200903037 九、發明說明： 【發明所屬之技術領域】 本發明係關於可使來自液晶背光單元之光源成爲均 勻、且亮度之角度相依性爲小之光擴散薄膜、及使用它之 液晶背光單元。 【先前技術】 迄今爲止，在使用於液晶背光單元（backlight unit) 之光學薄片方面，爲提高對顯示螢幕平面成法線方向的亮 度，亦即正面亮度（front brightness)而已有各種光擴散薄 片或稜鏡片等之提高亮度的薄片。然而，在使用此等光學 薄片之液晶背光單元，其正面亮度雖然高，但是從斜方向 觀看時’則其對比（contrast )或色再現性卻有降低的情況。 以傳統習知的粒子與黏結劑樹脂所製造之擴散薄膜，一直 係以聚光在顯示螢幕之法線方向爲目的進行開發（發明專 利文獻1、2)。最近在瑞典之TCO Development公司所出 版的T C Ο規格中’對於平板面板顯示之亮度之角度相依性 則有加以規定，而該規定則已受到液晶顯示器製造商重 視’對於平扳面板顯示之亮度的角度相依性之抑制，目前 則已變得非常重要。 (發明專利文獻1)曰本發明專利特開第200 1 - 1 5 4004 號公報 (發明專利文獻2 )日本發明專利特開第2 〇 〇丨_丨6 6丨i 4 號公報 【發明內容】 200903037 〔所欲解決之技術問題〕 然而，針對此等先前的光擴散薄片或稜鏡片等之提高 亮度薄片而言，其係例如在直下型背光（direct backlight-type backlight)設置擴散板，並在其上積層光擴 散薄片或稜鏡片的情況下，一直藉由將以擴散板消除亮度 不均句性（unevenness of brightness)且已經擴大視野角之 光，以珠粒薄片或稜鏡片等將光聚光於顯示之法線方向， 以提高正面亮度。此情況下，雖然可提高正面亮度，但是 例如若由對於顯示平面之法線朝畫面之長邊方向爲30°的位 置、或朝畫面之短邊方向爲1 5°的位置觀看時，則由於液晶 顯示面的位置而產生亮度差，以致有可能導致對比或色再 現性降低的情況。 本發明係有鑑於此等先前技術之背景，而以在液晶背 光單元方面能提供一種可充分地滿足消除亮度不均勻性、 抑制亮度之角度相依性之優越的光擴散薄膜及液晶背光單 元爲其課題。 〔解決問題之技術方法〕 本發明爲解決如上所述之課題而採用如下所述之方 法。亦即，本發明之光擴散薄膜，其特徵爲其中在基質樹 脂（matrix resin)內部含有機粒子之擴散成分（diffusing component)所構成的內部光擴散薄膜（internal light-diffusing film )之至少單面上形成光擴散層，且該光擴散層係至少由 黏結劑樹脂與粒子所構成。 此外’本發明之液晶背光單元，其特徵爲其係使用如 200903037 上所述之光擴散薄膜所構成。 〔發明之功效〕 根據本發明，則由於可提供一種可降低亮度不均勻性 且抑制亮度之角度相依性之優越的光擴散薄膜，因此可提 供一種能充分地滿足對比或色再現性之液晶顯示裝置用之 液晶背光單元。 【實施方式】 〔本發明之最佳實施方式〕 本發明係關於如前所述之技術問題，亦即在液晶背光 單元方面，針對能充分地滿足消除亮度不均勻性、抑制亮 度之角度相依性之優越的光擴散薄膜加以專心檢討，而試 製一種在特定的內部光擴散薄膜之至少單面上積層含有粒 子之特定的光擴散層所獲得之光擴散薄膜，結果可確認以 特定的光擴散層即能發揮擴散性與透鏡效應之聚光性兩種 功能，而一舉成功地解決如前所述之技術問題。 以下，就本發明之實施模式與第1圖同時加以說明。 第1圖係展示在本發明之實施模式之光擴散薄膜之一實例 截面圖。第1圖（a)係經在內部光擴散薄膜之單面上積層 光擴散層所獲得之光擴散薄膜；第1圖（b )係經在內部光 擴散薄膜之兩面上積層光擴散層所獲得之光擴散薄膜。 本發明之光擴散薄膜係在基質樹脂1之內部含有機粒 子之擴散成分2所構成的內部光擴散薄膜5、與在該內部光 擴散薄膜5之至少單面上形成光擴散層6所構成。此時， 重要的是該光擴散層必須爲至少由黏結劑樹脂7與粒子3 200903037 所構成。 本發明之如前所述之內部光擴散薄膜5，由於其係在基 質樹脂1內部含有機粒子之擴散成分2所構成，係屬於具 有可將入射之光加以擴散的功能之薄膜。此外，用於積層 在此等內部光擴散薄膜5上之由黏結劑樹脂7與粒子3所 構成的光擴散層6係同時具有因光之多重折射作用的擴散 性與因透鏡效應的聚光性之層。 對於此等光擴散層6之粒子3,雖然並無特殊的限制， 但是該粒子3較佳爲使用數量平均粒徑爲至50μιη 者，更佳爲至20/zm者。若平均粒徑小於0.5/zm時’ 則有可能在折射、反射或散射時造成波長相依性增大。此 外，若大於5 0 /z m時，則有可能因在光擴散層中之粒子塡 充率降低、在光擴散層中粒子不存在的空間之比率增大而 造成漏光使得擴散性降低的情況。即使在使用平均粒徑爲 較大粒子的情況下，如欲提高擴散性，若藉由增加粒子添 加量、增加光擴散層之厚度、在內部光擴散薄膜之兩面設 置光擴散層、或倂用平均粒徑較小的粒子以塡充粒子之間 的空間之方法也可達成。 此外，此等粒子3之實例是可使用聚甲基丙嫌酸甲醋 系樹脂、聚苯乙烯系樹脂及其等之共聚合物等之有機粒 子、或多晶砂（polysilicon)、一氧化砍、氧化駄等之無機 粒子、及由有機與無機之複合材料所構成的粒子等。 如前所述之黏結劑樹脂較佳爲使用選自由丙稀酸醋 系、聚酯系、環氧系、三聚氰胺系、及胺基甲酸醋系所組 200903037 成的族群中之一種以上。 在本發明之光擴散薄膜中之光擴散層，相對於1 〇〇重 量份之黏結劑樹脂’則粒子較佳爲0.1至5 0重量份。若粒 子相對於黏結劑樹脂之含量爲少於〇. 1重量份時’則有可能 光擴散層無法獲得充分的光擴散性的情況。此外，若超過 5 〇重量份時，則有可能造成在塗布塗液時發生困難的情況。 如前所述之光擴散層之厚度較佳爲0.5/im至100/zm， 更佳爲5 # m至5 0 a m。光擴散層相對於黏結劑樹脂的粒子 之含率與粒子的平均粒徑爲相同時，層厚度一增厚，則擴 散性將增大。由於平均粒徑之較佳的大小爲0.5 // m以上， 光擴散層之較佳的厚度之下限値則與使用此粒子並以單層 塗布粒子時的情況相同。此外，若層厚超過1 00 A m時，則 將可提高擴散性，但是在另一方面卻有可能由於全光線透 射率降低而導致亮度降低的情況。 將光擴散層塗布於內部光擴散薄膜之方法，例如可由 風刀方式、凹版輪轉方式、反轉輥方式、噴塗方式或刮刀 方式等中任意選擇使用。 經將光擴散層塗布於內部光擴散薄膜後，藉由利用熱 風、紅外線、遠紅外線等加熱’即可形成塗布層。 此外，如前所述之內部光擴散薄膜，其基質樹脂！雖 然並無特殊的限制’但是因聚酯樹脂係價廉且具有優越的 透明性、機械強度，且對於來自背光單元之光或熱具有充 分耐性而適合使用。 此外’用於包含在此等內部光擴散薄膜之擴散成分2 200903037 必須爲有機粒子。有機粒子較佳爲使用例如丙烯酸系樹 脂、有機聚矽氧樹脂、聚苯乙烯、聚烯烴、聚酯、尿素樹 脂、甲醛縮合物、氟樹脂等。雖然以無機物用作爲擴散成 分也能獲得擴散性，但是由於有機成分之透明性高，可製 得光之損失爲少的高擴散性且高透射性之內部光擴散薄 膜。其結果，若將經使用該內部光擴散薄膜之光擴散薄膜 適用於液晶背光單元時，則可使液晶背光成爲高亮度。基 於此等理由，在本發明則以有機粒子用作爲擴散成分2。 內部光擴散薄膜之製法，係例如將預先經熔融捏合成 均勻所調配得之切粒（pellet)直接地供應至捏合擠壓機等 加以熔融捏合。茲就成形法加以說明。其係包括例如熔融 射出於模具之射出成形、或由擠壓機經由T-模等而熔融擠 壓之擠壓成形等之方法。成形於薄膜上後，視需要則藉由 延伸步驟、熱處理步驟等，即可製得目的之內部光擴散薄 膜。其中，若需要延伸步驟時，在延伸後則有可能在薄膜 中形成空隙（void )。若在薄膜中發生形成空隙時，則有可 能降低全光線透射率，因此有時候也需要藉由熱處理等步 驟來消除空隙。 然而，就經在此等內部光擴散薄膜、及透明基材薄膜 塗布由（塗布珠粒）黏結劑樹脂7與粒子3所構成的樹脂 組成物以形成光擴散層6所製得之光擴散薄膜而言，即使 分別單獨使用也具有可將光加以擴散之功能，但是即使將 各薄膜單純地加以積層，則也無法顯現與本發明之光擴散 薄膜相同之功能。 -10- 200903037 亦即，就單純地積層此等內部光擴散薄膜與擴散薄膜 所獲得者而言，由於空氣層存在於薄膜之間，對於由透明 基材薄膜所構成的光擴散薄膜之視野角特性將造成極大影 響，因此雖然能稍微提高光擴散性，但是一經測定如第3 圖（a )所示之變角光度時，則在0°視野角附近可確認到突 起狀之波峰。此現象一發生，在使用於例如直下型液晶背 光單元的情況下，則有可能由正面即能視認到螢光管之不 均勻性（第3圖（a)係展示將在透明基材薄膜之單面上塗 布由黏結劑樹脂與粒子所構成的光擴散層所製得之光擴散 薄膜，疊合在內部光擴散薄膜上，並由內部光擴散薄膜側 而入射光時之變角光度特性。第3圖（b )係在經在以（a ) 所使用的內部光擴散薄膜之單面上塗布以（a )所使用的光 擴散層所製得之本發明之光擴散薄膜，顯示由未塗布光擴 散層之面而入射光時之變角光度特性。）。此外，若測定 全光線透射率時，與本發明之光擴散薄膜相比較，則有可 能透射率會降低。 此外，由第4圖之視野角測定的結果也得知，就在透 明基材薄膜上形成光擴散層6所獲得之擴散薄膜、與將其 擴散薄膜單純地與內部光擴散薄膜積層所獲得之構成者而 言，雖然具有相同之視野角特性，但是在本發明之光擴散 薄膜則具有角度相依性爲非常小之優越的視野角特性（第4 圖（a )係展示經在透明基材薄膜之單面上塗布由黏結劑樹 脂與粒子所構成的光擴散層所製得之光擴散薄膜之水平方 向的視野角特性。第4圖（b )係展示經在內部光擴散薄膜 -11- 200903037 之單面上塗布以（a)所使用的光擴散層所製得之本發明之 光擴散薄膜之水平方向的視野角特性。第4圖（c )係展示 經積層（a )之光擴散薄膜與以（b )所使用的內部光擴散薄 膜所製得之擴散薄膜之水平方向的視野角特性。）。 本發明之光擴散薄膜，係不至於發生如前所述之漏 光，且與單純地積層內部光擴散薄膜、與在透明基材薄膜 具有由黏結劑樹脂與粒子所構成的光擴散層之光擴散薄膜 所製得者相比較’則爲同時具有其以上之擴散性與遮蔽性 f ' 、 者。 本發明之光擴散薄膜，其藉由在平行於薄膜面，且互 相成正交之至少兩方向所測定的變角光度所計算得之擴散 度較佳爲皆爲20以上、60以下，更佳爲25以上、60以下。 該測定所使用的變角光度計是三維變角光度計 (GoniophotoMeter) GP-200 (村上色彩技術硏究所股份有 限公司（Murakami Color Research Laboratory Co·,· Ltd.) 製造）。擴散度可由下式計算得，該値係表示由法線方向 c 入射光時之光傳播情況參數，此値愈大，則表示光愈能加 以擴散。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-diffusing film which can make a light source from a liquid crystal backlight unit uniform and whose angle dependence of brightness is small, and a liquid crystal backlight unit using the same. [Prior Art] Heretofore, in order to improve the brightness in the normal direction of the display screen plane, that is, the front brightness, in the optical sheet used for the backlight unit of the liquid crystal, various light-diffusing sheets or A thin sheet of brightness, such as a crepe. However, in a liquid crystal backlight unit using such an optical sheet, although the front luminance is high, the contrast or color reproducibility is lowered when viewed from an oblique direction. A diffusion film made of a conventionally known particle and a binder resin has been developed for the purpose of collecting light in the normal direction of the display screen (Invention Patent Documents 1 and 2). Recently, in the TC Ο specification published by TCO Development of Sweden, 'the angle dependence of the brightness of the flat panel display is specified, and the regulation has been valued by the LCD manufacturer's for the brightness of the flat panel display. The suppression of angular dependence has become very important at present. (Patent Document 1) Japanese Laid-Open Patent Publication No. 2001-150400 (Invention Patent Document 2) Japanese Patent Application Laid-Open No. 2 〇〇丨 丨 6 6丨i 4 (Invention) 200903037 [Technical Problem to be Solved] However, for such a brightness-increasing sheet such as a conventional light-diffusing sheet or a cymbal sheet, for example, a diffusing plate is provided in a direct backlight-type backlight, and In the case where a light-diffusing sheet or a slab is laminated thereon, light is collectively condensed by a bead sheet or a ruthenium by eliminating the unevenness of brightness and diffusing the light of the viewing angle by the diffusion plate. Light in the normal direction of the display to increase the front brightness. In this case, although the front luminance can be increased, for example, when the normal line of the display plane is viewed at a position of 30° in the longitudinal direction of the screen or at a position of 15° in the short side direction of the screen, The position of the liquid crystal display surface causes a difference in luminance, so that there is a possibility that contrast or color reproducibility is lowered. The present invention is based on the background of the prior art, and provides a light diffusing film and a liquid crystal backlight unit which are excellent in the angle dependence of brightness non-uniformity and brightness suppression in the liquid crystal backlight unit. Question. [Technical method for solving the problem] The present invention adopts the method described below in order to solve the above problems. That is, the light-diffusing film of the present invention is characterized in that at least one side of an internal light-diffusing film composed of a diffusing component of machine particles inside a matrix resin is used. A light diffusion layer is formed thereon, and the light diffusion layer is composed of at least a binder resin and particles. Further, the liquid crystal backlight unit of the present invention is characterized in that it