CN113838842A

CN113838842A - Display panel

Info

Publication number: CN113838842A
Application number: CN202111114302.8A
Authority: CN
Inventors: 江宇涵; 王中原; 李家豪; 林上强; 田堃正
Original assignee: AU Optronics Corp
Current assignee: AU Optronics Corp
Priority date: 2020-12-22
Filing date: 2021-09-23
Publication date: 2021-12-24
Anticipated expiration: 2041-09-23
Also published as: TW202226570A; CN113838842B; TWI751850B

Abstract

The invention provides a display panel. The display panel comprises a substrate and a plurality of display units. The display units are arranged on the substrate and respectively comprise a plurality of bonding pads, a plurality of micro light-emitting elements, a convex structure and a low-reflection structure. The micro light-emitting devices are electrically connected to the bonding pads respectively. The convex structure surrounds the micro light-emitting elements and defines a light-emitting area. The raised structures have a structured surface remote from the substrate. The micro light-emitting elements are respectively provided with a light-emitting surface far away from the substrate, and the light-emitting surface of each micro light-emitting element is far away from the substrate compared with the structure surface of the convex structure. The low reflection structure does not overlap the light exit region. The low reflection structures of the display units are located between the convex structures of the display units.

Description

Display panel

Technical Field

The present disclosure relates to display technologies, and particularly to a display panel.

Background

In recent years, in the case that the manufacturing cost of an Organic light-emitting diode (OLED) Display panel is high and the service life thereof cannot compete with that of a current mainstream Display, a Micro LED Display panel has attracted the investment of each technology industry. The micro light emitting diode display panel has optical performance equivalent to that of an organic light emitting diode display technology, such as high color saturation, high response speed and high contrast, and has the advantages of low energy consumption and long service life of materials. However, since the refractive index of the epitaxial material layer of the micro light emitting diode is large (e.g. greater than 2), light emitted from the active layer (or the light emitting layer) cannot be efficiently emitted from the interface between the epitaxial material layer and air, and the overall light emitting efficiency is low. In addition, the driving circuit of the micro led display panel has a large number of metal signal lines, so that the reflectivity of the whole display panel is high, and the dark display effect is poor.

Disclosure of Invention

The invention aims to provide a display panel with better light-emitting efficiency and lower overall reflectivity.

The display panel comprises a substrate and a plurality of display units. The display units are arranged on the substrate and respectively comprise a plurality of bonding pads, a plurality of micro light-emitting elements, a convex structure and a low-reflection structure. The micro light-emitting devices are electrically connected to the bonding pads respectively. The convex structure surrounds the micro light-emitting elements and defines a light-emitting area. The raised structures have a structured surface remote from the substrate. The micro light-emitting elements are respectively provided with a light-emitting surface far away from the substrate, and the light-emitting surface of each micro light-emitting element is far away from the substrate compared with the structure surface of the convex structure. The low reflection structure does not overlap the light exit region. The low reflection structures of the display units are located between the convex structures of the display units.

In view of the above, in the display panel of an embodiment of the invention, the periphery of the plurality of micro light emitting elements of each display unit is provided with the protrusion structure defining the light emitting area of the micro light emitting elements, and the structure surface of the protrusion structure is lower than the light emitting surface of each micro light emitting element. Therefore, the light emitting efficiency of the micro light emitting elements can be effectively increased. In addition, the low reflection structure is arranged in the region outside the light emergent region, so that the overall reflectivity of the display panel can be reduced, and the display quality (such as dark contrast) of the display panel can be improved.

Drawings

Fig. 1 is a schematic top view of a display panel according to a first embodiment of the invention.

Fig. 2 is a schematic cross-sectional view of the display panel of fig. 1.

Fig. 3 is a schematic cross-sectional view of a display panel of a second embodiment of the present invention.

Fig. 4 is a schematic cross-sectional view of a display panel of a third embodiment of the present invention.

Fig. 5 is a graph of the overall reflectance of the display panel of fig. 4 versus the reflectance of the low reflection structure.

Fig. 6 is a schematic cross-sectional view of a display panel of a fourth embodiment of the present invention.

