KR101596585B1 - Liquid crystal display - Google Patents

Abstract

A liquid crystal display device is provided. The liquid crystal display device includes a transmissive light source unit including a reflective plate and an organic light emitting device including an active layer for emitting polarized light, the polarizing plate being positioned on the transmissive light source, the liquid crystal layer, and the polarizing plate And is operable in a reflective mode using external light or a transmissive mode using polarized light of the transmissive light source unit. Therefore, a liquid crystal display device that operates in a reflective mode or a transmissive mode using a polarized light emitting device can be realized.

Description

[0001] Liquid crystal display [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device using a polarized light emitting element and capable of selecting a reflection and transmission mode.

In general, a liquid crystal display device can be classified into a transmission type and a reflection type according to a light source used.

The transmissive type uses a back light located at the back of the liquid crystal panel as a light source, and the reflective type uses an external natural or artificial light source instead of the back light.

Since the transmissive type uses an artificial backlight source, there is a disadvantage in that the power consumption is large and the picture quality is degraded in a bright place. In the reflective type, the brightness is lowered in a dark place depending on the light input from the outside.

Due to these problems, a transflection type liquid crystal display device has been proposed as disclosed in Korean Patent Laid-Open No. 10-2007-0027918 (Mar. In a reflective transmissive liquid crystal display device, a transmissive region and a reflective region coexist in one pixel, and the transmissive region is used as a transmissive type through a transmissive region in a dark environment, and the liquid crystal display Device.

However, since the transmissive area and the reflective area exist in such a manner that the transmissive area and the reflective area exist, the structure of the transmissive area is complicated and the resolution and the luminance of each mode are lowered.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device of high quality which has both a reflective type and a transmissive type functioning singly or in combination and having excellent visibility.

According to one aspect of the present invention, there is provided a liquid crystal display device. The liquid crystal display device includes a transmissive light source unit including a reflective plate and an organic light emitting device including an active layer that emits polarized light, the transmissive light source unit being located on the reflective plate, and a liquid crystal layer disposed on the transmissive light source, And is operable in a reflective mode using external light or a transmissive mode using polarized light of the transmissive light source unit.

The organic light emitting diode may include a lower electrode, an active layer that emits polarized light, and an upper transparent electrode that is positioned on the active layer.

The reflection plate may be a lower electrode of the organic light emitting diode.

When the lower electrode of the organic light emitting diode is separately provided on the reflection plate, the lower electrode may be a transparent electrode.

The reflection plate may be made of Ag, Al, Ni, Cu, Pt, Pd, Rh, or an alloy thereof.

In addition, the active layer may include a single-axis liquid crystal polymer or oligomer arranged in one direction.

The active layer may include a light emitting material having a nematic phase.

The upper transparent electrode may be formed of ITO, FTO, IZO, AZO, ZnO, or Au.

Further, the liquid crystal layer may be a nematic liquid crystal layer having a phase value of? / 4.

In addition, the liquid crystal layer may be formed of at least one selected from the group consisting of Twisted Nematic (TN), Super Twisted Nematic (STN), Electrically Controlled Birefringence (ECB), Optical Mode Interference (OMI), Optically Compensated Birefringence (OCB), Hybrid Aligned Nematic Plane Switching, and VA (Vertical Alignment) mode.

The optical axis of the polarized light emitted from the active layer coincides with the axis of the polarizing plate.

The transmissive light source unit may be driven by an active matrix method or a passive matrix method.

According to the present invention, by using the polarizing organic light emitting element, it is possible to provide a liquid crystal display device of high quality and excellent in visibility, in which the reflective type and the transmissive type can function singly or in combination.

In addition, the entire liquid crystal cell can be selectively used as a transmissive mode or a reflective mode while having a simple structure.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 is a cross-sectional view showing a schematic configuration of a liquid crystal display device according to an embodiment of the present invention.
2 is a cross-sectional view of an organic light emitting device.
3 is a view for explaining a transmission mode operation of a liquid crystal display device according to an embodiment of the present invention.
4 is a view for explaining a reflective mode operation of the liquid crystal display device according to an embodiment of the present invention.
FIG. 5 is a graph showing the characteristics of the liquid crystal display manufactured according to Preparation Example.

