JP2004204122A - Light-diffusing resin composition, and molding obtained by molding the same - Google Patents
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Abstract
Description
【０００１】
【発明の属する技術分野】
本発明は、光拡散性樹脂組成物及びそれを成形してなる成形体に関する。さらに詳しくは、本発明は、微粒子状の光拡散剤を使用することなく、少なくとも２種の透明樹脂の組み合わせにより良好な光拡散性が発現する光拡散性樹脂組成物及び該組成物を成形してなる光拡散性、輝度、色調などに優れた成形体に関する。
【０００２】
【従来の技術】
電圧をかけると分子の並び方が変化するという液晶の性質を利用した液晶表示装置は、携帯情報端末、車載用パネル、パソコンなどに広く用いられている。今後液晶表示装置の大型化、高性能化が進むことにより、ＣＲＴ表示装置を代替することが期待されている。液晶自体は発光しないので、液晶表示装置は外部の光源を必要とし、液晶表示装置の側縁に光源が配置されるサイドライト方式と、液晶表示装置の背部に光源が配置される直下方式が実用化されている。サイドライト方式は、装置ユニットを薄くすることができるが、輝度が低いので、輝度が要求される大型の液晶表示装置には、直下方式が適している。
直下方式の液晶表示装置では、装置筐体の背部に複数本の蛍光管などの光源を配置し、光拡散板により入射した光を拡散させて輝度の均一な面状の光に変換する。必要に応じて、蛍光管の背後に反射板を設け、光拡散板の裏面にグラデーション印刷を施し、光拡散板の前面に集光シートを貼着する。光拡散板には、光拡散性と全光線透過率のバランスがよく、輝度の斑を生じないことが要求される。
光拡散板の材料として、通常は光拡散剤を含有する熱可塑性樹脂組成物（光拡散性樹脂組成物）が用いられる。また、光拡散板の成形法として、射出成形法、押出成形法、キャスト法などがある。光拡散剤としては、ポリスチレン系重合体、ポリシロキサン系重合体又はこれらの架橋物からなる微粒子、フッ素系樹脂の微粒子、硫酸バリウム、炭酸カルシウム、シリカ、タルクなどの微粒子などが用いられる。これらの微粒子は、通常は直径１〜１０μｍ程度の真球状である。射出成形法により光拡散板を成形する場合は、使用する熱可塑性樹脂の全量と光拡散剤の全量を混合して混練押出して調製した光拡散板成形用ペレットを用いるか、あるいは、使用する熱可塑性樹脂の一部と光拡散剤の全量を混合して混練押出して調製したマスターバッチを用いている。
光拡散剤と熱可塑性樹脂を混合し、混練押出するときに、両者の混合物をホッパーなどに投入すると、光拡散剤が空気中に舞って作業環境が悪化したり、静電気などにより光拡散剤がホッパーに付着して、熱可塑性樹脂と正確に所定量混合されない場合がある。また、光拡散剤と熱可塑性樹脂とを混練するために、二軸押出機などを用いて溶融押出すると、熱可塑性樹脂が熱劣化して、色調が黄変する場合がある。光拡散剤の配合量が多いと、樹脂組成物の機械的強度が低下する。
このために、微粒子状の有機又は無機光拡散剤を含有しない光拡散性樹脂組成物が求められていた。
【０００３】
【発明が解決しようとする課題】
本発明は、微粒子状の光拡散剤を使用することなく、少なくとも２種の透明樹脂の組み合わせにより良好な光拡散性が発現する光拡散性樹脂組成物及び該組成物を成形してなる光拡散性、輝度及び色調などに優れた成形体を提供することを目的としてなされたものである。
【０００４】
【課題を解決するための手段】
本発明者は、上記の課題を解決すべく鋭意研究を重ねた結果、２５℃における屈折率の差が０.０１以上であり、成形温度において剪断速度１,８２０ｓ-1で測定した溶融粘度の差が８０Ｐａ・ｓ以下である２種以上の透明樹脂を組み合わせて成形することにより、光拡散性、輝度及び色調などに優れた光拡散性成形体が得られることを見いだし、この知見に基づいて本発明を完成するに至った。
すなわち、本発明は、
（１）２５℃における屈折率の差が０.０１以上であり、成形温度において剪断速度１,８２０ｓ-1で測定した溶融粘度の差が８０Ｐａ・ｓ以下である少なくとも２種の透明樹脂を組み合わせてなることを特徴とする光拡散性樹脂組成物、
（２）少なくとも２種の透明樹脂の組み合わせが、ノルボルネン系重合体と、ビニル脂環式炭化水素重合体の組み合わせである第１項記載の光拡散性樹脂組成物、
（３）第１項記載の光拡散性樹脂組成物を成形してなることを特徴とする成形体、
（４）射出成形法により成形してなる第３項記載の成形体、
（５）スクリューの有効長さをＬ、ミキシング機構の長さをＬ1としたとき、
０.０３ ≦ Ｌ1／Ｌ ≦ ０.５
を満たす混練スクリューを備えた射出成形機を用いて射出成形してなる第４項記載の成形体、及び、
（６）光拡散板である第３項乃至第５項のいずれかに記載の成形体、
を提供するものである。
さらに、本発明の好ましい態様として、
（７）２種の透明樹脂の組み合わせが、ノルボルネン系重合体５〜９５重量％とビニル脂環式炭化水素重合体５〜９５重量％である第２項記載の光拡散性樹脂組成物、
を挙げることができる。
【０００５】
【発明の実施の形態】
本発明の光拡散性樹脂組成物は、２５℃における屈折率の差が０.０１以上であり、成形温度において剪断速度１,８２０ｓ-1で測定した溶融粘度の差が８０Ｐａ・ｓ以下である少なくとも２種の透明樹脂を組み合わせてなる樹脂組成物である。３種以上の透明樹脂を組み合わせたとき、屈折率の差とは、最大の屈折率と最小の屈折率との差であり、溶融粘度の差とは、最大の溶融粘度と最小の溶融粘度との差である。
透明樹脂とは、厚さ１ｍｍの試験片について、ＪＩＳ Ｋ ７３６１−１にしたがって測定した全光線透過率が８０％以上の樹脂である。２５℃における屈折率は、ＪＩＳ Ｋ ００６２ ５.固体試料の測定方法にしたがって、アッベ屈折計などを用いて測定することができる。成形温度において剪断速度１,８２０ｓ-1で測定した溶融粘度は、ＪＩＳ Ｋ ７１９９にしたがって、キャピラリーレオメータを用いて求めることができる。２５℃における屈折率の差が０.０１未満であると、成形体に透明感が現れ、十分な光拡散性が発現しないおそれがある。成形温度において剪断速度１,８２０ｓ-1で測定した溶融粘度の差が８０Ｐａ・ｓを超えると、溶融状態で成形するときに樹脂どうしの混合が不十分になり、成形体に斑が現れるおそれがある。
【０００６】
本発明においては、少なくとも２種の透明樹脂の組み合わせが、ノルボルネン系重合体と、ビニル脂環式炭化水素重合体の組み合わせであることが好ましい。ノルボルネン系重合体とビニル脂環式炭化水素重合体とを組み合わせることにより、光拡散性に優れ、輝度の大きい成形体を得ることができる。ノルボルネン系重合体としては、例えば、ノルボルネン系単量体の開環重合体、ノルボルネン系単量体とこれと開環共重合可能な他の単量体との開環共重合体、ノルボルネン系単量体の付加重合体、ノルボルネン系単量体とこれと付加共重合可能な他の単量体との付加共重合体、これらの重合体の水素添加物などを挙げることができる。
ノルボルネン系単量体としては、例えば、ビシクロ[２.２.１]ヘプト−２−エン（慣用名：ノルボルネン）及びその誘導体（環に置換基を有するもの）、トリシクロ[４.３.０.１2,5]デカ−３,７−ジエン（慣用名：ジシクロペンタジエン）及びその誘導体、７,８−ベンゾトリシクロ[４.３.０.１2,5]デカ−３−エン（１,４−メタノ−１,４,４ａ,９ａ−テトラヒドロフルオレンともいう：慣用名：メタノテトラヒドロフルオレン）及びその誘導体、テトラシクロ[４.４.０.１2,5.１7,10]ドデカ−３−エン（慣用名：テトラシクロドデセン）及びその誘導体、などが挙げられる。
