CRT monitors grew in size to the point where they have been supplanted by new technology, the flat screens. At the same time costs have been by controlled by limiting the amount of gold and other valuable metals required in their manufacture.
A CRT monitor consists of a vacuum tube with three electron guns - one each for red, green, and blue, with separate signals for each of the three colours. The three electron guns fire electrons at the screen, which contains a phosphorous coating which is sensitive to the beams. Yttrium (III) oxide, is used to make phosphors which create the red colours on the screen. The CRT also contains lead in the glass panel, within a glass funnel towards the narrow end of the monitor, and in the weld between the two. The glass can be re-used as glass cullet. The cone that encircles the electron gun at the rear and directs the electron streams produced by the electron guns includes copper components. There is also a circuit board, which controls the operation of the electron guns, and this contains copper together with very small amounts of gold and other valuable metals and these have some positive scrap value. The plastic casing of the CRT monitor can be recycled.