TWI240904B - LCD with improved gray-scale display - Google Patents

Abstract

An LCD with improved gray-scale display comprises a plurality of pixel areas. Each pixel area has first and second substrates disposed opposite each other and a liquid crystal layer interposed there between. A first pixel electrode and a first TFT device electrically connected thereto are formed on part of the first substrate. A second pixel electrode and a second TFT device electrically connected thereto are formed on part of the first substrate. A common electrode is formed on the interior of the second substrate. The first and second TFT devices have mutually different ON currents to cause the first and second pixel electrodes to have mutually different voltages, thereby improving viewing characteristics.

Description

1240904

[Technical field to which the invention belongs] The present invention relates to a liquid crystal display device (^ CD), and particularly to a liquid crystal display device having a device capable of improving grayscale inversion (or viewing angle characteristics). [Prior art] Traditional TN (Twlst Nematic) mode LCD (hereinafter referred to as TN_LCD) has a serious gray-scaie inversion phenomenon in the lower viewing direction, and therefore has a problem of poor viewing angle characteristics. Please refer to FIG. 1, which shows the relative luminance difference of each gray level of the conventional TN_LCD with the normal operation mode (n0rmaUy wMte) at each lower viewing angle. Curve 12 represents the brightness difference between the first and second gray scales, curve 23 represents the brightness difference between the second and third gray scales, curve 34 represents the brightness difference between the third and fourth gray scales, and curve 45 Represents the difference in luminance between the fourth and fifth gray scales. It can be seen from Fig. 1 that the conventional tn_lc (gray-scale inversion) GS ° occurs at a lower viewing angle of about 20 degrees. In US Patent No. 6,342,939, Hirata has disclosed a TN-LCD with improved viewing angle characteristics. The patent is to form a dielectric layer pattern on a day element electrode to form cells with different cell thicknesses (cel 1 gap), thereby improving viewing angle characteristics. Although this method can increase the viewing angle range, the patent does not teach the LCD structure of the present case. In US Patent Early Publication No. 2002/0105614, Nakayama has disclosed a TN-LCD with improved viewing angle characteristics. The patent system forms a different flat

0690-A5011 TWf (Nl); 92067; .ptd Page 5 1240904 V. Description of the invention (2) Two layers of day element electrodes to improve the viewing angle characteristics. Although this method can increase the viewing angle range, the patent does not teach the LCD structure of the present case. SUMMARY OF THE INVENTION In view of this, an object of the present invention is to provide a liquid crystal display device having an improved grayscale inversion phenomenon (ie, viewing angle characteristics). To achieve the above object, the present invention provides a liquid crystal display device. The liquid crystal display device has a plurality of daylight regions, and each daylight region includes: a first and a second substrate with a liquid crystal layer sandwiched therebetween; a first daylight A pixel electrode is electrically connected to one of the first day element electrodes, and a first day element driving element is formed on part of the first substrate. A second pixel electrode is electrically connected to one of the second day element electrodes. The day driving element is formed on part of the first substrate; and a common electrode is formed on the inner surface of the second substrate; wherein the first and second day driving elements have different open currents (1 ^ ), So that the first and second celestial electrodes have different voltage values. Compared with the conventional liquid crystal display device, since the first and second celestial electrodes in each celestial element in the liquid crystal display device of the present invention have different voltage values, the gray-scale inversion angle can be increased to achieve improved viewing angle characteristics. The effect. In order to make the above-mentioned objects, features, and advantages of the present invention more comprehensible, the following exemplifies preferred embodiments, and in conjunction with the accompanying drawings, the detailed description is as follows: [Embodiment]

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The first embodiment of the liquid crystal display device with improved grayscale inversion is described below to illustrate the present invention (ie, viewing angle characteristics). The second embodiment shows a single metal element in an LCD according to the first embodiment of the present invention. View from above the array substrate of region p. Figure 3 is a cross-sectional view along the section. Fig. 6 is a cross-sectional view showing the first part 2 of the structure according to the present invention. Here, π-yesterday + this rd — 7々 "of f is particularly strong. Although the above-mentioned pattern only has a cheek that is not earlier than a daytime prime region p, the LCD of the present invention may contain the daytime prime element. The region P is defined by interlaced gate lines (source lines): source lines (or data lines). ', Please refer to FIG. 2 and FIG. A laterally extending gate line 2 丨 0 and a laterally extending storage capacitor, pole line 212 (st〇rage capacitance electr heart 1 ine, abbreviated as C s line) are formed on the first substrate 2000. The gate line 2 1〇 further includes a gate 2; [5. The material of the gate line 2 10 and the Cs line 2 12 is, for example, a I, cr, M 0 or an alloy thereof. Then, a gate insulation is formed. The layer 2 2 completely covers the first substrate 200, and the gate insulating layer 2 2 0 is, for example, a Si 2 layer. Then, a semiconductor layer 230 serving as a channel channel 230 is formed. On the gate insulating layer 220. The material of the channel layer 230 is, for example, silicon. Next, a longitudinally extending source line 240 is formed on the gate insulating layer 220. The source line 240 includes a source electrode 242 extending to a portion of the channel layer 230 and forming a first at the same time; and a pole 244 and a second electrode 245 are partially insulated from the gate electrode at a portion of the channel layer 230. On layer 220, the first drain electrode 244

