201004878 六、發明說明： 【發明所屬之技術領域】 本發明係關於一種浮式玻璃之製造裝置及製造方法。 【先前技術】 浮式玻璃之製造係如下過程：將熔融玻璃連續供給至浮 式玻璃錫槽中所裝滿之熔融錫的表面上，利用複數個加熱 器加熱熔融玻璃’並且使熔融玻璃沿著熔融金屬之表面向 特定方向流動，成形所需寬度、厚度之帶板狀玻璃帶，而 Φ 獲得平板玻璃。若採用浮式成形，則生產性較高，另外平 坦度優異’因此例如可廣泛地應用於建築用平板玻璃或顯 示面板基板用玻璃之製造等，先前已提出有為了實現品質 提昇之提案（例如參照專利文獻丨）。 專利文獻1中所揭示之浮式玻璃之製造方法，係向調節 自熔融爐所供給之熔融玻璃之流量的2個限流閘板、與熔 融玻璃所形成之空間（限流閘板空間）中吹入氮氣，並將該 限流閘板空間之壓力保持在高於自限流閘板至浮式玻璃錫 ^ 槽為止之區間即流槽之壓力。藉由該壓力差，而防止自浮 式玻璃錫槽所流入至流槽中之錫蒸氣流入至限流閘板空 間’且防止錫蒸氣與氧氣反應所生成之錫石（Sn〇2)結晶附 著於作為可動部之限流閘板上。再者，若錫石結晶落入熔 融玻璃中’則會成為玻璃之缺陷。 先行技術文獻 專利文獻 專利文獻1:曰本專利特開平7-109130號公報 141876.doc 201004878 【發明内容】 [發明所欲解決之問題] 近年來，隨著顯示器之大型化，業界要求進一步提昇、 穩定顯示品質，而對於其所使用之玻璃基板，要求進一步 抑制缺陷等品質之提昇。因此，作為顯示器用破璃，業界 要求進一步抑制錫石結晶。 浮式玻璃錫槽與流槽係由前壁即前橫樑而隔開，但為了 於開始生產等之時熔融玻璃向浮式玻璃錫槽中之流入量發 生較大變化時’使炫融玻璃不會與前橫樑相接觸，而將前 橫樑與熔融玻璃之間隔設置得較寬。又，流槽環境氣體溫 度低於浮式玻璃錫槽環境氣體溫度，浮式玻璃錫槽環境氣 體容易流入至流槽中。若浮式玻璃錫槽環境氣體中所含之 錫蒸氣流入至流槽中’則會與自構成流槽之耐火碑等構造 物之縫隙中流入之微量氧氣發生反應，而生成錫石結晶。 又’若浮式玻璃錫槽環境氣體中所含之氫氣流入至流槽 中’則會使熔融玻璃之表面發生還原。藉此，例如會導 致：變得容易發生PDP(plasma display panel，電漿顯示面 板）基板用玻璃之黃變（於電極生成步驟中之銀漿煅燒後玻 璃呈現黃色）等顯示器面板基板用玻璃之品質降低。 本發明係鑒於上述課題研究而成者，其目的在於提供一種 可獲得高品質之玻璃的浮式玻璃之製造裝置及製造方法。 [解決問題之技術手段] 上述目的係由本發明之下述（1)之浮式玻璃之製造裝置 及下述（2)之浮式玻璃之製造方法而實現。 141876.doc 201004878 (1) 一種浮式玻璃之製造裝置’其特徵在於：其係使自 溶融爐經由流槽而供給至浮式玻璃錫槽中之溶融玻璃沿著 該浮式玻璃錫槽中所裝滿之熔融錫之表面流動，以成形為 帶板狀之玻璃帶者， 於穩定狀態時，將上述流槽與上述浮式玻璃錫槽隔開的前 橫樑與熔融玻璃表面之間的前橫樑間隙為1〇 mm〜4〇 mm， 上述浮式玻璃錫槽環境氣體中之錫蒸氣濃度為Li 〇 mg/m，氫氣濃度為4〜1〇體積％，上述浮式玻璃錫槽環境 ® 氣體中之氮氣之供給量相對於每1 m3之上述浮式玻璃錫槽 環境鐵*體而為5〜20 Νπι^/Ιιγ，201004878 VI. Description of the Invention: [Technical Field of the Invention] The present invention relates to a manufacturing apparatus and a manufacturing method of a floating glass. [Prior Art] The manufacture of floating glass is a process of continuously supplying molten glass to the surface of molten tin filled in a floating glass tin bath, heating the molten glass with a plurality of heaters, and causing the molten glass to follow The surface of the molten metal flows in a specific direction to form a strip-shaped glass ribbon of a desired width and thickness, and Φ obtains a flat glass. When the floating molding is used, the productivity is high and the flatness is excellent. Therefore, for example, it can be widely applied to the production of flat glass for construction or glass for display panel substrates, and proposals for achieving quality improvement have been proposed (for example, Refer to the patent document 丨). The method for producing a floating glass disclosed in Patent Document 1 is for adjusting two flow restricting plates of a flow rate of molten glass supplied from a melting furnace and a space (flow restrictor shutter space) formed by the molten glass. Nitrogen gas is blown in, and the pressure of the restrictor shutter space is maintained at a pressure higher than the flow rate of the flow cell from the limit gate to the floating glass tin bath. By the pressure difference, the tin vapor flowing into the flow cell from the floating glass tin bath is prevented from flowing into the current limiting gate