Active backlight LED light source board and backlight module driven by a-Si TFT device

Abstract

The present invention is applicable to the field of display technology, and provides an active backlight LED light source board and a backlight module driven by an a-Si TFT device, wherein a substrate of the light source board includes a plurality of light-emitting units, each light-emitting unit includes a light-emitting element and a driving thin film transistor for driving the light-emitting element, and the driving thin film transistor includes a first gate, a first active layer, a first source electrode and a first drain electrode, and the first source electrode and the first drain electrode are staggered and form a tortuous gap to increase the width of a channel formed by a portion of the first active layer corresponding to the gap. The present invention staggers the first source electrode and the first drain electrode of the driving thin film transistor to form a tortuous gap, and the first active layer forms a channel at a portion of the gap between the first source electrode and the first drain electrode, and the tortuous channel significantly improves the width-to-length ratio of the channel and its driving capability, so that the driving thin film transistor allows a larger driving current to pass through to drive the light-emitting element to emit light, meeting the requirements for use as a backlight.

Description

Technical Field

[0001] The invention belongs to the field of display technology, and particularly relates to an active backlight LED light source board and a backlight module driven by an a-Si TFT device. Background Art

[0002] At present, TFT (Thin Film Transistor) is mainly used to drive each pixel, such as liquid crystal display arrays, organic light-emitting diode display arrays, etc. According to the different semiconductor materials used, the current mainstream TFT can be divided into three categories: a-Si (Amorphous Silicon), IGZO (Indium Gallium Zinc Oxide) and LTPS (Low Temperature Poly-silicon). The a-Si material has low quality and low carrier mobility, so the current density that a-Si TFT can withstand is small, while the carrier mobility in IGZO and LTPS is large and can withstand a larger current density.

[0003] For a single TFT, at a specific current density, the maximum current that can pass through it is proportional to the ratio of its channel width to length (width-to-length ratio). In order to limit the leakage current of the TFT and ensure device stability, the channel length of the TFT must be greater than a certain value.

[0004] The current LCD array and OLED array have a high resolution, so the pitch between two adjacent pixels is relatively small, about 0.1mm to 1mm. Figure 1 and 2 As shown. For a current driven element such as an organic light emitting diode 001 ( Figure 1 ), the area occupied by TFT 002 usually accounts for a large proportion of the total pixel area, and there is little room to further increase the current density by increasing the area. In another case, for liquid crystal display applications, the area occupied by the liquid crystal (opening area) 003 must reach a certain proportion ( Figure 2 ), so the area occupied by TFT 002' is limited. Therefore, in these traditional applications, the area of ​​TFT cannot be very large. When a larger current is required, only TFTs with higher mobility, such as IGZO or LTPS, can be used to obtain a higher current density.

[0005] Mini-LED (mini light-emitting diode) backlight technology is one of the new display technologies that have emerged in recent years. It has the advantages of high dynamic resolution, power saving, and simple algorithm. The current common Mini-LED backlight technology uses a driving method that solders integrated circuits on the PCB (Printed Circuit Board) backplane, which causes problems such as high difficulty in PCB design, high welding times, and high production costs. TFT driving technology, which is widely used in the OLED field, is rarely used in Mini-LED backlight displays. The main reason for this phenomenon is that the current density required by the backlight LED is usually relatively large (mA level), and traditional a-Si TFTs are difficult to meet its current density requirements, while new technologies such as LTPS are more expensive.

[0006] In the backlight Mini-LED array, the size of the Pitch can usually reach 10-100mm, which is much larger than the traditional application scenario of TFT. In this case, there is a large amount of available area in the Pitch, and even if a-Si is used as the TFT material, it is very likely to use this large area to obtain a TFT with a larger driving current. Summary of the invention

[0007] The purpose of the present invention is to provide an active backlight LED light source board driven by an a-Si TFT device, aiming to apply traditional a-Si TFT to LED to meet the technical problem of using it as a backlight module.

[0008] The present invention is implemented as follows: a light source panel includes a plurality of light-emitting units; each of the light-emitting units includes a light-emitting element and a driving thin film transistor for driving the light-emitting element; the driving thin film transistor includes a first gate, a first active layer, a first source and a first drain, the first source and the first drain are staggered, and a continuous and tortuous gap is formed between the first source and the first drain.

[0009] In one embodiment, the projections of the first source and the first drain in the substrate plane are defined as a plane geometric body A and a plane geometric body B, respectively, and A and B satisfy the following conditions:

[0010] The areas of A and B are not 0;

[0011] In the point set on the edge of B, more than 80% of the points have the same distance to A, which is d1, and less than 20% of the points have a distance to A greater than d1; in the point set on the edge of A, more than 80% of the points have the same distance to B, which is d2, and less than 20% of the points have a distance to B greater than d2;

[0012] The length of the side of A and B is L A With L B , Area SA With S B Meet the following conditions: L A 2 / S A >10 4 , L B 2 / S B >10 4 .

[0013] In one embodiment, the projection of the driving thin film transistor accounts for 70% to 95% of the area of ​​the light emitting unit.

[0014] In one embodiment, the staggered distribution includes a comb-tooth-shaped staggered distribution, and at least a portion of the channel is in a square wave shape.

[0015] In one embodiment, the staggered distribution includes a spiral staggered distribution, and at least a portion of the channel is spiral.

[0016] In one embodiment, a passivation layer is disposed on the driving thin film transistor, and the light emitting element is electrically connected to the first drain electrode of the driving thin film transistor via a first via hole on the passivation layer.

