200912389 九、發明說明 【發明所屬之技術領域】 本發明有關一種光擴散板。 【先前技術】 如圖1所示，彩色液晶顯示器包含一影像顯示器（4) 與一從影像顯示器（4)背面照明之光源（5)，並且廣泛用作 液晶電視或其他之顯示器。該影像顯示器（4)通常包含一 液晶單元（1 )、設於該液晶單元（1)各側之偏光片（2 )以及使 通過該液晶單元之透射光具有顏色以顯示彩色影像的濾色 片（3)。在介於光源（5)與影像顯示器（4)之間的光徑上，設 置一光擴散板（6)以將從冷陰極螢光燈（5)所發出的光均勻 地照明該影像顯示器（4 )(J P - A - 2 0 0 1 - 3 0 5 3 3 5 )。 作爲該光擴散板（6)，一通常使用由包含諸如苯乙烯 之透明樹脂和光擴散體的樹脂組成物所製成之光擴散板， 而所企求的是能以少量光擴散體充分擴散透射光的光擴散 體。 【發明內容】 本發明的目的爲提供使用較少量光擴散體而具有高度 光擴散性質之光擴散板。 因此，本發明提供一種光擴散板，其包括含有透明樹 脂與光擴散體之透明樹脂組成物，其中該光擴散體之平均 粒徑爲0.6 μιη至1.5 μπι且粒徑標準差爲〇·〇1 Pm至〇.5 -5- 200912389 μ«ι ’該透明樹脂與光擴散體間之折射率差的絕對値μη丨爲 至少0.0 5。 本發明之光擴散板以少量光擴散體達到高度光擴散性 質。因此，可減少光擴散體數量’或可減低令該光擴散板 厚度。 作爲本發明該光擴散板中所使用之透明樹脂，可使用 傳統光擴散板中所使用的任何透明樹脂。該透明樹脂之實 例包括苯乙烯系樹脂、聚甲基丙烯酸甲酯、聚碳酸酯、環 烯聚合物、環烯共聚物、聚丙烯等等。 以該苯乙烯系樹脂總重量計，本發明中所使用之苯乙 烯系樹脂包含50至100重量％之苯乙烯系單體單元。該 苯乙烯系單體之實例包括苯乙烯與經取代苯乙烯。該經取 代苯乙烯之實例包括鹵化苯乙烯，諸如氯苯乙烯、溴苯乙 烯等等；經烷基取代之苯乙烯，諸如乙烯基甲苯、α-甲 基苯乙烯等等；及類似物。該苯乙烯系單體可獨自使用或 其中二或更多者合倂使用。 由抗吸濕性觀點來看，本發明中所使用之較佳透明樹 脂係聚苯乙烯、苯乙烯-甲基丙烯酸甲酯共聚物、環烯聚 合物與共聚物以及聚丙烯。尤以聚苯乙烯爲佳。 就耐熱性觀點來看，本發明中所使用之較佳透明樹脂 爲苯乙烯系單體一甲基丙烯酸共聚物。此處，該苯乙烯系 單體-甲基丙烯酸共聚物意指一種令苯乙烯系單體與甲基 丙烯酸共聚而製備之共聚物。從耐熱性觀點來看，該苯乙 烯系單體一甲基丙烯酸共聚物中之苯乙烯系單體單元的含 -6 - 200912389 量通常爲80莫耳％至95莫耳％，較佳爲88莫耳％至93 莫耳％，而甲基丙烯酸單元之含量爲20莫耳％至5莫耳 %，較佳爲1 2莫耳％至7莫耳％。 除了苯乙烯系單體與甲基丙烯酸之外，該苯乙烯系單 體-甲基丙烯酸共聚物可包含其他單體單元。該其他單體 之實例包括甲基丙烯酸酯（例如甲基丙烯酸甲酯、甲基丙 烯酸乙酯、甲基丙烯酸丁酯、甲基丙烯酸環己酯、甲基丙 烯酸十八酯、甲基丙烯酸苯酯、甲基丙烯酸苄酯、甲基丙 烯酸2-乙基己酯、甲基丙烯酸2-羥基乙酯 '甲基丙烯酸 金剛烷酯、甲基丙烯酸三環癸酯、甲基丙烯酸葑酯、甲基 丙烯酸降萡酯、甲基丙烯酸降萡基甲酯、等等）、丙烯酸 酯（例如丙嫌酸甲酯、丙嫌酸乙酯、丙稀酸丁酯、丙烯酸 環己酯、丙烯酸苯酯、丙烯酸苄酯、丙烯酸2 -乙基己 酯、丙烯酸2-羥基乙酯、丙烯酸三環癸酯、等等）、不飽 和酸類（例如丙烯酸、等等）、丙烯腈、甲基丙烯腈、順丁 烯二酸、苯基順丁烯二醯亞胺、環己基順丁烯二醯亞胺、 戊二酸酐、戊二醯亞胺、及類似物。此等單體可獨自使用 或其中二或更多者倂用。 該苯乙烯系單體-甲基丙烯酸共聚物通常呈透明狀。 本發明中，可使用市售苯乙烯系單體一甲基丙烯酸共聚 物。該市售苯乙烯系單體-甲基丙烯酸共聚物之實例包括 TOYO STYROL® T080(由 Toyo Styrene Co., Ltd.所製）、 Ryulex® A14(由 Dainippon Ink and Chemicals, Inc.所 製）、G9001(由 PS Japan，Co·, Ltd.所製）、及類似者。 200912389 本發明中所使用之光擴散體係當分散於光擴散板之透 明樹脂中時能使通過該光擴散板之光線擴散的材料。 本發明中所使用之光擴散體的平均粒徑通常爲〇. 6 μιη 至1.5 μιη，較佳爲至少0.65 μηι，然而以1.2 μιη或更小爲 佳，以0 · 9 μ m或更小更佳，特別是0.8 5 μ m或更小。若 該平均粒徑不過小也不過大，則可減少待添加之光擴散體 的數量。 該光擴散體粒徑的標準差較佳爲0.5 μιη或更小，更 佳爲0.2 μιη或更小。該光擴散體粒徑的標準差理想値爲〇 μηι，但就成本考量，其通常爲至少0.01 μιη。 待添加於該透明樹脂之光擴散體數量可視透明樹脂與 光擴散體間之折射率差的絕對値|Δη|與所需之總透光率而 隨意選擇。該光擴散體之數量通常爲每100重量份透明樹 脂0.1重量份至20重量份，較佳爲0.3至3重量份，更 佳爲〇 · 5至2重量份。 此處，該光擴散體之平均粒徑與粒徑標準差係以 5000倍、1 0000倍或5 0000倍放大倍率拍攝該光擴散體粒 子之掃描電子顯微鏡（SEM)照片，藉由三點圓半徑法測量 隨機選擇之40個粒子的半徑，計算該等粒子之直徑（即， 粒徑），然後從所獲得之粒徑計算平均粒徑與粒徑標準差 而得。 本發明中所使用之光擴散體的材料並無特定限制，而 且只要該透明樹脂與該光擴散體間之折射率差的絕對値 |Δη|在本發明範圍內，則可使用有機材料或無機材料之任 200912389 何粒子。該折射率差的絕對値I Δ η I通常爲至少ο . 〇 5 (I △ η丨2 〇_〇5)，較佳爲至少0.10(| Δη |g〇.1〇)。當該折射率差夠大 時，可減少該光擴散體之數量。 無機fii子之實例包括碳酸纟弓粒子、硫酸鋇粒子、氧化 鈦粒子、氫氧化鋁粒子、矽石粒子、玻璃粒子、滑石粒 子、雲母粒子、白碳粒子、氧化鎂粒子、氧化鋅粒子、等 等。該等無機粒子可利用諸如脂肪酸之表面處理劑予以表 面處理。 有機粒子之實例包括苯乙烯系樹脂粒子、丙烯酸系樹 脂粒子、聚矽氧粒子、等等。較佳爲使用丙烯酸系樹脂粒 子或聚矽氧粒子。該苯乙烯系樹脂粒子可爲交聯苯乙烯系 樹脂粒子或高分子量苯乙烯系樹脂粒子。該丙烯酸系樹脂 粒子可爲交聯丙烯酸系樹脂粒子或高分子量丙烯酸系樹脂 粒子。該等交聯樹脂粒子（諸如該交聯苯乙烯系樹脂粒子 與該交聯丙烯酸系樹脂粒子）意指當溶解於室溫（約25 °C ) 之丙酮時具有之凝膠部分爲至少1 0%的樹脂粒子。高分子 量樹脂粒子（諸如該高分子量苯乙烯系樹脂粒子與該高分 子量丙烯酸系樹脂粒子）意指具有諸如 500,000至 5,000,000之重量平均分子量的筒分子量樹脂粒子。 該苯乙烯系樹脂粒子的實例包括： (1)高分子量苯乙烯系樹脂粒子，其係藉由聚合苯乙 烯系單體，或藉由聚合含有至少50重量％之苯乙烯系單 體與在分子中具有一個可自由基聚合之雙鍵的單體的單體 混合物而製備；與 -9- 200912389 (2)交聯苯乙烯系樹脂粒子，其係藉由聚合含有苯乙 烯系單體與在分子中具有至少兩個可自由基聚合之雙鍵的 單體之單體混合物，或藉由聚合含有至少5〇重量％之苯 乙嫌系單體、在分子中具有一個可自由基聚合之雙鍵的單 體及在分子中具有至少兩個可自由基聚合之雙鍵的單體之 單體混合物而製備。 該苯乙靖系單體之實例包括苯乙烯與其衍生物。該苯 乙嫌衍生物之非限制性實例包括鹵化苯乙烯，諸如氯苯乙 傾、溴苯乙嫌、等等；經烷基取代之苯乙烯，諸如乙烯基 甲苯、α-甲基苯乙烯、等等；及類似物。該苯乙烯系單體 可獨自使用或其中二或更多者合倂使用。 只要有別於苯乙烯系單體，該在分子中具有一個可自 由基聚合之雙鍵的單體並無特定限制。此種單體之具體實 例包括（甲基）丙烯酸酯類諸如（甲基）丙烯酸甲酯、（甲基） 丙烯酸乙酯、（甲基）丙烯酸丁酯、（甲基）丙烯酸環己酯、 (甲基）丙烯酸苯酯、（甲基）丙烯酸苄酯、（甲基）丙烯酸2-乙基己酯、（甲基）丙烯酸2-羥基乙酯、等等；丙烯腈；及 類似物。其中，以丙烯酸烷酯類爲佳，諸如丙烯酸甲酯。 此等單體可獨自使用或其中二或更多者倂用。 此處，「（甲基）丙烯酸酯」意指「甲基丙烯酸酯與丙 烯酸酯j 。 該在分子中具有至少兩個可自由基聚合之雙鍵的單體 係具有兩個或更多個可自由基聚合的雙鍵並且可與上述單 體共聚之單體，但共軛二烯除外。此種單體之具體實例包 -10- 200912389 括二（甲基）丙烯酸烷基二醇酯，諸如二（甲基）丙烯酸i,4_ 丁二醇酯、二（甲基）丙烯酸新戊基二醇酯、等等；二（甲 基）丙烯酸伸烷基二醇酯，諸如二（甲基）丙烯酸乙二醇 酯、（甲基）丙烯酸二甘醇酯、二（甲基）丙烯酸四甘醇酯、 二（甲基）丙烯酸丙二醇酯、二（甲基）丙烯酸四丙二醇酯、 等等；多官能基芳族化合物，諸如二乙烯苯、苯二甲酸二 烯丙酯、等等；多元醇之二（甲基）丙烯酸酯，諸如三（甲 基）丙烯酸三羥甲基丙酯、四（甲基）丙烯酸季戊四醇酯、 等等；及類似物。此等單體可獨自使用或其中二或更多者 倂用。 該丙烯酸系樹脂粒子之實例包括： (1) 高分子量丙烯酸系樹脂粒子，其係藉由聚合丙烯 酸系單體，或藉由聚合含有至少5〇重量％之丙烯酸系單 體與在分子中具有一個可自由基聚合之雙鍵的單體之單體 混合物而製備；與 (2) 交聯丙烯酸系樹脂粒子，其係藉由聚合含有丙烯 酸系單體與在分子中具有至少兩個可自由基聚合之雙鍵的 單體之單體混合物，或藉由聚合含有至少50重量％之丙 烯酸系單體、在分子中具有一個可自由基聚合之雙鍵的單 體及在分子中具有至少兩個可自由基聚合之雙鍵的單體之 單體混合物而製備。 該丙烯酸系單體之實例包括（甲基）丙烯酸酯類（例如 (甲基）丙烯酸甲酯、（甲基）丙烯酸乙酯、（甲基）丙烯酸丁 酯、（甲基）丙烯酸環己酯、（甲基）丙烯酸苯酯、（甲基）丙 -11 - 200912389 烯酸苄酯、（甲基）丙烯酸2-乙基己醋 基乙酯、等等）、丙烯酸、甲基丙烯 丙烯酸系單體可獨自使用或其中二或 只要有別於該丙烯酸系單體，該 自由基聚合之雙鍵的單體並無特定限 包括苯乙烯與苯乙烯衍生物。該苯乙 包括鹵化苯乙烯，諸如氯苯乙烯、溴 基取代之苯乙烯，諸如乙烯基甲苯 等；及類似物。其中，以苯乙烯爲佳 用或其中二或更多者倂用。 該分子中具有至少兩個可自由基 具有二或更多個可自由基聚合之雙鍵 聚之單體，但共軛二烯除外。此種單 體以及（甲基）丙烯酸烯丙酯。 作爲該丙烯酸系樹脂粒子，可使 層之核-殻型粒子。 該核-殼型粒子之內層可包含一 係藉由聚合在分子中具有至少兩個碳 單體與包含丙烯酸丁酯作爲主要組份 得，以所有單體總重量計，該多官能 至1 0重量％，較佳爲0 · 2至5重量％ 作爲主要組份之單官能基單體意指該 量％之丙烯酸丁酯與隨意之其他可與 飽和單體。 、（甲基）丙烯酸2 -羥 酸、及類似物。此等 更多者倂用。 在分子中具有一個可 制。此種單體之實例 烯衍生物之具體實例 苯乙烯、等等；經烷 、α-甲基苯乙烯、等 。此等單體可獨自使 聚合之雙鍵的單體係 並且可與上述單體共 體之實例包括上述單 用具有一內層與一外 種共聚物，該共聚物 -碳雙鍵之多官能基 之單官能基單體而製 基單體之數量爲0.1 。該包含丙烯酸丁酯 單體含有至少5 0重 丙烯酸丁酯共聚的不 -12- 200912389 該多官能基單體之具體實例包括二（甲基）丙烯酸乙二 醇酯、二甲基丙烯酸1，3-丁二醇酯、三丙烯酸三羥甲基丙 酯、四丙烯酸季戊四醇酯、三烯丙基氰尿酸二乙烯苯酯、 桂皮酸烯丙酯、（甲基）丙烯酸烯丙酯、山梨酸烯丙酯、苯 二甲酸二烯丙酯、順丁烯二酸二烯丙酯、等等。較佳爲使 用（甲基）丙烯酸烯丙酯。 該核-殼型粒子之外層可包含一種共聚物，其係藉由 聚合包含甲基丙烯酸甲酯作爲主要組份的單官能基單體而 製得。該外層可爲單層或隨意之具有二或更多層之多重 層°該包含甲基丙烯酸甲酯作爲主要組份之單官能基單體 意指該單體含有至少50重量％之甲基丙烯酸甲酯以及隨 意之其他可與甲基丙烯酸甲酯共聚的乙烯式不飽和單體。 該核殼-型粒子中，內層對外層之重量比通常爲1:9 至 9 : 1。 該苯乙烯系樹脂粒子與該丙烯酸系樹脂粒子可藉由傳 統聚合方法聚合該單體或該等單體而製造，此等傳統聚合 方法係諸如懸浮聚合、微懸浮聚合、乳液聚合、分散聚 合、等等。可藉由以乳液聚合爲基礎之連續兩步驟聚合法 輕易製造該核-殼型粒子。亦即，首先藉由乳液聚合形成 構成核心之內層，然後在該內層存在下藉由乳液聚合而形 成外層。 該光擴散體之粒子形狀並無特定限制，惟以球形粒子 爲佳。 本發明之光擴散板的厚度並無限制。其通常爲5mm -13- 200912389 或更小，較佳爲3 m m或更小，然而就該板強度而言，其 通常至少爲〇.8mm’較佳爲至少1mm。 本發明之光擴散板可隨意含有傳統添加劑中之任一 者。該等添加劑之具體實例包括抗靜電劑（例如烷基磺酸 鈉、烷基硫酸鈉、硬脂酸單甘油酯、聚醚酯醯胺、等 等）、抗氧化劑（例如位阻酚、等等）、阻焰劑（例如磷酸 酯 '等等）、潤滑劑（例如棕櫚酸、硬脂醇、等等）、光安 定劑（例如位阻胺、等等）、抗氧化劑（例如位阻酚、等 等）、染料、光學增亮劑、加工安定劑、UV吸收劑（例如 苯并三唑UV吸收劑、二苯甲酮UV吸收劑、氰基丙烯酸 酯UV吸收劑、丙二酸酯UV吸收劑、草醯替苯胺UV吸 收劑、醋酸酯UV吸收劑、三哄UV吸收劑、水楊酸酯 UV吸收劑、苯甲酸酯UV吸收劑、等等）及類似者。此等 添加劑可獨自使用或其中二或更多者倂用。 本發明之光擴散板可藉由帶式摻合機、Henschel混合 機、Banbury混合機、鼓式桶、單螺桿擠出機、雙螺桿擠 出機、多螺桿擠出機等等來熔融捏合透明樹脂與光擴散 體，並使所得之熔體通過模擠出形成板而製得。當該光擴 散板含有添加劑時，該等添加劑通常與透明樹脂及該光擴 散體一起熔融捏合。或者，本發明之光擴散板可藉由射出 成形法而製造，其中將上述熔融捏合步驟中所製備之熔體 注入一射出模具。 本發明之光擴散板隨意具有位於該板之至少一個表面 上的包含透明樹脂與UV吸收劑之UV吸收層，並且可作 -14- 200912389 爲多層光擴散板。此種多層光擴散板可防止因紫外線所造 成之該板的變質。由於待包含在該UV吸收層中之UV吸 收劑可爲傳統U V吸收劑，其實例包括苯并三唑U V吸收 劑、二苯甲酮UV吸收劑、氰基丙烯酸酯UV吸收劑、丙 二酸酯UV吸收劑、草醯替苯胺UV吸收劑、醋酸酯UV 吸收劑、三哄u V吸收劑、水楊酸酯U V吸收劑、苯甲酸 酯UV吸收劑、等等。 作爲包含在該UV吸收層中之透明樹脂，較佳係使用 甲基丙烯酸甲酯樹脂或苯乙烯系樹脂，而且更佳係使用甲 基丙烯酸甲酯一苯乙烯共聚物。 該甲基丙烯酸甲酯樹脂意指一種包含以構成該甲基丙 烯酸甲酯樹脂之單體單元計至少50重量％之甲基丙烯酸 甲酯單元的聚合物，且可爲甲基丙烯酸甲酯之均聚物、或 包含50重量％或更多甲基丙烯酸甲酯與50重量％或更少 之其他可與甲基丙烯酸甲酯共聚之單體的共聚物。 該其他可與甲基丙烯酸甲酯共聚之單體的實例包括除 甲基丙烯酸甲酯之外的甲基丙烯酸酯（例如甲基丙烯酸乙 酯、甲基丙烯酸丁酯、甲基丙烯酸環己酯、甲基丙烯酸十 八酯、甲基丙烯酸苯酯、甲基丙烯酸苄酯、甲基丙烯酸 2 -乙基己酯、甲基丙烯酸2 -羥基乙酯、甲基丙烯酸金剛烷 酯、甲基丙烯酸三環癸酯、甲基丙烯酸葑酯、甲基丙烯酸 降萡酯、甲基丙烯酸降萡基甲酯、等等、丙烯酸酯（例如 丙烯酸甲酯、丙烯酸乙酯、丙烯酸丁酯、丙烯酸己酯、丙 烯酸苯酯、丙烯酸苄酯、丙烯酸2·乙基己酯、丙烯酸2- -15- 200912389 羥基乙酯、丙烯酸三環癸酯、等等）、不飽和酸類（例如甲 基丙烯酸、丙烯酸、等等）、丙烯腈、甲基丙烯腈、順丁 烯二酸、苯基順丁烯二醯亞胺、環己基順丁烯二醯亞胺、 戊二酸酐、戊二醯亞胺、苯乙烯系單體、及類似物。此等 單體可獨自使用或其中二或更多者倂用。作爲該苯乙烯系 單體，除了苯乙烯之外，可使用經取代苯乙烯。該甲基丙 烯酸甲酯可包含戊二酸酐單元或戊二醯亞胺單元。 該苯乙烯系樹脂意指一種包含以構成該苯乙烯系樹脂 之單體單元計50至100重量％之苯乙烯系單體的樹脂。 作爲該苯乙烯系單體，除了苯乙烯之外，可使用經取代苯 乙烯。該經取代苯乙烯之實例包括鹵化苯乙烯，諸如氯苯 乙烯、溴苯乙烯、等等；經烷基取代之苯乙烯，諸如乙烯 基甲苯、α-甲基苯乙烯、等等；及類似物。該苯乙烯系單 體可獨自使用或其中二或更多者倂用。 可構成該苯乙烯系樹脂之其他單體的實例包括甲基丙 烯酸甲酯及前述例示之可隨意構成該甲基丙烯酸甲酯樹脂 之其他單體（苯乙烯除外）。 該UV吸收層中所包含之甲基丙烯酸甲酯樹脂或苯乙 烯系樹脂可爲苯乙烯與甲基丙烯酸甲酯之共聚物，亦即甲 基丙烯酸甲酯一苯乙烯共聚物。