Foldable display device

A foldable display device having a first display region, a second display region, and a foldable display region connecting the first display region and the second display region includes a flexible substrate, a plurality of first light emitting units disposed on the flexible substrate in the first display region, a plurality of second light emitting units disposed on the flexible substrate in the foldable display region, a first protector protecting at least one of the first light emitting units, and a second protector protecting at least one of the second light emitting units. A first ratio of a thickness of the first protector to a thickness of the flexible substrate in the first display region is less than a second ratio of a thickness of the second protector to a thickness of the flexible substrate in the foldable display region.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure is related to a display device, and more particularly, to a foldable display device.

2. Description of the Prior Art

In recent years, foldable electronic device has become one of next generation technologies. The foldable electronic device offers portability when in a folded state and expands into a relatively large sized display when in an unfolded state, and accordingly, the foldable electronic device may have various applications in electronic displays, such as used in televisions, monitors, mobile computing devices, such as smartphones, tablet computers, mobile personal computers (PCs), and electronic book readers, and wearable devices, such as smart watches. In addition, light emitting elements have been applied to display devices for providing light source or displaying images. However, the light emitting elements may much easily have defects when they are disposed in foldable parts of the foldable display device. Therefore, it is an important issue for the manufacturers to improve the yield of the foldable display device with light emitting elements.

SUMMARY OF THE DISCLOSURE

One of the objectives of the present disclosure is to provide a foldable display device and related electronic device, wherein the foldable display device includes light emitting units for display images. Another objective of the present disclosure is to provide an electronic device including a foldable region connected to a flat region.

In one embodiment, the foldable display device includes a first display region, a second display region, and a foldable display region connecting the first display region and the second display region, and the foldable display device comprises a flexible substrate, a plurality of first light emitting units disposed on the flexible substrate in the first display region, a plurality of second light emitting units disposed on the flexible substrate in the foldable display region, a first protector protecting at least one of the first light emitting units, and a second protector protecting at least one of the second light emitting units. A ratio of a thickness of the first protector to a thickness of the flexible substrate in the first display region is defined as a first ratio, a ratio of a thickness of the second protector to a thickness of the flexible substrate in the foldable display region is defined as a second ratio, and the second ratio is greater than the first ratio.

In one embodiment, a foldable electronic device including a first region, a second region, and a foldable region connecting the first region and the second region is disclosed. The foldable electronic device comprises a flexible substrate, a plurality of first electronic units disposed on the flexible substrate in the first region, a plurality of second electronic units disposed on the flexible substrate in the foldable region, a first protector protecting at least one of the first electronic units, and a second protector protecting at least one of the second electronic units. A ratio of a thickness of the first protector to a thickness of the flexible substrate in the first region is defined as a first ratio, a ratio of a thickness of the second protector to a thickness of the flexible substrate in the foldable region is defined as a second ratio, and the second ratio is greater than the first ratio.

DETAILED DESCRIPTION

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will understand, electronic equipment manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms “include”, “comprise” and “have” are used in an open-ended fashion, and thus should be interpreted to mean “include, but not limited to . . . ”.

Referring toFIG. 1toFIG. 3,FIG. 1is a schematic diagram of a top view of an electronic device or a foldable display device according to a first embodiment of the present disclosure,FIG. 2is a schematic diagram of a sectional view of the electronic device or foldable display device shown inFIG. 1, andFIG. 3is a schematic diagram of a sectional view with more details of the electronic device or foldable display device shown inFIG. 1, wherein the electronic device shown inFIG. 2is in a folding state. As shown inFIG. 1andFIG. 2, the electronic device ED of the present disclosure can be a foldable electronic device, which can be folded along a folding axis FX between 180° to −180°. For example, the foldable electronic device ED inFIG. 2shows the inwardly folding state and the folding angle is 180°. The foldable electronic device ED includes a first region R1, a second region R2, and a foldable region RF connecting the first region R1and the second region R2. In some embodiments, the first region R1and the second region R2can be flat, or can be flatter than the foldable region RF. The foldable electronic device ED in the foldable region RF is capable of being curved, bent, and/or folded. In some embodiments, the foldable electronic device ED can include more than one foldable region RF. Referring toFIG. 1andFIG. 2, the foldable electronic device ED of the present disclosure can include a flexible substrate SUB, a plurality of first electronic units51disposed on the flexible substrate SUB in the first region R1and/or in the second region R2, and a plurality of second electronic units52disposed on the flexible substrate SUB in the foldable region RF. In some embodiments, the first electronic units51and the second electronic units52can have display function. For example, the first electronic units51can be a plurality of first light emitting units LE1disposed in the first region R1and/or in the second region R2, and the second electronic units52can be a plurality of second light emitting units LE2disposed in the foldable region RF. In such situation, the first region R1, the second region R2, and the foldable region RF may have display function, thus they could also be called as first display region R1, second display region R2, and foldable display region RF respectively in some embodiments. The light emitting units can be arranged in a matrix, for example, arranged in a plurality of rows in a direction D1and a plurality of columns in a direction D2. The direction D1and direction D2can be different, for example, perpendicular to each other. However, the arrangement of the light emitting units is not limited.

