JP5655776B2 - ELECTRON EMITTING SOURCE PASTE, ELECTRON EMITTING SOURCE AND ELECTRON EMITTING DEVICE USING THE SAME - Google Patents

Description

  The present invention relates to a paste for an electron emission source, an electron emission source and an electron emission element using the paste, and a method for producing them.

  Carbon materials such as carbon nanotubes, carbon nanocoils, carbon nanohorns, and carbon nanofibers have excellent physical and chemical durability and a sharp tip shape, and are suitable for electron emission materials. For this reason, research and development of electron emission sources using these in the fields of displays, lighting, and the like have been actively conducted.

  A mechanism for obtaining light emission by an electron emission source using such a carbon material will be briefly described by taking the most general three-electrode structure (cathode electrode, gate electrode, anode electrode) as an example. First, in a vacuum-sealed container, a high electric field is applied to the gate electrode with respect to an electron emission source including a carbon material (for example, carbon nanotube) formed on the cathode electrode. Then, the electric field concentrates on the sharp tip of the carbon nanotube having a high aspect ratio. When this electric field intensity exceeds a certain threshold value, electron emission occurs due to a tunnel phenomenon. The emitted electrons are accelerated by the high electric field applied to the anode electrode, collide with the phosphor layer formed on the anode electrode, and light emission can be obtained from the phosphor layer.

  One method for producing an electron emission source using carbon nanotubes is to paste carbon nanotubes and apply them to a cathode substrate. The method includes a step of forming a carbon nanotube-containing paste on the cathode electrode by screen printing or the like, a step of removing organic substances that cause deterioration of the vacuum in the container by heat treatment from the carbon nanotube-containing paste coating, and It includes a step of performing an activation treatment such as a tape peeling method or a laser irradiation method on the heat-treated electron emission source surface.

  As a carbon nanotube paste material used in this method, a material in which glass powder is added to adhere carbon nanotubes to a cathode substrate is known. By softening or melting the glass powder in the heat treatment step, the carbon nanotube and the cathode substrate can be bonded. In order to suppress the oxidative deterioration of the carbon nanotube, the heat treatment is often performed at 400 to 500 ° C., and generally a low softening point glass is used. Lead-based glass is typical as the low softening point glass, but in consideration of environmental impact, phosphate glass (for example, see Patent Document 1), bismuth-based glass (for example, see Patent Document 2), or the like should be used. Has been proposed. Further, since glass powder is an insulator, Patent Document 1 proposes to add metal and graphite in order to impart conductivity. Patent Document 2 proposes that conductive particles such as a conductive oxide having a diameter of 0.1 to 1 μm are added to keep the electrical contact between the carbon nanotube and the cathode electrode even better.

JP 2006-164965 A JP 2008-243789 A

  However, in the methods described in Patent Documents 1 and 2, when the content of the glass powder is increased in order to further enhance the adhesion between the carbon material for the electron emission source and the cathode substrate, the conductivity of the electron emission source is decreased. In addition, when the content of the conductive substance is increased in order to further improve the conductivity of the electron emission source, there is a problem that the adhesion between the carbon material for the electron emission source and the cathode substrate is lowered.

  The present invention pays attention to the above-mentioned problems, and can maintain both the adhesion between the carbon material for the electron emission source and the cathode electrode substrate and the conductivity of the electron emission source, and can emit electrons at a low voltage. The purpose is to provide.

That is, the present invention is an electron emission source paste comprising a carbon material for an electron emission source, a phosphate glass, and conductive particles having an average particle size of 0.1 to 1.0 μm, wherein the phosphate glass is P Electron emission that contains 30 to 70 mol% of ₂ O ₅ component, and the conductive particles are particles containing a conductive oxide, or particles in which a part or all of the oxide surface is coated with the conductive oxide. A source paste and an electron emission source using the paste.

  According to the present invention, it is possible to provide an electron emission source capable of emitting electrons at a low voltage while maintaining good adhesion between the carbon material for the electron emission source and the cathode electrode substrate and the conductivity of the electron emission source. . Furthermore, according to the present invention, an electron emission source having excellent durability (lifetime) can be provided.

The paste for an electron emission source of the present invention includes a carbon material for an electron emission source, a phosphate glass, and conductive particles having an average particle diameter of 0.1 to 1.0 μm. The phosphate glass is P ₂ O _5. Particles containing 25 to 70 mol% of the component, and the conductive particles include a conductive oxide, or particles in which a part or all of the oxide surface is coated with a conductive oxide (hereinafter referred to as “conductive oxidation”). It is called “physical particles”).