置換基としては、アルキル基、アルキレン基、ビニル基、アルコキシカルボニル基などが例示でき、上記ノルボルネン系モノマーは、これらを２種以上有していてもよい。具体的には、８−メチル−テトラシクロ[４.４.０.１2,5.１7,10]−ドデカ−３−エン、８−エチル−テトラシクロ[４.４.０.１2,5.１7,10]−ドデカ−３−エン、８−メチリデン−テトラシクロ[４.４.０.１2,5.１7,10]−ドデカ−３−エン、８−エチリデン−テトラシクロ[４.４.０.１2,5.１7,10]−ドデカ−３−エン、８−メトキシカルボニル−テトラシクロ[４.４.０.１2,5.１7,10]−ドデカ−３−エン、８−メチル−８−メトキシカルボニル−テトラシクロ[４.４.０.１2,5.１7,10]−ドデカ−３−エンなどが挙げられる。
これらのノルボルネン系単量体は、それぞれ単独であるいは２種以上を組み合わせて用いられる。
ビニル脂環式炭化水素重合体としては、例えば、ビニル脂環式炭化水素単量体の重合体又は共重合体、これらの重合体の水素添加物、ビニル芳香族炭化水素単量体の重合体又は共重合体の芳香環を含む不飽和結合の水素添加物などを挙げることができる。ビニル脂環式炭化水素単量体としては、例えば、ビニルシクロプロパン、ビニルシクロヘキサン、ビニルシクロヘキセンなどを挙げることができる。ビニル芳香族炭化水素単量体としては、スチレン、α−メチルスチレン、ビニルトルエン、ビニルナフタレン、ビニルアントラセンなどを挙げることができる。なお、共重合体の場合は、ランダム共重合体、ブロック共重合体などの共重合体及びその水素添加物など、いずれでもよい。ブロック共重合体としては、ジブロック、トリブロック、またはそれ以上のマルチブロックや傾斜ブロック共重合体などが挙げられ、特に制限はない。
【０００７】
本発明において、透明樹脂としてノルボルネン系重合体とビニル脂環式炭化水素重合体を組み合わせるとき、その混合比は、ノルボルネン系重合体５〜９５重量％とビニル脂環式炭化水素重合体５〜９５重量％であることが好ましく、ノルボルネン系重合体３０〜９０重量％とビニル脂環式炭化水素重合体１０〜７０重量％であることがより好ましい。ノルボルネン系重合体の混合比が５重量％未満であっても、９５重量％を超えても、成形体のヘーズが低下して、光拡散性が不十分となるおそれがある。ノルボルネン系重合体の混合比が３０〜９０重量％であると、光拡散性と全光線透過率のバランスがよく、優れた性能を有する光拡散板を得ることができる。
本発明においては、透明樹脂の重量平均分子量が、３,０００〜３００,０００であることが好ましく、１０,０００〜２００,０００であることがより好ましい。重量平均分子量が３,０００未満であると、成形体の強度と耐熱性が不足するおそれがある。重量平均分子量が３００,０００を超えると、成形性と樹脂相互の混合性が低下するおそれがある。透明樹脂の重量平均分子量が１０,０００〜２００,０００であると、成形性と樹脂相互の混合性が特に良好である。
本発明の樹脂組成物においては、成形時における酸化劣化や熱劣化を防止するために、酸化防止剤を添加することができる。また、成形品の耐光性などを向上させるために、耐光安定剤を添加することができる。
酸化防止剤としては、例えば、フェノール系酸化防止剤、リン系酸化防止剤、イオウ系酸化防止剤などを挙げることができる。これらの酸化防止剤は、１種を単独で用いることができ、あるいは、２種以上を組みあわせて用いることができる。これらの中で、フェノール系酸化防止剤、特にアルキル置換酸化防止剤を好適に用いることができる。酸化防止剤の添加量は、透明樹脂１００重量部に対して、０.０１〜２重量部であることが好ましく、０.０２〜１重量部であることがより好ましい。
耐光安定剤としては、例えば、ヒンダードアミン系耐光安定剤（ＨＡＬＳ）、ベンゾエート系耐光安定剤などを挙げることができる。これらの耐光安定剤は、１種を単独で用いることができ、あるいは、２種以上を組み合わせて用いることもできる。これらの中で、ヒンダードアミン系耐光安定剤を特に好適に用いることができる。耐光安定剤の添加量は、透明樹脂１００重量部に対して、０.０１〜２重量部であることが好ましく、０.０２〜１重量部であることがより好ましく、０.０５〜０.５重量部であることがさらに好ましい。
本発明においては、必要に応じて、さらに他の添加剤を添加することができる。他の添加剤としては、例えば、熱安定剤、紫外線吸収剤、近赤外線吸収剤などの安定剤；滑剤、可塑剤などの樹脂改質剤；染料、顔料などの着色剤；帯電防止剤、光拡散剤などを挙げることができる。
本発明の成形体は、２５℃における屈折率の差が０.０１以上であり、成形温度において剪断速度１,８２０ｓ-1で測定した溶融粘度の差が８０Ｐａ・ｓ以下である少なくとも２種の透明樹脂を組み合わせた光拡散性樹脂組成物を成形してなる成形体である。本発明において、組み合わせた樹脂の成形方法に特に制限はなく、例えば、射出成形法、押出成形法、圧縮成形法、Ｔダイ法、インフレーション法などのフィルム成形法、中空成形法、熱成形法などを挙げることができる。これらの中で、射出成形法を特に好適に用いることができる。射出成形法によれば、多くの場合、必要とする形状の成形体を一工程で製造することができ、後加工が不要であり、射出成形機のホッパーに投入する透明樹脂の組み合わせの比率を任意に変えることができるので、樹脂の損失を招くことなく、多種多様の特性の成形体を製造することができる。
透明樹脂を射出成形機のホッパーへ投入する方法としては、特に制限されず、例えば、組み合わせる透明樹脂のペレットを特定比率で混合させておいて投入する方法、組み合わせる透明樹脂をあらかじめ二軸混練機などで混練させておいたものを投入する方法などが挙げられる。
【０００８】
本発明において、射出成形法による成形体の製造には、スクリューの有効長さをＬ、ミキシング機構の長さをＬ1としたとき、
０.０３ ≦ Ｌ1／Ｌ ≦ ０.５
を満たす混練スクリューを備えた射出成形機を用いることが好ましく、
０.０５ ≦ Ｌ1／Ｌ ≦ ０.４
を満たす混練スクリューを備えた射出成形機を用いることがより好ましい。ミキシング機構の長さとは、スクリューの１条の主フライト以外に、混練効果を高めるための機構が設けられている部分の合計の長さである。例えば、シングルフライトスクリューの計量部にダルメージが設けられているスクリューにおいては、ダルメージの後端側から先端側までの距離がミキシング機構の長さであり、主フライトに加えて副フライトが設けられたダブルフライトスクリューにおいては、副フライトが存在する領域の長さがミキシング機構の長さである。
混練スクリューのミキシング機構の長さＬ1がスクリューの有効長さＬの０.０３倍未満であると、十分なミキシングが得られず、組み合わせた透明樹脂の混合が不十分となって、斑が生ずるおそれがある。混練スクリューのミキシング機構の長さＬ1がスクリューの有効長さＬの０.５倍を超えると、樹脂の吐出量の減少や、温度上昇による焼け、熱劣化などが発生するおそれがある。混練スクリューのミキシング機構の長さＬ1とスクリューの有効長さＬとの比Ｌ1／Ｌを０.０５〜０.４とすることにより、成形体に安定して斑が発生せず、歩留まりが向上する。
本発明の成形体は、光拡散性及び色調に優れ、高い輝度が要求される液晶表示装置の光拡散板として好適に用いることができる。
