200912470 九、發明說明 【發明所屬之技術領域】 本發明主要是關於大型液晶顯示器等所使用之直下型 背光。 【先前技術】 作爲液晶顯示器等所使用之光源，是以冷陰極螢光燈 或外部電極螢光等之直徑小之線狀光源爲主流。但是，近 年來’開發有使用大直徑之熱陰極螢光燈的背光。其理由 是熱陰極螢光燈之光量大於冷陰極螢光燈或外部電極螢光 燈之光量，故可以刪減燈管數之故。使用熱陰極螢光燈之 背光記載於日本特開平8 - 1 73 97號公報（以下專利文獻1 )、日本特開平9- 146094號公報（以下稱爲專利文獻2 )、日本特開平6-67 1 76號公報（以下稱爲專利文獻3 ) 〇 在使用如此之熱陰極螢光燈之背光中，因如上述般自 燈所取得之光量大，故可知在燈正上方之發光面容易產生 亮部，在燈間之發光面容易產生暗部。因此，爲了緩和燈 間之暗部，通常設計縮小相鄰燈的間距。 但是，確認出當縮小相鄰燈之間距時’發光面之亮度 效率爲下降。經本發明者硏究之結果，判明該發光面之亮 度效率下降爲所釋放出之光背燈本身吸收而產生損失。再 者，明白其光吸收所產生之亮度效率下降於燈之直徑爲 6.0mm以上之時，更造成問題。 -5- 200912470 〔專利文獻〕 曰本特開平8-17397號公報 〔專利文獻2〕 日本特開平9 - 1 4 6 0 9 4號公報 〔專利文獻3〕 日本特開6-67 1 76號公報 【發明內容】 本發明之目的在於提供使用直徑大之螢光燈，發光面 之亮度效率高之直下型背光。 爲了達成上述目的，本發明之直下型背光具備具有有 底開口之框體；被多數配置在上述框體內部之直徑R爲 6 · 0mm以上之螢光燈；和配置在上述框體之開口部之光學 構件，將相鄰之螢光燈之間距設爲P ( mm )之時，則滿 足P2 3.5R之關係。 【實施方式】 以下，針對本發明之實施例之直下型背光參照圖面予 以說明。第1圖爲第1實施例之直下型背光之斜視圖，第 2圖爲沿著第1圖之直下型背光之A-A線的剖面圖。 本實施形態之直下型背光之框體是以前框架1 a和後 框架1 b所構成。作爲其材料，可以使用鋁等之金屬或聚 碳酸酯等之白色塑膠。於其框架la形成有成爲背光之發 光面之出光部lal’以全體而言形成框體之蓋體。後框架 -6 - 200912470 1 b爲具有底部1 b 1、側部1 b2及開口部1 b3之有底開口形 狀之框體。在其底部1 b 1及側部1 b2之內側形成有具有高 反射性之反射薄片。 在後框架lb之內部，以各個之管軸幾乎平行之方式 配置多數根直管型之螢光燈2。螢光燈2爲第3圖所示之 熱陰極鱼光燈。其谷益是由軟質玻璃所構成之直徑R爲 6.0〜20.0mm之玻璃管21所構成。玻璃管21是由圓筒部 2 1 a和形成在其兩端之照明莖部2丨b所構成。在玻璃管2 1 之內部封入有水銀或稀有氣體以作爲放電媒體。稀有氣體 可以使用單體或混合氬、氙、氖等。在圓筒部21a之內周 面塗佈有螢光體22。在照明莖部21b於螢光燈2之內外 方向封入有導入線23a、23b。一般而言，導入線23a、 2 3 b各以一對導電線所構成。位於玻璃管2 1內之導入線 23a、23b之前端連接有由螺旋狀之鎢線所構成之燈絲24a 、24b。燈絲24a、24b是導入線23a、24b間之略中央附 近又形成螺旋狀，在該部份塗佈以（BaO、CaO、SrO )爲 主成分之熱電子放射物質（射極）。並且，燈絲24a、 24b之連接是藉由彎折導入線23a、23b之前端，並夾緊 燈絲2 4 a、2 4 b之兩端而執行。此時，夾緊燈絲2 4 a、2 4 b 之導入線23a、23b因一部份具有平坦面之剖面爲略半橢 圓形狀，故藉由夾緊所產生之連接強度高。如此之形狀可 以藉由平坦壓碎剖面爲圓形之導電線並且其平坦面中之導 入線23 a、23b之直徑相對於於加工前之直徑以30〜90% 爲佳。 -7- 200912470 在第1圖中，於背框架lb之開口部lb3平行配置有 當作光學構件之擴散板3。擴散板3以其透過率爲50 %〜 85%爲佳。其理由是可以降低發光不均，並且不會使效率 過於下降之故， 在此，在本實施例中，是以抑制螢光燈2之配置上， 在發光面所產生之條紋狀之亮度不均爲目的’採用縮小螢 光燈2之正上方和相鄰燈間之中央附近之發光面亮度差之 手段。 第1手段爲多數螢光燈2之配置方法。多數螢光燈2 被配置成將燈之直徑R ( mm )和相鄰燈之間距設爲P ( mm)之時的關係滿足P23.5R。再者，將後框架1B之底 部lbl (反射面）和螢光燈2之距離設爲LI ( mm)之關 係則爲LI 3 0.2R。藉由如此之配置方法，即使使用直徑 R爲6.0mm以上之大直徑燈，亦可以減少因光射入至燈而 產生之損失，並可以提高背光之亮度效率。 第2手段爲採用沿著螢光燈2之燈軸施予網點印刷之 擴散板3。該擴散板3是以隨著朝向燈間中央漸漸縮小網 點之大小之方式而形成，並藉由從燈正上方至燈間調節輸 出光量，可以更抑制亮度不均。 並且，即在擴散板3之上方又配設光學薄片亦可。作 爲光學薄片配合目的可以使用使用一片或多數片擴散薄片 、稜鏡片、偏光薄片等。 以下，表示本發明之實施例所涉及之背光之具體規格 -8- 200912470 (實施例1 ) 背光：尺寸二32吋（約760mmx約440mm)，有效發 光區域= 700mmx400mm，內部厚度D = 20.0mm 螢光燈2:熱陰極螢光燈、內徑= 6_9mm，直徑R = 8.0mm，燈電流=70mA，使用數量=8根，燈間距p = 50.0mm，螢光燈2和後框架lb之底部lbl之距離Ll = 2.0mm，與擴散板3之距離L2=10_0mm，與側部lb2之 距離 L3 = 20.0mm。 擴散板3 :透過率=60%，位於螢光燈2之正上方之 部份施予網點印刷 光學薄片：擴散薄片 第4圖爲表示針對直徑R不同之螢光燈，使燈電力予 以變化之時之相對燈效率之變化之曲線圖。在此，直徑R =3.0mm爲冷陰極營光燈，直徑R=6.0〜15.5 mm爲熱陰 極螢光。再者，相對燈效率是以6.0W點燈直徑R = 3.0mm之冷陰極螢光燈單體之時之燈效率（im/W)爲基 準者。 由該曲線圖可知，相對燈效率雖然在燈之直徑R = 6.0mm、8_0mm變化不大，但有當成爲大於此之直徑時， 相對燈效率變高之傾向。在R = 1 0. 〇mm時大約20%，在 R=15.5mm時大約爲30%，兩者皆提升。再者，當燈之直 徑R變大時’可投入之電力也變大。即是，自每一根燈所 取得之光量變大，比起直徑R= 3.0mm之燈，可以取得在 -9- 200912470 R=6.0mm之燈時大約兩倍，在R=8.0mm時大約2 ，在R=10.0mm時大約3_0倍，在R=15.5mm大約4 光量。因爲，若使用直徑R之大燈時，可以邏輯上可 減燈數量，並實現亮度之背光。 但是，由發明者之試驗結果，可知於使用直徑R 螢光燈2之時，則有背光之亮度效率顯著較低之情形 原因考察出以下之情形。 自螢光燈2所釋放出之光可以大致分別出第5圖 般，在底部1 b 1 (反射面）所反射之光X，和在擴散 所反射之光Y，不在該些反射之光Z的3種類。並且 X可以分爲在底部1 b 1反射後，透過擴散板3之光 射入至螢光燈2本身之光X2，射入至其他螢光燈2 X3。並且，光Z可以分爲直接到達至擴散板3並透 光Z 1，直接射入至其他螢光燈2之光Z2。 光X〜Z中，光XI、Yl、Z1是當作背光之光被 。另外，射入至螢光燈2本身或其他螢光燈2之光 X3 ' Y2、Y3、Z2爲損失。因此，該些之光以極力減 佳。光X2、X3、Y2、Y3、Z2因射入至螢光燈 2本 其他螢光燈2之光，故最影響至燈之直徑R。即是， 陰極螢光燈中，光射入至燈之確率低，故光X2、X3 、Y3、Z2較少，但是在熱陰極螢光燈中，光X2、 Y2、Y3、Z2變多。發明者之試驗之結果，可知當螢 2之直徑R爲6.0mm以上之時，光X2、X3、Y2、Y3 變多，成爲使效率下降之原因。 .5倍 倍之 以刪 大之 。