TW202207197A - Micro light emitting diode display panel - Google Patents

Abstract

A micro light emitting diode display panel including a plurality of display units and a controlling element is provided. The plurality of display units are arranged in an array and each of the plurality of display units includes a first sub-pixel. The first sub-pixel includes a first micro light emitting diode and a second micro light emitting diode. The controlling element is configured to control light emission of the first micro light emitting diode and the second micro light emitting diode and determines operating currents of the first micro light emitting diode and the second micro light emitting diode. In the same display image, the operating current of the first micro light emitting diode increases as an operating temperature of the first sub-pixel increases.

Description

Miniature Light Emitting Diode Display Panel

The present invention relates to a display panel, and more particularly, to a miniature light emitting diode display panel.

With the evolution of optoelectronic technology, solid-state light sources (such as light-emitting diodes) have been widely used in various fields, such as road lighting, large outdoor signboards, traffic lights, etc. Recently, a miniature light emitting diode display panel has been developed. The miniature light emitting diodes are used as sub-pixels in the display panel, so that each sub-pixel can be independently driven to emit light. A display panel that combines the light beams emitted by these independently emitting micro-LEDs to form an image is a micro-LED display panel.

In the existing high-resolution or large-size micro LED display panels, since the current supply time for each data line is very short, the current density transmitted by each data line needs to be increased, which is easily damaged by heat . In addition, with the increase of operating temperature, the micro-LEDs are prone to the problem of reduced luminous efficiency or wavelength shift, resulting in inconsistent performance of the micro-LED display panels in terms of brightness or color.

The present invention provides a miniature light emitting diode display panel, which helps to improve the problem of brightness reduction or color shift during high temperature operation.

According to an embodiment of the present invention, a micro light emitting diode display panel includes a plurality of display units and control elements. A plurality of display units are arranged in an array and each display unit includes a first sub-pixel. The first sub-pixel includes a first miniature light-emitting diode and a second miniature light-emitting diode. The control element is used for controlling the light emission of the first micro light emitting diode and the second micro light emitting diode and determining the operating current of the first micro light emitting diode and the second micro light emitting diode. Under the same display screen, the operating current of the first micro light-emitting diode increases as the operating temperature of the first sub-pixel increases.

In an embodiment of the present invention, the impedance of the first micro light-emitting diode is smaller than the impedance of the second micro light-emitting diode.

In an embodiment of the present invention, the operating current of the first micro light-emitting diode is controlled and input by the control element.

In an embodiment of the present invention, the operating current of the second micro-LED decreases as the operating temperature of the first sub-pixel increases.

In an embodiment of the present invention, when the first sub-pixel operates at a high temperature, the operating current of the first micro-LED is greater than the operating current of the second micro-LED. When the first sub-pixel operates at a low temperature, the operating current of the second micro-LED is greater than the operating current of the first micro-LED.

In an embodiment of the present invention, the micro light-emitting diode display panel further includes a substrate. The control element, the first miniature light emitting diode and the second miniature light emitting diode in the display unit are bonded on the substrate.

In an embodiment of the present invention, the micro LED display panel further includes a plurality of micro chips. A plurality of microchips are bonded on the substrate, and each microchip is located between and electrically connected with the plurality of display units.

In an embodiment of the present invention, the first micro light emitting diode and the second micro light emitting diode are different in at least one of the following: the area of the current spreading layer, the thickness of the current spreading layer, the thickness of the electrode and the epitaxial layer The junction area and the material of at least one of the electrode and the epitaxial layer.

In an embodiment of the present invention, each display unit further includes a second sub-pixel. The first sub-pixel and the second sub-pixel emit different colors, wherein the first micro-LED of the first sub-pixel has a shorter wavelength than the second micro-LED.

In an embodiment of the present invention, the first sub-pixel further includes a variable impedance element. The variable impedance element is connected to the first micro light emitting diode and the second micro light emitting diode.

In an embodiment of the present invention, in the first sub-pixel, the first micro-LED and the second micro-LED are connected in series, and the variable impedance element is connected in parallel with the first micro-LED.

In one embodiment of the invention, the impedance of the variable impedance element increases as the operating temperature of the first sub-pixel increases.

In an embodiment of the present invention, the operating current of the first micro-LED increases as the operating temperature of the first sub-pixel increases.

In an embodiment of the present invention, the first micro-LED has a shorter wavelength than the second micro-LED.

