Patent Publication Number: US-2020292874-A1

Title: Display panel and display device

Description:
TECHNICAL FIELD 
     The present invention relates to a display panel and a display device. 
     BACKGROUND ART 
     Liquid crystal display devices whose shape of a display region is formed into a non-rectangular shape, such as a circular shape, have hitherto been known. In such a liquid crystal display device, pixels located at a boundary portion between a display region of a curved shape and a non-display region include both a display region and a non-display region. Therefore, there are problems that smooth display cannot be achieved at the curved line portion, and the color balance is liable to be lost due to occurrence of coloring of a specific color in the pixels located at the boundary portion. 
     To solve such problems, in a liquid crystal display device described in JP 5112961B, pixels located at the boundary portion of the curved line portion are classified into three types (a normal picture element, an aperture ratio adjustment picture element, and a non-lighting picture element) according to the size of a non-display region included in each pixel, and the size of a light blocking portion to be provided in each pixel is adjusted according to the classification. Specifically, the normal picture element is configured such that the entire region thereof is lighted without providing a light blocking portion, the aperture ratio adjustment picture element is configured such that a partial region thereof is lighted by providing a light blocking portion in another partial region thereof, and the non-lighting picture element is configured to be in a non-lighting state by providing a light blocking portion in its entire region. 
     SUMMARY OF INVENTION 
     However, it is the case with the liquid crystal display device described in JP 5112961B that smooth display is not invariably achieved at the curved line portion, such as in a situation where the entire region of the non-lighting picture element is configured to be a non-lighting state despite the fact that the non-lighting picture element includes both the display region and the non-display region. 
     The one embodiment of the present invention is made in view of the circumstances as described above, and has an object to achieve smooth display of a shape of a peripheral portion of a display region while maintaining a satisfactory color balance, even even with a display region including a peripheral portion including a curved line portion. 
     (1) One embodiment of the present invention is a display panel including a plurality of display pixels arrayed in a surface of a substrate, 
     wherein a boundary between a display region and a non-display region has a shape including a curved line portion, 
     each of the plurality of display pixels includes colored pixels of n colors including different colored portions, and 
     in a case where a colored pixel being one of the colored pixels including the curved line portion and being located at an outermost end side in an array direction is defined as a display end pixel, the array direction being a direction in which the colored pixels are repeatedly arrayed with the colored pixels of the n colors being a unit, 
     a first light blocking portion is provided in line with a shape of the curved line portion in the display end pixel, and 
     a second light blocking portion having a shape and a size substantially the same as a shape and a size of the first light blocking portion is provided in each of the colored pixels of (n−1) colors consecutively arrayed next to the display end pixel toward the display region in the array direction. 
     (2) One embodiment of the present invention is the display panel, in addition to (1) described above, wherein the display end pixel includes display end pixels, and the first light blocking portion is provided in all of the display end pixels. 
     (3) One embodiment of the present invention is the display panel, in addition to (1) or (2) described above, wherein each of the plurality of display pixels includes the colored pixels of three colors including colored portions of red, green, and blue. 
     (4) One embodiment of the present invention is the display panel, in addition to (3) described above, wherein each of the plurality of display pixels includes the colored pixels of four colors further including a colored portion of white or yellow. 
     (5) One embodiment of the present invention is the display panel, in addition to any one of (1) to (4) described above, wherein each of the colored pixels has substantially the same shape and size. 
     (6) One embodiment of the present invention is the display panel, in addition to any one of (1) to (5) described above, wherein the first light blocking portion and the second light blocking portion are made of a light blocking material formed on the substrate. 
     (7) One embodiment of the present invention is the display panel, in addition to any one of (1) to (6) described above, wherein the display panel is a liquid crystal panel using liquid crystals. 
     (8) One embodiment of the present invention is a display device including: the display panel of any one of (1) to (7) described above; and an illumination device configured to emit light to be used for display to the display panel. 
     Advantageous Effects of Invention 
     According to one embodiment of the present invention, smooth display of a shape of a peripheral portion of a display region can be achieved while maintaining a satisfactory color balance, even with a display region including a peripheral portion including a curved line portion. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of a liquid crystal display device according to a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of a liquid crystal panel of  FIG. 1  taken along the line II-II. 
         FIG. 3  is an enlarged view of a border line portion III of the liquid crystal panel of  FIG. 1 . 