The reference numbers are as follows:

10. 10A, 11, 12 display panel

100 substrate

110 display driver layer

120. 120A convex structure

120e outer edge

120s, 120As structured surface

130. 130A low reflection structure

140. 140A protective layer

140s inner surface

150 anti-reflection layer

160 light absorbing material layer

160G light absorbing material

BP-type bonding pad

DU display unit

E1 first electrode

E2 second electrode

ES epitaxial structure layer

ESs surface

LB1, LB2 light

LED, LED1, LED2, LED3, micro light-emitting element

Light emitting surface of LEDs

LER, LER' light-emitting area

L1, L2 Length

S1, S2 distance

X, Y, Z direction

A-A' is a cutting line

Detailed Description

As used herein, "about", "approximately", "essentially", or "substantially" includes the stated value and the average value within an acceptable range of deviation of the specified value as determined by one of ordinary skill in the art, taking into account the measurement in question and the specified amount of error associated with the measurement (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated value, or within, for example, ± 30%, ± 20%, ± 15%, ± 10%, ± 5%. Further, as used herein, "about", "approximately", "essentially", or "substantially" may be selected with respect to measured properties, cutting properties, or other properties, to select a more acceptable range of deviation or standard deviation, and not to apply one standard deviation to all properties.

In the drawings, the thickness of layers, films, panels, regions, etc. have been exaggerated for clarity. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" or "connected to" another element, it can be directly on or connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" or "directly connected to" another element, there are no intervening elements present. As used herein, "connected" may refer to physical and/or electrical connections. Further, "electrically connected" may mean that there are other elements between the two elements.

Reference will now be made in detail to exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings and the description to refer to the same or like parts.

Fig. 1 is a schematic top view of a display panel according to a first embodiment of the invention. Fig. 2 is a schematic cross-sectional view of the display panel of fig. 1. Specifically, fig. 2 corresponds to a sectional line a-a' of fig. 1, and fig. 1 omits the illustration of the protective layer 140 of fig. 2. Referring to fig. 1 and fig. 2, the display panel 10 includes a substrate 100, a display driving layer 110, and a plurality of display units DU. The display driving layer 110 is disposed on the substrate 100. The display units DU are disposed on the display driving layer 110 and each include a plurality of bonding pads BP and a plurality of micro light emitting devices LED. In the present embodiment, the plurality of display units DU are arranged in a plurality of rows and a plurality of columns in the direction X and the direction Y, respectively. That is, the display units DU are arranged on the substrate 100 in an array.

For example, the micro light emitting device LED has a first electrode E1, a second electrode E2, and an epitaxial structure layer ES, and a side surface ESs of the epitaxial structure layer ES away from the substrate 100 may define a light emitting surface LED of the micro light emitting device LED. The first electrode E1 and the second electrode E2 are disposed on a side of the epitaxial structure layer ES away from the light emitting surface LEDs, and are electrically connected to two of the bonding pads BP, respectively. More specifically, the micro light-emitting element LED of the present embodiment is, for example, a flip-chip type micro light-emitting diode. However, the invention is not limited thereto, and according to other embodiments, the micro light emitting device may be a vertical type micro light emitting diode or a horizontal type micro light emitting diode.

It should be noted that, in the present embodiment, the number of the micro-light emitting elements LED of each display unit DU is exemplarily illustrated by three (for example, the first micro-light emitting element LED1, the second micro-light emitting element LED2, and the third micro-light emitting element LED3), and the light emitting colors of the micro-light emitting elements LED may be different from each other, such as red, green, and blue, but not limited thereto. In other embodiments, the number of micro-lighting elements LED and the corresponding lighting color types of each display unit DU can be adjusted according to the actual optical design.

The number of bonding pads BP of each display unit DU may be twice as many as the number of micro light emitting elements LED corresponding to the number of electrodes of each micro light emitting element LED, but is not limited thereto. In other embodiments, the bonding pads BP of each display unit DU may further include bonding pads BP for bonding a micro light emitting device for repair (repair). That is, the number of bonding pads BP of each display unit DU can be adjusted according to the repair requirement of the process, and is not necessarily a multiple of the number of micro light emitting elements LED.