其 所示 板3 ，光 XI - 之光 過之 利用 X2、 少爲 身或 在冷 、Y2 X3、 光燈 、Z2 -10- 200912470 使用如此大直徑之螢光燈2而減少光X2、Χ3、Υ2、 Υ 3、Ζ 2 ’燈間距Ρ、螢光燈2和底部1 b 1之距離L1、螢 光燈2和擴散板3之距離L 2爲重要。燈間距p因與光χ 3 、Y3及Z2之產生有密切關係，距離L1與光X2之產生 有密切關係’距離L 2與光Υ 2之產生有密切關係。在此 ’執行使每螢光燈2之直徑R變化燈間距ρ等之試驗。 第6圖爲表示針對直徑R不同之螢光燈，使燈間距ρ 變化之時之相對板面亮度效率之變化之曲線圖。在該試驗 中，執行配置與以燈間距Ρ除3 2吋背光之框架內部尺寸 之4 0 0 m m所取得之數値相等之數量的燈。即是，當燈間 距選定成40mm之時則配置10根，當選定成50mm之時 則配置8根，當選定成8 0mm之時則配置5根之燈而執行 試驗。在此，相對面亮度效率是在將直徑R=3.0mm之冷 陰極螢光燈配置成燈間距P = 20mm，燈數量爲20根之32 吋背光中，以6.0W點燈各燈之時所取得之板面亮度效率 (cd/W )爲基準者。 由該曲線圖可知，在所有燈中，越增大燈間距P，越 提升相對板面亮度效率。但是，也可知在直徑R大於 6.0mm之燈中，也有藉由燈間距P使得相對板面亮度效率 則低於1 0 0 %之情形。相對板面亮度效率低於1 〇 〇 %，是指 在亮度效率低之狀態下使用之意。因此，爲了實現亮度高 之背光，必須至少以相對板面亮度效率超過1 〇〇%之條件 來使用。因此，藉由第6圖’直徑R=6.0mm之時’必須 將燈間距P設爲約23.0mm以上，於R= 8.0mm之時必須 -11 - 200912470 設爲約2 8 0 m m以上’於R = 1 〇 . 〇 m m之時必須設爲約 37.0mm以上，於R= 15.5mm之時必須設爲約55.〇mm以 上。若該以滿足P2 3.5R之方式配置燈即可。並且，當滿 足P24.5R時又更提升亮度效率，故爲佳。但是，當對直 徑R過於增大燈間距P時，背光之亮度下降，並且亮度 不均變大，故以13. OR爲上限爲佳。 再者，螢光燈2和底部lbl之距離L1以L120.2R爲 佳，又以設計成滿足L120.4R爲更佳。依此，因反射光 射入至燈之比率變少，故可以更提升亮度效率。但是，在 其關係式中，當左邊之距離L1過大時，因內部厚度D變 大，產生背光之厚度增加等之弊害，故以在LI S 1.OR之 範圍內設計爲佳。 (實施例2 ) 在該實施例中，雖然基本上與實施例1爲相同構成， 但是使用通常之擴散板，並且將螢光燈2和擴散板3之距 離2設計成滿足L22 0.45P-0.5R。具體而言，對於燈直徑 8.0mm，燈間距P = 50mm，距離L2爲1 9_0mm (內部 厚度D= 29.0mm)。驚訝的是若藉由該設計，可知即使不 用使用施予網點印刷等之特殊加工之擴散板，亦與實施例 1相同，可以抑制亮度不均。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct type backlight used in a large liquid crystal display or the like. [Prior Art] As a light source used for a liquid crystal display or the like, a linear light source having a small diameter such as a cold cathode fluorescent lamp or an external electrode fluorescent light is mainly used. However, in recent years, backlights using large-diameter hot cathode fluorescent lamps have been developed. The reason is that the amount of light of the hot cathode fluorescent lamp is larger than that of the cold cathode fluorescent lamp or the external electrode fluorescent lamp, so that the number of lamps can be reduced. A backlight of a hot-cathode fluorescent lamp is described in Japanese Laid-Open Patent Publication No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei 9-146094 (hereinafter referred to as Patent Document 2) and Japanese Patent Laid-Open No. Hei 6-67 Japanese Patent Publication No. 1 76 (hereinafter referred to as Patent Document 3). In the backlight using such a hot cathode fluorescent lamp, since the amount of light obtained from the lamp is large as described above, it is understood that the light-emitting surface directly above the lamp is likely to be bright. In the part, the light-emitting surface between the lamps is likely to generate a dark portion. Therefore, in order to alleviate the dark portion of the lamp, it is usually designed to reduce the spacing of adjacent lamps. However, it was confirmed that the luminance efficiency of the light-emitting surface was lowered when the distance between adjacent lamps was reduced. As a result of the study by the inventors, it was found that the luminance efficiency of the light-emitting surface was reduced to be absorbed by the emitted light backlight itself, resulting in loss. Further, it is understood that the luminance efficiency caused by the light absorption is lowered when the diameter of the lamp is 6.0 mm or more, which causes a problem. Japanese Patent Laid-Open Publication No. Hei 6-67-169 (Patent Document 2) Japanese Patent Laid-Open Publication No. Hei No. Hei. SUMMARY OF THE INVENTION An object of the