JPH06299149A - Fluorescent material and its production - Google Patents

Abstract

PURPOSE:To provide a fluorescent material having high luminous efficiency even by exciting especially with an electron beam of low-acceleration voltage. CONSTITUTION:The fluorescent material is provided with a fluorescent region 1 and a barrier layer 2 contacting with the fluorescent region and covering the surface of the region. The potential of the lowermost part of the conduction band of at least the barrier layer is higher than that of the fluorescent region or the potential of the uppermost part of the valence band of the barrier layer is lower than that of the fluorescent region. For example, the fluorescent region 1 is ZnS:Ag having particle diameter of several mum to ten-odd mum and the barrier layer 2 is Zn0.8Mg0.2S having a thickness of about 10-30nm. The electrons and/or holes among the thermally equilibrated carriers generated in the fluorescent region 1 are not diffused to the surface region having high concentration of non-emission center and, accordingly, light is emitted in high efficiency in the fluorescent region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention particularly relates to an electron beam excited phosphor used in a CRT or the like, and relates to a phosphor used in a display field such as an image display device and a method for producing the same.

[0002]

2. Description of the Related Art At present, CRTs are most often used as displays because of their high brightness, high quality, and relatively large screens. Most of the phosphors currently used in CRTs are those obtained by mixing an appropriate activator with a matrix composed of II-VI group compound semiconductors or oxides. Specifically, ZnS: Ag, ZnS: Cu, Al, Y ₂ O ₃ S:
Eu ^{3+ and the} like. Since the CRT is configured to scan the entire phosphor screen with one electron beam, in order to scan a large area, the electron gun has to be separated from it according to the size of the phosphor screen to be scanned, that is, the deep There is a problem that depth is required.

Therefore, in recent years, a color flat panel (hereinafter referred to as CFP) has been developed as a flat panel display that solves this problem. This is the S'D'85 digest, pages 185-186, April 1985 (SID'85 Digest 185p-186p, Apr.1
985) etc.

FIG. 6 shows an example of the electrode structure. CFP is
A plurality of electron beams formed from a plurality of linear cathodes 51 using a grid 52 are each deflected by a deflection electrode group 53 to scan a fluorescent screen 54.
The area where the individual electron beams are responsible for scanning is part of the phosphor screen 54. Therefore, even if the deflection angle of each electron beam is small, since a plurality of electron beams are used, an image can be displayed on the entire surface of a wide screen. That is, C
The FP depth may be much thinner than the CRT depth required to scan the same area screen.

Currently, the depth is 50 mm to 80 mm and CR.
A CFP, which is much shorter than the T, is being prototyped. As shown in FIG. 6, a plurality of grids 52 and a deflection electrode group 53 are provided close to each other between the cathode and the anode.
A high voltage of about 0 kV is applied.

FIG. 7 shows a sectional view of a CFP fluorescent screen 54. A phosphor layer 56 having a predetermined thickness is provided on the surface of a glass face plate 55, and an aluminum metal back 57 having a thickness of about 100 nm is provided thereon. Conventionally, the same phosphor as a general CRT has been used as the phosphor constituting the phosphor layer 56.

[0007]

The luminous efficiency η of the phosphor in CFP was considerably lower than that of CRT, despite using the same phosphor as CRT. Specifically, C
It is as high as η = 20% at RT, but is inferior as η = about 12% (at V = 10 kV) in CFP. The difference in luminous efficiency η occurs because the acceleration voltage V is different between CFP and CRT. The acceleration voltage V in a normal CRT is 20 to 30 kV
Is. However, the acceleration voltage V in CFP is 10k.
It is as low as V.

The accelerating voltage in the CFP is set lower than that in the CRT for the following reason. CFP is
Because the electrode spacing is narrow and the electric field concentration is easy to occur,
A high voltage is likely to cause a discharge between them. The electric discharge not only disturbs the image but also damages the electrodes and the phosphor screen. Therefore, it is difficult for CFP to apply a high acceleration voltage like CRT.
If the voltage applied between the cathode and the anode can be made lower than in the conventional case, the discharge start voltage is lowered, and the depth of the CFP can be further shortened. Also, the deflection voltage can be reduced. However, as long as the conventional phosphor is used, the light emission efficiency η becomes extremely low, so that the acceleration voltage cannot be reduced further.