According to some embodiments, the first electronic units51and the second electronic units52can have no display function; for example, can be antenna units, for example liquid crystal antenna units. Electromagnetic wave can be emitted from or received by the antenna units.

According to some embodiments, the foldable electronic device ED may be a foldable display device100. The foldable electronic device ED has an outer surface OS, which includes a first surface part P1defining the first display region R1, a second surface part P2defining the second display region R2, and a third surface part P3defining the foldable display region RF. When the foldable electronic device ED is expanded to an unfolded state, the first surface part P1, the second surface part P2and the third surface part P3are in level with the same plane. When the foldable electronic device ED is folded to a folded state as shown inFIG. 2, the first surface part P1is flat and in level with a plane PLN1, the second surface part P2is flat and in level with another plane PLN2, and the third surface part P3is bent and not in level with the above-mentioned planes. Accordingly, when the foldable electronic device ED is at the folded state, the third surface part P3can be defined between the plane PLN1and the plane PLN2. In detail, a first boundary B1is defined at a position departing away from the first surface part P1, and a second boundary B2is defined at a position departing away from the second surface part P2. In other words, the foldable region RF can be defined by a region between the first boundary B1and the second boundary B2.

For easy explanation, some examples are taken when the foldable electronic device ED is the foldable display device100in the following embodiments. Referring toFIG. 3, the foldable display device100include a plurality of first light emitting units LE1disposed on the flexible substrate SUB in the first display region R1and in the second display region R2, a plurality of second light emitting units LE2disposed on the flexible substrate SUB in the foldable display region RF, a first protector PT1protecting at least one of the first light emitting units LE1, and a second protector PT2protecting at least one of the second light emitting units LE2. A circuit layer110may be further disposed on the flexible substrate SUB. The circuit layer110can include conductive lines and/or driving elements (for example, transistors), but is shown as a single layer inFIG. 3for easy illustration. Detailed structure of the circuit layer110will be described in the following embodiments. The circuit layer110can include a plurality of cavities112for disposing the first light emitting units LE1and second light emitting units LE2. The first protector PT1may cover and fill the cavities112in which the first light emitting units LE1are disposed. The second protector PT2may cover and fill the cavities112in which the second light emitting units LE2are disposed. A cover layer114may be further disposed on the first protector PT1and the second protector PT2.

In some embodiments, the first and second light emitting units LE1, LE2can be organic light emitting diodes (OLED), inorganic LEDs, or quantum dot LEDs (QLED). Inorganic LED can be mini-LED or micro-LED. In some embodiments, the size of a mini-LED can be in a range from 100 μm to 300 μm. In some embodiment, the size of a micro-LED can be in a range from 1 μm to 100 μm. The first light emitting units LE1and the second light emitting units LE2may be flip chip-type or vertical type. Taking the first light emitting unit LE1as an example, it may include a first electrode116, a second electrode118, a first semiconductor layer120, a light emitting layer122, and a second semiconductor layer124. The light emitting layer122may be, but not limited to, a multiple quantum well (MQW) layer for example. The first light emitting unit LE1is electrically connected to the circuit layer110through the first bonding material126,128. In detail, the circuit layer110can include a plurality of bonding pads130and a plurality of bonding pads134. Taking one first light emitting unit LE1for an example, the first electrode116of the first light emitting unit LE1can be electrically connected to one of the bonding pads130through the first bonding material126, and the second electrode118of the first light emitting unit LE1can be electrically connected to the bonding pad134through the first bonding material128. The connection between the second light emitting units LE2and the circuit layer110may be similar to the above-mentioned connection between the first light emitting units LE1and the circuit layer110, thus no redundant details will be described. When the circuit layer110includes driving elements for driving light emitting units, the foldable display device100is an active-type display device. The foldable display device100may be a passive-type display device, and the first light emitting units LE1and the second light emitting units LE2may be not directly connected to driving elements.

In some embodiments, the first light emitting units LE1in the first display region R1and the second display region R2are covered by the first protector PT1, and the second light emitting units LE2in the foldable display region RF are covered by the second protector PT2, as shown inFIG. 3, but not limited thereto. The first protector PT1has a thickness H1, and the second protector PT2has a thickness H2. Referring toFIG. 1andFIG. 3together, the definition of the thicknesses of the protectors may refer to the enlarged views of the first light emitting units LE1in the bottom part ofFIG. 1. For example, the method of determining the thickness H1of the first protector PT1may include the following steps: (1) selecting a first light emitting unit LE1; (2) determining the geometric center GC of the selected first light emitting unit LE1; (3) forming a sectional cutting (shown as a cross line102) that passes through the geometric center GC to obtain a cross-section profile; and (4) along the cross-section profile, measuring the maximum thickness of the first protector PT1from the bottom surface to the top surface of the first protector PT1to obtain the thickness of the first protector PT1. In some embodiments, the steps (1) to (4) may be performed for total five times to measure the thicknesses of five different selected first light emitting units LE1to obtain an average value, so as to determine the above-mentioned thickness H1of the first protector PT1. In addition, a thickness H3of the flexible substrate SUB in the first display region R1that corresponds to the thickness H1of the first protector PT1may also be determined in the above-mentioned cross-section profile. For example, the sectional cutting (the cross line102) can be perpendicular to the folding axis FX. A little shift or deviation of the sectional cutting may be accepted. For example, the tolerance difference of the sectional cutting may be less than ±5 μm, represented by the tolerance difference dt1and dt2between the tolerance cross lines1021and1022and the accurate cross line102as shown in the part (A) ofFIG. 1. In another example, the tolerance rotation angle of the sectional cutting may be less than 3°-5°, represented by the tolerance rotation angles θ1and θ2of the tolerance cross lines1023and1024as shown in the part (B) ofFIG. 1. The determination of the thickness H2of the second protector PT2and the corresponding thickness H4of the flexible substrate SUB in the foldable display region RF may be similar to the determining method of the thickness H1and thickness H3, and redundant details will not be repeated.