[0017] In one embodiment, the driving thin film transistor includes a plurality of layers of sub-thin film transistors, and two adjacent layers of the sub-thin film transistors are separated by a passivation layer. Each of the sub-thin film transistors includes a sub-gate, a sub-source and a sub-drain. The sub-gates of each layer of the plurality of sub-gates are connected by a first electrical conductor, the sub-sources of each layer are connected by a second electrical conductor, and the sub-drains of each layer are connected by a third electrical conductor.

[0018] In one embodiment, the first electrical conductor penetrates each of the passivation layers and each of the gate insulating layers, the second electrical conductor penetrates each of the passivation layers and each of the gate insulating layers, and the third electrical conductor penetrates each of the passivation layers and each of the gate insulating layers.

[0019] In one embodiment, the light source panel also includes a plurality of row control lines and column control lines, the light-emitting unit also includes a switching thin film transistor and a capacitor, the switching thin film transistor includes a second gate, a second active layer, a second source and a second drain, the second gate is connected to the row control line, the second source is connected to the column control line, the second drain is connected to the first gate, one end of the capacitor is connected between the first gate and the second drain, and the other end of the capacitor is connected between the first drain and the negative electrode of the driving power supply.

[0020] In one embodiment, the projections of the switch thin film transistor and the capacitor are located on one side or the center of the driving thin film transistor; and the projection of the light emitting element is located at the center or edge of the light emitting unit.

[0021] In one embodiment, the side length of the light emitting unit is 10-100 mm.

[0022] Another object of the present invention is to provide a backlight module, comprising the light source panel described in the above embodiments.

[0023] The light source board provided by the present invention has a beneficial effect over the prior art in that the light source board includes a plurality of light-emitting units, each of the light-emitting units includes a light-emitting element and a driving thin film transistor for driving the light-emitting element, the first source and the first drain of the driving thin film transistor are staggered and form a continuous and tortuous gap, the first active layer of the driving thin film transistor forms a channel corresponding to the portion of the gap between the first source and the first drain, the continuous and tortuous channel significantly improves the width-to-length ratio of the channel and improves its driving capability, so that the TFT allows a larger driving current to pass through, can drive the light-emitting element to emit light, and meets the driving current requirements for use as a backlight. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the existing LCD array structure;

[0025] Figure 2 is a schematic diagram of the existing OLED array structure;

[0026] Figure 3 is a schematic structural diagram of a liquid crystal display device provided by an embodiment of the present invention;

[0027] Figure 4 is a schematic side view of the structure of a backlight module provided by an embodiment of the present invention;

[0028] Figure 5 It is a side view structural schematic diagram of a light emitting unit on an active backlight LED light source board driven by an a-Si TFT device provided in one embodiment of the present invention;

[0029] Figure 6 is a schematic diagram of a driving circuit in a light-emitting unit provided in an embodiment of the present invention;

[0030] Figure 7 is a schematic structural diagram of a driving TFT provided by a first embodiment of the present invention;

[0031] Figure 8 is a schematic structural diagram of a light emitting unit provided in a second embodiment of the present invention;

[0032] Fig. 9 is a schematic structural diagram of a driving TFT provided by a third embodiment of the present invention;

[0033] Fig.10is a schematic structural diagram of a light emitting unit provided in a fourth embodiment of the present invention;

[0034] Fig.11 is a schematic structural diagram of a light emitting unit provided in a fifth embodiment of the present invention;

[0035] Figure 12 to Figure 14 is a structural schematic diagram of a light emitting unit provided in a sixth embodiment of the present invention;

[0036] Figures 15 to 17 1 is a schematic diagram of a top view of the structure of a light emitting unit provided in the seventh embodiment of the present invention.

[0037] The meanings of the marks in the figure are:

[0038] Liquid crystal display device 1, liquid crystal display panel 2, backlight module 3;

[0039] Light source plate 4, diffusion plate 5;

[0040] Substrate 40, light emitting unit 41, light emitting element 42, driving TFT 44, switch TFT 45, capacitor 46, auxiliary element 47, row control line 48, column control line 49;

[0041] A gate insulating layer 52;

[0042] A first gate electrode 441 , a first active layer 442 , a first intrinsic semiconductor layer 4421 , an ohmic contact layer 4422 , a first source electrode 443 , and a first drain electrode 444 ;

[0043] A second gate electrode 451, a second active layer 452, a second source electrode 453, and a second drain electrode 454;

[0044] Channel 4420, first channel 4425, second channel 4426;

[0045] A first comb handle 4431, first comb teeth 4432, a second comb handle 4441, second comb teeth 4442;

[0046] Source electrode strip 4433, source electrode comb teeth 4434, drain electrode strip 4443, drain electrode comb teeth 4444;

[0047] Passivation layer 71, wire 72, power line 73;

[0048] first via hole 74, first metal conductive column 75, second via hole 76, second metal conductive column 77,

[0049] Sub-TFT 80 , first electrical conductor 87 , second electrical conductor 88 , third electrical conductor 89 . DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0051] It should be noted that when a component is referred to as being "fixed on" or "disposed on" another component, it may be directly or indirectly on the other component. When a component is referred to as being "connected to" another component, it may be directly or indirectly connected to the other component. The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", etc. is based on the orientation or positional relationship shown in the accompanying drawings and is only for the convenience of description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as a limitation of this patent. The terms "first" and "second" are only used for the convenience of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features. "Multiple" means two or more, unless otherwise clearly and specifically defined.

[0052] In order to illustrate the technical solution of the present invention, a detailed description is given below in conjunction with specific drawings and embodiments.