In order to solve the above conventional problems, it is an object of the present invention to provide a phosphor having a high luminous efficiency even when excited by an electron beam having a low acceleration voltage.

[0010]

In order to achieve the above object, the phosphor of the present invention comprises a fluorescent region and a barrier layer which forms a junction with the fluorescent region and covers the surface thereof, and at least the barrier layer is formed. The configuration is such that the conduction band lowest end potential is higher than that of the fluorescent region, or the valence band uppermost potential of the barrier layer is lower than that of the fluorescent region.

In the above structure, it is preferable that the conduction band bottom end potential of the barrier layer is shallower than that of the fluorescent region, and the valence band top end potential of the barrier layer is lower than that of the fluorescent region.

Further, in the above structure, it is preferable that an activator is present in the fluorescent region, the activator is an acceptor impurity, and the conduction band bottom end potential of the barrier layer is higher than that in the fluorescent region.

In the above structure, it is preferable that at least the conduction band bottom end potential of the barrier layer is higher as it approaches the surface, or the valence band top end potential of the barrier layer is lower as it approaches the surface.

In the above structure, it is preferable that the barrier layer has a conductivity type or an active impurity concentration different from that of the fluorescent region. In the above structure, the fluorescent region and the barrier layer are
Zinc sulfide, zinc selenide, at least one compound semiconductor selected from cadmium sulfide and cadmium selenide, or a compound semiconductor further containing at least one element selected from magnesium, calcium, strontium, barium and manganese in the compound semiconductor. It is preferable.

Further, in the above structure, it is preferable that the fluorescent region and the barrier layer are a compound semiconductor containing at least one element selected from Y ₂ O ₃ and Y ₂ O ₂ S. Further, in the above structure, the thickness of the barrier layer is preferably 1 nm or more and 100 nm or less.

Further, in the above structure, it is preferable to use for an electron beam having an accelerating voltage of at least 15 kV. Next, the method for producing a phosphor of the present invention comprises placing phosphor particles in a gas or a liquid containing an element forming a barrier layer, epitaxially growing a barrier layer on the surface of the phosphor particles, and a fluorescent region, A barrier layer that forms a junction with the fluorescent region and covers the surface thereof, at least the lowest conduction band potential of the barrier layer is higher than that of the fluorescent region, or the uppermost valence band potential of the barrier layer is It is characterized in that a phosphor lower than that in the fluorescent region is obtained.

In the above-mentioned structure, a phosphor having a compound semiconductor containing at least one compound selected from zinc sulfide, zinc selenide, cadmium sulfide and cadmium selenide as a matrix is manganese, magnesium, calcium, strontium and barium. It is preferable to perform heat treatment in a gas or liquid containing at least one element selected from the above to form a barrier layer from the surface of the phosphor to a predetermined depth.

Further, in the above structure, the matrix is Y ₂ O ₂
It is preferable to heat-treat the phosphor that is S in an oxygen atmosphere to form a barrier layer from the surface to a predetermined depth.
Further, in the above structure, it is preferable that the donor or acceptor is diffused from the surface of the phosphor particles to form a barrier layer from the surface to a predetermined depth.

[0019]

According to the above-mentioned constitution of the present invention, when the phosphor is irradiated with the electron beam, the luminous efficiency is improved as compared with the conventional phosphor by the following effects.

When the phosphor of the present invention is irradiated with an electron beam having a kinetic energy such that the range is longer than the thickness of the barrier layer, secondary electron multiplication occurs in both the barrier layer and the fluorescent region, and a large number of electrons, Holes are generated along the trajectory of incident electrons. The generated secondary electrons consist of hot carriers and thermal equilibrium carriers.

