KR101713946B1 - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device, First and second polarizers positioned on the lower and upper portions of the liquid crystal panel; A backlight unit positioned below the first polarizer and supplying light to the liquid crystal panel; And a selective reflection layer disposed between the second polarizer and the liquid crystal panel and including at least a first layer and a second layer, wherein the first and second layers are made of a material having a different refractive index And when the backlight unit does not supply light, light having a wavelength of? Is reflected by the selective reflection layer.

Description

[0001] Liquid crystal display device [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly to a liquid crystal display capable of exhibiting a specific color in an off state due to its reflection characteristic.

As the information society has developed, demand for display devices has been gradually increasing in various forms. In response to this demand, in recent years, LCD (Liquid Crystal Display Device), PDP (Plasma Display Panel), VFD (Vacuum Fluorescent Display) Electro Luminescent Display) have been studied, and some of them have already been used as display devices in various devices.

Among them, liquid crystal display devices are mostly used while substituting CRT (Cathode Ray Tube) for the purpose of a portable image display device because of their excellent image quality, light weight, thinness and low power consumption. A monitor for receiving and displaying a broadcast signal, a monitor for a computer, and the like.

The driving principle of such a liquid crystal display device utilizes the optical anisotropy and the polarization property of the liquid crystal, and since the liquid crystal has a long structure, the liquid crystal has directionality in the arrangement of molecules, and an electric field is artificially applied to the liquid crystal to control the direction can do.

Therefore, when the molecular alignment direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light is refracted in the molecular alignment direction of the liquid crystal due to optical anisotropy, so that image information can be expressed.

Currently, active matrix liquid crystal display (AM-LCD), in which a thin film transistor and pixel electrodes connected to the thin film transistor are arranged in a matrix manner, has been receiving the most attention because of its excellent resolution and video realization capability.

Hereinafter, a conventional liquid crystal display device will be described with reference to the accompanying drawings.

1 is a cross-sectional view schematically showing a conventional liquid crystal display device.

As shown in the figure, a conventional liquid crystal display device 1 includes a first substrate 5 and a second substrate 10, a first substrate 5 and a second substrate 5, A liquid crystal layer 15, and a backlight unit 90 positioned on the backside spaced apart from the first substrate 5. In this case, the liquid crystal panel 30 includes the first and second substrates 5 and 10 and the liquid crystal layer 15. A transparent glass substrate is mainly used for the first and second substrates 5 and 10.

The first substrate 5 is divided into a pixel region P defined by a gate line (not shown) and a data line (not shown) perpendicularly intersecting and a switching region S formed with a thin film transistor Tr.

A thin film transistor Tr serving as a switching is formed for each intersection of the gate line and the data line. The thin film transistor Tr may include a gate electrode 25, a gate insulating film 45, a semiconductor layer 42, and source and drain electrodes 32 and 34. The gate electrode 25 is connected to the gate wiring, and the gate insulating film 45 covers the gate electrode 25. The semiconductor layer 42 is located on the gate insulating layer 45 and is located corresponding to the gate electrode 25. The semiconductor layer 42 may include an active layer made of pure amorphous silicon (a-Si: H) and an ohmic contact layer made of amorphous silicon (n + a-Si: H) containing impurities. The source electrode 32 is connected to the data line and the drain electrode 34 is spaced apart from the source electrode 32. The source electrode 32 and the drain electrode 34 are located on the semiconductor layer 42.

A protective layer 55 including a drain contact hole DCH exposing the drain electrode 34 is formed on the upper portion of the thin film transistor Tr. A pixel electrode 70 connected to the drain electrode 34 of the thin film transistor Tr through the drain contact hole DCH is formed on the protective film 55 for each pixel region P. [

The pixel electrode 70 may be formed of one selected from a group of transparent conductive materials including indium-tin-oxide (ITO) and indium-zinc-oxide (IZO) .

