DE19959674B4 - Multi-domain liquid crystal display device - Google Patents

Abstract

Multi-domain liquid crystal display device comprising:
a first substrate (31) and a second substrate (33) which face each other,
a liquid crystal layer between the first substrate (31) and the second substrate (33),
a plurality of gate bus lines (1) arranged in a first direction on the first substrate (31) and a plurality of data bus lines (3) arranged in a second direction on the first substrate (31), thereby defining pixel areas wherein each pixel region is divided into at least two domains and liquid crystal molecules in the liquid crystal layer in each of the at least two domains are driven differently from each other,
a pixel electrode (13) which is electrically chargeable by the data bus line (3) in each pixel area, and
an auxiliary electrode (15) formed surrounding the pixel electrode (13) on the same layer on which the gate bus line (1) is formed, the auxiliary electrode (15) being arranged to generate an electric field applied to the pixel electrode (13), and wherein the pixel electrode ...

Description

The The invention relates to a liquid crystal display device (LCD), in particular a liquid crystal display device, which has a side or auxiliary electrode.

Recently, an LCD has been proposed in which the liquid crystal material is not aligned and driven by common electrodes which are isolated from the pixel electrodes. Out 1 Fig. 10 is a sectional view of a pixel unit of a conventional LCD. Such an LCD is eg off US 5,309,264 A known.

In conventional LCDs, a plurality of gate bus lines are arranged in a first direction on a first substrate, and a plurality of data bus lines are arranged in a second direction on the first substrate, so that the first substrate is divided into a plurality of pixel areas. From a thin film transistor (TFT), an image signal to a pixel electrode 13 on a passivation layer 37 applied, which is supplied from the data bus. In each pixel region, a TFT is formed, and has a gate electrode, a gate insulating layer, a semiconductor layer, a source electrode, and a drain electrode, etc. A side electrode 21 is the pixel electrode 13 formed on the gate insulating layer, whereupon the passivation layer is formed over the entire first substrate. A part of a pixel electrode 13 overlaps the side electrode 21 ,

Alternatively, the pixel electrode is 13 formed on the gate insulating layer and the passivation layer 37 is formed over the entire first substrate.

On the second substrate is a common electrode 17 formed, of which together with the pixel electrode 13 an electric field is applied to the liquid crystal material.

Through a side electrode 21 and an open area (slot) 27 the electric field which is applied to the liquid crystal layer is distorted. As a result, the liquid crystal molecules are driven differently in a pixel unit. That is, when voltage is applied to the LCD, the liquid crystal directors are placed in required or desired positions due to the dielectric energy due to the distorted electric field.

However, in conventional LCDs, it is an open area 27 in the common electrode 17 or the pixel electrode 13 required and the liquid crystal molecules could be stably driven, if this open area would be larger. If the electrodes do not have an open area or the width of the open area is too small, the electric field distortion is too weak to control the pixel area. Then, when a voltage above a threshold voltage V _{th is} applied, the time required to stabilize the liquid crystal directors is increased. In particular, the reaction time can be over 100 milliseconds. At this time, skew occurs from the areas where the liquid crystal directors are aligned parallel to the transmittance axis of the polarizer, thereby reducing the brightness. In addition, the liquid crystal material is irregular due to the surface condition of the LCDs.

DE 44 07 043 A1 discloses a storage electrode surrounding the pixel electrode. EP 0 805 373 A2 discloses an auxiliary electrode formed under the pixel electrode.

task The invention is to provide a multi-domain LCD which a fast response time and high brightness at more stable Arrangement of the liquid crystal molecules has.

This is achieved according to the invention with a multi-domain liquid crystal display device, according to one the attached Claims.

Especially shows the multi-domain liquid crystal display device according to the invention a first substrate and a second substrate facing each other are and a liquid crystal layer between the first substrate and the second substrate. A majority of gate bus lines are in a first direction on the first one Substrate arranged and a plurality of data bus lines arranged in a second direction on the first substrate, thereby Pixel areas are defined, each pixel area in at least two domains is divided and liquid crystal molecules in the liquid crystal layer in each of the at least two domains be driven differently from each other. A pixel electrode, which is electrically rechargeable by the data bus line is in formed the pixel region and an auxiliary electrode, which is the pixel electrode is formed surrounding on the same layer on which the Gatebus line is formed, is formed, wherein the auxiliary electrode for generating an electric current applied to the pixel electrode Field is arranged, and wherein the pixel electrode, the auxiliary electrode does not overlap.