【０００９】
【実施例】
以下に、実施例を挙げて本発明をさらに詳細に説明するが、本発明はこれらの実施例によりなんら限定されるものではない。
なお、実施例及び比較例において、物性の測定及び射出成形は、下記の方法により行った。
（１）溶融粘度
キャピラリーレオメータ［(株)東洋精機製作所、キャピログラフ］を用いて、温度２７０℃、剪断速度１,８２０ｓ-1で測定した。
（２）屈折率
ＪＩＳ Ｋ ００６２ ５.固体試料の測定方法にしたがい、２５℃において測定した。
（３）射出成形
射出成形機［(株)ソディック、ＴＲ１００Ｈ］に、Ｄ＝３２ｍｍφ、Ｌ／Ｄ＝１８、スクリューの有効長さＬ＝５７６ｍｍ、ミキシング機構として計量部に長さ４８ｍｍのダルメージを有するＬ1／Ｌ＝０.０８の高混練スクリューを装着した。成形温度２７０℃で、サイドゲート金型を用い、縦１００ｍｍ、横１５０ｍｍ、厚さ２ｍｍの光拡散板を成形した。
（４）輝度
上記の光拡散板を用いて、直径２ｍｍ、長さ１５０ｍｍの冷陰極管２本を備え付けた直下型バックライト装置を組み立て、光拡散板から５００ｍｍ離れた直上から、光拡散板上の９点について、輝度計［(株)トプコン、ＢＭ−７］を用いて視野角０.１度で輝度を測定し、平均値を求めた。
（５）ΔＹＩ（イエローネスインデックス）
ＪＩＳ Ｚ ８７２２に準拠して、分光式色差計［日本電色工業(株)、ＳＥ２０００］を用いて反射モードで測定した。ただし、
ＹＩ ＝［１００×(１.２８Ｘ−１.０６Ｚ)／Ｙ］
ΔＹＩ ＝ ＹＩ（測定試料）− ＹＩｓｔ（標準白板）
（標準白板のＸは９４.１８、Ｙは９６.０４、Ｚは１１３.７７）
（６）ヘーズ
ＪＩＳ Ｋ ７１０５に準拠して、濁色系［日本電色工業(株)、ＮＤＨ３００Ａ］を用いて、積分球式光電光度法により測定した。
【００１０】
また、実施例及び比較例においては、下記の透明樹脂及び光拡散剤を用いた。
製造例１（ノルボルネン系重合体Ａの製造）
脱水したシクロヘキサン５００部、１−ヘキセン０.８２部、ジブチルエーテル０.１５部、及びトリイソブチルアルミニウム０.３０部を室温で十分に乾燥し、窒素置換したステンレス製耐圧容器に入れて混合した後、４５℃に保ちながら、トリシクロ[４.３.０.１2,5]デカ−３,７−ジエン（ジシクロペンタジエン、以下、「ＤＣＰ」と略記する。）１７０部と、８−エチリデン−テトラシクロ[４.４.０.１2,5.１7,10]−ドデカ−３−エン（エチリデンテトラシクロドデセン、以下、「ＥＴＤ」と略記する。）３０部と、六塩化タングステン（０.７％トルエン溶液）４０部とを、２時間かけて連続的に添加し重合した。重合溶液にブチルグリシジルエーテル１.０６部とイソプロピルアルコール０.５２部を加えて重合触媒を不活性化し重合反応を停止させた。
次いで、得られた開環重合体を含有する反応溶液１００部に対して、シクロヘキサン３５部を加え、さらに水素添加触媒としてニッケル−アルミナ触媒（日揮化学社製）５部を加え、水素により５ＭＰａに加圧して撹拌しながら温度２００℃まで加温した後、4時間反応させ、ＤＣＰ／ＥＴＤ開環重合体水素添加物を２０％含有する反応溶液を得た。濾過により水素添加触媒を除去した後、前記水素添加物１００部に対してフェノール系酸化防止剤（ペンタエリスリチル−テトラキス[３−(３,５−ジ−ｔ−ブチル−４−ヒドロキシフェニル)プロピオネート]）０.１部を、得られた溶液に添加して溶解させた。次いで、円筒型濃縮乾燥器（日立製作所製）を用いて、温度２７０℃、圧力１ｋＰａ以下で、溶液から、溶媒であるシクロヘキサン及びその他の揮発成分を除去しつつ水素添加物を溶融状態で押出機からストランド状に押出し、冷却後、ＤＣＰ／ＥＴＤ開環重合体水素添加物のペレットを得た。この開環重合体水素添加物の、重量平均分子量（Ｍｗ）は３１,０００、水素添加率は９９.９％、Ｔｇは１００℃、屈折率は１.５３１、溶融粘度は８７.２Ｐａ・ｓ、全光線透過率は９２％であった。
製造例２（ノルボルネン系重合体Ｂの製造）
１−ヘキセンを０.６部とした他は、製造例１と同様にしてＤＣＰ／ＥＴＤ開環重合体水素添加物を得た。この開環重合体水素添加物の、重量平均分子量（Ｍｗ）は４２,０００、水素添加率は９９.９％、Ｔｇは１０２℃、屈折率は１.５３１、溶融粘度は２２１.３Ｐａ・ｓ、全光線透過率は９２％であった。
製造例３（ビニル脂環式炭化水素重合体Ａの製造）
十分に乾燥し、窒素置換したステンレス製耐圧容器に、スチレン（Ｓｔ）７６部とイソプレン（ＩＰ）４部を密封して混合攪拌し、組成が、重量比で（Ｓｔ／ＩＰ）＝（９５／５）である混合モノマーを調整した。
次に、十分に乾燥し、窒素置換した電磁撹拌装置を備えたステンレス鋼製オートクレーブに、脱水シクロヘキサン３２０部、混合モノマー４部及びジブチルエーテル０.１部を仕込み、５０℃で撹拌しながらｎ−ブチルリチウム溶液（１５％含有ヘキサン溶液）０.１８部を添加して重合を開始した。同条件下で０.５時間重合反応を行った後（この時点での転化率は９６％であった）、同条件下での重合反応を継続しながらオートクレーブ中の重合反応溶液中に、７６部の混合モノマーを１時間かけて連続的に添加した。添加終了後（この時点での転化率は９５％であった）、同条件下で０.５時間重合を行った後、イソプロピルアルコール０.１部を添加して反応を停止させ、スチレン−イソプレン共重合体を合成した。
次いで、得られた上記共重合体を含有する反応溶液４００部に、安定化ニッケル水素添加触媒Ｅ２２Ｕ（日揮化学社製；６０％ニッケル担持シリカ−アルミナ担体）８部を添加混合し、水素添加反応温度を調節するための電熱加熱装置と電磁撹拌装置を備えたステンレス鋼製オートクレーブに仕込んだ。仕込み終了後、オートクレーブ内部を水素ガスで置換し、撹拌しながら、１６０℃で、オートクレーブ内部の圧力が４.５ＭＰａを保つように水素を供給しながら６時間水素添加反応を行った。
濾過により水素添加触媒を除去した後、重合体固形分１００部に対して、フェノール系酸化防止剤（ペンタエリスリチル−テトラキス[３−(３,５−ジ−ｔ−ブチル−４−ヒドロキシフェニル)プロピオネート]）０.０２部を加えて溶解させた。
次いで、上記で得られた濾液（重合体濃度＝２０％）を予備加熱装置で２５０℃に加熱し、圧力３ＭＰａで円筒型濃縮乾燥機（日立製作所製）に連続的に供給した。濃縮乾燥機の運転条件は、圧力６０ｋＰａ、内部の濃縮された重合体溶液の温度が２６０℃となるように調節した。濃縮された溶液は、濃縮乾燥機から連続的に導出し、さらに同型の濃縮乾燥機に温度２６０℃を保ったまま、圧力１.５ＭＰａで供給した。運転条件は、圧力１.５ｋＰａ、温度２７０℃とした。溶融状態の重合体は、濃縮乾燥機から連続的に導出し、クラス１００のクリーンルーム内でダイから押し出し、水冷後、ペレタイザー（ＯＳＰ−２、長田製作所製）でカッティングしてビニル脂環式炭化水素系重合体Ａのペレットを得た。
また、このペレットについて、重量平均分子量（Ｍｗ）は１３２,０００、分子量分布（Ｍｗ／Ｍｎ）は１.１９、水素添加率はほぼ１００％、Ｔｇは１２５℃、屈折率は１.５１１、溶融粘度は７３.８Ｐａ・ｓ、全光線透過率は９２％であった。
製造例４（ビニル脂環式炭化水素重合体Ｂの製造）
十分に乾燥し、窒素置換された攪拌装置を備えた反応器に脱水シクロヘキサン３２０部、脱水スチレン１２部、ｎ−ジブチルエーテル０.０９５部を入れ、６０℃で攪拌しながらｎ−ブチルリチウム（１５％シクロヘキサン溶液）０.１０３部を加えて重合を開始した。攪拌しながら６０℃で６０分反応させた。この時点で重合転化率は９９.５％であった。次に脱水イソプレン４部を加えそのまま３０分攪拌を続けた。この時点で重合転化率は９９％であった。その後更に、脱水スチレンを４部加え、６０分攪拌した。この時点での重合転化率はほぼ１００％であった。ここでイソプロピルアルコール２５部を加えて反応を停止した。
