KR100989256B1 - Liqude crystal display - Google Patents

Abstract

The present invention discloses a liquid crystal display device capable of improving the luminance and image quality of the liquid crystal display device by improving the reflection efficiency in the reflection area where external light is incident and improving the transmission efficiency in the transmission area. The disclosed subject matter includes a first substrate; A second substrate; A reflecting plate having a plurality of pixel regions in the first substrate, each pixel region having a reflecting region and a transmitting region, the reflecting plate being disposed on the reflecting region on the first substrate; A first retardation plate disposed throughout the reflection area and the transmission area on the first substrate; A common electrode disposed on an inner surface of the second substrate; A liquid crystal layer including a dichroic dye filled between the first substrate and the second substrate; A second retardation plate disposed on an outer surface of the first substrate; And a polarizer disposed on the second retardation plate.

The dichroic dye and the liquid crystal molecules are horizontally aligned in the off state, the liquid crystal layer is vertically aligned in the off state of the dichroic dye, and the first retardation plate is disposed on the reflector. It is characterized by.

Transflective plate, Polarizing plate, Retardation plate, Reflecting plate, Pixel electrode, In cell

Description

Liquid crystal display {LIQUDE CRYSTAL DISPLAY}

1 is an exploded perspective view showing a typical transflective color liquid crystal display device.

2 is a vertical cross-sectional view of a pixel region of a transflective liquid crystal display device generally used.

FIG. 3 is a diagram illustrating a pixel area of a generally used transmissive guest host mode liquid crystal display device; FIG.

4 is a cross-sectional view showing a pixel area of a transflective guest host mode liquid crystal display device according to the present invention;

5A and 5B are diagrams for explaining the operation principle in an on / off state of the transflective guest host mode liquid crystal display according to the present invention;

6 is a view for explaining an optical configuration of a transflective guest host mode liquid crystal display device according to the present invention.

7 is a cross-sectional view illustrating a pixel area of a transflective guest host mode liquid crystal display according to another exemplary embodiment of the present invention.

8A and 8B are diagrams for explaining the operation principle of the transflective guest host mode liquid crystal display in the on / off state.

9 is a view for explaining an optical configuration of a transflective guest host mode liquid crystal display device according to the present invention.

* Description of the symbols for the main parts of the drawings *

50a: lower substrate 50b: upper substrate

51: gate electrode 52a: second retardation plate

52b: first retardation plate 54: gate insulating film

55: channel layer 56: ohmic contact layer

57a: source electrode 57b: drain electrode

58: protective film 59: insulating film

60: reflecting plate 62: common electrode

63a: liquid crystal molecule 63b: dichroic dye

63: liquid crystal layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device. More particularly, the polarizing plate may be removed to improve reflection efficiency in a reflection area, while improving transmission efficiency in a transmission area to improve contrast ratio and improve screen quality. It relates to a liquid crystal display device.

Recently, as the information society has progressed rapidly, a display field for processing and displaying a large amount of information has been developed. Until recently, cathode ray tube (CRT) has been the mainstream of display devices and has been developing.

However, in recent years, the need for a flat panel display has emerged in order to meet the times of miniaturization, light weight, and low power consumption. Accordingly, a thin film transistor-liquid crystal display (hereinafter referred to as TFT-LCD) having excellent color reproducibility and thinness has been developed.

Referring to the operation of the TFT-LCD, when an arbitrary pixel is switched by the thin film transistor, the arbitrary pixel that is switched makes it possible to adjust the light transmission amount of the lower light source.

The switching device is mainly composed of an amorphous silicon thin film transistor (a-Si: H TFT) in which a semiconductor layer is formed of amorphous silicon. This is because the amorphous silicon thin film can be formed at a low temperature on a large insulating substrate such as a low-cost glass substrate.

Commonly used TFT-LCDs have used a method of representing an image by the light of a light source called a backlight located under the panel.

However, TFT-LCDs are very inefficient light modulators that transmit only 3-8% of the light incident by the backlight.

