Patent Description:
Recently, a flexible display device that can be bent has been developed. Such a flexible display device may be used in a folded or in a curved form, and thus, may be used in various technical applications. In a flexible display device, a display element is generally disposed on a flexible substrate.

Display elements that can be applied to a flexible display device may include a light emitting diode (LED), a liquid crystal display (LCD) element, and an electrophoretic display (EPD) element. Among the display elements, light emitting diodes generally have a thin-film stacked structure with excellent flexibility, and thus, LEDs have been spotlighted as display devices of flexible display devices.

A flexible display device may be classified as a rollable display device that is rollable like a roll, a foldable display device that is foldable like a paper, a stretchable display device that can be scaled up and down in size, and the like, depending on the extent of bending. In particular, some structures disposed in a folding portion of the foldable display device may be removed, such that the display device can be folded easily. Repeated folding of the folding portion of the display device can produce defects, such as wrinkles.

Applicant discovered that defects, such as wrinkles, in a foldable display device can be caused by misalignment due to certain internal structures or layers in the display device. Display devices constructed according to exemplary embodiments of the invention are capable of reducing wrinkles in a folding portion of a display device.

According to an exemplary embodiment, a display device is provided as defined in claim <NUM>. According to further alternative exemplary embodiments, display devices are provided as defined in claims <NUM> and <NUM>.

Further embodiments are defined in dependent claims.

Hereinafter, one or more display devices according to one or more exemplary embodiments of the invention will be described in detail with reference to the drawings.

The display device according to the exemplary embodiment illustrated in <FIG> may be a foldable display device. <FIG> illustrates a rear surface of a display device without showing a set bracket according to an exemplary embodiment.

Referring to <FIG>, a portion indicated with A is a folding portion, by which a display device may be folded. The display device includes a first adhesive layer <NUM>, which attaches a set bracket (such as set bracket <NUM> in <FIG>) on the rear surface of the display device. The first adhesive layer <NUM> is disposed along edges of a metal layer <NUM>, which includes a first metal layer <NUM> and a second metal layer <NUM>.

The first metal layer <NUM> and the second metal layer <NUM> are spaced apart from each other, such that the display device may be folded in a region where the first metal layer <NUM> and the second metal layer <NUM> are not disposed. As such, the first metal layer <NUM> and the second metal layer <NUM> may define the folding portion A, and the display device may be folded in an area on which the first and second metal layers <NUM> and <NUM> are not disposed.

The display device further includes a compressible member, such as a cushion layer <NUM>, which includes a first cushion layer <NUM> and a second cushion layer <NUM>. The first cushion layer <NUM> and the second cushion layer <NUM> may be positioned in central regions of the first metal layer <NUM> and the second metal layer <NUM>, respectively, and have a thickness greater than that of the first adhesive layer <NUM>. In this manner, the cushion layer <NUM> may support the display device in the folding portion A of the display device, and minimize generation of wrinkles in the folding portion A, which will be described in more detail below.

<FIG> is a cross-sectional view taken along line II-II' of <FIG> according to an exemplary embodiment.

Referring to <FIG>, the display device includes a display panel <NUM> and a window <NUM> disposed on one surface of the display panel <NUM>.

The display panel <NUM> may include a light emitting diode. In particular, the display panel <NUM> may include a light emitting diode connected to a plurality of transistors. The light emitting diode may include an emission layer positioned between two electrodes. The emission layer may include an organic material, or may include an inorganic material, such as a quantum dot.

The display device may further include a passivation layer <NUM> disposed on one surface of the display panel <NUM>. The passivation layer <NUM> may be elastic to protect the display panel <NUM> from external impact. The passivation layer <NUM> may include a polymer, such as a polyurethane foam. The passivation layer <NUM> may overlap a front surface of the display panel <NUM>.

The metal layer <NUM> including the first metal layer <NUM> and the second metal layer <NUM> is attached to the passivation layer <NUM> through a second adhesive layer <NUM>. As described above, the first metal layer <NUM> and the second metal layer <NUM> are spaced apart from each other, and a portion between the first metal layer <NUM> and the second metal layer <NUM> may be defined as the folding portion A, in which the display device may be folded. Since the metal layer <NUM> is not disposed in the folding portion A, the display device may be folded easily.

