JP5867798B2 - Method for producing porous polyimide membrane, method for producing porous polystyrene membrane, method for producing porous electrode, and porous electrode - Google Patents
Method for producing porous polyimide membrane, method for producing porous polystyrene membrane, method for producing porous electrode, and porous electrode Download PDFInfo
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Description
本発明は、電子機器のフレキシブルプリント基板（FPC）等で用いられる多孔質ポリイミド膜の製造方法に関する。また、本発明の方法は多孔質ポリスチレン膜の製造にも適用することができる。さらに、本発明は、上記方法により作製される多孔質ポリイミド膜を用いた多孔質電極及びその製造方法に関する。この方法により作製される多孔質電極は、リチウムイオン電池の負極に好適に用いられるものである。 The present invention relates to a method for producing a porous polyimide film used in a flexible printed circuit board (FPC) of an electronic device. The method of the present invention can also be applied to the production of a porous polystyrene membrane. Furthermore, this invention relates to the porous electrode using the porous polyimide membrane produced by the said method, and its manufacturing method. The porous electrode produced by this method is suitably used for the negative electrode of a lithium ion battery.
FPCは柔軟性があって変形可能な板材の表面に導線がプリントされたものであり、電子機器の可動部（例えば折り畳み式携帯電話の蝶番部）や、基板を曲げなければ収容できない小さい空間で用いられる。FPCの板材の材料には、耐熱性、耐溶剤性及び絶縁信頼性が優れているという理由でポリイミドが広く用いられている。 FPC is a flexible and deformable plate with conductive wires printed on it, and it can be used in movable parts of electronic devices (for example, hinges of foldable mobile phones) or small spaces that cannot be accommodated without bending the board. Used. Polyimide is widely used as a material for FPC plate materials because of its excellent heat resistance, solvent resistance, and insulation reliability.
FPCでは、導線間に存在する板材がキャパシタとして作用するため、高周波電流が導線を流れる間に該高周波電流の強度が減衰する、という問題が生じる。この減衰を抑えるためには、板材の誘電率をできるだけ低くすることが望ましい。そのため、従来より、板材の誘電率を低くするための以下の手法が検討されている。
(1)ポリイミドの化学構造を改変することにより高分子の極性を小さくする。そのためには、ポリイミドにフッ素原子を導入することが有効である（非特許文献１）。
(2)ポリイミドの化学構造を改変することにより自由体積を増加させる。例えば、芳香族テトラカルボン酸二無水物とジアノフェニルエーテル構造の3-3'ジアミン体から得られるポリイミドは、高分子の鎖が整列し難い構造を有するため、自由体積が大きい。また、ポリイミドに芳香族置換基や脂環族基等、体積が大きい置換基を導入することにより、自由体積を増加させることもできる（非特許文献１）。
(3)板材内に空孔を多数導入する（非特許文献１〜４、特許文献１）。例えば非特許文献２〜４には、ポリイミドの前駆体をイミド化するための加熱時に熱分解する側鎖を該前駆体に導入したり、加熱時に熱分解する物質を該前駆体に混合しておくことにより、径が数nm〜数十nmである孔を多数有するポリイミドの多孔質成形体（板材）を作製することが記載されている。また、特許文献１には、熱可塑性ポリイミドの成形体に、二酸化炭素等の非反応性ガスを加圧下で接触させることにより該ガスを浸透させ、減圧した後に成形体を加熱することにより成形体を軟化させつつ発泡させることで、径が0.01〜10μmの孔を多数有するポリイミドの多孔質成形体を作製することが記載されている。これらの空孔導入法によれば、ポリイミドの誘電率を、孔が無い場合の3.2〜3.8から2.9以下にまで低くすることができる。
In FPC, since the plate material existing between the conductors acts as a capacitor, there arises a problem that the strength of the high-frequency current is attenuated while the high-frequency current flows through the conductor. In order to suppress this attenuation, it is desirable to make the dielectric constant of the plate material as low as possible. Therefore, conventionally, the following methods for reducing the dielectric constant of the plate material have been studied.
(1) The polarity of the polymer is reduced by modifying the chemical structure of the polyimide. For this purpose, it is effective to introduce fluorine atoms into polyimide (Non-patent Document 1).
(2) Increase the free volume by modifying the chemical structure of the polyimide. For example, a polyimide obtained from an aromatic tetracarboxylic dianhydride and a 3-3 ′ diamine having a dianophenyl ether structure has a structure in which polymer chains are difficult to align, and thus has a large free volume. Moreover, a free volume can also be increased by introduce | transducing a substituent with a large volume, such as an aromatic substituent and an alicyclic group, into a polyimide (nonpatent literature 1).
(3) Many holes are introduced into the plate (Non-Patent Documents 1 to 4, Patent Document 1). For example, in Non-Patent Documents 2 to 4, a side chain that thermally decomposes upon heating to imidize a polyimide precursor is introduced into the precursor, or a substance that thermally decomposes upon heating is mixed with the precursor. It is described that a porous molded body (plate material) of polyimide having a large number of holes having a diameter of several nanometers to several tens of nanometers is described. Further, Patent Document 1 discloses that a molded body of thermoplastic polyimide is infiltrated by contacting a non-reactive gas such as carbon dioxide under pressure, and the molded body is heated after the pressure is reduced. It is described that a porous molded body of polyimide having a large number of pores having a diameter of 0.01 to 10 μm is produced by foaming while softening. According to these hole introduction methods, the dielectric constant of polyimide can be lowered from 3.2 to 3.8 when there is no hole to 2.9 or less.
化学構造を改変する手法（上記(1), (2)）には、ポリイミド本来の特長である耐熱性、耐溶剤性及び絶縁信頼性が低下するという欠点がある。 The methods for modifying the chemical structure (above (1) and (2)) have the disadvantage that the heat resistance, solvent resistance and insulation reliability, which are the original characteristics of polyimide, are reduced.
また、非特許文献２〜４に記載の空孔導入法では、径が数nm〜数十nmという微小な孔しか形成することができず、空隙率をあまり高くすることができない、という問題がある。 In addition, in the hole introduction methods described in Non-Patent Documents 2 to 4, there is a problem that only minute holes having a diameter of several nanometers to several tens of nanometers can be formed, and the porosity cannot be increased so much. is there.
更に、特許文献１に記載のガスを用いた空孔導入法では、非反応性ガスの浸透後、発泡前に該ガスの一部が逃げてしまうため、十分に発泡させることができず、誘電率低下の効果が損なわれる、という問題がある。特に、成形体（板材）の厚みが薄くなるほどガスが逃げやすくなることから、この方法を厚さ20μm以下の薄膜に適用することは困難である。 Furthermore, in the hole introduction method using the gas described in Patent Document 1, since a part of the gas escapes before the foaming after the penetration of the non-reactive gas, the gas cannot be sufficiently foamed. There is a problem that the effect of rate reduction is impaired. In particular, it is difficult to apply this method to a thin film having a thickness of 20 μm or less because the gas escapes more easily as the thickness of the molded body (plate material) becomes thinner.
本発明が解決しようとする課題は、ポリイミド本来の特長を損なうことなく誘電率を低くすることができる低誘電率ポリイミド膜等に用いられる多孔質ポリイミド膜の製造方法を提供することである。なお、この方法は多孔質ポリスチレン膜の製造にも適用できるものである。併せて、多孔質ポリイミド膜を用いた多孔質電極の製造方法、及び多孔質電極を提供する。 The problem to be solved by the present invention is to provide a method for producing a porous polyimide film used for a low dielectric constant polyimide film or the like that can lower the dielectric constant without impairing the original characteristics of polyimide. This method can also be applied to the production of a porous polystyrene film. In addition, a method for producing a porous electrode using a porous polyimide film and a porous electrode are provided.
上記課題を解決するために成された本発明に係る多孔質ポリイミド膜の製造方法は、
a) 極性を有する揮発性の溶媒に、ポリイミド前駆体と、三級アミンを有する光硬化性樹脂前駆体を溶解させた溶液を作製し、
b) 基板上に前記溶液を塗布することにより膜を形成し、
c) 前記膜中の前記ポリイミド前駆体の体積含有率及び前記光硬化性樹脂前駆体の体積含有率の各々よりも前記溶媒の体積含有率が小さくなるように、該溶媒の一部を前記膜から蒸発させる予備乾燥を行い、
d) 高圧下で前記膜に二酸化炭素を溶解させることにより、該膜内に前記溶媒の液滴を生成し、
e) 前記高圧下で前記膜に光を照射することにより前記光硬化性樹脂前駆体が硬化した光硬化性樹脂を生成し、
f) 前記高圧の印加を止め、前記液滴を蒸発させることにより、前記膜内に空孔を形成し、
g) 前記膜を加熱することにより前記ポリイミド前駆体をイミド化すると共に前記光硬化性樹脂を気化させる
ことを特徴とする。
In order to solve the above problems, a method for producing a porous polyimide film according to the present invention,
a) A solution in which a polyimide precursor and a photocurable resin precursor having a tertiary amine are dissolved in a polar volatile solvent is prepared,
b) forming a film by applying the solution on a substrate;
c) Part of the solvent is added to the film so that the volume content of the solvent is smaller than each of the volume content of the polyimide precursor and the volume content of the photocurable resin precursor in the film. Perform preliminary drying to evaporate from
d) dissolving carbon dioxide in the membrane under high pressure to produce droplets of the solvent in the membrane;
e) generating a photocurable resin obtained by curing the photocurable resin precursor by irradiating the film with light under the high pressure;
f) stopping the application of the high pressure and evaporating the droplets to form vacancies in the film;
g) The polyimide precursor is imidized by heating the film and the photocurable resin is vaporized.
