BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME

• US 20070153548A1
• Filed: 11/21/2006
• Published: 07/05/2007
• Est. Priority Date: 05/21/2004
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: SUZUKI, Toshihiro, HAMADA, Tetsuya, ISHIWA, Masaru
• Granted Patent: US 7,488,104 B2
• Time in Patent Office: Days
• US Class Current: 362/615
• CPC Class Codes: G02B 6/003 Lens or lenticular sheet or layer
• CPC Class Codes: G02B 6/0036 2-D arrangement of prisms, protrusions, indentations or roughened surfaces
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0085 Means for removing heat created by the light source from the package heat extraction or cooling elements for semiconductor light sources in general H01L33/64
• CPC Class Codes: G02F 1/133615 Edge-illuminating devices, i.e. illuminating from the side
• CPC Class Codes: G02F 1/133628 with cooling means

Abstract

A backlight unit has a light source, a reflection sheet, a light guide plate, an air space, and a diffuser, wherein the reflection sheet, the light guide plate, the air space, and the diffuser are overlaid in this order. The light source is configured to arrange individual light sources having different spectra or different light emission quantities near an incident plane of the light guide plate, and on a plane facing the reflection sheet of the light guide plate, scatter dots are disposed which take light propagating through the light guide plate out of the reflection sheet side. The backlight unit and a liquid crystal display device including the same have excellent display quality.

Claims

1-107. -107. (canceled)

108. A backlight unit comprising:

a discrete light source section, a reflecting section, a light guide section, a first optical mixing section, and a second optical mixing section;

wherein

the reflecting section, the light guide section, the first optical mixing section, and the second optical mixing section are overlaid in this order;

the discrete light source section includes individual light sources having different spectra or different light emission quantities arranged near an incident plane of the light guide section;

a light drawing section configured to take a light propagating through the light guide section out on a reflecting section side or on a first optical mixing section side is provided on a surface of the light guide section facing the reflecting section or a surface facing the first optical mixing section;

the first optical mixing section is configured to mix color lights of different spectra or lights of different light quantities substantially in an in-plane direction to make the light uniform; and

the second optical mixing section is configured to mix lights at different angles in a same point in a plane to angularly realign the light to make a luminous light color and a luminous light quantity uniform in the plane.

109. The backlight unit according to claim 108, wherein the light guide section has the light drawing section on a side of a plane facing a light emission plane, the reflecting section is disposed on the light drawing section side of the light guide section, the discrete light source section has a plurality of LEDs and a reflector disposed around the LEDs, and the second optical mixing section is disposed at a predetermined space from the light emission plane of the light guide section.

110. The backlight unit according to claim 108, wherein the first optical mixing section is an air space having a predetermined thickness sandwiched between the light guide section and the second optical mixing section.

111. The backlight unit according to claim 110, wherein the predetermined thickness is about 2 mm to about 50 mm.

112. The backlight unit according to claim 108, wherein the light drawing section includes scatter dots disposed on the light guide section.

113. The backlight unit according to claim 108, wherein the light drawing section includes fine projections and recesses.

114. The backlight unit according to claim 108, wherein the light drawing section has a fine lens shape.

115. The backlight unit according to claim 108, wherein the light drawing section is disposed so that an arrangement density is low near the incident plane and the arrangement density is higher away from the incident plane.

116. The backlight unit according to claim 108, wherein the light drawing section is not disposed from the incident plane at a predetermined distance.

117. The backlight unit according to claim 116, wherein the predetermined distance is about 2 mm to about 50 mm.

118. The backlight unit according to claim 108, wherein the discrete light source section has a plurality of red LEDs, green LEDs, and blue LEDs.

119. The backlight unit according to claim 118, wherein the red LEDs, the green LEDs, and the blue LEDs are linearly arranged at almost equal spaces along a longitudinal direction of the incident plane.

120. The backlight unit according to claim 118, wherein the red LEDs, the green LEDs, and the blue LEDs are linearly mounted along a longitudinal direction of an LED circuit board, and arranged on one side of a short direction of the LED circuit board.

121. The backlight unit according to claim 120, wherein a surface of the LED circuit board on the light guide section side is a mirror reflection surface or a diffuse reflection surface.

122. The backlight unit according to claim 108, wherein a diffuser is used as the second optical mixing section.

123. The backlight unit according to claim 108, wherein a diffuser sheet is used as the second optical mixing section.

124. The backlight unit according to claim 108, wherein the side of the first optical mixing section is a mirror reflection surface or a diffuse reflection surface.

