TW594643B - Bistable chiral nematic liquid crystal display apparatus and method of addressing the same - Google Patents
Bistable chiral nematic liquid crystal display apparatus and method of addressing the same Download PDFInfo
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- G—PHYSICS
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- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on liquid crystals, e.g. single liquid crystal display cells
- G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
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Abstract
Description
594643 A7 B7 五、發明説明(1 ) 本發明與一種利用不對稱中心向列反射型雙穩態液晶材 料的顯示器及此類顯示器的驅動方法有關。這個材料也稱 為膽固醇。尤其,本發明與一種主動矩陣像素排列及驅動 機制有關。 膽固醇液晶材料是一種提供色彩鮮明之二進位影像的反 射型材料。這種材料屬於雙穩態材料,其具有寬視角,並 且不需要偏光器、彩色濾光板或像超雙紋中心向列(super twisted nei2_atic ; STN)型顯示器一樣磨擦。因此,這種材料 可提供低功率且低成本的顯示器,並且顯示具有高解析度 並具有良好品質的單色影像。這種類型的顯示器建議運用 在攜帶型裝置,以及運用在電子文件檢視裝置,如電子書 或報紙裝置。 膽固醇材料具有三穩態。平面(Planar ; P)狀態是材料的反 射狀態,並且是在零施加場(zero applied field)下呈現穩定。 焦點二次曲線(Focal Conic ; FC)材料的透光散光狀態,並且 也是在零施加場下呈現穩定。Homeotropic (H)狀態是只有在 大約30V的高門限電壓以上才會呈現穩定,並且也會透明。 放置在材料後面的黑色吸收層表示Η及F C狀態呈現黑色。 還存在第四(不穩定)狀態,這會在材料從Η狀態緩和時 發生。這被稱為瞬間平面(Transient Planar ; Ρ*)狀態。這個 狀態只會發生於處於Η狀態中之材料上的高電壓迅速降 低(例如,2ms或以下)的情況下。在沒有供應電壓的情況下 ,瞬間平面狀態緩和成平面(P)狀態。 使用這種材料時,設計出一種驅動機制,用以在P與 -4- 本紙張尺度適用中國國家標準(CNS) A4規格(210 X 297公釐) 五、發明説明(2 ) ^大〜、之間切換材料,這兩種狀態均是以零供應電壓呈現 穩,目為P與F C狀態之間任何的轉換均需要材料通過高 電壓Η狀態,而引發第一個問題。因此,已知的被動矩陣 切換機制需要迅速的高電壓切換。傳統驅動機制的排列促 使每當定址像素時,導致材料轉換成⑽態。$意謂著導 致處於反射型Ρ狀態的像素通過透光型Η狀態,即使在下一 圖框週期(field period)期間會將像素驅動至反射型ρ狀態。 这會造成熟知的黑色定址條的視覺后生現象。 這種材料的進—步問題起因於遲緩相應時間。例如, :要:應電壓達至少20 ms,才能使材料的狀態轉換成Η狀 悲。這種材料也具有極強的溫度依賴性。 材料在零供應電壓的雙穩態性質表示使用這種材料的顯 不器不需要持續更新或重新整理。如果顯示器資訊未變更 丄則可寫人顯示器-次’並使顯示器維持在資訊運送組_ 恶’以延長無耗電期間。使用膽固醇型液晶顯示器的結果 是可在相當長的時間期間慢慢更新影像。但是,如上文所 述的問題(尤其是遲緩的定址回應)已限制顯示器技術在各 種應用領域方面的進一步發展。 美國專利5 748 277發表-種適用於膽固醇型顯示器的被 動矩陣定址機制,以試圖縮短定址時間。這種機制憑藉從 Η狀態迅速轉換成p*狀態。如果迅速關閉電壓,則會實現 轉換成Ρ*狀態(接著轉換成Ρ狀態),而如果緩慢關閉電壓 ,則會發生轉換成FC狀態驅動機制提供具有三階段的位址 電壓量變曲線。其甲一個階段是「選擇階段」,其只有^ -5- 本紙張尺度適用中國國家標準(CNS) Α4規格(210X297公I) 594643 A7 -----~______ _B7 五、發明説明(3 ) -- 寺門並且指疋疋否有迅速或遲緩電壓關閉。另外兩個 階段可同時執行,以至大量列像素的平均列定址週期將趨 向1⑽。雖然這種定址機制改良定址時間,但是未解決溫 又依賴(1迅速南電壓切換或黑色定址條等問題。 根據本發明,本發明提供一種顯示裝置包括: 一雙穩態不對稱中心向列型液晶材料層; 主動陣列基板’其界定像素位址電路的行列,每個像 素位址電路均具有一個輸出,用以將一信號供應至該液晶 材料的各自部份; 其中每個像素位址電路均包括 第一切換裝置,用以將一供應電壓切換至該像素位址 電路的其餘部件,並且係由一列位址線控制; 一第二切換裝置,用以允許或防止將該供應電壓提供給 液晶材料的各自部件,並且係由一行選擇線控制。 - 材料係維持在p或FC狀態時,像素的切換裝置能夠避免 轉換成Η狀態。具體而言,如果避免從p狀態轉換成H狀態 則了避免黑色定址條后生現象(black addressing bar artifact) 。使用列位址線來控制該第一切換裝置,以及使用一行選 擇線來控制該第二切換裝置,促使能夠分別將該供應電壓 供應給個別的像素。該供應電壓係導致將膽固醇材料轉換 成Η狀態所需的電壓。 該裝置可進一步包括供該液晶材料之各自部件使用的一 電流放電路徑’藉此使該液晶材料之各自部件上的電壓量 從供應電壓量向下降。這促使狀態從Η狀態轉換成FC或ρ -0 - 本紙張尺度適用中國國家標準(CMS) A4規格(210 X 297公釐)594643 A7 B7 V. Description of the invention (1) The present invention relates to a display using an asymmetric center nematic reflection type bi-stable liquid crystal material and a driving method of such a display. This material is also called cholesterol. In particular, the present invention relates to an active matrix pixel arrangement and driving mechanism. The cholesteric liquid crystal material is a reflective material that provides a vivid binary binary image. This material is a bistable material, which has a wide viewing angle and does not require polarizers, color filters, or friction like a super twisted nei2_atic (STN) type display. Therefore, this material can provide a low-power, low-cost display, and display monochrome images with high resolution and good quality. This type of display is recommended for portable devices as well as electronic document viewing devices such as e-book or newspaper devices. Cholesterol materials have a tristable state. The plane (Planar; P) state is the reflection state of the material and is stable under a zero applied field. The focal conic (Focal Conic; FC) material's light transmission and astigmatism state is also stable under zero applied field. The Homeotropic (H) state is stable only when it is above a high threshold voltage of about 30V, and it is also transparent. A black absorbing layer placed behind the material indicates that the Η and Fc states appear black. There is also a fourth (unstable) state, which occurs when the material relaxes from the puppet state. This is called a transient plane (Transient Planar; P *) state. This condition can only occur if the high voltage on the material in the Η state drops rapidly (for example, 2 ms or less). In the absence of a supply voltage, the instantaneous planar state eases into a planar (P) state. When using this material, a driving mechanism is designed to apply the Chinese National Standard (CNS) A4 specification (210 X 297 mm) to P and -4- paper sizes. 