JP2005145735A - Method for producing quartz glass and quartz glass produced by the same - Google Patents

Method for producing quartz glass and quartz glass produced by the same Download PDF

Info

Publication number
JP2005145735A
JP2005145735A JP2003382412A JP2003382412A JP2005145735A JP 2005145735 A JP2005145735 A JP 2005145735A JP 2003382412 A JP2003382412 A JP 2003382412A JP 2003382412 A JP2003382412 A JP 2003382412A JP 2005145735 A JP2005145735 A JP 2005145735A
Authority
JP
Japan
Prior art keywords
quartz glass
microwave
temperature
heating
heat insulating
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
JP2003382412A
Other languages
Japanese (ja)
Inventor
Katsuya Tajiri
勝也 田尻
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Sumitomo Metal Industries Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sumitomo Metal Industries Ltd filed Critical Sumitomo Metal Industries Ltd
Priority to JP2003382412A priority Critical patent/JP2005145735A/en
Publication of JP2005145735A publication Critical patent/JP2005145735A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B19/00—Other methods of shaping glass
    • C03B19/06—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
    • C03B19/066—Other methods of shaping glass by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction for the production of quartz or fused silica articles
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B20/00—Processes specially adapted for the production of quartz or fused silica articles, not otherwise provided for
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B2201/00—Type of glass produced
    • C03B2201/02—Pure silica glass, e.g. pure fused quartz
    • C03B2201/03—Impurity concentration specified
    • C03B2201/04—Hydroxyl ion (OH)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing quartz glass in which the in-plane distribution of OH groups is uniform and which has excellent internal quality by using inexpensive equipment by sintering a very brittle soot having high purity without being contaminated or broken. <P>SOLUTION: The method for producing the quartz glass is characterized by sintering a quartz glass preform by heating it with microwave in a vessel having a heat insulating material. A preferable dielectric constant of the heat insulating material is ≤10, and a suitable frequency of the microwave is ≥28 GHz. The quartz glass of this invention is characterized by being produced by such a method. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

本発明は、石英ガラスの製造方法に関し、詳細には、内質に優れ、面内ＯＨ基分布の均一な石英ガラスの製造方法に関する。   The present invention relates to a method for producing quartz glass, and more particularly, to a method for producing quartz glass having excellent inner quality and uniform in-plane OH group distribution.

一般に、ＶＡＤ法により製造した多孔質石英ガラス母材から、石英ガラスを製造する方法としては、カーボン部品を用い、高真空容器内で抵抗加熱により焼成する方法がある。この加熱方法は、カーボン部品を発熱させることにより、その輻射熱で多孔質石英ガラス母材を表面より昇温する。しかし、母材表面からの加熱により、表面温度が急激に上昇すると、母材表面の緻密化が先行し、母材中心部の焼結が遅れ、母材中の粒子間の空隙にガスが閉じ込められて気泡として残留してしまう傾向がある。   In general, as a method of producing quartz glass from a porous quartz glass base material produced by the VAD method, there is a method of firing by resistance heating in a high vacuum vessel using a carbon component. In this heating method, by heating the carbon component, the porous quartz glass base material is heated from the surface by the radiant heat. However, if the surface temperature rises sharply due to heating from the base material surface, the base material surface will be densified, sintering of the base material center will be delayed, and gas will be trapped in the voids between the particles in the base material. Tend to remain as bubbles.

また、脱ＯＨ基反応も抑止され、ＯＨ基濃度が十分に低減できないまま、焼結を完了してしまう事態が生じ得る。多孔質母材の製造においては、気化したＳｉＣ１４の加水分解により、ＳｉＯ２ネットワーク構造を生成していくが、この際、Ｓｉ−Ｏ結合の内いくらかはＳｉ−ＯＨとなり、焼結の際、ガラス中にＯＨ基として残留する。ＯＨ基はガラスの耐熱性に影響し、ＯＨ基の分布に起因して屈折率の分布が形成され、光学特性に多大な影響を及ぼす。 Further, the deOH group reaction is also suppressed, and a situation may occur in which the sintering is completed while the OH group concentration cannot be sufficiently reduced. In the manufacture of the porous preform, by hydrolysis of the vaporized SiCl 4, but continue to produce a SiO 2 network structure, this time, when the some of SiO bonds Si-OH, and the sintering, It remains as OH groups in the glass. The OH group affects the heat resistance of the glass, and a refractive index distribution is formed due to the distribution of the OH group, which greatly affects the optical characteristics.

したがって、ＯＨ基濃度は低減する必要があるが、真空中での抵抗加熱法では、母材の中心部の昇温が遅れることにより、脱ＯＨ基反応が遅れ、石英ガラス内にＯＨ基が封止されたまま焼結が完了してしまうことがある。また、脱ＯＨ基反応を十分に行なえるように時間をかける必要があり、コストアップとなる。   Therefore, it is necessary to reduce the OH group concentration. However, in the resistance heating method in vacuum, the temperature rise at the center of the base material is delayed, so that the deOH group reaction is delayed and the OH group is sealed in the quartz glass. Sintering may be completed while stopped. In addition, it is necessary to spend time so that the deOH group reaction can be sufficiently performed, resulting in an increase in cost.

このため、真空あるいは減圧雰囲気下で加熱し、透明化する方法（特許文献１参照）、また、昇温パターンをいくつかに区分し、それぞれの区分で圧力調整を行なう方法（特許文献２参照）が提案されている。確かに、雰囲気の調整により、ガラス微粒子間の空隙から脱ガスさせ、気泡を低減できる可能性はある。しかし、抵抗加熱による母材表面からの加熱では、どうしても母材内部の昇温が遅れ、表面の緻密化が進行するするため、焼結温度以下で長時間保持する工程が必要となり、コストアップとなる。   For this reason, a method of heating in a vacuum or a reduced pressure atmosphere to make transparent (see Patent Document 1), and a method of dividing the temperature rising pattern into several parts and adjusting the pressure in each section (see Patent Document 2) Has been proposed. Certainly, there is a possibility that bubbles can be reduced by degassing the voids between the glass particles by adjusting the atmosphere. However, heating from the surface of the base material by resistance heating inevitably delays the temperature rise inside the base material, and the surface is densified. Become.

