region Rb may be identical or non-identical. For example, the number of the first light emitting units LE 1  per unit area and the number of the third light emitting units LE 3  per unit area may be less than the number of the second light emitting units LE 2  per unit area in this embodiment, but not limited thereto. In addition, the areas or shapes of the first light emitting units LE 1 , the second light emitting units LE 2 , and the third light emitting units LE 3  may be identical or non-identical. For example, the second light emitting units LE 2  may have a round shape while the first light emitting units LE 1  and the third light emitting units LE 3  may have rectangular-like shapes in this embodiment, but not limited thereto. 
     According to the present disclosure, at least one of the plurality of bending sensor units BS are disposed between and spaced apart from at least two adjacent light emitting units LE of the plurality of light emitting units LE in a top view of the display device  100 . In other words, at least one of the plurality of bending sensor units BS do not overlap at least two adjacent light emitting units LE in a top view of the display device  100 . In this embodiment, all the bending sensor units BS are spaced apart from light emitting units LE, but not limited thereto. 
     Specifically, referring to  FIG.  2    and  FIG.  3   , the bending sensor layer  108  may include a first conductive layer  1081  and a second conductive layer  1082  disposed on the first conductive layer  1081 . The first conducive layer  1081  includes a plurality of first conductive lines CL 1  extending along the first direction D 1 . The second conductive layer  1082  includes a plurality of second conductive lines CL 2  extending along the second direction D 2 . In some embodiments, the first conductive lines CL 1  and the second conductive lines CL 2  can be in a linear shape (as shown in  FIG.  2   ). In some embodiments, the first conductive lines CL 1  and the second conductive lines CL 2  can be in a non-linear shape, for example, a wavy shape or a zigzag shape, or can include a curved shape. The bending sensor layer  108  further includes an insulating layer  1083  disposed between the first conductive lines CL 1  (the first conductive layer  1081 ) and the second conductive lines CL 2  (the second conductive layer  1082 ) in a vertical direction Z perpendicular to the front surface  102 A of the substrate structure  102 . Thus, the plurality of first conductive lines CL 1  and the plurality of second conductive lines CL 2  intersect each other to form a plurality of bending sensor units BS. In other words, one bending sensor unit BS is defined by an overlapping portion of one first conductive line CL 1  and one second conductive line CL 2 , together with the insulating layer  1083  corresponding to the overlapping portion. The bending sensor unit BS may be a capacitive-type sensor in this embodiment. Furthermore, a protection layer  118  may be selectively disposed on and cover the bending sensor layer  108 . The protection layer  118  may include insulating material and provide protection to the bending sensor layer  108 . 
     To compare the arrangement of the bending sensor units BS and the light emitting units LE, a density of the plurality of bending sensor units BS is less than a density of the plurality of light emitting units LE. The above-mentioned “density” means the total number of the referred elements per unit area (such as square inch), and the above-mentioned “density” can be calculated with reference to the whole display region Rb, or calculated with reference to an arbitrary region in the display region Rb. For example, the density of the bending sensor units BS (defined as D B ) can be calculated by dividing the total number of the bending sensor units BS by the total area of the display region Rb. Similarly, the density of the light emitting units LE (defined as D L ) can be calculated by dividing the total number of the light emitting units LE by the total area of the display region Rb. Or, alternatively, the density of the bending sensor units BS and the density of the light emitting units LE can also be calculated based on an arbitrary region in the display region Rb. Specifically, a given region in the display region Rb can be chosen, and this given region includes at least one bending sensor units BS and at least two light emitting units LE. In the given region, the density of the bending sensor units BS can be calculated by dividing the number of the bending sensor units BS by the area of the given region. Similarly, the density of the light emitting units LE can be calculated by dividing the number of the light emitting units LE by the area of the given region. For example, the given region can be a square shape, and can have an area of 1 inch×1 inch, or an area of 1 cm×1 cm. 
     In some embodiments, the given region can be an entire region of the first portion R 1  (bendable region). In some embodiments, the given region can be chosen as a part of (not entire of) the first portion R 1  (bendable region). For example, if the length of the first portion R 1  along the second direction D 2  is L, the given region can be chosen as a square or rectangular shape region with a length of one tenth of L (L/10) along the second direction D 2 .  FIG.  1    shows two possible given region  20 R and  25 R, in which region  20 R is in a rectangular shape and region  25 R is in a square shape, but not limited thereto. 
