A kind of LCD of low driving voltage
The invention provides the method that a kind of making has wide viewing angle and low driving voltage LCD.
LCD has that external form is frivolous, power consumption is few and characteristic such as radiationless pollution, be widely used on the portable type information products such as notebook computer (notebook), PDA(Personal Digital Assistant), even the existing trend that replaces the CRT monitor of traditional desktop computer gradually.Liquid crystal molecule has different polarizations or refraction effect to light under different ordered states, LCD promptly is to utilize this specific character of liquid crystal molecule to control the amount of penetrating of light, and then makes LCD produce abundant image.Yet the visual angle of conventional liquid crystal can be subjected to the influence of liquid crystal molecule structure and optical characteristics, therefore is necessary to develop a kind of LCD of new structure, so that preferable wider visual angle to be provided.
Please refer to Figure 1A and Figure 1B, (Figure 1B is the synoptic diagram of traditional dark attitude of reversing wire LCD 10 to Figure 1B for twistnematic, the TN) synoptic diagram of the bright attitude of LCD 10 for traditional wire of reversing.Shown in Figure 1A, traditional TN-LCD 10 includes one first substrate 12, one second substrate 14 is parallel relative with first substrate 12, one first electrode 16 is located at the below of first substrate 12, one second electrode 18 is located at the top of second substrate 14, one first polaroid 20, one second polaroid (polarizer) 22 is located at the top of first substrate 12 and the below of second substrate 14 respectively, and the liquid crystal molecule 24 of the positive specific inductive capacity anisotropic of a plurality of tools (positive dielectric constant anisotropy) is filled between first substrate 12 and second substrate 14.The absorption axes direction P1 of the polarization absorption of first polaroid 20 (polarizating absorption) is parallel to paper, the absorption axes direction P2 of the polarization absorption of second polaroid 22 is perpendicular to paper, and the orientation of liquid crystal molecule 24 is converted to direction perpendicular to paper by the direction that is parallel to paper from top to bottom gradually.
Shown in Figure 1A, when first electrode 16 of LCD 10 and second electrode 18 did not apply voltage, liquid crystal molecule 24 was not subjected to electric field influence and is parallel with first polaroid 20, second polaroid 22 respectively.One light (not shown) is injected from the below, produces polarization via second polaroid 22, makes the polarized light of vertical paper be passed second substrate 14.Then polarized light is injected liquid crystal molecule 24, and produces the phenomenon of refraction.Incident light is followed the orientation of liquid crystal molecule 24, and the polarized light absorption direction is transferred gradually to the direction of parallel paper by the direction of vertical paper.At last, when the polarized light desire saw through first substrate 12, because the direct of travel of polarized light is parallel with the polarized light absorption direction of first polaroid 20, this was the bright attitude of TN-LCD 10.
Shown in Figure 1B, when between first electrode 16 and second electrode 18, applying a voltage, and between first substrate 12 and second substrate 14, produce an electric field.Arrange because its major axis of positive liquid crystal molecule of the positive specific inductive capacity of tool can be inclined to parallel electric field direction 26, so liquid crystal molecule 24 will be arranged with the direction perpendicular to first, second substrate 12,14.Therefore, the direct of travel of light is vertical with first Polarizer 20, and light can't pass through first polaroid 20.Therefore, the observer who is positioned at first substrate, 12 tops can't see any light, and this is the dark attitude of TN-LCD 10.
