KR100350014B1 - Backlight including External electrode fluorescent lamp and the driving method thereof - Google Patents

Abstract

Disclosed are a backlight and a driving method including an external electrode fluorescent lamp. The present invention provides a fluorescent lamp formed with an external electrode made of a conductive material to surround the outer peripheral surface including the edge end surface of both ends of the glass plate coated with a phosphor layer, and a plurality of such fluorescent lamps are installed outside the light guide plate, or between the reflecting plate and the diffuser plate. AC power is supplied from the outside to be electrically connected to each other, or installed at a predetermined interval between the upper and lower substrates to which the phosphor layer is applied, and alternating from both inside or outside of the combined upper and lower substrates. An electrode to which power is applied is formed. According to the present invention, the electrodes of the fluorescent lamp are formed on the outside and overlapped to be connected and driven by a single power source in a parallel connection method, and the fluorescent lamp functions as a partition wall and emits light at the same time, thereby providing uniform luminance. Performance and thinning are possible. In the present invention, the backlight is driven by a square wave from a switching circuit inverter, and is characterized by the utilization of an overshooting waveform and a self-discharge effect, which are advantageous for initial discharge, thereby realizing high brightness and high efficiency with low frequency driving of several 10 kHz.

Description

Backlight including external electrode fluorescent lamp and the driving method

The present invention relates to a backlight including an external electrode fluorescent lamp and a driving method thereof. More specifically, an external electrode is installed at both ends of an electrodeless fluorescent lamp, and an external AC voltage of 100 kHz or less is applied by a switching inverter. The present invention relates to a backlight including an electrode fluorescent lamp and a driving method thereof.

In general, a flat panel display is classified into a light emitting type and a light receiving type. The light emitting type includes a flat cathode ray tube, a plasma display panel, an electroluminescent device, a fluorescent display device, a light emitting diode, and the like. The light-receiving type includes a liquid crystal display.

Among these, since the liquid crystal display itself emits light and does not form an image, and light is incident from the outside to form an image, there is a problem that the image cannot be observed in a dark place.

In order to solve this problem, a backlight is provided on the back of the liquid crystal display to irradiate light. Thus, the image can be seen even in a dark place. Typical requirements for backlights include high brightness, high efficiency, uniformity of brightness, long life, thinness, low weight and low cost. In the case of notebook PCs, high efficiency long life lamps are required to reduce power consumption, and backlights for monitors and TVs require high brightness.

As a backlight, a cold cathode fluorescent lamp (CCFL) is disposed, and a fluorescent lamp is coated with a flat fluorescent lamp. The CCFL can be classified into an edge light method using a light guide plate and a direct light method arranged in a plane according to the arrangement of the light source on the display surface.

However, the CCFL according to the prior art operates at a high brightness of about 30,000 cd / m ² and the life of the lamp is a problem. In particular, the edge emitting method is CCFL itself emits high luminance, but the panel brightness is low, which is not suitable for large screen panels. In the direct type, CCFLs cannot be connected in parallel to be driven by a single inverter, and the number of CCFLs arranged in a plane is limited for proper brightness of the panel. The thickness of the panel is large because the distance between the diffuser plate and the lamp increases.

In the flat fluorescent lamp method, since the internal pressure of the upper and lower substrates to be assembled is lower than atmospheric pressure, the glass substrate should have sufficient thickness to prevent breakage. As a result, the weight is heavy. In addition, in the planar fluorescent lamp system, spacers and partitions having a bead or cross shape are installed between upper and lower substrates in order to increase the screen area, and a problem of weight according to the thickness of the substrate and generation of heat due to low efficiency are serious. In the case of using the partition wall, the stripe pattern of the partition wall appears on the screen, so that uniformity of luminance cannot be guaranteed.

Therefore, it is necessary to develop a backlight which can ensure high brightness and high efficiency of liquid crystal displays in a large-scale trend, and at the same time, can lead to long life and light weight.

The electrode structure of a conventional External Electrode Fluorescent Lamp (EEFL) has a variety of methods, such as a belt type, a glass tube bonding type of a metal cap, and a bulging type space at both ends of the glass tube (FIG. 10). Reference). In the meantime, the EEFL has a longer lifespan than the CCFL, but in general, the EEFL obtains high brightness due to the high frequency driving of several MHz. Therefore, the EEFL has not been adopted as a light source of the backlight due to the problem of high frequency EMI, low efficiency, and high frequency power supply. In addition, when driving an EEFL using an LC-resonant inverter, brightness and efficiency are extremely low and cannot be employed as a light source of a backlight.

Fig. 11 shows a conventional form of an external electrode fluorescent lamp compared with the present invention. Fig. 11A is a belt type external electrode, characterized in that a belt electrode is provided in a plurality of pairs in a glass tube cylinder, and the length of each belt electrode is made small and driven by a high frequency of MHz or higher. The belt-type EEFL of FIG. 11A has an advantage of installing an electrode in the middle portion of the glass tube because the electrode is installed in the cylinder of the glass tube. Recently, the backlight is configured by directly placing a belt type external electrode fluorescent lamp on the reflection plate, and the external electrode fluorescent lamp achieves high luminance of several 10,000 ck / m ² by driving a high frequency of several MHz. It was. In particular, when the length of the glass tube is long in such a high frequency drive, a belt-shaped electrode is provided in the middle portion of the glass tube, but there is a problem in realizing the uniformity and thinness of the panel due to the decrease in luminance of the electrode portion. have. However, driving by high frequency basically has a problem of emission of electromagnetic waves (EMI), low efficiency, and the inability to miniaturize a high frequency power supply. This is shown in Japanese Patent No. 60-25488 (1985.2.13), Korean Patent Application No. 10-1999-0052964, and Japanese Patent No. 98-336926 (1998.11.27).