A ratio of the thickness H1of the first protector PT1to a thickness H3of the flexible substrate SUB in the first display region R1is defined as a first ratio Ra1(i.e. Ra1=H1/H3), and a ratio of the thickness H2of the second protector PT2to a thickness H4of the flexible substrate SUB in the foldable display region RF is defined as a second ratio Ra2(i.e. Ra2=H2/H4). As shown inFIG. 3, by designing the second ratio Ra2being different from the first ratio Ra1, the neutral plane NP of the foldable display device100can be adjusted. For example, in some embodiments, it is designed that the second ratio is greater than the first ratio (Ra2>Ra1), such that the neutral plane NP in the foldable display region RF may be more close to the interface of the second light emitting units LE2and the bonding pads130,134. Thus, when the foldable display device100is in a folded state, a better adhesion performance or reliability for the second light emitting units LE2can be obtained. The above-mentioned neutral plane NP means the plane composed of the minimum-stress points along a direction D3of the foldable display device100, wherein the direction D3is perpendicular to the surface of the flexible substrate SUB.

In some embodiments, the thickness H2of the second protector PT2may be greater than the thickness H1of the first protector PT1, and the thickness H3of the flexible substrate SUB corresponding to the first display region R1or second display region R2may be substantially equal to the thickness H4of the flexible substrate SUB corresponding to the foldable display region RF (i.e. H2>H1and H4=H3), such that the second ratio Ra2can be greater than the first ratio Ra1, as shown inFIG. 3. In some embodiments, the thickness H2of the second protector PT2may be greater than or equal to the thickness H1of the first protector PT1while the thickness H3of the flexible substrate SUB may be greater than the thickness H4of the flexible substrate SUB, such that the second ratio Ra2may be still greater than the first ratio Ra1(i.e. H2≥H1and H4<H3). For example, the thickness H2may be in a range from about 5 μm to about 15 μm; the thickness H4may be in a range from about 10 μm to about 100 μm; the thickness H1may be in a range from about 3 μm to about 10 μm; and the thickness H3may be in a range from about 10 μm to about 120 μm, but not limited thereto.

In some embodiments, the first ratio Ra1and the second ratio Ra2may meet at least one of the following equations:
0.1≤Ra2≤1.5;
0.02≤Ra1<0.1; and
0.005≤Ra2−Ra1≤1.5.

If the value of the first ratio Ra1or the second ratio Ra2is too great, the flexible substrate SUB may lack enough supporting ability to the light emitting unit; and if the value of the first ratio Ra1or the second ratio Ra2is too small, the first protector PT1or the second protector PT2cannot provide enough protection to the corresponding light emitting unit when the foldable display device100is folded. Therefore, according to some embodiments, the first ratio Ra1and the second ratio Ra2can be designed in suitable values, in order to prevent the probability of damage or falling down of the light emitting units in the folding state, influencing on the yield of the foldable display device100. Accordingly, when the first ratio Ra1and the second ratio Ra2are maintained in suitable ranges, such as the values listed above, the reliability of the foldable display device100may be improved. The reliability, cracking probability, or damage can be determined according to a folding test. The foldable display device100can be folded, for example, for 100000 times (without limitation to the present disclosure) and the sample can be checked by an optical microscope (OM). The design of relative value that the first ratio Ra1is less than the second ratio Ra2may be applied to any other embodiments and variant embodiments of the present disclosure, which may not be repeated in detail.

In some embodiments, the first protector PT1and the second protector PT2can be of the same material. Or, in variant embodiments, the material of the first protector PT1may be non-identical to the material of the second protector PT2. For example, the Young's modulus of the second protector PT2may be less than the Young's modulus of the first protector PT1. The first protector PT1may have better degree of rigidity and/or resilience. The second protector PT2with the less Young's modulus may provide better elongation property so as to reduce cracking probability of the second protector PT2when the foldable display device100is folded. The first protector PT1can be an organic material, and the organic material of the first protector PT1may include at least one selected from an acryl-based resin and an epoxy based resin. The Young's modulus of the first protector PT1may be in a range of about 2 to about 20 Gpa. The second protector PT2may comprise organic material that includes silicon-based resin. The Young's modulus of the second protector PT2of the organic material may be in a range of about 0.001 to about 0.05 Gpa.

The electronic device and foldable display device of the present disclosure are not limited by the aforementioned embodiment, and may have other different embodiments and variant embodiments. To simplify the description, the identical components in each of the following embodiments are marked with identical symbols. For making it easier to compare the difference between the embodiments, the following description will detail the dissimilarities among different embodiments and the identical features will not be redundantly described.

