CN106875845A - Foldable display device - Google Patents

Abstract

A foldable display device comprising: a display panel including a first surface and a second surface opposite to the first surface; A shock-absorbing film with two shock-absorbing layers; wherein the second shock-absorbing layer includes a soft portion corresponding to a first region of the second shock-absorbing layer and a hard portion corresponding to a second region of the second shock-absorbing layer, and the second shock-absorbing layer The elastic modulus value of the soft portion of the absorbing layer and the first shock absorbing layer is smaller than the elastic modulus value of the hard portion.

Description

foldable display device

Cross References to Related Applications

This application claims Korean Patent Application No. 10-2015-0169503 filed in Korea on November 30, 2015, Korean Patent Application No. 10-2016-0048801 filed in Korea on April 21, 2016, and Korean Patent Application No. 10-2016-0120655 filed in Korea on September 21, 2016, all of which are incorporated herein by reference in their entirety.

technical field

The present disclosure relates to foldable display devices, and more particularly, to foldable display devices having improved impact resistance.

Background technique

With the development of information technology and mobile communication technology, display devices capable of displaying visual images have also been developed. Flat panel display devices have been developed.

For example, flat panel display devices include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display (FED) devices, and organic light emitting display (OLED) devices. Flat panel display devices are used to replace cathode ray tubes (CRTs) due to their excellent capabilities of thin profile, light weight, and low power consumption.

Generally, a glass substrate suitable for high temperature in the manufacturing process of the flat panel display device is used for the flat panel display device. Therefore, there are limitations on thin profile, light weight and flexibility.

In order to overcome the limitations of glass substrates, flexible substrates such as plastic substrates are used to provide flexible display devices.

Flexible display devices can be classified into unbreakable display devices, bendable display devices, rollable display devices, and foldable display devices. Recently, among these flexible display devices, foldable display devices that can be folded and unfolded have been extensively studied. A foldable display device is portable in a folded state, and displays an image in an unfolded state. The foldable display device can be used in mobile devices such as mobile phones, ultra-mobile PCs, e-books and e-papers, televisions or monitors.

A foldable display device may include a display panel, a back panel, and a cover window. A backplane is disposed under the display panel to support the display panel, and a cover window is disposed above the display panel to protect the display panel.

On the other hand, since the foldable display device should be folded and unfolded, the display panel, the back panel and the cover window should all be very thin film types. However, in film-type elements, external shocks are transmitted in the vertical direction.

That is, the impact applied to the cover window or the back plate is directly transmitted into the display panel. Therefore, there is damage on the display panel, and the display quality of the foldable display device is degraded.

Contents of the invention

Accordingly, the present invention is directed to a foldable device that substantially obviates one or more problems due to limitations and disadvantages of the related art.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, a foldable display device includes: a display panel including a first surface and a second surface opposite to the first surface; A shock-absorbing film at the second surface of the panel comprising a first shock-absorbing layer and a second shock-absorbing layer; wherein the second shock-absorbing layer includes a soft portion corresponding to the first region of the second shock-absorbing layer and corresponding to the second The hard portion of the second region of the impact-absorbing layer, and the soft portion of the second impact-absorbing layer and the first impact-absorbing layer have an elastic modulus value that is less than the elastic modulus value of the hard portion.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

Description of drawings

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1 is a schematic cross-sectional view of a foldable display device according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a display panel for a foldable display device according to the present invention.

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

FIG. 4 is a diagram illustrating a ball drop test of a foldable display device according to the present invention.

detailed description

Reference will now be made in detail to the preferred embodiments, examples of which are illustrated in the accompanying drawings.

1 is a schematic cross-sectional view of a foldable display device according to a first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of a display panel for a foldable display device according to the present invention.

As shown in FIG. 1 , the foldable display device 100 includes a display panel 110 for providing images, a back plate 130 supporting the display panel 110 , and a cover window 140 protecting the display panel 110 .

The back plate 130 is disposed on one side of the display panel 110 , and the cover window 140 is disposed on the opposite side of the display panel 110 . That is, the display panel 110 is located between the back plate 130 and the cover window 140 .

The foldable display device 100 may further include a touch panel 120 including a touch sensor (not shown). The touch panel 120 may be disposed between the display panel 110 and the cover window 140 .

For example, the display panel 110 may be one of a Liquid Crystal Display (LCD) device, a Plasma Display Panel (PDP) device, a Field Emission Display (FED) device, and an Organic Light Emitting Display (OLED) device. Preferably, the display panel 110 may be an OLED device because the OLED device has excellent capabilities of thin profile, light weight, low power consumption, and the like.

Referring to FIG. 2 , a display panel 110 for an OLED device includes a substrate 101 , a driving thin film transistor (TFT) DTr, an organic light emitting diode E, and a protective film 102 . The driving TFT DTr and the organic light emitting diode E may be formed on the substrate 101 and may be encapsulated by the protective film 102 .

A plurality of pixel regions P are defined on the substrate 101, and a driving TFT DTr and an organic light emitting diode E are located in each pixel region P.

