JP5259875B1 - Battery electrode coating film drying method and drying furnace - Google Patents

Battery electrode coating film drying method and drying furnace Download PDF

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JP5259875B1
JP5259875B1 JP2012287978A JP2012287978A JP5259875B1 JP 5259875 B1 JP5259875 B1 JP 5259875B1 JP 2012287978 A JP2012287978 A JP 2012287978A JP 2012287978 A JP2012287978 A JP 2012287978A JP 5259875 B1 JP5259875 B1 JP 5259875B1
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良夫 近藤
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Abstract

【課題】電極の厚さ方向におけるバインダーの分布をより均一化する。
【解決手段】電極材が塗膜の表面に露出するまでの間は、塗膜からの溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１が領域Ａに含まれるように塗膜を加熱する工程を行う。これにより、乾燥後の塗膜すなわち電極の、厚さ方向におけるバインダーの分布をより均一化することができる。また、第１平均蒸発速度Ｓｖａ１が領域Ｂに含まれるようにすることで、上述したバインダーの分布を均一化する効果がより高いものとなる。
【選択図】図５A binder distribution in the thickness direction of an electrode is made more uniform.
Until the electrode material is exposed on the surface of the coating film, the coating film is heated so that a first average evaporation rate Sva1, which is an average value of the evaporation rate of the solvent from the coating film, is included in region A. The process to do is performed. Thereby, distribution of the binder in the thickness direction of the coating film after drying, ie, an electrode, can be made more uniform. In addition, by making the first average evaporation rate Sva1 included in the region B, the above-described effect of making the binder distribution uniform is higher.
[Selection] Figure 5

Description

本発明は、電池用電極塗膜の乾燥方法及び乾燥炉に関する。   The present invention relates to a method for drying an electrode coating film for a battery and a drying furnace.

従来、電池用の電極の製造方法として、正極材または負極材である活物質（電極材ともいう）とバインダーと導電材と溶剤とを混合して電極材ペーストとし、これをシート上に塗布して電極塗膜とし、この塗膜を乾燥させて電池用の電極とする方法が知られている。このような電極塗膜の乾燥においては、塗膜の表面から溶剤が乾燥するため、塗膜中のバインダーが溶剤と共に塗膜表面側に移動し、塗膜表面側のバインダー濃度が高まるという現象が生じる。バインダーは電極材同士や導電材同士を接着する役割を果たすため、電極中のバインダーの分布はできるだけ均一であることが好ましい。この課題を解決するため、例えば特許文献１には、初期段階では塗膜温度を速やかに上昇させ、溶剤が蒸発して電極材が塗膜の表面に露出した以降は、中期段階としてシート温度より低い温度の熱風と赤外線照射により塗膜全体を加熱することが記載されている。これにより、電極の厚さ方向におけるバインダーの分布が均一化され、電極の剥離やひび割れの発生を防止できるとしている。   Conventionally, as an electrode manufacturing method for a battery, an active material (also referred to as an electrode material) that is a positive electrode material or a negative electrode material, a binder, a conductive material, and a solvent are mixed to form an electrode material paste, which is applied onto a sheet. There is known a method of forming an electrode coating film and drying the coating film to obtain an electrode for a battery. In the drying of such an electrode coating film, the solvent is dried from the surface of the coating film, so that the binder in the coating film moves to the coating film surface side together with the solvent, and the binder concentration on the coating film surface side increases. Arise. Since the binder plays a role of bonding the electrode materials to each other and the conductive materials, the distribution of the binder in the electrode is preferably as uniform as possible. In order to solve this problem, for example, in Patent Document 1, the coating temperature is rapidly increased in the initial stage, and after the solvent evaporates and the electrode material is exposed on the surface of the coating film, the sheet temperature is determined as the middle stage. It is described that the entire coating film is heated by hot air of low temperature and infrared irradiation. Thereby, the distribution of the binder in the thickness direction of the electrode is made uniform, and the occurrence of peeling and cracking of the electrode can be prevented.

特許第４８０１２３３号公報Japanese Patent No. 4801233

特許文献１に記載の乾燥方法では、電極の厚さ方向におけるバインダーの分布が均一化される。これをさらに改良して、バインダーの分布をより均一化することが望まれていた。   In the drying method described in Patent Document 1, the binder distribution in the thickness direction of the electrode is made uniform. It has been desired to further improve this to make the binder distribution more uniform.

本発明はこのような課題を解決するためになされたものであり、電池用電極塗膜を乾燥するにあたり、電極の厚さ方向におけるバインダーの分布をより均一化することを主目的とする。   The present invention has been made to solve such problems, and its main object is to make the distribution of the binder in the thickness direction of the electrode more uniform when drying the electrode coating film for a battery.

本発明者らは、電極材とバインダーと導電材と溶剤とを含む電極材ペーストをシート上に塗布した電池用電極塗膜を乾燥するにあたり、塗膜からの溶剤の蒸発速度がバインダーの分布と関連があることを見いだした。そして、さらに検討した結果、電極材が塗膜の表面に露出するまでの間の蒸発速度と、乾燥開始時の電極材ペースト中の溶剤質量割合との関係を適切に制御することでバインダーの分布をより均一にできることを見いだし、本発明を完成するに至った。   When drying the electrode coating film for a battery in which an electrode material paste containing an electrode material, a binder, a conductive material, and a solvent is applied on a sheet, the present inventors have determined that the evaporation rate of the solvent from the coating film is the distribution of the binder. I found it relevant. And as a result of further investigation, the distribution of the binder by appropriately controlling the relationship between the evaporation rate until the electrode material is exposed on the surface of the coating film and the solvent mass ratio in the electrode material paste at the start of drying. Has been found to be more uniform, and the present invention has been completed.

すなわち、本発明の第１の電池用電極塗膜の乾燥方法は、
電極材とバインダーと導電材と溶剤とを含む電極材ペーストをシート上に塗布した電池用電極塗膜の乾燥方法であって、
前記電極材が前記塗膜の表面に露出するまでの間、該塗膜の溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１［ｍｇ／（ｓ・ｃｍ2）］が次式（１）を満たすように該塗膜を加熱する工程、
を含むものである。 That is, the first method for drying an electrode coating film for a battery of the present invention is as follows.
A method for drying an electrode coating film for a battery in which an electrode material paste including an electrode material, a binder, a conductive material, and a solvent is applied on a sheet,
Until the electrode material is exposed on the surface of the coating film, the first average evaporation rate Sva1 [mg / (s · cm 2 )] which is an average value of the evaporation rate of the solvent of the coating film is expressed by the following formula (1). Heating the coating film so as to satisfy
Is included.

Figure 0005259875
Figure 0005259875

この本発明の第１の電池用電極塗膜の乾燥方法では、電極材が塗膜の表面に露出するまでの間は、塗膜からの溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１が上記式（１）を満たすように塗膜を加熱する工程を行う。こうすることで、乾燥後の塗膜すなわち電極の、厚さ方向におけるバインダーの分布をより均一化することができる。なお、バインダーの分布をより均一化することができる理由は次のように考えられる。加熱により塗膜表層から溶剤が蒸発すると、溶剤の塗膜表層への移動に伴ってバインダーも表層へ移動する。バインダーは蒸発できないため、この移動により、塗膜の表層側のバインダー濃度は一時的に上昇する。しかし、塗膜の表層側のバインダー濃度が高まることにより、塗膜の表層側と下層側とでバインダーの濃度差が生じ、この濃度差が駆動力となって、表層から下層へバインダーの拡散が生じる（以下、これを逆拡散とも表記する）。本発明の第１の電池用電極塗膜の乾燥方法では、第１平均蒸発速度Ｓｖａ１が上記式（１）の下限以上となるように塗膜を加熱することで塗膜の表層側のバインダー濃度が急激に上昇し、逆拡散の駆動力がより高いものとなると考えられる。そして、逆拡散の駆動力がより高いものとなることで、電極材が塗膜の表面に露出した後の期間において逆拡散の駆動力によりバインダーが塗膜の下層側に移動して、バインダーの分布をより均一化できていると考えられる。また、第１加熱における蒸発速度が高すぎると、塗膜中の溶剤が早期に減少してしまい、逆拡散の駆動力が高くてもバインダーが塗膜中を移動しにくくなってしまう。第１平均蒸発速度Ｓｖａ１を上記式（１）の上限以下とすることで、逆拡散の駆動力によりバインダーが塗膜の下層に移動可能な期間を確保でき、バインダーの分布をより均一化できていると考えられる。なお、蒸発速度の単位として示したｍｇ／（ｓ・ｃｍ2）は、塗膜の表面積１ｃｍ2あたりの１秒間の溶剤の蒸発量（ｍｇ）を意味する。この場合において、シートは例えばアルミニウムや銅などの金属であるものとしてもよい。また、電池用電極塗膜は、正極，負極いずれの電極塗膜であってもよい。また、電池用電極塗膜は、例えばリチウムイオン電池用の電極塗膜としてもよい。 In the first method for drying an electrode coating film for a battery according to the present invention, the first average evaporation rate which is an average value of the evaporation rate of the solvent from the coating film until the electrode material is exposed on the surface of the coating film. The process of heating a coating film is performed so that Sva1 may satisfy | fill said Formula (1). By carrying out like this, distribution of the binder in the thickness direction of the coating film after drying, ie, an electrode, can be made more uniform. The reason why the binder distribution can be made more uniform is considered as follows. When the solvent evaporates from the coating film surface layer by heating, the binder also moves to the surface layer as the solvent moves to the coating film surface layer. Since the binder cannot evaporate, the binder concentration on the surface layer side of the coating film temporarily rises due to this movement. However, as the binder concentration on the surface layer side of the coating film increases, a difference in binder concentration occurs between the surface layer side and the lower layer side of the coating film, and this concentration difference becomes a driving force, and the binder diffuses from the surface layer to the lower layer. Occurs (hereinafter also referred to as despreading). In the first method for drying an electrode coating film for a battery according to the present invention, the binder concentration on the surface layer side of the coating film is heated by heating the coating film so that the first average evaporation rate Sva1 is not less than the lower limit of the above formula (1). Is expected to rise rapidly, and the driving force for despreading becomes higher. And since the driving force of the reverse diffusion becomes higher, the binder moves to the lower layer side of the coating film by the driving force of the reverse diffusion in the period after the electrode material is exposed on the surface of the coating film. It is thought that the distribution can be made more uniform. On the other hand, if the evaporation rate in the first heating is too high, the solvent in the coating film is reduced at an early stage, and even if the driving force for reverse diffusion is high, the binder is difficult to move in the coating film. By setting the first average evaporation rate Sva1 to be equal to or lower than the upper limit of the above formula (1), it is possible to secure a period during which the binder can move to the lower layer of the coating film due to the reverse diffusion driving force, and to make the binder distribution more uniform. It is thought that there is. In addition, mg / (s · cm 2 ) shown as a unit of the evaporation rate means the amount of evaporation (mg) of the solvent per second per 1 cm 2 of the surface area of the coating film. In this case, the sheet may be a metal such as aluminum or copper. Moreover, the electrode coating film for a battery may be an electrode coating film of either a positive electrode or a negative electrode. Moreover, the electrode coating film for batteries is good also as an electrode coating film for lithium ion batteries, for example.

この本発明の第１の電池用電極塗膜の乾燥方法において、前記工程では、前記第１平均蒸発速度Ｓｖａ１が次式（２）を満たすように前記塗膜を加熱するものとしてもよい。第１平均蒸発速度Ｓｖａ１が式（２）を満たすようにすることで、上述したバインダーの分布を均一化する効果がより高いものとなる。   In the first method for drying an electrode coating film for a battery of the present invention, in the step, the coating film may be heated so that the first average evaporation rate Sva1 satisfies the following formula (2). By making 1st average evaporation speed Sva1 satisfy | fill Formula (2), the effect of equalizing the distribution of the binder mentioned above becomes higher.

Figure 0005259875
Figure 0005259875

この本発明の第１の電池用電極塗膜の乾燥方法において、前記電極材が前記塗膜の表面に露出した後、前記塗膜を加熱する工程、を含むものとしてもよい。   The first method for drying an electrode coating film for a battery according to the present invention may include a step of heating the coating film after the electrode material is exposed on the surface of the coating film.

本発明の第２の電池用電極塗膜の乾燥方法は、
電極材とバインダーと導電材と溶剤とを含む電極材ペーストをシート上に塗布した電池用電極塗膜の乾燥方法であって、
（ａ）前記電極材が前記塗膜の表面に露出するまでの間、該塗膜の溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上となるように該塗膜を加熱する第１加熱を行うステップと、
（ｂ）前記電極材が前記塗膜の表面に露出した後、前記塗膜の溶剤の蒸発速度の平均値である第２平均蒸発速度Ｓｖａ２が前記第１平均蒸発速度Ｓｖａ１以下となるように該塗膜を加熱する第２加熱を行うステップと、
を含むものである。 The method for drying the second electrode coating film for a battery of the present invention is as follows.
A method for drying an electrode coating film for a battery in which an electrode material paste including an electrode material, a binder, a conductive material, and a solvent is applied on a sheet,
(A) Until the electrode material is exposed on the surface of the coating film, the first average evaporation rate Sva1, which is an average value of the evaporation rate of the solvent of the coating film, is 0.4 mg / (s · cm 2 ) or more. Performing a first heating to heat the coating film so that
(B) After the electrode material is exposed on the surface of the coating film, the second average evaporation rate Sva2, which is an average value of the evaporation rate of the solvent of the coating film, is equal to or less than the first average evaporation rate Sva1. Performing a second heating to heat the coating;
Is included.

この本発明の第２の電池用電極塗膜の乾燥方法では、まず、電極材が塗膜の表面に露出するまでの間は、塗膜からの溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上となるように塗膜を加熱する第１加熱を行う。続いて、電極材が塗膜の表面に露出した後、塗膜の溶剤の蒸発速度の平均値である第２平均蒸発速度Ｓｖａ２が第１平均蒸発速度Ｓｖａ１以下となるように塗膜を加熱する第２加熱を行う。こうすることで、乾燥後の塗膜すなわち電極の、厚さ方向におけるバインダーの分布をより均一化することができる。なお、バインダーの分布をより均一化することができる理由は、次のように考えられる。まず、第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上となるように第１加熱を行うことで塗膜の表層側のバインダー濃度が急激に上昇し、バインダーの逆拡散の駆動力がより高いものとなると考えられる。また、電極材が前記塗膜の表面に露出した後の第２加熱における蒸発速度が高すぎると、溶剤の蒸発に伴い塗膜の表層側へバインダーが移動しやすくなったり、塗膜中の溶剤が早期に減少してしまい、逆拡散の駆動力が高くてもバインダーが塗膜中を移動しにくくなってしまう。本発明の電池用電極塗膜の乾燥方法では、第２平均蒸発速度Ｓｖａ２が第１平均蒸発速度Ｓｖａ１以下となるように塗膜を加熱することで、バインダーが塗膜中を移動可能な期間を比較的長く確保でき、その間に逆拡散の駆動力によりバインダーが下層に移動して、バインダーの分布をより均一化できていると考えられる。このように、本発明の第２の電池用電極塗膜の乾燥方法では、まず第１加熱により逆拡散の駆動力をより高くし、その後の第２加熱では、溶剤の蒸発に伴うバインダーの表層への移動を抑え、且つ逆拡散によりバインダーが下層に移動可能な期間をより長く確保することで、バインダーの分布をより均一化できていると考えられる。この場合において、前記第１平均蒸発速度Ｓｖａ１は０．４ｍｇ／（ｓ・ｃｍ2）以上１．０ｍｇ／（ｓ・ｃｍ2）以下であることが好ましい。第１平均蒸発速度Ｓｖａ１を１．０ｍｇ／（ｓ・ｃｍ2）以下とすることで、塗膜が乾燥過多となるのを抑制することができる。 In the second method for drying an electrode coating film for a battery according to the present invention, first, the first average which is an average value of the evaporation rate of the solvent from the coating film until the electrode material is exposed on the surface of the coating film. First heating is performed to heat the coating film so that the evaporation rate Sva1 is 0.4 mg / (s · cm 2 ) or more. Subsequently, after the electrode material is exposed on the surface of the coating film, the coating film is heated so that the second average evaporation rate Sva2, which is an average value of the evaporation rate of the solvent of the coating film, is equal to or lower than the first average evaporation rate Sva1. Second heating is performed. By carrying out like this, distribution of the binder in the thickness direction of the coating film after drying, ie, an electrode, can be made more uniform. The reason why the binder distribution can be made more uniform is considered as follows. First, by performing the first heating so that the first average evaporation rate Sva1 is 0.4 mg / (s · cm 2 ) or more, the binder concentration on the surface layer side of the coating film rapidly increases, and the reverse diffusion of the binder The driving force is considered to be higher. In addition, if the evaporation rate in the second heating after the electrode material is exposed on the surface of the coating film is too high, the binder easily moves to the surface layer side of the coating film due to the evaporation of the solvent, or the solvent in the coating film Decreases at an early stage, and even if the driving force for back diffusion is high, it becomes difficult for the binder to move in the coating film. In the method for drying an electrode coating film for a battery according to the present invention, by heating the coating film so that the second average evaporation rate Sva2 is equal to or lower than the first average evaporation rate Sva1, the period during which the binder can move in the coating film is increased. It is considered that the binder can be secured for a relatively long period, and the binder is moved to the lower layer by the driving force of the reverse diffusion during that time, so that the distribution of the binder can be made more uniform. As described above, in the second method for drying an electrode coating film for a battery according to the present invention, first, the driving force for reverse diffusion is further increased by the first heating, and the surface layer of the binder accompanying the evaporation of the solvent in the subsequent second heating. It is considered that the distribution of the binder can be made more uniform by suppressing the movement of the binder and securing a longer period during which the binder can move to the lower layer by reverse diffusion. In this case, the first average evaporation rate Sva1 is preferably 0.4 mg / (s · cm 2 ) or more and 1.0 mg / (s · cm 2 ) or less. By setting the first average evaporation rate Sva1 to 1.0 mg / (s · cm 2 ) or less, it is possible to prevent the coating film from being excessively dried.

本発明の第２の電池用電極塗膜の乾燥方法において、前記ステップ（ｂ）では、前記第２平均蒸発速度Ｓｖａ２が前記第１平均蒸発速度Ｓｖａ１未満となるように前記塗膜を加熱するものとしてもよい。こうすれば、第２加熱における蒸発速度が小さくなることで、溶剤の減少がより抑えられるため、バインダーが移動しにくくなるまでの時間をより長く確保することができる。これにより、逆拡散の駆動力を用いてバインダーを下層に十分移動させることができ、バインダーの分布がより均一化される。   In the second method for drying an electrode coating film for a battery according to the present invention, in the step (b), the coating film is heated so that the second average evaporation rate Sva2 is less than the first average evaporation rate Sva1. It is good. In this case, since the evaporation rate in the second heating is reduced, the decrease in the solvent is further suppressed, and therefore it is possible to secure a longer time until the binder becomes difficult to move. Thereby, the binder can be sufficiently moved to the lower layer by using the driving force of the reverse diffusion, and the distribution of the binder is made more uniform.

この場合において、本発明の第２の電池用電極塗膜の乾燥方法は、（ｃ）前記ステップ（ｂ）の後、前記塗膜の溶剤の蒸発速度が前記第２平均蒸発速度Ｓｖａ２超過となる期間を有するように該塗膜を加熱する第３加熱を行うステップを含むものとしてもよい。こうすれば、第２加熱でバインダーの分布を均一化したあとに、第２平均蒸発速度Ｓｖａ２と比べて蒸発速度の高い期間を有する第３加熱を行って速やかに残りの溶剤を蒸発させることが可能となる。これにより、全体の乾燥時間を短縮することができる。   In this case, according to the second method for drying an electrode coating film for a battery of the present invention, (c) after the step (b), the evaporation rate of the solvent of the coating film exceeds the second average evaporation rate Sva2. A step of performing third heating for heating the coating film so as to have a period may be included. In this way, after uniformizing the binder distribution by the second heating, the remaining solvent can be quickly evaporated by performing the third heating having a period during which the evaporation rate is higher than the second average evaporation rate Sva2. It becomes possible. Thereby, the whole drying time can be shortened.

