200900795 PT947 24219twf.doc/n 九、發明說明： 【發明所屬之技術領域】 本發明是有關於一種光源模組（light source module )，且特別是有關於一種背光模組（backlight module)。 【先前技術】 圖1為一種習知側邊入光式（side incident type )背光 模組的局部剖面圖。請參照圖1，習知側邊入光式背光模 組 100 包括一背框 110、一 導光板（light guide plate) 120、 一冷陰極螢光燈管組（cold cathode fluorescent lamp assembly，CCFL assembly) 130、一反射片 140 以及一膠框 150。背框110是由底板112與側板114所組成。導光板 120具有一出光面122、一相對於出光面122的底面124 以及一連接出光面122與底面124的入光側面126。底面 124朝向背框11〇的底板112。入光側面126朝向背框110 的側板114。反射片140配置於導光板120的底面124與 背框110的底板112之間。膠框150配置於背框110的邊 緣與導光板120的邊緣上。導光板120的入光側面126、 膠框150的頂部152與背框11〇之間形成一滑槽S，而冷 陰極螢光燈管組130可沿著與圖面垂直的方向置入滑槽S 或由滑槽S中抽離，以便於在維修側邊入光式背光模組1 〇〇 時更換冷陰極螢光燈管組13〇。 導光板120之底面124鄰近入光側面126的邊緣與背 框110之間維持有一間隙G，以使冷陰極螢光燈管組130 6 200900795 PT947 24219twf.doc/n 便於置人滑槽s，然而這亦會導致反射片14G位於間隙G 處的部^易於朝向背框110彎曲。如此—來，當進行側邊 入光式月光模組100的維修而欲將冷陰極螢光燈管組 置=滑槽S時，冷陰極螢光燈管組130易於與反射片140 的彎曲部分互相干涉’造敍射4140賴損、鈹褶或冷 陰極螢光燈管組13〇置入時的阻力。 為減少冷陰極螢光燈管組13〇與反射片14〇的彎曲部 分互相干涉的機會，可將間隙G放大。然而，這會造成^ 陰極螢光燈管組13G所發出的部分光線投射在反射片Jo j f曲部分，並經由其反射後在出光面122的區域A產生 亮線，導致侧邊入光式背光模組議無法提供亮度均勻的 面光源。 【發明内容】 本發明提供一種背光模組，其易於維修且能提供亮度 均勻的面光源。 本發明之一實施例提出一種背光模組，其包括一背 框、一導光板、一發光單元以及一反射片。背框具有一底 板至夕第側板與至少一第二側板。第一側板與第二 側板分別與底板相連接。導光板配置於背框中，並具有一 出光面、底面、至少一入光側面以及一側面。底面朝向 底板’並位於該出光面與該底面之間。入光側面接觸出光 面/、底面，並朝向第一側板。側面與出光面、底面及入光 側面接觸，並朝向第二侧板。發光單元可拆卸地配置於入 光側面與第-側板之間，並適於朝向人光側面發光。反射 200900795 PT947 24219twf.doc/n 片具有-主反射部以及至少—結構補強部。主反射部配置 於導光板的底©與底板之間。結構_部連接主反射部， 並貼附導光板的側面。 於本發明之-實施例中，上述反射片彳為一體成形。 此外’結構·部可連接至主反射部的—肢。結構補強 部與主反射部的交界處可為—褶線，而結構補強部在與稽 線平=之方向上的寬度小於主反射部在與褶線平行之方向 上的寬度之-半。財’結構補強部在與糟線垂直之方向 上的高度可實質上等於導光板之出光面至底面的距離。 於本發明之-實施例中，入光側面與第一側板之間可 形成-滑槽’且背框形成—缺口，位於第—側板 板之間，並與賴的-端減，而發光單元適於經由= 置入滑槽或自滑槽取出。結構補強部可藉由—雙面膠或一 黏著劑貼附至導光板的側面。發光單元可包括至少一冷陰 極螢光燈管或至少-發光二極體。此外，背光模纟且可^ 括-光學膜片，其配置於出光面上。光學則可包括一擴 (diffusion film) ( brightness enhancement film, BEF )或其組合。 於本發明之-f施例巾，上述背光模組可更包括一前 框，其配置於第-織上，並延輕導光㈣邊緣，盆中 前框可包括膠框。背光模組可包括二發光單元，1中導光 板具有相對的二人光侧面’且這⑽光單元分別朝向這些 入光側面。此外’反射片可具有二結構補強部，分別位於 主反射部的相鄰兩角洛或相對兩角落。 200900795 PT947 24219twf.doc/n 、在背光模組中，反射片具有貼附於導光板的側面之姓 構補強=，這可減少反射片鄰近導光板的入光側面之部^ 往底板彎曲的程度，進而降低發光單元在置入背光模組中 時與反射片互相干涉的機會。 為讓本發明之上述特徵和優點能更明顯易懂，下文特 舉較佳實施例，並配合所附圖式，作詳細說明如下。 【實施方式】 下列各實施例的說明是參考附加的圖式，用以例示本 發明可用以實施之特定實施例。本發明所提到的方向用 語’例如「上」、「下」、「前」'「後」、「左」、「右」 等，僅是參考附加圖式的方向。因此，使用的方向用語是 用來說明’而非用來限制本發明。 請參照圖2A至圖2C，本實施例之背光模組2〇〇包括 一背框210、一導光板220、一發光單元23〇以及一反射片 240。背框210具有一底板212、至少一第一側板214與至 少一第一側板216，其中第一側板2M及第二侧板216分 別與底板212相連接。導光板220配置於背框210中，並 具有一出光面222、一相對於出光面的底面224、至少一入 光側面226以及至少一側面228 (如圖2B所示）。底面 224朝向底板212 ’位於出光面222與底板212之間。至少 一入光側面226接觸出光面222與底面224，並朝向第一 側板214。側面228與出光面222、底面224及入光側面 226接觸，且朝向第二側板216。至少一發光單元230可拆 卸地配置於入光側面226與第一側板214之間，發光單元 9 200900795 PT947 24219twf.doc/n 230分別朝向入光側面226，並適於朝向入光侧面226發 光，而導光板220適於將發光單元23〇所發出的光導引至 出光面222而形成面光源。在本實施例中，發光單元23〇 可包括至少一冷陰極螢光燈管232。然而，在其他實施例 中，發光單元230亦可以包括至少一發光二極體或其他適 當的發光元件。此外’發光單元23〇還可包括一燈罩234， 用以固定冷陰極螢光燈管232。 反射片240具有一主反射部242以及一結構補強部 244。主反射部242配置於導光板22〇的底面224與底板 212之間，以將發光單元23〇所發出的光反射至出光面 222。結構補強部244連接至主反射部242 ’並貼附導光板 220的側面228。具體而言，結構補強部244可藉由雙面膠、 黏著劑或以其他適當方式貼附至導光板220的側面228。 反射片240可為一體成形，亦即主反射部242與結構補強 部244為一體成形，由同一板片所構成。此外，結構補強 部244位於主反射部242的一角落。結構補強部244與主 反射部242的交界處可為一褶線246 (如圖2B所示），而 結構補強部244在與權線246平行之方向上的寬度wi可 小於主反射部242在與褶線246平行之方向上的寬度W2 (如圖2C所示）之一半。再者’結構補強部244在與稽 線246垂直之方向上的高度H1可實質上等於導光板220 之出光面222至底面224的距離H2。 導光板220的側面228可朝向第二側板216。入光側 面226與第一側板214之間可形成一滑槽s’，且背框210 10 200900795 PT947 24219twf.doc/n 形成一缺口 218’位於第一側板214與第二側板216之間， 並與滑槽S’的一端相通，而發光單元230適於沿著圖2B 所繪示之方向D(即與圖2A之圖面垂直的方向）並經由 缺口 218置入滑槽S’或自滑槽S，取出。 在本實施例中，背光模組200可更包括一光學膜片 250,其配置於出光面222上。光學膜片250可包括一擴散 片、一增光片、其他適當光學膜片或這些膜片的組合。此 外’背光模組200可更包括一前框260，其配置第一側板 214上，並延伸至導光板220的邊緣’其中前框260例如 為膠框或其他適當材質所構成的框體。 