JP3726366B2 - Fluorescent lamp - Google Patents
Fluorescent lamp Download PDFInfo
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- JP3726366B2 JP3726366B2 JP20716596A JP20716596A JP3726366B2 JP 3726366 B2 JP3726366 B2 JP 3726366B2 JP 20716596 A JP20716596 A JP 20716596A JP 20716596 A JP20716596 A JP 20716596A JP 3726366 B2 JP3726366 B2 JP 3726366B2
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- titanium oxide
- fluorescent lamp
- sol
- lamp according
- thin film
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- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 84
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 84
- 239000010409 thin film Substances 0.000 claims description 42
- 239000011521 glass Substances 0.000 claims description 39
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 claims description 25
- 239000002245 particle Substances 0.000 claims description 24
- 238000006243 chemical reaction Methods 0.000 claims description 22
- 238000006460 hydrolysis reaction Methods 0.000 claims description 22
- 230000007062 hydrolysis Effects 0.000 claims description 17
- 238000000034 method Methods 0.000 claims description 17
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 13
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 claims description 11
- 229910000041 hydrogen chloride Inorganic materials 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 239000007864 aqueous solution Substances 0.000 claims description 8
- 238000010304 firing Methods 0.000 claims description 7
- 238000010992 reflux Methods 0.000 claims description 7
- 229920003169 water-soluble polymer Polymers 0.000 claims description 6
- 239000011248 coating agent Substances 0.000 claims description 5
- 238000000576 coating method Methods 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims description 4
- 239000002904 solvent Substances 0.000 claims description 3
- 230000001699 photocatalysis Effects 0.000 description 14
- 239000010419 fine particle Substances 0.000 description 13
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 9
- 239000010408 film Substances 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 239000000243 solution Substances 0.000 description 5
- 238000002834 transmittance Methods 0.000 description 5
- 238000006298 dechlorination reaction Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 238000011156 evaluation Methods 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 230000015572 biosynthetic process Effects 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 235000006408 oxalic acid Nutrition 0.000 description 3
- 239000011941 photocatalyst Substances 0.000 description 3
- 239000011164 primary particle Substances 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 239000010936 titanium Substances 0.000 description 3
- -1 titanium alkoxide Chemical class 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 230000003197 catalytic effect Effects 0.000 description 2
- 238000011109 contamination Methods 0.000 description 2
- 239000002612 dispersion medium Substances 0.000 description 2
