Cathode-ray tube with interference filter

A cathode-ray tube having a face plate comprising:

• (a) a plate having an inner surface to which irradiation of a cathode-ray beam is directed;
• (b) a phosphor layer formed on said inner surface of said plate;
• and
• (c) an optical interference filter formed between said inner surface and said phosphor layer and comprising an odd number, not less than five, of layers in which high-refractive index layers consisting of a high refractive index material and low-refractive index layers consisting of a low refractive index material are alternately stacked, said low-refractive index layers consisting essentially of Al.sub.2 O.sub.3 and said high-refractive index layers consisting essentially of TiO.sub.2, said optical interference filter having a cutoff wavelength .lambda..sub.o with a value between 1.06 .lambda. and 1.46 .lambda., and .lambda. is a center wavelength of an emission spectrum of a phosphor constituting said phosphor layer;
• wherein said optical interference filter is constituted by sequentially stacking, from said inner surface of said plate;
• (i) a low-refractive index layer having an optical thickness of about 0.125 .lambda..sub.o ;
• (ii) a periodically alternating layer in which high-refractive index layers having an optical thickness of about 0.25 .lambda..sub.o and low-refractive index layers having an optical thickness of about 0.25 .lambda..sub.o are alternately stacked an odd number of times and a layer closest to said phosphor layer is a high-refractive index layer;
• and
• (iii) a low-refractive index layer having an optical thickness of about 0.125 .lambda..sub.o.

A cathode-ray tube having a face plate comprising:

• (a) a plate having an inner surface to which irradiation of a cathode-ray beam is directed;
• (b) a phosphor layer;
• and
• (c) an optical interference filter, formed between said inner surface f said plate and said phosphor layer, comprising, by sequentially stacking from said inner surface of said plate:
• (i) a high-refractive index layer having an optical thickness of about 0.25 .lambda.+0.125 .lambda..sub.o, where .lambda..sub.o is the cutoff wavelength of said optical interference filter and has a value between 1.05 .lambda. and 1.50 .lambda., where .lambda. is the center wavelength of an emission spectrum of a phosphor constituting said phosphor layer;
• (ii) a periodically alternating layer having an odd number, not less than three nor more than thirty-one of layers in which low-refractive index layers having an optical thickness of about 0.25 .lambda..sub.o and high-refractive index layers having an optical thickness of about 0.25 .lambda..sub.o are alternately stacked and a layer closest to said phosphor layer is a low-refractive index layer;
• (iii) a high-refractive index layer having an optical thickness of about 0.25 .lambda..sub.o +0.125 .lambda..sub.o ;
• and
• (iv) an outermost layer in contact with said phosphor layer, said outermost layer having a physical thickness of not less than 10 nm and consisting of Al.sub.2 O.sub.3 of ZrO.sub.2.