KR100856671B1 - Electron emission source forming composition and formation of electron emission source film - Google Patents

Abstract

An object of the present invention is to provide a composition for forming a film and a method for forming an electron emission source, in which carbon nanotubes are not lost during firing and are properly fixed and can form an electron emission source film having excellent luminescence.

According to the structure of this invention, the composition for electron emission source formation contains a carbon nanotube, a glass frit, an organic binder resin, and an organic solvent, The softening point of a glass frit is 500 degrees C or less. The coating film obtained by removing an organic solvent from the composition for electron emission source formation apply | coated to a board | substrate is baked at the temperature of 400 degreeC-450 degreeC, organic binder resin is removed, and the film containing a carbon nanotube and glass is formed.

Carbon nanotubes, glass frits, organic binder resins, organic solvents

Description

The composition for forming an electron emission source and the film formation method for an electron emission source {ELECTRON EMISSION SOURCE FORMING COMPOSITION AND FORMATION OF ELECTRON EMISSION SOURCE FILM}

1 is a scanning electron micrograph of a film formed from the composition of Sample 2. FIG.

2 is a scanning electron micrograph of a film formed from the composition of Sample 14.

3 is a scanning electron micrograph of a film formed from the composition of Sample 19.

4 is a DTA curve of the film formed from the composition of Sample 1. FIG.

[Patent Document 1] Japanese Unexamined Patent Publication No. 2000-123712

[Patent Document 2] Japanese Patent Application Laid-Open No. 11-260249

[Patent Document 3] Japanese Patent Publication No. 2003-331713

The present invention relates to a composition for forming an electron emission source for forming a film suitable for an electron emission source for emitting electrons by the application of an electric field, and a method for forming the film for an electron emission source.

Since carbon nanotubes have a high aspect ratio and can emit electrons with high efficiency by applying an electric field, many reports have recently been used as electron emission sources of self-luminous panel display devices. For example, Patent Literature 1 discloses that a film serving as an electron emission source is produced by applying a spin coater and drying a paste obtained by dispersing carbon nanotubes and conductive particles such as graphite and carbon black in a liquid such as ethanol. It is described. In addition, Patent Document 2 describes that a paste obtained by mixing carbon nanotubes (column graphite) with silver paste is coated, dried, and baked by screen printing to produce a film that becomes an electron emission source. . In addition, Patent Document 3 discloses carbon nanotubes, glass frits, organic binders such as ethyl cellulose resins, acrylic resins, terpineol, etc., for the purpose of improving exposure properties, developability and emission current characteristics. The electron emission source composition using the organic solvent of is proposed.

The film for an electron emission source comprised of carbon nanotubes and electroconductive particles, such as graphite and carbon black, as described in patent document 1 is called a curing (curing treatment) film, and is performed by patent document 3 Although the baking process as described above is unnecessary, it is advantageous in terms of the work process, but the strength of the obtained film is weak, so that peeling of the coating film due to vibration or application of an electric field may cause peeling of carbon nanotubes or conductive particles. have. Therefore, it is necessary to improve the strength of the film.

On the other hand, the film for electron emission source formed in patent document 2 consists of silver and a carbon nanotube, Although the strength of a film is suitable, after forming this film, it forms a film, such as a conductive layer and a dielectric layer, When the panel is heated to a temperature of about 400 to 450 ° C. for encapsulation, the carbon nanotubes in the film are burned and the function as an electron emission source is impaired. Therefore, when actually applied to the manufacture of display devices, it is not possible to achieve satisfactory light emission function.

In addition, the electron emission source composition of Patent Document 3 contains an organic binder and a glass frit, and after drying the thick film formed by using the composition, the organic binder is burned by firing, and electron emission consisting of carbon nanotubes and glass is burned. A raw film is obtained. However, when the composition is actually fired according to this document, even if the heat resistance temperature of the raw material carbon nanotubes in the oxidizing atmosphere exceeds 450 ° C, the carbon nanotubes are lost in the heat treatment at 400 to 450 ° C. When the firing temperature is lowered in order to prevent the carbon nanotubes from disappearing, combustion of the organic binder becomes incomplete and remains in the coating, and in the panel after vacuum encapsulation, the degree of vacuum in the panel is a gas generated by decomposition of the residual organic binder. The surroundings are contaminated by the decomposition gas component. In addition, since the strength of the coating decreases, the carbon nanotubes may be peeled off by application of an electric field.

SUMMARY OF THE INVENTION An object of the present invention is a composition for forming an electron emission source, which has a suitable luminescence as an electron emission source of a display device, and which can form a film having an appropriate strength that does not cause peeling of carbon nanotubes by application of an electric field, and It is providing a method for forming an electron emission source film using the same.

It is also an object of the present invention to provide a film which can ensure good luminescence without losing carbon nanotubes in the film formed as an electron emission source by heating in an oxidizing atmosphere in the film forming and subsequent display device manufacturing processes. There is provided a composition for forming an electron emission source that can be formed and a method for forming an electron emission source film using the same.

In order to achieve the above object, according to one aspect of the present invention, the composition for electron emission source formation is a composition for electron emission source formation containing carbon nanotubes, glass frit, organic binder resin, and an organic solvent, The softening point of a glass frit is made into 500 degrees C or less.

Moreover, according to another aspect of the present invention, the composition for electron emission source formation is a composition for electron emission source formation containing carbon nanotubes, glass frit, organic binder resin, and organic solvent, wherein the glass composition of the glass frit are either not contain V ₂ O ₅ in a substantially, or, and the content is less than 5㏖%, does not contain PbO substantially, or, when the content is to be a base is not more than 3㏖%.

Moreover, according to one aspect of the present invention, in the method for forming an electron emission source coating film, an organic solvent is removed from the composition for forming an electron emission source applied to a substrate to form a coating film, and the coating film is formed at a temperature of 400 to 450 ° C. It is made to form a film containing carbon nanotubes and glass by baking and removing an organic binder resin.

