KR20160144912A - Foldable display device - Google Patents

Abstract

A foldable display device of the present invention increases an elastic deformation section of a back plate by forming an opening pattern in a folding area of the back plate. The opening pattern formed in the folding area functions as a spring to increase elastic restoring energy, thereby reducing a restoring time. Accordingly, the foldable display device has improved folding properties without an increase in thickness.

Description

Foldable display device < RTI ID = 0.0 >

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a foldable display device, and more particularly, to a foldable display device capable of preventing a damage caused in folding and unfolding a display device.

(LCD), an organic light emitting display (OLED) display device, an organic light emitting diode (OLED) display device, and the like have been rapidly developed in the display field for processing and displaying a large amount of information, And a light emitting display device (OELD).

A liquid crystal display device includes a liquid crystal panel including an upper substrate and a lower substrate bonded together with a liquid crystal layer including liquid crystal molecules sandwiched therebetween as an essential component and the liquid crystal layer is formed by an electric field formed between the pixel electrode and the common electrode And displays an image.

The organic light emitting display includes a light emitting diode including an anode and a cathode facing each other with an organic light emitting layer sandwiched therebetween. The holes and electrons injected from each of the anode and the cathode are combined and emitted from the organic light emitting layer, .

On the other hand, in recent years, there is an increasing demand for a foldable display device manufactured using a flexible substrate. Since the foldable display device can be carried in a folded state and displays an image in a unfolded state, it is possible to carry out display on a large screen and has an advantage of being portable easily.

1 is a schematic cross-sectional view of a conventional foldable display device.

1, the display device 10 includes a display panel 20, a back plate 30, and a cover window 40. As shown in FIG.

The display panel 20 includes a flexible substrate 22 and a display element 24 formed on the flexible substrate 22. For example, the flexible substrate 22 may be a polyimide substrate.

When the display panel 20 is a light emitting diode panel, the display device 24 may include a light emitting diode and a thin film transistor for driving the light emitting diode. The light emitting diode may include an anode connected to the thin film transistor, an organic light emitting layer formed on the anode, and a cathode formed on the organic light emitting layer. In addition, a barrier film covering the light emitting diode and preventing moisture from penetrating the outside may be formed.

When the display panel 20 is a liquid crystal panel, the display device 24 includes a thin film transistor formed on the flexible substrate 22, a pixel electrode connected to the thin film transistor, , A common electrode formed on the flexible substrate 22 or the counter substrate, and a liquid crystal layer interposed between the flexible substrate 22 and the counter substrate.

The flexible display panel 20 can be obtained by forming components such as the thin film transistor and releasing the carrier substrate in the state where the carrier substrate (not shown) is attached to the lower portion of the flexible substrate 22. [

The back plate 30 capable of supporting the display panel 20 is attached to the lower portion of the flexible substrate 22 because the flexible substrate 22 is too thin in the display panel 20 manufactured as described above. For example, the back plate 20 may be made of polyethylene terephthalate (PET) and attached to the flexible substrate 22 by an adhesive layer 32.

The cover window 40 is attached to the upper portion of the display panel 20 to protect the display panel 20 from an external impact. Although not shown, the cover window 40 may be attached to the display panel 20 by an adhesive layer.

PET film having a thickness of about 100 micrometers is used as the back plate 30. Plastic deformations are generated in the back plate 30 when the foldable display device 10 is repeatedly folded and unfolded And the restoration of the display device 10 is disabled.

That is, as shown in Figs. 2A and 2B, since the back plate as the PET film is plastically deformed, the folding / unfolding of the foldable display device 10 is limited. In other words, there arises a problem that the folding characteristic of the display device 10 is lowered.

By reducing the thickness of the back plate (30), plastic deformation problems of the back plate (30) can be reduced. However, when the thickness of the back plate 30 is reduced, the elastic restoring energy is reduced, and the restoration takes a long time.

An object of the present invention is to solve the problem of lowering the folding characteristic of the conventional display apparatus.

The back play of the display device of the present invention has at least two opening patterns corresponding to the folding area.

Further, the folding region may have a thickness smaller than the unfolding region, and the opening pattern formed in the folding region may have a different size or a different distance depending on the position.

In the foldable display device of the present invention, two or more opening patterns spaced apart from each other in the folding area of the back plate are formed, so that the folding / unfolding operation of the foldable display device can be restored even if the folding / unfolding operation is repeated.

That is, the elastic deformation section is increased by the opening pattern formed in the folding region, and restoration is possible.

In addition, the opening pattern formed in the folding region acts as a spring to increase the elastic restoring energy, thereby reducing the restoration time.

Therefore, the folding characteristic can be improved without increasing the thickness of the display device.

Further, by forming the step difference compensation layer on at least one surface of the back plate on which the opening pattern is formed, it is possible to prevent the image quality degradation problem due to the opening pattern.

Further, the back plate reduces the thickness in the folding region to alleviate the folding stress, and by adjusting the distance between the opening patterns or the size of the opening pattern, it is possible to prevent the display panel from being damaged by folding.