- 238000000909 electrodialysis Methods 0.000 description 2
- 238000004880 explosion Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000003301 hydrolyzing effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 229920000609 methyl cellulose Polymers 0.000 description 2
- 239000001923 methylcellulose Substances 0.000 description 2
- 235000010981 methylcellulose Nutrition 0.000 description 2
- 238000007146 photocatalysis Methods 0.000 description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 239000000779 smoke Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- NWUYHJFMYQTDRP-UHFFFAOYSA-N 1,2-bis(ethenyl)benzene;1-ethenyl-2-ethylbenzene;styrene Chemical compound C=CC1=CC=CC=C1.CCC1=CC=CC=C1C=C.C=CC1=CC=CC=C1C=C NWUYHJFMYQTDRP-UHFFFAOYSA-N 0.000 description 1
- 241000894006 Bacteria Species 0.000 description 1
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 239000001856 Ethyl cellulose Substances 0.000 description 1
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical group OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 1
- 239000000020 Nitrocellulose Substances 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000003373 anti-fouling effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 238000005660 chlorination reaction Methods 0.000 description 1
- 239000000460 chlorine Substances 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000011437 continuous method Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000000382 dechlorinating effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000001877 deodorizing effect Effects 0.000 description 1
- 238000003618 dip coating Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 229920001249 ethyl cellulose Polymers 0.000 description 1
- 235000019325 ethyl cellulose Nutrition 0.000 description 1
- 230000007717 exclusion Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 239000003456 ion exchange resin Substances 0.000 description 1
- 229920003303 ion-exchange polymer Polymers 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 229920001220 nitrocellulos Polymers 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 235000019422 polyvinyl alcohol Nutrition 0.000 description 1
- 239000012286 potassium permanganate Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 238000004062 sedimentation Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 230000001954 sterilising effect Effects 0.000 description 1
- 239000006228 supernatant Substances 0.000 description 1
- 229910000348 titanium sulfate Inorganic materials 0.000 description 1
- 238000004448 titration Methods 0.000 description 1
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- Surface Treatment Of Glass (AREA)
- Catalysts (AREA)
- Vessels And Coating Films For Discharge Lamps (AREA)
Description
【0001】
【発明の属する技術分野】
本発明は蛍光ランプに関し、さらに詳しくは蛍光ランプのガラス管表面に酸化チタン薄膜を形成し、該酸化チタンの光触媒作用により油煙等の有機物を分解することによりガラス管表面の汚れを防止した蛍光ランプに関する。
【0002】
【従来の技術】
酸化チタンの光触媒機能については近年、盛んに研究開発が行われている。この光触媒の利用方法には有害物質の除去による防汚、アンモニアなどの悪臭ガスの脱臭、細菌類の殺菌などがあるが、その利用目的により酸化チタンの形態は、バルク粒子、薄膜、ゾルと様々である。この光触媒機能はさらに透明性を付加しようとする場合はもっぱら薄膜にされる場合が多い。そのために酸化チタンはゾルの形で薄膜生成材料として使用される。
