JP2004075845A

JP2004075845A - Adhesive sheet

Info

Publication number: JP2004075845A
Application number: JP2002238192A
Authority: JP
Inventors: Kazuhiro Takahashi; 高橋　一弘; Kenichi Yamaguchi; 山口　健一
Original assignee: Dai Nippon Printing Co Ltd
Current assignee: Dai Nippon Printing Co Ltd
Priority date: 2002-08-19
Filing date: 2002-08-19
Publication date: 2004-03-11
Anticipated expiration: 2022-08-19
Also published as: JP4515016B2

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a beautiful appearance from being damaged by an observed pattern caused by unevenness when securing easiness of air ventilation by forming the unevenness on the surface of an adhesive layer so that the air may not be held at sticking. <P>SOLUTION: The adhesive sheet has many convex bodies 2a attached to the surface of the adhesive layer 2 on a base material sheet 1 so that a vertical cross section shape from the tip part to the valley bottom part 2bv of a valley part 2b in a groove shape may form a smooth continuous curve, the shape of the valley bottom part may be sharper than that of the shoulder part 2as of the convex body, and the width w of the valley part and the height h of the convex body may satisfy the relation of w≤h. A releasing sheet 3 having a releasing surface having a convex and concave pattern reverse to the convex and concave pattern of the adhesive layer is preferably laminated on the surface of the adhesive layer. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、粘着剤層表面に凹凸を設けた粘着シートに関する。特に、被着体に貼り付け時に空気を抱き込み難い「空気抜け容易性」を有する粘着シートに関する。
【０００２】
【従来の技術】
一般的に粘着シートの粘着剤層表面は平坦面であり、その為に、被着体に粘着シートを貼り付けるときは、注意して貼らないと空気を抱き込み易い。この様な場合、粘着剤層表面を凹凸面とした粘着シートを使用すれば、粘着剤層表面の凸部と凸部との間に空気の逃げ道ができるので、空気の抱き込みは改善する。この様に粘着剤層表面が凹凸を有し空気を抱き込み難い性質（本明細書では、これを「空気抜け容易性」と称することにする。）を備えている粘着シートとしては、例えば、特許第２９９４４１１号公報、実用新案登録第２５０３７１７号公報等に開示の粘着シートが挙げられる。例えば、実用新案登録第２５０３７１７号公報で開示する粘着シートでは、図４の斜視図で示す粘着シート３０の如く、基材シート３１上の粘着剤層３２の表面の凹凸形状として、その凸部形状が、下端部の外径ｄが０．３ｍｍで高さｈが２０μｍの凸部３２ａを、縦横に間隔１ｍｍで散在する様に配列した形状等を開示している。
【０００３】
【発明が解決しようとする課題】
しかしながら、図４の様に、隣接する凸部３２ａ間の凹部３２ｂの幅が広いと、粘着シートを被着体に貼着した後には、該凹部３２ｂは粘着剤層と被着体とが接触していない空間（空気抜け層）として残ることになる。この為、貼着後に、凸部の配置がそのまま模様として見えてしまい、美観を損ねるという外観上の問題があった。特に、被着体が透明ガラス等の場合、或いは、基材シートが樹脂シート等で薄い場合等では、前記模様が目立ち易かった。それは、透明ガラスの場合には、特に被着体側から容易に見えてしまい、また、被着体と粘着シートとが共に不透明の場合では、粘着シートの表側面に粘着シートを通して現出する微妙な凹凸として見えてしまうからであった。
【０００４】
すなわち、本発明の課題は、貼着時の「空気抜け容易性」を粘着剤層表面の凹凸により確保すると共に、該凹凸による模様が見えてしまい美観を損ねることがない様にすることである。
【０００５】
【課題を解決するための手段】
そこで、上記課題を解決すべく、本発明の粘着シートでは、基材シート上に粘着剤層が設けられた粘着シートにおいて、該粘着剤層はその表面から外方に突出する多数の凸状体を有し、互いに隣接する凸状体間には溝状の谷部を有し、凸状体の頂上部分から谷部の谷底部分にかけての垂直断面形状が滑らかな連続曲線を成し、且つ谷部の谷底部分が、谷部入口部分である凸状体の肩部分に比べてより尖った形状で、且つ谷部の幅ｗが凸状体の高さｈに対してｗ≦ｈである、構成とした。
【０００６】
この様な構成とすることで、粘着剤層表面に凸状体によって形成される凹凸によって、空気抜け容易性が確保される。しかもその上、凸状体頂上の部分から谷部の谷底部分にかけての垂直断面形状を滑らかな連続曲線形状とし、更に谷部の幅ｗを凸状体の高さｈ以下（つまり同等又はそれ未満）とし、且つ、谷底部分を谷部入口部分（凸状体の肩部分）よりも尖った形状としてあるので、貼着時に粘着シートを被着体に押しつける圧力で、谷部の両側の凸状体を谷部に向かってせり出させて、谷部内の空気を谷底部分も含めて容易に抜きながら谷部を消滅させる事ができる。また、仮に谷部が残ったとしても（凸状体の高さも含めた粘着剤層の厚みはせいぜい数十μｍオーダーであるので）、谷底部分に空気を抱き込み難く、しかも谷部は極小さくなる。従って、貼着後の粘着剤層表面の凹凸は残り難く、また、仮に残ったとしても谷部は僅かとなり、粘着剤層の表面凹凸が貼着後に美観を損ねるのを防げる。
【０００７】
また、本発明の粘着シートは、上記構成に於いて更に、粘着剤層の表面に、該表面の凹凸形状とは逆凹凸形状の離型面を有する離型シートが積層されて成る構成とした。
