JPH08127769A - Phosphor and display device - Google Patents

Abstract

PURPOSE: To heighten the efficiency of high-luminance light emission, prevent an electron source of a display device from causing pollution, and improve the reliability and life of the device by covering a sulfide phosphor with a specific phosphor which emits ultraviolet upon excitation with electron beams. CONSTITUTION: A sulfide phosphor selected among (Zn1-x Cdx ) S:M, N (wherein x is 0-0.8; M is Ag, Cu, or Au; and N is Cl, I, P, Al, or Iu), CaS:Eu, CaS:Ce, CaS:Cu, Na, and Lu2 O2 S:Re (wherein Ln is Y, Gd, or La and Re is Eu or Tb) is covered with a ZnO phosphor which upon excitation with low-speed electron beams, emits light containing ultraviolet having a wavelength shorter than 400nm in an amount of 30-80wt.% based on the sum of the two materials. The resulting phorphor is used in a display device as a phosphor layer formed on the anode conductor of a light-transmitting electrode, in which device the phosphor layer is bombarded with electrons emitted from the electron source of a cathode upon application of an electric field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor composed of two kinds of phosphors and a display device having such phosphor in a light emitting portion.

[0002]

2. Description of the Related Art In a fluorescent display tube or a fluorescent display device using a field emission device as an electron source, a ZnS-based or CaS-based phosphor is used for displaying in a plurality of types of emission colors. It may be used for the light emitting part of the anode.

For example, as a red-emitting phosphor, (Z
n _x , Cd _1-x ) S: Ag, Cl (x = 0.22), Z
nS: Cu, Al, Y ₂ O ₂ S: Eu, etc. are known, ZnS: Zn is known as a blue light emitting phosphor, and ZnS: Zn is known as a green light emitting phosphor.
Cu, Al, (Zn _x , Cd _1-x ) S: Ag, Cl (x
= 0.6) is known.

The sulfide-based phosphor is gradually decomposed from the surface by being bombarded with electrons in the fluorescent display tube. The decomposed phosphor scatters around and adheres to the surface of the filament cathode or the field emission device, which is an electron emission portion, and reduces the electron emission capability.

In order to avoid such a problem, a means is proposed in which an ultraviolet light emitting phosphor such as BaSi ₂ O ₅ : Pb is laminated on the phosphor layer to protect the underlying phosphor. Has been done. In a fluorescent display tube having such a two-layer structure phosphor, the electrons are BaSi ₂ O _{5 in the} upper layer:
There is no possibility that the sulfide-based phosphor in the lower layer, which hits the Pb phosphor and does not directly hit the electrons, is decomposed and scattered. The BaSi ₂ O ₅ : Pb phosphor irradiated with the electrons emits ultraviolet rays, and the ultraviolet rays excite the sulfide-based phosphor in the lower layer to emit light.

[0006]

In a conventional fluorescent display tube or the like, the acceleration voltage of electrons is generally 1 kV or less, and the resistance of the phosphor layer is required to make the phosphor emit light with a practical brightness under this driving condition. It needs to be low to some extent. According to the conventional two-layer structure phosphor described above, BaSi ₂ O ₅ : Pb
The resistance of the phosphor was high, and sufficient brightness could not be obtained at an acceleration voltage of 1 kV or less.

The sulfide type phosphor is BaSi.
₂ O _5: but it is protected Pb phosphor, BaSi ₂ O ₅ which electrons impinge directly: Pb phosphor lifetime is disadvantageously short.

The present invention relates to a phosphor composed of a sulfide-based phosphor such as the above-mentioned conventional two-layer structure phosphor and another phosphor, and the electron bombardment is accelerated at a low voltage of, for example, 1 kV or less. Is intended to emit light with sufficient brightness and prolong life.

[0009]

The phosphor according to claim 1 is a sulfide-based fluorescent substance obtained by an electron beam-excited ultraviolet light-emitting phosphor that emits light containing ultraviolet rays having a wavelength shorter than 400 nm when excited by a slow electron beam. It covers the body.

The phosphor according to claim 2 is the phosphor according to claim 1.
In the phosphor described above, the particles of the electron beam excited ultraviolet light emitting phosphor cover the particles of the sulfide-based phosphor.

The phosphor according to claim 3 is the phosphor according to claim 1.
The phosphor described above is characterized in that the layer of the electron beam-excited ultraviolet light-emitting phosphor covers the layer of the sulfide-based phosphor.