The light transmittance of the TFT-LCD is about assuming that the transmittance of the two polarizers is 45%, the transmittances of the two glass plates of the lower and upper plates are 94%, the TFT array and the pixel transmittance are about 65%, and the color filter transmittance is 27%. 7.4%.

Thus, a transflective liquid crystal display device that can use an external light source and an internal light source of a liquid crystal display device as a light source for a display has been proposed. The structure thereof is as follows.

FIG. 1 is an exploded perspective view illustrating a general reflective transmissive color liquid crystal display device.

As shown in FIG. 1, the structure of a general reflection-transmissive liquid crystal display device is largely divided into a color filter substrate, an array substrate, and a liquid crystal layer. The color filter substrate is formed of a black matrix using chromium on a transparent insulating substrate 20. (23) are formed, and the R, G, B color filter layers 25 are formed in the inner space where the black matrix 23 is formed, and are arranged by a transparent metal to apply a common voltage used in the pixel. The common electrode 21 is included.

The array substrate corresponding to the color filter substrate may define a unit pixel area by vertically crossing a plurality of gate bus lines 12 and data bus lines 11 on the transparent insulating substrate 10, The TFT 15 performing the switching operation, the pixel electrode 13b in the transmissive region, and the reflecting plate 13a in the reflective region are arranged on the pixel region.

The array substrate and the color filter substrate are bonded together with the liquid crystal layer 17 interposed therebetween. When the TFT is turned on by a drive signal from the gate bus line 12 disposed on the array substrate, the data bus line The data signal from 11 is transmitted to the pixel electrode connected to the drain electrode of the TFT turned on.

By varying the transmittance of each pixel by changing the arrangement of liquid crystals under the voltages of the common electrode 21 disposed on the color filter substrate and the pixel electrode to which the data signal voltage is applied, the transmittance of each pixel is changed, The image is displayed using the light incident from the backlight.

As described above, the transflective liquid crystal display displays an image mainly by using external light during a bright day, and reduces power consumption while maintaining image quality by mainly using an internal light source in a dark night or a space.

2 is a cross-sectional view showing a pixel area of a transflective liquid crystal display device which is generally used.

As shown in FIG. 2, when the pixel area of the transflective liquid crystal display is largely divided into three parts, the lower substrate 30a on which the pixel electrode 35 and the reflecting plate 37 are disposed, and the common electrode 33. ) And an upper substrate 30b on which a color filter layer (not shown) is disposed, and a liquid crystal layer 39 interposed between the lower substrate 30a and the upper substrate 30b.

In detail, the lower substrate 30a is disposed on the lower substrate 30a formed of a transparent insulating substrate, and pixel electrodes 35 made of transparent metal ITO are disposed for each pixel, and a reflective plate is formed on the pixel electrode 35. In order to arrange 37), the passivation layer 36 was applied on the pixel electrode 35, and then the transparent region and the reflective region were separated and patterned to have a predetermined step. The reflective plate 37 is disposed on the protective film 36.

On the other side of the lower substrate 30a on which the pixel electrode 35 and the reflecting plate 37 are disposed, a lower retardation plate 32a and a lower polarizer 31a are attached to the internal light source incident from the backlight. Is polarized in a constant direction.                         

In addition, the upper substrate 30b is similarly disposed on the upper substrate 30b made of a transparent insulating substrate, and the common electrode 33 is disposed in a region in contact with the liquid crystal layer 37, and the common electrode 33 is disposed. On the other side of the part, the upper retardation plate 32b and the upper polarizing plate 31b are attached.

In the transflective liquid crystal display having the above structure, the distance between the common electrode 33 disposed on the upper substrate 30b and the pixel electrode 35 in the transmissive region disposed on the array substrate is d. _When the distance between the common electrode 33 and the reflecting plate 37 was d ₂ , the distance ratio was set to d ₁ = 2d ₂ .