present invention is to provide a direct-type backlight using a fluorescent lamp having a large diameter and having a high luminous efficiency of a light-emitting surface. In order to achieve the above object, a direct type backlight of the present invention includes a frame having a bottomed opening, a fluorescent lamp having a plurality of diameters R of 6 mm or more disposed inside the frame, and an opening disposed in the frame In the optical member, when the distance between adjacent fluorescent lamps is P (mm), the relationship of P2 3.5R is satisfied. [Embodiment] Hereinafter, a direct type backlight reference plane of an embodiment of the present invention will be described. Fig. 1 is a perspective view showing a direct type backlight of the first embodiment, and Fig. 2 is a cross-sectional view taken along line A-A of the direct type backlight of Fig. 1. The frame of the direct type backlight of this embodiment is constituted by the front frame 1 a and the rear frame 1 b. As the material thereof, a metal such as aluminum or a white plastic such as polycarbonate can be used. In the frame la, a light-emitting portion 1a' which is a light-emitting surface of the backlight is formed to cover the entire body. The rear frame -6 - 200912470 1 b is a frame having a bottomed opening shape having a bottom portion 1 b 1 , a side portion 1 b2 and an opening portion 1 b3. A reflective sheet having high reflectivity is formed on the inner side of the bottom portion 1b1 and the side portion 1b2. Inside the rear frame lb, a plurality of straight tube type fluorescent lamps 2 are arranged in such a manner that the respective tube axes are almost parallel. The fluorescent lamp 2 is a hot cathode fishlight shown in Fig. 3. The gluten is composed of a glass tube 21 made of soft glass and having a diameter R of 6.0 to 20.0 mm. The glass tube 21 is composed of a cylindrical portion 21a and an illumination stem portion 2'b formed at both ends thereof. Mercury or a rare gas is sealed inside the glass tube 2 1 as a discharge medium. The rare gas may be a monomer or a mixture of argon, helium, neon or the like. The phosphor 22 is coated on the inner circumference of the cylindrical portion 21a. The introduction stems 23a and 23b are sealed in the inside and outside of the fluorescent lamp 2 in the illumination stem portion 21b. In general, the lead-in wires 23a, 23b are each formed by a pair of conductive wires. Filaments 24a and 24b composed of a spiral tungsten wire are connected to the front ends of the lead wires 23a and 23b located in the glass tube 2 1. The filaments 24a and 24b are formed in a spiral shape near the center of the introduction lines 23a and 24b, and a hot electron emitting material (emitter) mainly composed of (BaO, CaO, SrO) is applied to the filaments 24a and 24b. Further, the connection of the filaments 24a, 24b is performed by bending the leading ends of the lead wires 23a, 23b and clamping the ends of the filaments 24a, 2bb. At this time, since the lead wires 23a, 23b of the clamp filaments 2 4 a, 2 4 b have a slightly semi-elliptical shape in a portion having a flat surface, the joint strength by clamping is high. Such a shape can be made by flatly crushing a circular conductive line and the diameter of the lead wires 23a, 23b in the flat surface is preferably 30 to 90% with respect to the diameter before processing. -7- 