LP‐3: <i>Late‐News Poster:</i> Photoalignment Materials Based on ω‐(4 ‐Chalconyloxy) Alkyl Groups Providing TN Alignment with Pretilt Angle by One‐Step Exposure of Polarized Near‐UV Light

Tsutsumi

2002

Polym J

ABSTRACT:We investigated the photoreaction of the side chain type liquid crystalline polymers with a chalcone derivative in the side chain. The polymer films were irradiated with linearly polarized UV (LPUV) light (350 nm) under different conditions. The photodimerization of the chalconyl moieties would mainly occur due to a decrease in the peak assigned to the chalconyl moiety by UV-vis spectroscopy measurements. The extent of the photoreaction in the liquid crystalline (LC) state is larger than that in the solid state after spin-coating and in the locked-in LC state after annealing. The LC cell was fabricated from the polymer film irradiated with LPUV light to examine the alignment properties of low molar mass LC molecules on them. A mixture of low molecular liquid crystal with the dichroic dye was filled in the LC cell. The low molecular liquid crystal was easily aligned parallel to the electric vector of the incident exposed LPUV light in the LC cell with the polymer film irradiated in the LC state.KEY WORDS Chalcone / Liquid Crystalline Polymer / Photodimerization / Photoalignment / The alignment of liquid crystalline (LC) molecules plays an important role for liquid crystalline displays (LCDs). The rubbing process has been mainly employed for the uniaxial orientation of the LC molecules. However, the rubbing process has many disadvantages for LCDs such as generation of electrostatic charge and dust. Therefore, many methods of alignment technique for LC molecules are focused on rubbing free methods. Photoalignment procedure is recognized as one of rubbing free methods and is investigated as one of candidates that overcome the generation of electrostatic charge and dust for the rubbing process. 1,2 Photoalignment procedure is based on photochemical reactions such as photoisomerization, photodimerization (photocrosslinking) and photodecomposition. With respect to photoisomerization, polymers containing an azobenzene derivative were intensively investigated. [3][4][5] The reversible photoreaction of the azobenzene moieties in the polymer induced a reversible change in the alignment direction of low molecular weight LC molecules. Generally photodimerization of photosensitive groups in the polymer was employed to obtain a stable alignment of low molecular weight LC molecules.Photodimerization of the cinnamoyl chromophore in the polymer film have been studied in detail. The polymer films containing dimerized moiety of cinnamoyl group have been investigated as a photoalignment material by many researches. 2, 6-10 Schadt et al. have obtained the alignment film by photodimerization of cinnamoyl group in the poly(vinyl 4-methoxycinnamate). LC molecules in the LC cell were aligned perpendicular to the electric vector of the incident LPUV light. 6 Alignment behavior of LC molecules would be easily improved by the liquid crystalline polymer surface where mesogenic groups are aligned. Kawatsuki et al. had reported alignment properties of side chain type liquid crystalline polymers with the cinnamoyl groups as an alignmen...

mentioning

confidence: 99%

Photoreaction of New Chalcone-Based Side Chain Type Liquid Crystalline Polymers and Alignment Behavior of Liquid Crystal on the Irradiated Films

Tsutsumi

2002

Polym J

“…[13][14][15][16][17][18][19]22,26,27,32 The alignment direction of 5CB in the LC cell using the irradiated poly(4-methacryloyloxy chalcone) (PM4Ch) film was perpendicular to the electric vector of the incident LPUV light.…”

Section: Alignment Of 5cb In Lc Cell Fabricated From Irradiated Polyimentioning

confidence: 99%

“…Non-mesogenic photosensitive polymers containing chalcone derivatives have been studied for the photo-alignment film. [13][14][15][16][17][18][19] The alignment of LC molecules is easily improved by the surface of LC polymers that exhibit a mesophase. This idea arises from the simple role of solubility for organic compounds, that is, like dissolves like.…”

mentioning

confidence: 99%

Photo-alignment Properties of Main-Chain Liquid-Crystalline Polyimides Containing Chalcone Derivative

