KR20040005040A - Reflection type and transmission type LCD with CLC color filter - Google Patents

Abstract

PURPOSE: A reflection type and transmission type liquid crystal displays including a cholesteric liquid crystal color filter is provided to improve contrast ratio of the liquid crystal displays. CONSTITUTION: A reflection type liquid crystal display includes the first and second substrates(100,200) having pixel regions, a black matrix(102) that is formed on one side of the first substrate, facing the second substrate and placed in a region other than the pixel regions, thin film transistors, gate lines(106) and data lines(118) formed on the black matrix. The reflection type liquid crystal display further includes a quarter wave plate(130) formed on the other side of the first substrate, a line polarizing plate(132) formed on the quarter wave plate, and an absorption layer(202) formed on one side of the second substrate, facing the first substrate. The reflection type liquid crystal display also has a cholesteric liquid crystal color filter(204) formed on the absorption layer, and a liquid crystal layer formed between the first and second substrates.

Description

Reflective and transmissive liquid crystal display including cholesteric liquid crystal color filter {Reflection type and transmission type LCD with CLC color filter}

The present invention relates to a liquid crystal display device, and more particularly, to a transmissive color liquid crystal display device including a cholesteric liquid crystal color filter (hereinafter referred to as "CLC color filter").

In general, the driving principle of the liquid crystal display device uses the optical anisotropy and polarization of the liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

Therefore, when the molecular arrangement of the liquid crystal is changed by arbitrarily adjusting the magnitude of the electric field applied to the liquid crystal, the polarization characteristic of the light passing through the liquid crystal layer is changed, and the amount of light passing through the polarizing plate is adjusted to express image information. Can be.

Currently, active matrix LCDs (AM-LCDs) in which the above-described thin film transistors and pixel electrodes connected thereto are arranged in a matrix manner have attracted the most attention because of their excellent resolution and video performance.

In general, the structure of a liquid crystal panel, which is a basic component of a liquid crystal display, will be described.

1 is a view schematically showing a general liquid crystal display device.

As shown, the liquid crystal display device 11 includes a color filter 7 including a black matrix 6 and a sub-color filter (red, green, blue) 8, and a common electrode transparent on the color filter 7. And an upper substrate 5 having an 18 formed thereon, and a lower substrate 22 having an array wiring including a pixel region P and a pixel electrode 17 formed on the pixel region and a switching element T. The liquid crystal 14 is filled between the upper substrate 5 and the lower substrate 22.

The lower substrate 22 is also referred to as an array substrate, and the thin film transistor T, which is a switching element, is positioned in a matrix type, and the gate wiring 13 and the data wiring 15 passing through the plurality of thin film transistors cross each other. Is formed.

The pixel area P is an area defined by the gate line 13 and the data line 15 intersecting each other. The pixel electrode 17 formed on the pixel region P uses a transparent conductive metal having a relatively high light transmittance, such as indium-tin-oxide (ITO).

A backlight 30 for providing light to the liquid crystal display device is formed under the liquid crystal display device 11 configured as described above.

In general, the liquid crystal display 11 has a structure using light emitted from the backlight 30. In order for the light emitted from the backlight 30 to pass through the color filter 8 to be represented as an image, a plurality of functionalities are required. It is a very inefficient optical modulator because it must pass through a thin film.

The functional thin film includes two linear polarizers (not shown) for adjusting the polarization state of the backlight light, a color filter 8 for coloring the backlight light, and the like.

However, since the linear polarizer (not shown) transmits only linear components of the backlight 30 light, that is, linear polarization in one direction, only about half or less of the light emitted from the backlight 30 transmits the backlight 30 efficiently. It can not be used as a disadvantage. That is, there is a problem that the luminance is considerably lowered.

In addition, the color filter 8 generally used in the liquid crystal display device is an absorption type color filter, and even when it passes through the color filter, a lot of light emitted from the backlight 30 is generated.

In order to solve the problem of falling luminance as described above, the transmittance of the color filter should be improved. For this purpose, the color purity of the color filter should be lowered, but there is a limit in improving the luminance by simply lowering the color purity.

In order to solve the problem of luminance in the above-mentioned liquid crystal display, a liquid crystal display including a cholesteric liquid crystal (CLC) color filter using characteristics of a cholesteric liquid crystal has been researched and developed.