Based on the above, in the embodiment of the present invention, the first sub-pixel has two micro-LEDs, and the operating current of at least one micro-LED is controlled according to the operating temperature of the first sub-pixel to compensate The problem of brightness reduction or color shift of the micro light-emitting diodes during high temperature operation, thereby improving the consistency of the brightness or color performance of the micro light-emitting diode display panels.

In order to make the above-mentioned features and advantages of the present invention more obvious and easy to understand, the following embodiments are given and described in detail with the accompanying drawings as follows.

Directional terms mentioned herein, such as "up", "down", "front", "rear", "left", "right", etc., only refer to the directions of the drawings. Accordingly, the directional terms used are intended to illustrate rather than limit the present invention.

In the drawings, each figure illustrates the general characteristics of methods, structures or materials used in particular embodiments. However, these drawings should not be construed to define or limit the scope or nature encompassed by these embodiments. For example, the relative sizes, thicknesses and positions of various layers, regions or structures may be reduced or exaggerated for clarity.

Terms such as "first" and "second" mentioned in this specification or the scope of the patent application are only used to name different elements or to distinguish different embodiments or ranges, and are not used to limit the upper or lower limit of the number of elements, nor Used to define the order of manufacture or arrangement of components. Furthermore, the disposition of an element/film layer on (or over) another element/film layer may encompass that the element/film layer is disposed directly on (or over) the other element/film layer, and both elements/film layers are disposed directly on (or over) the other element/film layer. The case where the film layers are in direct contact; and the element/film layer is indirectly disposed on (or over) the other element/film layer, and there is one or more elements/film layers between the two elements/film layers. condition.

FIG. 1 is a schematic partial top view of a miniature light emitting diode display panel according to an embodiment of the present invention. FIG. 2 is a first simple circuit diagram of the control element and the first sub-pixel in FIG. 1 . 3A and 3B are schematic cross-sectional views of the first miniature light-emitting diode and the second miniature light-emitting diode in FIG. 2 , respectively. FIG. 4 is a second simple circuit diagram of the control element and the first sub-pixel in FIG. 1 . FIG. 5 is a schematic diagram illustrating wavelengths and light intensities of the first micro-LED and the second micro-LED in the first sub-pixel of FIG. 2 . 6 to 8 are schematic partial top views of micro-LED display panels according to other embodiments of the present invention, respectively.

In FIGS. 1 to 8 , the same or similar elements will be given the same or similar reference numerals, and redundant descriptions thereof will be omitted. In addition, the features in different embodiments can be combined with each other without conflict, and simple equivalent changes and modifications made according to the present specification or the scope of the claimed patent are still within the scope of the present patent.

Referring to FIG. 1 , the miniature light-emitting diode display panel 100 may include a plurality of display units U, each of which is composed of a first sub-pixel 112 , a second sub-pixel 114 and a third sub-pixel 116 . A plurality of display units U are arranged in an array, so that the micro-LED display panel 100 can display images (only four display units U are schematically shown in FIG. 1 ). The first sub-pixel 112 . The first sub-pixel 112 may include a plurality of miniature light emitting diodes. 1 schematically illustrates that the first sub-pixel 112 includes a micro LED 112A (also referred to as a first micro LED) and a micro LED 112B (also referred to as a second micro LED) polar body). However, the number of miniature light-emitting diodes in the first sub-pixel 112 is not limited thereto. In some embodiments, the plurality of miniature light-emitting diodes may have the same size to facilitate the bonding process and circuit design, but not limited thereto.

In some embodiments, as shown in FIG. 2 , the micro LEDs 112A and the micro LEDs 112B may be electrically independent of each other. For example, the micro light emitting diode display panel 100 may further include a control element 120 . The control element 120 is used to control the light emission of the micro LEDs 112A and the micro LEDs 112B and determine the operating currents of the micro LEDs 112A and 112B. Specifically, the control element 120 can control the light-emitting state (light-emitting, non-emitting or light-emitting intensity) of the micro-LEDs, wherein the micro-LEDs 112A and 112B can be electrically connected to the control element 120 independently. , so that the control element 120 can individually control the current I112A input to the micro LED 112A and the current I112B input to the micro LED 112B. The control element 120 may be a circuit chip or a driver of a miniature light emitting diode, but is not limited thereto.

