Patent Publication Number: US-2016223855-A1

Title: Liquid-crystal display device and a manufacturing method of it

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2015-019222, filed on Feb. 3, 2015; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments of the present invention relate to a liquid-crystal display (LCD) device displaying images, and particularly relate to an LCD device, in which lateral-electric field including fringe-electric field is applied to a liquid crystal layer at a time of driving the device and a manufacturing method of it. 
     BACKGROUND 
     The LCD devices are most typical among flat-panel display (FPD) devices and are widely used as display devices for PCs and TV sets, for computer terminals, for vehicle-mounted display devices such as car navigators and rear-view monitors, and for mobile devices such as smart phones and other mobile phones as well as information terminals or digital assists. The display panel of the liquid-crystal display (LCD) device comprises an array substrate and a counter substrate, which are adhered to each other through a sealing material, and a liquid crystal layer interposed between these substrates. The array substrate generally has: on a viewing area, in which pixels are arrayed, scanning lines and signal lines that are arranged in a lattice; and switching elements and pixel electrodes, each of which is arranged in vicinity of respective intersection of the scanning and signal lines. 
     When the viewing area of the LCD device is obliquely observed, or when observation angle is very large, it occasionally happens that, along a fringe of a pixel dot or a single-color subpixel, light leakage from adjacent pixel dot appears to be mixed in. For example, along a fringe of red pixel dot, it might occur “color mixing”, by which a green light leaked from adjacent green pixel dot is mixed into red color light. 
     In particular, recently widely used are: the LCD devices of lateral-electric field mode, which is often referred to as In-Plane Switching (IPS) mode. In the lateral-electric field mode LCD devices, common electrodes or counter electrodes are arranged in the array substrates; electric fields, which are mainly in directions along the array substrates, are applied to the liquid-crystal layers so that levels of light transmittance through the liquid-crystal layers are controlled; and in this way, images are displayed with high resolutions and, in same time, with almost no dependency to observation angle. In Fringe Field Switching (FFS) mode LCD devices in particular among the lateral-electric field mode LCD devices, the pixel electrodes are arranged as overlapped with the common electrodes, with an insulator layer interposed between layers of the pixel and common electrodes, so that the fringe-electric fields are applied to the liquid crystal layers to control their light transmittance. The FFS mode LCD devices are advantageous in that energy consumption efficiency is able to be enhanced, and hence are widely used in the mobile devices. In the lateral-electric field mode LCD devices, electric field shielding between adjacent pixel dots would not be perfect and, hence, the “color mixing” would tend to occur in particular. 
     To cope with such problems, JP2014-006427A proposes that: color filter layers are arranged on the array substrate; and by a pattern formed subsequent to the color filter layer, wall structures (“1st wall structures WL 1 ”) are respectively formed along signal lines (“signal wirings DL”). Please see  FIGS. 1-2  in particular. Projections of the wall structures protrude through the liquid crystal layer up to the counter substrate; and have a layer of the pixel electrodes (“source electrodes SE”) on almost vertically extending wall faces. By such “on-wall electrodes IPS-LCD”, it is asserted that “nearer-to-parallel electric field is applicable to the liquid-crystal layer” ([0004]). Meanwhile, JP2014-021267A proposes that: at along borders of the pixel dots, thickness of common electrodes (“common electrodes 1101”) is increased to 5 times to 30 times of other parts of the common electrodes. 
