Patent Description:
A display device may display images to provide information to users. Recently, a flexible display device that can be deformed into various shapes has been developed. Unlike a flat display device, the flexible display device may be foldable, rollable or bendable like a piece of paper. The flexible display device may be easily portable, and may improve convenience of users. <CIT> and <CIT>are directed to foldable display devices.

Applicant realized that undesired deformations due to restoring forces can occur in the flexible portion of a foldable display device. Foldable display devices constructed according to the principles and exemplary implementations of the invention, and methods of operating the same, are capable of preventing a foldable display module from being deformed into undesirable configurations. For example, a plate can rotatably support the display surface of the display device in various folded and unfolded configurations to prevent the deformation of a folded portion in certain configurations.

According to one aspect of the invention, a foldable display device, includes: a foldable display module including a first non-folding portion, a second non-folding portion, and a folding portion disposed between the first non-folding portion and the second non-folding portion; a first support member disposed on the first non-folding portion supporting the first non-folding portion; a second support member disposed on the second non-folding portion supporting the second non-folding portion; and a third member rotatably coupled to the first support member. The first support member includes a first plate, the second support member includes a second plate, the third member includes a first rotatable plate, wherein a first end of the first rotatable plate is rotatably connected to the first plate and a second end of the first rotatable plate is a free end, so that the flexible display device is capable of folding in an out-folded mode. In an out-folded mode, the folding portion is folded such that a non-display surface of the first non-folding portion and a non-display surface of the second non-folding portion face each other.

In an un-folded mode in which the folding portion is not folded, the first rotatable plate may be generally parallel to the first plate.

In the un-folded mode, the first rotatable plate may support the folding portion.

In an out-folded mode, the first rotatable plate may not generally be parallel to the first plate.

In the out-folded mode, the first rotatable plate may be generally perpendicular to the first plate.

In the out-folded mode, the first rotatable plate may not support a main portion of the folding portion. The main portion of the folding portion may cover an area, which is at least the half area of the folding portion.

In an inwardly folded mode when the folding portion is folded such that a display surface of the first non-folding portion and a display surface of the second non-folding portion face each other, the first rotatable plate may be generally parallel to the first plate.

In the inwardly folded mode, the first rotatable plate may support a main portion of the folding portion. The main portion of the folding portion may cover an area,
which is at least the half area of the folding portion.

The folding portion may include a first region adjacent to the first non-folding portion and a second region adjacent to the second non-folding portion, and, in the inwardly folded mode, the first region may not be folded and the second region may be folded.

The first regions may include the substantial portion of the folding portion,
and in the inwardly folded mode, the first rotatable plate may support the first region of the folding portion.

The foldable display module may be foldable in an out-folded mode when the folding portion is folded around a first folding axis such that a non-display surface of the first non-folding portion and a non-display surface of the second non-folding portion face each other and in an inwardly folded mode when the folding portion is folded around a second folding axis such that a display surface of the first non-folding portion and a display surface of the second non-folding portion may face each other.

A radius of curvature of the folding portion in the inwardly folded mode may be less than a radius of curvature of the folding portion in the out-folded mode.

The shortest distance from the first folding axis to the first non-folding portion may be substantially the same as the shortest distance from the first folding axis to the second non-folding portion.

The shortest distance from the second folding axis to the first non-folding portion may be greater than the shortest distance from the second folding axis to the second non-folding portion.

The third member may be coupled to the first support member through a gear portion.

A fourth member may be rotatably connected to the second support member.

In an un-folded mode when the folding portion is not folded, the third member may be generally parallel to the first support member, and the fourth member may be generally parallel to the second support member.

In the un-folded mode, the third member and the fourth member may support the folding portion.

In an out-folded mode when the folding portion is folded such that a non-display surface of the first non-folding portion and a non-display surface of the second non-folding portion face each other, the third member may be not generally parallel to the first support member, and the fourth member may be not generally parallel to the second support member.

In the out-folded mode, the first support member may be generally perpendicular to the first support member, and the second support member may be generally perpendicular to the second support member.

In the out-folded mode, the third member and the fourth member may not substantially support the folding portion.

In an inwardly folded mode when the folding portion is folded such that a display surface of the first non-folding portion and a display surface of the second non-folding portion face each other, the third member may be generally parallel to the first support member, and the fourth member may be generally parallel to the second support member.

The folding portion may include a first region adjacent to the first non-folding portion, a second region adjacent to the second non-folding portion, and a third region between the first region and the second region, and wherein, in the inwardly folded mode, the first region and the second region may be not folded and the third region may be folded.

In the inwardly folded mode, the third member may support the first region of the folding portion, and the fourth member may support the second region of the folding portion.

The foldable display module may be foldable in an out-folded mode when the folding portion is folded around a first folding axis such that a non-display surface of the first non-folding portion and a non-display surface of the second non-folding portion may face each other and in an inwardly folded mode when the folding portion is folded around a second folding axis such that a display surface of the first non-folding portion and a display surface of the second non-folding portion may face each other.

The shortest distance from the first folding axis to the first non-folding portion may be substantially the same as the shortest distance from the first folding axis to the second non-folding portion. The shortest distance from the second folding axis to the first non-folding portion may be substantially the same as the shortest distance from the second folding axis to the second non-folding portion.

The third member may include a first rotatable plate connected to the first support member through a first gear portion, and the fourth member may include a second rotatable plate connected to the second support member through a second gear portion.

According to another aspect of the invention, a method of operating a foldable display device having a foldable display module including a first non-folding portion, a second non-folding portion and a folding portion between the first non-folding portion and the second non-folding portion, a first support member supporting the first non-folding portion, a second support member supporting the second non-folding portion, and a third member rotatably connected to at least one of the first support member and the second support member, the method includes the steps of: folding the foldable display module; and rotating the third member.

The step of folding the foldable display module by rotating the third member to outwardly fold the folding portion such that a non-display surface of the first non-folding portion and a non-display surface of the second non-folding portion may face each other.

The step of folding the foldable display module by rotating the third member to inwardly folding the folding portion such that a display surface of the first non-folding portion and a display surface of the second non-folding portion may face each other.

<FIG> is an exploded perspective view illustrating an exemplary embodiment of a foldable display device constructed according to principles of the invention. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in an unfolded position. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in an outwardly folded position. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in an inwardly folded position.

Referring to <FIG>, <FIG>, <FIG> and <FIG>, a flexible or foldable display device <NUM> according to an exemplary embodiment may include a foldable display module <NUM>, a first support member, which may be in the form of a plate <NUM>, a second support member, which may be in the form of a plate <NUM>, a third member, which may be in the form of a rotating plate <NUM>, a first gear portion <NUM>, and a jig <NUM>.

The foldable display module <NUM> includes a first non-folding portion <NUM>, a second non-folding portion <NUM>, and a folding portion <NUM>. The folding portion <NUM> is disposed between the first non-folding portion <NUM> and the second non-folding portion <NUM>. The first non-folding portion <NUM> and the second non-folding portion <NUM> are spaced apart from each other with the folding portion <NUM> therebetween. The first non-folding portion <NUM> and the second non-folding portion <NUM> may be substantially flat, unfolded portions in the foldable display module <NUM>. The folding portion <NUM> may be the portion that can be bent, folded, and/or displaced relative to the other portions of the foldable display module <NUM>.

The foldable display module <NUM> may have a display surface <NUM> and a non-display surface <NUM>. The foldable display module <NUM> may display an image toward the display surface <NUM>. The non-display surface <NUM> may be opposite to the display surface <NUM>.

The first plate <NUM> is disposed on the first non-folding portion <NUM> of the foldable display module <NUM> and supports the first non-folding portion <NUM>. The first plate <NUM> is disposed on the non-display surface <NUM> of the first non-folding portion <NUM>. In an exemplary embodiment, an adhesive layer may be interposed between the first non-folding portion <NUM> of the foldable display module <NUM> and the first plate <NUM> so that the first plate <NUM> may be attached on the non-display surface <NUM> of the first non-folding portion <NUM>. For example, the adhesive layer may be an optically clear adhesive (OCA), a pressure sensitive adhesive (PSA), or the like.

