TW561293B - Bistable LCD driving method - Google Patents

Abstract

In consideration of saving electrical power, the present invention utilizes the bistable feature of cholesterol LCD (liquid crystal display) to achieve the purpose of suitably adjusting the voltage of the structure status for each stage (including homeotropic texture, planar texture and focal conic texture, so that the liquid crystal without being supplied with power still remains in the original stable status, so as to reduce the required power supply. When the cholesterol liquid crystal is in the above three main structure statuses, the screen exhibits different colors. The LCD display panel (having cholesterol or chiral liquid crystal) is applied with a suitable voltage at the initial display time to arrange the liquid crystal molecules in homeotropic texture. The voltage is suddenly dropped to a certain level to make the liquid crystal present a stable status of planar texture. Then, a lower voltage is added to make the liquid crystal remain in the stable status of planar texture, or a higher voltage is added to make the liquid crystal transform to the stable status of the focal conic texture. Finally, a development voltage is added, so that the stable status of liquid crystal structure, whether the liquid crystal continues to remain in the stable status of planar texture or changes the stable status of focal conic texture, can be developed more completely. The liquid crystal without being supplied with power still can be in the original stable status, and thus the required power supply is reduced.

Description

561293

[Technical field] (U two and two stable = previous technology wailing: under the trend of the mainstream of the market, flat display of various advanced technologies in addition to traditional LCD products, including new bistable = (B Bu Stable) LCD, ultra-high brightness Organic displays, such as high-efficiency and low-cost, are the niche products, and are ready to enter the future full-color flat-panel display market competition. Bistable LCDs are based on traditional super-twisted nematic (STN) ) LCD production line process uses "cholesteric liquid crystal" which is different from the traditional liquid crystal molecules in the past. The arrangement of the liquid crystal molecules causes the Bragg refiect ion to show the colors visible to the human eye. The biggest advantage of this LCD is that When the data screen is displayed, the previous screen can be maintained without power before the previous day is replaced by the next different screen, so almost zero power consumption can be achieved. 'For future actions When a phone or PDA can download data online for reading, it can save a lot of power. At the same time, the structure of the liquid crystal itself does not require polarizers. And the color filter has the function of reflecting colors, so the utilization of light can be greatly improved. [Summary of the Invention]

561293 _Case No. 89117877 _ Revised Year, Month and Day V. Description of the invention (2) Three main structures of cholesteric liquid crystal (as shown in the first and second figures) · (A) · Planar texture: liquid crystal molecules Aligned on two substrates in parallel, the incident light can be selectively reflected. The reflected wavelength can be adjusted according to the pitch of the pitch. Formula: wavelength = refractive index X pitch; λ = η X ρ. (B) · Focal Conic Texture: Liquid crystal molecules are scattered on two substrates. The incident light travels between the liquid crystal molecules and belongs to weak scatter ing. The color is usually milky white. When the background is black , Can be absorbed and appear black. (C) · Homeotropic Texture: · Liquid crystal molecules are arranged vertically on the two substrates, the path of incident light is not affected, and the color is transparent. When the background is black, it can be absorbed and appear black.

Bistable LCD has two stable states: Planar texture and Focal Conic texture. When the voltage is added to a Bistable LCD and gradually increases, the liquid crystal changes from the original Planar texture to the Focal Conic texture and then to the Homeotropic texture. If the voltage increases to a certain level The degree is completely homeotropic. If this time

561293 --- tit, 89117877__ year, month, day, and revision_ 5. Description of the invention (3) When the voltage is quickly removed, the unstable state of Η 〇me 〇tr 〇 picte Xture changes, and the stable state of P 1 anartexture appears at this time Color reflection; if the voltage is slowly removed, the molecular arrangement will return to the stable state of 'Focal Conic texture' 'Wang Xianyuejing color', and these two steady states (atzerofie 1 d) also have a good relative contrast in optical properties. The B i s t a b 1 e L C D driving method has been driven by using the above characteristics. At present, several methods have been proposed, but most of them have similar structures. Its architecture is first added to the Bistable LCD-high voltage enough to transform into a Homeotropic texture.

