KR100502090B1 - Liquid crystal display device having a new electrode array and manufacturing method thereof - Google Patents

Abstract

Liquid crystal display with different electrode arrangements. A transparent planar electrode is formed in the transverse direction on the inner surface of the substrate, and the insulating film is covered thereon. On the insulating film, a plurality of transparent or opaque linear electrodes are formed parallel to each other in the longitudinal direction. Applying a voltage to the two electrodes gives a potential difference between the two electrodes, which is symmetrical with respect to the longitudinal centerline on the linear electrode and the longitudinal centerline of the region between the linear electrodes, and a parabolic or semi-elliptic electrical line centered at the boundary between the two electrodes An electric field is formed. These electric field lines have vertical and horizontal components on the boundary between the two electrodes and between the two electrodes, and the liquid crystal molecules are rearranged with the twist angle and the tilt angle by the electric field. Due to the rearrangement of the liquid crystal molecules, the polarization of the incident light changes, thereby enabling the display operation.

Description

Liquid crystal display device having novel electrode array and manufacturing method thereof

The present invention relates to a liquid crystal display device of a novel driving method and a driving method thereof.

In general, a liquid crystal display device has electrodes on both substrates or an inner surface of one substrate, and is an optical switching medium having a liquid crystal material layer between two electrodes. When a potential difference is applied to both electrodes, liquid crystal molecules are re-used due to the potential difference. Arranged and rearranged liquid crystal molecules display an image by scattering light or changing light transmission properties.

As an example of a conventional liquid crystal display device, a nematic liquid crystal material is inserted between upper and lower electrodes formed on the inner surfaces of two lower and upper substrates, respectively, and the liquid crystal molecules are twisted and oriented parallel to the substrate. And a twisted nematic liquid crystal display disclosed in Patent No. 5,576,861. In this liquid crystal display, when a voltage is applied to the upper and lower electrodes to give a potential difference, an electric field perpendicular to both substrates is formed, and a torque for arranging the long axis direction of the liquid crystal molecules in parallel with the direction of the electric field (the magnitude of this torque is Depending on the strength of the electric field), ie, torque and rubbing due to the dielectric anisotropy, and the liquid crystal molecules are rearranged so as to balance the elastic torque for arranging the long axis direction of the liquid crystal molecules in a specific direction.

Another example of a conventional liquid crystal display device is disclosed in US Pat. No. 5,598,285, in which two rows of electrodes are arranged in parallel on one substrate with a liquid crystal material layer between them, and the liquid crystal molecules are oriented parallel to the substrate. And a liquid crystal display device. In this liquid crystal display device, an electric potential is applied between electrodes to form an electric field essentially parallel to the substrate and perpendicular to the two electrodes, and the liquid crystal is balanced so that the torque due to the dielectric anisotropy of the liquid crystal material and the elastic torque due to the alignment treatment are balanced. The molecules rearrange.

Each of these conventional liquid crystal display devices has a problem.

The biggest problem of the twisted nematic liquid crystal display is that the viewing angle is narrow. In this liquid crystal display device, the birefringence Δn, which is a difference in refractive index between the long axis direction and the short axis direction of the liquid crystal molecules, increases as the angle between the direction of the eye of the person viewing the display device and the direction perpendicular to the surface of the display device increases. The product of the thickness d of the liquid crystal layer, that is, the value of Δn · d, becomes large, and accordingly, the contrast (a value obtained by dividing the brightness of the brightest state by the brightness of the darkest state) is rapidly reduced. In addition, there is a phenomenon of gray level inversion in which brightness is reversed. Therefore, the viewing angle (the angle at which the contrast is maintained at 10 is called a viewing angle) is very narrow, and the image quality deteriorates sharply compared to the image viewed from the front when the display device is viewed at an angle larger than the viewing angle.

In order to compensate the viewing angle, as described in the above-mentioned US Patent No. 5,576,861, a method of widening the viewing angle using a phase difference compensation plate or the like has been proposed, but since an additional process of attaching an additional compensation plate is required. In addition to higher costs and increased processing, the use of compensation plates still limits the viewing angle.

In the second device, the electric field located in the region between the two electrodes becomes smaller as it moves away from the two electrodes, so that the minimum voltage (threshold voltage) for passing light in the normally black mode is not only high. Since the voltage (saturation voltage) that passes the light as much as possible is high, there is a problem in that the power consumption is large. In addition, not only all the electrodes are formed on one substrate, but in order to ensure sufficient capacitance, the pixel electrode and the common electrode must have an overlapping portion with an insulating layer therebetween, so that the aperture ratio through which light passes is small.

