Patent Publication Number: US-2018031930-A1

Title: Pixel unit and array substrate

Description:
FIELD OF THE INVENTION 
     The present disclosure relates to the technical field of liquid crystal display, and in particular it relates to a pixel unit and an array substrate. 
     BACKGROUND OF THE INVENTION 
     As the flat-display panels represented by liquid crystal device (LCD) and organic light emitting diode (OLED) are developing toward large size and high resolution, thin film transistor (TFT) has also been widespread concern since it is used as the core component of the flat-display panels. In the prior arts, the commonly used thin film transistors include amorphous silicon thin film transistor and oxide thin film transistor, wherein the oxide thin film transistor is widely applied because of its advantages, such as high carrier mobility, and no substantial changes to the existing LCD panel production line when applied. 
     While the liquid crystal display device is widely used, the resolution requirement of the liquid crystal display image to the users is higher and higher, in order to ensure high resolution, a sufficient potential of the TFT is required during display, therefore, in the production process of the display device, a storage capacitor is provided in the pixel unit for ensuring the potential. 
     However, the storage capacitor is generally made by sandwiching an insulating layer between two metal electrodes, since the metal electrodes are opaque, the aperture ratio of the display device is therefore reduced, affecting the display effect. 
     SUMMARY OF THE INVENTION 
     The objective of the present disclosure is providing a pixel unit and an array substrate, which are capable of effectively improving the aperture ratio of a liquid crystal display device, under the premise that the resolution of which is guaranteed. 
     In order to solve the above problem, the present disclosure provides a technical solution of: providing a pixel unit, which comprises: a thin film transistor, and a storage capacitor electrically connected to the thin film transistor, the storage capacitor comprises a first metal layer and a second metal layer disposed opposite to the first metal layer, a concave-convex pattern is provided on a surface of the first metal layer facing to the second metal layer; the concave-convex pattern is a grid structure formed by providing grooves on the surface of the first metal layer. 
     Wherein, the concave-convex pattern is formed by treating the first metal layer with at least one of embossing, laser machining, or photolithography process. 
     Wherein, an insulating layer is sandwiched between the first metal layer and the second metal layer. 
     Wherein, the pixel unit further comprises a pixel electrode, the pixel electrode is connected to the storage capacitor in parallel. 
     Wherein, the thin film transistor is an oxide thin film transistor. 
     In order to solve the above problem, the present disclosure provides another technical solution of: providing a pixel unit, which comprises: a thin film transistor, and a storage capacitor electrically connected to the thin film transistor, the storage capacitor comprises a first metal layer and a second metal layer disposed opposite to the first metal layer, a concave-convex pattern is provided on a surface of the first metal layer facing to the second metal layer. 
     Wherein, the concave-convex pattern is formed by providing grooves on the surface of the first metal layer. 
     Wherein, the concave-convex pattern is formed by treating the first metal layer with at least one of embossing, laser machining, or photolithography process. 
     Wherein, the concave-convex pattern comprises a grid structure. 
     Wherein, an insulating layer is sandwiched between the first metal layer and the second metal layer. 
     Wherein, the pixel unit further comprises a pixel electrode, the pixel electrode is connected to the storage capacitor in parallel. 
     Wherein, the thin film transistor is an oxide thin film transistor. 
     In order to solve the above problem, the present disclosure provides yet another technical solution of: providing an array substrate, which comprises: a plurality of pixel units composed of a plurality of scan lines and a plurality of data lines intersecting with each other, the pixel unit comprises a thin film transistor, and a storage capacitor electrically connected to the thin film transistor, the storage capacitor comprises a first metal layer and a second metal layer disposed opposite to the first metal layer, a concave-convex pattern is provided on a surface of the first metal layer facing to the second metal layer. 
     Wherein, the concave-convex pattern is formed by providing grooves on the surface of the first metal layer. 
     Wherein, the concave-convex pattern is formed by treating the first metal layer with at least one of embossing, laser machining, or photolithography process. 
     Wherein, the concave-convex pattern comprises a grid structure. 
     Wherein, an insulating layer is sandwiched between the first metal layer and the second metal layer. 