薄膜の利用形態として最近照明器具、例えば蛍光ランプのガラス管やそのカバーに酸化チタンゾルを塗布して薄膜を形成し、光触媒作用により上記ガラス管やカバーに油煙等の有機物が付着した場合、それを分解し、ガラス管やカバーの汚れを防止する方法が提案されている。
酸化チタンゾルの生成方法に関しては、結晶性或いはアモルファスの酸化チタン粒子を分散媒に分散させるか、分散媒中にチタンアルコキシド、硫酸チタン、四塩化チタンなどの酸化チタンの前駆体を混入させ中和、加水分解などの方法によりゾルを形成させることが一般的である。しかし、透明性の高い薄膜を形成させることが可能であるものは少ない。
【0003】
【発明が解決しようとする課題】
酸化チタン薄膜を蛍光ランプのガラス管表面(外面)に形成して光触媒として利用する場合、その薄膜は触媒活性及び透明性が高いことが要求される。光触媒作用は粒子表面での反応であるため高活性を持たせるには粒子が高い表面積をもつ微粒子であること、また結晶性が良いことが必要である。透明性をよくするためにも同様に微粒子であり、かつ単分散であるものが望ましい。
さらに酸化チタン薄膜とガラス管との密着性をよくし、容易に薄膜が剥離しないようにしなければならない。
【0004】
従来の四塩化チタンを加水分解する方法では、粒子径が非常に小さい微粒子で、かつ結晶性がよく、薄膜にしたとき透明性がよい酸化チタンゾルをつくることが困難であった。
チタンアルコシド化合物の加水分解ではゾル中の酸化チタンは非常に小さい微粒子となるなど粉体特性としては優れているが、ゾル中にアルコールが含まれ、薄膜にして焼成する場合爆発などの安全上の問題がある。また、爆発を防ぐには防爆の大型設備が必要となり、経済的に不利である。
またチタンアルコシド化合物は四塩化チタンに比べ非常に高価である。
本発明は蛍光ランプ用のガラス管表面に光触媒作用が大きく、透明性が高く、かつガラス管との密着性に優れた酸化チタン薄膜を設け、有機物付着によるガラス管の汚れを防止した蛍光ランプを提供することを目的とする。
【0005】
【課題を解決するための手段】
本発明者らは、入手が容易であり、経済的にも有利な四塩化チタンの加水分解に着目し、これから光触媒として優れた薄膜を蛍光ランプのガラス管に形成する方法について研究した結果、本発明に到達したものである。
即ち、本発明は四塩化チタンの加水分解により酸化チタン含有ゾルを生成させて、該ゾルを蛍光ランプ用のガラス管表面に塗布し、焼成して該表面に薄膜を形成することを特徴とする蛍光ランプである。
【0006】
【発明の実施の形態】
本発明は四塩化チタンを加水分解して酸化チタン含有ゾルを生成させ、そのゾルの状態でガラス管に塗布することが重要である。一般に酸化チタンの微粒子は酸化チタンの前駆体を中和、加水分解して濾過、乾燥、熱処理等により得られているが、この微粒子を水などの溶媒に分散させてゾルにしたものは薄膜形成用には適さない。これは酸化チタンの粒子は表面活性が高く、微粒子になればなるほど活性度が上昇するため水への分散は非常に困難になる、すなわち凝集体となってしまい、これからつくられた薄膜は透明性に劣り、光触媒作用も低下するためである。
【0007】
本発明者らは先に粒子径が小さく、結晶性のよい酸化チタン粒子を製造する方法を特許出願した(特願平7−245446)。この方法は四塩化チタンの加水分解反応を、生成する塩化水素の逸出を抑制しながら行う方法である。塩化水素の逸出を抑制する好ましい方法は、加水分解反応槽に還流冷却器を設置し、蒸発する塩化水素ガスを凝縮して反応槽に戻す方法である。
上記特許では得られた酸化チタン含有ゾルを濾過、乾燥、必要により熱処理して酸化チタン粒子としているが、本発明はこの途中で生成する酸化チタン含有ゾルを用いて薄膜を形成する。
加水分解する四塩化チタン水溶液中の四塩化チタンの濃度は低過ぎると生産性が悪く、生成する酸化チタン含有ゾルから薄膜を形成する際に効率が低く、また濃度が高過ぎると反応が激しくなり、得られる酸化チタンの粒子が微細になりにくく、かつ分散性も悪くなるために透明薄膜形成材としては適さない。
【0008】
本発明の酸化チタンゾルは生成したまま、あるいはこれを脱塩素処理や必要により水溶性高分子の1次結合材を少量加えてガラス管に塗布することが好ましく、その場合に酸化チタン濃度があまり薄いと塗布効率が悪く、また濃度が高いと酸化チタンの透明薄膜形成が難しくなる。
これらのことを考慮して加水分解における四塩化チタンの濃度は0.05〜1モル/リットルが好ましい。
この加水分解によって得られるゾルあるいはこれを脱塩素処理等したゾル中の酸化チタンの濃度は、加水分解の際あるはその後の脱塩素処理等における溶液の体積変化は少ないので、四塩化チタンの濃度とほぼ同様0.05〜1モル/リットル程度である。
【0009】
本発明における酸化チタン含有ゾルの好ましい製法は、四塩化チタンの加水分解において発生する塩化水素が反応槽から逸出するのを抑制し、できるだけ水溶液中に残留させる方法である。
加水分解により発生する塩化水素は完全に逸出が防止されていなくても抑制されておればよい。またその方法も抑制できるものであれば特に限定されず、例えば加圧することによっても可能であるが、最も容易にして効果的な方法は加水分解の反応槽に還流冷却器を設置して加水分解を行う方法である。この装置を図1に示す。図において1が四塩化チタンの水溶液2を充填した反応槽で、これに還流冷却器3が設置されている。4は撹拌機、5は温度計、6は反応槽を加熱するための装置である。加水分解反応によって水及び塩化水素の蒸気が発生するが、その大部分は還流冷却器により凝縮し、反応槽に戻されるので反応槽から外に塩化水素が逸出することは殆どない。
【0010】
加水分解における温度は50℃以上、四塩化チタン水溶液の沸点迄の範囲が好ましい。50℃未満では加水分解反応に長時間を要する。加水分解は上記の温度に昇温し、10分から12時間程度保持して行われる。この保持時間は加水分解の温度が高温側にある程短くてよい。
四塩化チタン水溶液の加水分解は四塩化チタンと水との混合溶液を反応槽中で所定の温度に加熱してもよく、また水を反応槽中で予め加熱しておき、これに四塩化チタンを添加し、所定の温度にしてもよい。四塩化チタン水溶液の昇温速度は早い方が得られる粒子が細かくなるので、好ましくは0.2℃/min以上、さらに好ましくは0.5℃/min以上である。
以上はバッチ式反応により酸化チタン含有ゾルを得る場合について説明したが、反応槽を連続槽にして四塩化チタンと水を連続投入しながら、投入口の反対側で反応液を取り出し、引き続き脱塩素処理するような連続方式も可能である。
【0011】
この方法によってゾル中の酸化チタン粒子は平均粒径が0.01〜0.08μmの範囲の結晶性のよいものとなる。
酸化チタン含有ゾルには塩化水素が含まれており、ゾルをガラス管に塗布焼成して薄膜を形成する場合、塩化水素の濃度が高いと薄膜の透明性が下がり、また焼成中に発生する塩化水素ガスによる装置上の問題が生じるのでゾルを予め脱塩素処理することが好ましい。