Referring toFIG. 4,FIG. 4is a schematic sectional-view of an electronic device or a foldable display device according to a second embodiment of the present disclosure. In the second embodiment, the first light emitting units LE1and the second light emitting units LE2may be vertical-type LEDs for example. Similarly, the first light emitting units LE1and the second light emitting units LE2may include mini-LEDs and/or micro-LEDs. The second electrode118of one of the first light emitting units LE1or the second light emitting units LE2may be electrically connected to a common electrode132that laterally extends over the first light emitting units LE1, the second light emitting units LE2, and the circuit layer110. In other words, the common electrode(s)132electrically connected to the second electrodes118of different first light emitting units LE1and second light emitting units LE2may be connected to each other. In some embodiments, the thickness H1of the first protector PT1covering the first light emitting units LE1may be substantially equal to the thickness H2of the second protector PT2covering the second light emitting units LE2, but the thickness H4of the flexible substrate SUB in the foldable display region RF is smaller than the thickness H3of the flexible substrate SUB in the first display region R1or in the second display region R2. In detail, the flexible substrate SUB may have at least one recess138in the foldable display region RF, thus the thickness H4corresponding to the recess138is thinner. The sidewall138sof the recess138may be approximately perpendicular to the surface of the flexible substrate SUB or parallel to the direction D3in some embodiments, but not limited thereto. In such design of the recess138of the flexible substrate SUB, the second ratio Ra2of the thickness H2to the thickness H4may be greater than the first ratio Ra1of the thickness H1to the thickness H3.

In another aspect, one of the first light emitting units LE1is electrically connected to the circuit layer110through a first bonding material1261, one of the second light emitting units LE2is electrically connected to the circuit layer110through a second bonding material1262, and the first bonding material1261and the second bonding material1262may have different areas. For example, the area of the first bonding material1261may be smaller than the area of the second bonding material1262, but not limited thereto. As shown inFIG. 4, the first bonding material1261may have an area L1representing the contact area of the first bonding material1261and the first electrode116of the first light emitting unit LE1and may have a maximum area L2corresponding to a projection area of the first bonding material1261on the surface of the flexible substrate SUB, and the second bonding material1262may have an area L3representing the contact area of the second bonding material1261and the first electrode116of the second light emitting unit LE2and may have a maximum area L4corresponding to a projection area of the second bonding material1262on the surface of the flexible substrate SUB. The area L3is greater than the area L1, and the area L4is greater than the area L2. In such design, the quantity of the second bonding material1262corresponding to one of the second light emitting units LE2may be greater than the quantity of the first bonding material1261corresponding to one of the first light emitting units LE1, and therefore the bonding area of the second bonding material1262can be larger than the bonding area of the first bonding material1261. The larger bonding area of the second bonding material1262may provide a firmer bonding performance of the second light emitting unit LE2to the bonding pad130, so as to reduce the falling-down or damage probability when the foldable display device100is in a folding state. In addition, the foldable display device100can further include a self-reflective layer136. The self-reflective layer136can be disposed on the sidewall of the first light emitting units LE1and/or on the sidewall of the second light emitting units LE2. The self-reflective layer136can prevent the light produced by the light emitting unit from emitting laterally, such that the light can vertically emit out the light emitting unit, thus avoiding occurrence of crosstalk and/or mixing of color lights. The disposition of the self-reflective layers136may be applied to other embodiments or variant embodiments of the present disclosure and will not be redundantly detailed.

Referring toFIG. 5,FIG. 5is a schematic sectional-view of an electronic device or a foldable display device according to a third embodiment of the present disclosure. In the third embodiment, the first protector PT1and the second protector PT2may be a continuous layer extending laterally over the first light emitting units LE1or the second light emitting units LE2respectively. The first protector PT1and the second protector PT2may include the same or non-identical material. The first protector PT1and the second protector PT2may have apparent or unapparent boundary therebetween. In some embodiments, the second protector PT2may comprise a material non-identical to the material of the first protector PT1, and the second protector PT2may overlap with the foldable display region RF and some portions of the first display region R1or the second display region R2near the foldable display region RF. In the third embodiment, the sidewall138sof the recess138in the flexible substrate SUB may be tilted with respect to the direction D3. For example, as shown inFIG. 5, the sidewall138sand the bottom surface SUB1of the flexible substrate SUB may have an included angle β that is an obtuse angle. In addition, in some embodiments, the bonding material for electrically connecting the first light emitting units LE1and the second light emitting units LE2to the circuit layer110may include an anisotropic conductive film (ACF)140. As shown inFIG. 5, the ACF140is disposed between the first protector PT1, the second protector PT2, the first light emitting units LE1, the second light emitting units LE2, and the bonding pads130,134of the circuit layer110, which are disposed on the flexible substrate SUB. The ACF140may include a plurality of conductive particles142. When bonding first light emitting units LE1and the second light emitting units LE2onto the circuit layer110, the light emitting units are pressed downward to compress the conductive particles142therebelow, thus the compressed conductive particles142between the first electrodes116and the bonding pads130or between the second electrodes118and the bonding pads134can electrically connecting the corresponding light emitting unit to the circuit layer110. In some embodiments, the pressing strength of the second light emitting units LE2may be greater than the pressing strength of the first light emitting units LE1, and therefore the height h1of one of the first conductive particles1421between one of the first light emitting units LE1and the circuit layer110may be greater than the height h2of one of the second conductive particles1422between the second light emitting units LE2and the circuit layer110. In some embodiments, for the same reason, the projection area of the first conductive particle1421may be smaller than the projection area of the second conductive particle1422. In some embodiments, the height h1of the first conductive particle1421and the height h2of the second conductive particle are different.