     Wherein, the pixel unit further comprises a pixel electrode, the pixel electrode is connected to the storage capacitor in parallel. 
     Wherein, the thin film transistor is an oxide thin film transistor. 
     The beneficial effects of the present disclosure are: apart from the existing prior arts, the pixel unit of the present embodiment comprises a thin film transistor, and a storage capacitor electrically connected to the thin film transistor, the storage capacitor comprises a first metal layer and a second metal layer disposed opposite to the first metal layer, a concave-convex pattern is provided on a surface of the first metal layer facing to the second metal layer. The concave-convex pattern of the first metal layer increases the enfilade area of the first metal layer and the second metal layer which are disposed on two sides of the storage capacitor, and further increases a capacity of the storage capacitor. Thus, it is capable of reducing the physical size of the storage capacitor, without changing or even increasing the capacity of the storage capacitor, the aperture ratio of the liquid crystal display device is therefore increased, and the display image of the liquid crystal display device is improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing a cross-section of a pixel unit according to a preferred embodiment of the present disclosure. 
         FIG. 2  is a schematic diagram of a storage capacitor according to a preferred embodiment of the present disclosure. 
         FIG. 3  is a schematic diagram showing a plane view of a first metal layer of a storage capacitor according to a preferred embodiment of the present disclosure. 
         FIG. 4  is a schematic diagram of an array substrate according to a preferred embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to  FIG. 1 , which is a schematic diagram showing a cross-section of a pixel unit according to a preferred embodiment of the present disclosure. As shown in  FIG. 1 , the pixel unit of the present disclosure comprises a thin film transistor  101 , and a storage capacitor  102  electrically connected to the thin film transistor  101 , wherein the storage capacitor  102  comprises a first metal layer  1021  and a second metal layer  1022  disposed opposite to the first metal layer, the thin film transistor  101  can be an oxide thin film transistor, or other types of transistors as long as they carry a turn-on function, the types of the transistors are not limited herein. 
     As shown in  FIG. 1 , the thin film transistor  101  comprises a gate  1012  disposed on a glass substrate  1011 , an insulating layer  1013  formed on the gate  1012 , an active layer  1014  disposed above the insulating layer  1013 , and also comprises a source  1015  and a drain  1016  that are separated by a channel which exposing a partial active layer  1014  and being disposed at two sides of the active layer  1014 . The surface of pixel electrode is further disposed with a passivation layer  1017 , an overcoat layer  1018 , and a touch electrode  1019  used for electrically connected to the storage capacitor  102 . 
     Furthermore, the pixel unit further comprises a pixel electrode (not shown), the pixel electrode and the storage capacitor are electrically connected to the drain  1016  of the thin film transistor  101  via the touch electrode, the gate  1012  of the thin film transistor  101  is electrically connected to the scan line, the scan line provides a control signal to the thin film transistor  101 , the source  1015  of the thin film transistor  101  is electrically connected to the data line, the data line provides a driving signal to the pixel unit. Particularly, when the thin film transistor  101  is conducted to an electrical signal, a charging voltage is provided to the storage capacitor  102 , while a working voltage is provided to the pixel electrode. The storage capacitor stores charges, so as to supply a required potential for the pixel electrode when the thin film transistor  101  is off. 
     In order to provide a sufficient voltage to the pixel electrode, furthermore, a concave-convex pattern is provided on a surface of the first metal layer  1021  facing to the second metal layer  1022 . Particularly, as shown in  FIG. 2 , which is a schematic diagram of a storage capacitor, a concave-convex pattern  2011  is provided on a surface of the first metal layer  1021  facing to the second metal layer  1022 . 
     Furthermore, an insulating layer  203  is sandwiched between the first metal layer  201  and the second metal layer  202 , the insulating layer  203  comprises inorganic oxides, such as silicon dioxide, or other insulating materials which are not limited herein. 