     According to this embodiment, a ratio of the density of the bending sensor units BS to the density of the light emitting units in the top view of the display region Rb of the display device  100  is greater than or equal to 0.0001 and less than 0.5 (i.e., 0.0001≤D B /D L &lt;0.5). 
     Referring to  FIG.  2   , one second conductive line CL 2  includes a plurality of first parts  31  overlapping with the first conductive lines CL 1 , and a plurality of second parts  32  not overlapping with the first conductive line CL 1 . In some embodiments, the first parts  31  are the parts corresponding to the bending sensor units BS, and the second parts  32  are the parts not corresponding to the bending sensor units BS. In some embodiments, in one second conductive line CL 2 , the first parts  31  and the second parts  32  can have the same widths along the first direction D 1 . 
     In some embodiments, in one second conductive line CL 2 , the first parts  31  and the second parts  32  can have different widths along the first direction D 1 . For example, a first width W 1  of the first part  31  (corresponding to the bending sensor unit BS) of the second conductive line CL 2  can be greater than a second width W 2  of the second part  32  (not corresponding to the bending sensor unit BS), along the first direction D 1 . In addition, the first conductive line CL 1  corresponding to the bending sensor unit BS can have a width (not shown) greater than a width (not shown) not corresponding to the bending sensor unit BS. Thus, by means of the wider parts of the first conductive line CL 1  and the second conductive line CL 2 , the bending sensor will have improved sensitivity. 
     The first conductive layer  1081  that forms the first conductive lines CL 1  and the second conductive layer  1082  that forms the second conductive lines CL 2  may include metal material (s) and/or metal oxide material(s), but not limited thereto. Examples of the metal material may include Mg, Ca, Al, Ag, W, Cu, Ni, Cr, or an alloy of one or more of the above-mentioned material. Examples of the metal oxide material may include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide, or indium oxide. In some embodiments, the first conductive layer  1081  and the second conductive layer  1082  may include nanosilver wires. The first conductive layer  1081  and the second conductive layer  1082  independently can be a single layer or multiple layers. For example, the first conductive layer  1081  and the second conductive layer  1082  independently can be Mo/Al/Mo multiple layers or Ti/Cu/Ti multiple layers. 
     As shown in  FIG.  3   , the substrate structure  102  may include the flexible substrate  1021  and a supporting film  1022 , and the flexible substrate  1021  can be adhered to the supporting film  1022  through a glue layer. The flexible substrate  1021  may include polymer material, thin glass, or any suitable material. Examples of material of the flexible substrate  1021  and the supporting film  1022  may include polyethylene terephthalate (PET), polyimide (PI), or polyethylene naphthalate (PEN), but not limited thereto. 
     The display layer  106  may include a plurality of driving elements  1061  and a plurality of display units  1062  arranged in an array, wherein each of the display units  1062  serves as one of the light emitting units LE mentioned above. Each driving element  1061  is electrically connected to a corresponding display unit  1062  for driving the corresponding display unit  1062 . The driving elements  1061  in this embodiment are shown as driving TFTs, but not limited thereto.  FIG.  3    shows that one driving element  1061  may overlap the corresponding display unit  1062  along a vertical direction perpendicular to the front surface  102 A of the substrate structure  102 , but not limited thereto. 
     The display units  1062  may be any type of display cells or elements, such as organic light-emitting diode (OLED), micro light-emitting diode (micro-LED), mini-LED, or quantum dot LED (QLED), but not limited thereto. As shown in  FIG.  3   , one display unit  1062  includes a first electrode  1062   a , a second electrode  1062   c , and a light emitting layer  1062   b  disposed between the first electrode  1062   a  and the second electrode  1062   c . The first electrode  1062   a  may be an anode and the second electrode  1062   c  may be a cathode of the display unit  1062  in this embodiment for example, but not limited thereto. The light emitting region of each display unit  1062  can be defined by a dielectric layer  1064 , which may serve as a pixel defining layer (PDL). The light emitting layer  1062   b  may include one or more layers of emissive material, and the emissive material can be inorganic or organic material. Different display units  1062  can emit lights with different colors, such as red, green and blue colors. For example, the light emitting layer  1062   b  in different display units  1062  can be made of different materials for emitting light of red, green, and blue. As shown in  FIG.  3   , blue light emitting units LE 1  and red light emitting units LE 3  are disposed alternately and repeatedly. In some embodiments, the light emitting layers  1062   b  in different display units  1062  can also be of the same material and emits the same light. The first electrode  1062   a  and the second electrode  1062   c  may include metal or transparent conductive material, but not limited thereto. Examples of the metal material of the electrodes may include Mg, Ca, Al, Ag, W, Cu, Ni, Cr, or an alloy of one or more of the above-mentioned material. Examples of the transparent conductive material may include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide, or indium oxide. 
