KR20080079097A - Back light unit - Google Patents

Abstract

A back light unit is provided to improve the uniformity of luminance by diversifying a shape of a reflecting plate to reflect multiple light to the both ends of an external electrode lamp. A back light unit includes a cover bottom(121), a reflector(122), a plurality of lamps(130), and an optical sheet portion(129). The cover bottom is a plate made from metal or synthetic resin. The reflector is positioned on the cover bottom. A center part of the reflector is protruded or depressed. The plurality of lamps are arranged on the reflecting plate parallel with each other. The optical sheet portion is positioned on the plurality of lamps. The optical sheet portion includes a diffusion plate(124) positioned on a vertical upper end of the lamp, a diffusion sheet(125) positioned on a upper end of the diffusion plate, a prism sheet(126) positioned on a upper end of the diffusion sheet, and a reflecting polarized film(127) positioned on a upper end of the prism sheet.

Description

Backlight Unit {BACK LIGHT UNIT}

1 is a configuration diagram of an embodiment of a general direct type backlight unit.

Figure 2 is an external configuration of one embodiment of a typical external electrode lamp (EEFL).

Figure 3 is a plan view of one embodiment showing a lamp fixing device of a direct type backlight unit using a conventional external electrode lamp.

Figure 4 is another cross-sectional view of the lamp fixing device of the direct type backlight unit using a conventional external electrode lamp.

5 is an exemplary view showing a dark line generated in a conventional direct type backlight unit.

6 and 7 are graphs showing a longitudinal luminance distribution of the external electrode lamp illustrated in FIG. 4.

8 is a configuration diagram of an embodiment of a backlight unit according to the present invention;

9 is a plan view showing a state in which the lamp fixing device of the backlight unit according to the present invention is disposed on the cover bottom.

FIG. 10 is a front view illustrating a state in which a lamp fixing device of the backlight unit illustrated in FIG. 9 is disposed at a cover bottom.

FIG. 11 is a side view illustrating a state in which a lamp fixing device of the backlight unit illustrated in FIG. 9 is disposed at a cover bottom.

12 is a diagram illustrating a tube voltage versus luminance relationship of an external electrode lamp with or without an auxiliary electrode;

13 is a cross-sectional view of an embodiment of a backlight unit according to the present invention shown in FIG. 8.

14A to 14H are exemplary views illustrating various types of reflecting plates 122 applied to the backlight unit according to the present invention shown in FIG. 8.

<Explanation of symbols for main parts of the drawings>

130: external electrode lamp 131: external electrode

132: glass tube (lamp) 151: holder

152: common electrode 153: auxiliary electrode

154: common electrode support 122: reflector

121: cover bottom

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit, and more particularly, to a backlight unit in which shapes of a lamp fixing device and a reflecting plate are modified.

Recently, as the society enters the information age, the display industry that processes and displays a large amount of information has developed rapidly.

As a result, a liquid crystal display device (LCD device) is being developed that can meet various demands of the user, such as thinning, light weight, and low power consumption, and replaces a conventional cathode-ray tube (CRT). It is attracting attention as the next generation display device.

In general, a liquid crystal display may be classified into a liquid crystal panel displaying an image largely seen by a user, and a back light unit for increasing the brightness of the image.

The liquid crystal panel has a structure in which a lower substrate and an upper substrate on which one electric field generating electrode is formed are arranged to face each other, and then a liquid crystal layer is interposed therebetween. In this case, the liquid crystal has a thin and long molecular structure, optical anisotropy having an orientation in the array, and polarization property in which the array direction changes when an electric field is artificially applied. On the other hand, the liquid crystal panel changes the arrangement direction of the liquid crystal by applying an electric field to the liquid crystal interposed between the upper substrate, the lower substrate and the field generating electrodes provided on each of them, and expresses the image with the refractive index of the changed light. However, the brightness of the image implemented only by the liquid crystal panel is very low, making it difficult for the user to identify. Accordingly, a backlight unit including a plurality of light sources is provided on the back of the liquid crystal panel to supply light to the liquid crystal panel, thereby displaying an image that can be identified by the user.