Among them, the heat equilibrium carrier diffuses according to the concentration gradient. Since the barrier layer has a higher potential at the bottom of the conduction band or a lower potential at the top of the valence band than the fluorescent region, electrons on the fluorescent region side,
For at least one thermal equilibrium carrier of holes,
The fluorescent region-barrier layer interface acts as a potential barrier. Therefore, diffusion of thermal equilibrium carriers of at least one of electrons and holes from the fluorescent region side into the barrier layer is hindered. After that, the difference between the bottom edge of the conduction band of the barrier layer and that of the fluorescent region is Δε _c (when the barrier layer is higher, it is positive), and the uppermost potential of the valence band of the barrier layer and that of the fluorescent region. The difference is expressed as Δε _v (when the barrier layer is lower, it is positive). By the way, in the phosphor of the present invention, like the conventional phosphor, many non-emission centers are present on the surface of the barrier layer or in the vicinity of the surface. The concentration of non-radiative centers is highest on the surface and decreases toward the inside. However, the phosphor of the present invention is covered with the barrier layer to a depth of about 1 to 100 nm at which the concentration of non-emission centers is sufficiently lower than that at the surface or near the surface. A heterojunction is formed at the fluorescent region-barrier layer interface. That is, the concentration of non-radiative centers at the interface is low. As described above, at least one of electrons and holes in the thermal equilibrium carriers generated in the fluorescent region does not diffuse into the surface region where the concentration of non-emission center is high, so that light is efficiently emitted in the fluorescent region. Δε _c > 0
In the case of a phosphor having Δε _v > 0, both the electron and hole functions as a potential barrier at the fluorescent region-barrier layer interface.
It is more effective because the diffusion of both of them is hindered at the interface. Further, since the barrier layer thickness is sufficiently thin as described above, V
_d is smaller than conventional phosphors. That is, the luminous efficiency is improved as compared with the conventional phosphor.

Further, according to the structure of the manufacturing method of the present invention, the phosphor of the present invention can be manufactured efficiently and rationally.

[0023]

EXAMPLES The present invention will be described in more detail with reference to the following examples. FIG. 2 shows data obtained by measuring the dependence of the emission luminance of CFP on the acceleration voltage. B is a measurement result when a conventional phosphor is used. Based on this measurement result, C
FIG. 3 shows a graph of the luminous efficiency-accelerating voltage characteristics in FP. Similarly, B is a case where a conventional phosphor is used.

Generally, the phosphor has a property that the lower the accelerating voltage V, the lower the luminous efficiency. This is CFP
This is the reason why the luminous efficiency η in CRT is lower than that in CRT. FIG. 4 shows the luminance-acceleration voltage characteristics of the phosphor when the phosphor is placed on the conductive substrate and the electron beam is irradiated from above. No metal back was provided in this measurement.
B is a measurement result when a conventional phosphor is used. FIG. 5 shows a graph of the luminous efficiency-accelerating voltage characteristics of the phosphor based on the measurement results.

It is considered that the property shown in FIG. 5 that the luminous efficiency decreases with a decrease in accelerating voltage is due to the presence of non-emissive centers on or near the surface of the phosphor. As shown in FIG. 4, the phenomenon that the phosphor hardly emits light at an accelerating voltage of about 2 to 3 kV or less is shown. It does not emit light when the acceleration voltage is V _d or less. V _d is generally called dead voltage.

The cause of the above properties of the phosphor is considered as follows. The electron beam injected into the phosphor is decelerated while repeatedly scattering in the phosphor. High-speed electrons excite the phosphor and generate new hot carriers each time they are inelastically scattered with the constituent atoms. They excite the phosphor again and generate more carriers. Such secondary electron multiplication in the solid is repeated until the kinetic energy of electrons becomes lower than the ionization threshold energy. Many thermal equilibrium carriers (electrons,
(Holes) are trapped in the emission center in the process of diffusion,
Recombines and emits light.

