WO2007052967A1

WO2007052967A1 - Surface light source device and backlight unit having the same

Info

Publication number: WO2007052967A1
Application number: PCT/KR2006/004545
Authority: WO
Inventors: Hyun Sook Kim; Woo Seok Kang; Jin Wook Shin; Kil Ho Kim; Won Ho Jung
Original assignee: Samsung Corning Co., Ltd.
Priority date: 2005-11-04
Filing date: 2006-11-02
Publication date: 2007-05-10
Also published as: TW200719059A

Abstract

Provided is a surface light source device for a liquid crystal display device with a large screen. The surface light source device includes: a main body having an inner space where a discharge gas is provided; at least one main partition wall for partitioning the inner space into a plurality of discharge spaces; and an electrode for applying a discharge voltage to the discharge gas, wherein a transverse length of the main body is longer than a vertical length of the main body, and the main partition wall is formed in a vertical direction.

Description

SURFACE LIGHT SOURCE DEVICE AND BACKLIGHT UNIT

HAVING THE SAME

Technical Field

[I] The present invention relates to a surface light source device and a backlight unit having the same; and more particularly, to a surface light source device for a liquid crystal display device with a large screen and a backlight unit having the same.

[2]

Background Art [3] A liquid crystal display (LCD) device displays images by controlling the amount of light using liquid crystals injected between a thin film transistor (TFT) substrate and a color filter substrate. Due to various advantages of an LCD device, the demand for an

LCD device has highly increased. [4] However, since an LC panel itself can not emit light, the LCD device needs a light source such as a backlight unit to provide light to the LC panel. The image quality of the LCD device is highly influenced by the performance of the backlight unit. [5] As a conventional backlight unit, a cold cathode fluorescent lamp (CCFL) in a tube shape or a light emitting diode (LED) in a dot shape has been widely used. [6] A CCFL provides high luminance, has a longer life time, and generates a low heat compared to an incandescent lamp. An LED also provides high luminance. However, a

CCFL and an LED commonly have bad luminance uniformity. [7] Therefore, a backlight unit having a CCFL or a LED as a light source device requires an optical member such as a light guide panel (LGP), a diffusion member and a prism sheet to improve the luminance uniformity. However, such an optical member increases the volume and weight of an LCD device. [8] In order to overcome these shortcomings in the conventional backlight unit, a surface light source device having a flat shape was introduced. [9] A surface light source device is classified into one with an independent partition wall and one with an integrated partition wall. [10] The former type of surface light source device includes a main body, a main partition wall and an electrode. The main body includes a first panel, a second panel, and a sealing member disposed between the first panel and the second panel along their periphery.

[II] The latter type of surface light source device also includes a main body 10, a main partition wall 21 and electrodes 41 and 43.

[12] Fig. 1 is a perspective view illustrating the latter type of surface light source device according to a related art.

[13] As shown in Fig. 1, the main body 10 includes a first panel 20, a second panel 30, and the main partition wall 21 is integrally formed with the first panel 20.

[14] The introduction of a home-theater system, a HD (High Definition) TV, and satellite digital broadcasting increases the demands for high quality display devices with a large screen. Accordingly, the demand for liquid crystal display devices with a large screen also increases.

[15] In order to display a large size image, an LCD device also requires a large size surface light source device. However, the conventional surface light source device in Fig. 1 has following problems to be used for an LCD device with a large screen.

[16] The conventional surface light source device includes the main partition wall 21 extending in a transverse direction that is the direction of the major axis of the surface light source device. Since the main partition wall 21 defines a discharge space, the discharge space is formed in the transverse direction. As a result, the length of the discharge space is relatively long.

[17] Furthermore, when the conventional surface light source device is used for an LCD device with a large screen, the length of the discharge space becomes still longer than an allowable length thereof. Due to the long discharge space, the discharge starting voltage and the power consumption excessively increases. As a result, it is difficult to stably supply a discharge voltage required for the long discharge space using a currently available inverter and to obtain a stable discharging performance accordingly.

[18] Particularly, the discharging performance at the central area of the discharge space is still worse. This imposes restriction on the use of a single inverter. That is, the surface light source device with the transversely long discharge space has a limitation that it is not suitable for an LCD device with a large screen.