is constituted by a light-diffusing film as described in 200903037. [Effect of the Invention] According to the present invention, it is possible to provide a light-diffusing film which can reduce brightness unevenness and suppress the angular dependence of brightness, thereby providing a liquid crystal display which can sufficiently satisfy contrast or color reproducibility. Liquid crystal backlight unit for devices. [Embodiment] [Best Embodiment of the Invention] The present invention relates to the technical problem as described above, that is, in terms of a liquid crystal backlight unit, it is possible to sufficiently satisfy the angle dependence of eliminating luminance unevenness and suppressing luminance. The superior light-diffusing film was intensively reviewed, and a light-diffusing film obtained by laminating a specific light-diffusing layer containing particles on at least one side of a specific internal light-diffusing film was experimentally produced, and as a result, a specific light-diffusing layer was confirmed. That is, the two functions of diffusibility and concentrating of the lens effect can be exerted, and the technical problems as described above are successfully solved in one fell swoop. Hereinafter, the embodiment mode of the present invention will be described together with the first drawing. Fig. 1 is a cross-sectional view showing an example of a light-diffusing film in an embodiment mode of the present invention. Fig. 1(a) is a light diffusing film obtained by laminating a light diffusing layer on one side of an internal light diffusing film; Fig. 1(b) is obtained by laminating a light diffusing layer on both sides of an internal light diffusing film. Light diffusing film. The light-diffusing film of the present invention comprises an internal light-diffusing film 5 comprising a diffusion component 2 of organic particles in the matrix resin 1 and a light-diffusing layer 6 formed on at least one surface of the internal light-diffusing film 5. At this time, it is important that the light diffusion layer be composed of at least the binder resin 7 and the particles 3 200903037. The internal light-diffusing film 5 of the present invention described above is composed of a diffusion component 2 containing organic particles in the matrix resin 1, and is a film having a function of diffusing incident light. Further, the light-diffusing layer 6 composed of the binder resin 7 and the particles 3 for laminating on the internal light-diffusing film 5 has a diffusibility due to the multiple refraction of light and a condensing property due to a lens effect. Layer. The particles 3 of the light-diffusing layers 6 are not particularly limited, but the particles 3 are preferably those having a number average particle diameter of 50 μm, more preferably 20 μm. If the average particle diameter is less than 0.5/zm, it is likely to cause an increase in wavelength dependence upon refraction, reflection or scattering. In addition, when it is larger than 50 / z m, there is a possibility that light leakage is lowered due to a decrease in the particle charge ratio in the light diffusion layer and a ratio of a space in which the particles do not exist in the light diffusion layer. Even when the average particle diameter is larger, if the diffusibility is to be increased, if the amount of the particles is increased, the thickness of the light diffusion layer is increased, or the light diffusion layer is provided on both sides of the internal light diffusion film, or Particles having a smaller average particle diameter can also be obtained by filling the space between the particles. Further, examples of such particles 3 are organic particles such as polymethyl ketone acid vinegar resin, polystyrene resin, and the like, or polysilicon, and oxidized chopping. Inorganic particles such as cerium oxide, particles composed of a composite material of organic and inorganic, and the like. The binder resin as described above is preferably one or more selected from the group consisting of acrylic acid vinegar, polyester, epoxy, melamine, and urethane phthalate. In the light-diffusing layer in the light-diffusing film of the present invention, the particles are preferably from 0.1 to 50 parts by weight based on 1 part by weight of the binder resin'. If the content of the particles relative to the binder resin is less than 0.1 part by weight, there is a possibility that the light diffusion layer cannot obtain sufficient light diffusibility. Further, when it exceeds 5 parts by weight, it may cause difficulty in applying the coating liquid. The thickness of the light diffusion layer as described above is preferably from 0.5/im to 100/zm, more preferably from 5 #m to 50 a. When the content of the particles of the light-diffusing layer with respect to the binder resin is the same as the average particle diameter of the particles, when the thickness of the layer is increased, the diffusibility is increased. Since the preferable size of the average particle diameter is 0.5 / m or more, the lower limit of the preferable thickness of the light-diffusing layer is the same as when the particles are used and the particles are coated in a single layer. Further, if the layer thickness exceeds 100 Å, the diffusibility can be improved, but on the other hand, there is a possibility that the luminance is lowered due to a decrease in the total light transmittance. The method of applying the light-diffusing layer to the internal light-diffusing film can be arbitrarily selected, for example, by an air knife method, a gravure rotation method, a reverse roll method, a spray method, or a doctor blade method. After the light diffusion layer is applied to the internal light diffusion film, the coating layer is formed by heating with hot air, infrared rays, far infrared rays or the like. In addition, as described above, the internal light diffusing film, its matrix resin! Although there is no particular limitation, the polyester resin is suitable for use because it is inexpensive, has excellent transparency, mechanical strength, and is sufficiently resistant to light or heat from a backlight unit. In addition, the diffusion component 2 200903037 contained in the internal light diffusing film contained therein must be an organic particle. The organic particles are preferably, for example, an acrylic resin, an organic polyoxyn resin, polystyrene, polyolefin, polyester, urea resin, formaldehyde condensate, fluororesin or the like. Although diffusibility can be obtained by using an inorganic substance as a diffusion component, since the transparency of the organic component is high, an internal light-diffusing film having high diffusibility and high transmittance with little loss of light can be obtained. As a result, when the light-diffusing film using the internal light-diffusing film is applied to a liquid crystal backlight unit, the liquid crystal backlight can be made high in brightness. For the reasons described above, in the present invention, organic particles are used as the diffusion component 2. The internal light-diffusing film is produced by, for example, directly supplying a pellet which has been previously melt-kneaded and uniformly blended to a kneading extruder or the like to be melt-kneaded. The forming method is explained. The method includes, for example, a method of injection molding by melt injection into a mold, or extrusion molding by melt extrusion by an extruder through a T-die or the like. After being formed on the film, the desired internal light-diffusing film can be obtained by an extension step, a heat treatment step, or the like as needed. Among them, if an extension step is required, it is possible to form voids in the film after stretching. If a void is formed in the film, the total light transmittance may be lowered. Therefore, it is sometimes necessary to eliminate the void by a heat treatment or