次いで、上記重合体を含有する反応溶液１００部を攪拌装置を備えた耐圧反応器に移送し、水素添加触媒としてシリカ−アルミナ担持型ニッケル触媒（日揮化学社製；Ｅ２２Ｕ、ニッケル担持量６０％）８部を添加して混合した。反応器内部を水素ガスで置換し、さらに溶液を攪拌しながら水素を供給し、温度１７０℃、圧力４.５ＭＰａにて６時間水素添加反応を行った。
水素添加反応終了後、反応溶液をろ過して水素添加触媒を除去した後、樹脂１００部に対してトミノックスＴＴ（吉冨ファインケミカル株式会社製）を０.１部添加混合した。その樹脂溶液を２６０℃減圧下で溶媒を除去し、押出機でストランド状に押し出しながら、ビニル脂環式炭化水素重合体Ｂのペレットを得た。得られたビニル脂環式炭化水素重合体Ｂは、重量平均分子量（Ｍｗ）は８５,０００、分子量分布（Ｍｗ／Ｍｎ）は１.１４、水素添加率９９.９％、Ｔｇは１２９℃、屈折率は１.５０４、溶融粘度は８４.０Ｐａ・ｓ、全光線透過率は９２％であった。
製造例５
（ビニル脂環式炭化水素重合体Ｃの製造）
混合モノマーをスチレン（Ｓｔ）７６.８重量部とイソプレン（ＩＰ）３.２重量部を密封して混合撹拌し、組成を、重量比で（Ｓｔ／ＩＰ）＝（９６／４）とし、ｎ−ブチルリチウム（１５％シクロヘキサン溶液）の添加量を０.４５４部、水素添加触媒の添加量を３部とした他は、製造例３と同様にして、ビニル脂環式炭化水素重合体Ｃのペレットを得た。
また、このビニル脂環式炭化水素重合体Ｃの、重量平均分子量（Ｍｗ）は８５,０００、分子量分布（Ｍｗ／Ｍｎ）は１.１８、水素添加率はほぼ１００％、Ｔｇは１２５℃、屈折率は１.５０９、溶融粘度３３.１Ｐａ・ｓ、全光線透過率は９２％であった。
（５）ポリシロキサン系光拡散剤
ＧＥ東芝シリコーン(株)、トスパール１２０
【００１１】
実施例１
製造例１で得られたノルボルネン系重合体Ａと製造例３で得られたビニル脂環式炭化水素重合体Ａの重量比７０：３０の混合物を射出成形機のホッパーに投入して、光拡散板の射出成形を行った。両樹脂の屈折率の差は０.０２０であり、溶融粘度の差は１３.４Ｐａ・ｓである。
得られた光拡散板の輝度は５,４７８ｃｄ／ｍ2であり、ΔＹＩは−１０.５９であり、ヘーズは９２.１８であった。光拡散板に、斑は認められなかった。
実施例２
製造例１で得られたノルボルネン系重合体Ａと製造例４で得られたビニル脂環式炭化水素重合体Ｂの重量比７０：３０の混合物を射出成形機のホッパーに投入して、光拡散板の射出成形を行った。両樹脂の屈折率の差は０.０２７であり、溶融粘度の差は３.２Ｐａ・ｓである。
得られた光拡散板の輝度は５,４８０ｃｄ／ｍ2であり、ΔＹＩは−７.９４であり、ヘーズは９２.３９であった。光拡散板に、斑は認められなかった。
比較例１
製造例１で得られたノルボルネン系重合体Ａ９９重量部とポリシロキサン系光拡散剤［ＧＥ東芝シリコーン(株)、トスパール１２０］１重量部を混合し、二軸押出機を用いてストランド状に押し出し、ペレタイザーで切断することにより、光拡散板用ペレットを製造した。このペレットを射出成形機のホッパーに投入して、光拡散板の射出成形を行った。
得られた光拡散板の輝度は４,９７９ｃｄ／ｍ2であり、ΔＹＩは−４.４７であり、ヘーズは９２.２４であった。光拡散板に、斑は認められなかった。
比較例２
製造例２で得られたノルボルネン系重合体Ｂと製造例５で得られたビニル脂環式炭化水素重合体Ｃの重量比７０：３０の混合物を射出成形機のホッパーに投入して、光拡散板の射出成形を行った。両樹脂の屈折率の差は０.０２２であり、溶融粘度の差は１８８.２Ｐａ・ｓである。
得られた光拡散板の輝度は５,１００ｃｄ／ｍ2であり、ΔＹＩは−１０.３８であり、ヘーズは９２.２５であった。光拡散板に、顕著な斑が認められた。
比較例３
製造例３で得られたビニル脂環式炭化水素重合体Ａと製造例４で得られたビニル脂環式炭化水素重合体Ｂとの重量比５０：５０の混合物を射出成形機のホッパーに投入して、光拡散板の射出成形を試みた。両樹脂の屈折率の差は０.００７であり、溶融粘度の差は１０.２Ｐａ・ｓである。
得られた射出成形板は透明で、光拡散板としての性能を満たさなかった。
実施例１〜２及び比較例１〜３の結果を、第１表に示す。
【００１２】
【表１】
第１表に見られるように、屈折率差が０.０２０、溶融粘度差が１３.４Ｐａ・ｓのノルボルネン系重合体Ａとビニル脂環式炭化水素重合体Ａを組み合わせた実施例１の光拡散板と、屈折率差が０.０２７、溶融粘度差が３.２Ｐａ・ｓのノルボルネン系重合体Ａとビニル脂環式炭化水素重合体Ｂを組み合わせた実施例２の光拡散板は、いずれも輝度が高く、斑もなく、色調に優れている（ΔＹＩが小さい）。
これに対して、ノルボルネン系重合体Ａにポリシロキサン系光拡散剤を配合した比較例１の従来の光拡散板は、実施例１〜２の光拡散板に比べて輝度が低く、ΔＹＩが大きい。溶融粘度差が１８８.２Ｐａ・ｓのノルボルネン系重合体Ｂとビニル脂環式炭化水素重合体Ｃを組み合わせた比較例２の光拡散板は、色調に優れている（ΔＹＩが小さい）が、輝度が低く、顕著な斑が発生している。屈折率差０.００７の２種類のビニル脂環式炭化水素重合体を組み合わせた比較例３の成形体は、透明で光拡散板としての性能を有しない。
【００１４】
【発明の効果】
本発明の光拡散性樹脂組成物は、屈折率の差が０.０１以上であり、成形温度において剪断速度１,８２０ｓ-1で測定した溶融粘度の差が８０Ｐａ・ｓ以下である少なくとも２種の透明樹脂を組み合わせることにより、微粒子状の光拡散剤を配合することなく光拡散性が発現し、光拡散剤の配合量の変動による光学特性の変動を生ずることがない。また、成形前に樹脂と光拡散剤を二軸押出機などで混練してペレット化する必要がなく、透明樹脂のペレットをブレンドして直接成形することができるので、製造工程を減少することができ、樹脂の熱履歴も少なくなり、色調の良好な成形体を得ることができる。さらに、多数のユーザーからの多種多様な特性についての要求にも、樹脂ペレットをブレンドして成形するだけなので早急に対応することができる。本発明により、透明樹脂に光拡散剤を配合した光拡散板よりも、輝度の高い光拡散板を得ることができる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a light-diffusing resin composition and a molded product obtained by molding the same. More specifically, the present invention provides a light-diffusing resin composition exhibiting good light-diffusing properties by a combination of at least two types of transparent resins without using a fine-particle light-diffusing agent, and molding the composition. The present invention relates to a molded article having excellent light diffusing properties, luminance, color tone and the like.