一方、マイクロ波により、加熱し、焼結する方法が知られている。たとえば、ガラスまたは多孔質ガラスを、電気ヒータを具備したマイクロ波加熱装置（周波数２４５０ＭＨｚ）で加熱して脱水処理を行ない、焼結する方法が考案されている（特許文献３参照）。しかし、発熱量は周波数に比例し、周波数２４５０ＭＨｚのマイクロ波では石英を十分に加熱することが難しく、電気ヒータに依存する所が大きい。したがって、母材の表面からの加熱が先行し、表面温度の上昇に伴い、母材表面の緻密化が先行し、中心部の焼結が遅れて、内質が劣化し、ＯＨ基面内分布の不均一なガラスしか得られない。また、電気ヒータを別途具備したマイクロ波加熱装置を必要とするため、設備コストが高くなる。
特開平１−２７５４４１号公報 特開平５−１６３０３８号公報 特開平５−９７４６６号公報（第４頁、実施例１〜３） On the other hand, a method of heating and sintering with microwaves is known. For example, a method has been devised in which glass or porous glass is heated with a microwave heating device (frequency 2450 MHz) equipped with an electric heater to perform dehydration treatment and sintering (see Patent Document 3). However, the amount of heat generation is proportional to the frequency, and it is difficult to sufficiently heat quartz with microwaves having a frequency of 2450 MHz, and it largely depends on the electric heater. Therefore, heating from the surface of the base material precedes, and as the surface temperature rises, densification of the surface of the base material precedes, sintering of the central part is delayed, the internal quality deteriorates, and the OH base surface distribution Only non-uniform glass can be obtained. Moreover, since the microwave heating apparatus separately equipped with the electric heater is required, an installation cost becomes high.
JP-A-1-275441 JP-A-5-163038 JP-A-5-97466 (Page 4, Examples 1 to 3)

本発明の課題は、高純度で非常に脆いスートを汚染または破損することなく焼結して、ＯＨ基の面内分布が均一で、内質の優れる石英ガラスを安価な設備で製造する方法を提供することにある。   An object of the present invention is to sinter high-purity and very brittle soot without contamination or damage, and to produce a method for producing quartz glass having a uniform in-plane distribution of OH groups and excellent in quality with inexpensive equipment. It is to provide.

本発明の石英ガラスの製造方法は、断熱材を有する容器内において、石英ガラス母材をマイクロ波により加熱し焼結することを特徴とする。断熱材の比誘電率は１０以下が好ましく、マイクロ波の周波数は２８ＧＨｚ以上が好適である。本発明の石英ガラスは、かかる方法により製造することを特徴とする。   The method for producing quartz glass of the present invention is characterized in that a quartz glass base material is heated and sintered by microwaves in a container having a heat insulating material. The relative dielectric constant of the heat insulating material is preferably 10 or less, and the microwave frequency is preferably 28 GHz or more. The quartz glass of the present invention is manufactured by such a method.

本発明によれば，内質に優れ、ＯＨ基の面内分布が均一な石英ガラスを製造することができる。   According to the present invention, it is possible to produce quartz glass having excellent inner quality and uniform in-plane distribution of OH groups.

本発明の石英ガラスの製造方法は、断熱材を有する容器内において、石英ガラス母材をマイクロ波により加熱し焼結することを特徴とする。石英ガラス母材の焼成に際して、マイクロ波を用いた加熱方式を採用することにより、分子振動により母材の中心部から外周部にかけて均一に加熱することができる。したがって、抵抗加熱方式のように、母材の表面からの加熱が先行し、母材表面の緻密化が進行し、中心部の焼結が遅れるという現象が生じることはなく、母材に内包される気泡およびＯＨ基を均一に低減することができる。このため、内質に優れ、ＯＨ基の面内分布が均一な石英ガラスを製造することができ、面内のＯＨ基濃度のバラツキを１０ｐｐｍ以下とすることも容易となる。   The method for producing quartz glass of the present invention is characterized in that a quartz glass base material is heated and sintered by microwaves in a container having a heat insulating material. When the quartz glass base material is fired, a heating method using a microwave is employed, so that the quartz glass base material can be uniformly heated from the center portion to the outer peripheral portion of the base material by molecular vibration. Therefore, unlike the resistance heating method, the heating from the surface of the base material precedes, the densification of the surface of the base material proceeds, and the phenomenon that the sintering of the center part is delayed does not occur, and is included in the base material. Bubbles and OH groups can be reduced uniformly. For this reason, it is possible to produce a quartz glass having excellent internal quality and uniform in-plane distribution of OH groups, and it is easy to make the variation of the in-plane OH group concentration 10 ppm or less.

マイクロ波は、周波数１ＧＨｚ〜１０００ＧＨｚ程度の電波であり、本発明の製造方法においては、断熱材を有する容器を使用する。石英は、比誘電率が低いため、断熱材からなる容器または断熱材を備える容器内において加熱しないと、周波数２８ＧＨｚ程度のマイクロ波では電力を増加させても、マイクロ波による発熱量よりも放熱量の方が上回り、十分に昇温することは困難であり、加熱効率も悪くなる。さらに高い周波数のマイクロ波を照射することにより発熱量を増加させる方法も考えられるが、そのような高い周波数のマイクロ波を連続して照射できる工業用の設備は存在せず、断熱材を有する容器を使用することなく、マイクロ波のみにより石英ガラス母材を焼結することは現状では困難である。   The microwave is a radio wave having a frequency of about 1 GHz to 1000 GHz, and a container having a heat insulating material is used in the manufacturing method of the present invention. Since quartz has a low relative dielectric constant, if it is not heated in a container made of a heat insulating material or a container provided with a heat insulating material, even if the power is increased in a microwave with a frequency of about 28 GHz, the heat dissipation is larger than the heat generated by the microwave. It is difficult to raise the temperature sufficiently, and the heating efficiency is also deteriorated. Although a method of increasing the calorific value by irradiating a microwave with a higher frequency is also conceivable, there is no industrial facility that can continuously irradiate such a high frequency microwave, and a container having a heat insulating material It is difficult at present to sinter a quartz glass base material only by microwaves without using.

