KR101124396B1 - Transflective mode In-Plane switching type liquid crystal display device - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transverse field type liquid crystal display device, and more particularly, to a transverse field type liquid crystal display device in which images can be viewed from both sides.

In the reflective and transmissive transverse electric field type liquid crystal display device according to the present invention for forming a double-sided display function, a rod-shaped opaque pixel electrode and a common electrode are formed in a single pixel, and the retardation film is formed between the common electrode and the pixel electrode and the liquid crystal layer. A transverse electric field liquid crystal panel including a (QWP) and a first polarizing plate and a transparent light source on one side of the liquid crystal panel, and a reflective polarizing plate and a second polarizing plate positioned so that the optical axis is perpendicular to the first polarizing plate on the other side of the liquid crystal panel. It is characterized by the configuration.

Through this configuration, it is possible to manufacture a transverse electric field type liquid crystal display device having a double-sided display function in which one side can express an image in a reflection mode and the other side can express an image in a transmissive mode.

Description

Transflective mode In-Plane switching type liquid crystal display device

1 is a cross-sectional view of a general transflective liquid crystal display device.

2 is an enlarged plan view of one pixel of an array substrate for a transverse electric field type liquid crystal display device;

3 is an enlarged cross-sectional view schematically showing the configuration of a reflection / transmission mode transverse electric field type liquid crystal display device according to the present invention;

FIG. 4 is a cross-sectional view illustrating only configurations having polarization characteristics in the configuration of FIG. 3. FIG.

FIG. 5 is a view showing angles formed between the upper and lower polarizing plates, the reflective polarizing plate, and the optical axis of the liquid crystal layer in the configuration of FIG. 4.

6A and 6B illustrate polarization characteristics when a voltage is off and on in reflection mode;

7A and 7B illustrate polarization characteristics when a voltage is off and on in a transmission mode.

<Brief description of the main parts of the drawing>

100: first substrate 102: gate electrode

108a: active layer 108b: ohmic contact layer

110: source electrode 112: drain electrode

114: pixel electrode 116: common electrode

200: second substrate 202: black matrix

204a, b: color filter 300: retardation film

410a: upper polarizer 410b: lower polarizer

500: front light

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a reflection transmission mode transverse electric field type liquid crystal display device.

In general, a liquid crystal display device is formed by arranging two substrates on which electric field generating electrodes are formed so that the surfaces on which two electrodes are formed face each other, injecting a liquid crystal material between the two substrates, and then applying a voltage to the two electrodes. By moving the liquid crystal molecules by an electric field, the device expresses an image by the transmittance of light that varies accordingly.

Such a liquid crystal display includes a vertical field type liquid crystal display device in which the common electrode and the pixel electrode are positioned up and down and driven according to a driving mode, and a horizontal field type liquid crystal in which the common electrode and the pixel electrode are located on the same plane and driven in a slit shape. It relates to a display device.

Hereinafter, the structure of a transverse electric field type liquid crystal display device is demonstrated with reference to attached drawing.

1 is an enlarged cross-sectional view showing a cross section of a general transverse electric field type liquid crystal display device.

As shown in the drawing, the conventional transverse electric field type liquid crystal display device B includes a color filter substrate B1 and an array substrate B2 facing each other, and a liquid crystal layer between the color filter substrate and the array substrates B1 and B2. (LC) is interposed.

The array substrate B2 includes a thin film transistor T, a common electrode 58, and a pixel electrode 72 for each of the pixels P1 and P2 defined in the transparent insulating substrate 50.

The thin film transistor T includes a gate electrode 52, a semiconductor layer 62 having an insulating layer 60 interposed therebetween, and a source configured to be spaced apart from each other on the semiconductor layer 62. And drain electrodes 64 and 66.

In the above configuration, the common electrode 58 and the pixel electrode 72 are configured to be spaced apart from each other in parallel on the same substrate.

In general, to simplify the process, the common electrode 58 is made of the same material as the gate electrode 52, and the pixel electrode 72 is made of the same layer as the source and drain electrodes 64 and 66. Consists of the same substance.