本発明の第１，第２の電池用電極塗膜の乾燥方法において、前記塗膜の加熱は、赤外線及び熱風により行うものとしてもよい。こうすることで、熱風のみにより塗膜を乾燥する場合と比べて、赤外線も併用することで塗膜表面だけでなく塗膜内部の溶剤を速やかに加熱して蒸発させることができる。また、熱風により蒸発した溶剤を速やかに除去することができる。なお、赤外線のうち近赤外線（例えば、波長が０．７〜３．５μｍの電磁波）により前記塗膜の加熱を行うことが好ましい。近赤外線は、被加熱物中の水，溶剤などの分子中の水素結合を効率よく切断できるため、被加熱物の加熱や乾燥を効率よく行うことができる。例えば、ピーク波長が近赤外線領域（例えば、波長が０．７〜３．５μｍの領域）にある電磁波を用いて加熱を行うものとしてもよい。   In the first and second battery electrode coating film drying methods of the present invention, the coating film may be heated by infrared rays and hot air. By carrying out like this, compared with the case where a coating film is dried only with hot air, not only the coating film surface but the solvent inside a coating film can be heated rapidly and evaporated by using infrared rays together. Moreover, the solvent evaporated by the hot air can be quickly removed. In addition, it is preferable to heat the said coating film by near infrared rays (for example, electromagnetic waves with a wavelength of 0.7-3.5 micrometers) among infrared rays. Near-infrared rays can efficiently cut hydrogen bonds in molecules such as water and solvents in the heated object, and thus can efficiently heat and dry the heated object. For example, heating may be performed using an electromagnetic wave having a peak wavelength in the near infrared region (for example, a region having a wavelength of 0.7 to 3.5 μm).

本発明の第１の電池用電極塗膜の乾燥炉は、
電極材とバインダーと導電材と溶剤とを含む電極材ペーストをシート上に塗布した電池用電極塗膜の乾燥炉であって、
前記電極材が前記塗膜の表面に露出するまでの間、該塗膜の溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１［ｍｇ／（ｓ・ｃｍ2）］が次式（１）を満たすように該塗膜を加熱する加熱手段、
を備えたものである。 The drying furnace for the first electrode coating for a battery according to the present invention comprises:
A battery electrode coating film drying furnace in which an electrode material paste containing an electrode material, a binder, a conductive material, and a solvent is applied on a sheet,
Until the electrode material is exposed on the surface of the coating film, the first average evaporation rate Sva1 [mg / (s · cm 2 )] which is an average value of the evaporation rate of the solvent of the coating film is expressed by the following formula (1). Heating means for heating the coating film so as to satisfy
It is equipped with.

Figure 0005259875
Figure 0005259875

この本発明の第１の電池用電極塗膜の乾燥炉では、上述した本発明の第１の電池用電極塗膜の乾燥方法により乾燥が行われる。そのため、上述した本発明の第１の電池用電極塗膜の乾燥方法と同様の効果、例えばバインダーの分布をより均一化することができる効果が得られる。ここで、前記加熱手段は、前記電極材が前記塗膜の表面に露出するまでの間の前記塗膜の加熱を行う第１加熱と、前記電極材が前記塗膜の表面に露出した後、前記塗膜を加熱を行う第２加熱をを行うものとしてもよい。また、前記加熱手段は、前記第１加熱を行う第１加熱手段と、前記第２加熱を行う第２加熱手段とをそれぞれ有するものとしてもよい。この場合、前記第１加熱手段が加熱する領域に前記電池用電極塗膜を移動し、前記電極材が前記塗膜の表面に露出した後に、前記第２加熱手段が加熱する領域に前記電池用電極塗膜を移動する移動手段をさらに備えるものとしてもよい。あるいは、加熱手段の出力を制御する制御手段を備え、該制御手段は、前記加熱手段が前記第１加熱を行うよう制御し、前記電極材が前記塗膜の表面に露出した後に、前記加熱手段が前記第２加熱を行うよう制御するものとしてもよい。なお、この本発明の第１の電池用電極塗膜の乾燥炉において、上述した本発明の第１の乾燥方法の種々の態様を採用してもよいし、上述した本発明の第１の乾燥方法の各工程を実現するような構成を追加してもよい。   In the drying furnace for the first battery electrode coating film of the present invention, the drying is performed by the above-described drying method of the first battery electrode coating film of the present invention. Therefore, the effect similar to the drying method of the 1st electrode coating film for batteries of this invention mentioned above, for example, the effect which can make more uniform the distribution of a binder, is acquired. Here, the heating means includes first heating for heating the coating film until the electrode material is exposed on the surface of the coating film, and after the electrode material is exposed on the surface of the coating film, It is good also as what performs the 2nd heating which heats the said coating film. The heating means may include a first heating means for performing the first heating and a second heating means for performing the second heating. In this case, the battery electrode coating film is moved to a region heated by the first heating means, and after the electrode material is exposed on the surface of the coating film, the second heating means heats the region for the battery. A moving means for moving the electrode coating film may be further provided. Alternatively, it comprises control means for controlling the output of the heating means, the control means controlling the heating means to perform the first heating, and after the electrode material is exposed on the surface of the coating film, the heating means May be controlled to perform the second heating. In the drying furnace for the first electrode coating film for a battery of the present invention, various aspects of the first drying method of the present invention described above may be employed, or the first drying of the present invention described above. A configuration that realizes each step of the method may be added.

本発明の第２の電池用電極塗膜の乾燥炉は、
電極材とバインダーと導電材と溶剤とを含む電極材ペーストをシート上に塗布した電池用電極塗膜の乾燥炉であって、
前記電極材が前記塗膜の表面に露出するまでの間、該塗膜の溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上となるように該塗膜を加熱する第１加熱と、前記電極材が前記塗膜の表面に露出した後、前記塗膜の溶剤の蒸発速度の平均値である第２平均蒸発速度Ｓｖａ２が前記第１平均蒸発速度Ｓｖａ１以下となるように該塗膜を加熱する第２加熱と、を行う加熱手段、
を備えたものである。 The drying furnace for the second electrode coating film for a battery of the present invention comprises:
A battery electrode coating film drying furnace in which an electrode material paste containing an electrode material, a binder, a conductive material, and a solvent is applied on a sheet,
Until the electrode material is exposed on the surface of the coating film, the first average evaporation rate Sva1, which is the average value of the evaporation rate of the solvent of the coating film, is 0.4 mg / (s · cm 2 ) or more. And the first average heating rate Sva2 that is an average value of the evaporation rate of the solvent of the coating film after the electrode material is exposed on the surface of the coating film. Heating means for performing second heating for heating the coating film so that the evaporation rate is less than Sva1;
It is equipped with.

この本発明の第２の電池用電極塗膜の乾燥炉では、上述した本発明の第２の電池用電極塗膜の乾燥方法により乾燥が行われる。そのため、上述した本発明の第２の電池用電極塗膜の乾燥方法と同様の効果、例えばバインダーの分布をより均一化することができる効果が得られる。ここで、加熱手段は、前記第１加熱を行う第１加熱手段と、第２加熱を行う第２加熱手段とをそれぞれ有するものとしてもよい。この場合、前記第１加熱手段が加熱する領域に前記電池用電極塗膜を移動し、前記電極材が前記塗膜の表面に露出した後に、前記第２加熱手段が加熱する領域に前記電池用電極塗膜を移動する移動手段をさらに備えるものとしてもよい。あるいは、加熱手段の出力を制御する制御手段を備え、該制御手段は、前記加熱手段が前記第１加熱を行うよう制御し、前記電極材が前記塗膜の表面に露出した後に、前記加熱手段が前記第２加熱を行うよう制御するものとしてもよい。   In the drying furnace for the second electrode coating film for a battery of the present invention, the drying is performed by the above-described drying method for the electrode coating film for a battery of the present invention. Therefore, the same effect as that of the second method for drying an electrode coating film for a battery of the present invention described above, for example, an effect capable of making the binder distribution more uniform can be obtained. Here, the heating unit may include a first heating unit that performs the first heating and a second heating unit that performs the second heating. In this case, the battery electrode coating film is moved to a region heated by the first heating means, and after the electrode material is exposed on the surface of the coating film, the second heating means heats the region for the battery. A moving means for moving the electrode coating film may be further provided. Alternatively, it comprises control means for controlling the output of the heating means, the control means controlling the heating means to perform the first heating, and after the electrode material is exposed on the surface of the coating film, the heating means May be controlled to perform the second heating.

乾燥炉１０の縦断面図である。1 is a longitudinal sectional view of a drying furnace 10. FIG. 赤外線ヒーター３０の縦断面図である。2 is a longitudinal sectional view of an infrared heater 30. FIG. 図２のＡ−Ａ断面図である。It is AA sectional drawing of FIG. 各加熱領域と塗膜５２からの溶剤の蒸発速度との関係を示す蒸発曲線の説明図である。It is explanatory drawing of the evaporation curve which shows the relationship between each heating area | region and the evaporation rate of the solvent from the coating film 52. FIG. 第１平均蒸発速度Ｓｖａ１と補正後初期溶剤質量割合Ｒａ（％）との関係を示す説明図である。It is explanatory drawing which shows the relationship between 1st average evaporation rate Sva1 and corrected initial stage solvent mass ratio Ra (%). 実験例１〜７の第１平均蒸発速度Ｓｖａ１と相対偏析指数との関係を示すグラフである。It is a graph which shows the relationship between 1st average evaporation rate Sva1 and relative segregation index | exponent of Experimental Examples 1-7. 実験例８〜１４の第１平均蒸発速度Ｓｖａ１と相対偏析指数との関係を示すグラフである。It is a graph which shows the relationship between 1st average evaporation rate Sva1 of Experimental Examples 8-14, and a relative segregation index. 実験例１５〜２０の第１平均蒸発速度Ｓｖａ１と相対偏析指数との関係を示すグラフである。It is a graph which shows the relationship between 1st average evaporation rate Sva1 and relative segregation index | exponent of Experimental Examples 15-20. 実験例２１〜２８の第１平均蒸発速度Ｓｖａ１と相対偏析指数との関係を示すグラフである。It is a graph which shows the relationship between 1st average evaporation rate Sva1 and relative segregation index | exponent of Experimental example 21-28. 実験例１〜２８の結果に基づきバインダーの分布をより均一化できる範囲を示したグラフ。The graph which showed the range which can make distribution of a binder more uniform based on the result of Experimental Examples 1-28. 実験例２９〜３３の第１平均蒸発速度Ｓｖａ１と相対偏析指数との関係を示すグラフである。It is a graph which shows the relationship between 1st average evaporation rate Sva1 and relative segregation index | exponent of Experimental example 29-33.

［第１実施形態］
次に、本発明の好適な一実施形態について、図面を用いて説明する。図１は乾燥炉１０の縦断面図である。乾燥炉１０は、シート５０上に塗布された塗膜５２の加熱及び乾燥を赤外線及び熱風を用いて行うものであり、炉体１４と、搬送通路１９と、送風装置２０と、赤外線ヒーター３０と、コントローラー６０と、を備えている。また、乾燥炉１０は、第１加熱領域１１，第２加熱領域１２，第３加熱領域１３を有する。 [First Embodiment]
Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of the drying furnace 10. The drying furnace 10 performs heating and drying of the coating film 52 applied on the sheet 50 by using infrared rays and hot air, and the furnace body 14, the conveyance passage 19, the blower 20, the infrared heater 30, and the like. And a controller 60. The drying furnace 10 has a first heating region 11, a second heating region 12, and a third heating region 13.

炉体１４は、略直方体に形成された断熱構造体であり、前端面１５及び後端面１６にそれぞれ開口１７，１８を有している。この炉体１４は、前端面１５から後端面１６までの長さが例えば４〜１０ｍである。   The furnace body 14 is a heat insulating structure formed in a substantially rectangular parallelepiped shape, and has openings 17 and 18 on the front end face 15 and the rear end face 16, respectively. The furnace body 14 has a length from the front end face 15 to the rear end face 16 of, for example, 4 to 10 m.

搬送通路１９は、開口１７から開口１８に至る通路であり、炉体１４を水平方向に貫通している。片面に塗膜５２が塗布されたシート５０は、この搬送通路１９を通過していく。シート５０は、塗膜５２が塗布された面を上にして、開口１７から搬入され、炉体１４の内部を水平方向に進行し、開口１８から搬出される。   The conveyance passage 19 is a passage from the opening 17 to the opening 18 and penetrates the furnace body 14 in the horizontal direction. The sheet 50 having the coating film 52 applied on one side passes through the conveyance path 19. The sheet 50 is carried in from the opening 17 with the surface to which the coating film 52 is applied facing upward, proceeds in the furnace body 14 in the horizontal direction, and is carried out from the opening 18.

送風装置２０は、熱風を送風して乾燥炉１０内を通過する塗膜５２を乾燥させる装置である。送風装置２０は、第１加熱領域１１，第２加熱領域１２，第３加熱領域１３の上側にそれぞれ配置された送風装置２０ａ，２０ｂ，２０ｃと、第１加熱領域１１，第２加熱領域１２，第３加熱領域１３の下側にそれぞれ配置された送風装置２０ｄ，２０ｅ，２０ｆと、を有している。送風装置２０ａ〜２０ｆはそれぞれ、熱風発生器２２ａ〜２２ｆと、パイプ構造体２４ａ〜２４ｆと、通気口２６ａ〜２６ｆとを備えている。以下、送風装置２０ａを用いて説明する。送風装置２０ａは、熱風発生器２２ａと、パイプ構造体２４ａと、通気口２６ａとを備えている。熱風発生器２２ａは、パイプ構造体２４ａに取り付けられており、熱風をパイプ構造体２４ａの内部へ供給するものである。熱風は、例えば空気を加熱したものである。この熱風発生機２２ａは、発生させる熱風の風量や温度の調節が可能となっている。熱風の風量は、特に限定するものではないが、例えば１００Ｎｍ3／ｈ〜２０００Ｎｍ3／ｈの範囲で調節可能である。熱風の温度は、特に限定するものではないが、例えば４０〜２００℃の範囲で調節可能である。パイプ構造体２４ａは、熱風発生器２２ａからの熱風の通路となるものであり、熱風発生器２２ａから炉体１４内に向かって分岐した複数の通路を有している。パイプ構造体２４ａは、分岐した通路の部分で炉体１４の天井を貫通しており、分岐した通路は鉛直下方向を向いている。この分岐した通路の下端が通気口２６ａとなっており、通気口２６ａも鉛直下方向を向いている。本実施形態では、パイプ構造体２４ａは分岐した通路を７つ有してをおり、通気口２６ａも７つ形成されているものとした。これにより、送風装置２０ａの熱風発生器２２ａからの熱風は、７つの通気口２６ａから鉛直下方向に送風され、第１加熱領域１１において塗膜５２の表面に垂直に当たるようになっている。また、通気口２６ａは、第１加熱領域１１の前端面１５側から後端面１６側にわたって略均等に設けられている。熱風発生器２２ｂ〜２２ｆ，パイプ構造体２４ｂ〜２４ｆ，通気口２６ｂ〜２６ｆについても、それぞれ熱風発生器２２ａ，パイプ構造体２４ａ，通気口２６ａと同様の構成である。ただし、送風装置２０ｄ〜２０ｆは、それぞれ送風装置２０ａ〜２０ｃを図１における上下に逆転させた構成をしており、鉛直上方向の熱風を発生させる。すなわち、熱風発生器２２ｄ〜２２ｆからの熱風は、それぞれ通気口２６ｄ〜２６ｆから鉛直上方向に送風され、シート５０の裏面（塗膜５２が形成された面とは反対側の面）に垂直に当たるようになっている。なお、以下では、熱風発生器２２ａ〜２２ｆを熱風発生器２２と総称し、パイプ構造体２４ａ〜２４ｆをパイプ構造体２４と総称し、通気口２６ａ〜２６ｆを通気口２６と総称する。 The blower 20 is a device that blows hot air and dries the coating film 52 that passes through the drying furnace 10. The blower 20 includes blowers 20a, 20b, and 20c disposed above the first heating region 11, the second heating region 12, and the third heating region 13, respectively, the first heating region 11, the second heating region 12, Blowers 20d, 20e, and 20f are disposed below the third heating region 13, respectively. The blower devices 20a to 20f include hot air generators 22a to 22f, pipe structures 24a to 24f, and vent holes 26a to 26f, respectively. Hereinafter, description will be given using the blower 20a. The air blower 20a includes a hot air generator 22a, a pipe structure 24a, and a vent hole 26a. The hot air generator 22a is attached to the pipe structure 24a and supplies hot air to the inside of the pipe structure 24a. Hot air is, for example, heated air. The hot air generator 22a can adjust the air volume and temperature of the generated hot air. Air volume of hot air, it is not particularly limited and can be adjusted in the range of, for example, 100Nm 3 / h~2000Nm 3 / h. Although the temperature of a hot air is not specifically limited, For example, it can adjust in the range of 40-200 degreeC. The pipe structure 24a serves as a passage for hot air from the hot air generator 22a, and has a plurality of passages branched from the hot air generator 22a into the furnace body. The pipe structure 24a penetrates the ceiling of the furnace body 14 at the branched passage portion, and the branched passage faces vertically downward. The lower end of the branched passage is a vent 26a, and the vent 26a is also directed vertically downward. In the present embodiment, the pipe structure 24a has seven branched passages, and seven vent holes 26a are formed. Thereby, the hot air from the hot air generator 22a of the blower device 20a is blown vertically downward from the seven vents 26a, and hits the surface of the coating film 52 perpendicularly in the first heating region 11. The vent holes 26a are provided substantially evenly from the front end face 15 side to the rear end face 16 side of the first heating region 11. The hot air generators 22b to 22f, the pipe structures 24b to 24f, and the vent holes 26b to 26f have the same configurations as the hot air generator 22a, the pipe structure 24a, and the vent hole 26a, respectively. However, the air blowers 20d to 20f have a structure in which the air blowers 20a to 20c are reversed up and down in FIG. 1, and generate hot air in the vertically upward direction. That is, hot air from the hot air generators 22d to 22f is blown vertically upward from the vents 26d to 26f, respectively, and hits the back surface of the sheet 50 (surface opposite to the surface on which the coating film 52 is formed) perpendicularly. It is like that. Hereinafter, the hot air generators 22a to 22f are collectively referred to as the hot air generator 22, the pipe structures 24a to 24f are collectively referred to as the pipe structure 24, and the vent holes 26a to 26f are collectively referred to as the vent hole 26.

赤外線ヒーター３０は、赤外線を照射して乾燥炉１０内を通過する塗膜５２を乾燥させる装置であり、炉体１４の天井近くに複数取り付けられている。赤外線ヒーター３０は、第１加熱領域１１，第２加熱領域１２，第３加熱領域１３にそれぞれ配置された赤外線ヒーター３０ａ，３０ｂ，３０ｃを有している。特に限定するものではないが、本実施形態では、赤外線ヒーター３０ａは第１加熱領域１１の前端面１５側から後端面１６側にわたって略均等に６本配置され、赤外線ヒーター３０ｂは、第２加熱領域１２の前端面１５側に１本，後端面１６側に１本配置され、赤外線ヒーター３０ｃは、第３加熱領域１３の前端面１５側に２本，後端面１６側に２本配置されている。これらの各赤外線ヒーター３０は、同様の構成を有しており、いずれも長手方向が搬送方向と直交するように取り付けられている。   The infrared heater 30 is a device that irradiates infrared rays and dries the coating film 52 that passes through the drying furnace 10, and a plurality of infrared heaters 30 are attached near the ceiling of the furnace body 14. The infrared heater 30 includes infrared heaters 30a, 30b, and 30c disposed in the first heating region 11, the second heating region 12, and the third heating region 13, respectively. Although not particularly limited, in the present embodiment, six infrared heaters 30a are arranged substantially evenly from the front end face 15 side to the rear end face 16 side of the first heating area 11, and the infrared heater 30b is arranged in the second heating area. 12 on the front end face 15 side and one on the rear end face 16 side, and two infrared heaters 30c are arranged on the front end face 15 side of the third heating region 13 and two on the rear end face 16 side. . Each of these infrared heaters 30 has the same configuration, and is attached so that the longitudinal direction is orthogonal to the transport direction.