In the present embodiment, the display driving layer 110 includes, for example, a plurality of active devices (not shown) and a plurality of signal lines (not shown), wherein one of the bonding pads BP of the bonding pad set (e.g., including two bonding pads BP) corresponding to each of the micro light emitting devices LED can be electrically connected to at least one of the active devices. The plurality of signal lines are, for example, a combination of a plurality of data lines (data lines), a plurality of scan lines (scan lines), and a plurality of power lines (power lines), but not limited thereto. For example, the circuit architecture of the display driving layer 110 for driving each display unit DU may be a driving unit of an architecture 1T1C, an architecture 2T1C, an architecture 3T1C, an architecture 3T2C, an architecture 4T1C, an architecture 4T2C, an architecture 5T1C, an architecture 5T2C, an architecture 6T1C, an architecture 6T2C, an architecture 7T2C, or any possible architectures, and the invention is not limited thereto.

Further, a protrusion structure 120 is disposed around the micro light emitting elements LED of each display unit DU. In the present embodiment, the protrusion structure 120 may continuously surround the micro light emitting elements, which is not limited to this. In other embodiments, the raised structures may also be disposed around the micro light emitting elements LED in a partially broken manner. The material of the bump structure 120 may include a metal material (e.g., molybdenum, aluminum, copper), or titanium. For example, in the present embodiment, the protrusion structure 120 may be formed by etching a metal material layer, but not limited thereto. In other embodiments, the protrusion structure may be formed by etching the photoresist material layer to form the protrusion structure 120 of the present embodiment, and then covering a metal reflective layer thereon.

In the present embodiment, the outer edge 120e of the protrusion structure 120 may define the light exit region LER of the display unit DU, but not limited thereto. Specifically, the symmetrical center lines of the two protrusion structures 120 of two adjacent display units DU arranged along a direction (e.g., the direction X or the direction Y) may define the boundary of the two display units DU in the direction (as shown by the virtual grid line in fig. 1). In the present embodiment, the cross-sectional profile (e.g., XZ plane or YZ plane) of the protrusion structure 120 is, for example, a triangle, and the structure surface 120s of the protrusion structure 120 is a slope disposed toward the micro light emitting device LED, but the invention is not limited thereto. In other embodiments, the protrusion structure may also be an isosceles triangle having two inclined planes, and the two inclined planes face the micro light emitting device LED and the low reflection structure 130, respectively.

It is particularly noted that the protruding structure 120 has a structure surface 120s far away from the substrate 100, and the light emitting surface LEDs (i.e., the surface ESs of the epitaxial structure layer ES) of the micro light emitting device LED are far away from the substrate 100 than the structure surface 120s of the protruding structure 120. For example, light emitted from the micro light-emitting element LED at an unexpected angle (e.g., the light LB1 emitted from the sidewall of the epitaxial structure layer ES) can be reflected by the structure surface 120s of the protrusion structure 120 to exit from the light exit region LER of the display unit DU, which is helpful to improve the light-emitting efficiency of the micro light-emitting element LED.

On the other hand, the micro light emitting device LED has a length L1 and a length L2 in the direction Y and the direction X, respectively, and the protrusion structure 120 is far away from the outer edge 120e of the micro light emitting device LED (i.e., the boundary of the light exiting region LER) and the micro light emitting device LED (e.g., the second micro light emitting device LED2) has a distance S1 and a distance S2 in the direction Y and the direction X, respectively. In a preferred embodiment, the ratio of the distance S1 between the outer edge 120e of the protrusion 120 and the micro light emitting device LED to the length L1 of the micro light emitting device LED, and the ratio of the distance S2 between the outer edge 120e of the protrusion 120 and the micro light emitting device LED to the length L2 of the micro light emitting device LED are both less than or equal to 1.216 and greater than 0. Therefore, the display panel has better light-emitting efficiency.

In order to avoid the excessive increase of the overall reflectivity of the display panel 10 caused by the arrangement of the protrusion structures 120, the percentage value of the vertical projection area of the protrusion structures 120 on the substrate 100 to the vertical projection area of each display unit DU on the substrate 100 may be greater than 0% and less than or equal to 20%. In a preferred embodiment, the percentage of the vertical projection area of the protrusion structure 120 on the substrate 100 to the vertical projection area of each display unit DU on the substrate 100 is greater than or equal to 10% and less than or equal to 20%.