The phosphor described in claim 4 is the phosphor according to claim 1.
The described phosphor is characterized in that the electron beam excited ultraviolet light emitting phosphor is ZnO.

The phosphor described in claim 5 is the phosphor according to claim 1.
The phosphor described above is characterized in that the mixing ratio of the electron beam excited ultraviolet light emitting phosphor is 30 to 80% by weight of the whole.

The phosphor described in claim 6 is the phosphor according to claim 1.
In the phosphor described above, the sulfide-based phosphor is (Zn
_1-x Cd _x ) S: M, N (where x = 0 to 0.8, M = A
g, Cu or Au, N = Cl, I, P, Al or In)
The phosphor is represented by

The phosphor according to claim 7 is the phosphor according to claim 1.
In the phosphor described above, the sulfide-based phosphor is CaS:
Eu, CaS: Ce, CaS: Cu, Na, Ln ₂ O ₂
S: Re (where Ln is 1 selected from Y, Gd and La)
The phosphor is selected from among the phosphors of the species Re = Eu or Tb).

The display device according to claim 8 is a display device in which electrons emitted from an electron source are projected onto a phosphor layer provided on an anode conductor, and the phosphor constituting the phosphor layer is , 400nm by excitation with slow electron beam
It is characterized in that it is a phosphor obtained by coating a sulfide-based phosphor with an electron beam-excited ultraviolet light-emitting phosphor that emits light containing ultraviolet light having a shorter wavelength.

A display device according to a ninth aspect is the display device according to the eighth aspect, characterized in that the particles of the electron beam excited ultraviolet light emitting phosphor cover the particles of the sulfide-based phosphor. And

According to a tenth aspect of the present invention, in the display device according to the eighth aspect, the sulfide-based phosphor is provided on the anode conductor in a layered form, and the electron beam-excited ultraviolet light-emitting phosphor is the above-mentioned. It is characterized in that it is deposited on the surface of a sulfide-based phosphor.

According to an eleventh aspect of the present invention, in the display device according to the eighth aspect, the electron beam excitation ultraviolet ray emitting phosphor emits ultraviolet ray and visible light.

According to a twelfth aspect of the present invention, there is provided the display device according to the eighth or eleventh aspect, wherein the electron beam excited ultraviolet light emitting phosphor is ZnO.

A display device according to a thirteenth aspect is the display device according to the eighth aspect, wherein the sulfide-based phosphor is (Zn _1-x Cd _x ) S: M, N (where x = 0 to 0). .8,
M = Ag, Cu or Au, N = Cl, I, P, Al or In).

The display device according to claim 14 is a display device.
Item 9. The display device according to Item 8, wherein the sulfide-based phosphor is C
aS: Eu, CaS: Ce, CaS: Cu, Na, Ln
₂O ₂S: Re (however, Ln is selected from Y, Gd, La)
Selected from among the phosphors of Re = Eu or Tb).
It is characterized by being an exposed phosphor.

According to a fifteenth aspect of the present invention, in the display device according to the eighth aspect, the anode conductor is a translucent electrode.

According to a sixteenth aspect of the present invention, in the display device according to the eighth aspect, the intensity ratio of ultraviolet rays and visible light generated by the electron beam excited ultraviolet light emitting phosphor is: ultraviolet component / visible light component = It is characterized by being 100/0 to 10/90.

A display device according to a seventeenth aspect is the display device according to the eighth aspect, wherein the electron source is a field emission type cathode.

The display device according to an eighteenth aspect is the display device according to the eighth aspect, wherein the electron source is a linear thermionic emission type cathode.

The display device according to a nineteenth aspect is the display device according to the eighth aspect, wherein the light emission of the phosphor layer is displayed through a color filter.

[0028]

The electrons emitted from the electron source impinge on the electron beam excited ultraviolet light emitting phosphor. The electron-beam-excited ultraviolet light-emitting phosphor emits ultraviolet light having a wavelength shorter than 400 nm. The sulfide-based phosphor under the electron-beam-excited ultraviolet light-emitting phosphor is excited by the ultraviolet light generated by the electron-beam-excited ultraviolet light-emitting phosphor to emit light. Electrons do not directly hit the sulfide-based phosphor, so it is difficult to decompose and scatter.