5. Description of the invention (2) ^ 大 ~ 、 Switching materials between these two states is stable at zero supply voltage. Any transition between the P and FC states requires the material to pass through the high-voltage 引发 state, causing the first problem. Therefore, known passive matrix switching mechanisms require rapid high-voltage switching. The arrangement of the conventional driving mechanism causes the material to be converted into a pseudo state whenever a pixel is addressed. $ Means that the pixels in the reflective P state pass through the transmissive P state, even if the pixels are driven to the reflective P state during the next frame period. This can cause the visual epigenesis of the well-known black address bar. The problem with the advancement of this material arises from the delay in response time. For example,: To: The voltage should be at least 20 ms to change the state of the material into a sorrow. This material also has extremely strong temperature dependence. The bistable nature of the material at zero supply voltage means that displays using this material do not need to be continuously updated or rearranged. If the display information has not changed, then you can write the display-time ’and keep the display in the information delivery group_evil’ to extend the period of no power consumption. The result of using a cholesterol-type LCD is that the image can be updated slowly over a considerable period of time. However, the problems described above (especially the slow addressing response) have limited the further development of display technology in various applications. U.S. Patent No. 5,748,277 discloses a passive matrix addressing mechanism suitable for cholesterol-type displays in an attempt to shorten the addressing time. This mechanism relies on a rapid transition from the Η state to the p * state. If the voltage is turned off quickly, the transition to the P * state (and then to the P state) will be realized, and if the voltage is turned off slowly, the transition to the FC state will occur. The driving mechanism provides a three-stage address voltage curve. The first stage is the "selection stage", which is only ^ -5- This paper size applies to the Chinese National Standard (CNS) A4 specification (210X297 male I) 594643 A7 ----- ~ ______ _B7 V. Description of the invention (3) -Temple gate and indicate whether there is rapid or slow voltage shutdown. The other two phases can be performed at the same time, so that the average column addressing period of a large number of column pixels will tend to 1⑽. Although this addressing mechanism improves the addressing time, it does not solve the problems of temperature dependence (1 rapid south voltage switching or black addressing bar, etc.) According to the present invention, the present invention provides a display device including: a bistable asymmetric center nematic type Liquid crystal material layer; the active array substrate 'defines the ranks of pixel address circuits, and each pixel address circuit has an output for supplying a signal to a respective portion of the liquid crystal material; wherein each pixel address circuit Each includes a first switching device for switching a supply voltage to the remaining components of the pixel address circuit and is controlled by a row of address lines; a second switching device for allowing or preventing the supply voltage from being provided to Each component of the liquid crystal material is controlled by a selection line.-When the material is maintained in the p or FC state, the pixel switching device can avoid the transition to the Η state. Specifically, if the transition from the p state to the H state is avoided, In order to avoid the black addressing bar artifact, using a column address line to control the first switching device, And using a row of selection lines to control the second switching device to enable the supply voltage to be individually supplied to individual pixels. The supply voltage is the voltage required to cause the cholesterol material to be converted into a cymbal state. The device may further include a circuit for the A current discharge path used by the respective parts of the liquid crystal material to thereby reduce the amount of voltage on the respective parts of the liquid crystal material from the amount of supply voltage. This promotes the transition from the Η state to the FC or ρ -0-this paper standard applies China National Standard (CMS) A4 specification (210 X 297 mm)