     Meanwhile, JP2013-186148A shows an LCD device, in which column spacers are formed by “spacer portions  4 ”, which are protruded from the array substrate  1 , and “spacer portions  5 ” that are protruded from the counter substrate  2  as the “spacer portions  4 ” abut respectively on the “spacer portions  5 ” in vertical direction. In particular, the “spacer portions  4 ” on the array substrate run in a direction of the scanning lines while the “spacer portions  5 ” on the counter substrate run in a direction of the signal lines so that the spacer portions would not scratch the substrates within the viewing area. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a thickness-direction sectional view taken in a direction along scanning lines, showing an essential part of an embodiment of the LCD device, in which a rib-shaped protrusion and pixel-dot apertures appear, as a cross section along I-I line in  FIGS. 4-5 ; 
         FIG. 2  is a thickness-direction sectional view taken in a direction along scanning lines, showing apart of the LCD device of  FIG. 1 , in which a counter protrusion appears, as a cross section along II-II line in  FIGS. 4-5 ; 
         FIG. 3  is a thickness-direction sectional view taken in a direction along signal lines, showing a part of the LCD device of  FIG. 1 , as a cross section along line in  FIG. 4 ; 
         FIG. 4  is a plan view showing an example of overall construction of the pixel dot on an array substrate in the LCD device of  FIG. 1 ; 
         FIG. 5  is a plan view corresponding to  FIG. 4 , indicating the rib-shaped protrusion on the array substrate and the counter protrusion on the counter substrate; 
         FIG. 6  is a thickness-direction sectional view corresponding to  FIG. 1 , showing a comparative example of an LCD device in a prior-art construction; 
         FIG. 7  is a graph showing distributions of light modulation ratios, in the LCD device of  FIG. 1  as the embodiment and in the LCD device of  FIG. 6  as the comparative example; and 
         FIG. 8  is a thickness-direction sectional view corresponding to  FIG. 1 , showing a modified embodiment of an LCD device. 
     
    
    
     DETAILED DESCRIPTION 
     1. An LCD device according to preferred embodiments comprises: an array substrate, on which signal and scanning lines and pixel electrodes are arrayed and a resin film is provided; a counter substrate; a liquid-crystal layer interposed between the array and counter substrates; and rib-shaped protrusions, which are arranged on the array substrate within a viewing area so as to respectively run along the signal lines and to respectively cover the signal lines, and which are formed by a resin layer of first resin film as integral with the first resin film, and top parts of the rib-shaped protrusions being distanced from inner face of the counter substrate. By such embodiments, even when observation angle is large, it is prevented or decreased to induce display defect at along a fringe of a pixel dot, into which a light leaked from adjacent pixel dot is mixed. In the embodiments, counter substrate is formed by using a transparent substrate such as a glass plate; and the array substrate is preferably formed by using a transparent substrate such as a glass plate. 
     2. In preferred embodiments, in the device according to clause 1, the first resin film covers at least the signal lines and switching elements. 
     3. An LCD device according to preferred embodiments comprises first and second substrates and a liquid-crystal layer interposed between the substrates; the first substrate comprising: first transparent substrate; signal lines that are arrayed with an interval in a first direction; scanning lines that are arrayed with an interval in a second direction that intersects the first direction; switching elements, each of which is electrically connected with one of the scanning lines and with one of the signal lines; and a first resin film that at least covers the switching elements and the signal lines; the second substrate comprising second transparent substrate; wherein a first gap (D 1 -D 2 ), which is a distance between the first resin film and the second transparent substrate at regions overlapped with the signal lines, is smaller than a second gap (D 1 ) that is a distance between the first resin film and the second transparent substrate at regions overlapped with the pixel electrodes. 
     4. In preferred embodiments, in the device according to any one of clauses 1-3, the rib-shaped protrusions, which respectively run along the signal lines and respectively cover the signal lines, are abutted on counter protrusions arranged on the counter substrate so as to form spacers between the substrates. Preferably, the counter protrusions are elongated in a direction intersecting the signal lines and the rib-shaped protrusions. 
     5. In preferred embodiments, in the device according to clause 4, the counter protrusions are formed by second resin film that is arranged on the counter substrate or the second substrate. In preferred embodiments, the second resin film covers substantially whole of the viewing area of the counter substrate or the second substrate. 
     6. In preferred embodiments, in the device according to clause 4 or 5, the counter protrusions are arranged in a light-shielded area within the viewing area and are elongated in a direction along the scanning lines. 
