JP3890791B2 - Sharp carbonaceous fiber at both ends and method for producing the same - Google Patents
Sharp carbonaceous fiber at both ends and method for producing the same Download PDFInfo
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【０００１】
【発明の属する技術分野】
本発明は、先端が鋭角な炭素質繊維及びその製造方法に関するものである。
更に詳しくは、主として電界電子放出源等に有用である両端の鋭角な炭素質繊維及びその製造方法に関するものである。
【０００２】
【従来の技術】
近年、電子表示装置、画像形成装置等に使用される冷陰極用の電子放出素子について炭素質繊維を電子源とすることが検討されている。
その炭素質繊維の製造に関しては、例えば、特開平８−１１５６５２では、絶縁基盤上に設定した２つの電極間の微小間隙に、炭化水素ガスを原料とし、それを熱分解させた結果生じた炭素質繊維を堆積させる製造方法が示されている。
また、特開平１０−１１２２５７では、基盤陰極表面に炭素イオン又は炭素クラスターイオンをイオン注入し、これから形成される核発生サイトを核にし、ダイヤモンド状カーボンを気相合成する方法が述べられている。
これらは、いずれも技術的に製造は可能であるが、陰極部材への熱影響が問題となるので、炭素質繊維の熱処理が難しくそのため炭素質繊維の電子放出効果が制限される。
また、いずれも基盤等の陰極上に直接炭素を合成するもので、量産にはメーカー固有のノウハウ、設備技術が必要であり、工程が複雑なため陰極材メーカーが一般に用いられる方法ではない。
【０００３】
一方、数１０ｎｍ以下の径の微小なカーボンナノチューブが電子放出材料としてここ数年脚光をあびてきている。これは、通常太さ１ｎｍ〜５０ｎｍ程度の黒鉛のチューブであり、その製法は、炭素電極のアーク放電により電極上に発生させる、あるいは強力なレーザー光線を炭素電極に当てることにより、周辺のガス中に生成させる。このナノチューブの形状は、現代化学 Ｐ５７（１９９８年７月）に見られるように片方の先端が尖った形状が一般的である。
カーボンナノチューブは、化学的に安定であり、機械的にも強靱であり電界放出型の電子源として検討が進んでいる。例えば斉藤らは、セラミックス ３３（１９９８）Ｎｏ．６ にて、これを多数陰極板上に貼り付けたもので蛍光表示管として使用する例を示し、省エネルギー型の平面ディスプレー、高精細カラーＣＲＴへの利用の可能性を示唆している。
【０００４】
しかし、カーボンナノチューブについては、その工業的な製造法が確立されておらず、安定した品質のものが安価に供給されていない。
カーボンナノチューブに近い性状のものとして、ここ数年で、気相法炭素繊維が量産化されるようになった。これは、特公平０４−２４３２０や特許２７７８４３４等の製造法で示されるように有機化合物を反応槽内に吹き付け熱分解により炭素繊維を生成させるもので、径が数μｍ以下の炭素繊維が量産規模で得られている。これらの形状を詳細に調べると、縮合環状の炭素面が繊維軸を中心に年輪状に積層した外観を示し、これらの端面を見ると丸い球状で閉じているものや、あるいは分断され、その断面が繊維軸方向にほぼ垂直な状態を示している。
先に述べたように、電界電子放出源として用いる場合は、先端が鋭角なほうが縮合環状の炭素面端面が現れ、エッジが出ているため電界電子放出特性が向上する。
特に、両端面が尖った炭素質繊維については、現在発見されておらず、電子放出材として利用できれば、電子放出の効率が向上することが予想される。
【０００５】
【発明が解決しようとする課題】
本発明者らは、現在工業的に製造方法が確立されている気相法炭素繊維に着目し、電子放出材料としての用途に使用できると考える先端の両端形状を細く尖らせた該炭素質繊維を量産規模で得ようとするものである。
すなわち、本発明の目的は、従来製造出来なかった両端の尖った形状の炭素質繊維を得るものであり、その量産する方法を提供するものである。
【０００６】
【課題を解決するための手段】
本発明者らは、上記炭素質繊維の先端の形状を鋭角にすべく、機械的な衝撃や摩耗による粉砕をはじめとし種々の方法を検討したが、酸素の存在下で加熱することにより効率よく両端が鋭角になることを見いだし本発明を完成させ、従来見られなかった両端形状の尖った炭素質繊維を得ることができた。
すなわち、
１）縮合環状の炭素面が繊維軸を中心に年輪状に積層した炭素質繊維において、繊維の先端が両端とも鋭角であることを特徴とする炭素質繊維。であり
２）炭素質繊維が焼成又は黒鉛化されていることを特徴とする上記１）の炭素質繊維。であり
３）上記１）又は２）は、炭素質繊維の繊維軸部分に、中空構造を持つことを特徴としている。更に
