KR20080047701A - Hot cathode for surface light source, surface light source device and backlight unit having the same - Google Patents

Abstract

A hot cathode for a planar light source device, a planar light source device and a backlight unit having the same are provided to maximize the stability of electrodes by applying the hot cathode having superior durability to the planar light source device. A hot cathode for a planar light source device includes a filament(152) with a non-linearity shape and at least one wire(153). The wire, which physically supports the filament, is electrically connected to externals. The filament is supported by at least two wires. The filament is supported by at least three wires including an auxiliary wire. The hot cathode includes two or more filaments with polygon or circle shapes.

Description

Hot cathode for surface light source, surface light source device and backlight unit including the same {HOT CATHODE FOR SURFACE LIGHT SOURCE, SURFACE LIGHT SOURCE DEVICE AND BACKLIGHT UNIT HAVING THE SAME}

1 is a plan view showing an embodiment of a surface light source device of the present invention.

Figure 2 is a plan view showing the electrode portion of the surface light source device of the present invention.

3 is an enlarged view of a portion A of FIG. 1;

4 is a sectional view taken along the line Y-Y 'of FIG.

5 is a cross-sectional view taken along the line Y-Y 'of another FIG.

6 is a plan view showing a detailed structure of the filament constituting the hot cathode of the present invention.

7 is a front view of the hot cathode of FIG. 6;

8 is a channel sectional view of a surface light source using a single filament.

9 is a channel cross-sectional view of the surface light source using the double filament of the present invention.

10 to 12 are schematic views showing various structures of the hot cathode of the present invention.

13 to 16 are cross-sectional views taken along line X-X 'of FIG. 1 showing various types of discharge channels.

17 is a plan view showing a surface light source device in which discharge channels are vertically arranged;

18 is a plan view showing a surface light source device extending both ends of a discharge channel.

19 is an exploded perspective view showing a backlight unit of the present invention.

*** Explanation of symbols for the main parts of the drawing ***

100: surface light source device 110: light source body

120: discharge channel 130: partition wall

140: edge 150: hot cathode

152: filament 153: wire

154: lead wire 156: auxiliary wire

The present invention relates to a hot cathode for a surface light source, and provides a hot cathode and a surface light source device and a backlight unit including the same, which have improved durability and excellent heat transfer characteristics.

Unlike other light emitting displays, a liquid crystal display does not emit light by itself, and thus requires a separate backlight.

A variety of light sources are used for the backlight used in the liquid crystal display, and a cold cathode fluorescent lamp (CCFL) with a cold cathode inside the tubular bulb, a hot cathode fluorescent lamp (HCFL) with a hot cathode instead of a cold cathode, and a plurality of tubular types External electrode fluorescent lamps (EEFL) employing a common electrode outside the valve, and the like. Recently, a surface light source device (FFL) in which a discharge space is formed of a flat substrate instead of a tubular bulb has been proposed.

The backlight light source should have low power consumption and excellent luminous efficiency, and should have high brightness and uniform brightness.

Cold cathode fluorescent lamps have a disadvantage in that the luminous efficiency is low, and external electrode fluorescent lamps have a large power consumption problem. Hot cathode fluorescent lamps have low power consumption and excellent bladder efficiency, but require a plurality of lamps to be used in backlights, which causes manufacturing difficulties.

On the other hand, in the case of the planar surface light source device, a plurality of discharge channels are formed on the light source body to facilitate the manufacturing process automation and mass production, but the luminous efficiency is inferior because the external electrodes are used. In particular, there is a disadvantage that an initial luminance stabilization time of the discharge gas enclosed in the discharge space is required.

Recently, liquid crystal displays have been required for large-sized TVs and require ultra-thin backlights. However, the light sources for backlights, which have been proposed to date, have difficulty in meeting large-area while satisfying power consumption and luminous efficiency. Therefore, there is an urgent need for new light sources useful for large area ultra-thin backlights.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface light source device for a backlight and a backlight having the same, which can be manufactured in an ultra-thin and large area.

It is also an object of the present invention to provide a hot cathode suitable for a surface light source.

Other objects and features of the present invention will be presented in more detail below.

The present invention provides a hot cathode for a surface light source including a non-linear filament and at least one wire that physically supports the filament and electrically connects with the outside.

The filament is preferably supported by at least two or more wires, more preferably by at least three wires including auxiliary wires to improve structural stability. The hot cathode may include two or more filaments, and the filament may have a polygonal shape or a circular shape to enable uniform heat transfer in the discharge channel of the surface light source.

The present invention also provides a planar light source body including at least one discharge channel, and a surface light source device comprising a nonlinear filament as a hot cathode encapsulated in the discharge channel.

