CN113410262A - Micro light-emitting diode display panel - Google Patents
Micro light-emitting diode display panel Download PDFInfo
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- CN113410262A CN113410262A CN202110805683.8A CN202110805683A CN113410262A CN 113410262 A CN113410262 A CN 113410262A CN 202110805683 A CN202110805683 A CN 202110805683A CN 113410262 A CN113410262 A CN 113410262A
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- emitting diode
- micro light
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
- H01L27/15—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission
- H01L27/153—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission in a repetitive configuration, e.g. LED bars
- H01L27/156—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components with at least one potential-jump barrier or surface barrier specially adapted for light emission in a repetitive configuration, e.g. LED bars two-dimensional arrays
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
Abstract
The invention provides a micro light-emitting diode display panel which comprises a plurality of display units and a control element. The display units are arranged in an array and each display unit comprises a first sub-pixel. The first sub-pixel comprises a first micro light-emitting diode and a second micro 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 operation current of the first micro light-emitting diode and the second micro light-emitting diode. Under the same display image, the operating current of the first micro light-emitting diode increases along with the increase of the operating temperature of the first sub-pixel.
Description
Technical Field
The present disclosure relates to display panels, and particularly to a micro light emitting diode display panel.
Background
With the development of the photoelectric technology, solid-state light sources (such as light emitting diodes) have been widely used in various fields, such as road lighting, large outdoor billboards, traffic lights, and the like. Recently, a micro light emitting diode display panel has been developed, which uses micro light emitting diodes as sub-pixels in the display panel, so that each sub-pixel can be driven to emit light individually. The display panel which combines the light beams emitted by the micro light-emitting diodes capable of independently emitting light into an image is the micro light-emitting diode display panel.
In the conventional high-resolution or large-size micro led display panel, the current supply time of each data line is short, so the current density transmitted by each data line needs to be increased, and the panel is easily damaged by heat. In addition, as the operating temperature increases, the micro-leds are prone to have problems of reduced light emitting efficiency or wavelength shift, which results in inconsistent brightness or color performance of the micro-led display panel.
Disclosure of Invention
The invention provides a micro light-emitting diode display panel which is beneficial to solving the problem of brightness reduction or color cast 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 a control element. The display units are arranged in an array and each display unit comprises a first sub-pixel. The first sub-pixel comprises a first micro light-emitting diode and a second micro 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 operation current of the first micro light-emitting diode and the second micro light-emitting diode. Under the same display image, the operating current of the first micro light-emitting diode increases along with the increase of the operating temperature of the first sub-pixel.
In an embodiment according to the 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 according to the invention, the operating current of the first micro light emitting diode is controlled by the control element.
In an embodiment according to the present invention, the operating current of the second micro light emitting diode decreases as the operating temperature of the first sub-pixel increases.
In an embodiment according to the present invention, when the first sub-pixel operates at a high temperature, the operating current of the first micro light emitting diode is greater than the operating current of the second micro light emitting diode. When the first sub-pixel operates at low temperature, the operating current of the second micro light-emitting diode is larger than that of the first micro light-emitting diode.
In an embodiment according to the present invention, the micro light emitting diode display panel further includes a substrate. The control element is jointed with the first micro light-emitting diode and the second micro light-emitting diode in the display unit on the substrate.
In an embodiment according to the present invention, the micro light emitting diode display panel further includes a plurality of micro chips. The plurality of micro chips are bonded on the substrate, and each micro chip is positioned among the plurality of display units and is electrically connected with the plurality of display units.
In an embodiment according to the invention, the first and second micro light emitting diodes differ 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.
In an embodiment according to 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 light emitting diode of the first sub-pixel has a shorter wavelength than the second micro light emitting diode.
In an embodiment according to the invention, the first sub-pixel further comprises an impedance variable element. The impedance variable element is connected with the first micro light-emitting diode and the second micro light-emitting diode.
In an embodiment of the invention, in the first sub-pixel, the first micro light emitting diode and the second micro light emitting diode are connected in series, and the impedance variable element is connected in parallel with the first micro light emitting diode.
In an embodiment according to the present invention, the resistance of the resistance variable element increases as the operating temperature of the first subpixel increases.
In an embodiment according to the present invention, the operating current of the first micro light emitting diode increases as the operating temperature of the first sub-pixel increases.
In an embodiment according to the invention, the first micro light emitting diode has a shorter wavelength than the second micro light emitting diode.