４）上記１）又は２）又は３）について、先端の両端とも鋭角な炭素質繊維と、一方または両方とも鋭角でない炭素質繊維とが混在しているものが得られ、
その方法として、
５）縮合環状の炭素面が繊維軸を中心に年輪状に積層した炭素質繊維を酸素の存在下、４００℃以上１２００℃以下の温度で加熱することにより得られる。
【０００７】
【発明の実施の形態】
さらに詳細に本発明について説明すれば、本発明の縮合環状の炭素面が繊維軸を中心に年輪状に積層した炭素質繊維は、気相成長炭素繊維やカーボンナノチューブ等に代表される炭素繊維であり、繊維軸部分が中空構造であっても良い。
気相法成長炭素繊維は、特公平４−２４３２０、特許２７７８４３４号等で示されている。カーボンナノチューブは飯島らにより発見され、種々の製法が提案されているが、本発明は気相法炭素繊維、カーボンナノチューブともにその製法には限定されない。しかし、本発明者らの研究によれば、気相成長による炭素繊維特有の縮合環状の炭素面が繊維軸を中心に年輪状に積層した炭素質繊維についてのみ、本発明の両端の鋭角な形状を持った炭素質繊維が得られた。
【０００８】
また、本発明の先端の鋭角な状態の定義は、図−１に示すように、炭素質繊維の繊維径をｄ０、先端の径をｄ１とし繊維径が細くなりはじめる点と先端との距離をＬとすると、ｄ１／ｄ０＜０．５かつ０．５＜Ｌ／ｄ０で示される。
また、鋭角な炭素質繊維の先端の多くは繊維中心軸上に存在するが、図−１に示すように繊維中心軸からずれていてもよい。
先端の構造は、図−２に示すように、繊維軸を中心に縮合環状の炭素面が年輪状に開いて存在し、先端の中心軸は中空構造をとっても良いし取らなくても良い。
本発明の先端が鋭角な炭素質繊維は、先端の両端とも鋭角な炭素質繊維と、一方又は両方とも鋭角でない炭素質繊維とが混在していても良い。その存在比率は、先端の両端が鋭角な炭素質繊維が全体の１０％以上を占めている。
本発明の炭素質繊維の繊維径や長さには特に制限はないが、通常繊維径は０．０００５μｍから５０μｍであり、繊維長は０．５μｍから数ｍｍであるが、好ましくは繊維径は０．０００５μｍから１μｍであり、繊維長は０．５μｍから５００μｍ程度である。また、炭素質繊維表面の一部は酸化等により、他の部分より細くなっていても良い。
本発明の両端が鋭角な炭素質繊維の製造方法は、縮号環状の炭素面が繊維軸を中心に年輪状に積層した炭素質繊維を酸素の存在下、４００℃以上１２００℃以下の温度で加熱する。４００℃未満では、酸化が起こらず先端の鋭角化が進まない。また、１２００℃を超えると、酸化の速度が速く、適切な時間の制御が難しくなる。
また、材料となる炭素質繊維の熱処理状態は、８００℃以上で焼成されているか、２０００℃以上で黒鉛化されていても良い。未焼成または未黒鉛化品は、４００℃未満で酸化が進み、同様に制御が難しい。
なお、炭素質繊維の熱処理履歴により処理温度及び時間を調整する。また、本酸化処理を行った後で、黒鉛化処理を行っても良い。
【０００９】
【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。
（実施例１）
特許２７７８４３４号に示したように、内径１７０×長さ１５００の反応管を備えた縦型加熱炉を用い、反応管の頂部に二流体噴霧ノズルを取り付け、反応管を１２００℃に加熱維持する。４重量％のフェロセンを含有する原料２０ｇ／分と水素１００Ｌ／分を用いて、二流体噴霧ノズルにより、反応管内壁に原料を噴霧供給する。反応管内に生成した気相法炭素繊維を５分間隔でかきおとしながら、反応を１時間行い、気相法炭素繊維を回収した。得られた気相法炭素繊維を２８００℃で黒鉛化を行った。
それを坩堝に詰め、７５０℃に加熱したマッフル炉に入れ４時間加熱した。その際の炭素質繊維残存率は２１ｗｔ％であった。
得られた酸化処理した炭素質繊維を透過電子顕微鏡（ＴＥＭ）にて観察した。その写真を図−３、図−４に示す。
図−３から測定した先端の両端が鋭角な炭素質繊維の径、形状寸法を表−１に示すが、図−３の炭素質繊維の一方は、ｄ１／ｄ０＝０．０８、Ｌ／ｄ０＝３．４；ｄ１／ｄ０＝０．０５，Ｌ／ｄ０＝５．４であり、もう一方はｄ１／ｄ０＝０．１３、Ｌ／ｄ０＝１．３；ｄ１／ｄ０＝０．０６、Ｌ／ｄ０＝１．９であった。
【００１０】
☆
【表１】
【発明の効果】
本発明によれば、電子放出材として望まれる両端の尖った炭素質繊維が量産規模の気相法炭素繊維から簡単な製法にて安価に得られる。
【００１２】
【図面の簡単な説明】
【図１】本発明の先端の鋭角な状態を定義する説明図である。
【図２】先端の鋭角な炭素質繊維の構造を示す図である。
【図３】本発明による先端の鋭角な炭素質繊維の１例を示す透過電子顕微鏡写真である。
【図４】本発明による先端の鋭角な炭素質繊維の他の例の透過電子顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a carbonaceous fiber having a sharp tip and a method for producing the same.
