Angle adjustment device, support, and display device

An angle adjustment device capable of being kept at a desired angle is provided. The angle adjustment device can fix and keep the relative positions of the first base component and the second base component, and a support with a combination of the angle adjustment device and components such as a flat plate can keep the entire body in a shape opened on a plane, a folded shape, a shape kept at a desired angle, or the like. In addition, the angle adjustment device can make a bending movement in one direction, which prevents bending in a reverse direction. Therefore, it is possible to prevent an accidental bending movement of an apparatus including the angle adjustment device to prevent breakage or the like of the apparatus.

TECHNICAL FIELD

The present invention relates to an object, a method, or a manufacturing method. Alternatively, the present invention relates to a process, a machine, manufacture, or a composition of matter. In particular, one embodiment of the present invention relates to a semiconductor device, a light-emitting device, a display device, an electronic device, a lighting device, a driving method thereof, or a manufacturing method thereof. In particular, one embodiment of the present invention relates to an angle adjustment device, a flexible component support, and a display device including the flexible component support.

In this specification and the like, a semiconductor device refers to every device that can function by utilizing semiconductor characteristics. A transistor, a semiconductor circuit, an arithmetic device, a memory device, and the like are each one embodiment of the semiconductor device. Moreover, a light-emitting apparatus, a display device, a lighting device, and an electronic device each include a semiconductor device in some cases.

BACKGROUND ART

Electronic devices such as cellular phones, smartphones, tablet type computers, and laptop computers are fabricated with appropriate sizes depending on their functions, usability, design, portability, and the like. Meanwhile, it is inconvenient to carry a plurality of electronic devices with overlapping functions. Accordingly, a form in which functions of a plurality of electronic devices are integrated is desired. For example, Patent Document 1 discloses a tri-fold light-emitting panel. The use of the light-emitting panel enables integration of functions of a plurality of electronic devices and manufacture of an electronic device whose size is variable.

REFERENCE

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

In a display apparatus with a foldable display portion, at least part of a display panel formed over a flexible substrate is fixed to a support, and a folding movement or the like is made by bending the support. At this time, when the display panel is bent in a direction opposite to design intention of the support, for example, the display panel, a hinge portion included in the support, and the like might be broken; therefore, the display panel is preferably well designed so as not to be easily bent in the reverse direction.

The display apparatus is used with being variously transformed. For example, use in a state of being opened on a plane, in a folded state, in a state of being bent at a desired angle (intermediate state), and in other states is assumed. Therefore, the support is preferably capable of keeping the form regardless of the state.

Thus, an object of one embodiment of the present invention is to provide an angle adjustment device that adjusts a relative angle between components. Another object is to provide an angle adjustment device capable of fixing a relative angle between components to a desired angle. Another object is to provide a support for supporting a flexible component. Another object is to provide a support for making a bending movement without decreasing the reliability of a flexible component. Another object is to provide a novel support for a flexible component. Another object is to provide a novel light-emitting device.

Another object is to provide a folding display device with high portability. Another object is to provide a folding display device with high display visibility. Another object is to provide a folding display device having a power saving function. Another object is to provide a novel display device.

Note that the description of these objects does not preclude the existence of other objects. One embodiment of the present invention does not need to achieve all these objects. In addition, objects other than the above will be apparent from the description of the specification and the like, and objects other than the above can be derived from the description of the specification and the like.

Means for Solving the Problems

One embodiment of the present invention relates to an angle adjustment device capable of being kept at an desired angle, a support including the angle adjustment device, or a display device including the support.

One embodiment of the present invention is an angle adjustment device including a first base component, a second base component, a first joining component, a second joining component, a first columnar component, a second columnar component, a third columnar component, and a fourth columnar component. The first base component and the second base component each include a first region and a second region. The first joining component and the second joining component each include a first opening portion and a notch portion. The first opening portion and the notch portion are provided side by side in a longitudinal direction of each of the first joining component and the second joining component. The first columnar component or the third columnar component is inserted into the first opening portion. The second columnar component or the fourth columnar component is inserted into the notch portion. The first region of the first base component is joined to the second region of the second base component with the first columnar component, the first joining component, and the fourth columnar component. The first region of the second base component is joined to the second region of the first base component with the third columnar component, the second joining component, and the second columnar component.

The first base component and the second base component each include a first surface, a second surface, a third surface, a fourth surface, and a fifth surface. The first surface has the same shape as the second surface. The third surface has the same shape as the fourth surface. The first surface is parallel to the second surface. The first surface is positioned to face the second surface. The third surface is adjacent to the first surface. The fourth surface is adjacent to the second surface. An angle formed by the third surface and the first surface is greater than 180° and less than or equal to 270°. An angle formed by the fourth surface and the second surface is greater than 180° and less than or equal to 270°. An angle formed by the third surface and the fourth surface is greater than 180° and less than 360°. The fifth surface is adjacent to each of the first surface to the fourth surface. The first region and the second region can be provided on the fifth surface.

The first columnar component is inserted into the first opening portion of the first joining component. The second columnar component is inserted into the notch portion of the second joining component. The third columnar component is inserted into the first opening portion of the second joining component. The fourth columnar component is inserted into the notch portion of the first joining component. The major axes of the first columnar component to the fourth columnar component can be parallel to each other.

The first columnar component is fixed to the first region of the first base component. The second columnar component is fixed to the second region of the first base component. The third columnar component is fixed to the first region of the second base component. The fourth columnar component can be fixed to the second region of the second base component.

The first joining component and the second joining component each have elasticity. The shape of the notch portion can be elastically deformed.

The notch portion includes a third region, a fourth region, and a fifth region. The fourth region is positioned between the third region and the fifth region. The fifth region is positioned between the third region and the first opening portion. Top surface shapes of the third region to the fifth region can each include an arc.

The position of the second columnar component is switched from one of the third region and the fourth region of the second joining component to the other of the third region and the fourth region of the second joining component, and the position of the fourth columnar component is switched from one of the third region and the fourth region of the first joining component to the other of the third region and the fourth region of the first joining component, whereby a relative angle between the first base component and the second base component can be switched.

When the second columnar component is in the third region of the second joining component and the third columnar component is in the fourth region of the first joining component, the first surface of the first base component can be in contact with the second surface of the second base component.

When the second columnar component is in the third region of the second joining component and the fourth columnar component is in the third region of the first joining component, the third surface of the first base component can be in contact with the fourth surface of the second base component.

A third joining component, a fourth joining component, and a fifth columnar component are further included. The third joining component and the fourth joining component each include a second opening portion. The third joining component is fixed to the first base component. The fourth joining component is fixed to the second base component. The fifth columnar component is inserted into the second opening portion of the third joining component and the second opening portion of the fourth joining component. The major axis of the fifth columnar component is parallel to each of the major axes of the first columnar component to the fourth columnar component. The fifth columnar component can be positioned in the vicinity of a region where the first base component is in contact with the second base component.

A support for a flexible component can be formed when the angle adjustment device is provided in a hinge portion. A display device can be formed when the support is provided with a flexible display panel.

It is preferable that the display panel include a light-emitting device.

Effect of the Invention

According to one embodiment of the present invention, an angle adjustment device that adjusts a relative angle between components can be provided. An angle adjustment device capable of fixing a relative angle between components to a desired angle can be provided. Alternatively, a support for supporting a flexible component can be provided. Alternatively, a support for making a bending movement without decreasing the reliability of a flexible component can be provided. Alternatively, a novel support for a flexible component can be provided. Alternatively, a novel light-emitting device can be provided.

Alternatively, a folding display device with high portability can be provided. Alternatively, a folding display device with high display visibility can be provided. Alternatively, a folding display device having a power saving function can be provided. Alternatively, a folding display device that is easy to hold can be provided. Alternatively, a novel display device can be provided.

Note that the description of these effects does not preclude the existence of other effects. One embodiment of the present invention does not have to have all of these effects. Other effects will be apparent from and can be derived from the description of the specification, the drawings, the claims, and the like.

MODE FOR CARRYING OUT THE INVENTION

Embodiments will be described in detail with reference to the drawings. Note that the present invention is not limited to the following description, and it will be readily understood by those skilled in the art that modes and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of embodiments below. Note that in structures of the invention described below, the same portions or portions having similar functions are denoted by the same reference numerals in different drawings, and the description thereof is not repeated in some cases. Note that the hatching of the same component that constitutes a drawing is sometimes omitted or changed as appropriate in different drawings.

Even in the case where a single component is illustrated in a circuit diagram, the component may be composed of a plurality of parts as long as there is no functional inconvenience. For example, in some cases, a plurality of transistors that operate as a switch are connected in series or in parallel. In some cases, capacitors are divided and arranged in a plurality of positions.

In addition, one conductor has a plurality of functions such as a wiring, an electrode, and a terminal in some cases. In this specification, a plurality of names are sometimes used for one component. Even in the case where components are illustrated in a circuit diagram as if they were directly connected to each other, the components may actually be connected to each other through one conductor or a plurality of conductors. In this specification, even such a configuration is included in direct connection.

In this specification, a display panel is typically treated as a flexible component; however, the flexible component may be another component. Examples of the flexible component include a solar battery, a primary battery, a secondary battery, an antenna, a charging coil, a speaker, a microphone, a cable, illumination, a variety of terminals, a variety of wirings, a variety of sensors, a variety of circuits, a composite device including any of these, and the like.

In addition, in this specification, a display device generally means a device that has a display function. In other words, an electronic device including a display portion is included in a display device. For example, an electronic device including a display portion, such as a cellular phone, a smartphone, a smartwatch, a tablet type computer, or a television, is included in a display device.

In this embodiment, an angle adjustment device, a support, and a display device of embodiments of the present invention will be described with reference to drawings.

One embodiment of the present invention is an angle adjustment device that includes a first base component, a second base component, and a mechanism that switches a relative angle between them. Another embodiment of the present invention is a support that includes the angle adjustment device.

The angle adjustment device can fix and keep the relative positions of the first base component and the second base component. For example, a support with a combination of the angle adjustment device and components such as a flat plate can keep the entire body in a shape opened on a plane, a folded shape, a shape kept at a desired angle, or the like.

In addition, the angle adjustment device can make a bending movement in one direction, which prevents bending in a reverse direction. Therefore, it is possible to prevent an accidental bending movement of an apparatus including the angle adjustment device to prevent breakage or the like of the apparatus.

FIG.1Ais a diagram illustrating an angle adjustment device100of one embodiment of the present invention. The angle adjustment device100includes base components101aand101b, joining components102aand102b, and columnar components103a,103b,104a, and104b. The base component101ais joined to the base component101bwith another component. As the columnar components103a,103b,104a, and104b, cylindrical-shaped or polygonal-prism-shaped components can be used; in this embodiment, cylindrical-shaped components are used in an example described below.