Although not shown, a gate line (not shown) extending along one side of the pixels P1 and P2 and a data line (not shown) extending in a direction perpendicular thereto are formed, and the common electrode 58 is formed. The common wiring (not shown) which applies a voltage to is comprised.

The color filter substrate B1 includes a black matrix 32 formed on a transparent insulating substrate 30 corresponding to the gate line (not shown), the data line (not shown), and the thin film transistor T. Color filters 34a and 34b are formed corresponding to the pixels P1 and P2.

The liquid crystal layer LC is operated by the horizontal electric field 95 of the common electrode 58 and the pixel electrode 72.

Hereinafter, referring to FIG. 2, a planar configuration of an array substrate constituting the transverse electric field type liquid crystal display device as described above will be described. (An example in which the common electrode and the pixel electrode are formed of transparent electrodes unlike the configuration of FIG. 1 will be described. Explain.)

2 is an enlarged plan view of one pixel of a conventional array substrate for a transverse electric field type liquid crystal display device.

As shown in the drawing, the gate wiring 54 extending in one direction on the substrate 50 and the data wiring 68 are formed so as to vertically intersect the gate wiring 54 to define the pixel region P. As shown in FIG. .

The common wiring 56 is formed in a region spaced in parallel with the gate wiring 54.

At the intersection of the gate line 54 and the data line 68, the gate electrode 52 connected to the gate line 54, the semiconductor layer 62 above the gate electrode 52, and the upper portion of the semiconductor layer 62. The thin film transistor T including the source electrode 64 and the drain electrode 66 is formed.

The pixel region P includes a common electrode 58 vertically extending from the common line 56 and spaced apart from each other in parallel with each other, and the pixel electrode 72 spaced apart in parallel between the common electrodes 58. ) Is configured.

The above-described transverse field type liquid crystal display device is widely used as a display device because the viewing angle is superior to that of a general vertical field type liquid crystal display device.

By the way, the vertical field type liquid crystal panel is capable of double-sided display by properly using the reflection mode and the transmission mode, but the horizontal field type liquid crystal panel is difficult to apply as a double-sided display element, such as a cellular phone designed to view images on both sides There was a limit to the application in the product.

Accordingly, an object of the present invention is to propose a transverse electric field type liquid crystal display device capable of realizing images on both sides.

To this end, one side represents the image in a reflection mode using a reflective electrode (pixel electrode and common electrode) and a reflective polarizing plate, and the other side passes the light through a region between the reflective electrodes to represent the image in a transmission mode. It is done.

According to an aspect of the present invention, there is provided a reflection / transmission mode transverse electric field type liquid crystal display device comprising: a first substrate and a second substrate having a plurality of pixel regions defined therebetween; A reflective electrode having a rod shape for each pixel region corresponding to the first substrate; A liquid crystal layer having a long axis arranged in a horizontal direction in a spaced area between the first substrate and the second substrate; A phase difference film (QWP film) formed between the liquid crystal layer and the reflective electrode; An upper polarizer plate positioned on the first substrate; A transparent light source configured on the upper polarizing plate; A reflective polarizer formed under the second substrate; The lower polarizing plate is disposed under the reflective polarizing plate, and the polarizing axis is perpendicular to the polarizing axis of the upper polarizing plate.

The reflective electrode is a pixel electrode and a common electrode configured to be spaced apart from each other in parallel on the same surface.

The display device may further include a switching element connected to the pixel electrode. When an electric field is generated between the pixel electrode and the common electrode, the liquid crystal layer corresponding to the reflective electrode (pixel electrode and common electrode) may be connected to an optical axis of the upper polarizing plate. And 45 ^° , and the liquid crystal layer corresponding to the upper portion of the reflective electrode is arranged to form 22.5 ^° with the optical axis of the upper polarizer.

The reflective polarizer has a characteristic of reflecting linearly polarized light in the direction of the reflection axis and transmitting the linearly polarized light in the direction of 90 ^° with the reflection axis, and the retardation film has a phase value of λ / 4.

In addition, the liquid crystal layer is characterized in that the phase value of the effective λ / 2, when no electric field is applied.