         FIG. 4  is an enlarged view of a liquid crystal panel according to a first comparative example, at a position of a border line portion III of  FIG. 1 . 
         FIG. 5  is an enlarged view of a liquid crystal panel according to a second comparative example, at a position of a border line portion III of  FIG. 1 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     A first embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 3 . The present embodiment exemplifies a liquid crystal display device  100  including a liquid crystal panel  10 . Note that the X axis, the Y axis, and the Z axis are illustrated in a part of the drawings, and each axial direction is illustrated to be a common direction in each drawing. The +Z-axis direction (liquid crystal panel  10  side) herein represents the front side of the liquid crystal display device  100 , and its opposite side (−Z-axis direction) represents the back side. 
     As illustrated in  FIG. 1 , the liquid crystal display device  100  (one example of a display device) includes the liquid crystal panel  10  (one example of a display panel) whose outer shape in a plan view includes a curved line portion, and an illumination device that is disposed on the back side of the liquid crystal panel  10  and emits light to be used for display to the liquid crystal panel  10 . The central portion of the liquid crystal panel  10  is defined as a display region A 1  in which an image is displayed. A frame-like outer peripheral portion surrounding the display region A 1  is defined as a non-display region A 2  in which an image is not displayed. Ideally, the boundary between the display region A 1  and the non-display region A 2  has a shape including a curved line portion L 2  as indicated by the one-dot chain line of  FIG. 1 , and specifically includes a straight line portion L 1  that extends along the X-axis direction and the curved line portion L 2  that connects both ends of the straight line portion L 1 . 
     In the above-described non-display region A 2  on the straight line portion L 1  side, an IC chip  12  and a flexible substrate  14  are mounted. The IC chip  12  is an electronic component for driving the liquid crystal panel  10 . The flexible substrate  14  is a substrate for connecting a control substrate  16 , which supplies various input signals from the outside to the IC chip  12 , to the liquid crystal panel  10 . 
     As illustrated in the cross-sectional view of  FIG. 2 , the liquid crystal panel  10  includes a pair of substrates  20  and  30 , and a liquid crystal layer  18  including liquid crystal molecules that change its optical characteristics according to application of an electric field. Both the substrates  20  and  30  constituting the liquid crystal panel  10  are bonded together by a sealant  40  in such a manner that a cell gap as large as the thickness of the liquid crystal layer  18  is maintained therebetween. The sealant  40  is disposed to surround the display region A 1 . Of both the substrates  20  and  30 , the substrate  20  located on the front side (front surface side) serves as a CF substrate (counter substrate)  20 , and the substrate  30  located on the back side (back surface side) serves as an array substrate (active matrix substrate)  30 . Alignment films  10 A and  10 B for aligning liquid crystal molecules included in the liquid crystal layer  18  are formed on the inner surface side of both the substrates  20  and  30 , respectively. Polarizers  10 C and  10 D are respectively bonded to the outer surface side of glass substrates  20 A and  30 A that respectively constitute both the substrates  20  and  30 . 
     Next, a configuration inside the display region A 1  in the array substrate  30  and the CF substrate  20  will be described. An operation mode of the liquid crystal panel  10  according to the present embodiment is a Fringe Field Switching (FFS) mode. As illustrated in  FIG. 2 , pixel electrodes  34  and common electrodes  35  are formed together on the array substrate  30  side. Each pixel electrode  34  and each common electrode  35  interpose an insulating film  39  so that the pixel electrode  34  and the common electrode  35  are disposed in different layers. On the array substrate  30 , thin film transistors (TFTs)  32  each serving as a switching element and the pixel electrodes  34  connected to respective TFTs  32  are arrayed in a matrix shape in a plan view. Through use of the potential of the pixel electrode  34 , the electric field to be applied to the liquid crystal layer  18  is controlled, the alignment state of the liquid crystal molecules is appropriately switched, and the liquid crystal panel  10  is thereby driven. 
     On the inner surface side (liquid crystal layer  18  side) of the glass substrate  20 A constituting the CF substrate  20 , as illustrated in  FIG. 2 , color filters are formed in line. The color filters are disposed in a matrix shape at positions to overlap respective pixel electrodes  34  of the array substrate  30  in a plan view. The color filters include respective colored portions  22  of red (R), green (G), and blue (B), for example. A black matrix  23  substantially having a lattice shape for preventing color mixing is formed between the respective colored portions  22  constituting the color filters. The black matrix  23  is made of a light blocking material such as titanium (Ti), for example. 