該甲基丙烯酸甲酯一苯乙 烯共聚物中之苯乙烯單元的含量通常爲5重量％至95重 量％，而甲基丙烯酸甲酯單元之含量通常爲95重量％至5 重量％。 本發明之光擴散板係在該透明樹脂中包含前文所界定 -16- 200912389 之光擴散體。因此，即使當光擴散體含量低時亦能降低該 透明樹脂的總透光率。由於該總透光率已經藉由該光擴散 體降低之透明樹脂能良好擴散通過該樹脂的光，所以本發 明之光擴散板能以少量該光擴散體充分地擴散通過之光。 因此，本發明亦提供一種用於降低透明樹脂之總透光率的 方法，其包含添加用於本發明光擴散板中之光擴散體。 【實施方式】 實施例 茲以下列實施例例示說明本發明，此等實施例均非以 任何方式限制本發明範圍。在該等實施例中，除非另外指 示，否則「％」與「份」係以重量計。 總透光率之測量 根據JIS K 73 6 1，使用混濁透光率計（HR-100，由 MURAKAMI COLOR RESEARCH LABORATORY CO., LTD. 所製）測量總透光率T t。 粒徑之測量 將光擴散體之粒子壓實固定在樣本檯上，並令碳氣相 沉積於其上，以製備樣本片。該樣本片上之光擴散體粒子 的SEM照片係使用場發射掃描電子顯微鏡（FE-SEM S-420 ，由Hitachi Limited所製）並選用適於個別粒徑之放 大倍率而攝得，該放大倍率爲5000倍、1 0000倍與5 0000 -17- 200912389 倍。然後，藉由三點圓半徑法測量各粒子的半徑，並由所 測得之半徑計算該粒子之直徑。 平均粒徑與粒徑之標準差 在該粒徑的上述測量方法中，隨機選擇40個粒子， 並計算該等粒子之直徑。然後，計算該光擴散體之粒徑的 平均値與標準差。 比較實例1 於 1 00 份聚苯乙烯（HRM 40 由 Toyo Styrene Co.，Ltd. 所製；折射率：1.59)中添加1份折射率爲1.43、平均粒 徑爲2.49 μιη且粒徑之標準差爲0.14 μιη的聚矽氧粒子， 並予乾式摻合以獲得樹脂組成物。然後使用配備有多重歧 管模之40 mm單螺桿擠出機（由Tanabe Plastics Co·, Ltd. 所製），以溫度範圍爲190至260°C擠出模製該樹脂組成 物，製得厚度爲2 mm之單層光擴散板。該單層光擴散板 之總透光率（下文稱爲” Tt")爲5 6 · 2 %。 比較實例2 以與比較實例1相同之方式製造一單層光擴散板，但 於 100 份聚苯乙烯（HRM 40 由 Toyo styrene Co_, Ltd.所 製；折射率：1·59)中添加1份折射率爲1.43、平均粒徑 爲2.17 μιη且粒徑之標準差爲0_ 29 μιη的聚矽氧粒子。該 厚度爲2 mm之單層光擴散板的Tt爲54.8%。 -18- 200912389 實施例1 以與比較實例1相同之方式製造一單層光擴散板’但 於 100 份聚苯乙烯（HRM 40 由 Toyo Styrene Co.，Ltd.所 製；折射率：1 . 5 9)中添加1份折射率爲1.4 3、平均粒徑 爲0.67 μιη且粒徑之標準差爲〇·〇7 μιη的聚矽氧粒子。該 厚度爲2 mm之單層光擴散板的Tt爲49.6%。 比較實例3 以與比較實例1相同之方式製造一單層光擴散板’但 於 1〇〇 份聚苯乙烯（HRM 40 由 T〇y〇 Styrene co.，Ltd.所 製；折射率：1.59)中添加1份折射率爲1.43、平均粒徑 爲0.12 μιη且粒徑之標準差爲〇·01 的聚砂氧粒子。該 厚度爲2 mm之單層光擴散板的Tt爲5 5.0 %。 比較實例4 以與比較實例1相同之方式製造一單層光擴散板’但 於 1〇〇 份聚苯乙烯（HRM 40 由 T〇y〇 Styrene c〇·，Ltd•所 製；折射率：1 . 5 9)中添加1份折射率爲1 · 4 9、平均粒徑 爲2.44 μιη且粒徑之標準差爲0.52 μπι的丙烯酸系樹脂粒 子。該厚度爲2 mm之單層光擴散板的Tt爲69.3%。 實施例2 以與比較實例1相同之方式製造一單層光擴散板’但 -19- 200912389 方 < 100 份聚本乙嫌（HRM 40 由 Toyo Styrene Co.，Ltd.戶斤 製；折射率：1 . 5 9)中添加1份折射率爲1 .49、平均粒徑 爲〇·85 μιη且粒徑之標準差爲〇.〇3 μιη的丙烯酸系樹脂粒 子。該厚度爲2 mm之單層光擴散板的1^爲55.1%。 比較實例5 以與比較實例1相同之方式製造一單層光擴散板，但 於 100 份聚苯乙嫌（HRM 40 由 Toyo Styrene Co., Ltd.所 製；折射率·· 1 . 5 9)中添加1份折射率爲1.4 9、平均粒徑 爲0·5 0 μηα且粒徑之標準差爲〇.04 μπ1的丙烯酸系樹脂粒 子。該厚度爲2 mm之單層光擴散板的Tt爲70.2%。 結果彙總於表1。 表1 比較 實例1 比較 實例2 實施例 1 比較 實例3 比較 實例4 實施例 2 比較 實例5 平均粒徑(μιη) 2.49 2.17 0.67 0.12 2.44 0.85 0.50 粒徑之標準差(μιη) 0.14 0.29 0.07 0.02 0.52 0.03 0.04 Tt1) (%) 56.2 54.8 49.6 55.0 69.3 55.1 70.2200912389 IX. Description of the Invention [Technical Field of the Invention] The present invention relates to a light diffusing plate. [Prior Art] As shown in Fig. 1, a color liquid crystal display includes an image display (4) and a light source (5) illuminated from the back of the image display (4), and is widely used as a liquid crystal television or other display. The image display (4) generally comprises a liquid crystal cell (1), a polarizer (2) disposed on each side of the liquid crystal cell (1), and a color filter for causing the transmitted light passing through the liquid crystal cell to have a color to display a color image. (3). A light diffusing plate (6) is disposed on the optical path between the light source (5) and the image display (4) to uniformly illuminate the image display from the light emitted from the cold cathode fluorescent lamp (5) ( 4) (JP - A - 2 0 0 1 - 3 0 5 3 3 5 ). As the light diffusing plate (6), a light diffusing plate made of a resin composition containing a transparent resin such as styrene and a light diffusing body is generally used, and it is desirable to sufficiently diffuse transmitted light with a small amount of light diffusing body. Light diffuser. SUMMARY OF THE INVENTION An object of the present invention is to provide a light diffusing plate having a high light diffusing property using a small amount of light diffusing body. Accordingly, the present invention provides a light diffusing plate comprising a transparent resin composition comprising a transparent resin and a light diffuser, wherein the light diffuser has an average particle diameter of 0.6 μm to 1.5 μm and a standard deviation of particle diameters is 〇·〇1 Pm to 〇.5 -5- 200912389 μ«ι 'The absolute 値μη丨 of the refractive index difference between the transparent resin and the light diffuser is at least 0.05. The light diffusing plate of the present invention achieves a high light diffusing property with a small amount of light diffusing body. Therefore, the number of light diffusers can be reduced or the thickness of the light diffusing plate can be reduced. As the transparent resin used in the light diffusing plate of the present invention, any transparent resin used in the conventional light diffusing plate can be used. Examples of the transparent resin include styrene resin, polymethyl methacrylate, polycarbonate, cycloolefin polymer, cycloolefin copolymer, polypropylene, and the like. The styrene-based resin used in the present invention contains 50 to 100% by weight of a styrene-based monomer unit based on the total weight of the styrene resin. Examples of the styrenic monomer include styrene and substituted styrene. Examples of the substituted styrene include halogenated styrene such as chlorostyrene, bromostyrene, and the like; alkyl-substituted styrene such as vinyl toluene, ?-methylstyrene, and the like; and the like. The styrene monomer may be used alone or in combination of two or more of them. From the viewpoint of moisture absorption resistance, preferred transparent resin polystyrene, styrene-methyl methacrylate copolymer, cycloolefin polymer and copolymer, and polypropylene used in the present invention. Especially polystyrene is preferred. From the viewpoint of heat resistance, the preferred transparent resin used in the present invention is a styrene monomer-methacrylic acid copolymer. Here, the styrene monomer-methacrylic acid copolymer means a copolymer prepared by copolymerizing a styrene monomer with methacrylic acid. From the viewpoint of heat resistance, the styrene monomer unit in the styrene monomer-methacrylic acid copolymer preferably has a content of from -6 to 200912389 of from 80 mol% to 95 mol%, preferably 88. Molar% to 93% by mole, and the content of methacrylic acid units is from 20 mol% to 5 mol%, preferably from 12 mol% to 7 mol%. The styrene-based monomer-methacrylic acid copolymer may contain other monomer units in addition to the styrene monomer and methacrylic acid. Examples of the other monomer include methacrylate (e.g., methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, octadecyl methacrylate, phenyl methacrylate). , benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate 'adamantyl methacrylate, tricyclodecyl methacrylate, decyl methacrylate, methacrylic acid Epoxy ester, methyl methacrylate, etc.), acrylate (such as methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate Ester, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, tricyclodecyl acrylate, etc.), unsaturated acids (eg acrylic acid, etc.), acrylonitrile, methacrylonitrile, butylene Acid, phenyl maleimide, cyclohexyl maleimide, glutaric anhydride, pentaneimine, and the like. These monomers may be used alone or in two or more of them. The styrene monomer-methacrylic acid copolymer is usually transparent. In