1 is a schematic cross-sectional view of a conventional foldable display device.
2A and 2B are views showing the plastic deformation problem of the back plate.
3 is a schematic cross-sectional view of a foldable display device according to a first embodiment of the present invention.
4A and 4B are schematic cross-sectional views showing an example of a display panel.
5A to 5D are plan views showing the back plate, respectively.
6 is a schematic cross-sectional view of a foldable display device according to a second embodiment of the present invention.
7A to 7C are sectional views showing the back plate, respectively.
8A to 8C are views for explaining a back plate of a foldable display device according to a third embodiment of the present invention.
9A to 9C are views for explaining a back plate of a foldable display device according to a fourth embodiment of the present invention.

According to an aspect of the present invention, there is provided a display device including a display panel and a display panel, the display panel being divided into a folding area and an unfolded area on both sides of the folding area, And a back plate disposed on the back plate.

The open pattern includes at least one first pattern located in the (2n-1) th column and at least one second pattern located in the (2n) th column, The space between the patterns may be located corresponding to the first pattern.

In the present invention, the aperture pattern includes at least one first pattern located in the (2n-1) -th column and at least one second pattern located in the (2n) -th column, The patterns may be positioned corresponding to the second patterns.

(2n-1) -th column and at least two second patterns located in the (2n) -th column, wherein the opening pattern includes a first pattern located in the , And the distance between the second patterns may be equal to or less than the length of the second pattern.

In the display device of the present invention, the opening pattern may have a rectangular shape, a rhombic shape, or an elliptical shape having a constant minor axis length.

In the foldable display of the present invention, one side of the back plate may be discontinuous in the folded area.

In the present invention, the display panel may include a flexible substrate, and the modulus of the back plate may be larger than that of the flexible substrate.

In the foldable display of the present invention, a step difference compensating layer covering the folding area may be disposed on at least one surface of the back plate.

In the foldable display of the present invention, the step difference compensation layer may have a smaller modulus than the back plate.

In the foldable display of the present invention, the back plate may have a recess corresponding to the folding area and having a first thickness in the folding area and a second thickness in the unfolding area that is greater than the first thickness .

The foldable display device of the present invention may include a step difference compensation layer attached to one surface of the back plate on which the concave portion is formed.

In the present invention, the display panel may include a plurality of pixel regions, and an edge of the concave portion may correspond to a boundary between the pixel regions.

In the present invention, the display panel may be an organic light emitting diode panel, and an edge of the recess may correspond to a bank covering the first electrode edge of the organic light emitting diode.

In the foldable display device of the present invention, the step difference compensation layer may have a flat surface with the back plate.

In the present invention, the concave portion may be located on the outer surface of the back plate, and the display device may be folded toward the display panel.

In the foldable display of the present invention, the recess may be located on the inner side of the back plate, and the display device of the foldable type may be folded toward the back plate.

In the foldable display of the present invention, the folding area is divided into an edge portion and a center portion along a folding direction, the opening pattern being spaced apart from the edge portion by a first distance along the folding direction, The second distance being less than the first distance.

In the foldable display device of the present invention, along the folding direction, the distance between the opening patterns may decrease from the edge toward the center.

In the foldable display of the present invention, the folding area is divided into an edge part and a center part along a folding direction, and the opening pattern has a first width along the folding direction at the edge part, And may have a second width greater than the first width.

In the foldable display of the present invention, along the folding direction, the size of the opening pattern may increase from the edge to the center.

Hereinafter, preferred embodiments according to the present invention will be described with reference to the drawings.

3 is a schematic cross-sectional view of a foldable display device according to a first embodiment of the present invention.

1, the display device 100 includes a display panel 110, a display panel 110, and a display panel 110. The display panel 110 includes a display panel 110, A back plate 180 having the opening pattern 182 and a cover window 190 located above the display panel 110. [

The display panel 110 includes a flexible substrate 112 and a display element 114 formed on the flexible substrate 112. For example, the flexible substrate 112 may be a polyimide substrate.

The flexible substrate 112 is not suitable for the formation process of the display device 114 and the flexible substrate 112 is attached to a carrier substrate (not shown) such as a glass substrate, As shown in FIG. After the display element 114 is formed on the flexible substrate 112, the display panel 110 can be obtained by separating the carrier substrate and the flexible substrate 112 from each other.

4A and 4B are schematic cross-sectional views showing an example of a display panel. As shown in FIG. 4A, the display panel 110 may be a light emitting diode panel.

A buffer layer 120 is formed on the flexible substrate 112 and a thin film transistor Tr is formed on the buffer layer 120. The buffer layer 120 may be omitted.

A semiconductor layer 122 is formed on the buffer layer 120. The semiconductor layer 122 may be made of an oxide semiconductor material or polycrystalline silicon.

When the semiconductor layer 122 is made of an oxide semiconductor material, a light shielding pattern (not shown) may be formed under the semiconductor layer 122, and the light shielding pattern may prevent the light from being incident on the semiconductor layer 122. [ Thereby preventing the semiconductor layer 122 from being deteriorated by light. Alternatively, the semiconductor layer 122 may be made of polycrystalline silicon. In this case, impurities may be doped on both edges of the semiconductor layer 122.