[0029]

EXAMPLES The present inventors conducted experiments using various phosphors in order to achieve the above object. As a result, it was recognized that if the sulfide-based phosphor is covered with a ZnO phosphor having a low resistance, the sulfide-based phosphor can emit light with sufficient brightness even by electron bombardment accelerated at a low voltage of 1 kV or less. It was

The present inventors have found that Z, which is a phosphor having a low resistance,
As a result of further research on a phosphor in which a sulfide-based phosphor is coated with an nO phosphor, the following facts have been found. That is, the emission spectrum of a ZnO phosphor is usually 4
Since it is in the range of 00 nm to 700 nm, a sulfide-based phosphor having an excitation peak in this wavelength range, for example, ZnC
By combining the phosphor that emits yellow to red light such as the dS: Ag phosphor with the ZnO phosphor, good results can be obtained as described above.

However, ZnS: Ag and ZnS: C
Regarding a blue-light-emitting sulfide-based phosphor having an excitation peak in a wavelength region shorter than 400 nm, such as u and Al, even if the ZnO phosphor is laminated thereon, the sulfide-based phosphor Cannot be emitted. This is because the ZnO phosphor irradiated with electrons hardly emits light having a wavelength shorter than 400 nm, and thus the sulfide-based phosphor in the lower layer cannot be excited to emit light.

Therefore, the inventors of the present invention, in the study of a phosphor obtained by coating a sulfide-based phosphor with a ZnO phosphor, aim to obtain not only yellow and red but also blue emission. While trying various manufacturing methods while paying attention to the emission spectrum of the phosphor, the following facts were discovered. That is, a normal ZnO phosphor has an emission peak near 505 nm, but among ZnO phosphors, a ZnO phosphor having an emission peak near 385 nm can be obtained by a specific manufacturing method.

FIG. 1 shows Z obtained by the method of the embodiment.
emission spectrum of nO phosphor, ZnS: Ag phosphor,
Fig. 3 shows respective excitation (absorption) spectra of ZnS: Cu, Al phosphor and Zn, CdS: Ag phosphor. In this way, the ZnO phosphor and the visible wavelength light are 400 nm.
If UV light of shorter wavelength is generated, ZnCdS: A
ZnS: Ag phosphor with red emission by g phosphor
It is also possible to emit blue and green light with a ZnS: Cu, Al phosphor or the like.

According to the knowledge of the present inventors, the peak at 385 nm in the emission spectrum of the ZnO phosphor is caused by the interband emission. A ZnO phosphor having such a light emission peak can be obtained by firing a normal ZnO phosphor produced by a reduction treatment in an O ₂ atmosphere. The ZnO phosphor having a peak of 385 nm thus obtained has a slightly higher matrix resistance than the conventional ZnO phosphor, but there is practically no problem as a phosphor used for the display portion of the fluorescent display tube.

Next, Zn applied to the display device of this embodiment
A phosphor layer having a two-layer structure in which a sulfide-based phosphor is coated with an O phosphor and a manufacturing method thereof will be described. ZnO is obtained by firing Zn powder in an atmosphere containing oxygen (for example, in air). This phosphor was annealed to prepare a sample having an emission peak only at 385 nm and a sample having an emission peak at two points of 385 nm and 505 nm. In addition,
This annealing treatment reduces the resistance value of the phosphor itself.

The ZnO may be annealed by using an ordinary furnace or lamp annealing. In the case of lamp annealing, the current flows along the surface of the ZnO particles, so that only the surface layer of the phosphor particles is processed. Since the light emission comes from not only the surface of the phosphor particles but also from the inside, the lamp annealing can improve the conductivity of the phosphor without attenuating the ultraviolet component.

As shown in FIG. 2, an ITO electrode 2 which is a translucent electrode is formed as an anode conductor on an anode substrate 1 which is an insulating glass substrate. A sulfide-based phosphor 3 is deposited thereon. The sulfide-based phosphor 3 may be mixed with a conductive substance such as In ₂ O _{3 in} order to reduce the resistance. A ZnO phosphor 4 as a visible light emitting phosphor is applied so as to cover the surface of the sulfide-based phosphor 3. The anode substrate 1 is baked at 400 to 500 ° C. to complete the anode substrate 1 for a fluorescent display tube or the like.

Although only a single layer of sulfide-based phosphor 3 is shown in FIG. 2, specific sulfide-based phosphors include blue-emitting ZnS: Ag phosphor and green-emitting phosphor. ZnS: Cu, Al phosphor, red light emitting Zn _0.2 Cd
_{The 0.8} S: Ag phosphors were separately used to form the anodes, which are independent light emitting display units, on the anode substrate.

