TWI821731B - Bottom-emission light-emitting diode display - Google Patents

Abstract

A bottom-emission light-emitting diode (LED) display includes a transparent substrate, a plurality of LEDs bonded on the substrate, a packaging layer formed on the substrate to cover the LEDs, and a reflecting layer formed on the packaging layer to reflect light emitted by the plurality of LEDs. The reflecting layer has a non-smooth shape or the packaging layer has different refractivities.

Description

Bottom-emitting light-emitting diode display

The present invention relates to a bottom-emission light-emitting diode display (LED display), and in particular to a bottom-emission light-emitting diode display with high luminous efficiency.

MicroLED (microLED, mLED or μLED) display panel is a type of flat panel display, which is composed of individual microscopic light-emitting diodes with a size range of 1 to 10 microns. Compared with traditional liquid crystal display panels, micro-light-emitting diode display panels have larger contrast ratios, faster response times, and consume less power. Although micro-light-emitting diodes and organic light-emitting diodes (OLED) also have low power consumption characteristics, micro-light-emitting diodes use Group III-V diode technology (such as gallium nitride), so compared with Organic light-emitting diodes have higher brightness, higher luminous efficiency and longer life.

A bottom-emitting light-emitting diode display is a type of light-emitting diode display in which the light-emitting diodes emit downward light. In a bottom-emitting LED display, the light emitted by the LED is first reflected and then travels downward, but may be blocked by the bonding pad of the LED or the corresponding contact area (such as an electrode) of the substrate. wiring), thus reducing the luminous efficiency. In addition, the reflected light may be absorbed by the light-emitting diode, thereby further reducing the luminous efficiency.

Therefore, it is urgent to propose a novel bottom-emitting light-emitting diode display to overcome the shortcomings of the traditional bottom-emitting light-emitting diode display.

In view of the above, one of the purposes of embodiments of the present invention is to provide a bottom-emitting light-emitting diode display with a non-smooth reflection/encapsulation layer or an encapsulation layer with different refractive indexes (refractivity), which can enhance the Efficacy.

According to embodiments of the present invention, a bottom-emitting light-emitting diode display includes a transparent substrate, a plurality of light-emitting diodes, an encapsulation layer, and a reflective layer. The light emitting diode is bonded to the substrate. An encapsulation layer is formed on the substrate to cover the light emitting diode. The reflective layer is formed on the encapsulation layer to reflect the light emitted by the light emitting diode. In one embodiment, the reflective layer has a non-smooth shape. In another embodiment, the encapsulation layers have different refractive indices.

The first figure shows a cross-sectional view of a bottom-emission light emitting diode (LED) display 100 according to the first embodiment of the present invention.

In this embodiment, the bottom-emitting light-emitting diode display (hereinafter referred to as the display) 100 may include a transparent substrate 11, such as glass. The light-emitting diode 12 can be (flip) bonded to the substrate 11 through bonding pads 13 such as solder bumps. The display 100 of this embodiment may include a packaging layer 14 formed on the substrate 11 to cover the light emitting diode 12 .

In this embodiment, the display 100 may include a reflective layer 15 formed on the encapsulation layer 14 to reflect the light emitted by the light emitting diode 12 . According to one of the features of this embodiment, the reflective layer 15 and/or the encapsulation layer 14 has a non-smooth (external) shape or surface. In this embodiment, the reflective layer 15 has a recess 151 that is bent toward the light-emitting diodes 12 and aligned with the light-emitting diodes 12 (in this embodiment, red light-emitting diodes, green light-emitting diodes, and blue light-emitting diodes). light emitting diodes).

Compared with the traditional bottom-emitting light-emitting diode display with a smooth reflective layer, according to the display 100 shown in the first figure, the light reflected by the reflective layer 15 has more directions (as shown by arrows). Thereby, the reflected light is more likely to avoid the corresponding contact area (not shown) between the bonding pad 13 of the light-emitting diode 12 and the substrate 11 . In addition, the reflected light is more likely to avoid being absorbed by the light emitting diode 12 . Therefore, the luminous efficiency of the display 100 can be greatly improved.

In this embodiment, the encapsulation layer 14 may include a transparent material with high transmittance, such as photoresist, epoxy resin, silicon-based glue, acrylic ) or polymer. The reflective layer 15 may include reflective material (for example, the reflectivity is greater than 70%), such as metal coating, reflective film or reflective glue.