図２は、赤外線ヒーター３０の縦断面図であり、図３は図２のＡ−Ａ断面図である。赤外線ヒーター３０は、図２及び図３に示すように、フィラメント３２を内管３６が囲むように形成されたヒーター本体３８と、このヒーター本体３８を囲むように形成された外管４０と、外管４０の両端に気密に嵌め込まれた有底筒状のキャップ４２と、ヒーター本体３８と外管４０との間に形成され冷却流体が流通可能な流路４８と、外管４０の表面温度を検出する温度センサ３７と、を備えている。フィラメント３２は、電力供給源８０から電力が供給されて、例えば７００〜１５００℃（例えば１７００℃など、１５００℃以上に通電加熱可能であってもよい）に通電加熱され、波長が３μｍ付近にピークを持つ赤外線を放射する。このフィラメント３２に接続された電気配線３４は、キャップ４２に設けられた配線引出部４４を介して気密に外部へ引き出され、電力供給源８０に接続されている。内管３６は、石英ガラスやホウ珪酸クラウンガラスなどで作製されており、３．５μｍ以下の波長の赤外線を通過し、３．５μｍを超える波長の赤外線を吸収するフィルタとして機能する。ヒーター本体３８は、両端がキャップ４２の内部に配置されたホルダー４９に支持されている。外管４０は、内管３６と同様、石英ガラスやホウ珪酸クラウンガラスなどで作製されており、３．５μｍ以下の波長の赤外線を通過し、３．５μｍを超える波長の赤外線を吸収するフィルタとして機能する。各キャップ４２は、流体出入口４６を有している。流路４８は、冷却流体供給源７０から供給された冷却流体が、一方の流体出入口４６から他方の流体出入口４６へ冷却流体が流れるようになっている。流路４８を流れる冷却流体は、例えば空気や不活性ガスなどであり、内管３６と外管４０に接触して熱を奪うことにより各管３６，４０を冷却する。こうした赤外線ヒーター３０は、フィラメント３２から波長が３μｍ付近にピークを持つ赤外線が放射されると、そのうち３．５μｍ以下の波長の赤外線は内管３６や外管４０を通過して搬送通路を通過するシート５０の塗膜５２に照射される。これにより、赤外線ヒーター３０は、塗膜５２に対してピーク波長が３．５μｍ以下である赤外線を照射することになる。３．５μｍ以下の波長の赤外線は、シート５０の塗膜５２に含まれる溶剤の水素結合を切断する能力に優れるといわれており、効率的に溶剤を蒸発させることができる。一方、内管３６や外管４０は、３．５μｍを超える波長の赤外線を吸収するが、流路４８を流れる冷却流体によって冷却されるため、塗膜５２から蒸発する溶剤の着火点未満の温度（例えば２００℃以下など）に維持することが可能である。   FIG. 2 is a longitudinal sectional view of the infrared heater 30, and FIG. 3 is a sectional view taken along the line AA of FIG. As shown in FIGS. 2 and 3, the infrared heater 30 includes a heater body 38 formed so that the inner tube 36 surrounds the filament 32, an outer tube 40 formed so as to surround the heater body 38, and an outer tube 40. A bottomed cylindrical cap 42 that is airtightly fitted to both ends of the tube 40, a flow path 48 that is formed between the heater body 38 and the outer tube 40, and through which the cooling fluid can flow, and a surface temperature of the outer tube 40. And a temperature sensor 37 for detection. The filament 32 is supplied with electric power from the electric power supply source 80 and is heated to 700 to 1500 ° C. (for example, 1700 ° C. or 1500 ° C. or higher), and the wavelength peaks at about 3 μm. Radiates infrared with The electrical wiring 34 connected to the filament 32 is drawn out to the outside airtightly via a wiring drawing portion 44 provided in the cap 42, and is connected to the power supply source 80. The inner tube 36 is made of quartz glass, borosilicate crown glass, or the like, and functions as a filter that passes infrared rays having a wavelength of 3.5 μm or less and absorbs infrared rays having a wavelength exceeding 3.5 μm. The heater body 38 is supported at both ends by holders 49 disposed inside the cap 42. As with the inner tube 36, the outer tube 40 is made of quartz glass, borosilicate crown glass, or the like, and passes through infrared rays having a wavelength of 3.5 μm or less and absorbs infrared rays having a wavelength exceeding 3.5 μm. Function. Each cap 42 has a fluid inlet / outlet 46. In the channel 48, the cooling fluid supplied from the cooling fluid supply source 70 flows from one fluid inlet / outlet 46 to the other fluid inlet / outlet 46. The cooling fluid flowing through the flow path 48 is, for example, air or an inert gas, and cools the tubes 36 and 40 by contacting the inner tube 36 and the outer tube 40 and taking heat away. In the infrared heater 30, when infrared rays having a peak near 3 μm are emitted from the filament 32, infrared rays having a wavelength of 3.5 μm or less pass through the inner tube 36 and the outer tube 40 and pass through the conveyance path. The coating film 52 of the sheet 50 is irradiated. Thereby, the infrared heater 30 irradiates the coating film 52 with infrared rays having a peak wavelength of 3.5 μm or less. Infrared rays having a wavelength of 3.5 μm or less are said to be excellent in the ability to break the hydrogen bond of the solvent contained in the coating film 52 of the sheet 50 and can efficiently evaporate the solvent. On the other hand, the inner tube 36 and the outer tube 40 absorb infrared rays having a wavelength exceeding 3.5 μm, but are cooled by the cooling fluid flowing through the flow path 48, and therefore, have a temperature below the ignition point of the solvent evaporating from the coating film 52 ( For example, it can be maintained at 200 ° C. or lower.

コントローラー６０は、ＣＰＵを中心とするマイクロプロセッサとして構成されている。このコントローラー６０は、送風装置２０の熱風発生器２２ａ〜２２ｆに制御信号を出力して、熱風発生器２２ａ〜２２ｆで発生させる熱風の温度及び風量を個別に制御する。また、コントローラー６０は、熱電対である温度センサ３７が検出した外管４０の温度を入力したり、冷却流体供給源７０と流体出入口４６とを接続する配管の途中に設けられた開閉弁７２及び流量調整弁７４に制御信号を出力したりして、赤外線ヒーター３０ａ〜３０ｃの流路４８を流れる冷却流体の流量を個別に制御する。更に、コントローラー６０は、電力供給源８０からフィラメント３２へ供給される電力の大きさを調整するための制御信号を電力供給源８０へ出力して、赤外線ヒーター３０ａ〜３０ｃのフィラメント温度を個別に制御する。また、コントローラー６０は、ロール５４，５６の回転速度を制御することで炉体１４内の塗膜５２の通過時間を調整することができる。   The controller 60 is configured as a microprocessor centered on a CPU. This controller 60 outputs a control signal to the hot air generators 22a to 22f of the blower device 20, and individually controls the temperature and air volume of the hot air generated by the hot air generators 22a to 22f. Further, the controller 60 inputs the temperature of the outer pipe 40 detected by the temperature sensor 37 which is a thermocouple, and the open / close valve 72 provided in the middle of the pipe connecting the cooling fluid supply source 70 and the fluid inlet / outlet 46. A control signal is output to the flow rate adjusting valve 74 to individually control the flow rate of the cooling fluid flowing through the flow path 48 of the infrared heaters 30a to 30c. Further, the controller 60 outputs a control signal for adjusting the magnitude of the power supplied from the power supply source 80 to the filament 32 to the power supply source 80 to individually control the filament temperature of the infrared heaters 30a to 30c. To do. Further, the controller 60 can adjust the passage time of the coating film 52 in the furnace body 14 by controlling the rotation speed of the rolls 54 and 56.

シート５０は、特に限定するものではないが、例えば、アルミニウムや銅等の金属シートである。また、シート上の塗膜５２は、乾燥後に電池用の電極として用いられるものであり、特に限定するものではないが、例えばリチウムイオン二次電池用の電極となる塗膜である。塗膜５２としては、例えば、電極材（正極活物質又は負極活物質）とバインダーと導電材と溶剤とを共に混練した電極材ペーストを、シート５０上に塗布したもの等が上げられる。電極材は、正極活物質としてはコバルト酸リチウムなどが挙げられ、負極活物質としてはグラファイトなどの炭素材が挙げられる。バインダーとしては、ポリフッ化ビニリデン（ＰＶＤＦ）などが挙げられる。導電材としては、カーボン粉末などが挙げられる。溶剤としては、Ｎ−メチル−２−ピロリドン（ＮＭＰ）などが挙げられる。塗膜５２の厚みは、特に限定するものではないが、例えば５０〜１０００μｍである。塗膜の厚みは５０μｍ以下としてもよい。   Although the sheet | seat 50 is not specifically limited, For example, it is metal sheets, such as aluminum and copper. In addition, the coating film 52 on the sheet is used as an electrode for a battery after drying, and is not particularly limited. For example, the coating film 52 serves as an electrode for a lithium ion secondary battery. As the coating film 52, for example, an electrode material paste obtained by kneading an electrode material (positive electrode active material or negative electrode active material), a binder, a conductive material, and a solvent on the sheet 50 can be used. Examples of the electrode material include lithium cobaltate as the positive electrode active material, and carbon materials such as graphite as the negative electrode active material. Examples of the binder include polyvinylidene fluoride (PVDF). Examples of the conductive material include carbon powder. Examples of the solvent include N-methyl-2-pyrrolidone (NMP). Although the thickness of the coating film 52 is not specifically limited, For example, it is 50-1000 micrometers. The thickness of the coating film may be 50 μm or less.

次に、こうして構成された乾燥炉１０を用いて塗膜５２を乾燥する様子について説明する。まず、乾燥炉１０の左端に配置されたロール５４からシート５０が巻き外され、乾燥炉１０に搬入される直前に図示しないコーターによって上面に塗膜５２が塗布され、乾燥炉１０の開口１７を通って乾燥炉１０内へ搬入される。続いて、シート５０は、第１加熱領域１１，第２加熱領域１２，第３加熱領域１３を通過し、その間に送風装置２０及び赤外線ヒーター３０により加熱されることにより塗膜５２から溶剤が蒸発する。より具体的には、塗膜５２は、第１加熱領域１１を通過する際に送風装置２０ａ，２０ｄ及び赤外線ヒーター３０ａにより加熱され、第２加熱領域１２を通過する際に送風装置２０ｂ，２０ｅ及び赤外線ヒーター３０ｂにより加熱され、第３加熱領域１３を通過する際に送風装置２０ｃ，２０ｆ及び赤外線ヒーター３０ｃにより加熱される。なお、第１加熱領域１１，第２加熱領域１２，第３加熱領域１３における塗膜５２の加熱をそれぞれ第１加熱，第２加熱，第３加熱とも称する。塗膜５２から加熱により蒸発した溶剤は図示しない排気口から例えばブロワによって外部へ排出される。塗膜５２は、最終的に乾燥炉１０の開口１８から搬出され、乾燥炉１０の右端に設置されたロール５６にシート５０とともに巻き取られる。塗膜５２から溶剤が蒸発するのは、赤外線ヒーター３０から照射される赤外線と送風装置２０から供給される熱風の作用による。   Next, how the coating film 52 is dried using the thus configured drying furnace 10 will be described. First, the sheet 50 is unwound from the roll 54 disposed at the left end of the drying furnace 10, and immediately before being loaded into the drying furnace 10, the coating film 52 is applied to the upper surface by a coater (not shown), and the opening 17 of the drying furnace 10 is opened. It passes through the drying furnace 10. Subsequently, the sheet 50 passes through the first heating region 11, the second heating region 12, and the third heating region 13, and the solvent is evaporated from the coating film 52 by being heated by the blower 20 and the infrared heater 30 during that time. To do. More specifically, the coating film 52 is heated by the blower devices 20a and 20d and the infrared heater 30a when passing through the first heating region 11, and the blower devices 20b and 20e and when passing through the second heating region 12. When heated by the infrared heater 30b and passing through the third heating region 13, it is heated by the blowers 20c and 20f and the infrared heater 30c. In addition, the heating of the coating film 52 in the 1st heating area | region 11, the 2nd heating area | region 12, and the 3rd heating area | region 13 is also called 1st heating, 2nd heating, and 3rd heating, respectively. The solvent evaporated from the coating film 52 by heating is discharged to the outside from an exhaust port (not shown) by, for example, a blower. The coating film 52 is finally carried out from the opening 18 of the drying furnace 10, and is taken up together with the sheet 50 on a roll 56 installed at the right end of the drying furnace 10. The solvent evaporates from the coating film 52 due to the action of infrared rays irradiated from the infrared heater 30 and hot air supplied from the blower 20.

本実施形態の乾燥炉１０は、このように第１加熱領域１１，第２加熱領域１２，第３加熱領域１３において塗膜５２を加熱する際に、各加熱領域における塗膜５２からの溶剤の蒸発速度を制御するように構成されている。図４は、各加熱領域と塗膜５２からの溶剤の蒸発速度との関係を示す蒸発曲線の説明図である。図４において、時刻０〜時刻Ｔ１は塗膜５２が第１加熱領域１１を通過する期間を示し、時刻Ｔ１〜時刻Ｔ２は塗膜５２が第２加熱領域１２を通過する期間を示し、時刻Ｔ２〜時刻Ｔ３は塗膜５２が第３加熱領域１３を通過する期間を示している。まず、第１加熱領域１１においては、塗膜５２の蒸発速度は時刻０から時刻Ｔ１に向けて時間の経過とともに上昇していき、第１加熱領域１１における蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１は０．４ｍｇ／（ｓ・ｃｍ2）以上となっている。続いて、第２加熱領域１２においては、時刻Ｔ１から蒸発速度が急激に減少していき、その後、略一定の蒸発速度が保たれる。第２加熱領域１２における蒸発速度の平均値である第２平均蒸発速度Ｓｖａ２は、図示するように第１平均蒸発速度Ｓｖａ１未満となっている。そして、第３加熱領域１３においては、時刻Ｔ２から蒸発速度が急激に上昇し、時刻ｔ１〜ｔ２の期間は第２平均蒸発速度Ｓｖａ２よりも高い蒸発速度となる。その後、蒸発速度は第２平均蒸発速度Ｓｖａ２よりも小さい値になり、徐々に減少していく。第３加熱領域１３により塗膜５２の溶剤がほぼ全て蒸発するため、第３加熱領域１３の終了時である時刻Ｔ３では、蒸発速度はほぼ値０になる。本実施形態の乾燥炉１０は、予め図４に示した蒸発曲線が得られるように、送風装置２０の熱風の風量及び温度、赤外線ヒーター３０のフィラメント温度及び冷却流体の流量が例えば実験により定められているものとした。例えば、第１加熱領域１１においては送風装置２０ａ，２０ｄの熱風の温度を高温、風量を強風とし、赤外線ヒーター３０ａのフィラメント温度も高温として、急速に塗膜５２を加熱する。第２加熱領域１２においては、送風装置２０ｂ，２０ｅの熱風の温度を中温、風量を弱風とし、赤外線ヒーター３０ｂのフィラメント温度を低温として、第１加熱領域１１と比べて比較的弱く加熱する。第３加熱領域１３においては、送風装置２０ｃ、２０ｆの熱風の温度を高温、風量を強風とし、赤外線ヒーター３０ｃのフィラメント温度を高温として、第２加熱領域１２と比べて比較的強く加熱する。 When the drying furnace 10 of this embodiment heats the coating film 52 in the 1st heating area | region 11, the 2nd heating area | region 12, and the 3rd heating area | region 13 in this way, of the solvent from the coating film 52 in each heating area | region. It is configured to control the evaporation rate. FIG. 4 is an explanatory diagram of an evaporation curve showing the relationship between each heating region and the evaporation rate of the solvent from the coating film 52. 4, time 0 to time T1 indicate a period during which the coating film 52 passes through the first heating region 11, and time T1 to time T2 indicate a period during which the coating film 52 passes through the second heating region 12, and time T2. ~ Time T3 indicates a period during which the coating film 52 passes through the third heating region 13. First, in the 1st heating area | region 11, the evaporation rate of the coating film 52 rises with progress of time from the time 0 to the time T1, and the 1st average which is an average value of the evaporation rate in the 1st heating area | region 11 is carried out. The evaporation rate Sva1 is 0.4 mg / (s · cm 2 ) or more. Subsequently, in the second heating region 12, the evaporation rate decreases rapidly from time T1, and thereafter, a substantially constant evaporation rate is maintained. The second average evaporation rate Sva2, which is the average value of the evaporation rates in the second heating region 12, is less than the first average evaporation rate Sva1, as shown in the figure. And in the 3rd heating area | region 13, an evaporation rate rises rapidly from the time T2, and becomes a higher evaporation rate than 2nd average evaporation rate Sva2 during the period of time t1-t2. Thereafter, the evaporation rate becomes smaller than the second average evaporation rate Sva2 and gradually decreases. Since almost all of the solvent of the coating film 52 is evaporated by the third heating region 13, the evaporation rate becomes substantially zero at the time T3 when the third heating region 13 ends. In the drying furnace 10 of the present embodiment, the amount and temperature of hot air of the blower 20, the filament temperature of the infrared heater 30, and the flow rate of the cooling fluid are determined by experiments, for example, so that the evaporation curve shown in FIG. 4 is obtained in advance. It was supposed to be. For example, in the 1st heating area | region 11, the temperature of the hot air of the air blowers 20a and 20d is made into high temperature, the air volume is made into a strong wind, the filament temperature of the infrared heater 30a is also made into high temperature, and the coating film 52 is heated rapidly. In the 2nd heating area | region 12, it heats comparatively weakly compared with the 1st heating area | region 11 by making the temperature of the hot air of the air blowers 20b and 20e into a medium temperature, making an air volume into a weak wind, and making the filament temperature of the infrared heater 30b into a low temperature. In the 3rd heating area | region 13, compared with the 2nd heating area | region 12, the temperature of the hot air of the air blowers 20c and 20f is made into high temperature, the air volume is made into a strong wind, and the filament temperature of the infrared heater 30c is made into high temperature.

なお、第１加熱領域１１と第２加熱領域１２との境界である時刻Ｔ１は、塗膜５２の電極材が塗膜５２の表面に露出する時刻として定められている。ここで、塗膜５２から溶剤が蒸発して塗膜５２が薄くなるにつれて、塗膜５２の表面の反射率が変化する。一方、さらに溶剤の蒸発が進行して塗膜５２の表面に電極材が現れると、塗膜５２の表面の反射率はほとんど変化しなくなる。そこで、予め乾燥炉１０を通過する際の塗膜５２の表面の反射率を測定しておき、第１加熱領域１１と第２加熱領域１２との境界で塗膜５２の表面に電極材が現れるように、第１加熱領域１１における送風装置２０ａ，２０ｄ及び赤外線ヒーター３０ａの出力や第１加熱領域１１の長さ（図１の左右方向長さ）、シート５０の移動速度などを定めておくものとした。   The time T1 that is the boundary between the first heating region 11 and the second heating region 12 is determined as the time when the electrode material of the coating film 52 is exposed on the surface of the coating film 52. Here, as the solvent evaporates from the coating film 52 and the coating film 52 becomes thinner, the reflectance of the surface of the coating film 52 changes. On the other hand, when the evaporation of the solvent further proceeds and an electrode material appears on the surface of the coating film 52, the reflectance of the surface of the coating film 52 hardly changes. Therefore, the reflectance of the surface of the coating film 52 when passing through the drying furnace 10 is measured in advance, and the electrode material appears on the surface of the coating film 52 at the boundary between the first heating region 11 and the second heating region 12. As described above, the outputs of the blowers 20a and 20d and the infrared heater 30a in the first heating region 11, the length of the first heating region 11 (the length in the left-right direction in FIG. 1), the moving speed of the sheet 50, and the like are determined. It was.