In general, the backlight unit may be classified into an edge type and a direct type according to the arrangement of the light sources. The edge type backlight unit may include a light source installed at one edge of the liquid crystal display, and a plurality of light incident from the light source may be applied to the light guide plate. Irradiates the liquid crystal display panel through an optical sheet of light, and the direct-type backlight unit unit arranges a plurality of light sources directly below the liquid crystal display device, and transmits light incident from the light sources through the diffusion plate and the plurality of optical sheets. Investigate the panel.

1 is a configuration diagram of an embodiment of a general direct type backlight unit.

That is, as shown in FIG. 1, a general direct type backlight unit includes a cover bottom 21 on a plate made of a metal or a synthetic resin material, and a white or silver metal material seated on a cover bottom. And a reflector 22 on a plate, a lamp 23 arranged in parallel on the reflecting plate, and an optical sheet portion 29 seated on the plurality of lamps. At this time, the inner surface of the cover bottom 21 is coated with a material (reflective plate) having a high optical reflectivity so that the light emitted backward from the lamp is reflected toward the front (to the liquid crystal panel side) to effectively use the luminous flux emitted from the lamp. Thereby increasing efficiency (efficiency expressed as the ratio of the luminous flux emitted from the light emitting surface to the luminous flux emitted from the lamp). Since the general direct type backlight unit illustrated in FIG. 1 may implement a high brightness by connecting a plurality of lamps in parallel, it is widely used as a backlight unit of a large screen liquid crystal panel as compared to an edge type backlight unit.

On the other hand, the lamp 23 used as a light source in the direct backlight unit is a cold cathode fluorescent lamp (CCFL) (hereinafter, simply referred to as 'CCFL') or an external electrode lamp (EEFL: External Electrode Fluorescent Lamp) (Hereinafter, simply referred to as 'EEFL') is used. However, EEFL, which can be driven by connecting several lamps in parallel, is simpler in wiring and fixture assembly than in direct-type backlight unit using CCFL which connects inverter to each lamp. It is widely used because of the low number of people, equipment, and defective rate.

2 is a diagram illustrating an external configuration of a typical external electrode lamp (EEFL).

That is, as shown in FIG. 2, the external electrode lamp (EEFL) 30 is formed of a transparent tube and is coated at both ends of the glass tube 32 and the glass tube coated with a phosphor on an inner wall thereof. It includes two external electrodes 31 for receiving power and transmitting the power to the glass tube.

The external electrode lamp (EEFL) 30 as described above applies a fluorescent material to the inner surface of the cylindrical electrodeless glass tube 32, injects and discharges a discharge gas therein, and then seals the external electrode 31 at both ends. As a result, a continuous high frequency voltage or a pulsed high frequency voltage is applied to the external electrode 31 to light it. At this time, the high frequency voltage applied to the pair of external electrodes 31 generates a discharge in the inner space of the glass tube fitted to the external electrode, and the ultraviolet rays generated by the discharge cause the fluorescent material applied to the inner surface of the glass tube 32 to emit light. The light generated by the discharge is emitted outside the glass tube 32, and the light is irradiated onto the irradiated object.

3 is a plan view showing an embodiment of a lamp fixing apparatus of a direct type backlight unit using a conventional external electrode lamp. In addition, Figure 4 is another cross-sectional view of the lamp fixing device of the direct type backlight unit using a conventional external electrode lamp, Figure 5 is an exemplary view showing a dark line generated in the conventional direct type backlight unit. 6 and 7 are graphs showing the longitudinal luminance distribution of the external electrode lamp illustrated in FIG. 4.