More particularly, the present invention relates to a carbonaceous fiber having sharp edges at both ends, which is useful mainly for a field electron emission source, and a method for producing the same.
[0002]
[Prior art]
In recent years, it has been studied to use a carbonaceous fiber as an electron source for an electron-emitting device for a cold cathode used in an electronic display device, an image forming apparatus or the like.
Regarding the production of the carbonaceous fiber, for example, in Japanese Patent Application Laid-Open No. 8-115652, carbon produced as a result of thermally decomposing hydrocarbon gas as a raw material in a minute gap between two electrodes set on an insulating substrate. A production method is shown in which the fibrous material is deposited.
Japanese Patent Application Laid-Open No. 10-112257 describes a method in which carbon ions or carbon cluster ions are ion-implanted on the surface of a substrate cathode, and nucleation sites formed therefrom are used as nuclei to synthesize diamond-like carbon in a gas phase.
All of these can be technically manufactured, but since the thermal influence on the cathode member becomes a problem, the heat treatment of the carbonaceous fiber is difficult, and thus the electron emission effect of the carbonaceous fiber is limited.
In addition, all of them synthesize carbon directly on a cathode such as a substrate. Mass production requires know-how and equipment technology unique to the manufacturer, and the process is complicated, so that it is not a method generally used by cathode material manufacturers.
[0003]
On the other hand, minute carbon nanotubes with a diameter of several tens of nm or less have been in the spotlight for several years as electron emission materials. This is usually a graphite tube with a thickness of about 1 nm to 50 nm, and its production method is performed on the surrounding electrode by generating a carbon electrode on the electrode by arc discharge or applying a powerful laser beam to the carbon electrode. Generate. The shape of this nanotube is generally a shape with one pointed tip as seen in Hyundai Kagaku P57 (July 1998).
Carbon nanotubes are chemically stable and mechanically strong, and are being studied as field emission electron sources. For example Saito et al., Ceramics 33 (1998) No. 6 shows an example in which a large number of these are attached on a cathode plate and used as a fluorescent display tube, suggesting the possibility of use in an energy-saving flat display and a high-definition color CRT.
[0004]
However, for carbon nanotubes, an industrial production method has not been established, and stable quality products are not supplied at low cost.
In recent years, vapor-grown carbon fibers have been mass-produced as having properties similar to carbon nanotubes. This is a method of spraying an organic compound into a reaction vessel to produce carbon fibers by thermal decomposition as shown in the production methods of Japanese Patent Publication Nos. 04-24320 and Japanese Patent No. 2778434. Carbon fibers having a diameter of several μm or less are mass-produced. Is obtained. Examining these shapes in detail, the condensed ring carbon surface shows the appearance of laminated annual rings around the fiber axis, and when these end surfaces are viewed, it is closed in a round sphere or is divided, and its cross section Indicates a state substantially perpendicular to the fiber axis direction.
As described above, when used as a field electron emission source, a condensed ring-shaped carbon surface end face appears at an acute angle and an edge appears, so that field electron emission characteristics are improved.
In particular, carbonaceous fibers with sharp end faces have not been discovered at present, and if they can be used as electron emission materials, it is expected that the efficiency of electron emission will be improved.
[0005]
[Problems to be solved by the invention]
The present inventors pay attention to vapor-grown carbon fibers for which industrial production methods are currently established, and consider that the carbonaceous fibers are sharply sharpened at both ends at the tips that can be used for electron emission materials. Is to be obtained on a mass production scale.