A semiconductor layer 104 is formed on the substrate 101 and in the pixel region P. As shown in FIG. The semiconductor layer 104 is formed of silicon, and includes an active region 104a, a source region 104b, and a drain region 104c. The active region 104a serving as a channel is the center of the semiconductor layer 104, and the source region 104b and the drain region 104c are located on both sides of the active region 104a, respectively. The source region 104b and the drain region 104c are doped with high concentration impurities.

A gate insulating layer 105 is formed on the semiconductor layer 104 , and a gate electrode 107 is formed on the gate insulating layer 105 . The gate electrode 107 corresponds to the active region 104 a of the semiconductor layer 104 . In addition, a gate line (not shown) extending along the first direction is formed on the gate insulating layer 105 .

A first interlayer insulating layer 106 a is formed on the entire surface of the substrate 101 on the gate electrode 107 . A first semiconductor contact hole and a second semiconductor contact hole 109 exposing the source region 104 b and the drain region 104 c respectively are formed through the first interlayer insulating layer 106 a and the gate insulating layer 105 .

A source electrode 108a and a drain electrode 108b spaced apart from each other are formed on the first interlayer insulating layer 106a. The source electrode 108 a and the drain electrode 108 b contact the source region 104 b and the drain region 104 c through the first semiconductor contact hole and the second semiconductor contact hole 109 , respectively. In addition, data lines (not shown) and power lines (not shown) extending along the second direction are formed on the first interlayer insulating layer 106a.

The semiconductor layer 104, the gate electrode 107, the source electrode 108a, and the drain electrode 108b constitute a driving TFT DTr.

Although not shown, a switching TFT having substantially the same structure as the driving TFT DTr is formed. The switching TFT is electrically connected to the gate line, the data line and the driving TFT DTr.

In FIG. 2, the gate electrode 107, the source electrode 108a, and the drain electrode 108b are located over the semiconductor layer 104, and the semiconductor layer 104 contains an oxide semiconductor material or polysilicon. That is, the TFT DTr has a coplanar structure. Alternatively, the gate electrode may be located below the semiconductor layer, and the source and drain electrodes may be located above the semiconductor layer, so that the TFT DTr may have a reverse staggered structure. In this case, the semiconductor layer may contain amorphous silicon.

A second interlayer insulating layer 106b including a drain contact hole 112 exposing the drain electrode 108b is formed on the source electrode 108a and the drain electrode 108b.

A first electrode 111 is formed on the second interlayer insulating layer 106b in the image display region. For example, the first electrode 111 may have a relatively high work function to serve as an anode. The first electrode 111 may include a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The first electrode 111 is connected to the drain electrode 108b of the driving TFT DTr through the drain contact hole 112, and is separated in each pixel region P. Referring to FIG.

A bank 119 is formed at the boundary of the pixel region P over the first insulating interlayer 106b. The bank 119 covers the edges of the first electrode 111 and exposes the center of the first electrode 111 .

An organic light emitting layer 113 is formed on the first electrode 111 . The organic light emitting layer 113 may have a single layer structure of light emitting material. Alternatively, the organic light emitting layer 113 may have a multilayer structure of a hole injection layer, a hole transport layer, a light emitting material layer, an electron transport layer, and an electron injection layer in order to improve light emission efficiency. The organic light emitting layer 113 may include a red light emitting pattern 113a, a green light emitting pattern 113b, and a blue light emitting pattern 113c in each pixel region P.

A second electrode 115 is formed over the entire surface of the substrate 101 on the organic light emitting layer 113 . The second electrode 115 may have a relatively low work function to function as a cathode. For example, the second electrode 115 may be a translucent thin metal film of aluminum (Al), magnesium (Mg), or Al-Mg alloy. Alternatively, the second electrode 115 may have a double layer structure of a transparent conductive material layer on a translucent tin metal film. Light from the organic light emitting layer 113 passes through the second electrode 115, so that the organic light emitting diode E including the first electrode 111 and the second electrode 115 with the organic light emitting layer 113 therebetween operates in a top emission type. In this case, a reflective electrode or a reflective layer may be formed under the first electrode 111 .

Alternatively, light from the organic light emitting layer 113 may pass through the first electrode 111 using the second electrode 115 of an opaque metal layer, so that the organic light emitting diode E may operate in a bottom emission type.

In the OLED panel 110, when a voltage is applied to the first electrode 111 and the second electrode 115, holes from the first electrode 111 and electrons from the second electrode 115 are transferred into the organic light emitting layer 113 to form excitons. Excitons transition from an excited state to a ground state to emit light. Accordingly, the OLED panel 110 may display an image on the first electrode 111 or the second electrode 115 side.

A protective film 102 as a thin film is formed over the driving TFT DTr and the organic light emitting diode E so that the organic light emitting diode E is encapsulated by the protective film 102 . Water penetration into the organic light emitting diode E and/or the driving TFT DTr is prevented by the protective film 102 . For example, the protective film 102 may include first and second inorganic layers and an organic layer therebetween.

To provide flexibility, the substrate 101 may include polyimide. A polyimide substrate is not suitable for a manufacturing process of an element such as a driving TFT DTr. Therefore, elements such as the driving TFT DTr are formed on the polyimide substrate 101 by attaching a carrier substrate (not shown) to the lower surface of the polyimide substrate 101, and then the carrier substrate is removed from the polyimide substrate 101. freed.

