JPH0830184B2 - Luminescent composition and low-speed electron beam excited fluorescent display using the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to a light emitting composition and a slow electron beam excited fluorescent display tube which emit light with high efficiency particularly under slow electron beam excitation.

(Prior Art) As is well known, a low-speed electron beam excitation fluorescent display tube (hereinafter referred to as “fluorescent display tube”) includes an anode plate having a fluorescent film on one surface, and a cathode provided so as to face the fluorescent film. Is enclosed in a container with a vacuum inside, and a low-speed electron beam emitted from the cathode (generally
The phosphor film on the anode plate is excited by a slow electron beam (100 V or less) to emit light. This fluorescent display tube is widely used as a display element for various measuring instruments and the like.

As the low-speed electron beam phosphor used as the phosphor film of the fluorescent display tube, zinc-activated zinc oxide phosphor (ZnO: Zn)
Is widely known as a typical phosphor that exhibits highly efficient green-white emission, but as the field of use of fluorescent display tubes has expanded, it has become desirable to diversify the emission color of fluorescent display tubes. Along with this, the development of a phosphor that emits light other than green under the excitation of a slow electron beam has been advanced. As a result, phosphors emitting light other than green under slow electron beam excitation were found, and one of them was a phosphor represented by the composition formula (Zn _1-X , Cdx) S: Ag as an example. There is a (Zn _1-X , Cdx) S-based phosphor (sulfide-based phosphor) that does.

On the other hand, it has been required at the same time to make the light emission of the phosphor even brighter, and as a result of repeated research, even if the phosphor has an extremely low luminous efficiency under the excitation of a low-speed electron beam, a certain amount Conductive metal oxides such as In ₂ O ₃ , ZnO, SnO ₂ and Cd
It was found that when a light-emitting composition is prepared by mixing a conductive substance such as a conductive metal sulfide such as S, Cu ₂ S, these light-emitting compositions exhibit highly efficient light emission even when excited by slow electron beams. Was done. Therefore, by using such a luminescent composition, a desired luminescent color can be produced by appropriately selecting the phosphor, and the luminescent brightness is insufficient when the phosphor is allowed to emit light by itself. However, by mixing the above-mentioned conductive substance, the emission brightness can be greatly improved. For this reason, a light emitting composition obtained by mixing a phosphor and a conductive substance has been widely put into practical use in recent years, particularly as a phosphor film of a fluorescent display tube for multicolor display.

(Problems to be Solved by the Invention) However, the above-mentioned light-emitting composition also has a low emission efficiency as compared with the conventional ZnO: Zn phosphor exhibiting the above-mentioned green emission, and a problem that sufficient emission luminance cannot be obtained. There is. Therefore, when the fluorescent film made of the above-mentioned light emitting composition and the fluorescent film made of ZnO: Zn are used side by side in one fluorescent display tube,
There are disadvantages such that the light emission luminances of the two are different and the display is difficult to see, and the drive circuit is complicated due to the difference in the light emission start voltage and the operating voltage. Therefore, there is a demand for a light-emitting material that emits light other than green light under high-speed electron beam excitation and has higher light emission efficiency.

The present invention has been made based on the above demands, and provides a light-emitting composition having higher light emission efficiency than a conventional light-emitting composition obtained by mixing a phosphor and a conductive substance.
Further, it is an object of the present invention to provide a fluorescent display tube using the light emitting composition as a fluorescent film.

(Means for Solving Problems) The present inventor has conducted extensive studies on both the phosphor and the conductive substance constituting the light-emitting composition in order to achieve the above-mentioned object, and as a result, the phosphor was first described above. Did (Zn _1-X , Cd
x) S-based phosphor, that is, zinc sulfide (ZnS), cadmium sulfide (CdS), and their solid solution {(Zn, Cd) S}
When lithium (Li) is contained as a sensitizer in a sulfide-based phosphor whose base material is (Zn _1-X , Cd
x) S-based phosphors only show emission brightness equal to or lower than that of conventional S-based phosphors that do not contain Li (Zn _1-X , Cdx) under high-speed electron beam excitation with an acceleration voltage of several kv or more. However, it has been found that the emission brightness under the slow electron beam excitation is significantly improved over the conventional phosphor containing no Li.

