Flexible micro-LED display module

The present invention discloses a flexible micro-LED display module, comprising: a flexible substrate, a substrate protection layer, a lattice matching layer, an LED array, a transparent conductive substrate, and a light conversion layer. The light conversion layer is constituted by a plurality of red light conversion units, a plurality of green light conversion units, and a plurality of blue light conversion units, such that one pixel is formed by one red light conversion unit, one green light conversion unit, one blue light conversion unit, and several light-emitting elements. In the case of some light-emitting elements failing to radiate light normally, the defective pixel correction circuit is used to apply luminous intensity adjusting process to other light-emitting elements working normally, so as to make the flexible micro-LED display module able to display video or images with the lowest number of defective pixels capable of meeting the requirements of pixel standards.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the technology field of display devices, and more particularly to a flexible micro-LED display module.

2. Description of the Prior Art

With the high development of display technologies, traditional cathode ray tube (CRT) displays have been replaced by thin film transistor liquid crystal displays (TFT-LCD) completely.FIG. 1shows a cross-sectional side view of a TFT-LCD module. FromFIG. 1, it is understood that the TFT-LCD module1acomprises: a backlight unit11a, a lower polarization sheet12a, a lower glass substrate13a, a plurality of optical valves14a, a liquid crystal layer15a, a transparent conductive layer16a, a color filter sheet17a, an upper glass substrate18a, and a lower polarization sheet19a. In which, the said optical valve14ais a thin film transistor (TFT), and the color filter sheet17acomprises at least one red light conversion portion, at least one green light conversion portion and at least one blue light conversion portion.

It is worth mentioning that, pixel density (resolution) of the TFT-LCD module1ahas now largely enhanced due to the advanced TFT manufacturing technologies. It is well known that the liquid crystal layer15ais not a self-luminous material. Accordingly, to make the TFT-LCD module1adisplay an image, it needs to control the orientational order of the molecules of the liquid crystal layer15aby driving the optical valves14a, such that a white light beam provided by the backlight unit11ais able to pass through the liquid crystal layer15a. As a result, the white light beam is converted to a plurality of red light beams, a plurality green light beams and a plurality blue light beams by the color filter sheet17a, and then the red light beams, the green light beams and the blue light beams are further mixed for presenting a plurality of color dots (i.e., pixels). Engineers skilled in design and development of TFT-LCDs should know that, the optical efficiency, the luminous intensity, and the dynamic contrast performance of the TFT-LCD module1aare relied on the light transmittance of the liquid crystal layer15a. On the other hand, owing to the fact that the white light provided by the backlight unit11ais generated from a plurality of white LED components, the depth of colour saturation perform by the TFT-LCD module1acan merely reach 72% NTSC.

Recently, LED display module is widely applied in plane displays because of having advantages of power saving, wide color gamut (˜140% NTSC), high luminous intensity, and high dynamic contrast.FIG. 2shows a stereo exploded diagram of an LED display module. The LED display module1′ comprises: a glass substrate11′, an adhesive layer12′, an LED array comprising a plurality of red LED components14R′, a plurality of green LED components14G′ and a plurality of blue LED components14B′, a first substrate15′ provided with a plurality of row conductors16R′, and a second substrate15b′ provided with a plurality of column conductors16C′. During the operation of the LED display module1′, a (colour) pixel is exhibited by achieving the lighting of one red LED component14R′, one green LED component14G′ and one blue LED component14B′. Therefore, it is able to calculate that each of pixels in a Full HD (1920×1080) 5.5-inch LED display module1′ has an area size of 63 μm×63 μm.

As the engineers skilled in development and manufacture of LED chips know, GaN and InGaN are the common materials adopted for making an active layer of an LED chip. It has been found that, the GaN material not only includes high-density defects but also exhibits poor lattice match with sapphire substrate. For commercial LED chips, the poor lattice match is solved by inserting an AlN buffer layer between the sapphire substrate and the GaN layer. It is a pity, however, that the AlN buffer layer also includes high-density defects.

Continuously referring toFIG. 2, and please simultaneously refer toFIG. 3showing a block diagram of the LED display module and a control circuit thereof. The control circuit2′ is used to control the lighting of the LED components (14R′,14G′,14B) in the LED display module1′, and comprises: a column drive unit2C′, a row drive unit2R′, a controlling and processing unit20′, and a defective pixel correction unit2PC′. Since there is a non-uniform lighting phenomenon resulted from errors of manufacturing process occurring between the LED components (14R′,14G′,14B′), the defective pixel correction unit2PC′ is now arranged in the control circuit2′ for correcting luminance and chrominance defects of the LED display module1′ having LED matrix. It is worth explaining that, if there are some specific pixels cannot be corrected or repaired by the defective pixel correction unit2PC′, these specific pixels are regarded as defective (dead) pixels of the LED display module1′. Please refer to following Table (1), different standards for requiring the maximum defective pixels of various laptop computers are defined by IBM.

