KR20070071086A - Backlight unit and display device having the same - Google Patents

Abstract

A backlight unit and a display device having the same are provided to improve the efficiency and brightness of a lamp by forming a major diameter longer than a minor diameter and thus forming the maximum discharging space. A display device includes a liquid crystal panel(20). A bar type lamp(50) irradiates light to a rear of the liquid crystal panel. A major diameter of an external diameter of a section cut in a vertical direction of an extension direction of the lamp is longer than a minor diameter. A major diameter of an external diameter of a section cut in a vertical direction of an extension direction of the lamp is 2mm to 3mm. A minor diameter of an external diameter of a section cut in a vertical direction of an extension direction of the lamp is 1.2mm to 2mm.

Description

BACKLIGHT UNIT AND DISPLAY DEVICE HAVING THE SAME}

1 is an exploded perspective view of a display device according to a first embodiment of the present invention;

2 is a cross-sectional view along the longitudinal direction of the lamp according to the first embodiment of the present invention;

3 is a cross-sectional view along the vertical in the longitudinal direction of the lamp according to the first embodiment of the present invention;

4 is a cross-sectional view of a lamp according to a second embodiment of the present invention.

Explanation of Signs of Major Parts of Drawings

10: top chassis 20: liquid crystal panel

30: mold frame 40: optical sheet

50: lamp 60: reflective sheet

70: backlight unit 80: bottom chassis

The present invention relates to a backlight unit and a display device including the same, and more particularly, to a backlight unit with improved brightness and a display device including the same.

Recently, a flat panel display such as a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting diode (OLED) has been developed in place of the conventional CRT. The liquid crystal display device includes a thin film transistor substrate, a color filter substrate, and a liquid crystal panel in which a liquid crystal layer is positioned between both substrates. Here, since the liquid crystal panel is a non-light emitting device, the backlight unit may be positioned on the rear surface of the liquid crystal panel.

The lamp used for the backlight unit of the liquid crystal display device largely includes a linear light source, a surface light source and a point light source. Here, the cold light source includes a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), etc., and is mainly used as a backlight unit because of its price competitiveness.

The lamp includes a glass tube and electrodes provided inside both ends of the glass tube. The discharge gas of mercury, argon, and neon is enclosed inside the glass tube. The inner surface of the glass tube is coated with a fluorescent film. When a high voltage is applied to both electrodes of the lamp, electron emission is caused by the electric field from the electrode. The term cold cathode is given because the electron emission is not by heat but by electric field. The emitted electrons excite mercury and excite mercury to emit ultraviolet rays, which are converted into visible light by the fluorescent film and emitted to the outside.

However, since the lamp usually has a circular cross section, a bright line is visually recognized in the liquid crystal panel. In addition, there is a problem that the brightness of the lamp is relatively poor because the internal space of the lamp in which the discharge occurs is not manufactured to an optimal size.

Accordingly, it is an object of the present invention to provide a display device with improved luminance.

Another object of the present invention is to provide a backlight unit with improved brightness.

The above object is, according to the present invention, a liquid crystal panel; It includes a rod-shaped lamp for irradiating light to the back of the liquid crystal panel, the long diameter of the outer diameter of the cross section cut in the transverse direction of the lamp is longer than the diameter is achieved by a display device.

Here, the long diameter of the inner diameter of the cross section cut in the transverse direction of the lamp may be 2mm to 3mm and the diameter may be 1.2mm to 2mm.

The inner diameter of the cross section cut in the transverse direction of the lamp may be a circle having a diameter of 2 mm to 2.5 mm.

In addition, the lamp may be arranged such that the long diameter of the outer diameter is parallel to the liquid crystal panel.

The liquid crystal panel may further include a light guide plate disposed on a rear surface of the liquid crystal panel, and the lamp may be disposed such that the long diameter thereof is parallel to one side of the light guide plate.

