Patent Publication Number: US-2018031877-A1

Title: Liquid crystal display

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of display, and in particular to a liquid crystal display (LCD). 
     2. The Related Arts 
     The liquid crystal display (LCD) provides the advantages of thin, low power consumption, radiation-free, and so on, and is widely applied to, such as, mobile phones, personal digital assistant (PDA), digital camera, computer monitors and notebook computers. 
     The conventional liquid crystal display devices on the market are mostly of the backlight type, comprising a case, a liquid crystal panel and a backlight module disposed inside the case. The traditional structure of the liquid crystal panel comprises a color filter (CF) substrate, a TFT array substrate, and a liquid crystal layer sandwiched between two substrates. The working principle is to apply a driving voltage to the two glass substrates to control the rotation of the liquid crystal molecules of the liquid crystal layer to refract the light from backlight to display. 
     LTPS technology is a new generation TFT substrate manufacturing technology, and the major difference between the conventional amorphous silicon (a-Si) technology and LTPS technology is that the LTPS provides that advantages of high response speed, high brightness, high-resolution and low power consumption. Because the LPTS has the high migration property, the ratio between the channel width W and the channel length L (W/L) of the TFT substrate switch when designing the pixels can be small so that the aperture ratio of corresponding to the pixels can be higher to provide market competitiveness. 
     Refer to  FIG. 1  for a schematic view of a known LCD, which comprises: a liquid crystal (LC) panel  100 , and a backlight module  200  disposed below the LC panel  100 , the LC panel  100  comprising a CF substrate  110 , a TFT array substrate  120  disposed opposite to the CF substrate  110 , an LC layer sandwiched between the CF substrate  110  and the TFT array substrate  120 , and a sealant to bond the CF substrate  110  and the TFT array substrate  120 . 
       FIG. 2  is a schematic view showing the cross-sectional structure of the LC panel  100  of the LCD in  FIG. 1 , wherein the CF substrate  110  comprises a first base substrate  400 , a black matrix  220  and a color-resist layer  340  disposed on the first base substrate  400 , a first planarization layer  350  disposed on the color-resist layer  340 , and a main photo-resist space  370  and an auxiliary photo-resist spacer  360  disposed on the first planarization layer  350 ; the TFT substrate  120  comprises a second base substrate  210 , a shielding metal layer  390  disposed on the second base substrate  210 , a first insulating layer  230  disposed on the second base substrate  210  and the shielding metal layer  390 , a polysilicon layer  240  disposed on the first insulating layer  230 , a second insulating layer  250  disposed on the first insulating layer  230  and the polysilicon layer  240 , a gate  260  disposed on the second insulating layer  250 , a third insulating layer  270  disposed on the second insulating layer  260  and the gate  260 , a source and a drain (source/drain)  280  disposed on the third insulating layer  270 , a second planarization layer  290  disposed on the third insulating layer  270  and the source/drain  280 , a common electrode layer  300  disposed on the second planarization layer  290 , a passivation layer  310  disposed on the common electrode layer  300 , a pixel electrode layer  320  disposed on the passivation layer  310 ; the passivation layer  310  and the second planarization layer  290  being disposed with vias  500  at locations corresponding to and above the source/drain  280 , the pixel electrode layer  320  connected through vias  500  to the source/drain  280 . 
     In the above LCD, to prevent light leakage from the pixel edge, a black matrix  220  is disposed at the CF substrate  110  side to shield. The black matrix  220  can also prevent the problem of lowering the contrast of panel caused by the metal (mainly the source/drain  280 ) on TFT substrate  120  side reflecting the incident light from the CF substrate  110  side. The above problems mainly come from the known LCD being formed by combining the CF substrate  110  and the TFT substrate  120 . As such, the alignment precision between the black matrix  220  on the CF substrate  110  side and the metal on TFT substrate  120  side. In the current process, it is impossible to achieve error-free alignment. With an error up to ±5 um, the actual aperture ratio of the LC panel will be very different from the design, and also a large deviation will exist among the aperture ratios of the LCDs from the same manufactured batch. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide an LCD with higher alignment precision and aperture ratio. 
