JP2005122930A - Nano-scale carbon tube paste, and electron emission source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paste in which aggregating tendency of nano-scale carbon tubes is restrained to the utmost, and to provide an electron emission source having an electron emission material layer excellent in uniformity, by using the paste. <P>SOLUTION: The nano-scale carbon tube paste contains nano-scale carbon tubes, a dispersion promoting agent, a binder, and solvent, and the electron emission source comprises (A) a base plate having conductivity at least at a part thereof, or a patterned base plate; and (B) the electron emission material layer formed by baking a painted film of the nano-scale carbon tube paste formed on the above base plate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a paste containing a nanoscale carbon tube, in particular, a nanoscale carbon tube paste for producing an electron emission source, and an electron emission source obtained using the paste.

Conventionally, a conductive paste in which carbon nanotubes are dispersed in a vehicle in which a resin is dissolved in an organic solvent is known (see Patent Document 1). Examples of the vehicle include glycol ethers such as butyl carbitol acetate, glycol esters, or organic solvents such as alcohols belonging to monocyclic terpenes such as terpineol (terpineol), and resins such as cellulose or acrylic resins. It is a dissolved material and basically a material with good decomposition and volatility. For example, it can be removed by heating at about 300 to 400 ° C. in atmospheric air. Specific examples thereof include a conductive paste in which 1 part by weight of carbon nanotubes is dispersed in a vehicle in which 0.2 part by weight of ethyl cellulose is dissolved in 2 parts by weight of butyl carbitol acetate.
JP 2000-63726 A (see claims, paragraph 0010)

  However, nanoscale carbon tubes represented by carbon nanotubes originally have low dispersibility in the paste, and pastes including carbon nanotubes, organic solvents, and resin pastes as described in Patent Document 1, In general, the viscosity is adjusted to be high, and has a viscosity of, for example, mayonnaise.

  Therefore, there is a problem that not only carbon nanotubes tend to aggregate during storage, but also when the paste is applied to a substrate, the carbon nanotubes tend to aggregate over time as the solvent evaporates from the coating film. For this reason, an electron-emitting material layer formed by applying and baking such paste on a substrate does not always satisfy the electron emission characteristics sufficiently.

  Therefore, the main object of the present invention is to provide a paste that suppresses the aggregation tendency of the nanoscale carbon tube as much as possible.

  It is another object of the present invention to provide an electron emission source provided with an electron emission material layer having excellent uniformity and obtained using such a paste.

  As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.

  (1) A specific compound functions as a dispersion promoter that suppresses the aggregation tendency of the nanoscale carbon tube.

  (2) The paste to which the dispersion accelerator is added has excellent storage stability because aggregation of the nanoscale carbon tube is suppressed even during storage.

  (3) In addition, the nanoscale carbon tube is prevented from agglomerating even in the wet coating film immediately after the paste is applied to the substrate, and the nanoscale carbon tube is generated along with the volatilization of the solvent during the subsequent heat treatment. Therefore, it is possible to manufacture an electron emission source having an electron emission material layer that has excellent dispersion uniformity of the nanoscale carbon tube and has excellent electron emission characteristics.

  The present invention has been completed based on these findings and has been completed. The present invention provides the following nanoscale carbon tube paste and an electron emission source obtained by using the paste.

  Item 1. A nanoscale carbon tube paste comprising a nanoscale carbon tube, a dispersion accelerator, a binder, and a solvent.

  Item 2 The dispersion accelerator is at least one of C3-12 polyhydric alcohols having 3 to 8 hydroxyl groups, and at least one boiling point constituting the dispersion accelerator is higher than the boiling point of the solvent Item 10. The nanoscale carbon tube paste according to Item 1, wherein

  Item 3 The binder is at least one selected from a phenol resin, an epoxy resin, a cellulose derivative, a polyamide resin, a vinyl resin, a polyester resin, a polyurethane resin, and a rubber resin, and the decomposition temperature of the binder is the nanoscale. Item 3. The nanoscale carbon tube paste according to item 1 or 2, which is lower than a decomposition temperature of the carbon tube.

  Item 4 The solvent according to any one of Items 1 to 3, wherein the solvent is at least one selected from the group consisting of alcohols, esters, ketones, ethers, N, N-dimethylformamide, and N-methylpyrrolidone. Nanoscale carbon tube paste.

Item 5 Nanoscale carbon tube
(i) Single-walled carbon nanotube
(ii) amorphous nanoscale carbon tube,
(iii) A carbon tube selected from the group consisting of a nano flake carbon tube and a multi-walled carbon nanotube with a nested structure
(iv) an iron-carbon composite comprising the carbon tube of (iii) above and iron carbide or iron, wherein iron carbide or iron is filled in a range of 10 to 90% of the space in the tube of the carbon tube; Or
(v) The nanoscale carbon tube paste according to any one of Items 1 to 4, which is a mixture of two or more of the above (i) to (iv).

  Item 6 Any one of Items 1 to 5 containing 0.1 to 50 parts by weight of a dispersion accelerator, 1 to 95 parts by weight of a binder, and 100 to 2000 parts by weight of a solvent with respect to 100 parts by weight of the nanoscale carbon tube. The described nanoscale carbon tube paste.

  Item 7 The nanoscale carbon tube paste according to any one of Items 1 to 6, further comprising conductive particles.

  Item 8 The nanoscale carbon tube paste according to Item 7, which contains 1 to 2000 parts by weight of conductive particles with respect to 100 parts by weight of the nanoscale carbon tube.

Item 9 (A) A substrate having at least a part of conductivity or a patterned substrate, and (B) the nanoscale carbon tube paste according to any one of Items 1 to 8 formed on the substrate An electron emission source comprising an electron emission material layer formed by firing a film.

  The nanoscale carbon tube paste of the present invention has excellent storability, and the tendency of the nanoscale carbon tube to aggregate in the coating film even when applied to a substrate is suppressed. It is particularly useful.

  Further, in the coating film of the nanoscale carbon tube paste of the present invention, the nanoscale carbon tube has no thermal degradation and is difficult to aggregate, so that the electron emission obtained using the nanoscale carbon tube paste of the present invention is used. The source has the advantage that the nanoscale carbon tube is uniformly distributed on the substrate in the electron emission material layer, and has excellent electron emission characteristics.

Nanoscale carbon tube The nanoscale carbon tube used in the present invention refers to a carbon tube having a nano-sized diameter, and iron or the like may be included in the inner space of the carbon tube.

  As such nanoscale carbon tubes, (1) single-walled carbon nanotubes, (2) multi-walled carbon nanotubes, (3) amorphous nanoscale carbon tubes developed by the present applicant, (4) nanoflake carbon tubes, (5) ( a) a carbon tube selected from the group consisting of nano flake carbon tubes and nested multi-walled carbon nanotubes; and (b) iron carbide or iron, and 10 to 90% of the space in the tube of the carbon tube (a). Examples of the range include (b) iron carbide or iron-carbon composite filled with iron.

  Among these, the amorphous nanoscale carbon tube, the nano flake carbon tube, and the iron-carbon composite are particularly preferable because of good dispersion in a solvent and a binder. The reason why these tubes are well dispersed in solvents and binders has not been fully elucidated, but because the carbon network surface of the outermost layer of these tubes is discontinuous, the affinity with solvents, binders, etc. It is assumed that it is higher.

