JP3683166B2

JP3683166B2 - Substrate heat treatment method and continuous heat treatment furnace used therefor

Info

Publication number: JP3683166B2
Application number: JP2000238538A
Authority: JP
Inventors: 聡谷口; 一二夫野入; 道郎青木
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2000-08-07
Filing date: 2000-08-07
Publication date: 2005-08-17
Anticipated expiration: 2020-08-07
Also published as: KR20020012497A; TW469338B; KR100440667B1; JP2002048475A

Description

【０００１】
【発明の属する技術分野】
本発明は、プラズマディスプレイパネル用のガラス基板に代表される膜形成素材を含む基板の熱処理方法とそれに用いる連続式熱処理炉に関する。
【０００２】
【従来の技術】
近年、壁掛けテレビやマルチメディア用ディスプレイとして利用できる大画面フラットパネルディスプレイ（以下、「ＦＰＤ」という。）の実用化が着々と進行しつつある。このような大画面ＦＰＤとしては、自発光型で広い視野角を持ち、品質表示が良いという品質面のメリットと、作製プロセスが簡単で大型化が容易という製造面でのメリットを兼ね備えた、プラズマディスプレイパネル（以下、「ＰＤＰ」という。）が最有力候補として挙げられている。
【０００３】
ＰＤＰの製造は、例えば図３に示すように、前面ガラス、背面ガラスと称する大型ガラス基板の表面に、印刷、乾燥、焼成の工程を複数回繰り返す厚膜法により、電極、誘導体、蛍光体等の種々の部材を逐次形成して行き、最終的に前面ガラスと背面ガラスとを封着することにより行われる。
【０００４】
このＰＤＰ用ガラス基板のような膜形成素材を含む基板の熱処理は、被熱処理体の搬送方向に対して区画された複数の加熱室と、隣接する加熱室へ被熱処理体を間欠的に搬送するための搬送手段とを備えた連続式熱処理炉を使用し、各加熱室を個別に温度制御することにより、所望の温度曲線に従って、昇温、保温、及び降温する方法で行うのが一般的である。
【０００５】
このように区画された加熱室にて熱処理を行うのは、基板表面の温度をできる限り均一にするためである。基板表面の温度分布が大きい状態で熱処理を行うと基板や基板上に形成した部材（膜）に歪みが生じ、更にこれに起因して割れ、欠け等の欠陥が生じる。各加熱室は、基板を載置したセッターを、一般的には１枚内包する大きさを持ち、被熱処理体の搬送方向（炉の長手方向）及び炉の幅方向に対していくつかに分割された加熱手段が設けられている。
【０００６】
それら分割された加熱手段は、一般に、各々が独立した制御系にて個別に温度制御できるようになっており、従来の膜形成素材を含む基板の熱処理においては、区画された各加熱室内の温度（雰囲気温度）がそれぞれ一定となるように各加熱手段の温度制御がなされていた。
【０００７】
【発明が解決しようとする課題】
通常、各加熱室間には、隣接する加熱室からの熱的影響を防ぐために隔壁などが設けられているが、温度設定の異なる隣接する加熱室間では、相互の熱的影響を完全に防止することは困難である。このため、前記のように、各加熱室内の温度が一定となるように加熱手段の温度を制御しても、その加熱室内で所定時間熱処理を受けた基板の温度は、隣接する他の加熱室からの熱的影響によって、搬送方向で異なりを見せるようになり、均一な熱処理品質が得られないという問題があった。
【００１０】
本発明は、このような従来の事情に鑑みてなされたものであり、加熱室内で膜形成素材を含む基板の熱処理を行う際に、室内の平均温度が異なる他の隣接する加熱室からの熱的影響によって、基板内に温度分布が生じるのを抑制し、基板全体を均一に熱処理することができる基板の熱処理方法を提供することを目的とする。また、本発明は、その熱処理方法に好適に用いることのできる連続式熱処理炉を提供することを目的とする。
【００１１】
【課題を解決するための手段】
本発明によれば、被熱処理体の搬送方向に対して区画されているが隣接する各加熱室の間にはシャッタを有しない複数の加熱室と、隣接する加熱室へ被熱処理体を搬送するための搬送手段とを備え、各加熱室に、少なくとも被熱処理体の搬送方向に対していくつかに分割され、各々が独立した制御系にて個別に温度制御可能な加熱手段が設けられた連続式熱処理炉を用いて、膜形成素材を含む基板を熱処理する方法であって、前記複数の加熱室のうち、隣接する他の加熱室の少なくとも一方と室内の平均温度が異なる加熱室においては、当該加熱室に設けられた各加熱手段の設定温度を、昇温工程及び降温工程において被熱処理体の搬送方向で異なる値となるように制御して、加熱室内の温度に勾配を設けることにより、当該加熱室内にて熱処理されている基板に対して、隣接する他の加熱室が及ぼす熱的影響を相殺し、前記基板を均一に熱処理することを特徴とする基板の熱処理方法、が提供される。