On the other hand, on the second substrate 10, a gate and a data wiring on the first substrate 5 and a black matrix 12 for shielding the thin film transistor Tr are formed. Color filters 16a, 16b, and 16c including red (R), green (G), and blue (B) sub-color filters sequentially patterned with the black matrix 12 as a boundary are formed below the black matrix 12. [ A filter layer 16 is formed. A common electrode 80 made of a transparent conductive material group including indium-tin-oxide (ITO) and indium-zinc-oxide (IZO) is formed on the lower surface of the color filter layer 16.

In this case, first and second alignment layers (not shown) may be further formed on the upper and lower surfaces of the pixel electrode 70 and the common electrode 80, respectively, although not shown in detail in the drawings.

The liquid crystal display 1 described above uses the pixel electrode 70 to which the thin film transistors T are individually connected as the first electrode and the common electrode 80 formed on the front surface of the second substrate 10 as the second electrode . The liquid crystal layer 15 is driven by using the vertical electric field between the pixel electrode and the common electrode which are selectively located in the corresponding pixel region by using the thin film transistor T serving as the switching and the light emitted from the backlight unit 90 It is possible to control the amount of permeation. The desired image is realized through the light passing through the color filter layer on / off by driving the liquid crystal layer.

Particularly, as the light source of the backlight unit 90, a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), an external electrode fluorescent lamp (EEFL) And a light-emitting diode (LED) may be used.

In recent years, there has been a demand for a liquid crystal display device in which colors are implemented at off-time. Particularly in mobile phones and the like, it is required that a specific color is implemented so as to harmonize with the color of the case at the time of off. In general, the liquid crystal display device implements black or white color at the time of off according to the mode, and it can not achieve harmony with the color of the cellular phone case and the like.

In accordance with this demand, a liquid crystal display device using reflection characteristics of a cholesteric liquid crystal has been proposed. 2 is a cross-sectional view of a reflective liquid crystal display device using a conventional cholesteric liquid crystal.

1 and 2, a liquid crystal display 50 includes a liquid crystal panel 30, a backlight unit 90 under the liquid crystal panel 30, Film (80).

1, the liquid crystal panel 30 includes a first substrate 5 on which a thin film transistor Tr and a pixel electrode 70 are formed, a color filter layer 16 and a common electrode 75, And a liquid crystal layer 15 interposed between the second substrate 10 and the first and second substrates 5 and 10.

The liquid crystal panel 30 is irradiated with light from a light source of the backlight unit 90 when the liquid crystal panel 30 is driven on and the color image is transmitted through the cholesteric liquid crystal film 80 by driving the liquid crystal panel 30 .

The cholesteric liquid crystal film 80 is disposed between the third and fourth substrates 82 and 84 facing each other and between the third and fourth substrates 82 and 84, And a cholesteric liquid crystal layer 86 located in a space defined by the third and fourth substrates 82 and 84 and the barrier rib 88. [

The cholesteric liquid crystal layer 86 includes a cholesteric liquid crystal molecule 87.

On the other hand, the liquid crystal display device 50 selectively reflects light by the cholesteric liquid crystal film 80 when the liquid crystal panel 30 is turned off, thereby realizing a specific color.

The cholesteric liquid crystal molecules 87 are arranged in a twisted state in a twisted state. When a 360-degree twisted shape of the cholesteric liquid crystal molecules 87 is referred to as a unit helix pitch, a hue reflected by the unit helix pitch and the thickness of the helical shape is determined.

That is, the cholesteric liquid crystal molecules 87 reflect only the light having a specific wavelength among the light that has been transmitted through the right-handed polarized light and is left-handed, and the unit helix pitch of the cholesteric liquid crystal molecules 87 and the thickness The wavelength of the light reflected by the light source is determined. That is, the color of the light reflected by the unit helix pitch and the spiral thickness of the cholesteric liquid crystal molecules 87 is determined.

In the case of the conventional reflective liquid crystal display device 50 including the cholesteric liquid crystal film 80 as described above, the thickness of the cholesteric liquid crystal layer 80 including the two opposing substrates 82 and 84 and the cholesteric liquid crystal layer 86 Since the liquid crystal film 80 is required, the manufacturing process is complicated and the manufacturing cost is also increased.

