200936677 九、發明說明 【發明所屬之技術領域】 本發明係關於高耐光、高耐熱、低吸水、高亮度、高 光擴散之光擴散板及其所使用之樹脂組成物。 . 【先前技術】 以樹脂爲主要材料之具有光擴散透過性之光擴散板係 〇 可得到均勻的亮度面。因此，光擴散板係廣泛地使用於照 明遮板、內部照明式看板、透過型顯示器等之用途。近年 來，液晶顯示器或液晶電視之直下型背光用之面光源體之 光擴散板之需求增加。 光擴散板係爲最適合發揮上述機能，要求儘可能不使 光線直進而使散亂，並且儘可能由散亂而抑制光透過損失 〇 爲得到使表現如此要求特性之光擴散板，藉由添加碳 G 酸鈣、硫酸鋇、氧化鈦、氧化矽、滑石、雲母、氫氧化鋁 、氧化鎂等之無機系粒子於透明樹脂之方法、添加苯乙烯 系聚合物粒子、丙烯酸系聚合物粒子、矽氧烷系聚合物粒 子等之部份交聯之聚合物微粒子之方法、或倂用此等之方 法，採用由添加物使光散射之方法（例如參考專利文獻1 至3)。 作爲光擴散板所使用之透明樹脂，可列舉丙烯酸樹脂 、聚碳酸酯、另外，甲基丙烯酸甲酯-苯乙烯共聚物，但 此等不具有滿足耐熱性、硬度、吸水性面上之物性。另外 -5- 200936677 ’專利文獻4、5中揭示配合擴散劑於苯乙烯系單體與甲 基丙烯酸共聚物之方法，關於耐熱性提升雖被改善，但因 爲苯乙烯系單體爲主要成份，所以耐光性差，倂用另外設 有紫外線吸收層等之方法。另外，專利文獻6係揭示含甲 基丙烯酸甲酯-苯乙烯系共聚物與甲基丙烯酸-苯乙烯系共 聚物之高耐熱性樹脂組成物。 [專利文獻1]特許3 1 95543公報 [專利文獻2]特許3195544公報 ^ Ο [專利文獻3]特許25 1 2544公報 [專利文獻4]特開2006-124522號公報 [專利文獻5]特開2007-2 1 9456號公報 [專利文獻6]特開2002-053720號公報 【發明內容】 發明之揭示 發明所欲解決之課題 q 最近，達成提升液晶顯示器或液晶電視之構件特性中 ，因爲使用丙烯樹脂之光擴散板具有高吸水性，所以背光 點燈時之反翹成爲問題。 另外，顯示器使用中，因爲背光發熱，所以其正上方 之光擴散板亦要求耐熱性。但是，先前技術之丙烯酸樹脂 係不能滿足該特性者。 另外，耐熱苯乙烯樹脂雖改善吸水性及耐熱性，但耐 光性差，於長期之背光照射下發生著色或機械物性降低， -6 - 200936677 作爲顯示器時之顏色不均或斷裂。 如上所述，先前技術的光擴散板係不能充份地滿足作 爲以高耐光、高亮度、高光擴散、低吸水爲必要之光擴散 板之機能者。 . 本發明係有鑑於上述課題所實施者，以提供高耐光、 _ 高耐熱、高效低吸水、高亮度、高光擴散之光擴散板爲目 的。 ❹ 課題之解決手段 本發明者努力檢討的結果，發現藉由使用具有特定組 成之甲基丙烯酸甲酯-苯乙烯系共聚物、甲基丙烯酸-苯乙 烯系共聚物及光擴散劑而成之光擴散板用樹脂組成物所成 形之光擴散板，可達成上述目的，達成完成本發明。 有關本發明之光擴散板用樹脂組成物其特徵係以相對 於100重量份之配合20至80重量份之甲基丙烯酸甲酯-〇 苯乙烯系共聚物、80至20重量份之甲基丙烯酸-苯乙烯系 共聚物而成之樹脂組成物，配合0.1至10.0重量份之光擴 散劑。 上述甲基丙烯酸甲酯-苯乙烯系共聚物中苯乙烯系單 位之含有率爲30至80重量％，甲基丙烯酸-苯乙烯系共聚 物中苯乙烯系單位之含有率爲80至98重量％爲宜。另外 ，上述光擴散劑係部份交聯之矽氧烷系聚合物粒子、丙烯 酸系聚合物粒子或碳酸鈣，粒徑爲1至ΙΟμπι爲宜。 另外’本發明係關於將上述光擴散板用樹脂組成物， 200936677 藉由熔融擠壓成形或射出成形，成形成厚度爲0.5至3mm 之板狀之光擴散板。 本發明之光擴散板用樹脂組物使用之甲基丙烯酸甲 酯-苯乙烯系共聚物及甲基丙烯酸-苯乙烯系共聚物（以下 ，總稱兩者爲共聚物）之製造法係使用完全混合型反應器 之連續塊狀聚合法或連續溶液聚合法’就保持組成或分子 量均勻性及良好外觀上係適宜’但亦可爲批式的塊狀或溶 液聚合。聚合時，以使開始劑存在爲宜，作爲開始劑係可 使用通常自由基聚合使用之過氧化物及/或偶氮化合物。 另外，爲調節分子量，添加適量的如烷基硫醇之鏈轉移劑 亦無妨。聚合結束後，由常法脫氣、進行製錠化等之處理 ，可得到使用本發明之光擴散板用樹脂組成物使用之共聚 物。 甲基丙烯酸甲酯-苯乙烯系共聚物中苯乙烯系單位之 含有率爲30至80重量％，以45至75重量％爲宜。甲基 丙烯酸甲酯-苯乙烯系共聚物中苯乙烯系單位之比率若未 滿3 0重量％時，因爲最終組成物具有高吸濕性，所以容易 成爲引起反翹之材料’若超過80重量％時’耐光性能有容 易變差之趨勢。 另外，甲基丙烯酸-苯乙烯系共聚物中苯乙烯系單位 之含有率爲80至98重量％ ’以85至93重量％爲宜。甲 基丙烯酸-苯乙烯系共聚物中甲基丙烯酸單位之比率若未 滿2重量％時，耐熱性有過低之趨勢，若超過20重量％時 ，聚合時因交聯之凝膠發生量過剩’表面容易成爲具有走 -8- 200936677 紋之薄片。 在此，苯乙烯系單位係構成上述共 位，亦稱爲爲了製造共聚物所使用之來 單位。 接著，配合此等共聚物，構成產生 成物之樹脂組成物（樹脂成份）所含之 有率爲50至77重量％，甲基丙烯酸甲 1〇至40重量％，甲基丙烯酸單位之含$ %者爲宜。區別光擴散板用樹脂組成物 成物（樹脂成份）時，稱前者爲光擴散 稱後者爲樹脂組成物。 作爲此甲基丙烯酸甲酯-苯乙烯系 酸-苯乙烯系共聚物中苯乙烯系單位， ，有取代苯乙烯單位類，亦可具有1種 有效的是苯乙烯單位。 作爲提供如此苯乙烯系單位之單體 如氯苯乙烯、溴苯乙烯之鹵化苯乙烯類 α-甲基苯乙烯之烷基苯乙烯類等之取代 另外，關於甲基丙烯酸甲酯-苯乙 具有少量的甲基丙烯酸甲酯單位以外之 )丙烯酸酯類單位。作爲提供（甲基） 單體，可列舉甲基丙烯酸乙酯、甲基丙 烯酸環己酯、甲基丙烯酸十八烷基酯、 甲基丙烯酸苯甲酯、甲基丙烯酸十八烷 聚物之苯乙烯系單 自苯乙烯系單體之 光擴散板用樹脂組 苯乙烯系單位之含 酯單位之含有率爲 率爲3至10重量 及構成其之樹脂組 板用樹脂組成物， 共聚物及甲基丙烯 苯乙烯系單位之外 以上之此等單位。 ，苯乙烯除外，有 、如乙烯基甲苯、 :苯乙烯類。 嫌系共聚物，亦可 1種以上之（甲基 丙烯酸酯類單位之 烯酸丁酯、甲基丙 甲基丙烯酸苯酯、 基酯、甲基丙烯酸 -9- 200936677 2-乙基己酯等之甲基丙烯酸酯類、丙烯酸甲酯、丙烯酸乙 酯、丙烯酸丁酯、丙烯酸環己酯、丙烯酸苯酯、丙烯酸苯 甲酯、丙烯酸2-乙基己酯等之丙烯酸酯類等。 本發明中所使用之甲基丙烯酸甲酯-苯乙烯系共聚物 及甲基丙烯酸-苯乙烯系共聚物係由已知方法聚合製造。 此甲基丙烯酸甲酯-苯乙烯系共聚物及甲基丙烯酸-苯乙烯 系共聚物之重量平均分子量係以皆爲10000至400000爲 宜。若未滿100000時，流動性變高，將難以控制薄片厚 度。另外，若爲400000以上時，流動性低，不得不提升 成形溫度，造成著色。 另外，上述2種共聚物之熔融流率係分別於0.5至 3.0g/10min之範圍爲宜。以0.5至2.5/10min尤佳。熔融 流率若高於3.0 g/10min時，容易形成厚度不均勻的薄片 ，熔融流率若未滿〇.5g/10min時，因流動性過低，將難以 成形。 另外，此光擴散板用樹脂組成物之維卡軟化溫度（ Vicat Softening Temperature，VST)係 103 °C 以上，以 105 至130°C爲宜。維卡軟化溫度若未滿103 °C時，因爲對背 光之發熱之耐熱性低，所以容易發生基材之變形等。 另外，上述光擴散板用樹脂組成物係吸水率爲0.30% 以下，以0.25%以下爲宜。吸水率若超過0.30%時，容易 發生因吸水而反翹之問題。 