[19] Furthermore, electrodes 41 and 43 are formed in the vertical direction corre- spondently to the transversely formed discharge spaces. This induces a temperature gradient in the surface light source device. Such a temperature gradient causes mercury to migrate. As a result, the luminance and luminance uniformity of the surface light source device are degraded.

[20]

Disclosure of Invention Technical Problem

[21] It is, therefore, an object of the present invention to provide a surface light source device suitable for an LCD device with a large screen.

[22] It is another object of the present invention to provide a surface light source device that can reduce a discharge starting voltage and have high luminance and efficiency with low power consumption. [23] It is further another object of the present invention to provide a surface light source device that can prevent mercury migration by keeping the temperature distribution uniform, thereby have high luminance and luminance uniformity. [24]

Technical Solution

[25] In accordance with one aspect of the present invention, there is provided a surface light source device includes: a main body having an inner space where a discharge gas is provided; at least one main partition wall for partitioning the inner space into a plurality of discharge spaces; and an electrode for applying a discharge voltage to the discharge gas, wherein a transverse length of the main body is longer than a vertical length of the main body, and the main partition wall is formed in a vertical direction.

[26] Preferably, the surface light source device further includes a sub partition wall for partitioning the discharge space into discharge channels successively connected with one another.

[27] In accordance with another aspect of the present invention, there is provided a backlight unit including: a surface light source device including a main body having an inner space where a discharge gas is provided, at least one main partition wall for partitioning the inner space into a plurality of discharge spaces, and an electrode for applying a discharge voltage to the discharge gas, wherein a transverse length of the main body is longer than a vertical length of the main body, and the main partition wall is formed in a vertical direction; and an inverter for driving the surface light source device by supplying a discharge voltage to the electrode.

[28]

Advantageous Effects

[29] A surface light source device according to the present invention can have following advantages.

[30] The surface light source device according to the present invention is suitable for an

LCD device with a large screen.

[31] The surface light source device can reduces a discharge starting voltage and provide high luminance and efficiency with low power consumption.

[32] The surface light source device can prevent mercury migration by keeping the temperature distribution uniform, thereby have high luminance and luminance uniformity.

[33]

Brief Description of the Drawings [34] The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which: [35] Fig. 1 is a perspective view of a surface light source device according to a related art; [36] Fig. 2 is a perspective view of a surface light source device according to the first embodiment of the present invention;

[37] Fig. 3 is a cross-sectional view taken along the line III-III of Fig. 2;

[38] Fig. 4 is a perspective view of a surface light source device according to the second embodiment of the present invention; [39] Fig. 5 is a cross-sectional view of the surface light source device taken along the line V-V of Fig. 4; [40] Fig. 6 is a graph comparing temperature distributions in the surface light source devices of Fig. 4 and Fig. 1 ; [41] Fig. 7 is a perspective view of a surface light source device according to the third embodiment of the present invention; [42] Fig. 8 is a perspective view of a surface light source device according to the fourth embodiment of the present invention; [43] Fig. 9 is a perspective view of a surface light source device according to the fifth embodiment of the present invention;

[44] Fig. 10 is a plane view of the surface light source device shown in Fig. 9;

[45] Fig. 11 is a plane view of a surface light source device according to the sixth embodiment of the present invention; [46] Fig. 12 is a plane view of a surface light source device according to the seventh embodiment of the present invention; [47] Fig. 13 is a plane view of a surface light source device according to the eighth embodiment of the present invention; [48] Fig. 14 is a plane view of a surface light source device according to the ninth embodiment of the present invention; [49] Fig. 15 is a perspective view of a backlight unit according to the tenth embodiment of the present invention; [50] Fig. 16 is a perspective view of a backlight unit according to the eleventh embodiment of the present invention; and [51] Fig. 17 is a plane view of a back light unit according to the twelfth embodiment of the present invention. [52]

Best Mode for Carrying Out the Invention [53] Other objects and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter.

[54]

[55] First embodiment

[56] Fig. 2 is a perspective view of a surface light source device 100 according to the first embodiment of the present invention, and Fig. 3 is a cross-sectional view taken along the line III-III of Fig. 2.

[57] Referring to Figs. 2 and 3, the surface light source device 100 according to the first embodiment includes a main body 110, at least one main partition wall 160 and electrodes 141 and 143.