Furthermore,FIG. 5illustrates a black matrix (BM) layer BML disposed between the first protector PT1or the second protector PT2and the circuit layer110. The BM layer BML includes a shielding portion113between two adjacent light emitting units. The black matrix layer BML can decrease the amount of light emitted from one light emitting unit to progress to another light emitting unit. The disposition of the black matrix layer BM may be applied to other embodiments or variant embodiments of the present disclosure.

FIG. 6is a schematic sectional-view of an electronic device or a foldable display device according to a fourth embodiment of the present disclosure. In some embodiments, the circuit layer110includes a first bonding pad1301disposed in the first display region R1and a second bonding pad1302disposed in the foldable display region RF. The first bonding pad1301corresponding to one of the first light emitting units LE1may have an area Wp1different from the area Wp2of the second bonding pad1302corresponding to one of the second light emitting units LE2. InFIG. 6, the different widths of the first bonding pad1301and the second bonding pad1302may represent the different areas of the two bonding pads. For example, the area Wp2may be larger than the area Wp1. The second bonding pad1302with a larger area in the foldable display region RF may improve the bonding effect or make the bonding stability more firmly, so as to reduce the chance of damage of the elements in the foldable display region RF when the foldable display region100is folded. In addition, the connection part138cof the sidewall of the recess138of the flexible substrate SUB and the bottom surface SUB1of the flexible substrate SUB may be curved in this embodiment, and the sidewall may have an included angle θ with the bottom surface SUB1of the flexible substrate SUB. In some embodiments, the included angle θ may be an obtuse angle, but not limited thereto.

FIG. 7is a schematic top-view of an electronic device or a foldable display device according to a variant embodiment of the fourth embodiment of the present disclosure. In this variant embodiment, some or all of the second bonding pads1302in the foldable display region RF may have one or more openings OPN. The openings OPN may be arranged regularly or randomly in one of the second bonding pads1302. The second bonding pads1302with the openings OPN may reduce the chance of cracking and help to release the stress accumulated in the second bonding pads1302when the foldable display device100is folded. The area of one single second bonding pad1302may be greater than the area of one single first bonding pad1301, wherein the area of one single second bonding pad1302indicates that the occupied area or region of the second bonding pad1302, including the occupied areas of the openings OPN or may be defined by the outer edges of the second bonding pad1302. In some variant embodiments, the second bonding pads1302with the openings OPN in the foldable display region RF may have the same areas as that of the first bonding pads1301in the first display region R1or the second display region R2. Similarly, the area of the second bonding pad1302includes the occupied area of the openings OPN.

FIG. 8is a schematic sectional-view of an electronic device or a foldable display device according to a fifth embodiment of the present disclosure. In some embodiments, the foldable display device100may be an active-type display device, wherein the circuit layer110may include a plurality of driving elements, but not limited thereto. For example, the driving elements for driving the light emitting units may include thin film transistors (TFT)142. One thin film transistor142may include a gate GE, a source SE, a drain DE, and a semiconductor layer SC, wherein the source SE and the drain DE are electrically connected to the semiconductor layer SC respectively and an insulating layer IN is positioned between the gate GE and the semiconductor layer SC. The source SE may be electrically connected to a signal line. The drain DE may be electrically connected to a bonding pad130or a connecting layer that is electrically connected to the corresponding first electrode116of the light emitting unit. Thus, the thin film transistor142can drive the corresponding light emitting unit. In this embodiment, the first light emitting units LE1and the second light emitting units LE2are vertical-type LEDs, their second electrodes118are electrically connected to a common electrode132respectively, and the adjacent common electrodes132may not connect to each other, but not limited thereto. As shown inFIG. 8, a plurality of first black matrix parts BM1are disposed between two adjacent first light emitting units LE1in the first display region R1or the second display region R2, and a plurality of second black matrix parts BM2are disposed between two adjacent second light emitting units LE2in the foldable display region RF. A height H5of the first black matrix parts BM1can be less than a height H6of the second black matrix parts BM2. The higher second black matrix parts BM2may mitigate the cross talk issue resulted from the layer-shifting or element-shifting in the foldable display region RF when the foldable display device100is folded.

