JP4074987B2 - Polyimide film and stiffener for flexible circuit board using the same - Google Patents

Description

【００３０】
本発明のフィルムを得るためには、架橋剤を添加することが好ましい。
【００３１】
ここでいう架橋剤とは、加熱、光照射、硬化剤の添加などにより分子鎖が伸長、硬化することを特徴とする化合物をいう。例えばローヌプーラン社製“ケルイミド”、三菱ガス化学社製“ＢＴレジン”などのビスマレイミド型熱硬化型ポリイミド、アメリカ航空宇宙局（ＮＡＳＡ）で開発された“ＰＭＲ−１５”、“ＬＡＲＫ−１６０”などのノルボルネン末端反応型熱硬化型ポリイミド、あるいはＨｕｇｅｓエアクラフト社製の”ＴＨＥＲＭＩＤ”、大日本インキ化学（株）のエピクロン、ジャパンエポキシレジン（株）のエピコートなどエポキシを例示することが出来るが、これに限定するものではない。
【００３２】
架橋剤の添加時期は各々の架橋剤でポリアミック酸重合後、重合前のジアミン溶液、酸無水物の添加後など適切に求められるものであるが、添加の容易さからポリアミック酸重合後に添加することが望ましい。
【００３３】
架橋剤の添加量はポリアミック酸に対して０．１〜１０重量％であり、更に好ましくは１〜８重量％、更に好ましくは２〜７％であると引裂強さの変動幅が本願の規定する範囲となり、打ち抜き性が良くなるため好ましい。架橋剤の添加量が０．１重量％より少ないと架橋剤の効果が見られないことがある。また添加量が１０重量％を越えるようだと、架橋が進みすぎ堅くもろいフィルムになってしまうことがある。
【００３４】
ここで得られるポリアミック酸溶液は、固形分を５〜４０重量％、好ましくは１０〜３０重量％を含有しており、またその粘度はブルックフィールド粘度計による測定値で１０〜２０００Ｐａ・ｓ、好ましくは、１００〜１０００Ｐａ・ｓのものが、安定した送液のために好ましく使用される。また、有機溶媒溶液中のポリアミック酸は部分的にイミド化されていてもよい。
【００３５】
次に、本発明のフィルムの製造方法について説明する。
【００３６】
ポリイミドフィルムを製膜する方法としては、ポリアミック酸溶液をフィルム状にキャストし熱的に脱環化脱溶媒させてポリイミドフィルムを得る方法、およびポリアミック酸溶液に環化触媒及び脱水剤を混合し化学的に脱環化させてゲルフィルムを作成しこれを加熱脱溶媒することによりポリイミドフィルムを得る方法が挙げられ、いずれの方法を用いてもよく、化学的方法と熱的方法を併用しても良い。本発明のフィルムを得るためには後者の化学的に脱環化させる方法を用いる方がフィルムの厚み方向の機械的特性が均一化するため、打ち抜き性の改善には好ましい結果が得られる。
【００３７】
化学的に脱環化させる方法においては、まず上記ポリアミック酸溶液を調製する。
【００３８】
なお、このポリアミック酸溶液は、必要に応じて、酸化チタン、シリカ、炭酸カルシウム、リン酸カルシウム、リン酸水素カルシウムおよびポリイミドフィラーなどの化学的に不活性な有機フィラーや無機フィラーを、３０重量％未満濃度で含有することができる。
【００３９】
ここで使用するポリアミック酸溶液は、予め重合したポリアミック酸溶液であっても、またフィラー粒子を含有させる際に順次重合したものであってもよい。
【００４０】
上記ポリアミック酸溶液は、環化触媒（イミド化触媒）、脱水剤およびゲル化遅延剤などを含有することができる。
【００４１】
本発明で使用される環化触媒の具体例としては、トリメチルアミン、トリエチレンジアミンなどの脂肪族第３級アミン、ジメチルアニリンなどの芳香族第３級アミン、およびイソキノリン、ピリジン、ベータピコリンなどの複素環第３級アミンなどが挙げられるが、複素環式第３級アミンから選ばれる少なくとも一種類のアミンを使用するのが好ましい。
【００４２】
本発明で使用される脱水剤の具体例としては、無水酢酸、無水プロピオン酸、無水酪酸などの脂肪族カルボン酸無水物、および無水安息香酸などの芳香族カルボン酸無水物などが挙げられるが、無水酢酸および／または無水安息香酸が好ましい。
【００４３】
ポリアミック酸溶液からポリイミドフィルムを製造する方法としては、環化触媒および脱水剤を含有せしめたポリアミック酸溶液をスリット付き口金から支持体上に流延してフィルム状に成形し、支持体上でイミド化を一部進行させて自己支持性を有するゲルフィルムとした後、支持体より剥離し、加熱乾燥／イミド化し、熱処理を行う。