Embodiment of the Invention

The composition for forming an electron emission source of the present invention is a film-forming composition in which carbon nanotubes and glass frits are dispersed in an organic binder resin and an organic solvent (the mixture of which is called a vehicle), and the composition is applied to a substrate. Then, the film for electron emission source is formed by removing the vehicle by drying and firing the coating film. Drying of a coating film is possible by heating at about 150 degreeC. Organic binder resin is a component which gives a composition the moderate viscosity, and improves the dispersibility of carbon nanotubes, The uniformity of the carbon nanotubes in a film becomes high by the improvement of dispersibility, and the light emission characteristic of a film is improved. Going up In addition, the fluidity of the composition at the time of pattern formation can be optimized, and fine and smooth patterns can be formed by screen printing. However, if the coating film containing the resin component is used as an electron emission source as it is, in the panel after vacuum encapsulation, the vacuum degree in the panel due to the decomposition products of the organic binder and the contamination of the surroundings are generated, so that the resin component cannot be burned out. It is necessary and the temperature required for this is about 350-450 degreeC. On the other hand, in the display device manufacturing process after forming the electron emission source film, the temperature of the encapsulation step requiring heating is about 450 ° C., so if the temperature at the time of firing is about 450 ° C., which can completely burn the resin, Since the problem after film forming concerning an organic binder is eliminated, it is preferable.

During firing, the glass frit is softened, and the film in which the carbon nanotubes are fixed is formed by fixing the carbon nanotubes by the glass particles, the glass particles and the substrate being fixed, and the glass particles. However, if the glass frit melts completely during firing, the carbon nanotubes are buried in the molten glass and light emission becomes difficult. In addition, since the film after baking performs surface treatment which moderately orients carbon nanotubes in order to make light-emitting carbon nanotubes suitably, it is not preferable that carbon nanotubes adhere firmly by glass. Therefore, although the glass frit at the time of baking softens moderately, it is important not to melt even to the low-viscosity liquid state which can flow. By such baking, the glass particles are bonded to each other in contact with each other, adhere to the glass substrate, form a film by the porous glass layer, and exert strength as the entire film. In addition, the glass particles deform in correspondence with the external shape of the carbon nanotubes, thereby partially retaining the carbon nanotubes or locally fixing them, whereby the carbon nanotubes dispersed in the glass coating are fixed. In the film, minute gaps remain between the glass particles, and such a porous structure is advantageous for standing alignment of the carbon nanotubes.

In order to realize the softening of such glass frit, the preservation of the actual coating film using inorganic oxide glass of various compositions was made on the premise of baking at about 450 degreeC, and the softening point is 500 degrees C or less. When using the composition for electron emission source formation using the glass frit of inorganic oxide glass, it turned out that the film in which the carbon nanotube was fixed by appropriate intensity | strength was formed. In particular, when a glass frit of inorganic oxide glass having a softening point of 400 to 500 ° C. or an inorganic oxide glass having a composition containing SnO is used, adhesion of the film is good, and loss of carbon nanotubes during firing and after film formation is appropriately suppressed. It is also possible to obtain a coating film.

Hereinafter, the composition for electron emission source formation of this invention is demonstrated.

The composition for forming an electron emission source contains carbon nanotubes, an organic binder resin, a glass frit, and an organic solvent, and the organic binder resin and the organic solvent have a role of a vehicle. By providing this composition to the above-mentioned film forming suitably, the film for electron emission sources in which carbon nanotubes were fixed to the board | substrate with glass is obtained. When the powder of carbon materials, such as silver and nickel, and carbon materials, such as graphite and carbon black, is added to this composition for electron emission source formation, electroconductivity of the formed film becomes high by electroconductive particle, Since the conductivity of a film can be adjusted by changing the usage-amount of electroconductive particle suitably, the conduction of a cathode wiring and a carbon nanotube of a film can also be improved using this. Each component which comprises the composition for electron emission source formation is explained in full detail below.

Carbon nanotubes are produced by the arc discharge method, laser evaporation method, CVD method, or the like, and carbon nanotubes having structures such as single layer, double layer, and multilayer are obtained. In the present invention, carbon nanotubes having any structure of a single layer, two layers, and multiple layers can be used. In consideration of the firing step in producing the coating film for the electron emission source, carbon nanotubes which do not burn at the firing temperature when the carbon nanotubes are heated alone in an oxidizing atmosphere are suitably used. Although carbon nanotubes contain carbon materials, such as graphite, fullerene, and amorphous carbon, as impurities, carbon nanotubes containing such carbon materials can also be used as carbon nanotubes for electron emission sources.

If the carbon nanotubes to be used have a good crystallinity and a small diameter, the electron emission characteristics of the formed electron emission source film are good, and electrons can be emitted at a low voltage. It is possible to manufacture a self-luminous panel type display device. In this regard, in order to exhibit good electron emission characteristics, it is preferable to use carbon nanotubes having a diameter of 20 nm or less, and preferably 10 nm or less.

Organic binder resin is a component which improves the dispersibility of the carbon nanotube in a composition, For example, Cellulose-type resins, such as ethyl cellulose, nitrocellulose, cellulose acetate, hydroxymethyl cellulose; Acrylic resins such as acrylic acid esters, methacrylic acid esters and cyanoacrylic acid esters; Acrylic copolymers with acrylic monomers and other monomers; Vinyl acetate type resin; Polyvinyl alcohol-based resins; Polyvinyl acetal resins; Resin, such as polyester resin, can be used.

As an organic solvent, it can select suitably from the various solvents normally used for the composition formed into a film by screen printing, etc., For example, butyl cellosolve acetate, butyl carbitol, butyl carbitol acetate, (alpha)-terpineol Although low vapor pressure solvents, such as (gamma)-butyrolactone, can be mentioned, It is not limited to these. For example, in order to speed up a drying rate, you may use low boiling point solvents, such as ethyl acetate, methyl ethyl ketone, toluene, benzyl alcohol.

Glass frit is powder glass obtained by melting and homogenizing the combination of glass raw materials, vitrifying by quenching, and crushing to a suitable particle size.

