JPH0589786A - Display apparatus and its manufacture - Google Patents

Abstract

PURPOSE:To prevent the side face of base metal from being exposed and heighten the covering efficiency of the underlayered metal with an electron emitting material regarding a display apparatus which has a covered-type cathode structure. CONSTITUTION:In a display apparatus having a covered-type cathode structure wherein the structure is composed of many lines of cathodes prepared by coating a base metal with an electron emitting material 5, the gaps among the lines of a large number of covered-type cathodes 20 and the side faces are filled with a coated dielectric body 8. As the electron emitting material, a mixture of lanthanum hexaboride with 5-30wt.% of one or more kinds of auxiliaries selected from among titanium oxide, yttrium oxide, and barium silicate is deposited to coat the cathodes by plasma spraying. Further, the cathodes are coated with electron emitting material having 10mum or smaller particle size. The base metal 3 is prevented from being sputtered and evaporating and covering efficiency of the metal with the electron emitting material is improved and thus a display apparatus having high display quality and a long life is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device having a coated cathode in which the cathode is coated with an electron emitting material, and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 14 is a sectional view showing a conventional display device disclosed in, for example, Japanese Patent Laid-Open No. 1-225040. In the figure, 1 is a substrate, 2 is a surface plate, 3 is a base metal (cathode) formed on the substrate 1 by a thick film printing method, 4 is an anode formed on the surface plate 2, and 6 is a display dot. A partition plate, 7 is a base dielectric of the base metal 3, and 9 is LaB ₆ which is an electron emitting material, and the surface of the base metal 3 is coated by a printing method or plasma spraying.

In a display device having a matrix of electrodes and a discharge gas, it is common to make a Ni powder into a paste and print it as a cathode base metal and sinter it, but it has a high work function of 4.5 eV and an ion. It has the drawback of being vulnerable to shock. Therefore, as shown in the above-mentioned conventional example, a coating type cathode coated with a hexaboride such as LaB ₆ has been proposed.
The hexaboride used for this has the following characteristics. (A) The work function is low. (LaB ₆ ... 2.7eV) (b) a high melting point. Having (LaB ₆ ... 2600 ℃) (iii) conductive. (D) Little wear due to ion bombardment.

Next, the operation of the above display device will be described. First, a discharge gas of several hundred TO is placed between the substrate 1 and the surface plate 2.
RR filled and sealed confidentially. Then, a voltage is applied to the base metal 3 and the anode 4, and display is performed by discharging the discharge gas.
This discharge is partitioned by the partition plate 6 to form a display dot. The electron emission at the time of discharge is performed by LaB ₆ 9 which is an electron emission material coated on the base metal 3.
The LaB ₆ 9 is coated on a powder of Ni, Al, Ag or the like which is made into a paste and printed as a base metal 3 (or a cathode base metal) and sintered. The coating of LaB ₆ 9 is performed by a thick film printing method, a plasma spraying method, vapor deposition or the like. In the thick film printing method, a printing paste in which LaB ₆ powder is dispersed in an organic vehicle is used, and patterning printing is applied to the surface of the base metal 3 by the screen printing method, and this is coated at 500 to 600 ° C. Bake. The printing paste contains lead oxide, magnesium oxide, silicon oxide and the like as a baking aid. In the plasma spray method, the particle size is 10 to 30 μm
Some LaB ₆ particles are melt coated using a rare gas discharge plasma jet device of argon, helium or mixed gas. In the plasma spraying method, LaB ₆ particles adhere to the entire surface of the substrate 1, and therefore, patterning is performed using a tape or a metal mask. For example, FIG. 15 is a cross-sectional view of a LaB ₆ coated cathode by plasma spraying described in JP-A-56-118243.

[0005]