脱塩素処理は一般の公知手段でよく電気透析、イオン交換樹脂、電気分解などが可能である。脱塩素の程度はゾルのpHを目安にすればよく、例えばpH0.5〜5の範囲であり、好ましくはpH2〜3である。
【0012】
酸化チタン含有ゾルをガラス管に塗布する場合、塗膜の成膜性をよくするためゾルに溶解する水溶性高分子の1次結合材をゾルに添加することが好ましい。水溶性高分子は、特に制限はないがポリビニルアルコール、メチルセルロース、エチルセルロース、ニトロセルロースなどが好適である。その量はゾル中に含有する酸化チタンに対し10重量%以下が適当である。高分子の添加時期は脱塩素処理の前でもよいが、処理後がより好ましい。
このようにして得られた酸化チタン含有ゾルを蛍光ランプ用のガラス管(蛍光ランプとして製品化される以前の材料としてのガラス管)に塗布するにはガラス管をゾル中に浸漬する方法、ガラス管にゾルをスプレーする方法、ゾルを刷毛でガラス管に塗布するなどの方法が採用される。ゾルの塗布量は厚さにして0.01〜0.2mmが適当である。
【0013】
酸化チタンゾルを塗布したガラス管は次に焼成する。焼成により生成する酸化チタン薄膜の強度が向上し、またガラス管と薄膜との密着性が向上する。焼成温度は100℃以上で効果があるが、好ましくは200℃以上である。焼成温度の上限には特に制限はなく、ガラス管が変形しない範囲であればよい。一般的には焼成の上限温度は800℃位、好ましくは600℃位である。
焼成の雰囲気は特に制限されず、大気中でよい。焼成時間は特に制限はなく、例えば1〜60分の範囲で行えばよい。焼成によって得られる酸化チタン薄膜の厚さは、前記の塗布量の場合0.05〜1.0μm位である。
本発明による酸化チタンゾルを用いて製造される酸化チタン薄膜が高い光触媒能力を示し、かつ透明性も高いのは、酸化チタンが結晶性であること、酸化チタン微粒子が非常に微細な粒子であること、不純物を含んでいないこと、さらにこの酸化チタン微粒子が1次粒子に限りなく近く分散している状態であることによると考えられる。
本発明の蛍光ランプはそのガラス管が前記した特定の酸化チタン薄膜を有するものである以外は従来のと変わりはなく、すべての蛍光ランプを対象とすることができる。
【0014】
【実施例】
以下、実施例により具体的に説明する。
実施例1
四塩化チタン(純度99.9%)に水を加え、四塩化チタン濃度が0.25モル/リットル(酸化チタン換算2重量%)となるように溶液を調整した。この時、水溶液の液温が50℃以上に上昇しないように氷冷など適当な冷却装置を設けた。次に、この水溶液1リットルを図1に示す還流冷却器付きの反応槽に装入し、沸点付近(104℃)まで加熱し、60分間保持して加水分解した。冷却後、反応で生成した残留塩素を電気透析により取り除き、pH=2とした後、成膜用助剤として水溶性高分子であるポリビニルアルコールを酸化チタン含有量に対して0.1%添加して、酸化チタンゾルとした。このゾルは安定であり、1日以上経過しても生成した酸化チタン微粒子の沈降は認められなかった。透過型電子顕微鏡でこの粒子を観察したところ平均粒子径は0.015nmであり、X線回折装置から前記粒子の同定を行ったところ結晶性の酸化チタンであった。
このゾルを用いてディップコートによりガラス板上に塗布して乾燥後、500℃で1時間空気中で熱処理して酸化チタン薄膜を得た。熱処理後の酸化チタン薄膜の厚さは0.15μmであった。
【0015】
実施例2
水溶性高分子をメチルセルロースに変えた以外は実施例1と同様にして酸化チタンゾルを作成し、同様に酸化チタン薄膜を得た。
【0016】
比較例1
1次粒子径が0.01μmであるアモルファスの酸化チタン粒子を用い、実施例1と同じ酸化チタン濃度を2重量%として水に超音波分散器を用いて分散させた。この際、塩酸を添加してpHを実施例1と同じ値にし、さらに実施例1と同様の操作をして酸化チタンゾルとした。この酸化チタンのゾルは時間の経過と共に酸化チタンの微粒子が沈降した。沈降後の上澄み液で成膜した膜には光触媒能力が認められなかったため、ゾルを再び超音波分散器で分散させてから実施例1と同じ方法でガラス板上に成膜し、光触媒能力の評価を行った。
【0017】
比較例2
1次粒子径が0.05μmである結晶性の酸化チタン粒子を用いた以外は比較例1と同様にして酸化チタンゾルを得た。このゾルも比較例1と同様酸化チタン微粒子の沈降が認められたので再分散させて成膜した。
成膜の評価
実施例、比較例それぞれの酸化チタンゾルから得た酸化チタン薄膜の光透過率、光触媒能力及びガラス板との密着性を測定した。
【0018】
光透過率の測定方法は、ガラス板上に成膜した酸化チタン薄膜を日本分光(株)製分光光度計にセットして700〜200nmまで波長を連続的に変化させることで光透過率を測定した。そして550nmにおける光透過率を本発明における光透過率として表わした。その結果を表1に示す。
シュウ酸の分解方法は、成膜した酸化チタン薄膜付ガラス板で反応容器を作製し、これに5ミリモル/リットルのシュウ酸を入れ、酸素を吹込みながら100Wの水銀ランプを照射し、4時間後のシュウ酸の分解量を過マンガン酸カリウムの酸化還元滴定により求めた。その結果を表2に示す。
また焼成後のガラス板と薄膜との密着性は鉛筆硬度試験法ならびにごばん目剥離試験法(JIS K5400)により求めた。その結果を表3に示す。
【0019】
【表1】
【0020】
【表2】
【0021】
比較例1においては、酸化チタンの凝集体がガラス板上に形成され表面が不均一であった。
比較例2においては、透明な酸化チタン薄膜が得られなかったため、光触媒能力の評価は実施しなかった。
【0022】
【表3】
【0023】
【発明の効果】
本発明の酸化チタンゾルは有機溶媒を全く含まず溶媒が水であり、これに結晶性の酸化チタン微粒子を効率よく分散させている。さらに、触媒活性を低下させるような不純物の含有量も少ないために、成膜して得られる酸化チタン薄膜は紫外線吸収による光触媒能力を有する透明薄膜材料として好適である。また、酸化チタン薄膜は透明性がよく、かつガラス管との密着性がよい。従って、この薄膜を蛍光ランプのガラス管に形成させることによりガラス管の透明性を損なうことなく、しかも耐久性がよいので長期に亘って光触媒作用により有機物を分解し汚れを防止することができる。
本発明におけるゾル組成が基本的に水系であるために成膜時に防爆設備等の有機成分の除外設備を必要としないために装置的、経済的に有利である。
【図面の簡単な説明】
【図1】本発明の方法に用いられる反応槽の概略断面図である。
【符号の説明】
1 反応槽
2 四塩化チタン水溶液
3 還流冷却器
4 撹拌機
5 温度計
