Electron emission source containing a high-density carbon structure-based film, method for manufacturing the same, and X-ray tube utilizing the same

Abstract

This application relates to a method for manufacturing a high-density carbon structure-based film, and may include a step of providing a carbon structure-based film, and a step of densifying a carbon structure-based film, which involves immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution to obtain a high-density carbon structure-based film, or immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent to obtain a high-density carbon structure-based film.

Description

Technical Field

[0001] The present invention relates to an electron emission source including a film based on a high-density carbon structure, a method for manufacturing the same, and an X-ray tube using the same.

Background Art

[0002] Generally, a cold cathode X-ray source applies a voltage to a gate electrode to extract an electron beam from a carbon nanotube electron emission source, and then focuses the electron beam at a high density through a focusing electrode and guides it to an anode electrode. At this time, when a high voltage is applied between the cathode electrode and the anode electrode, electrons are accelerated in the direction of the anode electrode and strongly collide with the anode electrode, thereby generating X-rays from the anode electrode.

[0003] In conventional cold cathode electron emission, carbon nanotubes are mainly used as an electron emission source. The carbon nanotubes are mixed with a conductive organic substance to form a paste and manufactured as an electron emission source. However, such a carbon nanotube paste electron emission source may be contaminated by unnecessary organic substances in the manufacturing process, and it is very difficult to orient the carbon nanotubes in the vertical direction. Furthermore, the carbon nanotube paste electron emission source has a problem that the field emission characteristics are greatly reduced due to the ionization phenomenon of gas molecules generated by the organic substances remaining in the paste during operation, and the life of the carbon nanotubes that emit electrons is shortened.

[0004] Also, in conventional cold cathode X-ray sources, a metal mesh or a metal hole is mainly used as a gate electrode. In this case, there is a problem that the transmission efficiency of electrons passing through the gate electrode is reduced. On the other hand, the present invention proposes a method for improving the transmission efficiency of electrons by using a gate electrode having a narrow slit shape.

[0005] In this regard, Korean Registered Patent No. 10-1239395 (Title of Invention: Field Emission Source, Element Using the Same, and Method for Manufacturing the Same) discloses a field emission source having a stable electron-emitting material support structure, a field emission element using the same, and a method for manufacturing the same. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention relates to an electron emission source comprising a film based on a high-density carbon structure, a method for manufacturing the same, and an X-ray source utilizing the same.

[0007] The present invention aims to solve the problems of the prior art described above, and some embodiments of the present invention aim to provide an electron emission source in which a carbon structure-based film is densified in order to improve the stability of the carbon structure-based film used as an electron emission source and to improve the electron emission performance, a method for manufacturing the same, and an X-ray source utilizing the same.

[0008] Furthermore, the aim is to provide an X-ray source that improves the transmission efficiency of the electron beam by using a slit-shaped gate electrode.

[0009] However, the problems that the present invention aims to solve are not limited to those described above, and other problems not described can be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0010] A first aspect of the present invention provides a method for producing a high-density carbon structure-based film, comprising the steps of providing a carbon structure-based film and a step of densifying the carbon structure-based film, which involves immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution to obtain a high-density carbon structure-based film, or immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent to obtain a high-density carbon structure-based film.

[0011] A second aspect of the present invention provides a high-density carbon structure-based film produced by a method for producing a high-density carbon structure-based film, which includes the steps of: providing a carbon structure-based film; and immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution to obtain a high-density carbon structure-based film, or immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent to obtain a high-density carbon structure-based film.

[0012] A third aspect of the present invention provides a method for manufacturing a carbon structure substrate electron emission source, comprising the steps of: providing a carbon structure-based film; immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution to obtain a high-density carbon structure-based film, or immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent to obtain a high-density carbon structure-based film; and fixing the carbon structure-based film, which is placed between at least two conductive metal members, by lateral pressure.

[0013] A fourth aspect of the present invention provides an X-ray tube comprising a tube housing having a space formed inside, a cathode housed within the tube housing and positioned at one end of the tube housing, an anode housed within the tube housing and positioned at the other end of the tube housing so as to face the cathode, wherein the cathode comprises a base material portion, a carbon structure substrate electron emission source positioned above the base material portion and bonded to a linearly cut carbon structure-based film, a gate electrode having a slit formed to expose the carbon structure substrate electron emission source, and a focusing lens positioned between the gate electrode and the anode. [Effects of the Invention]

[0014] Among the means for solving the problems of the present invention described above, by using the method for manufacturing a carbon structure substrate electron emission source, it is possible to achieve strong bonding forces within the nanomaterial and strong adhesion between the nanomaterial thin film emitter and the cathode electrode without using pastes or other adhesives containing organic matter. As a result, unlike nanomaterials that use pastes or other adhesives, the present invention can eliminate various electrical arc phenomena and instabilities caused by ion generation by organic matter, making it possible to produce an X-ray source with high field emission efficiency and excellent lifetime characteristics.

[0015] Furthermore, among the means for solving the problems of the present invention described above, using a gate electrode with a slit shape having a thin gap has the advantage of increasing the transmittance of the electron beam to the gate electrode and obtaining an electron beam focusing effect at the anode electrode. [Brief explanation of the drawing]

[0016] [Figure 1a] This is a flowchart relating to a method for manufacturing a high-density carbon structure-based film according to an embodiment of the present invention. [Figure 1b] This is a flowchart relating to a method for manufacturing a high-density carbon structure-based film according to an embodiment of the present invention. [Figure 2]It is a schematic diagram showing the principle of densifying a carbon nanotube film according to an embodiment of the present invention by immersing it in an acidic aqueous solution. [Figure 3] It is a schematic diagram showing the principle of densifying a carbon nanotube film according to an embodiment of the present invention by immersing it in a polar solvent. [Figure 4] It is a schematic diagram showing the principle of densifying a carbon nanotube film according to an embodiment of the present invention by immersing it in a solvent containing a benzene ring. [Figure 5] It is a cross-sectional view showing an X-ray tube using a carbon structure substrate electron emission source according to an embodiment of the present invention. [Figure 6] It is a diagram showing a carbon structure substrate electron emission source according to an embodiment of the present invention. [Figure 7] It is a diagram showing a carbon structure substrate electron emission source according to an embodiment of the present invention. [Figure 8] It is a diagram showing a manufacturing photograph of an X-ray tube according to an embodiment of the present invention. [Figure 9] (a) and (b) are diagrams showing a focusing lens according to an embodiment of the present invention. [Figure 10] (a) to (h) respectively show the state of an electron beam movement path (a - b), electron beam focusing (c), focusing lens shape (d), and voltage distribution (e to h) according to the shape of a focusing lens according to an embodiment of the present invention. [Figure 11] (a) to (h) respectively show the state of an electron beam movement path (a - b), electron beam focusing (c), focusing lens shape (d), and voltage distribution (e to h) according to the shape of a focusing lens according to another embodiment of the present invention. [Figure 12] It is a diagram for explaining the operating characteristics of a cold cathode X-ray tube according to an embodiment of the present invention. [Figure 13] It is a diagram showing an X-ray tube using a carbon structure substrate electron emission source according to another embodiment of the present invention. [Figure 14] It is a diagram showing an X-ray tube using a carbon structure substrate electron emission source according to another embodiment of the present invention. [Figure 15]A diagram showing an X-ray tube using a carbon structure substrate electron emission source according to another embodiment of the present invention. [Figure 16] A diagram showing the detailed configuration of an X-ray tube according to an embodiment of the present invention. [Figure 17] A diagram showing the detailed configuration of an X-ray tube according to an embodiment of the present invention. [Figure 18] A diagram showing the detailed configuration of an X-ray tube according to an embodiment of the present invention. [Figure 19] A diagram showing the detailed configuration of a cathode according to an embodiment of the present invention. [Figure 20] A diagram showing the detailed configuration of a cathode according to an embodiment of the present invention. [Figure 21] A diagram showing the detailed configuration of a cathode according to an embodiment of the present invention. [Figure 22] A diagram showing the detailed configuration of a cathode according to an embodiment of the present invention. [Figure 23] A diagram showing the detailed configuration of a cathode according to an embodiment of the present invention. [Figure 24] A diagram showing the detailed configuration of a cathode according to another embodiment of the present invention. [Figure 25] A diagram showing the detailed configuration of a cathode according to another embodiment of the present invention. [Figure 26] A diagram showing the detailed configuration of a cathode according to another embodiment of the present invention. [Figure 27] A diagram showing the connection structure of electrode pins in an X-ray tube according to an embodiment of the present invention. [Figure 28] A diagram showing an X-ray tube according to another embodiment of the present invention. [Figure 29] A diagram showing the connection structure of electrode pins in an X-ray tube according to another embodiment of the present invention. [Figure 30] A photograph related to the test result of an X-ray image of an X-ray tube according to an embodiment of the present invention. [Figure 31] (a) and (b) are schematic diagrams showing the principle of a two-step carbon nanotube film densification process. [Figure 32](a) to (d) are scanning electron microscope (SEM) images of the cross-sectional thickness of carbon nanotube films that have not undergone the densification process, carbon nanotube films that have been densified with a polar solvent (ethylene carbonate), carbon nanotube films that have been densified with an acidic aqueous solution (acetic acid), and carbon nanotube films that have been densified with a polar solvent (ethylene carbonate, 1 step) and an acidic aqueous solution (acetic acid, 5M, 2 steps), respectively. [Figure 33] This graph shows the triode field electron emission characteristics of carbon nanotube thin-film emitters using carbon nanotube films that have not undergone a densification process, carbon nanotube films that have been densified with a polar solvent (ethylene carbonate), carbon nanotube films that have been densified with an acidic aqueous solution (acetic acid), and carbon nanotube films that have been densified with a polar solvent (ethylene carbonate, 1 step) and an acidic aqueous solution (acetic acid, 5M, 2 steps). [Figure 34] This graph shows the triode field electron emission characteristics of carbon nanotube thin-film emitters using carbon nanotube films that have not undergone a densification process, carbon nanotube films that have been densified with a polar solvent (ethylene carbonate), carbon nanotube films that have been densified with an acidic aqueous solution (acetic acid), and carbon nanotube films that have been densified with a polar solvent (ethylene carbonate, 1 step) and an acidic aqueous solution (acetic acid, 5M, 2 steps). [Figure 35]This graph shows the triode field electron emission characteristics of carbon nanotube thin-film emitters using carbon nanotube films that have not undergone a densification process, carbon nanotube films that have been densified with a polar solvent (ethylene carbonate), carbon nanotube films that have been densified with an acidic aqueous solution (acetic acid), and carbon nanotube films that have been densified with a polar solvent (ethylene carbonate, 1 step) and an acidic aqueous solution (acetic acid, 5M, 2 steps). [Figure 36] This graph shows the triode field electron emission characteristics of carbon nanotube thin-film emitters using carbon nanotube films that have not undergone a densification process, carbon nanotube films that have been densified with a polar solvent (ethylene carbonate), carbon nanotube films that have been densified with an acidic aqueous solution (acetic acid), and carbon nanotube films that have been densified with a polar solvent (ethylene carbonate, 1 step) and an acidic aqueous solution (acetic acid, 5M, 2 steps). [Figure 37] This table compares the triode field electron emission characteristics of carbon nanotube thin-film emitters using carbon nanotube films that have not undergone a densification process, carbon nanotube films that have been densified with a polar solvent (ethylene carbonate), carbon nanotube films that have been densified with an acidic aqueous solution (acetic acid), and carbon nanotube films that have been densified with a polar solvent (ethylene carbonate, 1 step) and an acidic aqueous solution (acetic acid, 5M, 2 steps). [Modes for carrying out the invention]