在本實施例之背光模組200中，反射片240具有貼附 於導光板220的側面228之結構補強部244，這可減少反 射片240鄰近導光板220的入光侧面226之部分往底板212 彎曲的程度，進而降低發光單元230在置入滑槽S，中時與 反射片240互相干涉的機會。因此，當背光模組2〇〇的發 光單το 230故障時，發光單元230易於被更換或修復後重 新置入，而使得維修較為容易。此外，在本實施例中，由 於反射片240往底板212彎曲的程度可以被有效抑制，這 使得發光單元230所發出的光不會投射在如習知技術中反 射片往底板彎曲的部分而在出光面產生亮線，所以本實施 例之背光模組200能夠提供亮度均勻的面光源。再者，結 構補強部244可具有將傳遞至導光板22〇的側面228之光 線反射至出光面222的功能。 值得注意的是，本發明並不限定結構補強部244的寬 11 200900795 PT947 24219twf.doc/n 度Wl小於主反射部242的寬度W2之一半，亦不限定結 構補強部244的高度H1等於導光板220之出光面222至 底面224的距離H2。在其他實施例中，寬度wi亦可以是 等於W2或大於寬度W2之一半，高度H1亦可以小於距 離H2’而仍然能夠達到抑制反射片240鄰近入光侧面226 之部分往底板212彎曲之功效。 此外，本發明不限定發光單元230、第一侧板214、 p 入光側面226的數量為一個。在未繪示的實施例中，背光 模組可包括二發光單元，其中導光板可具有相對的二入光 側面’且這些發光單元分別配置於導光板之相對兩侧，分 別朝向這些入光側面，並適於分別朝向這些入光側面發 光。此外’第一侧板之數量亦可以是二個，而各發光單元 分別配置於其中一入光側面與其中一第一側板之間。 ^本發明亦不限定反射片所具有之結構補強部的數 量。請參照圖3A，在另—實施例中，反射片240a可具有 f 二結構補強部244’分別位於主反射部242的相鄰兩角落， k 如此之反射片240a可應用在具有二發光單元之背光模組 中。請參照圖3B，在又—實施例中，反射片24〇b的二結 構補強部244可分別位於主反射部242的相對兩角落。請 參照圖3C，在再一實施例中，反射片240c可具有四個結 構補強部244，分別位於主反射部242的四個角落。 &上所述’在本發明之實施例的背光模組中，反射片 具有貼附於導光板的侧面之結構補強部，這可減少反射片 鄰近導光板的入光側面之部分往底板彎曲的程度，進而降 12 200900795 PT947 24219twf.doc/n 低發光單元在置入滑槽中時與反射片互相干涉的機會。因 此，當背賴_發光單元故_，發光單元易於被更換 或修復後重新置入，而使得維修較為容易。此外，由於反 射片往底板彎曲的程度可以被有效抑制，這使得發光單元 所發出的光不會投射在如習知技術中反射片往底板彎曲的 部分而在出光面產生亮線，所以本發明之實施例的背光模 組能夠提供亮度均勻的面光源。再者，結構補強部可具有 ( 將傳遞至導光板的側面之光線反射至出光面的功能。、 雖然本發明已以較佳實施例揭露如上，然其並非用以 限定本發明，任何所屬技術領域中具有通常知識者，在不 脫離本發明之精神和範圍内，當可作些許之更動與潤飾， 因此本發明之保護範圍當視後附之申請專利範圍所界定者 為準。另外本發明的任一實施例或申請專利範圍不須達成 本發明所揭露之全部目的或優點或特點。此外，摘要部分 和標題僅是用來輔助專利文件搜尋之用，並非用來限制^ 發明之權利範圍。 、 【圖式簡單說明】 圖1為一種習知側邊入光式背光模組的局部剖面圖。 圖2A為本發明一實施例之背光模組的局部剖視圖。 圖2B為圖2A中之導光板、背框與反射片的局部立體 圖。 圖2C為圖2A中之反射片的立體圖。 圖3A為本發明另一實施例之背光模組的反射片之立 Ί3 200900795 PT947 24219twf.doc/n 圖3B為本發明又一實施例之背光模組的反射片之立 體圖。 圖3C為本發明再一實施例之背光模組的反射片之立 體圖。 【主要元件符號說明】 100 :側邊入光式背光模組 110、210 :背框 112、212 :底板 114 :側板 120、220 :導光板 122、222 :出光面 124、224 :底面 126、226 :入光側面 130 :冷陰極螢光燈管組 140、240、240a、240b、240c :反射片 150 :膠框 152 :頂部 200 :背光模組 214 :第一側板 216 :第二側板 218 :缺口 228 :侧面 230 :發光單元 232 :冷陰極螢光燈管 14 200900795 PT947 24219twf.doc/n 234 :燈罩 242 :主反射部 244 :結構補強部 246 :褶線 250 :光學膜片 260 :前框 A ： 區域 D ： 方向 G ： 間隙 HI :高度 H2 :距離 S、S’ ：滑槽 Wl、W2 :寬度200900795 PT947 24219twf.doc/n IX. Description of the Invention: [Technical Field] The present invention relates to a light source module, and more particularly to a backlight module. [Prior Art] Fig. 1 is a partial cross-sectional view showing a conventional side incident type backlight module. Referring to FIG. 1 , the conventional edge-lit fluorescent backlight assembly 100 includes a back frame 110 , a light guide plate 120 , and a cold cathode fluorescent lamp assembly (CCFL assembly). 130, a reflective sheet 140 and a plastic frame 150. The back frame 110 is composed of a bottom plate 112 and a side plate 114. The light guide plate 120 has a light exit surface 122, a bottom surface 124 opposite to the light exit surface 122, and a light incident side surface 126 connecting the light exit surface 122 and the bottom surface 124. The bottom surface 124 faces the bottom plate 112 of the back frame 11〇. The light incident side 126 faces the side panel 114 of the back frame 110. The reflection sheet 140 is disposed between the bottom surface 124 of the light guide plate 120 and the bottom plate 112 of the back frame 110. The plastic frame 150 is disposed on the edge of the back frame 110 and the edge of the light guide plate 120. A sliding slot S is formed between the light incident side surface 126 of the light guide plate 120, the top portion 152 of the plastic frame 150 and the back frame 11〇, and the cold cathode fluorescent tube assembly 130 can be placed into the sliding slot in a