TWI711199B - Microled display panel - Google Patents

Abstract

A micro light-emitting diode (microLED) display panel includes microLEDs; a substrate for supporting the microLEDs, the substrate being divided into a plurality of sub-regions; and a plurality of chip-on-film (COF) packages mounted on surfaces of the sub-regions respectively, a plurality of drivers being disposed on the COF packages respectively.

Description

Micro-luminescence diode display panel

The present invention relates to a display panel, in particular to a microLED display panel.

The micro LED (microLED, mLED or μLED) display panel is a type of flat panel display, which is composed of individual microscopic LEDs with a size level of 1-10 microns. Compared with the traditional liquid crystal display panel, the micro light emitting diode display panel has a larger contrast ratio and a faster response time, and consumes less power. Although micro-light-emitting diodes and organic light-emitting diodes (OLED) have the same low power consumption characteristics, micro-light-emitting diodes use three-to-five group diode technology (such as gallium nitride), so they are more Organic light-emitting diodes have higher brightness, higher luminous efficacy and longer life.

The active driving method using thin film transistors (TFT) is a commonly used driving mechanism, which can be combined with micro light emitting diodes to manufacture display panels. However, thin-film transistors use a complementary metal oxide semiconductor (CMOS) process, while micro-light-emitting diodes use flip chip technology. The two will cause thermal mismatch problems, and the thin film The manufacturing process of the transistor is more complicated. In the low-gray-scale display, since the driving current is very small, the leakage current of the micro light emitting diode will affect the gray-scale display.

Passive driving is another driving mechanism. In the traditional passive driving display panel, the column driving circuit and the row driving circuit are arranged on the edge of the display panel. However, when the size of the display panel becomes larger or the resolution becomes higher, the output load of the driver is too large, and the too long delay time makes the display panel unable to drive normally. Therefore, the passive driving mechanism cannot be applied to large-size micro-light-emitting diode display panels.

Therefore, there is an urgent need to provide a novel micro-light-emitting diode display panel, especially a large-size or high-resolution display panel, so that it retains the advantages of micro-light-emitting diodes and can improve the shortcomings of traditional driving mechanisms.

In view of the foregoing, one of the objectives of the embodiments of the present invention is to provide a micro-light-emitting diode display panel, which can effectively reduce the load of the driver, so as to realize a single large-size high-resolution micro-light-emitting diode display panel.

According to an embodiment of the present invention, the micro light emitting diode display panel includes a plurality of micro light emitting diodes, a substrate, and a plurality of thin film flip chip packages. The substrate is used for supporting the micro light emitting diode, and the surface of the substrate is divided into multiple sub-regions. The chip on film package is respectively arranged on the surface of the sub-area, and the plurality of drivers are arranged on the chip on film package respectively.

FIG. 1A shows a top view of a microLED display panel 100 according to an embodiment of the present invention, and FIG. 1B shows a side view of the microLED display panel 100 in FIG. 1A. The structure of the micro light emitting diode display panel 100 of this embodiment is preferably suitable for a large-size high-resolution display panel, such as a display panel with a resolution of 3840RGB×2160. In this specification, the size grade of the micro light emitting diode is 1-10 microns. However, it will be smaller due to the application field of the product or the development of future technology. In this manual, a "large size" display panel is defined as a display panel larger than 10 inches in accordance with current industry practices. However, the definition of "large-size" display panels may change due to product application fields or future technological developments. In this manual, a "high-resolution" display panel is defined as a display panel with more than 1080 scan lines in accordance with current industry practices. However, the definition of "high-resolution" display panels will also change due to product application fields or future technological developments.

In this embodiment, the micro-light-emitting diode display panel 100 includes a substrate 11 for carrying a plurality of micro-light-emitting diodes (not shown in the drawings). The material of the substrate 11 is preferably an insulator (for example, glass, acrylic), and may also be other materials suitable for carrying micro light-emitting diodes.