For the starting potential (threshold voltage) that reduces TN-LCD 10, and make that liquid crystal molecule 24 is easier to be subjected to electric field influence and to rotate, the liquid crystal molecule 24 among Figure 1A accompanies a tilt angle (not shown) with first substrate 12 or second substrate 14 usually.Yet this kind tilt angle but causes liquid crystal molecule 24 asymmetric when dark attitude, makes to make the visual angle of TN-LCD 10 when showing be restricted by light intensity that the observer sees in different angles and inequality.And when showing, because the adhesion of liquid crystal molecule 24 and first, second substrate 12,14, in fact only have 12,14 middle bodies of first, second substrate liquid crystal molecule 24 can with go to fully vertically with first, second substrate 12,14, be close to the liquid crystal molecule 24 of first, second substrate 12,14 and then can possess an angle (not shown) with first, second substrate 12,14.In addition, consider the effect of aforementioned tilt angle more in the lump, the liquid crystal molecule 24 when making dark attitude is not as evenly distributed as Fig. 2, therefore dark attitude poor effect, and contrast descends.In addition, therefore the visual angle of TN-LCD 10 also is severely limited, even has the different phenomenon of last downwards angle of visibility to produce.Therefore, how can effectively reduce the starting potential of TN-LCD 10, and make liquid crystal molecule 24 can quicken to rotate, add simultaneously with great visual angle, promptly become the big problem that TN-LCD 10 must break through.
Have many technology of improving the visual angle to develop, one of them is applied in the plane torsion type that is on the display (IPS, In-plane Switching mode) LCD, and its structure as shown in Figure 2.Traditional IPS-LCD 50 includes one first substrate 52, one second substrate 54, and it is with parallel relative, one first electrode 56 of first substrate 52 and one second electrode 58 is located on second substrate 54, one first polaroid 53a and one second polaroid 53b are located at the top of first substrate 52 and the below of second substrate 54 and the liquid crystal molecule 57 of the positive specific inductive capacity anisotropic of a plurality of tool (positive dielectric constant anisotropy) respectively and are filled between first substrate 52 and second substrate 54.Its principle of operation is found in U.S. Pat 6,094, in 250, does not repeat them here.Though use plane torsion type LCD can improve the visual angle problem of traditional twist mode LCD, but still can't effectively reduce the trigger voltage of display.In addition, first electrode 56 and second electrode 58 are the opaque metal electrode, will reduce the transmittance of LCD.
Therefore fundamental purpose of the present invention is to provide a kind of plane torsion type LCD with low driving voltage.
Please refer to Fig. 3, Fig. 3 has the synoptic diagram of the LCD 30 of low driving voltage for the present invention.As shown in Figure 3, LCD 30 of the present invention includes second substrate 200 that first substrate 100 and with a first surface 102 has a second surface 202, second surface 202 is parallel relative with first surface 102, and is that definition has a pixel region (not shown) on the second surface 202.First substrate 100 can be a upper substrate or an infrabasal plate, and is relative, and second substrate 200 is an infrabasal plate or a upper substrate.In the present invention, only introducing first substrate 100 is a upper substrate, and second substrate 200 is the structure of an infrabasal plate, but notion of the present invention still can be applicable to two substrates about in the of 100,200 on the opposite configuration.
As shown in Figure 3, the first surface 102 of first substrate 100 is provided with one first electrode 104, and the surface of the opposite side relative with first surface 102 then is provided with one first polaroid 112.Then be provided with one second electrode, an insulation course (isolation layer) 206 and one third electrode on the second surface 202 of second substrate 200 in regular turn.Second electrode 208 is used for being used as pixel (pixel) electrode 208, and second electrode 208 is to be located in the pixel region of second substrate 200.Insulation course 206 is to be located at second substrate 200 surface abreast and to be covered on second electrode 208.Third electrode 210 is to be used for being used as shared (common) electrode 210 down, and it is located at insulation course 206 surfaces and is arranged in this pixel region.Wherein, pixel electrode 208 and following common electrode 210 are first breach (slit) 218 and second breach 216 that contain along the approximate strip of first direction 114 extensions, first breach and second breach are to be crisscross arranged, thus pixel electrode 208 and down the projected position of common electrode 210 on the horizontal surface of second substrate 200 also be the configuration that intermeshes.First electrode 104, pixel electrode 208 and following common electrode 210 all can be made of a transparent conductive material, can increase the aperture opening ratio and the transmittance of LCD.In addition, another surface relative with second surface 102 is provided with one second polaroid 212 in addition on second substrate 200.