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

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. Rather, the intention is not to limit the invention to the particular forms disclosed, but rather, the invention includes all modifications, equivalents and substitutions that are consistent with the spirit of the invention as defined by the claims.

It will be appreciated that when an element such as a layer, region or substrate is referred to as being present on another element "on," it may be directly on the other element or there may be an intermediate element in between .

Although the terms first, second, etc. may be used to describe various elements, components, regions, layers and / or regions, such elements, components, regions, layers and / And should not be limited by these terms.

1 is a cross-sectional view showing a schematic configuration of a liquid crystal display device according to an embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a transmission light source 10 and a liquid crystal panel 20, which are self-luminescence sources.

The transmitted light source 10 may include a reflection plate 100 and an organic light emitting diode 200 disposed on the reflection plate 100 and including an active layer 220 for emitting polarized light. This organic light emitting diode 200 is referred to as a polarizing OLED.

The reflection plate 100 reflects the external light or the polarized light emitted from the organic light emitting diode 200 upward.

The reflector 100 may be made of Ag, Al, Ni, Cu, Pt, Pd, Rh, or an alloy thereof.

The reflection plate 100 may serve as a lower electrode 210 of the organic light emitting diode 200, which will be described later. That is, when the reflection plate 100 serves as the lower electrode 210, the reflection plate 100 may be a reflection electrode.

The organic light emitting device 200 is positioned on the reflection plate 100. The organic light emitting device 200 will be described with reference to FIG.

2 is a cross-sectional view of an organic light emitting device.

2, the organic light emitting diode 200 includes a lower electrode 210, an active layer 220 disposed on the lower electrode 210 to emit polarized light, and an upper transmissive layer 220 disposed on the active layer 220, Electrode 230 may be included.

The lower electrode 210 may be a cathode. In some cases, the lower electrode 210 may be an anode.

When the lower electrode 210 is provided separately on the reflection plate, the lower electrode 210 may be a transparent electrode.

When the reflection plate 100 serves as an electrode, the reflection plate 100 serves as a lower electrode 210 of the organic light emitting device, and it is not necessary to provide a separate electrode on the reflection plate. In this case, the lower electrode 210 may be a reflective electrode.

The active layer 220 may include a material that emits polarized light. When a voltage is applied to the upper electrode 230 and the lower electrode 210 of the organic light emitting diode 200, electrons move from the anode to the active layer 220 in the anode, and electrons and holes are coupled to form excitons. State to the ground state and emits light. The emitted light may emit polarized light depending on the kind of the active layer 220.

The active layer 220 may include a luminescent material having a nematic phase. For example, the active layer 220 may include PPV (poly (phenylene vinylene)) or PFO (polyfluorenes).

In addition, the active layer 220 may include a single-axis liquid crystal polymer or oligomer arranged in one direction.

Referring again to FIG. 1, the upper transparent electrode 230 is located on the active layer 220. The upper transparent electrode 230 may be an anode. Meanwhile, if the lower electrode 210 is an anode, the upper electrode 230 may be a cathode.

The upper transparent electrode 230 may be formed of ITO (Indium Tin Oxide), FTO (Fluorine-doped Tin Oxide), IZO (Indium Zinc Oxide), AZO (Al-doped ZnO), ZnO or Au thin film.

The liquid crystal panel 20 may include a liquid crystal layer 300 and a polarizer 400 positioned on the liquid crystal layer 300 and positioned on the transmissive light source unit 10.

The liquid crystal panel 20 functions to modulate light to form an image. The liquid crystal layer 300 of the liquid crystal panel 20 may be formed of a material selected from the group consisting of Twisted Nematic (TN), Super Twisted Nematic (STN), Electrically Controlled Birefringence (ECB), Optical Mode Interference (OMI), Optically Compensated Birefringence Nematic, In Plane Switching (IPS), and Vertical Alignment (VA) modes. For example, the liquid crystal panel 20 may be an VA-ECB (Electrically Controlled Birefringence) mode.