この様な構成とすることにより、粘着剤層への凸状体の形成が容易となる上、更には、粘着シート保存時、流通時、使用時等に於いて、凸状体による表面凹凸の形状維持が容易となる。
【０００８】
【発明の実施の形態】
以下、図面を参照しながら本発明の実施の形態を説明する。
【０００９】
〔概要〕
本発明の粘着シートは、その或る一形態を概念的に例示する図１の断面図で示される粘着シート１０の如く、基材シート１上に粘着剤層２が設けらており、該粘着剤層２は、その表面から外方（図面上方）に突出する多数の凸状体２ａを有し、互いに隣接する凸状体２ａ間には溝状の谷部２ｂを有する。しかも、凸状体２ａの頂上部分から谷部の谷底部分にかけての垂直断面形状が滑らかな連続曲線を成し、且つ谷部の谷底部分２ｂｖが、谷部入口部分である凸状体の肩部分２ａｓに比べてより尖った形状で、且つ谷部の幅ｗと、凸状体２ａの高さｈとの関係が、ｗ≦ｈとなる様な表面凹凸形状としてある。
なお、本発明の粘着シート１０としては、更に、好ましくは、図面の如く、粘着剤層２の表面上には、粘着剤層２表面の凹凸形状とは逆凹凸形状の離型面を有する離型シート３を積層した構成とする。
【００１０】
〔粘着剤層の表面凹凸形状〕
先ず、谷部の谷底が、尖った形状とは、曲率半径の大小で表すことができる。すなわち、図２の断面図で概念的に示す如く、（垂直断面形状に於ける）谷底部分の曲率半径Ｒｖが、谷部の入口部分である凸状体の肩部分の曲率半径Ｒｓよりも小さい事（Ｒｖ＜Ｒｓ）である。曲率半径を計る位置は、谷底部分ではその中心で最も深い部分であり鉛直方向の半径となる位置とすれば良く、肩部分は、凸状体２ａの頂上部分から凸状体乃至は谷部分の斜面へ至る部分の中間位置、具体的には曲率半径の方向が水平面から上（離型シート側）に４５度の方向となる位置とすれば良い。
【００１１】
次に、凸状体の高さｈとは、注目する（垂直）断面において、凸状体の底部（＝谷部の谷底）と、凸状体の頂上との高低差である。
一方、谷部の幅ｗとは、谷部の側面に斜面を有する場合では、図２で示す如く、凸状体２ａの高さｈ（＝谷部２ｂの深さ）の半分である１／２ｈの高さに於ける幅で代表させると良い。なお、水平面内で、谷部が占める面積が１／２となる高さに於ける幅で代表させる事も可能である。なお、凸状体の頂上部分から谷部の谷底部分にかけての垂直断面形状は滑らかな連続曲線とするので、谷部の側面には少なくとも斜面を有することになるが、側面の一部に垂直面があっも良い。但し、谷底に近くなる程幅が漸減する様な側面（斜面）として垂直面が無い方が、谷底部分の空気をより逃がし易い点で好ましい。
【００１２】
図３は、粘着剤層の表面凹凸形状について、その垂直断面形状として肩部分から谷底部分に至る形状において、本発明に該当する形状（図中「ＯＫ」）と、該当しない形状（図中「ＮＧ」）との幾つかを概念的に例示する断面図である。
【００１３】
図３（Ａ）の形状は、該当（ＯＫ）形状の一例であり、谷底部分での曲率半径Ｒｖが肩部分の曲率半径Ｒｓより若干小さい（同程度）場合であり、また、凸状体の頂上部分に平坦な天面部を有する場合でもある。
図３（Ｂ）の形状は、該当（ＯＫ）形状の一例であり、谷底部分での曲率半径Ｒｖが肩部分の曲率半径Ｒｓより小さい場合である。
図３（Ｃ）の形状は、該当（ＯＫ）形状の一例であり、Ｒｖ＜Ｒｓではあるが、谷（或いは凸状体）の側面が、その一部に垂直面を有する形状である。
図３（Ｄ）の形状は、非該当（ＮＧ）形状の一例であり、肩部分から側面にかけては滑らかな曲線であるが、谷底が或る広さを持った平坦面を有する結果、全体としては滑らかな曲線では無い場合である。
図３（Ｅ）の形状は、非該当（ＮＧ）形状の一例であり、谷底部分から側面にかけては滑らかな曲線であるが、肩部分が折れ曲がっており、全体としては滑らかな曲線では無い場合である。
図３（Ｆ）の形状は、非該当（ＮＧ）形状の一例であり、谷底部分での曲率半径Ｒｖが肩部分の曲率半径Ｒｓより逆に大きい場合である。
なお、図３（Ａ）〜（Ｆ）は、尖った形状を主体として概念的に例示するものであり、凸状体の頂上部分に関しては平坦の場合で例示し、谷部（或いは凸状体）の側面に関しては直線部分を含む場合で例示したが、本発明に該当する場合において、頂上部分及び側面部分はこれら形状に限定されるものではない。
【００１４】
粘着剤層の表面凹凸形状を、上述した如き特定形状に規定することで、幅に対して深くした谷部は、貼着時に粘着シートを被着体に押しつける圧力で、谷部の両側の凸状体を谷部に向かってせり出させて、谷底部分に空気を残さない様にして、谷部を消滅させることができる。また、仮に谷部が残ったとしても谷底部分の空気は残さずに谷部を極小さくできる。この結果、粘着剤層の表面凹凸形状は貼着後には残らないか或いは残り難く極僅かとなり、粘着剤層の表面にあった凹凸の残存によって、美観を損ねるのを防げる様になる。
【００１５】
粘着剤層の表面凹凸形状としては、上述した特定形状とする以外は、特に制限は無い。但し、谷部は少なくとも貼着時は空気抜け層として、空気を逃がす道を作る必要がある事から、散発的に点在していたのでは、用を成さない。この為、谷部は、空気の逃げ道が出来る様に水平面内で連続している、つまり「溝状」を成す必要がある。谷部の連続性は、最低限、貼着時に空気が逃げ得る程度の距離（少なくとも５ｍｍ以上、より好ましくは１０ｍｍ以上）は連続しているのが好ましいが、連続部分の終端での空気の抱き込みを回避する点で、より好ましくは、粘着シートの全水平面に亘って端から端まで連続しているのが良い。
【００１６】
次に、凸状体２ａの水平面での水平断面形状は、例えば、三角形、四角形、五角形、六角形等の正多角形を含む多角形、円形、楕円形、或いは有限幅で無限長又は有限長の線形状（直線や曲線）等である。凸状体の垂直断面形状は、近似的に（凸状体頂上部分から谷部の谷底部分まで滑らかに連続曲線とするので、例えば台形では厳密にはそうならないが、これらの角を丸めた様な形状という意味での例示として）、台形、半円形、半楕円形、三角形等である。また、各凸状体の水平面での水平断面形状は、不揃いであっても良い。
また、凸状体の水平面内での配置は、格子状等と規則的に配列しても良いし、不規則に配置しても良い。
一方、谷部の形状は、凸状体の形状及びその配置に応じた形状となる。
【００１７】
ところで、凸状体２ａの具体的な大きさは、用途によるが、通常、その高さｈは、３〜５０μｍ、より好ましくは１０〜１００μｍである。高さｈが１０μｍ未満、特に３μｍ未満であると十分な空気抜け容易性を確保できず、逆に１００μｍ超過であると、たとえ、滑らかで深さが深く尖った谷部を設けたとしても、粘着剤層面の凹凸が貼着後も残り美観を損ない易い。
【００１８】
また、凸状体が、垂直断面形状が台形の例えば四角錐台状に基く類似形状の場合では、その頂上部分に平坦な天面部２ｄを有する形状とすることができる（図１参照）。その場合には、天面部があまりに広いと、せっかく谷部によって空気抜け容易性を確保できたとしも、天面部内に於いて空気が残留し易くなる。この為、この様な平面を成す天面部を凸状体がその頂上部分に有する場合には、該天面部の面積を１００ｍｍ^２以下とするのが好ましい。平坦な天面部の面積を１００ｍｍ^２以下とすれば、該天面部に於いても、空気抜け容易性を確保できる。なお、天面部が正方形の場合、１００ｍｍ^２とは、丁度１０ｍｍ角の正四角形となる。一方、平坦な天面部の場合の該面積の下限は、通常１ｍｍ^２程度である。該面積が１ｍｍ^２未満となると、粘着剤層の被着体との接着力（粘着力）が小さくなり過ぎる傾向があるからである。
