• 제목/요약/키워드: Antiferroelectric

검색결과 43건 처리시간 0.023초

Synthesis and Mesomorphic Properties of New Achiral Liquid Crystals with 3-Alkoxy-2-(alkoxymethyl)-1-propoxy Swallow-Tails

  • Kang, Kyung-Tae;Kim, Jeong-Tak;Hwang, Ryeo-Yun;Park, Song-Ju;Lee, Seng-Kue;Lee, Jong-Gun;Kim, Yong-Bae
    • Bulletin of the Korean Chemical Society
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    • 제28권11호
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    • pp.1939-1944
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    • 2007
  • New liquid crystalline (biphenylcarbonyloxy)benzoates with an achiral swallow-tail derived from 3-alkoxy-2- (alkoxymethyl)-1-propanol [(ROCH2)2CHCH2OH, R = Me, Et, Pr, Bu] were prepared. These liquid crystals exhibited the phase sequence (I-SmA-SmCalt-(SmCX)-Cr) and showed antiferroelectric-like Smectic C phase (SmCalt) at temperature lower, and temperature range broader than do the compounds containing a branched alkyl group as a swallow-tail. The temperature ranges of antiferroelectric phase were found to be 30-90 oC and crystallization temperatures were 4-60 oC. The binary mixture of an achiral swallow-tailed liquid crystal and a chiral antiferroelectric liquid crystal, (S)-MHPOBC showed antiferroelectric smectic C phase at temperature much lower than the single chiral antiferroelectric liquid crystal does.

Dual-Antiferroelectric Liquid Crystal Display with High Transmittance Efficiency and Dispersion-Free

  • Jhun, Chul-Gyu;Park, Won-Sang;Kang, Jin-Woo;Han, Kwan-Young;Yoon, Tae-Hoon;Kim, Jae-Chang
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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    • pp.441-444
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    • 2002
  • If an antiferroelectric liquid crystal (AFLC) cell is set between crossed polarizers for optical modulators or displays, it has low transmittance efficiency. This happens because AFLC materials have inherent tilt angles of typically $18^{\circ}{\sim}38^{\circ}$, not $45^{\circ}$. To improve the low transmittance efficiency, we propose a new optical configuration for antiferroelectric liquid crystal displays, which also improves color dispersion.

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2단 소성시간이 7.6/70/30 PLZT 세라믹의 전기적 특성에 미치는 영향 (Electro-optic Characteristics of 7.5/70/30 PLZT Ceramics According to the Second Stage Sintering Time)

  • 박창엽;정익채;정희승
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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    • pp.220-223
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    • 1987
  • In this paper, electro-optic characteristics of PLZT 7.6/70/30 composition in MPB regions, which antiferroelectric and ferroelectric phases coexist together, were studied. As sintering times are increased, Curie temperatures ore linearly decreased. And the antiferroelectric phase becomes more stronger when Curie temperatures are decreased. The crystal structure investigated by lie of X-ray analysis is proved to cubic in the thermally depoled specimen and rhombohedral in the poled specimen. Accordingly, the applicability of 7.6/70/30 specimen as image storage and display device is expected by the method for applying field induced reversible transitions between antiferroelectric(AFE) and ferroelectric(FE) phase.

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X-ray and dielectric study of the phase transition in PbFe1/2Nb1/2O3-PbCo1/2W1/2O3 ceramics

  • 박융;이홍민;김호기
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1997년도 하계학술대회 논문집 C
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    • pp.1239-1243
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    • 1997
  • A phase analysis in the solid solution of (1-x) PbFe1/2Nb1/2O3-xPbCo1/2W1/2O3 is conducted by dielectric properties, heat capacity and E-P hysteresis at x=0.1 interval. Lattice constants and superlattice intensity are analyzed by the x-ray diffraction, and the temperature - composition phase diagram is determined. The system is found to form a solid solution of perovskite structure throughout the entire composition range, but the nature of phase transitions changes from ferroelectric-paraelectric for $0{\leq}x{\leq}0.5$ to antiferroelectric-paraelectric for $0.6{\leq}x{\leq}1.0$. The transitions of ferroelectric-paraelectric and antiferroelectric-paraelectric for $0.2{\leq}x{\leq}0.5$ and for $0.6{\leq}x{\leq}0.8$, respectively, are diffuse, while those of the ferroelectric-paraelectric and the antiferroelectric-paraelectric for $0.0{\leq}x{\leq}0.1$ and $0.9{\leq}x{\leq}1.0$, respectively are sharp.

