KR20060121625A - Backlight unit of liquid crystal display device - Google Patents

Abstract

A backlight unit for an LCD is provided to achieve high brightness and high color reproducibility and improve the uniformity of brightness, by forming the backlight unit of passive luminescence type of lamps and self-luminescence type of lamps. A first light emitting part(120) is composed of a plurality of first lamps(128), wherein the first lamps are passively luminous. A second light emitting part(130) is disposed below the first light emitting part. The second emitting part is composed of a plurality of second lamps(138), wherein the second lamps are self-luminous. A reflective film(139) is formed at the outer circumferential surface of a lower part of each first lamp. The reflective film scatters the vertical light, which is emitted from the second lamps, toward a lateral surface of a backlight unit. A reflective plate(133) is provided below the second light emitting part. A light scattering member is provided above the first light emitting part.

Description

BACKLIGHT UNIT OF LIQUID CRYSTAL DISPLAY DEVICE}

1 is a view showing a liquid crystal display device according to the present invention.

2 is a view showing a first lamp configured in the first light emitting unit of the backlight unit according to the present invention;

3 is a view showing a second lamp configured in the second light emitting unit of the backlight unit according to the present invention;

4 is a view showing the arrangement of the first lamp and the second lamp respectively configured in the first light emitting unit and the second light emitting unit of the backlight unit according to the present invention.

** Description of the symbols for the main parts of the drawings **

110: liquid crystal panel 120: the first light emitting unit

121: light scattering means 128: passive light emitting lamp

130: second light emitting unit 131: MCPCB

133: reflector 135: light guide plate

139: reflecting film 140: backlight unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a backlight unit capable of improving luminance uniformity and color reproducibility of a liquid crystal display.

In general, a liquid crystal display device is bonded to a thin film transistor array substrate and a color filter substrate facing each other at regular intervals, and the thin film transistor array substrate and a color filter substrate are bonded to each other. It includes a liquid crystal panel (Liquid Crystal Display Panel) consisting of a liquid crystal layer provided, a driving unit for driving the liquid crystal panel and a backlight unit for supplying light to the liquid crystal panel.

In the thin film transistor array substrate, a plurality of data lines arranged at regular intervals vertically and a plurality of gate lines arranged at regular intervals laterally intersect with each other, and a pixel is defined in an area partitioned therebetween. Arranged in matrix form.

In addition, a color filter layer of red, green, and blue is formed at a position corresponding to the pixels on the color filter substrate, to prevent light leakage between the color filter layers, and to prevent color interference of light passing through the pixels. A black matrix is formed between the color filter layers.

Common electrodes and pixel electrodes are formed on opposite inner surfaces of the color filter substrate and the thin film transistor array substrate to apply an electric field to the liquid crystal layer. In this case, the pixel electrode is formed for each pixel on the thin film transistor array substrate, while the common electrode is integrally formed on the front surface of the color filter substrate. Therefore, by controlling the voltage applied to the pixel electrode while applying the voltage to the common electrode, the light transmittance of the pixels can be individually controlled by changing the arrangement state of the liquid crystal molecules of the liquid crystal layer.

The backlight unit supplies light to a liquid crystal display device which does not emit light by itself. When light emitted from the backlight unit passes through the liquid crystal layer, light transmittance is determined by an arrangement state of liquid crystals so that an image is displayed.

The backlight unit is divided into an edge method and a direct method according to the position of the lamp used as the light source.

The edge method is a method in which a lamp is disposed on one side or both sides of the liquid crystal panel, and projects light generated from the lamp onto the entire screen of the liquid crystal panel by the light guide plate.

In addition, the direct method began to be developed mainly as the size of the liquid crystal panel began to be enlarged to 20 inches or more. A plurality of fluorescent lamps were arranged in a row on the lower surface of the diffuser plate to directly irradiate light directly onto the front surface of the liquid crystal panel. That's the way. The direct method is mainly used for a large screen liquid crystal display device requiring high luminance because the light utilization efficiency is higher than that of the edge method.

