JPS6219793B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a luminescent composition for excitation by slow electron beams and a fluorescent display tube for excitation by slow electron beams which uses this luminescent composition as a fluorescent film.

As is well known, a low-speed electron beam-excited fluorescent display tube (hereinafter abbreviated as a "fluorescent display tube") has an anode plate having a fluorescent film on one side, and a cathode facing the fluorescent film. The device essentially has a structure in which it is sealed in a vacuum container, and the fluorescent film on the anode plate is excited by the low-speed electron beam emitted from the cathode, causing it to emit light. 1 and 2 are schematic diagrams of typical examples of fluorescent display tubes, with FIG. 1 showing a diode tube and FIG. 2 a triode tube. 1st
As shown in the drawings and FIG. 2, a fluorescent film 12 is provided on one side of an anode plate 11 made of an aluminum plate or the like. Anode plate 11 is supported by ceramic substrate 13. Anode plate 1
A cathode 14 is provided opposite the fluorescent film 12 provided on one side of the fluorescent film 1, and the fluorescent film 12 is excited by the low-speed electron beam emitted from the cathode 14 to emit light. In particular, in the triode shown in Fig. 2, the cathode 14
A grid electrode 15 is provided in the gap between the cathode 14 and the fluorescent film 12 for controlling or diffusing the low-speed electron beam emitted from the cathode 14. Although one cathode 14 is used in the fluorescent display tube shown in FIGS. 1 and 2, two or more cathodes may be provided when the fluorescent film 12 has a large area. There is no particular limit to the number. Fluorescent film 1 on one side
2, the anode plate 11, ceramic substrate 13 and cathode 14 (FIG. 1), or the anode plate 11, ceramic substrate 13, cathode 14 and grid electrode 15 (FIG. 2) having a fluorescent film 12 on one side, are made of glass. The inside 17 is kept at a high vacuum of 10 ^-5 to ^{10 -9} Torr.

Conventionally, zinc-activated zinc oxide phosphor (ZnO:
Zn) is known. Fluorescent display tubes with the above structure having a fluorescent film made of ZnO:Zn phosphor are widely used industrially as display elements for desktop computers, various measuring instruments, etc., and also as multicolor display elements. It is being put into practical use in audio equipment volume meters, automobile speedometers, etc.

By the way, since the body color of ZnO:Zn phosphor is white, in a fluorescent display tube whose phosphor film is ZnO:Zn phosphor, the color of each segment constituting characters, figures, etc. Due to the influence of ambient light reflection, it is difficult to distinguish between light-emitting and non-light-emitting segments depending on the intensity of the ambient light. In other words, a fluorescent display tube using a ZnO:Zn phosphor as a fluorescent film has the disadvantage of poor display contrast due to the white body color of the ZnO:Zn phosphor. There is. Therefore, when putting into practical use a fluorescent display tube using a ZnO:Zn phosphor as a phosphor film, it is generally necessary to cut out part of the visible light of the emission spectrum of the ZnO:Zn phosphor. At the same time, a filter (green filter) that absorbs some of the ambient light is installed in front of the fluorescent display tube to enhance the contrast of the display. However, installing a filter is not preferable because it increases the number of accessories attached to the fluorescent display tube, and furthermore, each display segment has multiple types of fluorescent films with different luminescent colors including ZnO:Zn fluorescent material. In the case of a fluorescent display tube consisting of a phosphor, that is, a multicolor fluorescent display tube, the filter installed in front of the fluorescent display tube
Although it is effective in increasing the contrast for light emission from segments with ZnO:Zn phosphors as their phosphor films, It is undesirable because it absorbs a lot of light. Therefore, there is a need for a fluorescent display tube having a ZnO:Zn phosphor as a fluorescent film and exhibiting good display contrast without the need for a filter on the front surface of the fluorescent display tube.

The present invention has been made in view of the above-mentioned current situation, and an object of the present invention is to provide a green-emitting phosphor that exhibits good display contrast when used as a fluorescent film in a fluorescent display tube. It is.

Furthermore, the present invention exhibits good display contrast,
The object of the present invention is to provide a green-emitting fluorescent display tube that does not require a filter for improving contrast on the front surface when used as a display element.