In some embodiments, as shown in FIG. 1 , the control element 120 may be disposed on one side of the MLED display panel 100 , and each sub-pixel is individually connected by wires (not shown), so as to individually Controls the current input to the micro LEDs in each sub-pixel. However, in other embodiments, the micro LED display panel 100 may include a plurality of control elements 120 , and the plurality of control elements 120 may be correspondingly disposed in individual sub-pixels.

In some embodiments, the micro-LED 112A and the micro-LED 112B may have the same or similar emission wavelengths. The light-emitting wavelength refers to the wavelength corresponding to the maximum light intensity in the spectrum of the micro light-emitting diode. A plurality of miniature light-emitting diodes with close emission wavelengths means that the difference in emission wavelengths of the plurality of miniature light-emitting diodes does not exceed 10 nm, for example, within the range of 1 nm to 10 nm, and preferably within the range of 3 nm to 5 nm. range, but not limited thereto.

In the first sub-pixel 112, the operating current of the at least one micro-LED varies as the operating temperature of the first sub-pixel 112 changes. Specifically, the operating current of at least one micro-LED (eg, micro-LED 112A or micro-LED 112B) is controlled according to the operating temperature of the first sub-pixel 112 to compensate for the The problem of brightness reduction or color shift during high temperature operation can further improve the consistency of the brightness or color performance of the micro LED display panel 100 .

For example, under the structure of FIG. 2 , the micro LEDs 112A and the micro LEDs 112B may have different impedances. When operating at high temperature, the micro-LED with low impedance can have a larger operating current, and when operating at low temperature or normal temperature, the micro-LED with large impedance can have a larger operating current. The method of making the micro LED 112A and the micro LED 112B have different impedances may include making the micro LED 112A and the micro LED 112B different in at least one of: the area of the current spreading layer, The thickness of the current spreading layer, the junction area of the electrode and the epitaxial layer, and the material of at least one of the electrode and the epitaxial layer.

Taking the impedance of the micro light emitting diode 112A smaller than that of the micro light emitting diode 112B as an example, the micro light emitting diode 112A may have a smaller area and thickness of the current spreading layer than the micro light emitting diode 112B. Or the junction area of the electrode and the epitaxial layer, or the material of at least one of the electrode and the epitaxial layer can be adjusted so that the impedance of the micro light emitting diode 112A is smaller than that of the micro light emitting diode 112B.

3A and 3B schematically illustrate that the impedance of the micro-LED 112A is made smaller than that of the micro-LED 112B by adjusting the area of the current spreading layer. As shown in FIGS. 3A and 3B , each of the micro LEDs 112A and 112B may include, for example, an epitaxial layer 1120 , a current spreading layer 1121 , and an electrode layer 1123 .

The epitaxial layer 1120 may include an n-type semiconductor layer (eg, n-GaN or the like) 1120-1, a Multiple-Quantum Well (MQW) layer 1120-2, and a p-type semiconductor layer (eg, p-GaN or the like) 1120-3, wherein the multiple quantum well layer 1120-2 is located between the n-type semiconductor layer 1120-1 and the p-type semiconductor layer 1120-3, and the p-type semiconductor layer 1120-3 is located between the multiple quantum well layer 1120-2 and the p-type semiconductor layer 1120-3. between the current spreading layers 1121 . In some embodiments, the thickness T1120-1 of the n-type semiconductor layer 1120-1 is 3000 nm, the thickness T1120-2 of the multiple quantum well layer 1120-2 is 300 nm, and the thickness T1120-3 of the p-type semiconductor layer 1120-3 is 600 nm , and the thickness of the epitaxial layer 1120 (ie, the sum of the thickness T1120-1, the thickness T1120-2 and the thickness T1120-3) is 4 μm to 5 μm, but not limited thereto.

The current diffusion layer 1121 is provided on the epitaxial layer 1120 . In some embodiments, the current spreading layer 1121 is a metal oxide layer (such as an ITO layer or the like), and the thickness T1121 of the current spreading layer 1121 is 100 nm, but not limited thereto.

The larger the area of the current spreading layer 1121, the smaller the current density and the greater the impedance. Therefore, by making the area of the current spreading layer 1121 of the micro LED 112A smaller than the area of the current spreading layer 1121 of the micro LED 112B, The micro LEDs 112A can be made to have a lower impedance than the micro LEDs 112B. The area of the current diffusion layer 1121 refers to the area of the orthographic projection of the current diffusion layer 1121 on the n-type semiconductor layer 1120-1.