The light source includes a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), an electro luminescence (EL), a light emitting diode (LED), and the like. Cold cathode fluorescent lamps and LED lamps with low power consumption are widely used.

The cold cathode fluorescent lamp can implement high brightness and improve luminance evenly, but it is impossible to control partial brightness and it is difficult to realize high color reproduction.

In addition, the LED lamp is capable of controlling the partial luminance and realizing high color reproduction, but has a disadvantage in that the luminance and the uniformity of the luminance are lowered compared to the cold cathode fluorescent lamp.

Accordingly, the present invention has been made to solve the conventional problems as described above, and an object of the present invention is to provide a backlight unit of a liquid crystal display device capable of controlling partial luminance and enabling high luminance and high color reproduction.

Another object of the present invention is to provide a liquid crystal display device capable of controlling partial luminance and capable of high luminance and high color reproduction.

The backlight unit of the present invention for achieving the object of the present invention as described above comprises: a first light emitting unit in which a plurality of passive light emitting first lamps are arranged; A second light emitting unit in which a plurality of second light emitting lamps are arranged under the first light emitting unit corresponding to the first lamp; A reflection film formed on a lower outer circumferential surface of the first lamp to scatter vertical light emitted from the second lamp to the side; A reflection plate provided below the second light emitting unit; And light scattering means provided on the first light emitting unit.

The first lamp may be selected from one of a Cold Cathode Fluorescent Lamp (CCFL) and a Hot Cathode Fluorescent Lamp (HCFL), and the second lamp may be an EL (Electro Luminescence) or LED. It can be selected and used as one of (Light Emitting Diode).

The light scattering means may include a diffuser plate for dispersing light incident from the first and second light emitting units, a prism sheet for improving front luminance of light transmitted through and reflected from the upper plate, and an upper portion of the prism sheet. It consists of a protective sheet.

The light guide plate may further include a light guide plate interposed between the first light emitter and the second light emitter to guide light incident from the second light emitter to the first light emitter.

In addition, the liquid crystal display device according to the present invention comprises a liquid crystal panel and a backlight unit for supplying light to the liquid crystal panel, wherein the backlight unit comprises: a first light emitting unit in which a plurality of passive light emitting lamps are arranged; A second light emitting unit in which a plurality of second light emitting lamps are arranged under the first light emitting unit corresponding to the first lamp; A reflection film formed on a lower outer circumferential surface of the first lamp to scatter vertical light emitted from the second lamp to the side; A reflection plate provided below the second light emitting unit; And it comprises a light scattering means provided on the first light emitting portion.

The passive light emitting lamp may be selected from one of a Cold Cathode Fluorescent Lamp (CCFL) and a Hot Cathode Fluorescent Lamp (HCFL), and the self-luminous lamp is an EL (Electro Luminescence), LED. It may be selected as one of (Light Emitting Diode).

As described above, the present invention provides a backlight unit of a liquid crystal display device capable of implementing high brightness and high color reproduction by combining a passive light emitting lamp such as a cold cathode lamp and a self-emitting lamp such as an LED. That is, since the cold cathode lamp is capable of controlling the overall brightness and generates white light from the lamp itself, there is an advantage that high brightness can be realized, but the color reproducibility is low and the partial brightness cannot be controlled. On the other hand, LED has the advantage of partial luminance and high color reproduction, but the brightness of luminance and luminance is realized because the light of R, G, B color emitted from R, G, B LED lamp is mixed to realize white light. There is a problem of inferior uniformity.

Therefore, in the present invention, the cold cathode lamp and the LED lamp are used together to improve the luminance and the uniformity of the luminance, and to implement a backlight capable of high color reproduction and partial control.

In addition, the present invention provides a liquid crystal display device that implements high brightness and high color reproduction by implementing a backlight of high brightness and high color reproduction.

