KR20030081695A - Backlight for Liquid Crystal Displays - Google Patents

Abstract

PURPOSE: A back light of a liquid crystal display is provided to form a carbon nano tube film with excellent adhesion characteristic to an electrode substrate and with high density, thereby obtaining uniform luminance and extending the life span of the back light. CONSTITUTION: An upper substrate(1) used as an anode is coated with an ITO film(2), and a fluorescent layer(3) is coated on the ITO film. A conductive thin film(6) is coated on the surface of a lower substrate(7) used as a cathode, and a metal thin film(9) is formed on the conductive thin film through an electroplating or sputtering. A carbon nano tube(10) is formed on the metal thin film, and fine metal grains(4) for improving adhesion to an electrode substrate and the carbon nano tube are filled between carbon nano tubes. A spacer(5) is placed between the upper and lower substrates, and the space inbetween is vacuumed.

Description

Backlight for Liquid Crystal Displays

TECHNICAL FIELD The present invention relates to backlight production for use in liquid crystal displays or liquid crystal television devices of personal computers and monitors.

In general, liquid crystal display devices have the advantages of low weight and low power consumption, and thus are widely used in display devices in the computer or television fields. However, since the liquid crystal display itself does not form an image by emitting light, but forms an image only after receiving uniform light from the rear, the backlight used to overcome this problem is an important device of the liquid crystal display device.

3 is a cross-sectional view showing a conventional edge light backlight structure shown in Japanese Patent Application Laid-Open No. Hei 8-313710 and Japanese Patent Application Laid-Open No. Hei 9-251807. In the drawing, the light emitting body F is a cold cathode fluorescent tube. It is disposed at the bottom of the end surface of the device A, and the light emitted therefrom is transmitted to the bottom of the liquid crystal panel by the reflecting plate E. On the upper surface of the light guide plate (D) made of a transmissive material, there is a diffusion plate (C) which distributes the light of the illumination surface evenly over the entire liquid crystal plate, and the light is emitted by the prism plate (B) located above the diffusion plate (C). Aggregate and the front brightness of a liquid crystal panel is improved.

Conventional backlight devices of Japanese Patent Application Laid-Open Nos. 8-313710 and 9-251807, which are configured as described above, are generally complicated in construction, which leads to high production costs, and the light source is used to reflect power consumption due to reflection and transmission of light at the sides. There is a problem that the efficiency is significantly lowered and it is difficult to ensure uniformity of brightness. In addition, due to the large area and high image quality of various displays, the conventional backlight device may not exhibit sufficient luminance characteristics.

In order to solve the problem of the liquid crystal display, technology development has been made by various methods such as a flat panel cold cathode fluorescent tube method, a plasma method, and a field emission method.

In the case of a flat cold cathode fluorescent lamp type backlight, a barrier rib is formed at regular intervals between a front glass plate and a corresponding rear glass plate to form discharge passages, and electrodes are installed at both sides thereof, as in Korean Patent Application Laid-Open No. 2000-26971. A backlight was manufactured by disposing a dielectric layer on top of the two electrodes, applying a phosphor layer on an inner surface of a partition wall and a front glass plate to form an electric discharge passage, and sealing the gas. However, this method is not environmentally friendly due to the use of mercury and the problem of cost increase and power consumption during manufacturing.

On the other hand, in the plasma method, a transparent electrode is coated on the entire upper plate and a surface electrode is applied to the entire lower plate to form a fluorescent layer, respectively. The phosphor emits light from the plasma by the discharge between the upper and lower plates. However, since the upper and lower electrode structures have a very low discharge efficiency, high heat is generated and thus practicality is low as a backlight (Korean Patent Laid-Open No. 2002-12096).