The second adhesive layer <NUM> attaches the metal layer <NUM> and the passivation layer <NUM> at edges of the first metal layer <NUM> and the second metal layer <NUM>. A tape <NUM> is disposed in an area of the metal layer <NUM> where the second adhesive layer <NUM> is not disposed. The tape <NUM> may have a thickness similar to that of the second adhesive layer <NUM>, and may substantially fill a step between the passivation layer <NUM> and the metal layer <NUM>, and is thus referred to herein as a "stepped tape". More particularly, the stepped tape <NUM> compensates for and fills in at least part of the step formed by the second adhesive layer <NUM>. The thickness of the stepped tape <NUM> may be similar to that of the second adhesive layer <NUM>, but may be thinner than the second adhesive layer <NUM>. In this case, a gap may be formed between the passivation layer <NUM> and the metal layer <NUM>. In some exemplary embodiments, even when the thickness of the stepped tape <NUM> is formed to be the same as that of the second adhesive layer <NUM>, the thickness of the stepped tape <NUM> may be less than that of the second adhesive layer <NUM> due to process variation during manufacture. The stepped tape <NUM> may have a black color.

The first adhesive layer <NUM> is disposed at a lower portion of the metal layer <NUM>. The first adhesive layer <NUM> may be disposed at the edges of the first metal layer <NUM> and the second metal layer <NUM>. The first adhesive layer <NUM>, however, may not be disposed at the edges of the first metal layer <NUM> and the second metal layer <NUM> adjacent to the folding portion A, as shown in <FIG>.

The display device further includes a cushion layer <NUM>, which includes a first cushion layer <NUM> and a second cushion layer <NUM> disposed on the metal layer <NUM>. The cushion layer <NUM> may include a polymer having elasticity, such as polyurethane. In this case, the density of the polyurethane may be about <NUM>/fcm<NUM> or less. The cushion layer <NUM> may be disposed at inner edges of the first metal layer <NUM> and the second metal layer <NUM> adjacent to the folding portion A.

The first cushion layer <NUM> is disposed on the first metal layer <NUM>, and the second cushion layer <NUM> is disposed on the second metal layer <NUM>. The first cushion layer <NUM> and the second cushion layer <NUM> may be spaced apart from the first adhesive layer <NUM>.

The thicknesses of the first cushion layer <NUM> and the second cushion layer <NUM> is greater than the thickness of the first adhesive layer <NUM>. As will be described in detail later, since the thicknesses of the first cushion layer <NUM> and the second cushion layer <NUM> are greater than the thickness of the first adhesive layer <NUM>, the first cushion layer <NUM> and the second cushion layer <NUM> are compressed to support the display panel <NUM>, when the set bracket is attached thereto during subsequent manufacturing process.

In this manner, the gap between the metal layer <NUM> and the passivation layer <NUM> may be filled, thereby preventing or at least suppressing generation of wrinkles in the folding portion A, which may be caused from repeated folding of the display device.

According to an exemplary embodiment, the thickness of the first adhesive layer <NUM> may be in a range of about <NUM> to about <NUM>, and the thickness of the cushion layer <NUM> may be in a range of <NUM> about µm to <NUM> about µm.

For example, the thickness of the cushion layer <NUM> may be about <NUM> % to about <NUM> % greater than the thickness of the first adhesive layer <NUM>. When the difference of thickness between the cushion layer <NUM> and the first adhesive layer <NUM> is less than about <NUM> %, the cushion layer <NUM> may not have sufficient supporting force, and when the thickness difference is greater than about <NUM> %, a reactive force (or repulsive force) may be excessive so that the set bracket <NUM> may not be attached well to the display device.

<FIG> is a cross-sectional view taken along line II-II' according to another exemplary embodiment. The display device of <FIG> is substantially the same as that shown in <FIG>, except for further including a third adhesive layer <NUM>, a protective film layer <NUM>, a polarizing layer <NUM>, and a fourth adhesive layer <NUM>. As such, repeated descriptions of the substantially the same elements described above will be omitted to avoid redundancy.

Referring to <FIG>, the third adhesive layer <NUM> is disposed between the passivation layer <NUM> and the protective film layer <NUM> to attach the passivation layer <NUM> and the protective film layer <NUM> to each other.

The protective film layer <NUM> is disposed at a lower portion of the display panel <NUM>. The protective film layer <NUM> may include a polyimide film, for example. The polarization layer <NUM> may be disposed at an upper portion of the display panel <NUM>. The fourth adhesive layer <NUM> may be disposed between the polarization layer <NUM> and the window <NUM>. However, the inventive concepts are not limited thereto, and in some exemplary embodiments, at least one or more layers described above may be omitted or at least one or more layers well known in the art may be added to the display device.

<FIG> is a schematic cross-sectional view illustrating the cushion layer <NUM> supporting the display panel <NUM> when the set bracket <NUM> is applied to the display device according to an exemplary embodiment.