Based on the above, in the embodiment of the invention, the first sub-pixel has two micro light emitting diodes, and the operating current of at least one micro light emitting diode is controlled according to the operating temperature of the first sub-pixel, so as to compensate the problem of brightness reduction or color shift of the micro light emitting diode during high temperature operation, thereby improving the uniformity of the brightness or color expression of the micro light emitting diode display panel.
In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and together with the description serve to explain the principles of the invention.
FIG. 1 is a schematic top view of a micro light emitting diode display panel according to an embodiment of the present invention;
FIG. 2 is a first simplified circuit diagram of the control element and the first sub-pixel of FIG. 1;
fig. 3A and 3B are schematic cross-sectional views of the first micro light-emitting diode and the second micro light-emitting diode in fig. 2, respectively;
FIG. 4 is a second simplified circuit diagram of the control element and the first sub-pixel of FIG. 1;
FIG. 5 is a schematic diagram showing the wavelength and light intensity of the first micro light-emitting diode and the second micro light-emitting diode in the first sub-pixel of FIG. 2;
fig. 6 to 8 are schematic partial top views of micro led display panels according to other embodiments of the invention.
Description of the reference numerals
100. 200, 300, 400: a micro light emitting diode display panel;
112: a first sub-pixel;
112A, 112B: a micro light emitting diode;
112C: an impedance variable element;
114: a second sub-pixel;
114A, 114B: a micro light emitting diode;
116: a third sub-pixel;
116A, 116B: a micro light emitting diode;
120: a control element;
130: a substrate;
140: a microchip;
1120: an epitaxial layer;
1120-1: an n-type semiconductor layer;
1120-2: a multiple quantum well;
1120-3: a p-type semiconductor layer;
1121: a current diffusion layer;
1122: an insulating layer;
1123: an electrode layer;
a1121: opening a hole;
e1: a first electrode;
e2: a second electrode;
g: a groove;
I112A, 112B, 112C: current flow;
o1, O2: an opening;
SW: a side wall;
t1120-1, T1120-2, T1120-3, T1121, T1122, T1123: thickness;
u: a display unit;
w: a center of gravity wavelength;
W112A, W112B: the wavelength of the emitted light.
Detailed Description
Directional phrases used herein include, for example: "upper", "lower", "front", "rear", "left", "right", etc., refer only to the orientation of the figures. Accordingly, the directional terminology is used for purposes of illustration and is in no way limiting.
In the drawings, which illustrate general features of methods, structures, and/or materials used in certain embodiments. These drawings, however, should not be construed as defining or limiting the scope or nature encompassed by these embodiments. For example, the relative sizes, thicknesses, and locations of various layers, regions, or structures may be reduced or exaggerated for clarity.
The terms "first", "second", and the like in the description or in the claims are only used for naming discrete elements or distinguishing different embodiments or ranges, and are not used for limiting the upper limit or the lower limit of the number of elements, nor for limiting the manufacturing order or the arrangement order of the elements. Further, an element/layer being disposed on (or over) another element/layer can encompass instances where the element/layer is disposed directly on (or over) the other element/layer, and the two elements/layers are in direct contact; and where the element/layer is disposed indirectly on (or over) the other element/layer, and one or more elements/layers are present between the two elements/layers.
Fig. 1 is a schematic top view of a micro led display panel according to an embodiment of the invention. Fig. 2 is a first simple circuit diagram of the control element and the first sub-pixel in fig. 1. Fig. 3A and 3B are schematic cross-sectional views of the first micro light-emitting diode and the second micro 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 of the wavelength and the light intensity of the first micro light emitting diode and the second micro light emitting diode in the first sub-pixel of fig. 2. Fig. 6 to 8 are schematic partial top views of micro led display panels according to other embodiments of the invention.
In fig. 1 to 8, the same or similar elements will be denoted by the same or similar reference numerals, and the description thereof will be omitted. Furthermore, features from different embodiments may be combined without conflict and simple equivalent changes and modifications made in the present specification or claims may still fall within the scope of the present invention.