Further, the present inventors have found that if the particle size distribution of the conductive material mixed with the sulfide-based phosphor containing Li is within a specific range, it is possible to further improve the emission brightness of the light emitting composition. The present invention has been completed.

The luminescent composition of the present invention based on such an invention has a general formula: (Zn _1-X , Cdx) S: aM ^I , bLi; cX (where M ^I is Na, K, Rb, Cs, Ag, At least one element selected from the group consisting of Au and Cu, X is Al, Cl, Br and I
At least one element selected from the group consisting of
x, a, b and c are 0 ≦ x ≦ 1,0 ≦ a ≦ 1 × 10 ^-2 g /
It is a number that satisfies the conditions of g, 0 <b ≦ 1 × 10 ⁻² g / g and 0 <c ≦ 1 × 10 ⁻² g / g. It should be noted that a, b and c all represent the weights of M ^I , Li and X with respect to (Zn _1-X , Cdx) S 1g which is the matrix of the phosphor. ).

And at least one of a conductive metal oxide and a conductive metal sulfide having a particle size distribution with a median value of 3μ or less and a standard deviation value (logδ) of 0.7 or less. It is characterized by being mixed with a kind of conductive substance.

Further, the fluorescent display tube of the present invention is a fluorescent display tube having a structure in which an anode plate having a fluorescent film on one surface and a cathode facing the fluorescent film are enclosed in a container having a vacuum inside. Is represented by the general formula (Zn _1-X , Cdx) S: aM ^I , bLi, cX (see M ^I , X and x,
The definitions of a, b, and c are the same as those in the above-mentioned light emitting composition), the median value is 3 μm or less, and the standard deviation value (log δ) is 0.7.
It is characterized by comprising a light-emitting composition obtained by mixing a conductive metal oxide having the following particle size distribution and at least one conductive substance selected from conductive metal sulfides.

 Hereinafter, the present invention will be described in more detail.

One of the constituents of the light emitting composition of the present invention (Zn _1-X ,
The Cdx) S: aM ^I , bLi, cX phosphor is generally manufactured by the method described below. That is, zinc sulfide (ZnS)
¹ ) as a compound of the M ^I element as the activator (M ^I ) and a co-activator (X) in a predetermined amount of mixed sulfide obtained by mixing a predetermined amount of raw powder and cadmium sulfide (CdS) raw powder Valvalent metal halide (AgCl, etc.) or trivalent metal salt {Al (NO ₃ ) ₃
Etc.} and a predetermined amount of lithium compound (LiCl etc.) are added and mixed thoroughly, and then calcined at 500 ° C. to 1200 ° C. for 0.2 hours to 5 hours in a sulfurizing atmosphere such as hydrogen sulfide atmosphere, sulfur atmosphere or the like or in air. After that, it is obtained by washing with water, dehydration and drying. The amount of M ^I (a), the amount of Li (b) and the amount of X (c) of the (Zn _1-X , Cdx) S: aM ^I , bLi, cX phosphor are 0 ≦ a ≦ 1 ×, respectively. 10 ^-2 g / g, 0 <b ≤ 1 x 10 ^-2 g / g and 0
<C ≦ 1 × 10 ^-2 g / g, and the median value of the particle system is 0.5 μ
When the (Zn _1-X , Cdx) S: aM ^I , bLi, cX phosphor in the range of 10 to 10 μm is used, a light emitting composition having particularly high brightness can be obtained. Even if the content of Li in the sulfide-based phosphor is a trace amount (1 ppm or less), which is about the detection limit of the current analytical technology, the brightness is improved compared to the conventional sulfide-based phosphor that does not contain Li. It turned out to be obtained. The type of lithium salt used and the number of combinations can be arbitrarily adjusted.
Further, the upper limit of the Li content is preferably about 10 ^-2 g / g (10000 ppm) from the viewpoint of the emission brightness of the obtained light emitting composition.

Furthermore, Li has a content of 1 ppm to 71% with respect to the phosphor matrix.
The range of 00 ppm is particularly preferable, and the most preferable content is in the range of 35 ppm to 5000 ppm.