[0002]
[Prior art]
A liquid crystal display device utilizing the property of liquid crystal, in which the arrangement of molecules changes when a voltage is applied, is widely used in portable information terminals, in-vehicle panels, personal computers, and the like. As the size and performance of liquid crystal display devices increase in the future, it is expected to replace CRT display devices. Since the liquid crystal itself does not emit light, the liquid crystal display device requires an external light source, and the side light type where the light source is arranged on the side edge of the liquid crystal display device and the direct type where the light source is arranged on the back of the liquid crystal display device are practical. Has been The sidelight method can reduce the thickness of the device unit, but has a low luminance. Therefore, the direct-lighting method is suitable for a large-sized liquid crystal display device that requires luminance.
In the liquid crystal display device of the direct type, a plurality of light sources such as fluorescent tubes are arranged at the back of the device housing, and the incident light is diffused by a light diffusion plate to be converted into planar light having uniform luminance. If necessary, a reflection plate is provided behind the fluorescent tube, gradation printing is performed on the back surface of the light diffusion plate, and a light-collecting sheet is attached to the front surface of the light diffusion plate. The light diffusing plate is required to have a good balance between the light diffusing property and the total light transmittance and not to cause unevenness in luminance.
As a material of the light diffusion plate, a thermoplastic resin composition (light diffusion resin composition) containing a light diffusion agent is usually used. In addition, examples of the method for forming the light diffusion plate include an injection molding method, an extrusion molding method, and a casting method. As the light diffusing agent, fine particles made of a polystyrene-based polymer, polysiloxane-based polymer or a crosslinked product thereof, fine particles of a fluororesin, fine particles of barium sulfate, calcium carbonate, silica, talc and the like are used. These fine particles are usually in the form of a true sphere having a diameter of about 1 to 10 μm. When molding the light diffusion plate by the injection molding method, use a light diffusion plate molding pellet prepared by mixing and kneading and extruding the total amount of the thermoplastic resin and the entire amount of the light diffusion agent to be used, or use the heat diffusion plate. A masterbatch prepared by mixing a part of the plastic resin and the entire amount of the light diffusing agent and kneading and extruding the mixture is used.
When the light diffusing agent and the thermoplastic resin are mixed and kneaded and extruded, if the mixture of both is put into a hopper or the like, the light diffusing agent will fly in the air and the working environment will deteriorate, There is a case where it adheres to the hopper and is not accurately mixed with the thermoplastic resin by a predetermined amount. Further, when melt extruding using a twin screw extruder or the like in order to knead the light diffusing agent and the thermoplastic resin, the thermoplastic resin may be thermally degraded and the color tone may turn yellow. If the amount of the light diffusing agent is large, the mechanical strength of the resin composition decreases.
For this reason, a light diffusing resin composition containing no finely divided organic or inorganic light diffusing agent has been required.
[0003]
[Problems to be solved by the invention]
The present invention provides a light-diffusing resin composition exhibiting good light-diffusing properties by a combination of at least two types of transparent resins without using a fine-particle light-diffusing agent, and a light-diffusing resin formed by molding the composition. The purpose of the present invention is to provide a molded article excellent in properties, luminance, color tone, and the like.
[0004]
[Means for Solving the Problems]
The inventor of the present invention has conducted intensive studies to solve the above-mentioned problems. As a result, the difference in the refractive index at 25 ° C. was 0.01 or more, and the shear rate was 1,820 s at the molding temperature. -1 It is found that a light diffusing molded article excellent in light diffusivity, luminance, color tone, etc. can be obtained by molding by combining two or more kinds of transparent resins having a difference in melt viscosity of not more than 80 Pa · s measured in the above. Based on this finding, the present invention has been completed.
That is, the present invention
(1) The difference in refractive index at 25 ° C. is 0.01 or more, and the shear rate is 1,820 s at the molding temperature. -1 A light-diffusing resin composition comprising a combination of at least two types of transparent resins having a difference in melt viscosity measured at or below 80 Pa · s.
(2) The light diffusing resin composition according to (1), wherein the combination of at least two kinds of transparent resins is a combination of a norbornene-based polymer and a vinyl alicyclic hydrocarbon polymer.
(3) A molded article obtained by molding the light diffusing resin composition according to (1),
(4) The molded article according to item 3, which is molded by an injection molding method,
(5) The effective length of the screw is L, and the length of the mixing mechanism is L 1 And when
0.03 ≦ L 1 /L≦0.5
The molded article according to claim 4, which is obtained by injection molding using an injection molding machine equipped with a kneading screw satisfying
(6) The molded article according to any one of Items 3 to 5, which is a light diffusion plate,
Is provided.
Further, as a preferred embodiment of the present invention,
(7) The light diffusing resin composition according to (2), wherein the combination of the two transparent resins is 5 to 95% by weight of a norbornene-based polymer and 5 to 95% by weight of a vinyl alicyclic hydrocarbon polymer.
Can be mentioned.
[0005]
BEST MODE FOR CARRYING OUT THE INVENTION
The light diffusing resin composition of the present invention has a difference in refractive index at 25 ° C. of 0.01 or more and a shear rate of 1,820 s at a molding temperature. -1 A resin composition comprising a combination of at least two types of transparent resins having a difference in melt viscosity of 80 Pa · s or less as measured in (1). When three or more transparent resins are combined, the difference in refractive index is the difference between the maximum refractive index and the minimum refractive index, and the difference in melt viscosity is the maximum melt viscosity and the minimum melt viscosity. Is the difference.
The transparent resin is a resin having a total light transmittance of 80% or more measured on a test piece having a thickness of 1 mm according to JIS K7361-1. The refractive index at 25 ° C. can be measured using an Abbe refractometer or the like according to JIS K 0062 5. Measurement method for solid samples. 1,820 s shear rate at molding temperature -1 Can be determined using a capillary rheometer according to JIS K 7199. If the difference in the refractive index at 25 ° C. is less than 0.01, the molded article may have a transparent feeling and may not have sufficient light diffusing properties. 1,820 s shear rate at molding temperature -1 If the difference in the melt viscosity measured in the above step exceeds 80 Pa · s, mixing of the resins becomes insufficient when molding in a molten state, and spots may appear on the molded article.
[0006]
In the present invention, the combination of at least two transparent resins is preferably a combination of a norbornene-based polymer and a vinyl alicyclic hydrocarbon polymer. By combining a norbornene-based polymer and a vinyl alicyclic hydrocarbon polymer, it is possible to obtain a molded article having excellent light diffusion properties and high luminance. Examples of the norbornene-based polymer include a ring-opening polymer of a norbornene-based monomer, a ring-opening copolymer of a norbornene-based monomer and another monomer capable of being ring-opening-copolymerized, and a norbornene-based monomer. Examples of the polymer include a monomeric addition polymer, an addition copolymer of a norbornene-based monomer and another monomer capable of being addition-copolymerized with the norbornene-based monomer, and hydrogenated products of these polymers.
Examples of the norbornene-based monomer include, for example, bicyclo [2.2.1] hept-2-ene (common name: norbornene) and its derivative (having a substituent on the ring), tricyclo [4.3.0. 1 2,5 ] Deca-3,7-diene (common name: dicyclopentadiene) and its derivatives, 7,8-benzotricyclo [4.3.0.1] 2,5 ] Deca-3-ene (also referred to as 1,4-methano-1,4,4a, 9a-tetrahydrofluorene: common name: methanotetrahydrofluorene) and its derivative, tetracyclo [4.4.0.1 2,5 .1 7,10 ] Dodeca-3-ene (common name: tetracyclododecene) and its derivatives.
Examples of the substituent include an alkyl group, an alkylene group, a vinyl group, an alkoxycarbonyl group, and the like. The norbornene-based monomer may have two or more of these. Specifically, 8-methyl-tetracyclo [4.4.0.1 2,5 .1 7,10 ] -Dodeca-3-ene, 8-ethyl-tetracyclo [4.4.0.1 2,5 .1 7,10 ] -Dodeca-3-ene, 8-methylidene-tetracyclo [4.4.0.1 2,5 .1 7,10 ] -Dodeca-3-ene, 8-ethylidene-tetracyclo [4.4.0.1 2,5 .1 7,10 ] -Dodeca-3-ene, 8-methoxycarbonyl-tetracyclo [4.4.0.1 2,5 .1 7,10 ] -Dodeca-3-ene, 8-methyl-8-methoxycarbonyl-tetracyclo [4.4.0.1 2,5 .1 7,10 ] -Dodeca-3-ene and the like.
