1307351 (1) 九、發明說明 【發明所屬之技術領域】 本發明提供一種含有金屬氧化物粉末，黏度調節劑及 水溶性黏合劑之水性分散液。本發明進一步提供一種藉使 4 用此種分散液所得之在基底上之層。 【先前技術】 已知藉所謂之溶膠-凝膠方法來塗覆金屬氧化物層在 Φ 基底上。溶膠-凝膠方法之缺點是：由於高溶劑含量及低 固體含量，故即使極緩慢且小心地乾燥，也會發生嚴重的 收縮及龜裂。此方法之進一步之缺點是··在單一塗覆操作 之情況中，層厚度一般小於1微米。 再者，由 EP-A- 1 3 2 1 444得知一種方法，其中由 一種含有熱解產製之矽及鈦之混合氧化物之水性分散液開 始，且隨後燒結可以產製各層。這些層可以有顯著較高之 層厚度且同時甚爲不含雜質。已證明用此方法有一缺點是 · :即使在此方法之最佳情況中，當塗覆基底時某種層厚度 不能被超過，若要得到稍粗糙之無龜裂層時。已顯明：在 EP-A- 1 3 2 1 444中所述之水性分散液是上述缺點之主 因。 . 【發明內容】 本發明之目的是要得到一種分散液，其使基底能在一 單一塗覆步驟中用厚而無龜裂之金屬氧化物層來塗覆。厚 -5 - (2) 1307351 層被了解是具有至少1微米之層厚度。本發明提供一種含 有金屬氧化物之水性分散液，該分散液特徵在於他還含有 黏度調節劑及水溶性黏合劑，黏度調節劑及黏合劑可能藉 熱處理來完全除去。 黏度調節劑及黏合劑可能完全藉熱處理來除去之特點 是與用分散液塗覆各層有關。在此情況中，已確定：除了 金屬氧化物之外，分散液的構成成分可以在層之燒結步驟 之前或期間被除去，因爲僅用此方式才能獲得高純度之金 屬氧化物層。 已發現：所有的金屬氧化物粉末是合適的，原則上， 以熱解產製之金屬氧化物粉末是較佳的。熱解產製之金屬 氧化物粉末是那些可以藉金屬氧化物先質之火焰水解或火 焰氧化而得者。就此而論，首先高分散之非孔性主要粒子 被形成，其而後在反應之進一步階段中能聚集以形成聚集 體，此聚集體能進一步集合以形成附聚物。 再者，若金屬氧化物粉末是僅梢微結構化’則可能是 有利的。此意指主要粒子顯現出低度之中間成長（ intergrowth)。例如，就此而論，這可能是由Degussa所 產製之具有約50平方米/克之BET表面積的二氧化矽粉 末 Aerosil® 0X 50 之問題。 原則上，所有熱解產製之金屬氧化物粉末適於依本發 明之分散液。依本發明之分散液較佳可以含有 Si02、 A1 2 0 3、T i 0 2、Z1. 0 2及/或所述之氧化物的物理及/或化 學混合物。在特別較佳之方式中，分散液可以含有二氧化 -6 - (3) (3)1307351 矽，其就本發明而言，被認爲是金屬氧化物。 這些主要粒子之BET表面積通常介於1平方米/克及 6 〇 〇平方米/克之間。爲了使用依本發明之分散液以將層 塗在基底上，已證明若BET表面積介於5平方米/克及 2 〇 〇平方米/克間，則是有利的。 依本發明之分散液較佳可以具有5重量％至70重量 %間之金屬氧化物粉末含量，係相較於分散液之總量。具 有少於5重量％含量之分散液不適於產製具有大於2.5微 米層厚之層。在有利的方式中，在分散液中之金屬氧化物 粉末的含量介於10重量％及50重量％間，在15重量％ 及4 〇重量％間之範圍是特別較佳的。 依本發明之分散液進一步含有黏度調節劑。就此而論 ，這是在分散液中存在之酸反應或鹼反應物質的問題，爲 要降低其黏度。酸反應或鹼反應物質存在於分散液中與否 主要依金屬氧化物而定。在氧化鋁之情況中，酸性黏度調 節劑如氫氯酸是較佳的。在二氧化矽的情況中，鹼反應及 酸反應之黏度調節劑如氨，氫氧化銨及/或氫氧化四甲基 銨或氫氯酸是適合的。 在利用熱解的氧化物的情況中，也可能添加黏度調節 劑以分散。通常，這些氧化物含有鹵化物殘餘到利用含鹵 化合物於其產製過程中之程度上，其是因方法而起且在水 性分散液中水解以形成黏度調節劑。 依本發明之分散液進一步含有水溶性黏合劑。此較佳 可以是聚（乙烯基醇）或甲基纖維素。在此情況中，若這 -7 - (4) (4)1307351 些物質具有較短之聚合物鏈長度，例如具有少於20,000 之平均分子量Mw的聚（乙烯基醇）或具有少於20,0 0 0之 平均分子量Mn之甲基纖維素，則可以是特別較佳的。 水溶性黏合劑相對於金屬氧化物粉末之量之比例較佳 可以是介於0.05重量％及5重量％間。介於0.5重量％及3 重量％間之範圍是特別較佳的。若金屬氧化物粉末是氧化 鋁，已證明利用較高比例，高達20重量％ ’特別較佳的 10重量％之黏合劑是有利的。 依本發明之分散液可以進一步含有消泡劑，其類似於 黏度調節劑及水溶性黏合劑，可以完全藉熱處理來除去。 這較佳可以是基於脂肪酸及烴之消泡劑。 消泡劑之含量相對於黏合劑之量較佳可以是介於2重 量％及200重量％間。介於10重量％及1〇〇重量％間之 範圍可以是特別較佳的。 然而，可能完全用消泡劑來分散且若分散液中存在麻 煩之泡沫時反而會藉分散液之真空處理而除去。 黏度調節劑，黏合劑及可選擇的消泡劑可以被除去之 溫度較佳是不超過600 °C。 進一步特別較佳地是依本發明之分散液，其含有 -作爲熱解產製之金屬氧化物粉末之具有介於5平方 米/克及2 00平方米/克間之BET表面積之二氧化 砂粉末， 一作爲黏度調節劑之氫氧化四甲基銨， •-作爲黏合劑之具有小於2 0000之平均分子量Mw之 (5) (5)1307351 聚（乙烯基醇），及 一作爲消泡劑之基於脂肪酸及烴者。 再者’特別較佳者是依本發明之分散液，其含有 一作爲熱解產製之金屬氧化物粉末之具有介於5平方 米/克及200平方米/克間之bet表面積之二氧化 矽粉末， 一作爲黏度調節劑之氫氧化四甲基銨， 一作爲黏合劑之具有小於20,000之分子量Μη之甲基 纖維素，及 -作爲消泡劑之基於脂肪酸及烴者。 本發明進一步提供一種產製依本發明之分散液之方法 ，該方法特徵在於 -在第一步驟中，藉著在分散條件下金屬氧化物粉末 被連續或所有一次倒入含有水之接收燒瓶中且藉在 添加金屬氧化物粉末期間或之後添加黏度調節劑直 到上升至所要之黏度之量，以生成預分散液， -在第二步驟中’在預分散液中添加下列物質以得到 分散液： -黏合劑之水溶液’其量使黏合劑相對於金屬氧化劑 粉末之量的比例介於〇 . 〇 5重量％及5重量％間，及 一可選擇地’消泡劑之水溶液’及 -可選擇地’小量之黏度調節劑以調節原始之pH値 預分散液及分散液之產製在類似或不同之能量輸入下 -9- (6) (6)1307351 進行。 適合供預分散及分散之目的者是例如溶解器，齒碟’ 轉子一靜子（rotor-stator)機如 Ultra Turrax (由 IKA 所 製）或由Ystral所製者，進一步之球磨，攪拌器球磨。較 高之能量輸入用行星式捏合機/混合機是可能的。然而此 系統之效率與經加工之混合物之充分高之黏度有關，爲要 引入將分離粒子所需之高切變能量。用高壓勻化機則可能 有極高之能量輸入。 使用這些裝置，在高壓下懸浮液之二道預分散液流經 由一噴嘴來降壓。分散液之二噴射物確實碰撞且粒子彼此 粉碎。 在另一具體表現中，預分散液同樣放置在高壓下，但 粒子之碰撞是相對甲狀板壁區來實施。此操作常能任意地 重複以得到較小的粒子尺寸。 本發明進一步提供一種個別的金屬氧化物層，其係藉 使用依本發明之分散液而得，具有至少2.5微米之層厚度 在基底上。在較佳之方式中’層厚度可以介於3微米至15 微米間。層可以是類似玻璃或陶瓷。 適合的基底可以是金屬基底及合金基底，具有及低熱 膨脹係數之材料（超低膨脹之材料），硼较酸鹽玻璃，砂 石玻璃或玻璃陶瓷，特別較佳是玻璃基底。 具有少於30奈米之表面粗糙度之層可以是較佳的。 本發明進一步提供一種在單一步驟中被塗覆之層的產 製方法’該方法特徵在於 -10 - (7) (7)1307351 一藉浸漬塗覆依本發明之分散液在基底上形成__ β 而塗覆一個別層， -粗胚隨後首先在少於1 0 0 °c溫度下乾燥， -隨後加熱至黏合劑及可選擇的消泡劑被部份或完全 自粗胚除去的溫度，且 一隨後燒結之。 