Flexible substrate with improved performance under bending stress

According to one embodiment, a flexible substrate includes an insulating base including first and second strip portions, and island-shaped portions, electrical elements, scanning lines each extending while overlapping the first strip portions, signal lines each extending while overlapping the second strip portions, connection wiring lines each extending while overlapping the second strip portions, a scanning line driver, a signal line driver, a support body including a first side edge, and scanning lines are connected to different connection wiring lines on different island-shaped portion, and the scanning line driver and the signal line driver are located on a side of the first side edge.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-063650, filed Apr. 2, 2021, the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a flexible substrate.

BACKGROUND

In recent years, the use of flexible substrates having flexibility and elasticity has been studied in various fields. As an example of such use, a flexible substrate on which electrical elements arranged in a matrix shape can be attached to a curved surface such as a housing of an electronic device or a human body. As the electrical elements, for example, various sensors such as touch sensors and temperature sensors, and display elements can be applied.

In the flexible substrates, it is necessary to take measures to prevent the wiring portions from being damaged by stress caused by bending and stretching. As such measures, for example, it has been proposed that honeycomb-shaped openings be provided in the substrate which supports the wiring portion, and that the wiring portion are formed into a meandering shape.

DETAILED DESCRIPTION

In general, according to one embodiment, a flexible substrate comprises an insulating base including a plurality of first strip portions extending along a first direction and aligned along a second direction intersecting the first direction, and a plurality of second strip portions extending along the second direction and aligned along the first direction and a plurality of island-shaped portions located at respective intersections of the first strip portions and the second strip portions, a plurality of electrical elements overlapping the island-shaped portions, respectively, a plurality of scanning lines each extending while overlapping the respective first strip portion, a plurality of signal lines each extending while overlapping the respective second strip portion, a plurality of connection wiring lines each extending while overlapping the respective second strip portion and the respective signal line, a scanning line driver to which the connection wiring lines are connected, a signal line driver to which the signal lines are connected, a support body supporting the insulating base, the scanning line driver and the signal line driver and including a first side edge, and multiple scanning lines are connected to different connection wiring lines on different island-shaped portion, respectively, and the scanning line driver and the signal line driver are located on a side of the first side edge.

FIG.1is a perspective view schematically showing a configuration of a flexible substrate100of the present embodiment.

In this embodiment, a first direction D1, a second direction D2and a third direction D3are defined as shown in the figure. The first direction D1and the second direction D2are parallel to the main surface of the flexible substrate100and intersect each other. The third direction D3is perpendicular to the first direction D1and the second direction D2, and corresponds to the thickness direction of the flexible substrate100. In this embodiment, the first direction D1and the second direction D2intersect at right angles, but they may intersect at an angle other than right angles. In this document, the direction toward the tip of the arrow indicating the third direction D3is referred to as “up” and the direction from the tip of the arrow to the opposite direction is referred to as “down”. Further, when it is assumed that there is an observation position to observe the flexible substrate100on a side of the tip of the arrow indicating the third direction D3, viewing from this observation position toward a D1-D2plane defined by the first direction D1and the second direction D2is referred to as a planar view.

As shown inFIG.1, the flexible substrate100comprises a plurality of scanning lines1, a plurality of signal lines2, a plurality of connection wiring lines WR, a plurality of electrical elements3, a resin layer (support)81, a scanning line driver DR1, a signal line driver DR2.

The scanning lines1, the signal lines2, the connection wiring lines WR, the electrical elements3, the scanning line driver DR1and the signal line driver DR2are provided on the resin layer81. In other words, the resin layer81supports an insulating substrate4, which will be described later, the scanning line driver DR1and the signal line driver DR2. In the example illustrated, the resin layer81is formed into a rectangular shape in plan view. The resin layer81includes a first side edge EG1and a second side edge EG2, extending along the first direction D1, and a third side edge EG3and a fourth side edge EG4, extending along the second direction D2.

The scanning line driver DR1and the signal line driver DR2are located on a first side edge EG1side. The signal line driver DR2is located between the scanning line driver DR1and the first side edge EG1.

The scanning lines1each extend along the first direction D1and are aligned along the second direction D2. The scanning lines1are connected to respective connection wiring lines WR at positions which overlap respective electrical elements3. The scanning lines are connected to the connection wiring lines WR via contact holes CH12, respectively.

The connection wiring lines WR each extend along the second direction D2and are aligned along the first direction D1. The connection wiring lines WR are each connected to the scanning line driver DR1. For example, the number of connection wiring lines WR is equal to the number of scanning lines1.

The signal lines2each extend along the second direction D2and are aligned along the first direction D1. The signal lines2are each connected to the signal line driver DR2. A plurality of signal lines2pass through the area where the scanning line driver DR1is located.

