Patent Publication Number: US-2018039139-A1

Title: Liquid crystal display panel structure and manufacturing method thereof

Description:
FIELD OF THE INVENTION 
     The present invention relates to a liquid crystal display panel structure and a manufacturing method thereof, and more particularly to a liquid crystal display panel structure and a manufacturing method thereof which can fix an orientation of liquid crystal molecules by disposing photo-reactive monomers on a surface of alignment films. 
     BACKGROUND OF THE INVENTION 
     Liquid crystal displays (LCD) are now the most widely used flat panel displays, they have a high resolution color screen, and are widely applied to various electronic devices, such as mobile phones, personal digital assistants (PDA), digital cameras, computer displays, or laptop computer displays. Currently, a widely common used liquid crystal display is composed of upper and lower substrates and a middle liquid crystal layer, wherein the upper and lower substrates are composed of glass substrates and electrodes. If the upper and lower substrates both have electrodes, they can be formed as a kind of longitudinal electric field mode display, such as a TN (Twist Nematic) mode, a VA (Vertical Alignment) mode, and a MVA (Multi-Domain Vertical Alignment) mode which is developed to solve a problem of narrow viewing angle. In another kind of display, the electrodes are only disposed on the side of the lower substrate, and are formed as a kind of transverse electric field mode display, such as an IPS (In-Plane Switching), an FFS (Fringe Field Switching) mode, etc. 
     The above-mentioned FSS liquid crystal actuation mode is a wide viewing angle technology derived from the IPS actuation mode. In structural design, the FFS mode disposes a common electrode below an interval of pixel electrodes. When applying a voltage, a boundary electric field is generated to twist liquid crystal above the electrodes. By the boundary electric field, the almost evenly arranged liquid crystal molecules are twisted on the surface of the electrodes, so as to achieve a high penetration property and a large viewing angle characteristic. The electric field distribution of this kind has a greater vector in the z-direction, and also has a greater liquid crystal area which can be modulated, so that this electric field distribution design substantially increases a twisting power for the liquid crystal molecules in the liquid crystal flat panel display after applying the voltage, and improves defects of the IPS wide viewing angle technology, such as slow twisting speed, low aperture ratio, and requesting more backlight sources. Additionally, the FFS panel also has the widest viewing angle of all the wide viewing angle technologies. 
     Furthermore, there are many alignment methods used in the FFS liquid crystal display, wherein a rubbing alignment is the widest used method. The rubbing alignment not only has good optical characteristics, but also has good reliability at high temperature. However, because the rubbing alignment is according to a mechanical rubbing alignment between an alignment film and a rubbing cloth, the uniformity of the liquid crystal molecules on the surface of the alignment film is worse, so that it causes a dark-state light leakage, and then influences the contrast of the liquid crystal display. For example, refer now to  FIGS. 1A to 1C , which are assembled schematic views of a traditional liquid crystal display panel structure. This traditional liquid crystal display panel structure  10  belongs to a liquid crystal display panel of a Fringe Field Switching (FFS) type, and mainly comprises an array substrate, a color filter substrate, and a liquid crystal layer, an assembled manufacturing method of which comprises following steps of:
         (a) Refer to  FIG. 1A , providing a first substrate  11 , which includes a first alignment film  11   a,  wherein the first alignment film  11   a  is formed on a upper surface of the first substrate  11 , and the first alignment film  11   a  of the first substrate  11  is rubbed and aligned by a rubbing roll A;   (b) Refer to  FIG. 1B , providing a second substrate  12 , which includes a second alignment film  12   a,  wherein the second alignment film  12   a  is formed on a upper surface of the second substrate  12 , and the second alignment film  12   a  of the second substrate  12  is rubbed and aligned by a rubbing roll A;   (c) Refer to  FIG. 1C , assembling the first substrate  11  and the second substrate  12  correspondingly, wherein the first alignment film  11   a  of the first substrate  11  and the second alignment film  12   a  of the second substrate  12  are facing inwardly and corresponding to each other; next, a liquid crystal layer  13  is injected between the first substrate  11  and the second substrate  12  (namely between the first alignment film  11   a  and the second alignment film  12   a ), and the liquid crystal layer  13  includes a plurality of liquid crystal molecules  13   a;  and because of an alignment effect of the first alignment film  11   a  of the first substrate  11  and the second alignment film  12   a  of the second substrate  12 , an arrangement of the liquid crystal molecules  13   a  has a pretilt angle θ in the horizontal direction (a horizontal direction of the liquid crystal layer  13 ).       