Please refer to Fig. 4 A and Fig. 4 B, it is the top view of the LCD 30 of Fig. 3.Shown in Fig. 4 A, second substrate 200 is provided with a plurality of first and second breach 218,216 and respectively is located on pixel electrode 208 and the following common electrode 210 along first direction 114.Be filled with the liquid crystal molecule 40 of a plurality of tool negative permittivity anisotropics (negative dielectric constant anisotropy) between first substrate 100 and second substrate 200, be dispersed between first electrode 104 and the following common electrode 210.
When not applying electric field, liquid crystal molecule 40 major axis are to be horizontally arranged between first electrode 104 and the following common electrode 210 along a second direction 214, and accompany an angle theta between second direction 214 and the first direction 114
1Wherein, second direction 214 is that the polarisation of second polaroid 212 absorbs direction 214, and the polarisation of first polaroid 112 to absorb direction be third direction 115, third direction 115 is vertical with second direction 214.In addition, LCD 30 is being provided with an on-off element (not shown) on the first surface 102 of first substrate 100 or on the second surface 202 at second substrate 200, a thin film transistor (TFT) (thin film transistor) for example is used for controlling the breakdown action of LCD 30.
Shown in Fig. 4 A, when on-off element is not opened, that is first do not apply a voltage between electrode 104 and the pixel electrode 208 and cause any electric field, this moment, liquid crystal molecule was to arrange according to second direction 214, and it is vertical with the polarisation absorption direction 115 of first polaroid 112, thereby cause light can't pass through first polaroid 112, so the observer will can't see any light and penetrate in LCD 30, this is the dark attitude of LCD 30.And because the orientation of liquid crystal molecule is vertical with the polarisation absorption direction 115 of first polaroid 112 fully, therefore, the dark attitude of LCD of the present invention gained when added electric field not is the dark attitude of very perfect (prefect).Refer again to Fig. 4 B, when on-off element is opened, liquid crystal molecule is subjected to electric field effects, be diverted to the first direction 114 of parallel first breach 218 orientations gradually by original second direction 214, thereby cause the bright attitude of LCD, detailed explanation will be introduced in Fig. 5, at this only in contrast than than usefulness.
Refer again to Fig. 4 C and Fig. 4 D, it shows the mode that another kind of breach distributes.Shown in Fig. 4 C, second substrate 200 is provided with a plurality of first and second breach 218,216 and respectively is located on pixel electrode 208 and the following common electrode 210 along first direction 114, is provided with the a plurality of the 3rd and the 4th breach 219,217 simultaneously and respectively is located on pixel electrode 208 and the following common electrode 210 to 116 along the four directions.When not applying electric field, liquid crystal molecule 40 major axis are to be horizontally arranged between first electrode 104 and the following common electrode 210 along second direction 214.Accompany angle theta between second direction 214 and the first direction 114
1, the four directions to 116 and second direction 214 between accompany angle theta
2When on-off element is opened, shown in Fig. 4 D, liquid crystal molecule is subjected to electric field effects, by original second direction 214 be diverted to respectively 218,219 orientations of parallel the first, the 3rd breach first, the four directions is to 114,116, thereby causes the bright attitude of LCD.
In addition, first polaroid 112 and second polaroid 212 are also interchangeable, just, the polarisation of not necessarily parallel second polaroid 212 of the arrangement of liquid crystal absorbs direction 214 when applying voltage, also might be to arrange with the polarisation absorption direction 115 of parallel first polaroid 112.
