Film Appearance performance test distinctness of image

What is distinctness of image?

Distinctness of image refers to the clarity of the image reflected by the film, expressed by DI value (dis-tinctness of image). This performance is mainly for further evaluation of the flatness of high-gloss coatings, that is to say, high-decoration coatings need performance evaluation in this regard.

The principle of testing the distinctness of image of the coating film

The test principle is shown in Figure 8-7. The light source maps images or numbers on the surface of the coating film, and is reflected by the coating film into the eyepiece, and the reflected image is observed by human eyes. Due to the difference in the flatness of the surface of the coating film, the clarity of the reflected image is different.

There are 13 rows of numbers that change in size on the digital board, and DOI values ​​are marked next to each row of numbers, which are 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.2, 1.5, 2.0, etc., the higher the DOI value, the smaller the row of numbers, and the more difficult to identify. The smallest row of numbers that can be clearly identified during the test, and the DOI value marked next to it is the distinctness of image of the paint film.

Standard requirements for distinctness of image of coating film

In GB/T13492-92, there are regulations on the distinctness of image for the type I topcoat of various colors of automotive topcoats, and the requirement is to reach 0.6-0.8. In fact, the DOI value of high-end new car coating is required to be above 1.0 DOI value, and the luxury car is required to be above 1.2 DOI value, which has the imaging clarity of mirror surface.

The distinctness of image Testers include the domestic QYG type, the American Pellegrini imager and the Japanese PGO-4 distinctness of imager.