     In the liquid crystal panel  10 , a set of colored portions  22  of three colors of red (R), green (G), and blue (B) and their respective opposing three pixel electrodes  34  constitutes one display pixel  90 . The display pixel  90  includes three colored pixels (subpixels)  92 , i.e., a red pixel including a colored portion  22  for R, a green pixel including a colored portion  22  for G, and a blue pixel including a colored portion  22  for B. In other words, each display pixel  90  includes a plurality of colors (three colors) of colored pixels  92  including different colored portions  22 . In the following description, a suffix R, G, or B is added to a reference sign as in “red pixel  92 R”, “green pixel  92 G”, or “blue pixel  92 B” to distinguish the colors of the colored pixels, whereas such a suffix is not added as in “colored pixel  92 ” to make collective reference without distinguishing the colors. 
     As illustrated in  FIG. 3 , on a substrate surface of the liquid crystal panel  10 , the colored pixels  92  are repeatedly arrayed along a row direction (X-axis direction) with colored pixels  92  of a plurality of colors (three colors) being a unit so as to constitute a pixel group, and a large number of such pixel groups are arrayed along a column direction (Y-axis direction). Each colored pixel  92  has substantially the same shape (rectangular shape), and has substantially the same size. Regarding the colored pixels  92 , as illustrated in  FIG. 3 , on the central side of the display region A 1 , the entire region within each pixel belongs to the display region A 1 , and therefore the red pixel  92 R, the green pixel  92 G, and the blue pixel  92 B have an equal aperture ratio, and the display pixels  90  are displayed with a satisfactory color balance. In contrast, the colored pixels  92  including the curved line portion L 2  include both the display region A 1  and the non-display region A 2 , with the curved line portion L 2  being a boundary. 
     Incidentally, as illustrated in a liquid crystal panel  810  according to a first comparative example of  FIG. 4 , provided that display is performed by separating a lighting region and a non-lighting (light blocking) region along an ideal curved line portion L 2  in colored pixels  892  including the curved line portion L 2 , the boundary between the lighting region and the light blocking region substantially matches the curved line portion L 2 , and therefore the outline of the peripheral portion of the display region A 1  is smoothly displayed. In the first comparative example, in the colored pixels  892  including the curved line portion L 2 , a first light blocking portion  824  for blocking light from the illumination device is provided in line with the shape of the curved line portion L 2 . However, such light blocking adjustment performed along the curved line portion L 2  makes the shape and the size of a red pixel  892 R, a green pixel  892 G, and a blue pixel  892 B to be lighted different from one another at the peripheral portion (portion enclosed by the border line portion BL 6  in  FIG. 4 ) of the display region A 1 , and therefore the color balance of display pixels  890  is lost at the peripheral portion, and coloring is caused. Note that the first light blocking portion  824  is made of a light blocking material such as titanium (Ti), for example, and is formed on the CF substrate  20 , in a similar manner to the black matrix  23 . 
     As illustrated in a liquid crystal panel  910  according to a second comparative example of  FIG. 5 , provided that light blocking adjustment is performed on the peripheral portion of the display region A 1  per colored pixel  992 , a red pixel  992 R, a green pixel  992 G, and a blue pixel  992 B to be lighted have the same shape and size, and the color balance is maintained satisfactorily. In the second comparative example, a first light blocking portion  924  is provided so that the entire region of the colored pixels  992  including the curved line portion L 2  a non-lighting state, which enables light blocking adjustment per colored pixel  992 . However, such light blocking adjustment makes the shape of the peripheral portion of the display region A 1  a stepped shape as illustrated in  FIG. 5 , and smooth display is not be achieved. 
