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Home Physics Plasma equipment & processes for liquid crystal alignment

Plasma equipment & processes for liquid crystal alignment

Description

The liquid crystal (LC) alignment is a key process in the production of modern display devices having big market. The traditional alignment procedure, dealing with rubbing of organic films, is not able to satisfy increasing demands of modern LCD technology. The radical improvement is anticipated from alternative methods among which the so-called “particle beam” alignment methods are of the best promise. It is a generalized name of methods operating with the beams of different particles (ions, neutrals, electrons and mixtures thereof). These particles enter into the substrate obliquely to generate surface anisotropy, which is an obligatory condition of planar/tilted LC alignment.

The Institute of Physics of National Academy of Science of Ukraine, Kyiv, Ukraine, developed novel plasma-based laboratory facility for liquid crystal alignment on different materials. The multifunctional setup has the vacuum chamber with diameter of 500 mm and length about 1000 mm pumped by a high-vacuum pump. The setup has 2 main horizontal ports for plasma sources of different functions. There are used so named anode layer sources designed for etching and sputtering deposition processes, respectively. In the first case the aligning layer is modified, while in the second case it is formed due to the sputtering. The sources can be rotated to set desirable angle of treatment. The setup has hardware to control vacuum and gas pressure. It is also equipped with a sample moving system: the substrates are moved horizontally along the axis of chamber, i.e. across the particle flux. The developed equipment allows to treat substrates with up to 200x300 mm2 dimension.

Innovative Aspect and Main Advantages

The particle beam alignment treatment is realized by using anode layer sources developed in former SU. They excel in simple construction, high reliability and easy maintenance. Moreover, they can be easily scaled up to realize treatment of large-area substrates (1870x2200 mm2 in the 7th generation fabs).

The plasma beam etching process is especially effective for low-pretilt LC alignment used in TN, STN and IPS LCD modes. It yields controllable pretilt angle and anchoring energy, as well as high alignment uniformity on both microscopic and macroscopic level (Fig. 2a).

The plasma beam sputtering deposition process is especially productive for a high pretilt angle needed to realize VAN LCD mode. Fig. 2b shows the cell based of SiO2 alignment layers. Comparing with thermal deposition, plasma beam sputtering process provides higher productivity and lower energy consumption. Same as etching process, it can be easily adapted for the alignment treatment of large area substrates.

The alignment processes on the base of developed setup can be also effectively used for the alignment of non-standard liquid crystalline compounds such as polymerizable LC. They are used in production of passive optical films (compensators, polarizers, etc).

Areas of Application

The new method can be easily adapted for the alignment treatment of large area substrates used in the advanced LCD manufacturing processes.


Fig. 1a Plasma beam processing setup: general view


Fig. 1b anode layer source of etching type and sample moving
system in a vacuum chamber.


Fig. 2 LC cells viewed in crossed polarizers. The cells contain the following alignment layers:
(a) obliquely deposited SiO2, vertical alignment;
(b) plasma beam etched polyimide, low-tilt alignment.

Stage of Development

The elaborated laboratory facility is based on our basic research and method optimization. We have made some test treatments that demonstrated good quality of liquid crystal alignment. The processes described above are patented.

Contact Details

Andriy Dobrovol`s`kii, Dr.
Organization: Institute of Physics of NASU
Address: 46, Nauky Avenue, 03680, Kyiv, Ukraine
(380-44) 525-2329, (380-44) 525-7824
This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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