Field emission backlights have excellent characteristics such as large area, high brightness, and low power consumption, but they have not been put to practical use due to the high manufacturing costs generated by repeating complex processes such as deposition and etching of semiconductor materials during microtip manufacturing. have. In addition, most of the field emission types are being developed in the field emission display (FED) field, but the actual backlight is not developed. On the other hand, a number of patents have been applied for the field emission display using carbon nanotubes without using a micro tip as the electron emission source of the field emission display. (Korean Patent Laid-Open No. 2000-71281, Special 1998-24794, Special 2000 -23347, Japanese Patent Laid-Open No. 2001-2786, Japanese Patent Laid-Open No. 2000-86216, Japanese Patent Laid-Open No. 2000-203821)

The present invention provides a field emission type backlight using carbon nanotubes as an electron emission source using a field emission display technology. However, in the field emission display patent using carbon nanotubes, a method of manufacturing a carbon nanotube emitter is a method of protruding nanotubes through an etching process after printing a paste made of metal, organic polymer and nanotubes, nano A method of dispersing a tube in an organic solvent to evaporate an organic solvent on a conductive plate to form a nanotube film, and a method of forming an emitter by electrophoresis by dispersing a nanotube in a solvent together with a charging agent. However, nanotube emitters manufactured in this way have poor number distribution of nanotubes, which are effective for electron emission, and in particular have poor adhesion between electrode substrates and nanotubes. do.

In the present invention, in order to solve such a problem, it is possible to form a carbon nanotube film which is excellent in adhesion with an electrode substrate and is arranged at a high density to exhibit uniform luminance and to manufacture a backlight that can be used for a long time. Still another object of the present invention is to provide a manufacturing method that reduces the production cost and power consumption by using a carbon nanotube, due to a simpler configuration than a conventional backlight.

1 is a cross-sectional view showing an embodiment of the present invention.

2 is an enlarged cross-sectional view of the cathode serving as the electron emission source of FIG.

3 is a cross-sectional view of a backlight used in a conventional liquid crystal display.

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

1: upper substrate 2: indium tin oxide (ITO) layer

3: phosphor layer 4: fine metal particles

5 spacer 6 thin film conductive layer

7: lower substrate 8: vacuum exhaust glass tube

9 metal thin film layer 10 carbon nanotube

A: liquid crystal display B: prism plate

C: diffuser plate D: light guide plate

E: reflector F: cold cathode fluorescent tube

In the present invention, the upper substrate used as the anode to solve the above problems is coated with an indium tin oxide (ITO) layer (2), the phosphor layer (3) is applied on the ITO layer, the lower portion used as a cathode A thin film conductive layer 6 is coated on the upper side of the substrate, and a metal thin film 9 having a particle size of 0.001 to 1 μm and a layer thickness of 0.01 to 10 μm is formed on the thin film conductive layer by electroplating or sputtering. On the metal thin film layer 9, carbon nanotubes treated with a charging agent are formed on the metal thin film layer 9 by electrophoresis to form a carbon nanotube layer 10 so as to have a layer thickness of 0.01 to 10 μm, and adhesion between the electrode substrate and the carbon nanotubes thereon. In order to improve the properties, the empty metal between carbon nanotubes is filled with micrometallic particles produced by electroplating. A spacer 5 is provided between the upper substrate and the lower substrate, and a flat light emitting device is formed therein, which is discharge gas or vacuum.

The insulating substrate used as a support for the cathode and the anode is one selected from glass, plastic film and sheet, and silicon wafer, and on the cathode, Au, Pt, Al, Cu, Co having a thickness of 0.1 nm to 1 μm. And a thin film conductive layer 6 made of a metal selected from Ag, or a metal oxide such as ITO (Indium Tin Oxide) is applied, and the metal thin film layer 9 provided on the thin film conductive layer 6 is made of Ag, Cu, Ni. , Zn, Au, Co, Al was selected from 10 to 10 minutes by plating at 0.5-10 volts (V) by electroplating.

