KR100433218B1 - Backlight unit - Google Patents

Abstract

The present invention relates to a backlight unit capable of realizing full whiteness and achieving full white.

In the backlight unit of the present invention, one red light emitting diode for generating red light, one blue light emitting diode for generating blue light, and two green light emitting diodes for generating green light are disposed in a rhombic shape to provide light to the liquid crystal panel. A light source to be irradiated, a reflecting plate disposed below the light source to reflect light from the light source upwards, and embossed, and a diffusion sheet disposed above the light source to diffuse the light.

According to the present invention, the luminance can be made uniform and full white can be realized.

Description

Backlight Unit {BACKLIGHT UNIT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight of a liquid crystal display device, and more particularly, to a backlight unit that can improve brightness while making luminance uniform.

Typically, a liquid crystal display (LCD) is a liquid crystal panel composed of a plurality of liquid crystal cells arranged in a matrix form and a plurality of control switches for switching the video signal to be supplied to each of these liquid crystal cells. A transmission amount of the light beam supplied from the backlight unit is adjusted to display a desired image on the screen.

Referring to FIG. 1, a conventional backlight unit includes a lamp 1 for generating light, a lamp housing 3 installed to surround the lamp 1, and light incident from the lamp 1 as a planar light source. The light guide plate 5 to be converted, the reflector 7 positioned below the light guide plate 5 to reflect the light traveling toward the lower surface and the side surface of the light guide plate 5 toward the upper surface, and light passing through the light guide plate 5 are diffused. The first and second prism sheets 11 and 13 and the prism sheets 11 and 13 for adjusting the advancing direction of light via the first diffusion sheet 9 and the first diffusion sheet 9 A second diffusion sheet 15 for diffusing light is provided.

As the lamp 1, a light emitting diode (hereinafter, referred to as a “LED”) that emits light of red (R), green (G), and blue (B) is used, and light generated from the lamp 1 is used. Is incident on the light guide plate 5 through an incident surface present on the side of the light guide plate 5. The lamp housing 3 has a reflecting surface on its inner surface to reflect light from the lamp 1 toward the incident surface of the light guide plate 5. The light guide plate 5 serves to convert the point light source from the lamp 1 into a surface light source. The rear side of the light guide plate 5 is provided so that the reflecting plate 7 faces. The reflector 7 serves to reduce light loss by reflecting light incident to itself through the back of the light guide plate 5 toward the light guide plate 5. When the light from the lamp 1 is incident on the light guide plate 5, the light is reflected at a predetermined inclination angle from the rear surface to uniformly move toward the front surface. At this time, the light propagated toward the lower surface and the side surface of the light guide plate 5 is reflected by the reflecting plate 7 and proceeds toward the front side. Light passing through the light guide plate 5 is diffused to the entire area by the first diffusion sheet 9. On the other hand, the light incident on the liquid crystal panel (not shown) increases the light efficiency when it is vertical. To this end, it is preferable to stack two forward prism sheets so that the traveling angle of the light emitted from the light guide plate 5 is perpendicular to the liquid crystal panel. Light passing through the first and second prism sheets 11 and 13 is incident on the liquid crystal panel via the second diffusion sheet 15.

Referring to FIG. 2, the backlight unit is arranged on one side of the first to fourth light guide regions 5a to 5d and the first to fourth light guide regions 5a to 5d in which the light guide plate 5 is divided into four regions. First to fourth trichromatic light sources 1a to 1d.

When the red (R), green (G), and blue (B) LEDs formed in the first trichromatic light source 1a are turned on, the light that is turned on is incident into the first light guide region 5a of the light guide plate 5. It is converted to a surface light source and emitted toward the upper surface. Subsequently, when the red (R), green (G), and blue (B) LEDs formed in the second trichromatic light source 1b are turned on, the light is incident into the second light guiding region 5b of the light guide plate 5. It is converted to surface light and emits toward the upper surface. Then, when the red (R), green (G), and blue (B) LEDs formed in the third trichromatic light source 5c are turned on, the light is incident into the third light guide region 5c of the light guide plate 5. It is converted into a surface light source and emitted toward the upper surface. Subsequently, when LEDs of red (R), green (G), and blue (B) formed in the fourth trichromatic light source 1d are turned on, the light is incident into the fourth light guiding region 5d of the light guide plate 5. It is converted to a surface light source and emitted toward the upper surface.

It is easy to control each of these red (R), green (B), and blue (G) LEDs. However, since the area of the light guide plate capable of controlling the LED is divided into four blocks, the LED color of red (R), green (B), and blue (G) corresponding to each block may appear differently for each block. In this case, there arises a problem that the luminance becomes uneven and it is difficult to realize full white.

Accordingly, an object of the present invention is to provide a backlight unit that can realize full white light while making luminance uniform.

1 is a cross-sectional view showing the configuration of a conventional backlight unit.

FIG. 2 is a plan view illustrating the lamp and the light guide plate illustrated in FIG. 1. FIG.

3 is a cross-sectional view illustrating a configuration of a backlight unit according to an exemplary embodiment of the present invention.

4 is a plan view illustrating the backlight unit of FIG. 3.

FIG. 5 is an enlarged view of a backlight unit corresponding to the unit liquid crystal cell shown in FIG. 4;

6 is a view illustrating the backlight driving module shown in FIG. 4.

<Description of Symbols for Main Parts of Drawings>

1, 30: light source 3: lamp housing

5: LGP 7, 32: Reflector

9, 15, 34: diffusion sheet 11, 13: prism sheet

36: liquid crystal panel 40: backlight driving module

42: driving voltage source

In order to achieve the above object, in the backlight unit of the present invention, one red light emitting diode for generating red light, one blue light emitting diode for generating blue light, and two green light emitting diodes for generating green light each have a rhombus shape. A light source disposed at the bottom of the light source to reflect light from the light source upwards, and an embossed reflector, and a diffusion sheet disposed above the light source to diffuse light. Equipped.