In one embodiment, the non-smooth shape (of encapsulation layer 14) of display 100 may be formed using a semiconductor process. For example, a mask with areas of different transmittances (eg, a half-tone mask or a slit mask) may be used to form specific structures, such as recesses 151 . In another embodiment, multiple photolithographic exposures may be performed on a certain area to form specific structures, such as recesses 151 .

In another embodiment, the non-smooth shape of the display 100 may be formed using a coating process. For example, coating techniques (such as inkjet printing, screen printing, spray or dispensing) can be used to form specific structures (such as depressions 151), which can be molded (molding). In another embodiment, compression molding can be used and the viscosity of the coating material can be adjusted to form specific structures, such as depressions 151 .

In yet another embodiment, the non-smooth shape of display 100 may be formed using adhesion technology. For example, a pre-structured film may be used to form specific structures, such as depressions 151 .

The second figure shows a cross-sectional view of a bottom-emitting light-emitting diode display 200 according to a second embodiment of the present invention. The bottom-emitting light-emitting diode display (hereinafter referred to as the display) 200 is similar to the display 100 in the first figure, and the differences are explained as follows.

The reflective layer 15 and/or the encapsulating layer 14 of this embodiment have a non-smooth (external) shape or surface. In this embodiment, the reflective layer 15 has a plurality of recesses 151, which are respectively bent toward the light-emitting diodes 12 (such as red light-emitting diodes, green light-emitting diodes, and blue light-emitting diodes) and are respectively aligned with the light-emitting diodes 12. Polar body 12.

The third figure shows a cross-sectional view of a bottom-emitting light-emitting diode display 300 according to a third embodiment of the present invention. The bottom-emitting light-emitting diode display (hereinafter referred to as the display) 300 is similar to the display 100 in the first figure, and the differences are explained as follows.

The reflective layer 15 of this embodiment has a non-smooth (external) shape or surface. In this embodiment, the reflective layer 15 has a plurality of convex bumps 152 protruding outward away from the light-emitting diode 12 .

The fourth shows a cross-sectional view of a bottom-emitting light-emitting diode display 400 according to a fourth embodiment of the present invention. The bottom-emitting light-emitting diode display (hereinafter referred to as the display) 400 is similar to the display 100 in the first figure, and the differences are explained as follows.

The reflective layer 15 of this embodiment has a non-smooth (external) shape or surface. In this embodiment, the reflective layer 15 has a plurality of concave cavities 153 that are concave inwards toward the light-emitting diode 12 .

The fifth shows a cross-sectional view of the bottom-emitting light-emitting diode display 500 according to the fifth embodiment of the present invention. The bottom-emitting light-emitting diode display (hereinafter referred to as the display) 500 is similar to the display 100 in the first figure, and the differences are explained as follows.

The reflective layer 15 of this embodiment has a non-smooth (external) shape or surface. In this embodiment, the reflective layer 15 has a (convex) polyhedron shape with a plurality of polygonal surfaces 154 .

The sixth diagram shows a cross-sectional view of the bottom-emitting light-emitting diode display 600 according to the sixth embodiment of the present invention. The bottom-emitting light-emitting diode display (hereinafter referred to as the display) 600 is similar to the display 100 in the first figure, and the differences are explained as follows.

The reflective layer 15 of this embodiment has a non-smooth (external) shape or surface. In this embodiment, the surface of the reflective layer 15 has an irregular shape. In one embodiment, nanoparticles 155 cover the encapsulation layer 14 , and the reflective layer 15 is formed on the nanoparticles 155 , thereby forming irregular shapes on the outer surface of the reflective layer 15 .

The seventh diagram shows a cross-sectional view of the bottom-emitting type light-emitting diode display 700 according to the seventh embodiment of the present invention.

In this embodiment, the bottom-emitting light-emitting diode display (hereinafter referred to as the display) 700 may include a transparent substrate 11, such as glass. The light emitting diode 12 can be (flip) bonded to the substrate 11 via bonding pads (or solder bumps) 13 . The display 700 of this embodiment may include an encapsulation layer 14 formed on the substrate 11 to cover the light-emitting diode 12; and may include a reflective layer 15 formed on the encapsulation layer 14 to reflect the light emitted by the light-emitting diode 12. .