     As mentioned above, the driving element  1061  maybe a thin film transistor (TFT) in this embodiment, which is a top-gate type TFT, but not limited thereto. Bottom-gate type TFT maybe adopted in other embodiments, and the TFT structures may not be limited to only one type in a display device  100 . One driving element  1061  may include a semiconductor layer  1061 C, a dielectric layer  1065 , a gate electrode  1061 G, a dielectric layer  1066 , a drain electrode  1061 D, and a source electrode  1061 S. The semiconductor layer  1061 C may be formed with a semiconductor material, such as silicon or metal oxide, but not limited thereto. For example, the semiconductor layer  1061 C may be an amorphous silicon layer, a polysilicon layer, or an indium gallium zinc oxide (IGZO) layer. Furthermore, the semiconductor layer  1061 C includes a source contact, a drain contact, and a channel disposed between the source contact and the drain contact in one driving element  1061 . The source electrode  1061 S is electrically connected to the corresponding source contact through a via hole in the dielectric layer  1065  and the dielectric layer  1066 . The drain electrode  1061 D is electrically connected to the corresponding drain contact through another via hole in the dielectric layer  1065  and the dielectric layer  1066 . The gate electrode  1061 G is separated from the semiconductor layer  1061 C by the dielectric layer  1065  which serves as the gate insulating layer of the driving element  1061 . The gate electrode  1061 G, the source electrode  1061 S, and the drain electrode  1061 D are formed of conductive materials (such as metal), but not limited thereto. Suitable material for the gate electrode  1061 G, the source electrode  1061 S, and the drain electrode  1061 D may refer to the material mentioned above for the first electrode  1062   a  and the second electrode  1062   c . In the present disclosure, one driving element  1061  may be electrically connected to the corresponding display unit  1062  directly through the drain electrode  1061 D for driving the display unit  1062 . In detail, the drain electrode  1061 D may be connected to the first electrode  1062   a  of the display unit  1062 . In addition, a dielectric layer  1067  may be disposed between the first electrode  1062   a  of the display unit  1062  and the conductive layer forming the source electrode  1061 S and the drain electrode  1061 D. 
     Furthermore, in addition to the driving element  1061  mentioned above, the display layer  106  may further include one or more other electronic elements, such as, but not limited to, reset element(s), compensation element(s), operation control element(s), and capacitor(s). Although the driving element  1061  has a top-gate type of TFT structure, it is merely an example of the present disclosure and is not meant to limit the types or structures of the TFTs of the display layer  106  of the present disclosure. In addition, a buffer layer  110  may be disposed between the flexible substrate  1021  and the display layer  106 . In this embodiment, the buffer layer  110  may include an oxide layer, a nitride layer or other suitable insulating layer, but not limited thereto. Furthermore, an encapsulation layer  112  may be disposed on the display layer  106 . The encapsulation layer  112  may provide protection, encapsulation and/or planarization function for the display layer  106  and may include organic material, inorganic material, or a mixture thereof, but not limited thereto. For example, the encapsulation layer  112  can be multiple layers including an inorganic layer, an organic layer, and an inorganic layer. 
     As mentioned above, in some embodiments, the bending sensor units BS are space apart from and do not overlap the light emitting units LE. In some embodiments, one of the bending sensor units BS may be disposed between two adjacent light emitting units LE and right above the dielectric layer  1064 . In this embodiment, for one bending sensor unit BS, the distance S 1  between a side of the bending sensor unit BS and an adjacent light emitting units LE may be the same as the distance S 2  between the other side of the bending sensor unit BS and another adjacent light emitting units LE, as shown in  FIG.  3   , but not limited thereto. In some embodiments, the distance S 1  may be different from the distance S 2 . 
