1. Field of the Invention
The present invention relates to a liquid crystal display and a method of manufacturing the same and, more particularly, to a transflective liquid crystal display capable of display in both of transmissive and reflective modes and a method of manufacturing the same.
2. Description of the Related Art
Recently, active matrix liquid crystal displays having a thin film transistor (TFT) at each of pixels are widely used as displays in every field of application. Under such a circumstance, transflective liquid crystal displays capable of display in both of reflective and transmissive modes have been put in use as displays for mobile terminals or notebook type personal computers.
FIGS. 47A and 47B show a configuration of a transflective liquid crystal display according to the related art disclosed in Non-Patent Document 1. FIG. 47A shows a configuration of a pixel of the transflective liquid crystal display, and FIG. 47B shows a sectional configuration of the transflective liquid crystal display taken along the line X-X in FIG. 47A. As shown in FIGS. 47A and 47B, the pixel region is divided into a transmissive area T and a reflective area R. In the reflective area R on a TFT substrate 102, an insulator (resin layer) 130 is formed such that the reflective area R has a cell thickness that is one-half of a cell thickness of the transmissive area T. A reflective electrode 116 having an irregular surface is formed on the insulator 130. In the middle of the transmissive area T on an opposite substrate 104, a protrusion 132 for regulating the alignment of a vertical alignment type liquid crystal 106 is formed. A pair of ¼ wave plates 120 are provided on respective sides of the TFT substrate 102 and the opposite substrate 104 that constitute the exterior of the panel. A pair of polarizers 122 is provided outside the ¼ wave plates 120, respectively. A step for forming and patterning the insulators 130 is required for this transflective liquid crystal display to make the cell thickness of the reflective areas R smaller than the cell thickness of the transmissive areas T. This results in a problem in that the manufacturing cost of the liquid crystal display is increased because of increased complicatedness of manufacturing steps.
As a solution to this problem, a transflective liquid crystal display having a configuration as shown in FIG. 48 was proposed in a Japanese Patent Application (numbered 2003-95329) made by the applicant. As shown in FIG. 48, a plurality of gate bus lines 150 extending in the horizontal direction in the figure are formed substantially in parallel with each other on a TFT substrate of a liquid crystal display. A plurality of drain bus lines 152 extending in the vertical direction in the figure are formed substantially in parallel with each other such that they intersect the gate bus lines 150, an insulation film, which is not shown, being interposed between them. A TFT 154 is formed in the vicinity of each of intersections between the gate bus lines 150 and the drain bus lines 152. Regions surrounded by the gate bus lines 150 and the drain bus lines 152 constitute pixel regions. Storage capacitor bus lines 156 substantially in parallel with the gate bus lines 150 are formed such that they extend across the pixel regions substantially in the middle thereof. A storage capacitor electrode 158 is formed on the storage capacitor bus line 156 at each pixel region.
A pixel electrode constituted by a transparent conductive film is formed at a pixel region. A pixel electrode has a rectangular circumference, and it has a plurality of electrode units 162 smaller than the pixel region, electrode blank sections (slits) 164 formed between adjoining electrode units 162, and connecting electrodes 166 for electrically connecting electrode units 162 separated by the slits 164 with each other. A plurality of spaces 168 are formed at the periphery of the electrode units 162, the spaces being cutouts on respective side edges which extend substantially in parallel with the gate bus lines 150 or drain bus lines 152. A black matrix (BM) 170 for shielding a region outside the pixel region from light is formed on the opposite substrate.
In this configuration, the storage capacitor electrode 158 is used as a reflector, and circular reflectors 172 are separately formed in the pixel region. The reflectors 172 are formed of the same material as that of a gate electrode or source and drain electrodes of the TFT 154 and are provided such that they substantially overlap the centers of the electrode units 162 when viewed in a direction perpendicular to a substrate surface. The reflectors 172 are in an electrically floating state.
In this configuration, the cell thickness of a reflective area is the same as the cell thickness of a transmissive area. Therefore, the birefringence of the reflective area is twice that of the transmissive area because light passes through the same liquid crystal layer twice to enter and exit the cell. A problem therefore arises in that yellow is displayed in the reflective area while white is displayed in the transmissive area when the same voltage is applied to the transmissive area and the reflective area. A measure taken to suppress birefringence is to decrease the tilt of liquid crystal molecules during display in the reflective mode by decreasing the applied voltage.
Although the configuration shown in FIG. 48 allows manufacturing steps simpler than those for the configuration shown in FIGS. 47A and 47B, it requires an applied voltage to be adjusted for display in the transmissive mode and for display in the reflective mode. Another problem arises in that when intense external light enters during display in the transmissive mode, the color of light reflected by a reflective area can be greatly different from the color of light transmitted by a transmissive area.
The followings are the description of related arts,
Patent Document 1: Japanese Patent Laid-Open No. JP-A-H11-183892
Patent Document 2: Japanese Patent Laid-Open No. JP-A-2001-341366
Patent Document 3: Japanese Patent Laid-Open No. JP-A-2001-166289
Patent Document 4: Japanese Patent No. 3380482
Patent Document 5: Japanese Patent Laid-Open No. JP-A-S57-155582
Patent Document 6: Japanese Patent Laid-Open No. JP-A-2001-242452
Patent Document 7: Japanese Patent Laid-Open No. JP-A-2002-350853
Patent Document 8: Japanese Patent Laid-Open No. JP-A-2000-47215
Patent Document 9: Japanese Patent Laid-Open No. JP-A-2000-111902
Patent Document 10: Japanese Patent Laid-Open No. JP-A-H11-242226
Patent Document 11: Japanese Patent Laid-Open No. JP-A-H11-281972
Non-Patent Document 1: Asia Display/IDW′ 01, p. 133 (2001)
Non-Patent Document 2: SID 96 Digest, pp. 618-621
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