The touch panel 120 may be disposed on or over the display panel 110 . For example, the display panel 110 and the touch panel 120 are attached using an adhesive layer (not shown).

Although not shown, the touch panel 120 may include a first touch film including first touch electrodes and a second touch film including second touch electrodes. The first touch film and the second touch film are spaced apart from each other and face each other. The first touch electrodes and the second touch electrodes may constitute a touch sensor.

For example, the first touch electrodes may be formed on the entire surface of the first touch film. The first touch electrodes may include a transparent conductive material such as ITO or IZO. The second touch electrodes may have a stripe shape along a certain direction and spaced apart from each other by a predetermined distance. The second touch electrode may include a metal material such as Al, Al alloy (AlNd), Mg, gold (Au), and silver (Ag). The first touch electrodes and the second touch electrodes constitute a touch sensor.

By a touch of a touch object at a position of the touch panel 120, the first touch electrode and the second touch electrode at the touched position are electrically connected so that the touched position can be detected.

The touch panel 120 and the display panel 110 are modularized through the cover window 140 and the back plate 130 . The touch panel 120 is located on the image display side of the display panel 110 , and the cover window 140 is attached to the touch panel 120 using the first optical adhesive layer 150 . In the absence of any touch panel 120 , the cover window 140 is attached to the image display side of the display panel 110 using the first optical adhesive layer 150 . The back sheet 130 is attached to the rear side of the display panel 110 , ie, the opposite side of the display panel 110 from the image display side, using the second optical adhesive layer 160 .

For example, each of the first optical adhesive layer 150 and the second optical adhesive layer 160 is formed of an optically transparent adhesive material and has a thickness of about 100 μm to 300 μm.

When the thickness of each of the first optical adhesive layer 150 and the second optical adhesive layer 160 is less than 100 μm, adhesive strength is insufficient, causing problems in modularization of the foldable display device 100 . On the other hand, when the thickness of each of the first optical adhesive layer 150 and the second optical adhesive layer 160 is greater than 300 μm, there is a problem in the folding operation of the foldable display device 100 .

The display panel 110 (and the touch panel 120 ) may be protected from external impact by the cover window 140 , and an image from the display panel 110 is displayed on the cover window 140 .

Impact resistance (or impact resistance) performance and transmission performance are required in the cover window 140 . For example, the cover window 140 may be made of polymethyl methacrylate (PMMA), polycarbonate (PC), cycloolefin polymer (COP), polyethylene terephthalate (PET), polyimide ( PI) and one of polyaramid (PA).

The relatively small-thickness substrate 101 of the display panel 110 is supported by the backplane 130 . For example, the back plate 130 may be formed of a metal material such as stainless steel (SUS) or a polymer such as PMMA, PC, polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), or PET.

Each of the first optical adhesive layer 150 and the second optical adhesive layer 160 has a modulus value, ie, Young's Modulus value or modulus of elasticity value. In more detail, the modulus value of the first optical adhesive layer 150 is less than the modulus value of the cover window 140 and the display panel 110 (and/or the touch panel 120), and the modulus of the second optical adhesive layer 160 is less than Moduli of the display panel 110 and the backplane 130 . That is, each of the first optical adhesive layer 150 and the second optical adhesive layer 160 has less rigidity than each of the cover window 140 , (the touch panel 120 ,) the display panel 110 , and the backplane 130 .

For example, each of the cover window 140, the touch panel 120, and the display panel 110 has a modulus value of about 5GPa to 8GPa, and the back plate 130 has a modulus value of about 8GPa to 10GPa. Each of the first optical adhesive layer 150 and the second optical adhesive layer 160 has a modulus value of about 10 ³ Pa to 10 ⁴ Pa. In other words, in the foldable display device 100, high modulus elements and low modulus elements are alternately arranged in the vertical direction.

Specifically, the modulus value of the first optical adhesive layer 150 between the cover window 140 and the touch panel 120 is smaller than that of each of the cover window 140 and the touch panel 120, and the display panel 110 and the back plate 130 The modulus value of the second optical adhesive layer 160 in between is smaller than the modulus value of each of the display panel 110 and the back plate 130 .

Accordingly, external impact applied to the cover window 140 and/or the back plate 130 and transmitted to the display panel 110 and/or the touch panel 120 is minimized, so that damage on the display panel 110 and/or the touch panel 120 is minimized or prevented.

The film in the foldable display device transmits external impact (ie, absorbs external impact) in a vertical direction instead of a horizontal direction. For example, when an external impact is applied to the cover window 140 , the external impact is directly (ie, vertically) transferred into the touch panel 120 and/or the display panel 110 . Accordingly, damage occurs to electrodes or elements in the touch panel 120 and/or the display panel 110 .

However, in the foldable display device 100 of the present invention, due to the high modulus elements (such as the cover window 140, the touch panel 120, the display panel 110 and the back plate 130) and the low modulus elements (such as the first optical bonding The agent layer 150 and the second optical adhesive layer 160) are alternately stacked in the vertical direction, so when the external impact passes through the high modulus element and the low modulus element, the external impact is released or mitigated. Accordingly, external impact transmitted to the touch panel 120 and/or the display panel 110 is minimized or prevented.