< Carbon nanotube >
A carbon nanotube is a hollow carbon material in which a graphite sheet (that is, a carbon atom plane or graphene sheet of a graphite structure) is closed like a tube, its diameter is nanometer scale, and the wall structure has a graphite structure. . Among the carbon nanotubes, one with a single graphite sheet whose wall structure is closed in a tube shape is called a single-walled carbon nanotube, and a plurality of graphite sheets are each closed in a tube shape and are nested. It is called a multi-walled carbon nanotube with a nested structure. In the present invention, both single-walled carbon nanotubes and multi-walled carbon nanotubes can be used.

  The single-walled carbon nanotube that can be used in the present invention preferably has a diameter of about 0.4 to 10 nm and a length of about 1 to 500 μm, and more preferably has a diameter of about 0.7 to 5 nm and a length of about 1 to 100 μm. In particular, those having a diameter of about 0.7 to 2 nm and a length of about 1 to 20 μm are preferable.

  The multi-walled carbon nanotube that can be used in the present invention preferably has a diameter of about 1 to 100 nm and a length of about 1 to 500 μm, and further has a diameter of about 1 to 50 nm and a length of about 1 to 100 μm. Particularly preferred are those having a diameter of about 1 to 40 nm and a length of about 1 to 20 μm.

< Amorphous nanoscale carbon tube >
The amorphous nanoscale carbon tube is described in WO00 / 40509 (Patent No. 3355442), has a main skeleton made of carbon, has a diameter of 0.1 to 1000 nm, and has an amorphous structure. The carbon tube has a linear shape, and in the X-ray diffraction method (incident X-ray: CuKα), the plane interval (d002) of the carbon mesh plane (002) measured by the diffractometer method is 3.54 mm. In particular, it is 3.7 mm or more, the diffraction angle (2θ) is 25.1 degrees or less, particularly 24.1 degrees or less, and the half-value width of 2θ band is 3.2 degrees or more, particularly 7.0 degrees or more. It is characterized by.

  The amorphous nanoscale carbon tube is a thermally decomposable resin having a decomposition temperature of 200 to 900 ° C. in the presence of a catalyst made of at least one metal chloride such as magnesium, iron, cobalt, nickel, etc. It can be obtained by subjecting tetrafluoroethylene, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl alcohol or the like to excitation treatment.

  The shape of the thermally decomposable resin as a starting material may be any shape such as a film shape, a sheet shape, a powder shape, or a lump shape. For example, when obtaining a carbon material in which a thin amorphous nanoscale carbon tube is formed on a substrate, excitation treatment may be performed under appropriate conditions with a thermally decomposable resin applied or placed on the substrate. .

  As the excitation treatment, for example, heating is performed in an inert atmosphere, preferably in a temperature range of about 450 to 1800 ° C. and at or above the thermal decomposition temperature of the raw material, and in a temperature range of about room temperature to 3000 ° C. and the thermal decomposition temperature of the raw material. Examples of the processing such as the above plasma processing can be given.

  The amorphous nanoscale carbon tube used in the present invention is a nanoscale carbon nanotube having an amorphous structure (amorphous structure), has a hollow linear shape, and the pores are highly controlled. The shape is mainly a cylinder, a quadrangular prism, etc., and at least one of the tips often has no cap (open). When the tip is closed, the shape is often flat.

  The outer diameter of the amorphous nanoscale carbon tube is usually in the range of about 1 to 1000 nm, preferably in the range of about 1 to 200 nm, and more preferably in the range of about 1 to 100 nm. The aspect ratio (tube length / diameter) is 2 times or more, preferably 5 times or more.

  Here, “amorphous structure” means a carbonaceous structure consisting of an irregular carbon network plane, not a graphite structure consisting of a continuous carbon layer of regularly arranged carbon atoms. The graphene sheets are irregularly arranged. From an image obtained by a transmission electron microscope, which is a typical analysis technique, the nanoscale carbon tube having an amorphous structure according to the present invention has a spread in the plane direction of the carbon network plane that is one time larger than the diameter of the amorphous nanoscale carbon tube. small. As described above, the amorphous nanoscale carbon tube has an amorphous structure in which a large number of fine graphene sheets (carbon network surface) are irregularly distributed instead of a graphite structure, so that the outermost layer is formed. The carbon mesh surface is not continuous over the entire length in the tube longitudinal direction but is discontinuous. In particular, the length of the carbon network surface constituting the outermost layer is less than 20 nm, particularly less than 5 nm.

Amorphous carbon generally does not exhibit X-ray diffraction, but exhibits broad reflection. In the graphitic structure, the carbon mesh planes are regularly stacked, so the carbon mesh plane spacing (d ₀₀₂ ) is narrowed, and the broad reflection shifts to the high angle side (2θ) and becomes gradually sharper (in the 2θ band). It becomes observable as d ₀₀₂ diffraction lines (d ₀₀₂ = 3.354 mm when they are regularly stacked due to the graphite positional relationship).

In contrast, an amorphous structure generally does not exhibit X-ray diffraction as described above, but partially exhibits very weak coherent scattering. The theoretical crystallographic properties of the amorphous nanoscale carbon tube according to the present invention measured by the diffractometer method in the X-ray diffraction method (incident X-ray = CuKα) are defined as follows: carbon network plane The interval (d ₀₀₂ ) is 3.54 mm or more, more preferably 3.7 mm or more; the diffraction angle (2θ) is 25.1 degrees or less, more preferably 24.1 degrees or less; the half width of the 2θ band Is 3.2 degrees or more, more preferably 7.0 degrees or more.

Typically, the amorphous nanoscale carbon tube used in the present invention has a diffraction angle (2θ) by X-ray diffraction in the range of 18.9 to 22.6 degrees, and the carbon network plane spacing (d ₀₀₂ ) is 3.9 to 4.7 mm. The full width at half maximum of the 2θ band is in the range of 7.6 to 8.2 degrees.

The phrase “linear”, which is one term representing the shape of the amorphous nanoscale carbon tube of the present invention, is defined as follows. That is, when the length of the amorphous nanoscale carbon tube image obtained by a transmission electron microscope is L and the length when the amorphous nanoscale carbon tube is extended is L ₀ , L / L ₀ is 0.9 or more. It shall mean shape characteristics.

  The tube wall portion of such an amorphous nanoscale carbon tube has an amorphous structure composed of a plurality of fine carbon network planes (graphene sheets) oriented in all directions, and the active point is determined by the carbon plane spacing of these carbon network planes. This has the advantage that it has excellent affinity with the solvent, binder resin, and dispersion accelerator as the medium.

< Iron-carbon composite >
The iron-carbon composite used in the present invention is described in Japanese Patent Application Laid-Open No. 2002-338220, and (a) a carbon tube selected from the group consisting of a nano flake carbon tube and a multi-layer carbon nanotube with a nested structure. And (b) iron carbide or iron, and 10 to 90% of the space in the tube of the carbon tube (a) is filled with the iron carbide or iron (b). That is, 100% of the space in the tube is not completely filled, and the iron carbide or iron is filled in the range of 10 to 90% of the space in the tube (that is, partially). It is characterized in that it is filled in). The wall portion is a patchwork-like or machete-like (so-called paper mache-like) nano-flake carbon tube.

  In the claims and the specification of the present application, the “nano flake carbon tube” is composed of a plurality of (usually many) flake-like graphite sheets assembled into a patchwork shape or a paper mache shape. This refers to a carbon tube made of an aggregate of graphite sheets.

