Patent Publication Number: US-2018031905-A1

Title: Color filter substrate, method for manufacturing color filter substrate, and liquid crystal display panel

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the priority of Chinese patent application CN201510625950.8, entitled “Color Filter Substrate, Method for Manufacturing Color Filter Substrate, and Liquid Crystal Display Panel” and filed on Sep. 28, 2015, the entirety of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present disclosure relates to the technical field of liquid crystal display device, and particularly to a color filter substrate, a method for manufacturing color filter substrate, and a liquid crystal display panel. 
     BACKGROUND OF THE INVENTION 
     With continuous development of liquid crystal display technology in recent years, there are many display technologies which can provide a wide viewing-angle display effect, such as In-Plate Swiching (IPS) technology and Fringe Field Switching (FFS) technology. According to the FFS technology and the IPS technology, not only the wide viewing-angle can be realized, but also other desirable characteristics of a display device can be realized, such as a high light transmittance, a high picture contrast, a high brightness, and a low color shift. 
     The FFS technology and the IPS technology are both realized through a horizontal electric field control mode.  FIG. 1  schematically shows a structure of a liquid crystal display panel of an IPS mode in the prior art. The liquid crystal display panel comprises a color filter substrate  110  and an array substrate  120  that are arranged facing each other, and a liquid crystal layer  130  that is arranged between the color filter substrate  110  and the array substrate  120 . A black matrix  113  and a color filter layer  115  are arranged on an inner surface of the color filter substrate, and in general, a protection layer  117  is arranged on the black matrix and the color filter layer. A common electrode  123  and a pixel electrode  125  are formed on an inner surface of the array substrate  120 , so that liquid crystal molecules in the liquid crystal layer can deflect under control of the horizontal electric field. 
     During manufacturing procedure or using procedure of a liquid crystal display device, electrostatic charges would accumulate on the color filter substrate. When the electrostatic charges accumulate thereon to a certain extent, an electrostatic field can be formed. The electrostatic field would bring about interference on the liquid crystal molecules in the liquid crystal layer, and thus an abnormal image would be displayed on the display device. 
     In order to prevent the influence of electrostatic charge on the liquid crystal layer, a transparent conductive Indium tin oxide (ITO) layer  119  is generally formed on an upper surface of the color filter substrate  110  through vacuum sputtering technology. Moreover, a thickness of the ITO layer should be increased so as to reduce a surface resistance thereof and obtain a better conductive effect. However, if the thickness of the ITO layer is increased, a light transmittance of the ITO layer would be reduced apparently. As shown in  FIG. 2 , when the thickness of the ITO layer is 200 Å, the surface resistance thereof is 2000Ω, and the transmittance of light with a wavelength of 400 nm is 98%; when the thickness of the ITO layer is increased to 400 Å, the surface resistance thereof is reduced to 500Ω, but the transmittance of light with a wavelength of 400 nm decreases to 80%. As a result, the overall brightness of the liquid crystal display panel would be reduced to a large extent. 
     Therefore, a color filter substrate on which an electrostatic charge conduction layer with a low surface resistance and a high light transmittance is formed is needed. 
     SUMMARY OF THE INVENTION 
     The present disclosure aims to solve the technical problem that when a surface resistance of an electrostatic charge conduction layer of a color filter substrate decreases, a light transmittance thereof is excessively reduced in the prior art. 
     The present disclosure provides a color filter substrate, which comprises: 
     a baseplate; 
     a black matrix layer, which comprises a frame that is formed on a first surface of the baseplate; and 
     a metal grid layer, which comprises a grid line that is formed on a second surface of the baseplate opposite to the first surface thereof, wherein the grid line of the metal grid layer is arranged corresponding to the frame of the black matrix layer, and a projection of the grid line of the metal grid layer on the baseplate falls inside a projection of the frame of the black matrix layer on the baseplate. 
     According to one embodiment, the grid line of the metal grid layer forms a plurality of grid units, which are arranged corresponding to a plurality of rectangular units of the black matrix layer one-to-one. 
     According to one embodiment, the grid line of the metal grid layer forms a plurality of grid units, and each grid unit is arranged corresponding to at least one rectangular unit of the black matrix layer. 
     According to one embodiment, a width of the grid line of the metal grid layer is less than a width of the frame of the black matrix layer. 