在有利的方式中，依本發明知方法可以用如下方式實 施：基底由分散液中拉出之拉伸速度介於1毫米/秒及 1 00毫米/秒間。2毫米/秒及40毫米/秒間之範圍是特 別較佳的。 層之燒結可以依精於此技藝者已知知方法來實施，例 如藉火焰燒結或雷射燒結。在依本發明之方法中，雷射燒 結是特別較佳的。 就此而論，預先加熱基底至約3 0 0 °C之溫度可能是有 利的。 在一較佳之方式中，粗胚在雷射光束下移動之速度介 於1毫米/秒及]0毫米/秒間。 本發明進一步提供依本發明之在基底上之金屬氧化物 層在供具有極低膨脹係數之材料（超低膨脹材料，ULE材 料），供光催化應用，作爲自身淸潔鏡子之塗覆物（超親 水性構成成分）’供光學物件如鏡片，作爲氣體及液體之 密封物，作爲機械保護層，及在複合材料中之用途。 本發明描述一種水性分散液，使用此分散液則可能藉 著在單一步驟中之浸漬塗覆來將具有大於2.5微米層厚度 -11 - (8) (8)1307351 之金屬氧化物層塗在基底上。所得之層沒有龜裂且有低的 表面粗楗度。 [實施方式】 藉溶解器（Nl-SIP，VMA-Getzmann)產製經熱解產製 之二氧化砂粉末（Aerosil® OX 50，DegussaAG)在經二次 蒸餾之水中所得的3 0重量％的分散液。 分散液D 1 : 以上所產製之分散液隨後藉添加另外之經二次蒸餾之 水及氫氧化四甲基銨溶液而調節成20重量％之固體含量 及9.7之pH値。 分散液D2 : 30重量％之分散液進一步藉添加含有短聚合物鏈長（ 約1 4,0 0 0之Μ n )之甲基纖維素作爲黏合劑的溶液，消泡 劑（contraspum KWE，Zschimmer & Schwarz)及氮氧化四 甲基銨溶液而稀釋以得到具有2 0重量％二氧化矽粉末含 量之分散液。在此分散液中甲基纖維素相對於二氧化砂粉 末之比例是2重量％ ;去沫劑相對於黏合劑之比例達1 0 0 重量％。分散液之pH達9.2。 浸漬塗覆 藉浸漬塗覆裝置以2毫米/秒及4 〇毫米/秒之拉伸 -12 - 1307351 Ο) 速度僅一次浸在分散液D 1及D 2中且隨後接觸空氣來乾 燥而塗覆硼矽酸鹽玻璃碟。 隨後黏合劑及消泡劑在2小時期間內在約2 5 0 °C溫度 下自塗覆有D2之碟中部分地除去。塗覆有D1 (不含有黏 合劑）之碟同樣地被處理。 所得之粗胚隨後藉具有700W最大功率及10.6波長之 雷射（C02雷射，R〇fin-Sinar，RS 7 00 )來燒結。就此而論 ’雷射光束藉可移動之鏡子在經塗覆之材料之表面上移動 。鏡子之速度被調整以使雷射光束以2 0 0 Η z之頻率在樣品 上被引導。爲了避免表面上之應力，預熱樣品至3 0 0 t是 有利的。層用5.5W/平方毫米之功密度來燒結。隨後測量 所得之層厚度。 分散液D3 : 以類似於D 2之方式者來產製，但卻是用具有短聚合 物鏈長度（Mw 9,000至10,000)之聚（乙烯基醇），藉由 黏合劑而非甲基纖維素。以類似於D2之方式者來實施浸 漬塗覆。 表淸楚顯示用含有黏合劑之分散液塗覆會造成顯著較 高之層厚度。在40毫米/秒之拉伸速度下，可能用單— 之塗覆步驟來塗覆超過3微米之層厚度。在供除去黏合劑 之熱處理之後且在燒結後，用D2或D 3所得之層沒有龜 裂且與D ]所得之層比較有較低之表面粗糙度。所塗覆之 墙在燒結後顯出極良好之黏合性在基底上。 -13 - (10) 1307351 表：用D 1至D 3所得之層的最大層厚度’ μπί 層厚度[μιη] V Η * v draw 在2 5 0 °C之 在雷射燒 在燒結後平 [m m / s 1 處理後 結後. 均粗糙度 D1 (參考） 2 3.0 1.2 3 5 40 3.9 1.4 3 5 D 2 (依本發明 2 5.6 2.6 2 6 ) 40 7.3 3 . 1 26 D 3 (依本發明 2 4.6 2.5 24 ) 40 7.6 3.2 24 * vdraw =拉伸速率 藉改變 -金屬氧化物粉末， 一金屬氧化物粉末之bet表面積， —在分散液中之固體含量， -在分散液中金屬氧化物粒子的聚集體尺寸’ -黏合劑之形式， -黏合劑之比例， -在浸漬過程中之拉伸速率， 也可以得到較高層厚度。 經燒結之樣品就其機械及化學性質來檢查。 爲了比較未經塗覆之玻璃之破裂強度與經塗覆之玻璃 -14 - (11) (11)1307351 者’遵循DIN 52292之模式實施雙環彎曲測試。在此情 況中樣品量之測量是60毫米x60毫米。藉Weibull方法 進行評估。 雙環彎曲測試顯示玻璃碟之破裂強度可以藉OX 5 0之 層來改良。塗覆有依本發明之分散液D 1及D2之樣品的 破裂強度約超過未經塗覆之玻璃碟者的20%至30%。此 外，W e i b u Π評估顯示經塗覆之樣品之失效之機率是較佳 的，此係以直線之較高梯度表示。此理由在於對基底之表 面損壞的區域（其作爲龜裂起始者）被層所覆蓋。 耐化學性藉著依本發明之分散液D 1及D2所產製之 層及未塗覆之基底被40%氫氟酸蝕刻20分鐘而得測量。 爲了能分析在蝕刻過程中控掘品質，用輪廓計來測定蝕刻 深度。就此而論，已證實：在未經塗覆玻璃之基底的情況 中蝕刻深度是24微米，然而在經塗覆之玻璃之基底的情 況中蝕刻深度是〗5微米。此意指玻璃之基底的耐化學性 藉塗覆而改良。 分散液D 4 A ] u C分散液 3〇克氧化鋁C(DegUSSa AG)藉溶解器攪拌入243克 之經二次蒸餾之水中。而後，3 0克之甲基纖維素溶液（1 〇 重量％甲基纖維素’ S i gm a Μ 7 1 4 0 ’於水中）被添加。分 散液倒入超音波粉碎機（Sonifier II，W-4 5 0 )中且在約 4 5 0W下在其中分散3分鐘。由於此超音波處理，在分散 過程中之泡沫之產生被減低。隨後，分散液在約]〇 〇毫巴 -15 - (12) 1307351 下進行後處理1 〇分鐘。結果’殘餘的泡沫被消除。 鋁片（AlMg3 ;預處理二用Na〇H來起初蝕刻及/或 噴砂）及玻璃基底在浸漬塗覆設備中以4 0毫米/秒之速 率用此分散液來塗覆。 . 層之厚度用輪廓計來測定’範圍在約5微米及約2 0 微米間，與基底無關。層沒有龜裂。 在A 1基底上之氧化鋁層之粗糙度之値就平均粗糙度 而言是在200奈米至1=〇〇〇奈米範圍間’就峰對谷之値而 馨 言則在1，0 〇 0奈米至1 〇，0 0 0奈米範圍間。 在硼矽酸鹽玻璃上之氧化鋁層的粗糙度之値就平均粗 糙度而言在7奈米至40奈米之範圍間’就峰對谷之値而 言在1 0 0至5 0 0奈米之範圍間。 層藉助於二氧化碳雷射以約5W/平方毫米之電力密 度來燒結，基底以約5毫米/秒之速度在雷射光束下移動 。得到約2微米至3微米之層厚度。爲了避免應力龜裂， 經塗覆之玻璃基底在5 0 0 °C下之爐中儲存6小時且而後在 g 8小時內冷卻至室溫。 經塗覆之玻璃的破裂強度藉助於雙環彎曲測試（DIN 52 292)來測定。 經塗覆之鋁片之磨損行爲藉助於Taber Abraser方法 來測定且與未經塗覆之鋁片之磨損來比較。 在燒結後，氧化鋁層之層厚度約爲綠體厚度之5 0 %。 * 由於氧化鋁層，玻璃基底之機械強度被加強2 0 %至 5 〇 % ° -16 - (13) (13)1307351 鋁基底之耐磨損性可以藉氧化鋁層而加強（藉“ T a b e r A b 1· a s e r測試”來特徵化）。 氧化鋁層加強鋁基底及玻璃基底對鹼液（NaOH )及 酸（H F，H C 1 )之耐化學性。