First, as shown in FIG. 3, the lamp fixing device 40 is arranged at both sides of the external electrode 31 of the EEFL in a state fixed to the cover bottom 21 to receive power from the outside. The common electrode part 41 and the holder are fixed to the common electrode part and are configured in a ring shape to fix the external electrode of the EEFL.

On the other hand, in the EEFL as described above, the tube voltage is higher than the CCFL, and the tube voltage needs to be increased to increase the brightness. However, when the tube voltage exceeds 2000 Vrms, ozone is generated.

As a method for reducing the tube voltage, the method of lengthening the external electrode 31 is best. However, the method has a limitation because the size of the bezel (border) of the LCD is limited. Thus, a method as shown in FIG. 4 has been proposed in which a portion of the external electrode 31 is exposed inside the backlight unit. But. In the case of applying this method, when the length of the exposed external electrode 31 becomes long, there is a problem that dark dark lines 35 are generated around the side support 28 of the backlight unit as shown in FIG. 5.

That is, the external electrode fluorescent lamp is a method using wall-charge of glass tube, and the capacitance of the external electrode 31 is proportional to the contact area between the glass tube 32 and the external electrode 31 and Since it is inversely proportional to the thickness, the longer the length of the external electrode 31 wrapped along the outer circumferential surface of the glass tube, the higher the brightness can be obtained. Therefore, in order to achieve high brightness and high efficiency in the display panel, the external electrode 31, which is a non-light emitting area, should occupy a predetermined portion or more. However, when the length of the external electrode 31 is increased, the effective light emitting surface in the glass tube (lamp) is relatively reduced, and the non-light emitting area is increased, and when it is substantially employed in the backlight, the external electrode 31 There is a problem in that an edge region of the display panel corresponding to the non-light emitting region, that is, a bezel 28 region having a rectangular frame shape as shown in FIG. 5 surrounding the image display region is widened. As a result, in order to configure a display device employing an external electrode lamp (EEFL) with an image display area having the same size as a conventional cold cathode tube lamp (CCFL) model, it is necessary to increase the outer dimensions of the bezel area, which is a non-display area. It is done.

In detail, when the length of the external electrode 31 is increased for high brightness and high efficiency, and the external electrode 31 is configured to extend into the image display area as shown in FIG. 4, the external electrode 31 extends. The light emitted from the glass tube 32 is not transmitted to the liquid crystal panel at the upper end of the portion, and as a result, the dark line 35 is generated as shown in FIG. 5. That is, the dark line 35 becomes a portion where light is not transmitted by the external electrode 31 extending into the image display area. Therefore, in order to cover the female line 35 while maintaining the external size of the bezel 28 having a rectangular frame shape surrounding the outside of the liquid crystal panel, the bezel 28 should be further extended inward, in this case The area for displaying an image is narrowed. On the contrary, in order to use the above-described method while keeping the image display area at the same size as in the related art, since the thickness of the outer portion of the bezel 28 is increased, there is a problem that the overall size of the liquid crystal display device is increased.

The above problem is due to the fact that the luminance in the longitudinal direction of the lamp is not uniform. That is, as shown in FIG. 6, in a general lamp including an external electrode lamp, the brightness of the center of the lamp is bright and the brightness of the left and right ends is lowered. In addition, depending on the characteristics of the lamp, as shown in FIG. 7, the luminance at the center may be lower, and the luminance at the left and right ends may be bright. On the other hand, the conventional liquid crystal display device to reflect the light emitted to the lower end of the lamp 30 in the direction of the liquid crystal panel placed on the upper end of the lamp, in order to cancel the non-uniformity of the brightness as described above, FIG. 4 As shown in the drawing, the reflector 22 is included. However, since the flat reflector 22 as shown in FIG. 4 cannot efficiently reflect light toward the external electrode 31 of the lamp 30, the external electrode 31 is positioned. There is a problem that can not increase the brightness of the top. That is, the flat plate reflector 22 may perform a function of diffusely reflecting the light emitted to the bottom of the lamp to reflect the light to the top of the lamp, but because it is not a structure that can effectively reflect the light to the left and right ends of the lamp, As described above, the problem that the luminance of the left and right ends of the lamp are lowered by the external electrode 31 has not been solved.