Specifically, between high modulus components (such as cover window 140, touch panel 120, display panel 110, and backplane 130) and low modulus components (such as first optical adhesive layer 150 and second optical adhesive With a greater difference in modulus values between the layers 160), damage to the touch panel 120 and/or the display panel 110 by external impacts is minimized.

Table 1

The results of the drop ball test on the foldable display device in the folding region are listed in Table 1 with respect to the modulus values of the optical adhesive layer and the impact absorbing film.

In the drop ball test, after the upper group and the lower group are combined to the foldable display device, balls having various heights are dropped on the foldable display device to detect whether there is damage. The durability of the display device is higher as the location of the falling ball that starts to cause damage to the foldable display device is higher. In this case, the lower group includes the folding region "FR" (FIG. 3) and the non-folding region "NFR" (FIG. 3), and the lower group contacts the foldable display device in the folding region "FR" and contacts the foldable display device in the non-folding region "FR". The region "NFR" is spaced apart from the foldable display device to form a gap. For example, a gap between the lower group and the foldable display device may be about 1mm in the non-folding region "NFR".

"Sample A" is the result of a drop ball test on a foldable display device having an optical adhesive layer with a modulus value of 2.2× ^{10 5} Pa, and "Sample B" is the result of a Drop ball test results of foldable display devices with optical adhesive layers.

In "Sample A" and "Sample B", each of cover window 140, touch panel 120, and display panel 110 has a modulus value of about 5 GPa to about 8 GPa, and backplane 130 has a modulus value of about 8 GPa to about 10 GPa. magnitude.

As listed in Table 1, the drop ball test (<10 cm) was improved due to the lower modulus values of optical adhesive layers 150 and 160 ("Sample B"). That is, as described above, when the optical adhesive layer has a relatively small modulus value with respect to the high modulus member, damage caused by external impact is further reduced.

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

The same reference numerals are used for the same elements, and the description focuses on the differences from the first embodiment.

As shown in FIG. 3 , the foldable display device 100 includes a display panel 110, a back plate 130 supporting the display panel 110, a cover window 140 protecting the display panel 110, and a shock absorbing film 170, and optionally includes a touch panel 120 (the touch panel 120 including a touch sensor (not shown)). That is, the foldable display device 100 according to the second embodiment may correspond to the foldable display device 100 according to the first embodiment in which the impact absorbing film 170 is added.

The impact absorbing film 170 is disposed on the rear side of the back plate 130 , that is, the opposite side of the back plate 130 from the side of the back plate 130 on which the display panel 110 is disposed. The impact absorbing film 170 is attached to the backsheet 130 using a third optical adhesive layer 180 . The third optical adhesive layer 180 has a smaller modulus value than each of the cover window 140 , the touch panel 120 , the display panel 110 and the backplane 130 .

For example, each of the cover window 140, the touch panel 120, and the display panel 110 has a modulus value of about 5GPa to 8GPa, and the back plate 130 has a modulus value of about 8GPa to 10GPa. The third optical adhesive layer 180 has a modulus value of about 10 ³ Pa to 10 ⁴ Pa. That is, the first to third optical adhesive layers 150, 160, and 180 may have the same modulus value.

The third optical adhesive layer 180 having a relatively low modulus value is disposed under the backsheet 130 having a relatively high modulus value such that impact transmitted into the display panel 110 and/or the touch panel 120 is minimized or prevented.

The third optical adhesive layer 180 is formed of an optically transparent adhesive material, and has a thickness of about 100 μm to 300 μm.

The shock absorbing film 170 includes a first shock absorbing layer 171 and a second shock absorbing layer 173 , that is, the shock absorbing film 170 may be formed of a double layer including the first shock absorbing layer 171 and the second shock absorbing layer 173 . The first impact absorbing layer 171 may be formed of a foam type material. The second impact absorbing layer 173 may include a soft part 173a corresponding to the folded region "FR" and a hard part 173b corresponding to the non-folded region "NFR". The soft part 173a may be inserted into a space between the two parts of the hard part 173b. That is, when the non-folding region "NFR" includes a first non-folding region and a second non-folding region on both sides of the folding region "FR", the soft portion 173a corresponds to the folding region "FR" and is inserted into the In the space between the first rigid portion 173b corresponding to a non-folding region and the second rigid portion 173b corresponding to the second non-folding region. The soft portion 173a is positioned to correspond only to the folded region FR. However, in the non-folding region "NFR", the soft portion 173a may be positioned to cover the hard portion 173b. Alternatively, the second impact absorbing layer 173 may have a two-layer structure in which the soft portion 173a includes a base portion corresponding to both the folded region “FR” and the non-folded region “NFR”, and a base portion corresponding to the folded region “FR”. Projection. The protrusion may be inserted into a space between the first and second parts of the hard part 173b in the first and second non-folding regions.