FIG.2Ais a perspective view illustrating the shapes of the base components101aand101b. The base components101aand101bcan have the same shape and each include surfaces111,112,113,114, and115. The surface111and the surface112can have the same shape. The surface113and the surface114can have the same shape.

The surface111and the surface112are positioned to be parallel to and face each other. The surface113is positioned adjacent to the surface111. The surface114is positioned adjacent to the surface112. The surface113is inclined at an angle greater than 180° and less than or equal to 270° for the surface111. The surface114is inclined at an angle greater than 180° and less than or equal to 270° for the surface112. The surface113is inclined at an angle greater than 180° and less than 360° for the surface114. The surface115is positioned adjacent to each of the surface111to the surface114.

A relative angle generated between the base component101aand the base component101bby a movement of the angle adjustment device100can be adjusted when the inclination angles of the surface113and the surface114are adjusted. Here, the relative angle refers to an angle generated between the base component101aand the base component101bwhen the positions of the base component101aand the base component101bare changed depending on a mechanism included in the angle adjustment device.

The surface115includes regions151and152. Each of the regions151and152may be provided with an opening portion. Note that in this embodiment, the regions151and152of the base component101aare referred to as regions151aand152a. The regions151and152of the base component101bare referred to as regions151band152b.

It is preferable that the base components101aand101band the columnar components103a,103b,104a, and104bnot be deformed at the time of a movement and be formed using a hard material such as a metal, a resin, ceramics, or a complex including one or more of them.

FIG.2Bis a top view for explaining the shapes of the joining components102aand102b. The joining components102aand102bcan have the same shape and each include an opening portion121and a notch portion122.

In the top view, the center of the opening portion121can be provided on a straight line that is parallel to the longitudinal direction of the notch portion122and passes through the center of the notch portion122. The shapes of the joining components102aand102bcan each be line-symmetric with the straight line as the axis. The columnar component103aor the columnar component103bcan be inserted into the opening portion121.

The notch portion122includes regions122a,122b, and122c. The columnar component104aor the columnar component104bcan be inserted into the region122aor the region122b. The region122aand the region122bare connected, and each of their top surface shapes includes two arcs.

As illustrated inFIG.2B, one of the arcs of the region122ahas a point A and the other of the arcs has a point B; one of the arcs of the region122bhas a point C and the other of the arcs has a point D; the point A and the point B face each other; and the point C and the point D face each other. At this time, a distance L1between the point A and the point B and between the point C and the point D is preferably substantially equal to or smaller than the diameter of a cross section of the columnar component104aor104bperpendicular to the major axis. A region where the region122aand the region122bare connected is provided with a region in which the width of the notch portion122in the minor axis direction is L2that is smaller than L1.

The columnar component104aor the columnar component104bcan be sandwiched between the two arcs; therefore, the position of the columnar component104aor the columnar component104binserted into the notch portion122can be fixed easily.

The region122cis provided between the opening portion121and the region122b. The region122band the region122care connected, and the top surface shape of the region122chas an arc.

The joining components102aand102bare preferably formed using a material that is a hard material such as a metal, a resin, or a complex thereof and has elasticity. Here, the shortest distance between a point E included in the arc of the region122cand a periphery of the joining component102a(or102b) excluding the notch portion122is referred to as L4. At this time, when L4is set to an appropriate value, part of the joining component102a(or102b) can be elastically deformed with the vicinity of the region122cas a pivot, so that the lengths of L1and L2can be changed.

For example, the initial state is assumed to be a state where the columnar component104bis inserted into the region122bin the joining component102aas illustrated inFIG.3A. Next, as illustrated inFIG.3B, when a force of transfer in the direction of the region122aacts on the columnar component104b, the joining component102ais elastically deformed with the vicinity of the region122cas a pivot, so that L1is temporarily changed to L1′ (L1<L1′). In addition, L2is changed to L2′ (L2<L2′).

Then, as illustrated inFIG.3C, with an additional force of transfer in the same direction acting on the columnar component104b, elastic deformation of the joining component returns to the normal when the columnar component104benters the region122a. Consequently, the columnar component104bis inserted into the region122a. Note that when a force of transfer in the opposite direction acts on the columnar component104b, the columnar component104bcan return from the state illustrated inFIG.3Cto the state illustrated inFIG.3A. The regions122aand122bcan also be referred to as stable positions of the columnar component104bin the notch portion122. Note that although the two stable positions, the region122cand the region122b, are provided in the illustrated notch portion122in the example in this embodiment, the number of stable regions may be three or more.

The degree of the elastic deformation can be adjusted by the length of L4illustrated inFIG.2B. As the length of L4becomes longer, elastic deformation is less likely to occur; as the length of L4becomes shorter, elastic deformation is more likely to occur. Therefore, the length of L4is adjusted depending on the usage.

Note that it is also possible to adjust the degree of the elastic deformation by adjusting the length of L3that is the shortest distance between a point F included in a region between the region122cand the region122band the periphery of the joining component102a(or102b) excluding the notch portion122. The degree of the elastic deformation may be adjusted by change in the thickness (the length in a depth direction ofFIG.2B) of the joining component102a(or102b).

FIG.4is an exploded view of the angle adjustment device100. In a form of the angle adjustment device100, the surface111of the base component101aand the surface112of the base component101bare positioned to be in contact with each other.

One end portion of the columnar component103ain a longitudinal direction is joined to the region151a. One end portion of the columnar component104ain a longitudinal direction is joined to the region152a. One end portion of the columnar component103bin a longitudinal direction is joined to the region151b. One end portion of the columnar component104bin a longitudinal direction is joined to the region152b.

At this time, the major axes of the columnar components103a,103b,104aand104bare parallel to one another and perpendicular to the surfaces115of the base components101aand101b. The columnar components103aand103band the columnar components104aand104bmay be fixed to the base component101aand the base component101b. Alternatively, the columnar components103aand103band the columnar components104aand104bmay each be in a state of being capable of rotating with the center line as an axis. Alternatively, the columnar components103aand104aand the base component101amay be one structure. The columnar components103band104band the base component101bmay be one structure.

In the above state, the columnar component103bis inserted into the opening portion121of the joining component102b, and the columnar component104ais inserted into the region122ain the notch portion122of the joining component102b. The columnar component103ais inserted into the opening portion121of the joining component102a, and the columnar component104bis inserted into the region122ain the notch portion122of the joining component102a. With the structure, the form illustrated inFIG.1is obtained.

At this time, the joining component102bis in a state of being capable of rotating with the center line of the columnar component103bas an axis. The joining component102ais in a state of being capable of rotating with the center line of the columnar component103aas an axis.

Here, as illustrated inFIG.5A, the following case is considered: a rotation movement is made in the base components101aand101busing a side H, which is a side between the surface111and the surface113of the base component101a, as a center axis, so that the state where the surface111of the base component101ais in contact with the surface112of the base component101b(FIG.5A) is changed to the state where the surface113of the base component101ais in contact with the surface114of the base component101b(FIG.5B). Note that the side H can also be referred to as a side between the surface112and the surface114of the base component101b.

When the same movement as in the above is made in the structure of one embodiment of the present invention illustrated inFIG.1, the joining component102bmoves so as to rotate with the center line of the columnar component103bas an axis, and the position of the columnar component104ainserted into the notch portion122is changed from the region122ato the region122b, as illustrated inFIG.5CandFIG.5D. Furthermore, the joining component102amoves so as to rotate with the center line of the columnar component103aas an axis, and the position of the columnar component104binserted into the notch portion122is changed from the region122ato the region122b.

To change the state ofFIG.5Cto the state ofFIG.5Dor change in the reverse manner, it is necessary to apply a force that causes elastic deformation of the joining components102aand102b. Therefore, the state ofFIG.5Cor the state ofFIG.5Dcan be kept as long as the force is not applied. The change from the state ofFIG.5Cto the state ofFIG.5Dor the change in the reverse manner can be regarded as a change in the relative angle between the base component101aand the base component101b. Therefore, one embodiment of the present invention can be used as the angle adjustment device.

Furthermore, as illustrated inFIG.6AandFIG.6B, joining components131aand131bmay be added to the angle adjustment device of one embodiment of the present invention and a physical rotation axis (a columnar component105) may be provided in the position of the side H.

FIG.6Aillustrates the state where the base components101aand101band the joining components131aand131bare assembled.FIG.6Bis an exploded view thereof. The joining components131aand131band the columnar component105are provided, whereby the movement of the angle adjustment device100can be made more smoothly and the mechanical strength can be further enhanced.

A notch106into which the columnar component105can be inserted is provided in a region corresponding to the position of the side H illustrated inFIG.5Aand the vicinity thereof in the base components101aand101b. Note that the notch106is divided into a notch region provided in the base component101aand a notch region provided in the base component101b. A cylindrical-shaped component can be used as the columnar component105, and at least one end portion is inserted into the notch106. The center axis of the columnar component105preferably overlaps with the side H illustrated inFIG.5A.

The joining component131aincludes opening portions141aand142a, and the columnar component104ais inserted into the opening portion141a. The joining component131bincludes opening portions141band142b, and the columnar component104bis inserted into the opening portion141b. Part of the joining component131aand part of the joining component131bare positioned to overlap with each other, and the columnar component105is inserted into the opening portion142aand the opening portion142b.

Note that inFIG.6AandFIG.6B, the joining component131band the joining component131aare positioned in the inner side and the outer side, respectively, from the base components101aand101bside, and therefore, the joining component131ais provided with a spacer132for stabilizing the position. The thickness of the spacer132is preferably equal to or larger than the thickness of the joining component131b. Note that in the case where the joining component131band the joining component131aare positioned in the outer side and the inner side, respectively, from the base components101aand101bside, the joining component131bis provided with the spacer132.

Here, the joining component131ais preferably fixed to the base component101a. Alternatively, the joining component131acan be fixed to the columnar component104afixed to the base component101a. The joining component131bis preferably fixed to the base component101b. Alternatively, the joining component131bcan be fixed to the columnar component104bfixed to the base component101b. Alternatively, the base component101a, the columnar component104a, and the joining component131amay be one structure. Alternatively, the base component101b, the columnar component104b, and the joining component131bmay be one structure.

The columnar component105is preferably fixed to either the joining component131aor the joining component131b. Alternatively, the columnar component105may be fixed to either the notch region provided in the base component101aor the notch region provided in the base component101b, which form the notch106. Such a structure allows a rotation movement of the base components101aand101bwith the columnar component105as an axis as illustrated inFIG.7AandFIG.7B.