     As mentioned above, the assembled manufacturing method of the traditional liquid crystal display panel structure  10  of a Fringe Field Switching (FFS) type will cause the liquid crystal molecules  13   a  therein producing a pretilt angle, and then influences the contrast of the liquid crystal display. 
     Hence, it is necessary to provide a liquid crystal display panel structure and a manufacturing method thereof, so as to solve the problems existing in a traditional liquid crystal display panel of the Fringe Field Switching type. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a method which improves a problem that the contrast of a liquid crystal display is decreased due to a rubbing alignment. After the method is used, the contrast of the rubbing alignment liquid crystal display is substantially increased. 
     To achieve the above object, the present invention provides a liquid crystal display panel structure, which comprises:
         a first substrate including at least one first transparent conductive layer and a first alignment film, wherein the first alignment film is formed on an inner surface of the first substrate;   a second substrate disposed corresponding to the first substrate and including at least one second transparent conductive layer and a second alignment film, wherein the second alignment film is formed on an inner surface of the second substrate, and is disposed corresponding to the first alignment film of the first substrate; and   a liquid crystal layer including a plurality of liquid crystal molecules and disposed between the first substrate and the second substrate;   wherein the surfaces of the first alignment film and the second alignment film respectively have a plurality of photo-reactive monomers which fix an orientation of the liquid crystal molecules, so that the orientation of the liquid crystal molecules is horizontal in relation to the liquid crystal layer.       

     In one embodiment of the present invention, the first substrate is an array substrate, and the second substrate is a color filter substrate. 
     In one embodiment of the present invention, the first transparent conductive layer is a pixel electrode layer, and the first alignment film is disposed on the pixel electrode layer. 
     In one embodiment of the present invention, the second transparent conductive layer is an electrostatic shielding layer disposed on a back surface of the second substrate. 
     In one embodiment of the present invention, the first substrate has two of the transparent conductive layers, including of a pixel electrode layer and a common electrode layer, and wherein a passivation layer is disposed between the pixel electrode layer and the common electrode layer. 
     To achieve the above object, the present invention further provides a manufacturing method of a liquid crystal display panel structure, which comprises steps of:
         (a) providing a first substrate, wherein the first substrate includes at least one first transparent conductive layer and a first alignment film, and the first alignment film is formed on a upper surface of the first substrate;   (b) processing a rubbing alignment on the first alignment film of the first substrate;   (c) providing a second substrate, wherein the second substrate includes at least one second transparent conductive layer and a second alignment film, and the second alignment film is formed on a upper surface of the second substrate;   (d) executing a rubbing alignment on the second alignment film of the second substrate;   (e) assembling the first substrate and the second substrate correspondingly, wherein the first alignment film of the first substrate and the second alignment film of the second substrate are facing inwardly and corresponding to each other;   (f) injecting a liquid crystal layer between the first substrate and the second substrate, wherein the liquid crystal layer includes a plurality of liquid crystal molecules and a plurality of photo-reactive monomers; and the liquid crystal molecules are arranged by an alignment effect of the first alignment film of the first substrate and the second alignment film of the second substrate, and each of the liquid crystal molecules has a pretilt angle θ in relation to a horizontal direction of the liquid crystal layer;   (g) executing an electric current conduction process to the first transparent conductive layer of the first substrate and the second transparent conductive layer of the second substrate, so that a longitudinal electric field is formed between the first substrate and the second substrate;   (h) applying an ultraviolet ray exposure when applying the longitudinal electric field, wherein the photo-reactive monomers of the liquid crystal layer are adhered to the surfaces of the first alignment film and the second alignment film, so as to fix an orientation of the liquid crystal molecules of the liquid crystal layer, and to eliminate the pretilt angle of the liquid crystal molecules, until the orientation of the liquid crystal molecules is horizontal in relation to the liquid crystal layer; and   (i) removing the longitudinal electric field and the ultraviolet ray exposure, wherein the orientation of the liquid crystal molecules is kept horizontal.       