A gate insulating layer 124 made of an insulating material is formed on the semiconductor layer 122. The gate insulating layer 124 may be formed of an inorganic insulating material such as silicon oxide or silicon nitride.

A gate electrode 130 made of a conductive material such as metal is formed on the gate insulating layer 124 to correspond to the center of the semiconductor layer 122.

4A, the gate insulating layer 124 is formed on the entire surface of the flexible substrate 112, but the gate insulating layer 124 may be patterned to have the same shape as the gate electrode 130.

An interlayer insulating layer 132 made of an insulating material is formed on the gate electrode 130. The interlayer insulating film 132 may be formed of an inorganic insulating material such as silicon oxide or silicon nitride, or may be formed of an organic insulating material such as benzocyclobutene or photo-acryl.

The interlayer insulating layer 132 has first and second contact holes 134 and 136 exposing both sides of the semiconductor layer 122. The first and second contact holes 134 and 136 are spaced apart from the gate electrode 130 on both sides of the gate electrode 130.

Here, the first and second contact holes 134 and 136 are also formed in the gate insulating film 124. Alternatively, when the gate insulating film 124 is patterned to have the same shape as the gate electrode 130, the first and second contact holes 134 and 136 may be formed only in the interlayer insulating film 132.

A source electrode 140 and a drain electrode 142 made of a conductive material such as a metal are formed on the interlayer insulating layer 132.

The source electrode 140 and the drain electrode 142 are spaced apart from each other around the gate electrode 130 and are electrically connected to both sides of the semiconductor layer 122 through the first and second contact holes 134 and 136, / RTI >

The semiconductor layer 122 and the gate electrode 130, the source electrode 140 and the drain electrode 142 constitute the thin film transistor Tr. The thin film transistor Tr includes a driving element ).

The thin film transistor Tr has a coplanar structure in which the gate electrode 130, the source electrode 142, and the drain electrode 144 are positioned on the semiconductor layer 120.

Alternatively, the thin film transistor Tr may have an inverted staggered structure in which a gate electrode is positioned below the semiconductor layer and a source electrode and a drain electrode are located above the semiconductor layer. In this case, the semiconductor layer may be made of amorphous silicon.

Although not shown, a gate line and a data line cross each other to define a pixel region, and a switching element connected to the gate line and the data line is further formed. The switching element is connected to the thin film transistor Tr which is a driving element.

In addition, a storage capacitor is formed for keeping the voltage of the gate electrode of the thin film transistor (Tr), which is a driving element, constant during one frame, the power wiring being formed in parallel with the data wiring or the data wiring Lt; / RTI >

A protective layer 150 having a drain contact hole 152 exposing the drain electrode 142 of the thin film transistor Tr is formed to cover the thin film transistor Tr.

A first electrode 160 connected to the drain electrode 142 of the thin film transistor Tr through the drain contact hole 152 is formed on the passivation layer 150 for each pixel region. The first electrode 160 may be an anode and may be formed of a conductive material having a relatively large work function value. For example, the first electrode 160 may be made of a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO) .

Meanwhile, when the display panel 110 of the present invention is a top-emission type, a reflective electrode or a reflective layer may be further formed under the first electrode 160. For example, the reflective electrode or the reflective layer may be formed of an aluminum-palladium-copper (APC) alloy.

A bank layer 166 covering the edge of the first electrode 160 is formed on the passivation layer 150. The bank layer 166 exposes the center of the first electrode 160 corresponding to the pixel region.

An organic light emitting layer 162 is formed on the first electrode 160. The organic light emitting layer 162 may be a single layer structure of a light emitting material layer made of a light emitting material. The organic light emitting layer 162 may include a hole injection layer, a hole transporting layer, a light emitting material layer, and an electron transporting layer sequentially stacked on the first electrode 160. [ (electron transporting layer) and an electron injection layer (multilayer structure).

A second electrode 164 is formed on the flexible substrate 112 on which the organic light emitting layer 162 is formed. The second electrode 164 is disposed on the entire surface of the display region and is made of a conductive material having a relatively small work function value and can be used as a cathode. For example, the second electrode 164 may be formed of any one of aluminum (Al), magnesium (Mg), and aluminum-magnesium alloy (AlMg).

The first electrode 160, the organic light emitting layer 162, and the second electrode 164 form an organic light emitting diode (D).

An encapsulation film 170 is formed on the second electrode 164 to prevent external moisture from penetrating into the organic light emitting diode D. [ The encapsulation film 170 may have a laminated structure of a first inorganic insulating layer 172, an organic insulating layer 174 and a second inorganic insulating layer 174, but is not limited thereto.

In addition, a polarizing plate (not shown) may be attached on the encapsulation film 170 to reduce external light reflection. For example, the polarizer may be a circular polarizer.

Meanwhile, as shown in FIG. 4B, the liquid crystal panel 210 may be used as the display panel 110.

