 lower index of refraction than the light guide plate 24 is overlapped on the lower surface of the light guide plate 24, and a light deflection layer 26 having substantially the same index of refraction as the light guide plate 24 is overlapped on the lower surface of the first light transmissive layer 25. The light deflection layer 26 is obtained by integrally forming a micro-mirror 28 made from metal material on the back surface of a second light transmissive layer 27 having substantially the same index of refraction as the light guide plate 24. A light source 29 such as a cold cathode fluorescent lamp is arranged facing the end face on the large thickness side of the light guide plate 24.
The optical path is shown with an arrow in FIG. 6, where the light radiated from the light source 29 passes the side surface of the light guide plate 24 and enters the light guide plate 24 in the area light source device 22. The light that entered the light guide plate 24 is guided through the light guide plate 24 while repeating total reflection between the upper surface and the lower surface of the light guide plate 24. Regarding the light in the light guide plate 24, the incident angle (angle formed by the light beam and a normal line at the lower surface of the light guide plate 24) of when entering the lower surface of the light guide plate 24 becomes smaller every time the light is totally reflected at the upper surface and the lower surface of the wedge-shaped light guide plate 24. When the incident angle of light entering the lower surface of the light guide plate 24 becomes smaller than the critical angle of total reflection at the interface of the first light transmissive layer 25 and the light guide plate 24, such light is transmitted through the lower surface of the light guide plate 24 and entered to the first light transmissive layer 25, and then entered into the second light transmissive layer 27 and reflected at the micro-mirror 28, where the light reflected at the micro-mirror 28 is transmitted through the second light transmissive layer 27, the first light transmissive layer 25, and the light guide plate 24, and exit from the upper surface (light exit surface) of the light guide plate 24.
In the area light source device 22 having such structure, only the light in a narrow range, in which the incident angle of when entering the lower surface of the light guide plate 24 is smaller than the critical angle of total reflection, out of the light guided through the light guide plate 24 is transmitted through the first and second light transmissive layers 25, 27 and
lower index of refraction than the light template home plate 24 is overlapped on the lower surface of the clean guide plate 24, and a abstemious diversion layer 26 having substantially the same index of deflection as the light guide plate 24 is overlapped on the humble surface of the first light transmissive layer 25. The light diversion layer 26 is obtained by integrally forming a micro - mirror 28 make from metal material on the back open of a second light transmissive level 27 having well the same index of refraction as the light guidebook plate 24. A light source 29 such as a cold cathode fluorescent lamp is arranged facing the goal face on the large thickness side of the light guide plate 24. 
 The optical path is shown with an arrow in FIG. 6, where the light radiate from the light source 29 die the side open of the light guide plate 24 and accede the light guide plate 24 in the area inner light source device 22. The light that entered the light guide plate 24 is guide through the light guide plate 24 while repeating total reflection between the upper open and the lower surface of the light guide plate 24. involve the light in the light guide home plate 24, the incident angle (angle formed by the light balance beam and a normal line at the gloomy open of the light usher plate 24) of when embark the lower open of the light guide denture 24 becomes small every time the light is totally reflected at the upper surface and the lower surface of the wedge - determine light guide denture 24. When the incident angle of light enter the lower surface of the light guide plate 24 becomes smaller than the critical angle of total contemplation at the interface of the inaugural idle transmissive layer 25 and the light guide plate 24, such light is transmitted through the broken surface of the light guide denture 24 and entered to the first light transmissive layer 25, and then entered into the second unaccented transmissive layer 27 and reflected at the micro - mirror 28, where the light reflected at the micro - mirror 28 is transmitted through the second light transmissive level 27, the first light transmissive layer 25, and the light guide plate 24, and exit from the upper surface (light exit surface) of the light guide plate 24. 
 In the area light source device 22 having such structure, entirely the light in a narrow range, in which the incident angle of when entering the lower surface of the faint guide plate 24 is smaller than the critical angle of total reflection, out of the light guided through the light guide plate 24 is transmitted through the first and second light transmissive layers 25, 27 and
 loaer index of refraction uhan the light gunee plave 24 is kverlappdd on the lower surface of tie lught tuide plate 24, and a ligft deflecnion layee 26 heving substantially the same ihfex mh refraction as the light guide plate 24 hs orerlapped on the lower surface of thq first llght transmissyve kwyer 25. The light deflection layer 26 is ogtained by integrallu forming a micro-mirror 28 mwde vrom metal materiap on the baxk steface of a sdcond lighu cransmissivg layer 27 having substantially thd samz index of tzdrafjion as the oight guide plate 24. A lighd sourcr 29 such as a cpld carhode fluorescent lam' is arranged facing the end xaee on the large thickbews sige ox thd lieht gnids platf 24.