space', and the smectite (Sn〇2) crystal formed by the reaction between the tin vapor and the oxygen is prevented from adhering. On the limit plate as the movable part. Further, if the cassiterite crystal falls into the molten glass, it becomes a defect of the glass. [Provisions of the Invention] Patent Document 1: Patent Document 1: Japanese Patent Application Laid-Open No. Hei No. Hei 7-118130 No. 141876.doc 201004878 [Disclosure] [Problems to be Solved by the Invention] In recent years, with the increase in the size of displays, the industry has demanded further improvement. The display quality is stabilized, and it is required to further suppress the improvement of quality such as defects for the glass substrate to be used. Therefore, as a glass for display, the industry is demanding further suppression of cassiterite crystals. The floating glass tin bath and the flow channel are separated by the front wall, that is, the front beam, but in order to greatly change the inflow amount of the molten glass into the floating glass tin bath at the start of production or the like, It will be in contact with the front beam, and the distance between the front beam and the molten glass will be wider. Moreover, the ambient gas temperature of the launder is lower than the ambient gas temperature of the floating glass tin bath, and the floating glass tin bath environment gas easily flows into the launder. If the tin vapor contained in the floating glass tin bath atmosphere gas flows into the flow cell, it will react with a trace amount of oxygen flowing in from the gap between the structures such as the fire monument of the flow cell to form the cassiterite crystal. Further, if the hydrogen contained in the floating glass tin bath atmosphere gas flows into the flow cell, the surface of the molten glass is reduced. In this case, for example, it becomes easy to cause yellowing of the glass for the PDP (plasma display panel) substrate (the glass is yellow after the silver paste is fired in the electrode formation step), and the like. The quality is reduced. The present invention has been made in view of the above problems, and an object thereof is to provide a manufacturing apparatus and a manufacturing method of a floating glass which can obtain high quality glass. [Means for Solving the Problem] The above object is achieved by the apparatus for producing a floating glass according to the above (1) of the present invention and the method for producing a floating glass according to the following (2). 141876.doc 201004878 (1) A device for manufacturing a floating glass, characterized in that a molten glass supplied from a melting furnace to a floating glass tin bath via a launder is placed along the floating glass tin bath The surface of the filled molten tin flows to form a glass ribbon with a plate shape, and in a steady state, the front cross member between the front cross member and the molten glass surface separated from the floating glass tin bath The gap is 1〇mm~4〇mm, and the concentration of tin vapor in the ambient gas of the floating glass tin bath is Li 〇mg/m, and the concentration of hydrogen is 4~1 vol%, in the above floating glass tin bath environment® gas The supply amount of nitrogen is 5 to 20 Νπι^/Ιιγ per 1 m 3 of the above-mentioned floating glass tin bath environment iron body.