The ZnO phosphor, which is an electron-beam-excited ultraviolet light-emitting phosphor, has an intensity ratio of an ultraviolet ray component having a peak at a wavelength of 385 nm and a visible light ray component having a peak at a wavelength of 505 nm, that is, ultraviolet ray component / visible ray component = 100 / 0-0
Various kinds of samples, such as / 100, were prepared. In addition,
In the present description, the intensity ratio of the ultraviolet ray component and the visible ray component is simply referred to as the wavelength component intensity ratio.

A fluorescent display tube is constructed using the anode substrate. In the ITO electrode of the anode substrate of the fluorescent display tube, 100 to
10 to 100 mA / cm ² by applying a voltage of 1000 V
The electric current of. At that time, the emission luminance and life characteristics of the phosphor layer of each anode were measured, and the results were used for evaluation.
The evaluation of each luminescent phosphor of each emission color will be described below with reference to FIGS.

For comparison, a sample having only a sulfide-based phosphor that emits each of the above-mentioned red, blue, and green colors as a phosphor, and Z having an emission peak only at a wavelength of 505 nm.
A sample having only the nO phosphor as a phosphor was also prepared.

(1) In the case of ZnS: Ag phosphor emitting blue light The relationship between the wavelength component intensity ratio of the ZnO phosphor provided on the ZnS: Ag phosphor and the relative brightness of the entire phosphor layer is shown in FIG. . The evaluation was performed at an anode voltage of 200V. When the component of 505 nm is abundant in the ZnO phosphor, ZnO
Since the ratio of components other than the blue component in the phosphor increases and the color purity of blue deteriorates, evaluation was performed using a blue filter.
As a comparative example, the brightness of a ZnO phosphor having an emission spectrum peak of only 505 nm in combination with a filter is shown in FIG.

In this example, the wavelength component intensity ratio is 385 nm.
In the range of / 505nn = 100/0 to 10/90, the relative luminance exceeded 50, and the result was obtained that was better for practical use than the comparative example. Within this range, more preferable results can be obtained if the wavelength component intensity ratio is 97/3 to 40/60. Within this range, the wavelength component intensity ratio is 9
If it is 0/10 to 75/25, an even more preferable result is obtained.

When the wavelength component intensity ratio is smaller than 5/95, the blue component of the 505 nm component of the ZnO phosphor is diffusely reflected and attenuated by the lower ZnS: Ag phosphor layer, so that the combination of ZnO and the filter is used. The characteristics are inferior to those of the sample. In addition, the wavelength component intensity ratio is 99/1
If it is larger, the matrix resistance of the ZnO phosphor becomes higher, resulting in a decrease in brightness.

(2) Case of green-emitting ZnS: Cu, Al phosphor FIG. 4 shows the result of an experiment carried out in the same manner as in the case of the ZnS: Ag phosphor. In this example, in the light generated by the ZnO phosphor, not only the blue component or ultraviolet rays having a wavelength of 385 nm as a center but also a part of the component having a wavelength of 505 nm as a center is used for exciting the sulfide-based phosphor. Therefore, the preferable wavelength component intensity ratio is expanded to 100/0 to 7/93. Within this range, the wavelength component intensity ratio is 90/10 to 40/6.
If 0, a more preferable result is obtained. Within this range, even more preferable results can be obtained if the wavelength component intensity ratio is 75/25 to 55/45. CaS: C
Similar results were obtained for the e phosphor.

(3) Red light-emitting Zn _0.2 Cd _0.8 S: Ag
Case of Phosphor FIG. 5 shows the result of an experiment conducted in the same manner as the case of the ZnS: Ag phosphor. In this example, the preferable wavelength component intensity ratio was 100/0 to 0/100. This is
This is because the excitation band of the red light emitting phosphor extends to the visible region, which is the 505 nm component of the emission spectrum of the ZnO phosphor, as shown in FIG. In the above-mentioned sulfide-based phosphor of this example, the Cd was set to 80%, but if the Cd amount is 80% or less, the band gap structure approaches the structure of the ZnS phosphor, so that the ZnO phosphor emits ultraviolet rays. The effect will be greater. On the other hand, when Cd is larger than 80%, it is mainly excited by light rays in the visible region.