On the other hand, the penetration depth when the electron beam enters the phosphor becomes shallower as the acceleration voltage becomes lower. For example, in the case of a phosphor having ZnS as a matrix, the penetration depth is about 1.5 μm at an acceleration voltage of 10 kV, but at 2.5 kV, the penetration depth is about 100 nm, which is very shallow. Many non-emission centers such as surface states or lattice defects exist on or near the surface of the phosphor. When the accelerating voltage is low, the electron beam does not penetrate deep inside the phosphor,
Since the generated electrons and holes are limited to the surface or a place near the surface where there are many non-emissive centers, they are trapped by these and recombine without emitting light. Therefore, the phosphor does not emit light below a certain acceleration voltage (V _d ). Even when the accelerating voltage is high, carriers generated near the surface also recombine non-radiatively.
The diffusion distance L of the thermal equilibrium carrier is about 0.1 μm for ZnS: Ag, so the depth from the surface is 0.1 μm.
The thermal equilibrium carriers generated in the place of about m or less easily diffuse to the vicinity of the surface of the phosphor and are trapped in the non-radiative center. Due to the above mechanism, the brightness as shown in FIG.
It is considered that acceleration voltage characteristics can be obtained. as a result,
The light emission efficiency-accelerating voltage characteristic shown in FIG. 5 is obtained.

Comparing FIG. 2 and FIG. 4, V _d is different.
Apparently, V _d is larger when the phosphor is made to emit light by CFP, as compared with the luminance-accelerating voltage characteristic of the phosphor. This is C
This is because in the FP, the incident electrons pass through the metal back before reaching the phosphor layer and lose part of the kinetic energy at that time. The CFP apparently increases V _{d accordingly} .

Example 1 FIG. 1 is a sectional view of the phosphor of Example 1. The barrier layer 2 covers the surface of the fluorescent region 1. In this embodiment, ZnS: Ag having a particle size of several μm to several tens of μm is used for the fluorescent region 1, and the barrier layer 2 has a thickness of about 10 μm.
Zn _0.8 Mg _0.2 S of ˜30 nm was used.

FIG. 4A shows the case of the phosphor of the present embodiment.
It is a result of measuring emission luminance-accelerating voltage characteristics. A bright blue emission was obtained. V _d could reduced compared to 1kV about the conventional phosphor B. FIG. 5A is a graph showing the luminous efficiency-accelerating voltage characteristics of the phosphor of this example based on the measurement results. The luminous efficiency was improved as compared with the conventional phosphor B. This is considered to be the effect of reducing the dead voltage V _d . The data obtained by measuring the dependence of the emission luminance on the acceleration voltage when this phosphor is used in CFP is A shown in FIG. V _d = about 3kV and when the conventional phosphor B emit light with CFP V _d (approximately 4.5k
It was possible to reduce compared to V). Based on these measurement results, the emission efficiency-accelerating voltage characteristic when the phosphor A of this example was used in CFP is A shown in FIG.

The phosphor of this example had the effect of improving the luminous efficiency η for both CRT and CFP.
In particular, it had a great effect on CFP. When the phosphor of this example is caused to emit light by CFP, the acceleration voltage V = 10 kV
At that time, the luminous efficiency η was about 16%, which was about 30% higher than that of the conventional phosphor B. The effect of improving the luminous efficiency was more remarkable when the acceleration voltage was lower. For example,
When V = 7 kV, η = about 7% was obtained using the conventional phosphor B, whereas η = about 13% and about 80% when using the phosphor of this example. The luminous efficiency was also improved. On the other hand, it was possible to obtain the same luminous efficiency as that of the prior art, even if it was driven at an accelerating voltage of about 10 kV in the related art, but at about 6 kV. Since it was possible to drive at an acceleration voltage lower than that of the conventional CFP, discharge did not easily occur. As a result, the depth can be made thinner than before.

The reason why the luminous efficiency of the phosphor of this example is improved is considered as follows. Since the barrier layer 2 of the phosphor of this embodiment has a thickness of about 10 to 30 nm, it has a thickness of about 0.7 to 1.
The range of the electron beam accelerated to about 2 keV or more reaches the fluorescent region 1 beyond the barrier layer 2. Secondary electron multiplication occurs in both the barrier layer and the fluorescent region, and a large number of electrons and holes are generated along the trajectory of incident electrons. The generated secondary electrons consist of hot carriers and thermal equilibrium carriers.