These norbornene monomers are used alone or in combination of two or more.
Examples of the vinyl alicyclic hydrocarbon polymer include, for example, polymers or copolymers of vinyl alicyclic hydrocarbon monomers, hydrogenated products of these polymers, and polymers of vinyl aromatic hydrocarbon monomers. Alternatively, a hydrogenated product of an unsaturated bond containing an aromatic ring of a copolymer may be used. Examples of the vinyl alicyclic hydrocarbon monomer include vinyl cyclopropane, vinyl cyclohexane, vinyl cyclohexene and the like. Examples of the vinyl aromatic hydrocarbon monomer include styrene, α-methylstyrene, vinyl toluene, vinyl naphthalene, and vinyl anthracene. In the case of a copolymer, any of a copolymer such as a random copolymer and a block copolymer and a hydrogenated product thereof may be used. Examples of the block copolymer include a diblock, a triblock, and a multiblock or a gradient block copolymer of higher levels, and are not particularly limited.
[0007]
In the present invention, when a norbornene-based polymer and a vinyl alicyclic hydrocarbon polymer are combined as the transparent resin, the mixing ratio is 5 to 95% by weight of the norbornene-based polymer and 5 to 95% by weight of the vinyl alicyclic hydrocarbon polymer. %, More preferably 30 to 90% by weight of a norbornene-based polymer and 10 to 70% by weight of a vinyl alicyclic hydrocarbon polymer. If the mixing ratio of the norbornene-based polymer is less than 5% by weight or more than 95% by weight, the haze of the molded article may be reduced and the light diffusibility may be insufficient. When the mixing ratio of the norbornene-based polymer is 30 to 90% by weight, a light diffusion plate having a good balance between light diffusivity and total light transmittance and having excellent performance can be obtained.
In the present invention, the weight average molecular weight of the transparent resin is preferably from 3,000 to 300,000, and more preferably from 10,000 to 200,000. If the weight average molecular weight is less than 3,000, the strength and heat resistance of the molded article may be insufficient. When the weight average molecular weight exceeds 300,000, the moldability and the mixing property between the resins may be reduced. When the weight average molecular weight of the transparent resin is 10,000 to 200,000, the moldability and the mixing property between the resins are particularly good.
In the resin composition of the present invention, an antioxidant can be added in order to prevent oxidative deterioration and thermal deterioration during molding. Further, in order to improve the light resistance and the like of the molded product, a light resistance stabilizer can be added.
Examples of the antioxidant include a phenolic antioxidant, a phosphorus-based antioxidant, and a sulfur-based antioxidant. One of these antioxidants may be used alone, or two or more thereof may be used in combination. Among them, phenolic antioxidants, particularly alkyl-substituted antioxidants, can be suitably used. The addition amount of the antioxidant is preferably 0.01 to 2 parts by weight, more preferably 0.02 to 1 part by weight, based on 100 parts by weight of the transparent resin.
Examples of the light stabilizer include hindered amine light stabilizers (HALS) and benzoate light stabilizers. One of these light stabilizers can be used alone, or two or more of them can be used in combination. Among them, hindered amine light stabilizers can be particularly preferably used. The light stabilizer is preferably added in an amount of 0.01 to 2 parts by weight, more preferably 0.02 to 1 part by weight, and more preferably 0.05 to 0.2 part by weight, based on 100 parts by weight of the transparent resin. More preferably, it is 5 parts by weight.
In the present invention, other additives can be added as needed. Other additives include, for example, stabilizers such as heat stabilizers, ultraviolet absorbers, and near infrared absorbers; resin modifiers such as lubricants and plasticizers; coloring agents such as dyes and pigments; antistatic agents; Diffusing agents and the like can be mentioned.
The molded article of the present invention has a difference in refractive index at 25 ° C. of 0.01 or more and a shear rate of 1,820 s at a molding temperature. -1 A molded article obtained by molding a light diffusing resin composition obtained by combining at least two types of transparent resins having a difference in melt viscosity of not more than 80 Pa · s measured in the above step. In the present invention, there is no particular limitation on the method of molding the combined resin, and examples thereof include a film molding method such as an injection molding method, an extrusion molding method, a compression molding method, a T-die method, an inflation method, a hollow molding method, and a thermoforming method. Can be mentioned. Among these, the injection molding method can be particularly preferably used. According to the injection molding method, in many cases, a molded article having a required shape can be manufactured in one step, no post-processing is required, and the ratio of a combination of transparent resins to be put into a hopper of an injection molding machine is reduced. Since it can be changed arbitrarily, it is possible to produce a molded article having various characteristics without causing loss of resin.
The method for charging the transparent resin into the hopper of the injection molding machine is not particularly limited. For example, a method in which the transparent resin pellets to be combined are mixed at a specific ratio and then charged, and the transparent resin to be combined in advance is a twin-screw kneader or the like. And the method of putting in what has been kneaded.
[0008]
In the present invention, the effective length of the screw is L and the length of the mixing mechanism is L for the production of a molded article by the injection molding method. 1 And when
0.03 ≦ L 1 /L≦0.5
It is preferable to use an injection molding machine equipped with a kneading screw satisfying,
0.05 ≤ L 1 /L≦0.4
It is more preferable to use an injection molding machine provided with a kneading screw satisfying the following. The length of the mixing mechanism is the total length of a portion provided with a mechanism for enhancing the kneading effect, in addition to the single main flight of the screw. For example, in a screw provided with a dalmage in the measuring section of a single flight screw, the distance from the rear end side to the front end side of the dalmage is the length of the mixing mechanism, and a secondary flight is provided in addition to the main flight. In the double flight screw, the length of the region where the sub-flight exists is the length of the mixing mechanism.
Length L of mixing mechanism of kneading screw 1 If is less than 0.03 times the effective length L of the screw, sufficient mixing cannot be obtained, and the combined transparent resin may be insufficiently mixed to cause spots. Length L of mixing mechanism of kneading screw 1 Exceeds 0.5 times the effective length L of the screw, there is a possibility that the discharge amount of the resin decreases, burning due to temperature rise, thermal deterioration, and the like occur. Length L of mixing mechanism of kneading screw 1 And the effective length L of the screw L 1 By setting / L to be in the range of 0.05 to 0.4, unevenness is not stably generated in the molded body, and the yield is improved.
The molded article of the present invention can be suitably used as a light diffusion plate of a liquid crystal display device which is excellent in light diffusivity and color tone and requires high luminance.
[0009]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
In the examples and comparative examples, measurement of physical properties and injection molding were performed by the following methods.
(1) Melt viscosity
Using a capillary rheometer [Toyo Seiki Seisakusho, Capillograph], temperature 270 ° C, shear rate 1,820 s -1 Was measured.
(2) Refractive index
JIS K 0062 5. Measured at 25 ° C. according to the method for measuring a solid sample.
(3) Injection molding
Injection molding machine [Sodick Co., Ltd., TR100H], D = 32 mmφ, L / D = 18, effective length L of screw = 576 mm, and weighing part having a length of 48 mm as a mixing mechanism. 1 /L=0.08 high kneading screw was installed. A light diffusion plate having a length of 100 mm, a width of 150 mm, and a thickness of 2 mm was molded at a molding temperature of 270 ° C. using a side gate mold.
(4) Brightness
Using the above light diffusion plate, a direct-type backlight device equipped with two cold cathode tubes having a diameter of 2 mm and a length of 150 mm was assembled, and nine points on the light diffusion plate from immediately above, 500 mm away from the light diffusion plate. The luminance was measured at a viewing angle of 0.1 degree using a luminance meter [Topcon Co., Ltd., BM-7], and the average value was determined.
(5) ΔYI (yellowness index)
Based on JIS Z 8722, it was measured in reflection mode using a spectroscopic color difference meter [Nippon Denshoku Industries Co., Ltd., SE2000]. However,
YI = [100 × (1.28X-1.06Z) / Y]
ΔYI = YI (measurement sample) −YIst (standard white plate)
(X of standard white board is 94.18, Y is 96.04, Z is 113.77)
(6) Haze
In accordance with JIS K 7105, it was measured by an integrating sphere photoelectricity method using a cloudy color system [Nippon Denshoku Industries Co., Ltd., NDH300A].