1307351 (1) Description of the Invention [Technical Field] The present invention provides an aqueous dispersion containing a metal oxide powder, a viscosity modifier, and a water-soluble binder. The invention further provides a layer on a substrate obtained by using such a dispersion. [Prior Art] It is known to coat a metal oxide layer on a Φ substrate by a so-called sol-gel method. The disadvantage of the sol-gel process is that due to the high solvent content and low solids content, severe shrinkage and cracking can occur even with very slow and careful drying. A further disadvantage of this method is that the thickness of the layer is typically less than 1 micron in the case of a single coating operation. Further, a process is known from EP-A-1 321 444, in which an aqueous dispersion of a mixed oxide of cerium and titanium containing pyrolysis is started, and then sintered to produce layers. These layers can have a significantly higher layer thickness and are at the same time very free of impurities. A disadvantage of using this method has been demonstrated to be that: even in the best case of this method, a certain layer thickness cannot be exceeded when the substrate is applied, in order to obtain a slightly rough crack-free layer. It has been shown that the aqueous dispersions described in EP-A-1 2 2 1 444 are the main disadvantages of the above disadvantages. SUMMARY OF THE INVENTION The object of the present invention is to obtain a dispersion which enables the substrate to be coated with a thick, crack-free metal oxide layer in a single coating step. Thick -5 - (2) 1307351 layers are known to have a layer thickness of at least 1 micron. The present invention provides an aqueous dispersion containing a metal oxide which is characterized in that it further contains a viscosity modifier and a water-soluble binder, and the viscosity modifier and the binder may be completely removed by heat treatment. Viscosity modifiers and binders may be completely removed by heat treatment and are associated with coating the layers with a dispersion. In this case, it has been determined that the constituents of the dispersion can be removed before or during the sintering step of the layer in addition to the metal oxide, since only a high purity metal oxide layer can be obtained in this manner. It has been found that all metal oxide powders are suitable, and in principle, metal oxide powders produced by pyrolysis are preferred. Pyrogenically produced metal oxide powders are those which can be oxidized by flame or flame by metal oxide precursors. In this connection, first, highly dispersed non-porous primary particles are formed which are then aggregated in a further stage of the reaction to form aggregates which can be further aggregated to form agglomerates. Furthermore, it may be advantageous if the metal oxide powder is only microstructured. This means that the main particles exhibit a low degree of intergrowth. For example, in this connection, this may be a problem with the cerium oxide powder Aerosil® 0X 50 having a BET surface area of about 50 m 2 /g produced by Degussa. In principle, all pyrogenically produced metal oxide powders are suitable for dispersions according to the invention. The dispersion according to the invention may preferably comprise a physical and/or chemical mixture of SiO 2 , A 1 2 0 3 , T i 0 2, Z1. 