FIG. 11B is a view in which a metal capsule is bonded to an end of a glass tube, and a ferroelectric is applied to the inside of the metal capsule. This is shown in US Pat. No. 2,624,858 (1953.6.6). The scheme of FIG. 11B is employed when the glass tube diameter is large. That is, this method is adopted because of the capacitive voltage drop applied to the glass tube itself when the glass tube is thick, but the joint is easily damaged because the coefficient of thermal expansion between the glass tube and the metal is fundamentally different. However, in the case of microtubes with a glass tube outer diameter of 2.6 mm and a glass tube thickness of 0.5 mm or less, such as a cold cathode tube commonly used in backlights, metal capsules and glass tubes have a small capacitive voltage drop due to the glass tube thickness. There is no reason to employ a method of joining.

11C and 11D form a space wider than both ends of the glass tube for the purpose of high brightness and high efficiency. This is shown in US Pat. Nos. 1,612,387 (1926.11.28) and 1,676,790 (1928.7.10). When the space at both ends of the glass tube is thus enlarged, the brightness and efficiency of the lamp are increased, but it is difficult to employ such a structure in the microtube.

In the present invention, the external electrode to which a spherical alternating voltage of 100 kHz or less is applied by the switching inverter has a variety of methods based on an end-cap type electrode covering both ends of a sealed glass tube as a microtube having a diameter of several mm. have. The end-cap type electrode which surrounds the cylindrical surface including the edges of both ends of the glass tube is advantageous to realize high brightness and high efficiency as compared to the belt type that simply covers the cylindrical surface. According to the experimental results of the applicant, the longer the length of the electrode in the glass tube direction, the higher the brightness is obtained. However, when the electrode length is long, the effective light emitting surface is reduced, and when the backlight is employed, the electrode portion is wide, and thus the edge region where the panel is not emitted is widened. Therefore, the end-cap type is advantageous over the belt type in that the length of the electrode can be as short as possible, and the fluorescent lamp according to the present invention has a belt type in the middle in the direction of the glass tube. There is no reason to form. On the other hand, the method of increasing the space at both ends of the glass tube is difficult to adopt in the manufacturing process of the microtube. The fluorescent lamp according to the present invention adopts the method of bending the end of the glass tube in addition to the straight capsule type to minimize the non-emitting area of the edge when appropriately selecting the length of the electrode of both ends, and when employed as the edge light emitting type or direct backlight type light source The high brightness and high efficiency are obtained by securing the length of the external electrode at the end of the glass tube.

Another aspect of the present invention relates to the driving of a backlight employing an external electrode fluorescent lamp, and more particularly, to provide a driving circuit for realizing the uniformity, high brightness and high efficiency of the luminance of a large area backlight.

A well-known example of driving a cold cathode fluorescent lamp employed in a conventional backlight is well shown in Korean Patent Publication No. 1998-028921.

12 is a circuit diagram showing a CCFL drive IC for a LCD panel and a peripheral circuit according to the known example, wherein the lamp driver IC 100 having a plurality of input / output pins and the main power circuit unit 120 having a half bridge circuit are shown. ), And lamp 140.

Meanwhile, the lamp driving IC 100 may include a first pin 1 connected to an input voltage terminal, a second pin 2 connected to a predetermined minimum frequency terminal, and a third pin connected to a predetermined maximum frequency terminal ( 3), the fourth pin 4 connected to the ground voltage terminal, the fifth pin 5 connected to the feedback voltage terminal, the sixth pin 6 connected to the predetermined comparison terminal, and the predetermined internal high voltage terminal. A seventh pin 7 connected thereto and an eighth pin 8 connected to a predetermined external control signal terminal to determine whether an IC circuit is on or off.

In addition, the main power circuit unit 120 is composed of a half-bridge circuit consisting of a plurality of passive elements in response to the output signal of a predetermined pin of the lamp driving IC 100, and the lamp 140 is the main power circuit unit ( It is configured to be driven in response to a predetermined output signal of 120.

The voltage applied to the CCFL commonly used in LCD backlights is in the form of sine waves. As in the above example, in the case of CCFL, a high alternating voltage of several tens of kHz obtained from an LC resonant inverter is obtained by using a boost transformer to obtain a high voltage necessary to maintain the discharge start light of the CCFL. Such LC resonant inverter has the advantage of relatively simple device and high efficiency. However, CCFLs cannot be driven by one inverter in parallel. Therefore, backlights combined with light guide plates employing CCFLs or direct type require an inverter corresponding to the number of CCFLs.

Meanwhile, the EEFLs may be connected in parallel to each other to drive a plurality of EEFLs by one inverter. The reason is that since EEFL is not exposed to the discharge space and the electrode exists outside the glass tube, a real current does not flow to the electrode, wall charges are accumulated on both electrode portions, and discharge is caused by the formation of a reverse voltage by wall charges on both ends of the lamp. This stops, then another lamp is discharged and likewise wall charges are formed, then another lamp is discharged sequentially so that a plurality of lamps emit light by one inverter. However, when the EEFL is driven using an inverter that outputs a sine wave used to drive the CCFL, brightness and efficiency are extremely low because the wall charge cannot be effectively controlled. In addition, when a plurality of EEFLs are connected in parallel and driven by such an inverter, the time required to apply high voltage in one cycle is limited, so that the number of emitted EEFLs is limited. Castle can not be realized.

Thus, since the EEFL cannot be driven by an LC resonant inverter of several tens of kHz, unlike the CCFL, it is difficult to realize a backlight using the EEFL. In addition, the conventional drive of the EEFL by a high frequency of several MHz is difficult to overcome the problems of EMI, low efficiency, miniaturization of the high frequency power supply.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and includes a backlight for disposing a glass tube with external electrodes disposed on a light guide plate or on a reflector and applying a spherical alternating voltage of 100 kHz or less, and uniformity and high brightness of these backlights. And to provide a backlight driving method for achieving high efficiency.