In the above conventional display device, the underlying metal 3 cannot be completely covered with the LaB ₆ 9 which is an electron emitting material because of the following reason, and the cathode material (Ni, Ni, There is a problem that Al, Ag, etc.) are sputtered. (1) For example, when coating LaB ₆ by plasma spraying, the phenomenon of so-called "shrinkage" during melting LaB ₆ particles hardens, LaB ₆ is underlying metal upper surface of the side surface of the underlying metal 3
It was pulled and fixed on the (surface). Also, La
Since the particle size of B ₆ was as large as 10 to 30 μm, the porosity was likely to be large and the coverage was low as shown in FIG. (2) When LaB ₆ is coated by the printing method, even if LaB ₆ is printed wider than the width of the base metal 3, it is printed as shown in FIG. 16, and it is difficult to cover the side surface of the base metal 3. Met. Furthermore, since the melting point and sintering temperature of LaB ₆ are high,
The adhesion of LaB _{6 to} the base metal 3 (cathode) is weak, so that it cannot be surely adhered, and the coating thickness varies depending on the location. In addition, the printing and coating with the paste mixed with the sintering aid has a problem that the sintering aid is sputtered and evaporated during the display operation to shorten the life of the display device. (3) When coating LaB ₆ by the vapor deposition method, the coating thickness is at most several thousand angstroms, and it is difficult to cover the side surface of the base metal having a thickness of several tens of μm, and high temperature heat treatment, etc. In this case, there was a problem that stress cracking occurred and the underlying metal 3 was exposed.

The present invention has been made in order to solve the above-mentioned problems, and by forming a coated cathode in which the side surface of the underlying metal is not exposed, and by increasing the coverage of the underlying metal with the electron emitting material. The purpose is to obtain a display device with high display quality and long life.

[0007]

The invention according to claims 1 and 2 is a display device provided with a covered cathode composed of a large number of rows and coated with an electron-emitting material, wherein a space or a side surface of the covered cathode composed of a large number of rows is provided. Is covered with a coating dielectric.

The invention according to claims 3 and 4 is a display device having a coated cathode coated with an electron emitting material, wherein the electron emitting material is lanthanum hexaboride, titanium oxide, yttrium oxide, or barium silicate. It is characterized in that one or a plurality of auxiliary agents are mixed in a ratio of 5 to 30 wt%, and that the cathode is coated with this electron emission material by plasma spraying.

The present invention according to claims 5, 6 and 7 is a display device having a coating type cathode having a cathode coated with an electron emitting material, wherein the cathode is coated with an electron emitting material having a particle size of 10 μm or less by plasma spraying. Is characterized in that As a manufacturing method thereof, an electron emitting material having a particle size of 10 μm or less is prepared, and the particle size is adjusted to 10 μm or more by granulation.
Plasma spraying is performed in a state of 0 μm or less, and the cathode is coated with an electron emitting material having a particle size of 10 μm or less.

[0010]

According to the first and second aspects of the present invention, by covering the rows and the side faces of the coated cathode composed of a large number of rows with the coated dielectric, it is possible to suppress the sputtering and evaporation of the underlying metal.

According to the third and fourth aspects of the invention, 5 to 30 wt% of lanthanum hexaboride is supplemented with one or more of titanium oxide, yttrium oxide, and barium silicate.
%, The mixture is plasma-sprayed, so that it has a binder effect and the like, the coverage is increased, the display quality is high, and the life is long.

According to the fifth, sixth and seventh aspects of the present invention, since the cathode can be coated with the electron-emitting material having a particle size of 10 μm or less, it is possible to form a coated cathode having a small porosity and a high coating rate. Material sputtering and evaporation can be prevented.

[0013]

【Example】

[Embodiment of the Invention According to Claims 1 and 2] First, an embodiment of the invention in which the space between the rows or the side surface of the coated cathode is covered with a coated dielectric will be described. Example 1. 1 and 2 are a sectional view and a perspective view showing a substrate portion of the display device of the present embodiment. In the figure, 1 is a substrate usually made of glass, 3 is a base metal made of Ni, Al, Ag, etc., 5 is an electron emission material such as LaB ₆ , 7 is a base dielectric of the base metal 3, and 8 is a coating dielectric. It is the body. First, in order to print and sinter the base metal 3, the base dielectric 7 is printed on the substrate 1. Here, there is a display device in which an electrode called a trigger electrode is provided between the base dielectric 7 and the substrate 1, but this is not taken into consideration here. Naturally, the effect of the present embodiment does not change even if the trigger electrode is present. Next, the upper surface of the base metal 3 is coated with an electron emitting material 5 such as LaB ₆ by a plasma spraying method, a printing method, a vapor deposition method or the like to form a coated cathode 20. After that, the coated dielectric 8 is filled between the rows of the coated cathode 20 composed of a large number of rows. The coated dielectric 8 is printed and sintered by the thick film printing method. A black or white glass frit or the like is used as the coating dielectric 8.