[0010]
In Examples and Comparative Examples, the following transparent resins and light diffusing agents were used.
Production Example 1 (Production of norbornene-based polymer A)
After 500 parts of dehydrated cyclohexane, 0.82 parts of 1-hexene, 0.15 parts of dibutyl ether, and 0.30 parts of triisobutylaluminum are sufficiently dried at room temperature, mixed in a nitrogen-substituted stainless steel pressure vessel, and mixed. While maintaining at 45 ° C., tricyclo [4.3.0.1. 2,5 ] Deca-3,7-diene (dicyclopentadiene, hereinafter abbreviated as "DCP") 170 parts and 8-ethylidene-tetracyclo [4.4.0.1] 2,5 .1 7,10 30 parts of] -dodec-3-ene (ethylidenetetracyclododecene, hereinafter abbreviated as "ETD") and 40 parts of tungsten hexachloride (0.7% toluene solution) were continuously fed for 2 hours. And polymerized. 1.06 parts of butyl glycidyl ether and 0.52 parts of isopropyl alcohol were added to the polymerization solution to inactivate the polymerization catalyst and terminate the polymerization reaction.
Next, 35 parts of cyclohexane was added to 100 parts of the reaction solution containing the obtained ring-opening polymer, and 5 parts of a nickel-alumina catalyst (manufactured by Nikki Chemical Co., Ltd.) was further added as a hydrogenation catalyst. After heating to a temperature of 200 ° C. while stirring under pressure, the reaction was carried out for 4 hours to obtain a reaction solution containing 20% of hydrogenated DCP / ETD ring-opening polymer. After removing the hydrogenation catalyst by filtration, a phenolic antioxidant (pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate) was added to 100 parts of the hydrogenated product. ]) 0.1 part was added and dissolved in the resulting solution. Then, using a cylindrical concentrator / dryer (manufactured by Hitachi, Ltd.), the hydrogenated product was extruded in a molten state at a temperature of 270 ° C. and a pressure of 1 kPa or less while removing cyclohexane and other volatile components as a solvent from the solution. After cooling, a pellet of the hydrogenated DCP / ETD ring-opening polymer was obtained. The hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 31,000, a hydrogenation rate of 99.9%, a Tg of 100 ° C., a refractive index of 1.531, and a melt viscosity of 87.2 Pa · s. And the total light transmittance was 92%.
Production Example 2 (Production of norbornene-based polymer B)
A hydrogenated DCP / ETD ring-opening polymer was obtained in the same manner as in Production Example 1 except that 1-hexene was changed to 0.6 part. The hydrogenated ring-opened polymer had a weight average molecular weight (Mw) of 42,000, a hydrogenation rate of 99.9%, a Tg of 102 ° C., a refractive index of 1.531, and a melt viscosity of 221.3 Pa · s. And the total light transmittance was 92%.
Production Example 3 (Production of vinyl alicyclic hydrocarbon polymer A)
76 parts of styrene (St) and 4 parts of isoprene (IP) are hermetically sealed and mixed and stirred in a stainless steel pressure-resistant container that has been sufficiently dried and purged with nitrogen, and the composition is (St / IP) = (95 / The mixed monomer of 5) was prepared.
Next, 320 parts of dehydrated cyclohexane, 4 parts of a mixed monomer and 0.1 part of dibutyl ether were charged into a stainless steel autoclave equipped with an electromagnetic stirring device which was sufficiently dried and purged with nitrogen, and stirred at 50 ° C. while n- 0.18 parts of a butyllithium solution (15% hexane solution) was added to initiate polymerization. After conducting the polymerization reaction under the same conditions for 0.5 hour (the conversion at this point was 96%), 76% of the polymerization reaction solution in the autoclave was added while continuing the polymerization reaction under the same conditions. Parts of the mixed monomer were added continuously over 1 hour. After completion of the addition (conversion at this point was 95%), polymerization was carried out for 0.5 hours under the same conditions, and 0.1 part of isopropyl alcohol was added to stop the reaction. A copolymer was synthesized.
Then, 8 parts of a stabilized nickel hydrogenation catalyst E22U (manufactured by JGC Chemicals; 60% nickel-supported silica-alumina carrier) was added to 400 parts of the obtained reaction solution containing the copolymer, and the mixture was subjected to a hydrogenation reaction. It was charged in a stainless steel autoclave equipped with an electric heating device for controlling the temperature and an electromagnetic stirring device. After completion of the charging, the inside of the autoclave was replaced with hydrogen gas, and a hydrogenation reaction was performed at 160 ° C. for 6 hours while supplying hydrogen so as to keep the pressure inside the autoclave at 4.5 MPa while stirring.
After removing the hydrogenation catalyst by filtration, a phenolic antioxidant (pentaerythrityl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl)) was added to 100 parts of the polymer solids. Propionate]) was added and dissolved.
Next, the filtrate (polymer concentration = 20%) obtained above was heated to 250 ° C. by a preheating device, and continuously supplied to a cylindrical concentration dryer (manufactured by Hitachi, Ltd.) at a pressure of 3 MPa. The operating conditions of the concentration dryer were adjusted such that the pressure was 60 kPa and the temperature of the polymer solution concentrated inside was 260 ° C. The concentrated solution was continuously drawn out from the concentration dryer, and further supplied to the same concentration dryer at a pressure of 1.5 MPa while maintaining the temperature at 260 ° C. The operating conditions were a pressure of 1.5 kPa and a temperature of 270 ° C. The polymer in a molten state is continuously led out of a concentration dryer, extruded from a die in a class 100 clean room, cooled with water, and then cut with a pelletizer (OSP-2, manufactured by Nagata Seisakusho) to produce a vinyl alicyclic hydrocarbon. A pellet of the polymer A was obtained.
The weight average molecular weight (Mw) of the pellet was 132,000, the molecular weight distribution (Mw / Mn) was 1.19, the degree of hydrogenation was almost 100%, the Tg was 125 ° C., the refractive index was 1.511, and the The viscosity was 73.8 Pa · s, and the total light transmittance was 92%.
Production Example 4 (Production of vinyl alicyclic hydrocarbon polymer B)
A reactor equipped with a sufficiently dried and nitrogen-substituted stirring device was charged with 320 parts of dehydrated cyclohexane, 12 parts of dehydrated styrene and 0.095 part of n-dibutyl ether, and stirred at 60 ° C. while stirring n-butyllithium (15 parts). (0.1% cyclohexane solution) to initiate polymerization. The reaction was carried out at 60 ° C. for 60 minutes with stirring. At this time, the polymerization conversion was 99.5%. Next, 4 parts of dehydrated isoprene was added and stirring was continued for 30 minutes. At this point, the polymerization conversion was 99%. Thereafter, 4 parts of dehydrated styrene was further added, followed by stirring for 60 minutes. At this time, the polymerization conversion was almost 100%. Here, 25 parts of isopropyl alcohol was added to stop the reaction.
Next, 100 parts of the reaction solution containing the polymer was transferred to a pressure-resistant reactor equipped with a stirrer, and a silica-alumina-supported nickel catalyst (manufactured by Nikki Chemical Co., Ltd .; E22U, nickel supported amount 60%) was used as a hydrogenation catalyst. 8 parts were added and mixed. The inside of the reactor was replaced with hydrogen gas, hydrogen was supplied while stirring the solution, and a hydrogenation reaction was performed at a temperature of 170 ° C. and a pressure of 4.5 MPa for 6 hours.
After the completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst, and then 0.1 part of TOMINOX TT (manufactured by Yoshitomi Fine Chemical Co., Ltd.) was added to 100 parts of the resin and mixed. The solvent was removed from the resin solution at 260 ° C. under reduced pressure, and a pellet of a vinyl alicyclic hydrocarbon polymer B was obtained while extruding the resin solution into a strand with an extruder. The obtained vinyl alicyclic hydrocarbon polymer B had a weight average molecular weight (Mw) of 85,000, a molecular weight distribution (Mw / Mn) of 1.14, a hydrogenation rate of 99.9%, and a Tg of 129 ° C. The refractive index was 1.504, the melt viscosity was 84.0 Pa · s, and the total light transmittance was 92%.