     Referring to  FIG.  4   ,  FIG.  4    is a partial-enlargement schematic diagram of a cross-sectional view illustrating a bending state of the display device shown in  FIG.  3   . As shown in  FIG.  4   , When the display device  100  is in a bending state, the first portion R 1  may be bended, curved, folded, stretched, flexed, or the like, while the second portion R 2  may not be deformed or may remain a flat state. Accordingly, the layers in the first portion R 1  may be pulled and stretched such that their thicknesses are thereby reduced. Accordingly, the distance between the first conductive line CL 1  and the second conductive layer CL 2  may be changed, such as becoming smaller than the original distance when the display device  100  is not bended or flexed. As shown in  FIG.  4   , the bending sensor unit BS near the central part of the first portion R 1  or corresponding to the bending axis AX has a distance d 1  between its first conductive line CL 1  and second conductive layer CL 2 , which forms a first capacitor C 1 , and another bending sensor unit BS farther from the bending axis AX or near the second portion R 2  has a distance d 2  between its first conductive line CL 1  and second conductive layer CL 2 , which forms a second capacitor C 2 . Since the central part of the first portion R 1  has a larger curvature when the display device  100  is in a bending state, both the distance d 1  and the distance d 2  may be reduced in compare with the original distance. However, the distance d 1  may further be smaller than the distance d 2 . Therefore, the capacitance variation of the first capacitor C 1  formed of the bending sensor unit BS near the central part of the first portion R 1  is greater than the capacitance variation of the second capacitor C 2  formed of the bending sensor unit BS farther farm the central part of the first portion R 1 . Specifically, in the bending state, the capacitance of the first capacitor C 1  is greater than the capacitance of the second capacitor C 2  since the distance d 1  is smaller than the distance d 2  in the bending state. Accordingly, by collecting the capacitance values and variations of the bending sensor units BS at different parts of the first portion R 1 , the bending degree of the display device  100  and the bending state may be obtained. 
     Furthermore, in one aspect, the insulating layer  1083  may include organic material(s), such as hydrophobic organic material, piezoelectric material (such as polyvinylidene (PVDF)), and/or dielectric elastomers (such as rubber, acrylic elastomer, polyurethane elastomer, acrylonitrile butadiene rubber, vinylidene fluoride trifluoroethylene, or composite thereof), but not limited thereto. When the insulating layer  1083  is an organic material, the suitable insulating layer  1083  may have a Young&#39;s modulus in a range from 0.01 GPa to 10 GPa, and may have a thickness in a range from 0.8 μm to 10 μm, but not limited thereto. In another aspect, the insulating layer  1083  may include inorganic material, such as silicon oxide (SiO x ), silicon nitride (SiN x ), barium titanate (BaTiO 3 ), lead titanate (PbTiO3), or lead zirconate titanate (PZT), but not limited thereto. When the insulating layer  1083  is an inorganic material, suitable insulating layer  1083  may have a dielectric constant in a range from 3 to 30, and may have a thickness in a range from 0.01 μm to 1 μm, but not limited thereto. By means of the above special design of the insulating layer  1083 , a better flexing property and better sensitivity can be obtained, and probability of crack during folding can be reduced. 
     The display device of the present disclosure is not limited to the above mentioned embodiments. Further embodiments or variant embodiments of the present disclosure are described below. It should be noted that the technical features in different embodiments described can be replaced, recombined, or mixed with one another to constitute another embodiment without departing from the spirit of the present disclosure. For making it easier to compare the difference between the embodiments and variant embodiments, the following description will detail the dissimilarities among different variant embodiments or embodiments and the identical features will not be redundantly described. 