The liquid crystal panel 210 includes first and second flexible substrates 212 and 250 facing each other and a liquid crystal layer 212 interposed between the first and second flexible substrates 212 and 250, Layer 260 as shown in FIG.

A first buffer layer 220 is formed on the first flexible substrate 212 and a thin film transistor Tr is formed on the first buffer layer 220. The first buffer layer 220 may be omitted.

A gate electrode 222 is formed on the first buffer layer 220 and a gate insulating layer 224 is formed to cover the gate electrode 222. A gate wiring (not shown) connected to the gate electrode 222 is formed on the buffer layer 220.

A semiconductor layer 226 is formed on the gate insulating layer 224 in correspondence with the gate electrode 222. The semiconductor layer 226 may be made of an oxide semiconductor material. Meanwhile, the semiconductor layer 226 may include an active layer made of amorphous silicon and an ohmic contact layer made of impurity amorphous silicon.

A source electrode 230 and a drain electrode 232 are formed on the semiconductor layer 226. In addition, a data line (not shown) connected to the source electrode 230 intersects the gate line to define a pixel region.

The gate electrode 222, the semiconductor layer 226, the source electrode 230, and the drain electrode 232 constitute a thin film transistor Tr.

A protective layer 234 having a drain contact hole 236 exposing the drain electrode 232 is formed on the thin film transistor Tr.

A pixel electrode 240 connected to the drain electrode 232 through the drain contact hole 236 and a common electrode 242 alternately arranged with the pixel electrode 240 are formed on the passivation layer 234, .

A second buffer layer 252 is formed on the second flexible substrate 250 and a black matrix (not shown) covering the non-display regions such as the thin film transistor Tr, the gate line, 254 are formed. Further, a color filter layer 256 is formed corresponding to the pixel region. The second buffer layer 252 and the black matrix 254 may be omitted.

The first and second flexible substrates 212 and 250 are bonded to each other with the liquid crystal layer 260 therebetween and an electric field generated between the pixel electrode 240 and the common electrode 242 causes the liquid crystal layer 260 are driven.

Although not shown, an orientation film may be formed on each of the first and second flexible substrates 212 and 250 in contact with the liquid crystal layer 260, and the first and second flexible substrates 212 and 250 A polarizing plate having transmission axes perpendicular to each other may be attached.

Referring back to FIG. 3, the back plate 180 is positioned below the display panel 110 and supports the display panel 110. For example, the back plate 180 may be attached to the flexible substrate 112 using an adhesive layer (not shown).

The back plate 180 has greater stiffness than the flexible substrate 112. That is, the back plate 180 has a higher Young's modulus than the flexible substrate 112.

For example, the back plate 180 may be formed of a metal material such as stainless steel (SUS) or a metal material such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyacrylate (PA) , Polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), and polyethylene terephthalate (PET).

When the back plate 180 is made of a highly rigid material such as SUS, it has a high restoring force. Therefore, the thickness of the back plate 180 can be reduced.

When the back plate 180 is made of a high rigidity material such as SUS, the back plate 180 can maintain a desired rigidity even if the thickness thereof is reduced, and thus can serve as a support for the display panel 110. In addition, plastic deformation of the back plate 180 can be reduced by reducing the thickness.

However, since the elastic deformation region of the back plate 180 made of a high-rigidity material and having a small thickness is narrow, restoration after deformation is very difficult. That is, unfolding does not occur after folding, and the time for maintaining the shape at the time of folding increases.

The foldable display device 100 of the present invention enlarges the elastic deformation region of the back plate 180 by forming at least one opening pattern 182 in the folding region FR of the back plate 180. [ The opening pattern 182 formed in the folding region FR acts like a spring and the restoring property of the back plate 180 is improved. Therefore, the problem of increase in the restoration time due to reduction in thickness of the back plate 180 can be solved.

In other words, the back plate 180 of the present invention is made of a highly rigid material and has a high restoring force, and the elastic deformation section is enlarged by the opening pattern 182. Therefore, the backing plate 180 has a small thickness (for example, 2 mm), and the foldable characteristic of the display device 100 is improved.

On the other hand, display failure may occur due to the opening pattern 182 formed on the back plate 180.

First and second level compensating layers 186 and 188 may be formed on the bottom and top surfaces of the back plate 180 to prevent such problems and to protect the opening pattern 182.

The first and second level compensating layers 186 and 188 are made of a material having a lower rigidity than the back plate 180. For example, each of the first and second level difference compensation layers 186 and 188 may be formed of any one of polyurethane (PU), thermoplastic polyurethane (TPU), polyacrylate, rubber, and silicon Lt; / RTI >

The first and second level difference compensating layers 186 and 188 cover and protect the opening pattern 182 and remove the stepped portion by the opening pattern 182. It is possible to prevent display defects such that the step by the opening pattern 182 is visible on the display surface. The first and second level difference compensating layers 186 and 188 can prevent the occurrence of such display defects .