  Carbon nanotubes, carbon nanocoils, carbon nanohorns, carbon nanofibers and the like can be used as the carbon material for the electron emission source. In the following description, the case where carbon nanotubes are used as the carbon material will be described in detail. However, the contents are similarly applied even when the carbon material is replaced with carbon nanocoils, carbon nanohorns, carbon nanofibers, or the like.

  As the carbon nanotube, any one of single-walled, double-walled, and multi-walled carbon nanotubes of three or more layers may be used. A mixture of carbon nanotubes having different number of layers may be used. Further, it is preferable to purify impurities such as amorphous carbon and catalytic metal by heat treatment, acid treatment, or the like. Since carbon nanotubes often exist as aggregates in which a plurality of carbon nanotubes are entangled, carbon nanotube powders may be pulverized in advance with a ball mill or bead mill.

  The carbon nanotube concentration is preferably 0.1 to 10 wt% with respect to the solid content of the paste because the viscosity is suitable for application such as screen printing.

  Further, the electron emission source paste of the present invention is compared with an electron emission source material containing general lead-based glass or bismuth-based glass as a low softening point glass, or an electron emission source material containing metal as conductive particles. And it has excellent durability. The reason is presumed that the carbon nanotubes are not decomposed in the paste. From the reaction Gibbs energy change, carbon of carbon nanotubes is oxidized by oxygen of lead oxide component and bismuth oxide component constituting lead-based glass and bismuth-based glass, but for the electron emission source of the present invention. Some glass contained in the paste is not oxidized. In addition, in an electron emission source material containing a metal, metal particles such as silver, copper, nickel, and iron may have catalytic activity, and carbon of carbon nanotubes may be formed by oxygen of metal oxide formed on the metal surface. May be oxidized. However, the conductive particles in the present invention contain a conductive oxide and do not affect the decomposition of the carbon nanotubes.

Preferable examples of the phosphate glass include P ₂ O ₅ —SnO, P ₂ O ₅ —SnO—ZnO, and P ₂ O ₅ —ZnO. As will be described later, ITO, SnO, ZnO, AZO, GZO and the like are preferably used as the conductive oxide which is at least a part of the components constituting the conductive particles. It is preferable that the glass component and the conductive oxide component are common.

Note that the _P 2 _O 5 -SnO-based glass _herein, refers to the total amount of P 2 _{O 5} component and SnO component is not less than 40 mol% in oxide equivalent mole percentages. Similarly, for the P ₂ O ₅ —SnO—ZnO system and the P ₂ O ₅ —ZnO system, the total amount of each component is 40 mol% or more in terms of oxide expressed in mol%.

The P ₂ O ₅ component is essential as a network-forming oxide as a glass structure. The content of the P ₂ O ₅ component is preferably 25 to 70% in terms of oxide expressed in mol%. Crystallization can be suppressed during remelting and water resistance can be maintained. More preferably, it is 30 to 70%.

  The SnO component can lower the softening point of the glass and increase the fluidity. The content of the SnO component is 0 to 70% in terms of oxide in terms of mole.

  The ZnO component can lower the softening point of the glass and increase the fluidity, and has the effect of stabilizing the glass and improving the chemical durability. The content of the ZnO component is 0 to 55% in terms of oxide in terms of mole.

In addition, Li ₂ O, K ₂ O, Na ₂ O, BaO, CaO, B ₂ O ₃ , In ₂ O ₃ , ZrO ₂ , MgO, TiO ₂ , SiO ₂ , Al ₂ O ₃ , SrO component, etc. may be included. Good.

The point that inclusion of phosphate glass is excellent in electron emission durability will be described in more detail. About the glass component contained in the paste for electron emission source of the present invention,
aM _x O _y + bC = cM + dCO ₂ (1)
When the Gibbs energy change of the reaction is calculated, a component that does not proceed to the right is preferable. Here, M is metal or metalloid, O is oxygen, C is carbon constituting carbon nanotube (graphite carbon is substituted), x, y, a, b, c, and d are the composition formula and stoichiometry of each component. It is a coefficient corresponding to the logical ratio.