     Referring to  FIG.  5    and  FIG.  6   ,  FIG.  5    is a partial-enlargement schematic diagram of a top view of a display device according to a first variant embodiment of the first embodiment of the present disclosure, and  FIG.  6    is a partial-enlargement schematic diagram illustrating one of the conductive lines according to other variant embodiments of the first embodiment of the present disclosure. The first variant embodiment is different from the first embodiment in that the first conductive lines CL 1  and the second conductive lines CL 2  further include a plurality of openings. Specifically, at least one first conductive line CL 1  can have a plurality of first openings OP 1  and at least one second conductive line CL 2  can have a plurality of second openings OP 2 . The first openings OP 1  in the first conductive line CL 1  can be adjacent to each other and arranged in the first direction D 1 , and the second openings OP 2  in the second conductive line CL 2  can be adjacent to each other and arranged in the second direction D 2 , but not limited to. The first opening OP 1  and second opening OP 2  can have curved shape or angular shape. The design of the first openings OP 1  and the second openings OP 2  may reduce the crack probability of the second conductive lines CL 2  and the first conductive lines CL 1  during bending. In some embodiments, the arrangement, numbers, shapes or patterns of the first openings OP 1  and second openings OP 2  may not be completely the same. In some other embodiments, the openings in the first conductive lines CL 1  and the second conductive lines CL 2  may have other kinds of shapes or have different sizes, numbers, or arrangement. As shown in  FIG.  6   , example (a) shows that the openings OP may have ellipse shapes and are arranged in a zigzag pattern, and example (b) shows that the openings OP are divided in several groups. For example, referring to example (b) in  FIG.  6   , one group G 1  is spaced apart from another group G 2  by a distance  60  greater than a distance  62  between two adjacent openings OP in the same group G 1 . It should be noted that the arrangement and shapes of the openings OP, the first openings OP 1 , and the second openings OP 2  shown in  FIG.  5    and  FIG.  6    are only examples and are not meant to limit the present disclosure. In some embodiments, the first openings OP 1  and second opening OP 2  can have areas less than the area of the light emitting units LE. In some embodiments, the first openings OP 1  and second opening OP 2  can have areas less than the area of the bending sensor units BS. In some embodiments, the first openings OP 1  and second opening OP 2  can have areas greater than or equal to 5 μm 2  (square micrometers) and less than or equal to 500 μm 2 . If the areas of the first openings OP 1  and second opening OP 2  are too large (such as greater than 500 μm 2 ), the resistance of the conductive lines may be too high. If the areas of the first openings OP 1  and second opening OP 2  are too small (such as less than 5 μm 2 ), the performance of reducing stress may not be significant. 
     Referring to  FIG.  7   ,  FIG.  7    is a partial-enlargement schematic diagram of a top view of a display device according to a second variant embodiment of the first embodiment of the present disclosure. The main difference between this variant embodiment and the first embodiment is that the first conductive lines CL 1  and the second conductive lines CL 2  can have recess portions. As shown in  FIG.  7   , in a top view of the display device, at least one first conductive line CL 1  can have at least one first recess portion  51 , and at least one second conductive line CL 2  can have at least one second recess portion  52 . For example,  FIG.  7    shows that each first conductive line CL 1  includes a plurality of first recess portions  51 , and each second conductive line CL 2  includes a plurality of second recess portions  52 . At least one light emitting unit LE can be disposed in the first recess portion  51 , and at least one light emitting unit LE can be disposed in the second recess portion  52 . In  FIG.  7   , the first light emitting units LE 1  are disposed in the first recess portions  51 , the third light emitting units LE 3  are disposed in other first recess portions  51 , and the second light emitting units LE 2  are disposed in the second recess portions  52 . 
     Referring to  FIG.  8    and  FIG.  9   ,  FIG.  8    is a partial-enlargement schematic diagram of a top view of a display device according to a second embodiment of the present disclosure, and  FIG.  9    is a schematic diagram illustrating a cross-sectional view along line A-B of the display device shown in  FIG.  8   . Compared to the first embodiment as shown in  FIG.  2   , the display device  100  of  FIG.  8    includes the first bending sensor units BS 1  similar to the bending sensor units BS shown in  FIG.  2   , and further includes second bending sensor units BS 2 . 
     Similar to  FIG.  2   , referring to  FIG.  8   , one second conductive line CL 2  includes a plurality of second parts  32  not overlapping with the first conductive lines CL 1 . In addition, one second conductive line CL 2  includes a first part  31  and a third part  33 , which overlap with the first conductive lines CL 1 . One second conductive line CL 2  can include a plurality of first parts  31 , a plurality of second parts  32 , and a plurality of third parts  33 . The first parts  31  correspond to the first bending sensor units BS 1 , and the third parts  33  correspond to the second bending sensor units BS 2 . The first part  31  and the second part  32  can have the same width or different widths along the first direction D 1 . In  FIG.  8   , the first parts  31  and the second parts  32  have the same width. The third parts  33  can have a third width W 3  greater than the first width W 1  of the first part  31  along the first direction D 1 , and the third part  33  can have a greater area than the area of the first part  31 . 