the present invention, a commercially available styrene monomer-methacrylic acid copolymer can be used. Examples of the commercially available styrene monomer-methacrylic acid copolymer include TOYO STYROL® T080 (manufactured by Toyo Styrene Co., Ltd.), Ryulex® A14 (manufactured by Dainippon Ink and Chemicals, Inc.), G9001 (made by PS Japan, Co., Ltd.), and the like. 200912389 The light diffusing system used in the present invention is a material which can diffuse light passing through the light diffusing plate when dispersed in the transparent resin of the light diffusing plate. The average particle diameter of the light diffuser used in the present invention is usually 〇6 μιη to 1.5 μηη, preferably at least 0.65 μηι, but preferably 1.2 μηη or less, and 0·9 μ m or less. Good, especially 0.8 5 μ m or less. If the average particle diameter is not too small or too large, the amount of the light diffusing body to be added can be reduced. The standard deviation of the particle diameter of the light diffuser is preferably 0.5 μm or less, more preferably 0.2 μm or less. The standard deviation of the particle size of the light diffuser is ideally 〇 μηι, but it is usually at least 0.01 μηη in terms of cost. The amount of the light diffusing body to be added to the transparent resin can be arbitrarily selected by the absolute 値 | Δη| of the refractive index difference between the transparent resin and the light diffusing body and the desired total light transmittance. The amount of the light diffusing body is usually from 0.1 part by weight to 20 parts by weight, preferably from 0.3 to 3 parts by weight, more preferably from 5% to 2 parts by weight, per 100 parts by weight of the transparent resin. Here, the average particle diameter of the light diffuser and the standard deviation of the particle diameters are taken at 5000 times, 100,000 times or 50,000 times magnification, and a scanning electron microscope (SEM) photograph of the light diffuser particles is taken by a three-point circle. The radius method measures the radius of the randomly selected 40 particles, calculates the diameter of the particles (ie, the particle diameter), and then calculates the average particle diameter from the particle diameter obtained from the obtained particle diameter. The material of the light diffuser used in the present invention is not particularly limited, and as long as the absolute 値|Δη| of the refractive index difference between the transparent resin and the light diffuser is within the scope of the present invention, an organic material or inorganic may be used. Material of 200912389 He particles. The absolute 値I Δ η I of the refractive index difference is usually at least ο 5 I 5 (I Δ η 丨 2 〇 _ 〇 5), preferably at least 0.10 (| Δη | g 〇 .1 〇). When the refractive index difference is large enough, the number of the light diffusers can be reduced. Examples of the inorganic fii include strontium carbonate particles, barium sulfate particles, titanium oxide particles, aluminum hydroxide particles, vermiculite particles, glass particles, talc particles, mica particles, white carbon particles, magnesium oxide particles, zinc oxide particles, and the like. Wait. These inorganic particles can be surface treated with a surface treating agent such as a fatty acid. Examples of the organic particles include styrene resin particles, acrylic resin particles, polyoxyn oxide particles, and the like. It is preferred to use acrylic resin particles or polysiloxane particles. The styrene resin particles may be crosslinked styrene resin particles or high molecular weight styrene resin particles. The acrylic resin particles may be crosslinked acrylic resin particles or high molecular weight acrylic resin particles. The crosslinked resin particles (such as the crosslinked styrene resin particles and the crosslinked acrylic resin particles) mean that the gel portion has at least 10 when dissolved in acetone at room temperature (about 25 ° C). % resin particles. The high molecular weight resin particles such as the high molecular weight styrene resin particles and the high molecular weight acrylic resin particles mean barrel molecular weight resin particles having a weight average molecular weight of, for example, 500,000 to 5,000,000. Examples of the styrene resin particles include: (1) high molecular weight styrene resin particles by polymerizing a styrene monomer or by polymerizing at least 50% by weight of a styrene monomer with a molecule Prepared with a monomer mixture of a monomer capable of radically polymerizing double bonds; and -9-200912389 (2) crosslinked styrene resin particles which are polymerized to contain a styrene monomer and a molecule a monomer mixture having at least two monomers capable of radically polymerizing double bonds, or having at least 5% by weight of a phenethyl styrene monomer in the polymerization, having a radical polymerizable double bond in the molecule It is prepared by mixing a monomer and a monomer mixture of monomers having at least two radically polymerizable double bonds in the molecule. Examples of the phenylene monomer include styrene and its derivatives. Non-limiting examples of such styrene derivatives include halogenated styrenes such as chlorophenylethyl, bromobenzene, and the like; alkyl substituted styrenes such as vinyl toluene, alpha-methyl styrene, Etc.; and the like. The styrene monomer may be used alone or in combination of two or more of them. The monomer having a double bond capable of free radical polymerization in the molecule is not particularly limited as long as it is different from the styrene monomer. Specific examples of such a monomer include (meth) acrylates such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, ( Phenyl methacrylate, benzyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, etc.; acrylonitrile; and the like. Among them, alkyl acrylates such as methyl acrylate are preferred. These monomers may be used alone or in two or more of them. Here, "(meth) acrylate" means "methacrylate" and acrylate j. The single system having at least two radically polymerizable double bonds in the molecule has two or more a radical polymerized double bond and a monomer copolymerizable with the above monomer, except for a conjugated diene. Specific examples of such a monomer include -10, 2009, 389, including an alkyl (meth) acrylate, such as i,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and the like; alkylene glycol di(meth)acrylate, such as di(meth)acrylic acid Ethylene glycol ester, diethylene glycol (meth)acrylate, tetraethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, tetrapropylene glycol di(meth)acrylate, etc.; multifunctional Aromatic compounds such as divinylbenzene, diallyl phthalate, etc.; di(meth)acrylates of polyols such as trimethylolpropyl tris(meth)acrylate, tetrakis (methyl) ) pentaerythritol acrylate, and the like; and the like. Examples of the acrylic resin particles include: (1) high molecular weight acrylic resin particles by polymerizing an