JPS61166594A - Liquid crystal display unit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that utilizes the thermo-optic effect of liquid crystal and is suitable for displaying a large amount of information.

[Prior Art] Liquid crystal display devices have traditionally been used mainly in wristwatches, pocket calculators, portable game machines, etc., terminal displays for various office equipment and measurement equipment, and even monitors for TVs and video cameras. CRT (cathode ray tube) displays have been widely used to display a large amount of information like displays, but CRT displays tend to be large in size and difficult to handle in terms of weight. Recently, the use of thin and lightweight liquid crystal display devices has been considered in this field as well. In this case, it is difficult to increase the display capacity of conventional twisted nematic liquid crystal display devices, so a thermal writing liquid crystal display element is used. Thermal writing liquid crystal display elements partially apply heating bias to the liquid crystal cell to change the liquid crystal from a smectic phase to a nematic phase and then to an isotropic liquid phase, and then in the process of returning this to the liquid crystal phase, the liquid crystal molecules A desired image is written by actively changing the arrangement of the images to provide optically transparent and opaque areas.

[Problems to be Solved by the Invention] FIG. 2 is a partial structural diagram showing an example of a conventional thermal writing liquid crystal display device, showing electrode patterns on substrates sandwiching a liquid crystal layer. In FIG. 2, one substrate 2 row electrode XO
, Xl, X2. --Xn are provided, and another substrate is provided with column electrodes Yo, Yl, in a direction substantially perpendicular to the row electrodes.
Y2. -- Y, is provided. The row electrode x□-
xn is formed of a low resistance metal material, and the column electrodes y□-y,
are formed of a transparent electrode material, and the row electrodes x□, x1.
X2. -- When electrode pulses are sequentially applied to Xn, the liquid crystals on the electrodes are sequentially heated. The heating is carried out for a sufficient period of time for the liquid crystal layer to become an isotropic liquid crystal, and as the current pulse moves, the liquid crystal layer is sequentially cooled and changes from an isotropic liquid phase to a nematic phase and then to a smectic phase. . When a voltage is applied during this cooling, the liquid crystal becomes vertically aligned due to the alignment effect of the electric field while it is in the nematic phase, and is stabilized as it is in the smectic phase.
It is transparent in appearance. On the other hand, if the material is cooled without applying any voltage, the random state of the isotropic liquid phase is carried over to the smecti-7 phase and stabilized, so that it appears cloudy in appearance. Therefore, the column electrode Yo.

Yl, Y2. -- By distributing a voltage signal corresponding to an image to Ym, a pixel at the intersection of a row electrode and a column electrode can be drawn as either transparent or cloudy, thereby configuring a display device.

According to such a thermal writing method, since the selection of writing is performed by three different entities: thermal signals and electricity, so-called crosstalk does not occur, and a thin display with a large capacity can be obtained. However, increasing the display capacity also increases the number of points of contact between the electrodes and the driving elements, making the wiring complicated and reducing reliability. In addition, as a practical matter, there is a limit to the wiring, and it has been impossible to increase the density further. These drawbacks were particularly problematic for row electrodes driven with somewhat higher powers.

The purpose of the present invention is to solve the above problems, significantly reduce the number of contact points between electrodes and drive elements, simplify wiring, and increase the capacity and density of a highly reliable thermal writing liquid crystal display element. The object of the present invention is to provide a liquid crystal display device that enables the following.

[Means for Solving the Problems] The present invention provides a liquid crystal layer that is sandwiched between a pair of opposing substrates and that changes into three states of a smectic phase, a nematic phase, and an isotropic phase according to temperature changes; A row electrode group for heating current formed on the inner wall surface of one of the substrates, and a group of row electrodes for image signals formed on the inner wall surface of another one of the pair of substrates in the column direction substantially perpendicular to the row direction. In a liquid crystal display device comprising a column electrode group, the row electrode group is divided into a plurality of blocks, the input side of each row electrode is connected to a common lead end for each block, and the output side of each row electrode is connected to a common lead end for each block. Each block is connected to a common lead end in the same order, and diodes are interposed in the same forward direction between the lead end on either the input side or the output side and each row electrode.

The above liquid crystal layer may be a normal thermal writing liquid crystal element that exhibits a smectic phase at room temperature. The pair of substrates that sandwich the liquid crystal layer are known substrates on which thin films of electrodes can be formed, and may be either transparent or translucent depending on the application, and both of the pair may be made of different materials. There is no problem even if you do. Similarly, the row electrode group and the column electrode group may be of different types.

[Function] Dividing the row electrode group into multiple blocks, and providing lead ends on the input side for each block and on the output side for each arrangement order within each block, makes the row electrode group easier to wire. The first step is to construct a matrix. (Structurally, the row electrode groups remain arranged in parallel and form an image signal matrix with the column electrode group). With this matrix wiring, if the total number of row electrodes is (nXm), the number of contacts that used to require (nXm)N2 locations for both input and output is reduced to (nXm).
m) Only one location is required. However, a new problem of losstalk arises due to matrix wiring, so in order to prevent this, it is necessary to connect diodes directly to either the input side or the output side of each row electrode in the same forward direction. .

