JPS5821476A - Blue light-emitting composition and fluorescent display tube excited by low energy electron ray - Google Patents

Abstract

PURPOSE:To prepare the titled composition capable of giving a highly luminous fluorescent film and keeping the high luminance even after the baking in the screen printing process, by mixing a self-activated zinc sulfide fluorescent material and an electrically conductive material such as electrically conductive metallic oxide, etc. at a specific ratio. CONSTITUTION:The objective composition is prepared by mixing (A) a self- activated zinc sulfide fluorescent material[ZnS:(Zn)]with an electrically conductive material selected from electrically conductive metallic oxides (preferably indium oxide, tin oxide or zinc oxide) and electrically conductive metallic sulfides at a weight ratio of 99:1-1:99. A fluorescent display tube excitable with low energy electron ray can be manufactured by sealing an anodic plate having a fluorescent film made of the above light-emitting composition and a cathode placed opposite to the fluorescent film, in an evacuated vessel.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a luminescent composition that emits high-intensity blue light under excitation with a slow electron beam, and a blue-emitting, slow-electron-beam-excited fluorescent display tube using this luminescent composition.

As is well known, a low-speed electron beam-excited fluorescent display tube (hereinafter abbreviated as "fluorescent display tube") consists of an anode plate having a fluorescent film on one side, a cathode facing the fluorescent film, and a vacuum inside. It has the essential structure of being enclosed in a container, and the fluorescent film on the anode plate is excited by a low-speed electron beam (generally a low-speed electron beam with an accelerating voltage of 100V or less) emitted from the cathode, causing it to emit light. So, there it is. 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. Figures 1 and 2
As shown in the figure, a fluorescent film 12 is provided on one side of an anode plate 11 made of an aluminum plate or the like. The anode plate (11) is supported by a ceramic substrate (13).

A cathode 14 is provided opposite the fluorescent film 12 provided on one side of the anode grate 11, and the fluorescent film 12 is excited by a low-speed electron beam emitted from the cathode 14 to emit light. In particular, in the triode shown in Fig. 2, the cathode 14 and the fluorescent film 1
A grid electrode 15 for controlling or diffusing the low-speed electron beam emitted from the cathode 14 is provided in the gap between the cathode 14 and the cathode 14 . Although one cathode 14 is used in the fluorescent display tube shown in FIGS. 1 and 2, the fluorescent film 1
2 has a wide area, two or more cathodes may be provided, and the number is not particularly limited. (Fig. 2) or an anode plate 11 having a fluorescent film 12 on one side, a ceramic substrate 13, a negative plate 14, and a grid electrode 15 (Fig. 2) are made of a transparent container 16 made of glass or the like.
It is enclosed in a monkey, and its interior 17 is 10"" ~ 10
It is maintained at a high vacuum of -9 Torr.

Conventionally, compositions that emit high-intensity blue light upon excitation with slow electron beams include, for example, indium oxide < In2O3).
and a silver-activated zinc i-ide phosphor (ZnS:Ag) in a predetermined amount (Japanese Patent Publication No. 52-23911),
Luminescent composition made by mixing zinc oxide (ZnO) and ZnS in a predetermined amount with an Ag phosphor (Japanese Patent Publication No. 53-25719
In2O3tZ is a specific phosphor that emits high-brightness blue light under high-speed electron beam excitation with an accelerating voltage of several kV or more.
A luminescent composition formed by mixing a predetermined amount of at least one of conductive metal oxides such as nO and tin oxide (5nO2) and conductive metal sulfides such as cadmium sulfide (Cd8) and copper sulfide (Cu, S). (Japanese Unexamined Patent Publication No. 55-23106), etc.
A large number of compositions are known, and blue-emitting fluorescent display tubes having fluorescent films made of these luminescent compositions are in practical use as display elements for various measuring instruments and the like.

By the way, when forming a fluorescent film on an anode plate when manufacturing a fluorescent display tube, for example, the above-mentioned Japanese Patent Application Laid-Open No. 55-23
As explained in detail in No. 106, conventionally, an anode plate was placed in a suspension of phosphors dispersed in water, and the phosphors were allowed to settle onto the anode plate by their own weight. After that, the so-called sedimentation coating method was used, in which the water was removed and the coating film was dried.