前記予備乾燥を行った段階では、膜は、光硬化性樹脂前駆体が溶解した揮発性極性溶媒中に、高分子から成るポリイミド前駆体が揮発性極性溶媒の一部及び光硬化性樹脂前駆体の一部を吸収して膨潤した状態で存在する粘稠液の状態にある。 In the stage where the preliminary drying is performed, the film is a volatile polar solvent in which the photocurable resin precursor is dissolved, a polyimide precursor made of a polymer is part of the volatile polar solvent, and the photocurable resin precursor. It is in the state of a viscous liquid that exists in a swelled state by absorbing a part of it.
そして、この膜（粘稠液）に二酸化炭素を溶解させると、三級アミンを有する光硬化性樹脂前駆体の分子がその求核性により二酸化炭素の分子と結合して両性イオンを形成し（特許文献２参照）、光硬化性樹脂前駆体の分子における極性が遮蔽される。これにより、高分子のポリイミド前駆体の隙間において、揮発性極性溶媒と、極性が低下した光硬化性樹脂前駆体が相分離する。その際、揮発性極性溶媒は光硬化性樹脂前駆体よりも膜中での体積含有率が小さいことから、1μm〜数十μmの径で揮発性極性溶媒が凝集したもの（本願ではこれを「液滴」と呼ぶ）が光硬化性樹脂前駆体の中に分散して形成される。こうして、膜内では、高分子のポリイミド前駆体の隙間に、揮発性極性溶媒による液滴と光硬化性樹脂前駆体が分離して存在することとなる。 When carbon dioxide is dissolved in this film (viscous liquid), the photocurable resin precursor molecules having tertiary amines bind to carbon dioxide molecules due to their nucleophilicity to form zwitterions ( The polarity in the molecule | numerator of a photocurable resin precursor is shielded. As a result, the volatile polar solvent and the photocurable resin precursor having a reduced polarity are phase-separated in the gap between the polymer polyimide precursors. At that time, the volatile polar solvent has a volume content in the film smaller than that of the photocurable resin precursor, so that the volatile polar solvent is aggregated with a diameter of 1 μm to several tens of μm (in the present application, Droplets) are formed in the photocurable resin precursor in a dispersed manner. Thus, in the film, the droplets of the volatile polar solvent and the photocurable resin precursor exist separately in the gap between the polymer polyimide precursors.
その後、光硬化性樹脂前駆体に光を照射することにより、高分子のポリイミド前駆体の間において、液滴の周囲にある光硬化性樹脂前駆体の分子が重合して硬化した光硬化性樹脂が生成され、それにより液滴の位置及び形状が固定される。そして、光硬化性樹脂及びポリイミド前駆体の隙間を通して液滴内の揮発性極性溶媒を蒸発させることにより、溶媒が存在していた部分が空孔になる。最後に、膜を加熱することにより、ポリイミド前駆体をイミド化すると共に、光硬化性樹脂を熱分解させて気化させる。こうして、多孔質のポリイミド膜が得られる。 Thereafter, the photocurable resin precursor is irradiated with light to polymerize and cure the photocurable resin precursor molecules around the droplets between the polymer polyimide precursors. Is generated, thereby fixing the position and shape of the droplet. And the part in which the solvent existed becomes a void | hole by evaporating the volatile polar solvent in a droplet through the clearance gap between photocurable resin and a polyimide precursor. Finally, by heating the film, the polyimide precursor is imidized and the photocurable resin is thermally decomposed and vaporized. In this way, a porous polyimide film is obtained.
以上のように、本発明では光硬化性樹脂前駆体を硬化させる工程を有するため、その後に空孔が壊れることを防ぐことができる。これにより、空隙率が高く、それゆえFPCに適した低誘電率のポリイミド膜を得ることができる。また、ポリイミド自体の化学構造を改変しないため、ポリイミド本来の特長である高耐熱性、高耐溶剤性及び高絶縁信頼性を損なうことがない。 As described above, since the present invention includes a step of curing the photocurable resin precursor, it is possible to prevent the pores from being broken thereafter. Thereby, it is possible to obtain a polyimide film having a high porosity and hence a low dielectric constant suitable for FPC. In addition, since the chemical structure of the polyimide itself is not altered, high heat resistance, high solvent resistance, and high insulation reliability, which are inherent characteristics of the polyimide, are not impaired.
なお、二酸化炭素を溶解させた後、光硬化性樹脂前駆体を硬化させる前に高圧の印加を止めると、光硬化性樹脂前駆体の分子から二酸化炭素分子が離脱するため、揮発性極性溶媒に光硬化性樹脂前駆体が溶解し、液滴が破壊される。そのため、本発明では、膜に二酸化炭素を溶解させてから光硬化性樹脂前駆体を硬化させるまでの工程は高圧下で行う。 In addition, if the application of high pressure is stopped after the carbon dioxide is dissolved and before the photocurable resin precursor is cured, the carbon dioxide molecules are detached from the molecules of the photocurable resin precursor. The photocurable resin precursor dissolves and the droplets are broken. Therefore, in the present invention, the steps from dissolving carbon dioxide in the film to curing the photocurable resin precursor are performed under high pressure.
上述のように、予備乾燥は膜中のポリイミド前駆体の体積含有率及び光硬化性樹脂前駆体の体積含有率の各々よりも溶媒の体積含有率が小さくなり、且つ、完全には乾燥しないように行う。従って、この条件により、予備乾燥を行う時間の長さの範囲が定まる。その範囲の中でも、予備乾燥の時間が長い、すなわち溶媒の蒸発量が多く、膜に残存する溶媒が少ないほど、作製された多孔質ポリイミド膜において空孔が占める体積の割合（空隙率）は小さくなる。また、予備乾燥の時間が長い（溶媒の蒸発量が多い、溶媒の残存量が少ない）場合には空孔同士が完全に分離されるのに対して、予備乾燥の時間が短い（蒸発量が少ない、残存量が多い）場合には空孔と空孔が接触し、両者が完全には分離せずに連通する。FPCでは、空孔同士が連通すると、空孔内に侵入した水分により電流の経路が形成されてショートするおそれがある。そのため、多孔質ポリイミド膜をFPCに用いる場合には、膜内の空孔同士が分離するように、長時間（但し、上記範囲内で）予備乾燥を行う。この予備乾燥の時間は、例えば、実際に予備乾燥の時間の異なる複数の多孔質ポリイミド膜の試料を作製して各試料の断面を顕微鏡で観察するという予備実験を行うことにより、定めることができる。 As described above, pre-drying causes the volume content of the solvent to be smaller than each of the volume content of the polyimide precursor and the volume content of the photocurable resin precursor in the film, and does not completely dry. To do. Therefore, this condition determines the range of the length of time for performing preliminary drying. Within that range, the proportion of the volume occupied by pores in the produced porous polyimide film (porosity) becomes smaller as the pre-drying time is longer, that is, the amount of solvent evaporation is larger and the amount of solvent remaining in the membrane is smaller. Become. In addition, when the predrying time is long (the amount of evaporation of the solvent is large and the residual amount of the solvent is small), the pores are completely separated from each other, whereas the predrying time is short (the evaporation amount is small). If the remaining amount is small), the vacancies come into contact with each other, and the two communicate with each other without being completely separated. In the FPC, when the holes communicate with each other, there is a possibility that a current path is formed due to moisture that has entered the holes, causing a short circuit. Therefore, when a porous polyimide membrane is used for FPC, preliminary drying is performed for a long time (but within the above range) so that pores in the membrane are separated from each other. The preliminary drying time can be determined, for example, by conducting a preliminary experiment in which a plurality of porous polyimide film samples having different preliminary drying times are actually prepared and a cross section of each sample is observed with a microscope. .
一方、空孔同士が連通した多孔質ポリイミド膜は、後述のように多孔質電極を製造する際に好適に用いることができる。その場合には、膜内の空孔同士が連通するように短時間（但し、上記範囲内で）予備乾燥を行う。この場合も、上記と同様の予備実験を行うことにより、予備乾燥の時間を定めることができる。 On the other hand, the porous polyimide film in which the pores communicate with each other can be suitably used when producing a porous electrode as described later. In that case, preliminary drying is performed for a short time (within the above range) so that the pores in the membrane communicate with each other. Also in this case, the preliminary drying time can be determined by performing a preliminary experiment similar to the above.
本発明に係る多孔質ポリイミド膜の製造方法において、前記膜の形成後であって、高圧下で該膜に二酸化炭素を溶解させる前に、該膜に前記光硬化性樹脂前駆体を硬化させる光を照射し、該光硬化性樹脂前駆体が完全に硬化する前に該照射を停止することが望ましい。以下、この工程における光の照射を「予備照射」と呼ぶ。なお、予備乾燥と予備照射は、いずれを先に行ってもよいし、両者を同時に行ってもよい。 In the method for producing a porous polyimide film according to the present invention, after the film is formed and before carbon dioxide is dissolved in the film under high pressure, the light that cures the photocurable resin precursor on the film It is desirable to stop the irradiation before the photo-curing resin precursor is completely cured. Hereinafter, the light irradiation in this step is referred to as “preliminary irradiation”. Note that either preliminary drying or preliminary irradiation may be performed first, or both may be performed simultaneously.