[0017] Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings, so that those skilled in the art in which the present invention pertains can easily implement it. However, the present invention can be implemented in various different forms and is not limited to the embodiments and examples described herein. Furthermore, in order to clearly illustrate the present invention, parts that are not relevant to the description have been omitted from the drawings, and the same reference numerals are used for similar parts throughout the specification.

[0018] Throughout this specification, when a part is referred to as being "connected" to another part, this includes not only cases where it is "directly connected" but also cases where it is "electrically connected" to another part via other elements.

[0019] Throughout this specification, when a member is described as being "on top of" another member, this includes not only cases where the member is in contact with another member, but also cases where another member exists between the two members.

[0020] Throughout this specification, where a part is described as "containing" a component, unless otherwise stated, this does not exclude other components, but rather means that other components may be further included.

[0021] Terms used herein to indicate degree, such as “about” and “substantially,” mean a range from or close to a given numerical value, where there are inherent manufacturing and material tolerances inherent in the stated meaning, and are used to prevent unauthorized infringers from unfairly exploiting disclosures that contain specific or absolute numerical values ​​to aid in understanding the invention.

[0022] As used throughout this specification, the terms “process from” or “process from” do not mean “process for from.”

[0023] Throughout this specification, the term “these combinations” as used in any expression in Markush form means one or more mixtures or combinations selected from the components described in the expression in Markush form, and includes one or more of those components.

[0024] Throughout this specification, the phrase "A and / or B" means "A or B, or A and B."

[0025] Throughout this specification, the terms "film," "thin film," and "membrane" may be used interchangeably.

[0026] Throughout this specification, both "densification" and "densification" may be used to mean increasing the density of a carbon structure-based film.

[0027] Although embodiments of the present invention have been described in detail above, the present invention is not limited thereto.

[0028] A first aspect of the present invention provides a method for producing a high-density carbon structure-based film, comprising the steps of providing a carbon structure-based film and a step of densifying the carbon structure-based film, which involves immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution to obtain a high-density carbon structure-based film, or immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent to obtain a high-density carbon structure-based film.

[0029] In one embodiment of the present invention, the process of obtaining a high-density carbon structure-based film can be carried out in the following order.

[0030] (1) A first densification step of immersing a carbon structure-based film in a polar solvent to obtain a carbon structure-based film that has been primary densified, and a second densification step of immersing the primary densified carbon structure-based film in an acidic aqueous solution to obtain a carbon structure-based film that has been secondary densified, or (2) A first densification step of obtaining a carbon structure-based film that has been primary densified by immersing the carbon structure-based film in an acidic aqueous solution, and a second densification step of obtaining a carbon structure-based film that has been secondary densified by immersing the primary densified carbon structure-based film in a polar solvent.

[0031] In this case, when a carbon structure-based film is first immersed in an acidic aqueous solution and then immersed in a polar solvent, the ionization of the carbon structure-based film surface by the acidic aqueous solution relatively reduces the effectiveness of the subsequent densification process using the polar solvent. Therefore, by performing the process of first immersing the carbon structure-based film in a polar solvent and then immersing it in an acidic aqueous solution, a better densification effect can be obtained.

[0032] In one embodiment of the present invention, the densification step of a carbon structure-based film may include immersing the carbon structure-based film in an acidic aqueous solution, then immersing it in a polar solvent, washing it with deionized water, and drying it.

[0033] In one embodiment of the present invention, the densification step of a carbon structure-based film may include immersing the carbon structure-based film in a polar solvent, then immersing it in an acidic aqueous solution, washing it with deionized water, and drying it.

[0034] In one embodiment of the present invention, the carbon structure may be one or more selected from carbon nanotubes, graphene, nanocarbon, and carbon nanowires. In one embodiment of the present invention, the carbon structure may be carbon nanotubes. Here, the carbon nanotubes may include one or more selected from single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0035] In one embodiment of the present invention, the polar solvent may be an aprotic solvent.

[0036] In one embodiment of the present invention, the dipole moment of the polar solvent may be about 2D or more, or about 2.2D or more.

[0037] The densification process for a carbon structure-based film according to one embodiment of the present invention is required to produce a stable carbon structure-based film. A carbon structure-based film exhibits a structure in which countless carbon structures are bonded together by van der Waals forces, and the magnitude of the van der Waals forces acting between different carbon structures increases as the distance between carbon structures decreases. Therefore, in order to produce a stable carbon structure-based film, a densification process that reduces the distance between individual carbon structures is essential. Here, there are three main methods for reducing the distance between individual carbon structures.

[0038] (1) High-density production of carbon structure-based films (especially carbon nanotube films) by direct protonation. Referring to Figure 2, when a carbon structure-based film is immersed in an acidic aqueous solution, a hydrogenation phenomenon can occur in which hydrogen ions bind to the surface of individual carbon structures. When hydrogen ions bind to the surface of the carbon structures, the hydrogen ions bound to the surface temporarily weaken the van der Waals attractive forces acting between the carbon structures, rearranging the carbon structures within the thin film. Subsequently, when the hydrogen ions rapidly detach during the washing process, the carbon structure-based film may shrink due to the difference in hydrogen ion concentration, leading to an increase in the density of the carbon structure-based film. Here, water molecules present in the aqueous solution combine with the hydrogen ions to form H3O. + By forming a defect, the hydrogenation of the carbon structure is inhibited. Therefore, the lower the pH of the acidic aqueous solution, the greater the number of hydrogen ions, and the more likely the hydrogenation phenomenon is to occur. On the other hand, the more defects there are on the outer wall of the carbon structure, the smoother the bonding of hydrogen ions occurs, and the more the hydrogenation phenomenon is promoted.

[0039] (2) High-density production of carbon structure-based films (especially carbon nanotube films) by dipole-induced dipole attraction. Referring to Figure 3, when a carbon structure-based film is immersed in a polar solvent, induced dipoles are formed on the carbon structure surface by polar solvent molecules. When a voltage is applied, the polar molecules orient themselves in a specific direction, forming uniform induced dipoles on the carbon structure-based film surface. In the subsequent washing process, the polar molecules are removed, and the density of the carbon structure-based film proceeds due to the action of the induced dipoles. Therefore, when densifying a carbon structure-based film using a polar solvent, it is necessary for the polar solvent to have a high dipole moment and low surface tension to facilitate the penetration of polar molecules. For example, polar protic solvents with hydrogen bonds generally have high surface tension, making uniform penetration into the carbon nanotube substrate film difficult and resulting in a low density-enhancing effect. Therefore, polar aprotic solvents may be more suitable in some cases.