Hereinafter, an array substrate for a transflective liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Example

An embodiment of the present invention is characterized by providing a transverse electric field type liquid crystal display device which can display an image on both sides by using a reflection mode on one side and a transmission mode on the other side.

3 is a cross-sectional view schematically showing a reflection-transmission mode transverse electric field type liquid crystal display device according to the present invention.

As shown in the figure, the transverse electric field type liquid crystal display device B according to the present invention comprises a color filter substrate B1 and an array substrate B2 facing each other, and a liquid crystal between the color filter substrate and the array substrates B1 and B2. The layer LC is interposed.

The array substrate B2 includes a thin film transistor T, a common electrode 112, and a pixel electrode 114 for each of the plurality of pixels P defined in the transparent insulating substrate 50.

The thin film transistor T is formed on the gate electrode 112, the semiconductor layers 108a and 108b formed with the insulating layer 110 interposed therebetween, and on the semiconductor layers 108a and 108b. Source and drain electrodes 110 and 112 spaced apart are included.

In the above-described configuration, the common electrode 114 and the pixel electrode 116 are configured to be spaced apart from each other in parallel on the same substrate 100.

In this case, both the common electrode 114 and the pixel electrode 116 may be formed using an opaque conductive metal material having excellent reflectance. Thus, the common electrode 114 and the pixel electrode 116 may be opaque. In general, the common electrode 114 is formed of the same material as the gate electrode 102 and the pixel electrode 116 is formed of the same material as the source and drain electrodes 110 and 112. Configure.

Although not shown, a gate line (not shown) extending along one side of the pixel P and a data line (not shown) extending in a direction perpendicular thereto are formed, and a voltage is applied to the common electrode 114. The common wiring (not shown) to apply is comprised.

The color filter substrate B1 includes a black matrix 202 formed on a transparent insulating substrate 200 corresponding to the gate wiring (not shown), the data wiring (not shown), and the thin film transistor (T). The color filters 204a and 204b are configured to correspond to the pixels P.

The liquid crystal layer LC is operated by the horizontal electric field 118 of the common electrode 114 and the pixel electrode 116.

A characteristic feature of the above-described configuration is the construction of a λ / 4 phase difference plate 300 (hereinafter referred to as "QWP") between the common electrode and the pixel electrodes 114 and 116 and the liquid crystal layer LC.

In this case, the QWP 300 uses a nematic liquid crystal (nematic LC) to orient it in a predetermined direction to have a phase value of λ / 4.

In addition, a transparent light source 500 is configured on the transverse electric field type liquid crystal panel B, and an upper polarizing plate 410a is configured between the transparent light source 500 and the liquid crystal panel B.

In addition, a reflective polarizer 450 is formed under the liquid crystal panel B, and a lower polarizer 410b is configured under the reflective polarizer 450.

In the above configuration, one side of the liquid crystal panel B in which the transparent light source 500 is positioned is used in a reflection mode, and the other side of the liquid crystal panel B in which the lower polarizer 450 is located is used in a transmission mode.

This will be described below with reference to FIG. 4.

FIG. 4 is a cross-sectional view illustrating only configurations having polarization characteristics in the configuration of FIG. 3.

As illustrated, the QWP 300 and the liquid crystal layer LC are disposed on the pixel electrode and the common electrode 114 and 116 (hereinafter, referred to as “reflective electrode”), and the upper polarizer plate is formed on the liquid crystal layer LC. 410a and the transparent light source 500 are sequentially formed.

The reflective polarizer 110b and the lower polarizer 410b are sequentially formed below the reflective electrodes 114 and 116.

In the above-described configuration, when a voltage is applied to the reflective electrodes 114 and 116, the liquid crystal LC positioned above the pixel electrode and the common electrode 116 and 114 is 22.5 ^° , and is positioned in the region between the pixel electrode and the common electrode. The liquid crystal to have an effective twist angle of 45 ^o .

In this case, when the reflective electrodes 114 and 116 are designed, the bar-shaped configuration is relatively close compared to the conventional one, so that the liquid crystal layer has an effective phase difference value of λ / 2 when no voltage is applied.