200912470 In Fig. 1, a diffusing plate 3 as an optical member is disposed in parallel with the opening portion 1b3 of the back frame 1b. The diffusion plate 3 preferably has a transmittance of 50% to 85%. The reason for this is that the unevenness of the light emission can be reduced, and the efficiency is not lowered too much. Here, in the present embodiment, the brightness of the stripe-like light generated on the light-emitting surface is suppressed by suppressing the arrangement of the fluorescent lamp 2. For the purpose of 'reducing the brightness difference of the light-emitting surface near the center of the fluorescent lamp 2 and the vicinity of the adjacent lamp. The first means is a method of arranging a plurality of fluorescent lamps 2. Most of the fluorescent lamps 2 are arranged such that the relationship between the diameter R (mm) of the lamp and the distance between adjacent lamps is P (mm) satisfies P23.5R. Further, the relationship between the bottom portion lbl (reflecting surface) of the rear frame 1B and the fluorescent lamp 2 as LI (mm) is LI 3 0.2R. According to such a configuration method, even if a large-diameter lamp having a diameter R of 6.0 mm or more is used, the loss due to light incident on the lamp can be reduced, and the luminance efficiency of the backlight can be improved. The second means is to apply the diffusion plate 3 which is printed on the dot along the lamp shaft of the fluorescent lamp 2. The diffusing plate 3 is formed so as to gradually decrease the size of the halftone dots toward the center between the lamps, and by adjusting the amount of output light from directly above the lamp to between the lamps, unevenness in brightness can be further suppressed. Further, an optical sheet may be disposed above the diffusion plate 3. One or a plurality of diffusion sheets, ruthenium sheets, polarizing sheets, and the like can be used as the optical sheet for the purpose of blending. Hereinafter, the specific specifications of the backlight according to the embodiment of the present invention are shown in the specification-8-200912470 (Embodiment 1). Backlight: size 32 吋 (about 760 mm x about 440 mm), effective light-emitting area = 700 mm x 400 mm, internal thickness D = 20.0 mm Light 2: hot cathode fluorescent lamp, inner diameter = 6_9mm, diameter R = 8.0mm, lamp current = 70mA, number of use = 8, lamp spacing p = 50.0mm, fluorescent lamp 2 and bottom of the rear frame lb lbl The distance Ll = 2.0 mm, the distance from the diffusion plate 3 L2 = 10_0 mm, and the distance from the side portion lb2 L3 = 20.0 mm. Diffuser 3: Transmittance = 60%, the portion directly above the fluorescent lamp 2 is applied to the dot printing optical sheet: the diffusion sheet is shown in Fig. 4 for the fluorescent lamp having a different diameter R to change the lamp power. A graph of the relative change in lamp efficiency. Here, the diameter R = 3.0 mm is a cold cathode camping lamp, and the diameter R = 6.0 to 15.5 mm is hot cathode fluorescent. Further, the relative lamp efficiency is based on the lamp efficiency (im/W) of the cold cathode fluorescent lamp unit of 6.0 W lighting diameter R = 3.0 mm. As can be seen from the graph, the relative lamp efficiency does not vary greatly depending on the diameter of the lamp R = 6.0 mm and 8_0 mm. However, when the diameter is larger than this, the relative lamp efficiency tends to be high. It is about 20% at R = 1 0. 