KR101679866B1 - Liquid Crystal Display Device - Google Patents

Abstract

A liquid crystal display according to an exemplary embodiment of the present invention includes a lower substrate, a lower electrode positioned on the lower substrate, a photonic crystal color filter located on the lower electrode and partitioned by a black matrix, A first common electrode, a protective film disposed on the first common electrode, a pixel electrode disposed on the protective film, a polymer dispersed liquid crystal layer disposed on the pixel electrode, and a second common electrode disposed on the polymer dispersed liquid crystal layer. A common electrode, and an upper substrate positioned on the second common electrode.

Description

[0001] The present invention relates to a liquid crystal display device,

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 including a color filter using photonic crystals.

2. Description of the Related Art [0002] Recently, various portable electronic devices such as mobile phones, PDAs, and notebooks have been developed, and thus a demand for a lightweight thin flat panel display device is increasing. As such flat panel display devices, a liquid crystal display (LCD), a plasma display panel (PDP) and an organic light emitting diode (OLED) have been actively studied. A liquid crystal display device in which the ease of driving means and the realization of a high image quality are easily spotlighted.

The liquid crystal display device includes a light source, a lower substrate including a pixel electrode connected to the thin film transistor and the thin film transistor, an upper substrate and a lower substrate opposing the lower substrate and including red, green and blue color filters and a black matrix, And a liquid crystal layer positioned between the upper substrates.

Therefore, the liquid crystal arrangement of the liquid crystal layer changes according to the on / off operation of the thin film transistor, and light emitted from the light source passes through the liquid crystal layer and displays red, green, and blue through the color filter.

In such a liquid crystal display device, a process of laminating a lower substrate on which a pixel region is divided and an upper substrate on which a color filter is located is performed. In this case, when the alignment of the lower substrate and the upper substrate is inaccurate, . Further, there is a problem that the power consumed by the light source is increased and the thickness of the display device is increased.

The present invention provides a liquid crystal display device capable of improving the aperture ratio and lowering the driving voltage to reduce power consumption.

According to an aspect of the present invention, there is provided a liquid crystal display comprising a lower substrate, a lower electrode positioned on the lower substrate, a photonic crystal color filter located on the lower electrode, A first common electrode disposed on the photonic crystal color filter, a protective film disposed on the first common electrode, a pixel electrode disposed on the protective film, a polymer dispersed liquid crystal layer disposed on the pixel electrode, A second common electrode positioned on the liquid crystal layer, and an upper substrate positioned on the second common electrode.

A first thin film transistor located on the lower substrate and applying a voltage to the lower electrode, and a second thin film transistor applying a voltage to the pixel electrode.

And a spacer positioned between the pixel electrodes.

The photonic crystal color filter may reflect red, green and blue light or absorb light according to an electric field applied between the lower electrode and the first common electrode.

The photonic crystal color filter may reflect white light by reflecting red, green, and blue light, respectively.

The photonic crystal color filter can realize black by absorbing light.

The polymer dispersed liquid crystal layer may be driven by applying a voltage to the pixel electrode and the second common electrode.

The color mode can be realized by simultaneously driving the photonic crystal color filter and the polymer dispersed liquid crystal layer.

In the liquid crystal display device according to an embodiment of the present invention, the photonic crystal color filter is formed on the lower substrate, the alignment margin can be reduced when the substrates are bonded together, and the aperture ratio can be improved.

In addition, when driving the mono mode of white and black, there is an advantage that the driving voltage can be lowered and the power consumption can be reduced by using only the photonic crystal color filter. Further, by using the polymer dispersed liquid crystal layer, there is an advantage that a reflection type liquid crystal display device excellent in reflectance can be provided without separately providing a polarizing plate.

1 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.
Fig. 2 is a view showing a color reflected according to a voltage applied to a photonic crystal color filter; Fig.
3 is a diagram illustrating a white implementation of a liquid crystal display device according to the present invention.
4 illustrates a black implementation of a liquid crystal display device according to the present invention.
5 illustrates a color implementation of a liquid crystal display device according to the present invention.

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

FIG. 1 is a view illustrating a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is a diagram showing colors reflected according to a voltage applied to a photonic crystal color filter.

