【発明の詳細な説明】[Detailed description of the invention]
本発明は管球たとえばけい光水銀ランプ、けい
光ランプ等のけい光被膜を静電塗装法によつて形
成する場合に適するけい光体の製造方法に関す
る。
従来、管球たとえばけい光水銀ランプにおいて
は外管バルブ内面に形成されるけい光体被膜は、
硝化綿を有機溶剤に溶解してなる有機バインダー
溶液中にけい光体を分散した懸濁液を用いる湿式
法が使用されている。しかしながら、この方法は
有機溶剤の危険性、価格の問題、さらにはバイン
ダーをベーキングして焼散させる工程を必要とす
るため、これ等の改良を目的として、近年けい光
体粉末を直接管球バルブ内面に被着させる静電塗
装法が開発されつゝある。ところが、この方法は
従来の湿式法に比較して上記利点がある反面、け
い光体粉末はその内部摩擦に起因して流動性が非
常に悪いため、スプレーガンからの吐出量の変動
が大きく、バルブへの被着量が一定せず、ランプ
の光束に変動を生じて均一な製品が得られにくい
とか、またけい光体被膜のバルブへの被着性が悪
く剥離しやすい等の欠点があつた。この対策とし
て、けい光体に数％の微粒子シリカ等を混合する
ことによつて流動性を向上する方法が提案されて
いるが、この方法によつても、なお流動性の経時
変化が大きく、シリカ混合後のけい光体の保存時
間に制約を受ける欠点があつた。
本発明はこのような欠点に対処してなされたも
ので、流動性が良く、しかも流動性の経時変化の
小さい静電塗装用けい光体の製造方法を提供する
ことを目的とする。
本発明の特徴は、けい光体に混合される微粒子
シリカを、800℃以上の乾燥雰囲気中で焼成する
工程を備えている点にある。
すなわち、従来の微粒子シリカを混合したけい
光体の流動性が経時変化する原因が、一般に数％
〜数10％の水分を含有する上記微粒子シリカにあ
ることを発見し、混合けい光体に含まれる微粒子
シリカの吸着された水分を少なくすると共に、吸
湿性を大幅に低下させるようにするものである。
以下、本発明の詳細を実施例を参照して説明す
る。
一般照明用けい光体たとえばYVPSiO4／Euけ
い光体およびこのけい光体に対し0.5〜10重量％
の範囲内でサブミクロンの粒径の微粒子シリカ
（例えば米国Ｐ，Ｐ，Ｇ，社製LO―VEL27）を
混合した混合けい光体を調製し、さらにこれ等け
い光体試料について100℃―10分間乾燥のものと
800℃―30分例えば大気中等の乾燥雰囲気で焼成
したものとを作り、これ等各試料を室内に放置し
てその流動性の経時変化を調べた。結果を次表に
示す。なお、流動性の良否の判定基準（測度）と
しては、各試料粉体の息角（粉粒体を水平板上に
静かに推積してゆくと、推積物の形はつねに円錐
状となり、この円錐面で粉粒体はすべり落ちる。
このとき円錐の母線が水平面となす角を息角とい
い、息角の小さいほど粉粒体の流動性は良いこと
になる。）によつた。表において（ ）内は100℃
―10分間乾燥のもの、（ ）のないものは800℃―
30分焼成のものの息角をそれぞれ示す。
The present invention relates to a method for producing a phosphor suitable for forming a fluorescent coating on a tube such as a fluorescent mercury lamp or a fluorescent lamp by an electrostatic coating method. Conventionally, in a tube such as a fluorescent mercury lamp, the phosphor coating formed on the inner surface of the outer bulb is
A wet method is used in which a suspension of a phosphor is dispersed in an organic binder solution made by dissolving nitrified cotton in an organic solvent. However, this method is dangerous due to organic solvents, is expensive, and requires a process of baking and burning off the binder. Electrostatic coating methods are being developed for application to internal surfaces. However, although this method has the above-mentioned advantages compared to the conventional wet method, the phosphor powder has very poor fluidity due to its internal friction, so the amount discharged from the spray gun fluctuates greatly. There are disadvantages such as the amount of coating on the bulb is not constant, causing fluctuations in the luminous flux of the lamp, making it difficult to obtain a uniform product, and the phosphor coating has poor adhesion to the bulb and is easily peeled off. Ta. As a countermeasure to this problem, a method has been proposed in which the fluidity is improved by mixing several percent of fine particle silica or the like into the phosphor, but even with this method, the fluidity changes significantly over time. There was a drawback that the storage time of the phosphor after mixing with silica was limited. The present invention has been made to address these drawbacks, and it is an object of the present invention to provide a method for producing a phosphor for electrostatic coating which has good fluidity and shows little change in fluidity over time. A feature of the present invention is that it includes a step of firing the particulate silica mixed into the phosphor in a dry atmosphere at 800° C. or higher. In other words, the reason why the fluidity of conventional phosphors mixed with fine-particle silica changes over time is generally a few percent.