The electrical elements3are arranged in a matrix along the first direction D1and the second direction D2. The electrical elements3are located at intersections of the scanning lines1and the signal lines2, respectively, and are electrically connected to the scanning lines1and the signal lines2.

For example, let us focus on the mth (m is a positive integer) scanning line1from a second side edge EG2side, and the nth (n is a positive integer) connection wiring line WR from a third side edge EG3side. The mth scanning line1is connected to the nth connecting wiring lines WR, and m and n are equal to each other. Further, the scanning line1is connected to the connection wiring line at the position which overlaps with the electric element3located at the mth row and nth column. The connection position between the scanning line1and the connection wiring line WR is not limited to that of this example.

A scanning signal is supplied to the electrical element3via the connection wiring line WR and the respective scanning line1. When the electric element3is, for example, of a type such as a sensor, which outputs signals, the signal line2receives the output signal from the electric element3. Note that the scanning lines1, the signal lines2and the connection wiring lines WR are an example of the wiring lines of the flexible substrate100. In addition to the scanning lines1, the signal lines2and the connection wiring lines WR, the flexible substrate100may comprise other types of wiring lines including a power supply line that supplies power to the electric elements3.

The scanning line driver DR1functions as a supply source that supplies scanning signals to each of the scanning lines1via the respective connection wiring line WR. The signal line driver DR2functions as a supply source that supplies drive signals to each of the signal lines2, or as a signal processing unit that processes the output signals output to each of the signal lines2.

According to this embodiment, the scanning line driver DR1and the signal line driver DR2are located on the same first side edge EG1side. Although they may interfere with the expansion and contraction of the flexible substrate10, the scanning line driver DR1and the signal line driver DR2are located on the same first side edge EG1. With this configuration, it is possible to prevent them from interfering with the expansion and contraction of vicinities of the second side edge EG2, the third side edge EG3and the fourth side edge EG4. That is, the elasticity of the flexible substrate100can be improved as compared to the case where the scanning line driver DR1and the signal line driver DR2are placed on different side edges.

FIG.2shows a partially enlarged plan view of the flexible substrate100shown inFIG.1.

As shown inFIG.2, the flexible substrate100comprises, in addition to those mentioned above, an insulating base4that supports the scanning lines1, the signal lines2and the connection wiring lines WR. The insulating base4has elasticity and flexibility. The insulating base4is formed of, for example, polyimide, but the material is not limited to this.

The insulating base4comprises a plurality of island-shaped portions40and strip portions41and42formed to be integrated with each island-shaped portion40. The insulating base4is formed into a mesh fashion. The island-shaped portions40are arranged in a matrix along the first direction D1and the second direction D2so as to be spaced from each other. Each of the island-shaped portions40is formed into, for example, a rectangular shape in plan view. Note that the island-shaped portions40may be formed in other polygonal shapes or circular or elliptical shapes. The electrical elements3are superimposed respectively on the island-shaped portions40.

The strip portions41each extend substantially along the first direction D1and are aligned along the second direction D2. The strip portions41connect those island-shaped portions40which are aligned along the first direction D1, to each other. The strip portions42extends substantially along the second direction D2and are aligned along the first direction D1. The strip portions42connect those island-shaped portions40which are aligned along the second direction D2, to each other. The strip portions41and42are each formed in a wavy shape in plan view. In other words, the strip portions41and42are formed in a meandering shape in plan view. The island-shaped portions40are located at the intersections of the respective first strip portions41and the respective second strip portions42.

The scanning lines1extend while overlapping the strip portions41, respectively. The signal lines2extend while overlapping the strip portions42, respectively. That is, the scanning lines1and the signal lines2are all formed into a meandering shape. The connection wiring lines WR extend while overlapping the second strip portions42and the signal lines2, respectively. In other words, the scanning lines1, the signal lines2and the connection wiring lines WR are all formed in a meandering pattern. A plurality of scanning lines1are connected to respective connection wiring lines WR on respective island-shaped portions40.

FIG.3is an enlarged plan view of the island-shaped portion40shown inFIG.2.FIG.3shows the island-shaped portion40at a position where a scanning line1and a connection wiring line WR are not connected to each other. InFIG.3, the electrical element3is omitted from the illustration.

The connection wiring line WR is located in the area indicated by dots in the figure. The connection wiring line WR has a first width W1at the position overlapping the second strip portion42, and a second width W2at the position overlapping the island-shaped portion40. The first width W1is greater than the second width W2.