[0053] Figure 3 The LCD device 1 includes a backlight module 3 and a LCD panel 2. The light emitted by the backlight module 3 enters the LCD panel 2 and is refracted by liquid crystal molecules in the liquid crystal layer to form a picture for display.

[0054] See also Figure 4 and Figure 5 The backlight module 3 includes a light source board 4 for providing light. In this embodiment, the backlight module 3 is a direct-type backlight module, and a diffusion plate 5 is arranged in front of the light source board 4. The light source board 4 includes a substrate 40 and a plurality of light-emitting elements 42 evenly arranged on the substrate 40. The light emitted by the light-emitting elements 42 is incident forward and enters the diffusion plate 5 through the rear surface of the diffusion plate 5. The light is diffused and homogenized by the diffusion plate 5 to form a surface light source, and then emitted from the front surface of the diffusion plate 5 and provided to the liquid crystal display panel 2.

[0055] Please refer to Figure 6 The substrate 40 is also provided with row control lines 48 and column control lines 49, which are used to control the multiple light-emitting units 41 to work independently, thereby enabling the backlight module 3 to independently control each light-emitting unit 41, which is beneficial to improving the display effect. Specifically, the light-emitting unit 41 includes the light-emitting element 42 mentioned above and a driving circuit for driving the light-emitting element 42 to emit light.

[0056] The driving circuit may include a switch element 45, a driving element 44 and a capacitor 46. The switch element is a thin film transistor (hereinafter referred to as the switch TFT 45), which is connected to the row control line 48 and the column control line 49, and controls the introduction of the column control line 49 signal according to the timing signal of the row control line 48. The driving element 44 is a thin film transistor (hereinafter referred to as the driving TFT 44), which is turned on according to the column control line 49 signal from the switch TFT 45 to drive the light emitting element 42 to emit light. The capacitor 46 is used to store the column control line 49 signal from the switch TFT 45, and can provide a bias and a maintenance voltage for controlling the driving TFT 44.

[0057] Specifically, Figure 5 and Figure 6 As shown, a plurality of row control lines 48, a first gate 441, and a second gate 451 are formed on the substrate 40 through a photomask process, and the second gate 451 is connected to the row control line 48. A gate insulating layer 52 is formed on the row control line 48, the first gate 441, and the second gate 451, and a first active layer 442 and a second active layer 452 are formed on the gate insulating layer 52. A first source 443 and a first drain 444 are formed on both sides of the first active layer 442, a second source 453 and a second drain 454 are formed on both sides of the second active layer 452, and a plurality of column control lines 49 are formed through another photomask process, and the second source 453 is connected to the column control line 49. In addition, the second drain 454 is also connected to the first gate 441 through a connection hole penetrating the gate insulating layer 52.

[0058] The switch TFT 45 mentioned above includes a second gate 451, a second active layer 452, a second source 453 and a second drain 454. The switch TFT 45 can be an a-Si TFT or an oxide semiconductor TFT, which is not limited in the present invention. In addition, the driving current required by the switch TFT 45 is usually small, and an a-Si TFT is preferred.

[0059] One end of the capacitor 46 is connected to the negative electrode of the driving power source, and the other end is connected between the first gate 441 and the second drain 454 .

[0060] The driving TFT 44 mentioned above includes a first gate electrode 441, a first active layer 442, a first source electrode 443 and a first drain electrode 444. When the driving TFT 44 is turned on, a current flows between the first source electrode 441 and the first drain electrode 443 to drive the light emitting element 42 to work. The light emitting element 42 can be connected between the positive electrode of the driving power source and the first source electrode 443, or between the first drain electrode 444 and the negative electrode of the driving power source. Figure 6 The light emitting element 42 is shown to be connected between the first drain electrode 444 and the negative electrode of the driving power source.

[0061] The maximum current that can pass between the first source 443 and the first drain 444 of the driving TFT 44 determines the driving current of the light source panel 4. When used in a backlight module, the driving current of the light source panel 4 usually needs to be at the milliampere level to meet the brightness requirements. Therefore, a driving TFT 44 that can withstand the corresponding driving current should be designed or used.

[0062] In the liquid crystal display device 1 provided in the embodiment of the present invention, the light emitting element 42 is a mini light emitting diode (mini-LED), and its size is about 200 microns. In the light source board 4, the total number of mini-LED tubes on the substrate 40 is about several thousand, and the distance between two adjacent mini-LEDs is about 10 to 100 microns. It can also be said that the side length of a light emitting unit 41 is 10 to 100 mm, which is much larger than the size of the mini-LED. The area ratio occupied by the mini-LED, the switch element 45 and the capacitor 46 in a light emitting unit 41 is relatively small. Therefore, the area other than the area occupied by the mini-LED, the switch TFT 45 and the capacitor 46 can be used for the design of the driving TFT 44. In one embodiment, the area ratio occupied by the driving TFT 44 in a light emitting unit 41 is 70% to 95, preferably 75% to 85%, and further preferably 80% to 85%, which can ensure that the driving TFT 44 occupies a larger area to provide a larger width-to-length ratio of the channel 4420.

[0063] The technical solution provided by the present invention is not only applicable to Mini-LED backlight sources, but also to light-emitting arrays composed of light-emitting units of other sizes, such as light-emitting arrays composed of traditional LEDs and other components. For light-emitting elements of other sizes, the proportion of TFTs in each unit varies accordingly depending on the size of the light-emitting unit. The technical solution provided by the present invention can provide drive for all light-emitting elements that require a large drive current.

