JP2746192B2 - Phosphor for slow electron beam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor coated with a protective layer without deteriorating the surface. INDUSTRIAL APPLICABILITY The phosphor of the present invention is suitable for a display unit such as a fluorescent display tube or a field emission device using a bombardment of electrons accelerated at a relatively low voltage.

[0002]

_2. Description of the Related Art CaS-based phosphor, ZnGa ₂ O ₄ -based phosphor, alkaline earth silicate phosphor such as Sr ₃ MgSi ₂ O ₈ : Eu ²⁺ and alkaline earth titanate phosphor such as SrTiO ₃ : Pr. When using a phosphor or a Y ₂ O ₃ -based phosphor in a light emitting display section of a fluorescent display tube or a field emission device, it is necessary to apply these phosphors in a predetermined pattern according to the emission color. There is. As a method for this, C
A slurry method, a printing method, an electrodeposition method, and the like can be considered as in the case of the phosphor pattern manufacturing process in RT.

[0003]

According to the knowledge obtained by the present inventors, each of the above-listed phosphors is susceptible to a treatment involving oxidization such as baking or moisture, thereby deteriorating the surface thereof. . For example, taking CaS as an example, the alkaline earth sulfide phosphor such as CaS: Ce is chemically unstable.
It can hardly be practically used as a phosphor for a display element. Here, “chemically unstable” means a point which is easily oxidized in air and easily hydrolyzed. This Ca
The S: Ce phosphor is oxidized in the air to form calcium thiosulfate, and generates hydrogen sulfide by the action of moisture and carbon dioxide. Although it is hardly soluble in cold water, it is gradually hydrolyzed to form calcium sulfate and calcium hydroxide. Other phosphors, like the CaS: Ce phosphor, are vulnerable to treatments involving oxidation, such as firing, and to moisture, thereby deteriorating their surfaces.

[0004] Due to such a property, each of the phosphors listed above is easily decomposed in a process for attaching the phosphors to a predetermined pattern as a light emitting display section, as described below. It is easily oxidized in the step of firing the phosphor adhered in a predetermined pattern.

First, in a screen printing method, which is a general method of depositing a phosphor, a phosphor and a vehicle are mixed to form a paste, which is printed on a substrate in a predetermined pattern, and then fired in the air. To evaporate the paste components to CO ₂ . In order to decompose and decompose the organic substance used at the time of deposition, it is necessary to perform firing in an oxidizing atmosphere, but in such a case, the phosphor itself is also oxidized.

In the electrodeposition method, which is another method of depositing a phosphor,
The phosphor was dispersed in an organic solvent containing water, and the phosphor was attached to the anode by the principle of electrophoresis. In this method, since the water is contained, the phosphor is hydrolyzed.

In the slurry method, which is another method of depositing the phosphor, the phosphor is dispersed in a liquid containing polyvinyl alcohol and ammonium dichromate as a main medium, and the phosphor is coated with a mask having a predetermined pattern. Exposure is performed, and polyvinyl alcohol is removed by water development to obtain a predetermined pattern. This method also uses water and cannot be applied to the phosphor.

From the above circumstances, it is considered that even if each of the phosphors is formed on the light emitting portion of the display element by a conventional forming method, the surface of the phosphor is roughened, and the light emitting state is poor, so that it is not practical. Can be

In order to prevent the above-mentioned deterioration of the surface of the phosphor, the surface of the phosphor may be protected by covering it with a coating layer. For example, a method of coating the surface of the phosphor with SiO ₂ or the like may be considered. However, in order to form a SiO ₂ film on the surface of the phosphor, it is necessary to apply a raw material containing Si to the phosphor and then calcinate it by air to oxidize it. Is degraded by oxidation. Therefore, apart from the case where each of the phosphors coated with the SiO ₂ film emits light to the inside of the phosphor by a high-speed electron beam, a fluorescent display tube or a field emission device that emits light on the surface of the phosphor by a low-speed electron beam is used. Could not be applied.