2 is a cross-sectional view schematically illustrating a reflective liquid crystal display device including a cholesteric liquid crystal color filter.

As shown in the drawing, the conventional reflective liquid crystal display device 50 including the CLC color filter includes an upper first substrate 52 and a lower second substrate 54 spaced by a predetermined distance, and the second substrate 54. On one surface of the first substrate 52 facing the thin film transistor T including the gate electrode 56, the active layer 58, the source electrode 60, and the drain electrode 62, and the gate wiring (not shown) And data wirings (not shown).

On the other surface of the first substrate 52, a λ / 4 film (QWF) 64 and a linear polarizing plate 66 are sequentially formed.

An opaque absorbent layer 68 is formed on one surface of the second substrate 54 facing the first substrate 52, and a CLC color filter 70 is formed on the absorbent layer 68.

The liquid crystal layer 72 is positioned between the first substrate 52 and the second substrate 54.

In the above-described configuration, the cholesteric liquid crystal (hereinafter referred to as "CLC") used as the color filter has a circular structure in which the alignment vector of the liquid crystal forms a spiral structure. If it is reflected and the spiral direction is twisted in the left direction, it has the characteristic of reflecting the left circularly polarized light. (In other words, the polarized state of the incident light is the same as the spiral direction, and the light of the wavelength satisfying Bragg's reflection condition is reflected.)

Therefore, the cholesteric liquid crystal color filter having the above-described characteristics uses selective reflection characteristics differently from the general absorption type color filter, and thus may improve light efficiency by using the light lost in the absorption type color filter.

On the other hand, since the thin film transistor and the array wiring are configured on the upper substrate, the above-described configuration has a disadvantage in that the contrast ratio is lowered by the light reflected by the metal wiring.

A description with reference to FIG. 3 is as follows.

3 is a view for explaining a polarization characteristic of light traveling through the liquid crystal display of FIG. 2.

First, only linearly polarized light having a component parallel to the optical axis of the upper linearly polarizing plate 66 of light incident from the outside passes through the linearly polarizing plate 66, and the linearly polarized light passes through the retardation film (QWP) 64 to be λ / Circular polarization occurs while experiencing a phase delay of 4.

Circularly polarized light passes through the upper substrate 52 and the liquid crystal layer 72 to reach the CLC color filter 70. At this time, some circularly polarized light reaching the upper substrate 52 through the retardation film 64 is reflected by the metal electrode 56 or the metal wiring (not shown) formed on the upper substrate 52 and passes the upper retardation film. It is converted into linearly polarized light and passes through the linear polarizing plate 66.

In this case, the CLC color filter 70 may be configured as a left circle or a right circle pitch, and the pitch is adjusted to correspond to the peak wavelength of the color for each pixel to express red, green, and blue.

If the CLC color filter is configured to have a right pitch, the circularly polarized light having the right pitch among the circularly polarized light passing through the retardation film 64 will be reflected, and the left circularly polarized light passes through the CLC color filter 70 to absorb the layer. Will be absorbed at (68).

The light reflected by the CLC color filter 70 passes through the liquid crystal layer 72, the upper substrate 52, and the retardation film 64 to undergo a phase retardation value of λ / 4, thereby changing the polarization characteristic to linear polarization. do.

At this time, in the white state according to the alignment direction of the liquid crystal layer 72, light passing through the liquid crystal layer 72 and the retardation film 64 is parallel to the optical axis of the upper linear polarizing plate 66. In the black state, the light passing through the liquid crystal layer 72 and the retardation film 64 is perpendicular to the transmission axis of the upper linear polarizer 66. It becomes linear polarization of the component and is absorbed by the linear polarizing plate.

In this process, the light emitted from the liquid crystal panel is mixed with the light emitted through the liquid crystal layer 72 and the other color filters and the light reflected by the metal wiring as described above.

At this time, the light reflected by the metal wiring is generated in the same way regardless of the on / off (black and white state). However, even if the same amount is increased, the contrast ratio is reduced because the increase ratio of the black luminance to the increase of the luminance in the white state is larger.

Therefore, as described above, the conventional reflective liquid crystal display device can use a considerable amount of light incident from the outside through the CLC color filter to improve the brightness, but it can be applied to the light reflected by the metal wiring or the metal electrode. There is a problem in that the image quality is lowered due to the decrease in the contrast ratio.