Please refer to Fig. 5, Fig. 5 is the diagrammatic cross-section of the LCD 30 of Fig. 3 along second direction 214, when on-off element is unlocked, can be present between first electrode 104 and the pixel electrode 208 once adding pressure drop, and this moment first electrode 104 with following common electrode 210 equipotentials, so electric field 120 is partial in meeting formation one between first electrode 104 and the pixel electrode 208.And between following common electrode 210 and the pixel electrode 208, have another deflection electric field 220 and produce.Can near contiguous second breach 216, produce first horizontal electric field component 1201 perpendicular to first direction 114 near the deflection electric field 120 that produces second breach 216 of following common electrode 210, and negative liquid crystal molecule 40 is arranged with the direction of vertical electric field with tendency, therefore, after applying voltage, near the liquid crystal molecule 403 second breach 216 of contiguous common electrode 210 down can be diverted to the first direction 114 of parallel second breach 216 orientations gradually by original second direction 214.Moreover, also can produce the electric field component 1202 on vertical second substrate 200 surfaces near contiguous second breach 216, and the major axis of these electric field component 1202 equal vertical liquid crystal molecules 40 maintains on the fixing plane liquid crystal molecule 40 and rotates.
In addition, deflection electric field 120 there is no the horizontal deflection electric field component in contiguous first electrode 104 places, and makes liquid crystal molecule 401 major axis of contiguous this first electrode 104 maintain second direction 214.So the liquid crystal molecule between first electrode 104 and following common electrode second breach 216 is to be diverted to first direction 114 gradually by second direction 214, and produces (the TwistNematic of twist mode in similar traditional skill; Bright attitude when TN) liquid crystal does not apply voltage.Just, after liquid crystal molecule 40 turned to, light along with the orientation of liquid crystal molecule, changed into first direction 114 by second direction 214 after being passed through by second polaroid 212 gradually.Absorb direction 115 because the orientation of liquid crystal molecule has not been the polarisation of vertical first polaroid fully, so light can pass through first polaroid 112, and arrive the observer in, this is the bright attitude of LCD 30.
In other words, deflection electric field 120 can be between first substrate 100 and second substrate 200, produce a ll vertical electric field component 1201 perpendicular to first direction 114, making liquid crystal molecule 40 maintain fixed pan rotates, and a horizontal electric field component 1202, second breach 216 that makes liquid crystal molecule 40 be diverted to parallel common electrode is down gradually arranged.Therefore, under adding during shared (common) electrode 210, because another deflection electric field 220 produces simultaneously, the horizontal electric field component 1202 that this deflection electric field 220 can provide another horizontal electric field component (not shown) to add to force liquid crystal molecule to rotate makes near the liquid crystal molecule of breach is easier to be rotated.As for the vertical electric field (not shown) component of electric field 220, because of effect also for making liquid crystal molecule 40 maintain fixed pan rotation, do not go through and illustrate so do not do at this.
The characteristics of LCD 30 of the present invention are to add on the second surface 202 of second substrate 200 into a following common electrode 210, with stronger transverse electric field, promotion is more prone to the rotation of liquid crystal molecule 40 near the liquid crystal molecule of indentation, there, and then reduces the driving voltage of LCD 30.Secondly, be formed at down the insulation course 206 between common electrode 210 and the pixel electrode 208, also insulation blockings that another layer is provided so that the chance that pixel electrode 208 and first electrode 104 (that is common electrode of first substrate 100) are short-circuited diminishes more.And, as previously mentioned, first electrode 104, pixel electrode 208 and the following common electrode 210 that are formed on the LCD 30 are constituted (certain also electric conductivity demand of visible liquid crystal display 30 by a transparent conductive material, and part is selected a non-transparent material for use), therefore the transmittance of LCD 30 increases, and the size of pixel electrode 208 and following common electrode 210 also can be dwindled the aperture opening ratio that increases LCD 30 relatively.
