KR20060129680A - Transflective liquid crystal display - Google Patents

Abstract

A semi-transmission type of LCD is provided to prevent the yellowing of screen, by forming blue color filters to have larger thicknesses than green color filters and red color filters. Gate lines and data lines(171) are formed above a first substrate(110). Thin film transistors are electrically connected to the gate and data lines. Pixel electrodes(190) are connected to the thin film transistors, wherein each of the pixel electrodes has a transmission electrode(192) and a reflection electrode(194). A second substrate(210) is opposite to the first substrate. A plurality of color filters(230) are formed above the second substrate. The color filters include a plurality of red color filters, a plurality of green color filters, and a plurality of blue color filters. The blue color filters have thicker than the green color filters and the red color filters.

Description

Transflective Liquid Crystal Display {TRANSFLECTIVE LIQUID CRYSTAL DISPLAY}

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

2 and 3 are cross-sectional views of the liquid crystal display shown in FIG. 1 taken along the lines II-II 'and III-III', respectively.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to liquid crystal displays, and more particularly to transflective liquid crystal displays.

In general, a liquid crystal display device includes a liquid crystal layer positioned between a field generating electrode and a pair of display panels provided with a polarizing plate. The field generating electrode generates an electric field in the liquid crystal layer and the arrangement of the liquid crystal molecules changes as the intensity of the electric field changes. For example, in the state where an electric field is applied, the liquid crystal molecules of the liquid crystal layer change its arrangement to change the polarization of light passing through the liquid crystal layer. The polarizer displays a desired image by appropriately blocking or transmitting polarized light to create bright and dark areas.

Since the liquid crystal display is a light-receiving display device that does not emit light by itself, light from a lamp of a separately provided backlight unit passes through the liquid crystal layer, or light from external sources such as natural light passes through the liquid crystal layer once again. Reflects and passes the liquid crystal layer again. The former case is called a transmissive liquid crystal display device, and the latter case is called a reflective liquid crystal display device. The latter case is mainly used for small and medium size display devices. In addition, a semi-transmissive or reflective-transmissive liquid crystal display device using either a backlight device or an external light is developed according to the environment, and is mainly applied to a small and medium display device.

In the transflective liquid crystal display, each pixel includes a transmission area and a reflection area. In the transmission area, light passes through the liquid crystal layer only once and twice in the reflection area. The difference in the number of passes of the liquid crystal layer affects the polarization state of the light passing through.

Therefore, in order to solve this problem, a double cell spacing method and a double voltage method are used. The double cell spacing is a technique of differentiating the cell spacing of the reflection region and the cell spacing of the transmission region so that the cell spacing of the transmission region is about twice the cell spacing of the reflection region. The dual voltage method is a technique of applying different voltages to the reflection area and the transmission area. When the light passes through the liquid crystal layer, they change the polarization state of the light in the two regions by varying the refractive index anisotropy value and the cell spacing value in the reflection region RA and the transmission region TA that affect the polarization state. It is a technique that approximates each other.

However, in the case of the dual cell spacing technology, there are a method of controlling cell spacing using an overcoat of a thin film transistor array panel and a method of adjusting cell spacing using an overcoat on a common electrode display panel. The method of controlling cell spacing using the overcoat of the common electrode display panel is easy to manufacture and has a high yield. However, if the cell spacing is adjusted in this manner, the display screen may be yellowish due to the difference in cell spacing.

Accordingly, an object of the present invention is to provide a liquid crystal display device that solves the yellowing of the display screen.

According to an embodiment of the present invention, a liquid crystal display device having a transmissive region and a reflective region includes a first substrate, a gate line and a data line formed on the first substrate, and a gate line and a data line. A thin film transistor connected to the thin film transistor, a pixel electrode having a transparent electrode and a reflective electrode, a second substrate facing the first substrate, and a plurality of color filters formed on the second substrate; The plurality of color filters may include a plurality of red color filters, a plurality of green color filters, and a plurality of blue color filters, and the thickness of the blue color filter is thicker than that of each of the green color filter and the red color filter. .