予備照射を行うことにより、光硬化性樹脂前駆体が重合した重合体が生成される。ただし、この段階での重合体の重合度は、完全に硬化した光硬化性樹脂の場合よりも低い。そして、膜に二酸化炭素を溶解させることで溶媒の液滴を形成した際に、それら液滴の間に重合体が存在するため、液滴同士をより確実に分離することができる。その後、さらに光を照射することにより、重合体同士が重合し、光硬化性樹脂前駆体が完全に硬化した光硬化性樹脂となる。 By performing preliminary irradiation, a polymer in which the photocurable resin precursor is polymerized is generated. However, the degree of polymerization of the polymer at this stage is lower than that of a completely cured photocurable resin. And when a droplet of a solvent is formed by dissolving carbon dioxide in a film, a polymer is present between the droplets, so that the droplets can be more reliably separated. Thereafter, by further irradiating light, the polymers are polymerized, and the photocurable resin precursor becomes a completely cured photocurable resin.
本発明の方法は、多孔質ポリスチレン膜の製造にも適用することができる。本発明に係る多孔質ポリスチレン膜の製造方法は、
a) 極性を有する揮発性の溶媒に、ポリスチレンと、三級アミンを有する光硬化性樹脂前駆体を溶解させた溶液を作製し、
b) 基板上に前記溶液を塗布することにより膜を形成し、
c) 前記膜中の前記ポリスチレンの体積含有率及び前記光硬化性樹脂前駆体の体積含有率の各々よりも前記溶媒の体積含有率が小さくなるように、該溶媒の一部を前記膜から蒸発させる予備乾燥を行い、
d) 前記膜に二酸化炭素ガスにより圧力を印加して該ガスを該膜に溶解させることにより、該膜内に前記溶媒の液滴を生成し、
e) 前記圧力を印加したまま、前記膜に光を照射することにより、前記光硬化性樹脂前駆体が硬化した光硬化性樹脂を生成し、
f) 前記圧力の印加を止め、前記液滴を蒸発させることにより、前記膜内に空孔を形成する
ことを特徴とする。
The method of the present invention can also be applied to the production of porous polystyrene membranes. The method for producing a porous polystyrene film according to the present invention is as follows.
a) A solution in which polystyrene and a photocurable resin precursor having a tertiary amine are dissolved in a polar volatile solvent is prepared.
b) forming a film by applying the solution on a substrate;
c) A part of the solvent is evaporated from the film so that the volume content of the solvent is smaller than each of the volume content of the polystyrene and the volume content of the photocurable resin precursor in the film. Perform preliminary drying,
d) Applying pressure to the membrane with carbon dioxide gas to dissolve the gas in the membrane, thereby generating droplets of the solvent in the membrane;
e) By irradiating the film with light while applying the pressure, the photocurable resin precursor is cured to produce a photocurable resin,
f) The application of the pressure is stopped, and the droplets are evaporated to form pores in the film.
上記方法により作製される、膜内の空孔同士が連通した多孔質ポリイミド膜は、多孔質電極を製造する際に使用することができる。本発明に係る多孔質電極の製造方法は、
上記多孔質ポリイミド膜の製造方法により、膜内の空孔同士が連通した多孔質ポリイミド膜を作製し、
前記多孔質ポリイミド膜の前記空孔の内面を導電性材料で被覆する
ことを特徴とする。
The porous polyimide membrane produced by the above method and having pores in the membrane communicated with each other can be used when producing a porous electrode. A method for producing a porous electrode according to the present invention includes:
By the method for producing a porous polyimide film, a porous polyimide film in which pores in the film communicate with each other is produced,
An inner surface of the pores of the porous polyimide film is covered with a conductive material.
この方法によれば、多孔質ポリイミド膜内の空孔同士が連通しているため、空孔の内面に被覆された導電性材料による電流の経路が膜の両表面で繋がった、膜状の多孔質電極が得られる。導電性材料による被覆には、鍍金法、化学気相蒸着法、スパッタ法等の方法を用いることができる。 According to this method, since the pores in the porous polyimide film communicate with each other, the current path by the conductive material coated on the inner surface of the pore is connected on both surfaces of the membrane. A quality electrode is obtained. For coating with a conductive material, a plating method, a chemical vapor deposition method, a sputtering method, or the like can be used.
また、本発明に係る多孔質電極は、
内部に多数の空孔が連通するように設けられた多孔質ポリイミド膜から成る基材と、
前記空孔の内面を被覆するように設けられた導電性部材と
を備えることを特徴とする。
The porous electrode according to the present invention is
A substrate made of a porous polyimide film provided so that a large number of pores communicate with each other;
And a conductive member provided so as to cover the inner surface of the hole.
このような多孔質電極は、以下に述べるように、リチウムイオン電池の負極に好適に用いられる。リチウムイオン電池では、充電時に負極（材料は黒鉛、錫−ニッケル合金等）の表面に金属リチウムが析出し、放電時にその金属リチウムがイオン化して電解液中に放出される、という充放電のサイクルを繰り返す。この負極に多孔質電極を用いることにより、電極の表面積が大きくなり、多量の金属リチウムを担持することができるため、通常の板状電極よりも充電容量を増加させることができる。 Such a porous electrode is suitably used for a negative electrode of a lithium ion battery as described below. In the lithium ion battery, a charge / discharge cycle in which metal lithium is deposited on the surface of the negative electrode (material is graphite, tin-nickel alloy, etc.) during charge, and the metal lithium is ionized and discharged into the electrolyte during discharge. repeat. By using a porous electrode for the negative electrode, the surface area of the electrode is increased, and a large amount of metallic lithium can be supported, so that the charge capacity can be increased as compared with a normal plate electrode.
さらに、リチウムイオン電池では、負極の表面に付着する金属リチウムの量が増加すると電解液の圧力が高くなるという問題が生じるが、本発明に係る多孔質電極は多孔質ポリイミド膜を基材とすることにより電極全体が収縮可能であるため、板状の導電性部材の内部に空孔が多数設けられた多孔質電極（特許文献３）よりも電解液の圧力上昇を抑えることができるという利点を有する。 In addition, in the lithium ion battery, when the amount of metallic lithium attached to the surface of the negative electrode increases, there is a problem that the pressure of the electrolytic solution increases. However, the porous electrode according to the present invention is based on a porous polyimide film. As a result, the entire electrode can be shrunk, so that an increase in the pressure of the electrolytic solution can be suppressed more than a porous electrode (Patent Document 3) in which a large number of pores are provided inside a plate-like conductive member. Have.
本発明により、空隙率が高いポリイミド膜又はポリスチレン膜を容易に作製することができる。特に、ポリイミド膜の場合には、空隙率が高まるだけでなく、それに伴って、ポリイミド本来の特長である柔軟性、高耐熱性、高耐溶剤性及び高絶縁信頼性を損なうことなく誘電率を低くすることができる。 According to the present invention, a polyimide film or a polystyrene film having a high porosity can be easily produced. In particular, in the case of a polyimide film, not only does the porosity increase, but the dielectric constant is increased without compromising the inherent characteristics of polyimide, such as flexibility, high heat resistance, high solvent resistance, and high insulation reliability. Can be lowered.
また、本発明に係る多孔質電極の製造方法及び多孔質電極により、充電容量を増加させる共に電解液の圧力上昇を抑えることができるという点でリチウムイオン電池の負極に好適に用いることができる電極を得ることができる。 Moreover, the electrode which can be used suitably for the negative electrode of a lithium ion battery at the point that the manufacturing method of the porous electrode which concerns on this invention, and a porous electrode can suppress charge pressure increase and the pressure rise of electrolyte solution can be suppressed. Can be obtained.
本発明に係る多孔質ポリイミド膜の製造方法、多孔質ポリスチレン膜の製造方法、多孔質電極の製造方法、及び多孔質電極の実施形態を、図１〜図１４を用いて説明する。 Embodiments of a method for producing a porous polyimide film, a method for producing a porous polystyrene film, a method for producing a porous electrode, and a porous electrode according to the present invention will be described with reference to FIGS.