the like. However, a light-diffusing film obtained by forming a light-diffusing layer 6 by applying a resin composition composed of (coating bead) binder resin 7 and particles 3 to the internal light-diffusing film and the transparent base film is applied thereto. In addition, even if it is used separately, it has a function which can diffuse light, However, even if each film is simply laminated, the function similar to the light-diffusion film of this invention cannot be exhibited. -10- 200903037 That is, for those who simply laminate these internal light diffusing films and diffusing films, since the air layer exists between the films, the viewing angle of the light diffusing film composed of the transparent substrate film is Since the characteristics are greatly affected, the light diffusibility can be slightly improved. However, when the variable angle illuminance shown in Fig. 3(a) is measured, a peak of a protrusion shape can be confirmed in the vicinity of the viewing angle of 0°. When this phenomenon occurs, in the case of, for example, a direct-type liquid crystal backlight unit, it is possible to visually recognize the unevenness of the fluorescent tube from the front side (Fig. 3(a) shows that it will be in the transparent substrate film. A light-diffusing film obtained by coating a light-diffusing film composed of a binder resin and particles on one surface, is laminated on the internal light-diffusing film, and has a variable-angle luminosity characteristic when the light is incident from the side of the internal light-diffusing film. Fig. 3(b) shows the light diffusing film of the present invention obtained by coating the light diffusing layer used in (a) on one side of the internal light diffusing film used in (a), which is shown by A variable angle photometric characteristic when the surface of the light diffusion layer is coated and incident light. Further, when the total light transmittance is measured, the transmittance may be lowered as compared with the light-diffusing film of the present invention. Further, as a result of measuring the viewing angle of FIG. 4, it was also found that the diffusion film obtained by forming the light diffusion layer 6 on the transparent base film and the diffusion film formed by simply laminating the diffusion film with the internal light diffusion film were obtained. The constituents have the same viewing angle characteristics, but the light-diffusing film of the present invention has a very small viewing angle characteristic with a very small angular dependence (Fig. 4(a) shows a transparent substrate film. The horizontal viewing angle characteristic of the light diffusing film made of the light diffusing layer composed of the binder resin and the particles is coated on one surface. Fig. 4(b) shows the internal light diffusing film-11-200903037 The horizontal direction viewing angle characteristic of the light diffusing film of the present invention obtained by using the light diffusing layer used in (a) is coated on one surface. Fig. 4(c) shows the light diffusing film laminated with (a) The viewing angle characteristic in the horizontal direction of the diffusion film obtained by the internal light-diffusing film used in (b). The light-diffusing film of the present invention does not cause the light leakage as described above, and the light diffusion of the light diffusion layer composed of the binder resin and the particles in the transparent base film The film produced by the film is 'having more than the above diffusibility and shielding f'. In the light-diffusing film of the present invention, the degree of diffusion calculated by the variable angle illuminance measured in at least two directions orthogonal to the film surface and orthogonal to each other is preferably 20 or more and 60 or less, more preferably It is 25 or more and 60 or less. The variable angle photometer used in the measurement was a GoniophotoMeter GP-200 (manufactured by Murakami Color Research Laboratory Co., Ltd.). The degree of diffusion can be calculated from the equation for the light propagation condition when the light is incident from the normal direction c. The larger the temperature, the more the light can be diffused.
•擴散度={ (L2(T+L7〇。）/ 2} / Ls^XlOO 其中，L5.、L2。·、L7〇·係受光角分別爲5°、20°、70°時 之光度値。 在液晶背光，特別是在使用冷陰極管（CCFL)時，則 其冷陰極管上係呈明亮，在冷陰極管之間則呈暗淡。因此’ 欲使來自不均勻的冷陰極管之光加以面光源化及減小亮度 -12- 200903037 之角度相依性時’則必須使來自冷陰極管之放射光有效率 地加以擴散。 在本發明之光擴散薄膜，若擴散度爲低於2 〇時，則擴 散性並不足夠’由背光面之法線方向觀看時，則有可能視 認到冷陰極管之不均勻性’並且，有可能導致亮度之角度 相依性變大。相反地，若擴散度爲超過60時，則有可能無 法視認到冷陰極管之不均勻性，且亮度之角度相依性減少 之可能性高’但是正面亮度卻有可能降低的情況。 此外’本發明之光擴散薄膜更佳爲其擴散度在平行於 薄膜面之所有方向爲20以上' 60以下。若在所有方向之擴 散度爲2 0以上、6 0以下時’則在將光擴散薄膜組配於背光 時，即使在不在乎光擴散薄膜之方向下來設置，也可使如 後所述之平行方向•垂直方向的背光擴散度達成較佳値。 但是擴散度在互相成正交之至少兩方向爲20以上、60以下 時’則藉由使其兩方向一致於背光之冷陰極管之長度方 向、垂直方向來設置’即可使如後所述之平行方向•垂直 方向的背光擴散度達成較佳値。 欲控制擴散度時，則綜合地藉由將內部光擴散薄膜之 厚度、擴散成分的平均粒徑、添加量、折射率、或光擴散 層之粒子的平均粒徑、折射率、添加量等加以最適化，即 可任意設定擴散度。例如，如第6圖所示，在基質樹脂中 之有機擴散成分的濃度及平均粒徑爲相等的情況下，其擴 散性則因內部光擴散薄膜之厚度而不相同。第6圖（a )係 厚度厚於第6圖（b)者，在此情況下，第6圖（a)與（b) 200903037 相比較時，則其入射於內部光擴散薄膜之光在基質樹脂與 有機擴散成分之界面進行反射的頻率高，其結果擴散性即 將增大。 此外，如第7圖所示，在內部光擴散薄膜之擴散成分 的添加量爲相等的情況下，若增大平均粒徑時，則因基質 樹脂與有機擴散成分之界面所佔有之面積比率將變得狹 小，而使得所入射之光受到界面反射之比率減少，其結果 內部光擴散薄膜之擴散性將減少（第7圖（a))。在另一 方面，若減小平均粒徑時，則因基質樹脂與有機擴散成分 之界面所佔有之面積比率將變得廣闊，而使得所入射之光 受到界面反射之比率增多，其結果擴散性將增大（第7圖 (b ))。但是若平均粒徑爲低於0.5 # m時，則有可能因 光之波長相依性增高而使得擴散光帶色。如第8圖所示， 在內部光擴散薄膜之厚度及平均粒徑爲相等的情況下，第8 圖（b)係基質樹脂中之有機擴散成分的添加量多於第8圖 (a )者，在此情況下，經入射於內部光擴散薄膜之光在基 質樹脂與有機擴散成分之界面進行反射的頻率將增高，其 結果擴散性即將增高。在內部光擴散薄膜中，基質樹脂與 擴散成分之折射率差愈大，臨界角則愈小，使得在界面的 光之反射率增高，其結果擴散性即將增大。 在光擴散層的情況下，雖然粒子之內部光擴散薄膜表 面的塡充率爲重要，但是一般而言，平均粒徑爲愈大’則 塡充率爲愈小而使得擴散度減小。如第9圖所示，在用於 構成光擴散層之粒子的添加量爲相等的情況下，若增大平均 -14- 200903037 粒徑並使粒子之排列爲一層而舖陳在全部薄膜表面上時，則 光之聚光性則因粒子之透鏡效應而增高（第9圖（a))。 若減小平均粒徑時，粒子之配列則與爲大的情況不同而成 爲多層結構，使得粒子之間的多重反射之參與增大而提高 光之擴散性，其結果擴散度則將增大。（第9圖（b ))欲 增大擴散度時，則藉由例如減小平均粒徑，使得光擴散層 之結構加以多層化，以提高在粒子表面之多重反射，或在 即使使用平均粒徑較大者的情況下，藉由增加添加量、控 制塗布層之厚度、或藉由倂用平均粒徑爲較小者以塡滿大 的粒子之間隙來提高粒子之間的多重反射、或在內部光擴 散薄膜之兩面設置光擴散層，則可增大擴散度。 本發明之光擴散薄膜之全光線透射率較佳爲5 0%以 上，更佳爲55%以上。若此等全光線透射率爲低於50%時， 雖然有可能導致亮度之角度相依性減小，但是卻有可能正 面亮度會降低。 本發明之光擴散薄膜藉由下列測定方法來測定時之平 行方向的背光擴散度較佳爲75以上、100以下，更佳爲80 以上、1 00以下。此外，藉由下列測定方法測定時之垂直方 向的背光擴散度較佳爲80以上、100以下，更佳爲85以上、 100以下。 亦即，如後所述之「評估項目及評估方法」中第（3 ) 項背光擴散度之項中所說明，測定方法係將本發明之光擴 散薄膜擺放在液晶背光上來測定亮度之視野角之方法。該 亮度之視野角測定係使用如第2圖所示之液晶背光單元 200903037 1 00，在液晶背光單元上載置擴散板1 1 (全光線透射率爲 65%、厚度爲2 mm)，並在其上設置本發明之光擴散薄膜 1 2來實施。測定係使用EYESCALE-3 ( I-System股份有限 公司製造）。背光擴散度係以下式計算得，該値係表示在 液晶背光上之光傳播情況之參數，此値愈大則表示視野角 相依性愈小。此外，第2圖（a )係直下型背光之截面圖。 第2圖（b)係直下型背光之放大截面圖，其中a係代表從 螢光管中心至擴散板之距離、b係代表螢光管中心之間的距 離、c係代表從螢光管中心至反射板之距離。 •背光擴散度（平行方向）={ ( Β2〇·+ Β7〇·) / 2 } / Β5·χ 100 •背光擴散度（垂直方向）={ (Β2〇·+Β5〇·)/2}/Β5·Χ100 其中，Β5·、Β2〇·、Β5〇_、Β7〇·係受光角分別爲5°、20°、 5 0°、70°時之亮度値。在直下型背光的情況下，其平行方向 爲平行於背光之冷陰極管之長度方向之方向的視野角。垂 直方向係與冷陰極管之長度方向成垂直且平行於光擴散薄 膜面之方向的視野角。 ? 在液晶顯示中，一般則將背光之冷陰極管之長度方向 爲畫面之長邊方向，若平行方向的背光擴散度爲低於75 時*則由畫面之長邊方向的斜向觀看液晶顯不時’即有可 能發生對比降低或色再現性不良。相反地，若平行方向的 背光擴散度爲超過100時，則由斜向觀看時之對比或色再 現性雖然良好，但是卻有可能正面亮度會降低。 該現象，對於畫面之短邊方向而言，也是相同，亦即’ 若垂直方向的背光擴散度爲低於80時，則由畫面之短邊方 -16- 200903037 向的斜向觀看液晶顯示時，則有可能發生對比降低或色再 現性不良。相反地，若垂直方向的背光擴散度爲超過100 時，則由畫面之短邊方向的斜向觀看時之對比或色再現性 雖然良好，但是卻有可能正面亮度會降低。 欲控制平行方向及垂直方向的背光擴散度時，則藉由 調整本發明之擴散薄膜之擴散度即可實現。例如，欲增大 平行方向的背光擴散度時，則在設置於背光時’將屬於其 方向的本發明之擴散薄膜之擴散度加以增大即可達成。關 於擴散薄膜之擴散度的控制，則如前文所述，藉由綜合地 將內部光擴散薄膜之擴散成分的平均粒徑、添加量、折射 率、或光擴散層之粒子的平均粒徑、折射率、添加量等加 以最適化，即可任意設定擴散度。欲增大垂直方向的背光 擴散度時，也是相同。 一般而言，在作爲光擴散薄膜而使用液晶背光單元的 情況下，雖然使作爲光擴散薄膜之基材的內部光擴散薄膜 大致具有等方向擴散性時，則並無任何不妥當，但是必要 時可選擇性地加以控制爲平行方向與垂直方向。例如，若 考慮及內部光擴散薄膜之製法時，則在擠壓機供應在聚酯 樹脂混合調配熱塑性樹脂所獲得之切粒（chip )，並以特定 方法進行溶融擠出，以製造未延伸薄片，接著，則實施逐 次雙軸向延伸或同時雙軸向延伸。此時，若熱塑性樹脂爲 如在延伸時可與聚酯進行共延伸者時，則藉由以長度方向 與寬度方向大幅度變更延伸倍率即可使內部光擴散薄膜之 異方向性顯現。此外，在使用大致棒狀的擴散成分的情況， -17- 200903037 例如在擠壓機供應經在聚酯樹脂混合調配大致棒狀之擴散 成分所獲得之切粒’並以特定方法進行溶融擠出，而以靜 電流延法（electrostatic casting meth〇d)在鏡面之流延轉 筒上加以冷卻時’將流延轉筒之速度比通常速度快來延伸 熔融狀態之聚酯樹脂時，大致棒狀之擴散成分之長度方向 與薄膜之延伸方向將成爲大致平行。然後，將該薄膜加以 逐次雙軸向延伸或同時雙軸向延伸。此時，若形成空隙時， 則藉由熱處理使基質樹脂熔融以使空隙消失，則可使得內 部光擴散薄膜顯現異方向性。 本發明之液晶背光單兀’首先，若在內部光擴散薄膜 之單面使用經形成光擴散層所獲得之光擴散薄膜時，則將 光擴散薄膜設置成可由經形成光擴散層的面之相反面入射 來自液晶背光單元之出射光。與此相對，在內部光擴散薄 膜之兩面使用經形成光擴散層所獲得之光擴散薄膜時，則 可使任何面爲液晶背光單元之出射光面側來設置。 