An object of the present invention is a bar-shaped glass tube of which the long diameter of the outer diameter of the cross section cut in the transverse direction is longer than the diameter; Electrodes provided at both ends of the glass tube; It is achieved by a backlight unit comprising a discharge gas filling the inside of the glass tube.

In addition, the long diameter of the inner diameter of the cross section cut in the transverse direction of the lamp may be 2 mm to 3 mm and the jar diameter may be 1.2 mm to 2 mm.

In addition, the diameter of the inner diameter of the cross section cut in the transverse direction of the lamp may be a circle of 2mm to 2.5mm.

Hereinafter, a first embodiment according to the present invention will be described with reference to FIGS. 1 is an exploded perspective view of a display device according to a first embodiment of the present invention, FIG. 2 is a longitudinal sectional view of the lamp according to the first embodiment of the present invention, and FIG. 3 is a view of the lamp according to the first embodiment of the present invention. Cross section view. In the following description, a liquid crystal display device is described as an example among various display devices. However, the present invention is not limited thereto and may be applied to other display devices to which a backlight unit can be applied.

As shown in FIG. 1, the liquid crystal display device 1 according to the first embodiment of the present invention includes a liquid crystal panel 20 for forming an image, a driver 25 for driving the liquid crystal panel 20, The mold frame 30 supporting the edge of the liquid crystal panel 20, the backlight unit 70 for irradiating light to the rear surface of the liquid crystal panel 20, the bottom chassis 80 for accommodating the backlight unit 70, and The top chassis 10 is coupled to the bottom chassis 80 to cover the front surface of the liquid crystal panel 20.

The liquid crystal panel 20 is injected between the thin film transistor substrate 21, the color filter substrate 22 attached to face the thin film transistor substrate 21, and the thin film transistor substrate 21 and the color filter substrate 22. It includes a liquid crystal (not shown). The liquid crystal (not shown) is injected between the thin film transistor substrate 21 and the color filter substrate 22 and then sealed. In addition, the liquid crystal panel 20 further includes a front polarizer (not shown) attached to the front surface of the color filter substrate 22 and a rear polarizer (not shown) attached to the rear surface of the thin film transistor substrate 21. The liquid crystal panel 20 is arranged in a matrix form of the liquid crystal cells forming a pixel unit, and forms an image by adjusting the light transmittance of the liquid crystal cells according to the image signal information transmitted from the driver 25.

In the thin film transistor substrate 21, a plurality of gate lines and a plurality of data lines are formed in a matrix form, and pixel electrodes and thin film transistors (TFTs) are formed at intersections of the gate lines and the data lines. The signal voltage applied through the thin film transistor is applied to the liquid crystal (not shown) by the pixel electrode, and the liquid crystal (not shown) is aligned according to the signal voltage to determine the light transmittance.

The color filter substrate 22 is formed with a common filter made of a color filter made of RGB pixels through which light passes and a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). . The color filter substrate 22 has a smaller area than the thin film transistor substrate 21, and a portion where the color filter substrate 22 and the thin film transistor substrate 21 overlap with each other becomes a display area of the liquid crystal panel 20 and does not overlap. The peripheral area of the display area becomes the non-display area of the liquid crystal panel.

The front polarizer and the rear polarizer are arranged to cross-polarize each other, the rear polarizer polarizes the light incident on the liquid crystal panel 20, and the front polarizer serves as an analyzer.

One side of the thin film transistor substrate 21 is provided with a driver 25 for applying a drive signal. The driver 25 includes a flexible printed circuit board (FPC) 26, a driving chip 27 mounted on the flexible printed circuit board 26, and a circuit board connected to the other side of the flexible printed circuit board 26. 28). The driver 25 shown illustrates a method of a chip on film (COF), and other known methods such as a taper carrier package (TCP) and a chip on glass (COG) may be used. In addition, the driver 25 may be mounted on the thin film transistor substrate 21.

The mold frame 30 is formed along the edge of the liquid crystal panel 20 and has a substantially rectangular shape, and supports the liquid crystal panel 20 spaced apart from the backlight unit 70.