The present invention has been made based on the findings of the inventors of the present invention described above, and a fluorescent display tube and an electric field for emitting light from the surface of a phosphor by the impact of electrons accelerated at a relatively low voltage. An object of the present invention is to provide a low-speed electron beam phosphor coated with a protective layer without deteriorating the surface so as to be suitable for a display unit such as an emission element.

[0011]

SUMMARY OF THE INVENTION According to the first aspect,
The phosphor for slow electron beams is made of a paper attached to the surface of phosphor particles.
Bake the solution of hydrohydrosilazane in a nitrogen atmosphere
Coated with silicon nitride Si ₃ N ₄ .

[0013] have been low voltage electron beam phosphor according to claim 2, in low-speed electron beam phosphor according to claim 2, wherein said phosphor is characterized in that an alkaline earth sulfide phosphor.

[0014] have been low voltage electron beam phosphor according to claim 3 is the low-speed electron beam phosphor according to claim 2, wherein said phosphor is characterized by a CaS-based phosphor.

[0015] have been low voltage electron beam phosphor according to claim 4, in the low speed electron beam phosphor of claim 1, wherein said phosphor is characterized by a ZnGa ₂ O ₄ phosphor .

The low voltage electron beam phosphor according to claim 5, in the low speed electron beam phosphor of claim 1, wherein said phosphor is characterized in that an alkaline earth silicate phosphor.

[0017] have been low voltage electron beam phosphor according to claim 6 is the low voltage electron beam phosphor of claim 1, it is characterized in that the phosphor is an alkaline earth titanates phosphor .

[0018] it has been low voltage electron beam phosphor according to claim 7, in the low speed electron beam phosphor of claim 1, wherein it is characterized in that said phosphor is Y ₂ O ₃ based phosphor.

[0019]

By treating the organometallic compound at a relatively low temperature in a nitrogen atmosphere, a metal nitride can be formed on the surface of the phosphor, and the surface of the phosphor is not oxidized.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have made several kinds of low-speed electron beam phosphors mentioned in the section of [Prior Art] emit light on the surface of the phosphor by the impact of electrons accelerated at a relatively low voltage. We succeeded in covering the surface with a protective layer without deteriorating it so that it can be used for a display unit such as a fluorescent display tube or a field emission device. The present inventors have adopted Si nitride as such a protective layer for the following reason.

First, the present inventors considered that an oxide was unsuitable as a protective layer for coating without deteriorating the surface of the phosphor. This is because when oxidizing the raw material provided on the surface of the phosphor, the surface of the phosphor is also oxidized and deteriorated. In addition, the present inventors also examined metal carbides and the like as candidates for the protective layer. However, there were many difficulties in the step of carbonizing the metal, such as adjusting the atmospheric conditions and the like, and there was a problem that it was not practical. Accordingly, the present inventors have results were compared to various other materials, nitride of Si
Was selected as the protective layer. This is because a nitrogen atmosphere for nitriding the metal and an organic nitrogen compound as a raw material can be easily obtained from a technical and economical point of view, and a process of obtaining a metal nitride from a nitrogen compound can be performed at a relatively low temperature. This is because there is an advantage.

[0022] In several embodiments described below, the Si
A method for producing a phosphor for a low-speed electron beam covered with a nitride protective layer will be described. (1) Example 1 This example relates to silicon nitride (Si ₃ N ₄ ) as a nitride of Si.
And a CaS: Ce ³⁺ phosphor. CaS: Ce ³⁺
The phosphor emits green light. Polysilazane (trademark, manufactured by Tonen Corp.) diluted to 20 wt% with xylene is used. This polysilazane has a chemical formula (SiH _a N _b )
_n (where a = 1 to 3, b = 1 ) perhydropolysilazane. In this polysilazane solution, CaS: Ce ³⁺
The phosphor is charged and the solvent xylene is removed by evaporation,
Polysilazane is deposited on the surface of the CaS: Ce ³⁺ phosphor. The CaS: Ce ³⁺ phosphor coated with polysilazane is put into a Pt crucible, and 600 to
By firing at 1100 ° C., a protective film of silicon nitride is formed on the surface of the CaS: Ce ³⁺ phosphor.