The contrast (C) on the phosphor surface of the fluorescein display tube is C=B/E ₀ K+1 (where B is the luminous intensity of the phosphor surface, E ₀ is the intensity of the ambient light, and K is the phosphor surface ) is the reflectance of Therefore, in order to improve the display contrast of a fluorescent display tube using a ZnO:Zn phosphor as a phosphor film, it is necessary to reduce the reflectance of the ZnO:Zn phosphor without reducing its emission intensity as much as possible. is necessary. As a means to reduce the reflectance of the ZnO:Zn phosphor, it is possible to color the ZnO:Zn phosphor by mixing pigment particles into the ZnO:Zn phosphor, but in this case, the ZnO: In order to reduce the reflectance of the Zn phosphor without reducing its emission intensity as much as possible, it is preferable to use pigment particles having a green body color, which is the same color as the emission color of the ZnO:Zn phosphor. it is conceivable that. In fact, the use of green pigment particles generally gives favorable results, and the present applicant previously prepared a ZnO:Zn phosphor by mixing appropriate amounts of specific green pigment particles, and used it as a phosphor film for a fluorescent display tube. A patent application has been filed for a luminescent composition that exhibits better display contrast than conventional ZnO:Zn phosphors when used, and a fluorescent display tube using the luminescent composition as a fluorescent film (Japanese Patent Application No. 53-128754) No. 53-128755
issue). Considering pigment particles with body colors other than green, such as blue pigment particles and red pigment particles, these pigment particles with body colors other than green are not green pigments in terms of reducing the reflectance of the ZnO:Zn phosphor. Although the same effect as that of particles can be expected, the absorption of the emitted light by the ZnO:Zn phosphor is greater than that by the green pigment particles, and therefore the emission intensity of the ZnO:Zn phosphor is lowered more than that by the green pigment particles. It happens. Therefore, when using pigment particles with a body color other than green, generally the improvement in display contrast that can be expected when using green pigment particles (as described above, when using specific green pigment particles) However, it is expected that the improvement of display contrast will not be possible.

However, according to the experiments of the present inventors,
In a luminescent composition obtained by mixing indium sulfide red pigment particles with a ZnO:Zn phosphor, although the indium sulfide has a red body color, the ZnO:Zn phosphor is The decrease in luminescence intensity is extremely small, and even more surprisingly, when the amount of indium sulfide red pigment particles is within a certain range, the luminescence intensity of the luminescent composition obtained is
It was found that the emission intensity was higher than that of ZnO:Zn phosphor. A luminescent composition prepared by mixing an appropriate amount of ZnO:Zn phosphor and indium sulfide red pigment particles can be used as a fluorescent film for a fluorescent display tube.
It has been found that ZnO: exhibits better display contrast than Zn phosphors. As a result of further research,
ZnO:Zn has not been put to practical use as a green-emitting phosphor for slow electron beam excitation because its emission intensity when excited by slow electron beams is lower than that of ZnO:Zn phosphors.
When an appropriate amount of indium sulfide red pigment particles are mixed with a green-emitting phosphor other than a phosphor, surprisingly, the emission intensity of the green-emitting phosphor due to slow electron beam excitation is lower than that of the indium sulfide red pigment. Although the green-emitting phosphor has a color, it also improves the display contrast when used as a phosphor film in a fluorescent display tube, and the green-emitting phosphor can be used as a green-emitting phosphor for slow electron beam excitation. The present inventors have discovered that the present invention is highly practical as a body, and have completed the present invention.

The luminescent composition for excitation with slow electron beams of the present invention is characterized by being formed by mixing a green light-emitting phosphor and indium sulfide red pigment particles.

Further, the fluorescent display tube of the present invention has a structure in which an anode plate having a fluorescent film on one side and a cathode facing the fluorescent film are enclosed in a container having a vacuum inside. The tube is characterized in that the fluorescent film is made of a luminescent composition comprising a mixture of a green luminescent phosphor and indium sulfide red pigment particles.

The present invention will be explained in detail below.