When the electrons impinge on the phosphor and excite it to emit light, most of the energy of the electrons becomes heat, causing the phosphor to generate heat and lowering the emission brightness of the phosphor. The relationship between the temperature of the phosphor and the emission brightness is called temperature extinction characteristic.
In each of the examples described above, 385 nm of ZnO phosphor is used.
The light emission having a peak is excellent in temperature quenching characteristics. As shown in FIG. 6, as compared with the case where the light emission with inferior temperature quenching characteristics such as the light emission centered around the wavelength of 505 nm in the conventional ZnO phosphor is used and the red, blue and green colors are obtained by using this together with the filter, The phosphor of this example has excellent temperature quenching characteristics.

From the experimental results described above, ZnO in the phosphor of the display device of this embodiment has a wavelength component intensity ratio of 385 nm / 505 nn = 100/0 to 10 /.
It is considered that the selection within the range of 90 is practically effective.

A life test was conducted to confirm that the above-described ZnO phosphor suppresses decomposition and deterioration of the sulfide-based phosphor of the lower layer. FIG. 7A shows the case of only ZnS: Ag, and FIG. 7B shows the case of the above example (1) in which the surface of ZnS: Ag is coated with ZnO. In the graphs shown in these figures, the horizontal axis represents time and the vertical axis represents the residual rate of the anode current. When the upper layer of the sulfide-based phosphor layer was covered with ZnO, no reduction in the anode current was observed, and it was confirmed that it is effective as an emission measure for preventing contamination of the cathode or the emitter.

In addition to the phosphors described above, CaS: Cu,
Na (blue emission), Ln ₂ O ₂ S: Eu (red emission, L
n = at least one of Y, La, and Gd), CaS: Eu
The same effect is observed in the system (red emission) and the like.

According to the embodiment described above, since the sulfide-based phosphor is covered with the phosphor that emits visible light and ultraviolet rays having a wavelength shorter than 400 nm, for example, 1 kV
By the collision of electrons accelerated with a relatively low voltage as described below, it is possible to efficiently emit light with high brightness even with a sulfide-based phosphor having any emission color of red, blue, and green. In addition, since the sulfide-based phosphor is covered with another phosphor and decomposition and scattering of the sulfide-based phosphor due to direct bombardment of electrons can be prevented, there is no risk of contaminating the electron source of the display device, and the display device Reliability and life are improved.

The phosphors described in the above examples had a structure in which a sulfide-based phosphor was formed in layers on the anode conductor and the surface thereof was covered with a layered ZnO phosphor. However,
The structure of the phosphor of the present invention in which the sulfide-based phosphor is coated with the ZnO phosphor does not necessarily indicate only the structure of the two kinds of laminated phosphors as described above. For example, when observed microscopically, a phosphor having a structure in which particles of an electron beam-excited ultraviolet light-emitting phosphor coat particles of a sulfide-based phosphor also falls within the scope of the present invention, and such a phosphor of a display device is used. Even when it is used for the light emitting portion, the same effect as that of the above-described embodiment can be obtained.

Therefore, next, the particles of the ZnO phosphor are sulfides.
Of a structure in which particles of a system phosphor are covered, and
An example of a display device using an optical body will be described. Book
The sulfide-based phosphor used in the examples is (Zn_0.22, Cd
_0.78) S: Ag, Cl phosphor. This phosphor is red
In order to reduce electric resistance, it is In
₂O₃Has been added. Electron beam excitation used in this example
The ultraviolet light emitting phosphor is a ZnO phosphor. Shown in FIG.
Thus, the conventional ordinary ZnO phosphor has a wavelength of around 505 nm.
Although it has an emission spectrum with a peak, this Example
The ZnO phosphor used in Example 1 is the same as that described in the above embodiment.
, The visible light intensity is suppressed to 385 nm.
It has a remarkable peak and can emit UV light efficiently.
it can. The ZnO phosphor has such an emission spectrum.
In the process of manufacturing the ZnO phosphor in the above embodiment,
If the amount of reduced Zn is reduced,
Good.

(Zn _0.22 , Cd _0.78 ) S: Ag, Cl phosphor has an average particle size of 5 to 10 μm, and ZnO phosphor has an average particle size of 0.1 to 2 μm (more preferably 0.1 to 1 μm).
And Both phosphors and other additives are added to form a paste. In this example, a plurality of samples with different amounts of ZnO phosphor mixed were prepared and tested. For example, 0, 30, 5
An experiment was conducted by preparing a sample to which a ZnO phosphor of 0.8 wt% was added.