The first plate <NUM> may have the shape generally the same as that of the first non-folding portion <NUM> of the foldable display module <NUM> in a plan view, and may substantially overlap the first non-folding portion <NUM>. For example, the area of the first plate <NUM> may be substantially equal to that of the first non-folding portion <NUM>. The first plate <NUM> may include any material capable of rigidly supporting the non-folding portion <NUM>, such as metal, plastic, or the like. For example, the metal may include at least one alloy or any combination thereof that may be generically known as 64FeNi and sold under the trade designation INVAR® by Aperam Alloys Imphy Joint Stock Company, of Imphy, France, an iron based nobinite alloy, or a stainless steel alloy.

The second plate <NUM> is disposed on the second non-folding portion <NUM> of the foldable display module <NUM> and supports the second non-folding portion <NUM>. The second plate <NUM> is disposed on the non-display surface <NUM> of the second non-folding portion <NUM>. In an exemplary embodiment, an adhesive layer may be interposed between the second non-folding portion <NUM> of the foldable display module <NUM> and the second plate <NUM> so that the second plate <NUM> may be attached on a non-display surface <NUM>, which may be the same or similar to the non-display surface <NUM>, of the second non-folding portion <NUM>. For example, the adhesive layer may be an optically clear adhesive, a pressure sensitive adhesive, or the like.

The second plate <NUM> may have substantially the shape the same as that of the second non-folding portion <NUM> of the foldable display module <NUM> in a plan view, and may substantially overlap the second non-folding portion <NUM>. For example, the area of the second plate <NUM> may be substantially equal to that of the second non-folding portion <NUM>. The second plate <NUM> may include any material capable of rigidly supporting the non-folding portion <NUM>, such as metal, plastic, or the like. For example, the metal may be, independently, an alloy as described above for the first plate <NUM>. In the illustrated exemplary embodiment, the second plate <NUM> may include a material substantially the same as that of the first plate <NUM>.

The first rotating plate <NUM> is rotatably connected to the first plate <NUM>. The first rotating plate <NUM> may be rotatably connected to the first plate <NUM> through the first gear portion <NUM>. The first gear portion <NUM> may include a first gear <NUM> and a second gear <NUM>. The first gear <NUM> may be rotatably supported in and disposed on the side <NUM> of the first plate <NUM>, and the second gear <NUM> may be fixedly supported in and disposed on the side <NUM> of the first rotating plate <NUM>. The first gear <NUM> and the second gear <NUM> may be engaged with each other for supporting the first rotating plate <NUM> for rotation relative to the first plate <NUM>, and the direction of rotation of the first gear <NUM> and the direction of rotation of the second gear <NUM> may be opposite to each other, e.g., one may be clockwise and the other counter-clockwise. The first rotating plate <NUM> may be rotated with respect to the first plate <NUM> by the rotation of the first gear <NUM> and the second gear <NUM> by a user moving the first rotating plate <NUM>, e.g., counter-clockwise as shown in <FIG>.

The area of the first rotating plate <NUM> may be less than the area of the folding portion <NUM>. For example, the width of the first rotating plate <NUM> in an X-axis direction may be less than the width of the folding portion <NUM> in the X-axis direction. For example, the width of the first rotating plate <NUM> in the X-axis direction may be about <NUM>% to about <NUM>% of the width of the folding portion <NUM> in the X-axis direction. The first rotating plate <NUM> may include metal, plastic, or the like. For example, the metal may be, independently, an alloy as described above for the first plate <NUM>. In an exemplary embodiment, the first rotating plate <NUM> may include a material substantially the same as those of the first plate <NUM> and/or the second plate <NUM>.

The jig <NUM> may be disposed on the first plate <NUM> and the second plate <NUM>. The jig <NUM> may be disposed on the foldable display module <NUM> with the first plate <NUM> and the second plate <NUM> therebetween. In other words, the first plate <NUM> and the second plate <NUM> may be disposed between the foldable display module <NUM> and the jig <NUM>. The jig <NUM> may support the foldable display module <NUM>, the first plate <NUM>, and the second plate <NUM>.

The jig <NUM> may include a first jig <NUM> and a second jig <NUM>. The first jig <NUM> may be disposed on the first plate <NUM>, and the second jig <NUM> may be disposed on the second plate <NUM>. In the illustrated embodiment, the jig <NUM> may include a hinge portion disposed between the first jig <NUM> and the second jig <NUM>. The first jig <NUM> and the second jig <NUM> may be rotatably connected to each other through the hinge portion.

As illustrated in <FIG>, the foldable display module <NUM> may be unfolded. In the illustrated exemplary embodiment, the folding portion <NUM> of the foldable display module <NUM> may not be folded, and the display surface <NUM> of the first non-folding portion <NUM> and the display surface <NUM> of the second non-folding portion <NUM> of the foldable display module <NUM> may face the same direction, for example, a Z-axis direction. Hereinafter, a state in which the foldable display module <NUM> is unfolded is referred as an un-folded mode.

In the un-folded mode, the first rotating plate <NUM> may be disposed on the folding portion <NUM> and support the folding portion <NUM>. In this case, the first rotating plate <NUM> may be disposed on the non-display surface <NUM> of the folding portion <NUM>.

As illustrated in <FIG>, the foldable display module <NUM> may be outwardly folded with respect to a first folding axis FX1. In the illustrated exemplary embodiment, the folding portion <NUM> of the foldable display module <NUM> is folded such that the non-display surface <NUM> of the first non-folding portion <NUM> and the non-display surface <NUM> of the second non-folding portion <NUM> of the foldable display module <NUM> may face each other. For example, the display surface <NUM> of the first non-folding portion <NUM> and the display surface <NUM> of the second non-folding portion <NUM> face the outside of the foldable display device <NUM>. Hereinafter, the position in which the foldable display module <NUM> is outwardly folded is referred as an out-folded mode.

In the out-folded mode, the folding portion <NUM> may be folded with a first radius of curvature <NUM>. For example, the first radius of curvature <NUM> may be about <NUM> or more. In the out-folded mode, the folding portion <NUM> may be folded with a relatively large curvature in consideration of the thickness of the first plate <NUM>, the thickness of the second plate <NUM>, the thickness of the first jig <NUM>, and the thickness of the second jig <NUM>.

In the out-folded mode, the folding portion <NUM> may be symmetrically folded with respect to the first folding axis FX1 in a Y-axis direction. In other words, in the out-folded mode, the folding portion <NUM> may be folded such that the first non-folding portion <NUM> and the second non-folding portion <NUM> are symmetrically located with respect to the first folding axis FX1. For example, the shortest distance <NUM> from the first folding axis FX1 to the first non-folding portion <NUM> may be generally equal to the shortest distance <NUM> from the first folding axis FX1 to the second non-folding portion <NUM>. A distance in the X-axis direction from the first folding axis FX1 to the first non-folding portion <NUM> may be generally equal to a distance in the X-axis direction from the first folding axis FX1 to the second non-folding portion <NUM>, and a distance <NUM> in the Z-axis direction from the first folding axis FX1 to the first non-folding portion <NUM> may be generally equal to a distance <NUM> in the Z-axis direction from the first folding axis FX1 to the second non-folding portion <NUM>.

In the out-folded mode, the first rotating plate <NUM> may not be parallel to the first plate <NUM>. In this case, the first rotating plate <NUM> may not fully support the folding portion <NUM>. In the illustrated exemplary embodiment, the first rotating plate <NUM> may be generally perpendicular to the first plate <NUM>. For example, the first plate <NUM> may extend along the X-axis direction, and the first rotating plate <NUM> may extend along the Z-axis direction, in which case the rotating plate <NUM> does not support a substantial portion of the folding portion <NUM>.

As illustrated in <FIG>, the foldable display module <NUM> may be in-folded with respect to a second folding axis FX2. In the illustrated exemplary embodiment, the folding portion <NUM> of the foldable display module <NUM> may be folded such that the display surface <NUM> of the first non-folding portion <NUM> and the display surface <NUM> of the second non-folding portion <NUM> of the foldable display module <NUM> may face each other. For example, the display surface <NUM> of the first non-folding portion <NUM> and the display surface <NUM> of the second non-folding portion <NUM> may face the inside of the foldable display device <NUM>. Hereinafter, the position in which the foldable display module <NUM> is in-folded is referred as an in-folded mode.