【００１３】
更に、本発明によれば、被熱処理体の搬送方向に対して区画されているが隣接する各加熱室の間にはシャッタを有しない複数の加熱室と、隣接する加熱室へ被熱処理体を搬送するための搬送手段とを備え、各加熱室に、少なくとも被熱処理体の搬送方向に対していくつかに分割され、各々が独立した制御系にて個別に温度制御可能な加熱手段が設けられた連続式熱処理炉であって、前記加熱室に設けられた各加熱手段の設定温度が被熱処理体の搬送方向で異なる値となるように制御して、加熱室内の温度に勾配を設けることができる温度制御装置を有することを特徴とする連続式熱処理炉、が提供される。
【００１５】
【発明の実施の形態】
本発明の熱処理方法に使用される連続式熱処理炉は、被熱処理体の搬送方向に対して区画された複数の加熱室と、隣接する加熱室へ被熱処理体を搬送するための搬送手段とを備える。各加熱室には、少なくとも被熱処理体の搬送方向に対していくつかに分割された加熱手段が設けられている。それら分割された加熱手段は、各々が独立した制御系にて個別に温度制御できるようになっている。
【００１６】
なお、前記搬送手段には、隣接する加熱室へ被熱処理体を間欠的に搬送する間欠送り方式の搬送手段を用いることが好ましい。ここで、「間欠的に搬送する」とは、炉の入口側からｎ番目の加熱室にて被熱処理体を静止させて所定時間熱処理を行った後、当該被熱処理体を可及的速やかに隣接する炉の入口側からｎ＋１番目の加熱室に移動し、再び被熱処理体を静止させて所定時間熱処理を行うという操作を繰り返す搬送方法をいう。このような搬送方法が可能な限りにおいて、搬送手段の種類は特に限定されず、例えばウォーキングビームを用いたり、ローラーコンベア、チェーンコンベアを間欠的に駆動させてもよい。
【００１７】
本発明の熱処理方法では、前記のように区画された複数の加熱室のうち、隣接する他の加熱室の少なくとも一方（炉の入口側方向に隣接する加熱室と炉の出口側方向に隣接する加熱室の何れか一方又は両方）と室内の平均温度が異なる加熱室において、当該加熱室に設けられた各加熱手段の設定温度を被熱処理体の搬送方向で異なる値となるように制御して、加熱室内の温度に勾配を設けることにより、当該加熱室内にて熱処理されている膜形成素材を含む基板に対して、隣接する他の加熱室が及ぼす熱的影響を相殺する。
【００１８】
すなわち、ＰＤＰ用ガラス基板のような膜形成素材を含む基板（以下、単に「基板」という。）は、一般に、各加熱室を順次移動しながら、所望の温度曲線に従い、昇温、保温、降温（冷却）という工程を経て熱処理されるが、例えば基板の昇温を行う昇温域の加熱室では、炉の出口側に近いものほど室内の平均温度が高く設定されるので、昇温域の加熱室内に搬送された基板は、炉の入口側に近い部位においては、隣接する室内平均温度のより低い加熱室の熱的影響を受けて、基板の温度が目標値より低くなりやすく、逆に炉の出口側に近い部位においては、隣接する室内平均温度のより高い加熱室の熱的影響を受けて、基板の温度が目標値より高くなりやすい。
【００１９】
このため、従来のように各加熱室内の温度がそれぞれ一定となるように加熱手段の温度を制御したとしても、隣接する他の加熱室が基板に対して及ぼす熱的影響によって、基板内に搬送方向の温度分布が生じ、基板や基板に形成された膜の歪み、割れ、欠け等の欠陥の原因となる。
【００２０】
そこで、本発明の熱処理方法においては、隣接する他の加熱室の熱的影響によって基板温度が目標値より低くなりやすい部位を加熱する加熱手段については、その熱的影響による温度低下を相殺するように設定温度を高い値に制御して当該部位周辺の雰囲気温度を上昇させ、逆に隣接する他の加熱室の熱的影響によって基板温度が目標値より高くなりやすい部位を加熱する加熱手段については、その熱的影響による温度上昇を相殺するように設定温度を低い値に制御して当該部位周辺の雰囲気温度を下降させるというように、同一の加熱室に設けられた各加熱手段の設定温度を被熱処理体の搬送方向で異なる値となるように制御して、加熱室内の温度に勾配を設ける。
【００２１】
例えば、隣接する加熱室との室内平均温度の差が７０℃である昇温域の加熱室の上部（炉天井）に、図１(ａ)のようにＡ〜Ｉの９つに分割され各々が独立した制御系にて個別に温度制御可能な加熱手段を設けて、４０インチのＰＤＰ用ガラス基板の加熱を行う場合において、図１(ｂ)のように分割された加熱手段Ａ〜Ｉの設定温度をすべて同一としたとき（平坦設定）と、図１(ｃ)のように中央部の加熱手段Ｄ〜Ｆの設定温度（３３７℃）に対し、入口側の加熱手段Ｇ〜Ｉの設定温度を高めの値（３４２℃）とし、出口側の加熱手段Ａ〜Ｃの設定温度を低めの値（３３２℃）としたとき（勾配設定）とで、所定時間加熱した後の基板の温度分布を調べると、図１(ｄ)のように(1)〜(9)の９箇所に温度計を設置したガラス基板の当該各設置箇所の温度とその偏差は表１のようになり、平坦設定時より勾配設定時のほうが基板内の温度分布が小さかった。
【００２２】
【表１】