On the other hand, since the materials of the soft portion 173a and the hard portion 173b have different refractive indices, the observer can observe the boundary between the soft portion 173a and the hard portion 173b. Therefore, the image quality of the foldable display device 110 may be degraded. In order to prevent this problem, the boundary between the soft part 173 a and the hard part 173 b corresponds to the boundary of adjacent pixel regions in the display panel 110 . For example, the boundary between soft portion 173a and hard portion 173b may correspond to bank 119 (FIG. 2).

The soft part 173a may be formed of one of polyurethane (PU), thermoplastic polyurethane (TPU), silicon (Si), and polydimethylacrylamide (PDMA). The hard part 173b may be formed of a metal material (eg, SUS) or a polymer (eg, PMMA, PC, PVA, ABS, or PET).

Each of the soft portion 173a of the second shock absorbing layer 173 and the first shock absorbing layer 171 has a modulus value smaller than that of the cover window 140, the touch panel 120, the display panel 110, and the back plate 130, and the second shock absorbing layer The hard portion 173b of 173 has a modulus value substantially equal to that of the cover window 140 , the touch panel 120 , the display panel 110 and the back plate 130 .

For example, each of the cover window 140, the touch panel 120, the display panel 110, and the hard portion 173b of the second impact absorbing layer 173 has a modulus value of about 5GPa to 8GPa, and the back plate 130 has a modulus of about 8GPa to 10GPa. value. Each of the soft portion 173a of the second shock absorbing layer 173 and the first shock absorbing layer 171 has a modulus value of about 10 ³ Pa to 10 ⁴ Pa.

Therefore, in the shock absorbing film 170, high modulus elements (ie, the hard part 173b) and low modulus elements (ie, the soft part 173a and the first shock absorbing layer 171) are mixed, and shocks are safely released or mitigated.

When the shock-absorbing film includes the low-modulus portion without the high-modulus portion, deformation of the shock-absorbing film easily occurs. On the other hand, when the impact absorbing film includes the high modulus portion without the low modulus portion, external impact is directly transmitted into the display panel 110 and/or the touch panel 120 .

The first shock absorbing layer 171 and the second shock absorbing layer 173 may be attached to each other using a fourth optical adhesive layer 175 . The fourth optical adhesive layer 175 is formed of an optically transparent adhesive material and has a thickness of about 100 microns to 300 microns. Since the fourth optical adhesive layer 175 is an element of the shock absorbing film 170, the modulus value of the fourth optical adhesive layer 175 is not limited.

Since the first impact absorbing layer 171 and the third optical adhesive layer 180 sequentially stacked on the fourth optical adhesive layer 175 have a lower modulus value than the back sheet 130, in the non-folding region "NFR" A stacked layer of the fourth optical adhesive layer 175, the first impact absorbing layer 171, and the third optical adhesive layer 180 serves as a low modulus member.

The first impact absorbing layer 171 has a thickness of about 100 microns to 300 microns. When the thickness of the first shock absorbing layer 171 is less than 100 micrometers, shock absorption is insufficient. On the other hand, when the thickness of the first impact absorbing layer 171 is greater than 300 μm, there is a problem in the folding operation of the foldable display device 100 .

In the non-folding region 'NFR', the second impact absorbing layer 173 may have a total thickness of about 0.1 millimeter (mm) to 1 mm, and the soft part 173 a has a thickness of about 0 to 0.9 mm. When the thickness of the second shock absorbing layer 173 is less than 0.1 mm, shock absorption is insufficient. On the other hand, when the thickness of the second impact absorbing layer 173 is greater than 1 mm, there is a problem in the folding operation of the foldable display device 100 .

In addition, when the thickness of the hard portion 173b is less than 0.1 mm, the effect of the hard portion 173b is insufficient, and the hard portion 173b having a thickness of less than 0.1 mm cannot be reliably manufactured. On the other hand, when the thickness of the hard portion 173b is greater than 1 mm, there is a problem in the folding operation of the foldable display device 100 .

In the foldable display device 100 according to the second embodiment of the present invention, due to the high modulus elements (such as the cover window 140, the touch panel 120, the display panel 110 and the back plate 130) and the low modulus elements (such as the second An optical adhesive layer 150 and a second optical adhesive layer 160) are alternately stacked in a vertical direction, so that when an external impact passes through the high modulus component and the low modulus component, the external impact is released or mitigated. In addition, due to the impact absorbing film 170 under the back plate 130, damage to the display panel 110 and/or the touch panel 120 is further reduced.

Table 2

The results of the drop ball test of the foldable display device in the folding region are listed in Table 2 with respect to the modulus values of the backsheet and the impact absorbing film.

"Sample A" is the drop ball test result of a foldable display device having an optical adhesive layer with a modulus value of 2.2×10 ⁵ Pa and no impact absorbing film. Impact resistance was tested by a ball drop test using the first impact absorbing layer having various thicknesses. "Sample C" is a drop ball test result of a foldable display device having the first shock absorbing layer 171 without the second shock absorbing layer 173 . In "Sample C", optical adhesive layers 150, 160 and 180 having a modulus value of 1.3×10 ³ Pa were used. "Sample D" is a drop ball test result of a foldable display device having a shock absorbing film 170 including a first shock absorbing layer 171 and a second shock absorbing layer 173 . That is, in the foldable display device of 'Sample D', the second impact absorbing layer 173 is also included in the foldable display device of 'Sample C'. Also, in "Sample D", the soft portion 173a has a thickness of 300 micrometers, and the hard portion 173b has a thickness of 300 micrometers in the non-folded region.