According to one of the features of the present embodiment, the surface of the substrate 11 is divided into multiple sub-regions (sub-regions) 101. The divided sub-regions 101 are not physically cut, and the substrate 11 is not formed by integrating a plurality of small blocks, so the substrate 11 is a complete uncut entity. In other words, the micro light emitting diode display panel 100 of this embodiment is a single (single or whole) or uncut (uncut) display panel. The first figure A only shows a simplified example of the division of the sub-region 101. Taking the micro light emitting diode display panel 100 with a resolution of 3840RGBx2160 as an example, the substrate 11 can be divided into 80x54 sub-regions 101, and the resolution of each primary region 101 is 48RGBx40, but it can also be divided into more or less sub-regions. 101.

According to another feature of this embodiment, the micro light emitting diode display panel 100 includes a plurality of drivers 12, which are respectively provided on the surface (for example, the top surface) of the sub-regions 101. The driver 12 shown in FIG. 1A is located at the center of the surface of the corresponding sub-region 101, but it is not limited to this. The first diagram A illustrates that each sub-area 101 is provided with a driver 12, but in other embodiments, each sub-area 101 may also be provided with a plurality of drivers 12. The driver 12 of this embodiment can be fabricated as an integrated circuit in the form of a chip, and the driver 12 is bonded by surface mount technology (SMT), such as chip-on-glass (COG) or flip chip technology. (Bond) on the surface of sub-region 101. In one example, the driver 12 and the micro light emitting diode system are provided on the same surface of the sub-region 101 of the substrate 11.

The micro light emitting diode display panel 100 of this embodiment further includes a plurality of timing controllers (TCON) 13, which can be electrically connected to the substrate 11 by wires (such as a flexible circuit board, not shown in the figure), and then through the device The traces (not shown in the drawings) on the surface of the substrate 11 are electrically connected to the corresponding driver 12. In this embodiment, a timing controller 13 can be electrically connected to at least two drivers 12. In other words, the number of timing controllers 13 is less than the number of drivers 12. The timing controller 13 can be directly connected to the corresponding driver 12 through wiring, or connected to a driver 12 through wiring, and after signal buffering, it is connected to another driver 12 through wiring.

According to another feature of this embodiment, the micro light emitting diode display panel 100 adopts a passive driving method to drive the micro light emitting diode. The second figure shows a schematic diagram of a micro light emitting diode display panel 100 in a passive driving mode. The timing controller 13 transmits timing control signals and display data signals to the driver 12. The driver 12 includes a column drive circuit 121 and a column (row or scan) drive circuit 122. The row drive circuit 121 is connected by a row wire 1211 and transmits a row drive signal to the first electrode of the micro light emitting diode 14 in the same row. (For example, anode), the column driving circuit 122 is connected by column wires 1221 and transmits the column driving signal to the second electrode (for example, cathode) of the same column of micro light emitting diode 14. In this embodiment, the row driving circuit 121 and the column driving circuit 122 are made as a single integrated circuit.

According to the above embodiment, since the substrate 11 of the micro light emitting diode display panel 100 is divided into a plurality of sub-regions 101, and each sub-region 101 is provided with a corresponding driver 12, the load of the row driving circuit 121 and the column driving circuit 122 can be effectively reduced. , In order to realize a single large-size high-resolution micro-light-emitting diode display panel. In addition, compared to the active driving method using thin film transistors (TFT), the micro light emitting diode display panel 100 of this embodiment adopts a passive driving method to drive the micro light emitting diode 14, so the manufacturing process of the display panel can be simplified. The turn on time of the micro light emitting diode 14 is shortened, the driving current is increased, and the influence of the leakage current of the micro light emitting diode 14 on the grayscale display caused by the leakage current is effectively reduced.

The third figure shows a cross-sectional view of the frontside illuminating micro-light emitting diode display panel 300 according to the first specific embodiment of the present invention. In this embodiment, the micro light emitting diode 14 and the driver 12 are provided on the top surface of the substrate 11. The light generated by the micro light emitting diode 14 mainly emits light from the top surface of the substrate 11 (that is, the front light), as indicated by the arrow.