[0064] In the present embodiment, the driving TFT 44 is an a-Si TFT, and the light source panel 4 of the present invention is an active backlight LED light source panel driven by an a-Si TFT device. The first active layer 442 of the driving TFT 44 includes a first intrinsic semiconductor layer 4421 formed on the gate insulating layer 52 and an ohmic contact layer 4422 formed on both sides of the first intrinsic semiconductor layer 4421. The material of the first intrinsic semiconductor layer 4421 is amorphous silicon, and the ohmic contact layer 4422 is amorphous silicon doped with N-type ions, such as nitrogen (N), phosphorus (P), and arsenic (As). The a-Si TFT has the advantages of simple manufacturing process, low cost, high yield, and low off-state leakage current, but its material mobility is low. Therefore, for the use of mini-LED in the backlight module 3, what needs to be solved is how to improve the driving capability of the a-Si TFT.

[0065] A specific structure of the a-Si TFT will be described below to provide the driving TFT 44 with a large driving capability.

[0066] In the driving TFT 44 provided in the embodiment of the present invention, the first source 443 and the first drain 444 are designed to be staggered to form a continuous and tortuous gap between the first source 443 and the first drain 444, rather than the existing rectangular shape (refer to Figure 1 and Figure 2 ), the first active layer 442 forms a continuous and tortuous channel 4420 corresponding to the tortuous gaps between the first source 443 and the first drain 444 that are staggered. The minimum distance for current to flow between the first source 443 and the first drain 444 is the length of the channel 4420, and the total length of the tortuous gaps between the first source 443 and the first drain 444 is the width of the channel 4420. The channel 4420 is formed in a continuous and tortuous manner, thereby increasing the width of the channel 4420 and its aspect ratio, thereby allowing a larger driving current to pass.

[0067] The projections of the first source 443 and the first drain 444 in the substrate plane are defined as plane geometric bodies A and plane geometric bodies B, respectively. A and B satisfy the following conditions:

[0068] The areas of A and B are not 0;

[0069] In the point set on the edge of B, more than 80% of the points have the same distance to A, which is d1, d1>0; less than 20% of the points have a distance to A greater than d1; symmetrically, in the point set on the edge of A, more than 80% of the points have the same distance to B, which is d2, d2>0; less than 20% of the points have a distance to B greater than d2.

[0070] The length of the side of A and B is L A With LB , Area S A With S B Meet the following conditions: L A 2 / S A >10 4 , L B 2 / S B >10 4 ;

[0071] Neither A nor B need to be consecutive.

[0072] Specifically, see Figure 7 , is a schematic diagram of the structure of the driving TFT 44 provided in the first embodiment of the present invention. The so-called "staggered distribution" is a comb-shaped staggered distribution. The first source electrode 443 is in a comb shape, including a first comb handle 4431 and a plurality of first comb teeth 4432 connected to the first comb handle 4431, and the first drain electrode 444 is in a comb shape, including a second comb handle 4441 and a plurality of second comb teeth 4442 connected to the second comb handle 4441. The first comb teeth 4432 and the second comb teeth 4442 are arranged in a mutually spaced manner between the first comb handle 4431 and the second comb handle 4441, and a second comb tooth 4442 is sandwiched between two first comb teeth 4432, and a first comb tooth 4432 is sandwiched between two second comb teeth 4442.

[0073] In one embodiment, the first comb handle 4431 and the first comb teeth 4432 are respectively disposed on two sides of the first active layer 442 to maximize the width of the channel 4420 , and the channel 4420 is square-wave-shaped between the first comb teeth 4432 and the second comb teeth 4442 .

[0074] The first comb handle 4431 and the first comb teeth 4432 are preferably connected at a vertical angle, and the second comb handle 4441 and the second comb teeth 4442 are preferably connected at a vertical angle, which is beneficial to improving the utilization rate of the area of ​​the light emitting unit 41 .

[0075] The distance between a first comb tooth 4432 and the nearest second comb tooth 4442, that is, the width of the cross section of the square wave is the length L of the channel 4420, and the total length of the square wave is the width W of the channel 4420. Therefore, within a limited area, the width-to-length ratio of the channel 4420 is greatly improved, thereby improving the maximum current and driving capability of the driving TFT 44.

[0076] In one embodiment, the distance between a first comb tooth 4432 and the nearest second comb tooth 4442, that is, the length L of the channel 4420, is 1 micron to 10 microns, and L can be as small as 1 micron, which can obtain the maximum width and the maximum width-to-length ratio of the channel of the driving TFT 44. On the basis of such a small length L, the width of the channel 4420 is substantially proportional to the sum of the number of the first comb teeth 4432 and the second comb teeth 4442, thereby greatly improving the width-to-length ratio of the driving TFT 44.

[0077] The number of the first comb teeth 4432 and the second comb teeth 4442 can be multiple, for example, 2, 3...N, N is a natural number. At the same time, the number of the first comb teeth 4432 and the second comb teeth 4442 can be the same or different; for example: the first source 443 may include 10 first comb teeth 4432, and the first drain 444 includes 11 second comb teeth 4442; for another example: the first source 443 includes 12 first comb teeth 4432, and the first drain 444 includes 11 second comb teeth 4442; for another example: the first source 443 includes 10 first comb teeth 4432, and the first drain 444 includes 10 second comb teeth 4442. Figure 7 The illustration is only used to illustrate the present embodiment, and the present invention is not limited thereto.

[0078] The first gate 441 is in a square wave shape and is disposed corresponding to the channel 4420 . The first gate 441 partially overlaps with the first source 443 and the first drain 444 .