(1) 多孔質ポリイミド膜の製造方法の第１実施形態
まず、図１及び図２を用いて、多孔質ポリイミド膜の製造方法の第１実施形態を説明する。本実施形態では初めに、揮発性極性溶媒１１にポリイミドの前駆体又はその材料と、三級アミンを有する分子から成る光硬化性樹脂前駆体を混合することにより溶液１２を作製する（図１(a)）。このとき、溶液全体における揮発性極性溶媒１１の体積含有率はポリイミド前駆体の体積含有率及び光硬化性樹脂前駆体の体積含有率よりも大きい。揮発性極性溶媒１１には例えば、N,N-ジメチルアセトアミド、N-メチルピロドリン、N, N-ジメチルホルムアミド等の低分子から成るものを用いることができる。ポリイミド前駆体の材料には、例えばピロメリット酸無水物と4,4-ジアミノフェニルエーテルを用いることができる。この場合、溶液内でピロメリット酸無水物と4,4-ジアミノフェニルエーテルが重合反応し、ポリイミド前駆体であるポリアミド酸が得られる。光硬化性樹脂前駆体には、例えばN-(3-ジメチルアミノプロピル)メタクリルアミド、メタクリル酸2-(ジエチルアミノ)エチル、N-[3-(ジメチルアミノ)プロピル]アクリルアミド、アクリル酸2-(ジエチルアミノ)エチル、メタクリル酸2-(ジメチルアミノ)エチル、アクリル酸2-(ジメチルアミノ)エチル等の低分子から成るものを用いることができる。なお、溶液１２には併せて、光が照射された時に光硬化性樹脂前駆体を硬化させるための助剤である光開始剤を溶解させてもよい。光開始剤には、上記6種の光硬化性樹脂前駆体に対して、ジフェニル(2,4,6-トリメチルベンゾイル)ホスフィン=オキシドを用いることができる。
(1) First Embodiment of Method for Producing Porous Polyimide Film First, a first embodiment of a method for producing a porous polyimide film will be described with reference to FIGS. 1 and 2. In this embodiment, first, a solution 12 is prepared by mixing a polyimide precursor or a material thereof and a photocurable resin precursor composed of a molecule having a tertiary amine in a volatile polar solvent 11 (FIG. 1 ( a)). At this time, the volume content of the volatile polar solvent 11 in the whole solution is larger than the volume content of the polyimide precursor and the volume content of the photocurable resin precursor. As the volatile polar solvent 11, for example, a solvent composed of a low molecule such as N, N-dimethylacetamide, N-methylpyrodrin, N, N-dimethylformamide or the like can be used. For example, pyromellitic anhydride and 4,4-diaminophenyl ether can be used as the polyimide precursor material. In this case, pyromellitic anhydride and 4,4-diaminophenyl ether undergo a polymerization reaction in the solution to obtain a polyamic acid which is a polyimide precursor. Examples of the photocurable resin precursor include N- (3-dimethylaminopropyl) methacrylamide, 2- (diethylamino) ethyl methacrylate, N- [3- (dimethylamino) propyl] acrylamide, 2- (diethylaminoacrylate) ) Ethyl, 2- (dimethylamino) ethyl methacrylate, 2- (dimethylamino) ethyl acrylate, or the like can be used. In addition, you may dissolve | melt the photoinitiator which is an adjuvant for hardening a photocurable resin precursor when light is irradiated to the solution 12 together. As the photoinitiator, diphenyl (2,4,6-trimethylbenzoyl) phosphine = oxide can be used for the above six kinds of photocurable resin precursors.
次に、ガラス基板１３上に前記溶液１２を塗布することにより膜１４を形成する（図１(b)）。そして、膜１４から揮発性極性溶媒１１の一部を、ポリイミド前駆体や光硬化性樹脂前駆体よりも体積含有率が少なくなるように蒸発させる予備乾燥を行う（図１(c)、図２(a)）。この時、膜１４は、光硬化性樹脂前駆体が溶解した揮発性極性溶媒中に、ポリイミド前駆体が膨潤した状態で存在する粘稠液になっている。なお、この時の溶媒の蒸発量は、例えば容器内で予備乾燥を行い、予備乾燥の前後における膜の重量差や該容器の内面に付着する溶媒の量を計測することで見積もることができる。あるいは、このような計測を予備実験として行っておき、実際に多孔質ポリイミド膜を作製する際には、その予備実験と同じ条件（時間、温度等）で予備乾燥を行う（この時には溶媒の蒸発量は計測しない）ようにしてもよい。 Next, the film 14 is formed by applying the solution 12 on the glass substrate 13 (FIG. 1B). Then, preliminary drying is performed to evaporate a part of the volatile polar solvent 11 from the film 14 so that the volume content is smaller than that of the polyimide precursor or the photocurable resin precursor (FIG. 1 (c), FIG. 2). (a)). At this time, the film 14 is a viscous liquid in which the polyimide precursor is swollen in the volatile polar solvent in which the photocurable resin precursor is dissolved. The amount of evaporation of the solvent at this time can be estimated by, for example, performing preliminary drying in a container and measuring the weight difference of the film before and after the preliminary drying and the amount of solvent adhering to the inner surface of the container. Alternatively, such measurement is performed as a preliminary experiment, and when a porous polyimide film is actually produced, preliminary drying is performed under the same conditions (time, temperature, etc.) as the preliminary experiment (at this time, evaporation of the solvent) The amount may not be measured).
続いて、高圧（3MPa以上）下で膜１４に二酸化炭素を溶解させる（図１(d)）。これにより、光硬化性樹脂前駆体２２の分子はその求核性により二酸化炭素の分子と結合して両性イオンを形成するため極性が遮蔽され、揮発性極性溶媒１１と相分離する。その結果、膜１４内の溶媒及び溶質は、揮発性極性溶媒１１の液滴２１、光硬化性樹脂前駆体２２とポリイミド前駆体２３に分離する（図２(b)）。ここで液滴２１及び光硬化性樹脂前駆体２２は、多数のポリイミド前駆体２３の間に存在する。 Subsequently, carbon dioxide is dissolved in the membrane 14 under high pressure (3 MPa or more) (FIG. 1 (d)). As a result, the molecules of the photocurable resin precursor 22 are bonded to the carbon dioxide molecules due to their nucleophilicity to form amphoteric ions, so that the polarity is shielded and phase-separated from the volatile polar solvent 11. As a result, the solvent and solute in the film 14 are separated into the droplet 21 of the volatile polar solvent 11, the photocurable resin precursor 22 and the polyimide precursor 23 (FIG. 2 (b)). Here, the droplets 21 and the photocurable resin precursor 22 exist between a large number of polyimide precursors 23.
そして、高圧を維持したままの状態で、光硬化性樹脂前駆体２２を硬化させることができる波長を有する光を膜１４に照射することにより、光硬化性樹脂前駆体２２が重合した高分子から成る光硬化性樹脂２２Ａがポリイミド前駆体２３の間に形成される（図１(e)、図２(c)）。 Then, the film 14 is irradiated with light having a wavelength capable of curing the photocurable resin precursor 22 while maintaining the high pressure, whereby the photocurable resin precursor 22 is polymerized. A photocurable resin 22A is formed between the polyimide precursors 23 (FIG. 1 (e), FIG. 2 (c)).
その後、高圧の印加を止めることにより、液滴２１内の揮発性極性溶媒１１を、光硬化性樹脂２２Ａ及びポリイミド前駆体２３の隙間から膜１４外に蒸発させる。これにより、液滴２１が存在していた所に空孔（空隙）２１Ａが形成される（図１(f)、図２(d)）。 Thereafter, the application of the high pressure is stopped to evaporate the volatile polar solvent 11 in the droplet 21 from the gap between the photocurable resin 22A and the polyimide precursor 23 to the outside of the film 14. As a result, holes (voids) 21A are formed where the droplets 21 were present (FIG. 1 (f), FIG. 2 (d)).
最後に、膜１４を加熱することにより、ポリイミド前駆体２３をイミド化すると共に、光硬化性樹脂及び光開始剤を気化させることにより、ポリイミド２３Ａ内に空孔２１Ｂが形成された多孔質ポリイミド膜１０が得られる（図１(g)、図２(e)）。 Finally, the polyimide film 23 is heated to imidize the polyimide precursor 23 and the photocurable resin and the photoinitiator are vaporized to form a porous polyimide film in which pores 21B are formed in the polyimide 23A. 10 is obtained (FIG. 1 (g), FIG. 2 (e)).
なお、上記両性イオンは水が存在すると形成され難くなるため、膜１４には不純物として水ができるだけ混入しないようにすることが望ましい。特に、揮発性極性溶媒１１として例示した上記各材料は吸水性を有するため、脱水溶媒として市販されているものを使用する等、水の混入に注意して取り扱う必要がある。 The amphoteric ions are difficult to be formed in the presence of water. Therefore, it is desirable to prevent water from entering the film 14 as much as possible. In particular, since each of the materials exemplified as the volatile polar solvent 11 has water absorbency, it is necessary to handle it with care in mixing water, such as using a commercially available dehydrating solvent.
また、前記予備乾燥の時間により、多孔質ポリイミド膜の空隙率、空孔の大きさや空孔同士が分離しているか連通しているか、等を調整することができる。この点については、後述の実施例５において説明する。 Further, the porosity of the porous polyimide film, the size of the pores, whether the pores are separated or communicated, and the like can be adjusted by the preliminary drying time. This will be described in Example 5 described later.
(2) 多孔質ポリイミド膜の製造方法の第２実施形態
次に、図３及び図４を用いて、多孔質ポリイミド膜の製造方法の第２実施形態を説明する。第２実施形態の多孔質ポリイミド膜の製造方法は、予備照射を用いるものである。
始めに、第１実施形態と同様の方法により溶液１２を作製し（図３(a)）、ガラス基板１３上に溶液１２を塗布することにより膜１４を形成する（図３(b)）。次に、膜１４から揮発性極性溶媒１１の一部を、ポリイミド前駆体や光硬化性樹脂前駆体よりも体積含有率が少なくなるように蒸発させる（図３(c-1)）。
(2) Second Embodiment of Method for Producing Porous Polyimide Membrane Next, a second embodiment of a method for producing a porous polyimide membrane will be described with reference to FIGS. The method for producing the porous polyimide film of the second embodiment uses preliminary irradiation.
First, the solution 12 is prepared by the same method as that in the first embodiment (FIG. 3A), and the film 14 is formed by applying the solution 12 on the glass substrate 13 (FIG. 3B). Next, a part of the volatile polar solvent 11 is evaporated from the film 14 so that the volume content is smaller than that of the polyimide precursor or the photocurable resin precursor (FIG. 3 (c-1)).