acrylic monomer or by polymerization to contain at least 5 Å by weight And (2) cross-linking acrylic resin particles by polymerization containing acrylic monomers, wherein a monomer mixture of a monomer of acrylic acid and a monomer having a radically polymerizable double bond in the molecule is prepared; a monomer mixture with a monomer having at least two radically polymerizable double bonds in the molecule, or a monomer having at least 50% by weight of an acrylic monomer by polymerization, having a radical polymerizable double bond in the molecule Prepared by a monomer mixture of a monomer having at least two radically polymerizable double bonds in the molecule. Examples of the acrylic monomer include (meth) acrylates (for example, (meth) acrylate Methyl ester, ethyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)prop-11 - 200912389 (2-ethylhexyl acetoxyethyl (meth)acrylate, etc.), acrylic acid, methacrylic acrylic monomer may be used alone or in two or as long as it is different from the acrylic monomer, the radical polymerization The monomer of the double bond is not particularly limited to include a styrene and a styrene derivative, and the styrene includes a halogenated styrene such as chlorostyrene, a bromine-substituted styrene such as vinyl toluene, or the like; and the like. Preferably, styrene is used or two or more of them are used. The molecule has at least two free radicals having two or more radically polymerizable double bond monomers, except for the conjugated dienes. Such a monomer and allyl (meth)acrylate. As the acrylic resin particles, a core-shell type particle of a layer may be provided. The inner layer of the core-shell type particle may comprise a series of molecules by polymerization. Having at least two carbon monomers and comprising butyl acrylate as a main component, the polyfunctionality to 10% by weight, preferably 0. 2 to 5% by weight, based on the total weight of all monomers, as a main component Monofunctional monomer means the amount % The butyl acrylate and optionally other saturated monomers. , (meth)acrylic acid 2-hydroxy acid, and the like. These more are used. There is one that can be made in the molecule. Examples of such monomers Specific examples of the olefin derivatives are styrene, etc.; by alkane, ?-methylstyrene, and the like. Examples of such monomers which may be a single system of a polymerized double bond and which may be copolymerized with the above monomers include the above-mentioned single use having an inner layer and a foreign copolymer, the copolymer-carbon double bond polyfunctional The number of monomer groups based on the monofunctional monomer is 0.1. The butyl acrylate monomer containing at least 50 butyl acrylate copolymerization is not -12-200912389. Specific examples of the polyfunctional monomer include ethylene glycol di(meth)acrylate, 1,3 methacrylic acid. - Butylene glycol ester, Trimethylol propyl triacrylate, Pentaerythritol tetraacrylate, Divinyl phenyl methacrylate, Allyl cinnamate, Allyl (meth) acrylate, Sorbic acid acryl Ester, diallyl phthalate, diallyl maleate, and the like. Preferably, allyl (meth)acrylate is used. The outer layer of the core-shell type particle may comprise a copolymer obtained by polymerizing a monofunctional monomer comprising methyl methacrylate as a main component. The outer layer may be a single layer or a random multiple layer having two or more layers. The monofunctional monomer containing methyl methacrylate as a main component means that the monomer contains at least 50% by weight of methacrylic acid. Methyl ester and optionally other ethylenically unsaturated monomers copolymerizable with methyl methacrylate. In the core-shell type particles, the weight ratio of the inner layer to the outer layer is usually from 1:9 to 9:1. The styrene resin particles and the acrylic resin particles can be produced by polymerizing the monomer or the monomers by a conventional polymerization method such as suspension polymerization, microsuspension polymerization, emulsion polymerization, dispersion polymerization, and many more. The core-shell particles can be easily produced by a two-step polymerization process based on emulsion polymerization. Namely, the inner layer constituting the core is first formed by emulsion polymerization, and then the outer layer is formed by emulsion polymerization in the presence of the inner layer. The particle shape of the light diffuser is not particularly limited, but spherical particles are preferred. The thickness of the light diffusing plate of the present invention is not limited. It is usually 5 mm -13 to 200912389 or less, preferably 3 m or less, but in terms of the strength of the sheet, it is usually at least 〇8 mm', preferably at least 1 mm. The light diffusing plate of the present invention may optionally contain any of conventional additives. Specific examples of such additives include antistatic agents (e.g., sodium alkyl sulfonate, sodium alkyl sulfate, monoglyceryl stearate, polyether ester decylamine, etc.), antioxidants (e.g., hindered phenols, etc.) a flame retardant (such as phosphate ', etc.), a lubricant (such as palmitic acid, stearyl alcohol, etc.), a light stabilizer (such as a hindered amine, etc.), an antioxidant (such as a hindered phenol, Etc.), dyes, optical brighteners, processing stabilizers, UV absorbers (eg benzotriazole UV absorbers, benzophenone UV absorbers, cyanoacrylate UV absorbers, malonate UV absorbers) Agent, grassy aniline UV absorber, acetate UV absorber, triterpenoid UV absorber, salicylate UV absorber, benzoate UV absorber, etc.) and the like. These additives may be used alone or in two or more of them. The light diffusing plate of the present invention can be melt-kneaded and transparent by a belt blender, a Henschel mixer, a Banbury mixer, a drum barrel, a single screw extruder, a twin screw extruder, a multi-screw extruder or the like. The resin and the light diffuser are obtained, and the obtained melt is extruded through a die to form a sheet. When the optical diffusion plate contains an additive, the additives are usually melt-kneaded together with the transparent resin and the optical dispersion. Alternatively, the light diffusing plate of the present invention can be produced by an injection molding method in which the melt prepared in the above melt-kneading step is injected into an injection mold. The light diffusing plate of the present invention optionally has a UV absorbing layer comprising a transparent resin and a UV absorbing agent on at least one surface of the plate, and can be used as a multilayer light diffusing plate from -14 to 200912389. Such a multilayer light diffusing plate prevents deterioration of the board due to ultraviolet rays. Since the UV absorber to be contained in the UV absorbing layer may be a conventional UV absorber, examples thereof include a benzotriazole UV absorber, a benzophenone UV absorber, a cyanoacrylate UV absorber, malonic acid. An ester UV absorber, a grassy anilide UV absorber, an acetate