The luminance of the light source is characterized by satisfying the following conditional expression.

(Conditional expression)

Y = 0.30R + 0.59G + 0.11B

Here, Y denotes luminance, R denotes red light, G denotes green light, B denotes blue light, and each numeral denotes a degree of brightness of light.

And a backlight driving module connected to the light source to drive the light source.

The backlight driving module may select any one of a driving voltage source for supplying a driving voltage, first and second resistors connected to the driving voltage source through different input lines, and output lines of the first and second resistors. And a switch for connecting with the light source.

Other objects and features of the present invention other than the above object will become apparent from the description of the embodiments with reference to the accompanying drawings.

A preferred embodiment of the present invention will be described with reference to FIGS. 3 to 6.

3 and 4, the backlight unit according to an exemplary embodiment of the present invention is a direct type light source 30 that generates light, and is installed under the light source 30 and upwards light from the light source 30. And a reflecting plate 32 to be totally reflected by the light source, a diffusion sheet 34 disposed on the light source 30 to diffuse light, a liquid crystal panel 36, and a backlight driving module 40.

LEDs generating red (R), green (G), and blue (B) light are used as the light source 30, and the light source 30 corresponds to the unit cells of the liquid crystal panel 36 to correspond to four LEDs (A). ) Will be placed in the shape of a lozenge. Here, the four LEDs are composed of two green (G) light LEDs installed to face each other with one LED of red (R) and blue (B) light as shown in FIG. 5. The reason why two LEDs of green (G) light are included is to increase the brightness of the light. As shown in FIG. 5, the reflecting plate 32 is embossed to enclose four LEDs A arranged for each unit cell of the liquid crystal panel 36 having a predetermined size. Since the light is collected in the unit cell of the liquid crystal panel 36 by the embossing process, the light loss is reduced. At this time, the luminance is changed by adjusting the amount of current supplied to the red (R), green (G), and blue (B) light LEDs corresponding to the unit cells of the liquid crystal panel 36. As such, since the luminance of light can be adjusted for each unit cell of the liquid crystal panel 36, it is possible to implement uniform luminance on the entire display surface when an image is implemented.

Equation 1 below is a conditional expression that can realize an optimal full white light.

Y = 0.30R + 0.59G + 0.11B

Here, Y represents luminance.

When the luminance of the red (R) and blue (B) light satisfies Equation 1 based on the luminance of the green (G) light, optimal white light may be realized. This will be used to find the optimal brightness in the LCD of the TV and monitor integrated to be described later.

The white light implemented by the LEDs A travels to the upper surface via the reflecting plate 32. The diffusion sheet 34 diffuses light from the light source 30 to be incident on the liquid crystal panel 36. The light is uniformly spread by the diffusion sheet 34 to improve the uniformity of the luminance. The backlight unit displays the luminance corresponding to the luminance value input from the backlight driving module 40.

Referring to FIG. 6, the backlight driving module 40 includes a driving voltage source 42 for supplying a voltage, first and second resistors R1 and R2 having different resistance values, and a switch S. FIG. .

The driving voltage source 42 is connected to the first and second resistors R1 and R2 through two input lines. The voltage supplied from the driving voltage source 42 causes a voltage drop due to the first and second resistors R1 and R2. In this case, since the first and second resistors R1 and R2 have different resistance values, the voltages applied to the first resistor R1 and the voltages applied to the second resistor R2 are different from each other. The switch S serves to select one of a voltage via the first resistor R1 and a voltage via the second resistor R2. The voltage selected by the switch S is supplied to the backlight unit 30.

The backlight driving module 40 may be applied to a TV monitor integrated LCD having a TV and a monitor function. When the luminance suitable for the TV mode is to be selected, the voltage applied to the first resistor R1 is set to a luminance value suitable for the TV mode. In this case, the switch S selects the output line of the first resistor R1 so that the backlight unit 30 displays the luminance corresponding to the luminance value for the TV. In addition, when a luminance suitable for the monitoring mode is to be selected, the voltage applied to the second resistor R2 is set to a luminance value suitable for the monitoring mode. In this case, the switch S selects the output line of the second resistor R2 so that the backlight unit 30 displays the luminance corresponding to the brightness value of the monitor. As described above, the backlight unit according to the present invention can select a luminance suitable for a TV or monitor mode, respectively, so that a TV image and a monitor image can be simultaneously implemented in one LCD.

As described above, the backlight unit according to the present invention can implement a uniform luminance across the entire display surface by placing four LEDs in a lozenge per unit cell of the liquid crystal panel and embossing the reflector. In addition, the backlight unit according to the present invention can realize the optimal full white by changing the respective LED brightness.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (6)

delete A red light emitting diode for generating red light, one green light emitting diode for generating blue light, and two green light emitting diodes for generating green light, respectively, arranged in a rhombus to irradiate light to the liquid crystal panel; A reflection plate installed under the light source to reflect light from the light source upwards and to be embossed; And a diffusion sheet installed on the light source and diffusing light. The method of claim 2, And the green light emitting diodes face each other. The method of claim 2, And the luminance of the light source satisfies the following conditional expression. (Conditional expression) Y = 0.30R + 0.59G + 0.11B Here, Y denotes luminance, R denotes red light, G denotes green light, B denotes blue light, and each numeral denotes a degree of brightness of light. The method of claim 2, And a backlight driving module connected to the light source to drive the light source. The method of claim 5, wherein The backlight driving module, A driving voltage source for supplying a driving voltage; First and second resistors connected to the driving voltage source through different input lines; And a switch configured to select one of the output lines of the first and second resistors and to connect the light source to the light source.