[58] The main body 110 has an inner space where a discharge gas is injected. The main body 110 includes a first panel 120, a second panel 130 facing the first panel 120, and a sealing member 170. The sealing member 170 is disposed between the first panel 120 and the second panel 130 along their periphery. The first panel 120 and the sealing member 170, and the second panel 130 and the sealing member 170 are adhered to each other, for example by an adhesive such as frit.

[59] The transverse length of the main body 110 is longer than the vertical length thereof.

[60] The main partition wall 160 partitions the inner space of the main body 110 into a plurality of discharge spaces 150. The main partition wall 160 is independently disposed between the first panel 120 and the second panel 130. The main partition wall 160 and the first panel 120, and the main partition wall 160 and the second panel 130 may be also adhered to each other, for example by an adhesive such as frit.

[61] The main partition wall 160 has a passage hole (not shown) so that the discharge spaces 150 can communicate with one another. After exhausting air from the discharge spaces 150 through the passage holes, the discharge gas is injected to the discharge spaces 150 therethrough.

[62] A fluorescent layer (not shown) is formed on the inner surface of the first panel

120. A reflective layer (not shown) is formed on the inner surface of the second panel 130, and a fluorescent layer (not shown) is formed on the reflective layer.

[63] The electrodes 141 and 143 apply a discharge voltage to a discharge gas. While the discharge voltage is applied to the discharge gas, ultra violet ray is generated, and then the ultra violet ray excites the fluorescent layer to generate visible ray.

[64] As shown in Figs. 2 and 3, the main partition wall 160 of the present invention is formed in a vertical direction. Therefore, the discharge space 150 defined by the main partition wall 160 is shorter. Accordingly, the surface light source device 100 can be easily turned on even with low voltage. In addition, the surface light source device 100 can be easily turned on, even when the ambient temperature is low. Therefore, the surface light source device 100 according to the first embodiment is suitable for an

LCD device with a large screen. [65] Furthermore, the temperature gradient of the surface light source device 100 can be reduced as much as about 50% because the electrodes 141 and 143 formed in a transverse direction make the heating areas closer. [66]

[67] Second embodiment

[68] Fig. 4 is a perspective view of a surface light source device 200 according to the second embodiment of the present invention, and Fig. 5 is a cross-sectional view of the surface light source device taken along the line V-V of Fig. 4. [69] As shown in Figs. 4 and 5, the surface light source device 200 according to the second embodiment also includes a main body 210, at least one main partition wall

221, and electrodes 241 and 243. [70] The main body 210 has an inner space where a discharge gas is injected. The main body 210 includes a first panel 220 and a second panel 230, which face each other. The first and second panels 220 and 230 are adhered to each other along their periphery, for example by an adhesive such as frit. [71] The first panel 220 includes convex parts protruding outwardly to form discharge spaces 250. [72] The transverse length of the main body 210 is longer than the vertical length thereof. [73] The main partition wall 221 partitions the inner space of the main body 210 into a plurality of discharge spaces 250. The main partition wall 221 is integrally formed with the first panel 220. [74] The main partition wall 221 has a passage hole 222 so that the adjacent discharge spaces 250 can communicate with one another. After exhausting air form the discharge spaces through the passage holes 222, the discharge gas is injected through the passage holes 222. [75] A fluorescent layer (not shown) is formed on the inner surface of the first panel

220. A reflective layer (not shown) is formed on the inner surface of the second panel

230, and a fluorescent layer (not shown) is formed on the reflective layer. [76] The electrodes 241 and 243 apply a discharge voltage to the discharge gas.

[77] As show in Figs. 4 and 5, the main partition wall 221 is formed in a vertical direction. Therefore, the discharge space 150 defined by the main partition wall 250 is shorter. Accordingly, the surface light source device 200 can easily be turned on even with low voltage. In addition, the surface light source device 200 can be easily turned on, even when the ambient temperature is low. [78] Fig. 6 is a graph comparing temperature distributions in the surface light source devices of Fig. 4 and Fig. 1. [79] In Fig. 6, a dotted line denotes the temperature distribution in the conventional surface light source device shown in Fig. 1, and a solid line denotes the temperature distribution in the surface light source device according to the second embodiment shown in Fig. 4. [80] As shown, the temperature is higher at the central area in the conventional surface light source device of Fig. 1. However, the temperature is uniformly distributed throughout the entire area in the surface light source device 200 according to the second embodiment. [81] Therefore, the surface light source device 200 according to the second embodiment can prevent mercury migration between the discharge spaces 250, and improve the luminance and the luminance uniformity. [82]