断熱材としては、比誘電率が石英と同程度またはそれに近く、高温に耐えられるものが好ましい。したがって、入手のしやすさおよび価格なども考慮すると、断熱材にはアルミナが好適である。ただし、アルミナでも石英より比誘電率が高く、照射するマイクロ波の周波数が高くなればなるほど、断熱材として使用するアルミナの発熱量の方が、石英の発熱量よりも大きくなる。このため、マイクロ波により加熱する場合においても、厳密には、輻射による、試料の外表面からの加熱も多少は含まれることになる。しかし、外表面からの加熱を一定量以下に抑えることにより、ＯＨ基濃度の均一な石英ガラスを得るために、断熱材として用いる材料の比誘電率は１０以下が望ましく、石英の比誘電率に近い６以下がより望ましい。また、合成する石英ガラスは高純度である点に大きな特徴があるから、本発明の製造方法に用いる断熱材は、少なくとも石英母材に対向する面には、高純度のＳｉＯ２を配する態様が好ましい。一方、断熱材は、熱の遮断作用が大きい点で、嵩密度が０．３５ｇ/ｃｍ３以下が好ましく、０．３ｇ／ｃｍ３以下がより好ましい。 As the heat insulating material, a material having a relative dielectric constant similar to or close to that of quartz and capable of withstanding high temperatures is preferable. Therefore, alumina is suitable for the heat insulating material in consideration of availability and price. However, alumina also has a higher dielectric constant than quartz, and the higher the frequency of the irradiated microwave, the greater the calorific value of alumina used as a heat insulating material than the calorific value of quartz. For this reason, even when heating by microwaves, strictly speaking, heating from the outer surface of the sample due to radiation is included to some extent. However, in order to obtain quartz glass having a uniform OH group concentration by suppressing heating from the outer surface to a certain amount or less, the relative dielectric constant of the material used as the heat insulating material is desirably 10 or less, and the relative dielectric constant of quartz is Closer 6 or less is more desirable. In addition, since the quartz glass to be synthesized is highly characterized in that it has a high purity, the heat insulating material used in the production method of the present invention is a mode in which high-purity SiO 2 is disposed at least on the surface facing the quartz base material. Is preferred. On the other hand, insulation, in terms blocking the action of heat is large, the bulk density of preferably 0.35 g / cm 3 or less, 0.3 g / cm 3 or less is more preferable.

図１に、電波（マイクロ波）を照射した場合の概念図を示す。図１（ａ）に示すように、金属は電波を反射するため、加熱されない。また、図１（ｂ）に示すように、誘電体のうち損失係数が小さい場合は、電波が透過するため、有効に加熱することはできない。一方、図１（ｃ）に示すように、誘電体のうち損失係数が大きい場合は、マイクロ波は吸収され発熱するため、加熱することができる。   FIG. 1 shows a conceptual diagram when a radio wave (microwave) is irradiated. As shown in FIG. 1A, metal reflects radio waves and is not heated. Further, as shown in FIG. 1B, when the loss factor is small among the dielectrics, radio waves are transmitted, so that it cannot be heated effectively. On the other hand, as shown in FIG. 1C, when the loss factor of the dielectric is large, the microwave is absorbed and generates heat, so that it can be heated.

図２（ａ）に、周波数９１５ＭＨｚの電波を照射した場合の比誘電率を示す。また、図２（ｂ）に、周波数２４５０ＭＨｚの電波を照射した場合の比誘電率を示す。図２に示すとおり、石英の比誘電率は低いため、電波が透過しやすく、一般には発熱させにくい。しかし、電波による発熱量（Ｗ/ｍ３）は、
Ｐ＝２πｆε０εｒtanδＥ２
（Ｐ：発熱量、ｆ：周波数、ε０：真空中の誘電率、εｒ：比誘電率、tanδ：誘電体損失角、Ｅ：電界の強さ）
で表され、高周波数の電波であるマイクロ波を照射すると、誘電損失係数（ε０εｒtanδ）が大きくなって、図１（ｃ）に示すように、マイクロ波は誘電体に吸収され、発熱させることができる。したがって、マイクロ波の周波数は大きいほど好ましいことになるが、高周波数の電波を連続で発信できる工業用の設備は製造が困難であるため、本発明では、好ましくは２８ＧＨｚ以上のマイクロ波、より好ましくは３０ＧＨｚ以上のマイクロ波を使用する。 FIG. 2A shows the relative permittivity when a radio wave having a frequency of 915 MHz is irradiated. FIG. 2B shows the relative permittivity when a radio wave having a frequency of 2450 MHz is irradiated. As shown in FIG. 2, since the relative dielectric constant of quartz is low, radio waves are easily transmitted, and generally it is difficult to generate heat. However, the amount of heat generated by radio waves (W / m 3 ) is
P = 2πfε 0 ε r tanδE 2
(P: calorific value, f: frequency, ε 0 : dielectric constant in vacuum, ε r : relative dielectric constant, tan δ: dielectric loss angle, E: electric field strength)
When a microwave that is a high-frequency radio wave is irradiated, the dielectric loss coefficient (ε 0 ε r tan δ) increases, and the microwave is absorbed by the dielectric as shown in FIG. Can generate heat. Accordingly, the higher the frequency of the microwave, the better. However, since it is difficult to manufacture an industrial facility capable of continuously transmitting a high-frequency radio wave, in the present invention, a microwave of 28 GHz or higher is preferable. Uses microwaves of 30 GHz or higher.