     Particularly, when the surface of the first metal layer  201  is disposed with the concave-convex pattern, it is able to effectively increase a relative enfilade area of the electrodes that form the storage capacitor. According to the capacitance formula, C=εS/(4 κ πd), wherein, ε, κ, π are both constant, S is an enfilade area of the first metal layer  401  and the second metal layer  402 , d is a relative distance between the first metal layer  401  and the second metal layer  402 . In the condition that the relative distance d remains unchanged, the larger the enfilade area, the greater is the capacity of the storage capacitor. 
     Therefore, providing the undulating concave-convex pattern on the surface of the first metal layer  201 , by increasing the enfilade area of the first metal layer  401  and the second metal layer  402 , the capacity of the storage capacitor can be increased without changing the volume of the storage capacitor of the original thin film transistor. 
     Furthermore, based on the above technical solution, it is capable of reducing the area occupied by the storage capacitor, and increasing the aperture ratio of the liquid crystal display device. 
     Wherein, the concave-convex pattern can be formed by treating the first metal layer with at least one of embossing, laser machining, or photolithography process, so as to form undulating grooves on the surface of the first metal layer  201 , different shapes of the concave-convex patterns can therefore be formed, and the surface area of the first metal layer  201  is increased. 
     Wherein, the embossing process is placing a sheet material between an upper mold and a lower mold, making changes in material thickness under pressure effect, and filling the sheet material into the mold cavity and mold core having undulating fine lines, so as to obtain bulging characters or patterns on the surface of working products. Laser machining is a process by laser engraving various concave-convex patterns on the surface of the first metal layer. Photolithography process refers to a process by removing specific parts on the surface of the first metal layer, and leaving uneven patterns on the first metal layer. In the present embodiment, as long as the undulating concave-convex pattern can be formed on the surface of the first metal layer  201 , the concave-convex pattern forming processes are not limited herein. 
     The concave-convex pattern is not limited by specific forms, such as a grid structure as shown in  FIG. 3 , in other embodiments, the concave-convex pattern can be any animal shape, specific Chinese characters, and so on, as long as it is capable of increasing the relative surface area of the first metal layer. 
     In another embodiment, the first metal layer  201  can also compose a storage capacitor with the pixel electrode of the thin film transistor, that is not limited herein. 
     Apart from the existing prior arts, the pixel unit of the present embodiment comprises a thin film transistor, and a storage capacitor electrically connected to the thin film transistor, the storage capacitor comprises a first metal layer and a second metal layer disposed opposite to the first metal layer, a concave-convex pattern is provided on a surface of the first metal layer facing to the second metal layer. The concave-convex pattern of the first metal layer increases the enfilade area of the first metal layer and the second metal layer which are disposed on two sides of the storage capacitor, and further increases a capacity of the storage capacitor. Thus, it is capable of reducing the physical size of the storage capacitor, without changing or even increasing the capacity of the storage capacitor, the aperture ratio of the liquid crystal display device is therefore increased, and the display image of the liquid crystal display device is improved. 
     Please refer to  FIG. 4 , which is a schematic diagram of an array substrate according to a preferred embodiment of the present disclosure. The array substrate of the present embodiment comprises a plurality of scan lines  401  and data lines  402 , and a plurality pixel units composed of the plurality of scan lines and data lines intersecting with each other, each of the pixel units comprises a thin film transistor  4031 , a storage capacitor  4032  electrically connected to the thin film transistor  4031 , and a pixel electrode  4033  connected to the storage capacitor  4032  in parallel. Wherein, the thin film transistor  4031  comprises an oxide thin film transistor, a gate of the thin film transistor  4031  is connected to the scan line  401  for receiving a scanning control signal transmitted from the scan line  401 , a source of the thin film transistor  4031  is connected to the data line  402  for receiving a data signal transmitted from the data line  402 , a drain of the thin film transistor  4031  is connected to the storage capacitor  4032  and the pixel electrode  4033 . 
     When the thin film transistor  4031  is conducted to an electrical signal, a charging voltage is provided to the storage capacitor  4032 , while a working voltage is provided to the pixel electrode  4033 . The storage capacitor stores charges, so as to supply a required potential for the pixel electrode  4033  when the thin film transistor  4031  is off. 