有關本發明之光擴散板用樹脂組成物，相對於1 〇〇份 (重量份）之配合20至80重量份之甲基丙烯酸甲酯-苯 -10- 200936677 乙烯系共聚物、80至20重量份之甲基丙烯酸-苯乙烯系共 聚物而成之樹脂組成物，配合光擴散劑，使存在0.1至 10.0份，以0.2至5.0份爲宜所得。配合量若未滿0.1份 時，因爲缺乏光源之隱蔽性，所以將成爲起因於背光光源 . 之影像而明顯亮度不均之光擴散板。若超過10.0份時， 透過光量將不足，成爲明度不足之光擴散板。 作爲光擴散劑，雖可使用已知之微粒子，但以粒徑爲 @ 1至ΙΟμπι之部份交聯之矽氧烷系聚合物粒子、丙烯酸系 聚合物粒子或碳酸鈣爲宜。此等擴散劑係可僅使用1種， 亦可使用數種。另外，作爲其他擴散劑，雖亦可倂用硫酸 鋇、氧化鈦、氧化矽、滑石、雲母、氫氧化鋁、氧化鎂等 之無機系粒子或苯乙烯系聚合物粒子，但以未滿擴散劑之 5 0重量％爲宜。 混合共聚物與擴散劑係可以已知方法進行成爲均勻混 合物。如此操作所得之光擴散板用樹脂組成物係有效地藉 ❹ 由擠壓成形或射出成形，成形成厚度爲0.5至3mm之板狀 。厚度若未滿0.5mm時，不能確保作爲背光用擴散板之強 度。另外，厚度若超過3 mm時，因爲擴散板重量變大， 所以不能對應大型化、薄型化。將其原本狀態或切斷成規 定尺寸或進行表面處理等，作爲本發明相關之光擴散板。 然而，此製造方法係只要能滿足本發明之目的，並非特別 限定者。 本發明之光擴散板係只要由上述光擴散板用樹脂組成 物所構成，可以單一層所構成，亦可以二層以上之多層所 200936677 構成。 本發明之光擴散板係使用甲基丙烯酸甲酯-苯乙烯系 樹脂及甲基丙烯酸-苯乙烯系樹脂及擴散劑，實現高耐光 、高耐熱、高效低吸水、高亮度、高光擴散等之物性者， 於不明顯阻礙此目的之範圍時，因應需要，亦可使用防靜 電劑、抗氧化劑、難燃劑、光安定劑、紫外線吸收劑、螢 光增白劑等之各種添加劑。 發明之功效 本發明之光擴散板係使用於要求光擴散性及光透過性 平衡之用途，主要係液晶顯示器或液晶電視直下型背光用 擴散板，尤其適合伴隨大型、薄型化所要求之高耐光、耐 熱性、高硬度之用途。接著，由本發明相關之光擴散板用 樹脂組成物所得之光擴散板係高耐熱、低吸水、耐光性優 異。 用以實施發明之最佳型態 以下，由實施例具體地說明本發明，但本發明並非局 限於此等實施例者。 測定光擴散板用樹脂組成物所使用之共聚物之物性係 由下述方法進行。 (1 )分子量 使用凝膠滲透層析儀，測定聚苯乙烯換算之重量平均 -12- 200936677 分子量。 (2)共聚物中之各單位組成 甲基丙烯酸甲酯·苯乙烯系共聚物之各單位組成係由 . 熱分解型氣相層析儀之單體面積比，算出各單體單位組成 ，甲基丙烯酸-苯乙烯系共聚物之各單位組成係以電位差 自動滴定裝置滴定，算出共聚物之甲基丙烯酸單位。 ❹ (3 ) 熔融流率（MFR) 依據JIS K-7210，於200 °C，5kg之負重下進行。 (4) 維卡軟化溫度（VST) 依據JIS K-7206，進行測定。 (5 ) 吸水率 H 依據JIS K-7209，進行測定。 光擴散板之物性評估係由下述方法進行。 (1 )總光線透過率 依據JIS K7 105之B法進行。 (2 )光擴散性 以2cm間隔排列冷陰極管4支，於10mm上，平行固 定光擴散板試樣，依據目測，光源之冷陰極管未透過者以 -13- 200936677 〇，透過者以X表示。 (3 )亮度不均勻 以2cm間隔排列冷陰極管4支’於l〇mm上’平行固 定光擴散板試樣，依據目測，影像上亮度均勻者以〇’亮 度不均勻者以X，有些許不均勻，但無使用問題程度者以 △表示。 ❹ (4 )耐光性 使用以金屬鹵素燈作爲光源之促進耐光性試驗機’濾 器：KF-1 (透過波長範圍；295〜780nm)、運轉模式：連續 照射、UV照度：75mW/cm3、BP溫度：80°C 、槽內濕度 :5 0%RH、噴射：無、試驗時間：24小時、試樣厚度爲2mm 薄膜。使用分光型測色計，以透過光ΔΕ評估耐光試驗後 之試樣。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusing plate having high light resistance, high heat resistance, low water absorption, high brightness, and high light diffusion, and a resin composition used therefor. [Prior Art] A light diffusing plate having a light diffusing property using a resin as a main material can obtain a uniform brightness surface. Therefore, the light diffusing plate is widely used for applications such as a lighting shutter, an interior lighting panel, and a transmissive display. In recent years, there has been an increase in demand for a light diffusing plate for a surface light source body for a direct type backlight of a liquid crystal display or a liquid crystal television. The light diffusing plate is most suitable for exerting the above-mentioned functions, and it is required to prevent the light from being scattered as much as possible, and to suppress the light transmission loss as much as possible by scattering, so as to obtain a light diffusing plate which exhibits such a required characteristic, by adding a method of adding inorganic particles such as carbon calcium silicate, barium sulfate, titanium oxide, cerium oxide, talc, mica, aluminum hydroxide or magnesium oxide to a transparent resin, adding styrene polymer particles, acrylic polymer particles, and cerium A method of partially cross-linking polymer microparticles such as oxyalkylene polymer particles, or a method of scattering light by an additive (for example, refer to Patent Documents 1 to 3). Examples of the transparent resin