JP4131306B2 - Electron emission material - Google Patents
Electron emission material Download PDFInfo
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- JP4131306B2 JP4131306B2 JP35113598A JP35113598A JP4131306B2 JP 4131306 B2 JP4131306 B2 JP 4131306B2 JP 35113598 A JP35113598 A JP 35113598A JP 35113598 A JP35113598 A JP 35113598A JP 4131306 B2 JP4131306 B2 JP 4131306B2
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Description
【０００１】
【発明の属する技術分野】
本発明は、陰極電子源である電界放出型の電子放出素材を提供するものである。
【０００２】
【従来の技術及び発明が解決しようとする課題】
冷陰極電子源である電界放出型の電子放出素材としては、先端が細く尖った導電性物質が求められている。
例えば先端が尖った円錐状のＳｐｉｎｄｔ型の冷陰極が知られている。それは、穴の開いたゲートとＳｉＯ2 の絶縁層に、ゲートを通して冷陰極の材料であるＭｏを成膜すると、ＳｉＯ2 層に開けた穴に，Ｍｏが堆積し円錐の構造物が形成される。
こうして得られたＳｐｉｎｄｔ型の冷陰極は、製造工程が複雑なこと、また冷陰極の耐久性が劣り寿命が短い欠点がある。
また、１９９１年に飯島等により発見されたカーボンナノチューブは、先端が尖鋭であり、化学的に安定で機械的にも強靱であり、電界放出型の電子源として有利な性質を持っており、電界放出型の電子源として使用することが検討されている。
例えば、斉藤らはＮａｔｕｒｅ ３８９ ５５４（’９７）に示されるように電界電子放出顕微鏡等を用いて、単層カーボンナノチューブや多層カーボンナノチューブからの電界電子放出特性を検討している。
しかし、カーボンナノチューブ類は、耐久性はあるが、その工業的な製造方法は確立されておらず、品質の安定したものが安価に供給されていない。
【０００３】
【課題を解決するための手段】
本発明者らは、カーボンナノチューブの代わりに工業的な製造方法が確立されている気相法炭素繊維に着目し、該炭素繊維を電界放出型の電子放出素材として用いることを検討し、該炭素繊維の熱処理条件、粉砕や酸化処理等による破断を検討することにより、より多く安定して電子が放出されることを見いだし、本発明を完成させた。
すなわち、
１）直径が０．０１〜５μｍの気相法炭素繊維であって、該炭素繊維を不活性雰囲気下で８００℃〜３３００℃の温度で熱処理を行い、更に粉砕処理することにより先端を破断させたことを特徴とする電子放出素材であり、
２）直径が０．０１〜５μｍの気相法炭素繊維であって、該炭素繊維を不活性雰囲気下で８００℃〜３３００℃の温度で熱処理を行い、更に酸化処理を行うことにより先端を破断させたことを特徴とする電子放出素材であり、
３）直径が０．０１〜５μｍの気相法炭素繊維であって、該炭素繊維を不活性雰囲気下で８００℃〜３３００℃の温度で熱処理を行い、更に粉砕処理し、更に酸化処理を行うことにより先端を破断させたことを特徴とする電子放出素材である。
【０００４】
【発明の実施の形態】
以下、本発明の気相法炭素繊維をもとにした電子放出材について更に詳しく説明する。
本発明の縮号環状の炭素面が繊維軸を中心に年輪状に積層した直径が０．０１〜５μｍの気相法炭素繊維は、特公平４−２４３２０に開示されているように、メタロセンを気相にて導入し、熱分解させ基盤上に析出させるものや、特許２７７８４３４号に開示されているような遷移金属又はその化合物を含む有機化合物の微小液滴を加熱炉壁面に吹き付け、炉壁面に生成させるような製造法で代表される物質であって、該炭素繊維を不活性雰囲気下で８００℃以上、３３００℃以下の温度で熱処理を行った気相法炭素繊維である。不活性雰囲気下での熱処理温度は、８００℃以上が好ましく、熱処理温度を２０００℃以上、より好ましくは２６００℃以上として黒鉛構造に近づけたものも電子放出素材として使用することができる。
熱処理温度の上限は、黒鉛化温度３０００℃程度までが望ましいが、炉構造から上限は３３００℃に限界がある。
不活性雰囲気は、アルゴン雰囲気が望ましい。
更に、上記製造方法で得られた気相法炭素繊維は、分岐状で網膜状に発達しているものが多く、また繊維同士が互着しており、そのままでは電子放出特性が劣る。
そこで、それらを粉砕処理することにより、繊維同士をほぐしたり、一部繊維を切断することにより、より良い電子放出特性が得られる。その際の粉砕方法は、スクリーンミル、ハンマーミル、ボールミル等が挙げられ、粉砕方式にはとらわれない。