Referring to <FIG>, the set bracket <NUM> according to the claimed inventions includes a first portion <NUM> and a second portion <NUM> separated from each other. When the set bracket <NUM> is attached on to the first adhesive layer <NUM>, the cushion layer <NUM> is compressed and has substantially the same thickness as the first adhesive layer <NUM>, as indicated in area B of <FIG>.

As the cushion layer <NUM> is compressed, the gap between the passivation layer <NUM> and the metal layer <NUM> is substantially removed by the reactive force. In addition, while the display panel <NUM> is supported by the compressive reactive force of the cushion layer <NUM>, generation of wrinkles may be minimized or at least be suppressed in the folding portion A.

The reactive force supporting the display device is indicated by arrows in <FIG>.

As illustrated in <FIG>, when a rigid structure, such as the metal layer <NUM>, is not disposed in the folding portion A of the display device, the rigid structure may not be sufficiently supported. In this case, wrinkles may be generated when folding and unfolding are repeated in the folding portion A.

In display devices constructed according to the principles and exemplary embodiments of the invention, a structure disposed in the folding portion A may be supported when the cushion layer <NUM> is compressed, thereby minimizing or at least suppressing generation of wrinkles in the folding portion A.

<FIG> illustrate a display device according to a comparative embodiment, which is not according to the claimed inventions. <FIG> is a schematic plan view of a display device according to a comparative embodiment, and <FIG> is a cross-sectional view taken along line VI-VI' of <FIG>.

Referring to <FIG> and <FIG>, in the display device according to the comparative embodiment, the thickness of the cushion layer <NUM> is less than that of the first adhesive layer <NUM>.

<FIG> is a cross-sectional view of a display device, on which wrinkles are generated, according to a comparative embodiment. <FIG> illustrates only a partial region of the display device.

Referring to <FIG>, when the set bracket <NUM> is attached and used, the cushion layer <NUM> is not supported by the set bracket <NUM>, and thus, wrinkles may be generated in the structure disposed in the bending area A. In addition, the display device may also be affected by a difference in thickness (step) formed between the first portion <NUM> and the second portion <NUM> of the set bracket <NUM>, which may also cause wrinkles.

In display devices constructed according to the principles and exemplary embodiments of the invention, however, the cushion layer <NUM> has a thickness greater than that of the first adhesive layer <NUM>. As such, when the set bracket <NUM> is attached, the cushion layer <NUM> is compressed to support the structure of the display device by the reactive force generated during the compression. Accordingly, generation of wrinkles in the folding portion A from repetitive folding and unfolding of the display device may be suppressed and/or minimized.

Hereinafter, an effect of the display device according to the exemplary embodiments will be described through experimental results. More particularly, various experiments were conducted on the display device of <FIG>, whereby the first adhesive layer <NUM> was formed to have a thickness of <NUM> and the cushion layer <NUM> was formed to have a thickness of <NUM>, and the amount of deformation in various regions of the folding portion A of the display device was measured after repetitive folding and unfolding. In addition, as a comparative example, the amount of deformation in various areas of the folding portion A of a display device, which does not include a cushion layer, was measured after repetitive folding and unfolding.

<FIG> illustrates regions Line <NUM>, Line <NUM>. Line <NUM> of the folding portion A, at which the amount of deformation is measured. <FIG> illustrates a method of measuring the amount of deformation in the folding portion A. More particularly, the depth of the wrinkles formed in the display panel <NUM> (as indicated by arrows of <FIG>) was measured.

Table <NUM> below shows the amount of deformation in each line of the folded portion A, when the display device includes the first adhesive layer having a thickness of <NUM> and the cushion layer having a thickness of <NUM> according to an exemplary embodiment. The experiment was repeated three times.

In addition, Table <NUM> below shows the amount of deformation in each line of the folded portion A, when the display device does not include a cushion layer according to a comparative embodiment, which is not according to the claimed inventions. The experiment was repeated three times.

Referring to Table <NUM> and Table <NUM>, it can be seen that the average amount of deformation in the folding portion A is about <NUM> in the comparative embodiment, while the average amount of deformation in the folding portion A is about <NUM> in the display device according to an exemplary embodiment.

These results confirm that the display device according to an exemplary embodiment significantly reduces the amount of deformation in the folding portion A.

Hereinafter, a display device according to another exemplary embodiment will be described with reference to the drawings.

<FIG> is a cross-sectional view taken line II-II' of <FIG> according to another exemplary embodiment.

Referring to <FIG>, the display device according to the illustrated exemplary embodiment is substantially the same as the display device of <FIG>, except for the shape of the cushion layer <NUM>. As such, repeated descriptions of substantially the same elements described above will be omitted to avoid redundancy.