     In one embodiment of the present invention, the first substrate is an array substrate, and the second substrate is a color filter substrate. 
     In one embodiment of the present invention, the first transparent conductive layer is a pixel electrode layer, and the first alignment film is disposed on the pixel electrode layer. 
     In one embodiment of the present invention, the second transparent conductive layer is an electrostatic shielding layer disposed on a back surface of the second substrate. 
     In one embodiment of the present invention, the first substrate has two of the transparent conductive layers, including of a pixel electrode layer and a common electrode layer, and wherein a passivation layer is disposed between the pixel electrode layer and the common electrode layer. 
     In one embodiment of the present invention, the electric current conduction process is a direct current conduction process or an alternating current conduction process. 
     To achieve the above object, the present invention further provides a manufacturing method of a liquid crystal display panel structure, which comprises steps of:
         (a) providing a first substrate, wherein the first substrate includes at least one first transparent conductive layer and a first alignment film; the first alignment film is formed on a upper surface of the first substrate; and a plurality of photo-reactive monomers are mixed into the first alignment film;   (b) processing a rubbing alignment on the first alignment film of the first substrate;   (c) providing a second substrate, wherein the second substrate includes at least one second transparent conductive layer and a second alignment film; the second alignment film is formed on a upper surface of the second substrate; and a plurality of photo-reactive monomers are mixed into the second alignment film;   (d) executing a rubbing alignment on the second alignment film of the second substrate;   (e) assembling the first substrate and the second substrate correspondingly, wherein the first alignment film of the first substrate and the second alignment film of the second substrate are facing inwardly and corresponding to each other;   (f) injecting a liquid crystal layer between the first substrate and the second substrate, wherein the liquid crystal layer includes a plurality of liquid crystal molecules; and the liquid crystal molecules are arranged by an alignment effect of the first alignment film of the first substrate and the second alignment film of the second substrate, and each of the liquid crystal molecules has a pretilt angle θ in relation to a horizontal direction of the liquid crystal layer;   (g) executing an electric current conduction process to the first transparent conductive layer of the first substrate and the second transparent conductive layer of the second substrate, so that a longitudinal electric field is formed between the first substrate and the second substrate;   (h) applying an ultraviolet ray exposure when applying the longitudinal electric field, wherein the photo-reactive monomers of the first alignment film of the first substrate and the second alignment film of the second substrate are reacted thereon respectively, so as to fix an orientation of the liquid crystal molecules of the liquid crystal layer, and to eliminate the pretilt angle of the liquid crystal molecules, until the orientation of the liquid crystal molecules is horizontal in relation to the liquid crystal layer; and   (i) removing the longitudinal electric field and the ultraviolet ray exposure, wherein the orientation of the liquid crystal molecules is kept horizontal.       

     In one embodiment of the present invention, the first substrate is an array substrate, and the second substrate is a color filter substrate. 
     In one embodiment of the present invention, the first transparent conductive layer is a pixel electrode layer, and the first alignment film is disposed on the pixel electrode layer. 
     In one embodiment of the present invention, the second transparent conductive layer is an electrostatic shielding layer disposed on a back surface of the second substrate. 
     In one embodiment of the present invention, the first substrate has two of the transparent conductive layers, including of a pixel electrode layer and a common electrode layer, and wherein a passivation layer is disposed between the pixel electrode layer and the common electrode layer. 