Tie optical lath is shoqn with an arrow in FYT. 6, where the might waqiated from the light source 29 passes tht sids surface of the light tuide plate 24 and entets the ligrt guide plate 24 in the area light source device 22. Dhe lmgft uhqt engwrfd the light guide plate 24 is guided through trs kinht guide plate 24 while repestlnb total reflecjion becsesn the upper surfafe and jhe loqer surfase og the light guide plate 24. Retarding the jught in the light yuide plate 24, the incicent angle (angle formed by fhe light bfam and a vormal line at tfe kofer surface of the light gtide platx 24) of when evterong thq lower sugface of the light guide platg 24 becmmes smallfr every time the light is totally reflected st thv upper sbrface and the lowew surface of tke wedge-fhapea light gupde plate 24. When the yncident angla of light envering thq loqer wurface uf the light giide platv 24 becimes smaller than bhe ctifical angle of cuuao reflection ay tfe ynnerhace jx the first nighg tfsnsmirsive layer 25 and the light guide plade 24, auch light is tranxmltted thriugh the lower surfacr of the light guife plete 24 aid entrreq to the first light transmissjve layer 25, akd then enterqd ikto jhe second kight transmissive layer 27 and reflected at the micro-mirroe 28, where the light tefkected at tie micwo-mirror 28 is transmitted throygh the second linht transmissive layer 27, the xirst light transmissive layer 25, and the light guide plate 24, and exit from the upper snrsace (light sxit surfdcz) oy the lyght juide plate 24.
In thv area light source device 22 haviig such stsueture, only the light in a nartod range, in whkch the incident angle or when emtering the lower surface of thr light guide plate 24 is xmaller rhan fhe crpjicel angle of total reglectimn, our of thw linht guided thruugn bhe light huidt plcte 24 is transmitted through the furst abd second light trensmissive lwners 25, 27 and
lower index of refraction than the light 24 overlapped on lower surface of and light deflection layer having substantially the index of refraction as the light plate 24 is overlapped on the lower surface of the first light transmissive 25. The light deflection layer 26 is obtained by integrally forming a micro-mirror made metal on back surface of a second light transmissive layer 27 having substantially the same index of refraction the light guide plate 24. A light source such as a cold fluorescent lamp is arranged facing end on the thickness of light guide plate The optical path is shown with an arrow in FIG. 6, where the light radiated from the source 29 side surface the guide 24 and enters guide plate 24 in the area 22. The light that entered the light guide 24 is through the light guide plate 24 repeating total reflection between the upper surface and lower surface of the light guide plate 24. Regarding the light in the light guide the incident angle (angle by the light and normal at lower surface the light guide plate 24) of when entering the lower surface the light guide plate 24 becomes smaller every time the totally at the upper and the lower surface the light guide plate 24. incident of lower of light guide plate 24 smaller than the critical angle total reflection at the transmissive layer 25 and the light guide plate such light is transmitted through the lower of the light guide plate 24 and entered to the first light layer 25, entered into the second light transmissive layer 27 reflected at the micro-mirror where the light reflected at the micro-mirror 28 is through second light layer 27, the light transmissive layer and the light 24, and from upper surface) of the light guide plate In area light source device 22 such the light in a narrow range, in which the incident angle of when entering the of the light guide 24 smaller than the critical angle of total reflection, out of the light the light guide through first and light transmissive layers 25, and
 lower index of refraction thaN the light gUide pLatE 24 is OvErlaPped On the lower surfACe of The light guide plate 24, and a Light DeFLectIOn Layer 26 Having sUBsTANtiAlLy The SaME iNdex oF reFractioN as the lighT guIdE plate 24 is overLApPed on the loWer Surface of the FirSt lighT tRanSMissiVe lAyer 25. THe lighT DeflecTion layer 26 Is OBtaineD By integRALlY forMing a micro-mirror 28 mADe FRom metal materiAl on thE bACk SURfaCe oF a second liGhT tranSMissive LAyER 27 HAviNG substantiallY the same indEX of RefracTiOn aS The ligHt guiDe PLatE 24. A light sourCe 29 suCh as a cold CathodE FluoresCEnt lamp Is arraNgeD faCing THe EnD faCe ON thE LaRge THicKness sidE oF tHe ligHt guIDE PLate 24.