Note that in the state ofFIG.7A, the columnar component105is the rotation axis and the surface111of the base component101aand the surface112of the base component101bare in contact with each other, and therefore, a rotation movement in a reverse direction can be inhibited.

FIG.7CandFIG.7Dillustrate the structure where the columnar components103aand103band the joining components102aand102bare added to the structure illustrated inFIG.6AandFIG.6Band a change in shape due to a movement of the structure. This structure can increase the reliability in movement and the strength of the angle adjustment device100.

A minimum structure where the base component101aand the base component101bare one pair has been described above; however, the total number of base components101aand101bmay be three or more.FIG.8AandFIG.8Billustrate a structure where the total number of base components101aand101bis seven, as an example.FIG.8AandFIG.8Billustrate only the base components101aand the base components101b.

Note that in this embodiment, the expression “folding” is used for a movement for changing the state ofFIG.8Ato the state ofFIG.8B. In addition, the expression “opening” is used for a movement for changing the state ofFIG.8Bto the state ofFIG.8A.

It is possible to change the relative angle between the base component101aand the base component101bthat is generated due to folding by adjusting inclination angles of the surfaces113and the surfaces114in the base component101aand the base component101b. The angle becomes smaller as the inclination of the surface113for the surface114is reduced and becomes larger as the inclination of the surface113for the surface114is increased. Furthermore, it is possible to adjust the maximum value of an angle at which the angle adjustment device is foldable as a whole by adjusting the number of base components101aand101b.

In the structure ofFIG.8AandFIG.8B, the base components101aand the base components101bare alternately arranged. Thus, the notch106is provided between adjacent two of all the base components101aand101b.

FIG.9AandFIG.9Bare diagrams each illustrating a state where the joining components131aand131bare combined with the structure ofFIG.8AandFIG.8B.FIG.9Aillustrates an opened state andFIG.9Billustrates a folded state.

Here, a structure different from that illustrated inFIG.6Bis employed for the joining components131aand131b. As illustrated inFIG.9C, an opening portion143ais provided in the joining component131aso as to be symmetrical with the opening portion142awith the opening portion141aas the center. In addition, an opening portion143bis provided in the joining component131bso as to be symmetrical with the opening portion142bwith the opening portion141bas the center.

As illustrated inFIG.9AandFIG.9B, the base component101ais provided with the joining component131aand the base component101bis provided with the joining component131b. The opening portion142aand the opening portion142boverlap with each other and the columnar component105is inserted into them. The opening portion143aand the opening portion143boverlap with each other and the columnar component105is inserted into them.

FIG.10AandFIG.10Bare diagrams each illustrating a state where the structure ofFIG.9AandFIG.9Bis combined with the joining components102aand102b.FIG.10Aillustrates an opened state andFIG.10Billustrates a folded state.

In the structure ofFIG.10AandFIG.10B, the base components101aand the base components101bare alternately arranged. Thus, adjacent two of all the base components101aand101bare provided with the joining component102aand the joining component102b.

This structure allows a plurality of folded forms and makes it possible to keep the forms. Therefore, the structure can be effectively used as a hinge of a support that will be described next.

FIG.11Ais a perspective view illustrating a support200provided with the angle adjustment device100of one embodiment of the present invention. The support200includes two angle adjustment devices100(angle adjustment devices100aand100b), flat-plate portions161and162, and a bend portion165.FIG.11Acorresponds to a state where the support200is opened.

The bend portion165includes a plurality of columnar bodies166, and one end portion of each of the columnar bodies166in a longitudinal direction is joined to the base component101aor the base component101bof the angle adjustment device100a. The other end portion of each of the columnar bodies166in the longitudinal direction is joined to the base component101aor the base component101bof the angle adjustment device100b. Such a combination of the bend portion165and the angle adjustment devices100can be referred to as a hinge. The flat-plate portion161is joined to one end portion of the hinge, and the flat-plate portion162is joined to the other end portion of the hinge.

FIG.11Bis a perspective view illustrating a cross section in a position along line A1-A2inFIG.11A. The columnar body166has a trapezoid-shaped or substantially-trapezoid-shaped cross section perpendicular to the major axis, and as illustrated inFIG.11C, the columnar body166includes a side surface167a(surface including one leg of the trapezoid), a side surface167b(surface including the other leg of the trapezoid), a side surface167c(surface including a bottom base of the trapezoid), and a side surface167d(surface including a top base of the trapezoid). The bend portion165includes the plurality of columnar bodies166with a structure in which the side surface167aof one of adjacent two of the columnar bodies166is adjacent to the side surface167bof the other of the two columnar bodies166.

The columnar bodies166are joined so that the side surfaces167c(surfaces including the bottom bases of the trapezoids) form a substantially continuous surface. Furthermore, the side surface167cof the columnar body166in the one end portion of the hinge is joined so as to be continuous with a first surface of the flat-plate portion161. The side surface167cof the columnar body166in the other end portion of the hinge is joined so as to be continuous with a first surface of the flat-plate portion162. Note that the shape of the side surface167d(surface including the top base of the trapezoid) of each columnar body166is freely determined as long as it does not interfere with the other columnar bodies166or the flat-plate portions161and162. Accordingly, the cross section of the columnar body166perpendicular to the major axis may be a triangle or a substantial triangle.

As described above, the flat-plate portion161, the bend portion165(the bottom surfaces of the plurality of columnar bodies166), and the flat-plate portion162are continuous planes, and the distance between a given point A3on the flat-plate portion162and a given point A4on the flat-plate portion161illustrated inFIG.11Bis constant regardless of the state of the bend portion165. Therefore, in the case where a flexible component or the like is attached to the support, it is preferably attached to the planes. The support of one embodiment of the present invention enables the form to be kept even in the opened state as illustrated inFIG.11AandFIG.11B. It is further preferable that the planes be designed to be below a plane including the axes of the plurality of columnar components105and the plane including the axes of the plurality of columnar components105be closer to a neutral plane of the flexible component.

FIG.12Ais a diagram illustrating an example of a case where the support200is transformed from the opened state to the folded state or a transitional state (intermediate state) in the reverse manner.FIG.12Bis a perspective view illustrating a cross section in a position along line B1-B2inFIG.12A.

FIG.12AandFIG.12Billustrates a form in which a region where the side surface167aof one of two adjacent columnar bodies166faces and is in contact with the side surface167bof the other of the two adjacent columnar bodies166and a region where the side surface167aof one of different adjacent two columnar bodies166is not in contact with the side surface167bof the other of the different two adjacent columnar bodies166are mixed. The support of one embodiment of the present invention enables the form to be kept even in the transitional state illustrated inFIG.12AandFIG.12B.

FIG.13Ais a diagram illustrating a state where the support200is folded.FIG.13Bis a perspective view illustrating a cross section in a position along line C1-C2inFIG.13A.

In the form illustrated inFIG.13AandFIG.13B, in adjacent two of all the columnar bodies166, the side surface167aof one of the two columnar bodies faces and is in contact with the side surface167bof the other of the two columnar bodies. The support of one embodiment of the present invention enables the form to be kept even in the folded state illustrated inFIG.13AandFIG.13B

The support200can be used for supporting a flexible component. When a display panel is used as the flexible component, a flexible display device can be formed.

FIG.14AandFIG.14Bare diagrams illustrating and example of a two-foldable display device. Note that the angle adjustment devices100aand100bincluded in the support200are simplified in the diagrams.FIG.14Aillustrates the display device in the opened state, andFIG.14Billustrates the display device in the folded state.

A display panel170is flexible, and an EL display device provided over a thin-plate-shaped resin or glass can be used, for example.

The display panel170can be provided along a continuous plane portion included in the flat-plate portion161, the bend portion165(the bottom surfaces of the plurality of columnar bodies166), and the flat-plate portion162illustrated inFIG.11Aand the like. Thus, as illustrated inFIG.14B, a display surface of the display panel forms a convex curved surface in the folded state.

Although the angle adjustment devices100aand100b, the flat-plate portion161, the flat-plate portion162, and the like are illustrated inFIG.14AandFIG.14B, they may be stored in a housing of the display device.

FIG.15AandFIG.15Bare diagrams illustrating an example of a three-foldable display device. The angle adjustment devices100a,100b,100c, and100dincluded in the support200are simplified in the diagrams.FIG.15Aillustrates the display device in the opened state, andFIG.15Billustrates the display device in the folded state.

The three-fold display device is different from the two-fold display device in that the angle adjustment devices100cand100dand a flat-plate portion163are provided in the support. The flat-plate portion163is joined to the flat-plate portion162with the angle adjustment devices100cand100d.

Although the angle adjustment devices100a,100b,100c, and100d, the flat-plate portion161, the flat-plate portion162, the flat-plate portion163, and the like are illustrated inFIG.15AandFIG.15B, they may be stored in a housing of the display device.

Here, as illustrated inFIG.15B, a concave curved surface is formed on the display surface of the display panel to extend to the flat-plate portion162and the flat-plate portion163. Therefore, a structure different from those of the angle adjustment devices100aand100bis preferably used for the angle adjustment devices100cand100d.

For example, a structure illustrated inFIG.16AtoFIG.16Ccan be used for the angle adjustment devices100cand100d. Note that since the angle adjustment device100cand the angle adjustment device100dillustrated inFIG.15AandFIG.15Bare continuous, only one of the angle adjustment devices illustrated inFIG.16AtoFIG.16Cis denoted by the reference numeral.

The angle adjustment device100cincludes a plurality of columnar bodies181each with a rectangular or substantially rectangular cross section perpendicular to the major axis. The columnar body181includes a first side surface (surface including one side of the substantial rectangle) and a second side surface (surface including a side facing the one side of the substantial rectangle). In the plurality of columnar bodies181, the first side surface of one of two adjacent columnar bodies181is adjacent to the second side surface of the other of the two adjacent columnar bodies181.

The columnar bodies181are joined so that third side surfaces (surfaces each including a side substantially perpendicular to the one side) form continuous surfaces. The third side surface of the columnar body181in one end portion of the angle adjustment device100cis joined so as to be continuous with the first surface of the flat-plate portion162. The third side surface of the columnar body181in the other end portion of the angle adjustment device100cis joined so as to be continuous with the first surface of the flat-plate portion163. Note that the shape of a fourth side surface (surface facing the third side surface) of each columnar body181is freely determined as long as it does not interfere with the other columnar bodies or the housing.

As illustrated inFIG.16A, when adjacent two of the columnar bodies181are transformed in a direction in which the first side surface of one of the two adjacent columnar bodies181and the second side surface of the other of the two adjacent columnar bodies181are apart from each other, the display device can be in the folded state. At this time, the third side surfaces of the plurality of columnar bodies181extend with a certain angle, and therefore a region where the whole cross section has a substantially circular arc shape is formed. Accordingly, the flexible display panel can form a concave curved surface in a portion overlapping with the region.

