RU2118839C1 - Liquid-crystal screen with active matrix - Google Patents

Abstract

FIELD: liquid-crystal screens. SUBSTANCE: proposed screen includes first insulating substrate, assemblage of address wires formed on first insulating substrate one in parallel to another, assemblage of data wires formed on first insulating substrate perpendicular to address wires, assemblage of image elements formed on first insulating substrate in the form of matrix of lines and columns arranged between address and data wires correspondingly. Each image element has at least tow image electrodes insulated one from another and two switching over transistors as minimum. In compliance with invention each image element includes two additional capacitors

and

. First additional capacitor is connected

to second data wire and to first image electrode and second additional capacitor is connected

Description

 This invention relates to active matrix liquid crystal screens (LCDs), in particular LCDs with compensation for the effect of uneven screen luminescence caused by the influence of stray capacitances between the image electrodes and the data lines on the voltage of the image electrode of the liquid crystal cell.

A known design of a liquid crystal screen containing two substrates, between which is placed a layer of liquid crystal. An active matrix is formed on one substrate, containing a plurality of address buses 1-2 - 1-n, a plurality of data buses 2-1 - 2-m located orthogonally with respect to the address buses, and a plurality of image elements located between the address buses and data buses and forming a matrix consisting of n rows and m columns (Fig. 1). Each image element contains a thin-film switching transistor 3 (hereinafter referred to as TFT) and an image electrode 4, which is connected to the address bus and the data bus through the switching transistor 3. A common electrode 5 is formed on another substrate, to which a common voltage V _o is applied. The electrodes 4, 5 and the liquid crystal contained between them form a capacitor C _LCD , which is a memory element of each image cell.

где
U_g - напряжение на затворе ТПТ, поступаемое с адресной шины;
C_gs - паразитная емкость между затвором и истоком ТПТ;
C_LC - емкость между электродом изображения и общим электродом.The disadvantage of the design of the liquid crystal screen is the presence of a known effect of flickering due to the influence of stray capacitance between the gate and the source of the switching transistors on the voltage of the image electrode. In this case, the voltage at the image electrode changes by ΔU:

Where
U _g is the voltage at the gate of the TFT coming from the address bus;
C _gs is the parasitic capacitance between the gate and the source of the TFT;
C _LC is the capacitance between the image electrode and the common electrode.

Since C _LC varies depending on the state of the liquid crystal, the change in voltage ΔU is not a constant value for all image cells, which causes great difficulties in compensating for this change.

и

сформированных с помощью двух электродов изображения 4' и 4'' и общего электрода 5, изолированного от других общих электродов других элементов изображения.A known design of a flat screen with an active matrix, which allows to eliminate this drawback. In this design (FIG. 2), the liquid crystal cell capacitor consists of two series-connected capacitors

and

formed using two image electrodes 4 'and 4''and a common electrode 5, isolated from other common electrodes of other image elements.

и

подключены с помощью двух переключающих транзисторов 3' и 3'' к двум шинам данных и одной адресной шине. Так как на электроды 4' и 4'' от адресной шины через одинаковые паразитные емкости C_gs переключающих транзисторов 3' и 3'' поступает одно и то же напряжение, то изменения напряжения между электродами 4' и 4'' не происходит и так называемый эффект "мерцания" практически исключается.In this design, the common electrode 5 is a "floating" electrode. Capacitors

and

connected using two switching transistors 3 'and 3''to two data buses and one address bus. Since the same voltage is applied to the electrodes 4 'and 4''from the address bus through the same stray capacitances C _{gs of the} switching transistors 3' and 3 '', the voltage does not change between the electrodes 4 'and 4''and the so-called the flicker effect is virtually eliminated.