FIG. 9is a schematic sectional-view of an electronic device or a foldable display device according to a sixth embodiment of the present disclosure. In some embodiments, the foldable display device100may be an active-type display device, wherein the circuit layer110may include a plurality of driving elements, and the light emitting units may be flip-chip type LEDs, but not limited thereto. One light emitting unit may be driven by a driving element, which can be a thin film transistor142. For example, the first electrode116of the light emitting unit is electrically connected to the bonding pad130of the circuit layer110, the bonding pad130may be further electrically connected to a common source, and the drain DE of the thin film transistor142may be electrically connected to the second electrode118through the bonding pad134. The thickness H2of the second protector PT2may be greater than the thickness H1of the first protector PT1, and the thickness H4of the flexible substrate SUB in the foldable display region RF may be less than the thickness H3of the flexible substrate SUB in the first display region R1or second display region R2, thus the second ratio Ra2is greater than the first ratio Ra1. In addition, the second black matrix parts BM2disposed between two adjacent second light emitting units LE2in the foldable display region RF include a first black-matrix layer BM21and a second black-matrix layer BM22stacked on the first black-matrix layer BM21, and the first black-matrix layer BM21and the second black-matrix layer BM22can comprise non-identical materials. In some embodiments, the second black-matrix layer BM22is composed of a material with lower density than the first black-matrix layer BM21, or the Young's modulus of the second black-matrix layer BM22is less than that of the first black-matrix layer BM21. When the foldable display device100is folded, the upper layer of the second black matrix parts BM2may suffer greater stress, thus the second black-matrix layer BM22with lower density or less Young's modulus may decrease the damage probability of the second black matrix parts BM2. In some embodiments, the height H6of the second black matrix parts BM2may be greater than the height H5of the first black matrix parts BM1to mitigate light leakage between adjacent second light emitting units LE2when the foldable display device100is folded. In some other embodiments, the height H6may be substantially the same as the height H5.

FIG. 10is a schematic sectional-view of an electronic device or a foldable display device according to a seventh embodiment of the present disclosure. In some embodiments, in order to mitigate light leakage, the black matrix parts BM are disposed between any two adjacent ones of the first light emitting units LE1in the first display region R1and the second display region R2. However, in the foldable display region RF, no black matrix parts are disposed between any two adjacent ones of the second light emitting units LE2. Self-reflective layers136can be disposed on sidewalls of the second light emitting units LE2and some portions of bottom surfaces for mitigating light leakage. The self-reflective layers136replacing the black matrix parts BM in the foldable display region RF can improve the light shielding because light leakage resulted from layer-shift issue of the black matrix parts BM will not occur in the foldable display region RF.

As shown inFIG. 10, the bottom surface SUB1of the flexible substrate SUB may have patterns with recesses1381,1382and protrusions SUB11, SUB12. The recesses1381,1382may include curved sidewalls respectively, but not limited thereto. The recesses1381in the first display region R1and second display region R2are disposed alternately with the first light emitting units LE1. In other words, the recesses1381do not overlap the first light emitting units LE1in the direction D3and are disposed between two adjacent first light emitting units LE1in the direction D1. Similarly, the recesses1382in the foldable display region RF and the second light emitting units LE2are disposed alternately. The recesses1382do not overlap the second light emitting units LE2in the direction D3and are disposed between any two adjacent second light emitting units LE2in the direction D1. Since the recesses1381,1382do not overlap the first light emitting units LE1and the second light emitting units LE2, the flexible substrate SUB can provide good structural strength to the light emitting units for that the light emitting units are disposed on the part of the flexible substrate SUB with thicker thickness. In another aspect, the optical performance corresponding to each light emitting unit may be maintained. One protrusion SUB11may correspond to two or more first light emitting units LE1, such as corresponding to three of the first light emitting units LE1as a pixel. One protrusion SUB12may correspond to one of the second light emitting units LE2, which may be considered as one sub-pixel. The recesses1381are disposed between any two adjacent protrusions SUB11respectively, the recesses1382are disposed between any two adjacent protrusions SUB12, and therefore the arrangement density (the number of the recesses per area) of the recesses1382is greater than that of the recesses1381. In some other embodiments, the arrangement density of the recesses1382,1381may be substantially the same, wherein one protrusion SUB11corresponds to one of the first light emitting units LE1and one recess1381is positioned between any two adjacent first light emitting units LE1. As shown inFIG. 10, although the thickness H4(largest thickness, or the thickness of the protrusion SUB12) of the flexible substrate SUB in the foldable display region RF may be the same as the thickness H3(largest thickness, or the thickness of the protrusion SUB11) of the flexible substrate SUB in the first display region R1, the thickness H2of the second protector PT2can be greater than the thickness H1of the first protector PT1, such that the second ratio Ra2can be greater than the first ratio Ra1.

FIG. 11is a schematic sectional-view of an electronic device or a foldable display device according to an eighth embodiment of the present disclosure. In some embodiments, the first light emitting units LE1have different areas or sizes from the second light emitting units LE2. As an example, the width WL1of the first light emitting units LE1in the direction D1may be greater than the width WL2of the second light emitting units LE2in the same direction D1, which may indicate that the size or the area (or projection area) of the first light emitting units LE1is greater than that of the second light emitting units LE2. As shown inFIG. 11, in some embodiments, the first light emitting units LE1and the second light emitting units LE2may be blue LEDs for example, a plurality of first light converters QD11, QD12are disposed on at least a portion of the first light emitting units LE1, and a plurality of second light converters QD21, QD22are disposed on at least a portion of the second light emitting units LE2. The first light converters QD11and the second light converters QD21can convert blue light into red light. The first light converters QD12and the second light converters QD22can convert blue light into green light. Accordingly, in the foldable display device100, the sub-pixel unit U11and U21may represent a red sub-pixel that can produce red light, and the sub-pixel unit U12and U22may represent a green sub-pixel that can produce green light, and the sub-pixel unit U13and U23not covered by the light converter may represent a blue sub-pixel that can produce blue light. One sub-pixel U11, one sub-pixel U12, and one sub-pixel U13may form a pixel PX in the first display region R1or second display region R2. One sub-pixel U21, one sub-pixel U22, and one sub-pixel U23may form a pixel PX in the foldable display region RF. In some embodiments, the first light converters QD11or QD12may have different areas WQ1or sizes from the areas WQ2of the second light converters QD21or QD22. For example, the areas WQ2(or widths) of the second light converters QD21or QD22may be greater than the areas WQ1(or widths) of the first light converters QD11or QD12. The larger covering area of the second light converters QD21or QD22with greater areas can mitigate the cross-talk issue or undesired light-mixing issue when the foldable display device100is folded. The first light converters QD11, QD12and the second light converters QD21, QD22may include quantum dot materials, but not limited thereto.