125. The backlight unit according to claim 108, wherein a color sensor is disposed on the side of the first optical mixing section.

126. The backlight unit according to claim 125, wherein the color sensor is disposed substantially at a center portion of the side on which the discrete light source is not disposed.

127. The backlight unit according to claim 108, wherein a color sensor is disposed on a side of the surface of the light guide section facing the reflecting section at a position at least about 10 mm away from the incident plane as a surface of the sensor faces the light guide section side.

128. The backlight unit according to claim 120, wherein a radiator plate or a radiation fin is provided on a back side of the LED circuit board.

129. The backlight unit according to claim 128, wherein a high heat radiation member is disposed on a surface of the radiator plate or the radiating fin.

130. The backlight unit according to claim 128, further comprising a housing configured to hold the light guide plate, wherein the housing includes a high heat radiation member.

131. The backlight unit according to claim 120, further comprising a housing configured to hold the light guide plate, wherein the LED circuit board has an L shape and contacts the housing.

132. The backlight unit according to claim 131, wherein the housing includes a high heat radiation member.

133. The backlight unit according to claim 108, wherein the light guide section has two light guide plates, and the two light guide plates are disposed so that opposing surfaces thereof facing the incident plane face each other.

134. The backlight unit according to claim 133, wherein the two light guide plates have a wedge shape in which a thickness on the incident plane side is thicker than a thickness on the opposing surface side.

135. The backlight unit according to claim 133, wherein a mirror reflection member or a diffused reflection member is provided between the opposing surfaces of the two light guide plates.

136. The backlight unit according to claim 108, wherein the light guide section has a light guide plate in a wedge shape in which a thickness on the incident plane side is thicker than a thickness on the opposing surface side facing the incident plane.

137. The backlight unit according to claim 136, wherein the light emission plane of the light guide plate is disposed at a predetermined space from the second optical mixing section.

138. The backlight unit according to claim 136, wherein the light guide plate is disposed so that the light emission plane is tilted toward the second optical mixing section, and a plane facing the light emission plane is disposed substantially in parallel.

139. The backlight unit according to claim 136, further comprising two plates on the light guide plates, wherein the two light guide plates are disposed so that a predetermined space is provided between opposing surfaces.

140. The backlight unit according to claim 139, wherein the reflecting section has a projecting shape so that a distance from the second optical mixing section is at a minimum near a center portion in the plane.

141. The backlight unit according to claim 108, wherein the light guide section has the light emission plane with a mountain shape in cross section which is tilted at a predetermined angle with respect to a surface of the light guide section facing the reflecting section.

142. The backlight unit according to claim 118, wherein the green LED, the red LED, and the blue LED are arranged adjacently in this order from one end portion of the incident plane to the other end portion along a longitudinal direction;

a plurality of LED groups are arranged adjacent to the blue LEDs, in which a plurality of the red LEDs, the green LEDs, and the blue LEDs are adjacently arranged in a predetermined order; and

the red LED and the green LED are adjacently arranged in this order adjacent to the LED group.

143. The backlight unit according to claim 142, wherein in the LED group, the green LED, the red LED, the green LED, and the blue LED are adjacently arranged in this order from the one end portion side to the other end portion side.

144. The backlight unit according to claim 142, wherein in the LED group, the red LED, the green LED, the red LED, and the blue LED are adjacently arranged in this order from the one end portion side to the other end portion side.

145. A liquid crystal display device comprising:

a backlight unit according to claim 108, the backlight unit further provided with a light guide plate and a light source portion; and

a liquid crystal display panel disposed on a light emission plane side of the light guide plate.

146. The liquid crystal display device according to claim 145, wherein a lens sheet or a polarizer sheet is disposed between the backlight unit and the liquid crystal display panel.

147. A liquid crystal display device comprising:

a side lit backlight unit provided with a light guide plate and a light source portion disposed near at least one side end surface of the light guide plate; and

a liquid crystal display panel disposed on a light emission plane side of the light guide plate;

wherein

a flexible substrate or a printed circuit board is disposed in a peripheral portion of the liquid crystal display panel; and

the flexible substrate or the printed circuit board is disposed so as not to cover the light source portion.

148. The liquid crystal display device according to claim 147 wherein the flexible substrate or the printed circuit board is disposed near an upper portion of the light source portion when folded.

149. The liquid crystal display device according to claim 147, wherein the flexible substrate or the printed circuit board extends from an end surface side on which the light source portion of the light guide plate is not disposed, and is connected to a control circuit portion which drives the liquid crystal display panel.