Referring to <FIG>, the first cushion layer <NUM> and the second cushion layer <NUM> include a first region C1 and a second region C2 having different thicknesses. The first region C1 has a thickness greater than that of the second region C2, such that a step is formed therebetween. The first region C1 is disposed closer to the folding portion A than the second region C2.

When the cushion layer <NUM> is formed with the step as described above, the folding portion A of the display device can be more stably supported when the set bracket <NUM> is attached. More particularly, the display device according to the illustrated exemplary embodiment has a thicker cushion layer <NUM> adjacent to the folding portion A, such that the supporting effect by the cushion layer <NUM> from the compressive/reactive force may be improved in the folding portion A. Since the compressive/reactive force of the cushion layer <NUM> is higher in regions adjacent to the folding portion A, the generation of wrinkles in the folding portion A may be further suppressed.

<FIG> is a cross-sectional view taken along line II-II' of <FIG> according to another exemplary embodiment. The display device of <FIG> is substantially the same as that of <FIG>, except for further including a third adhesive layer <NUM>, a protective film layer <NUM>, a polarizing layer <NUM>, and a fourth adhesive layer <NUM>, which may be substantially the same as those illustrated above with reference to <FIG>. As such, repeated descriptions of the substantially same elements will be omitted to avoid redundancy.

<FIG> is a cross-sectional view taken along line II-II' of <FIG> according to yet another exemplary embodiment. The display device according to the illustrated exemplary embodiment is substantially the same as the display device of <FIG>, except for the shape of the cushion layer <NUM>. As such, repeated descriptions of substantially the same elements will be omitted.

Referring to <FIG>, the cushion layer <NUM> according to the illustrated exemplary embodiment has a shape, in which the thickness thereof gradually increases from one end to another end adjacent to the folding portion A. More particularly, the first cushion layer <NUM> becomes thicker in a direction from the first adhesive layer <NUM> to the folding portion A. Similarly, the second cushion layer <NUM> becomes thicker in a direction from the first adhesive layer <NUM> to the folding portion A.

In this case, as the cushion layer <NUM> is compressed when the set bracket <NUM> is attached thereto in the folding portion A, the reactive force caused by the compression and the supporting force for the display device may be improved, which may effectively prevent or at least suppress the generation of wrinkles. In particular, the cushion layer <NUM> is formed to be thicker in a region where the bending is likely to occur, thereby effectively supporting the display device.

<FIG> is a cross-sectional view taken along line II-II' of <FIG> according to another exemplary embodiment. The display device of <FIG> is substantially the same as that of <FIG>, except for further including a third adhesive layer <NUM>, a protective film layer <NUM>, a polarizing layer <NUM>, and a fourth adhesive layer <NUM>, which are substantially the same as those described above with reference to <FIG>. As such, repeated descriptions of the substantially the same elements will be omitted.

<FIG> is schematic plan view of another exemplary embodiment of a display device constructed according to the principles of the invention. <FIG> is a cross-sectional view taken along line XV-XV' of <FIG>.

Referring to <FIG> and <FIG>, the display device according to the illustrated exemplary embodiment, which is not according to the claimed inventions, is substantially the same as the display device <FIG> and <FIG>, except for shapes of the first adhesive layer <NUM> and the cushion layer <NUM>.

Referring to <NUM> and <NUM>, in the display device according to the illustrated exemplary embodiment, the cushion layer <NUM> is disposed on a front surface of the metal layer <NUM> that faces away the display panel <NUM>. The first adhesive layer <NUM> may not be disposed on the metal layer <NUM>, but may be disposed on the front surface of the cushion layer <NUM> that faces away the display panel <NUM>. As such, when the set bracket <NUM> is attached thereto in subsequent process, the display device is attached to the set bracket <NUM> through the first adhesive layer <NUM> disposed on the front surface of the cushion layer <NUM>. When the cushion layer <NUM> is disposed on the front surface of the display device, generation of wrinkles may be effectively prevented or at least suppressed on substantially the entire area of the display device. <FIG> is a cross-sectional view taken along line XV-XV' of <FIG> according to another exemplary embodiment, which is not according to the claimed inventions. The display device of <FIG> is substantially the same as that of <FIG>, except for further including a third adhesive layer <NUM>, a protective film layer <NUM>, a polarizing layer <NUM>, and a fourth adhesive layer <NUM>, which are substantially the same as those of <FIG>. As such, repeated descriptions of substantially the same elements will be omitted.