In this embodiment, the barrier layer material is Zn _0.8 M.
g _0.2 S was used. This ternary compound semiconductor material has a wider band gap than ZnS, which is the matrix of the fluorescent region. Also,
The conduction band bottom end potential is shallower than ZnS, and the valence band top end potential is lower than ZnS. That is, Δε _c > 0 and Δε _v > 0. Therefore, the fluorescent region 1 is not affected by any of the heat balance carriers (electrons, holes).
The interface between the barrier layer 2 and the barrier layer 2 functions as a potential barrier.
Therefore, the thermal equilibrium carriers diffuse according to the concentration gradient, but their diffusion from the fluorescent region side into the barrier layer is hindered. In addition, Zn _0.8 which constitutes the barrier layer
Mg _0.2 S has the same zinc blende type crystal structure as ZnS in the fluorescent region. The latter has a slightly larger lattice constant,
Its thickness is as thin as about 10 to 20 nm, so that dislocations are not introduced into the barrier layer due to it. Therefore,
The interface between the two forms a good heterojunction. The concentration of non-radiative centers is highest on the surface, decreases toward the inside, and is lower around the interface than on the surface. As described above, the thermal equilibrium carriers generated in the fluorescent region do not diffuse into the surface region where the concentration of non-emission centers is high, so that the light efficiently emits in the fluorescent region. It is considered that the emission efficiency of the phosphor of this example is higher than that of the conventional one by the above mechanism.

By increasing the composition ratio of Mg in the barrier layer within the predetermined range, V _d could be further reduced. This can be considered to be an effect due to a larger band gap, in particular, a larger Δε _{c as} the Mg composition ratio increases.

By doping the barrier layer material with appropriate donor or acceptor impurities, Δε _c and Δε _v
Can be controlled to some extent. In the above embodiment, Zn _0.8 Mg _0.2 S of the barrier layer is not doped with a donor or acceptor impurity. However, for example, by doping the barrier layer with an appropriate amount of donor impurity Cl, Δε
_{Although c} decreases, Δε _v increases on the contrary, and diffusion of holes in the fluorescent region into the barrier layer can be further hindered.

On the other hand, ZnS _0.5 Se _0.5 : Ag having a particle size of several μm to several tens of μm is used for the fluorescent region 1, and Zn _0.9 Mg _0.1 S _0.9 Se having a thickness of about 10 to 30 nm is used for the barrier layer 2.
_{Even when 0.1} was used, the luminous efficiency was improved as compared with the conventional phosphor, as in the above-mentioned example. It emitted a bright green color. Also,
The same effect was obtained by using Zn _0.7 Cd _0.3 S: Ag for the fluorescent region 1 and Zn _0.9 Mg _0.1 S _0.9 Se _0.1 for the barrier layer 2.

Also, instead of Mg as the barrier layer material, M
A compound semiconductor in which n has a predetermined composition may be used. For example, Zn is used as the barrier layer material in the above embodiment.
_0.9 Mn _0.1 S _0.9 Se _0.1 may be used.

As a material for forming the fluorescent region and the barrier layer, zinc sulfide, zinc selenide, cadmium sulfide, cadmium selenide, or a mixed crystal thereof may be used. For example, Zn _0.7 Cd _0.3 S: Ag in the fluorescent region
The barrier layer material is Zn, which has a larger bandgap.
The same effect was obtained by using S. Also II-VI above
A mixed crystal semiconductor containing calcium, strontium, or barium can be used as the group compound semiconductor.

Example 2 As a material for forming the fluorescent region and the barrier layer, Y ₂ O ₃ , Y ₂ O ₂ S, or a compound semiconductor containing at least one of these compounds may be used. Particle size of several μm to several tens of μm in the fluorescent region 1
Y ₂ O ₂ S: Eu ³⁺ is used, and the barrier layer 2 has a thickness of Y ₂
When O ₃ was used, the luminous efficiency was improved as compared with the conventional phosphor, as in Example 1. It emitted a bright red color. Y
₂ O ₂ S has a smaller band gap than Y ₂ O ₃ ,
Δε _c > 0 and Δε _v > 0. It is considered that this has brought about the effect.