From above descriptions, it is clear that how to effectively control the total number of defective (dead) pixels of the LED display module1′ has become an important issue. In view of that, inventors of the present application have made great efforts to make inventive research and eventually provided a flexible micro-led display module.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to disclose a flexible micro-LED display module, comprising: a flexible substrate, a substrate protection layer, a lattice matching layer, a light-emitting structure, a transparent conductive substrate, and a light conversion layer. In the present invention, particularly, the light conversion layer is designed to constituted by a plurality of red light conversion units, a plurality of green light conversion units, and a plurality of blue light conversion units, such that a single pixel is formed by one red light conversion unit, one green light conversion unit, one blue light conversion unit, and several light-emitting elements. By such arrangement, in the case of the fact that there are one or two light-emitting elements failing to radiate light normally, the defective pixel correction circuit is immediately used to apply a luminous intensity adjusting process to other light-emitting elements working normally, so as to make the flexible micro-LED display module able to display video or images with the lowest number of defective pixels capable of meeting the requirements of pixel standards.

In order to achieve the primary objective of the present invention, the inventor of the present invention provides an embodiment for the flexible micro-LED display module, comprising:a flexible substrate, made of a thin metal material;a substrate protection layer, formed on or covering the flexible substrate;a lattice matching layer, formed on the substrate protection layer;a light emitting array comprising a plurality of light emitting elements, formed on the lattice matching layer, and each of the plurality of light emitting elements comprising:a first semiconductor layer, being formed on the lattice matching layer;an active layer, being formed on the first semiconductor layer;a second semiconductor layer, being formed on the active layer;a first electrode, being electrically connected to the first semiconductor layer; anda second electrode, being electrically connected to the second semiconductor layer; anda light conversion layer, disposed on the transparent conductive substrate and comprising a plurality of red light conversion units, a plurality of green light conversion units and a plurality of blue light conversion units;wherein each of the plurality of red light conversion units, each of the plurality of green light conversion units and each of the plurality of blue light conversion units all simultaneously shield multi light emitting elements under the isolation provided by the transparent conductive substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To more clearly describe a flexible micro-LED display module disclosed by the present invention, embodiments of the present invention will be described in detail with reference to the attached drawings hereinafter.

With reference toFIG. 4, there is provided a stereo exploded diagram of a first embodiment of a flexible micro-LED display module according to the present invention. AsFIG. 4shows, the flexible micro-LED display module1of the present invention is designed for use in various LED displays, and comprises: a flexible substrate10, a substrate protection layer11, a lattice matching layer12, an LED array comprising a plurality of light emitting elements13, a transparent conductive substrate14, and a light conversion layer15. According to the present invention, the flexible substrate10is made of a thin metal material and has a thickness in a range from 20 μm to 500 μm, wherein the thin metal material is selected from the group consisting of stainless steel, copper (Cu), gold (Au), nickel (Ni), molybdenum (Mo), titanium (Ti), tungsten (W), and combination of aforesaid two or more materials. In addition, the flexible substrate10is provided with a substrate protection layer11thereon. It is worth noting, however, that the flexible substrate10can also be enclosed by the substrate protection layer11in other embodiments even thoughFIG. 4describing that the substrate protection layer11is formed on the flexible substrate10. Moreover, according to the present invention, the substrate protection layer11has a thickness in a range between 50 nm and 1000 nm, and is made of a specific material selected from the group consisting of SiO2, TiO2, NiO, Al2O3, ZnO, nitride, halide, Si-based compound, and combination of aforesaid two or more materials. Thus, by the use of the substrate protection layer11, the flexible substrate10would be protected from being polluted by epitaxial materials during the formation of the multi-layered semiconductor epitaxial film.

It is worth noting that, the lattice matching layer12is formed on the substrate protection layer11and made of a crystalline material having a specific crystal orientation, such as AlN, undoped-GaN, and ZnO. Herein SiO2and AlN are taken as exemplary materials for making the substrate protection layer11and the lattice matching12, respectively. The AlN has a hexagonal wurtzite structure with lattice constants (a=0.311 nm, c=0.498 nm). On the other hand, β-cristobalite SiO2has a lattice constant a=0.499 nm. What it must emphasize the fact that the substrate protection layer11made of SiO2can not only protect the flexible substrate10from being polluting by epitaxial vapor-phase substances, but also facilitate the AlN film (i.e., the lattice matching layer12) be formed on the substrate protection layer11along c-axis orientation. Moreover, other possible materials can be processed to be the substrate protection layer11and the lattice matching layer12are listed in following Table (2) and Table (3).

