JPH0259435A - Production of silica glass - Google Patents
Production of silica glassInfo
- Publication number
- JPH0259435A JPH0259435A JP21180188A JP21180188A JPH0259435A JP H0259435 A JPH0259435 A JP H0259435A JP 21180188 A JP21180188 A JP 21180188A JP 21180188 A JP21180188 A JP 21180188A JP H0259435 A JPH0259435 A JP H0259435A
- Authority
- JP
- Japan
- Prior art keywords
- silica glass
- gel
- sol
- silicon alkoxide
- dimethylacetamide
- 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
Links
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 24
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 13
- 239000010703 silicon Substances 0.000 claims abstract description 13
- -1 silicon alkoxide Chemical class 0.000 claims abstract description 13
- 239000002904 solvent Substances 0.000 claims abstract description 12
- FXHOOIRPVKKKFG-UHFFFAOYSA-N N,N-Dimethylacetamide Chemical compound CN(C)C(C)=O FXHOOIRPVKKKFG-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229920001515 polyalkylene glycol Polymers 0.000 claims abstract description 7
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims abstract description 7
- 230000003301 hydrolyzing effect Effects 0.000 claims abstract 2
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 abstract description 9
- 239000002202 Polyethylene glycol Substances 0.000 abstract description 6
- 229920001223 polyethylene glycol Polymers 0.000 abstract description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 6
- 238000000034 method Methods 0.000 abstract description 5
- 238000003980 solgel method Methods 0.000 abstract description 3
- XTHFKEDIFFGKHM-UHFFFAOYSA-N Dimethoxyethane Chemical compound COCCOC XTHFKEDIFFGKHM-UHFFFAOYSA-N 0.000 abstract description 2
- 239000003054 catalyst Substances 0.000 abstract description 2
- OEYIOHPDSNJKLS-UHFFFAOYSA-N choline Chemical compound C[N+](C)(C)CCO OEYIOHPDSNJKLS-UHFFFAOYSA-N 0.000 abstract description 2
- 229960001231 choline Drugs 0.000 abstract description 2
- 238000005336 cracking Methods 0.000 abstract description 2
- 150000004703 alkoxides Chemical class 0.000 abstract 1
- 239000000499 gel Substances 0.000 description 14
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 235000019441 ethanol Nutrition 0.000 description 4
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 3
- XEKOWRVHYACXOJ-UHFFFAOYSA-N Ethyl acetate Chemical compound CCOC(C)=O XEKOWRVHYACXOJ-UHFFFAOYSA-N 0.000 description 3
- 125000000217 alkyl group Chemical group 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 2
- LCGLNKUTAGEVQW-UHFFFAOYSA-N Dimethyl ether Chemical compound COC LCGLNKUTAGEVQW-UHFFFAOYSA-N 0.000 description 2
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 239000002585 base Substances 0.000 description 2
- 238000001879 gelation Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- XNWFRZJHXBZDAG-UHFFFAOYSA-N 2-METHOXYETHANOL Chemical compound COCCO XNWFRZJHXBZDAG-UHFFFAOYSA-N 0.000 description 1
- VXEGSRKPIUDPQT-UHFFFAOYSA-N 4-[4-(4-methoxyphenyl)piperazin-1-yl]aniline Chemical compound C1=CC(OC)=CC=C1N1CCN(C=2C=CC(N)=CC=2)CC1 VXEGSRKPIUDPQT-UHFFFAOYSA-N 0.000 description 1
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical compound CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 150000001298 alcohols Chemical class 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 125000002947 alkylene group Chemical group 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 125000000484 butyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 150000002148 esters Chemical class 0.000 description 1
- 150000002170 ethers Chemical class 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000003349 gelling agent Substances 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 150000002576 ketones Chemical class 0.000 description 1
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 239000013307 optical fiber Substances 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 229920000233 poly(alkylene oxides) Polymers 0.000 description 1
- 229920001451 polypropylene glycol Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 125000001436 propyl group Chemical group [H]C([*])([H])C([H])([H])C([H])([H])[H] 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000000741 silica gel Substances 0.000 description 1
- 229910002027 silica gel Inorganic materials 0.000 description 1
- 239000005049 silicon tetrachloride Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
- C03C1/006—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels to produce glass through wet route
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Silicon Polymers (AREA)
- Glass Melting And Manufacturing (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、光学用、半導体工業用、電子工業用、理化学
用等に使用されるシリカガラスの製造法に関する。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing silica glass used for optical applications, semiconductor industry, electronic industry, physical and chemical applications, etc.