FIG. 12is a schematic top-view of an electronic device or a foldable display device according to a ninth embodiment of the present disclosure. Most of the layers and elements on the flexible substrate SUB are omitted for simplicity, and only the light emitting units and the recess138are shown inFIG. 12. In some embodiments, a distance d1between two adjacent first light emitting units LE1may be different from a distance d2between two adjacent second light emitting units LE2. For example, the distance d1may be less than the distance d2. Therefore, a number of the first light emitting units LE1per inch in the first display region R1or the second display region R2may be greater than a number of the second light emitting units LE2per inch in the foldable display region RF. In other words, the arrangement density of the first light emitting units LE1in the first display region R1or the second display region R2may be greater than the arrangement density of the second light emitting units LE2in the foldable display region RF. The less density of the second light emitting units LE2may decrease the damage probability of the second light emitting units LE2in the foldable display region RF.

Furthermore, as shown inFIG. 12, the flexible substrate SUB may include a plurality of recesses138at least located in the foldable display region RF. The recesses138(labeled as slant lines) may have strip shapes and extend along the direction D2and positioned between two adjacent second light emitting units LE2. In some embodiments, a number of the first light emitting units LE1per inch in the first display region R1or the second display region R2can be different from a number of the second light emitting units LE2per inch in the foldable display region RF.

FIG. 13is a schematic top-view of an electronic device or a foldable display device according to a tenth embodiment of the present disclosure. As shown inFIG. 13, the recesses138of the flexible substrate SUB may be disposed in the first display region R1, the second display region R2, and the foldable display region RF, and the recesses138may have square-like shapes. The dispositions of the recesses138and the light emitting units can be staggered, i.e., one recess138may be disposed between two of adjacent first light emitting units LE1or two of adjacent second light emitting units LE2. InFIG. 13, the distance between any two adjacent light emitting units may be approximately the same, but not limited thereto.

FIG. 14is a schematic sectional-view of an electronic device or a foldable display device according to an eleventh embodiment of the present disclosure. As shown inFIG. 14, in the first display region R1and second display region R2, a plurality of first light emitting units LE1mentioned in the previous embodiments are disposed, thus one individual light-emitting unit LE1may produce one kind of color light, such as red light, green light or blue light. In contrast, in the foldable display region RF, a plurality of light-emitting packages LEP2are disposed. One light-emitting package LEP2includes integrated LEDs. In detail, two or more than two of the second light emitting units LE2can be integrated and packed as one light-emitting package LEP2. For example, three light emitting units can be integrated in one light emitting package LEP2. In detail, for example, three blue LEDs may be packaged in a light-emitting package LEP2, and a light converter1521, a light converter1522, and a filler1523may be disposed on one of the second light emitting units LE2respectively. The light converter1521may convert blue light into red light, the light converter1522may convert blue light into green light, and the filler1523may be a transparent layer. A filter layer150may be optionally further disposed on the light converter1521and the light converter1522to filter out blue light. Accordingly, the second light emitting units LE2in the light-emitting package LEP2together with the light converter1521, the light converter1522, and the filler1523may produce red light, green light, and blue light, and the light-emitting package LEP2can produce the light with a mixture of three kinds of color lights. This design can improve the light mixture in the foldable display region RF. In some other embodiments, the second light-emitting package LEP2may package three kinds of LEDs that can produce different color lights respectively.

Referring toFIG. 15,FIG. 15is a schematic sectional-view of an electronic device or a foldable display device according to a twelfth embodiment of the present disclosure. As shown inFIG. 15, integrated LEDs can also be used in the first display region R1and the second display region R2. For example, a plurality of light-emitting packages LEP1can be disposed in the first display region R1and/or the second display region R2, and a plurality of light-emitting packages LEP2can be disposed in the foldable display region RF. Two or more than two of the first light emitting units LE1can be integrated in one light-emitting package LEP1, and two or more than two of the second light emitting units LE2can be integrated in one light-emitting package LEP2. The number of the first light emitting units LE1integrated in one of the light-emitting packages LEP1may be different from, for example, greater than the number of the second light emitting units LE2integrated in one of the light-emitting packages LEP2. In some embodiments, as shown inFIG. 15, the number of the first light emitting units LE1integrated in one light emitting package LEP1is 12, and the number of the second light emitting units LE2integrated in one light-emitting package LEP2is 3, but not limited thereto.

