201003238 九、發明說明： 【發明所屬之技術領域】 本發明涉及一種背光模組及其光學板，尤其涉及一種 用於液晶顯示之背光模組及其光學板。 【先前技術】 請參閱圖1，所示為一種習知之直下式背光模組100， 其包括框架11與設置在該框架11内部之複數光源12、及設 置在光源12上方並蓋住框架11之擴散板13。 使用時，由複數光源12產生之光線進入擴散板13後被 擴散。然而，在經擴散板13擴散後，光線從擴散板13之出 射角度變得較為雜亂，使得其在特定視角範圍内之亮度不 高；並且由於光源12朝其正上方傳輸之光線較多，擴散板 13還是常常難以直接將來自光源12光線擴散均勻，使得從 擴散板13出射之光線容易產生光源殘影，即出現光強強弱 不同之區域。 為提高背光模組100在特定視角範圍内之亮度，以及避 免光源殘影之產生，從而提高背光模組100出射光之均勻 性，通常在擴散板13上方還設置有一光學板10與一上擴散 片14。如圖2所示，光學板10包括透明基板101及形成於透 明基板101上之稜鏡層103。棱鏡層103上具有複數長條形V 型凸起105。光學板10之長條形V型凸起105可使出射光線 發生一定程度之聚集，從而提高背光模組100在特定視角範 圍内之亮度。上擴散片14可對從光學板10出射之光線作進 一步擴散。 7 201003238 然而，光線在光學板10與上擴散片14中傳輸時，部分 光線會被吸收而造成光線損失；並且在光學板1〇與上擴散 =14之間有空氣層，其會增加光線在傳輸過程中之介面數 1，增加光線傳輸之介面損失，降低光線利用率。 【發明内容】 "鐾於上述狀況，有必要提供一種可提高光線有效利用 率、出光均勻之背光模組及其光學板。 一種背光模組，其包括㈣、光源及光學板，該光源 位於該框該光學板設置於該錢上^，該 由 透明本體構成，其包括[表面及與該第-表面相對之Ϊ 二表面，該透明本體之第一表 狀弧形凹槽，該第1面上=有複數相互平行之長條 表面上乂替設置有相互平行之複數長201003238 IX. Description of the Invention: The present invention relates to a backlight module and an optical plate thereof, and more particularly to a backlight module for liquid crystal display and an optical plate thereof. [Prior Art] Referring to FIG. 1, a conventional direct type backlight module 100 includes a frame 11 and a plurality of light sources 12 disposed inside the frame 11, and a light source 12 disposed above the frame 11 and covering the frame 11. Diffuser plate 13. In use, the light generated by the complex light source 12 enters the diffusing plate 13 and is diffused. However, after being diffused through the diffusion plate 13, the angle of light exiting from the diffusion plate 13 becomes more disordered, so that the brightness thereof is not high in a specific viewing angle range; and since the light source 12 transmits more light directly above it, diffusion It is often difficult for the plate 13 to directly diffuse the light from the light source 12 uniformly, so that the light emitted from the diffusing plate 13 is liable to cause image sticking of the light source, that is, a region where the intensity of light is different. In order to improve the brightness of the backlight module 100 in a specific viewing angle range and avoid the generation of residual light of the light source, thereby improving the uniformity of the light emitted by the backlight module 100, an optical plate 10 and an upper diffusion are usually disposed above the diffusion plate 13. Sheet 14. As shown in Fig. 2, the optical plate 10 includes a transparent substrate 101 and a ruthenium layer 103 formed on the transparent substrate 101. The prism layer 103 has a plurality of elongated V-shaped projections 105 thereon. The elongated V-shaped projections 105 of the optical plate 10 cause a certain degree of convergence of the outgoing light, thereby increasing the brightness of the backlight module 100 over a particular viewing angle. The upper diffusion sheet 14 can further diffuse the light emitted from the optical plate 10. 