In general, glass is broadly divided into inorganic glass, metal glass (metal alloy) and organic glass (organic high molecular weight), and inorganic glass is also classified into oxide glass, chalcogenide glass and halide glass. The glass frit of the present invention belongs to oxide glass, and a glass frit having a softening point of 500 ° C. or less is used. The change in the state of glass does not occur remarkably at the softening point, but as can be seen from the broad peak in the DTA curve (for example, see FIG. 4), ± 50 ° C. of the softening point or the like. It occurs slowly over a wider temperature range. Specifically, the glass having a softening point of 500 ° C. generates a viscosity decrease even at about 450 ° C., so that some deformation and adhesion can be performed. However, the glass is not completely liquefied at 500 ° C. Therefore, in baking at about 450 degreeC, the carbon nanotube can be fixed by the glass frit whose softening point is 500 degrees C or less. However, when the glass is completely melted and liquefied, the molten glass covers the carbon nanotubes, making it difficult to release electrons, and the carbon nanotubes are firmly fixed in the film after firing. Considering this point, it is also not preferable that the softening point is too low, and based on firing at about 450 ° C, the softening point of the glass frit is preferably about 400 to 500 ° C. However, this does not correspond to the case where the glass composition contains SnO, and even if the softening point is less than 400 ° C., specifically, a softening point of about 300 to 500 ° C. can be suitably used. The reason for this is that when the glass frit contains SnO, when heated in a state where carbon coexists in an oxidizing atmosphere, SnO suppresses the oxidation of carbon and itself is oxidized to SnO ₂ , and the composition of the glass particle surface This change is considered to be caused (the change in 300-500 degreeC of the DTA curve of FIG. 4 is considered to show this). When SnO changes to SnO ₂ , the softening point of the glass is considerably higher, so that the glass frit increases the softening point of the particle surface, and does not completely liquefy even if the inside melts, but only adheres to the neighbors. Thus, a glass frit with a composition comprising SnO bonds or is in close contact with its neighbors, even if the softening point is less than 400 ° C., without leaving the particle prototype of the frit completely lost. As a result, similarly to the case of the glass frit whose softening point is about 400-500 degreeC, the fixation of the grade which can orientate the carbon nanotube after film forming, and the suitable fixation to a glass substrate are formed. Glass frit having a composition containing SnO is particularly preferable because it inhibits oxidation of carbon nanotubes and raises heat resistance (combustion temperature) in the coating.

The composition of the glass frit includes various things depending on the glass raw material and the combination.

In the present invention, as the glass raw material, B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ , V ₂ O ₅ , Sb ₂ O ₅ , ZrO ₂ , ZnO, SnO, BaO, Bi ₂ O ₃ , TeO ₂ , GeO ₂ , MgO, CaO, SrO, TiO ₂ , MnO, Sb ₂ O ₃ , CaO, NiO, Y ₂ O ₃ , MoO, Rh ₂ O ₃ , PdO, Ag ₂ O, In ₂ O ₃ , can include inorganic oxides such as WO _3, and is vitrified by melting the raw material is appropriately selected from these oxides. As needed, you may add refractory fillers, such as cordierite, willemite, and mullite, and can adjust the expansion coefficient of glass by addition of a refractory filler.

A general low melting point glass is lead glass containing PbO (lead oxide) as a main component. However, PbO acts as an oxidizing agent on a carbon material, and therefore, in firing in an oxidizing atmosphere, combustion of carbon nanotubes in the coating film is accelerated and lost. Therefore, in this invention, it is preferable to use the glass frit which does not use PbO as a raw material instead of the conventional lead glass (However, it does not necessarily require to exclude PbO completely, and this point is mentioned later. do). In addition, when lead is concerned about the harmfulness of lead from the viewpoint of a work process or the environment, it is strongly required to remove lead.

Regarding the softening point of glass, of the glass raw material oxides, Bi ₂ O ₃ , TeO ₂ and SnO are components that can lower the softening point of glass by addition, and by adjusting the amount of these components blended into the glass raw material as necessary , The softening point of the glass frit obtained can be adjusted. In short, when the component which lowers such a softening point is used, a low melting glass can be comprised suitably without using PbO. When the composition for electron emission source formation prepared using the glass frit which softening point obtained in this way is 500 degrees C or less is used, the film with favorable film strength and adhesiveness is obtained by heat processing of the coating film in about 400 degreeC-450 degreeC.

The above-mentioned glass raw material oxides include oxides (net nose forming oxides) having a glass forming ability of forming a three-dimensional mesh, which is a skeleton of glass (amorphous), in a glass composition; An oxide which cannot form glass by itself and enters in the mesh of the mesh forming oxide and constitutes a part of the glass (net-modified oxide); And glass alone cannot be formed, and may be classified into an oxide (intermediate oxide) that participates in mesh formation by substituting with an oxide forming a three-dimensional network. The intermediate oxide may also serve as a mesh modified oxide, and the mesh shaped oxide affects the physical properties of the glass. The mesh formation oxide includes B ₂ O ₃ , SiO ₂ , P ₂ O ₅ , Al ₂ O ₃ (oxygen coordination number of Al = 4), V ₂ O ₅ , Sb ₂ O ₅ , ZrO ₂ (oxygen coordination number of Zr). = 6) and the like. Examples of the mesh oxide include SnO, BaO, ZnO, PbO, TeO ₂ , Bi ₂ O _3, and the like. Examples of the intermediate oxide include ZnO, PbO, Al ₂ O ₃ (oxygen coordination number of Al = 6), TeO ₂ , Bi ₂ O ₃ , ZrO ₂ (oxygen coordination number of Zr = 8) and the like.

In the present invention, the oxide constituting the glass composition of the glass frit includes at least one kind of mesh forming oxide and at least one kind of intermediate oxide or mesh modifying oxide, and particularly, the mesh forming oxide is B ₂ O. _It is selected from the group consisting of ₃ , SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ , and the intermediate oxide or mesh-form oxide is appropriately selected from the group consisting of ZnO, SnO, BaO, Bi ₂ O ₃ , and TeO ₂ . In such a glass composition, the mesh forming oxide forms a glass skeleton which does not promote combustion of carbon nanotubes, and a softening point of 500 ° C. or lower is realized by the presence of the intermediate oxide or mesh modification oxide. In addition, the stability of the glass is improved. As a result, in the film obtained by baking (heat-processing) a dry coating film at the temperature of about 450 degreeC in an oxidizing atmosphere, a carbon nanotube is fixed suitably and peeling of a carbon nanotube by vibration or application of an electric field does not arise, In addition, since degradation of heat resistance due to oxidation of the carbon nanotubes is suppressed, combustion of the carbon nanotubes is prevented. Thus, the glass composition of the present invention and a base wherein the glass composition in a range that does not impair the validity of the above, GeO _2, MgO, CaO, SrO, TiO _2, MnO, Sb ₂ O _3, CaO, NiO, Y _It can be applied to include ₂ O ₃ , ZrO ₂ , MoO, Rh ₂ O ₃ , PdO, Ag ₂ O, In ₂ O ₃ , WO ₃ and the like, and also refractory fillers such as cordierite, willemite and mullite It is possible to adjust the expansion coefficient of the glass by adding.

