Foldable display device

A foldable display device can include a display panel including a first non-folding part, a second non-folding part and a folding part disposed between the first and second non-folding parts; a support disposed on a rear surface of the display panel; and a back cover disposed on a rear surface of the support, in which the back cover includes open patterns exposing the support, and folding patterns disposed on an area of the rear surface of the support corresponding to the folding part, the support includes protruding patterns disposed on an area of the support corresponding to the open patterns of the back cover, and the protruding patterns are fitted into the open patterns.

This application claims the benefit of Korean Patent Application No. 10-2016-0162340, filed on Nov. 30, 2016, which is hereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a foldable display device, and more particularly, to a foldable display device capable of preventing distortion of a folding part of a display screen due to deformation of the folding part.

Discussion of the Related Art

An image display device, which realizes various pieces of information on a screen, is a core technology of the information and communication age, and is being developed in the direction of becoming thinner, lighter, more portable, and having higher performance. In response, a flat panel display device, which is thinner and lighter than a cathode ray tube (CRT), for example, an organic light-emitting display device, which controls the amount of light emitted from an organic light-emitting layer to display an image, is in the spotlight.

In an organic light-emitting display device, a plurality of pixels is arranged in a matrix form to display an image. Here, each pixel includes a light-emitting element, and a pixel drive circuit including, for example, a plurality of transistors to independently drive the light-emitting element.

Since such an organic light-emitting display device employs a self-luminous organic light-emitting element, the need for an additional light source is eliminated. In addition, since the organic light-emitting display device can be embodied as an ultrathin display device, research into an in-cell touch-type foldable display device, which employs organic light-emitting elements and includes a touch electrode array in a light-emitting cell, has been actively conducted in recent years.

The foldable display device is designed to be folded in conjunction with a display panel contained therein. In order to protect the display panel having the flexible property, the foldable display device is provided with a back cover. Accordingly, the back cover, which is disposed on the rear surface of the display panel to protect the display panel, should also be designed to be foldable.

A back cover of a related-art foldable display device includes a region corresponding to a folding part, which is made of silicon resin or the like to have a flexible structure, and a region corresponding to a non-folding part, which is made of metal, rigid plastic or the like to protect the display panel.

In the related-art foldable display device adopting the back cover, the folding part and the non-folding part are usually made of different materials. Here, because the two materials have different physical properties, such as rigidity, elasticity, flexibility and the like, and are compressed to different extents while passing through processes, there is a high possibility that unevenness is generated at the boundary surface between the two different materials. The unevenness generated between the folding part and the non-folding part causes a phenomenon whereby a display screen is transferred or distorted. Furthermore, the related-art foldable display device adopting a back cover has other problems in that the flexible folding part is curled upward or droops due to concentration of stress after being folded a number of times, and is deformed in its appearance or cured under the condition of high temperature and humidity.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a foldable display device, which is able to reduce a phenomenon of transfer and distortion of a folding part and to prevent a display panel from drooping, and which has an excellent folding property.

To achieve the above object, a foldable display device according to the present invention includes a display panel including a folding part and non-folding parts, a support disposed on a rear surface of the display panel, and a back cover disposed on a rear surface of the support, in which the back cover includes open patterns exposing the support and folding patterns provided on an area of the rear surface of the support that corresponds to the folding part, and in which the support includes protruding patterns, which are provided on an area of the support corresponding to the open patterns of the back cover and fit into the open patterns.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings. In the entire specification, the same or similar elements are denoted by the same reference numerals even though they are depicted in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. Also, the terms used in the following description are terms defined taking into consideration the functions obtained in accordance with the present invention, and may differ from the names of parts of actual products.

When an element or layer is referred to as being “on” another element or layer, it means not only the situation where the element or layer is directly on the another element or layer but also the situation where a further element or layer is interposed therebetween. In addition, when an element or layer is referred to as being in contact with another element or layer, it means the situation where there is no intervening element or layer therebetween.

Sizes and thicknesses of parts shown in the drawings are illustrated for convenience of explanation, and the present invention is not necessarily limited to the sizes and thicknesses shown in the drawings.

FIG. 1is an exploded perspective view of a foldable display device according to the present invention.