     Furthermore, the storage capacitor  4032  comprises a first metal layer and a second metal layer disposed opposite to each other. In order to provide a sufficient voltage to the pixel electrode  4033 , furthermore, a concave-convex pattern is provided on a surface of the first metal layer facing to the second metal layer. 
     Particularly, the concave-convex pattern is not limited by specific forms, such as a grid structure, in other embodiments, the concave-convex pattern can be any animal shape, specific Chinese characters, and so on, as long as it is capable of increasing the relative surface area of the first metal layer. 
     Furthermore, an insulating layer is sandwiched between the first metal layer and the second metal layer, the insulating layer comprises inorganic oxides, such as silicon dioxide, or other insulating materials which are not limited herein. 
     Particularly, when the surface of the first metal layer is disposed with the concave-convex pattern, it is able to effectively increase a relative enfilade area of the electrodes that form the storage capacitor. According to the capacitance formula, C=εS/(4 κ π d), wherein, ε, κ, π are both constant, S is an enfilade area of the first metal layer  401  and the second metal layer  402 , d is a relative distance between the first metal layer  401  and the second metal layer  402 . In the condition that the relative distance d remains unchanged, the larger the enfilade area, the greater is the capacity of the storage capacitor. 
     Therefore, providing the undulating concave-convex pattern on the surface of the first metal layer, by increasing the enfilade area of the first metal layer and the second metal layer, the capacity of the storage capacitor can be increased without changing the volume of the storage capacitor of the original thin film transistor. 
     Furthermore, based on the above technical solution, it is capable of reducing the area occupied by the storage capacitor, and increasing the aperture ratio of the liquid crystal display device. 
     Wherein, the concave-convex pattern can be formed by treating the first metal layer with at least one of embossing, laser machining, or photolithography process, so as to form undulating grooves on the surface of the first metal layer, different shapes of the concave-convex patterns can therefore be formed, and the surface area of the first metal layer is increased. 
     Wherein, the embossing process is placing a sheet material between an upper mold and a lower mold, making changes in material thickness under pressure effect, and filling the sheet material into the mold cavity and mold core having undulating fine lines, so as to obtain bulging characters or patterns on the surface of working products. Laser machining is a process by laser engraving various concave-convex patterns on the surface of the first metal layer. Photolithography process refers to a process by removing specific parts on the surface of the first metal layer, and leaving uneven patterns on the first metal layer. In the present embodiment, as long as the undulating concave-convex pattern can be formed on the surface of the first metal layer, the concave-convex pattern forming processes are not limited herein. 
     In another embodiment, the first metal layer can also compose a storage capacitor with the pixel electrode of the thin film transistor, that is not limited herein. 
     Apart from the existing prior arts, the pixel unit of the present embodiment comprises a thin film transistor, and a storage capacitor electrically connected to the thin film transistor, the storage capacitor comprises a first metal layer and a second metal layer disposed opposite to the first metal layer, a concave-convex pattern is provided on a surface of the first metal layer facing to the second metal layer. The concave-convex pattern of the first metal layer increases the enfilade area of the first metal layer and the second metal layer which are disposed on two sides of the storage capacitor, and further increases a capacity of the storage capacitor. Thus, it is capable of reducing the physical size of the storage capacitor, without changing or even increasing the capacity of the storage capacitor, the aperture ratio of the liquid crystal display device is therefore increased, and the display image of the liquid crystal display device is improved. 
     Besides, the present disclosure further provides a liquid crystal display device, which comprises an array substrate as described in any one of the above embodiments, a color filter substrate, and liquid crystal cells sandwiched between the color filter substrate and the array substrate. The liquid crystal display device applies similar technical solutions as described above, which will not repeat herein. 
     The embodiments were chosen and described in order to explain the principles of the disclosure and their practical application so as to activate others skilled in the art to utilize the disclosure and various embodiments and with various modifications as are suited to the particular use contemplated. Alternative embodiments will become apparent to those skilled in the art to which the present disclosure pertains without departing from its spirit and scope. Accordingly, the scope of the present disclosure is defined by the appended claims rather than the foregoing description and the exemplary embodiments described therein.