The green-emitting phosphor that is one of the constituent components of the luminescent composition for slow electron beam excitation of the present invention includes ZnO:
In addition to Zn phosphors, gold and aluminum activated zinc sulfide phosphors (ZnS: Au, Al), copper, gold and aluminum activated zinc sulfide phosphors (ZnS: Cu, Au,
Al), copper-activated zinc sulfide/cadmium phosphor [(Zn _1-a , Cd _a )S:Cu, where 0≦a≦0.1], copper- and aluminum-activated zinc sulfide/cadmium phosphor [(Zn _1-a , Cd _b ) S: Cu, Al, however, 0≦b≦
0.1], silver-activated zinc sulfide/cadmium phosphor [(Zn _1-c , Cd _c )S:Ag, where 0.2≦c≦0.5], silver-activated zinc sulfide/cadmium phosphor [(Zn _1-e , Cd _e ) S: Ag, Al, however, 0.2≦e
≦0.5], terbium-activated rare earth oxysulfide phosphor (Ln ₂ O ₂ S: Tb, where Ln is Y, Gd, Lu and La
), cerium-activated rare earth gallium aluminate phosphor [Ln ₃ (Al _1-x ,
Ga _x ) ₅ O ₁₂ :Ce, where Ln has the same definition as above, x is 0≦x≦0.5], europium activated strontium gallium sulfide phosphor (SrGa ₂ S ₄ :Eu ²⁺ ), manganese- and arsenic-activated zinc silicate phosphor (Zn ₂ SiO ₄ :Mn, As), manganese-activated zinc silicate phosphor (Zn ₂ SiO ₄ :Mn), etc. ZnO:Zn phosphor,
ZnS: Au, Al phosphor, ZnS: Cu, Au, Al phosphor, (Zn _1-b , Cd _b )S: Cu, Al phosphor, (Zn _1-c ,
More preferably, Cd _c )S:Ag fluorescers and SrGa ₂ S ₄ :Eu ²⁺ fluorescers are used. These green-emitting phosphors are manufactured by conventionally known manufacturing methods.

On the other hand, as the indium sulfide red pigment particles, which is the other component of the luminescent composition for excitation with slow electron beams of the present invention, generally commercially available pigment particles may be used, but indium oxide, indium chloride, indium nitrate, etc. indium compound in a sulfur atmosphere,
A method of firing in a sulfidic atmosphere such as a carbon disulfide atmosphere, a method in which hydrogen sulfide is bubbled through a solution containing indium ions (In ³⁺ ) to precipitate indium sulfide,
Better results can be obtained by using a material manufactured by a method such as firing the obtained indium sulfide. The reflection spectra of indium sulfide red pigment particles vary considerably depending on their method of manufacture. Therefore, the indium sulfide red pigment particles used in the luminescent composition of the present invention are appropriately selected from a wide variety of indium sulfide red pigment particles produced by various methods, taking into account the reflection spectrum and the like. Figure 3,
Curve f illustrates the reflection spectrum of the indium sulfide red pigment particles used in the luminescent composition for excitation with slow electron beams of the present invention. In FIG. 3, the reflectance on the vertical axis is shown as a relative value with the reflectance of the magnesium oxide diffuser plate as 100%. The indium sulfide red pigment used in the luminescent composition of the present invention preferably has an average particle size of 4 μm or less. A more preferable average particle diameter is 0.1μ to 2.0μ.

The luminescent composition of the present invention can be obtained by mixing the green luminescent phosphor described above and indium sulfide red pigment particles. The mixing of the two may be carried out mechanically using a mortar, ball mill, mixer mill, etc., or the indium sulfide red pigment may be attached to the green-emitting phosphor by a special method. Methods for producing the luminescent composition of the present invention by attaching indium sulfide red pigment particles to the surface of a green luminescent phosphor include a production method using an electrostatic coating method (Japanese Unexamined Patent Publication No. 133088/1988), and a suspension polymerization method. A manufacturing method using a copolymerization method (Japanese Patent Application No. 53-3980), a method using a mixture of gelatin and gum arabic as an adhesive (Japanese Patent Application No. 53-5088), Recommended manufacturing methods include mixing a phosphor suspension with an acrylic or polystyrene emulsion in which pigment particles are dispersed.