In the in-folded mode, the folding portion <NUM> may be folded with having a second radius of curvature <NUM>. For example, the second radius of curvature <NUM> may be about <NUM> or less. In the in-folded mode, the folding portion <NUM> may be folded with a relatively small curvature. Accordingly, the radius of curvature <NUM> of the folding portion <NUM> in the in-folded mode may be less than the radius of curvature <NUM> of the folding portion <NUM> in the out-folded mode. In other words, the second radius of curvature <NUM> of the folding portion <NUM> may be less than the first radius of curvature <NUM> of the folding portion <NUM>.

The folding portion <NUM> may include a first region <NUM> adjacent to the first non-folding portion <NUM> and a second region <NUM> adjacent to the second non-folding portion <NUM>. As described above, because the radius of curvature <NUM> of the folding portion <NUM> in the in-folded mode is less than the radius of curvature <NUM> of the folding portion <NUM> in the out-folded mode, the folding portion <NUM> may include an unfolded region and a folded region in the in-folded mode. In the illustrated exemplary embodiment, the first region <NUM> of the folding portion <NUM> may not be folded, and the second region <NUM> of the folding portion <NUM> may be folded. In this case, the first region <NUM> may be substantially planar.

In the in-folded mode, the folding portion <NUM> may be asymmetrically folded with respect to the second folding axis FX2 in a Y-axis direction. In other words, in the in-folded mode, the folding portion <NUM> may be folded such that the first non-folding portion <NUM> and the second non-folding portion <NUM> are asymmetrically located with respect to the second folding axis FX2. For example, the shortest distance <NUM> from the second folding axis FX2 to the first non-folding portion <NUM> may be greater than the shortest distance <NUM> from the second folding axis FX2 to the second non-folding portion <NUM>. The distance in the X-axis direction from the second folding axis FX2 to the first non-folding portion <NUM> may be greater than the distance in the X-axis direction from the second folding axis FX2 to the second non-folding portion <NUM>, and the distance <NUM> in the Z-axis direction from the second folding axis FX2 to the first non-folding portion <NUM> may be substantially equal to a distance <NUM> in the Z-axis direction from the second folding axis FX2 to the second non-folding portion <NUM>. In the in-folded mode, the folding portion <NUM> may be asymmetrically folded due to the fact that the first region <NUM> of the folding portion <NUM> is not folded and only the second region <NUM> of the folding portion <NUM> is folded.

In the in-folded mode, the first rotating plate <NUM> may be substantially parallel to the first plate <NUM>. The first rotating plate <NUM> may be disposed underneath a part of the folding portion <NUM>, and support the part of the folding portion <NUM>. In this case, the first rotating plate <NUM> may be disposed on the non-display surface <NUM> of the part of the folding portion <NUM>. For example, the first rotating plate <NUM> may be disposed on the first region <NUM> of the folding portion <NUM> and support the first region <NUM> of the folding portion <NUM>. In other words, the first rotating plate <NUM> may be disposed on an unfolded part of the folding portion <NUM> and support the unfolded part in the in-folded mode.

<FIG> is a cross-sectional view illustrating a comparative embodiment of a foldable display device in an inwardly folded position. Referring to <FIG>, a foldable display device according to a comparative example may not include a rotating plate. When the foldable display device according to the comparative example is in-folded, parts of the folding portion <NUM> that are respectively adjacent to the first non-folding portion <NUM> and the second non-folding portion <NUM> may not be folded, and only a part of the folding portion <NUM> that is spaced apart from the first non-folding portion <NUM> and the second non-folding portion <NUM> may be folded ideally. However, in the in-folded mode, the folding portion <NUM> may have a relatively small radius of curvature, and a restoring force FR may be applied to the folding portion <NUM> in the Z-axis direction and the Z-axis direction in response to the inward folding of the folding portion <NUM>. Accordingly, the shape of the folding portion <NUM> may be deformed and a foldable display module <NUM> may have an undesirable dumbbell shape.

As described above, the foldable display device <NUM> according to the illustrated exemplary embodiment may include the first rotating plate <NUM> rotatably connected to the first plate <NUM>. When the foldable display device <NUM> according to the illustrated exemplary embodiment is in-folded, the first region <NUM> in the folding portion <NUM> adjacent to the first non-folding portion <NUM> may not be folded, and only the second region <NUM> in the folding portion <NUM> adjacent to the second non-folding portion <NUM> may be folded. Although restoring force is applied to the folding portion <NUM> in the Z-axis direction and the Z-axis direction in response to the inward folding of the folding portion <NUM>, the first rotating plate <NUM> may support the first region <NUM> of the folding portion <NUM>. Accordingly, the shape of the folding portion <NUM> may be maintained, and undesirable deformation of the foldable portion <NUM> due to the inwardly folding may be reduced or prevented.

<FIG> is a cross-sectional view illustrating an exemplary embodiment of the foldable display module of the foldable display device of <FIG>.

Referring to <FIG>, the foldable display module <NUM> may include a display panel <NUM>, a sensing layer <NUM>, a polarizing layer <NUM>, and a window <NUM>. As described above, because the foldable display module <NUM> may be outwardly folded or inwardly folded according to the folding of the folding portion <NUM>, the display panel <NUM>, the sensing layer <NUM>, the polarizing layer <NUM>, and the window <NUM> may have flexible characteristics.

The display panel <NUM> may include a plurality of pixels, and may generate an image formed by light emitted from each of the pixels. The display panel <NUM> may include a first surface and a second surface opposite to each other. For example, the first surface of the display panel <NUM> may be toward the Z-axis direction, and the second surface of the display panel <NUM> may be toward the Z-axis direction. The display panel <NUM> may display an image to the first surface, and the second surface of the display panel <NUM> may be the non-display surface <NUM> of the foldable display module <NUM>.

The sensing layer <NUM> may be disposed on the display panel <NUM>. The sensing layer <NUM> may sense an external input such as an external object contacting or approaching the sensing layer <NUM>. For example, the sensing layer <NUM> may sense the external input with a static capacitive method.

The polarizing layer <NUM> may be disposed on the sensing layer <NUM>. The polarizing layer <NUM> may reduce reflection of external light. For example, when the external light having passed through the polarizing layer <NUM> is reflected from below the polarizing layer <NUM> (e.g., the display panel <NUM>) and then passes through the polarizing layer <NUM> again, the phase of the reflected external light may be changed as the incoming external light passes through the polarizing layer <NUM> twice. As a result, the phase of reflected external light may be different from the phase of the incoming external light entering the polarizing layer <NUM> to the extent that a destructive interference occurs. Accordingly, the reflection of external light may be reduced to increase visibility.

The window <NUM> may be disposed on the polarizing layer <NUM>. The window <NUM> may protect the display panel <NUM>, the sensing layer <NUM>, and the polarizing layer <NUM> from external impact, and may provide the display surface <NUM> of the foldable display module <NUM>. In an exemplary embodiment, the window <NUM> may include glass, a polymer resin such as at least one of polycarbonate (PC), polymethyl methacrylate (PMMA), polyarylate (PAR), polyethersulfone (PES), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc., or the like.

<FIG> is a plan view illustrating an exemplary embodiment of a display panel of the foldable display module of <FIG>. <FIG> is a cross-sectional view taken along line I-I' of <FIG>. Referring to <FIG> and <FIG>, the display panel <NUM> includes a plurality of pixels, each of the pixels including a switching thin film transistor (TFT) T1, a driving TFT T2, a capacitor CAP, and a light emitting element EE. As used herein, the term "pixel" refers to a smallest unit for displaying an image, and the display panel <NUM> may display an image using the plurality of pixels.

Although <FIG> and <FIG> illustrate each of the pixels including two TFTs and one capacitor, the exemplary embodiments are not limited thereto. In another exemplary embodiment, each of the pixels may include three or more TFTs and two or more capacitors.

The display panel <NUM> may include a substrate <NUM>, a gate line <NUM> on the substrate <NUM>, a data line <NUM> and a common power line <NUM> insulated from and intersecting the gate line <NUM>. In general, each of the pixels may be defined by the gate line <NUM>, the data line <NUM>, and the common power line <NUM> as the boundary, however, the definition of the pixel is not limited thereto. The pixels may be defined by a pixel defining layer or a black matrix.