The The invention will be explained in more detail with reference to the drawing. In show the drawing:

1 a sectional view of a conventional liquid crystal display device,

2a . 2 B . 2c . 2d . 2e . 2f and 2g Top views and sectional views of a multi-domain liquid crystal display device,

3a . 3b . 3c . 3d . 3e . 3f . 3g and 3h And sectional views of the multi-domain liquid crystal display devices according to a first preferred embodiment of the invention;

4a and 4b . 4c . 4d . 4e . 4f Top and sectional views of a multi-domain liquid crystal display device,

5a . 5b and 5c . 5d Top and sectional views of the multi-domain liquid crystal display device according to a second preferred embodiment of the invention,

6a and 6b Top and sectional views of the multi-domain liquid crystal display device according to a third preferred embodiment of the invention,

7 a plan view of the multi-domain liquid crystal display device according to a fourth preferred embodiment of the invention, and

8a to 8g Top views from which different electrical fields causing windows and dielectric frames according to the embodiments of the invention can be seen.

From the 2a and 2 B FIG. 10 is a plan view of a multi-domain liquid crystal display device. From the 2c to 2g are sectional views taken along the lines II 'and II-II 2a seen.

The multi-domain liquid crystal display device has first and second substrates, a plurality of gate bus lines 1 which are arranged in a first direction on a first substrate and a plurality of data bus lines 3 which are arranged in a second direction on the first substrate, a common auxiliary electrode 15 , a TFT, a passivation layer 37 and a pixel electrode 13 on.

On a second substrate is a light-shielding layer 25 formed by the gate and data bus lines 1 and 3 and shields the TFT forth passing light. A color filter layer 23 is formed on the light-shielding layer. A common electrode 17 is formed on the color filter layer, and a liquid crystal layer is formed between the first and second substrates.

The first substrate is through the data bus lines 3 and the gate bus lines 1 divided into a plurality of pixel areas. The common auxiliary electrode distorts the electric field and is formed on the same layer on which the gate bus lines are formed. The TFT is formed at each pixel area and has a gate electrode 11 a gate insulating layer 35 , a semiconductor layer 5 , an ohmic contact layer (not shown) and source and drain electrodes 7 and 9 on. A passivation layer 37 is over the entire first substrate 31 educated. The pixel electrode 13 is to the drain electrode 9 connected.

In fabricating the multi-domain LCD, a TFT with a gate electrode is formed in each pixel area on the first substrate 11 a gate insulating layer 35 , a semiconductor layer 5 an ohmic contact layer (not shown) and source and drain electrodes 7 respectively. 9 educated. A plurality of gate bus lines 1 and a plurality of data bus lines 3 are the first substrate 31 formed dividing into a plurality of pixel areas.

A gate electrode 11 and gate bus lines 1 are formed by sputtering and patterning a metal such as Al, Mo, Cr, Ta, Al alloy, etc. The common auxiliary electrode 15 is formed surrounding the pixel area. The gate insulating layer 35 is by applying SiN _x or SiO _x . trained thereon by means of a PECVD method. The semiconductor layer 5 and the ohmic contact layer are formed by deposition by a PECVD (Plasma Enhanced Vapor Deposition) method and patterning of amorphous silicon (a-Si) and doped amorphous silicon (n ⁺ a-Si), respectively. The gate insulating layer 35 the amorphous silicon (a - Si) and the doped amorphous silicon (n ⁺ a - Si) are formed and patterned by PECVD method. The data bus line 3 as well as the source and drain electrodes 7 respectively. 9 are formed by sputtering and patterning a metal such as Al, Mo, Cr, Ta, Al alloys, etc.

At the same time, a storage electrode 43 the gate bus line 1 and / or the common auxiliary electrode 15 formed overlapping, wherein the storage electrode 43 together with the gate bus line 1 and / or the common auxiliary electrode 15 forms a storage capacity.