【００１９】
なお、凸状体の頂上部分が、外方に凸の湾曲した三次元曲面である場合には、凸状体には「平坦な天面部」は存在しない。この様な場合には、その頂上の主要部分（例えば、凸状体の高さｈの半分２／ｈ以上の部分が占める部分）の水平断面積が１００ｍｍ^２以上であっても、湾曲している為に空気は抜け易く、空気抜け容易性の点では問題になり難い。但し、その分、谷部（空気抜け層）の容積は増加するので、たとえ、貼着時の圧力で谷部容積が減少するにしても、貼着後の粘着シート表面へは凹凸が現出し易くなる傾向となる。
【００２０】
次に、谷部の具体的な大きさとして、その幅は、凸状体の高さｈとの大小関係から、通常、３〜１０μｍ、より好ましくは１０〜１００μｍとなる。例えば、凸状体の高さｈが３０μｍであれば、谷部の幅ｗは２５μｍ等とする。
なお、谷部は溝状を呈するが、凸状体の形状及びその配置如何によっては（例えば凸状体として、円錐台をその底部が縦横方向の凸状体同士で一部重なる様に正方格子状に配列した場合等）、谷部が呈する溝の幅は、全ての水平面内の方向で（任意の垂直断面で）均一幅とはならず不均一となる。また、凸状体の高さｈ（谷の深さ）も、全ての水平面内の方向で（任意の垂直断面で）、不均一となる。
【００２１】
また、粘着剤層２が有する多数の凸状体２ａは、図１の断面図で例示する粘着シート１０の如く、谷部２ｂの谷底２ｂｖの下側（基材シート１側）にも粘着剤層部分があっても良い。谷底２ｂｖよりも下側の粘着剤層部分を基層２ｃとすれば、粘着剤層２は、基層２ｃと該基層２ｃ上の凸状体２ａとから構成される。
但し、図示は省略するが、基層２ｃを省略した構成としても良い。しかし、基層を省略した場合は、隣接する凸状体同士が基層で連結していないので、貼着後、粘着シートが不要になり粘着シートを剥離する際に、粘着剤層（凸状体）の一部が、粘着シートから脱落して被着体側に残って綺麗に剥がし難いという問題が起こることもある。この点で、基層２ｃ上に凸状体２ａを設けた構成の粘着剤層２とするのが好ましい。なお、凸状体の高さｈには、基層２ｃの厚みは含まない。注目する断面における凸状体の高さｈと、凸状体底部から基材シートまでの基層２ｃとの合計が粘着剤層２（全体）の厚さとなる。
【００２２】
なお、粘着剤層（全体）の厚さは、用途に応じたものとすれば良く、基層２ｃを設ける場合は該基層も含めて、１０μｍ〜２００μｍ程度である。厚さが１０μｍ未満であると、接着力（粘着力）が不十分となり、逆に２００μｍ超過ではコスト高となる。なお、基層２ｃ部分のみの厚さは、凸状体部分の（最大）高さにもよるが、通常、粘着剤層の厚みの３〜５割程度とする。また、基層の部分の粘着剤は、凸状体の部分の粘着剤と通常は同一材料で同時に形成するが、異なる材料で構成しても良い。
【００２３】
〔粘着剤層の材料及び形成法〕
粘着剤層２は、その表面に上述した如き表面凹凸形状を有するものであるが、この様な粘着剤層の形成に用いる粘着剤としては、従来公知のものを用途に応じて適宜使用すれば良い。例えば、ゴム系粘着剤、アクリル系粘着剤、シリコーン系粘着剤等の粘着剤である。
【００２４】
また、上述所望の凹凸形状を表面に有する粘着剤層を形成する方法としては、特に限定されるものではないが、該凹凸形状とは逆凹凸形状の離型面を有する離型シートを用意して、該離型シート上に粘着剤層を、ロールコート等の公知の塗工法等によって形成するのが、該凹凸形状を容易に形成できる点で好ましい一方法である。基材シートは、離型シート上に粘着剤層を形成して積層シートとした後、この積層シートの粘着剤層面に対して基材シートを貼り付けて積層することで、所望の粘着シートが得られる。
【００２５】
〔離型シート〕
次に、離型シート３としては、その離型面が平坦面の離型シートでも、使用することはできる（粘着剤層表面に所望の凹凸形状を形成した後で離型シートを積層する場合で、粘着剤層の谷部と離型シート間には空気が存在する）。しかし、離型シートとしては、粘着剤層表面の凹凸形状に対応した（該凹凸形状とは逆）凹凸形状を離型面に有する離型シートを用いるのが、好ましい。これによって、前記した如く、離型シート上に粘着剤層を塗工法等で形成することで、該粘着剤層表面に所望の凸状体及び谷部による表面凹凸形状を容易に形成できる。しかも、粘着シートの保存時、或いは流通時や使用時等に於いて、凸状体による粘着剤層の表面凹凸が潰れず、その形状維持も容易となる。
【００２６】
この様な離型面に所望の凹凸形状を設けた離型シートとしては、離型シートとして従来公知のシートに、エンボス加工等の従来公知の賦形手段を適用することで得られる。なお、肩部分よりも谷底部分をより尖った形状とするには、レジスト、露光、エッチング条件、サンドブラスト、レーザー加工、切削加工等の公知の賦形条件を調整すれば良い。
【００２７】
例えば、離型シートの材料としては、例えばポリエチレンテレフタレート等の樹脂シートや紙等のシートに、シリコーン樹脂、メラミン樹脂、ポリオレフィン系樹脂、或いは、ワックス等の離型剤を添加した樹脂等で離型層を積層したもの、或いは、ポリオレフィン系樹脂等のそれ自体が離型性を有する樹脂シート等である。
なお、離型シートの厚みは、用途に応じたものとすれば良く、例えば２０〜３００μｍ程度である。
【００２８】
離型シートの離型面を、所望の凹凸形状とするには、従来公知のエンボス加工を適用すれば良いが、エンボス加工としては、例えば、加熱されたシートにエンボス版としてエンボスローラを押圧して賦形する方法が代表的である。この他、樹脂シートや紙上への樹脂層の溶融塗工法による成膜時に、その冷却ローラの表面をエンボス面としたエンボスローラを用いる成膜同時賦形法等でも良い。或いは、樹脂層を溶融塗工法に代えて、紫外線や電子線等で硬化する電離放射線硬化性樹脂を用いてその塗工・硬化と同時に、硬化物としての樹脂層に賦形する方法でも良い。また、スクリーン印刷等の公知の印刷法を利用した盛上げ印刷等によって、離型面に所望の凹凸形状を賦形しても良い。
なお、エンボス版に所望の凹凸形状を設ける方法は、機械的な切削法、レーザ加工法等の公知の形成方法によれば良い。
【００２９】
〔基材シート〕
基材シート１としては、従来公知のものを用途に応じて適宜採用すれば良い。例えば、樹脂シート、金属箔、或いは、紙、不織布、織布、突板等の繊維質シート等、或いは、これら２種以上の積層シートや、樹脂含浸不織布等の様な複合シート等からなるシートである。なお、樹脂シートは、透明（無着色、着色）、不透明、半透明等のシートを用いる。なお、基材シートの厚みは、用途に応じたものとすれば良く、例えば、５〜５００μｍ程度、通常は２０〜３００μｍ程度である。
【００３０】
なお、粘着シートには、必要に応じて適宜、絵柄や凹凸等による模様、印字、コード、記号、画像等による可視或いは不可視情報を、公知の印刷・塗工手段等により施した構成としても良い。通常、これらは基材シートの片面（表面或いは裏面）、或いは両面に対して施される。絵柄等の模様を施したものは、建材用途にて化粧シートとして使用され得る。なお、模様とする絵柄には、全面着色等の全面ベタ模様もある。また、不可視情報とは、例えば、蛍光インキや赤外線吸収インキの印刷等による紫外線や赤外線照射にて判読可能な模様や文字等の情報等である。