In addition, a crystalline material with a lattice constant almost integral multiples of the lattice constant of GaN can also be processed to be the lattice matching layer12. For instance, Group II-VI compounds such as ZnS and ZnSe have the lattice constant a=0.623 nm and a=0.653 nm, respectively. Please simultaneously refer toFIG. 5andFIG. 6, whereinFIG. 5shows a diagram for depicting the top view of the light conversion layer15and the plurality of light emitting elements13, andFIG. 6provides a diagram for depicting the cross-sectional side view of the light conversion layer15, the light emitting elements13, and the transparent conductive substrate14. The light color of the light-emitting element13is dependent on the manufacturing materials of the first semiconductor layer131, the active layer132and the second semiconductor layer133. It is well known that GaP, GaAsP and AlGaAs are the traditional manufacturing materials of the active layer13for making the light-emitting element13emit a visible light with a wavelength in a range between 580 nm and 740 nm. However, with the continuous advances of manufacture processing technology of metal-organic chemical vapor deposition (MOCVD), GaN, Al═Ga1-xN and InxGa1-xN have become the major material for the fabrication of the active layer13nowadays. It is worth explaining that, active layer13made of GaN is able to emit blue light.

Electronic device engineers skilled in development and manufacture of LED dies (or chips) should know that, light wavelength of the active layer132made of InxGa1-xN can be regulated to be longer by increasing x (<1). On the other hand, increasing x can make light wavelength of the active layer132be regulated to be shorter. Herein, it needs to further describe that the active layer132made of GaN, AlxGa1-xN or InxGa1-xN may form a single multiple quantum well (MQW) structure between the first semiconductor layer131and the second semiconductor layer132. In contrast to the active layer132, the first semiconductor layer131is made of n-type gallium nitride (n-GaN) such as Si-doped GaN), and the second semiconductor layer133is made of p-type gallium nitride (p-GaN) like Mg-doped GaN. Moreover, for enhancing electron-hole recombination rate in the active layer132, the active layer132can be made to a multiple quantum well (MQW) structure between the first semiconductor layer131and the second semiconductor layer133, wherein the MQW structure is selected from the group consisting of a multiple stacked structure of GaN and InxGa1-xN, a multiple stacked structure of GaN and AlGa1-xN, and a multiple stacked structure of AlxGa1-xN and InxGa1-xN.

FromFIG. 4,FIG. 5andFIG. 6, it is found that the first electrode134is electrically connected to the first semiconductor layer131, and the second electrode135is formed on the second semiconductor layer133. According to the present invention, the manufacturing material of the first electrode and the second electrode is selected from the group consisting of aluminum (Al), silver (Ag), titanium (Ti), nickel (Ni), gold (Au), copper (Cu), chromium (Cr), platinum (Pt), and combination of aforesaid two or more materials. It is noted that the LED array comprising the plurality of light emitting elements13is disposed on the lattice matching layer12, and the transparent conductive substrate14and the light conversion layer15are sequentially disposed on the LED array. According to the present invention, the transparent conductive substrate14has a plurality of first conductive wires141and a plurality of second conductive wires142, wherein each of the plurality of first conductive wires141is connected to one first electrode134, and each of the plurality of second conductive wires142is connected to one second electrodes135.

The primary technology feature of the present invention is to particularly design the light conversion layer15comprising a plurality of red light conversion units15R, a plurality of green light conversion units15G and a plurality of blue light conversion units15B, so as to make each of the plurality of red light conversion units15R, each of the plurality of green light conversion units15G and each of the plurality of blue light conversion units15B all simultaneously shield multi light emitting elements13under the isolation provided by the transparent conductive substrate14. AsFIG. 5andFIG. 6show, blue light beams radiated from multi light emitting elements13are converted to red light beams by one signal red light conversion unit15R. Moreover, blue light beams radiated from multi light emitting elements13are converted to green light beams by one signal green light conversion unit15G at the same time. Simultaneously, blue light beams radiated from multi light emitting elements13are also converted to blue light beams by one signal blue light conversion units15B. Therefore, it is able to calculate that each of pixels in a Full HD (1920×1080) flexible micro-LED display module1′ of 5.5-inch has an area size of 63 μm×63 μm, wherein each area size comprises one red light conversion unit15R, one green light conversion unit15G and one blue light conversion unit15B. Moreover, the present invention particularly designs that each of three light conversion units (15R,15G,15B) shields multi light emitting elements13under the isolation provided by the transparent conductive substrate14.