     The present disclosure provides a method for manufacturing a color filter substrate, which comprises following steps: 
     providing a baseplate; 
     forming a frame of a black matrix layer on a first surface of the baseplate; and 
     forming a grid line of a metal grid layer on a second surface of the baseplate opposite to the first surface thereof, such that the grid line of the metal grid layer is arranged corresponding to the frame of the black matrix layer, and a projection of the grid line of the metal grid layer on the baseplate falls inside a projection of the frame of the black matrix layer on the baseplate. 
     According to one embodiment, the step of forming a grid line of a metal grid layer on a second surface of the baseplate opposite to the first surface thereof comprises following sub steps: 
     coating the second surface of the baseplate with a photoresist; 
     exposing and developing the photoresist with a photomask so as to form a gap region and a residual region; 
     depositing a metal film on the gap region and the residual region; and 
     removing the photoresist on the residual region and the metal film that is deposited on the residual region, and reserving the metal film that is deposited on the gap region through a developing technology so as to obtain the metal grid layer. 
     According to one embodiment, the metal grid layer comprises a plurality of grid units, which are arranged corresponding to a plurality of rectangular units of the black matrix layer one-to-one. 
     According to one embodiment, a width of the gap region is less than a width of the frame of the black matrix layer. 
     The present disclosure further provides a liquid crystal display panel, which comprises: 
     the aforesaid color filter substrate; and 
     an array substrate, which is arranged facing the color filter substrate, wherein the metal grid layer is connected with a ground end of the array substrate. 
     In the color filter substrate according to the present disclosure, the metal grid layer serves as an electrostatic charge conduction layer, and thus the electrostatic charge conduction layer has a high light transmittance and a low surface resistance. Moreover, the metal grid layer has a good bendability and thus can be used in a curved substrate. Furthermore, in traditional Indium tin oxide (ITO) layer, indium (In) is a rare metal element, and thus there is a risk of raw material shortage. According to the present disclosure, the metal grid layer can be made of common metal materials, such as tungsten (W), titanium (Ti), molybdenum (Mo), or copper (Cu), and thus has a good practical applicability. 
     Other features and advantages of the present disclosure will be further explained in the following description, and partially become self-evident therefrom, or be understood through the embodiments of the present disclosure. The objectives and advantages of the present disclosure will be achieved through the structure specifically pointed out in the description, claims, and the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings provide further understandings of the present disclosure and constitute one part of the description. The drawings are used for interpreting the present disclosure together with the embodiments, not for limiting the present disclosure. In the drawings: 
         FIG. 1  schematically shows a structure of a liquid crystal display panel of an IPS mode in the prior art; 
         FIG. 2  schematically shows a relationship among a thickness of an ITO layer, a surface resistance, and a light transmittance thereof in the prior art; 
         FIG. 3  schematically shows a sectional view of a color filter substrate according to embodiment 1 of the present disclosure; 
         FIG. 4  schematically shows a structure of a black matrix and a metal grid according to embodiment 1 of the present disclosure; 
         FIG. 5  schematically shows another structure of a black matrix and a metal grid according to embodiment 1 of the present disclosure; 
         FIG. 6  schematically shows a third structure of a black matrix and a metal grid according to embodiment 1 of the present disclosure; 
         FIG. 7  is a flow chart of a method for manufacturing a color filter substrate according to embodiment 2 of the present disclosure; 
         FIG. 8 a    schematically shows a structure of a color filter substrate after a photoresist is coated thereon according to embodiment 2 of the present disclosure; 
         FIG. 8 b    schematically shows a structure of the color filter substrate after exposing and developing procedures according to embodiment 2 of the present disclosure; 
         FIG. 8 c    schematically shows a structure of the color filter substrate after a metal film is deposited thereon according to embodiment 2 of the present disclosure; 
         FIG. 8 d    schematically shows a structure of the color filter substrate after a second developing procedure according to embodiment 2 of the present disclosure; and 
         FIG. 9  schematically shows a structure of a liquid crystal display panel according to embodiment 3 of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The present disclosure will be illustrated in detail hereinafter in combination with the accompanying drawings to enable the purpose, technical solutions, and advantages of the present disclosure more clear. 
     The embodiment of the present disclosure will be explained in detail hereinafter with reference to the accompanying drawings. It can be understood that, the preferred embodiments described herein are only used for explaining and illustrating, rather than restricting, the present disclosure. The technical features in the embodiments can be combined together in any manner, as long as there is no conflict. 