In some embodiments, the area ratio of the current spreading layer 1121 of the micro LED 112B to the current spreading layer 1121 of the micro LED 112A may fall within the range of 1.2 to 2. For example, the area of the current spreading layer 1121 of the micro LED 112A is 10 μm ² to 30 μm ² (substantially less than 15 μm ² ), and the area of the current spreading layer 1121 of the micro LED 112B is 30 μm ² to 100 μm ² , but not limited to this.

The electrode layer 1123 is provided on the current diffusion layer 1121 . In some embodiments, the electrode layer 1123 is a metal layer (eg, a copper layer or the like), and the thickness T1123 of the electrode layer 1123 is 2 nm, but not limited thereto.

In some embodiments, each of the micro LEDs 112A and 112B may further include an insulating layer 1122, for example. The insulating layer 1122 covers the current spreading layer 1121 and the epitaxial layer 1120 (eg, the insulating layer 1122 covers the sidewall SW of the epitaxial layer 1120 ). The material of the insulating layer 1122 may include silicon oxide, silicon nitride or the like, and the thickness T1122 of the insulating layer 1122 may be 700 nm, but not limited thereto.

The insulating layer 1122 may have an opening O1 exposing the current diffusing layer 1121 and an opening O2 exposing the epitaxial layer 1120, and the electrode layer 1123 may have a first electrode E1 contacting the epitaxial layer 1120 through the opening O2 and a first electrode E1 passing through the opening O1. The second electrode E2 in contact with the current spreading layer 1121, and the first electrode E1 and the second electrode E2 are electrically insulated from each other. In the micro light emitting diode 112A, the current diffusion layer 1121 overlaps with the second electrode E2 and is larger than the opening O1. In the miniature light-emitting diode 112B, the current spreading layer 1121 covers the epitaxial layer 1120 , and the opening A1121 of the current spreading layer 1121 exposes the groove G of the epitaxial layer 1120 .

It should be understood that FIG. 3A and FIG. 3B only schematically illustrate the structure of a micro light emitting diode, but the structure, number of film layers and/or each layer, each of the micro light emitting diode 112A and the micro light emitting diode 112B The shape or size of the opening or openings may vary as desired. The miniature light emitting diodes 112A and 112B herein are intended to generalize any form of known miniature light emitting diodes.

Referring to FIG. 2 , in the first sub-pixel 112 , the operating current of the micro LEDs 112A (miniature light-emitting diodes with low impedance) may increase, for example, as the operating temperature of the first sub-pixel 112 increases, The operating current of the micro LEDs 112B (micro LEDs with high impedance) may decrease as the operating temperature of the first sub-pixel 112 increases, for example. In other words, the operating current of the micro LEDs 112A during high temperature operation is greater than the operating current of the micro LEDs 112A during normal temperature operation, and the operating current of the micro LEDs 112B during normal temperature operation is greater than Operating current of the micro LEDs 112B at high temperature operation.

In some embodiments, when the first sub-pixel 112 operates at a high temperature, the operating current of the micro LEDs 112A (miniature LEDs with low impedance) may be larger than that of the micro LEDs 112B (micro LEDs with high impedance). diode) operating current. On the other hand, when the first sub-pixel 112 operates at a low temperature, the operating current of the micro LEDs 112B may be greater than the operating current of the micro LEDs 112A. Specifically, when operating at low temperature or normal temperature, the micro light-emitting diode with large impedance (such as the micro light-emitting diode 112B) can have a large operating current to maintain the required brightness; Both the light-emitting diode 112A and the micro-LED 112B have a problem of high temperature light decay (that is, the brightness of the micro-LED 112A and the micro-LED 112B will both be reduced), and at this time, the micro-LEDs with low impedance can be made to emit light. The diodes (eg, the micro LEDs 112A) have larger operating currents (eg, boosting the operating current of the micro LEDs with low impedance) to increase the brightness through high current density, thereby increasing the brightness at different operating temperatures Maintain uniform brightness. It should be understood that at any operating temperature, the micro LED 112A and the micro LED 112B can be turned on and off, or both can be turned on. When the operating temperature of any micro light emitting diode is too high, the micro light emitting diode can be turned off or the operating current of the micro light emitting diode can be reduced based on considerations such as safety or life.