In general, the fluorescent lamp is driven by an LC resonant inverter. However, in the present invention, the external electrode fluorescent lamp is driven by a switching inverter circuit that outputs a spherical AC pulse wave, thereby achieving more than twice the luminance and efficiency as compared to driving the LC resonant inverter. That is, a high luminance of several 10,000 cd / m ^{2 and} a high efficiency of 10 lm / W or more were achieved for a single tube of an external electrode fluorescent lamp having an outer diameter of 2.6 mm, which is generally employed in LCD-backlight. In particular, according to the experimental results of the applicant, the EEFL of the backlight according to the present invention achieved a higher efficiency than the CCFL at a luminance of about 10,000 cd / m ² . Therefore, utilizing these characteristics to operate at the brightness with the highest efficiency makes it easy to adopt EEFL as the light source of the backlight. In particular, it has advantages such as longer lifespan, easier manufacturing of electrodeless lamps than CCFLs, and can be driven by a single inverter by connecting a plurality of external electrode fluorescent lamps in parallel.

In the present invention, the external electrode fluorescent lamps are disposed in the direct light emitting method and the edge light emitting method as in the CCFL. Another object of the present invention is to provide a backlight using a plurality of fluorescent lamps as partition walls by disposing a plurality of fluorescent lamps having external electrodes between upper and lower substrates on which phosphor layers are formed. Another object of the present invention is to provide a driving method for realizing the uniformity, high brightness and high efficiency of luminance of a large area backlight manufactured by arranging a plurality of external electrode fluorescent lamps.

1A is a perspective view of an end-cap linear external electrode fluorescent lamp according to the present invention;

Figure 1b is a perspective view of a curved external electrode fluorescent lamp according to the present invention.

2 is a diagram illustrating a backlight arrangement method in which an external electrode fluorescent lamp according to a first exemplary embodiment of the present invention is disposed at an edge of a light guide plate.

Figure 3a is an illustration of the arrangement of the linear end-cap fluorescent lamp of the direct backlight according to the second embodiment of the present invention.

Figure 3b is an illustration of the arrangement of the curved electrode fluorescent lamp of the direct backlight according to the second embodiment of the present invention.

Figure 3c is an illustration of another arrangement of the curved electrode fluorescent lamp of the direct backlight according to the second embodiment of the present invention.

Figure 3d is an illustration of a connection scheme by the overlap capsule of the direct backlight according to the second embodiment of the present invention.

Figure 3e is an illustration of the overlapping arrangement of the lamp direction of the large-screen direct-type backlight according to the second embodiment of the present invention. Figure 3f is a layout of the EEFL for configuring a super-large backlight according to a second embodiment of the present invention An illustration of the.

Figure 4 is an exploded perspective view showing a direct backlight according to a second embodiment of the present invention.

5 is an exemplary view illustrating a method of arranging a reflecting plate and a fluorescent lamp of a direct backlight according to a second embodiment of the present invention.

Figure 6a is an exploded perspective view showing a state before the partition-emitting backlight according to the third embodiment of the present invention is coupled.

FIG. 6B is a perspective view partially showing the state after the backlight of FIG. 6A is coupled; FIG.

FIG. 6C is a conceptual diagram illustrating an electrode structure illustrating a coupling method of an internal socket type multi-capsule electrode and an electrodeless fluorescent lamp installed inside a flat fluorescent lamp of a partition-emitting backlight according to a third exemplary embodiment of the present invention. FIG.

7 is a schematic diagram illustrating a signal waveform applied to a switching inverter and a gate according to an embodiment of the present invention.

FIG. 8 is a schematic diagram illustrating changes in a switching inverter output waveform before and after the start of discharge according to an embodiment of the present invention. FIG.

9 is a schematic view illustrating a self discharge phenomenon in square wave driving according to an embodiment of the present invention.

10 is a schematic diagram showing in-phase split driving for driving a large area backlight according to another embodiment of the present invention.

11 is an illustration of a conventional external electrode fluorescent lamp.

Fig. 12 is a circuit diagram showing a conventional CCFL drive IC for an LCD panel and a peripheral circuit.

* Explanation of symbols for main parts of the drawings

10, 22, 35: fluorescent lamp 11: glass tube

12: phosphor layer 13, 23, 36: external electrode

20, 30: backlight 21: reflector

24, 300: electrode connection line 25: diffusion plate

31: upper substrate 32: lower substrate

33: upper phosphor layer 34: lower phosphor layer

37: upper electrode 38: lower electrode

39: edge support

In order to achieve the above object, the present invention is composed of a glass tube in which a discharge gas is injected and a phosphor layer is coated on an inner circumferential wall, and both ends are sealed, and a straight, L-shaped, C-shaped, spiral or wave-shaped bent form, and both ends of the glass tube Provided is a backlight including an external electrode fluorescent lamp having an end-cap type external electrode formed to enclose, and a switching inverter connected to the external electrode and applying a spherical alternating voltage of 100 kHz or less. An upper substrate coated with an upper phosphor layer, a lower substrate disposed to face the upper substrate and having a lower phosphor layer coated thereon, an edge support interposed between the upper and lower substrates to seal them, a discharge gas is injected into the inner circumferential wall A phosphor tube is coated and both ends are enclosed and end-formed to surround both ends of the glass tube. A plurality of external electrode fluorescent lamps including a type external electrode and spaced apart from each other by a predetermined distance, discharge gas injected into an inner space during sealing of the upper and lower substrates, and corresponding upper and lower substrates Provided with a backlight is formed on each of both outer surfaces and the electrode connected to the electrode connecting line to which the AC power is applied, and a switching inverter connected to the electrode for applying a spherical AC voltage of 100kHz or less. Dividing the plurality of fluorescent lamps into a plurality of regions by a method of driving a large area backlight; connecting external electrodes of the fluorescent lamps of the divided regions with the same electrode connection line, respectively; Connecting switching inverters each outputting a spherical low frequency of 100 kHz or less to the connected electrode connecting line, Group and provides a driving method of the switching inverter comprises a step of supplying a rectangular AC voltage of less than 100kHz-phase at the same time in each external electrode fluorescent lamp in accordance with the steps and the gate signal applied to the same gate signal to each switching inverter.