〇mm and about 30% at R = 15.5mm, both of which increase. Further, when the diameter R of the lamp becomes large, the power that can be input also becomes large. That is, the amount of light obtained from each lamp becomes larger than that of a lamp having a diameter of R = 3.0 mm, which is approximately twice as large as that of a lamp of -9-200912470 R = 6.0 mm, and approximately at R = 8.0 mm. 2, about 3_0 times when R=10.0mm, about 4 light quantity at R=15.5mm. Because, if a headlight with a diameter of R is used, it is possible to logically reduce the number of lamps and achieve backlighting of brightness. However, as a result of the test by the inventors, it has been found that when the diameter R fluorescent lamp 2 is used, the luminance efficiency of the backlight is remarkably low. The following is considered. The light emitted from the fluorescent lamp 2 can be substantially as shown in Fig. 5, the light X reflected at the bottom 1 b 1 (reflecting surface), and the light Y reflected in the diffusion, not in the reflected light Z 3 types. Further, X can be divided into light X2 which is incident on the bottom portion 1 b 1 and which is incident on the fluorescent lamp 2 itself through the light of the diffusing plate 3, and is incident on the other fluorescent lamp 2 X3. Further, the light Z can be divided into the light Z2 which directly reaches the diffusing plate 3 and transmits the light Z1 directly into the other fluorescent lamp 2. In the light X to Z, the lights XI, Y1, and Z1 are light as a backlight. Further, the light X3 'Y2, Y3, Z2 incident on the fluorescent lamp 2 itself or other fluorescent lamps 2 is a loss. Therefore, the light is greatly reduced. The light X2, X3, Y2, Y3, and Z2 are incident on the fluorescent lamp 2, and the light of the other fluorescent lamp 2 is most affected by the diameter R of the lamp. That is, in the cathode fluorescent lamp, since the light incident rate to the lamp is low, the light X2, X3, Y3, and Z2 are small, but in the hot cathode fluorescent lamp, the light X2, Y2, Y3, and Z2 become large. As a result of the test by the inventors, it has been found that when the diameter R of the firefly 2 is 6.0 mm or more, the amount of light X2, X3, Y2, and Y3 increases, which causes a decrease in efficiency. .5 times double to delete. The board 3, the light XI - the light is used to reduce the light X2, Χ3 by using X2, less for the body or in the cold, Y2 X3, light, Z2-10-200912470 using such a large diameter fluorescent lamp 2. Υ2, Υ3, Ζ 2 'The distance between the lamps Ρ, the distance between the fluorescent lamp 2 and the bottom 1 b 1 L1, and the distance L 2 between the fluorescent lamp 2 and the diffusing plate 3 are important. The lamp pitch p is closely related to the generation of the pupils 3, Y3, and Z2, and the distance L1 is closely related to the generation of the light X2. The distance L 2 is closely related to the generation of the pupil 2 . Here, a test is performed in which the diameter R of each of the fluorescent lamps 2 is changed by the lamp pitch ρ or the like. Fig. 6 is a graph showing changes in the luminous efficiency with respect to the panel surface when the lamp pitch ρ is changed for a fluorescent lamp having a different diameter R. In this test, a lamp having a number equal to the number 値 obtained