As illustrated in the third figure, each pixel includes a red micro light emitting diode 14R, a green micro light emitting diode 14G, and a blue micro light emitting diode 14B. A wiring layer 15 is provided between the surface (for example, the top surface) of the substrate 11, the micro light emitting diode 14 and the driver 12 to electrically connect the driver 12, the micro light emitting diode 14 and the timing controller 13. Between the micro light-emitting diodes 14 of adjacent pixels, a light blocking layer 16 is formed above the wiring layer 15. The material of the light blocking layer 16 in this embodiment may be a black matrix (BM) or other suitable materials that can shield light. In an embodiment, the light blocking layer 16 may also be formed between the red micro light emitting diode 14R, the green micro light emitting diode 14G, and the blue micro light emitting diode 14B of the same pixel, but it does not have to be formed.

The red micro light emitting diode 14R, the green micro light emitting diode 14G, and the blue micro light emitting diode 14B may also be provided with a light guide layer 17 above. The micro-light-emitting diode display panel 300 with front light emitting in this embodiment further includes a cover plate 18 disposed on the bottom surface of the substrate 11. The material of the cover plate 18 of this embodiment may be an opaque material.

The fourth figure shows a cross-sectional view of a backside illuminating micro light emitting diode display panel 400 according to the second specific embodiment of the present invention. In this embodiment, the micro light emitting diode 14 and the driver 12 are provided on the top surface of the substrate 11. The light generated by the micro light emitting diode 14 mainly emits light downward from the back surface of the substrate 11 (that is, the back surface emits light), as shown by the arrow.

As illustrated in the fourth figure, each pixel includes a red micro light emitting diode 14R, a green micro light emitting diode 14G, and a blue micro light emitting diode 14B. Between the micro light emitting diodes 14 of adjacent pixels, a light blocking layer 16 is formed on the surface (for example, the top surface) of the substrate 11. The material of the light blocking layer 16 in this embodiment may be black matrix (BM) or other suitable materials that can shield light. A wiring layer 15 is provided above the light blocking layer 16 for electrically connecting the driver 12, the micro light emitting diode 14 and the timing controller 13. In an embodiment, the light blocking layer 16 may also be formed between the red micro light emitting diode 14R, the green micro light emitting diode 14G, and the blue micro light emitting diode 14B of the same pixel, but it does not have to be formed.

The red micro light emitting diode 14R, the green micro light emitting diode 14G, and the blue micro light emitting diode 14B may also be provided with a light guide layer 17 above. The back-emitting micro-light-emitting diode display panel 400 of this embodiment further includes a cover plate 18 disposed above the driver 12, the wiring layer 15, the light blocking layer 16, and the light guide layer 17. The material of the cover plate 18 of this embodiment may be an opaque material.

The fifth figure illustrates the current-voltage curve of the micro light emitting diode 14. When the operating voltage is greater than the turn-on voltage Vf (for example, 3 volts), the current can be greater than the preset current value, so the micro light emitting diode 14 can be normally operated to light up. In the micro light emitting diode display panel 100 shown in FIG. 1A, the rated system power supply of the driver 12 is VDDA. However, due to the impedance inside the metal wire that transmits the power, a voltage drop ΔV is generated at the center of the micro light emitting diode display panel 100. Therefore, at the center of the micro light emitting diode display panel 100, the power supply value obtained by the driver 12 actually is VDDA-ΔV. As for the edge of the micro light emitting diode display panel 100, the power supply value obtained by the driver 12 is VDDA. For example, assuming that the voltage drop ΔV is 1 volt and the turn-on voltage Vf is 3 volts, for the driver 12 to operate normally, the condition VDDA-1>3 must be met, so VDDA must be greater than 4 volts (for example, 5 volts are used). In this case, the driver 12 can be manufactured using a low-voltage metal oxide semiconductor (MOS) process.

However, when the number of micro light-emitting diodes 14 increases so that the required current becomes larger, the voltage drop ΔV will increase significantly, for example, to 4 volts. In order for the driver 12 to operate normally, the condition VDDA-4>3 must be met, so VDDA must be greater than 7 volts (for example, 8 volts are used). In this case, the driver 12 needs to be manufactured using a high-voltage metal oxide semiconductor (MOS) process, which significantly increases the area of the circuit chip, which is not conducive to the manufacture of large-size or high-resolution (for example, 3840RGBx2160) display panels . In order to solve the above problems, a novel driver 12 architecture is proposed below.