used for the light-diffusing sheet include an acrylic resin, a polycarbonate, and a methyl methacrylate-styrene copolymer. However, these properties do not satisfy the physical properties such as heat resistance, hardness, and water absorption. Further, -5 - 200936677 'Patent Documents 4 and 5 disclose a method of blending a diffusing agent with a styrene monomer and a methacrylic acid copolymer, and although the heat resistance is improved, the styrene monomer is a main component. Therefore, the light resistance is poor, and a method in which an ultraviolet absorbing layer or the like is additionally provided is used. Further, Patent Document 6 discloses a highly heat-resistant resin composition containing a methyl methacrylate-styrene copolymer and a methacrylic acid-styrene copolymer. [Patent Document 1] Japanese Patent Laid-Open No. Hei. No. Hei. No. 2006-124522 (Patent Document 5). [Patent Document 6] JP-A-2002-053720 SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION The present invention has recently been made to improve the component characteristics of a liquid crystal display or a liquid crystal television because of the use of acrylic resin. The light diffusing plate has high water absorption, so that the backlash when the backlight is lit becomes a problem. In addition, in the use of the display, since the backlight generates heat, the light diffusing plate directly above it also requires heat resistance. However, the prior art acrylic resin cannot satisfy this characteristic. Further, although the heat-resistant styrene resin has improved water absorbability and heat resistance, it has poor light resistance, and coloring or mechanical properties are deteriorated under long-term backlight irradiation, and -6 - 200936677 is uneven or broken as a display. As described above, the prior art light diffusing plate cannot sufficiently satisfy the function as a light diffusing plate which is required to have high light resistance, high brightness, high light diffusion, and low water absorption. The present invention has been made in view of the above problems, and is directed to a light diffusing plate which provides high light resistance, high heat resistance, high efficiency, low water absorption, high brightness, and high light diffusion.解决 Solution of the problem As a result of intensive review, the inventors found that light by using a methyl methacrylate-styrene copolymer having a specific composition, a methacrylic acid-styrene copolymer, and a light diffusing agent The light diffusing plate formed by the resin composition for a diffusing plate can achieve the above object, and the present invention has been achieved. The resin composition for a light-diffusing sheet according to the present invention is characterized by being 20 to 80 parts by weight of a methyl methacrylate-anthracene styrene copolymer and 80 to 20 parts by weight of methacrylic acid based on 100 parts by weight. A resin composition obtained by using a styrene copolymer, and 0.1 to 10.0 parts by weight of a light diffusing agent is blended. The content of the styrene unit in the methyl methacrylate-styrene copolymer is 30 to 80% by weight, and the content of the styrene unit in the methacrylic acid-styrene copolymer