The reason why the cell gap in the transmission region and the cell gap in the reflection region is different as described above is that when the cell gap in the transmission region is twice as large as the cell gap in the reflection region, the transmission efficiency of the two regions is simultaneously optimized. Designed with Δnd ₂ = λ / 4)

3 illustrates a pixel area of a commonly used transmissive guest host mode liquid crystal display. As shown in FIG. 3, a lower substrate 40a on which a pixel electrode 46 is disposed and a lower substrate 40a are shown. The upper substrate 40b on which the transparent common electrode 43 is disposed in the opposite direction is bonded to each other with the liquid crystal layer 48 made up of the liquid crystal molecules 48b mixed with the dichroic dye 48a interposed therebetween.

The polarizer 45 is attached to the other side on which the pixel electrode 46 is disposed on the lower substrate 40a.

A method of driving the transmissive guest host mode liquid crystal display having the structure as described above will be described as follows.

When the transmissive guest host mode liquid crystal display is in an off state, a light source generated from a backlight is polarized in a horizontal direction through the polarizing plate 45 attached to the lower substrate 40a.

The polarized light passes through the lower substrate 40a of the transparent insulating substrate and the pixel electrode 46 of the transparent ITO metal, wherein the dichroic dye 48a of the liquid crystal layer 48 is arranged horizontally. The polarized light is absorbed so that the light exiting to the upper substrate 40b does not exist.

When the transmissive guest host mode liquid crystal display is in an on state, the light source generated in the backlight is polarized in the horizontal direction on the polarizer 45 attached to the lower substrate 40a.

The polarized light passes through the lower substrate 40a of the transparent insulating substrate and the pixel electrode 46 of the transparent ITO metal. In this case, the liquid crystal layer 48 is applied by the voltage applied to the pixel electrode 46. ), The dichroic dye is also vertically arranged so that the polarized light passes through the common electrode and the upper substrate 40b without light absorption.

As described above, the transmissive guest host mode liquid crystal display device has an advantage of removing the polarizer disposed on the upper substrate because light is blocked or transmitted by the dichroic dye.

However, although the transflective liquid crystal display device reduces the power consumption by allowing the external light source to be used for the display, there is a problem that the reflection efficiency by the light absorbed by the polarizing plate is not sufficient.

In addition, since an additional process for forming the dual cell gap of the lower substrate is required, there is a problem in that the production yield is reduced due to the increase in manufacturing cost.

The present invention applies a guest host mode to a transflective liquid crystal display device to improve the reflection efficiency of external light in the reflection area, while improving the transmission efficiency of the internal light generated in the backlight in the transmission area to display an image contrast ratio. It is an object of the present invention to provide a liquid crystal display device capable of improving image quality while improving.

In order to achieve the above object, the liquid crystal display device according to the present invention,

A first substrate;

A second substrate;

A reflecting plate having a plurality of pixel regions in the first substrate, each pixel region having a reflecting region and a transmitting region, the reflecting plate being disposed on the reflecting region on the first substrate;

A first retardation plate disposed throughout the reflection area and the transmission area on the first substrate;

A common electrode disposed on an inner surface of the second substrate;                     

A liquid crystal layer including a dichroic dye filled between the first substrate and the second substrate;

A second retardation plate disposed on an outer surface of the first substrate;

And a polarizer disposed on the second retardation plate.

The dichroic dye and the liquid crystal molecules are horizontally aligned in the off state, the liquid crystal layer is vertically aligned in the off state of the dichroic dye, and the first retardation plate is disposed on the reflector. It is characterized by.

Further, a pixel electrode is further included on the first retardation plate, wherein the first retardation plate and the second retardation plate have optical axes perpendicular to each other, and the phase retardation value of the first retardation plate and the phase retardation of the second retardation plate. The value is characterized by the same.

In addition, the liquid crystal display device according to another embodiment of the present invention,

A first substrate;

A second substrate;

A reflecting plate having a plurality of pixel regions in the first substrate, each pixel region having a reflecting region and a transmitting region, the reflecting plate being disposed on the reflecting region on the first substrate;

A first retardation plate disposed on a reflection area on the first substrate;

A common electrode disposed on an inner surface of the second substrate;

A liquid crystal layer including a dichroic dye filled between the first substrate and the second substrate;

And a polarizer disposed on the outer surface of the first substrate.

The dichroic dye and the liquid crystal molecules are horizontally aligned, the dichroic dye and the liquid crystal molecules are vertically aligned, and the first retardation plate is disposed only on the reflector. .

