200903036 九、發明說明： 【發明所屬之技術領域】 本發明係關於配置於顯示單元（液晶顯示單元）與用於 由背面照光於該顯示單元之複數支管狀光源（螢光管）之 間，且在未降低亮度之下，有用於在視覺上不會看見面光 源單元之管狀光源的各向異性擴散板’並具備該各向異性 擴散板之面光源或背光單元（垂直型背光）。 【先前技術】 在由背面照明顯示面板（液晶顯示單元等）的背光型顯 示裝置（液晶顯示裝置等）中，在顯示面板之背面配置著面 光源單元（或背光單元）。又，爲了均勻化針對顯示面板之 照射光以作爲面光源，並且提升液晶顯示裝置之正面的亮 度，則在顯示面板與面光源單元之間使用擴散薄片或稜鏡 薄片、亮度提升薄片等。在該等顯示裝置之畫面尺寸爲小 的情況下，則利用導光板、配置於該導光板之側部的管狀 光源、配置於前述導光板與顯示單元之間的擴散薄片。在 該等構造之顯示裝置中，由導光板之前面發射並擴散來自 管狀光源之光線，以照明顯示單元。然而，在該等裝置中， 由於伴隨著畫面變大而降低由導光板所發射之光線的亮 度，無法應付大畫面的顯示裝置。 另外，隨著顯示裝置（液晶電視等）的大畫面化，則利 用並列地配置用於由顯示單元之背面照光的複數支管狀光 源（螢光燈等）的面光源單元（或垂直型背光單元）。然而，在 上述垂直型背光單元中，由於並列地配置複數支管狀光源 200903036 (螢光燈等），故對應於管狀光源（螢光燈等）之部分變明亮， 來自顯示單元之前面的亮度變得不均勻化。再者，在管狀 光源之前側，依次配置對於管狀光源之遮蔽性高的光擴散 板與複數個同向性擴散膜，不僅構成零件數目多，而且使 構造複雜化。 在特開平1 1 -2706號公報（專利文獻1)中，揭示其爲在 顯示模組與投光手段之間配置光擴散透過手段的顯示裝 置，前述光擴散透過手段係在薄膜之平面上，於連續相中， 藉由以超過1之平均縱橫比將分散相於單軸方向分散的擴 散膜所構成，同時該擴散膜之分散相的長軸方向沿著螢光 管軸方向所配置的顯示裝置。在特開2002-1858號公報（專 利文獻2)中，揭示具有折射率彼此不同之連續相與粒子狀 分散相，而且前述粒子狀分散相之平均縱橫比大於1，並 以配向粒子狀分散相之長軸方向於一側方向之各向異性光 散射層（1 )，與積層於該光散射層中至少一側面上的透明樹 脂層（2)所構成之積層膜。在該文獻中，亦記載著在各向異 性光散射層（1)之雙面上積層透明樹脂層（2)、粒子狀分散相 之平均縱橫比爲5〜1 00 0、各向異性光散射層（1)與透明樹脂 層（2)之厚度比爲光散射層/透明樹脂層= 50/50〜99/1、全體 厚度爲6〜600μιη、全光線透過率爲85%以上。 然而，即使應用該等擴散膜或積層膜於垂直型背光單 元，對應於管狀光源（螢光燈等）之部分變明亮，通過擴散 板而可辨識管狀光源的存在，產生亮度不均。另外，當無 200903036 亮度不均時，則液晶顯示裝置之正面的亮度降低。 在特開20〇4 - 1 27 6 8 0號公報（專利文獻3)中，揭示在具 備並列地所配置之複數支線狀光源、反射來自光源之光的 反射板、擴散照射來自光源之直射光及來自反射板之反射 光的光擴散板的垂直型背光裝置中，光擴散板在光源側具 有截面鋸齒狀之稜鏡條列群的垂直型背光裝置。在該文獻 中，記載由含有光擴散劑之芳香族乙烯系單體與（甲基）丙 烯酸酯系單體之共聚物、或含有光擴散劑之具有脂環族構 造的聚合物樹脂構成光擴散板，並由聚苯乙烯系聚合物、 聚矽氧烷系聚合物或彼等之交聯物所構成之微粒子作爲光 擴散劑，並且記載著調製厚度2mm的光擴散板。 然而，由於該光擴散板係等方性地光擴散，故適用於 並列地配置複數支管狀光源之垂直型背光時，不能均勻化 顯示單元之正面的亮度。而且，由於接近光源而配置光擴 散板，因加熱而產生添加劑之外溢，故有光學特性降低的 情況。再者，由於必須形成稜鏡條列群，故無法提高生産 性。 在特開2 0 04-272 1 8 9號公報（專利文獻4)中，揭示其爲 含有平均粒徑爲 1~50μηι之微粒子狀光擴散劑之厚度 0.3〜3 mm的聚碳酸酯製光擴散板，以冷陰極螢光燈投影而 使亮度成爲5 000〜6000cd/m2的範圍時，亮度不均爲3%以 下的聚碳酸酯製垂直型背光用光擴散板。在特開 2004-29091號公報（專利文獻5)中，揭示藉由以碳酸酯樹脂 200903036 99.7〜80重量％及平均粒徑1〜30/zm之透明微粒子0_3〜20 重量％之合計100重量份、與螢光增白劑0.0005~0.1重量 份所構成之樹脂組成物所形成之厚度〇_5〜3mm的聚碳酸酯 樹脂製垂直型背光用光擴散板。 然而，由於彼等光擴散板係等方性地進行光擴散，故 應用於並列地配置複數支管狀光源的垂直型背光時，無法 均勻化來自顯示單元之正面的亮度。 專利文獻1 :特開平1 1 -2 706號公報（申請專利範圍） 專利文獻2 :特開2 0 0 2 - 1 8 5 8號公報（申請專利範圍） 專利文獻3:特開2004- 1 27680號公報（申請專利範圍、 段落編號[〇〇〇9]、實施例） 專利文獻4 :特開2004-272 1 89號公報（申請專利範圍） 專利文獻5 :特開2004-2909 1號公報（申請專利範圍） 【發明內容】 發明所欲解決之課題 因此，本發明之目的在於提供即使適用於垂直型背 光，亦不會看見管狀光源（螢光燈等），可均勻化來自顯示 單元之亮度的垂直型背光用光擴散板及使用該光擴散板的 背光單元（垂直型背光）。 本發明之其他目的在於提供即使應用於垂直型背光， 亦顯示耐久性高且經過長期間仍安定之光擴散特性的垂直 型背光用光擴散板及使用該光擴散板之背光單元（垂直型 背光）。 200903036 本發明之再其他目的在於可減低顯示裝置之構成零件 數目，同時可簡化構造之垂直型背光用光擴散板及使用該 光擴散板的背光單元（垂直型背光）。 解決課題之手段 本發明者等，爲了達成前述課題所進行之專心一志的 硏究結果，發現使用不僅具有既定厚度，而且關於光散射 具有特定之各向異性與既定之霧度値的光擴散板時，即使 , 應用於垂直型背光，亦不會看見（或辨認）管狀光源的存在 或形狀，而且可在未特別降低亮度之下均勻化來自顯示單 元的亮度，而完成本發明。 ，本發明之各向異性擴散板係以具有折射率彼此不 同之連續相與粒子狀分散相，而且粒子狀分散相之平均縱 橫比大於1，並以配向粒子狀分散相之長軸方向於一側方 向的各向異性散射層所構成。因而，各向異性擴散板係用 來配置於顯示單元與用於由背面照光該顯示單元之複數支 管狀光源之間而使用，在顯示散射角0與散射光強度F之 關係的散射特性F(0)中，於粒子狀分散相之長軸方向之光 散射特性爲Fx( 0 )、相對於粒子狀分散相之長軸方向垂直 之方向的散射特性爲Fy( 0 )時，在散射角0 =18°之各向異 性度 F18(Fy(l 8°)/Fx(l 8°))>2(例如，各向異性度 Fl8 = 2.5~5)，霧度値爲95%以上、厚度爲0.5〜5mm。 前述各向異性散射層係可由例如熱可塑性樹脂之各種 成形材料所形成。較具體而言，各向異性散射層亦可包含 -10- 200903036 (1)構成連續相之聚烯烴系樹脂、與構成粒子狀分散相之聚 苯乙烯系樹脂；或（2)構成連續相之聚碳酸酯系樹脂、與構 成粒子狀分散相之聚烯烴系樹脂。又，各向異性散射層亦 可包含構成連續相之碳酸酯系樹脂、與構成粒子狀分散相 之聚烯烴系樹脂。前述各向異性散射層亦可進一步包含相 溶化劑。連續相與分散相之比例亦可爲連續相/分散相=99 /1〜3 0/7 0(重量比）左右。各向異性散射層係可朝向管狀光源 之長軸方向配置粒子狀分散相的長軸方向。各向異性擴散 板亦可由各向異性散射層、與積層於該各向異性散射層中 至少一側面、特別是雙面上的透明樹脂層所構成。 本發明亦包含具備互相並列地配置之複數支管狀光 源，與在彼等管狀光源與顯示單元之間、朝向管狀光源之 長軸方向配置粒子狀分散相之長軸方向之前述各向異性擴 散板的背光單元（垂直型背光單元）。在該背光單元中，複 數支管狀光源之間隔爲W、管狀光源與各向異性擴散板之 距離爲L時，各向異性度Fl8>(W/L)亦可。又，前述顯示單 兀亦可爲液晶顯不單元。 再者’本發明亦包含前述背光單元、可藉由以該背光 單元照光之顯示單元所構成的顯示裝置。 發明效果 於本發明中，由於以連續相與粒子狀分散相構成各向 異性散射層’並且具有特定之各向異性與霧度値以及厚 度’即使適用於垂直型背光，亦不會看見管狀光源（螢光燈 -11 - 200903036 等），而可均勻化來自顯示單元的亮度。又，以特定之樹脂 形成各向異性散射層時，即使適用於垂直型背光，亦顯示 無添加劑之外溢、耐久性高、且經過長期時間爲安定的光 擴散特性。再者，由於可由各向異性擴散板達成習知光擴 散板及擴散膜的機能，故可減低顯示裝置之構成零件數 目，同時可簡單化構造。因此，光擴散板亦有用作爲背光 單元（垂直型背光）的構成零件。 【實施方式】 以下，參照附加圖式，並且詳細說明本發明。 第1圖係顯示本發明之垂直型背光單元（或面光元裝 置），與具備該單元之液晶顯示裝置之一範例的槪略分解截 面圖；第2圖係顯示光擴散板與管狀.光源之關係的模式圖。 液晶顯不裝置（液晶電視等）係以液晶顯示單元1、與用 於由背面照光該液晶顯示單元1之垂直型背光單元（或面光 源裝置）2 1所構成；液晶顯示單元1具備液晶胞2、設置於 該液晶胞2前面之第1偏光板7、與設置於前述液晶胞2 背面之第2偏光板12。液晶胞2係以一對透明零件（玻璃板 等）3a、3b;形成於彼等透明電極之相對方向面、亦可具備 配向膜之一對透明電極（ITO透明電極等）4 a、4b ;與封裝於 彼等之一對透明電極間的液晶5所構成；在彩色液晶顯示 裝置中係相對於液晶而在背面側之透明電極與透明零件之 間裝設著彩色濾光片6。 又，第1偏光板7係由偏光層8、設置於該偏光層8 -12- 200903036 之雙面的保護層9a、9b、彼等保護層中積層位於前方方向 (或液晶顯示單元之前面側）之一者的保護層9a之抗反射層 1 〇 '積層於另一保護層9 b的相位差膜1 1所構成。另外， 第2偏光板12係以偏光層13、設置於偏光層雙面之保護 層14a、14b、彼等保護層中積層位於前方方向之一者的保 護層1 4 a之相位差膜1 5所構成。 用於由背面照明液晶顯示單元1之背光單元2 1，具備 互相並列地所設置之複數支管狀光源（冷陰極放電管或螢 光燈）22、用於反射來自該管狀光源22之光線至管狀光源 22之前方方向的反射板23、設置於放電管（螢光燈）之前側 的光擴散板24、設置於該光擴散板前側（即，液晶顯示單元 1與光擴散板24之間）之1或複數個鏡片膜（或稜鏡薄 片）25。在該鏡片膜中於液晶顯示單元1側的表面上，爲了 將擴散光集光以照明顯示單元1，故形成截面形狀爲鋸齒 狀之凹凸列（或截面三角形狀之微小稜鏡列）25a。 在該等裝置中，來自前述管狀光源22之光線係藉由光 擴散板24擴散，而照明顯示單元。然而，一般而言，來自 管狀光源22之光線的亮度分布不均勻，且相對於管狀光源 22之X軸方向（長方向）垂直之Y軸方向的亮度分佈不均 勻。因此，即使通過光擴散板24並以擴散光照明顯示單元 1，亦不能均勻地照明顯示單元1。特別地，在顯示單元1 之正下方，並列地設置複數支管狀光源22，而且對應於管 狀光源22之部位的亮度最高，由於從管狀光源22行進至 -13- 200903036 周邊而亮度衰減，因此通過光擴散板24而辨識出複數支管· 狀光源2 2的形狀或存在（或配列狀態），而產生亮度不均。 另外，降低光擴散板24之光線透過率成爲不會看見複數支 管狀光源22的形狀或存在時，變得不能以高亮度照明顯示 單元。 其中，在本發明中係以特定之各向異性擴散板構成前 述光擴散板2 4。即，各向異性擴散板至少具備各向異性散 射層24a，該各向異性散射層24a係以連續相C、與分散於 該連續相且平均縱橫比大於1之大粒子狀分散相D所構 成，且連續相C與分散相D係折射率彼此不相同。又，在 各向異性散射層24a中，粒子狀分散相D之長軸方向係配 向於一側的方向（X軸方向）。 還有，在該範例中，爲了以芳香族聚碳酸酯系樹脂構 成連續相C、以聚丙烯系樹脂構成粒子狀分散相D、同時 提升連續相C與分散相D之親和性’故各向異性散射層含 有相溶化劑。再者’在各向異性散射層2 4 a之雙面上’積 層以透明之耐熱性樹脂（芳香族聚碳酸系樹脂）所構成之透 明樹脂層24b。 再者，各向異性擴散板24係朝向管狀光源22之長軸 方向（X軸方向）以設置粒子狀分散相D的長軸方向。因此’ 可藉由各向異性擴散板24使來自管狀光源22之光線透過 擴散於垂直於管狀光源22之長軸方向（軸方向）的方向。 良p，在顯示散射角θ與散射光特性F之關係的散射特性F(e) -14- 200903036 中’在粒子狀分散相D之長軸方向的光散射特性爲F x ( θ )、 垂直於粒子狀分散相D之長軸方向之方向的散射特性爲 Fy(e)時’則爲Fy(e)/Fx(e)>i，可光擴散至垂直於管狀光源 22之長軸方向（X軸方向）的方向（Y軸方向），可均勻化亮 度。 在本發明中’在以既定間隔並列地配置有複數支管狀 光源2 2的背光單元2 1中’爲了以均勻亮度照明液晶顯示 單元1，故在各向異性擴散板24中，設計成散射角Θ = 1 8° 之各向異性度 F18(Fy(l 8°)/Fx(l 8°)) = 2.5〜5 、霧度値 99.0〜99.7%，同時厚度爲1.5〜4mm。各向異性度F18爲小 時’不能均勻化在背光單元21的亮度，在顯示單元1之正 面上產生亮度不均。又，霧度値爲小時，在顯示單元1之 照明中不能以各向異性擴散板24遮蔽管狀光源22，而辨 識複數支管狀光源22之配列狀態爲條紋狀。再者，厚度過 小時，則不能兼具亮度之均勻化與管狀光源2 2之遮蔽，厚 度過大時，亮度容易降低，而變得不能以高亮度照明顯示 單元1。 還有，亮度或亮度不均亦依存於複數支管狀光源22之 間隔W、管狀光源22與各向異性擴散板2 4之距離L。因 此，在本發明中，各向異性度F18>(W/L = 2.5〜5)，無關於複 數支管狀光源22之間隔W、管狀光源22與各向異性擴散 板24之距離L，可均勻化亮度同時以高亮度照明顯示單元 1。還有，較佳爲管狀光源22之間隔W愈大，各向異性度 -15- 200903036 F r8之値愈大’管狀光源22與各向異性擴散板24之距離L 愈大，則各向異性度F ! 8之値愈小。 在該等裝置中，即使是具有20吋以上之大型畫面的液 晶顯示裝置（液晶電視），亦看不到管狀光源22之陰影，均 勻化亮度同時可以高亮度見到鮮明的畫面。而且，可藉由 一片各向異性擴散板達到以往依次配置管狀光源之前方側 的光擴散板與複數片擴散膜的機能，可減低構成零件之數 目，同時簡化構造。 本發明之各向異性擴散板的各向異性散射層係可由折 射率彼此不同之連續相（基質）與粒子狀分散相（散射因子） 構成。連續相係可由熱可塑性樹脂或熱硬化性樹脂（環氧樹 脂、不飽和聚酯樹脂、酞酸二烯丙酯樹脂、矽氧樹脂等）所 構成，粒子狀分散柑係可由有機物質（熱可塑性樹脂或熱硬 化性樹脂等）或無機物質所構成。連續相及粒子狀分散相通 常多爲個別以熱可塑性樹脂所構成的情況。前述連續相與 分散相係折射率彼此不同，同時通常互爲非相溶或難相 溶。又，構成前述連續相及/或分散相之樹脂爲結晶性或非 晶性均可，亦可由非結晶性樹脂構成連續相及分散相。連 續相及分散相通常可由透明性物質形成。 構成連續相及分散相之熱可塑性樹脂方面，可舉例有 聚烯烴系樹脂（包含環狀聚烯烴系樹脂）、含鹵素樹脂（包含 氟系樹脂）、乙烯醇系樹脂、乙烯酯系樹脂（或脂肪酸乙烯 酯系樹脂）、（甲基）丙烯酸系樹脂、苯乙烯系樹脂、聚酯系 -16 - 200903036 樹脂、聚醯胺系樹脂、聚碳酸酯系樹脂、熱可塑性聚胺甲 酸酯樹脂、聚颯系樹脂（聚醚颯、聚颯等）、聚伸苯醚系樹 脂（2,6-二甲酚之聚合物等）、纖維素衍生物（纖維素酯類、 纖維素胺甲酸醋類、纖維素醚類等）、砂氧樹脂（聚二甲基 矽氧烷 '聚甲苯基矽氧烷等）、彈性體（烯烴系、聚酯系、 聚醯胺系、胺甲酸酯系、苯乙烯系彈性體等）等。 在聚烯烴系樹脂中，可舉例有C2.6烯烴之單獨或共聚 物（聚乙烯、乙烯-丙烯共聚物等之乙烯系樹脂；聚丙稀、 丙烯-乙烯共聚物、丙烯-丁烯共聚物等之聚丙烯系樹脂； 聚（甲基戊-卜烯）等）、c2-6烯烴與共聚合性單體的共聚物（乙 烯-乙酸乙烯共聚物、乙烯-(甲基）丙烯酸共聚物、乙烯-(甲 基）丙烯酸共聚物或其鹽（例如多離子聚合物樹脂）、乙烯 -(甲基）丙烯酸酯共聚物等之共聚物。環狀聚烯烴系樹脂（或 脂肪族環狀聚烯烴系樹脂）方面’可舉例有環狀烯烴（降萡 烯、二環戊二烯等）之單獨或共聚物（例如，具有立體性剛 直之三環癸基等之脂環族烴基的單獨或共聚物等）、前述環 狀烯烴與共聚合性單體的共聚物（乙燒-降萡烯共聚物、丙 烯-降萡烯共聚物等）等。脂環族聚烯烴系樹脂可由例如商 品名「亞頓（ARTON)」、商品名「傑翁奈克斯（ZEONEX)」 等購得。 含鹵素樹脂方面，舉出有鹵化乙烯系樹脂（聚氯乙烯、 聚氟乙烯等之含鹵素單體之單獨聚合物；四氟乙烯-全氟烷 基乙烯基醚共聚物等之含鹵素單體的共聚物；四氟乙烯-乙 -17- 200903036 烯共聚物等之含鹵素單體與共聚合性單體的共聚物等）、鹵 化亞乙烯系樹脂（聚偏二氟乙烯、二氯乙烯甲基）丙烯酸酯 共聚物等之含鹵素亞乙烯單體與其他單體的共聚物）等。 在乙烯醇系樹脂之衍生物中，除了聚乙烯醇、乙烯-乙 烯醇共聚物等之外，亦包含聚乙烯縮醛系樹脂（聚乙烯甲醛 系樹脂、聚乙烯丁醛系樹脂等）。乙烯酯系樹脂方面，舉出 有乙烯酯系單體之單獨或共聚物（聚乙酸乙烯等）、乙烯酯 系單體與共聚合性單體之共聚物（乙酸乙烯-乙烯共聚物、 乙酸乙烯-氯乙烯共聚物、乙酸乙烯_(甲基）丙烯酸酯共聚物 等）。 (甲基）丙烯酸系樹脂方面，舉例有聚甲基丙烯酸甲酯 等之聚（甲基）丙烯酸酯、甲基丙烯酸甲酯-(甲基）丙烯酸共 聚物、甲基丙烯酸甲酯-(甲基）丙烯酸酯共聚物、甲基丙烯 酸甲酯-丙烯酸酯-(甲基）丙烯酸共聚物、（甲基）丙烯酸酯· 苯乙烯共聚物（MS樹脂等）等。較佳之（甲基）丙烯酸系樹脂 方面，舉出有以甲基丙烯酸甲酯爲主成分（50〜100重量％ 、 較佳爲70〜100重量％左右）之甲基丙烯酸甲酯系樹脂。（甲 基）丙烯酸系樹脂亦可爲具有三環癸基等之脂環族烴基的 (甲基）丙烯酸酯之單獨或共聚物。 苯乙烯系樹脂方面，舉例有苯乙烯-丙烯腈共聚物（AS 樹脂）、苯乙烯與（甲基）丙烯酸系單體之共聚物（苯乙烯-甲 基丙烯酸甲酯共聚物等）、苯乙烯-順丁烯二酸酐共聚物、 苯乙烯-順丁烯二醯亞胺共聚物等。在較佳之苯乙烯系樹脂 -18- 200903036 中，包含聚苯乙烯、苯乙烯與（甲基）丙烯酸系單體之共聚 物（苯乙烯-甲基丙烯酸甲酯共聚物等）、AS樹脂、苯乙烯· 丁二烯共聚物等。 在聚酯系樹脂中，可舉例有使用對苯二甲酸等之芳香 族二羧酸的芳香族聚酯（包含聚對苯二甲酸乙一醋、聚對本 二甲酸丁二酯等之聚對苯二甲酸C2-4烷基二酯或聚萘一甲 酸C2-4烷基二酯等之單聚酯、C2·4伸烷基芳基酯單位（C2·4 對苯二甲酸伸烷酯及/或萘二酸伸烷酯單位）作爲主成分（例 ' r, 如，50莫耳％以上、較佳爲75〜100莫耳％ 、更佳爲80~1 〇〇 莫耳％左右）的共聚酯等）、液晶性聚酯等。共聚酯方面’ 係在聚C2_4伸烷基芳基酯之中’包含以聚氧基C2_4伸院基 二醇、C6-1Q伸烷基二醇、脂環族二醇（環己二甲醇、氫化雙 酚A等）、具有芳香環之二醇（具有莽側鏈之9,9_雙（4_(2· 羥乙氧基）苯基）莽、雙酚A、雙酚A-烯化氧加成物等）等’ 取代一部分c2-4伸烷基二醇之共聚酯；以酞酸、異酞酸等 , 之非對稱芳香族二羧酸、己二酸等之脂肪族C 6 _ 1 2二羧酸等 取代芳香族二羧酸之一部分的共聚酯。在聚酯系樹脂中’ 亦包含聚芳基酯系樹脂、使用己二酸等之脂肪族二羧酸的 脂肪族聚酯、ε -己內酯等之內酯單獨或共聚物。較佳之聚 酯系樹脂通常爲如非結晶性共聚酯（例如，C2_4伸烷基芳基 酯系共聚酯等）等之非結晶性。 聚醯胺系樹脂方面，舉出有耐綸46、耐綸6、耐綸66、 耐綸610、耐綸612、耐綸11、耐綸12等之脂肪族聚醯胺、 -19 - 200903036 己二酸二甲苯二胺酯（MXD-6)等芳香族聚醯胺等。在聚醯 胺系樹脂中，ε-己內醯胺等之內醯胺的單獨或共聚物、或 不限於單聚醯胺之共聚醯胺均可。 在聚碳酸酯系樹脂中，包含以雙酚類（雙酚A、雙酚A D、雙酚F、具有莽側鏈之9，9-雙（4-(2羥乙氧基）苯基）莽 等）爲基礎之芳香族聚碳酸酯、碳酸二乙二醇雙烯丙酯等之 脂肪族聚碳酸酯等。彼等聚碳酸酯系樹脂之中，通常使用 < 芳香族聚碳酸酯。 纖維素衍生物中，纖維素酯類方面，可舉例有例如醯 酸纖維素（二乙酸纖維素、三乙酸纖維素等之乙酸纖維素； 丙酸纖維素、丁酸纖維素、乙酸丙酸纖維素、乙酸丁酸纖 維素等）。 彼等樹脂之中，較佳爲透明性高的樹脂。又，至少構 成連續相之樹脂較佳爲耐熱性（熱安定性）高的樹脂。構成 連續相之樹脂的熔點或玻璃轉移溫度亦可爲1 5 0〜2 8 0 °C左 ^ 右’較佳爲1 6 0〜2 7 0 °C左右，更佳爲1 7 0〜2 6 0。(：（例如， 18 0〜2 5 0 °C )左右。此種熱可塑性樹脂包含聚丙烯系樹脂、 (甲基）丙烯酸系樹脂、苯乙烯系樹脂、聚酯系樹脂、聚醯 胺系樹脂、芳香族聚碳酸酯系樹脂、纖維素酯類（特別是乙 酸纖維素）。構成連續相之熱可塑性樹脂，較佳爲聚烯烴系 樹脂（聚丙嫌系樹脂等）、聚碳酸酯系樹脂等，特佳爲聚碳 酸酯系樹脂。 分散相（光散射因子）係可藉由對於基質樹脂添加無機 -20- 200903036 或有機異形微粒子或纖維、對於基質樹脂添加及混練折射 率不同之樹脂等而形成。在纖維狀分散相中，包含有機纖 維（耐熱性有機纖維’例如芳香族聚醯胺纖維、全芳香族聚 酯纖維、聚醯亞胺纖維等）、無機纖維（例如纖維狀塡料（玻 璃纖維、矽石纖維、氧化鋁纖維，氧化鍩纖維等之無機纖 維）、薄片狀塡料（雲母等）等）等。 較佳之分散相係使用透明性高、在單軸延伸溫度等之 配向處理溫度下容易變形、具有實用之熱安定性的樹脂。 構成分散相之樹脂的熔點或玻璃轉移溫度大多爲較前述構 成連續相之樹脂低的情況，例如，亦可爲1 2 0〜2 5 0 °c左右、 較佳爲130〜2 3 0 °C左右、更佳爲140〜20 0。(：左右的樹脂。較 佳之分散相可由聚烯烴系樹脂、（甲基）丙烯酸系樹脂、苯 乙稀系樹脂、聚酯系樹脂、聚醯胺系樹脂等構成。特佳之 分散相可由苯乙烯系樹脂、聚烯烴系樹脂等所構成，特別 是以聚烯烴系樹脂[聚丙烯系樹脂（結晶性聚丙烯樹脂等）等] 所構成。 連續相與分散相係以折射率彼此不同之成分所構成。 連續相與分散相之折射率差爲例如0.001以上（例如， 0.001~〇.3左右）、較佳爲〇·01〜〇.3左右、更佳爲〇.〇1〜〇 ι 左右。折射率差爲小時，則變得無法賦予光擴散性。 