On the other hand, as the conductive metal oxide and the conductive metal sulfide used as the conductive substance which is the other constituent component of the light emitting composition of the present invention, In ₂ O ₃ , ZnO, SnO ₂ , TiO ₂ and WO _{3 are used.} , NB
₂ O _{5 and the} like and CdS, In ₂ O ₃ , Li ₂ S, Cu ₂ S and the like, particularly In ₂ O ₃ , SnO ₂ and from the viewpoint of the emission brightness of the resulting light-emitting composition.
ZnO is more preferable, and In ₂ O ₃ is particularly preferable among these.

As these conductive metal oxides and conductive metal sulfides, those having a particle size distribution with a median value of 3 μm or less and a standard change value of 0.7 or less are used. Among them, the more preferable median range of the particle diameter is 0.1 μm to 1 μm, although it varies slightly depending on the kind of the conductive substance and the composition of the phosphor mixed with the conductive substance.

The conductive substance having a particle size distribution as described above is a general reagent or a calcined product obtained by calcining the same in air, a neutral atmosphere or a weakly reducing atmosphere as it is or in a solvent such as water or alcohol. It is obtained by pulverizing in a suspended state with a ball mill, a roll mill or the like, and then classifying with a water sieving or the like.

The luminescent composition of the present invention has the above-mentioned (Zn _1-X , Cdx) S: aM ^I , bL
i, cX phosphor and each predetermined amount of the conductive substance having the above-mentioned specific particle size distribution are mixed as they are or in a state of being suspended in a solvent such as water or alcohol by a ball mill, a mixer mill or the like, and then the solvent is removed. Can be obtained by doing. (Zn _1-X , Cdx) S: aM ^I , b in the obtained light-emitting composition
The optimum mixing ratio of Li, cX phosphor and the conductive substance that can maximize the emission brightness varies depending on the particle size of the conductive substance, and the smaller the median particle diameter of the conductive substance is,
The optimum mixing ratio of the conductive substance to the (Zn _1-X , Cdx) S: aM ^I , bLi, cX phosphor tends to be small, and the emission brightness of the light emitting composition at that time tends to be high. Generally, when a conductive substance having a median particle diameter of less than 3 μ is used, the mixing ratio of the conductive substance and the phosphor is preferably about 1: 9 to 2: 998 by weight.

Next, the relationship between the particle size of the conductive substance and the emission brightness in the light emitting composition of the present invention will be described. Figure 1 shows (Zn
_0.65 , Cd _0.35 ) S: Ag, Li, Cl For the light emitting composition of the present invention comprising a phosphor and In ₂ O ₃ , the relationship between the particle size of In ₂ O ₃ and the emission brightness of the obtained light emitting composition is illustrated. It was done. First
The particle size of In ₂ O _{3 on} the horizontal axis of the figure is the median value of the particle sizes obtained by the Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-CP3,
The standard deviation value (logδ) is 0.7 or less. The relative emission brightness on the vertical axis is a relative value when the emission brightness of the light emitting composition using In ₂ O ₃ having an average particle size of 5 μ is 1.0. _{Incidentally, (Zn 0.65, Cd 0.35)} S: Ag, Li, mixing weight ratio of Cl phosphor and In ₂ O _3, since the optimum mixing weight ratio by particle diameter of the In ₂ O ₃ used is different, an In ₂ The mixing weight ratio is such that the maximum emission brightness is obtained when the particle size of O ₃ is the respective value, and varies with the change of the particle size of In ₂ O ₃ . As is clear from Fig. 1, (Zn _0.65 , Cd _0.35 ) S: Ag,
In a light emitting composition comprising a mixture of a Li, Cl phosphor and In ₂ O ₃ , a conductive material of In ₂ O ₃ having a median particle diameter of less than about 3 μ, particularly 1 μ or less of In ₂ O 3. _It can be seen that when ₃ is used, a light emitting composition with higher brightness can be obtained. In addition, when using (Zn _1-X , Cdx) S: aM ^I , bLi, cX phosphor other than (Zn _0.65 , Cd _0.35 ) S: Ag, Li, Cl phosphor as the phosphor, the conductive material is also used. When a conductive metal oxide or a conductive metal sulfide other than In ₂ O ₃ is used as the light emitting composition having the same composition, the conductive material used has a particle diameter of about 3 μm or less. Then, it was confirmed that the emission brightness of the obtained light emitting composition was particularly high. Further, as shown in FIG. 1, in order to always obtain a good result when the median value is 3 μ or less, the standard deviation value (log δ) needs to be 0.7 or less.