Nakao

2005

Polym J

ABSTRACT:We investigated photo-alignment properties of main-chain polyimides prepared from acid anhydrides [4,4 0 -(hexafluoro-isopropylidene) diphthalic anhydride (6FDA) or 4,4 0 -biphthalic anhydride (BPDA)] and diamine derivatives containing a chalcone group. The polyimides in the film state were irradiated with linearly polarized UV (LPUV) light under different conditions. The liquid-crystalline (LC) cell was fabricated from the polyimide film irradiated with LPUV light. A mixture of a low molecular liquid crystal (4-cyano-4 0 -n-pentylbiphenyl: 5CB) and a dichroic dye was filled in the LC cell. 5CB in the LC cell was easily aligned perpendicular to the electric vector of the incident LPUV light. [DOI 10.1295/polymj.37.162] KEY WORDS Chalcone / Liquid-Crystalline Polymer / Photo-alignment / Polyimide / Alignment of liquid-crystalline (LC) molecules is important for liquid-crystalline displays (LCDs). Rubbing has been mainly employed for the uniaxial orientation of the LC molecules. However, rubbing has many disadvantages for LCDs such as generation of electrostatic charge and dust. Therefore, many methods of alignment technique for LC molecules focus on rubbing free methods. Photo-alignment procedure is a rubbing free method and is investigated as one of candidates that overcome the generation of electrostatic charge and dust for the rubbing process. 1,2The photo-alignment procedure is based on photochemical reactions such as photo-isomerization, photo-dimerization (photo-crosslinking) and photodecomposition.3-5 Photo-dimerization of photosensitive groups in polymers is employed to obtain a stable alignment of LC molecules. 2,[6][7][8][9][10][11][12] It is desirable that photo-dimerization occurs by the exposure of relatively longer wavelength of the UV light to avoid partial degradation of polymers by the irradiation.13 Photoreaction of chalcone moieties takes place by the irradiation with relatively longer wavelength of the UV light. Non-mesogenic photosensitive polymers containing chalcone derivatives have been studied for the photo-alignment film. 13-19The alignment of LC molecules is easily improved by the surface of LC polymers that exhibit a mesophase. This idea arises from the simple role of solubility for organic compounds, that is, like dissolves like. We already investigated thermal and photo-alignment properties of side-chain LC methacrylate polymers and side-chain polyimides bearing the chalcone derivative in the side chain. [20][21][22] Generally, main-chain polyimides demonstrate good thermal and mechanical properties based upon the rigid rod-like chemical structure of the polymer backbone. Therefore, main-chain polyimides would be suitable candidates for the polymeric materials applied to the photo-alignment film, because many polyimide derivatives have been used as an alignment film of LCDs owing to excellent thermal and mechanical properties.In this study, we investigate the extent of photoreaction of the chalcone-based main-chain polyimides prepared from two anhydride compounds [4,4 0 -(...

“…Photosensitive polymers containing chalcone derivatives have been studied for the photo-alignment film. [14][15][16][17][18][19][20] The alignment behavior of the LC molecules would be easily improved by the liquid crystalline polymer surface where mesogenic groups having similar chemical structure to that of the LC molecules existed. This idea would arise from similar behavior to the solubility of the organic compounds, that is to say, like dissolves like.…”

Section: Introductionmentioning

confidence: 99%

Photocrosslinked film of polymers having chalconyl moiety and their alignment capability for liquid crystal materials

2003

SPIE Proceedings

We synthesized side chain polymethacrylate derivatives (polymers 1 and 2), side chain polyimide derivatives (polymer 3 and 4), and main chain polyimide derivative (polymer 5) containing a chalconyl moiety to investigate both the extent of photo-reaction and photo-alignment behavior of liquid crystalline (LC) molecules. A smectic A phase was exhibited for the polymethacrylate derivatives, while polyimide derivatives did not show any mesophases. Only glass transition temperature was observed for the polyimides. Polymethacrylate derivatives showed large values of the extent of photo-reaction in the LC phase, while the extent of photo-reaction for polyimides above glass transition temperature was larger than that below glass transition temperature. Mixtures of low molar mass liquid crystal (MBBA or 5CB) and dichroic dye were filled in the LC cells fabricated from the polymer. In the case of the LC cells fabricated from polymer 1 irradiated with linearly polarized UV (LPUV) light in the LC phase, LC molecules were easily aligned parallel to the electric vector of the incident LPUV light. Parallel alignment behavior of LC molecules was also observed for the LC cells fabricated from the polymers 3 and 4 irradiated with LPUV light, while LC molecules in the LC cells fabricated from the polymer 5 were aligned perpendicular to the electric vector of the incident LPUV light.