As listed in Table 2, when the modulus value of the backing plate 130 is small (eg, 0˜1 GPa), the ball drop test is substantially maintained in “Sample A” and “Sample C”. That is, although the modulus values of the optical adhesive layers 150 and 160, the presence of the first shock absorbing layer 171, and the conditions of the thickness of the first shock absorbing layer 171 are different in "Sample A" and "Sample C", but The drop ball test is maintained. That is, it is preferred that the backing sheet 130 has a modulus value greater than about 4 GPa.

In addition, in the case where the back sheet has a modulus value higher than 10 GPa, there is a problem in the folding operation of the foldable display device. Accordingly, it is preferred that the backing sheet 130 may have a modulus value of about 4 GPa to about 10 GPa.

In "Sample C" comprising the first impact absorbing layer 171 of 0.05 t and the back sheet 130 having a modulus value of 4 GPa to 7 GPa, the drop ball test at a height of 5 cm caused damage to the touch panel 120 and/or the display panel 110 . However, in “Sample C” including the first impact absorbing layer 171 of 0.10˜0.30 t and the back sheet 130 having a modulus value of 4 GPa to 7 GPa, the drop ball test at a height higher than 10 cm was not effective for the touch panel 120 and/or The display panel 110 is damaged. That is, preferably, the first impact absorbing layer 171 may have a thickness of about 100 μm to 300 μm.

In "Sample A", the drop ball test at a height of 5 cm produced damage to the touch panel 120 and/or the display panel 110 regardless of the modulus value of the backplane 130 .

On the other hand, the impact resistance of "Sample D" was significantly improved compared with "Sample A".

That is, after having the shock absorbing film 170 including the first shock absorbing layer 171 and the second shock absorbing layer 173 and the first to third optical adhesive layers having a modulus value of about 10 ³ Pa In the foldable display device 100 of the layers 150 , 160 and 180 , an external impact is released or mitigated, so that damage to the display panel 110 and/or the touch panel 120 caused by the external impact is minimized or prevented.

As described above, in the foldable display device 100 according to the second embodiment of the present invention, since the high modulus elements and the low modulus elements are stacked alternately in the vertical direction, when an external impact passes through the high modulus elements and the low modulus elements The external shock is released or alleviated when the element is removed. In addition, due to the impact absorbing film 170 under the back plate 130, damage to the display panel 110 and/or the touch panel 120 is further reduced.

FIG. 4 is a diagram illustrating a ball drop test of a foldable display device according to the present invention.

In the graph of FIG. 4, the vertical axis is the height of the ball. "Sample A" is a foldable display device having an optical adhesive layer with a modulus value of 2.2×10 ⁵ Pa and no impact absorbing layer.

"Sample D" is a foldable display device according to the second embodiment of the present invention. That is, the foldable display device in "Sample D" includes the first shock absorbing layer 171 and the second shock absorbing layer 173, and the first to third optical adhesive layers 150, 160, and 180 Each has a modulus value of 1.3×10 ³ Pa. The second impact absorbing layer 173, the soft portion 173a, and the hard portion 173b in the unfolded region each have a thickness of 300 micrometers.

"Sample E" is a foldable display device having the second shock absorbing layer 173 without the first shock absorbing layer 171 . The modulus value of each of the first to third optical adhesive layers 150, 160, and 180 is 1.3×10 ³ Pa, and the soft portion 173a and the hard portion 173b in the non-folded region have 300 micron thickness. That is, the foldable display device of "Sample E" had the same structure except for the first shock absorbing layer.

The folded region "FR" is a folded region having a curvature in a folding operation, and the non-folded region "NFR" is a region having a substantially flat state in a folding operation. The non-folding region "NFR" is located on both sides of the folding region "FR". The bar graph is the minimum height of the ball to produce damage on the foldable display device.

As shown in Figure 4, in the folding region "FR", there is damage on the foldable display device at a ball height of 5 cm (sample A), and damage on the foldable display device at a ball height of 15 cm (Sample D).

In the non-folding region "NFR", there was damage on the foldable display device at a ball height of 20 cm (sample A) and at a ball height of 30 cm (sample D).

That is, since the high-modulus elements and the low-modulus elements are stacked alternately in the vertical direction, and the shock-absorbing film including the first shock-absorbing layer and the second shock-absorbing layer is formed on the back plate in the foldable display device of the present invention Therefore, the foldable display device of the present invention has improved impact resistance compared with the foldable display device of the related art. Accordingly, damage to the foldable display device 100 by impact is minimized or prevented.

In addition, as shown in the drop ball test in "Sample D" and "Sample E", without the first impact absorbing layer, damage is easily generated on the foldable display device.

That is, as shown in the drop ball test in "Sample C" and "Sample D" of Table 2, compared with a foldable display device including the first impact-absorbing layer without the second impact-absorbing layer, including the first impact Damage to the foldable display device of the absorbing layer and the second impact absorbing layer is reduced. In addition, as shown in the drop ball test in "Sample D" and "Sample E" of FIG. The damage of the foldable display device of the second impact absorbing layer is reduced.