【００２３】
本発明の熱処理方法では、上記したように、隣接する各加熱室の間にはシャッタを有しない構成において、同一の加熱室内において、分割された各加熱手段の設定温度を被熱処理体の搬送方向で異なる値となるように制御して、加熱室内の温度に勾配を設けることにより、隣接する他の加熱室が基板に及ぼす熱的影響を相殺して、ガラス基板を均一に熱処理する。なお、基板の降温を行う降温域の加熱室については、入口側の加熱手段の設定温度を低めの値に制御し、出口側の加熱手段の設定温度を高めの値に制御して、前記の例とは逆の温度勾配を設けることにより、基板の均熱化を達成することができる。
【００２４】
加熱室内の温度勾配の設定の目安としては、基板を、昇温、保温及び降温（冷却）という工程で熱処理する場合において、基板が保温を行う加熱室に存在するときに、当該基板の最高温度の部位と最低温度の部位との温度差ΔＴが６℃以下となっているように、温度勾配を設定することが好ましい。
【００２５】
また、炉壁等からの熱的影響により、炉の幅方向においても基板の温度分布が生じるような場合には、加熱手段を被熱処理体の搬送方向（炉の長手方向）のみならず、炉の幅方向にも分割し、各加熱手段の設定温度を当該幅方向においても異なる値となるように制御して、加熱室内に温度勾配を設けることにより、前記熱的影響を相殺し、より均一な熱処理を行うことが可能である。
【００３７】
次に、本発明の熱処理方法に好適に使用できる連続式熱処理炉について説明する。まず、本発明の熱処理方法を実施するのに好適な連続式熱処理炉は、前述のように、その基本的な構成として、被熱処理体の搬送方向に対して区画された複数の加熱室と、隣接する加熱室へ被熱処理体を搬送するための搬送手段とを備える。各加熱室には、少なくとも被熱処理体の搬送方向に対していくつかに分割された加熱手段が設けられており、それら分割された加熱手段は、各々が独立した制御系にて個別に温度制御できるようになっている。
【００３８】
また、この連続式熱処理炉は、その特徴的な構成として、加熱室に設けられた各加熱手段の設定温度が被熱処理体の搬送方向で異なる値となるように制御して、加熱室内の温度に勾配を設けることができる温度制御装置を有し、これにより本発明の熱処理方法を容易に実施することができる。
【００４０】
前記の熱処理炉においては、加熱手段としては温度制御が容易な電気ヒーターを用いることが好ましいが、運転コストの面で有利なガス燃焼式間接加熱式バーナー（ラジアントチューブバーナー）を加熱手段の一部又は全部に用いてもよい。なお、ラジアントチューブには、ストレート型、シングルエンド型、Ｕ字型などがあるが、それらの何れを用いてもよい。また、ガス燃焼式間接加熱式バーナーとしては、蓄熱体を内蔵した排熱回収型のリジェネレーティブバーナーが好ましい。
【００４１】
図２はリジェネレーティブバーナーの構造の一例を示す概要図であり、ラジアントチューブ１３の両端にそれぞれバーナーとセラミックハニカム等からなる蓄熱体１５とを備えている。このラジアントチューブ１３の両端に備えたバーナーを交互に切り替えて燃焼させると、高い省エネ効果が得られる。
【００４２】
すなわち、チューブの一端のバーナーが燃焼しているときは、チューブの他端から排気を行いつつ排熱を蓄熱体で回収し、当該他端のバーナーに燃焼を切り替えた際に、蓄熱体で回収した排熱を利用して燃焼空気を予熱することにより、バーナー加熱に要する燃料使用量を低減できる。また、短い周期で切り替えを行うことによりラジアントチューブ表面の温度分布が小さくなり、均一な加熱が可能となる。
【００４３】
加熱手段と被熱処理体の移動領域との間には、マッフルを配置することが好ましく、そのマッフルの一部又は全部が赤外線照射率の高い材質からなるものであることが特に好ましい。加熱手段から発せられる熱を、一旦、マッフルで受けることにより、マッフルから遠赤外線若しくは近赤外線が照射されるため、被熱処理体をより迅速に加熱することが可能となるからである。また、当該マッフルで加熱手段と被熱処理体の移動領域とを機密的に隔離することにより、被熱処理体の移動領域におけるクリーン度が確保されるという効果もある。
【００４４】
マッフルを構成する赤外線照射率の高い材質としては、ＳｉＣを含有する焼結体が好ましく、中でもＳｉ含浸ＳｉＣが特に好ましい。Ｓｉ含浸ＳｉＣは、炭化珪素と炭素とを主成分とする成形体を、金属珪素が存在する減圧の不活性ガス雰囲気又は真空中にて、金属珪素を含浸させながら焼結させることによって得られるものであり、例えば結晶化ガラスとの比較においても、図４に示すように顕著に高い赤外線照射率を示し、また、熱伝導率も非常に高い。
【００４５】
搬送手段には、前述したような被熱処理体を間欠的に搬送する間欠送り方式のものと、被熱処理体を各加熱室に静止させず、常に移動させながら連続的に搬送する連続送り方式のものとがある。本発明においては、間欠送り方式の搬送手段が好適に用いられるが、被熱処理体の昇温を行う昇温域の加熱室間及び被熱処理体の保温を行う保温域の加熱室間の搬送には、連続送り方式の搬送手段を用い、被熱処理体の降温（冷却）を行う降温域の加熱室間の搬送には間欠送り方式の搬送手段を用いるというように、区域によって両者を使い分けるようにしてもよい。
【００４６】
ただし、前記のように昇温域の加熱室間及び保温域の加熱室間の搬送に連続送り方式の搬送手段を用いる場合には、被熱処理体が隣接する加熱室間に跨った状態で移動している際に生ずる温度分布を小さくするため、被熱処理体の全体が同一加熱室内に位置している期間の搬送速度に対して、被熱処理体が隣接する加熱室間に跨った状態で移動している期間の搬送速度を十分に速くする必要がある。具体的には前者の期間の搬送速度に対して、後者の期間の搬送速度が２０倍以上であることが好ましく、５０倍以上であると更に好ましい。このような搬送速度の変更が可能な連続送り方式の搬送手段としては、例えばローラーコンベアやチェーンコンベアを挙げることができる。
【００４８】
【発明の効果】
以上説明したように、本発明によれば、隣接する各加熱室の間にはシャッタを有しない構成において、加熱室内で膜形成素材を含む基板を熱処理する際に、室内の平均温度が異なる他の隣接する加熱室からの熱的影響によって、基板内に温度分布が生じるのを抑制し、基板全体を均一に熱処理することができる。
【図面の簡単な説明】
【図１】本発明の熱処理方法に係る実施形態の一例を示す説明図で、(ａ)は加熱手段の構成の概略を示し、(ｂ)は平坦設定時における加熱手段の設定温度を示し、(ｃ)は勾配設定時における加熱手段の設定温度を示し、(ｄ)は被熱処理体であるガラス基板と当該基板上に設置された温度計の位置を示す。
【図２】リジェネレーティブバーナーの構造の一例を示す概要図である。
【図３】ＰＤＰの製造工程を示す工程図である。
【図４】Ｓｉ含浸ＳｉＣの赤外線照射率を示すグラフである。
【符号の説明】
１３…ラジアントチューブ、１５…蓄熱体。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a substrate heat treatment method including a film forming material typified by a glass substrate for a plasma display panel and a continuous heat treatment furnace used therefor.
[0002]
[Prior art]
In recent years, a large-screen flat panel display (hereinafter referred to as “FPD”) that can be used as a wall-mounted television or a multimedia display has been steadily being put into practical use. As such a large screen FPD, it is a self-luminous plasma that has a wide viewing angle, a quality advantage of good quality display, and a manufacturing advantage that the production process is simple and easy to enlarge. A display panel (hereinafter referred to as “PDP”) is cited as the most promising candidate.
[0003]
For example, as shown in FIG. 3 , the PDP is manufactured by using a thick film method in which printing, drying, and firing steps are repeated a plurality of times on the surface of a large glass substrate called a front glass and a back glass. The various members are sequentially formed and finally the front glass and the rear glass are sealed.