Referring to fig. 1, the micro led display panel 100 may include a plurality of display units U, each of which is formed by a first sub-pixel 112, a second sub-pixel 114 and a third sub-pixel 116. The plurality of display units U are arranged in an array to allow the micro-led display panel 100 to display an image (fig. 1 schematically shows only four display units U). A first sub-pixel 112. The first sub-pixel 112 may include a plurality of micro light emitting diodes. Fig. 1 schematically illustrates that the first sub-pixel 112 includes a micro light emitting diode 112A (which may also be referred to as a first micro light emitting diode) and a micro light emitting diode 112B (which may also be referred to as a second micro light emitting diode). However, the number of micro leds in the first sub-pixel 112 is not limited thereto. In some embodiments, the micro light emitting diodes may have the same size to facilitate the bonding process and the circuit design, but not limited thereto.
In some embodiments, as shown in fig. 2, the micro light emitting diodes 112A and 112B may be electrically independent from each other. For example, the micro led display panel 100 may further include a control element 120. The control element 120 is used for controlling the light emission of the micro light emitting diodes 112A and 112B and determining the operating current of the micro light emitting diodes 112A and 112B. Specifically, the control element 120 may control the light emitting state (light emitting, non-light emitting or light emitting intensity) of the micro light emitting diodes, wherein the micro light emitting diodes 112A and the micro light emitting diodes 112B may be independently electrically connected to the control element 120, so that the control element 120 may individually control the current I112A input to the micro light emitting diodes 112A and the current I112B input to the micro light emitting diodes 112B. The control element 120 may be a circuit chip or a driver of a micro light emitting diode, but is not limited thereto.
In some embodiments, as shown in fig. 1, the control element 120 may be disposed at one side of the micro led display panel 100 and individually connected to each sub-pixel through a conducting wire (not shown) to individually control the current input to the micro led 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 respectively disposed in the respective sub-pixels.
In some embodiments, the micro light emitting diodes 112A and 112B may have the same or close emission wavelength. The emission wavelength refers to the wavelength corresponding to the maximum value of the light intensity in the spectrum of the micro light emitting diode. The plurality of micro light emitting diodes have close light emitting wavelengths, which means that the light emitting wavelength difference of the plurality of micro light emitting diodes does not exceed 10nm, for example, falls within a range of 1nm to 10nm, and preferably falls within a range of 3nm to 5nm, but not limited thereto.
In the first sub-pixel 112, an operating current of at least one micro light emitting diode changes as an operating temperature of the first sub-pixel 112 changes. Specifically, the operating current of at least one micro led (such as the micro led 112A or the micro led 112B) is controlled according to the operating temperature of the first sub-pixel 112, so as to compensate the problem of brightness reduction or color shift of the micro led during high temperature operation, thereby improving the uniformity of the brightness or color expression of the micro led display panel 100.
For example, under the architecture of fig. 2, the micro light emitting diodes 112A and 112B may have different impedances. The micro light emitting diode with small impedance may have a larger operation current at a high temperature operation, and the micro light emitting diode with large impedance may have a larger operation current at a low or normal temperature operation. The method for making the micro-leds 112A and 112B have different impedances may comprise making the micro-leds 112A and 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 led 112A smaller than the impedance of the micro led 112B as an example, the micro led 112A may have a smaller area of the current spreading layer, a smaller thickness of the current spreading layer, or a smaller junction area between the electrode and the epitaxial layer than the micro led 112B, or at least one of the electrode and the epitaxial layer may be made of a material such that the impedance of the micro led 112A is smaller than the impedance of the micro led 112B.
Fig. 3A and 3B schematically show that the impedance of the micro light emitting diode 112A is made smaller than that of the micro light emitting diode 112B by adjusting the area of the current diffusion layer. As shown in fig. 3A and 3B, each of the micro light emitting diodes 112A and 112B may include, for example, an epitaxial layer 1120, a current diffusion layer 1121, and an electrode layer 1123.
The epitaxial layer 1120 may include an n-type semiconductor layer (e.g., n-GaN or the like) 1120-1, a Multiple Quantum Well (MQW) layer 1120-2, and a p-type semiconductor layer (e.g., p-GaN or the like) 1120-3, wherein the Multiple Quantum Well 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 1120-2 and the current diffusion layer 1121. In some embodiments, the thickness T1120-1 of the n-type semiconductor layer 1120-1 is 3000nm, the thickness T1120-2 of the multiple quantum well 1120-2 is 300nm, the thickness T1120-3 of the p-type semiconductor layer 1120-3 is 600nm, and the thickness of the epitaxial layer 1120 (i.e., 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.