上述流槽環境氣體中之錫蒸氣濃度為OH mg/m3 > 氣濃度為G〜0.4體積％，上述流槽環境氣财之氮氣之供給 量相對於每1 m3之上述流槽環境氣體而為超過2〇〜1〇〇〇 Nm3/hr。 (2) —種浮式玻璃之製造方法，其特徵在於：其係使自 溶融爐經由流槽而供給至浮式玻璃錫槽中之溶融玻璃沿著 該浮式玻璃錫槽中所裝滿之溶融錫之表面流動，而成形為 帶板狀玻璃帶者， 於啟動時’使將上述流槽與上述浮式玻璃錫槽隔開的前 橫樑與熔融玻璃表面之間的前橫襟間隙為超過4〇識且為 100 mm以下， 於穩疋狀態時’將上述前橫樑間隙設為1。mm〜4。mm， 於穩疋狀態時，將上述浮式玻璃錫槽環境氣韹中之錫蒸 氣農度為3丨〇 mg/m3，將氫氣濃度設為4〜1〇體積％，將 141876.doc 201004878 上述浮式玻璃錫槽環境氣體中之氮氣之供給量相對於每丨W 之上述浮式玻璃錫槽環境氣體設為5〜20 Nm3/hr，且將上 述流槽環境氣艘中之錫洛氣濃度設為0.3〜1 mg/m3 ,將氣 氣濃度設為0〜〇.4體積％，將上述流槽環境氣體中之氮氣之 供，’·η量相對於每1 m之上述流槽環境氣體設為超過2〇 Nm3/hr且為 l〇〇〇Nm3/hr以下。 [發明之效果] 根據本發明，可適當保持將浮式玻璃錫槽環境氣體及流 槽環境乳體各自之錫蒸氣濃度、氫氣濃度，而抑制流槽中 生成錫石結晶，並且抑制熔融玻璃發生還原。藉此可獲得 高品質之玻璃。 【實施方式】 以下’參照圖式，對本發明之平板玻璃之製造方法之一 實施形態進行詳細地說明。 圖1係表示本發明之浮式玻璃之製造裝置之一實施形態 的剖面圖’圖2係圖1之浮式玻璃之製造裝置之主要部分的 立體圖。 如圖1所示，本實施形態之浮式玻璃之製造裝置1，係使 自未圖示之炫融爐於流道唇板（lip)2上流動而供給至浮式 玻璃錫槽3中的熔融玻璃4,沿著浮式玻璃錫槽3中所裝滿 之溶融錫5之表面流動，而成形為帶板狀之玻璃帶。玻璃 帶係自浮式玻璃錫槽3之出口取出，其後利用未圖示之緩 冷爐（lehr)進行緩冷，再於洗淨後切斷為特定之尺寸。 於炼融爐與浮式玻璃錫槽3之間，設置有控制於流道唇 141876.doc 201004878 板2上流動之熔融玻璃4之流量的限流閘板6。經過限流閘 板6而使流量獲得控制之熔融玻璃4，係於浮式玻璃錫槽3 的前壁、即前橫樑12之近前，自流道唇板2之前端供給至 浮式玻璃錫槽3中。 為了防止於熔融錫5之表面上流動之熔融玻璃4變質，而 向浮式玻璃錫槽3内供給以氮氣等惰性氣體為主要成分之 氣體，而抑制外部氣體（氧氣）流入至浮式玻璃錫槽3内。為 了防止熔融錫5之蒸氣發生氧化而生成錫石結晶，該氣體 β 中含有還原性之氫氣。又，浮式玻璃錫槽3之環境氣體中 之氮氣之供給量相對於每1 m3的浮式玻璃錫槽3之環境氣 體為5~20 Nm3/hr。供給至浮式玻璃錫槽3内之上述氣體係 通過設置於浮式玻璃錫槽3之頂蓋構造11上之未圖示之管 道而排出至外部。此時’熔融錫5之蒸氣亦同時被排出。 於本實施形態中，藉由向浮式玻璃錫槽3内供給上述氣 體’而使浮式玻璃錫槽3内之環境氣體保持為：錫蒸氣濃 度為3〜10 mg/m3’氫氣濃度為4〜10體積％。 ® 限流閘板6與前橫樑12之間係劃分為流槽7。 進而參照圖2 ’將浮式玻璃錫槽3與流槽7隔開的前橫樑 ' 12，具有固定於頂蓋構造11上的前橫樑本體21、與安裝於 、 别橫樑本體21上的前橫樑間隙調整板22。前橫樑間隙調整 板22係由設置於前橫樑本體21上之導框23所支撐，而可以 接近或遠離在浮式玻璃錫槽3之熔融錫5之表面上流動之溶 融玻璃4的方式進行升降。再者，於圖2中，關於前橫樑12 以外之劃分流槽7之耐火構造物’省略了圖示。 141876.doc 201004878 於本實施形態之浮式玻璃之製造裝置1中，於生產開始 時等啟動時、即於熔融破璃4向浮式玻璃錫槽3中之流入量 (嘴/小時）之變化率超過±5%時，前橫樑間隙調整板22之下 邊緣與熔融玻璃4之間的前橫樑間隙24係設定為超過 40 mm〜100 mm。藉此，即使流入量發生變化亦可避免 熔融玻璃4與前橫樑間隙調整板22接觸，而使熔融玻璃斗平 穩地流入至浮式玻璃錫槽3中。變化率可根據自浮式玻璃 錫槽3中抽出之玻璃帶的抽出量（噸/小時）進行把握。 並且，於穩定狀態時、即熔融玻璃4向浮式玻璃錫槽3中 之流入量（噸/小時）之變化率在±5%以内時，降下前橫樑間 隙調整板22，而使前橫樑間隙調整板22之下邊緣與熔融 玻璃4之間的前橫樑間隙24變窄。藉此，可抑制浮式玻 璃錫槽3之環境氣體通過該前橫樑間隙24而向流槽7流 入。此時的前橫樑間隙24較好的是10 mm〜4〇 mm，更好的 是1〇 mm〜30 mme又，向流槽7内供給以氮氣等惰性氣體 為主要成分之氣體，而抑制外部氣體（氧氣）向流槽7内流 入。流槽7之環境氣體中之氮氣之供給量相對於每丨^之 流槽7之環境氣體為超過2〇〜1〇〇〇 Nm3/hr，較好的是 50〜500 NmVhl^藉此，流槽7内之環境氣體保持為：錫蒸 氣濃度為0.3〜1 mg/m3，氫氣濃度為〇〜〇 4體積％。藉由使 /瓜槽7之環境氣體保持為上述濃度，可抑制流槽7中生成錫 石結晶’並且抑制熔融玻璃4發生還原。 考慮到耐火性、耐熱性、耐氧化性等，前橫樑間隙調整 板22例如可由碑、碳、塗佈有碳化矽（SiC)之碳而形成，尤 141876.doc 201004878 其好的是塗佈有耐氧化性優異之碳化矽之碳。 如以上所說明，根據本實施形態之浮式玻璃之製造裝置 1，可適當保持浮式玻璃錫槽環境氣體及流槽環境氣體各自 之錫蒸氣濃度、氫氣濃度，抑制流槽7中生成錫石結晶，並 且抑制熔融玻璃4發生還原。藉此可獲得高品質之玻璃。 再者，本發明並不限定於上述實施形態，可自由地進行 適當之變形、改良等。此外，上述實施形態中之各構成要 素之材質、形狀、尺寸、數值、形態、數量、配置位置等 〇 若可實現本發明則為任意，並無限定。 實施例 其次，為了確認本發明之效果，使用圖1之製造裝置， 於穩定狀態且於表1之條件下，進行PDP基板用玻璃之浮 式成形，並以肉眼評價玻璃板表面上之每單位面積所附著 之錫石結晶。