As shown in FIG. 9, the anode conductor 11 and the cross layer 12 surrounding the anode conductor 11 are formed on the substrate 10. The paste is printed and applied in a predetermined pattern on the anode conductor 11, and then the substrate 10 is fired. The coating film thickness is 10 to 20 μm. A display device is constructed by using the substrate 10 as an anode substrate.

Microscopically looking at the phosphor 13 obtained as described above, as shown in FIG. 10, (Zn _0.22 , Cd
_0.78 ) S: Ag, Cl
It has a structure in which particles of the O phosphor 21 are adhered. Driving a display device having such a phosphor 13 in the display section,
When the phosphor 13 is bombarded with electrons, Zn
The O phosphor 21 receives the electron bombardment and emits ultraviolet rays 22. Ultraviolet rays 22 are internally (Zn _0.22 , Cd _0.78 ) S: A
The g, Cl phosphor 20 is excited, and the particles of the phosphor 20 emit red light 23.

FIG. 11 shows the emission spectrum of the phosphor of this example. As a comparative example, 0% mixture (ie (Zn _0.22 ,
Cd _0.78 ) S: Ag, Cl phosphor alone) and the ZnO phosphor mixed with 50% and 80% were compared, the chromaticity values x, y and peak values were almost the same. Is. That is, even if the ZnO phosphor is added, the emission color of the phosphor as a whole is (Zn _0.22 , Cd _0.78 ).
There is almost no change as compared with the case of the S: Ag, Cl phosphor alone. This is because the ZnO phosphor of this example emits almost no visible light and has a peak at 385 nm which is ultraviolet light. Therefore, when the ZnO phosphor of the present example covers the sulfide-based phosphor, it does not affect the emission color of the sulfide-based phosphor.

FIG. 12 shows the ZnO phosphor (U in the figure).
V-ZnO) and the amount of light emitted from the display device.
The relationship between the relative brightness and the relative brightness is shown. This experiment result
If the amount of the ZnO phosphor mixed is 80% or less,
The relative brightness is 50% or more of 0%. this is,
(Zn_0.22, Cd_0.78) S: Ag, Cl Phosphor particle table
ZnO phosphor covers the entire surface without gaps, or (Z
n_0.22, Cd_0.78) S: Ag, Cl
If the ZnO phosphor covers several layers, (Zn _0.22,
Cd_0.78) S: Ag, Cl phosphor emission does not go out
It is considered that this is because the brightness decreases and the brightness decreases. Obedience
(Zn_0.22, Cd_0.78) S: Ag, Cl phosphor
There is a portion of the surface not covered by the ZnO phosphor, and (Z
n_0.22, Cd_0.78) S: Ag, Cl phosphor is partially exposed
The electron emission section of the display device,
Both the child and the ultraviolet rays coming from the surrounding ZnO phosphor are
Since it is a barrel, the phosphor as a whole emits light brighter. Well
If the particle size of the ZnO phosphor is 1 μm or less, (Zn
_0.22, Cd_0.78) Is S: Ag, Cl phosphor emission external?
It is observed brighter.

FIG. 13 shows the result of the life test of the display device using the phosphor of this example. The phosphor of this example is a sulfide-based phosphor (Zn _0.22 , Cd _0.78 ) S: Ag,
Since at least a part of the surface of the Cl phosphor particles is covered with the ZnO phosphor, the risk that the sulfide-based phosphor will be decomposed by the electron bombardment is higher than that when the sulfide-based phosphor is used alone. Few. As shown in FIG. 13, when the ZnO phosphor was not mixed (0% mixture), the anode current residual rate sharply decreased after 200 hours of lighting time (life time). This is because the sulfide-based phosphor is decomposed by the bombardment of electrons, and the decomposed product contaminates the electron emission portion of the display device to reduce its electron emission ability. However, when a ZnO phosphor is mixed (30, 50, 80
%), The probability of electrons directly hitting the sulfide-based phosphor decreases, so the electron emission capability of the electron emission part of the display device does not decrease, and the anode current remaining rate is stable and the life time is long. Is obtained.

From the above experimental results, when the amount of ZnO phosphor mixed is large, the brightness of the phosphor as a whole tends to decrease, but the life characteristics are improved. When the amount of the ZnO phosphor mixed is small, the brightness of the phosphor as a whole tends to be high, but the life characteristics are slightly inferior. Addition amount of ZnO phosphor is 3
If it is 0% or less, the decomposition of the sulfide-based phosphor is severe and the emission of the electron emission part of the display device is reduced. When the addition amount of the ZnO phosphor is 80% or more, less light is emitted from the sulfide-based phosphor and reaches the observer, and the relative brightness is 50% or less of that when the ZnO phosphor is not added. Considering the above tendency, the ZnO phosphor can be added in the range of 30 to 80% by weight, and the range of 50 to 80% by weight is the preferred range of use.