     To achieve the above object, the present invention provides an LCD, which comprises: a liquid crystal (LC) panel, and a backlight module disposed below the LC panel, the LC panel comprising a first substrate, a second substrate disposed opposite to the first substrate, an LC layer sandwiched between the first substrate and the second substrate, and a sealant to bond the first substrate and the second substrate; the second substrate comprising a base substrate, a shielding metal layer disposed on the base substrate, a first insulating layer disposed on the base substrate and the shielding metal layer, a TFT layer disposed on the first insulating layer, a first passivation layer disposed on the TFT layer, a color-resist layer disposed on the first passivation layer, a first planarization layer disposed on the color-resist layer, and a photo-resist spacer disposed on the first planarization layer; the TFT layer comprising a polysilicon layer disposed on the first insulating layer, a second insulating layer disposed on the first insulating layer and the polysilicon layer, a gate disposed on the second insulating layer, a third insulating layer disposed on the second insulating layer and the gate, a source and a drain (source/drain) disposed on the third insulating layer, a second planarization layer disposed on the third insulating layer and the source/drain, a common electrode layer disposed on the second planarization layer, a second passivation layer disposed on the second planarization layer and the common electrode layer, a pixel electrode layer disposed on the second passivation layer; the second passivation layer and the second planarization layer being disposed with vias at locations corresponding to and above the source/drain, the pixel electrode layer connected through vias to the source/drain. 
     The material of the shielding metal layer is chromium. 
     The first substrate and the base substrate are both glass substrates. 
     The backlight module is disposed at the side near the first substrate of the LC panel. 
     The color-resist layer comprises a plurality of spaced red color-resist blocks, a plurality of spaced green color-resist blocks, and a plurality of spaced blue color-resist block; the shielding metal layer covers completely over the space between two adjacent color-resist blocks on the color-resist layer in the horizontal direction. 
     The first insulating layer, the second insulating layer, and the third insulating layer are made of a silicon nitride layer, a silicon oxide layer, or a composite structure of both; the common electrode layer and the pixel electrode layer are made of indium tin oxide (ITO). 
     The photo-resist spacer comprises a primary photo-resist spacer and an auxiliary photo-resist spacer; the main photo-resist spacer is in contact with the first substrate; and a gap exists between the auxiliary photo-resist spacer and the first substrate. 
     The TFT layer also comprises a plurality of data lines disposed on the third insulating layer. 
     The shielding metal layer completely shields the polysilicon layer, the gate and the source/drain in the horizontal direction. 
     The present invention also provides an LCD, which comprises: a liquid crystal (LC) panel, and a backlight module disposed below the LC panel, the LC panel comprising a first substrate, a second substrate disposed opposite to the first substrate, an LC layer sandwiched between the first substrate and the second substrate, and a sealant to bond the first substrate and the second substrate; the second substrate comprising a base substrate, a shielding metal layer disposed on the base substrate, a first insulating layer disposed on the base substrate and the shielding metal layer, a TFT layer disposed on the first insulating layer, a first passivation layer disposed on the TFT layer, a color-resist layer disposed on the first passivation layer, a first planarization layer disposed on the color-resist layer, and a photo-resist spacer disposed on the first planarization layer; wherein the TFT layer comprises a polysilicon layer disposed on the first insulating layer, a second insulating layer disposed on the first insulating layer and the polysilicon layer, a gate disposed on the second insulating layer, a third insulating layer disposed on the second insulating layer and the gate, a source and a drain (source/drain) disposed on the third insulating layer, a second planarization layer disposed on the third insulating layer and the source/drain, a common electrode layer disposed on the second planarization layer, a second passivation layer disposed on the second planarization layer and the common electrode layer, a pixel electrode layer disposed on the second passivation layer; the second passivation layer and the second planarization layer being disposed with vias at locations corresponding to and above the source/drain, the pixel electrode layer connected through vias to the source/drain; wherein the material of the shielding metal layer is chromium; wherein the first substrate and the base substrate are both glass substrates; wherein the backlight module is disposed at the side near the first substrate of the LC panel; wherein the color-resist layer comprises a plurality of spaced red color-resist blocks, a plurality of spaced green color-resist blocks, and a plurality of spaced blue color-resist block; the shielding metal layer covers completely over the space between two adjacent color-resist blocks on the color-resist layer in the horizontal direction. 