連續相與分散相之比例，相對於光擴散性等，可從例 如前者/後者（重量比）=99/1〜30/70(例如，97/3〜25/75)左 右、較佳爲95/5〜20/80(例如，90/10〜20/80)左右之範圍來 -21- 200903036 適宜地選擇。 各向異性散射層亦可包含相溶化劑。使用相溶化劑 時，則提高連續相與分散相之親和性，即使進行配向處理 亦可防止生成缺陷（空隙等缺陷）。 相溶化劑方面，可因應連續相及分散相之種類而從慣 用之相溶化劑中選擇，可舉例有例如，噚唑啉化合物、以 改質基（羧基、酸酐基、環氧基、噚唑啉基等）改質之改質 樹脂、含二烯或橡膠聚合物、或以前述改質基（環氧基等） 改質之含二烯或橡膠聚合物等。彼等相溶化劑係可單獨或 組合二種以上來使用。 相溶化劑通常使用具有與聚合物混合系統之構成樹脂 相同或共通之成分的聚合物（無規、嵌段或接枝共聚物）、 對於聚合物混合系統之構成樹脂具有親和性的聚合物（無 規、嵌段或接枝共聚物）等。可舉例有酸改質烯烴系樹脂（順 丁烯二酸酐改質聚丙烯系樹脂、順丁烯二酸酐改質聚乙烯 系樹脂等之順丁烯二酸酐改質烯烴系樹脂；（甲基）丙烯酸 改質烯烴系樹脂等）、環氧基改質烯烴系樹脂（環氧丙基改 質聚乙烯系樹脂、環氧丙基改質聚丙烯系樹脂、已環氧化 之苯乙稀-丁二烯-苯乙烯（SBS)嵌段共聚物等之環氧化二 烯系嵌段共聚物或環氧基改質二烯系嵌段共聚物等）；在聚 碳酸酯系樹脂上接枝烯烴系樹脂、苯乙稀系樹脂（聚苯乙 烯、丙烯腈-苯乙烯共聚物等）、改質苯乙烯系樹脂等而成的 聚碳酸酯系接枝共聚物等。彼等相溶化劑係可單獨或組合二 -22- 200903036 種以上來使用。聚碳酸酯系接枝共聚物係有用於使用碳酸 酯系樹脂作爲連續相之樹脂的情況。聚碳酸酯系接枝共聚 物係可由曰本油脂股份有限公司以商品名「Mo dip er」購得。 還有’相溶化劑之折射率亦可爲與分散相樹脂約略相 同程度（例如，與分散相樹脂之折射率差爲〇〜〇 . 〇 1左右、 較佳爲0〜0.005左右）。 相溶化劑的使用量係可選自例如相對於連續相與分散 相之樹脂組成物全體爲0.1〜20重量％ 、較佳爲0.15〜15重 量％ 、更佳爲0.2〜10重量％左右之範圍。 再者’各向異性散射層亦可含有慣用之添加劑，例如 安定劑（抗氧化劑、紫外線吸收劑、熱安定劑、紫外線安定 劑、光安定劑等）、可塑劑、抗靜電劑、難燃劑等。 在各向異性散射層中，粒子狀分散相係平均縱橫比（長 軸之平均長L2相對於短軸之平均長的比例L2/L!)大於 1 ’而且粒子狀分散相之長軸方向係配向於一側的方向（光 擴散板的X軸方向）。爲了賦予適度之各向異性，故粒子狀 分散相（異形分散相）之平均縱橫比爲例如1.1〜100左右、較 佳爲1.2〜50(例如1.3〜10)左右、更佳爲1.5〜10(例如1.7〜5) 左右’亦可爲1.5〜3左右。該等分散相亦可爲橄欖球型形 狀（旋轉橢圓狀等）、纖維形狀、長方形狀等。縱橫比大者， 可提高各向異性的光散射性。還有，分散相之長軸的平均 長度爲例如 0.1~200μιη(例如 1〜ΙΟΟμηι)左右、較佳爲 2~80μιη(例如 3〜5〇μιη)左右，通常爲 5〜1〇〇μιη(例如， -23- 200903036 1 0〜5 0 μ m )左右。又，分散相之短軸的平均長度爲例如 0·05~100μιη(例如0.1〜50μιη)左右、較佳爲例如 1〜ΙΟμιη)左右，通常爲〇.5~5μιη·左右。 各向異性散射層亦可至少以各向異性散射層所構成， 亦可積層透明層於各向異性散射層。透明層方面’雖可使 用各種透明基材（例如，玻璃等），但通常使用透明樹脂層。 積層透明樹脂層於各向異性散射層時，則可由透明樹脂層 保護散射層。 構成透明樹脂層之透明樹脂雖可選自前述舉例之樹 脂，但爲了提高耐熱性或耐結塊性，較佳爲耐熱性樹脂（芳 香族聚碳酸酯系樹脂等之玻璃轉移溫度或熔點高的樹脂 等）、結晶性樹脂等。構成透明樹脂層之樹脂的玻璃轉移溫 度或熔點亦可爲與前述構成連續相之樹脂的玻璃轉移溫度 或熔點相同程度。又，透明性樹脂較佳爲具有與構成連續 相之樹脂相同或共通之骨架的樹脂。 各向異性散射層與透明層（或透明樹脂層）之厚度比例 爲例如散射層/透明層=5/95~99/1左右、較佳爲50/50~99/1 左右、更佳爲70/3 0〜95/5左右。 光擴散板之厚度爲0.5〜5mm(例如1〜5mm)、較佳爲 1-5 4mm、更佳爲2~3.5mm(例如2〜3mm)左右。光擴散板之 厚度爲小時，則不僅難以得到均勻的亮度，而且有透視管 #光 '源的情況；光擴散板之厚度過大時，則亮度降低，變 得無法以高亮度照明顯示單元。還有，光擴散板之厚度爲 -24- 200903036 小時’機械強度（包含剛性）降低，而耐久性容易降低。 光擴散板之霧度値（JI S K 7 1 3 6)爲 9 5 %以上（例如 9 7〜9 9，9 % )、較佳爲9 8 . 5〜9 9.8 % 、更佳爲9 9 ~ 9 9.7 % (例如 9 9· 1〜9 9.6% )左右。霧度値爲小時，可辨識管狀光源之形 狀’同時無法均勻地擴散光線，降低在顯示面板的顯示品 質。 光擴散板之全光線透過率（S K 7 1 3 6 )爲6 0 %以上（例 如63〜90%左右）、較佳爲65〜85% 、更佳爲70〜80%左右。 全光線透過率小時，則亮度變得容易降低。又，光擴散板 之平行光線透過率（Π S K 7 1 3 6 )爲例如2.5 %以下（例如 〇-1〜2%左右）、較佳爲〇.2〜1.5%(例如0_25~1.2%)、更佳 爲〇 _ 3〜1 %左右。平行光線透過率變大時，可辨識管狀光源 的形狀，遮蔽性低。 本發明之各向異性擴散板係在顯示散射角0與散射光 強度F之關係的散射特性F ( Θ )中，在粒子狀分散相之長軸 方向的光散射特性爲Fx( 0 )、相對於粒子狀分散相之長軸 方向垂直之方向的散射特性爲Fy( 6» )時，顯示所謂在散射 角0 = 18°之各向異性度F18(Fy(18°)/Fx(18°))>2之大的 値。在散射角Θ = 1 8 °之各向異性度F i s爲例如2 . 1〜1 0 (例 如2.2〜7)、較佳爲2.3〜5(例如2.5〜4)、更佳爲2.7〜3·7(例 如3〜3 .5)左右，通常爲2.5〜5左右。各向異性度F18爲小時， 則難以均勻化亮度。 還有’在各向異性擴散板之表面上，在不妨害光學特 -25- 200903036 性的範圍中’亦可塗布聚较氧油等離型劑’亦可進行電暈 放電處理。再者，爲了賦予各向異之光散射性’在各向異 性擴散板上，亦可形成延伸於分散相之長軸方向的凹凸部 分。 [各向異性擴散板的製造方法] 各向異性擴散板係可藉由分散並配向構成分散相之成 分（樹脂成分、纖維狀成分等）於構成連續相之樹脂中而 得。例如，視需要以慣用之方法進行攪拌、熔融混合構成 連續相之樹脂與構成分散相之成分（樹脂成分'纖維狀成分 等），可藉由從T狀模頭或環狀模頭等擠出而進行薄片狀成 形以分散分散相。又，亦可在基材（例如’透明樹脂層、玻 璃板等）上，藉由利用塗布以光散射成分與黏合劑樹脂所構 成之組成物的塗布法、或積層前述組成物之積層法、鑄模 法等之慣用的成形法以進行成形而製造。 還有，具有以各向異性散射層、與積層於該散射層中 至少一面上之透明樹脂層所構成之積層構造的光擴散板， 係可藉由將以對應於散射層之成分所構成之樹脂組成物、 與以對應於透明樹脂層之成分所構成之樹脂組成物予以共 擠出成形的共擠出成形法；藉由對預先製作之一層擠出積 層另一層而積層的方法；積層個別製作之散射層與透明樹 脂層的乾式積層法而形成。 又’分散相之配向處理係可藉由例如（1 )拉伸擠出成形 薄片同時製膜的方法、（2)單軸延伸擠出成形薄片的方法、 -26- 200903036 (3)組合前述（1)之方法與（2)之方法的方法、（4)溶液攪拌前 述各成分而藉由流延法成膜的法等而進行。較佳爲在熔融 製膜中拉伸擠出成形薄片同時進行製膜’拉伸比（拉伸倍率） 爲例如1 .5~20倍左右、較佳爲2~10倍左右、更佳爲3~7 倍左右，通常爲1.5〜6倍（例如1.5〜5倍）、特別是2〜5倍左 右。熔融溫度爲樹脂成分（連續相樹脂、分散相樹脂）之熔 點以上的溫度，例如150〜2 90 °C、較佳爲200〜260 °C左右。 還有，厚度大之光擴散板在熔融擠出成形中無法在短 時間內冷卻該薄片，而有得不到各向異性大之光擴散板的 情況。在該等情況下，較佳爲利用冷卻輥等在短時間內冷 卻由模頭所擠出之薄片。 [光擴散板之用途] 本發明之光擴散板係因具有異向擴散光線的機能，而 有用於各向異性地散射來自光源之光線而照明顯示單元。 因此，光擴散板通常配置於顯示單元、與用於由背面照光 該顯示單元之複數支管狀光源之間。 光擴散板之配置形態係可因應管狀光源之配列方向來 選擇，通常各向異性散射層之分散相的長軸方向（X軸方 向），係配置於約略垂直（大約X軸方向）於背光單元之管狀 光源的軸方向（Y軸方向）。即，各向異性擴散板係可使粒 子狀分散相之長軸方向朝向管狀光源之長軸方向以配置各 向異性散射層。還有，各向異性散射層之分散相的長軸方 向（X軸方向）不必完全垂直（X軸方向）於背光單元之管狀光 -27- 200903036 源軸方向（Y軸方向），例如，亦可在角度±15°左右之範圍 朝向斜方向來配置。通常，各向異性擴散板係使粒子狀分 散相之長軸方向朝向管狀光源長軸方向（或使其沿著或一 致於管狀光源之長軸方向）而配置。配置各向異性散射層於 該等方向時，可均勻化亮度分布，照明顯示單元。 在具有複數支管狀光源之背光單元（垂直型背光單元） 中，管狀光源係互相並列地配置著。管狀光源之間隔W及 管狀光源與各向異性擴散板之距離L，可隨顯示單元（或畫 面）之尺寸等而選擇，例如，管狀光源之間隔 W爲 10〜100mm、較佳爲20~70mm、更佳爲25〜50mm左右均可。 又，管狀光源與各向異性擴散板之距離L爲2〜2 0mm、較 佳爲3〜15tnm、更佳爲7〜13mm左右均可。再者，複數支管 狀光源之間隔爲W、管狀光源與各向異性擴散板之距離爲 L時，則各向異性度F18>(W/L)，（W/L)之値通常爲2~10、 較佳爲2.2~8(例如，2.3~7)、更佳爲2.5~5左右均可。還有， 各向異性度F i 8之値係如前述。 背光單元（垂直型背光單元）通常爲了利用在管狀光源 之直射光與反射光以有效地照明顯示單元，大多爲在背面 具備有反射板的情況。又，在背光單元中，在配置於管狀 光源前側之光擴散板的前面，若有必要，亦可配置1片或 複數片棱鏡板，將擴散光集光以照明顯示單元。 本發明亦包含前述背光單元、與以可由該背光單元照 明之顯示單元所構成的顯示裝置。顯示裝置之種類雖無限 -28- 200903036 制於具備必須從背面照明之顯示單元，但顯示單元方面’ 通常使用液晶顯示單元。液晶顯示單元的構造係可採用不 限於前述範例之各種構造。 產業上之可利用件 由於本發明係可藉由背光單元均勻地照明顯示單元’ 而可適當地適用於大畫面的顯示單元。在垂直型背光單元 中，由於可對應於各種畫面尺寸，故顯示單元之畫面尺寸 並無特別限制，例如，20吋以上（例如2 3〜3 00吋、較佳爲 3 0〜2 0 0时"左右）均可。 【實施例】 以下，雖基於實施例以較詳細地說明本發明，但本發 明係非受彼等實施例所限制者。 [實施例1] 混合作爲基質樹脂之聚丙烯（日本聚丙烯（股）（japan Propylene Corporation)製「WFW-4」）100 重量份、聚苯乙 烯（東洋苯乙烯（股）製「G1 00」）5重量份、相溶化劑（戴西 爾化學工業（股）製「Epo-Friend AT202」）〇.3重量份、抗結 塊劑（日本聚丙烯（股）製「TX 1 92 5」）2重量份、紫外線吸收 劑（汽巴•特化品（股）製「Tinuvin 234」）〇.4重量份，使用 擠出成形機，以樹脂溫度23 0°C、模頭開度8mm從模頭熔 融擠出，以水冷冷卻輥4 0。(：冷卻，調製厚度1 m m及2 m m 的光擴散板。在彼等光擴散板中，聚苯乙烯形成散射粒子 (粒子狀分散相），粒子狀分散相之形狀爲楕圓體形狀，厚 -29- 200903036 度（短軸）2 μπι及長度（長軸）26μιη。 [實施例2] 製作二種三層之光擴散板（以各向異性散射層爲中間 層、在該中間層之雙面上積層作爲表層之透明樹脂層的光 擴散板）。即，使用聚丙烯（日本聚丙烯（股）製「WFW-4」）100 重量份、抗結塊劑（日本聚丙烯（股）製「TX 1925」）2重量份 之樹脂組成物，作爲表層用樹脂組成物。又，使用作爲基 質樹脂之聚丙烯（日本聚丙烯（股）製「WFW-4」）100重量 份、聚苯乙烯（東洋苯乙烯（股）製「G1 00」）5重量份、相溶 化劑（戴西爾化學工業（股）製「Epo-Friend ΑΤ202」）0.3重 量份、紫外線吸收劑（汽巴•特化品（股）製「T i n u v i η 2 34」）〇·4重量份之樹脂組成物，作爲中間層用樹脂組成 物。然後，供給表層用樹脂組成物與中間層用樹脂組成物 於共擠出成形機，以樹脂溫度23 0 °C、模頭開度8mm從模 頭熔融擠出，以水冷冷卻輥4 0 °C冷卻，製作上述具有二種 三層之積層構造、厚度1mm及2mm之光擴散板（厚度比例 =1 : 1 : 1 )。在彼等光擴散板中，在中間層聚苯乙烯形成 散射粒子（粒子狀分散相），而粒子狀分散相的形狀爲橢圓 體开^狀’厚度（短軸）2/zm及長度（長軸）40μιη。 [實施例3 ] 混合作爲基質樹脂之聚碳酸酯系樹脂（三菱工程塑膠 (股）製「Upiron S-2000」）100重量份、聚丙烯（日本聚丙烯 (股）製「WFW-4」）5重量份、紫外線吸收劑（汽巴•特化品 -30- 200903036 (股）製「Tinuvin 234」）0.4重量份，使用擠出成形機，以 樹脂溫度3 0 0 °C、模頭開度8mm從模頭熔融擠出，以油溫 調整3支鑄模輥1 5 0 °C冷卻，調製厚度1 m m及2 m m的光擴 散板。在彼等光擴散板中，聚丙烯形成散射粒子（粒子狀分 散相），粒子狀分散相之形狀爲楕圓體形狀，厚度（短軸）2 μιη及長度（長軸）20μιη。 [實施例4] 製作二種三層之光擴散板（以各向異性散射層爲中間 f " 層，在該中間層之雙面上積層作爲表層之透明樹脂層的光 擴散板）。即，使用聚碳酸酯系樹脂（三菱工程塑膠（股）製 「Upiron S-2000」）100重量份、紫外線吸收劑（汽巴•特化 品（股）製「Tinuvin 2 3 4」）0.4重量份之樹脂組成物，作爲 表層用樹脂組成物。又，使用作爲基質樹脂之聚碳酸酯系 樹脂（三菱工程塑膠（股）製「Upiron S-2000」）1〇〇重量份、 聚丙烯（日本聚丙烯（股）製「WFW-4」）5重量份之樹脂組成 1 , 物，作爲中間層用樹脂組成物。然後供給表層用樹脂組成 物與中間層用樹脂組成物於共擠出成形機，以樹脂溫度3 0 0 °C、模頭開度8 m m從模頭熔融擠出，以油溫調整3支鑄模 輥150 °C冷卻，製作上述具有二種三層之積層構造、厚度 1mm及2mm的光擴散板（厚度比例=1: 1: 1)。在彼等光 擴散板中，在中間層中聚丙烯形成散射粒子（粒子狀分散 相）’粒子狀分散相之形狀爲楕圓體形狀，厚度（短軸）2 // m 及長度（長軸）34μιη。 -31 - 200903036 [比較例1 ] 在聚碳酸酯系樹脂（三菱工程塑膠（股）製「Upiron S-2000」）100重量份中，混合球狀之交聯聚苯乙烯系樹脂 粒子（積水化成品工業（股）製「S B X - 6」）1重量份，使用擠 出成形機，以樹脂溫度3 0 0 °C、模頭開度8 m m從模頭熔融 擠出，以油溫調整3支鑄模輥150°C冷卻，調製厚度2 mm 的光擴散板。粒子狀分散相之形狀爲球狀，直徑6μιη。 [比較例2] 在丙烯酸系樹脂（住友化學（股）製「MG5」）100重量份 中，混合球狀之交聯聚苯乙烯系樹脂粒子（積水化成品工業 (股）製「SBX-6」）1重量份，使用擠出成形機，以樹脂溫度 2 3 0 °C '模頭開度8mm從模頭熔融擠出，以水冷輥40 °C冷 卻，調製厚度2mm的光擴散板。粒子狀分散相之形狀爲球 狀，直徑6 y m。 然後，如以下硏究實施例及比較例所得之光擴散板的 特性。 顯示品質評估 裝設光擴散板於垂直型液晶顯示裝置，並製作示於第 1圖之構造的顯示裝置。即，在以間隔3 3 m m並列地配置之 陰極放電管（螢光燈）之上，放置光擴散板成爲擠出成形之 流動方向（在實施例之光擴散板爲粒子狀分散相的長軸方 向）與陰極放電管（螢光燈）之長方向相同，點亮顯示器，於 1 〇分鐘後以目視觀察，由以下基準評估顯示品質。 -32- 200903036 A:不會看見陰極放電管（螢光燈）的形狀（成爲均勻的 發光狀態） B:雖爲約略均勻的發光狀態但知道陰極放電管（螢光 燈）的位置 C:雖不易看見但可辨識陰極放電管（螢光燈）燈 D:看見陰極放電管（螢光燈） 耐久件評估200903036 IX. Description of the Invention: [Technical Field] The present invention relates to a display unit (liquid crystal display unit) and a plurality of tubular light sources (fluorescent tubes) for backlighting the display unit, and Under the condition that the brightness is not lowered, there is an anisotropic diffusion plate for visually not seeing the tubular light source of the surface light source unit and a surface light source or a backlight unit (vertical type backlight) having the anisotropic diffusion plate. [Prior Art] In a backlight type display device (such as a liquid crystal display device) that illuminates a display panel (such as a liquid crystal display unit), a surface light source unit (or a backlight unit) is disposed on the back surface of the display panel. Further, in order to homogenize the illumination light to the display panel as a surface light source and to increase the brightness of the front surface of the liquid crystal display device, a diffusion sheet, a ruthenium sheet, a brightness enhancement sheet, or the like is used between the display panel and the surface light source unit. When the screen size of the display device is small, a light guide plate, a tubular light source disposed on a side portion of the light guide plate, and a diffusion sheet disposed between the light guide plate and the display unit are used. In the display device of the configuration, light from the tubular light source is emitted and diffused from the front surface of the light guide plate to illuminate the display unit. However, in such devices, the display device of a large screen cannot be coped with due to the decrease in the brightness of the light emitted by the light guide plate as the screen becomes larger. In addition, as the display device (such as a liquid crystal television) is enlarged, a surface light source unit (or a vertical type backlight unit) for arranging a plurality of tubular light sources (such as fluorescent lamps) illuminated by the back surface of the display unit is arranged in parallel. ). However, in the above-described vertical type backlight unit, since a plurality of tubular light sources 200903036 (fluorescent lamps, etc.) are arranged in parallel, a portion corresponding to a tubular light source (fluorescent lamp or the like) becomes bright, and brightness from a front surface of the display unit is changed. Not even. Further, on the front side of the tubular light source, a light diffusing plate having a high shielding