In plane switching liquid crystal displaying apparatus for improving luminance

#The present invention relates to an IPS (In Plane Switching) liquid crystal displaying apparatus by generating an electric field parallel to an array substrate to drive the liquid crystal. More particularly, the present invention relates to a construction of a highly bright liquid crystal displaying apparatus increased in aperture ratio by reducing influences of the leakage of electric field from a signal line, thereby reducing the light shielding area.

#In an active matrix type liquid crystal displaying apparatus, an IPS system where the direction of the electric field to be applied on the liquid crystal is made parallel to the array substrate is mainly used as a method of obtaining a wider viewing angle (for example, see Japanese Unexamined Patent Publication No. 254712/1996). It is reported that this system enables to remove the almost all of the change in the contrast and the inversion of the gradation level in changing the viewing-angle direction (see, for example, AsiaDisplay, 95, page, 577 to 580 by M. Oh-e, and others).

#A construction of one pixel of the conventional IPS liquid crystal displaying apparatus is depicted in FIGS. 43a and 43b. FIG. 43a is the plain view thereof. FIG. 43b is a sectional view taken along a line A—A of FIG. 43a. FIG. 44 is a circuit diagram showing an equivalent circuit of one pixel of the pixel electrode of an IPS liquid crystal displaying apparatus. FIG. 45 is a circuit diagram for illustrating the circuit of the IPS liquid crystal displaying apparatus. Referring to FIGS. 43a and 43b, reference numeral 1 denotes a glass substrate, numeral 2 denotes a scanning line, numeral 3 denotes a signal line, numeral 4 denotes a thin film transistor (TFT), numeral 5 denotes a driving electrode, numeral 6 denotes an opposite electrode, numeral 7 denotes an electrode for forming the storage capacitance, numeral 8 denotes common line, numeral 9 denotes a gate insulating film, numeral 10′ denotes a passivation film, numeral 11 denotes a liquid crystal, numeral 12 denotes a BM (black matrix), numeral 14 denotes a contact hole, numeral 15 denotes a source electrode, and numeral 16 denotes a drain electrode. Numeral 20 denotes an array substrate comprising glass substrate 1, a signal line 3, a driving electrode 5, an opposite electrode 6. Numeral 30 denotes an opposite substrate arranged opposite to the array substrate 20. Numeral 40 denotes a slit which is a gap between the signal line 3 and the opposite electrode 6, and numeral 50 denotes an opening. Referring to FIG. 44 and FIG. 45, the same reference numerals as those of FIGS. 43a and 43b depict the same parts or its equivalents as those of FIGS. 43a and 43b.

#FIG. 1 is a sectional view showing the construction of one pixel of an IPS liquid crystal displaying apparatus of Embodiment 1 of the present invention;

#FIG. 2 is a plain view showing the construction of one pixel of an IPS switching type liquid crystal displaying apparatus of Embodiment 1 of the present invention;

#FIGS. 3a and 3b are a plain view and a sectional view showing the construction of one pixel of an IPS liquid crystal displaying apparatus of the embodiment 1 of the present invention;

#Embodiment 1

#One embodiment of the present invention will be described in accordance with drawings. The reference numerals in Embodiment 1 are the same as those of the conventional reference numerals. FIG. 1 is a sectional view showing the construction of one pixel of the IPS type liquid crystal displaying apparatus in Embodiment 1 of the present invention. FIG. 2 is its plain view. FIG. 1 is a sectional view taken along a line of A—A in FIG. 2. Referring to the drawing, reference numeral 1 denotes a glass substrate, numeral 2 denotes a scanning line, numeral 3 denotes a signal line, numeral 4 denotes a TFT, numeral 5 denotes a driving electrode, numeral 6 denotes an opposite electrode, numeral 7 denotes an electrode for forming the storage capacitance, numeral 8 denotes a common line, numeral 9 denotes a gate insulating film, numeral 10 denotes a passivation film, numeral 11 denotes a liquid crystal, numeral 12 denotes a BM, numeral 14 denotes a contact hole, numeral 15 denotes a source electrode of the transistor, and numeral 16 denotes a drain electrode of the transistor. Numeral 20 denotes an array substrate comprising a glass substrate 1, a signal line 3, a driving electrode 5, an opposite electrode 6. Numeral 30 denotes an opposite substrate cerving as a displaying picture face arranged opposite to the array substrate 20. Numeral 40 denotes a slit which is a gap between the signal line 3 and the opposite electrode 6. Numeral 50 denotes an opening of a pixel. FIG. 3 depicts the construction of one pixel of the IPS type liquid crystal displaying apparatus when a channel passivation TFT 21 which is one type of a TFT 4 is provided as a TFT to be used in the IPS type liquid crystal displaying apparatus shown in FIG. 2. FIG. 3a is its plain view. FIG. 3b is a sectional view.

#The construction of the pixel of the IPS type liquid crystal displaying apparatus will be described in accordance with FIG. 1 and FIG. 2. Referring to the drawings, numeral 1 denotes a glass substrate with a scanning line 2 being formed on the glass substrate 1. A gate insulating film 9 is laminated to cover the scanning line 2 and a signal line 3 is provided on the gate insulating film 9. A passivation film 10 is laminated on the signal line 3. A driving electrode 5 and an opposite electrode 6 are provided on the passivation film 10. The TFT array substrate 20 is made as described above. A substrate 30 which is provided to be opposed to the TFT array substrate 20 is an opposite substrate for grasping a liquid crystal 11 with respect to the TFT array substrate 20. The IPS liquid crystal displaying apparatus of the present invention causes an electric field along the surface of the TFT array substrate, and thereby to drive the liquid crystal 11 by controlling the direction of the electric field.