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Latvian Journal of Physics and Technical Sciences

The Journal of Institute of Physical Energetics

6 Issues per year


CiteScore 2016: 0.42

SCImago Journal Rank (SJR) 2015: 0.174
Source Normalized Impact per Paper (SNIP) 2015: 0.332

Open Access
Online
ISSN
0868-8257
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Volume 52, Issue 5

Issues

Reduction of Electric Breakdown Voltage in LC Switching Shutters / Elektriskās Caursites Sprieguma Samazināšana Šķidro Kristālu Šūnās

G. Mozolevskis
  • LEO Research Centre 93 Dzirnavu Str., Riga, LV-1011, LATVIA
  • EuroLCDs Ltd. Ventspils High Technology Park 2, 9 Kaiju Str., Ventspils, LV-3602, LATVIA
  • Research Laboratory of Semiconductor Physics, Institute of Technical Physics, Riga Technical University 3 Paula Valdena Str., Riga, LV-1048, LATVIA
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  • Other articles by this author:
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/ A. Ozols
  • LEO Research Centre 93 Dzirnavu Str., Riga, LV-1011, LATVIA
  • EuroLCDs Ltd. Ventspils High Technology Park 2, 9 Kaiju Str., Ventspils, LV-3602, LATVIA
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  • De Gruyter OnlineGoogle Scholar
/ E. Nitiss
  • Institute of Solid State Physics, University of Latvia 8 Kengaraga Str., Riga, LV-1063, LATVIA
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/ E. Linina
  • Institute of Solid State Physics, University of Latvia 8 Kengaraga Str., Riga, LV-1063, LATVIA
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/ A. Tokmakov
  • Institute of Solid State Physics, University of Latvia 8 Kengaraga Str., Riga, LV-1063, LATVIA
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/ M. Rutkis
  • Institute of Solid State Physics, University of Latvia 8 Kengaraga Str., Riga, LV-1063, LATVIA
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Published Online: 2015-11-26 | DOI: https://doi.org/10.1515/lpts-2015-0028

Abstract

Liquid crystal display (LCD) industry is among the most rapidly growing and innovating industries in the world. Here continuously much effort is devoted towards developing and implementing new types of LCDs for various applications. Some types of LCDs require relatively high voltages for their operation. For example, bistable displays, in which an altering field at different frequencies is used for switching from clear to scattering states and vice versa, require electric fields at around 10 V/μm for operation. When operated at such high voltages an electrical breakdown is very likely to occur in the liquid crystal (LC) cell. This has been one of the limiting factors for such displays to reach market.

In the present paper, we will report on the results of electrical breakdown investigations in high-voltage LC cells. An electrical breakdown in the cell is observed when current in the liquid crystal layer is above a specific threshold value. The threshold current is determined by conductivity of the liquid crystal as well as point defects, such as dust particles in LC layer, pinholes in coatings and electrode hillocks. In order to reduce the currents flowing through the liquid crystal layer several approaches, such as electrode patterning and adding of various buffer layers in the series with LC layer, have been tested. We demonstrate that the breakdown voltages can be significantly improved by means of adding insulating thin films.

Kopsavilkums

Šķidro kristālu ekrānu (LCD) industrija ir viena no visstraujāk augošajām industrijām pasaulē. Daudz pūļu un resursu tiek veltīti jauna tipa LCD izstrādē dažādiem pielietojumiem. Atsevišķa tipa LCD funkcionēšanai nepieciešami augsti spriegumi. Piemēram, bistabilos LCD, kuros izkliedējošs (ieslēgts) un dzidrs (izslēgts) stāvoklis tiek iegūts ar dažādu frekvenču maiņsprieguma palīdzību, elektriskā lauka intensitāte šķidrā kristāla slānī var sasniegt pat 10 V/μm. Augstās elektriskā lauka intensitātes dēļ ir liela varbūtība šķidro kristālu (LC) šūnā novērot elektrisko caursiti, kuras laikā LC šūna tiek sabojāta. Šis ir viens no galvenajiem iemesliem, kāpēc šāda tipa ekrāni pagaidām vēl nav komerciāli plaši pieejami.

Šajā darbā mēs skaidrojam rezultātus, kas iegūti, veicot LC šūnu caursites pētījumus. Elektrisko caursiti LC šūnā novēro brīdī, kad strāva tajā pārsniedz noteiktu sliekšņa vērtību. Strāvas stipruma sliekšņa vērtību nosaka šķidrā kristāla īpatnējā vadītspējā, kā arī punktu defekti LC šūnā, piemēram, putekļi, elektrodu raupjums, caurumi u.c. Strāvas stipruma ierobežošanai šūnā šajā darbā tika izmantotas dažādas metodes - buferslāņu iekļaušana, elektroda izlīdzinošā slāņa iekļaušana, kā arī elektroda sadalīšana ar lāzera ablācijas metodi. Tiek demonstrēts, ka elektrisko lauku, pie kura novēro caursiti šūnās, ir iespējams būtiski palielināt, šūnā iekļaujot elektriskos izolējošus buferslāņus un sadalot elektrodu.

Keywords: electric breakdown; bistable; liquid crystal displays; PEDOT: PSS

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About the article

Published Online: 2015-11-26

Published in Print: 2015-10-01


Citation Information: Latvian Journal of Physics and Technical Sciences, Volume 52, Issue 5, Pages 47–57, ISSN (Online) 0868-8257, DOI: https://doi.org/10.1515/lpts-2015-0028.

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© by G. Mozolevskis. This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License. BY-NC-ND 4.0

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