A current spreading layer 1121 is disposed on the epitaxial layer 1120. In some embodiments, the current diffusion layer 1121 is a metal oxide layer (such as an ITO layer or the like), and the thickness T1121 of the current diffusion layer 1121 is 100nm, but not limited thereto.
Since the larger the area of the current diffusion layer 1121, the smaller the current density and the larger the impedance, the smaller the area of the current diffusion layer 1121 of the micro light-emitting diode 112A is made to be than the area of the current diffusion layer 1121 of the micro light-emitting diode 112B, whereby the micro light-emitting diode 112A can be made to have a smaller impedance than the micro light-emitting diode 112B. The area of the current diffusion layer 1121 refers to an area of an orthogonal projection of the current diffusion layer 1121 on the n-type semiconductor layer 1120-1.
In some embodiments, the current spreading layer 1121 of the micro led 112B and the micro ledThe area ratio of the current diffusion layer 1121 of the light emitting diode 112A may fall within a range of 1.2 to 2. For example, the current diffusion layer 1121 of the micro light emitting diode 112A has an area of 10 μm2To 30 μm2(substantially less than 15 μm)2) And the current diffusion layer 1121 of the micro light emitting diode 112B has an area of 30 μm2To 100 μm2But not limited thereto.
The electrode layer 1123 is disposed on the current diffusion layer 1121. In some embodiments, the electrode layer 1123 is a metal layer (e.g., a copper layer or the like), and the thickness T1123 of the electrode layer 1123 is 2nm, but not limited thereto.
In some embodiments, each of the micro light emitting diodes 112A and 112B may also include an insulating layer 1122, for example. The insulating layer 1122 covers the current spreading layer 1121 and the epitaxial layer 1120 (e.g., the insulating layer 1122 covers the sidewalls 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 700nm, but is not limited thereto.
The insulating layer 1122 may have an opening O1 exposing the current diffusion layer 1121 and an opening O2 exposing the epitaxial layer 1120, the electrode layer 1123 may have a first electrode E1 contacting the epitaxial layer 1120 through the opening O2 and a second electrode E2 contacting the current diffusion layer 1121 through the opening O1, 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 the second electrode E2 and is larger than the opening O1. In the micro led 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 3B only schematically illustrate one structure of the micro light emitting diode, however, the structure, the number of layers and/or the shape or size of each layer, each opening or each opening of the micro light emitting diode 112A and the micro light emitting diode 112B may be changed according to the requirement. The micro leds 112A and 112B are intended to be generalized herein to any type of micro leds known.
Referring to fig. 2, in the first sub-pixel 112, the operating current of the micro light emitting diode 112A (micro light emitting diode with small impedance) may increase as the operating temperature of the first sub-pixel 112 increases, and the operating current of the micro light emitting diode 112B (micro light emitting diode with large impedance) may decrease as the operating temperature of the first sub-pixel 112 increases. In other words, the operation current of the micro light emitting diode 112A at the high temperature operation is greater than the operation current of the micro light emitting diode 112A at the normal temperature operation, and the operation current of the micro light emitting diode 112B at the normal temperature operation is greater than the operation current of the micro light emitting diode 112B at the high temperature operation.
In some embodiments, when the first sub-pixel 112 operates at a high temperature, the operating current of the micro light emitting diode 112A (micro light emitting diode with small impedance) may be larger than the operating current of the micro light emitting diode 112B (micro light emitting diode with large impedance). On the other hand, when the first sub-pixel 112 operates at a low temperature, the operating current of the micro light emitting diode 112B may be greater than that of the micro light emitting diode 112A. Specifically, at low or normal temperature operation, the micro light emitting diode (such as the micro light emitting diode 112B) with large impedance can have a larger operation current to maintain the required brightness; in high temperature operation, since the micro leds 112A and 112B have high temperature light decay (i.e. the brightness of the micro leds 112A and 112B is decreased), the micro leds with small impedance (e.g. the micro leds 112A) can have larger operation current (e.g. the operation current of the micro leds with small impedance) to increase the brightness through high current density, thereby maintaining uniform brightness at different operation temperatures. It should be understood that at any operating temperature, micro-leds 112A and micro-leds 112B may be on or off or both. 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 safety or life-span considerations.
Herein, the high temperature in the high temperature operation refers to a temperature at which the micro light emitting diode generates a significant brightness or lifetime degradation, and is generally 60 degrees celsius or more, but not limited thereto. The normal temperature in the normal temperature operation refers to a typical operating temperature of the micro light emitting diode, and is usually 25 degrees celsius, but not limited thereto. The operating current of the micro light emitting diode refers to a current flowing through the micro light emitting diode. The operating temperature of the first subpixel refers to a temperature of an area where the first subpixel is located.