is 80 to 98% by weight. It is appropriate. Further, the light diffusing agent is preferably a partially polymerized siloxane polymer particle, an acrylic polymer particle or a calcium carbonate having a particle diameter of 1 to ΙΟμπι. Further, the present invention relates to a resin composition for a light-diffusing sheet, which is formed by melt extrusion molding or injection molding to form a plate-shaped light-diffusing sheet having a thickness of 0.5 to 3 mm. The method for producing a methyl methacrylate-styrene copolymer and a methacrylic acid-styrene copolymer (hereinafter, collectively referred to as a copolymer) used in the resin composition for a light-diffusing sheet of the present invention is completely mixed. The continuous block polymerization or continuous solution polymerization of the type reactor is 'suitable for maintaining uniformity in composition or molecular weight and good appearance' but can also be batch or solution polymerization in batch mode. In the case of polymerization, it is preferred to use a starting agent, and as the starting agent, a peroxide and/or an azo compound which is usually used for radical polymerization can be used. Further, in order to adjust the molecular weight, it is also possible to add an appropriate amount of a chain transfer agent such as an alkyl mercaptan. After the completion of the polymerization, the copolymer used in the resin composition for a light-diffusing sheet of the present invention can be obtained by a process such as degassing by a usual method and tableting. The content of the styrene unit in the methyl methacrylate-styrene copolymer is preferably from 30 to 80% by weight, preferably from 45 to 75% by weight. When the ratio of the styrene unit in the methyl methacrylate-styrene copolymer is less than 30% by weight, since the final composition has high hygroscopicity, it is likely to be a material causing anti-warping. When % is used, the light resistance performance tends to deteriorate. Further, the content of the styrene unit in the methacrylic acid-styrene copolymer is preferably from 80 to 98% by weight in terms of from 85 to 93% by weight. When the ratio of the methacrylic acid unit in the methacrylic acid-styrene copolymer is less than 2% by weight, the heat resistance tends to be too low, and if it exceeds 20% by weight, the amount of gelation due to cross-linking during polymerization is excessive. 'The surface is easy to become a thin sheet with a -8-200936677 pattern. Here, the styrene unit constitutes the above-mentioned co-location, and is also referred to as a unit used for producing a copolymer. Next, with these copolymers, the resin composition (resin component) constituting the resultant product is contained in an amount of 50 to 77% by weight, from 1 to 40% by weight of methacrylic acid, and the methacrylic unit is contained in $ % is appropriate. When the resin composition (resin component) for a light diffusing plate is distinguished, the former is referred to as light diffusion, and the latter is referred to as a resin composition. The styrene-based unit of the methyl methacrylate-styrene-styrene-based copolymer may have a substituted styrene unit or may have one effective styrene unit. As a substitute