When a transformation movement (opening movement) is made from the state inFIG.16A, adjacent two of the columnar bodies181move so that the first side surface of one of the two columnar bodies181is closer to the second side surface of the other of the two columnar bodies181, whereby a curvature radius of the substantial circular arc changes to be larger as illustrated inFIG.16B. At this time, a curvature radius of a curved surface portion changes so as to be larger also in the display panel.

When a transformation movement is further made from the state inFIG.16B, as illustrated inFIG.16C, the first surface of the flat-plate portion162, the third side surface of each of the columnar bodies181, and the first surface of the flat-plate portion163are continuous with each other so as to be flat. At this time, the curved surface portion of the display panel also changes so as to be flat, and the entire display panel is set in an opened state so as to be flat. When a transformation movement is made in a reverse order of the above, the display panel can be folded.

Note that since the cross section of the columnar body181is a rectangle, when the display panel is opened so as to be flat, in adjacent two of the columnar bodies181, the first side surface of one of the columnar bodies181is in contact with the second side surface of the other of the columnar bodies181. Accordingly, the angle adjustment device100cdoes not cause bending in the display panel in a reverse direction, and mechanism to inhibit reverse bending may be unnecessary. Note that a spacer for keeping a gap between housings during folding may be provided.

FIG.17AtoFIG.17Cillustrate another example of the angle adjustment devices100cand100d. Although the angle adjustment device100dis described below, the angle adjustment device100chas the same structure.

The angle adjustment device100dincludes a gear186aand a gear186b. The gear186ais fixed to the flat-plate portion162. The gear186bis fixed to the flat-plate portion163. The center axis of the gear186apreferably overlaps with the first surface of the flat-plate portion162. The center axis of the gear186bpreferably overlaps with the first surface of the flat-plate portion163.

As illustrated inFIG.17A, the gear186aand the gear186bare engaged with each other in a particular position in a folded state. Since the center axis of the gear186ais on the first surface of the flat-plate portion162and the center axis of the gear186bis on the first surface of the flat-plate portion161at this time, a gap is generated between the flat-plate portion162and the flat-plate portion163(between facing display surfaces of the display panel). Therefore, the flexible display panel can form a concave curved surface whose curvature radius is about the half of the gap.

When a transformation movement (opening movement) is made from the state ofFIG.17A, the flat-plate portion162and the flat-plate portion163are synchronized in accordance with engagement of the gear186aand the gear186b, and move to open with the angle adjustment device100das a pivot (seeFIG.17B). At this time, the curvature radius of the curved surface portion changes so as to be larger also in the display panel.

When the movement of transformation is further made from the state ofFIG.17B, as illustrated inFIG.17C, the first surface of the flat-plate portion162and the first surface of the flat-plate portion163extend to be flat. At this time, the curved surface portion of the display panel also changes so as to be flat, and the entire display panel is set in an opened state so as to be flat. When a transformation movement is made in a reverse order of the above, the display panel can be folded.

Note that a mechanism for keeping the engagement between the gear186aand the gear186bmay be provided. When the display panel is opened to be flat, the side surface of the flat-plate portion162and the side surface of the flat-plate portion163are in contact with each other. Accordingly, the angle adjustment device100ddoes not cause bending in a reverse direction in the display panel, and a mechanism for inhibiting reverse bending may be unnecessary. Note that a spacer for keeping the gap between the flat-plate portion162and the flat-plate portion163at the time of folding may be provided. Alternatively, a mechanism for keeping the gap may be provided in the gear186aand the gear186b.

Application Example

FIG.18illustrates an example in which the flexible display device described in this embodiment is applied to an information terminal such as a smartphone. Note that components common to the display device are denoted by the same reference numerals. A display device250illustrated inFIG.18Aincludes the display panel170, audio input/output units235aand235b, cameras236aand236b, a sensor237, and a sensor220.

When one of the audio input/output units235aand235bfunctions as a microphone, the other of the audio input/output units235aand235bcan function as a speaker. Therefore, when a telephone function is utilized, for example, it is possible to have a conversation without any inconvenience regardless of the side of the display a user holds. The microphone function and the speaker function can be switched with each other by the sensor220that senses a tilt. In addition, either the cameras236aand236bcan similarly function with a high priority by the sensor220.

The input/output units235aand235bmay include both of a device that functions as a microphone and a device that functions as a speaker or may include one device that has both functions.

Alternatively, both the input/output units235aand235bcan function as microphones to record stereo sound. Alternatively, both the input/output units235aand235bcan function as speakers to reproduce stereo sound.

In addition, both the cameras236aand236bcan function and can capture 3D images. The sensor237is an optical sensor and can adjust display luminance so that the images can be easily seen in accordance with ambient illuminance.

Moreover, as illustrated inFIG.18B, a display panel171may be provided on a rear surface that is on a side opposite to a front surface of the display device250where the display panel170is provided. The display panel171can display the same image as the display panel170. The display panel171can also be utilized as a sub-display that displays simple information, painting, a pattern, a picture, or the like; lighting; or the like. A display panel using a light-emitting device or a liquid crystal device can be used as the display panel171, and low-power electronic paper or the like may be used as the display panel171. A display panel using a hard substrate as a support can also be used as the display panel171.

Note that as illustrated inFIG.19A, the display panel171may be provided on the flat-plate portion161, a display panel172may be provided on the flat-plate portion162, and a display panel173may be provided on the flat-plate portion163. Display panels equivalent to the display panel171can be used as the display panels172and173.

Alternatively, as illustrated inFIG.19B, a flexible display panel175may be provided on the rear surface of the display device250. In that case, the display panel175can be bent, and thus the display panel175can be provided across the flat-plate portions161to163, like the display panel170provided on the front surface.

Furthermore, as illustrated inFIG.19C, a solar battery240may be provided on the rear surface of the display device250. A battery in the display device250can be charged with power generated by the solar battery240, and the power can be supplied to the outside through an external interface245.

Note thatFIG.19Cillustrates an example of a solar battery including a hard support. As the solar battery, for example, a silicon solar battery using crystalline silicon for a photoelectric conversion layer, a solar battery with a tandem structure of a silicon solar battery and a perovskite type solar battery, or the like can be used.

Alternatively, as illustrated inFIG.19D, a solar cell in which a flexible substrate is used as a support may be used. As the solar battery, for example, a thin-film solar battery141such as an amorphous silicon solar battery, a CIGS (Cu—In—Ga—Se) type solar battery, an organic solar battery, or a perovskite type solar battery, or the like can be used. The solar battery using a flexible substrate as a support can be provided across the flat-plate portion161to163, like the display panel171.

In this embodiment, a structure example of a display panel that can be applied to the display device according to one embodiment of the present invention is described.

Structure Example

FIG.20illustrates a top view of a display panel700. The display panel700employs a flexible support substrate745and can be used as a flexible display. Furthermore, the display panel700includes a pixel portion702provided over the flexible support substrate745. Furthermore, a source driver circuit portion704, a pair of gate driver circuit portions706, a wiring710, and the like are provided over the support substrate745. Moreover, a plurality of display devices are provided in the pixel portion702.

In addition, part of the support substrate745is provided with an FPC (flexible printed circuit) terminal portion708to which an FPC716is connected. The pixel portion702, the source driver circuit portion704, and the gate driver circuit portions706are each supplied with a variety of signals and the like from the FPC716through the FPC terminal portion708and the wiring710.

The pair of gate driver circuit portions706is provided on both sides with the pixel portion702sandwiched therebetween. Note that the gate driver circuit portions706and the source driver circuit portion704may be formed separately on semiconductor substrates or the like to form packaged IC chips. The IC chips can be mounted on the support substrate745by a COF (Chip On Film) technique or the like.

Transistors including an OS are preferably applied to transistors included in the pixel portion702, the source driver circuit portion704, and the gate driver circuit portions706.

Light-emitting devices or the like can be used as the display devices in the pixel portion702. Examples of light-emitting devices are self-luminous light-emitting devices such as an LED (Light Emitting Diode), an OLED (Organic LED), a QLED (Quantum-dot LED), a semiconductor laser, and the like. Alternatively, liquid crystal devices such as transmissive liquid crystal devices, reflective liquid crystal devices, or semi-transmissive liquid crystal devices can also be used as the display devices. Alternatively, shutter type or optical interference type MEMS (Micro Electro Mechanical Systems) devices; display devices employing a microcapsule method, an electrophoretic method, an electrowetting method, an Electronic Liquid Powder (registered trademark) method, or the like; and the like can also be used.

FIG.20illustrates an example where the support substrate745has a shape in which a portion provided with the FPC terminal portion708is projected. In a region P1inFIG.20, part of the support substrate745that includes the FPC terminal portion708can be bent backward. Bending the part of the support substrate745backward enables the FPC716to be placed in a state overlapping a rear side of the pixel portion702when the display panel700is mounted on an electronic device or the like, so that the electronic device or the like can be space-saving or small-sized.

An IC717is mounted on the FPC716connected to the display panel700. The IC717has a function of a source driver circuit, for example. In that case, a structure can be employed in which the source driver circuit portion704in the display panel700includes at least one of a protection circuit, a buffer circuit, a demultiplexer circuit, and the like.

Cross-Sectional Structure Example

Structures using organic EL as the display device are described below usingFIG.21andFIG.22. Each ofFIG.21andFIG.22is a schematic cross-sectional view of the display panel700illustrated inFIG.20along a dash-dot line S-T.

First, portions common to the display panels illustrated inFIG.21andFIG.22are described.

FIG.21andFIG.22illustrate cross sections including the pixel portion702, the gate driver circuit portion706, and the FPC terminal portion708. The pixel portion702includes a transistor750and a capacitor790. The gate driver circuit portion706includes a transistor752

Each of the transistor750and the transistor752is a transistor in which an oxide semiconductor is employed for a semiconductor layer where a channel is formed. Note that the transistors are not limited thereto, and a transistor using silicon (amorphous silicon, polycrystalline silicon, or single-crystal silicon) or a transistor using an organic semiconductor for a semiconductor layer can be employed.

The transistor used in this embodiment includes a highly purified oxide semiconductor film in which formation of oxygen vacancies is suppressed. The transistor can have extremely low off-state current. Accordingly, in the pixel employing such a transistor, the retention time of an electric signal such as an image signal can be extended, and an interval between writings of an image signal or the like can also be set longer. Accordingly, the frequency of refresh operations can be reduced, so that power consumption can be reduced.