Further, the liquid crystal layer 300 may be a nematic liquid crystal layer having a phase value of? / 4.

This liquid crystal layer 300 can be driven by an electric field generated by a voltage difference applied to two electrodes (not shown).

For example, an upper substrate (not shown) and a lower substrate (not shown) may be disposed on the upper and lower portions of the liquid crystal layer 300. Further, an alignment film (not shown) for the liquid crystal layer may be further disposed between the substrate and the liquid crystal layer. Meanwhile, in this case, the polarizing plate 400 will be located on the upper substrate.

The lower substrate may be a TFT array substrate. Data lines, gate lines, TFTs (thin film transistors), and storage capacitors (Cst) may be formed on the TFT array substrate. The pixel electrode connected to the TFT may be located on the lower substrate.

In this case, the upper substrate may be a color filter array substrate. Such a color filter array substrate may be formed with a black matrix (BM), a color filter, and a common electrode.

Therefore, an electric field is formed in the liquid crystal layer 300 by the difference between the common voltage applied to the common electrode and the pixel voltage applied to the pixel electrode, whereby the liquid crystal can be driven.

The polarizing plate 400 serves to polarize external light that is unpolarized. The polarizing plate 400 serves to emit only polarized light that coincides with the optical axis of the polarizing plate 400 among the polarized light emitted to the outside through the liquid crystal layer 300.

The axis of the polarizing plate 400 may coincide with the optical axis of the polarized light emitted from the active layer 220. In some cases, the axis of the polarizer may be orthogonal to the optical axis of the polarized light emitted from the active layer 220.

3 is a view for explaining a transmissive mode operation of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 3, a polarized light OLED is driven by PM (PM OLED) as an example.

In the transmissive mode, the polarization OLED serves as a backlight source, so that the polarization OLED remains on (PMOLED on). In addition, a white state or a black state can be realized through liquid crystal switching (LC switching).

In addition, the optical axis (0 degree) of the polarized light emitted from the polarized light OLED coincides with the axis (0 degree) of the polarizing plate.

If the field is not applied to the liquid crystal layer (field off), the liquid crystal is vertically standing, and the polarized light emitted from the polarized light OLED passes through the liquid crystal layer without phase delay change. , And white (white) state.

If an electric field is applied to the liquid crystal layer (field on), the liquid crystal exhibits a phase retardation value (half wave plate), and the phase of the polarized light passing through the liquid crystal layer changes by about 90 degrees. Bar, and black state.

Meanwhile, such a polarized OLED can be used not only for PM driving but also AM driving (AM OLED). In the transmissive mode, the liquid crystal layer is vertically oriented, and the optical axis of the polarized OLED coincides with the polarizer axis of the upper part, so that the light emitted from the polarized OLED is transmitted by 96% or more compared to the conventional backlight source. The light efficiency of the ship can be shown. On the other hand, such a light efficiency enhancement effect appears in the PM drive as well.

4 is a view for explaining a reflective mode operation of a liquid crystal display device according to an embodiment of the present invention.

Referring to FIG. 4, the polarized light OLED is driven by PM (PM OLED) as an example.

In the reflection mode, since the external light serves as a light source, the polarized light OLED is maintained in the OFF state (PMOLED off). In addition, a white state or a black state can be realized through liquid crystal switching (LC switching).

In addition, the optical axis (0 degree) of the polarized light emitted from the polarized light OLED coincides with the axis (0 degree) of the polarizing plate.

In this case, external light first becomes polarized external light passing through the polarizing plate.

Then, if no electric field is applied to the liquid crystal layer (Field off), the liquid crystal is vertically standing, and the polarized external light passes through the organic light emitting element after passing through the liquid crystal layer without phase delay change , The light is reflected through the reflection plate, passes through the polarizer without passing through the organic light emitting element and the liquid crystal layer without a change in the phase delay, and becomes a white state.