The present invention has been made for the purpose of solving the above problems, and constitutes a low reflection layer (blocking layer: black matrix) that covers the metal wiring from the light incident on the inside of the liquid crystal panel.

Such a configuration makes it possible to manufacture a high quality liquid crystal display device.

1 is a view schematically showing a general liquid crystal display device,

2 is a cross-sectional view schematically illustrating a liquid crystal display device including a conventional cholesteric liquid crystal color filter.

3 is a view for explaining a polarization characteristic of light traveling through the liquid crystal display shown in FIG.

4 is a plan view schematically showing a configuration of an upper substrate according to the present invention;

5 is a plan view schematically showing the configuration of a lower substrate according to the present invention,

FIG. 6 is a cross-sectional view taken along the line VI-VI ′ of FIG. 4;

7 is a schematic cross-sectional view of a reflective liquid crystal display device according to a first embodiment of the present invention;

8 is a schematic cross-sectional view of a transmissive liquid crystal display according to a second exemplary embodiment of the present invention.

<Brief description of the main parts of the drawing>

100: first substrate 102: low reflection layer

104: gate electrode 106: gate wiring

118 data wiring 130 lambda / 4 film

132: linear polarizing plate 200: second substrate

202: absorber layer 204: cholesteric liquid crystal color filter

According to an aspect of the present invention, there is provided a reflective liquid crystal display device comprising: an upper first substrate and a lower second substrate configured to be spaced apart from each other, and to define pixel regions; A blocking layer formed on one surface of the first substrate facing the second substrate and formed in an area excluding a pixel area; A thin film transistor, a gate wiring and a data wiring formed on the blocking layer; A λ / 4 film formed on the other surface of the first substrate; A linear polarizer configured on the λ / 4 film; An absorbing layer formed on one surface of the second substrate facing the first substrate; A cholesteric liquid crystal color filter formed on the absorbing layer;

A backlight configured under the second substrate; And a liquid crystal layer formed between the first substrate and the second substrate.

The blocking layer is characterized by consisting of a double layer of chromium / chromium oxide (Cr / CrO _X ).

According to another aspect of the present invention, a transmissive liquid crystal display device includes: an upper first substrate and a lower second substrate configured to be spaced apart from each other, and to define pixel regions; A blocking layer formed on one surface of the first substrate facing the second substrate and formed in a region excluding a pixel region; a thin film transistor, a gate wiring, and a data wiring formed on the blocking layer; A cholesteric liquid crystal color filter configured on one surface of the second substrate facing the first substrate; A λ / 4 film formed on a surface of a first substrate not facing the second substrate; A linear polarizer configured on the λ / 4 film; A cholesteric liquid crystal polarizing plate configured on one surface of the second substrate not facing the first substrate; A liquid crystal layer formed between the first substrate and the second substrate; It includes a backlight configured below the cholesteric liquid crystal polarizing plate.

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

First Embodiment

The first embodiment of the present invention is characterized in that a low reflective layer is further formed inside the reflective color liquid crystal panel.

4 is a plan view schematically showing the configuration of the upper substrate according to the first embodiment of the present invention.

As shown in the drawing, the gate wiring 106 and the data wiring 118 are formed on the substrate 100 to vertically cross each other to define the pixel region P. Referring to FIG.

The thin film transistor T including the gate electrode 104, the active layer 110, the source electrode 114, and the drain electrode 116 is positioned at the intersection of the two wires 106 and 118.

In the pixel region P, a transparent pixel electrode 122 in contact with the drain electrode T is formed.

The source electrode 114 is connected to the data line 118 and to the gate electrode 104 and the gate line 106.

In the above-described configuration, a separate low reflection layer 102 is formed under the gate line 106, the data line 118, and the thin film transistor T.

In other words, the low reflection layer 102 may be a black matrix, and an opaque metal material having low reflectance such as a chromium / chromium oxide layer (Cr / CrO _x ) may be used.

The aluminum forming the gate electrode 104 has a reflectance of 80% and a chromium / chromium oxide (composition of 50% to 60% of the chromium (Cr) single layer forming the data line and the source and drain electrodes). The Cr / CrO _x ) layer has a low reflectance of 4%.

Therefore, when the low reflection layer 102 is formed before the metal wiring or the metal electrode is formed, the reflectance of light incident from the outside is significantly reduced.