Hereinafter, the liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic view of a liquid crystal display device according to an embodiment of the present invention. In particular, FIG. 2 is a cross-sectional view showing a specific gravity of a backlight unit, and FIGS. 2 and 3 illustrate a lamp configured in a first light emitting unit of a backlight unit according to the present invention. 4 shows the arrangement of the first lamp of the first light emitting unit and the second lamp of the second light emitting unit.

As shown in FIG. 1, the liquid crystal display device 100 according to the present invention includes a thin film transistor array substrate 110a and a color filter substrate 110b, and the thin film transistor array substrate 110a and a color filter substrate 110b. A liquid crystal panel 110 composed of a liquid crystal layer (not shown) provided in the fixed spaces bonded thereto; It is configured to include a backlight unit 150 for supplying light to the liquid crystal panel 110.

Although not shown in detail in the drawing, the thin film transistor array substrate 110a includes a plurality of gate lines arranged in a first direction, and a plurality of pixel regions defining a plurality of pixel regions arranged in a matrix form perpendicular to the gate lines. And a switching element for switching each pixel.

In addition, a color filter layer of red, green, and blue is formed on the color filter substrate to correspond to the pixels, and black prevents light leakage between the color filter layers and prevents color interference of light passing through the pixels. A matrix is formed.

In addition, a pixel electrode and a common electrode are formed on inner surfaces of the thin film transistor array substrate and the color filter substrate, respectively, to apply an electric field to the liquid crystal layer, and to control a voltage applied between the common electrode and the pixel electrode to control the liquid crystal layer. By changing the arrangement of the liquid crystal molecules of the light transmittance of the pixels are individually controlled.

The backlight unit 150 includes a first light emitter 120 including a passive light emitting first lamp 128 and a second light emitter 130 including a self-emitting second lamp 138. .

The first lamp 128 configured in the first light emitting unit 120 may be configured as one of a cold cathode fluorescent lamp and a hot cathode fluorescent lamp. 2 and 3, in the direct method, the first lamp 128 is fixed to grooves formed on both sides of the outer case 129 and is disposed at regular intervals. The first lamp 128 has electrodes 128 'for applying an external power source (not shown) at both ends of the glass tube filled with the discharge gas, and wires 128a are formed at the electrodes 128'. It is connected. Since the wire 128a is connected to a separate inverter (not shown) and connected to a driving circuit, a separate inverter is required for each lamp 128.

When the first lamp 128 configured as described above is applied with voltage through the wire 128a, residual electrons existing in the glass tube move to the anode, and as the moving residual electrons collide with argon (Ar), the argon is excited. The cation increases and the increased cation strikes the cathode and releases secondary electrons. At this time, when the emitted secondary electrons start discharging in the tube, the flow of electrons collide with the mercury vapor and ionize by the discharge to emit ultraviolet rays and visible light, and the emitted ultraviolet rays excite the phosphor coated on the inner wall of the lamp to display visible light. By emitting light, light is generated.

Referring to FIG. 1, the first light emitting unit 120 will be continuously described, and light scattering means for improving the uniformity of light transmitted through the liquid crystal panel 110 is formed on the first lamp 128. The light scattering means includes a diffusion plate 123, first and second prism sheets 125a and 125b and a protection sheet 127 provided on the diffusion plate 123.

The diffusion plate 123 formed on the upper portion of the first lamp 128 disperses the light incident from the lamp 128, so that spots due to partial concentration of light are not generated. In addition, the diffusion plate 123 also serves to vertically raise the direction of the light traveling toward the first prism sheet 125a. The first prism sheet 125a has a flat lower surface and a corrugated surface corrugated in the front and rear directions, while the second prism sheet 125b has a flat lower surface and a corrugated surface corrugated in the left and right directions. 125a condenses the light traveling toward the second prism sheet 125b in the front-rear direction, and the second prism sheet 125b condenses the light traveling toward the protective sheet 127 in the left-right direction, resulting in a diffusion plate. The light proceeds from 145 toward the protective sheet 127 so as to vertically proceed. Accordingly, the light passing through the first and second prism sheets 125a and 125b is vertically distributed and uniformly distributed with respect to the entire surface of the protective sheet 127, thereby improving luminance.