и

на величину

где
C_ds=C′_ds=C″_ds- суммарная емкость между стоком и истоком ТПТ и между электродом изображения и шиной данных;

На фиг. 3 приведена эквивалентная схема одной жидкокристаллической ячейки с емкостями между стоком и истоком ТПТ и между электродами изображения и шинами данных -

обозначенными 6' и 6'' соответственно и емкостями между электродами изображения и адресной шиной и между затвором и истоком ТПТ

обозначенных 7' и 7'' соответственно.However, such an active matrix flat screen design has the following significant drawback. During the operation of the screen in one half-time period, the data buses 2 + 2 ', 2-2' - 2-m ', 2-1'',2-2''-2-m''receive voltage + V _d and - V _d (or + 2V _d and 0), respectively, and during another half-cycle, respectively -V _D and + V _D (or 0 and + 2V _d ). When you change the polarity of the video signal on the data bus is recharging

and

by the amount

Where
C _ds = C ′ _ds = C ″ _ds is the total capacitance between the drain and the source of the TFT and between the image electrode and the data bus;

In FIG. 3 shows the equivalent circuit of one liquid crystal cell with capacitances between the drain and the source of the TFT and between the image electrodes and the data buses -

marked 6 'and 6''respectively and capacitances between the image electrodes and the address bus and between the gate and the source of the TFT

designated 7 'and 7'', respectively.

In FIG. 4 shows the voltage waveform at various points in the circuit of FIG. 3, where U _α is the voltage on the data buses, U _α1 is the voltage on the address bus located at the top of the screen, U _αn is the voltage on the address bus located at the bottom of the screen, U _LC1 is the voltage between the image electrode and the common electrode for liquid crystal cell located in the upper part of the screen, U _LCn is the voltage between the image electrode and the common electrode of the liquid crystal cell located in the lower part of the screen. From FIG. 4 it follows that the effective voltage applied to the LCD cells at the top and bottom of the screen will be different, which leads to different screen brightness in these parts, and therefore, the image quality is significantly deteriorated. The considered LCD design also has low reliability, since the failure of any of the two TFT image elements leads to the failure of this image element. In addition, the considered LCD design has a low aperture ratio, since a decrease in the gap between the image electrodes and data buses leads to an increase in capacitance between them and, consequently, to an increase in the unevenness of the screen glow, as discussed above.

 The basis of the invention is the creation of an active matrix liquid crystal screen having high image transmission quality by reducing the influence of the capacitance between the drain and the source of the switching transistors and the capacitance between the image electrodes and data buses on the voltage value on the image electrodes, increasing the reliability of the liquid crystal screen due to reservation switching transistors, as well as increasing the aperture ratio by reducing the gap between the electrodes Images and data buses.

, между вторым электродом изображения и адресной шиной имеется емкость

, между первым электродом изображения и первой шиной данных имеется емкость C′_ds′ , между вторым электродом изображения и второй шиной данных имеется емкость

, вторую изолирующую подложку, множество общих электродов, сформированных на второй изолирующей подложке, причем каждый из этих общих электродов изолирован друг от друга и расположен над первым и вторым электродами изображения, жидкий кристалл, помещенный между первым и вторым электродами изображения и общим электродом, согласно изобретению каждый элемент изображения содержит два дополнительных конденсатора

и C″_ad′ , причем первый дополнительный конденсатор C′_ad присоединен к второй шине данных и к первому электроду изображения, а второй дополнительный конденсатор C″_ad присоединен к первой шине данных и к второму электроду изображения.The problem is solved in that in a liquid crystal screen with an active matrix containing a first insulating substrate, a plurality of address lines 1-1 to 1-n formed on the first insulating substrate parallel to each other, a plurality of first data lines 2-1 ', 2-2 '- 2-m' and a plurality of second data buses 2-1 ''',2-2''-2-m''located parallel to it, formed on the first insulating substrate perpendicular to the address lines, a plurality of image elements formed on the first insulating substrate in the form of a matrix of rows and columns, located between the address buses and data buses, respectively, each image element contains at least two image electrodes isolated from each other and at least two switching transistors, the drain of the first switching transistor connected to the first data bus, the drain of the second switching transistor connected to to the second image electrode, the source of the first switching transistor is connected to the first image electrode, the source of the second switching transistor is connected to the second bus data, and the gates of the first and second switching transistors are connected to the 1-n address bus, where n = 1, 2, 3, and there is a capacitance between the first image electrode and the address bus

, there is a capacitance between the second image electrode and the address bus

, there is a capacitance C ′ _{ds ′} between the first image electrode and the first data bus, there is a capacitance between the second image electrode and the second data bus

, a second insulating substrate, a plurality of common electrodes formed on the second insulating substrate, each of these common electrodes being isolated from each other and located above the first and second image electrodes, a liquid crystal placed between the first and second image electrodes and the common electrode according to the invention each image element contains two additional capacitors

and C ″ _{ad ′} , wherein the first additional capacitor C ″ _{ad is} connected to the second data bus and to the first image electrode, and the second additional capacitor C ″ _{ad is} connected to the first data bus and to the second image electrode.