Hereinafter, a fluorescent lamp and a backlight employing the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a fluorescent lamp 10 according to the present invention.

Referring to the drawings, the fluorescent lamp 10 includes a cylindrical glass tube 11. The phosphor 12 is coated on the inner circumferential wall of the glass tube 11. The glass tube 11 is coated with a phosphor 12 and then injected with a discharge gas made of mixed inert gas, mercury (Hg), or the like, and then sealed at both ends. The cross section of the glass tube 11 may be not only circular but also flat oval, but also integrally bent and multi-cylindrical.

In FIG. 1A, end-cap type external electrodes 13 are formed at both ends of a straight outer circumferential surface of both ends of the sealed glass tube 11. According to the experimental results of the applicant, the length of the cap of the outer electrode portion should be sufficiently secured to achieve high brightness and high efficiency. Therefore, the external electrode is formed by lengthening the end-cap electrode or by bending both ends of the glass tube. In this case, as shown in FIG. 1B, there are various forms such as an “L” shape, a “C” shape, a spiral shape, and a wave shape. The curved external electrode is manufactured by directly bending the end of the straight glass tube, or by separately manufacturing a curved glass tube in which the electrode is installed, and bonding them to both ends of the straight glass tube coated with phosphor.

The external electrode 13 is formed of a conductive material, and completely surrounds the end of the glass tube 11, and does not apply phosphor to the inside of the glass tube corresponding to the external electrode. The external electrode 13 may be formed by a method of attaching a metal cap or a metal tape, or by dipping both ends of the glass tube 11 in a metal solution. The external electrode 13 is preferably aluminum, silver, copper, or the like, which is a conductive material having low electrical resistance.

In the present invention, when the length of the glass tube is long, it is not necessary to employ a belt-type electrode in the middle portion of the glass tube in addition to the end-cap of both ends of the glass tube. The reason for this is that the longer the glass tube, the farther the distance between the electrodes, the more advantageous the luminance and efficiency of the EEFL. In addition, the belt type electrode is disadvantageous in terms of brightness and efficiency relative to the end-cap type electrode, and is disadvantageous in thinness due to the nonuniformity of the luminance of the electrode portion provided in the middle of the glass tube.

On the other hand, the glass tube 11 is coated with a ferroelectric to the inner side corresponding to the external electrode 13 for the purpose of increasing the long life and the generation of secondary electrons, or insert a separate installation with a dielectric applied to both ends of the inner glass tube The sealing method can be adopted. In addition, magnesium oxide, calcium oxide, or the like may be applied in order to apply a ferroelectric and to facilitate the role of the protective film and the electron emission.

2 illustrates an edge-emitting backlight according to a first embodiment of the present invention. As shown in the drawing, the EEFL may be arranged in various ways around the light guide plate. Like the cold-cathode fluorescent lamp, the external electrode fluorescent lamp of the present invention can be adopted as an edge emission type because of the end-cap type electrode and the bent electrode structure as shown in FIG. 1 and the driving scheme employed in the present invention. This is because the lamp can be realized. A plurality of lamps of the present invention are installed on the edge of the light guide plate, and the plurality of lamps are connected to each other in parallel to be driven by one inverter. It can be provided in both sides or all edges of a light guide plate, and multiple pieces can also be provided in each side surface.

3 illustrates a direct placement method of an EEFL according to a second embodiment of the present invention. In the present invention, the EEFL is connected in parallel to drive a switching inverter to realize high efficiency and uniformity of brightness. In the case of a microtube having an outer diameter of 2.6 mm, the efficiency is high when the brightness is about 10,000 cd / m ^2. . Therefore, the high luminance surface light source having a planar luminance of 10,000 cd / m ² or more in the panel by the direct placement of the EEFL arranges the EEFL on the planar reflector with a small gap between lamps. However, in the case of a surface light source for the purpose of luminance of several thousand cd / m ² , a high efficiency backlight is realized by adopting a special reflector structure to properly arrange the interval between lamps and improve the reflectance.

All lamps placed on the reflector are connected in parallel and are based on driving a single inverter. In the arrangement method, the straight EEFLs are arranged at appropriate intervals as shown in FIG. 3A, the “L” shaped electrodes are placed on the plane as shown in FIG. 3B, or the “L” shaped electrodes are laid on the plane as shown in FIG. Minimize the light emitting area. FIG. 3D is a method of arranging a long lamp at the edge of the panel, which is employed for the purpose of increasing the luminous efficiency of the lamp. It is also possible to insert the electrodeless lamp into the external socket-type multi-capsule electrode structure as shown in Figure 3e.

3F illustrates an arrangement of EEFLs for constructing an ultra-large backlight. A plurality of EEFLs are arranged in the longitudinal direction of the lamp, but in order to prevent a sharp decrease in luminance at the electrode portion, the electrode surface is coated with a reflector or the electrode itself is made of a transparent electrode material. In order to compensate for the deterioration in brightness of the overlapping portion of the electrode portions of the lamp, the electrode portions are arranged in parallel in the longitudinal direction in the middle of the panel. The reflector is further applied to the electrode surface of the metal material located in the middle of the panel, or the electrode positioned in the middle is made of a conductive transparent electrode material to minimize the decrease in luminance.

4 is a backlight employing a direct placement of the EEFL according to the second embodiment.