このように揮発性極性溶媒１１の一部を蒸発させている間に、光硬化性樹脂前駆体を硬化させることができる波長を有する光（紫外線）を膜１４に照射する（予備照射、図３(c-2)）。この光の照射は、光硬化性樹脂前駆体が完全に硬化する前に停止する。この光の照射の開始から停止の時間は、予備実験により定めることができる。この工程により、膜１４内の液は、揮発性極性溶媒中に、膨潤したポリイミド前駆体が存在すると共に、光硬化性樹脂前駆体の分子が重合した重合体２２Ｂが硬化することなく存在する粘稠液になっている（図４(a)）。 Thus, while part of the volatile polar solvent 11 is evaporated, the film 14 is irradiated with light (ultraviolet rays) having a wavelength capable of curing the photocurable resin precursor (preliminary irradiation, FIG. 3). (c-2)). This light irradiation stops before the photocurable resin precursor is completely cured. The time from the start to the stop of the light irradiation can be determined by a preliminary experiment. By this step, the liquid in the film 14 has a viscosity in which the swelled polyimide precursor is present in the volatile polar solvent and the polymer 22B in which the molecules of the photocurable resin precursor are polymerized is not cured. It is a solid liquid (FIG. 4 (a)).
続いて、第１実施形態と同様に高圧（3MPa以上）下で膜１４に二酸化炭素を溶解させる（図３(d)）。これにより、膜１４内の溶媒は光硬化性樹脂前駆体の重合体２２Ｂ及びポリイミド前駆体と分離し、該溶媒の液滴が多数形成される。この時、液滴と液滴の間には、ポリイミド前駆体と共に光硬化性樹脂前駆体の重合体２２Ｂが存在するため、第１実施形態と比較して、液滴と液滴がより確実に分離される（図４(b)）。 Subsequently, carbon dioxide is dissolved in the membrane 14 under high pressure (3 MPa or more) as in the first embodiment (FIG. 3 (d)). Thereby, the solvent in the film 14 is separated from the polymer 22B of the photocurable resin precursor and the polyimide precursor, and a large number of droplets of the solvent are formed. At this time, since the polymer 22B of the photocurable resin precursor is present together with the polyimide precursor between the droplets, the droplets and the droplets are more reliably compared with the first embodiment. They are separated (FIG. 4 (b)).
続いて、高圧を維持したままの状態で、光（紫外線）を膜１４に照射することにより、光硬化性樹脂前駆体を硬化させる（図３(e)）。ここで照射する光は、前記予備照射と同じ光源から発せられる光（同じ波長の光）を用いればよいが、それには限定されず、光硬化性樹脂前駆体を硬化させることができる波長を有する光であればよい。その後、第１実施形態と同様に、液滴２１内の揮発性極性溶媒１１を蒸発させることにより、液滴２１が存在していた所に空孔２１Ａを形成する（図３(f)）。そして、膜１４を加熱することにより、ポリイミド前駆体２３をイミド化すると共に、光硬化性樹脂及び光開始剤を気化させることにより、多孔質ポリイミド膜１０が得られる（図３(g)）。 Subsequently, the light curable resin precursor is cured by irradiating the film 14 with light (ultraviolet rays) while maintaining the high pressure (FIG. 3E). The light emitted here may be light emitted from the same light source as the preliminary irradiation (light having the same wavelength), but is not limited thereto, and has a wavelength capable of curing the photocurable resin precursor. It only needs to be light. Thereafter, as in the first embodiment, the volatile polar solvent 11 in the droplet 21 is evaporated to form a hole 21A where the droplet 21 was present (FIG. 3 (f)). And by heating the film | membrane 14, while imidating the polyimide precursor 23, the porous polyimide film | membrane 10 is obtained by vaporizing a photocurable resin and a photoinitiator (FIG.3 (g)).
(3) 多孔質ポリスチレン膜の製造方法の実施形態
多孔質ポリスチレン膜の製造方法の実施形態は、溶液１２を作製する際にポリイミド前駆体（ポリアミド酸）の材料の代わりにポリスチレンを溶解させることと、イミド化のための加熱を行わない点を除いて、上述の多孔質ポリイミド膜の製造方法の第１又は第２の実施形態と同様である。
(3) Embodiment of Method for Producing Porous Polystyrene Membrane An embodiment of a method for producing a porous polystyrene membrane includes dissolving polystyrene instead of a material of polyimide precursor (polyamic acid) when producing solution 12. Except that heating for imidization is not performed, the method is the same as that of the first or second embodiment of the method for manufacturing a porous polyimide film described above.
(4) 多孔質電極の製造方法及び多孔質電極の実施形態
次に、図５を用いて、多孔質電極の製造方法及び多孔質電極の実施形態を説明する。
まず、上記第１又は第２実施形態の多孔質ポリイミド膜の製造方法により、ポリイミド２３Ｂ内の空孔２１Ｃが連通した多孔質ポリイミド膜１０Ａを作製する(a)。次に、空孔２１Ｃ内（内面）を導電性材料３１で被覆する(b)。導電性材料には、例えば、錫−ニッケル合金、アルミニウム等を用いることができる。また、この被覆の方法には、鍍金を用いることができる。これにより、多孔質電極３０が得られる。
(4) Porous Electrode Manufacturing Method and Porous Electrode Embodiment Next, referring to FIG. 5, a porous electrode manufacturing method and a porous electrode embodiment will be described.
First, the porous polyimide film 10A in which the pores 21C in the polyimide 23B communicate with each other is produced by the porous polyimide film manufacturing method of the first or second embodiment (a). Next, the inside (inner surface) of the hole 21C is covered with the conductive material 31 (b). As the conductive material, for example, a tin-nickel alloy, aluminum, or the like can be used. Moreover, a plating can be used for this coating method. Thereby, the porous electrode 30 is obtained.
以下、実際に多孔質ポリイミド膜、多孔質ポリスチレン膜及び多孔質電極を作製した例につき、より具体的に説明する。 Hereinafter, an example in which a porous polyimide film, a porous polystyrene film, and a porous electrode were actually produced will be described more specifically.
まず、N,N-ジメチルアセトアミド（揮発性極性溶媒１１、脱水溶媒として市販のもの）5.5gとピロメリット酸無水物0.55gを混合して攪拌した後、4,4-ジアミノフェニルエーテルを0.50g加えて攪拌することにより、ポリアミド酸の溶液を作製した。この溶液1gに、N-(3-ジメチルアミノプロピル)メタクリルアミド（光（紫外線）硬化性樹脂）とジフェニル(2,4,6-トリメチルベンゾイル)ホスフィン=オキシド（光開始剤）をモル比が15:1、合計質量が0.22gになるように加え、更に攪拌することにより、透明な溶液１２を得た。 First, 5.5 g of N, N-dimethylacetamide (volatile polar solvent 11, commercially available as dehydrating solvent) and 0.55 g of pyromellitic anhydride were mixed and stirred, and then 0.50 g of 4,4-diaminophenyl ether was mixed. In addition, a polyamic acid solution was prepared by stirring. 1 g of this solution was mixed with N- (3-dimethylaminopropyl) methacrylamide (light (ultraviolet) curable resin) and diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (photoinitiator) at a molar ratio of 15 : 1, added to a total mass of 0.22 g, and further stirred to obtain a clear solution 12.
次に、スピンコータを用いて溶液１２をガラス基板１３上に均一に塗布することにより、該溶液１２の膜１４を形成した。そして、膜１４が形成されたガラス基板１３を、石英窓１５１を有し内部の温度が40℃に維持された圧力容器１５に収容し、約2分間置いた。すると、石英窓１５１に液体が付着した。また、この時の膜１４は、溶液１２と同様の透明な色を維持したまま粘稠性が高まっているように見受けられた。なお、本実施例とは別に、ここまでと同じ工程を行った後に石英窓１５１に付着した液体を赤外分光光度計で測定すると共に膜１４の重量を測定する実験をしたところ、赤外分光光度計で得られたスペクトルは揮発性極性溶媒１１のものと一致し、膜１４の重量は当初含有していた揮発性極性溶媒１１の約90％が蒸発したのに相当する値であった。 Next, the film 12 of the solution 12 was formed by uniformly applying the solution 12 on the glass substrate 13 using a spin coater. Then, the glass substrate 13 on which the film 14 was formed was accommodated in a pressure vessel 15 having a quartz window 151 and having an internal temperature maintained at 40 ° C., and was placed for about 2 minutes. Then, the liquid adhered to the quartz window 151. In addition, the film 14 at this time appeared to have increased viscosity while maintaining the same transparent color as the solution 12. Separately from this example, after performing the same steps as heretofore, the liquid adhering to the quartz window 151 was measured with an infrared spectrophotometer and the weight of the film 14 was measured. The spectrum obtained with the photometer coincided with that of the volatile polar solvent 11, and the weight of the film 14 was a value corresponding to the evaporation of about 90% of the volatile polar solvent 11 originally contained.