【００４４】
上記ポリアミック酸溶液は、スリット状口金を通ってフィルム状に成型され、加熱された支持体上に流延され、支持体上で熱閉環反応をし、自己支持性を有するゲルフィルムとなって支持体から剥離される。
【００４５】
上記支持体とは、金属製の回転ドラムやエンドレスベルトであり、その温度は液体または気体の熱媒によりおよび／または電気ヒーターなどの輻射熱により液体または気体の熱媒によりおよび／または電気ヒーターなどの輻射熱により制御される。
【００４６】
上記ゲルフィルムは、支持体からの受熱および／または熱風や電気ヒーターなどの熱源からの受熱により３０〜２００℃、好ましくは４０〜１５０℃に加熱されて閉環反応し、遊離した有機溶媒などの揮発分を乾燥させることにより自己支持性を有するようになり、支持体から剥離される。
【００４７】
上記支持体から剥離されたゲルフィルムは、通常回転ロールにより走行速度を規制しながら走行方向に延伸される。延伸は、１４０℃以下の温度で１．０５〜１．９倍、好ましくは１．１〜１．６倍、さらに好ましくは１．１〜１．５倍の倍率で実施される。走行方向に延伸されたゲルフィルムは、テンター装置に導入され、テンタークリップに幅方向両端部を把持されて、テンタークリップと共に走行しながら、幅方向へ延伸される。上記の乾燥ゾーンで乾燥したフィルムは、熱風、赤外ヒーターなどで１５秒から１０分加熱される。次いで、熱風および／または電気ヒーターなどにより、２５０〜５００℃の温度で１５秒から２０分熱処理を行う。
【００４８】
【実施例】
本発明の物性の測定方法、効果の評価方法は次の方法による。
（１）引裂強さの変動幅ｄ、および平均Ｆ、Ｒ
引裂強さの変動幅ｄ、および平均Ｆは直角形引裂法（ＪＩＳ Ｋ７１２８−３）に準じて、以下のようにして測定した。
【００４９】
図１に示す試験片の両端をつまみ具で固定し２０ｍｍ／ｍｉｎの速度で上下に引っ張る。その時引裂力−引裂長さグラフが記録される。引裂強さは引裂力をフィルム厚みで割ることによって求められる。得られたグラフから、波長０．５ｍｍ以上のうねり成分をカットオフし、引裂開始時からの１５ｍｍを除外した２５ｍｍを測定範囲とし、その平均値を引裂強さの平均Ｆとし、また引裂強さの最大値と最小値を求め、この差を変動幅ｄとした。ここでいう波長とは実際の引裂長さにもとづくものである。得られた平均Ｆおよび変動幅ｄからＲを式１によって求めた。
【００５０】
Ｒ（％）＝（ｄ／Ｆ）×１００・・・・・・・・・・・・（式１）
（２）Ｌ値
スガ試験機株式会社製の「ＳＭ７ カラーコンピュータ ｍｏｄｅｌ ＳＭ−７ Ｖｅｒ １．００」を使用し、それぞれ以下のように条件を選定して測定した。
【００５１】
光学系 ：２光路光学系 反射
光源・視野：Ｃ光 ２゜視野
表示選択 ：Ｌａｂ
測定後、Ｌ，ａ，ｂが自動的に印刷されるが、このうちＬの値をＬ値として扱った。
（３）打ち抜き性の評価
ポリイミドフィルムを４μｍクリアランスに設定されたダイ上に載せ、ピンにより０．５ｍｍ径の穴を５００個打ち抜いた。その時バリ・切り屑の発生した穴の数により以下のように評価した。
【００５２】
◎：バリ、切り屑の発生した穴の数が ２５個以下
○：バリ、切り屑の発生した穴の数が ２６個以上７５個以下
△：バリ、切り屑の発生した穴の数が ７６個以上１５０個以下
×：バリ、切り屑の発生した穴の数が １５１個以上
［実施例１］
ＤＣスターラーを備えた３００ｍｌセパラブルフラスコ中に４，４’−ジアミノジフェニルエーテル１９．４３ｇ（９７ｍｍｏｌ）、Ｎ，Ｎ’−ジメチルアセトアミド１４９．５ｇをいれ窒素雰囲気下、室温で撹拌した。３０分撹拌後、５−ノルボルネン−２，３−ジカルボン酸二無水物０．１５９ｇ（０．９７ｍｍｏｌ）を加えて撹拌した。更に３０分から１時間後にピロメリット酸二無水物２０．５３ｇ（９４ｍｍｏｌ）を数回に分けて投入した。１時間撹拌した後、ピロメリット酸二無水物のＮ，Ｎ’−ジメチルアセトアミド溶液（６重量％）１０．５８ｇを３０分かけて滴下し更に１時間撹拌した。これをポリアミック酸溶液Ａとする。
【００５３】
一方、ＰＭＲ−１５溶液の調整は下記のように行った。ＤＣスターラーを備えた３００ｍｌセパラブルフラスコ中に４，４’−ジアミノジフェニルメタン９．９１ｇ（５０ｍｍｏｌ）、Ｎ，Ｎ’−ジメチルアセトアミド１０３．８６ｇをいれ窒素雰囲気下、室温で撹拌した。３０分撹拌後、ベンゾフェノンテトラカルボン酸二無水物１０．６３ｇ（３３ｍｍｏｌ）を数回に分けて投入した。１時間撹拌したのち５−ノルボルネン−２，３−ジカルボン酸無水物５．４１ｇ（３３ｍｍｏｌ）を投入し更に３０分撹拌した。