The sixth figure shows a system block diagram of the driver 12 according to an embodiment of the present invention. In this embodiment, the driver 12 includes a low-dropout (low-dropout or LDO) regulator 123, which receives the system power VDDA, generates a regulated power supply VR (for example, 5 volts), and supplies it to the driving circuit 120 as a power supply. The low-dropout (LDO) regulator 123 of this embodiment can be implemented using the circuit design of a traditional low-dropout (LDO) regulator, and its details are therefore omitted. The driving circuit 120 of this embodiment may include a row driving circuit 121 and a column driving circuit 122. The low dropout (LDO) regulator 123 is a type of DC linear regulator, which allows the regulated power supply VR to be very close to the system power supply VDDA. Compared with a switching regulator, the low-dropout regulator 123 has the advantages of small area, simple design, etc., and does not generate switching noise. In this embodiment, a smoothing capacitor C can be connected between the regulated power supply VR and the ground to filter out high-frequency noise. The voltage stabilizing capacitor C can be formed using the process technology of the metal layer in the display panel process, and no additional process technology is required.

According to the driver 12 of this embodiment described above, only the low-dropout (LDO) regulator 123 needs to be manufactured using a high-voltage (for example, greater than 8 volts) metal oxide semiconductor (MOS) process, and the remaining driving circuits 120 can be manufactured using low-voltage (for example, Below 8 volts) metal oxide semiconductor (MOS) process. In contrast to the aforementioned architecture that does not use the low-dropout (LDO) regulator 123, the entire driver 12 needs to be manufactured using a high-voltage metal oxide semiconductor (MOS) process. Therefore, the driver 12 of this embodiment can greatly reduce the circuit area, which is beneficial to the manufacture of large-size or high-resolution display panels.

FIG. 7A shows a schematic diagram of a chip-on-film or chip-on-flex (COF) package 700 of a driver 12 (such as a display driver integrated circuit (DDIC)) according to an embodiment of the present invention. The chip-on-film package 700 may include a flexible printed circuit board (FPCB) 71 which may include at least one main area 711 and a bonding area 712. The size of the bonding area 712 is smaller than the main area 711, and the bonding area 712 is adjacent to one side of the main area 711.

The chip-on-film package 700 of this embodiment may include the driver 12, which is disposed in the main area 711. Among them, the chip (for example, the driver 12) has pins 713, which are arranged on four sides of the chip. The pins 713 of the chip are electrically connected to the finger connectors 714 of the bonding area 712 through traces of the main area 711. In this way, the pins 713 on the four sides of the chip are thus converted into the finger connectors 714 on one side of the flexible printed circuit board 71 (that is, the bonding area 712).

FIG. 7B shows a side view of the chip-on-film package 700 of FIG. 7A, which is disposed on the substrate 11 of the micro light emitting diode display panel according to the embodiment of the present invention. In this embodiment, the bonding area 712 is bent along the boundary between the bonding area 712 and the main area 711 and then bonded to the substrate 11. Thereby, the driver 12 is suspended above the substrate 11. Although the main area 711 of the flexible printed circuit board 71 illustrated in FIG. 7B stands at a right angle on the substrate 11, in general, the angle between the flexible printed circuit board 71 and the substrate 11 can be between 0 and 180 degrees.

Figures 8A to 8C respectively show a top view, a front view, and a right side view of the thin-film-on-chip package 700 of the micro light emitting diode display panel 800. In this embodiment, the micro-light-emitting diode display panel 800 is preferably a back-emitting micro-light-emitting diode display panel (as illustrated in the fourth figure), and the generated light is emitted downward from the back surface of the substrate 11.