The foldable display device according to the present invention includes a panel100having at least one folding part F/A capable of being folded and non-folding parts N/A occupying the remaining area of the panel100excluding the folding part, a support108disposed on the rear surface of the display panel and including a soft part106at an area thereof corresponding to the folding part F/A, and a back cover1000disposed on the rear surface of the support108and including at least one open pattern1107at an area thereof corresponding to the folding part F/A to expose the display panel. The support108includes protruding patterns107, which extend downward from the areas of the soft part106that correspond to the open patterns1107in the back cover1000, and which are inserted into the open patterns1107. The display panel100and the support108can be attached to each other via an adhesive layer. The folding part F/A of the display panel100may be folded about the folding axis. Although the folding axis is illustrated as being oriented in the horizontal direction inFIG. 1, the present invention is not necessarily limited thereto.

The display panel100will be described in more detail with reference toFIG. 2. The display panel100according to the embodiment of the present invention can include a first substrate120, a first buffer layer130disposed on the first substrate120, a thin-film transistor array140defining pixels on the first buffer layer130in a matrix fashion in which each of the pixels has a thin-film transistor, an organic light-emitting array150connected to the respective thin-film transistors of the pixels, a protective layer160covering the thin-film transistor array140and the organic light-emitting array150, excluding a pad part, a touch electrode array230attached to the protective layer160with a second adhesive layer400disposed therebetween, a second buffer layer220and a second substrate210, which are formed on the touch electrode array230in that order.

The display panel100according to the present invention is not necessarily limited to the above embodiment, and various foldable display devices including the thin-film transistor array140and the organic light-emitting array150may be applied.

An active area A/A and a dead area D/A are defined in each of the first buffer layer130and the second buffer layer220, and thin-film transistors contained in the thin-film transistor array140excluding the touch electrode array230, the organic light-emitting array150and the pad part are formed in the active area A/A. A touch pad part and a pad part of the thin-film transistor array are defined in a part of the dead area D/A.

Here, the first substrate120and the second substrate210serve to prevent damage to the internal array during a laser radiation or etching process. In some situations, the first substrate120and the second substrate210serve to protect the display device from the outside. The first substrate120and the second substrate210can be made of a polymer material such as polyimide and photoacryl, without being limited thereto.

Each of the first buffer layer130and the second buffer layer220is made in a manner of successively layering the same kind of inorganic film such as oxide film (SiO2) or nitride film (SiNx), or alternately layering different kinds of inorganic film, such as oxide film (SiO2) and nitride film (SiNx). The first buffer layer130and the second buffer layer220serve as barriers for preventing moisture or external air from infiltrating the organic light-emitting array150during a subsequent process of attaching an upper board to a lower board.

The touch electrode array230and a touch pad2350are formed on the same surface of the second buffer layer220. The touch pad2350is coupled to the pad of the thin-film transistor array140via a seal450containing a conductive ball455through a process of attaching the upper element to the lower element using the adhesive layer400. The adhesive layer400functions to prevent the infiltration of moisture, and also functions to reliably prevent external air and moisture from infiltrating the organic light-emitting array150in cooperation with the protective layer160.

The thin-film transistor array140including the pad is configured to project further at a side thereof than the touch electrode array230. The projected portion can be provided with a driving circuit for driving the touch electrode array, the thin-film transistor array and the organic light-emitting array together, without being limited thereto. Also, the thin-film transistor driving pad and a dummy pad include a plurality of dummy electrodes, and are connected to the driving circuit through wiring. The driving circuit may be connected to a flexible printed circuit board (FPCB) through bonding, and may be controlled by a micro control unit (MCU) and a timing controller, which are included in the FPCB. The dummy pad is formed on the same layer as the metal constituting a gate line or data line in the region of the dead area outside the active area, which corresponds to the touch pad. The driving circuit can be mounted on the FPCB or an anisotropic conductive film (ACF), and can then be provided on the rear surface of the display panel100.

The driving circuit may be mounted on the FPCB or the ACF in a chip on film (COF) manner.

In this disclosure, the constituent elements shown inFIG. 2are collectively referred to as the display panel100for convenience of explanation. As mentioned above, the display panel100is not necessarily limited to the construction shown inFIG. 2, and various display devices including the thin-film transistor array140and the organic light-emitting array150may be applied.