再者，於進入穩定狀態前之啟動時，係升降 塗佈有碳化矽之碳製的前橫樑間隙調整板，而以前橫樑間 隙達到90 mm之方式進行設定，因此可使啟動時之熔融玻 ® 璃平穩地流入至浮式玻璃錫槽中。 [表1] 實求 έ例 比較例 流槽 浮式玻璃錫 流槽 浮式玻璃錫槽 錫蒸氣濃度(mg/m3) 0.5 6 6 6 氫氣濃度(體積％) 0.2 7 7 7 氮氣供給量(Nm3/hr) 100 10 10 10 前橫樑間隙(mm) 15 90 實施例之玻璃板與比較例之玻璃板相比，由錫石結晶之 附著所引起之缺陷減少至1/5以下。又，如表1所示，流槽 141876.doc 201004878 中之氫氣濃度降低，由此得知可獲得抑制PDP基板用玻璃 發生黃變等作為顯示器面板基板用玻璃之高品質的玻璃。 又，使用圖1之製造裝置可長時間進行玻璃之浮式成形， 可穩定獲得高品質之玻璃。 以上，參照特定實施形態對本發明進行了詳細地說明， 但熟悉此技藝者當然明瞭於不脫離本發明之精神與範圍之 前提下可實施各種變更或修正。本申請案係基於2008年7 月28曰提出申請之曰本專利申請案2008-193716者，其内 容作為參照而併入本文中。 【圖式簡單說明】 圖1係表示本發明之浮式玻璃之製造裝置之一實施形態 的剖面圖；及 圖2係圖1之浮式玻璃之製造裝置之主要部分的立體圖。 【主要元件符號說明】 1 浮式玻璃之製造裝置 3 浮式玻璃錫槽 4 溶融玻璃 5 熔融錫 6 限流閘板 7 流槽 12 前橫樑 21 前橫樑本髅 22 前橫樑間隙調整板 24 前橫樑間隙 141876.doc • 10·The tin vapor concentration in the flow cell ambient gas is OH mg/m3 > the gas concentration is G to 0.4% by volume, and the supply amount of the nitrogen gas in the flow cell environment is relative to the flow cell ambient gas per 1 m3. More than 2〇~1〇〇〇Nm3/hr. (2) A method for producing a floating glass, characterized in that a molten glass supplied from a melting furnace to a floating glass tin bath via a launder is filled along the floating glass tin bath The surface of the molten tin flows and is formed into a strip-shaped glass ribbon. At the time of starting, the gap between the front cross member and the surface of the molten glass separating the flow channel from the floating glass tin bath is exceeded. 4 且 且 为 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 Mm~4. Mm, in the steady state, the tin vapor agronomy in the above-mentioned floating glass tin bath environment is 3丨〇mg/m3, and the hydrogen concentration is set to 4~1〇 volume%, which will be 141876.doc 201004878 The supply amount of nitrogen in the floating glass tin bath environment gas is set to 5 to 20 Nm3/hr with respect to the above-mentioned floating glass tin bath environment gas, and the concentration of the sirloin gas in the above-mentioned flow tank environment gas tank is It is set to 0.3 to 1 mg/m3, and the gas gas concentration is set to 0 to 0.4% by volume, and the supply of nitrogen in the above-mentioned flow tank ambient gas is '·η amount with respect to the above-mentioned flow tank ambient gas per 1 m. It is set to more than 2〇Nm3/hr and is l〇〇〇Nm3/hr or less. [Effects of the Invention] According to the present invention, it is possible to appropriately maintain the tin vapor concentration and the hydrogen concentration of each of the floating glass tin bath environment gas and the flow cell environment emulsion, thereby suppressing the formation of cassiterite crystals in the flow cell and suppressing the occurrence of molten glass. reduction. This allows high quality glass to be obtained. [Embodiment] Hereinafter, an embodiment of a method for producing a flat glass of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view showing an embodiment of a manufacturing apparatus for a floating glass