本發明之光擴散薄膜也可積層複數片使用。 《實施例》 以下，藉由實施例將更詳細地說明本發明，但是本發 明並不受限於此等。 (評估項目及評估方法） 就光擴散薄片實施如下所述之評估。 (1)全光線透射率•霧度（haze) 將裁剪成50 mm見方之光擴散薄膜，使用Suga試驗機 股份有限公司（Suga Test Instruments Co.)製造之全自動 200903037 直接讀取霧度電腦型號HGM-2DP (光源爲5 90 nm鈉燈）進 行測定。在藉由在薄膜之單面形成光擴散層所獲得之光擴 散薄膜的情況下，則由與設置光擴散層的面成相反面之側 入射光，而以測定三次所獲得之平均値爲該試樣之平均 値。在藉由在薄膜之兩面形成光擴散層所獲得之光擴散薄 膜的情況下，則由各面入射光來測定，並以各測定三次合 計六次所獲得之平均値爲該試樣之平均値。 (2 )擴散度 將裁剪成100 mm見方之光擴散薄膜，使用村上色彩技 術硏究所股份有限公司製造之三維變角光度計GP-2 00進行 測定。假設對於光擴散薄膜之入射角爲0°，並在垂直於薄 膜面之平面上使受光器以對於光擴散薄膜之法線爲- 90至 90°之範圍移動以測定變角光度。在藉由在薄膜之單面形成 光擴散層所獲得之光擴散薄膜的情況下，則由與經由形成 光擴散層的面之相反面側入射光所獲得之測定結果的數 値’以下式計算得擴散度。至於在藉由在薄膜之兩面形成 光擴散層所獲得之光擴散薄膜的情況下，則以由各面入射 光所獲得之測定結果之平均値，以下式計算得擴散度： •擴散度={ (L2(r + L7(r) / 2} / L5'X100 其中’ L5·、L2〇·、L70·係受光角分別爲5°、20°、70。時 之光度値。 在實際測定擴散度時，則分別計算由受光角爲5。、 2〇°、70°時之光度値所計算得之擴散度（+ )、與由受光角 爲-5°、- 2(Γ、- 70°時之光度値所計算得之擴散度（一）， -19- 200903037 然後由此等兩個擴散度之平均値來計算得其擴散度。 其次，將光擴散薄膜朝面內方向各15°，合計成爲165° 爲止加以旋轉（或旋轉受光器之移動方向），並在各位置 以相同的方式來測定擴散度。以如上所述之方式測定平行 於光擴散薄膜之面且在每隔15°的12方向之擴散度。 (3 )背光擴散度 在第2圖所示，直下型背光1〇〇 (冷陰極管爲12支、 a = 13 mm、b = 24.9 mm、c = 4 mm)之冷陰極管 14 上面 放置擴散板11(日東樹脂股份有限公司製造之Clarex DR-65C、厚度爲2 mm)，在其上面則設置光擴散薄膜12。 若光擴散薄膜爲其在平行於薄膜面之所有方向的擴散度爲 20以上、60以下時，則光擴散薄膜可在任何方向來設置。 若光擴散薄膜爲其在互相成正交之至少兩方向之擴散度爲 20以上、60以下時，則將光擴散薄膜設置成使其兩方向與 冷陰極管之長度方向、垂直方向成爲一致。將冷陰極管點 燈 60分鐘以使光源趨於穩定後，由測定試樣側使用 “ EYESCALE-3 ( I-System股份有限公司製造），在距自直下 型背光之中心爲500 mm之處將附屬之CCD相機設置成對 於直下型背光之面成正面。然後，將CCD相機之影像中心 及C CD相機之旋轉中心對準於設置在液晶背光單元的光擴 散薄膜面之對角線的交叉點，並以其位置爲0°而以朝平行 於冷陰極管之長度方向的方向、及垂直於冷陰極管之長度 方向的方向使相機分別以受光角爲_ 80°至80°之範圍加以 旋轉，以測定在各受光角之亮度。由所測定之亮度値以下 -20 - 200903037 式計算得背光擴散度： •背光擴散度（平行方向）={ ( Β2〇·+ Β7〇·) / 2} / Β^ΧΙΟΟ •背光擴散度（垂直方向）={ ( Β2〇·+ B5。。）/ 2} / Β5·Χ100 其中’ Β5·、Β2(Γ、B5q.、Β7。.係受光角分別爲5°、20°、 50°、70°時之亮度値。在直下型背光的情況下，平行方向係 與冷陰極管之長度方向成平行之方向，垂直方向係與冷陰 極管之長度方向成垂直且平行於光擴散薄膜面的方向之視 野角。 實際測定背光之擴散度時，則分別測定由受光角爲5 °、 20°、50°、7(Γ時之亮度値所計算得之擴散度（+ )、與受 光角爲一 5°、_ 20°、一 50°、一 70°時之亮度値所計算得之擴 散度（-），然後由該兩個背光擴散度之平均値計算得背 光擴散度。 (4 )亮度不均勻性 在第2圖所示，直下型背光100之冷陰極管14上面放 置擴散板 1 1 (日東樹脂股份有限公司製造之 Clarex DR-65C、厚度2 mm )，在其上面則設置本發明之光擴散薄 膜1 2。將冷陰極管點燈60分鐘以使光源趨於穩定後，由測 定試樣側使用 EYESCALE-3 ( I-System股份有限公司製 造），在距自直下型背光之中心爲5 00 mm之處將附屬之 CCD相機設置成對於直下型背光之面成正面。然後，將CCD 相機之影像中心及CCD相機之旋轉中心對準於液晶背光單 元的面之對角線的交叉點以測定亮度（cd/m2 )。測定處係 如第5圖所示，由液晶背光單元的面之對角線的交叉點朝 -21- 200903037 與冷陰極管成垂直之方向，且位於中心附近之4支份螢光 管測定亮度。測定將測定處加以99等分（L 1至L99 )時之 亮度之平均値（Lave )、亮度之最大値（Lmax )、亮度之 最小値（L m i η )，平均亮度、亮度不均勻性則以下式計算 得’並以下列基準評估： • Lave = L1至L99的數値之平均値 •亮度不均勻性={ ( Lmax — Lmin ) / Lave } X 1 00 ( % ) A： 亮度不均勻性爲小於1 %，以目視無法觀察到營光 管不均勻性； B ： 亮度不均勻性爲1 %以上、小於3 %，以目視無法觀 察到螢光管之不均勻性； C ： 亮度不均勻性爲3%以上、小於5%，以目視可確認 到螢光管之不均勻性； D :亮度不均勻性爲5%以上，以目視可確認到螢光管 之不均勻性。 〔實施例1〕 將聚對苯二甲酸乙二醇酯（PET)(與17 mol%之間苯 二甲酸成分共聚合所獲得之聚酯樹脂）（熔點爲2 1 0 °C、密 度爲1·3 5、玻璃轉移溫度爲70T：、折射率爲1.58) 、5重 量％之聚甲基戊烯（熔點爲2 3 5 °C、密度爲〇 · 8 3、折射率爲 1.46 )、及0.5重量％之Hytrel 7247 (東麗·杜邦股份有限 公司（DuPont-Toray Co·，Ltd.)製造）混合之切粒混合供 應至主擠壓機（B層）。此外，將PET(熔點爲265 °C、密 度爲1.35)供應至副擠壓機（ancillary extruder) ( A層）。 -22 - 200903037 然後’以特定方法實施在兩側表面層爲PET之熔融三層共 擠壓’並以靜電流延法在鏡面之流延轉筒上加以冷卻，以 製造未延伸三層積層薄片（積層薄片膜厚：1,700#ιη、積 層比率：Α層：Β層：C層=1:8:1)。將藉此所獲得之三層 積層薄片在90 °C朝長度方向延伸3.3倍，然後以拉幅機經 由90 °C預熱區而在95 °C朝寬度方向延伸3.5倍，並且，進 一步在230 °C熱處理20秒鐘，藉此製得膜厚爲150；απι、擴 散度爲43.8、全光線透射率爲66.9%之內部光擴散薄膜。 ' 其次，對於1〇〇重量份之由20重量％之丙烯酸多元醇 系黏結劑樹脂、3重量％之異氰酸酯系硬化劑、25重量％之 聚甲基丙烯酸甲酯平均粒徑爲20/zm之多分散粒子、3重量 %之聚甲基丙烯酸甲酯平均粒徑爲12/zm之多分散粒子、及 49重量％之甲苯所構成的組成物，與作爲平滑劑之0.1重量 份之多晶矽混合調配得光擴散層用塗布液。將該光擴散層 用塗布液使用Mayer Bar在如前所述之內部光擴散薄膜之 單面塗布成乾燥後之膜厚爲25^ιη’然後在120 °C將其乾燥 ^ 硬化4分鐘，藉此製得光擴散薄膜。 〔實施例2〕 製備以與實施例1相同的方法所獲得之內部光擴散薄 膜、及以與實施例1相同的方法所獲得之光擴散層用塗布 液。將該光擴散層用塗布液使用M a ye r B a r在內部光擴散薄 膜之兩面塗布成乾燥後之膜厚爲25#m，然後在120 °c將其 乾燥硬化4分鐘，藉此製得光擴散薄膜。 〔實施例3〕 -23- 200903037 製備除了變更供應至主擠壓機之聚甲基戊烯爲1.4重 量％、取消Hytrel 7247 (東麗•杜邦股份有限公司製造） 以外，其餘則以與實施例1相同的方法所獲得之膜厚爲1 8 8 #m、擴散度爲13.6、全光線透射率爲95.9之內部光擴散 薄膜、及以與實施例1相同的方法所獲得之光擴散層用塗 布液。將該光擴散層用塗布液使用Mayer Bar在內部光擴散 薄膜之單面塗布成乾燥後之膜厚爲2 5 /z m，然後在1 2 (TC將 其乾燥硬化4分鐘，藉此製得光擴散薄膜。 〔實施例4〕 製備除了變更供應至主擠壓機之聚甲基戊烯爲3.5重 量％以外，其餘則以與實施例1相同的方法所獲得之膜厚爲 125 # m、擴散度爲27.7、全光線透射爲率83.8之內部光擴 散薄膜、及以與實施例1相同的方法所獲得之光擴散層用 塗布液。將該光擴散層用塗布液使用Mayer Bar在內部光擴 散薄膜之單面塗布成乾燥後之膜厚爲25/zm，然後在120 °C 將其乾燥硬化4分鐘，藉此製得光擴散薄膜。 〔實施例5〕 製備除了變更供應至主擠壓機之聚甲基戊烯爲3.3重 量％、使用0.5重量％之聚乙二醇以取代Hytrel 7247(東麗. 杜邦股份有限公司製造）以外’其餘則以與實施例1相同 的方法所獲得之膜厚爲# m、擴散度爲29.0、全光線透 射率爲85.5之內部光擴散薄膜、及以與實施例1相同的方 法所獲得之光擴散層用塗布液’將該光擴散層用塗布液使 用Mayer Bar在內部光擴散薄膜之單面塗布成乾燥後之膜 -24 - 200903037 厚爲25"m，然後在120 °C將其乾燥硬化4分鐘，藉此製得 光擴散薄膜。 〔實施例6〕 製備除了變更供應至主擠壓機之聚甲基戊烯爲3.3重 量％、使用0.5重量％之聚乙二醇以取代Hytrel 7247(東麗· 杜邦股份有限公司製造）以外’其餘則以與實施例1相同 的方法所獲得之膜厚爲1 〇 〇 # m、擴散度爲2 9.0、全光線透 射率爲85.5之內部光擴散薄膜、及以與實施例1相同的方 法所獲得之光擴散層用塗布液’將該光擴散層用塗布液使 用Mayer Bar在內部光擴散薄膜之兩面塗布成乾燥後之膜 厚爲25 # m，然後在120°C將其乾燥硬化4分鐘，藉此製得 光擴散薄膜。 〔實施例7〕 製備除了變更供應至主擠壓機之聚甲基戊烯爲6.7重 量％、使用0.5重量％之聚乙二醇以取代Hytrel 7247(東麗. 杜邦股份有限公司製造）以外，其餘則以與實施例1相同 的方法所獲得之膜厚爲1〇〇 μ m、擴散度爲46.1、全光線透 射率爲6 8 . 1之內部光擴散薄膜、及以與實施例1相同的方 法所獲得之光擴散層用塗布液，將該光擴散層用塗布液使 用Mayer Bar在內部光擴散薄膜之單面塗布成乾燥後之膜 厚爲25//m，然後在120 °C將其乾燥硬化4分鐘，藉此製得 光擴散薄膜。 〔比較例1〕 光擴散薄膜係使用188GM2(KimotoCo·，Ltd,製造）。 -25 - 200903037 〔比較例2〕 在厚度爲125^«1之透明聚酯薄膜（東麗股份有限公司 (Toray Industries，Inc.)製造之 Lumirror(註冊商標）U34) 之單面，將以與實施例1相同的方法所獲得之光擴散層用 塗布液使用Mayer Bar塗布成乾燥後之膜厚爲25/im，然後 在1 20 °C將其乾燥硬化4分鐘，藉此製得光擴散薄膜。 〔比較例3〕 光擴散薄膜係使用100〇1^3(1^111〇1〇(：〇.，1^£1_製造）。• Diffusion = { (L2(T+L7〇.) / 2} / Ls^XlOO where L5., L2, · L7〇·the luminosity when the received angles are 5°, 20°, 70°, respectively In liquid crystal backlights, especially when using cold cathode tubes (CCFLs), the cold cathode tubes are bright and dilute between the cold cathode tubes. Therefore, the light from the uneven cold cathode tubes is intended to be When the surface light source is reduced and the angle dependence of the brightness -12-200903037 is reduced, the emitted light from the cold cathode tube must be efficiently diffused. In the light diffusing film of the present invention, if the diffusivity is less than 2 〇 At the time of the diffusion, the diffusibility is not sufficient. 'When viewed from the normal direction of the backlight surface, it is possible to visually recognize the unevenness of the cold cathode tube' and it is possible to cause an increase in the angle dependence of the brightness. Conversely, if the diffusion is spread When the degree is more than 60, the unevenness of the cold cathode tube may not be recognized, and the possibility that the angle dependence of the brightness is lowered is high, but the front luminance may be lowered. Further, the light diffusing film of the present invention may be used. Better for all of its diffusivity parallel to the film side The direction is 20 or more '60 or less. If the diffusivity in all directions is 20 or more and 60 or less, then when the light-diffusing film is assembled in the backlight, even if it is disposed in the direction of the light-diffusing film, It is preferable to make the backlight diffusion degree in the parallel direction and the vertical direction as described later. However, when the diffusion degree is 20 or more and 60 or less in at least two directions orthogonal to each other, 'the two directions are aligned with the backlight. The cold cathode tube is disposed in the longitudinal direction and the vertical direction to achieve better contrast in the parallel direction and vertical direction of the backlight as described later. To control the diffusion degree, the internal light is diffused comprehensively. The thickness of the film, the average particle diameter of the diffusing component, the amount of addition, the refractive index, or the average particle diameter of the particles of the light-diffusing layer, the refractive index, the amount of addition, and the like can be optimized, and the degree of diffusion can be arbitrarily set. For example, as shown in FIG. As shown in the figure, when the concentration and average particle diameter of the organic diffusing component in the matrix resin are equal, the diffusibility is different depending on the thickness of the internal light diffusing film. Fig. 6(a) is the thickness In Fig. 6(b), in this case, when comparing Fig. 6(a) with (b) 200903037, the light incident on the internal light diffusing film is reflected at the interface between the matrix resin and the organic