（従来の技術）
シリカガラスは耐熱性、耐食性および光学的性質に優れ
ていることから、半導体製造に欠かせない重要な材料で
あり、さらには光ファイバやＩＣ製造用フォトマスク基
板、ＴＰＴ基板などに使用されその用途はますます拡大
されている。(Prior art) Silica glass has excellent heat resistance, corrosion resistance, and optical properties, so it is an important material indispensable for semiconductor manufacturing, and is also used for optical fibers, photomask substrates for IC manufacturing, TPT substrates, etc. It has been used for many years, and its applications are expanding more and more.
従来のシリカガラスの製造法には、天然石英を電気炉ま
たは酸水素炎により溶解する方法、あるいは四塩化ケイ
素を酸水素炎又はプラズマ炎中で高温酸化し溶解する方
法があるが、いずれの方法も製造工程に２０００℃ある
いはそれ以上の高温を必要とするため、大量のエネルギ
ーを消費しまた製造時にそのような高温に耐える材料が
必要であり、また高純度のものが得にくいなど経済的、
品質的にいくつかの問題点をもっている。Conventional methods for manufacturing silica glass include melting natural quartz in an electric furnace or oxyhydrogen flame, or oxidizing and melting silicon tetrachloride at high temperature in an oxyhydrogen flame or plasma flame. Since the manufacturing process requires high temperatures of 2000℃ or higher, it consumes a large amount of energy, and materials that can withstand such high temperatures are required during manufacturing, and it is difficult to obtain high purity materials, making it economical.
There are some quality issues.
これに対し、近年ゾル−ゲル法と呼ばれるシリカガラス
を低温で合成する方法が注目されている。On the other hand, in recent years, a method of synthesizing silica glass at low temperature called the sol-gel method has been attracting attention.
その概要を簡単に述べる。The outline will be briefly described below.
一般式Ｓｔ （ＯＲ）ａ （Ｒ：アルキル基）で表わ
されるシリコンアルキシド（本発明に於いては、その重
縮合物を含む０例えば（ＲＯ）ｓｓ ｌ・ （ＯＳ ｉ
（ＯＲ）ｇ）−・Ｏ３ｉ （ＯＲ）ｓ、（ｎ＝Ｏ〜
８、Ｒ：アルキル基））に水（アルカリまたは酸でｐＨ
を調整してもよい）を加え、加水分解し、シリカヒドロ
シル（本発明に於てはシリカゾルという）とする、この
時、シリコンアルコキシドと水が均一な系となる様、一
般には溶媒として適当なアルコールが添加されている。Silicon alkoxide represented by the general formula St (OR) a (R: alkyl group) (in the present invention, silicon alkoxide including its polycondensate, for example (RO) ss l, (OS i
(OR)g)-・O3i (OR)s, (n=O~
8. R: Alkyl group)) to water (pH with alkali or acid)
may be adjusted) and hydrolyzed to form silica hydrosil (referred to as silica sol in the present invention). At this time, a suitable solvent is generally used to form a homogeneous system of silicon alkoxide and water. Alcohol is added.
このシリカゾルを静置、昇温、ゲル化剤の添加等によっ
てゲル化させる。その後ゲルを蒸発乾燥することにより
シリカ乾燥ゲルとする。この乾燥ゲルを適当な雰囲気中
で焼結することによりシリカガラスを得る。This silica sol is gelled by standing still, increasing the temperature, adding a gelling agent, etc. Thereafter, the gel is evaporated to dryness to obtain a dry silica gel. Silica glass is obtained by sintering this dried gel in a suitable atmosphere.
（発明が解決しようとする問題点）
しかし、ブルーゲル法によるシリカガラスの製造にはま
だ未解決の問題が残されている。特にゲルを乾燥してい
（過程でゲルにクラックや割れが発生し易く、クラック
や割れのないモノリシックな大形の乾燥ゲルを歩留り良
く製造することが困難である。(Problems to be Solved by the Invention) However, there are still unresolved problems in the production of silica glass by the Bluegel method. In particular, when the gel is dried (the gel tends to crack or break during the process), it is difficult to produce a monolithic large-sized dried gel without cracks or breaks with a good yield.
本発明はクラックや割れの発生ずることのないシリカガ
ラスの製造法を提供するものである。The present invention provides a method for producing silica glass that does not cause cracks or breaks.
（問題点を解決するための手段）
本発明は、ゾル−ゲル法によるシリカガラスの製造法に
於て、ゾル調整時に、シリコンアルコキドの溶媒として
Ｎ、Ｎ−ジメチルアセトアミドを含む溶媒を使用する共
にポリアルキレングリコール及び／又はその誘導体を添
加することを特徴とするものである。(Means for Solving the Problems) The present invention uses a solvent containing N,N-dimethylacetamide as a solvent for silicon alkoxide during sol preparation in a method for producing silica glass by a sol-gel method. It is characterized in that polyalkylene glycol and/or its derivatives are added to both.