以上のようにして図４の蒸発曲線に沿って塗膜５２の乾燥を行うことで、乾燥後の塗膜５２すなわち電極の厚さ方向におけるバインダーの分布がより均一化される。これについて以下説明する。加熱により塗膜５２の表層から溶剤が蒸発すると、溶剤の塗膜５２表層への移動に伴ってバインダーも表層へ移動する。バインダーは蒸発できないため、この移動により、塗膜の表層側のバインダー濃度は一時的に上昇する。しかし、塗膜の表層側のバインダー濃度が高まることにより、塗膜の表層側と下層側とでバインダーの濃度差が生じ、この濃度差が駆動力となって、表層から下層へバインダーの拡散が生じる（以下、これを逆拡散とも表記する）。塗膜５２を乾燥する際には、溶剤の蒸発に伴うバインダーの表層側への移動と、逆拡散によるバインダーの下層への移動との両方が起きていると考えられ、これらを適切に制御することでバインダーをより均一化することができる。本実施形態の乾燥炉１０では、第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上となるように第１加熱を行うことで塗膜５２の表層側のバインダー濃度が急激に上昇し、逆拡散の駆動力がより高いものとなると考えられる。また、電極材が塗膜の表面に露出した後の第２加熱における蒸発速度が高すぎると、溶剤の蒸発に伴い塗膜５２の表層側へバインダーが移動しやすくなったり、塗膜中の溶剤が早期に減少してしまい逆拡散の駆動力が高くてもバインダーが塗膜中を移動しにくくなってしまう。本実施形態の乾燥炉１０では、第２平均蒸発速度Ｓｖａ２が第１平均蒸発速度Ｓｖａ１未満となるように塗膜を加熱することで、バインダーが塗膜中を移動可能な期間を比較的長く確保でき、その間に逆拡散の駆動力によりバインダーが下層に移動して、バインダーの分布をより均一化できていると考えられる。このように、本実施形態の乾燥炉１０では、まず第１加熱により逆拡散の駆動力をより高くし、その後の第２加熱では、溶剤の蒸発に伴うバインダーの表層への移動を抑え、且つ逆拡散によりバインダーが下層に移動可能な期間をより長く確保することで、バインダーの分布をより均一化できていると考えられる。なお、第１平均蒸発速度Ｓｖａ１は０．４ｍｇ／（ｓ・ｃｍ2）以上１．０ｍｇ／（ｓ・ｃｍ2）以下であることが好ましい。第１平均蒸発速度Ｓｖａ１を１．０ｍｇ／（ｓ・ｃｍ2）以下とすることで、塗膜が乾燥過多となるのを抑制することができる。 As described above, the coating film 52 is dried along the evaporation curve of FIG. This will be described below. When the solvent evaporates from the surface layer of the coating film 52 by heating, the binder also moves to the surface layer as the solvent moves to the surface layer of the coating film 52. Since the binder cannot evaporate, the binder concentration on the surface layer side of the coating film temporarily rises due to this movement. However, as the binder concentration on the surface layer side of the coating film increases, a difference in binder concentration occurs between the surface layer side and the lower layer side of the coating film, and this concentration difference becomes a driving force, and the binder diffuses from the surface layer to the lower layer. Occurs (hereinafter also referred to as despreading). When the coating film 52 is dried, it is considered that both the movement of the binder to the surface layer side due to the evaporation of the solvent and the movement of the binder to the lower layer due to back diffusion occur, and these are appropriately controlled. Thus, the binder can be made more uniform. In the drying furnace 10 of this embodiment, the binder concentration on the surface layer side of the coating film 52 is rapidly increased by performing the first heating so that the first average evaporation rate Sva1 is 0.4 mg / (s · cm 2 ) or more. It is considered that the driving force of despreading is higher and higher. In addition, if the evaporation rate in the second heating after the electrode material is exposed on the surface of the coating film is too high, the binder easily moves to the surface layer side of the coating film 52 along with the evaporation of the solvent, or the solvent in the coating film Decreases at an early stage, and even if the driving force for back diffusion is high, it becomes difficult for the binder to move in the coating film. In the drying furnace 10 of the present embodiment, the coating film is heated so that the second average evaporation rate Sva2 is less than the first average evaporation rate Sva1, thereby ensuring a relatively long period during which the binder can move through the coating film. In the meantime, it is considered that the binder is moved to the lower layer by the driving force of reverse diffusion, and the distribution of the binder can be made more uniform. Thus, in the drying furnace 10 of the present embodiment, first, the driving force of back diffusion is further increased by the first heating, and in the subsequent second heating, the movement of the binder to the surface layer accompanying the evaporation of the solvent is suppressed, and It is considered that the distribution of the binder can be made more uniform by ensuring a longer period during which the binder can move to the lower layer by reverse diffusion. The first average evaporation rate Sva1 is preferably 0.4 mg / (s · cm 2 ) or more and 1.0 mg / (s · cm 2 ) or less. By setting the first average evaporation rate Sva1 to 1.0 mg / (s · cm 2 ) or less, it is possible to prevent the coating film from being excessively dried.

また、第１加熱領域１１においては、第１平均蒸発速度Ｓｖａ１以上となるまで第１加熱開始時から蒸発速度が上昇していき、その後第１加熱の終了まで蒸発速度を第１平均蒸発速度Ｓｖａ１以上の領域で維持することが好ましい。第１加熱領域１１においては、蒸発速度が０．５ｍｇ／（ｓ・ｃｍ2）以上，好ましくは０．６ｍｇ／（ｓ・ｃｍ2）以上，より好ましくは０．７ｍｇ／（ｓ・ｃｍ2）以上となる期間を有するように加熱することが好ましい。第１加熱領域１１においては、加熱開始から蒸発速度が０．６ｍｇ／（ｓ・ｃｍ2）以上となるまで加熱し、その後第１加熱の終了まで蒸発速度を０．６ｍｇ／（ｓ・ｃｍ2）以上１．０ｍｇ／（ｓ・ｃｍ2）以下の領域で維持することが好ましい。第２加熱領域１２においては、第２平均蒸発速度Ｓｖａ２は０．４ｍｇ／（ｓ・ｃｍ2）以下とすることが好ましい。第２加熱領域１２においては、第２平均蒸発速度Ｓｖａ２以下となるまで第２加熱開始時から蒸発速度が低下していき、その後第２加熱の終了まで蒸発速度を第２平均蒸発速度Ｓｖａ２以下の領域で維持することが好ましい。第２加熱領域１２においては、蒸発速度が値０．２ｍｇ／（ｓ・ｃｍ2）以下となるまで第２加熱開始時から蒸発速度が低下していき、その後第２加熱の終了まで蒸発速度を値０．０５ｍｇ／（ｓ・ｃｍ2）以上０．２ｍｇ／（ｓ・ｃｍ2）以下の領域で維持することが好ましい。 Further, in the first heating region 11, the evaporation rate increases from the start of the first heating until the first average evaporation rate Sva1 is equal to or higher than the first average evaporation rate Sva1, and then the evaporation rate is changed to the first average evaporation rate Sva1 until the end of the first heating. It is preferable to maintain in the above region. In the first heating region 11, the evaporation rate is 0.5 mg / (s · cm 2 ) or more, preferably 0.6 mg / (s · cm 2 ) or more, more preferably 0.7 mg / (s · cm 2 ). Heating is preferably performed so as to have the above-described period. In the 1st heating area | region 11, it heats until an evaporation rate will be 0.6 mg / (s * cm < 2 >) or more from the heating start, and after that, an evaporation rate is 0.6 mg / (s * cm < 2 > until the completion | finish of 1st heating. ) Is preferably maintained in the region of 1.0 mg / (s · cm 2 ) or less. In the second heating region 12, the second average evaporation rate Sva2 is preferably 0.4 mg / (s · cm 2 ) or less. In the second heating region 12, the evaporation rate decreases from the start of the second heating until the second average evaporation rate Sva2 or less, and then the evaporation rate is less than or equal to the second average evaporation rate Sva2 until the end of the second heating. It is preferable to maintain in the region. In the second heating region 12, the evaporation rate decreases from the start of the second heating until the evaporation rate reaches a value of 0.2 mg / (s · cm 2 ) or less, and then the evaporation rate is decreased until the end of the second heating. It is preferable to maintain in the region of 0.05 mg / (s · cm 2 ) or more and 0.2 mg / (s · cm 2 ) or less.

また、第３加熱領域１３では、塗膜５２の溶剤の蒸発速度が第２平均蒸発速度Ｓｖａ２よりも高くなる期間（時刻ｔ１〜ｔ２）を有する。これにより、第２加熱領域１２で塗膜５２の厚み方向のバインダーの分布を均一化した後に、速やかに残りの溶剤を蒸発させて全体の乾燥時間を短縮することができる。なお、図４における第２加熱領域１２と第３加熱領域１３との境界である時刻Ｔ２は、第２加熱領域１２においてバインダーが逆拡散により下層に移動して分布が均一化されるのに十分な時間を確保したあとの時刻であればよく、例えば実験により定めることができる。時刻Ｔ２は、例えば第２加熱領域１２における送風装置２０ｂ，２０ｅ及び赤外線ヒーター３０ｂの出力や第２加熱領域１２の長さ（図１の左右方向長さ）、シート５０の移動速度などを調整することによって定めることができる。なお、塗膜５２から溶剤がある程度蒸発すると、バインダーが移動しにくくなり、その後に溶剤が蒸発してもバインダーが表層に移動しにくくなる。そのため、バインダーの分布の均一化の観点からは、このようなバインダーが移動しにくくなる時刻以降になるように時刻Ｔ２を定めることが好ましい。   Moreover, in the 3rd heating area | region 13, it has a period (time t1-t2) when the evaporation rate of the solvent of the coating film 52 becomes higher than 2nd average evaporation rate Sva2. Thereby, after equalizing the binder distribution in the thickness direction of the coating film 52 in the second heating region 12, the remaining solvent can be quickly evaporated to shorten the entire drying time. It should be noted that time T2, which is the boundary between the second heating region 12 and the third heating region 13 in FIG. 4, is sufficient for the binder to move to the lower layer by back diffusion in the second heating region 12 and to make the distribution uniform. It is sufficient that the time is after a certain amount of time is secured, and can be determined by experiment, for example. At time T2, for example, the outputs of the blowers 20b and 20e and the infrared heater 30b in the second heating region 12, the length of the second heating region 12 (the length in the left-right direction in FIG. 1), the moving speed of the sheet 50, and the like are adjusted. Can be determined by When the solvent evaporates from the coating film 52 to some extent, the binder becomes difficult to move, and even if the solvent evaporates thereafter, the binder becomes difficult to move to the surface layer. Therefore, from the viewpoint of uniforming the binder distribution, it is preferable to set the time T2 so that it is after the time when such a binder becomes difficult to move.

ここで、本実施形態の構成要素と本発明の構成要素との対応関係を明らかにする。本実施形態の塗膜５２が電池用電極塗膜に相当し、第１加熱を行う送風装置２０ａ，２０ｄ及び赤外線ヒーター３０ａや、第２加熱を行う送風装置２０ｂ，２０ｅ及び赤外線ヒーター３０ｂやコントローラー６０が加熱手段に相当する。なお、本実施形態では、乾燥炉１０の動作を説明することにより本発明の電池用電極塗膜の乾燥方法の一例も明らかにしている。   Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The coating film 52 of the present embodiment corresponds to an electrode coating film for a battery, and the blowing devices 20a and 20d and the infrared heater 30a that perform the first heating, the blowing devices 20b and 20e and the infrared heater 30b that perform the second heating, and the controller 60. Corresponds to a heating means. In the present embodiment, an example of the method for drying the electrode coating film for a battery of the present invention is also clarified by explaining the operation of the drying furnace 10.

以上説明した第１実施形態の乾燥炉１０によれば、まず、電極材が塗膜５２の表面に露出するまでの間は、塗膜５２からの溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上となるように塗膜を加熱する第１加熱を行う。続いて、電極材が塗膜５２の表面に露出した後、塗膜５２の溶剤の蒸発速度の平均値である第２平均蒸発速度Ｓｖａ２が第１平均蒸発速度Ｓｖａ１未満となるように塗膜を加熱する第２加熱を行う。こうすることで、乾燥後の塗膜５２すなわち電極の、厚さ方向におけるバインダーの分布をより均一化することができる。また、塗膜５２の溶剤の蒸発速度が第２平均蒸発速度Ｓｖａ２超過となる期間を有するように塗膜５２を加熱する第３加熱を行うため、全体の乾燥時間を短縮することができる。さらに、塗膜５２の加熱は、赤外線及び熱風により行うため、赤外線も併用することで塗膜５２の表面だけでなく塗膜５２の内部の溶剤を速やかに加熱して蒸発させることができる。さらにまた、赤外線のうち近赤外線を用いて塗膜５２の加熱を行うため、塗膜５２の加熱や乾燥を効率よく行うことができる。 According to the drying furnace 10 of the first embodiment described above, first, the first average that is the average value of the evaporation rate of the solvent from the coating film 52 until the electrode material is exposed on the surface of the coating film 52. First heating is performed to heat the coating film so that the evaporation rate Sva1 is 0.4 mg / (s · cm 2 ) or more. Subsequently, after the electrode material is exposed on the surface of the coating film 52, the coating film is formed so that the second average evaporation rate Sva2, which is the average value of the evaporation rate of the solvent of the coating film 52, is less than the first average evaporation rate Sva1. Second heating is performed. By carrying out like this, the distribution of the binder in the thickness direction of the coating film 52 after drying, ie, an electrode, can be made more uniform. Moreover, since the 3rd heating which heats the coating film 52 so that it may have the period when the evaporation rate of the solvent of the coating film 52 exceeds 2nd average evaporation rate Sva2 can be performed, the whole drying time can be shortened. Furthermore, since the coating film 52 is heated by infrared rays and hot air, not only the surface of the coating film 52 but also the solvent inside the coating film 52 can be quickly heated and evaporated by using infrared rays together. Furthermore, since the coating film 52 is heated using near infrared rays in infrared rays, the coating film 52 can be efficiently heated and dried.

なお、本発明は上述した第１実施形態に何ら限定されることはなく、本発明の技術的範囲に属する限り種々の態様で実施し得ることはいうまでもない。   The present invention is not limited to the above-described first embodiment, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

例えば、上述した第１実施形態では、図４に示した蒸発曲線に従って塗膜５２の加熱を行うものとしたが、これに限られない。例えば、第１加熱は時刻０からＴ１に向けて時間の経過とともに蒸発速度が上昇するように行うものとしたが、第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上であればよく、例えば一度ピークを迎えたあと減少する期間を有していたり、複数のピークを有していたりしてもよい。また、第２平均蒸発速度Ｓｖａ２が第１平均蒸発速度Ｓｖａ１未満となるように塗膜を加熱する第２加熱を行うものとしたが、第２平均蒸発速度Ｓｖａ２は第１平均蒸発速度Ｓｖａ１と同じであってもよい。すなわち、第２平均蒸発速度Ｓｖａ２は第１平均蒸発速度Ｓｖａ１以下であればよい。ただし、溶剤の蒸発に伴うバインダーの表層への移動を抑え、且つ逆拡散によりバインダーが下層に移動可能な期間をより長く確保するためには、第２平均蒸発速度Ｓｖａ２は第１平均蒸発速度Ｓｖａ１未満とすることが好ましい。また、第２加熱は時刻Ｔ１から蒸発速度が急激に減少していき、その後、略一定の蒸発速度が保たれるものとしたが、これに限らず複数のピークを有していたりしてもよい。ただし、溶剤の蒸発に伴うバインダーの表層への移動を抑えるためには、第２加熱はなるべく一定の蒸発速度を保つように行うことが好ましい。あるいは、図４の第３加熱領域１３において、蒸発速度が第２平均蒸発速度Ｓｖａ２を上回る期間を有さないようにするものとしてもよい。さらに、第３加熱領域１３を省略するものとしてもよい。この場合、第２加熱領域１２により溶剤をほぼ全て蒸発させるようにすればよい。 For example, in the first embodiment described above, the coating film 52 is heated according to the evaporation curve shown in FIG. 4, but is not limited thereto. For example, the first heating is performed so that the evaporation rate increases with time from time 0 to T1, but the first average evaporation rate Sva1 is 0.4 mg / (s · cm 2 ) or more. For example, it may have a period of decreasing after reaching a peak once, or may have a plurality of peaks. In addition, the second heating for heating the coating film is performed so that the second average evaporation rate Sva2 is less than the first average evaporation rate Sva1, but the second average evaporation rate Sva2 is the same as the first average evaporation rate Sva1. It may be. That is, the second average evaporation rate Sva2 may be equal to or lower than the first average evaporation rate Sva1. However, in order to suppress the movement of the binder to the surface layer accompanying the evaporation of the solvent and to ensure a longer period during which the binder can move to the lower layer by reverse diffusion, the second average evaporation rate Sva2 is set to the first average evaporation rate Sva1. It is preferable to make it less than. In addition, in the second heating, the evaporation rate decreases rapidly from the time T1, and after that, a substantially constant evaporation rate is maintained. However, the second heating is not limited to this and may have a plurality of peaks. Good. However, in order to suppress the movement of the binder to the surface layer accompanying the evaporation of the solvent, it is preferable to perform the second heating so as to keep the evaporation rate as constant as possible. Alternatively, the third heating region 13 in FIG. 4 may not have a period in which the evaporation rate exceeds the second average evaporation rate Sva2. Further, the third heating region 13 may be omitted. In this case, almost all the solvent may be evaporated by the second heating region 12.

［第２実施形態］
次に、第２実施形態について説明する。なお、本実施形態の乾燥炉の構成は第１実施形態の乾燥炉１０と同じであるため、同じ符号を付して説明する。本実施形態では、第１実施形態で第１加熱において第１平均蒸発速度Ｓｖａ１が０．４ｍｇ／（ｓ・ｃｍ2）以上となるように塗膜５２を加熱するものとしたのに対し、第１平均蒸発速度Ｓｖａ１が次式（１）を満たすように塗膜５２を加熱するものとした点が異なる。なお、式（１）の初期溶剤質量割合Ｒの導出式における「乾燥開始時の電極材ペースト質量（ｍｇ）」は、本実施形態では、例えば乾燥炉１０の開口１７を通過する際など、第１加熱が開始されるとき（第１加熱が開始される直前）の電極材ペースト（塗膜５２）の質量を意味する。また、「乾燥開始時の溶剤質量（ｍｇ）」は、本実施形態では、第１加熱開始時の電極材ペースト中の溶剤の質量を意味する。すなわち、式（１）における初期溶剤質量割合Ｒ（％）とは、乾燥開始時（第１加熱開始時）において、電極材ペーストの質量を１００としたときの電極材ペースト中の溶剤の質量を意味する。初期溶剤質量割合Ｒは０超過１００未満の値である。また、補正後初期溶剤質量割合Ｒａは、初期塗膜厚みｔ（μｍ）及び乾燥時間Ｔ（ｓ）に基づいて初期溶剤質量割合Ｒの値を補正した値である。式（１）は、初期溶剤質量割合Ｒから導出した補正後初期溶剤質量割合Ｒａを用いる式になっている。ここで、初期塗膜厚みｔは、乾燥開始時（第１加熱開始時）における塗膜５２の厚み、すなわち乾燥前（乾燥直前）の厚みを意味する。また、乾燥時間Ｔは、塗膜５２の乾燥工程に要する時間を意味し、本実施形態では、塗膜５２が乾燥炉１０の開口１７を通過してから開口１８を通過するまでの時間である。換言すると、乾燥時間Ｔは、第１加熱開始時から第３加熱終了時までの時間である。補正後初期溶剤質量割合Ｒａは、導出式からわかるように、初期塗膜厚みｔに比例し乾燥時間Ｔに反比例しており、初期塗膜厚みｔの値が大きいほど、乾燥時間Ｔの値が小さいほど、大きい値が導出されるようになっている。また、乾燥時間Ｔと初期塗膜厚みｔとの関係がＴ＝０．４ｔを満たすときには、補正後初期溶剤質量割合Ｒａ＝初期溶剤質量割合Ｒとなり、初期溶剤質量割合Ｒを補正する必要がない。これは、式（１）がＴ＝０．４ｔを満たす場合を基準として導出されたものだからである。なお、式（１）は乾燥時間Ｔと初期塗膜厚みｔとの関係がＴ＝０．４ｔを満たす場合に限らず適用可能であるが、０．３ｔ≦Ｔ≦０．５ｔであることが好ましく、Ｔ＝０．４ｔであることがより好ましい。 [Second Embodiment]
Next, a second embodiment will be described. In addition, since the structure of the drying furnace of this embodiment is the same as the drying furnace 10 of 1st Embodiment, it attaches | subjects and demonstrates the same code | symbol. In the present embodiment, the coating film 52 is heated so that the first average evaporation rate Sva1 is 0.4 mg / (s · cm 2 ) or more in the first heating in the first embodiment, whereas The difference is that the coating film 52 is heated so that one average evaporation rate Sva1 satisfies the following formula (1). In the present embodiment, the “electrode material paste mass (mg) at the start of drying” in the derivation formula for the initial solvent mass ratio R in Formula (1) is, for example, when passing through the opening 17 of the drying furnace 10. It means the mass of the electrode material paste (coating film 52) when one heating is started (immediately before the first heating is started). Further, “solvent mass (mg) at the start of drying” means the mass of the solvent in the electrode material paste at the start of the first heating in the present embodiment. That is, the initial solvent mass ratio R (%) in the formula (1) is the mass of the solvent in the electrode material paste when the mass of the electrode material paste is 100 at the start of drying (at the start of the first heating). means. The initial solvent mass ratio R is a value exceeding 0 and less than 100. The corrected initial solvent mass ratio Ra is a value obtained by correcting the initial solvent mass ratio R based on the initial coating film thickness t (μm) and the drying time T (s). Expression (1) is an expression using the corrected initial solvent mass ratio Ra derived from the initial solvent mass ratio R. Here, the initial coating film thickness t means the thickness of the coating film 52 at the start of drying (at the start of the first heating), that is, the thickness before drying (immediately before drying). Moreover, the drying time T means the time required for the drying process of the coating film 52, and in this embodiment, it is the time from the coating film 52 passing through the opening 17 of the drying furnace 10 to passing through the opening 18. . In other words, the drying time T is the time from the start of the first heating to the end of the third heating. As can be seen from the derivation formula, the corrected initial solvent mass ratio Ra is proportional to the initial coating film thickness t and inversely proportional to the drying time T. The larger the initial coating film thickness t, the larger the value of the drying time T. A smaller value is derived as the value is smaller. Further, when the relationship between the drying time T and the initial coating film thickness t satisfies T = 0.4t, the corrected initial solvent mass ratio Ra = the initial solvent mass ratio R, and there is no need to correct the initial solvent mass ratio R. . This is because the expression (1) is derived on the basis of the case where T = 0.4t is satisfied. Equation (1) is applicable not only when the relationship between the drying time T and the initial coating film thickness t satisfies T = 0.4t, but 0.3t ≦ T ≦ 0.5t. Preferably, T = 0.4t.