The direction of this reaction can be calculated as follows. The production Gibbs energy of M _x O _y is
xM + (y / 2) O ₂ = M _x O _y
As a reaction formula
Δ _f G (M _x O _y )
When this is converted into the Gibbs energy generated per mol of oxygen,
(2x / y) M + O ₂ = (2 / y) M _x O _y
(2 / y) Δ _f G (M _x O _y ) = Δ _f G (M _x O _y per mol of O ₂ )
Given in. Also, the Gibbs energy generated for CO ₂ is
C + O ₂ = CO ₂
As a reaction formula
Δ _f G (CO ₂ )
Given in. When these are compared, Δ _f G (CO ₂ ) −Δ _f G (M _x O _y per mol of O ₂ ) ≧ 0 (2)
In this case, the reaction of formula (1) does not proceed to the right.
_{Δ f G = Δ f H-} TΔ f S
Therefore, if the standard generation enthalpy Δ _f H ⁰ and the standard generation entropy Δ _f S ⁰ are known, it is possible to know the direction in which the reaction proceeds at each temperature T (K).

Hereinafter, P ₄ O ₁₀ (the composition formula of phosphorus oxide is P ₂ O ₅ but the molecular formula is P ₄ O ₁₀ ) and Bi ₂ O ₃ are specifically calculated as examples. "Standard generation enthalpy, standard entropy, standard generation Gibbs of simple substance and inorganic compound" on pages II-291-300 of Chemical Handbook Basic Edition (5th revision, Chapter 10, Thermal Properties, The Chemical Society of Japan, Maruzen, 2004) Using the energy (T = 298.15K) data, each Gibbs energy generated is
Δ _f G (Bi ₂ O ₃ per mol O ₂ ) = − 382.7+ (179.7 / 1000) T
Δ _f G (P ₄ O ₁₀ per mol O ₂ ) = − 539.6+ (192.1 / 1000) T
Δ _f G (CO ₂ ) = − 393.5− (2.9 / 1000) T
It is. Comparing each generated Gibbs energy at 298.15K,
Δ _f G (CO ₂ ) −Δ _f G (Bi ₂ O ₃ per mol of O ₂ ) <0
Δ _f G (CO ₂ ) −Δ _f G (P ₄ O ₁₀ per mol O ₂ )> 0
Thus, it can be seen that Bi ₂ O ₃ decomposes carbon nanotubes, and P ₄ O ₁₀ does not decompose carbon nanotubes. That is, it is preferable to use phosphate glass in the present invention.

Specific examples include SnO, SnO ₂ , In ₂ O ₃ , Li ₂ O ₂ , Li ₂ O, K ₂ O, Na ₂ O, SrO, BaO ₂ , ZnO, B ₂ O ₃ , SiO ₂ , TiO. ₂ , BaO, Al ₂ O ₃ , ZrO ₂ , MgO, CaO, Sb ₄ O ₆ , NiO, Fe _0.947 O, Fe ₂ O ₃ , Fe ₃ O _{4 and the} like. Such a component satisfies the formula (2) at 298.15K and does not decompose the carbon nanotubes, and therefore may be contained in the phosphate glass component.

On the other hand, Ag ₂ O, CuO, Cu ₂ O, PbO, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ , Bi ₂ O _{3 and the} like calculated the Gibbs energy change of the reaction represented by the above formula (1). At this time, at 298.15 K, Δ _f G (CO ₂ ) −Δ _f G (M _x O _y per mol of O ₂ ) <0. Since these can decompose the carbon nanotubes, they may be contained in the phosphate glass component in a small amount, but the content is preferably as small as possible and more preferably substantially not contained. Note that “substantially not included” means that the energy is not detected by an energy dispersive X-ray analyzer (EMAX ENERGY EX-250) combined with a scanning electron microscope (S-4800).

Moreover, it is preferable that the reaction represented by the formula (1) does not occur even in the paste baking step. For that purpose, it is preferable that Formula (2) is satisfied also in the maximum temperature of baking. Such _{examples, SnO, SnO 2, In 2} O 3, Li 2 O 2, Li 2 O, K 2 O, Na 2 O, SrO, BaO 2, ZnO, B 2 O 3, SiO 2, _{TiO 2, BaO, Al 2 O} 3, ZrO 2, MgO, CaO and the like. On the other hand, for example, in the case of NiO, Δ _f G (CO ₂ ) −Δ _f G (NiO per mol of O ₂ ) = 28.8> 0 at 298.15K.
However, at 723.15 K (450 ° C.), Δ _f G (CO ₂ ) −Δ _f G (NiO per mol of O ₂ ) = − 52.8 <0
Therefore, decomposition of carbon nanotubes may occur during firing. Other examples of such components include Sb ₄ O ₆ , Fe _0.947 O, Fe ₂ O ₃ , Fe ₃ O _{4 and the} like.

