The Sony Trinitron cathode ray tubes (CRT) were well-received in the market for TVs and computer displays because of their bright, high-resolution images and flat screens.

Whatsit?

Trinitron, a registered trademark of the Sony corporation, refers to a patented aperture grill masking technology that was developed because Sony wanted to avoid paying royalties on the existing shadow mask technology of the time. It was patented in 1967 and first appeared in a commercial product in 1968, a 7-in. portable TV set by Sony. The technology began to be applied to CRT computer displays in 1982 and were standard in the Macintosh II series of personal computers. When the patent expired in the early 1990s, Mitsubishi and other manufacturers were quick to adopt the newly free technology, and the prices of bright, high-resolution flat-screen TVs and monitors dropped just as quickly.

The technology

The conventional shadow mask is basically a thin metal plate with very small circular holes in it that is placed between the electron gun of the CRT and the phosphor screen. For each hole in the mask, there is a triad of red, green and blue phosphors on the phosphor screen. The electron beams from the cathodes of the electron gun pass through the holes and strike the phosphors to create the image.

Trinitron technology replaces the metal plate with fine wires stretched tightly from the top of the screen to the bottom, creating grid of vertical slots for the electron beams to pass through instead of holes. This is called an aperture grille. The phosphor screen is likewise made up of vertical stripes of red, green and blue phosphors instead of the phosphor triad dots of the shadow mask screen. Three electron beams from a single gun pass through each slot to strike the appropriate phosphor strip to illuminate each color pixel. That's what inspired the name Trinitron. Sony had previously tried to produce TVs with a different technique called the Chromotron tube, but it was defeated by production problems.

What makes it better?

The use of slot apertures formed by stretched wires allowed the Trinitron screen to be perfectly flat in the vertical direction, and only slightly curved in the horizontal direction. This feature did much to differentiate these CRTs in the market, and ignited the whole flat screen craze. But, even that advantage was less impressive than the much brighter screen. The aperture grille put much less metal between the electron gun and the phosphor screen, resulting in a very noticeable increase in brightness for the same power. Still, the most impressive feature was probably the increased resolution that came from the small pitch of the wires and the vertical stripe phosphor configuration. A somewhat lesser advantage that comes with the flat screen is reduced reflection and glare from the screen.

So what's the catch?

One price to be paid for all that superiority was, well, the price. The Trinitrons had premium price tags until the patent expired. But there was also the notorious thin grey lines that stretched horizontally across the screen. They are seldom noticeable on TVs, where moving images are the rule, but on relatively static computer displays with white backgrounds, those little lines leap out at you and somehow command your attention. I remember when I first fired up my new Mac II (5 minutes out of the box) about two decades ago, the first thing I noticed was that single grey line. "Uh-oh." I thought, "Defective monitor." I decided it wasn't worth the hassle of returning and waiting. It quickly becomes unnoticed. Later, I learned that those lines are caused by horizontal wires placed across the aperture grille to stabilize the vertical wires. There's one on displays up to 15" and two on larger displays. In the two tubes that I dismantled, the stabilizing wires were made from plastic, like very fine nylon fishing line.