0 2 and/or the oxides described. In a particularly preferred manner, the dispersion may contain -6-(3)(3)1307351 矽, which for the purposes of the present invention is considered to be a metal oxide. The BET surface area of these primary particles is typically between 1 square meter per gram and 6 square meters per gram. In order to use the dispersion according to the invention to coat the layer on the substrate, it has proven to be advantageous if the BET surface area is between 5 m 2 /g and 2 〇 〇m 2 /g. The dispersion according to the present invention preferably has a metal oxide powder content of from 5% by weight to 70% by weight based on the total amount of the dispersion. Dispersions having a level of less than 5% by weight are not suitable for producing layers having a layer thickness greater than 2.5 microns. In an advantageous manner, the content of the metal oxide powder in the dispersion is between 10% by weight and 50% by weight, particularly preferably in the range between 15% by weight and 4% by weight. The dispersion according to the present invention further contains a viscosity modifier. In this connection, this is a problem of an acid reaction or an alkali reaction substance present in the dispersion in order to lower the viscosity. Whether the acid reaction or the alkali reaction substance is present in the dispersion depends mainly on the metal oxide. In the case of alumina, an acidic viscosity modifier such as hydrochloric acid is preferred. In the case of cerium oxide, a viscosity adjusting agent such as ammonia, ammonium hydroxide and/or tetramethylammonium hydroxide or hydrochloric acid of a base reaction and an acid reaction is suitable. In the case of using pyrolyzed oxides, it is also possible to add a viscosity modifier to disperse. Typically, these oxides contain halide residues to the extent that the halogen-containing compound is utilized in the process of its production, which is initiated by the process and hydrolyzed in an aqueous dispersion to form a viscosity modifier. The dispersion according to the invention further contains a water-soluble binder. This may preferably be poly(vinyl alcohol) or methyl cellulose. In this case, if the -7 - (4) (4) 1307351 materials have a shorter polymer chain length, such as a poly(vinyl alcohol) having an average molecular weight Mw of less than 20,000 or have less than 20, Methylcellulose having an average molecular weight of Mn of 0 0 0 may be particularly preferred. The ratio of the water-soluble binder to the amount of the metal oxide powder may preferably be between 0.05% by weight and 5% by weight. A range between 0.5% by weight and 3% by weight is particularly preferred. If the metal oxide powder is aluminum oxide, it has proven to be advantageous to utilize up to 20% by weight, particularly preferably 10% by weight, of the binder in a relatively high proportion. The dispersion according to the present invention may further contain an antifoaming agent similar to a viscosity modifier and a water-soluble binder, which can be completely removed by heat treatment. This may preferably be an antifoaming agent based on fatty acids and hydrocarbons. The content of the antifoaming agent may preferably be between 2% by weight and 200% by weight based on the amount of the binder. A range between 10% by weight and 1% by weight may be particularly preferred. However, it may be completely dispersed with an antifoaming agent and if a