In particular, the pixel electrode is further included on the first retardation plate.

According to the present invention, the guest host mode is applied to the transflective liquid crystal display device, thereby improving the reflection efficiency of external light in the reflection area and improving the transmittance of the internal light generated in the backlight in the transmission area, thereby improving screen quality. have.

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

4 is a cross-sectional view illustrating a pixel area of a transflective guest host mode liquid crystal display according to the present invention.

As shown in FIG. 4, since the pixel structure of the transflective liquid crystal display device is manufactured in various ways, the present invention may be applied to the pixel structure of various other transflective liquid crystal display devices by using the pixel structure as an example. To mention.

If the structure of the transflective liquid crystal display device is divided into three regions, it can be classified into a color filter substrate, a liquid crystal layer, and an array substrate.

In the array substrate, a gate bus line and a gate electrode are formed on a lower substrate 50a that is a transparent insulating substrate, and a gate insulating layer 54 is formed on the lower substrate 50a on which the gate electrode 51 is formed. It is applied. On the lower substrate 50a to which the gate insulating layer 54 is coated, switching element TFTs including a channel layer 55, an ohmic contact layer 56, and source / drain electrodes 57a and 57b are disposed in each unit pixel region. It is. A protective film 58 is coated on the lower substrate 50a on which the TFT is disposed, and an insulating film 62 is coated on the reflective film 60 and the reflective plate 60 on the protective film 58. A first retardation plate 52b is disposed on the insulating film 62, and an ITO pixel electrode 61 made of a transparent metal is formed on the first retardation plate 52b.

The second retardation plate 52a and the polarizing plate 53 are attached to the other side of the lower substrate 50a on which the above devices are not formed.

The upper substrate 50b is formed of an ITO common electrode 59 made of a transparent metal on the upper substrate 50b made of a transparent insulating substrate. The polarizing plate was removed.

The liquid crystal layer 63 is mixed with a dichroic dye 63b so as to absorb a liquid crystal molecule 63a having a constant refractive index anisotropy and a light source of a long-axis component of the liquid crystal molecule.

Since the dichroic dye 63b has a property of moving in the same direction as the direction in which the liquid crystal molecules 63a move, the liquid crystal molecules 63a are re-used by application of a driving signal and a data signal. Move together when arranged.

Thus, when the liquid crystal molecules 63a are arranged vertically or horizontally by an electric field, light transmittance is adjusted according to the application of an electric field according to the degree of absorption of the dichroic dye disposed in parallel with the long axis direction of the liquid crystal molecules 63a. Can do it.

Although the liquid crystal molecules 63a are horizontally aligned in the drawing, the liquid crystal molecules 63a may be vertically aligned when the liquid crystal display device is turned off according to the formation of the alignment layer. In this case, the liquid crystal display is in a white mode when off, and in a black mode when in an on state.

That is, the dichroic dye can be used in accordance with various alignment directions in the liquid crystal direction to exhibit the polarization effect.

5A and 5B are diagrams for describing an operating principle in an on / off state of the transflective guest host mode liquid crystal display according to the present invention.

As shown in FIG. 5A, when no power is applied to the transflective guest host mode liquid crystal display, the liquid crystal layer 63 is interposed between the upper substrate 50b and the lower substrate 50a. The liquid crystal molecules 63a and the dichroic dye 63b molecules are aligned in the horizontal direction.

At this time, the light incident from the outside passes through the upper substrate 50b and the common electrode 59, and then the polarization component corresponding to the major axis direction of the dichroic dye 63b is absorbed by the liquid crystal layer 63, thereby preventing the light. Light incident on the one retardation plate 52b is an optical component having only a vertical component. Since the 45 ° Slow Axis is formed in the first retardation plate 52b, the optical component of the incident vertical component becomes left circularly polarized light.

The light that has changed to left circularly polarized light through the first retardation plate 52b passes through the pixel electrode 61 and is reflected by the reflecting plate 60 to be 180 ° phase-converted to become right circularly polarized light. The right circularly polarized light reflected by the reflective plate 60 passes again through the first retardation plate 52b having a 45 ° slow axis, and is polarized with an optical component in a horizontal direction. The polarized light is absorbed by the liquid crystal layer 63 and becomes black.