また、その粉砕の程度は、気相法炭素繊維は生成熱処理後の段階では、上記のように互着していて嵩密度が大きい。上記粉砕処理により、該炭素繊維がほぐれ始め、嵩比重は急激に０．０１ｇ／ｃｍ3 以下まで小さくなる。更に粉砕を続けると分断、細分された繊維が今度は徐々に凝集し嵩密度が０．１５ｇ／ｃｍ3 程度まで上がってくる。
電子放出材として適しているのは、生成熱処理後粉砕処理を行い繊維を完全に分断させた後、嵩密度を０．０１ｇ／ｃｍ3 以上、好ましくは０．０３ｇ／ｃｍ3 以上に調整したものである。
更に、熱処理された気相法炭素繊維あるいはその粉砕処理品は、一方は粉砕処理により切断されているが、もう一方は丸みを帯びている。電子放出素材としては、両端とも切断されていた方が電子放出特性が良いと考えられ、そこでもう一方の端も破断させる方法を検討した結果、酸化処理を行うことにより、繊維のもう一方の端も破断され、それにより電子放出特性が向上することを確認した。その酸化処理方法は、消失率で２０ｗｔ％以上が必要である。
酸化処理を行う際の気相法炭素繊維は、熱処理後粉砕処理を行っていないもの、または熱処理後粉砕処理を行ったもののいずれでも良い。
【０００５】
【実施例】
以下、実施例により本発明を更に詳細に説明する。なお、本発明は以下の実施例に限定されるものではない。
（比較例１）
特許２７７８４３４号に記された方法にて、フェロセンを含有するベンゼンを水素ガスにて１２００℃の縦型加熱炉炉壁に噴霧し炉壁に成長させた気相法炭素繊維を５分間隔で掻き落とし、得られた気相法炭素繊維を２８００℃でアルゴン雰囲気下で黒鉛化を行った。この気相法炭素繊維をピンミルで途中まで解砕した。その際の嵩密度は、０．０６ｇ／ｃｍ3 であった。
得られた気相法炭素繊維を、Ｎａｔｕｒｅ ３８９ ５５４（９７’）で示された電界電子放出顕微鏡により、電子放出特性を測定した。
その電界電子放出顕微鏡を図−１に示す。測定方法は、直径０．２ｍｍのタングステン製ヘアピンの先端に気相法炭素繊維を導電性ペーストで接着し、その先端と蛍光スクリーンとの間を６０ｍｍに調節する。ヘアピンと蛍光スクリーンとの間にティップ電圧をかけ、その際に放出され、蛍光スクリーンに開けた直径１ｍｍのプローブ孔を通過した電子をプローブ電流として検出し、電子放出特性を評価した。その際、この測定系内を５×１０-6Ｐａに保った。
その結果を表−１に示す。
（実施例１）
比較例１で得られた熱処理後ピンミルで解砕した気相法炭素繊維を更に、ハンマーミルで嵩比重が０．０１ｇ／ｃｍ3 以下まで粉砕を行い、更に粉砕を続けた結果、その嵩密度は、０．０３ｇ／ｃｍ3 となった。
得られた気相法炭素繊維を、比較例１と同様に電子放出特性を測定した。その結果を表−１に示す。
（実施例２）
比較例１で得られた熱処理後ピンミルで解砕した気相法炭素繊維を、坩堝に詰め７５０℃に加熱したマッフル炉に入れ３時間加熱した。その際の酸化消失率は４０ｗｔ％であった。
この繊維も比較例１と同様に電子放出特性を測定した。その結果を表ー１に示す。
（実施例３）
実施例１で得られた気相法炭素繊維を坩堝に詰め、７５０℃に加熱したマッフル炉に入れ３時間加熱した。その際の酸化消失率は４０ｗｔ％であった。
この繊維も実施例１と同様に電子放出特性を測定した。その結果を表−１に示す。
【０００６】
【表１】
【発明の効果】
本発明によれば、カーボンナノチューブの代わりに気相法炭素繊維を使用することにより、工業的に安価な材料を電子放出材として製造及び利用できる。
【図面の簡単な説明】
【図１】本発明中で電子放出特性を測定した装置の概略を示す図である。
【符号の説明】
１ 気相法炭素繊維
２ プローブ孔
３ 蛍光スクリーン
４ ファラデーカップ
５ ＣＣＤカメラ
６ ジンバル
７ 電圧端子
８ 排気系[0001]
BACKGROUND OF THE INVENTION
The present invention provides a field emission type electron emission material which is a cathode electron source.
[0002]
[Prior art and problems to be solved by the invention]
As a field emission type electron emission material which is a cold cathode electron source, a conductive material having a thin and sharp tip is required.
For example, a conical Spindt-type cold cathode with a sharp tip is known. It insulating layer of gate and SiO 2 with a hole and forming the Mo which is the material of the cold cathode through the gate, the holes drilled in the SiO 2 layer, the structure of Mo is deposited cone is formed .