The scanning line1includes a first portion11, a second portion12, and a third portion13. The first portion11and the third portion13overlap the first strip portion4. The first portion11and the third portion13are formed in the same layer as that of the signal line2. The third portion13intersects the connection wiring line WR. The second portion12is located between the first portion11and the third portion13in plan view, and overlaps the island-shaped portion40. The second portion12is formed in a different layer from that of the signal line2. The second portion12is located between the connection wiring line WR and the signal line2in plan view in the position overlapping the island-shaped portion40, and partially intersects the signal line2. The first portion11and the second portion12are connected to each other via a contact hole (first contact hole) CH10, and the second portion12and the third portion are connected to each other via a contact hole (second contact hole) CH11.

The flexible substrate100comprises switching elements SW. The switching elements SW each include a semiconductor layer SC, gate electrodes GE1and GE2, a source electrode SE, and a drain electrode DE. The semiconductor layer SC extends in the second direction D2. One end portion SCA of the semiconductor layer SC overlaps the signal line2, and the other end portion SCB of the semiconductor layer SC overlaps the drain electrode DE. The region of the signal line2, which overlaps the semiconductor layer SC, functions as the source electrode SE. The semiconductor layer SC intersects with the second portion11of the scanning line1at two locations in the position where it overlaps the drain electrode DE. The regions of the scanning line1, which overlap the semiconductor layer SC, function as the gate electrodes GE1and GE2, respectively. That is, the switching elements SW in the example shown in the figure have a double-gate structure. The semiconductor layer SC is connected to the signal line2in the one end portion SCA via a contact hole CH20, and is electrically connected to the drain electrode DE via a contact hole CH21in the other end portion SCB. The drain electrode DE is connected to the lower electrode EL1, which will be described later, via a contact hole CH22.

FIG.4is an enlarged plan view of an island-shaped portion40shown inFIG.2.FIG.4shows the island-shaped portion40at the position where the scanning line1and the connection wiring line WR are connected to each other. Further, inFIG.4, the electrical element3is omitted from illustration. The configuration shown inFIG.4, other than the connection between the scanning line1and the connection wiring line WR, is the same as the configuration shown inFIG.3.

The connection wiring line WR is connected to the third portion40extending to the island-shaped portion40via a contact hole (third contact hole) CH12. The contact hole CH12, the contact hole CH11and the contact hole CH10are aligned along the first direction D1in this order.

FIG.5is a plan view of an electrical element3, which is omitted from the illustrations inFIGS.3and4.

The electrical element3includes a lower electrode EL1, an upper electrode EL2located above the lower electrode EL1, and an active layer30, which will be described later. The lower electrode EL1and the upper electrode EL2are formed identical in shape. In the example illustrated, the lower electrode EL1and the upper electrode EL2are formed into a rectangular shape on the island-shaped portion40.

FIG.6is a cross-sectional view of the flexible substrate100taken along line A-B shown inFIG.4.

As shown inFIG.6, the flexible substrate100further comprises insulating layers51to56, a sealing layer57, light-shielding layers LS and a resin layer82.

The insulating base4is located on the resin layer81. The insulating layer51is located on the insulating base4. The light-shielding layers LS are located on the insulating layer51. The light-shielding layers LS overlaps the gate electrodes GE1and GE2, respectively. With this configuration, the light-shielding layers LS can shield the light from a lower side toward the gate electrodes GE1and GE2. The light-shielding layer LS is made of, for example, a metal material such as aluminum (Al), titanium (Ti), silver (Ag), molybdenum (Mo), tungsten (W), copper (Cu) or chromium (Cr).

The insulating layer52is located on the insulating layer51to cover the light-shielding layer LS. The semiconductor layer SC is located on the insulating layer52. The semiconductor layer SC is formed, for example, of a polycrystalline silicon (for example, a low-temperature polysilicon), but may as well be formed of an amorphous silicon or oxide semiconductor. The insulating layer53is located on the insulating layer52to cover the semiconductor layer SC. The contact wiring lines WR, and the gate electrodes GE1and GE2are located on the insulating layer53. The insulating layer54is located on the insulating layer53to cover the contact wiring lines WR, and the gate electrodes GE1and GE2.

The signal lines2and the drain electrode DE are located on the insulating layer54. The signal lines2are connected to the semiconductor layer SC via the contact hole CH20formed in the insulating layers53and54. The signal lines2can be formed, for example, of a metal material or a transparent conductive material, and may be of a single-layer or stacked-layered structure. The drain electrode DE is connected to the semiconductor layer SC via the contact hole CH21formed in the insulating layers53and54. The drain electrode DE is formed, for example, of the same material as that of the signal lines2. The drain electrode DE covers the gate electrodes GE1and GE2. With this configuration, the drain electrode DE can shield the light from an upper side towards the gate electrodes GE1and GE2. The insulating layer55is located on the insulating layer54to cover the signal lines2and the drain electrode DE. The insulating layer56is located on the insulating layer55. The insulating layers51to56are stacked in this order.

