JP2004123211A

JP2004123211A - Shock absorbing packaging material having conductivity and its manufacturing method

Info

Publication number: JP2004123211A
Application number: JP2002292996A
Authority: JP
Inventors: Toshinobu Furuki; 古木　俊信; Yoshikazu Takenaka; 竹中　義和
Original assignee: Sekisui Plastics Co Ltd
Current assignee: Sekisui Kasei Co Ltd
Priority date: 2002-10-04
Filing date: 2002-10-04
Publication date: 2004-04-22
Anticipated expiration: 2022-10-04
Also published as: JP3937090B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive shock absorbing material which has appropriate strength and a shape-keeping property, shows high conductivity between a normal surface and a reverse surface, has not only reduced surface resistivity but volume resistivity and is suitable for stacking. <P>SOLUTION: The conductive shock absorbing material is obtained by thermoforming a laminate foamed sheet2 made of laminating thermoplastic resin films on each other which are printed or coated with a conductive ink wherein the resin films of both the normal surface and the reverse surface are welded to each other into one body in the whole or a part of the outer circumferential edge surface of the shock absorbing packaging material. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、例えばＩＣ部品等の電子部品、液晶表示パネル（ＬＣＤ）、携帯情報端末装置（ＰＤＡ）等の静電気障害を受けやすい物品の包装や運搬に使用される導電性を有するトレイ、容器等の緩衝包装材及びその製造方法に関するものである。
【０００２】
【従来の技術】
従来より、ＩＣ部品等の電子部品、液晶表示パネル（ＬＣＤ）、携帯情報端末装置（ＰＤＡ）等の静電気障害を受けやすい物品の包装や運搬のための緩衝包装材として、静電気による帯電防止のために、導電性のプラスチック発泡シートが用いられている。
【０００３】
かかる導電性プラスチック発泡シートは、これを成形して、被包装物を収容する一つの凹部もしくは複数の凹部を有するトレイや容器等の緩衝包装材として、段ボール箱等の外装箱と組み合わせて使用するのが普通である。また、その使用においては、前記複数の成形トレイ等の緩衝包装材を、被包装物を収容した状態で外装箱内で積み重ね使用することも多い。
【０００４】
前記の導電性プラスチック発泡シートとしては、例えば基材としてのプラスチック発泡シートの片面もしくは両面に、導電性塗料やインキ等を塗布もしくは印刷して導電層を設けたものが知られている。トレイ形状に成形して用いる場合、その基材としては、一般に、シートからの成形が容易で、適度に保形性のある合成樹脂発泡シートが用いられている。
【０００５】
また、包装材としての柔軟性を持たせるために、オレフィン系樹脂の発泡シートもしくはフィルムを素材として、その片面もしくは両面に印刷あるいは塗布した発泡性インキを加熱発泡させた導電性の発泡皮膜を設けたものも提案されている（下記の特許文献１参照）。
【０００６】
【特許文献１】
特公平５−３２２１７号公報　　（第１−３頁、第１−４図）
【０００７】
【発明が解決しようとする課題】
ところで、発泡シートの表面に導電層を設けただけの従来の導電性プラスチック発泡シートよりなる緩衝包装材は、表面抵抗率は低くなるものの、シート厚み方向の導電性は殆ど得られず、体積抵抗率は充分に低くはならない。特に、被包装物を収納した複数の成形トレイ等の緩衝包装材を外装箱内において積み重ねる使用の場合には、表裏面間の厚み方向の導電性が充分でないと、静電気による帯電が生じるという問題がある。
【０００８】
また、前記の特許文献１の導電性プラスチック発泡シート等の場合は、シートからの成形品についての記載がないばかりか、基材の発泡シート等がオレフィン系樹脂（実施例はポリエチレン）を素材とするもの、つまり柔軟性の高い包装材であって、仮に前記発泡シートからトレイ等を成形しても、前記の段積み使用に耐える強度を持つものにはならない。しかも、発泡性インキを基材に直接印刷あるいは塗布するため、基材が発泡シートの場合は、表面に細かい凹凸があるので、インキののりが不十分であったり、不均一になる等の問題がある。
【０００９】
さらに、前記特許文献１では、表裏面間の導電性を得るために、多数の貫通孔を穿設し、その内周面まで前記発泡性インキによる導電性の発泡皮膜を設けることとしているが、この場合、前記貫通孔を形成するための工程が必要になる上、この貫通孔の内周面にまで発泡性インキを印刷もしくは塗布しなければならないことになる。しかも、多数の貫通孔があると、強度を低下させる上、該孔からのゴミや塵の侵入のおそれがあり、ゴミ等を嫌う電子部品等の包装材としての機能を損なうことになる。
【００１０】
なお、基材としてシートからの成形性がよく強度的に優れるポリエステル系樹脂等の発泡シートを用いたものであっても、その表面に導電性のインキ等を直接塗布もしくは印刷すると、その表面がインキ等の溶剤に若干侵され劣化する。また、その表面には凹凸があって、フィルムの場合に比してインキ等を厚く塗る必要があり、劣化に対してさらに不利となる。その上、発泡シートはフィルムに比べて厚みが大きく、印刷後に使用する一般のフィルム用の巻き取り機は使用できないため、特殊な装置が必要になり、設備費用がかかることになる。
【００１１】