использовались два дополнительных переключающих транзистора, причем у одного из них сток присоединен к первой шине данных, исток присоединен к второму электроду изображения, у другого из них сток присоединен к первому электроду изображения, исток присоединен к второй шине данных, а затворы обоих дополнительных переключающих транзисторов присоединены к адресной шине следующего ряда, причем затворы дополнительных переключающих транзисторов последней строки матрицы присоединены к дополнительной адресной шине 1- (n+1).It is desirable that as the first and second additional capacitors

two additional switching transistors were used, one of them having a drain connected to the first data bus, the source connected to the second image electrode, the other of them connected to the first image electrode, the source connected to the second data bus, and the gates of both additional switching transistors connected to the address bus of the next row, and the gates of the additional switching transistors of the last row of the matrix are connected to the additional address bus 1- (n + 1).

были сформированы путем перекрытия электродами изображения шин данных и адресных шин или путем перекрытия шинами данных и адресными шинами электродов изображения.Preferably capacitors

were formed by overlapping with the image electrodes the data buses and address lines or by overlapping the data lines and address lines of the image electrodes.

определялись из уравнений

.It is desirable that the capacitance of the capacitors

determined from equations

.

 Using the distinguishing features of this invention allows to solve the problem of creating a liquid crystal screen with an active matrix having high image transmission quality by reducing the influence of capacitance between the drain and source of switching transistors and capacitance between image electrodes and data buses on the magnitude of voltage on image electrodes, increasing reliability LCD screen due to the reservation of switching transistors, as well as increasing the aperture Nogo ratio by reducing the gap between the electrodes of the image and data buses.

и

на величину

При этом эффективное напряжение между электродом изображения и общим электродом для жидкокристаллических ячеек, находящихся в верхней части экрана, будет составлять величину ~V_α, а для нижней части экрана ~(V_D-ΔV/2). Это приводит к различной яркости свечения экрана в верхней и нижней частях. В отличие от этого в патентуемой конструкции жидкокристаллического экрана с активной матрицей, показанной на фиг. 5, между электродами изображения и шинами данных подключены дополнительные конденсаторы 8' и 8'', которые позволяют величину ΔV сделать малой и таким образом ликвидировать эффект неравномерности свечения экрана в различных частях. На фиг. 6 приведена эквивалентная схема одной жидкокристаллической ячейки экрана с дополнительными емкостями

Для того, чтобы в патентуемой конструкции ЖКЭ полностью исключить эффект неравномерности свечения экрана в верхней и нижней частях, величины дополнительных емкостей

и

должны быть определены в соответствии со следующими двумя условиями (требованиями). Во-первых, при изменении напряжения на шине данных 2-1' (при выключенных транзисторах 3' и 3'') в точках b и c изменения напряжений должны быть одинаковыми по величине и по знаку. Во-вторых, при изменении напряжения на шине данных 2-1'' (при выключенных транзисторах 3' и 3'') в точках b и c изменения напряжений также должны быть одинаковыми по величине и по знаку. При выполнении этих условий перезарядки емкостей

и

не происходит при изменении напряжений на шинах данных 2-1' и 2-1''. Указанные условия выражаются двумя уравнениями:

Кроме того, если емкости

и

являются достаточно большим, то необходимо выполнение еще одного условия, которое должно исключать появление эффекта "мерцания" ЖКЭ и которое имеет место вследствие перезарядки

и

при изменении напряжения на адресной шине. Это условие заключается в следующем. При изменении напряжения на адресной шине 1-1 (при выключенных транзисторах 3' и 3'') в точках b и c изменения напряжения должны быть одинаковыми по величине и по знаку. При выполнении этого условия перезарядки емкостей