One object of the present invention is to ensure a wide viewing angle.

Another object of the present invention is to drive the liquid crystal at a low voltage to lower the power consumption.

Another object of the present invention is to increase the aperture ratio.

In order to solve the above problems, the present invention updates the arrangement of the electrodes.

That is, the first electrode and the second electrode which are insulated from each other are arranged so that the edges overlap each other, and the second electrode has a structure consisting of a continuous surface between the first electrodes, and at least one pixel It consists of a first electrode and a second electrode.

In such a liquid crystal display, when a voltage is applied to the first electrode and the second electrode to give a potential difference, an electric field is generated, and the shape of the electric force line is a semi-elliptic or parabola centered on the boundary or boundary region between the first electrode and the second electrode. This results in a vertical and horizontal component of the electric field on each electrode.

The liquid crystal molecules on the first electrode or the second electrode and in the boundary region between the two electrodes are rearranged by the horizontal and vertical components of the electric field and are rearranged, and the polarization of the light is changed by the rearranged liquid crystal material layer. do.

As such, the liquid crystal molecules rearrange and have both a twist angle and an inclination angle, thereby widening the viewing angle.

In addition, since the electric field has vertical and horizontal components not only on the boundary region of the two electrodes but also on the first electrode and the second electrode, the liquid crystal molecules on the first electrode and the second electrode also participate in the display of the image.

In addition, since the intensity of the electric field is large at the boundary region between the first electrode and the second electrode, power consumption is low because the threshold voltage and the saturation voltage for driving the liquid crystal layer thereon are low.

In addition, in the case of applying a voltage to the first electrode and the second electrode by using a thin film transistor as a switching element, since the two electrodes overlap each other with an insulating film therebetween, it is not necessary to provide a separate storage capacitor to secure the capacitance so that the aperture ratio can be reduced. I can make it big.

Next, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings so that a person skilled in the art may easily implement the present invention.

First, the first embodiment of the present invention will be described in detail with reference to FIGS. 1 to 11.

FIG. 1 is a diagram illustrating an arrangement of electrodes in a liquid crystal display according to a first exemplary embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II 'of FIG. 1 to show both the upper substrate and the lower substrate. The electric field lines and the equipotential lines are shown together.

First, the structure of the lower substrate in which an electrode is formed is demonstrated.

The planar electrode 2 is formed of a transparent conductive material such as indium tin oxide (ITO) on the inner surface of the lower substrate 10 made of a transparent insulating material such as glass or quartz, and has a long width in the horizontal direction. The insulating film 3 covers the planar electrode 2, and many linear electrodes 1 which are narrow in width are formed in parallel with each other in the vertical direction. The linear electrode 1 can be used as a transparent or opaque material, the width of which is smaller than the distance between the linear electrodes 1, that is, the distance between adjacent border lines of two adjacent linear electrodes 1. An alignment layer 30 made of a material such as polyimide is coated on the linear electrode 1. On the other hand, a polarizing plate 20 is attached to the outer surface of the lower substrate 10.

An alignment layer 31 made of a material such as polyimide is formed on the inner surface of the substrate 11 made of a transparent insulating material such as glass or quartz, and a polarizing plate 21 is attached to the outer surface thereof.

Finally, a liquid crystal material layer having optical anisotropy is inserted between the alignment layers 30 and 31 of the two substrates 10 and 11.

The liquid crystal display device may perform a display operation by adjusting the transmittance of light from a backlight unit (not shown) positioned below the lower substrate 10, but may enter the upper portion of the upper substrate 11. The display operation may be performed using natural light, and in this case, the lower polarizer 20 is not necessary. In the case of a reflective liquid crystal display using natural light, it is preferable to make both the linear electrode 1 and the planar electrode 2 made of a material having a high opacity and high reflectance, for example, aluminum (Al).

Next, the general shape of the electric field of the liquid crystal display will be described in detail with reference to FIG. 2.

When a voltage is applied to the two electrodes 1 and 2 to give a potential difference between the two electrodes 1 and 2, an electric field as shown in FIG. 2 is generated. The solid line in FIG. 2 represents an equipotential line, and the dotted line represents an electric force line.