According to one of the features of this embodiment, the encapsulation layer 14 may include a plurality of encapsulation sub-layers (for example, 14a to 14d), covering the light-emitting diode 12 in sequence from the light-emitting diode 12 to the reflective layer 15. Particularly, in this embodiment, the refractive index of the packaging sublayer of the lower layer (or inner layer) is higher than the refractive index of the packaging sublayer of the upper layer (or outer layer).

According to the display 700 shown in the seventh figure, the light emitted by the light emitting diode 12 may be reflected back in a direction different from the original emission direction. As shown in the seventh figure, due to the high refractive index of the packaging sublayer 14a, some of the light emitted by the light emitting diode 12 will be total reflection (shown as arrow 141). Other light emitted by the light-emitting diode 12 is refracted sequentially by the encapsulating sub-layers 14a to 14d (as shown by arrow 142), and is finally reflected by the reflective layer 15. Other light emitted by the light-emitting diode 12 is refracted by the packaging sub-layers 14a˜14c in sequence, and then due to the low refractive index of the packaging sub-layer 14d, the light is totally reflected (as shown by arrow 143).

The eighth diagram shows a cross-sectional view of a bottom-emitting light-emitting diode display 800 according to the eighth embodiment of the present invention.

In this embodiment, the bottom-emitting light-emitting diode display (hereinafter referred to as the display) 800 may include a transparent substrate 11, such as glass. The light emitting diode 12 can be (flip) bonded to the substrate 11 via bonding pads (or solder bumps) 13 . The display 800 of this embodiment may include an encapsulation layer 14 formed on the substrate 11 to cover the light-emitting diode 12; and may include a reflective layer 15 formed on the encapsulation layer 14 to reflect the light emitted by the light-emitting diode 12. .

According to one of the features of this embodiment, particles 144 or powders with different refractive indexes are added to the encapsulation layer 14 so that the traveling direction of the light emitted by the light-emitting diode 12 is changed by the particles 144 or powder (as shown by arrows) . In this embodiment, the particles 144 or powder may be powder with a high refractive index, such as quantum dot powder or metal balls.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the patentable scope of the present invention; all other equivalent changes or modifications made without departing from the spirit of the invention shall be included in the following. Within the scope of patent application.

100: Bottom-emitting light-emitting diode display 200: Bottom-emitting light-emitting diode display 300: Bottom-emitting light-emitting diode display 400: Bottom-emitting light-emitting diode display 500: Bottom-emitting light-emitting diode display 600: Bottom-emitting light-emitting diode display 700: Bottom-emitting light-emitting diode display 800: Bottom-emitting light-emitting diode display 11:Substrate 12:Light emitting diode 13:Joining pad 14: Encapsulation layer 14a~14d: Encapsulation sub-layer 141~143: Light traveling direction 144:Particles 15: Reflective layer 151:dent 152: Bump 153: cavity 154:Polygonal surface 155: Nanoparticles

The first figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to a first embodiment of the present invention. The second figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to a second embodiment of the present invention. The third figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to a third embodiment of the present invention. The fourth figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to a fourth embodiment of the present invention. The fifth figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to the fifth embodiment of the present invention. The sixth figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to the sixth embodiment of the present invention. The seventh figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to the seventh embodiment of the present invention. The eighth figure shows a cross-sectional view of a bottom-emitting light-emitting diode display according to the eighth embodiment of the present invention.

200: Bottom-emitting light-emitting diode display

11:Substrate

12:Light emitting diode

13:Joining pad

14: Encapsulation layer

15: Reflective layer

151:dent

Claims (5)

A bottom-emitting light-emitting diode display includes: a transparent substrate; a plurality of light-emitting diodes connected to the substrate; a packaging layer formed on the substrate to cover the light-emitting diodes; and a reflective layer to form on the packaging layer to reflect the light emitted by the light-emitting diodes; wherein the reflective layer has a non-smooth shape; wherein the reflective layer directly above each light-emitting diode has a corresponding depression with a smooth curved surface and Bend toward the corresponding light-emitting diode and align with the corresponding light-emitting diode. The bottom-emitting light-emitting diode display of claim 1, wherein the substrate includes glass. The bottom-emitting light-emitting diode display of claim 1 further includes: a bonding pad for bonding the light-emitting diode to the substrate. For example, in the bottom-emitting light-emitting diode display of claim 1, the encapsulation layer includes a transparent material. For example, the bottom-emitting light-emitting diode display of claim 1, wherein the reflective layer includes a reflective material with a reflectivity higher than 70%.

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