6 加熱装置[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fluorescent lamp, and more particularly, a fluorescent lamp in which a titanium oxide thin film is formed on the surface of a glass tube of the fluorescent lamp, and organic matter such as oily smoke is decomposed by the photocatalytic action of the titanium oxide to prevent contamination on the surface of the glass tube. About.
[0002]
[Prior art]
In recent years, research and development has been actively conducted on the photocatalytic function of titanium oxide. This photocatalyst can be used for antifouling by removing harmful substances, deodorizing malodorous gases such as ammonia, and sterilizing bacteria, but there are various forms of titanium oxide such as bulk particles, thin films, and sols depending on the purpose of use. It is. This photocatalytic function is often made into a thin film exclusively in order to add transparency. For this purpose, titanium oxide is used as a thin film forming material in the form of a sol.
As a form of thin film use, when a thin film is formed by applying a titanium oxide sol to a lighting tube, for example, a glass tube of a fluorescent lamp or its cover, and an organic substance such as oily smoke adheres to the glass tube or cover by photocatalysis, it is A method for disassembling and preventing the glass tube and the cover from being soiled has been proposed.
Regarding the production method of the titanium oxide sol, the crystalline or amorphous titanium oxide particles are dispersed in a dispersion medium, or a titanium oxide precursor such as titanium alkoxide, titanium sulfate, titanium tetrachloride is mixed in the dispersion medium and neutralized. In general, a sol is formed by a method such as hydrolysis. However, few can form a highly transparent thin film.
[0003]
[Problems to be solved by the invention]
When a titanium oxide thin film is formed on the glass tube surface (outer surface) of a fluorescent lamp and used as a photocatalyst, the thin film is required to have high catalytic activity and transparency. Since the photocatalytic action is a reaction on the particle surface, it is necessary that the particles are fine particles having a high surface area and have good crystallinity in order to have high activity. Similarly, in order to improve transparency, fine particles and monodispersed particles are desirable.
Furthermore, the adhesion between the titanium oxide thin film and the glass tube should be improved so that the thin film does not easily peel off.
[0004]
In the conventional method of hydrolyzing titanium tetrachloride, it has been difficult to produce a titanium oxide sol having fine particles having a very small particle diameter, good crystallinity, and good transparency when formed into a thin film.
In the hydrolysis of titanium alkoxide compounds, titanium oxide in the sol has excellent powder characteristics such as very small fine particles. However, when the sol contains alcohol and is baked as a thin film, it is safe for explosion and other reasons. There is a problem. Moreover, large explosion-proof equipment is required to prevent explosion, which is economically disadvantageous.