原料である石英ガラス母材は、たとえば、スート粉またはスート塊であり、多孔質石英ガラス材料を使用することができる。焼結時の加熱炉内の雰囲気は、減圧下で行なう態様が好ましく、Ｎ２またはＨｅなどの不活性ガス雰囲気下あるいはＨ２雰囲気下で焼結することもできる。また、焼結温度までの昇温パターンは、必ずしも均一なくてもよく、製造する石英ガラスの内質に応じて、温度保持帯を導入することもできる。 The raw material quartz glass base material is, for example, soot powder or soot lump, and a porous quartz glass material can be used. The atmosphere in the heating furnace during sintering is preferably performed under reduced pressure, and sintering can also be performed in an inert gas atmosphere such as N 2 or He or in an H 2 atmosphere. The temperature rising pattern up to the sintering temperature is not necessarily uniform, and a temperature holding zone can be introduced according to the quality of the quartz glass to be produced.

実施例１
図３に、本実施例に供したマイクロ波加熱炉の概略図を示す。図３に示すように、ジャイラトロン発振管３１により、周波数２８ＧＨｚ、最大出力１０ＫＷのマイクロ波を発振させ、ジャイラトロン発振管３１より発振させたマイクロ波を、導波管３２により照射室３３へ導いた。ステンレス製の照射室３３の外周部は冷却することができ、照射室３３の中には試料台３４を配した。照射室３３内の試料台３４上の石英ガラス母材にマイクロ波を照射し、照射されたマイクロ波が、ガラス母材に吸収され、昇温する仕組みである。 Example 1
FIG. 3 shows a schematic diagram of a microwave heating furnace provided for this example. As shown in FIG. 3, a microwave having a frequency of 28 GHz and a maximum output of 10 KW is oscillated by a gyrotron oscillating tube 31, and the microwave oscillated from the gyrotron oscillating tube 31 is guided to an irradiation chamber 33 by a waveguide 32. It was. The outer periphery of the stainless steel irradiation chamber 33 can be cooled, and a sample stage 34 is arranged in the irradiation chamber 33. The quartz glass base material on the sample stage 34 in the irradiation chamber 33 is irradiated with microwaves, and the irradiated microwave is absorbed by the glass base material to raise the temperature.

ガラス母材によるマイクロ波の吸収効率が高いと、マイクロ波は消費されるが、ガラス母材による吸収率が低いと、消費されないマイクロ波が、再度、導波管３２を逆行して、ジャイラトロン発振管３１へ戻り、ジャイラロトン発振管３１を加熱損傷する虞がある。このため、ジャイラトロン発振管３１に到達する前で、消費されないマイクロ波を吸収させて、設備を保護する仕組みとした（図示していない。）。   When the absorption efficiency of the microwave by the glass base material is high, the microwave is consumed, but when the absorption rate by the glass base material is low, the unconsumed microwave goes back through the waveguide 32 again, and the gyrotron Returning to the oscillation tube 31, there is a possibility that the gyroroton oscillation tube 31 may be damaged by heating. For this reason, before reaching the gyrotron oscillating tube 31, a microwave that is not consumed is absorbed to protect the equipment (not shown).

まず、予備試験として、昇温実験を行ない、非常に比誘電率が低い石英からなるガラス母材が、周波数２８ＧＨｚのマイクロ波により昇温できるかどうか、また、抵抗加熱とは異なる昇温パターンが得られるかどうかを確認した。昇温試験は、つぎのように行なった。図４に、本実施例におけるスート粉のマイクロ波加熱に際しての試料のセット状態を示す。図４に示すように、内径Ｄが２６０ｍｍ、高さＨが２００ｍｍの石英製坩堝４６にスート粉を充填した。坩堝４６の中心には温度制御用の熱電対４１を配し、さらに、その外側には測温用の熱電対４２〜４５を等間隔に配した。坩堝４６の外側には、厚さ５０ｍｍのアルミナ製断熱材４７を設けた。アルミナ製断熱材４７は、成分が、Ａ１２Ｏ３：９７．０％、ＳｉＯ２：３．０％であり、嵩密度が０．３３ｇ／ｃｍ３であった。 First, as a preliminary test, a temperature rise experiment was conducted, and whether or not a glass base material made of quartz having a very low relative dielectric constant could be heated by a microwave with a frequency of 28 GHz, and there was a temperature rise pattern different from resistance heating. It was confirmed whether it could be obtained. The temperature increase test was performed as follows. In FIG. 4, the set state of the sample at the time of the microwave heating of the soot powder in a present Example is shown. As shown in FIG. 4, soot powder was filled in a quartz crucible 46 having an inner diameter D of 260 mm and a height H of 200 mm. A thermocouple 41 for temperature control is disposed at the center of the crucible 46, and thermocouples 42 to 45 for temperature measurement are disposed at equal intervals on the outside thereof. On the outside of the crucible 46, an alumina heat insulating material 47 having a thickness of 50 mm was provided. The heat insulating material 47 made of alumina had components of A1 2 O 3 : 97.0%, SiO 2 : 3.0%, and a bulk density of 0.33 g / cm 3 .