However, recently, in order to form a fluorescent film on an anode plate during the production of fluorescent display tubes, screen printing has been used instead of the precipitation coating method because it is easier to mass-produce and there is less loss of the luminescent composition. The law has been adopted.

This screen printing method involves preparing a luminescent composition ink by mixing a luminescent composition with a suitable organic binder, printing the luminescent composition ink on an anode plate by a mimeograph method, and then printing the resulting coating film. In this method, the organic binder is removed by peeling at a temperature of 400 to 50'C to form a fluorescent film. However, it has been found that when a conventional luminescent composition that has been formed into a fluorescent film by a conventional method - a drop coating method is made into a fluorescent film by a screen printing method, the luminance of the luminescent composition is significantly reduced by baking. .

Therefore, there is a strong desire for a blue light-emitting composition that emits high-brightness light under low-speed electron beam excitation, and at the same time does not reduce the light-emission brightness due to baking when it is made into a fluorescent film by screen printing.

The present invention has been made in view of the above-mentioned situation, and exhibits high luminance emission under low-speed electron beam excitation, and when it is made into a fluorescent film for a fluorescent display tube by screen printing, the luminescence is reduced by baking. The object of the present invention is to provide a blue light-emitting composition for low-speed electron beams that does not reduce brightness and a fluorescent display tube that emits high-brightness blue light.

The present inventors have conducted various studies to achieve the above object, and as a result, we have developed a self-activating zinc sulfide phosphor (ZnS: (Z
A luminescent composition formed by mixing a predetermined amount of a conductive substance with a conductive substance emits high-intensity blue light under excitation with a slow electron beam, and surprisingly, the luminance does not decrease even after baking in the screen printing method. This discovery led to the invention of a blue-emitting fluorescent display tube using this luminescent composition as a fluorescent film.

The luminescent composition of the present invention is a self-activated zinc sulfide phosphor (ZnS
: [Zn]) with a small amount of conductive metal oxide and conductive metal sulfide (all of which are characterized by a mixed weight ratio of conductive substances consisting of 11 types in the range of 99:1 to 1:9) It is.

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 vacuum container. In the display tube, the fluorescent film is composed of a self-activating zinc sulfide phosphor (ZnS: [:Zn]) and a conductive substance consisting of a conductive metal oxide and a conductive metal sulfide (both of which are made of one kind). It is characterized in that it is made of a luminescent composition mixed in a weight ratio of 9:1 to 1:9.

ZnS, which is one of the constituent components of the luminescent composition of the present invention
: [Zn] phosphors are manufactured by conventionally well known methods. That is, high-purity ZnS raw powder is mixed with compounds containing nitrogen elements such as sodium chloride (NaCl) and potassium chloride (CMCI), and aluminum sulfate (A12).
(SO4)3. ) and other compounds containing group B elements such as hydrogen sulfide (H2S) atmosphere, sulfur (8) atmosphere, nitrogen gas (N2) atmosphere, etc.
It is obtained by firing at a temperature of 1200°C to 1200°C for 30 minutes to 6 hours, washing with water to remove water-soluble substances such as flux, and drying.

Zn8: In the [Zn] phosphor, chlorine (CCI), bromine (Br), and other chlorine elements added during the preparation of the phosphor affect the sulfur (N2-) lattice points in the Zn8 crystal, and the aluminum Ckl). Group IIb elements such as these substitute the zinc <Zn 2 + > lattice points in the Zn8 crystal, enter into the Zn8 crystal, and work together as co-activators, resulting in Zn
It is thought that the luminescent center of the phosphor is formed together with the Zn2+ vacancy in the S crystal, but in this specification, these elements and group II b elements (one of which is used as a co-activator) are considered to form the luminescent center of the phosphor. Self-activated zinc sulfide phosphors containing Z
nS: (Zn) will be displayed.