【００３１】
また、粘着シートには、必要に応じて、各種機能性を付与した構成としても良い。機能性としては、例えば、耐摩耗性、耐擦傷性、耐汚染性、防曇性、反射防止性、帯電防止性、断熱性、抗菌性、電磁波シールド性等である。これらは、その機能に応じて、樹脂シート等の基材シート中に、それに必要な物質を添加するか、基材シート上に該物質或いは該物質を添加したインキや塗液等の層を形成する等して実現する。例えば、耐摩耗性や耐擦傷性等は、シリカ等の耐摩剤を、樹脂シート中に添加するか、該耐摩剤を含む塗液で基材シート表面に塗工形成するる。
【００３２】
【実施例】
以下、実施例及び比較例により本発明を更に詳述する。
【００３３】
〔実施例１〕
図１及び図３（Ｂ）の如き粘着シート１０を次の様にして作製した。
先ず、離型シートとして、厚み１５０μｍのポリプロピレン系樹脂シートの離型面とする面に対して、エンボスローラを用いて、所望の粘着剤層表面凹凸形状と逆凹凸形状の凹凸を形成して、離型シート３を得た。離型シートの離型面には、水平断面形状が縦横約５ｍｍで角を丸めた正方形で深さが３０μｍの凹部（粘着剤層で凸状体２ａとなる）と、この凹部と凹部との間（粘着剤層で溝状の谷部２ｂとなる）には、半分の深さ部分での幅が１５μｍで正方格子を成す峰状の凸部を全面に有し、凸部の峰中央部分から凹部中央部分にかけて、その断面形状は滑らかな連続曲線を無し、峰及び凹部の中央部共に丸みを帯びた形状である。
【００３４】
次に、上記離型シート３の凹凸が形成された離型面に対して、粘度１Ｐａ・ｓ（１０００ｃｐｓ）のアクリル系２液型粘着剤を、離型面の凹部を完全に充填し、更にその上に粘着剤層として２０μｍの厚さになる様に塗布し、１２０℃で１分間乾燥して粘着剤層２を形成して、離型シートと粘着剤層とが積層された積層シートを得た。
【００３５】
そして、上記積層シートの粘着剤層２の面に、基材シート１として厚さ５０μｍのポリエチレンテレフタレートシートをラミネータを用いて貼り合わせて、図１の断面図の如き、所望の粘着シート１０を得た。
【００３６】
この粘着シートの粘着剤層２は、厚さ２０μｍの基層２ｃの上（離型シート側）に、水平断面形状が縦横約５ｍｍで頂上部が面積２５ｍｍ^２の平坦で角が若干丸みを帯びた正方形の天面部を成し高さｈが３０μｍで垂直断面が図１の如き角を丸めた台形状の四角錐体の凸状体２ａを、正方格子状に多数配置した表面凹凸形状を有する。また、縦横で隣接する凸状体の間には、全面に走る溝状の谷部２ｂを有するが、凸状体の天面部から谷部の谷底までは、図３（Ｂ）の断面図の様に、その断面形状が滑らかな連続曲線を呈し、谷部は谷底に近いほど幅が狭くなる傾斜した側面を有し、ｈ／２の部分に於ける幅ｗが１５μｍで、谷底部分は凸状体の肩部分より尖っているが丸みを帯び平坦部分が無い形状をしている。
【００３７】
〔実施例２〕
実施例１に於いて、エンボス時の離型シートの離型面の凹凸形状を変更して、次の如き表面形状の粘着剤層とした他は、実施例１と同様にして粘着シートを作成した。凸状体は天面部の大きさを縦横６ｍｍ（面積３６ｍｍ^２）で、高さｈを５０μｍ、谷部は幅ｗを４０μｍに変更。
【００３８】
〔比較例１〕
実施例１に於いて、エンボス時の離型シートの離型面の凹凸形状を変更して、次の如き表面形状の粘着剤層とした他は、実施例１と同様にして粘着シートを作成した。凸状体は天面部の大きさを縦横５ｍｍ（面積２５ｍｍ^２）で、高さｈを２０μｍ、谷部は幅ｗを３０μｍに変更。
【００３９】
〔比較例２〕
実施例１に於いて、エンボス時の離型シートの離型面の凹凸形状を変更して、次の如き表面形状の粘着剤層とした他は、実施例１と同様にして粘着シートを作成した。凸状体は天面部の大きさを縦横７ｍｍ（面積４９ｍｍ^２）で、高さｈを３０μｍ、谷部は幅ｗを５０μｍに変更。
【００４０】
〔比較例３〕
実施例１に於いて、エンボス時の離型シートの離型面の凹凸形状を変更して、次の如き表面形状の粘着剤層とした他は、実施例１と同様にして粘着シートを作成した。凸状体は天面部の大きさを縦横５ｍｍ（面積２５ｍｍ^２）で、高さｈを４０μｍ、谷部は幅ｗを３５μｍ、谷部の尖り具合は図３（Ｆ）の如く、肩部分よりも緩く尖っていない形状に変更。
【００４１】
〔性能評価〕
上記各実施例及び比較例の粘着シートを、それぞれ、透明ガラス板にゴム製スキージでしごいて空気を抜きながら貼り付けて、２４時間放置後の、空気残りと面状態（粘着剤層の表面凹凸による模様の可視性）とを、目視観察して評価した。評価結果は、表１に示す。
【００４２】
【表１】

【００４３】
表１の如く、各実施例はいずれも、空気残り無く空気抜け容易性は良好であり、また、面状態も良好で美観を損ねる事は無かった。しかしながら、比較例は、いずれも、空気抜け容易性と面状態と両方共に良好なものは無かった。すなわち、比較例１及び２は空気抜け容易性こそ良好であるものの、面状態が悪かった。また、谷底が尖って無く緩い形状の比較例３は、面状態は良好であるものの、若干空気が残り、空気抜け容易性は若干劣った。
【００４４】
【発明の効果】
（１）本発明の粘着シートによれば、空気抜け容易性が確保される上、しかも、貼着後には、空気抜け容易性の為に設けた粘着剤層表面の凹凸は消滅乃至は極僅かとなり、該凹凸によって美観が損なわれるのを防げる。しかも、粘着剤層に設けた谷部の谷底部分も容易に空気を抜きながら谷部を消滅させる事ができる。従って、空気抜け容易性と美観の両立が図れる。
（２）更に、粘着剤層の表面に、該表面の凹凸形状とは逆凹凸形状の離型面を有する離型シートが積層されて成る構成とすれば、粘着剤層への凸状体の形成が容易となる上、更には、粘着シート保存時、流通時、使用時等に於いて、凸状体による表面凹凸の形状維持が容易となる。
【図面の簡単な説明】
【図１】本発明による粘着シートを概念的に説明する断面図。
【図２】本発明による粘着剤層の表面凹凸形状を概念的に説明する断面図。
【図３】粘着剤層の表面凹凸形状について、該当／非該当を概念的に例示する断面図。
【図４】従来の粘着シートの一例を示す斜視図。
【符号の説明】
１　　　基材シート
２　　　粘着剤層
２ａ　　凸状体
２ａｓ　肩部分
２ｂ　　谷部
２ｂｖ　谷底部分
２ｃ　　基層
２ｄ　（平坦な）天面部
３　　離型シート
１０　粘着シート
３０　粘着シート
３１　基材シート
３２　粘着剤層
３２ａ　凸部
３２ｂ　凹部
ｈ　　凸状体の高さ（＝谷部の深さ）
Ｒｓ　肩部分の曲率半径
Ｒｖ　谷底分の曲率半径
ｗ　　谷部の幅[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer surface with irregularities. In particular, the present invention relates to a pressure-sensitive adhesive sheet having "easiness of air bleeding" in which air is not easily entrapped when affixed to an adherend.