5 is a plan view schematically illustrating a lower substrate of a liquid crystal display according to the present invention. As shown, a CLC color filter 204 having a pitch corresponding to red, green, and blue wavelengths is formed corresponding to each pixel region (red, green, and blue pixels) of the substrate 200.

Although not shown, an opaque absorbing layer 202 is formed under the CLC color filter 204.

Hereinafter, the process of the upper substrate including the thin film transistor and the array wiring will be described with reference to the cross section of FIG. 6.

6 is a cross-sectional view taken along the line VI-VI ′ of FIG. 4.

As shown, in the reflective LCD according to the present invention, a chromium and a chromium oxide (Cr / CrO _x ) layer are stacked on the substrate 100 and then patterned to form a black matrix 102 as a low reflective layer. .

The low reflection layer 102 is patterned so as to correspond to the thin film transistor T formed in a later process, the gate wiring and the data wiring.

A low resistance metal including aluminum (Al) or an aluminum alloy (AlNd) is deposited and patterned on the low reflection layer 102 to form the gate electrode 104 and the gate wiring 106.

A first insulating layer is formed by depositing one selected from the group of inorganic insulating materials including silicon nitride (SiN _X ) and silicon oxide (SiO ₂ ) on the entire surface of the substrate 100 on which the gate electrode 104 and the gate wiring 106 are formed. An in-gate insulating film 108 is formed.

An island-shaped active pattern formed by stacking a pure amorphous silicon (a-Si: H) layer and an impurity amorphous silicon (n + a-Si: H) layer on the gate insulating layer 108 on the gate electrode 104. The layer 110 and the ohmic contact layer 112 are formed.

Next, a conductive metal including chromium (Cr), tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta), and the like is deposited and patterned to contact the ohmic contact layer 112 with each other. A data line 118 connected to the spaced apart source electrode 114, the drain electrode 116, and the drain electrode is formed.

After applying the selected one selected from the group of transparent organic insulating material including benzocyclobutene (BCB) and acrylic resin (resin) on the front surface of the substrate 100 on which the source and drain electrodes 114, 116 are formed The passivation layer 120, which is a second insulating layer exposing a part of the drain electrode 116, is formed.

Next, the transparent pixel electrode 122 positioned in the pixel region P is formed while contacting the exposed drain electrode 116.

The pixel electrode 122 is formed of one selected from a group of transparent conductive metals including indium tin oxide (ITO) and indium zinc oxide (IZO).

When the upper substrate 100 manufactured by the process as described above and the lower substrate 200 described above are combined, the cross-sectional view shown in FIG. 7 is as follows. (The upper substrate is cut along VI-VI ′ of FIG. 4. The lower substrate is a cross-sectional view taken along the line VII-VII of FIG. 5.)

7 is a schematic cross-sectional view of a reflective liquid crystal display device according to the present invention.

As illustrated, the reflective liquid crystal display device 300 includes an upper first substrate 100 and a lower second substrate 200, and one surface of the first substrate 100 facing the second substrate 200. The thin film transistor T, the gate wiring 106 and the data wiring 118 are formed, and on one surface of the second substrate 200 facing the first substrate 100, the absorption layer 202 and the CLC color filter layer ( 204).

The retardation film 130 and the linear polarizer 132 are formed on the other surface of the first substrate 100.

In the configuration as described above, the low reflection layer 102 is formed on the thin film transistor T, the gate wiring 106 and the data wiring 118, which is the same amount in all cases of the white / black state. Causes a decrease in luminance.

However, since the contrast ratio is given by the ratio of the white luminance and the black luminance, and the reduction ratio to the white luminance is smaller than the reduction ratio to the black luminance, the ratio can obtain the effect of increasing the contrast.

Therefore, the liquid crystal display device having a clearer picture quality than the conventional one can be manufactured.

The configuration of the upper substrate 100 as described above has the same advantages in the case of a transmissive liquid crystal display device including the CLC color filter 204.

Hereinafter, a transmissive color liquid crystal display device having a low reflection layer will be described with reference to the second embodiment.

Second Embodiment

A second embodiment of the present invention is characterized in that a low reflection layer is formed in a transmissive liquid crystal display including a CLC color filter and a CLC polarizing plate.