In addition, there is a problem that a desired color is realized at the front view angle but another color is observed at the side view angle.

There is a polarizing plate for transmitting only a specific linearly polarized light above and below the liquid crystal panel 30 and light passing through the polarizing plate located above the liquid crystal panel 30 is transmitted through a cholesteric liquid crystal film The transmittance is greatly reduced while passing through the transparent substrate 80. As a result, the transmittance of the liquid crystal display device 50 is reduced.

As described above, the present invention aims to solve the disadvantages in the manufacturing process and manufacturing cost of the conventional liquid crystal display device. That is, in order to replace a cholesteric liquid crystal film having a complicated structure, a configuration capable of reflecting a specific color is used.

Also, the problem of color change at the side viewing angle is solved.

In order to solve the above problems, the present invention provides a liquid crystal display comprising: a liquid crystal panel; First and second polarizers positioned on the lower and upper portions of the liquid crystal panel; A backlight unit positioned below the first polarizer and supplying light to the liquid crystal panel; And a selective reflection layer disposed between the second polarizer and the liquid crystal panel and including at least a first layer and a second layer, wherein the first and second layers are made of a material having a different refractive index And when the backlight unit does not supply light, light having a wavelength of? Is reflected by the selective reflection layer.

The first layer is made of titanium oxide (TiO ₂ ), and the second layer is made of silicon oxide (SiO ₂ ).

Wherein the liquid crystal panel includes first and second substrates facing each other, a liquid crystal layer positioned between the first and second substrates, a pixel electrode and a common electrode for driving the liquid crystal layer, Is located between the second substrate and the first layer.

The liquid crystal panel includes: first and second substrates facing each other; A thin film transistor located on the first substrate; A pixel electrode located on the first substrate and connected to the thin film transistor; A common electrode disposed on one of the first and second substrates; And a liquid crystal layer disposed between the first and second substrates.

The first polarizing plate has a first polarizing axis and the second polarizing plate has a second polarizing axis perpendicular to the first polarizing axis.

And the selective reflection layer has a two-layer to thirty-layer structure in which the first and second layers are alternately arranged.

Wherein the selective reflection layer is formed by alternately arranging the first and second layers to have an 18-layer structure, wherein the first layer is located at the lowest layer, the second layer is located at the uppermost layer, and the second layer located at the uppermost layer And has the largest thickness, and the above-mentioned? Is a blue wavelength band.

The present invention can display a specific color when the liquid crystal display device is turned off by reflecting light of a specific wavelength using alternately arranged titanium oxide layer and silicon oxide layer.

Since it has a very simple structure as compared with the conventional cholesteric liquid crystal film, the manufacturing process is simple and the manufacturing cost can be reduced. Further, it has an advantage that a thin liquid crystal display device can be provided.

Further, by locating the laminated structure of the titanium oxide layer and the silicon oxide layer between the upper substrate and the polarizing plate, the color shifting problem at the side viewing angle can be prevented.

1 is a cross-sectional view schematically showing a conventional liquid crystal display device.
2 is a cross-sectional view of a reflective liquid crystal display device using a conventional cholesteric liquid crystal.
3 is a schematic cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention.
4 is a photograph showing a color shift phenomenon in the liquid crystal display device according to the first embodiment of the present invention.
5 is a schematic cross-sectional view of a liquid crystal display device according to a second embodiment of the present invention.
6A and 6B are graphs showing a color shift phenomenon in the liquid crystal display according to the first and second embodiments of the present invention.

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

3 is a schematic cross-sectional view of a liquid crystal display device according to a first embodiment of the present invention.

1, the liquid crystal display 100 includes a liquid crystal panel 110, first and second polarizers 152 and 154 below and above the liquid crystal panel 110, A third substrate 160 positioned above the second polarizing plate 154 and a selective reflection layer 170 disposed on the third substrate 160. The first polarizing plate 154 and the second polarizing plate 154 may have different polarities.

