Recently, a spacer prepared from a photosensitive resin composition is employed in order to maintain a constant distance between the upper and lower transparent substrates in liquid crystal cells of a liquid crystal display (LCD). In an LCD, which is an electro-optical device driven by a voltage applied to a liquid crystal material injected into a constant gap between two transparent substrates, it is very critical to maintain the gap between the two substrates to be constant. If the gap between the transparent substrates is not constant, the voltage applied thereto as well as the transmittance of light penetrating this area may vary, resulting in a defect of spatially non-uniform luminance. According to a recent demand for large LCD panels, it is even more critical to maintain a constant gap between two transparent substrates in an LCD.
Such a spacer may be prepared by coating a photosensitive resin composition onto a substrate and exposing the coated substrate to ultraviolet light, etc., using a mask, followed by development thereof. Recently, efforts of using a light shielding material for a spacer have been made; accordingly, various colored photosensitive resin compositions have been actively developed.
Recently, a black column spacer (BCS), i.e., a light shielding spacer, in which a column spacer and a black matrix are integrated into a single module using a colored photosensitive resin composition has been provided to simplify the process steps. Such a light shielding spacer is required to have high sensitivity and excellent development margin characteristics. A conventional light shielding spacer, however, has the defect that the voltage holding ratio (VHR) that may affect the driving of liquid crystals after the assembly of upper and lower display plates is low; or that color washout occurs, which may cause a poor transmission of electric signals, thereby hampering the reliability of the product.
In particular, a light shielding spacer prepared from a colored photosensitive resin composition, which contains a pigment by nature, has the problem that the voltage holding ratio is relatively low.
USPTO Backgrounds
USPTO Backgrounds