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五、發明説明(4 ) 狀態。 該放電路徑最好包括一隔離開關及一電流接收(current sink) ’其中通過該電流接收的電流可被控制,以促使能夠 控制電壓量的下降速率。然後,控制速率促使能夠選擇是 否要轉換為P*狀態或轉換為FC狀態。例如,電流接收可包 括電曰曰體,遠電晶體的閘極係耦合至一電容器,其中在 電谷器上的電壓係由一電流鏡射(current mirr〇r)電路決定, 该電流鏡射電路取樣一輸入電流,該輸入電流被選取以提 供所要的電壓量下降速率。輸入電流可採用兩個數值的一 個數值,其中一個數值會導致轉換為FC狀態,而另一個數 值會導致轉換為P*狀態。 最好提供一第二行選擇線,用以將該輸入電流提供給像 素。因此’必須逐列執行輸入電流取樣。但是,一旦已取 樣一列的輸入電流,當取樣其他列的輸入電流時,就可將一 液晶材料放電。這意謂著,針對許多列,列定址週期趨向 於位於列定址線上之控制脈衝的持續時間,或取樣輸入電 流所需取樣時間。這些僅是非同時執行之不同列的像素驅 動h號。因此,可實施一種快速驅動機制。 該裝置最好包括一圖框儲存,用以依據前一及現行圖框 的像素輸出來決定要將該供應電壓提供給哪一些像素。 本發明還提供一種定址一雙穩態不對稱中心向列型液晶 顯示裝置的方法,該裝置包括一界定像素位址電路之行列 的主動陣列基板,其中每個像素位址電路均具有一個輸出 用以將一 k號供應至該液晶材料的各自部份,該方法包 594643 A75. Description of the invention (4) State. The discharge path preferably includes an isolating switch and a current sink ', wherein the current received through the current can be controlled to enable the rate of voltage drop to be controlled. The control rate then enables the selection of whether to transition to the P * state or to the FC state. For example, the current receiving may include an electric body, the gate of the remote transistor is coupled to a capacitor, and the voltage on the valley device is determined by a current mirror circuit, which is The circuit samples an input current that is selected to provide the desired rate of voltage drop. The input current can take one of two values, one of which will cause a transition to the FC state and the other will cause a transition to the P * state. A second row of select lines is preferably provided for supplying the input current to the pixels. Therefore, the input current sampling must be performed column by column. However, once the input current of one column has been sampled, a liquid crystal material can be discharged when the input current of other columns is sampled. This means that for many columns, the column addressing period tends to the duration of the control pulse on the column address line, or the sampling time required to sample the input current. These are only pixel numbers h of different columns that are not executed simultaneously. Therefore, a fast driving mechanism can be implemented. The device preferably includes a frame storage for deciding which pixels to supply the supply voltage to based on the pixel output of the previous and current frame. The invention also provides a method for addressing a bistable asymmetric center nematic liquid crystal display device. The device includes an active array substrate defining a row and a column of pixel address circuits, wherein each pixel address circuit has an output for In order to supply a k number to the respective parts of the liquid crystal material, the method pack 594643 A7
括下列步驟: 選擇一列像素,藉此將一 供應電壓提供給每個像素,該 供應電壓足以使該液晶材料到達膽固醇狀態; 決定該液晶材料的各自部件雲 ^ 1千而要將泫供應電壓供應給哪 一些像素’當不需要該供應電壓丰 电/至吋,會決定在前一圖框中 哪一些像素處於反射型平面妝 卞囬狀怨,而在現行圖框中哪一些 像素維持在反射型平面狀態。 將該供屢電壓提供給已決定需要該供應電壓的像素; 將-輸人電流提供列中的每個像素,該輸人電流具有兩 個數值的一個數值; 取樣該輸入電流; 促使該液晶材料之各自部件上的電壓量以一取決於該取 樣輸入電流的速率變更,其中針對被供應該供應電壓的像 素,該輸入電流的第一數值會導致該液晶材料採用一反射 型平面(P)狀態,而該輸入電流的第二數值會導致該液晶材 料採用一透光型焦點二次曲線(FC)狀態。 該方法促使能夠排除黑色定址條后生現象,並且避免高 電壓迅速切換。該輸入電流的第一數值最好大於該輸入電 流的第二數值,並且會導致加速該液晶材料上的電壓變化, 藉此導致從homeotropic (H)狀態轉換為瞬間平面(p*)狀態。 現在將參考附圖來詳細說明本發明的範例,其中: 圖1顯示雙穩態反射型膽固醇液晶的電光回應; 圖2顯示根據本發明之膽固醇顯示器的主動陣列像素電 路圖;The following steps are included: Select a row of pixels, thereby providing a supply voltage to each pixel, the supply voltage is sufficient to bring the liquid crystal material to the cholesterol state; determine the respective parts of the liquid crystal material ^ 1 thousand and supply the supply voltage Which pixels are given? When the supply voltage is not needed, it will determine which pixels in the previous frame are in the reflective plane, and which pixels remain in the reflective frame in the current frame. status. Provide the supply voltage to the pixels that have decided to require the supply voltage; supply-each pixel in the column with a current input that has one of two values; sample the input current; drive the liquid crystal material The amount of voltage on their respective components changes at a rate that depends on the sampled input current, where the first value of