property for the tubular light source and a plurality of isotropic diffusing films are sequentially disposed, which not only constitutes a large number of parts but also complicates the structure. Japanese Laid-Open Patent Publication No. Hei No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. In the continuous phase, the diffusion film is dispersed in the uniaxial direction by an average aspect ratio of more than one, and the long axis direction of the dispersed phase of the diffusion film is arranged along the axis of the fluorescent tube. Device. Japanese Patent Publication No. 2002-1858 (Patent Document 2) discloses a continuous phase having a refractive index different from each other and a particulate dispersed phase, and the average aspect ratio of the particulate dispersed phase is more than 1, and is dispersed in a dispersed particle phase. The anisotropic light-scattering layer (1) having a major axis direction in one direction and a laminated film formed of a transparent resin layer (2) laminated on at least one side of the light-scattering layer. In this document, it is also described that a transparent resin layer (2) is laminated on both sides of the anisotropic light-scattering layer (1), and an average aspect ratio of the particulate dispersed phase is 5 to 100, anisotropic light scattering. The thickness ratio of the layer (1) to the transparent resin layer (2) is a light scattering layer/transparent resin layer = 50/50 to 99/1, the entire thickness is 6 to 600 μm, and the total light transmittance is 85% or more. However, even if such a diffusion film or a laminate film is applied to the vertical type backlight unit, the portion corresponding to the tubular light source (fluorescent lamp or the like) becomes bright, and the existence of the tubular light source can be recognized by the diffusion plate, resulting in uneven brightness. Further, when there is no unevenness in brightness of 200903036, the brightness of the front surface of the liquid crystal display device is lowered. Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. In the vertical type backlight device of the light diffusing plate from the reflected light of the reflecting plate, the light diffusing plate has a vertical type backlight device having a zigzag-shaped string group on the light source side. In this document, a light diffusion is described in which a copolymer of an aromatic vinyl monomer and a (meth)acrylate monomer containing a light diffusing agent or a polymer resin having an alicyclic structure containing a light diffusing agent is formed. A fine particle composed of a polystyrene polymer, a polyoxyalkylene polymer or a crosslinked product thereof is used as a light diffusing agent, and a light diffusing plate having a thickness of 2 mm is prepared. However, since the light diffusing plate is optically diffused in an isotropic manner, when it is applied to a vertical type backlight in which a plurality of tubular light sources are arranged in parallel, the brightness of the front surface of the display unit cannot be uniformized. Further, since the light diffusion plate is disposed close to the light source, the additive overflows due to heating, so that the optical characteristics are lowered. Furthermore, since it is necessary to form a string group, productivity cannot be improved. It is disclosed in JP-A-2002-272 No. 9 (Patent Document 4) that it is a light diffusion of polycarbonate having a thickness of 0.3 to 3 mm of a fine particle-shaped light diffusing agent having an average particle diameter of 1 to 50 μm. When the brightness is in the range of 5 000 to 6000 cd/m 2 by a cold cathode fluorescent lamp, the plate is not limited to 3% or less. JP-A-2004-29091 (Patent Document 5) discloses 100 parts by weight of a total of 0 to 3% by weight of transparent fine particles of 99.7 to 80% by weight of carbonate resin 200903036 and an average particle diameter of 1 to 30/zm. A vertical light diffusing plate for a backlight made of a polycarbonate resin having a thickness of 〇5 to 3 mm formed of a resin composition composed of a fluorescent whitening agent of 0.0005 to 0.1 part by weight. However, since the light diffusing plates are optically diffused in the same manner, when applied to a vertical type backlight in which a plurality of tubular light sources are arranged in parallel, the brightness from the front surface of the display unit cannot be uniformized. Patent Document 1: Japanese Laid-Open Patent Publication No. Hei No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. (Japanese Patent Application Laid-Open Publication No. 2004-272 No. Hei. No. 2004-90 1 (Publication) OBJECT OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION Accordingly, it is an object of the present invention to provide a tubular light source (fluorescent lamp or the like) that is uniform even when applied to a vertical type backlight, and can uniformize brightness from a display unit. A vertical type light diffusing plate for backlight and a backlight unit (vertical type backlight) using the light diffusing plate. Another object of the present invention is to provide a vertical type light diffusing plate having high durability and stable light diffusion characteristics over a long period of time even when applied to a vertical type backlight, and a backlight unit using the same (vertical type backlight) ). 200903036 A further object of the present invention is to reduce the number of components of the display device, and to simplify the vertical light diffusing plate for backlight and the backlight unit (vertical type backlight) using the light diffusing plate. Means for Solving the Problems As a result of intensive research conducted by the inventors of the present invention, it has been found that a light diffusing plate having a specific thickness and a specific anisotropy and a predetermined haze 光 with respect to light scattering is used. Even when applied to a vertical type backlight, the existence or shape of the tubular light source is not seen (or recognized), and the brightness from the display unit can be homogenized without particularly reducing the brightness, and the present invention has been completed. The anisotropic diffusion plate of the present invention has a continuous phase having a refractive index different from each other and a dispersed phase of particles, and an average aspect ratio of the dispersed phase of the particles is greater than 1, and is oriented in a long axis direction of the dispersed phase of the dispersed particles. It consists of an anisotropic scattering layer in the side direction. Therefore, the anisotropic diffusion plate is used to be disposed between the display unit and a plurality of tubular light sources for backlighting the display unit, and exhibits a scattering characteristic F in relation to the scattering angle 0 and the scattered light intensity F ( In 0), when the light scattering characteristic in the long axis direction of the particulate dispersed phase is Fx(0) and the scattering characteristic in the direction perpendicular to the long axis direction of the dispersed phase is Fy(0), the scattering angle is 0. =18° anisotropy F18 (Fy(l 8°)/Fx(l 8°))>2 (for example, anisotropy Fl8 = 2.5~5), haze 値 95% or more, thickness It is 0.5~5mm. The aforementioned anisotropic scattering layer may be formed of various molding materials such as thermoplastic resins. More specifically, the anisotropic scattering layer may also include -10 200903036 (1) a polyolefin-based resin constituting a continuous phase and a polystyrene-based resin constituting a particulate dispersed phase; or (2) a continuous phase A polycarbonate resin and a polyolefin resin constituting a particulate dispersed phase. Further, the anisotropic scattering layer may contain a carbonate-based resin constituting a continuous phase and a polyolefin-based resin constituting a particulate dispersed phase. The anisotropic scattering layer may further contain a phaseing agent. The ratio of the continuous phase to the dispersed phase may also be about the continuous phase/dispersion phase = 99 /1 to 3 0/70 (weight ratio). The anisotropic scattering layer can arrange the long axis direction of the dispersed phase of the particles toward the long axis direction of the tubular light source. The anisotropic diffusion plate may also be composed of an anisotropic scattering layer and a transparent resin layer laminated on at least one side surface of the anisotropic scattering layer, particularly on both sides. The present invention also includes the above-described anisotropic diffusion plate having a plurality of tubular light sources arranged in parallel with each other and a longitudinal axis direction of the tubular light source disposed between the tubular light source and the display unit in the longitudinal direction of the tubular light source. Backlight unit (vertical type backlight unit). In the backlight unit, when the interval between the plurality of tubular light sources is W, and the distance between the tubular light source and the anisotropic diffusion plate is L, the anisotropy Fl8 > (W/L) may be used. Further, the display unit may be a liquid crystal display unit. Furthermore, the present invention also includes the above-described backlight unit and a display device which can be constituted by a display unit illuminated by the backlight unit. EFFECTS OF THE INVENTION In the present invention, since the anisotropic scattering layer 'and the specific anisotropy and haze 値 and the thickness □ are formed in a continuous phase and a particulate dispersed phase, even if it is suitable for a vertical type backlight, the tubular light source is not seen. (Fluorescent light-11 - 200903036, etc.), and the brightness from the display unit can be homogenized. Further, when an anisotropic scattering layer is formed of a specific resin, even if it is applied to a vertical type backlight, it exhibits no light absorption characteristics, high durability, and stable light diffusion characteristics over a long period of time. Further, since the function of the conventional light diffusing plate and the diffusing film can be achieved by the anisotropic diffusion plate, the number of components of the display device can be reduced, and the structure can be simplified. Therefore, the light diffusing plate is also useful as a constituent part of the backlight unit (vertical type backlight). [Embodiment] Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. 