[0004]
In the heat treatment of the substrate including the film forming material such as the glass substrate for PDP, the object to be heat-treated is intermittently conveyed to a plurality of heating chambers divided in the conveying direction of the object to be heat-treated and the adjacent heating chamber. It is common to use a continuous heat treatment furnace equipped with a transfer means for controlling the temperature of each heating chamber individually, and thereby heating, keeping and cooling according to a desired temperature curve. is there.
[0005]
The reason why the heat treatment is performed in the heating chamber thus partitioned is to make the temperature of the substrate surface as uniform as possible. When heat treatment is performed in a state where the temperature distribution on the substrate surface is large, the substrate and the member (film) formed on the substrate are distorted, and further, defects such as cracks and chips occur. Each heating chamber is generally large enough to contain one setter on which a substrate is placed, and is divided into several parts in the transport direction (longitudinal direction of the furnace) and the width direction of the furnace. Heating means are provided.
[0006]
In general, these divided heating means can be individually controlled in temperature by an independent control system. In the conventional heat treatment of a substrate including a film forming material, the temperature in each partitioned heating chamber is controlled. The temperature control of each heating means was performed so that (atmosphere temperature) was constant.
[0007]
[Problems to be solved by the invention]
Normally, partition walls are provided between the heating chambers to prevent thermal effects from adjacent heating chambers, but mutual thermal effects are completely prevented between adjacent heating chambers with different temperature settings. It is difficult to do. For this reason, as described above, even if the temperature of the heating means is controlled so that the temperature in each heating chamber becomes constant, the temperature of the substrate subjected to the heat treatment for a predetermined time in the heating chamber remains the same as that of the other adjacent heating chamber. Due to the thermal influence from the above, there has been a problem in that a uniform heat treatment quality cannot be obtained due to the difference in the conveying direction.
[0010]
The present invention has been made in view of such a conventional situation. When heat treatment is performed on a substrate including a film-forming material in a heating chamber, heat from other adjacent heating chambers having different average temperatures in the chamber. It is an object of the present invention to provide a substrate heat treatment method that can suppress the temperature distribution in the substrate due to the influence of the target and can uniformly heat the entire substrate . Also, the present invention aims to provide a continuous heat treatment furnace which can be suitably used for the heat treatment method.
[0011]
[Means for Solving the Problems]
According to the present invention, a plurality of heating chambers that are partitioned with respect to the transfer direction of the heat-treated body but do not have a shutter between adjacent heating chambers and the heat-treated body are transferred to the adjacent heating chambers. Each of the heating chambers is divided into several parts at least in the conveying direction of the object to be heat-treated, and each of the heating chambers is provided with heating means that can be individually temperature controlled by an independent control system. In a heating chamber in which a substrate containing a film forming material is heat-treated using a heat treatment furnace, and