For example, when 1000 mg of Si ₃ N ₄ is deposited per kg of CaS: Ce ³⁺ phosphor, ie, CaS:
The deposition amount of Si ₃ N _{4 on} the Ce ³⁺ phosphor is 1000 m
In the case of g / kg, 0.0046 g of polysilazane is used for 1 g of the CaS: Ce ³⁺ phosphor. In this example,
A plurality of values in the range of 10 to 20,000 mg / kg were adopted as the amount of Si ₃ N ₄ deposited. For comparison, a sample without a protective film (non-coated) is used.

The plurality of samples obtained as described above and the sample of the comparative example were dispersed in an organic solvent using ethyl cellulose as a binder, and each was used as a paste. A predetermined pattern and a predetermined thickness were applied on the anode conductor of the glass substrate by the screen printing method, and baked at 500 ° C. for 30 minutes in the atmosphere to produce each anode substrate. Using each of the anode substrates, a fluorescent display tube was manufactured. Each fluorescent display tube was driven at an anode voltage of 400 V, and the emission luminance of each phosphor was evaluated.

FIG. 1 is a graph showing the relationship between the amount of Si ₃ N ₄ deposited and the initial luminance. The display of luminance is a relative luminance when the maximum luminance is 100. As can be seen from this graph, the deposition amount of Si ₃ N ₄ is 30-1000.
In the range of 0 mg / kg, the relative luminance is about 70% or more, which is practically effective. The deposition amount of Si ₃ N ₄ is 50
The relative luminance is about 80 in the range of ~ 5000 mg / kg.
% Or more, which is more preferable. The deposition amount of Si ₃ N ₄ is
The relative luminance is about 95% or more in the range of 100 to 1000 mg / kg, which is the most preferable.

FIG. 2 is a graph showing the relationship between the amount of Si ₃ N ₄ deposited and the luminance after 500 hours of the life test. The display of the luminance is a relative luminance when the initial luminance is 100. As can be seen from this graph, when the deposition amount of Si ₃ N ₄ was 10 mg / kg or more, a result superior to that of the comparative example was obtained. When the deposition amount was 100 mg / kg or more, the initial luminance hardly deteriorated.

With respect to the fluorescent display tube using the sample of this example,
After the life test, the amount of S scattered on the windshield surface was determined by AE.
When investigated by S analysis (Auger analysis), Si
Deposition amount of ₃ N ₄ and S throwoff was in inverse relationship. That is, when the amount of Si ₃ N ₄ deposited increases, the amount of S scattered decreases, and when the amount of Si ₃ N ₄ deposited is 200 mg / kg or more, the amount of S scattered decreases.
No scattering was observed. Si ₃ N ₄ deposition of 200
In the range of mg / kg or more, excellent results are obtained also in FIGS.

From the above results, it was found that C ₃ coated with Si ₃ N ₄
The aS: Ce ³⁺ phosphor is excellent in initial luminance without deterioration of the surface due to a firing step or the like when producing a fluorescent display tube. Further, scattering of S expected at the time of use is small, and deterioration of luminance is small.

The sample of this example was left in an environment of 95% humidity for 72 hours, and then emitted light by excitation with ultraviolet light. Table 1 shows the results of the relative luminance.

[0030]

[Table 1]

Although the luminance after the test is significantly deteriorated by the influence of humidity in the non-coated sample, the luminance hardly changes in each sample of this example. Therefore, Si ₃ N
_The CaS: Ce ³⁺ phosphor coated with ₄ is hardly deteriorated by humidity.

In the process of the first embodiment described above, the phosphor and polysilazane may be discharged into the space from different discharge devices, respectively, to form a polysilazane film on the surface of the phosphor.