[0079] like Figure 8 As shown, it is a schematic diagram of the structure of the light-emitting unit 41 provided in the second embodiment of the present invention. The driving TFT 44 is as described in the first embodiment above, and its area (projected area) accounts for 70% to 95% of the area of ​​the light-emitting unit 41, preferably 75% to 85%, and more preferably 80% to 85%, which can ensure that the driving TFT 44 occupies a larger area to provide a larger width-to-length ratio of the channel 4420. The area of ​​the light-emitting element 42, the switch TFT 45 and the capacitor 46 (hereinafter, the switch TFT 45 and the capacitor 46 are collectively referred to as the auxiliary element 47) accounts for less than or equal to 30% of the area of ​​the light-emitting unit 41, preferably 15% to 25%, and more preferably 15% to 20%. The advantage of this is that it can ensure that both the light-emitting element 42 and the auxiliary element 47 have sufficient area for design, avoiding the difficulty of design or production due to the small area of ​​the auxiliary element 47. The driving TFT 44 occupies a larger area in the light emitting unit 41 , and a larger area is available for designing the first source electrode 443 and the first drain electrode 444 , thereby greatly improving the driving capability of the driving TFT 44 .

[0080] In one embodiment, the light emitting element 42 and the auxiliary element 47 may be disposed on any side of the driving TFT 44, preferably, on a side close to the first drain 444, specifically, on a side of the second comb handle 4441 or on a side of the second comb teeth 4442, so as to facilitate the connection between the light emitting element 42 and the auxiliary element 47 and the first drain 444. Figure 8 In the embodiment, the light emitting element 42 and the auxiliary element 47 are arranged on one side of the second comb tooth 4442, and the first source electrode 443 and the first drain electrode 444 are adjusted corresponding to the shapes of the light emitting element 42 and the auxiliary element 47. The second comb handle 4441 of the first drain electrode 444 is divided into two parts, and accordingly, the lengths of some of the second comb teeth and the first comb teeth are shortened. The channel 4420 is still formed in a square wave shape, but the height of a part of the square wave is correspondingly reduced.

[0081] Of course, it is understandable that the light emitting element 42 and the auxiliary element 47 can also be arranged on one side of the second comb handle 4441 of the first drain electrode 444, and the middle part of the second comb handle 4441 is arranged close to the first comb handle 4431. Any design that does not change the comb-tooth-shaped staggered distribution of the first source electrode 443 and the first drain electrode 444 can be applied here.

[0082] like Fig. 9 , which is a schematic diagram of the structure of the driving TFT 44 provided in the third embodiment of the present invention. The so-called "staggered distribution" is a spiral staggered distribution. The first source 443 and the first drain 444 are both strip-shaped and spirally distributed. The first source 443 is arranged between the gaps of the spiral first drain 444. Fig. 9 In the embodiment, the gap between the first source electrode 443 and the first drain electrode 444 forms a channel 4420, and the channel 4420 is also strip-shaped and spirally distributed. The current flows from the first source electrode 443 to the first drain electrode 444, and the width of the gap between the first source electrode 443 and the first drain electrode 444 is the length of the channel 4420, and the total length of the spiral is the width of the channel 4420, thereby greatly improving the width and width-to-length ratio of the channel 4420, which is beneficial to improving the driving capability of the driving TFT 44.

[0083] The first source electrode 443 and the first drain electrode 444 are both in a rectangular spiral shape to correspond to the shape of the light emitting unit 41 , thereby improving the area utilization of the light emitting unit 41 .

[0084] The width of the gap between the first source electrode 443 and the first drain electrode 444 , that is, the length L of the channel 4420 , is in the range of 1 micrometer to 10 micrometers, and can be as small as 1 micrometer.

[0085] The first gate 441 is strip-shaped and spirally distributed, and is arranged corresponding to the spiral channel 4420 and overlaps a portion of the first source 443 and the first drain 444. It should be understood that the first gate 441 may only correspond to the channel 4420. Fig. 9 In the embodiment, the first gate 441 is a gap corresponding to the first source 443 and the first drain 444.

[0086] It should be understood that the comb-shaped staggered distribution and the spiral-shaped staggered distribution given above are not mutually exclusive. In a driving TFT 44, the staggered distribution of the first source 443 and the first drain 444 may not be the same.

[0087] like Fig.10 As shown, the structural schematic diagram of the light-emitting unit 41 provided by the fourth embodiment of the present invention, wherein the driving TFT 44 is as described in the third embodiment above, and its projection area accounts for 70% to 95% of the area of ​​the light-emitting unit 41, preferably 75% to 85%, and more preferably 80% to 85%, and the area of ​​the light-emitting element 42 and the auxiliary element 47 accounts for less than or equal to 30% of the area of ​​the light-emitting unit 41, preferably 15% to 25%, and more preferably 15% to 20%. The driving TFT 44 occupies a larger area in the light-emitting unit 41, and there is a larger area for designing the first source 443 and the first drain 444, thereby greatly improving the driving ability of the driving TFT 44.

[0088] The light emitting element 42 and the auxiliary element 47 may be disposed on either side of the driving TFT 44. Fig.10 As shown, the spiral shapes of the first source electrode 443 and the first drain electrode 444 are adaptively adjusted according to the light emitting element 42 , the switch TFT 45 and the capacitor 46 to maximize the use of the area of ​​the light emitting unit 41 .

[0089] As shown in this embodiment, the light emitting element 42 and the auxiliary element 47 are arranged on one side of the driving TFT 44 and occupy a corner of the light emitting unit 41. At this time, the first source 443 and the first drain 444 can be distributed in a rectangular spiral shape on one side of the light emitting element 42 and the auxiliary element 47, which will inevitably waste a part of the area of ​​the light emitting unit 41. If the area of ​​the light emitting unit 41 is to be used as much as possible, the first source 443 and the first drain 444 cannot be staggered in a simple rectangular spiral shape, and other staggered distributions can be designed on the basis of the spiral shape, such as comb-shaped staggered distribution. At least a part of the first source 443 and the first drain 444 is strip-shaped and staggered in a spiral shape, and another part can be designed as a strip but staggered in other ways.