[0002]
[Prior art]
Generally, the surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is flat, and therefore, when the pressure-sensitive adhesive sheet is stuck to an adherend, it is easy to embrace air unless it is stuck carefully. In such a case, if a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer surface having an uneven surface is used, an air escape path is formed between the protrusions on the surface of the pressure-sensitive adhesive layer, so that the entrapment of air is improved. Examples of the pressure-sensitive adhesive sheet having such a property that the surface of the pressure-sensitive adhesive layer has irregularities and is hard to entrap air (this is referred to as “easiness of air release” in this specification) include, for example, The pressure-sensitive adhesive sheets disclosed in Japanese Patent No. 2994411, Utility Model Registration No. 2503717 and the like can be mentioned. For example, in the pressure-sensitive adhesive sheet disclosed in Utility Model Registration No. 2503717, as shown in the pressure-sensitive adhesive sheet 30 shown in the perspective view of FIG. However, it discloses a shape or the like in which protrusions 32a having an outer diameter d of 0.3 mm at the lower end and a height h of 20 μm are scattered vertically and horizontally at an interval of 1 mm.
[0003]
[Problems to be solved by the invention]
However, as shown in FIG. 4, when the width of the concave portion 32b between the adjacent convex portions 32a is large, after the adhesive sheet is attached to the adherend, the concave portion 32b comes into contact with the adhesive layer and the adherend. It will remain as a space (air bleed layer) that has not been made. For this reason, after sticking, the arrangement of the projections appears as a pattern as it is, and there is a problem in appearance that the appearance is impaired. In particular, when the adherend is made of transparent glass or the like, or when the base material sheet is a thin resin sheet or the like, the pattern is easily noticeable. That is, in the case of transparent glass, it is particularly easy to see from the adherend side, and when both the adherend and the adhesive sheet are opaque, the subtlety that appears through the adhesive sheet on the front side of the adhesive sheet This was because they appeared as irregularities.
[0004]
That is, an object of the present invention is to ensure “easiness of air bleeding” at the time of sticking by the unevenness of the surface of the pressure-sensitive adhesive layer, and to prevent a pattern due to the unevenness from being seen and spoiling the aesthetic appearance. .
[0005]
[Means for Solving the Problems]
Therefore, in order to solve the above problems, in the pressure-sensitive adhesive sheet of the present invention, in a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer provided on a base sheet, the pressure-sensitive adhesive layer has a large number of convex bodies protruding outward from the surface thereof. Having a groove-shaped valley between the adjacent convex bodies, the vertical cross-sectional shape from the top portion of the convex body to the valley bottom portion of the valley forms a smooth continuous curve, and The valley bottom portion has a more sharp shape than the shoulder portion of the convex body that is the valley entrance portion, and the width w of the valley is w ≦ h with respect to the height h of the convex body. Configuration.
[0006]
With such a configuration, ease of air release is ensured by the unevenness formed by the convex body on the surface of the pressure-sensitive adhesive layer. In addition, the vertical cross-sectional shape from the top of the convex body to the bottom of the valley is a smooth continuous curve, and the width w of the valley is equal to or less than the height h of the convex body (that is, equal or less than the height). ) And the bottom of the valley is sharper than the entrance of the valley (the shoulder of the convex body). The valley can be extinguished while the body is protruded toward the valley and the air in the valley including the valley bottom is easily removed. Even if valleys remain (since the thickness of the pressure-sensitive adhesive layer including the height of the convex body is at most on the order of several tens of μm), it is difficult to embrace air at the bottoms of the valleys, and the valleys are extremely small. Become. Therefore, the unevenness of the surface of the pressure-sensitive adhesive layer after the adhesion is hard to remain, and even if it remains, the valley becomes small, and it is possible to prevent the surface unevenness of the pressure-sensitive adhesive layer from impairing the appearance after the application.
[0007]
Further, the pressure-sensitive adhesive sheet of the present invention, in the above-described configuration, further has a configuration in which a release sheet having a release surface having a concave-convex shape reverse to the concave-convex shape of the surface is laminated on the surface of the pressure-sensitive adhesive layer. .
With such a configuration, it is easy to form a convex body on the pressure-sensitive adhesive layer, and further, at the time of storage of the pressure-sensitive adhesive sheet, at the time of distribution, at the time of use, and the like, the surface unevenness due to the convex body. The shape can be easily maintained.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
〔Overview〕
The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer 2 provided on a base sheet 1 like a pressure-sensitive adhesive sheet 10 shown in a cross-sectional view of FIG. The agent layer 2 has a large number of convex bodies 2a protruding outward (upward in the drawing) from the surface thereof, and has groove-shaped valleys 2b between the adjacent convex bodies 2a. Moreover, the vertical cross-section from the top to the valley bottom of the convex body 2a forms a smooth continuous curve, and the valley bottom 2bv is the shoulder of the convex body that is the valley entrance. The surface unevenness is more sharp than 2as, and the relationship between the width w of the valley and the height h of the convex body 2a satisfies w ≦ h.
In addition, as the pressure-sensitive adhesive sheet 10 of the present invention, more preferably, as shown in the drawing, on the surface of the pressure-sensitive adhesive layer 2, a release surface having a concave-convex shape reverse to the concave-convex shape of the pressure-sensitive adhesive layer 2 surface is used. The configuration is such that the mold sheets 3 are stacked.
[0010]
(Surface unevenness of adhesive layer)
First, the shape in which the valley bottom is pointed can be expressed by the magnitude of the radius of curvature. That is, as conceptually shown in the cross-sectional view of FIG. 2, the radius of curvature Rv of the bottom of the valley (in the vertical cross-sectional shape) is smaller than the radius of curvature Rs of the shoulder of the convex body which is the entrance of the valley. (Rv <Rs). The position at which the radius of curvature is measured may be the deepest portion at the center of the valley bottom portion and a position having a radius in the vertical direction, and the shoulder portion may be from the top of the convex body 2a to the convex or valley portion. The intermediate position of the portion reaching the slope, specifically, the position where the direction of the radius of curvature is 45 degrees above the horizontal plane (toward the release sheet) may be used.
[0011]
Next, the height h of the convex body is a height difference between the bottom of the convex body (= valley bottom of the valley) and the top of the convex body in the (vertical) cross section of interest.
On the other hand, the width w of the valley is 1 / half of the height h of the convex body 2a (= the depth of the valley 2b), as shown in FIG. It is good to represent the width at a height of 2h. In addition, it is also possible to represent by the width at the height where the area occupied by the valleys is 水 in the horizontal plane. In addition, since the vertical cross-sectional shape from the top part of the convex body to the valley bottom part is a smooth continuous curve, the side surface of the valley part has at least a slope, but a part of the side surface has a vertical surface. There is good. However, it is preferable that there is no vertical surface as a side surface (slope) whose width gradually decreases toward the bottom of the valley because air at the bottom of the valley can be more easily released.