For the above reasons, the electron emission source paste of the present invention has durability in electron emission as long as the glass satisfying the formula (2) is included even when the phosphate glass is not included. It is understood that it contributes to. That is, at least a part of the component represented by M _x O _y in the glass is
aM _x O _y + bC = cM + dCO ₂ (1)
When calculating the Gibbs energy change of the reaction represented by: Δ _f G (CO ₂ ) −Δ _f G (M _x O _y per mol of O ₂ ) ≧ 0 at 298.15 K (2)
(Here, Δ _f G (CO ₂ ) is the Gibbs energy of formation of CO ₂ , and Δ _f G (M _x O _y per mol of O ₂ ) is the Gibbs energy of formation of M _x O _y per mol of oxygen.)
It is also mentioned as a preferable aspect that the glass component which becomes becomes like the case where phosphoric acid type glass is included. In particular, when the glass is composed only of a component that satisfies the formula (2), since the component that decomposes the carbon nanotube is not included, durability in electron emission can be further improved. In addition, the case where glass consists only of the component which satisfy | fills Formula (2) means the energy dispersive X-ray-analysis apparatus with which the component which does not satisfy Formula (2) was combined with the scanning electron microscope (S-4800) (EMAX ENERGY EX-250) includes a case where it is not detected and can be regarded as substantially not included.

  On the other hand, the coexistence of phosphate glass and conductive oxide particles in the electron emission source paste is another feature of the present invention. Generally, an electron emission source paste containing glass powder as an adhesive component is applied to a cathode electrode substrate, and then the glass powder is softened in a heat treatment process to obtain adhesion between the carbon nanotube and the cathode electrode. Can do. However, since glass powder is an insulator, good electrical contact between the carbon nanotube and the cathode electrode cannot be maintained, and the voltage at which electrons can be emitted increases. On the other hand, when conductive particles are added to the electron emission source paste in order to impart conductivity, the conductive particles impede adhesion by the glass powder, and the adhesion between the carbon nanotubes and the cathode electrode decreases. In particular, when metal, graphite, or the like is used as the conductive particles, it is difficult to maintain good adhesiveness. This is considered because metal, graphite, etc. are poor in wettability with glass. When the adhesiveness is lowered, peeling of the electron emission source increases in an activation process such as a tape peeling method, which is a subsequent process.

  On the other hand, it has been found that when the phosphate glass and the conductive oxide in the conductive oxide particles are brought into contact, the glass can be firmly bonded. This is presumably because the surface of the conductive oxide is dissolved in the glass region in the heat treatment step. Therefore, it is preferable to use phosphate glass and conductive oxide particles in terms of obtaining both durability of the electron emission source and strong adhesion between the electron emission source carbon material and the cathode electrode substrate.

  The phosphate glass is required to be softened in the step of removing the organic substance from the paste film for the electron emission source by heat treatment, and to bond the carbon nanotube and the cathode electrode substrate. Considering that the heat resistance of the carbon nanotube is 500 to 600 ° C. and using an inexpensive soda lime glass (strain point of about 500 ° C.) as the substrate, the softening point of the phosphate glass is preferably 500 ° C. or less, More preferably, it is 400 ° C. or lower. By using the phosphoric acid-based glass having the softening point, it is possible to suppress the burning of the carbon nanotubes in the heat treatment step and to use an inexpensive substrate glass such as soda lime glass. Moreover, in order to remove an organic substance from the paste film for electron emission sources, the softening point of the phosphate glass is preferably 320 ° C. or higher. This is because it is difficult for organic firing residues to adhere to the phosphate glass surface.

  The softening point of the glass in the present invention is the first endotherm in the DSC curve obtained by increasing the temperature from room temperature to 20 ° C./min using a differential scanning calorimeter (DSC) using alumina powder as a standard sample. The temperature at the peak top of the peak.

  The weight ratio of the phosphate glass to the total weight of the carbon nanotubes and the phosphate glass is preferably 0.30 to 0.90. By setting it within this range, it is possible to emit electrons at a lower voltage while maintaining sufficient adhesion between the carbon nanotube and the cathode electrode.