1, a liquid crystal display 100 according to an exemplary embodiment of the present invention includes a lower substrate 110, a lower electrode 140 positioned on the lower substrate 110, And includes a photonic crystal color filter 160 partitioned by a black matrix 150, a first common electrode 162 located on the photonic crystal color filter 160, a second common electrode 162 located on the first common electrode 162, A protective layer 165, a pixel electrode 170 disposed on the protective layer 165, a polymer dispersed liquid crystal layer 190 disposed on the pixel electrode 170, a polymer dispersed liquid crystal layer 190 disposed on the polymer dispersed liquid crystal layer 190, A second common electrode 210 positioned on the second common electrode 210, and an upper substrate 220 positioned on the second common electrode 210.

The lower substrate 110 includes a first thin film transistor 120 and a second thin film transistor 125 formed on a lower substrate 110. The first thin film transistor 120 is electrically connected to the lower electrode 140 to apply a signal to the lower electrode 140 and the second thin film transistor 125 is electrically connected to the pixel electrode 170, 170).

The first thin film transistor 120 and the second thin film transistor 125 each include an active layer, a gate electrode, a source electrode, and a drain electrode. On the first thin film transistor 120 and the second thin film transistor 125, a passivation film 130 for insulating them is formed.

The lower electrode 140 is positioned on the passivation film 130. The lower electrode 140 is electrically connected to the first thin film transistor 120 to receive a signal. The lower electrode 140 is formed of a transparent material such as indium tin oxide (ITO), indium zinc oxide (IZO), or the like.

A photonic crystal color filter 160 is disposed on the lower electrode 140. The photonic crystal constituting the photonic crystal color filter 160 has such a property that when the electric field is applied, the size of the active polymer changes and the interval of the photonic crystal particle structure changes. Thus, the intervals of the respective photonic crystal particle structures change, and external light can be reflected to a specific color.

Such a photonic crystal can be a three-dimensional photonic crystal having an opal structure, and the photonic crystal is mixed with the electroactive polymer. Here, the electroactive polymer may be composed of, for example, a material obtained by synthesizing a hydrophobic block-hydrophilic polyelectrolyte block polymer.

The photonic crystal color filter 160 using the photonic crystal exhibits a light reflectance of 90% or more, which is superior to that of a conventional reflective liquid crystal display device.

Referring to FIG. 2, in the photonic crystal color filter 160, a wavelength band for reflecting light is changed according to an applied electric field. Accordingly, the electric field applied to the photonic crystal color filter 160 can be adjusted to reflect visible light of a desired wavelength band to realize a desired color.

A black matrix 150 is disposed between the photonic crystal color filters 160. The black matrix 150 is disposed between the photonic crystal color filters 160 to improve the contrast of the light reflected from the photonic crystal color filter 160 and emitted.

A first common electrode 162 is located on the photonic crystal color filter 160 and the black matrix 150. The first common electrode 162 is formed on the entire surface of the lower substrate 110 to apply an electric field to the photonic crystal color filter 160 together with the lower electrode 140. The first common electrode 162 may be formed of the same material as the lower electrode 140.

A protective film 165 for isolating the first common electrode 162 is located on the first common electrode 162. The protective film 165 may be made of silicon oxide (SiOx), silicon nitride (SiNx) or a multilayer thereof.

A pixel electrode 170 is placed on the protective film 165. The pixel electrode 170 may be patterned for each pixel to individually drive each pixel. The pixel electrode 170 may receive a signal from the first thin film transistor 120 and apply a voltage to the liquid crystal layer 190.

As described above, the first and second thin film transistors 120 and 125, the lower electrode 140, the photonic crystal color filter 160, the first common electrode 162, the black matrix 150, And may include a pixel electrode 170.

The polymer dispersed liquid crystal layer 190 is disposed on the lower substrate 110. The polymer dispersed liquid crystal layer 190 includes a polymer ball 193 in the form of a capsule and a liquid crystal 195 filled in the liquid crystal layer 190. The polymerizable liquid crystal layer 190 includes a pixel electrode 170 and a second common electrode 210 The arrangement of the liquid crystals 195 is changed. At this time, the polymer balls 193 are irregularly dispersed in the polymer layer 191 of the polymer dispersed liquid crystal layer 190.