Referring to the figure, the backlight 20 is provided with a reflecting plate 21. The fluorescent lamp 22 is provided on the upper surface of the reflecting plate 21. As described above, the fluorescent lamp 22 is an external electrode fluorescent lamp (EEFL) in which a phosphor is coated on an inner circumferential surface thereof and an outer electrode 23 made of a conductive material is formed on both ends of the outer circumferential surface, respectively. The plurality of fluorescent lamps 22 are arranged in close contact with each other at regular intervals on the upper surface of the reflector 21 in order to maintain uniformity of luminance.

In order to electrically connect the fluorescent lamps 22, the external electrodes 23 may be energized with each other, and electrode connection lines 24 are connected to the outermost external electrodes 23a, respectively. For this reason, the fluorescent lamp 22 can be driven in parallel when AC power is applied.

The diffusion plate 25 is disposed on the fluorescent lamp 22 to face the reflecting plate 21. In order to prevent the diffusion plate 25 from appearing in the image of the fluorescent lamp 22, it may be advantageous to maintain an appropriate distance from the fluorescent lamp 22 to increase the uniformity of luminance.

Here, the distance from the fluorescent lamp 22 of the diffusion plate 25 corresponds to the diameter of the fluorescent lamp 22. For example, if the diameter of the fluorescent lamp 22 is 2.6 mm, the distance from the diffuser plate 25 is about 2.6 mm. As a result, the minimum thickness will be about 5.2 mm.

According to the applicant's experiment, the backlight 30 employing an EEFL having an outer diameter of 2.6 mm has a luminance of 10000 cd / m ² or more, an efficiency of 50 lm / W or more, and no high heat is generated. In particular, by adopting the EEFL with a long EEFL, the longer the length of the lamp direction of the panel, the higher the luminance and the higher the efficiency.

5 is a backlight according to a second embodiment of the present invention in the form of an EEFL and a half market. FIG. 5A shows a case where the intervals between the lamps are arranged at intervals of about the lamp diameter, and the EEFL is disposed on a simple flat reflector. In this case, as shown in FIG. 4, the backlight is aimed for high luminance over a luminance emitted by a single lamp. However, in the case where the luminance of the panel is aimed at a luminance smaller than that of a single lamp, it is shown in FIGS. 5B-5D that arrange the intervals between the lamps at intervals of several times the outer diameter of the lamp, and in this case, as shown in FIG. The base is provided to increase the reflectance, or install a concave mirror wave pattern reflector as shown in FIG. 5C. Also, as shown in FIG. 5D, a groove may be provided in the light guide plate to insert a lamp into the groove, and a reflecting plate and a diffusion plate may be installed to increase the reflectivity and the uniformity of luminance. According to the experimental results of the applicant, the EEFL having an outer diameter of 2.6 mm is disposed on the reflecting plate at intervals of about 15 mm, and the distance between the lamp and the diffuser is 25 mm, and the luminance is not less than 50 lm / W at a luminance number of 10000 cd / m ² or more. High efficiency backlight is realized.

FIG. 6A illustrates a state before the backlight 30 according to the third embodiment of the present invention is coupled, and FIG. 6B illustrates a state after the backlight 30 of FIG. 6A is coupled.

6A and 6B, the backlight 30 includes an upper substrate 31 and a lower substrate 32 that is installed to face the upper substrate 31. An upper phosphor layer 33 is formed on the lower surface of the upper substrate 31. The lower phosphor layer 34 is also formed on the lower surface of the lower substrate 32.

A plurality of fluorescent lamps 35 are provided on the lower substrate 32 so as to be spaced apart by a predetermined interval. The fluorescent lamp 35 serves as a partition wall while supporting the upper and lower substrates 31 and 32 when they are coupled. The fluorescent lamp 35 is provided with an external electrode 36 made of a conductive material at both ends of the outer circumferential surface of the fluorescent lamp 35.

The upper and lower substrates 31 and 32 are respectively provided with an upper electrode 37 and a lower electrode 38 to supply power to the backlight 30 along the outer surface of the corresponding side during assembly. The upper and lower electrodes 37 and 38 surround part of the outer surface of the upper and lower substrates 31 and 32 in the form of a cover, and are made of a conductive metal material. At this time, since the lower electrode 38 is advantageous in obtaining a stable discharge, it is preferable to extend the lower electrode 38 to the lower surface of the lower substrate 32.

An edge support 39 is provided between the upper and lower substrates 31 and 32 to seal them together along their edges to maintain airtightness. Discharge gas is injected into the backlight 30 before sealing it in the state where the edge support 39 is interposed between the upper and lower substrates 31 and 32.

The upper and lower electrodes 37 and 38 may be separately formed on the substrates 31 and 32, and then may be manufactured to enable energization on both sides of the substrates 31 and 32, respectively. 32) may be assembled to form an integral cover after assembly.

The upper and lower electrodes 37 and 38 are respectively connected to the electrode connection lines 300 on both sides of the substrates 31 and 32 to supply power.

On the other hand, the external electrode 36 formed on the fluorescent lamp 35 is not directly connected to the upper and lower electrodes 37 and 38, but is disposed in a floating state so that the electrodes 37 and 38 are disposed. The discharge is generated in a manner induced by the power supplied to. The external electrode 36 may be excluded in some cases, but it may be advantageous to obtain a stable discharge by installing the external electrode 36.

Since the backlight 30 having the structure as described above is manufactured and disposed separately between the upper and lower substrates 31 and 32 when the external electrode fluorescent lamp 35 is applied with power through the electrode connection line 300. At the same time as the partition wall can emit light.