1 is a schematic exploded cross-sectional view showing an example of a vertical type backlight unit (or a surface light element device) of the present invention, and a liquid crystal display device having the unit; FIG. 2 is a view showing a light diffusing plate and a tubular light source. A pattern diagram of the relationship. A liquid crystal display unit (such as a liquid crystal display unit) is configured by a liquid crystal display unit 1 and a vertical type backlight unit (or surface light source unit) 21 for backlighting the liquid crystal display unit 1; the liquid crystal display unit 1 is provided with a liquid crystal cell. 2. The first polarizing plate 7 disposed in front of the liquid crystal cell 2 and the second polarizing plate 12 disposed on the back surface of the liquid crystal cell 2. The liquid crystal cell 2 is a pair of transparent parts (glass plates or the like) 3a, 3b; formed on the opposite direction surface of the transparent electrodes, and may also have one of the alignment films, a transparent electrode (ITO transparent electrode, etc.) 4a, 4b; The liquid crystal 5 is packaged between one of the transparent electrodes and one of the transparent electrodes. In the color liquid crystal display device, the color filter 6 is disposed between the transparent electrode and the transparent member on the back side with respect to the liquid crystal. Further, the first polarizing plate 7 is formed by the polarizing layer 8 and the protective layers 9a and 9b provided on both sides of the polarizing layer 8-12-200903036, and the protective layers of the protective layers are located in the front direction (or the front side of the liquid crystal display unit). One of the antireflection layers 1a of the protective layer 9a is composed of a retardation film 11 laminated on the other protective layer 9b. Further, the second polarizing plate 12 is a retardation film 15 in which the polarizing layer 13 and the protective layers 14a and 14b provided on both sides of the polarizing layer and the protective layer 14a in which one of the protective layers is laminated in the front direction. Composition. The backlight unit 2 1 for backlighting the liquid crystal display unit 1 is provided with a plurality of tubular light sources (cold cathode discharge tubes or fluorescent lamps) 22 arranged side by side for reflecting light from the tubular light source 22 to the tubular shape The reflector 23 in the front direction of the light source 22, the light diffusing plate 24 provided on the front side of the discharge tube (fluorescent lamp), and the front side of the light diffusing plate (that is, between the liquid crystal display unit 1 and the light diffusing plate 24) are disposed. 1 or a plurality of lens films (or enamel sheets) 25. In the lens film, on the surface of the liquid crystal display unit 1 side, in order to condense the diffused light to illuminate the display unit 1, a concave-convex array (or a micro-column of triangular cross-sections) 25a having a zigzag cross-sectional shape is formed. In such devices, the light from the tubular light source 22 is diffused by the light diffusing plate 24 to illuminate the display unit. However, in general, the light distribution from the light source of the tubular light source 22 is uneven, and the luminance distribution in the Y-axis direction perpendicular to the X-axis direction (long direction) of the tubular light source 22 is not uniform. Therefore, even if the display unit 1 is illuminated by the light diffusing plate 24 and with diffused light, the display unit 1 cannot be uniformly illuminated. In particular, a plurality of tubular light sources 22 are arranged side by side directly below the display unit 1, and the portion corresponding to the tubular light source 22 has the highest brightness, and since the brightness is attenuated from the tubular light source 22 to the periphery of -13-200903036, The light diffusing plate 24 recognizes the shape or presence (or arrangement state) of the plurality of branch pipes and the light source 2 2, and causes unevenness in brightness. Further, when the light transmittance of the light diffusing plate 24 is lowered so that the shape or presence of the plurality of tubular light sources 22 is not seen, it becomes impossible to illuminate the display unit with high luminance. In the present invention, the above-described light diffusing plate 24 is constituted by a specific anisotropic diffusion plate. That is, the anisotropic diffusion plate includes at least an anisotropic scattering layer 24a composed of a continuous phase C and a large dispersed phase D dispersed in the continuous phase and having an average aspect ratio of more than 1. And the refractive indices of the continuous phase C and the dispersed phase D are different from each other. Further, in the anisotropic scattering layer 24a, the long-axis direction of the dispersed phase D of the particles is aligned in one direction (X-axis direction). In addition, in this example, in order to form the continuous phase C of the aromatic polycarbonate resin, the particulate dispersed phase D by the polypropylene resin, and the affinity of the continuous phase C and the dispersed phase D are improved, The opposite scattering layer contains a compatibilizing agent. Further, 'the transparent resin layer 24b made of a transparent heat-resistant resin (aromatic polycarbonate resin) is laminated on both sides of the anisotropic scattering layer 24a. Further, the anisotropic diffusion plate 24 is disposed in the long axis direction (X-axis direction) of the tubular light source 22 to set the long axis direction of the dispersed phase D. Therefore, the light from the tubular light source 22 can be diffused by the anisotropic diffusion plate 24 in a direction perpendicular to the long axis direction (axial direction) of the tubular light source 22. Good p, in the scattering characteristic F(e) -14- 200903036 showing the relationship between the scattering angle θ and the scattered light characteristic F, 'the light scattering characteristic in the long-axis direction of the dispersed phase D is F x ( θ ), vertical When the scattering characteristic in the direction of the major axis direction of the particulate dispersed phase D is Fy(e), then Fy(e)/Fx(e)>i, the light can be diffused to the direction perpendicular to the long axis of the tubular light source 22. In the direction of the (X-axis direction) (Y-axis direction), the brightness can be uniformized. In the present invention, 'in the backlight unit 2 1 in which a plurality of tubular light sources 2 2 are arranged side by side at a predetermined interval, 'in order to illuminate the liquid crystal display unit 1 with uniform brightness, in the anisotropic diffusion plate 24, a scattering angle is designed. Θ = 1 8° anisotropy F18 (Fy (l 8 °) / Fx (l 8 °)) = 2.5 to 5, haze 値 99.0 to 99.7%, and thickness of 1.5 to 4 mm. When the degree of anisotropy F18 is small, the brightness of the backlight unit 21 cannot be uniformized, and luminance unevenness is generated on the front surface of the display unit 1. Further, when the haze is small, the tubular light source 22 cannot be shielded by the anisotropic diffusion plate 24 in the illumination of the display unit 1, and the arrangement state of the plurality of tubular light sources 22 is determined to be stripe-like. Further, when the thickness is too small, the uniformity of the brightness and the shielding of the tubular light source 22 cannot be achieved. When the thickness is too large, the brightness is liable to lower, and the display unit 1 cannot be illuminated with high brightness. Further, the luminance or luminance unevenness also depends on the interval W between the plurality of tubular light sources 22 and the distance L between the tubular light source 22 and the anisotropic diffusion plate 24. Therefore, in the present invention, the degree of anisotropy F18 > (W/L = 2.5 to 5), regardless of the interval W between the plurality of tubular light sources 22, the distance L between the tubular light source 22 and the anisotropic diffusion plate 24, can be uniform The brightness is simultaneously illuminated by the display unit 1 with high brightness. Further, it is preferable that the interval W of the tubular light source 22 is larger, and the anisotropy degree -15-200903036 F r8 is larger. The larger the distance L between the tubular light source 22 and the anisotropic diffusion plate 24, the more anisotropic Degree F! 8 is getting smaller. In such devices, even in a liquid crystal display device (liquid crystal television) having