  Phosphoric glass can be used in powder form. From the viewpoint of softening the phosphate glass in the electron emission source to form a dense network and obtaining better adhesion between the carbon nanotube and the cathode electrode, and reducing the surface irregularities of the electron emission source, phosphoric acid is used. The average particle size of the system glass powder is preferably 1.0 μm or less. More preferably, it is 0.8 μm or less. Here, the average particle diameter of glass is the number average particle diameter, and can be measured using a scanning electron microscope (S4800, Hitachi, Ltd.). In the present invention, the number average particle diameter is an average value obtained by dividing the longest line in the line passing through the center of the particle by the measured number. The particle size of each particle is measured by randomly selecting 100 particles that can be measured at 20,000 times. In addition, when the number of particles having a particle size of 0.1 μm or less is 90% or more, measurement is performed by randomly selecting 100 particles that can be measured at 50,000 times. Those with an average particle size of 0.1 μm or more are rounded to the second decimal place, and those with an average particle size of less than 0.1 μm are rounded to the third decimal place.

  The conductive particles used in the present invention are particles containing a conductive oxide, or particles in which a part or all of the oxide surface is coated with a conductive oxide. As the conductive oxide, ITO, SnO, ZnO, AZO, GZO and the like are preferable. Moreover, what coated the electroconductive oxide in part or all of oxide surfaces, such as a titanium oxide and a silicon oxide, is also preferable. In view of easy control of the particle size, a part or all of the oxide surface is more preferably coated with a conductive oxide, and in terms of easy coating, the conductive oxide is more preferably SnO. .

  Furthermore, when the average particle diameter of the conductive particles is 0.1 to 1.0 μm, good conductivity can be obtained, and electrons can be emitted at a low voltage. If it is smaller than 0.1 μm, the number of contact points of the conductive particles increases, and conversely the resistance increases. The reason for this is that amorphous carbon derived from the firing residue of organic components such as binders often accumulates on the contacts, so when the number of contacts increases, the resistance between the conductive particles is added by the number of contacts, It is estimated that this is because the series resistance increases. On the other hand, if it is larger than 1.0 μm, the softened glass cannot form a dense network structure, and the adhesion between the carbon nanotube and the cathode electrode is lowered. Furthermore, the unevenness of the surface of the electron emission source becomes large, and it becomes difficult to obtain uniform electron emission. The average particle diameter of the conductive particles is more preferably 0.1 to 0.6 μm. When the thickness is 0.6 μm or less, the surface unevenness of the electron emission source can be further reduced. In addition, the average particle diameter of electroconductive particle is a number average particle diameter, and is measured and calculated by the method similar to the case of glass.

  The conductive particles preferably have a weight ratio of the glass to the total weight of the glass and the conductive particles of 0.30 to 0.80. By setting it within this range, it is possible to emit electrons at a lower voltage while maintaining sufficient adhesion between the carbon nanotubes and the cathode electrode and having good conductivity.

  Moreover, it is preferable that the paste for electron emission sources of this invention contains a binder and a solvent. Addition of dispersants, photocurable monomers, UV absorbers, polymerization inhibitors, sensitizing aids, plasticizers, thickeners, antioxidants, organic or inorganic suspending agents and leveling agents as necessary Ingredients may be included.

  Binders include cellulose resins such as ethyl cellulose, methyl cellulose, nitrocellulose, acetyl cellulose, cellulose propionate, hydroxypropyl cellulose, butyl cellulose, benzyl cellulose, and modified cellulose, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl Acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2 -Hydroxypropyl acrylate, 2-hydroxy Propyl methacrylate, benzyl acrylate, benzyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, isobornyl acrylate, isobornyl methacrylate, glycidyl methacrylate, styrene, α-methylstyrene, 3-methylstyrene, 4-methylstyrene, acrylamide, meta Acrylic resins such as polymers consisting of at least one of monomers such as acrylamide, acrylonitrile, methacrylonitrile, ethylene-vinyl acetate copolymer resin, polyvinyl butyral, polyvinyl alcohol, propylene glycol, urethane resin, melamine resin , Phenol resin, alkyd resin and the like.

  The thermal decomposition temperature of the binder is preferably 20 ° C. or more lower than the softening point of the glass. It becomes difficult for the baking residue of a binder to adhere to the glass surface. Therefore, the thermal decomposition temperature of the binder is preferably 470 ° C. or lower, more preferably 370 ° C. or lower. Here, the thermal decomposition temperature of the binder was 30 ° C. to 500 ° C. at 10 ° C./min in an air atmosphere (flow rate 20 ml / min) using a thermogravimetric measuring device (TGA-50, manufactured by Shimadzu Corporation). Measure the weight at each temperature when the temperature is raised to a temperature at which the ratio to the weight at room temperature is 1% by weight or less.