6A and 6B in the present invention are the basic type of the partition-emitting flat plate lamp, which is convenient because the voltage is applied to the plate external electrode, but the driving voltage is high due to the capacitive voltage drop due to the thickness of the upper and lower glass plates. In order to improve this point, a method of providing an electrode of a metal material coated with a dielectric inside the flat plate can be adopted. That is, as shown in FIG. 6C, an internal socket type multi-capsule electrode structure for mounting an electrodeless fluorescent tube may be installed at both ends of the lower plate inside the plate, and the upper plate may be sealed to guide the electrode connecting line to the outside to connect the power supply. . At this time, all surfaces of the internal socket-type multi-capsule electrode structure are coated with a ferroelectric to prevent direct current from flowing directly to the electrode during discharge. As shown in the drawing, the ferroelectric is separated into two upper and lower pieces (top electrode and lower electrode) so as to easily apply the ferroelectric to the inside of the groove, and the ferroelectric is applied to all surfaces, and the electrodeless fluorescent tube is mounted to combine the two pieces.

Therefore, in the conventional backlight, when the fluorescent lamp is used as the partition wall, the partition wall is dark so that the uniformity of the brightness cannot be maintained. According to the feature of the present invention, the fluorescent lamp 35 can also emit light by itself so that the uniformity of the brightness is achieved. You can get it. In addition, since the fluorescent lamp 35 serves as a partition wall, the thickness of the upper and lower substrates 31 and 32 glass may be reduced to be light and advantageous to large area.

An inverter, a driving method, and an operation according to another embodiment of the present invention for driving the backlight according to the edge arrangement and the direct type arrangement of the EEFL as described above will be described in detail.

Switching inverter according to an embodiment of the present invention is a combination of a switching circuit and a boost transformer, the power supply is a square wave output suitable for driving a plurality of parallel connected external electrode fluorescent lamps, and easily adjust the frequency and output waveform conditions There is an overshooting part in the output waveform.

The divided driving method according to another embodiment of the present invention is applied to a large area flat lamp which adopts an alternating current type discharge by applying a large area backlight or an electrode by a planar arrangement of EEFL to a dielectric layer, and the large area is divided into several regions. By dividing and driving each phase with the in-phase waveform, it was devised to reduce the size of the driving device and enable stable high speed driving.

7 illustrates a signal waveform applied to a switching inverter and a gate according to an embodiment of the present invention. The device is designed to effectively drive multiple paralleled EEFLs. Its circuit features four high-speed FETs and boosts, unlike LC resonant inverters used to drive conventional CCFLs. The transformer is combined to output a high pressure square wave. Also, the frequency and voltage holding ratio of the output square wave can be easily adjusted by adjusting the respective FET gate signals shown in FIG. The operating principle of the switching inverter of the present invention is as follows. A gate signal of the type shown in Fig. 7 is applied to each FET while DC is applied to the FETs provided on the circuit top and the drains of A and C. Each FET then turns A and D on and off over time, and C and B do the same. At this time, since the boost transformer is connected to the left and right FET output stages, current flows compatible with the primary coil of the boost transformer during the time when each FET is turned on. Therefore, the high voltage square wave output is generated in the secondary coil of the boost transformer as shown in FIG. 8. Unlike the sine wave, this output waveform has a fast voltage rise time and a constant voltage holding period. In addition, a transient over shooting voltage occurs in a section in which the voltage changes rapidly due to the characteristics of the coil.

Details of the operation of the inverter are as follows. Unlike the conventional LC resonant inverter, the square wave output voltage waveform generated from the switching inverter can stably operate a plurality of parallel-connected EEFLs with uniform luminance with only one switching inverter. The reason is that the square wave has a constant voltage holding period unlike the sine wave, and when the square wave is applied to the EEFLs simultaneously and turned on, even though each EEFL lamp is sequentially turned on within a period of the applied voltage, the applied voltage Unlike the sine wave, since it maintains a constant discharge voltage, the degree of lighting of each lamp is uniform, thereby maintaining a uniform light emission uniformity. Another reason is that the rise time of the voltage over time is always short compared to the sine wave of the same frequency. After being sequentially turned on and off by an initially applied voltage, a large number of space charges and excited molecules remain inside the tube, among which space charges are formed between the wall charges formed around the electrode during the initial discharge. The electrical field is then slowly recombined with the wall charge. These spatial charges and excitation molecules are dependent on the strength and temporal change of the electric field across the tube. For sine waves, the slope of the voltage rise is always slower than the square wave of the same frequency. During this time, a kind of wall charge erase phenomenon occurs in which the space charges combine with the wall charges formed during the initial discharge by the electric field formed by the voltage being applied. As a result, the amount of wall charges is lowered, which results in a smaller voltage range, that is, a sustain voltage margin, in which stable discharge can be maintained, and the intensity of discharge is also reduced, resulting in a decrease in brightness and efficiency. However, since the square wave output from the switching inverter according to the present invention has a voltage rise time relatively faster than the sine wave, it is possible to cause the discharge to start because the applied voltage exceeds the discharge start voltage before the space charge recombines with the wall charge. Therefore, the above-mentioned wall charge erase phenomenon becomes insignificant, so that the sustain voltage margin is increased relative to the sine wave, thereby enabling stable operation. In addition, the steep rise of the voltage effect allows the rapid rapid movement of space charges, thereby increasing the effective collision between them and neutral and excitation molecules, thereby increasing the generation of secondary electrons, thereby strengthening the discharge and maintaining the sustain voltage margin. It also has the side effect of making it bigger.