In some embodiments, a temperature sensor (not shown) may be used to measure the temperature of a single sub-pixel or a single display unit in the micro led display panel, or to measure the temperature of an area containing multiple sub-pixels or multiple display units. In other embodiments, the temperature sensor may be omitted by pushing back the operating temperature of the sub-pixel by the operating current of the micro light emitting diode in the sub-pixel. In still other embodiments, in a configuration in which the micro-leds are driven by Pulse-Width Modulation (PWM), the temperature sensor can be omitted by pushing back the operating temperature of the sub-pixels according to the operating time of the micro-leds in the sub-pixels. In still other embodiments, the temperature sensor may be omitted by pushing back and forth the operating temperature of the sub-pixel by the voltage drop (voltage drop) across the micro-led caused by the increase in operating temperature. Obtaining the operating temperature of the sub-pixel in the above manner and feeding this information back to the control element helps the control element to make a corresponding treatment (e.g. changing the operating current or operating time of the micro-leds based on the operating temperature of the sub-pixel).
In some embodiments, an optical sensor (not shown) may be utilized to measure the brightness or the light-emitting wavelength of a single sub-pixel or a single display unit in the micro led display panel, or measure the brightness or the light-emitting wavelength of a region including a plurality of sub-pixels or a plurality of display units, so as to be used as a basis for the control element to determine whether a corresponding treatment needs to be performed, or to confirm the validity of the adjustment after the control element adjusts the light-emitting state of the micro led. For example, the brightness or the light emitting wavelength measured by the light sensor may be compared with a preset brightness or a preset light emitting wavelength to determine whether the light emitting state of the micro light emitting diode 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 perform corresponding treatment. After the control element has made the corresponding treatment, the adjusted brightness or emission wavelength may be measured with a light sensor to determine if the adjustment is valid or appropriate. If the adjustment is effective to adjust the brightness or emission wavelength back to an acceptable range, a two-degree adjustment may be avoided. If the adjustment does not adjust the brightness or the emission wavelength back to the acceptable range, the adjustment may be performed one or more times again until the brightness or the emission wavelength is adjusted back to the acceptable range. If the brightness or the light emitting wavelength cannot be adjusted back to the acceptable range after multiple adjustments or when the operation parameter to be adjusted exceeds the operable range (for example, the operation current to be adjusted exceeds the maximum current that the micro light emitting diode can bear), the adjustment is terminated.
In some embodiments, as shown in fig. 1, the micro led display panel 100 may further include a second sub-pixel 114 and a third sub-pixel 116 in addition to the first sub-pixel 112. The second sub-pixel 114 has, for example, a micro light emitting diode (e.g., micro light emitting diode 114A), and the third sub-pixel 116 has, for example, a micro light emitting diode (e.g., micro light emitting diode 116A), but not limited thereto. The control element 120 is further electrically connected to the micro light emitting diode 114A in the second sub-pixel 114 and the micro light emitting diode 116A in the third sub-pixel 116 to control the light emitting states of the micro light emitting diode 114A and the micro light emitting diode 116A.
In some embodiments, the first sub-pixel 112, the second sub-pixel 114, and the third sub-pixel 116 are different color sub-pixels. Thus, the micro led 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, micro leds 112A and 112B are red micro leds, micro leds 114A are green micro leds, and micro leds 116A are blue micro leds.
Since the red light has a significant high-temperature light decay problem compared with the green light or the blue light, the present embodiment maintains the uniformity of the light intensity of the red light at different operating temperatures by arranging two red micro light emitting diodes with different impedances in the red sub-pixel and changing the input current of at least one of the two red micro light emitting diodes based on the operating temperature, so that the micro light emitting diode 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 the red sub-pixel, it is not limited thereto. In other embodiments, the above method or structure for improving light attenuation can 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 method or structure for improving the light attenuation problem.
In addition, although fig. 1 shows that four display units U are electrically connected to one control element 120, that is, the four display units U share one control element 120, but not limited thereto. 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 micro-leds in the display unit U may be commonly 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 a Circuit, or a ceramic substrate with a Circuit, but not limited thereto.