Thus, when the liquid crystal molecules 63a are turned off in the reflection region of the guest host mode transflective liquid crystal display and the liquid crystal molecules 63a are oriented in the horizontal direction, the light applied from the outside is incident on the dichroic dye 63b when reflected. All of them are absorbed to maintain a black state in which light is not transmitted.

Although not shown in the drawing, in the transmissive region, when light is incident on a backlight serving as an internal light source of the liquid crystal display, the light passes through the lower polarizer 53 attached to the lower substrate 50a so that only the horizontal optical component is used. It becomes polarized. The light polarized in the horizontal direction passes through the second retardation plate 52a. Since the second retardation plate 52a has a 135 ° slow axis, the light in the horizontal direction becomes right circularly polarized light.

The right polarized light passes through the lower substrate 50a and the pixel electrode 61 and passes through the first retardation plate 52b having a 45 ° slow axis to be polarized with an optical component in a horizontal direction. Absorbed in layer 63.

Thus, when the liquid crystal display is in the off state, the light generated in the backlight is not transmitted, but is polarized by the polarizing plate 53 and absorbed by the liquid crystal layer 63 to maintain the black state.

When the liquid crystal molecules constituting the liquid crystal layer 63 are arranged in the vertical direction, neither the light passing through the reflective region nor the transmissive region is absorbed by the liquid crystal layer 63, and the white mode is maintained when the liquid crystal layer 63 is transmitted and is turned off. do.

That is, the same mode as in the on state in the horizontal alignment mode and the off state in the vertical alignment mode will be described below.

As shown in FIG. 5B, when the guest host mode transflective liquid crystal display is turned on, all liquid crystal molecules of the liquid crystal layer are arranged in a horizontal direction to a vertical direction.

In this state, when external light is incident on the reflective region, the external light source is not absorbed in the liquid crystal layer 63 and immediately proceeds to the first retardation plate 52b. In the first retardation plate 52b, since an external light source having horizontal and vertical omnidirectional components proceeds, the light is reflected by the reflecting plate 60 therein without change, and again, without absorbing light from the liquid crystal layer 63 again. Will be reflected.

Therefore, when the liquid crystal molecules are horizontally aligned in the transflective guest host mode liquid crystal display, the white mode can be maintained in the reflection region in the on state.

Similarly, in the transmissive region, the light source generated in the backlight is polarized only by the light component in the horizontal direction of the polarizing plate 53 attached to the lower substrate 50a, and then the second retardation plate 52a and the first retardation plate 52b are continued. Only the light component of the horizontal component is passed through, so that the horizontal polarization component passing through the first retardation plate 52b is transmitted through the liquid crystal layer 63 without absorbing light and proceeds to the outside to perform a white mode. Will be maintained.                     

In the case where the liquid crystal molecules are turned on when the liquid crystal molecules are vertically aligned, the light transmitting phenomenon occurs in the same way as the off state of the horizontally aligned transflective guest host mode. The following description refers to the description of the transflective guest host mode off state in which the liquid crystal molecules are horizontally oriented, and the description is omitted.

6 is a view for explaining an optical configuration of a transflective guest host mode liquid crystal display according to the present invention.

As shown in FIG. 6, in the case of the pixel structure of the guest host mode transflective liquid crystal display device as shown in FIGS. 5A and 5B, when the liquid crystal display device is turned on or off, The changing figure is shown integrally.

(a) The guest host mode transflective liquid crystal display shows a slow axis of the first retardation plate and the second retardation plate with respect to the polarization transmission axis polarized by the polarization plate attached only on the lower substrate, and changes as the light progresses. An optical component is shown.

(b) When the liquid crystal display device is in an off state, when an external light source first enters the reflecting plate region, the external light source is light including both horizontal and vertical components. When such light enters the guest host mode liquid crystal layer through the upper substrate and the common electrode, the light component of the horizontal component is absorbed by the dichroic dye component, and only when the light component passes through the liquid crystal layer, only the polarization component of the vertical component It will exist.