試料をセットした後、炉内を６６７Ｐａまで減圧し、熱電対４１により温度を制御した。昇温前のスート粉の嵩密度は０.１５ｇ／ｃｍ３であった。マイクロ波加熱は、試料温度が高いほど比誘電率が上昇するため、試料がマイクロ波を吸収しやすくなる。したがって、室温付近ではマイクロ波が十分に吸収されず、プログラムした昇温パターンどおりには昇温できず、遅れがちであった。しかし、８００℃近辺からは、マイクロ波の吸収が良くなり、プラグラムしたとおりの昇温が可能となった。 After setting the sample, the pressure in the furnace was reduced to 667 Pa, and the temperature was controlled by the thermocouple 41. The bulk density of the soot powder before the temperature increase was 0.15 g / cm 3 . In microwave heating, the relative permittivity increases as the sample temperature increases, so that the sample easily absorbs microwaves. Therefore, the microwaves were not sufficiently absorbed near room temperature, and the temperature could not be increased according to the programmed temperature increase pattern, which was likely to be delayed. However, from around 800 ° C., the absorption of microwaves was improved, and the temperature could be raised as programmed.

温度は、表面からの距離を変えて、温度制御用熱電対４１とともに測温用の熱電対４２〜４５により５点で測定し、記録した。図５に、プログラムした昇温パターンと昇温実績を示す。表面に近い熱電対のみが少し遅れる程度で、５点の測定結果は、ほぼ同様の軌跡を辿った。したがって、マイクロ波が、試料の表面だけでなく、試料の内部でもよく吸収されて、全体的に均一に発熱していることがわかった。表面に近い測定点に配した熱電対４５の昇温が、他の熱電対４１〜４４と比較して少し遅れたのは、坩堝４６は断熱材４７で保温しているとはいえ、ある程度は表面より放熱していたためと考察された。しかし、表面に近い測定点に配した熱電対４５の示した昇温の遅れも、坩堝４６内の試料が収縮し、試料の表面積が小さくなってくると、放熱が減少したためか、他の熱電対４１〜４４と同様の軌跡となった。   The temperature was measured and recorded at five points by the thermocouples 42 to 45 for temperature measurement together with the thermocouple 41 for temperature control while changing the distance from the surface. FIG. 5 shows the programmed temperature increase pattern and the temperature increase results. Only the thermocouple close to the surface was delayed a little, and the measurement results at the five points followed a similar locus. Therefore, it was found that the microwave was well absorbed not only on the surface of the sample but also inside the sample, and heat was generated uniformly throughout. The temperature rise of the thermocouple 45 arranged at the measurement point close to the surface is slightly delayed compared to the other thermocouples 41 to 44, although the crucible 46 is kept warm by the heat insulating material 47, to some extent It was considered that heat was radiated from the surface. However, the temperature rise delay indicated by the thermocouple 45 arranged at the measurement point close to the surface is also due to the decrease in heat dissipation when the sample in the crucible 46 contracts and the surface area of the sample becomes smaller. It became the locus similar to pairs 41-44.

本昇温試験により、周波数２８ＧＨｚのマイクロ波を用いれば、比誘電率の低い石英ガラス母材でも断熱材を併用することにより、昇温可能であり、しかも、試料の内部の方が早く加熱し得ることが確認できた。   In this temperature rise test, if a microwave with a frequency of 28 GHz is used, it is possible to raise the temperature by using a heat insulating material in combination with a quartz glass base material having a low relative dielectric constant, and the inside of the sample is heated faster. I was able to confirm it.

つぎに、周波数２８ＧＨｚのマイクロ波を用いて焼結した場合の石英ガラスの内質を調べるために、スート塊を焼成した。図６に、プログラムした昇温パターンを示す。昇温は、あらかじめ炉内を６６７Ｐａまで減圧してから行ない、昇温プログラムの実行後も真空ポンプの運転を継続し、スート塊の焼成に伴って発生するガスを脱気し続けた。図７に、本実施例におけるスート塊のマイクロ波加熱に際しての試料のセット状態を示す。スート塊７１は、外径Ｄが２８０ｍｍ、高さＨが２７０ｍｍ、重さＷが７６００ｇ、嵩密度が０．４６ｇ／ｃｍ３であった。スート塊７１の周囲には、前述と同様のアルミナ製断熱材７２を配し、また、スート塊７１の下の熱電対７３により温度制御をし、プログラムした昇温パターンに沿ってほぼ制御することができた。 Next, the soot lump was fired in order to examine the quality of the quartz glass when sintered using a microwave with a frequency of 28 GHz. FIG. 6 shows a programmed temperature increase pattern. The temperature was raised after the pressure in the furnace was reduced to 667 Pa in advance, and the operation of the vacuum pump was continued after the temperature raising program was executed, and the gas generated as the soot lump was baked was continuously degassed. FIG. 7 shows a set state of the sample during microwave heating of the soot lump in this example. The soot lump 71 had an outer diameter D of 280 mm, a height H of 270 mm, a weight W of 7600 g, and a bulk density of 0.46 g / cm 3 . Around the soot lump 71, the same heat insulating material 72 made of alumina as described above is disposed, and the temperature is controlled by the thermocouple 73 under the soot lump 71, and the temperature is controlled almost according to the programmed temperature rising pattern. I was able to.

マイクロ波加熱の結果、試料は十分に緻密化し、外形１６６ｍｍ、高さ１６０ｍｍ、嵩密度２．２ｇ／ｃｍ３のガラス塊を得た。得られたガラス塊の高さ方向のほぼ中央部から厚さ１０ｍｍの円盤を切り出し、切り出した円盤の中心部から外側に向かって、等間隔でＯＨ基の濃度を測定した。測定には、日立製作所製Ｉ−２０００型赤外分光光度計を用い、基準透過率ＡとＯＨ基の吸収ピークＢとの比に基づき、ＯＨ基濃度（ｐｐｍ）を算出した。 As a result of the microwave heating, the sample was sufficiently densified to obtain a glass lump having an outer shape of 166 mm, a height of 160 mm, and a bulk density of 2.2 g / cm 3 . A disk having a thickness of 10 mm was cut out from a substantially central part in the height direction of the obtained glass lump, and the concentration of OH groups was measured at regular intervals from the center part of the cut out disk toward the outside. For the measurement, an I-2000 infrared spectrophotometer manufactured by Hitachi, Ltd. was used, and the OH group concentration (ppm) was calculated based on the ratio of the standard transmittance A and the absorption peak B of the OH group.