     In one embodiment of the present invention, the electric current conduction process is a direct current conduction process or an alternating current conduction process. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A-1C  are assembled schematic views of a traditional liquid crystal display panel structure; 
         FIGS. 2A-2F  are assembled schematic views of a liquid crystal display panel structure according to a first embodiment of the present invention; 
         FIGS. 3A-3F  are assembled schematic views of a liquid crystal display panel structure according to a second embodiment of the present invention; and 
         FIG. 4  is an assembled schematic view of a liquid crystal display panel structure according to a third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The foregoing objects, features, and advantages adopted by the present invention can be best understood by referring to the following detailed description of the preferred embodiments and the accompanying drawings. Furthermore, the directional terms described in the present invention, such as upper, lower, front, rear, left, right, inside, outer, side, etc., are only directions with reference to the accompanying drawings, so that the used directional terms are used to describe and understand the present invention, but the present invention is not limited thereto. In the drawings, units with similar structures use the same numerals. 
     Refer now to  FIGS. 2A-2F , which are assembled schematic views of a liquid crystal display panel structure according to a first embodiment of the present invention. A liquid crystal display panel structure  20  according to the present invention belongs to a liquid crystal display panel of a Fringe Field Switching (FFS) type, and mainly comprises an array substrate, a color filter substrate, and a liquid crystal layer. An assembled manufacturing method of the liquid crystal display panel structure  20  comprises the following steps of:
         (a) Refer to  FIG. 2A , providing a first substrate  21 , wherein the first substrate  21  includes a first transparent conductive layer  21   a  and a first alignment film  21   b,  and the first alignment film  21   b  is formed on a upper surface of the first substrate  21 ;   (b) Continue to refer to  FIG. 2A , processing a rubbing alignment on the first alignment film  21   b  of the first substrate  21 ;   (c) Refer to  FIG. 2B , providing a second substrate  22 , wherein the second substrate  22  includes a second transparent conductive layer  22   a  and a second alignment film  22   b,  and the second alignment film  22   b  is formed on a upper surface of the second substrate  22 ;   (d) Continue to refer to  FIG. 2B , executing a rubbing alignment on the second alignment film  22   b  of the second substrate  22 ;   (e) Refer to  FIG. 2C , assembling the first substrate  21  and the second substrate  22  correspondingly, wherein the first alignment film  21   b  of the first substrate  21  and the second alignment film  22   b  of the second substrate  22  are facing inwardly and corresponding to each other; that is they respectively define and form inner surfaces of the first substrate  21  and the second substrate  22 ;   (f) Continue to refer to  FIG. 2C , injecting a liquid crystal layer  23  between the first substrate  21  and the second substrate  22  (namely between the first alignment film  21   b  of the first substrate  21  and the second alignment film  22   b  of the second substrate  22 ), wherein the liquid crystal layer  23  includes a plurality of liquid crystal molecules  23   a  and a plurality of photo-reactive monomers  24 ; and the liquid crystal molecules  23   a  are arranged by an alignment effect of the first alignment film  21   b  of the first substrate  21  and the second alignment film  22   b  of the second substrate  22 , and each of the liquid crystal molecules  23   a  has a pretilt angle θ in relation to a horizontal direction (a horizontal direction of a vertical cross section of the liquid crystal layer  23 );   (g) Refer to  FIG. 2D , executing an electric current conduction process to the first transparent conductive layer  21   a  of the first substrate  21  and the second transparent conductive layer  22   a  of the second substrate  22  (a direct current is used in this embodiment), so that a longitudinal electric field is formed between the first substrate  21  and the second substrate  22 ;   (h) Refer to  FIG. 2E , applying a ultraviolet ray exposure when applying the longitudinal electric field, wherein the photo-reactive monomers  24  of the liquid crystal layer  23  are produced a phase separation, and adhered to the surfaces of the first alignment film  21   b  and the second alignment film  22   b,  so as to fix an orientation of the liquid crystal molecules  23   a  of the liquid crystal layer  23 , and to eliminate the pretilt angle of the liquid crystal molecules  23   a,  until the orientation of the liquid crystal molecules  23   a  is horizontal in relation to the liquid crystal layer  23  thereby; and   (i) Refer to  FIG. 2F , removing the longitudinal electric field and the ultraviolet ray exposure, wherein the orientation of the liquid crystal molecules  23   a  is kept horizontal (approaching horizontal).       