さらに、導電性インキを印刷もしくは塗布した後には、通常、乾燥工程が必要であるが、乾燥工程で赤外線ヒーター等を使用して、発泡シートを加熱し乾燥させると、その素材がポリエステル系樹脂の場合には、発泡体の結晶化が上昇し、非常に脆くなるという問題がある。
【００１２】
本発明は、上記に鑑みてなしたものであり、トレイ等の成形品としての使用に耐える強度、保形性を持ちながら、表裏面間の導電性が高くて、表面抵抗率のみでなく、体積抵抗率も低減でき、積み重ね使用するのに好適な導電性を有する緩衝包装材を提供するものであり、さらには前記の緩衝包装材を容易に得ることができる製造方法を提供するものである。
【００１３】
【課題を解決するための手段】
上記の課題を解決する本発明は、熱可塑性樹脂発泡シートの表裏両面に、導電性インキが印刷もしくは塗布された熱可塑性樹脂フィルムが積層された積層発泡シートから熱成形されて得られた導電性を有する緩衝包装材であって、緩衝包装材の外周端面の全部あるいは一部において、前記表裏両面の樹脂フィルム同士が融着一体化されていることを特徴とする。
【００１４】
この発明の緩衝包装材は、発泡シートの表裏両面に非発泡の樹脂フィルムが積層された積層発泡シートからなるので、トレイ等の成形品としての使用上において必要な強度、保形性を保有できる上、その外周端面の少なくとも一部において、表裏両面に積層されている導電性の樹脂フィルム、すなわち表面に導電性インキが印刷あるいは塗布された樹脂フィルム同士が融着一体化しているため、この部分で表裏面間の導電性を確保できることになり、以て表面抵抗率のみでなく、体積抵抗率も低減できる。
【００１５】
しかも、導電性インキを発泡シートに直接塗布するのではなく、樹脂フィルムに印刷あるいは塗布して、該フィルムを発泡シートに積層するので、導電性インキの印刷等による皮膜も全面に渡って均一化し、且つ十分な強度を有して被覆される上、発泡シートがインキにより侵されて劣化するおそれもない。また、インキの乾燥工程は樹脂フィルムで行えるので、発泡シートの表面にインキを直接塗布した場合のような加熱乾燥による影響をうけず、仮に素材がポリエステル系樹脂の発泡シートであっても脆くならず、耐久性を向上できる。
【００１６】
前記の緩衝包装材において、その外周端面における前記表裏両面の導電性の樹脂フィルム同士が融着一体化されている領域が、全外周端面の５０％以上であるのが好ましい。これにより、表裏面間の導電性を充分に確保でき、満足できる体積抵抗率が得られる。すなわち、前記領域が５０％未満では、満足できる体積抵抗率〔１．０×１０^９（Ωｃｍ）以下〕は得られない。したがって、好ましくは外周端面の５０％以上、特に好ましくは全周に渡って表裏両面の導電性の樹脂フィルム同士を融着一体化させておくものとする。
【００１７】
また、前記の熱可塑性樹脂発泡シート、及び表裏両面の熱可塑性樹脂フィルムについては、ポリエステル系樹脂からなるものが好ましく、特にはポリエチレンテレフタレート系樹脂からなるものが好適である。すなわち、ポリエステル系樹脂は、シートからの成形加工、特に比較的深い絞り加工も容易に可能で、しかも強度、保形性にも優れており、被包装物を収容した状態での積み重ね使用も耐える強度を保有できる。特にポリエチレンテレフタレート系樹脂は、外観的に光沢があって美麗で体裁が良く、緩衝包装材としての強度が一層高くなり、ヒンジ特性にも優れる。また、ポリエステル系樹脂の発泡シートは、ポリスチレン系樹脂の発泡シート等と違い、微粉が発生せず、ゴミを嫌う電子部品等の緩衝包装材として好適に使用できる。
【００１８】
本発明は、上記の発明の緩衝包装材の製造方法として、熱可塑性樹脂発泡シートの表裏両面に、導電性インキが印刷もしくは塗布された熱可塑性樹脂フィルムが積層された積層発泡シートを熱成形した後、加熱刃を有する切断装置で切断して個々の緩衝包装材に分離する際に、緩衝包装材の外周の切断端面を加熱し、表裏両面の樹脂フィルム同士を融着一体化させることを特徴とする。
【００１９】
これにより、緩衝包装材の外周端面において、表裏両面の導電性の樹脂フィルム同士を融着一体化させた緩衝包装材を容易に得ることができる。特に、発泡シートの表裏両面に導電性インキを塗布もしくは印刷した樹脂フィルムを積層しておいて、これを加熱刃により切断するので、この切断の際に、表裏両面の樹脂フィルム同士を融着一体化させることが容易に可能になる。しかも、前記の融着一体化は、熱成形後のトリミングと同時に行えるので、工程増にならず、従来同様の製造工程により得ることができる。
【００２０】
【発明の実施の形態】
次に本発明の実施の形態を図面に示す実施例に基づいて説明する。
【００２１】
図１は本発明の緩衝包装材の１実施例を示す一部欠截斜視図、図２は同上の一部の拡大断面図、図３は熱成形前の積層発泡シートの拡大断面図、図４は加熱刃による切断時の拡大断面図、図５は同上の緩衝包装材の製造工程の概略説明図である。
【００２２】
図１に示す緩衝包装材Ａは、適度に強度、保形性を有する基材としての熱可塑性樹脂発泡シート２の表裏両面に、導電性インキが比較的薄く印刷あるいは塗布された前記発泡シートと同系の熱可塑性樹脂フィルム３，３が、前記導電性インキ層（図示省略）を外側にして積層された積層発泡シート１から熱成形されてなり、包装対象物品（図示せず）の形態に応じた１個もしくは複数個（図の場合は４個）の収納凹部１１を有するトレイ形状をなしている。
【００２３】
そして、前記包装緩衝材Ａは、その外周端面４の全部あるいは一部において、前記樹脂フィルム３，３同士が融着一体化されている。５はその融着一体化された部分を示す。この両樹脂フィルム３，３同士の融着一体化は、後述のように長尺の積層発泡シート１からの熱成形後、個々の緩衝包装材Ａに分離する際の切断工程において、切断装置に備える加熱刃を利用して融着一体化させる。
【００２４】
前記の緩衝包装材Ａの外周端面４において、表裏両面の導電性の樹脂フィルム３，３同士を融着一体化する領域は、全外周端面の５０％以上であるのが好ましく、これにより、静電気防止効果上において満足できる体積抵抗率を得ることができる。
【００２５】
なお、前記の積層発泡シート１の基材となる熱可塑性樹脂発泡シート２及び表裏両面の導電性の樹脂フィルム３，３としては、この種の緩衝包装材に利用される種々の熱可塑性樹脂、例えばポリスチレン系樹脂、ポリプロピレン系樹脂、ポリエステル系樹脂等を用いることができるが、中でも成形性、強度や保形性、微粉の発生防止等の点から、ポリエステル系樹脂が好適に用いられる。このポリエステル系樹脂のうち、ポリエチレンテレフタレート系樹脂（ＰＥＴ）からなるものが特に好適に用いられる。
【００２６】
前記熱可塑性樹脂発泡シート２の発泡倍率や厚みは、その材質や被包装物によっても異なるが、ポリエステル系樹脂よりなる場合、発泡倍率は通常２〜２０倍、好ましくは３〜１０倍、厚みは０．５〜１０ｍｍ、好ましくは１．０〜５．０ｍｍの範囲のものが好適に用いられる。
【００２７】
