JP2732621B2 - Blue pigment-coated phosphor and cathode ray tube using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a blue pigment-coated phosphor suitable for use as a fluorescent film of a cathode ray tube such as a color cathode ray tube, and a cathode ray tube using the same. About.

(Prior Art) In recent years, a pigment-coated phosphor has been used on a blue light emitting surface of a cathode ray tube, for example, a color cathode ray tube, and the contrast under bright external light has been improved. The effect of improving the contrast is due to the reduction of the external light reflectance by the pigment-coated phosphor. In other words, the pigment attached to the phosphor surface does not significantly weaken the light emission by the phosphor itself, but also absorbs the component of the external light incident on the phosphor surface that does not match the emission color of the phosphor itself. Because.

However, none of the existing pigments have the exact same color as the emission color of the phosphor and slightly absorbs the emission of the phosphor itself. To some extent, the brightness is reduced. The same applies to the case where silver-activated zinc sulfide phosphor (ZnS / Ag) is used as the blue phosphor and cobalt aluminate (CoO.nAl ₂ O ₃ ) is used as the blue pigment. There is a strong demand for a cobalt aluminate blue pigment that suppresses as much as possible.

That is, a blue pigment that absorbs as little as possible at around 450 nm, which is the emission peak of the blue light-emitting phosphor, and as much as possible at a wavelength of 500 nm or more, and which is chemically and physically stable, is desired. .

On the other hand, as a method of obtaining a pigment-coated phosphor, pigment particles are generally adhered to the surface of phosphor particles using an organic or inorganic adhesive, but polyvinyl alcohol which forms a fluorescent film of a color CRT is generally used. In a phosphor slurry mainly containing a surfactant, it is very difficult to obtain a pigment-coated phosphor having excellent dispersibility without peeling of a pigment, and has the following problems.

(Problems to be Solved by the Invention) First, when forming a fluorescent film of a color CRT,
When the phosphor is highly dispersed, the pigment may be peeled off from the phosphor surface and mixed into the phosphor screen which emits light of another color, thereby lowering the luminance or deteriorating the color purity of light emission.

Second, if the amount of the adhesive is increased to prevent pigment peeling or a stronger adhesive is used, a pigment-coated phosphor without pigment peeling can be obtained, but the phosphors also adhere to each other. Worsens the dispersion of the phosphor.

Further, in JP-A-59-227973, by changing the amount of cobalt in cobalt aluminate, the reflectance characteristics of the pigment are improved, and by using a cobalt aluminate pigment having excellent coloring power, the pigment coating is performed. The amount of pigment in the phosphor is reduced to improve pigment exfoliation and dispersion of the phosphor.

However, as described in the above publication, in the case of a blue pigment, it is desirable that the reflectance of the blue portion (around 450 nm) shows as high a value as possible and the reflectance of the portions other than the blue portion is low. In addition, since the reflectance of the blue portion is high, since the emission color of the phosphor is not absorbed, the luminance increases,
In the blue pigment used in the pigment-coated phosphor, it is desirable that the reflectance of the blue portion is high and the reflectance of the other portions is as low as possible.

However, in the blue pigment described in the above publication, when a pigment having an excellent tinting strength is obtained by increasing the amount of cobalt, the reflectance of the blue portion also becomes low, thereby causing absorption of luminescent color and causing a decrease in luminance.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide a more excellent blue pigment-coated phosphor and a cathode ray tube provided with a phosphor film made of the blue pigment-coated phosphor.

[Means for Solving the Problems] The present invention provides a blue pigment-coated phosphor obtained by coating a surface of a blue light-emitting phosphor with a cobalt aluminate blue pigment, wherein the cobalt oxide component in the blue pigment is reduced. A blue pigment-coated phosphor containing 35% by weight or more, 0.001 to 7.0% by weight of magnesium, and having a blue pigment adhesion amount of 8% by weight or less based on the phosphor.

Further, the present invention is a cathode ray tube provided with a phosphor film made of the above-described blue pigment-coated phosphor.

(Function) According to the present invention, a cobalt aluminate pigment having improved reflectance characteristics as cobalt aluminate, further improved coincidence with the emission spectrum of the blue light-emitting phosphor, and further reduced absorption of the fluorescence spectrum is used. So
Brightness and contrast characteristics of the obtained blue pigment-coated phosphor are remarkably improved.