【００５４】
１００ｇのポリアミック酸溶液ＡにＰＭＲ１５溶液を５．０８ｇ添加し、撹拌、脱泡して得られたポリアミック酸混合物溶液の一部をポリエステルフィルム上にとり、スピンコーターを用いて均一な膜を形成した。これを１００℃のオーブンで１時間加熱することにより自己保持性のポリアミック酸フィルムを得た。得られたポリアミック酸フィルムを２００℃３０分、３００℃２０分、４００℃５分の条件で熱処理を行うことにより、厚さ１７５μｍのポリイミドフィルムを得た。得られたポリイミドフィルムの引裂強さを測定したところ、表１に示す通りＲは２０％、Ｌ値は９、打ち抜き性を評価したところ○であり、フレキシブル回路基板用スティフナーとして良好な特性を示した。
［実施例２］
５−ノルボルネン−２，３−ジカルボン酸二無水物を加えない以外は実施例１と同様の操作でポリアミック酸溶液を得た。これをポリアミック酸溶液Ｂとする。
【００５５】
１００ｇのポリアミック酸溶液Ｂに実施例１で得られたＰＭＲ−１５溶液を５．０８ｇ添加し、得られたポリアミック酸混合物溶液を用いて実施例１と同様に製膜し、ポリイミドフィルムを得た。このフィルムの特性は表１に示すとおり打ち抜き性は○であり、フレキシブル回路基板用スティフナーとして良好な特性を示した。
［実施例３］
実施例２で得たポリアミック酸溶液Ｂ１００ｇに実施例１で得たＰＭＲ−１５溶液を１．０２ｇを添加し、得られたポリアミック酸混合物溶液を用いて実施例１と同様に製膜しポリイミドフィルムを得た。このフィルムの特性は表１に示すとおり打ち抜き性は△であり、フレキシブル回路基板用スティフナーとして実用レベルであった。
［実施例４］
実施例２と同様にして得られた１００ｇのポリアミック酸溶液Ｂに実施例１で得たＰＭＲ−１５溶液を５．０８ｇ添加し、−５℃まで冷却した後、βピコリン４．９７ｇと無水酢酸５．４５ｇを加えた。こうして得られたポリアミック酸混合物溶液を用いて、実施例１と同様に製膜しポリイミドフィルムを得た。このフィルムの特性は表１に示すとおり打ち抜き性は◎であり、フレキシブル回路基板用スティフナーとして優れた特性を示した。これは化学的イミド化を採用することにより、厚み方向の物性がより均一になったためと考えられる。
［比較例１］
実施例２で得られたポリアミック酸溶液Ｂを用いて実施例１と同様に製膜しポリイミドフィルムを得た。このフィルムの特性は表１に示すとおり打ち抜き性は×であり、フレキシブル回路基板用スティフナーとして実用に耐える物ではなかった。これは架橋していないために層状破壊が起こりＲが大きくなり、結果として打ち抜き性が悪化したものと考えられる。
［比較例２］
実施例２で得られたポリアミック酸溶液Ｂ１００ｇに実施例１で得られたＰＭＲ−１５溶液１２．１８ｇを添加し、得られたポリアミック酸混合物溶液を用いて実施例１と同様に製膜しポリイミドフィルムを得た。このフィルムの特性は表１に示すとおり打ち抜き性は×であり、フレキシブル回路基板用スティフナーとして実用に耐える物ではなかった。これは架橋剤が過剰なため、可撓性に欠け、それに伴いＲが大きくなってしまい、結果として打ち抜き性が悪化したものと考えられる。
［比較例３］
自己保持性のポリアミック酸フィルムの熱処理を２００℃３０分、３００℃２０分、４３０℃１０分としたほかは、実施例２と同様に重合、製膜し、ポリイミドフィルムを得た。このフィルムの特性は表１に示すとおり打ち抜き性は×であり、フレキシブル回路基板用スティフナーとして実用に耐える物ではなかった。これは熱処理温度が高く、時間も長いために架橋剤が変性してしまい、本来の効果を失ったためと考えられる。
【００５６】
【表１】

【００５７】
【発明の効果】
本発明のポリイミドフィルムは、打ち抜き性に優れフレキシブル回路基板のコネクター部及び部品実装部のスティフナーとして好適に用いることができる。
【図面の簡単な説明】
【図１】引き裂き強さを測定するための試験片である。
【図２】ハンター色差によるＬａｂ系色座標である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polyimide film that has excellent punchability and can be suitably used as a stiffener for a connector portion and a component mounting portion of a flexible circuit board.