In this embodiment, the micro-light-emitting diode display panel 800 may include a substrate 11 for carrying a plurality of micro-light-emitting diodes (not shown in the drawings). The material of the substrate 11 is preferably an insulator (for example, glass or Acrylic), and may also be other materials suitable for carrying micro light-emitting diodes. The surface of the substrate 11 is divided into multiple sub-regions 101. According to one of the features of this embodiment, the micro-light-emitting diode display panel 800 may include a plurality of thin-film-on-chip packages 700, which are respectively provided on the upper surface of the sub-region 101 of the substrate 11. The micro-light-emitting diode display panel 800 of this embodiment may include a plurality of drivers 12, which are respectively disposed in the main area 711 of the film-on-chip package 700. As described in FIG. 7B, the film-on-chip package 700 is disposed (or bonded) to the substrate 11 through the bonding area 712, so that the driver 12 is suspended on the substrate 11. Since the area required for the bonding area 712 is smaller than that of the main area 711 or the driver 12, the thin-film-on-chip package 700 only occupies a very small area of the substrate 11, so that the precious area of the substrate 11 can be provided for more micro light emitting diodes.

Compared with other embodiments using chip-on-glass (COG) technology to directly provide the pins of the chip (such as the driver 12) on the substrate 11, the thin film flip chip package 700 of this embodiment occupies a much larger area than the chip The glass (COG) examples come less. Figures ninth A to ninth C respectively show a top view, a front view and a right side view of the micro light emitting diode display panel 900 using the glass on chip (COG) technology to install the driver 12. Since the driver 12 is directly arranged on the substrate 11, the driver 12 therefore occupies a considerable amount of precious area of the substrate 11, so there is no extra area left to install more micro-light emitting diodes. In view of this, the drive 12 needs to be made smaller, but it will increase the technical difficulty and cost. In addition, the film-on-chip package 700 can overcome the voltage drop effect caused by the long traces of the large-size micro-light-emitting diode display panel. Furthermore, the trace width can be reduced, thereby effectively improving the resolution of the micro light emitting diode display panel.

FIG. 10A shows a schematic diagram of a chip on film package 700B of the driver 12 according to another embodiment of the present invention. The chip-on-film package 700B is similar to the chip-on-film package 700 in Figure 7A. The difference is that the flexible printed circuit board 71 of the chip-on-film package 700B can include a main area 711, a first bonding area 712A, and a second bonding area 712B. The first joining area 712A and the second joining area 712B are respectively adjacent to two opposite sides of the main area 712. In this embodiment, the first bonding area 712A uses outer lead bonding (OLB) technology to bond to glass, and the second bonding area 712B uses inner lead bonding (ILB) technology to bond To the printed circuit board.

Figure 10B shows a side view of the thin film chip-on-chip package 700B of Figure 10A, which is provided on the substrate 11 (such as glass) of the micro light emitting diode display panel of the embodiment of the present invention by the first bonding region 712A. The second bonding area 712B is provided on the printed circuit board 11B (for example, a flexible printed circuit board). In one example, the printed circuit board 11B is electrically connected to a control system, such as a timing controller (TCON).

FIG. 11 shows a top view of the micro light emitting diode display panel 1100. In this embodiment, the driver (not shown in the figure) can be installed on the edge sub-region 101 (non-slashed) using glass on chip (COG) or chip on film (COF) technology, while other drivers can use chip on film (COF) COF) technology is located in the central sub-region 101 (slashed). In this way, the drivers of the central sub-region 101 can be connected to the timing controller.

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

100: Micro LED display panel 101: Sub-region 300: Micro LED display panel with front light emitting 400: Micro light emitting diode display panel with back light 11: substrate 11B: Printed circuit board 12: Drive 120: drive circuit 121: Row drive circuit 1211: Line wire 122: column drive circuit 1221: column wire 123: low dropout regulator 13: timing controller 14: Micro-luminescent diode 14R: red light emitting diode 14G: Green light emitting diode 14B: blue light emitting diode 15: Wiring layer 16: light blocking layer 17: Light guide layer 18: cover 700: Thin film flip chip package 700B: Thin film flip chip package 711: main area 712: Joint Zone 712A: first junction area 712B: second junction area 713: Pin 714: Finger Connector 800: Micro LED display panel 900: Micro LED display panel 1100: Micro LED display panel VDDA: system power supply VR: Regulated power supply C: voltage regulator capacitor TCON: Timing Controller LDO: low dropout regulator OLB: Outer pin bonding ILB: inner pin bonding COG: Wafer glass COF: Chip on Film