The fluorescent display tube of the present invention is characterized in that the fluorescent film contains the light emitting composition according to the present invention, and the other structure is the same as that of a conventionally known fluorescent display tube. You may 2 and 3 are schematic configuration diagrams showing specific examples of the fluorescent display tube of the present invention. FIG. 2 shows a diode and FIG. 3 shows a triode.

2 and 3 are schematic configuration diagrams showing an example of the fluorescent display tube of the present invention. FIG. 2 shows a diode and FIG. 3 shows a triode. As shown in FIGS. 2 and 3, in these fluorescent display tubes, a fluorescent film 12 is provided on one surface of an anode plate 11 made of an aluminum plate or the like. The anode plate 11 is supported by the ceramic substrate 13. A cathode 14 is provided so as to face the fluorescent film 12 provided on one surface of the anode plate 11, and the fluorescent film 12 is excited by a low-speed electron beam emitted from the cathode 14 to emit light. Particularly in the triode of FIG. 3, the cathode 14 and the fluorescent film
A grid electrode 15 for controlling or diffusing a low-speed electron beam emitted from the cathode 14 is provided in the gap between the lattice electrode 12 and the electrode 12. Although one cathode 14 is used in the fluorescent display tube shown in FIGS. 2 and 3, two or more cathodes may be provided when the area of the fluorescent film 12 is large. The number is not particularly limited. The anode plate 11 having the fluorescent film 12 on one surface, the ceramic substrate 13 and the cathode 14 (second
(Or) an anode plate 11 having a fluorescent film 12 on one side,
Ceramic substrate 13, cathode 14 and grid electrode 15 (Fig. 3)
Is enclosed in a transparent container 16 such as glass.
17 is kept in a high vacuum above 10 ^-7 Torr.

Since the fluorescent film on the anode plate is flat and the cathode is linear, in order to diffuse the low-speed electron beam emitted from the cathode, a diffusion electrode is provided between the cathode and the fluorescent film as shown in FIG. It is desirable to install a mesh grid electrode. In this case, good results can be obtained by making the mesh as fine as possible so that the loss of the light emission amount of the fluorescent film is small and the low-speed electron beam diffuses well. Specifically, it is desirable that the diameter of the mesh is 500 μm or less, and the aperture ratio (area of the hole through which the low-speed electron beam permeates the entire area of the lattice electrode) is 50% or more.

If the anode plate is divided into the required letters and figures for the electrode form and the voltage required for each electrode can be selectively applied, any letters and figures can be displayed. You can Further, the anode plate is divided into dots or lines, a fluorescent film containing the light-emitting composition of the present invention is formed on a part of the electrodes thereof, and a low-speed emission color different from that of this phosphor is formed on the other electrodes. A fluorescent display tube capable of multicolor display can be obtained by forming a fluorescent film containing an electron beam excitation phosphor.

The fluorescent display tube of the present invention is produced, for example, by the method described below. That is, first, the paste-like luminescent composition obtained by mixing the above-described luminescent composition of the present invention with a suitable organic binder is poured onto a silk screen placed on the anode plate and rubbed with a squeegee to form the anode plate. A fluorescent film having a desired shape is formed on top. The fluorescent film thus formed is baked in air to decompose the organic binder present in the fluorescent film. The method for producing the fluorescent film in the fluorescent display tube of the present invention is not limited to such a screen printing method. Next, a cathode made by coating a linear tungsten heater with an electron emitting agent such as BaCO ₃ or SrCO _{3 is made} to face the fluorescent film on the anode plate.
Place at intervals of 5 mm or less. Then, this pair of electrodes and getters such as Ba and Ti are installed in a transparent container made of glass or the like, the gas in the container is baked, and the cathode is energized to discharge electrons while exhausting with a vacuum pump such as a rotary pump. Activated agent, at least 10 ^-3 Torr in container
After reaching the above vacuum degree, sealing is performed. After sealing, the getter is blown to increase the degree of vacuum in the container to obtain the fluorescent display tube of the present invention.