direction perpendicular to the plane of the drawing. S is either pulled out from the chute S to facilitate replacement of the cold cathode fluorescent lamp tube set 13 when the in-light-in backlight module 1 is repaired. A gap G is maintained between the bottom surface 124 of the light guide plate 120 adjacent to the edge of the light incident side 126 and the back frame 110, so that the cold cathode fluorescent tube group 130 6 200900795 PT947 24219twf.doc/n is convenient for placing the chute s, however This also causes the portion of the reflection sheet 14G located at the gap G to be easily bent toward the back frame 110. In this way, when the maintenance of the side entrance light type moonlight module 100 is performed and the cold cathode fluorescent lamp tube is set to be set to the chute S, the cold cathode fluorescent lamp tube group 130 is easily bent with the curved portion of the reflection sheet 140. Interference with each other's resistance to the formation of the 4140 damage, pleats, or cold cathode fluorescent tube set. The gap G can be enlarged in order to reduce the chance that the cold cathode fluorescent tube group 13A and the curved portion of the reflection sheet 14A interfere with each other. However, this causes a part of the light emitted by the cathode fluorescent lamp tube group 13G to be projected on the curved portion of the reflection sheet Jo jf, and is reflected by the reflection light to generate a bright line in the area A of the light-emitting surface 122, resulting in a side-into-light backlight mode. It is not possible to provide a surface light source with uniform brightness. SUMMARY OF THE INVENTION The present invention provides a backlight module that is easy to maintain and can provide a surface light source with uniform brightness. An embodiment of the present invention provides a backlight module including a back frame, a light guide plate, a light emitting unit, and a reflective sheet. The back frame has a bottom plate to the first side plate and at least one second side plate. The first side plate and the second side plate are respectively connected to the bottom plate. The light guide plate is disposed in the back frame and has a light emitting surface, a bottom surface, at least one light incident side surface and a side surface. The bottom surface faces the bottom plate 'and is located between the light exiting surface and the bottom surface. The light incident side contacts the light surface/bottom surface and faces the first side plate. The side faces the light exit surface, the bottom surface, and the light incident side, and faces the second side panel. The light emitting unit is detachably disposed between the light incident side surface and the first side plate, and is adapted to emit light toward the human light side. Reflection 200900795 PT947 24219twf.doc/n The sheet has a primary reflector and at least a structural reinforcement. The main reflection portion is disposed between the bottom of the light guide plate and the bottom plate. The structure_ portion is connected to the main reflection portion and attached to the side surface of the light guide plate. In the embodiment of the invention, the reflection sheet is integrally formed. Further, the 'structure portion can be connected to the limb of the main reflection portion. The boundary between the structural reinforcing portion and the main reflecting portion may be a pleat line, and the width of the structural reinforcing portion in the direction perpendicular to the line