The present invention is directed to a liquid crystal display having a pair of carrier plates spaced apart by a frame to provide a chamber receiving a liquid crystal layer, each of the pair of carrier plates on a surface facing the chamber and engaging the layer being provided with electrically conductive coatings with at least one of the coatings being subdivided into separably operable segments and means for maintaining the spacing between the facing surfaces of the carrier plates. The invention also is directed to different processes of producing the plates with the means for maintaining the spacing.
Liquid crystal displays that are provided with means for maintaining the space between carrier plate are known and constructed in various designs. One example of a design is disclosed in German Pat. No. 21 60 469 and another type is disclosed in U.S. Pat. No. 3,863,332.
since important display characteristic data of a liquid crystal display are impaired with an increasing liquid crystal layer thickness, particularly the increasing of switching times, and the increasing of threshold voltages, it is desirable that the liquid crystal display have the smallest possible spacing between the carrier plates. Plate spacing of less than 10 .mu.m and in certain cases even at a maximum of 2 .mu.m are currently being required in modern liquid crystal displays. These spacing requirements cannot be readily obtained and usually involve particular production problems when the display is a large area display or has thin wall substrates for the carrier plates.
The above mentioned problems that occur with spacing of the carrier plate, have for some years been the subject of intensive efforts and has lead to a series of proposed solutions. Insomuch as these solutions go further than a pure development of the frame of the display, these contributions may be grouped in one of the two types of categories. The first category or type is the entire volume of the chamber outside of the region of the operative segments is filled with a compound as disclosed in German Pat. No. 21 60 469. The other type or category is providing a plurality of more or less irregularly distributed spacing bodies between the two carrier plates. These spacing bodies may be either granules such as disclosed in German Offenlegungsschrift 21 59 165, which corresponds to British Patent Specification No. 1,337,551; laser produced mounds on a surface of a carrier plate as disclosed in German Pat. No. 23 44 050; or glass solder columns formed between the carrier plates as disclosed in U.S. Pat. No. 4,050,786 on which German Offenlegungsschrift 22 42 389 is based.
Both of these types of solutions have their advantages and disadvantages. The first category or type provides relatively accurate spacing values and facilitates an economic liquid crystal consumption, but, on the other hand, impedes the inroduction of the liquid crystal material into the display device. In the case of the second category or type, although the filling of the chamber with the liquid crystal material does not involve any problems, it does require a larger amount of liquid crystal material. In addition, in the case of using granules or glass solder columns as spacing members between the two plates, the spacing accuracy occasionaly is unsatisfactory. The use of spacing bodies which are created by use of a laser has the disadvantage that this method has not been completely developed. Thus, each type of solution has disadvantages or short comings.