[0012]
FIG. 3 shows the shape of the surface unevenness of the pressure-sensitive adhesive layer as a vertical cross-sectional shape from the shoulder portion to the valley bottom portion, which corresponds to the present invention (“OK” in the figure) and the shape that does not correspond to the shape (“OK” in the figure). NG ") is a cross-sectional view conceptually illustrating some of them.
[0013]
The shape of FIG. 3A is an example of a corresponding (OK) shape, in which the radius of curvature Rv at the bottom of the valley is slightly smaller (similarly) than the radius of curvature Rs of the shoulder portion. In some cases, the top portion has a flat top surface.
The shape in FIG. 3B is an example of the corresponding (OK) shape, in which the radius of curvature Rv at the valley bottom is smaller than the radius of curvature Rs at the shoulder.
The shape in FIG. 3C is an example of the corresponding (OK) shape, and although Rv <Rs, the side surface of the valley (or the convex body) has a vertical surface in a part thereof.
The shape shown in FIG. 3D is an example of a non-applicable (NG) shape. Although the shape is a smooth curve from the shoulder to the side, the valley bottom has a flat surface having a certain width. Is not a smooth curve.
The shape of FIG. 3E is an example of a non-corresponding (NG) shape, which is a smooth curve from the valley bottom to the side surface, but has a bent shoulder portion and is not a smooth curve as a whole. is there.
The shape in FIG. 3F is an example of a non-applicable (NG) shape, in which the radius of curvature Rv at the valley bottom is larger than the radius of curvature Rs at the shoulder.
3 (A) to 3 (F) conceptually exemplify a pointed shape as a main body, and illustrate an example in which a top portion of a convex body is flat, and illustrates a valley (or a convex body). Although the side surface of ()) has been illustrated as including a straight line portion, in the case of the present invention, the top portion and the side surface portion are not limited to these shapes.
[0014]
By defining the surface unevenness of the pressure-sensitive adhesive layer to the specific shape as described above, the valley portion that is made deeper with respect to the width is pressed by the pressure of the pressure-sensitive adhesive sheet against the adherend at the time of sticking, and the convex portions on both sides of the valley portion are formed. The valley can be extinguished by projecting the shape toward the valley so that no air remains at the bottom of the valley. Even if the valley remains, the valley can be made extremely small without leaving air at the bottom of the valley. As a result, the surface unevenness of the pressure-sensitive adhesive layer does not remain, or hardly remains, after application, and becomes extremely small, thereby preventing the appearance of the pressure-sensitive adhesive layer from being impaired due to the remaining unevenness on the surface of the pressure-sensitive adhesive layer.
[0015]
There is no particular limitation on the surface unevenness of the pressure-sensitive adhesive layer, except for the specific shape described above. However, since the valleys need to be formed as air bleeding layers at least at the time of sticking, and a way to allow air to escape is used, it is useless if they are scattered sporadically. For this reason, the valleys need to be continuous in a horizontal plane, that is, have a “groove shape” so that an escape path for air can be formed. As for the continuity of the valleys, it is preferable that the valleys are continuous at least for a distance (at least 5 mm or more, more preferably 10 mm or more) at which air can escape at the time of sticking. From the viewpoint of avoiding jamming, it is more preferable that the pressure-sensitive adhesive sheet be continuous from end to end over the entire horizontal plane.
[0016]
Next, the horizontal cross-sectional shape of the convex body 2a in the horizontal plane is, for example, a polygon including a regular polygon such as a triangle, a quadrangle, a pentagon, and a hexagon, a circle, an ellipse, or an infinite length or a finite length with a finite width. (Straight line or curve). The vertical cross-sectional shape of the convex body is approximately (Since it is a smoothly continuous curve from the top of the convex body to the bottom of the valley, for example, it is not exactly the case with a trapezoid, , Trapezoidal, semi-circular, semi-elliptical, triangular, etc. The horizontal cross-sectional shape of each convex body in the horizontal plane may be irregular.
The arrangement of the convex bodies in the horizontal plane may be regularly arranged in a lattice or the like, or may be irregularly arranged.
On the other hand, the shape of the valley becomes a shape corresponding to the shape of the convex body and its arrangement.
[0017]
By the way, the specific size of the convex body 2a depends on the application, but usually, the height h is 3 to 50 μm, more preferably 10 to 100 μm. If the height h is less than 10 μm, especially less than 3 μm, it is not possible to secure sufficient air bleeding easily. Conversely, if the height h is more than 100 μm, even if a smooth, deep and sharp valley is provided, Irregularities on the surface of the pressure-sensitive adhesive layer remain even after being adhered, and the aesthetic appearance is easily damaged.
[0018]
Further, when the convex body has a similar shape based on a trapezoidal vertical cross-sectional shape, for example, a truncated quadrangular pyramid, the convex body may have a flat top surface portion 2d at the top (see FIG. 1). In this case, if the top surface is too wide, air tends to remain in the top surface even if the valleys ensure the ease of air release. For this reason, when the convex body has the top surface forming such a plane at the top, the area of the top surface is preferably 100 mm ² or less. If the area of the flat top surface is set to 100 mm ² or less, easy air escape can be ensured even at the top surface. In the case where the top surface is a square, 100 mm ² is a regular square of exactly 10 mm square. On the other hand, in the case of a flat top surface, the lower limit of the area is usually about 1 mm ² . If the area is less than 1 mm ² , the adhesive strength (adhesive strength) of the pressure-sensitive adhesive layer to the adherend tends to be too small.
[0019]
When the top of the convex body is a three-dimensional curved surface that is curved outwardly, there is no “flat top surface” in the convex body. In such a case, even if the horizontal cross-sectional area of the main portion at the top (for example, a portion occupied by a portion equal to or more than half 2 / h of the height h of the convex body) is 100 mm ² or more, it is curved. Because of this, air is easily evacuated, and it is unlikely to cause a problem in terms of easiness of air evasion. However, since the volume of the valley (air bleeding layer) increases by that amount, even if the valley volume decreases due to the pressure at the time of application, irregularities appear on the surface of the adhesive sheet after application. It tends to be easier.
[0020]
Next, as a specific size of the valley, the width is usually 3 to 10 μm, more preferably 10 to 100 μm, from the magnitude relationship with the height h of the convex body. For example, if the height h of the convex body is 30 μm, the width w of the valley is 25 μm or the like.
The valleys have a groove shape, but depending on the shape and the arrangement of the convex bodies (for example, as a convex body, a truncated cone may be formed in a square lattice so that the bottoms partially overlap with the vertical and horizontal convex bodies. In such a case, the widths of the grooves formed by the valleys are not uniform in all directions in the horizontal plane (at any vertical cross section), but are non-uniform. In addition, the height h (depth of the valley) of the convex body becomes non-uniform in all directions in the horizontal plane (at any vertical cross section).
[0021]
Further, as shown in the pressure-sensitive adhesive sheet 10 illustrated in the cross-sectional view of FIG. There may be a layer part. Assuming that the pressure-sensitive adhesive layer portion below the valley bottom 2bv is the base layer 2c, the pressure-sensitive adhesive layer 2 is composed of the base layer 2c and the convex body 2a on the base layer 2c.