Herein, high temperature in high temperature operation refers to the temperature at which the micro LEDs produce significant brightness or lifetime degradation, usually above 60 degrees Celsius, but not limited thereto. The normal temperature in the normal temperature operation refers to the typical working temperature of the micro light-emitting diode, which is usually 25 degrees Celsius, but not limited thereto. The operating current of the micro light emitting diode refers to the current flowing through the micro light emitting diode. The operating temperature of the first sub-pixel refers to the temperature of the region where the first sub-pixel is located.

In some embodiments, a temperature sensor (not shown) can be used to measure the temperature of a single sub-pixel or a single display unit in the MLED display panel, or to measure the temperature of a single sub-pixel or a single display unit including a plurality of sub-pixels or Temperatures of areas of multiple display units. In other embodiments, the temperature sensor can be omitted by returning the operating current of the micro LEDs in the sub-pixel to the operating temperature of the sub-pixel. In still other embodiments, under the structure of driving the micro-LEDs by means of Pulse-Width Modulation (PWM), the fader picture is returned by the operation time of the micro-LEDs in the sub-pixels. the operating temperature of the element, the temperature sensor can be omitted. In still other embodiments, the temperature sensor can be omitted by using the voltage drop across the micro-LED due to the increase in operating temperature to fade the operating temperature of the pixel back and forth. The operating temperature of the sub-pixel is obtained by the above method, and this information is fed back to the control element, which is helpful for the control element to make corresponding actions (such as changing the operating current of the micro light-emitting diode based on the operating temperature of the sub-pixel or operating time).

In some embodiments, a light sensor (not shown) can be used to measure the brightness or emission wavelength of a single sub-pixel or a single display unit in a micro-LED display panel, or to measure the brightness or emission wavelength of a single sub-pixel or a single display unit including a plurality of sub-pixels. The brightness or light-emitting wavelength of a pixel or a region of a plurality of display units is used as a basis for the control element to determine whether a corresponding action needs to be taken, or to confirm the adjustment after the control element adjusts the light-emitting state of the micro-LEDs. effectiveness. For example, the brightness or emission wavelength measured by the light sensor can be compared with the preset brightness or the preset emission wavelength, so as to determine whether the lighting state of the micro LEDs needs to be adjusted. For example, when the brightness or the light-emitting wavelength of the micro light-emitting diode varies, the information of the variation can be fed back to the control element, so that the control element can make corresponding treatment. After the control element performs the corresponding treatment, the adjusted brightness or light emission wavelength can be measured by the light sensor to determine whether the adjustment is effective or appropriate. If the adjustment is effective to bring the brightness or emission wavelength back into an acceptable range, a second degree adjustment can be avoided. If the adjustment does not bring the brightness or emission wavelength back to an acceptable range, one or more adjustments may be made until the brightness or emission wavelength is adjusted back to an acceptable range. If the brightness or light-emitting wavelength cannot be adjusted back to an acceptable range after multiple adjustments, or when the operating parameters to be adjusted exceed the operable range (for example, the operating current to be adjusted exceeds the maximum current that the micro LEDs can withstand) ), the adjustment is terminated.

In some embodiments, as shown in FIG. 1 , in addition to the first sub-pixel 112 , the micro LED display panel 100 may further include a second sub-pixel 114 and a third sub-pixel 116 . The second sub-pixel 114 has, for example, a micro-LED (eg, micro-LED 114A), and the third sub-pixel 116 has, for example, a micro-LED (eg, micro-LED 116A), but Not limited to this. The control element 120 is also electrically connected to the micro-LEDs 114A in the second sub-pixel 114 and the micro-LEDs 116A in the third sub-pixel 116 to control the micro-LEDs 114A and the micro-LEDs 114A. The light-emitting state of the pole body 116A.

In some embodiments, the first sub-pixel 112, the second sub-pixel 114 and the third sub-pixel 116 are sub-pixels of different colors. In this way, the micro light-emitting diode display panel 100 can perform full-color display. For example, the first sub-pixel 112, the second sub-pixel 114, and the third sub-pixel 116 may be a red sub-pixel, a green sub-pixel, and a blue sub-pixel, respectively. That is, the micro LEDs 112A and 112B are red micro LEDs, the micro LED 114A is a green micro LED, and the micro LED 116A is a blue micro LED Light Emitting Diodes.

Since the problem of high temperature light decay of red light is more serious than that of green light or blue light, in this embodiment, two red miniature light-emitting diodes with different impedances are arranged in the red sub-pixel, and the two red miniature light-emitting diodes are The input current of at least one is changed based on the operating temperature, so as to maintain the consistency of the light intensity of the red light under different operating temperatures, so that the MLED display panel 100 can have good display quality.