[0002]
[Prior art]
A flexible circuit board has a basic structure in which a circuit pattern is formed on a flexible and thin base film and a surface is covered with a coverlay. In recent years, a flexible circuit board has excellent functions such as flexibility. As a result, it has been widely used in the field of electronic technology. Further, due to recent advances in mounting technology, the demand for high-density mounting has rapidly increased, and component mounting flexible circuit boards that are directly mounted on flexible circuit boards have been widely used. In such a component-mounted flexible circuit board, it is backed with a reinforcing material (stiffener) or used with a thick insulating film.
[0003]
Polyimide films are widely used as stiffeners for component-mounted flexible circuit boards because of their excellent mechanical properties, electrical properties, chemical resistance, heat resistance, environmental resistance, and the like.
[0004]
And when applying a polyimide film for said use, the operation | work which makes holes, such as a sprocket hole and a pinhole, is generally applied to the film for the purpose of conveyance, conduction | electrical_connection, etc.
[0005]
Here, as a method of making a hole in the polyimide film, there are methods such as a punching method using a mold, a laser processing method, and an alkali etching method, but by using a die that is an inexpensive and capable of making a large amount of holes. Punching is widely used.
[0006]
However, when applying a die-cutting method to a polyimide film, due to non-uniformity in the thickness direction and insufficient strength, burrs and debris generated from the film are generated at the film cut edge, which may cause poor conduction. When the chips adhere to the mold, the chips that have adhered as the punching process is repeated may fall on the adhesive and cause poor adhesion.
[0007]
In order to solve these drawbacks, it has been conventionally practiced to limit end tear resistance, maximum shear load, and tear propagation resistance within a certain range (see Patent Documents 1 to 3). However, even the films specified in these cases have poor punchability. In addition, there is an example (see Patent Document 4) in which punching improvement is attempted with a fluctuation range of tear strength by the trouser tear method, but there is no mention of the film thickness, and the film thickness shown in the examples is 75 μm. It was too thin for the purposes of the invention and was sometimes insufficient for use as a stiffener application.
[0008]
[Patent Document 1]
JP-A-6-334110 [Patent Document 2]
Japanese Patent Laid-Open No. 11-274390 [Patent Document 3]
JP-A-8-48795 [Patent Document 4]
Japanese Patent Laid-Open No. 2002-80623
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned conventional problems and to provide a polyimide film having excellent punchability when used as a stiffener application.
[0010]
[Means for Solving the Problems]
The object of the present invention described above is based on a polyamic acid mixture containing 0.1 to 10% by weight of a crosslinking agent with respect to a polyamic acid obtained by polymerizing an aromatic diamine and an acid anhydride. A polyimide film in which an organic solvent solution of the mixture is heated or added with a cyclization catalyst to form a film and imidization is completed, the thickness is 120 μm or more, and the variation range of tear strength is d (N / Mm), when the average tear strength is F (N / mm), the polyimide film is characterized in that R represented by Formula 1 is 35% or less.
[0011]
R (%) = (d / F) × 100 (Equation 1)
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The thickness of the film of the present invention is 120 μm or more. The stiffener application is preferably 150 μm or more, more preferably 170 μm or more. When the thickness of the film is less than 120 μm, the stiffness of the film is insufficient and it may not be used as a stiffener.