     7. In preferred embodiments, in the device according to any one of clauses 1-6, a ratio of protrusion height of the rib-shaped protrusions covering the signal lines, with respect to thickness of the liquid-crystal layer at regions of the pixel electrodes on flat areas within pixel-dot apertures, is in a range of 15% to 70%, preferably in a range of 25% to 55%, more preferably in a range of 30% to 50%. 
     8. In preferred embodiments, in the device according to any one of clauses 1-7, a ratio of the first gap or a distance between top of the rib-shaped projection and inner face of the counter substrate, with respect to the second gap or a distance between the substrates or thickness of the liquid-crystal layer at regions of the pixel electrodes on flat areas within pixel-dot apertures, is in a range of 30% to 85%, preferably in a range of 45% to 75%, more preferably in a range of 50% to 70%. 
     9. In preferred embodiments, in the device according to anyone of clauses 1-8, a ratio of width of each of the rib-shaped protrusions at a half height of their protrusion height, with respect to a width of respective line part of the black matrix, is in a range of 0.8 to 1.3, more preferably in a range of 0.9 to 1.2. Preferably, a ratio of width of each of the rib-shaped protrusions at a half height of their protrusion height, with respect to a width of the signal line, is in a range of 1.5 to 4, more preferably in a range of 2 to 3. 
     10. In preferred embodiments, in the device according to any one of clauses 1-9, common electrodes are arranged in the array substrate or the first substrate, to be nearer to inner surface of the substrate than the first resin film, by which the rib-shaped protrusions are formed. 
     11. In preferred embodiments, in the device according to clause 10, the common electrodes cover the flat areas in the pixel-dot apertures, or regions forming the second gap (D 1 ), in a construction of FFS mode LCD device; and the common electrodes also cover the rib-shaped protrusions at regions sandwiching the flat areas in the pixel-dot apertures. 
     12. In preferred embodiments, in the device according to any one of clauses 1-11, the rib-shaped protrusions covering the signal lines or regions forming the first gap are arranged along the signal lines, at least throughout their regions sandwiching the flat area of each of the pixel-dot apertures. 
     13. In preferred embodiments, in the device according to any one of clauses 1-12, the rib-shaped protrusions are, in a cross section, outlined as a circular or oval arc or a parabola, or a trapezoid having rounded angles. 
     14. In preferred embodiments, in the device according to any one of clauses 1-13, thickness of the first resin film is in a range of 0.5 μm to 2 μm. 
     15. In preferred embodiments, in the device according to any one of clauses 1-14, the second gap or a distance between the substrates, or thickness of the liquid-crystal layer, at regions of the pixel electrodes on the flat area within pixel-dot apertures is in a range of 2 μm to 5 μm, preferably in a range of 2 μm to 3 μm. 
     16. In preferred embodiments, in the device according to any one of clauses 1-15, an end portion of each of pixel dots, which are elongated in a direction of the signal lines, is provided with a conduction area, through which the switching element and the pixel electrode is electrically connected; in respect of at least some of the pixel dots, the conduction area is sandwiched in a direction of the scanning lines by first and second regions; through the first region, the rib-shaped protrusion runs in a direction of the signal line; and at the second region, the rib-shaped protrusion is discontinued to form a distance larger than the first gap and smaller than the second gap. Preferably, aspect ratio or length-to-width ratio of each of the pixel dots is in a range of 2 to 8, more preferably in a range of 3 to 5. 
     17. In preferred embodiments, in the device according to clause 16, the rib-shaped protrusion at the first region is abutted on the counter protrusion on the array substrate or the second substrate to form a column spacer. Preferably, number ratio of the column spacers to the pixel dots is in a range of 2 to 8, more preferably in a range of 3 to 5. 
     18. In preferred embodiments, in the device according to any one of clauses 1-17, inner surface of the counter substrate or the second substrate, which contacts the liquid-crystal layer, is substantially flat within the viewing area except the protrusions for the column spacers. 
     19. In preferred embodiments, in manufacturing method for the device according to any one of clauses 1-18, the rib-shaped protrusions or resin layers forming the first gap are simultaneously formed with the resin film in remaining areas by a single resin-film forming process, which includes applying of light curable (including UV curable) resin on the array substrate of the first substrate as well as its half-tone exposure or by ink-jet technique. 