In addition, the transistor used in this embodiment can have comparatively high field-effect mobility and thus is capable of high-speed driving. For example, with such a transistor capable of high-speed driving used for the display panel, a switching transistor in a pixel portion and a driver transistor used in a driver circuit portion can be formed over the same substrate. In other words, a structure in which a driver circuit formed using a silicon wafer or the like is not employed is possible, and the number of components of the display device can be reduced. Furthermore, the use of the transistor capable of high-speed driving also in the pixel portion can provide a high-quality image.

The capacitor790includes a lower electrode formed by processing the same film as a film for a first gate electrode of the transistor750and an upper electrode formed by processing the same metal oxide film as a film for the semiconductor layer. The upper electrode has reduced resistance like a source region and a drain region of the transistor750. In addition, part of an insulating film functioning as a first gate insulating layer of the transistor750is provided between the lower electrode and the upper electrode. That is, the capacitor790has a stacked-layer structure in which an insulating film functioning as a dielectric film is sandwiched between a pair of electrodes. Furthermore, a wiring obtained by processing the same film as a film for a source electrode and a drain electrode of the transistor750is connected to the upper electrode.

In addition, an insulating layer770that functions as a planarization film is provided over the transistor750, the transistor752, and the capacitor790.

As the transistor750included in the pixel portion702and the transistor752included in the source driver circuit portion704, transistors having different structures may be used. For example, a structure may be employed in which a top-gate transistor is used as one of the transistors750and752and a bottom-gate transistor is used as the other of the transistors750and752. Note that the same applies to the source driver circuit portion704, as in the gate driver circuit portion706.

The FPC terminal portion708includes a wiring760part of which functions as a connection electrode, an anisotropic conductive film780, and the FPC716. The wiring760is electrically connected to a terminal included in the FPC716through the anisotropic conductive film780. Here, the wiring760is formed using the same conductive film as the source electrode and the drain electrode of the transistor750or the like.

The display panel700illustrated inFIG.21includes the support substrate745and a support substrate740. As each of the support substrate745and the support substrate740, a glass substrate or a flexible substrate such as a plastic substrate can be used, for example.

The transistor750, the transistor752, the capacitor790, and the like are provided over the insulating layer744. The support substrate745and the insulating layer744are attached to each other with an adhesive layer742.

The display panel700includes a light-emitting device782, a coloring layer736, a light-blocking layer738, and the like.

The light-emitting device782includes a conductive layer772, an EL layer786, and a conductive layer788. The conductive layer772is electrically connected to the source electrode or the drain electrode included in the transistor750. The conductive layer772is provided over the insulating layer770and functions as a pixel electrode. In addition, an insulating layer730is provided to cover an end portion of the conductive layer772. Over the insulating layer730and the conductive layer772, the EL layer786and the conductive layer788are stacked and provided.

For the conductive layer772, a material having a property of reflecting visible light can be used. For example, a material including aluminum, silver, or the like can be used. For the conductive layer788, a material having a property of transmitting visible light can be used. For example, an oxide material including indium, zinc, tin, or the like is preferably used. Thus, the light-emitting device782is a top-emission light-emitting device that emits light to a side opposite a formation surface (a support substrate740side).

The EL layer786includes an organic compound or an inorganic compound such as quantum dots. The EL layer786includes a light-emitting material that exhibits blue light when current flows.

As the light-emitting material, a fluorescent material, a phosphorescent material, a thermally activated delayed fluorescence (TADF) material, an inorganic compound (a quantum dot material or the like), or the like can be used. Examples of materials that can be used for quantum dots include a colloidal quantum dot material, an alloyed quantum dot material, a core-shell quantum dot material, a core quantum dot material, and the like.

The light-blocking layer738and the coloring layer736are provided on one surface of an insulating layer746. The coloring layer736is provided in a position overlapping the light-emitting device782. In addition, the light-blocking layer738is provided in a region not overlapping the light-emitting device782in the pixel portion702. Furthermore, the light-blocking layer738may also be provided to overlap the gate driver circuit portion706or the like.

The support substrate740is attached to the other surface of the insulating layer746with an adhesive layer747. Furthermore, the support substrate740and the support substrate745are attached to each other with a sealing layer732.

Here, for the EL layer786included in the light-emitting device782, a light-emitting material that exhibits white light emission is employed. White light emission by the light-emitting device782is colored by the coloring layer736to be emitted to the outside. The EL layer786is provided over the pixels that exhibit different colors. The pixels provided with the coloring layer736transmitting any of red (R), green (G), and blue (B) are arranged in a matrix in the pixel portion702, so that the display panel700can perform full-color display.

In addition, a conductive film having a transmitting property and a reflective property may be used for the conductive layer788. In that case, a microcavity structure is achieved between the conductive layer772and the conductive layer788such that light of a specific wavelength can be intensified to be emitted. Also at this time, a structure may be employed in which an optical adjustment layer for adjusting an optical distance is placed between the conductive layer772and the conductive layer788such that the thickness of the optical adjustment layer differs between pixels of different colors and accordingly the color purity of light emitted from each pixel is increased.

Note that a structure in which the coloring layer736or the optical adjustment layer is not provided may be employed when the EL layer786is formed into an island shape for each pixel or into a stripe shape for each pixel column, i.e., the EL layer786is formed by separate coloring.

Here, an inorganic insulating film that functions as a barrier film having low permeability is preferably used for each of the insulating layer744and the insulating layer746. With a structure in which the light-emitting device782, the transistor750, and the like are sandwiched between the insulating layer744and the insulating layer746, degradation thereof can be inhibited and a highly reliable display panel can be achieved.

In a display panel700A illustrated inFIG.22, a resin layer743is provided between the adhesive layer742and the insulating layer744illustrated inFIG.21. In addition, a protective layer749is provided instead of the support substrate740.

The resin layer743is a layer including an organic resin such as polyimide or acrylic. The insulating layer744includes an inorganic insulating film of silicon oxide, silicon oxynitride, silicon nitride, or the like. The resin layer743and the support substrate745are attached to each other with the adhesive layer742. The resin layer743is preferably thinner than the support substrate745.

The protective layer749is attached to the sealing layer732. A glass substrate, a resin film, or the like can be used as the protective layer749. Alternatively, as the protective layer749, an optical member such as a polarizing plate (including a circularly polarizing plate) or a scattering plate, an input device such as a touch sensor panel, or a structure in which two or more of these are stacked may be employed.

The EL layer786included in the light-emitting device782is provided over the insulating layer730and the conductive layer772in an island shape. The EL layers786are formed separately so that respective subpixels emit light of different colors, so that color display can be performed without the use of the coloring layer736.

A protective layer741is provided to cover the light-emitting device782. The protective layer741has a function of preventing diffusion of impurities such as water into the light-emitting device782. The protective layer741has a stacked-layer structure in which an insulating layer741a, an insulating layer741b, and an insulating layer741care stacked in this order from the conductive layer788side. In that case, it is preferable that inorganic insulating films with a high barrier property against impurities such as water be used as the insulating layer741aand the insulating layer741cand an organic insulating film that functions as a planarization film be used as the insulating layer741b. Furthermore, the protective layer741is preferably provided to extend also to the gate driver circuit portion706.

An organic insulating film covering the transistor750, the transistor752, and the like is preferably formed in an island shape inward from the sealing layer732. In other words, an end portion of the organic insulating film is preferably inward from the sealing layer732or in a region overlapping an end portion of the sealing layer732.FIG.22illustrates an example in which the insulating layer770, the insulating layer730, and the insulating layer741bare processed into island shapes. The insulating layer741cand the insulating layer741aare provided in contact with each other in a portion overlapping the sealing layer732, for example. Thus, when a structure is employed in which a surface of the organic insulating film covering the transistor750and the transistor752is not exposed to the outside of the sealing layer732, diffusion of water or hydrogen from the outside to the transistor750and the transistor752through the organic insulating film can be favorably prevented. This can reduce variations in electrical characteristics of the transistors, so that a display device with extremely high reliability can be achieved.

In addition, inFIG.22, the region P1that can be bent includes a portion where the support substrate745, the adhesive layer742, and the inorganic insulating film such as the insulating layer744are not provided. Furthermore, the region P1has a structure in which the insulating layer770including an organic material covers the wiring760so that the wiring760is not exposed. When a structure is employed in which an inorganic insulating film is not provided as long as possible in the region P1that can be bent and only a conductive layer containing a metal or an alloy and a layer containing an organic material are stacked, generation of cracks caused at bending can be prevented. Moreover, when the support substrate745is not provided in the region P1, part of the display panel700A can be bent with an extremely small curvature radius.

Furthermore, inFIG.22, a conductive layer761is provided over the protective layer741. The conductive layer761can be used as a wiring or an electrode.

In addition, in the case where a touch sensor is provided to overlap the display panel700A, the conductive layer761can function as an electrostatic shielding film for preventing transmission of electrical noise to the touch sensor during pixel driving. In that case, a structure in which a predetermined constant potential is applied to the conductive layer761may be employed.

Alternatively, the conductive layer761can be used as an electrode of the touch sensor, for example. This enables the display panel700A to function as a touch panel. For example, the conductive layer761can be used as an electrode or a wiring of a capacitive touch sensor. In that case, the conductive layer761can be used as a wiring or an electrode to which a sensor circuit is connected or a wiring or an electrode to which a sensor signal is input. When the touch sensor is formed over the light-emitting device782in this manner, the number of components can be reduced, and manufacturing cost of an electronic device or the like can be reduced.

The conductive layer761is preferably provided in a portion not overlapping the light-emitting device782. The conductive layer761can be provided in a position overlapping the insulating layer730, for example. Thus, a transparent conductive film with a comparatively low conductivity is not necessarily used for the conductive layer761, and a metal or an alloy having high conductivity or the like can be used, so that the sensitivity of the sensor can be increased.

Note that as the type of the touch sensor that can be formed using the conductive layer761, a variety of types such as a resistive type, a surface acoustic wave type, an infrared type, an optical type, and a pressure-sensitive type can be used, without limitation to a capacitive type. Alternatively, two or more of these may be combined and used.

Components such as a transistor that can be employed in the display device will be described below.

The transistors each include a conductive layer functioning as a gate electrode, a semiconductor layer, a conductive layer functioning as a source electrode, a conductive layer functioning as a drain electrode, and an insulating layer functioning as a gate insulating layer.

Note that there is no particular limitation on the structure of the transistor included in the display device according to one embodiment of the present invention. For example, a planar transistor, a staggered transistor, or an inverted staggered transistor may be used. In addition, a top-gate or bottom-gate transistor structure may be employed. Alternatively, gate electrodes may be provided above and below a channel.