Planar texture or Focal Conic texture is stable. Therefore, based on the specificity of the molecular structure and the control of the driving voltage, we can design reflective color LCDs that do not require polarizers, color filters, and reflectors to achieve high brightness requirements.

Formula embodiment LL An embodiment of the present invention is a dot-matrix display, which will be described in conjunction with the third figure: We initially display on an LCD display substrate (cholesteric or liquid crystal with optical chiral) An appropriate voltage makes the liquid crystal molecules align in the Homeotropic texture, and then the voltage suddenly drops to a certain level, so that the liquid crystal in the substrate shows a P 1 anartexture stable state.

561293 _Case No. 89117877 Amendment __ V. Description of Invention (4) State. With this stable state as the reference state, a lower voltage is applied to the daylight plane to continue to stay in the p 1 anarte X ture stable state, or a higher voltage is applied to the liquid crystal in the pixel to Planar texture transitions from stable to Focal Conic texture. Finally, a further development voltage is added to make the liquid crystal structure in its stable state develop more completely regardless of whether the liquid crystal stays in the stable state of p 1 anarte X ture or changes to the stable state of Foca 1 C ο nictexture. The LCD can still be in the original stable state without power supply. [Driving method] I. Bistable LCD reflective black and white driver, as shown in Figures 4 (a) to 4 (g): Figure 4 (d) shows the structure of a bistable liquid crystal display panel. Scanning electrodes Row 1 ~ m are applied to the substrate, display electric columns Columnl to η are displayed in the lower glass substrate, and bistable cholesterol-type night crystals are arranged between the upper and lower glass substrates. In the fourth image (a), the left image is to make the liquid crystal finally present a plane reflective texture (Planar texture), and the right image is to make the liquid crystal finally exhibit a pyramidal texture (Focal Conic Texture). The voltage, time and voltage applied to the bistable liquid crystal display Relationship between liquid crystal states. The description is as follows: ^ pole 1 · A voltage VI is applied before the LCD Panel to make the liquid crystal present a vertical structure

561293 ---- Wei 89117877_year month ^ _ V. Description of the invention (5) " (Homeotropic texture), at this time, regardless of the previous day, the surface is cleared. 'The time required is inversely proportional to the applied voltage V1, The higher the applied voltage V1, the shorter the time required for the liquid crystal to exhibit a vertical texture, and vice versa. 2. Make the liquid crystal molecules in the vertical structure (Hommetropic texture) voltage VI, and instantly reduce the voltage applied to this display to a certain level (from VI-V2), so that the liquid crystal turns to a plane reflecting tissue (Plariar texture) Steady state, usually the voltage V2 is below 1 OV, we can add 0V to the scan electrode and the signal electrode respectively, so that the LCD Panel drops from VI to 0ν. 3. With the plane reflection texture (pianar texture) stable state as the reference state, the voltage V2 rises to V3, and the voltage V3 keeps the liquid crystal state in the plane reflection texture (Planar texture) but not enough to change it into a pyramidal texture (Focal Conic Texture) ) State, if V2 rises to V4, and the voltage V4 is sufficient to change the liquid crystal state from a planar reflective texture (Planar texture) to a pyramidal texture (Focal Conic Texture) status. 4 · Finally, a development voltage V 5 is added to complete the development of the liquid crystal structure in a stable state. In the figure, Η indicates a vertical structure (Homeotropic texture), P indicates a planar reflection structure (Planar texture), and F indicates a pyramidal structure (Focal Conic Texture). ); VI ~ V5 are the voltages applied to the bistable liquid crystal display (ie, the voltage difference between the scan electrode and the display electrode).