0690-A50110TWf (Nl); 92067; .ptd Page 7 1240904 V. Description of the invention (4) It has a first extension 244 'and overlaps the cs line 212, and the second drain 245 has a second extension The portion 245 overlaps the cs line 212. Among them, the material of the source line 24, the source 2 4 2, and the drains 2 4 4 and 2 4 5 are, for example, Al, Cr, Mo, or an alloy thereof. In this way, the gate electrode 215, the gate insulating layer 220, the channel layer 230, the source electrode 242, and the first drain electrode 244 constitute a first thin-film transistor element as a first daylight driving element. Ί7Τ1, and the gate electrode 215, the gate insulating layer 220, the channel layer 230, the source electrode 2 4 2 and the second drain electrode 2 4 5 constitute a second thin-film electrical element of a second celestial driving element. The crystal element hit 2. These thin-film transistor elements TFT1 and TFT2 function as switching elements and are used to control the charge and discharge of charge to the daylight electrode described below. Although the thin film transistor elements TFT 1 and TFT 2 in this embodiment are exemplified by f containing the same gate electrode 215, channel layer 2 3 0, and source electrode 242, these thin film transistor elements TFT 1 are actually It can be a separate element from TFT2. The important point is that the first thin film transistor element TFT1 and the second thin film transistor element TFT2 must have different on currents (1⑽, 〇N current of TFT) ° 〇n, and then an insulating layer 2 50 is formed to cover the entire The first substrate "ο, the material of the edge layer 2 50 is, for example, an organic material or an inorganic material. Then, a first pass through which exposes the first extension portion 2 4 $ is formed by a 4'5V money engraving process. 2 52 and a second perforation 254 exposing the second extension 245 '. Then, it becomes a first day element electrode 260 with a first area (A1) and a side with a brother, (A2) A second pixel electrode 2 6 5 is on the insulating layer, and the first day pixel electrode 2 60 is filled in the first perforated bracket 2 to be electrically connected to the first hole holder 2.

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The first drain electrode 244 and the second pixel electrode 2 65 are filled in the second through hole 2 54 to be electrically connected to the second drain electrode 245. The day element electrodes 26 and 265 are, for example, (indium tin oxide) or τ0 or (indium zinc oxide) IZ0 layers formed by the > pediatric method. Because of the first thin film transistor element ^ 丨The second thin film transistor element TFT2 has a different open current (丨 ⑽), so that the first pixel electrode 2 60 has a first voltage value (V1), and the second day element electrode 265 has a first Two voltage values (V2), the first voltage value (vi) and the second voltage value (V2) have a voltage difference (Δν). Please refer to FIG. 4 and FIG. 5 to explain the design method of making the day electrode 260 and 265 have different voltage values in this embodiment. Fig. 4 is a partial enlarged view of the thin film transistor elements TFT1 and TFT2 in this embodiment. Figure 5 is a schematic diagram showing the operation of the thin film transistor elements TFT1 and TFT2. In FIG. 4, the first drain electrode 244 has a first width (W1), there is a first distance (L1) between the first drain electrode 244 and the source electrode 242, and the second drain electrode 2 45 Has a second width (W2), a second distance (L2) between the second drain electrode 245 and the source electrode 242, and conforms to the relationship: W1 / L1 off W2 / L2, so that the films are electrically The crystal elements TFT1 and TFT2 have different on-currents (100n). Please refer to FIG. 5, when the source line 240 provides a driving voltage Vs, and the gate turn on time of the gate 215 is set ton (for example, 10 ~ 30 // sec), because The thin film transistor elements TFT1 and TFT2 have different open currents (IQn), so that there is a voltage difference (Δν) between the daylight electrodes 260 and 265 after charging. Then refer to FIG. 6 to form an alignment film.