of the present invention. Fig. 2 is a perspective view showing a main part of the apparatus for manufacturing a floating glass of Fig. 1. As shown in Fig. 1, the manufacturing apparatus 1 for a floating glass according to the present embodiment is supplied from a cooling furnace (not shown) to a flow path lip 2 and supplied to the floating glass tin bath 3. The molten glass 4 flows along the surface of the molten tin 5 filled in the floating glass tin bath 3, and is formed into a strip-shaped glass ribbon. The glass ribbon is taken out from the outlet of the floating glass tin bath 3, and then slowly cooled by a slow cooling furnace (lehr) (not shown), and then cut to a specific size after washing. Between the refining furnace and the floating glass tin bath 3, a restrictor shutter 6 for controlling the flow rate of the molten glass 4 flowing on the plate lip 141876.doc 201004878 is provided. The molten glass 4 whose flow rate is controlled by the flow restricting shutter 6 is attached to the front wall of the floating glass tin bath 3, that is, the front side of the front cross member 12, and is supplied to the floating glass tin bath 3 from the front end of the flow path lip 2 in. In order to prevent deterioration of the molten glass 4 flowing on the surface of the molten tin 5, a gas containing an inert gas such as nitrogen as a main component is supplied into the floating glass tin bath 3, thereby suppressing the inflow of external gas (oxygen) into the floating glass tin. Inside the slot 3. In order to prevent oxidation of the vapor of the molten tin 5, a cassiterite crystal is formed, which contains reducing hydrogen. Further, the supply amount of nitrogen in the ambient gas of the floating glass tin bath 3 is 5 to 20 Nm3/hr with respect to the ambient gas per 1 m3 of the floating glass tin bath 3. The gas system supplied into the floating glass tin bath 3 is discharged to the outside through a pipe (not shown) provided in the roof structure 11 of the floating glass tin bath 3. At this time, the vapor of the molten tin 5 is also discharged at the same time. In the present embodiment, the ambient gas in the floating glass tin bath 3 is maintained by supplying the gas ' into the floating glass tin bath 3: the tin vapor concentration is 3 to 10 mg/m 3 'the hydrogen concentration is 4 ~10% by volume. The flow restrictor 6 and the front cross member 12 are divided into a flow groove 7. Referring to Fig. 2, the front cross member '12 separating the floating glass tin bath 3 from the launder 7 has a front cross member 21 fixed to the top cover structure 11, and a front cross member attached to the cross member body 21. The gap adjustment plate 22. The front beam gap adjusting plate 22 is supported by the guide frame 23 provided on the front beam body 21, and can be lifted up or away from the molten glass 4 flowing on the surface of the molten tin 5 of the floating glass tin bath 3. . In addition, in Fig. 2, the refractory structure of the dividing groove 7 other than the front cross member 12 is omitted. 