[0090] Specifically, the first source 443 includes a source strip 4433 distributed in a spiral shape, the first drain 444 includes a drain strip 4443 distributed in a spiral shape, the source strip 4433 and the drain strip 4443 are distributed in a spiral shape and staggered to form a spiral first gap, and the first active layer 442 includes a spiral first channel 4425 formed corresponding to the first gap between the source strip 4433 and the drain strip 4443. The first source 443 also includes a source comb tooth 4434 extending from the source strip 4433, the second drain 454 also includes a drain comb tooth 4444 extending from the drain strip 4443, the source comb tooth 4434 and the drain comb tooth 4444 are distributed at intervals to form a wave-proof second gap, and the channel 4420 also includes a square wave second channel 4426 formed between the source comb tooth 4434 and the drain comb tooth 4444.

[0091] The first channel 4425 and the second channel 4426 are connected to form a complete channel 4420 . By further designing a comb-shaped staggered distribution on the basis of the spiral staggered distribution, the overall length of the channel 4420 is consistent, which is beneficial to ensure the stability of the driving current of the driving TFT 44 .

[0092] It can be understood that the staggered distribution is not limited to the comb-shaped staggered distribution and spiral staggered distribution given above, and the comb-shaped staggered distribution and spiral staggered distribution are not limited to the specific illustrations of the above two embodiments. Any staggered distribution that can make the channel 4420 tortuously formed and maximize the use of the area of ​​the light-emitting unit 41 should belong to the disclosure of the present invention.

[0093] like Fig.11 FIG. 4 is a schematic diagram of the structure of the light-emitting unit 41 provided in the fifth embodiment of the present invention. On the basis of the third and fourth embodiments, the light-emitting element 42 and the auxiliary element 47 are arranged at the center of the light-emitting unit 41, and the light-emitting element 42 is connected to the first drain electrode 444 at the end of the first drain electrode 444 located at the center of the light-emitting unit 41. The advantage of this is that it can not only make the light emitted by the light-emitting element 42 more symmetrical, but also make the electrical connection between the light-emitting element 42 and the driving TFT 44 more convenient, without the need for Fig.10 The spiral shapes of the first source 443 and the first drain 444 are changed as in the fourth embodiment, thereby reducing the difficulty of process design and manufacturing.

[0094] According to the description of the above embodiments, in the scheme provided by the present invention, in the entire light-emitting unit 41, the driving TFT 44 is made with a larger area, the first source 443 and the first drain 444 of the driving TFT 44 are designed to be staggered, and the channel 4420 is formed tortuously and continuously. For the driving TFT 44, its driving current I can be approximately described by the following relationship (1): Formula (1); wherein W is the width of the channel 4420, L is the length of the channel 4420, and k1 is the proportionality coefficient. In the present invention, when the length L of the channel 4420 is constant, the width W of the conductive channel 4420 is increased as much as possible, thereby improving the current driving capability of the a-Si TFT. For the scheme provided by the present invention, it is not easy to make other changes after the length L of the channel 4420 is minimized, and in order to make the TFT element fill the entire area as much as possible, Formula (2) should be satisfied; wherein A is the total area of ​​the driving TFT 44, and k2 is the proportionality coefficient. The driving TFT 44 should occupy most of the area of ​​the light-emitting unit 41 to increase W, the length L of the channel 4420 remains unchanged, and the width W is approximately proportional to the area of ​​the light-emitting unit 41. Combining equations (1) and (2) can obtain equation (3); therefore, in the solution of the present invention, the driving current is proportional to the area of ​​the driving TFT 44.

[0095] The driving current of a-Si TFT of conventional size is (10 -6 -10 -5 )A uA level, and in the present invention, in the backlight module 3 using Mini-LED, the side length of the light-emitting unit 41 is (10 1 -10 3 ) times, the area is (10 2 -10 6 ) times, so the drive current can also be expanded by about (10 2 -10 6 ) times, reaching (10 -4 -10 1 )mA level, which can meet the driving requirements of Mini-LED used in backlight module 3.

[0096] The above embodiments describe how to improve the area utilization of the driving TFT 44 within the planar area of ​​the light-emitting unit 41 to improve the aspect ratio and driving capability of the driving TFT 44. On this basis, the following embodiments are also provided to further improve the area occupancy of the driving TFT 44.

[0097] like Figure 12 to Figure 14, which is a schematic diagram of the structure of the light-emitting unit 41 of the sixth embodiment provided by the present invention. The driving TFT 44 and the auxiliary element 47 of the light-emitting unit 41 are arranged as a layer on the substrate 40, and the projected area occupied by the driving TFT 44 and the auxiliary element 47 is the area of ​​the entire light-emitting unit 41. The light-emitting element 42 is arranged as another layer above the driving TFT 44 and the auxiliary element 47 (the filling of the light-emitting element 42 indicates that the light-emitting element 42 and the driving TFT 44 are arranged in different layers). Therefore, the area of ​​the light-emitting element 42 is saved for the design of the driving TFT 44, which can further improve the area ratio and the width-to-length ratio occupied by the driving TFT 44, thereby improving the driving ability of the driving TFT 44. A passivation layer 71 is formed on the first source 443 and the first drain 444, and the passivation layer 71 has a first via hole 74 corresponding to the first drain 444 and a second via hole 76 corresponding to the first source 443. The first via hole 74 is filled with a first metal conductive column 75, and the second via hole 76 is filled with a second metal conductive column 77, so as to lead the first source 443 and the first drain 444 to the surface of the passivation layer 71, respectively. A wire 72 for connecting the first drain 444 and the light-emitting element 42 and a power line 73 for connecting the driving power supply and the first source 443 are further formed on the passivation layer 71. As a result, the light-emitting element 42 does not occupy the area of ​​the light-emitting unit 41, the area of ​​the driving TFT 44 can be further increased, the width of the channel 4420 can be further increased, and the driving capability can also be further increased.