     Embodiments 
     The LCD device of a detailed embodiment of the invention will be described with reference to  FIGS. 1-5 . In the detailed embodiment, the LCD device is of lateral-electric field mode, and of FFS mode in particular. 
     As shown in  FIGS. 1-3 , display panel  10  of the LCD device comprises: an array substrate  1 ; a counter substrate  2 ; a liquid-crystal layer  26  held in a gap between the substrates  1  and  2 ; and a sealing material  29  that bonds together peripheral portions of the substrates  1  and  2  and seals off the liquid-crystal layer  26  from outside. 
       FIG. 4  shows a detailed example of overall construction of the pixel dot  3  on the array substrate  1 . Signal and scanning lines  15  and  16 , which are formed by light-shielding metal films, are arranged in a lattice; and corresponding to each intersection of the signal and scanning lines  15  and  16 , there are arranged: TFTs (thin film transistors)  17 A and  17 B as switching elements; and a pixel dot  3  that has a pixel electrode  14  formed by transparent conductive material. The pixel electrode  14  and the pixel dot  3  are elongated in a direction along the signal lines  15 . Most of a lengthwise region of each of the pixel dot  3  corresponds to the pixel-dot aperture  31 , in which the pixel electrode  14  is arranged. In an end portion of the pixel-dot aperture  31 , a switching-conductance area  32  is formed, in which an extended portion  14 A is arranged as extended from the pixel electrode  14 . 
       FIG. 5  shows main construction of the array substrate  2  as overlaid to that of  FIG. 4 . A black matrix  24 , which is formed in a latticework on the counter substrate  2  by light-shielding film, comprises: first parts, each of which runs along, and covers up a vicinity, of one of the signal lines; and second parts, each of which covers up at least one of the switching-conductance areas  32 , and its vicinity. In an illustrated embodiment, each of the second parts continuously runs along respective one of the scanning lines  16 ; and the latticework consists of the first parts and the second parts. Each opening of the black matrix  24  makes the pixel-dot aperture  31 . 
     As shown in  FIGS. 1-2 and 5 , on the array substrate  1 , each of the signal lines and its vicinity are covered by thick layer of resin film  12 , by which a rib-shaped protrusion  11  is formed. In  FIG. 5 , each of the rib-shaped protrusions  11  is represented by its contour line that runs through points having half protrusion height relative to protrusion height D 2 , as presented in  FIG. 1 , of the rib-shaped protrusion  11 . As shown in  FIG. 5 , in this embodiment, the rib-shaped protrusions  11  are continuously arranged throughout regions sandwiching in right-left or width direction, each of the pixel-dot apertures  31 , which is elongated in a signal-line direction. In a detailed embodiment shown in  FIG. 5 , each of the switching-conductance areas  32  is sandwiched in the right-left direction by discontinued regions  11 B, in which the rib-shaped protrusion  11  is omitted, except for regions forming the column spacers. 
     Meanwhile, within each of the pixel-dot apertures  31 , the resin film  12  has relatively small thickness, except along fringes of the aperture  31 , to form a flat area  12 A in the aperture  31 . In the illustrated embodiment, each of the pixel electrodes  14  is almost entirely arranged within the flat area  12 A. Here, in this flat area  12 A, the resin film  12  does not cover any conductive pattern; and thus, the resin film  12  may be omitted. 