In addition, when the back plate 130 has a relatively low modulus value, damage through the back plate 130 is prevented by the impact absorbing film 170, so that the production cost of the back plate 130 is reduced.

table 3

The results of the drop ball test on the foldable display device are listed in Table 3 with respect to the modulus values of the optical adhesive layer and the presence of the impact absorbing film.

"Sample F" is a drop ball test result for a foldable display device without a shock absorbing film, and "Sample D" is for a foldable display device with a shock absorbing film 170 including a first shock absorbing layer 171 and a second shock absorbing layer 173. Displays the drop ball test results for the device. In "Sample D", the thickness of the first impact absorbing layer was 200 micrometers, and the thickness of each of the soft portion 173a and the hard portion 173b in the unfolded region was 300 micrometers. That is, the total thickness of the second impact absorbing layer was 600 micrometers.

In the foldable display device, each of the cover window 140, the touch panel 120, the display panel 110 has a modulus value of 5GPa to 8GPa, and the back plate 130 has a modulus value of 8GPa to 10GPa.

As listed in Table 3, each of the first optical adhesive layer 150 between the cover window 140 and the touch panel 120 and the second optical adhesive layer 160 between the display panel 110 and the backplane 130 has a relatively low The modulus value of , ie, 1.3×10 ³ Pa, improves the impact resistance performance in both the foldable display device without the impact absorbing film (“Sample F”) and with the impact absorbing film (“Sample D”).

In more detail, in "Sample F", in the case where the optical adhesive layer has a high modulus value, i.e., about 2.2×10 ⁵ , the impact on the touch panel 120 and/or The damage of the display panel 110, while in the case of the optical adhesive layer having a low modulus value, namely about 1.3×10 ³ , produced damage to the touch panel 120 and/or the display panel 110 in the drop ball test at a height of 10 cm damage.

That is, damage on the display panel 110 and/or the touch panel 120 depends on the modulus values of the optical adhesive layers 150 and 160 . Compared with a foldable display device having optical adhesive layers 150 and 160 each having a relatively high modulus value, such as 2.2×10 ⁵ , having a relatively low modulus value, such as 1.3×10 ³ The damage on the display panel 110 and/or the touch panel 120 in the foldable display device of the optical adhesive layers 150 and 160 is minimized.

In addition, in "Sample D" having a low modulus optical adhesive layer and a shock absorbing film 170 including a first shock absorbing layer 171 and a second shock absorbing layer 173, the shock resistance of the foldable display device was further improved.

That is, in the foldable display device 100 according to the second embodiment of the present invention, since the high modulus elements and the low modulus elements are stacked alternately in the vertical direction, when an external impact passes through the high modulus elements and the low modulus elements The external shock is released or alleviated when the element is removed. In addition, due to the impact absorbing film 170 under the back plate 130, damage to the display panel 110 and/or the touch panel 120 is further reduced.

In FIGS. 1 and 3 , the foldable display device 100 includes a touch panel 120 at one side of the display panel 110 . However, the touch panel 120 may be omitted. In this case, the first optical adhesive layer 150 contacts the display panel 110 without the touch panel 120 .

It will be apparent to those skilled in the art that various modifications and changes can be made in the present invention without departing from the scope of the invention.

The following is a list of preferred embodiments:

A foldable display device comprising: a display panel; a cover window at a first side of the display panel; a shock absorbing film including a first shock absorbing layer and a second shock absorbing layer at a second side of the display panel; and a back sheet between the display panel and the shock absorbing film and including folded regions and non-folded regions, wherein the second shock absorbing layer includes a soft portion corresponding to the folded region and a hard portion corresponding to the non-folded region, and the first impact Each of the absorbent layer and the soft portion has a lower modulus value than the hard portion.

The first shock-absorbing layer preferably comprises a foam type material, and the soft part comprises one of polyurethane (PU), thermoplastic polyurethane (TPU), silicon (Si) and polydimethylacrylamide (PDMA), and wherein the hard part comprises One of stainless steel (SUS), PMMA, polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), and polyethylene terephthalate (PET) .

The first impact absorbing layer preferably has a thickness of about 100 microns to 300 microns. The second impact absorbing layer preferably has a thickness of about 0.1 mm to 1 mm. The soft portion preferably has a thickness of about 0 to 0.9 mm in the unfolded region. The hard portion preferably has a thickness of about 0.1 mm to 1 mm.

The modulus value of the first impact absorbing layer preferably has a range of about 10 ³ Pa to 10 ⁴ Pa. The modulus value of the soft portion preferably has a range of about 10 ³ Pa to 10 ⁴ Pa, and the modulus value of the hard portion has a range of about 5 GPa to 8 GPa.

The display device preferably further comprises a first optical adhesive layer between the cover window and the display panel and having a modulus value smaller than that of the cover window and the display panel; Modulus values for the faceplate and backsheet of the second optical adhesive layer. The modulus value of each of the first optical adhesive layer and the second optical adhesive layer preferably has a range of about 10 ³ Pa to 10 ⁴ Pa.