The above embodiment is described in which the micro leds 112A and the micro leds 112B have different impedances, and the control element 120 individually controls the operating currents of the micro leds 112A and the micro leds 112B, but the disclosure is not limited thereto. Under the architecture 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 light emitting diode 112B is electrically connected between the control element 120 and the micro light emitting diode 112A, and the first sub-pixel 112 further includes an impedance variable element 112C. The resistance variable element 112C is connected in parallel with the micro light emitting diode 112A, wherein the resistance of the resistance variable 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 impedance varying element 112C. Under the constant current operation (i.e., the current I112B is maintained at a constant value), the current I112C flowing through the impedance variable device 112C decreases as the impedance of the impedance variable device 112C increases, so that the current I112A flowing through the micro light emitting diode 112A increases. In other words, the current I112A flowing through the micro light emitting diode 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 led 112A and the brightness of the micro led 112B are both decreased, and at this time, the resistance of the resistance variable device 112C is increased to increase the current I112A flowing through the micro led 112A, so as to increase the brightness of the micro led 112A, thereby compensating the problem of the brightness decrease of the micro led during the high temperature operation, and further improving the uniformity of the brightness performance of the micro led display panel.
Although the embodiments of fig. 2 and 4 are illustrated in which the micro light emitting diodes 112A and 112B have the same wavelength, the disclosure is not limited thereto. Under the architectures of fig. 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 light emitting diode 112B and the spectrum of the micro light emitting diode 112A may partially overlap, and the light emitting wavelength W112B of the micro light emitting diode 112B is greater than the light emitting wavelength W112A of the micro light emitting diode 112A. In some embodiments, the difference between the light emitting wavelength W112A of the micro light emitting diode 112A and the light emitting wavelength W112B of the micro light emitting diode 112B falls within a range of 1nm to 10nm, and preferably falls within a range of 3nm to 5 nm.
In the first sub-pixel 112, the first sub-pixel,the size of the gravity center wavelength W can be controlled by changing the input current ratio of the micro light-emitting diodes with different light-emitting wavelengths, and the current density required by each micro light-emitting diode can be reduced. Since the smaller the change amount of the current density, the smaller the shift amount of the center of gravity wavelength, replacing a single micro light emitting diode with a plurality of micro light emitting diodes helps to reduce the color shift amount of each micro light emitting diode. Therefore, the consistency of the center of gravity wavelength and the light intensity can be maintained under different gray scales. In some embodiments, the control component 120 controls the current density passing through the micro light emitting diode 112A and the micro light emitting diode 112B to be less than 3A/cm respectively2The problem of color cast can be obviously improved.
In addition, the micro light emitting diode is likely to shift the light emitting wavelength to a long wavelength when operating at a high temperature, and the light emitting wavelength is shifted to a short wavelength as the operating current of the micro light emitting diode is larger. Therefore, in high temperature operation, the larger operating current (or larger current density) of the short-wavelength micro led (e.g., the micro led 112A) helps compensate the color shift caused by the wavelength shift.
Since the human eye is most sensitive to green light (appears brighter at the same brightness) among red light, green light, and blue light, the color shift problem (blue shift phenomenon) of the green micro-led is more significant. The embodiment can maintain the consistency of the gravity center wavelength and the light intensity of the green light at different operating temperatures by arranging the two green micro light-emitting diodes with different light-emitting wavelengths in the green sub-pixel and changing the input current of at least one of the two green micro light-emitting diodes based on 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 method or structure for improving the light attenuation and color shift problem is illustrated by the green sub-pixel, it is not limited thereto. In other embodiments, the above method or structure for improving the light attenuation and color shift problem can be applied to other sub-pixels. In addition, the sub-pixels of one or more colors in the micro light emitting diode display panel can adopt the method or the structure for improving the light attenuation problem.
As shown in fig. 6, the method for improving light attenuation and/or color shift can be further applied to the second sub-pixel 114 in the micro led display panel 200. Specifically, in the micro led display panel 200, the second sub-pixel 114 (e.g., the green sub-pixel) includes a micro led 114A and a micro led 114B. The micro leds 114A and the micro leds 114B may have the same size to facilitate the bonding process and the circuit design, but not limited thereto. The design of the micro leds 114A and 114B can be described with reference to fig. 2, 4 or 5, and will not be repeated here.