Figure 0005259875
Figure 0005259875

図５は、第１平均蒸発速度Ｓｖａ１と補正後初期溶剤質量割合Ｒａ（％）との関係を示す説明図である。第１平均蒸発速度Ｓｖａ１が式（１）を満たす（図５の領域Ａに含まれる）ように第１加熱を行うことで、電極の厚さ方向におけるバインダーの分布をより均一化することができる。なお、図５の領域Ａは後述する領域Ｂを含む領域である。このようにして第１加熱を行うことでバインダーの分布をより均一化できる理由は以下のように考えられる。まず、第１平均蒸発速度Ｓｖａ１が上記式（１）の下限（＝０．００００４Ｒａ2＋０．００２８６Ｒａ）以上となるように塗膜５２を加熱することで塗膜５２の表層側のバインダー濃度が急激に上昇し、逆拡散の駆動力がより高いものとなると考えられる。そして、逆拡散の駆動力がより高いものとなることで、電極材が塗膜５２の表面に露出した後の期間において逆拡散の駆動力によりバインダーが塗膜５２の下層側に移動して、バインダーの分布をより均一化できていると考えられる。また、第１加熱における蒸発速度が高すぎると、塗膜５２中の溶剤が早期に減少してしまい、逆拡散の駆動力が高くてもバインダーが塗膜５２中を移動しにくくなってしまう。第１平均蒸発速度Ｓｖａ１を上記式（１）の上限（＝０．００００３Ｒａ2＋０．００８３２Ｒａ）以下とすることで、逆拡散の駆動力によりバインダーが塗膜５２の下層に移動可能な期間を確保でき、バインダーの分布をより均一化できていると考えられる。 FIG. 5 is an explanatory diagram showing the relationship between the first average evaporation rate Sva1 and the corrected initial solvent mass ratio Ra (%). By performing the first heating so that the first average evaporation rate Sva1 satisfies the formula (1) (included in the region A in FIG. 5), the distribution of the binder in the thickness direction of the electrode can be made more uniform. . In addition, the area | region A of FIG. 5 is an area | region containing the area | region B mentioned later. The reason why the binder distribution can be made more uniform by performing the first heating in this way is considered as follows. First, the binder concentration on the surface layer side of the coating film 52 is rapidly increased by heating the coating film 52 so that the first average evaporation rate Sva1 is equal to or higher than the lower limit (= 0.00004Ra 2 + 0.00286Ra) of the above formula (1). It is considered that the driving force for despreading becomes higher. And, since the driving force of reverse diffusion becomes higher, the binder moves to the lower layer side of the coating film 52 by the driving force of reverse diffusion in the period after the electrode material is exposed on the surface of the coating film 52, It is considered that the binder distribution can be made more uniform. Further, if the evaporation rate in the first heating is too high, the solvent in the coating film 52 is reduced at an early stage, and the binder is difficult to move through the coating film 52 even if the driving force for reverse diffusion is high. By ensuring that the first average evaporation rate Sva1 is not more than the upper limit (= 0.00003Ra 2 + 0.00832Ra) of the above formula (1), a period during which the binder can move to the lower layer of the coating film 52 by the driving force of back diffusion is secured. It is considered that the distribution of the binder can be made more uniform.

なお、図５の領域Ａのように、第１平均蒸発速度Ｓｖａ１の値が式（１）を満たしていればよく、第２加熱領域１２や第３加熱領域１３における蒸発速度は第１実施形態と異なるものとしてもよい。例えば、第２平均蒸発速度Ｓｖａ２の値は必ずしも第１平均蒸発速度Ｓｖａ１以下である必要はない。また、第３加熱領域１３において、蒸発速度が第２平均蒸発速度Ｓｖａ２を上回る期間を有してもよいし、有さなくてもよい。   As in the area A of FIG. 5, the value of the first average evaporation rate Sva1 only needs to satisfy the formula (1), and the evaporation rate in the second heating area 12 and the third heating area 13 is the same as that in the first embodiment. And may be different. For example, the value of the second average evaporation rate Sva2 is not necessarily equal to or less than the first average evaporation rate Sva1. Moreover, in the 3rd heating area | region 13, it may have the period when an evaporation rate exceeds 2nd average evaporation rate Sva2, and does not need to have it.

また、第１平均蒸発速度Ｓｖａ１の値が式（１）の上限付近や下限付近から離れているほど、バインダーの分布をより均一化できる効果は高まる。すなわち、第１平均蒸発速度Ｓｖａ１の値は領域Ａのうちの図５に示す最適ライン（Ｓｖａ１＝０．００００５Ｒａ2＋０．００５２Ｒａ）に近いほど好ましい。例えば、第１平均蒸発速度Ｓｖａ１が次式（２）を満たす（図５の領域Ｂに含まれる）ように塗膜５２を加熱することが好ましい。また、第１平均蒸発速度Ｓｖａ１の値が図５に示す最適ライン上であることがより好ましい。 In addition, as the value of the first average evaporation rate Sva1 is farther from the vicinity of the upper limit or the lower limit of the expression (1), the effect of making the binder distribution more uniform increases. That is, the value of the first average evaporation rate Sva1 is preferably closer to the optimum line (Sva1 = 0.00005Ra 2 + 0.0052Ra) shown in FIG. For example, the coating film 52 is preferably heated so that the first average evaporation rate Sva1 satisfies the following formula (2) (included in the region B in FIG. 5). Further, it is more preferable that the value of the first average evaporation rate Sva1 is on the optimum line shown in FIG.

Figure 0005259875
Figure 0005259875

以上説明した第２実施形態の乾燥炉１０によれば、電極材が塗膜５２の表面に露出するまでの間は、塗膜５２からの溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１が上記式（１）を満たすように塗膜５２を加熱する工程を行うため、乾燥後の塗膜５２すなわち電極の、厚さ方向におけるバインダーの分布をより均一化することができる。また、第１平均蒸発速度Ｓｖａ１が上記式（２）を満たすようにすることで、上述したバインダーの分布を均一化する効果がより高いものとなる。   According to the drying furnace 10 of the second embodiment described above, the first average evaporation rate that is an average value of the evaporation rate of the solvent from the coating film 52 until the electrode material is exposed on the surface of the coating film 52. Since the step of heating the coating film 52 is performed so that Sva1 satisfies the above formula (1), the distribution of the binder in the thickness direction of the coating film 52 after drying, that is, the electrode, can be made more uniform. In addition, when the first average evaporation rate Sva1 satisfies the above formula (2), the above-described effect of making the binder distribution uniform is higher.

なお、本発明は上述した第２実施形態に何ら限定されることはなく、本発明の技術的範囲に属する限り種々の態様で実施し得ることはいうまでもない。   The present invention is not limited to the second embodiment described above, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

例えば、上述した第２実施形態において、第３加熱領域１３を省略するものとしてもよい。この場合、第２加熱領域１２により溶剤をほぼ全て蒸発させるようにすればよい。   For example, in the second embodiment described above, the third heating region 13 may be omitted. In this case, almost all the solvent may be evaporated by the second heating region 12.

上述した第１，第２実施形態では、送風装置２０及び赤外線ヒーター３０により乾燥を行うものとしたが、第１実施形態では各加熱領域における蒸発速度が上述した範囲となるように加熱ができればよく、送風装置２０の構成や赤外線ヒーター３０の構成はこれに限られない。同様に、第２実施形態では第１平均蒸発速度Ｓｖａ１の値が式（１）を満たすように乾燥ができればよく、送風装置２０の構成や赤外線ヒーター３０の構成はこれに限られない。例えば、通気口２６の数や、赤外線ヒーター３０ａ，３０ｂ，３０ｃの配置位置，本数などは適宜変更可能である。例えば、赤外線ヒーター３０ａ，３０ｂ，３０ｃの配置や本数を同一としてもよい。送風装置２０ｄ，２０ｅ，２０ｆを省略するものとしたり、赤外線ヒーター３０を図１におけるシート５０の下側にも配置するものとしたりしてもよい。また、送風装置２０と赤外線ヒーター３０の一方を備えない構成としたり、送風装置２０や赤外線ヒーター３０以外の加熱手段により塗膜５２を乾燥させるものとしたりしてもよい。   In the first and second embodiments described above, drying is performed by the blower 20 and the infrared heater 30. However, in the first embodiment, it is sufficient if heating can be performed so that the evaporation rate in each heating region is in the above-described range. The configuration of the blower 20 and the configuration of the infrared heater 30 are not limited to this. Similarly, in the second embodiment, it is only necessary to be able to dry so that the value of the first average evaporation rate Sva1 satisfies the formula (1), and the configuration of the blower 20 and the configuration of the infrared heater 30 are not limited thereto. For example, the number of vent holes 26, the arrangement positions and the number of infrared heaters 30a, 30b, and 30c can be changed as appropriate. For example, the arrangement and number of the infrared heaters 30a, 30b, and 30c may be the same. The blower devices 20d, 20e, and 20f may be omitted, or the infrared heater 30 may be disposed below the seat 50 in FIG. Moreover, you may make it the structure which does not provide either the ventilation apparatus 20 and the infrared heater 30, or shall dry the coating film 52 with heating means other than the ventilation apparatus 20 or the infrared heater 30.

上述した第１，第２実施形態では、乾燥炉１０が１つの炉体１４を備えており、炉体１４の中に第１加熱領域１１，第２加熱領域１２，第３加熱領域１３を備えるものとしたが、これに限られない。例えば、乾燥炉１０が第１加熱を行うユニットと、第２加熱を行うユニットと、第３加熱を行うユニットとを連ねて構成したものであるなど、乾燥炉１０が複数のユニットからなるものであってもよい。この場合、各ユニットで塗膜５２の通過時間（塗膜５２の搬送速度）を変えてもよい。   In the first and second embodiments described above, the drying furnace 10 includes one furnace body 14, and the first heating area 11, the second heating area 12, and the third heating area 13 are included in the furnace body 14. It was supposed to be, but it is not limited to this. For example, the drying furnace 10 is composed of a plurality of units, such as a unit in which the drying furnace 10 is connected to a unit that performs the first heating, a unit that performs the second heating, and a unit that performs the third heating. There may be. In this case, you may change the passage time (coating speed of the coating film 52) of the coating film 52 in each unit.

上述した第１，第２実施形態では、乾燥炉１０は、ロール５４，５６が回転することによりシート５０及び塗膜５２を搬送することで、ロール５４，５６が第１加熱領域１１に塗膜５２を移動し、電極材が塗膜５２の表面に露出した後に第２加熱領域１２に塗膜５２を移動し、その後に塗膜５２を第３加熱領域１３に移動するものとしたが、これに限られない。例えば、塗膜５２を搬送せずに、赤外線ヒーター及び送風装置の出力を調整することにより上述した蒸発速度が得られるように塗膜５２を乾燥するものであってもよい。例えば、塗膜５２を乾燥炉内に固定しておき、コントローラーが、まず上述した第１加熱を行うように赤外線ヒーター及び送風装置の出力を制御し、続いて電極材が塗膜５２の表面に露出した後に上述した第２加熱を行うように赤外線ヒーター及び送風装置の出力を制御し、その後に上述した第３加熱を行うように赤外線ヒーター及び送風装置の出力を制御するものとしてもよい。   In the first and second embodiments described above, the drying furnace 10 conveys the sheet 50 and the coating film 52 by rotating the rolls 54 and 56, so that the rolls 54 and 56 are applied to the first heating region 11. 52, and after the electrode material is exposed on the surface of the coating film 52, the coating film 52 is moved to the second heating area 12, and then the coating film 52 is moved to the third heating area 13. Not limited to. For example, you may dry the coating film 52 so that the evaporation rate mentioned above may be obtained by adjusting the output of an infrared heater and an air blower, without conveying the coating film 52. FIG. For example, the coating film 52 is fixed in the drying furnace, and the controller first controls the output of the infrared heater and the blower so as to perform the first heating described above, and then the electrode material is applied to the surface of the coating film 52. It is good also as what controls the output of an infrared heater and an air blower so that the 3rd heating mentioned above may be performed after controlling the output of an infrared heater and an air blower so that the 2nd heating mentioned above may be performed after exposure.

上述した第１，第２実施形態では、送風装置２０や赤外線ヒーター３０の出力は予め実験により定められているものとしたが、可変としてもよい。この場合、例えば、塗膜５２から蒸発した溶剤の蒸発量を検出する蒸発量センサを炉体１４内の各加熱領域に複数取り付け、これに基づいてコントローラー６０が送風装置２０及び赤外線ヒーター３０の出力を制御するものとしてもよい。より具体的には、この蒸発量センサからの検出信号を入力したコントローラー６０が、蒸発量センサからの検出信号に基づく蒸発速度が予め定めた蒸発曲線に近づくように駆動信号を出力して、送風装置２０及び赤外線ヒーター３０の出力を制御するものとしてもよい。   In the first and second embodiments described above, the outputs of the blower 20 and the infrared heater 30 are determined in advance by experiments, but may be variable. In this case, for example, a plurality of evaporation amount sensors for detecting the evaporation amount of the solvent evaporated from the coating film 52 are attached to each heating region in the furnace body 14, and based on this, the controller 60 outputs the blower 20 and the infrared heater 30. It is good also as what controls. More specifically, the controller 60 that has input the detection signal from the evaporation amount sensor outputs a drive signal so that the evaporation rate based on the detection signal from the evaporation amount sensor approaches a predetermined evaporation curve. It is good also as what controls the output of the apparatus 20 and the infrared heater 30. FIG.

上述した第１，第２実施形態において、搬送通路１９には、シート５０を下方から支える支持ローラを数個設けてもよい。こうすれば、重力によってシート５０が撓むのを防止することができる。   In the first and second embodiments described above, the conveying path 19 may be provided with several support rollers that support the sheet 50 from below. In this way, it is possible to prevent the sheet 50 from being bent by gravity.

上述した第１，第２実施形態では、赤外線ヒーター３０として、フィラメント３２の外周が３．５μｍを超える波長の赤外線を吸収するフィルタとして機能する複数の管３６，４０によって同心円状に覆われ、これらの複数の管３６，４０の間に赤外線ヒーター３０の表面温度の上昇を抑制する冷却流体の流路４８を形成したものを用いたが、その他の赤外線ヒーターを用いても構わない。また、赤外線ヒーター以外の他のヒーターを用いてもよい。   In the first and second embodiments described above, as the infrared heater 30, the outer periphery of the filament 32 is concentrically covered by a plurality of tubes 36 and 40 that function as filters that absorb infrared rays having a wavelength exceeding 3.5 μm. The cooling fluid channel 48 that suppresses the increase in the surface temperature of the infrared heater 30 is formed between the plurality of tubes 36 and 40, but other infrared heaters may be used. Moreover, you may use heaters other than an infrared heater.

上述した第１，第２実施形態では、各乾燥炉１０の雰囲気ガスとして空気を用いたが、空気の代わりに窒素などの不活性ガスを用いてもよい。   In the first and second embodiments described above, air is used as the atmosphere gas of each drying furnace 10, but an inert gas such as nitrogen may be used instead of air.

［実験例１］
図１〜３に示した構成の乾燥炉１０を実験例１とした。なお、炉体１４のうち第１加熱領域１１，第２加熱領域１２，第３加熱領域１３の長さ（図１の左右方向長さ）はそれぞれ２ｍとし、乾燥時間Ｔは８０ｓ（シート５０の搬送速度が４．５ｍ／ｍｉｎ）とした。塗膜５２を塗布するシート５０は幅約６００ｍｍ、厚み２０μｍのアルミニウムとし、炉体１４に入る前のシート上の初期塗膜厚みｔは２００μｍ（ｗｅｔ），とした。これにより、乾燥時間Ｔと初期塗膜厚みｔとの関係はＴ＝０．４ｔを満たしている。また、塗膜５２は、リチウム二次電池の電極用塗膜とし、電極材としてのコバルト酸リチウムと、バインダーとしてのＰＶＤＦと、導電材としてのカーボン粉末と、溶剤としてのＮＭＰとを混練した電極材ペーストからなるものとした。また、乾燥開始時の溶剤質量は８８８ｋｇ／ｍ3，乾燥開始時の電極材ペースト質量は１４８０ｋｇ／ｍ3とした。すなわち、初期溶剤質量割合Ｒを６０％とした。塗膜５２を乾燥する（乾燥後の塗膜５２中の溶剤の質量割合が１０００ｐｐｍ以下となるようにする）にあたり、赤外線ヒーター３０（赤外線ヒーター３０ａ〜３０ｃ）のフィラメント温度を１０００℃〜１７００℃の範囲で調整し、送風装置２０（熱風発生器２２ａ〜２２ｆ）の熱風の温度を４０℃〜１５０℃，風量を１００Ｎｍ3／ｈ〜７００Ｎｍ3／ｈの範囲で調整して、第１平均蒸発速度Ｓｖａ１が０．２９２ｍｇ／（ｓ・ｃｍ2）となるようにした。赤外線ヒーター３０ａ〜３０ｃの流路４８には冷却流体として所定流量の空気を流すものとし、外管４０の外周面温度が２００℃以下に維持されるようにした。 [Experimental Example 1]
The drying furnace 10 having the configuration shown in FIGS. In addition, the length (left-right direction length of FIG. 1) of the 1st heating area | region 11, the 2nd heating area | region 12, and the 3rd heating area | region 13 among the furnace bodies 14 shall be 2 m, respectively, and the drying time T shall be 80 s (sheet 50 The conveyance speed was 4.5 m / min). The sheet 50 on which the coating film 52 was applied was aluminum having a width of about 600 mm and a thickness of 20 μm, and the initial coating thickness t on the sheet before entering the furnace body 14 was 200 μm (wet). Thereby, the relationship between the drying time T and the initial coating film thickness t satisfies T = 0.4t. The coating film 52 is a coating film for an electrode of a lithium secondary battery, and is an electrode obtained by kneading lithium cobaltate as an electrode material, PVDF as a binder, carbon powder as a conductive material, and NMP as a solvent. The material paste was used. The solvent mass at the start of drying was 888 kg / m 3 , and the electrode material paste mass at the start of drying was 1480 kg / m 3 . That is, the initial solvent mass ratio R was 60%. In drying the coating film 52 (so that the mass ratio of the solvent in the coating film 52 after drying is 1000 ppm or less), the filament temperature of the infrared heater 30 (infrared heaters 30a to 30c) is 1000 ° C to 1700 ° C. was adjusted in the range, 40 ° C. to 150 DEG ° C. the temperature of the hot air blower 20 (hot air generator 22 a to 22 f), by adjusting the air volume in the range of 100Nm 3 / h~700Nm 3 / h, the first average evaporation rate Sva1 was set to 0.292 mg / (s · cm 2 ). A predetermined flow rate of air was allowed to flow as a cooling fluid in the flow path 48 of the infrared heaters 30a to 30c, and the outer peripheral surface temperature of the outer tube 40 was maintained at 200 ° C. or lower.