On the other hand, in order to reduce the overall reflectivity of the display panel 10 on the side (i.e., the display side) of the light emitting surface LEDs of the micro light emitting elements LED, each display unit DU further includes a low reflection structure 130. The low reflection structure 130 is disposed on a side of the convex structure 120 of the same display unit DU away from the micro light emitting element LED, and is located between the convex structure 120 of the same display unit DU and the convex structure 120 of the adjacent display unit DU. More specifically, the convex structure 120 of the same display unit DU is located between the micro light emitting elements LED and the low reflection structure 130. The low reflection structure 130 may be a stacked structure of single or multiple layers of materials, and the material thereof may be selected from a black resin material, a blackened metal (e.g., metal oxide, metal nitride, metal oxynitride), a brown organic material, and the like. In a preferred embodiment, the reflectivity of the low reflection structure 130 is less than or equal to 5.

In the present embodiment, the low-reflection structures 130 of the display units DU are connected to each other, and the low-reflection structures 130 extend between the protrusion structures 120 of the display units DU, and do not overlap with the light-emitting region LER defined by the protrusion structures 120 in the normal direction (e.g., the direction Z) of the light-emitting surface LEDs of the micro light-emitting device LED. That is, these low reflection structures 130 are non-light exit regions disposed outside the plurality of light exit regions LER and cover the display driving layer 110. For example, the display driving layer 110 may be a stacked structure of a plurality of metal conductive layers including a plurality of metal signal lines (e.g., data lines, scan lines, power lines, and transfer lines), which easily reflect external ambient light on the display side to affect the display quality of the display panel in a dark state. Therefore, the low reflection structure 130 is disposed between the light exiting regions LER (or the protruding structures 120), so as to effectively reduce the visibility of the metal conductive layers of the display driving layer 110 under the external ambient light, and further improve the display quality (for example, dark contrast) of the display panel 10.

In order to achieve both the light-emitting efficiency of the micro light-emitting device LED and the overall reflectivity of the display panel 10 on the display side, the vertical projection area of the protrusion structure 120 on the substrate 100 is smaller than the vertical projection area of the low-reflection structure 130 on the substrate 100. For example, the percentage of the vertical projection area of the low reflection structure 130 on the substrate 100 to the vertical projection area of each display unit DU on the substrate 100 is greater than or equal to 50% and less than 100%. The percentage ratio of the vertical projection areas of the protrusion structures 120 and the low reflection structures 130 on the substrate 100 to the vertical projection area of each display unit DU on the substrate 100 is greater than or equal to 70% and less than 100%.

In a preferred embodiment, the percentage ratio of the vertical projection areas of the protrusion structures 120 and the low reflection structures 130 on the substrate 100 to the vertical projection area of each display unit DU on the substrate 100 is greater than or equal to 70% and less than or equal to 98.5%, and the percentage ratio of the vertical projection area of the protrusion structures 120 on the substrate 100 to the vertical projection area of each display unit DU on the substrate 100 is greater than or equal to 10% and less than or equal to 20%. Therefore, the display panel has relatively better light-emitting efficiency under the condition that the overall reflectivity does not exceed 10 percent.

It should be noted that, in the present embodiment, the low reflection structure 130 may directly contact the outer edge 120e of the protrusion structure 120, but the invention is not limited thereto. In other embodiments, the low reflection structure 130 and the protrusion structure 120 may be spaced apart from each other due to a difference in process or a consideration of process flexibility. That is, the low reflection structure 130 and the protrusion structure 120 may have a gap therebetween.

In the present embodiment, the display panel 10 may further optionally include a protective layer 140. The protection layer 140 covers the micro light emitting devices, the plurality of protruding structures 120, and the plurality of low reflection structures 130. The material of the protection layer 140 may be selected from acrylic (acrylic), Epoxy (Epoxy), Hexamethyldisiloxane (HMDSO), or other suitable organic materials. For example, due to the refractive index difference between the protection layer 140 and the external environment (e.g., air), a portion of the light emitted from the micro light emitting device LED (e.g., the light beam LB2 of fig. 2) is totally reflected at the inner surface 140s of the protection layer 140 facing the substrate 100. It is particularly noted that such light reflected by the inner surface 140s of the protection layer 140 can also be reflected by the protrusion structure 120 and then emitted from the light exit region LER of the display unit DU, which is helpful for improving the light emitting efficiency of the micro light emitting device LED.