7 201003238 However, when light is transmitted through the optical plate 10 and the upper diffusion sheet 14, part of the light is absorbed to cause light loss; and there is an air layer between the optical plate 1 and the upper diffusion = 14, which increases the light. The number of interfaces in the transmission process increases the interface loss of light transmission and reduces the light utilization rate. SUMMARY OF THE INVENTION "In view of the above situation, it is necessary to provide a backlight module and an optical plate thereof which can improve the effective utilization of light and uniform light emission. A backlight module comprising: (4) a light source and an optical plate, wherein the light source is disposed on the frame, the optical plate is disposed on the money, and the transparent light body comprises a surface and a surface opposite to the first surface a first scalloped concave groove of the transparent body, the first surface = a plurality of parallel strips on the surface of the strip having a plurality of parallel lengths
條狀弧形凸起及複數長條狀V形凸起，且第一I面上 ==與第二表面上之長條狀弧形凸起及長條狀V 人八田边阴本體構成，該透明本體包括第 一；面及與該第-表面相對之第二表面，該透明本體之: 2=具有複數相互平行之長條狀弧形凹槽，該第二表面 =替設置有相互平行之複數長絲弧形凸起及複數長條 /凸起’並且第-表面上之長條狀弧形一表 面上之長條狀弧形凸起及長條狀V形凸起相平行表 上述背光模組中之光學柘ώ Μ势 互半;r夕且玫α π 板由於第一表面上具有複數相 互形凹槽，第二表面上交替設置有複數相a strip-shaped curved protrusion and a plurality of long strip-shaped V-shaped protrusions, and the first I surface == is formed with a long strip-shaped curved protrusion on the second surface and a long strip-shaped V-shaped eight-field side body, The transparent body comprises a first surface and a second surface opposite to the first surface, wherein the transparent body has: 2 = a plurality of elongated arcuate grooves parallel to each other, the second surface being arranged parallel to each other a plurality of filament arc-shaped protrusions and a plurality of strips/protrusions' and a long strip-shaped arc-shaped protrusion on the surface of the strip-shaped arc on the first surface and a strip-shaped V-shaped protrusion are parallel to each other The optical 柘ώ Μ Μ ; ; ; ; ; ; ; ; ; 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 玫 由于 由于 由于 由于 由于 由于 由于
千订之複數絲㈣形凸起及難相互平行之長條狀V 8 201003238 形凸起，並且第一表面上之長條狀弧形凹槽與第二表面上 之長條狀弧形凸起及長條狀v形凸起相平行，從而構成變 化之曲面結構，其有利於讓射入光學板之光線發生特定之 折射、反射與繞射等光學作用，進而可使從光學板出射之 光線在一特定之視角範圍聚集，與此同時，還可使光線發 生擴散，以減弱甚至避免光源殘影，提高背光模組之出光 均勻性’避免了採用上擴散片而產生之介面損失，提升光 線利用率。 【實施方式】 下面將結合附圖及實施例對本發明之背光模組及其光 學板作進一步詳細說明。 请參見圖3與圖4，所示為本發明較佳實施例一之光學 板2〇,其由一透明本體構成，該透明本體包括第一表面201 及與第一表面201相對之第二表面2〇3。第一表面2〇1具有複 數相互平行之長條狀弧形凹槽202，第二表面203上交替設 置有相互平行之複數長條狀弧形凸起2〇4及複數相互平行 之長條狀V形凸起205，複數長條狀弧形凸起2〇4和複數長 條狀V形凸起205相平行，並且第一表面2〇1上之長條狀弧 形凹槽202與第二表面2〇3上之長條狀弧形 凸起204及長條 狀V形凸起205相平行。a plurality of multi-filament (four)-shaped protrusions and long strips V 8 201003238 which are difficult to be parallel to each other, and a long arc-shaped groove on the first surface and a long arc-shaped protrusion on the second surface And the long strip-shaped v-shaped protrusions are parallel, thereby forming a curved surface structure, which is beneficial for optical effects such as specific refraction, reflection and diffraction of the light incident on the optical plate, thereby enabling light emitted from the optical plate. At a certain angle of view, at the same time, the light can be diffused to reduce or even avoid the residual image of the light source, and improve the uniformity of the light output of the backlight module, which avoids the interface loss caused by the upper diffusion sheet and enhances the light. Utilization rate. [Embodiment] Hereinafter, a backlight module and an optical plate thereof according to the present invention will be further described in detail with reference to the accompanying drawings and embodiments. Referring to FIG. 3 and FIG. 4, an optical plate 2 is shown in FIG. 3, which is composed of a transparent body. The transparent body includes a first surface 201 and a second surface opposite to the first surface 201. 