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Antiferroelectric and antiferrodistortive phase transitions in Ruddlesden-Popper Pb2TiO4 from first-principles

  • Xu, Tao;Shimada, Takahiro;Wang, Jie;Kitamura, Takayuki
    • Coupled systems mechanics
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    • 제6권1호
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    • pp.29-40
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    • 2017
  • This work employed density functional theory to investigate the structural and ferroelectric properties of the Ruddlesden-Popper (RP) phase of lead titanate, $Pb_2TiO_4$, as well as its phase transitions with epitaxial strain. A wealth of novel structural instabilities, which are absent in the host $PbTiO_3$ material, were identified in the RP phase through phonon soft-mode analysis. Our calculations showed that the ground state of $Pb_2TiO_4$ is antiferroelectric, distinct from the dominant ferroelectric phase in the corresponding host material. In addition, applied epitaxial strain was found to play a key role in the interactions among the instabilities. The induction of a sequence of antiferroelectric and antiferrodistortive (AFD) phase transitions by epitaxial strain was demonstrated, in which the ferroic instability and AFD distortion were cooperative rather than competitive, as is the case in the host $PbTiO_3$. The RP phase in conjunction with strain engineering thus represents a new approach to creating ferroic orders and modifying the interplay among structural instabilities in the same constituent materials, enabling us to tailor the functionality of perovskite oxides for novel device applications.

Antiferroelectric Liquid Crystal Display with High Image Quality

  • Chang, Young-Joo;Yu, Jeong-Seon;Yoo, Jeong-Geun;Jeong, Dong-Jin;Park, Sung-Chon;Chae, Su-Yong;Yang, Hong-Geun
    • Journal of Information Display
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    • 제3권4호
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    • pp.1-3
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    • 2002
  • The antiferroelectric liquid crystal display (AFLCD) is a unique display that can at demonstrate a moving image perfectly the passive matrix driving scheme. We optimised driving the waveform and introduced a dual-driving method. Also, by improving this driving method and using line inversion method, we realize the AFLC display of high image quality with $160(RGB){\times}240$, 32768 colors, crosstalk free and flicker free contrast ratio is greater than 60:1, and the brightness is above 200 $cd/m^2$.

AFLC Cell을 이용한 반투과 LCD 모드이 새로운 광학적 구조 (A new optical configuration for a transflective display mode using an antiferroelectric liquid crystal cell)

  • 최덕운;김성철;강진우;박원상;심사용
    • 한국광학회지
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    • 제13권2호
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    • pp.162-165
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    • 2002
  • 본 논문에서는 반투과 반사판과 22.5$^{\circ}$의 in-plane tilt각을 가지며 λ/2로 설계된 반강유전성 액정 셀을 이용하여 새로운 형태의 반투과형 LCD모드의 구조를 제시하였다. 제안된 구조에서, 투과형 모드뿐만 아니라 광대역 λ/4 필름을 사용한 반사형 모드에서도 높은 밝기와 명암대비비를 구현해 낼 수 있었다.

A New Reflective Display Mode for Antiferroelectric Liquid Crystal

  • Park, Won-Sang;Kim, Sung-Chul;Lee, Gi-Dong;Yoon, Tae-Hoon;Kim, Jae-Chang
    • Journal of Information Display
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    • 제1권1호
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    • pp.48-51
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    • 2000
  • In this work, we proposed a reflective antiferroelectric liquid crystal display (AFLCD) using a half-wave cell whose inplane tilt angle is $22.5^{\circ}$. To check the validity of our design, we fabricated a reflective half-wave AFLC cell of which inplane tilt angle is $24.9^{\circ}$, and measured VIS reflection spectra, contrast ratio and response time. In the results, the half-wave AFLC cell in the reflective configuration exhibits high brightness, high contrast ratio of 20:1, and fast response time of $700{\mu}s$.

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Synthesis and Mesomorphic Properties of Achiral Liquid Crystals with 1,3-Dialkoxy-2-propyl Swallow-Tail

  • Lee, Seng-Kue;Bang, Mi-Yeon;Lee, Jong-Gun;Kang, Kyung-Tae;Kim, Yong-Bae
    • 한국정보디스플레이학회:학술대회논문집
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    • 한국정보디스플레이학회 2003년도 International Meeting on Information Display
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    • pp.575-577
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    • 2003
  • Achiral swallow-tailed liquid crystals derived from 1,3-dialkoxy-2-propanol were prepared and their mesomorphic properties were investigated. 1,3-Dialkoxy-2-propyl swallow-tailed material showed antiferroelectric-like smectic C phase at lower temperature and in broader temperature range than the corresponding compounds with a branched alkyl group as a swallow-tail. They could serve as suitable host for antiferroelectric mixtures.

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