KR101596374B1 - Liquid crystal display - Google Patents

Abstract

A liquid crystal display device according to an embodiment of the present invention includes a first substrate including a reflective region and a transmissive region, a first substrate including a reflective region and a transmissive region, A thin film transistor connected to a gate line and a data line, a gate line and a data line formed on the substrate, a pixel electrode including a reflective electrode and a transparent electrode, And the retardation retardation layer is doped with nanoparticles.

Thus, the nano particles having a dielectric constant of 5 or more can be doped in the internal retardation layer to prevent an increase in the driving voltage of the transflective liquid crystal display device.

Transflective liquid crystal display, internal retardation retardation layer, nanoparticle, dielectric constant

Description

[0001] LIQUID CRYSTAL DISPLAY [0002]

The present invention relates to a transflective liquid crystal display device.

The liquid crystal display device is one of the most widely used flat panel display devices, and is composed of two display panels having electrodes formed thereon and a liquid crystal layer interposed therebetween, and applying voltage to the electrodes to rearrange the liquid crystal molecules of the liquid crystal layer It is a display device that adjusts the amount of transmitted light.

Since such a liquid crystal display device is a light-receiving display device that can not emit light by itself, an image is displayed by using external light such as a backlight or natural light. A method in which light emitted from a backlight passes through a liquid crystal layer to display an image is referred to as a transmission liquid crystal display device and a method in which external light is incident on a liquid crystal layer and then reflected to display an image is called a reflective liquid crystal It is called a display device. A method of using both transmission and reflection is referred to as a transrelective liquid crystal display.

Generally, in a transflective liquid crystal display device, since the length of light passing through the liquid crystal at the reflective portion is longer than the length of light passing through the liquid crystal at the transmissive portion, a step is formed between the reflective electrode and the transmissive electrode In this case, since the process becomes complicated, a retardation retardation layer is formed inside the liquid crystal cell in order to eliminate a step.

However, when the retardation layer is formed inside the liquid crystal cell, the driving voltage of the liquid crystal display increases.

A problem to be solved by the present invention is to prevent an increase in driving voltage in a transflective liquid crystal display device including an internal retardation layer.

A liquid crystal display device according to an embodiment of the present invention includes a first substrate including a reflective region and a transmissive region, a gate line and a data line formed on the first substrate, a thin film transistor connected to the gate line and the data line, A pixel electrode including a reflective electrode and a transparent electrode, and a retardation layer formed on the pixel electrode, wherein the retardation retardation layer is doped with nanoparticles.

The reflective electrode may be formed in the reflective region.

The dielectric constant of the nanoparticles can be at least 5.

The nanoparticle may be TiO ₂ or MoSiO ₂ .

The retardation layer may be doped with 5 wt% of TiO ₂ .

The dielectric constant of the retardation layer may be 17.2.

And a second substrate facing the first substrate and including a common electrode.

According to the embodiments of the present invention, the nano particles having a dielectric constant of 5 or more can be doped in the internal retardation layer to prevent an increase in the driving voltage of the transflective liquid crystal display device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. Whenever a portion of a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case where it is "directly on" another portion, but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

A liquid crystal display according to an embodiment of the present invention will now be described in detail with reference to FIGS. 1 and 2. FIG.

FIG. 1 is a layout view of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II of the liquid crystal display device of FIG.

1 and 2, a liquid crystal display according to an exemplary embodiment of the present invention includes a thin film transistor panel 100, a common electrode panel 200 facing the panel 100, and a liquid crystal layer (3).

First, the thin film transistor display panel 100 will be described.

A plurality of gate lines 121 are formed on a substrate 110 made of an insulating material such as transparent glass or plastic. A plurality of resistive contact members 163 and 165, a plurality of data lines 171 and a plurality of drain electrodes 175 are sequentially formed on the gate insulating film 140, the plurality of semiconductors 154, the plurality of resistive contact members 163 and 165, .

The gate line 121 transmits the gate signal and extends mainly in the horizontal direction. Each gate line 121 includes a plurality of gate electrodes 124 protruding upward.