       FIG. 1  is a schematic, thickness-direction sectional view in a direction along the scanning lines  16 , i.e., a direction almost perpendicular to the signal lines  15 , showing the pixel-dot apertures  31 . As shown in  FIG. 1 , firstly, vicinity of each of the signal lines  15  is surely covered and electrically isolated by thick layer of the resin film  12  that forms the rib-shaped protrusions  11 ; and in same time, undesired parasitic capacitance between a conductive layer on the resin film  12  and each of the signal lines  15  is sufficiently minimized. Moreover, because each of the pixel electrodes  14  is arranged almost entirely within the flat area  12 A, the liquid-crystal layer  26  may have a predetermined, uniform thickness D 1  at along the pixel electrodes  14 , which is larger than thickness at along the rib-shaped protrusions  11 . In other words, thickness of the liquid-crystal layer  26  may become smaller at along the vicinity of each of the signal lines  15 , which delimits the pixel-dot apertures  3 , than the predetermined thickness D 1  at along the pixel electrodes  14 . In many occasions, with decreasing of the thickness of the liquid-crystal layer  26 , light transmittance of the layer as modulated or controlled may be decreased; and in this way, the “color mixing” would be mitigated. 
       FIG. 6  is a thickness-direction sectional view corresponding to  FIG. 1 , showing a display panel  10 ′ of a comparative example of the LCD device. In the comparative example of  FIG. 6 , the resin film  12  is formed as a flattening film; and thus, a surface of the resin film  11  is flat and has uniform projection height from the glass substrate  1 A of the array substrate  1 . A resin film as a flattening film usually has a thickness in a range of 0.5 μm to 2 μm; thus, in this embodiment, maximum thickness of the resin film may be set in a range of 0.5 μm to 2 μm, and for example, preferably set in a range of 0.8 μm to 1.2 μm. Thickness of a metal layer that forms the signal lines  15  may be in a range of 0.1 μm to 0.3 μm. Thickness of transparent conductive layer that forms the pixel electrodes  14  and the common electrodes  13  is usually in a range of 10 nm to 30 nm or 0.01 μm to 0.03 μm. 
     As seen from comparison between the embodiment of  FIG. 1  and the comparative example of  FIG. 6 , it is able to decrease a distance in a thickness or vertical direction from the signal lines  15  as a light-shielding layer on the array substrate  1  to the black matrix  24  on the counter substrate  2 , by adopting the embodiment as compared to the comparative example. In detail, according to the embodiment of  FIG. 1 , the vertical distance between the signal lines  15  and the black matrix  24  may be decreased by protrusion height D 2  of the rib-shaped protrusions  11  or by height difference between the flat area  12 A and the protrusions  11 , as compared to the comparative example. 
     In  FIGS. 1 and 6 , there is indicated an obliquely transmitted light  28  that passes through from one  31 - 1  of the pixel-dot apertures to adjacent one  31 - 2  of the pixel-dot apertures. There is also indicated a color-mixing critical angle  28 A, which is a minimum possible angle for the obliquely transmitted light  28 , with respect to the vertical direction. Different primary colors are allocated to adjacent pixel dots  3  delimited by the signal lines  15 ; and thus, the “color mixing” may occur at fringes of the pixel dots  3  by intermixing with light leaked from adjacent one of the pixel dots  3 . As seen from the comparison between  FIG. 1  and  FIG. 6 , the vertical distance from the signal lines  15  to the black matrix  24  is decreased so as to decrease the light-transmittance of the liquid-crystal layer, which is modulated or controlled, and increase the color-mixing critical angle  28 A so that the color mixing is prevented or mitigated. 
     In following, it is explained further curbing of the color mixing by the rib-shaped protrusions  11 , in an LCD device of lateral-electric field mode such as FFS mode. 
     In this embodiment, the common electrodes  13  formed of transparent conductive material are arranged to cover almost whole area, in which pixel dots are arrayed, on the array substrate  1 . Thus, the common electrodes  13  cover not only the flat areas  12 A, on which the pixel electrode  14  are arranged, but also the rib-shaped protrusions  11 . In an illustrated detailed embodiment, the common electrodes  13  are arranged to directly cover the resin film  12 . Meanwhile, the pixel electrodes  14  have slits  14 B. In the illustrated detailed embodiment, number of the pixel electrodes  14  on each of the pixel dot  3  is one; number of the slits  14 B on each of the pixel electrodes  14  is one; and the slit  14 B runs almost throughout a length dimension of the pixel electrode  14 . Nevertheless, the pixel electrode  14  may be shaped as a single linear electrode having no slit. 