[83] Third embodiment

[84] Fig. 7 is a perspective view of a surface light source device 300 according to the third embodiment of the present invention. [85] As shown in Fig. 7, both a first panel 320 and a second panel 330 include a plurality of convex parts at the discharge spaces 350 to be outwardly convex. [86] Main partition walls are integrally formed with the first panel 320 and the second panel 330, respectively. [87] The surface light source device 300 of Fig. 7 has an advantage that it is not easily bended in a transverse direction compared to the surface light source device 200 of

Fig. 4. [88] Reference numerals 310, 341 and 343 denote a main body, a first electrode, and a second electrode, respectively. [89]

[90] Fourth embodiment

[91] Fig. 8 is a perspective view of a surface light source device 400 according to the fourth embodiment of the present invention. [92] The surface light source device 400 according to the fourth embodiment has four differences compared to the surface light source device 200 shown in Fig. 4 as follows. [93] At first, assuming that a discharge space is divided into a first area adjacent to electrodes 441 and 443, and a second area apart from the electrodes 441 and 443, the cross section area of the first area is larger than that of the second area. By forming the first area adjacent to the electrodes 441 and 443 to be greater than the second area, the amount of current applied to the discharge space can increase, thereby improving the luminance thereof. [94] Secondly, the first areas of outermost discharge spaces are formed to have a larger cross section area than the first areas of central discharge spaces. Since the outermost discharge spaces loss heat and current more than the central discharge spaces, the luminance of the outermost discharge space is lower than any other discharge spaces.

By forming the first areas of outermost discharge spaces to have a still larger cross section area, the luminance degradation in the outermost discharge spaces can be compensated, thereby improving the luminance uniformity. [95] Thirdly, a part of the electrodes 441 and 443 formed at the outermost discharge spaces have a larger area than a part of the electrodes 441 and 443 formed at the central discharge spaces. [96] Although the surface light source device 400 according to the fourth embodiment includes the above described three advantageous structures as shown in Fig. 8, surface light source devices according to other embodiments of the present invention can have one or two among the three described structures. [97] Undescribed reference numerals 420, 421 and 430 denote a first panel, a main partition wall, and a second panel, respectively. [98]

[99] Fifth embodiment

[100] Fig. 9 is a perspective view of a surface light source device 500 according to the fifth embodiment of the present invention, and Fig. 10 is a plane view of the surface light source device 500 shown in Fig. 9. [101] Luminance depends on the area of a light emitting area in a discharge space. That is, the luminance of the surface light source device increases in proportion to the area of the light emitting area in the discharge space. [102] In a surface light source device, a discharge space 550 includes a non-emitting area where the electrodes 541 and 543 are formed. The non-emitting area of the discharge space cannot emit the light. Accordingly, the surface light source device with the linear discharge space has a small light emitting area, and thus it is hindered from achieving high luminance and efficiency. [103] Such a shortcoming becomes more serious in a surface light source device in which a discharge space 550 is formed in a vertical direction that is the direction of a minor axis, like the surface light source device in Fig. 4. [104] In order to overcome this shortcoming, the surface light source device 500 according to the fifth embodiment shown in Fig. 9 includes a sub partition wall 527 in a discharge space 550. The discharge space 550 is partitioned into discharge channels

551 which are successively connected with one another. [105] The sub partition wall 527 is integrally formed with one of the first panel 520 and the second panel 530. However, in some embodiments, the sub partition wall 527 may be formed independently from the panels 520 and 530.

[106] The sub partition wall 527 of Fig. 9 is formed in parallel with the main partition wall 521. One end of the sub partition wall 527 closely contacts to the edge of the main body 510, and the other end of the sub partition wall 527 is separated from the edge of the main body 510. Therefore, the discharge space 550 has a "U" shape.

[107] A first electrode 541 and a second electrode 543 are formed at both ends of the discharge space 550, respectively. The electrode 541 and 543 are formed on the outer surface of the main body 510.

[108] By lengthening the discharge space 550 where discharging is performed, the positive column area can be lengthened accordingly, thereby improving luminance and efficiency.