また、表裏両面の導電性を有する樹脂フィルム３，３は、その片面に導電性インキ、例えばカーボン等の導電性材料を含むインキを印刷もしくは塗布したものからなり、その厚みは例えば２０〜８０μｍ（ミクロンメーター）、例えば３０μｍ程度である。この厚みが薄くなりすぎると、加熱刃による切断の際の表裏両面のフィルム同士の融着一体化が難しくなり、導電性が得にくくなる。
【００２８】
前記の導電性を有する樹脂フィルム３，３が、ポリエステル系樹脂のフィルムであっても、前記の導電性インキの塗布もしくは印刷により僅かに侵され劣化するものの、溶剤の量が発泡シートに比べて少なくてよいため、発泡シートにインキを直接塗布もしくは印刷する場合に比して劣化の問題は小さい。従って、この樹脂フィルム３，３を前記発泡シート２に積層することにより、劣化の問題は殆どなくなる。なお、導電性インキの印刷などによる皮膜（図示せず）の厚みは、通常一般に２〜２０μｍ（ミクロンメーター）程度である。
【００２９】
また、樹脂フィルムに導電性インキを塗布もしくは印刷しておくので、塗布もしくは印刷後に使用する一般のフィルム用の巻き取り機をそのまま使用でき、特殊な装置は不要である。
【００３０】
上記の積層発泡シート１から、上記の緩衝包装材Ａを製造する方法について説明する。
【００３１】
図５に示すように、ポリエステル系樹脂等の熱可塑性樹脂発泡シート２の表裏両面に、前記の導電性インキを印刷もしくは塗布して導電性を付与したポリエステル系樹脂等の熱可塑性樹脂フィルム３，３を積層した積層発泡シート１、特に長尺の積層発泡シート１を、熱成形工程に送り、この熱成形工程において、加熱ゾーンＺ１において積層発泡シート１を加熱軟化させた後、後続の成形ゾーンＺ２において、上下一対の成形金型７を用いて被包装物に対応した収納凹部１１を所要数備えるトレイ等の所定形状の緩衝包装材Ａの形態に熱成形する。この熱成形は、積層発泡シート１の幅によっても異なるが、例えば、上記した１回の成形により、緩衝包装材Ａを幅方向２列で４個取りするように成形する。
【００３２】
この熱成形の後、加熱刃８を有する切断装置８０による切断工程に送り、図４のように、トムソン刃式の加熱刃８の降下により所定の位置で切断して個々の緩衝包装材Ａに分離する。この切断の際、前記加熱刃８による切断端面を該加熱刃８により加熱して溶融させ、表裏両面の樹脂フィルム３，３同士を融着一体化させる。
【００３３】
すなわち、前記加熱刃８は、刃部側ほど薄肉の断面略くさび形をなすものよりなり、この加熱刃８を、ヒータにより素材樹脂の軟化点以上に、例えばポリエステル系樹脂を用いる場合、１１０〜２００℃に加熱しておく。そして、図４のように、加熱刃８を降下させて前記熱成形後の積層発泡シート１を切断する際、表面側（上面）の樹脂フィルム３を加熱刃８により下方に引き込みながら切断するとともに、この切断した状態、すなわち該加熱刃８の両側面８１，８１を該積層発泡シート１の切断端面に接触させた状態のまま所定の時間、例えば２〜３０秒間保持して切断端面を表裏の前記樹脂フィルム３，３とともに溶融させる。これによって、積層発泡シート１の表裏両面の導電性を有する熱可塑性樹脂フィルム３，３同士が切断端面において融着一体化することになり、図１に示す緩衝包装材Ａが得られる。
【００３４】
なお、素材樹脂がポリエステル系樹脂の場合、前記の加熱刃８の温度が１１０℃未満では樹脂フイルム３，３同士が融着しにくく、また２００℃を越えると、ポリエステル系樹脂が結晶化して脆くなる。前記の切断工程は、インラインによって熱成形直後に行ってもよいし、熱成形とは別の工程で行ってもよい。
【００３５】
上記のようにして得られる本発明の緩衝包装材Ａは、例えば電子部品その他の静電気障害を受けやすい被包装物を、各収容凹部に収容した状態で、段ボール箱などの外装箱内で積み重ね状態で収納して運搬するのに使用する。この使用において、緩衝包装材Ａの表裏両面に積層された樹脂フィルム３，３、該フィルムの表面に印刷もしくは塗布されている導電性インキの皮膜による導電性により、表面抵抗率を低減できるばかりか、外周端面の少なくとも一部における前記導電性の樹脂フィルム同士が融着一体化している部分で、表裏面間の導電性を確保できることになり、体積抵抗率も低減できる。そのため、静電気による帯電防止を確実になすことができる。
【００３６】
しかも、表裏の樹脂フィルム３，３同士を外周端面でのみ融着一体化させるだけであるため、貫通孔を設けた場合のようなゴミや塵の侵入の問題はなく、収納した電子部品等のゴミ等を嫌う被包装物の保護を良好になすことができる。
【００３７】
なお、表面抵抗率および体積抵抗率は、それぞれ下記の方法で得られる抵抗率である。
【００３８】
（１）表面抵抗率
ＪＩＳ　Ｋ６９１１：１９９５「熱硬化性プラスチック一般試験方法」記載の方法により測定した。即ち、試験装置（（株）アドバンテスト製デジタル超高抵抗／微少電流計Ｒ８３４０及びレジスティビティ・チェンバＲ１２７０２Ａ）を使用し、試料サンプルに、約３０Ｎの荷重にて電極を圧着させ５００Ｖ１分間充電後の抵抗値を測定し、次式により算出した。試料サンプルは、１００　ｍｍ×１００　ｍｍ×原厚み（１０　ｍｍ以下）とした。
【００３９】
Ρｓ＝π（Ｄ＋ｄ）／（Ｄ−ｄ）×Ｒｓ
ρｓ　：　表面抵抗率（Ω）
Ｄ　：　表面の環状電極の内径（ｃｍ）
ｄ　：　表面電極の内円の外径（ｃｍ）
Ｒｓ：　表面抵抗（Ω）
（２）体積抵抗率
ＪＩＳ　Ｋ６９１１：１９９５「熱硬化性プラスチック一般試験方法」記載の方法により測定した。即ち、試験装置（（株）アドバンテスト製デジタル超高抵抗／微少電流計Ｒ８３４０及びレジスティビティ・チェンバＲ１２７０２Ａ）を使用し、試料サンプルに、約３０Ｎの荷重にて電極を圧着させ１分間充電後の抵抗値を測定し、次式により算出した。試料サンプルは、１００　ｍｍ×１００　ｍｍ×原厚み（１０　ｍｍ以下）とした。
【００４０】
Ρｖ＝πｄ２／４ｔ×Ｒｖ
ρｖ　：　体積抵抗率（Ωｃｍ）
ｄ　：　表面電極の内円の外径（ｃｍ）
ｔ　：　試験片の厚さ（ｃｍ）
Ｒｖ：　体積抵抗（Ω）
【００４１】
【実施例】
熱可塑性樹脂発泡シートとして、発泡倍率４倍、厚み１．５ｍｍのポリエチレンテレフタレート樹脂発泡シートを用い、導電性を有する熱可塑性樹脂フィルムとして、ポリエチレンテレフタレート樹脂フィルムに導電性材料（カーボン）を含むインキを印刷した厚み３０μｍのフィルムを用いて、該樹脂フィルムを前記印刷による導電性インキの皮膜を外側にして前記発泡シートの両面に積層し、熱成形前の積層発泡シートを得た。
【００４２】
緩衝包装材に熱成形する前の前記の積層発泡シートの任意の箇所から、１００ｍｍ×１００ｍｍの大きさのサンプルを切り出し、そのサンプルの外周端面を加熱刃を使用して、全周の１００％、約５０％、約４０％、約３０％、約２０％、約１０％の割合で表裏の樹脂フィルム同士を融着一体化させた。それぞれのサンプルの表面抵抗率、体積抵抗率を上記の方法で測定した。その結果を実施例１〜６として、下記の表１に示す。また、比較のために、外周端面の融着無しのサンプルについても、表面抵抗率、体積抵抗率を測定した結果を比較例１として併せて示す。
【００４３】
【表１】