In an embodiment of the preferred glass composition of the glass frit of the present invention, SnO-P ₂ O ₅ based _{glass, Bi 2 O 3 -B 2 O} 3 based glass, TeO ₂ -B ₂ O ₃ -BaO based glasses, SnO -B ₂ O ₃ -based glass and SnO-B ₂ O ₃ -P ₂ O ₅ -based glass. These glasses are low melting glass which does not contain oxidation promoting components, such as PbO, and are suitable as a glass frit applied to the paste-like composition for forming a carbon nanotube film.

P ₂ O ₅ based glass-SnO, as a mesh forming oxide comprises a SnO a P ₂ O _5, as a component for adjusting the softening point of below 500 ℃, is configured by them as a main component. This glass suppresses the combustion of carbon nanotubes. In Examples described later, in the case of the composition for electron emission source formation using SnO ₂ -P ₂ O ₅ based glass having a softening point of 308 ° C or SnO-P ₂ O ₅ based glass having a softening point of 350 ° C, The combustion temperature of carbon nanotube is the highest around 620 degreeC, and combustion of carbon nanotube is not seen in about 450 degreeC which is also the sealing operation temperature of a panel. Therefore, when the temperature of 500 degreeC or more is required for baking of the conductive layer and dielectric layer formed in a panel, it is also possible to respond to changing the order of the film forming process of a conductive layer and a dielectric layer, and the freedom of design of a manufacturing process is also supported. Is large, and is advantageous not only for product performance but also for simplification of the process.

Bi ₂ O ₃ -B ₂ O ₃ based glass, as a mesh forming oxide comprises a Bi ₂ O ₃ to B ₂ O _3, as a component for lowering the softening point of below 500 ℃, is configured by them as a main component. This glass suppresses the combustion of carbon nanotubes. In the embodiment to be described later for example, a softening point of 430 ℃ of Bi ₂ O ₃ -B ₂ O ₃ system, if the composition for an electron emission source formed using glass, the combustion temperature of the carbon nanotube in the coating film 504 ℃, a softening point of 462 ℃ In the case of the composition using the phosphorus Bi ₂ O ₃ -B ₂ O ₃ -based glass, the combustion of the carbon nanotubes was not observed at about 450 ° C., which is also the encapsulation working temperature of the panel. Good.

The TeO ₂ -B ₂ O ₃ -BaO-based glass contains B ₂ O ₃ as a mesh forming oxide, TeO ₂ as a component for lowering the softening point to 500 ° C. or lower, and BaO as a component having a stabilizing effect of the glass. It consists of these as a main component. This glass suppresses the combustion of carbon nanotubes. In Examples described later, in the case of the composition for electron emission source formation using TeO ₂ -B ₂ O ₃ -BaO-based glass having a softening point of 472 ° C, the combustion temperature of the carbon nanotubes in the coating was 512 ° C, and the panel was encapsulated. The combustion of carbon nanotubes is not observed at about 450 ° C, which is also a working temperature, and the electron emission characteristics after firing are good.

SnO-B ₂ O ₃ based glass, a B ₂ O ₃ as a mesh forming oxide, including SnO, and as a component for adjusting the softening point of below 500 ℃, is configured by them as a main component. This glass component suppresses combustion of carbon nanotubes. In the embodiment to be described later for example, also a softening point of 393 ℃ the SnO-B ₂ O ₃ system, if the composition for an electron emission source formed using a glass, and the combustion temperature of the carbon nanotube in the coating film 506 ℃, sealing the working temperature of the panel At about 450 ° C., combustion of the carbon nanotubes was not observed, and the electron emission characteristics after firing were good.

The SnO-B ₂ O ₃ -P ₂ O ₅ -based glass includes B ₂ O ₃ and P ₂ O ₅ as mesh forming oxides, and SnO is included as a component for lowering the softening point, and these components are composed mainly of them. This glass suppresses the combustion of carbon nanotubes. In Examples described later, in the case of the composition for electron emission source formation using SnO-B ₂ O ₃ -P ₂ O ₅ -based glass having a softening point of 391 ° C, the combustion temperatures of the carbon nanotubes are 506 ° C and 511 ° C, The combustion of carbon nanotubes was not observed at about 450 ° C., which is also the sealing operation temperature of the panel, and the electron emission characteristics after firing were also good.

The maximum particle diameter is 10 micrometers or less, Preferably it is 2-5 micrometers, More preferably, about 3 micrometers is used for the glass frit mix | blended with the composition for electron emission source formation of this invention. In order for electrons to be uniformly emitted from the electron emission source formed, the carbon nanotubes in the film need to be uniformly distributed. When the particles of the glass frit are coarse, only a small amount of carbon nanotubes are present on the glass particles, and a large amount of carbon nanotubes is present between the glass particles, resulting in uneven electron emission of the resulting film. In addition, since the flatness of the surface of the coating decreases and the electric field is not uniformly concentrated on the carbon nanotubes, the light emission also becomes nonuniform. In addition, when the coarse glass particles soften in the heat treatment (calcination at about 450 ° C.) in an oxidizing atmosphere, the entire carbon nanotubes are covered and it is easy to generate an electron. For this reason, the particle size of the glass frit is 10 μm or less.

On the other hand, if the content of the case that contains the V ₂ O ₅ and / or PbO in the oxides forming the glass composition of the glass frit, the content of V ₂ O ₅ is less than 5㏖%, PbO is preferably not more than 3㏖%. This is based on the following reasons.

Pb is an element having a low melting point of carbon and cognate (Group IV). When PbO (lead oxide) is heated to high temperature in the presence of carbon, the reaction represented by the following formula 1 proceeds and PbO is metallized (reduced) and PbO Oxygen dissociated from reacts with carbon easily. V ₂ O _{5 is} also the same in that it has a property of oxidizing carbon by heating.