The display device preferably also includes a third optical adhesive layer between the impact absorbing film and the backsheet and having a lower modulus value than the backsheet. The modulus value of the third optical adhesive layer preferably has a range of about 10 ³ Pa to 10 ⁴ Pa.

The display device preferably further includes a touch panel between the display panel and the cover window; and an optical adhesive layer between the touch panel and the cover window. The modulus value of the optical adhesive layer is preferably smaller than that of the touch panel and cover window. The modulus value of the optical adhesive layer preferably has a range of about 10 ³ Pa to 10 ⁴ Pa.

The first impact absorbing layer and the second impact absorbing layer are preferably attached to each other by an optical adhesive layer.

The non-folding area preferably includes a first non-folding area and a second non-folding area on both sides of the folding area. The rigid portion preferably comprises first and second portions in the first and second non-folding regions, respectively. The part of the soft part corresponding to the folding area is preferably inserted into the space between the first part and the second part of the hard part.

The display panel preferably includes a plurality of pixel areas. The borders of the folded and non-folded regions preferably correspond to the borders of adjacent pixel regions.

According to another preferred embodiment, a foldable display panel includes: a display panel; a cover window on one side of the display panel; a first optical adhesive layer between the display panel and the cover window; a backsheet on both sides; and a second optical adhesive layer between the display panel and the backsheet, wherein the modulus value of the first optical adhesive layer is less than that of the display panel and the cover window, and the second optical adhesive layer The modulus value of the layer is smaller than that of the display panel and cover window.

The foldable display device preferably further comprises an impact absorbing layer under the back plate; and a third optical adhesive layer between the impact absorbing layer and the back plate, wherein the impact absorbing layer has a lower modulus value than the back plate.

Claims (17)

1. a kind of foldable display device, including：

Display panel, the display panel includes first surface and the second surface opposite with the first surface；With

Be arranged at the second surface of the display panel including the first impact absorbing layer and the second impact absorbing layer Impact absorbing film；

Wherein described second impact absorbing layer includes soft portion and the correspondence of the first area corresponding to second impact absorbing layer In the huttriall of the second area of second impact absorbing layer, and

The elastic mould value of the described soft portion of second impact absorbing layer and first impact absorbing layer is less than the huttriall Elastic mould value.

2. foldable display device according to claim 1, wherein the two of the second area are inserted in the first area Between individual part, and wherein described first area corresponds to fold domain, and the second area corresponds to non-collapsible district Domain.

3. foldable display device according to claim 1, wherein first impact absorbing layer includes foam type material.

4. foldable display device according to claim 1, wherein first impact absorbing layer is arranged on described second Between impact absorbing layer and the display panel.

5. foldable display device according to claim 1, wherein the thickness of first impact absorbing layer is at 100 microns To in the range of 300 microns.

6. foldable display device according to claim 1, wherein in first impact absorbing layer and the soft portion extremely One of few elastic modelling quantity is 10³Pa to 10⁴In the range of Pa.

7. foldable display device according to claim 1, wherein the thickness of the huttriall of second impact absorbing layer Degree is in the range of 100 microns to 1000 microns.

8. foldable display device according to claim 1, wherein the thickness of the huttriall of second impact absorbing layer Degree is in the range of 100 microns to 500 microns.

9. foldable display device according to claim 1, wherein the described soft portion and institute of second impact absorbing layer State huttriall and form double-decker.

10. foldable display device according to claim 9, wherein the soft portion is included in the first area and described The foundation that both second areas top extends, and it is corresponding with the first area and from foundation protrusion Ledge, the ledge is between two parts of the huttriall.

11. foldable display devices according to claim 1, wherein between the first area and the second area Boundary alignment between the adjacent pixel regions of interface and the display panel.

12. foldable display devices according to claim 1, also include：

It is arranged on the lid window at the first surface of the display panel；With

It is arranged on the backboard between the display panel and the impact absorbing film；

The first optical adhesive layer for the lid window to be attached to the display panel；And

The second optical adhesive layer for the backboard to be attached to the display panel,

The elastic modelling quantity of wherein described first optical adhesive layer is less than the elastic modelling quantity of the display panel and the lid window, with And the elastic modelling quantity of second optical adhesive layer is less than the display panel and the elastic modelling quantity of the backboard.

13. foldable display devices according to claim 12, also include：

The 3rd optical adhesive layer for the impact absorbing film to be attached to the backboard,

The elastic modelling quantity of wherein described 3rd optical adhesive layer is less than the display panel and the elastic modelling quantity of the backboard.

14. foldable display devices according to claim 13, wherein first optical adhesive layer is to the described 3rd The thickness of at least one of optical adhesive layer is in the range of 100 microns to 300 microns.

15. foldable display devices according to claim 13, wherein first optical adhesive layer is to the described 3rd The elastic modelling quantity of at least one of optical adhesive layer is 10³Pa to 10⁴In the range of Pa.

16. foldable display devices according to claim 1, also include：It is arranged on described the first of the display panel Touch panel on surface.

17. foldable display devices according to claim 12, wherein the described soft portion of second impact absorbing layer and Modulus of the modulus value of each less than the lid window, the display panel and the backboard in first impact absorbing layer Value.