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World's First Black-stripe Color Cathode-ray Tube

Clearer and brighter – an innovative product incorporating a world-standard color cathode-ray tube.

World's First Black-stripe Color Cathode-ray Tube

In the late 1950's, joint research into trial production of color cathode-ray tubes took place among all television manufacturers, centered on the NHK Science & Technical Research Laboratories. A gradual shift to production took place in the 1960's, with the color television market growing rapidly due to the Tokyo Olympics held in 1964.

At the time, delta electric gun and round shadow masking methods based on U.S. technology were used. However, beginning in the latter half of the 1960s the shift from 70-degree tubes to 90-degree tubes took place. Performance improved massively with adoption of new technologies, such as improved brightness from use of rare-earth phosphors, use of bimetal technology for the heat expansion of shadow masking, and improved clarity from use of blackmatrix (BM) screens. However, there were many areas that needed improvement, and since color and convergence adjustments were complex, so too was the required circuitry, which made it costly. The core of the problem was to increase resolution and shorten the length of the tube, by widening it.

These issues were resolved by developing a color tube with an inline arrangement of three electron guns, together with a newly developed slit-shadow mask combination, and stripe screen. However, although this combination of technologies promised many benefits for color tubes in terms of performance and other factors, manufacture of such tubes was a lot more complex, since new parts and processes had to be developed to realize the new technologies.

Design and process conditions for the slit mask, the feasibility of which itself was unclear, were nevertheless determined through repeated trial and error. This led to the prospect of completion of a slit mask structure that had resolution, hole ratios, and power at levels that could be implemented at the practical level. This slit mask, which had a high hole ratio, achieved brightness levels 20% higher than previous tubes. For the screen, an inline color tube and a BM screen were used. Manufacture of BM screens was complicated by factors related to phase and out-of-sync slit mask holes. These were resolved over time by fluctuation of long light sources and adoption of a new exposure method using a shutter.

Inline color tubes not only achieved higher brightness levels and lower cost, they also made possible accurate landing not just for the upper and lower portions of the screen but horizontally as well, and further, they improved color performance and made adjustments easy. In 1971, a 14-inch screen using a phosphor stripe tube was brought to market, followed by a 110-degree 20-inch BKS tube. A non-BS tube also took the world by storm. This color cathode-ray tube was the origin of the global standard for present day color TV cathode-ray tubes (i.e., inline electron gun, slit mask, and stripe screen).

Structural drawing of black-stripe color cathode-ray tube

Structural drawing of black-stripe color cathode-ray tube

20C223  Adoption of brighter and clearer, high-contrast cathode-ray tube

20C223 Adoption of brighter and clearer, high-contrast cathode-ray tube

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