Patent Publication Number: US-2023139469-A1

Title: Electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-178748, filed Nov. 1, 2021, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to an electronic device. 
     BACKGROUND 
     In recent years, the use of flexible substrates having flexibility and elasticity has been considered in various fields. For example, the following utilization form has been considered. A flexible substrate in which electric elements are arrayed in matrix is attached to a curved surface of the housing of an electronic device, a human body, etc. As the electric elements, for example, various types of sensors such as a touch sensor and a temperature sensor and display elements could be applied. 
     In the flexible substrate, measures should be taken to prevent damage to lines because of stress by flection or expansion and contraction. As the measures, for example, the following structures have been suggested. An opening having a honeycomb shape may be provided in a base which supports lines, or a shape (meander shape) in which lines meander may be adopted. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic plan view of an electronic device according to an embodiment. 
         FIG.  2    is a plan view in which part of the flexible substrate shown in  FIG.  1    is enlarged. 
         FIG.  3    is a schematic cross-sectional view of part of the flexible substrate along the A-B line shown in  FIG.  2   . 
         FIG.  4    is a schematic cross-sectional view of part of the flexible substrate along the C-D line shown in  FIG.  2   . 
         FIG.  5    is a schematic cross-sectional view of part of the flexible substrate along the I-J line shown in  FIG.  2   . 
         FIG.  6    is a diagram for explaining an example of the structure applied to a first portion. 
         FIG.  7    is a diagram for explaining how a compressive stress is applied when the compressive stress is applied to the structure shown in  FIG.  6   . 
         FIG.  8    is a diagram for explaining another example of the structure applied to the first portion. 
         FIG.  9    is a diagram for explaining yet another example of the structure applied to the first portion. 
         FIG.  10    is a diagram for explaining examples of conditions of samples. 
         FIG.  11    is a diagram showing the result of the compressive test of each sample. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, an electronic device comprises an insulating base having elasticity, a plurality of lines provided on the insulating base, and a plurality of electric elements connected to the lines. The insulating base comprises a plurality of island-shaped portions in which the electric elements are located, and a plurality of band-like portions in which the lines are provided and which connect the adjacent island-shaped portions. Each of the band-like portions includes a curved portion which meanders, and a straight line portion which connects the curved portion and the island-shaped portion. The curved portion includes a first curved portion, a second curved portion and a third curved portion. The first curved portion is connected to the straight line portion and is curved so as to move away from the straight line portion in both a first direction in which the straight line portion extends and a second direction orthogonal to the first direction. The second curved portion is connected to the first curved portion and is curved so as to move away from the straight line portion in both of the directions. The third curved portion is connected to the second curved portion and is curved so as to move away from the straight line portion in the first direction and so as to approach the straight line portion in the second direction. A width of the second curved portion is less than a width of the third curved portion. 
     According to another embodiment, an electronic device comprises an insulating base having elasticity, a plurality of lines provided on the insulating base, and a plurality of electric elements connected to the lines. The insulating base comprises a plurality of island-shaped portions in which the electric elements are located, and a plurality of band-like portions in which the lines are located and which connect the adjacent island-shaped portions. Each of the band-like portions includes a curved portion which meanders, and a straight line portion which connects the curved portion and the island-shaped portion. The curved portion includes a first curved portion, a second curved portion and a third curved portion. The first curved portion is connected to the straight line portion and is curved so as to move away from the straight line portion in both a first direction in which the straight line portion extends and a second direction orthogonal to the first direction. The second curved portion is connected to the first curved portion and is curved so as to move away from the straight line portion in both of the directions. The third curved portion is connected to the second curved portion and is curved so as to move away from the straight line portion in the first direction and so as to approach the straight line portion in the second direction. A radius of curvature of the second curved portion is greater than a radius of curvature of the third curved portion. 
     Embodiments will be described hereinafter with reference to the accompanying drawings. The disclosure is merely an example, and proper changes in keeping with the spirit of the invention, which are easily conceivable by a person of ordinary skill in the art, come within the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes, etc., of the respective parts are illustrated schematically in the drawings, rather than as an accurate representation of what is implemented. However, such schematic illustration is merely exemplary, and in no way restricts the interpretation of the invention. In addition, in the specification and drawings, structural elements which function in the same or a similar manner to those described in connection with preceding drawings are denoted by like reference numbers, detailed description thereof being omitted unless necessary. 