и

не происходит при изменении напряжения на адресной шине 1-1. Это условия выражается уравнением

Решая уравнения (3), (4), (5) относительно

и

получим

Обычно в конструкциях ЖКЭ с активной матрицей

.As mentioned above in the prototype, when changing the polarity of the video signal on the data buses, the capacitors recharge

and

by the amount

In this case, the effective voltage between the image electrode and the common electrode for liquid crystal cells located in the upper part of the screen will be ~ V _α , and for the lower part of the screen ~ (V _D -ΔV / 2). This leads to different brightness of the screen in the upper and lower parts. In contrast, in the patented design of the active matrix liquid crystal screen shown in FIG. 5, between the image electrodes and the data buses, additional capacitors 8 'and 8''are connected, which allow the ΔV value to be made small and thus eliminate the effect of uneven illumination of the screen in different parts. In FIG. Figure 6 shows an equivalent circuit of one liquid crystal cell of the screen with additional capacities

In order to completely eliminate the effect of non-uniformity of the luminescence of the screen in the upper and lower parts in the patented LCD design, the values of additional capacities

and

must be determined in accordance with the following two conditions (requirements). Firstly, when the voltage on the data bus 2-1 'changes (when the transistors 3' and 3 '' are off) at points b and c, the voltage changes should be the same in magnitude and sign. Secondly, when the voltage on the data bus 2-1 '' changes (when the transistors 3 'and 3''are off) at points b and c, the voltage changes should also be the same in magnitude and sign. When these recharge conditions are met

and

does not occur when voltage changes on 2-1 'and 2-1''data buses. These conditions are expressed by two equations:

Also, if the tanks

and

are large enough, it is necessary to fulfill one more condition, which should exclude the appearance of the “flicker” effect of the LCD and which occurs due to recharging

and

when the voltage on the address bus changes. This condition is as follows. When the voltage on the address bus 1-1 changes (when the transistors 3 'and 3''are off) at points b and c, the voltage changes should be the same in magnitude and sign. When this condition is recharged containers

and

does not occur when the voltage on the address bus 1-1 changes. This condition is expressed by the equation

Solving equations (3), (4), (5) with respect to

and

we get

Usually in LCD designs with an active matrix

.

Выбор емкостей конденсаторов

и

в соответствии с уравнениями (6) и (7) обеспечивает исключение эффекта неравномерности свечения экрана и эффекта мерцания в патентуемой конструкции ЖКЭ.Therefore, for such LCD designs

Capacitor Capacitance Selection

and

in accordance with equations (6) and (7), it eliminates the effect of uneven screen glow and flicker in the patented LCD design.

и

используются два дополнительных переключающих транзистора, у которых емкости между стоком и истоком и между затвором и истоком соответствуют уравнению (6) или (7). Схема подключения дополнительных переключающих транзисторов 9' и 9'' показана на фиг. 7. Исток переключающего транзистора 9'' подключен к электроду изображения 4'', а исток - к шине данных 2-1', исток переключающего транзистора 9' подключен к шине данных 2-1'', а сток - к электроду изображения 4'. Затворы обоих переключающих транзисторов подключены к последующей адресной шине 1-2. Затворы дополнительных переключающих транзисторов последней строки матрицы подключены к дополнительной адресной шине 1 - (n + 1). Надежность работы такого ЖКЭ с активной матрицей значительно выше, чем надежность работы ЖЭК по схеме фиг. 5, так как выход из строя в одной жидкокристаллической ячейке одного или двух переключающих транзисторов, подключенных к одной адресной шине, не приводит к отказу этой жидкокристаллической ячейки.To increase the reliability of the LCD with an active matrix as additional capacitors

and

two additional switching transistors are used, in which the capacities between the drain and the source and between the gate and the source correspond to equation (6) or (7). A connection diagram for additional switching transistors 9 ′ and 9 ″ is shown in FIG. 7. The source of the switching transistor 9 '' is connected to the image electrode 4 '', and the source to the data bus 2-1 ', the source of switching transistor 9' is connected to the data bus 2-1 '', and the drain to the image electrode 4 ' . The gates of both switching transistors are connected to a subsequent address bus 1-2. The gates of the additional switching transistors of the last row of the matrix are connected to the additional address bus 1 - (n + 1). The reliability of such an active matrix LCD is significantly higher than the reliability of the housing operation according to the scheme of FIG. 5, since failure in one liquid crystal cell of one or two switching transistors connected to the same address bus does not lead to failure of this liquid crystal cell.