     Similar to the design of the second conductive lines CL 2 , one first conductive line CL 1  can include a plurality of first parts  41  corresponding to the first bending sensor units BS 1 , a plurality of second parts  42  not overlapping with the second conductive lines CL 2 , and a plurality of third parts  43  corresponding to the second bending sensor units BS 2 , and detailed descriptions are not repeated. Specifically, the first parts  31  of the second conductive lines CL 2  and the first parts  41  of the first conductive lines CL 1  overlap in the vertical direction Z to form a plurality of first bending sensor units BS 1 . The third parts  33  of the second conductive lines CL 2  and the third parts  43  of the first conductive lines CL 1  overlap in the vertical direction Z to form a plurality of second bending sensor units BS 2 . 
     Referring to  FIG.  8    and  FIG.  9   , one of the third parts  33  of the second conductive line CL 2  can include a plurality of second openings OP 2 , and one of the third parts  43  of the first conductive line CL 1  can include a plurality of first openings OP 1 . In the top view, the first openings OP 1  and the second openings OP 2  overlap to form a plurality of overlapping openings. Some of the pluralities of light emitting units LE are disposed in the positions corresponding to the plurality of overlapping openings OP 1  (OP 2 ). In this way, the second bending sensor units BS 2  will not shield the light emitted from the corresponding light emitting units LE. 
     Accordingly, the area of the second bending sensor unit BS 2  is greater than the area of the first bending sensor unit BS 1 . By means of the greater area of the second bending sensor units BS 2 , the sensitivity can be improved. In addition, one first bending sensor unit BS 1  can have an area less than the area of one light emitting unit LE, while one second bending sensor unit BS 2  can have an area greater than the area of one light emitting unit LE. 
     In addition, this embodiment is different from the previous embodiments that the light emitting units LE 1 , the light emitting units LE 2 , and the light emitting units LE 3  shown in  FIG.  8    have the same shapes, which are round shapes for example, but not limited thereto. 
     Referring to  FIG.  10    and  FIG.  11   ,  FIG.  10    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a third embodiment of the present disclosure, and  FIG.  11    is a schematic diagram illustrating a cross-sectional view along line A-B of the display device shown in  FIG.  10   . As shown in  FIG.  10    and  FIG.  11   , this embodiment is different from the first embodiment in that the bending sensor layer  108  shown in  FIG.  11    only has one conductive layer. The conductive layer  108  includes a plurality of conductive lines CL extending along the second direction D 2  and parallel to the bending axis, but not limited thereto. Each of the conductive lines CL itself is defined as one bending sensor unit BS. The bending sensor units BS are resistive-type sensors, which can determine the bending state of the display device  100  by detecting the resistance variations of each conductive line CL. Specifically, when the display device  100  is folded or bended, each of the resistive-type bending sensor units BS in different positions of the display region Rb may be deformed in various degrees. Accordingly, the resistance of each bending sensor unit BS may be different, and therefore the degree of folding or curvature of the display device  100  maybe obtained by calculating the difference of the resistance variations. By collecting input signals and output signals through the bending sensor units BS, the folding degree of the display device  100  may be obtained, but not limited thereto. The bending sensor units BS may further include a plurality of openings OP for reducing stress. In some embodiments, the openings OP can have areas less than the areas of the light emitting units LE. In some embodiments, the openings OP can have areas less than the areas of the bending sensor units BS. In some embodiments, the openings OP can have areas greater than or equal to 5 μm 2  and less than or equal to 500 μm 2 . It is noted that the bending sensor units BS may be disposed only in the first portions R 1  of the display region Rb. However, in some other embodiments, the bending sensor units BS may be disposed in the whole display region Rb. The method for calculating the density of the bending sensors units BS and the density of the light emitting units LE is the same as the above-mentioned method, and will not be repeated. According to some embodiments, a ratio of the density of the plurality of bending sensor units BS (D B ) to the density of the plurality of light emitting units LE (D L ) maybe greater than or equal to 0.00001 and less than 0.1 (i.e., 0.00001≤D B /D L &lt;0.1). Moreover, the plurality of conductive lines CL which form the bending sensor units BS in this embodiment may have uniform width in the first direction D 1 , which is perpendicular to their extending direction (the second direction D 2 ), but not limited thereto. 