       FIG.  1    is a schematic plan view of an electronic device  1  according to an embodiment. In the present embodiment, a first direction D 1 , a second direction D 2  and a third direction D 3  are defined as shown in the figures. The first direction D 1  and the second direction D 2  are parallel to the main surface of the electronic device  1  and intersect each other. The third direction D 3  is perpendicular to the first direction D 1  and the second direction D 2  and is equivalent to the thickness direction of the electronic device  1 . The first direction D 1  and the second direction D 2  intersect at right angles in the present embodiment. However, they may intersect at an angle other than a right angle. In this specification, the direction of the arrow indicating the third direction D 3  is referred to as a direction to an upper side. The opposite direction of the arrow is referred to as a direction to a lower side. It is assumed that an observation position for observing the electronic device  1  is on the tip side of the arrow of the third direction D 3 . When the D 1 -D 2  plane defined by the first direction D 1  and the second direction D 2  is viewed at the observation position, the appearance is referred to as a plan view. 
     The electronic device  1  comprises a flexible substrate  2 , a circuit board  3  and a controller  4 . The circuit board  3  is, for example, a flexible printed circuit board, and is electrically connected to each terminal in the terminal area TA of the flexible substrate  2 . The controller  4  is mounted on the circuit board  3 . However, the controller  4  may be mounted on the flexible substrate  2 . 
     The flexible substrate  2  has flexibility and elasticity. The specific structural example to realize elasticity is explained later. 
     The flexible substrate  2  comprises a plurality of scanning lines  11 , a plurality of signal lines  12 , a plurality of electric elements  13 , a scanning line driver DR 1 , a signal line driver DR 2 , etc. The scanning lines  11  extend in the first direction D 1  and are arranged in the second direction D 2 . The scanning lines  11  are connected to the scanning line driver DR 1 . The signal lines  12  extend in the second direction D 2  and are arranged in the first direction D 1 . The signal lines  12  are connected to the signal line driver DR 2 . The electric elements  13  are located in the respective intersections of the scanning lines  11  and the signal lines  12 , and are electrically connected to the scanning lines  11  and the signal lines  12 . The details of the function of the electric elements  13  are described later. 
       FIG.  2    is a plan view in which part of the flexible substrate  2  shown in  FIG.  1    is enlarged. In addition to the above elements, the flexible substrate  2  comprises an insulating base  14  which supports the scanning lines  11  and the signal lines  12 . 
     The insulating base  14  is formed into a mesh shape. As seen in plan view, the insulating base  14  comprises a plurality of first portions (line portions) PT 1  extending in the first direction D 1  and arranged in the second direction D 2 , a plurality of second portions (line portions) PT 2  extending in the second direction D 2  and arranged in the first direction D 1 , and a plurality of island-shaped portions IL provided in the intersections of the first portions PT 1  and the second portions PT 2 . As seen in plan view, each of the first portions PT 1  and the second portions PT 2  is formed in a wavelike fashion. The island-shaped portions IL are connected to the first portions PT 1  and the second portions PT 2 . The insulating base  14  has flexibility and elasticity, and can be formed of, for example, polyimide. However, the insulating base  14  is not limited to this example. 
     The scanning lines  11  are provided on the first portions PT 1  of the insulating base  14  in a wavelike fashion. The signal lines  12  are provided on the second portions PT 2  of the insulating base  14  in a wavelike fashion. The scanning lines  11  and the signal lines  12  are examples of the lines provided in the flexible substrate  2  (provided in the electronic device  1 ). The scanning lines  11  and the signal lines  12  can be formed of, for example, a metal material or a transparent conductive material, and may have either a single-layer structure or a multilayer structure. In addition to the scanning lines  11  and the signal lines  12 , the flexible substrate  2  may comprise other types of lines such as power lines for supplying electricity to the electric elements  13 . 
     Each scanning line  11  comprises a first portion  11 A shown by a solid line and a second portion  11 B shown by a broken line. The second portion  11 B overlaps the electric element  13 . The first portion  11 A and the second portion  11 B are provided in different layers and are electrically connected to each other through contact holes CH 1  and CH 2 . 
     The scanning lines  11  supply a scanning signal to the electric elements  13 . For example, when each electric element  13  is an element which outputs a signal such as a sensor, an output signal from the electric element  13  is supplied to the signal line  12 . For example, when each electric element  13  is an element which operates based on the input signal such as a light emitting element or an actuator, a drive signal is supplied to the signal line  12 . 