[0040] (2) Example 2 This example, silicon nitride as the nitride of Si (Si ₃ N ₄₎
If, ZnGa as ZnGa ₂ O ₄ phosphor ₂ O _4:
Mn ²⁺ phosphor is used. The emission color of this phosphor is green. The polysilazane diluted to 20 wt% with xylene is used. In this polysilazane solution, ZnGa ₂ O
₄ : Charge Mn ²⁺ phosphor, remove xylene as a solvent by evaporation, and apply polysilazane on the surface of the phosphor. The phosphor coated with polysilazane is placed in a Pt crucible and fired at 600 to 1100 ° C. in a nitrogen gas atmosphere to form a silicon nitride protective film on the surface of the phosphor.

For example, Si ₃ N ₄ per kg of the phosphor is used.
Is applied, that is, when the amount of Si ₃ N _{4 applied to} the phosphor is 1000 mg / kg,
0.0046 g of polysilazane is used for 1 g of the phosphor. In this example, the deposition amount of Si ₃ N ₄ is 10 to 2
Multiple values within the range of 0000 mg / kg were employed. For comparison, a sample without a protective film (non-coated) was used.

A plurality of the samples obtained as described above and a sample of the comparative example were dispersed in an organic solvent using ethyl cellulose as a binder to obtain pastes. A predetermined pattern and a predetermined thickness were applied on the anode conductor of the glass substrate by the screen printing method, and baked at 520 ° C. for 30 minutes in the air to produce each anode substrate. Using each of the anode substrates, a fluorescent display tube was manufactured. Each fluorescent display tube was driven at an anode voltage of 400 V, and the emission luminance of each phosphor was evaluated.

FIG. 3 is a graph showing the relationship between the amount of Si ₃ N ₄ deposited and the initial luminance. The luminance display is a relative luminance when the maximum luminance is 100. As can be seen from this graph, the deposition amount of Si ₃ N ₄ is 10 to 1000
In the range of 0 mg / kg, the relative luminance is about 70% or more, which is practically effective. The deposition amount of Si ₃ N ₄ is 20
The relative luminance is about 80 in the range of ~ 5000 mg / kg.
% Or more, which is more preferable. The deposition amount of Si ₃ N ₄ is
The relative luminance is about 95% or more in the range of 100 to 1000 mg / kg, which is the most preferable.

( 3 ) Embodiment 3 This embodiment is directed to a silicon nitride (Si ₃ N ₄ ) as a nitride of Si.
And SrTi which is an alkaline earth titanate phosphor
O ₃ : Pr ³⁺ phosphor is used. The emission color of this phosphor is red. SrTiO ₃ : Pr added with Al or Ga
The same treatment as in Example 2 was performed on the ³⁺ phosphor. This was applied to a glass substrate by a slurry method using PVA using water as a solvent, and baked at 500 ° C. for 30 minutes in the air to produce an anode substrate. Using this, a fluorescent display tube was manufactured, and the emission of the phosphor at the anode was evaluated. Table 4
Represents the initial luminance (relative luminance) of four kinds of samples having different amounts of Si ₃ N ₄ and the comparative example. As shown in Table 4, the sample of this example exhibited higher initial luminance than the non-coated sample.

[0049]

[Table 2]

( 4 ) Embodiment 4 The present embodiment relates to silicon nitride (Si ₃ N ₄ ) as a nitride of Si.
And a Y ₂ O ₃ : Eu ³⁺ phosphor, which is a Y ₂ O ₃ -based phosphor. The emission color of this phosphor is red. The same processing as in Example 2 was performed. This was applied to a glass substrate by a slurry method using PVA using water as a solvent,
Baking was performed at 00 ° C. for 30 minutes to produce an anode substrate. Using this, a fluorescent display tube was manufactured, and the emission of the phosphor at the anode was evaluated. Table 5 shows the initial luminance (relative luminance) of four kinds of samples having different amounts of Si ₃ N ₄ and the comparative example. table
As shown by No. 3 , the sample of this example exhibited higher initial luminance than the non-coated sample.

[0051]

[Table 3]

In the second embodiment, ZnGa ₂
The characteristics of the O ₄ : Mn ²⁺ phosphor in which a part of Ga is replaced by Al or a part of Zn is replaced by Mg are also ZnGa ₂ O ₄ : Mn. ²⁺
Similar effects can be obtained as in the case of the phosphor.