That is, an object of the present invention is to obtain a carbonaceous fiber having pointed ends that could not be produced conventionally, and to provide a method for mass production.
[0006]
[Means for Solving the Problems]
In order to make the shape of the tip of the carbonaceous fiber an acute angle, the present inventors have studied various methods including pulverization by mechanical impact and wear. The inventors have found that both ends have acute angles and have completed the present invention, and have obtained carbonaceous fibers with sharp ends that have not been seen in the past.
That is,
1) A carbonaceous fiber in which condensed cyclic carbon surfaces are laminated in an annual ring shape with a fiber axis as the center, and the tip of the fiber is acute at both ends. 2) The carbonaceous fiber according to 1) above, wherein the carbonaceous fiber is fired or graphitized. 3) The above 1) or 2) is characterized in that the fiber axis portion of the carbonaceous fiber has a hollow structure. 4) For the above 1) or 2) or 3), there is obtained a mixture of carbonaceous fibers having acute angles at both ends of the tip and carbonaceous fibers having one or both of which are not acute angles,
As a method,
5) It is obtained by heating a carbonaceous fiber in which condensed cyclic carbon surfaces are laminated in an annual ring shape around the fiber axis at a temperature of 400 ° C. or higher and 1200 ° C. or lower in the presence of oxygen.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in more detail. The carbonaceous fiber in which the condensed cyclic carbon surface of the present invention is laminated in an annual ring shape around the fiber axis is a carbon fiber typified by vapor grown carbon fiber or carbon nanotube. Yes, the fiber shaft portion may have a hollow structure.
The vapor grown carbon fiber is disclosed in Japanese Patent Publication No. 4-24320, Japanese Patent No. 2778434, and the like. Carbon nanotubes have been discovered by Iijima et al. And various production methods have been proposed, but the present invention is not limited to the production methods for both vapor-grown carbon fibers and carbon nanotubes. However, according to the study by the present inventors, only the carbonaceous fibers in which condensed carbon surfaces peculiar to carbon fibers obtained by vapor phase growth are laminated in an annual ring shape around the fiber axis, the acute shape at both ends of the present invention. A carbonaceous fiber with a high yield was obtained.
[0008]
In addition, as shown in FIG. 1, the definition of the acute angle state of the tip of the present invention is as follows: the fiber diameter of the carbonaceous fiber is d 0 , the tip diameter is d 1, and the point where the fiber diameter starts to decrease and the tip When the distance is L, d 1 / d 0 <0.5 and 0.5 <L / d 0 are indicated.
Further, most of the sharp carbon fiber tips are present on the fiber center axis, but may be displaced from the fiber center axis as shown in FIG.
As shown in FIG. 2, the structure of the tip is such that a condensed annular carbon surface exists in an annual ring shape around the fiber axis, and the center axis of the tip may or may not take a hollow structure.
The carbonaceous fiber having a sharp tip of the present invention may contain a carbonaceous fiber having a sharp angle at both ends of the tip and a carbonaceous fiber having one or both of which are not acute angles. As for the abundance ratio, carbon fibers having sharp edges at both ends account for 10% or more of the total.
The fiber diameter and length of the carbonaceous fiber of the present invention are not particularly limited. Usually, the fiber diameter is 0.0005 μm to 50 μm, and the fiber length is 0.5 μm to several mm. Preferably, the fiber diameter is The fiber length is about 0.0005 μm to 1 μm, and the fiber length is about 0.5 μm to 500 μm. Further, a part of the carbonaceous fiber surface may be thinner than the other part by oxidation or the like.
In the method for producing carbonaceous fibers having sharp edges at both ends of the present invention, carbonaceous fibers obtained by laminating condensed carbon surfaces in the shape of annual rings around the fiber axis are present at a temperature of 400 ° C. or higher and 1200 ° C. or lower in the presence of oxygen. Heat. Below 400 ° C., oxidation does not occur and sharpening of the tip does not proceed. Moreover, when it exceeds 1200 degreeC, the speed | rate of oxidation is quick and control of appropriate time becomes difficult.
Moreover, the heat-treated state of the carbonaceous fiber used as a material may be baked at 800 ° C. or higher, or graphitized at 2000 ° C. or higher. Unfired or non-graphitized products undergo oxidation at temperatures below 400 ° C. and are similarly difficult to control.
In addition, process temperature and time are adjusted with the heat processing log | history of carbonaceous fiber. Moreover, after performing this oxidation process, you may perform a graphitization process.
[0009]
【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.
