Illumination device and liquid crystal display device using the same

Abstract

An illumination device is provided which can reduce a movement blur and a tailing phenomenon on a motion picture display while a drop in display brightness is suppressed, and which can suppress power consumption, can be made small and light, and can prolong the lifetime, and a liquid crystal display device using the same is provided. A light source control part of a control circuit synchronizes a latch pulse signal outputted from a gate driver control part to a gate driver, and outputs light emission control signals to respective light source power supply circuits. The respective light source power supply circuits change emission states of cold cathode fluorescent lamps to one of a first to a third emission states on the basis of the inputted light emission control signals, and illuminate an LCD panel from a rear surface of a display area. A first stage emission state is a non-lighting state, a second stage emission state is a maximum lighting state in which maximum lighting brightness is obtained, and a third emission state is an intermediate lighting state in which brightness of about one half of the second stage emission state is obtained.

1 . An illumination device for illuminating a display area of an active matrix type liquid crystal display device, comprising:
 at least one light source capable of changing light emission brightness; at least one light-emitting area for emitting light from the light source; and   a light source power supply circuit for switching between a maximum lighting state in which the light source is supplied with a first current to emit light at a specified maximum brightness and an intermediate lighting state in which the light source is supplied with a second current to emit light at a specified intermediate brightness lower than the maximum brightness, wherein said first current is greater than said second current;   wherein the light source power supply circuit synchronizes with one of gate pulses sequentially outputted to plural gate bus lines formed in the liquid crystal display device and switches between the maximum lighting state and the intermediate lighting state, and   when a gate pulse is outputted to a gate bus line as a display start line in the light-emitting area, the light emission brightness of the light-emitting area becomes the intermediate lighting state.   
     
     
         2 . An illumination device according to  claim 1 , wherein the light-emitting area includes a light emission opening to be used when the display area is illuminated and disposed substantially in parallel to an extension direction of a gate bus line formed in the liquid crystal display device. 
     
     
         3 . An illumination device according to  claim 1 , wherein the intermediate lighting state is set to have a brightness level of 50% or less of a brightness level of the maximum lighting state. 
     
     
         4 . An illumination device according to anyone of  claim 1 , wherein an illumination time in the maximum lighting state is a time of 50% or less of one frame period. 
     
     
         5 . An illumination device according to  claim 1 , further comprising:
 a first light source unit including a first light guide plate and a first light source disposed at an end thereof, for mainly illuminating a first light-emitting area and supplying part of light to an adjacent second light-emitting area; and   a second light source unit laminated on the first light source unit and including a second light guide plate and a second light source disposed at an end thereof, for mainly illuminating the second light-emitting area and supplying part of light to the adjacent first light-emitting area.   
     
     
         6 . An illumination device according to  claim 1 , wherein the light source power supply circuit includes a brightness adjusting volume for adjusting brightness of emission light from the light-emitting area. 
     
     
         7 . A liquid crystal display device of an active matrix type, comprising: an illumination device according to  claim 1 . 
     
     
         8 . An illumination device according to  claim 1 , wherein the light-emitting area includes a plurality of the light sources, and
 a light source control system that controls currents fed to the plurality of the light sources, respectively, to switch between the maximum lighting state in which the light-emitting area is made to emit light at the maximum brightness and the intermediate lighting state in which the light-emitting area is made to emit light at the specified intermediate brightness lower than the maximum brightness.   
     
     
         9 . An illumination device according to  claim 8 , wherein the light source control system feeds a current to at least one of the plurality of the light sources so that the maximum lighting state occurs at a specified period and a non-lighting state occurs at a time other than that, and
 feeds a current to the remaining light source so that the non-lighting state occurs at a time of the maximum lighting state and the intermediate lighting state occurs at a time other than that.   
     
     
         10 . An illumination device according to  claim 8 , wherein the light source control system feeds a current to at least one of the plurality of the light sources so that a first intermediate lighting state lower than the maximum lighting state occurs at a specified period, and a second intermediate lighting state lower than the first intermediate lighting state occurs at a time other than that, and
 feeds a current to the remaining light source so that a third intermediate lighting state occurs so as to cause the illumination area to have the maximum lighting state at a time of the first intermediate lighting state, and a fourth intermediate lighting state occurs so as to cause the illumination area to have the intermediate lighting state at a time of the second intermediate lighting state.   
     
     
         11 . An illumination device according to  claim 8 , wherein the light source control system feeds a current to at least one of the plurality of the light sources so that the intermediate lighting state always occurs, and
 feeds a current to the remaining light source so that the illumination area has the maximum lighting state at a specified period and has a non-lighting state at a time other than that.   
     
     
         12 . An illumination device according to  claim 8 , wherein the light source control system controls a current so that a non-lighting state occurs between the maximum lighting state and the subsequent intermediate lighting state. 
     
     
         13 . An illumination device according to  claim 8 , wherein the light source control system controls a current so that a lighting state lower than the intermediate lighting state occurs between the maximum lighting state and the subsequent intermediate lighting state. 
     
     
         14 . A liquid crystal display device of an active matrix type, comprising:
 an illumination device according to  claim 8 .