for providing such a styrene unit such as chlorostyrene or a styrene group of a halogenated styrene type α-methylstyrene of bromostyrene, the methyl methacrylate-phenethyl group has A small amount of methacrylate units other than methyl methacrylate units. Examples of the (meth) monomer include ethyl methacrylate, cyclohexyl methacrylate, octadecyl methacrylate, benzyl methacrylate, and styrene methacrylate. The content ratio of the ester-containing unit of the styrene-based unit of the resin-based light-diffusing sheet of the ethylene-based styrene-based monomer is 3 to 10 parts by weight, and the resin composition for the resin composition sheet, the copolymer and the nail These units are based on units other than the propylene styrene unit. Except for styrene, such as vinyl toluene, styrene. The copolymer may be one or more kinds (methacrylate units such as butyl acrylate, phenyl propyl methacrylate, ester, methacrylic acid-9-200936677 2-ethylhexyl ester, etc.) In the present invention, methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate or the like. The methyl methacrylate-styrene copolymer and the methacrylic acid-styrene copolymer used are produced by a known method. This methyl methacrylate-styrene copolymer and methacrylic acid-benzene The weight average molecular weight of the ethylene-based copolymer is preferably from 10,000 to 400,000. If it is less than 100,000, the fluidity becomes high, and it is difficult to control the thickness of the sheet. Further, when it is 400,000 or more, the fluidity is low and it has to be improved. Further, the melt flow rate of the above two kinds of copolymers is preferably in the range of 0.5 to 3.0 g/10 min, preferably 0.5 to 2.5/10 min, and the melt flow rate is more than 3.0 g/10 min. When it is easy to form thick In the uneven sheet, if the melt flow rate is less than 5 g/10 min, the fluidity is too low, and it is difficult to form. Further, the Vicat Softening Temperature (VST) of the resin composition for the light diffusing plate is used. The temperature is 103 ° C or higher, preferably 105 to 130 ° C. If the Vicat softening temperature is less than 103 ° C, the heat resistance to heat generated by the backlight is low, so that deformation of the substrate is likely to occur. The resin composition for a diffusing plate has a water absorption of 0.30% or less, preferably 0.25% or less. When the water absorption exceeds 0.30%, the problem of rebound due to water absorption is likely to occur. 20 to 80 parts by weight of methyl methacrylate-benzene-10-200936677 ethylene copolymer, 80 to 20 parts by weight of methacrylic acid-styrene copolymer with respect to 1 part by weight (parts by weight) The resin composition is compounded with a light diffusing agent in an amount of 0.1 to 10.0 parts, preferably 0.2 to 5.0 parts. If the amount is less than 0.1 part, the backlight is lacking, so it will be caused by the backlight. Light source. When the amount is more than 10.0 parts, the amount of transmitted light will be insufficient to become a light diffusing plate having insufficient brightness. As the light diffusing agent, although known fine particles can be used, the particle size is from @1 to ΙΟμπι. It is preferred to use a crosslinked