The substrate <NUM> may include a flexible material such as plastic or the like. For example, the substrate <NUM> may include at least one of polyethersulfone (PES), polycarbonate (PC), polyimide (PI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyacrylate (PAR), fiber reinforced plastic (FRP), or the like.

The substrate <NUM> may have a thickness in a range from about <NUM> to about <NUM>. When the substrate <NUM> has a thickness of less than about <NUM>, it is difficult for the substrate <NUM> to stably support the light emitting element EE. When the substrate <NUM> has a thickness of greater than about <NUM>, the flexible characteristics of the substrate <NUM> may be degraded.

A buffer layer <NUM> may be disposed on the substrate <NUM>. The buffer layer <NUM> may prevent or reduce permeation of impurities and planarize a surface therebelow. The buffer layer <NUM> may include at least one of silicon nitride, silicon oxide, silicon oxynitride, or the like. However, the buffer layer <NUM> may be omitted based on the kinds of the substrate <NUM> and process conditions thereof.

A switching semiconductor layer <NUM> and a driving semiconductor layer <NUM> may be disposed on the buffer layer <NUM>. The switching semiconductor layer <NUM> and the driving semiconductor layer <NUM> may be formed of at least one of a polycrystalline silicon, an amorphous silicon, and/or an oxide semiconductor including, for example, an indium gallium zinc oxide (IGZO) and/or an indium zinc tin oxide (IZTO). For example, when the driving semiconductor layer <NUM> is formed of the polycrystalline silicon, the driving semiconductor layer <NUM> may include a channel region that is not doped with impurities and doped source and drain regions that are formed on opposite sides of the channel region. In such an exemplary embodiment, p-type impurities, such as boron (B), may be used as dopant ions and diborane (B<NUM>H<NUM>) is often used. Such impurities may vary depending on the kinds of TFTs. The driving TFT T2, according to the exemplary embodiments, is a p-channel metal oxide semiconductor (PMOS) TFT including p-type impurities, however, the driving TFT T2 is not limited thereto. In another exemplary embodiment, the driving TFT T2 may be an n-channel metal oxide semiconductor (NMOS) TFT or a complementary metal oxide semiconductor (CMOS) TFT.

A gate insulation layer <NUM> may be disposed on the switching semiconductor layer <NUM> and the driving semiconductor layer <NUM>. The gate insulation layer <NUM> may include at least one of a tetraethyl orthosilicate (TEOS), a silicon nitride, and/or a silicon oxide. In the illustrated exemplary embodiment, the gate insulation layer <NUM> may have a double-layer structure in which a silicon nitride layer having a thickness of about <NUM> and a TEOS layer having a thickness of about <NUM> are sequentially stacked.

A gate wiring including gate electrodes <NUM> and <NUM> may be disposed on the gate insulation layer <NUM>. The gate wiring may further include the gate line <NUM>, a first capacitor plate <NUM>, or the likes. The gate electrodes <NUM> and <NUM> may be disposed to overlap at least a portion of the semiconductor layers <NUM> and <NUM>, for example, the channel region thereof. The gate electrodes <NUM> and <NUM> may serve to substantially prevent the channel region from being doped with impurities when source and drain regions of the semiconductor layers <NUM> and <NUM> are doped with impurities during the process of forming the semiconductor layers <NUM> and <NUM>.

The gate electrodes <NUM> and <NUM> and the first capacitor plate <NUM> may be disposed on the same or substantially similar layer and include the same or substantially similar metal material. For example, the gate electrodes <NUM> and <NUM> and the first capacitor plate <NUM> may be formed of at least one of molybdenum (Mo), chromium (Cr), and/or tungsten (W).

An insulation interlayer <NUM> covering the gate electrodes <NUM> and <NUM> may be disposed on the gate insulation layer <NUM>. The insulation interlayer <NUM>, similar to the gate insulation layer <NUM>, may include or may be formed of silicon nitride, silicon oxide, tetraethyl orthosilicate, or the like, however, the material of the insulation interlayer <NUM> is not limited thereto.

A data wiring including source electrodes <NUM> and <NUM> and drain electrodes <NUM> and <NUM> may be disposed on the insulation interlayer <NUM>. The data wiring may further include the data line <NUM>, the common power line <NUM>, a second capacitor plate <NUM>, or the like. The source electrodes <NUM> and <NUM> and the drain electrodes <NUM> and <NUM> may be connected to a source region and a drain region of the semiconductor layers <NUM> and <NUM>, respectively, through a contact hole defined in the gate insulation layer <NUM> and the insulation interlayer <NUM>.

The switching TFT T1 may include the switching semiconductor layer <NUM>, the switching gate electrode <NUM>, the switching source electrode <NUM>, and the switching drain electrode <NUM>, and the driving TFT T2 may include the driving semiconductor layer <NUM>, the driving gate electrode <NUM>, the driving source electrode <NUM>, and the driving drain electrode <NUM>. The capacitor CAP may include the first capacitor plate <NUM> and the second capacitor plate <NUM> with the insulation interlayer <NUM> interposed therebetween.

The switching TFT T1 may function as a switching element to select pixels to perform light emission. The switching gate electrode <NUM> may be connected to the gate line <NUM>. The switching source electrode <NUM> may be connected to the data line <NUM>. The switching drain electrode <NUM> may be spaced apart from the switching source electrode <NUM> and connected to the first capacitor plate <NUM>.

The driving TFT T2 may apply driving power to a pixel electrode <NUM>, which allows an emission layer <NUM> of the light emitting element EE in the selected pixel to emit light. The driving gate electrode <NUM> may be connected to the first capacitor plate <NUM>. Each of the driving source electrode <NUM> and the second capacitor plate <NUM> may be connected to the common power line <NUM>. The driving drain electrode <NUM> may be connected to the pixel electrode <NUM> of the light emitting element EE through a contact hole.

With the aforementioned structure, the switching TFT T1 may be driven by a gate voltage applied to the gate line <NUM> and may transmit data voltage applied to the data line <NUM> to the driving TFT T2. A voltage equivalent to a difference between a common voltage applied to the driving TFT T2 from the common power line <NUM> and the data voltage transmitted from the switching TFT T1 may be stored in the capacitor CAP, and a current corresponding to the voltage stored in the capacitor CAP may flow to the light emitting element EE through the driving TFT T2, such that the light emitting element EE may emit light.

A planarization layer <NUM> may be disposed to cover the data wiring (e.g., the data line <NUM>, the common power line <NUM>, the source electrodes <NUM> and <NUM>, the drain electrodes <NUM> and <NUM>, and the second capacitor plate <NUM>, which are patterned into a substantially same layer on the insulation interlayer <NUM>).

The planarization layer <NUM> may substantially eliminate a step difference and planarize a surface so as to increase luminance efficiency of the light emitting element EE formed thereon. The planarization layer <NUM> may include at least one of a polyacrylate resin, an epoxy resin, a phenolic resin, a polyamide resin, a polyimide resin, an unsaturated polyester resin, a polyphenylene ether resin, a polyphenylene sulfide resin, and/or a benzocyclobutene (BCB).

The pixel electrode <NUM> of the light emitting element EE may be disposed on the planarization layer <NUM>. The pixel electrode <NUM> may be connected to the drain electrode <NUM> through a contact hole defined in the planarization layer <NUM>.

A pixel defining layer <NUM> exposing at least a portion of the pixel electrode <NUM> to define a pixel area may be disposed on the planarization layer <NUM>. The pixel electrode <NUM> may be disposed corresponding to the pixel area of the pixel defining layer <NUM>. The pixel defining layer <NUM> may include at least one of a resin, such as a polyacrylate resin and/or a polyimide resin.

In the pixel area, the emission layer <NUM> may be disposed on the pixel electrode <NUM>, and a common electrode <NUM> may be disposed on the pixel defining layer <NUM> and the emission layer <NUM>. The emission layer <NUM> may include a low molecular weight organic material or a high molecular weight organic material. A hole injection layer HIL and/or a hole transporting layer HTL may also be disposed between the pixel electrode <NUM> and the emission layer <NUM>, and an electron transporting layer ETL and/or an electron injection layer EIL may be further disposed between the emission layer <NUM> and the common electrode <NUM>.