ＯＨ基濃度＝９５１／Ｔ×log（Ａ/Ｂ）
（Ａ：（３８４４ｃｍ−１の透過率＋３８４８ｃｍ−１の透過率）×０．５、Ｂ：３６６３ｃｍ−１の最小透過率、Ｔ：試料厚み、３８４４ｃｍ−１と３８４８ｃｍ−１と３６６３ｃｍ−１は各々波長の逆数である。）
図８に、算出したＯＨ基濃度と中心からの距離との関係を示す。図８に示すとおり、マイクロ波加熱では、中心部と外周部とのＯＨ基の濃度の差は９.９ｐｐｍであり、中心からの距離にかかわらず、ＯＨ基の濃度が均一であることがわかった。この結果より、マイクロ波加熱では、抵抗加熱のように表面からの加熱ではなく、試料全体が発熱しているため、試料の中心部と外周部とを問わず、脱ＯＨ基反応が均一に行なわれたものと考察された。また、ＯＨ基濃度の均一化に伴い、ＯＨ基濃度に大きく影響される屈折率も面内で均一化しているものと推定された。 OH group concentration = 951 / T × log (A / B)
(A: (transmittance) × 0.5 transmittance + 3848cm -1 in 3844cm -1, B: minimum transmittance of 3663cm -1, T: specimen thickness, 3844cm -1 and 3848cm -1 and 3663cm -1 are each It is the reciprocal of the wavelength.)
FIG. 8 shows the relationship between the calculated OH group concentration and the distance from the center. As shown in FIG. 8, in the microwave heating, the difference in OH group concentration between the center and the outer periphery is 9.9 ppm, and it can be seen that the OH group concentration is uniform regardless of the distance from the center. It was. From this result, in microwave heating, the whole sample generates heat, not heating from the surface like resistance heating, so that the deOH group reaction is uniformly performed regardless of the central portion and the outer peripheral portion of the sample. It was considered that. In addition, with the homogenization of the OH group concentration, it was estimated that the refractive index greatly influenced by the OH group concentration was also uniform in the plane.

比較例１
実施例１のマイクロ波加熱炉に代えて、図９に示すような抵抗加熱炉を用いて、多孔質石英ガラス母材を加熱し焼結した。抵抗加熱炉は、図９に示すように、石英製坩堝９６の周囲にカーボンヒータ９８を配し、カーボンヒータ９８の周囲にカーボン製の厚さ５０ｍｍの断熱材９７を配した構造を有するものであり、石英製坩堝９６と、石英製坩堝９６に配した熱電対９１〜９５は、実施例１と同様とした。この石英製坩堝９６に、スート粉を充填し、実施例１と同様に、減圧し、加熱を開始した。 Comparative Example 1
Instead of the microwave heating furnace of Example 1, a porous quartz glass base material was heated and sintered using a resistance heating furnace as shown in FIG. As shown in FIG. 9, the resistance heating furnace has a structure in which a carbon heater 98 is arranged around a quartz crucible 96 and a carbon-made heat insulating material 97 is arranged around the carbon heater 98. Yes, the quartz crucible 96 and the thermocouples 91 to 95 arranged in the quartz crucible 96 were the same as in Example 1. The quartz crucible 96 was filled with soot powder, and the pressure was reduced and heating was started in the same manner as in Example 1.

抵抗加熱は、試料の外部からの加熱であり、試料の中心部に配した熱電対９１で温度を制御するため、試料の昇温実績は、図１０に示すように、中心部はプログラムした昇温パターンどおりの軌跡を描いたが、外周部は中心部より先行して加熱されるため、外周部の温度は中心部より常に高くなった。したがって、外周部の表面から緻密化したものと考察された。   Resistance heating is heating from the outside of the sample, and the temperature is controlled by a thermocouple 91 disposed in the center of the sample. Therefore, the temperature rise performance of the sample is as shown in FIG. Although the locus according to the temperature pattern was drawn, since the outer peripheral portion was heated prior to the central portion, the temperature of the outer peripheral portion was always higher than that of the central portion. Therefore, it was considered that it was densified from the surface of the outer periphery.

つぎに、焼結による内質を調査するため、スート塊を焼成した。焼成は、図１１に示すように、スート塊１１１の周囲に、カーボンヒータ１１４を配し、カーボンヒータ１１４の周囲にカーボン製の断熱材を配して行なった。スート塊１１１と熱電対１１３、その他の焼成条件は、実施例１と同様とした。   Next, in order to investigate the internal quality by sintering, the soot lump was baked. As shown in FIG. 11, the firing was performed by disposing a carbon heater 114 around the soot lump 111 and a carbon heat insulating material around the carbon heater 114. The soot lump 111, the thermocouple 113, and other firing conditions were the same as in Example 1.

焼成の結果、スート塊は十分に緻密化し、外形１６６ｍｍ、高さ１６０ｍｍ、嵩密度２．２ｇ／ｃｍ３のガラス塊を得た。得られたガラス塊の面内ＯＨ基分布を調べるため、実施例１と同様に、円盤を切り出し、切り出した円盤の中心部から外側に向かって、等間隔でＯＨ基の濃度を調査した。図８に、ＯＨ基濃度と中心からの距離との関係を示す。 As a result of firing, the soot lump was sufficiently densified to obtain a glass lump having an outer shape of 166 mm, a height of 160 mm, and a bulk density of 2.2 g / cm 3 . In order to examine the in-plane OH group distribution of the obtained glass lump, the disk was cut out in the same manner as in Example 1, and the concentration of OH groups was investigated at equal intervals from the center of the cut out disk toward the outside. FIG. 8 shows the relationship between the OH group concentration and the distance from the center.