150. The liquid crystal display device according to claim 149, wherein the light source portion has a plurality of LEDs arranged in a direction along a side of an incident plane of the light guide plate.

151. A liquid crystal display device comprising:

a backlight unit provided with a light guide plate, a light source portion, and a control portion; and

a liquid crystal display panel disposed on a light emission plane side of the light guide plate;

wherein

the liquid crystal display panel has a micro area from which a red light, a green light, and a blue light are emitted from a backlight unit side separately from a display pixel, and a light quantity sensor configured to detect a light quantity is disposed in each of the micro areas on a viewer side; and

the control portion controls the light source portion based on the light quantity.

152. A backlight unit comprising:

a discrete light source section configured to have individual light sources having different spectra or different light emission quantities;

a light guide section configured to have one end surface which is provided with an incident plane which receives a light emitted from the discrete light source section, a light guiding area which guides the light having entered from the incident plane, and a light emission plane which emits the light guided in the light guiding area;

a heat conduction section configured to conduct heat generated in the discrete light source section; and

a heat dissipation section disposed on a back side of the light emission plane and configured to dissipate heat conducted through the heat conduction section.

153. The backlight unit according to claim 152, wherein the heat conduction section has a substantially L-shaped heat conduction member which is bent along the light guide section and is substantially L-shaped in cross section.

154. The backlight unit according to claim 152, wherein the heat conduction section has a light source fixing member which is bent along the light guide section and has a substantially L-shaped configuration in cross section, and which fixes the discrete light source section.

155. The backlight unit according to claim 154, wherein at least one of the substantially L-shaped heat conduction member and the light source fixing member is thermally contacted with the heat dissipation section.

156. The backlight unit according to claim 154, further comprising a protecting section configured to protect the light guide section between the light guide section and the heat dissipation section, wherein the protecting section is thermally contacted with the heat conduction section.

157. The backlight unit according to claim 156, wherein the protecting section is thermally contacted with at least one of the substantially L-shaped heat conduction member and the light source fixing member.

158. The backlight unit according to claim 152, wherein the discrete light source section has an LED.

159. The backlight unit according to claim 158, wherein the LED is a DIP type.

160. The backlight unit according to claim 152, wherein the discrete light source section is covered with a heat conduction reflection member, wherein the heat conduction reflection member is made of a material having a high heat conductivity to conduct heat to the heat conduction section and reflect and guide emitted light to the light guide section in which an emission side of the light is opened.

161. The backlight unit according to claim 160, wherein the heat conduction reflection member has a light reflecting section on an inner wall surface covering the discrete light source section.

162. A liquid crystal display device comprising:

a backlight unit provided with a discrete light source section configured to have individual light sources having different spectra or different light emission quantities, a light guide section configured to have one end surface provided with an incident plane which receives a light emitted from the discrete light source section, a light guiding area which guides the light having entered from the incident plane, and a light emission plane which emits the light guided in the light guiding area, a heat conduction section configured to conduct heat generated in the discrete light source section, and a heat dissipation section disposed on a back side of the light emission plane and configured to dissipate heat conducted through the heat conduction section;

a liquid crystal display panel disposed on a light emission plane side of the light guide plate; and

an accommodating section configured to accommodate the backlight unit and the liquid crystal display panel which is made of a high heat radiating material to thermally contact with the backlight unit to dissipate heat generated in the discrete light source section.

163. The liquid crystal display device according to claim 162, wherein the heat conduction section has a substantially L-shaped heat conduction member which is bent along the light guide section and is substantially L-shaped in cross section.

164. The liquid crystal display device according to claim 162, wherein the accommodating section is thermally contacted with a protecting section configured to protect the light guide section, which is disposed between the light guide section and the heat dissipation section.

165. The liquid crystal display device according to claim 162, wherein the accommodating section is thermally contacted with the heat dissipation section.

166. The liquid crystal display device according to claim 164, wherein at least one of the protecting section or the heat dissipation section is screwed and fixed to the accommodating section.

167. The liquid crystal display device according to claim 162, wherein the backlight unit has a diffusing section between the light guide section and the liquid crystal display panel, and an area of the light emission plane of the light guide section is smaller than an area of a display area of the liquid crystal display panel or an area of the diffusing section.

168. The liquid crystal display device according to claim 167, wherein a length of the incident plane of the light guide section and a plane facing the incident plane is shorter than a length of the display area of the liquid crystal display panel or a length of the diffusing section measured in a same direction.

