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

Dong, Won Seok; Paek, Sang Hyon

doi:10.1007/bf03218396

Cited by 10 publications

(15 citation statements)

References 23 publications

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“…Figure shows the VHR values of LC‐filled cells using photo‐aligned PI layer by exposure of 500 mJ/cm 2 . In comparison, the VHR of the empty cells was estimated as about 99.65% . The alkylated PI‐4 (‐C (CH 3 ) 2 ‐) produces an LC cell with the highest VHR value (>98%) while the fluorinated PI‐5 (‐CF 3 ‐) gives the lowest VHR (82%).…”

Section: Resultsmentioning

confidence: 99%

“…Figure 8 displays the uniformity and stability of LC alignment by identifying the LC texture of antiparallel cells exposed at 500 mJ/cm 2 and LC-filling. Photo-aligned PI-1 layer shows a defect-free and uniform LC texture as represented by Dong W et al, 16 and photo-aligned PI-2 with relatively higher UV sensitivity and the highest LC retardation, exhibits a perfect defect-free and uniform LC texture. In comparison, a different LC texture having multi-domains with various local LC directors was yield in photo- .…”

Section: Uniformity Of the Lc Molecules On The Photo-aligned Pi Layersmentioning

confidence: 87%

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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%

Section: Uniformity Of the Lc Molecules On The Photo-aligned Pi Layersmentioning

confidence: 87%

Photo‐aligning of polyimide layers for liquid crystals

Song

Yuan

Wang

et al. 2019

Polymers for Advanced Techs

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“…[1][2][3][4][5][6][7][8][9][10][11][12][13] The rubbing technology of the polyimide (PI) substrate is the most widely used alignment process for producing LC alignment layers, [14][15][16][17][18][19][20][21][22][23][24][25][26][27] which can induce planar or homeotropic alignment of LC cells by changing the molecular structure of the polyimide derivatives. In particular, polyimides with fluorinated groups have been studied widely to obtain homeotropic alignment layers.…”

Section: Introductionmentioning

confidence: 99%

Liquid crystal alignment properties of polystyrene derivatives containing fluorinated side groups

2010

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The liquid crystal (LC) alignment properties of a series of polystyrene derivatives containing various fluorinated side chain terminal moieties, such as 4-fluorophenoxymethyl, 3,4,5-trifluorophenoxymethyl, pentafluorophenoxymethyl, and 4-trifluoromethoxyphenoxymethyl groups, were investigated. These polymers could induce homeotropic and/or homogeneous planar LC alignment on their surfaces by changing the LC molecules and rubbing conditions. For example, when a positive (MJ001929 from Merck) and negative dielectric anisotropic LC mixture (MLC-7026-000 from Merck) were used, homeotropic LC alignment was observed in the LC cells made from unrubbed films of pentafluorophenoxymethyl-and 4-trifluoromethoxyphenoxymethyl-substituted polystyrenes with a smaller surface energy, whereas random planar LC alignment was observed in those made from the other polymers with a larger surface energy. On the other hand, homeotropic LC alignment behavior was observed in all the LC cells made from unrubbed films of all the polystyrene derivatives when 5CB was used as the LC material.

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“…Aromatic polyimides are versatile engineering polymers that have been widely used in many applications, such as membrames for gas separation 1,2 and proton exchange, [3][4][5][6] non-linear optical materials, 7,8 liquid crystal displays, [9][10][11] photoresists 12,13 and other microelectronics and optoelectronics 14 applications because of their outstanding thermal stability, mechanical and electrical characteristics. 15,16 Unless carefully designed, however, polyimides have high softening temperatures and are often insoluble in most organic solvents in their imidized form, making them extremely difficult to fabricate.…”

Section: Introductionmentioning

confidence: 99%

Novel organosoluable aromatic polyimides derived from unsymmetrical 1,3-bis(4-aminophenoxy)naphthalene and aromatic dianhydrides

Chen

Wang

2010

Macromol. Res.

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A novel unsymmetrical diamine, 1,3-bis(4-aminophenoxy)naphthalene, was prepared through the nucleophilic displacement of 1,3-dihydroxynaphthalene with p-fluoronitrobenzene in the presence of potassium carbonate, followed by catalytic reduction with hydrazine. A series of novel aromatic polyimides containing bis(phenoxy)naphthalene units were synthesized from the unsymmetrical diamine and a range of aromatic tetracarboxylic dianhydrides via the usual two-step procedures that included ring-opening polyaddition and thermal/ chemical cyclodehydration. The poly(amic acid)s had inherent viscosities ranging from 0.65 to 2.01 dL/g. All the poly(amic acid)s could be converted thermally into transparent, flexible, and tough polyimide films. Most of the polyimides were soluble in organic solvents, such as dimethylacetamide, N-methyl-2-pyrrolidone, m-cresol, or ochlorophenol due to the unsymmetrical and bulky pendant naphthalene groups. The tensile strength and elongation at break of the polyimide films ranged from 74 to 97 MPa and 4 to 7%, respectively. These polyimides had glass transition temperatures ranging from 221 to 312 ºC. Thermogravimetric analysis revealed these polymers to be fairly stable up to 500 ºC, and the 10% weight loss temperature were recorded in the range of 531-580 ºC in nitrogen and 522-570 ºC in air. The substituted position effect of bis(phenoxy)naphthalene on the properties of the polyimides were investigated. The polyimides derived from unsymmetrical 1,3-substituted bis(4-aminophenoxy)naphthalene showed better solubility without sacrificing their thermal and mechanical properties due to the unsymmetrical and bulky pendant effects.

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

Cited by 10 publications

References 23 publications

Photo‐aligning of polyimide layers for liquid crystals

Photo‐aligning of polyimide layers for liquid crystals

Liquid crystal alignment properties of polystyrene derivatives containing fluorinated side groups

Novel organosoluable aromatic polyimides derived from unsymmetrical 1,3-bis(4-aminophenoxy)naphthalene and aromatic dianhydrides

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