[109] Adjacent discharge spaces 550 are formed symmetrically to one another with respect to a vertical axis, for example, an A-A axis shown in Fig. 11, which forms a boundary between the adjacent discharge spaces. The first and second electrodes 541 and 543 at the adjacent discharge spaces 550 are also disposed symmetrically to one another with respect to the vertical axis.

[110] This prevents potential difference from being created between the adjacent discharge spaces 550, and makes a boundary plane between the adjacent discharge spaces 550 an equipotential plane. Therefore, it is possible to perform a stable discharging. This will be described in more detail with reference to Fig. 11.

[Ill]

[112] Sixth embodiment

[113] Fig. 11 is a plane view of a surface light source device according to the sixth embodiment of the present invention.

[114] At a time t, voltages applied by a first electrode 641 and a second electrode 643 are

-Vsin (wt) and +Vsin (wt), respectively, and thus have a 180 phase difference. Therefore, if the adjacent discharge spaces 650 are not symmetrical with respect to the vertical axis as shown in Fig. 11, the potential difference is created between the adjacent discharge spaces 650. It obstructs the stable discharging.

[115] The arrangement of the discharge spaces 650 and electrodes in the surface light source device 500 shown in Fig. 9 is preferable to the surface light source device 600 shown in Fig. 11.

[116] Undescribed reference numerals 621, 627 and 651 denote a main partition wall, a sub partition wall, and a discharge channel.

[117]

[118] Seventh embodiment

[119] Fig. 12 is a plane view illustrating a surface light source device 700 according to the seventh embodiment of the present invention. [120] As shown in Fig. 12, the surface light source device 700 includes two sub partition walls, a first sub partition wall 727 and a second sub partition wall 728 in each discharge space 750. The first sub partition wall 727 and the second sub partition wall 728 are formed in parallel with the main partition wall 721.

[121] One end of the first sub partition wall 727 closely contacts with the edge of the main body, and the other end is separated from the edge of the main body. Also, one end of the second sub partition wall 728 which is adjacent to the one end of the first sub partition wall 727, is separated from the edge of the main body, and the other end closely contacts to the edge of the main body.

[122] Therefore, the discharge space has an "S" shape.

[123] The discharge space 750 of Fig. 12 is 1.5 times longer than the discharge space 550 of Fig. 9. Therefore, the luminance thereof can be improved.

[124] An undescribed reference numeral 751 denotes a discharge channel.

[125]

[126] Eighth embodiment

[127] Fig. 13 is a plane view of a surface light source device 800 according to the eighth embodiment of the present invention.

[128] As shown in Fig. 13, in the surface light source device 800 according to the eighth embodiment, each discharge space 850 also includes two sub partition walls, a first sub partition wall 827 and a second sub partition wall 828.

[129] The first sub partition wall 827 includes a first separated wall 827a and a first contacting wall 827b, and the second sub partition wall 828 includes a second separated wall 828a and a second contacting wall 828b.

[130] The first contacting wall 827b extends from one main partition wall 821 located at one side of the discharge space 850 toward another main partition wall 821 located at the other side of the discharge space 850. The first separated wall 827a extends from the first contacting wall 827b toward the second contacting wall 828b in parallel with the one main partition wall 821, but is apart from the second contacting wall 828b.

[131] The second contacting wall 828b extends from the other main partition wall 821 located at the other side of the discharge space toward the one main partition wall 821 located at the one side. The second separated wall 282a extends from the second con tacting wall 828b toward the first contacting wall 827b in parallel with the other main partition wall 821 but is apart from the first contacting wall 827b.

[132] Therefore, the discharge space 850 has an "S" shape overall.

[133] A first electrode 841 and a second electrode 843 are formed at ends of the discharge space 850, respectively.

[134] An undescribed reference numeral 851 denotes a discharge channel.

[135] [136] Ninth embodiment

[137] Fig. 14 is a plane view illustrating a surface light source device 900 according to the ninth embodiment of the present invention.

[138] A first sub partition wall 927, a second sub partition wall 928, and a discharge space

950 in the surface light source device in Fig. 14 are identical to those in the surface light source device 800 shown in Fig. 13.