As can be seen in FIG. 2, the shape of the electric field is in the longitudinal center line C (actually the plane) of the narrow region NR above the linear electrode 1 and the wide region WR between the linear electrode 1. It is symmetric with respect to the longitudinal center line B (actually corresponding to the face). In the region from the centerline C of the narrow region NR to the centerline B of the large region WR, the vertex is at the boundary line A (actually a plane) between the narrow region NR and the large region WR. An electric field having an electric field line shape having a half ellipse shape or parabolic shape (hereinafter, referred to as a half ellipse shape for convenience) having a shape is generated. The tangent of the electric line of force is almost parallel to the substrate 10 on the boundary line A between the narrow region NR and the large region WR, and the substrate 10 at the central position of the narrow region NR and the large region WR. It is almost perpendicular to. In addition, the center and longitudinal vertices of the ellipse are located on the boundary line A between the narrow region NR and the wide region WR, and the two vertices of the horizontal direction are positioned in the large region WR and the narrow region NR, respectively. do. At this time, the horizontal vertex located in the narrow area NR has a shorter distance from the center of the ellipse than the horizontal vertex located in the wide area WR. Thus, the ellipse does not have symmetry with respect to the boundary line A. FIG. In addition, the density of electric field lines varies with position, and the strength of the electric field varies proportionally thereto. Thus, the intensity of the electric field is greatest on the boundary line AA between the narrow region NR and the large region WR, and toward the centerline CC, BB of the narrow region NR and the large region WR, and above. It becomes smaller toward the board | substrate 11.

Then, the state in which the liquid crystal molecules are rearranged by the electric field is divided into components that are horizontal to the substrate and components that are perpendicular thereto.

First, the initial state will be described.

The two alignment layers 30 and 31 are aligned by rubbing or ultraviolet irradiation, so that the liquid crystal molecules are all aligned in one direction, but have a slight pretilt angle with respect to the substrates 10 and 11 but are substantially horizontal. , And arranged at a certain angle with respect to the direction of the linear electrode 1 and the direction perpendicular thereto when viewed from a plane parallel to 11). The polarization axes of the polarizing plates 20 and 21 are arranged to be orthogonal to each other, and the polarization axes of the lower polarizing plate 20 substantially coincide with the buffing direction. The liquid crystal material contained between the two alignment layers 30 and 31 is a nematic liquid crystal having a positive dielectric anisotropy.

Next, a voltage is applied to the linear electrode 1 and the planar electrode 2, respectively, and a high voltage is applied to the linear electrode 1. At this time, the arrangement of the liquid crystal molecules is determined by equilibrium between the force due to the electric field (depending on the direction and intensity of the electric field) and the elastic restoring force generated by the alignment process.

The rearrangement state of the liquid crystal molecules is divided into components parallel to the substrate and perpendicular to the substrate. For convenience of explanation, the direction perpendicular to the substrate is z-axis, the direction perpendicular to the substrate and also perpendicular to the direction of the linear electrode 1 is the x-axis, and the direction parallel to the direction of the linear electrode 1 is the y-axis. That is, the direction from left to right in FIG. 1 is the x axis, the direction from bottom to top along the linear electrode 1 is the y axis, and the direction from the lower substrate 11 to the upper substrate 10 in FIG. 2 is z. Let's grab the axis.

First, the change in the angle between the twist angle of the liquid crystal molecules, that is, the plane in which the long axis of the liquid crystal molecules is parallel to the substrate, that is, on the xy plane with respect to the x-axis or the initial alignment direction, will be described with reference to FIGS. 3, 4, and 5. do.

As illustrated in FIG. 3, the buffing direction is represented by a vector, the xy plane component of the electric field is represented by a vector _xy , the optical axis of the lower polarizing plate 20 is represented by a vector, and the angle between the buffing direction and the x axis is represented by ψ _R , The angle between the major axis of the liquid crystal molecules and the x axis is represented by ψ _LC . However, since the optical axis of the lower polarizing plate 20 coincides with the buffing direction, the optical axis of the lower polarizing plate 20 is the angle ψ _P = ψ _R forming the x axis.

Away from the center line (B) in the xy direction of the plane component _(xy) of the field has a large area (WR) from the boundary line (A), and x in the positive direction, then the boundary (D from the center line (B) of large area (WR) ) Is in the negative x direction. The intensity of the electric field component is largest on the boundaries A and D and becomes smaller toward the center line BB and becomes zero on the center line BB.

The magnitude of the elastic restoring force by the orientation treatment is constant regardless of the position on the xy plane.

Since the liquid crystal molecules should be arranged so that these two forces are in equilibrium, as shown in FIG. 4, in the boundary lines A and D, the long-axis direction of the liquid crystal molecules is almost parallel to the electric field component _xy and the buffing direction. Although having a large angle, the angle (|ψ _R- ψ _LC |) of the long axis of the liquid crystal molecules with respect to the buffing direction decreases toward the center lines C and B of the regions NR and WR. In (B, C), the long axis and the buffing direction of the liquid crystal molecules become the same. Since the optical axis of the lower polarizing plate 20 is parallel to the buffing direction, the angle formed between the optical axis of the lower polarizing plate 20 and the long axis of the liquid crystal molecules also has the same distribution, and this value is closely related to the transmittance of light.