The Spindt-type cold cathode thus obtained has a drawback that the manufacturing process is complicated, and the durability of the cold cathode is inferior and the life is short.
The carbon nanotube discovered by Iijima et al. In 1991 has a sharp tip, is chemically stable and mechanically strong, and has an advantageous property as a field emission electron source. Use as an emission type electron source is under study.
For example, Saito et al. Are examining field electron emission characteristics from single-walled carbon nanotubes and multi-walled carbon nanotubes using a field electron emission microscope as shown in Nature 389 554 ('97).
However, carbon nanotubes have durability, but their industrial production methods have not been established, and those with stable quality have not been supplied at low cost.
[0003]
[Means for Solving the Problems]
The inventors of the present invention have focused on vapor-grown carbon fibers for which an industrial production method has been established instead of carbon nanotubes, and have studied the use of carbon fibers as field emission type electron emission materials. By studying the heat treatment conditions of the fiber, breaking due to pulverization, oxidation treatment, etc., it was found that more electrons were stably emitted, and the present invention was completed.
That is,
1) A vapor grown carbon fiber having a diameter of 0.01 to 5 μm, the carbon fiber is heat-treated at a temperature of 800 ° C. to 3300 ° C. in an inert atmosphere, and further pulverized to break the tip. An electron emission material characterized by
2) Vapor grown carbon fiber having a diameter of 0.01 to 5 μm, the carbon fiber is heat-treated at a temperature of 800 ° C. to 3300 ° C. in an inert atmosphere, and further oxidized to break the tip. It is an electron emission material characterized by
3) Vapor grown carbon fiber having a diameter of 0.01 to 5 μm, which is heat treated at a temperature of 800 ° C. to 3300 ° C. in an inert atmosphere, further pulverized, and further oxidized. Thus, the electron emission material is characterized in that the tip is broken.
[0004]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the electron emission material based on the vapor grown carbon fiber of the present invention will be described in more detail.
The vapor grown carbon fiber having a diameter of 0.01 to 5 μm, in which the condensed ring-shaped carbon surface of the present invention is laminated in the shape of an annual ring around the fiber axis, is disclosed in Japanese Patent Publication No. 4-24320. Introduced in the gas phase, pyrolyzed and deposited on the substrate, or fine droplets of an organic compound containing a transition metal or its compound as disclosed in Japanese Patent No. 2778434 is sprayed on the heating furnace wall surface, It is a substance represented by a production method such as that produced in the above, and is a vapor grown carbon fiber obtained by heat-treating the carbon fiber at a temperature of 800 ° C. or higher and 3300 ° C. or lower in an inert atmosphere. The heat treatment temperature in an inert atmosphere is preferably 800 ° C. or higher, and a heat treatment temperature of 2000 ° C. or higher, more preferably 2600 ° C. or higher, close to the graphite structure can be used as the electron emission material.
The upper limit of the heat treatment temperature is preferably up to about 3000 ° C., but the upper limit is 3300 ° C. due to the furnace structure.
The inert atmosphere is preferably an argon atmosphere.
Furthermore, many vapor grown carbon fibers obtained by the above production method are branched and retinal, and the fibers are attached to each other, and as such, the electron emission characteristics are inferior.
Thus, by pulverizing them, fibers can be loosened or a part of the fibers can be cut to obtain better electron emission characteristics. The pulverization method in that case includes a screen mill, a hammer mill, a ball mill, and the like, and is not limited to the pulverization method.
Further, the degree of pulverization is that the vapor grown carbon fibers are attached together as described above and have a high bulk density at the stage after the heat treatment. By the above pulverization treatment, the carbon fibers begin to loosen, and the bulk specific gravity rapidly decreases to 0.01 g / cm 3 or less. If the pulverization is further continued, the divided and subdivided fibers are gradually aggregated and the bulk density is increased to about 0.15 g / cm 3 .
What is suitable as an electron emission material is a product in which the bulk density is adjusted to 0.01 g / cm 3 or more, preferably 0.03 g / cm 3 or more after pulverization after generation heat treatment to completely cut the fiber. It is.
Further, one of the heat-treated vapor grown carbon fiber or a pulverized product thereof is cut by pulverization, but the other is rounded. As an electron emission material, it is considered that the electron emission characteristic is better when both ends are cut, and as a result of studying a method of breaking the other end, the other end of the fiber is obtained by oxidation treatment. It was also confirmed that the electron emission characteristics were improved. The oxidation treatment method requires 20 wt% or more in terms of disappearance rate.
The vapor grown carbon fiber used in the oxidation treatment may be either one not subjected to pulverization after heat treatment or one subjected to pulverization after heat treatment.
[0005]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. In addition, this invention is not limited to a following example.