なお、塗膜５２の第１平均蒸発速度Ｓｖａ１は以下のようにして求めた。まず、塗膜５２の蒸発速度を以下のようにして算出した。シート５０に塗膜５２を塗布した際の塗膜５２の質量を測定し、第１加熱時の電極材ペ−スト質量（初期質量）とした。次に、塗膜５２を塗布したシート５０が開口１７から炉体１４に入り、第１加熱領域１１を通過した直後の位置を測定ポイントとして、この測定ポイントに塗膜５２が到達するまで加熱・送風を行った。測定ポイントに到達後は加熱・送風を停止し、炉体１４の開口１８から出た塗膜５２を取り出して、塗膜５２の質量を測定した。この質量を、第１加熱後の塗膜５２の質量とした。そして、この第１加熱後の塗膜５２の質量と初期質量との差を、第１加熱領域１１を通過する際の移動時間で除した値として、第１平均蒸発速度Ｓｖａ１を算出した。   In addition, 1st average evaporation rate Sva1 of the coating film 52 was calculated | required as follows. First, the evaporation rate of the coating film 52 was calculated as follows. The mass of the coating film 52 when the coating film 52 was applied to the sheet 50 was measured and used as the electrode material paste mass (initial mass) during the first heating. Next, the sheet 50 on which the coating film 52 is applied enters the furnace body 14 through the opening 17, and the position immediately after passing through the first heating region 11 is taken as a measurement point. Blowing was performed. After reaching the measurement point, heating and air blowing were stopped, the coating film 52 exiting from the opening 18 of the furnace body 14 was taken out, and the mass of the coating film 52 was measured. This mass was defined as the mass of the coating film 52 after the first heating. And 1st average evaporation rate Sva1 was computed as a value which remove | divided the difference of the mass of the coating film 52 after this 1st heating, and initial mass by the movement time at the time of passing through the 1st heating area | region 11. FIG.

［実験例２〜７］
赤外線ヒーター３０ａ〜３０ｃのフィラメント温度，熱風発生器２２ａ〜２２ｆからの熱風の温度及び風量を、上述した範囲で実験例１から変更することで第１平均蒸発速度Ｓｖａ１を種々変更したものを実験例２〜７とした。実験例２〜７の乾燥炉１０のそれ以外の構成は、実験例１と同じとした。具体的には、実験例２は、第１平均蒸発速度Ｓｖａ１を０．３８１ｍｇ／（ｓ・ｃｍ2）とした。実験例３は、第１平均蒸発速度Ｓｖａ１を０．４２７ｍｇ／（ｓ・ｃｍ2）とした。実験例４は、第１平均蒸発速度Ｓｖａ１を０．４３４ｍｇ／（ｓ・ｃｍ2）とした。実験例５は、第１平均蒸発速度Ｓｖａ１を０．４７７ｍｇ／（ｓ・ｃｍ2）とした。実験例６は、第１平均蒸発速度Ｓｖａ１を０．５３５ｍｇ／（ｓ・ｃｍ2）とした。実験例７は、第１平均蒸発速度Ｓｖａ１を０．５７９ｍｇ／（ｓ・ｃｍ2）とした。 [Experimental Examples 2 to 7]
Experimental examples in which the filament temperature of the infrared heaters 30a to 30c, the temperature of the hot air from the hot air generators 22a to 22f, and the air volume are changed from the experimental example 1 in the above-described range, and the first average evaporation rate Sva1 is variously changed. 2-7. The other configuration of the drying furnace 10 of Experimental Examples 2 to 7 was the same as that of Experimental Example 1. Specifically, in Experimental Example 2, the first average evaporation rate Sva1 was set to 0.381 mg / (s · cm 2 ). In Experimental Example 3, the first average evaporation rate Sva1 was set to 0.427 mg / (s · cm 2 ). In Experimental Example 4, the first average evaporation rate Sva1 was 0.434 mg / (s · cm 2 ). In Experimental Example 5, the first average evaporation rate Sva1 was 0.477 mg / (s · cm 2 ). In Experimental Example 6, the first average evaporation rate Sva1 was set to 0.535 mg / (s · cm 2 ). In Experimental Example 7, the first average evaporation rate Sva1 was set to 0.579 mg / (s · cm 2 ).

［実験例８〜１４］
初期溶剤質量割合Ｒを５０％（乾燥開始時の溶剤質量は８３０ｋｇ／ｍ3，乾燥開始時の電極材ペースト質量は１６６０ｋｇ／ｍ3）とし、赤外線ヒーター３０ａ〜３０ｃのフィラメント温度，熱風発生器２２ａ〜２２ｆからの熱風の温度及び風量を、上述した範囲で実験例１から変更することで第１平均蒸発速度Ｓｖａ１を種々変更したものを実験例８〜１４とした。実験例８〜１４の乾燥炉１０のそれ以外の構成は、実験例１と同じとした。具体的には、実験例８は、第１平均蒸発速度Ｓｖａ１を０．２６１ｍｇ／（ｓ・ｃｍ2）とした。実験例９は、第１平均蒸発速度Ｓｖａ１を０．３１２ｍｇ／（ｓ・ｃｍ2）とした。実験例１０は、第１平均蒸発速度Ｓｖａ１を０．３５４ｍｇ／（ｓ・ｃｍ2）とした。実験例１１は、第１平均蒸発速度Ｓｖａ１を０．３８２ｍｇ／（ｓ・ｃｍ2）とした。実験例１２は、第１平均蒸発速度Ｓｖａ１を０．４２１ｍｇ／（ｓ・ｃｍ2）とした。実験例１３は、第１平均蒸発速度Ｓｖａ１を０．４４９ｍｇ／（ｓ・ｃｍ2）とした。実験例１４は、第１平均蒸発速度Ｓｖａ１を０．４８０ｍｇ／（ｓ・ｃｍ2）とした。 [Experimental Examples 8 to 14]
Initial solvent mass ratio R is 50% (solvent mass at the start of drying is 830 kg / m 3 , electrode material paste mass at the start of drying is 1660 kg / m 3 ), filament temperature of infrared heaters 30a-30c, hot air generator 22a Experimental examples 8 to 14 were obtained by changing the first average evaporation rate Sva1 variously by changing the temperature and air volume of hot air from ˜22f from Experimental Example 1 within the above-described range. The other configuration of the drying furnace 10 of Experimental Examples 8 to 14 was the same as that of Experimental Example 1. Specifically, in Experimental Example 8, the first average evaporation rate Sva1 was set to 0.261 mg / (s · cm 2 ). In Experimental Example 9, the first average evaporation rate Sva1 was set to 0.312 mg / (s · cm 2 ). In Experimental Example 10, the first average evaporation rate Sva1 was set to 0.354 mg / (s · cm 2 ). In Experimental Example 11, the first average evaporation rate Sva1 was set to 0.382 mg / (s · cm 2 ). In Experimental Example 12, the first average evaporation rate Sva1 was 0.421 mg / (s · cm 2 ). In Experimental Example 13, the first average evaporation rate Sva1 was set to 0.449 mg / (s · cm 2 ). In Experimental Example 14, the first average evaporation rate Sva1 was set to 0.480 mg / (s · cm 2 ).

［実験例１５〜２０］
初期溶剤質量割合Ｒを４０％（乾燥開始時の溶剤質量は７５６ｋｇ／ｍ3，乾燥開始時の電極材ペースト質量は１８９０ｋｇ／ｍ3）とし、赤外線ヒーター３０ａ〜３０ｃのフィラメント温度，熱風発生器２２ａ〜２２ｆからの熱風の温度及び風量を、上述した範囲で実験例１から変更することで第１平均蒸発速度Ｓｖａ１を種々変更したものを実験例１５〜２０とした。実験例１５〜２０の乾燥炉１０のそれ以外の構成は、実験例１と同じとした。具体的には、実験例１５は、第１平均蒸発速度Ｓｖａ１を０．１９４ｍｇ／（ｓ・ｃｍ2）とした。実験例１６は、第１平均蒸発速度Ｓｖａ１を０．２１３ｍｇ／（ｓ・ｃｍ2）とした。実験例１７は、第１平均蒸発速度Ｓｖａ１を０．２４７ｍｇ／（ｓ・ｃｍ2）とした。実験例１８は、第１平均蒸発速度Ｓｖａ１を０．２７５ｍｇ／（ｓ・ｃｍ2）とした。実験例１９は、第１平均蒸発速度Ｓｖａ１を０．３３５ｍｇ／（ｓ・ｃｍ2）とした。実験例２０は、第１平均蒸発速度Ｓｖａ１を０．４１７ｍｇ／（ｓ・ｃｍ2）とした。 [Experimental Examples 15 to 20]
Initial solvent mass ratio R is 40% (solvent mass at the start of drying is 756 kg / m 3 , electrode material paste mass at the start of drying is 1890 kg / m 3 ), filament temperature of infrared heaters 30a-30c, hot air generator 22a Experimental examples 15 to 20 were obtained by changing the first average evaporation rate Sva1 variously by changing the temperature and air volume of hot air from ˜22f from Experimental Example 1 within the above-described range. The other configuration of the drying furnace 10 of Experimental Examples 15 to 20 was the same as that of Experimental Example 1. Specifically, in Experimental Example 15, the first average evaporation rate Sva1 was set to 0.194 mg / (s · cm 2 ). In Experimental Example 16, the first average evaporation rate Sva1 was set to 0.213 mg / (s · cm 2 ). In Experimental Example 17, the first average evaporation rate Sva1 was 0.247 mg / (s · cm 2 ). In Experimental Example 18, the first average evaporation rate Sva1 was set to 0.275 mg / (s · cm 2 ). In Experimental Example 19, the first average evaporation rate Sva1 was set to 0.335 mg / (s · cm 2 ). In Experimental Example 20, the first average evaporation rate Sva1 was set to 0.417 mg / (s · cm 2 ).

［実験例２１〜２８］
初期溶剤質量割合Ｒを３０％（乾燥開始時の溶剤質量は６６３ｋｇ／ｍ3，乾燥開始時の電極材ペースト質量は２２１０ｋｇ／ｍ3）とし、赤外線ヒーター３０ａ〜３０ｃのフィラメント温度，熱風発生器２２ａ〜２２ｆからの熱風の温度及び風量を、上述した範囲で実験例１から変更することで第１平均蒸発速度Ｓｖａ１を種々変更したものを実験例２１〜２８とした。実験例２１〜２８の乾燥炉１０のそれ以外の構成は、実験例１と同じとした。具体的には、実験例２１は、第１平均蒸発速度Ｓｖａ１を０．０９０ｍｇ／（ｓ・ｃｍ2）とした。実験例２２は、第１平均蒸発速度Ｓｖａ１を０．１２７ｍｇ／（ｓ・ｃｍ2）とした。実験例２３は、第１平均蒸発速度Ｓｖａ１を０．１３９ｍｇ／（ｓ・ｃｍ2）とした。実験例２４は、第１平均蒸発速度Ｓｖａ１を０．１５３ｍｇ／（ｓ・ｃｍ2）とした。実験例２５は、第１平均蒸発速度Ｓｖａ１を０．１８６ｍｇ／（ｓ・ｃｍ2）とした。実験例２６は、第１平均蒸発速度Ｓｖａ１を０．２２９ｍｇ／（ｓ・ｃｍ2）とした。実験例２７は、第１平均蒸発速度Ｓｖａ１を０．２８３ｍｇ／（ｓ・ｃｍ2）とした。実験例２８は、第１平均蒸発速度Ｓｖａ１を０．２９８ｍｇ／（ｓ・ｃｍ2）とした。 [Experimental Examples 21 to 28]
Initial solvent mass ratio R is 30% (solvent mass at the start of drying is 663 kg / m 3 , electrode material paste mass at the start of drying is 2210 kg / m 3 ), filament temperature of infrared heaters 30a-30c, hot air generator 22a Experimental examples 21 to 28 were obtained by changing the first average evaporation rate Sva1 variously by changing the temperature and air volume of hot air from ˜22f from Experimental Example 1 within the above-described range. The other configuration of the drying furnace 10 of Experimental Examples 21 to 28 was the same as that of Experimental Example 1. Specifically, in Experimental Example 21, the first average evaporation rate Sva1 was set to 0.090 mg / (s · cm 2 ). In Experimental Example 22, the first average evaporation rate Sva1 was set to 0.127 mg / (s · cm 2 ). In Experimental Example 23, the first average evaporation rate Sva1 was set to 0.139 mg / (s · cm 2 ). In Experimental Example 24, the first average evaporation rate Sva1 was set to 0.153 mg / (s · cm 2 ). In Experimental Example 25, the first average evaporation rate Sva1 was set to 0.186 mg / (s · cm 2 ). In Experimental Example 26, the first average evaporation rate Sva1 was set to 0.229 mg / (s · cm 2 ). In Experimental Example 27, the first average evaporation rate Sva1 was set to 0.283 mg / (s · cm 2 ). In Experimental Example 28, the first average evaporation rate Sva1 was set to 0.298 mg / (s · cm 2 ).

なお、実験例２１では、赤外線ヒーター３０ａによる赤外線加熱の温度は３３０℃，赤外線ヒーター３０ｂによる赤外線加熱の温度は３２０℃，赤外線ヒーター３０ｃによる赤外線加熱の温度は３１０℃とした。また、熱風発生器２２ａからの熱風の風量は１９．５ｍ3／ｍｉｎ，熱風の温度は１２０℃とした。熱風発生器２２ｂからの熱風の風量は１９．５ｍ3／ｍｉｎ，熱風の温度は１１０℃とした。熱風発生器２２ｃからの熱風の風量は１９．５ｍ3／ｍｉｎ，熱風の温度は１００℃とした。熱風発生器２２ｄからの熱風の風量は１２ｍ3／ｍｉｎ，熱風の温度は１２０℃とした。熱風発生器２２ｅからの熱風の風量は１２ｍ3／ｍｉｎ，熱風の温度は１１０℃とした。熱風発生器２２ｆからの熱風の風量は１２ｍ3／ｍｉｎ，熱風の温度は１００℃とした。 In Experimental Example 21, the temperature of infrared heating by the infrared heater 30a was 330 ° C., the temperature of infrared heating by the infrared heater 30b was 320 ° C., and the temperature of infrared heating by the infrared heater 30c was 310 ° C. The air volume of the hot air from the hot air generator 22a was 19.5 m 3 / min, and the temperature of the hot air was 120 ° C. The amount of hot air from the hot air generator 22b was 19.5 m 3 / min, and the temperature of the hot air was 110 ° C. The amount of hot air from the hot air generator 22c was 19.5 m 3 / min, and the temperature of the hot air was 100 ° C. The amount of hot air from the hot air generator 22d was 12 m 3 / min, and the temperature of the hot air was 120 ° C. The amount of hot air from the hot air generator 22e was 12 m 3 / min, and the temperature of the hot air was 110 ° C. The amount of hot air from the hot air generator 22f was 12 m 3 / min, and the temperature of the hot air was 100 ° C.

［評価試験１］
実験例１〜２８の乾燥炉１０について、塗膜５２を乾燥させたときのバインダーの分布を調べた。バインダー分布の評価は以下のように行った。第１加熱領域１１，第２加熱領域１２，第３加熱領域１３を通過したあとの塗膜５２を厚さ方向に３分割して上層，中層，下層とし、バインダー分布比＝（上層のバインダー質量／下層のバインダー質量）を算出した。そして、実験例１のバインダー分布比を基準（値１）として、実験例１〜２８のバインダー分布比の相対値を求めた。この値を相対偏析指数と称する。相対偏析指数が０．９以下の実験例はバインダーの分布が良好と判定した。なお、いずれの実験例においても、乾燥後の塗膜５２内部では上層側へのバインダーの偏析が認められ、バインダー分布比の値は１以上であった。そのため、相対偏析指数が小さいほど、バインダー分布比が値１に近い、すなわちバインダーの分布がより均一化されていることを意味する。 [Evaluation Test 1]
About the drying furnace 10 of Experimental Examples 1-28, distribution of the binder when the coating film 52 was dried was investigated. Evaluation of binder distribution was performed as follows. The coating film 52 after passing through the first heating region 11, the second heating region 12, and the third heating region 13 is divided into three in the thickness direction to form an upper layer, a middle layer, and a lower layer, and the binder distribution ratio = (binder mass of the upper layer) / Binder mass of lower layer) was calculated. And the relative value of the binder distribution ratio of Experimental Examples 1-28 was calculated | required on the basis of the binder distribution ratio of Experimental Example 1 (value 1). This value is called the relative segregation index. Experimental examples with a relative segregation index of 0.9 or less were judged to have good binder distribution. In any of the experimental examples, the segregation of the binder toward the upper layer side was observed in the coating film 52 after drying, and the value of the binder distribution ratio was 1 or more. Therefore, it means that the smaller the relative segregation index, the closer the binder distribution ratio is to 1, that is, the more uniform the binder distribution.

実験例１〜２８における、初期溶剤質量割合Ｒ、第１平均蒸発速度Ｓｖａ１，相対偏析指数，バインダー分布の良否判定結果を表１にまとめて示す。また、図６〜９は、それぞれ実験例１〜７，８〜１４，１５〜２０，２１〜２８における第１平均蒸発速度Ｓｖａ１と相対偏析指数との関係を示すグラフである。   Table 1 summarizes the initial solvent mass ratio R, the first average evaporation rate Sva1, the relative segregation index, and the binder distribution quality determination results in Experimental Examples 1 to 28. 6 to 9 are graphs showing the relationship between the first average evaporation rate Sva1 and the relative segregation index in Experimental Examples 1 to 7, 8 to 14, 15 to 20, and 21 to 28, respectively.

Figure 0005259875
Figure 0005259875

表１及び図６に示すように、初期溶剤質量割合Ｒが６０％である実験例１〜７のうち、実験例２〜６は相対偏析指数が０．９以下となっており良好な結果が得られた。すなわち、第１平均蒸発速度Ｓｖａ１が０．３８１ｍｇ／（ｓ・ｃｍ2）以上０．５３５ｍｇ／（ｓ・ｃｍ2）以下の範囲において、バインダーの分布をより均一化することができることがわかった。実験例２〜６はいずれも相対偏析指数が０．８以下となっていた。また、図６から分かるように、第１平均蒸発速度Ｓｖａ１を横軸、相対偏析指数を縦軸にとると、両者は下に凸の曲線で表されるような関係があり、バインダーの分布をより均一化するための第１平均蒸発速度Ｓｖａ１の上下限や最適値が存在することがわかった。図６から考察すると、初期溶剤質量割合Ｒが６０％の場合における第１平均蒸発速度Ｓｖａ１の最適値は０．４６ｍｇ／（ｓ・ｃｍ2）であり、相対偏析指数を０．９以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．３２ｍｇ／（ｓ・ｃｍ2）、上限値は０．５７５ｍｇ／（ｓ・ｃｍ2）と考えられる。また、相対偏析指数を０．８以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．３６ｍｇ／（ｓ・ｃｍ2）、上限値は０．５３ｍｇ／（ｓ・ｃｍ2）と考えられる。 As shown in Table 1 and FIG. 6, among Experimental Examples 1 to 7 in which the initial solvent mass ratio R is 60%, Experimental Examples 2 to 6 have a relative segregation index of 0.9 or less and good results. Obtained. That is, it was found that the binder distribution can be made more uniform when the first average evaporation rate Sva1 is in the range of 0.381 mg / (s · cm 2 ) to 0.535 mg / (s · cm 2 ). In all of Experimental Examples 2 to 6, the relative segregation index was 0.8 or less. Further, as can be seen from FIG. 6, when the first average evaporation rate Sva1 is taken on the horizontal axis and the relative segregation index is taken on the vertical axis, both have a relationship expressed by a downwardly convex curve, and the distribution of the binder is It has been found that there are upper and lower limits and optimum values for the first average evaporation rate Sva1 for more uniformization. Considering from FIG. 6, the optimum value of the first average evaporation rate Sva1 when the initial solvent mass ratio R is 60% is 0.46 mg / (s · cm 2 ), and the relative segregation index is 0.9 or less. Therefore, the lower limit value of the first average evaporation rate Sva1 is considered to be 0.32 mg / (s · cm 2 ), and the upper limit value is considered to be 0.575 mg / (s · cm 2 ). Further, the lower limit value of the first average evaporation rate Sva1 for setting the relative segregation index to 0.8 or less is considered to be 0.36 mg / (s · cm 2 ), and the upper limit value is 0.53 mg / (s · cm 2 ). It is done.