     A driving voltage applied to the liquid-crystal layer at between the common electrodes  13  on one side and the pixel electrodes  14  on another side induces loop-shaped electric lines  27  of force, each of which runs from the array substrate  1 , as shown in  FIGS. 1 and 6 . As schematically shown in  FIG. 1 , due to existence of the rib-shaped protrusions  11 , curbed is extending of the electric lines  27  of force up to vicinities of the signal lines  15  on right-hand and left-hand sides in  FIG. 1 . 
       FIG. 7  is a graph showing, in respect of the display panel  10  of the embodiment of  FIG. 1  and of the display panel  10 ′ of the comparative example of  FIG. 6 , a relationship between a position and light transmittance (%) of the liquid-crystal layer at a time the driving voltage for white display is applied to the liquid-crystal layer. Here, the position represents a distance (μm) from centerline of the pixel-dot aperture  31  when measured in a manner to run across the pixel-dot aperture  31  in the scanning-line direction as shown in  FIG. 1 . No significant difference in the light transmittance between the embodiment and the comparative example is observed in a region near the centerline of the pixel-dot aperture  31 , which accounts for about 70% of width dimension of the pixel-dot aperture  31  and is other than fringe parts of pixel-dot aperture  31  on its both ends in width direction. On contrary, remarkable difference is observed in the light-shielded areas coinciding the black matrix  24  and its vicinities, which are the right-hand and left-hand side fringe parts of the pixel-dot aperture  31 . In particular, the light transmittance at along each centerline of the black matrix  24  or at along the signal lines is almost 0% for the embodiment and is about 5% for the comparative example. Hence, in the embodiment, the color mixing is reliably curbed by low value of the light transmittance in vicinities of the light-shielded areas. 
     Decrease of the light transmittance in vicinities of the light-shielded areas is presumably because extending of the electrical lines of force is curbed by the rib-shaped protrusions  11  and because the light transmittance is decreased by decreasing of thickness of the liquid-crystal layer by the protrusions  11 . 
     In following, the detailed embodiment illustrated in  FIGS. 1-5  is explained more thoroughly. 
     Firstly, manufacturing of the array substrate  1  may be outlined by following processes 1) through 9) in a sequence. Process 1): on a glass substrate  1 A for the array substrate  1 , polysilicon wirings  17  are formed and then are covered by a gate insulator film  16 B, which may be formed of silicon oxides and/or silicon nitrides. Process 2): by a metal layer such as molybdenum alloy, the scanning lines  16  and branch lines  16 A branched out from the scanning lines  16  are formed and then covered by an interlayer insulator film  15 B that may be formed of silicon oxides and/or silicon nitrides. Process 3): contact holes  19 A are formed to penetrate through the interlayer insulator film  15 B and the gate insulator film  16 B so as to expose both ends of each of the polysilicon wirings  17 . Process 4): on the interlayer insulator film  15 B, the signal lines  15  and first island-shaped patterns  15 A are formed by metal layer such as a layer of aluminum and/or its alloy. Process 5): the resin film  12 , which is transparent and has the rib-shaped protrusions  11 , is formed to cover the signal lines  15  and the first island-shaped patterns  15 A; and in same time, contact holes  19 B are formed to expose a portion of each of the first island-shaped patterns  15 A. Process 6): on the resin film  12 , there are formed the common electrodes  13 , which are formed of transparent conductive material such as ITO (Indium tin oxides) and/or IZO (Indium zinc oxides); and in same time, in the switching-conductance area  32 , second island-shaped patterns  13 A are formed. Process 7): a common-electrode insulator film  18 A is formed to cover up the common electrodes  13 ; and then, contact holes  19 C are formed to expose a portion of each of the second island-shaped patterns  13 A. Process 8): there are formed the pixel electrodes  14 , which are formed of transparent conductive material such as ITO and/or IZO. Process 9): finally, to form an alignment film  18 , a resin layer is formed and then subjected to rubbing procedure or to photo-alignment procedure by irradiation of ultra violet lights. 
