Sony first developed Trinitron technology, in 1968. At that time it was designed for televisions. It was in the 1980s that it was applied to computing and integrated into CRT monitors. It works on a simple principle. Rather than grouping the phosphor dots into a triangle, they are aligned by color type in the form of unbroken stripes. The rays are straight along the left and right edges and curved at the top and bottom. The Shadow Mask is replaced here by a different mask perforated not with holes but with vertical stripes, unbroken like the phosphor. The matrix, the opaque part that doesn't allow beams to cross, takes up less room than in the previous technology, and this results in images that are clearer and brighter.
The only trouble is that the mask is made up of thousands of very fine filaments and must be held firmly in place. So there are two horizontal damper wires stretched to the full, designed to absorb shocks and expansion when the materials heat up to a certain degree. This produces two dark lines that can be seen on screen against a light background. This can be tiresome for some users, especially if they work with a white background. But the eye gets used to it after a while, and has to look hard to see the lines. Note, too, that the number of lines you can see depends on the size of the screen and especially the size of the mask. There will only be one on a screen of less than 17" and two on bigger screens. To sum up, the three main advantages of the Trinitron are: a reduction in heat dispersion; more brightness for equal power and better contrasts; and, of course, a completely flat screen.
Only two manufacturers make tubes with Trinitron technology - Sony, with the FD Trinitron, and Mitsubishi, with the DiamondTron. The PerfectFlat by ViewSonic is actually an adaptation of the latter. The main difference between the two is that Sony uses three electron guns for the three basic RGB colors and Mitsubishi only uses one. In all cases, the different technologies go by the name of Aperture Grill, less well known but more widespread than Trinitron, which belongs to Sony.