In the luminescent composition for slow electron beam excitation of the present invention, when the amount of indium sulfide red pigment particles mixed into the green luminescent phosphor is increased, the luminescent composition obtained while the pigment particle amount is within a specific range. The luminescence intensity of the object will be higher than without pigment particles (ie, a green-emitting phosphor). On the other hand, the reflectance of the obtained luminescent composition gradually decreases as the amount of pigment particles increases. Therefore, a luminescent composition in which the amount of indium sulfide red pigment particles is within a specific range exhibits higher contrast than the green-emitting phosphor alone, and at the same time emits light with higher brightness than the green-emitting phosphor alone. show. In the luminescent composition of the present invention, the amount of pigment particles required to obtain a higher contrast than the green-emitting phosphor alone or to obtain higher contrast and luminescence intensity than the green-emitting phosphor alone. The amount of pigment particles required for this depends on the type of green-emitting phosphor used. For example, as a green-emitting phosphor.
When using a ZnO:Zn phosphor, the contrast and luminescence intensity of the luminescent composition obtained when pigment particles are up to approximately 10 percent by weight of the total luminescent composition is the same as when no pigment particles are used (i.e., ZnO:Zn fluorophore). When the amount of pigment particles exceeds 10% by weight, the luminance of the luminescent composition increases.
Although lower than that of ZnO:Zn phosphors, pigment particle amounts up to 25 weight percent of the total luminescent composition still exhibit higher contrast than ZnO:Zn phosphors. In addition, ZnS:Au,
When using an Al phosphor, the contrast and luminescence intensity of the resulting luminescent composition are higher than those of ZnS:Au and Al phosphors because the amount of pigment particles is 85% by weight of the total luminescent composition. In the following cases, and the contrast is
The value is higher than that of ZnS:Au and Al phosphors when the amount of pigment particles is 90% by weight or less.

Figure 3 shows the reflection spectra of the luminescent composition of the present invention, ZnO:Zn phosphor and indium sulfide red pigment particles, with curves a, b, c and d.
The indium sulfide red pigment particle content is respectively
The reflection spectra of the luminescent compositions of the present invention, curve e, are 3.0, 10, 25 and 50 weight percent.
The reflection spectrum of ZnO:Zn phosphor, curve f, is the reflection spectrum of indium sulfide red pigment particles. As mentioned above, the reflectance on the vertical axis is expressed as a relative value, assuming that the reflectance of the magnesium oxide diffuser plate is 10%. As is clear from FIG. 3, the indium sulfide red pigment particles used in the luminescent composition of the present invention have an extremely low reflectance for light in the wavelength range of 600 nm or less, and therefore have a high reflectance over the entire visible wavelength range. When mixed with a ZnO:Zn phosphor having a white body color, it absorbs light in the visible region other than red, as shown by curves a, b, c, and d, and becomes a ZnO:Zn phosphor. Reduces reflection of ambient light on body surfaces. On the other hand, ZnO by mixing indium sulfide red pigment particles:
There is no or only a slight reduction in the emission intensity of the Zn phosphor, which improves the contrast.