by removing the internal dimensions of the frame of the backlight of 3 2 吋 from the lamp pitch is performed. That is, when the distance between the lamps is selected to be 40 mm, 10 pieces are arranged, when 50 mm is selected, 8 pieces are arranged, and when 8 mm is selected, 5 pieces of lamps are arranged to perform the test. Here, the relative surface brightness efficiency is such that a cold cathode fluorescent lamp having a diameter of R = 3.0 mm is arranged in a 32 吋 backlight with a lamp pitch of P = 20 mm and a number of lamps of 20, and the lamps are illuminated at 6.0 W. The board brightness efficiency (cd/W) obtained is the benchmark. As can be seen from the graph, in all the lamps, the lamp pitch P is increased, and the relative plate surface luminance efficiency is improved. However, it is also known that in a lamp having a diameter R of more than 6.0 mm, there is a case where the relative plate surface luminance efficiency is lower than 100% by the lamp pitch P. The relative brightness of the board is less than 1 〇 〇 %, which means that it is used in a state where the brightness is inefficient. Therefore, in order to achieve a high-brightness backlight, it is necessary to use at least a condition that the relative panel surface luminance efficiency exceeds 1%. Therefore, it is necessary to set the lamp pitch P to about 23.0 mm or more when the diameter R = 6.0 mm in Fig. 6, and to set it to -11 - 200912470 to about 280 mm or more when R = 8.0 mm. R = 1 〇. When 〇mm, it must be set to about 37.0mm or more, and when R=15.50mm, it must be set to about 55.〇mm or more. If the lamp is configured to meet the P2 3.5R. Also, it is better to increase the brightness efficiency when the P24.5R is satisfied. However, when the relative distance R is excessively increased by the lamp pitch P, the luminance of the backlight is lowered, and the luminance unevenness is increased, so that the upper limit of 13. OR is preferable. Further, the distance L1 between the fluorescent lamp 2 and the bottom portion lb1 is preferably L120.2R, and more preferably designed to satisfy L120.4R. Accordingly, since the ratio of the reflected light to the lamp is reduced, the brightness efficiency can be further improved. However, in the relational expression, when the distance L1 on the left side is too large, since the internal thickness D becomes large, and the thickness of the backlight is increased, etc., it is preferable to design it in the range of LI S 1.OR. (Embodiment 2) In this embodiment, although basically the same configuration as Embodiment 1, a usual diffusion plate is used, and the distance 2 between the fluorescent lamp 2 and the diffusion plate 3 is designed to satisfy L22 0.45P-0.5. R. Specifically, for a lamp diameter of 8.0 mm, a lamp pitch P = 50 mm, and a distance L2 of 1 9_0 mm (internal thickness D = 29.0 mm). Surprisingly, according to this design, it is understood that the unevenness of brightness can be suppressed as in the first embodiment without using a special processing diffusion plate such as dot printing.