Such iron-carbon composites are
(1) Ratio when the pressure is adjusted to 10 ⁻⁵ Pa to 200 kPa in an inert gas atmosphere, the oxygen concentration in the reactor is A (liter), and the oxygen amount is B (Ncc). Heating the iron halide to 600 to 900 ° C. in a reaction furnace adjusted to a concentration at which B / A is 1 × 10 ⁻¹⁰ to 1 × 10 ⁻¹ , and
(2) It is manufactured by a manufacturing method including a step of introducing an inert gas into the reaction furnace, introducing a pyrolytic carbon source at a pressure of 10 ⁻⁵ Pa to 200 kPa, and performing a heat treatment at 600 to 900 ° C. The

  Here, “Ncc”, which is a unit of the oxygen amount B, means a volume (cc) when converted to a standard state of gas at 25 ° C.

  The iron-carbon composite is composed of (a) a carbon tube selected from the group consisting of nano flake carbon tubes and nested multi-walled carbon nanotubes, and (b) iron carbide or iron. The space portion (that is, the space surrounded by the tube wall) is not completely filled, but a part of the space portion, more specifically, about 10 to 90%, particularly about 30 to 80%. Preferably, about 40 to 70% is filled with iron carbide or iron.

  In the iron-carbon composite used in the present invention, as described in JP-A No. 2002-338220, the carbon portion is produced at a specific rate after performing the production steps (1) and (2). When cooled, it becomes a nano flake carbon tube, and after performing the manufacturing steps (1) and (2), heat treatment is performed in an inert gas, and cooling is performed at a specific cooling rate, thereby forming a multi-walled carbon nanotube with a nested structure. .

<(A-1) Nano flake carbon tube>
The nano-flake carbon tube of the present invention and the iron-carbon composite comprising iron carbide or iron are typically cylindrical, but such a cylindrical iron-carbon composite (obtained in Reference Example 2 described later). A transmission electron microscope (TEM) photograph of a cross section across the longitudinal direction is shown in FIG. 6, and a side TEM photograph is shown in FIG.

  FIG. 7 (a-1) shows a schematic diagram of a TEM image of such a columnar nano-flake carbon tube. In (a-1) of FIG. 7, 100 schematically shows a TEM image in the longitudinal direction of the nano flake carbon tube, and 200 shows a TEM image in a cross section substantially perpendicular to the longitudinal direction of the nano flake carbon tube. This is shown schematically.

  The nanoflake carbon tube constituting the iron-carbon composite used in the present invention typically has a hollow cylindrical shape, and when the cross section is observed by TEM, arc-shaped graphene sheet images are concentrically assembled. Each graphene sheet image forms a discontinuous ring, and when the longitudinal direction is observed with TEM, the substantially straight graphene sheet images are arranged in multiple layers almost parallel to the longitudinal direction. The individual graphene sheet images are not continuous over the entire length in the longitudinal direction, but are discontinuous.

  More specifically, the nanoflake carbon tube constituting the iron-carbon composite used in the present invention is perpendicular to the longitudinal direction, as is apparent from 200 in FIGS. 6 and 7 (a-1). When the cross section is observed by TEM, many arc-shaped graphene sheet images are concentrically (multi-layered tube shape), but each graphene sheet image is completely closed as shown in 210 and 214, for example. It does not form a continuous ring, but forms a discontinuous ring that is interrupted. Some graphene sheet images may be branched as indicated by 211. At the discontinuous point, a plurality of arc-shaped TEM images constituting one discontinuous ring may have a partially disturbed layer structure as indicated by 222 in FIG. As shown by 223, there may be a space between adjacent graphene sheet images, but a large number of arc-shaped graphene sheet images observed by TEM form a multilayer tube structure as a whole. Yes.

  Further, as is clear from 100 in FIGS. 2 and 7 (a-1), when the longitudinal direction of the nanoflake carbon tube is observed by TEM, a large number of substantially straight graphene sheet images are used in the present invention. Although it is arranged in multiple layers substantially parallel to the longitudinal direction of the iron-carbon composite, the individual graphene sheet images 110 are not continuous over the entire length in the longitudinal direction of the iron-carbon composite, and are discontinuous in the middle. It has become. Some graphene sheet images may be branched as indicated by reference numeral 111 in FIG. Further, at the discontinuous point, among the TEM images arranged in a layered manner, the TEM image of one discontinuous layer is at least partly adjacent to the adjacent graphene sheet image as indicated by 112 in (a-1) of FIG. In some cases, they may overlap each other, or as shown at 113, they may be slightly apart from the adjacent graphene sheet images, but a large number of substantially linear TEM images form a multilayer structure as a whole.

  The structure of the nanoflake carbon tube of the present invention is greatly different from the conventional multi-walled carbon nanotube. That is, as indicated by reference numeral 400 in FIG. 7A-2, the multi-walled carbon nanotube with a nested structure has a TEM image of a cross section perpendicular to the longitudinal direction thereof, as shown by 410, and a completely circular TEM image. A concentric tube, and a structure in which linear graphene sheet images 310 and the like continuous over the entire length in the longitudinal direction are arranged in parallel as shown by 300 in FIG. (Concentric cylindrical or nested structure).

  Although the details have not been fully elucidated yet, the nano-flake carbon tube constituting the iron-carbon composite used in the present invention has a large number of flake-like graphene sheets overlapped in a patchwork or tension form. It seems to form a tube as a whole.

  Such a nano-flake carbon tube of the present invention and an iron-carbon composite made of iron carbide or iron encapsulated in the inner space of the tube are nested multi-walled carbon nanotubes as described in Japanese Patent No. 2546114. Compared with the composite in which the metal is included in the inner space of the tube, the structure of the carbon tube is greatly different, and this is a novel carbon material that has not been known so far.

  In the case of TEM observation of the nano-flake carbon tube constituting the iron-carbon composite used in the present invention, each graphene sheet image relates to a number of substantially linear graphene sheet images oriented in the longitudinal direction. The length is usually about 2 to 500 nm, particularly about 10 to 100 nm. That is, as indicated by 100 in (a-1) of FIG. 7, a large number of TEM images of the substantially linear graphene sheet indicated by 110 are gathered to constitute a TEM image of the wall portion of the nanoflake carbon tube. The length of each substantially linear graphene sheet image is usually about 2 to 500 nm, particularly about 10 to 100 nm.

  Thus, in the iron-carbon composite, the outermost layer of the nanoflake carbon tube constituting the wall portion is formed of a discontinuous graphene sheet that is not continuous over the entire length in the tube longitudinal direction. The length of the outer carbon net surface is usually about 2 to 500 nm, particularly about 10 to 100 nm.

  As described above, the carbon portion of the wall portion of the nano-flake carbon tube constituting the iron-carbon composite used in the present invention has a tube shape in which a large number of flake-like graphene sheets are oriented in the longitudinal direction. However, when measured by the X-ray diffraction method, the average distance (d002) between the carbon network surfaces has a graphite structure of 0.34 nm or less.

  Moreover, the thickness of the wall part which consists of a nano flake carbon tube of the iron-carbon composite used by this invention is 49 nm or less, Especially about 0.1-20 nm, Preferably it is about 1-10 nm, Comprising: Over the full length, And substantially uniform.

<(A-2) Nested multi-walled carbon nanotubes>
As described above, by performing the specific heating step after performing the steps (1) and (2), the carbon tube constituting the obtained iron-carbon composite becomes a multi-walled carbon nanotube having a nested structure.

  The multi-walled carbon nanotube thus obtained is a concentric tube in which a TEM image of a cross section perpendicular to the longitudinal direction forms a complete circle, as indicated by 400 in FIG. 7 (a-2), And it is the structure (concentric cylindrical shape or nested structure) where the graphene sheet images continuous over the entire length in the longitudinal direction are arranged in parallel.