It should be understood that although the above method or structure for improving the light attenuation problem is illustrated by taking the red sub-pixel as an example, it is not limited thereto. In other embodiments, the above-mentioned method or structure for improving the light attenuation problem can also be applied to sub-pixels of other colors. In addition, the sub-pixels of one or more colors in the micro LED display panel 100 can adopt the above-mentioned method or structure for improving the light decay problem.

In addition, although FIG. 1 shows that the four display units U are electrically connected to one control element 120 , that is, the four display units U share one control element 120 , it is not limited to this. In another embodiment, one display unit U may be connected to one control element 120 .

In some embodiments, as shown in FIG. 1 , the micro-LED display panel 100 may further include a substrate 130 . The control element 120 and the miniature light emitting diodes in the display unit U can be jointly bonded on the substrate 130 . For example, the substrate 130 may be a Printed Circuit Board (PCB), a Flexible Printed Circuit Board (FPCB), a glass carrier with circuits, or a ceramic substrate with circuits, but not limited to limit.

In the above embodiment, the micro LED 112A and the micro LED 112B have different impedances, and the control element 120 individually controls the operating currents of the micro LED 112A and the micro LED 112B. The disclosure is not limited to this. In the structure of FIG. 4 , the micro LEDs 112A and 112B may have the same impedance, and the micro LEDs 112A and 112B are arranged in series. Specifically, the micro LED 112B is electrically connected between the control element 120 and the micro LED 112A, and the first sub-pixel 112 further includes a variable impedance element 112C. The variable impedance element 112C is connected in parallel with the micro LED 112A, wherein the impedance of the variable impedance element 112C increases as the operating temperature of the first sub-pixel 112 increases.

According to FIG. 4 , the current I112B flowing through the micro LED 112B is equal to the sum of the current I112A flowing through the micro LED 112A and the current I112C flowing through the variable impedance element 112C. Under constant current operation (ie, the current I112B maintains a constant value), the current I112C flowing through the variable impedance element 112C decreases as the impedance of the variable impedance element 112C increases, so that the current I112A flowing through the micro LEDs 112A increases . In other words, the current I112A flowing through the micro LEDs 112A increases as the operating temperature of the first sub-pixel 112 increases. Under the constant current operation, when the first sub-pixel 112 is at a high temperature, the brightness of the micro LEDs 112A and 112B will decrease. At this time, the impedance of the variable impedance element 112C can be increased. The current I112A flowing through the micro LEDs 112A is increased to increase the brightness of the micro LEDs 112A, thereby compensating for the problem that the brightness of the micro LEDs decreases during high temperature operation, thereby improving the micro LED display panel Consistency in brightness performance.

Although the embodiments of FIG. 2 and FIG. 4 are both illustrated with the micro LEDs 112A and the micro LEDs 112B having the same wavelength, the present disclosure is not limited thereto. Under the structure of FIGS. 2 and 4 , the micro LEDs 112A may also have a shorter wavelength than the micro LEDs 112B. As shown in FIG. 5 , the spectrum of the micro LED 112B and the spectrum of the micro LED 112A may partially overlap, and the emission wavelength W112B of the micro LED 112B is greater than the emission wavelength W112A of the micro LED 112A. In some embodiments, the difference between the emission wavelength W112A of the micro LEDs 112A and the emission wavelength W112B of the micro LEDs 112B falls within the range of 1 nm to 10 nm, and preferably falls within the range of 3 nm to 5 nm .

In the first sub-pixel 112, by changing the input current ratio of the micro-LEDs with different light-emitting wavelengths, the magnitude of the center of gravity wavelength W can be controlled, and the current density required by each micro-LED can be reduced. Since the smaller the change in current density, the smaller the shift in the center of gravity wavelength, the replacement of a single micro-LED with multiple micro-LEDs helps to reduce the color shift of each micro-LED . In this way, the consistency of the wavelength of the center of gravity and the light intensity can be maintained under different gray scales. In some embodiments, the control element 120 controls the current density of the micro LEDs 112A and the micro LEDs 112B to be less than 3 A/cm ² respectively, which can significantly improve the color shift problem.

