JPH059897B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fluorescent surface of a cathode ray tube.

A useful means of increasing the image contrast of the fluorescent surface of a cathode ray tube is to reduce the light transmittance of the face plate glass of the fluorescent surface. This principle will be explained in detail with reference to FIG.

FIG. 1 is a cross-sectional model of the fluorescent surface of a color cathode ray tube. 1 is a face plate glass, and on its inner surface there are three color phosphor elements 2 of red (R), green (G), and blue (B).
is provided. Now, the intensity of the external light incident on the face plate glass 1 of the color cathode ray tube configured in this way is (E ₀ ), and the intensity of the external light that is reflected from the fluorescent surface and then reflected back to the outside of the face plate glass 1 is the intensity (E 0 ). Light intensity (E ₁ ), face plate glass 1
The light transmittance of (T _f ), the reflectance of the three-color phosphor element group 2 (red (R), green (G), and blue (B)) (R _p ), and the intensity of light emission of the phosphor element group (F ₀ ), and the fluorescent surface light output coming out of the face plate glass 1 is (F ₁ ), then E ₁ = E ₀ · R _p · T _f ² ... () F ₁ = F ₀ · T _f ...() becomes. Also, contrast C can be defined as C=E ₁ +F ₁ /E ₁ ...(), so by substituting equations () and () into equation (), we get C=1+F ₀ /E ₀・R _p・T _f ……( ) becomes. Strictly speaking, factors such as the reflection of external light on the surface of the face plate glass 1, multiple reflections within the face plate glass 1, and halation caused by scattered electrons must also be introduced, but these effects are sufficient here. I ignored it as being small. It is clear from equation () that the contrast of the cathode ray tube image can be improved by lowering the light transmittance (T _f ) of the face plate glass 1. Conventionally, the glass used as face plate glass 1 for cathode ray tubes is generally clear glass with a visible light transmittance of 75% or more.
They are used separately as 60-75% gray glass and 60% or less taint glass. Figure 2 a shows the typical spectral transmittance curves for clear glass, e for gray glass, and c for taint glass. It also shows the emission spectrum of the three-color red (R), green (G), and blue (B) phosphor elements of a cathode ray tube.

On the other hand, as is clear from Figure 2 and equation (), the light output of the fluorescent surface, that is, the brightness of the fluorescent surface, is opposite to the contrast as the light transmittance (T _f ) of the face plate glass 1 becomes lower. I see, it gets lower. In other words, contrast performance and brightness performance of images are difficult to reconcile as far as the light transmittance (T _f ) of the face plate glass 1 is concerned, and it depends on which performance is more important.
A selection of types had been made.

As a means to solve this dilemma regarding brightness performance and contrast performance and to improve both performances, as shown in Fig. 2, instead of the conventional face plate glass which has almost flat light transmittance in the visible range, a three-dimensional fluorescent surface is used. It has been proposed to selectively provide the face plate glass 1 with light absorbing properties in the wavelength region between the valleys of the emission spectra of the color phosphor elements, that is, in the region of low emission energy. Figure 3 shows the spectral transmittance curve of face plate glass 1, which has been proposed as a material that almost satisfies these _purposes . It was formed by adding 0.5% by weight of O ₃ ). (Hereinafter referred to as neodymium-containing glass.) This neodymium-containing glass has a steep main absorption band ranging from 560 to 615 nm and a sub-absorption band ranging from 490 to 545 nm due to the inherent characteristics of neodymium oxide ( _{Nd 2 O 3} ). These absorption bands are very steep, so even though neodymium-containing glass has high light transmittance outside these absorption bands, almost as high as conventional clear glass, the average light transmittance over the entire visible range is low. It is almost equivalent to gray glass and contributes to improving image contrast without impairing the brightness characteristics of the fluorescent surface.

FIG. 4 shows a spectral transmittance curve d of such neodymium-containing glass and a spectral transmittance curve a of a conventional clear glass. (The emission spectrum of the red (R), green (G), and blue (B) three-color phosphor elements of the color cathode ray tube is also shown at the same time.) When such neodymium-containing glass is used as face plate glass, the fluorescence As mentioned above, the brightness and contrast characteristics of the surface are greatly improved, but the color of the fluorescent surface is significantly different from that of conventional cathode ray tubes, which has the disadvantage that the appearance tends to give a sense of discomfort to the viewer.
Figure 5 is a diagram explaining the body color of the fluorescent surface using a conventional clear glass face plate glass, where a is the spectral transmittance curve of the face plate glass, and f is the three-color phosphor element of the fluorescent surface. This is a spectral reflectance curve of the group. Each of the phosphors constituting the red (R), green (G, and blue) three-color phosphor element group 2 on the phosphor surface originally has a high light reflectance over the entire visible range as a powder. As shown in f, the three-color phosphor element group as a whole has a high reflectance over the entire visible range. If the light transmittance of the face plate glass 1 is (T _f ) and the reflectance of the three-color phosphor element group is (R _p ), then from the above equation (), the reflectance of the phosphor surface (R _s ) is R _s = E ₁ /E ₀ =R _p・T _f ² . The fluorescent surface spectral reflectance curve obtained in this way is as shown in (g). This fluorescent surface spectral reflectance curve
As shown in the figure, (g) is almost flat over the entire visible light region, and when white extraneous light is incident on the fluorescent surface, reflected light with almost the same wavelength component as the incident light is emitted, so the body color of the fluorescent surface is gray. The color tone is calm and neutral.

