KR20060026811A - Backlight unit including magnetic field generator and liquid crystal display device using the same - Google Patents

Abstract

The present invention relates to a structure of a backlight unit of a liquid crystal display device, and more particularly to a backlight unit having a magnetic field generating unit. The backlight unit of the present invention includes a bar lamp; Electrodes formed at both ends of the lamp; A gaseous substance filled in the lamp; A magnetic field generating unit formed at a predetermined position of the lamp; And an inverter for providing a voltage to the electrode, and the fluorescent lamp of the backlight unit may have a uniform brightness by providing the electromagnetic generator.

Backlight unit, fluorescent lamp, magnetic field generator

Description

BACKLIGHT UNIT INCLUDING MAGNETIC FIELD GENERATOR AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

1 is a cross-sectional view showing a module structure of a general liquid crystal display device.

Figure 2 is a perspective view showing the structure of a conventional backlight unit.

Figure 3a is a perspective view showing the structure of the backlight unit of the present invention.

3B is a plan view showing the structure of one fluorescent lamp constituting the backlight unit of the present invention.

Figure 3c is a cross-sectional view of the fluorescent lamp of the present invention.

4 is a plan view showing the structure of a fluorescent lamp according to another embodiment of the present invention.

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

301: lower cover 302: fluorescent lamp

303; lamp support 304; lamp support

305: reflector 310: electromagnetic field generating unit

310a: N pole 310b: S pole

302a: electrode portion 302b: light emitting portion

The present invention relates to a backlight unit of a liquid crystal display device, and more particularly, to a backlight unit having a magnetic field generating unit.

With the advent of the information age, the development of display devices is being actively performed. In particular, a flat panel display device that is light and simple and portable and has various functions such as low power consumption is being developed, and is rapidly replacing a cathode-ray tube (CRT).

In general, a flat panel display device may be classified into a light emitting display device that emits light itself and a light receiving display device that cannot emit light by itself.

For example, a plasma display panel, a field emission display, an electroluminescence display, etc. correspond to a light emitting flat panel display, and are mainly used in laptops and computer monitors. The liquid crystal display device corresponds to a light receiving type flat panel display device.

In general, a liquid crystal display includes a liquid crystal display panel for displaying an image and a backlight unit for supplying light to the liquid crystal display panel.

The liquid crystal display panel includes an array substrate on which a thin film transistor, which is a switching element, is arranged in a matrix, a color filter substrate facing the array substrate, and a color filter layer is formed, and a liquid crystal layer filled between the two substrates.                         

In addition, a plurality of gate lines are formed on the array substrate, a plurality of data lines perpendicular to the gate lines are formed, and unit pixels are defined by intersections of the gate lines and the data lines.

The switching element for driving the unit pixel is a thin film transistor.

In addition, a pixel electrode is formed in each of the unit pixels, and a screen is displayed by applying an electric field to the liquid crystal layer together with a common electrode which may be formed on the color filter substrate.

The liquid crystal is a material whose arrangement direction may be controlled by an applied electric field, and transmission and blocking of light may be determined according to a direction in which light passes through the liquid crystal.

However, the liquid crystal display device requires a light source to display an image, and the backlight unit serves as a light source in the liquid crystal display device.

The backlight unit is composed of a lamp and a plurality of parts supporting the lamp, and the backlight unit is divided into an edge type and a direct type according to the position where the lamp is formed.

In the edge type backlight unit, a lamp, which is a light source, is formed at the edge of the liquid crystal display panel, and in the direct type, the lamp is formed below the vertical of the liquid crystal display panel.

Hereinafter, a structure of a direct type liquid crystal display module will be described with reference to FIG. 1.

1 is a cross-sectional view of a direct type liquid crystal display device, in which a backlight unit is formed under the liquid crystal display panel 110.

In the backlight unit, a plurality of bar lamps 103 (for example, cold cathode fluorescent lamps) are formed in parallel with each other as a light source and are protected by a lower cover 101 which is a mold frame. The upper surface of the lower cover 101 is provided with a reflecting plate 102 for reflecting the light of the lamp 103 to the liquid crystal display panel, a plurality of lamps 103 are arranged on the reflecting plate 102. In addition, the diffusion plate 104a for uniformly diffusing the light generated from the lamp 103 to the liquid crystal display panel, the diffusion sheet 104b disposed on the diffusion plate 104a, and a prism for collecting incident light An optical sheet 104 is further provided including the sheet 104c. The optical sheet 104 is supported by the edge of the lower cover.