On the other hand, the second lamp 138 configured in the second light emitting unit 130 may be configured as one of the LED lamp or EL lamp. In this case, the second lamp 138 should be disposed so as to correspond between the first lamps 128.

That is, as shown in FIG. 4, the second lamp 138 should be disposed at a position corresponding to the first lamp 128. The second lamps 138 are continuously disposed on a straight line at regular intervals of the R, G, and B lamps 138a, 138b, and 138c. Each of the R, G, and B lamps 138a, 138b, and 138c is disposed. The monochromatic light emitted from) is mixed to generate white light. Therefore, when only the second lamp (LED lamp) is used as a light source, bright spots occur at the front viewing angle, causing luminance unevenness. Therefore, according to the present invention, by disposing the second lamp 138 at a position corresponding to the first lamp 128, the luminance decrease due to the uneven brightness and the LED efficiency deterioration, which are disadvantages of the LED backlight, can be solved. That is, the reflective film 139 is formed on the lower outer circumferential surface of the first lamp 128, wherein the reflective film 139 vertically enters light incident from the second lamp 138 to the side of the second lamp 138. By scattering, luminance unevenness is solved. Accordingly, the first lamp 128 and the second lamp 138 are disposed at positions corresponding to each other, and are emitted from the second lamp 138 by the reflective film 139 formed on the lower peripheral surface of the first lamp 128. You should be able to scatter vertical light.

The second lamp 138 is formed on a metal core printed circuit board (MCPCB), and the light scattered downward between the second lamp 138 and the MCPCB 131 is upward. The reflecting plate 133 is configured to reflect, and the reflecting plate 133 may be formed of Al material having excellent reflection characteristics.

Self-luminous lamps, especially LED lamps, have superior brightness and color reproducibility compared to fluorescent lamps (cold cathode, hot cathode), but the internal temperature inevitably increases with increasing brightness, and the internal temperature of LED lamps may increase. The output luminance is reduced. Therefore, a heat sink 137 is provided on the back of the MCPCB 131, and the heat sink 137 receives heat from the lamp 138 and releases it to the outside, thereby preventing an increase in internal temperature. That is, as the LED lamp generates light, heat is generated in the LED, and the generated heat is absorbed by the reflector 133 and transferred to the MCPCB 131. Then, the heat transferred to and absorbed by the MCPCB 131 is transferred to the external heat sink 137 and finally released to the outside.

In addition, a light guide plate 135 is formed between the first light emitting unit 120 and the second light emitting unit 130, and the light guide plate 135 mostly receives light incident from the second lamp 138. It is transmitted through (120), and is formed of a transparent material, such as PMMA (Poly Methly Meth Acrylate), glass substrate, PC (Poly Carbonate).

The light guide plate 135 may be omitted, and in the case where the light guide plate 135 is omitted, it is possible to reduce the volume of the backlight to reduce the weight of the liquid crystal display device.

On the lower outer circumferential surface of the first lamp 128 facing the upper portion of the second lamp 138, a reflective film 139 for scattering light incident vertically from the second lamp 138 to the side to improve uniformity of light is provided. Coated and some of the light scattered by the reflective film 139 is reflected back to the reflective plate 133 to pass through the diffuser plate 123.

In general, in the case of using an LED lamp, a light scattering member called a diverter is formed on the top of the LED lamp to scatter laterally the vertical light emitted from the LED lamp. The diverter should be configured to correspond 1: 1 to the upper portion of the LED lamp, and the number of diverters increases as the number of lamps increases as the liquid crystal panel is enlarged. However, as the number of lamps and diverters increases, their alignment is difficult, and in particular, it is difficult to form diverters at regular intervals.