Referring toFIG. 16andFIG. 17,FIG. 16is a schematic top-view of an electronic device or a foldable display device according to a thirteenth embodiment of the present disclosure, andFIG. 17shows enlarged schematic sectional-views of the light emitting units and circuit layer along the cross-line A-A′ and the cross-line B-B′ inFIG. 16. A plurality of pixels PX are defined on the flexible substrate SUB. As shown inFIG. 16, the first display region R1includes a plurality of first pixel regions32, the foldable display region RF includes a plurality of second pixel regions34. As used herein, a pixel region is intended to mean a smallest repeating region that has display function. One pixel region can include primary color subpixels, for example, three primary color subpixels such as red, green and blue. In some embodiments, a group of light emitting diodes is repeated as one pixel region. Or, in some embodiments, a region in which an electrode (for example, an anode) or a group of electrodes is repeated can be regarded as one pixel region. In some further embodiments, a region in which a group of bonding pads (such as bonding pads13) is repeated can be regarded as one pixel region. For example, each bonding pad in the group may correspond to a primary color light emitting diodes, but not limited thereto. According to some embodiments, in one pixel region, in addition to one set of basic RGB LEDs, at least one redundant set of RGB LEDs can be disposed. The redundant light emitting unit can be electrically connected to the corresponding basic light emitting unit. When the basic light emitting unit is faulty, the corresponding redundant light emitting unit can operate in place of the basic light emitting unit and emit light. Thus, according to some embodiment, redundant light emitting units can be disposed in some pixel regions. In detail, in one pixel region32of the first display region R1, two red LEDs, two green LEDs, and two blue LEDs may be disposed, and in one pixel region34of the foldable display region RF, three red LEDs, three green LEDs, and three blue LEDs may be disposed. In some embodiments, the light emitting units arranged in row LN1along the direction D1may serve as the basic light emitting units, and the light emitting units arranged in row LN2or row LN3along the direction D1may serve as redundant light emitting units. Since the second light emitting units LE2in the foldable display region RF may have greater chance of damage than the first light emitting units LE1, it can be designed that the number of the second light emitting units LE2in one pixel region in the foldable display region RF can be greater than the number of the first light emitting units LE1in one pixel region in the first display region R1. In detail, for example, in one first pixel region32, a first portion325of the plurality of first light emitting units LE1is disposed. In one second pixel region34, a second portion345of the plurality of second light emitting units LE2is disposed. The number of the first portion325of the first light emitting units LE1(6 LEDs) is different from, for example, less than, the number of the second portion345(9 LEDs) of the second light emitting units LE2. In some other embodiments, the redundant first light emitting units LE1, redundant second light emitting units LE2in row LN2and row LN3may not be bonded on the flexible substrate SUB before performing a test, and only redundant pads are disposed in row LN2and row LN3. When a test, such a folding test, is performed and some defects occurs, the spare light emitting units can then be bonded on the corresponding bonding pads so as to replace the damaged light emitting units.

FIG. 18shows an enlarged schematic top-view of one pixel of the foldable display device according to a fourteenth embodiment of the present disclosure. In some embodiments, one pixel PX may have a predetermined bonding region PCR for bonding light emitting units, wherein the predetermined bonding region PCR may include bonding pads130for electrically connecting to the red LED, green LED, blue LED, and the common electrode of the light emitting units, which are represented as “R”, “G”, “B”, “C” inFIG. 18respectively. In addition, a redundant bonding region PCR′ may be optionally disposed, and the redundant bonding region PCR′ can also include redundant bonding pads130′, which are represented as “R1”, “G1”, “B1”, “C1”. The redundant bonding region PCR′ may be rotated with an angle α from the predetermined bonding region PCR, and the redundant bonding pads130′ do not overlap the bonding pads130. If a damage occurs, the originally bonded light emitting unit can be removed from the predetermined bonding region PCR, and a new light emitting unit can be bonded on the redundant bonding region PCR′.

FIG. 19is a schematic top-view of an electronic device or a foldable display device according to a fifteenth embodiment of the present disclosure. The first display region R1includes a plurality of first pixel regions32, and the foldable display region RF includes a plurality of second pixel regions34. According to some embodiments, in one pixel region, in addition to one set of basic bonding pads, at least one redundant set of bonding pads can be disposed. If a damage occurs, the originally bonded light emitting unit will be removed, and the same or different light emitting unit can be bonded to the redundant bonding pad. Thus, according to some embodiments, redundant bonding pads can be disposed in some pixel regions. In detail, the number of the first bonding pads327in one pixel region32of the first display region R1can be different from, for example, less than, the number of the second bonding pads347in one pixel region34of the foldable display region RF. In some embodiments, the bonding pads arranged in row LN1along the direction D1may serve as the basic bonding pads, and the bonding pads arranged in row LN2or row LN3along the direction D1may serve as redundant bonding pads.FIG. 19shows that the light emitting units are bonded to the basic bonding pads arranged in row LN1, but not limited thereto.

According to the present disclosure, in the foldable display device, the first ratio of the thickness of the first protector to the thickness of the flexible substrate in the first display region is less than the second ratio of the thickness of the second protector to the thickness of the flexible substrate in the foldable display region. Therefore, the reliability of the bonding of the second light emitting units in the foldable display region may be improved.