[0013]
When the fluctuation width of the tear strength of the film of the present invention is d (N / mm) and the average tear strength is F (N / mm), R represented by Formula 1 needs to be 35% or less. It is.
[0014]
R (%) = (d / F) × 100 (Equation 1)
It is important to obtain the film of the present invention that this relationship is satisfied in any tear direction.
[0015]
Here, the fluctuation range d and the average F of the tear strength are values determined according to the right-angled tear method (JIS K7128-3), and are measured as follows.
[0016]
The both ends of the test piece shown in FIG. 1 are fixed with a knob and pulled up and down at a speed of 20 mm / min. A tear force-tear length graph is then recorded. The tear strength is determined by dividing the tear force by the film thickness. From the obtained graph, the undulation component having a wavelength of 0.5 mm or more is cut off, the measurement range is 25 mm excluding 15 mm from the start of tearing, the average value is the average F of the tear strength, and the tear strength is The maximum value and the minimum value are obtained, and this difference is defined as a fluctuation range d.
[0017]
The right-angled tear method, which is the basis of this measurement method, was originally intended to measure the force at the start of tearing, and the trouser tear method is often used as a method for measuring tear strength. . However, when considering punching in a stiffener application for the purpose of improvement in the present invention, it can be said that the method of measuring from a state without a cut as in the present measurement is more suitable for the actual process.
[0018]
If the mechanical properties in the thickness direction of the film are not uniform, the tear strength varies greatly with time, that is, R indicating the ratio of the variation range of the tear strength to the average tear strength also varies greatly. . On the other hand, when the mechanical characteristics in the thickness direction of the film are uniform, the fluctuation width with time is small and R is also small.
[0019]
When R is preferably 30% or less, more preferably 25% or less, a film having excellent punchability is obtained.
[0020]
When R is larger than 35%, the mechanical properties in the thickness direction of the film are not uniform, so that layer breakage or the like may occur and the punchability may deteriorate.
[0021]
The film of the present invention preferably has an L value of 11 or less. Preferably, the L value is 10 or less, more preferably 9 or less, because the punchability is improved.
[0022]
The L value in the present invention is defined in the color difference display method of JIS Z 8730. Specifically, it has Lab color coordinates (FIG. 2) based on Hunter color difference, and the L value is calculated from the tristimulus values X, Y, and Z defined in JIS Z 8722 by the following equation.
[0023]
L value = 10Y ^1/2
a = 17.5 (1.02X−Y) / Y ^1/2
b = 7.0 (Y-0.847Z) / Y1 / ²
(A, b = chromaticity index X, Y, Z in Hunter's color difference formula: tristimulus values in XYZ system)
The film of the present invention can be produced, for example, by the following method, but the present invention is not limited to this.
[0024]
In producing the film of the present invention, first, an aromatic diamine component and an acid anhydride component are polymerized in an organic solvent to obtain a polyamic acid solution.
[0025]
Specific examples of the aromatic diamines include paraphenylenediamine, metaphenylenediamine, benzidine, paraxylylenediamine, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylsulfone, 3,3′-dimethyl-4,4′-diaminodiphenylmethane, 1,5-diaminonaphthalene, 3,3′-dimethoxybenzidine, 1,4-bis (3methyl-5 Aminophenyl) benzene and amide-forming derivatives thereof.
[0026]
Specific examples of the acid anhydride component include pyromellitic acid, 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 2,3 ′, 3,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-benzophenone tetracarboxylic acid, 2,3,6,7-naphthalenedicarboxylic acid, 2,2-bis (3,4-dicarboxyphenyl) ether, pyridine-2,3,5,6-tetracarboxylic And acid anhydrides such as acids and their amide-forming derivatives.
[0027]
In the present invention, specific examples of the organic solvent used for forming the polyamic acid solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-diethylformamide and the like. Formamide solvents, N, N-dimethylacetamide, acetamide solvents such as N, N-diethylacetamide, pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, phenol, o-, Examples thereof include phenolic solvents such as m- or p-cresol, xylenol, halogenated phenol and catechol, or aprotic polar solvents such as hexamethylphosphoramide and γ-butyrolactone, and these may be used alone or as a mixture. It is desirable to use But further xylene, the use of aromatic hydrocarbons such as toluene are also possible.
[0028]
Moreover, in order to obtain the film of this invention, it is preferable to add the acid anhydride which has a crosslinking ability as shown in following Chemical formula, and to block the terminal of a polymer. The acid anhydride having crosslinking ability may be added at any stage of the polymerization as long as the polymerization reaction is not inhibited.