the average temperature in the chamber is different from at least one of the adjacent other heating chambers among the plurality of heating chambers, By controlling the set temperature of each heating means provided in the heating chamber so as to have different values in the conveying direction of the heat-treated body in the temperature raising step and the temperature lowering step, and providing a gradient in the temperature in the heating chamber, Heat in the heating chamber The substrate being sense, offset thermal impact of other heating chamber adjacent the heat treatment method of a substrate, characterized by heat-treating the substrate uniformly, it is provided.
[0013]
Furthermore, according to the present invention, a plurality of heating chambers that are partitioned with respect to the conveyance direction of the heat-treated body but do not have a shutter between adjacent heating chambers, and the heat-treated body is placed in the adjacent heating chambers. Each of the heating chambers is divided into at least several parts in the direction of conveyance of the object to be heat-treated, and each of the heating chambers is provided with heating means that can be individually temperature controlled by an independent control system. A continuous heat treatment furnace, in which the set temperature of each heating means provided in the heating chamber is controlled to have a different value in the conveying direction of the object to be heat treated, and the temperature in the heating chamber is provided with a gradient. There is provided a continuous heat treatment furnace characterized in that it has a temperature control device capable of.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Continuous heat treatment furnace used in the thermal processing method of the present invention comprises a conveying means for conveying a plurality of heating chambers which are partitioned with respect to the conveying direction of the object to be thermally treated, the object to be thermally treated into the heating chamber adjacent Is provided. Each heating chamber is provided with heating means divided into several parts at least in the transport direction of the object to be heat treated. Each of the divided heating means can be individually temperature controlled by an independent control system.
[0016]
In addition, it is preferable to use the conveyance means of the intermittent feed system which conveys to-be-processed body to an adjacent heating chamber intermittently as the said conveyance means. Here, “intermittently convey” means that the heat-treated body is stopped in the n-th heating chamber from the furnace inlet side and subjected to heat treatment for a predetermined time, and then the heat-treated body is moved as quickly as possible. This is a transfer method in which the operation of moving from the entrance side of the adjacent furnace to the (n + 1) th heating chamber, stopping the heat-treated body again, and performing heat treatment for a predetermined time is repeated. As long as such a transport method is possible, the type of transport means is not particularly limited. For example, a walking beam may be used, or a roller conveyor or a chain conveyor may be driven intermittently.
[0017]
In the heat treatment method of the present invention , among the plurality of heating chambers divided as described above, at least one of the other adjacent heating chambers (adjacent the heating chamber adjacent to the furnace inlet side direction and the furnace outlet side direction). In the heating chamber where the average temperature in the heating chamber is different from any one or both of the heating chambers), the set temperature of each heating means provided in the heating chamber is controlled to be different in the conveyance direction of the heat-treated body. By providing a gradient in the temperature in the heating chamber, the thermal effect exerted by other adjacent heating chambers on the substrate including the film forming material that has been heat-treated in the heating chamber is offset.