本発明において、シリコンアルコキシドのアルキル基に
ついて、特に制限はないが、加水分解のし易さ、ゲル化
時間の点から、メチル基、エチル基、プロピル基、ブチ
ル基を有するシリコンアルコキシドを使用することが好
ましい。またこれらのシリコンアルコキシドを部分的に
重合させたものを用いることもできる。In the present invention, there are no particular restrictions on the alkyl group of silicon alkoxide, but from the viewpoint of ease of hydrolysis and gelation time, silicon alkoxide having a methyl group, ethyl group, propyl group, or butyl group is used. is preferred. Furthermore, partially polymerized silicon alkoxides can also be used.
水と共に加える触媒は、塩基、酸等特に制限しないが、
ゲル化時間、また得られる乾燥ゲルの焼結のし易すさの
点から塩基の方が好ましい結果が得られる。The catalyst added with water is not particularly limited, such as bases and acids, but
From the viewpoint of gelation time and ease of sintering of the resulting dry gel, a base gives more preferable results.
ポリアルキレングリコール及び／又はその誘導体として
は、例えばポリエチレングリコール、ポリプロピレング
リコール、ポリエチレングリコールモノメチルエーテル
、ポリエチレングリコールジメチルエーテル等が使用し
得る。これらはポリアルキレンオキシド
（−Ｒ−０−）、（Ｒ：アルキレン基）を主鎖にもつ化
合物である。As the polyalkylene glycol and/or its derivative, for example, polyethylene glycol, polypropylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, etc. can be used. These are compounds having polyalkylene oxide (-R-0-), (R: alkylene group) in the main chain.
これらのポリアルキレングリコール及び／又はその誘導
体の分子量については本発明では特に限定を設けないが
、水、溶媒への溶解性、ゾル中でのシリカ微粒子の成長
の度合に応じて選択される。The molecular weight of these polyalkylene glycols and/or derivatives thereof is not particularly limited in the present invention, but is selected depending on the solubility in water and solvents and the degree of growth of silica fine particles in the sol.
シリコンアルコキシドの溶媒として使用するＮ、Ｎ−ジ
メチルアセトアミドの量に関しては本発明では特に限定
を設けないが、ゾル中でのシリカ微粒子の成長の度合に
応じて選択される。Ｎ、Ｎ−ジメチルアセトアミドと共
に用いられる溶媒成分トシては、メチルアルコール、エ
チルアルコール、１−プロピルアルコール、２−プロピ
ルアルコール、ブチルアルコール等のアルコール類、ジ
メチルエーテル等のエーテル類、アセトン、エチルメチ
ルケトン等のケトン類、酢酸エチル等のエステル類の少
なくとも一種が使用可能である。The amount of N,N-dimethylacetamide used as a solvent for silicon alkoxide is not particularly limited in the present invention, but is selected depending on the degree of growth of fine silica particles in the sol. Solvent components used with N,N-dimethylacetamide include alcohols such as methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, butyl alcohol, ethers such as dimethyl ether, acetone, ethyl methyl ketone, etc. At least one of ketones and esters such as ethyl acetate can be used.
シリカガラスは、上記のようにして調整したシリカゾル
をシャーレ等の容器に移し、室温〜７０℃に保ってゲル
化し、次いで室温以上の温度で数週間乾燥して、乾燥ゲ
ルとし、更に公知の方法、例えば空気中で１４）００〜
１４００℃に昇温しで焼結することにより得られる。Silica glass is produced by transferring the silica sol prepared as described above to a container such as a petri dish, gelling it by keeping it at room temperature to 70°C, then drying it at a temperature above room temperature for several weeks to form a dry gel, and then using a known method. , for example in the air 14)00~
It is obtained by raising the temperature to 1400°C and sintering it.
（作用）
Ｎ、Ｎ−ジメチルアセトアミドを含む溶媒を用いること
によって、乾燥過程で起こるゲルの割れが防止される原
因については詳細は不明であるが、Ｎ、Ｎ−ジメチルア
セトアミドはポリアルキレングリコール及び／又はその
誘導体と共にゾル中でのシリカ微粒子の生成、成長の制
御に関与し、また、沸点が１６６℃とアルコール等の他
の溶媒及び水よりも高いため、乾燥過程での蒸発速度が
遅く、ゲル中に発生する応力の緩和に寄与することによ
り、ゲルの大形化が可能になったものと考えられる。(Function) The reason why gel cracking that occurs during the drying process is prevented by using a solvent containing N,N-dimethylacetamide is not known in detail, but N,N-dimethylacetamide is a polyalkylene glycol and/or It is involved in the production and growth of silica particles in the sol together with its derivatives, and its boiling point is 166°C, which is higher than other solvents such as alcohol and water, so the evaporation rate during the drying process is slow and the gel It is thought that the gel was able to grow in size by contributing to the relaxation of stress generated inside the gel.