[0040] (3) High-density formation of carbon structure-based films (especially carbon nanotube films) through π-π interactions. Referring to Figure 4, in the case of a substance containing a benzene ring, the electrons in the p-orbitals of the benzene ring interact with the electrons in the p-orbitals of the carbon structure, forming a π-π attraction. This π-π attraction reduces the distance between carbon structures within the carbon structure-based film, resulting in increased density of the carbon structure-based film. Similarly, in this case, a low surface tension value of the solution is desirable.

[0041] Therefore, as mentioned above, selecting an appropriate solvent for densifying carbon structure-based films is extremely important, and it is desirable to use a combination of a polar aprotic solvent that has a high dipole moment, does not form hydrogen bonds, and has low surface tension, and an acidic aqueous solution in which many molecules can be ionized in aqueous solution to generate a large number of hydrogen ions.

[0042] Specifically, the polar solvent used in the process of obtaining the high-density carbon structure-based film according to the present invention can be determined by considering a solvent that has a relatively high dipole moment, does not form hydrogen bonds, and has a relatively low surface tension.

[0043] [Table 1]

[0044] Furthermore, the acidic aqueous solution used in the process of obtaining a high-density carbon structure-based film according to the present invention can be determined by considering the following: (1) As the above acidic aqueous solution, a strong acid aqueous solution can be used in which most molecules are ionized in the aqueous solution state and a large amount of hydrogen ions are generated. However, if the molar concentration of the strong acid aqueous solution is too high, the crystallinity of the carbon structure may decrease, so it is important to adjust it to an appropriate concentration.

[0045] (2) In addition, as the above-mentioned acidic aqueous solution, an aliphatic carboxylic acid that is a weak acid but also polar can be used. In aqueous solution, a portion of the aliphatic carboxylic acid ionizes to generate hydrogen ions, and the remaining large amount of carboxylic acid molecules that are not ionized exist as polar molecules. Therefore, the densification effect of the carbon structure-based film due to hydrogen ions and the densification effect of the carbon structure-based film due to polar molecules can be obtained simultaneously. For example, a 5M aqueous acetic acid solution generates hydrogen ions at a pH of about 2. Furthermore, acetic acid has a very low surface tension of about 0.027 N / m and a dipole moment value of about 1.7 D, so it can effectively penetrate into the carbon nanotube film and induce densification of the carbon nanotube film.

[0046] (3) In the case of aromatic carboxylic acids, they are weak acids and polar, and at the same time, they have a benzene ring. That is, in aqueous solution, some aromatic carboxylic acids ionize to produce hydrogen ions, while the remaining large amount of carboxylic acid molecules that are not ionized exist as polar molecules with a benzene ring. Therefore, aromatic carboxylic acids can obtain all of the following effects on the density of carbon structure-based films: the density of carbon structure-based films due to hydrogen ions, the density of carbon structure-based films due to polar molecules, and the density of carbon structure-based films due to π-π interactions. However, in the case of aromatic carboxylic acids, because they have a benzene ring, the maximum molar concentration that can exist in aqueous solution is limited. For example, salicylic acid can dissolve in water up to a maximum of about 0.45 M at a temperature of 95°C.

[0047] [Table 2]

[0048] In one embodiment of the present invention, the polar solvent may include, but is not limited to, one or more selected from heteroaromatics, ketones, carbonates, ethers, esters, acetonitrile, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide (DMAc), and hexamethylphosphoramide (HMPA). For example, the polar solvent may include one or more selected from pyridine, acetone, ethylene carbonate, propylene carbonate, tetrahydrofuran (THF), methyl acetate, ethyl acetate, acetonitrile, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide (DMAc), and hexamethylphosphoramide (HMPA).

[0049] In one embodiment of the present invention, the acidic aqueous solution may contain one or more selected from hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, salicylic acid, and benzoic acid. In one embodiment of the present invention, the acidic aqueous solution may be acetic acid. In one embodiment of the present invention, the concentration of the acidic aqueous solution can be optimized depending on the type of acid. In one embodiment of the present invention, the concentration of the acidic aqueous solution may be from about 0.1 M to about 10 M. For example, the concentration of the acidic aqueous solution may be from about 0.1 M to about 10 M, from about 0.1 M to about 8 M, or from about 0.1 M to about 5 M. As a non-limiting example, when an inorganic acid, such as a strong acid like nitric acid, hydrochloric acid, or sulfuric acid, is used as the acidic aqueous solution, about 3 M may be preferred; when an aliphatic carboxylic acid such as acetic acid or formic acid is used, about 5 M may be preferred; and when an aromatic carboxylic acid such as salicylic acid or benzoic acid is used, about 0.4 M to about 0.5 M, or about 0.45 M may be preferred.

[0050] In one embodiment of the present invention, the carbon structure-based film may be produced by a step of mixing and dispersing distilled water, sodium dodecyl sulfate (SDS), and a carbon structure, and a step of filtering the mixed solution through an anodic aluminum oxide membrane (AAO membrane) and drying it into a film. The carbon structure may be one or more selected from carbon nanotubes, graphene, nanocarbon, and carbon nanowires. In one embodiment of the present invention, the carbon structure may be carbon nanotubes. Here, the carbon nanotubes may include one or more selected from single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

[0051] For example, distilled water is mixed with SDS and carbon nanotubes, and the mixture is ultrasonically treated for approximately 50 to 65 minutes to disperse the mixture, followed by centrifugation for approximately 40 minutes. Subsequently, the mixture is filtered through an AAO membrane, allowing only distilled water to pass through, resulting in the carbon nanotubes being trapped and layered on the AAO membrane. At this time, each carbon nanotube becomes strongly entangled with others by van der Waals forces, and then the AAO membrane is removed using a sodium hydroxide solution or a carbon nanotube dispersion (CNT Solution) to form a carbon nanotube film.

[0052] In one embodiment of the present invention, a method for producing a high-density carbon structure-based film may further include a pretreatment step to remove a dispersant present in the provided carbon structure-based film. Here, the dispersant may be sodium dodecyl sulfate. In one embodiment of the present invention, the dispersant may be a dispersant that can be removed by washing with one or more solvents selected from ketones, alcohols, and water. Here, the ketones may be acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, ethyl propyl ketone, or dipropyl ketone, and the alcohols may be methanol, ethanol, propyl alcohol, isopropyl alcohol, butanol, pentanol, or hexanol. For example, the dispersant may be removed by washing with acetone or isopropyl alcohol.

[0053] In one embodiment of the present invention, the step of removing the dispersant may include (1) a method of removing the dispersant inside the carbon structure-based film by sequentially flowing acetone, isopropyl alcohol, and deionized water through the carbon structure-based film in a vacuum filtration step, or (2) a method of removing the dispersant by sequentially immersing the carbon structure-based film in deionized water and acetone after peeling the carbon structure-based film from the membrane.

[0054] In one embodiment of the present invention, one or more heat treatment steps may be further included before, after, or both before and after the densification step of the carbon structure-based film. Herein, the heat treatment may be performed to remove any solvent remaining in the carbon structure-based film.

[0055] In one embodiment of the present invention, the heat treatment step may be carried out in an atmospheric atmosphere or an inert gas (e.g., Ar) atmosphere.

[0056] In one embodiment of the present invention, the heat treatment step may be carried out in a temperature range of approximately 100°C to approximately 500°C, approximately 100°C to approximately 400°C, approximately 100°C to approximately 300°C, approximately 200°C to approximately 500°C, approximately 200°C to approximately 400°C, or approximately 200°C to approximately 300°C.

[0057] A second aspect of the present invention provides a high-density carbon structure-based film manufactured by a method for manufacturing a high-density carbon structure-based film, which includes the steps of providing a carbon structure-based film and a step of densifying the carbon structure-based film, which involves immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution to obtain a high-density carbon structure-based film, or immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent to obtain a high-density carbon structure-based film.

[0058] Detailed explanations of parts that overlap with the first aspect of the present invention will be omitted, but the content explained in relation to the first aspect will also apply in the same way even if the explanation is omitted in relation to the second aspect.

[0059] In one embodiment of the present invention, the thickness of the high-densification carbon structure-based film may be reduced by about 20% or more, or about 30% or more, compared to the thickness of the carbon structure-based film before high-densification.

[0060] In one embodiment of the present invention, the anodic current of the high-density carbon structure-based film may increase by approximately 25 mA or more, approximately 30 mA or more, or approximately 40 mA or more compared to the anodic current of the carbon structure-based film before high-density processing.

[0061] A third aspect of the present invention provides a method for manufacturing a carbon structure substrate electron emission source, comprising the steps of: providing a carbon structure-based film; immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution to obtain a high-density carbon structure-based film, or immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent to obtain a high-density carbon structure-based film; and fixing the carbon structure-based film, which is placed between at least two conductive metal members, by lateral pressure.

[0062] Detailed explanations of the parts that overlap with the first and second aspects of the present invention will be omitted, but the content explained with respect to the first and second aspects will also apply to the third aspect even if the explanation is omitted.

[0063] In one embodiment of the present invention, the method for manufacturing a carbon structure substrate electron emission source may further include a step of cutting the carbon structure-based film before or after the densification step.