Figures 4 and 5 show the indium sulfide red pigment particle content (expressed in weight percent relative to the green emitting phosphor), luminescent intensity (curve a) and average reflectance (curve b) of the luminescent composition of the present invention. FIGS. 4 and 5 are graphs showing the relationship between the two, and FIGS. 4 and 5 respectively illustrate cases in which a ZnO:Zn phosphor is used and a ZnS:Au, Al phosphor is used as a green-emitting phosphor. It is. Emission intensity and average reflectance are both the emission intensity and average reflectance of a green-emitting phosphor without pigment particles mixed in.
The values are shown relative to 100%. Note that the average reflectance is a value expressed as a percentage of the integral value of the reflection spectrum from 400 nm to 700 nm with respect to that of the reflection spectrum of magnesium oxide. As is clear from FIGS. 4 and 5, as the content of indium sulfide red pigment particles increases, the average reflectance of the resulting luminescent composition gradually decreases, while the luminescent intensity increases once. , then decreases (to approximately 10 weight percent when using ZnO:Zn phosphor as the green-emitting phosphor, ZnS:Au, Al
When using a phosphor, the luminescence intensity is higher than that of the green-emitting phosphor alone up to approximately 85% by weight). ZnO:Zn as a green-emitting phosphor
When a phosphor is used, the rate of decrease in average reflectance is greater than the rate of decrease in luminescence intensity until the content of indium sulfide red pigment particles reaches approximately 25% by weight, but when the content exceeds approximately 25% by weight, luminescence stops. The rate of decrease in intensity will be greater than the rate of decrease in average reflectance, and therefore the contrast of the resulting luminescent composition will be lower than that of a ZnO:Zn phosphor with no pigment particles mixed therein. The purpose is not achieved. Similarly, as a green-emitting phosphor
When a ZnS:Au, Al phosphor is used, the contrast of the luminescent composition obtained when the pigment particle content exceeds approximately 90% by weight is different from that of a ZnS:Au, Al phosphor with no pigment particles mixed therein. The contrast becomes lower than that, and the object of the present invention is not achieved. In other words, as mentioned earlier, the contrast (C) on the fluorescent surface of a fluorescent display tube is generally C=B/E ₀ K+1 (where B is the luminous intensity of the fluorescent surface and E ₀ is the ambient light intensity. The intensity, K, is the reflectance of the fluorescent film surface. When emitting light under E ₀ , the contrast is
C ₀ and C, the luminescence intensity on the fluorescent film surface, respectively.
B ₀ and B, the reflectance on the fluorescent film surface are respectively K ₀
and K, the difference between the contrasts C ₀ and C is C ₀ −C=1/E ₀ ·B ₀ /K ₀ {1−(B/B ₀ )/(K/K ₀ )}. Therefore, the ratio of the luminescence intensity (B/B ₀ ) and the reflectance of the fluorescent film surface made of the luminescent composition of the present invention and the fluorescent film surface made of the green-emitting phosphor with no pigment particles mixed therein. When the ratio of (K/K ₀ ), that is, the value of (B/B ₀ )/(K/K ₀ ), is 1 or more, C can be larger than C ₀ regardless of the intensity of ambient light. Recognize. This shows that when comparing a fluorescent film surface made of the luminescent composition of the present invention and a fluorescent film surface made of a green-emitting phosphor with no pigment particles mixed, the relative luminescence intensity of the former to that of the latter. When the value (B/B ₀ ) is larger than the relative value (K/K ₀ ) of the average reflectance of the former to the average reflectance of the latter, the former, that is, the fluorescent film surface made of the luminescent composition of the present invention is better. This means that the contrast is higher than that of a phosphor film surface made of a green-emitting phosphor with no pigment particles mixed therein.

As is clear from FIGS. 4 and 5, in the case of a luminescent composition using a ZnO:Zn phosphor as a green-emitting phosphor, when the content of indium sulfide red pigment particles is 25% by weight or less, , and for luminescent compositions using ZnS:Au and Al phosphors as green-emitting phosphors, the relative values of luminescence intensity are higher when the content of indium sulfide red pigment particles is 90% by weight or less. The average reflectance is greater than the relative value, giving a phosphor film with higher contrast than a green-emitting phosphor without pigment particles mixed therein. As described above, the preferred content of indium sulfide red pigment particles necessary for achieving the object of the present invention in the luminescent composition of the present invention depends on the type of green-emitting phosphor used as one of its constituent components. different.

In the luminescent composition of the present invention, although indium sulfide has a red body color, the reduction in luminescence intensity of the green-emitting phosphor due to mixing it with the green-emitting phosphor is extremely small. The reason is that, especially when the amount of indium sulfide red pigment particles is within a certain range, the luminescent intensity of the luminescent composition is higher than that of a green luminescent phosphor in which the red pigment particles are not mixed. Because the indium sulfide red pigment particles are electrically conductive, they serve to prevent the charge up that occurs when a green-emitting phosphor is excited by a slow electron beam; This is thought to be due to higher efficiency. Considering that the indium sulfide red pigment particles absorb the light emitted from the green-emitting phosphor considerably, it seems that the improvement in excitation efficiency by mixing the indium sulfide red pigment particles is very large. In particular, when the amount of indium sulfide red pigment particles is within a specific range, the increase in emission intensity due to improved excitation efficiency is greater than the decrease in emission intensity due to absorption.
For this reason, the luminescent intensity of the luminescent composition is higher than that of a green luminescent phosphor in which indium sulfide red pigment particles are not mixed. It is normally unthinkable that a green-emitting phosphor mixed with pigment particles would have a higher luminescence intensity than a green-emitting phosphor without pigment particles. This is a truly surprising fact.