<FIG> is a cross-sectional view taken along line XV-XV' of <FIG> according to still another exemplary embodiment. Referring to <FIG>, the display device according to the illustrated exemplary embodiment is substantially the same as the display device of <FIG>, except for the shape of the cushion layer <NUM>. As such, repeated descriptions of substantially the same elements will be omitted.

Referring to <FIG>, each of the first cushion layer <NUM> and the second cushion layer <NUM> according to the illustrated exemplary embodiment includes a first region C1 and a second region C2 having different thicknesses. The first region C1 has a thickness greater than that of the second region C2. The first region C1 is disposed closer to the folding portion A than the second region C2.

The first adhesive layer <NUM> is disposed on the cushion layer <NUM>. As such, when the set bracket <NUM> is attached thereto later during subsequent process, the display device is attached to the set bracket <NUM> through the first adhesive layer <NUM> disposed on the front surface of the cushion layer <NUM>. When the cushion layer <NUM> is formed with a step as described above, the folding portion A of the display device can be more stably supported when the set bracket is attached.

<FIG> is a cross-sectional view taken along line XV-XV' of <FIG> according to yet another exemplary embodiment. The display device of <FIG> is substantially the same as that of <FIG>, except for further including a third adhesive layer <NUM>, a protective film layer <NUM>, a polarizing layer <NUM>, and a fourth adhesive layer <NUM>, which are substantially the same as those of <FIG>. As such, repeated descriptions of substantially the same elements will be omitted.

<FIG> is a cross-sectional view taken along line XV-XV' of <FIG> according to yet still another exemplary embodiment. Referring to <FIG>, the display device according to the illustrated exemplary embodiment is substantially the same as the display device of <FIG>, except for the shape of the cushion layer <NUM>. As such, repeated descriptions of substantially the same elements will be omitted.

The cushion layer <NUM> according to the illustrated exemplary embodiment has a shape, in which the thickness thereof gradually increases along a direction towards the folding portion A. More particularly, as illustrated in <FIG>, the first cushion layer <NUM> becomes thicker in a direction from one end thereof towards the folding portion A. Similarly, the second cushion layer <NUM> becomes thicker in a direction from one end thereof towards the folding portion A.

The first adhesive layer <NUM> is disposed on the cushion layer <NUM>. As such, when the set bracket <NUM> is attached thereto later during subsequent process, the display device is attached to the set bracket <NUM> through the first adhesive layer <NUM> disposed on the front surface of the cushion layer <NUM>.

In addition, when the thickness of the cushion layer <NUM> gradually increases, as the cushion layer <NUM> is compressed in the folding portion A, the reactive forces from the compression are increased and the supporting force for the display device may be improved, which may effectively prevent or at least suppress the generation of wrinkles.

<FIG> is a cross-sectional view taken along line XV-XV' of <FIG> according to still yet another exemplary embodiment. The display device of <FIG> is substantially the same that of <FIG>, except for further including a third adhesive layer <NUM>, a protective film layer <NUM>, a polarizing layer <NUM>, and a fourth adhesive layer <NUM>, which are substantially the same as those of <FIG>. As such, repeated descriptions of substantially the same elements will be omitted.

According to the principles and exemplary embodiments of the invention, it is possible to provide a display device that reduces or at least suppresses generation of wrinkles in a folding portion.

Claim 1:
A display device comprising:
a display panel (<NUM>) including a folding portion (A);
a metal layer (<NUM>) disposed on one surface of the display panel (<NUM>), and including a first metal layer (<NUM>) and a second metal layer (<NUM>) spaced apart from each other in the folding portion (A);
a first adhesive layer (<NUM>) disposed at edges of the first metal layer (<NUM>) and the second metal layer (<NUM>); and
a first compressible member (<NUM>) disposed on the first metal layer (<NUM>) and a second compressible member (<NUM>) disposed on the second metal layer (<NUM>), the first and second compressible members (<NUM>, <NUM>) being disposed closer to the folding portion (A) than the first adhesive layer (<NUM>);
a set bracket (<NUM>) including a first portion (<NUM>) and a second portion (<NUM>) spaced apart from each other, the first portion (<NUM>) of the set bracket (<NUM>) being attached to the first metal layer (<NUM>) through the first adhesive layer (<NUM>) and the second portion (<NUM>) of the set bracket (<NUM>) being attached to the second metal layer (<NUM>) through the first adhesive layer (<NUM>),
wherein the first and second compressible members (<NUM>, <NUM>) are configured to be compressed by the set bracket (<NUM>),
the first and second compressible members (<NUM>, <NUM>) compressed by the set bracket (<NUM>) have a same thickness with the thickness of the first adhesive layer (<NUM>), and
the first and second compressible members (<NUM>, <NUM>) support the display panel (<NUM>).