можно формировать путем перекрытия электродами изображения шин данных и адресных шин или перекрытия шинами данных и адресными шинами электродов изображения. На фиг. 8 показана топология участка активной матрицы ЖКЭ, выполненной таким образом, что электроды изображения 4' и 4'' перекрывают в плане шины данных и адресные шины. При этом в местах перекрытия сформированы конденсаторы

Такая конструкция ЖКЭ обеспечивает очень высокое апертурное отношение.To increase the aperture ratio of LCE capacitors

can be formed by overlapping image buses of data buses and address buses, or overlapping data buses and address buses of image electrodes. In FIG. 8 shows the topology of the portion of the active matrix of the LCD, made in such a way that the image electrodes 4 'and 4''overlap in terms of data buses and address buses. At the same time, capacitors are formed in the overlapping places

Such an LCD design provides a very high aperture ratio.

 Below with reference to the accompanying drawings are examples of specific implementations of the present invention.

 In FIG. 1 shows a diagram of a known active matrix LCE.

 In FIG. 2 shows a diagram of an LCD with an active matrix and a “floating” common electrode, selected by the authors as a prototype.

 In FIG. 3 shows a diagram of one liquid crystal cell with spurious capacitances between the drain and the source of the switching transistors.

 In FIG. 4 shows the voltage waveform at various points of the liquid crystal cell.

 In FIG. 5 shows a diagram of an active matrix LCE made in accordance with claim 1 of the claims of the patented invention.

 In FIG. 6 shows an equivalent circuit of a liquid crystal cell of an LCD made in accordance with claim 1 of the claims of the patented invention.

 In FIG. 7 shows a diagram of an active matrix LCE made in accordance with claim 2 of the claims of the patented invention.

 In FIG. 8 shows the topology of a portion of an active matrix of an LCE made in accordance with claim 3 of the claims of the patented invention.

 In FIG. 9 shows a cross section along axis AA of FIG. eight.

 In FIG. 10 shows a variant of the LCD scheme made in accordance with claim 2 of the claims of the patented invention.

 In FIG. 11 shows the topology of a portion of an active matrix made in accordance with claim 2 of the claims of the patented invention.

обозначенными на схеме индексами 8' и 8'' соответственно, выполненного в соответствии с п.1 патентуемого изобретения.In FIG. 12 shows a cross section along axis BB of FIG. eleven
Practical Example 1. In FIG. 5 shows a diagram of an LCD with additional capacitors

indicated on the diagram by indices 8 'and 8'', respectively, made in accordance with claim 1 of the patented invention.

In FIG. 4 shows the voltage waveform on the data buses U _d , on the address buses U _a , on the liquid crystal capacitors C _LC formed by the image electrodes 4 'and 4''and the common electrode 5.

до напряжения +V_d, а конденсатора

до напряжения -V_d (или наоборот). При этом общий электрод 5 всегда находится под нулевым напряжением относительно электродов 4' и 4''. В обычной схеме ЖКЭ при смене полярности напряжения на шинах данных с +V_d на -V_d или наоборот и при отсутствии напряжения U_a на адресной шине происходит перезарядка конденсаторов

и

на величину ΔU, которая определяется величинами конденсаторов

которые являются, как правило, паразитными конденсаторами между электродами изображения и шинами данных и адресными шинами. Для исключения этого эффекта в патентуемой конструкции ЖКЭ фиг. 5 сформированы два дополнительных конденсатора

и

величины которых выбираются такими, чтобы при изменении напряжения на любой шине данных изменения напряжения на электродах изображения 4' и 4'' одного и того же элемента изображения были одинаковыми по величине и по знаку. Поэтому перезарядка конденсаторов

и

не происходит и, следовательно, эффект неравномерно свечения экрана в такой конструкции ЖКЭ исключается. При этом величины

