The hallmarks of HTPS technology are superior image quality, high resolution, brightness, and excellent luminous efficiency. Epson has been a pioneer in developing and improving on this technology. In 1999
the company developed a new HTPS processing technology called D1 that enabled higher aperture ratios despite a scaling down in size. This technology has since evolved, with the latest D4 panels - released in September 2003 - featuring improved image quality, resolution, and light-use efficiency.
Flattering technology for better image
quality
On D3 panels, thin-film transistors were formed inside the quartz glass substrate in such a way that tiny bumps remained on the internal surface of the substrate. This height difference disturbed the arrangement of liquid crystal elements,
leading to minor light leaks. To iron out this difficulty, Epson has made every effort to flatten the surface. Virtually perfect flatness was finally achieved on D4 panels by using a polishing process used for semiconductors. The flatter topology means that light leaks are reduced and the contrast ratio is raised from 400:1 on earlier panels to 500:1 on the D4. Epson is now developing technologies that will boost the ratio to 3,000:1 to achieve even higher luminous efficiency and image quality.
In addition to flattening the surface of the glass substrate, the thickness of the liquid crystal layer has been reduced from 3 micrometers (
m) to 2.5
m. The narrower gap has improved the response speed and contrast ratio. D4 panels respond 25% faster than D3 panels. Faster response means that the afterimage disappears more quickly and images become sharper. Higher contrast ratios mean that images are clear and firm, with dark areas appearing darker and bright areas shining brighter. The contrast ratio is particularly important for home projectors because many movies contain very dark scenes.
Light-shielding layer for enhanced
protection
TFTs are sensitive to intense light, so Epson developed a light-shielding layer for the glass substrate
to prevent light from accidentally reaching the pixel transistor. If the alignment or bonding of the glass substrate is poor, though, the light-shielding layer can shift, in some cases allowing light to reach the wiring or transistor area. On D4 panels, therefore, the light-shielding layer completely surrounds the TFT so as to shut out the light and its effects on the
TFTs.
*Check the Website of your local
Epson sales company for details of Epson
projectors containing unique HTPS technology.