561293 Case No. 89117S77 V. Description of the invention (6) Monthly correction of the 2-point matrix display implementation bin (None in j & use the above-mentioned electric dust directly ^ 'Because all daylight elements will be all bright or all dark. Use the above "'Xiaohe timing difference scan generation-feasible method, hereby explain as follows: The fourth figure (b) is the voltage v 1' Make the liquid crystal present a vertical structure (jome〇tropic texture) in the scan electrode and display electrode implementation method> ^ The tracing electrode voltage is a periodic change of V1A0 volts, and the display electrode is 0 and volts. The scan electrode and the display electrode are out of phase, and the voltage applied to the liquid crystal is a cyclic change of + V1 and -V1. This = The four pictures show that the planar reflection texture (planar texture) is stable: the reference shape makes the liquid crystal remain in the planar reflection texture (p anar = xtUre) or develops into a pyramidal texture (Focal connic). To realize the method of stinging the voltage between the scanning electrode and the signal electrode: = Planar texture (Planar texture) stable state as the reference state to perform the time difference scanning method. V6, the voltage between non-selective days is V7, and the selection voltage for the display electrodes is V8, and the OFF voltage is V9. If the daylight is ⑽ during the selection period, the selection voltage for the scan electrodes is V6 The voltage of the display electrode is V8, and the voltage IV6-V8 applied to the LCD Panel needs to be sufficient to change the liquid crystal from a planar reflective structure (Planar texture) stable state to a pyramidal structure (Focal Conic Texture) stable state. Conversely, if the daylight is OFF during the selection period, the voltage applied to the LCD Panel | V6—V9 | should not be sufficient to cause the liquid crystal to transition from the stable state of the Planar texture to the stable state of the Focal Coonic Texture. Page 10 561293

2 · During the daytime non-selection period, V7, 俨 觫 f + r will be added to the selection voltage of the old known electrode is disgust IV7 wi々iV or 9, which is added to the 1 ^ Panel's electric calendar | V V V8 or V7- VQI Hh ^ ^, ^ / ρ 1 I, white should not be enough for the liquid crystal to reflect from the plane, and and 'I (P1 anarte X ture) 卞 ^ · J ^ 怨 怨 向 toward the pyramidal structure (Focal

Conic Texture) steady state transition. 3. Where | V7-V8 | = | V7—VQ II uo ,, I 1 ^ V9 丨, 丨 V6 — V8 I is equal to V4 in the fourth figure (a), | V6-V9 I is equal to the fourth figure (a) V3. The fourth figure (e) is the relationship between voltage and time of the scanning electrode in a scanning frame during spiritual use. The fourth graph (f) is a graph of the voltage and time of the signal electrode within a scanning frame time. The fourth graph (g) is a graph of the voltage and time relationship of the liquid crystal applied to the pixels in the scanning frame time within each scanning frame, that is, the graph (e) the scanning electrode voltage minus the graph (f) the signal electrode voltage. It is known from the day element 11 (1) 46111) that the voltage applied to the pixel 11 first adds a VI to make the liquid crystal present a vertical structure (Homeotropic texture) and then suddenly drop to V2, so that the liquid crystal turns to a plane reflective structure (P1 anar texture). During the scanning time, we found that in addition to | V7-V8 |, | V7-V9 | voltage, there is still a V4 voltage applied to pixel 11, this V4 voltage causes the liquid crystal to change from a planar reflective structure (Planar texture) to a pyramid shape. Tissue (Foca 1 C nic T e X ture) steady state.

Page 11 561293 -89117877 _ only month _ correction _____ V. Description of the invention (8) However, the day element 12 and 21 only have yg voltage and 丨 |, | V7-V9 丨 voltage during the time of the description, so The two pixels are kept in a stable state of the planar reflection tissue (pianar te X ture). 2. Bistable LCD gray-scale driving, as shown in the fifth graph (a) to the fifth graph (c): The fifth graph (a) shows the applied voltage and reflectivity in a fixed period of time (relative to the color brightness) The relationship diagram; the fifth diagram (b) is the relationship between the application time and the reflectance at a constant voltage.