In the above embodiments, the case where the fluorescent region-barrier layer interface is steep is explained. However, at least the conduction band bottom end potential gradually becomes shallower as it approaches the surface, or the barrier layer top end of the valence band of the barrier layer. A barrier layer having a band structure in which the potential becomes deeper as the potential approaches the surface may be used. The same effect as in the above example was obtained with a phosphor having a structure in which the fluorescent region was ZnS: Ag and the barrier layer was Zn _1-x Mg _x S having a composition distribution in which x increased as the surface approached the surface.

(Embodiment 3) In the present embodiment, the fluorescent region and the barrier layer have the same base material, but the type or concentration of doped impurities are different. ZnS: Cu and Al are used for the fluorescent region and ZnS: Cu is used for the barrier layer.
When using, the same effect as above was observed. In this case, it is considered that since the barrier layer has a lower donor concentration than the fluorescent region, a diffusion potential appears between the barrier layer and the potential barrier Δε _c (> 0) for electrons. The effect of this embodiment is that the thickness of the barrier layer is set to 1 to 100.
It appeared well when set in the range of about nm.

(Embodiment 4) Next, an example of a method for manufacturing the phosphor of this embodiment will be described. Typically 0.01-0.5 mo
1 / l zinc sulfate (ZnSO ₄ ) aqueous solution, and 0.01-
0.5 mol / l magnesium sulfate (MgSO ₄ ) aqueous solution and 0.1 to 1 mol / l thiourea ((H ₂ N))
₂ CS) aqueous solution and 0.1 to 1 mol / l sodium hydroxide (NaOH) aqueous solution mixed in a predetermined ratio, and phosphor particles made of ZnS: Ag having a diameter of several μm to several dozen μm. , And the liquid temperature at 50-80 ° C (0-
It can be carried out in the range of 100 ° C. When the reaction is carried out for several minutes while stirring, the Zn _1-x Mg _x S layer having a thickness of about 10 to 30 nm can be grown on the surface of the phosphor particles. This layer was epitaxially grown using the phosphor particles as nuclei. A highly crystalline layer was obtained.

When the phosphor of this example manufactured by the above method was excited by an electron beam and its characteristics were evaluated, the luminous efficiency was improved as compared with the conventional phosphor, as in the above example. The effect was particularly remarkable in the low acceleration voltage region of about 15 kV or less.

It is considered that the Zn _1-x Mg _x S layer functioned as a barrier layer in the phosphor of this example, and the ZnS: Ag particles functioned as the same fluorescent region. By using the manufacturing method of this example, the phosphor of this example could be easily manufactured at low cost.

The composition ratio x of Zn _1-x Mg _x S forming the barrier layer can be controlled by changing the mixing ratio of the zinc sulfate aqueous solution, the magnesium sulfate aqueous solution and the thiourea aqueous solution. On the other hand, the constituent material of the barrier layer to be grown can be changed by changing the type of ions contained in the solution. For example, when the phosphor particles are placed in a mixed solution of a zinc sulfate aqueous solution, a manganese sulfate aqueous solution, a thiourea aqueous solution, and a sodium hydroxide aqueous solution, each having a predetermined concentration, the surface of the phosphor particles has a thickness. 10-30
It was possible to grow a Zn _1-x Mn _x S layer of about nm. This phosphor was also able to obtain the same effect as in the above-mentioned embodiment.

Example 5 Next, an example of another method for producing the phosphor of the present invention will be described. The phosphor of this example could also be manufactured by using the vapor phase epitaxial growth method as described below. A general atmospheric pressure MOCVD apparatus was used as the growth apparatus. The diameter is several μm to 1 on the graphite susceptor.
Phosphor particles made of ZnS: Cu with a thickness of 0 to several μm are thinly arranged, heated to about 450 ° C., and dimethylzinc, biscyclopentadienylmagnesium and diethylsulfur are introduced at an appropriate mixing ratio, and the phosphor surface A barrier layer was grown on. During the growth, the phosphor particles were frequently rolled on the susceptor, and care was taken to make the thickness of the growing barrier layer as uniform as possible. The surface of the phosphor particles has a thickness of 10 to 30.
It was possible to epitaxially grow a barrier layer of Zn _1-x Mg _x S of about nm. The obtained phosphor was also able to obtain the same effects as in the above-mentioned example.