The present disclosure will be described in detail below with reference to other embodiments, wherein like components are denoted by like reference numerals, and descriptions of the same technical content are omitted, and reference is made to the foregoing embodiments for omitting details.

Fig. 3 is a schematic cross-sectional view of a display panel of a second embodiment of the present invention. Referring to fig. 3, the difference between the display panel 10A of the present embodiment and the display panel 10 of fig. 2 is: the cross-sectional profiles of the raised structures are different. In the present embodiment, the cross-sectional profile (for example, XZ plane or YZ plane) of the protrusion structure 120A is, for example, a semi-ellipse, the structure surface 120As of the protrusion structure 120A is a curved surface disposed toward the micro light emitting device LED, and the low reflection structure 130A does not cover the protrusion structure 120A. It is particularly noted that, in the present embodiment, the light exiting region LER' of each display unit DU is not defined by the outer edge of the protrusion structure 120A away from the micro light-emitting element LED, but is defined by the portion of the structure surface 120As of the protrusion structure 120A farthest away from the substrate 100.

Fig. 4 is a schematic cross-sectional view of a display panel of a third embodiment of the present invention. Fig. 5 is a graph of the overall reflectance of the display panel of fig. 4 versus the reflectance of the low reflection structure. Referring to fig. 4 and 5, the difference between the display panel 11 of the present embodiment and the display panel 10 of fig. 2 is: the display panel 11 may further optionally include an anti-reflection layer 150 and a light-absorbing material layer 160. The anti-reflection layer 150 is disposed on the protection layer 140 (or the plurality of display units DU), and overlaps the plurality of light exiting regions LER of the plurality of display units DU. The light absorbing material layer 160 is disposed between the anti-reflection layer 150 and the plurality of display units DU. The material of anti-reflective layer 150 may include a metal oxide (e.g., titanium dioxide), a nitride (silicon nitride), silicon dioxide, an oxynitride, or combinations thereof. In particular, the anti-reflection layer 150 is disposed here to inhibit the external ambient light from being reflected on the surface of the light-absorbing material layer 160 contacting the anti-reflection layer 150, which is helpful to reduce the overall reflectivity of the display panel 11.

On the other hand, in the embodiment, the light absorbing material layer 160 may be a dye film (dye film), but not limited thereto. The dye film includes, for example, a polymer substrate and a plurality of dye molecules, and the dye molecules are dispersedly disposed in the polymer substrate. By disposing the light absorbing material layer 160, the overall reflectivity of the display panel 11 on the display side (i.e., the side of the light emitting surface LEDs of the micro light emitting device LED) can be further reduced. From another point of view, the design margin of the protrusion structure 120 and the low reflection structure 130 can be increased, for example: the area of the protrusion structures 120 may be increased, or a low reflection structure material having a reflectivity slightly larger than that of the low reflection structure 130 of fig. 2 may be used.

As shown in fig. 5, the reflectivity of the low reflection structure 130 of the display panel 11 of the present embodiment may have a larger optional range, for example, between 1% and 10%. In contrast, in a comparative example, the display panel uses a general color filter (color filter) layer instead of the light absorbing material layer 160 of the present embodiment. As can be seen from fig. 5, in order to satisfy the requirement that the overall reflectivity of the display panel is less than 10%, the selectable range of the reflectivity of the low-reflection structure of the comparative example is significantly smaller, for example, between 1% and 3%. It should be noted that the reflectivity of the low reflection structure 130 is, for example, a material reflectivity, but not limited thereto. In other embodiments, the reflectivity of the low-reflection structure may be smaller than the reflectivity of the material itself, that is, the surface of the low-reflection structure may be provided with an anti-reflection optical microstructure so that the reflectivity of the whole low-reflection structure is lower than the reflectivity of the material itself.