is smaller than a half of the width of the main reflecting portion in a direction parallel to the pleat line. The height of the structural reinforcement portion in the direction perpendicular to the bad line may be substantially equal to the distance from the light exit surface to the bottom surface of the light guide plate. In the embodiment of the present invention, a -slot ' can be formed between the light-incident side and the first side plate, and the back frame is formed as a notch, which is located between the first side plates and is reduced with the - terminal, and the light-emitting unit It is suitable to be taken out via the = chute or from the chute. The structural reinforcing portion can be attached to the side of the light guide plate by a double-sided tape or an adhesive. The lighting unit may comprise at least one cold cathode fluorescent tube or at least a light emitting diode. In addition, the backlight module can also include an optical film disposed on the light exit surface. The optics may include a diffusion enhancement film (BEF) or a combination thereof. In the embodiment of the present invention, the backlight module may further include a front frame disposed on the first weave and extending the light guide (four) edge, and the front frame of the basin may include a plastic frame. The backlight module may include two light emitting units, wherein the light guide plate has opposite light side surfaces and the (10) light units face the light incident sides, respectively. Further, the reflection sheet may have two structural reinforcement portions respectively located at adjacent corners or opposite corners of the main reflection portion. 200900795 PT947 24219twf.doc/n In the backlight module, the reflective sheet has a surfacing strength attached to the side of the light guide plate, which can reduce the degree to which the reflective sheet is adjacent to the light incident side of the light guide plate. In turn, the opportunity for the light-emitting unit to interfere with the reflective sheet when placed in the backlight module is reduced. The above described features and advantages of the present invention will become more apparent from the following description. The following description of the various embodiments is intended to be illustrative of the specific embodiments of the invention. The directions used in the present invention, such as "upper", "lower", "front", "post", "left", "right", etc., refer only to the direction of the additional drawing. Therefore, the directional terminology used is for the purpose of description and is not intended to limit the invention. Referring to FIG. 2A to FIG. 2C, the backlight module 2A of the embodiment includes a back frame 210, a light guide plate 220, a light emitting unit 23A, and a reflective sheet 240. The back frame 210 has a bottom plate 212, at least one first side plate 214 and at least one first side plate 216, wherein the first side plate 2M and the second side plate 216 are respectively connected to the bottom plate 212. The light guide plate 220 is disposed in the back frame 210 and has a light exit surface 222, a bottom surface 224 opposite to the light exit surface, at least one light incident side surface 226, and at least one side surface 228 (shown in FIG. 2B). The bottom surface 224 faces the bottom plate 212' between the light exit surface 222 and the bottom plate 212. At least one light incident side 226 contacts the light exit surface 222 and the bottom surface 224 and faces the first side panel 