[0064] In one embodiment of the present invention, the step of fixing a carbon structure-based film may include fixing the carbon structure-based film with the cut surface facing upwards.

[0065] A fourth aspect of the present invention relates to an X-ray tube and provides an X-ray tube comprising: a tube housing having a space formed inside; a cathode housed within the tube housing and positioned at one end of the tube housing, to which a linearly cut carbon structure-based film is coupled as an electron emission source; a gate electrode positioned above the cathode and having a slit formed to align with the carbon structure-based film; a focusing lens positioned above the gate electrode; and an anode housed within the tube housing and positioned at the other end of the tube housing facing the cathode.

[0066] Detailed explanations of parts that overlap with the first to third aspects of the present invention will be omitted, but the content explained in relation to the first to third aspects will also apply in the case where explanation is omitted in relation to the fourth aspect.

[0067] Figure 5 is a cross-sectional view of an X-ray tube using a carbon structure substrate electron emission source according to one embodiment of the present invention, and Figures 6 and 7 show the carbon structure substrate electron emission source according to one embodiment of the present invention.

[0068] Referring to Figure 5, the X-ray tube (10) using the carbon structure substrate electron emission source of the present invention includes a tube housing (100) with a space formed inside, a cathode (200) and an anode (300) arranged facing each other within the tube housing, and a gate electrode (400) and a focusing lens (500) arranged between the cathode (200) and the anode (300).

[0069] The tube housing (100) is a vacuum vessel that maintains a vacuum inside and may have a tubular shape. The tube housing (100) may be made of a glass tube or a ceramic tube. A cathode (200) is located at one end of the tube housing (100), and an anode (300) is located at the other end, facing the cathode (200). A window (110) from which X-rays are emitted may be formed on one side of the tube housing (100). The window (110) may be made of a beryllium (Be) thin film, an aluminum (Al) thin film, or glass, but is not limited to these. Furthermore, a getter (120) may be located below or above the cathode (200), or in an intermediate position, in order to maintain the vacuum state of the tube housing (100).

[0070] A cathode (200) is located at one end of a tube housing (100) and is coupled to a carbon structure substrate electron emission source (220) for electron emission. The cathode (200) includes a base portion (210) and a carbon structure substrate electron emission source (220) located on top of the base portion (210) and coupled to a linearly cut carbon structure base film. As shown in Figure 6, the carbon structure substrate electron emission source (220) includes a densified carbon structure base film (222) and conductive metal members (224) located on both sides of the carbon structure base film (222) to fix the film (222). The conductive metal members (224) have a recess (226) formed to a predetermined depth from the top surface (228), and the carbon structure base film (222) is positioned across the center of the recess (226). In this case, the height of the carbon structure-based film (222) is formed to be the same as or slightly lower than the depth of the recess (226), thereby further improving the electron emission characteristics of the carbon structure-based film (222). On the other hand, the conductive metal member (224) may be a structure in which a plurality of plate-shaped metal members are joined in parallel to each other, as shown in Figure 6(b), in order to fix the carbon structure-based film (222), or it may be configured in a form in which the carbon structure-based film (222) is inserted between the two metal members.

[0071] Furthermore, in some embodiments, as shown in Figure 7, multiple carbon structure-based films (222, 223) can be bonded to an electron emission source (220). In this case, multiple recesses (225, 226) are formed in the metal member (224) of the electron emission source (220), to which each carbon structure-based film (222, 223) is bonded. The recess depth of the recesses (225, 226) is formed to be the same as or slightly deeper than the height of each carbon structure-based film (222, 223).

[0072] A carbon structure substrate electron emission source (220) in which multiple carbon structure-based films are arranged in an array has the advantage that, compared to an embodiment including a single carbon structure-based film, the output current increases in proportion to the number of films with respect to the applied voltage.

[0073] On the other hand, the conductive metal member (224) of the carbon structure substrate electron emission source (220) may be grounded via the base material (210). Furthermore, an ammeter or current-voltage supply source may be further coupled between the conductive metal member (224) and ground for current measurement.

[0074] Referring again to Figure 5, the anode (300) is housed within the tube housing (100) and positioned opposite the cathode (200) at the other end of the tube housing (100). One side of the anode (300) facing the inside of the tube may be coupled to a target surface upon which electrons emitted from the carbon structure substrate electron emission source (220) collide. In this case, the end of the anode (300) is inclined at a predetermined angle, allowing adjustment of the X-ray emission angle. The voltage difference between the cathode (200) and the anode (300) accelerates electrons field-emitted from the carbon structure substrate electron emission source (220) toward the anode (300), where they collide with the target surface and emit X-rays. Exemplarily, the target surface may be composed of tungsten (W) or a tungsten alloy in close contact with the surface of a copper rod. A high voltage is also applied to the anode (300) for electron emission. On the other hand, in some embodiments, the anode (300) may be configured as a rotating electrode. Specifically, the anode (300) consists of a target provided on the rotating electrode, and a rotor (not shown) and a rotation axis (not shown) that support it. With this configuration, the target rotates when X-rays are generated, forming a circular track-shaped electron beam collision region, which enables the generation of high-power X-rays.

[0075] The gate electrode (400) is located above the cathode electrode (200) and may include at least one or more openings (410) at positions corresponding to the carbon structure-based film (222). The openings (410) may be formed in the shape of slits or holes. Furthermore, if the carbon structure-based film (222) is bonded in an array on the cathode electrode (200), the gate electrode (400) may include multiple openings (410).

[0076] A focusing lens (500) is positioned between the gate electrode (400) and the anode (300) to direct the electron beam toward the target plane of the anode (300). The gate electrode (400) and the focusing lens (500) may be supplied with different drive voltages (Vg, Vfl), or a common drive voltage may be applied.

[0077] Figure 8 shows a photograph of the fabrication of an X-ray tube according to one embodiment of the present invention.

[0078] As shown in the figure, a gate electrode (400) and a focusing lens (500) are fixed to a cathode (200) which includes a carbon structure substrate electron emission source (220). It can be confirmed that a slit corresponding to the carbon structure base film is formed in the gate electrode (400). It can also be confirmed that the anode (300) is configured as a rotating electrode. Here, the anode (300) may be a fixed electrode or a rotating electrode.

[0079] Figure 9 shows the electron beam focusing characteristics based on a focusing lens shape according to one embodiment of the present invention, and Figures 10(a) to (h) and 11(a) to (h) show the electron beam movement path, electron beam focusing form, and potential distribution state according to the focusing lens shape according to one embodiment of the present invention, respectively.

[0080] As shown in Figures 9(a) and (b), the outer surface (520) of the focusing lens may be formed in an elliptical or circular shape. The aperture (510) of the focusing lens may be curved and generally formed in an elliptical shape.

[0081] Furthermore, as shown in the embodiment of Figure 9(a), the upper surface (530) of the focusing lens may be formed in a planar shape, but it may also be formed in a curved shape as shown in Figure 9(b).

[0082] First, referring to the embodiment in Figure 9(a), the outer surface (520) of the focusing lens is formed in an elliptical or circular shape, the opening (510) is curved and generally elliptical, and the top surface (530) is formed in a planar shape.

[0083] Figure 10 shows the simulation results of the electron beam trajectory and potential distribution when the focusing lens shape in the embodiment of Figure 9(a) is applied. Figures 10(a) and (b) are side cross-sectional views of the electron beam trajectory from the carbon structure-based film (222) to the anode (300). Specifically, (a) shows a cross-sectional view in the direction (x) perpendicular to the longitudinal direction of the aperture (510) of the focusing lens, and (b) shows a cross-sectional view in the longitudinal direction (y) of the aperture (510). As can be seen in Figures 10(a) and (b), the height (z) of the focusing lens is the same in both cases.

[0084] Figure 10(c) shows a plan view of the focusing lens and the electron beam focusing state, and Figure 10(d) shows the component forms and assembly method of the substrate, carbon structure substrate electron emission source, gate electrode and focusing lens.

[0085] Figure 10(e) is a side cross-sectional view showing the potential distribution between the focusing lens (500) and the anode (300) (cross-section in the direction (x) perpendicular to the longitudinal direction of the aperture (510) of the focusing lens), and Figure 10(f) is a side cross-sectional view showing the potential distribution between the focusing lens (500) and the anode (300) (cross-section in the longitudinal direction (y) of the aperture (510).

[0086] Figure 10(g) is a side cross-sectional view (cross-section in the direction perpendicular to the longitudinal direction (x) of the aperture (510)) showing the potential distribution between the carbon structure substrate electron emission source (220) and the focusing lens (500), and Figure 10(h) is a side cross-sectional view (cross-section in the longitudinal direction (y) of the aperture (510)) showing the potential distribution between the carbon structure substrate electron emission source (220) and the focusing lens (500).

[0087] Next, referring to the embodiment in Figure 9(b), the outer surface (520) of the focusing lens is formed in an elliptical or circular shape, the opening (510) is curved and generally elliptical, and the top surface (530) is curved.

