KR20060092386A - Transflective fringe field switching mode liquid crystal display - Google Patents

Abstract

The present invention relates to a transflective fringe field switching mode liquid crystal display device capable of improving quality. The transflective fringe field switching mode liquid crystal display device is a transflective fringe field switching mode liquid crystal display device having a single cell gap structure having a cell gap of the same transmissive area and a reflecting area, wherein a lower substrate having a counter electrode and a pixel electrode is formed of a liquid crystal. An upper substrate is disposed to face the upper substrate, and an upper polarizer is disposed outside the upper substrate, a lower polarizer is disposed outside the lower substrate, and a reflector is provided inside the lower substrate of the reflective area. An upper λ / 4 plate is provided between the lower substrate having a reflector and the liquid crystal layer, a lower λ / 4 plate is provided between the lower substrate and the lower polarizing plate, and a first passivation layer is provided between the counter electrode and the pixel electrode. And a second passivation layer on the pixel electrode of the reflective region, wherein the counter electrode of the transmissive region is formed. The thickness of the first passivation layer formed between the pixel electrodes is equal to the sum of the thickness of the first passivation layer formed between the reflecting plate and the pixel electrode of the reflection region and the thickness of the second passivation layer additionally formed on the pixel electrode of the reflection region. The phase delay value of the liquid crystal layer of the reflective region is switched to 0 or λ / 2, and the phase delay value of the transparent region liquid crystal layer is switched to 0 or λ / 2.

Description

Transflective fringe field switching mode liquid crystal display

1 is a cross-sectional view showing a conventional single cell gap transflective liquid crystal display device.

2 is a graph for explaining the V-T curve of the transmission mode and the V-R curve of the reflection mode in the conventional single cell gap transflective liquid crystal display device.

3 is a cross-sectional view showing a conventional dual cell gap transflective liquid crystal display device.

4 is a graph for explaining the V-T curve of the transmission mode and the V-R curve of the reflection mode in the conventional dual cell gap transflective liquid crystal display device.

5 is a cross-sectional view showing the optical cell structure of a single cell gap transflective fringe field switching mode liquid crystal display device for explaining the present invention;

FIG. 6 is a view showing an optical axis of a reflection area of a single cell gap transflective fringe field switching mode liquid crystal display device for explaining the present invention; FIG.

FIG. 7 is a view showing an optical axis of a transmission region of a single cell gap transflective fringe field switching mode liquid crystal display device for explaining the present invention; FIG.

8 is a view for explaining the driving principle of a reflection area of a single cell gap transflective fringe field switching mode liquid crystal display device for explaining the present invention;

9 is a view for explaining the driving principle of the transmission region of the single cell gap transflective fringe field switching mode liquid crystal display device for explaining the present invention.

10 is a graph showing the difference between the V-R / V-T curves of the reflection / transmission portion of the single cell gap transflective fringe field switching mode liquid crystal display device;

11 is a cross-sectional view illustrating an array pixel structure of a single cell gap transflective fringe field switching mode liquid crystal display according to the present invention;

FIG. 12 is a graph illustrating driving voltage simulation results according to a passivation layer thickness between a counter electrode and a pixel electrode and a passivation layer thickness on an upper portion of a pixel electrode in a fringe field switching mode LCD.

The present invention relates to a transflective liquid crystal display device, and more particularly, to a transflective fringe field switching mode liquid crystal display device capable of obtaining a high quality and ensuring a wide viewing angle.

The liquid crystal display may be classified into two types: a transmissive liquid crystal display using a backlight as a light source and a reflective liquid crystal display using natural light as a light source. The transmissive liquid crystal display uses a backlight as a light source, so that a bright image can be realized even in a dark environment. However, the transmissive liquid crystal display has a disadvantage of high power consumption. The power consumption is small because it uses natural light, but the disadvantage is that it is impossible to use when the surrounding environment is dark.

Accordingly, in order to solve the disadvantages of the transmissive and reflective liquid crystal display, a transflective liquid crystal display has been proposed. Since the transflective liquid crystal display device can use both a reflection type and a transmissive type as needed, it has a relatively low power consumption and can be used even in a dark environment.