[0018]
That is, a substrate containing a film forming material such as a glass substrate for PDP (hereinafter simply referred to as “substrate”) is generally heated, held, and cooled according to a desired temperature curve while sequentially moving through each heating chamber. Although the heat treatment is performed through a process called (cooling), for example, in the heating chamber in the heating region where the temperature of the substrate is raised, the average temperature in the chamber is set higher as the temperature is closer to the outlet side of the furnace. The substrate transported into the heating chamber is subject to the thermal effect of the adjacent heating chamber with a lower average room temperature in the vicinity of the furnace inlet side, and the substrate temperature tends to be lower than the target value. In a portion near the exit side of the furnace, the temperature of the substrate tends to be higher than the target value due to the thermal influence of the adjacent heating chamber having a higher average room temperature.
[0019]
For this reason, even if the temperature of the heating means is controlled so that the temperature in each heating chamber becomes constant as in the conventional case, the heating means transfers it into the substrate due to the thermal effect that the other adjacent heating chambers have on the substrate. A temperature distribution in the direction occurs, which causes defects such as distortion, cracking, and chipping of the substrate and the film formed on the substrate.
[0020]
Therefore, in the heat treatment method of the present invention , the heating means for heating the portion where the substrate temperature is likely to be lower than the target value due to the thermal influence of other adjacent heating chambers cancels the temperature drop due to the thermal influence. For heating means that controls the set temperature to a high value and raises the ambient temperature around the part, and conversely heats the part where the substrate temperature tends to be higher than the target value due to the thermal effect of other adjacent heating chambers. The set temperature of each heating means provided in the same heating chamber is controlled so that the set temperature is controlled to a low value so as to offset the temperature rise due to the thermal influence and the ambient temperature around the part is lowered. The temperature in the heating chamber is provided with a gradient by controlling the heat-treated body to have different values in the conveyance direction.
[0021]
For example, in the upper part (furnace ceiling) of the heating chamber in the temperature rising zone where the difference in indoor average temperature from the adjacent heating chamber is 70 ° C., each is divided into nine parts A to I as shown in FIG. In the case of heating a 40-inch PDP glass substrate by providing heating means that can be individually controlled by an independent control system, the heating means A to I divided as shown in FIG. When all the set temperatures are the same (flat setting), the setting of the heating means G to I on the inlet side with respect to the set temperature (337 ° C.) of the heating means D to F in the center as shown in FIG. The temperature distribution of the substrate after heating for a predetermined time when the temperature is set to a high value (342 ° C.) and the set temperature of the outlet heating means A to C is set to a low value (332 ° C.) (gradient setting). As shown in Fig. 1 (d), the temperature at each installation location of the glass substrate with thermometers installed at 9 locations (1) to (9) as shown in Fig. 1 (d). The temperature and the deviation are as shown in Table 1. The temperature distribution in the substrate was smaller when the gradient was set than when the flat was set.
[0022]
[Table 1]