表１及び図７に示すように、初期溶剤質量割合Ｒが５０％である実験例８〜１４のうち、実験例９〜１３は相対偏析指数が０．９以下となっており良好な結果が得られた。すなわち、第１平均蒸発速度Ｓｖａ１が０．３１２ｍｇ／（ｓ・ｃｍ2）以上０．４４９ｍｇ／（ｓ・ｃｍ2）以下の範囲において、バインダーの分布をより均一化することができることがわかった。また、実験例９〜１２の結果から、第１平均蒸発速度Ｓｖａ１が０．３１２ｍｇ／（ｓ・ｃｍ2）以上０．４２１ｍｇ／（ｓ・ｃｍ2）以下の範囲において、相対偏析指数が０．８以下となっており、さらに良好な結果が得られた。また、図７から分かるように、第１平均蒸発速度Ｓｖａ１を横軸、相対偏析指数を縦軸にとると、両者は下に凸の曲線で表されるような関係があり、バインダーの分布をより均一化するための第１平均蒸発速度Ｓｖａ１の上下限や最適値が存在することがわかった。図７から考察すると、初期溶剤質量割合Ｒが５０％の場合における第１平均蒸発速度Ｓｖａ１の最適値は０．３６５ｍｇ／（ｓ・ｃｍ2）であり、相対偏析指数を０．９以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．２７ｍｇ／（ｓ・ｃｍ2）、上限値は０．４７ｍｇ／（ｓ・ｃｍ2）と考えられる。また、相対偏析指数を０．８以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．３０５ｍｇ／（ｓ・ｃｍ2）、上限値は０．４３ｍｇ／（ｓ・ｃｍ2）と考えられる。 As shown in Table 1 and FIG. 7, among the experimental examples 8 to 14 in which the initial solvent mass ratio R is 50%, the experimental examples 9 to 13 have a relative segregation index of 0.9 or less and good results. Obtained. That is, it was found that the binder distribution can be made more uniform when the first average evaporation rate Sva1 is in the range of 0.312 mg / (s · cm 2 ) to 0.449 mg / (s · cm 2 ). In addition, from the results of Experimental Examples 9 to 12, the relative segregation index is 0.1 when the first average evaporation rate Sva1 is 0.312 mg / (s · cm 2 ) or more and 0.421 mg / (s · cm 2 ) or less. It was 8 or less, and even better results were obtained. Further, as can be seen from FIG. 7, when the first average evaporation rate Sva1 is taken on the horizontal axis and the relative segregation index is taken on the vertical axis, both have a relationship expressed by a downwardly convex curve, and the distribution of the binder is It has been found that there are upper and lower limits and optimum values for the first average evaporation rate Sva1 for more uniformization. Considering from FIG. 7, when the initial solvent mass ratio R is 50%, the optimum value of the first average evaporation rate Sva1 is 0.365 mg / (s · cm 2 ), and the relative segregation index is 0.9 or less. the lower limit of the first average evaporation rate Sva1 is 0.27mg / (s · cm 2) for the upper limit is considered to 0.47mg / (s · cm 2) . Further, the lower limit value of the first average evaporation rate Sva1 for setting the relative segregation index to 0.8 or less is considered to be 0.305 mg / (s · cm 2 ), and the upper limit value is 0.43 mg / (s · cm 2 ). It is done.

表１及び図８に示すように、初期溶剤質量割合Ｒが４０％である実験例１５〜２０のうち、実験例１６〜１９は相対偏析指数が０．９以下となっており良好な結果が得られた。すなわち、第１平均蒸発速度Ｓｖａ１が０．２１３ｍｇ／（ｓ・ｃｍ2）以上０．３３５ｍｇ／（ｓ・ｃｍ2）以下の範囲において、バインダーの分布をより均一化することができることがわかった。また、実験例１７〜１９の結果から、第１平均蒸発速度Ｓｖａ１が０．２４７ｍｇ／（ｓ・ｃｍ2）以上０．３３５ｍｇ／（ｓ・ｃｍ2）以下の範囲において、相対偏析指数が０．８以下となっており、さらに良好な結果が得られた。また、図８から分かるように、第１平均蒸発速度Ｓｖａ１を横軸、相対偏析指数を縦軸にとると、両者は下に凸の曲線で表されるような関係があり、バインダーの分布をより均一化するための第１平均蒸発速度Ｓｖａ１の上下限や最適値が存在することがわかった。図８から考察すると、初期溶剤質量割合Ｒが４０％の場合における第１平均蒸発速度Ｓｖａ１の最適値は０．２７５ｍｇ／（ｓ・ｃｍ2）であり、相対偏析指数を０．９以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．２ｍｇ／（ｓ・ｃｍ2）、上限値は０．３７ｍｇ／（ｓ・ｃｍ2）と考えられる。また、相対偏析指数を０．８以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．２３５ｍｇ／（ｓ・ｃｍ2）、上限値は０．３３ｍｇ／（ｓ・ｃｍ2）と考えられる。 As shown in Table 1 and FIG. 8, among the experimental examples 15 to 20 in which the initial solvent mass ratio R is 40%, the experimental examples 16 to 19 have a relative segregation index of 0.9 or less and good results. Obtained. That is, it was found that the binder distribution can be made more uniform when the first average evaporation rate Sva1 is in the range of 0.213 mg / (s · cm 2 ) to 0.335 mg / (s · cm 2 ). Further, from the results of Experimental Examples 17 to 19, the relative segregation index is 0.1 in the range where the first average evaporation rate Sva1 is 0.247 mg / (s · cm 2 ) or more and 0.335 mg / (s · cm 2 ) or less. It was 8 or less, and even better results were obtained. Further, as can be seen from FIG. 8, when the first average evaporation rate Sva1 is taken on the horizontal axis and the relative segregation index is taken on the vertical axis, both have a relationship expressed by a downwardly convex curve, and the distribution of the binder is It has been found that there are upper and lower limits and optimum values for the first average evaporation rate Sva1 for more uniformization. Considering from FIG. 8, when the initial solvent mass ratio R is 40%, the optimum value of the first average evaporation rate Sva1 is 0.275 mg / (s · cm 2 ), and the relative segregation index is 0.9 or less. the lower limit of the first average evaporation rate Sva1 is 0.2mg / (s · cm 2) for the upper limit is considered to 0.37mg / (s · cm 2) . Further, the lower limit value of the first average evaporation rate Sva1 for setting the relative segregation index to 0.8 or less is considered to be 0.235 mg / (s · cm 2 ), and the upper limit value is 0.33 mg / (s · cm 2 ). It is done.

表１及び図９に示すように、初期溶剤質量割合Ｒが３０％である実験例２１〜２８のうち、実験例２３〜２６は相対偏析指数が０．９以下となっており良好な結果が得られた。すなわち、第１平均蒸発速度Ｓｖａ１が０．１３９ｍｇ／（ｓ・ｃｍ2）以上０．２２９ｍｇ／（ｓ・ｃｍ2）以下の範囲において、バインダーの分布をより均一化することができることがわかった。また、実験例２５〜２６の結果から、第１平均蒸発速度Ｓｖａ１が０．１８６ｍｇ／（ｓ・ｃｍ2）以上０．２２９ｍｇ／（ｓ・ｃｍ2）以下の範囲において、相対偏析指数が０．８以下となっており、さらに良好な結果が得られた。また、図９から分かるように、第１平均蒸発速度Ｓｖａ１を横軸、相対偏析指数を縦軸にとると、両者は下に凸の曲線で表されるような関係があり、バインダーの分布をより均一化するための第１平均蒸発速度Ｓｖａ１の上下限や最適値が存在することがわかった。図９から考察すると、初期溶剤質量割合Ｒが３０％の場合における第１平均蒸発速度Ｓｖａ１の最適値は０．１９２ｍｇ／（ｓ・ｃｍ2）であり、相対偏析指数を０．９以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．１３ｍｇ／（ｓ・ｃｍ2）、上限値は０．２６ｍｇ／（ｓ・ｃｍ2）と考えられる。また、相対偏析指数を０．８以下とするための第１平均蒸発速度Ｓｖａ１の下限値は０．１６５ｍｇ／（ｓ・ｃｍ2）、上限値は０．２２５ｍｇ／（ｓ・ｃｍ2）と考えられる。 As shown in Table 1 and FIG. 9, among the experimental examples 21 to 28 in which the initial solvent mass ratio R is 30%, the experimental examples 23 to 26 have a relative segregation index of 0.9 or less and good results. Obtained. That is, it was found that the binder distribution can be made more uniform when the first average evaporation rate Sva1 is in the range of 0.139 mg / (s · cm 2 ) to 0.229 mg / (s · cm 2 ). Further, from the results of Experimental Examples 25 to 26, the relative segregation index is 0.1 in the range where the first average evaporation rate Sva1 is 0.186 mg / (s · cm 2 ) or more and 0.229 mg / (s · cm 2 ) or less. It was 8 or less, and even better results were obtained. Moreover, as can be seen from FIG. 9, when the first average evaporation rate Sva1 is taken on the horizontal axis and the relative segregation index is taken on the vertical axis, both have a relationship expressed by a downwardly convex curve, and the distribution of the binder is It has been found that there are upper and lower limits and optimum values for the first average evaporation rate Sva1 for more uniformization. Considering from FIG. 9, the optimum value of the first average evaporation rate Sva1 when the initial solvent mass ratio R is 30% is 0.192 mg / (s · cm 2 ), and the relative segregation index is 0.9 or less. the lower limit of the first average evaporation rate Sva1 is 0.13mg / (s · cm 2) for the upper limit is considered to 0.26mg / (s · cm 2) . Further, the lower limit value of the first average evaporation rate Sva1 for setting the relative segregation index to 0.8 or less is considered to be 0.165 mg / (s · cm 2 ), and the upper limit value is 0.225 mg / (s · cm 2 ). It is done.

図１０は、実験例１〜２８の結果に基づき、初期溶剤質量割合Ｒの値を横軸とし、第１平均蒸発速度Ｓｖａ１の値を縦軸として、上述した相対偏析指数を０．９以下とすることができる第１平均蒸発速度Ｓｖａ１の上下限値、上述した相対偏析指数を０．８以下とすることができる第１平均蒸発速度Ｓｖａ１の上下限値、及び第１平均蒸発速度Ｓｖａ１の最適値をプロットしたグラフである。また、図１０には、相対偏析指数を０．９以下とすることができる第１平均蒸発速度Ｓｖａ１の上下限値のプロットから算出した、第１平均蒸発速度Ｓｖａ１の上限値の近似曲線（第１近似曲線）及び下限値の近似曲線（第２近似曲線）を併せて示した。この第１，第２近似曲線で囲まれる領域が、上述した式（１）を満たす領域（図５の領域Ａ）であり、初期溶剤質量割合Ｒに応じてこの式（１）を満たすような第１平均蒸発速度Ｓｖａ１で塗膜５２を乾燥することで、バインダーの分布をより均一化することができると考えられる。同様に、図１０には、相対偏析指数を０．８以下とすることができる第１平均蒸発速度Ｓｖａ１の上下限値のプロットから算出した、第１平均蒸発速度Ｓｖａ１の上限値の近似曲線（第３近似曲線）及び下限値の近似曲線（第４近似曲線）を併せて示した。この第３，第４近似曲線で囲まれる領域が、上述した式（２）を満たす領域（図５の領域Ｂ）であり、初期溶剤質量割合Ｒに応じてこの式（２）を満たすような第１平均蒸発速度Ｓｖａ１で塗膜５２を乾燥することで、バインダーの分布をさらに均一化することができると考えられる。また、図１０には、第１平均蒸発速度Ｓｖａ１の最適値のプロットから算出した、第１平均蒸発速度Ｓｖａ１の最適ラインについても併せて示した。この最適ラインが、上述した図５の最適ラインである。   FIG. 10 is based on the results of Experimental Examples 1 to 28, where the value of the initial solvent mass ratio R is the horizontal axis, the value of the first average evaporation rate Sva1 is the vertical axis, and the above-mentioned relative segregation index is 0.9 or less. The upper and lower limit values of the first average evaporation rate Sva1 that can be set, the upper and lower limit values of the first average evaporation rate Sva1 that allow the above-mentioned relative segregation index to be 0.8 or less, and the optimum of the first average evaporation rate Sva1 It is the graph which plotted the value. FIG. 10 also shows an approximate curve (first curve) of the upper limit value of the first average evaporation rate Sva1 calculated from the plot of the upper and lower limit values of the first average evaporation rate Sva1 that can make the relative segregation index 0.9 or less. 1 approximate curve) and the lower limit approximate curve (second approximate curve) are also shown. The region surrounded by the first and second approximate curves is a region that satisfies the above-described equation (1) (region A in FIG. 5), and satisfies this equation (1) according to the initial solvent mass ratio R. It is considered that the distribution of the binder can be made more uniform by drying the coating film 52 at the first average evaporation rate Sva1. Similarly, FIG. 10 shows an approximate curve of the upper limit value of the first average evaporation rate Sva1 calculated from the plot of the upper and lower limit values of the first average evaporation rate Sva1 that can make the relative segregation index 0.8 or less. The third approximate curve) and the lower limit approximate curve (fourth approximate curve) are also shown. The region surrounded by the third and fourth approximate curves is a region that satisfies the above-described equation (2) (region B in FIG. 5), and satisfies this equation (2) according to the initial solvent mass ratio R. It is considered that the distribution of the binder can be further uniformized by drying the coating film 52 at the first average evaporation rate Sva1. FIG. 10 also shows the optimum line of the first average evaporation rate Sva1 calculated from the plot of the optimum value of the first average evaporation rate Sva1. This optimum line is the optimum line shown in FIG.

［実験例２９〜３３］
初期溶剤質量割合Ｒを２０％（乾燥開始時の溶剤質量は５１８ｋｇ／ｍ3，乾燥開始時の電極材ペースト質量は２５９０ｋｇ／ｍ3）とし、赤外線ヒーター３０ａ〜３０ｃのフィラメント温度，熱風発生器２２ａ〜２２ｆからの熱風の温度及び風量を、上述した範囲で実験例１から変更することで第１平均蒸発速度Ｓｖａ１を種々変更したものを実験例２９〜３３とした。実験例２９〜３３の乾燥炉１０のそれ以外の構成は、実験例１と同じとした。具体的には、実験例２９は、第１平均蒸発速度Ｓｖａ１を０．０８ｍｇ／（ｓ・ｃｍ2）とした。実験例３０は、第１平均蒸発速度Ｓｖａ１を０．０８４ｍｇ／（ｓ・ｃｍ2）とした。実験例３１は、第１平均蒸発速度Ｓｖａ１を０．１０４ｍｇ／（ｓ・ｃｍ2）とした。実験例３２は、第１平均蒸発速度Ｓｖａ１を０．１２４ｍｇ／（ｓ・ｃｍ2）とした。実験例３３は、第１平均蒸発速度Ｓｖａ１を０．１４９ｍｇ／（ｓ・ｃｍ2）とした。 [Experimental Examples 29 to 33]
Initial solvent mass ratio R is 20% (solvent mass at the start of drying is 518 kg / m 3 , electrode material paste mass at the start of drying is 2590 kg / m 3 ), filament temperature of infrared heaters 30a-30c, hot air generator 22a Experimental examples 29 to 33 were obtained by changing the first average evaporation rate Sva1 variously by changing the temperature and air volume of hot air from ˜22f from Experimental Example 1 within the above-described range. The other configuration of the drying furnace 10 of Experimental Examples 29 to 33 was the same as that of Experimental Example 1. Specifically, in Experimental Example 29, the first average evaporation rate Sva1 was set to 0.08 mg / (s · cm 2 ). In Experimental Example 30, the first average evaporation rate Sva1 was set to 0.084 mg / (s · cm 2 ). In Experimental Example 31, the first average evaporation rate Sva1 was set to 0.104 mg / (s · cm 2 ). In Experimental Example 32, the first average evaporation rate Sva1 was set to 0.124 mg / (s · cm 2 ). In Experimental Example 33, the first average evaporation rate Sva1 was set to 0.149 mg / (s · cm 2 ).

［評価試験２］
実験例２９〜３３の乾燥炉１０について、実験例１〜２８と同様に、塗膜５２を乾燥させたときのバインダーの分布を調べた。実験例２９〜３３における、初期溶剤質量割合Ｒ、第１平均蒸発速度Ｓｖａ１，相対偏析指数，バインダー分布の良否判定結果を表１にまとめて示す。また、図１１は、実験例２９〜３３における第１平均蒸発速度Ｓｖａ１と相対偏析指数との関係を示すグラフである。なお、いずれの実験例においても、乾燥後の塗膜５２内部では上層側へのバインダーの偏析が認められ、バインダー分布比の値は１以上であった。そのため、相対偏析指数が小さいほど、バインダー分布比が値１に近い、すなわちバインダーの分布がより均一化されていることを意味する。また、相対偏析指数は、実験例１〜２８と同様に、実験例１のバインダー分布比を基準（値１）として示した。 [Evaluation Test 2]
About the drying furnace 10 of Experimental example 29-33, distribution of the binder when the coating film 52 was dried was investigated similarly to Experimental example 1-28. Table 1 summarizes the initial solvent mass ratio R, the first average evaporation rate Sva1, the relative segregation index, and the binder distribution quality determination results in Experimental Examples 29 to 33. FIG. 11 is a graph showing the relationship between the first average evaporation rate Sva1 and the relative segregation index in Experimental Examples 29 to 33. In any of the experimental examples, the segregation of the binder toward the upper layer side was observed in the coating film 52 after drying, and the value of the binder distribution ratio was 1 or more. Therefore, it means that the smaller the relative segregation index, the closer the binder distribution ratio is to 1, that is, the more uniform the binder distribution. Further, the relative segregation index is shown by using the binder distribution ratio of Experimental Example 1 as a reference (value 1) as in Experimental Examples 1 to 28.

表１及び図１１に示すように、初期溶剤質量割合Ｒが２０％である実験例２９〜３３はいずれも相対偏析指数が０．９以下となっており良好な結果が得られた。また、初期溶剤質量割合Ｒが２０％である場合には、式（１）から、第１平均蒸発速度Ｓｖａ１が０．０７３２ｍｇ／（ｓ・ｃｍ2）以上０．１７８４ｍｇ／（ｓ・ｃｍ2）以下であればバインダーの分布をより均一化することができることになるが、実験例２９〜３３はいずれも第１平均蒸発速度Ｓｖａ１がこの範囲内であった。このことから、初期溶剤質量割合Ｒが２０％の場合においても、式（１）を満たすときにバインダーの分布をより均一化できることが確認できた。 As shown in Table 1 and FIG. 11, all of Experimental Examples 29 to 33 having an initial solvent mass ratio R of 20% had a relative segregation index of 0.9 or less, and good results were obtained. Further, when the initial solvent mass ratio R is 20%, the first average evaporation rate Sva1 is 0.0732 mg / (s · cm 2 ) or more and 0.1784 mg / (s · cm 2 ) from the formula (1). The binder distribution can be made more uniform as long as it is below, but in each of Experimental Examples 29 to 33, the first average evaporation rate Sva1 was within this range. From this, it was confirmed that even when the initial solvent mass ratio R is 20%, the binder distribution can be made more uniform when the formula (1) is satisfied.

