WO2007004809A1

WO2007004809A1 - Flat fluorescent lamp and backlight unit having the same

Info

Publication number: WO2007004809A1
Application number: PCT/KR2006/002538
Authority: WO
Inventors: Ki Yeon Lee
Original assignee: Samsung Corning Co., Ltd.
Priority date: 2005-06-30
Filing date: 2006-06-29
Publication date: 2007-01-11
Also published as: TW200715343A; KR20070002178A; KR100811896B1

Abstract

A flat fluorescent lamp 100, 300 includes a main body 110, 310 having an inner space in which discharge gas is provided and barriers 115, 215, 315 partitioning the inner space into a plurality of discharge spaces 117, 217, 317, protruding parts 140, 240, 340 being formed at both ends of the barrier 115, 215, 315; and an electrode 150, 350 formed on the main body 110, 310 and applying discharge voltage to the inner space. A panel closely contacts with the barriers 115, 215, 315 by aid of the protruding parts 140, 240, 340 and thus current leakage toward adjacent discharge spaces 117, 217, 317 can be effectively prevented. Accordingly, discharge can be carried out simultaneously at all the discharge spaces 117, 217, 317 under low temperature and low input voltage.

Description

FLAT FLUORESCENT LAMPAND BACKLIGHT UNIT

HAVING THE SAME

Technical Field

[1] The present invention relates to a flat fluorescent lamp and a backlight unit, more particularly, to a flat fluorescent lamp which effectively prevents channeling to have high luminance uniformity and a backlight unit having the same.

[2]

Background Art

[3] An LCD (liquid crystal display) device displays images utilizing the electric and optical characteristics of LC (liquid crystal). An LCD device has an advantage of small thickness and lightness in comparison with other display devices such as a cathode ray tube (CRT). Thus, an LCD device has been widely used in various products, such as a mobile computer, a communication device, a liquid crystal TV, an airplane, etc.

[4] An LCD device generally includes a backlight unit for supplying the liquid crystal with light. The quality of image displayed on an LCD device is largely influenced by the luminance characteristics of the backlight unit. Typically, high luminance and luminance uniformity improve the image quality of an LCD device.

[5] A conventional backlight unit has generally used a cold cathode fluorescent lamp

(CCFL) or a light emitting diode (LED). A CCFL has high luminance and long lifetime and generates a small amount of heat compared to an incandescent lamp. An LED also has high luminance. However, a CCFL or an LED has poor luminance uniformity.

[6] Therefore, a conventional backlight unit requires additional optical members such as a light guide panel, a diffusion sheet and a prism sheet to improve its luminance uniformity. The addition of the optical members inevitably increases the size and weight of the backlight unit.

[7] To solve the above problem, a flat fluorescent lamp was developed. A flat fluorescent lamp can be divided into a lamp with barriers provided independently from a panel and a lamp with barriers integrally formed on a panel.

[8] Fig. 1 is a cross-sectional view illustrating a conventional flat fluorescent lamp.

[9] Referring to Fig. 1, the conventional flat fluorescent lamp includes a first panel 11 having barriers 14 integrally formed thereon, a second panel 12 disposed under the first panel 11.

[10] The barriers 14 contact with an upper surface of the second panel 12 to form a plurality of discharge spaces 15. Electrodes 16 are formed on outer surfaces of the first panel 11 and the second panel 12.

[11] A frit 17 is formed on a periphery of the panels 11, 12. Accordingly, the periphery of the first panel 11 is bonded to the second panel 12 but the barriers 14 of the first panel 11 simply contact with the second panel 12.

[12] The main function of the barriers 14 is to prevent interference of current or plasma between adjacent discharge spaces 15. The interference does not occur intensively at a positive column area with a small electric potential difference. However, the interference occurs intensively at an area adjacent to the electrode 16 with a large electric potential difference. Accordingly, at the area adjacent to the electrode 16, the function of the barriers 14 (that is, the function of preventing current leakage toward adjacent discharge spaces 15) needs to be enhanced.

[13]

Disclosure of Invention Technical Problem

[14] As shown in Fig. 1, the barriers simply contact with the second panel, and thus a micro-gap is easily formed between the barrier and the second panel. Although the gap is very small, channeling or current leakage occurs very intensively. Especially, the channeling or current leakage occurs mainly at both ends of the barriers which correspond to both ends of the discharge spaces at which the electrodes are formed.

[15] The channeling or current leakage decreases luminance uniformity of a lamp and increases electric power consumption. Accordingly, it is required to develop a lamp which can prevent such channeling or current leakage.