the input current for the pixel to which the supply voltage is supplied will cause the liquid crystal material to adopt a reflective planar (P) state And the second value of the input current will cause the liquid crystal material to adopt a transmissive focus quadratic curve (FC) state. This method facilitates the elimination of black addressing epigenetics and avoids rapid switching at high voltages. The first value of the input current is preferably greater than the second value of the input current, and will cause the voltage change on the liquid crystal material to be accelerated, thereby causing a transition from the homeotropic (H) state to the instantaneous plane (p *) state. An example of the present invention will now be described in detail with reference to the accompanying drawings, in which: FIG. 1 shows an electro-optical response of a bistable reflective cholesteric liquid crystal; FIG. 2 shows an active array pixel circuit diagram of a cholesterol display according to the present invention;
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圖3顯示圖2所示之電路的時序圖; 圖4顯示根據本發明之膽固醇顯示器的第二主動陣列像 素電路圖,用以允許交替供應電壓; 圖5顯示圖4所示之電路的時序圖; 圖6 ·’、員不根據本發明之膽固醇顯示器的第三主動陣列像 素電路圖,用以允許交替供應電壓; 圖7顯示圖6所示之電路的時序圖;以及 圖8顯禾根據本發明的顯示器。 在下面的說明書及申請專利範圍中有點任意定義「列」 及「行」。這些術語僅用來標示二維陣列元件,其中元件 群組對齊於兩條正交軸線。因此,顯示器「列」或「行」 可攸側邊至側邊或從上至下排列。 圖1顯示雙穩態反射型膽固醇液晶的電光回應。曲線呈 現從穩定的低電壓平面(Planar)或焦點二次曲線(F〇cal c〇nic) -狀態開始’在供應給定電壓的方波脈衝後的反射性。低於 V1的電壓不會改變材料的狀態。介於V 2與V 3之間的電壓脈 衝將材料切換成焦點二次曲線(F〇cal Conic)狀態,而高於v4 的電壓會導致平面(Planar)狀態。若要在液晶顯示器中使用 這種材料,材料被驅動至低供應電壓(<V〇的穩定平面 (Planar)或焦點二次曲線(F〇cai conic)狀態。然而,若要在平 面(Planar)與焦點二次曲線(Focal conic)狀態之間切換,則必 須將材料驅動至高電壓狀態(圖1中未顯示),其中材料透 光。在接著將這個高電壓從材料撤除的狀況指定材料緩和 至穩定的低壓狀態的方式。如果迅速撤除電壓,則材料會 -9 - 本紙張尺度通财® 8家標準(CNS) M規格㈣x 297公爱) —-FIG. 3 shows a timing diagram of the circuit shown in FIG. 2; FIG. 4 shows a second active array pixel circuit diagram of a cholesterol display according to the present invention to allow alternating voltage supply; FIG. 5 shows a timing diagram of the circuit shown in FIG. 4; Fig. 6 'shows a circuit diagram of a third active array pixel of a cholesterol display according to the present invention to allow alternating voltage supply; Fig. 7 shows a timing diagram of the circuit shown in Fig. 6; and Fig. 8 shows a circuit diagram according to the present invention. monitor. "Columns" and "rows" are defined somewhat arbitrarily in the description below and the scope of patent applications. These terms are only used to identify two-dimensional array elements where the group of elements is aligned on two orthogonal axes. Therefore, the display "columns" or "rows" can be arranged side-to-side or top-to-bottom. Figure 1 shows the electro-optical response of a bistable reflective cholesteric liquid crystal. The curve appears from a stable low-voltage plane (Planar) or focal quadratic curve (Focal-conic-state) 'after the supply of a square wave pulse of a given voltage. Voltages below V1 do not change the state of the material. A voltage pulse between V 2 and V 3 switches the material into a Focal Conic state, while a voltage higher than v4 will result in a Planar state. To use this material in a liquid crystal display, the material is driven to a stable plane (Planar) or focal quadratic (Focai conic) state with a low supply voltage (< VO). ) And the Focal conic state, the material must be driven to a high voltage state (not shown in Figure 1), where the material transmits light. Then the condition of removing this high voltage from the material designates the material to relax To a stable low voltage state. If the voltage is quickly removed, the material will be -9-this paper standard Tong Cai ® 8 standards (CNS) M specifications ㈣ x 297 public love) ---
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先通過瞬間平面(Transient Planar)狀態,接著才會緩和至穩 定的平面(Planar)狀態。如果緩慢撤除電壓,則材料緩和至 焦點二次曲線(F〇cai Conic)低電壓穩定狀態。 傳統的膽固醇顯示器驅動機制使用被動矩陣定址機制, 這可犯疋由於液晶記憶體效應。於定址機制的每個圖框週 期(field peri〇d)期間,均會造成材料逐漸變成透光的The transient plane (Transient Planar) state is passed first, and then it is eased to the stable plane (Planar) state. If the voltage is slowly removed, the material relaxes to a low voltage steady state of the Focai Conic. The traditional cholesterol display driving mechanism uses a passive matrix addressing mechanism, which can be a problem due to the liquid crystal memory effect. During each field period of the addressing mechanism, the material will gradually become transparent.