(Comparative Example 1)
According to the method described in Japanese Patent No. 2778434, benzene containing ferrocene is sprayed with hydrogen gas on the vertical heating furnace wall at 1200 ° C., and vapor grown carbon fiber grown on the furnace wall is scraped at intervals of 5 minutes. The vapor grown carbon fiber was graphitized at 2800 ° C. under an argon atmosphere. This vapor grown carbon fiber was crushed halfway with a pin mill. The bulk density at that time was 0.06 g / cm 3 .
The obtained vapor grown carbon fiber was measured for electron emission characteristics by a field electron emission microscope shown by Nature 389 554 (97 ′).
The field electron emission microscope is shown in FIG. In the measurement method, vapor grown carbon fiber is bonded to the tip of a tungsten hairpin having a diameter of 0.2 mm with a conductive paste, and the distance between the tip and the fluorescent screen is adjusted to 60 mm. A tip voltage was applied between the hairpin and the fluorescent screen. Electrons emitted at that time and passed through a probe hole having a diameter of 1 mm opened in the fluorescent screen were detected as a probe current, and the electron emission characteristics were evaluated. At that time, the inside of the measurement system was kept at 5 × 10 −6 Pa.
The results are shown in Table-1.
(Example 1)
The vapor grown carbon fiber crushed with a pin mill after heat treatment obtained in Comparative Example 1 was further pulverized with a hammer mill to a bulk specific gravity of 0.01 g / cm 3 or less, and the pulverization was continued. Was 0.03 g / cm 3 .
The obtained vapor grown carbon fiber was measured for electron emission characteristics in the same manner as in Comparative Example 1. The results are shown in Table-1.
(Example 2)
The vapor grown carbon fiber crushed by a pin mill after heat treatment obtained in Comparative Example 1 was placed in a muffle furnace packed in a crucible and heated to 750 ° C. and heated for 3 hours. The oxidation loss rate at that time was 40 wt%.
The electron emission characteristics of this fiber were measured in the same manner as in Comparative Example 1. The results are shown in Table-1.
(Example 3)
The vapor grown carbon fiber obtained in Example 1 was packed in a crucible, placed in a muffle furnace heated to 750 ° C., and heated for 3 hours. The oxidation loss rate at that time was 40 wt%.
The electron emission characteristics of this fiber were measured in the same manner as in Example 1. The results are shown in Table-1.
[0006]
[Table 1]
【The invention's effect】
According to the present invention, by using vapor grown carbon fiber instead of carbon nanotube, an industrially inexpensive material can be produced and used as an electron emission material.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of an apparatus for measuring electron emission characteristics in the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gas phase
Claims (7)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35113598A JP4131306B2 (en) | 1998-12-10 | 1998-12-10 | Electron emission material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35113598A JP4131306B2 (en) | 1998-12-10 | 1998-12-10 | Electron emission material |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| JP2000173449A JP2000173449A (en) | 2000-06-23 |
| JP2000173449A5 JP2000173449A5 (en) | 2005-08-11 |
| JP4131306B2 true JP4131306B2 (en) | 2008-08-13 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP35113598A Expired - Fee Related JP4131306B2 (en) | 1998-12-10 | 1998-12-10 | Electron emission material |
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| Country | Link |
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| JP (1) | JP4131306B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3981568B2 (en) * | 2001-03-21 | 2007-09-26 | 守信 遠藤 | Carbon fiber for field electron emitter and method for producing field electron emitter |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS524162A (en) * | 1975-06-27 | 1977-01-13 | Hitachi Ltd | Electric field radiation cathode and its manufacturing method |
| JPS52115159A (en) * | 1976-03-24 | 1977-09-27 | Hitachi Ltd | Production method of field radiating cathode |
| DE2810736A1 (en) * | 1978-03-13 | 1979-09-27 | Max Planck Gesellschaft | FIELD EMISSION CATHODE AND MANUFACTURING METHOD AND USE FOR IT |
| JP2778434B2 (en) * | 1993-11-30 | 1998-07-23 | 昭和電工株式会社 | Method for producing vapor grown carbon fiber |
| AU689702B2 (en) * | 1995-02-15 | 1998-04-02 | Lightlab Sweden Ab | A field emission cathode and methods in the production thereof |
| JPH11273551A (en) * | 1998-03-23 | 1999-10-08 | Nec Corp | Electron emitting element employing boron nitride and its manufacture |
| JP3790045B2 (en) * | 1998-05-13 | 2006-06-28 | 株式会社ノリタケカンパニーリミテド | Fluorescent display device and manufacturing method thereof |
| JP3890791B2 (en) * | 1998-11-20 | 2007-03-07 | 昭和電工株式会社 | Sharp carbonaceous fiber at both ends and method for producing the same |
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| JP2000173449A (en) | 2000-06-23 |
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