Titanium alkoxide compounds are very expensive compared to titanium tetrachloride.
The present invention provides a fluorescent lamp that is provided with a titanium oxide thin film having a high photocatalytic action, high transparency, and excellent adhesion to a glass tube on the surface of the glass tube for the fluorescent lamp, and preventing contamination of the glass tube due to adhesion of organic substances. The purpose is to provide.
[0005]
[Means for Solving the Problems]
The present inventors paid attention to hydrolysis of titanium tetrachloride, which is easily available and economically advantageous, and as a result of studying a method for forming a thin film excellent as a photocatalyst on a glass tube of a fluorescent lamp. The invention has been reached.
That is, the present invention is characterized in that a titanium oxide-containing sol is produced by hydrolysis of titanium tetrachloride, the sol is applied to a glass tube surface for a fluorescent lamp, and baked to form a thin film on the surface. It is a fluorescent lamp.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, it is important that titanium tetrachloride is hydrolyzed to form a titanium oxide-containing sol, and the sol is applied to a glass tube. In general, fine particles of titanium oxide are obtained by neutralizing, hydrolyzing, and filtering, drying, heat treatment, etc., the precursor of titanium oxide. Thin particles are formed by dispersing these fine particles in a solvent such as water. Not suitable for use. This is because titanium oxide particles have a high surface activity, and the finer the particles, the higher the activity. Therefore, dispersion in water becomes very difficult, that is, aggregates are formed. This is because the photocatalytic action is also lowered.
[0007]
The inventors previously filed a patent application for a method for producing titanium oxide particles having a small particle size and good crystallinity (Japanese Patent Application No. 7-245446). In this method, the hydrolysis reaction of titanium tetrachloride is performed while suppressing escape of hydrogen chloride to be generated. A preferable method for suppressing escape of hydrogen chloride is a method in which a reflux condenser is installed in the hydrolysis reaction tank, and the hydrogen chloride gas to be evaporated is condensed and returned to the reaction tank.
In the above-mentioned patent, the obtained titanium oxide-containing sol is filtered, dried, and heat-treated as necessary to form titanium oxide particles. In the present invention, a thin film is formed using the titanium oxide-containing sol generated in the middle.
If the concentration of titanium tetrachloride in the aqueous solution of titanium tetrachloride to be hydrolyzed is too low, the productivity is poor, the efficiency is low when forming a thin film from the resulting titanium oxide-containing sol, and if the concentration is too high, the reaction becomes intense. Since the obtained titanium oxide particles are difficult to be fine and the dispersibility is also deteriorated, it is not suitable as a transparent thin film forming material.
[0008]
It is preferable to apply the titanium oxide sol of the present invention to a glass tube as it is produced, or to add a small amount of a water-soluble polymer primary binder as necessary, and in this case, the titanium oxide concentration is too low. When the coating efficiency is low and the concentration is high, it becomes difficult to form a transparent thin film of titanium oxide.
Considering these, the concentration of titanium tetrachloride in the hydrolysis is preferably 0.05 to 1 mol / liter.
The concentration of titanium oxide in the sol obtained by this hydrolysis or the sol obtained by dechlorinating the sol is low in the volume of the solution during hydrolysis or in the subsequent dechlorination. And about 0.05 to 1 mol / liter.
[0009]
A preferred method for producing the titanium oxide-containing sol in the present invention is a method in which hydrogen chloride generated in the hydrolysis of titanium tetrachloride is prevented from escaping from the reaction tank and is left in the aqueous solution as much as possible.
Hydrogen chloride generated by hydrolysis may be suppressed even if escape is not completely prevented. The method is not particularly limited as long as it can also be suppressed. For example, it is possible to apply pressure, but the easiest and most effective method is to install a reflux condenser in the hydrolysis reaction tank to perform hydrolysis. It is a method to do. This apparatus is shown in FIG. In the figure, 1 is a reaction tank filled with an aqueous solution 4 of titanium tetrachloride, and a
[0010]
The temperature in the hydrolysis is preferably in the range of 50 ° C. or higher and the boiling point of the aqueous titanium tetrachloride solution. Below 50 ° C., the hydrolysis reaction takes a long time. The hydrolysis is carried out by raising the temperature to the above temperature and holding it for about 10 minutes to 12 hours. This holding time may be shorter as the hydrolysis temperature is higher.