Meanwhile, the liquid crystal display panel 110 and the optical sheets 104 are supported by a guide panel 120 that protects and supports the edge of the liquid crystal display panel, and the guide panel 120 is the liquid crystal display panel 110. It is formed on the upper surface of and coupled to the top case 130 to protect the liquid crystal display panel. In addition, the top case 130, the guide panel 110, and the lower cover 101 are coupled by a plurality of threads 115 and 116 formed at the edge of the liquid crystal display panel. In the case of large liquid crystal display panels, the bonding is performed by screws that can be strongly bonded.

Next, referring to FIG. 2, the arrangement of the light source of the liquid crystal display panel and the backlight unit mounted on the lower cover and the lower cover will be described.

As shown in FIG. 2, a plurality of bar lamps 103, which are light sources, are formed on the reflecting plate 102 in parallel with each other, and the lamps 103 are supported by the lamp fixing members 111.

Electrodes for supplying power to the lamp are formed at both ends of the lamp, and the lamp electrode is supported by the lamp support 112 formed at both sides of the lower substrate 101. In addition, an electrode supply line (not shown) for supplying power to the lamp is connected to both electrodes of the lamp 103. The power supply lines are connected to each other to form a closed circuit around a single lamp. In the closed circuit, an inverter for converting a DC voltage applied from the outside into an AC voltage and supplying current to the lamp is installed.

In general, a cold cathode fluorescent lamp (CCFL) or the like is used as the lamp, and the lamp is divided into a light emitting part coated with a fluorescent material and an electrode part applying a voltage to the lamp.

The lamp, which is a light source, has a long rod shape, when voltage is applied from an electrode portion formed at the end of the lamp, electrons are emitted, and ultraviolet rays are generated while the emitted electrons collide with a gas such as a mercury lamp filled in the lamp. The fluorescent material is stimulated to emit light. The emitted light is used as a light source of the liquid crystal display device.

Therefore, the light emitted from the lamp is required to be uniform regardless of the position. Today, as the size of the liquid crystal display increases, the size of the backlight unit also increases.

However, as the size of the lamp increases, a problem arises in that the intensity of light emitted varies according to the position of the lamp. This problem occurs more seriously when the AC voltage applied from the inverter does not achieve a perfect sine wave.

That is, in general, a large cold cathode lamp has a problem that the brightness of the center portion is relatively low compared to the magnetic field.

The reason why the light intensity in the center of the cold cathode lamp is relatively low is that the electrons generated at the edge of the cold cathode tube are relatively low density in the center of the lamp, so that the number of collisions with the gas filled in the lamp is small so that the light intensity is low in the center of the lamp. It is known.

It is therefore a first object of the present invention to provide a backlight unit with uniform brightness. In particular, it is an object of the present invention to provide a backlight unit having a uniform brightness by solving a different luminance according to the position of the lamp as a light source in the backlight unit of the liquid crystal display device.

In order to achieve the above object, the backlight unit of the present invention includes a lamp having a rod shape; electrodes formed at both ends of the lamp; A gas material filled in the lamp; A magnetic field generating unit formed at a predetermined position of the lamp; And a backlight unit, characterized by comprising an inverter for providing a voltage to the electrode.

In addition, the liquid crystal display device of the present invention having the backlight unit includes a liquid crystal display panel; A bar lamp included in the backlight unit providing light to the liquid crystal display panel; Means for adjusting the distribution density of gaseous substances and electrons filled in the rod-shaped lamp to make the brightness of the lamp uniform; Electrodes formed at both ends of the bar lamp; And an inverter for applying an alternating voltage to the electrode.

The liquid crystal display device includes a liquid crystal layer in which an arrangement direction can be controlled by an electric field. Since the liquid crystal cannot emit light by itself, the liquid crystal display device must include a backlight unit for supplying light to the liquid crystal layer.

In general, the backlight unit is formed at the edge side of the liquid crystal display panel or is installed at the bottom to supply light to the liquid crystal layer.

Cold cathode fluorescent lamps and the like are mainly used for the backlight unit, which is a light source, and the fluorescent lamps are lengthened with the increase in size of the liquid crystal display device.