diffusing component. When the frequency is high, the diffusivity is about to increase. Further, as shown in Fig. 7, when the amount of the diffusion component added to the internal light-diffusing film is equal, if the average particle diameter is increased, the matrix resin is used. The ratio of the area occupied by the interface with the organic diffusing component becomes narrow, and the ratio of the incident light to the interface reflection is reduced, and as a result, the diffusibility of the internal light diffusing film is reduced (Fig. 7(a)). On the other hand, when the average particle diameter is decreased, the ratio of the area occupied by the interface between the matrix resin and the organic diffusion component will be broad, and the ratio of the incident light to the interface reflection will increase, and as a result, the diffusibility will be Increase (Fig. 7(b)). However, if the average particle diameter is less than 0.5 #m, there is a possibility that the diffused light is colored due to an increase in the wavelength dependence of light. As shown in Fig. 8, when the thickness and the average particle diameter of the internal light-diffusing film are equal, the amount of the organic diffusing component in the matrix resin of Fig. 8(b) is larger than that of Fig. 8(a). In this case, the frequency at which the light incident on the internal light-diffusing film is reflected at the interface between the matrix resin and the organic diffusion component is increased, and as a result, the diffusibility is about to increase. In the internal light-diffusing film, the larger the refractive index difference between the matrix resin and the diffusing component, the smaller the critical angle, so that the reflectance of light at the interface is increased, and as a result, the diffusivity is about to increase. In the case of the light-diffusing layer, although the charge ratio of the surface of the internal light-diffusing film of the particles is important, in general, the larger the average particle diameter is, the smaller the charge ratio is, and the smaller the degree of diffusion is. As shown in Fig. 9, in the case where the amount of the particles for constituting the light-diffusing layer is equal, if the average particle size of -14,030,030,37 is increased and the particles are arranged in one layer and spread on the entire film surface Then, the condensing property of light is increased by the lens effect of the particles (Fig. 9(a)). When the average particle diameter is decreased, the arrangement of the particles is different from that in the case of being large, and the multi-reflection of the particles is increased to increase the diffusibility of light, and as a result, the degree of diffusion increases. (Fig. 9(b)) When it is desired to increase the degree of diffusion, the structure of the light diffusion layer is multi-layered by, for example, reducing the average particle diameter to increase multiple reflection at the surface of the particle, or even if an average particle is used. In the case of a larger diameter, the multiple reflection between the particles is increased by increasing the amount of addition, controlling the thickness of the coating layer, or by using a gap between the particles having a smaller average particle diameter. When a light diffusion layer is provided on both surfaces of the internal light diffusion film, the degree of diffusion can be increased. The light diffusing film of the present invention preferably has a total light transmittance of 50% or more, more preferably 55% or more. If the total light transmittance is less than 50%, although the angle dependence of the brightness may be reduced, there is a possibility that the front side brightness is lowered. In the light-diffusing film of the present invention, the degree of backlight diffusion in the parallel direction when measured by the following measurement method is preferably 75 or more and 100 or less, more preferably 80 or more and 100 or less. Further, the degree of backlight diffusion in the vertical direction when measured by the following measurement method is preferably 80 or more and 100 or less, more preferably 85 or more and 100 or less. That is, as described in item (3) of the "Evaluation Items and Evaluation Methods", which will be described later, the measurement method is to measure the brightness of the light diffusing film of the present invention on a liquid crystal backlight. The method of the corner. The viewing angle of the brightness is measured by using the liquid crystal backlight unit 200903037 100 shown in FIG. 2, and the diffusion plate 1 1 (full light transmittance: 65%, thickness: 2 mm) is placed on the liquid crystal backlight unit, and The light diffusing film 12 of the present invention is provided thereon. The measurement system used EYESCALE-3 (manufactured by I-System Co., Ltd.). The backlight diffusivity is calculated by the following equation, which indicates the parameter of light propagation on the liquid crystal backlight, and the larger the maximum, the smaller the dependence of the viewing angle. Further, Fig. 2(a) is a cross-sectional view of the direct type backlight. Figure 2(b) is an enlarged cross-sectional view of the direct type backlight, where a represents the distance from the center of the fluorescent tube to the diffuser, b represents the distance between the centers of the fluorescent tubes, and c represents the center of the fluorescent tube. The distance to the reflector. • Backlight diffusivity (parallel direction) = { ( Β 2 〇 · + Β 7 〇 · ) / 2 } / Β 5 · χ 100 • Backlight diffusivity (vertical direction) = { (Β2〇·+Β5〇·)/2}/ Β5·Χ100 Among them, Β5·, Β2〇·, Β5〇_, Β7〇· are brightness 値 when the received light angles are 5°, 20°, 50°, and 70°, respectively. In the case of a direct type backlight, the parallel direction is a viewing angle parallel to the direction of the longitudinal direction of the cold cathode tube of the backlight. The vertical direction is a viewing angle perpendicular to the longitudinal direction of the cold cathode tube and parallel to the direction of the light-diffusing film surface. In the liquid crystal display, generally, the length direction of the cold cathode tube of the backlight is the long side direction of the screen, and if the backlight diffusion degree in the parallel direction is lower than 75*, the liquid crystal display is observed from the oblique direction of the long side of the screen. From time to time, it is possible that contrast reduction or poor color reproducibility may occur. Conversely, if the degree of backlight diffusion in the parallel direction is more than 100, the contrast or color reproducibility when viewed obliquely is good, but there is a possibility that the front luminance is lowered. This phenomenon is the same for the short-side direction of the picture, that is, if the backlight diffusion degree in the vertical direction is lower than 80, the liquid crystal display is viewed obliquely from the short side of the screen to the period of -16,030,037. , there may be a decrease in contrast or poor color reproducibility. On the other hand, if the degree of backlight diffusion in the vertical direction is more than 100, the contrast or color reproducibility when viewed obliquely from the short side direction of the screen is good, but there is a possibility that the front luminance is lowered. When the degree of diffusion of the backlight in the parallel direction and the vertical direction is to be controlled, it is achieved by adjusting the diffusion degree of the diffusion film of the present invention. For example, when it is desired to increase the degree of backlight diffusion in the parallel direction, it is achieved by increasing the diffusivity of the diffusion film of the present invention in the direction of the backlight. Regarding the control of the diffusivity