Meanwhile, the conventional transflective liquid crystal display device described above uses a single cell gap structure in which the cell gap dt of the transmission region and the cell gap dr of the reflection region are the same, as shown in FIG. 1, and FIG. As shown in Fig. 3, the cell gap of the transmission region dt is designed in such a manner that a dual cell gap structure is used which is twice as large as the cell gap dr of the reflection region. 1 and 3, reference numeral 1 denotes a lower substrate, 2a a pixel electrode, 2b a reflective electrode, 3 an upper substrate, 4 a common electrode, 5 a liquid crystal, and 6 an organic insulating film.

However, when the semi-transmissive liquid crystal display device is manufactured by applying the same liquid crystal mode with the single cell gap structure shown in FIG. 1, the phase delay value Δn · d of the reflective region is twice the phase delay value of the transmission region. As shown in FIG. 2, the gray curve of the reflection mode and the VT curve of the transmission mode are inconsistent, causing gray level mismatch and deterioration of electro-optic characteristics.

Accordingly, recently, many transflective liquid crystal displays have been manufactured using a dual cell gap structure in which the cell gap of the transmissive region is designed to be about twice as large as the cell gap of the reflective region. When the transflective liquid crystal display device is manufactured by applying the same liquid crystal mode with the dual cell gap structure, the cell gap of the reflection area is 1/2 of the cell gap of the transmission area, but the optical path is twice, so that the phase delay value of the reflection area is It has the same phase delay value as that shown in Fig. 4, so that the VR curve and the VT curve can be easily matched, so that the gray level mismatch and the deterioration of the electro-optical characteristics can be effectively suppressed as compared with the case where the single cell gap is applied. Because it can.

However, when the semi-transmissive liquid crystal display device is manufactured by applying the dual cell gap as described above, the step difference due to the difference in the cell gap between the transmissive region and the reflective region occurs twice as compared to the single cell gap structure, resulting in an uneven liquid crystal alignment process. Difficulties exist in the manufacturing process and the productivity is reduced, there is a problem that the viewing angle is narrow because the liquid crystal adjacent to the alignment layer is not perfectly standing when an electric field is applied.

Therefore, the present invention was created to solve the problems as described above inherent in the transflective liquid crystal display device according to the prior art, the object of the present invention, the difficulty in the manufacturing process in applying a dual cell gap structure and thus The present invention provides a semi-transmissive fringe field switching mode liquid crystal display which can improve the disparity between the VT curve and the VR curve when the single cell gap structure is applied and improve the viewing angle.

In order to achieve the above object, according to one aspect of the present invention, there is provided a transflective fringe field switching mode liquid crystal display device, wherein the liquid crystal display device has a transflective fringe having a single cell gap structure having the same cell gap as the transmissive area and the reflective area. In the field switching mode LCD table, a lower substrate having a counter electrode and a pixel electrode is disposed to face the upper substrate under the liquid crystal layer, and an upper polarizer is disposed outside the upper substrate, and an outer side of the lower substrate. A lower polarizing plate is disposed on the lower substrate, a reflecting plate is provided inside the lower substrate of the reflective region, and an upper λ / 4 plate is provided between the lower substrate having the reflecting plate and the liquid crystal layer, and between the lower substrate and the lower polarizing plate. A lower λ / 4 plate is provided, a first passivation layer is provided between the counter electrode and the pixel electrode, and is disposed on the pixel electrode of the reflective region. The second passivation layer is formed on the second passivation layer, wherein the thickness of the first passivation layer formed between the counter electrode and the pixel electrode of the transmissive region is formed between the reflecting plate and the pixel electrode of the reflecting region. Is equal to the sum of the thickness and the thickness of the second passivation layer additionally formed on the pixel electrode of the reflective region, the phase delay value of the liquid crystal layer of the reflective region is switched to 0 or λ / 2, and the phase delay value of the transmissive liquid crystal layer is It is characterized in that it is switched to 0 or λ / 2.

The dielectric constants of the first and second passivation layers are 2 to 7.

The thickness of the first passivation layer formed between the counter electrode and the pixel electrode in the transmission region is 3,500 to 10,000 1.

The upper λ / 4 plate has a phase delay value of 100 to 200 nm.