[0088] Figure 11 shows the simulation results of the electron beam trajectory and potential distribution in the embodiment when the focusing lens shape according to the embodiment of Figure 9(b) is applied. Figures 11(a) and (b) are side cross-sectional views of the electron beam trajectory from the carbon structure substrate electron emission source (220) to the anode (300). Specifically, (a) shows a cross-sectional view cut in the direction (x) perpendicular to the longitudinal direction of the aperture (510) of the focusing lens, and (b) shows a cross-sectional view cut in the longitudinal direction (y) of the aperture (510) of the focusing lens. As shown in Figures 11(a) and (b), it can be seen that the height (z) of the focusing lens increases towards the end of the x-axis. That is, the height of the upper surface of the focusing lens gradually increases along the longitudinal direction of the aperture (510) or the direction perpendicular to the extension direction of the carbon structure base film, and is formed so that the height of each end (540, 550) of the upper surface is maximized.

[0089] Figure 11(c) shows a plan view of the focusing lens and the electron beam focusing state, and (d) shows the component forms and assembly method of the substrate, carbon structure substrate electron emission source, gate electrode and focusing lens.

[0090] Figure 11(e) is a side cross-sectional view showing the potential distribution between the focusing lens (500) and the anode (300) (a cross-section cut perpendicular to the longitudinal direction (x) of the aperture (510) of the focusing lens), and (f) is a side cross-sectional view showing the potential distribution between the focusing lens (500) and the anode (300) (a cross-section cut perpendicular to the longitudinal direction (y) of the aperture (510) of the focusing lens).

[0091] Figure 11(g) is a side cross-sectional view showing the potential distribution between the carbon structure substrate electron emission source (220) and the focusing lens (500) (a cross-section cut perpendicular to the longitudinal direction (x) of the aperture (510) of the focusing lens), and (h) is a side cross-sectional view showing the potential distribution between the carbon structure substrate electron emission source (220) and the focusing lens (500) (a cross-section cut perpendicular to the longitudinal direction (y) of the aperture (510) of the focusing lens).

[0092] Comparing the embodiments in Figures 10 and 11, it can be seen that when the upper surface of the focusing lens is formed as a curved surface, the electron beam focal point is formed to be relatively small, as shown in Figure 11(a). Furthermore, comparing Figures 10(a), 11(a), 10(b), and 11(b), it can be seen that the electron beam is more concentrated in the direction (x) intersecting the length of the aperture compared to the longitudinal direction (y) of the aperture.

[0093] Figure 12 is a diagram illustrating the operating characteristics of an X-ray tube according to one embodiment of the present invention.

[0094] As shown in the figure, when a voltage is applied to the gate electrode (400) in the form of a voltage pulse, it can be confirmed that X-rays in the form of a digital pulse are output accordingly. In particular, if a uniform pulse voltage at an appropriate level is applied to the gate electrode (400), a constant dose of X-rays is emitted immediately and rapidly, and when the voltage application is stopped, the generation of X-rays can be instantly shut off. This makes it possible to easily and accurately control the generation time and dose of X-rays.

[0095] Thus, unlike conventional analog X-ray tubes, the cold cathode X-ray tube of the present invention enables digital X-ray tube drive.

[0096] Figures 13 to 15 show an X-ray tube using a carbon structure-based film according to another embodiment of the present invention, and Figures 16 to 22 show a detailed configuration of an X-ray tube including a cathode, electron emission source, gate electrode, and focusing lens according to one embodiment of the present invention.

[0097] Figure 13 is a cross-sectional view of the X-ray tube (1000), Figure 14 is a perspective view of the X-ray tube (1000) from above, and Figure 15 is a perspective view of the X-ray tube (1000) from below.

[0098] Referring to Figure 13, the X-ray tube (1000) using a carbon structure-based film of the present invention includes a tube housing (1100) with a space formed inside, a cathode (1200) and an anode (1500) arranged facing each other within the tube housing (1100), and a gate electrode (1300) and a focusing lens (1400) arranged between the cathode (1200) and the anode (1500).

[0099] The tube housing (1100) is a vacuum vessel that maintains a vacuum inside and may have a tubular shape. The tube housing (1100) may be composed of a glass tube or a ceramic tube. In a configuration housed within the tube housing (1100), a cathode (1200) is positioned at one end of the tube housing (1100), and an anode (1500) is positioned at the other end so as to face the cathode (1200). Furthermore, a window (not shown) from which X-rays are emitted may be formed on one side of the tube housing (1100). In addition, a getter (1140) may be positioned below the cathode (1200) along the inner circumference to maintain the vacuum state of the tube housing (1100).

[0100] An anode (1500) is bonded to the upper part of the tube housing (1100). The anode (1500) may be formed by adjusting its diameter so as to partially cover the upper opening of the tube housing (1100) or to cover the entire upper opening. A first adapter ring (1110) is bonded between the anode (1500) and the tube housing (1100). The first adapter ring (1110) can compensate for the difference in thermal expansion coefficients between the anode (1500) and the tube housing (1100) and prevent damage to the tube housing (1100). The tube housing (1100) may generally be made of ceramic (e.g., Al2O3), and the first adapter ring (1110) may be made of Kovar material, which has a thermal expansion coefficient similar to that of ceramic. In this invention, copper can be used as the anode (1500) to improve electrical and thermal conductivity. However, when copper and ceramic are brazed together at high temperatures and then cooled, the ceramic may break due to the difference in thermal expansion coefficients between copper and ceramic. To solve this problem, a first adapter ring (1110) is placed between the anode (1500) and the tube housing (1100), and the anode (1500) and the first adapter ring (1110) are brazed together, and the first adapter ring (1110) and the tube housing (1100) are also brazed together.

[0101] Figure 16 shows a detailed configuration of an X-ray source including a cathode, electron emission source, gate electrode, and focusing lens according to one embodiment of the present invention; Figure 17 is a cross-sectional view of the X-ray source according to one embodiment of the present invention, cut in the y-axis direction; and Figure 18 is a cross-sectional view of the X-ray source according to one embodiment of the present invention, cut in the x-axis direction.

[0102] The cathode (1200) is housed within the tube housing (1100) and may be positioned in a groove located at one end of the tube housing (1100), more specifically on the upper side of the bottom surface (1130). A carbon structure-based film (1210) for electron emission is bonded to the cathode (1200). In the embodiment described in Figure 29, a Kovar metal bottom surface (1130) is used, and a ceramic substrate (1150) is separately placed to insulate the bottom surface (1130) from the cathode (1200), gate electrode (1300), and focusing lens (1400). However, as shown in Figure 16, when a ceramic bottom surface (1130) is used, the cathode (1200), gate electrode (1300), and focusing lens (1400) may be directly bonded to the top of the bottom surface (1130).

[0103] Furthermore, a gate electrode (1300) is positioned above the cathode (1200), with a slit (1310) formed therein that exposes a carbon structure-based film (1210). The gate electrode (1300) may be formed in a leg-like shape, with its main body supported by support parts (1320, 1330) at both ends, as shown in Figure 8. The cathode (1200) can be positioned in the space formed by the support parts (1320, 1330) of the gate electrode (1300).

[0104] Furthermore, a focusing lens (1400) is positioned on the upper side of the gate electrode (1300). The focusing lens (1400), as also shown in Figure 8 or Figure 9, includes an upper surface (1440) supported by support portions (1420, 1430) at both ends, with an opening (1410) formed in the center of the upper surface (1440). The outer circumferential surface of the upper surface (1440) may be formed in the shape of an ellipse, a circle, or a rectangle with rounded corners. In this way, the cathode (1200), gate electrode (1300), and focusing lens (1400) are coupled to grooves located on the upper side of the bottom surface (1130), and electrode pins (1600) are configured to penetrate the bottom surface (1130) and apply voltage to the cathode (1200), gate electrode (1300), and focusing lens (1400), respectively.

[0105] On the other hand, the support parts (1320, 1330) of the gate electrode (1300) and the support parts (1420, 1430) of the focusing lens (1400) are arranged so as not to interfere with each other. For example, they can be arranged so that an imaginary line connecting the support parts (1320, 1330) of the gate electrode (1300) and an imaginary line connecting the support parts (1420, 1430) of the focusing lens (1400) intersect each other. With this configuration, a voltage can be applied independently to the support parts (1320, 1330) of the gate electrode (1300) and the support parts (1420, 1430) of the focusing lens (1400) via the electrode pin (1600).

[0106] Furthermore, the electrode pin (1600) may penetrate the bottom surface (1130) and be coupled to the support parts (1320, 1330), support parts (1420, 1430), or the lower side of the cathode (1200). The coupling structure of the electrode pin (1600) will be described later.

[0107] Figure 19 is a perspective view showing the detailed configuration of a cathode according to one embodiment of the present invention, Figure 20 is an exploded assembly view of the cathode, Figures 21 and 22 show the clamp configurations of the cathode according to one embodiment of the present invention, respectively, and Figure 23 is a diagram illustrating the recess configuration according to one embodiment of the present invention.

[0108] The cathode (1200) extends along the longitudinal direction of the carbon structure-based film (1210) and includes a first clamp (1220) and a second clamp (1230) that are in close contact with the sides thereof to secure the carbon structure-based film (1210), and includes a fastening member (1240) that connects them.