214. The side surface 228 is in contact with the light exit surface 222, the bottom surface 224, and the light incident side surface 226, and faces the second side plate 216. At least one light emitting unit 230 is detachably disposed between the light incident side surface 226 and the first side plate 214, and the light emitting unit 9 200900795 PT947 24219twf.doc/n 230 respectively faces the light incident side surface 226 and is adapted to emit light toward the light incident side surface 226. The light guide plate 220 is adapted to guide the light emitted by the light emitting unit 23A to the light exit surface 222 to form a surface light source. In the present embodiment, the light emitting unit 23A may include at least one cold cathode fluorescent lamp tube 232. However, in other embodiments, the light emitting unit 230 may also include at least one light emitting diode or other suitable light emitting element. Further, the light-emitting unit 23A may further include a lamp cover 234 for fixing the cold cathode fluorescent lamp tube 232. The reflection sheet 240 has a main reflection portion 242 and a structural reinforcement portion 244. The main reflection portion 242 is disposed between the bottom surface 224 of the light guide plate 22 and the bottom plate 212 to reflect the light emitted from the light-emitting unit 23A to the light-emitting surface 222. The structural reinforcing portion 244 is connected to the main reflecting portion 242' and attached to the side surface 228 of the light guide plate 220. In particular, the structural reinforcement portion 244 can be attached to the side 228 of the light guide plate 220 by a double-sided tape, an adhesive, or in other suitable manner. The reflection sheet 240 may be integrally formed, that is, the main reflection portion 242 and the structural reinforcement portion 244 are integrally formed and formed of the same sheet. Further, the structural reinforcing portion 244 is located at a corner of the main reflecting portion 242. The boundary between the structural reinforcing portion 244 and the main reflecting portion 242 may be a pleat line 246 (as shown in FIG. 2B), and the width wi of the structural reinforcing portion 244 in a direction parallel to the weight line 246 may be smaller than that of the main reflecting portion 242. One half of the width W2 (shown in Fig. 2C) in the direction parallel to the pleat line 246. Further, the height H1 of the structural reinforcing portion 244 in the direction perpendicular to the line 246 may be substantially equal to the distance H2 from the light exiting surface 222 to the bottom surface 224 of the light guide plate 220. The side 228 of the light guide plate 220 may face the second side plate 216. A sliding slot s' may be formed between the light-incident side 226 and the first side plate 214, and the back frame 210 10 200900795 PT947 24219 twf.doc/n forms a notch 218 ′ between the first side plate 214 and the second side plate 216, and The light-emitting unit 230 is adapted to be in the direction D (ie, the direction perpendicular to the plane of FIG. 2A) of FIG. 2B and is placed in the chute S' or self-sliding via the notch 218. Slot S, taken out. In this embodiment, the backlight module 200 further includes an optical film 250 disposed on the light emitting surface 222. Optical film 250 can include a diffusion sheet, a brightness enhancement sheet, other suitable optical film, or a combination of these films. The backlight module 200 can further include a front frame 260 disposed