PbO + C → Pb + CO (Equation 1)

Therefore, in the case of using a composition containing a glass frit containing such an oxide and a relatively defective crystal structure such as carbon nanotubes, and a carbon material having a large specific surface area dispersed with an organic binder resin, heating the coated film after drying The combustion starts at a temperature lower than the intrinsic heat resistance temperature of the carbon nanotubes. In short, in order not to reduce the heat resistance of the carbon nanotubes, it is necessary to reduce the components for oxidizing the carbon as described above with full force. However, the mixing of PbO and V ₂ O ₅ to the glass raw material is effective for improving the wettability of the frit to the glass substrate, the adhesion between the film for electron emission source and the substrate, and also for the adjustment of the melting point of the glass frit. have. In consideration of this point, as a result of examining a compounding amount in which the heat resistance temperature of the carbon nanotubes does not fall below the firing temperature (about 450 ° C), the content of PbO is 3 mol% or less of the glass raw material, and the content of V ₂ O ₅ is It turned out that it is necessary to limit it to 5 mol% or less. Therefore, when the composition for electron emission sources in which the composition of the glass frit is adjusted in this range is used, the loss due to combustion of the carbon nanotubes is suppressed even in the firing at around 450 ° C., whereby a film having good electron emission characteristics can be produced.

In order to form a coating film satisfactorily by screen printing etc., the compounding ratio of each component in the composition for electron emission source formation is carbon nanotube: 2-10 mass%, organic binder resin: 5-12 mass%, glass frit: 2- 25 mass% and organic solvent: About 60-85 mass% is preferable. When mix | blending electroconductive particle, it is preferable that the ratio in a composition is about 5-80 mass%. According to such a compounding ratio, the paste-form composition for electron emission source formation is prepared by uniformly mixing and dispersing the above components. It is also possible to mix and use the several types of glass frit from which a glass composition differs.

The film for electron emission sources is obtained by the following manufacturing methods, for example. First, the composition for electron emission source formation is patterned by screen printing etc. on the board | substrate which forms a film, such as the glass substrate in which the cathode wiring for power supply was formed in the surface, and the coating film of a desired shape is formed. As for the thickness of a coating film, about 0.5-10 micrometers is preferable. By heating this coating film about 150 degreeC, the organic solvent is removed and a dry coating film is obtained. You may change suitably the drying temperature of a coating film according to the vaporization temperature of the organic solvent to be used. By baking the obtained dry film at a temperature of about 400 to 450 ° C. in an oxidizing atmosphere such as air, the resin component is decomposed and removed, and an electron emission source film in which carbon nanotubes are fixed is formed by a film formed by a softened glass frit. do. In the case of using a glass frit having a composition substantially free of PbO and V ₂ O ₅ , even if the firing temperature rises to about 480 ° C., the loss of carbon nanotubes is suppressed, and in the case of a glass frit having a composition containing SnO It becomes possible to raise to about 500 degreeC or more. The film for electron emission source after baking is surface-raised by peeling after adhering an adhesive tape etc., for example to orientate carbon nanotubes suitably. By employing the glass frit having the composition described above, oxidation and combustion of the carbon nanotubes at the firing temperature are prevented, and the obtained film exhibits good electron emission characteristics by the carbon nanotubes uniformly distributed. Therefore, the display device using this film as the electron emission source can be driven with low power consumption.

<Example>

Hereinafter, although an Example is given and the effectiveness of this invention is made clear, this invention is not limited to the following Example.

The manufacturing method of a glass frit (glass composition), the preparation method of the composition for electron emission source formation using a glass frit, and the evaluation method of each composition are demonstrated.

<Making of glass frit>

According to the ratio shown to Tables 1-4, glass raw material oxide was combined and mixed, it put in the platinum crucible, and it heated and melted at 800-1400 degreeC in air atmosphere for 1 hour. However, in the case of manufacturing a glass containing SnO is, SnO were melted in a non-oxidizing atmosphere such as nitrogen to avoid oxidation of SnO _2. Thereafter, the melt was quenched to 60 ° C. or lower and vitrified, and a glass frit was produced by grinding using a planetary ball mill or the like.

<Measurement of particle size>

The particle diameter of the glass frit mentioned above was measured using the laser diffraction type particle size distribution analyzer (SALD-2100, the Shimadzu Corporation).

<Preparation of the composition for electron emission source formation>

To 27 parts by mass of the glass frit, 3 parts by mass of carbon nanotubes, and 9 parts by mass of ethyl cellulose resin, 61 parts by mass of α-terpineol was added as an organic solvent, and mixed and kneaded with a three roll-mill or the like. , The paste-form composition for electron emission source formation (samples 1-19) was prepared. On the other hand, the carbon nanotubes used here are produced by CVD and have a diameter of 10 nm (samples 1 to 11, 14 to 19), 20 nm (sample 12), or 30 nm, which have heat resistance of 450 ° C. or higher in an oxidizing atmosphere. It is a multilayer carbon nanotube which is (sample 13).

<Production of film>

Using the composition for electron emission source formation (Samples 1 to 19) described above, a square pattern having a side thickness of 3 mm was printed on the cathode wiring formed on the glass substrate by a screen printing method with a film thickness of 5 μm at 150 ° C. After drying for 15 minutes by heating, the film was baked (heat treated) at 450 ° C. for 30 minutes in an air atmosphere to prepare a film for an electron emission source.

<Evaluation of heat resistance>

The heat resistance of carbon nanotubes was evaluated by observing the film produced above with the scanning electron microscope. The evaluation is shown in Tables 1 to 4, in which the disappearance of carbon nanotubes due to firing was not observed, the case in which partial disappearance was observed in Δ, and the complete disappearance were ×. On the other hand, as a reference for evaluation, Figure 1 is a photograph when no disappearance of carbon nanotubes, Figure 2 is a photograph when partial disappearance is shown, Figure 3 is a photograph when completely disappeared.