The thickness of the blue color filter may be about 2% to about 20% thicker than the thickness of each of the green and red color filters.

The transparent electrode is disposed in the reflective region and the transmissive region, and the reflective electrode is disposed in the reflective region.

The reflective electrode is formed on the transparent electrode.

The liquid crystal display may further include an upper passivation layer and a lower passivation layer formed between the thin film transistor and the pixel electrode.

Unevenness may be formed on a surface of the upper passivation layer.

The liquid crystal display may further include a light blocking member formed on the second substrate.

The liquid crystal display may further include an overcoat formed on the color filter, wherein the overcoat is thinner in the transmissive region than in the reflective region so that the cell spacing in the transmissive region is about twice the cell spacing in the reflective region. to be.

The liquid crystal display may further include a common electrode formed on the overcoat.

The liquid crystal display may further include a backlight device disposed outside the first substrate.

The backlight device may include a white LED.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a part of a layer, film, area, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A liquid crystal display according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 is a layout view of a liquid crystal display according to an exemplary embodiment of the present invention, and FIGS. 2 and 3 are each cut along the lines II-II 'and III-III' of the liquid crystal display shown in FIG. It is a cross section.

The liquid crystal display according to the present exemplary embodiment includes a thin film transistor array panel 100 facing each other, a common electrode panel 200, and a liquid crystal layer 3 interposed between the two display panels 100 and 200.

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

A plurality of gate lines 121 and a plurality of storage electrode lines 131 are formed on an insulating substrate 110 made of transparent glass or plastic.

The gate line 121 transmits a gate signal and mainly extends in a horizontal direction. Each gate line 121 includes a plurality of gate electrodes 124 protruding upward and end portions 129 having a large area for connection with another layer or an external driving circuit. A gate driving circuit (not shown) for generating a gate signal may be mounted on a flexible printed circuit film (not shown) attached to the substrate 110 or directly mounted on the substrate 110, It may be integrated into the substrate 110. When the gate driving circuit is integrated on the substrate 110, the gate line 121 may extend to be directly connected to the gate driving circuit.

The storage electrode line 131 receives a predetermined voltage and almost extends in parallel with the gate line 121. Each storage electrode line 131 is positioned between two adjacent gate lines 121 and is close to a lower side of the two gate lines 121. The storage electrode line 131 includes an expansion 137 extending up and down. However, the shape and arrangement of the storage electrode line 131 may be modified in various ways.

The gate line 121 and the storage electrode line 131 may be formed of aluminum-based metal such as aluminum (Al) or aluminum alloy, silver-based metal such as silver (Ag) or silver alloy, copper-based metal such as copper (Cu) or copper alloy, or molybdenum ( It may be made of molybdenum-based metals such as Mo) or molybdenum alloy, chromium (Cr), tantalum (Ta) and titanium (Ti). However, they may have a multilayer structure including two conductive films (not shown) having different physical properties. One of the conductive films is made of a metal having low resistivity, such as aluminum-based metal, silver-based metal, or copper-based metal, so as to reduce signal delay or voltage drop. On the other hand, other conductive films are made of other materials, particularly materials having excellent physical, chemical and electrical contact properties with indium tin oxide (ITO) and indium zinc oxide (IZO), such as molybdenum-based metals, chromium, titanium, tantalum, and the like. Good examples of such a combination include a chromium bottom film, an aluminum (alloy) top film, and an aluminum (alloy) bottom film and a molybdenum (alloy) top film. However, the gate line 121 and the storage electrode line 131 may be made of various other metals or conductors.

Side surfaces of the gate line 121 and the storage electrode line 131 are inclined with respect to the surface of the substrate 110, and the inclination angle is preferably about 30 ° to about 80 °.

A gate insulating layer 140 made of silicon nitride (SiNx) or silicon oxide (SiOx) is formed on the gate line 121 and the storage electrode line 131.