UV absorber, a triterpenoid V absorber, a salicylate UV absorber, a benzoate UV absorber, and the like. As the transparent resin contained in the UV absorbing layer, a methyl methacrylate resin or a styrene resin is preferably used, and a methyl methacrylate monostyrene copolymer is more preferably used. The methyl methacrylate resin means a polymer comprising at least 50% by weight of methyl methacrylate units constituting the monomer unit of the methyl methacrylate resin, and may be methyl methacrylate. a polymer, or a copolymer comprising 50% by weight or more of methyl methacrylate and 50% by weight or less of other monomers copolymerizable with methyl methacrylate. Examples of the other monomer copolymerizable with methyl methacrylate include methacrylate other than methyl methacrylate (e.g., ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, Octadecyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, adamantyl methacrylate, tricyclomethacrylate Ester ester, decyl methacrylate, decyl methacrylate, methyl methacrylate, etc., acrylate (eg methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, benzene acrylate) Ester, benzyl acrylate, 2·ethylhexyl acrylate, 2- 0.001- 200912389 hydroxyethyl ester, tricyclodecyl acrylate, etc.), unsaturated acids (eg methacrylic acid, acrylic acid, etc.), Acrylonitrile, methacrylonitrile, maleic acid, phenyl maleimide, cyclohexyl maleimide, glutaric anhydride, pentaneimine, styrene monomer, And analogues Used alone or in two or more thereof. As the styrene-based monomer, substituted styrene may be used in addition to styrene. The methyl methacrylate may contain glutaric anhydride unit or glutarylene The styrene-based resin means a resin containing 50 to 100% by weight of a styrene-based monomer based on the monomer unit constituting the styrene-based resin. As the styrene-based monomer, in addition to styrene Further, substituted styrene may be used. Examples of the substituted styrene include halogenated styrene such as chlorostyrene, bromostyrene, and the like; alkyl-substituted styrene such as vinyl toluene, ?-methyl Styrene, etc.; and the like. The styrene monomer may be used alone or in combination of two or more thereof. Examples of other monomers which may constitute the styrene resin include methyl methacrylate and the foregoing The other monomer of the methyl methacrylate resin (excluding styrene) may be arbitrarily exemplified. The methyl methacrylate resin or the styrene resin contained in the UV absorbing layer may be styrene and methyl propylene. a copolymer of methyl ester, that is, a methyl methacrylate-styrene copolymer. The content of the styrene unit in the methyl methacrylate-styrene copolymer is usually 5% by weight to 95% by weight, and The content of the methyl acrylate unit is usually from 95% by weight to 5% by weight. The light diffusing plate of the present invention comprises the light diffusing body defined in the above-mentioned-16-200912389 in the transparent resin. Therefore, even when the light diffusing body is contained When the temperature is low, the total light transmittance of the transparent resin can also be lowered. Since the transparent light resin whose total light transmittance has been lowered by the light diffusing body can diffuse light through the resin well, the light diffusing plate of the present invention can be used in a small amount. The light diffuser diffuses sufficiently through the light. Therefore, the present invention also provides a method for reducing the total light transmittance of the transparent resin, which comprises adding a light diffuser for use in the light diffusing plate of the present invention. The invention is illustrated by the following examples, which are not intended to limit the scope of the invention in any way. In the examples, "%" and "parts" are by weight unless otherwise indicated. Measurement of total light transmittance The total light transmittance T t was measured according to JIS K 73 6 1, using a turbid light transmittance meter (HR-100, manufactured by MURAKAMI COLOR RESEARCH LABORATORY CO., LTD.). Measurement of particle size The particles of the light diffuser were compacted on a sample stage, and carbon was vapor-deposited thereon to prepare a sample piece. The SEM photograph of the light diffusing body particles on the sample piece was obtained by using a field emission scanning electron microscope (FE-SEM S-420, manufactured by Hitachi Limited) and selecting a magnification suitable for individual particle diameters, and the magnification was obtained. 5000 times, 1 0000 times and 5 0000 -17- 200912389 times. Then, the radius of each particle is measured by a three-point circle radius method, and the diameter of the particle is calculated from the measured radius. Standard difference between average particle diameter and particle diameter In the above measurement method of the particle diameter, 40 particles were randomly selected, and the diameters of the particles were calculated. Then, the average 値 and standard deviation of the particle diameter of the light diffuser were calculated. Comparative Example 1 In 100 parts of polystyrene (HRM 40 manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59), 1 part of a refractive index of 1.43, an average particle diameter of 2.49 μm, and a standard deviation of particle diameters were added. 0.10 μηη of polyfluorene oxide particles were dry blended to obtain a resin composition. Then, the resin composition was extrusion molded at a temperature ranging from 190 to 260 ° C using a 40 mm single screw extruder equipped with a multi manifold mold (manufactured by Tanabe Plastics Co., Ltd.) to obtain a thickness. It is a 2 mm single-layer light diffuser. The total light transmittance (hereinafter referred to as "Tt") of the single-layer light diffusing plate was 5 6 · 2 %. Comparative Example 2 A single-layer light diffusing plate was produced in the same manner as in Comparative Example 1, but was gathered at 100 parts. Styrene (HRM 40 manufactured by Toyo styrene Co., Ltd.; refractive index: 1.59) was added with 1 part of a polypyrene having a refractive index of 1.43, an average particle diameter of 2.17 μηη, and a standard deviation of the particle diameter of 0-29 μηη. Oxygen particles. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 54.8%. -18- 200912389 Example 1 A single-layer light diffusing plate was fabricated in the same manner as in Comparative Example 1, but in 100 parts of polystyrene. (HRM 40 is manufactured by Toyo Styrene Co., Ltd.; refractive index: 1.59), 1 part of refractive index is 1.43, average particle diameter is 0.67 μηη, and the standard deviation of particle diameter is 〇·〇7 μιη The polycrystalline silicon oxide particles. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 49.6%. Comparative Example 3 A single-layer light diffusing plate was produced in the same manner as in Comparative Example 1, but in the case of 1 part of polyphenylene Ethylene (HRM 40 manufactured by T〇y〇Styrene co., Ltd.; refractive index: 1.59) was added with 1 part of refractive index of 1.43, average particle The polycrystalline silicon oxide particles having a diameter of 0.12 μηη and a standard deviation of the particle diameter of 〇·01. The Tt of the single-layer light-diffusing sheet having a thickness of 2 mm was 55.0%. Comparative Example 4 Manufactured in the same manner as in Comparative Example 1. A single-layer light diffusing plate' but with 1 part of polystyrene (HRM 40 manufactured by T〇y〇Styrene c〇·, Ltd.; refractive index: 1.59) with 1 refractive index of 1 · 4 9. Acrylic resin particles having an average particle diameter of 2.44 μηη and a standard deviation of the particle diameter of 0.52 μm. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 69.3%. Example 2 and Comparative Example 1 In the same way, a single-layer light diffusing plate is manufactured, but -19-200912389 square < 100 parts of the poly-beneficiary (HRM 40 is made by Toyo Styrene Co., Ltd.; refractive index: 1.59) One part of the acrylic resin particle having a refractive index of 1.49, an average particle diameter of 〇·85 μηη, and a standard deviation of the particle diameter of 〇.〇3 μιη. The single-layer light diffusing plate having a thickness of 2 mm is 1 55.1%. Comparative Example 5 A single-layer light diffusing plate was produced in the same manner as in Comparative Example 1, but in 100 parts of polystyrene (HRM 40 by Toyo S Manufactured by tyrene Co., Ltd.; refractive index·· 1. 5 9) Adding 1 part of acrylic acid having a refractive index of 1.4 9 and an average particle diameter of 0.5·5 μηα and a standard deviation of particle diameter of 〇.04 μπ1 Resin particles. The Tt of the single-layer light diffusing plate having a thickness of 2 mm was 70.2%. The results are summarized in Table 1. Table 1 Comparative Example 1 Comparative Example 2 Example 1 Comparative Example 3 Comparative Example 4 Example 2 Comparative Example 5 Average particle diameter (μιη) 2.49 2.17 0.67 0.12 2.44 0.85 0.50 Standard deviation of particle diameter (μιη) 0.14 0.29 0.07 0.02 0.52 0.03 0.04 Tt1) (%) 56.2 54.8 49.6 55.0 69.3 55.1 70.2
註：當1份光擴散體加入1 00份透明樹脂（聚苯乙烯） 時的TT 實施例3 於 100 份苯乙烯一甲基丙烯酸共聚物（TOYO STYROL® T080(由 Toyo Styrene Co.，Ltd.所製；折射率： -20- 200912389 1.59;苯乙烯單元含量：90莫耳％，且甲基丙烯酸單元含 量：10莫耳％(以NMR分析））中添加1份折射率爲1.48、 平均粒徑爲1·〇〇 μηι且粒徑之標準差爲0.05 μηι的交聯丙 烯酸系樹脂粒子，並予乾式摻合以獲得樹脂組成物。然後 使用配備有多重歧管模之40 mm單螺桿擠出機（由Tanabe Plastics Co.，Ltd.所製），以溫度範圍爲190至26 0°C擠出 模製該樹脂組成物，製得厚度爲2 mm之光擴散板。該光 擴散板之Tt爲58.8%。 以與上述相同方式製造厚度爲2mm之光擴散板，但 其中該交聯丙烯酸系樹脂粒子之數量改成1 · 5份或2 · 5 份。其Tt分別爲54.3%或50.5%。 比較實例6 以與實施例3相同之方式製造厚度爲2mm之光擴散 板，但使用1份折射率爲1.49、平均粒徑爲2.44 μιη且粒 徑之標準差爲0.52 μηι的交聯丙烯酸系樹脂粒子代替實施 例3之交聯丙烯酸系樹脂粒子。該光擴散板之Tt爲 78.0%。 以與上述相同方式製造厚度爲2 mm之光擴散板，但 其中該交聯丙烯酸系樹脂粒子之數量改成1.5份或2.5 份。其Tt分別爲69.1%或60.1%。 實施例4 以與實施例3相同之方式製造厚度爲2mm之光擴散 -21 - 200912389 板’但使用1份折射率爲1.49、平均粒徑爲0.85 μιη且粒 徑之標準差爲0.03 μιη的交聯丙烯酸系樹脂粒子代替實施 例3之交聯丙烯酸系樹脂粒子。該光擴散板之Tt爲 57.8%。 實施例5 以與實施例3相同之方式製造厚度爲2mm之光擴散 板，但使用1份折射率爲1 .4 9、平均粒徑爲0 · 72 μιη且粒 徑之標準差爲0.07 μιη的聚矽氧粒子代替實施例3之交聯 丙烯酸系樹脂粒子。該光擴散板之Tt爲5 1 . 1 %。 以與上述相同方式製造厚度爲2mm之光擴散板，但 其中該聚矽氧粒子之數量改成1.5份或2.5份。其Tt分別 爲 4 3 · 4 % 或 3 8 _ 9 %。 實施例6 以與實施例3相同之方式製造厚度爲2mm之光擴散 板，但使用1份折射率爲1 · 4 9、平均粒徑爲0 · 8 2 μιη且粒 徑之標準差爲〇·〇2 μηα的交聯丙烯酸系樹脂粒子代替實施 例3之交聯丙嫌酸系樹脂粒子。該光擴散板之Tt爲 57.7%。 以與上述相同方式製造厚度爲2 mm之光擴散板’但 其中該交聯丙烯酸系樹脂粒子之數量改成1. 5份或2.5 份。其Tt分別爲54.6%或51.1%。 -22- 200912389 實施例7 以與實施例3相同之方式製造厚度爲2mm之光擴散 板，但使用1份折射率爲1.49、平均粒徑爲0.64 μιη且粒 徑之標準差爲〇 · 〇4 μιη的交聯丙烯酸系樹脂粒子代替’實施 例3之交聯丙烯酸系樹脂粒子。該光擴散板之Tt爲 5 7.2%。 以與上述相同方式製造厚度爲2mm之光擴散板，但 其中該交聯丙烯酸系樹脂粒子之數量改成1 · 5份或2.5 份。其Tt分別爲54.3 %或5 0.4%。 實施例8 光擴散體母體混合物A之製備 將 0.04份之噚唑光學增亮劑（WHITE FLOW® PSN cone，由 SUMIKA COLOR CO.，LTD.所製）添加至 83.96 份苯乙烯一甲基丙烯酸共聚物（TOYO STYROL® T080由 Toyo Styrene Co.，Ltd.所製）、14.0份與實施例3中所使 用者相同之交聯丙烯酸系樹脂粒子、1 . 0份之U V吸收劑 (SUMISORB® 200，由 Sumitomo Chemical Co.，Ltd.所製） 加工安定劑（SUMIRIZER® GP，由 Sumitomo Chemical Co·， Ltd.所製）之混合物，並予以乾式摻合。然後使用雙螺桿 擠出機在溫度範圍爲190至25 0 °C下將該混配料粒化，以 製得呈小粒形式之光擴散體母體混合物A。 UV吸收混配料A之製備 -23- 200912389 將90.55份之苯乙烯一甲基丙烯酸甲酯共聚物 (Estyrene® MS200NT，由 Nippon Steel Chemical Co., Ltd. 所製；苯乙烯單元含量：80%;甲基丙烯酸甲酯單元含 量：20%)、8.0份之交聯丙烯酸系樹脂粒子（折射率： 1.49;平均粒徑：30 μιη)、0.2份之加工安定劑 (SUMIRIZER® GP，由 Sumitomo Chemical C〇 ·，Ltd.所 製）、l_〇 份之 UV 吸收劑（TINUVIN® 1 5 77，由 Ciba Specialty Chemicals Inc.所製）與 0.25份之加工安定劑 (MONOGLY D由NOF Corporation所製）加以乾式摻合。 然後使用雙螺桿擠出機在溫度範圍爲200至25 0°C下將該 混合物粒化，以製得呈小粒形式之UV吸收混配料A。 多層光擴散板之製造 將 90份之苯乙烯一甲基丙烯酸共聚物（TOYO STYROL® T080 由 Toyo Styrene Co.，Ltd.所製）與 10 份上 述製備之光擴散體母體混合物A加以乾式摻合。然後， 將該摻合物供應至螺桿直徑爲120 mm之擠出機，並於 2 00至250°C之溫度下熔融捏合之。另外將上述製備之UV 吸收混配料A供應至螺桿直徑爲45 mm之輔助擠出機， 並於210至250 °c之溫度下熔融捏合之。然後，在T模溫 度爲245至25 5 °C下經由一進料塊與T模將該苯乙烯一甲 基丙烯酸共聚物與光擴散體母體混配料A之摻合物的熔 體以及UV吸收混配料A之熔體共擠出，製得三層光學擴 散板’其包含厚度爲1.86 mm之光擴散板，與層合在該擴 -24- 200912389 散板兩側表面上且厚度各爲0.07 uv吸收層。此多 層光擴散板之Tt爲53.4%。 實施例9 多層光擴散板之製造 將 97份之苯乙烯一甲基丙烯酸共聚物（TOYO STYROL® T080 由 Toyo S ty r ene C 〇 _，Lt d ·所製）與 3 _ 0 份 於實施例8中製備之光擴散體母體混合物A加以乾式摻 合。然後，將該摻合物供應至螺桿直徑爲1 20 mm之擠出 機，並於200至250 °C之溫度下溶融捏合之。另外將實施 例8中製備之UV吸收混配料A供應至螺桿直徑爲45 mm 之輔助擠出機，並於210至25 0 °C之溫度下熔融捏合之。 然後，在T模溫度爲245至25 5 °C下經由一進料塊與T模 將該苯乙烯-甲基丙烯酸共聚物與光擴散體母體混合物A 之摻合物的熔體以及UV吸收混配料A之熔體共擠出，製 得三層光學擴散板，其包含厚度爲1.86 mm之光擴散板， 與層合在該擴散板兩側表面上且厚度各爲0.07 mm之UV 吸收層。此多層光擴散板之Tt爲60.6%。 實施例1 〇 UV吸收混配料B之製備 將90.55份之苯乙嫌-甲基丙嫌酸甲酯共聚物 (Estyrene® MS200NT，由 Nippon Steel Chemical Co.，Ltd. 所製；苯乙烯單元含量：80%;甲基丙烯酸甲醋單元含 -25- 200912389 量：20%)、8.0份之交聯丙烯酸系樹脂粒子（折射率·· 1.49;平均粒徑· 30 μηι)、0.2份之加工安定劑 (SUMIRIZER® GP，由 Sumitomo Chemical Co·, Ltd.所 製）、1_0份之1^吸收劑（1^31，由入〇£1<1八 CORPORATION所製）與0.25份之加工安定劑（MONOGLY D由NOF Corporation所製）加以乾式摻合。然後，使用雙 螺桿擠出機在溫度範圍爲200至250。(：下將該混合物粒 化，以製得呈小粒形式之UV吸收混配料B。 多層光擴散板之製造 將 96.8份之苯乙儲一甲基丙烯酸共聚物（TOYO STYROL® T080 由 Toyo Styrene Co·，Ltd.所製）與 3.2 份 於實施例8中製備之光擴散體母體混合物A加以乾式摻 合。然後，將該摻合物供應至螺桿直徑爲120 mm之擠出 機，並於200至25 0°C之溫度下熔融捏合之。另外將上述 製備之UV吸收混配料B供應至螺桿直徑爲45 mm之輔 助擠出機，並於2 1 0至2 5 0 °C之溫度下熔融捏合之。然 後，在T模溫度爲245至2 5 5 °C下經由一進料塊與T模將 該苯乙烯-甲基丙烯酸共聚物與光擴散體母體混合物A 之摻合物的熔體以及UV吸收混配料B之熔體共擠出，製 得三層光學擴散板，其包含厚度爲2.86 mm之光擴散板， 與層合在該擴散板兩側表面上且厚度各爲〇·〇7 mm之UV 吸收層。此總厚度爲3mm之多層光擴散板的 Tt爲 53.5%。 -26- 200912389 實施例11 多層光擴散板之製造 將88.0份之苯乙烯一甲基丙烯酸共聚物（τογο STYROL® T080 由 Toyo Styrene Co.，Ltd.所製）與 12.0 份 於實施例8中製備之光擴散體母體混合物A加以乾式摻 合。然後，將該摻合物供應至螺桿直徑爲1 2 0 mm之擠出 機，並於200至2 5 0 °C之溫度下熔融捏合之。另外將實施 例9中製備之UV吸收混配料B供應至螺桿直徑爲45 mm 之輔助擠出機，並於210至25 0 °C之溫度下熔融捏合之。 然後，在T模溫度爲245至255 °C下經由一進料塊與T模 將該苯乙烯-甲基丙烯酸共聚物與光擴散體母體混合物A 之摻合物的熔體以及UV吸收混配料B之熔體共擠出，製 得三層光學擴散板，其包含厚度爲1.61 mm之光擴散板， 與層合在該擴散板兩側表面上且厚度各爲0.07 mm之UV 吸收層。此總厚度爲1.75mm之多層光擴散板的Tt爲 52_4〇/〇。 實施例1 2 光擴散體母體混合物B之製備 將 0.05 份噚唑光學增亮劑（WHITE FLOW® PSN cone，由 SUMIKA COLOR CO.，LTD.所製）添力口 至 83.95 份之苯乙烯—甲基丙烯酸共聚物（TOYO STYROL® Τ080 由Toyo Styrene Co·, Ltd.所製）、14.0份與實施例3中所 -27- 200912389 使用者相同之交聯丙烯酸系樹脂粒子、1.0份之uv吸收 齊[[(SUMISORB® 200 由 Sumitomo Chemical Co.，Ltd.所製） 與1.0份之加工安定劑（SUMIRIZER® GP，由 Sumitomo Chemical Co.，Ltd.所製）的混合物中，並加以乾式摻合。 然後，使用雙螺桿擠出機在溫度範圍爲190至250 °C下將 該混配料粒化，以製得呈小粒形式之光擴散體母體混合物 B。 多層光擴散板之製造 將90份之苯乙烯一甲基丙烯酸共聚物（ΤΟΥ Ο STYROL® T080 由 Toyo Styrene Co.，Ltd.所製）與 1 0.0 份 上述製備之之光擴散體母體混合物B加以乾式摻合。然 後，將該摻合物供應至螺桿直徑爲120 mm之擠出機，並 於200至25〇°C之溫度下熔融捏合之。另外將實施例10 中製備之UV吸收混配料B供應至螺桿直徑爲45 mm之 輔助擠出機，並於210至25 0 °C之溫度下熔融捏合之。然 後，在T模溫度爲2 4 5至2 5 5 °C下經由一進料塊與T模將 該苯乙烯-甲基丙烯酸共聚物與光擴散體母體混合物B之 摻合物的熔體以及UV吸收混配料B之熔體共擠出，製得 三層光學擴散板’其包含厚度爲1.36 mm之光擴散板，與 層合在該擴散板兩側表面上且厚度各爲0.07 mm之UV吸 收層。