In the embodiment described above, the sulfide type phosphor is used.
As (Zn_0.22, Cd_0.78) S: Ag, Cl phosphor
Although listed, this is merely an example. With the ZnO phosphor
Sulfide-based fluorescence that can be combined to obtain the effects described above
As the body, (Zn_1-xCd _x) S: M, N (however, x =
0-0.8, M = Ag, Cu or Au, N = Cl, I,
P, Al or In), CaS: Eu, CaS: Ce, C
aS: Cu, Na, Ln₂O₂S: Re (however, Ln is
One kind selected from Y, Gd and La, Re = Eu or T
Examples thereof include phosphors such as b).

[0062]

According to the present invention, the sulfide-based phosphor is covered with the electron-beam-excited UV-emitting phosphor that emits UV light having a wavelength shorter than 400 nm, so that it can be accelerated at a relatively low voltage of, for example, 1 kV or less. With the electron bombardment, sulfide-based phosphors of any emission color of red, blue, and green can be efficiently emitted with high brightness. Further, since the sulfide-based phosphor is covered with the electron-beam-excited ultraviolet light-emitting phosphor, decomposition and scattering of the sulfide-based phosphor due to direct bombardment of electrons can be prevented, so that there is no risk of contaminating the electron source of the display device. ,
The reliability and life of the display device are improved. For this reason, it has become possible to use sulfide-based phosphors in high-voltage driven color graphic display tubes, field emission devices, and the like.

Among the sulfide-based phosphors, especially (Zn,
In the case of the Cd) S-based phosphor, an electron beam-excited ultraviolet light-emitting phosphor is mixed and used, so that the amount of Cd contained in the sulfide-based phosphor can be reduced.

Among the sulfide type phosphors, especially Y
₂ O ₂ : S, CaTiO ₃ : Pr, etc. were conventionally said to have a rapid deterioration in brightness due to the electron beam, but in the present invention, since they are made to emit light by ultraviolet rays, the deterioration in brightness of these phosphors can be prevented and a long life can be achieved. Became.

[Brief description of drawings]

FIG. 1 is a diagram showing an emission spectrum of each phosphor used in an example of the present invention.

FIG. 2 is a sectional view of an anode substrate according to an embodiment of the present invention.

FIG. 3 is a diagram showing an embodiment of the present invention in which a ZnS: Ag phosphor is coated with a ZnO phosphor. 6 is a graph showing the relationship with the overall relative luminance.

FIG. 4 is a graph showing an intensity ratio of an ultraviolet ray component having a peak wavelength of 385 nm and a visible light ray component having a peak wavelength of 505 nm in an embodiment of the present invention in which a ZnS: Cu, Al phosphor is coated with a ZnO phosphor; It is a graph which showed the relation with the relative brightness of the whole body layer.

FIG. 5 shows a wavelength of 385n in an embodiment of the present invention in which a Zn _0.2 Cd _0.8 S: Ag phosphor is coated with a ZnO phosphor.
6 is a graph showing a relationship between an intensity ratio of an ultraviolet ray component having a peak of m and a visible light ray component having a wavelength of 505 nm and a relative luminance of the entire phosphor layer.

FIG. 6 is a graph showing a comparison between temperature extinction characteristics of an example of the present invention and a comparative example.

FIG. 7A is a graph showing the relationship between the remaining rate of the anode current and the continuous lighting time in a life test of a comparative example,
(B) is a graph showing the relationship between the remaining rate of the anode current and the continuous lighting time in the life test of one example of the present invention.

FIG. 8 is a diagram showing spectra of a conventional ZnO phosphor and a ZnO phosphor emitting ultraviolet light in another example.

FIG. 9 is a cross-sectional view of an anode substrate of a display device of another embodiment.

FIG. 10 is an enlarged view of phosphor particles of another example.

FIG. 11 is a diagram showing emission spectra of a phosphor in another example (ZnO phosphor content of 50% and 80%) and a sulfide-based phosphor (ZnO phosphor content of 0%) which is a comparative example. .