a large screen of 20 inches or more, the shadow of the tubular light source 22 is not seen, and the brightness is uniformized while the bright image can be seen with high brightness. Further, the function of the light diffusing plate and the plurality of diffusing films on the side before the tubular light source can be arranged in the past by an anisotropic diffusing plate can reduce the number of components and simplify the structure. The anisotropic scattering layer of the anisotropic diffusion plate of the present invention may be composed of a continuous phase (matrix) having a different refractive index from each other and a particulate dispersed phase (scattering factor). The continuous phase system may be composed of a thermoplastic resin or a thermosetting resin (epoxy resin, unsaturated polyester resin, diallyl phthalate resin, oxime resin, etc.), and the particulate dispersed citrus may be made of an organic substance (thermoplasticity). It is composed of a resin or a thermosetting resin or the like. The continuous phase and the dispersed phase of the particles are usually composed of a thermoplastic resin alone. The refractive indices of the continuous phase and the dispersed phase are different from each other, and are generally mutually incompatible or difficult to be mutually soluble. Further, the resin constituting the continuous phase and/or the dispersed phase may be crystalline or amorphous, and the continuous phase and the dispersed phase may be composed of an amorphous resin. The continuous phase and the dispersed phase are usually formed of a transparent substance. Examples of the thermoplastic resin constituting the continuous phase and the dispersed phase include a polyolefin resin (including a cyclic polyolefin resin), a halogen-containing resin (including a fluorine resin), a vinyl alcohol resin, and a vinyl ester resin (or Fatty acid vinyl ester resin, (meth)acrylic resin, styrene resin, polyester-16 - 200903036 resin, polyamine resin, polycarbonate resin, thermoplastic polyurethane resin, Polyfluorene-based resin (polyether oxime, polyfluorene, etc.), poly(phenylene ether) resin (polymer of 2,6-xylenol, etc.), cellulose derivative (cellulose ester, cellulose amine formic acid vinegar , cellulose ethers, etc.), sand oxide resin (polydimethyl methoxy oxane 'polymethyl sulfoxane, etc.), elastomer (olefin type, polyester type, polyamidoline type, urethane type, A styrene-based elastomer or the like). The polyolefin resin may, for example, be a single or copolymer of C2.6 olefin (ethylene resin such as polyethylene or ethylene-propylene copolymer; polypropylene, propylene-ethylene copolymer, propylene-butene copolymer, etc.) a polypropylene resin; a poly(methylpenta-bene) or the like; a copolymer of a c2-6 olefin and a copolymerizable monomer (ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid copolymer, ethylene a copolymer of a (meth)acrylic acid copolymer or a salt thereof (for example, a polyionic polymer resin) or an ethylene-(meth)acrylate copolymer, etc. A cyclic polyolefin resin (or an aliphatic cyclic polyolefin system) The resin) can be exemplified by a single or a copolymer of a cyclic olefin (northene, dicyclopentadiene, etc.) (for example, a single or copolymer of an alicyclic hydrocarbon group having a stereocyclic straight tricyclic fluorenyl group or the like). And a copolymer of a cyclic olefin and a copolymerizable monomer (such as an ethylene-norbornene copolymer or a propylene-norbornene copolymer), etc. The alicyclic polyolefin-based resin may be, for example, a trade name "Asia". ARTON", trade name "ZEONEX" The halogen-containing resin is exemplified by a halogenated vinyl resin (a single polymer of a halogen-containing monomer such as polyvinyl chloride or polyvinyl fluoride; a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, etc.). a copolymer of a halogen-containing monomer; a copolymer of a halogen-containing monomer such as a tetrafluoroethylene-B-17-200903036 olefin copolymer and a copolymerizable monomer, etc.), a vinylidene halide resin (polyvinylidene fluoride) a copolymer of a halogen-containing vinylidene monomer such as a dichloroethylene methyl acrylate copolymer and another monomer). The derivative of the vinyl alcohol-based resin includes a polyvinyl acetal resin (polyethylene formaldehyde resin, polyvinyl butyral resin, etc.) in addition to polyvinyl alcohol or ethylene-vinyl alcohol copolymer. Examples of the vinyl ester-based resin include a single or copolymer of a vinyl ester monomer (polyvinyl acetate or the like), a copolymer of a vinyl ester monomer and a copolymerizable monomer (vinyl acetate-ethylene copolymer, vinyl acetate). - a vinyl chloride copolymer, a vinyl acetate - (meth) acrylate copolymer, etc.). Examples of the (meth)acrylic resin include poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, and methyl methacrylate-(methyl). An acrylate copolymer, a methyl methacrylate-acrylate-(meth)acrylic acid copolymer, a (meth) acrylate-styrene copolymer (MS resin, etc.), etc. The preferred (meth)acrylic resin is a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably about 70 to 100% by weight). The (meth)acrylic resin may be a single or copolymer of a (meth) acrylate having an alicyclic hydrocarbon group such as a tricyclic fluorenyl group. Examples of the styrene resin include a styrene-acrylonitrile copolymer (AS resin), a copolymer of styrene and a (meth)acrylic monomer (styrene-methyl methacrylate copolymer, etc.), and styrene. a maleic anhydride copolymer, a styrene-maleimide copolymer, and the like. Preferred styrene resin -18-200903036, including polystyrene, copolymer of styrene and (meth)acrylic monomer (styrene-methyl methacrylate copolymer, etc.), AS resin, benzene Ethylene-butadiene copolymer and the like. The polyester-based resin may, for example, be an aromatic polyester using an aromatic dicarboxylic acid such as terephthalic acid (including polyethylene terephthalate or polyparaphenylene dicarboxylate). Monoester of C2-4 alkyl diester of formic acid or C2-4 alkyl diester of poly(naphthalene)carboxylate, C2·4 alkyl aryl ester unit (C2·4 alkylene terephthalate and/or Copolymer of naphthyl naphthalate) as a main component (for example, r, for example, 50 mol% or more, preferably 75 to 100 mol%, more preferably 80 to 1 mol%) Ester, etc.), liquid crystalline polyester, and the like. The copolyester aspect 'between the poly C2_4 alkyl aryl esters' contains polyoxy C2_4 stretching diol, C6-1Q alkyl diol, alicyclic diol (cyclohexanedimethanol, Hydrogenated bisphenol A, etc.), a diol having an aromatic ring (9,9-bis(4-(2. hydroxyethoxy)phenyl) fluorene having a fluorene side chain, bisphenol A, bisphenol A-alkylene oxide An adduct, etc., etc., which replaces a part of a copolyester of a c2-4 alkylene glycol; an aliphatic C6 of an asymmetric aromatic dicarboxylic acid, adipic acid, etc., such as citric acid or isophthalic acid; A copolyester such as a dicarboxylic acid or a substituted one of an aromatic dicarboxylic acid. The polyester resin also includes a polyarylate resin, an aliphatic polyester such as an aliphatic dicarboxylic acid such as adipic acid, or a lactone such as ε-caprolactone alone or a copolymer. The preferred polyester resin is usually amorphous such as an amorphous copolyester (e.g., a C2_4 alkyl aryl ester-based copolyester). Examples of polyamine-based resins include aliphatic polyamines such as nylon 46, nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, and nylon 12, -19 - 200903036 An aromatic polyamine such as xylene diamine dicarboxylate (MXD-6). In the polyamine-based resin, a single or a copolymer of decylamine such as ε-caprolactam or a copolymerized decylamine which is not limited to a monomeric decylamine may be used. The polycarbonate resin contains bisphenols (bisphenol A, bisphenol AD, bisphenol F, 9,9-bis(4-(2-hydroxyethoxy)phenyl) fluorene having a fluorene side chain. An aliphatic polycarbonate or the like based on an aromatic polycarbonate or diethylene glycol diallyl carbonate. Among them, polycarbonate resins are usually used. < Aromatic polycarbonate. Among the cellulose derivatives, examples of the cellulose esters include cellulose acetate phthalate (cellulose acetate, cellulose acetate triacetate, etc.; cellulose propionate, cellulose butyrate, and cellulose acetate propionate). , cellulose acetate butyrate, etc.). Among these resins, a resin having high transparency is preferred. Further, at least the resin constituting the continuous phase is preferably a resin having high heat resistance (thermal stability). The melting point or glass transition temperature of the resin constituting the continuous phase may also be 1 50 0 to 2 80 ° C left ^ right ' preferably 1 6 0 to 2 70 ° C or so, more preferably 1 7 0 2 2 6 0. (: (for example, 18 0 to 25 ° C). The thermoplastic resin includes a polypropylene resin, a (meth)acrylic resin, a styrene resin, a polyester resin, and a polyamide resin. An aromatic polycarbonate resin or a cellulose ester (particularly cellulose acetate). The thermoplastic resin constituting the continuous phase is preferably a polyolefin resin (such as a polyacrylic resin) or a polycarbonate resin. Particularly preferred is a polycarbonate resin. The dispersed phase (light scattering factor) can be obtained by adding inorganic-20-200903036 or organic shaped microparticles or fibers to a matrix resin, adding and kneading a resin having a different refractive index to a matrix resin. Formed in the fibrous dispersed phase, including organic fibers (heat resistant organic fibers