naphthenic polymer particle, an acrylic polymer particle or calcium carbonate. These diffusing agents may be used alone or in combination of several kinds, and may be used as other diffusing agents. The inorganic particles or styrene polymer particles such as barium sulfate, titanium oxide, cerium oxide, talc, mica, aluminum hydroxide or magnesium oxide are preferably used, but 50% by weight of the non-diffusion agent is preferably used. The mixed copolymer and the diffusing agent can be made into a homogeneous mixture by a known method. The resin composition for a light-diffusing sheet obtained in this manner is effectively formed by extrusion molding or injection molding to form a sheet having a thickness of 0.5 to 3 mm. If the thickness is less than 0.5 mm, the strength of the diffusing plate for backlighting cannot be ensured. In addition, when the thickness exceeds 3 mm, the weight of the diffusion plate becomes large, so that it is not suitable for enlargement and thickness reduction. The original state is either cut into a predetermined size or subjected to surface treatment or the like as a light diffusing plate according to the present invention. However, this manufacturing method is not particularly limited as long as it satisfies the object of the present invention. The light-diffusing sheet of the present invention may be composed of a single resin layer as long as it is composed of a resin composition for a light-diffusing sheet, or may be composed of two or more layers of 200936677. The light diffusing plate of the present invention uses methyl methacrylate-styrene resin, methacrylic acid-styrene resin and a diffusing agent to realize physical properties such as high light resistance, high heat resistance, high efficiency, low water absorption, high brightness, and high light diffusion. When the range of the purpose is not significantly hindered, various additives such as an antistatic agent, an antioxidant, a flame retardant, a light stabilizer, a UV absorber, and a fluorescent whitening agent may be used as needed. EFFECT OF THE INVENTION The light diffusing plate of the present invention is used for applications requiring balance of light diffusibility and light transmittance, and is mainly a liquid crystal display or a liquid crystal television direct type backlight diffusing plate, and is particularly suitable for high light resistance required for large-scale and thinning. , heat resistance, high hardness use. Then, the light-diffusing sheet obtained from the resin composition for a light-diffusing sheet according to the present invention is high in heat resistance, low in water absorption, and excellent in light resistance. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to the examples. The physical properties of the copolymer used for the resin composition for a light-diffusing sheet were measured by the following methods. (1) Molecular weight The molecular weight of the polystyrene-converted weight average -12-200936677 was measured using a gel permeation chromatography. (2) The unit composition of each unit of the methyl methacrylate-styrene copolymer in the copolymer is calculated from the monomer area ratio of the thermal decomposition type gas chromatograph, and the unit