  The carbon portion of the wall portion of the multi-walled carbon nanotube of the nested structure constituting the iron-carbon composite used in the present invention has an average distance (d002) between carbon network surfaces of 0, as measured by X-ray diffraction. It has a graphite structure of 34 nm or less.

  Further, the thickness of the wall portion composed of the multi-walled carbon nanotube of the iron-carbon composite nested structure used in the present invention is 49 nm or less, particularly about 0.1 to 20 nm, preferably about 1 to 10 nm. Substantially uniform.

<(B) Iron carbide or iron contained>
In the present specification, the filling rate (10 to 90%) of the space inside the carbon tube selected from the group consisting of the nano flake carbon tube and the multi-walled carbon nanotube of the nested structure with iron carbide or iron is the iron used in the present invention. -Observing the carbon composite with a transmission electron microscope, and comparing the area of the image of the space of each carbon tube (ie, the space surrounded by the tube wall of the carbon tube) with the portion filled with iron carbide or iron. It is the ratio of the area of the image.

  The filling form of iron carbide or iron includes a form in which the space in the carbon tube is continuously filled and a form in which the space in the carbon tube is filled intermittently. Filled. Therefore, the iron-carbon composite used in the present invention should also be referred to as a metal-encapsulated carbon composite, an iron compound-encapsulated carbon composite, iron carbide, or an iron-encapsulated carbon composite.

  In addition, the iron carbide or iron included in the iron-carbon composite used in the present invention is oriented in the longitudinal direction of the carbon tube, has high crystallinity, and is in a range where iron carbide or iron is filled. The ratio of the area of the crystalline iron carbide or iron TEM image to the area of the TEM image (hereinafter referred to as “crystallization rate”) is generally about 90 to 100%, particularly about 95 to 100%.

  The high crystallinity of the iron carbide or iron contained is apparent from the fact that the TEM images of the inclusions are arranged in a lattice form when observed from the side of the iron-carbon composite of the present invention, It is clear from the fact that a clear diffraction pattern can be obtained in electron beam diffraction.

  Moreover, it can be easily confirmed by an electron microscope and EDX (energy dispersive X-ray detector) that iron carbide or iron is included in the iron-carbon composite used in the present invention.

<Overall shape of iron-carbon composite>
The iron-carbon composite used in the present invention is less curved, straight, and has a uniform thickness over the entire length of the wall, so it is homogeneous over the entire length. It has a shape. The shape is columnar and mainly cylindrical.

  The outer diameter of the iron-carbon composite according to the present invention is usually about 1 to 100 nm, particularly about 1 to 50 nm, preferably about 1 to 30 nm, more preferably about 10 to 30 nm. It is in. The aspect ratio (L / D) of the tube length (L) to the outer diameter (D) is about 5 to 10,000, and particularly about 10 to 1,000.

  The term “linear”, which is one term representing the shape of the iron-carbon composite used in the present invention, is defined as follows. That is, when the carbonaceous material containing the iron-carbon composite used in the present invention is observed in a range of 200 to 2000 nm square by a transmission electron microscope, the length of the image is W, and the image is linearly extended. In this case, the shape characteristic means that the ratio W / Wo is 0.8 or more, particularly 0.9 or more.

  The iron-carbon composite used in the present invention has the following properties when viewed as a bulk material. That is, in the present invention, iron- or iron carbide is filled in a range of 10 to 90% of the space in the tube of the carbon tube selected from the nano flake carbon tube and the nested multi-walled carbon nanotube as described above. The carbon composite is not a minute amount that can be barely observed by microscopic observation, but is a bulk material containing a large number of the iron-carbon composite, and is a carbonaceous material containing iron-carbon composite, or iron carbide or iron. It can be obtained in large quantities in the form of a material that should also be called an embedded carbonaceous material.

  FIG. 3 shows an electron micrograph of the carbonaceous material of the present invention consisting of the nano-flake carbon tube produced in Reference Example 2 described later and iron carbide filled in the inner space of the tube.

  As can be seen from FIG. 3, in the carbonaceous material including the iron-carbon composite used in the present invention, basically, in almost all (particularly 99% or more) carbon tubes, the space portion (that is, In general, iron carbide or iron is filled in a range of 10 to 90% of the space surrounded by the tube wall of the carbon tube, and there is usually substantially no carbon tube in which the space is not filled. However, in some cases, a small amount of carbon tubes not filled with iron carbide or iron may be mixed.

  Further, in the carbonaceous material of the present invention, an iron-carbon composite in which 10 to 90% of the space in the carbon tube as described above is filled with iron or iron carbide is a main constituent component. In addition to the iron-carbonaceous composite, soot may be contained. In such a case, components other than the iron-carbonaceous composite of the present invention are removed to improve the purity of the iron-carbonaceous composite in the carbonaceous material of the present invention, which is substantially used in the present invention. A carbonaceous material consisting only of an iron-carbon composite can also be obtained.

  In addition, unlike materials that could only be confirmed in microscopic amounts by conventional microscopic observation, the carbonaceous material containing the iron-carbon composite used in the present invention can be synthesized in large quantities, and its weight can easily be increased to 1 mg or more. can do.

The carbonaceous material of the present invention is attributed to iron or iron carbide contained in powder X-ray diffraction measurement in which X-rays of CuKα are irradiated with an irradiation area of 25 mm ² or more with respect to 1 mg of the carbonaceous material. The integrated intensity of the peak showing the strongest integrated intensity among the peaks of ° <2θ <50 ° is Ia, and 26 ° <2θ <27 ° attributed to the average distance (d002) between the carbon network surfaces of the carbon tubes. When the integrated intensity Ib of the peak is set, the ratio R (= Ia / Ib) of Ia to Ib is preferably about 0.35 to 5, particularly about 0.5 to 4, more preferably 1 to 3. Degree.

In this specification, the ratio of Ia / Ib is referred to as an R value. This R value peaks as an average value of the entire carbonaceous material when the carbonaceous material containing the iron-carbon composite used in the present invention is observed in an X-ray diffraction method with an X-ray irradiation area of 25 mm ² or more. Since the strength is observed, not the inclusion rate or filling rate in one iron-carbon composite that can be measured by TEM analysis, but the entire carbonaceous material as an aggregate of iron-carbon composites, It shows the average value of iron filling rate or inclusion rate.

  In addition, the average filling rate as a whole carbonaceous material containing a large number of the present invention iron-carbon composites is observed by TEM, and a plurality of iron carbides in a plurality of iron-carbon composites observed in each field of view. It can also be obtained by measuring the average filling rate of iron and calculating the average value of the average filling rates of a plurality of visual fields. When measured by such a method, the average filling rate of iron carbide or iron as a whole carbonaceous material comprising the iron-carbon composite used in the present invention is about 10 to 90%, particularly about 40 to 70%.

< Nano flake carbon tube >
The iron or carbon carbide in which the iron or iron carbide is partially encapsulated in the inner space of the nano flake carbon tube is acid-treated to dissolve and remove the encapsulated iron or iron carbide. A hollow nanoflake carbon tube in which no iron or iron carbide is present can be obtained.

  Examples of the acid used for the acid treatment include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and the like, and the concentration is preferably about 0.1 to 5N. As an acid treatment method, various methods can be used. For example, 1 g of iron-encapsulated nanoflake carbon tube is dispersed in 100 ml of 1N hydrochloric acid, and stirred at room temperature for 6 hours, followed by filtration and separation. After that, a hollow nanoflake carbon tube can be obtained by performing the same treatment twice with 100 ml of 1N hydrochloric acid twice.