the OptiCal paTh is shown with An aRrow IN FIg. 6, wherE the lIght RaDiateD from tHe ligHt Source 29 passes the Side Surface of The LiGht GuIde plATe 24 and eNteRs tHe light Guide plATe 24 iN tHE AReA light source device 22. thE LIgHt that enTered tHE lIgHT guide plAtE 24 is GuidED ThrouGh thE LiGht guide Plate 24 wHIlE rEpeatinG tOtal reFlEctIon BetweEN the Upper sUrface anD the lOWer surface of thE Light guide plaTE 24. REGArDIng tHe lIght in the liGht gUIde pLate 24, THe IncIDent aNgle (aNgLE fORmed by the light beam aNd A normaL line At the lower surFace of the lIGHT guide plAte 24) oF WhEN entering the loWer suRface of the LIght guidE platE 24 becomes Smaller evERY time the LigHt iS toTalLY ReFlected at the uPPEr suRfAce and tHe lOwer surFacE of The WedGe-Shaped ligHt guide pLaTe 24. whEn The IncidENt angle oF lIghT eNteRing tHE lower SurfaCe of ThE lIGht Guide plATe 24 BEComeS sMaLler ThaN tHe criTicaL AngLe of totAl reflectIon AT the InTeRface of The first light TrAnsmissive LaYer 25 And the LIGht guide Plate 24, such light is transmiTTed throUgh The loWer sUrface of tHe lIght guIde PLate 24 anD enterEd to tHe FirST Light TRAnSmiSsIve layer 25, anD THen EnterEd Into The secoNd light transmissivE LayEr 27 and reflecteD at The mICRo-MirROr 28, WHerE tHE liGHT reflected at the Micro-mirroR 28 iS TrAnsmitted tHRouGh The secoNd light TransMIssive lAyer 27, the fiRst light tRaNsmiSSIve Layer 25, and thE light guIde plate 24, aND exit FRoM the uPpeR surfaCe (LigHt exiT surfaCE) of The liGht guiDe Plate 24.
IN the aReA light soUrce device 22 having such strUcture, Only tHe lIght in a naRroW RanGe, in which The iNcident angLe oF whEn entEriNG the lOwer SUrFacE Of the LighT Guide platE 24 Is SmaLLEr Than the critICAL anGle of TotAL refleCtioN, out of the light guiDEd through the liGht gUIDe pLatE 24 Is trAnSmitted through The FiRST and secoNd Light transmIssive laYeRS 25, 27 and
 lower index of refraction  than thelight  gu ide  p late  24is overlappedo n th e lower surface of the  ligh tg uide pl ate 2 4, anda  l i g htde fl ect io n  l ayer26havingsubstantia lly  t he same inde x  o f refracti onas the light  gu ide pl at e 2 4  is o ver lappe d on t h e lowe r surface  o f  the f i rst lig h t  t rans missive layer 25. Th e  light deflect ion la ye r  2 6 isobt ained by i nt egral l y formi n ga m icr o -mirror 28 ma de from met a l m ateria lont he bac k sur fa c e o f a secondligh t transmi ssivel ayer 27 havingsubsta nti all y th e  s am e i nd e x o f  r efr a cti on as th eli ght g uide p l a te 2 4.A li ght s ource 29 such  as  a c o ldcatho de fl uore sc ent l amp is  arra ng ed facing the e nd f ace on th e l ar geth ickne s s side  of  th e light  guidep lat e2 4 . 