There is no particular limitation on the crystallinity of a semiconductor material used for the transistors, and any of an amorphous semiconductor, a single crystal semiconductor, and a semiconductor having crystallinity other than single crystal (a microcrystalline semiconductor, a polycrystalline semiconductor, or a semiconductor partly including crystal regions) may be used. It is preferable to use a single crystal semiconductor or a semiconductor having crystallinity because degradation of transistor characteristics can be inhibited.

In particular, a transistor that uses a metal oxide film for a semiconductor layer where a channel is formed will be described below.

As a semiconductor material used for the transistors, a metal oxide whose energy gap is greater than or equal to 2 eV, preferably greater than or equal to 2.5 eV, further preferably greater than or equal to 3 eV can be used. Typically, an oxide semiconductor containing indium, or the like can be used, and for example, a CAAC-OS, a CAC-OS, or the like described later can be used. A CAAC-OS has a crystal structure including stable atoms and is suitable for a transistor that puts emphasis on reliability, and the like. A CAC-OS exhibits excellent mobility characteristics and thus is suitable for a transistor that is driven at high speed, for example.

In an OS transistor, a semiconductor layer has a large energy gap, and thus the OS transistor can exhibit characteristics with an extremely low off-state current of several yoctoamperes per micrometer (a current value per micrometer of channel width). In addition, an OS transistor has features such that impact ionization, an avalanche breakdown, a short-channel effect, and the like do not occur, which are different from those of a Si transistor, and can form a highly reliable circuit. Furthermore, variations in electrical characteristics due to crystallinity unevenness, which are issues in Si transistors, are less likely to occur in OS transistors.

A semiconductor layer can be, for example, a film represented by an In-M-Zn-based oxide that contains indium, zinc, and an element M (M is one or more selected from metals such as aluminum, titanium, gallium, germanium, yttrium, zirconium, lanthanum, cerium, tin, neodymium, and hafnium). The In-M-Zn-based oxide can be formed by, for example, a sputtering method, an ALD (Atomic layer deposition) method, an MOCVD (Metal organic chemical vapor deposition) method, or the like.

In the case where an In-M-Zn-based oxide is deposited by a sputtering method, it is preferable that the atomic ratio of metal elements in a sputtering target satisfy In≥M and Zn≥M. The atomic ratio of metal elements in such a sputtering target is preferably, for example, In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=3:1:2, In:M:Zn=4:2:3, In:M:Zn=4:2:4.1, In:M:Zn=5:1:6, In:M:Zn=5:1:7, In:M:Zn=5:1:8, or the like. Note that the atomic ratio in the deposited semiconductor layer varies from the atomic ratio of metal elements of the sputtering target in a range of ±40%.

A metal oxide film with a low carrier density is used as the semiconductor layer. For example, for the semiconductor layer, a metal oxide whose carrier density is lower than or equal to 1×1017/cm3, preferably lower than or equal to 1×1015/cm3, further preferably lower than or equal to 1×1013/cm3, still further preferably lower than or equal to 1×1011/cm3, even further preferably lower than 1×1010/cm3, and higher than or equal to 1×10−9/cm3can be used. Such a metal oxide is referred to as a highly purified intrinsic or substantially highly purified intrinsic metal oxide. The oxide semiconductor has a low density of defect states and thus can be regarded as a metal oxide having stable characteristics.

Note that, without limitation to those described above, an oxide semiconductor with an appropriate composition may be used in accordance with required semiconductor characteristics and electrical characteristics (field-effect mobility, threshold voltage, and the like) of the transistor. In addition, to obtain the required semiconductor characteristics of the transistor, it is preferable that the carrier density, the impurity concentration, the density of defect states, the atomic ratio between a metal element and oxygen, the interatomic distance, the density, and the like of the semiconductor layer be set to appropriate values.

When silicon or carbon, which is one of Group 14 elements, is contained in the metal oxide contained in the semiconductor layer, oxygen vacancies are increased in the semiconductor layer, and the semiconductor layer becomes n-type. Thus, the concentration of silicon or carbon (concentration obtained by secondary ion mass spectrometry) in the semiconductor layer is set to lower than or equal to 2×1018atoms/cm3, preferably lower than or equal to 2×1017atoms/cm3.

Alkali metal and alkaline earth metal might generate carriers when bonded to a metal oxide, in which case the off-state current of the transistor might be increased. Thus, the concentration of alkali metal or alkaline earth metal in the semiconductor layer that is obtained by secondary ion mass spectrometry is set to lower than or equal to 1×1018atoms/cm3, preferably lower than or equal to 2×1016atoms/cm3.

When nitrogen is contained in the metal oxide contained in the semiconductor layer, electrons serving as carriers are generated and the carrier density increases, so that the semiconductor layer easily becomes n-type. As a result, a transistor using a metal oxide that contains nitrogen is likely to have normally-on characteristics. Accordingly, the nitrogen concentration in the semiconductor layer that is obtained by secondary ion mass spectrometry is preferably set to lower than or equal to 5×1018atoms/cm3.

In addition, when hydrogen is contained in an oxide semiconductor included in the semiconductor layer, hydrogen reacts with oxygen bonded to a metal atom to be water, and thus sometimes causes an oxygen vacancy in the oxide semiconductor. When a channel formation region in the oxide semiconductor includes oxygen vacancies, the transistor sometimes has normally-on characteristics. Furthermore, in some cases, a defect that is an oxygen vacancy into which hydrogen enters functions as a donor and generates an electron serving as a carrier. In other cases, bonding of part of hydrogen to oxygen bonded to a metal atom generates electrons serving as carriers. Thus, a transistor using an oxide semiconductor that contains a large amount of hydrogen is likely to have normally-on characteristics.

A defect in which hydrogen has entered an oxygen vacancy can function as a donor of the oxide semiconductor. However, it is difficult to evaluate the defect quantitatively. Thus, the oxide semiconductor is sometimes evaluated by not its donor concentration but its carrier concentration. Therefore, in this specification and the like, the carrier concentration assuming the state where an electric field is not applied is sometimes used, instead of the donor concentration, as the parameter of the oxide semiconductor. That is, “carrier concentration” described in this specification and the like can be replaced with “donor concentration” in some cases.

Therefore, hydrogen in the oxide semiconductor is preferably reduced as much as possible. Specifically, the hydrogen concentration in the oxide semiconductor that is obtained by secondary ion mass spectrometry (SIMS) is set to lower than 1×1020atoms/cm3, preferably lower than 1×1019atoms/cm3, further preferably lower than 5×1018atoms/cm3, still further preferably lower than 1×1018atoms/cm3. When an oxide semiconductor with a sufficiently low concentration of impurities such as hydrogen is used for a channel formation region of a transistor, the transistor can have stable electrical characteristics.

In addition, oxide semiconductors (metal oxides) can be classified into a single crystal oxide semiconductor and a non-single-crystal oxide semiconductor. Examples of the non-single-crystal oxide semiconductors include a CAAC-OS (C-Axis-Aligned Crystalline Oxide Semiconductor), a polycrystalline oxide semiconductor, an nc-OS (nanocrystalline oxide semiconductor), an amorphous-like oxide semiconductor (a-like OS), an amorphous oxide semiconductor, and the like. Among non-single-crystal structures, an amorphous structure has the highest density of defect states, whereas the CAAC-OS has the lowest density of defect states.

An oxide semiconductor film having an amorphous structure has disordered atomic arrangement and no crystalline component, for example. Alternatively, an oxide film having an amorphous structure has, for example, a completely amorphous structure and no crystal part.

Note that the semiconductor layer may be a mixed film including two or more of a region having an amorphous structure, a region having a microcrystalline structure, a region having a polycrystalline structure, a CAAC-OS region, and a region having a single crystal structure. The mixed film has, for example, a single-layer structure or a stacked-layer structure including two or more of the above regions in some cases.

In addition, a CAC-OS (Cloud-Aligned Composite oxide semiconductor) may be used for a semiconductor layer of a transistor disclosed in one embodiment of the present invention.

Note that the non-single-crystal oxide semiconductor or CAC-OS can be suitably used for a semiconductor layer of a transistor disclosed in one embodiment of the present invention. In addition, as the non-single-crystal oxide semiconductor, the nc-OS or the CAAC-OS can be suitably used.

Note that in one embodiment of the present invention, a CAC-OS is preferably used for a semiconductor layer of a transistor. The use of the CAC-OS allows the transistor to have high electrical characteristics or high reliability.

Note that the semiconductor layer may be a mixed film including two or more kinds of a region of a CAAC-OS, a region of a polycrystalline oxide semiconductor, a region of an nc-OS, a region of an amorphous-like oxide semiconductor, and a region of an amorphous oxide semiconductor. The mixed film has, for example, a single-layer structure or a stacked-layer structure including two or more kinds of the above regions in some cases.

The composition of a CAC (Cloud-Aligned Composite)-OS that can be used in a transistor disclosed in one embodiment of the present invention is described below.

The CAC-OS is, for example, a composition of a material in which elements that constitute a metal oxide are unevenly distributed to have a size of greater than or equal to 0.5 nm and less than or equal to 10 nm, preferably greater than or equal to 1 nm and less than or equal to 2 nm, or a similar size. Note that in the following description, a state in which one or more metal elements are unevenly distributed and regions including the metal element(s) are mixed to have a size of greater than or equal to 0.5 nm and less than or equal to 10 nm, preferably greater than or equal to 1 nm and less than or equal to 2 nm, or a similar size in a metal oxide is referred to as a mosaic pattern or a patch-like pattern.

Note that the metal oxide preferably contains at least indium. In particular, indium and zinc are preferably contained. Moreover, in addition to these, one kind or a plurality of kinds selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like may be contained.

For example, a CAC-OS in an In—Ga—Zn oxide (an In—Ga—Zn oxide in the CAC-OS may be particularly referred to as CAC-IGZO) has a composition in which materials are separated into indium oxide (hereinafter referred to as InOX1(X1 is a real number greater than 0)) or indium zinc oxide (hereinafter referred to as InX2ZnY2OZ2(each of X2, Y2, and Z2 is a real number greater than 0)) and gallium oxide (hereinafter referred to as GaOX3(X3 is a real number greater than 0)), gallium zinc oxide (hereinafter referred to as GaX4ZnY4OZ4(each of X4, Y4, and Z4 is a real number greater than 0)), or the like so that a mosaic pattern is formed, and mosaic-like InOX1or InX2ZnY2OZ2is evenly distributed in the film (this composition is hereinafter also referred to as a cloud-like composition).

That is, the CAC-OS is a composite metal oxide having a composition in which a region where GaOX3is a main component and a region where InX2ZnY2OZ2or InOX1is a main component are mixed. Note that in this specification, for example, when the atomic ratio of In to an element M in a first region is larger than the atomic ratio of In to the element M in a second region, the first region is regarded as having a higher In concentration than the second region.