     As shown in  FIG.  11   , this embodiment is further different from the first embodiment in that the second electrodes  1062   c  of different display units  1062  may be connected to each other and cover both the active area and the non-active area of the display layer  106 . However, the bending sensor units BS still do not overlap two adjacent light emitting units LE (the light emitting areas of the display units  1062 ) in the top view of the display device  100 . Besides, the substrate structure  102  shown in  FIG.  11    may further include a supporting film glue  1023  disposed between the flexible substrate  1021  and the supporting film  1022 , but not limited thereto. Moreover, a polarizer layer  116  may be disposed between the protection layer  118  and the bending sensor units BS. The protection layer  118  of the display device  100  in this embodiment may include an optical clear adhesive (OCA) layer  1181  and a cover layer  1182 , wherein the OCA layer  1181  is disposed between the polarizer layer  116  and the cover layer  1182 , but not limited thereto. 
     Referring to  FIG.  12   ,  FIG.  12    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a fourth embodiment of the present disclosure. The display device  100  of this embodiment is a touch display device and further includes a plurality of touch units  122  disposed on the flexible substrate  1021 . The touch units  122  can provide the functionality of detecting touch of the user for providing touch control signal. The touch units  122  of this embodiment may be formed with one conductive layer or may be formed with two conductive layers. In addition, the touch units  122  may be capacitive-type touch-sensing units or resistance-type touch-sensing units, but not limited thereto. In some embodiments, the touch units  122  may be formed with two conductive layers and an insulating layer. For example, two conductive layers may include touch electrodes and connecting bridges to form the touch units  122 . The touch units  122  may be arranged in an array in the display region of the display device  100 . According to this embodiment, the density of the plurality of bending sensor units BS (D B ) is less than the density of the plurality of touch units  122  (D T ). The density of the bending sensor units BS can be calculated as the previous description, and will not be repeated. Similarly, the density of the touch units  122  can be calculated based on the entire area of the display region, based on an arbitrary region in the display region, or based on an arbitrary region in the bendable region. For example, the density of the touch units  122  can be calculated by dividing the number of the touch units  122  by an area of a given region in the bendable region. With regard to the capacitive-type touch units, a ratio of the density of the bending sensor units BS to the density of the touch units  122  may be greater than or equal to 0.1 and less than 1 (i.e., 0.1≤D B /D T &lt;1). The value of the ratio D B /D T  less than 1 may bring the advantage to reduce the interference between the touch signals and the bending sensor signals. 
       FIG.  13    is a cross-sectional schematic diagram of a cross-sectional view of a display device according to another embodiment. As shown in  FIG.  13   , the bending sensors BS of this embodiment are capacitive-type sensors and are formed with the first conductive lines CL 1  and the second conductive lines CL 2 . The touch units  122  are disposed on the bending sensor units BS and do not overlap or cover the bending sensor units BS in the direction Z perpendicular to the front surface  102 A of the substrate structure  102 . In addition, a time-sharing driver may be provided to control the bending sensor units BS and the touch units  122  such that the detecting time of the bending sensor units BS would not overlap the detecting time of the touch units  122 , so as to further reduce signal coupling or signal interference, but not limited thereto. The touch units  122  can be in a metal mesh type. Furthermore, in the cross-sectional view, the width of the bending sensor units BS can be greater than the width of the plurality of touch units  122  according to the present disclosure along the same direction. For example, the width of one of the plurality of bending sensor units BS along a direction  13 D is defined as a width W 4 , and a width of one of the plurality of touch units  122  along the direction  13 D is defined as width W 5 , wherein the width W 4  is greater than the width W 5 . The conductive layer for forming the touch units  122  may include transparent conductive material or may be a metal mesh layer, but not limited thereto. When the touch units  122  are formed with metal mesh layer, the touch units  122  may not overlap the light emitting units LE along the direction perpendicular to the front surface  102 A of the substrate structure  102 . When the touch units  122  are formed with transparent conductive layer, the touch units  122  may overlap the light emitting units LE. In some embodiments, the width W 5  can be the width of one metal mesh. In addition, an anti-reflection layer  124  may cover the touch units  122  to mitigate the reflection issue caused by the touch units  122  or to improve the appearance of the display device  100 . In some embodiments, a minimum width of one bending sensor (such as capacitive-type) can be greater than a minimum width of one touch unit. 