【００４４】
上記から明らかなように、表面抵抗率については差はないが、体積抵抗率については、外周端面での表裏両面の樹脂フィルム同士の融着範囲が多いものほど小さくなり、特に前記融着範囲が５０％を越えると、その抵抗率は格段に小さくなり、表裏両面間の導電性が大幅に改善される。
【００４５】
従って、本発明のように外周端面の少なくとも一部で前記導電性の樹脂フィルム同士を融着一体化させること、好ましくは全外周端面の５０％以上を融着一体化させることにより、表面抵抗率のみでなく、体積抵抗率も低減でき、静電気による帯電防止を確実になすことができる。
【００４６】
【発明の効果】
上記したように本発明の緩衝包装材によれば、トレイ等の成形品として適度の強度、保形性を持ちながら、表裏面間の導電性が高くて、表面抵抗率のみでなく、体積抵抗率も低減でき、積み重ね使用した場合の静電気防止効果に優れ、被包装物の保護、特に電子部品その他の静電気障害を受けやすい物品の保護を良好になすことができる。
【００４７】
また、本発明の製造方法によれば、熱成形後の切断工程でのトリミングを利用して、外周端面の少なくとも一部で表裏両面の導電性を有する樹脂フィルム同士を融着一体化でき、これにより表裏両面間の導電性を改善した緩衝包装材を容易に得ることができる。
【図面の簡単な説明】
【図１】本発明の緩衝包装材の１実施例を示す一部欠截斜視図である。
【図２】同上の一部の拡大断面図である。
【図３】熱成形前の積層発泡シートの拡大断面図である。
【図４】加熱刃による切断時の拡大断面図である。
【図５】同上の緩衝包装材の製造工程の概略説明図である。
【符号の説明】
Ａ　　緩衝包装材
１　　積層発泡シート
２　　熱可塑性樹脂発泡シート
３，３　　熱可塑性樹脂フィルム
４　　外周端面
５　　融着一体化した部分
７　　成形金型
８　　加熱刃
８０　　切断装置
８１，８１　　両側面
Ｚ１　　加熱ゾーン
Ｚ２　　成形ゾーン[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, conductive trays and containers used for packaging and transporting electronic components such as IC components, liquid crystal display panels (LCD), and personal digital assistants (PDAs) that are susceptible to static electricity. And a method for producing the same.
[0002]
[Prior art]
Conventionally, as a cushioning packaging material for packaging and transporting electronic components such as IC components, liquid crystal display panels (LCD), personal digital assistants (PDAs), and other products susceptible to static electricity, to prevent static electricity due to static electricity. In addition, a conductive plastic foam sheet is used.
[0003]
Such a conductive plastic foam sheet is molded and used as a cushioning packaging material such as a tray or a container having one recess or a plurality of recesses for accommodating an article to be packaged, in combination with an outer box such as a cardboard box. Is common. Further, in the use thereof, the buffer packaging materials such as the plurality of forming trays are often stacked and used in an outer box in a state in which the articles to be packaged are accommodated.
[0004]
As the above-mentioned conductive plastic foam sheet, for example, there is known a plastic foam sheet as a base material in which a conductive layer is formed by applying or printing a conductive paint or ink on one or both surfaces. When used in the form of a tray, a synthetic resin foam sheet that is easy to mold from a sheet and has a moderate shape retention is generally used as the base material.
[0005]
In addition, in order to give flexibility as a packaging material, a conductive foam film made by heating and foaming a foaming ink printed or applied on one or both sides is provided on one or both sides of a foam sheet or film of an olefin resin. The following has been proposed (see Patent Document 1 below).
[0006]
[Patent Document 1]
Japanese Patent Publication No. 5-32217 (Page 1-3, Figure 1-4)
[0007]
[Problems to be solved by the invention]
By the way, the cushioning wrapping material made of a conventional conductive plastic foam sheet in which only a conductive layer is provided on the surface of the foam sheet has a low surface resistivity, but hardly obtains conductivity in the sheet thickness direction, and has a low volume resistivity. The rate is not low enough. In particular, in the case where buffer packaging materials such as a plurality of molding trays containing the items to be packaged are stacked in an outer box, if the conductivity in the thickness direction between the front and back surfaces is not sufficient, charging due to static electricity occurs. There is.
[0008]
In addition, in the case of the conductive plastic foam sheet and the like of Patent Document 1 described above, not only is there no description about a molded product from the sheet, but also the foam sheet or the like of the base material is made of an olefin-based resin (example: polyethylene). In other words, even if a packaging material having high flexibility is formed from a foamed sheet and a tray or the like is formed, the packaging material does not have strength enough to withstand the above-described use in a stacked state. Moreover, since the foaming ink is directly printed or applied to the base material, when the base material is a foam sheet, the surface has fine irregularities, so that there is a problem that the ink is insufficiently or unevenly applied. There is.
[0009]
Further, in Patent Document 1, in order to obtain conductivity between the front and back surfaces, a large number of through holes are formed, and a conductive foam film made of the foamable ink is provided up to the inner peripheral surface thereof. In this case, a step for forming the through hole is required, and the foamable ink must be printed or applied to the inner peripheral surface of the through hole. In addition, if there are a large number of through holes, the strength is reduced, and there is a possibility that dirt and dust may enter the holes, which impairs the function as a packaging material for electronic components and the like that dislike dirt and the like.
[0010]
Even if a foamed sheet of polyester resin or the like, which has good moldability from a sheet and is excellent in strength, is used as the base material, if the surface is directly applied or printed with conductive ink or the like, the surface becomes Deteriorated slightly by solvent such as ink. Further, the surface has irregularities, and it is necessary to apply a thicker ink or the like than in the case of a film, which is further disadvantageous for deterioration. In addition, since the foamed sheet is thicker than the film and a general film winding machine used after printing cannot be used, a special device is required and equipment cost is required.
[0011]
Further, after printing or applying the conductive ink, a drying step is usually required, but when the foamed sheet is heated and dried using an infrared heater or the like in the drying step, the material is a polyester resin. In such a case, there is a problem that the crystallization of the foam increases and the foam becomes very brittle.
[0012]