続いて、圧力容器１５内に5MPaの圧力で二酸化炭素ガスを導入することにより、膜１４に二酸化炭素を溶解させた。これにより、膜１４は白濁した。これは、光硬化性樹脂前駆体の分子が二酸化炭素の分子と結合して両性イオンを形成することにより極性が遮蔽され、揮発性極性溶媒１１と相分離することにより、膜１４内に揮発性極性溶媒１１から成る液滴２１が形成され、その液滴２１により光が散乱されるからであると考えられる。なお、比較のために、ここまでと同じ工程を行った後に二酸化炭素ガスの圧力の印加を止める実験を行ったところ、膜１４は圧力印加前と同様に透明になった。これは、圧力の印加を止めると液滴状態を維持できないことを意味する。一方、本実施例の場合よりも低い3MPaの圧力で二酸化炭素ガスを導入した場合には、本実施例と同様に膜１４が白濁し、液滴２１が形成されることが確認された。 Subsequently, carbon dioxide was dissolved in the membrane 14 by introducing carbon dioxide gas into the pressure vessel 15 at a pressure of 5 MPa. Thereby, the film | membrane 14 became cloudy. This is because the photocurable resin precursor molecules are combined with carbon dioxide molecules to form amphoteric ions, the polarity is shielded, and phase separation from the volatile polar solvent 11 causes volatility in the film 14. This is probably because a droplet 21 made of the polar solvent 11 is formed and light is scattered by the droplet 21. For comparison, an experiment was conducted to stop the application of the pressure of carbon dioxide gas after performing the same steps as heretofore. As a result, the film 14 became transparent as before the application of pressure. This means that the droplet state cannot be maintained when the application of pressure is stopped. On the other hand, when carbon dioxide gas was introduced at a lower pressure of 3 MPa than in the present example, it was confirmed that the film 14 became cloudy and droplets 21 were formed as in the present example.
次に、二酸化炭素ガスによる圧力を加えたまま、石英窓１５１を通して、圧力容器１５内の膜１４に紫外線を照射することにより、光硬化性樹脂２２を硬化させた。 Next, the photocurable resin 22 was cured by irradiating the film 14 in the pressure vessel 15 with ultraviolet rays through the quartz window 151 while applying the pressure by the carbon dioxide gas.
その後、圧力容器１５内の圧力を徐々に下げて常圧にし、膜１４を圧力容器１５から取り出して大気中に放置することにより、膜１４から揮発性極性溶媒１１を蒸発させた。これにより、多数の空孔２１Ａを有する多孔質膜が得られた。この多孔質膜を窒素雰囲気下で110℃、次いで280℃で熱処理することにより、ポリアミド酸をイミド化すると共に、光硬化性樹脂及び光開始剤を気化させた。こうして、多孔質ポリイミド膜１０が得られた。この膜を赤外分光光度計で測定したところ1720cm-1にイミド基に由来する吸収ピークが確認された。 Thereafter, the pressure in the pressure vessel 15 was gradually lowered to normal pressure, and the membrane 14 was taken out of the pressure vessel 15 and left in the atmosphere to evaporate the volatile polar solvent 11 from the membrane 14. Thereby, a porous film having a large number of pores 21A was obtained. The porous film was heat-treated at 110 ° C. and then at 280 ° C. in a nitrogen atmosphere to imidize the polyamic acid and vaporize the photocurable resin and the photoinitiator. Thus, a porous polyimide film 10 was obtained. When this film was measured with an infrared spectrophotometer, an absorption peak derived from an imide group was confirmed at 1720 cm −1 .
光硬化性樹脂前駆体としてメタクリル酸2-(ジエチルアミノ)エチルを用いた点を除いて、実施例１と同様の方法により多孔質ポリイミド膜を作製した。 A porous polyimide film was prepared in the same manner as in Example 1 except that 2- (diethylamino) ethyl methacrylate was used as the photocurable resin precursor.
光硬化性樹脂前駆体としてN-[3-(ジメチルアミノ)プロピル]アクリルアミドを用いた点を除いて、実施例１と同様の方法により多孔質ポリイミド膜を作製した。 A porous polyimide film was produced in the same manner as in Example 1 except that N- [3- (dimethylamino) propyl] acrylamide was used as the photocurable resin precursor.
これら実施例１〜３で得られた多孔質ポリイミド膜の断面の電子顕微鏡写真（図６〜図８）から、膜の内部に細長い形状の空孔が多数形成されていることがわかる。空孔の径の平均値は長径1.4〜4.6μm、短径0.5〜2.6μmであり、空隙率（膜全体の中で空孔が占める体積の割合）は27〜80％であった（表１参照）。
実施例１の多孔質ポリイミド膜につき、誘電率を測定したところ、1.3であった。これは、空孔のないポリイミドの誘電率（3.2〜3.8）と比較すると1/3程度という、従来のポリイミド膜では得ることのできなかった低い値である。 The dielectric constant of the porous polyimide film of Example 1 was measured and found to be 1.3. This is about 1/3 of the dielectric constant (3.2 to 3.8) of polyimide without voids, which is a low value that cannot be obtained with a conventional polyimide film.
実施例１において、二酸化炭素ガスで圧力を印加したことにより白濁した状態の膜１４につき、光学顕微鏡写真（図９）を撮影したところ、膜内に粒状のものが多数存在することが示された。この粒は溶媒の液滴であると考えられる。 In Example 1, when an optical micrograph (FIG. 9) was taken with respect to the film 14 in a state of being clouded by applying pressure with carbon dioxide gas, it was shown that a large number of particles exist in the film. . These grains are considered to be solvent droplets.
揮発性極性溶媒１１には、上記実施例におけるN,N-ジメチルアセトアミドの他にN,N-ジメチルホルムアミド、N-メチルピロリドン等を用いることができる。また、溶液１２を作製するために揮発性極性溶媒１１に溶解させる溶質には、上記実施例におけるピロメリット酸無水物と4,4-ジアミノフェニルエーテルの組み合わせの他に、芳香族テトラカルボン酸二無水物と芳香族ジアミンの組み合わせ等を用いることができる。 As the volatile polar solvent 11, N, N-dimethylformamide, N-methylpyrrolidone, or the like can be used in addition to N, N-dimethylacetamide in the above examples. In addition to the combination of pyromellitic anhydride and 4,4-diaminophenyl ether in the above examples, the solute dissolved in the volatile polar solvent 11 for preparing the solution 12 includes aromatic tetracarboxylic acid dicarboxylic acid. A combination of an anhydride and an aromatic diamine can be used.
（参考例）
膜１４に二酸化炭素を溶解させた時に、三級アミンを有する光硬化性樹脂前駆体の分子が二酸化炭素の分子と結合して両性イオンが形成されることを確認するために、ポリイミド前駆体を含有せず、揮発性極性溶媒及び光硬化性樹脂前駆体を含有する溶液を用いて以下の実験を行った。まず、揮発性極性溶媒（N,N-ジメチルアセトアミド）を5.0重量％、光硬化性樹脂前駆体（N-[3-(ジメチルアミノ)プロピル]アクリルアミド、液体）を94.5重量％、水を0.5重量％含有する溶液（溶液Ａとする）に二酸化炭素ガスで6.1MPaの圧力を印加したところ、液体中に浮遊物が析出した。次に、揮発性極性溶媒を6.2重量％、光硬化性樹脂前駆体を84.0重量％、水を9.8重量％含有する溶液（溶液Ｂとする）に二酸化炭素ガスで6.1MPaの圧力を印加したところ、液体中への浮遊物の析出は見られなかった。これは、溶液Ａでは両性イオンが形成されることにより浮遊物の析出が生じたのに対して、溶液Ｂでは水の含有率が高いため両性イオンの形成が妨げられた（特許文献２参照）ためであると考えられる。なお、この実験では、上記各実施例よりも光硬化性樹脂前駆体の量が多いことから、二酸化炭素ガスの圧力を印加しても光硬化性樹脂前駆体の液体が残存するため、揮発性極性溶媒の液滴は形成されない。
(Reference example)
In order to confirm that when the carbon dioxide is dissolved in the film 14, the photocurable resin precursor molecule having a tertiary amine is combined with the carbon dioxide molecule to form a zwitterion. The following experiment was conducted using a solution containing no volatile polar solvent and a photocurable resin precursor. First, volatile polar solvent (N, N-dimethylacetamide) 5.0 wt%, photo-curing resin precursor (N- [3- (dimethylamino) propyl] acrylamide, liquid) 94.5 wt%, water 0.5 wt% When a pressure of 6.1 MPa was applied to the solution containing 5% (referred to as solution A) with carbon dioxide gas, suspended matter was precipitated in the liquid. Next, when a pressure of 6.1 MPa was applied with carbon dioxide gas to a solution (solution B) containing 6.2% by weight of a volatile polar solvent, 84.0% by weight of a photocurable resin precursor, and 9.8% by weight of water. No deposits of suspended matter were observed in the liquid. This is because the solution A caused the formation of zwitterions due to the formation of zwitterions, whereas the solution B prevented the formation of zwitterions because of the high water content (see Patent Document 2). This is probably because of this. In this experiment, since the amount of the photocurable resin precursor is larger than that in each of the above examples, the liquid of the photocurable resin precursor remains even when the pressure of carbon dioxide gas is applied. Polar solvent droplets are not formed.
溶液１２中の光（紫外線）硬化性樹脂の濃度による空孔の形状等の相違を観察した実験の結果を示す。本実施例では、光硬化性樹脂前駆体は、実施例２と同じメタクリル酸2-(ジエチルアミノ)エチルを用いた。 The result of the experiment which observed the difference in the shape of a void | hole etc. by the density | concentration of the light (ultraviolet ray) curable resin in the solution 12 is shown. In this example, the same 2- (diethylamino) ethyl methacrylate as in Example 2 was used as the photocurable resin precursor.