     In view of this, in the present embodiment, as illustrated in  FIG. 3 , a second light blocking portion  24  as described below is provided, as well as the first light blocking portion  824  having a shape in line with the curved line portion L 2  as in the first comparative example. First of all, a colored pixel  92  that is one of the colored pixels  92  including the curved line portion L 2  and that is located at the outermost end side in an array direction (X-axis direction) is defined as a display end pixel  94 . The array direction is a direction in which the colored pixels  92  are repeatedly arrayed with colored pixels  92  of three colors being a unit. In this case, the second light blocking portion  24  having a shape and a size substantially the same as those of the first light blocking portion  824  of the display end pixel  94  is provided in each of colored pixels  92  of two colors that are consecutively arrayed next to the display end pixel  94  toward the display region A 1  in the array direction (toward a side opposite to the end side). Further detailed description is given by taking an example of the display pixels  90  enclosed by the border line portion BL 1  of  FIG. 3 . The display pixel  90  in the border line portion BL 1  includes a red pixel  92 R including the curved line portion L 2 . A display end pixel  94  that is one of three colored pixels  92 R,  92 G, and  92 B constituting the display pixel  90  and that is located at the outermost end side in the array direction corresponds to the red pixel  92 R. In this case, the second light blocking portion  24  having a shape and a size substantially the same as those of the first light blocking portion  824  of the display end pixel  94  (red pixel  92 R) is provided in each of colored pixels  92  of two colors (green pixel  92 G and blue pixel  92 B) that are consecutively arrayed next to the display end pixel  94  toward the display region A 1  in the array direction (from the left side to the right side in the X-axis direction). In a similar manner, regarding the display pixels  90  indicated by the border line portions BL 2 , BL 3 , BL 4 , and BL 5  of  FIG. 3  as well, the first light blocking portion  824  is provided in the display end pixel  94 , and the second light blocking portion  24  is provided in each of colored pixels  92  of two colors that are consecutively arrayed next to the display end pixel  94  toward the display region A 1  in the array direction. The second light blocking portion  24  is made of a light blocking material such as titanium (Ti), and is formed on the CF substrate  20 , in a similar manner to the black matrix  23  and the first light blocking portion  824 . 
     According to this configuration, regarding the display pixels  90  including the colored pixels  92  including the curved line portion L 2 , colored pixels  92  of three colors constituting the display pixel  90  are lighted in line with the shape of the display end pixel  94 , and therefore the colored pixels  92  of the three colors have a lighting region of the same shape and the same size in their corresponding display pixel  90 . As a result, also in the display pixel  90 , the colored pixels  92  have an equal aperture ratio, and a satisfactory color balance can be maintained. Although the shape of the lighting region of each colored pixel  92  is arranged to match the shape of the lighting region of the display end pixel  94 , the shape of the curved line portion of the display end pixel  94  matches the shape of the curved line portion L 2 . This enables smooth display of the shape of the peripheral portion (outline) of the display region A 1 . 
     The first light blocking portion  894  having a shape in line with the shape of the curved line portion L 2  is provided in all of the display end pixels  94 . This configuration prevents a situation that the entire region of some of the display end pixels  94  enters a non-lighting state, which is the case with JP 5112961B. As a result, smooth display of the shape of the peripheral portion (outline) of the display region A 1  can be secured. 
     Note that the number of colors and the combination of the colored portions  22  of the display pixel  90  can be modified as appropriate within the range of n different colors (n: a natural number of 2 or greater). The above description takes an example of a case where n is 3 (n=3). However, for example, in a case where n is 4 (n=4) with another colored portion of white (W) or yellow (Y) being provided in addition to R, G, and B, each display pixel  90  includes four colors of colored pixels  92 , and thus color reproducibility can be enhanced, for example. 
     OTHER EMBODIMENTS 
     The present invention is not limited to the embodiments described above and illustrated by the drawings, and embodiments such as those described below are also included within the technical scope of the present invention. 
     (1) The above embodiments illustrate one example of the shape of the display region. The shape, however, is not limited to the above shape as long as the shape includes a curved line. The non-display region is not limited to an outer peripheral portion. For example, in a case where the display region has a donut-like shape, both of an inner peripheral portion and an outer peripheral portion of the donut-like shape correspond to the non-display region, and the boundary between the display region and the non-display region exists both on the inner peripheral side and the outer peripheral side. 
     (2) Each of the above embodiments exemplifies a liquid crystal panel whose operation mode is an FFS mode. The operation mode, however, may be another operation mode, such as an in-plane switching (IPS) mode and a vertical alignment (VA) mode. The liquid crystal panel may also be provided with a touch panel function of detecting a position of user&#39;s input, based on a display image. 
     (3) Each of the above embodiments exemplifies a liquid crystal panel as the display panel. However, the present invention can also be applied to other types of display panels (such as an organic EL panel, a plasma display panel (PDP), an electrophoretic display panel (EPD), and a display panel of micro electro mechanical systems (MEMS)).