The liquid crystal panel 110 includes a first substrate 101, a second substrate 102 facing the first substrate 101, and a liquid crystal layer interposed between the first and second substrates 101 and 102. [ Layer 103 and first and second polarizers 152 and 154 located outside the first and second substrates 101 and 102, respectively.

A gate electrode 112 and a gate wiring 114 connected to the gate electrode 112 and extending along a first direction are disposed on the first substrate 101. Each of the gate electrode 112 and the gate wiring 114 may be formed of a single layer of a metal material such as aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), copper (Cu) On the other hand, it may alternatively have a triple layer structure having a first layer made of copper (Cu) and a second layer and a third layer made of molybdenum-titanium alloy (MoTi), which are located above and below the first layer.

A gate insulating layer 116 is disposed to cover the gate electrode 112 and the gate wiring 114. For example, the gate insulating layer 116 may be formed of an inorganic insulating material such as silicon oxide or silicon nitride.

A semiconductor layer 120 including an active layer 120a and an ohmic contact layer 120b is disposed on the gate insulating layer 116. [ The semiconductor layer 120 is located corresponding to the gate electrode 112. The active layer 120a is made of pure amorphous silicon and the ohmic contact layer 120b is made of impurity amorphous silicon.

A pixel electrode 124 having a plate shape corresponding to the pixel region P is located on the gate insulating film 116. The pixel electrode 124 is made of a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO). The pixel electrode 124 may be in contact with a side surface of the semiconductor layer 120 or may be spaced apart from the semiconductor layer 120 by a predetermined distance. The pixel electrode 124 overlaps with a part of the gate line 114 to form a storage capacitor Cst. That is, the overlapped portion of the gate line 114 becomes the first electrode, the overlapped portion of the pixel electrode 124 becomes the second electrode, and the overlap between the pixel electrode 124 and the gate line 114 The gate insulating film 116 of the gate insulating film 116 becomes a dielectric layer, thereby forming a storage capacitor Cst.

A data line 130 extending in the second direction is disposed on the gate insulating layer 116 so as to intersect the gate line 114. The pixel region P is defined by the intersection of the data line 130 and the gate line 114.

A source electrode 132 and a drain electrode 134 are positioned on the semiconductor layer 120. The source electrode 132 is connected to the data line 130 and the drain electrode 134 is spaced apart from the source electrode 132. The drain electrode 132 is in contact with the pixel electrode 124. The active layer 120a is exposed corresponding to a space between the source and drain electrodes 132 and 134. [

Each of the data line 130, the source electrode 132 and the drain electrode 134 is formed of a metal material such as aluminum (Al), an aluminum alloy (AlNd), molybdenum (Mo), copper (Cu) It can be made of a single layer. On the other hand, it may alternatively have a triple layer structure having a first layer made of copper (Cu) and a second layer and a third layer made of molybdenum-titanium alloy (MoTi), which are located above and below the first layer.

The gate electrode 112, the gate insulating layer 116, the semiconductor layer 120, the source electrode 132, and the drain electrode 134 form a thin film transistor Tr which is a switching element. The thin film transistor Tr is connected to the gate line 114, the data line 130, and the pixel electrode 124.

A protective layer 136 is disposed to cover the thin film transistor Tr, the data line 130, and the pixel electrode 124. The passivation layer 136 may be formed of an inorganic insulating material such as silicon oxide, silicon nitride, or an organic insulating material such as benzocyclobutene (BCB) or photo acryl.

A common electrode 138 having at least one hole 139 corresponding to the pixel electrode 124 and having a plate shape with respect to the entire first substrate 101 is disposed on the passivation layer 136. The common electrode 138 is made of a transparent conductive material such as ITO or IZO. When a voltage is applied to the common electrode 138 and the pixel electrode 124, a fringe field is formed.