<Measurement of combustion temperature of carbon nanotubes>

When using the differential thermal balance (TAS-100, Rigaku Co., Ltd.), the dry coating film before firing in the production of the coating film described above was heated from room temperature to 800 ° C. at a temperature rising rate of 10 ° C. in 1 minute in an air atmosphere. The DTA curve was measured and the combustion temperature of the carbon nanotubes was determined from the exothermic peak when the carbon nanotubes were burned according to TG-DTA (thermogravimetric-differential heating) analysis. On the other hand, the sample plate is used in the platinum, uses the Al ₂ O ₃ as a control sample, sampling conditions in the measurement was 0.8 seconds. 4 is a DTA curve measured using 9.54 mg of the coating of Sample 1. FIG.

<Evaluation of adhesion>

The peeling test which peels after sticking the adhesive tape (trade name: Scotch Mending Tape, the product made by 3M) on the surface of the film on the glass substrate produced above was performed, and the adhesive force of the film was evaluated according to the state of the film after a peeling test. Evaluation was performed when the film remained after the adhesive tape peeled, and the case where the negative electrode wiring was not exposed was ○, and the film remained, but the case where the negative electrode wiring was partially exposed was △ and the case where the coating was not left was set to Tables 1 to 4 It describes in.

<Evaluation of Luminance Uniformity>

After evaluating the adhesiveness described above, in a vacuum state of 10 ⁻⁶ Torr, an anode electrode was provided at a distance of 300 μm from the surface of the glass substrate on which the film was produced, and electrons were emitted, and the light emission state of the film was observed to emit light. Uniformity was evaluated. The evaluation is described in Tables 1 to 4, with the case where the entire surface of the coating uniformly emits light, the case where light emission was partially observed, and the case where no light emission was observed at all.

Samples 1 to 5 of Table 1 use multilayer carbon nanotubes having a diameter of 10 nm produced by CVD method, glass frits having a softening point of 500 ° C. or lower, ethyl cellulose as an organic binder resin, and α-terpineol as an organic solvent. It is the composition for electron emission source formation produced by the said process. These compositions can easily form the coating film which becomes a film for electron emission sources by screen printing on a cathode wiring. And by selecting the composition of the glass frit which comprises the film for electron emission sources from the glass composition of 500 degrees C or less of softening point, it turns out that baking of the carbon nanotube in a coating film is suppressed when baking a coating film at 450 degreeC in air | atmosphere. . Further, by firing at 450 ° C. in the air, a film having sufficient adhesion to fix the carbon nanotubes is obtained, and these films exhibit uniform light emission suitable for the electron emission source of the display device.

The glass frit used in Samples 1 to ₅ contains at least one of B ₂ O ₃ , SiO ₂ , P ₂ O ₅ , Al ₂ O ₃ as a mesh forming oxide, and ZnO, SnO as a mesh modification oxide or intermediate oxide. , BaO, Bi ₂ O ₃ , TeO ₂ and one or more are included, and the softening point is 500 ° C. or less. In these compositions for electron emission source formation, combustion of carbon nanotubes in the coating is not promoted. On the other hand, in the composition for electron emission source formation of Sample 8 using the SiO ₂ -B ₂ O ₃ -ZnO-based glass frit having a softening point of 518 ° C., the glass did not soften at firing at 450 ° C. in the air. The nanotubes are not firmly fixed, and the adhesion of the film is weak. Therefore, the carbon nanotubes are likely to peel off due to vibration or application of an electric field. In addition, in the evaluation of luminescence uniformity, only sparse luminescence is seen.

Regarding the glass composition, the glass frits of Samples 1 and 2 are SnO-P ₂ O ₅ -based glasses. Glass composition according to the sample 1 is _{SnO: 71.2㏖%, P 2 O} 5: a 28.8㏖%, the softening point of the glass is 308 ℃, the maximum particle size of the frit is 6㎛. The glass composition in Sample 2 was SnO: 46.5 mol%, P ₂ O ₅ : 26.5 mol%, SiO ₂ : 21.0 mol%, Al ₂ O ₃ : 6.0 mol%, the softening point of the glass was 350 ° C., The maximum particle diameter is 5 micrometers. In any case, the combustion temperature of the carbon nanotubes in the formed film was about 620 ° C (sample 1: Figure 4), which is the highest among all the samples, and no loss of carbon nanotubes was observed even in the firing at 450 ° C in the atmosphere. (Sample 2: see FIG. 1). Moreover, since the softening point of glass frit is low, the adhesive force of the film formed by baking is also obtained suitably. Even in evaluation of luminescence uniformity, uniform luminescence is obtained. In these glass frits, P ₂ O ₅ is a mesh forming oxide which is an essential component of glass, and when this is insufficient, the glass becomes unstable. SnO is a component that lowers the softening point of glass, and is effective for stabilizing the glass. The SnO surface is formed by the oxidation suppression and self-oxidation of carbon nanotubes during firing to moderately soften the glass. SiO ₂ and Al ₂ O ₃ are effective components for stabilizing the glass, but if excessive, the softening point of the glass is increased.

The glass frits of Samples 3 and 4 are Bi ₂ O ₃ -B ₂ O ₃ based glasses. The glass composition of the sample 3 is _{Bi 2 O 3: 48.3㏖%,} B 2 O 3: 47.1㏖%, SiO 2: and 4.6㏖%, the softening point of the glass is 430 ℃, the maximum particle size of the frit is 3㎛ . The glass composition of the sample 4 is _{Bi 2 O 3: 33.4㏖%,} B 2 O 3: 29.5㏖%, ZnO: 25.2㏖%, Al 2 O 3: 6.4㏖%, BaO: 5.5㏖% , and the glass The softening point is 462 ° C., and the maximum particle size of the frit is 6 μm. In any case, the combustion temperatures of the carbon nanotubes in the formed film were high at 504 ° C (sample 3) and 521 ° C (sample 4), and no loss of carbon nanotubes was observed even at firing at 450 ° C in the atmosphere. Moreover, the adhesive force of the film formed by baking is also obtained suitably. Even in evaluation of luminescence uniformity, uniform luminescence is obtained. In these glass frits, B ₂ O ₃ is a mesh forming oxide which is an essential component of glass, and when this is insufficient, the glass becomes unstable. Bi ₂ O ₃ is a component that lowers the softening point of the glass, and if insufficient, the softening point of the glass exceeds 500 ° C. SiO ₂ , ZnO, Al ₂ O ₃ , and BaO are effective components for stabilizing the glass, but excessively increases the softening point of the glass.