     The electric elements  13  are provided on the island-shaped portions IL. Each electric element  13  is smaller than each island-shaped portion IL. In  FIG.  2   , each island-shaped portion IL protrudes from the edge of the electric element  13 . For example, each electric element  13  is a sensor, a semiconductor element or an actuator. To the sensor, for example, an optical sensor which receives visible light or near-infrared light, a temperature sensor, a pressure sensor or a touch sensor can be applied. To the semiconductor element, for example, a light emitting element, a photoreceiver, a diode or a transistor can be applied. When each electric element  13  is a light emitting element, a flexible display having flexibility and elasticity can be realized. To the light emitting element, for example, a light emitting diode or organic electroluminescent element having a size of approximately 100 μm such as a mini LED or a micro LED can be applied. When each electric element  13  is an actuator, for example, a piezoelectric element can be applied. It should be noted that each electric element  13  is not limited to the examples shown here. Elements having various other types of functions could be applied. The electric elements  13  may be, for example, capacitors or resistances. The positions or shapes of the electric elements  13  are not limited to the example shown in  FIG.  2   . 
     In the present embodiment, the first portions PT 1  and second portions PT 2  of the insulating base  14 , the scanning lines  11 , the signal lines  12 , the first organic insulating layer  15  and second organic insulating layer  16  described later are collectively called a line portion LP. The island-shaped portions IL of the insulating base  14 , the organic insulating layer  19  described later and the electric elements  13  are collectively called island-shaped portions IP. As seen in plan view, the line portion LP includes a plurality of wavy first line portions LP 1  extending in the first direction D 1  and arranged in the second direction D 2 , and a plurality of wavy second line portions LP 2  extending in the second direction D 2  and arranged in the first direction D 1 . Each island-shaped portion IP is located in the intersection of the first line portion LP 1  and the second line portion LP 2 . The first line portion LP 1  includes the first portion PT 1  of the insulating base  14  described above and the scanning line  11 . The second portion LP 2  includes the second portion PT 2  of the insulating base  14  and the signal line  12 . In the area surrounded by two adjacent first line portions LP 1  and two adjacent second line portions LP 2 , the insulating base  14  is not formed, and an opening OP is formed. In other words, the opening OP may be called the area surrounded by two adjacent first portions PT 1  and two adjacent second portions PT 2 . The openings OP are arranged in matrix in the first direction D 1  and the second direction D 2 . 
       FIG.  3    is a schematic cross-sectional view of part of the flexible substrate  2  along the A-B line shown in  FIG.  2   . 
     In addition to the above elements, the flexible substrate  2  comprises the first organic insulating layer  15 , the second organic insulating layer  16 , a first elastic member EM 1  and a second elastic member EM 2 . 
     The first elastic member EM 1  comprises an outer surface EM 1 A, and an inner surface EM 1 B on the opposite side of the outer surface EM 1 A. The first line portion LP 1  is located on the inner surface EM 1 B. The first line portion LP 1  comprises a first side surface SS 1 , a second side surface SS 2  on the opposite side of the first side surface SS 1 , and an upper surface US. 
     The first portion PT 1  of the insulating base  14  is located on the inner surface EM 1 B of the first elastic member EM 1 . The first organic insulating layer  15  covers the insulating base  14 . The scanning line  11  is located on the first organic insulating layer  15 . The second organic insulating layer  16  covers the first organic insulating layer  15  and the scanning line  11 . Both the first organic insulating layer  15  and the second organic insulating layer  16  are formed of an organic material. 
     The second elastic member EM 2  comprises an outer surface EM 2 A, and an inner surface EM 2 B on the opposite side of the outer surface EM 2 A. The second elastic member EM 2  covers the first side surface SS 1 , second side surface SS 2  and upper surface US of the first line portion LP 1 . In other words, the second elastic member EM 2  covers the scanning line  11 , the insulating base  14 , the first organic insulating layer  15  and the second organic insulating layer  16 . Of the first line portion LP 1 , the second elastic member EM 2  is in contact with the insulating base  14 , the first organic insulating layer  15  and the second organic insulating layer  16 . The inner surface EM 2 B of the second elastic member EM 2  is in contact with the inner surface EM 1 B of the first elastic member EM 1  in the opening OP. The first elastic member EM 1 , the insulating base  14 , the scanning line  11  and the second elastic member EM 2  overlap each other in the third direction D 3 . The insulating base  14  and the scanning line  11  are located between the first elastic member EM 1  and the second elastic member EM 2 . 