The backlight unit 70 disposed on the rear surface of the liquid crystal panel 20 includes an optical sheet 40, a lamp 50, and a reflective sheet 60.

The optical sheet 40 is located on the rear surface of the liquid crystal panel 20 and includes a diffusion sheet 45, a prism sheet 43, and a protective sheet 41. Here, the diffusion sheet 45 is composed of a base plate and a bead-shaped coating layer formed on the base plate. The diffusion sheet 45 diffuses the light from the lamp 50 to supply the liquid crystal panel 20. The diffusion sheet 45 may be used by overlapping two or three sheets. Since the diffusion sheet 45 is not supported by the light guide plate, unlike the edge type, the diffusion sheet 45 may be somewhat thicker for strength. The prism sheet 43 is formed with a triangular prism-like prism on an upper surface thereof. The prism sheet 43 collects light diffused from the diffusion sheet 45 in a direction perpendicular to the plane of the upper liquid crystal panel 20. Two prism sheets 43 are usually used, and the micro prisms formed on each prism sheet 43 are at an angle. Light passing through the prism sheet 43 almost passes vertically to provide a uniform luminance distribution. The uppermost protective sheet 41 protects the prism sheet 43 that is weak to scratches.

As shown in FIG. 2, the lamp 50 includes a glass tube 51 forming an appearance, a lamp electrode 53 provided at both ends of the glass tube, and a lamp wire 55 connected to the lamp electrode 53. And a fluorescent film 57 applied to the outer wall surface of the glass tube 51, and a discharge gas 59 filling the inside of the glass tube 51. The lamp electrode 53 is connected to an inverter (not shown) through the lamp wire 55 to receive a voltage. The discharge gas 59 of the lamp 50 according to the present invention contains mercury. In addition, the discharge gas 59 may further include argon and neon in order to facilitate discharge. When a high voltage is applied to both lamp electrodes 53 of the lamp 50, electron emission by the electric field occurs from the lamp electrode 53. The emitted electrons excite mercury and excite mercury to emit ultraviolet rays, which are converted into visible light by the fluorescent film 57 and are emitted to the outside.

As shown in Fig. 3, the lamp 50 according to the first embodiment of the present invention has a rod shape, and the long diameter of the cross section cut in the transverse direction of the extension direction of the lamp 50 is longer than the diameter. That is, the outer diameter and the inner diameter of the cross section of the glass tube 51 have a cross-sectional shape whose long diameter is longer than the diameter of the glass, and the inner diameter of the glass tube 51 forming the discharge space has a diameter d1 of 1.2 mm to 2 mm and a long diameter. (d2) may be 2mm to 3mm. This is to form an optimal discharge space. If the discharge space is too large, the path of the generated ultraviolet rays reaches the fluorescent film 57 may be long, and thus ultraviolet rays may be scattered in the middle or collide with other components. In addition, if the discharge space is too small, the lifetime of the lamp 50 is reduced, the absorption occurs between the ultraviolet rays, the efficiency and brightness is reduced. As a result, the efficiency and brightness of the lamp 50 are lowered. As a result of studying the optimum discharge space size in consideration of this shape, it was confirmed that the cross-sectional size of the optimum discharge space is 1.2mm to 2.4mm, more preferably 1.2mm to 2mm in diameter. Therefore, in the present invention, in order to improve the efficiency and brightness of the lamp 50, the diameter d1 is manufactured in a size of 1.2 mm to 2 mm, and in order to improve the life of the lamp 50, the long diameter d2 is 2 mm to Produce 3mm. Since the light of the elliptical lamp 50 is mainly emitted from a flat curved surface (single diameter direction), the size of the jar d1 is manufactured to form an optimal discharge space. On the other hand, as the discharge space is reduced, the life of the lamp can be relatively reduced, in the present invention by making the size of the long diameter (d2) relatively large to compensate for this. As a result, the efficiency and brightness of the lamp 50 are improved, and more specifically, the brightness is improved by about 10% to 15%.