Only one of the first and second level difference compensating layers 186 and 188 may be formed and both the first and second level compensating layers 186 and 188 may be omitted. Also, the first and second level difference compensating layers 186 and 188 are shown covering the entire surface of the back plate 180, but they may be formed only in the folding area FR.

In addition, the first and second level difference compensation layers 186 and 188 may be formed to fill the opening pattern 182.

The cover window 190 protects the display panel 110 from an external impact and prevents scratches or the like from being prevented from being damaged.

Meanwhile, although not shown, a touch panel may be positioned between the display panel 110 and the cover window 190.

The foldable display device 100 of the present invention can reduce the thickness by including the highly rigid back plate 180 and reduce the thickness of the folded back display 180 By forming the opening pattern 182, the restoring force of the back plate 180 can be increased. That is, the back plate 180 having a small thickness and high restoring force can be provided.

Accordingly, it is possible to provide the thin, foldable display device 100 having excellent folding / unfolding characteristics.

5A to 5D are plan views showing the back plate, respectively.

5A, a first pattern 182a formed in the (2n-1) -th row and a second pattern 182b formed in the (2n) -th column are formed in the folding region FR of the back plate 180 An opening pattern 182 is formed. (Where n is a positive integer).

In FIG. 5A, the folding area FR is shown as being located at the center of the back plate 180, but the position of the folding area FR is not limited. Further, two or more folding regions FR may be defined.

Each of the first and second patterns 182a and 182b may have a rectangular shape. The space between the second patterns 182b formed in the (2n) th column may correspond to the first pattern 182a formed in the (2n-1) th column.

Both ends of the first pattern 182a may be located in the folding region FR and one end of the second pattern 182b may be located on one side of the back plate 180 in the folding region FR .

That is, one side of the back plate 180 is discontinuous in the (2n) th row. In other words, in the folding region FR, one side of the back plate 180 is connected to a portion between the first and second patterns 182a and 182b and a portion between the two second patterns 182b And the folding region FR functions as a spring.

In FIG. 5A, one first pattern 182a is formed in the odd-numbered columns and two second patterns 182b are formed in the even-numbered columns. However, two or more of the first patterns 182a may be formed, and three or more of the second patterns 182b may be formed.

Each of the first and second patterns 182a and 182b extends in the column direction. That is, the long axes of the first and second patterns 182a and 182b may be parallel to the column direction.

The first distance D1 between two of the second patterns 182b may be equal to or less than the first length L1 of each of the second patterns 182b, (D1) may be smaller than the first length (L1).

Therefore, the folding area FR formed with the opening pattern 182 functions as a spring when the foldable display device 100 (Fig. 3) unfolds, and increases the elastic restoring energy of the back plate 180 . Therefore, the unfolding time of the display device 100 can be reduced.

5B, a first pattern 282a formed in the (2n-1) -th column and a second pattern 282b formed in the (2n) -th column are formed in the folding region FR of the back plate 280 An opening pattern 282 is formed. (Where n is a positive integer).

In FIG. 5B, the folding region FR is shown as being located at the center of the back plate 280, but the position of the folding region FR is not limited. Further, two or more folding regions FR may be defined.

Each of the first and second patterns 282a and 282b may have a rhombic shape. The first pattern 282a formed in the (2n-1) th column may correspond to the second pattern 282b formed in the (2n) th row, and the first and second patterns 282a and 282b of the respective columns may correspond to the second pattern 282b formed in the Are spaced apart from each other.

For example, the first patterns 282a of the (2n-1) th column are spaced apart from each other, and the second patterns 282b of the (2n) th column are disposed apart from each other. Also, the first pattern 282a of the (2n-1) th column and the second pattern 282b of the (2n) th column are also spaced from each other.

For example, each of the first and second patterns 282a and 282b may be spaced apart from each other by a second distance D2, and a second distance D2 may be formed between the first and second patterns 282a and 282b, May be equal to or less than the second length L2, and preferably the second distance D2 may be less than the second length L2.

Therefore, the folded area FR formed with the opening pattern 282 functions as a spring when the foldable display device 100 (Fig. 3) is unfolded, and increases the elastic restoring energy of the back plate 280 . Therefore, the unfolding time of the display device 200 can be reduced.

5C, a first pattern 382a formed in the (2n-1) -th row and a second pattern 382b formed in the (2n) -th row are formed in the folding region FR of the back plate 380 An opening pattern 382 is formed. (Where n is a positive integer).

In FIG. 5C, the folding area FR is shown as being located at the center of the back plate 380, but the position of the folding area FR is not limited. Further, two or more folding regions FR may be defined.

Each of the first and second patterns 382a and 382b may have a rhombic shape. In addition, the first pattern 382a formed in the (2n-1) th column may correspond to the second pattern 382b formed in the (2n) th column. For example, the center of the first pattern 382a corresponds to the space between the second patterns 382b, and the center of the second pattern 382b corresponds to the space between the first patterns 382a.