     Embodiment 1 
     The present embodiment provides a color filter substrate. As shown in  FIG. 3 , the color filter substrate  300  comprises a baseplate  310 , and a black matrix layer  320  and a metal grid layer  330  that are arranged on two sides of the baseplate  310  respectively. Specifically, the black matrix layer  320  comprises a frame  321  that is formed on a first surface of the baseplate  310 , and the metal grid layer  330  comprises a grid line  331  that is formed on a second surface of the baseplate opposite to the first surface thereof. Compared with traditional ITO layer, the metal grid layer  330  has a low impedance. When electrostatic charges accumulate on the color filter substrate  300 , the electrostatic charges can be conducted by the metal grid layer  330 . 
       FIG. 4  schematically shows a structure of a metal grid and a black matrix of the color filter substrate. As shown in  FIG. 4 , the black matrix layer comprises a plurality of rectangular units BM 11  to BM 23  formed by the frame  321 , and the metal grid layer comprises a plurality of grid units M 11  to M 23  formed by the grid line  331 . 
     Since the grid line  331  is a non-transparent metal line, the grid line  331  should be arranged overlapping with the frame  321  as much as possible so as to ensure a light transmittance of the color filter substrate. That is, the positions of the grid units M 11  to M 23  should be arranged in a reasonable manner so that a projection of the grid line of the metal grid layer on the baseplate falls inside a projection of the frame of the black matrix layer on the baseplate. In this manner, a light transmission region of the rectangular units BM 11  to BM 23  cannot be shaded by the grid line  331 . According to the example as shown in  FIG. 4 , the grid units M 11  to M 23  are preferably arranged corresponding to the rectangular units BM 11  to BM 23  one-to-one. 
     However, if the grid line is arranged overlapping with the frame of the black matrix, moire fringe would be generated when light that is emitted by a backlight module of a liquid crystal display device passes through the metal grid layer and the black matrix layer. As a result, a quality of an image displayed on the display device would be reduced. In order to eliminate the moire fringe, a width of the grid line  331  is arranged less than a width of the frame  321  of the black matrix. In general, the width of the frame of the black matrix is larger than 5 and thus the width of the grid line  331  is preferably set in a range from 150 nm to 5 μm. 
     Alternatively, each grid unit can also be arranged corresponding to at least one rectangular unit of the black matrix layer. According to the example as shown in  FIG. 5 , the grid unit M 11  is arranged corresponding to a rectangle that is constituted by the rectangular units BM 11  and BM 12 . Similarly, according to the example as shown in  FIG. 6 , the grid unit M 11  is arranged corresponding to a rectangle that is constituted by the rectangular units BM 11 , BM 12 , BM 21 , and BM 22 . In the metal grid layer as shown in  FIGS. 5 and 6 , part of grid line can be saved. Therefore, a manufacturing difficulty of the metal grid can be reduced, the metal raw material can be saved, and a manufacturing cost thereof can be reduced accordingly. 
     It can be understood that, the abovementioned shapes of the grid units are only examples, and are not used for restricting the present disclosure. The grid units with other shapes can be designed by those skilled in the art according to actual needs. 
     In a word, in the color filter substrate according to the present embodiment, the metal grid layer serves as an electrostatic charge conduction layer, and thus the electrostatic charge conduction layer has a high light transmittance and a low surface resistance. Moreover, the metal grid layer has a good bendability and thus can be used in a curved substrate. Furthermore, in traditional Indium tin oxide (ITO) layer, indium (In) is a rare metal element, and thus there is a risk of raw material shortage. According to the present embodiment, the metal grid layer can be made of common metal materials, such as tungsten (W), titanium (Ti), molybdenum (Mo), or copper (Cu), and thus has a good practical applicability. 
     Embodiment 2 
     The present embodiment provides a method for manufacturing a color filter substrate. The method mainly comprises a step of forming a metal grid layer on a baseplate. The method will be illustrated in detail below with reference to  FIGS. 7, and 8   a  to  8   d.    
     In step S 701 , a baseplate is provided, and then the baseplate is washed and baked. In step S 702 , a frame  802  of a black matrix layer is formed on a first surface of the baseplate  801 . As shown in  FIG. 8   a,  in step S 703 , a second surface of the baseplate is coated with a photoresist  803 . Then, the photoresist is dried in a low pressure so that the photoresist can be fully fixed. The photoresist  803  is preferably a positive photoresist. For example, Polymer film on array (PFA) that is prepared by Japan Synthetic Rubber Co (JSR) can be used. A coating accuracy of the photoresist should reach 150 nm, and a thickness thereof ranges from 1.5 μm to 5 μm. 