169. The liquid crystal display device according to claim 167, wherein the backlight unit has a frame shaped member between the light guide section and the diffusing section, in which an opening area on the light guide section side is narrower than an opening area on the diffusing section side.

170. A backlight unit comprising:

a discrete light source section, a first reflecting section, a light guide section, a first optical mixing section, and a second optical mixing section;

wherein

the first reflecting section, the light guide section, the first optical mixing section, and the second optical mixing section are overlaid in this order;

the discrete light source section includes individual light sources having different spectra or different light emission quantities arranged near an incident plane of the light guide section;

a light drawing section configured to take a light propagating through the light guide section out on a first reflecting section side or on a first optical mixing section side is provided on a surface of the light guide section facing the first reflecting section or a surface facing the first optical mixing section; and

a relationship, 0≦

Lp/H≦

2.5 is maintained, where a height of the first optical mixing section is H, and a length of a minimum unit of a cycle of an array of the discrete light source section is Lp.

171. The backlight unit according to claim 170, wherein the first optical mixing section is an air space sandwiched between the light guide section and the second optical mixing section.

172. The backlight unit according to claim 170, further comprising a second reflecting section which is disposed on the side of the first optical mixing section.

173. The backlight unit according to claim 170, wherein the second reflecting section is a scattering reflector.

174. The backlight unit according to claim 173, wherein the reflector is made of a plastic or resin.

175. The backlight unit according to claim 170, wherein the second optical mixing section is a transmissive diffuser.

176. The backlight unit according to claim 175, wherein the transmissive diffuser is a bulk diffuser having a transmittance of about 80% or below and a plate thickness of about 2 mm or greater.

177. The backlight unit according to claim 170, wherein the discrete light source section has a plurality of red LEDs, green LEDs, and blue LEDs.

178. The backlight unit according to claim 177, wherein the length Lp of the minimum unit of the cycle of the array of the discrete light source section is an arrangement pitch of an LED array unit group having at least one of the red LEDs, the green LEDs, and the blue LEDs.

179. The backlight unit according to claims 170, further comprising a third reflecting section which is disposed adjacently to the second optical mixing section and reflects light entering in a substantially perpendicular direction.

180. The backlight unit according to claim 179, wherein the third reflecting section is a prism sheet.

181. A liquid crystal display device comprising:

a liquid crystal display panel provided with a pair of substrates disposed facing each other, and liquid crystals sealed between the pair of the substrates; and

the backlight unit according to claim 170 disposed on a back side of the liquid crystal display panel.

182. A backlight unit comprising:

a discrete light source section configured to have individual light sources having different spectra or different light emission quantities;

a light guide section configured to have one end surface provided with an incident plane which receives a light emitted from the discrete light source section, a light guiding area which guides the light having entered from the incident plane, and a light emission plane which emits the light guided in the light guiding area;

a heat conduction section configured to conduct heat generated in the discrete light source section; and

a heat insulating section configured to have a contact surface which covers and thermally contacts with a portion of an outer surface of the heat conduction section and to insulate heat as a temperature of the heat conduction section substantially uniformly.

183. The backlight unit according to claim 182, wherein the heat conduction section has a heat dissipation surface which dissipates heat.

184. The backlight unit according to claim 183, wherein a surface treatment is applied to the heat dissipation surface in order to increase infrared emissivity.

185. The backlight unit according to claim 184, wherein the surface treatment includes an anodized surface.

186. The backlight unit according to claim 184, wherein the surface treatment includes a coated surface.

187. The backlight unit according to claim 183, wherein a thermal resistance of the heat insulating section from the contact surface to the back side of the contact surface is higher than a thermal resistance of the heat conduction section from an inflow portion of the heat to the heat dissipation surface.

188. The backlight unit according to claim 187, wherein a thermal resistance of the heat insulating section is higher than a thermal resistance of the heat conduction section in a plane in parallel with the contact surface.

189. The backlight unit according to claim 182, wherein the heat insulating section is made of a plastic or resin.

190. The backlight unit according to claim 183, wherein the light guide section further has the incident plane on an opposing surface of the one end surface, and the discrete light source section is disposed on the one end surface side and on the opposing surface side.

191. The backlight unit according to claim 190, wherein a total electric power input to the discrete light source section disposed on the one end surface side is varied from a total electric power inputted to the discrete light source section disposed on the opposing surface side.