In2O3゜Zn02Sn02. TiO2
, WO2, Nb2O3 etc. and CdS, Cu2S
etc. In particular, it is preferable to use conductive metal oxides from the viewpoint of luminance of the resulting composition, and among these, In2O3°SnO2 and ZnO are more preferable. The above-mentioned conductive metal oxides and conductive metal sulfides are obtained by calcining general reagents or general reagents in air, a neutral atmosphere, or a weakly reducing atmosphere. 4. After pulverizing with a ball mill or the like, it is obtained by classifying with a water sieve or the like. Regarding conductive metal oxides, compounds such as carbonates, sulfates, oxalates, and hydroxides that can be easily converted into metal oxides at high temperatures can be calcined in air to obtain metal oxides.
This may be obtained by classifying it.

The luminescent composition of the present invention can be obtained by thoroughly mixing the above-mentioned Zn8:[Zn] phosphor and a conductive substance in a mortar, ball mill, mixer mill, or the like. Both are ZnS: (Zn) phosphor/conductive substance value is 9
They are mixed at a weight ratio of 9/1 to 1/9. The preferred mixing amount of the conductive substance, which is one of the components of the luminescent composition of the present invention, varies depending on the particle size of the conductive substance, and the larger the particle size of the conductive substance used, the larger the preferable mixing amount of the conductive substance tends to be. However, regardless of the particle size of the conductive substance used, when the value of Zn8: [Zn] phosphor/conductive substance is greater than 99/1 (the content of the conductive substance is less than the total amount of the composition) (less than 1% by weight),
The charge-up prevention effect due to conductive substances cannot be obtained,
Therefore, the composition has properties close to those of ZnS: [Zn] phosphor and does not emit light under slow electron beam excitation. (% by weight), the resulting composition has very weak luminescence.

Figure 3 shows the In2O3 content ( % by weight) and the emission brightness of this fluorescent display tube, curves a, b, and C are for fluorescent films made of luminescent compositions in which the average particle diameters of In20a are 8 μ, 4 μ, and 1 μ, respectively. This example shows the case of a fluorescent display tube having an anode plate voltage of 50 V. Note that in FIG. 3, the luminance brightness (vertical axis) is shown as a relative value when the maximum value of brightness is 100 for each curve.

As is clear from FIG. 3, the preferred content of In2O3 in the luminescent composition when focusing on luminance is I
When the average particle size of nρ3 is 8μ, it is about 10 to 90% by weight, whereas when In203Y with an average particle size of 4μ is used, it is about 2.5 to 70% by weight, and when In203Y with an average particle size of 1μ is used, it is about 2.5 to 70% by weight. When used, the amount is approximately 1 to 60% by weight. In this way, when the particle size of In2O3 is reduced, the content of In203, which is preferable in terms of luminance, tends to decrease, but the luminance and I content in the luminescent composition tend to decrease.
The relationship with the content of n2O3 showed a tendency similar to curve a when the average particle diameter of In2O3 used was larger than 8μ, and curve C when it was smaller than 1μ. Furthermore, even when a conductive metal oxide or a conductive metal sulfide other than In 20 a is used as the conductive substance, the content of the conductive substance in the luminescent composition used and the resultant fluorescent display tube are determined. It was confirmed that the relationship with luminance was almost the same as the tendency shown in FIG.

Table 1 shows ZnS: (Zn
) phosphor, silver and chlorine activated zinc sulfide phosphor (Zn
S: Ag, CI), silver and aluminum activated zinc sulfide phosphor (ZnS: Ag, Al), silver and aluminum activated zinc sulfide phosphor (ZnS: Ag, Al),
Gold and aluminum activated zinc sulfide phosphor (ZnS:A
g y Au * M) and lead and aluminum activated zinc sulfide cadmium phosphor ((Zno3. Cao,
) S:Ag, Al), using In2O3 with an average particle size of 4μ as a conductive substance, and having an In20s content of 10% by weight, a fluorescent film t consisting of four types of luminescent compositions, respectively. The fluorescent films were produced by a precipitation coating method and a screen printing method, and the luminescence brightness was compared when these fluorescent films were excited with a slow electron beam at an accelerating voltage of 50V. As is clear from Table 1, ZnS:Ag, C1 phosphor, and ZnS are used as blue-emitting phosphors that are one of the constituent components of the luminescent composition.
:Ag, Al phosphor, ZnS:Ag, Au,
Al phosphor and (z”0.9, Cdo,)S:A
In the case of conventional luminescent compositions containing g+AIAl phosphors, when a fluorescent film is produced by screen printing, the luminance is significantly lower than that of a fluorescent film produced by precipitation coating, but ZnS: In the case of the luminescent composition of the present invention using (Zn)t-, there is very little reduction in luminance even during baking when creating a fluorescent film by screen printing.