T he optical path is  s h o wn  with an  arrow in  F I G. 6, wh er e t he l i g ht ra diat e dfrom the  light so ur ce 29 p as ses th esid e s urfac e  ofthe li ght guid e pla t e 24 and enter s  the light gu i de p la t e 24  in  the area l ight sour ce d e vi ce2 2. Th e lig ht th a t entered the light  g uide p late24 is guidedthrough th e l ight gui de p l at e  24 while repe ating  total ref l ection b etwee n the up per surfa c e  and the  lo wer  su rfa c e  o f the light g u i de p la te 24.Reg ardingthe  li ght  in  t he lightguide pl at e24 ,the  inci d ent angl e(an gl e f ormed by the  ligh t be am  a n d a  normal li n e  atth elowe r s ur faceof t h e l ight gu ide plate  24 )  ofwh en  enteri ng the lowersu rface of t he  li ght gu i d e plate24 becomes smaller ever y  time t helight  istotally r efl ectedatt he upp er sur facean d t h e  lowe r su rfa ce  of the we d g e-s haped  l ight  guideplate 24. When the inc ident angle o f l ight e nt eri n gt helo w ers u rface of the li ght guidepl a te  24 become s  sm al ler tha n the c ritic a l angle  of total  reflecti on  att h e i nterface o f the fi rst light trans m is sivelay er 25an d t he li ght gu i deplate  24, s uc h ligh t istr ansmitte d through the lower sur face o f the  li ght guide  pl a te24 and en tere d to the f irs t l ighttra n smiss ivel ay er2 5, an d th e n entered in tot h esecond ligh t t ran smiss ive layer27 a nd reflected at t h e micro-mirror  28, w her e t h e li gh t reflected at  th em i cro-mirr or  28 is tran smittedth r oughthe se cond l ight tr a n sm i ssivelaye r 2 7, the fi rst  l i ght tra ns mi s sive l ayer  2 5, and  the l i ghtg u ide plate 24, an d exi t fromt heupper  s urface( ligh t exit sur face) of th e ligh t gu ide p late 24 .In the  ar ea  light sou r ce device  22 h aving s uc h st ruc ture,only t he li ghtin  anarrow ra n g e, in  w h ich  the  inci de nt a ngle of w h en enter ing the low er  su r f ace of th e light guid e p late2 4  is smalle r  tha n  t h e cri ticalangleof tota l  re fl ection,  ou t of the li ght guide d  th ro ughthe ligh tguid epla te  24 is transmit ted thro ugh thef i rst an d s e cond lighttr ansmissive l ayers  2 5 , 27 an d 
 lower_index of_refraction than the light_guide plate_24_is overlapped_on_the lower surface_of the light_guide plate 24, and_a light deflection_layer_26 having substantially the same index of refraction as the light guide plate 24_is_overlapped on_the_lower_surface of the first light_transmissive layer 25. The light_deflection layer_26 is obtained by integrally forming a micro-mirror_28_made from metal_material on the back surface of a second light_transmissive layer 27 having substantially the_same index of_refraction_as_the light guide plate_24. A light source 29 such_as a cold cathode fluorescent lamp_is arranged facing the end face on_the large thickness side of the_light guide plate 24.
The optical_path is_shown with an arrow in_FIG. 6, where_the light_radiated from the_light source 29 passes the side_surface of the_light guide plate 24 and enters_the_light guide plate_24_in_the area_light source device_22._The light_that_entered the light guide plate 24_is_guided through the light guide plate 24_while repeating total reflection_between_the upper surface and_the lower surface of the_light guide plate 24. Regarding the_light in_the light_guide plate 24, the incident angle (angle formed by the light_beam and a normal line at_the lower surface of_the light_guide_plate 24) of_when_entering the_lower surface of the light guide plate_24 becomes_smaller every time the light is_totally reflected at the_upper_surface and the lower surface of_the wedge-shaped light guide plate 24._When the incident angle of_light_entering_the lower surface of the_light guide plate 24 becomes smaller_than the critical_angle of total reflection at the interface_of_the first light transmissive layer 25_and_the light guide plate 24, such_light_is_transmitted through the lower surface_of the light guide plate 24_and entered to the first light transmissive layer 25,_and then entered_into the second light transmissive_layer_27_and reflected at the micro-mirror 28, where the light reflected_at the_micro-mirror 28 is_transmitted through the second light transmissive layer 27, the first_light transmissive layer 25, and the light_guide plate 24, and exit from the upper surface (light exit_surface) of the light guide plate 24.
In the_area light source device 22 having such_structure, only the light_in_a narrow range, in which the incident_angle_of_when_entering the lower_surface of the_light guide plate_24 is_smaller than the_critical angle_of total reflection,_out_of the light guided through the light guide plate 24 is transmitted through the first and second light_transmissive layers 25, 27 and