on the first side plate 214 and extending to the edge of the light guide plate 220. The front frame 260 is, for example, a frame formed by a plastic frame or other suitable material. In the backlight module 200 of the embodiment, the reflective sheet 240 has a structural reinforcing portion 244 attached to the side surface 228 of the light guide plate 220, which can reduce the portion of the reflective sheet 240 adjacent to the light incident side surface 226 of the light guide plate 220 toward the bottom plate 212. The degree of bending further reduces the chance of the light-emitting unit 230 interfering with the reflective sheet 240 when placed in the chute S. Therefore, when the light-emitting unit το 230 of the backlight module 2 fails, the light-emitting unit 230 is easily replaced or repaired and re-inserted, making maintenance easier. In addition, in the present embodiment, the degree of bending of the reflective sheet 240 toward the bottom plate 212 can be effectively suppressed, so that the light emitted by the light emitting unit 230 is not projected on the portion of the reflective sheet that is bent toward the bottom plate as in the prior art. The light emitting surface generates a bright line, so the backlight module 200 of the embodiment can provide a surface light source with uniform brightness. Furthermore, the structural reinforcement portion 244 may have a function of reflecting the light transmitted to the side surface 228 of the light guide plate 22 to the light exit surface 222. It should be noted that the present invention does not limit the width 11 200900795 PT947 24219 twf.doc/n degree W1 of the structural reinforcement portion 244 is less than one half of the width W2 of the main reflection portion 242, and does not limit the height H1 of the structural reinforcement portion 244 to be equal to the light guide plate. The distance H2 from the light exit surface 222 of the 220 to the bottom surface 224. In other embodiments, the width wi may also be equal to W2 or greater than one-half of the width W2. The height H1 may also be less than the distance H2' and still achieve the effect of suppressing the portion of the reflective sheet 240 adjacent to the light-incident side 226 from bending toward the bottom plate 212. Further, the present invention does not limit the number of the light emitting unit 230, the first side plate 214, and the p light incident side 226 to one. In an embodiment, the backlight module may include two light-emitting units, wherein the light guide plate may have opposite light-incident side surfaces, and the light-emitting units are respectively disposed on opposite sides of the light guide plate, respectively facing the light-incident side surfaces. And adapted to emit light toward the respective light incident sides, respectively. Further, the number of the first side plates may be two, and each of the light emitting units is disposed between one of the light incident sides and one of the first side plates. The present invention also does not limit the number of structural reinforcing portions of the reflective sheet. Referring to FIG. 3A, in another embodiment, the reflective sheet 240a may have f-two structural reinforcing portions 244' respectively located at adjacent corners of the main reflecting portion 242, and k such a reflective sheet 240a may be applied to have two light emitting units. In the backlight module. Referring to FIG. 3B, in another embodiment, the two structure reinforcing portions 244 of the reflection sheet 24A