Note that IGZO is a commonly known name and sometimes refers to one compound formed of In, Ga, Zn, and O. A typical example is a crystalline compound represented by InGaO3(ZnO)m1(m1 is a natural number) or In(1+x0)Ga(i−x0)O3(ZnO)m0(−1≤x0≤1; m0 is a given number).

The crystalline compound has a single crystal structure, a polycrystalline structure, or a CAAC structure. Note that the CAAC structure is a crystal structure in which a plurality of IGZO nanocrystals have c-axis alignment and are connected in an a-b plane without alignment.

Meanwhile, the CAC-OS relates to the material composition of a metal oxide. In the material composition of a CAC-OS containing In, Ga, Zn, and O, some regions that contain Ga as a main component and are observed as nanoparticles and some regions that contain In as a main component and are observed as nanoparticles are each randomly dispersed in a mosaic pattern. Therefore, the crystal structure is a secondary element for the CAC-OS.

Note that the CAC-OS is regarded as not including a stacked-layer structure of two or more kinds of films with different compositions. For example, a two-layer structure of a film containing In as a main component and a film containing Ga as a main component is not included.

Note that a clear boundary between the region where GaOX3is a main component and the region where InX2ZnY2OZ2or InOX1is a main component cannot be observed in some cases.

Note that in the case where one kind or a plurality of kinds selected from aluminum, yttrium, copper, vanadium, beryllium, boron, silicon, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, magnesium, and the like are contained instead of gallium, the CAC-OS refers to a composition in which some regions that contain the metal element(s) as a main component and are observed as nanoparticles and some regions that contain In as a main component and are observed as nanoparticles are each randomly dispersed in a mosaic pattern.

The CAC-OS is characterized in that no clear peak is observed at the time of measurement using θ/2θ scan by an Out-of-plane method, which is one of the X-ray diffraction (XRD) measurement methods. That is, it is found from X-ray diffraction measurement that no alignment in an a-b plane direction and a c-axis direction is observed in a measured region.

In an electron diffraction pattern of the CAC-OS that is obtained by irradiation with an electron beam with a probe diameter of 1 nm (also referred to as a nanobeam electron beam), a ring-like region with high-luminance and a plurality of bright spots in the ring-like region are observed. It is therefore found from the electron diffraction pattern that the crystal structure of the CAC-OS includes an nc (nano-crystal) structure with no alignment in a plan-view direction and a cross-sectional direction.

Moreover, for example, it can be confirmed by EDX mapping obtained using energy dispersive X-ray spectroscopy (EDX) that the CAC-OS in the In—Ga—Zn oxide has a composition in which regions where GaOX3is a main component and regions where InX2ZnY2OZ2or InOX1is a main component are unevenly distributed and mixed.

The CAC-OS has a composition different from that of an IGZO compound in which metal elements are evenly distributed, and has characteristics different from those of the IGZO compound. That is, the CAC-OS has a composition in which regions where GaOX3or the like is a main component and regions where InX2ZnY2OZ2or InOX1is a main component are phase-separated from each other, and the regions including the respective elements as the main components form a mosaic pattern.

Here, a region where InX2ZnY2OZ2or InOX1is a main component is a region whose conductivity is higher than that of a region where GaOX3or the like is a main component. In other words, when carriers flow through regions where InX2ZnY2OZ2or InOX1is a main component, the conductivity of a metal oxide is exhibited. Accordingly, when the regions where InX2ZnY2OZ2or InOX1is a main component are distributed like a cloud in a metal oxide, high field-effect mobility (μ) can be achieved.

In contrast, a region where GaOX3or the like is a main component is a region whose insulating property is higher than that of a region where InX2ZnY2OZ2or InOX1is a main component. In other words, when regions where GaOX3or the like is a main component are distributed in a metal oxide, leakage current can be suppressed and favorable switching operation can be achieved.

Accordingly, when the CAC-OS is used for a semiconductor element, the insulating property derived from GaOX3or the like and the conductivity derived from InX2ZnY2OZ2or InOX1complement each other, so that high on-state current (Ion) and high field-effect mobility (μ) can be achieved.

In addition, a semiconductor element using the CAC-OS has high reliability. Thus, the CAC-OS is suitable for a variety of semiconductor devices typified by a display.

Since a transistor including the CAC-OS in a semiconductor layer has high field-effect mobility and high drive capability, the use of the transistor in a driver circuit, a typical example of which is a scan line driver circuit that generates a gate signal, can provide a display device with a narrow bezel width (also referred to a narrow bezel). Furthermore, with the use of the transistor in a signal line driver circuit that is included in a display device (particularly in a demultiplexer connected to an output terminal of a shift register included in a signal line driver circuit), a display device to which a small number of wirings are connected can be provided.

Furthermore, unlike a transistor including low-temperature polysilicon, the transistor including the CAC-OS in the semiconductor layer does not need a laser crystallization step. Thus, the manufacturing cost of a display device can be reduced even when the display device is formed using a large area substrate. In addition, the transistor including the CAC-OS in the semiconductor layer is preferably used for a driver circuit and a display portion in a large display device having high resolution such as ultra-high definition (“4K resolution,” “4K2K,” and “4K”) or super high definition (“8K resolution,” “8K4K,” and “8K”) because writing can be performed in a short time and display defects can be reduced.

Alternatively, silicon may be used for a semiconductor in which a channel of a transistor is formed. Although amorphous silicon may be used as silicon, silicon having crystallinity is particularly preferably used. For example, microcrystalline silicon, polycrystalline silicon, single crystal silicon, or the like is preferably used. In particular, polycrystalline silicon can be formed at a temperature lower than that for single crystal silicon and has higher field-effect mobility and higher reliability than amorphous silicon.

Examples of materials that can be used for conductive layers of a variety of wirings and electrodes and the like included in the display device in addition to a gate, a source, and a drain of a transistor include metals such as aluminum, titanium, chromium, nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, and tungsten and an alloy containing such a metal as its main component. Alternatively, a single layer or a stacked-layer structure including a film containing these materials can be used. For example, a single-layer structure of an aluminum film containing silicon, a two-layer structure in which an aluminum film is stacked over a titanium film, a two-layer structure in which an aluminum film is stacked over a tungsten film, a two-layer structure in which a copper film is stacked over a copper-magnesium-aluminum alloy film, a two-layer structure in which a copper film is stacked over a titanium film, a two-layer structure in which a copper film is stacked over a tungsten film, a three-layer structure in which an aluminum film or a copper film is stacked over a titanium film or a titanium nitride film and a titanium film or a titanium nitride film is formed thereover, a three-layer structure in which an aluminum film or a copper film is stacked over a molybdenum film or a molybdenum nitride film and a molybdenum film or a molybdenum nitride film is formed thereover, and the like can be given. Note that an oxide such as indium oxide, tin oxide, or zinc oxide may be used. In addition, copper containing manganese is preferably used because controllability of a shape by etching is increased.

Examples of an insulating material that can be used for each insulating layer include, in addition to a resin such as acrylic or epoxy and a resin having a siloxane bond, an inorganic insulating material such as silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, or aluminum oxide.

The light-emitting device is preferably provided between a pair of insulating films with low water permeability. In that case, impurities such as water can be inhibited from entering the light-emitting device, and a decrease in the reliability of the device can be inhibited.

Examples of the insulating film with low water permeability include a film containing nitrogen and silicon, such as a silicon nitride film and a silicon nitride oxide film, and a film containing nitrogen and aluminum, such as an aluminum nitride film. Alternatively, a silicon oxide film, a silicon oxynitride film, an aluminum oxide film, or the like may be used.

For example, the moisture vapor transmission rate of the insulating film with low water permeability is lower than or equal to 1×10−5[g/(m2·day)], preferably lower than or equal to 1×10−6[g/(m2·day)], further preferably lower than or equal to 1×10−7[g/(m2·day)], still further preferably lower than or equal to 1×10−8[g/(m2·day)].

The above is the description of the components.

At least part of the structure examples, the drawings corresponding thereto, and the like exemplified in this embodiment can be implemented in combination with the other structure examples, the other drawings, and the like as appropriate.

In this embodiment, structure examples of a display device are described with reference toFIG.23A,FIG.23B, andFIG.23C.

The display device illustrated inFIG.23Aincludes a pixel portion502, a driver circuit portion504, protection circuits506, and a terminal portion507. Note that a structure in which the protection circuits506are not provided may be employed.

The pixel portion502includes a plurality of pixel circuits501that drive a plurality of display devices arranged in X rows and Y columns (X and Y each independently represent a natural number of 2 or more).

The driver circuit portion504includes driver circuits such as a gate driver504athat outputs scan signals to gate lines GL_1to GL_X and a source driver504bthat supplies data signals to data lines DL_1to DL_Y. The gate driver504aincludes at least a shift register. In addition, the source driver504bis formed using a plurality of analog switches, for example. Alternatively, the source driver504bmay be formed using a shift register or the like.

The terminal portion507refers to a portion provided with terminals for inputting power, control signals, image signals, and the like to the display device from external circuits.

The protection circuit506is a circuit that, when a potential out of a certain range is applied to a wiring to which the protection circuit506is connected, establishes continuity between the wiring and another wiring. The protection circuit506illustrated inFIG.23Ais connected to a variety of wirings such as gate lines GL that are wirings between the gate driver504aand the pixel circuits501and data lines DL that are wirings between the source driver504band the pixel circuits501, for example. Note that the protection circuits506are hatched inFIG.23Ato distinguish the protection circuits506from the pixel circuits501.

The gate driver504aand the source driver504bmay each be provided over the same substrate as the pixel portion502, or a substrate over which a gate driver circuit or a source driver circuit is separately formed (e.g., a driver circuit board formed using a single crystal semiconductor film or a polycrystalline semiconductor film) may be mounted on the substrate by COF, TCP (Tape Carrier Package), COG (Chip On Glass), or the like.

The plurality of pixel circuits501illustrated inFIG.23Acan have a structure illustrated inFIG.23BorFIG.23C, for example.

The pixel circuit501illustrated inFIG.23Bincludes a liquid crystal device570, a transistor550, and a capacitor560. In addition, the data line DL_n, the gate line GL_m, a potential supply line VL, and the like are connected to the pixel circuit501.

The potential of one of a pair of electrodes of the liquid crystal device570is set as appropriate in accordance with the specifications of the pixel circuit501. The alignment state of the liquid crystal device570is set depending on written data. Note that a common potential may be applied to one of the pair of electrodes of the liquid crystal device570included in each of the plurality of pixel circuits501. Alternatively, a different potential may be applied to one of the pair of electrodes of the liquid crystal device570of the pixel circuit501in each row.