[16] The present invention is provided to solve the aforementioned problems of the conventional lamp.

[17] An object of the present invention is to prevent a micro-gap from being created between barriers and panels to provide a flat fluorescent lamp with high luminance uniformity.

[ 18] Another object of the present invention is to provide a backlight unit having the flat fluorescent lamp.

[19]

Technical Solution

[20] To achieve the above objects, the present invention provides a flat fluorescent lamp including: a main body having an inner space in which discharge gas is provided and barriers partitioning the inner space into a plurality of discharge spaces, protruding parts being formed at both ends of the barrier; and an electrode formed on the main body and applying discharge voltage to the inner space.

[21] According to one embodiment of the present invention, the main body includes a first panel and a second panel at an upper place and a lower place respectively, and the barriers are integrally formed on the first panel.

[22] Here, the protruding part is formed on at least one of a lower surface of the barrier and an upper surface of the second panel.

[23] According to another embodiment of the present invention, the main body includes a first panel and a second panel at an upper place and a lower place respectively, and a sealing part formed between the first panel and the second panel along the periphery of the panels.

[24] Here, the protruding part is formed on at least one of an upper surface and a lower surface of the barrier.

[25] Preferably, the protruding part is integrally formed on the barrier.

[26] Preferably, the barrier has a discharge gas passage hole which enables the discharge spaces to communicate with one another.

[27] Preferably, the protruding part has a height of 0.005 ~ 2mm.

[28] Preferably, the protruding part has a length of 5 ~ 500mm.

[29] In addition, the present invention provides a backlight unit including: a flat fluorescent lamp including a main body having an inner space in which discharge gas is provided and barriers partitioning the inner space into a plurality of discharge spaces, protruding parts formed at both ends of the barrier, and an electrode formed on the main body and applying discharge voltage to the inner space; an upper case and a lower case for receiving the flat fluorescent lamp; an optical sheet disposed between the upper case and the flat fluorescent lamp; and an inverter for generating the discharge voltage.

[30]

Advantageous Effects

[31] According to the present invention, the protruding parts are formed at both ends of the barriers to effectively prevent micro-gaps from being created between the barriers and the panel and thus to prevent current from leaking through the micro-gaps. Consequently, the present invention can keep the pressure of the discharge spaces equal throughout the lamp, and can provide a flat fluorescent lamp with high luminance uniformity and a backlight unit having the same.

[32]

Brief Description of the Drawings

[33] The above objects and other advantages of the present invention will become more apparent by describing preferred embodiments thereof in detail with reference to the accompanying drawings, in which:

[34] Fig. 1 is a cross-sectional view illustrating a conventional flat fluorescent lamp; [35] Fig. 2 is a perspective view illustrating a flat fluorescent lamp according to an embodiment of the present invention;

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

[37] Fig. 4 is a rear perspective view illustrating a first panel of the flat fluorescent lamp of Fig. 2; [38] Fig. 5 is a rear perspective view illustrating a first panel of a flat fluorescent lamp according to another embodiment of the present invention; [39] Fig. 6 is a perspective view illustrating a flat fluorescent lamp according to still another embodiment of the present invention; and [40] Fig. 7 is an exploded perspective view illustrating a backlight unit according to still another embodiment of the present invention. [41]

Mode for the Invention [42] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. [43] Fig. 2 is a perspective view illustrating a flat fluorescent lamp 100 according to an embodiment of the present invention. Fig. 3 is a cross-sectional view taken along a line

III-iπ of Fig. 2. [44] Referring to Figs. 2 and 3, the flat fluorescent lamp 100 includes a main body 110 having an inner space in which discharge gas is provided, and electrodes 150 for applying discharge voltage to the discharge spaces 117.

[45] The main body 110 includes a first panel 111, a second panel 112 and barriers 115.

[46] A plurality of barriers 115 makes the first panel 111 have a waved shape. Each barrier extends in a first direction. Preferably, each barrier has a width of about 1 ~