     By the above-mentioned assembled manufacturing steps, a liquid crystal display panel structure  20  according to the present invention (as shown in  FIG. 2F ) is therefore accomplished, and comprises: a first substrate  21 , a second substrate  22 , and a liquid crystal layer  23 , wherein the first substrate  21  includes a first transparent conductive layer  21   a  and a first alignment film  21   b,  and the first alignment film  21   b  is formed on an inner surface of the first substrate  21 ; the second substrate  22  disposed corresponding to the first substrate  21  includes a second transparent conductive layer  22   a  and a second alignment film  22   b,  and the second alignment film  22   b  is formed on an inner surface of the second substrate  22  and is corresponding to the first alignment film  21   b  of the first substrate  21 ; the liquid crystal layer  23  including a plurality of liquid crystal molecules  23   a  is disposed between the first substrate  21  and the second substrate  22  (namely between the first alignment film  21   b  of the first substrate  21  and the second alignment film  22   b  of the second substrate  22 ); and the surfaces of the first alignment film  21   b  and the second alignment film  22   b  respectively has a plurality of photo-reactive monomers  24  which can fix the orientation of the liquid crystal molecules  23   a,  so that the orientation of the liquid crystal molecules  23   a  is horizontal. 
     Preferably, the first substrate  21  is an array substrate, and the second substrate  22  is a color filter substrate. 
     Preferably, the first transparent conductive layer  21   a  is a pixel electrode layer, and the first alignment film  21   b  is disposed on the pixel electrode layer; and the second transparent conductive layer  22   a  is an electrostatic shielding layer disposed on a back surface of the second substrate  22 . Additionally, in this embodiment, the number of the transparent conductive layers  21   a,    22   a  of the first substrate  21  and the second substrate  22  both are one (at least one), but in other possible embodiments of the present invention, the first substrate  21  and the second substrate  22  can include more than one of the transparent conductive layer. 
     Furthermore, the electric current conduction process can be a direct current (DC) conduction process or an alternating current (AC) conduction process, and is not limited in the present invention. 
     As mentioned above, in the foregoing assembled manufacturing steps, and in the liquid crystal display panel structure  20  according to the present invention, because the liquid crystal layer  23  includes the photo-reactive monomers  24 , so that in the following electric current conduction and ultraviolet ray exposure processes, the photo-reactive monomers  24  can be adhered to the first alignment film  21   b  and the second alignment film  22   b,  and can fix the orientation of the liquid crystal molecules  23   a  to be horizontal, so as to improve the contrast of the liquid crystal display of the Fringe Field Switching type. 