The present invention has been made in view of the above, and has strength to withstand use as a molded product such as a tray, while having shape retention, high conductivity between the front and back, not only the surface resistivity, Another object of the present invention is to provide a buffer wrapping material having a volume resistivity which can be reduced, and has conductivity suitable for stacking use, and further provides a manufacturing method capable of easily obtaining the above-mentioned buffer wrapping material. .
[0013]
[Means for Solving the Problems]
The present invention for solving the above-mentioned problems is a conductive resin obtained by thermoforming from a laminated foam sheet in which a thermoplastic resin film on which a conductive ink is printed or applied is laminated on both front and back surfaces of a thermoplastic resin foam sheet. Wherein the resin films on the front and back surfaces are fused and integrated with each other at all or a part of the outer peripheral end surface of the buffer packaging material.
[0014]
The cushioning wrapping material of the present invention is made of a laminated foamed sheet in which a non-foamed resin film is laminated on both sides of the foamed sheet, so that the cushioning wrapping material can have the necessary strength and shape retention necessary for use as a molded product such as a tray. On at least a part of the outer peripheral end surface, the conductive resin film laminated on both the front and back surfaces, that is, the resin films having the conductive ink printed or applied on the surface are fused and integrated with each other. Thus, the conductivity between the front and back surfaces can be ensured, so that not only the surface resistivity but also the volume resistivity can be reduced.
[0015]
Moreover, since the conductive ink is not directly applied to the foam sheet, but is printed or applied to a resin film and the film is laminated on the foam sheet, the film formed by the printing of the conductive ink and the like is also uniformed over the entire surface. In addition to being coated with sufficient strength, there is no possibility that the foam sheet is deteriorated by being attacked by the ink. In addition, since the drying process of the ink can be performed with a resin film, it is not affected by heating and drying as when the ink is directly applied to the surface of the foam sheet, and if the material is brittle even if the material is a polyester resin foam sheet, And durability can be improved.
[0016]
In the cushioning packaging material described above, it is preferable that a region of the outer peripheral end surface where the conductive resin films on the front and back surfaces are fused and integrated is 50% or more of the entire outer peripheral end surface. Thereby, the conductivity between the front and back surfaces can be sufficiently secured, and a satisfactory volume resistivity can be obtained. That is, if the region is less than 50%, a satisfactory volume resistivity [1.0 × 10 ⁹ (Ωcm) or less] cannot be obtained. Therefore, it is preferable that the conductive resin films on both front and back surfaces are fused and integrated over 50% or more of the outer peripheral end face, particularly preferably over the entire circumference.
[0017]
The thermoplastic resin foam sheet and the thermoplastic resin film on both front and back sides are preferably made of a polyester resin, and particularly preferably made of a polyethylene terephthalate resin. That is, the polyester-based resin can be easily formed from a sheet, in particular, a relatively deep drawing process, and has excellent strength and shape retention, and can withstand stacking in a state in which a packaged object is accommodated. Can retain strength. In particular, polyethylene terephthalate-based resin is glossy in appearance, beautiful and good in appearance, has higher strength as a cushioning packaging material, and has excellent hinge characteristics. Further, unlike the polystyrene resin foam sheet and the like, the polyester resin foam sheet does not generate fine powder and can be suitably used as a cushioning packaging material for electronic parts and the like that dislike dust.
[0018]
The present invention, as a method of manufacturing the cushioning packaging material of the above invention, thermoformed a laminated foam sheet in which a thermoplastic resin film on which a conductive ink is printed or applied is laminated on both front and back surfaces of a thermoplastic resin foam sheet. After that, when cutting with a cutting device having a heating blade and separating into individual buffer packaging materials, the cut end surface on the outer periphery of the buffer packaging material is heated, and the resin films on both front and back surfaces are fused and integrated. And
[0019]
This makes it possible to easily obtain a buffer packaging material in which conductive resin films on both front and back surfaces are fused and integrated with each other on the outer peripheral end surface of the buffer packaging material. In particular, a resin film coated or printed with conductive ink is laminated on both sides of the foam sheet, and this is cut with a heating blade. At this time, the resin films on both sides are fused together. It is possible to easily make it. Moreover, since the above-mentioned fusion and integration can be performed simultaneously with the trimming after the thermoforming, the number of steps is not increased, and it can be obtained by the same manufacturing process as before.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described based on examples shown in the drawings.
[0021]
FIG. 1 is a partially cutaway perspective view showing one embodiment of the cushioning packaging material of the present invention, FIG. 2 is an enlarged sectional view of a part of the same, FIG. 3 is an enlarged sectional view of a laminated foam sheet before thermoforming. 4 is an enlarged sectional view at the time of cutting by a heating blade, and FIG. 5 is a schematic explanatory view of a manufacturing process of the cushioning packaging material of the above.
[0022]
The cushioning wrapping material A shown in FIG. 1 has a moderate strength, a foamed sheet in which conductive ink is printed or applied relatively thinly on both sides of a thermoplastic resin foam sheet 2 as a base material having shape retention.