     Procedures for forming the resin film  12  at the process 5) may be as follows. At first, the substrate is coated with light curable resin, which may be mainly formed of acrylate resin and/or epoxy resin. Subsequently, the substrate is subjected to halftone exposure technique, by which UV-light irradiation dose is varied from region to region to achieve predetermined thicknesses in the regions. Subsequently, the substrate is subjected to developing procedure, by which not-cured resin materials are removed, and then to heating procedure, by which the resin film is completely cured. Meanwhile, in the process 7), the common-electrode insulator film  18 A may be formed by a resin layer; and may be made in a same manner with the process 5) except that, instead of the halftone exposure technique, an exposure technique using a usual mask is used for forming the contact holes  19 C. 
     Secondly, explanation is made to the switching-conductance area  32  and switching elements. In the illustrated embodiment, each of the polysilicon wirings  17  is L-shaped as in  FIG. 4  and has a first linear part, which is overlaid on the signal line  15  and then crosses the scanning line  16 , and has a second linear part, which runs into the switching-conductance area  32  in parallel with the scanning line  16  as bent from the first linear part. As shown in  FIG. 4  as well as  FIGS. 2-3 , ends of each of the polysilicon wirings  17  are connected through the contact holes  19 A, respectively to a portion of the signal line  15  and to the first island-shaped pattern  15 A. The first island-shaped patterns  15 A are connected, through the contact holes  19 B that penetrate through the resin film  12 , to the second island-shaped patterns  13 A. The second island-shaped patterns  13 A are connected, through the contact holes  19 C that penetrate through the common-electrode insulator film  18 A, to the pixel electrodes  14 . 
     In the switching-conductance area  32 , the branch line  16 A branches out from the scanning line  16 , in the signal-line direction and crosses the polysilicon wiring  17  as to form here a TFT  17 B. In the illustrated detailed embodiment, another TFT  17 A is formed at a crossing of the polysilicon wiring  17  and the scanning line  16 . Thus, each switching element is formed of a pair of TFTs  17 A and  17 B. 
     In a detailed embodiment illustrated in  FIG. 2 , within the switching-conductance area  32 , the island-shaped pattern  15 A, which has a relatively large thickness and has been formed simultaneously with the signal lines  15 , should be covered by the resin film  12 ; thus, thickness of the resin film  12  within the switching-conductance area  32  is larger than that within the flat area  12 A in the pixel-dot aperture  3 . In particular, in the illustrated detailed embodiment, the resin film  12  makes a plateau  11 A throughout the switching-conductance area  32 . Thus, thickness D 3  of the liquid-crystal layer  26  at the switching-conductance area  32  is smaller than thickness D 1  at the flat area  12 A. 
     In the detailed embodiment illustrated in  FIGS. 2-3  and  FIG. 5 , the counter substrate  2  has counter protrusions  21  that are formed at a time of film forming process, integrally with the resin film  22  at a time of formation of a resin film  22 . In a plan view of  FIG. 5 , each of the counter protrusions  21  is shaped as a rectangle with rounded angles, which is elongated in the scanning-line direction. As shown in  FIGS. 2-3 , top parts of the counter protrusions  21  are abutted against top parts of the rib-shaped protrusions  11 , which run in the signal-line direction so as to form column spacers or photo spacers. In particular, one of the rib-shaped protrusions  11  running in the signal-line direction is crosswise combined with one of the counter protrusions  21  elongated in the scanning-line direction to form one of the column spacers. 
     The column spacers formed in this way may be arranged as distributed in a ratio of one to several or more of the pixel dots  3 ; and, for example, one to four of the pixel dots  3  or one to eight of the pixel dots  3 . In the detailed example of  FIG. 5 , each of the counter protrusions  21  is arranged to a corner of a rectangular shape of the pixel dot  3  that is presented at a non-fringe main part of the  FIG. 5 . 