composition of each monomer is calculated. Each unit composition of the acryl-styrene-based copolymer was titrated by a potentiometric automatic titrator to calculate a methacrylic unit of the copolymer. ❹ (3) The melt flow rate (MFR) is carried out according to JIS K-7210 at 200 ° C under a load of 5 kg. (4) Vicat softening temperature (VST) Measured in accordance with JIS K-7206. (5) Water absorption rate H Measured in accordance with JIS K-7209. The physical property evaluation of the light diffusing plate was carried out by the following method. (1) Total light transmittance is carried out in accordance with the B method of JIS K7 105. (2) Light diffusivity: 4 cold cathode tubes are arranged at intervals of 2 cm, and light diffusing plate samples are fixed in parallel on 10 mm. According to visual inspection, the cold cathode tube of the light source is not transmitted through -13-200936677 〇, and the transmitted person is X. Said. (3) Uneven brightness: 2 pieces of cold cathode tube are arranged at intervals of 2 cm. 'Parallel fixed light diffusing plate sample on l〇mm. According to visual inspection, the brightness on the image is uniform. The brightness is uneven. X is slightly. It is not uniform, but the degree of no-use problem is indicated by △. ❹ (4) Light resistance using a metal halide lamp as a light source to promote light resistance tester 'Filter: KF-1 (transmission wavelength range; 295 to 780 nm), operation mode: continuous irradiation, UV illumination: 75 mW/cm3, BP temperature : 80 ° C, humidity in the tank: 50% RH, spray: none, test time: 24 hours, sample thickness of 2 mm film. The sample after the light resistance test was evaluated by transmitting light ΔΕ using a spectrophotometer.
另外，實施例及比較例中使用之簡稱係具有下述意義 U 〇 ΜΜΑ :甲基丙烯酸甲酯 ΜΑΑ :甲基丙烯酸 St :苯乙烯 開始劑：Perkadoxl2-EB20 參考例1至9 加入如表1之聚合物組成之原料單體及聚合開始劑’ -14- 200936677 於反應溫度爲120 °C，5小時滯留條件下，使用連接一槽 型完全混合反應器與去揮發槽之設備，進行連續塊狀聚合 、去揮發、製錠化，得到目的之透明共聚物。由75t成形 機（三菱重工製），將該樹脂，於樹脂溫度爲240°C進行 射出成形，得到縱50x橫75mmx厚4mm之吸水率測定用盤 、縱l〇x橫10 mmx厚4mm之VST測定試驗片。所得之共 聚物之組成係如表1記載。表1中，共聚物組成係MAA 單位/MMA單位/St單位。關於分子量及各種物性之測定結 果亦如表1所示。 [表1] 參考例 共聚物組成 (重量％比） 分子量 (Mw) MFR VST (°C ) 吸水率 (%) 1 0/0/100 310000 2.7 97 0.06 2 0/29/71 240000 1.7 98 0.17 3 0/50/50 180000 1.5 98 0.24 4 0/79/21 110000 1.2 99 0.33 5 8/0/92 230000 1.6 118 0.15 【實施方式】 [實施例] 實施例1至4及比較例1至2 將參考例製作之共聚物、及表2所示之擴散劑，以二 軸擠壓機混練、製錠化而成光擴散板用樹脂組成物。將此 光擴散板用樹脂組成物’以樹脂溫度220°C擠壓成形’製 -15- 200936677 作厚度爲2mm之光擴散板。關於所得之光擴散板之總光 線透過率、光擴散性、亮度不均勻，如表3記載。在此使 用之矽氧烷系聚合物粒子係平均粒徑爲2μιη，丙烯酸系聚 合物粒子係平均粒徑爲ΙΟμιη，碳酸鈣係平均粒徑爲1·8μιη 。表2中’簡稱矽氧烷系聚合物粒子爲矽氧烷系，簡稱丙 烯酸系聚合物粒子爲丙烯酸系，簡稱碳酸鈣爲碳鈣。配合 比係重量比。 ❹ 表2 共聚物 (Α) 共聚物 (Β)_ 配合比 (A)/(B) 擴散劑 擴散劑添 加量（phr) 實施例1 參考例5 參考例2 50/50 矽氧烷系 0.3 實施例2 參考例5 參考例3 40/60 丙烯酸系 3.0 實施例3 參考例5 參考例3 80/20 碳鈣+ 丙烯酸系 2.0 + 3.0 實施例4 參考例5 參考例4 50/50 矽氧烷系 0.2 比較例1 參考例5 參考例1 50/50 矽氧烷系 0.2 比較例2 參考例5 參考ifT 50/50 Air. Μ 0 -16- 200936677Further, the abbreviations used in the examples and comparative examples have the following meanings U 〇ΜΜΑ : methyl methacrylate ΜΑΑ : methacrylic acid St : styrene starter: Perkadoxl 2 - EB 20 Reference Examples 1 to 9 Add as shown in Table 1. Raw material monomer and polymerization initiator of polymer composition '-14- 200936677 At a reaction temperature of 120 °C, under a condition of 5 hours of residence, a