In addition, when the micro light-emitting diode is operated at high temperature, the light-emitting wavelength is easily shifted to a long wavelength, and the greater the operating current of the micro light-emitting diode, the light-emitting wavelength is shifted to a short wavelength. Therefore, when operating at high temperature, making the micro-LEDs with short wavelengths (such as the micro-LEDs 112A) have a larger operating current (or a larger current density) to help compensate for the color shift caused by wavelength shifts Phenomenon.

Since the human eye is most sensitive to green light (appears brighter at the same brightness) among red, green, and blue light, the color shift problem (blue-shift phenomenon) of green microLEDs is more pronounced. In this embodiment, two green micro-LEDs with different light-emitting wavelengths are arranged in the green sub-pixels, and the input current of at least one of the two green micro-LEDs is changed based on the operating temperature, so as to be able to operate at different wavelengths. The consistency of the wavelength of the center of gravity of the green light and the light intensity is maintained under the operating temperature, so that the micro light emitting diode display panel can have good display quality.

It should be understood that although the above-mentioned method or structure for improving the problem of light attenuation and color shift is exemplified by the green sub-pixel, it is not limited thereto. In other embodiments, the above-mentioned methods or structures for improving light decay and color shift problems can also be applied to sub-pixels of other colors. In addition, the sub-pixels of one or more colors in the micro-LED display panel can adopt the above-mentioned method or structure for improving the problem of light decay.

As shown in FIG. 6 , in the miniature light-emitting diode display panel 200 , the above-mentioned method for improving light attenuation and/or color shift can be further applied to the second sub-pixel 114 . Specifically, in the micro-LED display panel 200 , the second sub-pixel 114 (eg, a green sub-pixel) includes a micro-LED 114A and a micro-LED 114B. The miniature LEDs 114A and 114B may have the same size to facilitate the bonding process and circuit design, but not limited thereto. The design of the micro LED 114A and the micro LED 114B can be referred to the description of FIG. 2 , FIG. 4 or FIG. 5 , and will not be repeated here.

As shown in FIG. 7 , in the miniature light-emitting diode display panel 300 , the above-mentioned method for improving light attenuation and/or color shift can be further applied to the third sub-pixel 116 . Specifically, in the micro-LED display panel 300 , the third sub-pixel 116 (eg, a blue sub-pixel) includes a micro-LED 116A and a micro-LED 116B. The miniature light-emitting diodes 116A and the microscopic light-emitting diodes 116B may have the same size to facilitate the bonding process and circuit design, but not limited thereto. The design of the micro LEDs 116A and 116B can be referred to the description of FIG. 2 , FIG. 4 or FIG. 5 , and will not be repeated here.

Referring to FIG. 8 , the micro LED display panel 400 is similar to the micro LED display panel 100 of FIG. 1 , except that the micro LED display panel 400 further includes a plurality of micro ICs 140 . A plurality of microchips 140 are bonded on the substrate 130, and each microchip 140 is located between and electrically connected with a plurality of (such as four, but not limited to) display units U, and is electrically connected to the plurality of display units U, In order to control the plurality of miniature light-emitting diodes located in the plurality of display units U. In some embodiments, the thickness ratio of the microchips 140 to the microLEDs may fall within the range of 0.8 to 1.2, but not limited thereto. In some embodiments, the thickness of the microchip 140 is 5 μm to 10 μm, and the thickness of the micro light emitting diode is 5 μm to 10 μm, but not limited thereto. The above-mentioned small size (eg thickness) design helps transfer process or display quality.

To sum up, in the embodiment of the present invention, the first sub-pixel has two micro-LEDs, and the operating current of at least one micro-LED is controlled according to the operating temperature of the first sub-pixel, In order to compensate for the problem of brightness reduction or color shift of the micro light emitting diodes during high temperature operation, the consistency of the brightness or color performance of the micro light emitting diode display panel can be improved.

Although the present invention has been disclosed above by the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, The protection scope of the present invention shall be determined by the scope of the appended patent application.