[0109] The cathode (1200), when the first clamp (1220) and the second clamp (1230) are joined together, has a shape similar to a rectangular parallelepiped overall, and its flat upper surface includes a recess (1250) recessed to a predetermined depth. The height of the edges (1260) of each clamp (1220, 1230) is set to be the same so that the recess (1250) is formed when the first clamp (1220) and the second clamp (1230) are joined together. The recess (1250) is formed on the upper surface of the cathode (1200) with a clearance space equal to the edge (1260) of the upper surface of the cathode (1200). Furthermore, the carbon structure-based film (1210) is exposed to the outside at a height equal to or slightly lower than the depth of the recess (1250). In other words, the length in the z-axis direction over which the carbon structure-based film (1210) is exposed to the outside is set to be the same as or slightly shorter than the distance from the top surface of the cathode (1200) to the top surface of the recess (1250). That is, as shown in Figure 23, the height of the uppermost edge of the carbon structure-based film (1210) can be set to be lower by a predetermined distance (1270) than the upper edge (1260) of the cathode (1200). For example, the predetermined distance (1270) may be in the range of 0.1 mm to 1 mm, preferably 0.2 mm, but this is just an example and can be changed. When a voltage is applied between the cathode (1200) and the gate electrode (1300), the electric field over the upper edge of the carbon structure-based film (1210) is affected by the depth of the recess (1250). When a voltage is actually applied between the cathode (1200) and the gate electrode (1300), electrons are emitted through the upper cross section of the region exposed to the outside of the carbon structure-based film (1210). Therefore, the recess (1250) is recessed to an appropriate depth to maintain the optimal electric field strength.

[0110] A carbon structure-based film (1210) is bonded between the first clamp (1220) and the second clamp (1230) with their opposing surfaces. At least one projection (1234, 1236) may be formed protruding from the inner surface of the second clamp (1230). For example, the first projection (1234) may be formed at one corner of the inner surface of the second clamp (1230), and the second projection (1236) may be formed at the other corner.

[0111] Furthermore, to accommodate the projections (1234, 1236) of the second clamp (1230), a first housing portion (1224) and a second housing portion (1226) may be formed on the inner surface of the first clamp (1220). Space is secured for the length of the projections (1234, 1236) that protrude in the x-axis direction and the length that extends in the z-axis direction, so that each projection (1234, 1236) is adequately accommodated. With this configuration, the first clamp (1220) and the second clamp (1230) can interlock precisely and have a firm connection. In addition, the surfaces that each projection (1234, 1236) and the housing portions (1224, 1226) contact are formed as curved surfaces so that the first clamp (1220) and the second clamp (1230) can be fastened smoothly. Furthermore, fastening grooves (1222, 1232) are formed in the center of the first clamp (1220) and the second clamp (1230), respectively, and fastening members (1240) are connected through these fastening grooves (1222, 1232), thereby joining the first clamp (1220) and the second clamp (1230). The fastening grooves (1222, 1232) are formed below the area where the carbon structure-based film (1210) is in close contact.

[0112] In addition to supporting the carbon structure-based film (1210), the projections (1234, 1236) and their housing portions (1224, 1226) can also play a role in stably maintaining the fastened state of the first clamp (1220) and the second clamp (1230).

[0113] Figure 24 is an exploded assembly diagram of a cathode according to another embodiment of the present invention, and Figures 25 and 26 show the clamp configurations of the cathode according to another embodiment of the present invention, respectively.

[0114] The cathode (1200') extends along the longitudinal direction of the carbon structure-based film (1210') and includes a first clamp (1220') and a second clamp (1230') that are in close contact with the sides thereof to secure the carbon structure-based film (1210'), and includes a fastening member (1240') that connects them.

[0115] The cathode (1200') with the first clamp (1220') and the second clamp (1230') joined together has a shape that is generally similar to a rectangular parallelepiped, and its upper surface includes a recess (1250') recessed to a predetermined depth. The configuration of the recess (1250') is the same as in the previously described embodiment, so a detailed explanation is omitted.

[0116] A carbon structure-based film (1210') is bonded between the opposing surfaces of the first clamp (1220') and the second clamp (1230'). A projection (1234') may be formed protruding from the inner surface of the second clamp (1230'). The projection (1234') may be formed to have a predetermined height in the z-axis direction from the lower end of the inner surface of the second clamp (1230'). This configuration allows the first clamp (1220') and the second clamp (1230') to fit together precisely and have a firm bond. The projection (1234') may be integrally formed to have a predetermined length along the longitudinal direction in the y-axis direction of the second clamp (1230'). For example, the projection (1234') may be set to be the same length as the y-axis direction, but in some embodiments it may be formed to be longer or shorter.

[0117] Furthermore, the first clamp (1220') is coupled to the space above the projection (1234') of the second clamp (1230'). The thickness of the first clamp (1220') in the x-axis direction may roughly correspond to the length that the projection (1234') protrudes in the x-axis direction, but it may also be designed so that the thickness of the first clamp (1220') in the x-axis direction is greater than the protruding length of the projection (1234'). At a minimum, it is desirable that the shortest distance between the upper edge (1260') of the first clamp (1220') and the carbon structure base film (1210') be the same as the shortest distance between the upper edge (1260') of the second clamp (1230') and the carbon structure base film (1210').

[0118] Furthermore, fastening grooves (1222', 1232') are formed in the center of the first clamp (1220') and the second clamp (1230'), respectively, with a shape that penetrates the main body. The first clamp (1220') and the second clamp (1230') are joined by fastening members (1240') being connected through the fastening grooves (1222', 1232'). The fastening grooves (1222', 1232') are formed below the area where the carbon structure-based film (1210') is in close contact.

[0119] Figure 27 shows the coupling structure of an electrode pin according to one embodiment of the present invention.

[0120] As shown in the figure, at least one electrode pin (1600) may be individually coupled to the cathode (1200), the support portion (1320, 1330) of the gate electrode (1300), and the support portion (1420, 1430) of the focusing lens (1400). In this case, it can also be implemented in a form in which it is coupled to either one of the two support portions (1320, 1330) of the gate electrode (1300) or either one of the two support portions (1420, 1430) of the focusing lens (1400).

[0121] Multiple feedthroughs (1132) may be pre-formed on the bottom surface (1130) through which multiple electrode pins (1600) can pass. The ends of the electrode pins (1600) are formed into a threaded shape (1610), and grooves for the threads to fit into the support parts (1320, 1330) of the cathode (1200), gate electrode (1300), or focusing lens (1400) (1420, 1430) are formed so that each electrode pin (1600) can be easily connected by screw coupling. As a result, each electrode pin (1600) passes through the feedthrough (1132) of the bottom surface (1130) and is easily screw-connected to the support parts (1320, 1330) of the cathode (1200), gate electrode (1300), or the support parts (1420, 1430) of the focusing lens (1400), thus eliminating the need for a separate alignment process to align the positions of each component.

[0122] Figure 28 shows an X-ray tube using a carbon structure substrate electron emission source according to another embodiment of the present invention.

[0123] Unlike the embodiment in Figure 13, this embodiment is characterized in that the bottom surface (1130) is made of a metallic material such as Kovar. As a result, in this embodiment, as shown in Figure 29, the configuration of the second adapter ring (1120) is omitted, and a substrate (1150) made of an insulating material such as ceramic is included to insulate the cathode (1200), gate electrode (1300), and focusing lens (1400) from the conductive bottom surface (1130).

[0124] Figure 29 shows the coupling structure of electrode pins in an X-ray tube according to one embodiment of the present invention.

[0125] As shown in the figure, feedthroughs (1650) made of an insulating material such as ceramic may be connected to each electrode pin (1600) in such a way that they can insulate the gaps between multiple electrode pins (1600). The electrode pins (1600) may be screw-connected to the supports (1320, 1330) of the cathode (1200), gate electrode (1300), or focusing lens (1400) (1420, 1430) by passing through the bottom surface (1130) and the substrate (1150). To achieve this, the end of the electrode pin (1600) is formed into a threaded shape (1620), and grooves are formed in the support parts (1320, 1330) of the cathode (1200) or gate electrode (1300) or the support part (1420, 1430) of the focusing lens (1400) into which the threads fit, as described above.

[0126] Figure 30 shows the results of an X-ray image test of an X-ray tube according to one embodiment of the present invention.

[0127] We have confirmed that the cold cathode X-ray tube according to the present invention can output excellent high-resolution X-ray images even at relatively low X-ray doses and low tube voltages.

[0128] Furthermore, it was confirmed that the cold cathode X-ray tube of the present invention has a higher tube current (approximately 100 mA or more) and a smaller electron beam focus size (0.5 mm) compared to conventional cold cathode X-ray tubes.

[0129] This makes it applicable to various medical diagnostic X-ray equipment. Furthermore, it can be applied not only to medical X-ray equipment but also to a wide range of industrial applications, such as X-ray-based inspection devices and security scanners. [Examples]

[0130] The following description of this specification will be made more specifically with reference to examples, but these examples are illustrative to aid in understanding the present invention, and the content of the present invention is not limited to these examples.