Home〇tropic狀態。這會引起如上文所述的黑色定址條后生 現象。 ~~ 本發明提供一種主動陣列定址機制,其中供應至列像素 的高電壓可選擇性切換至列中每個像素的液晶材料。因此 ’可私疋每個像素是否要通過H〇meotr〇pic狀態。針對處於 反射型平面(Planar)狀態的像素及維持在反射型平面(pianar) 狀態的像素,抑制Homeotropic狀態以避免黑色定址條問題。 圖2顯示本發明的第一主動陣列像素設定。每個像素均 是由第一列導線1〇「子列〇」定址,其用來定址一列像素 ,並且允許將高供應電壓Vprep供應至液晶材料。這個供應 電壓Vprep是在一供應電壓線12上提供。列導線10係耦合至 第一電晶體14的閘極,用以允許或防止將供應電壓供應至 其餘的像素。當一列像素被列導線1〇定址時,則會開啟列 中的所有的電晶體,使供應電壓到達該列中其餘像素的每 一像素。第二電晶體16允許或防止將供應電壓供應至膽固 醇液晶單元18,並且這個第二電晶體16的閘極係由行選擇 線20「子行〇」提供。列位址線1〇及行選擇線2〇 一起允許將 供應電壓供應給或隔離每列的個別像素。以此方式將某些 -10 · 本紙張尺度適财S S家標準(CNS) A4規格(210 X 297公^ ---—--Home〇tropic state. This will cause the black addressing bar as described above. The present invention provides an active array addressing mechanism in which a high voltage supplied to a column pixel can be selectively switched to the liquid crystal material of each pixel in the column. Therefore, it can be determined whether each pixel should pass the Homotrop Pic state. For pixels in a reflective plane (Planar) state and pixels maintained in a reflective plane (Pianar) state, suppress the Homeotropic state to avoid black address bar problems. FIG. 2 shows a first active array pixel setting of the present invention. Each pixel is addressed by a first column of wires 10 "sub-column 0", which is used to address a column of pixels and allows a high supply voltage Vprep to be supplied to the liquid crystal material. This supply voltage Vprep is supplied on a supply voltage line 12. The column conductor 10 is coupled to the gate of the first transistor 14 to allow or prevent the supply voltage from being supplied to the remaining pixels. When a column of pixels is addressed by the column conductor 10, all transistors in the column are turned on, so that the supply voltage reaches each pixel of the remaining pixels in the column. The second transistor 16 allows or prevents the supply voltage from being supplied to the cholesteric liquid crystal cell 18, and the gate of this second transistor 16 is provided by the row selection line 20 "subrow 0". Together, the column address line 10 and the row selection line 20 allow the supply voltage to be supplied to or isolate the individual pixels of each column. In this way, some of the -10 · This paper size is suitable for SS Standards (CNS) A4 specifications (210 X 297 public ^ --- ---
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594643 A7 B7 五、發明説明(8 ) 像素隔離供應電壓,以至這個像素不會導致或進入 Homeotropic狀態。具體而言,如果將像素從一圖框週期 (field period)的反射狀態驅動至下一圖框週期(field period)的 反射狀態,則第二電晶體16會被行選擇線20上的信號關閉 。當然,這需要圖框儲存,以至能夠記錄像素的現行狀態。 如上文所述,針對將膽固醇材料驅動至Homeotropic狀態 的像素,從Homeotropic狀態放電的狀況指定像素是否回到 透光型焦點二次曲線(Focal Conic)狀態,或回到反射型平面 (Planar)狀態。為了能夠控制放電狀況,提供電流鏡射電路 22以取樣位於第二行選擇線24「子行1」上的輸入電流。為 了實現這個取樣作業,將信號提供給第二列導線26「子列 1」,促使電流鏡射電路22執行取樣作業。第二列導線26 上的信號促使電流鏡射電路22中的兩個電晶體28、30變成 導電狀態,以至電流通過這兩個電晶體28、30沿著第二行 選擇線24流動。在這個階段,電流鏡射電路22的組件與其 餘的像素隔離’並且取樣電流’措此使電流從取樣電晶體 32流至接地34。當到達穩定狀態狀況,則會將取樣電晶體 32的適當閘極電壓儲存在電容器36上。另外,在這個穩定 狀態下,沒有任何電流流至電容器36。忽略取樣電晶體32 的閘極電流,沿著第二行選擇線24提供的所有電流均會通 過取樣電晶體32。 在取樣作業結束時,電晶體28、30被關閉,因為第二列 導線26上的脈衝終止。然後,隔離取樣電晶體32,但是具 有由電容器36決定的閘極-源極電壓,相當於汲極-源極電 -11 - 本紙張尺度適用中國國家標準(CNS) A4規格(210 X 297公釐) 594643594643 A7 B7 V. Description of the Invention (8) The pixel isolates the supply voltage so that this pixel will not cause or enter the Homeotropic state. Specifically, if the pixel is driven from the reflection state of one frame period to the reflection state of the next frame period, the second transistor 16 will be turned off by a signal on the row selection line 20 . Of course, this requires frame storage so that the current state of the pixels can be recorded. As described above, for pixels driving the cholesterol material to the Homeotropic state, the state of discharge from the Homeotropic state specifies whether the pixel returns to the Focal Conic state or the Planar state to the reflective state. . In order to be able to control the