The light source body may include a plurality of discharge channels and partition walls that partition the discharge channels, and the light source body may include a fluorescent layer formed on an inner surface of the light source body except for the partition walls. The light source body may include an upper substrate and a lower substrate that are transparent to visible light, and in this case, a discharge channel is formed on at least one surface of the upper substrate and the lower substrate.

The present invention also provides a surface light source device including a plate-shaped light source body including at least one discharge channel, and a nonlinear filament as a hot cathode encapsulated in the discharge channel; A case accommodating the surface light source device; And an inverter for applying a voltage to the hot cathode.

According to the present invention, there is provided a high efficiency surface light source device and a backlight unit which are easy to manufacture by effectively utilizing the advantages of high driving efficiency of a hot cathode and process automation of a flat fluorescent lamp. In particular, the durability of the filament constituting the hot cathode is enhanced so that the shape of the filament is not deformed even during long time use, and the heat transfer is uniform in the discharge channel to prevent damage due to local heating of the light source body, and various types of discharge channels The surface light source device to which the structure is applied can be manufactured.

1 is a plan view showing the surface light source device 100 according to the present invention by way of example. A plurality of discharge channels 120 are formed in the light source body 110. The discharge channel is partitioned by the partition wall 130. In the discharge channel 120, a discharge gas, for example, a gas such as mercury, xenon, argon, neon, or the like is sealed alone or mixed. A fluorescent layer (not shown) is formed on the inner surface of the discharge channel 120. The number, shape, and arrangement of the discharge channels can be variously changed as described later.

Hot cathodes 150 are provided at both ends of the discharge channel 120. The hot cathode includes a filament and is connected to the outside of the light source body by a lead wire. Referring to FIG. 2, the filament 152 is supported by the support wire 153 and is electrically connected to the lead wire 154. A thermal expansion alleviation material 155 is interposed between the support wire 153 and the lead wire 154. The thermal expansion alleviating material 155 has electrical conductivity and serves to adjust thermal expansion between the filament and the lead wire. As the thermal expansion alleviating material, for example, GNC (Ni, Cr, Fe, BaI) or DUMET may be used, and may be formed in the form of a wire or a small strip. The thermal expansion alleviating material, the lead wire and the support wire can be joined using, for example, a laser. The filament 152 may be coated with an oxidant such as Ba, Sr, or Ca to promote hot electron generation due to heat generation of the filament.

The filament 152 of the hot cathode 150 should be exposed to the inner space of the light source body, ie the discharge channel, and the lead wire 154 should extend out of the light source body (for electrical connection). Therefore, it can be said that the proper installation of the hot cathode on the light source body is very important in the manufacture of the surface light source device. In the present invention, a sub-channel is formed on the at least one substrate constituting the light source body together with the discharge channel to facilitate mounting of the hot cathode. Referring to FIG. 3, a sub channel 125 connected to the discharge channel 120 is further formed at an edge of the light source body 110, and a hot cathode is mounted on the sub channel. Preferably, the sub-channel 125 has a thermal expansion alleviating material 155 of the hot cathode. Usually, the thermal expansion coefficient difference between the glass substrate constituting the light source body and the hot cathode is adjusted by the thermal expansion alleviating material, thereby maintaining the bonding property and durability of the hot cathode.

4 is a cross-sectional view taken along the line Y-Y 'of FIG. 3, in which the hot cathode is sealed to the edge of the light source body. The light source body is bonded to the upper substrate 112 and the lower substrate 114 by a bonding layer 160 such as a frit. The hot cathode is sealed and fixed to the sub-channel 125 of the edge of the light source body, and as shown, the thermal expansion alleviating material 155 of the hot cathode is inserted into the bonding layer 160. Subchannels may be formed separately for each thermal expansion mitigating material as in FIG. 5. In the manufacturing process, the hot cathode is preferably inserted into the subchannel in the step of bonding the upper substrate 112 and the lower substrate 114.

The present invention has improved the structure of the hot cathode in order to prevent the durability of the filaments constituting the hot cathode during long-term use while applying the hot cathode to the surface light source device.

Referring to FIG. 6, it can be seen that the filaments constituting the hot cathode are nonlinear. Such non-linear filaments may use a single filament or two filaments 152a, 152b as shown.

Nonlinear filaments are preferably supported on at least two wires, more preferably three or more wires. In one embodiment of the present invention using the auxiliary wire 156 in addition to the two wires 153 for the electrical connection to improve the structural stability of the filament. Referring to the front view of FIG. 7, two filaments 152a and 152b are connected to each other by a wire 153 and are supported by an auxiliary wire 156 to form a nonlinear structure that maintains a predetermined angle to each other.