troublesome foam is present in the dispersion, it may be removed by vacuum treatment of the dispersion. The temperature at which the viscosity modifier, binder and optional defoamer can be removed is preferably not more than 600 °C. Further particularly preferred is a dispersion according to the invention comprising - as a metal oxide powder for pyrolysis, a sulphur dioxide having a BET surface area of between 5 m 2 /g and 200 m 2 /g a powder, a tetramethylammonium hydroxide as a viscosity modifier, a binder having an average molecular weight Mw of less than 20,000 (5) (5) 1307351 poly(vinyl alcohol), and a defoaming agent Based on fatty acids and hydrocarbons. Further, 'particularly preferred is a dispersion according to the present invention which contains a metal oxide powder as a pyrolysis and has a bet surface area of between 5 m 2 /g and 200 m 2 /g. A bismuth powder, a tetramethylammonium hydroxide as a viscosity modifier, a methylcellulose having a molecular weight of less than 20,000 as a binder, and a fatty acid-based and hydrocarbon-based as an antifoaming agent. The invention further provides a process for the production of a dispersion according to the invention, characterized in that - in the first step, the metal oxide powder is poured into the receiving flask containing water continuously or all at once under the conditions of dispersion And by adding a viscosity modifier during or after the addition of the metal oxide powder until it reaches the desired viscosity to form a pre-dispersion, - in the second step 'add the following materials to the pre-dispersion to obtain a dispersion: - the aqueous solution of the binder is present in an amount such that the ratio of the binder to the amount of the metal oxidant powder is between 〇. 5% by weight and 5% by weight, and optionally an aqueous solution of the 'antifoaming agent' and - optionally The 'small amount of viscosity modifier to adjust the original pH 値 pre-dispersion and dispersion production under similar or different energy input -9- (6) (6) 1307351. Suitable for pre-dispersion and dispersion are, for example, dissolvers, rotor-rotor-stator machines such as Ultra Turrax (made by IKA) or by Ystral, further ball milling, agitator ball milling. It is possible to use a planetary kneader/mixer for higher energy input. However, the efficiency of this system is related to the sufficiently high viscosity of the processed mixture to introduce the high shear energy required to separate the particles. High-pressure homogenizers can have extremely high energy inputs. Using these devices, the two predispersions of the suspension under high pressure flow through a nozzle to reduce pressure. The two sprays of the dispersion do collide and the particles pulverize each other. In another embodiment, the predispersion is also placed under high pressure, but the collision of the particles is carried out relative to the wall of the slab. This operation can often be repeated arbitrarily to obtain a smaller particle size. The invention further provides an individual metal oxide layer obtained by using a dispersion according to the invention having a layer thickness of at least 2.5 microns on a substrate. In a preferred manner, the layer thickness can be between 3 microns and 15 microns. The layer can be similar to glass or ceramic. Suitable