Hydrolysis of the titanium tetrachloride aqueous solution may be performed by heating a mixed solution of titanium tetrachloride and water to a predetermined temperature in the reaction vessel, or by preheating water in the reaction vessel, May be added to a predetermined temperature. The faster the rate of temperature increase of the aqueous titanium tetrachloride solution, the finer the particles that can be obtained, so that it is preferably at least 0.2 ° C./min, more preferably at least 0.5 ° C./min.
The above describes the case where a titanium oxide-containing sol is obtained by a batch-type reaction. However, while continuously adding titanium tetrachloride and water using the reaction tank as a continuous tank, the reaction solution is taken out on the opposite side of the inlet, and subsequently dechlorinated. A continuous method of processing is also possible.
[0011]
By this method, the titanium oxide particles in the sol have good crystallinity with an average particle size in the range of 0.01 to 0.08 μm.
The titanium oxide-containing sol contains hydrogen chloride. When a sol is applied to a glass tube and baked to form a thin film, if the concentration of hydrogen chloride is high, the transparency of the thin film decreases, and the chlorination generated during calcination occurs. It is preferable to dechlorinate the sol in advance because problems on the apparatus due to hydrogen gas occur.
The dechlorination treatment may be performed by a general known means, and electrodialysis, ion exchange resin, electrolysis and the like are possible. The degree of dechlorination may be determined based on the pH of the sol, for example, in the range of pH 0.5 to 5, preferably
[0012]
When a titanium oxide-containing sol is applied to a glass tube, it is preferable to add a water-soluble polymer primary binder that dissolves in the sol to improve the film formability of the coating film. The water-soluble polymer is not particularly limited, but polyvinyl alcohol, methyl cellulose, ethyl cellulose, nitrocellulose and the like are suitable. The amount is suitably 10% by weight or less based on the titanium oxide contained in the sol. The polymer may be added before the dechlorination treatment, but more preferably after the treatment.
In order to apply the titanium oxide-containing sol thus obtained to a glass tube for a fluorescent lamp (a glass tube as a material before being commercialized as a fluorescent lamp), a method of immersing the glass tube in the sol, glass A method of spraying the sol onto the tube or a method of applying the sol to the glass tube with a brush is employed. The coating amount of sol is suitably 0.01 to 0.2 mm in terms of thickness.
[0013]
The glass tube coated with the titanium oxide sol is then fired. The strength of the titanium oxide thin film produced by firing is improved, and the adhesion between the glass tube and the thin film is improved. The firing temperature is effective at 100 ° C. or higher, but is preferably 200 ° C. or higher. There is no restriction | limiting in particular in the upper limit of baking temperature, What is necessary is just the range which a glass tube does not deform | transform. Generally, the upper limit temperature for firing is about 800 ° C, preferably about 600 ° C.
The firing atmosphere is not particularly limited and may be in the air. There is no restriction | limiting in particular in baking time, For example, what is necessary is just to carry out in the range of 1 to 60 minutes. The thickness of the titanium oxide thin film obtained by firing is about 0.05 to 1.0 μm in the case of the above coating amount.
The titanium oxide thin film produced using the titanium oxide sol according to the present invention exhibits high photocatalytic ability and high transparency because the titanium oxide is crystalline and the titanium oxide fine particles are very fine particles. This is considered to be due to the fact that they do not contain impurities and that the titanium oxide fine particles are dispersed as close as possible to the primary particles.
The fluorescent lamp of the present invention is the same as the conventional one except that the glass tube has the specific titanium oxide thin film described above, and all fluorescent lamps can be targeted.
[0014]
【Example】
Hereinafter, specific examples will be described.
Example 1
Water was added to titanium tetrachloride (purity 99.9%), and the solution was adjusted so that the titanium tetrachloride concentration was 0.25 mol / liter (2% by weight in terms of titanium oxide). At this time, an appropriate cooling device such as ice cooling was provided so that the temperature of the aqueous solution would not rise above 50 ° C. Next, 1 liter of this aqueous solution was charged into the reaction tank equipped with a reflux condenser shown in FIG. 1, heated to near the boiling point (104 ° C.), and maintained for 60 minutes for hydrolysis. After cooling, the residual chlorine produced by the reaction is removed by electrodialysis and adjusted to pH = 2. Then, 0.1% of the water-soluble polymer polyvinyl alcohol is added to the titanium oxide content as a film forming aid. Thus, a titanium oxide sol was obtained. This sol was stable, and no precipitation of titanium oxide fine particles formed was observed even after 1 day or more. When the particles were observed with a transmission electron microscope, the average particle size was 0.015 nm. When the particles were identified using an X-ray diffractometer, the particles were crystalline titanium oxide.