  The solvent is preferably a solvent that dissolves an organic component such as a binder resin. For example, polyhydric alcohols such as diol and triol typified by ethylene glycol and glycerin, ethylene glycol monoalkyl ether, ethylene glycol dialkyl ether, ethylene glycol alkyl ether acetate, diethylene glycol monoalkyl ether acetate, diethylene glycol dialkyl ether, propylene glycol mono Examples include compounds obtained by etherification and / or esterification of alcohols such as alkyl ethers, propylene glycol dialkyl ethers, and propylene glycol alkyl ether acetates. More specifically, terpineol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol dipropyl ether, diethylene glycol dibutyl ether, methyl cellosolve acetate , Ethyl cellosolve acetate, propyl cellosolve acetate, butyl cellosolve acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyle DOO, organic solvent mixture containing one or more of such or these butyl carbitol acetate is used.

  The paste for an electron emission source of the present invention can be prepared by preparing various components so as to have a predetermined composition and then uniformly mixing and dispersing the mixture using a kneader such as a three-roller, ball mill, or bead mill. The paste viscosity is appropriately adjusted depending on the addition ratio of glass powder, thickener, organic solvent, plasticizer, suspending agent, etc., but the range is 2 to 200 Pa · s. For example, when the application to the substrate is performed by a spin coating method, a spray method or an ink jet method other than the slit die coater method or the screen printing method, 0.001 to 5 Pa · s is preferable.

  Hereinafter, an electron emission source and an electron emission element manufacturing method using the electron emission source paste of the present invention will be described. Note that other known methods may be used for manufacturing the electron-emitting source and the electron-emitting device, and the method is not limited to the manufacturing method described later.

  First, a method for manufacturing an electron emission source will be described. As will be described below, the electron emission source can be obtained by forming a pattern made of the paste for an electron emission source of the present invention on a substrate and baking it. First, an electron emission source pattern is formed on a substrate using the electron emission source paste of the present invention. Any substrate can be used as long as it fixes the electron emission source, but a glass substrate is preferable because it is inexpensive and easily available. Further, a cathode electrode having conductivity is preferably formed on the substrate. As a method for forming the pattern of the electron emission source on the substrate, a printing method such as a general screen printing method or an ink jet method is preferably used. Further, when an electron emission source paste imparted with photosensitivity is used, a fine electron emission source pattern can be collectively formed by photolithography. Specifically, after the electron emission source paste imparted with the photosensitivity of the present invention is printed on the substrate by a screen printing method or a slit die coater, the coating film of the electron emission source paste is dried by a hot air dryer. Get. The coating film may be irradiated with ultraviolet rays through a photomask from the upper surface (electron emission source paste side), and then developed with an alkali developer or an organic developer to form an electron emission source pattern. Next, the pattern of the electron emission source is baked. The firing is performed in air or an inert gas atmosphere such as nitrogen, and the firing temperature is 400 to 500 ° C.

  An electron-emitting device can be obtained by making the substrate provided with the electron emission source manufactured as described above face the front plate having the anode electrode and the phosphor layer. There are two methods of electron-emitting devices, a diode structure that mainly draws electrons by an electric field applied by an anode electrode, and a triode structure that draws electrons by a gate electrode in addition to the anode electrode. The electron emission source of the invention can be applied.

  The electron emission source produced using the electron emission source paste of the present invention is, for example, by an energy dispersive X-ray analyzer (EMAX ENERGY EX-250) combined with a scanning electron microscope (S-4800), etc. Its composition can be analyzed. As a specific analysis method using the above method, first, by observing an electron emission source using a scanning electron microscope, from the shape of each component, for example, an electron emission material having a fiber-like structure, a particulate shape The conductive oxide and the glass component as the matrix can be generally specified. Further, by using an energy dispersive X-ray analyzer, elemental analysis of each component can be performed and the composition can be specified. However, the analysis of the electron emission source may be any method as long as the composition of the electron emission source can be specified, and is not limited to these methods.

  Hereinafter, the present invention will be specifically described by way of examples. However, the present invention is not limited to these. The raw materials used in the electron emission source paste in each example and comparative example, and the evaluation methods in each example and comparative example are as follows.