The composition ratio x of Zn _1-x Mg _x S constituting the barrier layer could be easily controlled by changing the flow rate ratio of dimethyl zinc, biscyclopentadienyl magnesium and diethyl sulfur. Further, the constituent material of the barrier layer can be easily changed by changing the type of gas to be introduced. Alternatively, a thermal CVD method such as a low pressure MOCVD method or a vapor transport method may be used as the growth method. However, in any method, the result when the growth was performed at the growth temperature of about 250 to 700 ° C. was good. This is probably because if the growth temperature is too low, a highly crystalline barrier layer cannot be obtained, and conversely, if it is too high, the constituent elements of the fluorescent region and the barrier layer interdiffuse and a potential barrier cannot be formed. To be

(Embodiment 6) Next, another example of a method for producing the phosphor of the present invention will be described. Phosphor particles made of ZnS: Cu, Al having a diameter of several μm to several tens of μm are placed on a substrate placed in a quartz tube and heated to about 700 ° C., and biscyclopentadienyl magnesium and nitrogen are appropriately added. When the mixture was introduced at a different mixing ratio and heated for about 10 minutes, Mg diffused from the surface of the ZnS: Ag, Cl, and a region within about 30 nm from the surface was Zn _1-x Mg _x S: Ag,
It became a Cl layer. The phosphor of this example was also able to obtain the same effect as that of the above example.

(Embodiment 7) Next, an example of still another method for producing the phosphor of the present invention will be described. Magnesium chloride was placed in a quartz crucible and heated and melted. Phosphor particles made of ZnS: Ag, Cl having a diameter of several μm to several tens of μm were put therein and allowed to act for about 10 minutes while stirring.
Then, after cooling to room temperature, the solidified mixture was washed with water to remove magnesium chloride. Zn _1-x Mg _x S: Ag, C is formed on the surface of the obtained phosphor by diffusion of Mg and Cl.
A barrier layer having a thickness of about 10 to 30 nm composed of 1 was formed. The phosphor of this example was also able to obtain the same effect as that of the above example.

Next, a fifth embodiment of the phosphor manufacturing method of the present invention will be described. Y ₂ O with a diameter of a few μm to a few μm
₂ Put S: Eu ³⁺ phosphor particles in a porcelain crucible,
It was heated to about 800 ° C., oxygen was introduced therein, and it was baked for about 10 minutes. As a result, a region within about 30 nm from the surface of the Y ₂ O ₂ S: Eu ³⁺ is oxidized and Y ₂ O ₃ : Eu
It became ³⁺ . The phosphor of this example was also able to obtain the same effect as that of the above example.

(Embodiment 8) Next, an example of still another method for producing the phosphor of the present invention will be described. Phosphor particles made of ZnS: Cu, Al having a diameter of several μm to several tens of μm are placed on a substrate placed in a quartz tube and heated to about 700 ° C.,
A doping gas obtained by bubbling a copper sulfate aqueous solution with nitrogen gas was introduced therein. After heating for about 10 minutes, Z
The concentration of Cu in a region within about 30 nm from the surface of nS: Cu, Al was higher than that in the inside. The phosphor of this example was also able to obtain the same effect as that of the above example. It is considered that in the phosphor of this example, the above-described region having a high Cu concentration acted as a barrier layer. That is, it is considered that since the region has a higher acceptor concentration than the inside, a diffusion potential appears between them and a potential barrier Δε _c (> 0) for electrons occurs.

[0052]

According to the present invention, the luminous efficiency of the phosphor can be easily improved at low cost. As a result, the brightness of the CRT or CFP could be increased without increasing the input power. In particular, when operating in a low acceleration voltage region of about 15 kV or less like CFP, the luminous efficiency could be significantly improved. Moreover, the acceleration voltage in CFP was able to be reduced significantly compared with the past.
As a result, the depth of the CFP could be made significantly thinner than before. Also, the deflection voltage of the electron beam could be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a phosphor according to an embodiment of the present invention.