図８に示すとおり、抵抗加熱では、マイクロ波加熱と異なり、中心部のＯＨ基濃度は６７.０ｐｐｍであり、外周部のＯＨ基濃度は３１.０ｐｐｍであり、中心部と外周部とのＯＨ基の濃度の差は３６.０ｐｐｍであった。この結果から、抵抗加熱は、試料の外表面からの加熱であるため、外表面から緻密化が進行し、外表面から中心部に近づくにつれて、脱ＯＨ化が十分に行なわれないままに焼結が進行したものと考察された。また、ＯＨ基濃度に大きく影響される屈折率も面内で大きく変化しているものと推定された。   As shown in FIG. 8, in resistance heating, unlike microwave heating, the OH group concentration in the center is 67.0 ppm, the OH group concentration in the outer periphery is 31.0 ppm, and the OH between the center and the outer periphery The difference in group concentration was 36.0 ppm. From this result, resistance heating is heating from the outer surface of the sample, so that densification proceeds from the outer surface, and as it approaches the center from the outer surface, sintering is performed without sufficient deOHization. Was considered to have progressed. Further, it was estimated that the refractive index greatly influenced by the OH group concentration also changed greatly in the plane.

実験に供した試料が小片であったため、実施例１と比較例１との間で内質に差は認められなかった。しかし、スート塊は多孔質体であり、内部に多くの気泡を内包している。したがって、マイクロ波加熱は、試料の中心部と外周部とを問わず、試料全体を均一に加熱されるため、中心部からの脱気もスムーズに進行し、内質に優れた石英ガラスが得られるのに対して、抵抗加熱では外周部から緻密化が進行するため、内部の気泡の多くが閉じ込められ、内質の劣るガラスになりやすいものと予想された。   Since the sample used for the experiment was a small piece, there was no difference in the internal quality between Example 1 and Comparative Example 1. However, the soot mass is a porous body and contains many bubbles inside. Therefore, because microwave heating uniformly heats the entire sample regardless of the center and outer periphery of the sample, degassing from the center proceeds smoothly, and quartz glass with excellent internal quality is obtained. On the other hand, in the resistance heating, since the densification progresses from the outer peripheral portion, it is expected that many of the internal bubbles are confined and the glass tends to be inferior in quality.

比較例２
本比較例では、断熱材がない状態でマイクロ波加熱を行なった。図１２に示すように、石英製坩堝１２６の中央に、外形Ｄが８５ｍｍ、高さＨが８０ｍｍ、重量Ｗが１１６ｇ、嵩密度が０．２５６ｇ／ｃｍ３のスート塊１２２を配した後、スート粉１２３を充填した。坩堝１２６とスート粉１２３は、実施例１と同様のものを用いた。また、スート塊１２２の中央直下には、熱電対１２１を、スート塊１２２の下部に接触するように挿入し、熱電対１２１で温度制御をした。 Comparative Example 2
In this comparative example, microwave heating was performed without a heat insulating material. As shown in FIG. 12, after placing a soot lump 122 having an outer shape D of 85 mm, a height H of 80 mm, a weight W of 116 g, and a bulk density of 0.256 g / cm 3 at the center of a quartz crucible 126, Powder 123 was filled. The crucible 126 and the soot powder 123 were the same as those in Example 1. Further, a thermocouple 121 was inserted immediately below the center of the soot lump 122 so as to contact the lower part of the soot lump 122, and the temperature was controlled by the thermocouple 121.

昇温実績を図１３に示す。図１３に示すとおり、プログラムした昇温パターンのとおりには温度が上がらず、設備の保護のため、照射開始１０時間経過後に、照射を中止した。最高温度は６６０℃程度であった。これは、スート塊およびスート粉がマイクロ波を吸収し、発熱しても、放熱量が多く、周波数２８ＧＨｚ、７ＫＷ程度のマイクロ波では、発熱による温度上昇と、試料表面からの放熱による温度降下とが等しくなり、６６０℃で恒温状態となったものと考察された。   The temperature rise results are shown in FIG. As shown in FIG. 13, the temperature did not increase according to the programmed temperature increase pattern, and irradiation was stopped after 10 hours from the start of irradiation for protection of the equipment. The maximum temperature was about 660 ° C. This is because the soot lump and soot powder absorb microwaves and generate heat even if they generate heat. With microwaves with a frequency of about 28 GHz and 7 kW, the temperature rises due to heat generation and the temperature drops due to heat dissipation from the sample surface. And became constant temperature at 660 ° C.

今回開示された実施の形態および実施例はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。   It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

ＯＨ基の面内分布が均一で、内質の優れる石英ガラスを安価な設備で製造することができる。   Quartz glass having a uniform OH group in-plane distribution and excellent quality can be produced with inexpensive equipment.

電波（マイクロ波）を照射した場合の概念図である。It is a conceptual diagram at the time of irradiating a radio wave (microwave). 電波を照射した場合の比誘電率を示す図である。It is a figure which shows the dielectric constant at the time of irradiating an electromagnetic wave. 実施例１で用いたマイクロ波加熱炉の概略図である。1 is a schematic view of a microwave heating furnace used in Example 1. FIG. 実施例１におけるスート粉のマイクロ波加熱に際しての試料のセット状態を示す図である。It is a figure which shows the set state of the sample at the time of the microwave heating of the soot powder in Example 1. FIG. 実施例１における昇温パターンと昇温実績を示す図である。It is a figure which shows the temperature rising pattern and temperature rising performance in Example 1. 実施例１における昇温パターンを示す図である。It is a figure which shows the temperature rising pattern in Example 1. FIG. 実施例１におけるスート塊のマイクロ波加熱に際しての試料のセット状態を示す図である。It is a figure which shows the set state of the sample at the time of the microwave heating of the soot lump in Example 1. FIG. 算出したＯＨ基濃度と中心からの距離との関係を示す図である。It is a figure which shows the relationship between the calculated OH group density | concentration and the distance from a center. 比較例１で用いた従来の抵抗加熱炉の概略図である。2 is a schematic view of a conventional resistance heating furnace used in Comparative Example 1. FIG. 比較例１における昇温パターンと昇温実績を示す図である。It is a figure which shows the temperature rising pattern and temperature rising performance in the comparative example 1. 比較例１におけるスート塊の抵抗加熱に際しての試料のセット状態を示す図である。It is a figure which shows the set state of the sample at the time of the resistance heating of the soot lump in the comparative example 1. 比較例２におけるマイクロ波加熱に際しての試料のセット状態を示す図である。6 is a diagram illustrating a set state of a sample during microwave heating in Comparative Example 2. FIG. 比較例２における昇温パターンと昇温実績を示す図である。It is a figure which shows the temperature rising pattern and temperature rising performance in the comparative example 2.