However, although illustration is omitted, a configuration in which the base layer 2c is omitted may be adopted. However, when the base layer is omitted, since the adjacent convex bodies are not connected by the base layer, the pressure-sensitive adhesive sheet becomes unnecessary after application and the pressure-sensitive adhesive layer is peeled off when the pressure-sensitive adhesive sheet is peeled off. In some cases, a problem arises in that some of the particles fall off the adhesive sheet and remain on the adherend side, making it difficult to remove them neatly. In this respect, it is preferable that the pressure-sensitive adhesive layer 2 has a configuration in which the convex body 2a is provided on the base layer 2c. Note that the height h of the convex body does not include the thickness of the base layer 2c. The sum of the height h of the convex body in the cross section of interest and the base layer 2c from the bottom of the convex body to the base sheet is the thickness of the pressure-sensitive adhesive layer 2 (entire).
[0022]
The thickness of the pressure-sensitive adhesive layer (entire) may be determined according to the intended use. When the base layer 2c is provided, the thickness of the pressure-sensitive adhesive layer including the base layer 2c is about 10 μm to 200 μm. If the thickness is less than 10 μm, the adhesive strength (adhesive strength) becomes insufficient, and if it exceeds 200 μm, the cost increases. The thickness of the base layer 2c alone depends on the (maximum) height of the convex portion, but is usually about 30 to 50% of the thickness of the pressure-sensitive adhesive layer. The pressure-sensitive adhesive in the base layer portion is usually formed simultaneously with the same material as the pressure-sensitive adhesive in the convex portion, but may be formed of a different material.
[0023]
(Material of adhesive layer and formation method)
The pressure-sensitive adhesive layer 2 has a surface unevenness as described above on its surface, and as a pressure-sensitive adhesive used for forming such a pressure-sensitive adhesive layer, a conventionally known pressure-sensitive adhesive may be appropriately used depending on the application. good. For example, an adhesive such as a rubber-based adhesive, an acrylic-based adhesive, or a silicone-based adhesive is used.
[0024]
Further, the method of forming the pressure-sensitive adhesive layer having the above-mentioned desired unevenness on the surface is not particularly limited, but a release sheet having a release surface having an uneven shape reverse to the unevenness is prepared. Forming the pressure-sensitive adhesive layer on the release sheet by a known coating method such as roll coating is one preferable method in that the uneven shape can be easily formed. The base sheet is formed by forming a pressure-sensitive adhesive layer on a release sheet to form a laminated sheet, and then attaching and laminating the base sheet to the pressure-sensitive adhesive layer surface of the laminated sheet, whereby a desired pressure-sensitive adhesive sheet is formed. can get.
[0025]
[Release sheet]
Next, as the release sheet 3, a release sheet having a flat release surface can be used (when the release sheet is laminated after forming a desired uneven shape on the surface of the pressure-sensitive adhesive layer). Thus, air exists between the valley of the pressure-sensitive adhesive layer and the release sheet). However, as the release sheet, it is preferable to use a release sheet having a concave / convex shape corresponding to the concave / convex shape on the surface of the pressure-sensitive adhesive layer (reverse to the concave / convex shape) on the release surface. Thus, as described above, by forming the pressure-sensitive adhesive layer on the release sheet by a coating method or the like, it is possible to easily form a desired surface uneven shape due to a desired convex body and valley on the surface of the pressure-sensitive adhesive layer. In addition, when the pressure-sensitive adhesive sheet is stored, distributed, used, or the like, the surface irregularities of the pressure-sensitive adhesive layer due to the convex body are not crushed, and the shape can be easily maintained.
[0026]
Such a release sheet having a desired uneven shape on the release surface can be obtained by applying a conventionally known shaping means such as embossing to a conventionally known release sheet. In order to make the valley bottom portion sharper than the shoulder portion, known shaping conditions such as resist, exposure, etching conditions, sandblasting, laser processing, and cutting may be adjusted.
[0027]
For example, as a material of the release sheet, for example, a resin sheet such as polyethylene terephthalate or a sheet such as paper, a silicone resin, a melamine resin, a polyolefin resin, or a resin obtained by adding a release agent such as a wax, or the like. It is a laminate of layers, or a resin sheet or the like which itself has releasability, such as a polyolefin-based resin.
The thickness of the release sheet may be determined according to the intended use, and is, for example, about 20 to 300 μm.
[0028]
In order to make the release surface of the release sheet a desired uneven shape, conventionally known embossing may be applied, but as the embossing, for example, an embossing roller is pressed as an embossing plate on a heated sheet. A typical example is a method of shaping by shaping. In addition, when forming a resin layer on a resin sheet or paper by a melt coating method, a film forming simultaneous shaping method using an embossing roller having the surface of a cooling roller as an embossing surface may be used. Alternatively, instead of the melt coating method, a method may be used in which an ionizing radiation-curable resin that is cured by ultraviolet rays or electron beams is used, and the resin layer is formed as a cured product at the same time as the application and curing. Also, a desired uneven shape may be formed on the release surface by stencil printing using a known printing method such as screen printing.
The embossing plate may be provided with a desired uneven shape by a known forming method such as a mechanical cutting method or a laser processing method.
[0029]
(Base sheet)
As the base sheet 1, a conventionally known base sheet may be appropriately used depending on the application. For example, a sheet made of a resin sheet, a metal foil, or a fibrous sheet such as paper, nonwoven fabric, woven fabric, veneer, or a composite sheet such as a laminated sheet of two or more of these or a resin-impregnated nonwoven fabric. is there. Note that a transparent (uncolored, colored), opaque, translucent, or other sheet is used as the resin sheet. The thickness of the base sheet may be determined according to the intended use, and is, for example, about 5 to 500 μm, usually about 20 to 300 μm.
[0030]
The pressure-sensitive adhesive sheet may have a configuration in which visible or invisible information such as a pattern, a pattern, an unevenness, or the like, a print, a code, a symbol, an image, or the like is applied to the adhesive sheet by a known printing / coating means or the like as needed. . Usually, these are applied to one side (front or back) or both sides of the substrate sheet. Those on which a pattern such as a picture is given can be used as a decorative sheet in building material applications. It should be noted that there is also a solid pattern on the entire surface such as coloring on the entire surface as the pattern. The invisible information is, for example, information such as patterns and characters that can be read by irradiation of ultraviolet rays or infrared rays by printing fluorescent ink or infrared absorbing ink.
[0031]
Further, the pressure-sensitive adhesive sheet may have a configuration in which various functions are imparted as necessary. The functional properties include, for example, abrasion resistance, scratch resistance, stain resistance, antifogging property, antireflection property, antistatic property, heat insulation property, antibacterial property, electromagnetic wave shielding property, and the like. Depending on their functions, these may be added to a base material sheet such as a resin sheet or the like, or may be formed on the base material sheet with a layer such as the substance or an ink or coating liquid containing the substance. And so on. For example, abrasion resistance, abrasion resistance, and the like are determined by adding a lubricant such as silica to a resin sheet or by applying a coating solution containing the lubricant on the surface of a base sheet.
[0032]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
[0033]
[Example 1]
An adhesive sheet 10 as shown in FIG. 1 and FIG. 3 (B) was produced as follows.