On the metal thin film layer 9, the diameter d is 1-100 nm, the length L is 0.01-20 micrometers, and L / d which is the ratio of the length L and the diameter d is 5-200000, The single layer -Wall carbon nanotubes or multi-wall carbon nanotubes are installed at a density of 10 ³ to 10 ¹⁰ / ㎣, and the adhesion between the electrode substrate and the carbon nanotubes on the carbon nanotube layer 10 In order to improve the performance, plating is performed for 1 to 10 seconds at 2 to 8 volts by electroplating using one kind of metal selected from Ag, Cu, Ni, Zn, Au, Co, and Al, and then additionally 0.5 to 3 volts. Electroplating for 5 minutes to produce a fine metal particles (4) having a particle size of 0.001 ~ 0.5㎛ to prepare a flat panel light emitting device filled with the empty space between the carbon nanotubes.

Referring to the present invention in detail with the drawings, the carbon nanotubes in Figure 1 for the anode and cathode substrates (1,7) can be used a variety of materials, such as glass, plastic film and sheet, silicon wafer, in particular the flexibility to change the shape Polyester, polycarbonate, polyimide, polymethyl methacrylate, polyamide, etc. can be used as a plastic substrate suitable for a planar lighting apparatus.

The thin film conductive layer 6 is coated on the upper side of the lower substrate used as the cathode, and the carbon nanotubes can be easily blown by electrophoresis on the thin film conductive layer, and the carbon nanotubes can be arranged vertically. By the plating method and the sputtering method, a metal thin film 9 having a particle size of 0.001 to 1 µm and a layer thickness of 0.01 to 10 µm was formed. Preferably, the particle size is 0.01 to 0.5 µm and the layer thickness is 0.05 to 1 µm.

On the metal thin film layer 9, carbon nanotubes, which are substantially used as electron emission sources, are formed, and carbon nanotubes are manufactured by arc discharge, and are oxidized in an oxidizing agent mixed with nitric acid and sulfuric acid for at least 8 hours in diameter (d ) Is 1 to 100 nm, the length (L) is 0.01 to 20 μm, and L / d, which is the ratio of the length (L) to the diameter (d), is 5 to 20,000, followed by electrophoresis by treatment with a general charging agent. The carbon nanotube layer 10 was formed to have a layer thickness of 0.01 to 10 μm. More preferably, when the diameter (d) of the carbon nanotubes is 10 to 50nm, the length (L) is 0.1 to 5㎛, L / d is a ratio of the length (L) and diameter (d) is 2 to 500 The electron emission ability was more excellent.

In order to improve the adhesion between the electrode substrate and the carbon nanotubes on the carbon nanotube layer 10, 2 to 8 by electroplating using one metal selected from Ag, Cu, Ni, Zn, Au, Co, Al After plating for 1 to 10 seconds on the bolt, electroplating for 1 to 5 minutes with additional 0.5 to 3 volts to fill the empty space between the carbon nanotubes with fine metal particles (4) having a particle size of 0.001 to 0.5㎛. It was. If the adhesion between the electrode substrate and the carbon nanotubes is poor, it may not be able to exert a sufficient lifetime as an electron emission source due to overload during electron emission.

The density of the nanotubes effective for electron emission on the negative electrode substrate was 10 ³ to 10 ¹⁰ / ㎣, which showed sufficient luminescent effect without any illuminance deviation during luminescence, and better at 10 ³ to 10 ⁷ / ㎣. Luminescent properties were shown. When the density of the nanotubes was less than 10 ³ / m 3, they did not show sufficient light emission and thus could not be used as illumination, and more than 10 ¹⁰ / m 2 could not be produced substantially.

Embodiment of the Invention

An example of embodiment of this invention is demonstrated with reference to FIG.