  The basic structure of the nano flake carbon tube is not particularly changed by this acid treatment. Therefore, even in a hollow nanoflake carbon tube in which iron or iron carbide does not exist in the inner space of the tube, the length of the carbon network surface constituting the outermost surface is 500 nm or less, particularly 2 to 500 nm, particularly 10 to 10. 100 nm.

Dispersion Accelerator In the present invention, it is important to use a compound that functions as a substance that promotes the dispersion of the nanoscale carbon tube in the process of removing the solvent from the uniform paste state to form a film-formed body.

  In particular, the paste is generally difficult to maintain a high degree of dispersion since the concentration of the nanoscale carbon tube is higher than that of a resin coating solution containing the nanoscale carbon tube and the viscosity is about mayonnaise. Also, when the paste is applied to the substrate to form a coating film, and the solvent is evaporated from the obtained wet coating film to dry, or the obtained wet coating film is immediately dried without drying. In the present invention, when the solvent is volatilized, uniform film formation tends to be difficult and dumpling aggregates tend to be formed. A uniform dispersion of the scale carbon tube is possible, and a nanoscale carbon tube dispersion state suitable for an electron emission material is created. Therefore, in the present invention, a uniform dry coating film free from dumpling-like aggregates is obtained, and the electron-emitting material layer obtained by heat treatment has excellent electron-emitting characteristics.

  Examples of the dispersion accelerator include 3 to 8 hydroxyl groups in a molecule such as glycerin, diglycerin, pentaerythritol, xylose, xylitol, trimethylolpropane, mannitol, sorbitol, glucose, fructose, ditrimethylolpropane, sucrose. Examples thereof include polyhydric alcohols having 3 to 12 carbon atoms. Of these, glycerin, diglycerin and the like are preferable.

  When selecting the dispersion accelerator, it is preferable to use at least one having a boiling point higher than that of the solvent used. This is because when the solvent is being volatilized, it is considered that the dispersion accelerator remaining in the system is advantageous for suppressing aggregation of the nanoscale carbon tube.

  The above dispersion accelerators can be used alone or in admixture of two or more. The amount of the dispersion accelerator used can be appropriately selected from a wide range, but in general, it is used in the range of 0.1 to 50 parts by weight, particularly 0.1 to 10 parts by weight with respect to 100 parts by weight of the nanoscale carbon tube. preferable.

Binder As the binder used in the present invention, any of the resins used in conventional conductive pastes can be used. In particular, phenol resins, epoxy resins, cellulose derivatives, polyamide resins, vinyl resins, polyester resins, A polyurethane resin, a rubber-based resin or the like is preferable. Among these, when a nanoscale carbon tube is used for the electron emission electrode, in consideration of heat resistance and device productivity, a binder that disappears or carbonizes or solidifies at a low temperature is particularly desirable.

  As the phenol resin used in the present invention, known resins can be used, and examples thereof include novolak type phenol resins, resol type phenol resins, xylene resin modified resole type resins, and rosin modified phenol resins. Of these, resol-type and modified resol-type resins are preferred.

As the epoxy resin used in the present invention, known ones can be used. For example, epoxy resins obtained by reaction of bisphenols such as bisphenol A and bisphenol F with epichlorohydrin, brominated epoxy resins, cycloaliphatic epoxy resins, Triglycidyl isocyanurate type epoxy resins, glycidyl ester type epoxy resins, glycidyl amine type epoxy resins, heterocyclic epoxy resins and the like can be used.
Examples of the cellulose derivative include celluloses such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, ethyl cellulose, ethyl cellulose, and nitrocellulose. Of these, hydroxypropylcellulose is particularly preferable.

  Examples of the polyamide resin include polyamides soluble in the paste solvent used in the present invention, such as nylon 6, nylon 66, nylon 610, nylon 11, copolymer nylon, and alkoxymethylated nylon.

  Examples of vinyl resins include polyolefin resins, polystyrene resins, polyvinyl chloride resins, polyvinylidene chloride resins, polyacrylonitrile resins, vinyl acetate resins, polyvinyl acetals (eg, polyvinyl butyral), acrylic resins (particularly acrylic resins). Acid ester, especially lower alkyl ester polymer, methacrylic acid ester, particularly lower alkyl ester polymer, acrylic acid ester and / or other comonomer based on methacrylic acid ester (for example, styrene, methyl styrene, maleic acid) Examples thereof include copolymers obtained by copolymerizing one or two or more acids, etc.), polyvinyl alcohol, and polyvinylpyrrolidone.

  Examples of the polyester resin include polyester resins that are soluble in the paste solvent used in the present invention, such as polyarylate, polyethylene terephthalate, and polybutylene terephthalate.

  Although it does not specifically limit as a polyurethane resin, A polyurethane resin soluble in the solvent for pastes used by this invention can be used.

  Examples of the rubber resin include chlorinated rubber and gum arabic.

  The above binders may be used alone or in combination of two or more. The amount of the binder used can be appropriately selected from a wide range, but is generally 1 to 95 parts by weight, preferably 1 to 50 parts by weight, particularly 5 to 30 parts by weight with respect to 100 parts by weight of the nanoscale carbon tube. Is preferably used.

  The binder can be fired in vacuum, in a reducing gas atmosphere, or in air. Among the binders, those having a decomposition temperature lower than the decomposition temperature of the nanoscale carbon tube to be used are preferable, and those that decompose and volatilize by heat treatment at 550 ° C. or lower are particularly preferable.

  In the present specification and claims, the “decomposition temperature” of the nanoscale carbon tube is the thermogravimetric method (condition: the same atmosphere as the actual firing of the binder, at a sweep rate of 10 ° C./min. In the case where the temperature is increased at a speed), the temperature at which the weight reduction starts is meant. This decomposition temperature probably corresponds to the temperature at which the nanoscale carbon tube retains the shape of the tube, but the outermost graphene sheet begins to oxidize.

  The decomposition temperature of the nanoscale carbon tube varies depending on the thickness of the tube wall, the manufacturing method, and the like, but when heated in air, the decomposition temperature of the single-walled carbon nanotube is generally about 300 ° C., The decomposition temperature of the nested multi-walled carbon nanotube is about 800 ° C., the decomposition temperature of the amorphous nanoscale carbon tube is about 500 ° C., the decomposition temperature of the nano flake carbon tube is about 550 ° C. The decomposition temperature of the encapsulated nano flake carbon tube is about 550 ° C.

  The paste after evaporation of the solvent is in the form of a film formed, but depending on the paste preparation conditions such as the paste concentration and the paste mixing condition, the nanoscale carbon tube alone may not form the film well. For this reason, it is desirable to add a binder so that the nanoscale carbon tube and the binder coexist at the time of film formation. Therefore, it is recommended that the decomposition temperature of the binder is higher than the boiling point of the solvent used.

Solvent The solvent used in the present invention can be selected from a wide range of organic solvents for dissolving or dispersing the above dispersion accelerator and binder. Examples of such solvents include alcohols, esters, ketones, ethers, N, N-dimethylformamide, N-methylpyrrolidone and the like.

  Examples of alcohols include C1-C4 aliphatic saturated alcohols such as methanol, ethanol, and butanol, and terpineol.

  Examples of the esters include C1-C3 fatty acid lower (C1-C4) alkyl esters such as methyl formate, ethyl formate, and ethyl acetate, and glycol esters such as propylene glycol monomethyl ether acetate.

  Examples of ketones include cyclohexanone and methyl ethyl ketone (also known as 2-butanone).