The liquid crystal layer in the reflection region and the transmission region has a phase delay value of 250 to 400 nm.

The transmission axis of the lower polarizing plate coincides with the initial rubbing direction of the liquid crystal layer, the transmission axis of the upper polarizing plate is orthogonal to the lower polarizing tube, and the optical axes of the lower λ / 4 plate and the upper λ / 4 plate are perpendicular to each other, and the lower side The λ / 4 plate forms 135 ° with the rubbing axis of the initial liquid crystal, and the upper λ / 4 plate forms 45 ° with the rubbing axis of the initial liquid crystal.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

First, briefly describing the present invention, the present invention improves productivity reduction or manufacturing process difficulties caused by applying a conventional dual cell gap structure by applying a single cell gap structure. Drives to secure wide viewing angle characteristics.

5 is a cross-sectional view illustrating an optical cell structure of a single cell gap transflective fringe field switching mode liquid crystal display for explaining the present invention.

As shown in FIG. 5, the single cell gap transflective fringe field switching mode liquid crystal display includes a reflecting portion and a transmissive portion, and the upper substrate 10 and the lower substrate 20 face each other under the liquid crystal layer 30. It is arranged. The upper polarizing plate 11 is disposed outside the upper substrate 10. A reflecting plate 22 is provided inside the lower substrate 20 corresponding to the reflecting unit, and an upper λ / 4 plate 23 is provided between the reflecting plate 22 and the liquid crystal layer 30. In addition, a lower polarizer 21 is disposed outside the lower substrate 20, and a lower λ / 4 plate 24 is provided between the lower substrate 20 and the lower polarizer 21. The upper λ / 4 plate 23 between the reflecting plate 22 and the liquid crystal layer 30 has a phase delay value of 100 to 200 nm. The phase delay value Δn · d of the liquid crystal layer 30 is 0 or λ / 2. The liquid crystal layer 30 of the reflector functions as a phase delay value of zero when no electric field is applied, and converges to a phase delay value of λ / 2 when an electric field is applied. The liquid crystal layer 30 of the transmission part also serves as a zero phase delay value when no electric field is applied, and converges to a phase delay value of λ / 2 when an electric field is applied. The liquid crystal layer 30 in the reflection region and the transmission region has a phase delay value of 250 to 400 nm in order to serve as λ / 2.

Looking at the axis of each optical material when forming the optical cell structure as described above is as follows. FIG. 6 is a view illustrating an optical axis of a reflective region of a single cell gap transflective fringe field switching mode liquid crystal display for explaining the present invention, and FIG. 7 is a single cell gap transflective fringe field switching mode liquid crystal display for explaining the present invention. 6 and 7, the transmission axis of the lower polarizing plate 21 coincides with the initial rubbing direction of the liquid crystal, and the transmission axis of the upper polarizing plate 11 is connected to the lower polarizing plate 21. It can be seen that it is orthogonal. The optical axes of the lower λ / 4 plate 24 and the upper λ / 4 plate 23 are orthogonal to each other, and the lower λ / 4 plate 24 is 135 ° from the rubbing axis of the initial liquid crystal. The upper λ / 4 plate 23 forms 45 ° with the rubbing axis of the initial liquid crystal.

8 is a view illustrating a driving principle of a reflective region of a liquid crystal display device, and FIG. 9 is a single cell gap transflective fringe field switching mode for explaining the present invention. It is a figure for explaining the driving principle of the transmission area of a liquid crystal display device.

First, the driving principle in the reflection area is as follows.

As shown in FIG. 8, the linearly polarized light does not change because the polarized light is 90 ° linearly passing through the upper polarizing plate 11 having the initial 90 ° transmission axis (a) and the liquid crystal layer 30 is the 0 degree axis (b). ), And then circularly polarized while passing through the upper λ / 4 plate 23 at the top of the reflector 22 (c), and the light is reflected from the reflector 22 (d), and again the upper λ / 4 plate 23 As a result, the light incident to the initial incident light and the linear flat light in the 0 ° direction twisted 90 ° (e) through the liquid crystal layer 30 as it is (f), and eventually absorbed by the upper polarizing plate 11, It is dark.