On the other hand, if an electric field is applied to the liquid crystal layer (field on) and the phase delay of the liquid crystal layer is adjusted by a quarter wave plate, the polarized external light is reflected through the liquid crystal layer through the reflection plate, The phase of the polarized external light is changed by about 90 degrees. Therefore, the polarized light can not pass through the polarizing plate, so that the polarized light enters a black state.

According to the present invention, by using the polarizing organic light emitting element, it is possible to provide a liquid crystal display device of high quality and excellent in visibility, in which the reflective type and the transmissive type can function singly or in combination.

In addition, the entire liquid crystal cell can be selectively used as a transmissive mode or a reflective mode while having a simple structure.

In addition, the substrate used for forming the OLED layer can be integrally attached to the liquid crystal panel. Thus, it is possible to implement a display device without an additional backlight module.

Manufacturing example

Thereby manufacturing a liquid crystal display device according to an embodiment of the present invention.

The specimens were fabricated on the basis of the structures shown in FIGS. 3 and 4.

MLC-6608 (negative LC) was used for the liquid crystal (LC) of the liquid crystal layer, and AL60702 (JSR) was used as the alignment film for orienting the liquid crystal.

Further, the liquid crystal mode of the liquid crystal layer is the VA-ECB mode, and the substrate is positioned above / below the liquid crystal layer. At this time, the upper / lower substrate was an anti-parallel rubbed substrate.

The rubbing axis was set at 45 degrees, the axis of the polarizing plate was set at 0 degree, and the axis of the OLED light was set at 0 degree.

Experimental Example

The characteristics of the liquid crystal display manufactured according to Production Example were measured.

In the transmissive mode experiment, the characteristics of the liquid crystal display device were measured by applying a voltage to the liquid crystal layer in the on state of the OLED. In the reflective mode experiment, when the OLED was turned off, The characteristics of the display device were measured.

FIG. 5 is a graph showing the characteristics of the liquid crystal display manufactured according to Preparation Example.

Referring to FIG. 5, it can be seen that both the transmissive mode and the reflective mode operate in the normally white mode. Thus, it can be seen that the use of each mode can be determined according to the external light condition.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

10: transmission light source part 20: liquid crystal panel
100: reflector 200: organic light emitting element
210: lower electrode 220: active layer
230: upper transparent electrode 300: liquid crystal layer
400: polarizer

Claims (11)

A transmissive light source unit including a reflective plate and an organic light emitting diode disposed on the reflective plate and including an active layer for emitting polarized light; And
And a liquid crystal panel disposed on the transmissive light source unit, the liquid crystal panel including a liquid crystal layer and a polarizer positioned on the liquid crystal layer,
Wherein the organic light emitting device includes a lower electrode, an active layer that is disposed on the lower electrode and emits polarized light, and an upper transparent electrode that is located on the active layer,
Wherein the active layer comprises a luminescent material having a nematic phase,
And the optical axis of the polarized light emitted from the active layer coincides with the axis of the polarizing plate,
Wherein the liquid crystal display is operable in a reflective mode using external light or in a transmissive mode using polarized light of the transmissive light source unit. delete The method according to claim 1,
And the reflective plate is a lower electrode of the organic light emitting device. The method according to claim 1,
Wherein the lower electrode is a transparent electrode. The method according to claim 1,
Wherein the reflection plate is made of Ag, Al, Ni, Cu, Pt, Pd, Rh or an alloy thereof. delete The method according to claim 1,
Wherein the upper transparent electrode is made of ITO, FTO, IZO, AZO, ZnO or an Au thin film. The method according to claim 1,
Wherein the liquid crystal layer is a nematic liquid crystal layer having a phase value of? / 4. The method according to claim 1,
The liquid crystal layer may be formed of one selected from the group consisting of Twisted Nematic (TN), Super Twisted Nematic (STN), Electrically Controlled Birefringence (ECB), Optical Mode Interference (OMI), Optically Compensated Birefringence (OCB), Hybrid Aligned Nematic ), And a VA (vertical alignment) mode. delete The method according to claim 1,
Wherein the transmissive light source unit is driven by an active matrix method or a passive matrix method.

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