By varying the ratio of the width of the narrow area NR to the wide area WR, various types of electric fields can be generated. When the linear electrode 1 is used as an opaque electrode, the narrow area NR on the linear electrode 1 cannot be used as the display area. However, when the linear electrode 1 is made of a transparent material, the narrow area NR can also be used as the display area. .

On the other hand, the surface of xy-plane component _(xy) of the electric field up to the upper alignment film 31 from the following alignment film (30), that becomes increasingly smaller while following the z-axis, elastic restoring force due to the orientation of the alignment film 30, 31 It is the largest at, and becomes smaller toward the center of the liquid crystal layer between the two alignment layers 30 and 31.

5 shows a torsion angle at the position from the lower alignment layer 30 to the upper alignment layer 31, that is, along the z axis and in which the major axis direction of the liquid crystal molecules forms the x axis, as shown in FIG. 5. The case where the cell spacing is d is shown. Here, the horizontal axis means the height from the lower alignment layer 30, and the vertical axis indicates the twist angle.

5, it can be seen that the torsion angle is large because the force due to the alignment force is strong on the surfaces of the alignment layers 30 and 31, and becomes smaller toward the center of the liquid crystal layer, thereby becoming closer to the direction of the electric field. 31) Immediately above, the long axes of the liquid crystal molecules are arranged in the same direction as the buffing direction. Here, when the difference in the twist angles of adjacent liquid crystal molecules is called twist, the twist in FIG. 5 corresponds to the slope of the curve, which is larger on the surfaces of the alignment layers 30 and 31 and smaller toward the center of the liquid crystal layer.

Next, with reference to FIGS. 6, 7, and 8, the angle of inclination of the liquid crystal molecules, that is, the plane of the liquid crystal molecules perpendicular to the substrate with respect to the x-axis or the initial alignment direction, for example, on the zx plane is described with reference to FIGS. 6, 7, and 8. Explain. In FIG. 6, only the substrates 10 and 11 are shown for convenience, and components of the zx plane of the vector representing the buffing direction shown in FIG. 3 are represented by the vector _zx , and the zx plane components of the electric field are represented by the vector _zx . The angle formed by the zx plane component _zx with the x axis is θ _E , and the inclination angle formed by the long axis of the liquid crystal molecules with the x axis is represented by θ _LC . However, since the vector is on the xy plane (ignoring the pretilt angle), _zx is in the x direction.

Zx plane size of the component _(zx) of the electric field is gradually reduced as the substrate 11 in the substrate 10 below, the angle θ _E also becomes increasingly smaller as the substrate 11 in the substrate 10 below.

As described above, the magnitude of the elastic restoring force due to the alignment treatment is the largest on the surfaces of the two substrates 10 and 11 and decreases toward the center of the liquid crystal layer.

The liquid crystal molecules must be arranged such that these two forces are in equilibrium. As shown in FIG. 7, since the alignment force is strong on the surface of the lower substrate 10, the liquid crystal molecules are arranged parallel to the x-axis, but as the upward force increases relative to the x-axis, the magnitude of the inclination angle θ _LC is increased. It continues to increase until the point, and then decreases again to be aligned parallel to the x-axis on the upper substrate 11 surface. At this time, the peak of the curve appears at a position close to the lower substrate 10.

On the other hand, the angle θ _E formed by the zx plane component ( _zx ) of the electric field with respect to the x axis is closer to zero on the boundary lines (A, D) and increases toward the center line (BB), and the magnitude of the zx plane component ( _zx ) of the electric field is the boundary line. It is the largest on (A, D) and smaller toward the center line BB.

The magnitude of the elastic restoring force by the orientation treatment is constant regardless of position on the x axis.

Therefore, as shown in Figure 8, the boundary line (A, D), each close but the center line to substantially the angle of inclination of the liquid crystal molecules 0 (C, B) with increasingly large zx plane component of the electric field _(zx) are forms with the x-axis ( θ _E ) has a similar distribution. However, it changes more slowly than θ _E.

As such, when voltage is applied to the two electrodes 1 and 2, the liquid crystal molecules are rearranged at a torsion angle and an inclination angle, and the transmittance of light is changed due to a change in the torsion angle and the inclination angle. On the boundary lines A and D, there is little change in the inclination angle when viewed along the z axis, but the change in the torsion angle is large. On the other hand, on the center lines B and C, there is little change in the torsion angle when viewed along the z axis, but the inclination angle is slightly changed. Therefore, in the area between the boundary lines A and D and the center lines B and C, the torsion angle and the inclination angle are both changed. As a result, the transmittance curve according to the position becomes a shape similar to that of the electric field lines.