A black matrix 140, a color filter layer 142, and an overcoat layer 146 are disposed on the second substrate 102 facing the first substrate 101. The black matrix 140 is positioned corresponding to the thin film transistor Tr, the data line 130, and the gate line 114 to prevent light leakage. The color filter layer 142 is formed on the black matrix 140 in correspondence with the pixel region P. For example, the color filter layer 142 includes red, green, and blue color filter patterns 142a, 142b, and 142c. The overcoat layer 146 covers the black matrix 140 and the color filter layer 142 to planarize the surface.

A liquid crystal layer 103 is disposed between the first and second substrates 101 and 102 and a fringe field formed between the pixel electrode 124 and the common electrode 138, Layer 103 is driven.

The liquid crystal layer may be driven by a transversal electric field by alternately arranging the pixel electrodes and the common electrodes in a comb shape, By positioning on the overcoat layer 146, the liquid crystal layer may be driven by a vertical electric field.

The first and second polarizers 152 and 154 located outside the first and second substrates 101 and 102 respectively have polarization axes perpendicular to each other. Accordingly, the first polarizer 152 transmits only the light parallel to the first polarizing axis of the light emitted from the backlight unit 120, and the second polarizer 154 transmits the second polarizing axis perpendicular to the first polarizing axis Only light that is parallel to the incident light is transmitted.

The third substrate 160 is disposed on the second polarizer 154 and a selective reflection layer 170 including a first thin film layer 172 and a second thin film layer 174 is disposed on the third substrate 160. Wherein the other of the first thin film layer 172 is formed of any one of titanium oxide (TiO ₂₎ and silicon oxide (SiO _2), the second thin film layer 174 is titanium oxide (TiO ₂₎ and silicon oxide (SiO ₂₎ It is done in one. That is, the first thin film layer 172 and the second thin film layer 174 are made of materials having different refractive indexes. Although the selective reflection layer 170 is shown as a double layer of a first thin film layer 172 and a second thin film layer 174 in the figure, the first and second thin film layers 172 and 174 may be alternately stacked, Structure.

The selective reflection layer 170 is composed of thin film layers 172 and 174 having different refractive indexes, thereby reflecting light of a specific wavelength.

That is, when the backlight unit 120 is in the off state, when the external light is irradiated on the selective reflection layer 170, the light of the specific wavelength is reflected and the light of the remaining wavelength is transmitted. Therefore, in the off state of the backlight unit 120, the liquid crystal display device 100 has a specific color and is in harmony with the outer case (not shown) of the liquid crystal display device 100.

Compared with the case of using a conventional cholesteric liquid crystal film, the process is simple and has advantages in manufacturing cost and process efficiency. In addition, since the thickness of the selective reflection layer 170 is thin, it is possible to provide a thin liquid crystal display device.

However, the liquid crystal display device 100 of the first embodiment described above has a problem of color shift depending on the viewing angle. 4, which is a photograph showing the color shift phenomenon in the liquid crystal display device according to the first embodiment of the present invention, the color changes from the front viewing angle (left side) to the side. (? U'v 'increase)

The wavelength of the light reflected by the selective reflection layer 170 is expressed by the following equation.

Where n is the refractive index of the first thin film layer 172, n2 is the refractive index of the second thin film layer 172, Is the refractive index of the second thin film layer, and [theta] is the viewing angle.

In addition, n _a is as follows.

Therefore, a color shift phenomenon occurs in which the wavelength? Of the light reflected according to the viewing angle? Changes.

That is, in the first embodiment of the present invention, it is possible to provide a liquid crystal display device having a selective reflection characteristic that has advantages in manufacturing cost and process efficiency, but a color shift problem occurs depending on the viewing angle.

To solve such a problem, a liquid crystal display device of a selective reflection characteristic is proposed. 5 is a schematic cross-sectional view of a liquid crystal display device according to a second embodiment of the present invention.