The fluorescent display tube of the present invention is manufactured by the method described below. First, the above-described luminescent composition is coated onto an anode plate, which is usually supported by a ceramic substrate, by a precipitation coating method or the like to form a fluorescent film.
When creating a fluorescent film by the sedimentation coating method, an anode plate is placed in a suspension of a luminescent composition dispersed in water, and the luminescent composition is applied to one side of the anode plate by its own weight. Apply by settling on top,
The water is then removed and the coating is dried. In order to improve the adhesion of the fluorescent film obtained in this case to the anode plate, a small amount (0.01 to 0.1%) of water glass may be added to the suspension. Also, the coating density is 2mg/
cm ² to 30 mg/cm ² is suitable. Although the above-mentioned precipitation coating method is a common method for forming a fluorescent film and is widely practiced, the method for forming a fluorescent film in the fluorescent display tube of the present invention is not limited to this precipitation coating method. The fluorescent film may also be created by other coating methods such as silk screening. Next, add a wire heater
A cathode coated with oxides such as BaO, SrO, CaO, etc. is placed opposite the fluorescent film on the anode plate for about 1 mm to
After placing the pair of electrodes at an interval of about 5 mm in a transparent container made of glass or the like, the inside of the container is evacuated. After the inside of the container reaches a vacuum level of at least 10 ^-5 Torr, stop the exhaust and seal it. After sealing, the getter is removed to further increase the vacuum inside the container. In this way, the fluorescent display tube of the present invention can be obtained.

Note that the fluorescent film on the anode plate is flat,
Since the cathode is linear, it is desirable to install a mesh-like grid electrode as a diffusion electrode between the cathode and the fluorescent film, as shown in FIG. 2, in order to diffuse the low-speed electron beam emitted from the cathode. In this case, better results can be obtained if the mesh is as narrow as possible so that the loss of the amount of light emitted by the fluorescent film is small and the low-velocity electron beam is well diffused. Specifically, it is desirable that the diameter of the mesh is 500 microns or less and the aperture ratio (the area of the holes through which the low-speed electron beam passes relative to the total area of the grid electrode) is 50% or more. The anode plate can display arbitrary characters and figures by dividing the electrode form into the required character and figure shapes and making it possible to selectively apply the required voltage to each electrode. I can do it. In addition, the anode plate is divided into dots or lines, a fluorescent film of the luminescent composition of the present invention is formed on some of the electrodes, and a low-speed luminescent film with a different luminescent color from the luminescent composition is formed on the other electrodes. By forming a fluorescent film made of a fluorescent material for electron beam excitation, a fluorescent display tube capable of displaying multiple colors can be obtained.

As explained above, the present invention provides a luminescent composition for low-speed electron beam excitation that exhibits good display contrast when used as a fluorescent film in a fluorescent display tube, and a high-contrast luminescent composition using this luminescent composition as a fluorescent film. The present invention provides a fluorescent display tube.

When using the fluorescent display tube of the present invention as a display element, it is possible to obtain sufficient contrast without installing a filter in front of the tube to improve contrast.

In addition, when a green filter is installed in front of the fluorescent display tube of the present invention, the red component of the ambient light reflected by the fluorescent film surface of the fluorescent display tube is also removed, thereby further increasing the contrast of the display. I can do it.

Next, the present invention will be explained with reference to Examples.

Example 1 Indium oxide (In ₂ O ₃ ) was fired in a carbon disulfide atmosphere at a temperature of 800° C. for 2 hours to produce indium sulfide red pigment particles. 2 g of the indium sulfide red pigment particles and 98 g of the ZnO:Zn phosphor were thoroughly mixed in a mortar to obtain a luminescent composition for excitation with slow electron beams having a pigment particle content of 2% by weight.