In addition, since the light of the elliptical lamp 50 is mainly emitted from a flat curved surface (in the diameter direction), the elliptical lamp 50 of the direct type backlight unit 70 has a long diameter d2 parallel to the liquid crystal panel 20. It is preferably arranged to. On the other hand, although not shown, in the edge type backlight unit 70, the long diameter d2 of the elliptical lamp 50 is preferably disposed to be parallel to the incident surface of the light guide plate (not shown). The glass tube 51 may be injection molded into an oval shape, or may be formed into an oval shape by applying pressure to the circular tube before forming the lamp electrode 53 after the circular tube is manufactured.

The reflective sheet 60 is positioned between the lamp 50 and the bottom chassis 80 to reflect the light of the lamp 50 and to supply the light toward the diffusion film 45. The reflective sheet 60 may be made of polyethylene terephthalate (PET) or polycarbonate (PC).

Side molds 61 are located at both sides of the bottom chassis 80. More specifically, the ends of the lamp 50, which is positioned at both sides of the lamp 50 in the longitudinal direction, and inside the side mold 61, is provided with the lamp electrode 53 is inserted. The side mold 61 is provided with an insertion hole 62 into which the respective lamps 50 are inserted.

The bottom chassis 80 accommodates the backlight unit 70.

The top chassis 10 has a display window to expose the effective surface of the liquid crystal panel 20 to the outside, and is coupled to the bottom chassis 80.

Hereinafter, a liquid crystal display according to a second exemplary embodiment of the present invention will be described with reference to FIG. 4. Hereinafter, only the characteristic parts distinguished from the first embodiment will be described and described, and the descriptions omitted will be in accordance with the first embodiment and known techniques. 4 shows a cross section of a lamp according to a second embodiment of the invention. In the second embodiment of the present invention, for the convenience of description, the same components will be described with reference to the same reference numerals.

The liquid crystal display according to the second exemplary embodiment of the present invention includes a liquid crystal panel 20 and a backlight unit 70 for irradiating light to the rear surface of the liquid crystal panel 20, and the backlight unit 70 includes a lamp 50. It includes. In the lamp 50 according to the second embodiment, as shown in Fig. 4, the long diameter of the outer diameter of the cross section cut in the transverse direction of the lamp 50 is longer than the diameter, and the inner diameter has a circular shape. . Here, the inner diameter of the glass tube 51 forming the discharge space may have a diameter d3 of 2 mm to 2.5 mm. This is made in consideration of the life of the lamp 50 while forming the optimum discharge space.

As described above, according to the present invention, a backlight unit having improved luminance and a display device including the same are provided.

Claims (8)

A liquid crystal panel; It includes a rod-shaped lamp for irradiating light to the back of the liquid crystal panel, And the long diameter of the outer diameter of the cross section cut in the transverse direction of the lamp is longer than the diameter. The method of claim 1, The long diameter of the inner diameter of the cross section cut in the transverse direction of the lamp extends from 2mm to 3mm and the diameter is from 1.2mm to 2mm. The method of claim 1, The inner diameter of the cross section cut in the transverse direction of the lamp is a diameter of 2mm to 2.5mm cause. The method according to claim 2 or 3, And the lamp is arranged such that the long diameter of the outer diameter is parallel to the liquid crystal panel. The method according to claim 2 or 3, Further comprising a light guide plate disposed on the back of the liquid crystal panel, And the lamp has a long diameter parallel to one side of the light guide plate. A glass tube having a rod shape, the long diameter of the outer diameter of the cross section cut in the transverse direction longer than the diameter; Electrodes provided at both ends of the glass tube; And a discharge gas filling the inside of the glass tube. The method of claim 6, The long diameter of the inner diameter of the cross section cut in the transverse direction of the lamp extending direction is 2mm to 3mm and the diameter of the backlight unit is 1.2mm to 2mm. The method of claim 6, And a diameter of 2 mm to 2.5 mm of the inner diameter of the cross section cut in the transverse direction of the lamp.

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