2〇3. The first surface 2〇1 has a plurality of elongated arcuate grooves 202 parallel to each other, and the second surface 203 is alternately provided with a plurality of long strip-shaped curved protrusions 2〇4 and a plurality of parallel strips which are parallel to each other. a V-shaped projection 205, a plurality of elongated arcuate projections 2〇4 and a plurality of elongated V-shaped projections 205 are parallel, and the elongated arcuate grooves 202 and the second surface on the first surface 2〇1 The elongated arcuate projections 204 and the elongated V-shaped projections 205 on the surface 2〇3 are parallel.
本實施例中’第一表面2〇1上之長條狀弧形凹槽2〇2之 截面為半圓弧形。將第一表面2〇1上之相鄰兩長條狀弧形凹 槽202之中心間距記為Ρι，圓弧半徑記為&，圓弧最大深度 °己為Hl’則Pl、 Ri及Hi滿足如下關係式：0.025毫米S 201003238In the present embodiment, the section of the elongated arcuate groove 2〇2 on the first surface 2〇1 has a semicircular arc shape. The center-to-center spacing of the adjacent two elongated arc-shaped grooves 202 on the first surface 2〇1 is denoted by Ρι, the radius of the arc is recorded as &, the maximum depth of the arc is already H1', then Pl, Ri and Hi Meet the following relationship: 0.025 mm S 201003238
Pi S 1 毫米 ’ Ρ"4 $ Rl $ 2 Ρι，〇 〇1 毫米 $ Ηι $ Ri。換而言 之相鄰兩弧形凹槽202之中心間距Pl可為〇·〇25毫米至1毫 米，圓弧半徑R!可為0.006毫米至2毫米，圓弧最大深度仏 可為0.01毫米至2毫米。 第二表面203上之長條狀弧形凸起2〇4之截面為半圓弧 形。將長條狀弧形凸起2〇4之最大寬度記為？2，半徑記為 R2 ’則P2及R2滿足如下關係式：〇.〇25毫米$ 1.5毫米， IV4SR2S2P2，換而言之柱形凸起2〇4之最大寬度p2可為 0.025¾米至1.5宅米，半徑可為〇〇〇6毫米至3毫米；將長 條狀V形凸起205之最大寬度記為！>3，則&可為〇 〇25毫米至 1毫米；將長條狀弧形凸起204和該長條狀V形凸起2〇5之高 度記為Hr則H2滿足如下關係式：〇〇1毫米$H2gR2,換 而言之長條狀弧形凸起204和長條狀乂形凸起2〇5之高度H2 可為0.01毫米至3毫米。此外，該長條狀v形凸起2〇5之頂角 Θ為80度至1〇〇度。另，藉由調整長條狀v形凸起2〇5之頂角 ^ Θ之大小，可於一定程上調整光學板2〇之增光率及出光視 角。 光學板20之總體厚度Tl可為〇4毫米至4毫米。光學板 20可由聚甲基丙稀酸甲醋、聚碳酸酿、聚苯乙稀、苯乙稀_ 曱基丙烯酸曱醋共聚物中之一種或—種以上之材質注塑成 型而成。製備過程中需在模具上設置與長條狀弧形凸起2〇4 以及長條狀V形凸起2G5相應之凹陷結構，以便使光學板2〇 可在單次注塑過程中成型。 光學板2〇採用注塑成型之方式-體成型，其條 201003238 狀弧形凸起204及長條狀V形凸起205和光學板20之其他部 分一起形成，是以可使得長條狀弧形凸起2〇4以及長條狀v 形凸起205具有較高之結構強度，同時還能提升長條狀弧形 凸起204以及長條狀v形凸起205和光學板20其他部分之結 合力，從而可避免或減少長條狀弧形凸起2〇4以及長條狀v 形凸起205在使用中被損壞之危險。 為進一步驗證光學板20可對入射其中之光線起特定之 擴散作用，特別選取如表1所列樣品進行對比測試，其結果 如圖5至 圖7所示。 表 1測試樣品 樣品號 樣品組成 1 ___梦光二極體 2 發光二 二極體+光學板10 3 發光二 1極體+光學板20 分析圖5、圖6與圖7所示結果，發光二極體發出之光為 中心強度尚之凴點；從光學板1〇中出射之光線會形成兩 中心強度间之免點；而從光學板2〇出射之光線則擴散成一 條長度較長且亮度較均勻之光線帶。由此可見，光學板2〇 具備較強之擴散效果。 請參閱圖8,所示為本發明較佳實施例二之光學板3〇。 光學板30與較佳實施例一之光學板2〇相似。其不同在於： 第表面301上之長條狀弧形凹槽3〇2之戴面為半橢圓形， 將相鄰兩長條狀弧形凹槽3()2之中心間距記為h，長條狀弧 形凹槽302之最大寬度記為最大深度記為H3,光學板30 11 201003238 總體厚度記為m P5、 0.025毫米叫u毫米，p…㈣，0^^ 毫米，0.01亳米SH3gP5<T2。換而+之 未=Τ2$4 形凹槽302之中心間距Ρ4可為〇〇25^ι目鄰，長條狀弧 弧形凹槽302之最大寬度Ρ5可為㈣6毫米至2: 犬 3〇總體厚度丁2可為〇.4毫米至4毫 二予板 之最大深細可為0.01毫米至2毫米。長條狀弧形凹槽302 請參閱圖9,所示為本發明較佳實施例三 光學板40與較佳實施例一之光學板2〇相似。其不^在於0.° ^表面備上之長條狀弧形凸起彻之截面為半擴圓形: 形凸起4G4之截㈣可為平滑曲線等其他形 狀之長條狀弧形凸起。 請參見圖10，所示為本發明較佳實施例四之背光模植 200，其包括上述光學板20、框架21及光源22，該光源^ 位於該框架21内，該光學板2〇設置於該光源22上方。 上框架21可由具有高反射率之金屬或塑膠製成，或塗佈 有咼反射率塗層之金屬或塑膠製成。 光源22可為線光源或點光源，例如冷陰極螢光燈與發 光二極體，本實施例中為冷陰極螢光燈，該冷陰極螢光燈 之間較為緊密排佈，且該冷陰極螢光燈與光學板2〇第二表 面203上之長條狀v形凸起2〇5及長條狀弧形凸起2〇4之相 平行。 上述背光模組200中之光學板2〇之第一表面201靠近光 源而第二表面203遠離光源22。由於第一表面201上具有複 12 201003238 數相互平行之長條狀弧形凹槽2〇2，第二表面2〇3上具有複 數相互平行之長條狀弧形凸起204及長條狀v形凸起2〇5， 且該複數長條狀弧形凸起204與該複數長條狀v形凸起2〇5 .