The cold cathode fluorescent lamp includes a long bar lamp, an electrode formed at both ends of the lamp, and an inverter for supplying a voltage to the electrode. The lamp is filled with a gas that produces a plasma by collision with electrons.

The principle that the cold cathode fluorescent lamp emits light is generated by the collision of the gas and electrons charged in the lamp to produce a plasma, ultraviolet light is emitted in the process, the fluorescent material applied to the lamp by the emitted ultraviolet light is stimulated to emit light will be.

Therefore, when the number of collisions between electrons and the gas is large, the luminance of generated light is high.

Looking at the light emission principle of the cold cathode fluorescent lamp in more detail, when electrons are emitted from the electrodes across the lamp, the electrons collide with the gas in the lamp to ionize the gas and produce a plasma. Ultraviolet rays are generated in the above process, and the ultraviolet rays excite the fluorescent material applied to the inner wall of the lamp to emit light. The backlight unit uses the light.

However, as the cold cathode fluorescent lamp of the backlight unit becomes longer, a problem arises in that the density of electrons generated in the electrode varies with the lamp position. That is, as the fluorescent lamp becomes longer, a problem occurs that the density of electrons decreases in the central portion of the fluorescent lamp. Furthermore, an alternating current voltage is applied to the cold cathode fluorescent lamp. If an imbalance occurs in the sinusoidal curve of the alternating current voltage, the electrons are further unbalanced in the lamp.

The low density of electrons means that the brightness of the fluorescent lamp is low.

Therefore, the present invention maintains uniform brightness by correcting the difference in electron density and plasma density according to the position of the cold cathode fluorescent lamp in the large backlight unit.

The present invention further forms a magnetic field generating unit for increasing the distribution density of electrons in the place where the distribution density of electrons is low for this purpose.

The magnetic field generating unit may be a coil bundle capable of generating an electric field, or may be a magnet capable of generating a magnetic field.

When the magnetic field generating unit is formed at the center of the cold cathode fluorescent lamp, electrons generated at the electrode pass while rotating the lamp area in which the magnetic field generating unit is formed by the Lorentz law. In addition, some electrons may be caught by the magnetic field in the region where the magnetic field generating unit is formed, thereby increasing the low electron density.

When electrons are rotated or caught in a predetermined region of the fluorescent lamp in which the magnetic field generating unit is formed, the number of collisions with the gas filled in the fluorescent lamp is increased, so that a large amount of plasma is generated and the intensity at the center of the fluorescent lamp where low density electrons are distributed. Can increase.

Therefore, it is possible to generate a uniform light in the entire fluorescent lamp by the magnetic field generating unit.

Hereinafter, the structure of the backlight unit of the present invention will be described with reference to FIG. 3.

3 illustrates an example of a direct type liquid crystal display panel in which a backlight unit is formed below the liquid crystal display panel. However, the present invention is not limited to the direct type liquid crystal display device.

As shown in FIG. 3A, the backlight unit of the present invention includes a plurality of rod-shaped cold cathode fluorescent lamps 302 and a reflecting plate formed on a lower surface of the cold cathode fluorescent lamps 302 to reflect fluorescent lamp light to an upper surface thereof. 305, a fluorescent lamp support portion 304 for supporting both ends of the fluorescent lamp, a magnetic field generating portion 310 formed at a predetermined position of the fluorescent lamp 302, in particular, the backlight unit; A lower cover 301 is supported.

Electrodes for providing electrons to the fluorescent lamp are formed at both ends of the fluorescent lamp 302, and the electrodes are connected to an inverter (not shown) to receive an AC voltage. The electrode may be formed on the outer surface or the inner surface of the lamp.

Therefore, the fluorescent lamp 302 is formed with a light emitting part coated with a fluorescent material, an electrode part formed at both ends of the fluorescent lamp, and a magnetic field generating part 310 formed at the center of the fluorescent lamp.

In particular, the magnetic field generating unit 310 may be composed of a flexible magnet, and may be divided into two parts, an N pole and an S pole.

That is, two parts of the north pole and the south pole are configured to face each other with the fluorescent lamp interposed therebetween to provide a magnetic field to the fluorescent lamp.                     

The direction in which the N pole portion and the S pole portion are formed may be arranged up and down or left and right of the fluorescent lamp 302.

Therefore, the electrons generated in the electrode part proceed in the longitudinal direction of the fluorescent lamp and the magnetic field is formed perpendicular to the traveling direction of the electron. Therefore, according to Lorentz's law, the electrons are in the cylindrical direction of the fluorescent lamp in the fluorescent lamp region in which the magnetic field generating part is formed. Will rotate.