Further, since a cobalt aluminate pigment having excellent coloring power is used, a fluorescent film of a cathode ray tube with less pigment peeling and film defects can be obtained due to a decrease in the pigment coating amount.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

First, the present invention will be described in general terms based on various measurements and experiments, and then two embodiments will be described.

That is, the pigment used for the blue pigment-coated phosphor has a body color, coloring power, and consistency with the emission spectrum of the phosphor,
It is important that the absorption of luminescence is as low as possible, which has a significant effect on the luminance and contrast characteristics of the obtained blue pigment-coated phosphor.

There are various factors for determining the body color and the reflectance of the pigment, and there is a spectral reflectance characteristic as a method of evaluating both at the same time. In the body color of the pigment, it is important that the spectral reflectance curve of the pigment matches the emission spectrum of the phosphor. In the case of a blue pigment, the reflectance in the blue part (around 450 nm) is high, and the reflectance in the non-blue part is high. It needs to be low. Further, from the viewpoint of coloring power, it is necessary that the reflectance of each wavelength other than the blue portion is low.

FIG. 1 shows a spectral reflectance curve when the amount of cobalt in the cobalt aluminate pigment was changed. The vertical axis in the figure represents the reflectance value in percentage (%), and the horizontal axis represents the wavelength in nm. In the curves in the figure, curve 1 shows that cobalt oxide (CoO) in cobalt aluminate (CoO.nAl ₂ O ₃ )
Curve 2 corresponds to 35% by weight, and curve 3 corresponds to 40% by weight.

Curve 4 represents barium sulfate as a white standard powder, and each reflectance value is represented by converting the reflectance of this white standard powder to 100% (hereinafter referred to as reflectance).

As shown in FIG. 1, it can be seen that the reflectance also moves in the lower direction by increasing the cobalt oxide in the cobalt aluminate. However, in this case, although the coloring power is excellent, the reflectance of the blue portion is low, so that the light emission of the phosphor is also absorbed, which causes a decrease in the light emission luminance.

Next, FIG. 2 is a spectral reflectance curve of a pigment in which the amount of magnesium was changed to 35% by weight of cobalt oxide in cobalt aluminate. Curve 1 shows 0% of magnesium in cobalt aluminate and curve 2 Is 2.0% by weight, curve 3 is 4.0% by weight and curve 4 is 6.0% by weight.

Curve 5 is a reflectance curve of the same barium sulfate white powder as in FIG.

As shown in FIG. 2, the reflectance in the blue portion (around 450 nm) increases in proportion to the amount of magnesium in the cobalt aluminate, and the reflectance in other portions hardly changes. Therefore, without lowering the coloring power of cobalt aluminate,
It is expected that the brightness of the blue pigment coated phosphor will be increased.

FIG. 3 shows the relationship between the amount of CoO component of the cobalt aluminate pigment alone and the body color. In the figure, the vertical axis represents the reflectance, and the horizontal axis represents the amount of CoO component. Curve 1 is the reflectance of cobalt aluminate at 600 nm, and curve 2 is the reflectance at 450 nm. As shown in this figure, the body color tends to improve in proportion to the amount of CoO.

FIG. 4 is a graph showing the reflectance at 600 nm and 450 nm when the amount of magnesium component was changed with the cobalt oxide in the cobalt magnesium aluminate being 35% by weight. As shown in this graph, it can be confirmed that the reflectance at 600 nm does not change, the reflectance at 450 nm is high, and the body color is improved in proportion to the amount of magnesium.

That is, a high reflectance at 450 nm means that the absorption of blue light emission is small, which is very advantageous for the emission luminance of the blue pigment-coated phosphor.

As a result, in the present invention, in the blue pigment-coated phosphor obtained by coating the surface of the blue light-emitting phosphor with the cobalt aluminate blue pigment, the cobalt oxide component in the blue pigment is 35% by weight or more, and 0.001 ~
7.0 wt%, and the adhesion amount of the blue pigment is set to 8 wt% or less based on the phosphor.

A specific method for producing the blue pigment-coated phosphor according to the present invention will be described. The pigment is prepared by weighing aluminum oxide, cobalt oxide, and magnesium oxide so as to have a desired composition ratio, mixing them almost uniformly, and heating the mixture at 1000 to 1500 ° C. for several hours to obtain a desired composition ratio of cobalt magnesium aluminate. It is obtained by doing. The cobalt-magnesium aluminate has a crystal structure in which a part of cobalt of the conventional cobalt aluminate is replaced with magnesium.