Each of the pixel electrode <NUM> and the common electrode <NUM> may be formed as a transmissive electrode, a transflective electrode, or a reflective electrode.

A transparent conductive oxide (TCO) may be used to form the transmissive electrode. The TCO may include at least one of an indium tin oxide (ITO), an indium zinc oxide (IZO), a zinc oxide (ZnO), and/or an indium oxide (In<NUM>O<NUM>).

A metal, such as at least one of a magnesium (Mg), silver (Ag), gold (Au), calcium (Ca), lithium (Li), chromium (Cr), aluminum (Al), and copper (Cu), or an alloy thereof, may be used to form the transflective electrode and the reflective electrode. In such an exemplary embodiment, whether an electrode is a transflective type or a reflective type may depend on the thickness of the electrode. The transflective electrode may have a thickness of about <NUM> or less, and the reflective electrode may have a thickness of about <NUM> or more. As the thickness of the transflective electrode decreases, light transmittance and resistance increase. As the thickness of the transflective electrode increases, light transmittance decreases. In addition, the transflective electrode and the reflective electrode may have a multilayer structure which includes a metal layer including a metal or a metal alloy and a TCO layer stacked on the metal layer.

A thin film encapsulation layer TFE may be disposed on the common electrode <NUM>. The thin film encapsulation layer TFE may include inorganic layers <NUM>, <NUM>, and <NUM> and organic layers <NUM> and <NUM>. Further, the thin film encapsulation layer TFE may have a structure in which the inorganic layers <NUM>, <NUM>, and <NUM> and the organic layers <NUM> and <NUM> are alternately stacked. In such an exemplary embodiment, the inorganic layer <NUM> may be disposed at a lowermost portion or position. For example, the inorganic layer <NUM> may be disposed most adjacent to (e.g., nearest to or directly on) the light emitting element EE.

<FIG> illustrates that the thin film encapsulation layer TFE includes three inorganic layers <NUM>, <NUM>, and <NUM> and two organic layers <NUM> and <NUM>. However, the exemplary embodiments are not limited thereto.

The inorganic layers <NUM>, <NUM>, and <NUM> may include one or more inorganic materials including at least one of Al<NUM>O<NUM>, TiO<NUM>, ZrO, SiNx, SiO<NUM>, AlON, AIN, SiON, Si<NUM>N<NUM>, ZnO, and/or Ta<NUM>O<NUM>. The inorganic layers <NUM>, <NUM>, and <NUM> may be formed by methods, such as a chemical vapor deposition (CVD) method or an atomic layer deposition (ALD) method. The inorganic layers <NUM>, <NUM> and <NUM> may prevent or efficiently reduce permeation of, primarily, moisture and oxygen. Permeation of moisture and oxygen into the light emitting element EE may be largely prevented by the inorganic layers <NUM>, <NUM> and <NUM>.

The organic layers <NUM> and <NUM> may include polymer-based material. Examples of the polymer-based material may include, for example, at least one of an acrylic resin, an epoxy resin, a polyimide, and/or a polyethylene. In addition, the organic layers <NUM> and <NUM> may be formed by a thermal deposition process. The thermal deposition process for forming the organic layers <NUM> and <NUM> may be performed in a temperature range that may not damage the light emitting element EE.

The thin film encapsulation layer TFE may have a thickness of about <NUM> or less. Accordingly, the overall thickness of the display panel <NUM> may be small. By applying the thin film encapsulation layer TFE in such a manner, flexible characteristics of the display panel <NUM> may be improved.

Hereinafter, a method of operating a foldable display device <NUM> according to the illustrated exemplary embodiment will be described with reference to <FIG> and <FIG>.

<FIG> is a flowchart illustrating an exemplary method of operating a foldable display device according to the invention. <FIG> is a cross-sectional view illustrating an exemplary embodiment of a method of outwardly folding the unfolded foldable display device of <FIG>. <FIG> is a cross-sectional view illustrating an exemplary method of inwardly folding the outwardly folded foldable display device of <FIG>.

Referring to <FIG>, <FIG> and <FIG>, in the illustrated exemplary embodiment, when the foldable display module <NUM> is folded from the un-folded mode or the in-folded mode to the out-folded mode, the foldable display module <NUM> may be folded (S110) after rotating the first rotating plate <NUM> (S120). Hereinafter, an exemplary operating method in which the foldable display module <NUM> is folded from the un-folded mode to the out-folded mode will be described with reference to <FIG> and <FIG>, however, the operating method may be applied to an operating method in which the foldable display module <NUM> is folded from the in-folded mode to the out-folded mode.

First, the first rotating plate <NUM> may be rotated (S120) as illustrated in <FIG> and <FIG>. The first rotating plate <NUM> parallel to the first plate <NUM> may be rotated counter-clockwise by a user such that the first rotating plate <NUM> is not parallel to the first plate <NUM> (for example, the first rotating plate <NUM> may be generally perpendicular to the first plate <NUM>). The first gear <NUM> and the second gear <NUM> of the first gear portion <NUM> may be rotated in opposite directions from each other to rotate the first rotating plate <NUM> with respect to the first plate <NUM>. For example, the first gear <NUM> and the second gear <NUM> may be respectively rotated in a clockwise direction and in a counter-clockwise direction to rotate the first rotating plate <NUM> in the counter-clockwise direction.

Then, the foldable display module <NUM> may be folded (S110) as illustrated in <FIG>. The folding portion <NUM> may be folded around the first folding axis FX1 located in the Z-axis direction from the foldable display module <NUM> to outwardly fold the foldable display module <NUM>. In this case, the folding portion <NUM> may be symmetrically folded with respect to the first folding axis FX1 such that the first non-folding portion <NUM> and the second non-folding portion <NUM> are symmetrically located with respect to the first folding axis FX1.

In the un-folded mode or the in-folded mode, the first rotating plate <NUM> may support the folding portion <NUM>, and when the folding portion <NUM> is outwardly folded while the first rotating plate <NUM> supports the folding portion <NUM>, the folding portion <NUM> may be damaged by the first rotating plate <NUM>. Accordingly, the first rotating plate <NUM> may be rotated before outwardly folding the folding portion <NUM>, so that the folding portion <NUM> may not be damaged and the foldable display module <NUM> may be easily folded.

Referring to <FIG>, <FIG>, <FIG> and <FIG>, in an exemplary embodiment, when the foldable display module <NUM> is folded from the out-folded mode to the un-folded mode or the in-folded mode, the first rotating plate <NUM> may be rotated (S120) after folding the foldable display module <NUM> (S110). Hereinafter, an operating method in which the foldable display module <NUM> is folded from the out-folded mode to the in-folded mode will be described with reference to <FIG>, <FIG> and <FIG>, however, the operating method may be applied to an operating method in which the foldable display module <NUM> is folded from the out-folded mode to the un-folded mode.

First, the foldable display module <NUM> may be folded (S110) as illustrated in <FIG> and <FIG>. The folding portion <NUM> may be folded around the second folding axis FX2 in the Y-axis in a Z-axis direction from the foldable display module <NUM> to in-fold the foldable display module <NUM>. In this case, the folding portion <NUM> may be asymmetrically folded with respect to the second folding axis FX2 such that the first non-folding portion <NUM> and the second non-folding portion <NUM> are asymmetrically located with respect to the second folding axis FX2.

Then, the first rotating plate <NUM> may be rotated (S120) as illustrated in <FIG>. The first rotating plate <NUM> unparallel to (for example, generally perpendicular to) the first plate <NUM> may be rotated such that the first rotating plate <NUM> is generally parallel to the first plate <NUM>. The first gear <NUM> and the second gear <NUM> of the first gear portion <NUM> may be rotated in opposite directions from each other to rotate the first rotating plate <NUM> with respect to the first plate <NUM>. For example, the first gear <NUM> and the second gear <NUM> may be respectively rotated in a counter-clockwise direction and in a clockwise direction to rotate the first rotating plate <NUM> in the clockwise direction.