[0053] _{Further, S r 3 MgSi 2 O 8} : Eu 2+ phosphor, and as will be other non-alkaline earth silicate fluorescent material activated by Eu ^2+, characteristics relating to moisture resistance and oxidation resistance Is the same as the Sr ₃ MgSi ₂ O ₈ : Eu ²⁺ phosphor, and the same effect can be obtained.

Further, in the third embodiment, SrTiO
₃ : Even for a phosphor in which part of Sr of the Pr ³⁺ phosphor is replaced by another alkaline earth metal, Al or Ga, the characteristics regarding humidity resistance and oxidation resistance are the same as those of the SrTiO ₃ : Pr ³⁺ phosphor. The same effect can be obtained without any change.

Next, the low-speed electron beam of each of the embodiments described above.
For fluorescent display and field emission devices use a phosphor is applied will be described with reference to FIGS.

FIG. 4 is a sectional view showing an example of a graphic fluorescent display tube. The envelope 1a includes a translucent front plate 2a, a rear plate 3a facing the front plate 2a, and a side plate 4a provided between the outer peripheral portions of the front plate 2a and the rear plate 3a.
They are sealed together to form a box. This envelope 1
The inside of a is kept in a high vacuum state.

On the inner surface of the front plate 2a of the envelope 1a, a plurality of strip-shaped anodes 5a are provided at predetermined intervals in parallel with each other. Each anode 5a is composed of a translucent strip-shaped anode conductor 6a provided on the inner surface of the front plate 2a, and a phosphor layer 7a attached to the upper surface of the anode conductor 6a. Above the anode 5a in the envelope 1a, a plurality of linear control electrodes 9a are stretched at predetermined intervals in parallel with each other via a spacer 8a. The longitudinal direction of each control electrode 9a is orthogonal to the longitudinal direction of the anode 5a. Both ends of each control electrode 9a are drawn out of the envelope 1a through the hermetically sealed portion of the envelope 1a. On the inner surface of the back plate 3a in the envelope 1a, a linear cathode 11a serving as an electron source is stretched via an attachment frame 10a.

In order to drive the graphic fluorescent display tube, a scanning signal is simultaneously applied to two adjacent control electrodes 9a, 9a, and scanning is performed while moving these one by one sequentially. The anode 5a is synchronized with the scanning of the control electrode 9a.
To the display signal. A region surrounded by the belt-like anode 5a and two control electrodes 9a, 9a orthogonal to the band-like anode 5a is a unit light emitting region, and an arbitrary image is displayed by a set of the selected unit light emitting regions.

If the phosphor layer 7a provided on the anode 5a is made of a phosphor coated with the above-mentioned metal nitride, a fluorescent display tube having a high initial luminance, a little deterioration in life during use and a high display quality can be obtained. realizable. If each anode 5a is constituted by alternately using three kinds of phosphors having respective emission colors of red, green and blue, a full-color graphic fluorescent display tube can be obtained.

FIG. 5 is a sectional view showing an example of the field emission device. The field emission type fluorescent display device 1 has a first substrate 2 and a second substrate 3 facing each other at a predetermined interval. Although not shown, the outer peripheral portions of the substrates 2 and 3 are sealed with a sealing material also serving as a spacer, and an envelope 4 in which the inside is in a high vacuum state is configured.

On the inner surface of the first substrate 2, FEC is used as an electron source.
5 (Field Emission Cathode). That is, the resistance layer 7 is provided on the cathode conductor 6 provided on the inner surface of the first substrate 2, and the gate electrode 9 is provided on the resistance layer 7 via the insulating layer 8. A large number of holes 1 reaching the resistance layer 7 are formed in the gate electrode 9 and the insulating layer 8.
0 is formed, and a cone-shaped emitter 11 is formed on the resistance layer 7 in each hole 10.