Next, the operation will be described. Base metal 3
When exposed, the base metal 3 causes sputtering and evaporation due to ion bombardment and heat during the operation of the display device, and the surface plate 2 is contaminated, and the display quality is degraded and the life is shortened. In the above embodiment, the upper surface (surface) of the base metal 3 is covered with the electron emitting material 5 such as LaB ₆ which is strong against ion bombardment, and the base metal 3 is not exposed. Therefore, the base metal 3 is not sputtered or evaporated. Can be suppressed. Further, since the coating dielectric 8 is filled between the side surfaces of the base metal 3, that is, between the rows of the coated cathode 20 composed of a large number of rows, the base metal 3 is not exposed and the sputtering and evaporation of the base metal 3 from the side surfaces are suppressed. be able to. In the above embodiment, the coated dielectric 8 was printed and sintered after the coated cathode 20 was formed. However, before forming the coated cathode 20, the spaces between the base metal 3 are filled with the coated dielectric 8 in advance. May be.

Example 2. FIG. 3 is a sectional view of a substrate portion of a display device according to another embodiment of the present invention, showing a case where the side surface of the base metal 3 is covered with a coating dielectric 8. That is, the coated dielectric 8 made of glass paste is printed and sintered so as to cover the side surface of the base metal 3. After that, the coated cathode 20 is formed. The coating of the side surface of the base metal 3 with the coating dielectric 8 may be performed after the formation of the coating type cathode 20.

Even when the partition plate 6 is provided on the substrate portion of the display device, the same effect as that of the above embodiment can be obtained. This is shown in FIG. That is, when the partition plate 6 is provided on the substrate and the phosphor is attached to the display plate 2 by exposing a part of the anode, a color display device is obtained. Further, when the partition plate 6 is provided between the base metal 3 and the base dielectric 7 in the related art, a step due to the base metal 3 appears above the partition plate 6 and causes crosstalk. However, as shown in FIG. 4, since the space between the rows of the coated cathode 20 composed of a large number of rows is filled with the coated dielectric material 8, there are few irregularities on the surface where the partition plate 6 is formed, such as steps due to the underlying metal 3. There is also an advantage that the step difference above the partition plate 6 is reduced.

In the above embodiment, the case of the coated cathode using LaB ₆ as the electron emitting material 5 has been described, but barium oxide, boride other than LaB ₆ , TiC,
It may be the case of a coated cathode using a carbide such as WC as an electron emitting material, and the same effect as that of the above-described embodiment is obtained. Further, in the above-mentioned embodiment, the display device having the discharge gas is explained, but the same effect can be obtained by applying it to the cathode of the CRT, the fluorescent display tube or the cathode of the flat CRT.

[Embodiment of the Invention According to Claims 3 and 4] Here, LaB ₆ and T are used as electron-emitting materials for coating the cathode.
Examples of the invention using a mixture of an auxiliary agent such as iO ₂ will be described. Example 3. FIG. 5 is a sectional view showing a substrate portion of a display device according to an embodiment of the present invention. In the figure, 1 is a substrate which is usually made of glass, 3 is a base metal (cathode) formed by patterning Ni, Al, Ag, etc. by a thick film printing method, 20
Is a base metal 3 (cathode) produced by plasma spraying an electron emitting material.
Is a coated cathode. FIG. 6 is a conceptual diagram of a rare gas discharge plasma jet device, 11 is a plasma gun,
12 is a power supply for supplying a voltage to the plasma gun 11, 13 is a rare gas supplier, 14 is a feeder of electron emission material, 15 is a feeder line, 16 is a plasma jet containing electron emission material, 17 is LaB ₆ , 18 is Auxiliaries such as TiO ₂ , Y ₂ O ₃ , Ba
It is composed of one or more components of O · SiO ₂ and is mixed in the electron emission material at a ratio of 5 to 30 wt%.