Thereafter, a passivation layer 37 formed of BCB (benzocyclobuthene), acrylate, polyimide-based materials, SiN _x or SiO _x over the entire first substrate. The pixel electrode 13 is created by sputtering and structuring a Metal such as ITO (idium tin oxide) formed. A contact opening 39 is achieved by opening and structuring a portion of the passivation layer over the drain electrode 9 formed so that the pixel electrode can be connected to the drain and storage electrodes.

When the common auxiliary electrode 15 and the gate bus line 1 can be formed of the same material, the common auxiliary electrode and the gate electrode simultaneously formed using a single mask and electrically connected to the common electrode 17 get connected. However, it is also possible to form these electrodes from different materials or from a double layer using additional masks.

On the second substrate 33 becomes a light protection layer 25 formed, which light passages from the gate and data bus lines 1 and 3 , the TFT and the common auxiliary electrode 15 shields. A color filter layer 23 is formed of red (R) green (G) and blue (B) elements which are sequentially arranged on the light-shielding layer. A common electrode 17 is formed of ITO on the color filter layer, and a liquid crystal layer is formed by injecting liquid crystal material between the first and second substrates.

For applying a voltage V _com to the common auxiliary electrode 15 is Ag point piece at each corner portion of a driving area on the first substrate 31 educated. Between the first substrate and the second substrate 33 an electric field is applied. The liquid crystal molecules are controlled by the potential difference. A voltage V _com is obtained by connecting the Ag point piece to the common auxiliary electrode to the common auxiliary electrode 15 applied, which is performed simultaneously with forming the common auxiliary electrode. On at least one substrate is a compensation film 29 formed of a polymer. The compensation film is a negative uniaxial film which has an optical axis and compensates for the phase difference due to the direction corresponding to the viewing angle.

Therefore Is it possible negative effects through the viewing angle in the right-left direction Enlarge the Compensate area without gray inversion (gray inversion) effectively and here the contrast ratio in a weird way To improve direction by forming multi-domain pixels.

at the multi-domain liquid crystal display device it is also possible to use a negative biaxial film as a compensation film which two optical axes and another viewing angle has as the negative uniaxial film. The compensation film can be formed on both substrates or on one of the substrates.

To Forming the compensation film, the polarizer is at least formed one of the substrates. Here are the compensation film and the polarizer is preferably formed in one piece.

In the multi-domain liquid crystal display device according to 2 the pixel electrode overlaps the common auxiliary electrode 15 , The light protection layer 25 overlaps the common auxiliary electrode, thereby improving the aperture ratio. The storage electrode 43 forms a storage capacity C _st by overlapping with the gate bus line 1 , The storage electrode 43 can also be the common auxiliary electrode 15 overlap (not shown).

In addition, the LCD will after 2 B less shorts in the common auxiliary electrode and the gate bus line produces (short generation) than in that after 2a , From the 2d and 2f it can be seen that the passivation layer 37 SiN _x or SiO _x . Out 2e and 2g It can be seen that the passivation layer has BCB or acrylic resin. Besides, it is off 2d and 2e seen that dielectric frame 53 on the common electrode 17 are formed. From the 2f and 2g It can be seen that a window affecting an electric field 51 in the common electrode 17 is trained.

Out 3a and 3b FIG. 12 shows plan views of the multi-domain liquid crystal display device according to the first preferred embodiment of the invention. From the 3c and 3d are sectional views along the line III-III 'in 3 seen. From the 3e . 3f . 3g and 3h are sectional views along the line IV-IV 'in 3a seen.

The pixel electrode 13 overlaps the common auxiliary electrode 15 not and the light protection layer 25 overlaps the pixel electrode 13 , Here, the gate insulating layer 35 and the passivation layer 37 over the common auxiliary electrode 15 removed, eliminating the electric field generated by the common auxiliary electrode 15 is generated and to the pixel electrode 13 is created, is increased (see 3b ).

Out 3c areas are visible to which the gate insulating layer 35 and the passivation layer 37 were removed, whereby a part of the common auxiliary electrode 15 is exposed. From the 3d There are three exposed sides of the common auxiliary electrode.