5mm. The first panel 111 is preferably made of glass. For example, a glass which can transmit visible ray but block ultraviolet ray is selected for the first panel 111. [47] The second panel 112 has a rectangular plate shape. A glass which can transmit visible ray but block ultraviolet ray can be also selected for the second panel 112. [48] The first panel 111 is disposed over the second panel 112. The first panel 111 is disposed such that its barriers 115 contact with the second panel 112. Accordingly, the main body 110 has a section of an arch shape. The barriers 115 partition the inner space of the main body 110 into a plurality of discharge spaces 117. [49] The first panel 111 and the second panel 112 are bonded with each other by aid of a bonding layer 120. Glass such as frit or ceramic such as aluminum oxide can be used as the bonding layer 120. [50] A reflective layer 132 is formed on an upper surface of the second panel 112. A first fluorescent layer 134 is formed on the reflective layer 132. A second fluorescent layer 136 is formed on a lower surface of the first panel 111. In this case, the reflective layer 132, the first fluorescent layer 134, and the second fluorescent layer 136 are formed on areas of the panels 111, 112 exposed to the discharge spaces 117. More particularly, the reflective layer 132 is formed on an area of the second panel 112 exposed to the discharge spaces 117, and the first fluorescent layer 134 is formed only on the reflective layer 132. The second fluorescent layer 136 is formed on an area of the first panel 111 exposed to the discharge spaces 117.

[51] As mentioned above, the first panel 111 and the second panel 112 make the main body 110 have the discharge spaces 117 of an arch shape. As the discharge gas, mercury gas, argon gas, neon gas, xenon gas, or their mixture is injected into the discharge spaces 117.

[52] Each barrier 115 can have a discharge gas passage hole to enable the discharge spaces 117 to communicate with one another.

[53] Before the discharge gas is injected into the discharge spaces 117, the discharge spaces 117 are exhausted to be a vacuum for removing impurities existing in the discharge spaces 117.

[54] As the discharge spaces 117 are exhausted to be a vacuum, the pressure difference between the inside and the outside of the main body 110 makes the first panel 111 and the second panel 112 closely contact with each other. That is, the barriers 115 of the first panel 111 closely contact with the second panel 112.

[55] When the discharge spaces 117 are exhausted to be a vacuum, both ends of the barrier 115 contact with the second panel 112 more closely than a central part of the barrier 115 because of protruding parts. Hereinafter, the protruding part 140 will be described in detail.

[56] Fig. 4 is a rear perspective view illustrating the first panel 111 of the flat fluorescent lamp 100 of Fig. 2.

[57] Referring to Fig. 4, the protruding part 140 has a height (Hl) from a lower surface of the barrier 115 and a length (Ll). Preferably, the protruding part 140 has a height of 0.005 ~ 2mm and a length of 5 ~ 500mm. More preferably, the protruding part 140 has a height of 0.01 ~ lmm and a length of 10 ~ 200mm. Preferably, the protruding part 140 has the same width of 1 ~ 5mm as the barrier.

[58] The protruding part 140 can be made of the same material as the barrier. The protruding part 140 can be made independently from the barrier 115 and then attached thereto. However, it is preferable that it is integrally formed on the barrier. More preferably, the barrier 115 is integrally formed on the first panel 111 and the protruding part 140 is integrally formed on the barrier. That is, the first panel 111, the barrier, and the protruding part 140 are formed at the same time by a press forming method, an injection molding method, etc. [59] When the first panel 111 is simply placed over the second panel 112, both ends of the barrier 115 contact with the second panel 112 through the protruding part 140, but the central part of the barrier 115 may not contact with the second panel 112. However, when the discharge spaces 117 are exhausted to be a vacuum, the central part of the barrier 115 can contact with the second panel 112.

[60] As the discharge spaces 117 are exhausted to be a vacuum, the first panel 111 and the second panel 112 closely contact with each other and thus the whole surface of the barrier 115 with the protruding part 140 contacts with the second panel 112. Because a height of the protruding part 140 is small, the pressure difference between the inside and the outside of the main body 110 can make the whole surface of the barrier 115 closely contact with the second panel 112.

[61] Both ends of the barrier 115 contact with the second panel 112 more closely than the central part of the barrier 115 because the protruding parts 140 are formed on both ends of the barrier. The electrodes 150 for applying the discharge voltage into the discharge spaces 117 are formed at both ends of the barriers 115 on which the protruding parts 140 are formed.

[62] The electrodes 150 are formed on both sides of outer surfaces of the first panel 111 and the second panel 112 in a second direction which intersects the first direction. In this case, the protruding parts 140 are positioned under the electrodes 150. The electrodes 150 are made of a material with good conductivity such as Cu, Ag, Au, Al, Cr, etc. The electrodes 150 are formed by attaching a conductive tape of such a material or coating metal powder of such a material on the outer surface of the main body 110.

[63] In a conventional lamp, current leakage easily occurs at a part of the barrier 115 adjacent to the electrode. As a result, channeling occurs due to parasitic capacitance a nd drift of plasma occurs.