5, the liquid crystal display 200 includes a liquid crystal panel 210, first and second polarizers 252 and 254 on upper and lower sides of the liquid crystal panel 210, And a selective reflection layer 270 disposed between the liquid crystal panel 210 and the second polarizer 254. The backlight unit 220 includes a liquid crystal panel 210,

The liquid crystal panel 210 includes a first substrate 201, a second substrate 202 facing the first substrate 201, and a liquid crystal layer 203 interposed between the first and second substrates 201 and 202. Layer 203 and first and second polarizers 252 and 254 located outside the first and second substrates 201 and 202, respectively.

A gate electrode 212 and a gate wiring 214 connected to the gate electrode 212 and extending along a first direction are disposed on the first substrate 201. Each of the gate electrode 212 and the gate wiring 214 may be formed of a single layer of a metal material such as aluminum (Al), aluminum alloy (AlNd), molybdenum (Mo), copper (Cu) On the other hand, it may alternatively have a triple layer structure having a first layer made of copper (Cu) and a second layer and a third layer made of molybdenum-titanium alloy (MoTi), which are located above and below the first layer.

And a gate insulating layer 216 covering the gate electrode 212 and the gate wiring 214. For example, the gate insulating layer 216 may be formed of an inorganic insulating material such as silicon oxide or silicon nitride.

A semiconductor layer 220 including an active layer 220a and an ohmic contact layer 220b is disposed on the gate insulating layer 216. [ The semiconductor layer 220 is positioned corresponding to the gate electrode 212. The active layer 220a is made of pure amorphous silicon and the ohmic contact layer 220b is made of impurity amorphous silicon.

A pixel electrode 224 having a plate shape corresponding to the pixel region P is located on the gate insulating film 216. The pixel electrode 224 is made of a transparent conductive material such as indium-tin-oxide (ITO) or indium-zinc-oxide (IZO). The pixel electrode 224 may be in contact with a side surface of the semiconductor layer 220 or may be spaced apart from the semiconductor layer 220 by a predetermined distance. The pixel electrode 224 overlaps with a part of the gate wiring 214 to form a storage capacitor Cst. That is, the overlapped portion of the gate line 214 becomes the first electrode, the overlapped portion of the pixel electrode 224 becomes the second electrode, and the overlap between the pixel electrode 224 and the gate line 214 The gate insulating layer 216 of the gate insulating layer 216 becomes a dielectric layer, thereby forming a storage capacitor Cst.

A data line 230 extending in the second direction is disposed on the gate insulating layer 216 so as to intersect the gate line 214. The pixel region P is defined by the intersection of the data line 230 and the gate line 214.

A source electrode 232 and a drain electrode 234 are disposed on the semiconductor layer 220. The source electrode 232 is connected to the data line 230 and the drain electrode 234 is spaced from the source electrode 232. The drain electrode 232 is in contact with the pixel electrode 224. The active layer 220a is exposed corresponding to the space between the source and drain electrodes 232 and 234.

Each of the data line 230, the source electrode 232 and the drain electrode 234 may be formed of a metal material such as aluminum (Al), an aluminum alloy (AlNd), molybdenum (Mo), copper (Cu) It can be made of a single layer. On the other hand, it may alternatively have a triple layer structure having a first layer made of copper (Cu) and a second layer and a third layer made of molybdenum-titanium alloy (MoTi), which are located above and below the first layer.

The gate electrode 212, the gate insulating layer 216, the semiconductor layer 220, the source electrode 232, and the drain electrode 234 form a thin film transistor Tr that is a switching element. The thin film transistor Tr is connected to the gate line 214, the data line 230, and the pixel electrode 224.

A protective layer 236 is disposed to cover the thin film transistor Tr, the data line 230, and the pixel electrode 224. [ The passivation layer 236 may be formed of an inorganic insulating material such as silicon oxide, silicon nitride, or an organic insulating material such as benzocyclobutene (BCB) or photo acryl.

A common electrode 238 having at least one hole 239 corresponding to the pixel electrode 224 and having a plate shape with respect to the entire first substrate 201 is disposed on the passivation layer 236. The common electrode 238 is made of a transparent conductive material such as ITO or IZO. When a voltage is applied to the common electrode 238 and the pixel electrode 224, a fringe field is formed.