The sol was applied on a glass plate by dip coating and dried, followed by heat treatment in air at 500 ° C. for 1 hour to obtain a titanium oxide thin film. The thickness of the titanium oxide thin film after the heat treatment was 0.15 μm.
[0015]
Example 2
A titanium oxide sol was prepared in the same manner as in Example 1 except that the water-soluble polymer was changed to methylcellulose, and a titanium oxide thin film was obtained in the same manner.
[0016]
Comparative Example 1
Amorphous titanium oxide particles having a primary particle diameter of 0.01 μm were used, and the same titanium oxide concentration as in Example 1 was made 2% by weight and dispersed in water using an ultrasonic disperser. At this time, hydrochloric acid was added to adjust the pH to the same value as in Example 1, and the same operation as in Example 1 was further performed to obtain a titanium oxide sol. In the titanium oxide sol, fine particles of titanium oxide settled with time. Since the film formed with the supernatant liquid after sedimentation did not show the photocatalytic ability, the sol was dispersed again with the ultrasonic disperser and then formed on the glass plate in the same manner as in Example 1 to obtain the photocatalytic ability. Evaluation was performed.
[0017]
Comparative Example 2
A titanium oxide sol was obtained in the same manner as in Comparative Example 1 except that crystalline titanium oxide particles having a primary particle diameter of 0.05 μm were used. Similarly to Comparative Example 1, since the precipitation of titanium oxide fine particles was observed, this sol was redispersed to form a film.
Evaluation of film formation The light transmittance, photocatalytic ability, and adhesion to a glass plate of a titanium oxide thin film obtained from each of the titanium oxide sols of the evaluation examples and comparative examples were measured.
[0018]
The light transmittance is measured by setting the titanium oxide thin film formed on the glass plate to a spectrophotometer manufactured by JASCO Corporation and measuring the light transmittance by continuously changing the wavelength from 700 to 200 nm. did. The light transmittance at 550 nm was expressed as the light transmittance in the present invention. The results are shown in Table 1.
The method for decomposing oxalic acid is to prepare a reaction vessel with a film-formed glass plate with a titanium oxide thin film, put 5 mmol / liter oxalic acid into this, and irradiate a 100 W mercury lamp while blowing oxygen for 4 hours. The amount of oxalic acid decomposed later was determined by redox titration of potassium permanganate. The results are shown in Table 2.
The adhesion between the fired glass plate and the thin film was determined by a pencil hardness test method and a goblet peel test method (JIS K5400). The results are shown in Table 3.
[0019]
[Table 1]
[0020]
[Table 2]
[0021]
In Comparative Example 1, an aggregate of titanium oxide was formed on the glass plate and the surface was uneven.
In Comparative Example 2, since a transparent titanium oxide thin film was not obtained, evaluation of the photocatalytic ability was not performed.
[0022]
[Table 3]
[0023]
【The invention's effect】
The titanium oxide sol of the present invention does not contain any organic solvent, and the solvent is water, in which crystalline titanium oxide fine particles are efficiently dispersed. Furthermore, since the content of impurities that reduce the catalytic activity is small, the titanium oxide thin film obtained by film formation is suitable as a transparent thin film material having a photocatalytic ability by absorbing ultraviolet rays. Further, the titanium oxide thin film has good transparency and good adhesion to the glass tube. Therefore, by forming this thin film on the glass tube of a fluorescent lamp, the durability of the glass tube is not impaired and the durability is good, so that organic substances can be decomposed and prevented from being soiled by photocatalysis over a long period of time.
Since the sol composition in the present invention is basically water-based, it does not require an organic component exclusion facility such as an explosion-proof facility during film formation, which is advantageous in terms of equipment and economy.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of a reaction vessel used in the method of the present invention.
[Explanation of symbols]
1
Claims (13)
Priority Applications (1)
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JP20716596A JP3726366B2 (en) | 1996-08-06 | 1996-08-06 | Fluorescent lamp |
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JP20716596A JP3726366B2 (en) | 1996-08-06 | 1996-08-06 | Fluorescent lamp |
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JP3726366B2 true JP3726366B2 (en) | 2005-12-14 |
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JPH01169866A (en) * | 1987-12-25 | 1989-07-05 | Hitachi Ltd | Discharge lamp |
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JPH06293519A (en) * | 1992-07-28 | 1994-10-21 | Ishihara Sangyo Kaisha Ltd | Production of titanium oxide particles and film |
JP3309591B2 (en) * | 1993-12-28 | 2002-07-29 | 東陶機器株式会社 | Multifunctional material with photocatalytic function |
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