  Examples of ethers include di-lower (C1-C3) alkyl ethers such as diethyl ether, cyclic ethers such as tetrahydrofuran, ethylene glycol mono (C1-C4) such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, and ethylene glycol monobutyl ether. An alkyl ether etc. can be illustrated.

  Basically, any solvent may be used as long as it dissolves or disperses the binder and the dispersion accelerator. However, in the storage of the paste, in order to suppress the viscosity change due to solvent evaporation and the aggregation of the nanoscale carbon tube, and to suppress the aggregation of the nanoscale carbon tube due to the solvent evaporation after forming the paste, A method of combining solvents can be adopted, or a high boiling point solvent, for example, a solvent having a boiling point of 70 to 550 ° C., particularly 150 to 400 ° C. at normal pressure can be used.

  The above solvents may be used alone or in combination of two or more. The amount of solvent used can be appropriately selected from a wide range, but the amount of solvent used depends greatly on the binder, solvent, additive, electrode pattern, and electrode film thickness, so it is optimally appropriate for a good paste body. It is necessary to select the amount. For example, when used for printing, if the viscosity is too low, ink bleeding occurs, and if the viscosity is too high, paste clogging on the printing mask, repeated printability failure, mold release failure between the mask and printed matter, and the like are caused.

  Therefore, the amount of solvent used is often defined by the viscosity of the paste body. For example, the amount of solvent used is preferably in the range of 100 to 2000 parts by weight, more preferably 100 parts by weight of the nanoscale carbon tube. It is advantageous to select appropriately from the range of 200 to 500 parts by weight. Thus, the viscosity of the obtained paste at 20 ° C. (viscosity measured with an E-type viscometer rotor at 20 rpm) is adjusted to be in the range of 0.2 to 1 Pa · s, particularly 0.4 to 0.8 Pa · s. It is preferable to do this.

Other Components Conductive particles can be added to the nanoscale carbon tube paste of the present invention as necessary. Examples of such conductive particles include conductive particles such as silver, gold, platinum, nickel, copper, indium, tin, tin alloy, aluminum, and carbon.

  The average particle size of the conductive particles can be selected from a wide range, but generally, the particle size is preferably 10 to 50000 nm, particularly 30 to 5000 nm.

  The amount of the conductive particles to be used can be selected from a wide range, but in general, it is desirable to use 1 to 2000 parts by weight, particularly 5 to 1000 parts by weight with respect to 100 parts by weight of the nanoscale carbon tube. .

  Furthermore, if necessary, various additives can be added to the nanoscale carbon tube paste of the present invention as long as the effects of the present invention are not impaired. Examples of such additives include low-melting glass powders that function as a binder by heat treatment.

Nanoscale carbon tube paste The nanoscale carbon tube paste of the present invention comprises the nanoscale carbon tube, a dispersion accelerator, a binder and a solvent, and if necessary, the conductive fine particles and additives uniformly in the predetermined amounts. It can be manufactured by mixing.

  The order of addition of each component is not particularly limited, but in general, (a) a binder is dissolved in a solvent, (b) a dispersion accelerator is mixed in the resulting solution, and (c) the resulting binder, solvent, and dispersion accelerator are mixed. It is preferable that the nanoscale carbon tube paste of the present invention is produced by mixing the nanoscale carbon tube with the mixture containing, and kneading the resulting mixture.

  It is also possible to produce a paste by adding a binder and a solvent to a system in which a dispersion accelerator is uniformly mixed in a nanoscale carbon tube. Furthermore, after the dispersion accelerator is diluted with a small amount of solvent, it can be uniformly mixed with the nanoscale carbon tube, the remaining solvent is added, and then the binder is added to produce a paste.

  As the mixing method, any known method can be used. For example, a method of mixing using a known mixing apparatus such as a mixer, a mill, a bead mill, a paint shaker, or a three roll can be used.

  The nanoscale carbon tube paste of the present invention thus obtained has the advantage that the storage property is good because the tendency of the nanoscale carbon tube to aggregate during storage is suppressed.

  The nanoscale carbon tube paste of the present invention is excellent in storage stability as described above, and the tendency of the nanoscale carbon tube to aggregate in the coating film even when applied to a substrate is suppressed, so that an electron emission source It is particularly useful for the production of

  In general, although the paste of the present invention depends on the material composition of the paste, the viscosity at a temperature of 20 ° C. (viscosity measured with an E-type viscometer rotor at 20 rpm) is 0.2-1 Pa · s, particularly 0.4- It is preferably about 0.8 Pa · s.

Electron Emission Source As described above, the nanoscale carbon tube paste of the present invention is useful for producing an electron emission source, particularly a field emission type electron emission source. For example, the nanoscale carbon tube paste of the present invention is applied to a substrate having at least a part of conductivity, or a substrate patterned by a conventional method, and the obtained coating film is dried as necessary. An electron emission material layer can be formed on the substrate by heat-treating (baking) the coating film or the dried coating film, and thus an electron emission source can be manufactured.

  The substrate may be an ITO glass substrate, a substrate coated with a conductive paint on the glass substrate surface, a substrate coated with a conductive paint on the ceramic substrate surface, or sputtering, ion plating, CVD instead of these conductive paints. Examples thereof include a substrate on which a conductive film is formed by vapor deposition or the like.

  In manufacturing the electron emission source, a pattern can also be formed by a method such as a screen printing method, a spin coating method, or an ink jet method using the nanoscale carbon tube paste of the present invention.

  The coating amount of the nanoscale carbon tube paste of the present invention can be appropriately selected according to the device size and the like, but the thickness of the layer remaining after baking the paste is in the range of 0.1 to 500 μm, particularly 0.1 to 50 μm. Is preferred.

  The coating film obtained by applying the paste of the present invention may be directly subjected to heat treatment (firing), but if necessary, the solvent can be volatilized from the coating film to form a dry coating film. Although it does not specifically limit as conditions of a drying process, Generally, what is necessary is just to perform on the conditions of about 150 kPa or less at room temperature-about 700 degreeC.

  When performing such a drying process, or when performing a heat treatment process (firing) without performing a drying process, the solvent evaporates from the coating film. In the paste of the present invention, the dispersion accelerator Therefore, there is an advantage that the nanoscale carbon tube hardly aggregates.

  As the atmosphere of the heat treatment (baking) of the undried coating film or the dried coating film, treatment in air or in an inert gas atmosphere such as nitrogen or argon, in a vacuum, in a reducing gas atmosphere or the like is preferable. It is preferable to carry out in a temperature range of 150 to 700 ° C, particularly 200 to 550 ° C. This heat treatment is desirably performed under the conditions that the solvent and the dispersion accelerator disappear, the binder disappears or is partially or completely carbonized, and the nanoscale carbon tube is not decomposed.

  By this heat treatment, substantially all of the dispersion accelerator and the solvent are removed, and the electron emitting material layer consisting only of the nanoscale carbon tube or the nanoscale carbon tube and the binder is partially or completely carbonized on the substrate. An electron emission material layer composed of the above components is formed. When the conductive particles are used, the electron emission material layer includes conductive particles.

  Thus, in the present invention, at least a part of a conductive substrate or a patterned substrate, and electron emission formed on the substrate and formed by baking a coating film of the nanoscale carbon tube paste of the present invention An electron emission source comprising a material layer (ie, an electron emission material layer comprising nanoscale carbon tubes) is provided.