<Raw material used for paste for electron emission source>
Carbon nanotube: A multi-walled carbon nanotube (manufactured by Shenzhen Nanotechport Co., Ltd., diameter 10 nm) was used.
Glass powder: Nine kinds of compositions described in Tables 1 and 2 were used. Glasses 2-1 to 2-4 have the same composition but different average particle diameters.
Conductive particles 1: Conductive oxide (Ishihara Sangyo Co., Ltd., ET-500W, coated with SnO ₂ / SbO with spherical titanium oxide as a core, average particle size 0.3 μm) was used.
Conductive particles 2: Conductive oxide (manufactured by Mitsui Kinzoku Co., Ltd., Pastorlan Type IV tin oxide, average particle size 1.1 μm) was used.
Conductive particles 3: Conductive oxides (Ishihara Sangyo Co., Ltd., ET-300W, coated with SnO ₂ / SbO with spherical titanium oxide as the core, average particle size 0.05 μm) were used.
Conductive particles 4: Silver (Mitsui Metals Co., Ltd., EHD, average particle size 0.5 μm) was used.
Non-conductive particles 1: Titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., CR-EL, average particle size 0.3 μm) was used.
Binder: Poly (iso-butyl methacrylate) fine powder, [h] = 0.60 (manufactured by Wako Pure Chemical Industries, Ltd.)
Solvent: Terpineol (manufactured by Wako Pure Chemical Industries, Ltd.).

<Preparation of paste for electron emission source>
The paste for an electron emission source of the present invention was produced as follows. A predetermined amount of carbon nanotubes and glass powder shown in Table 3 (types are changed as shown in Tables 4 to 10 for each Example and Comparative Example), conductive particles, binder, and solvent are weighed in a zirconia container having a volume of 500 ml. , 0.3 mmφ zirconia beads (Traceram (trade name) manufactured by Toray Industries, Inc.) were added thereto, and predispersed at 100 rpm in a planetary ball mill (planet type ball mill P-5 manufactured by Fritsch Japan Co., Ltd.). The mixture from which the zirconia beads were removed was kneaded with three rollers.

<Measurement of average particle diameter of glass and conductive oxide particles>
Using a scanning electron microscope (Hitachi, Ltd. S4800), the average particle sizes of glass and conductive oxide particles were measured from the images. The average particle diameter was defined as an average value obtained by dividing the longest line in the line passing through the center of the particle by the measured number. The particle size of each particle was measured by randomly selecting 100 particles that can be measured at 20,000 times. When the number of particles having a particle size of 0.1 μm or less was 90% or more, measurement was performed by randomly selecting 100 particles that can be measured at 50,000 times. Those having an average particle size of 0.1 μm or more were rounded to the second decimal place, and those having an average particle size of less than 0.1 μm were rounded to the third decimal place.

<Measurement of glass softening point>
About 50 mg of glass powder was put in a platinum cell, and the temperature was increased from room temperature to 20 ° C./minute using a differential scanning calorimeter (DSC-50, manufactured by Shimadzu Corporation) as a standard sample. In the DSC curve, the temperature at the top of the first endothermic peak was taken as the softening point.

<Production of electron emission source>
The electron emission source paste was screen-printed on a soda lime glass substrate on which an ITO thin film was formed, using 25 screens of 1 mm × 1 mm square patterns using a SUS325 mesh screen. After drying at 100 ° C. for 10 minutes, firing was performed at 450 ° C. in the air.

<Adhesion evaluation>
A 25 mm electron emission source printed and baked on a 1 mm x 1 mm square was pasted with a tape with a peel adhesion strength of 0.5 N / 20 mm and peeled off at a speed of 300 mm / min while maintaining an angle of 180 ° C. The adhesion between the emission source and the cathode electrode substrate was evaluated. The number of areas where 50% or more of the 25 electron emission sources were peeled (the cathode substrate was exposed) was used as an index of adhesion. Specifically, it is best if the area where 50% or more of the area is peeled off is 0 (A), 1 is good (B), 2 is acceptable (C), 3 The above was regarded as impossible (D).

<Measurement of electron emission starting electric field strength>
In a vacuum chamber with a vacuum degree of 5 × 10 ⁻⁴ Pa, a substrate on which an electron emission source is formed and a copper plate are opposed to each other with a 200 μm spacer film interposed therebetween, and a voltage applying device (manufactured by Kikusui Electronics Co., Ltd.). A voltage was applied at 10 V / sec by a withstand voltage / insulation resistance tester TOS9201). The electric field strength at which the current density reached 1 mA / cm ² was determined from the obtained current-voltage curve. The field strength is rounded to the second decimal place and is best 2.0A or less (A), 2.1V to 2.4V is good (B), 2.5V or more is not acceptable (D).