1240904

film) 270 on the pixel electrodes 260 and 265 and the insulating layer 250. For example, a glass substrate including a color filter 6 is provided, and is used as a second substrate 600 facing the first substrate 200. A common electrode (c 〇mm ο ne 1 ectr 〇de) 6 2 0 is formed on an inner surface of the color filter 6 1 〇. The common electrode 6 2 〇 is, for example, I τ〇 formed by a deposition method or ιζο layer. Then, another alignment film is formed on the common electrode 62. Then, 'TN type liquid crystal molecules 6 3 5 are filled between the first substrate 200 and the second substrate 600, and a liquid crystal layer 64 is formed. The degree of the liquid crystal layer 64 is, for example, 疋 2 ~ 1 0 // m, preferably 5 // m. Please refer to FIG. 6. Because the voltage (V1) of the first day element electrode 260 is different from the voltage (V2) of the second day element electrode 265, the first book element electrode 260 and the second day element electrode 260 The liquid crystal molecules 635 above the element electrode 265 have different orientations (〇1 ^ 印 4 士 1011), thereby improving the grayscale inversion phenomenon (viewing angle characteristic). Refer to FIG. 7 ′ according to the present invention, under various voltage difference (Δν) conditions, the area (A1) of the first pixel electrode 26 ° is relative to the first and second pixel electrodes 26 °. The influence of the ratio of the total area (A1 + A 2) on the grayscale inversion angle of the lower viewing angle. It can be seen from FIG. 7 that compared with the conventional “one or two ⑶ (that is, Δ V = 0), the present invention lcd under the condition of 0 <voltage difference (AV) &lt; 0.6 Vs” when the first area (A1) The scale range is 0 &lt; Α1 / (Α1 + Α2) &lt; 0 · 8, and the lower viewing angle grayscale inversion angles are all larger than the conventional 20 degrees, so it proves that the present invention has the effect of improving the lower viewing angle grayscale inversion. In addition, when the voltage difference (ΔV) of the LCD of the present invention is 0.6Vs, when the ratio range of the first area (A1) is 0.45 &lt; Α1 / (Α1 + Α2) &lt; 0.8, The grayscale inversion angle of the lower viewing angle is greater than

Page 10 0690-A50110TWf (Nl); 92067; .ptd 1240904 V. Description of the invention (7) ---- Bai Zhi 20 degrees, so it proves that the present invention has the effect of improving the grayscale inversion of the lower viewing angle. Here is an example to illustrate a design example of the LCD of the present invention. For example, take an LCD with a scanning frequency of 75Hz and a resolution of 1 0 24 * 7 6 8 as an example. Please refer to Figure 4 and Figure 5. First define W1 / L1 of the first thin-film transistor TFT1 as 3. Define the W2 / L2 of the second thin-film transistor element 11 to 2 as 0 · 889, set the on-time tQn of the gate 215 to 10 // sec ', and provide the source line 240 The driving voltage (Vs) is set to 5V. In this way, the charging rate CR1 of the first daylight electrode 260 electrically connected to TFT1 can reach 9 9.3 6%, and the charge rate CR2 of the second daylight electrode 265 electrically connected to TFT2 can reach 76.71%. The calculation process is as follows: First, consider the driving operation of the LCD as an Rc circuit. As shown in Figure 8, Ron represents the equivalent impedance when the TFT is turned on, q represents the liquid crystal capacitor, and Ccs represents the storage capacitor. The voltage Vp of the day element electrode after the gate open time u is: (—_,

Vp = Vs I —

^ J and the charging rate C R of the day element electrode is: ί -ίΒΠ, C R = Vp / Vs = \) and the equivalent impedance when the TFT is turned on

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1 / Cox {Vgh-Vikf is calculated based on the following parameters: h Liquid crystal capacitor &lt; ^ = 0.4298E-12 (F) 2 · Storage capacitor Ccs = 0.189 6E-12 (F) 3 · Source The voltage difference between the electrode and the drain, Vs, 10 (v), that is, the polarity inversion voltage between the source and the drain is ± 5 (V) 4 · Mobility of the charge carrier # = 〇 · 35E-4 (m2 / V) 5 · Capacitance per unit area of the gate insulation layer c〇x = 1. 49E-4 (F / m2) 6 · Maximum voltage of the gate when the TFT is turned on Vgh = 22 (V) 7 · The starting voltage of the TFT vth = 2 (V) For the first thin film transistor element TFT1, since w / L = 3, Ron = 3.2 · 6E6 (Ω), and its charging rate CRl = 99.36 ° / 〇. For this second thin-film transistor element TFT2, because of W / LU89, Ron = 11.08E6 (Q), and its charging rate CR2 = 76 · 71%. Therefore, the voltage difference (AVXCR1-CR2) * Vs = 22 · 65% * 5 = 1.1 · (V) between the first daylight electrode 260 and the second daylight electrode 265. It can be seen from FIG. 7 that when the voltage difference (ΔVkOJVs), the gray-scale inversion angles of the lower viewing angles thereof are all above 25 degrees. FIG. 9 of the second embodiment shows an LCD in the LCD according to the second embodiment of the present invention. Single day