The structure of the polymer dispersed liquid crystal layer 190 is such that when the two kinds of liquids having different refractive indices are forcedly mixed while being transparent but not dissolving each other, the whole is milky white . This phenomenon occurs not only because each liquid in the mixed state becomes opaque, but also because light is scattered at the interface when light passes through the interface due to the different refractive indexes of the two liquids.

That is, when an electric field is applied between the two electrodes, the liquid crystal 195 is oriented in the direction of the electric field. When the refractive index of the liquid crystal 195 matches the refractive index of the polymer layer 191, The layer 190 becomes transparent.

On the other hand, when the electric field is removed, the director of the liquid crystal 195 is disordered by the surface anchoring energy, and the effective refractive index of the liquid crystal deviates greatly from the refractive index of the polymer, and the polymer dispersed liquid crystal layer 190 ) May become opaque.

The polymer dispersed liquid crystal layer 190 may be formed by a phase separation method or an emulsification method.

The common electrode 210 and the upper substrate 220 are positioned on the polymer dispersed liquid crystal layer 190. The second common electrode 210 applies a voltage to the polymer dispersed liquid crystal layer 190 through a voltage applied to the pixel electrode 170 to form a transparent electrode 190 such as indium tin oxide (ITO), indium zinc oxide (IZO) .

A spacer 180 may be further provided to maintain a gap between the lower substrate 110 and the upper substrate 220. The spacers 180 may be located in the non-display region between the pixel electrodes 170 to maintain a gap between the substrates.

Hereinafter, the mono mode and the color mode of the liquid crystal display device 100 will be described as follows.

FIG. 3 is a view illustrating a white implementation of a liquid crystal display device according to the present invention, FIG. 4 is a view illustrating a black implementation of the liquid crystal display device according to the present invention, FIG. Fig. In the following description, the same constituent elements as those of FIG. 1 described above are denoted by the same reference numerals and the description thereof is omitted.

Referring to FIG. 3, a liquid crystal display device that displays one unit pixel including three sub-pixels on a lower substrate 110 is disclosed.

First, a voltage is applied to the lower electrode 140 from the first thin film transistor 120 of each pixel. In each pixel, a scan line to which a scan signal is applied and a data line to which a data signal is applied are provided. A signal is applied to the first thin film transistor 120 from the scan line and the data line, .

A common voltage is applied to the first common electrode 162 located on the first to third photonic crystal color filters 160a, 160b and 160c to generate an electric field between the lower electrode 140 and the first common electrode 162 .

Here, the first photonic crystal color filter 160a applies an electric field to reflect red light, the second photonic crystal color filter 160b applies an electric field to reflect green light, and the third photonic crystal color filter 160b 160c apply an electric field to reflect blue light.

No voltage is applied to the pixel electrode 170 and the second common electrode 210 located on the upper substrate 220.

When external light is incident on the liquid crystal display device driven as described above, external light is scattered and reflected by the irregularly arranged liquid crystals 195 in the polymer dispersed liquid crystal layer 190, and white light close to opaque, Some reflection occurs. The light partially incident on the first to third photonic crystal color filters 160a, 160b and 160c is reflected by the respective photonic crystal color filters 160a, 160b and 160c as red, green and blue light.

Therefore, the white light reflected and emitted from the polymer dispersed liquid crystal layer 190 and the red, green, and blue lights reflected and emitted from the respective photonic crystal color filters 160a, 160b, and 160c are mixed to finally emit white light .

Referring to FIG. 4, unlike FIG. 3, the liquid crystal display device may implement black.

A common voltage is applied to the first common electrode 162 located on the first to third photonic crystal color filters 160a, 160b and 160c in the same manner as in the white implementation so that a voltage is applied between the lower electrode 140 and the first common electrode 162 Thereby forming an electric field.

Here, unlike the white implementation described above, the first to third photonic crystal color filters 160a apply an electric field to absorb external light to realize black. No voltage is applied to the pixel electrode 170 and the second common electrode 210 located on the upper substrate 220.