相互間隔分佈，且第一表面上之長條狀弧形凹槽與第二表 面上之長條狀弧形凸起及長條狀V形凸起相平行，從而構 成變化之曲面結構；同時，複數冷陰極螢光燈緊密排佈’ 且該複數冷陰極螢光燈和光學板2〇第二表面2〇3上之長條 狀V形凸起205及長條狀弧形凸起2〇4相平行，因而有利於 =射入光學板20之光線發生特定之折射、反射與繞射等光 學作用，進而可使從光學板2〇出射之光線發生特定之擴 散，從而形成亮度較均勻之光亮面。由此可見，上述背光 模組200可以減弱甚至避免光源殘影，提高背光模組之出光 均勻性，避免了採用上擴散片而產生之介面損失，提升光 2利用率。當然’當光源22為點光料 佈成陣列，可同樣達到使用線光源之效果。斤緊讀 i :以理解’當光源22之間之間距較大時，可於本發明 而可進核和光源22之間增設一擴散板，從 而了進-步將光線擴散均句，提升#光模組之出光均句性。 出專：二本發明確已符合發明專利要件，差依法提 舉凡孰=幸上所述者僅為本發明之較佳實施例， =输，皆應包含於以下之申請專作之等 【圖式簡單說明】 圖1係一種習知之背光模組之剖面示意圖。 13 201003238 圖2係圖1所示背光模組之光學板之立體圖。 圖3係本發明較佳實施例一所示光學板之立體示意 圖。 圖4係圖3所示光學板沿IV-IV線之剖視圖。 圖5係測試樣品1之光強測試圖。 圖6係測試樣品2之光強測試圖。 圖7係測試樣品3之光強測試圖。 圖8係本發明較佳實施例二之光學板之剖面示意圖。 圖9係本發明較佳實施例三之光學板之剖面示意圖。 圖10係本發明較佳實施例四之背光模組之剖面示意 圖。 【主要元件符號說明】 光學板 20、 30 ' 40 第一表面 201 、301 第二表面 203 、403 長條狀弧形凹槽 202 、302 長條狀弧形凸起 204 、404 長條狀V形凸起 205 背光模組 200 框架 21 光源 22 14Pi S 1 mm ‘ Ρ"4 $ Rl $ 2 Ρι,〇 〇1 mm $ Ηι $ Ri. In other words, the center distance P1 of the adjacent two curved grooves 202 may be 毫米·〇 25 mm to 1 mm, the arc radius R! may be 0.006 mm to 2 mm, and the maximum depth of the arc 仏 may be 0.01 mm to 2 mm. The elongated arcuate projection 2〇4 on the second surface 203 has a semicircular arc shape. What is the maximum width of the long curved protrusion 2〇4? 2, the radius is recorded as R2 'P2 and R2 satisfy the following relationship: 〇.〇25 mm $1.5 mm, IV4SR2S2P2, in other words, the maximum width p2 of the columnar protrusion 2〇4 can be 0.0253⁄4 m to 1.5 house The radius of the meter can be 〇〇〇6 mm to 3 mm; the maximum width of the long V-shaped projection 205 is recorded as! >3, then & can be 〇〇25 mm to 1 mm; the height of the elongated arcuate projection 204 and the elongated V-shaped projection 2〇5 is denoted as Hr, and H2 satisfies the following relationship: 〇〇1 mm $H2gR2, in other words, the height H2 of the long strip-shaped convex protrusion 204 and the long strip-shaped convex protrusion 2〇5 may be 0.01 mm to 3 mm. Further, the apex angle 该 of the elongated v-shaped projection 2〇5 is 80 degrees to 1 degree. Further, by adjusting the size of the apex angle ^ of the long v-shaped protrusions 2〇5, the brightness enhancement and the viewing angle of the optical plate 2 can be adjusted in a certain range. The overall thickness T1 of the optical plate 20 may be 〇4 mm to 4 mm. The optical plate 20 may be formed by injection molding one or more of polymethyl methacrylate methyl vinegar, polycarbonated styrene, polystyrene, styrene acrylonitrile vinegar copolymer. In the preparation process, a concave structure corresponding to the long arc-shaped protrusions 2〇4 and the long-shaped V-shaped protrusions 2G5 is provided on the mold so that the optical sheets 2 can be formed in a single injection molding process. The optical plate 2 is formed by injection molding, and the strips 201003238-shaped arc-shaped protrusions 204 and the elongated V-shaped protrusions 205 are formed together with other portions of the optical plate 20 to form a long curved shape. The protrusions 2〇4 and the elongated v-shaped protrusions 205 have a high structural strength, and at the same time, can also enhance the combination of the elongated arcuate projections 204 and the elongated v-shaped projections 205 and other portions of the optical plate 20. Force, thereby avoiding or reducing the risk of the elongated arcuate projections 2〇4 and the elongated