JPS6150116B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a pigmented red light-emitting phosphor mainly used in color picture tubes.

B. Prior Art and Problems When a phosphor with pigment particles attached to its surface is used in a color picture tube, part of the visible range of the emission spectrum of the phosphor is cut off due to the filter effect of the pigment particles, causing the emission of light. It is known that the color becomes a deep red, and the reflected light is attenuated by the absorption effect of external light due to the pigment coloring of the fluorescent film, which improves the contrast of the image.

Pigmented phosphors are required to have low reflectance to external light and as high luminance as possible in order to improve contrast. In order to achieve this purpose, red inorganic pigments such as cadmium selenide sulfide and red iron are used as red pigments that adhere to the surface of the phosphor.

When a pigmented phosphor is used in a color picture tube, it has the advantage of providing a clear luminescent color and high contrast due to the pigment attached to the surface. however,
Pigmented phosphors have the disadvantage that, compared to pigment-free phosphors, they have lower exposure sensitivity during exposure in the color picture tube manufacturing process. In particular, red pigment, which is a conventional red pigment, has a spectral reflectance as shown in curve A in Figure 1, and a pigmented red light-emitting phosphor to which this red pigment is attached to the surface has a spectral reflectance as shown in curve A in Figure 2. , there is strong absorption of external light in the range from ultraviolet to blue, green, and yellow, so in the color picture tube manufacturing process, the main ingredients are phosphor, PVA (polyvinyl alcohol), and ADC (ammonium dichromate). The exposure sensitivity of the slurry used for this purpose is significantly reduced.

In order to improve exposure sensitivity, if the amount of attached red pigment is reduced to increase the reflectance of the phosphor itself, the filter effect of the red pigment is reduced, and the contrast improvement effect is reduced. That is, in order to improve the filter effect of the red pigment, it is necessary to lower the reflectance of the phosphor in a specific wavelength range, but the lower the reflectance, the lower the exposure sensitivity. For this reason, the effect of improving contrast and the effect of improving exposure sensitivity are mutually contradictory properties, and as one property improves, the other property deteriorates, making it impossible to improve both properties at the same time.

The present invention utilizes an unprecedented and unique technical idea of changing the reflectance during the picture tube manufacturing process to create a pigmented red light-emitting phosphor that has high contrast and can reduce the decrease in exposure sensitivity. It is on offer.

C. Means for solving conventional problems Red-emitting phosphor for cathode ray tubes, e.g. Y ₂ O ₃ :
Eu, Y ₂ O ₂ S: Yellow iron oxide is mixed into Eu etc. instead of the conventional red iron oxide pigment, or the surface of the phosphor particles is coated with yellow iron oxide.

D Functions and Effects When the phosphor of the present invention is used in a color picture tube, yellow iron oxide is thermally decomposed by heat treatment during the picture tube manufacturing process and turns into a red pigment, making it appear as if a red pigment was used from the beginning. A deep red fluorescent film can be obtained.

Yellow iron oxide is originally a yellow pigment, and its spectral reflectance, as shown by curve B in Figure 1, is higher overall than that of red iron oxide shown by curve A.

Furthermore, the phosphor to which yellow iron oxide is attached, shown by curve B in FIG. As such, it has a considerably high spectral reflectance in the wavelength region of 600 nm or less.

By the way, for attaching phosphor to a cathode ray tube,
Regarding the exposure sensitivity of the PVA-ADC photosensitive liquid, it is said that this photosensitive liquid is well sensitive to ultraviolet rays and visible light having relatively short wavelengths. However, in slurries made by adding phosphors to photosensitive liquids, the phosphor particles absorb or scatter some of the ultraviolet rays and consume them, so compared to photosensitive liquids that do not contain phosphors, exposure to ultraviolet rays is less dominant. The role of short wavelength visible light becomes important.

For the above reasons, conventional phosphors with red pigments, which absorb more visible light, have lower light utilization efficiency than phosphors without red pigments, and the adhesion of the phosphors (to the glass surface of picture tubes) The disadvantage was that the adhesion force (adhesive force) was weakened.