Thermoplastic resin films

3 and 3 of the same type are thermoformed from a laminated foam sheet 1 laminated with the conductive ink layer (not shown) outside, depending on the form of an article to be packaged (not shown). It has a tray shape having one or more (four in the figure) storage recesses 11.
[0023]
In the packaging cushioning material A, the

resin films

3 and 3 are fused and integrated with each other on all or a part of the outer peripheral end surface 4. Numeral 5 indicates a portion integrated by fusion. The fusion bonding of the two

resin films

3 and 3 is performed by a cutting device in a cutting step of separating into individual buffer packaging materials A after thermoforming from the long laminated foam sheet 1 as described later. Using a provided heating blade, fusion and integration are performed.
[0024]
In the outer peripheral end surface 4 of the buffer packaging material A, the area where the

conductive resin films

3 and 3 on the front and back surfaces are fused and integrated with each other is preferably 50% or more of the entire outer peripheral end surface. It is possible to obtain a satisfactory volume resistivity in the prevention effect.
[0025]
As the thermoplastic resin foam sheet 2 and the

conductive resin films

3 and 3 on both front and back sides which are the base material of the laminated foam sheet 1, various thermoplastic resins used for this kind of cushioning packaging material are used. For example, polystyrene-based resins, polypropylene-based resins, polyester-based resins, and the like can be used. Among them, polyester-based resins are preferably used from the viewpoints of moldability, strength, shape retention, and prevention of generation of fine powder. Among these polyester resins, those made of polyethylene terephthalate resin (PET) are particularly preferably used.
[0026]
The expansion ratio and thickness of the thermoplastic resin foam sheet 2 vary depending on the material and the packaged object, but when the sheet is made of a polyester resin, the expansion ratio is usually 2 to 20 times, preferably 3 to 10 times, and the thickness is Those having a range of 0.5 to 10 mm, preferably 1.0 to 5.0 mm are suitably used.
[0027]
The

conductive resin films

3, 3 on both front and back sides are formed by printing or applying a conductive ink, for example, an ink containing a conductive material such as carbon, on one surface thereof, and has a thickness of, for example, 20 to 80 μm ( Micron meter), for example, about 30 μm. If the thickness is too thin, it becomes difficult to fuse and integrate the films on both the front and back surfaces when cutting with a heating blade, and it becomes difficult to obtain conductivity.
[0028]
Even if the

conductive resin films

3 and 3 are polyester resin films, they are slightly affected and deteriorated by the application or printing of the conductive ink, but the amount of the solvent is smaller than that of the foamed sheet. Since the amount of the ink may be reduced, the problem of deterioration is smaller than when the ink is directly applied or printed on the foam sheet. Therefore, by laminating the