同様に、初期溶剤質量割合Ｒが２０％未満の場合（例えば１０％など）についても、式（１）を満たすことで（第１平均蒸発速度Ｓｖａ１を０．０３２６ｍｇ／（ｓ・ｃｍ2）以上０．０８６２ｍｇ／（ｓ・ｃｍ2）以下とすることで）バインダーの分布をより均一化できると考えられる。初期溶剤質量割合Ｒが６０％超過の場合についても、同様であると考えられる。 Similarly, when the initial solvent mass ratio R is less than 20% (for example, 10%, etc.), the first average evaporation rate Sva1 is 0.0326 mg / (s · cm 2 ) or more by satisfying the formula (1). It is considered that the distribution of the binder can be made more uniform by setting it to 0.0862 mg / (s · cm 2 ) or less. The same applies to the case where the initial solvent mass ratio R exceeds 60%.

［実験例３４］
初期溶剤質量割合Ｒを４０％（乾燥開始時の溶剤質量は７５６ｋｇ／ｍ3，乾燥開始時の電極材ペースト質量は１８９０ｋｇ／ｍ3）とし、初期塗膜厚みｔを２２５μｍ，乾燥時間Ｔを９０ｓ（シート５０の搬送速度が４ｍ／ｍｉｎ）とし、赤外線ヒーター３０ａ〜３０ｃのフィラメント温度，熱風発生器２２ａ〜２２ｆからの熱風の温度及び風量を、上述した範囲で実験例１から変更することで第１平均蒸発速度Ｓｖａ１が０．３ｍｇ／（ｓ・ｃｍ2）となるようにしたものを実験例３４とした。実験例３４の乾燥炉１０のそれ以外の構成は、実験例１と同じとした。なお、実験例３４は、乾燥時間Ｔと初期塗膜厚みｔとの関係はＴ＝０．４ｔを満たしている。 [Experimental example 34]
The initial solvent mass ratio R is 40% (the solvent mass at the start of drying is 756 kg / m 3 , the electrode material paste mass at the start of drying is 1890 kg / m 3 ), the initial coating thickness t is 225 μm, and the drying time T is 90 s. (The conveyance speed of the sheet 50 is 4 m / min) and the filament temperature of the infrared heaters 30a to 30c, the temperature and the air volume of the hot air from the hot air generators 22a to 22f are changed from the experimental example 1 within the above-described range. An experiment example 34 was conducted in which the average evaporation rate Sva1 was 0.3 mg / (s · cm 2 ). The other configuration of the drying furnace 10 of Experimental Example 34 was the same as that of Experimental Example 1. In Experimental Example 34, the relationship between the drying time T and the initial coating thickness t satisfies T = 0.4t.

［評価試験３］
実験例３４の乾燥炉１０について、実験例１〜３３と同様に、塗膜５２を乾燥させたときのバインダーの分布を調べたところ、相対偏析指数は０．８であった。実験例３４における、初期溶剤質量割合Ｒ、第１平均蒸発速度Ｓｖａ１，相対偏析指数，バインダー分布の良否判定結果を表１にまとめて示す。実験例３４は、第１平均蒸発速度Ｓｖａ１が０．３ｍｇ／（ｓ・ｃｍ2）であり、式（１）及び式（２）を満たしており、相対偏析指数も０．８以下となっている。このことから、塗膜５２の厚みが２２５μｍの場合でも、厚みが２００μｍである実験例１〜２８（特に実験例１５〜２０）と同様の結果が得られることがわかった。また、乾燥時間Ｔと初期塗膜厚みｔとの関係がＴ＝０．４ｔを満たしていれば、厚みが異なる値であっても実験例１〜２８と同様に式（１）を満たすことでバインダーの分布をより均一化でき、式（２）を満たすことでバインダーの分布をさらに均一化できることが確認できた。 [Evaluation Test 3]
In the drying furnace 10 of Experimental Example 34, the distribution of the binder when the coating film 52 was dried was examined in the same manner as in Experimental Examples 1 to 33, and the relative segregation index was 0.8. Table 1 summarizes the initial solvent mass ratio R, the first average evaporation rate Sva1, the relative segregation index, and the binder distribution quality determination results in Experimental Example 34. In Experimental Example 34, the first average evaporation rate Sva1 is 0.3 mg / (s · cm 2 ), satisfies the expressions (1) and (2), and the relative segregation index is 0.8 or less. Yes. From this, it was found that even when the thickness of the coating film 52 was 225 μm, the same results as in Experimental Examples 1 to 28 (particularly Experimental Examples 15 to 20) having a thickness of 200 μm were obtained. Moreover, if the relationship between the drying time T and the initial coating film thickness t satisfies T = 0.4t, even if the thickness is a different value, the expression (1) is satisfied as in Experimental Examples 1 to 28. It was confirmed that the distribution of the binder can be made more uniform, and that the distribution of the binder can be made more uniform by satisfying the formula (2).

［実験例３５，３６］
実験例３５，３６では、乾燥時間Ｔと初期塗膜厚みｔとの関係がＴ＝０．４ｔを満たさない場合について調べた。初期溶剤質量割合Ｒを４０％（乾燥開始時の溶剤質量は７５６ｋｇ／ｍ3，乾燥開始時の電極材ペースト質量は１８９０ｋｇ／ｍ3）とし、初期塗膜厚みｔを２２５μｍ，乾燥時間Ｔを７５ｓ（シート５０の搬送速度が４．８ｍ／ｍｉｎ）とし、赤外線ヒーター３０ａ〜３０ｃのフィラメント温度，熱風発生器２２ａ〜２２ｆからの熱風の温度及び風量を、上述した範囲で実験例１から変更することで第１平均蒸発速度Ｓｖａ１を種々変更したものを実験例３５，３６とした。具体的には、実験例３５は、第１平均蒸発速度Ｓｖａ１を０．４ｍｇ／（ｓ・ｃｍ2）とした。実験例３６は、第１平均蒸発速度Ｓｖａ１を０．２ｍｇ／（ｓ・ｃｍ2）とした。 [Experimental Examples 35 and 36]
In Experimental Examples 35 and 36, the case where the relationship between the drying time T and the initial coating film thickness t did not satisfy T = 0.4t was examined. The initial solvent mass ratio R is 40% (the solvent mass at the start of drying is 756 kg / m 3 , the electrode material paste mass at the start of drying is 1890 kg / m 3 ), the initial coating thickness t is 225 μm, and the drying time T is 75 s. (The conveyance speed of the sheet 50 is 4.8 m / min), and the filament temperature of the infrared heaters 30a to 30c, the temperature and the air volume of the hot air from the hot air generators 22a to 22f are changed from the experimental example 1 within the above-described range. The first average evaporation rate Sva1 was changed in various ways as Experimental Examples 35 and 36. Specifically, in Experimental Example 35, the first average evaporation rate Sva1 was set to 0.4 mg / (s · cm 2 ). In Experimental Example 36, the first average evaporation rate Sva1 was set to 0.2 mg / (s · cm 2 ).

［評価試験４］
実験例３５，３６の乾燥炉１０について、実験例１〜３３と同様に、塗膜５２を乾燥させたときのバインダーの分布を調べたところ、相対偏析指数はそれぞれ０．８、１．０であった。実験例３５，３６における、初期溶剤質量割合Ｒ、第１平均蒸発速度Ｓｖａ１，相対偏析指数，バインダー分布の良否判定結果を表１にまとめて示す。ここで、実験例３５，３６における補正後初期溶剤質量割合Ｒａ（＝（０．４ｔ／Ｔ）×Ｒ）は４８％となる。そして、式（１），式（２）を適用すると、補正後初期溶剤質量割合Ｒａが４８％である場合には、第１平均蒸発速度Ｓｖａ１が０．２２９ｍｇ／（ｓ・ｃｍ2）以上０．４６８ｍｇ／（ｓ・ｃｍ2）以下であればバインダーの分布をより均一化することができ、第１平均蒸発速度Ｓｖａ１が０．２７９ｍｇ／（ｓ・ｃｍ2）以上０．４０６ｍｇ／（ｓ・ｃｍ2）以下であればバインダーの分布をさらに均一化することができると考えられる。実験例３５は第１平均蒸発速度Ｓｖａ１が０．４で相対偏析指数は０．８であり、この考察と一致する結果が得られた。また、実験例３６は第１平均蒸発速度Ｓｖａ１が０．２で相対偏析指数は１．０であり、こちらもこの考察と一致する結果が得られた。例えば、実験例３５，３６の第１平均蒸発速度Ｓｖａ１の値と相対偏析指数の値とを図１０における初期溶剤質量割合Ｒが４８％のところにプロットすると、実験例３５，３６の結果と、図１０の近似曲線との対応が整合していることがわかった。一方、初期溶剤質量割合Ｒの補正を行わずに図１０における初期溶剤質量割合Ｒが４０％のところに実験例３５，３６の結果をプロットすると、図１０の近似曲線との対応が整合しないことがわかった。 [Evaluation Test 4]
Regarding the drying furnace 10 of Experimental Examples 35 and 36, as in Experimental Examples 1 to 33, when the distribution of the binder when the coating film 52 was dried was examined, the relative segregation index was 0.8 and 1.0, respectively. there were. Table 1 shows the initial solvent mass ratio R, the first average evaporation rate Sva1, the relative segregation index, and the binder distribution quality determination results in Experimental Examples 35 and 36. Here, the corrected initial solvent mass ratio Ra (= (0.4 t / T) × R) in Experimental Examples 35 and 36 is 48%. When applying the formulas (1) and (2), when the corrected initial solvent mass ratio Ra is 48%, the first average evaporation rate Sva1 is 0.229 mg / (s · cm 2 ) or more and 0 If it is .468 mg / (s · cm 2 ) or less, the distribution of the binder can be made more uniform, and the first average evaporation rate Sva1 is 0.279 mg / (s · cm 2 ) or more and 0.406 mg / (s · If it is cm 2 ) or less, it is considered that the binder distribution can be made more uniform. In Experimental Example 35, the first average evaporation rate Sva1 was 0.4 and the relative segregation index was 0.8, and a result consistent with this consideration was obtained. In Experimental Example 36, the first average evaporation rate Sva1 was 0.2 and the relative segregation index was 1.0. This also obtained a result consistent with this consideration. For example, when the value of the first average evaporation rate Sva1 and the value of the relative segregation index in Experimental Examples 35 and 36 are plotted at the initial solvent mass ratio R in FIG. 10 of 48%, the results of Experimental Examples 35 and 36 are obtained. It was found that the correspondence with the approximate curve in FIG. 10 is consistent. On the other hand, if the results of Experimental Examples 35 and 36 are plotted when the initial solvent mass ratio R in FIG. 10 is 40% without correcting the initial solvent mass ratio R, the correspondence with the approximate curve in FIG. 10 does not match. I understood.

評価試験４の結果から、乾燥時間Ｔと初期塗膜厚みｔとの関係がＴ＝０．４ｔを満たさない場合でも、初期溶剤質量割合Ｒ，塗膜厚みｔ，乾燥時間Ｔに基づいて補正後初期溶剤質量割合Ｒａを導出することで、式（１），（２）を適用することができると考えられる。なお、補正後初期溶剤質量割合ＲａをＲａ＝（０．４ｔ／Ｔ）×Ｒとして導出して、このＲａに基づいて式（１），（２）を適用できる理由は以下のように考えられる。まず、図１０からもわかるように、初期溶剤質量割合Ｒが大きいほど、バインダーの分布をより均一化するために必要な第１平均蒸発速度Ｓｖａ１の値は大きくなる傾向にある。そして、塗膜厚みｔが大きい値であるほど、第１加熱を行うことによる塗膜５２のバインダーの逆拡散の駆動力を高いものとするのに必要な第１平均蒸発速度Ｓｖａ１は大きい値になると考えられる。また、乾燥時間Ｔが短いほど、第１加熱を行う時間が短くなり、第１加熱を行うことによる塗膜５２のバインダーの逆拡散の駆動力を高いものとするのに必要な第１平均蒸発速度Ｓｖａ１は大きい値となると考えられる。これらのことから、実験例１〜２８と比べて塗膜厚みｔが大きい場合や乾燥時間Ｔが小さい場合には、初期溶剤質量割合Ｒを大きくするように換算を行い、換算後の値を補正後初期溶剤質量割合Ｒａとして式（１），（２）に用いることで、上述した実験例１〜２８以外の任意の塗膜厚みｔや乾燥時間Ｔに対して、バインダーの分布をより均一化するために必要な第１平均蒸発速度Ｓｖａ１の値が導出できるものと考えられる。   From the result of the evaluation test 4, even when the relationship between the drying time T and the initial coating film thickness t does not satisfy T = 0.4t, it is corrected based on the initial solvent mass ratio R, the coating film thickness t, and the drying time T. It is considered that the formulas (1) and (2) can be applied by deriving the initial solvent mass ratio Ra. The reason why the corrected initial solvent mass ratio Ra is derived as Ra = (0.4 t / T) × R and the formulas (1) and (2) can be applied based on this Ra is considered as follows. . First, as can be seen from FIG. 10, the larger the initial solvent mass ratio R, the larger the value of the first average evaporation rate Sva1 necessary for making the binder distribution more uniform. And as the coating film thickness t is larger, the first average evaporation rate Sva1 necessary for increasing the driving force for reverse diffusion of the binder of the coating film 52 by performing the first heating is increased. It is considered to be. In addition, the shorter the drying time T, the shorter the time for performing the first heating, and the first average evaporation necessary for increasing the driving force for reverse diffusion of the binder of the coating film 52 by performing the first heating. The speed Sva1 is considered to be a large value. From these things, when the coating film thickness t is large or when the drying time T is small as compared with Experimental Examples 1 to 28, conversion is performed so as to increase the initial solvent mass ratio R, and the value after conversion is corrected. By using the formula (1) and (2) as the initial initial solvent mass ratio Ra, the distribution of the binder is made more uniform with respect to any coating film thickness t and drying time T other than the above-described Experimental Examples 1 to 28. It is considered that the value of the first average evaporation rate Sva1 necessary for this can be derived.

なお、実験例１〜３６のうち、実験例２〜６，９〜１３，１６〜１９，２３〜２６，２９〜３３，３４，３５が本発明の第１の乾燥方法及び本発明の第１の乾燥炉の実施例に相当し、それ以外が比較例に相当する。   Of Experimental Examples 1-36, Experimental Examples 2-6, 9-13, 16-19, 23-26, 29-33, 34, 35 are the first drying method of the present invention and the first of the present invention. The other examples correspond to the examples of the drying furnace and the other examples correspond to the comparative examples.

本発明は、電極材とバインダーと導電材と溶剤とを含む電極材ペーストが塗布されたシートを乾燥する必要のある産業、例えば塗膜を乾燥させてリチウムイオン二次電池の電極を製造する電池産業などに利用可能である。   The present invention relates to an industry in which a sheet coated with an electrode material paste including an electrode material, a binder, a conductive material, and a solvent is required to be dried, for example, a battery for producing an electrode of a lithium ion secondary battery by drying a coating film. It can be used for industries.

１０ 乾燥炉、１１ 第１加熱領域、１２ 第２加熱領域、１３ 第３加熱領域、１４ 炉体、１５ 前端面、１６ 後端面、１７，１８ 開口、１９ 搬送通路、２０，２０ａ〜２０ｆ 送風装置、２２，２２ａ〜２２ｆ 熱風発生器、２４，２４ａ〜２４ｆ パイプ構造体、２６，２６ａ〜２６ｆ 通気口、３０，３０ａ〜３０ｃ 赤外線ヒーター、３２ フィラメント、３４ 電気配線、３６ 内管、３７ 温度センサ、３８ ヒーター本体、４０ 外管、４２ キャップ、４４ 配線引出部、４６ 流体出入口、４８ 流路、４９ ホルダー、５０ シート、５２ 塗膜、５４，５６ ロール、６０ コントローラー、７０ 冷却流体供給源、７２ 開閉弁、７４ 流量調整弁、８０ 電力供給源。 DESCRIPTION OF SYMBOLS 10 Drying furnace, 11 1st heating area | region, 12 2nd heating area | region, 13 3rd heating area | region, 14 Furnace body, 15 Front end surface, 16 Rear end surface, 17, 18 Opening, 19 Conveyance path, 20, 20a-20f 22, 22a-22f Hot air generator, 24, 24a-24f Pipe structure, 26, 26a-26f Vent, 30, 30a-30c Infrared heater, 32 filament, 34 electrical wiring, 36 inner pipe, 37 temperature sensor, 38 Heater body, 40 Outer pipe, 42 Cap, 44 Wiring drawer, 46 Fluid inlet / outlet, 48 Flow path, 49 Holder, 50 sheets, 52 Coating film, 54, 56 Roll, 60 Controller, 70 Cooling fluid supply source, 72 Open / close Valve, 74 Flow control valve, 80 Power supply source.

Claims (4)

電極材とバインダーと導電材と溶剤とを含む電極材ペーストをシート上に塗布した電池用電極塗膜の乾燥方法であって、
（ａ）前記電極材が前記塗膜の表面に露出するまでの間、該塗膜の溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１［ｍｇ／（ｓ・ｃｍ2）］が次式（１）を満たすように該塗膜を加熱する第１加熱を行う工程と、
（ｂ）前記電極材が前記塗膜の表面に露出した後、前記塗膜の溶剤の蒸発速度の平均値である第２平均蒸発速度Ｓｖａ２が前記第１平均蒸発速度Ｓｖａ１以下となるように該塗膜を加熱する第２加熱を行う工程と、
を含む電池用電極塗膜の乾燥方法。
Figure 0005259875
 A method for drying an electrode coating film for a battery in which an electrode material paste including an electrode material, a binder, a conductive material, and a solvent is applied on a sheet,
(A) Until the electrode material is exposed on the surface of the coating film, the first average evaporation rate Sva1 [mg / (s · cm 2 )], which is the average value of the evaporation rate of the solvent of the coating film, is and performing a first heating for heating the coating film so as to satisfy the equation (1),
(B) After the electrode material is exposed on the surface of the coating film, the second average evaporation rate Sva2, which is an average value of the evaporation rate of the solvent of the coating film, is equal to or less than the first average evaporation rate Sva1. Performing a second heating for heating the coating film;
A method for drying an electrode coating film for a battery comprising:
Figure 0005259875
 前記工程（ａ）では、前記第１平均蒸発速度Ｓｖａ１が次式（２）を満たすように前記塗膜を加熱する、
請求項１に記載の電池用電極塗膜の乾燥方法。
Figure 0005259875
 In the step (a) , the coating film is heated so that the first average evaporation rate Sva1 satisfies the following formula (2):
The drying method of the electrode coating film for batteries of Claim 1.
Figure 0005259875
 前記塗膜の加熱は、赤外線及び熱風により行う、
請求項１又は２に記載の電池用電極塗膜の乾燥方法。 The coating film is heated by infrared rays and hot air.
The drying method of the electrode coating film for batteries of Claim 1 or 2. 電極材とバインダーと導電材と溶剤とを含む電極材ペーストをシート上に塗布した電池用電極塗膜の乾燥炉であって、
前記電極材が前記塗膜の表面に露出するまでの間、該塗膜の溶剤の蒸発速度の平均値である第１平均蒸発速度Ｓｖａ１［ｍｇ／（ｓ・ｃｍ2）］が次式（１）を満たすように該塗膜を加熱する第１加熱と、前記電極材が前記塗膜の表面に露出した後、前記塗膜の溶剤の蒸発速度の平均値である第２平均蒸発速度Ｓｖａ２が前記第１平均蒸発速度Ｓｖａ１以下となるように該塗膜を加熱する第２加熱と、を行う加熱手段、
を備えた電池用電極塗膜の乾燥炉。
Figure 0005259875
 A battery electrode coating film drying furnace in which an electrode material paste containing an electrode material, a binder, a conductive material, and a solvent is applied on a sheet,
Until the electrode material is exposed on the surface of the coating film, the first average evaporation rate Sva1 [mg / (s · cm 2 )] which is an average value of the evaporation rate of the solvent of the coating film is expressed by the following formula (1). And after the electrode material is exposed on the surface of the coating film, a second average evaporation rate Sva2 that is an average value of the evaporation rate of the solvent of the coating film is Heating means for performing second heating for heating the coating film so as to be equal to or lower than the first average evaporation rate Sva1 ;
A drying furnace for battery electrode coatings.
Figure 0005259875
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