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Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam.

Choi Y, Yoon TH, Kwon JH, Yi J, Gwag JS - Nanoscale Res Lett (2012)

Bottom Line: Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps.To confirm it, contact angle measurement was carried out.With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Yeungnam University, 214-1 Dae-dong, Gyeongsan 712-749, South Korea. sweat3000@ynu.ac.kr.

ABSTRACT
We investigate the pretilt characteristics of a nematic liquid crystal [LC] in terms of ion beam exposure conditions on the homeotropic polyimide alignment layer. The pretilt angle of LCs in the case of high-energy ion beam treatment was decreased considerably almost the same to that of the homogenous alignment layer though we used homeotropic polyimide film at first. Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps. We believe that this is because the side chain with hydrophobicity in the used polyimide is broken by ion beam exposure. To confirm it, contact angle measurement was carried out. With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality.

No MeSH data available.


Related in: MedlinePlus

The contact angle of droplet on a sample before and after ion beam treatment. For static mode, (a) the droplet image on the sample before ion beam treatment, (b) the droplet image taken parallel to the ion beam-irradiated direction after ion beam treatment, and (c) the droplet image taken perpendicular to the ion beam-irradiated direction after ion beam treatment. For dynamic mode, (d), (e), and (f) show that the angle difference is smaller for the direction perpendicular to the ion beam exposure.
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Figure 3: The contact angle of droplet on a sample before and after ion beam treatment. For static mode, (a) the droplet image on the sample before ion beam treatment, (b) the droplet image taken parallel to the ion beam-irradiated direction after ion beam treatment, and (c) the droplet image taken perpendicular to the ion beam-irradiated direction after ion beam treatment. For dynamic mode, (d), (e), and (f) show that the angle difference is smaller for the direction perpendicular to the ion beam exposure.

Mentions: The contact angle at static mode was reduced seriously after ion beam treatment as shown Figure 3a, b, c. Figure 3a is a droplet image taken on a sample before ion beam treatment. On the other hand, Figure 3b, c shows droplet images taken parallel and perpendicular to the ion beam-irradiated direction for the ion beam-treated sample, respectively. This result supports obviously the analysis that the side chain with hydrophobicity in the polyimide broke off or was destroyed by the ion beam as expected in the sharp decrease of the LC pretilt (see Figure 2). In an additional experiment, we measured the dynamic contact angle of this sample. The dynamic contact angle is the contact angle before slipping down the liquid on the substrate when we tilt the sample slowly and informs us macroscopically of the relative information about the surface roughness. Generally, if the angle difference between the advancing angle and receding angle is larger, then the surface is rougher. Figure 3d, e, f shows that the angle difference is small for the direction perpendicular to the ion beam exposure. Figure 3d is taken before treatment, and Figure 3e, f images are taken in the case of parallel and perpendicular ion beam irradiation, respectively. This means that the roughness of the surface in the case of parallel irradiation is bigger than that that of the perpendicular irradiation case. Note that this matches well to other ion beam treatment results [14]. Consequently, we verify what the LC pretilt change causes in ion beam exposure from the contact angle method.


Zenithal alignment of liquid crystal on homeotropic polyimide film irradiated by ion beam.

Choi Y, Yoon TH, Kwon JH, Yi J, Gwag JS - Nanoscale Res Lett (2012)

The contact angle of droplet on a sample before and after ion beam treatment. For static mode, (a) the droplet image on the sample before ion beam treatment, (b) the droplet image taken parallel to the ion beam-irradiated direction after ion beam treatment, and (c) the droplet image taken perpendicular to the ion beam-irradiated direction after ion beam treatment. For dynamic mode, (d), (e), and (f) show that the angle difference is smaller for the direction perpendicular to the ion beam exposure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3278366&req=5

Figure 3: The contact angle of droplet on a sample before and after ion beam treatment. For static mode, (a) the droplet image on the sample before ion beam treatment, (b) the droplet image taken parallel to the ion beam-irradiated direction after ion beam treatment, and (c) the droplet image taken perpendicular to the ion beam-irradiated direction after ion beam treatment. For dynamic mode, (d), (e), and (f) show that the angle difference is smaller for the direction perpendicular to the ion beam exposure.
Mentions: The contact angle at static mode was reduced seriously after ion beam treatment as shown Figure 3a, b, c. Figure 3a is a droplet image taken on a sample before ion beam treatment. On the other hand, Figure 3b, c shows droplet images taken parallel and perpendicular to the ion beam-irradiated direction for the ion beam-treated sample, respectively. This result supports obviously the analysis that the side chain with hydrophobicity in the polyimide broke off or was destroyed by the ion beam as expected in the sharp decrease of the LC pretilt (see Figure 2). In an additional experiment, we measured the dynamic contact angle of this sample. The dynamic contact angle is the contact angle before slipping down the liquid on the substrate when we tilt the sample slowly and informs us macroscopically of the relative information about the surface roughness. Generally, if the angle difference between the advancing angle and receding angle is larger, then the surface is rougher. Figure 3d, e, f shows that the angle difference is small for the direction perpendicular to the ion beam exposure. Figure 3d is taken before treatment, and Figure 3e, f images are taken in the case of parallel and perpendicular ion beam irradiation, respectively. This means that the roughness of the surface in the case of parallel irradiation is bigger than that that of the perpendicular irradiation case. Note that this matches well to other ion beam treatment results [14]. Consequently, we verify what the LC pretilt change causes in ion beam exposure from the contact angle method.

Bottom Line: Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps.To confirm it, contact angle measurement was carried out.With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physics, Yeungnam University, 214-1 Dae-dong, Gyeongsan 712-749, South Korea. sweat3000@ynu.ac.kr.

ABSTRACT
We investigate the pretilt characteristics of a nematic liquid crystal [LC] in terms of ion beam exposure conditions on the homeotropic polyimide alignment layer. The pretilt angle of LCs in the case of high-energy ion beam treatment was decreased considerably almost the same to that of the homogenous alignment layer though we used homeotropic polyimide film at first. Increasing irradiating energy, we could control the pretilt from 90° to 1° with several steps. We believe that this is because the side chain with hydrophobicity in the used polyimide is broken by ion beam exposure. To confirm it, contact angle measurement was carried out. With this result, we can easily control the LC pretilt in the pixel with appropriate exposure conditions which is critical to achieve excellent electrooptic characteristics and good image quality.

No MeSH data available.


Related in: MedlinePlus