符号の説明Explanation of symbols

３１ ジャイラトロン発振管、３２ 導波管、３３ 照射室、３４ 試料台、４１〜４５，７３ 熱電対、４６ 坩堝、４７，７２ アルミナ製断熱材、７１ スート塊。   31 Gyrotron Oscillator, 32 Waveguide, 33 Irradiation Chamber, 34 Sample Stand, 41-45, 73 Thermocouple, 46 Crucible, 47, 72 Alumina made of alumina, 71 Soot lump.

Claims (4)

断熱材を有する容器内において、石英ガラス母材をマイクロ波により加熱し焼結することを特徴とする石英ガラスの製造方法。   A method for producing quartz glass, characterized in that a quartz glass base material is heated and sintered by microwaves in a container having a heat insulating material. 断熱材の比誘電率が１０以下であることを特徴とする請求項１に記載の石英ガラスの製造方法。   The method for producing quartz glass according to claim 1, wherein the heat insulating material has a relative dielectric constant of 10 or less. マイクロ波の周波数が２８ＧＨｚ以上であることを特徴とする請求項１または２に記載の石英ガラスの製造方法。   The method for producing quartz glass according to claim 1 or 2, wherein the microwave frequency is 28 GHz or more. 請求項１〜３のいずれかに記載の方法により製造したことを特徴とする石英ガラス。   Quartz glass manufactured by the method according to claim 1.
JP2003382412A 2003-11-12 2003-11-12 Method for producing quartz glass and quartz glass produced by the same Pending JP2005145735A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2003382412A JP2005145735A (en) 2003-11-12 2003-11-12 Method for producing quartz glass and quartz glass produced by the same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2003382412A JP2005145735A (en) 2003-11-12 2003-11-12 Method for producing quartz glass and quartz glass produced by the same

Publications (1)

Publication Number Publication Date
JP2005145735A true JP2005145735A (en) 2005-06-09

Family

ID=34691494

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2003382412A Pending JP2005145735A (en) 2003-11-12 2003-11-12 Method for producing quartz glass and quartz glass produced by the same

Country Status (1)

Country Link
JP (1) JP2005145735A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013530115A (en) * 2010-05-27 2013-07-25 ヘレウス・クアルツグラース・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング・ウント・コンパニー・コマンディット・ゲゼルシャフト Method for producing a quartz glass crucible having a transparent inner layer made of synthetic quartz glass

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013530115A (en) * 2010-05-27 2013-07-25 ヘレウス・クアルツグラース・ゲゼルシャフト・ミット・ベシュレンクテル・ハフツング・ウント・コンパニー・コマンディット・ゲゼルシャフト Method for producing a quartz glass crucible having a transparent inner layer made of synthetic quartz glass

Similar Documents

Publication Publication Date Title
EP1333012B1 (en) Burning furnace, burnt body producing method, and burnt body
US6344634B2 (en) Hybrid method for firing of ceramics
JPH0849983A (en) Method and equipment for treating ceramic
JP4214040B2 (en) Operation method of microwave heating furnace and microwave heating furnace
CN105627760B (en) A kind of microwave material placing device of high temperature sintering
WO2015152019A1 (en) Carbon fiber manufacturing device and carbon fiber manufacturing method
JP2005268624A (en) Heating equipment
US6344635B2 (en) Hybrid method for firing of ceramics
CN1516750A (en) Plasma CVD apparatus
US11713280B2 (en) Method for thermal treatment of a ceramic part by microwaves
JP5048998B2 (en) Microwave heating device for ceramics and its heating element
JP2005145735A (en) Method for producing quartz glass and quartz glass produced by the same
JP2002130960A (en) Baking furance, burned product, and method for manufacturing the same
JP3799454B2 (en) Firing furnace
JP2005089268A (en) Method and apparatus for sintering boron carbide ceramic
US10893577B2 (en) Millimeter wave heating of soot preform
CN219218223U (en) Quick annealing equipment
JP2004168575A (en) Method for sintering ceramic
JPH1045472A (en) Dielectric ceramic product for high frequency and its manufacture
CN116411251A (en) Quick annealing equipment
TWM628545U (en) A fast annealing equipment
JP3404345B2 (en) Method and apparatus for manufacturing ceramics
JP2004210548A (en) Method of manufacturing quartz glass
JP2005179071A (en) Method for manufacturing silica glass using millimeter wave
JPS5869732A (en) Heating method of glass pipe by plasmatic cvd method

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20060216

A711 Notification of change in applicant

Effective date: 20080530

Free format text: JAPANESE INTERMEDIATE CODE: A711

A977 Report on retrieval

Effective date: 20081016

Free format text: JAPANESE INTERMEDIATE CODE: A971007

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20081021

A711 Notification of change in applicant

Free format text: JAPANESE INTERMEDIATE CODE: A711

Effective date: 20081110

A02 Decision of refusal

Effective date: 20090331

Free format text: JAPANESE INTERMEDIATE CODE: A02