Accordingly, the trajectory of electron movement in the fluorescent lamp region in which the magnetic field generator is formed increases, the number of collisions with the plasma filled in the fluorescent lamp increases, and the density of electrons also increases.

In addition, the magnetic field generating unit 310 may be formed to a predetermined thickness and also serve to support the fluorescent lamp 302. It is particularly effective when a large cold cathode fluorescent lamp is used.

Meanwhile, mercury or argon is used as the gas filled in the fluorescent lamp, and plasma such as mercury or argon is in the fluorescent lamp due to an uneven distribution of temperature in the fluorescent lamp and an asymmetric sinusoidal wave applied to the fluorescent lamp. Can be unevenly distributed. However, when the magnetic field generating unit of the present invention is formed at a predetermined position of the fluorescent lamp, particularly in a region where the distribution density of gas such as mercury is low, mercury particles may be caught by the magnetic field in the region of the fluorescent lamp where the magnetic field generating unit 310 is formed. Can increase the density of the gas. Increasing the density of the plasma means that the number of collisions with the electrons may be increased, thereby increasing the brightness.                     

Therefore, the density of plasma that can be unevenly distributed in the fluorescent lamp by the application of the temperature deviation and the asymmetrical alternating voltage generated in the fluorescent lamp can be adjusted using the magnetic field generator 310.

FIG. 3B illustrates one fluorescent lamp in the backlight unit of the present invention having the magnetic field generator 310.

As shown in FIG. 3B, the fluorescent lamp 302 of the present invention includes a cylindrical and long rod-shaped light emitting portion 302b, electrode portions 302a formed at both ends of the light emitting portion 302b, and the fluorescent light. A magnetic field generating unit 310 formed at a predetermined position outside the lamp and an inverter (not shown) for applying an AC voltage to a predetermined position of the electrode portion 302a.

In particular, the magnetic field generating unit 310 is composed of a magnet and may be divided into an N pole portion 310a and an S pole portion 310b. Therefore, the magnetic field is applied to the fluorescent lamp by the two magnetic poles.

By applying a magnetic field in a direction perpendicular to the direction of movement of the electrons in the fluorescent lamp at a predetermined position of the fluorescent lamp, the electrons in the lamp rotate in the region of the fluorescent lamp in which the magnetic field generator 310 is formed according to the Lorentz law. As it progresses, the number of collisions with gaseous substances increases, and the distribution density also increases.

In addition, the mercury lamp gas material distributed in the fluorescent lamp may be unevenly distributed in the fluorescent lamp due to the temperature deviation of the fluorescent lamp and the asymmetry of the applied AC voltage, the low-density gas by the magnetic field generator of the present invention By increasing the density of the gaseous material in the region it can be achieved a uniform distribution of gaseous material.                     

FIG. 3C is a cross-sectional view of the fluorescent lamp region in which the magnetic field generating unit is formed by using the line I-I of FIG. 3B as a cutting line.

As shown in FIG. 3C, the magnetic field generating unit 310 may be configured to surround an outer portion of the cylindrical fluorescent lamp 302 and may be configured of an N pole portion 310a and an S pole portion 310b. Therefore, the magnetic field generating unit 310 may be composed of a flexible magnet to surround the cylindrical fluorescent lamp 302. However, the magnetic field generating unit of the present invention is not limited to the cylindrical shape and may have a predetermined shape capable of applying a magnetic field to the fluorescent lamp. That is, it may be a plate-shaped magnet or a ring-shaped magnet corresponding in parallel.

The magnetic field generating unit of the present invention aims to control the movement of electrons and electrons in the fluorescent lamp. Therefore, another embodiment of the present invention illustrates the application of a magnetic field generated by a coil that can produce the same effect as a magnetic field in a fluorescent lamp.

4 illustrates a fluorescent lamp provided with a coil bundle capable of applying a magnetic field to the fluorescent lamp.

As shown in FIG. 4, a coil bundle 401 is installed on a lower surface of the fluorescent lamp 302 to apply a magnetic field to the fluorescent lamp 302.

When a current flows through the coil by a Fleming's right-hand rule that a magnetic field is generated in the current flowing coil, a magnetic field is formed around the coil. Thus, the magnetic field generating unit of the present invention may use a coil bundle in which the current flows.