FIG. 2 is a measurement result of emission luminance-accelerating voltage characteristics when the phosphor of one example of the present invention and the conventional phosphor are used in CFP.

FIG. 3 is a luminous efficiency-acceleration voltage characteristic of CFP obtained from an emission luminance-acceleration voltage characteristic when the phosphor of one example of the present invention and a conventional phosphor are used in CFP.

FIG. 4 shows measurement results of emission luminance-accelerating voltage characteristics of the phosphor of one example of the present invention and the conventional phosphor.

FIG. 5 shows emission efficiency-acceleration voltage characteristics of a phosphor obtained from emission luminance-acceleration voltage characteristics of a phosphor of an example of the present invention and a conventional phosphor.

FIG. 6 is a cross-sectional view of a conventional example of CFP.

FIG. 7 is a cross-sectional view of a fluorescent screen in a conventional CFP example.

[Explanation of symbols]

 1 Fluorescent Area 2 Barrier Layer 54 Fluorescent Screen 56 Fluorescent Material Layer 57 Metal Back

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinichi Yamamoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (13)

[Claims] 1. A fluorescent region, and a barrier layer that forms a junction with the fluorescent region and covers the surface of the fluorescent region. At least the lowest conduction band potential of the barrier layer is higher than that of the fluorescent region, or the barrier. A phosphor in which the topmost valence band potential of the layer is lower than that of the fluorescent region. 2. The bottom edge of the conduction band of the barrier layer is shallower than that of the fluorescent region, and the top edge potential of the valence band of the barrier layer is lower than that of the fluorescent region.
The phosphor according to 1. 3. The phosphor according to claim 1, wherein an activator is present in the fluorescent region, the activator is an acceptor impurity, and the bottom edge of the conduction band of the barrier layer is higher than that in the fluorescent region. . 4. The phosphor according to claim 1, wherein at least the conduction band bottom end potential of the barrier layer is higher as it approaches the surface, or the valence band top end potential of the barrier layer is lower as it approaches the surface. 5. The phosphor according to claim 1, wherein the barrier layer has a conductivity type or an active impurity concentration different from that of the fluorescent region. 6. The fluorescent region and the barrier layer are composed of at least one compound semiconductor selected from zinc sulfide, zinc selenide, cadmium sulfide and cadmium selenide, or magnesium, calcium, strontium, barium and manganese added to the compound semiconductor. 6. A compound semiconductor containing at least one selected element.
The phosphor according to any one of 1. 7. The fluorescent region and the barrier layer are Y ₂ O ₃ and Y.
The phosphor according to claim 1, which is a compound semiconductor containing at least one element selected from ₂ O ₂ S. 8. The phosphor according to claim 1, wherein the barrier layer has a thickness of 1 nm or more and 100 nm or less. 9. The phosphor according to claim 1, which is used for an electron beam having an acceleration voltage of at least 15 kV. 10. Phosphor particles are placed in a gas or a liquid containing an element constituting the barrier layer, and the barrier layer is epitaxially grown on the surface of the phosphor particles to form a fluorescent region and a junction with the fluorescent region. A barrier layer covering the surface of the fluorescent layer, at least the lowest conduction band potential of the barrier layer is higher than that of the fluorescent region, or the uppermost valence band potential of the barrier layer is lower than that of the fluorescent region. A method for producing a phosphor, which comprises obtaining a body. 11. A phosphor having a compound semiconductor as a host material containing at least one compound selected from zinc sulfide, zinc selenide, cadmium sulfide and cadmium selenide is selected from manganese, magnesium, calcium, strontium and barium. The method for producing a phosphor according to claim 10, wherein the barrier layer is formed from the surface of the phosphor to a predetermined depth by heat treatment in a gas or a liquid containing at least one element. 12. The method for producing a phosphor according to claim 11, wherein the phosphor having a matrix of Y ₂ O ₂ S is heat-treated in an oxygen atmosphere to form a barrier layer from the surface to a predetermined depth. 13. The method for producing a phosphor according to claim 10, wherein a donor or acceptor is diffused from the surface of the phosphor particles to form a barrier layer from the surface to a predetermined depth.