On the other hand, when neodymium-containing glass is used as the face plate glass 1, the spectral reflectance curve of the fluorescent surface is approximately as shown in FIG. 6h. In this case, since the spectral transmittance curve d of the neodymium-containing glass varies greatly with respect to wavelength, the spectral reflectance curve f of the three-color phosphor element group on the fluorescent surface covers the entire visible light region. Although the fluorescent surface is flat, the spectral reflectance curve of the fluorescent surface is extremely uneven, and when white light is incident on the fluorescent surface, the light reflected by the fluorescent surface has a completely different wavelength component from the incident light. The body color of the fluorescent surface becomes an unstable reddish-purple color, which is unfavorable in terms of the appearance of the fluorescent surface.

This invention was made in view of the problem that the color of the fluorescent surface becomes unstable when such neodymium-containing glass is used as the face plate glass of a color cathode ray tube. To provide a color cathode ray tube in which the body color of a fluorescent surface is stable even when glass is used as a face plate glass.

An embodiment of the present invention will be described below with reference to FIG. In the present invention, instead of using a three-color phosphor element group that has a flat spectral reflectance over the entire visible light region as in the past, the main absorption band region of the spectral transmittance curve d of neodymium-containing glass, that is, 560 to 615 nm, is used.
The peak of the spectral reflectance is between 490 and 545 nm, i.e. between 490 and 545 nm, and the other parts have a lower reflectance than before.To give an example, the spectral reflectance is as shown in 1 in the figure. A group of three color phosphor elements having a rate curve is provided on the inner surface of the face plate glass. As an example of a method for obtaining a three-color phosphor element group having such a special spectral reflectance curve, a green (G) color-emitting phosphor element of the three-color phosphor element group is used.
One example is the use of a pigmented green (G) color-emitting phosphor, which is a mixture of fringe color and yellow color pigments in the (G) color-emitting phosphor. The reason why this type of pigment is added only to green (G) color emitting phosphor elements is that the pigment absorbs little light emission energy. Examples of such green pigments include chromium oxide pigments, and examples of yellow pigments include G and R mixed pigments manufactured by Dainichiseika Kagyo Co., Ltd., and cadmium sulfide pigments.

A phosphor surface spectral reflectance curve m when a three-color phosphor element group having a spectral reflectance curve 1 as described above is provided on the inner surface of a neodymium-containing glass face plate glass having a spectral transmittance curve as shown in d. The unevenness is smoothed by the spectral reflection characteristics of the three-color phosphor element group, and it has the flat spectral reflection characteristics of the conventional 3.
The difference between the wavelength components of the incident light and the reflected light is smaller than when a group of colored phosphor elements is used, and the body color of the phosphor surface approaches neutral.

As described above, according to the present invention, the problem of instability of the body color of the fluorescent surface when neodymium-containing glass is used for the face plate glass is improved by the spectral reflection characteristics of the three-color phosphor element group, and it is sufficiently stabilized. A fluorescent surface with a calm body color can be obtained, and together with improvements in contrast and brightness characteristics, it becomes possible to provide a cathode ray tube of very high quality.

[Brief explanation of the drawing]

Figure 1 shows a cross-sectional model of the fluorescent surface of a color cathode ray tube, Figure 2 shows typical spectral transmittance curves of various glasses, and Figure 3 shows the spectral transmittance curve of neodymium-containing glass. Figure 4 shows the spectral transmittance curves of neodymium-containing glass and clear glass, Figure 5 shows the spectral reflectance curves of conventional fluorescent surfaces, and Figure 6 shows the spectral reflectance curves of neodymium-containing glass. FIG. 7 is a diagram showing the spectral reflectance curve etc. of the fluorescent surface according to the present invention. In the diagram, 1 is face plate glass, 2 is red (R) green
(G) Blue (B) three-color phosphor element group.

Claims (1)

[Claims] 1. A fluorescent surface is constituted by a face plate glass containing neodymium oxide (Nd ₂ O ₃ ) and a group of phosphor elements of multiple colors provided on the inner surface of the face plate glass. and the spectral reflectance of the phosphor element group is 490 nm to 545 nm and 560 nm to 560 nm.
A cathode ray tube characterized by having a maximum value in the 615nm wavelength band. 2. A cathode ray tube according to claim 1, characterized in that phosphors with green and yellow pigments are used as the green (G) color emitting phosphor elements of the phosphor element group.