Next, the transmittance and viewing angle characteristics of the liquid crystal display according to the first exemplary embodiment of the present invention will be described with reference to FIGS. 9, 10, and 11.

In the present experimental example, the linear electrode 1 is made of an opaque material, the width of the narrow region NR is 5 μm, the width of the large region is 17 μm, and the voltage applied to the planar electrode 2 is 0 V, The voltage applied to the linear electrode 1 was 5 V, ψ _R was 80 °, the pretilt angle was about 1.5 °, and the cell spacing was 4.5 μm.

FIG. 9 is a graph of transmittance according to the present experimental example, and looks at the change in transmittance while moving from the origin to the x-axis direction while taking the left boundary of the leftmost linear electrode 1 as the origin.

As shown in FIG. 9, the transmittance becomes zero in the opaque narrow region NR, decreases around the center line B of the large region WR, and decreases in the area between the boundary lines A and D and the center line B. Maximum in the middle

In addition, looking at the change in transmittance according to the applied voltage, it can be seen that the threshold voltage is about 1.5V and the saturation voltage is about 3V, as shown in FIG. 10 with the horizontal axis as the applied voltage and the vertical axis as the transmittance. Therefore, the liquid crystal display according to the present invention can be driven even at a low voltage.

FIG. 11 is a graph illustrating viewing angle characteristics according to the direction of the liquid crystal display according to the exemplary embodiment, and it may be confirmed that the boundary of an area of 10 degrees or more is almost 60 degrees above, below, right and left.

In the present experimental example, a wider viewing angle can be obtained by using the optical phase difference compensation plate between the polarizing plate and the substrate.

In the above embodiments and experimental examples, the type of liquid crystal material, the type of alignment film, the alignment method, the pretilt angle, the direction of the polarizing plate, the cell spacing, the type and presence of the retardation compensation plate, the material forming the electrode, the width and spacing of the electrode, etc. Is changeable according to the design of the liquid crystal display device.

For example, when the linear electrode 1 is formed of a transparent material, since the liquid crystal molecules on the linear electrode 1 are also used to control light, greater transmittance can be obtained.

Next, the liquid crystal display according to the second exemplary embodiment of the present invention will be described with reference to FIGS. 12 and 13.

In this embodiment, unlike in the first embodiment, the portion where the two electrodes overlap is removed. However, the planar electrodes 2 of two neighboring pixels should be connected to each other, and this connection portion may overlap with the linear electrode 1 as shown in FIG. 12, but otherwise may be formed outside the linear electrode 1 so as not to overlap. It may be. In FIG. 12, only the center portion of the portion overlapping with the linear electrode 1 of the planar electrode 2 is removed to form the opening 5, and the lower portion of the overlapping portion is left as it is for the signal transmission. For convenience of description, the area on the linear electrode 1 is defined as the narrow area NR, the area where the opening 5 is located, the boundary area BR, and the area occupied by the portion of the planar electrode 2 between two adjacent openings 5. It is called wide area | region WR, Let width of narrow area | region NR be a, width of boundary area | region BR, and width of wide area | region WR is b.

In FIG. 13, which is a cross-sectional view of the XIII-XIII 'line in FIG. 12, the electric force line occurs in a parabolic or semi-elliptic form between the center line C of the narrow region NR and the center line B of the large region WR. When the width c of the boundary region BR is constant, a parabolic electric line of force that changes depending on the value of a / b but whose vertices are located on the centerline I of the boundary region BR is obtained. The shape of the parabola is asymmetric when a and b are different, but nearly symmetric when a and b are the same. Here, when c is 0, an electric field almost similar to that of the first embodiment is formed, and an electric field having horizontal and vertical components is formed on the planar electrode 2 or the linear electrode 1 even if c is not zero. .

Therefore, in a transmissive display device in which one or both electrodes are formed of a transparent material, light passing through the transparent electrode is controlled by the twist and tilt of the liquid crystal layer positioned on the electrode. At this time, the threshold voltage of the liquid crystal material is lower as the c value is smaller.

In the case of the reflective type in which both electrodes 1 and 2 are used as a metal having high reflectance, for example, metal such as A1, the smaller c has a higher reflectance. In this case, as described above, the liquid crystal layer on the rearranged electrode having the change in the twist angle and the tilt angle changes the polarization of the light incident on the electrode and the light reflected from the electrode to display an image.