[64] In a flat fluorescent lamp, discharge has to be carried out simultaneously at all the discharge spaces 117. In order to achieve this, plasma has to be diffused equally throughout a lamp. However, a technology for effectively preventing current leakage which causes plasma to drift has not been developed. Current leakage occurs severely at a part of the barrier 115 adjacent to the electrode 150, especially under low temperature and low input voltage.

[65] In this embodiment of Fig. 4, the protruding parts 140 are formed on both ends of the barriers 115 adjacent to the electrodes 150. Accordingly, both ends of the barriers 115 adjacent to the electrodes 150 can closely contact with the second panel 112. As a result, current leakage toward adjacent discharge spaces 117 can be effectively prevented. Accordingly, discharge can be carried out simultaneously at all the discharg e spaces 117. Especially, even if the flat fluorescent lamp 100 is put under low temperature of -20 degrees Celsius or it is supplied with low input voltage in the range of 20-30% of the reference lamp voltage, discharge can be carried out simultaneously at all the discharge spaces 117.

[66] In the lamp 100 of Fig. 4, the protruding parts 140 are formed on the lower surfaces of the barriers 115 of the first panel 111. However, together with or instead of these protruding parts 140 formed on the barriers 115, the protruding parts 140 can be formed on the upper surface of the second panel 112.

[67] Fig. 5 is a rear perspective view illustrating a first panel 211 of a flat fluorescent lamp according to another embodiment of the present invention.

[68] A first panel 211 of Fig. 5 is similar to the first panel 111 of Fig. 4 except for barriers.

[69] The first panel 211 has a waved shape due to a plurality of barriers 215 extending in a first direction. As compared to a central part of the barriers 215, both ends of the barriers 215 positioned under electrodes (not shown) have a narrow width to expand discharge spaces 217. Preferably, the barriers 215 have a width of 1 ~ 5mm.

[70] Protruding parts 240 have the same width as the barriers 215 and have a height (H2) and a length (L2). Accordingly, the width of the protruding parts 240 can change in the range of 1 ~ 5mm correspondingly to the width of the barriers 215. The protruding parts 240 can have a height of about 0.005 ~ 2mm and a length of about 5 ~ 400mm. Preferably, the protruding parts 240 have a height of about 0.01 ~ lmm and a length of about 10 ~ 200mm.

[71] The protruding parts 240 can be made of the same material as the barriers 215. The protruding parts 240 can be made independently from the barriers 215 and then be attached to the barriers 215. However, it is preferable that the protruding parts 240 are integrally formed on the barriers 215. The barriers 215 with the protruding parts 240 are pressed against a second panel when the discharge spaces 217 are exhausted to be a vacuum.

[72] This embodiment can be applied to a lamp with barriers provided independently from a panel.

[73] Fig. 6 is a perspective view illustrating a flat fluorescent lamp 300 according to still another embodiment of the present invention.

[74] Referring to Fig. 6, the lamp 300 according to this embodiment has barriers 315 provided independently from panels 311, 312. The lamp 300 includes a main body 310 having a first panel 311, a second panel 312, a sealing part 313 and barriers 315 and electrodes 350.

[75] In an inner space formed by the first panel 311, the second panel 312, and the sealing part 313, the barriers 315 extend in a first direction. The barriers 315 partition the inner space into a plurality of discharge spaces 317 having a section of a rectangular shape. The barriers 315 are arranged in a serpentine formation or they are provided with discharge gas passage holes so that discharge gas can be equally injected into all the discharge spaces 317.

[76] As the discharge spaces 317 are exhausted to be a vacuum, the pressure difference between the inside and the outside of the panels 311, 312 makes the barriers 315 closely contact with the first panel 311 and the second panel 312. Especially, both ends of the barriers 315 are pressed more closely against the panels 311, 312 than a central part of the barriers 315 because protruding parts 340 are formed at both ends of the barriers 315.

[77] The protruding parts 340 have a height and a length. For example, the protruding parts 340 have a height of about 0.005 ~ 2mm and a length of about 5 ~ 500mm. Preferably, the protruding parts 340 have a height of about 0.01 ~ lmm and a length of about 10 ~ 200mm.

[78] A shape of the barrier 315 with the protruding parts 340 is similar to I . Accordingly, both ends of the barriers 315 contact with the first panel 311 and the second panel 312, but in an initial state, the central part of the barriers 315 may not contact with the panels 311, 312. However, after the discharge spaces 317 are exhausted to be a vacuum, the central part contacts with the panels 311, 312.