The polarization component of the vertical component is incident on the first retardation plate formed on the lower substrate. As shown in the drawing, the first retardation plate is a phase plate having a 135 ° axis, and polarizes the vertical optical component to the left circularly polarized light. . The light polarized by the left circularly polarized light in the first retardation plate is 180 ° phase shifted from the reflective electrode and polarized into the right circularly polarized light component.

The light polarized by the right circularly polarized light in the reflective plate passes through the first retardation plate again, and is then polarized in the horizontal direction. Thus, all of them are absorbed by the dichroic dye of the liquid crystal layer, thereby becoming a black state.

When the liquid crystal display is in the off state, the light source generated in the backlight is polarized in the horizontal direction in the transmissive region, as shown in the figure shown in the polarizing plate attached on the lower substrate. The light polarized in the polarizing plate passes through the second retardation plate. Since the second retardation plate has a 45 ° slow axis, the light having the polarization component in the horizontal direction has a right circular polarization component. Light polarized by right circularly polarized light in the second retardation plate passes through the first retardation plate having a slow axis of 135 ° and is polarized by the optical component of the horizontal component, and is absorbed in the liquid crystal layer to maintain the black mode.

(c) When the liquid crystal display device is turned on, all liquid crystal molecules of the liquid crystal layer are rearranged from the horizontal alignment state to the vertical alignment state. When an external light source enters the reflecting plate region, the external light source proceeds to the first retardation plate without absorbing horizontal or vertical components in the liquid crystal layer.

In the first retarder, since it is not external light of the polarized component, the light is passed through the reflecting electrode and passed through the first retardation plate. Keep it.                     

In the transmissive region, the light source generated in the backlight is polarized in the horizontal direction in the polarizing plate attached on the lower substrate, and then polarized in the right circular polarization in the second polarizing plate and polarized in the first retardation plate to have a horizontal component. Light polarized in the horizontal direction in the first retardation plate immediately proceeds to the outside without absorption in the horizontal direction in the liquid crystal layer.

7 is a cross-sectional view illustrating a pixel area of a transflective guest host mode liquid crystal display according to another exemplary embodiment of the present invention.

As shown in FIG. 7, in the array substrate of the transflective liquid crystal display, a gate bus line and a gate electrode are formed on a lower substrate 70a that is a transparent insulating substrate, and the gate electrode 71 is formed. A gate insulating film 74 is coated on the lower substrate 70a. On the lower substrate 70a to which the gate insulating layer 74 is coated, switching element TFTs including a channel layer 75, an ohmic contact layer 76, and source / drain electrodes 77a and 77b are disposed in each unit pixel region. have.

A protective film 78 is coated on the lower substrate 70a on which the TFT is disposed, and an insulating film 79 is coated on the reflective film 80 and the reflective plate 80 on the protective film 78. On the insulating film 79, a patterned retardation plate 72 is disposed only on a reflective region, that is, a region overlapping planarly with the reflecting plate 80, and on the retardation plate 72, an ITO pixel electrode 81 made of a transparent metal. ) Is formed and arranged.

The polarizing plate 73 is attached to the other side of the lower substrate 70a on which the above devices are not formed, and the retardation plate is removed.                     

The ITO common electrode 82 made of a transparent metal is formed on the upper substrate 70b made of the transparent insulating substrate, and the retardation plate and the upper polarizing plate, which are conventionally attached in the transflective liquid crystal display, are removed.

The liquid crystal layer 83 is mixed with a dichroic dye 83b in order to be able to absorb the liquid crystal molecules 83a having a constant refractive index anisotropy and the polarization of the long-axis component of the liquid crystal molecules.

Since the dichroic dye 83b has a property of moving in the same direction as the direction in which the liquid crystal molecules 83a move, the liquid crystal molecules 83a move together when the liquid crystals are arranged by application of a driving signal and a data signal. Therefore, when the vertical arrangement or the horizontal arrangement by the electric field, the transmittance of light can be adjusted according to the application of the electric field according to the degree of absorption of the dichroic dye disposed in parallel with the long axis direction of the liquid crystal molecules.

