The LCD industry in the FSU is concentrated geographically in three centers: Moscow, Saratov, and Minsk. In addition, several research institutes in Ukraine have LCD prototype capabilities, and concentrate on manufacturing issues such as new nonrubbing methods for liquid crystal orientation. In all three geographical areas, the fields of interest are in both passive and active matrix displays, as shown in Figure 3.15.
In all three geographical areas there are STN and TN active plants. For example, Platan claims to be the oldest maker of LCDs in the FSU. This organization, which is twenty years old, began with displays for watches and calculators. The technology was licensed to Zelenograd and Saratov plants. The interconnect approach is chip on glass (COG). In 1988, Platan began producing STN graphic displays with chip-on-glass built-in drivers. Current STN displays are operating in the yellow and blue modes. No compensation for white was shown since the capability of retardation films is nonexistent in the FSU. Platan claims that it could supply 10,000 STN large displays or 100,000 smaller displays per year. Table 3.1 shows some of the TN and STN units produced at Platan. Table 3.1 presents the segmented-type LCD units based on TN technology. Table 3.2 presents character- type LCD units (5 x 7), using TN technology both in reflective and transflective mode. Table 3.3 is a list of graphic medium-sized displays (matrix) utilizing TN and STN technologies, both in reflective and transflective mode. Table 3.4 presents the STN computer-type displays up to a resolution of 640 x 480. All the modules are using COG interconnect technology. Integral in Minsk is the largest producer of electronic watches using LCDs. As a result of the conversion policy from a defense-oriented industry to a commercial one, Integral is producing medical equipment, telephones, and so forth, that use LCD indicators. Integral informed the WTEC panel that a large proportion of its LCD indicators come from Saratov. Reflector in Saratov operates an STN facility with clean rooms in the range of class 1,000 to 10,000. The facility is capable of producing displays up to 8" diagonal.
Figure 3.15. Configuration of the FSU LCD industry.
Character-Type LCD Units
Segment-Type LCD Units
Medium-Sized Graphic-Type LCD Units (Chip-on-Glass Modules)
Large-Sized Graphic-Type LCD Units
It is important to note that all TN and STN facilities are using local production equipment and materials. Exceptions are polarizers and reflection films, which were from Japan (Nitto Denko). As a result, every production company has know-how and proprietary improvements that could be very useful. For example, at Platan, WTEC panelists were shown a unique coater for photoresist (Figure 3.16) that uses a special cloth in contact with the photoresist from one side and touching the substrate on the other one. The Platan technical people claim excellent uniformity (thickness 1 şm) and enormous photoresist savings.
Figure 3.16. Photoresist coater (Platan).
Exposure and alignment equipment, and other usual LCD equipment (coaters, printers, rubbing, filling, etc.), are in many cases supplied by Planar (Minsk).
Current active matrix activities in the FSU are triggered by: (1) the needs of the FSU avionics industry (for example, Ramenskoye Instrument Design Bureau in collaboration with Platan); and (2) conversion of defense-oriented industries to commercial applications (i.e., the Belarussian effort encompassing Integral, Nemiga, Planar, and two state universities). The AM technology is based both on two terminal devices (back-to-back diodes and MIMs) and TFTs (a-Si and p- Si).
The MIM technology was developed at the Radioengineering Institute in Minsk. The MIM technology was chosen due to its simplicity and potential high yield. A full- color 660 x 480 MIM LCD, 6" diagonal was shown. The MIM structure is based on Ta-Ta2O5-Cr lateral structure. The display topology is shown in Figure 3.17. Emphasis was put on the RIE etching of the Ta-Ta2O5 double layer structure (Smirnov 1990, 1992). In order to improve the MIM display performance, the Minsk group is using special liquid crystal materials and color film technology developed at the Sevtchenko Institute of Applied Problems. For example, high resistivity TN materials were developed based on difluorobenzol with a temperature range of -40 degrees centigrade to 80 degrees centigrade. New color filters based on water- soluble photosensitized materials are applied. It is important to note that the spacers and the optimization of the spacing for each color is done by etching the glass. The process, developed at the Belarus State University, is not damaging the substrate quality.
Figure 3.17. The Minsk MIM display topology.
With regard to substrates, the panel learned that all FSU LCD industry is using normal glass passivated with a protective layer of Ta2O5 or Al2O5, and not the boron-silicate glass substrate used in the West.
Platan has an R&D facility and is in the process of installing a pilot production for AMLCDs. Platan AM technology is based on a-Si and p-Si TFTs. The corporation's representatives showed prototypes of full-color, 60 mm x 80 mm a- Si and p-Si TFTs. The backlight is fluorescent. The image quality is comparable with western AMLCD samples although the number of localized defects is larger. Table 3.5 presents the specifications of a color TV LC screen using p-Si TFTs.
The market for Platan presently consists of avionics in the FSU. In Figure 3.18 the specifications of an avionic display are shown (the FSU avionic standard is 130 mm x 130 mm).
Platan is in the early phases of installing the equipment (mostly from Planar) for an AMLCD pilot plant of 10,000 square feet area using 300 mm2 x 400 mm2 glass substrate at a rate of 50,000 substrates per year. The plant is supposed to be operational in 12-18 months.
From the manufacturing point of view, the nonrubbing method developed by Dr. Yu. Reznikov (Ukraine) using polymers with light-induced anisotropy as orienting materials deserves special mention. Dr. Reznikov and his collaborators from Kyyiv developed a photosensitive material on the basis of fluorinated polyvinyl cinnamate.
Color TV LC Matrix Screen Using Polycrystalline Silicon TFTs
Figure 3.18. Multifunction active-matrix liquid-crystal display MFI.
By illuminating with polarized light, they achieve an orientational order of cross-linked polymer chains in the polarization direction, obtaining in such a way an easy axis direction for the alignment of the anisotropic LC molecules. This method can solve such current problems of mechanical rubbing as nonuniformity, electrostatics, and dust. The material has the following main characteristics:
o aligning type planar
o easy axis is controlled by the polarization of light
o thermostability up to 100 degrees centigrade
o polar anchoring energy may be controlled over the range
o pretilt angle may be controlled over 0-15) degree range
Other improvements in manufacturing are in the areas of color filters. In addition to the water soluble photosensitized color filter materials developed in Minsk, Platan also has a proprietary color filter technology based on Ftalocyanine dyes (Figure 3.19).
Figure 3.19. Platan filter dyes.
The metal additive will determine the color. The color filter is deposited by evaporation and is patterned using standard photolithography.