Nonlinear filaments may be formed by supporting three points using one wire.

Such a non-linear filament is applied to the surface light source device to prevent sag due to gravity during long time driving, and even heat transfer is possible in the discharge channel of the surface light source device, so that localized heat concentration is generated on the surface of the light source body. Can be prevented.

8 and 9, it can be seen that the distances to the inner surface of the discharge channel are different for the filaments of the same length. In the case of FIG. 8, since the distance t from the filament 152 to the inner surface of the light source body 110 is very close, local heat concentration may be caused in the light source body, and as a result, the high heat generated by the light source body in the filament May be damaged. On the other hand, in FIG. 9, the distance t 'from the filaments 152a and 152b to the light source body 110 is relatively long, thereby reducing heat concentration and thus preventing damage to the light source body.

In this way, the thermal problem can be solved by changing the structure of the hot cathode located in the internal discharge space (ie, the discharge channel) of the light source body, and the hot cathode can be used in the surface light source device to which various types of discharge channel structures are applied.

The structure of the hot cathode for the surface light source according to the present invention can be changed in various forms. Referring to Figures 10 to 12, it can be seen a structure such as a circle, a triangle, a square. In the case of FIG. 10, one filament 152 is formed in a circular shape and supported by two wires 153 and one auxiliary wire 156 to maximize structural stability. In the case of the circular filament of FIG. 10, only two wires can be stably supported.

In the embodiment of FIG. 11, three filaments 152a, 152b, and 152c are formed in a triangular structure, and wires 153a, 153b, and 153c are connected to respective connection points to secure structural stability. In the embodiment of FIG. 12, four filaments 152a, 152b, 152c, and 152d may be formed in a rectangular structure, and wires 153a, 153b, 153c, and 153d may be connected to respective connection points. In addition, other various modification structures will be possible.

In the surface light source device according to the present invention, a discharge channel may be formed on any one of an upper substrate and a lower substrate, and both substrates may form a discharge channel. The shape of the discharge channel may be changed into various shapes such as trapezoidal, semicircular, and elliptical. In addition, the lower substrate as well as the upper substrate can be utilized as the light emitting surface. In this case, it is preferable that the partition wall partitioning the discharge channel is not formed with a fluorescent layer or a protective film so as to be used as a transmission surface of light emitted from the lower substrate, that is, a pseudo light emitting surface. By using not only the discharge channel but also the partition wall as the light emitting surface, high luminance can be ensured as the surface light source, and luminance uniformity is also greatly improved.

13 to 16 are cross-sectional views taken along the line X-X 'of FIG. 1 to illustrate various types of discharge channels. As an example, referring to FIG. 13, a discharge channel is formed in both the upper substrate 112 and the lower substrate 114 so that the discharge space is wide, and in particular, reflects the back light (light emitted through the lower substrate) to emit the front surface. It is advantageous to In another embodiment, FIG. 14 illustrates a discharge channel formed on the upper substrate 112, and FIG. 15 illustrates a discharge channel formed on the lower substrate 114. The discharge channel can be formed, for example, by partially forming a flat glass substrate.

As another embodiment, referring to FIG. 16, discharge channels 120 are formed on both the upper substrate 112 and the lower substrate 114, and the reflector plate 170 is positioned under the lower substrate. Light emitted from the lower substrate 114 is reflected toward the upper substrate through the reflector plate 170, and in particular, is emitted upward through the partition wall. When the upper substrate 112 is used as the front portion (ie, the light emitting surface) of the surface light source device, the luminance is further improved by the light emitted from the lower substrate and emitted to the front surface through the reflecting plate.

The upper substrate and the lower substrate should be transparent to visible light so that the light generated by the discharge and the reflected light can be easily transmitted, and it is preferable that a fluorescent layer or the like is not formed on the partition wall.

The surface light source device according to the present invention may vary the arrangement, number, and shape of discharge channels. Referring to FIG. 17, it can be seen that the discharge channels 120 are vertically arranged with respect to the long sides of the rectangular light source body 110.

In FIG. 18, a plurality of discharge channels horizontal to the long sides of the rectangular light source body 110 are formed. It can be seen that both ends 121 of the discharge channel are larger in area. The end of the discharge channel is easily affected by the outside of the light source body, so it may be overcome by expanding the discharge space more.

The surface light source device according to the present invention may include a plurality of discharge channels, or a single discharge channel may be formed. In addition, the hot cathode encapsulated in each discharge channel may be supplied with voltage by a plurality of inverters, or may be supplied with voltage by one inverter. In addition, a plurality of inverters may be connected in series or in parallel to supply voltage.