  The electron emission source of the present invention can be advantageously used in various applications, for example, a field emission type device, a field emission display (FED), a high voltage type fluorescent display element, and the like.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

Reference example 1
Example of production of amorphous nanoscale carbon tube An amorphous nanoscale carbon tube was produced in the same manner as in Example 3 of Japanese Patent No. 3355442. More specifically, after 10 mg of anhydrous iron chloride powder (500 μm or less) is uniformly sprinkled on a PTFE film of 60 μm × 10 mm × 10 mm, it is placed in a vacuum furnace, the inside of the furnace is purged with nitrogen three times, and then the pressure is reduced to 3 Pa. And baked in vacuum at 900 ° C. for 10 minutes.

  As a result, the formation of amorphous nanoscale carbon tubes was observed by SEM and X-ray diffraction. The resulting product had a diameter = 10-60 nm and a length = 5-6 μm.

From observation by TEM, it was confirmed that the obtained amorphous nanoscale carbon tube had a spread in the plane direction of the carbon network plane of several nm or less. Further, the diffraction angle (2θ) by X-ray diffraction was 18.9 degrees, the carbon network plane interval (d ₀₀₂ ) calculated therefrom was 4.7 mm, and the half width of the 2θ band was 8.2 degrees.

Reference example 2
Example of Production of Iron-Carbon Composite Using a reactor as shown in FIG. 1, the iron-carbon composite of the present invention was obtained as follows. In FIG. 1, 1 indicates a reaction furnace, 2 indicates a heating device, and 10 indicates a porcelain boat.

Process (1)
Anhydrous FeCl ₃ (manufactured by Kanto Chemical Co., Inc.) 0.5 g is spread thinly in a magnetic boat. This is installed in the center of the furnace made of quartz tube, and the inside of the furnace is depressurized to a pressure of 50 Pa. At this time, argon gas containing 5000 ppm of oxygen is supplied at a rate of 30 ml / min from the side opposite to the end of the reactor to which the vacuum suction line is attached (left side of the reaction tube in FIG. 1). Thus, the ratio B / A when the reactor volume was A (liter) and the oxygen amount was B (Ncc) was 2.5 × 10 ⁻³ . Next, the temperature is raised to 800 ° C. with reduced pressure.

Process (2)
When the temperature reaches 800 ° C., argon is introduced and the pressure is controlled to 6.7 × 10 ⁴ Pa. On the other hand, argon gas was bubbled into a benzene tank as a pyrolytic carbon source, and a mixed gas of volatilized benzene and argon was introduced into the furnace at a flow rate of 30 ml / min per liter of reactor volume, and diluted gas As described above, argon gas is introduced at a flow rate of 20 ml / min.

  After reacting at a reaction temperature of 800 ° C. for 30 minutes, lowering the temperature to 500 ° C. in 20 minutes, removing the heater and air-cooling to room temperature in 20 minutes, 200 mg of a carbonaceous material containing the iron-carbon composite of the present invention was obtained. It was.

  From the results of SEM observation, the obtained iron-carbon composite was highly linear with an outer diameter of 15 to 40 nm and a length of 2 to 3 microns. Moreover, the thickness of the wall part which consists of carbon was 2-10 nm, and was substantially uniform over the full length. Further, it was confirmed from the TEM observation and the X-ray diffraction method that the wall portion was a nanoflake carbon tube having a graphite structure having an average distance (d002) between carbon network surfaces of 0.34 nm or less.

  Further, it was confirmed by X-ray diffraction and EDX that the iron-carbon composite of the present invention contained iron carbide.

  When many iron-carbon composites constituting the obtained carbonaceous material of the present invention were observed with an electron microscope (TEM), the space portion of the nanoflake carbon tube (that is, surrounded by the tube wall of the nanoflake carbon tube). Iron-carbon composites having various filling rates in the range of 10 to 80% of the filling rate of iron carbide in the space) were mixed.

  Incidentally, the average filling rate of iron carbide into the nanoflake carbon tube or carbon nanotube inner space of the large number of iron-carbon composites was 40%. Table 1 below shows the average filling rate of iron carbide calculated by observing a plurality of fields of TEM observation images of the obtained iron-carbon composite. The R value calculated from X-ray diffraction was 0.56.

本参考例２で得られた炭素質材料を構成する鉄−炭素複合体１本の電子顕微鏡(TEM)写真を図２に示す。

An electron microscope (TEM) photograph of one iron-carbon composite constituting the carbonaceous material obtained in Reference Example 2 is shown in FIG.

  FIG. 3 shows an electron microscope (TEM) photograph showing the existence state of many iron-carbon composites in the carbonaceous material obtained in Reference Example 2.

  The electron diffraction pattern of one iron-carbon composite obtained in Reference Example 2 is shown in FIG. FIG. 4 shows that a clear electron diffraction pattern is observed, and that the inclusions have high crystallinity. As a result of TEM observation, the crystallization rate of the inclusion (the ratio of the area of the TEM image of crystalline iron carbide to the area of the TEM image in the range filled with iron carbide) was about 100%.

  FIG. 5 shows an X-ray diffraction pattern of the carbonaceous material (an aggregate of iron-carbon composite materials) containing the iron-carbon composite obtained in Reference Example 2.

  FIG. 6 shows an electron microscope (TEM) photograph in which one iron-carbon composite obtained in Reference Example 2 is cut into a ring shape.

  As can be seen from FIG. 6, in the carbonaceous material obtained in the present Reference Example 2, the carbon wall surface is not nested or scrolled, but is patchwork (so-called paper mache or tension). It was a nano flake carbon tube.

  As can be seen from FIG. 6, the shape of the nanoflake carbon tube constituting the iron-carbon composite obtained in Reference Example 2 is cylindrical, and is observed in a TEM photograph of a cross section across the longitudinal direction. The graphene sheet image was not a closed ring, but a discontinuous ring having many discontinuous points.

  In addition, when the nano-flake carbon tube constituting the iron-carbon composite of the present invention is observed by TEM, each graphene sheet image is related to a number of substantially linear graphene sheet images oriented in the longitudinal direction. The length of was approximately in the range of 2-30 nm (FIG. 2).

  Furthermore, from the EDX measurement results measured at points 1 to 20 in the tube of FIG. 6, it was found that the carbon: iron atomic ratio was 5: 5 and a substantially uniform compound was included.

Example 1
First, an α-terpineol solution containing 5% by weight of hydroxypropylcellulose as a binder is prepared. Next, 10 parts by weight of glycerin as a dispersion accelerator is mixed with 300 parts by weight of the hydroxypropylcellulose solution.

  Furthermore, 75 parts by weight of an iron-carbon composite (a nanoflake carbon tube partially containing iron carbide) obtained in the same manner as in Reference Example 2 described above is mixed and kneaded to obtain a preliminary mixture.

  Finally, the preliminary mixture was kneaded with three rolls to obtain the nanoscale carbon tube paste of the present invention.

Example 2
First, an ethoxyethanol / α-terpineol (ethoxyethanol / terpineol = 1/1 weight ratio) solution containing 5% by weight of nitrocellulose as a binder is prepared. Next, 5 parts by weight of diglycerin as a dispersion accelerator and 50 parts by weight of Ag (silver) fine particles (average particle size: 3 μm) as conductive fine particles are sequentially mixed with 100 parts by weight of the nitrocellulose solution.

  Furthermore, 140 parts by weight of the amorphous nanoscale carbon tube obtained in the same manner as in Reference Example 1 is mixed with the obtained mixture to prepare a premix.

  Finally, the premixed article was kneaded with three rolls to obtain the nanoscale carbon tube paste of the present invention.

Example 3
First, a cyclohexanone-methyl ethyl ketone mixed solution (cyclohexanone / methyl ethyl ketone = 1/1 weight ratio) containing 5% by weight of polyvinyl butyral as a binder is prepared.