Next, a liquid crystal display device in which a thin film transistor is added as a switching element to the electrode structures shown in the first and second embodiments as a third embodiment of the present invention will be described with reference to FIGS. 14 to 16. do.

FIG. 14 is a layout view of one pixel formed on a lower substrate of the liquid crystal display according to the present embodiment, and hundreds of thousands of such pixels are arranged in a matrix structure in the liquid crystal display.

Scan signal lines 40 are formed horizontally on the transparent insulating substrate 10, and planar common electrodes 2 are formed horizontally between the scan signal lines 40.

The scan signal line 40 and the common electrode 2 are covered with the gate insulating film 3, and an amorphous silicon layer is disposed on a portion of the gate insulating film 3 positioned above the scan signal line 40 (hereinafter referred to as a gate electrode) 41. 60 is formed. On the amorphous silicon layer 60, amorphous silicon layers 71 and 72 which are heavily doped with n-type impurities are formed on both sides of the gate electrode 41, respectively.

On the other hand, the data line 80 is also formed in the longitudinal direction on the gate insulating film 3 to intersect with the gate line 40, and a part of the data line 80 extends and is formed on the doped amorphous silicon layer 71. To form the source electrode 81, and a drain electrode 82 is formed on the doped amorphous silicon layer 72 opposite to the source electrode 81 with respect to the gate electrode 41. The gate electrode 41, the source electrode 81, and the drain electrode 82 form each electrode of the thin film transistor, and the amorphous silicon layer 60 has a channel through which electrons move, and the doped amorphous silicon layer is formed of a source and It serves to improve the ohmic contact between the drain electrodes 81 and 82 and the amorphous silicon layer 60.

The drain electrode 82 extends to form a plurality of pixel electrodes 1 having a linear shape in the vertical direction. The data line 80, the source and drain electrodes 81 and 82, and the pixel electrode 1 may be passivation layers. Covered by 90, the alignment film 30 is again formed thereon.

Here, the common electrode 2 should be connected to the common electrode of the neighboring pixel because the common electrode signal should be received from the common electrode of the neighboring pixel. To this end, the common electrode 2 and the data line 80 overlap each other, and this overlapping portion generates parasitic capacitance to increase the RC delay of the image signal. To reduce this, the area in which the common electrode 2 and the data line 80 overlap each other is minimized, and a portion of the common electrode 2 disposed below the data line 80 overlapping the data line 80 is removed. . However, the upper and lower portions of the overlapping portion are left as they are so as not to be disconnected from the common electrodes of neighboring pixels.

At the portion where the first electrode 1 and the second electrode 2 overlap, a part of the second electrode 2 below the first electrode 1 is removed, so that the second electrode 2 has a vertically long hole 50 Has) This is to appropriately adjust the capacitance formed between the first electrode 1 and the second electrode 2, and may be formed such that the second electrode 2 and the first electrode 1 overlap with each other without doing so. have.

In addition, the passivation layer 90 is removed in the display area, that is, the portion where the pixel electrode 1 and the common electrode 2 are located, so that a sufficient electric field can be generated.

Next, a method of manufacturing the liquid crystal display according to the third embodiment of the present invention will be described in detail.

First, a common electrode 2 is formed by stacking and patterning a transparent conductive material such as ITO, and then depositing and patterning a Cr, Al, Mo, Ti, Ta film or an alloy film thereof to form the scan signal line 40 and the gate electrode. To form 41. A gate insulating film 3 made of a material such as a nitride film is stacked to cover the common electrode 2, the gate electrode 41, and the scan signal line 40. An amorphous silicon layer 60 and an n + type amorphous layer are disposed on the gate insulating film 3. The silicon layers 71 and 72 are laminated successively. The n + type amorphous silicon layers 71 and 72 and the amorphous silicon layer 60 are patterned, and Cr, Al, Mo, Ta, or alloys thereof are deposited and patterned to form the data line 80, the source electrode 81, and After forming the drain electrode 82 and the pixel electrode 10, the resistive contact layers 71 and 72 are completed by etching the n + type amorphous silicon layers 71 and 72 exposed using them as masks. Subsequently, the protective film 80 is deposited and patterned to form an opening on the pixel electrode 1, and then the alignment film 30 is applied to complete the liquid crystal display substrate according to the present embodiment.

In the liquid crystal display according to the exemplary embodiment of the present invention, it can be seen that a parabolic or elliptic electric field is formed even on a linearly formed pixel electrode. Therefore, when both the common electrode and the pixel electrode are formed using a transparent conductive material, light transmittance is formed. Can improve.

A fourth embodiment of the present invention provides a method of forming a pixel electrode using a transparent conductive material.