A black matrix 240, a color filter layer 242, and an overcoat layer 246 are disposed on the second substrate 202 facing the first substrate 201. The black matrix 240 is positioned corresponding to the thin film transistor Tr, the data line 230, and the gate line 214, thereby preventing light leakage. The color filter layer 242 is formed on the black matrix 240 to correspond to the pixel region P. [ For example, the color filter layer 242 includes red, green, and blue color filter patterns 242a, 242b, and 242c. The overcoat layer 246 covers the black matrix 240 and the color filter layer 242 to planarize the surface.

A liquid crystal layer 203 is positioned between the first and second substrates 201 and 202 and a fringe field formed between the pixel electrode 224 and the common electrode 238, Layer 203 is driven.

The liquid crystal layer may be driven by a transversal electric field by alternately arranging the pixel electrodes and the common electrodes in a comb shape, By positioning on the overcoat layer 246, the liquid crystal layer may be driven by a vertical electric field.

The first and second polarizers 252 and 254 located outside the first and second substrates 201 and 202 have polarization axes perpendicular to each other. The first polarizing plate 252 transmits only light parallel to the first polarizing axis of the light emitted from the backlight unit 220, and the second polarizing plate 254 transmits a second polarizing axis perpendicular to the first polarizing axis Only light that is parallel to the incident light is transmitted.

In the liquid crystal display 100 according to the first embodiment of FIG. 4, since the selective reflection layer 170 is disposed on the second polarizer 154, external light is directly irradiated onto the selective reflection layer 170.

However, in the liquid crystal display device 200 according to the second embodiment of the present invention, the selective reflection layer 270 is positioned between the second polarizer 254 and the second substrate 202. Therefore, the external light passes through the second polarizer 254, and then is irradiated onto the selective reflection layer 270.

The selective reflection layer 270 includes a first thin film layer 272 and a second thin film layer 274 having different refractive indexes. Wherein the other of the first thin film layer 272 is formed of any one of titanium oxide (TiO ₂₎ and silicon oxide (SiO _2), the second thin film layer 274 is titanium oxide (TiO ₂₎ and silicon oxide (SiO ₂₎ It is done in one. The refractive index of titanium oxide is about 2.40, and the refractive index of silicon oxide is about 1.45. Although the selective reflection layer 270 is shown as a double layer of a first thin film layer 272 and a second thin film layer 274 in the figure, the first and second thin film layers 272 and 274 may be stacked alternately. Structure.

For example, the selective reflection layer 270 may have a 2- to 30-layer structure in which the first thin film layer 272 and the second thin film layer 274 are alternately arranged.

For example, a selective reflection layer 270 having a laminated structure of Sample 1 shown in Table 1 below reflects blue light, a selective reflection layer 270 having a laminated structure of Sample 2 has a mirror property, and Sample 3 A selective reflection layer 270 having a laminated structure of red-wine-colored light is reflected.

Sample 1 Sample 2 Sample 3 layer Thickness [Å] layer Thickness [Å] layer Thickness [Å] SiO2 1095 SiO2 697 TiO2 398 TiO2 194 TiO2 721 SiO2 17 SiO2 222 SiO2 1267 TiO2 451 TiO2 726 TiO2 728 SiO2 581 SiO2 585 SiO2 1048 TiO2 11 TiO2 318 TiO2 531 SiO2 433 SiO2 673 TiO2 142 TiO2 328 SiO2 564 SiO2 1019 TiO2 582 SiO2 348 TiO2 591 SiO2 287 TiO2 392 SiO2 402 TiO2 276 SiO2 314 TiO2 216

For example, in the case of Sample 1, the titanium oxide layer and the silicon oxide layer are alternately stacked and have an 18-layer structure, with the titanium oxide layer being the lowest layer and the silicon oxide layer being the uppermost layer. At this time, the uppermost silicon oxide layer has the largest thickness.

Also, considering the contact characteristics with the second substrate 202, the lowermost layer of the selective reflection layer 270 contacting the second substrate 202 may be made of silicon oxide.