such as aromatic polyamide fibers, wholly aromatic polyester fibers, polyimine fibers, etc.), inorganic fibers (for example, fibrous materials (for example) Glass fiber, vermiculite fiber, alumina fiber, inorganic fiber such as cerium oxide fiber, flaky material (mica, etc.), etc. The preferred dispersed phase system has high transparency. a resin which is easily deformed at a processing temperature of a uniaxial stretching temperature or the like and has practical heat stability. The melting point or glass transition temperature of the resin constituting the dispersed phase is often lower than that of the resin constituting the continuous phase, for example, It may be about 1 2 0 to 2 50 ° C, preferably about 130 to 2 30 ° C, more preferably 140 to 20 0. (: a resin of about right side. Preferably, the dispersed phase may be a polyolefin resin, A methyl methacrylate resin, a styrene resin, a polyester resin, a polyamine resin, etc. The particularly preferred dispersed phase may be composed of a styrene resin, a polyolefin resin, or the like, particularly a polyolefin system. The resin is composed of a polypropylene resin (such as a crystalline polypropylene resin). The continuous phase and the dispersed phase are composed of components having different refractive indices. The difference in refractive index between the continuous phase and the dispersed phase is, for example, 0.001 or more (for example, 0.001~〇.3 or so), preferably 〇·01~〇.3 or so, more preferably 〇.〇1~〇ι. When the refractive index difference is small, the light diffusibility cannot be imparted. Ratio to dispersed phase, relative The light diffusibility or the like can be, for example, from the former/the latter (weight ratio) = 99/1 to 30/70 (for example, 97/3 to 25/75), preferably 95/5 to 20/80 (for example, 90). /10~20/80) The range of the left and right is -21,030,036. Appropriately selected. The anisotropic scattering layer may also contain a compatibilizing agent. When a compatibilizing agent is used, the affinity between the continuous phase and the dispersed phase is improved, even if The alignment treatment can also prevent the formation of defects (defects such as voids). In terms of the compatibilizing agent, it can be selected from the conventional compatibilizing agent depending on the type of the continuous phase and the dispersed phase, and for example, an oxazoline compound can be modified. a modified resin modified with a base (carboxyl group, acid anhydride group, epoxy group, oxazoline group, etc.), a diene- or rubber-containing polymer, or a diene modified with the aforementioned modified group (epoxy group or the like) Or rubber polymer, etc. These compatibilizing agents may be used singly or in combination of two or more. The compatibilizing agent generally uses a polymer (random, block or graft copolymer) having the same or a common component as the constituent resin of the polymer mixing system, and a polymer having affinity for the constituent resin of the polymer mixing system ( Random, block or graft copolymers, etc. For example, an acid-modified olefin-based resin (maleic anhydride-modified polypropylene-based resin, maleic anhydride-modified polyethylene-based resin, maleic anhydride-modified olefin-based resin; (meth)) Epoxy modified olefin resin (epoxy propylene modified polyethylene resin, epoxy propyl modified polypropylene resin, epoxidized styrene-butyl) An epoxidized diene block copolymer or an epoxy group-modified diene block copolymer such as an styrene-styrene (SBS) block copolymer; and an olefin-based resin grafted on a polycarbonate resin; A polycarbonate-based graft copolymer obtained by modifying a styrene-based resin such as a styrene-based resin (polystyrene or acrylonitrile-styrene copolymer) or the like. These compatibilizing agents may be used singly or in combination of two or more kinds of -22-200903036. The polycarbonate-based graft copolymer is used in the case of using a resin having a carbonate-based resin as a continuous phase. The polycarbonate-based graft copolymer is commercially available from Sakamoto Oil Co., Ltd. under the trade name "Mo dip er". Further, the refractive index of the compatibilizing agent may be approximately the same as that of the dispersed phase resin (for example, the difference in refractive index from the dispersed phase resin is 〇 〇 〇 〇 1 , preferably about 0 to 0.005). The amount of the compatibilizing agent to be used may be, for example, from 0.1 to 20% by weight, preferably from 0.15 to 15% by weight, more preferably from 0.2 to 10% by weight, based on the total of the resin composition of the continuous phase and the dispersed phase. . Furthermore, the anisotropic scattering layer may also contain conventional additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, ultraviolet stabilizers, light stabilizers, etc.), plasticizers, antistatic agents, flame retardants Wait. In the anisotropic scattering layer, the average aspect ratio of the particulate dispersed phase system (the ratio of the average length L2 of the long axis to the average length of the minor axis L2/L!) is larger than 1 ' and the long axis direction of the dispersed phase of the particles Oriented to one side (X-axis direction of the light diffusing plate). In order to impart moderate anisotropy, the average aspect ratio of the particulate dispersed phase (heteromorphic dispersed phase) is, for example, about 1.1 to 100, preferably about 1.2 to 50 (for example, 1.3 to 10), more preferably 1.5 to 10 ( For example, 1.7~5) left and right' can also be around 1.5~3. The dispersed phase may also be a football shape (rotational elliptical shape, etc.), a fiber shape, a rectangular shape, or the like. When the aspect ratio is large, the anisotropic light scattering property can be improved. Further, the average length of the long axis of the dispersed phase is, for example, about 0.1 to 200 μm (for example, 1 to ΙΟΟμηι), preferably about 2 to 80 μm (for example, 3 to 5 μmηη), and usually 5 to 1 μm (for example, , -23- 200903036 1 0~5 0 μ m ). Further, the average length of the minor axis of the dispersed phase is, for example, about 0.05 to 100 μm (for example, 0.1 to 50 μm), preferably about 1 to ΙΟμηη, and usually about 55 to 5 μm. The anisotropic scattering layer may also be composed of at least an anisotropic scattering layer, or a transparent layer may be laminated on the anisotropic scattering layer. In the case of the transparent layer, although various transparent substrates (for example, glass or the like) can be used, a transparent resin layer is usually used. When the transparent resin layer is laminated on the anisotropic scattering layer, the scattering layer can be protected by the transparent resin layer. The transparent resin constituting the transparent resin layer may be selected from the above-exemplified resins. However, in order to improve heat resistance and blocking resistance, a heat resistant resin (a glass transition temperature or a melting point of an aromatic polycarbonate resin or the like is preferably high). Resin or the like), a crystalline resin or the like. The glass transition temperature or melting point of the resin constituting the transparent resin layer may be the same as the glass transition temperature or melting point of the resin constituting the continuous phase. Further, the transparent resin is preferably a resin having a skeleton which is the same as or common to the resin constituting the continuous phase. The thickness ratio of the anisotropic scattering layer to the transparent layer (or transparent resin layer) is, for example, a scattering layer/transparent layer=about 5/95 to 99/1, preferably about 50/50 to 99/1, more preferably 70. /3 0~95/5 or so. The light diffusing plate has a thickness of about 0.5 to 5 mm (e.g., 1 to 5 mm), preferably 1-5 to 4 mm, more preferably 2 to 3.5 mm (e.g., 2 to 3 mm). When the thickness of the light diffusing plate is small, it is difficult to obtain uniform brightness, and there is a case where the light source of the see-through tube is light. When the thickness of the light diffusing plate is too large, the brightness is lowered, and it becomes impossible to illuminate the display unit with high brightness. Further, the thickness of the light diffusing plate is -24 to 200903036 hours, and the mechanical strength (including rigidity) is lowered, and the durability is easily lowered. The haze of the light-diffusing sheet (JI SK 7 1 3 6) is 95% or more (for example, 9 7 to 9 9 9 %), preferably 9 8 5 to 9 9.8 %, more preferably 9 9 ~ 9 9.7 % (for example, 9 9 · 1 to 9 9.6% ). When the haze is small, the shape of the tubular light source can be recognized while the light is not uniformly diffused, and the display quality on the display panel is lowered. The total light transmittance (S K 7 1 3 6 ) of the light diffusing plate is 60% or more (e.g., about 63 to 90%), preferably 65 to 85%, more preferably about 70 to 80%. When the total light transmittance is small, the brightness is easily lowered. Further, the parallel light transmittance (Π SK 7 1 3 6 ) of the light diffusing plate is, for example, 2.5% or less (for example, 〇-1 to 2% or so), preferably 〇2 to 1.5% (for example, 0-25 to 1.2%). More preferably, it is about _ 3~1%. When the parallel light transmittance becomes large, the shape of the tubular light source can be recognized, and the shielding property is low. In the anisotropic diffusion plate of the present invention, in the scattering characteristic F ( Θ ) showing the relationship between the scattering angle 0 and the scattered light intensity F, the light scattering characteristic in the long axis direction of the dispersed phase is Fx ( 0 ), and the relative When the scattering characteristic in the direction perpendicular to the long axis direction of the dispersed phase is Fy(6»), the so-called anisotropy F18 (Fy(18°)/Fx(18°) at the scattering angle 0 = 18° is displayed. )>2 big 値. The anisotropy F is at a scattering angle 1 = 1 8 ° is, for example, 2.1 to 1 0 (e.g., 2.2 to 7), preferably 2.3 to 5 (e.g., 2.5 to 4), more preferably 2.7 to 3· 7 (for example, 3 to 3. 