     Of the second elastic member EM 2 , the portion overlapping the first portions PT 1 , the second portions PT 2  and the island-shaped portions IL is defined as a first portion EM 21 . The portion located between the first portions PT 1  and the second portions PT 2 , in other words, the portion overlapping the openings OP, is defined as a second portion EM 22 . The second portion EM 22  is in contact with the first elastic member EM 1 . The first elastic member EM 1  and the second elastic member EM 2  can be formed of, for example, a transparent resinous material which can expand and contract. 
       FIG.  4    is a schematic cross-sectional view of part of the flexible substrate  2  along the C-D line shown in  FIG.  2   . 
     The second line portion LP 2  is located on the inner surface EM 1 B of the first elastic member EM 1 . 
     The second line portion LP 2  comprises a first side surface SS 1 , a second side surface SS 2  on the opposite side of the first side surface SS 1 , and an upper surface US. 
     The second portion PT 2  of the insulating base  14  is located on the inner surface EM 1 B of the first elastic member EM 1 . The first organic insulating layer  15  covers the insulating base  14 . The second organic insulating layer  16  covers the first organic insulating layer  15 . The signal line  12  is located on the second organic insulating layer  16 . The second elastic member EM 2  covers the first side surface SS 1 , second side surface SS 2  and upper surface US of the second line portion LP 2  and is in contact with the inner surface EM 1 B of the first elastic member EM 1  in the opening OP. In other words, the second elastic member EM 2  covers the insulating base  14 , the first organic insulating layer  15 , the second organic insulating layer  16  and the signal line  12  and is in contact with each of them. The first elastic member EM 1 , the insulating base  14 , the signal line  12  and the second elastic member EM 2  overlap each other in the third direction D 3 . The insulating base  14  and the signal line  12  are located between the first elastic member EM 1  and the second elastic member EM 2 . 
       FIG.  5    is a schematic cross-sectional view of part of the flexible substrate  2  along the I-J line shown in  FIG.  2   . 
     The electric element  13  is located on the island-shaped portion IL of the insulating base  14 . The inorganic insulating layer  19  (passivation layer) is provided between the electric element  13  and the island-shaped portion IL. The inorganic insulating layer  19  is formed into an island shape overlapping the electric element  13  (or the island-shaped portion IL) as seen in plan view. The first portion  11 A is provided on the first organic insulating layer  15  and is covered with the second organic insulating layer  16 . The second portion  11 B is provided on the inorganic insulating layer  19  and is electrically connected to the electric element  13 . In the example shown in  FIG.  5   , the both end portions of the second portion  11 B are covered with the first organic insulating layer  15 . 
     The contact holes CH 1  and CH 2  are provided in the first organic insulating layer  15 . The first portion  11 A is electrically connected to the second portion  11 B via connection members CM 1  and CM 2  provided in the contact holes CH 1  and CH 2 . The connection members CM 1  CM 2  may be part of the first portion  11 A or may be provided separately from the first portion  11 A. 
     Thus, the inorganic insulating layer  19  having an island shape is provided between the electric element  13  and the insulating base  14 . This inorganic insulating layer  19  functions as a protective film which prevents incursion of liquid, etc., into the electric element  13  and the second portion  11 B of the scanning line  11 . In this way, the reliability of the flexible substrate  2  is improved. In general, a crack is easily caused in inorganic films compared to organic films. However, since the inorganic insulating layer  19  is not provided under the first portion  11 A of the scanning line  11 , a break in the first portion  11 A is prevented. This explanation is also applied to the signal lines (not shown). Further, compared to a case where the inorganic insulating layer  19  is provided in the entire flexible substrate  2 , the elasticity or flexibility of the flexible substrate  2  is difficult to degrade. 
     In addition, in the scanning line  11 , the second portion  11 B overlapping the electric element  13  is provided in a layer different from the first portion  11 A. Thus, the degree of freedom of designing near the electric element  13  is improved. As the contact holes CH 1  and CH 2  are provided above the inorganic insulating layer  19 , a connection defect in the connection position of the first portion  11 A and the second portion  11 B is prevented. Moreover, the island-shaped portion IL of the insulating base  14  is provided under the electric element  13 . By this structure, the electric element  13  can be satisfactorily supported. 