     Referring to  FIG.  14   ,  FIG.  14    is a partial-enlargement schematic diagram illustrating a cross-sectional view of a display device according to a fifth embodiment of the present disclosure. This embodiment is different from the embodiment shown in  FIG.  13    in that the positions of the touch units  122  and the bending sensor units BS are exchanged in the direction perpendicular to the front surface  102 A of the substrate structure  102  in the structure of the display device  100  shown in  FIG.  14   . In other words, the touch units  122  are disposed between the display layer  106  and the bending sensor layer  108 . In this embodiment, the anti-reflection layer  124  can be in contact with the second conductive lines CL 2  and covers the second conductive lines CL 2 , and an insulating layer  126  may be disposed between the touch units  122  and the bending sensor units BS. 
     Referring to  FIG.  15   ,  FIG.  15    is a partial-enlargement schematic diagram illustrating a cross-sectional view of a display device according to a sixth embodiment of the present disclosure. This embodiment is different from the fourth embodiment in that the touch units  122  can be of the same layer as the second conductive lines CL 2 . That is, the second conductive layer  1082  includes the touch units  122  and the second conductive lines CL 2 . In other words, the touch units  122  and the second conductive lines CL 2  are formed with the same conductive layer. Specifically, a portion of the second conductive layer  1082  forms the second conductive lines CL 2  intersecting the first conductive lines CL 1  to form the bending sensor units BS, and another portion of the second conductive layer  1082  may form the touch units  122  that do not overlap the first conductive lines CL 1 . A time-sharing driver may be used for controlling the timing to transfer or receive touch signals and bending sensor signals alternately in this embodiment. 
     Referring to  FIG.  16   ,  FIG.  16    is a partial-enlargement schematic diagram of a top view of the display region of a display device according to a seventh embodiment of the present disclosure. This embodiment is different from the fourth embodiment shown in  FIG.  12    in that the bending sensor units BS shown in  FIG.  16    is a resistance-type sensor and each bending sensor unit BS is composed of only one conductive line CL, but not limited thereto. Each of the conductive lines CL itself is defined as one bending sensor unit BS. In addition, the density of the plurality of bending sensor units BS (D B ) is less than the density of the plurality of touch units  122  (D T ). The density D B  and density D T  can be calculated based on the previous-mentioned method, and will not be repeated. A ratio of the density of the plurality of bending sensor units BS to the density of the plurality of touch units  122  may be greater than or equal to 0.01 and less than 0.5 (i.e., 0.01≤D B /D T &lt;0.5), but not limited thereto. In some embodiments, a minimum width of one bending sensor (such as resistance-type) can be greater than a minimum width of one touch unit. For example, in  FIG.  16   , a minimum width W 6  of one resistance-type bending sensor BS can be greater than a minimum width W 7  of one touch unit  122 . 
       FIG.  17    is a schematic diagram of a cross-sectional view of a display device according to another embodiment of the present disclosure. As shown in  FIG.  17   , the bending sensors BS of this embodiment are resistance-type sensors and are formed with the conductive lines CL. The touch units  122  are disposed on the bending sensor units BS and do not overlap or cover the bending sensor units BS in the direction Z perpendicular to the front surface  102 A of the substrate structure  102 . The conductive layer for forming the touch units  122  may include transparent conductive material or may be a metal mesh layer, but not limited thereto. The touch units  122  can be in a metal mesh type. Furthermore, the width W 4  of the bending sensor unit BS is greater than the width W 5  of the touch units  122  along the same direction D 17 . 
     According to the present disclosure, bending sensor units are disposed on the display layer to detect the bending state of the display device. In some embodiments, the bending sensor units may not overlap the light emitting units or be spaced apart from the light emitting units in order to not affect the display performance. Moreover, in some embodiments, specific value of ratio of the density of the bending sensor units to the density of the light emitting units are introduced, so as to provide a better performance of the display device. 
     Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the disclosure. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.