In this method, the blue light emitting phosphor is dispersed by, for example, an acrylic emulsion, and the blue light emitting phosphor is coated with a pigment. The amount of the pigment to be coated can be arbitrarily set at the time of dispersion.

Next, FIG. 5 shows an example of a cathode ray tube provided with a phosphor film made of a blue pigment-coated phosphor as described above. Symbol 1 in the figure
Is a panel, and a funnel 2 and a neck 3 are joined to this panel 1 to form a vacuum envelope 4, and a neck 3
An electron gun 5 is mounted inside. Further, a fluorescent film 6 made of the blue pigment-coated phosphor of the present invention is provided on the inner surface of panel
Is formed, and the electron beam emitted by the electron gun 5 collides with the fluorescent film 6 to excite and emit light.

The present invention includes a cathode ray tube having the fluorescent film 6 to which the blue pigment-coated phosphor according to the present invention is applied as described above.

Example-1 The amount of magnesium having a CoO component amount of 35.5% by weight was 0, 2, 4, and 6% by weight based on 100 parts by weight of a silver activated zinc sulfide phosphor having a silver activator concentration of 0.018% by weight. 1.8 parts by weight of the four types of cobalt aluminate blue pigments were prepared by using an acrylic emulsion described in JP-A-59-227973, and the pigment-coated phosphor and the properties of a blue light-emitting phosphor film of a color cathode ray tube using the same were determined as follows It is shown in Table 1.

As shown in Table 1, 600 nm of the blue pigment-coated phosphor
And the reflectance of the blue light-emitting fluorescent film are almost the same, but the reflectance of the blue portion increases in proportion to the amount of magnesium, and the luminance of blue light increases because absorption of blue light decreases.

Example 2 The amount of magnesium having a CoO component of 39.0% by weight was 0, 2, 4, and 6% by weight based on 100 parts by weight of a silver activated zinc sulfide phosphor having a silver concentration of 0.016% by weight. Are applied at a ratio of 3.0 parts by weight of the four types of cobalt aluminate blue pigments, and a blue pigment-coated phosphor is obtained using the same method as in the first specific example. The characteristics of the pigment-coated phosphor and the blue light-emitting phosphor film of a color cathode-ray tube using the same in Example 2 are shown in Table 2 below.

Also in the case of Example 2, similarly to the case of Example 1, the emission luminance of the blue light emitting phosphor surface increases in proportion to the amount of magnesium.

[Effects of the Invention] As described above, according to the present invention, the cobalt aluminate used for the blue pigment-coated phosphor increases the coloring power by increasing the amount of cobalt oxide contained therein. In addition, the amount of pigment used to obtain a certain reflectance can be reduced. As a result, a fluorescent film with less pigment peeling and film defects can be obtained.

Further, by adding magnesium, it is possible to increase the reflectance of the blue portion, so that the absorption of light emitted by the blue light-emitting phosphor is reduced, and a phosphor and a phosphor film with high emission luminance can be obtained. .

[Brief description of the drawings]

FIG. 1 is a spectral reflectance curve diagram when the amount of CoO in cobalt aluminate is changed, FIG. 2 is a spectral reflectance curve diagram of the pigment when the amount of magnesium in cobalt aluminate is changed, FIG. 3 is a curve diagram of 600 nm and 450 nm in the spectral reflectance when the amount of CoO in cobalt aluminate was changed.
FIG. 5 is a characteristic curve diagram showing 600 nm and 450 nm of the spectral reflectance when the amount of magnesium in cobalt aluminate is changed, and FIG. 5 is a diagram showing a phosphor film comprising a blue pigment-coated phosphor according to the present invention. It is sectional drawing which shows the example of the provided cathode ray tube.

Continuation of front page (72) Inventor Toshifumi Takehara 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Toshiba Electronic Device Engineering Co., Ltd. (56) References JP-A-59-227973 (JP, A)

Claims (2)

(57) [Claims] 1. A blue pigment-coated phosphor obtained by coating a surface of a blue light-emitting phosphor with a cobalt aluminate blue pigment, wherein the cobalt oxide component in the blue pigment is 35% by weight or more, and magnesium is contained in 0.001 to 0.001%. 7. A blue pigment-coated phosphor, which contains 7.0% by weight and has an adhesion amount of the blue pigment of 8% by weight or less based on the phosphor. 2. A cathode ray tube comprising a phosphor film made of the blue pigment-coated phosphor according to claim 1.