In addition, 90 ° linearly polarized while passing through the upper polarizing plate 11 having an initial 90 ° transmission axis (a), and the liquid crystal layer 30 acts as a λ / 2 plate that is twisted at 22.5 °, resulting in a linear polarization of 135 ° (b Since the light is twisted 90 degrees with the optical axis of the upper λ / 4 plate 23, the axis does not change even when the polarized light passes back through the upper λ / 4 plate 23 through the reflecting plate 22 (c). , d, e). After passing through the liquid crystal layer 30 serving as a λ / 2 plate, the light is changed back to 90 ° linearly polarized light (f), thereby forming a bright state.

Hereinafter, the driving principle in the transmission region will be described.

As shown in FIG. 9, the lower polarizing plate 21 is formed in the 0 ° direction, and the light passing through the lower polarizing plate 21 passes through two λ / 4 plates 23 and 24 orthogonal to each other. Since the polarization direction does not change (a, b, c), since the liquid crystal layer 30 also forms 0 °, polarization is not comfortable (d), and eventually light is absorbed by the upper polarizer 11 to form a dark state. .

In addition, in the bright state, the lower polarizer 21 is formed in the 0 ° direction, and the light passing through the lower polarizer 21 is polarized while passing through two λ / 4 plates 23 and 24 orthogonal to each other. Since the direction does not change (a, b, c), and since the liquid crystal layer 30 also forms 45 °, the polarization is changed and twisted by 90 ° (d), so that light passes.

Here, in the transflective liquid crystal display device having a single cell gap structure, there is an important factor influencing driving. That is, in the dual cell gap structure, the cell gap influenced the driving voltage range, but in the single cell gap structure, the reflection region should twist only the liquid crystal from 0 ° to 22.5 ° for black and white, and in the transmission region. Twist 0 ° to 45 ° to achieve on / off. As a result, as shown in FIG. 10, the white of the reflection area reaches first, and the V-R curve of the reflection area and the V-T curve of the transmission area are inconsistent. Therefore, it is necessary to match the driving ranges of the reflection area and the transmission area, and the method for this is as follows.

FIG. 11 is a cross-sectional view illustrating an array pixel structure of a single cell gap transflective fringe field switching mode liquid crystal display device according to an exemplary embodiment of the present invention, and FIG. 12 is a passivation film thickness between a counter electrode and a pixel electrode in a fringe field switching mode liquid crystal display device. It is a graph showing the driving voltage simulation results according to the thickness of the protective film on the top of the electrode.

The array pixel structure of the single cell gap transflective fringe field switching mode liquid crystal display device according to the present invention is a transmissive area for displaying an image with light of a backlight and a reflecting area for displaying an image with ambient light, as shown in FIG. The transmissive region and the reflective region have a single cell gap structure having the same cell gap, and the thickness of the first passivation layer 109 between the relative electrode 107 and the pixel electrode 110 of the transmissive region is greater than that of the reflective region. Since the thickness of the first passivation layer 109 between the 108 and the pixel electrode 110 and the thickness of the second passivation layer 111 on the pixel electrode 110 are equal to each other, the cell gap difference between the reflection area and the transmission area does not occur. Do not. Although not shown in FIG. 11, as described above, the λ / 4 plate is positioned between the reflective plate 108 and the liquid crystal layer 112 of the reflective region for the optical configuration, and the liquid crystal layer 112 of the reflective region is located. The phase delay value Δn · d of is switched to 0 or λ / 2, and the phase delay value Δn · d of the transmissive region liquid crystal layer 112 is also switched to 0 or λ / 2. In FIG. 11, reference numeral 100 denotes a lower substrate, 101a a gate electrode, 101b a common electrode, 103 a first insulating layer, 104 an active layer, 105 a source and a drain electrode, and 106 a second insulating layer, respectively. Indicates.

On the other hand, as shown in FIG. 12, when the passivation layer is thinly formed between the counter electrode 107 and the pixel electrode 110, the driving voltage is lowered, and the passivation layer 111 is disposed on the pixel electrode 110. In the case of forming, the driving voltage is increased. Therefore, it can be seen that it is more effective to increase the driving voltage to deposit the protective film on top of the pixel electrode 110 than to increase the protective film thickness between the counter electrode 107 and the pixel electrode 110.