100, 200, 300, 400: Micro LED display panels 112: First sub-pixel 112A, 112B: Miniature light-emitting diodes 112C: Impedance variable element 114: Second subpixel 114A, 114B: Miniature Light Emitting Diodes 116: Third sub-pixel 116A, 116B: Miniature light-emitting diodes 120: Control elements 130: Substrate 140: Microchip 1120: epitaxial layer 1120-1: n-type semiconductor layer 1120-2: Multiple Quantum Well Layers 1120-3: p-type semiconductor layer 1121: Current Diffusion Layer 1122: Insulation layer 1123: Electrode layer A1121: Opening E1: The first electrode E2: Second electrode G: Groove I112A, 112B, 112C: Current O1, O2: Opening SW: Sidewall T1120-1, T1120-2, T1120-3, T1121, T1122, T1123: Thickness U: Display unit W: center of gravity wavelength W112A, W112B: light emission wavelength

FIG. 1 is a schematic partial top view of a miniature light emitting diode display panel according to an embodiment of the present invention. FIG. 2 is a first simple circuit diagram of the control element and the first sub-pixel in FIG. 1 . 3A and 3B are schematic cross-sectional views of the first miniature light-emitting diode and the second miniature light-emitting diode in FIG. 2 , respectively. FIG. 4 is a second simple circuit diagram of the control element and the first sub-pixel in FIG. 1 . FIG. 5 is a schematic diagram illustrating wavelengths and light intensities of the first micro-LED and the second micro-LED in the first sub-pixel of FIG. 2 . 6 to 8 are schematic partial top views of micro-LED display panels according to other embodiments of the present invention, respectively.

100: Miniature light-emitting diode display panel

112: First sub-pixel

112A, 112B: Miniature light-emitting diodes

114: Second subpixel

114A: Miniature Light Emitting Diode

116: Third sub-pixel

116A: Miniature Light Emitting Diode

120: Control elements

130: Substrate

U: Display unit

Claims (14)

A miniature light-emitting diode display panel, comprising: a plurality of display units arranged in an array and each display unit includes a first sub-pixel, the first sub-pixel includes a first miniature light-emitting diode and a second miniature light-emitting diode; and a control element for controlling the light emission of the first micro light emitting diode and the second micro light emitting diode and determining the operation of the first micro light emitting diode and the second micro light emitting diode current; Wherein, under the same display screen, the operating current of the first micro light-emitting diode increases as the operating temperature of the first sub-pixel increases. The miniature light emitting diode display panel of claim 1, wherein the impedance of the first miniature light emitting diode is smaller than the impedance of the second miniature light emitting diode. The micro-LED display panel of claim 2, wherein the operating current of the first micro-LED is controlled and input by the control element. The micro-LED display panel of claim 3, wherein the operating current of the second micro-LED decreases as the operating temperature of the first sub-pixel increases. The micro LED display panel of claim 3, wherein when the first sub-pixel operates at a high temperature, the operating current of the first micro LED is greater than that of the second micro LED the operating current of the polar body, and when the first sub-pixel operates at a low temperature, the operating current of the second micro-LED is greater than the operating current of the first micro-LED . The miniature light-emitting diode display panel according to claim 1, further comprising: A substrate, the control element, the first micro light emitting diode and the second micro light emitting diode in the display unit are bonded on the substrate. The miniature light-emitting diode display panel according to claim 6, further comprising: A plurality of microchips, the plurality of microchips are bonded on the substrate, and each microchip is located between a plurality of the display units and is electrically connected with the plurality of display units. The micro-LED display panel of claim 2, wherein the first micro-LED and the second micro-LED are different in at least one of the following: the area of the current spreading layer; the thickness of the current spreading layer; the junction area of the electrode and the epitaxial layer; and A material of at least one of the electrode and the epitaxial layer. The miniature light-emitting diode display panel of claim 1, wherein each display unit further comprises a second sub-pixel, the first sub-pixel and the second sub-pixel emit different colors, wherein the The first micro-LED of the first sub-pixel has a shorter wavelength than the second micro-LED. The miniature light-emitting diode display panel according to claim 1, wherein the first sub-pixel further comprises an impedance variable element, the impedance variable element is associated with the first miniature light-emitting diode and the first sub-pixel Two miniature LEDs are connected. The miniature light-emitting diode display panel of claim 10, wherein in the first sub-pixel, the first miniature light-emitting diode and the second miniature light-emitting diode are connected in series, and the An impedance variable element is connected in parallel with the first micro light emitting diode. The miniature light emitting diode display panel of claim 11, wherein the impedance of the variable impedance element increases as the operating temperature of the first sub-pixel increases. The micro LED display panel of claim 12, wherein the operating current of the first micro LED increases as the operating temperature of the first sub-pixel increases. The micro-LED display panel of claim 11, wherein the first micro-LED has a shorter wavelength than the second micro-LED.

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