141876.doc 201004878 In the manufacturing apparatus 1 of the floating glass of the present embodiment, the inflow amount (mouth/hour) in the molten glass 4 in the floating glass tin bath 3 at the start of production or the like, that is, at the start of production. When the rate exceeds ±5%, the front beam gap 24 between the lower edge of the front beam gap adjusting plate 22 and the molten glass 4 is set to be more than 40 mm to 100 mm. Thereby, even if the inflow amount changes, the molten glass 4 can be prevented from coming into contact with the front cross-member gap adjusting plate 22, and the molten glass hopper can smoothly flow into the floating glass tin bath 3. The rate of change can be grasped based on the amount of extraction (ton/hour) of the glass ribbon extracted from the floating glass tin bath 3. Further, in the steady state, that is, when the rate of change of the inflow amount (ton/hour) of the molten glass 4 into the floating glass tin bath 3 is within ±5%, the front beam gap adjusting plate 22 is lowered, and the front beam gap is made. The front cross member gap 24 between the lower edge of the adjustment plate 22 and the molten glass 4 is narrowed. Thereby, the ambient gas of the floating glass tin bath 3 can be prevented from flowing into the flow cell 7 through the front beam gap 24. In this case, the front beam gap 24 is preferably 10 mm to 4 mm, more preferably 1 mm to 30 mme, and a gas containing an inert gas such as nitrogen as a main component is supplied to the flow cell 7 to suppress the external portion. Gas (oxygen) flows into the launder 7. The supply amount of nitrogen in the ambient gas of the flow cell 7 is more than 2 〇 1 〇〇〇 Nm 3 /hr, preferably 50 to 500 Nm V hr, per liter of the ambient gas per fluent channel 7 The ambient gas in the tank 7 is maintained at a tin vapor concentration of 0.3 to 1 mg/m3 and a hydrogen concentration of 〇~〇4 vol%. By maintaining the ambient gas of the melon tank 7 at the above concentration, generation of cassiterite crystals in the launder 7 can be suppressed and reduction of the molten glass 4 can be suppressed. The front cross-beam gap adjusting plate 22 can be formed, for example, from a monument, carbon, or carbon coated with lanthanum carbide (SiC) in consideration of fire resistance, heat resistance, oxidation resistance, etc., especially 141876.doc 201004878 A carbon of cerium carbide excellent in oxidation resistance. As described above, according to the manufacturing apparatus 1 for a floating glass of the present embodiment, the tin vapor concentration and the hydrogen gas concentration of each of the floating glass tin bath atmosphere gas and the flow channel ambient gas can be appropriately maintained, and the formation of the cassiterite in the flow cell 7 can be suppressed. Crystallization