17 is a layout view of a liquid crystal display according to a fourth exemplary embodiment of the present invention, and FIG. 18 is a cross-sectional view of the liquid crystal display shown in FIG. 17 taken along the line XVIII-XVIII '.

As shown in FIGS. 17 and 18, a gate line 20 for transmitting a scan signal from the outside is formed in a horizontal direction on the transparent insulating substrate 100, and a gate electrode 21 is formed as a branch of the gate line. . In addition, a common electrode line 30 for transmitting a common signal is formed in parallel with the gate line 20, and a common electrode 31 formed in a continuous plane over the entire pixel area is connected to the common electrode line 30. It is. The gate electrode 21 and the common electrode 31 are double layers of lower layers 211 and 311 made of a transparent conductive material such as ITO and upper layers 212 and 312 made of Cr, Al, Mo, Ta, or an alloy thereof. A portion of the upper layer of the common electrode 31 in the pixel area is removed to expose the transparent conductive layer 312, which is a lower layer. Although not shown in the drawing, the gate line 20 and the common electrode line 30 also consist of a double layer.

The gate insulating film 40 covers the gate line 20, the gate electrode 21, the common electrode line 30, and the common electrode 31. The gate insulating film 40 on the upper portion of the common electrode 31 in the pixel area It is removed.

An amorphous silicon layer 50 used as a channel layer of a thin film transistor is formed on the gate insulating layer 40 on the gate electrode 21, and the n + amorphous silicon layers 61 and 62 form the gate electrode 21 thereon. It is formed in both centers.

On the n + amorphous silicon layers 61 and 62, a source electrode 71 and a drain electrode 72 made of metal are formed, respectively. The source electrode 71 is formed in the longitudinal direction on the gate insulating film 40 and is formed from the outside. It is connected to the data line 60 which transmits an image signal.

A protective film 80 made of silicon nitride or the like is covered on the entire surface of the substrate, and the protective film 80 has a contact hole for exposing the drain electrode 72. In the pixel region, a plurality of pixel electrodes 90 parallel to each other are formed of a transparent conductive material such as ITO, and the plurality of pixel electrodes 90 are connected to each other and through contact holes formed in the passivation layer 80. It is electrically connected to the drain electrode 72.

Now, a method of manufacturing the liquid crystal display according to the fourth exemplary embodiment of the present invention will be described. The manufacturing method according to the fourth embodiment of the present invention is a manufacturing method using six masks.

First, a transparent conductive material such as ITO and a metal such as Cr, Al, Mo, Ta, or an alloy thereof are sequentially deposited on the transparent insulating substrate 100 and patterned using a first mask to form a gate line 20 having a double layer. The gate electrode 21, the common electrode line 30, and the common electrode 31 are formed.

Next, a triple layer of the gate insulating film 40, the amorphous silicon layer 50, and the n + amorphous silicon layer is sequentially deposited and patterned using a second mask. The gate insulating film 40 in the pixel region is removed using a third mask.

Cr, Al, Mo, Ta, or an alloy thereof is deposited and patterned using a fourth mask to form a source electrode 71, a drain electrode 72, a data line 70, and the gate insulating film 40 is formed. The opaque metal layer 312 that is the upper layer of the common electrode 31 inside the exposed pixel area is removed. A protective film 80 is deposited on the entire surface of the substrate, and a contact hole exposing the drain electrode 72 is formed using a fifth mask. Finally, ITO is deposited and patterned using a sixth mask to form the pixel electrode 90. At this time, the thickness of the pixel electrode 90 is preferably formed to 1,500 kPa or less.

The gate line and the common electrode may be formed separately without forming a double layer. A fifth embodiment of the present invention provides a method of forming a gate line and a common electrode by depositing and patterning metal and ITO, respectively.

19 is a cross-sectional view of a liquid crystal display according to a fifth exemplary embodiment of the present invention.

In order to manufacture the liquid crystal display as illustrated in FIG. 19, first, Cr, Al, Mo, Ta, or an alloy thereof is deposited on the transparent insulating substrate 100, and patterned using a first mask to form a gate line and a gate electrode. 21, a common electrode line is formed. Next, a transparent conductive material such as ITO is deposited and patterned using a second mask to form a common electrode 30.

The gate insulating film 40, the amorphous silicon layer 50, and the triple layer of the n + amorphous silicon layer are sequentially deposited and patterned using a third mask.