0690-A50110TWf (Nl); 92067; .ptd Page 12 1240904 V. Description of the invention (9) Top view of the array substrate of the prime region P. The difference between the second embodiment and the first embodiment is that the second embodiment partially overlaps the gate electrode 2 6 0 and 2 65 with the gate line 2 1 0 instead of the C s line 2 1 2 . Since the other parts of the second embodiment are similar to the first embodiment, they will not be described again here. [Features and advantages of the present invention] The liquid crystal display device of the present invention uses the thin-film transistor elements TFT1 and TFT2 in each day element to have different open currents g ", so that the subsequent day element electrodes 26 0 The liquid crystal molecules in the liquid crystal layer 640 in the per-day element have a voltage between ° and 265 (aV), which has two kinds of ㈣ = bits (〇rientatlion), which can improve the grayscale inversion goodness. Effect of viewing angle characteristics. I ~ &amp; Although the present invention discloses the scope of the present invention with a preferred embodiment, anyone familiar with this spirit and scope, when it can do a little protection scope, see the attached patent application as above, but it is not intended to limit it Those skilled in the art will not deviate from the modifications and retouching of the present invention, so those defined by the scope of the present invention shall prevail.

1240904 Brief description of the diagram. Figure 1 is a viewing angle characteristic diagram of a traditional TN-LCD in the lower viewing direction, which shows that the gray-scale inversion angle is about 20 degrees. Figure 2 shows a LCD according to the first embodiment of the present invention. A top view of an array substrate of a single pixel region P; FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2; FIG. 4 is a view showing a thin film transistor element TFT1 in the first embodiment of the present invention Figure 5 is a partial enlarged view of TFT2; Figure 5 is a schematic diagram showing the operation of the thin film transistor elements TFT1 and TFT2 according to the present invention; Figure 6 is a sectional view showing a partial structure of an LCD according to the first embodiment of the present invention; Figure 8 is a graph showing the ratio of the area ratio of the first daylight electrode to the grayscale inversion angle of the lower viewing angle under various voltage difference (AV) conditions according to the present invention; FIG. 8 shows the voltage of each daylight electrode calculated by the present invention. FIG. 9 is a top view of an array substrate showing a single daylight region P in an LCD according to a second embodiment of the present invention. [Illustration of Symbols] 2 0 ~ first substrate; 2 1 0 ~ gate line; 2 1 2 ~ storage capacitor line (C s line); 2 1 5 ~ gate;

0690-A50110TWf (Nl); 92067; .ptd Page 14 1240904 The diagram briefly explains 2 2 ~ gate insulation layer; 2 3 0 ~ channel layer; 2 4 0 ~ source line; 2 4 2 ~ source; 2 4 4 ~ first pole; 244 '~ first extension; 2 4 5 ~ second drain; 2 4 5' ~ second extension; 2 5 0 ~ insulation layer; 2 5 2 ~ first perforation 254 ~ second perforation; 260 ~ first day element electrode; 265 ~ second day element electrode; 270, 630 ~ alignment film; 60 ~ second substrate; 610 ~ color filter; 6 2 0 ~ common electrode; 6 3 5 ~ liquid crystal molecules; 640 ~ liquid crystal layer; P ~ one day prime area; GS ~ where grayscale inversion phenomenon begins.

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Claims (1)