[0029]
[Chemical 1]

[0030]
In order to obtain the film of the present invention, it is preferable to add a crosslinking agent.
[0031]
The term “crosslinking agent” as used herein refers to a compound characterized in that a molecular chain is elongated and cured by heating, light irradiation, addition of a curing agent, or the like. For example, Rhône-Poulenc "Kerimide", Mitsubishi Gas Chemical "BT Resin" and other bismaleimide type thermosetting polyimides, "PMR-15" and "LARK-160" developed by the US National Aeronautics and Space Administration (NASA) Examples of the epoxy include norbornene-terminated thermosetting polyimide such as “THERMID” manufactured by Huges Aircraft, Epicron of Dainippon Ink Chemical Co., Ltd., and Epicoat of Japan Epoxy Resin Co., Ltd. However, the present invention is not limited to this.
[0032]
The addition time of the crosslinking agent is appropriately determined after polyamic acid polymerization with each crosslinking agent, after addition of the diamine solution before polymerization, and after the addition of acid anhydride, but should be added after polyamic acid polymerization for ease of addition. Is desirable.
[0033]
The amount of crosslinking agent added is from 0.1 to 10% by weight, more preferably from 1 to 8% by weight, more preferably from 2 to 7%, based on the polyamic acid. This is preferable because the punching property is improved. When the addition amount of the crosslinking agent is less than 0.1% by weight, the effect of the crosslinking agent may not be observed. On the other hand, if the amount added exceeds 10% by weight, the film may be hard and brittle due to excessive crosslinking.
[0034]
The polyamic acid solution obtained here contains 5 to 40% by weight, preferably 10 to 30% by weight of solid content, and the viscosity is 10 to 2000 Pa · s as measured by a Brookfield viscometer, preferably 100-1000 Pa · s is preferably used for stable liquid feeding. Moreover, the polyamic acid in the organic solvent solution may be partially imidized.
[0035]
Next, the manufacturing method of the film of this invention is demonstrated.
[0036]
As a method for forming a polyimide film, a polyamic acid solution is cast into a film and thermally decyclized and desolvated to obtain a polyimide film, and a polyamic acid solution is mixed with a cyclization catalyst and a dehydrating agent. A method of obtaining a polyimide film by creating a gel film by decyclization and heating and desolvating it, and any method may be used, or a chemical method and a thermal method may be used in combination. good. In order to obtain the film of the present invention, the latter chemical decyclization method makes uniform the mechanical properties in the thickness direction of the film, so that preferable results are obtained for improving the punchability.
[0037]
In the method of chemically decyclizing, first, the polyamic acid solution is prepared.
[0038]
In addition, this polyamic acid solution may contain a chemically inert organic filler or inorganic filler such as titanium oxide, silica, calcium carbonate, calcium phosphate, calcium hydrogen phosphate and polyimide filler, if necessary, at a concentration of less than 30% by weight. Can be contained.
[0039]
The polyamic acid solution used here may be a polyamic acid solution polymerized in advance, or may be polymerized sequentially when filler particles are contained.
[0040]
The polyamic acid solution can contain a cyclization catalyst (imidization catalyst), a dehydrating agent, a gelation retarder, and the like.
[0041]
Specific examples of the cyclization catalyst used in the present invention include aliphatic tertiary amines such as trimethylamine and triethylenediamine, aromatic tertiary amines such as dimethylaniline, and heterocyclic rings such as isoquinoline, pyridine and betapicoline. Although a tertiary amine etc. are mentioned, it is preferable to use at least 1 sort (s) of amine chosen from a heterocyclic tertiary amine.
[0042]
Specific examples of the dehydrating agent used in the present invention include aliphatic carboxylic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic carboxylic acid anhydrides such as benzoic anhydride, Acetic anhydride and / or benzoic anhydride are preferred.
[0043]
As a method for producing a polyimide film from a polyamic acid solution, a polyamic acid solution containing a cyclization catalyst and a dehydrating agent is cast on a support from a base with a slit and formed into a film, and an imide is formed on the support. The gel film is partially advanced to form a gel film having self-supporting properties, and then peeled from the support, heat-dried / imidized, and subjected to heat treatment.
[0044]
The polyamic acid solution is formed into a film shape through a slit-shaped die, cast on a heated support, undergoes a thermal ring-closing reaction on the support, and is supported as a gel film having self-supporting properties. It is peeled from the body.
[0045]
The above-mentioned support is a metal rotating drum or endless belt, and the temperature thereof is a liquid or gas heat medium and / or a liquid or gas heat medium by radiant heat such as an electric heater and / or an electric heater or the like. Controlled by radiant heat.