of the diffusion film, as described above, the average particle diameter, the addition amount, the refractive index, or the average particle diameter of the particles of the light diffusion layer, and the refractive index of the diffusion layer of the internal light diffusion film are comprehensively obtained. The degree of diffusion can be arbitrarily set by optimizing the rate, the amount of addition, and the like. The same is true when you want to increase the backlight diffusivity in the vertical direction. In general, when a liquid crystal backlight unit is used as a light-diffusing film, when the internal light-diffusing film which is a base material of the light-diffusion film has substantially equipotential diffusibility, there is no problem, but it is not necessary. It can be selectively controlled to be parallel and perpendicular. For example, in consideration of the production method of the internal light-diffusing film, the chip obtained by mixing the thermoplastic resin in the polyester resin is supplied to the extruder, and melt-extrusion is performed in a specific method to produce an unstretched sheet. Then, successive biaxial extensions or simultaneous biaxial extensions are carried out. In this case, when the thermoplastic resin is coextensive with the polyester when it is stretched, the directionality of the internal light-diffusing film can be exhibited by largely changing the stretching ratio in the longitudinal direction and the width direction. Further, in the case of using a substantially rod-shaped diffusion component, -17-200903037, for example, in an extruder, a pellet obtained by mixing a substantially rod-shaped diffusion component in a polyester resin is mixed and melt-extrusion is performed in a specific method. When the electrostatic casting meth〇d is cooled on the mirror casting drum, the rod-shaped drum is stretched in a molten state at a speed faster than the normal speed. The length direction of the diffusion component and the direction in which the film extends are substantially parallel. The film is then subjected to a secondary biaxial extension or a simultaneous biaxial extension. At this time, when a void is formed, the matrix resin is melted by heat treatment to cause the void to disappear, so that the inner light diffusing film can exhibit an anisotropy. In the liquid crystal backlight unit of the present invention, first, when a light diffusion film obtained by forming a light diffusion layer is used on one side of the internal light diffusion film, the light diffusion film is disposed to be opposite to the surface on which the light diffusion layer is formed. The incident light from the liquid crystal backlight unit is incident on the surface. On the other hand, when the light-diffusing film obtained by forming the light-diffusing layer is used on both surfaces of the internal light-diffusing film, any surface can be provided on the side of the light-emitting surface of the liquid crystal backlight unit. The light-diffusing film of the present invention can also be used in a plurality of layers. [Embodiment] Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited thereto. (Evaluation item and evaluation method) The evaluation as described below was carried out on the light diffusion sheet. (1) Full light transmittance • Haze The light diffusing film will be cut into 50 mm square, and the fully automatic 200903037 manufactured by Suga Test Instruments Co. will directly read the haze computer model. The HGM-2DP (light source is a 5 90 nm sodium lamp) was measured. In the case of a light-diffusing film obtained by forming a light-diffusing layer on one side of a film, light is incident from the side opposite to the surface on which the light-diffusing layer is provided, and the average enthalpy obtained by measuring three times is The average enthalpy of the sample. In the case of a light-diffusing film obtained by forming a light-diffusing layer on both surfaces of a film, the average enthalpy obtained by measuring light from each surface and measuring six times in total for three times is the average value of the sample. . (2) Diffusion The light diffusing film cut into a 100 mm square was measured using a three-dimensional variable angle photometer GP-2 00 manufactured by Murakami Color Technology Co., Ltd. It is assumed that the incident angle to the light-diffusing film is 0°, and the photoreceptor is moved in a range of -90 to 90° with respect to the normal to the light-diffusing film in a plane perpendicular to the film surface to determine the variable-angle luminosity. In the case of a light-diffusing film obtained by forming a light-diffusing layer on one side of a film, the number of measurement results obtained by incident light on the side opposite to the surface on which the light-diffusing layer is formed is calculated by the following formula Have a degree of spread. In the case of a light-diffusing film obtained by forming a light-diffusing layer on both sides of a film, the degree of diffusion is calculated by the following equation from the average 値 of the measurement results obtained by the incident light on each face: • Diffusion = { (L2(r + L7(r) / 2} / L5'X100 where 'L5·, L2〇·, L70· are the photometric angles of 5°, 20°, and 70°, respectively. When calculating the diffusivity (+) calculated from the luminosity of the light receiving angles of 5, 2〇, and 70°, and the light receiving angle of -5°, -2 (Γ, - 70°) The degree of diffusion calculated by the luminosity 一 (1), -19- 200903037 Then the average degree of diffusion of the two diffusion degrees is calculated to calculate the degree of diffusion. Secondly, the light diffusion film is 15° in the in-plane direction, totaling Rotate (or rotate the direction of movement of the photoreceiver) until it reaches 165°, and measure the degree of diffusion in the same manner at each position. The surface parallel to the light-diffusing film is measured in the manner described above and at every 15°. Diffusion in 12 directions. (3) Backlight diffusivity is shown in Figure 2, direct type backlight 1〇〇 (cold cathode tube is 12 On the cold cathode tube 14 of the branch, a = 13 mm, b = 24.9 mm, c = 4 mm), a diffusion plate 11 (Clarex DR-65C manufactured by Nitto Resin Co., Ltd., thickness 2 mm) is placed thereon. The light diffusing film 12 is provided. If the diffusing film has a diffusing degree of 20 or more and 60 or less in all directions parallel to the film surface, the light diffusing film can be disposed in any direction. When the degree of diffusion in at least two directions orthogonal to each other is 20 or more and 60 or less, the light-diffusing film is disposed such that both directions thereof coincide with the longitudinal direction and the vertical direction of the cold cathode tube. The cold cathode tube is turned on for 60 minutes. After the light source is stabilized, the ESDCALE-3 (manufactured by I-System Co., Ltd.) is used on the side of the measurement sample, and the attached CCD camera is set to be straight down at a distance of 500 mm from the center of the direct type backlight. The surface of the backlight is front. Then, the image center of the CCD camera and the center of rotation of the C CD camera are aligned with the intersection of the diagonal lines of the light diffusing film surface of the liquid crystal backlight unit, and the position is 0°. Chaoping The direction of the longitudinal direction of the cold cathode tube and the direction perpendicular to the longitudinal direction of the cold cathode tube cause the camera to rotate at a light receiving angle of _80 to 80, respectively, to measure the brightness at each light receiving angle. The measured brightness 値 is -20 - 200903037 The calculated backlight diffusivity: • Backlight diffusivity (parallel direction) = { ( Β 2 〇 · + Β 7 〇 ·) / 2} / Β ^ ΧΙΟΟ • Backlight diffusivity (vertical