discharge condition, a current mirror circuit 22 is provided to sample the input current on the second row select line 24 "subrow 1". In order to achieve this sampling operation, a signal is provided to the second column of wires 26 "sub-column 1", causing the current mirror circuit 22 to perform the sampling operation. The signals on the second column of wires 26 cause the two transistors 28, 30 in the current mirror circuit 22 to become conductive, so that current flows through the two transistors 28, 30 along the second row selection line 24. At this stage, the components of the current mirror circuit 22 are isolated from its remaining pixels' and the sampling current is taken so that the current flows from the sampling transistor 32 to the ground 34. When a steady state condition is reached, the appropriate gate voltage of the sampling transistor 32 is stored on the capacitor 36. In addition, in this steady state, no current flows to the capacitor 36. Ignoring the gate current of the sampling transistor 32, all the current provided along the second selection line 24 will pass through the sampling transistor 32. At the end of the sampling operation, the transistors 28, 30 are turned off because the pulses on the second row of wires 26 are terminated. Then, the sampling transistor 32 is isolated, but has a gate-source voltage determined by the capacitor 36, which is equivalent to a drain-source voltage-11. This paper size applies the Chinese National Standard (CNS) A4 specification (210 X 297 mm) Centimeter) 594643
流等於從第二行選擇線24取樣的電流。 為了起始放電液晶材料18的供應電壓,使第三列導線% 「子列2」產生脈衝以開啟放電電晶體4〇 ,以允許電流從 取樣電晶體32流至接地34 ,以此方式放電液晶材料18。電 流流出液晶材料的速率係由通過取樣電晶體32流動的電流 決定,因此是由沿著第二行選擇線24提供的電流決定。因 此,第二行選擇線24指定整個液晶材料上電壓的下降速率 ’並且藉此決定像素的最後狀態。 圖3的日守序圖顯示這個處理程序。如上文所述,列導線 10上脈衝50允許將供應電壓供應給其餘的像素。此時,位 於行選擇線20「子行〇」上的位準指定是否允許將供應電 壓傳送至液晶材料18。因此,位於第一行選擇線2〇上的信 號會在兩個數值之間振盪,其中在對應於至少脈衝5〇持續 時間的時間間隔期間會維護一個數值。在脈衝5〇結束時,-電晶體16被關閉,以至液晶材料18被隔離。在此方式中, 整個材料上的電壓會維持一段^週期時間,於這段時間放 電電晶體40維持關閉狀態。這段ti時間是第三列導線%「子 列2」維持低位準狀態的期間。這個一段預備時間,以允 許材料到達Homeotropk狀態,並且通常介於2〇與6〇毫秒範 圍内。快到預備時間^結束時,會促使電流鏡射電路22取樣 位於第二行選擇線24上的輸入電流。這是由供應至第二列 導線26「子列1」的脈衝52實現。於這段時間期間,位於第 一行選擇線24上的位準係由電流鏡射電路22取樣。位於第 一行選擇線24上的信號會在兩個數值之間振盪,其中在對The current is equal to the current sampled from the second line selection line 24. In order to initiate the discharge of the supply voltage of the liquid crystal material 18, the third row of wires% "sub-column 2" is pulsed to turn on the discharge transistor 40 to allow a current to flow from the sampling transistor 32 to ground 34 to discharge the liquid crystal Material 18. The rate at which the current flows out of the liquid crystal material is determined by the current flowing through the sampling transistor 32, and is therefore determined by the current provided along the second line selection line 24. Therefore, the second selection line 24 specifies the rate of voltage drop across the liquid crystal material 'and thereby determines the final state of the pixel. The sequence diagram in Figure 3 shows this process. As described above, the pulses 50 on the column wires 10 allow the supply voltage to be supplied to the remaining pixels. At this time, the level on the "subrow 0" of the row selection line 20 specifies whether or not the supply voltage is allowed to be transmitted to the liquid crystal material 18. Therefore, the signal on the first selection line 20 will oscillate between two values, where a value is maintained during the time interval corresponding to at least the duration of the pulse 50. At the end of the pulse 50, the -transistor 16 is turned off so that the liquid crystal material 18 is isolated. In this manner, the voltage across the material will be maintained for a period of time, during which the discharge transistor 40 remains off. This period of time ti is the period during which the third-row wire% "sub-row 2" remains low. This is a preparation time to allow the material to reach the Homeotropk state and is usually in the range of 20 and 60 milliseconds. To the end of the preparation time ^, the current mirror circuit 22 is caused to sample the input current on the selection line 24 of the second row. This is achieved by a pulse 52 supplied to the second column of wires 26 "sub-column 1". During this time, the levels on the selection line 24 in the first row are sampled by the current mirror circuit 22. The signal on the first selection line 24 oscillates between two values, where