並且，上述數式並不限定於燈直徑R= 8.0mm之情形 ，即使在其他直徑R之情形亦成立。第7圖爲表示在直徑 R爲6 . Omm〜1 5.5 mm之燈中抑制亮度不均之時之燈間距P -12 - 200912470 和擴散板之距離L 2之關係的曲線圖。在此，「抑制亮度 不均」是指以目視無法確認亮度不均之狀態，具體而言， 表示燈正上方和燈間之亮度差爲4 0 c d / m m 2以下之時。 由第7圖可知，即使直徑R爲6.0mm、10.〇mm、15.5mm 之時，若滿足L 2 = 0.4 5 P - 0 · 5 R時，燈正上方和燈間之亮 度差則成爲40cd/mm2。因此，即使在直徑R爲6.0mm以 上之時，設計成滿足L2 2 0.45P-0.5R，依此可以抑制亮度 不均。並且，當 L2 2 0.50P-0.5R時，因亮度差成爲 30cd/mm2以下故爲佳。但是，當左邊之距離L2過大時， 因產生背光之內部厚度D變大等之弊害，故以設計成L2 S1.0P-0.5R 爲佳。 並且，在本實施例中，即使在擴散板3上又配置稜鏡 片亦可。此時若滿足L22 0.35P-0.5R時，則取得與實施 例2相等之亮度不均抑制效果。因此，可以同時實現薄型 化。 因此，在第1實施例中，在將直徑R爲6.0 mm以上 之螢光燈2多數配置在後框架lb內部之直下型背光中， 藉由以相鄰之燈之間距P ( m m )滿足P 2 3.5 R之方式配 置螢光燈2，可以實現發光面中之亮度效率高之直下型背 光。此時，當將後框架1 b之底部1 b 1和螢光燈2之距離 設爲L 1 ( m m )之時，則以構成滿足L 1 2 0.2 R之關係， 更具效果。 再者，藉由組合以沿著螢光燈2之方式施予網點印刷 之擴散板3，則可以解除因上述構成容易產生之明暗的條 -13- 200912470 紋’可以實現亮度不均少的直下型背光。另外 對螢光燈2或擴散板3施予特別加工，於將螢 散板3之距離設爲L2(mm)時，藉由設計成 0.45P-0.5R時之關係，可以抑制明暗之條紋， 不均，實現低價之直下型背光。並且，本發明 不限定於上述，即使例如變更成下述般亦可。 螢光燈2即使爲直徑R爲6.0 mm以上之 燈或外面電極螢光燈等亦可。再者，其形狀並 線狀，可以使用 U字型、C字型、W字型等 。但是，彎曲型之螢光燈時之燈間距P針對相 之相鄰直線狀之管部間亦可適用。 作爲用以縮小發光面之亮度差之加工部， 、反射或減少射出至燈之正上方之光的膜或成 螢光燈2或/及擴散板3者亦可。在實施例2中 散板3上又配置稜鏡片亦可。此時，若滿足L2 2 時，則取得與實施例2同等之亮度不均抑制效 亦同時可以實現薄型化。 【圖式簡單說明】 第1圖爲本發明之第1實施例之直下型背 視圖。 第2圖爲沿著A-A線切斷第1圖之直下 面圖。 第3圖爲表示熱陰極螢光燈之構造之縱剖_ ，即使不用 光燈2和擴 :滿足L2 2 並減少亮度 之實施例並 冷陰極螢光 不限定於直 之彎曲光源 同彎曲型燈 即使將遮蔽 型，設置在 ，即使在擴 ：0.35P-0.5R 果。因此， 光之分解斜 型背光之剖 面圖。 -14- 200912470 第4圖爲針對直徑R之不同螢光燈，使燈電力變化之 時之相對燈效率之曲線圖。 第5圖爲用以針對使用直徑R大之螢光燈之時之光的 光路徑予以說明之圖式。 第6圖爲表示針對直徑R之不同螢光燈，使燈間距P 變化之時之相對板面亮度效率變化之曲線圖。 第7圖爲表示在直徑R爲6.0〇1111〜15_5111111之燈中， 抑制亮度不均之時之燈間距P和擴散板之距離L2之關係 之曲線圖。 【主要元件符號說明】 1 a :前框架 1 a 1 :出光部 1 b :後框架 1 b 1 :底部 lb2 :側部 1 b 3 :開口部 2 :螢光燈 3 :擴散板 21 :玻璃管 2 1 a :圓筒部 2 1 b :照明莖部 22 :螢光體 2 3 a :導入線 -15- 200912470 2 3 b :導入線 2 4 a :燈絲 2 4 b :燈絲Further, the above formula is not limited to the case where the lamp diameter R = 8.0 mm, and is satisfied even in the case of other diameters R. Fig. 7 is a graph showing the relationship between the lamp pitch P -12 - 200912470 and the distance L 2 of the diffusion plate when the luminance unevenness is suppressed in a lamp having a diameter R of 6. 0 mm to 1 5.5 mm. Here, "suppressing unevenness in brightness" means that the brightness unevenness cannot be confirmed by visual observation, and specifically, when the difference in luminance between the upper side of the lamp and the lamp is 4 0 cd / m m 2 or less. As can be seen from Fig. 7, even when the diameter R is 6.0 mm, 10. 〇 mm, or 15.5 mm, if L 2 = 0.4 5 P - 0 · 5 R is satisfied, the difference in brightness between the lamp directly above and between the lamps becomes 40 cd. /mm2. Therefore, even when the diameter R is 6.0 mm or more, it is designed to satisfy L2 2 0.45P - 0.5R, whereby unevenness in brightness can be suppressed. Further, when L2 2 is 0.50P-0.5R, it is preferable that the luminance difference is 30 cd/mm2 or less. However, when the distance L2 on the left side is too large, it is preferable to design L2 S1.0P-0.5R because of the disadvantage that the internal thickness D of the backlight becomes large. Further, in the present embodiment, even if a sheet is placed on the diffusion plate 3, it may be disposed. In this case, when L22 0.35P-0.5R is satisfied, the brightness unevenness suppression effect equivalent to that of the second embodiment is obtained. Therefore, it is possible to achieve thinning at the same time. Therefore, in the first embodiment, in the direct type backlight in which the fluorescent lamp 2 having a diameter R of 6.0 mm or more is disposed in the direct type backlight of the rear frame lb, P (mm) is satisfied by the distance between adjacent lamps. 