Figure 4 shows In 20 with an average particle size of 4μ as a conductive material.
Using a luminescent composition containing 10% by weight of 3 as a fluorescent film
・This is a graph showing the relationship between accelerating voltage and luminance of a fluorescent display tube whose fluorescent film was prepared by screen printing method. Song 1 @a uses ZnS: (Zn) fluorophore as a constituent component of the composition. This is the case of a fluorescent display tube using the luminescent composition of the present invention as a luminescent material, and songs #b and C contain ZnS:Ag, Al phosphor and (ZnS:Ag) as constituent components of the composition, respectively.
O09,Cdo,t)S:Ag,A conventional typical blue light-emitting composition using an Al phosphor was used as a fluorescent film.
An example of the fluorescent display tube used is shown below.

Some conventional blue-emitting compositions have higher luminescence brightness under slow electron beam excitation, but as is clear from FIG. 4, a fluorescent film was prepared by screen printing, When used as a fluorescent display tube, regardless of the accelerating voltage of the slow electron beam, a fluorescent display using a luminescent composition containing ZnS:(Zr+) phosphor as a constituent component of the composition as a fluorescent film. The tube exhibits higher luminance than fluorescent display tubes using conventional luminescent compositions as the fluorescent film, and this trend is consistent with the use of conventional luminescent compositions as conductive materials.

The same results were obtained when conductive metal oxides and conductive metal sulfides other than In2Q3 were used.

The fluorescent display tube of the present invention is manufactured by a conventional method as described below. first.

The luminescent composition described above is coated onto an anode plate, usually supported by a ceramic substrate, by a precipitation coating method, screen printing method, etc. to form a fluorescent film. Next, the linear heater was made of HaO and SrO.

A cathode coated with an oxide such as CaO is placed facing the fluorescent film on the anode plate with an interval of approximately 1 m to 5 inches, and this pair of electrodes is placed in a transparent container such as glass. After installing the container, exhaust the inside of the container. After the inside of the container reaches a high degree of vacuum of at least 10-5 Torr, the exhaust is stopped and the container is sealed. 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.

The fluorescent YT film on the anode plate is flat and the cathode is linear, so in order to diffuse the low-speed electron beam emitted from the cathode, a film is placed between the cathode and the fluorescent film as shown in Figure 2. It is desirable to install a mesh-like grid electrode as a diffusion electrode.

The anode plate can display any character or figure by dividing its electrode form into the required character or figure shapes (1) and making it possible to selectively apply the required voltage to each electrode. be able to. In addition, the anode plate is divided into dots or lines, and a fluorescent film of the luminescent composition of the present invention is formed on some of the electrodes, and a luminescent film of the luminescent composition of the present invention is formed on the other electrodes. By forming a fluorescent film made of the composition, a fluorescent display tube capable of displaying multiple colors can be obtained.

As explained above, when the present invention is made into a fluorescent film for a fluorescent display tube by the screen printing method, there is less reduction in luminance due to baking, and therefore blue luminescence is higher in luminance than conventional blue luminescent compositions. The present invention provides a starting composition that provides a fluorescent film exhibiting the following properties, and its industrial utility value is great.