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594643 A7 ______ B7 五、發明説^ί^--- 應於脈衝52時序的時間間隔期間會維護這兩個數值的-個 數值。 圖3〖、員不陣列兩個接續列的時序圖。假設脈衝50與52具有 相同的寬度’如圖中所示的實例,相鄰列的時序只被這些 脈衝的I度(加入考慮到信號切換的額外警戒(guard)頻段) 取代。廷個預準時間ti可在相鄰像素之間重疊。另外,可 使用另一列像素中的脈衝取樣52的第二行選擇線電流信號 ,將列脈衝50同時供應給一列像素。 如果脈衝50與52具有不同的寬度,則相鄰列之間時間偏 移大體上對應於這兩個脈衝的最長持續時間。這意謂可實 施一種快速定址機制。 脈衝50的持續時間係按以多快的速率將液晶充電至供應 電壓vprep來指定。脈衝52的持續時間係按將電流鏡射設定 為作業的均衡狀態所需的時間。 與被動矩陣機制相比,可降低列所需的高電壓切換量。 私日日體14需要最高的電壓切換功能,這是由第一列導線工〇 控制。 本發明的像素促使能夠非常容易補償溫度變化。例如, 如果需要保證確實轉換成Homeotropic狀態,則可按溫度函 數來修改供應電學Vprep。同時地,第二行選擇線24上提供 的電流可按溫度函數來改變,以確保取樣的兩個電流量能 夠以所要的方式來控制材料的緩和。 圖2的電路顯示供應電壓Vprep係當作供應至顯示器所有 像素的固定電壓。但是,大部份液晶材料均需要將材料上 -13- 本紙張尺度it用中®國家料(CNS) A4規格(210 X 297讀) _ ' ---- 594643594643 A7 ______ B7 Fifth, the invention ^ ί ^ --- The two values should be maintained during the time interval of the pulse 52 timing. Fig. 3: Timing diagram of two consecutive columns in the array. Assuming that the pulses 50 and 52 have the same width, as in the example shown in the figure, the timing of adjacent columns is only replaced by the I degree of these pulses (adding an extra guard band that takes into account signal switching). The predetermined time ti may overlap between adjacent pixels. In addition, the second line of the pulse sampling 52 in the other column of pixels can be used to select the line current signal and the column pulses 50 can be simultaneously supplied to one column of pixels. If the pulses 50 and 52 have different widths, the time offset between adjacent columns generally corresponds to the longest duration of the two pulses. This means that a fast addressing mechanism can be implemented. The duration of the pulse 50 is specified by how fast the liquid crystal is charged to the supply voltage vprep. The duration of the pulse 52 is the time required to set the current mirror to the equilibrium state of the operation. Compared to the passive matrix mechanism, the amount of high-voltage switching required for a column can be reduced. The private sun body 14 needs the highest voltage switching function, which is controlled by the first row of conductors. The pixels of the present invention enable very easy compensation of temperature changes. For example, if you need to ensure that you do transition to the Homeotropic state, you can modify the supply electrical Vprep as a function of temperature. At the same time, the current provided on the second selection line 24 can be changed as a function of temperature to ensure that the two current quantities sampled can control the relaxation of the material in the desired manner. The circuit of Fig. 2 shows that the supply voltage Vprep is regarded as a fixed voltage supplied to all pixels of the display. However, most of the liquid crystal materials need to be placed on the material. -13- This paper size is used in the national material (CNS) A4 size (210 X 297 reading) _ '---- 594643