Continuously referring toFIG. 4,FIG. 5andFIG. 6, and please simultaneously refer toFIG. 7showing a block diagram of the flexible micro-LED display module and a control circuit thereof. The control circuit2is used to control the lighting of the light emitting elements13in the flexible micro-LED display module1, and comprises: a column drive unit2C, a row drive unit2R, a controlling and processing unit20, and a defective pixel correction unit2PC.FIG. 8shows a diagram for depicting the top view of the light conversion layer15and the plurality of light emitting elements13. By applying a L-I-V test to the flexible micro-LED display module1through the control circuit2, there are two failure light emitting elements13found under one red light conversion unit15R, and two failure light emitting elements13are found to be failure under both one green light conversion unit15G as well as one blue light conversion unit15B. In this case, the defective pixel correction unit2PC is now used to correct luminance and chrominance defects of the flexible micro-LED display module1having the failure light emitting elements13. Briefly speaking, according to the design of the present invention, a single pixel is formed by one red light conversion unit15R, one green light conversion unit15G, one blue light conversion unit15B, and several light-emitting elements13, wherein the red light conversion unit15R, the green light conversion unit15G and the blue light conversion unit15B all simultaneously shield multi light emitting elements13under the isolation provided by the transparent conductive substrate14. By such particular arrangement, despite the fact that there are one or two light-emitting elements13failing to radiate light normally, it is able to apply luminous intensity adjusting process to other light-emitting elements13working normally through the use of the defective pixel correction circuit2PC. As a result, the flexible micro-LED display module1can still display video or images with the lowest number of defective pixels capable of meeting the requirements of pixel standards.

In addition,FIG. 9shows a diagram for depicting the cross-sectional side view of the light emitting element. After comparingFIG. 9withFIG. 6, it is able to know the light emitting element13further comprises a transparent conductive layer134a, wherein the transparent conductive layer134ais formed between the first electrode134and the first semiconductor layer131as well as the second electrode135and the second semiconductor layer133. Moreover, the transparent conductive layer134a, used for enhancing out coupling efficiency of the flexible micro-LED display module1can be made of indium tin oxide (ITO), ZnO, or Ni—Au composite material.

On the other hand, light conversion layer15comprises an encapsulation film, and a plurality of light converting particles are enclosed in the encapsulation film for forming the plurality of red light conversion units15R, the plurality of green light conversion units15G and the plurality of blue light conversion units15B. The light converting particles can be phosphor powder or quantum dots, and their exemplary materials are integrated and listed in following Table (4) and Table (5).

Besides,FIG. 10shows a stereo exploded diagram of a second embodiment of the flexible micro-LED display module. After comparingFIG. 10withFIG. 4, it is able to know the second embodiment of the flexible micro-LED display module1comprises a microlens array19, which is disposed on the light conversion layer15.

Therefore, above descriptions have introduced constituting elements and their features of the flexible micro-LED display module1disclosed by the present invention completely and clearly; in summary, the present invention includes the advantages of:

(1) Please refer toFIG. 2andFIG. 3. Because there are many defective pixels resulted from errors of manufacturing process or intrinsic defects of the LED components (14R′,14G′,14B′) occurring in LED display module1′, defective pixel correction unit2PC′ is now arranged in the control circuit2′ for correcting luminance and chrominance defects of the LED display module1′. However, owing to the fact that there are still two or more pixels cannot be corrected or repaired by the defective pixel correction unit2PC′, the LED display module1′ fails to display video or images with the defective pixels capable of meeting the requirements of pixel standards. In view of that, present invention discloses a flexible micro-LED display module1, comprising: a flexible substrate10, a substrate protection layer11, a lattice matching layer12, an LED array comprising a plurality of light emitting elements13, a transparent conductive substrate14, and a light conversion layer15. According to the present invention, the light conversion layer15is constituted by a plurality of red light conversion units15R, a plurality of green light conversion units15G, and a plurality of blue light conversion units15B, and one pixel is formed by one red light conversion unit15R, one green light conversion unit15g, one blue light conversion unit15B, and several light-emitting elements13. It is noted that, the red light conversion unit14R, the green light conversion unit14G and the blue light conversion unit14B all simultaneously shield multi light emitting elements13under the isolation provided by the transparent conductive substrate14. By such arrangement, in the case of some light-emitting elements13failing to radiate light normally, the defective pixel correction circuit2PC is used to apply luminous intensity adjusting process to other light-emitting elements13working normally, so as to make the flexible micro-LED display module1able to display video or images with the lowest number of defective pixels capable of meeting the requirements of pixel standards.

The above description is made on embodiments of the present invention. However, the embodiments are not intended to limit scope of the present invention, and all equivalent implementations or alterations within the spirit of the present invention still fall within the scope of the present invention.