1240904 6. The scope of the patent application includes: the seed liquid is not displayed day by day, has a plurality of pixel areas, each day element U a f two substrates, with a -liquid crystal layer sandwiched between them; day element driver element: element = The first element is electrically connected to one of the first day element electrodes and is formed on part of the first substrate; the day element drives the element and is electrically connected to one of the second day element electrodes. Second element: It is formed on part of the first substrate; and the same electrode is formed on the inner surface of the second substrate; with a different opening from Γ Wangshang _ ^ / τ λ M and the second day element driving element The electric value L / n 'makes the first and second celestial electrodes have different voltages m, such as the liquid crystal display device described in item 1 of the scope of the patent application, wherein the second :: layer contains different orientations. ^ Two liquid crystal sides &gt; 3. The liquid crystal display device as described in item 1 of the scope of patent application, wherein the three liquid crystal layers include twisted nematic (TN) type liquid crystal molecules. / 、: # 4 · The liquid crystal display device according to item 1 of the scope of the patent application, wherein the first day element electrode and the second day element electrode are indium tin oxide (ττ, indium zinc oxide (IZZ0) ) Layer.) Or 5. The liquid crystal display device described in item 1 of the scope of patent application, wherein the common electrode is an ITO or IZ0 layer. "Zhong 6 · The liquid crystal display device described in item 1 of the scope of patent application, the first daylight driving element is a first thin film transistor element. 1 in 7 · The liquid crystal described in item 6 of the scope of patent application Display device, 1 1240904 VI. Scope of patent application The second daylight driving element is a second thin film transistor element. 8. The liquid crystal display device according to item 7 of the scope of patent application, wherein the first thin film transistor element and the second thin film transistor element include the same gate, a channel layer, and a source. 9. The liquid crystal display device according to item 8 of the scope of patent application, wherein the first thin film transistor element has a first drain electrode electrically connected to the first daylight electrode, and the second thin film transistor element has A second electrode which is electrically connected to the second celestial electrode, the first electrode; and a electrode having a first width (W1), and a first distance (L1) between the first drain electrode and the source electrode ), The second drain has a second width (W2), and there is a second distance (L2) between the second drain and the source, which conforms to the following relationship: Wl / Ll ^ W2 / L2. 10. The liquid crystal display device according to item 1 of the scope of patent application, further comprising: a laterally extending storage capacitor electrode line (Cs line), which is located on the first substrate. 11. A liquid crystal display device having a plurality of daylight regions, each daylight region comprising: a laterally extending gate line and a longitudinally extending source line formed on a first substrate; a thin film transistor element Is located at the intersection of the gate line and the source line, wherein the thin film transistor element has a first drain and a second drain; a first day element electrode has a first area (A1), And via this 0690-A50110TWf (Nl); 92067; .ptd page 17 1240904 ', Application scope of patents_ 一 和 极 而 电 性 造 凶 #-The first voltage value; k &quot;, the polar line, so that the first day element electrode has a younger and a lower electricity% ^, which is ancient and poor.一 和 极 而 电 性 远远 # area (A 2), and the voltage value through the younger brother, the younger one has a voltage difference of (Δ V); ^ ^, the younger voltage value has a voltage difference The first substrate is opposite to the first substrate, and is formed on the inner surface of the second substrate; The liquid crystal display device described in # 11 Yueren Cheng Guganwei Item 11, wherein: the r-layer package has two liquid crystal orientation regions with different orientations. The liquid crystal display device described in Zhongxi, &quot; / δYue Patent Qianwei Item 11, wherein the liquid layer contains TN type liquid crystal molecules. The liquid crystal display device according to item 11 of the Zhongxi Yiyi patent scope, wherein the 'brown-denier electrode and the second pixel electrode are IT0 or ιζο layers. 15. The liquid crystal display device as described in item η of the patent application, wherein the common electrode is an ITO or ιζο layer. 16. The thin film transistor element in the liquid crystal display device 1 described in item U of the patent application scope includes a gate, a channel layer, and a gate, wherein the gate is electrically connected to the gate line, And the source is two source lines. 1 王 运 接 此 1 · According to the liquid crystal display device described in item 16 of the scope of patent application, the first drain electrode has a first width (W1), between the first drain electrode and the%, Has a first pitch (L1), and the second drain has a second 0690-A50110TWf (Nl); 92067; .ptd No. 18 1240904 Sixth, the scope of patent application (W 2), the second drain and the source have a second distance (L 2), and meet the following relationship : Wl / Ll # W2 / L2. 18 The liquid crystal display device as described in item 丨 of the scope of patent application, further comprising: a laterally extending storage capacitor electrode line (Cs line) on the first substrate. 1 9 · The liquid crystal display device described in item 丨 丨 of the patent application range, wherein the source line provides a driving voltage (Vs), when 0 <the voltage difference (Δν) &lt; 0.6 Vs' the first The area (A1) and the total area (A1 + A2) of the first and second areas conform to the following relationship: 0 &lt; Α1 / (Α1 + Α2) &lt; 0.8. 2 0. The liquid crystal display device according to item 11 of the scope of patent application, wherein the source line provides a driving voltage (V s), and when the voltage difference (△ V) = (K6Vs, the first area (A1 The sum of the first and second area (A1 + A2) is in accordance with the following relationship: 0.45 &lt; A1 / (A1 + A2) &lt; 0.8. 0690-A50110TWf (Nl); 92067; .ptd page 19