Hitachi Displays 4.5-inch RGB Stripe 1280×720 IPS LCD Using Amorphous Silicon (a-Si) Instead of Low Temperature Poly-Silicon (LTPS)

Hitachi Displays (Japanese) announced its 4.5-inch IPS LCD sporting a RGB stripe 1280×720 pixel format good for a resolution of 329 ppi.

  • Display: 8-bit IPS LCD
  • Pixel Format: 1280×720
  • Sub-Pixel Format: RGB Stripe
  • Colors: 16.77 million
  • Color Gamut: 70% NTSC (CIE 1931)
  • Viewing Angles: 160/160
  • Brightness: 500 nits
  • Contrast Ratio: 1000:1

One specification that seems to be not up to par are the viewing angles. At 160/160 these are considerably less than the 178/178 that we usually see on IPS LCDs.

One significant underlying technology that was used to manufacture this technological marvel is the amorphous silicon (a-Si) based TFT backplane. Typically, high performance mobile LCDs feature a TFT backplane made of low temperature polysilicon (LTPS). There are many reasons for this.

The structure of a-Si is randomly aligned and exhibits a higher electrical resistance restricting electron mobility. The LTPS process involves the crystallization of a-Si resulting in poly-crystalline silicon or poly-silicon. The new poly-silicon structure lowers electrical resistance and improves electron mobility by about 100 times compared to a-Si.

Higher electron mobility reduces the size, especially the bezel, of the LCD by integrating the driver ICs directly unto the glass. With a glass-integrated driver IC the pitch between pixels are finer enabling higher resolution mobile displays. Another benefit includes the reduction of components that leads to increased ruggedness with higher resistance to vibration and impact.

But there is one major drawback: LTPS is expensive. Hitachi Displays has somehow used a cheaper a-Si TFT backplane and crammed 1280×720 pixels into a 4.5-inch IPS LCD. This is an amazing feat as it combines high performance with low cost. I hope the performance doesn’t disappoint. Hitachi Displays will be showcasing its 4.5-inch a-Si 1280×720 IPS LCD during FPD International (October 26 – 28).