Next, the manufacturing process of the above display device will be described. Argon, helium, etc. are supplied to the plasma gun 11 from the rare gas supply system 13, and plasma is generated by the voltage applied by the power supply 12. Particles for thermal spraying in the feeder 14 are supplied into the plasma through the feeder line 15 to form a plasma jet 16. Particles for thermal spraying is an electron emission material, with LaB ₆ 17 is contained _{70~95wt%, TiO 2, Y 2} O 3, 1 kind or auxiliaries 18 multiple consisting of BaO · SiO ₂ is 5 Contains 30 wt%.
The particle size of each of the thermal spray particles is usually around 10 μm. The particle size is an example, and even if the particle size is 10 μm or less or 10 μm or more, the effect is the same in this embodiment. In the feeder 14, the electron emitting material (spray particles) is well stirred and filled. The electron emission material passing through the feeder line 15 is supplied to the plasma gun 11 with the above mixing ratio and becomes the plasma jet 16. Auxiliary 18 TiO ₂ , Y ₂
O ₃ is the melting point of each 1920 ° C., was 2410 ℃, LaB ₆ 17
Lower than 2600 ℃. Therefore easily auxiliaries 18 than LaB ₆ 17 melts. The molten LaB ₆ 17 and the auxiliary agent 18 are
The coated cathode 20 is formed by welding or adhering so as to be folded on the surface of the. At this time, since the auxiliary agent 18 melts more easily than LaB ₆ 17, the auxiliary agent 18 collides with the substrate 1 without melting.
with binder effect such or by attaching aB ₆ 17.
Further, by coating a part of the surface of the cathode 3 with the auxiliary agent 18, the sputtering and evaporation from the cathode 3 are prevented. Auxiliary 18
The TiO ₂ and Y ₂ O ₃ used in the above have a higher melting point than ordinary metals and are less likely to wear due to ion bombardment. LaB ₆ 17 covers the surface of the cathode 3 except for the portion coated with the auxiliary agent 18.
In this way, the coverage can be increased as compared with the case where the LaB ₆ 17 simple substance is coated by plasma spraying. Further, these auxiliary agents 18 are stable because they return to the ceramic state at the time of thermal spraying and fixing after melting. The patterning is performed using a method of limiting the sprayed area using a tape or a metal mask, or a lift-off method using a resist.

Example 4. As shown in FIG. 7, the method of supplying the electron emitting material to the plasma gun is plural (two in this case).
It may be configured by a feeder and a feeder line. In FIG. 3, one feeder 14a has LaB ₆ 17
However, the other feeder 14b is filled with the auxiliary agent 18 and supplied to the plasma gun 11 through the feeder lines 15a and 15b. For example, if the supply amount to the plasma gun 11 is set to be LaB ₆ : auxiliary agent = 9: 1, 90
It is possible to form the coated cathode 20 using an electron emitting material composed of wt% LaB ₆ 17 and 10 wt% of the auxiliary 18.

Embodiment 5. LaB ₆ 5 mixed rare gas plasma jet apparatus obtained by granulating the and auxiliaries 18 may be plasma sprayed using. For the granulation, either a method of mechanically stirring the particles for adhesion or a method of using an organic binder may be used.

In FIG. 8, 90 wt% LaB ₆ and 10 wt% T
and coating cathode coated with electron emissive material consisting iO ₂ Prefecture,
The discharge characteristics of a coating type cathode coated with an electron emitting material composed of 90 wt% LaB ₆ and 10 wt% Y ₂ O ₃ are shown. In both cases, the discharge sustaining voltage was lower than that of the Ni electrode, and LaB ₆
It can be seen that the discharge sustaining voltage is slightly higher than that of the single substance, but exhibits almost the same characteristics. In addition, in the above-mentioned embodiment, the display device having the discharge gas is explained, but the cathode of the CRT,
The same effect can be obtained by applying it to a fluorescent display tube or a cathode of a flat panel CRT.

[Embodiment of the Invention According to Claims 5, 6 and 7] Here, an embodiment of the invention in which the particle coverage of plasma spraying is improved by using fine particles of 10 μm or less as an electron emitting material will be described. Example 6. FIG. 9 is a sectional view showing the substrate portion of the display device of this embodiment. In the figure, 1 is a substrate which is usually made of glass, 3 is a base metal (cathode) formed by patterning Ni, Al, Ag, etc. by a thick film printing method, 30 is an electron emitting material having a particle size of 10 μm or less. It is a coated cathode in which the base metal 3 (cathode) is coated by plasma spraying. FIG. 10 shows a rare gas discharge plasma jet device used for manufacturing the display device of this embodiment, 11 is a plasma gun, and 12 is a plasma gun 11.
A power source for supplying a voltage, 13 is a noble gas supplier, 14 is a feeder of electron emission material, 15 is a feeder line, 16 is a plasma jet containing electron emission material, 40 is particles for thermal spraying
(Electron emitting material).