A plurality of linear semiconductors 151 made of hydrogenated amorphous silicon (hereinafter referred to as a-Si) or polysilicon are formed on the gate insulating layer 140. The linear semiconductor 151 mainly extends in the longitudinal direction and includes a plurality of projections 154 extending toward the gate electrode 124. The linear semiconductor 151 has a wider width in the vicinity of the gate line 121 and the storage electrode line 131 and covers them widely.

A plurality of linear and island ohmic contacts 161 and 165 are formed on the semiconductor 151. The ohmic contacts 161 and 165 may be made of a material such as n + hydrogenated amorphous silicon in which n-type impurities such as phosphorus are heavily doped, or may be made of silicide. The linear ohmic contact 161 has a plurality of protrusions 163, and the protrusion 163 and the island-type ohmic contact 165 are paired and disposed on the protrusion 154 of the semiconductor 151.

Side surfaces of the semiconductor 154 and the ohmic contacts 163 and 165 are also inclined with respect to the surface of the substrate 110, and the inclination angle is about 30 ° to 80 °.

A plurality of data lines 171 and a plurality of drain electrodes 175 separated therefrom are formed on the ohmic contacts 163 and 165 and the gate insulating layer 140.

The data line 171 transmits a data signal and mainly extends in the vertical direction to cross the gate line 121. Each data line 171 includes a plurality of source electrodes 173 extending toward the gate electrode 124 and an end portion 179 having a large area for connection with another layer or an external driving circuit. A data driving circuit (not shown) for generating a data signal is mounted on a flexible printed circuit film (not shown) attached to the substrate 110, directly mounted on the substrate 110, or integrated in the substrate 110. Can be. When the data driving circuit is integrated on the substrate 110, the data line 171 may be extended to be directly connected to the data driving circuit.

The drain electrode 175 is separated from the data line 171 and faces the source electrode 173 with respect to the gate electrode 124. Each drain electrode 175 has one end portion having a large area and the other end portion having a rod shape. The wide end overlaps the extension 137 of the storage electrode line 131, and the rod-shaped end is partially surrounded by the bent source electrode 173.

One gate electrode 124, one source electrode 173, and one drain electrode 175 together with the protrusion 154 of the semiconductor 151 form one thin film transistor (TFT). A channel of the transistor is formed in the protrusion 154 between the source electrode 173 and the drain electrode 175.

The data line 171 and the drain electrode 175 are preferably made of a refractory metal such as molybdenum, chromium, tantalum, and titanium, or an alloy thereof, and include a refractory metal film (not shown) and a low resistance conductive film. It may have a multilayer structure including (not shown). Examples of the multilayer structure include a double layer of chromium or molybdenum (alloy) lower layer and an aluminum (alloy) upper layer, and a triple layer of molybdenum (alloy) lower layer and aluminum (alloy) interlayer and molybdenum (alloy) upper layer. However, the data line 171 and the drain electrode 175 may be made of various metals or conductors.

The side of the data line 171 and the drain electrode 175 may also be inclined at an inclination angle of about 30 ° to about 80 ° with respect to the surface of the substrate 110.

The ohmic contacts 163 and 165 exist only between the semiconductor 154 below and the data line 171 and the drain electrode 175 thereon to lower the contact resistance. In most places, the width of the linear semiconductor 151 is smaller than the width of the data line 171. However, as described above, the width of the linear semiconductor 151 is widened at the portion where it meets the gate line 121 to smooth the profile of the surface. Prevents disconnection. The semiconductor 154 includes portions exposed between the source electrode 173 and the drain electrode 175 and not covered by the data line 171 and the drain electrode 175.

A passivation layer 180 is formed on the data line 171, the drain electrode 175, and the exposed semiconductor 154. The passivation layer 180 includes a lower layer 180p made of an inorganic insulator such as silicon nitride or silicon oxide and an upper layer 180q made of an organic insulator. The upper passivation layer 180q preferably has a dielectric constant of 4.0 or less, may have photosensitivity, and irregularities are formed on a surface thereof. However, the passivation layer 180 may have a single layer structure made of an inorganic insulator or an organic insulator. The upper passivation layer 180q is removed and only the lower passivation layer 180p remains on the pad portion where the extension portions 129 and 179 of the gate line 121 and the data line 171 are formed.