The Bistable LCD gray-scale driving is to use the result of the fifth figure (b), using a certain voltage to cause different reflection effects due to the length of time applied. In the driving method described above, a high voltage is applied to cause the liquid crystal molecules to change to the Homeotropic state, and then relax to the Planar state, and then perform timing difference scanning. The scan drive waveform is still the same as the above. During the scan selection time, the waveform of the display electrode distinguishes the voltage V8 that can change the liquid crystal molecules from the p ⑽ order state to the Focal Conic state and the incapable liquid crystal molecules from the punar state to Focal. The voltage V9 in the Conic state is determined by the grayscale state that the day element will present. V8 and V9 are selected, and then the time ratio occupied by the time is selected, resulting in different grayscale levels. The driving waveform of the display electrode is shown in the fifth figure. (C), where T1 is the time selected during scanning. 561293 _Case No. 89117877_ Modification of the month and year _ Brief description of the diagram [Schematic description] The first picture is a schematic diagram of the three main structures of the cholesterol-type liquid crystal The second picture is the schematic diagram of the three main structures of the cholesterol-type liquid crystal The third picture is The fourth schematic diagram of the liquid crystal structure of the dot matrix display according to the embodiment of the present invention. The fourth diagram (a) to the fourth diagram (g) are the schematic diagrams of the B is tab 1 e LCD reflective color driving method of the embodiment of the present invention. ) ~ Fifth figure (c) is a schematic diagram of a grayscale driving method for a Bistable LCD according to an embodiment of the present invention

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Claims (1)

561293 = ^ Emission type color driving method, in which Planar texture is used as a reference state, and the steps of the time-difference scanning method include: U) scanning electrodes to provide a selection voltage V6, a non-selection voltage V7, A signal electrode provides an ON voltage V8, and a 10FF voltage is V9; (If the b pixel is ⑽ during the selection period, the scan selection voltage is Vj " The Hai Hai voltage is V8 'added to the LCD Panel voltage V6-V8 丨 and Kuma, so that the liquid crystal from the Planar texture stable state to the CD industrial Conic texture stable state; (c) if the pixel is selected within the period of 0, ??, the voltage of lCD Panel IV6 V9 | , Which is not enough to make the liquid crystal transition from the pianar texture stable state to the Focal Conic texture state; (d) During the daytime non-selection period, the voltage of the scan electrode is V7, and the signal voltage is V8 or V9, where the voltage applied to the LCD Panel is | V7-V8 丨 or IV7-V9 丨 'are not enough to make the liquid crystal change from the stable state of pianar texture to the stable state of Focal Conic texture. (E) Apply a development voltage V5 to make the stable liquid crystal structure develop more completely. 5 · — The gray-scale driving method of a bistable liquid crystal display uses different lengths of time to apply a constant voltage, resulting in different degrees of reflection, including: adding a high voltage to make the liquid crystal molecules into a Η 〇me 〇tr 〇pic state Relax to Planar state; Perform a timing difference scan; 561293 6. Scope of patent application-^ Provide a voltage V4, which can change the liquid crystal molecules from the Planar state to the Focal Conic state; and a voltage V3 is not able to change the liquid crystal molecules from the Planar state to Focal Connic The voltage ratio of the state; the ratio of the time occupied by each voltage selected by the day-to-day knife (the level of grayscale that causes different passes) is determined by the grayscale state of the pixel to select the time of the voltage V3 or above. 6. The gray level driving method of the bistable liquid crystal display as described in item 5 of the scope of patent application, wherein the step of performing the timing difference scanning method on the driving waveform of the timing difference scanning includes: (a) scanning The electrode provides a selection voltage V6, a non-selection voltage V7, a signal electrode provides an ON voltage V8, and an OFF voltage is V9; (b) if the pixel is ON during the selection period, the scanning selection voltage is V6, The voltage ^ is vg, and the voltage applied to the LCD Panel | V6-V8 | and time 'causes the liquid crystal to change from the stable state of the Planar texture to the stable state of the pocai Conic texture; (c) If the pixel is 01 ^ during the selection period, Then the LCD panel voltage IV6-V9 | 'is not enough to make the liquid crystal transition from the pianar texture stable state to the Focal Conic texture state; (d) during the non-selection period of the pixel, the voltage V7 of the scan electrode, the signal voltage is V8 or V9, The voltage applied to the LCD Panel is | V7-V8 | or IV7-V9 |, which are not enough to change the liquid crystal from the stable state of p! Anar texture to the stable state of Focal Conic texture. (e) The selection of voltage V3 or voltage V4 is determined by the grayscale state that the pixel is intended to present. 561293 Page 17