For example, the first and second patterns 382a and 382b may be spaced apart from each other by a third distance D3, and the third distance D3 may be spaced from the first and second patterns 382a and 382b, May be equal to or less than the third length L3, and preferably the third distance D3 may be less than the third length L3.

Therefore, the folding area FR formed with the opening pattern 382 functions as a spring when the foldable display device (100 of FIG. 3) is unfolded and increases the elastic restoring energy of the back plate 380 . Therefore, the unfolding time of the display device 100 can be reduced.

5D, a first pattern 482a formed in the (2n-1) th column and a second pattern 482b formed in the (2n) th row are formed in the folding region FR of the back plate 480 An opening pattern 482 is formed. (Where n is a positive integer).

In FIG. 5D, the folding area FR is shown as being positioned at the center of the back plate 480, but the position of the folding area FR is not limited. Further, two or more folding regions FR may be defined.

Each of the first and second patterns 482a and 482b may have an elliptical shape having a constant minor axis. That is, each of the first and second patterns 482a and 482b has a shape in which a semicircle is coupled to both ends of a rectangle.

Also, the first pattern 482a formed in the (2n-1) th column may correspond to the second pattern 482b formed in the (2n) th column. For example, the center of the first pattern 482a may correspond to the space between the second patterns 482b, and the center of the second pattern 482b may correspond to the space between the first patterns 482a.

Each of the first and second patterns 482a and 482b extends in the column direction. That is, the long axes of the first and second patterns 482a and 482b may be parallel to the column direction. The fourth distance D4 between each of the first and second patterns 482a and 482b may be equal to or less than the fourth length L4 of each of the first and second patterns 482a and 482b, Preferably, the fourth distance D4 may be less than the fourth length L4. The end portions of the first and second patterns 482a and 482b have a predetermined radius of curvature RC.

Therefore, the folding area FR formed with the opening pattern 482 functions as a spring when the foldable display device (100 of FIG. 3) is unfolded and increases the elastic restoring energy of the back plate 480 . Therefore, the unfolding time of the display device 100 can be reduced.

5A to 5D, the opening patterns 180, 280, 380, and 480 are shown to be rectangular, rhombic, or elliptical with a constant minor axis length, but the shape is not limited. For example, the opening patterns 180, 280, and 380 may have various shapes such as a circle, an ellipse, a square, and a trapezoid.

6 is a schematic cross-sectional view of a foldable display device according to a second embodiment of the present invention.

6, the second embodiment of the present invention includes a display panel 510 and a folding region (FR) 520 located under the display panel 510 A back plate 580 having at least two opening patterns 582 on the display panel 510 and a cover window 590 located above the display panel 510. [

Although not shown, the display panel 510 includes a flexible substrate and a display element formed on the flexible substrate. For example, the flexible substrate may be a polyimide substrate, and the display device may be an organic light emitting diode.

The back plate 580 is positioned below the display panel 510 and supports the display panel 510. For example, the back plate 580 may be attached to the display panel 510 using an adhesive layer (not shown).

The back plate 580 has greater stiffness than the flexible substrate (not shown) of the display panel 510. That is, the back plate 580 has a larger Young's modulus than the flexible substrate.

In the foldable display device 500 of the present invention, the back plate 580 has a first thickness t1 in the folding region FR and is spaced apart from the unfolding region UFR on both sides of the folding region FR And has a second thickness t2 that is greater than the first thickness t1. That is, the back plate 580 is formed with a concave portion 584 corresponding to the folding region FR.

For example, if the back plate 580 has a first thickness t1 in both the folding area FR and the unfolding area UFR, the folding characteristics in the folding area FR can be satisfied, The stiffness of the plate 580 is reduced and a problem occurs in supporting the display panel 510 in the unfolding region FR.

On the other hand, if the back plate 580 has the second thickness t2 in both the folding area FR and the unfolding area UFR, a problem arises in folding characteristics in the folding area FR.

However, in the present invention, since the back plate 580 has a relatively large second thickness t2 in the unfolding area UFR and a comparatively small first thickness t1 in the folding area FR, the back plate 580 ) Are all satisfied.

In addition, by forming at least one opening pattern 582 on the back plate 580, the elastic deformation section of the back plate 580 is enlarged. That is, the opening pattern 582 is located in the concave portion 584 of the back plate 580. The opening pattern 582 formed in the folding region FR acts like a spring and the restoring property of the back plate 580 is improved.

The opening pattern 582 can be variously changed as shown in FIGS. 5A to 5D.

For example, as shown in FIG. 5D, when each of the first and second patterns 482a and 482b has an elliptical shape with a constant minor axis length, the diameter of the end circle is larger than the diameter of the back plate The folding characteristic is improved without reducing the rigidity of the back plate 580 in the folding region FR by making the thickness t1 equal to or smaller than 1.5 times the first thickness t1. (t1? 2RC? 1.5 * t1)

The base film constituting the back plate 580 is subjected to an etching process to lower the thickness in the folding region FR and form the opening pattern 582. [ That is, after the recessed portion 584 is formed through the etching process for the entire folding region FR, the opening pattern 582 is formed by performing an additional etching process on a part of the folded region FR.