Example 1
As shown in Japanese Patent No. 2778434, a vertical heating furnace equipped with a reaction tube having an inner diameter of 170 × length of 1500 is used, a two-fluid spray nozzle is attached to the top of the reaction tube, and the reaction tube is heated and maintained at 1200 ° C. The raw material is sprayed and supplied to the inner wall of the reaction tube by a two-fluid spray nozzle using 20 g / min of raw material containing 4% by weight of ferrocene and 100 L / min of hydrogen. The reaction was carried out for 1 hour while the vapor grown carbon fiber produced in the reaction tube was scraped at an interval of 5 minutes, and the vapor grown carbon fiber was recovered. The obtained vapor grown carbon fiber was graphitized at 2800 ° C.
It was packed in a crucible and placed in a muffle furnace heated to 750 ° C. and heated for 4 hours. At that time, the residual ratio of carbonaceous fibers was 21 wt%.
The obtained oxidized carbonaceous fiber was observed with a transmission electron microscope (TEM). The photographs are shown in Figs.
Table 1 shows the diameter and shape of carbonaceous fibers with sharp ends measured from FIG. 3, and one of the carbonaceous fibers in FIG. 3 is d 1 / d 0 = 0.08, L / D 0 = 3.4; d 1 / d 0 = 0.05, L / d 0 = 5.4, the other is d 1 / d 0 = 0.13, L / d 0 = 1.3 ; d 1 / d 0 = 0.06 , was L / d 0 = 1.9.
[0010]
☆
[Table 1]
【The invention's effect】
According to the present invention, carbonaceous fibers having sharp ends desired as an electron emission material can be obtained at low cost from a gas phase process carbon fiber on a mass production scale by a simple manufacturing method.
[0012]
[Brief description of the drawings]
FIG. 1 is an explanatory view defining an acute angle state of a tip of the present invention.
FIG. 2 is a view showing the structure of a carbonaceous fiber having a sharp tip.
FIG. 3 is a transmission electron micrograph showing an example of a sharp carbonaceous fiber having a sharp tip according to the present invention.
FIG. 4 is a transmission electron micrograph of another example of a carbon fiber having a sharp tip according to the present invention.
Claims (4)
Priority Applications (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP37863498A JP3890791B2 (en) | 1998-11-20 | 1998-11-20 | Sharp carbonaceous fiber at both ends and method for producing the same |
| US09/444,201 US6221489B1 (en) | 1998-11-19 | 1999-11-22 | Carbonaceous fiber acute-angled at both ends and production process therefor |
| US09/638,863 US6527988B1 (en) | 1998-11-20 | 2000-08-15 | Process of making carbon fiber with sharp ends |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP37863498A JP3890791B2 (en) | 1998-11-20 | 1998-11-20 | Sharp carbonaceous fiber at both ends and method for producing the same |
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| Application Number | Title | Priority Date | Filing Date |
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| JP2006279660A Division JP2007051410A (en) | 2006-10-13 | 2006-10-13 | Carbonaceous fiber and method for producing the same |
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| Publication Number | Publication Date |
|---|---|
| JP2000220039A JP2000220039A (en) | 2000-08-08 |
| JP2000220039A5 JP2000220039A5 (en) | 2005-08-11 |
| JP3890791B2 true JP3890791B2 (en) | 2007-03-07 |
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| Application Number | Title | Priority Date | Filing Date |
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| JP37863498A Expired - Fee Related JP3890791B2 (en) | 1998-11-19 | 1998-11-20 | Sharp carbonaceous fiber at both ends and method for producing the same |
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| JP (1) | JP3890791B2 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4131306B2 (en) * | 1998-12-10 | 2008-08-13 | 昭和電工株式会社 | Electron emission material |
| 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 |
| WO2003014441A1 (en) * | 2001-08-03 | 2003-02-20 | Showa Denko K. K. | Fine carbon fiber and composition thereof |
| JP3930335B2 (en) * | 2001-08-29 | 2007-06-13 | 株式会社Ｇｓｉクレオス | Carbon fiber, battery electrode material and carbon fiber manufacturing method by vapor phase growth method |
| JP4654363B2 (en) * | 2004-03-16 | 2011-03-16 | 独立行政法人物質・材料研究機構 | Method for producing graphitized fine wire |
| JP4723228B2 (en) * | 2004-11-19 | 2011-07-13 | 帝人株式会社 | Mustache fiber |
| JP4784109B2 (en) * | 2005-02-21 | 2011-10-05 | 独立行政法人物質・材料研究機構 | Fuel cell electrode material and method for producing the same |
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1998
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| JP2000220039A (en) | 2000-08-08 |
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