5), usually about 2.5 to 5. When the degree of anisotropy F18 is small, it is difficult to uniformize the brightness. Further, on the surface of the anisotropic diffusion plate, it is also possible to apply a release agent such as a polyoxo oil in a range which does not impair the optical properties of -25-200903036, or to perform a corona discharge treatment. Further, in order to impart light scattering property to the different directions, the uneven portion extending in the long axis direction of the dispersed phase may be formed on the anisotropic diffusion plate. [Manufacturing method of anisotropic diffusion plate] The anisotropic diffusion plate can be obtained by dispersing and aligning the components (resin component, fibrous component, etc.) constituting the dispersed phase in the resin constituting the continuous phase. For example, the resin constituting the continuous phase and the component constituting the dispersed phase (resin component 'fibrous component, etc.) may be stirred and melt-mixed by a conventional method as needed, and may be extruded from a T-die or a ring die. Sheet form is formed to disperse the dispersed phase. Further, a coating method using a composition comprising a light-scattering component and a binder resin, or a lamination method of laminating the above-mentioned composition, may be applied to a substrate (for example, a 'transparent resin layer, a glass plate, or the like), A conventional molding method such as a molding method is produced by molding. Further, the light diffusing plate having a laminated structure composed of an anisotropic scattering layer and a transparent resin layer laminated on at least one of the scattering layers can be formed by a component corresponding to the scattering layer. a co-extrusion molding method in which a resin composition and a resin composition composed of a component corresponding to a transparent resin layer are co-extruded; and a method of laminating another layer in advance by laminating one layer; It is formed by a dry lamination method of the produced scattering layer and transparent resin layer. Further, the alignment treatment of the dispersed phase can be carried out by, for example, (1) a method of stretching and extruding a sheet simultaneously, and (2) a method of uniaxially stretching and extruding a sheet, -26-200903036 (3) combining the foregoing ( The method of 1), the method of the method of (2), and (4) the method of stirring the above-mentioned components by a solution, and film formation by a casting method. It is preferable that the stretch-molded sheet is stretched in the melt film formation while the film forming 'stretch ratio (stretching ratio) is, for example, about 1.5 to 20 times, preferably about 2 to 10 times, more preferably 3 ~7 times or so, usually 1.5 to 6 times (for example, 1.5 to 5 times), especially about 2 to 5 times. The melting temperature is a temperature equal to or higher than the melting point of the resin component (continuous phase resin or dispersed phase resin), for example, 150 to 2 90 ° C, preferably about 200 to 260 ° C. Further, in the light-diffusing sheet having a large thickness, the sheet cannot be cooled in a short time in the melt extrusion molding, and a light-diffusing sheet having an anisotropic property cannot be obtained. In such cases, it is preferred to cool the sheet extruded by the die in a short time by means of a cooling roll or the like. [Use of Light Diffusing Plate] The light diffusing plate of the present invention has an function of anisotropically diffusing light from a light source to illuminate the display unit due to the function of diffusing light in an opposite direction. Therefore, the light diffusing plate is usually disposed between the display unit and a plurality of tubular light sources for backlighting the display unit. The configuration of the light diffusing plate can be selected according to the arrangement direction of the tubular light source. Generally, the long axis direction (X-axis direction) of the dispersed phase of the anisotropic scattering layer is disposed in the vertical direction (about the X-axis direction) in the backlight unit. The axial direction of the tubular light source (Y-axis direction). That is, the anisotropic diffusion plate can arrange the anisotropic scattering layer so that the major axis direction of the granular dispersed phase faces the long axis direction of the tubular light source. Further, the long-axis direction (X-axis direction) of the dispersed phase of the anisotropic scattering layer does not have to be completely perpendicular (X-axis direction) to the source light direction of the backlight unit -27-200903036 (Y-axis direction), for example, It can be arranged in an oblique direction in a range of about ±15°. Generally, the anisotropic diffusion plate is disposed such that the major axis direction of the particulate dispersed phase is directed toward the long axis direction of the tubular light source (or along or in the direction of the long axis of the tubular light source). When the anisotropic scattering layer is disposed in the same direction, the luminance distribution can be homogenized to illuminate the display unit. In a backlight unit (vertical type backlight unit) having a plurality of tubular light sources, the tubular light sources are arranged side by side. The interval between the tubular light sources and the distance L between the tubular light source and the anisotropic diffusion plate may be selected according to the size of the display unit (or the screen), for example, the interval W of the tubular light source is 10 to 100 mm, preferably 20 to 70 mm. More preferably, it is about 25~50mm. Further, the distance L between the tubular light source and the anisotropic diffusion plate may be 2 to 20 mm, preferably 3 to 15 tnm, more preferably about 7 to 13 mm. Furthermore, when the interval between the plurality of tubular light sources is W, and the distance between the tubular light source and the anisotropic diffusion plate is L, the anisotropy F18>(W/L), (W/L) is usually 2~. 10. Preferably, it is 2.2~8 (for example, 2.3~7), and more preferably about 2.5~5. Further, the anisotropy F i 8 is as described above. The backlight unit (vertical type backlight unit) usually uses a direct light and a reflected light from a tubular light source to effectively illuminate the display unit, and is often provided with a reflector on the back side. Further, in the backlight unit, one or a plurality of prism plates may be disposed in front of the light diffusing plate disposed on the front side of the tubular light source, and the diffused light may be collected to illuminate the display unit. The present invention also encompasses the aforementioned backlight unit and a display device comprising a display unit illuminable by the backlight unit. Although the type of display device is infinite -28-200903036 It is equipped with a display unit that must be illuminated from the back, but the display unit is usually used as a liquid crystal display unit. The configuration of the liquid crystal display unit can adopt various configurations not limited to the foregoing examples. Industrial Applicable Articles The present invention can be suitably applied to a display unit of a large screen because the display unit can be uniformly illuminated by the backlight unit. In the vertical type backlight unit, since the screen size can be corresponding to various screen sizes, the screen size of the display unit is not particularly limited, for example, 20 吋 or more (for example, 2 3 to 300 吋, preferably 3 0 to 2 0 0) "left and right) can be. [Examples] Hereinafter, the present invention will be described in more detail based on the examples, but the present invention is not limited by the examples. [Example 1] 100 parts by weight of a polypropylene ("WFW-4" manufactured by Japan Propylene Corporation) as a matrix resin, and polystyrene (G1 00 made from Toyo Styrene) 5 parts by weight, a compatibilizing agent ("Epo-Friend AT202" manufactured by Daisy Chemical Industry Co., Ltd.), 3 parts by weight, and an anti-caking agent ("TX 1 92 5" manufactured by Nippon Polypropylene Co., Ltd.) 2 parts by weight, a UV absorber ("Cinuba Special Chemicals" (Tinuvin 234)) 〇. 4 parts by weight, using an extrusion molding machine, with a resin temperature of 23 ° C, a die opening of 8 mm from the mold The head was melt extruded to cool the cooling roll 40 with water. (: Cooling, modulating a light diffusing plate having a thickness of 1 mm and 2 mm. In these light diffusing plates, polystyrene forms scattering particles (particle-like dispersed phase), and the shape of the dispersed phase of the particles is a round shape, thick -29- 200903036 degrees (short axis) 2 μm and length (long axis) 26 μm. [Example 2] Two kinds of three-layer light diffusing plates were fabricated (the anisotropic scattering layer was used as the intermediate layer, and the intermediate layer was doubled). A light-diffusing sheet