The overshooting voltage appearing on the rising or falling portion of the output waveform of the switching inverter shown in FIG. 9 makes it easy to start discharging and to omit a separate output voltage adjustment after the start of discharging. The magnitude of this overshooting voltage depends on the output transformer and the capacitance of the EEFL, which is about 20% to 30% before the discharge starts and decreases to less than 3% while the discharge starts and remains. Will be done. In other words, the overshooting voltage effect appears only before the start of discharge. The reason for this characteristic is that the EEFL has the characteristics of capacitive load and resistive load at the same time after initiation of discharge in capacitive load before initiation of discharge, resulting in vibration damping effect due to resistive components. . Eventually, the overshooting voltage effect means that it only affects before the discharge starts, which has the effect of facilitating the discharge start. Generally, the discharge tube is AC type or DC type, or the discharge start voltage is higher than the discharge sustain voltage. If the overshooting voltage is present in the output waveform, the applied voltage for discharge start may be lowered by that portion. For example, if the discharge start voltage of a discharge tube is 1.3 kV and the overshooting portion of the voltage waveform to be applied thereto is 30%, the discharge can be started with only an average output voltage of 1 kV. In particular, the longer the tube length of the EEFL, the higher the discharge start voltage. When a long tube is used, a waveform with overshooting is advantageous. Another important effect can be to omit the voltage regulation process which is generally carried out after the start of discharge. In fact, in the case of using a waveform without overshooting, a method of applying a voltage required to start discharging and artificially lowering the voltage due to the life and luminance adjustment of the discharge tube is adopted when the discharge starts. Since the switching inverter differs by about 20 ~ 30% from the highest voltage value before the start of discharge and after the start of discharge due to the presence of the overshooting voltage, the switching inverter is automatically adjusted to the holding voltage level after the start of discharge and there is no need to attach a separate voltage adjusting device. .

In addition, self-discharge effect of increasing efficiency and brightness is shown. Self-discharge is a unique phenomenon only seen in an AC discharge tube, and the intensity of the wall voltage induced by the wall charge formed by the discharge is higher than the discharge start voltage. When large, when the voltage applied from the outside falls to reach the zero potential, it is a phenomenon that the discharge between the wall charges. A square wave generated in the switching inverter and a self discharge phenomenon generated when it is applied to the EEFL are shown in FIG. 9. When a self discharge occurs, the number of discharge currents and emission times per voltage waveform cycle is twice as high as that of no occurrence, and its intensity is somewhat smaller than that of no self discharge. This is because wall charges are partially erased due to the occurrence of self discharge. When such self discharge occurs, there is an effect of increasing efficiency and luminance.

Another embodiment of the present invention is a split driving scheme of a large area backlight. The small area backlight configured by placing the EEFL in a plane can be driven by a single switching inverter. However, as the area becomes larger, the power consumed becomes larger, so that the size of the boost transformer used in the inverter becomes larger, making it difficult to manufacture a small switching inverter. In addition, when the length of the line applying the voltage becomes longer, problems such as signal interference and impedance matching may occur, which may cause luminance unevenness. In this case, this problem is solved by adopting a split driving scheme in which the entire backlight is divided into regions (sectors) of a suitable size as shown in FIG. 10, and the divided regions are driven by a switching inverter having a voltage waveform coincident in phase. do. The reason why the output waveform of each switching inverter should be in phase is that a short circuit may occur in adjacent parts between divided regions when phases are different from each other. The output waveform of each switching inverter is in-phase so that only the FET portion and the boost transformer portion, which serve as high-speed switching of the switching inverter, are independently connected to each region, but share the gate signals of the FET. In this case, since the gate signal generation circuit is shared, it is possible to reduce the cost more than when using several switching inverters, and the size of the boost transformer can be reduced, so that the manufacturing can be made compact.

As described above, in the backlight and the driving method including the external electrode fluorescent lamp of the present invention, the following effects can be obtained by installing the external electrodes at both ends of the outer circumferential surface of the fluorescent lamp and arranging them in a plane.

First, the electrode of the fluorescent lamp is formed on the outside, so it is easy to manufacture the fluorescent lamp and adopts a straight end-capsule method or a method of bending both ends of the glass tube to sufficiently length the glass tube anode, thereby realizing high brightness and high efficiency. It is arranged at the edge of the light guide plate or overlapping on the plane, and can be driven by connecting the fluorescent lamp to a single power source in a parallel connection method, thereby realizing a high brightness, high efficiency and thin backlight, which is simple to manufacture.

Second, as the fluorescent lamp serves as a partition wall and emits light at the same time, luminance uniformity can be maintained and a thin upper and lower substrates can be employed due to the use of the partition wall. As a result, a large-area surface light source that ensures uniform luminance can be produced.

Third, EMI problems can be avoided by driving at a low frequency of several tens of kHz in a backlight configured by disposing a plurality of external electrode fluorescent lamps.

Fourth, the switching inverter in the present invention combining a high-speed FET and a boost transformer outputs a high-voltage square wave and generates an overshooting voltage, thereby enabling high-speed driving with uniform brightness, and lowering the discharge start voltage by itself. There is a self-discharge action. This action has the effect of high brightness and high efficiency.

Fifth, the inverter of the present invention manufactured by sharing the gate signal of the FET device and sharing only the boost transformer part in order to divide and drive the screen in the large screen backlight is applied between the adjacent regions divided by applying the in-phase voltage to each of the divided screens. It prevents a short circuit and obtains uniform brightness in a large area backlight by stable discharge. In addition, since the length of applying the voltage can be reduced, interference and impedance matching problems of the signal can be avoided, which is effective to realize uniform luminance. In addition, the size of the boost transformer can be reduced, and the size of the inverter can be reduced by sharing the gate signal generator.