Accordingly, an object of the present invention for solving the above problems is to provide a backlight unit including an auxiliary electrode for driving an external electrode lamp and a reflector plate shaped to reflect light to left and right ends of the external electrode lamp. It is.

In order to achieve the above object, the backlight unit according to the present invention, the lamp fixing device including an auxiliary electrode for auxiliary driving the external electrode lamp; And a reflective structure configured to reflect light toward the center or both ends of the external electrode lamp.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

8 is a configuration diagram of an embodiment of a backlight unit according to the present invention.

As shown in FIG. 8, the backlight unit according to the present invention is mounted on a cover bottom 121 on a plate made of a metal or a synthetic resin material, and is seated on a cover bottom, and has a central portion raised or recessed. The reflector 122 is configured to include a plurality of lamps 130 arranged in parallel on the reflecting plate and the optical sheet portion 129 seated on the plurality of lamps.

The inner surface of the cover bottom 121 is coated with a material having a high optical reflectivity (reflective plate), so that the light emitted backward from the lamp is reflected toward the front (to the liquid crystal panel side) to effectively use the luminous flux emitted from the lamp. (Efficiency expressed as the ratio of the luminous flux emitted from the light emitting surface to the luminous flux emitted from the lamp) is increased. In addition, the cover bottom 121 may be configured in the same form as the reflective plate 122 to be described below with reference to FIGS. 13 and 14.

The optical sheet unit 129 includes a diffusion plate 124 seated on the vertical top of the lamp 130, a diffusion sheet 125 seated on the top of the diffusion plate, and a prism sheet 126 seated on the top of the diffusion sheet. And a reflective polarizing film (MOF) 127 having a multilayer structure seated on top of the prism sheet. In this case, the diffusion plate and the diffusion sheet are used to diffuse the direct light and the reflected light from the fluorescent lamp to the front to ensure uniform luminance throughout the light emitting surface. Meanwhile, a liquid crystal panel (not shown) manufactured by a separate process is mounted on the upper end of the optical sheet unit 129, and the liquid crystal panel is coupled to the direct type backlight unit through a top frame (not shown). As a result, the liquid crystal display device is completed.

An external electrode lamp (EEFL) (hereinafter, simply referred to as “EEFL”) is used as the lamp 130. A lamp fixing device for fixing the external electrode lamp to the cover boat 121 will be described in detail with reference to FIGS. 9 to 12.

The reflective plate 122 is a component seated on the cover bottom 121, and is made of a metallic material of white or silver color, and is formed in a form in which a central portion is raised or recessed. The function and configuration of the reflector 122 will be described in detail with reference to FIGS. 13 and 14 below.

FIG. 9 is a plan view illustrating a state in which a lamp fixing device of the backlight unit according to the present invention illustrated in FIG. 8 is disposed in a cover bottom. FIG. 10 is a front view illustrating a state in which a lamp fixing device of the backlight unit illustrated in FIG. 9 is disposed at a cover bottom, and illustrates an external electrode lamp (EEFL) 130 connected thereto. In addition, FIG. 11 is a side view illustrating a state in which a lamp fixing device of the backlight unit illustrated in FIG. 9 is disposed at a cover bottom, and illustrates a state in which an external electrode lamp is connected. FIG. 12 is a diagram illustrating a tube voltage versus luminance relationship of an external electrode lamp according to the presence or absence of an auxiliary electrode.