Please refer to Fig. 6, Fig. 6 is the diagrammatic cross-section of second embodiment of LCD 30 of the present invention.Upper substrate 100 among the embodiment of earlier figures 3 to Fig. 5 is to be a smooth platy structure, and second embodiment forms a plurality of thrust 122 structures on the first surface 102 of first substrate 100.As shown in Figure 6, include a plurality of thrusts 122 on the first surface 102 of first substrate 100, a plurality of thrusts 122 are signal line (the data line that are arranged on first electrode, demonstration) in the zone, and first electrode 104 promptly is arranged on first substrate 100 comprehensively, and be covered in thrust 122 surfaces, the following common electrode 210 on first electrode, 104 meetings, second substrate, 200 surfaces contacts, when being applied in a voltage drop between first electrode 104 and pixel electrode 208, first electrode 104 forms equipotential with following common electrode 210.
The advantage of said structure design is to reduce the phenomenon of shared signal delay (common signal delay), also therefore can dwindle the width of signal line and following common electrode 210.Instantly during common electrode 210 reduced width, then aperture opening ratio can increase relatively.Simultaneously, stored static charge on first electrode 104 can see through first electrode 104 and discharge with being electrically connected of following common electrode 210, so can prevent static discharge.In addition, because down common electrode 210 and pixel electrode 2,080 minutes are close, to have the electric field 220 of the last one under the event between common electrode 210 and the pixel electrode 208, this electric field also comprises one as the described horizontal component of electric field (not shown) of last embodiment, make liquid crystal molecule 40 quicken to turn to and become the state of bright attitude, reduce the delay when driving.In addition, in this second embodiment, the structure of thrust 122 more can be used to control the gap (cell gap) of first substrate 100 and second substrate 200, thus can avoid in the traditional LCD, because of using shortcomings such as ripples line that spherical filling material derives as spacer and light leak.
Compared to traditional plane torsion type LCD (IPS-LCD), the required driving voltage of LCD of the present invention 30 is less, and therefore the electric power that is consumed still less.And second embodiment disclosed as Fig. 7, when all upper and lower common electrodes link to each other, that is first electrode 104 when linking to each other with following common electrode 210, following common electrode 210 live widths reduce, more dwindled the distribution area, increase aperture area, and then the solution of a high image quality and high-speed driving is provided, and saved the cost of filling liner in the manufacture process and making lead.In addition, the insulation course in the structure of the present invention more can prevent electric pole short circuit, to solve abnormal bright spot problem on the screen.
The above preferred embodiment only of the present invention, all equalizations of doing according to claim of the present invention change and modify, and all should belong to the covering scope of patent of the present invention.
The simple declaration of accompanying drawing
Figure 1A and Figure 1B are respectively the synoptic diagram of the traditional bright attitude of reversing the wire LCD and dark attitude.
Fig. 2 is the structural representation of traditional plane torsion type LCD.
Fig. 3 has the synoptic diagram of the LCD of low driving voltage for the present invention.
Fig. 4 is the long strip type breach of LCD of Fig. 3 and the top view of liquid crystal molecule.
Fig. 5 is the diagrammatic cross-section of the LCD of Fig. 3 along second direction.
Fig. 6 is the diagrammatic cross-section of second embodiment of LCD of the present invention.The symbol description of accompanying drawing
10,50 LCD, 12,52 first substrates
14,54 second substrates, 16,56 first electrodes
18,58 second electrodes
20,53a first polaroid
22,53b second polaroid 24,57 liquid crystal molecules
26 directions of an electric field, 30 LCD
100 first substrates, 200 second substrates
102 first surfaces, 202 second surfaces
104 first electrodes, 206 insulation courses
210 times common electrodes of 208 pixel electrodes
112 first polaroids, 212 second polaroids
114 first directions, 214 second directions
216 second breach 217 the 4th breach
218 first breach 219 the 3rd breach
115 third directions, 122 thrusts
120,220 deflection electric fields, 121 directions of an electric field
1201 horizontal electric field component
1202 ll vertical electric field component
40,401,403 liquid crystal molecules