Although the liquid crystal molecules are horizontally aligned in the drawing, the liquid crystal molecules may be vertically aligned when the liquid crystal display is turned off depending on the alignment layer. In this case, the liquid crystal display is in a white mode when off, and in a black mode when in an on state.

That is, the dichroic dye can be used in accordance with various alignment directions in the liquid crystal direction to exhibit the polarization effect.

8A and 8B are diagrams for describing an operating principle of the transflective guest host mode liquid crystal display in an on / off state.

As shown in FIG. 8A, in the pixel structure of the transflective guest host mode liquid crystal display device, as shown in FIG. 7, the reflective plate 80 and the pixel electrode 81 formed on the lower substrate 70a may be formed. The retardation plate 72 is formed only on the reflection plate 80 region, and the retardation plate 72 does not exist on the transmission region where the pixel electrode 81 is located. In addition, the phase difference plate 72 attached between the lower substrate 70a and the polarizing plate 73 is removed.

When no power is applied to the guest host mode transflective liquid crystal display device having the above structure, when an external light source is incident on the horizontally aligned liquid crystal layer 83, an optical component in a horizontal direction is formed in the liquid crystal layer 83. Absorbed by the dichroic dye 83b, only an optical component having only a vertical component is incident on the internal retardation plate 72.

Since the retardation plate 72 is a retardation plate having a 45 ° slow axis, a light source having a vertical component is polarized by left circularly polarized light, and is reflected by the reflective plate 80 and polarized by right circularly polarized light. The light polarized by the right circularly polarized light in the reflective plate 80 passes through the retardation plate 72 to be polarized by a horizontal component, and is absorbed by the liquid crystal layer 83 to maintain the black mode.

In the transmissive region, since the phase difference plate disposed on the outer surface of the lower substrate 70a and the phase difference plate 72 disposed on the pixel electrode 81 do not exist, the light source generated in the backlight is the polarizing plate 73. After being polarized in the horizontal direction at, it is immediately absorbed by the liquid crystal layer 83 to maintain the black mode.

In the form in which the liquid crystal molecules are arranged vertically, the external light source and the internal light source pass through the liquid crystal layer to maintain the white mode, which is the same as in the on-state mode in the horizontal alignment direction described below.                     

As shown in FIG. 8B, in the case of the pixel structure of the guest host mode transflective liquid crystal display device having the structure of FIG. 7, when it is turned on by applying power, the polarization patterns in the reflection area and the transmission area are As follows.

First, when the power is turned on, the liquid crystal molecules of the liquid crystal layer are vertically arranged, and the dichroic dyes are also arranged in the same direction.

When an external light source is incident from the outside, the light source passes through the upper substrate 70b and the common electrode 82 and proceeds to the liquid crystal layer 83. The liquid crystal molecules 83a of the liquid crystal layer 83 are vertically arranged. Therefore, it is incident on the retardation plate 72 immediately without being absorbed. After the retardation plate 72 is reflected by the reflecting plate 80 without a change in the form of polarization, it passes through the retardation plate 72 and then proceeds to the outside.

Therefore, light absorption does not occur in the reflective region in the on state of the reflective guest host mode liquid crystal display, thereby maintaining the white mode.

Similarly, since the phase difference plate attached to the lower substrate 70a is removed in the transmissive region, the light source generated in the backlight passes through the polarizing plate 73 and is polarized to have only the optical component in the horizontal direction. The liquid crystal layer 83 proceeds without other polarization to maintain the white mode.

When the liquid crystal molecules are vertically aligned, optical component polarization, which is the same as the off state of the reflective guest host mode in the horizontal alignment state described with reference to FIG. 8A, may be omitted.

Therefore, in the present mode, when the liquid crystal molecules are vertically aligned, the black mode is always maintained in the on state.

9 is a view for explaining an optical configuration of a transflective guest host mode liquid crystal display according to the present invention.