まず、溶液１２中の光硬化性樹脂前駆体の重量を(a)1.1g、及びそれよりも多い(b)1.7gとした2つの例で実験を行った。図１０に、溶媒を蒸発させて空孔を形成した後、ポリイミド前駆体をイミド化する処理を行う前の膜（ポリイミド前駆体膜）の断面の電子顕微鏡写真を示す。この写真から、(a)よりも(b)の方が、すなわち溶液中の光硬化性樹脂前駆体の濃度が高い方が、空孔が小さく、かつ膜中で空孔が占める割合（空隙率）が小さいことがわかる。これは、光硬化性樹脂前駆体の濃度が高い方が、二酸化炭素の高圧印加を止めた際に生じる二酸化炭素の気泡の成長が抑制されるためであると考えられる。 First, an experiment was conducted using two examples in which the weight of the photo-curable resin precursor in the solution 12 was (a) 1.1 g and (b) 1.7 g higher than that. FIG. 10 shows an electron micrograph of a cross section of the film (polyimide precursor film) after the solvent is evaporated to form voids and before the polyimide precursor is imidized. From this photograph, the ratio of (b) to (b), that is, the higher the concentration of the photocurable resin precursor in the solution, the smaller the vacancies and the proportion of the vacancies in the film (porosity) ) Is small. This is presumably because the higher the concentration of the photo-curable resin precursor, the more the growth of carbon dioxide bubbles generated when the high-pressure application of carbon dioxide is stopped is suppressed.
次に、予備乾燥の時間による、空孔の形状等の相違を観察した実験の結果を示す。光硬化性樹脂前駆体は、実施例２及び４と同じメタクリル酸2-(ジエチルアミノ)エチルを用いた。溶液１２中の光硬化性樹脂前駆体の重量は1.1gとした。ここでは、銅箔（基板）上に溶液１２を塗布して形成した膜１４（図１）を、(a)形成後直ちに圧力容器１５に収容したもの、及び圧力容器１５に収容する前に(b)1時間、(c)2時間、(d)3時間及び(e)4時間乾燥させたもの、という5種類の試料を作製した。なお、実施例１の説明で述べたように、溶媒は、圧力容器１５に収容後、二酸化炭素を導入するまでの間にも蒸発している。 Next, the result of the experiment which observed the difference in the shape etc. of a hole by the time of preliminary drying is shown. As the photocurable resin precursor, the same 2- (diethylamino) ethyl methacrylate as in Examples 2 and 4 was used. The weight of the photocurable resin precursor in the solution 12 was 1.1 g. Here, the film 14 (FIG. 1) formed by applying the solution 12 on the copper foil (substrate) is accommodated in the pressure vessel 15 immediately after the formation (a) and before being accommodated in the pressure vessel 15 ( Five types of samples were prepared: b) 1 hour, (c) 2 hours, (d) 3 hours, and (e) dried for 4 hours. Note that, as described in the description of the first embodiment, the solvent is evaporated even after the carbon dioxide is introduced after being accommodated in the pressure vessel 15.
図１１に、ポリイミド前駆体膜の断面の電子顕微鏡写真を(a)〜(e)の試料について示す。また、図１２には、(a)〜(c)及び(e)の試料について、最終的に得られた多孔質ポリイミド膜の断面の電子顕微鏡写真を示す。 In FIG. 11, the electron micrograph of the cross section of a polyimide precursor film | membrane is shown about the sample of (a)-(e). FIG. 12 shows electron micrographs of the cross section of the finally obtained porous polyimide film for the samples (a) to (c) and (e).
これらの図より、予備乾燥の時間が長くなるほど、空隙率が小さくなり、各空孔の径も小さくなることがわかる。特に、予備乾燥の時間が最も長い4時間である(e)の試料では、空孔同士が連通していない（空孔同士が完全に分離している）。なお、図１２(e)では線状の模様が見られるが、これはポリイミドの部分に形成されたものであり、空孔は維持されている。このように空孔同士が連通していない多孔質ポリイミド膜は、空孔内に水分が侵入することを防ぐことができ、それゆえ水分による電流のショートを防ぐことができるため、FPCに特に好適に用いることができる。 From these figures, it can be seen that the longer the preliminary drying time, the smaller the porosity and the smaller the diameter of each hole. In particular, in the sample (e) having the longest pre-drying time of 4 hours, the vacancies are not in communication (the vacancies are completely separated). In FIG. 12 (e), a linear pattern can be seen, which is formed in the polyimide portion, and the pores are maintained. The porous polyimide film in which the pores do not communicate with each other in this way is particularly suitable for FPC because it can prevent moisture from entering into the pores and hence prevent short circuit of current due to moisture. Can be used.
また、予備乾燥の時間が短い(a)の試料では、空孔同士が接している。このような試料は空孔同士が連通し、後述の多孔質電極の製造方法において好適に用いることができる。なお、(b)の試料では、(a)よりも個々の空孔の径は大きくなっているが、空隙率は(a)の試料とほぼ同じである。 In the sample (a) having a short preliminary drying time, the pores are in contact with each other. Such a sample has pores communicating with each other, and can be suitably used in a method for producing a porous electrode described later. In the sample of (b), the diameter of each pore is larger than that of (a), but the porosity is almost the same as that of the sample of (a).
次に、予備照射を用いた多孔質ポリイミド膜の製造方法（上記第２実施形態）の実施例を説明する。本実施例では、予備乾燥の後であって二酸化炭素を溶解させる前に、波長365nm、強度52mW/cm2の紫外線を膜１４に5秒間照射した（予備照射）。また、二酸化炭素溶解後に光硬化樹脂前駆体を完全に硬化させる際には、予備照射と同じ波長及び強度の紫外線を30秒間照射した。その他の作製条件は実施例５の(a)と同じとした。図１３に、この方法により得られた、イミド化前のポリイミド前駆体膜の断面写真を示す。この結果から、実施例５の(a)におけるポリイミド前駆体膜（図１１(a)）よりも空孔の径が小さくなっていることがわかる。これは、予備照射により生成された光硬化樹脂前駆体の重合体が、二酸化炭素の溶解後に液滴と液滴の間に存在することにより、液滴同士が結合することを防ぎ、小さい径を維持することができたことによる。 Next, an example of a method for producing a porous polyimide film using preliminary irradiation (the second embodiment) will be described. In this example, after the preliminary drying and before the carbon dioxide was dissolved, the film 14 was irradiated with ultraviolet rays having a wavelength of 365 nm and an intensity of 52 mW / cm 2 for 5 seconds (preliminary irradiation). Further, when the photo-curing resin precursor was completely cured after carbon dioxide dissolution, ultraviolet rays having the same wavelength and intensity as the pre-irradiation were irradiated for 30 seconds. Other manufacturing conditions were the same as those in Example 5 (a). In FIG. 13, the cross-sectional photograph of the polyimide precursor film | membrane before imidation obtained by this method is shown. From this result, it can be seen that the pore diameter is smaller than the polyimide precursor film (FIG. 11 (a)) in Example 5 (a). This is because the polymer of the photo-curing resin precursor generated by the preliminary irradiation is present between the droplets after the dissolution of carbon dioxide, thereby preventing the droplets from being bonded to each other and reducing the diameter. By being able to maintain.
次に、本発明に係る多孔質ポリスチレン膜の製造方法の実施例について述べる。
まず、N,N-ジメチルアセトアミド（揮発性極性溶媒１１）5.5gにポリスチレン1.0g、メタクリル酸2-(ジエチルアミノ)エチル（光硬化性樹脂前駆体）1.2g及びジフェニル(2,4,6-トリメチルベンゾイル)ホスフィン=オキシド（光開始剤）0.2gを溶解させることにより溶液１２を作製した。次に、スピンコータを用いて溶液１２をガラス基板１３上に均一に塗布することにより、該溶液１２の膜１４を形成した。そして、膜１４が形成されたガラス基板１３を、石英窓１５１を有し内部の温度が40℃に維持された圧力容器１５に収容し、約2分間置くことにより、揮発性極性溶媒１１の一部を蒸発させた。続いて、圧力容器１５内に5MPaの圧力で二酸化炭素ガスを導入することにより膜１４に二酸化炭素を溶解させて、溶媒の液滴を生成した。さらに膜１４に紫外線を照射することにより、光硬化性樹脂前駆体を硬化させた。その後、膜１４を圧力容器１５から取り出して大気中に放置することにより、残りの揮発性極性溶媒１１を蒸発させた。こうして、多孔質ポリスチレン膜が得られた。なお、この多孔質ポリスチレン膜には光硬化性樹脂が残存している。得られた多孔質ポリスチレン膜を電子顕微鏡で観察したところ、10μm程度の孔が多数形成されていることが確認された。
Next, examples of the method for producing a porous polystyrene film according to the present invention will be described.
First, 5.5 g of N, N-dimethylacetamide (volatile polar solvent 11), 1.0 g of polystyrene, 1.2 g of 2- (diethylamino) ethyl methacrylate (photocurable resin precursor) and diphenyl (2,4,6-trimethyl) Solution 12 was made by dissolving 0.2 g of benzoyl) phosphine oxide (photoinitiator). Next, the film 12 of the solution 12 was formed by uniformly applying the solution 12 on the glass substrate 13 using a spin coater. Then, the glass substrate 13 on which the film 14 is formed is accommodated in a pressure vessel 15 having a quartz window 151 and having an internal temperature maintained at 40 ° C., and is placed for about 2 minutes. The part was evaporated. Subsequently, carbon dioxide gas was introduced into the pressure vessel 15 at a pressure of 5 MPa to dissolve the carbon dioxide in the film 14 to generate solvent droplets. Further, the photocurable resin precursor was cured by irradiating the film 14 with ultraviolet rays. Thereafter, the membrane 14 was taken out from the pressure vessel 15 and left in the atmosphere to evaporate the remaining volatile polar solvent 11. Thus, a porous polystyrene film was obtained. Note that the photocurable resin remains in the porous polystyrene film. When the obtained porous polystyrene film was observed with an electron microscope, it was confirmed that many pores of about 10 μm were formed.