As shown in fig. 7, the method for improving light attenuation and/or color shift can be further applied to the third sub-pixel 116 in the micro led display panel 300. Specifically, in the micro led display panel 300, the third sub-pixel 116 (e.g., blue sub-pixel) includes a micro led 116A and a micro led 116B. The micro light emitting diodes 116A and 116B may have the same size to facilitate the bonding process and the circuit design, but not limited thereto. The design of micro leds 116A and 116B can be described with reference to fig. 2, 4 or 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 chips (micro ICs) 140. The plurality of micro chips 140 are bonded on the substrate 130, and each micro chip 140 is located between and electrically connected to a plurality of (for example, four, but not limited to) display units U to control the plurality of micro light emitting diodes located in the plurality of display units U. In some embodiments, the thickness ratio of the microchip 140 to the micro light emitting diode may fall within a 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 small dimension (e.g., thickness) design described above facilitates the transfer process or display quality.
In summary, in the embodiments of the invention, the first sub-pixel has two micro light emitting diodes, and the operating current of at least one micro light emitting diode 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 diode during high temperature operation, so as to improve the uniformity of the brightness or color performance of the micro light emitting diode display panel.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (14)
1. A micro light emitting diode display panel, comprising:
the display device comprises a plurality of display units, a plurality of display units and a plurality of display units, wherein each display unit comprises a first sub-pixel, and each first sub-pixel comprises a first micro light-emitting diode and a second micro light-emitting diode; and
a control element for controlling the light emission of the first and second micro light emitting diodes and determining the operation current of the first and second micro light emitting diodes;
wherein the operating current of the first micro light emitting diode increases as the operating temperature of the first sub-pixel increases under the same display image.
2. The micro light-emitting diode display panel of claim 1, wherein the impedance of the first micro light-emitting diode is less than the impedance of the second micro light-emitting diode.
3. The micro light-emitting diode display panel of claim 2, wherein the operating current of the first micro light-emitting diode is controlled by the control element.
4. The micro light-emitting diode display panel of claim 3, wherein the operating current of the second micro light-emitting diode decreases as the operating temperature of the first sub-pixel increases.
5. The micro light-emitting diode display panel of claim 3, wherein the operating current of the first micro light-emitting diode is greater than the operating current of the second micro light-emitting diode when the first sub-pixel operates at a high temperature, and the operating current of the second micro light-emitting diode is greater than the operating current of the first micro light-emitting diode when the first sub-pixel operates at a low temperature.
6. The micro light-emitting diode display panel of claim 1, further comprising:
a substrate on which the control element is bonded with the first and second micro light emitting diodes in the display unit.
7. The micro light-emitting diode display panel of claim 6, further comprising:
the display device comprises a substrate, a plurality of display units and a plurality of micro chips, wherein the plurality of micro chips are jointed on the substrate, and each micro chip is positioned among the plurality of display units and is electrically connected with the plurality of display units.
8. The micro light-emitting diode display panel of claim 2, wherein the first micro light-emitting diode and the second micro light-emitting diode are different in at least one of:
area of the current spreading layer;
a 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.
9. The micro light-emitting diode display panel of claim 1, wherein each display unit further comprises a second sub-pixel, the first sub-pixel emitting a different color than the second sub-pixel, wherein the first micro light-emitting diode of the first sub-pixel has a shorter wavelength than the second micro light-emitting diode.
10. The micro light-emitting diode display panel of claim 1, wherein the first sub-pixel further comprises an impedance variable element connected to the first micro light-emitting diode and the second micro light-emitting diode.
11. The micro led display panel of claim 10, wherein in the first sub-pixel, the first micro led and the second micro led are connected in series, and the impedance-variable device is connected in parallel with the first micro led.
12. The micro light-emitting diode display panel of claim 11, wherein the impedance of the impedance-variable element increases as the operating temperature of the first sub-pixel increases.
13. The micro light-emitting diode display panel of claim 12, wherein the operating current of the first micro light-emitting diode increases as the operating temperature of the first sub-pixel increases.
14. The micro light-emitting diode display panel of claim 11, wherein the first micro light-emitting diode has a shorter wavelength than the second micro light-emitting diode.
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| US16/988,717 | 2020-08-10 | ||
| US16/988,717 US11289012B2 (en) | 2017-09-07 | 2020-08-10 | Micro light emitting diode display panel and driving method thereof |
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| CN113410262B (en) | 2023-07-04 |
| TW202207197A (en) | 2022-02-16 |
| TWI781689B (en) | 2022-10-21 |
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