     Refer now to  FIGS. 3A-3F , which are assembled schematic views of a liquid crystal display panel structure according to a second embodiment of the present invention. An assembled manufacturing method of the liquid crystal display panel structure  30  according to the second embodiment of the present invention comprises the following steps of:
         (a) Providing a first substrate  31 , wherein the first substrate  31  includes a first transparent conductive layer  31   a  and a first alignment film  31   b;  the first alignment film  31   b  is formed on a upper surface of the first substrate  31 ; and a plurality of photo-reactive monomers  34  are mixed into the first alignment film  31   b;      (b) Processing a rubbing alignment on the first alignment film  31   b  of the first substrate  31 ;   (c) Providing a second substrate  32 , wherein the second substrate  32  includes a second transparent conductive layer  32   a  and a second alignment film  32   b;  the second alignment film  32   b  is formed on a upper surface of the second substrate  32 ; and a plurality of photo-reactive monomers  34  are mixed into the second alignment film  32   b;      (d) Executing a rubbing alignment on the second alignment film  32   b  of the second substrate  32 ;   (e) Assembling the first substrate  31  and the second substrate  32  correspondingly, wherein the first alignment film  31   b  of the first substrate  31  and the second alignment film  32   b  of the second substrate  32  are facing inwardly and corresponding to each other; that is they respectively define and form inner surfaces of the first substrate  31  and the second substrate  32 ;   (f) Injecting a liquid crystal layer  33  between the first substrate  31  and the second substrate  32  (namely between the first alignment film  31   b  of the first substrate  31  and the second alignment film  32   b  of the second substrate  32 ), wherein the liquid crystal layer  33  includes a plurality of liquid crystal molecules  33   a;  and the liquid crystal molecules  33   a  are arranged by an alignment effect of the first alignment film  31   b  of the first substrate  31  and the second alignment film  32   b  of the second substrate  32 , and each of the liquid crystal molecules  33   a  has a pretilt angle θ in relation to a horizontal direction (a horizontal direction of a vertical cross section of the liquid crystal layer  33 );   (g) Executing an electric current conduction process to the first transparent conductive layer  31   a  of the first substrate  31  and the second transparent conductive layer  32   a  of the second substrate  32  (an alternating current is used in this embodiment), so that a longitudinal electric field is formed between the first substrate  31  and the second substrate  32 ;   (h) Applying an ultraviolet ray exposure when applying the longitudinal electric field, wherein the photo-reactive monomers  34  of the first alignment film  31   b  of the first substrate  31  and the second alignment film  32   b  of the second substrate  32  are reacted thereon respectively, and are bound with main chains or side chains of the liquid crystal molecules  33   a  of the liquid crystal layer  33 , so as to fix an orientation of the liquid crystal molecules  33   a  of the liquid crystal layer  33 , and to eliminate the pretilt angle of the liquid crystal molecules  33   a,  until the orientation of the liquid crystal molecules  33   a  is horizontal in relation to the liquid crystal layer  33  thereby; and   (i) Removing the longitudinal electric field and the ultraviolet ray exposure, wherein the orientation of the liquid crystal molecules  33   a  is kept horizontal (approaching horizontal).       

     As mentioned above, in the foregoing assembled manufacturing steps, and in the liquid crystal display panel structure  30  according to the present invention, because the photo-reactive monomers  34  are mixed into the first alignment film  31   b  and the second alignment film  32   b,  so that in the following electric current conduction and ultraviolet ray exposure processes, the photo-reactive monomers  34  can fix the orientation of the liquid crystal molecules  33   a  to be horizontal, so as to improve the contrast of the liquid crystal display of the Fringe Field Switching type. 
     Referring now to  FIG. 4 , which is an assembled schematic view of a liquid crystal display panel structure according to a third embodiment of the present invention. A liquid crystal display panel structure according to the third embodiment of the present invention is similar to the liquid crystal display panel structure according to the second embodiment of the present invention, thus using similar terms and numerals to the foregoing embodiment, the difference between the liquid crystal display panel structure  30 ′ according to the third embodiment of the present invention and the liquid crystal display panel structure  30  according to the second embodiment of the present invention is that: the first substrate  31 ′ has two of the transparent conductive layers, wherein the first transparent conductive layer  31   a  is a pixel electrode layer; another transparent conductive layer  31   c  is a common electrode layer; and wherein a passivation layer  31   d  is disposed between the pixel electrode layer and the common electrode layer. Therefore, when executing the electric current conduction process, the two of the transparent conductive layers (the pixel electrode layer and the common electrode layer) are applied to the voltage of the same polarity, namely the pixel electrode layer and the common electrode layer are parallel connection in an electric circuit, so as to further increase the effect of the longitudinal electric field when conducting the electric current. 
     The present invention has been described with preferred embodiments thereof and it is understood that many changes and modifications to the described embodiments can be carried out without departing from the scope and the spirit of the invention that is intended to be limited only by the appended claims.