JPH0143981B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a color cathode ray tube used, for example, as a computer terminal, and more particularly to a flicker-free color cathode ray tube that can be used with a light pen. Conventionally, in this type of color cathode ray tube, in order to prevent flicker, the afterglow time of the phosphor that makes up each picture element of the luminescent screen is usually 50 milliseconds or more at 10% afterglow time, although it varies depending on the device. It was hot. However, although such afterglow phosphors are effective in preventing flicker, they have a slow response even when excited by electron beams, so they have the disadvantage of causing misunderstanding of position when used with a light pen. In order to satisfy these contradictory demands, a luminescent screen has recently been developed in which a phosphor with an extremely short afterglow, that is, a phosphor with a quick response, is placed between the afterglow phosphor and the face plate. As shown in FIG. 1, this luminescent screen is made by forming a light absorption matrix 2 on the inner surface of a face plate 1 by a known method, and then coating the entire inner surface with a short afterglow phosphor layer 3. It is constructed by forming three types of light-emitting picture elements 4, 5, and 6 using a known photographic printing method. According to this luminescent screen, flickering can be prevented by the afterglow luminescent pixels 4, 5, and 6.
Moreover, the short afterglow phosphor layer 3 has the advantage of preventing malfunction of the light pen. However, the phosphors that can be used for the short afterglow phosphor layer 3 are 10
A % afterglow time of about 100 nanoseconds is required, and phosphors that satisfy this are P47 (Y ₂ SiO ₅ :Ce) and P46.
( _Y3Al5O12 : _{Ce )} , P37 (ZnS:Ag:Ni), P16
(Ca ₂ MgSi ₂ O ₇ :Ce), etc., but all of them are darker than the phosphors that make up the light-emitting pixels, and the emitted light is blue or blue-green, so the brightness of the light-emitting pixels decreases and This had the disadvantage of causing a decrease in the purity of the emitted light color. It is an object of the present invention to minimize these drawbacks and provide a color cathode ray tube with less reduction in brightness and color purity. The inventor completed this invention as a result of detailed research on the coating density of the short afterglow phosphor and the brightness and chromaticity of the light-emitting picture element. Figure 2 shows the case of using the above-mentioned P47 as a short afterglow phosphor and P39 phosphor (Zn ₂ SiO ₄ :Mn:As) as a light-emitting pixel.
FIG. 3 is a diagram showing the relationship between the coating density of P47 phosphor and the brightness and y value of CIE chromaticity. In the figure, solid lines indicate brightness, and broken lines indicate chromaticity. As is clear from this figure, when the coating density of the P47 phosphor exceeds 1.5 mg/cm ² , the brightness and color purity decrease rapidly. Also,
From the viewpoint of sensitivity to light pens, it has become clear that if the coating density of P47 phosphor is less than 0.5 mg/cm ² , sufficient light output cannot be obtained for the light pen to operate, causing malfunctions. Therefore, by setting the coating density of the P47 phosphor to 0.5 to 1.5 mg/cm ² , it is possible to reduce the loss of light output from the light-emitting picture elements to less than 10%, and also to prevent malfunctions of the light pen. This tendency was exactly the same for other short afterglow phosphors such as P46 and P16. Examples of this invention are shown below. Example After forming a light absorption matrix 2 of graphite on the inner surface of the face plate 1 by a known method, 1.0% of P47 phosphor with a 10% afterglow time of 150 nanoseconds was formed.
The coating was applied at a coating density of mg/cm ² , and red, blue, and green light-emitting pixels 4, 5, and 6 were formed thereon by a known photographic printing method. The following phosphors were used for these picture elements.

[Table] Light output of each luminescent picture element of this luminescent screen
Compared to the case without P47 phosphor, the light output loss is 8% for red, 5% for blue, and 7% for green.
Compared to the conventional product, which was coated with 2.5 mg/cm ² of P47 phosphor, the brightness was improved by about 25%. In addition, the CIE x value of the red light-emitting pixel was significantly improved from 0.614 to 0.630, which is close to the value of 0.636 when no P47 phosphor is coated. In addition, in the above examples, as a short afterglow phosphor
Although P47, P46, and P16 have been described, the present invention is not limited to these, and the same effect can be obtained even if phosphors having similar afterglow characteristics are used. As described above, the present invention has the effect of minimizing the reduction in brightness and color purity and preventing malfunctions of the light pen, and is therefore very advantageous, particularly in flicker-free color cathode ray tubes.

[Brief explanation of drawings]

Figure 1 is an enlarged cross-sectional view showing the luminescent screen of a fritz-free color cathode ray tube, and Figure 2 is a diagram depicting the relationship between the coating density of the short afterglow phosphor layer and the light output and chromaticity of the green luminescent pixel. It is. 1... Face plate, 3... Short afterglow phosphor layer, 4, 5, 6... Picture element.

Claims (1)

[Claims] 1. In a color cathode ray tube equipped with a luminescent screen having a picture element made of an afterglow phosphor and a short afterglow phosphor disposed between the picture element and the face plate, the short afterglow phosphor is Body application density
A color cathode ray tube characterized by having a concentration of 0.5 to 1.5 mg/cm ² .