From the storage electrode 43 which the gate bus line 1 overlaps, a storage capacity is formed. The storage electrode 43 can be the common auxiliary electrode 15 be formed overlapping (not shown).

From the 3e and 3g it can be seen that. the passivation layer 37 SiN _x or SiO _x . From the 3f and 3h it can be seen that the passivation layer 37 BCB or acrylic resin. Moreover, from the 3e and 3f seen that dielectric frame 53 on the common electrode 17 are formed. From the 3g and 3h It can be seen that a window affecting an electric field 51 in the common electrode 17 is trained.

Out 4a Fig. 10 is a plan view of another multi-domain liquid crystal display device. From the 4b and 4c . 4d . 4e . 4f are sectional views along the lines VV 'and VI-VI' off 4a seen.

In the multi-domain LCD, part of inverse or inverse pixels (upper-down pixels) is on the common auxiliary electrode 15 formed, which is a storage electrode 43 exhibit. The aperture ratio is off in comparison to the LCD 2 very much improved.

In addition, the pixel electrode overlaps 13 the common auxiliary electrode 15 , The light protection layer 25 overlaps the common auxiliary electrode 15 and the storage electrode 43 forms together with the common auxiliary electrode 15 a storage capacity. From the 4c and 4d it can be seen that dielectric frame 53 on the common electrode 17 are formed. Out 4e and 4f As can be seen, this is an electric field affecting window 51 in the common electrode 17 is trained. Moreover, from the 4d and 4f it can be seen that the light protection layer 25 is formed only on the thin film transistor.

From the 5a and 5b Fig. 12 is a plan view of the multi-domain liquid crystal display device according to the second preferred embodiment of the invention. From the 5c and 5d are sectional views along the line VII-VII 'from 5b seen.

The multi-domain LCD has the same structure as that of the third preferred embodiment except for the following:
The pixel electrode 13 does not overlap the common auxiliary electrode 15 , The light protection layer 25 overlaps the pixel electrode 13 , A region of the gate insulating layer and the passivation layer 37 are above the common auxiliary electrode 15 removed, causing the electric field of the common auxiliary electrode 15 is reinforced, which to the pixel electrode 13 is created (see 5b ).

Out 5c is a region of the gate insulating layer 35 and the passivation layer 37 , which have been removed to a part of the common auxiliary electrode 15 Clearly visible. Out 5d It can be seen that three sides of the common auxiliary electrode 15 are exposed.

Out 6a Fig. 10 is a plan view of the multi-domain liquid crystal display device according to the third preferred embodiment of the invention. Out 6b is a sectional view taken along the line VIII-VIII 'from 6a seen.

Out 7 Fig. 10 is a plan view of the multi-domain liquid crystal display device according to the fourth preferred embodiment of the invention.

In the multi-domain LCD of the present invention, a part of upside-down or inversely-constructed pixels is on the common auxiliary electrode 15 formed, which a common storage electrode 43 having. In comparison with the out 6 apparent LCD, the aperture ratio is greatly improved.

In the multi-domain LCD of the present invention, the aperture ratio is determined by optimum patterning of an "n-line" thin-film transistor or nonlinear-channel TFT (which is disclosed in US Pat. US 5,694,185 A disclosed), so that the power consumption is reduced, the luminous intensity is increased and the reflection is reduced, whereby the contrast ratio is improved. The aperture ratio is improved by forming the TFT above the gate line and providing an "n-line" TFT. The parasitic capacitance occurring between the gate bus line and the drain electrode can be reduced due to the effect of the channel length extension when making a TFT with the same channel length as the symmetrical TFT structure.

From the 8a to 8g are plan views of different electrical fields causing windows 51 and the electric frames 53 according to the preferred embodiments of the invention can be seen.

The multi-domain LCD according to the invention has dielectric frames 53 on the pixel electrode and / or an electric field-influencing window formed like an opening or a slit in the pixel electrode, a passivation layer, a gate insulating layer, a color filter layer and / or a common electrode, which is formed by patterning, and wherein the effects of electric field distortion are achieved in multiple areas.