As mentioned above, the support108is attached to the rear surface of the display panel100via the adhesive layer. The support108includes a soft part106, which is disposed on the rear surface of the folding part F/A and is flexible, and at least one protruding pattern107, which protrudes from the soft part in the rearward direction of the support108. The soft part can be provided on the entirety of the support108, that is, the entire rear surface of the display panel100. While the soft part106has flexibility and low rigidity, the support108can be provided on the rear surface thereof with the back cover1000having high rigidity to compensate for the low rigidity of the support108. In the situation where the support108is made of different materials, a stepped portion can be generated at the interface between the different materials when the back cover1000is attached to the support108. Accordingly, when the entire support108is constituted only of the soft part106, this is advantageous in improving the flatness of the back cover1000.

The non-folding part N/A of the display panel100can also be provided on the rear surface thereof with a hard part105, in place of the soft part106. Although the hard part105can additionally support the display panel100by virtue of its high rigidity, it is preferable that the hard part105also be made of the same material as the material of the soft part106to prevent the generation of a stepped portion at the interface between the hard part105and the soft part106. Furthermore, in order to improve the flatness of the display panel100, it is preferable that the hard part105be formed at the same level as the soft part106.

The soft part106can be attached to the display panel100via the adhesive layer, and the soft part106and the protruding patterns107can be simultaneously formed of the same material. Although the protruding patterns107are illustrated as being exaggerated in size for convenience of explanation, the protruding patterns107can actually have a fine size or height of 0.01-1 mm.

The protruding patterns107protrude toward the back cover1000.

The protruding patterns107have the same shapes as the shapes of the open patterns1107in the back cover1000, and are formed to be fitted into the open patterns1107. Specifically, when the open patterns1107in the back cover1000are formed into predetermined shapes by removing part of the material of the back cover folding part1110of the back cover1000, the protruding patterns have the same shapes as the open patterns. The protruding patterns107project toward the back cover1000to be fitted into the removed portions of the back cover1000.

The protruding patterns107are preferably disposed on the rear surface of the folding part F/A of the display panel100such that the display panel100becomes foldable. Accordingly, the protruding patterns107can be flexible, similar to the soft part106, and can be integrally formed with the soft part106, without being limited thereto.

As mentioned above, although the protruding patterns107may be formed of polymer material such as silicon resin, the present invention is not necessarily limited thereto.

The back cover1000is formed of a material having high rigidity, such as metal. As mentioned above, the rear surface of the folding part F/A of the back cover1000is provided with at least one open pattern1107. The back cover1000will be described in more detail with reference toFIG. 1. The back cover1000includes a plate1111disposed on the rear surface of the non-folding part N/A of the display panel100, the open patterns1107disposed on the rear surface of the folding part F/A of the display panel100, and folding patterns1108, which are formed in the remaining area of the back cover folding part1110, excluding the open patterns1107, which is disposed on the rear surface of the folding part F/A of the display panel100, by removing the portion of the material of the back cover1000corresponding to the open patterns1107.

The plate1111and the folding patterns1108can be formed of the same material. In particular, the plate1111and the folding patterns1108can be simultaneously formed in such a manner as to execute patterning of a single metal plate to form the open patterns1107.

As mentioned above, the open patterns1107in the back cover1000are incised patterns, which are formed by patterning a portion of a metal plate, and the protruding patterns107of the support108are raised patterns, which have the same shape as the shapes of the open patterns1107. Accordingly, when the back cover1000is attached to the support108, the open patterns1107engage with the protruding patterns107without a height difference therebetween. Preferably, the protruding patterns107have the same thickness as the thickness of the back cover1000such that there is no height difference in the engaging area between the two patterns after the open patterns1107engage with the protruding patterns107.

The open patterns1107serve to assist in folding of the back cover1000, which is made of a material having a high rigidity, such as metal. Since metal is not present in the area of the back cover1000in which the open patterns1107are formed, free folding is allowed in the area in which the open patterns1107are formed. Although the open patterns are illustrated as being exaggerated in size for convenience of explanation inFIG. 1, each of the open patterns1107also has a fine size of 0.03-1 mm. The back cover1000, which is provided with a large number of fine open patterns1107having no metal, has improved foldability.