In addition, the reflective polarizer 450 reflects linearly polarized light in the reflection axis direction and transmits linearly polarized light in the 90 ^° direction.

5 is a view illustrating angles formed between the upper and lower polarizing plates, the reflective polarizing plate, and the optical axis of the liquid crystal layer in the configuration of FIG. 4.

As shown, the optical axis ① of the upper polarizer and the reflection axis ① of the reflective polarizer are the same, and the optical axis ④ of the lower polarizer is the optical axis of the upper polarizer and the reflection axis ① of the reflective polarizer. Make up 90 ^o

At this time, when a voltage is applied, the liquid crystal layer positioned above the reflective electrode (see FIG. 4) forms 22.5 ^° with the optical axis of the upper polarizing plate and the reflective axis ① of the reflective polarizing plate, and is located between the reflective electrodes. The positioned liquid crystals are configured to achieve 45 ^o .

Such a reflection / transmission mode transverse electric field type liquid crystal display according to the present invention displays white when the voltage is in the off state in the reflection mode and black when the voltage is in the on state. Is displayed.

In contrast, the transmission mode displays black when the voltage is in an off state and white when the voltage is in an on state.

This will be described below with reference to 6 and FIG. 7.

6A and 6B illustrate polarization characteristics in reflection mode. In particular, FIG. 6A illustrates a polarization state when the voltage is in an off state, and FIG. 6B is a state in which a voltage is on. Is a diagram illustrating the polarization state.

As shown in FIG. 6A, when the voltage is in the off state in the reflection mode, light incident through the transparent light source is incident on the liquid crystal layer disposed below only linearly polarized light parallel to the optical axis of the upper polarizer.

At this time, since the optical axis of the liquid crystal layer is the same as the optical axis of the upper polarizing plate, the linearly polarized light passes through the liquid crystal layer and the QWP under the liquid crystal without changing the polarization state.

The light passing through the QWP is reflected on the reflective electrode or the reflective polarizer of the lower side without being changed in the polarization state and is incident on the upper polarizer.

In this case, since the light passing through the liquid crystal layer is linearly polarized light having the same linearity as the light passing through the first linear polarizing plate, the light passes through the upper polarizer as it is and is emitted to the outside.

Therefore, when the voltage is in the off state in the reflection mode, the white state is obtained.

As shown in FIG. 6B, when the voltage is in an on state in the reflection mode, a portion corresponding to the reflective electrode and a portion corresponding to the reflective electrode may be considered. This is because, as mentioned above, the twist angle of the liquid crystal layer in the region between the liquid crystal layer on the reflective electrode and the reflective electrode when the voltage is on is different.

First, it will be described below with reference to the liquid crystal layer located on the electrode.

Light incident through the transparent light source passes through the upper polarizing plate, and light having a component parallel to the optical axis of the upper polarizing plate passes through the liquid crystal layer.

In this case, since the liquid crystal layer on the reflective electrode forms an optical axis of the upper polarizer 22.5 ^o , the optical axis of light passing along the liquid crystal layer also undergoes a phase delay such that the optical axis of the upper polarizer is 45 ^o .

The light passing through the liquid crystal layer passes through the QWP and is circularly polarized, and the right polarizer is reflected by the reflecting plate and passes again through the QWP, and becomes linearly polarized light having an optical axis of 135 ^° .

The linearly polarized light is linearly polarized in a state perpendicular to the optical axis of the upper polarizing plate while passing through the liquid crystal layer, and is absorbed by the upper linear polarizing plate.

Therefore, when the voltage is in the on state, the portion corresponding to the reflective electrode displays the black state.

Second, the following description will be given with reference to the liquid crystal layer located between the electrodes.

Light incident through the transparent light source passes through the upper polarizing plate, and only linear flat light having a component parallel to the optical axis of the upper polarizing plate is incident on the liquid crystal layer.

In this case, since the liquid crystals positioned in the region between the reflective electrodes have an effective twist angle of 45 ^° and are arranged, the light passing through them becomes linearly polarized light in a direction perpendicular to the optical axis of the polarizer.