As shown in FIG. 9, the lamp fixing device applied to the present invention surrounds the external electrode of the external electrode lamp and is a holder 151 for transmitting a common voltage to the external electrode, the external electrode lamp mounted on the backlight unit. The number of holders is arranged at intervals of the external electrode lamps, and the common electrode 152 for receiving the common voltage from the outside and transmitting them to the holder and the common electrodes in the longitudinal direction of the external electrode lamps fixed by the holders. It includes auxiliary electrodes 153 protruding from the.

First, the holder 151 is coupled to the common electrode 152, one side of the open ring shape, the external electrode through the open portion in the state coupled to the common electrode 152 (131) can be fixed as if wrapped. That is, the holder 151 may be configured using a socket structure to fix the external electrode 131 in the common electrode 152.

In addition, the auxiliary electrode 153 is disposed in a one-to-one relationship with the holder 151 and extends from the common electrode 152 in the longitudinal direction of the external electrode 131 fixed to the holder 151. It is protruding. That is, the common electrode 152 of the lower portion where the holder 151 is positioned protrudes to form the auxiliary electrode 153. The wall charge is applied to the glass tube 132 by the auxiliary electrode 153. Since the auxiliary electrode 153 may perform a function of the external electrode 131 as it may be generated. In this case, the auxiliary electrode 153 is preferably formed longer than the length of the external electrode 131 of the external electrode lamp.

In addition, the height or thickness of the holder is preferably adjusted so that the external electrode 131 or the glass tube 132 and the auxiliary electrode 153 can be maintained at a predetermined interval G. In this case, the distance G between the external electrode 131 or the glass tube (lamp) 132 and the auxiliary electrode 153 is preferably 0 mm to 10 mm.

On the other hand, the common electrode 152, the holder 151 and the auxiliary electrode 153 are all made of a conductor, the cover bottom 121 is also made of a metal material, the common electrode 152 and the auxiliary The common electrode 152 and the auxiliary electrode 153 may be supported by the common electrode pedestal 154 of an insulating material to insulate the electrode 153 from the cover bottom 121 or the reflective plate 122. That is, the common electrode 152 and the auxiliary electrode 153 may be directly fixed to the cover bottom 121 or the reflecting plate 122, but the cover bottom 121 is formed by the common electrode pedestal 154 of an insulating material. Or fixed to the reflector plate 122. In other words, since the high voltage is applied to the auxiliary electrode 153 or the common electrode 152 together with the external electrode 131 of the external electrode lamp, a lower portion of the common electrode 152 or the auxiliary electrode 153 may be used for insulation. The common electrode pedestal 154 made of an insulator may be installed as shown in FIG. 10, wherein the shape of the common electrode pedestal 154 may be formed to cover only a portion of the lower portion of the auxiliary electrode 153 as shown in the left side of FIG. 10. The right side may be formed to cover the entire auxiliary electrode 153 as shown on the right side.

In addition, since the reflecting plate 122 is generally attached to the cover bottom 121 to reflect the light emitted from the external electrode lamp, the common electrode 152 or the common electrode pedestal 154 may also be formed of the cover bottom. It comes in contact with the reflector.

On the other hand, in order to support the function of the reflective plate 122, it is preferable to coat a reflective material capable of functioning as the reflective plate on the auxiliary electrode 153, or to configure the auxiliary electrode of a conductive reflective material. . That is, in the liquid crystal display device, it is most important to efficiently use the light of the external electrode lamp EEFL. Therefore, by using the upper surface of the auxiliary electrode 153 disposed at the lower end of the external electrode lamp EEFL as a reflector. It is possible to maximize the luminous efficiency of the external electrode lamp (EEFL).

In the lamp fixing apparatus of the backlight unit according to the present invention as described above, an auxiliary electrode 153 capable of performing the same function as the external electrode 131 of the external electrode lamp is added to the common electrode 152. .