In the out-folded mode, the first rotating plate <NUM> may not support the folding portion <NUM>, and when the first rotating plate <NUM> does not support the folding portion <NUM>, the foldable display module <NUM> may be deformed due to restoring force. Accordingly, the first rotating plate <NUM> may be rotated after inwardly folding the folding portion <NUM>, so that the first rotating plate <NUM> may support a part of the folding portion <NUM> which is not supported, and the deformation of the foldable display module <NUM> due to the restoring force may be prevented.

Hereinafter, a foldable display device <NUM> according to another illustrated embodiment will be described with reference to <FIG>.

<FIG> is an exploded perspective view illustrating another exemplary embodiment of a foldable display device constructed according to principles of the invention. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in an unfolded position. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in an outwardly folded position. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in an inwardly folded position.

Referring to <FIG>, <FIG>, <FIG> and <FIG>, a flexible or foldable display device <NUM> may include a foldable display module <NUM>, a first plate <NUM>, a second plate <NUM>, a first rotating plate <NUM>, a second rotating plate <NUM>, a first gear portion <NUM>, a second gear portion <NUM>, and a jig <NUM>. Detailed descriptions on elements of the foldable display device <NUM> described with reference to <FIG>, which are substantially the same as or similar to those of the foldable display device <NUM> described with reference to <FIG> and <FIG>, will not be repeated to avoid redundancy.

The second rotating plate <NUM> may be rotatably connected to the second plate <NUM>. The second rotating plate <NUM> may be rotatably connected to the second plate <NUM> through the second gear portion <NUM>. The second gear portion <NUM> may include a third gear <NUM> and a fourth gear <NUM>. The third gear <NUM> may be rotatably supported in and disposed on the side <NUM> of the second plate <NUM>, and the fourth gear <NUM> may be fixedly supported in and disposed on the side <NUM> of the second rotating plate <NUM>. The third gear <NUM> and the fourth gear <NUM> may be engaged with each other for supporting the second rotating plate <NUM> for rotation relative to the second plate <NUM>, and the direction of rotation of the third gear <NUM> and the direction of rotation of the fourth gear <NUM> may be opposite to each other, e.g., one may be clockwise and the other counter-clockwise. The second rotating plate <NUM> may be rotated with respect to the second plate <NUM> by the rotation of the third gear <NUM> and the fourth gear <NUM> by a user moving the first and second rotating plates <NUM> and <NUM>, e.g., respectively, counter-clockwise and clockwise as shown in <FIG>.

The sum of the area of the first rotating plate <NUM> and the area of the second rotating plate <NUM> may be less than the area of the folding portion <NUM>. For example, the sum of the width of the first rotating plate <NUM> in the X-axis direction and the width of the second rotating plate <NUM> in an X-axis direction may be less than the width of the folding portion <NUM> in the X-axis direction. For example, the sum of the width of the first rotating plate <NUM> in the X-axis direction and the width of the second rotating plate <NUM> in an X-axis direction may be about <NUM>% to about <NUM>% of the width of the folding portion <NUM> in the X-axis direction.

The second rotating plate <NUM> may be made from any rigid, supporting material including metal, plastic, or the like. For example, the metal may be, independently, an alloy as described above for the first plate <NUM>. In the illustrated exemplary embodiment, the second rotating plate <NUM> may include a material substantially the same as those of the first plate <NUM>, the second plate <NUM>, and/or the first rotating plate <NUM>.

As illustrated in <FIG>, in the un-folded mode, the first rotating plate <NUM> and the second rotating plate <NUM> may be disposed on the folding portion <NUM> and support the folding portion <NUM>. Specifically, the first rotating plate <NUM> may be disposed on a part of the folding portion <NUM> adjacent to the first non-folding portion <NUM> and support the part of the folding portion <NUM> adjacent to the first non-folding portion <NUM>, and the second rotating plate <NUM> may be disposed on a part of the folding portion <NUM> adjacent to the second non-folding portion <NUM> and support the part of the folding portion <NUM> adjacent to the second non-folding portion <NUM>. In this case, the first rotating plate <NUM> and the second rotating plate <NUM> may be disposed on the non-display surface <NUM> of the folding portion <NUM>.

As illustrated in <FIG>, in the out-folded mode, the first rotating plate <NUM> may not be parallel to the first plate <NUM>, and the second rotating plate <NUM> may not be parallel to the second plate <NUM>. In this case, the first rotating plate <NUM> and the second rotating plate <NUM> may not support all of the folding portion <NUM>. In the illustrated exemplary embodiment, the first rotating plate <NUM> may be generally perpendicular to the first plate <NUM>, and the second rotating plate <NUM> may be generally perpendicular to the second plate <NUM>. For example, the first plate <NUM> and the second plate <NUM> may extend along the X-axis direction, and the first rotating plate <NUM> and the second rotating plate <NUM> may extend along the Z-axis direction.

As illustrated in <FIG>, in the in-folded mode, the folding portion <NUM> may include a first region <NUM> adjacent to the first non-folding portion <NUM> and a second region <NUM> adjacent to the second non-folding portion <NUM>, and a third region <NUM> disposed between the first region <NUM> and the second region <NUM>. Because the radius of curvature of the folding portion <NUM> in the in-folded mode is less than the radius of curvature of the folding portion <NUM> in the out-folded mode, the folding portion <NUM> may include an unfolded region and a folded region in the in-folded mode. In the illustrated exemplary embodiment, the first region <NUM> and the second region <NUM> of the folding portion <NUM> may not be folded, and the third region <NUM> of the folding portion <NUM> may be folded. In this case, the first region <NUM> and the second region <NUM> may be substantially planar.

In the in-folded mode, the folding portion <NUM> may be symmetrically folded with respect to the second folding axis FX2. In other words, in the in-folded mode, the folding portion <NUM> may be folded such that the first non-folding portion <NUM> and the second non-folding portion <NUM> are symmetrically located with respect to the second folding axis FX2. For example, the shortest distance <NUM> from the second folding axis FX2 to the first non-folding portion <NUM> may be generally equal to the shortest distance <NUM> from the second folding axis FX2 to the second non-folding portion <NUM>. The distance in the X-axis direction from the second folding axis FX2 to the first non-folding portion <NUM> may be generally equal to the distance in the X-axis direction from the second folding axis FX2 to the second non-folding portion <NUM>, and the distance <NUM> in the Z-axis direction from the second folding axis FX2 to the first non-folding portion <NUM> may be generally equal to the distance <NUM> in the Z-axis direction from the second folding axis FX2 to the second non-folding portion <NUM>.

In the in-folded mode, the first rotating plate <NUM> may be generally parallel to the first plate <NUM>, and the second rotating plate <NUM> may be generally parallel to the second plate <NUM>. The first rotating plate <NUM> may be disposed on the first region <NUM> of the folding portion <NUM> and support the first region <NUM> of the folding portion <NUM>, and the second rotating plate <NUM> may be disposed on the second region <NUM> of the folding portion <NUM> and support the second region <NUM> of the folding portion <NUM>. In other words, the first rotating plate <NUM> and the second rotating plate <NUM> may be disposed on an unfolded part of the folding portion <NUM> and support the unfolded part in the in-folded mode. In this case, the first rotating plate <NUM> may be disposed on the non-display surface <NUM> of the first region <NUM> of the folding portion <NUM>, and the second rotating plate <NUM> may be disposed on the non-display surface <NUM> of the second region <NUM> of the folding portion <NUM>.

Hereinafter, a method of operating a foldable display device <NUM> according to an exemplary embodiment will be described with reference to <FIG>.

<FIG> is a flowchart illustrating an exemplary method of operating a foldable display device according to principles of the invention. <FIG> is a cross-sectional view illustrating an exemplary method of outwardly folding the unfolded foldable display device of <FIG>. <FIG> is a cross-sectional view illustrating an exemplary method of inwardly folding the outwardly folded foldable display device of <FIG>.

Referring to <FIG>, a method of operating a foldable display device <NUM> may include folding a foldable display module (S210) and rotating first and second rotating plates (S220). The order of the steps (S210 and S220) may be changed according to folding modes (the un-folded mode, the out-folded mode, and the inwardly folded mode). Detailed descriptions of the method of operating the foldable display device <NUM> described with reference to <FIG>, which are substantially the same as or similar to those of the method of operating the foldable display device <NUM> described with reference to <FIG> and <FIG>, will not be repeated to avoid redundancy.