     Compared to the known techniques, the present invention provides the following advantages: the present invention provides an LCD, wherein the color-resist layer, photo-spacer and TFT layer are disposed at the same second substrate of the LC panel so that when fabricating each layer on the second substrate, a higher alignment precision can be obtained by using the reserved markers on the mask to align with the previous layer in fabrication process; at the same time, because the backlight module is disposed at the side near the first substrate of the LC panel and the second substrate uses a top gate structure, when the light of the backlight module enters from the first substrate side of the LC panel, the gate can shield the channel region of the polysilicon layer to improve the current leakage of the second substrate and avoid the current leakage caused by light; moreover, if the shielding metal layer at the bottom of the second substrate side is made of a black metal, such as, chromium, the shielding metal layer at the bottom can prevent reflection of light from the second substrate side caused by metal to reduce the contrast. As such, the present invention has a simple structure, saves the black matrix fabrication and provides higher alignment precision and aperture ratio. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       To make the technical solution of the embodiments according to the present invention, a brief description of the drawings that are necessary for the illustration of the embodiments will be given as follows. Apparently, the drawings described below show only example embodiments of the present invention and for those having ordinary skills in the art, other drawings may be easily obtained from these drawings without paying any creative effort. In the drawings: 
         FIG. 1  is a cross-sectional view showing the structure of a known LCD; 
         FIG. 2  is a cross-sectional view showing the structure of the LC panel of a known LCD in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view showing the structure of the LCD provided by an embodiment of the present invention; 
         FIG. 4  is a schematic view showing the structure of the LC panel at the TFT of the LCD in  FIG. 3 ; and 
         FIG. 5  is a schematic view showing the structure of the LC panel at the data lines of the LCD in  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     To further explain the technical means and effect of the present invention, the following refers to embodiments and drawings for detailed description. 
     Refer to  FIGS. 3-5 . The present invention provides a LCD, which comprises: a liquid crystal (LC) pane  1 , and a backlight module  2  disposed below the LC panel  1 . 
     As shown in  FIG. 3 , the LC panel comprises a first substrate  11 , a second substrate  12  disposed opposite to the first substrate  11 , an LC layer  13  sandwiched between the first substrate  11  and the second substrate  12 , and a sealant  14  to bond the first substrate  11  and the second substrate  12 . 
     As shown in  FIG. 4 , the second substrate  12  comprises a base substrate  21 , a shielding metal layer  22  disposed on the base substrate  21 , a first insulating layer  23  disposed on the base substrate  21  and the shielding metal layer  22 , a TFT layer  20  disposed on the first insulating layer  23 , a first passivation layer  33  disposed on the TFT layer  20 , a color-resist layer  34  disposed on the first passivation layer  33 , a first planarization layer  35  disposed on the color-resist layer  34 , and a photo-resist spacer  39  disposed on the first planarization layer  35 . 
     Because the color-resist layer  34 , photo-spacer  39  and TFT layer  20  are disposed at the same second substrate  12  of the LC panel  1  so that when fabricating each layer on the second substrate  12 , a higher alignment precision can be obtained by using the reserved markers on the mask to align with the previous layer in fabrication process to achieve a smaller offset between layers. The precision can be around ±0.6 um. 
     Specifically, the first substrate  11  and the base substrate  21  are both glass substrates. 
     Specifically, the backlight module  2  is disposed at the side near the first substrate  11  of the LC panel  1 . 
     Specifically, the color-resist layer  34  comprises a plurality of spaced red color-resist blocks, a plurality of spaced green color-resist blocks, and a plurality of spaced blue color-resist block; the shielding metal layer  22  covers completely over the space between two adjacent color-resist blocks on the color-resist layer  34  in the horizontal direction so as to replace a black matrix to prevent the pixel light leakage. 