resin films

3 and 3 on the foamed sheet 2, the problem of deterioration is almost eliminated. The thickness of a film (not shown) formed by printing conductive ink is generally about 2 to 20 μm (micrometer).
[0029]
In addition, since the conductive ink is applied or printed on the resin film, a general film winding machine used after application or printing can be used as it is, and no special device is required.
[0030]
A method for manufacturing the cushioning packaging material A from the laminated foam sheet 1 will be described.
[0031]
As shown in FIG. 5, a thermoplastic resin film 3, such as a polyester-based resin or the like, to which conductivity is imparted by printing or applying the above-described conductive ink on both front and back surfaces of a thermoplastic resin foam sheet 2 such as a polyester-based resin. 3 is sent to a thermoforming step, and in this thermoforming step, the laminated foamed sheet 1 is heated and softened in a heating zone Z1, followed by a subsequent forming zone. In Z2, using a pair of upper and lower molding dies 7, thermoforming into a form of buffer packaging material A having a predetermined shape such as a tray having a required number of storage recesses 11 corresponding to a packaged object. This thermoforming differs depending on the width of the laminated foamed sheet 1. For example, the above-described one-time forming is performed so that four buffer packaging materials A are taken in two rows in the width direction.
[0032]
After this thermoforming, it is sent to a cutting process by a cutting device 80 having a heating blade 8, and as shown in FIG. To separate. At the time of this cutting, the end face cut by the heating blade 8 is heated and melted by the heating blade 8 to fuse and integrate the

resin films

3 and 3 on both front and back surfaces.
[0033]
That is, the heating blade 8 is made of a material having a substantially wedge-shaped cross section with a thinner thickness toward the blade portion side. Heat to 200 ° C. Then, as shown in FIG. 4, when the heating blade 8 is moved down to cut the thermoformed laminated foamed sheet 1, the heating blade 8 cuts the resin film 3 on the front side (upper surface) while pulling the resin film 3 downward. This cut state, that is, a state in which both side faces 81 of the heating blade 8 are kept in contact with the cut end face of the laminated foam sheet 1 for a predetermined time, for example, 2 to 30 seconds, is used to hold the cut end face on the front and back. The

resin films

3 and 3 are melted together. As a result, the

thermoplastic resin films

3 and 3 having conductivity on both the front and back surfaces of the laminated foam sheet 1 are fused and integrated at the cut end surfaces, and the cushioning packaging material A shown in FIG. 1 is obtained.
[0034]
When the material resin is a polyester resin, if the temperature of the heating blade 8 is lower than 110 ° C., the

resin films

3 and 3 do not easily fuse with each other. If the temperature exceeds 200 ° C., the polyester resin crystallizes and becomes brittle. Become. The cutting step may be performed immediately after thermoforming by in-line, or may be performed in a step different from thermoforming.
[0035]
The buffer wrapping material A of the present invention obtained as described above is, for example, a state in which electronic components and other susceptible items to be susceptible to static electricity are stacked in an outer box such as a corrugated cardboard box in a state of being stored in each storage recess. Used to store and transport in. In this use, not only the surface resistivity can be reduced due to the conductivity of the

resin films

3 and 3 laminated on both the front and back surfaces of the buffer packaging material A and the conductive ink film printed or applied on the surface of the film. In addition, in at least a part of the outer peripheral end face where the conductive resin films are fused and integrated, the conductivity between the front and back surfaces can be secured, and the volume resistivity can be reduced. Therefore, it is possible to reliably prevent static electricity from being charged.
[0036]
Moreover, since the front and back

resin films

3 and 3 are only fused and integrated only at the outer peripheral end surface, there is no problem of intrusion of dust or dust as in the case where a through-hole is provided, and there is no problem with the stored electronic parts. Good protection of packaged objects that dislike garbage and the like can be achieved.
[0037]
In addition, the surface resistivity and the volume resistivity are resistivity obtained by the following methods, respectively.
[0038]
(1) Surface resistivity Measured according to the method described in JIS K6911: 1995 “General thermosetting plastic test method”. That is, using a test device (Digital Ultra High Resistance / Micro Ammeter R8340 and Resistivity Chamber R12702A, manufactured by Advantest Corporation), an electrode is crimped to the sample sample with a load of about 30N, and the resistance after charging at 500 V for 1 minute. The value was measured and calculated by the following equation. Sample The sample was 100 mm x 100 mm x original thickness (10 mm or less).
[0039]
Ρs = π (D + d) / (D−d) × Rs
ρs: Surface resistivity (Ω)
D: inside diameter of the ring electrode on the surface (cm)
d: Outer diameter of inner circle of surface electrode (cm)
Rs: Surface resistance (Ω)
(2) Volume resistivity Measured according to the method described in JIS K6911: 1995 “General thermosetting plastic test method”. That is, using a test device (Digital Ultra High Resistance / Micro Ammeter R8340 and Resistivity Chamber R12702A manufactured by Advantest Co., Ltd.), an electrode is crimped on the sample sample with a load of about 30 N, and the resistance after charging for 1 minute. The value was measured and calculated by the following equation. Sample The sample was 100 mm x 100 mm x original thickness (10 mm or less).
[0040]
Ρv = πd2 / 4t × Rv
ρv: Volume resistivity (Ωcm)
d: Outer diameter of inner circle of surface electrode (cm)
t: thickness of test piece (cm)
Rv: Volume resistance (Ω)
[0041]
【Example】
As the thermoplastic resin foam sheet, a polyethylene terephthalate resin foam sheet having an expansion ratio of 4 times and a thickness of 1.5 mm is used. As the conductive thermoplastic resin film, an ink containing a conductive material (carbon) in the polyethylene terephthalate resin film is used. Using a printed film having a thickness of 30 μm, the resin film was laminated on both sides of the foamed sheet with the conductive ink film formed by the printing being on the outside, to obtain a laminated foamed sheet before thermoforming.
[0042]
A sample having a size of 100 mm × 100 mm is cut out from an arbitrary portion of the laminated foam sheet before being thermoformed into the buffer packaging material, and the outer peripheral end surface of the sample is heated to 100% of the entire circumference using a heating blade. About 50%, about 40%, about 30%, about 20%, and about 10% of the front and back resin films were fused and integrated at a ratio of about 10%. The surface resistivity and volume resistivity of each sample were measured by the methods described above. The results are shown in Table 1 below as Examples 1 to 6. For comparison, the results of measurement of the surface resistivity and the volume resistivity of a sample without fusion of the outer peripheral end face are also shown as Comparative Example 1.
[0043]
[Table 1]