First, as a release sheet, a surface of a 150 μm-thick polypropylene-based resin sheet as a release surface, using an embossing roller, to form irregularities of a desired pressure-sensitive adhesive layer surface irregularities and reverse irregularities, A release sheet 3 was obtained. On the release surface of the release sheet, a concave portion (having a convex body 2a with an adhesive layer) having a horizontal cross-sectional shape of about 5 mm in length and width and a rounded corner and a depth of 30 μm is formed. Between the gaps (the groove-like valleys 2b in the adhesive layer), a half-depth portion having a width of 15 μm and a peak-like convex portion forming a square lattice on the entire surface, and a central portion of the peak portion of the convex portion From the center of the recess to a central portion of the recess, the cross section has no smooth continuous curve, and both the peak and the central portion of the recess are rounded.
[0034]
Next, an acrylic two-component adhesive having a viscosity of 1 Pa · s (1000 cps) is completely filled in the concave portion of the release surface with respect to the release surface of the release sheet 3 on which the irregularities are formed, and further, An adhesive layer is applied thereon so as to have a thickness of 20 μm, dried at 120 ° C. for 1 minute to form an adhesive layer 2, and a laminated sheet in which a release sheet and an adhesive layer are laminated is formed. Obtained.
[0035]
Then, a 50 μm-thick polyethylene terephthalate sheet as a base sheet 1 is attached to the surface of the adhesive layer 2 of the laminated sheet using a laminator to obtain a desired adhesive sheet 10 as shown in the sectional view of FIG. Was.
[0036]
The pressure-sensitive adhesive layer 2 of this pressure-sensitive adhesive sheet had a flat surface with a horizontal cross section of about 5 mm in length and width of about 5 mm and a top area of 25 mm ² on a base layer 2 c having a thickness of 20 μm (release sheet side), and the corners were slightly rounded. It has a surface irregularity in which a large number of trapezoidal pyramid-shaped protrusions 2a having a square top surface, a height h of 30 μm, and a vertical cross section with rounded corners as shown in FIG. 1 are arranged in a square lattice. In addition, a groove-like valley 2b running over the entire surface is provided between adjacent convex bodies in the vertical and horizontal directions, but from the top surface of the convex body to the valley bottom of the valley, the cross-sectional view of FIG. Thus, the cross-sectional shape presents a smooth continuous curve, the valley has an inclined side surface whose width decreases as it approaches the valley bottom, the width w at the h / 2 portion is 15 μm, and the valley bottom is convex. It is sharper than the shoulder of the body but rounded and has no flat part.
[0037]
[Example 2]
In Example 1, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the uneven shape of the release surface of the release sheet during embossing was changed to a pressure-sensitive adhesive layer having the following surface shape. did. For the convex body, the size of the top surface is 6 mm in length and width (36 mm ^{2 in} area), the height h is changed to 50 μm, and the width w is changed to 40 μm for the valley.
[0038]
[Comparative Example 1]
In Example 1, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the uneven shape of the release surface of the release sheet during embossing was changed to a pressure-sensitive adhesive layer having the following surface shape. did. For the convex body, the size of the top surface was changed to 5 mm in length and width (area 25 mm ² ), the height h was changed to 20 μm, and the width w was changed to 30 μm for the valley.
[0039]
[Comparative Example 2]
In Example 1, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the uneven shape of the release surface of the release sheet during embossing was changed to a pressure-sensitive adhesive layer having the following surface shape. did. For the convex body, the size of the top surface was 7 mm in length and width (49 mm ^{2 in} area), the height h was changed to 30 μm, and the width w was changed to 50 μm for the valley.
[0040]
[Comparative Example 3]
In Example 1, a pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the uneven shape of the release surface of the release sheet during embossing was changed to a pressure-sensitive adhesive layer having the following surface shape. did. The height of the convex body is 5 mm in length and width (area 25 mm ² ), the height h is 40 μm, the width of the valley is 35 μm, and the sharpness of the valley is from the shoulder as shown in FIG. Also changed to a loosely pointed shape.
[0041]
(Performance evaluation)
The pressure-sensitive adhesive sheets of the above Examples and Comparative Examples were respectively adhered to a transparent glass plate while squeezing air with a rubber squeegee, and the air remaining and the surface state (surface of the pressure-sensitive adhesive layer) after standing for 24 hours. And the visibility of the pattern due to unevenness) was evaluated by visual observation. The evaluation results are shown in Table 1.
[0042]
[Table 1]

[0043]
As shown in Table 1, in each of the examples, there was no residual air, the air easiness was good, and the surface condition was good, and the appearance was not spoiled. However, none of the comparative examples had good air release easiness and good surface condition. In other words, Comparative Examples 1 and 2 had good air easiness, but had poor surface conditions. In Comparative Example 3 having a loose shape with no sharp valley bottom, although the surface condition was good, a little air remained, and the ease of air bleeding was slightly inferior.
[0044]
【The invention's effect】
(1) According to the pressure-sensitive adhesive sheet of the present invention, ease of air bleeding is ensured, and after sticking, irregularities on the surface of the pressure-sensitive adhesive layer provided for ease of air bleeding are eliminated or extremely small. This prevents the appearance from being impaired by the irregularities. In addition, the valley bottom portion of the valley portion provided in the pressure-sensitive adhesive layer can be eliminated while easily removing air. Therefore, both ease of air bleeding and aesthetic appearance can be achieved.
(2) Further, if a release sheet having a release surface having a concave-convex shape reverse to the concave-convex shape of the surface is laminated on the surface of the pressure-sensitive adhesive layer, the convex body to the pressure-sensitive adhesive layer is formed. In addition to being easy to form, it is easy to maintain the shape of the surface irregularities due to the convex body when storing, distributing, and using the pressure-sensitive adhesive sheet.
[Brief description of the drawings]
FIG. 1 is a sectional view conceptually illustrating a pressure-sensitive adhesive sheet according to the present invention.
FIG. 2 is a cross-sectional view conceptually illustrating the uneven shape of the surface of the pressure-sensitive adhesive layer according to the present invention.
FIG. 3 is a cross-sectional view conceptually illustrating whether the surface irregularities of the pressure-sensitive adhesive layer are applicable or not.
FIG. 4 is a perspective view showing an example of a conventional pressure-sensitive adhesive sheet.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base sheet 2 Adhesive layer 2a Convex body 2as Shoulder part 2b Valley part 2bv Valley bottom part 2c Base layer 2d (flat) Top surface part 3 Release sheet 10 Adhesive sheet 30 Adhesive sheet 31 Base sheet 32 Adhesive layer 32a Convex Part 32b Concavity h Height of convex body (= depth of valley)
Rs radius of curvature of shoulder Rv radius of curvature w of valley bottom width of valley

Claims

In a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer on a substrate sheet,
The pressure-sensitive adhesive layer has a number of convex bodies protruding outward from the surface thereof, has a groove-like valley between adjacent convex bodies, and has a valley portion from a top portion of the convex body. The vertical cross-sectional shape of the valley portion forms a smooth continuous curve, and the valley bottom portion has a sharper shape than the shoulder of the convex body that is the valley entrance portion, and the width of the valley portion. The pressure-sensitive adhesive sheet wherein w is w ≦ h with respect to the height h of the convex body.

The pressure-sensitive adhesive sheet according to claim 1, wherein a release sheet having a release surface having a concave-convex shape reverse to the concave-convex shape of the surface is laminated on the surface of the pressure-sensitive adhesive layer.