direction )={ ( Β2〇·+ B5. . ) / 2} / Β5·Χ100 where ' Β5·, Β2 (Γ, B5q., Β7.. brightness when the received angles are 5°, 20°, 50°, 70°, respectively. In the case of direct type backlights The parallel direction is parallel to the longitudinal direction of the cold cathode tube, and the vertical direction is a viewing angle perpendicular to the longitudinal direction of the cold cathode tube and parallel to the direction of the surface of the light diffusing film. When actually measuring the diffusivity of the backlight, Then, the diffusion angle (+) calculated from the light receiving angles of 5°, 20°, 50°, and 7 (the brightness of the time Γ is measured, and the light receiving angle is 5°, _ 20°, 50°, one The brightness at 70° is calculated as the diffusivity (-), and then the average diffusion of the two backlight diffusers is calculated as the backlight diffusivity. (4) Luminance non-uniformity is shown in Fig. 2, the direct type backlight A diffusing plate 1 1 (Clarex DR-65C manufactured by Nitto Resin Co., Ltd., thickness 2 mm) was placed on the cold cathode tube 14 of 100, and the light diffusing film 12 of the present invention was placed thereon. The cold cathode tube was lighted. After 60 minutes to stabilize the light source, EYESCALE-3 (I-System shares) was used on the side of the measurement sample. Manufactured by the company, set the attached CCD camera to the front side of the direct type backlight at a distance of 500 mm from the center of the direct type backlight. Then, the center of the image of the CCD camera and the center of rotation of the CCD camera The intersection of the diagonal lines of the surface of the liquid crystal backlight unit is measured to measure the brightness (cd/m2). The measurement is as shown in Fig. 5, and the intersection of the diagonal lines of the surface of the liquid crystal backlight unit faces 21- 200903037 Measure the brightness with four fluorescent tubes located in the direction perpendicular to the cold cathode tube and near the center. Measure the average 値 (Lave) and brightness of the brightness when the measurement is 99 aliquots (L 1 to L99 ) The maximum 値(Lmax), the minimum 値(L mi η ), the average brightness, and the brightness non-uniformity are calculated by the following formula and evaluated on the following basis: • Lave = the average of the numbers from L1 to L99 • The brightness is not Uniformity = { ( Lmax — Lmin ) / Lave } X 1 00 ( % ) A: The brightness unevenness is less than 1%, and the camping tube inhomogeneity cannot be observed visually; B : The brightness unevenness is 1% Above, less than 3%, the fluorescent tube cannot be observed by visual observation Non-uniformity; C : Brightness unevenness is 3% or more and less than 5%, and the unevenness of the fluorescent tube can be confirmed by visual observation; D: brightness unevenness is 5% or more, and fluorescence can be confirmed by visual observation. Tube non-uniformity [Example 1] Polyethylene terephthalate (PET) (polyester resin obtained by copolymerization of 17 mol% of a phthalic acid component) (melting point 2 1 0 °C, density of 1.35, glass transition temperature of 70T:, refractive index of 1.58), 5% by weight of polymethylpentene (melting point of 2 3 5 ° C, density of 〇 · 8 3, refractive index A pelletized mixture of 1.46) and 0.5% by weight of Hytrel 7247 (manufactured by DuPont-Toray Co., Ltd.) was supplied to a main extruder (layer B). Further, PET (melting point: 265 ° C, density: 1.35) was supplied to an ancillary extruder (layer A). -22 - 200903037 Then 'concrete three layers of co-extruded PET on both sides of the surface layer in a specific way' and perform cooling on the mirror casting drum by electrostatic casting to produce unstretched three-layer laminated sheets (Layered film thickness: 1,700 #ιη, laminate ratio: Α layer: Β layer: C layer = 1:8:1). The three-layer laminated sheet thus obtained was extended 3.3 times in the longitudinal direction at 90 ° C, and then extended by 3.5 times in the width direction at 95 ° C by a tenter via a preheating zone of 90 ° C, and further at 230 After heat treatment at ° C for 20 seconds, an internal light-diffusing film having a film thickness of 150; απι, a diffusivity of 43.8, and a total light transmittance of 66.9% was obtained. Next, the average particle diameter of 20% by weight of the acrylic polyol-based binder resin, 3% by weight of the isocyanate-based hardener, and 25% by weight of the polymethyl methacrylate is 20/zm. a composition comprising polydisperse particles, 3% by weight of polymethyl methacrylate having an average particle diameter of 12/zm, and 49% by weight of toluene, mixed with 0.1 part by weight of polycrystalline silicon as a smoothing agent A coating liquid for a light diffusion layer was obtained. The coating liquid for a light-diffusing layer was coated on a single side of the internal light-diffusing film as described above using a Mayer Bar to have a film thickness of 25 μm, and then dried at 120 ° C for 4 minutes. This produced a light diffusing film. [Example 2] An internal light-diffusing film obtained in the same manner as in Example 1 and a coating liquid for a light-diffusing layer obtained in the same manner as in Example 1 were prepared. The coating liquid for a light-diffusing layer was applied to both sides of the internal light-diffusing film by using a film to a dry film thickness of 25 #m, and then dried and cured at 120 ° C for 4 minutes. Light diffusing film. [Example 3] -23- 200903037 Preparation was carried out except that the polymethylpentene supplied to the main extruder was changed to 1.4% by weight, and the Hytrel 7247 (manufactured by Toray DuPont Co., Ltd.) was removed. An internal light-diffusing film having a film thickness of 1 8 8 #m, a diffusivity of 13.6, a total light transmittance of 95.9, and a light-diffusing layer obtained by the same method as in Example 1 obtained by the same method. liquid. The coating liquid for a light-diffusing layer was applied to a single surface of the internal light-diffusing film by a Mayer Bar to have a film thickness of 2 5 /zm after drying, and then dried and cured at 12 ° for 4 minutes to obtain light. Diffusion film. [Example 4] A film thickness of 125 # m, diffusion was obtained in the same manner as in Example 1 except that the polymethylpentene supplied to the main extruder was changed to 3.5% by weight. An internal light-diffusing film having a degree of total light transmission of 83.8 and a coating liquid for a light-diffusing layer obtained by the same method as in Example 1. The coating liquid for a light-diffusing layer was diffused by internal light using a Mayer Bar. The film was coated on one side to have a film thickness of 25/zm after drying, and then dried and cured at 120 ° C for 4 minutes, thereby producing a light-diffusing film. [Example 5] Preparation was carried out except for change to the main extruder The film obtained by the same method as in Example 1 except that the polymethylpentene was 3.3 wt%, and 0.5 wt% of polyethylene glycol was used instead of Hytrel 7247 (manufactured by Toray DuPont Co., Ltd.) Thickness #m, diffusivity 29.0, full light The internal light-diffusing film having an incidence of 85.5 and the coating liquid for a light-diffusing layer obtained in the same manner as in Example 1 were coated on one side of the internal light-diffusing film using a Mayer Bar. The dried film - 24, 200903037 was 25 " m, and then it was dry-hardened at 120 ° C for 4 minutes, thereby producing a light-diffusing film. [Example 6] Preparation was carried out except that the supply to the main extruder was changed. The film thickness obtained by the same method as that of Example 1 was 0.3% by weight of methylpentene, and 0.5% by weight of polyethylene glycol was used instead of Hytrel 7247 (manufactured by Toray DuPont Co., Ltd.). 