When external light is incident on the liquid crystal display device driven as described above, external light is scattered and reflected by the irregularly arranged liquid crystals 195 in the polymer dispersed liquid crystal layer 190, and white light close to opaque, Some reflection occurs. The light partially incident on the first to third photonic crystal color filters 160a, 160b, and 160c is absorbed by the photonic crystal color filters 160a, 160b, and 160c and is implemented in black.

Therefore, it is possible to finally realize black by the white light reflected and emitted from the polymer dispersed liquid crystal layer 190 and the black realized by the respective photonic crystal color filters 160a, 160b and 160c.

Unlike FIGS. 3 and 4, the liquid crystal display of the present invention can realize a color mode.

Referring to FIG. 5, a voltage is applied to the lower electrode 140 from the first thin film transistor 120 of each pixel. In each pixel, a scan line to which a scan signal is applied and a data line to which a data signal is applied are provided. A signal is applied to the first thin film transistor 120 from the scan line and the data line, .

A common voltage is applied to the first common electrode 162 located on the first to third photonic crystal color filters 160a, 160b and 160c to generate an electric field between the lower electrode 140 and the first common electrode 162 .

Here, the first to third photonic crystal color filters 160a, 160b, and 160c all apply an electric field to reflect red light. A voltage is applied to each of the pixel electrodes 170 and the second common electrode 210 located on the upper substrate 220 to drive the polymer dispersed liquid crystal layer 190 to arrange the liquid crystals 195. At this time, the arrangement of the liquid crystals 195 is arranged to transmit external light.

When outside light is incident on the liquid crystal display device driven as described above, the polymer dispersed liquid crystal layer 190 transmits the external light as it is due to the liquid crystal 195 arranged vertically. The light incident on the first to third photonic crystal color filters 160a, 160b and 160c is reflected by the first to third photonic crystal color filters 160a, 160b and 160c as red light.

Accordingly, the red light is reflected in each of the photonic crystal color filters 160a, 160b, and 160c to realize red.

In this embodiment, the red color is implemented. Alternatively, the electric fields of the photonic crystal color filters 160a, 160b, and 160c may be adjusted to realize green and blue colors.

As described above, the liquid crystal display device according to an embodiment of the present invention has an advantage that the aperture ratio can be improved because the alignment margin can be reduced when the substrates are bonded together by forming the photonic crystal color filter on the lower substrate.

In addition, when driving the mono mode of white and black, there is an advantage that the driving voltage can be lowered and the power consumption can be reduced by using only the photonic crystal color filter. Further, by using the polymer dispersed liquid crystal layer, there is an advantage that a reflection type liquid crystal display device excellent in reflectance can be provided without separately providing a polarizing plate.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (8)

A lower substrate;
A lower electrode disposed on the lower substrate;
A photonic crystal color filter located on the lower electrode and partitioned by a black matrix;
A first common electrode located on the photonic crystal color filter;
A protective film on the first common electrode;
A pixel electrode located on the protective film;
A polymer dispersed liquid crystal layer disposed on the pixel electrode;
A second common electrode disposed on the polymer dispersed liquid crystal layer; And
And an upper substrate positioned on the second common electrode,
Wherein the photonic crystal color filter reflects red, green, and blue light according to an electric field applied between the lower electrode and the first common electrode, and absorbs light.
The method according to claim 1,
A first thin film transistor located on the lower substrate and applying a voltage to the lower electrode, and a second thin film transistor applying a voltage to the pixel electrode.
The method according to claim 1,
And a spacer positioned between the pixel electrodes.
delete The method according to claim 1,
Wherein the photonic crystal color filter reflects red, green, and blue light to emit white light, respectively.
The method according to claim 1,
Wherein the photonic crystal color filter absorbs light to realize black.
The method according to claim 1,
Wherein the polymer dispersed liquid crystal layer is driven by applying a voltage to the pixel electrode and the second common electrode.
The method according to claim 1,
Wherein the color mode is realized by simultaneously driving the photonic crystal color filter and the polymer dispersed liquid crystal layer.

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