[0131] *110

[0132] 1. Manufacturing and densification process of carbon nanotube films 1-1. Manufacturing process of carbon nanotube film Multiwalled carbon nanotubes synthesized by catalytic chemical vapor deposition (CCVD) and 200 mg of sodium dodecyl sulfate (SDS) as a dispersant were added to 200 mL of distilled water (DI water). A dispersion process was performed using a tip sonication device at 150 W for 55 minutes. This process uniformly dispersed the aggregated carbon nanotubes and further cut them to a length suitable for field electron emission. Subsequently, the dispersed carbon nanotube solution was transferred to a plastic container and centrifuged for 40 minutes under conditions of 10,000 g to 20,000 g. This separated the uniformly dispersed carbon nanotubes from the insufficiently dispersed and aggregated carbon nanotubes. After centrifugation, the carbon nanotube solution at the top of the plastic container was collected with a pipette to obtain the uniformly dispersed carbon nanotube solution. Subsequently, using a vacuum filtration apparatus, the uniformly dispersed carbon nanotube solution was passed through an anodized aluminum oxide (AAO) membrane having a pore size of 100 nm or less (e.g., 20 to 60 nm), and a carbon nanotube film was formed by stacking carbon nanotubes on the membrane, with the remaining solution removed through the pores. Next, to remove the organic substance SDS, acetone, isopropyl alcohol (IPA), and distilled water, which readily dissolves polar substances, were sequentially poured onto the carbon nanotube film to remove the SDS. Then, to separate the carbon nanotube film from the AAO membrane, the carbon nanotube film / AAO membrane was immersed in an aqueous NaOH solution with a concentration of 1 M to 3 M (e.g., 1 M) for 1 hour. After the AAO membrane was completely removed in an aqueous NaOH solution, the carbon nanotube film was placed in distilled water for 30 minutes to remove any remaining aqueous NaOH solution, and then immersed in acetone, a solvent that can effectively remove SDS, for 6 to 24 hours (e.g., 12 hours).

[0133] 1-2. High-density process for carbon nanotube films After cutting the carbon nanotube film produced by the process described in 1-1 into rectangles, a densification process was performed. First, the carbon nanotube film was immersed in a polar solvent having appropriate polarity (e.g., ethylene carbonate), and a voltage of 1V to 20V (e.g., 5 to 10V) was applied to the polar solvent to align the polar molecules in a specific direction, thereby densifying the carbon nanotube film. After applying the voltage for 10 to 60 minutes, the carbon nanotube film was removed from the polar solvent and washed by sequentially immersing it in distilled water and acetone to perform a primary densification process. Subsequently, a secondary densification process using acid was carried out. In the secondary densification process, no voltage was applied, and the carbon nanotube film was immersed in a 5M aqueous acetic acid solution for 10 to 60 minutes to achieve densification. After that, the carbon nanotube film was removed from the aqueous acetic acid solution and washed by sequentially immersing it in acetone and distilled water. Finally, to remove any remaining polar solvents, acidic aqueous solutions, or foreign matter from the washed carbon nanotube films, the films were heat-treated under an argon (Ar) atmosphere at 100°C to 350°C for 30 minutes to 2 hours to remove any residual acidic aqueous solutions or polar solvents.

[0134] The principle of the two-stage densification process is explained with reference to Figure 31. Here, if the surface tension of the polar solvent is high, the polar solvent may not be able to effectively penetrate into the carbon nanotube film, reducing the densification effect. Furthermore, the surface tension of the polar solvent may cause a decrease in its effectiveness as densification progresses. On the other hand, hydrogen ions exist as ions in aqueous solutions regardless of surface tension, so the phenomenon of decreased effectiveness does not occur even as densification progresses. Therefore, in the first-stage densification process, a polar solvent with a high dipole moment value is used to densify the carbon nanotube film. After completely removing the polar solvent, the second-stage densification process is performed using an acidic aqueous solution that can effectively penetrate into the densified carbon nanotube film. In this process, the acidic aqueous solution can be selected from a strong acid aqueous solution or a weak acid aqueous solution (aliphatic or aromatic carboxylic acid) depending on the purpose.

[0135] 2. Thickness of carbon nanotube film after density increase process Figures 32(a) to (d) show scanning electron microscope (SEM) images of the cross-sectional thickness of carbon nanotube films that have not undergone a densification process, carbon nanotube films that have been densified with ethylene carbonate, carbon nanotube films that have been densified with an aqueous acetic acid solution, and carbon nanotube films that have been densified with ethylene carbonate (first stage) and acetic acid (5M, second stage), respectively. The thickness of the carbon nanotube film before the densification process was approximately 27.60 μm, while the thickness of the carbon nanotube films that were densified in a single stage using ethylene carbonate or an aqueous acetic acid solution was 22.48 μm and 22.49 μm, respectively, confirming a decrease of approximately 5 μm. This confirmed that both acidic aqueous solutions and polar solvents can effectively densify carbon nanotube films. On the other hand, the thickness of the carbon nanotube film to which the two-stage densification process was applied was approximately 18 μm, a decrease of approximately 9.5 μm compared to before densification, and it was confirmed that the thickness reduction was approximately 4.5 μm greater than that when a primary densification process was applied. This confirmed that carbon nanotube films can be more effectively densified by performing a second densification step with an acidic aqueous solution after a first densification step with a polar solvent.

[0136] 3. Changes in field electron emission characteristics of carbon nanotube film due to the densification process. When fabricating a cold cathode X-ray tube using a carbon nanotube thin-film emitter, the intensity of the generated X-rays is proportional to the anode current of the carbon nanotube film emitter, and the energy of the X-rays is proportional to the strength of the applied anode voltage. In this case, the generated anode current is hardly affected by the anode voltage. Therefore, when measuring the field electron emission characteristics of the carbon nanotube film emitter, the anode voltage was set to 15kV or less for smooth measurement. As a result of evaluating the field electron emission characteristics, referring to Figures 33 to 37, the maximum anode currents were 55.3mA, 80mA, 77mA, and 101mA for the untreated carbon nanotube film, the carbon nanotube film densed with a polar solvent (ethylene carbonate), the carbon nanotube film densed with an acidic aqueous solution (acetic acid), and the carbon nanotube film sequentially densed with a polar solvent (ethylene carbonate) and an acidic aqueous solution (acetic acid), respectively. On the other hand, the transmittance did not show a large difference in each case.

[0137] Therefore, it was confirmed that the field electron emission characteristics of a carbon nanotube thin-film emitter are greatly influenced by the degree of density of the carbon nanotube thin film. The performance degradation of the field electron emission characteristics of a carbon nanotube thin-film emitter is influenced by two main factors. The first is the applied electric field. Since the carbon nanotube thin film is bonded by van der Waals forces, if a part of the carbon nanotube is partially detached from the thin film or a part of the thin film is damaged by the electric field during field electron emission, the emitter performance may be greatly reduced or electrical arcing may occur. The second is the Joule heat generated by the movement of electrons during field electron emission. For field electron emission to occur, electrons need to move from the substrate (SUS304) through the carbon nanotube thin film to the tip of the carbon nanotube on the surface of the thin film. Therefore, during the electron movement process, Joule heat is generated due to the contact resistance between the substrate and the carbon nanotube thin film, the bulk resistance due to the contact characteristics between carbon nanotubes within the carbon nanotube thin film, and the self-resistance of individual carbon nanotubes present in the thin film. Therefore, in order to improve the field electron emission characteristics of carbon nanotube thin film emitters, it is necessary to minimize delamination of carbon nanotubes or damage to the thin film due to the electric field, while also improving the contact resistance and electrical conductivity of the carbon nanotube thin film.

[0138] Improving the electrical conductivity of a carbon nanotube thin film means increasing the number of carbon nanotubes that contribute to electron emission within the thin film. Increasing the density of a carbon nanotube thin film shortens the distance between individual carbon nanotubes, increasing the van der Waals forces acting between them. As a result, the contact area between carbon nanotubes increases, improving the electrical conductivity of the thin film. Therefore, the higher the density of the carbon nanotube film, the stronger the van der Waals forces between the carbon nanotubes, reducing delamination of carbon nanotubes or damage to the thin film due to electric fields. Furthermore, improved electrical conductivity reduces the generation of Joule heat, increasing the number of carbon nanotubes that contribute to electron emission within the thin film. In other words, the higher the density of the carbon nanotube film, the better the field electron emission characteristics of the thin film.

[0139] Actual experimental results confirmed that even when carbon nanotube films were densified using only polar solvents or acidic solutions, the field electron emission characteristics were significantly improved. This confirmed that both polar solvents and acidic aqueous solutions can effectively densify carbon nanotube films. Furthermore, it was confirmed that when a primary densification step was performed with a polar solvent followed by a secondary densification step with an acidic aqueous solution, the characteristics of the carbon nanotube film emitter were significantly improved compared to when densification was performed using only a single solvent or aqueous solution.

[0140] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the invention can be easily modified into other specific forms without altering the technical idea or essential features. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects. For example, each component described as a single form may be implemented in a distributed manner, and components described as a distributed form may also be implemented in a combined form.

[0141] The scope of the present invention is indicated not by the above detailed description but by the claims set forth below, and all modifications or variations derived from the meaning and scope thereof, as well as the concept of equivalents thereof, are to be interpreted as being within the scope of the present invention.