Next, the manufacturing process will be described. Argon, helium, etc. are supplied to the plasma gun 11 from the rare gas supply system 13, and plasma is generated by the voltage applied by the power supply 12. The thermal spraying particles 40 in the feeder 14 are supplied into the plasma through the feeder line 15 to form the plasma jet 16. The temperature in the plasma jet 16 reaches several thousands to several tens of thousands, and the melting point of LaB ₆ , TiO ₂ , Y is high.
Materials such as ₂ O ₃ and BaO / SiO ₂ can be easily melted. The thermal spray particles 40 include, for example, LaB _{6 having a} particle size of 10 μm or less.
Use particles. The melted LaB ₆ is welded onto the cathode 3 so as to be folded and overlapped to form a coating layer. Each layer of the coating layer is basically a porous layer, but since the particles for thermal spraying 14 have a particle size of 10 μm or less, a layer having a small number of pores and hence a small porosity and a large coating density is formed. Then, the coated cathode 30 having few pores as a whole is formed. Conventionally, LaB ₆ particles having a particle size of 10 μm or less cannot be supplied to the plasma gun 11 because they adhere to the feeder line 15, but for example, if the Nagata Iron Works' fan powder feeder “FP feeder” is used, it cannot be supplied to the plasma gun 11. It will be possible. In addition,
The patterning is performed by a lift-off method using a metal mask or a resist.

Example 7. Next, an example in which an electron emission material having a particle size of 10 μm or less is granulated to have a particle size of 10 μm to 50 μm as the thermal spraying particle 40 will be described. If the particle size is about 10 μm to 50 μm, a conventional feeder can be used without using a special feeder, and the rare gas plasma jet device becomes inexpensive. FIG. 11 is a schematic diagram of a granulating apparatus. Thermal spraying particles 40 composed of LaB ₆ particles having a particle size of 10 μm or less are put in a container 42 and stirred by a stirrer 41. By mechanically mixing and stirring the fine particles, La
The B ₆ particles are coagulated and granulated to have a particle size of 10 μm to 50 μm. This granulated particle is shown in FIG. 12, where 50 is the granulated particle (10 μm to 50 μm LaB ₆ particle) and 40 is the original thermal spray particle (10 μm or less LaB ₆ particle). When the granulated particles 50 are supplied to the plasma gun 11 after granulation, the granulated particles 50 are decomposed into the original spray particles 40 in the plasma jet 16 and melted. Then, it is welded onto the cathode 3 to form a coated cathode having a small porosity.

Example 8. Granulation can also be performed using an organic binder. As the organic binder, a cellulose resin such as ethyl cellulose or nitrocellulose or an acrylic resin is used. As shown in FIG. 13, an organic binder and thermal spraying particles are mixed in a container 60 and mixed by using a ball mill 61 or the like for granulation. When the granulated particles containing the organic binder are supplied to the plasma gun 11, the organic binder burns in the plasma jet and disappears. Then, the granulated particles are decomposed into particles for thermal spraying to cover the cathode.

Example 9. In the above embodiment, the case was described in which LaB ₆ having a particle diameter of 10 μm or less was used as the particles for thermal spraying. However, TiO ₂ , Y ₂ O ₃ , BaO.
5 to 30 wt% of one or more kinds of particles of SiO ₂
A mixture of LaB ₆ at a ratio of 4 may be used as the particles for thermal spraying. The melting temperatures of TiO ₂ , Y ₂ O ₃ , and BaO · SiO ₂ are 1920 ℃, 2410 ℃, and 1755 ℃, respectively, and LaB ₆ is 2600.
Lower than ℃. Therefore, the temperature of the plasma jet 16
TiO ₂ , Y ₂ O ₃ , BaO.Si even in the parts lower than 2600 ℃
O ₂ melts to serve as a binder, and LaB ₆ can be deposited on the cathode 3 to form a coated cathode. When the temperature of the plasma jet is low, damage to the substrate 1 can be reduced and the coverage rate can be increased. Also,
In the above-mentioned embodiment, the display device having the discharge gas has been described, but the same effect can be obtained by applying the display device to a cathode of a CRT, a fluorescent display tube or a cathode of a flat CRT.

[0028]

As described above, according to the first and second aspects of the present invention, the inter-rows or the side faces of the coated cathode composed of a large number of rows are covered with the coated dielectric, so that the sputtering and evaporation of the underlying metal can be suppressed, and the display can be achieved. There is an effect that a display device with high quality and long life can be obtained.

According to the third and fourth aspects of the present invention, lanthanum hexaboride is mixed with 5 to 3 auxiliaries consisting of one or more of titanium oxide, yttrium oxide, and barium silicate.
Since the mixture of 0 wt% was plasma-sprayed, it has a binder effect and the like, and the coverage is increased.
High display quality and long life.