The backlight using carbon nanotubes as the electron emission source is composed of anodes (1,2,3) and cathodes (4,6,7,9,10) capable of emitting electrons, and interposed between spacers (5). They face each other at regular intervals, and are filled with vacuum or inert gas so that electrons can be released between the substrates. The cathode includes a thin film conductive layer 5 made of ITO on an insulating material such as glass, plastic film and sheet, and a silicon wafer, and an average particle formed by electroplating at 1.5V for 2 minutes. There is a metal thin film layer 9 made of Ag (Silver) having a size of 0.05 to 0.3 µm and a layer thickness of 0.3 µm, and carbon nanotubes 10 substantially emitting electrons thereon are subjected to electrophoresis at 50 V for 1 minute. 2 μm thick. In order to improve the adhesion between the metal thin film layer 9 and the carbon nanotubes, using Ag, electroplating for 3 seconds at 4V followed by electroplating at 1.2V for 2 minutes, the fine metal particles having a particle size of 0.01 ~ 0.1㎛ (4) filled the voids between the carbon nanotubes. In this case, the nanotubes used as the electron emission source are multilayer carbon nanotubes having a diameter of 15 to 50 nm and a length distribution of 0.35 to 1.5 μm, and L / d having a ratio of the length (L) and the diameter (d) of the nanotubes is 7 To 100. And the effective nanotube density for electron emission installed on the negative electrode substrate was controlled to 10 ⁵ to 10 ⁷ / ㎣.

On the other hand, as the anode which exhibits substantial light, a fluorescent layer 3 commonly used on glass and plastic substrate 1 to which a transparent conductive layer 2 such as indium tin oxide (ITO) is applied was used.

As described above, according to the present invention, since the carbon nanotubes are disposed on a plane and directly emit uniform light, a plurality of components used in a conventional backlight, that is, a light source, a light guide plate, a light diffuser plate, a prism plate, and a reflector, are used. This leads to a simplification of the manufacturing process and the resulting reduction in production costs has a great industrial effect. In addition, due to the uncomplicated configuration, the light transmittance of the light can be greatly improved and a relatively high luminance can be obtained.

Claims (5)

The upper substrate used as the anode is coated with an indium tin oxide (ITO) layer 2, the phosphor layer 3 is coated on the ITO layer, and the thin film conductive layer 6 is disposed on the upper side of the lower substrate used as the cathode. ) Is coated on the thin film conductive layer 6 to form a metal thin film layer 9 having a particle size of 0.001 to 1 µm and a layer thickness of 0.01 to 10 µm by electroplating or sputtering. ) To form a carbon nanotube layer 10 so as to have a layer thickness of 0.01 to 10 μm by electrophoresis on the carbon nanotubes treated with a charging agent, and to improve adhesion between the electrode substrate and the carbon nanotubes. The micro metal particles (4) produced by the plating method is filled with a void space between the carbon nanotubes, the spacer 5 is provided between the upper substrate and the lower substrate, characterized in that the vacuum inside For flat panel liquid crystal display Backlight. The method of claim 1, wherein the carbon nanotubes are single-wall nanotubes or multi-wall nanotubes, have a diameter d of 1 to 100 nm, a length L of 0.01 to 20 m, a backlight for a flat panel type liquid crystal display apparatus characterized in that the ratio L / d of the length of the nanotube (L) and diameter (d) of 5 to 20,000 nanotubes is installed at a density of 10 ³ to 10 ¹⁰ / ㎣ . The metal thin film layer 9 of the lower substrate is plated at 10 to 10 minutes at 0.5 to 10 volts (V) by electroplating with one selected from Ag, Cu, Ni, Zn, Au, Co and Al. A backlight for a flat panel liquid crystal display, characterized in that formed. The method of claim 1, wherein the fine metal particle layer 4 for improving the adhesion between the electrode substrate and the carbon nanotubes of the lower substrate is used by using a metal selected from Ag, Cu, Ni, Zn, Au, Co, Al Electroplating is performed for 2 to 8 volts for 1 to 10 seconds, followed by an additional 1 to 5 minutes of electroplating at 0.5 to 3 volts to create a particle size of 0.001 to 0.5㎛ and thus the void space between the carbon nanotubes. Filled backlight for flat panel liquid crystal displays. The thin film conductive layer 6 of the lower substrate is a conductor such as gold, aluminum, indium tin oxide (ITO), platinum, copper, and the thickness of the metal thin film layer is 0.1nm -1㎛. Backlight for flat panel liquid crystal display.