The glass frit of Sample 5 is TeO ₂ -B ₂ O ₃ -BaO-based glass, and the glass composition is TeO ₂ : 40.2 mol%, SiO ₂ : 24.5 mol%, B ₂ O ₃ : 15.2 mol%, BaO: 11.2 mol% , ZnO: 8.9 mol%, the softening point of glass is 472 degreeC, and the largest particle diameter of a frit is 4 micrometers. The combustion temperature of the carbon nanotubes in the formed film was as high as 512 ° C, and no loss of the carbon nanotubes was observed even when firing at 450 ° C in the air. Since the softening point of glass is 472 degreeC, glass frit does not fully soften at the baking of 450 degreeC. For this reason, although peeling of a film surface layer is seen in the peeling test of a film, a carbon nanotube is fixed well without exposing a cathode wiring. Evaluation of the adhesion of the film in Table 1 "(triangle | delta)-(circle)" means such a state. In evaluation of luminescence uniformity, uniform luminescence is obtained. In this glass frit, B ₂ O ₃ is a mesh forming oxide which is an essential component of glass, and when this is insufficient, the glass becomes unstable. TeO ₂ is a component that lowers the softening point of glass, and if insufficient, the softening point of glass exceeds 500 ° C. BaO, SiO ₂ , and ZnO are effective components for stabilizing the glass, but when excessive, the softening point of the glass is increased.

The glass frit of Sample 6 is SnO-B ₂ O ₃ -based glass, the glass composition is SnO: 50.0 mol%, B ₂ O ₃ : 50.0 mol%, the softening point of the glass is 393 ° C., and the maximum particle size of the frit is 4 μm. to be. The combustion temperature of the carbon nanotubes in the formed film was 506 ° C, and no loss of carbon nanotubes was observed in the firing at 450 ° C in the atmosphere. Moreover, the adhesive force of the film formed by baking is also obtained suitably. Even in evaluation of luminescence uniformity, uniform luminescence is obtained. In this glass frit, B ₂ O ₃ is a mesh forming oxide which is an essential component of glass, and when this is insufficient, the glass becomes unstable. SnO is a component that lowers the softening point of glass, and is an effective component for stabilizing the glass. The SnO is oxidized during firing to film the frit surface to moderate the softening of the glass.

The glass frit of Sample 7 was SnO-B ₂ O ₃ -P ₂ O ₅ -based glass, and the glass composition was SnO: 66.6 mol%, B ₂ O ₃ : 16.7 mol%, P ₂ O ₅ : 16.7 mol%, and the glass The softening point of was 391 ° C, and the maximum particle size of the frit was 6 µm. The combustion temperature of the carbon nanotubes in the formed film was as high as 511 ° C, and no loss of carbon nanotubes was observed even in the firing at 450 ° C in the atmosphere. Moreover, the adhesive force of the film formed by baking is also obtained suitably. Even in evaluation of luminescence uniformity, uniform luminescence is obtained. In this glass frit, B ₂ O ₃ is a mesh forming oxide which is an essential component of glass, and when this is insufficient, the glass becomes unstable. SnO and P ₂ O ₅ are components that lower the softening point of glass, and are effective components for stabilizing the glass, and SnO is oxidized during firing to film the frit surface to moderate the softening of the glass.

From the above, in the film formation process using the composition for electron emission source formation of Samples 1 to 7, carbon nanotubes are not lost in firing at 450 ° C. in an oxidizing atmosphere, exhibit good adhesion, and are easily applied by application of an electric field. It can be seen that a film is obtained in which the carbon nanotubes do not come off, and the film is suitable as an electron emission source.

In sample 9 and sample 10 shown in Table 2, the film is formed using the same composition for electron emission source formation as in sample 3 except that the maximum particle diameter of the glass frit to be blended is different. Therefore, from these results, the influence of the particle diameter of a glass frit on the film for electron emission sources formed can be confirmed.

In Sample 9 and Sample 10, a composition for forming an electron emission source was prepared using a Bi ₂ O ₃ -B ₂ O ₃ -based glass frit, and the maximum particle diameter of the glass frit was 9 μm in Sample 9 and 13 in Sample 10. [Mu] m. In the evaluation of the light emission uniformity of the film for electron emission source, in Example 9, unevenness was observed in the light emission, but the entire surface was emitting light, and "Δ- ○" shown in Table 2 means such a state. In contrast, in Sample 10, the film showed only partial light emission. The reason for this is that the particle size of the glass frit is 13 µm, which results in uneven distribution of the carbon nanotubes in the film, and also flatness of the film, which makes it difficult to make the electric field applied to the carbon nanotubes uniform. It is considered to be uneven. Therefore, in order to obtain uniform light emission of a film from the result of the sample 9 and the sample 10, it is considered that the largest particle diameter of the glass frit suitable for use is 10 micrometers or less.

In samples 11-13 shown in Table 3, the film is formed using the composition for electron emission source formation similar to sample 3 except having the diameter of the carbon nanotube mix | blended. Therefore, from these results, the influence of the diameter of a carbon nanotube on the film for electron emission sources formed can be confirmed.

The carbon nanotubes used in the preparation of the composition for forming an electron emission source in Samples 11 to 13 are multilayer carbon nanotubes produced by the CVD method, and the diameter thereof is 10 nm in Sample 11, 20 nm in Sample 12, and Sample 13 30 nm. In the evaluation of the light emission uniformity of the film for electron emission source, uniform light emission was observed in Sample 11, while in Example 12, unevenness was observed in light emission, but the entire surface was emitting light. "Δ- ○" of Sample 12 shown in Table 3 means such a state. In contrast, in Sample 13, the film showed only partial light emission. Therefore, when the diameter of the carbon nanotubes to be used becomes excessive, it can be said that the light emission of the film becomes uneven. From the results of Samples 11 to 13, in order to obtain uniform light emission of the film, the diameter of the carbon nanotubes suitable for use can be considered to be 20 nm or less.

In samples 14-19 are shown in Table 4, thereby forming a coating film by using PbO or V ₂ O ₅ glass frit is a composition for forming an electron emission source of the blended glass composition comprising a. Therefore, from these results, it can be seen the effect of the electron-emitting film formed is incorporated PbO and P ₂ O ₅ included in the glass frit.