19 is an exploded perspective view showing a backlight unit including a surface light source device according to the present invention. As shown, the backlight unit includes a surface light source device 100, upper and lower cases 1100 and 1200, an optical sheet 900, a reflector plate 170, and an inverter 1300. The lower case 1200 includes a bottom portion 1210 and a plurality of sidewall portions 1220 extending to form an accommodation space from an edge of the bottom portion 1210 for accommodating the surface light source device 100. The surface light source device 100 is accommodated in a storage space of the lower case 1200.

The inverter 1300 is disposed on the rear surface of the lower case 1200 and generates a discharge voltage for driving the surface light source device 100. The discharge voltage generated from the inverter 1300 is applied to the electrode portion of the surface light source device 100 through the first and second power lines 1352 and 1354, respectively. The optical sheet 900 may include a diffuser plate for uniformly diffusing the light emitted from the surface light source device 100, and a prism sheet for imparting linearity to the diffused light. The upper case 1100 is coupled to the lower case 1200 to support the surface light source device 100 and the optical sheet 900. The upper case 1100 prevents the surface light source device 100 from being separated from the lower case 1200.

Unlike the illustrated figure, the upper case 1100 and the lower case 1200 may be formed as one integrated case. On the other hand, the backlight unit according to the present invention may not include the optical sheet 900 because the brightness and luminance uniformity of the surface light source device is excellent.

Although described above with reference to preferred embodiments of the present invention, those skilled in the art or those skilled in the art without departing from the spirit and scope of the invention described in the claims to be described later Various modifications and variations can be made in the present invention without departing from the scope thereof.

According to the present invention, by applying a hot cathode having excellent durability to the surface light source device to maximize the stability of the electrode even during long-term use, the concentration of heat is prevented it is possible to prevent local damage of the light source body. In addition, due to the hot electron emission effect of the hot cathode, the light emitting efficiency is superior to that of a flat fluorescent lamp having an external electrode, and high heat of 800 to 1000 ° C. is generated at the initial stage of discharge, thereby greatly reducing initial luminance stabilization time. In addition, power consumption is lowered due to high efficiency, and high brightness can be secured by reflecting back light and using a non-light emitting area as a light emitting surface. In addition, the process is easy to automate, making it suitable for mass production.

Claims (20)

Non-linear filaments, The hot cathode for the surface light source which physically supports the filament and includes at least one wire electrically connected to the outside. The hot cathode of claim 1, wherein the filament is supported by at least two wires. 3. The hot cathode of claim 2, wherein the filament is supported by at least three wires including auxiliary wires. The hot cathode of claim 1, wherein the hot cathode comprises two or more filaments. The hot cathode of claim 1, wherein the filament is polygonal or circular. A plate-shaped light source body including at least one discharge channel, A hot cathode encapsulated in the discharge channel comprising a non-linear filament Surface light source device. The surface light source device of claim 6, wherein the light source body includes a plurality of discharge channels and a partition wall partitioning the discharge channels. The surface light source device of claim 7, wherein the light source body has a fluorescent layer formed on an inner surface of the light source body. The surface light source device of claim 6, wherein the light source body includes a plurality of discharge channels that are rectangular and parallel to long sides. The surface light source device of claim 6, wherein the light source body includes a plurality of discharge channels that are rectangular and perpendicular to a long side. The surface light source device of claim 6, wherein the light source body includes an upper substrate and a lower substrate that are transparent to visible light. The surface light source device of claim 11, wherein a discharge channel is formed on at least one surface of the upper substrate and the lower substrate. The surface light source device of claim 6, wherein the hot cathode is electrically connected to the outside of the light source body by a lead wire. The surface light source device of claim 13, wherein the lead wire is fixed to the edge of the light source body by a frit. The surface light source device of claim 14, wherein a subchannel is formed at an edge of the light source body to which the lead wire is bonded. The surface light source device of claim 13, wherein the lead wire comprises a thermal expansion alleviating material. The surface light source device of claim 6, wherein the discharge channel has a relatively large area at the end where the hot cathode is sealed. A surface light source device including a plate-shaped light source body including at least one discharge channel, and a non-linear filament as a hot cathode encapsulated in the discharge channel; A case accommodating the surface light source device; And Including an inverter for applying a voltage to the hot cathode Backlight unit. 19. The backlight unit of claim 18, further comprising a reflector plate spaced apart from the surface light source device at a predetermined interval. The backlight unit of claim 18, wherein the plurality of inverters are connected in series or in parallel.

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