Referring to <FIG>, <FIG> and <FIG>, when the foldable display module <NUM> is folded from the un-folded mode or the inwardly folded mode to the out-folded mode, the foldable display module <NUM> may be folded (S210) after rotating the first and second rotating plates <NUM> and <NUM> (S220). Hereinafter, an operating method in which the foldable display module <NUM> is folded from the un-folded mode to the out-folded mode will be described with reference to <FIG> and <FIG>, however, the operating method may be applied to an operating method in which the foldable display module <NUM> is folded from the inwardly folded mode to the out-folded mode.

First, the first and second rotating plates <NUM> and <NUM> may be rotated (S220) as illustrated in <FIG> and <FIG>. The first rotating plate <NUM> generally parallel to the first plate <NUM> may be rotated such that the first rotating plate <NUM> is not parallel to (for example, substantially perpendicular to) the first plate <NUM>, and the second rotating plate <NUM> is substantially parallel to the second plate <NUM> may be rotated such that the second rotating plate <NUM> is not parallel to (for example, substantially perpendicular to) the second plate <NUM>. The first gear <NUM> and the second gear <NUM> of the first gear portion <NUM> may be rotated in opposite directions from each other to rotate the first rotating plate <NUM> with respect to the first plate <NUM>, and the third gear <NUM> and the fourth gear <NUM> of the second gear portion <NUM> may be rotated in opposite directions from each other to rotate the second rotating plate <NUM> with respect to the second plate <NUM>. For example, the first gear <NUM> and the second gear <NUM> may be respectively rotated in a clockwise direction and in a counter-clockwise direction to rotate the first rotating plate <NUM> in the counter-clockwise direction, and the third gear <NUM> and the fourth gear <NUM> may be respectively rotated in the counter-clockwise direction and in the clockwise direction to rotate the second rotating plate <NUM> in the clockwise direction.

Then, the foldable display module <NUM> may be folded (S210) as illustrated in <FIG>. In the un-folded mode or the inwardly folded mode, the first and second rotating plates <NUM> and <NUM> may support the folding portion <NUM>, and when the folding portion <NUM> is outwardly folded while the first and second rotating plates <NUM> and <NUM> support the folding portion <NUM>, the folding portion <NUM> may be damaged by the first and second rotating plates <NUM> and <NUM>. Accordingly, the first and second rotating plates <NUM> and <NUM> may be rotated before outwardly folding the folding portion <NUM>, so that the folding portion <NUM> may not be damaged and the foldable display module <NUM> may be easily folded.

Referring to <FIG>, <FIG>, <FIG> and <FIG>, when the foldable display module <NUM> is folded from the out-folded mode to the un-folded mode or the inwardly folded mode, the first and second rotating plates <NUM> and <NUM> may be rotated (S220) after folding the foldable display module <NUM> (S210). Hereinafter, an operating method in which the foldable display module <NUM> is folded from the out-folded mode to the inwardly folded mode will be described with reference to <FIG>, <FIG> and <FIG>, however, the operating method may be applied to an operating method in which the foldable display module <NUM> is folded from the out-folded mode to the un-folded mode.

First, the foldable display module <NUM> may be folded (S210) as illustrated in <FIG> and <FIG>. The folding portion <NUM> may be folded around the second folding axis FX2 located in the Z-axis direction from the foldable display module <NUM> to in-fold the foldable display module <NUM>. In this case, the folding portion <NUM> may be symmetrically folded with respect to the second folding axis FX2 such that the first non-folding portion <NUM> and the second non-folding portion <NUM> are symmetrically located with respect to the second folding axis FX2.

Then, the first and second rotating plates <NUM> and <NUM> may be rotated (S220) as illustrated in <FIG>. The first rotating plate <NUM> unparallel to (for example, substantially perpendicular to) the first plate <NUM> may be rotated such that the first rotating plate <NUM> is substantially parallel to the first plate <NUM>, and the second rotating plate <NUM> unparallel to (for example, substantially perpendicular to) the second plate <NUM> may be rotated such that the second rotating plate <NUM> is substantially parallel to the second plate <NUM>. The first gear <NUM> and the second gear <NUM> of the first gear portion <NUM> may be rotated in opposite directions from each other to rotate the first rotating plate <NUM> with respect to the first plate <NUM>, and the third gear <NUM> and the fourth gear <NUM> of the second gear portion <NUM> may be rotated in opposite directions from each other to rotate the second rotating plate <NUM> with respect to the second plate <NUM>. For example, the first gear <NUM> and the second gear <NUM> may be respectively rotated in a counter-clockwise direction and in a clockwise direction to rotate the first rotating plate <NUM> in the clockwise direction, and the third gear <NUM> and the fourth gear <NUM> may be respectively rotated in the clockwise direction and in the counter-clockwise direction to rotate the second rotating plate <NUM> in the counter-clockwise direction.

In the out-folded mode, the first and second rotating plates <NUM> and <NUM> may not support all of the folding portion <NUM>, and when the first and second rotating plates <NUM> and <NUM> do not support the folding portion <NUM>, the foldable display module <NUM> may be deformed due to restoring force. Accordingly, the first and second rotating plates <NUM> and <NUM> may be rotated after inwardly folding the folding portion <NUM>, so that the first and second rotating plates <NUM> and <NUM> may support a part of the folding portion <NUM> which is not supported, and the deformation of the foldable display module <NUM> due to the restoring force may be reduced or prevented.

Hereinafter, a foldable display device <NUM> according to an exemplary embodiment will be described with reference to <FIG>.

<FIG> is an exploded perspective view illustrating yet another exemplary embodiment of a foldable display device constructed according to principles of the invention. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in an unfolded position. <FIG> is a cross-sectional view illustrating the foldable display device of <FIG> in a folded position.

Referring to <FIG>, <FIG> and <FIG>, a flexible or foldable display device <NUM> may include a foldable display module <NUM>, a first plate <NUM>, a second plate <NUM>, a third plate <NUM>, a first rotating plate <NUM>, a second rotating plate <NUM>, a first gear portion <NUM>, a second gear portion <NUM>, and a jig <NUM>. Detailed descriptions on elements of the foldable display device <NUM> described with reference to <FIG>, which are substantially the same as or similar to those of the foldable display device <NUM> described with reference to <FIG> and <FIG>, will not be repeated to avoid redundancy.

The foldable display module <NUM> may include a first non-folding portion <NUM>, a second non-folding portion <NUM>, a third non-folding portion <NUM>, a first folding portion <NUM> and a second folding portion <NUM>. The second folding portion <NUM> may be disposed between the first non-folding portion <NUM> and the third non-folding portion <NUM>. The first non-folding portion <NUM> and the third non-folding portion <NUM> may be spaced apart from each other with the second folding portion <NUM> therebetween. The first non-folding portion <NUM>, the second non-folding portion <NUM>, and the third non-folding portion <NUM> may be unfolded portions in the foldable display module <NUM>. The first folding portion <NUM> and the second folding portion <NUM> may be folded portions in the foldable display module <NUM>.

The third plate <NUM> may be disposed on the third non-folding portion <NUM> of the foldable display module <NUM> and support the third non-folding portion <NUM>. The third plate <NUM> may be disposed on the non-display surface <NUM> of the third non-folding portion <NUM>. In an exemplary embodiment, an adhesive layer may be interposed between the third non-folding portion <NUM> of the foldable display module <NUM> and the third plate <NUM> so that the third plate <NUM> may be attached on the non-display surface <NUM> of the third non-folding portion <NUM>. For example, the adhesive layer may be at least one of an optically clear adhesive, a pressure sensitive adhesive, or the like.

The third plate <NUM> may have substantially the same shape as that of the third non-folding portion <NUM> of the foldable display module <NUM> in a plan view, and may generally overlap the third non-folding portion <NUM>. For example, the area of the third plate <NUM> may be substantially equal to that of the third non-folding portion <NUM>. The third plate <NUM> may include at least one of metal, plastic, or the like to provide rigid support. For example, the metal may be, independently, an alloy as described above for the first plate <NUM>. In an exemplary embodiment, the third plate <NUM> may include a material substantially the same as those of the first plate <NUM> and/or the second plate <NUM>.