Production Example 5
(Production of vinyl alicyclic hydrocarbon polymer C)
The mixed monomer was sealed with 76.8 parts by weight of styrene (St) and 3.2 parts by weight of isoprene (IP) and mixed and stirred. The composition was set to (St / IP) = (96/4) by weight ratio, and n Of vinyl alicyclic hydrocarbon polymer C in the same manner as in Production Example 3 except that the addition amount of -butyllithium (15% cyclohexane solution) was 0.454 parts and the addition amount of the hydrogenation catalyst was 3 parts. A pellet was obtained.
The weight average molecular weight (Mw) of this vinyl alicyclic hydrocarbon polymer C was 85,000, the molecular weight distribution (Mw / Mn) was 1.18, the degree of hydrogenation was almost 100%, Tg was 125 ° C., The refractive index was 1.509, the melt viscosity was 33.1 Pa · s, and the total light transmittance was 92%.
(5) Polysiloxane-based light diffusing agent
GE Toshiba Silicone Co., Ltd., Tospearl 120
[0011]
Example 1
A mixture of the norbornene-based polymer A obtained in Production Example 1 and the vinyl alicyclic hydrocarbon polymer A obtained in Production Example 3 in a weight ratio of 70:30 was put into a hopper of an injection molding machine, and light diffusion was performed. The plate was injection molded. The difference in refractive index between the two resins is 0.020, and the difference in melt viscosity is 13.4 Pa · s.
The luminance of the obtained light diffusion plate is 5,478 cd / m. Two And ΔYI was -10.59 and haze was 92.18. No spots were observed on the light diffusion plate.
Example 2
A mixture having a weight ratio of 70:30 of the norbornene-based polymer A obtained in Production Example 1 and the vinyl alicyclic hydrocarbon polymer B obtained in Production Example 4 was put into a hopper of an injection molding machine, and light diffusion was performed. The plate was injection molded. The difference in refractive index between the two resins is 0.027, and the difference in melt viscosity is 3.2 Pa · s.
The luminance of the obtained light diffusion plate is 5,480 cd / m. Two And ΔYI was −7.94 and haze was 92.39. No spots were observed on the light diffusion plate.
Comparative Example 1
99 parts by weight of the norbornene-based polymer A obtained in Production Example 1 and 1 part by weight of a polysiloxane-based light diffusing agent [GE Toshiba Silicone Co., Ltd., Tospearl 120] were mixed, and extruded into a strand using a twin-screw extruder. Then, pellets for a light diffusion plate were produced by cutting with a pelletizer. The pellets were put into a hopper of an injection molding machine, and injection molding of a light diffusion plate was performed.
The brightness of the obtained light diffusion plate is 4,979 cd / m. Two And ΔYI was -4.47 and haze was 92.24. No spots were observed on the light diffusion plate.
Comparative Example 2
A mixture of norbornene-based polymer B obtained in Production Example 2 and vinyl alicyclic hydrocarbon polymer C obtained in Production Example 5 in a weight ratio of 70:30 was put into a hopper of an injection molding machine, and light diffusion was performed. The plate was injection molded. The difference in refractive index between the two resins is 0.022, and the difference in melt viscosity is 188.2 Pa · s.
The brightness of the obtained light diffusion plate is 5,100 cd / m. Two And ΔYI was -10.38 and haze was 92.25. Prominent spots were observed on the light diffusion plate.
Comparative Example 3
A mixture of vinyl alicyclic hydrocarbon polymer A obtained in Production Example 3 and vinyl alicyclic hydrocarbon polymer B obtained in Production Example 4 at a weight ratio of 50:50 is put into a hopper of an injection molding machine. Then, injection molding of the light diffusion plate was attempted. The difference in refractive index between the two resins is 0.007, and the difference in melt viscosity is 10.2 Pa · s.
The obtained injection molded plate was transparent and did not satisfy the performance as a light diffusion plate.
Table 1 shows the results of Examples 1 and 2 and Comparative Examples 1 to 3.
[0012]
[Table 1]
As shown in Table 1, the light of Example 1 in which a norbornene-based polymer A having a refractive index difference of 0.020 and a melt viscosity difference of 13.4 Pa · s was combined with a vinyl alicyclic hydrocarbon polymer A was used. The light diffusing plate of Example 2 in which a norbornene-based polymer A having a refractive index difference of 0.027 and a melt viscosity difference of 3.2 Pa · s and a vinyl alicyclic hydrocarbon polymer B were combined with a diffusing plate, Also have high luminance, no spots, and excellent color tone (small ΔYI).
On the other hand, the conventional light diffusing plate of Comparative Example 1 in which the polysiloxane-based light diffusing agent was blended with the norbornene-based polymer A had lower luminance and larger ΔYI than the light diffusing plates of Examples 1 and 2. . The light diffusion plate of Comparative Example 2 in which the norbornene-based polymer B having a difference in melt viscosity of 188.2 Pa · s and the vinyl alicyclic hydrocarbon polymer C are combined has an excellent color tone (small ΔYI), but has a high luminance. Are low and remarkable spots are generated. The molded article of Comparative Example 3 in which two kinds of vinyl alicyclic hydrocarbon polymers having a refractive index difference of 0.007 were combined was transparent and did not have the performance as a light diffusion plate.
[0014]
【The invention's effect】
The light diffusing resin composition of the present invention has a difference in refractive index of 0.01 or more and a shear rate of 1,820 s at a molding temperature. -1 By combining at least two types of transparent resins having a difference in melt viscosity of not more than 80 Pa · s, light diffusibility is exhibited without compounding a fine particle light diffusing agent, and the amount of the light diffusing agent There is no change in optical characteristics due to the change. Also, it is not necessary to knead the resin and the light diffusing agent with a twin-screw extruder or the like before molding to form pellets, and it is possible to directly blend and mold the pellets of the transparent resin. As a result, the heat history of the resin is reduced, and a molded article having a good color tone can be obtained. Furthermore, it is possible to promptly respond to requests from a large number of users regarding a variety of characteristics, simply by blending and molding resin pellets. According to the present invention, it is possible to obtain a light diffusion plate having higher luminance than a light diffusion plate in which a light diffusion agent is blended with a transparent resin.
Claims (6)
０.０３ ≦ Ｌ1／Ｌ ≦ ０.５
を満たす混練スクリューを備えた射出成形機を用いて射出成形してなる請求項４記載の成形体。The effective length of screw L, when the length of the mixing mechanism and L 1,
0.03 ≦ L 1 /L≦0.5
The molded article according to claim 4, which is injection molded using an injection molding machine provided with a kneading screw satisfying the following.
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| JP2002376672A JP2004204122A (en) | 2002-12-26 | 2002-12-26 | Light-diffusing resin composition, and molding obtained by molding the same |
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| JP2002376672A JP2004204122A (en) | 2002-12-26 | 2002-12-26 | Light-diffusing resin composition, and molding obtained by molding the same |
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| JP2004204122A true JP2004204122A (en) | 2004-07-22 |
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| KR100886206B1 (en) | 2008-09-01 | 2009-02-27 | 바이엘쉬트코리아 주식회사 | Optical sheet and optical sheet manufacturing method |
| EP2578641A2 (en) * | 2010-05-28 | 2013-04-10 | LG Chem, Ltd. | Resin mixture for melt processing, pellet, and method for preparing resin molded product by using same |
| EP2628773A2 (en) * | 2010-10-14 | 2013-08-21 | LG Chem, Ltd. | Resin blend for melting process |
| US10655002B2 (en) | 2010-10-14 | 2020-05-19 | Lg Chem, Ltd. | Resin blend for melting process |
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| EP2628773A2 (en) * | 2010-10-14 | 2013-08-21 | LG Chem, Ltd. | Resin blend for melting process |
| EP2628773A4 (en) * | 2010-10-14 | 2014-03-19 | Lg Chemical Ltd | Resin blend for melting process |
| US10655002B2 (en) | 2010-10-14 | 2020-05-19 | Lg Chem, Ltd. | Resin blend for melting process |
| US10655003B2 (en) | 2010-10-14 | 2020-05-19 | Lg Chem, Ltd. | Resin blend for melting process |
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