[139] A first electrode 941 and a second electrode 943 are also formed at ends of each discharge space 950 similarly to those in Fig. 13. However, the surface light source device 900 according to the ninth embodiment is distinguished in that both the first electrodes and the second electrodes are connected to one another, thereby forming common electrodes 941, 943 in a strip shape. That is, a first common electrode 941 is formed along adjacent ends of the discharge spaces 950, and a second common electrode 943 is formed along the other adjacent ends of the discharge spaces 950.

[140] Since theses electrodes can be formed in a single manufacturing process, the productivity can be improved. Differently from the surface light source device 700 of Fig. 12 having the limitation in expanding the electrode area, the surface light source device 900 can expand the electrode area sufficiently. Therefore, the surface light source device 900 can provide high luminance.

[141] The adjacent discharge spaces 950 are formed symmetrically to one another with respect to a vertical axis that forms a boundary between the adjacent discharge spaces 950. The first common electrode 941 and the second common electrode 943 are also symmetrical to one another with respect to the vertical axis that forms the boundary between the adjacent discharge spaces 950.

[142] This prevents potential difference from being created between the adjacent discharge spaces 950, and makes a boundary plane between the adjacent discharge spaces 950 an equipotential plane. Therefore, it is possible to perform a stable discharging.

[143] Undescribed reference numerals 921 and 951 denote an main partition wall and a discharge channel, respectively.

[144]

[145] Tenth embodiment

[146] Fig. 15 is a perspective view of a backlight unit according to the tenth embodiment of the present invention.

[147] Referring to Fig. 15, the backlight unit includes first and second cases 1100 and

1300, a surface light source device 200, an optical sheet 1200, and an inverter 1400.

[148] The first case 1100 houses the surface light source device 200.

[149] The optical sheet 1200 is disposed at the front of the surface light source device

200. The optical sheet 1200 may include a diffusion sheet and a prism sheet. The diffusion sheet uniformly diffuses the light emitted from the surface light source device 200. The prism sheet collimates the light diffused by the diffusion sheet.

[150] The second case 1300 is assembled with the first case 1100 to fix the surface light source device 200 and the optical sheet 1200.

[151] The inverter 1400 supplies a discharge voltage to an electrode so as to drive the surface light source device 200.

[152] A liquid crystal panel will be placed at the front of the second case 1300 in an LCD device.

[153]

[154] Eleventh embodiment

[155] Fig. 16 is a perspective view of a backlight unit according to the eleventh embodiment of the present invention.

[156] A surface light source device 200 may include a plurality of lamp units. In Fig. 16, the surface light source device 200 includes two lamp units 200a and 200b.

[157]

[158] Twelfth embodiment

[159] Fig. 17 is a plane view of a back light unit according to the twelfth embodiment of the present invention.

[160] Referring to Fig. 17, the surface light source device 200 includes a plurality of lamp units 200a to 20On. The lamp units 200a to 20On are arranged in a tile form.

[161] Although a single inverter can be commonly used for a plurality of the lamp units, a plurality of inverters 1400a to 140On are preferably used for a plurality of the lamp units 200a to 20On in an LCD device with a large screen.

[162] By using the surface light source device 200 including a plurality of the lamp units

200a to 20On and driving the lamp units 200a to 20On with the inverters 1400a to 140On, a discharge starting voltage can be significantly reduced, and the surface light source device 200 can be easily turned on even with low power consumption. Therefore, the problem related to the inverter capacity in a conventional LCD device with a large screen is not occurred in the present invention.

[163] Since the surface light source device 200 can be easily formed by arranging the lamp units 200a to 20On in all directions, a large surface light source 200 for an LCD device with a large screen can be easily manufactured.

[164] While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

[165]

Claims

[I] A surface light source device comprising: a main body having an inner space where a discharge gas is provided; at least one main partition wall for partitioning the inner space into a plurality of discharge spaces; and an electrode for applying a discharge voltage to the discharge gas, wherein a transverse length of the main body is longer than a vertical length of the main body, and the main partition wall is formed in a vertical direction.

[2] The surface light source device of claim 1, wherein the main body includes a first panel and a second panel which face each other, and the main partition wall is independently disposed between the first and second panels.

[3] The surface light source device of claim 1, wherein the main body includes a first panel and a second panel which face each other, and the main partition wall is integrally formed with one of the first and second panels.