The first rotating plate <NUM> may be rotatably connected to a first side of the first plate <NUM>. For example, the first side of the first plate <NUM> may be located in the X-axis direction from a center of the first plate <NUM>. The first rotating plate <NUM> may be rotatably connected to the first side of the first plate <NUM> through the first gear portion <NUM>.

The second rotating plate <NUM> may be rotatably connected to a second side of the first plate <NUM>. The second side of the first plate <NUM> may be opposite to the first side of the first plate <NUM>. For example, the second side of the first plate <NUM> may be located in the X-axis direction from the center of the first plate <NUM>. The second rotating plate <NUM> may be rotatably connected to the second side of the first plate <NUM> through the second gear portion <NUM>. The second gear portion <NUM> may include a third gear <NUM> and a fourth gear <NUM>. The third gear <NUM> may be rotatably supported in and disposed on the side <NUM> of the first plate <NUM>, and the fourth gear <NUM> may be fixedly supported in and disposed on the side <NUM> of the second rotating plate <NUM>. The third gear <NUM> and the fourth gear <NUM> may be engaged with each other for supporting the second rotating plate <NUM> for rotation relative to the first plate <NUM>, and the direction of rotation of the third gear <NUM> and the direction of rotation of the fourth gear <NUM> may be opposite to each other, e.g., one may be clockwise and the other counter-clockwise. The second rotating plate <NUM> may be rotated with respect to the first plate <NUM> by the rotation of the third gear <NUM> and the fourth gear <NUM> by a user moving the second rotating plate <NUM>, e.g., clockwise.

The area of the second rotating plate <NUM> may be less than the area of the second folding portion <NUM>. For example, the width of the second rotating plate <NUM> in the X-axis direction may be less than the width of the second folding portion <NUM> in the X-axis direction. For example, the width of the second rotating plate <NUM> in the X-axis direction may be about <NUM>% to about <NUM>% of the width of the second folding portion <NUM> in the X-axis direction. The second rotating plate <NUM> may include at least one of metal, plastic, or the like to provide rigid support. For example, the metal may be, independently, an alloy as described above for the first plate <NUM>. In the illustrated exemplary embodiment, the second rotating plate <NUM> may include a material substantially the same as those of the first plate <NUM>, the second plate <NUM>, the third plate <NUM>, and/or the first rotating plate <NUM>.

The jig <NUM> may be disposed on the first plate <NUM>, the second plate <NUM> and the third plate <NUM>. The jig <NUM> may include a first jig <NUM>, a second jig <NUM> and a third jig <NUM>. The first jig <NUM> may be disposed on the first plate <NUM>, the second jig <NUM> may be disposed on the second plate <NUM>, and the third jig <NUM> may be disposed on the third plate <NUM>.

As illustrated in <FIG>, the foldable display module <NUM> may be unfolded. In the illustrated exemplary embodiment, the first folding portion <NUM> and the second folding portion <NUM> of the foldable display module <NUM> may not be folded, and the display surface <NUM> of the first non-folding portion <NUM>, the display surface <NUM> of the second non-folding portion <NUM>, and the display surface <NUM> of the third non-folding portion <NUM> of the foldable display module <NUM> may face the same direction, for example, the Z-axis direction.

In the un-folded mode, the first rotating plate <NUM> may be disposed on the first folding portion <NUM> and support the first folding portion <NUM>, and the second rotating plate <NUM> may be disposed on the second folding portion <NUM> and support the second folding portion <NUM>. In this case, the first rotating plate <NUM> may be disposed on the non-display surface <NUM> of the first folding portion <NUM>, and the second rotating plate <NUM> may be disposed on the non-display surface <NUM> of the second folding portion <NUM>.

As illustrated in <FIG>, the foldable display module <NUM> may be outwardly folded with respect to a first folding axis FX1, and may be inwardly folded with respect to a second folding axis FX2. In the illustrated exemplary embodiment, the first folding portion <NUM> of the foldable display module <NUM> may be folded such that the non-display surface <NUM> of the first non-folding portion <NUM> and the non-display surface <NUM> of the second non-folding portion <NUM> of the foldable display module <NUM> may face each other, and the second folding portion <NUM> of the foldable display module <NUM> may be folded such that the display surface <NUM> of the first non-folding portion <NUM> and the display surface <NUM> of the third non-folding portion <NUM> of the foldable display module <NUM> may face each other. For example, the display surface <NUM> of the second non-folding portion <NUM> may face the outside of the foldable display device <NUM>, and the display surface <NUM> of the third non-folding portion <NUM> may face the inside of the foldable display device <NUM>.

The first rotating plate <NUM> may not be parallel to the first plate <NUM>. In this case, the first rotating plate <NUM> may not support or substantially support the first folding portion <NUM>. In the illustrated exemplary embodiment, the first rotating plate <NUM> may be generally perpendicular to the first plate <NUM>. For example, the first plate <NUM> may extend generally along the X-axis direction, and the first rotating plate <NUM> may extend generally along the Z-axis direction.

The second rotating plate <NUM> may be generally parallel to the first plate <NUM>. The second rotating plate <NUM> may be disposed on a part of the second folding portion <NUM>, and support the part of the second folding portion <NUM>. In this case, the second rotating plate <NUM> may be disposed on the non-display surface <NUM> of the part of the second folding portion <NUM>. In other words, the second rotating plate <NUM> may be disposed on an unfolded part of the second folding portion <NUM> and support the unfolded part.

Although <FIG> illustrates an exemplary embodiment in which the foldable display module <NUM> is outwardly folded in the first folding portion <NUM> and in-folded in the second folding portion <NUM>, however, in another exemplary embodiment, the foldable display module <NUM> may be inwardly folded in the first folding portion <NUM> and outwardly folded in the second folding portion <NUM>. Further, the foldable display module <NUM> may be outwardly folded in each of the first folding portion <NUM> and the second folding portion <NUM>, or the foldable display module <NUM> may be inwardly folded in each of the first folding portion <NUM> and the second folding portion <NUM>.

<FIG> illustrate an exemplary embodiment in which the first rotating plate <NUM> and the second rotating plate <NUM> are rotatably connected to the first plate <NUM>, however, in another exemplary embodiment, the first rotating plate <NUM> may be rotatably connected to the second plate <NUM>, or the second rotating plate <NUM> may be rotatably connected to the third plate <NUM>, operate similarly as described above.

The foldable display device according to the exemplary embodiments may be applied to any type of display device including those in a computer, a notebook, a mobile phone, a smartphone, a smart pad, a PMP, a PDA, an MP3 player, or the like.

Claim 1:
A foldable display device (<NUM>, <NUM>, <NUM>), comprising:
a foldable display module (<NUM>) including a first non-folding portion (<NUM>), a second non-folding portion (<NUM>), and a folding portion (<NUM>) disposed between the first non-folding portion (<NUM>) and the second non-folding portion (<NUM>);
a first support member (<NUM>) disposed on a non-display surface (<NUM>) of the first non-folding portion (<NUM>) and supporting the first non-folding portion (<NUM>);
a second support member (<NUM>) disposed on a non-display surface (<NUM>) of the second non-folding portion (<NUM>) and supporting the second non-folding portion (<NUM>); and
a third member (<NUM>) rotatably coupled to the first support member (<NUM>),
wherein the first support member (<NUM>) comprises a first plate, the second support member (<NUM>) comprises a second plate, and the third member (<NUM>) comprises a first rotatable plate (<NUM>), and
a first end of the first rotatable plate (<NUM>) is rotatably connected to the first plate (<NUM>) and a second end of the first rotatable plate (<NUM>) is a free end,
characterised in that:
the flexible display device (<NUM>, <NUM>, <NUM>) is capable of folding in an out-folded mode,
wherein, in the out-folded mode, the folding portion (<NUM>) is folded such that the non-display surface (<NUM>) of the first non-folding portion (<NUM>) and the non-display surface (<NUM>) of the second non-folding portion (<NUM>) face each other while a display surface (<NUM>) of the first non-folding portion (<NUM>) and a display surface (<NUM>) of the second non-folding portion (<NUM>) face away from each other.