That is, since the auxiliary electrode 153 performs a function of assisting the function of the external electrode 131, in the case of obtaining the same brightness as that in the absence of the auxiliary electrode 153, When there is no auxiliary electrode 153, a tube voltage lower than the tube voltage to be applied to the external electrode 131 may be applied to the external electrode 131. In addition, in the case of obtaining the same luminance, it is possible to apply a low tube voltage to the external electrode 131 as described above, so that the length of the external electrode 131 is long to apply the high tube voltage. Since there is no need, the present invention is also applicable to a Narroe bezel structure.

On the other hand, Figure 12 shows the characteristics of the external electrode lamps before and after using the lamp fixing device of the backlight unit according to the present invention, when comparing the tube voltage at the same brightness 12000 [nit] when the auxiliary electrode 153 is used is about 1570 [Vrms], and when not used, it is about 1650 [Vrms] and about 80 [Vrms] is lowered.

At this time, the effect of the auxiliary electrode 153 is the distance between the length of the auxiliary electrode and the external electrode lamp (G), the length of the glass tube (lamp) 132 of the external electrode lamp, the length of the external electrode 131, the drive inverter (inverter) Although it may vary depending on the size, the influence of the length of the auxiliary electrode 153 and the gap G is greatest.

FIG. 13 is a cross-sectional view of an embodiment of the backlight unit according to the present invention illustrated in FIG. 8, and a detailed configuration of the lamp fixing device described above is not shown.

As described above, the backlight unit according to the present invention does not need to extend the length of the external electrode 131 even in the case of using an external electrode lamp. The pattern is not generated, and thus, it is possible to apply to a Narroe bezel structure.

However, it is a general phenomenon that a difference occurs in the luminance of the center portion and the end portion of the lamp. In the case of the external electrode lamp 130 applied to the present invention, the luminance difference between the center portion and the end portion occurs. That is, the center portion of the glass tube 132 is bright, the left and right ends have a relatively low luminance compared to the center portion, and in the case of using the auxiliary electrode as described in FIGS. The luminance difference between the ends may appear larger.

Accordingly, in the backlight unit according to the present invention, as shown in FIG. 13, the heights of both ends adjacent to the external electrode 131 are configured to be different from the height of the center portion adjacent to the glass tube 132. The reflecting plate 122 is used.

That is, when the height of the central portion of the reflecting plate 122 is formed relatively higher than the height of both ends of the reflecting plate, so that the inclined portion of the reflecting plate is configured to face both ends of the external electrode lamp 130, the external electrode Among the light emitted from the lamp 130 will be a lot of light reflected to both ends of the external electrode lamp 130, so that the brightness of the upper end of both ends of the external electrode lamp 130 compared to the central portion It doesn't get too low.

14A to 14H are exemplary views illustrating various types of reflecting plates 122 applied to the backlight unit according to the present invention illustrated in FIG. 8. However, the reflector may also be implemented as a cover bottom 121, as will be described below. Therefore, the reflective plate 122 or the cover bottom 121 having the function and configuration of the reflective plate to be described below are collectively referred to as a reflective structure.

First, a case in which the reflective structure applied to the present invention is the reflective plate 122 will be described.

That is, the shape of the reflector plate 122 applied to the present invention may be a form in which the height of the central portion of the reflector plate 122 rises relatively higher than the height of both ends of the reflector as described with reference to FIG. 13. The present invention is not limited thereto, and thus, the shape of the reflector 122 may be configured in various forms as shown in FIGS. 14A to 14H.

First, FIG. 14A illustrates the shape of the reflector plate 122 described with reference to FIG. 13. As described above, the center portion is formed in a form in which the center portion is raised by a predetermined height h from both ends. Therefore, a large amount of light of the external electrode lamp 130 incident to the inclined portion is directed toward both ends of the external electrode lamp 130, that is, toward both external electrodes 131, and thus, the external electrode 131. The brightness at the top is increased.

Next, FIG. 14B is a shape in which both ends are partially deformed in the form of the reflecting plate 122 shown in FIG. 14A, and the center portion is raised by a predetermined height h from both ends, and both ends are It is comprised by the plane which has a predetermined width v. In the above configuration, the height h and the width v may be determined in consideration of light distribution characteristics of the external electrode lamp (hereinafter, the same).