As shown in FIG. 9, the structure of the pixel area of the guest host mode LCD according to another exemplary embodiment of the present invention removes a phase difference plate attached between the polarizing plate and the lower substrate, as shown in FIG. 7. The retardation plate formed inside the display device allows the pattern to be formed only in the reflective region.

(a) Looking at the optical axis for polarizing the light incident from the outside and the inside, the retardation plate disposed inside the liquid crystal display device has a 45 degree slow axis, and the polarizing plate attached to the lower substrate has a horizontal polarization axis.

The retardation plate is used when external light is reflected only in the reflection region, and the light generated in the backlight has a structure in which the liquid crystal layer passes through the polarizing plate.

(b) In the transflective guest host mode liquid crystal display having the structure as shown in Figs. 8A to 8B, which is horizontally oriented, the external light applied from the outside in the reflection area absorbs the optical component in the horizontal direction in the liquid crystal layer. Only the optical component in the vertical direction is incident on the retardation plate. The vertical optical component incident on the retardation plate changes to the left circularly polarized state, which is reflected by the reflecting plate to become the right circularly polarized state.

The right polarized optical component passes through the retardation plate again to have an optical component in the horizontal direction, which is again absorbed by the liquid crystal layer and there is no light reflected from the outside to maintain the black state.                     

In the transmission region, the light source generated in the backlight is polarized to pass through the polarizing plate to have an optical component in the horizontal direction, and then immediately passes through the pixel electrode to be absorbed in the liquid crystal layer to maintain a black state.

(c) When turned on in the transflective guest host mode liquid crystal display device having the structure as shown in FIGS. 8A to 8B in the horizontal orientation, external light applied from the outside in the reflection area is vertically aligned in the liquid crystal layer. Since it is arranged, it is incident on the retardation plate without the optical component absorbed. The external light source incident on the retardation plate passes through the reflection plate and the retardation plate and passes through the liquid crystal layer.

That is, since there is no absorption of external light in the liquid crystal layer, the white state is maintained.

In the transmission region, the light source generated in the backlight is polarized to pass through the polarizing plate to have an optical component in the horizontal direction, and then immediately passes through the pixel electrode to pass through the liquid crystal layer arranged vertically to transmit light to the outside.

In this case, the white state is maintained in the transmission region.

The transflective guest host mode liquid crystal display in which the liquid crystal molecules are arranged vertically has an operation mode corresponding to the transflective guest host mode liquid crystal display in which the liquid crystal molecules are arranged horizontally. Corresponds to the on state.

As a result, in the present invention, since the polarizing plate and the retardation plate are partially removed, not only the transmittance due to light propagation can be improved, but also the contrast ratio can be improved.

As described in detail above, the present invention has an effect of improving the image quality by forming a guest host mode in the transflective liquid crystal display device, thereby improving reflectance in the reflective region and improving transmittance in the transmissive region.

In addition, by using a liquid crystal layer mixed with a dichroic dye for the guest host mode, the polarizing plate and the retardation plate attached to the upper substrate can be removed, and the dichroic dye and the retardation plate can prevent reflection and transmission of light without generating parallax. Since it can do this, there is an effect which can improve contrast ratio.

The present invention is not limited to the above-described embodiments, and various changes can be made by those skilled in the art without departing from the gist of the present invention as claimed in the following claims.

Claims (12)

delete delete delete delete delete delete delete A first substrate; A second substrate; A reflecting plate having a plurality of pixel regions in the first substrate, each pixel region having a reflecting region and a transmitting region, the reflecting plate being disposed on the reflecting region on the first substrate; A first retardation plate disposed on a reflection area on the first substrate; A common electrode disposed on an inner surface of the second substrate; A liquid crystal layer including a dichroic dye filled between the first substrate and the second substrate; And And a polarizer disposed on an outer surface of the first substrate. And light from the backlight passes through the first retardation plate and is directly emitted to the second substrate. The method of claim 8, And the dichroic dye and the liquid crystal molecules are horizontally aligned. The method of claim 8, And the dichroic dye and the liquid crystal molecules are vertically aligned. The method of claim 8, And the first retardation plate is disposed only on a reflecting plate.  The method of claim 8, And a pixel electrode is further included on the first retardation plate.

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