  Next, 10 parts by weight of glycerin as a dispersion accelerator and 37.5 parts by weight of Ag (silver) fine particles (average particle size: 3 μm) as conductive fine particles are sequentially mixed with 300 parts by weight of the polyvinyl butyral solution.

  Further, 37.5 parts by weight of an iron-carbon composite (a nano-flake carbon tube partially encapsulated with iron carbide) obtained in the same manner as in Reference Example 2 was mixed with the obtained mixture to prepare a preliminary mixture. .

  Finally, the premixed article was kneaded with three rolls to obtain the nanoscale carbon tube paste of the present invention.

Comparative Examples 1-3
Comparative pastes (Comparative Examples 1 to 3) were obtained in the same manner as in Examples 1 to 3 except that no dispersion accelerator was used.

Test example 1
(i) A 5 mm × 5 mm × 80 μm film formation precursor (that is, a wet coating film) was formed from the pastes obtained in Examples 1 to 3 using a doctor blade.

  This was fired at 500 ° C. in an argon atmosphere to form an electron emission source including an electron emission material layer including a nanoscale carbon tube on the ITO film on the glass substrate.

Next, as shown in FIG. 8, the electron emission source 500 composed of the electron emission material layer 502 obtained above and the glass substrate 501 having the ITO coating is opened in the vacuum chamber 510 by opening the sample introduction door 520 of the vacuum chamber 510. The sample introduction door 520 was closed and suction was performed using the molecular turbo pump 540 and the rotary pump 550, and the pressure in the vacuum chamber was adjusted to 5 × 10 ⁻⁶ Pa.

Next, the current-voltage characteristics were evaluated. In the evaluation, the ITO side of the electron emission source 500 is the cathode, the upper electrode 560 is the anode, the distance between the cathode and the anode is 300 μm, and the voltage is applied using the current-voltage applying device 530 in increments of 5V to 0 to 900V. The voltage was applied and the current value was monitored. An electric field value for obtaining an electron emission current density of 1 μA / cm ² was read from the obtained electric field-current density curve, and used as an electric field threshold value.

  (ii) The electric field threshold value was measured in the same manner as in the above (i) except that the pastes obtained in Comparative Examples 1 to 3 were used.

  Table 2 shows the results of the above tests (i) and (ii).

表２から明らかなように、分散促進剤を使用した実施例１〜３のペーストを用いて得られた電子放出源は電界閾値が小さく良好な電子放出特性を示した。これに対して、分散促進剤を使用することなく調製された比較例１〜３の比較ペーストを用いて得られた電子放出源は電界閾値が高く、比較例２及び比較例３では電子放出が認められず、電界閾値の測定ができなかった。

As is clear from Table 2, the electron emission sources obtained using the pastes of Examples 1 to 3 using a dispersion accelerator exhibited a small electron field threshold and good electron emission characteristics. On the other hand, the electron emission source obtained using the comparative pastes of Comparative Examples 1 to 3 prepared without using a dispersion accelerator has a high electric field threshold, and Comparative Examples 2 and 3 emit electrons. It was not recognized and the electric field threshold value could not be measured.

It is the schematic which shows an example of the manufacturing apparatus for manufacturing the iron-carbon composite used by this invention. 4 is a transmission electron microscope (TEM) photograph of one iron-carbon composite constituting the carbonaceous material obtained in Reference Example 2. FIG. 4 is a transmission electron microscope (TEM) photograph showing the existence state of an iron-carbon composite in the carbonaceous material obtained in Reference Example 2. 4 is an electron diffraction pattern of one iron-carbon composite obtained in Reference Example 2. FIG. 3 is an X-ray diffraction pattern of a carbonaceous material (an aggregate of iron-carbon composites) containing an iron-carbon composite obtained in Reference Example 2. FIG. 4 is a transmission electron microscope (TEM) photograph in which one iron-carbon composite obtained in Reference Example 2 is cut into a ring shape. The black triangle (三角) shown in the photograph of FIG. 6 indicates EDX measurement points for composition analysis. A schematic diagram of a TEM image of a carbon tube is shown, (a-1) is a schematic diagram of a TEM image of a cylindrical nanoflake carbon tube, and (a-2) is a TEM image of a multi-walled carbon nanotube with a nested structure. It is a schematic diagram. It is the schematic of the apparatus used for the measurement of the electric field threshold value in Test Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reactor 2 Heating apparatus 100 TEM image of nano flake carbon tube in longitudinal direction 110 Graph image of substantially straight graphene sheet 200 TEM image of cross section almost perpendicular to longitudinal direction of nano flake carbon tube 210 Arc-shaped graphene sheet image 300 Nested structure Linear graphene sheet image continuous over the entire length in the longitudinal direction of the multi-walled carbon nanotubes 400 TEM image of a cross section perpendicular to the longitudinal direction of the multi-walled carbon nanotubes with a nested structure 500 Electron emission source 501 Glass substrate with ITO coating 502 Electron emission material layer 510 Vacuum chamber 515 Valve 520 Sample introduction door 530 Current voltage application device 540 Molecular turbo pump 550 Rotary pump 560 Upper electrode

Claims (9)

A nanoscale carbon tube paste comprising a nanoscale carbon tube, a dispersion accelerator, a binder and a solvent. The dispersion accelerator is at least one of C3-12 polyhydric alcohols having 3 to 8 hydroxyl groups, and at least one boiling point constituting the dispersion accelerator is higher than the boiling point of the solvent. The nanoscale carbon tube paste according to claim 1, wherein the nanoscale carbon tube paste is characterized. The binder is at least one selected from phenol resin, epoxy resin, cellulose derivative, polyamide resin, vinyl resin, polyester resin, polyurethane resin and rubber resin, and the decomposition temperature of the binder is the nanoscale carbon tube The nanoscale carbon tube paste according to claim 1 or 2, wherein the nanoscale carbon tube paste is lower than a decomposition temperature of the nanoscale. 4. The nano according to claim 1, wherein the solvent is at least one selected from the group consisting of alcohols, esters, ketones, ethers, N, N-dimethylformamide, and N-methylpyrrolidone. Scale carbon tube paste. Nanoscale carbon tube
(i) Single-walled carbon nanotube
(ii) amorphous nanoscale carbon tube,
(iii) A carbon tube selected from the group consisting of a nano flake carbon tube and a multi-walled carbon nanotube with a nested structure
(iv) an iron-carbon composite comprising the carbon tube of (iii) above and iron carbide or iron, wherein iron carbide or iron is filled in a range of 10 to 90% of the space in the tube of the carbon tube; Or
(v) The nanoscale carbon tube paste according to any one of claims 1 to 4, which is a mixture of two or more of (i) to (iv). The dispersion accelerator is contained in 0.1 to 50 parts by weight, the binder is contained in 1 to 95 parts by weight, and the solvent is contained in 100 to 2000 parts by weight with respect to 100 parts by weight of the nanoscale carbon tube. Nanoscale carbon tube paste. The nanoscale carbon tube paste according to any one of claims 1 to 6, further comprising conductive particles. The nanoscale carbon tube paste according to claim 7, which contains 1 to 2000 parts by weight of conductive particles with respect to 100 parts by weight of the nanoscale carbon tube. (A) A substrate having at least a part of conductivity or a patterned substrate, and (B) a coating film of the nanoscale carbon tube paste according to any one of claims 1 to 8, which is formed on the substrate. An electron emission source provided with an electron emission material layer obtained by firing.

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