FIG. 12 is a diagram showing the relationship between the content of ZnO phosphor and the relative luminance in the phosphors of other examples.

FIG. 13 shows a phosphor of another example (ZnO phosphor content 3
It is a figure which shows the result of the life test of the display apparatus using 0%, 50%, 80%) and the display apparatus which used the sulfide type fluorescent substance (ZnO fluorescent substance content 0%) which is a comparative example.

[Explanation of symbols]

2 ITO electrode as an anode conductor which is a translucent electrode 3 Sulfide-based phosphor 4 ZnO phosphor as an electron-beam-excited ultraviolet light-emitting phosphor 13 Phosphor 20 As a sulfide-based phosphor (Zn _0.22 , Cd _0.78 )
S: Ag, Cl phosphor 21 ZnO phosphor as an electron beam excited ultraviolet light emitting phosphor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01J 29/20 29/89 31/12 B 31/15 E

Claims (19)

[Claims] 1. An excitation of 400 n by a slow electron beam
A phosphor obtained by coating a sulfide-based phosphor with an electron beam-excited ultraviolet light-emitting phosphor that emits light containing ultraviolet light having a wavelength shorter than m. 2. The phosphor according to claim 1, wherein the particles of the electron beam excited ultraviolet light emitting phosphor coat the particles of the sulfide-based phosphor. 3. The phosphor according to claim 1, wherein the layer of the electron beam excited ultraviolet light emitting phosphor covers the layer of the sulfide-based phosphor. 4. The electron beam excited ultraviolet light emitting phosphor is Zn.
It is O, The fluorescent substance of Claim 1 characterized by the above-mentioned. 5. The phosphor according to claim 1, wherein the mixing ratio of the electron beam excited ultraviolet light emitting phosphor is 30 to 80% by weight of the whole. 6. The sulfide-based phosphor is (Zn _1-x C
d _x ) S: M, N (where x = 0 to 0.8, M = Ag, C
The phosphor according to claim 1, which is a phosphor represented by u or Au, N = Cl, I, P, Al or In). 7. The sulfide-based phosphor is CaS: Eu, C
aS: Ce, CaS: Cu, Na, Ln ₂ O ₂ S: Re
(However, Ln is one kind selected from Y, Gd, and La, Re
= Eu or Tb), the phosphor selected from the phosphors according to claim 1. 8. A display device in which electrons emitted from an electron source are projected onto a phosphor layer provided on an anode conductor,
The phosphor constituting the phosphor layer is a phosphor obtained by coating a sulfide-based phosphor with an electron beam-excited ultraviolet light-emitting phosphor that emits light containing ultraviolet rays having a wavelength shorter than 400 nm when excited by a low-speed electron beam. A display device characterized by being. 9. The display device according to claim 8, wherein the particles of the electron beam excited ultraviolet light emitting phosphor cover the particles of the sulfide-based phosphor. 10. The sulfide-based phosphor is provided in layers on the anode conductor, and the electron-beam-excited ultraviolet light-emitting phosphor is deposited on the surface of the sulfide-based phosphor. Item 8. A display device according to item 8. 11. The electron-beam-excited ultraviolet-emitting phosphor emits ultraviolet light and visible light.
Display device described. 12. The electron beam excited ultraviolet light emitting phosphor is Z.
It is nO, The display apparatus of Claim 8 or 11 characterized by the above-mentioned. 13. The sulfide-based phosphor is (Zn _1-x Cd
_x ) S: M, N (where x = 0 to 0.8, M = Ag, Cu
9. The display device according to claim 8, which is a phosphor represented by Au, N = Cl, I, P, Al or In). 14. The sulfide-based phosphor is CaS: Eu,
CaS: Ce, CaS: Cu, Na, Ln ₂ O ₂ S: R
e (however, Ln is one kind selected from Y, Gd and La, R
9. The display device according to claim 8, wherein the display device is a phosphor selected from phosphors of e = Eu or Tb). 15. The display device according to claim 8, wherein the anode conductor is a translucent electrode. 16. The intensity ratio of ultraviolet light and visible light generated by the electron beam excited ultraviolet light emitting phosphor is ultraviolet light component / visible light component = 100/0 to 10/90. Display device. 17. The display device according to claim 8, wherein the electron source is a field emission type cathode. 18. The display device according to claim 8, wherein the electron source is a linear thermionic emission type cathode. 19. The display device according to claim 8, wherein the light emission of the phosphor layer is displayed through a color filter.