192. The backlight unit according to claim 190, wherein electric power supplied to each of the individual light sources having different spectra or different light emission quantities in the discrete light source section is varied between the discrete light source section disposed on the one end surface side and the discrete light source section disposed on the opposing surface side.

193. The backlight unit according to claim 190, further comprising a holding section disposed on the back side of the light emission plane and configured to hold the heat conduction section in a predetermined space.

194. The backlight unit according to claim 193, wherein the holding section is thermally contacted with the heat conduction section.

195. The backlight unit according to claim 193, wherein the holding section has the heat dissipation surface on the opposite side of a plane facing the back side of the light guide section.

196. The backlight unit according to claim 183, further comprising a heat dissipation section disposed on the back side of the light emission plane and configured to dissipate the heat conducted through the heat conduction section.

197. The backlight unit according to claim 190, further comprising a heat dissipation section disposed on the back side of the light emission plane and configured to dissipate the heat conducted through the heat conduction section, wherein the heat dissipation section extends to near the discrete light source sections disposed on the one end surface side and on the opposing surface side.

198. The backlight unit according to claim 196, wherein at least a portion of an outer surface of the heat dissipation section includes the heat dissipation surface.

199. The backlight unit according to claim 196, wherein the heat dissipation section includes a heatsink.

200. The backlight unit according to claim 199, wherein at least a portion of an outer surface of the heatsink includes the heat dissipation surface.

201. The backlight unit according to claim 183, wherein the heat conduction section has a substantially L-shaped heat conduction member which is formed in an L shape in planes substantially perpendicular to each of the light emission plane and the contact surface.

202. The backlight unit according to claim 201, wherein the substantially L-shaped heat conduction member includes the heat dissipation surface on the opposite side of a plane facing the back side of the light emission plane.

203. The backlight unit according to claim 183, wherein the heat conduction section has an inclusion type heat conduction member which sandwiches and includes the heat insulating section.

204. The backlight unit according to claim 203, wherein the inclusion type heat conduction member includes the heat dissipation surface in a plane substantially in parallel with the contact surface.

205. The backlight unit according to claim 190, wherein the heat conduction section has an integral, substantially U-shaped heat conduction member to conduct the heat generated on the discrete light source sections disposed on the one end surface side and on the opposing surface side and having a substantially U-shaped configuration in planes substantially perpendicular to each of the light emission plane and the contact surfaces.

206. The backlight unit according to claim 205, wherein the substantially U-shaped heat conduction member includes the heat dissipation surface on the opposite side of a plane facing the back side of the light emission plane.

207. The backlight unit according to claim 183, wherein the heat conduction section has a substantially L-shaped light source fixing member which has a substantially L-shaped configuration in planes substantially perpendicular to each of the light emission plane and the contact surface and fixes the discrete light source section.

208. The backlight unit according to claim 207, wherein the substantially L-shaped light source fixing member includes the heat dissipation surface on the opposite side of a plane facing the back side of the light emission plane.

209. The backlight unit according to claim 190, wherein the heat conduction section has a substantially U-shaped light source fixing member which has a substantially U-shaped configuration in planes substantially perpendicular to each of the light emission plane and the contact surfaces, wherein the substantially U-shaped light source fixing member fixes the discrete light source sections disposed on the one end surface side and on the opposing surface side.

210. The backlight unit according to claim 209, wherein the substantially U-shaped light source fixing member includes the heat dissipation surface on the opposite side of a plane facing the back side of the light emission plane.

211. The backlight unit according to claim 183, wherein the heat dissipation surface includes:

a circuit board fixing portion which thermally contacts and fixes a circuit board mounted to a predetermined electric circuit; and

a protection cover fixing portion which thermally contacts the heat conduction section at a position different from the circuit board fixing portion and fixes a protection cover of the circuit board.

212. The backlight unit according to claim 211, wherein at least a portion of front and back sides of the protection cover includes the heat dissipation surface.

213. The backlight unit according to claim 182, wherein the equation:

Lm/(t1+t2)≦

300

is maintained, and a thickness of the heat conduction section is t1, a thickness of the light source fixing member fixing the discrete light source section is t2, and a length of the light source fixing member in a direction of arranging the individual light sources is Lm (where t1, t2, and Lm are in the same units).

214. A liquid crystal display device comprising:

a liquid crystal display panel provided with a pair of substrates disposed facing each other, and liquid crystals sealed between the pair of the substrates; and

the backlight unit according to claim 182 disposed on the back side of the liquid crystal display panel.