Further, according to the inventions of claims 5, 6 and 7, since the cathode can be coated with the electron-emitting material having a particle size of 10 μm or less, a coated cathode having a small porosity and a high coverage can be formed. It is possible to prevent sputtering and evaporation of the cathode material.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a substrate portion of a display device showing an embodiment of the invention according to claims 1 and 2.

FIG. 2 is a perspective view of a substrate portion of a display device showing an embodiment of the invention according to claims 1 and 2.

FIG. 3 is a sectional view showing a substrate portion of a display device of another embodiment according to claims 1 and 2.

FIG. 4 is a perspective view showing a substrate portion of a display device of another embodiment according to claims 1 and 2.

FIG. 5 is a cross-sectional view of a substrate portion of a display device showing an embodiment of the invention according to claims 3 and 4.

FIG. 6 is a conceptual diagram showing a rare gas discharge plasma jet device.

FIG. 7 is a conceptual diagram showing a rare gas discharge plasma jet device.

FIG. 8 is a diagram showing discharge characteristics of the display device of the above-mentioned embodiment.

FIG. 9 is a cross-sectional view of a substrate portion of a display device showing an embodiment of the invention according to claims 5, 6, and 7.

FIG. 10 is a conceptual diagram showing a rare gas discharge plasma jet device.

FIG. 11 is a schematic view showing a granulating device.

FIG. 12 is a schematic diagram of granulation.

FIG. 13 is a schematic view showing a granulating device.

FIG. 14 is a cross-sectional view showing a conventional display device.

FIG. 15 is a cross-sectional view showing a surface of a coated cathode of a conventional display device.

FIG. 16 is a cross-sectional view showing a substrate portion of a conventional display device.

[Explanation of symbols]

1 Substrate 2 Surface Plate 3 Base Metal 4 Anode 5 Electron Emitting Material 6 Partition Plate 7 Base Dielectric 8 Coated Dielectric 11 Plasma Gun 12 Power Supply 13 Rare Gas Feeder 14 Feeder 15 Feeder Line 16 Plasma Jet 17 LaB ₆ 18 Auxiliary Agent 20 Coated Cathode 30 Coated Cathode 40 Spray Particles 41 Stirrer 42 Vessel 50 Granulated Particle 60 Vessel 61 Ball Mill Machine

Claims (7)

[Claims] 1. A display device having a multi-row coated cathode coated with an electron-emitting material and a multi-row anode corresponding to the multi-row cathode in a matrix form, and having a discharge gas therebetween, a multi-row coating. A display device characterized in that a space or a side surface of the mold cathode is filled or covered with a coating dielectric. 2. A display device having a covered cathode composed of a large number of rows coated with an electron-emitting material, characterized in that a space or a side surface of the covered cathode composed of a large number of rows is filled or covered with a covering dielectric. Display device. 3. A display device having a coated cathode coated with an electron-emitting material, wherein the electron-emitting material comprises lanthanum hexaboride and one or more of titanium oxide, yttrium oxide, and barium silicate. A display device, wherein the agent is mixed at a ratio of 5 to 30 wt%. 4. The method of manufacturing a display device according to claim 1, wherein the cathode is coated with the electron emitting material by plasma spraying. 5. A display device having a coating type cathode in which a cathode is coated with an electron emitting material, wherein the cathode is formed by coating an electron emitting material having a particle size of 10 μm or less by plasma spraying. 6. A method of manufacturing a display device in which a cathode is coated with an electron emitting material to form a coated cathode, an electron emitting material having a particle size of 10 μm or less is prepared, and the particle size is adjusted to 10 μm or more and 50 μm or less by granulation. Plasma spraying is performed in this state, and the cathode is coated with an electron emission material having a particle size of 10 μm or less. 7. A method of manufacturing a display device in which a cathode is coated with an electron emitting material to form a coated cathode, wherein the electron emitting material is lanthanum hexaboride having a particle size of 10 μm or less or hexaboride having a particle size of 10 μm or less. 5 to 3 lanthanum with an auxiliary agent consisting of one or more of titanium oxide, yttrium oxide, and barium silicate having a particle size of 10 μm or less
It is characterized in that a mixture of 0 wt% is prepared, plasma spraying is performed in a state where each particle size is adjusted to 10 μm or more and 50 μm or less by granulation, and the cathode is coated with an electron emitting material having a particle size of 10 μm or less. Manufacturing method of display device.