[0044]
As is clear from the above, there is no difference in the surface resistivity, but the volume resistivity is smaller as the fusion range between the resin films on both the front and back surfaces at the outer peripheral end surface is larger, and especially the fusion range is larger. If it exceeds 50%, the resistivity is significantly reduced, and the conductivity between the front and back surfaces is greatly improved.
[0045]
Therefore, as in the present invention, the conductive resin films are fused and integrated with each other on at least a part of the outer peripheral end face, and preferably, 50% or more of the entire outer peripheral end face is fused and integrated, so that the surface resistivity is increased. In addition, the volume resistivity can be reduced, and the static electricity can be reliably prevented from being charged.
[0046]
【The invention's effect】
As described above, according to the cushioning packaging material of the present invention, the molded article such as a tray has appropriate strength and shape retention, and has high conductivity between the front and back surfaces, not only the surface resistivity but also the volume resistivity. The ratio can be reduced, and the antistatic effect when used in a stack can be excellent, and the protection of the packaged object, particularly, the protection of electronic components and other articles which are easily affected by static electricity can be achieved.
[0047]
Further, according to the production method of the present invention, by using trimming in the cutting step after thermoforming, it is possible to fuse and integrate the conductive resin films having both front and back surfaces on at least a part of the outer peripheral end face, Thereby, a buffer packaging material having improved conductivity between the front and back surfaces can be easily obtained.
[Brief description of the drawings]
FIG. 1 is a partially cutaway perspective view showing one embodiment of a cushioning packaging material of the present invention.
FIG. 2 is an enlarged sectional view of a part of the above.
FIG. 3 is an enlarged sectional view of a laminated foam sheet before thermoforming.
FIG. 4 is an enlarged sectional view at the time of cutting by a heating blade.
FIG. 5 is a schematic explanatory view of a manufacturing process of the cushioning packaging material of the above.
[Explanation of symbols]
Reference Signs List A buffer packaging material 1 laminated foam sheet 2 thermoplastic

resin foam sheet

3, 3 thermoplastic resin film 4 outer peripheral end face 5 fused and integrated part 7 molding die 8 heating blade 80

cutting device

81, 81 both side faces Z1 heating zone Z2 Molding zone

Claims

熱可塑性樹脂発泡シートの表裏両面に、導電性インキが印刷もしくは塗布された熱可塑性樹脂フィルムが積層された積層発泡シートから熱成形されて得られた導電性を有する緩衝包装材であって、
緩衝包装材の外周端面の全部あるいは一部において、表裏両面の前記樹脂フィルム同士が融着一体化されていることを特徴とする導電性を有する緩衝包装材。A conductive cushioning packaging material obtained by thermoforming from a laminated foamed sheet laminated with a thermoplastic resin film printed or coated with a conductive ink on both front and back surfaces of the thermoplastic resin foamed sheet,
A buffer packaging material having conductivity, wherein the resin films on the front and back surfaces are fused and integrated with each other on all or a part of the outer peripheral end surface of the buffer packaging material.

緩衝包装材の外周端面において、前記表裏両面の樹脂フィルム同士が融着一体化されている領域が、全外周端面の５０％以上であることを特徴とする請求項１に記載の導電性を有する緩衝包装材。2. The conductive material according to claim 1, wherein, on the outer peripheral end surface of the buffer packaging material, a region where the resin films on the front and back surfaces are fused and integrated is 50% or more of the entire outer peripheral end surface. 3. Buffer packaging material.

前記の熱可塑性樹脂発泡シート、及び表裏両面の熱可塑性樹脂フィルムが、ポリエステル系樹脂からなる請求項１または２に記載の導電性を有する緩衝包装材。The conductive cushioning packaging material according to claim 1 or 2, wherein the thermoplastic resin foam sheet and the thermoplastic resin films on both front and back sides are made of a polyester resin.

ポリエステル系樹脂がポリエチレンテレフタレート系樹脂である請求項３に記載の導電性を有する緩衝包装材。The conductive cushioning packaging material according to claim 3, wherein the polyester resin is a polyethylene terephthalate resin.

熱可塑性樹脂発泡シートの表裏両面に、導電性インキが印刷もしくは塗布された熱可塑性樹脂フィルムが積層された積層発泡シートを熱成形した後、加熱刃を有する切断装置で切断して個々の緩衝包装材に分離する際に、緩衝包装材の外周の切断端面を加熱し、表裏両面の樹脂フィルム同士を融着一体化させることを特徴とする導電性を有する緩衝包装材の製造方法。After thermoforming a laminated foam sheet in which a thermoplastic resin film with conductive ink printed or coated on both front and back surfaces of a thermoplastic resin foam sheet, cut it with a cutting device having a heating blade, and then individual buffer packaging A method for producing a buffer wrapping material having conductivity, comprising heating a cut end surface of an outer periphery of a buffer wrapping material when separating the resin into materials, and fusing and integrating the resin films on both front and back surfaces.