1 〇〇# m, an internal light-diffusing film having a diffusivity of 29.0, a total light transmittance of 85.5, and a coating liquid for a light-diffusing layer obtained by the same method as in Example 1 The liquid was applied to both sides of the internal light-diffusing film by a Mayer Bar to have a film thickness of 25 #m, and then dried and cured at 120 ° C for 4 minutes, thereby producing a light-diffusing film. [Example 7] Preparation of Change supply to main squeeze The polymethylpentene of the machine was 6.7% by weight, and 0.5% by weight of polyethylene glycol was used instead of Hytrel 7247 (manufactured by Toray DuPont Co., Ltd.), and the others were obtained in the same manner as in Example 1. An internal light-diffusing film having a film thickness of 1 μm, a diffusivity of 46.1, a total light transmittance of 681, and a coating liquid for a light-diffusing layer obtained by the same method as in Example 1 The coating liquid for a light-diffusing layer was coated with a Mayer Bar on one side of the internal light-diffusing film to have a film thickness of 25/m, and then dried and cured at 120 ° C for 4 minutes, thereby producing a light-diffusing film. [Comparative Example 1] 188GM2 (manufactured by Kimoto Co., Ltd.) was used as the light-diffusing film. -25 - 200903037 [Comparative Example 2] On one side of a transparent polyester film (Lumirror (registered trademark) U34 manufactured by Toray Industries, Inc.) having a thickness of 125^«1, The coating liquid for a light-diffusing layer obtained in the same manner as in Example 1 was coated with a Mayer Bar to have a film thickness of 25 μm after drying, and then dried and cured at 10 ° C for 4 minutes to thereby obtain a light-diffusing film. . [Comparative Example 3] A light-diffusing film was produced by using 100 〇 1 ^ 3 (1^111 〇 1 〇 (: 〇., manufactured by Manufacture).
積層實施例4所使用的內部光擴散薄膜與比較例2所 使用的光擴散薄片，藉此製得光擴散薄膜群。 表1The internal light-diffusing film used in Example 4 and the light-diffusing sheet used in Comparative Example 2 were laminated, whereby a light-diffusing film group was obtained. Table 1
全光線 霧度 擴散度 背光擴散度 亮度 透射率 平行方向 垂直方向 不均勻性 實施例1 59.1% 93.7% 46.6+0.6 84.7 89.5 A 實施例2 57.2% 93.8% 49.7±1.2 91.2 93.4 A 實施例3 66.8% 92.9% 26.2+1.0 76.5 81.6 B 實施例4 67.0% 93.3% 33.010.7 88.6 96.0 B 實施例5 65.2% 93.3% 33.5±1.3 78.7 84.1 B 實施例6 64.8% 93.6% 41.1+0.5 89.4 93.4 A 實施例7 57.3% 93.7% 48.6±1.5 85.3 93.4 A 比較例1 67.7% 90.7% 13·6±1·3 70.0 76.4 D 比較例2 74.3% 90.1% 14.0+0.8 70.2 77.8 --—__ D 比較例3 64.7% 90.8% 14.211.1 71.3 76.4 ----- D 比較例4 60.2% 93.2% 33.0±0.7 69.3 76.0 ·· 〜 -c -26- 200903037 各實施例、比較例之擴散度的數値係表示在12方向的 擴散度之中心値與偏差。 如表1所示’實施例1至7之光擴散薄膜，與比較例！ 至4之光擴散薄膜相比較，其係可充分地滿足降低亮度不 均句性、亮度之角度相依性者。 若將實施例1與4、及實施例5與7相比較時，則得知 即使內部光擴散薄膜之製法爲相同，但是一增加擴散成分 的添加量，擴散度即將增大。若將實施例1與2、及實施例 5與6相比較時，則得知即使使用相同的內部光擴散薄膜與 光擴散層，若將光擴散層設置於兩面時，擴散度即將增大。 此外，由實施例3即得知即使減少內部光擴散薄膜中之擴 散成分的添加量，但是藉由形成光擴散層即可獲得足夠的 擴散性。 與此相對，在比較例1至3之透明基材薄膜上形成光 擴散層所獲得之光擴散薄片，則會造成亮度不均勻性不 良、對於亮度之視野角爲小之結果。此外’就經積層比較 例4之內部光擴散薄膜與在透明基材薄膜形成光擴散層所 獲得之光擴散薄片之構成而言’則其全光線透射率爲低’ 且亮度之角度相依性係大於實施例之光擴散薄片者’結果 導致不良的亮度不均勻性。 【圖式簡單說明】 第1圖係展示本發明之光擴散薄膜之構成一實例截面 圖。 第2圖係用於評估背光擴散度、亮度不均勻性之直下 -27 - 200903037 型背光截面圖。 第3圖係展示變角光度測定之結果的圖表。 第4圖係展示視野角測定之結果的圖表。 第5圖係用於說明亮度不均勻性評估方法的圖。 第6圖係用於說明擴散性係因內部光擴散薄膜之厚度 而變化的情況圖。 第7圖係用於說明擴散性係因內部光擴散薄膜中之擴 散成分平均粒徑而變化的情況圖。 fFull ray haze diffusivity backlight diffusivity luminance transmittance parallel direction vertical direction non-uniformity Example 1 59.1% 93.7% 46.6+0.6 84.7 89.5 A Example 2 57.2% 93.8% 49.7±1.2 91.2 93.4 A Example 3 66.8% 92.9% 26.2+1.0 76.5 81.6 B Example 4 67.0% 93.3% 33.010.7 88.6 96.0 B Example 5 65.2% 93.3% 33.5±1.3 78.7 84.1 B Example 6 64.8% 93.6% 41.1+0.5 89.4 93.4 A Example 7 57.3% 93.7% 48.6±1.5 85.3 93.4 A Comparative Example 1 67.7% 90.7% 13·6±1·3 70.0 76.4 D Comparative Example 2 74.3% 90.1% 14.0+0.8 70.2 77.8 ---__ D Comparative Example 3 64.7% 90.8 % 14.211.1 71.3 76.4 ----- D Comparative Example 4 60.2% 93.2% 33.0±0.7 69.3 76.0 ·· ~ -c -26- 200903037 The number of diffusion degrees of the respective examples and comparative examples is expressed in the 12 direction. The center of the spread and the deviation. As shown in Table 1, the light diffusing films of Examples 1 to 7, and comparative examples! Compared with the light diffusing film of 4, it can sufficiently satisfy the angle dependence of brightness unevenness and brightness. When Examples 1 and 4 and Examples 5 and 7 were compared, it was found that even if the internal light-diffusing film was produced in the same manner, the degree of diffusion was increased as soon as the amount of the diffusing component was increased. When Examples 1 and 2 and Examples 5 and 6 were compared, it was found that even when the same internal light-diffusing film and the light-diffusing layer were used, when the light-diffusing layer was provided on both surfaces, the degree of diffusion was increased. Further, it is known from the third embodiment that even if the amount of the diffusion component in the internal light-diffusing film is reduced, sufficient diffusibility can be obtained by forming the light-diffusing layer. On the other hand, in the light-diffusing sheet obtained by forming the light-diffusing layer on the transparent base film of Comparative Examples 1 to 3, the unevenness in brightness was small, and the viewing angle with respect to brightness was small. Further, in terms of the composition of the internal light-diffusing film of Comparative Example 4 and the light-diffusing sheet obtained by forming the light-diffusing layer on the transparent base film, 'the total light transmittance is low' and the angle dependence of the brightness is The result is greater than the light diffusing sheet of the embodiment, resulting in poor brightness unevenness. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view showing an example of the constitution of a light-diffusing film of the present invention. Figure 2 is used to evaluate the backlight diffusivity and brightness non-uniformity. -27 - 200903037 Backlight section. Figure 3 is a graph showing the results of variable angle photometry. Figure 4 is a graph showing the results of the viewing angle measurement. Fig. 5 is a view for explaining a method of evaluating luminance unevenness. Fig. 6 is a view for explaining a case where the diffusibility changes due to the thickness of the internal light-diffusing film. Fig. 7 is a view for explaining a case where the diffusibility is changed by the average particle diameter of the diffusion component in the internal light-diffusing film. f
第8圖係用於說明擴散性係因內部光擴散薄膜中之擴 散成分含量而變化的情況圖。 第9圖係用於說明擴散性係因光擴散層之結構而變化 的情況圖。 【主要元件符號說明】 1 基質樹脂 2 擴散成分 3 粒子 4 背塗層 5 內部光擴散薄膜 6 光擴散層 7 黏結劑樹脂 11 擴散板 12 光擴散薄膜 13 冷陰極管 14 反射薄膜 -28 - 200903037 15 框 體 20 突 起 狀 波 峰 100 對 於 直 下 型 背 光 之 冷 陰 極 管 成 垂 直 方 向 的 截 面 圖 200 對 於 直 下 型 背 光 之 冷 陰 極 管 成 垂 直 方 向 的 放 大 截 面 圖 300 由 對 於 直 下 型 背 光 之 冷 陰 極 管 面 成 法 線 方 向 所 看 的 圖 400 亮 度 測 疋 位 置 > 測 定位 置 之 各 端 係 螢 光 管 之 間 的 中 央 401 液 晶 背 光 單 元 之 面 之 對 角 線Fig. 8 is a view for explaining a case where the diffusibility is changed by the content of the diffusion component in the internal light-diffusing film. Fig. 9 is a view for explaining a case where the diffusibility changes due to the structure of the light diffusion layer. [Main component symbol description] 1 Matrix resin 2 Diffusion component 3 Particle 4 Back coat 5 Internal light diffusing film 6 Light diffusing layer 7 Adhesive resin 11 Diffuser plate 12 Light diffusing film 13 Cold cathode tube 14 Reflective film -28 - 200903037 15 Frame 20 Protrusion crest 100 Cross-sectional view of the cold cathode tube for the direct type backlight 200. Vertical cross-sectional view of the cold cathode tube for the direct type backlight 300. Formed by the cold cathode tube surface for the direct type backlight Figure 400 in the direction of the line. Brightness measurement position> The measurement position is the diagonal of the center of the 401 LCD backlight unit between the ends of the fluorescent tube.
C -29 -C -29 -