We are investigating the important physical factors for the reproduction of the high-order sensation, such as 'the sense of existence' and 'the naturalness', in a display of images. In our research, a key assessment word, 'image depth', is a useful indicator for the discovery of new physical factors. Focusing on the faithful reproduction of 'image depth', some physical factors of a display have been discovered. In this report, we will describe the newly discovered physical factor, the halation and the degradation of image quality. After observation of the images on two displays which have different types of coating on the surface of CRT, we have hypothesized that the halation around the surface of CRT might cause a serious degradation of image quality such as 'image depth'. Also we have considered that the coating might be one of important factors related to the halation characteristic. To confirm the above assumption, we prepared three types of CRT picture monitor which have different types of coating: 13 layer AR coating, 4 layer AR + non- glare coating and no-coating. The increase of luminance around a test target of white rectangle caused by the halation have been measured and the relationship between the halation characteristic and the reproduction of 'image depth' has been assessed.