     The island-shaped portion IL is located on the inner surface EM 1 B of the first elastic member EM 1 . The second elastic member EM 2  covers the electric element  13 . The first elastic member EM 1 , the island-shaped portion IL, the electric element  13  and the second elastic member EM 2  overlap each other in the third direction D 3 . 
     Now, this specification explains a method of controlling the line strain (compressive strain) when the first portion PT 1  is compressed. Here, the line strain was calculated by preparing the three samples (sample  1 , sample  2  and sample  3 ) explained below and conducting a compressive test for each sample. 
       FIG.  6    is a diagram for explaining the structure of sample  1 . The structure of sample  1  shown in  FIG.  6    is a structure called a basic structure. A band-like portion PT 10  connecting island-shaped portion IL 1  and island-shaped portion IL 2  meanders in an S-shape. The scanning line  11  is formed over island-shaped portion IL 1 , the band-like portion PT 10  and island-shaped portion IL 2 . The scanning line  11  formed in the band-like portion PT 10  meanders based on the shape of the band-like portion PT 10 . The band-like portion PT 10  comprises curved portions PT 11  to PT 13  forming the portion which meanders in an S-shape, and straight line portions PT 14  connecting the portion which meanders in an S-shape and island-shaped portions IL 1  and IL 2 . Curved portion PT 11  is connected to the straight line portion PT 14  and is curved so as to move away from the straight line portion PT 14  in both the extension direction of the straight line portion PT 14  and a direction orthogonal to the extension direction of the straight line portion TP 14 . Curved portion PT 12  is connected to curved portion PT 11  and is curved so as to move away from the straight line portion PT 14  in both the extension direction of the straight line portion PT 14  and a direction orthogonal to the extension direction of the straight line portion TP 14 . Curved portion PT 13  is connected to curved portion PT 12 , and is curved so as to move away from the straight line portion PT 14  in the extension direction of the straight line portion PT 14 , and is curved so as to approach the straight line portion PT 14  in a direction orthogonal to the extension direction of the straight line portion PT 14 . 
     The radii of curvature along the inner circumferences of curved portions PT 11  to PT 13  are defined as r 1  to r 3 , respectively. In the structure of sample  1  shown in  FIG.  6   , radii of curvature r 1  to r 3  show the same value. The line widths of curved portions PT 11  to PT 13  (more specifically, the distances between the middle points of the inner circumferences of curved portions PT 11  to PT 13  and the middle points of the outer circumferences) and the line width of the straight line portion PT 14  are defined as W 1  to W 4 , respectively. In the structure of sample  1  shown in  FIG.  6   , line widths W 1  to W 4  show the same value. The linear distance from an end of the scanning line  11  located in island-shaped portion IL 1  to the other end of the scanning line  11  located in island-shaped portion IL 2  (or the pitch of island-shaped portions IL 1  and IL 2 ) is defined as L 1 . The entire length of the scanning line  11  over island-shaped portion IL 1 , the band-like portion PT 10  and island-shaped portion IL 2  is defined as L 2 . The hinge length ratio L′ is defined by L 2 /L 1 . 
     The results of the compressive tests (line strain) are described later. Here, the following matter is confirmed. When a compressive stress is applied in a direction in which island-shaped portions IL 1  and IL 2  of sample  1  approach each other, the strongest compressive stress is applied to the portions shown by hatch lines in  FIG.  7   , in other words, to the outer circumferential portions of curved portions PT 12  which slightly shift from the boundary portions between curved portions PT 12  and curved portions PT 13  to the curved portion PT 12  sides. In other words, when the first portion PT 1  (band-like portion PT 10 ) is broken because of the application of a compressive stress, the possibility that the portions shown by the hatch lines in  FIG.  7    are broken is the highest. In the explanation below, the portions shown by the hatch lines in  FIG.  7    may be also called stress concentration portions. 
       FIG.  8    is a diagram for explaining the structure of sample  2 . Here, only portions different from the basic structure shown in  FIG.  6    are explained, and the explanation of the same portion is omitted. 
     The structure of sample  2  shown in  FIG.  8    is different from the basic structure shown in  FIG.  6    in respect that line width W of the band-like portion PT 10  gradually decreases (narrows) from the center O of the portion which meanders in an S-shape to curved portion PT 12 . In other words, line width W 2  of curved portion PT 12  is less than line width W 3  of curved portion PT 13 . In the structure of sample  2  shown in  FIG.  8   , line width W 1  of curved portion PT 11  and line width W 4  of the straight line portion PT 14  show the same value. Line width W 1  of curved portion PT 11  and line width W 4  of the straight line portion PT 14  are less than line width W 2  of curved portion PT 12  and show the same value as the line width of the boundary portion between curved portions PT 11  and PT 12 . In the structure of sample  2  shown in  FIG.  8   , radii of curvature r 1  to r 3  show the same value. 