substrates may be metal substrates and alloy substrates, materials having a low coefficient of thermal expansion (materials with ultra low expansion), boron with acid phosphate glass, sand glass or glass ceramics, and particularly preferably glass substrates. A layer having a surface roughness of less than 30 nm may be preferred. The present invention further provides a method for producing a layer coated in a single step. The method is characterized in that -10 - (7) (7) 1307351 is formed by dipping coating a dispersion according to the present invention on a substrate. β is coated with a separate layer, the coarse embryo is then first dried at a temperature of less than 100 ° C, and then heated to a temperature at which the binder and the optional antifoaming agent are partially or completely removed from the coarse embryo. And then sintered. In an advantageous manner, the method according to the invention can be carried out in such a way that the stretching speed of the substrate pulled out of the dispersion is between 1 mm/sec and 100 mm/sec. A range between 2 mm/sec and 40 mm/sec is particularly preferred. Sintering of the layers can be carried out by methods known to those skilled in the art, such as by flame sintering or laser sintering. In the method according to the invention, laser sintering is particularly preferred. In this connection, it may be advantageous to preheat the substrate to a temperature of about 300 °C. In a preferred mode, the speed at which the coarse embryo moves under the laser beam is between 1 mm/sec and 0 mm/sec. The invention further provides a metal oxide layer on a substrate according to the invention for supplying a material having a very low expansion coefficient (ultra-low expansion material, ULE material) for photocatalytic application as a coating for a self-cleaning mirror ( Super-hydrophilic constituents) 'For optical objects such as lenses, as gas and liquid seals, as mechanical protective layers, and in composites. The present invention describes an aqueous dispersion which, by means of dip coating in a single step, coats a metal oxide layer having a layer thickness of -11 - (8) (8) 1307351 greater than 2.5 microns on the substrate. on. The resulting layer was free of cracks and had a low surface roughness. [Embodiment] 30% by weight of a pyrolyzed silica sand powder (Aerosil® OX 50, Degussa AG) produced by secondary distillation in a solvent by a dissolver (Nl-SIP, VMA-Getzmann) Dispersions. Dispersion D 1 : The dispersion prepared above was then adjusted to a solid content of 20% by weight and a pH of 9.7 by adding another double-distilled water and a tetramethylammonium hydroxide solution. Dispersion D2: 30% by weight of the dispersion is further added by adding a solution containing a short polymer chain length (about 14%, Μn) of methylcellulose as a binder, defoamer (contraspum KWE, Zschimmer) & Schwarz) and a tetramethylammonium oxynitrate solution were diluted to obtain a dispersion having a content of 20% by weight of cerium oxide powder. The ratio of methylcellulose to silica sand powder in the dispersion was 2% by weight; the ratio of the defoaming agent to the binder was 100% by weight. The pH of the dispersion was 9.2. Dip coating by dipping coating device at 2 mm / sec and 4 〇 mm / sec tensile -12 - 1307351 Ο) speed is only once