The linear polarizing plate passes through the QWP under the liquid crystal layer without phase change and passes through the reflective polarizing plate at the bottom. (Since it is linearly polarized perpendicular to the reflective axis of the reflecting plate, the linear polarizing plate passes through the reflective polarizing plate without being reflected.)

Therefore, when the voltage is in the on state, the black color is displayed.

7A and 7B illustrate polarization characteristics in a transmission mode, and show display characteristics when viewed from the other side of a liquid crystal panel in which no transparent light source is located. Unlike the reflective mode, only the region between the reflective electrodes needs to be considered.

7A illustrates a polarization state when the voltage is in an off state, and FIG. 7B illustrates a polarization state when the voltage is in an on state.

As shown in FIG. 7A, when the voltage is in an off state in the transmissive mode, light incident to the upper polarizing plate through the transparent light source is incident only to the liquid crystal layer of the linearly polarized light linearly parallel to the optical axis of the upper polarizing plate. Done.

In this case, since the liquid crystal layer has an effective phase value of λ / 2, the linearly polarized light passes through the liquid crystal layer and the QWP as it is.

At this time, since the light passing through the QWP is reflected through the lower reflective polarizer, when viewed from the other side of the liquid crystal panel, black appears.

As shown in FIG. 7B, when the voltage is on in the transmissive mode, light incident to the upper polarizer through the transparent light source causes only linearly polarized light parallel to the optical axis of the upper polarizer to enter the lower liquid crystal layer. do.

In this case, since the liquid crystal layer is arranged at 45 ^° , the light passing through the liquid crystal layer becomes linearly polarized light in a direction perpendicular to the optical axis of the polarizing plate.

Subsequently, the linearly polarized light passing through the liquid crystal layer passes through the lower QWP, the lower reflective polarizer and the lower polarizer.

Therefore, when the voltage is in an on state, the transmission state becomes a white state in the transmission mode.

As a result, the reflection mode displays an image in a white state when the voltage is in an off state, and the transmission mode does not display an image in black, and the voltage is in an on state. When the reflection mode does not display an image in a black state, the transmission mode displays an image in a white state.

The transverse electric field type liquid crystal display device of the reflection / transmission mode according to the present invention manufactured as described above can use both sides as a display portion, which can expand the use of the product and increase the competitiveness of the product. Since driving in the lateral electric field mode, there is an effect that can implement a wide viewing angle.

Claims (6)

A first substrate and a second substrate on which a plurality of pixel regions are defined and spaced apart from each other; A reflective electrode having a rod shape for each pixel region corresponding to the first substrate; A liquid crystal layer having a long axis arranged in a horizontal direction in a spaced area between the first substrate and the second substrate; A phase difference film formed between the liquid crystal layer and the reflective electrode; An upper polarizer plate positioned on the second substrate; A transparent light source configured on the upper polarizing plate; A reflective polarizer formed under the first substrate; A lower polarizer configured under the reflective polarizer, and having a polarization axis perpendicular to the polarization axis of the upper polarizer; The reflective electrode is a pixel electrode and a common electrode configured to be spaced apart from each other in parallel on the same plane, When an electric field is generated between the pixel electrode and the common electrode, the liquid crystal layer corresponding to the pixel electrode and the common electrode is arranged to form 45 ^o with the optical axis of the upper polarizing plate, and the liquid crystal corresponding to the upper portion of the reflective electrode. And a layer arranged to form 22.5 ^° with the optical axis of the upper polarizer. Transmissive mode transverse electric field liquid crystal display device. delete The method of claim 1, A reflection. Transmissive mode transverse electric field type liquid crystal display further comprising a switching element connected to the pixel electrode. delete The method of claim 1, The reflective polarizing plate reflects linearly polarized light in the direction of the reflection axis and transmits linearly polarized light in the direction of 90 ^° to the reflection axis. Transmissive mode Transverse electric field liquid crystal display device. The method of claim 1, The retardation film has a phase value of λ / 4. A reflection mode transmissive electric field type liquid crystal display device.

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