In contrast, the phosphor of the present invention has a visible light reflectance that is lower than that of the conventional iron oxide shown by curve A in Figure 2, as seen from curve B in Figure 2, until it changes to a red pigment by heating. is about 20% higher overall, which has the effect of increasing the light utilization rate and reducing the decrease in adhesive strength.

Furthermore, when the yellow iron oxide pigment used in the phosphor of the present invention is heated to 300 to 500 degrees Celsius, it dehydrates and changes into a red pigment, and its spectral reflectance is shown by curve C in Figure 1.
As shown in , this is a desirable characteristic for a red filter. In other words, it has the property of turning into a pigment that strongly absorbs light with a wavelength of 550 nm or less when heated.

On the other hand, in the manufacturing process of color picture tubes, PVA and acrylic resin are incinerated and heated to 300 to 500 degrees Celsius during the process of joining the panel and funnel and the exhaust process. Therefore, when the yellow iron oxide-containing phosphor of the present invention, for example, the Y ₂ O ₂ S:Eu phosphor, is used in a color picture tube, heat treatment is not required until the steps of applying the phosphor, exposing it to light, and developing it. However, when it is completed as a color picture tube, the body color changes to red during the heat treatment process during manufacturing, and it exhibits the spectral reflectance shown in curve C in Figure 2. , it has the same contrast improvement effect as using a red-emitting phosphor with red pigment from the beginning.

E Preferred embodiment Hereinafter, the present invention will be explained in detail with reference to Examples.

Example 50 ml of a 1% aqueous polyvinyl pyrrolidone solution was added to 1.5 g of yellow iron oxide and dispersed in a ball mill for 5 hours to obtain a pigment dispersion. Next, 500 g of a red light-emitting phosphor for color television consisting of Y ₂ O ₂ S:Eu was added to 1 liter of 0.1% gelatin solution, stirred to disperse, and then left to stand to remove the supernatant. The precipitated phosphor is washed twice with 1 liter of water, removing the supernatant each time. The pigment dispersion is added to the washed phosphor, stirred, and left to stand to remove the supernatant, and the precipitated phosphor is washed twice with 1 liter of water. This phosphor was air-flow dried to obtain a pigmented phosphor.

The pigmented phosphor is Y ₂ O ₂ S:Eu containing 0.2% yellow iron oxide and has a yellow body color, and its spectral reflectance is as shown in curve B in FIG.

When the pigmented phosphor was fired for 30 minutes at 450 degrees Celsius under conditions similar to the cathode ray tube manufacturing process, the body color became red and the spectral reflectance was second to none.
As shown in curve C in the figure, it approximates the spectral reflectance of the Y ₂ O ₂ S:Eu phosphor containing 0.2% iron oxide (curve A in Figure 2).

When the pigmented phosphor of this example was used as a red light-emitting component for a color picture tube,
Compared to the Y ² O ₂ S:Eu phosphor containing 0.2%, the exposure sensitivity was increased by 15%, and the brightness and contrast were equivalent to those containing 0.2% red iron.

[Brief explanation of the drawing]

Figure 1 shows the spectral reflectance curve of the pigment, and Figure 2 shows the spectral reflectance curve of the pigment.
The figure shows the spectral reflectance curves of a pigmented phosphor and a pigment-free phosphor, respectively.

Claims (1)

[Scope of Claims] 1. In a pigmented red phosphor consisting of a coloring phosphor and an iron oxide pigment attached to the surface of the phosphor or mixed with the phosphor, yellow iron oxide is added to the iron oxide pigment. A pigmented red-emitting phosphor for picture tubes, characterized in that it uses. 2. A pigmented red light-emitting phosphor for a picture tube, in which the amount of yellow iron oxide attached or mixed is in the range of 0.05% to 1.0% by weight based on the amount of the red light-emitting phosphor.