取樣作業相同,以至將電壓再次儲存至電容器36上,這個 電壓相當於對應於取樣電流之電晶體60的源極_汲極電流。 但是,流、經電晶體60的電流是要供應至液晶單元18的電流 ’而不是自液晶單元贿取的電流。因此,於放電循環期 間’電流路徑是從接地34、經過開關64、經過開關6〇、經 過第二放電開關40b至液晶材料。因此,電路的運作方式與 圖2所示的電路相同,但是是以負電壓運作。 圖5顯示的時序圖類似於圖3所示的g寺序圖,其中每隔圖 框週期(field period)會交替供應電壓。 S供應電壓疋正電壓日守,時序圖相當於圖3所示的時序 圖’其中第二放電電晶體4〇b被子列1關閉、電晶體62被子 列3開啟以及電晶體64被子列4關閉。 當供應電壓是負電壓時,於預準週期tl期間,列波形完 全一樣。因此,使用脈衝52進行電流取樣再次發生,其中 電晶體64處於關閉狀態、電晶體62處於開啟狀態,以及放 電開關40a、40b均處於關閉狀態。一旦已發生電流取樣, 在脈衝52結束時,第二放電電晶體40b被子列丨關閉,並且 在此情況下’電晶體64被子列4開啟以及電晶體62被子列3 關閉。 如圖所示,列導線數量從三條增加至六條,促使能夠將 取樣電流從液晶材料切換至接地,或從接地切換至液晶材 料。但是,可減少實施這個功能所需的列導線數量,並且 圖6顯示減少列導線數量的像素電路。 從圖5所示的時序圖可得知,子列1及4均在正供應電壓 -15- 本紙張尺度適财國®家標準(CNS) A4規格(210 X 297公爱)~" 一 ''The sampling operation is the same, so that the voltage is again stored on the capacitor 36, and this voltage is equivalent to the source-drain current of the transistor 60 corresponding to the sampling current. However, the current flowing through the transistor 60 is a current to be supplied to the liquid crystal cell 18, not a current drawn from the liquid crystal cell. Therefore, during the discharge cycle, the current path is from the ground 34, through the switch 64, through the switch 60, and through the second discharge switch 40b to the liquid crystal material. Therefore, the circuit operates the same way as the circuit shown in Figure 2, but operates at a negative voltage. The timing diagram shown in Fig. 5 is similar to the g-sequence diagram shown in Fig. 3, in which voltage is alternately supplied every frame period. S supply voltage 疋 positive voltage, the timing diagram is equivalent to the timing diagram shown in FIG. 3 'where the second discharge transistor 40b is turned off by sub-column 1, transistor 62 is turned on by sub-row 3, and transistor 64 is turned off by sub-row 4. . When the supply voltage is a negative voltage, the column waveforms are exactly the same during the pre-alignment period t1. Therefore, the current sampling using the pulse 52 occurs again, with the transistor 64 in the off state, the transistor 62 in the on state, and the discharge switches 40a, 40b being in the off state. Once current sampling has occurred, at the end of the pulse 52, the second discharge transistor 40b is turned off by the sub-row 丨, and in this case, the 'transistor 64 is turned on by the sub-row 4 and the transistor 62 is turned off by the sub-row 3. As shown, the number of column conductors increased from three to six, enabling the sampling current to be switched from liquid crystal material to ground, or from ground to liquid crystal material. However, the number of column wires required to implement this function can be reduced, and FIG. 6 shows a pixel circuit that reduces the number of column wires. From the timing diagram shown in Figure 5, it can be known that the sub-columns 1 and 4 are at a positive supply voltage of -15- This paper size is suitable for the financial country® home standard (CNS) A4 specification (210 X 297 public love) ~ " a ''
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Claims (1)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GBGB0024487.1A GB0024487D0 (en) | 2000-10-05 | 2000-10-05 | Bistable chiral nematic liquid crystal display and method of driving the same |
Publications (1)
Publication Number | Publication Date |
---|---|
TW594643B true TW594643B (en) | 2004-06-21 |
Family
ID=9900776
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
TW090123931A TW594643B (en) | 2000-10-05 | 2001-09-27 | Bistable chiral nematic liquid crystal display apparatus and method of addressing the same |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP1327237A1 (en) |
JP (1) | JP2004511019A (en) |
KR (1) | KR20020095166A (en) |
TW (1) | TW594643B (en) |
-
2001
- 2001-09-24 KR KR1020027006981A patent/KR20020095166A/en not_active Application Discontinuation
- 2001-09-24 JP JP2002533270A patent/JP2004511019A/en not_active Withdrawn
- 2001-09-24 EP EP01980435A patent/EP1327237A1/en not_active Withdrawn
- 2001-09-27 TW TW090123931A patent/TW594643B/en active
Also Published As
Publication number | Publication date |
---|---|
JP2004511019A (en) | 2004-04-08 |
EP1327237A1 (en) | 2003-07-16 |
KR20020095166A (en) | 2002-12-20 |
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