DE2837431A1 - LIQUID CRYSTAL DISPLAY BOARD IN A MATRIX ARRANGEMENT - Google Patents

Abstract

The liquid-crystal display panel in a matrix arrangement has two substrates (18, 18') of which one (18) supports a plurality of gate lines (3), a plurality of source lines (40) perpendicular thereto, and one thin-film field-effect transistor each at each bossing point of the gate and source lines, and the other (18') supports a transparent electrically conductive film (23). Arranged in sandwich fashion between the transistor arrangement and the transparent and electrically conductive film is a layer made from a liquid-crystal material (20). A polychromatic dye is contained as "guest" in the liquid-crystal material as "host", so that use may be made of a so-called guest/host effect. <IMAGE>

Description

DESCRIPTION

The invention is in the field of liquid crystal displays and relates in particular to a display panel of this type in a matrix arrangement.

As a development by Westinghouse Electric Co. are liquid crystal display panels become known in a matrix arrangement in which in the course of the manufacturing process a thin film of the vapor phase is deposited over the field effect transistors and parasitic capacitors are built into the face of the display panel; see. in particular the technical article by T.P. Brody et al "A 6" x6 "20 l / inch Liquid Crystal Display Panel "in IEEE Trans. On Electron Devices ED-20 P995, 1973. In this publication it is mentioned that the liquid crystal display panel supporting the thin film transistors exhibited the twisted nematic field effect mode (TN-FEM) in a matrix arrangement. so however, it has been found that this known liquid crystal display panel is of the TN-FEM type only relatively complicated to manufacture and difficult to achieve a higher contrast ratio was to bring.

It is therefore an object of the invention to provide an improved liquid crystal display panel of the type mentioned to propose the disadvantages that the known display panel owns, does not have.

The inventive solution to this problem is in claim 1 indicated, advantageous developments can be found in the subclaims.

An essential feature of the invention is that the sandwich-like between the transistor on the one hand and the transparent and electrically conductive Film arranged on the other Nice layer with a guest / host effect is tainted and contains a multicolored color material.

The following are some incorporating features of the invention Embodiments explained in more detail in connection with a drawing. Show in it: Fig. 1 (a) and laub) are schematic representations of liquid crystal display cells according to the invention with guest / host effect, FIG. 2 is a schematic circuit diagram of a cell control circuit for a liquid crystal display panel in a matrix arrangement, Fig. 3 is a diagram with three different voltage curves from the control circuit of Fig. 2, Fig. 4 (a) to 4 (c) broken representations of during the manufacture of the inventive Matrix array liquid crystal display panels used masks, Figs. 5 (a) through 5 (d) perspective views of electrode patterns during fabrication of the liquid crystal display panel, Figs. 6 (a) to 6 (d) are schematic sectional views of the manufacturing flow of the liquid crystal display panel, and Fig. 7 is a broken line Cross-section through the finished liquid crystal display panel in a matrix arrangement.

As already briefly indicated in the introduction to the description, it is useful the invention in the liquid crystal display from the so-called guest / host effect, namely, it becomes multicolored as a guest to the host liquid crystal material Color material added and dissolved in it.

Such guest / host effects are used in liquid crystal materials in the Wise suggested that one should adopt such a system with a multicolored color material as a guest and a liquid crystal material as a host, applies an electric field, and then so-called electric field modification effects occur, the liquid crystal molecules are caused to rotate about the longitudinal axes of the multicolored color material and modulate the absorption of light for display purposes. See for example the technical publication Appl. Phys. Lett. 13, 91 (1968). The corresponding cell structure and the optical system are shown in Figs. 1 (a) and 1 (b).

In Fig. 1 (a) the basic structure is shown schematically a reflective type guest / host effect liquid crystal cell are included a liquid crystal material layer 20 with multicolor coloring material added, a pair of electrodes 19 and 19 ', a pair of pads 18 and 18', a polarizer 17 and a light diffusion plate 21 arranged at the rear of the cell. In One of the two electrodes can be modified according to FIG. 1 (b) 19 or 19 'be designed as a light scattering device, which is here by a Al electrode 23 applied to a polished glass plate 24 is formed and for a higher contrast ratio ensures.

The embodiment of Fig. 1 (b) forms a preferred embodiment of the invention for a guest / host effect liquid crystal display cell. An alternative option to form a light-scattering electrode consists, for example, in that a glass plate is first coated with a photoresist film, which is then partially irradiated with light through a suitable mask and partially with hydrofluoric acid (HF) or the like is dissolved, so that there is a fissured Surface is formed. Then a layer of Al is put on the cracked glass plate surface deposited.

This alternative route is recommended if there is only one display zone except for a thin film transistor (TFT) arrangement and X and Y electrodes polishing is.

Fig. 2 shows a preferred embodiment of a liquid crystal display panel in a matrix arrangement with guest / host effect, with each matrix crossing point through a thin film transistor 6 and a parasitic capacitor 8 is driven. This panel also includes a drain electrode 5, a liquid crystal cell 7, a Gate electrode 3, a source electrode 1 and X lines n, n + 1 and Y lines m, m + 1.