[4] The surface light source device of claim 3, wherein both the first and second panels include a plurality of convex parts formed at the discharge spaces to be outwardly convex.

[5] The surface light source device of claim 1, wherein the discharge space includes a first area adjacent to the electrode and a second area apart from the electrode, and the first area has a lager cross section area than the second area.

[6] The surface light source device of claim 1, wherein the discharge space includes a first area adjacent to the electrode and a second area apart from the electrode, and the first areas of outermost discharge spaces have a large cross section area than the first areas of central discharge spaces.

[7] The surface light source device of claim 1, wherein a part of the electrode at outermost discharge spaces has a larger area than a part of the electrode at central discharge spaces.

[8] The surface light source device of claim 1, further comprising a sub partition wall for partitioning the discharge space into discharge channels successively connected with one another.

[9] The surface light source device of claim 8, wherein the main body includes a first panel and a second panel which face each other, and the sub partition wall is independently disposed between the first and second panel.

[10] The surface light source device of claim 8, wherein the main body includes a first panel and a second panel which face each other, and the sub partition wall is integrally formed with one of the first and second panels.

[II] The surface light source device of claim 8, wherein the sub partition wall is formed in parallel with the main partition wall, and has one end closely contacting to the main body and the other end separated from the main body so that the discharge space has a "U" shape.

[12] The surface light source device of claim 8, wherein the sub partition wall includes a first sub partition wall and a second partition wall which are formed in parallel with the main partition wall, the first sub partition wall has one end closely contacting to the main body and the other end separated from the main body, and the second sub partition wall has one end, which is adjacent to the one end of the first sub partition wall, separated from the main body, and the other end closely contacting to the main body so that the discharge space has an "S" shape.

[13] The surface light source device of claim 8, wherein the sub partition wall includes a first sub partition wall and a second sub partition wall, wherein the first sub partition wall includes a first contacting wall and a first separated wall, and the second sub partition wall includes a second contacting wall and a second separated wall, the first contacting wall extends from one main partition wall placed at one side of the discharge space toward another main partition wall placed at the other side of the discharge space, the first separated wall extends from the first contacting wall toward the second contacting wall in parallel with the one main partition wall but is apart from the second contacting wall, the second contacting wall extends from the other main partition wall placed at the other side of the discharge space toward the one main partition wall placed at the one side of the discharge space, and the second separated wall extends from the second contacting wall toward the first contacting wall in parallel with the other main partition wall but is apart from the first contacting wall so that the discharge space has an "S" shape.

[14] The surface light source device of claim 13, wherein the electrode includes a first electrode and a second electrode formed at ends of the discharge space, respectively, and the first electrode is formed in common along adjacent ends of the discharge spaces and the second electrode is formed in common along the other adjacent ends of the discharge spaces.

[15] The surface light source device of claim 14, wherein the first electrode and the second electrode are formed along edges of the main body.

[16] The surface light source device of claim 8, wherein the electrode includes a first electrode and a second electrode formed at ends of the discharge space, re- spectively. [17] The surface light source device of claim 16, wherein the first electrode and the second electrode are formed at an outer surface of the main body. [18] The surface light source device of claim 8, wherein adjacent discharge spaces are formed symmetrically to one another with respect to a boundary therebetween, and the electrode includes a first electrode and a second electrode formed at ends of the discharge space, respectively, and the first and second electrodes of the adjacent discharge spaces are disposed symmetrically to one another with respect to the boundary. [19] The surface light source device of claim 8, wherein a passage hole is formed at the main partition wall to pass the discharge gas through the passage hole. [20] A backlight unit comprising: a surface light source device including: a main body having an inner space where a discharge gas is provided; at least one main partition wall for partitioning the inner space into a plurality of discharge spaces; and an electrode for applying a discharge voltage to the discharge gas, wherein a transverse length of the main body is longer than a vertical length of the main body, and the main partition wall is formed in a vertical direction; and an inverter for driving the surface light source device by supplying a discharge voltage to the electrode. [21] The backlight unit of claim 20, wherein the surface light source device includes a plurality of lamp units. [22] The backlight unit of claim 21, comprising a plurality of inverters for supplying power to the lamp units, respectively. [23] The backlight unit of claim 21, wherein a plurality of the lamp units are arranged in a tile form.