<Durability against electron emission>
In a vacuum chamber with a degree of vacuum of 5 × 10 ⁻⁴ Pa, a substrate on which 25 electron emission sources of 1 mm × 1 mm are formed and a copper plate are opposed to each other with a 200 μm spacer film interposed therebetween, and a voltage applying device ( The voltage with which the current density is 1 mA / cm ² is fixed by a withstand voltage / insulation resistance tester TOS9201 manufactured by Kikusui Electronics Industry Co., Ltd., and the time when the current value decays to 50% of the initial value is durable against electron emission. It was used as an index of sex. Rounded down to the first decimal place, best for 45 hours or more (A), good for 40 hours or more and 44 hours or less (B), acceptable for 30 hours or more and 39 hours or less (C), What was 29 hours or less was made impossible (D).

Examples 1-7, Comparative Examples 1-2 (Effect of glass type)
The results are shown in Tables 4-5. In Examples 1 to 7, in all cases, two or more items were good among the adhesiveness, the electron emission starting electric field strength, and the durability against electron emission, and there was no item that was remarkably inferior. The adhesion was particularly excellent. On the other hand, in Comparative Example 1, the electron emission starting electric field strength was good, but the other two items were inferior. In Comparative Example 2, the durability against electron emission was remarkably inferior.

Examples 2, 8 to 10 (effect of glass particle size)
The results are shown in Table 6 (Example 2 is shown again). In any case, adhesion, electron emission starting electric field strength, and durability against electron emission were good.

Examples 2, 11 to 14 (effect of glass weight ratio on total weight of carbon nanotube and glass)
The results are shown in Table 7 (Example 2 is shown again). In any case, two or more items were good among the adhesiveness, the electron emission starting electric field strength, and the durability against electron emission, and there was no item inferior in evaluation.

Examples 2, 13, 15-22 (effect of glass weight ratio on total weight of conductive particles and glass)
The results are shown in Tables 8 to 9 (Examples 2 and 13 are shown again). In any case, two or more items were good among the adhesiveness, the electron emission starting electric field strength, and the durability against electron emission, and there was no item inferior in evaluation.

Comparative Examples 3 to 4 (Effect of particle size of conductive particles)
The results are shown in Table 10. In Comparative Example 3, the adhesiveness was remarkably inferior. In Comparative Example 4, the electron emission starting electric field strength was extremely inferior.

Comparative Examples 5-6 (Effect of conductive particle type)
The results are shown in Table 10. In Comparative Example 5, the adhesion and durability against electron emission were remarkably inferior. In Comparative Example 6, adhesion and electron emission starting electric field strength were remarkably inferior.

Claims (9)

An electron emission source paste comprising an electron emission source carbon material, phosphate glass, and conductive particles having an average particle size of 0.1 to 1.0 μm, wherein the phosphate glass contains P ₂ O ₅ component. An electron emission source paste comprising 30 to 70 mol%, wherein the conductive particles are particles containing a conductive oxide, or particles in which a part or all of the oxide surface is coated with a conductive oxide. _2. The electron emission source paste according to claim 1, wherein the phosphate glass is a P ₂ O ₅ —SnO system, a P ₂ O ₅ —SnO—ZnO system, or a P ₂ O ₅ —ZnO system. The electron emission source paste according to any one of claims 1 and 2, wherein the electron emission source carbon material is at least one selected from the group consisting of carbon nanotubes, carbon nanohorns, carbon nanocoils, and carbon nanofibers. The electron emission source paste according to any one of claims 1 to 3, wherein a weight ratio of the phosphate glass to a total weight of the electron emission source carbon material and the phosphate glass is 0.30 to 0.90. The electron emission source paste according to any one of claims 1 to 4, wherein a weight ratio of the phosphate glass to a total weight of the phosphate glass and the conductive oxide particles is 0.30 to 0.80. The electron emission source manufactured using the paste for electron emission sources in any one of Claims 1-5. An electron-emitting device manufactured using the paste for an electron-emitting source according to claim 1. The manufacturing method of the electron emission source using the paste for electron emission sources in any one of Claims 1-5. An electron-emitting device manufacturing method using the electron-emitting source paste according to claim 1.