       FIG.  9    is a diagram for explaining the structure of sample  3 . Here, only portions different from the basic structure shown in  FIG.  6    are explained, and the explanation of the same portion is omitted. 
     The structure of sample  3  shown in  FIG.  9    is different from the basic structure shown in  FIG.  6    in respect that radius of curvature r 2  of curved portion PT 12  is greater than radius of curvature r 3  of curved portion PT 13 . In the structure of sample  3  shown in  FIG.  9   , radius of curvature r 1  of curved portion PT 11  shows the same value as radius of curvature r 3  of curved portion PT 13 . In the structure of sample  3  shown in  FIG.  9   , line widths W 1  to W 4  show the same value. 
       FIG.  10    is a diagram for explaining the examples of conditions (specific values) of radius of curvature r 2  and line width W 2  of sample  1 , sample  2  and sample  3 . 
     Radius of curvature r 2  of curved portion PT 12  of sample  1  shown in  FIG.  6    is 15 μm, and line width W 2  of curved portion PT 12  is 30 μm. 
     Radius of curvature r 2  of curved portion PT 12  of sample  2  shown in  FIG.  8    is 15 μm, and line width W 2  of curved portion PT 12  is 10 μm. 
     Radius of curvature r 2  of curved portion PT 12  of sample  3  shown in  FIG.  9    is 45 μm, and line width W 2  of curved portion PT 12  is 30 μm. 
       FIG.  11    is a diagram showing the result of the compressive test of each sample. In the compressive tests, the line strain of the first portion PT 1  (the line strain of the band-like portion PT 10 ) was calculated when a compressive stress in which the compression rate was 10% was applied in a direction in which island-shaped portions IL 1  and IL 2  of each sample approach each other. The compression rate is one of the indices showing the magnitude of the compressive stress, and is calculated by, for example, dividing the difference (compression amount) between linear distance L 1  before the application of the compressive stress and linear distance L 1 ′ after the application of the compressive stress by linear distance L 1  and subsequently multiplying it by 100. Here, the compressive tests assume a case where the compression rate is 10% as described above. Thus, a compressive stress to the extent that linear distance L 1  is shortened to 0.9*L 1  (=L 1 ′) was applied in a direction in which island-shaped portion IL 1  and IL 2  of each sample approach each other. The line strain of the first portion PT 1  shows the degree of strain of the first portion PT 1  when a compressive stress is applied to the first portion PT 1  such that a state in which no compressive stress is applied to the first portion PT 1  is a state without line strain (line strain 0%). It is confirmed that, as the line strain is increased, the possibility that a break occurs when a compressive stress is applied is increased. 
     As shown in  FIG.  11   , as a result of the above compressive rests, the line strain of sample  1  was 20%. The line strain of sample  2  was 5%. The line strain of sample  3  was 10%. According to the compressive tests, the following matters were confirmed. In the basic structure of sample  1 , the line strain is the greatest, and the possibility of a break when a compressive stress is applied is high. In the structures of sample  2  and sample  3 , compared to the basic structure, the line strain is less, and a break is difficult to occur even if a compressive stress is applied. 
     More specifically, the following matters were confirmed. By making line width W 2  of curved portion PT 12  including a stress concentration portion less than line width W 3  of curved portion PT 13  like the structure of sample  2 , the line strain is decreased, and a structure in which a break is difficult to occur even if a compressive stress is applied can be realized. 
     Further, the following matters were confirmed. By making radius of curvature r 2  of curved portion PT 12  including a stress concentration portion greater than radius of curvature r 3  of curved portion PT 13  like the structure of sample  3 , the line strain is decreased, and a structure in which a break is difficult to occur even if a compressive stress is applied can be realized. 
     The above results show that the line strain of the first portion PT 1  can be controlled by radius of curvature r 2  and line width W 2  of curved portion PT 12  including a stress concentration portion. Here, a method of controlling the line strain of the first portion PT 1  is explained. However, the line strain of the second portion PT 2  can be also controlled by the same method. 
     As explained above, the present embodiment can provide an electronic device comprising lines which are difficult to break when a compressive stress is applied. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.