Next, the present invention will be described with reference to examples. Needless to say, the present invention is not limited to the examples below.

(Examples) A plurality of phosphor raw materials are weighed in predetermined amounts as shown below, and then crushed and sufficiently mixed to prepare 12 kinds of phosphor raw materials (1 ') to (12'). did.

(1 ') Zinc sulfide (ZnS) 100g, Lithium chloride (LiCl ・ H ₂
O) 1.0g (2 ') Zinc sulfide (ZnS) 100g, Sodium chloride (NaCl)
1.0g (3 ') Zinc Sulfide (ZnS) 55.6g, Cadmium Sulfide (CdS)
44.4g, lithium chloride (LiCl ・ H ₂ O) 1.0g, silver chloride (AgCl)
0.026g (4 ') Zinc Sulfide (ZnS) 55.6g, Cadmium Sulfide (CdS)
44.4g, silver chloride (AgCl) 0.026g, sodium chloride (NaCl)
1.0g (5 ') Zinc Sulfide (ZnS) 26.6g, Cadmium Sulfide (CdS)
73.4g, lithium chloride (LiCl ・ H ₂ O) 0.5, silver chloride (AgCl)
0.132g (6 ') Zinc Sulfide (ZnS) 26.6g, Cadmium Sulfide (CdS)
73.4g, silver chloride (AgCl) 0.132g, sodium chloride (NaCl)
0.50g (7 ') Zinc Sulfide (ZnS) 73.0g, Cadmium Sulfide (CdS)
27.0 g, lithium chloride (LiCl ・ H ₂ O) 0.8 g, copper sulfate (CuSO ₄
・ 5H ₂ O) 0.047g, sodium chloride (NaCl) 0.8g (8 ') zinc sulfide (ZnS) 73.0g, cadmium sulfide (CdS)
27.0 g, copper sulfate _{(CuSO 4 · 5H 2 O)} 0.047g, sodium chloride (NaCl) 0.8g (9 ') of zinc sulfide (ZnS) 73.0 g, cadmium sulfide (CdS)
27.0 g, lithium sulfate (LiSO ₄ · H ₂ O) 0.2 g, copper sulfate (CuSO ₄
· 5H ₂ O) 0.047g, aluminum sulfate _{{Al 2 (SO 4) 3} · 18H
₂ O} 0.083g (10 ') Zinc sulfide (ZnS) 73.0g, Cadmium sulfide (CdS)
27.0g, copper sulfate (CuSO ₄ / 5H ₂ O) 0.047g, aluminum sulfate {Al ₂ (SO ₄ ) ₃・ 18H ₂ O} 0.083g (11 ′) zinc sulfide (ZnS) 85.8g, cadmium sulfide (CdS)
14.2g, lithium chloride (LiCl ・ H ₂ O) 0.1g, chloroauric acid (HAuC
l ₄₎ 0.27 g, aluminum sulfate _{{Al 2 (SO 4) 3} · 18H 2 O}
0.47g (12 ') Zinc Sulfide (ZnS) 85.8g, Cadmium Sulfide (CdS)
14.2g, chloroauric acid (HAuCl ₄ ) 0.27g, aluminum sulfate {Al
₂ (SO ₄ ) ₃ · 18H ₂ O} 0.47g Next, each of the above phosphor raw materials (1 ′) to (12 ′) is packed in a quartz crucible and placed in an electric furnace, and calcined at 800 ° C. for 2 hours, then water. After sieving, the conductivity of the supernatant is 10 μs / cm
The phosphors (1) to (12) having the compositions and particle sizes shown in the table below were washed by washing with water and dried. The phosphors (1) to (12) correspond to the above-mentioned phosphor raw materials (1 ') to (12'), respectively.

Separately, indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ) and zinc oxide (ZnO) reagents were suspended in ethyl alcohol and thoroughly crushed with a ball mill. Conductive materials In ₂ O ₃ , SnO ₂ or ZnO having various desired particle sizes (median values) as shown in the table were obtained.
The particle size of In ₂ O ₃ , SnO ₂ or ZnO is adjusted by changing the grinding time by a ball mill and the material and size of the balls used, and a Shimadzu centrifugal sedimentation type particle size distribution analyzer SA-
Each particle size was measured using CP3. In addition, the standard deviation value (log δ) of the particle size of any pulverized conductive material is
It is less than 0.7.