Therefore, instead of forming a diverter in the present invention, by coating a material having excellent reflection characteristics such as aluminum (Al) on the lower outer peripheral surface of the first lamp 128 disposed on the second lamp 138 (LED lamp) By forming the reflective film 139, the reflective film 139 takes the place of the diverter. The coating process of the reflective film 139 is not only simpler than the diverter forming process, but also advantageous in terms of material cost.

The backlight unit of the present invention configured as described above comprises a first light emitting part and a second light emitting part, and comprises a passive light emitting lamp such as a cold cathode fluorescent lamp or a hot cathode fluorescent lamp in the first light emitting part, and a second light emitting part. By constructing a self-luminous lamp such as an EL and an LED, the luminance is increased and the luminance is uniform through the first light emitting unit, and the partial light emission control and high color reproduction are possible through the second light emitting unit.

Accordingly, the present invention can provide a liquid crystal display device capable of high luminance and high color reproduction, control of partial luminance, and maintaining uniformity of luminance.

In addition, the present invention can reduce the material cost and simplify the process by forming a reflective film on the lower outer peripheral surface of the first light emitting unit instead of the diverter reflecting the vertical light of the second light emitting unit to the side.

As described above, according to the present invention, by combining a passive light-emitting lamp such as a cold cathode fluorescent lamp or a hot cathode fluorescent lamp and a self-luminous lamp such as an EL or LED, by constructing a backlight unit, high brightness, high color reproduction And it is possible to provide a high-quality liquid crystal display device through maintaining the uniformity of the brightness.

Claims (10)

A first light emitting unit in which a plurality of passive light emitting first lamps are arranged; A second light emitting unit in which a plurality of second light emitting lamps are arranged under the first light emitting unit corresponding to the first lamp; A reflection film formed on a lower outer circumferential surface of the first lamp to scatter vertical light emitted from the second lamp to the side; A reflection plate provided below the second light emitting unit; And And a light scattering means provided above the first light emitting unit. The method of claim 1, The first lamp may be one of a cold cathode fluorescent lamp (CCFL) and a hot cathode fluorescent lamp (HCFL). The method of claim 1, And the second lamp is selected from one of EL (Electro Luminescence) and LED (Light Emitting Diode). The method of claim 1, And a light guide plate interposed between the first light emitting part and the second light emitting part to guide the light incident from the second light emitting part to the first light emitting part. The method of claim 4, wherein The reflector is a backlight unit, characterized in that formed of aluminum. The method of claim 1, wherein the light scattering means,  A diffuser plate for dispersing light incident from the first and second light emitting units; A prism sheet for improving the front luminance of the light transmitted and reflected through the diffusion plate; The backlight unit of the liquid crystal display device, characterized in that consisting of a protective sheet attached to the upper prism sheet. A liquid crystal panel and a backlight unit for supplying light to the liquid crystal panel, the backlight unit, A first light emitting unit in which a plurality of passive light emitting lamps are arranged; A second light emitting unit in which a plurality of second light emitting lamps are arranged under the first light emitting unit corresponding to the first lamp; A reflection film formed on a lower outer circumferential surface of the first lamp to scatter vertical light emitted from the second lamp to the side; A reflection plate provided below the second light emitting unit; And And a light scattering means provided above the first light emitting unit. The method of claim 7, wherein The passive light emitting lamp is selected from one of a Cold Cathode Fluorescent Lamp (CCFL) and a Hot Cathode Fluorescent Lamp (HCFL). The method of claim 7, wherein The self-luminous lamp is selected from one of EL (Electro Luminescence) and LED (Light Emitting Diode). The method of claim 7, wherein And a light guide plate interposed between the first light emitting part and the second light emitting part to guide the light incident from the second light emitting part to the first light emitting part.

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