[0023]
In the heat treatment method of the present invention, as described above, in a configuration in which there is no shutter between adjacent heating chambers, the set temperature of each heating means divided in the same heating chamber is set in the conveying direction of the heat-treated body. By controlling the temperature so as to be different from each other and providing a gradient in the temperature in the heating chamber, the thermal effect of the other adjacent heating chamber on the substrate is offset, and the glass substrate is uniformly heat-treated. For the temperature-lowering heating chamber that cools the substrate, the set temperature of the heating means on the inlet side is controlled to a lower value, and the set temperature of the heating means on the outlet side is controlled to a higher value. By providing a temperature gradient opposite to the example, it is possible to achieve soaking of the substrate.
[0024]
As a guideline for setting the temperature gradient in the heating chamber, when the substrate is heat-treated in the steps of heating, holding, and cooling (cooling), the maximum temperature of the substrate when the substrate exists in the heating chamber that holds the temperature It is preferable to set the temperature gradient so that the temperature difference ΔT between this part and the lowest temperature part is 6 ° C. or less.
[0025]
In addition, when the temperature distribution of the substrate occurs in the width direction of the furnace due to the thermal influence from the furnace wall or the like, the heating means is used not only in the conveyance direction of the heat-treated body (longitudinal direction of the furnace) but also in the furnace By dividing the temperature in the width direction, and controlling the set temperature of each heating means to be a different value in the width direction as well, by providing a temperature gradient in the heating chamber, the thermal effect is offset and more uniform Heat treatment can be performed.
[0037]
Next, a continuous heat treatment furnace that can be suitably used in the heat treatment method of the present invention will be described. First, as described above, a continuous heat treatment furnace suitable for carrying out the heat treatment method of the present invention has, as its basic configuration, a plurality of heating chambers partitioned with respect to the transport direction of the heat-treated body, Transporting means for transporting the object to be heat-treated to the adjacent heating chamber. Each heating chamber is provided with heating means divided into several parts at least in the conveying direction of the object to be heat-treated, and these divided heating means are individually temperature controlled by independent control systems. It can be done.
[0038]
In addition, as a characteristic configuration of this continuous heat treatment furnace, the temperature in the heating chamber is controlled by controlling the set temperature of each heating means provided in the heating chamber to have a different value in the conveyance direction of the object to be heat treated. And a temperature control device capable of providing a gradient , whereby the heat treatment method of the present invention can be easily carried out.
[0040]
In the heat treatment furnace before reporting, it is preferable to use an easy electrical heater temperature control as a heating means, one heating means advantageous gas combustion type indirect heating burners in terms of operating costs (radiant tube burner) You may use for a part or all. The radiant tube includes a straight type, a single end type, and a U-shape, and any of them may be used. Further, as the gas combustion type indirect heating type burner, an exhaust heat recovery type regenerative burner incorporating a heat storage body is preferable.
[0041]
FIG. 2 is a schematic view showing an example of the structure of the regenerative burner, and the radiant tube 13 is provided with a heat storage body 15 made of a burner and a ceramic honeycomb at both ends. When the burners provided at both ends of the radiant tube 13 are alternately switched and burned, a high energy saving effect is obtained.
[0042]
That is, when the burner at one end of the tube is burning, the exhaust heat is recovered by the heat storage body while exhausting from the other end of the tube, and is recovered by the heat storage body when the combustion is switched to the burner at the other end. By using the exhausted heat to preheat the combustion air, the amount of fuel used for burner heating can be reduced. Further, by performing switching at a short cycle, the temperature distribution on the surface of the radiant tube becomes small, and uniform heating becomes possible.
[0043]
It is preferable to arrange a muffle between the heating means and the moving region of the heat-treated body, and it is particularly preferable that a part or all of the muffle is made of a material having a high infrared irradiation rate. This is because once the heat generated by the heating means is received by the muffle, far-infrared rays or near-infrared rays are irradiated from the muffle, so that the object to be heat-treated can be heated more rapidly. In addition, since the heating means and the moving area of the object to be heat-treated are secretly separated by the muffle, there is an effect that the cleanliness in the moving area of the object to be heat-treated is ensured.
[0044]
As a material having a high infrared irradiation rate constituting the muffle, a sintered body containing SiC is preferable, and Si-impregnated SiC is particularly preferable. Si-impregnated SiC is obtained by sintering a molded body mainly composed of silicon carbide and carbon while impregnating metal silicon in a reduced-pressure inert gas atmosphere or vacuum in which metal silicon is present. For example, in comparison with crystallized glass, the infrared irradiation rate is remarkably high as shown in FIG. 4 , and the thermal conductivity is very high.
[0045]
The conveying means includes an intermittent feed method that intermittently conveys the heat-treated body as described above, and a continuous feed method that conveys the heat-treated body continuously without moving it to each heating chamber. There is a thing. In the present invention, intermittent feeding type conveying means is preferably used, but for conveying between the heating chambers in the temperature raising region for raising the temperature of the object to be heat treated and between the heating chambers in the heat retaining region for keeping the temperature of the object to be heated. In this case, a continuous feeding method is used, and an intermittent feeding method is used for transporting between the heating chambers in the cooling zone where the temperature of the object to be heat-treated is lowered (cooling). May be.
[0046]
However, in the case of using the continuous feed type conveying means for conveying between the heating chambers in the temperature rising region and between the heating chambers in the heat retaining region as described above, the heat-treated body moves in a state straddling between adjacent heating chambers. In order to reduce the temperature distribution that occurs when the heat treatment body is moved, the heat treatment body moves between adjacent heating chambers relative to the transfer speed during the period in which the entire heat treatment body is located in the same heating chamber. It is necessary to sufficiently increase the conveyance speed during the running period. Specifically, the conveyance speed in the latter period is preferably 20 times or more, and more preferably 50 times or more with respect to the conveyance speed in the former period. Examples of the continuous feed type conveying means capable of changing the conveying speed include a roller conveyor and a chain conveyor.
[0048]
【The invention's effect】
As described above, according to the present invention, when a substrate including a film forming material is heat-treated in a heating chamber in a configuration having no shutter between adjacent heating chambers , the average temperature in the chamber is different. It is possible to suppress the temperature distribution in the substrate due to the thermal influence from the adjacent heating chambers and to uniformly heat the entire substrate.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of an embodiment according to a heat treatment method of the present invention , in which (a) shows an outline of a configuration of a heating unit, (b) shows a set temperature of the heating unit during flat setting, (c) shows the set temperature of the heating means at the time of setting the gradient, and (d) shows the position of the glass substrate which is the heat-treated body and the thermometer installed on the substrate.
FIG. 2 is a schematic diagram showing an example of the structure of a regenerative burner.
FIG. 3 is a process diagram showing a manufacturing process of a PDP.
FIG. 4 is a graph showing the infrared irradiation rate of Si-impregnated SiC.
[Explanation of symbols]
13 ... Radiant tube, 15 ... Thermal storage.