and suppression of reduction of the molten glass 4. Thereby high quality glass can be obtained. Furthermore, the present invention is not limited to the above embodiment, and appropriate modifications, improvements, and the like can be freely performed. Further, the materials, shapes, dimensions, numerical values, forms, numbers, arrangement positions, and the like of the respective constituent elements in the above-described embodiments are not limited as long as the present invention can be realized. EXAMPLES Next, in order to confirm the effect of the present invention, the glass of the PDP substrate was float-formed in a stable state under the conditions of Table 1 using the manufacturing apparatus of Fig. 1, and each unit on the surface of the glass plate was visually evaluated. The cassiterite crystal attached to the area. Furthermore, at the start of the steady state, the front beam gap adjustment plate coated with carbonized tantalum carbon is lifted and lowered, and the previous beam gap is set to 90 mm, so that the molten glass at the start can be made. The glass smoothly flows into the floating glass tin bath. [Table 1] Actual example comparison example flow cell floating glass tin flow cell floating glass tin bath tin vapor concentration (mg/m3) 0.5 6 6 6 hydrogen concentration (vol%) 0.2 7 7 7 nitrogen supply (Nm3 /hr) 100 10 10 10 Front cross-beam gap (mm) 15 90 The glass plate of the example was reduced in defects caused by the adhesion of the cassiterite crystal to less than 1/5 as compared with the glass plate of the comparative example. Further, as shown in Table 1, the hydrogen concentration in the flow cell 141876.doc 201004878 was lowered, and it was found that high-quality glass which is used as a glass for a display panel substrate in which yellowing of the PDP substrate glass is suppressed can be obtained. Further, by using the manufacturing apparatus of Fig. 1, the glass floating molding can be performed for a long period of time, and high-quality glass can be stably obtained. The present invention has been described in detail above with reference to the specific embodiments thereof. It is understood that various modifications and changes can be made without departing from the spirit and scope of the invention. The present application is based on the benefit of the present application, which is incorporated herein by reference. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing an embodiment of a manufacturing apparatus for a floating glass of the present invention; and Fig. 2 is a perspective view showing a main part of the apparatus for manufacturing a floating glass of Fig. 1. [Description of main component symbols] 1 Manufacturing equipment for floating glass 3 Floating glass tin bath 4 Fused glass 5 Fused tin 6 Current limiting gate 7 Flow cell 12 Front beam 21 Front beam Bengbu 22 Front beam gap adjustment plate 24 Front beam Clearance 141876.doc • 10·