[0098] In this embodiment, the shapes of the first source electrode 443 and the first drain electrode 444 can be substantially any shape. Preferably, the shapes of the first source electrode 443 and the first drain electrode 444 adopt the comb shape described in the first embodiment and / or the spiral shape described in the third embodiment, and since the auxiliary element 47 and the driving TFT 44 are both arranged below the passivation layer 71 and are in the same layer, i.e., they jointly occupy the total area of ​​the light emitting unit 41, the driving TFT 44 can adopt the following shapes: Fig.10 Thus, on the basis of increasing the area occupied by the driving TFT 44, the aspect ratio of the driving TFT 44 is also greatly improved.

[0099] Preferably, the first metal conductive pillar 75 and the second metal conductive pillar 77 are respectively arranged at positions close to the two ends of the channel 4420. The advantage of this is that the distance between the first metal conductive pillar 75 and the second metal conductive pillar 77 can be increased as much as possible or even maximized, thereby avoiding any possible electrical connection between the first metal conductive pillar 75 and the second metal conductive pillar 77 due to process problems in the process of depositing and etching the conductive pillar metal layer.

[0100] The auxiliary element 47 may be located at one side or the center of the driving TFT 44. Fig.10 and Fig.11 As shown. Since the connection between the light emitting element 42 and the first drain electrode 444 is realized through the wire 72 and the first metal conductive column 75, the projection of the light emitting element 42 in the light emitting unit 41 can actually be located at any position, such as an edge position or a center position. In a preferred embodiment, the light emitting element 42 is located at the center position in the light emitting unit 41. Similarly, the light emitted outward by the light emitting element 42 can be made more symmetrical, which is beneficial to improve the uniformity of the backlight source of the backlight module 3 when the light emitting unit 41 is used in the backlight module 3.

[0101] like Figures 15 to 17 , which is a schematic diagram of the structure of the light-emitting unit 41 of the seventh embodiment of the present invention. In this embodiment, the driving TFT 44 is composed of M layers (M is a positive integer greater than or equal to 2) of sub-TFTs 80 sequentially formed on the substrate 40. The layer of sub-TFTs 80 closest to the substrate 40 is the first layer of sub-TFTs 80, and the layer of sub-TFTs 80 farthest from the substrate 40 is the Mth layer of sub-TFTs 80. Each layer of sub-TFTs 80 is a bottom-gate type arrangement, including a sub-gate formed on the substrate 40, a sub-gate insulating layer 52 formed on the first substrate 40, a sub-active layer formed on the sub-gate insulating layer 52, and a sub-source and a sub-drain formed on the sub-active layer. The sub-active layer includes a sub-intrinsic semiconductor layer formed on the sub-gate insulating layer 52 and a sub-ohmic contact layer formed on both sides of the sub-intrinsic semiconductor layer. The material of the sub-intrinsic semiconductor layer is amorphous silicon, and the sub-ohmic contact layer is amorphous silicon doped with N-type ions, such as nitrogen (N), phosphorus (P), and arsenic (As), that is, each sub-TFT 80 is an a-SiTFT. A passivation layer 71 is disposed between two adjacent layers of sub-TFTs 80.

[0102] The M-layer sub-gate is electrically connected via the first electrical conductor 87. The first electrical conductor 87 is disposed outside the M-layer sub-source, sub-drain and sub-active layer, and only needs to penetrate the M-1-layer sub-gate insulating layer 52 and the M-1-layer passivation layer 71. Fig.17 As shown, the first electrical conductor 87 is illustrated in dashed lines, indicating that the first electrical conductor 87 is located Fig.17 It is easy to understand that the M-layer sub-gate constitutes the first gate 441.

[0103] The M-layer sub-source is electrically connected via the second electrical conductor 88. The second electrical conductor 88 penetrates the M-1-layer gate insulating layer 52 and the M-1-layer passivation layer 71. The M-layer sub-source constitutes the first source 443.

[0104] The second electrical conductor 88 is further electrically connected to the second metal conductive column 77 disposed on the M-th layer sub-source, so that the M-th layer sub-source is led out to above the passivation layer 71 and connected to the driving power supply through the power line 73.

[0105] The M-layer sub-drain is electrically connected via the third electrical conductor 89. The third electrical conductor 89 penetrates the M-1-layer gate insulating layer 52 and the M-1-layer passivation layer 71. The M-layer sub-drain constitutes the first drain 444.

[0106] The third electrical conductor 89 is further electrically connected to the first metal conductive column 75 disposed on the M-th layer sub-drain, so that the M-th layer sub-drain is led out to above the passivation layer 71 and connected to the light-emitting element 42 through the wire 72 .