The data line 171 transmits a data signal and extends mainly in the vertical direction and crosses the gate line 121. Each data line 171 includes a plurality of source electrodes 173 extending toward the gate electrode 124. The drain electrode 175 is separated from the data line 171 and faces the source electrode 173 with the gate electrode 124 as a center.

The semiconductor 154 is positioned above the gate electrode 124 and the resistive contact members 163 and 165 thereon are disposed between the semiconductor 154 and the data line 171 and the drain electrode 175 to provide a contact It lowers the resistance.

One gate electrode 124, one source electrode 173 and one drain electrode 175 constitute one thin film transistor (TFT) together with the semiconductor 154, and the channel of the thin film transistor Is formed in the semiconductor 154 between the source electrode 173 and the drain electrode 175. [

A protective layer 180 is formed on the gate insulating layer 140, the data line 171, and the drain electrode 175. A contact hole 185 is formed in the passivation layer 180 to expose the drain electrode 175. The surface of the contact hole 185 may have irregularities (not shown).

On the protective film 180, a pixel electrode 191 is formed. The pixel electrode 191 includes a transparent electrode 192 and a reflective electrode 194 thereon. The reflective electrode 194 may be formed along the irregularities of the surface of the protective film 180.

The transparent electrode 192 is made of a transparent conductive material such as ITO or IZO and the reflective electrode 194 is made of a reflective metal such as aluminum, silver, chromium or an alloy thereof. However, the reflective electrode 194 may be formed of a low resistance reflective upper film (not shown) such as aluminum, silver or an alloy thereof, a lower film (not shown) having good contact properties with ITO or IZO such as molybdenum metal, chromium, tantalum, Of the double-layer structure.

A retardation layer 14 is formed on the pixel electrode 191. The retardation layer 14 is doped with nanoparticles having a dielectric constant of 5 or more such as TiO ₂ or MoSiO ₂ to increase the dielectric constant.

Next, the common electrode display panel 200 will be described.

A plurality of light shielding members 220 called a black matrix are formed on a substrate 210 made of an insulating material such as glass or plastic.

A color filter 230 is formed on the insulating substrate 210 and the light shielding member 220 and a common electrode 270 is formed on the color filter 230.

Polarizing plates 12 and 22 are provided on the outer surfaces of the two substrates 110 and 210, respectively.

The pixel electrode 191 is physically and electrically connected to the drain electrode 175 through the contact hole 185 and receives the data voltage from the drain electrode 175. The pixel electrode 191 to which the data voltage is applied generates an electric field together with a common electrode 270 of the common electrode panel 200 to which a common voltage is applied to thereby apply a voltage between the two electrodes 191 and 270 The direction of the liquid crystal molecules of the liquid crystal layer 3 of the liquid crystal layer 3 is determined. Polarization of light passing through the liquid crystal layer 3 varies depending on the orientation of the liquid crystal molecules thus determined. The pixel electrode 191 and the common electrode 270 form a capacitor (hereinafter referred to as a "liquid crystal capacitor") to maintain the applied voltage even after the thin film transistor is turned off.

The transflective liquid crystal display device including the thin film transistor display panel 100, the color filter display panel 200 and the liquid crystal layer 3 has the transmissive area TA defined by the transparent electrode 192 and the reflective electrode 194, And a reflection area RA. Specifically, a portion of the transparent electrode 192 located below the portion not covered by the reflective electrode 194 is a transmissive region TA, and a portion located below the reflective electrode 194 is a reflective region RA. .

In the transmissive area TA, the light incident from the rear surface of the liquid crystal display device, that is, the thin film transistor display panel 100, passes through the liquid crystal layer 3 and is emitted to the front surface, that is, toward the color filter display panel 200. In the reflective region RA, light entering from the front surface enters the liquid crystal layer 3, is reflected by the reflective electrode 194, passes through the liquid crystal layer 3 again, and exits to the front surface to perform display. At this time, the wobbled surface (not shown) of the reflective electrode 194 may induce irregular reflection of light to prevent the object from being reflected on the screen.

Next, the relationship between the internal retardation layer and the driving voltage of the liquid crystal display will be described with reference to equations (1), (3) and (4).