In addition, the operation of the switching inverter in the present invention i) can drive a plurality of parallel-connected EEFL at a high speed to a single inverter with a uniform brightness, ii) can lower the discharge start voltage due to the presence of the overshoot voltage, iii) The self-discharge action has the effect of increasing the brightness and efficiency.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (17)

delete A light guide plate configured to diffuse and emit light emitted from the external electrode fluorescent lamp; A discharge tube is injected, a phosphor layer is applied to the inner circumferential wall, and an end cap-type external electrode formed of a straight, L-shaped, C-shaped, spiral, or wave-shaped and enclosing both ends of the glass tube is formed. An external electrode fluorescent lamp installed to surround an edge of the light guide plate; And And a switching inverter connected to an external electrode of the external electrode fluorescent lamp to apply a spherical AC voltage of 100 kHz or less. delete A diffusion plate for diffusing light emitted from the external electrode fluorescent lamp to emit light; A reflector reflecting light emitted from the external electrode fluorescent lamp; A discharge tube is injected, a phosphor layer is applied to the inner circumferential wall, and an end cap-type external electrode formed of a straight, L-shaped, C-shaped, spiral, or wave-shaped and enclosing both ends of the glass tube is formed. An external electrode fluorescent lamp disposed in parallel between the diffusion plate and the reflection plate; And And a switching inverter connected to an external electrode of the external electrode fluorescent lamp to apply a spherical AC voltage of 100 kHz or less. The backlight of claim 4, wherein the reflector further comprises a plurality of tripods disposed between the external electrode fluorescent lamps. The backlight of claim 4, wherein the reflector is formed in a wave pattern surrounding the external electrode fluorescent lamp. The method of claim 4, wherein The diffusion plate further includes a diffusion groove in a portion where the external electrode fluorescent lamp is located, The reflector is in the form of a triangular serrated pattern, The backlight is disposed between the diffuser plate and the reflector plate, the upper portion has a diffusion groove in which the external electrode fluorescent lamp is seated, and further comprising a light guide plate having a triangular serrated pattern in close contact with the reflector plate. A diffusion plate for diffusing light emitted from the external electrode fluorescent lamp to emit light; A reflector reflecting light emitted from the external electrode fluorescent lamp; The discharge socket is injected, the phosphor layer is applied to the inner circumferential wall, both ends are sealed, and the outer socket includes a plurality of glass tubes arranged in parallel between the diffusion plate and the reflecting plate and a plurality of external electrodes coupled to the glass tubes in parallel. External electrode fluorescent lamp comprising a multi-capsule electrode structure; And And a switching inverter connected to an external socket type multi-capsule electrode structure of the external electrode fluorescent lamp and applying a spherical alternating voltage of 100 kHz or less. A diffusion plate for diffusing light emitted from the external electrode fluorescent lamp to emit light; A reflector reflecting light emitted from the external electrode fluorescent lamp; A discharge tube is injected, a phosphor layer is applied to an inner circumferential wall, and a glass tube having both ends sealed and an end-cap type external electrode formed to surround both ends of the glass tube; A plurality of external electrode fluorescent lamps in which electrode portions are alternately overlapped; And And a switching inverter connected to an external electrode of the external electrode fluorescent lamp to apply a spherical alternating voltage of 100 kHz or less. The method of claim 9, The external electrode overlapping in the vertical direction in the middle of the panel is a backlight, characterized in that the conductive transparent electrode material. An upper substrate having an upper phosphor layer coated on a lower surface thereof; A lower substrate disposed to face the upper substrate and having a lower phosphor layer coated thereon; An edge support interposed between the upper and lower substrates to seal them; A discharge gas is injected, a phosphor layer is coated on an inner circumferential wall, and both ends are enclosed, and an end-cap type external electrode is formed to surround both ends of the glass tube, and a plurality of spaced intervals are installed on the lower substrate. External electrode fluorescent lamps; A discharge gas injected into an inner space when the upper and lower substrates are sealed; Electrodes formed on both corresponding outer surfaces of the upper and lower substrates coupled to each other and connected to electrode connection lines to which an AC power is applied; And And a switching inverter connected to the electrode for applying a spherical alternating voltage of 100 kHz or less. The backlight of claim 11, wherein the external electrode fluorescent lamp is not connected to the electrode and is installed in a floating state inside the upper and lower substrates. An upper substrate having an upper phosphor layer coated on a lower surface thereof; A lower substrate disposed to face the upper substrate and having a lower phosphor layer coated thereon; An edge support interposed between the upper and lower substrates to seal them; An inner socket-type multi-capsule electrode structure comprising a top electrode and a bottom electrode each having a ferroelectric applied to the surface thereof, and grooves having defects in the glass tube formed at predetermined intervals, respectively installed at both ends of the lower substrate; A glass tube in which discharge gas is injected, a phosphor layer is coated on an inner circumferential wall, and both ends thereof are sealed, and a groove is installed in a groove of the inner socket type multi-capsule electrode structure; A discharge gas injected into an inner space when the upper and lower substrates are sealed; And And a switching inverter connected to the internal socket type multi-capsule electrode structure and applying a spherical alternating voltage of 100 kHz or less. The method according to any one of claims 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, The switching inverter constitutes a bridge circuit with four FETs (A, B, C, D), applies DC to the drains of the FET A and FET C, grounds the sources of FET B and FET D, and the source of FET A. And a drain of FET B, a source of FET C and a drain of FET D, respectively, a boost transformer is connected between the connection points of FET A and FET B and the connection point of FET C and FET D, and the output of the boost transformer Backlight, characterized in that for outputting a spherical AC voltage of less than 100kHz. The method according to any one of claims 2, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, And a spherical alternating voltage output from the switching inverter includes an overshoot for inducing a discharge of the fluorescent lamp. In the backlight driving method comprising a plurality of external electrode fluorescent lamp, Dividing the plurality of fluorescent lamps into a plurality of predetermined areas; Connecting external electrodes of the fluorescent lamps of each of the divided regions with the same electrode connection line; Connecting switching inverters to electrode connection lines respectively connected to the regions; Applying the same gate signal to each switching inverter; And And simultaneously switching, by the switching inverter, a rectangular alternating voltage of 100 kHz or less in phase to each external electrode fluorescent lamp according to the gate signal. delete