The coil bundle 401 may be formed in any one of the up, down, left, and right directions of the fluorescent lamp 302, and FIG. 4 illustrates a bottom surface of the fluorescent lamp 302, that is, a reflecting plate (not shown).

A magnetic field is applied to the fluorescent lamp by the coil bundle 401, and the distribution density of electrons and plasma in the fluorescent lamp may be adjusted in the same manner as when the magnetic field is applied by the magnet by the magnetic field.

Although the above-described embodiment of the present invention has been described with respect to the direct type liquid crystal display device, the liquid crystal display device of the present invention having the magnetic field generator may be applied to the edge type.

Next, the structure of the liquid crystal display of the present invention having the magnetic field generating unit will be briefly described.

As described above, the present invention includes a liquid crystal display panel and a backlight unit formed on the bottom surface of the liquid crystal display panel. The backlight unit includes a plurality of fluorescent lamps parallel to each other, and has a magnetic field generating unit at a predetermined position, particularly in the center of the fluorescent lamp. In addition, a reflector is further provided below the backlight unit to collect light generated from the fluorescent lamp to the liquid crystal display panel, and a lower cover supporting the reflector and the backlight unit is formed under the reflector.

Meanwhile, a plurality of optical sheets such as a diffusion plate, a diffusion sheet, and a prism sheet are installed between the liquid crystal display panel and the backlight unit to supply uniform light to the liquid crystal display panel. In addition, a guide panel for supporting the liquid crystal display panel and the optical sheet is installed at four edges of the liquid crystal display panel, and the guide panel is coupled to the lower cover.                     

In addition, a top case is further formed at an edge of the upper surface of the liquid crystal display panel to protect the liquid crystal display panel. The top case may be coupled to the guide panel by screws or the like to fix the liquid crystal display.

Therefore, the present invention provides a magnetic field at a predetermined position of the fluorescent lamp in order to prevent the distribution of gaseous materials asymmetrically and the distribution density of electrons generated at the electrodes due to the temperature irregularity and the asymmetry of the applied AC voltage. By providing the generator, a backlight unit having a uniform brightness can be formed.

In addition, by providing a separate support portion for the support of the fluorescent lamp, the magnetic field generating portion of the present invention also serves as a function of the backlight unit can exhibit a uniform brightness without additional components.

Claims (14)

A rod-shaped lamp; Electrodes formed at both ends of the lamp; A gas material filled in the lamp; A magnetic field generating unit formed at a predetermined position of the lamp; And an inverter for providing a voltage to the electrode. The backlight unit of claim 1, wherein the magnetic field generating unit is formed at the center of the lamp. The backlight unit of claim 1, wherein the magnetic field generating unit is a flexible magnet surrounding the lamp. The backlight unit of claim 1, wherein the magnetic field generating unit is a coil disposed near the lamp. The backlight unit of claim 1, wherein the magnetic field generating unit supports the lamp and is a magnetic lamp supporting unit. The backlight unit of claim 1, wherein the magnetic field generating unit is a flat plate magnet facing each other with the lamp interposed therebetween. A liquid crystal display panel; A bar lamp included in the backlight unit providing light to the liquid crystal display panel; Means for adjusting the distribution density of the gaseous material filled in the bar lamp to make the brightness of the lamp uniform; Electrodes formed at both ends of the bar lamp; And an inverter for applying an alternating voltage to the electrode. 8. The liquid crystal display device according to claim 7, wherein the means for making the brightness uniform is a magnetic field generating unit. The liquid crystal display of claim 8, wherein the magnetic field generating unit is a magnet formed at the center of the lamp. The liquid crystal display of claim 7, wherein the bar lamp is formed on a side or a bottom of the liquid crystal display panel. The liquid crystal display device according to claim 8, wherein the distribution density of the fluorescent material and the electrons is increased in a predetermined region of the lamp in which the magnetic field generating unit is formed. The display device of claim 7, further comprising: a guide panel supporting the liquid crystal display panel and the backlight unit; A top case supporting an upper edge of the liquid crystal display panel; And a lower cover formed under the liquid crystal display panel. 10. The liquid crystal display device according to claim 8, wherein the magnetic field generating unit is a coil provided near the bar lamp. 8. The liquid crystal display device according to claim 7, wherein the means for making the brightness uniformity adjusts the electron density in the lamp.

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