Equation 1 is an equation for obtaining the total driving voltage of the liquid crystal display device. The total driving voltage of the liquid crystal display device according to formula 1 can be obtained as the sum of the drive voltage of the drive voltage and the internal phase delay layer of a liquid crystal layer, by increasing the dielectric value of the constant (ε _retarder) of the internal phase delay layer, total It can be seen that the driving voltage is decreased.

[Formula 1]

D _LC is the cell gap of the liquid crystal layer, d _retarder is the thickness of the internal retardation retardation layer _{,? 0} is the dielectric constant of air,? _LC is the thickness of the liquid crystal layer the dielectric constant, ε represents the dielectric constant of the _retarder internal phase delay layer.

FIG. 3 is a graph showing a change in a driving voltage according to an internal retardation layer in a reflection part, and FIG. 4 is a graph showing a change in driving voltage according to an internal retardation layer in a transmission part.

FIGS. 3 and 4 show changes in the driving voltage when the inner retardation layer is not doped, when the inner retardation layer is not doped with nanoparticles, and when the inner retardation layer is doped with nanoparticles.

In the example of the present invention, TiO ₂ was used as a nanoparticle and doped with 5 wt% of the total weight of the internal retardation layer.

The dielectric constant of the inner retardation layer not doped with TiO ₂ was 3.5, but the dielectric constant of the inner retardation layer doped with TiO ₂ was 17.2. By doping the inner retardation layer with TiO ₂ , the dielectric constant 5-fold increase.

Referring to FIG. 3, when the reflectivity is about 27%, the driving voltage is about 4.4 V when TiO ₂ is not doped in the internal retardation layer. However, when TiO ₂ is doped in the internal retardation layer, Respectively. Also, in the absence of the internal retardation retardation layer, the driving voltage showed about 2.7V.

Therefore, when the internal retardation layer doped with TiO ₂ is used, the increase in the driving voltage in the reflective portion decreases from 1.4V to 0.7V.

Referring to FIG. 4, when the transmittance is about 27% and the TiO ₂ is not doped in the internal retardation layer, the driving voltage is about 8 V. However, when the internal retardation layer is doped with TiO ₂ , the driving voltage is about 5.2 V, respectively. Further, in the absence of the internal retardation layer, the driving voltage was about 4.5V.

Therefore, it can be seen that the use of the inner retardation layer doped with TiO ₂ reduces the increase in driving voltage in the transmissive portion from 2.8 V to 0.7 V.

In addition, it can be seen that there is almost no change in the reflectance and the transmittance due to the doping of TiO ₂ in the reflective portion and the transmissive portion.

As described above, when the nanoparticle-doped phase difference retardation layer having a dielectric constant of 5 or more is formed in the liquid crystal cell in the transflective liquid crystal display device, the increase amount of the driving voltage can be reduced without changing the reflectance and the transmittance.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

1 is a layout diagram of a liquid crystal display device according to an embodiment of the present invention.

2 is a cross-sectional view of the liquid crystal display device of FIG. 1 taken along line II-II.

3 is a graph showing a change in driving voltage according to an internal retardation layer in a reflection portion.

4 is a graph showing a change in driving voltage according to an internal retardation layer in a transmissive portion.

Description of Main Drawings:

14: retardation retardation layer 191: pixel electrode

192: transparent electrode 194: reflective electrode

TA: transmissive area RA: reflective area

Claims (7)

A first substrate including a reflective region and a transmissive region, A gate line and a data line A thin film transistor connected to the gate line and the data line, A pixel electrode connected to the thin film transistor and including a reflective electrode and a transparent electrode, And a retardation layer formed on the pixel electrode Wherein the retardation layer is doped with nanoparticles, Wherein the nanoparticle is TiO ₂ , the dielectric constant of the nanoparticle is 5 or greater, Wherein the retardation layer is doped with 5 wt% of TiO _{2 based} on the total weight of the retardation layer. The method of claim 1, And the reflective electrode is formed in the reflective region. delete delete delete The method of claim 1, Wherein the retardation layer has a dielectric constant of 17.2. The method of claim 6, And a second substrate facing the first substrate and including a common electrode.

Images