FIG. 1A shows a top view of a micro light emitting diode display panel according to an embodiment of the invention. The first figure B shows a side view of the micro light emitting diode display panel of the first figure A. The second figure shows a schematic diagram of a micro light emitting diode display panel in a passive driving mode. The third figure shows a cross-sectional view of the micro light emitting diode display panel with front light emitting according to the first specific embodiment of the present invention. The fourth figure shows a cross-sectional view of the back-illuminated micro light emitting diode display panel of the second specific embodiment of the present invention. The fifth figure illustrates the current-voltage curve of the micro light emitting diode. The sixth figure shows a system block diagram of the driver of the embodiment of the present invention. FIG. 7A shows a schematic diagram of a thin film on chip package of a driver according to an embodiment of the present invention. FIG. 7B shows a side view of the chip on film package of FIG. 7A, which is disposed on the substrate of the micro light emitting diode display panel of the embodiment of the present invention. Figures 8A to 8C respectively show a top view, a front view and a right side view of the chip on film of the micro light emitting diode display panel. Figures ninth A to ninth C respectively show a top view, a front view, and a right side view of the micro light emitting diode display panel using chip glass technology to install the driver. FIG. 10A shows a schematic diagram of a thin film on chip package of a driver according to another embodiment of the present invention. Figure 10B shows a side view of the chip-on-film package of Figure 10A, which is provided on the substrate and printed circuit board of the micro light emitting diode display panel of the embodiment of the present invention. Figure 11 shows a top view of the micro light emitting diode display panel.

11: substrate

12: Drive

700: Thin film flip chip package

711: main area

712: Joint Zone

Claims (12)

A micro-light-emitting diode display panel, comprising: a plurality of micro-light-emitting diodes; a substrate for supporting the micro-light-emitting diode, the surface of the substrate is divided into multiple sub-regions; and a plurality of thin-film flip-chip packages, respectively provided On the surface of the sub-region, a plurality of drivers are respectively arranged on the thin film on chip package; wherein the thin film on chip package stands on the substrate, so that the corresponding driver is suspended on the substrate. According to the micro-light-emitting diode display panel described in claim 1, wherein the thin-film-on-chip package includes a flexible printed circuit board, which includes at least one main area and a bonding area, and the driver is disposed in the main area. According to the micro-light emitting diode display panel described in item 2 of the scope of patent application, the size of the bonding area is smaller than the main area, and the bonding area is adjacent to one side of the main area. According to the micro-light-emitting diode display panel described in item 2 of the scope of patent application, the pins of the driver are arranged on four sides of the driver, and the pins are electrically connected to the finger connectors of the bonding area. According to the micro-light-emitting diode display panel described in item 2 of the scope of patent application, the bonding area is bent along the boundary between the bonding area and the main area and then bonded to the substrate. According to the micro light emitting diode display panel described in item 2 of the scope of patent application, the flexible printed circuit board stands on the substrate and the angle with the substrate is between 0 and 180 degrees. The micro-light-emitting diode display panel according to item 1 of the scope of patent application, wherein the micro-light-emitting diode display panel is a back-emitting micro-light-emitting diode display panel, and the light generated by it is directed from the back of the substrate to Down launch. According to the micro light emitting diode display panel described in item 1 of the scope of patent application, the substrate includes an insulating material. According to item 8 of the scope of patent application, the micro light emitting diode display panel, wherein the substrate comprises glass or acrylic. According to the micro light emitting diode display panel described in claim 1, wherein the thin film flip chip package includes a main area, a first bonding area and a second bonding area, the first bonding area and the second bonding area The bonding area is respectively adjacent to two opposite sides of the main area. According to the micro-light emitting diode display panel described in item 10 of the scope of patent application, the first bonding area uses an outer pin bonding technology, and the second bonding area uses an inner pin bonding technology. According to the micro light-emitting diode display panel described in the first item of the scope of patent application, some of the drivers use chip glass technology or thin film flip chip technology to be installed in the sub-area of the edge, while other drivers use thin film flip chip technology to design This sub-region in the center.

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