In Fig. 6, the display device 500 is folded toward the cover window 590 side. That is, the back plate 580 is folded to be located on the outer side, and the recessed portion 584 is formed on the outer surface of the back plate 580.

Alternatively, the foldable display device 500 may be folded toward the back plate 580, in which case the recess 584 is formed on the inner surface of the back plate 580. That is, the concave portion 584 is formed on the surface facing the display panel 510. [

7A to 7C are sectional views showing the back plate, respectively.

As shown in FIG. 7A, a first level difference compensation layer 586 may be formed on one side of the back plate 580. That is, the first level difference compensation layer 586 is formed on the surface of the back plate 580 where the concave portion 584 is formed.

The first level difference compensating layer 586 has a third thickness t3 in the folding region FR and a fourth thickness t4 in the unfolding region UFR that is smaller than the third thickness t3 .

7B, the first level difference compensating layer 586 may be formed only on the concave portion 584. FIG. That is, the first level difference compensating layer 586 has a flat surface with the back plate 580.

Referring to FIG. 7C, a second level difference compensating layer 588 may be further formed on the other side of the back plate 580. The second level difference compensation layer 588 has a substantially uniform fifth thickness t5 and the fifth thickness t5 is smaller than the third thickness t3 and greater than the fourth thickness t4 .

The second level compensating layer 588 has a fifth thickness t5 that is less than the third thickness t3 of the first level compensating layer 586 in the recess 584, (Compressive state). Therefore, the folding / unfolding characteristic of the foldable display device 500 including the back plate 580 is further improved.

Each of the first and second level difference compensating layers 586 and 588 is made of a material having a stiffness lower than that of the back plate 580 and a stress compensation applied to the back plate 580 by a folding operation ). That is, each of the first and second level difference compensation layers 586 and 588 has a smaller modulus than the back plate 580.

For example, each of the first and second level difference compensation layers 586 and 588 may be formed of any one of polyurethane (PU), thermoplastic polyurethane (TPU), polyacrylate, rubber, and silicon Lt; / RTI >

The first and second level difference compensating layers 586 and 588 cover and protect the opening pattern 582 and remove the stepped portion by the opening pattern 582. It is possible to prevent the occurrence of such display defects by the first and second level difference compensating layers 586 and 588 because the display defect that the step by the opening pattern 582 is visible on the display surface may be generated .

The first level difference compensating layer 586 and the back plate 580 are formed at the end of the concave portion 584 because the first level compensating layer 586 is made of a different material from the back plate 580. [ Can be recognized. That is, the display quality may be degraded due to the difference in refractive index between the first compensating layer 586 and the back plate 580.

In order to prevent such a problem, the boundary between the first level difference compensating layer 586 and the concave portion 584, that is, the end (edge) of the concave portion 584 is arranged in the display panel And may correspond to a boundary between adjacent pixel regions. For example, the end of the recess 584 may correspond to a bank (166 in FIG. 4A) or a black matrix (254 in FIG. 4B).

8A to 8C are views for explaining a back plate of a foldable display device according to a third embodiment of the present invention.

A folding region FR and an unfolding region UFR are defined on the back plate 680 and the folding region FR is divided into a center portion CN and an edge portion ED .

At this time, the opening patterns 682 formed in the folding regions FR have the same size and different distances therebetween. (pitch variable)

That is, in the folding direction, the opening patterns 682 have a first distance d1 at the edge portion ED and a second distance d2 at the central portion CN that is less than the first distance d1 .

8B showing the back plate 680 in the folded state, the back plate 680 having a different distance between the opening patterns 682 is formed in the edge portion ED of the folding region (FR in FIG. 8A) Has a radius of curvature and a second curvature radius smaller than the first radius of curvature at the central portion (CN).

8A), the folded region (FR in FIG. 8A) is formed between the central portion CN and the first edge portion ED1, the second edge portion ED2 between the center portion CN and the first edge portion ED1, And the opening pattern 682 has a first distance from the first edge portion ED1 in the folding direction and a second distance from the center portion CN and is greater than the second distance from the second edge portion ED2 And a third distance less than the first distance.

That is, the distance from the edge of the folded area FR toward the center of the opening pattern 682 may gradually decrease.

The stress may concentrate at the point where the curvature of the display device of the foldable display starts (i.e., the edge portion ED or the first edge portion ED1), and the display panel may be damaged. In the present invention, by adjusting the distance between the opening patterns 682 formed in the folding region FR of the back plate 680, the radius of curvature at the folding start point is increased and stress concentration is alleviated. Thus, damage to the display panel is minimized or prevented.

9A to 9C are views for explaining a back plate of a foldable display device according to a fourth embodiment of the present invention.

9A, a folding region FR and an unfolding region UFR are defined on the back plate 780 and the folding region FR is divided into a center portion CN and an edge portion ED .

At this time, the opening patterns 782 formed in the folding regions FR are arranged at the same distance and have different sizes. (size variable)

That is, in the folding direction, the opening pattern 782 has a first width w1 at the edge portion ED and a second width w2 greater than the first width w1 at the central portion CN .