That is, by forming windows effecting electric fields 51 or dielectric frame 53 For example, the multi-domain effect is divided into four areas such as a "+,""x," or "double-Y" shaped structure, or dividing each pixel horizontally, vertically, and / or diagonally, and performing different alignment treatments achieved for forming orientation directions in each area and on each substrate.

In addition, in the multi-domain LCD of the present invention, an alignment layer (not shown) is formed over the entire first and / or second substrate. The alignment layer comprises a material such as polyamide or polyimide-based materials, PVA (polyvinyl alcohol), polyamic acid or SiO ₂ . When a rubbing method is used to determine the orientation direction, it is possible to use any material suitable for the rubbing method.

Furthermore Is it possible, the orientation layer with a photosensitive material such as PVCN (polyvenylcinamate), PSCN (polysiloxanecinamate), and CelCN (cellulose cinamate) -based To train materials. Every one for The photo alignment method suitable material can be used become. By once irradiating the alignment layer with Light becomes the orientation or pretilt direction and the pretilt angle certainly. The light used in the photo-alignment process is preferably light from the ultraviolet range as well as unpolarized Light, linearly polarized light or partially polarized light.

at the rubbing method or the photo-alignment method, it is possible to have one the substrates or both substrates to treat and different Apply orientation method on each substrate.

By the orientation method will be a multi-domain LCD with at least two Areas trained. The liquid crystal molecules of the liquid crystal layer are aligned differently within each area. This means, the multi-domain effect is made by dividing each pixel into four areas, such as in "plus" or "x" shape or divide each pixel horizontally, vertically and / or diagonally, performing different alignment procedures or forming different orientation directions in each area and reached on every substrate.

It is possible, at least one area of the subdivided areas is unaligned to leave. It is also possible, to leave all areas unoriented.

at the multi-domain LCD of the invention For example, the pixel electrode and the common auxiliary electrode are on the same Layer formed. A high voltage is to increase the Intensity of electric field which is applied between these two electrodes is not required. Furthermore is in the case of execution an alignment treatment a short reaction time and a stable liquid crystal structure reachable by means of a pretilt angle and an armature energy.

In addition, will Avoiding tipping effects and thus improving the brightness.

at the multi-domain LCD of the invention can the liquid crystal layer Liquid crystal molecules with positive dielectric anisotropy or liquid crystal molecules with negative have dielectric anisotropy. In addition, the liquid crystal layer chiral dopants.

Claims (31)