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

Example 1 Zinc sulfide (ZnS) and five-layer aluminum chloride (A
l (:13) in hydrogen sulfide (H2S) at 95%
After baking 7 parts by weight of ZnS: (Zn) phosphor obtained by firing at 0°C and InzQs reagent for 1 hour at 1000°C, 3 parts by weight of In203 with an average particle size of 8 μ obtained by classification were thoroughly mixed in a ball mill. The luminescent composition CI) containing 30% by weight of In2O5 was obtained by mixing [1) 20, ? 10g of diacetone alcohol
The luminescent composition was thoroughly kneaded in a ball mill with a binder consisting of 0.19 and nitrocellulose, and the paste-like luminescent composition was applied onto an anode plate supported by a ceramic substrate using a 200 mesh nylon screen, and then 450 The nitrocellulose was decomposed and removed by heat treatment at .degree. C. for 30 minutes to form a fluorescent film. Next, a cathode made of a tungsten wire heater coated with oxide was placed facing the fluorescent film on the anode plate for about 50 minutes.
Power was distributed at intervals of ys and m, and the pair of electrodes were installed in a hard glass container, and the inside of the container was evacuated.

When the degree of vacuum inside the container reached approximately 10-5 Torr, the exhaust was stopped and the container was sealed, and then the getter was removed to further increase the degree of vacuum inside the container. In this way, a fluorescent display tube (A) having the structure shown in FIG. 1 was manufactured.

Apart from this, the same In2O3 and ZnS:Ag as above
A fluorescent display tube [A'] was produced in the same manner as described above except that a blue light-emitting composition [1'] consisting of an AI phosphor and containing 30% by weight of In 203 was used.

The luminescent composition CI) and the luminescent composition [I'] were respectively coated on an aluminum substrate of the same area at the same coating density by a precipitation coating method, and the fluorescent films were excited with a low-speed electron beam at an accelerating voltage of soV.

A comparison of the luminance of the former revealed that the luminance of the former was approximately 1.5 times that of the latter. - Fluorescent display tube [A] and fluorescent display tube [A' ]The anode plate voltage is 50■.

When light was emitted at a cathode plate voltage of 1 and 5 V, the luminance of the former was about twice that of the latter.

Example 2 Zinc sulfide (Zn8) and potassium chloride (KCl)
) and 9 parts by weight of a Zn8:(Zn) phosphor obtained by firing a mixture with 1-128 gas at 950°C;
1 part of In20a having an average particle diameter of 4 μ obtained by baking the In2O3 reagent at 900° C. for 1 hour was thoroughly mixed in a ball mill to obtain a luminescent composition ([3]) containing 10% by weight of In2O5.

Using the luminescent composition thus obtained, a fluorescent film was prepared by screen printing in the same manner as in Example 1, and a fluorescent display tube having the structure shown in FIG. 1 (B ) was manufactured.

Apart from this, the same In20x as above and (Zno, *.

Cd o,s )8: Consisting of Ag wAl phosphor,
A fluorescent display tube [B'] was produced in the same manner as above except that the blue original composition [■'] containing 10Xt of IngO3 was used.

A firefly film formed by coating the luminescent composition (II) and the luminescent composition [■'] on an aluminum substrate having the same area between the coating columns by a precipitation coating method was exposed to a low-speed electron beam at an accelerating voltage of 50 V. Excite with.

When their luminances were compared, the luminance of the former was about twice that of the latter. Ten thousand.

The fluorescent display tube CB) and the fluorescent display tube [B'] obtained as described above were heated at an anode plate voltage of 50V.

When emitted at a cathode plate voltage of 1.5 V, the luminance of the former was about 10 times that of the latter.

Example 3 Zn8 obtained in the same manner as in Example 1: Zn03 with an average particle diameter of 1 μ obtained by baking 97 parts by weight of [Z,n] phosphor and a ZnO reagent at 1000° C. for 1 hour and then classifying for 1 hour. A luminescent composition (m) containing 3x'lii% of ZnQ was obtained by thoroughly mixing parts by weight in a ball mill. A fluorescent display tube [C] having the structure shown in was manufactured.

Apart from this, the same ZnO as above and (Zno, 9°C
d o, t) S: Consists of Ag, Al phosphor, Z
A fluorescent display tube [C'] was produced in the same manner as above except that the blue light-emitting composition [12'] containing n0Q3 was used.