9B showing the back plate 780 in the folded state, the back plate 780 having a different size of the opening pattern 782 has the first curvature at the edge portion ED of the folding region (FR in FIG. 9A) And has a second curvature radius smaller than the first radius of curvature at the central portion CN.

9A, the folded region (FR in FIG. 9A) is located between the center portion CN and the first edge portion ED1, and between the center portion CN and the first edge portion ED1, the second edge portion ED2 , And the opening pattern 782 has a first width at the first edge portion ED1 in the folding direction and a second width at the central portion CN and a width greater than the first width at the second edge portion ED2 And a third width smaller than the second width.

That is, the size of the opening pattern 782 may gradually increase from the edge of the folding region FR toward the center.

In the present invention, by adjusting the size of the opening pattern 782 formed in the folding region FR of the back plate 780, the radius of curvature at the folding start point is increased and stress concentration is relaxed. Thus, damage to the display panel is minimized or prevented.

In FIGS. 8A to 8C and FIGS. 9A to 9C, it is shown that the distance between the opening patterns or the size of the opening pattern in the back plate including the concave portion is adjusted. Alternatively, the back plate may have a constant thickness without including the recesses.

As described above, in the foldable display device of the present invention, two or more opening patterns spaced apart from each other in the folding area of the back plate are formed, so that even if the folding / unfolding operation of the foldable display device is repeated, restoration is possible. That is, the elastic deformation section is increased by the opening pattern formed in the folding region, and restoration is possible.

Therefore, the folding characteristic can be improved without increasing the thickness of the display device.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

100, 500: Foldable display device 110, 510: Display panel
180, 280, 380, 480, 580, 680, 780:
186, 188, 586, 588: step difference compensation layer
182, 282, 382, 482, 582, 682, 782:
584: concave part FR: folding area
UFR: unfolding area

Claims (20)

A display panel;
Wherein the display panel is divided into a folding area and an unfolding area on both sides of the folding area, the backing plate having at least two opening patterns spaced apart from each other in the folding area,
And a display unit.
The method according to claim 1,
Wherein the opening pattern includes at least one first pattern located in the (2n-1) -th column and at least one second pattern located in the (2n) -th column, and the space between the second patterns corresponds to the first pattern And a display unit for displaying the position of the display unit. (n is a positive integer)
The method according to claim 1,
Wherein the opening pattern includes at least one first pattern located in the (2n-1) th column and at least one second pattern located in the (2n) th column, the first pattern corresponding to the second pattern A folder display device is located. (n is a positive integer)
The method according to claim 1,
Wherein the opening pattern includes a first pattern located in the (2n-1) th column and two or more second patterns located in the (2n) th column, and in the (2n) th column, A display device of the same or smaller than the length of the pattern. (n is a positive integer)
The method according to claim 1,
Wherein the opening pattern has a rectangular shape, a rhombic shape, or an elliptical shape having a constant minor axis length.
The method according to claim 1,
Wherein one side of the back plate is discontinuous in the folded area.
The method according to claim 1,
Wherein the display panel includes a flexible substrate, and the modulus of the back plate is larger than that of the flexible substrate.
The method according to claim 1,
And a step difference compensation layer covering the folding area is disposed on at least one surface of the back plate.
9. The method of claim 8,
Wherein the step difference compensation layer has a smaller modulus than the back plate.
The method according to claim 1,
Wherein the back plate has a recess corresponding to the folding area and has a first thickness in the folding area and a second thickness in the unfolding area that is greater than the first thickness.
11. The method of claim 10,
And a step difference compensation layer attached to one surface of the back plate on which the concave portion is formed.
11. The method of claim 10,
Wherein the display panel includes a plurality of pixel regions, and an edge of the concave portion corresponds to a boundary between the pixel regions.
11. The method of claim 10,
Wherein the display panel corresponds to an organic light emitting diode panel and the edge of the recess corresponds to a bank covering a first electrode edge of the organic light emitting diode.
11. The method of claim 10,
And the level difference compensating layer forms a flat surface with the back plate.
11. The method of claim 10,
Wherein the concave portion is located on an outer surface of the back plate, and the folder-type display device is folded toward the display panel.
11. The method of claim 10,
Wherein the concave portion is located on the inner side of the back plate, and the foldable display device is folded toward the back plate.
The method according to claim 1,
Wherein the folding region is divided into an edge portion and a center portion along a folding direction and the opening pattern is spaced apart from the edge portion by a first distance along the folding direction and along the folding direction at the center portion, Foldable display device separated by a distance.
The method according to claim 1,
The distance between the opening patterns decreases along the folding direction from the edge toward the center.
The method according to claim 1,
Wherein the folding region is divided into an edge portion and a central portion along a folding direction, the opening pattern having a first width along the folding direction at the edge portion and a second width larger than the first width along the folding direction at the central portion, And a display unit.
The method according to claim 1,
The size of the opening pattern increases from the edge to the center along the folding direction.

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