[0046]
The gel film is heated to 30 to 200 ° C., preferably 40 to 150 ° C. by receiving heat from a support and / or receiving heat from a heat source such as hot air or an electric heater, and causes a ring-closing reaction to volatilize a free organic solvent or the like. By drying the part, it becomes self-supporting and is peeled off from the support.
[0047]
The gel film peeled off from the support is usually stretched in the running direction while regulating the running speed with a rotating roll. Stretching is performed at a temperature of 140 ° C. or less at a magnification of 1.05 to 1.9 times, preferably 1.1 to 1.6 times, and more preferably 1.1 to 1.5 times. The gel film stretched in the running direction is introduced into a tenter device, and both ends in the width direction are gripped by the tenter clip, and stretched in the width direction while running with the tenter clip. The film dried in the drying zone is heated for 15 seconds to 10 minutes with hot air, an infrared heater or the like. Next, heat treatment is performed at a temperature of 250 to 500 ° C. for 15 seconds to 20 minutes with hot air and / or an electric heater.
[0048]
【Example】
The physical property measuring method and the effect evaluating method of the present invention are as follows.
(1) Tear strength fluctuation range d and average F, R
The fluctuation range d and the average F of the tear strength were measured as follows according to the right-angled tear method (JIS K7128-3).
[0049]
The both ends of the test piece shown in FIG. 1 are fixed with a knob and pulled up and down at a speed of 20 mm / min. A tear force-tear length graph is then recorded. The tear strength is determined by dividing the tear force by the film thickness. From the obtained graph, the undulation component having a wavelength of 0.5 mm or more is cut off, the measurement range is 25 mm excluding 15 mm from the start of tearing, the average value is the average F of the tear strength, and the tear strength is The maximum value and the minimum value are obtained, and this difference is defined as a fluctuation range d. The wavelength here is based on the actual tear length. From the average F and the fluctuation range d thus obtained, R was obtained by Equation 1.
[0050]
R (%) = (d / F) × 100 (Equation 1)
(2) L value Suga Test Instruments Co., Ltd. “SM7 color computer model SM-7 Ver 1.00” was used, and the conditions were selected and measured as follows.
[0051]
Optical system: Two-path optical system Reflective light source / field of view: C light 2 ° field of view selection: Lab
After the measurement, L, a, and b are automatically printed. Of these, the value of L was treated as the L value.
(3) Evaluation of punchability A polyimide film was placed on a die set to a 4 μm clearance, and 500 0.5 mm diameter holes were punched with a pin. At that time, evaluation was performed as follows according to the number of holes where burrs and chips were generated.
[0052]
◎: Number of holes with burrs and chips 25 or less ○: Number of holes with burrs and chips 26 to 75 holes △: Number of holes with burrs and chips 76 150 or less x: The number of burrs and chips generated is 151 or more [Example 1]
In a 300 ml separable flask equipped with a DC stirrer, 19.43 g (97 mmol) of 4,4′-diaminodiphenyl ether and 149.5 g of N, N′-dimethylacetamide were placed and stirred at room temperature under a nitrogen atmosphere. After stirring for 30 minutes, 0.159 g (0.97 mmol) of 5-norbornene-2,3-dicarboxylic dianhydride was added and stirred. Further, 30 minutes to 1 hour later, 20.53 g (94 mmol) of pyromellitic dianhydride was added in several portions. After stirring for 1 hour, 10.58 g of an N, N′-dimethylacetamide solution (6 wt%) of pyromellitic dianhydride was added dropwise over 30 minutes, and the mixture was further stirred for 1 hour. This is designated as polyamic acid solution A.
[0053]
On the other hand, the PMR-15 solution was adjusted as follows. In a 300 ml separable flask equipped with a DC stirrer, 9.91 g (50 mmol) of 4,4′-diaminodiphenylmethane and 103.86 g of N, N′-dimethylacetamide were placed and stirred at room temperature under a nitrogen atmosphere. After stirring for 30 minutes, 10.63 g (33 mmol) of benzophenonetetracarboxylic dianhydride was added in several portions. After stirring for 1 hour, 5.41 g (33 mmol) of 5-norbornene-2,3-dicarboxylic acid anhydride was added, and the mixture was further stirred for 30 minutes.