2 3.5 R The fluorescent lamp 2 is configured to achieve a direct-lit backlight with high brightness efficiency in the light-emitting surface. At this time, when the distance between the bottom 1 b 1 of the rear frame 1 b and the fluorescent lamp 2 is set to L 1 (m m ), the relationship of satisfying the relationship of L 1 2 0.2 R is more effective. Further, by combining the diffusing plates 3 which are applied to the dot printing along the fluorescent lamp 2, it is possible to release the strips 13-200912470 which are easy to be formed by the above-described configuration, and it is possible to realize a low brightness unevenness. Type backlight. Further, the fluorescent lamp 2 or the diffusing plate 3 is specially processed. When the distance between the diffusing plates 3 is L2 (mm), the relationship between the light and dark can be suppressed by designing the relationship of 0.45P-0.5R. Uneven, low-cost direct backlighting. Further, the present invention is not limited to the above, and may be changed, for example, to the following. The fluorescent lamp 2 can be a lamp having a diameter R of 6.0 mm or more, or an external electrode fluorescent lamp. Further, the shape is linear, and a U-shape, a C-shape, a W-shape, or the like can be used. However, the pitch P of the curved fluorescent lamp can also be applied between the adjacent straight tube portions. As the processing portion for reducing the luminance difference of the light-emitting surface, the film which reflects or emits light directly above the lamp or the fluorescent lamp 2 or/and the diffusion plate 3 may be used. In the second embodiment, the slab may be disposed on the loose plate 3. In this case, when L2 2 is satisfied, the brightness unevenness suppression effect equivalent to that of the second embodiment is obtained, and the thickness can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a direct rear view of a first embodiment of the present invention. Fig. 2 is a plan view showing the lower side of Fig. 1 taken along line A-A. Fig. 3 is a longitudinal sectional view showing the structure of the hot cathode fluorescent lamp, even if the light lamp 2 and the expansion are not required: the embodiment satisfies L2 2 and reduces the brightness, and the cold cathode fluorescent light is not limited to the straight curved light source and the curved type lamp even if Set the shielding type, even if it is expanding: 0.35P-0.5R. Therefore, the light is decomposed into a cross-sectional view of the oblique backlight. -14- 200912470 Figure 4 is a graph of relative lamp efficiency for different lamp diameters for varying lamp power. Fig. 5 is a view for explaining a light path of light when a fluorescent lamp having a large diameter R is used. Fig. 6 is a graph showing the change in luminous efficiency with respect to the panel surface when the lamp pitch P is changed for the different fluorescent lamps of the diameter R. Fig. 7 is a graph showing the relationship between the lamp pitch P and the distance L2 of the diffusing plate when the luminance R is suppressed in the lamp having a diameter R of 6.0 1111 to 15_511111. [Main component symbol description] 1 a : Front frame 1 a 1 : Light exit portion 1 b : Rear frame 1 b 1 : Bottom lb2: Side portion 1 b 3 : Opening portion 2 : Fluorescent lamp 3 : Diffuser plate 21 : Glass tube 2 1 a : cylindrical portion 2 1 b : illumination stem portion 22 : phosphor 2 3 a : introduction line -15- 200912470 2 3 b : introduction line 2 4 a : filament 2 4 b : filament