8 is a cross-sectional view schematically illustrating a configuration of a liquid crystal display according to a second embodiment of the present invention.

As illustrated, the transmissive liquid crystal display device 400 according to the present invention is configured to be spaced apart from the upper first substrate 500 and the lower second substrate 600, and to face the second substrate 600. On one surface of 500, an opaque low reflective layer 502 is first formed.

A thin film transistor T including a gate electrode 504, an active layer 506, a source electrode 508, and a drain electrode 510 is formed under the low reflection layer 502, and the thin film transistor T is formed. The transparent pixel electrode 512 in contact with the drain electrode 510 is formed in the pixel region P. As shown in FIG.

The other surface of the first substrate 500 constitutes a retardation film (λ / 4 plate) 514 and an upper linear polarizer 516.

One surface of the second substrate 600 facing the first substrate 500 constitutes a CLC color filter 602, and the other surface of the second substrate 600 includes a CLC polarizer 604 and a backlight 606. Construct in turn

The configuration of the CLC color filter 602 in the transmissive liquid crystal display device constitutes a cholesteric liquid crystal having a left circle or right circle pitch corresponding to blue and green wavelengths in a red pixel. Of course, the same principle applies to green and blue pixels.

If the cholesteric liquid crystal is configured to have a right pitch, a cholesteric liquid crystal film having a right pitch corresponding to blue and red is formed in the green pixel.

In this configuration, light corresponding to the green wavelength of the circular polarized light emitted from the lower portion passes through the green pixel to display green.

If the pitch of the CLC color filter 602 has a right circle pitch, the CLC polarizer 604 configured at the bottom is configured to have a left circle pitch.

Therefore, right circular polarization of the light emitted from the backlight 606 passes through the CLC polarizer 604, and the right circular polarized light passes through the CLC color filter 602 to be directed to the liquid crystal layer 700. The circularly polarized light directed toward the liquid crystal layer 700 is converted into linearly polarized light through the liquid crystal layer 700 and the retardation film 514 and absorbed or passed through the upper linearly polarized light 516 to show a black state or a white state.

As described above, the transmissive liquid crystal display according to the second exemplary embodiment of the present invention can improve luminance by using a CLC color filter and a CLC polarizing plate, and further provides a low contrast layer in the liquid crystal panel to improve contrast ratio. The height can be obtained.

The reflective and transmissive liquid crystal display device according to the present invention has a structure in which a thin film transistor and an array wiring are formed on an upper substrate, further comprising a low reflection layer that blocks the thin film transistor and the array wiring from light incident from the outside, thereby providing high contrast. There is an effect that can manufacture a high-quality reflective and transmissive liquid crystal display device.

Claims (4)

An upper first substrate and a lower second substrate configured to be spaced apart from each other and to define pixel regions; A blocking layer formed on one surface of the first substrate facing the second substrate and formed in an area excluding a pixel area; A thin film transistor, a gate wiring and a data wiring formed on the blocking layer; A λ / 4 film formed on the other surface of the first substrate; A linear polarizer configured on the λ / 4 film; An absorbing layer formed on one surface of the second substrate facing the first substrate; A cholesteric liquid crystal color filter formed on the absorbing layer; A liquid crystal layer formed between the first substrate and the second substrate; Reflective liquid crystal display device comprising a. The method of claim 1, The blocking layer is a reflective liquid crystal display device consisting of a double layer of chromium / chromium oxide (Cr / CrO _X ). An upper first substrate and a lower second substrate configured to be spaced apart from each other and to define pixel regions; A blocking layer formed on one surface of the first substrate facing the second substrate and formed in an area excluding a pixel area; A thin film transistor, a gate wiring and a data wiring formed on the blocking layer; A cholesteric liquid crystal color filter configured on one surface of the second substrate facing the first substrate; A λ / 4 film formed on a surface of a first substrate not facing the second substrate; A linear polarizer configured on the λ / 4 film; A cholesteric liquid crystal polarizing plate configured on one surface of the second substrate not facing the first substrate; A liquid crystal layer formed between the first substrate and the second substrate; A backlight configured under the cholesteric liquid crystal polarizing plate Transmissive liquid crystal display device comprising a. The method of claim 1, The blocking layer is a reflective liquid crystal display device consisting of a double layer of chromium / chromium oxide (Cr / CrO _X ).