     Manufacturing of the counter substrate  2  may be outlined by following processes i) through iV) in a sequence. Process i): on a glass substrate  2 A for the counter substrate  2 , the black matrix is formed, which is formed of a resin layer having black pigments as dispersed therein, or of a metal layer. Process ii): three color-filter layers  23 R,  23 G and  23 B are sequentially formed by resin layers respectively having red, green and blue pigments as dispersed therein. Process iii): a resin film  22  is formed as a flattening film to cover up unevenness or difference in thickness among the three color-filter layers  23 R,  23 G and  23 B; and in same time, the counter protrusions  21  are formed at predetermined positions. Process iV): finally, to form an alignment film  25 , a resin layer is formed and then subjected to rubbing procedure or to photo-alignment procedure by irradiation of ultra violet lights. 
     The process iii) for forming the counter protrusions  21  and the resin film  22  on the counter substrate  2  may be made in same manner with the process  6 ) for forming the rib-shaped protrusions  11  and the resin film  12  on the array substrate  1 . 
       FIG. 8  is a thickness-direction sectional view corresponding to  FIG. 1 , showing essential part of an LCD panel  10 ″ according to a modified embodiment of an LCD device. Contour of each of the rib-shaped protrusions  11  in a cross section is trapezoidal or rectangular in the modified embodiment of  FIG. 8  while, in the embodiment of  FIG. 1 , the contour is arc-shaped or smoothly curved. Substantially same extent of curbing of the color mixing is achieved by the modified embodiment of  FIG. 8  as in the embodiment of  FIG. 1 . In particular, even the light transmittance curve as in  FIG. 7  is substantially same between the modified embodiment of  FIG. 8  and the embodiment of  FIG. 1 . 
     In a preferred embodiment, the resin film  1  within the flat area  12 A of the array substrate  1  may have a thickness in a range of 0.1 μm to 0.5 μm and more particularly in a range of 0.1 μm to 0.3 μm, and may be omitted as mentioned before. 
     In a preferred embodiment, a width of each of the rib-shaped protrusions  11  at a half height of their protrusion height D 2  may be 0.8 times to 1.3 times, 0.9 times to 1.2 times for example, of a width W 2  of respective line part of the black matrix  24 ; and may be 1.5 times to 4 times, 2 times to 3 times for example, of a width W 3  of the signal line  15 . 
     In a preferred embodiment, thickness of the resin film  12  within the plateau  11 B as mentioned in conjunction with  FIG. 2 , may be 1.0 times to 5 times, more preferably 1.5 times to 3 times, of a thickness of metal layer of the signal lines  15  and island-shaped patterns  15 A. Difference in thickness of the resin film  12  between the plateau  11 A and the flat area  12 A, or height difference between the plateau  11 A and the flat area  12 A, may be in a range of 20% to 80%, in a range of 40% to 50% for example, of the protrusion height D 2  of the rib-shaped protrusions  11 . 
     Although the LCD devices in the above-mentioned embodiments and the comparative example is of FFS-mode, curbing of the color mixing is achievable also in the LCD devices of the lateral-field mode other than the FFS-mode. For example, comb-shaped common electrodes may be adoptable in a manner that portions of the common electrodes are partly overlapped with the rib-shaped protrusions. Even when the common electrodes or counter electrodes are arranged in the counter substrates, curbing of the color mixing is achievable because the color-mixing critical angle  28 A is increased and because thickness of the liquid-crystal layer is decreased in vicinities of the signal lines. 
     In the above explanation of manufacturing processes, the rib-shaped protrusions  11  and the resin film  12  within the flat areas  12 A are simultaneously formed by the half-tone technique after uniformly coating the substrate with a resin material, but may also be formed by ink-jet technique for example. 
     In the above explanation, the rib-shaped protrusions are formed only on the array substrate; but some of them, a part of them or all of them may be arranged on the counter substrate  2 ; and by such a way, a similar effect in some extent would be achievable. In some occasions, the rib-shaped protrusions may be arranged on both of the array and counter substrates  1  and  2  in same regions overlapping the signal lines  15  so that, in these regions, the liquid-crystal layer is sandwiched in a narrow gap between the protrusions  11 . 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.