и

выбираются в соответствии с уравнениями (3) и (4).The scheme works as follows. When voltage U _a appears on the address bus, switching transistors (TPT) 3 'and 3''open and the capacitor charges

up to voltage + V _d , and the capacitor

to voltage -V _d (or vice versa). In this case, the common electrode 5 is always under zero voltage relative to the electrodes 4 'and 4''. In a conventional LCD, when changing the polarity of the voltage across the data buses from + V _d to -V _d or vice versa and when there is no voltage U _a on the address bus, capacitors are recharged

and

ΔU, which is determined by the capacitors

which are, as a rule, stray capacitors between the image electrodes and data buses and address buses. To eliminate this effect in the patented LCD design of FIG. 5 two additional capacitors are formed

and

the values of which are selected so that when the voltage across any data bus changes, the voltage changes at the image electrodes 4 'and 4''of the same image element are the same in magnitude and sign. Therefore recharging capacitors

and

does not occur and, therefore, the effect of uneven screen glow in such an LCD design is eliminated. Moreover, the quantities

and

are selected in accordance with equations (3) and (4).

, обозначенные нa фиг. 8 индексами 8', 8'', 6', 6'', 7', 7'' соответственно, сформированы путем перекрытия электродами изображения 4' и 4'' шин данных 2-1', 2-1'' и адресной шины 1-1. На фиг. 9 показано поперечное сечение А-А на фиг. 8, которое поясняет последовательность формирования технологических слоев конструкции ЖКЭ фиг. 8. Структуру, показанную на фиг. 8 и 9, изготавливали описываемым ниже образом. На изолирующую подложку 10 с помощью вакуумного напыления наносили пленку хрома. Используя фотолитографию, из этой пленки формировали адресные шины, не показанные на фиг. 9, и затворы 11 переключающих транзисторов. Затем осаждали пленку нитрида кремния 12, используемую в качестве затворного диэлектрика. Далее наносили последовательно пленку высокоомного аморфного кремния 13 и пленку аморфного кремния, легированную фосфором 14. С помощью фотолитографии формировали полупроводниковые области переключающих транзисторов. Полупроводниковые области переключающих транзисторов, выполненные из аморфного кремния, на фиг. 10 не показаны для упрощения рисунка. Затем последовательно наносили пленку хрома 15 и алюминия 16 и, используя фотолитографию и химическое травление, формировали шины данных, области стока и истока переключающих транзисторов. При этом для формирования низкоомного контакта к аморфному кремнию осуществляли избирательное травление легированного аморфоного кремния 14 по отношению к высокоомному кремнию в областях между стоком и истоком переключающих транзисторов. После этого наносили пленку нитрида кремния 17, служащую защитным диэлектриком, в которой с использованием фотолитографии вскрывали контактные окна к областям истока переключающих транзисторов. Далее наносили прозрачную проводящую пленку окиси индия, из которой с помощью фотолитографии формировали электроды изображения 4' и 4''. Затем на вторую изолирующую подложку 19 наносили прозрачную проводящую пленку окиси индия и, используя фотолитографию, формировали общие электроды 5, изолированные друг от друга. После этого подложки 17 и 18 совмещали друг с другом на расстоянии, определяемом размерами спейсеров, расположенных между подложками и не показанных на фиг. 9. Совмещение проводим таким образом, чтобы общий электрод располагается над электродами изображения 4' и 4''. Расположение общего электрода показано на фиг. 8 штрихпунктирной линией. Далее пространство между подложками заполнялось жидким кристаллом. Описанный способ изготовления ЖКЭ характерен для изготовления ЖКЭ, работающих на просвет. При изготовлении ЖКЭ отражательного типа достаточно вместо пленки окиси индия для создания электродов изображения 4' и 4'' напылять отражающую металлическую пленку, например, алюминия.A practical implementation of the design of such an LCD is shown in FIG. 8 and 9. FIG. 8 shows the topology of the LCD section, made in accordance with paragraph 3 of the patented invention. Capacitors