The area of the back cover1000that corresponds to the folding part F/A of the display panel100, is provided with the open patterns1107. With the formation of the open patterns1107, the remaining area of the back cover1000excluding the open patterns1107is also provided with predetermined patterns. The patterns of the back cover1000, which are formed by the removal of the open patterns1107, are just the folding patterns1108.

AlthoughFIG. 1shows an embodiment in which the folding patterns1108include a plurality of folding patterns, each of which has the shaped of a metal bar parallel to the folding axis, the folding patterns1108can be formed into various shapes depending on the design.

FIG. 3shows the rear surface of the back cover1000, which illustrates some of the various shapes of the folding patterns1108and the open patterns1107. The open patterns1107are coupled to protruding patterns107by engagement therebetween.

As mentioned above, the back cover1000includes the plate1111and the back cover folding part1110. The plate1111is made of a metal having high rigidity to support the non-folding parts N/A. Since the back cover folding part1110may be folded about the folding axis, the back cover folding part1110may be folded at the time of folding of the display panel100.

A1to A6ofFIG. 3, which are enlarged views of portion A ofFIG. 3, show various examples of shapes that the folding patterns1108and the open patterns1107can have. However, the shapes of the folding patterns1108and the open patterns1107are not limited to the above embodiments, and may be variously modified depending on the design.

Referring to A1ofFIG. 3, the folding patterns1108can be constituted by a plurality of metal bars, which are oriented to be parallel to the folding axis. Each of the metal bars can have the same length as the width of the display panel100. Since the folding patterns1108are constituted by the metal bars, the open patterns1107can also be oriented to be parallel to the folding axis.

Although each of the metal bars can have the same length as the width of the display panel100, the metal bars may not fully extend from one side to the opposite side of the display panel100and can have an interruption point. In other words, each of the open patterns1107, which is linearly disposed to be parallel to the folding axis, can have a connecting open pattern C to be connected to the adjacent open pattern via the connecting open pattern C. Consequently, the metal bar-shaped folding pattern1108may be interrupted at the point at which the connecting open pattern is located.

Referring to A3ofFIG. 3, one of the metal bar-shaped folding patterns1108can be connected to the adjacent folding pattern1108via a connecting pattern CP, and the corresponding open pattern1107may thus be interrupted at the connecting pattern CP. In this situation, the folding pattern1108can have the connecting open pattern C, and both the linear folding pattern1108and the linear open pattern1107may thus be interrupted.

Referring to A2ofFIG. 3, each of the open patterns1107can be formed to have a diamond shape. Since the open patterns1107have the diamond shape, the folding patterns1108can be disposed between the open patterns1107having a diamond shape. As shown in A2ofFIG. 3, the folding patterns1108can be formed into, for example, diamond shapes, which are connected to each other in the horizontal and vertical directions. When the open patterns1107are formed into diamond shapes, which are densely arranged, the folding patterns1108can form a net shape overall.

In addition, the open patterns1107can each have a circular or elliptic shape, as shown in A5ofFIG. 3, or can each have a square shape, as shown in A6ofFIG. 3.

The above-mentioned shapes of open patterns1107and the folding patterns1108are only some of various shapes that the open patterns1107and the folding patterns1108can have. The open patterns1107and the folding patterns1108may have various shapes. In this embodiment, for convenience of explanation, the coupling structure of the foldable display device according to the present invention will be described on the basis of the back cover1000, which includes the bar-shaped folding patterns1108, which are spaced apart from each other, and the linear open patterns1107defined between the folding patterns1108, as shown in A1ofFIG. 3. However, the folding patterns1108and the open patterns1107are not limited to the above-described structure.

Although each of the folding patterns1108is illustrated as having a large size for convenience of explanation inFIG. 3, it should be noted that each of the folding patterns1108can actually have a fine size. Each of the folding patterns1108can be formed to have a fine size. When each of the folding patterns1108has, for example, a bar shape as shown in A1ofFIG. 3, the bar-shaped folding pattern1107can be formed to have a diameter or a width of about 0.03-0.1 mm, and the open pattern1107can be formed to have a diameter or a width of about 0.1-0.4 mm.