此總厚度爲1.5 mm之多層光擴散板的Tt爲 5 8.6%。 實施例3 -7與對照實例6之結果係彙總於表2。 -28- 200912389 表2 實施例編號 3 比較6 4 5 6 7 平均粒徑(μηι) 1.00 2.44 0.85 0.72 0.82 0.64 粒徑之標準差(μιη) 0.05 0.52 0.03 0.07 0.02 0.04 Tt1) (%) -l_〇 份 58.8 78.0 57.8 51.1 57.7 57.2 -1.5 份 54.3 69.1 43.4 54.6 54.3 -2.5 份 50.0 60.1 — 38.9 51.1 50.4 註：1)添加指定數量之擴散體的總透光率 實施例8 -1 2之結果係彙總於表3。 表3 實施例編號 8 9 10 11 12 平均粒徑(μηι) 1.00 1.00 1.00 1.00 1.00 粒徑之標準差(μηι) 0.05 0.05 0.05 0.05 0.05 厚度(mm) 2.0 2.0 3.0 1.75 1.5 擴散體之數量(份） 1.42 0.42 0.45 1.68 1.40 Tt (%) 53.4 60.6 53.5 52.4 58.6 【圖式簡單說明】 圖1係一彩色液晶顯示器實例之示意橫剖面圖。 【主要元件符號說明】 1 :液晶單元 2 :偏光片 3 :濾色板 -29- 200912389 4 :影像顯示器 5 :光源 6 :光擴散板 -30Note: TT Example 3 when 1 part of the light diffuser was added to 100 parts of transparent resin (polystyrene) to 100 parts of styrene-methacrylic acid copolymer (TOYO STYROL® T080 (by Toyo Styrene Co., Ltd.) Made; refractive index: -20- 200912389 1.59; styrene unit content: 90 mol%, and methacrylic acid unit content: 10 mol% (by NMR analysis)) added 1 part of refractive index of 1.48, average grain Crosslinked acrylic resin particles having a diameter of 1·〇〇μηι and a standard deviation of the particle diameter of 0.05 μηι, and dry blending to obtain a resin composition, and then using a 40 mm single screw extrusion equipped with a multi-manifold mold The resin composition (manufactured by Tanabe Plastics Co., Ltd.) was extrusion-molded at a temperature ranging from 190 to 260 ° C to obtain a light diffusing plate having a thickness of 2 mm. 58.8%. A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, but the number of the crosslinked acrylic resin particles was changed to 1.5 parts or 2.5 parts, and the Tt thereof was 54.3% or 50.5%, respectively. Comparative Example 6 An optical expansion having a thickness of 2 mm was produced in the same manner as in Example 3. For the plate, one portion of the crosslinked acrylic resin particles of Example 3 was used instead of the crosslinked acrylic resin particles having a refractive index of 1.49, an average particle diameter of 2.44 μηη, and a standard deviation of the particle diameter of 0.52 μη. Tt was 78.0%. A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, but the number of the crosslinked acrylic resin particles was changed to 1.5 parts or 2.5 parts, and the Tt thereof was 69.1% or 60.1%, respectively. Example 4 A light-diffusion-21 - 200912389 plate having a thickness of 2 mm was produced in the same manner as in Example 3 except that 1 part of cross-linking having a refractive index of 1.49, an average particle diameter of 0.85 μm, and a standard deviation of particle diameter of 0.03 μm was used. The acrylic resin particles were used in place of the crosslinked acrylic resin particles of Example 3. The Tt of the light diffusing plate was 57.8%. Example 5 A light diffusing plate having a thickness of 2 mm was produced in the same manner as in Example 3, but using 1 part. The polyfluorene oxide particles having a refractive index of 1.49 and an average particle diameter of 0·72 μηη and a standard deviation of the particle diameter of 0.07 μηη were substituted for the crosslinked acrylic resin particles of Example 3. The Tt of the light diffusing plate was 5 1 . 1 %. A light diffusing plate having a thickness of 2 mm was produced, but the number of the polycrystalline silicon oxide particles was changed to 1.5 parts or 2.5 parts, and the Tt thereof was 4 3 · 4 % or 3 8 _ 9 %, respectively. 3 A light diffusing plate having a thickness of 2 mm was produced in the same manner, but using 1 part of crosslinked acrylic acid having a refractive index of 1 · 4 9 and an average particle diameter of 0 · 8 2 μηη and a standard deviation of particle diameter of 〇·〇2 μηα The resin particles were used in place of the crosslinked acrylic acid resin particles of Example 3. The light diffusing plate had a Tt of 57.7%. 5份或2.5份。 The light-transmitting plate of a thickness of 2 mm was produced in the same manner as above, but the number of the cross-linked acrylic resin particles was changed to 1.5 parts or 2.5 parts. Its Tt is 54.6% or 51.1%, respectively. -22- 200912389 Example 7 A light diffusing plate having a thickness of 2 mm was produced in the same manner as in Example 3 except that 1 part of the refractive index was 1.49, an average particle diameter was 0.64 μm, and the standard deviation of the particle diameter was 〇·〇4. The crosslinked acrylic resin particles of μιη were replaced by the crosslinked acrylic resin particles of Example 3. The light diffusing plate had a Tt of 5 7.2%. A light diffusing plate having a thickness of 2 mm was produced in the same manner as above, except that the number of the crosslinked acrylic resin particles was changed to 1.5 parts or 2.5 parts. Its Tt is 54.3 % or 5 0.4%, respectively. Example 8 Preparation of Light Diffusion Body Matrix Mixture A 0.04 part carbazole optical brightener (WHITE FLOW® PSN cone, manufactured by SUMIKA COLOR CO., LTD.) was added to 83.96 parts of styrene-methacrylic acid copolymer. (TOYO STYROL® T080, manufactured by Toyo Styrene Co., Ltd.), 14.0 parts of the same crosslinked acrylic resin particles as those of the user of Example 3, and 1.0 part of UV absorber (SUMISORB® 200, A mixture of a stabilizer (SUMIRIZER® GP, manufactured by Sumitomo Chemical Co., Ltd.) was processed by Sumitomo Chemical Co., Ltd., and dry blended. The compound was then granulated using a twin-screw extruder at a temperature ranging from 190 to 260 ° C to produce a light diffuser precursor mixture A in the form of small particles. Preparation of UV Absorbing Compound A-23-200912389 90.55 parts of a styrene-methyl methacrylate copolymer (Estyrene® MS200NT, manufactured by Nippon Steel Chemical Co., Ltd.; styrene unit content: 80%; Methyl methacrylate unit content: 20%), 8.0 parts of crosslinked acrylic resin particles (refractive index: 1.49; average particle diameter: 30 μm), and 0.2 parts of processing stabilizer (SUMIRIZER® GP, by Sumitomo Chemical C 〇·, Ltd.), a UV absorber (TINUVIN® 1 5 77, manufactured by Ciba Specialty Chemicals Inc.) and 0.25 parts of a processing stabilizer (MONOGLY D manufactured by NOF Corporation) Dry blending. The mixture was then granulated using a twin-screw extruder at a temperature ranging from 200 to 260 ° C to produce a UV absorbing compound A in the form of pellets. Production of multilayer light-diffusing sheet 90 parts of styrene-methacrylic acid copolymer (TOYO STYROL® T080 manufactured by Toyo Styrene Co., Ltd.) and 10 parts of the above-prepared light diffusing body precursor mixture A were dry blended. . Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and melt-kneaded at a temperature of 200 to 250 °C. Further, the UV absorbing compound A prepared above was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 250 °C. Then, the melt and UV absorption of the blend of the styrene-methacrylic acid copolymer and the light diffusing body precursor A are fed through a feed block and a T-die at a T-die temperature of 245 to 25 5 °C. The melt of the compound A was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 1.86 mm, and laminated on both sides of the expanded plate of the -24-200912389 and having a thickness of 0.07 each. Uv absorbing layer. The multi-layer light diffusing plate had a Tt of 53.4%. Example 9 Production of Multilayer Light-Diffusing Plate 97 parts of styrene-methacrylic acid copolymer (TOYO STYROL® T080 manufactured by Toyo Sty r ene C 〇, Lt d ·) and 3 _ 0 parts in Examples The light diffuser precursor mixture A prepared in 8 was dry blended. Then, the blend was supplied to an extruder having a screw diameter of 20 mm, and kneaded at a temperature of 200 to 250 °C. Further, the UV absorbing compound A prepared in Example 8 was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 0.25 °C. Then, the melt and UV absorption of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture A are fed through a feed block and a T-die at a T-die temperature of 245 to 25 5 °C. The melt of the batch A was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 1.86 mm, and a UV absorbing layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. The multilayer light diffusing plate had a Tt of 60.6%. Example 1 Preparation of 〇UV absorbing compound B 90.55 parts of styrene-methyl propyl methacrylate copolymer (Estyrene® MS200NT, manufactured by Nippon Steel Chemical Co., Ltd.; styrene unit content: 80%; methyl methacrylate unit containing -25- 200912389 amount: 20%), 8.0 parts of crosslinked acrylic resin particles (refractive index · 1.49; average particle size · 30 μηι), 0.2 parts of processing stabilizer (SUMIRIZER® GP, manufactured by Sumitomo Chemical Co., Ltd.), 1% by weight of absorbent (1^31, manufactured by 〇1 <1), and 0.25 parts of processing stabilizer (MONOGLY) D was dry blended by NOF Corporation. Then, a twin screw extruder was used at a temperature ranging from 200 to 250. (The mixture was granulated to obtain a UV absorbing compound B in the form of pellets. The manufacture of a multilayer light diffusing plate was 96.8 parts of phenylethyl methacrylate copolymer (TOYO STYROL® T080 by Toyo Styrene Co , manufactured by Ltd.), dry blended with 3.2 parts of the light diffuser precursor mixture A prepared in Example 8. Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and at 200 Melt-kneaded at a temperature of 250 ° C. The UV-absorbing compound B prepared above was supplied to an auxiliary extruder having a screw diameter of 45 mm and melted at a temperature of 210 to 250 ° C. Kneading. Then, the melt of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture A is fed through a feed block and a T-die at a T-die temperature of 245 to 2 5 5 °C. And the melt co-extrusion of the UV absorbing compound B, to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 2.86 mm, laminated on both sides of the diffusing plate and having a thickness of 〇·〇 7 mm UV absorbing layer. The Tt of the multilayer light diffusing plate with a total thickness of 3 mm is 53.5%. 200912389 Example 11 Production of multilayer light-diffusing sheet 88.0 parts of styrene-methacrylic acid copolymer (τογο STYROL® T080 manufactured by Toyo Styrene Co., Ltd.) and 12.0 parts of light prepared in Example 8 were diffused. The bulk matrix mixture A is dry blended. Then, the blend is supplied to an extruder having a screw diameter of 120 mm and melt-kneaded at a temperature of 200 to 250 ° C. Further examples The UV-absorbing compound B prepared in 9 is supplied to an auxiliary extruder having a screw diameter of 45 mm, and is melt-kneaded at a temperature of 210 to 250 ° C. Then, at a T-die temperature of 245 to 255 ° C The melt of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture A and the melt of the UV absorbing compound B are co-extruded through a feed block and a T-die to obtain a three-layer optical a diffusing plate comprising a light diffusing plate having a thickness of 1.61 mm and a UV absorbing layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. The Tt of the multilayer light diffusing plate having a total thickness of 1.75 mm is 52_4〇/〇. Example 1 2 Preparation of light diffuser precursor mixture B Add 0.05 part of carbazole optical brightener (WHITE FLOW® PSN cone, manufactured by SUMIKA COLOR CO., LTD.) to 83.95 parts of styrene-methacrylic acid copolymer (TOYO STYROL® Τ080 by Toyo Styrene 14.0 parts of the crosslinked acrylic resin particles which are the same as those of the user of -27-200912389 in Example 3, and 1.0 part of the uv absorption [[(SUMISORB® 200 by Sumitomo Chemical Co., Ltd.) was mixed with 1.0 part of a processing stabilizer (SUMIRIZER® GP, manufactured by Sumitomo Chemical Co., Ltd.) and dry blended. Then, the compound was granulated using a twin-screw extruder at a temperature ranging from 190 to 250 ° C to prepare a light diffuser precursor mixture B in the form of small particles. Production of a multilayer light-diffusing sheet 90 parts of a styrene-methacrylic acid copolymer (manufactured by Toyo Styrene Co., Ltd.) and 10.0 parts of the light diffuser precursor mixture B prepared above were used. Dry blending. Then, the blend was supplied to an extruder having a screw diameter of 120 mm, and melt-kneaded at a temperature of 200 to 25 °C. Further, the UV absorbing compound B prepared in Example 10 was supplied to an auxiliary extruder having a screw diameter of 45 mm, and melt-kneaded at a temperature of 210 to 0.25 °C. Then, the melt of the blend of the styrene-methacrylic acid copolymer and the light diffuser precursor mixture B is passed through a feed block and a T-die at a T-die temperature of 2 4 5 to 2 5 5 ° C and The melt of the UV-absorbing compound B was co-extruded to obtain a three-layer optical diffusing plate comprising a light diffusing plate having a thickness of 1.36 mm, and a UV layer laminated on both sides of the diffusing plate and having a thickness of 0.07 mm. Absorbing layer. The multilayer light diffusing plate having a total thickness of 1.5 mm has a Tt of 58.6%. The results of Examples 3-7 and Comparative Example 6 are summarized in Table 2. -28- 200912389 Table 2 Example No. 3 Comparison 6 4 5 6 7 Average particle size (μηι) 1.00 2.44 0.85 0.72 0.82 0.64 Standard deviation of particle size (μιη) 0.05 0.52 0.03 0.07 0.02 0.04 Tt1) (%) -l_ 558.8 78.0 57.8 51.1 57.7 57.2 -1.5 parts 54.3 69.1 43.4 54.6 54.3 -2.5 parts 50.0 60.1 — 38.9 51.1 50.4 Note: 1) Adding the total light transmittance of the specified number of diffusers Example 8 -1 2 results are summarized In Table 3. Table 3 Example No. 8 9 10 11 12 Average particle size (μηι) 1.00 1.00 1.00 1.00 1.00 Standard deviation of particle size (μηι) 0.05 0.05 0.05 0.05 0.05 Thickness (mm) 2.0 2.0 3.0 1.75 1.5 Number of diffusers (parts) 1.42 0.42 0.45 1.68 1.40 Tt (%) 53.4 60.6 53.5 52.4 58.6 [Simple description of the drawing] Fig. 1 is a schematic cross-sectional view showing an example of a color liquid crystal display. [Main component symbol description] 1 : Liquid crystal cell 2 : Polarizer 3 : Color filter -29- 200912389 4 : Image display 5 : Light source 6 : Light diffuser -30