A multi-domain liquid crystal display device comprising: a first substrate ( 31 ) and a second substrate ( 33 ), which face each other, of a liquid crystal layer between the first substrate (FIG. 31 ) and the second substrate ( 33 ), a plurality of gate bus lines ( 1 ), which in a first direction on the first substrate ( 31 ) and a plurality of data bus lines ( 3 ), which in a second direction on the first substrate ( 31 ), whereby pixel areas are defined, each pixel area being divided into at least two domains, and liquid crystal molecules in the liquid crystal layer in each of the at least two domains being driven differently from each other, a pixel electrode (Fig. 13 ) passing through the data bus line ( 3 ) is electrically rechargeable, in each pixel region, and an auxiliary electrode ( 15 ), which the pixel electrode ( 13 ) is formed surrounding on the same layer on which the gate bus line ( 1 ), wherein the auxiliary electrode ( 15 ) for generating a to the pixel electrode ( 13 ) is arranged, and wherein the pixel electrode ( 13 ) the auxiliary electrode ( 15 ) does not overlap. A multi-domain liquid crystal display device according to claim 1, further comprising: a gate insulating film (10) 35 ) over the entire first substrate ( 31 ) a passivation layer ( 37 ) on the gate insulating layer ( 35 ) over the entire first substrate ( 31 ), a light protective layer ( 25 ) on the second substrate ( 33 ), a color filter layer ( 23 ) on the light protection layer ( 25 ), a common electrode ( 17 ) on the color filter layer ( 23 ), and an alignment layer on at least one of the two substrates ( 31 . 33 ). A multi-domain liquid crystal display device according to claim 2, further comprising: a storage electrode ( 43 ) under the passivation layer ( 37 ) which are connected to the pixel electrode ( 13 ) and which the gate bus line ( 1 ) overlaps. A multi-domain liquid crystal display device according to claim 2, further comprising: a storage electrode ( 43 ) under the passivation layer ( 37 ) which are connected to the pixel electrode ( 13 ) and which the auxiliary electrode ( 15 ) overlaps. A multi-domain liquid crystal display device according to claim 2, wherein the light protective layer ( 25 ) the auxiliary electrode ( 15 ) overlaps. A multi-domain liquid crystal display device according to claim 2, wherein the light protective layer ( 25 ) the pixel electrode ( 13 ) overlaps. A multi-domain liquid crystal display device according to claim 1, wherein a gate insulating film ( 35 ) and a passivation layer ( 37 ) in a region except the auxiliary electrode ( 15 ) are formed. A multi-domain liquid crystal display device according to claim 2, wherein the auxiliary electrode ( 15 ) at the common electrode ( 17 ) is electrically connected. A multi-domain liquid crystal display device according to claim 1, further comprising: a dielectric land ( 53 ) on the pixel electrode ( 13 ) for distorting the electric field. A multi-domain liquid crystal display device according to claim 2, further comprising: a dielectric land ( 53 ) on the common electrode ( 17 ) for distorting the electric field. A multi-domain liquid crystal display device according to claim 2, wherein the pixel electrode ( 13 ) a field-influencing opening ( 51 ) having. A multi-domain liquid crystal display device according to claim 2, wherein the passivation layer ( 37 ) a field-influencing opening ( 51 ) having. A multi-domain liquid crystal display device according to claim 2, wherein said gate insulating film ( 35 ) a field-influencing opening ( 51 ) having. A multi-domain liquid crystal display device according to claim 2, wherein the common electrode ( 17 ) a field-influencing opening ( 51 ) having. A multi-domain liquid crystal display device according to claim 2, wherein said color filter layer ( 23 ) a field-influencing opening ( 51 ) having. A multi-domain liquid crystal display device according to claim 2, further comprising: a coating layer on said color filter layer ( 23 ). A multi-domain liquid crystal display device according to claim 16, wherein the overcoat layer has a field-influencing aperture (US Pat. 51 ) having. A multi-domain liquid crystal display device according to claim 16, wherein the passivation layer ( 37 ) BCB, acrylic resin or a polyimide compound. A multi-domain liquid crystal display device according to claim 2, wherein the passivation layer ( 37 ) Comprises silicon nitride or silicon oxide. A multi-domain liquid crystal display device according to claim 1, wherein the auxiliary electrode ( 15 ) ITO, aluminum, molybdenum, chromium, tantalum or titanium. A multi-domain liquid crystal display device according to claim 1, wherein the pixel electrode ( 13 ) ITO, aluminum or chromium. A multi-domain liquid crystal display device according to claim 2, wherein the common electrode ( 17 ) ITO. Multi-domain liquid crystal display device according to claim 2, wherein the alignment layer is in at least two Sections is divided and the liquid crystal molecules in the liquid crystal layer in each section of the at least two sections differ from each other are aligned. Multi-domain liquid crystal display device according to claim 23, wherein at least a portion of the at least two sections of the alignment layer with an alignment method is treated. Multi-domain liquid crystal display device according to claim 2, wherein the alignment layer is not aligned with an alignment method is treated. Multi-domain liquid crystal display device The device according to claim 1, wherein the liquid crystal layer is positive liquid crystal molecules having dielectric anisotropy. Multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal layer has negative crystal liquid molecules having dielectric anisotropy. A multi-domain liquid crystal display device according to claim 1, further comprising: a negative optically uniaxial layer on at least one of said substrates ( 31 . 33 ). A multi-domain liquid crystal display device according to claim 1, further comprising: a negative optical biaxial layer on at least one of said substrates ( 31 . 33 ). Multi-domain liquid crystal display device according to claim 1, wherein the liquid crystal layer is chiral Having dopants. A multi-domain liquid crystal display device according to claim 2, further comprising: a thin film transistor having an angled channel at crossing regions of said gate bus lines ( 1 ) with the data bus lines ( 3 ).