may be respectively located at opposite corners of the main reflection portion 242. Referring to FIG. 3C, in still another embodiment, the reflective sheet 240c may have four structural reinforcing portions 244 located at four corners of the main reflecting portion 242, respectively. In the backlight module of the embodiment of the present invention, the reflective sheet has a structural reinforcing portion attached to the side surface of the light guide plate, which can reduce the portion of the reflective sheet adjacent to the light incident side of the light guide plate to be bent toward the bottom plate. The degree, and thus the drop 12 200900795 PT947 24219twf.doc/n The opportunity for the low-lighting unit to interfere with the reflective sheet when placed in the chute. Therefore, when the light-emitting unit is turned off, the light-emitting unit is easily replaced or repaired and re-inserted, making maintenance easier. In addition, since the degree to which the reflection sheet is bent toward the bottom plate can be effectively suppressed, the light emitted from the light-emitting unit is not projected on a portion where the reflection sheet is bent toward the bottom plate as in the prior art, and a bright line is generated on the light-emitting surface, so the present invention The backlight module of the embodiment can provide a surface light source with uniform brightness. Furthermore, the structural reinforcing portion may have a function of reflecting light transmitted to the side surface of the light guide plate to the light emitting surface. Although the present invention has been disclosed above in the preferred embodiment, it is not intended to limit the present invention, and any related art. Those skilled in the art will be able to make some modifications and refinements without departing from the spirit and scope of the invention, and the scope of the invention is defined by the scope of the appended claims. The invention is not intended to limit the scope of the invention, and the scope of the invention is not intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a partial cross-sectional view of a conventional side-lit backlight module. Figure 2A is a partial cross-sectional view of a backlight module in accordance with an embodiment of the present invention. Figure 2B is a view of Figure 2A. FIG. 2C is a perspective view of the reflective sheet of FIG. 2A. FIG. 3A is a reflective sheet of a backlight module according to another embodiment of the present invention. 3B is a perspective view of a reflective sheet of a backlight module according to still another embodiment of the present invention. FIG. 3C is a perspective view of a reflective sheet of a backlight module according to still another embodiment of the present invention. Description: 100: side-input backlight module 110, 210: back frame 112, 212: bottom plate 114: side plates 120, 220: light guide plates 122, 222: light-emitting surface 124, 224: bottom surface 126, 226: light-incident side 130: cold cathode fluorescent tube group 140, 240, 240a, 240b, 240c: reflective sheet 150: plastic frame 152: top 200: backlight module 214: first side plate 216: second side plate 218: notch 228: side 230 : Light-emitting unit 232 : Cold cathode fluorescent lamp 14 200900795 PT947 24219twf.doc/n 234 : Lamp cover 242 : Main reflection portion 244 : Structure reinforcing portion 246 : Pleated line 250 : Optical film 260 : Front frame A : Area D : Direction G: Clearance HI: Height H2: Distance S, S': Chute Wl, W2: Width