v-shaped projections 205 being damaged in use. In order to further verify that the optical plate 20 can specifically diffuse light incident thereon, a sample as shown in Table 1 is specifically selected for comparison test, and the results are shown in Figs. 5 to 7. Table 1 test sample sample number sample composition 1 ___ dream light diode 2 light-emitting diodes + optical plate 10 3 light two-pole body + optical plate 20 analysis Figure 5, Figure 6 and Figure 7 results, light two The light emitted by the polar body is the center point of the intensity; the light emitted from the optical plate 1〇 forms a point of separation between the two centers; and the light emitted from the optical plate 2 is diffused into a longer length and brightness. Even light band. It can be seen that the optical plate 2 has a strong diffusion effect. Referring to Figure 8, there is shown an optical plate 3 of a preferred embodiment of the present invention. The optical plate 30 is similar to the optical plate 2 of the preferred embodiment 1. The difference is that: the wear surface of the long curved groove 3 〇 2 on the first surface 301 is semi-elliptical, and the center distance of the adjacent two long curved grooves 3 () 2 is recorded as h, long. The maximum width of the strip-shaped curved groove 302 is recorded as the maximum depth is recorded as H3, and the total thickness of the optical plate 30 11 201003238 is recorded as m P5, 0.025 mm is called u mm, p...(four), 0^^ mm, 0.01 亳m SH3gP5< T2. In the case of +===2$4, the center-to-center spacing Ρ4 of the groove 302 can be 〇〇25^ι目, and the maximum width of the long arc-shaped groove 302 can be (4) 6 mm to 2: Canine 3〇 overall The thickness of the diced layer 2 may be from 44 mm to 4 毫. The maximum depth of the plate may be from 0.01 mm to 2 mm. Long strip-shaped recessed groove 302 Referring to Figure 9, there is shown a preferred embodiment of the present invention. The optical plate 40 is similar to the optical plate 2 of the preferred embodiment 1. It is not in the 0. ° ^ surface of the long strip-shaped arc-shaped convex part of the section is a semi-expanded circle: the section of the convex 4G4 section (four) can be a smooth curve and other shapes of long arc-shaped protrusion . Referring to FIG. 10, a backlight mold 200 according to a fourth embodiment of the present invention includes the optical plate 20, the frame 21 and the light source 22. The light source is located in the frame 21, and the optical plate 2 is disposed on Above the light source 22. The upper frame 21 may be made of metal or plastic having high reflectivity or metal or plastic coated with a ruthenium reflectance coating. The light source 22 can be a line source or a point source, such as a cold cathode fluorescent lamp and a light emitting diode. In this embodiment, a cold cathode fluorescent lamp is arranged closely between the cold cathode fluorescent lamps, and the cold cathode is arranged. The fluorescent lamp is parallel to the elongated v-shaped projections 2〇5 and the elongated arcuate projections 2〇4 on the second surface 203 of the optical plate 2〇. The first surface 201 of the optical plate 2 in the backlight module 200 is close to the light source and the second surface 203 is away from the light source 22. Since the first surface 201 has