In the passivation layer 180, a plurality of contact holes 182 and 185 exposing the end portion 179 and the drain electrode 175 of the data line 171 are formed, respectively, and the passivation layer 180 and the gate insulating layer are formed. A plurality of contact holes 181 exposing the end portion 129 of the gate line 121 are formed at 140.

A plurality of pixel electrodes 190 and a plurality of contact assistants 81 and 82 are formed on the passivation layer 180.

Each pixel electrode 190 is curved along the unevenness of the upper passivation layer 180q and includes a transparent electrode 192 and a reflective electrode 194 thereon. The transparent electrode 192 is made of a transparent conductive material such as ITO or IZO, and the reflective electrode 194 is made of a reflective metal such as aluminum, silver, chromium or an alloy thereof. However, the reflective electrode 194 may have a double layer structure of a low resistance reflective upper layer such as aluminum, silver, or an alloy thereof, and a lower layer having good contact properties with ITO or IZO such as molybdenum-based metal, chromium, tantalum, and titanium.

The reflective electrode 194 is present only on a portion of the transparent electrode 192 to expose another portion of the transparent electrode 192.

The pixel electrode 190 is physically and electrically connected to the drain electrode 175 through the contact hole 185 and receives a data voltage from the drain electrode 175. The pixel electrode 190 to which the data voltage is applied is formed between the two electrodes 191 and 270 by generating an electric field together with the common electrode 270 of the common electrode display panel 200 to which the common voltage is applied. The direction of the liquid crystal molecules of the liquid crystal layer 3 is determined. The polarization of light passing through the liquid crystal layer 3 varies according to the direction of the liquid crystal molecules determined as described above. The pixel electrode 190 and the common electrode 270 form a capacitor (hereinafter, referred to as a "liquid crystal capacitor") to maintain an applied voltage even after the thin film transistor is turned off.

The transflective liquid crystal display device including the thin film transistor array panel 100, the common electrode display panel 200, the liquid crystal layer 3, and the like is a transmissive area TA defined by the transparent electrode 192 and the reflective electrode 194, respectively. And a reflection area RA. Specifically, the portion located below the exposed portion of the transparent electrode 192 becomes the transmission area TA, and the portion located below the reflective electrode 194 becomes the reflection area RA.

In the transmissive area TA, light is incident on the back side of the liquid crystal display, that is, the thin film transistor array panel 100, passes through the liquid crystal layer 3 and exits the front side, that is, toward the common electrode display panel 200. In the reflective area RA, the light enters the liquid crystal layer 3, enters the liquid crystal layer 3, is reflected by the reflective electrode 194, passes through the liquid crystal layer 3, and exits to the front surface. At this time, the bending of the reflective electrode 194 increases the reflection efficiency of the light.

The pixel electrode 190 is physically and electrically connected to the drain electrode 175 through the contact hole 185 and receives a data voltage from the drain electrode 175. The pixel electrode 190 to which the data voltage is applied generates an electric field together with the common electrode 270 (not shown) of the other display panel 200 to which the common voltage is applied, thereby generating a liquid crystal layer 3 between the two electrodes. Direction of the liquid crystal molecules. The polarization of light passing through the liquid crystal layer varies according to the direction of the liquid crystal molecules determined as described above. The pixel electrode 190 and the common electrode form a capacitor to maintain an applied voltage even after the thin film transistor is turned off.

The contact auxiliary members 81 and 82 are connected to the end portion 129 of the gate line 121 and the end portion 179 of the data line 171 through the contact holes 181 and 182, respectively. The contact auxiliary members 81 and 82 compensate for and protect the adhesion between the end portion 129 of the gate line 121 and the end portion 179 of the data line 171 and the external device.

A capacitor in which the pixel electrode 190 and the drain electrode 175 electrically connected thereto overlap with the storage electrode line 131 is referred to as a "storage capacitor", and the storage capacitor enhances the voltage holding capability of the liquid crystal capacitor. .