Next, among the above-mentioned phosphors (1) to (12), phosphors (1), (3), (5), which are phosphors containing Li,
(7), (9), and (11) are selected and any one of these phosphors and the above In ₂ O ₃ , SnO ₂ and ZnO are selected.
Select any one of the above, weigh each predetermined amount, put in a beaker containing ethyl alcohol, and heat to evaporate to dryness with stirring to obtain the luminescent compositions S1 to S15 shown in the table below. It was The conductive substances contained in these light emitting compositions S1 to S15 all have a median particle diameter of 3 μm or less.

On the other hand, for comparison, In ₂ O ₃ , SnO ₂ and ZnO reagents were sieved and classified, and the median particle size of In ₂ O was 5 μm.
After obtaining ₃ , ₃ , SnO ₂ and ZnO, any one of these conductive materials and the phosphors (1), (3), (5),
Predetermined amounts of any one of (7), (9), and (11) were weighed and thoroughly mixed in a mortar to produce luminescent compositions R1 to R10 having the compositions shown in the table below. . Further, for comparison, among the above phosphors (1) to (15), phosphors (2), (4), (6), which are phosphors containing no Li,
(8), (10), (12) are selected, and any one of these phosphors and any one of the above-mentioned conductive substances having a median particle diameter of 5 μ are mixed in predetermined amounts. Then, phosphors R11 to R20 having the compositions shown in the table below were manufactured.

The luminescent compositions S1 to S15 thus obtained and the luminescent compositions R1 to R20 were excited with a low-speed electron beam with an accelerating voltage of 30 V using a demountable electron beam stimulator and the emission luminance was measured below. The results shown in the table were obtained. The presence or absence of Li in the phosphor during the measurement of the emission luminance, and the effect of the particle size of the conductive material becomes clear, the desired light emitting composition from among the light emitting composition S1 ~ S15 and R1 ~ R20 Items were selected and comparative groups A to J were prepared. The relative luminescence brightness shown in the table is a relative value when the luminescence brightness of the luminescent compositions R1 to R10 in each comparative group is 100, and comparison between luminescent compositions of different comparative groups cannot be performed.
Also, the optimum mixing weight ratio of the conductive substance to the phosphor is
The mixed weight ratio shown in the table varies depending on the particle diameter of the conductive substance, and is the mixed weight ratio that gives the highest emission brightness in each light emitting composition (excluding the light emitting composition S8).

As is clear from the results shown in the table, phosphors (2), (4), which are conventional sulfide-based phosphors not containing Li,
Luminescent composition R1 using (6), (8), (10) and (12)
Light-emitting composition R1 using phosphors (1), (3), (5), (7), (9), and (11), which are sulfide-based phosphors containing Li, as compared with 1 to R20 ~ R10 has high emission brightness. Furthermore, when comparing the emission luminance between the light emitting compositions having the same combination of the phosphor containing Li and the conductive material, as compared with the light emitting compositions R1 to R10 in which the particle diameter of the conductive material is 5 μ, The light emitting compositions S1 to S15 in which the particle diameter of the conductive material was smaller than 3 μm had a significantly higher emission brightness.

Further, the luminescent compositions S1 to S15 and the luminescent compositions R1 to R20 were mixed into a binder composed of ethyl cellulose and carbitol to form an ink, which was coated on a plate using a 250-mesh silk screen, and at 450 ° C. A fluorescent display tube was created by using the phosphor film obtained by heating for 30 minutes and drying, and it was operated at an accelerating voltage of 30 V, and the emission brightness was measured. Compared to a fluorescent display tube having a fluorescent film composed of the objects R11 to R20,
Luminescent composition using phosphor containing Li S1-S15 and R
A fluorescent display tube having a fluorescent film composed of 1 to R10 has a remarkably high emission luminance, and the light emitting compositions S1 to S15 and R1 to R10.
In a fluorescent display tube having a fluorescent film made of, the emission brightness of the fluorescent display tube using the light emitting compositions S1 to S15 in which the particle diameter of the conductive material is 3 μ or less is 5 μm. It was significantly larger than the fluorescent display tube using the light emitting compositions R1 to R10.