     Then, in step S 704 , the photoresist  803  is exposed and developed with a photomask, so that a gap region  803   a  and a residual region  803   b  as shown in  FIG. 8 b    can be formed. The pattern of the photomask corresponds to the rectangular units of the black matrix. 
     Next, in step S 705 , a metal film is vapor plated on the gap region  803   a  and the residual region  803   b  through Physical Vapor Deposition (PVD) method. A thickness of the metal film ranges from 10 nm to 100 nm. Since there is a large height difference between a top of a metal film  804   a  on the gap region and a top of a metal film  804   b  on the residual region, after the deposition procedure, the metal film  804   a  on the gap region and the metal film  804   b  on the residual region are not connected together. 
     At last, in step S 706 , the photoresist and the metal film  804   b  on the residual region  803   b  are removed through a developing procedure, and the metal film  804   a  on the gap region is reserved, so that the grid line of the metal grid layer can be obtained, as shown in  FIG. 8   d.  The metal film can be made of common metal materials, such as tungsten (W), titanium (Ti), molybdenum (Mo), or copper (Cu). 
     The grid line of the metal grid layer can be formed on the second surface of the baseplate through the aforesaid steps  5703  to  5706 . It should be noted that, in step S 704 , the pattern of the photomask corresponding to the rectangular units of the black matrix means that, the gap region  803   a  that is formed by the photomask corresponds to the frame  321  of the black matrix, so that a projection of the gap region  803   a  on the baseplate falls inside a projection of the frame of the black matrix layer on the baseplate. The metal grid layer that is obtained in step S 706  comprises a plurality of grid units, which are arranged corresponding to a plurality of rectangular units of the black matrix layer one-to-one (as shown in  FIG. 4 ), or corresponding to at least one rectangular unit of the black matrix layer (as shown in  FIG. 5  or  FIG. 6 ). The metal grid layer has a high light transmittance and a low surface resistance. The width of the gap region  803   a  is less than the width of the frame of the black matrix layer. Preferably, the width of the gap region  803   a  is set in a range from 150 nm to 5 μm. 
     It can be seen that, according to the present embodiment, the method for manufacturing the color filter substrate is simple, and the expensive high temperature sputtering equipment which must be used during ITO layer deposition in the prior art is not used herein. Therefore, the method has a good practical applicability. 
     Embodiment 3 
     The present embodiment provides a liquid crystal display panel. Preferably, the liquid crystal display panel is driven in an FFS mode or an IPS mode. As shown in  FIG. 9 , the liquid crystal display panel comprises a color filter substrate  910  and an array substrate  920  that are arranged facing each other. A liquid crystal layer  930  is arranged between the color filter substrate  910  and the array substrate  920 . The color filter substrate  910  is made by the aforesaid method. 
     Specifically, a black matrix layer  913  and a color filter layer  915  are arranged on an inner surface of the color filter substrate  910 , and a metal grid layer  904  is arranged on an outer surface of the color filter substrate  910 . The grid line of the metal grid layer  904  is arranged corresponding to a frame of the black matrix, and the specific arrangement method thereof is the same as that in embodiment 1. The details of which are no longer repeated here. Here, the “inner surface” of the color filter substrate  910  refers to a surface thereof facing the array substrate  920 , and the “outer surface” of the color filter substrate  910  refers to a surface thereof far from the array substrate  920 . 
     A common electrode  923  and a pixel electrode  925  are formed on an inner surface of the array substrate  920 , so that liquid crystal molecules in the liquid crystal layer can deflect under control of a horizontal electric field. Here, the “inner surface” of the array substrate  920  refers to a surface thereof facing the color filter substrate  910 . 
     The array substrate  920  is provided with a ground end  921 , and the metal grid layer  904  is connected with the ground end  921  through a connector  940 . When electrostatic charges accumulate on the color filter substrate  910 , the electrostatic charges can be released by the metal grid layer  904  through the ground end  921 . In this manner, it can be ensured that the liquid crystal molecules in the liquid crystal layer are not interfered by the electrostatic field. 
     Moreover, since the metal grid layer  904  has a high light transmittance, according to the present embodiment, the liquid crystal display panel can have a higher brightness and a better display effect. 
     The above embodiments are described only for better understanding, rather than restricting, the present disclosure. Any person skilled in the art can make amendments to the implementing forms or details without departing from the spirit and scope of the present disclosure. The protection scope of the present disclosure shall be determined by the scope as defined in the claims.