indicated in FIG. 8 indices 8 ', 8'',6', 6 '', 7 ', 7'', respectively, are formed by overlapping by the electrodes of the image 4' and 4 '' data buses 2-1 ', 2-1''and the address bus 1-1. In FIG. 9 shows a cross section AA in FIG. 8, which explains the sequence of formation of the technological layers of the LCD design of FIG. 8. The structure shown in FIG. 8 and 9 were manufactured as described below. A chromium film was deposited on the insulating substrate 10 by vacuum deposition. Using photolithography, address buses not shown in FIG. 9, and the gates 11 of the switching transistors. Then, a silicon nitride film 12 used as a gate dielectric was deposited. Then, a film of high-resistance amorphous silicon 13 and a film of amorphous silicon doped with phosphorus 14 were sequentially deposited. Using photolithography, semiconductor regions of switching transistors were formed. The semiconductor regions of the switching transistors made of amorphous silicon, in FIG. 10 are not shown for simplicity. Then, a film of chromium 15 and aluminum 16 was successively applied, and using photolithography and chemical etching, data buses, drain areas, and the source of switching transistors were formed. Moreover, to form a low-resistance contact to amorphous silicon, selective doping of amorphous silicon 14 was carried out selectively with respect to high-resistance silicon in the regions between the drain and the source of switching transistors. After that, a silicon nitride film 17 was applied, which served as a protective dielectric, in which, using photolithography, the contact windows to the source regions of the switching transistors were opened. Then a transparent conductive film of indium oxide was deposited, from which image electrodes 4 'and 4''were formed using photolithography. Then, a transparent conductive film of indium oxide was applied to the second insulating substrate 19 and, using photolithography, common electrodes 5 were formed, isolated from each other. After that, the substrates 17 and 18 were aligned with each other at a distance determined by the sizes of the spacers located between the substrates and not shown in FIG. 9. The alignment is carried out so that the common electrode is located above the image electrodes 4 'and 4''. The arrangement of the common electrode is shown in FIG. 8 dash-dotted line. Further, the space between the substrates was filled with liquid crystal. The described method for manufacturing LCDs is characteristic for the manufacture of LCDs operating in the light. In the manufacture of reflective type LCEs, it is sufficient to spray a reflective metal film, for example, aluminum, instead of an indium oxide film, to create 4 'and 4''image electrodes.

 It can be seen from the above example that the aperture ratio of the described LCDs is very high, since the image electrodes occupy almost the entire screen area, with the exception of the gap between the electrodes.

в соответствии с уравнениями (3) и (4), (5).In addition, by varying the overlap between the image electrodes and the signal lines, it is easy to obtain any desired combination of the ratio between capacitances

in accordance with equations (3) and (4), (5).

и

выполненного в соответствии с п.2 патентуемого изобретения. Роль дополнительных конденсаторов играют емкости между стоком и истоком дополнительных переключающих транзисторов. Такую схему ЖКЭ выгодно реализовать, когда все переключающие транзисторы 3', 3'', 9' 9'' идентичны и имеют одинаковые межэлектродные емкости. В этом случае условия соответствия емкостей

уравнениям (6) и (7) выполняет автоматически ЖКЭ, выполненный по схеме фиг. 7, который кроме указанных выше достоинств обладает еще высокой надежностью в работе, так как переключающие транзисторы 9' и 9'' играют роль резервных переключающих транзисторов. В такой схеме отказ в работе одного или двух переключающих транзисторов любой пары переключающих транзисторов 3', 3'' или 9' 9'' не приводит к отказу в работе элемента изображения.Practical Example 2. In FIG. 7 shows the LCD circuit with additional switching transistors 9 'and 9''used as additional capacitors

and

made in accordance with paragraph 2 of the patented invention. The role of additional capacitors is played by the capacitance between the drain and the source of the additional switching transistors. It is advantageous to realize such an LCD scheme when all switching transistors 3 ', 3'',9' 9 '' are identical and have the same interelectrode capacitances. In this case, the conditions for the compliance of the containers

Equations (6) and (7) are automatically performed by the LCD, performed according to the scheme of FIG. 7, which, in addition to the above advantages, has even higher operational reliability, since the switching transistors 9 'and 9''play the role of backup switching transistors. In such a circuit, a failure in the operation of one or two switching transistors of any pair of switching transistors 3 ', 3''or9' 9 '' does not lead to a failure in the operation of the image element.