[0107] The auxiliary element 47 is arranged in the layer where the M-th layer sub-TFT 80 is located, and the switch TFT 45 can be arranged in the same layer as the M-th layer sub-TFT 80 (the second gate 451 is arranged in the same layer as the M-th layer sub-gate, and the second source 453 and the second drain 454 are arranged in the same layer as the M-th layer sub-source and sub-drain). The second drain 454 of the switch TFT 45 is connected to the sub-gate of the M-th layer sub-TFT 80, one end of the capacitor 46 is connected between the sub-gate of the M-th layer sub-TFT 80 and the second drain 454, and the other end of the capacitor 46 is connected between the positive electrode of the driving power supply and the M-th layer sub-source.

[0108] In this embodiment, the area of ​​the switch TFT 45 is increased by about M times by disposing M layers of sub-TFTs 80, thereby increasing its driving capability. When the aspect ratio of each layer of sub-TFTs 80 remains unchanged, the proportionality coefficient K2 is further increased to about M times.

[0109] In this embodiment, each sub-TFT 80 can adopt the comb-shaped staggered distribution described in the first embodiment and / or the spiral staggered distribution described in the third embodiment. In this way, on the basis of increasing the area occupied by the driving TFT 44, the width-to-length ratio of the driving TFT 44 is also greatly improved.

[0110] In a preferred embodiment, the third conductor 89 corresponds to the position of the first metal conductive column 75, and the second conductor 88 corresponds to the position of the second metal conductive column 77. The first metal conductive column 75 and the second metal conductive column 77 are respectively arranged at the two ends of the channel 4420. The advantage of this is not only that the distance between the second conductor 88 and the third conductor 89 can be maximized to avoid any possible electrical connection between the second conductor and the third conductor in each deposition and etching process, but also that a mask can be used when penetrating the gate insulation layer 52 and the passivation layer 71, which is beneficial to reduce production costs and reduce process complexity.

[0111] The projection of the light emitting element 42 in the light emitting unit 41 can actually be located at any position. In a preferred embodiment, the light emitting element 42 is located at the center of the light emitting unit 41. Similarly, the light emitted outward by the light emitting element 42 can be made more symmetrical, which is beneficial to improving the uniformity of the backlight source of the backlight module 3 when the light emitting unit 41 is used in the backlight module 3.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A light source panel, It is characterized in that Used in a backlight module, comprising a plurality of light-emitting units; each of the light-emitting units comprises a light-emitting element and a driving thin film transistor for driving the light-emitting element; the driving thin film transistor comprises a first gate, a first active layer, a first source electrode and a first drain electrode, the first source electrode and the first drain electrode are staggered, and a tortuous gap is formed between the first source electrode and the first drain electrode; The projection of the driving thin film transistor accounts for 70% to 95% of the area of ​​the light-emitting unit; The projections of the first source and the first drain in the substrate plane are defined as plane geometric bodies A and plane geometric bodies B respectively, and A and B satisfy the following conditions: The areas of A and B are not 0; In the point set on the edge of B, more than 80% of the points have the same distance to A, which is d1, and less than 20% of the points have a distance to A greater than d1; in the point set on the edge of A, more than 80% of the points have the same distance to B, which is d2, and less than 20% of the points have a distance to B greater than d2.

2. The light source panel according to claim 1, It is characterized in that The length of the side of A and B is L A With L B , Area S A With S B Meet the following conditions: L A 2 / S A >10 4 , L B 2 / S B >10 4 .

3. The light source panel according to claim 1, It is characterized in that The first active layer corresponds to a staggered distribution between the first source and the first drain to form a continuous and tortuous channel; the staggered distribution includes a comb-tooth-shaped staggered distribution, and at least a portion of the channel is square-wave shaped.

4. The light source panel according to claim 1, It is characterized in that The first active layer forms a continuous and tortuous channel through a tortuous gap between the first source and the first drain that are staggered in correspondence with the staggered distribution; the staggered distribution includes a spiral staggered distribution, and at least a portion of the channel is spiral.

5. The light source panel according to claim 1, It is characterized in that A passivation layer is disposed on the driving thin film transistor, and the light emitting element is electrically connected to the first drain electrode of the driving thin film transistor via a first via hole on the passivation layer.

6. The light source panel according to claim 1, It is characterized in that The driving thin film transistor includes a plurality of layers of sub-thin film transistors, and two adjacent layers of the sub-thin film transistors are separated by a passivation layer. Each of the sub-thin film transistors includes a sub-gate, a sub-source and a sub-drain. The sub-gates of each layer are connected by a first electrical conductor, the sub-sources of each layer are connected by a second electrical conductor, and the sub-drains of each layer are connected by a third electrical conductor.

7. The light source panel according to claim 6, It is characterized in that The first electrical conductor penetrates each of the passivation layers and each of the gate insulating layers, the second electrical conductor penetrates each of the passivation layers and each of the gate insulating layers, and the third electrical conductor penetrates each of the passivation layers and each of the gate insulating layers.

8. The light source panel according to claim 1, It is characterized in that The light source panel also includes a row control line and a column control line, the light-emitting unit also includes a switching thin film transistor and a capacitor, the switching thin film transistor includes a second gate, a second active layer, a second source and a second drain, the second gate is connected to the row control line, the second source is connected to the column control line, the second drain is connected to the first gate, one end of the capacitor is connected between the first gate and the second drain, and the other end of the capacitor is connected between the first drain and the negative electrode of the driving power supply.

9. The light source panel according to claim 8, It is characterized in that The switch thin film transistor and the capacitor are located at one side or the center of the driving thin film transistor; the projection of the light emitting element is located at the center or edge of the light emitting unit.

10. The light source panel according to claim 1, It is characterized in that The side length of the light emitting unit is 10 to 100 mm.

11. A backlight module, It is characterized in that The light source panel comprises the light source panel according to any one of claims 1 to 10.

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