Unusual Voltage-Holding Ratio Characteristics Using In-Plane Switching    of Nematic Liquid Crystals

Oh‐e, Masahito; Umeda, Yoshiyuki; Ohta, M.; Aratani, Sukekazu; Kondo, K.

doi:10.1143/jjap.36.l1025

Cited by 16 publications

(12 citation statements)

References 8 publications

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“…Clearly, the cell VHR is closely related with polymer backbone structures of photo‐aligned PI layers. In addition, the aforementioned LC (MAT‐19‐1284) is a mixture of several fluorinated LC molecules, which has higher resistivity and could induce higher VHR . The fluorinated PI layer has larger free volume than the corresponding un‐fluorinated one .…”

Section: Resultsmentioning

confidence: 99%

Photo‐aligning of polyimide layers for liquid crystals

Song

Yuan

Wang

et al. 2019

Polymers for Advanced Techs

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A series of soluble and highly transparent semi‐alicyclic polyimides (PIs) with designed flexible linkages have been synthesized derived from an alicyclic aromatic dianhydride (1,2,3,4‐cyclobutanetetracarboxylic dianhydride, CBDA) and various aromatic ether‐bridged diamines. The semi‐alicyclic PIs were evaluated as the photo‐alignment layers of liquid crystal (LC) molecules in liquid crystal display (LCD). Experimental results indicate that the photo‐alignment characteristics of LC molecules induced by the photo‐aligned PI layers and the electro‐optical (EO) properties of the LC cell devices are closely related with PI backbone structures. The retardation of the photo‐aligned PI layers is correlated with the ultraviolet (UV) absorption intensity of PI at 220 to approximately 330 nm. The higher UV absorption intensity PI has, the higher retardation and lower pre‐tilt angle the photo‐aligned PI layer exhibits. The defect‐free and photo‐aligned PI layer could result into the uniform LC texture, which is highly desired for in‐plane switching (IPS) mode LCD devices. In comparison, PI layer containing trifluoromethyl moiety shows poor photo‐aligning performance because of the strong electronic withdrawing effect of the fluorinated linkage.

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Section: Resultsmentioning

confidence: 99%

Photo‐aligning of polyimide layers for liquid crystals

Song

Yuan

Wang

et al. 2019

Polymers for Advanced Techs

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“…The fluorinated LC, MLC-6628 gave a higher value of VHR than the cyano LC, E7; it is known that a fluorinated LC has higher resistivity 31 and thus produces higher VHR. 14,32 The VHR of LC cells remarkably decreased at an elevated temperature. As temperature increases, the mobility of ion impurities in LCs increases while the resistivity of LCs decreases, which deteriorates the voltage holding characteristic.…”

Section: Electro-optical Properties Of Lc Cellmentioning

confidence: 99%

“…There have been the studies showing that the PI ALs affect the LC pretilt angle and the EO properties such as voltage holding ratio (VHR), residual DC voltage and so on. [9][10][11][12][13][14] However, most of these studies were limited to the specific type of PI or the specific properties of LC alignment or LCDs. Thus, we still lack a detailed connection between the PI structure and the properties of LC alignment and LCDs.…”

Section: Introductionmentioning

confidence: 99%

Chemical structural effects of polyimides on the alignment and electro-optical properties of liquid crystal cells

Dong

Paek

2004

Macromol. Res.

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The nature of the nematic liquid crystal (LC) alignment induced by the rubbed polyimide (PI) alignment layers (ALs) and the electro-optical (EO) properties of the LC cells are expected to depend on the chemical and physical features of the PI. By employing five pyromellitic dianhydride (PMDA)-type PIs having different functionalities, we have studied the effects of the PI's structure and chemistry on the alignment characteristics and the cell's EO properties. Increasing the flexibility of the PI increases the pretilt angle and tends to improve the alignment stability. On the other hand, the rigid, fluorinated PI displays poor stability for LCs and induces a less stable/uniform LC alignment and, subsequently, a small pretilt angle. It also transpired that fluorination of the PI deteriorated the voltage-transmittance characteristics and the voltage holding ratio; increasing the flexibility of the PI structure improves these EO properties. The finding that the qualitative trends for the PI's functionalities are similar for both the alignment and EO properties suggests that the EO properties are closely related to the alignment characteristics, which are determined by short-range interactions between LC and PI molecules.

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“…Although the equivalent circuits of the TN and IPS modes have been reported in previous studies, it has not been accurately analyzed [10]. In this study, an equivalent circuit was analyzed by comparing the impedance characteristics.…”

Section: Electrical Properties Of Guest-host-type Liquid Crystal Cellmentioning

confidence: 99%

Photoelectric Properties and Drive Characteristics of GH Liquid-Crystal Cells in Various Alignment Modes

Sato

Chikama

Ohuchi

2017

J. Photopol. Sci. Technol.

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Photoelectric properties and drive characteristics of guest-host (GH)-type liquid crystal cells with yellow, magenta, cyan, green, and gray colors using 4-cyano-4'-pentylbiphenyl (5CB) and three diazo-based dichroic dyes were systematically investigated in different driving modes. The dichroic dyes have structures similar to 5CB; therefore, they uniformly mixed and dispersed into the liquid crystal matrix. The green and gray colors were obtained by mixing appropriate ratios of two or more dyes. Impedance of the GH cells decreased upon the incorporation of the dyes into 5CB. However, the photoelectric properties and drive characteristics of the liquid crystal cells were not altered after the inclusion of the dye. In particular, the alignment of the molecules strongly depended on the cell structure. The GH cells in twisted nematic mode exhibited a low driving voltage of approximately 1.5 V.

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Unusual Voltage-Holding Ratio Characteristics Using In-Plane Switching of Nematic Liquid Crystals

Cited by 16 publications

References 8 publications

Photo‐aligning of polyimide layers for liquid crystals

Photo‐aligning of polyimide layers for liquid crystals

Chemical structural effects of polyimides on the alignment and electro-optical properties of liquid crystal cells

Photoelectric Properties and Drive Characteristics of GH Liquid-Crystal Cells in Various Alignment Modes

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