 An example of a practical implementation of an LCD with two additional switching transistors is shown in FIG. 10, 11 and 12.

 In FIG. 10 shows an embodiment of the circuit of FIG. 7, made in accordance with paragraph 2 of the claims of the patented invention and which is most advantageous for practical use. This option is characterized in that the switching transistors of adjacent rows of the matrix connected in the same address bus have the same drain and source connections to the signal buses and image electrodes.

 In FIG. 11 shows the topology of the LCD section, made according to the scheme of FIG. 10. In FIG. 12 shows a cross section BB of FIG. 11, which explains the sequence of formation of technological layers in the manufacture of LCD with two additional switching transistors in accordance with paragraph 2 of the claims of the patented invention.

 The structure shown in FIG. 11 and 12 were made as follows.

 Technological layers of chromium, nitride, silicon, amorphous silicon, amorphous silicon doped with boron were deposited on an insulating substrate 10, and a chromium layer using photolithography was formed in the same sequence as in FIG. 9, address buses 11, gate dielectric of the switching transistors 12, semiconductor regions 13, and the drain and source regions of the switching transistors 14, 15. An insulating dielectric (silicon nitride) was then applied (17). Using photolithography, windows were formed in the insulating dielectric to the drain and source electrodes of the switching transistors and then an aluminum film 16 was applied. From the aluminum film using photolithography, data buses and jumpers 20 and 21 were formed to the drain electrodes of the switching transistors. After that, a conductive film of indium oxide was applied and 4 'and 4' image electrodes were formed on the basis of photolithography. Indium oxide image electrodes are formed for a translucent type LCE. For reflective type LCEs, image electrodes are formed from the same material as data buses (for example, aluminum), and simultaneously with data buses in the same photolithographic process. To simplify the drawing in FIG. 12 is a cross-sectional view of one substrate. LCD elements located on the second substrate are performed similarly to those described above in practical example 1.

 The use of jumpers 20 and 21 in the patented LCD design allows, if necessary, to disconnect inoperative switching transistors from data buses by laser burning or chemical etching of these jumpers.

Claims (4)

1. An active matrix liquid crystal screen comprising a first insulating substrate, a plurality of address lines formed on the first insulating substrate parallel to each other, a plurality of data buses 2 - 1 '2 - 2' - 2 - m 'and a plurality of data lines formed on the first the insulating substrate perpendicular to the address lines, a plurality of image elements formed on the first insulating substrate as a matrix of rows and columns located between the address lines and the data lines, respectively, each image element contains at least two image electrodes isolated from each other and at least two switching transistors, wherein the drain of the first switching transistor is connected to the first data bus, the drain of the second switching transistor is connected to the second image electrode, the source of the first switching transistor is connected to the first image electrode , the source of the second switching transistor is connected to the second data bus, and the gates of the first and second switching transistors are connected to the first address bus not, and between the first electrode of the image and the address bus there is a capacitance

there is a capacitance between the second image electrode and the address bus

there is a capacitance between the first image electrode and the first data bus

there is a capacitance between the second image electrode and the second data bus

a second insulating substrate, a plurality of common electrodes formed on a second insulating substrate, each of these common electrodes being isolated from each other and located above the first and second image electrodes, a liquid crystal placed between the first and second image electrodes and the common electrode, characterized in that each pixel contains two additional capacitors

and the first additional capacitor

connected to the second data bus and the first image electrode, and the second additional capacitor

connected to the first data bus and to the second image electrode. 2. The screen according to claim 1, characterized in that as the first and second additional capacitors

and

two additional switching transistors were used, one of them having a drain connected to the first image bus, the source connected to the second image electrode, the other of them connected to the first image electrode, the source connected to the second data bus, and the gates of both additional switching transistors connected to the second address bus, and the gates of the additional switching transistors of the last row of the matrix are connected to the additional address bus. 3. The screen according to claim 1, characterized in that the capacitors

formed by overlapping with the image electrodes of the data lines and address lines or by overlapping the data lines and address lines of the image electrodes. 4. The screen according to claim 2, characterized in that the capacitance of the capacitors

determined from equations

and

Images