Next, 20 g of the luminescent composition obtained as described above was mixed with 20 c.c. of a butyl acetate solution containing 3% by weight of nitrocellulose, and the paste-like luminescent composition was made of 150 mesh nylon. It was applied onto an anode plate supported by a ceramic substrate using a screen, and then heat treated at 450°C for 30 minutes to decompose and remove the nitrocellulose to form a fluorescent film. Next, a cathode made of a tungsten wire heater coated with oxide is placed facing the fluorescent film on the anode plate with an interval of approximately 5 mm, and this pair of electrodes is placed in a hard glass container. , the inside of the container was evacuated. After the degree of vacuum inside the container reached a level of about 10 ^-5 Torr, the exhaust was stopped and the container was sealed, and then the getter was blown off to further increase the degree of vacuum inside the container. In this way, a fluorescent display tube having the structure shown in FIG. 1 was obtained.

When the fluorescent film was excited under the same conditions, the resulting fluorescent display tube showed ZnO:Zn without any pigment particles mixed in.
When the luminous intensity of a conventional fluorescent display tube made using a fluorescent material in the same manner as above is 300 ft-L, 370 ft.
-L emission intensity is shown. At this time, the contrast of this fluorescent display tube is such that the ambient light intensity is 200 ft-L.
, it is approximately 1.22 times that of a conventional fluorescent display tube, and even without a filter on the front of the fluorescent display tube, the contrast can be as good as when a filter is placed on the front of a conventional fluorescent display tube. It showed luminescence.

Example 2 Hydrogen sulfide was bubbled through an indium chloride solution to form a precipitate of indium sulfide. The obtained indium sulfide precipitate was dried and then calcined at a temperature of 500° C. for 1 hour to obtain indium sulfide red pigment particles.

99.5g of this indium sulfide red pigment particles
Add the ZnO:Zn phosphor to an aqueous dispersion suspension of the ZnO:Zn phosphor containing g of the ZnO:Zn phosphor and stir with a magnetic stirrer for 30 minutes to obtain a uniformly dispersed suspension of the ZnO:Zn phosphor and the pigment particles. It was made into a liquid. Next, acrylic emulsion (Nicasol RX-242 manufactured by Nippon Carbide, solid content
60%) was diluted 10 times and added to the phosphor-pigment particle uniformly dispersed suspension, followed by stirring for 15 minutes.
After standing, the supernatant liquid was removed by decantation, and the precipitate was dried at 100°C for 3 hours and passed through a 300 mesh sieve. In this way, the amount of pigment particles attached can be reduced.
A luminescent composition for excitation with a slow electron beam of 0.5% by weight was obtained.

Next, using the obtained pigmented phosphor, a fluorescent display tube having the structure shown in FIG. 1 was produced in the same manner as in Example 1. When the fluorescent film was excited under the same conditions, no pigment particles were attached to the resulting fluorescent display tube.
A conventional fluorescent display tube made using ZnO:Zn phosphor in the same manner as described above exhibited a luminescence intensity of 375 ft-L when the luminescence intensity was 300 ft-L. At this time, the contrast of this fluorescent display tube is approximately 1.28 that of a conventional fluorescent display tube when the ambient light intensity is 200 ft-L.
Even without a filter on the front surface of the fluorescent display tube, the fluorescent display tube emitted light with good contrast, similar to when a filter was placed on the front surface of a conventional fluorescent display tube.

Example 3 ZnS: 50 g of Au, Al phosphor and 50 g of indium sulfide red pigment particles produced in the same manner as in Example 1
These were thoroughly mixed using a ball mill to obtain a luminescent composition for excitation with a slow electron beam having a pigment particle content of 50% by weight.

Next, a fluorescent display tube having the structure shown in FIG. 1 was manufactured in the same manner as in Example 1 using the luminescent composition obtained as described above.

When the fluorescent film was excited under the same conditions, the resulting fluorescent display tube showed ZnS with no pigment particles mixed in:
When the luminous intensity of a fluorescent display tube made using Au and Al phosphors in the same manner as above is 2ft-L, 300ft
-L emission intensity is shown. At this time, when the ambient light intensity is 20 ft-L, the contrast of this fluorescent display tube is about 25 times that of a fluorescent display tube with a fluorescent film made of ZnS:Au, Al phosphor alone. Even without a filter on the front surface of the display tube, light emission with good contrast was obtained, similar to when a filter was placed on the front surface of a conventional fluorescent display tube.