The luminescent composition [I old] and the luminescent composition [■'] were coated on an aluminum substrate of the same area with the same coating density by a precipitation coating method, and a fluorescent film was excited with a low-speed electron beam at an accelerating voltage of 50 V. When comparing the luminance of the former, the luminance of the former was about 2.5 times that of the latter.

On the other hand, when the fluorescent display tube (C) and the fluorescent display tube [C'] obtained as described above were caused to emit light at an anode plate voltage of 50 V and a cathode plate voltage of 1.5 V, the luminance of the curved one was It was about 10.0 times that of .

Example 4 97 parts by weight of Zn8:(Zn''1 phosphor obtained in the same manner as in Example 2) and the :dnOz reagent were fired at 700°C for 1 hour and then classified to obtain an average particle size of 1 μm. 8nOz
Thoroughly mix the triple edges with a ball mill to make 8nQz triple? A light-emitting composition containing [a leapfrog was obtained.

A fluorescent display tube having the structure shown in FIG. 1 and having a fluorescent film produced by the screen printing method in the same manner as in Example 1 using the thus obtained luminescent composition [h'] D] was produced.

Apart from this, the same 5n02 and ZnS:Ag as above
A fluorescent display tube [D'] was produced in the same manner as above except that a blue light emitting composition [■'] consisting of a tAl phosphor and containing 5% by weight of 5n02 was used.

The luminescent composition [Seki] and the luminescent composition [■'] were each coated on an aluminum substrate of the same area with the same coating density by a precipitation coating method, and excited with a low-speed electron beam at an accelerating voltage of 50 V, When comparing the luminescent violet, @1
The luminance of the first cell was about twice that of the latter. on the other hand,
When the fluorescent display tube (L) and the fluorescent display tube (D) obtained as described above were made to emit light at an anode plate voltage of 5'OV and a cathode plate voltage of 1.5μ, the luminance of the former was similar to that of the latter. It was about 10 times that amount.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic diagrams of typical examples of fluorescent display tubes; Figure 1 is a diode tube, Figure 2 is a diode tube, and Figure 3 is a ZnS: (Zn) phosphor and In2O3. 2 is a graph showing the relationship between the content of InzOs in the luminescent composition and luminance in a fluorescent display tube using the luminescent composition consisting of the following as a fluorescent film. FIG. 4 shows the luminescent composition of the present invention consisting of In20a and ZnS:(Zn) phosphor, InzOa and ZnS:Ag.
, a luminescent composition consisting of an Al phosphor and 1nzO3 and (
1 is a graph showing the relationship between anode plate voltage and luminance in a fluorescent display tube using a luminescent composition comprising a phosphor of Zno, s, Cdo, +)S:Ag or Al as a phosphor film. 11... Anode plate 12... Firefly film 13
... Ceramic substrate 14 ... Cathode 15
...Grid electrode 16...Container 17.
...Figure 1 and 2 of the inside of the display tube kept in a high vacuum! [3v4t amount゛%

Claims (4)

[Claims] (1) Self-activated zinc sulfide phosphor (Zn8: (Zn)
), a conductive substance consisting of at least one of a conductive metal oxide and a conductive metal sulfide, and i99:l to l
A blue light-emitting composition mixed at a weight ratio of: :9. (2) The conductive metal oxide is indium oxide (I
r, zOsOstin oxide (8nOz) and zinc oxide (Z
The blue light-emitting composition according to claim 1, characterized in that t% is at least one of the following. (3) A low-speed electron beam-excited fluorescent display tube having an anode grating having a fluorescent film on one side, a cathode facing the fluorescent film, and a structure sealed in a vacuum container. The light film is made of self-activated zinc sulfide phosphor (Zn8: (
It is formed from a luminescent composition formed by mixing Zn)) with a conductive substance consisting of at least one of a conductive metal oxide and a conductive metal sulfide in a weight ratio of 99:1 to 1:9. A slow electron beam excitation wall ft,i characterized by
Show control. (4) The conductive metal oxide is indium oxide (I
n203), tin oxide (5nO2) and zinc oxide (Zn
4. The low-speed electron beam-excited fluorescent display tube according to claim 3, characterized in that the fluorescent display tube is at least one of O).