The pixel circuit501illustrated inFIG.23Cincludes transistors552and554, a capacitor562, and a light-emitting device572. Furthermore, the data line DL_n, the gate line GL_m, a potential supply line VL_a, a potential supply line VL_b, and the like are connected to the pixel circuit501.

Note that a high power supply potential VDD is applied to one of the potential supply line VL_a and the potential supply line VL_b, and a low power supply potential VSS is applied to the other of the potential supply line VL_a and the potential supply line VL_b. Current flowing through the light-emitting device572is controlled in accordance with a potential applied to a gate of the transistor554, so that the luminance of light emitted from the light-emitting device572is controlled.

At least part of the structure examples, the drawings corresponding thereto, and the like exemplified in this embodiment can be implemented in combination with the other structure examples, the other drawings, and the like as appropriate.

A pixel circuit including a memory for correcting gray levels displayed by pixels and a display device including the pixel circuit will be described below.

FIG.24Aillustrates a circuit diagram of a pixel circuit400. The pixel circuit400includes a transistor M1, a transistor M2, a capacitor C1, and a circuit401. In addition, a wiring S1, a wiring S2, a wiring G1, and a wiring G2are connected to the pixel circuit400.

In the transistor M1, a gate is connected to the wiring G1, one of a source and a drain is connected to the wiring S1, and the other of the source and the drain is connected to one electrode of the capacitor C1. In the transistor M2, a gate is connected to the wiring G2, one of a source and a drain is connected to the wiring S2, and the other of the source and the drain is connected to the other electrode of the capacitor C1and the circuit401.

The circuit401is a circuit including at least one display device. A variety of devices can be used as the display device, and typically, a light-emitting device such as an organic EL device or an LED device, a liquid crystal device, a MEMS (Micro Electro Mechanical Systems) device, or the like can be employed.

A node connecting the transistor M1and the capacitor C1is denoted as a node N1, and a node connecting the transistor M2and the circuit401is denoted as a node N2.

In the pixel circuit400, the potential of the node N1can be retained when the transistor M1is set in an off state. In addition, the potential of the node N2can be retained when the transistor M2is set in an off state. Furthermore, when a predetermined potential is written to the node N1through the transistor M1with the transistor M2being in an off state, the potential of the node N2can be changed in accordance with displacement in the potential of the node N1owing to capacitive coupling through the capacitor C1.

Here, the transistor employing an oxide semiconductor, which is illustrated in Embodiment 2, can be used as one or both of the transistor M1and the transistor M2. Accordingly, owing to extremely low off-state current, the potentials of the node N1and the node N2can be retained over a long period. Note that in the case where the period in which the potential of each node is retained is short (specifically, the case where frame frequency is higher than or equal to 30 Hz, for example), a transistor employing a semiconductor such as silicon may be used.

Driving Method Example

Next, an example of a method for operating the pixel circuit400is described usingFIG.24B.FIG.24Bis a timing chart of the operation of the pixel circuit400. Note that for simplification of the description, the influence of various kinds of resistance such as wiring resistance, parasitic capacitance of a transistor, a wiring, or the like, the threshold voltage of the transistor, and the like is not taken into account here.

In the operation shown inFIG.24B, one frame period is divided into a period T1and a period T2. The period T1is a period in which a potential is written to the node N2, and the period T2is a period in which a potential is written to the node N1.

In the period T1, a potential for setting the transistor in an on state is applied to both the wiring G1and the wiring G2. In addition, a potential Vrefthat is a fixed potential is supplied to the wiring S1, and a first data potential Vwis supplied to the wiring S2.

The potential Vrefis applied from the wiring S1to the node N1through the transistor M1. Furthermore, the first data potential Vwis applied from the wiring S2to the node N2through the transistor M2. Accordingly, a potential difference Vw−Vrefis retained in the capacitor C1.

Next, in the period T2, a potential for setting the transistor M1in an on state is applied to the wiring G1, and a potential for setting the transistor M2in an off state is applied to the wiring G2. In addition, a second data potential Vdatais supplied to the wiring S1. The wiring S2may be supplied with a predetermined constant potential or brought into a floating state.

The second data potential Vdatais applied from the wiring S1to the node N1through the transistor M1. In that case, capacitive coupling due to the capacitor C1changes the potential of the node N2in accordance with the second data potential Vdataby a potential dV. That is, a potential that is the sum of the first data potential Vwand the potential dV is input to the circuit401. Note that although the potential dV is shown as a positive value inFIG.24B, the potential dV may be a negative value. That is, the second data potential Vdatamay be lower than the potential Vref.

Here, the potential dV is roughly determined by the capacitance value of the capacitor C1and the capacitance value of the circuit401. In the case where the capacitance value of the capacitor C1is sufficiently larger than the capacitance value of the circuit401, the potential dV is a potential close to the second data potential Vdata.

As described above, a potential to be supplied to the circuit401including the display device can be generated by a combination of two kinds of data signals in the pixel circuit400, so that gray levels can be corrected in the pixel circuit400.

In addition, in the pixel circuit400, it is also possible to generate a potential exceeding the maximum potential that can be supplied to the wiring S1and the wiring S2. For example, in the case where a light-emitting device is used, high-dynamic range (HDR) display or the like can be performed. Furthermore, in the case where a liquid crystal device is used, overdriving or the like can be achieved.

Application Example

Example Using Liquid Crystal Device

A pixel circuit400LC illustrated inFIG.24Cincludes a circuit401LC. The circuit401LC includes a liquid crystal device LC and a capacitor C2.

In the liquid crystal device LC, one electrode is connected to the node N2and one electrode of the capacitor C2, and the other electrode is connected to a wiring supplied with a potential Vcom2. The other electrode of the capacitor C2is connected to a wiring supplied with a potential Vcom1.

The capacitor C2functions as a storage capacitor. Note that the capacitor C2can be omitted when not needed.

In the pixel circuit400LC, high voltage can be supplied to the liquid crystal device LC; thus, high-speed display can be performed by overdriving or a liquid crystal material with high drive voltage can be employed, for example. In addition, gray levels can also be corrected in accordance with operating temperature, the degradation state of the liquid crystal device LC, or the like by supply of a correction signal to the wiring S1or the wiring S2.

Example Using Light-Emitting Device

A pixel circuit400EL illustrated inFIG.24Dincludes a circuit401EL. The circuit401EL includes a light-emitting device EL, a transistor M3, and the capacitor C2.

In the transistor M3, a gate is connected to the node N2and one electrode of the capacitor C2, one of a source and a drain is connected to a wiring supplied with a potential VH, and the other of the source and the drain is connected to one electrode of the light-emitting device EL. The other electrode of the capacitor C2is connected to a wiring supplied with a potential Vcom. The other electrode of the light-emitting device EL is connected to a wiring supplied with a potential VL.

The transistor M3has a function of controlling current to be supplied to the light-emitting device EL. The capacitor C2functions as a storage capacitor. The capacitor C2can be omitted when not needed.

Note that although a structure in which the anode side of the light-emitting device EL is connected to the transistor M3is described here, the transistor M3may be connected to the cathode side. In that case, the values of the potential VHand the potential VLcan be changed as appropriate.

In the pixel circuit400EL, a large amount of current can flow through the light-emitting device EL when a high potential is applied to the gate of the transistor M3, which enables HDR display or the like, for example. Moreover, a variation in electrical characteristics of the transistor M3and the light-emitting device EL can also be corrected by supply of a correction signal to the wiring S1or the wiring S2.

Note that the structure is not limited to the circuits illustrated inFIG.24CandFIG.24D, and a structure to which a transistor, a capacitor, and the like are further added may be employed.

In this embodiment, structure examples of a pixel of a display panel according to one embodiment of the present invention will be described below.

Structure examples of a pixel300are illustrated inFIG.25AtoFIG.25E.

The pixel300includes a plurality of pixels301. The plurality of pixels301each function as a subpixel. One pixel300is formed of the plurality of pixels301exhibiting different colors, and thus full-color display can be achieved in a display portion.

The pixels300illustrated inFIG.25AandFIG.25Beach include three subpixels. The combination of colors exhibited by the pixels301included in the pixel300illustrated inFIG.25Ais red (R), green (G), and blue (B). The combination of colors exhibited by the pixels301included in the pixel300illustrated inFIG.25Bis cyan (C), magenta (M), and yellow (Y).

The pixels300illustrated inFIG.25CtoFIG.25Eeach include four subpixels. The combination of colors exhibited by the pixels301included in the pixel300illustrated inFIG.25Cis red (R), green (G), blue (B), and white (W). The use of the subpixel that exhibits white can increase the luminance of the display portion. The combination of colors exhibited by the pixels301included in the pixel300illustrated inFIG.25Dis red (R), green (G), blue (B), and yellow (Y). The combination of colors exhibited by the pixels301included in the pixel300illustrated inFIG.25Eis cyan (C), magenta (M), yellow (Y), and white (W).

When subpixels that exhibit red, green, blue, cyan, magenta, yellow, and the like are combined as appropriate with more subpixels functioning as one pixel, the reproducibility of halftones can be increased. Thus, display quality can be increased.

The display device according to one embodiment of the present invention can reproduce the color gamut of various standards. For example, the display device according to one embodiment of the present invention can reproduce the color gamut of the PAL (Phase Alternating Line) standard and the NTSC (National Television System Committee) standard used for TV broadcasting; the sRGB (standard RGB) standard and the Adobe RGB standard widely used for display devices used in electronic devices such as personal computers, digital cameras, and printers; the ITU-R BT.709 (International Telecommunication Union Radiocommunication Sector Broadcasting Service (Television) 709) standard used for HDTV (High Definition Television, also referred to Hi-Vision); the DCI-P3 (Digital Cinema Initiatives P3) standard used for digital cinema projection; the ITU-R BT.2020 (REC.2020 (Recommendation 2020)) standard used for UHDTV (Ultra High Definition Television, also referred to as Super Hi-Vision); and the like.

In addition, by arranging the pixels300in a matrix of 1920×1080, a display device that can perform full-color display with a resolution of what is called full high definition (also referred to as “2K resolution,” “2K1K,” “2K,” or the like) can be achieved. Alternatively, for example, by arranging the pixels300in a matrix of 3840×2160, a display device that can perform full-color display with a resolution of what is called ultra high definition (also referred to as “4K resolution,” “4K2K,” “4K,” or the like) can be achieved. Alternatively, for example, by arranging the pixels300in a matrix of 7680×4320, a display device that can perform full-color display with a resolution of what is called super high definition (also referred to as “8K resolution,” “8K4K,” “8K,” or the like) can be achieved. By increasing the number of pixels300, a display device that can perform full-color display with 16K or 32K resolution can also be achieved.

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