The switching element SW is located between the island-shaped portion40of the insulating base4and the lower electrode EL1. The switching element SW illustrated here is of a double-gate structure, but it may as well be of a single-gate structure. Further, the switching element SW is of a top gate structure in which the gate electrodes GE1and GE2are disposed above the semiconductor layer SC, but may as well be of a single gate structure in which the gate electrodes GE1and GE2are disposed below the semiconductor layer SC.

The insulating layers51to55are all inorganic insulating layers formed of an inorganic insulating material such as silicon oxide (SiO), silicon nitride (SiN), silicon oxynitride (SiON) or the like. The insulating layer56is an organic insulating layer formed of an organic insulating material such as acrylic resin. The upper surface of the insulating layer56is substantially planarized.

The electrical element3is located on the insulating layer56. The electrical element3is, for example, an organic photodetector (organic photo diode (OPD)). As described above, the electric element3comprises a lower electrode EL1, an active layer30and an upper electrode EL2.

The lower electrode EL1is located on the insulating layer56. The lower electrode EL1comprises a first layer L1and a second layer L2stacked one on another. The first layer L1is connected to the drain electrode DE via the contact hole CH22formed in the insulating layers55and56. That is, the first layer L1is in contact with the switching element SW. The first layer L1and the second layer L2are transparent electrodes formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The first layer L1includes an outer periphery PL1. The second layer L2includes an outer periphery PL2. The outer periphery PL2is located on an inner side of the outer periphery PL1.

The active layer30is located on the lower electrode EL1. The active layer30is made from an electron donor (p-type semiconductor) and an electron acceptor (n-type semiconductor), formed of an organic material.

The upper electrode EL2is located on the active layer30. In other words, the active layer30is located between the lower electrode EL1and the upper electrode EL2. The upper electrode EL2is a transparent electrode formed of a transparent conductive material such as ITO or IZO. The upper electrode EL2is connected to a power supply line (not shown), and a common potential, for example, is supplied thereto. Note that, although not shown in the figure, an electron transport layer is formed between the lower electrode EL1and the active layer30, and a hole transport layer is formed between the upper electrode EL2and the active layer30.

The active layer30, when it receives light, generates hole and electron pairs. The hole and electron pairs generated by the active layer30generate an electric current, and the electric signal corresponding to the intensity of the current is read out via the respective signal line2.

The sealing layer57covers the upper electrode EL2. The sealing layer57inhibits moisture from entering the active layer30from outside. The resin layer82covers the sealing layer57.

FIG.7is a cross-sectional view of the flexible substrate100taken along line C-D shown inFIG.4.

The connection wiring line WR and the second portion12of the scanning line1are located on the insulating layer53and covered by the insulating layer54. In other words, the connection wiring line WR and the second portion12are located between the insulating layer53(the first insulating layer) and the insulating layer54(the second insulating layer).

The first portion11and the third portion13of the scanning line1and the drain electrode DE are located on the insulating layer54and covered by the insulating layer55. The first portion11is connected to the second portion12via the contact hole CH10formed in the insulating layer54. The third portion13is connected to the second portion12via the contact hole CH11formed in the insulating layer54. Further, the third portion13is connected to the connection wiring line WR via the contact hole CH12formed in the insulating layer54. The contact hole CH10, the contact hole CH11and the contact hole CH12penetrate the insulating layer54.

The first portion11and the third portion13can be formed, for example, of a metal material or a transparent conductive material, and may be of a single-layer or a stacked-layer structure. The second portion12and the connecting wiring line WR are made of any of the metal materials mentioned above or an alloy of any combination of these metal materials, and may be of a single-layer or stacked-layer structure.

FIG.8is a plan view of a modified example of this embodiment. The configuration shown inFIG.8is different from that ofFIG.1in that the positions of the scanning line driver DR1and the signal line driver DR2are switched.

The scanning line driver DR1is located between the signal line driver DR2and the first side edge E G1. A plurality of connection wiring lines WR pass through the area where the signal line driver DR2is located.

In such a modified example as well, advantageous effect similar to those described above can be obtained.

As described above, according the embodiment, it is possible to obtain a flexible substrate with improved elasticity.

Note that this embodiment is described in connection with the case where the electric element3is an OPD, but the electric element3may be a sensor other than OPD. Further, the upper electrode EL2may not be of a rectangular shape, or may be placed on the entire surface of the flexible substrate100. In that case, as the material of the upper electrode EL2, not ITO or IZO, but an electrode material having elasticity can be used. Or, the upper electrode EL2may be formed into a pattern similar to that of the insulating base4.