In Fig. 3, the course of the control voltages for the Liquid crystal display panel shown in matrix arrangement of Fig. 2, the upper trace of the source voltage, the middle trace of the gate voltage and the lower line is assigned to the drain voltage. If the representation in Figs. 2 and 3 limited to only one cell or one element of a display matrix, so it should be noted that many such cells are located one behind the other in the X and Y directions and so form the display matrix.

Some mask shapes (application or photo masks) and manufacturing steps in the manufacture of the thin film transistor array substrate of the present invention described.

Step 1: Using a mask shown in Fig. 4 (a) Simultaneously one electrode 25 of the capacitor 8 and the gate electrode 3 on the Substrate applied, the electrode material is Al or the like.

In perspective, this step is in Fig. 5 (a) and sectioned in Fig. 6 (a).

Step 2: An insulating film 26 made of SiO2, for example is applied completely, see the perspective view of the film in Fig. 5 (b) and the cross section in Fig. 6 (b). This insulating film 26 has the following functions: 1) the gate electrode 3 is applied in the intersection area opposite one applied in step 4 Source electrode 40 electrically separated; 2) the insulating film 26 serves as an insulating layer for the gate electrode of the TFT element; and 3) the insulating film 26 forms a dielectric Layer for the capacitor 8.

Step 3: A semiconductor film 27 (e.g., CdS, CdSe, Te) is made applied on the insulating film 26 so as to overlie the gate electrode 3; here the mask of Fig. 5 (b) is used. In perspective, this film is shown in Fig. 5 (c) and shown in cross section in Fig. 6 (c).

Step 4: Using a mask shown in Fig. 4 (c), becomes a source electrode 40, a drain electrode and a picture element electrode 41 of the liquid crystal cell is formed on the side of the TFT substrate. These elements are made of Al, Au or the like. In perspective, these electrodes are shown in Fig. 5 (d) and shown in section in Fig. 6 (d).

With the steps described so far, one substrate or which manufactured a base of the matrix liquid crystal display panel according to the invention, and it also has a second base, which is a transparent and electrically conductive film 31 carries, which is associated with all picture elements in common is.

Then, a transparent insulating film 30 made of SiO, SiO2 or the like applied to both electrodes and by means of oblique evaporation or a rubbing technique treated on twisted nematic alignment.

Both documents are joined to one another by a sealing element 32 firmly connected. Thereafter, the liquid crystal material 20 together with the multicolored Color material injected. A single polarizer 17 is placed outside this liquid crystal display cell installed with guest / host effect and in this way the production of the display board completed in matrix arrangement.

According to the invention, it is possible to use the transparent electrode, the gate electrode and to apply the X-lead electrodes simultaneously and from the same material (Al). It is also possible to have one electrode of the liquid crystal cell and the source and drain electrodes of the thin film transistor (TFT) at the same time and with the to apply the same material (Al or Au). This becomes the fabrication of the liquid crystal display panel significantly simplified in matrix arrangement.

The section shown in FIG. 7 shows the finished matrix display panel using the alternative option mentioned above. Here is the gate electrode at 38 of the TFT and the one made of the same material, for example Al Electrode of capacitor 8 denotes, while the reference number 39 here for the source electrode, the drain electrode and the electrode of the liquid crystal cell on the side of the TFT arrangement document applies. It is also based on the possibility pointed out, an opaque ceramic pad instead of a glass pad to use so as to exclude the risk that Na ions of the glass material the Operating characteristics of the TFT deteriorate.

Of course, the invention is not limited to those described Embodiments, rather, are numerous within the scope of the claimed protection Modifications possible.

Claims (4)

Matrix arrangement liquid crystal display panel Priority: August 30th 1977, Japan, No. 105549/1977 PATENTANS PRÜCHE Liquid crystal display panel in matrix arrangement, not marked by a pair of documents (e.g. 18, 18 '), of which one of the several gate lines, several source lines perpendicular to them, as well as on each gate and source line crossing point one through a semiconductor layer Thin-film field effect transistor (TFT = Thin Film Field Effect) made from tellurium (Te) Transistor), and the other carries a transparent and electrically conductive film; and by being sandwiched between the Transistor and the transparent one and electrically conductive film disposed layer (20) of liquid crystal material with guest / host effect. 2. Liquid crystal display panel according to claim 1, d a -d u r c h g It is noted that the thin film field effect transistor (TFT) has a gate electrode (e.g. 3), an insulating layer (e.g. 26), a semiconductor layer (27), a Has a source electrode (e.g. 39) and a drain electrode; and that the sandwich between the transistor arrangement and the transparent and electrically conductive Film (e.g. 31) arranged layer (20) of the liquid crystal material is a multicolor Color material is added. 3. Liquid crystal display panel according to claim 2, d a -d u r c h g E k e n n n e i n e t that the source and drain electrodes of the thin film transistor (TFT) and one electrode of the liquid crystal cell made of the same material are made. 4. Liquid crystal display panel according to claim 1, d a -d u r c h g It is not noted that at least one base is made of a ceramic material is made.