immersed in the dispersions D 1 and D 2 and then exposed to air to dry and coated Boron silicate glass dish. Subsequently, the binder and the antifoaming agent were partially removed from the dish coated with D2 at a temperature of about 250 ° C over a period of 2 hours. Discs coated with D1 (without binder) are treated identically. The resulting rough embryos were then sintered by a laser having a maximum power of 700 W and a wavelength of 10.6 (C02 laser, R〇fin-Sinar, RS 7 00). In this connection, the laser beam moves on the surface of the coated material by means of a movable mirror. The speed of the mirror is adjusted so that the laser beam is directed over the sample at a frequency of 200 Η z. In order to avoid stress on the surface, it is advantageous to preheat the sample to 300 volts. The layer was sintered with a work density of 5.5 W/mm 2 . The resulting layer thickness was then measured. Dispersion D3: Produced in a manner similar to D 2 but using a poly(vinyl alcohol) having a short polymer chain length (Mw 9,000 to 10,000) by a binder instead of methyl cellulose . The immersion coating is carried out in a manner similar to D2. It is shown that coating with a dispersion containing a binder results in a significantly higher layer thickness. At a draw speed of 40 mm/sec, it is possible to coat a layer thickness of more than 3 microns with a single coating step. After the heat treatment for removing the binder and after sintering, the layer obtained with D2 or D3 has no crack and has a lower surface roughness than the layer obtained by D]. The coated wall showed excellent adhesion to the substrate after sintering. -13 - (10) 1307351 Table: Maximum layer thickness of layers obtained with D 1 to D 3 ' μπί Layer thickness [μιη] V Η * v draw at 2 0 0 °C after laser firing in sintered flat [ Mm / s 1 after treatment. Average roughness D1 (reference) 2 3.0 1.2 3 5 40 3.9 1.4 3 5 D 2 (2 5.6 2.6 2 6 according to the invention) 40 7.3 3 . 1 26 D 3 (according to the invention 2 4.6 2.5 24 ) 40 7.6 3.2 24 * vdraw = elongation rate by change - metal oxide powder, bet surface area of a metal oxide powder, - solid content in the dispersion, - metal oxide particles in the dispersion The aggregate size ' - the form of the binder, - the ratio of the binder, - the rate of stretching during the impregnation process, can also give a higher layer thickness. The sintered sample is inspected for its mechanical and chemical properties. In order to compare the burst strength of the uncoated glass with the coated glass -14 - (11) (11) 1307351, the double loop bending test was carried out in accordance with the model of DIN 52292. In this case, the measurement of the sample amount is 60 mm x 60 mm. The Weibull method is used for evaluation. The double loop bending test shows that the burst strength of the glass disc can be improved by the layer of OX 50. The rupture strength of the samples coated with the dispersions D 1 and D2 according to the present invention was about 20% to 30% higher than that of the uncoated glass. In addition, the evaluation of the W e i b u 显示 shows that the probability of failure of the coated sample is preferred, which is indicated by the higher gradient of the line. The reason for this is that the area damaged by the surface of the substrate, which is the initiator of the