FIG. 4is a schematic view illustrating a cross-section of the foldable display device according to the present invention, and a method of manufacturing the foldable display device. Referring to (A) ofFIG. 4, the display panel100is attached to the support108via an adhesive layer110. The back cover1000is disposed on the rear surface of the support108. The support108includes the protruding patterns107. The protruding patterns107have the same shapes as the shapes of the open patterns1107. Specifically, the areas of the back cover1000, which correspond to the protruding patterns107, are provided with the hole-shaped open patterns1107. Consequently, the protruding patterns107are fitted into the open patterns1107in the back cover1000. In this situation, since the protruding patterns107and the open patterns1107are configured to have the same height, there is no height difference between the protruding patterns107and the open patterns1107. Accordingly, the rear surface of the back cover folding part1110, at which the protruding patterns107and the folding patterns1108are present, appears flat, as illustrated in (B) ofFIG. 4.

The soft part106can be integrally formed with the protruding patterns107. In particular, since the non-folding parts N/A are firmly supported by the back cover1000, the hard part105can be integrally formed with the soft part106and the protruding patterns107using the same material as the soft part106and the protruding patterns107. In this embodiment, the support108is made of silicon resin, as mentioned above. The silicon resin can be composed to include a thermal curing agent or a UV curing agent. Accordingly, for the coupling of the support108to the back cover1000, silicon resin, which is a constituent material of the support108, is applied, the back cover1000is pressed onto the silicon resin of the support108, and the silicon resin of the support is cured using UV radiation or heat, thereby creating the support108. At this time, since the silicon resin is a viscous fluid, the silicon resin freely enters the open patterns1107of the back cover1000, and is then cured therein, thereby providing the support108with the protruding patterns107.

As mentioned above, since the back cover1000has high rigidity, there is no problem even when the area of the support that corresponds to the non-folding part N/A of the display panel100is provided with the soft part106, in place of the hard part105.

FIG. 5is a schematic view illustrating the foldable display device according to the present invention in a folded state.

Referring toFIG. 5, the foldable display device according to the present invention includes the fine-sized folding patterns1108. When the back cover1000and the display panel100are folded, the stress applied to the individual folding patterns1108is reduced because the folding patterns1108are at least partially separated from each other. In addition, since the back cover1000according to the present invention is made of metal or the like, the back cover1000has high rigidity and foldability.

As is apparent from the above description, the foldable display device according to the present invention includes the support108equipped with the protruding patterns107, which are fitted into the open patterns1107defined between the folding patterns1108of the back cover1000. Here, since the support108equipped with the protruding patterns107includes the soft part at the area thereof corresponding to the folding part F/A, the support108has high foldability. Furthermore, since the protruding patterns107having high foldability are disposed between the folding patterns1108to support them, it is possible to prevent deformation of the folding patterns1108without affecting the foldability.

In the situation where a back cover1000is not provided with the protruding patterns107and thus the open patterns1107between the folding patterns1108are empty, deformation, such as shifting or inclination of the folding patterns1108, may be caused when the folding patterns1108become spaced apart from each other. In this situation, the flatness of the folding part F/A of the display panel100, which is coupled to the folding patterns1108of the back cover1000, is reduced, and thus unevenness is generated at the folding part F/A, thereby causing a phenomenon whereby the display screen is distorted. In contrast, since the protruding patterns107according to the present invention are fitted into the open patterns1107, the folding patterns1108are supported by the protruding patterns107, thereby preventing deformation of the folding patterns1108. Consequently, the flatness of the folding part F/A of the display panel100is improved, and distortion of the display screen is prevented.

Although the embodiments of the present invention have been described above in detail with reference to the accompanying drawings, it will be apparent to those skilled in the art that the present invention described above is not limited to the embodiments described above, and various substitutions, modifications, and alterations may be devised within the spirit and scope of the present invention. Accordingly, various embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by the embodiments. Accordingly, the disclosed embodiments are provided for the purpose of description and are not intended to limit the technical scope of the disclosure, and the technical scope of the disclosure is not limited by the embodiments. The range of the disclosure should be interpreted based on the following claims, and all technical ideas that fall within the range equivalent to the claims should be understood as belonging to the scope of the disclosure.