実施例
０、ＯＩＭコリン水溶液４７ｇ１メチルアルコ−ル６８
ｇ、Ｎ、Ｎ−ジメチルアセトアミド２１ｇを混合し、こ
れにポリエチレングリコール（平均分子３１３０００）
を５ｇ添加し溶解させた。得られた溶液をテトラメチル
シロキサン９９ｇにゆっくりと加え充分混合しシリカゾ
ルを得た。これを直径２００−のテフロンでコーティン
グしたシャーレに入れ、アルミ箔で密封し室温でゲル化
した。Example 0, OIM choline aqueous solution 47g1 methyl alcohol 68g
g, N, N-dimethylacetamide (21 g) was mixed with polyethylene glycol (average molecular weight: 313,000).
5g was added and dissolved. The obtained solution was slowly added to 99 g of tetramethylsiloxane and thoroughly mixed to obtain a silica sol. This was placed in a 200-diameter Teflon-coated Petri dish, sealed with aluminum foil, and gelled at room temperature.
その後蓋に受孔を開け６０℃の恒温槽中で２週間乾燥し
、その後１７０℃まで昇温し、１日乾燥して乾燥ゲルを
得た。こうして得られた乾燥ゲルには、クラツ２や割れ
は全くなかった。得られた乾燥ゲルを、空気中１３００
℃まで加熱、焼結したところ、クラックや割れのない透
明なシリカガラスが得られた。Thereafter, a hole was made in the lid and the mixture was dried for two weeks in a constant temperature bath at 60°C, and then the temperature was raised to 170°C and dried for one day to obtain a dry gel. The dry gel thus obtained had no cracks or cracks at all. The obtained dry gel was heated in air for 1300 min.
When heated to ℃ and sintered, transparent silica glass with no cracks or breaks was obtained.
（発明の効果）(Effect of the invention)
Claims (1)
し、これをゲル化し、乾燥して乾燥ゲルとし、次いで焼
結するシリカガラスの製造法に於て、シリコンアルコキ
シドを加水分解してシリカゾルとする段階で、シリコン
アルコキシドの溶媒としてＮ，Ｎ−ジメチルアセトアミ
ドを含む溶媒を使用すると共にポリアルキレングリコー
ル及び／又はその誘導体を添加することを特徴とするシ
リカガラスの製造法。1. In a method for producing silica glass in which silicon alkoxide is hydrolyzed to form silica sol, this is gelled, dried to form a dry gel, and then sintered, at the step of hydrolyzing silicon alkoxide to form silica sol, A method for producing silica glass, characterized in that a solvent containing N,N-dimethylacetamide is used as a solvent for silicon alkoxide, and polyalkylene glycol and/or a derivative thereof is added.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21180188A JPH0259435A (en) | 1988-08-26 | 1988-08-26 | Production of silica glass |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21180188A JPH0259435A (en) | 1988-08-26 | 1988-08-26 | Production of silica glass |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0259435A true JPH0259435A (en) | 1990-02-28 |
Family
ID=16611832
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21180188A Pending JPH0259435A (en) | 1988-08-26 | 1988-08-26 | Production of silica glass |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0259435A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0345519A (en) * | 1989-07-13 | 1991-02-27 | Toyo Ink Mfg Co Ltd | Production of glass from liquid phase |
-
1988
- 1988-08-26 JP JP21180188A patent/JPH0259435A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0345519A (en) * | 1989-07-13 | 1991-02-27 | Toyo Ink Mfg Co Ltd | Production of glass from liquid phase |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JPH0259435A (en) | Production of silica glass | |
| JPS62265130A (en) | Production of silica glass | |
| JPH0259437A (en) | Production of silica glass | |
| JPH02248331A (en) | Production of silica glass | |
| JPH0259446A (en) | Production of silica glass | |
| JPH01138137A (en) | Production of silica glass | |
| JPH01119528A (en) | Production of silica glass | |
| JPH01119526A (en) | Production of silica glass | |
| JPH0259436A (en) | Production of silica glass | |
| JPH0259442A (en) | Production of silica glass | |
| JPH0259438A (en) | Production of silica glass | |
| JPH0259440A (en) | Production of silica glass | |
| JPH01138139A (en) | Production of silica glass | |
| JPH02248332A (en) | Production of silica glass | |
| JPH01138141A (en) | Production of silica glass | |
| JPH01119524A (en) | Production of silica glass | |
| JPH0259439A (en) | Production of silica glass | |
| JPH0259448A (en) | Production of silica glass | |
| JPH03137029A (en) | Production of silica glass | |
| JPH01138138A (en) | Production of silica glass | |
| JPH02248334A (en) | Production of silica glass | |
| JPH0259443A (en) | Production of silica glass | |
| JPH0259441A (en) | Production of silica glass | |
| JPH01138136A (en) | Production of silica glass | |
| JPH01138142A (en) | Production of silica glass |