a long strip-shaped curved groove 2〇2 parallel to each other, the second surface 2〇3 has a plurality of long strip-shaped curved protrusions 204 and strips v which are parallel to each other. a protrusion 2〇5, and the plurality of elongated arcuate protrusions 204 are spaced apart from the plurality of elongated v-shaped protrusions 2〇5, and the long curved grooves on the first surface are The long arc-shaped protrusions on the second surface and the long strip-shaped V-shaped protrusions are parallel to form a curved surface structure; at the same time, the plurality of cold cathode fluorescent lamps are closely arranged' and the plurality of cold cathode fluorescent lamps It is parallel with the long V-shaped protrusions 205 and the elongated arc-shaped protrusions 2〇4 on the second surface 2〇3 of the optical plate 2, thereby facilitating specific refraction of the light incident on the optical plate 20. Optical effects such as reflection and diffraction can further diffuse the light emitted from the optical plate 2 to form a bright surface with uniform brightness. It can be seen that the backlight module 200 can reduce or even avoid the residual image of the light source, improve the uniformity of the light output of the backlight module, avoid the interface loss caused by the upper diffusion sheet, and improve the utilization ratio of the light 2 . Of course, when the light source 22 is arranged in an array of dots, the effect of using the line source can be achieved.斤紧我: In order to understand 'When the distance between the light sources 22 is large, a diffusing plate can be added between the core and the light source 22 in the present invention, thereby further diffusing the light into the sentence, lifting # The light output of the light module is uniform. Out of the special: The second invention has indeed met the requirements of the invention patent, and the difference is according to the law. Fortunately, the above description is only the preferred embodiment of the present invention, and the input should be included in the following application. Brief Description of the Drawings Fig. 1 is a schematic cross-sectional view of a conventional backlight module. 13 201003238 FIG. 2 is a perspective view of an optical plate of the backlight module shown in FIG. 1. Figure 3 is a perspective view of an optical plate according to a preferred embodiment of the present invention. Figure 4 is a cross-sectional view of the optical plate of Figure 3 taken along line IV-IV. Figure 5 is a light intensity test chart of Test Sample 1. Figure 6 is a light intensity test chart of Test Sample 2. Figure 7 is a light intensity test chart of Test Sample 3. Figure 8 is a cross-sectional view showing an optical plate according to a second preferred embodiment of the present invention. Figure 9 is a cross-sectional view showing an optical plate according to a third preferred embodiment of the present invention. Figure 10 is a cross-sectional view showing a backlight module of a fourth preferred embodiment of the present invention. [Description of main component symbols] Optical plate 20, 30' 40 First surface 201, 301 Second surface 203, 403 Long arc-shaped groove 202, 302 Long arc-shaped projection 204, 404 Long V-shaped Bump 205 backlight module 200 frame 21 light source 22 14