Next, FIG. 14C is formed to round the overall appearance of the reflector 122 shown in FIG. 14A, and this configuration may also be formed in consideration of light distribution characteristics of the external electrode lamp.

Next, FIG. 14D is formed to round the line of the central portion of the reflecting plate 122 shown in FIG. 14B as a whole, while partially modifying the shape of both ends.

In addition, the reflecting plate 122 according to the present invention may be configured in a form in which the bent portion of the center portion and the end portion is rounded in FIGS. 14A, 14B, and 14D.

Meanwhile, as described above, the luminance of the center portion may be lower than the luminance of both ends according to the type, characteristic, and driving condition of the external electrode lamp. In this case, as shown in FIGS. 14E to 14H, The reflection plate 122 may be configured such that the center portion is recessed in comparison with both ends.

In addition, in the above, various forms of the reflective plate 122 mounted on the cover bottom 121 have been described, but the backlight unit according to the present invention faces the external electrode lamp 130 instead of removing the reflective plate 122. While the inner surface of the cover bottom 121 is coated with a material having a high reflectance, the beam may be configured as shown in FIGS. 14A to 14H.

That is, if the inner surface of the cover bottom 121 is coated with a material having a high reflectance, the cover bottom 121 may perform a function of a reflecting plate, in which case the cover bottom 121 is shown in FIGS. 14A to 14. It may be configured in the form as shown in 14h.

The lamp fixing apparatus of the backlight unit according to the present invention as described above, by forming an auxiliary electrode that can assist the function of the external electrode of the external electrode lamp in the common electrode, to minimize the non-light-emitting area due to the external electrode, There is an excellent effect that the length of the external electrode lamp can be reduced.

In addition, the present invention has an excellent effect that the luminance uniformity can be improved by varying the shape of the reflector so that a lot of light can be reflected to both ends of the external electrode lamp.

In addition, the present invention has an excellent effect of reducing the tube voltage of the external electrode lamp by using the auxiliary electrode.

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 (11)

A lamp fixing device including an auxiliary electrode for auxiliary driving of the external electrode lamp; And And a reflective structure configured to reflect light toward the center or both ends of the external electrode lamp. The method of claim 1, The reflective structure, The cover bottom may be a cover bottom in which a reflector is removed, and the cover bottom is coated with a reflective material. The method of claim 1, The reflective structure, And a reflector plate mounted on the cover bottom. The method of claim 1, The reflective structure, And a height of both ends adjacent to the external electrode of the external electrode lamp is different from that of a central portion adjacent to the glass tube of the external electrode lamp. The method of claim 1, The reflective structure, And a center portion adjacent to a glass tube of the external electrode lamp is raised or recessed in comparison with both ends adjacent to the external electrode of the external electrode lamp. The method of claim 1, The lamp fixing device, A holder surrounding the external electrode of the external electrode lamp and transmitting a common voltage to the external electrode; And The holder as many as the number of the external electrode lamps are disposed for each of the external electrode lamp intervals, the backlight unit including a common electrode for receiving a common voltage from the outside to transmit to the holder. The method of claim 6, The holder is a backlight unit, characterized in that the ring-shaped open one side that is not attached to the common electrode. The method of claim 6, And the auxiliary electrode is formed to be longer than the length of the external electrode. The method of claim 6, The backlight unit further comprises a common electrode support of an insulating material for supporting the common electrode and the auxiliary electrode. The method of claim 1, The backlight unit of the auxiliary electrode is made of a reflective material capable of reflecting light emitted from the external electrode lamp to the upper end of the external electrode lamp. The method of claim 6, The auxiliary electrode, And a projection protruding from the common electrode in a longitudinal direction of the external electrode lamps fixed by the holder.

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