Example 4 (Zn _0.98 , Cd _0.02 ) 70 g of S:Cu, Al phosphor and 30 g of indium sulfide red pigment particles produced in the same manner _as in Example ₂ were thoroughly mixed using a mortar. ,
A luminescent composition for excitation with slow electron beams having a pigment particle content of 30% by weight was obtained.

Next, a fluorescent display tube having the structure shown in FIG. 1 was manufactured in the same manner as in Example 1 using the luminescent composition obtained as described above.

When the fluorescent film was excited under _the same conditions, the obtained fluorescent display tube was produced using S:Cu, Al phosphors with no pigment particles mixed therein (Zn _0.98 , _{Cd 0.02} ). When the luminescence intensity of a fluorescent display tube prepared in the same manner as above was 1 ft-L, it exhibited a luminescence intensity of 260 ft-L. At this time, _the contrast of this fluorescent display tube is (Zn _0.98 ,
Cd _0.02 ) S: Approximately ₂₂ times as much as a fluorescent display tube whose fluorescent film is made of Cu, Al phosphor alone, and even without a filter on the front of the fluorescent display tube. It showed light emission with good contrast, similar to when a filter was placed in front of the screen.

[Brief explanation of the drawing]

1 and 2 are schematic diagrams of typical examples of fluorescent display tubes, with FIG. 1 being a diode and FIG. 2 being a triode. FIG. 3 is a graph showing the reflection spectra of the luminescent composition of the present invention, the ZnO:Zn phosphor, and the indium sulfide red pigment particles used in the luminescent composition of the present invention. Figures 4 and 5 are graphs showing the relationship between the indium sulfide red pigment particle content, relative luminescent intensity, and relative average reflectance in the luminescent composition of the present invention, and Figure 4 shows ZnO as a green luminescent phosphor. When a Zn phosphor is used, FIG. 5 shows a case where a ZnS:Au, Al phosphor is used as a green-emitting phosphor. 11... Anode plate, 12... Fluorescent film, 13
... Ceramic substrate, 14 ... Cathode, 15 ... Grid electrode, 16 ... Container, 17 ... Inside of display tube kept in high vacuum.

Claims (1)

[Scope of Claims] 1. A luminescent composition for excitation with a slow electron beam, comprising a mixture of a green luminescent phosphor and indium sulfide red pigment particles. 2. The green light emitting phosphor is a zinc activated zinc oxide phosphor (ZnO:Zn), and the amount of the indium sulfide red pigment particles is greater than 0 weight percent and not more than 25 weight percent of the total weight of the light emitting composition. The luminescent composition for slow electron beam excitation according to claim 1, characterized in that: 3. The green-emitting phosphor is a gold and aluminum activated zinc sulfide phosphor (ZnS: Au, Al),
2. The luminescent composition for excitation with a slow electron beam according to claim 1, wherein the amount of the indium sulfide red pigment particles is greater than 0% by weight and less than 90% by weight based on the total amount of the luminescent composition. 4. The luminescent composition for slow electron beam excitation according to claim 1, 2, or 3, wherein the indium sulfide red pigment particles are attached to the surface of the green light-emitting phosphor. thing. 5. A low-speed electron beam-excited fluorescent surface tube having a structure in which an anode plate having a fluorescent film on one side and a cathode facing the fluorescent film are enclosed in a vacuum container. 1. A low-speed electron beam-excited fluorescent display tube, characterized in that the fluorescent film is made of a luminescent composition formed by mixing a green-emitting phosphor and indium sulfide red pigment particles. 6. The green light-emitting phosphor is a zinc-activated zinc oxide phosphor (ZnO:Zn), and the amount of the indium sulfide red pigment particles is more than 0 weight percent and 25 weight percent or less of the total amount of the light-emitting composition. A low-speed electron beam-excited fluorescent display tube according to claim 5, characterized in that: 7. The green-emitting phosphor is a gold and aluminum activated zinc sulfide phosphor (ZnS: Au, Al),
6. The low-speed electron beam-excited fluorescent display tube according to claim 5, wherein the amount of the indium sulfide red pigment particles is greater than 0 weight percent and less than 90 weight percent of the total amount of the luminescent composition. 8. The slow electron beam excitation fluorescent display according to claim 5, 6 or 7, wherein the indium sulfide red pigment particles are attached to the surface of the green light emitting phosphor. tube.