[0054]
To 100 g of polyamic acid solution A, 5.08 g of PMR15 solution was added, and a part of the polyamic acid mixture solution obtained by stirring and defoaming was taken on a polyester film, and a uniform film was formed using a spin coater. This was heated in an oven at 100 ° C. for 1 hour to obtain a self-holding polyamic acid film. The obtained polyamic acid film was heat-treated at 200 ° C. for 30 minutes, 300 ° C. for 20 minutes, and 400 ° C. for 5 minutes to obtain a polyimide film having a thickness of 175 μm. When the tear strength of the obtained polyimide film was measured, as shown in Table 1, R was 20%, L value was 9, and the punchability was evaluated as ○, indicating good characteristics as a stiffener for flexible circuit boards. It was.
[Example 2]
A polyamic acid solution was obtained in the same manner as in Example 1 except that 5-norbornene-2,3-dicarboxylic dianhydride was not added. This is designated as polyamic acid solution B.
[0055]
5.08 g of the PMR-15 solution obtained in Example 1 was added to 100 g of the polyamic acid solution B, and a film was formed in the same manner as in Example 1 using the obtained polyamic acid mixture solution to obtain a polyimide film. . As shown in Table 1, this film had good punching properties as shown in Table 1, and exhibited good characteristics as a stiffener for flexible circuit boards.
[Example 3]
1.02 g of the PMR-15 solution obtained in Example 1 was added to 100 g of the polyamic acid solution B obtained in Example 2, and a polyimide film was formed in the same manner as in Example 1 using the obtained polyamic acid mixture solution. Got. As shown in Table 1, this film had a punching property of Δ and was at a practical level as a stiffener for a flexible circuit board.
[Example 4]
5.08 g of the PMR-15 solution obtained in Example 1 was added to 100 g of the polyamic acid solution B obtained in the same manner as in Example 2, and after cooling to -5 ° C, 4.97 g of βpicoline and acetic anhydride were added. 5.45 g was added. Using the polyamic acid mixture solution thus obtained, a film was formed in the same manner as in Example 1 to obtain a polyimide film. As shown in Table 1, this film had excellent punching properties as shown in Table 1, and exhibited excellent characteristics as a stiffener for flexible circuit boards. This is considered to be because the physical properties in the thickness direction became more uniform by employing chemical imidization.
[Comparative Example 1]
Using the polyamic acid solution B obtained in Example 2, a film was formed in the same manner as in Example 1 to obtain a polyimide film. As shown in Table 1, this film had a punchability of x, and was not practically usable as a stiffener for a flexible circuit board. Since this is not cross-linked, it is considered that layer breakage occurs and R increases, and as a result, punchability deteriorates.
[Comparative Example 2]
12.18 g of the PMR-15 solution obtained in Example 1 was added to 100 g of the polyamic acid solution B obtained in Example 2, and a film was formed in the same manner as in Example 1 using the obtained polyamic acid mixture solution. A film was obtained. As shown in Table 1, this film had a punchability of x, and was not practically usable as a stiffener for a flexible circuit board. This is considered to be due to the lack of flexibility due to the excessive amount of the crosslinking agent, resulting in an increase in R, resulting in a deterioration in punchability.
[Comparative Example 3]
A polyimide film was obtained by polymerizing and forming a film in the same manner as in Example 2 except that the heat treatment of the self-holding polyamic acid film was 200 ° C. for 30 minutes, 300 ° C. for 20 minutes, and 430 ° C. for 10 minutes. As shown in Table 1, this film had a punchability of x, and was not practically usable as a stiffener for a flexible circuit board. This is presumably because the heat treatment temperature was high and the time was long, so that the crosslinking agent was denatured and lost its original effect.
[0056]
[Table 1]

[0057]
【The invention's effect】
The polyimide film of the present invention has excellent punchability and can be suitably used as a stiffener for a connector part and a component mounting part of a flexible circuit board.
[Brief description of the drawings]
FIG. 1 is a test piece for measuring tear strength.
FIG. 2 shows Lab color coordinates based on Hunter color difference.

Claims (3)

For a polyamic acid obtained by polymerizing an aromatic diamine and an acid anhydride, a polyamic acid mixture containing 0.1 to 10% by weight of a crosslinking agent is used as a raw material, and an organic solvent solution of this polyamic acid mixture is heated or A polyimide film formed by adding a cyclization catalyst to form a film and completing imidization, having a thickness of 120 μm or more, a fluctuation range of tear strength of d (N / mm), and a tear strength of A polyimide film characterized in that, when the average is F (N / mm), R represented by Formula 1 is 35% or less.
R (%) = (d / F) × 100 (Equation 1) L value is 11 or less, The polyimide film of Claim 1 characterized by the above-mentioned. A stiffener for a flexible circuit board, wherein the polyimide film according to claim 1 or 2 is used as a reinforcing plate for a flexible circuit board .

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