Fig. 6 is a schematic cross-sectional view of a display panel of a fourth embodiment of the present invention. Referring to fig. 6, the difference between the display panel 12 of the present embodiment and the display panel 11 of fig. 4 is: the light absorbing material is arranged differently. In the present embodiment, the light absorbing material 160G is not disposed between the anti-reflection layer 150 and the protection layer 140A as a separate layer, but is disposed dispersedly in the protection layer 140A. That is, the protection layer 140A of the present embodiment is also a light absorbing material layer. The light absorbing material 160G is, for example, a black gel (black gel), but is not limited thereto. In other embodiments, the light absorbing material may also be a dye molecule (dye molecule). Since the light absorbing material 160G of the present embodiment functions similarly to the light absorbing material layer 160 of the display panel 11 in fig. 4, please refer to the related paragraphs of the previous embodiments for further description.

In summary, in the display panel of an embodiment of the invention, the plurality of micro light emitting devices of each display unit are surrounded by a protrusion structure defining the light emitting area of the micro light emitting devices, and the structure surface of the protrusion structure is lower than the light emitting surface of each micro light emitting device. Therefore, the light emitting efficiency of the micro light emitting elements can be effectively increased. In addition, the low reflection structure is arranged in the region outside the light emergent region, so that the overall reflectivity of the display panel can be reduced, and the display quality (such as dark contrast) of the display panel can be improved.

Claims

1. A display panel, comprising:

a substrate; and

a plurality of display units disposed on the substrate and each including:

a plurality of bonding pads;

a plurality of micro light emitting elements electrically connected to the bonding pads, respectively;

a convex structure surrounding the micro light-emitting elements and defining a light-emitting area, the convex structure having a structure surface far away from the substrate, wherein the micro light-emitting elements respectively have a light-emitting surface far away from the substrate, and the light-emitting surface of each micro light-emitting element is far away from the substrate than the structure surface of the convex structure; and

and the low-reflection structures are not overlapped with the light emergent area, and the low-reflection structures of the display units are positioned among the convex structures of the display units.

2. The display panel of claim 1, wherein a percentage of a vertical projection area of the protrusion structure on the substrate to a vertical projection area of each of the display units on the substrate is greater than 0% and less than or equal to 20%.

3. The display panel of claim 1, wherein a percentage of a vertical projection area of the protrusion structure on the substrate to a vertical projection area of each of the display units on the substrate is greater than or equal to 10% and less than or equal to 20%.

4. The display panel of claim 1, wherein a percentage of a vertical projection area of the low reflection structure and the protrusion structure on the substrate to a vertical projection area of each of the display units on the substrate is greater than or equal to 70% and less than or equal to 98.5%.

5. The display panel of claim 1, wherein the low reflection structure has a reflectivity of 5% or less.

6. The display panel of claim 1, wherein each of the micro light-emitting devices has a first length in a first direction, the protrusion has a first distance in the first direction between an outer edge of the protrusion away from the micro light-emitting devices and each of the micro light-emitting devices, and a ratio of the first distance to the first length is less than or equal to 1.216 and greater than 0.

7. The display panel of claim 1, wherein a percentage of a vertical projection area of the low reflection structure on the substrate to a vertical projection area of each of the display units on the substrate is greater than or equal to 50% and less than 100%.

8. The display panel of claim 1, wherein the cross-sectional profile of the low reflection structure of each display unit is triangular or semi-elliptical.

9. The display panel of claim 1, further comprising:

and the anti-reflection layer is arranged on the display units and is overlapped with the light emergent area of each display unit.

10. The display panel of claim 9, further comprising:

and the light absorption material layer is arranged between the anti-reflection layer and the plurality of display units.

11. The display panel of claim 1, wherein each of the micro light-emitting devices has a first electrode, a second electrode and an epitaxial structure layer, a surface of the epitaxial structure layer away from the substrate defines the light-emitting surface of each of the micro light-emitting devices, and the first electrode and the second electrode are disposed on a side of the epitaxial structure layer away from the light-emitting surface and electrically connected to two of the bonding pads, respectively.

12. The display panel of claim 1, wherein the protrusion structure is located between the micro light-emitting devices and the low reflection structure.

13. The display panel of claim 1, wherein a vertical projection area of the protrusion structure on the substrate is smaller than a vertical projection area of the low reflection structure on the substrate.