The glass frit of Sample 14 was a Bi ₂ O ₃ -B ₂ O ₃ based glass containing 4.8 mol% of V ₂ O ₅ , and the glass frit of Sample 15 was a Bi ₂ O ₃ -B ₂ O ₃ based containing 2.8 mol% of PbO. It is glass. The glass frit of Sample 16 was a Bi ₂ O ₃ -B ₂ O ₃ based glass containing 8 mol% of V ₂ O ₅ , and the glass frit of Sample 17 contained Bi ₂ O ₃ -B ₂ O containing 5 mol% of PbO. _{It is a three-} based glass. The combustion temperature of the carbon nanotubes in the formed film was 491 ° C in Sample 14 and 492 ° C in Sample 15, and the carbon nanotubes were slightly lost in firing at 450 ° C in the atmosphere (sample 14: see FIG. 2). . The description "(circle)-(triangle | delta)" of evaluation of the heat resistance of the carbon nanotubes of the samples 14 and 15 in Table 4 means such a state. In addition, about the evaluation of luminescence uniformity, although unevenness is seen in luminescence, the whole surface is emitting light, and "(triangle | delta)-(circle)" of the samples 14 and 15 shown in Table 4 mean such a state. These luminescence stains are thought to be due to some loss of carbon nanotubes. In contrast, the combustion temperature of the carbon nanotubes in the film of Sample 16 was 472 ° C and 464 ° C in Sample 17. In all cases, partial loss of the carbon nanotubes was observed in the firing at 450 ° C in the atmosphere, and the emission uniformity was observed. Also in the evaluation of the sex, only infrequent light emission is obtained. Samples 18 and 19 the sample 16 and 17 many more than the content of PbO or P ₂ O _5, the glass frit of the sample 18 is a V ₂ O ₅ -BaO-TeO ₂ type glass containing 32.5㏖% of V ₂ O _5, The glass frit of sample 19 is PbO-B ₂ O ₃ -SiO ₂ -based glass containing 52.0 mol% of PbO. The combustion temperature of the carbon nanotubes in the formed film was 436 ° C in Sample 18 and 370 ° C in Sample 19. In any case, the carbon nanotubes were completely lost in firing at 450 ° C in the air (Sample 19: Fig. 3). In the evaluation of luminescence uniformity, luminescence is not seen.

From the above, it is apparent that when PbO or V ₂ O ₅ is included in the composition of the glass frit, oxidation of the carbon nanotubes in the film to be formed is promoted, and it is easy to disappear during firing. However, it is understood from Samples 14 and 15 that the loss of carbon nanotubes can be prevented by limiting the ratio in these glass compositions. PbO and V ₂ O ₅ are effective components for improving the wettability and coating property of the glass substrate, and the softening point of the glass frit. Therefore, when used, V ₂ O ₅ is 5 mol% or less, and PbO is 3 mol. If it is% or less, the loss | disappearance of a carbon nanotube can be reduced during baking, and the film for electron emission sources can be formed.

According to the present invention, the organic binder resin in the composition can be decomposed and removed appropriately while preventing the carbon nanotubes from disappearing in firing when forming the film for electron emission source using the composition for electron emission source formation. In addition, since the adhesion of the film by the glass frit is satisfactorily performed, an electron emission source film excellent in strength and light emission uniformity is formed. The resulting film does not peel off the carbon nanotubes by vibration or application of an electric field, and provides an electron emission source that emits light uniformly by application of an electric field. In addition, the heat resistance of the carbon nanotubes in the film is high, and the loss of function as an electron emission source is avoided in the display device manufacturing process after film formation.

Claims (12)

As a composition for electron emission source formation containing a carbon nanotube, a glass frit, an organic binder resin, and an organic solvent, the softening point of the said glass frit is 300-500 degreeC, The glass frit is Consisting of B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ (oxygen coordination number of Al = 4), P ₂ O ₅ , V ₂ O ₅ , Sb ₂ O ₅ and ZrO ₂ (oxygen coordination number of Zr = 6) A glass composition comprising at least one oxide selected from the group and at least one oxide selected from the group consisting of SnO, BaO, TeO ₂ , and ZrO ₂ (oxygen coordinate number of Zr = 8), or At least one oxide selected from the group consisting of P ₂ O ₅ , V ₂ O ₅ , Sb ₂ O _5, and ZrO ₂ (oxygen coordinate number of Zr = 6), ZnO, Bi ₂ O _3, and Al ₂ O ₃ The composition for electron emission source formation characterized by having a glass composition containing at least 1 sort (s) of oxide chosen from the group which consists of (oxygen coordinate number of Al = 6). The composition for forming an electron emission source according to claim 1, wherein the glass constituting the glass frit is a glass having a softening point of 400 to 500 ° C, or a glass having a composition containing SnO. delete The glass constituting the glass frit is SnO-P ₂ O ₅ -based glass, TeO ₂ -B ₂ O ₃ -BaO-based glass, SnO-B ₂ O ₃ -based glass and SnO- B ₂ O ₃ -P ₂ O ₅ based glass, the inorganic oxide characterized by the composition for forming electron emission sources that is selected from the group consisting of glass. The composition for electron emission source formation according to claim 1 or 2, wherein the maximum particle size of the glass frit is 2 to 10 µm. The composition of claim 1, wherein the carbon nanotubes have a diameter of 20 nm or less. The composition for electron emission sources according to claim 1 or 2, wherein the glass composition of the glass frit has a content of V ₂ O ₅ of 5 mol% or less and a content of PbO of 3 mol% or less. The composition of claim 1 or 2, wherein the glass composition of the glass frit contains none of V ₂ O ₅ and PbO. The composition of claim 1 or 2, wherein the glass composition of the glass frit contains any one of Bi ₂ O ₃ , TeO _2, and SnO. The composition for electron emission source formation according to claim 1, further comprising conductive metal particles or carbon particles. delete Carbon nanotubes and glass are formed by removing an organic solvent from the composition for forming an electron emission source according to claim 1 applied to a substrate to form a coating film, and baking the coating film at a temperature of 400 to 450 ° C. to remove the organic binder resin. A method for forming an electron emission source film, comprising forming a film containing the same.

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