(Effects of the Invention) As described in detail above, according to the light-emitting composition of the present invention, in the light-emitting composition obtained by mixing the phosphor and the conductive substance, the compound represented by the general formula (Zn _1-X , Cdx) aM ^I , bLi, cX
By using a Li-containing sulfide-based phosphor represented by and a conductive material having a median particle diameter of 3 μm or less, the conductive material is The emission brightness can be significantly increased. Further, according to the fluorescent display tube of the present invention having the fluorescent film composed of such a composition, the emission brightness thereof can be remarkably improved as compared with the conventional fluorescent display tube.

[Brief description of drawings]

Figure 1 shows the conductive substance (In ₂ O ₃ ) contained in the luminescent composition.
Showing the relationship between the particle size of the luminescent composition and the emission brightness of the luminescent composition under low-speed electron beam excitation, FIG. 2 is a schematic view of a two-electrode fluorescent display tube according to the present invention, and FIG. It is a schematic diagram of a display tube. 11 …… Anode plate, 12 …… Fluorescent film 13 …… Ceramic substrate, 14 …… Cathode 15 …… Lattice electrode, 16 …… Container

Claims (8)

[Claims] 1. The general formula is (Zn _1-X , Cdx) S: aM ^I , bLi; cX (where M ^I is selected from the group consisting of Na, K, Rb, Cs, Ag, Au and Cu). At least one element, X is Al, Cl, Br and I
At least one element selected from the group consisting of
x, a, b and c are 0 ≦ x ≦ 1,0 ≦ a ≦ 1 × 10 ^-2 g /
g, 0 <b ≦ 1 × 10 ⁻² g / g, and 0 <c ≦ 1 × 10 ⁻² g / g), the Li-containing sulfide-based phosphor represented by Of 3 μm or less and a standard deviation value (log δ) of 0.7 or less, which is a mixture of at least one conductive substance of a conductive metal oxide and a conductive metal sulfide having a particle size distribution. And a luminescent composition. 2. The luminescent composition according to claim 1, wherein the conductive substance has a median value of 1 μm or less. 3. The light emitting composition according to claim 1 or 2, wherein the conductive substance is at least one of In ₂ O ₃ , SnO ₂ and ZnO. 4. The mixing weight ratio of the Li-containing sulfide-based phosphor and the conductive material is in the range of 998: 2 to 9: 1. Item or the luminescent composition according to Item 3. 5. A low-speed electron beam excitation fluorescent display tube having a structure in which an anode plate having a fluorescent film on one surface and a cathode facing the fluorescent film are enclosed in a container having a vacuum inside. The film has the general formula (Zn _1-X , Cdx) S: aM ^I , bLi, cX (where M ^I is at least one selected from the group consisting of Na, K, Rb, Cs, Ag, Au and Cu). Elements, x, a, b and c
Is 0 ≦ x ≦ 1,0 ≦ a ≦ 1 × 10 ⁻² g / g, 0 <b ≦ 1 ×
10 ⁻² g / g and 0 <c ≦ 1 × 10 ⁻² g / g, which is a number satisfying the condition), and a Li-containing sulfide-based phosphor having a median value of 3 μm or less and a standard deviation value (logδ ) Is 0.7 or less, and a low-speed electron comprising a light-emitting composition obtained by mixing a conductive metal oxide having a particle size distribution and at least one conductive substance selected from conductive metal sulfides. Line excitation fluorescent display tube. 6. The low-speed electron beam excitation fluorescent display tube according to claim 5, wherein the median value of the conductive material is 1 μm or less. 7. The slow electron beam excited fluorescence according to claim 5 or 6, wherein the conductive substance is at least one of In ₂ O ₃ , SnO ₂ and ZnO. Display tube. 8. The mixed weight ratio of the Li-containing sulfide-based phosphor and the conductive substance is in the range of 998: 2 to 9: 1, and the fifth and sixth aspects. Item 6. A low-speed electron beam excitation fluorescent display tube according to Item 7 or 7.