It was discovered that the above-mentioned fine particulate silica contains up to several tens of percent water, and it is possible to reduce the amount of water adsorbed by the fine particulate silica contained in the mixed phosphor and to significantly reduce the hygroscopicity. be. Hereinafter, details of the present invention will be explained with reference to Examples. Phosphors for general lighting e.g. YVPSiO 4 /Eu phosphors and 0.5 to 10% by weight based on this phosphor
A mixed phosphor was prepared by mixing fine particle silica (for example, LO-VEL27 manufactured by P, P, G, USA) with a submicron particle size within the range of Minute dry and
Samples were baked at 800°C for 30 minutes in a dry atmosphere such as air, and the samples were left indoors to examine changes in fluidity over time. The results are shown in the table below. The criterion (measure) for determining the quality of fluidity is the angle of repose of each sample powder (when powder is gently deposited on a horizontal plate, the shape of the deposit is always conical). , the powder material slides down on this conical surface.
At this time, the angle that the generating line of the cone makes with the horizontal plane is called the angle of repose, and the smaller the angle of repose, the better the fluidity of the granular material. ). In the table, the value in parentheses is 100℃.
-Dried for 10 minutes, 800℃ for those without ()-
The angle of repose of each product baked for 30 minutes is shown.
【表】
表から微粒子シリカのけい光体との混合は明ら
かに流動性向上の効果があることが判ると共に、
混合後の800℃焼成による流動性の経時変化防止
効果も顕著であることが判る。
800℃焼成処理の作用は微粒子シリカの表面が
シラノール結合状態にあり多量の水分が付着して
いるのが、上記焼成処理によつて脱水されシロキ
サン結合状態となり、その後も吸湿性を示さなく
なるためと考えられる。これに対し、100℃で乾
燥しただけのものは、一時的には水分が除かれる
が、放置しておくと再び水分を吸収し、シリカの
微粒子が水を介して凝集し、流動性が悪くなるも
のと考えられる。
微粒子シリカのけい光体に対する混合割合は１
％未満では流動性の改善が充分でなく、また５％
を越えると流動性改善の効果はあるが、混合けい
光体中に占めるけい光体自体の割合が少なくなる
ので当然発光強度が低下するので好ましくない。
なお、焼成温度は800℃未満になるとシラノー
ル結合状態からシロキサン結合状態への移行が不
充分となり、このため放置中の吸湿性が残り、好
ましくない。
以上詳述したように、本発明によれば微粒子シ
リカを800℃以上の乾燥雰囲気中で焼成したの
で、静電塗装用けい光体の吸湿性は低下し、流動
性の経時変化は少なくできるので、混合物の取扱
い、保管方法等にも特別の注意をはらう必要がな
くなり簡単化することができた。
尚、以上説明した実施例においては、微粒子シ
リカとけい光体とを混合させた後、800℃以上で
これらの混合物を焼成しているが、本発明はこれ
に限らず、例えば、微粒子シリカを焼成させた
後、けい光体に混合させても同様な効果が得られ
る。[Table] From the table, it can be seen that mixing fine particle silica with a phosphor clearly has the effect of improving fluidity.
It can be seen that baking at 800°C after mixing has a significant effect in preventing changes in fluidity over time. The effect of the 800°C firing process is that the surface of the fine silica particles is in a silanol bonded state and has a large amount of water attached to it, but through the above baking process, it is dehydrated and becomes a siloxane bonded state, and it no longer exhibits hygroscopicity. Conceivable. On the other hand, if the material is simply dried at 100℃, the moisture is removed temporarily, but if left for a while, it will absorb moisture again, causing fine silica particles to aggregate through the water, resulting in poor fluidity. This is considered to be the case. The mixing ratio of fine silica to phosphor is 1
If it is less than 5%, the improvement in fluidity will not be sufficient, and if it is less than 5%
Exceeding this is not preferred because, although there is an effect of improving fluidity, the proportion of the phosphor itself in the mixed phosphor decreases, which naturally lowers the luminous intensity. Note that if the firing temperature is lower than 800°C, the transition from the silanol bond state to the siloxane bond state will be insufficient, and therefore hygroscopicity will remain during storage, which is not preferable. As detailed above, according to the present invention, fine particle silica is fired in a dry atmosphere at a temperature of 800°C or higher, so the hygroscopicity of the phosphor for electrostatic coating is reduced, and changes in fluidity over time can be reduced. , handling of the mixture, storage method, etc. can be simplified as there is no need to take special precautions. Incidentally, in the embodiments described above, after mixing the particulate silica and the phosphor, the mixture is fired at 800°C or higher, but the present invention is not limited to this. A similar effect can be obtained by mixing the phosphor with the phosphor.