The selective reflection layer 270 is composed of thin film layers 272 and 274 having different refractive indices, thereby reflecting light of a specific wavelength.

That is, when the backlight unit 220 is in the off state, when the external light is irradiated on the selective reflection layer 270, the light of the specific wavelength is reflected and the light of the remaining wavelength is transmitted. Therefore, in the off state of the backlight unit 220, the liquid crystal display device 200 has a specific hue and color harmony with the outer case (not shown) of the liquid crystal display device 200.

Particularly, since the external light is irradiated to the selective reflection layer 270 after passing through the second polarizer 254, the color reflection of the light reflected by the selective reflection layer 270 is minimized according to the viewing angle.

6A and 6B, which are graphs showing the color shift phenomenon in the liquid crystal display device according to the first and second embodiments of the present invention, 2 'polarizing plate 254 and the second substrate 202, the color shift phenomenon? U'v' can be lowered up to 0.05 compared with the first embodiment. That is to say, a conventional liquid crystal display (LCM) structure, a bare GLS plate, a selective reflection layer of blue light (M / L), a selective reflection layer of gold light (M / L) The color shift phenomenon was improved in both the selective reflection layer (M / L (Pink)) and the selective reflection layer (M / L (Green)) of the green light.

The liquid crystal display device according to the present invention includes a selective reflection layer in which a titanium oxide layer and a silicon oxide layer having different refractive indices are stacked, and has a specific color in an off state of the backlight unit. Therefore, color matching with the outer case of the liquid crystal display device can be achieved.

In addition, since the selective reflection layer of the liquid crystal display of the present invention has a structure in which titanium oxide and silicon oxide are laminated, the manufacturing process is simple and has advantages in manufacturing cost and process efficiency. In addition, since the thickness of the selective reflection layer is thin, it is possible to provide a thin liquid crystal display device.

Further, by locating the selective reflection layer between the upper substrate and the upper polarizer of the liquid crystal panel, the color shift phenomenon according to the viewing angle is minimized.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It can be understood that

110, 210: liquid crystal panel
120, 220: Backlight unit
252, 254: polarizer
270: selective reflection layer

Claims (7)

A liquid crystal panel;
First and second polarizers positioned on the lower and upper portions of the liquid crystal panel;
A backlight unit positioned below the first polarizer and supplying light to the liquid crystal panel;
And a selective reflection layer disposed between the second polarizer and the liquid crystal panel and including at least a first layer and a second layer,
Wherein the first and second layers are made of a material having a different refractive index, and when the backlight unit does not supply light, light having a wavelength of? Is reflected by the selective reflection layer.
The method according to claim 1,
Wherein the first layer is made of titanium oxide (TiO ₂ ), and the second layer is made of silicon oxide (SiO ₂ ).
3. The method of claim 2,
Wherein the liquid crystal panel includes first and second substrates facing each other, a liquid crystal layer positioned between the first and second substrates, a pixel electrode and a common electrode for driving the liquid crystal layer,
And the second layer is located between the second substrate and the first layer.
The method according to claim 1,
In the liquid crystal panel,
A first substrate and a second substrate facing each other;
A thin film transistor located on the first substrate;
A pixel electrode located on the first substrate and connected to the thin film transistor;
A common electrode disposed on one of the first and second substrates;
And a liquid crystal layer disposed between the first and second substrates.
The method according to claim 1,
Wherein the first polarizing plate has a first polarizing axis and the second polarizing plate has a second polarizing axis perpendicular to the first polarizing axis.
The method according to claim 1,
Wherein the selective reflection layer has a two-layer to thirty-layer structure in which the first and second layers are alternately arranged.
The method according to claim 6,
Wherein the selective reflection layer is formed by alternately arranging the first and second layers to have an 18-layer structure, wherein the first layer is located at the lowest layer, the second layer is located at the uppermost layer, and the second layer located at the uppermost layer And has a largest thickness, and the lambda is a blue wavelength band.

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