of a transparent resin layer as a surface layer is laminated on the surface. In other words, 100 parts by weight of polypropylene ("WFW-4" manufactured by Nippon Polypropylene Co., Ltd.) and an anti-caking agent (made by Japanese Polypropylene Co., Ltd.) are used. "TX 1925") 2 parts by weight of a resin composition, and a resin composition for a surface layer. Further, 100 parts by weight of polypropylene ("WFW-4" manufactured by Nippon Polypropylene Co., Ltd.) as a matrix resin, polystyrene is used. (Toyo styrene ("G1 00") 5 parts by weight, a compatibilizing agent ("Epo-Friend ΑΤ202" manufactured by Daisy Chemical Industry Co., Ltd.) 0.3 parts by weight, and an ultraviolet absorber (Ciba Specialization) Product (stock) "T inuvi η 2 34") 〇·4 parts by weight The resin composition is used as a resin composition for the intermediate layer. Then, the resin composition for the surface layer and the resin composition for the intermediate layer are supplied to the co-extrusion molding machine at a resin temperature of 23 ° C and a die opening of 8 mm from the die. The product was melt-extruded and cooled by a water-cooling chill roll at 40 ° C to prepare a light diffusing plate (thickness ratio = 1: 1 : 1 ) having a laminated structure of two types and three layers having a thickness of 1 mm and 2 mm. In the intermediate layer, polystyrene forms scattering particles (particulate dispersed phase), and the shape of the dispersed phase of the particles is ellipsoidal opening-thickness (short axis) 2/zm and length (long axis) 40 μm. Example 3] 100 parts by weight of a polycarbonate resin ("Upiron S-2000" manufactured by Mitsubishi Engineering Plastics Co., Ltd.) and a polypropylene ("WFW-4" manufactured by Nippon Polypropylene Co., Ltd.) as a matrix resin. 0.4 parts by weight of UV absorber (Cumba Specialized Product -30-200903036 (Tinuvin 234)), using an extrusion molding machine, with a resin temperature of 300 ° C and a die opening of 8 mm The die was melt extruded, and the oil temperature was adjusted to 3 mold rolls at 150 ° C for cooling. A light diffusing plate having a thickness of 1 mm and 2 mm is prepared. In these light diffusing plates, polypropylene forms scattering particles (particle-like dispersed phase), and the shape of the dispersed phase of the particles is a round body shape, and the thickness (short axis) 2 Μιη and length (long axis) 20 μm. [Example 4] Two kinds of three-layer light diffusing plates were produced (the anisotropic scattering layer was an intermediate f " layer, and the layers on both sides of the intermediate layer were transparent as a surface layer. a light-diffusing sheet of a resin layer), that is, 100 parts by weight of a polycarbonate resin ("Upiron S-2000" manufactured by Mitsubishi Engineering Plastics Co., Ltd.) and a UV absorber ("Ciba" special product" Tinuvin 2 3 4") 0.4 parts by weight of a resin composition as a resin composition for a surface layer. Further, a polycarbonate resin ("Upiron S-2000" manufactured by Mitsubishi Engineering Plastics Co., Ltd.) as a matrix resin was used in an amount of 1 part by weight, and polypropylene ("WFW-4" manufactured by Nippon Polypropylene Co., Ltd.) 5 was used. The resin composition of the parts by weight is used as a resin composition for the intermediate layer. Then, the resin composition for the surface layer and the resin composition for the intermediate layer were supplied to a co-extrusion molding machine, and melt-extruded from the die at a resin temperature of 300 ° C and a die opening of 8 mm, and three molds were adjusted at the oil temperature. The roller was cooled at 150 ° C to prepare a light diffusing plate (thickness ratio = 1: 1: 1) having a laminated structure of two kinds of three layers and having a thickness of 1 mm and 2 mm. In these light-diffusing sheets, polypropylene forms scattering particles (particle-like dispersed phase) in the intermediate layer. The shape of the dispersed phase of the particles is in the shape of a round body, and the thickness (short axis) is 2 // m and the length (long axis). ) 34μιη. -31 - 200903036 [Comparative Example 1] The spherical crosslinked polystyrene resin particles were mixed in 100 parts by weight of a polycarbonate resin ("Upiron S-2000" manufactured by Mitsubishi Engineering Plastics Co., Ltd.). 1 part by weight of "SBX-6" manufactured by the finished product (stock), using an extrusion molding machine, melt-extruding from the die at a resin temperature of 300 ° C and a die opening of 8 mm, and adjusting the oil temperature by 3 The mold roll was cooled at 150 ° C to prepare a light diffusing plate having a thickness of 2 mm. The shape of the dispersed phase of the particles is spherical and has a diameter of 6 μm. [Comparative Example 2] Spherical cross-linked polystyrene-based resin particles were mixed in 100 parts by weight of an acrylic resin ("M5" manufactured by Sumitomo Chemical Co., Ltd.) ("Secretized Products" (SBX-6) 1) by weight, melt-extruded from a die at a resin temperature of 2300 ° C 'die opening degree of 8 mm, using an extrusion molding machine, and cooled by a water-cooling roll at 40 ° C to prepare a light-diffusing sheet having a thickness of 2 mm. The shape of the dispersed phase of the particles is spherical and has a diameter of 6 y m. Then, the characteristics of the light-diffusing sheet obtained in the examples and the comparative examples were examined as follows. Display quality evaluation A light diffusing plate was mounted on a vertical type liquid crystal display device, and a display device having the structure shown in Fig. 1 was produced. That is, on the cathode discharge tube (fluorescent lamp) arranged side by side at intervals of 3 3 mm, the light diffusion plate is placed in the flow direction of extrusion molding (the light diffusion plate of the embodiment is the long axis of the particulate dispersed phase). The direction is the same as the length of the cathode discharge tube (fluorescent lamp), and the display is illuminated. After 1 minute, the display is visually observed, and the display quality is evaluated by the following criteria. -32- 200903036 A: The shape of the cathode discharge tube (fluorescent lamp) is not seen (it becomes a uniform light-emitting state). B: Although the light-emitting state is approximately uniform, the position of the cathode discharge tube (fluorescent lamp) is known. C: Not easy to see but identifiable cathode discharge tube (fluorescent lamp) lamp D: see cathode discharge tube (fluorescent lamp)
在加熱槽內放置光擴散板於溫度60°C、9(TC及ll〇°C Γ: 下維持500小時並提供至高溫試驗後，以目視觀察外觀以 判定是否變形，同時硏究有無外溢。還有，以「Α」表示即 使以高溫試驗亦無變化的情況，以「外溢」表示發生外溢 之光擴散板、以「變形」表示有變形之光擴散板。 結果示於表 -33- 200903036 表1 厚度 霧度 各向異 顯示品質 耐久性 性度f18 60°C 90°C 110°C 實施例1 1mm 99% 3 A 外溢 外溢 變形、外溢 2mm 99% 3 A 外溢 外溢 變形、外溢 實施例2 1mm 98% 4 C 外溢 外溢 變形 2mm 99% 4 A 外溢 外溢 變形 實施例3 1mm 99% 2.7 A A A A 2mm 99% 2.7 A A A A 實施例4 1mm 98% 2.7 C A A A 2mm 99% 2.7 A A A A 比較例1 2mm 99%以上 1 B A A A 比較例2 2mm 99%以上 1 B A 變形 變形 【圖式簡單說明】 第1圖係顯示本發明之垂直型背光單元（或面光源裝置） 與具備該單元之液晶顯示裝置之一範例的槪略分解截面 圖。 第2圖係顯示光擴散板與管狀光源之關係的模式圖。 【主要元件符號說明】 1 液晶顯示單元 2 液晶胞 3a 透明零件 3b 透明零件 4a 透明電極 -34- 200903036 4b 透 明 電 極 5 液 晶 6 彩 色 濾 光片 7 第 1 偏 光板 8 偏 光 層 9a 保 護 層 9b 保 護 層 10 抗 反 射 層 11 相 位 差 膜 12 第 2 偏 光板 13 偏 光 層 14a 保 護 層 14b 保 護 層 15 相 位 差 膜 2 1 垂 直 型 背光單元（或面光源裝置） 22 管 狀 光 源（冷陰極放電管或螢光燈） 23 反 射 板 24 光 擴 散 板 24a 各 異 向 性散射層 24b 透 明 樹 脂層 25 鏡 片 膜 (或稜鏡板） 25 a 鋸 齒 狀 之凹凸列（或截面三角形狀之微小稜鏡歹[J ) -35-The light diffusing plate was placed in a heating bath at a temperature of 60 ° C, 9 (TC and ll ° ° C Γ: for 500 hours and supplied to a high temperature test, and the appearance was visually observed to determine whether or not the deformation was observed, and whether or not there was an overflow. In addition, "Α" indicates that there is no change even in the high-temperature test, and the light diffusing plate in which the overflow occurs is indicated by "overflow", and the light diffusing plate is deformed by "deformation". The results are shown in Table-33-200903036 Table 1 Thickness haze shows the quality durability degree f18 60 °C 90 °C 110 °C Example 1 1mm 99% 3 A Overflow overflow deformation, overflow 2mm 99% 3 A Overflow spillover deformation, spillover Example 2 1mm 98% 4 C Overflow Overflow Deformation 2mm 99% 4 A Overflow Overflow Deformation Example 3 1mm 99% 2.7 AAAA 2mm 99% 2.7 AAAA Example 4 1mm 98% 2.7 CAAA 2mm 99% 2.7 AAAA Comparative Example 1 2mm 99% or more 1 BAAA Comparative Example 2 2mm 99% or more 1 BA deformation deformation [Simplified description of the drawings] Fig. 1 shows an example of a vertical type backlight unit (or surface light source device) of the present invention and a liquid crystal display device having the same Fig. 2 is a schematic view showing the relationship between the light diffusing plate and the tubular light source. [Main component symbol description] 1 Liquid crystal display unit 2 Liquid crystal cell 3a Transparent part 3b Transparent part 4a Transparent electrode -34- 200903036 4b Transparent electrode 5 Liquid crystal 6 Color filter 7 First polarizing plate 8 Polarizing layer 9a Protective layer 9b Protective layer 10 Antireflection layer 11 Phase difference film 12 Second polarizing plate 13 Polarizing layer 14a Protective layer 14b Protective layer 15 Phase difference film 2 1 Vertical type backlight unit (or surface light source unit) 22 Tubular light source (cold cathode discharge tube or fluorescent lamp) 23 Reflector 24 Light diffusing plate 24a Anisotropic scattering layer 24b Transparent resin layer 25 Lens film (or slab) 25 a jagged embossed column (or small 截面 of triangular shape [J ) -35-