Illumination device and liquid crystal display device using the same

• US 7,277,079 B2
• Filed: 10/29/2003
• Issued: 10/02/2007
• Est. Priority Date: 10/29/2002
• 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: Yamada, Fumiaki, Hayashi, Keiji, Suzuki, Toshihiro, Hamada, Tetsuya, Furukoshi, Yasutake, Kobayashi, Tetsuya, Sugawara, Mari, Nishido, Masanori
• Primary Examiner(s): Lefkowitz; Sumati
• Assistant Examiner(s): Moon; Seokyun
• Application Number:
  US10/696,504
• Publication Number:
  US 20040114396A1
• Time in Patent Office: 1,434 Days
• Field of Search: 345/102, 362/615, 349/62, 349/63, 349/64, 349/65
• US Class Current: 345/102
• CPC Class Codes: G02B 6/0046 Tapered light guide, e.g. wedge-shaped light guide
• CPC Class Codes: G02B 6/0076 Stacked arrangements of multiple light guides of the same or different cross-sectional area
• CPC Class Codes: G02B 6/0078 Side-by-side arrangements, e.g. for large area displays
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G09G 2310/024 Scrolling of light from the illumination source over the display in combination with the scanning of the display screen
• CPC Class Codes: G09G 2310/0245 Clearing or presetting the whole screen independently of waveforms, e.g. on power-on G09G2310/063 takes precedence
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0261 in the context of movement of objects on the screen or movement of the observer relative to the screen
• CPC Class Codes: G09G 2320/064 by time modulation of the brightness of the illumination source
• CPC Class Codes: G09G 2320/0646 Modulation of illumination source brightness and image signal correlated to each other
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/342 using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3666 with the matrix divided into sections
• CPC Class Codes: G09G 5/10 Intensity circuits

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.

Claims

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;

a light source power supply circuit for switching between a maximum lighting state in which the light source is made to emit light at a specified maximum brightness and an intermediate lighting state in which the light source is made to emit light at a specified intermediate brightness lower than the maximum brightness;

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,

wherein the second light guide plate is disposed in the first and the second light-emitting areas, and the first light guide plate is disposed in only the first light-emitting area.

2. An illumination device according to claim 1, further comprising:

a third light source unit including a third light guide plate and a third light source disposed at an end thereof, for mainly illuminating a third light-emitting area and supplying part of light to an adjacent fourth light-emitting area; and

a fourth light source unit laminated on the third light source unit and including a fourth light guide plate and a fourth light source disposed at an end thereof, for mainly illuminating the fourth light-emitting area and supplying part of light to the adjacent third light-emitting area.

3. An illumination device according to claim 2, wherein the third light guide plate is disposed in the third and the fourth light-emitting areas, and

the fourth light guide plate is disposed in only the fourth light-emitting area.

4. An illumination device according to claim 3, wherein

the first light guide plate and the fourth light guide plate are disposed on a same plane, and

the second light guide plate and the third light guide plate are disposed on a same plane.

5. An illumination device according to claim 4, further comprising:

a transmission diffused plate disposed above the first to the fourth illumination areas; and

a light mixing area disposed between the transmission diffused plate and the first to the fourth illumination areas.

6. An illumination device according to claim 5, wherein the light mixing area is a space or a transparent member having a thickness of 0.5 mm to 4 mm.

7. An illumination device according to claim 4, wherein a double-sided reflection plate for performing regular reflection or diffuse reflection is disposed between opposite end parts of the second light guide plate and the third light guide plate.

8. An illumination device according to claim 7, wherein a portion between the opposite end parts of the second light guide plate and the third light guide plate is formed into a Λ

shape opening to a rear surface side.

9. An illumination device according to claim 8, wherein when refractivity of a light guide substance is n, an apex angle θ

of the Λ

shape satisfies a relation of θ

≦

180°

−

4×

sin<sup>−

1</sup>(1/n).