     Specifically, the TFT layer  20  comprises: a polysilicon layer  24  disposed on the first insulating layer  23 , a second insulating layer  25  disposed on the first insulating layer  23  and the polysilicon layer  24 , a gate  26  disposed on the second insulating layer  25 , a third insulating layer  27  disposed on the second insulating layer  25  and the gate  26 , a source and a drain (source/drain)  28  disposed on the third insulating layer  27 , a second planarization layer  29  disposed on the third insulating layer  27  and the source/drain  28 , a common electrode layer  30  disposed on the second planarization layer  29 , a second passivation layer  31  disposed on the second planarization layer  29  and the common electrode layer  30 , a pixel electrode layer  32  disposed on the second passivation layer  31 ; the second passivation layer  31  and the second planarization layer  29  being disposed with vias  301  at locations corresponding to and above the source/drain  28 , the pixel electrode layer  32  connected through vias  301  to the source/drain  28 . 
     Because the backlight module  2  is disposed at the side near the first substrate  11  of the LC panel  1  and the second substrate  12  uses a top gate structure, when the light of the backlight module  2  enters from the first substrate  11  side of the LC panel  1 , the gate  26  can shield the channel region of the polysilicon layer  24  to improve the current leakage of the second substrate  12  and avoid the current leakage caused by light. 
     Specifically, the shielding metal layer  22  completely shields the polysilicon layer  24 , the gate  26  and the source/drain  28  in the horizontal direction. Therefore, when an external light enters from the bottom of the second substrate  12 , the shielding metal layer  22  at the bottom of the second substrate  12  can shield the light and the TFT elements of the second substrate  12  from current leakage caused by channel lighting. 
     At the same time, by disposing the shielding metal layer  22  at the bottom of the second substrate  12 , the shielding metal layer  22  can also prevent reflection of light from the second substrate  12  side caused by metal, such as, source/drain  28 , to reduce the contrast. 
     Specifically, the shielding metal layer  22  is made of a black metal; and preferably, the material of the shielding metal layer is chromium. 
     Specifically, the first insulating layer  23 , the second insulating layer  25 , and the third insulating layer  27  are made of a silicon nitride layer, a silicon oxide layer, or a composite structure of both. 
     Specifically, the photo-resist spacer  39  comprises a primary photo-resist spacer  37  and an auxiliary photo-resist spacer  36 ; the main photo-resist spacer  37  is in contact with the first substrate  11 ; and a gap exists between the auxiliary photo-resist spacer  36  and the first substrate  11 . 
     Specifically, as shown in  FIG. 5 , the TFT layer  20  also comprises a plurality of data lines  38  disposed on the third insulating layer  27 . 
     Specifically, the common electrode layer  30  and the pixel electrode layer  32  are made of indium tin oxide (ITO). 
     In summary, the present invention provides an LCD, wherein the color-resist layer, photo-spacer and TFT layer are disposed at the same second substrate of the LC panel so that when fabricating each layer on the second substrate, a higher alignment precision can be obtained by using the reserved markers on the mask to align with the previous layer in fabrication process; at the same time, because the backlight module is disposed at the side near the first substrate of the LC panel and the second substrate uses a top gate structure, when the light of the backlight module enters from the first substrate side of the LC panel, the gate can shield the channel region of the polysilicon layer to improve the current leakage of the second substrate and avoid the current leakage caused by light; moreover, if the shielding metal layer at the bottom of the second substrate side is made of a black metal, such as, chromium, the shielding metal layer at the bottom can prevent reflection of light from the second substrate side caused by metal to reduce the contrast. As such, the present invention has a simple structure, saves the black matrix fabrication and provides higher alignment precision and aperture ratio. 
     It should be noted that in the present disclosure the terms, such as, first, second are only for distinguishing an entity or operation from another entity or operation, and does not imply any specific relation or order between the entities or operations. Also, the terms “comprises”, “include”, and other similar variations, do not exclude the inclusion of other non-listed elements. Without further restrictions, the expression “comprises a . . . ” does not exclude other identical elements from presence besides the listed elements. 
     Embodiments of the present invention have been described, but not intending to impose any unduly constraint to the appended claims. Any modification of equivalent structure or equivalent process made according to the disclosure and drawings of the present invention, or any application thereof, directly or indirectly, to other related fields of technique, is considered encompassed in the scope of protection defined by the claims of the present invention.