[79] Both ends of the barriers 315 are pressed more closely against the panels 311, 312 than the central part of the barriers 315 because the protruding parts 340 are formed on both ends of an upper surface and a lower surface of the barriers 315. Electrodes 350 for applying discharge voltage into the discharge spaces are formed at both ends of the barriers 315 on which the protruding parts 340 are formed

[80] The electrodes 350 are formed on both sides of outer surfaces of the first panel 311 and the second panel 312 in a second direction intersecting a first direction.

[81] The protruding parts 340 are formed at both ends of the upper surface and the lower surface of the barriers 315 adjacent to the electrodes 350. Accordingly, parts of the barriers 315 positioned under the electrodes 350 closely contacts with the panels 311, 312. As a result, current leakage toward adjacent discharge spaces 317 can be effectively prevented. Accordingly, discharge can be carried out simultaneously at all the discharge spaces 317. Especially, even if the flat fluorescent lamp 300 is put under low temperature of -20 degrees Celsius or it is supplied with low input voltage in the range of 20-30% of the reference lamp voltage, discharge is carried out simultaneously at all the discharge spaces 317.

[82] Fig. 6 shows that the protruding parts 340 are formed on both upper surfaces and lower surfaces of the barriers 315. However, the protruding parts 340 can be formed on either upper surfaces or lower surfaces of the barriers 315.

[83] Fig. 7 is an exploded perspective view illustrating a backlight unit 401 according to still another embodiment of the present invention. [84] Referring to Fig. 7, the backlight unit 401 according to this embodiment includes the flat fluorescent lamp 100 of Fig. 2, an upper case and a lower case 461, 462, an optical sheet 470, an inverter 480. [85] One of the lamps mentioned above may be used as a light source for the backlight unit 401. In this embodiment, the lamp 100 of Fig. 2 is selected for the illustrative purpose. [86] The lower case 462 includes a bottom 465 and an edge wall 466 elongated from a periphery of the bottom 465 for receiving the lamp 100. The lamp 100 is received in the lower case 462. [87] The inverter 480 generating discharge voltage for operating the lamp 100 is disposed under the lower case 462. The discharge voltage generated by the inverter

480 is transmitted via a first line 481 and a second line 482 to the electrodes 150 of the lamp 100. [88] The optical sheet 470 may include a diffusion sheet (not shown) for diffusing light emitted from the flat fluorescent lamp 100 and a prism sheet (not shown) for collimating the diffused light. [89] The upper case 461 and the lower case 462 are coupled with each other to fix the flat fluorescent lamp 100 and the optical sheet 470. Also, the upper case 461 prevents the lamp 100 from being separated from the lower case 462. [90] An LCD panel (not shown) may be disposed above the upper case 461.

Claims

[ 1 ] A flat fluorescent lamp comprising : a main body having an inner space in which discharge gas is provided and barriers partitioning the inner space into a plurality of discharge spaces, protruding parts being formed at both ends of the barrier; and an electrode formed on the main body and applying discharge voltage to the inner space. [2] The flat fluorescent lamp of claim 1, wherein the main body includes a first panel and a second panel at an upper place and a lower place respectively, and the barriers are integrally formed on the first panel. [3] The flat fluorescent lamp of claim 2, wherein the protruding part is formed on at least one of a lower surface of the barrier and an upper surface of the second panel. [4] The flat fluorescent lamp of claim 1, wherein the main body includes a first panel and a second panel at an upper place and a lower place respectively, and a sealing part formed between the first panel and the second panel along the periphery of the panels. [5] The flat fluorescent lamp of claim 4, wherein the protruding part is formed on at least one of an upper surface and a lower surface of the barrier. [6] The flat fluorescent lamp of claim 1, wherein the protruding part is integrally formed on the barrier. [7] The flat fluorescent lamp of claim 1, wherein the barrier has a discharge gas passage hole which enables the discharge spaces to communicate with one another. [8] The flat fluorescent lamp of claim 1, wherein the protruding part has a height of 0.005 ~ 2mm. [9] The flat fluorescent lamp of claim 1, wherein the protruding part has a length of 5 ~ 500mm. [10] A backlight unit comprising : a flat fluorescent lamp including a main body having an inner space in which discharge gas is provided and barriers partitioning the inner space into a plurality of discharge spaces, protruding parts formed at both ends of the barrier, and an electrode formed on the main body and applying discharge voltage to the inner space; an upper case and a lower case for receiving the flat fluorescent lamp; an optical sheet disposed between the upper case and the flat fluorescent lamp; and an inverter for generating the discharge voltage.