Cr, Al, Mo, Ta, alloys thereof, or the like are deposited and patterned using a fourth mask to form the source electrode 71, the drain electrode 72, and the data line 70. A protective film 80 is deposited on the entire surface of the substrate, and a contact hole exposing the drain electrode 72 is formed using a fifth mask. Finally, ITO is deposited and patterned using a sixth mask to form the pixel electrode 90. In this case, as in the fourth embodiment of the present invention, the pixel electrode 90 may be formed to have a thickness of 1,500 Å or less.

In such a liquid crystal display device, by renewing the electrode structure, the viewing angle can be widened, the driving voltage can be reduced, and the aperture ratio can be increased.

1 is a layout view illustrating an electrode of a liquid crystal display according to a first exemplary embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line II-II 'of FIG. 1, illustrating an equipotential line and an electric force line between the upper substrate, the lower substrate, and the two substrates.

3 is a view for explaining the change in the twist angle of the liquid crystal molecules in the first embodiment of the present invention,

FIG. 4 is a graph illustrating a change in the twist angle of liquid crystal molecules with respect to a line horizontal to a substrate and perpendicular to a linear electrode in the first embodiment of the present invention.

FIG. 5 is a graph showing a change in the twist angle of liquid crystal molecules with respect to the vertical line of the substrate in the first embodiment of the present invention.

6 is a view for explaining a change in the inclination angle of the liquid crystal molecules in the first embodiment of the present invention,

FIG. 7 is a graph illustrating a change in the twist angle of liquid crystal molecules with respect to a vertical line of a substrate in the first exemplary embodiment of the present invention.

FIG. 8 is a graph illustrating a change in the inclination angle of liquid crystal molecules with respect to a line horizontal to a substrate and perpendicular to a linear electrode in the first embodiment of the present invention.

9 is a graph illustrating a change in transmittance according to a position in the liquid crystal display according to the first exemplary embodiment of the present invention.

10 is a graph illustrating a change in transmittance according to an applied voltage in the liquid crystal display according to the first exemplary embodiment of the present invention.

11 is a graph showing a viewing angle in the liquid crystal display according to the first embodiment of the present invention;

12 is a layout view of a liquid crystal display according to a second exemplary embodiment of the present invention.

FIG. 13 is a cross-sectional view taken along the line XXIII-XIII 'of FIG. 12,

14 is a layout view of a liquid crystal display according to a third exemplary embodiment of the present invention.

FIG. 15 is a cross-sectional view taken along line XV-VV ′ of FIG. 14;

FIG. 16 is a cross-sectional view taken along line XVI-XVI 'of FIG. 14;

17 is a layout view of a liquid crystal display according to a fourth exemplary embodiment of the present invention.

FIG. 18 is a cross-sectional view taken along line XVIII-XVIII ′ of FIG. 17;

19 is a cross-sectional view of a liquid crystal display according to a fifth exemplary embodiment of the present invention.

Claims (4)

Board, A gate line formed on the substrate and a gate electrode connected to the gate line; A planar common electrode formed separately from the gate line on the substrate and made of a transparent conductive material and applying the same voltage to each pixel; A gate insulating film covering the gate line and the gate electrode; A semiconductor layer formed on the gate insulating film on the gate electrode, Source and drain electrodes formed on both sides of the gate electrode on the semiconductor layer; A data line formed on the gate insulating layer and connected to the source electrode; A passivation layer covering the source and drain electrodes and the data line; A plurality of linear pixel electrodes formed on the passivation layer and connected to the drain electrode and parallel to each other made of a transparent conductive material; And a region on the pixel electrode as part of an image display region. In claim 1, The gate line and the gate electrode include a lower layer made of a metal and an upper layer made of a transparent conductive material. Sequentially depositing a transparent conductive material and a metal on the substrate, Patterning the metal and the transparent conductive material to form a gate line, a gate electrode, and a planar common electrode; Sequentially depositing a gate insulating film, an amorphous silicon layer, and a doped amorphous silicon layer on the gate line, the gate electrode, and the planar common electrode; Patterning the doped amorphous silicon layer and the amorphous silicon layer, Patterning the gate insulating film; Depositing and patterning metal to form source and drain electrodes and data lines, Removing a metal layer, which is an upper layer of the common electrode, Forming a protective film, Depositing and patterning a transparent conductive material to form a linear pixel electrode. Depositing and patterning a metal on the substrate to form a gate line and a gate electrode; Depositing and patterning a transparent conductive material to form a planar common electrode, Depositing a triple layer of a gate insulating film, an amorphous silicon layer, and a doped amorphous silicon layer, and patterning the doped amorphous silicon layer and the amorphous silicon layer, Depositing and patterning metal to form source and drain electrodes and data lines, Forming a protective film, Depositing and patterning a transparent conductive material to form a linear pixel electrode.