On the inner surface of the second substrate 3 facing the FEC 5, a light-emitting display section 20 composed of three kinds of display sections for displaying three colors of red, green and blue is formed.
That is, anode conductors 12, 13, and 14 which are light-transmissive electrodes are repeatedly attached to the inner surface of the second substrate 3 at predetermined intervals. On each of the anode conductors 12, 13, and 14, three kinds of phosphors R, G, and B, which emit light of three colors, red, green, and blue, respectively, are attached.

Here, the first and second substrates 2 and 3 are glass plates, the cathode conductor 6, the gate electrode 9 and the emitter 11 are M
o, the resistance layer 7 is amorphous silicon (a-Si) doped with P or B, the insulating layer 8 is SiO ₂ , the anode conductor 1
2, 13, and 14 are made of ITO. The anode conductor 1
2, 13, and 14 need translucency, and besides ITO, other translucent and conductive thin films, aluminum or the like having a translucent structure such as a mesh or stripe shape. It can also be composed of a metal thin film or the like.

Each of the phosphors R, G, B of the light emitting display section 20
If a phosphor coated with the above-mentioned metal nitride is used for at least a part of the above, it is possible to realize a fluorescent display tube having a high initial luminance, a little deterioration in life during use, and a high display quality.

[0065]

Effects of the Invention low voltage electron beam phosphor of the present invention Peruhido
Apply a solution of ropolysilazane to the particles in a nitrogen atmosphere
Because it is covered with fired silicon nitride Si ₃ N ₄
The surface of the phosphor is not degraded during the coating process,
It is hardly deteriorated even during use, and emits light on the surface by the impact of electrons accelerated at a low voltage. Therefore, it can be applied to a display portion such as a fluorescent display tube or a field emission device.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the amount of Si ₃ N ₄ deposited and the initial luminance of a phosphor in a first embodiment.

FIG. 2 is a graph showing a relationship between a deposition amount of Si ₃ N ₄ and luminance after 500 hours of a life test in the first embodiment.

FIG. 3 is a graph showing the relationship between the amount of Si ₃ N ₄ deposited and the initial luminance of a phosphor in a second embodiment.

FIG. 4 is a cross-sectional view showing an example of a fluorescent display tube to which the low-speed electron beam phosphor of each embodiment of the present invention can be applied.

FIG. 5 is a cross-sectional view showing one example of a field emission device to which the phosphor for slow electron beams of each embodiment of the present invention can be applied.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09K 11/78 CPB C09K 11/78 CPB (72) Inventor Yoshitaka Sato 629 Oshiba, Mobara-shi, Chiba Futaba Electronics Industry Co., Ltd. 56) References JP-A-2-114193 (JP, A) JP-A-5-59357 (JP, A) JP-A-5-93188 (JP, A) JP-A-5-99744 (JP, A) JP-A-2-178386 (JP, A) JP-A-6-168683 (JP, A) JP-A-61-258890 (JP, A) JP-A-54-142083 (JP, A) JP-A-2-67391 (JP) JP-A-2-238085 (JP, A) JP-A-63-278990 (JP, A) JP-A-8-78162 (JP, A)

Claims (7)

(57) [Claims] The present invention relates to a method for producing a perhydrophobic particle.
Nitriding by firing a solution of polysilazane in a nitrogen atmosphere
Phosphor for low-speed electron beams coated with silicon Si ₃ N ₄ . 2. The method according to claim 1, wherein said phosphor is an alkaline earth sulfide fluorescent substance.
The phosphor for low-speed electron beams according to claim 1, which is a body. 3. The phosphor according to claim 1, wherein said phosphor is a CaS-based phosphor.
The phosphor for a low-speed electron beam according to claim 2. 4. The phosphor is a ZnGa ₂ O ₄ phosphor.
The phosphor for a low-speed electron beam according to claim 1, wherein 5. The method according to claim 1, wherein said phosphor is an alkaline earth silicate.
The phosphor for low-speed electron beams according to claim 1, which is a phosphor. 6. The method according to claim 1, wherein said phosphor is an alkaline earth titanate.
The phosphor for low-speed electron beams according to claim 1, which is a phosphor. 7. The phosphor is a Y ₂ O ₃ phosphor.
The phosphor for a low-speed electron beam according to claim 1.