crack, is covered by the layer. The chemical resistance was measured by etching a layer of the dispersions D 1 and D2 according to the present invention and an uncoated substrate by 40% hydrofluoric acid for 20 minutes. In order to be able to analyze the quality of the control during the etching process, a profilometer was used to determine the etching depth. In this connection, it has been confirmed that the etching depth is 24 μm in the case of the uncoated glass substrate, whereas the etching depth is 〖5 μm in the case of the coated glass substrate. This means that the chemical resistance of the substrate of the glass is improved by coating. Dispersion D 4 A ] u C Dispersion 3 g of alumina C (DegUSSa AG) was stirred by a dissolver into 243 g of twice-distilled water. Then, 30 g of a methylcellulose solution (1 重量 wt% methylcellulose 'S i gm a Μ 7 1 4 0 ' in water) was added. The dispersion was poured into an ultrasonic pulverizer (Sonifier II, W-4 50) and dispersed therein for about 3 minutes at about 4500 watts. Due to this ultrasonic treatment, the generation of foam during the dispersion process is reduced. Subsequently, the dispersion was post-treated for 1 minute at about 〇 〇 〇 -15 - (12) 1307351. As a result, the residual foam was eliminated. An aluminum sheet (AlMg3; pretreatment with Na〇H for initial etching and/or sand blasting) and a glass substrate were coated with this dispersion at a rate of 40 mm/sec in a dip coating apparatus. The thickness of the layer is measured by a profilometer to a range between about 5 microns and about 20 microns, independent of the substrate. There are no cracks in the layer. The roughness of the alumina layer on the A 1 substrate is in the range of 200 nm to 1 = 〇〇〇 nanometer in terms of average roughness, and the peak is on the valley and the sac is at 1,0. 〇0 nm to 1 〇, 0 0 0 nm range. The roughness of the aluminum oxide layer on the borosilicate glass is in the range of 7 nm to 40 nm in terms of average roughness, and the peak is in the range of 100 to 50,000. The range between the nanometers. The layer was sintered by means of a carbon dioxide laser at a power density of about 5 W/mm 2 and the substrate was moved under a laser beam at a speed of about 5 mm/sec. A layer thickness of about 2 microns to 3 microns is obtained. In order to avoid stress cracking, the coated glass substrate was stored in an oven at 500 ° C for 6 hours and then cooled to room temperature in g 8 hours. The burst strength of the coated glass was determined by means of a double loop bending test (DIN 52 292). The wear behavior of the coated aluminum sheets was determined by means of the Taber Abraser method and compared to the abrasion of the uncoated aluminum sheets. After sintering, the layer thickness of the aluminum oxide layer is about 50% of the thickness of the green body. * Due to the alumina layer, the mechanical strength of the glass substrate is strengthened by 20% to 5 〇% ° -16 - (13) (13) 1307351 The wear resistance of the aluminum substrate can be strengthened by the aluminum oxide layer (by "T aber" A b 1· aser test "to characterize". The aluminum oxide layer enhances the chemical resistance of the aluminum substrate and the glass substrate to the alkali solution (NaOH) and the acid (H F, H C 1 ).
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