Claims

1. A process for providing a carbon structure-based film, and A step of obtaining a high-density carbon structure-based film by immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution, or a densification step of obtaining a high-density carbon structure-based film by immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent. A method for producing a high-density carbon structure-based film, characterized by including the following:

2. The method for producing a high-density carbon structure-based film according to claim 1, characterized in that the carbon structure comprises at least one selected from carbon nanotubes, graphene, nanocarbon, and carbon nanowires.

3. The method for producing a high-density carbon structure-based film according to claim 2, characterized in that the carbon nanotube comprises at least one selected from single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes.

4. A method for producing a high-density carbon structure-based film according to claim 1, characterized in that the dipole moment of the polar solvent is 2D or greater.

5. The method for producing a high-density carbon structure-based film according to claim 1, characterized in that the polar solvent comprises at least one selected from heteroaromatic compounds, ketones, carbonates, ethers, esters, acetonitrile, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide (DMAc), and hexamethylphosphoramide (HMPA).

6. The method for producing a high-density carbon structure-based film according to claim 1, characterized in that the polar solvent includes at least one selected from pyridine, acetone, ethylene carbonate, propylene carbonate, tetrahydrofuran (THF), methyl acetate, ethyl acetate, acetonitrile, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), N,N'-dimethylacetamide (DMAc), and hexamethylphosphoramide (HMPA).

7. The method for producing a high-density carbon structure-based film according to claim 1, characterized in that the acidic aqueous solution contains at least one selected from hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, salicylic acid, and benzoic acid.

8. A method for producing a high-density carbon structure-based film according to claim 1, further comprising a pretreatment step to remove a dispersant.

9. The method for producing a high-density carbon structure-based film according to claim 8, characterized in that the dispersant is removed by washing with at least one solvent selected from ketones, alcohols, and water.

10. A method for producing a high-density carbon structure-based film according to claim 1, further comprising the step of performing a heat treatment before, after, or either before or after the high-density step of the carbon structure-based film.

11. A method for producing a high-density carbon structure-based film according to claim 1, characterized in that the process of increasing the density of the carbon structure-based film further includes a washing step.

12. A process for providing a carbon structure-based film, and A step of obtaining a high-density carbon structure-based film by immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution, or a densification step of obtaining a high-density carbon structure-based film by immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent. A high-density carbon structure-based film characterized by being manufactured by a method for manufacturing a high-density carbon structure-based film containing [a specific component].

13. A process for providing a carbon structure-based film, A step of obtaining a high-density carbon structure-based film by immersing the carbon structure-based film in a polar solvent and then in an acidic aqueous solution, or a densification step of obtaining a high-density carbon structure-based film by immersing the carbon structure-based film in an acidic aqueous solution and then in a polar solvent, and A step of fixing the carbon structure-based film, which is placed between at least two conductive metal members, by lateral pressure, A method for producing an electron emission source on a carbon structure substrate, characterized by including the following:

14. A method for manufacturing a carbon structure substrate electron emission source according to claim 13, characterized by including a step of cutting the carbon structure-based film before or after the densification step.

15. In an X-ray tube, A tube housing with a space formed inside, A cathode is housed within the tube housing and positioned at one end of the tube housing, with a linearly cut carbon structure-based film coupled as an electron emission source. A gate electrode positioned above the cathode and having a slit formed therein so as to be aligned with the carbon structure-based film, A focusing lens positioned above the gate electrode, and An anode housed within the tube housing and positioned at the other end of the tube housing so as to face the cathode, An X-ray tube characterized by containing [something].

16. The cathode is, A high-density carbon structure-based film, The carbon structure-based film includes a conductive metal member for fixing the film, The conductive metal member includes a recess formed to a predetermined depth from its upper surface. The recess is either the same depth as the height of the carbon structure base film, or it is recessed to be a predetermined length deeper than the height of the carbon structure base film. The X-ray tube according to claim 15, characterized in that the carbon structure-based film is arranged across the recess.

17. The cathode is, A film based on multiple high-density carbon structures, The carbon structure-based film includes a conductive metal member for fixing the film, It includes a plurality of recesses formed to a predetermined depth, Each recess is either the same depth as the height of the carbon structure base film, or is recessed to a predetermined length deeper than the height of the carbon structure base film. The X-ray tube according to claim 15, characterized in that each carbon structure-based film is arranged across its respective recess.

18. The X-ray tube according to claim 15, characterized in that the aperture of the focusing lens is formed in the shape of a curved or rounded rectangle, and the outer surface of the focusing lens is formed in the shape of an ellipse, a circle, or a rounded rectangle.

19. The upper surface of the focusing lens is formed in a flat or curved shape. The X-ray tube according to claim 15, characterized in that, when the upper surface is formed in a curved shape, the height of the upper surface increases towards the left and right ends along a direction perpendicular to the extending direction of the carbon structure-based film.

20. The X-ray tube according to claim 15, characterized in that the anode is a fixed electrode or a rotating electrode.

21. The cathode is, High-density carbon structure-based film, A first clamp and a second clamp extend along the longitudinal direction of the carbon structure-based film and are in close contact with both sides thereof to secure the carbon structure-based film. Furthermore, fastening members connecting the first clamp and the second clamp, The X-ray tube according to claim 15, characterized by including the following:

22. The cathode to which the first clamp, the second clamp, and the fastening member are connected includes a flat upper surface and a recess formed in the upper surface to a predetermined depth. The X-ray tube according to claim 21, characterized in that the depth of the recess is the same as the height of the carbon structure base film, or is recessed to a predetermined length deeper than the height of the carbon structure base film.

23. The inner surface of the second clamp that contacts the first clamp has at least one or more protrusions that project from that inner surface. The X-ray tube according to claim 21, characterized in that at least one or more accommodating portions are formed on the inner surface of the first clamp to receive the protruding portion.

24. The second clamp includes a first projection formed at one lower corner of its inner surface and a second projection formed at the other corner. The X-ray tube according to claim 23, characterized in that the first clamp includes a first housing portion formed to receive the first protrusion and a second housing portion formed to receive the second protrusion.

25. The inner surface of the second clamp that contacts the first clamp has a protruding portion that extends from that inner surface. The first clamp is connected to the space formed at the upper end of the protrusion. The X-ray tube according to claim 21, characterized in that the protruding portion is formed to extend for a predetermined length in the longitudinal direction along the lower end of the inner surface of the second clamp.

26. Fastening grooves are formed that penetrate the bodies of the first clamp and the second clamp, respectively. The fastening members are connected to each of the fastening grooves. The X-ray tube according to claim 21, characterized in that the fastening groove is formed below the region in which the carbon structure-based film is in close contact with the first clamp and the second clamp.

27. The anode is connected to one end of the tube housing. The system further includes a first adapter ring coupled between the anode and the tube housing, The anode is made of a copper-based material, and the tube housing is made of a ceramic material. The first adapter ring is made of a material having a coefficient of thermal expansion corresponding to the tube housing, The X-ray tube according to claim 15, characterized in that the anode and the first adapter ring and the first adapter ring and the tube housing are brazed together.

28. The bottom surface of the ceramic material that supports the cathode is formed to cover the opening at the other end of the tube housing, The present invention further includes a second adapter ring coupled between the bottom surface and the tube housing, The X-ray tube according to claim 15, characterized in that the space between the bottom surface and the second adapter ring, and the space between the second adapter ring and the tube housing are brazed.

29. The cathode, gate electrode, and focusing lens are arranged on the bottom surface. The gate electrode is formed in a bridge shape in which the main body is supported by support parts at both ends, and each support part is connected to the bottom surface. The focusing lens is formed in a bridge shape above the gate electrode, with its body supported by support parts at both ends, and each support part is connected to the bottom surface. The X-ray tube according to claim 28, characterized in that the carbon structure-based film, the slit of the gate electrode, and the opening of the focusing lens are aligned, and the imaginary lines connecting the support portions of the gate electrode and the imaginary lines connecting the support portions of the focusing lens are arranged to intersect each other.

30. It is formed to cover the opening at the other end of the tube housing and further includes a bottom surface that supports the cathode, The aforementioned bottom surface is made of a metal material. The X-ray tube according to claim 15, characterized in that the bottom surface and the tube housing are brazed together.

31. The present invention further includes a substrate located on the upper part of the bottom surface, on which the cathode, gate electrode, and focusing lens are arranged, The gate electrode is formed in a bridge shape in which the main body is supported by support portions at both ends, and each support portion is connected to the substrate. The focusing lens is formed in a bridge shape above the gate electrode, with its main body supported by support portions at both ends, and each support portion is connected to the substrate. The X-ray tube according to claim 30, characterized in that the carbon structure-based film, the slit of the gate electrode, and the opening of the focusing lens are aligned, and the imaginary lines connecting the support portions of the gate electrode and the imaginary lines connecting the support portions of the focusing lens are arranged to intersect each other.

32. The system further includes a plurality of electrode pins for applying voltage to the cathode, the gate electrode, and the focusing lens, respectively. The X-ray tube according to claim 15, characterized in that the electrode pin has a threaded end so as to be screw-coupled to the cathode, the gate electrode, or the focusing lens.

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