Claims

A plurality of heating chambers that are partitioned with respect to the conveyance direction of the heat-treated body but do not have a shutter between adjacent heating chambers, and a conveying means for conveying the heat-treated body to the adjacent heating chambers Using a continuous heat treatment furnace in which each heating chamber is divided into at least several parts in the conveying direction of the object to be heat-treated, and each is provided with heating means that can be individually controlled by an independent control system. , A method of heat-treating a substrate containing a film-forming material,
Among the plurality of heating chambers, in a heating chamber having an average indoor temperature different from that of at least one of the other adjacent heating chambers, the set temperature of each heating means provided in the heating chamber is set to a temperature increasing step and a temperature decreasing step. In order to provide a gradient in the temperature in the heating chamber by controlling the temperature to be different in the conveyance direction of the object to be heat-treated, the other heating chamber adjacent to the substrate being heat-treated in the heating chamber A method for heat-treating a substrate, wherein the substrate is subjected to uniform heat treatment while canceling out the thermal effects.

The heat treatment method according to claim 1, wherein the transfer means is an intermittent feed type transfer means for intermittently transferring the object to be heat-treated to adjacent heating chambers.

In the case where the substrate is heat-treated in the steps of temperature increase, temperature retention, and temperature decrease, when the substrate exists in a heating chamber that retains temperature, the temperature difference ΔT between the highest temperature portion and the lowest temperature portion of the substrate is The heat treatment method according to claim 1, wherein a gradient is provided in the temperature of the heating chamber so that the temperature is 6 ° C. or less.

A plurality of heating chambers that are partitioned with respect to the conveyance direction of the heat-treated body but do not have a shutter between adjacent heating chambers, and a conveying means for conveying the heat-treated body to the adjacent heating chambers A continuous heat treatment furnace in which each heating chamber is divided into several parts at least in the transport direction of the object to be heat treated, and each is provided with heating means capable of individually controlling the temperature with an independent control system. ,
It has a temperature control device that can control the set temperature of each heating means provided in the heating chamber to have a different value in the conveyance direction of the object to be heat treated, and can provide a gradient in the temperature in the heating chamber. A continuous heat treatment furnace.

The continuous heat treatment furnace according to claim 4, wherein the heating means is an electric heater.

The continuous heat treatment furnace according to claim 4, wherein a part or all of the heating means is a gas combustion indirect heating burner.

The continuous heat treatment furnace according to claim 6, wherein the gas combustion indirect heating burner is an exhaust heat recovery type regenerative burner with a built-in heat storage element.

The muffle is disposed between the heating means and the moving region of the object to be heat-treated, and a part or all of the muffle is made of a material having a high infrared irradiation rate. The continuous heat treatment furnace described.

The continuous heat treatment furnace according to claim 8, wherein the material having a high infrared irradiation rate is a sintered body containing SiC.

The continuous heat treatment furnace according to any one of claims 4 to 9, wherein the transfer means is an intermittent feed type transfer means for intermittently transferring the object to be heat-treated to adjacent heating chambers.

For transporting between the heating chambers in the temperature rising area where the temperature of the body to be heat-treated is raised and between the heating chambers in the heat-keeping area where the temperature of the body to be heat treated is kept, a continuous feed type transport means is used to lower the temperature of the body to be heat treated. The continuous heat treatment furnace according to any one of claims 4 to 9, wherein an intermittent feed type transfer means is used for transfer between heating chambers in the temperature-falling region.

The transfer means of the continuous feed method is a period in which the heat treatment target is moving in a state straddling between adjacent heating chambers with respect to the transfer speed during the period in which the whole heat treatment target is located in the same heating chamber. The continuous heat treatment furnace according to claim 11, wherein the speed can be changed so that the conveying speed can be increased by 20 times or more.