continuous block is used using a device connected to a tank-type fully mixed reactor and a de-volatile tank. Polymerization, devolution, and tableting to obtain a transparent copolymer of interest. The resin was injection-molded at a resin temperature of 240 ° C by a 75 t molding machine (manufactured by Mitsubishi Heavy Industries Co., Ltd.) to obtain a water absorption rate measuring disk having a length of 50 x 75 mm and a thickness of 4 mm, and a vertical length of 10 mm x a thickness of 4 mm. The test piece was measured. The composition of the obtained copolymer is as shown in Table 1. In Table 1, the copolymer composition is MAA unit / MMA unit / St unit. The results of the measurement of the molecular weight and various physical properties are also shown in Table 1. [Table 1] Reference Example Copolymer composition (% by weight) Molecular weight (Mw) MFR VST (°C) Water absorption (%) 1 0/0/100 310000 2.7 97 0.06 2 0/29/71 240000 1.7 98 0.17 3 0/50/50 180000 1.5 98 0.24 4 0/79/21 110000 1.2 99 0.33 5 8/0/92 230000 1.6 118 0.15 [Embodiment] [Embodiment] Examples 1 to 4 and Comparative Examples 1 to 2 will be referred to. The copolymer produced in the example and the diffusing agent shown in Table 2 were kneaded by a two-axis extruder and tableted to form a resin composition for a light-diffusing sheet. The light-diffusing sheet resin composition was extruded at a resin temperature of 220 ° C to prepare a light-diffusing sheet having a thickness of 2 mm from -15 to 200936677. The total light transmittance, light diffusibility, and luminance unevenness of the obtained light diffusing plate are as shown in Table 3. The siloxane polymer-based polymer particles used herein have an average particle diameter of 2 μm, the acrylic polymer particles have an average particle diameter of ΙΟμηη, and the calcium carbonate-based average particle diameter is 1·8 μm. In Table 2, the abbreviated siloxane polymer particles are a siloxane series, and the acryl-based polymer particles are acrylic, and the calcium carbonate is carbon calcium. The ratio of the weight ratio. ❹ Table 2 Copolymer (Α) Copolymer (Β) _ Mixing ratio (A) / (B) Diffusion agent diffusing agent addition amount (phr) Example 1 Reference Example 5 Reference Example 2 50/50 Hydrazine series 0.3 Implementation Example 2 Reference Example 5 Reference Example 3 40/60 Acrylic 3.0 Example 3 Reference Example 5 Reference Example 3 80/20 Carbon Calcium + Acrylic 2.0 + 3.0 Example 4 Reference Example 5 Reference Example 4 50/50 oxirane system 0.2 Comparative Example 1 Reference Example 5 Reference Example 1 50/50 decane series 0.2 Comparative Example 2 Reference Example 5 Reference ifT 50/50 Air. Μ 0 -16- 200936677
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VST (°c ) 吸水率 (%) 總光線透 過率（％) 光擴散 性 亮度 不均勻 耐光性 △ E 實施例1 105 0.16 60 〇 〇 2 實施例2 103 0.20 57 〇 〇 2 實施例3 111 0.17 52 〇 〇 1 實施例4 106 0.24 60 〇 Δ 1 比較例1 104 0.11 59 〇 X 6 比較例2 105 0.20 91 X X 1 -17-VST (°c) Water absorption (%) Total light transmittance (%) Light diffusivity Brightness unevenness Light resistance △ E Example 1 105 0.16 60 〇〇2 Example 2 103 0.20 57 〇〇2 Example 3 111 0.17 52 〇〇1 Example 4 106 0.24 60 〇Δ 1 Comparative Example 1 104 0.11 59 〇X 6 Comparative Example 2 105 0.20 91 XX 1 -17-