Accordingly, in order to match the VR curve of the reflection region and the VT curve characteristics of the transmission region, a material having a dielectric constant of 2 to 7 is used as the first and second passivation layers 109 and 111, and the counter electrode 107 of the transmission region is used. ) And the thickness of the first passivation layer 109 between the pixel electrode 110 is 3,500 to 10,000 mW. This is almost the same thickness as the sum of the thickness of the first passivation layer 109 between the reflecting plate 108 and the pixel electrode 110 in the reflecting region and the thickness of the second passivation layer 111 on the pixel electrode 110. At this time, the thickness of the first passivation layer 109 between the counter electrode 107 and the pixel electrode 110 in the transmission region and the thickness of the first passivation layer 109 between the reflector plate 108 and the pixel electrode 110 in the reflection region And a difference between the thicknesses of the sum of the thicknesses of the second passivation layer 111 on the pixel electrode 110 may occur due to a process or the like. In this case, even if the difference is 0.4 μm or less or 10% or less of the cell gap, It may be considered to be within the scope of this patent.

As described above of the present invention, the present invention can apply the single cell gap structure to match the VR curve in the reflection region and the VT curve in the transmission region while eliminating productivity degradation and difficulty in manufacturing process. By improving the electro-optical characteristics of the transmissive region, a high quality transflective liquid crystal display device can be obtained. In addition, since the present invention is driven in a fringe field switching mode having a wide viewing angle characteristic, it is possible to implement a transflective liquid crystal display device having a wide viewing angle.

While the invention has been shown and described with respect to certain preferred embodiments thereof, the invention is not so limited and it is intended that the invention be limited without departing from the spirit or field of the invention as set forth in the following claims It will be readily apparent to one of ordinary skill in the art that various modifications and variations can be made.

Claims (6)

In the transflective fringe field switching mode liquid crystal display device having a single cell gap structure having the same cell gap as the transmission region and the reflection region, A lower substrate having a counter electrode and a pixel electrode is disposed to face the upper substrate under the liquid crystal layer, an upper polarizer is disposed outside the upper substrate, and a lower polarizer is disposed outside the lower substrate, and the reflective region is disposed. A reflecting plate is provided inside the lower substrate of the upper substrate, and an upper λ / 4 plate is provided between the lower substrate having the reflecting plate and the liquid crystal layer, and a lower λ / 4 plate is provided between the lower substrate and the lower polarizing plate. A first passivation layer is provided between the counter electrode and the pixel electrode, and a second passivation layer is further provided on the pixel electrode of the reflective region, and is formed between the counter electrode and the pixel electrode of the transmission region. A thickness of the first passivation layer is formed between the reflective plate of the reflective region and the pixel electrode, and a second thickness is formed on the pixel electrode of the reflective region. It is equal to the sum of the thicknesses of the protective film, and the phase delay value of the liquid crystal layer of the reflective region is switched to 0 or λ / 2, and the phase delay value of the transmissive region liquid crystal layer is switched to 0 or λ / 2. Fringe field switching mode liquid crystal display. The method of claim 1, A transflective fringe field switching mode liquid crystal display device, wherein the dielectric constants of the first and second passivation layers are 2 to 7. The method of claim 1, A transflective fringe field switching mode liquid crystal display device, wherein the thickness of the first passivation layer formed between the counter electrode and the pixel electrode in the transmissive region is 3,500 to 10,000 Å. The method of claim 1, The upper λ / 4 plate has a phase delay value of 100 to 200 nm. The method of claim 1, The transflective fringe field switching mode liquid crystal display of claim 1, wherein the liquid crystal layer of the reflection area and the transmission area has a phase delay value of 250 to 400 nm. The method of claim 1, The transmission axis of the lower polarizing plate coincides with the initial rubbing direction of the liquid crystal layer, the transmission axis of the upper polarizing plate is orthogonal to the lower polarizing tube, and the optical axes of the lower λ / 4 plate and the upper λ / 4 plate are perpendicular to each other, and the lower side A λ / 4 plate is 135 ° with the rubbing axis of the initial liquid crystal, and the upper λ / 4 plate is 45 ° with the rubbing axis of the initial liquid crystal.

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