[Examples] Hereinafter, the present invention will be explained in detail with reference to Examples and the drawings.

FIG. 1 is a schematic diagram of a liquid crystal display device and its driving section showing an embodiment of the present invention. In FIG. 1, the liquid crystal display device includes an aluminum electrode l formed as a thin film on a ceramic substrate, a diode chip 2 mounted on the same ceramic substrate, and a glass substrate placed in a layer opposite to the ceramic substrate. A liquid crystal layer (
(not shown). The liquid crystal layer contains liquid crystal that exhibits a smectic phase at room temperature. In this example, a biphenyl-based mixed liquid crystal supplied by BDH under the name S-5 was used. Cell thickness is 5-50
pm is preferable. Assuming that the pixel is 480×840, the aluminum electrode 1 is the row electrode X1. X 2. --X
480, and the transparent electrode 3 corresponds to the column electrode Y1. Y
2+ --- Y 840, each diode D 1. D2. --I) aao is each row electrode X1
．． N2. -- They are connected in series to each X480. The row electrodes X1 to X480 are divided into 24 blocks, and the input side is connected to each block Xi, to X20 .
X21-X40. - For each X481 to X481, input switching element QNI, QN2゜--Q of the drive section
N24, and the output side is connected to (7) Xl, X21 . --Output switching of the drive section via diode chips for each xaet, etc., 1j elements QMI, QM2. -- Connected to QM20. 1. First, the row electrode x1 generates heat by turning on the first switching elements QNI and QO of each of the switching element groups and turning off the other elements. The liquid crystal in the portion corresponding to the row electrode x1 is heated and changes from a smectic phase to a nematic phase to an isotropic liquid phase, but the input switching elements QNI to Q
When the N24 is turned off, it cools and returns to the smectic phase. When passing through the nematic phase during cooling, a signal voltage Vy (corresponding to image information) is applied to the column electrodes Y1 to Y840.
v) or 0 (v), when the state returns to the smectic phase, the part to which vy was applied becomes a transparent homeotropic state, and the part to which no voltage was applied becomes a cloudy focal conic state. , the first element QNI on the input side and the second element QM2 on the output side
By turning on the element and turning off the other elements, writing can be performed in the part of the row electrode x2 in the second row. When moving to the second unit group, connect the input side to the second element QN2. By turning on the output side of the first element Q and turning off the other elements, it is possible to write to the row electrode X21 of the 21st row, and by sequentially performing such operations, All pixels can be written.

In the above operation process, the diode Dl ~0480
The presence of . . . plays a role in preventing the current from flowing backwards to the electrodes xl-x49Q, thereby preventing crosstalk. - If there are no diodes D1 to D480, for example, if element QNI and element Q old are turned on and the other switching elements are turned off, Q
NI"N2 → X22 = X21 → QM1 etc. will also exist, and the parts corresponding to x2° Since 0480 is connected, this will be prevented.

In this way, in this embodiment, the row electrodes x1 to x480 are arranged in 24
By dividing into X20 blocks, the number of connections required for input/output in conventional equipment was 480 N2 = 9eO, but it can be significantly reduced to 24 + 20 = 44, and the number of switching elements has also been reduced to 480. We were able to reduce the number of items from 1 to 44. Lostalk, which tends to occur with block division, is completely prevented by mounting a diode chip, making it possible to display a high-density liquid crystal display with a large capacity of 480 x 840 pixels.

[Effects of the Invention] As explained above, according to the present invention, by arranging one row of electrodes in a matrix configuration and connecting a diode to each row electrode, the number of contact points between the electrode and the drive element can be significantly reduced. It is possible to provide a highly reliable thermal writing liquid crystal display device with simplified wiring density, large capacity, and high density.

[Brief explanation of the drawing]

FIG. 1 is a schematic structural diagram showing an embodiment of the present invention, and FIG. 2 is a schematic structural diagram of a conventional example. l - one row electrode, 2 - one diode, 3 - one column electrode, QN
I~QN24 and QMI'''QM20--Drive element at lead end.

Claims (1)

[Claims] A liquid crystal layer that is sandwiched between a pair of opposing substrates and changes into three states: smectic phase, nematic phase, and isotropic phase due to temperature changes, and a heating current layer formed on the inner wall surface of one of the pair of substrates. A liquid crystal display device comprising a row electrode group and a column electrode group for image signals formed on the inner wall surface of another one of the pair of substrates in a column direction substantially perpendicular to the row direction. The electrode group is divided into a plurality of blocks, the input side of each row electrode is connected to a common lead end for each block, and the output side of each row electrode is connected to a common lead end for each of the same ranks within each block. A liquid crystal display device characterized in that diodes are interposed in the same forward direction between the lead ends on either the input side or the output side and each row electrode.