多孔質電極の製造方法の実施例を説明する。本実施例では、以下に述べるように、パラジウムを触媒とする無電解鍍金を用いて、多孔質ポリイミド膜の空孔の内面にニッケルを鍍金した。 An example of a method for producing a porous electrode will be described. In this example, as described below, nickel was plated on the inner surfaces of the pores of the porous polyimide film using electroless plating using palladium as a catalyst.
まず、実施例５の(a)と同様の方法により、多孔質ポリイミド膜を作製する。次に、事前に80℃に加熱した圧力容器内に、この多孔質ポリイミド膜とパラジウム錯体溶液を入れ、圧力容器内を10MPa超臨界二酸化炭素で満たし、2時間加熱した。これにより、多孔質ポリイミド膜にパラジウム錯体を含浸させた。次に、圧力容器内の温度を120℃まで上げてさらに1時間加熱し、パラジウム錯体から有機物を脱離させた。その後、二酸化炭素による圧力印加を止め、室温まで冷却した。そして、多孔質ポリイミド膜を真空乾燥機で1日間乾燥させた。これにより、金属パラジウムが担持された多孔質ポリイミド膜が得られた。 First, a porous polyimide film is produced by the same method as in Example 5 (a). Next, the porous polyimide membrane and the palladium complex solution were placed in a pressure vessel heated to 80 ° C. in advance, and the pressure vessel was filled with 10 MPa supercritical carbon dioxide and heated for 2 hours. Thereby, the porous polyimide film was impregnated with the palladium complex. Next, the temperature in the pressure vessel was raised to 120 ° C. and further heated for 1 hour to desorb organic substances from the palladium complex. Then, the pressure application by carbon dioxide was stopped and it cooled to room temperature. The porous polyimide film was dried with a vacuum dryer for 1 day. As a result, a porous polyimide film carrying metal palladium was obtained.
次に、蒸留水85mlにICPニコロンDK-1（奥野製薬）5ml及びICPニコロンDK-M（奥野製薬）10mlを加えることにより、ニッケル鍍金液を作製した。そして、金属パラジウムが担持された多孔質ポリイミド膜とニッケル鍍金液を容器に入れ、その容器を、温度を60℃に維持した恒温槽に入れ、10時間40分間反応させた。なお、浮力の影響により多孔質ポリイミド膜の一部がニッケル鍍金液に浸漬できなかったため、反応開始から7時間40分経過後に多孔質ポリイミド膜の上下を反転させた。これにより、多孔質ポリイミド膜の空孔の内面がニッケルで被覆された、本実施例の多孔質電極が得られた。なお、金属パラジウムは大部分がポリイミドの分子と分子の間に残留するものの、微量であるため、多孔質電極の柔軟性（収縮性）にはほとんど影響がない。 Next, 5 ml of ICP Nicolon DK-1 (Okuno Pharmaceutical) and 10 ml of ICP Nicolo DK-M (Okuno Pharmaceutical) were added to 85 ml of distilled water to prepare a nickel plating solution. Then, a porous polyimide film carrying metal palladium and a nickel plating solution were placed in a container, and the container was placed in a constant temperature bath maintained at 60 ° C. and allowed to react for 10 hours and 40 minutes. Since part of the porous polyimide film could not be immersed in the nickel plating solution due to the influence of buoyancy, the upper and lower sides of the porous polyimide film were inverted after 7 hours and 40 minutes from the start of the reaction. As a result, the porous electrode of this example in which the inner surface of the pores of the porous polyimide film was coated with nickel was obtained. Although most of the metal palladium remains between polyimide molecules, the amount of metal palladium is very small, and therefore has little influence on the flexibility (shrinkability) of the porous electrode.
図１４に、本実施例で得られた多孔質電極の電子顕微鏡写真を示す。(a)は鍍金前の試料、(b)は鍍金後の試料であり、(c)及び(d)はそれぞれ(a)及び(b)よりも高倍率で撮影したものである。鍍金前よりも鍍金後の方が空孔の径が小さくなっており、空孔の内面にニッケルが鍍金されたものと考えられる。また、膜の両表面間の導通試験を行ったところ、導通が確認された。 FIG. 14 shows an electron micrograph of the porous electrode obtained in this example. (a) is a sample before plating, (b) is a sample after plating, and (c) and (d) are taken at a higher magnification than (a) and (b), respectively. The diameter of the holes is smaller after plating than before plating, and it is considered that nickel was plated on the inner surface of the holes. Moreover, when the conduction | electrical_connection test between the both surfaces of a film | membrane was done, conduction | electrical_connection was confirmed.
１０、１０Ａ…多孔質ポリイミド膜
１１…揮発性極性溶媒
１２…溶液
１３…ガラス基板
１４…膜
１５…圧力容器
１５１…石英窓
２１…液滴
２１Ａ、２１Ｂ、２１Ｃ…空孔（空隙）
２２…光（紫外線）硬化性樹脂前駆体
２２Ａ…光（紫外線）硬化性樹脂
２２Ｂ…光（紫外線）硬化性樹脂前駆体の重合体
２３…ポリイミド前駆体
２３Ａ、２３Ｂ…ポリイミド
３０…多孔質電極
DESCRIPTION OF SYMBOLS 10, 10A ... Porous polyimide film 11 ... Volatile polar solvent 12 ... Solution 13 ... Glass substrate 14 ... Film 15 ... Pressure vessel 151 ... Quartz window 21 ... Droplets 21A, 21B, 21C ... Pore (void)
22 ... light (ultraviolet) curable resin precursor 22A ... light (ultraviolet) curable resin 22B ... light (ultraviolet) curable resin precursor polymer 23 ... polyimide precursor 23A, 23B ... polyimide 30 ... porous electrode
Claims (4)
b) 基板上に前記溶液を塗布することにより膜を形成し、
c) 前記膜中の前記ポリイミド前駆体の体積含有率及び前記光硬化性樹脂前駆体の体積含有率の各々よりも前記溶媒の体積含有率が小さくなるように、該溶媒の一部を前記膜から蒸発させる予備乾燥を行い、
d) 高圧下で前記膜に二酸化炭素を溶解させることにより、該膜内に前記溶媒の液滴を生成し、
e) 前記高圧下で前記膜に光を照射することにより前記光硬化性樹脂前駆体が硬化した光硬化性樹脂を生成し、
f) 前記高圧の印加を止め、前記液滴を蒸発させることにより、前記膜内に空孔を形成し、
g) 前記膜を加熱することにより前記ポリイミド前駆体をイミド化すると共に前記光硬化性樹脂を気化させる
ことを特徴とする多孔質ポリイミド膜の製造方法。 a) A solution in which a polyimide precursor and a photocurable resin precursor having a tertiary amine are dissolved in a polar volatile solvent is prepared,
b) forming a film by applying the solution on a substrate;
c) Part of the solvent is added to the film so that the volume content of the solvent is smaller than each of the volume content of the polyimide precursor and the volume content of the photocurable resin precursor in the film. Perform preliminary drying to evaporate from
d) dissolving carbon dioxide in the membrane under high pressure to produce droplets of the solvent in the membrane;
e) generating a photocurable resin obtained by curing the photocurable resin precursor by irradiating the film with light under the high pressure;
f) stopping the application of the high pressure and evaporating the droplets to form vacancies in the film;
g) A method for producing a porous polyimide film, wherein the polyimide precursor is imidized by heating the film and the photocurable resin is vaporized.
b) 基板上に前記溶液を塗布することにより膜を形成し、
c) 前記膜中の前記ポリスチレンの体積含有率及び前記光硬化性樹脂前駆体の体積含有率の各々よりも前記溶媒の体積含有率が小さくなるように、該溶媒の一部を前記膜から蒸発させる予備乾燥を行い、
d) 前記膜に二酸化炭素ガスにより圧力を印加して該ガスを該膜に溶解させることにより、該膜内に前記溶媒の液滴を生成し、
e) 前記圧力を印加したまま、前記膜に光を照射することにより、前記光硬化性樹脂前駆体が硬化した光硬化性樹脂を生成し、
f) 前記圧力の印加を止め、前記液滴を蒸発させることにより、前記膜内に空孔を形成する
ことを特徴とする多孔質ポリスチレン膜の製造方法。 a) A solution in which polystyrene and a photocurable resin precursor having a tertiary amine are dissolved in a polar volatile solvent is prepared.
b) forming a film by applying the solution on a substrate;
c) A part of the solvent is evaporated from the film so that the volume content of the solvent is smaller than each of the volume content of the polystyrene and the volume content of the photocurable resin precursor in the film. Perform preliminary drying,
d) Applying pressure to the membrane with carbon dioxide gas to dissolve the gas in the membrane, thereby generating droplets of the solvent in the membrane;
e) By irradiating the film with light while applying the pressure, the photocurable resin precursor is cured to produce a photocurable resin,
f) A method for producing a porous polystyrene film, wherein pores are formed in the film by stopping the application of pressure and evaporating the droplets.
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