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

A light blocking member 220 is formed on a substrate 210 made of an insulating material such as transparent glass or plastic. The light blocking member 220 prevents light leakage between the pixel electrodes 190 and defines an opening area facing the pixel electrode 190.

The color filter 230 is formed on the substrate 210 and the light blocking member 220, and the color filter 230 is disposed to substantially enter the opening region defined by the light blocking member 220.

The color filter 230 is made of a dyeing method, a dispersion method, an electrodeposition method, a printing method, or the like. For example, a pigment spray method using a photographic process may be used. The color filter 230 may represent primary colors such as three primary colors of blue, green, and red. When the three primary color filters 230 of blue, green, and red are provided, the thickness of the blue color filter may be a green color filter, It is about 2% to about 20% thicker than the thickness of the red color filter. In addition, the pigment included in the color filter 230 may be about 2% to 20% more than conventional.

An overcoat 250 made of an organic material is formed on the color filter 230 and the light blocking member 220. The thickness of the overcoat 250 is thinner in the transmission area TA than in the reflection area RA, so that the cell spacing in the transmission area TA is about twice the cell spacing in the reflection area RA. Therefore, the influence of the optical path difference of the light passing through the liquid crystal layer 3 in the reflection area RA and the transmission area TA may be compensated for.

The common electrode 270 made of a transparent conductive material such as ITO or IZO is formed on the overcoat 250.

An alignment layer (not shown) is disposed on the inner surfaces of the display panels 100 and 200, and one or more polarizers are disposed on the outer surfaces of the display panels 100 and 200. (Not shown) is provided.

The liquid crystal layer 3 is vertically or horizontally aligned.

The liquid crystal display further includes a plurality of elastic spacers (not shown) that hold the thin film transistor array panel 100 and the common electrode panel 200 to form a gap therebetween.

The liquid crystal display may further include a sealant (not shown) for coupling the thin film transistor array panel 100 and the common electrode panel 200. The sealing material is positioned at the edge of the common electrode display panel 200.

The liquid crystal display may further include a backlight device 900. In one embodiment of the invention, the backlight device 900 may include a white LED. White LED is a light source that supplies white light by adding a yellow phosphor to a blue LED, which can be manufactured in small size, and is used in small liquid crystal display devices requiring light weight and thinning since power consumption is low. In the white LED used in one embodiment of the present invention, about 2% to 20% less yellow phosphor may be added.

According to the present invention, yellowing of the screen of the transflective liquid crystal display device using the double cell spacing method can be reduced.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (12)

A liquid crystal display device having a transmission area and a reflection area, First substrate, A gate line and a data line formed on the first substrate; A thin film transistor connected to the gate line and the data line, A pixel electrode connected to the thin film transistor and having a transparent electrode and a reflective electrode, A second substrate facing the first substrate, and It includes a plurality of color filters formed on the second substrate, The plurality of color filters includes a plurality of red color filters, a plurality of green color filters, and a plurality of blue color filters, wherein the thickness of the blue color filter is greater than that of each of the green and red color filters. Device. In claim 1, The thickness of the blue color filter is about 2% to about 20% thicker than the thickness of each of the green color filter and the red color filter. In claim 1, And the transparent electrode is disposed in the reflective region and the transmissive region, and the reflective electrode is disposed in the reflective region. In claim 3, And the reflective electrode is formed on the transparent electrode. In claim 1, And an upper passivation layer and a lower passivation layer formed between the thin film transistor and the pixel electrode. In claim 5, A liquid crystal display device having irregularities formed on a surface of the upper passivation layer. In claim 1, And a light blocking member formed on the second substrate. In claim 1, The liquid crystal display device further comprising an overcoat formed on the color filter. In claim 8, The thickness of the overcoat is thinner in the transmissive region than in the reflective region, so that the cell spacing in the transmissive region is about twice the cell spacing in the reflective region. In claim 8, And a common electrode formed on the overcoat. In claim 1, And a backlight device disposed outside the first substrate. In claim 11, The backlight device includes a white LED.

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