Patent Application
20060290288
[Technical Field of the Invention and Related Art prior to the Invention]
The present invention relates to a field emission display, and more particularly, to field emission display and a manufacturing method thereof, which deflects an electron beam by providing a deflection electrode on a rear substrate on which a cold cathode is formed, and improves its reliability by providing a protective electrode on an uppermost layer of the rear substrate.
Generally, a field emission display applies an electric field from a gate electrode to emitters arranged on a cathode to be spaced apart from one another by a predetermined interval to thereby cause the emitters to emit electrons, and collides the emitted electrons against a phosphor layer on an anode to which a high voltage is applied to thereby cause the phosphor layer to emit light.
A cold cathode device in the above structure is formed on the rear substrate 10, and a front substrate 80 is installed in front of the rear substrate 10 in such a way to be spaced apart from the cold cathode device by a predetermined distance. An anode 85, to which a high voltage is applied, is provided on a rear surface (that is, a surface facing the rear substrate 10) of the front substrate 80, and a phosphor layer 90 is provided on the anode 85.
Gates hole 45A and first through holes 40A are formed at positions where the cathodes 20 and the gate electrodes 45 intersect each other, and emitters 100 are formed at the bottoms of the first through holes 40A. Generally, a data voltage is applied to each cathode 20, and a scanning voltage is applied to each gate electrode 45.
While this method can lower a frame frequency, it has drawbacks in that the size of the emitter 100 is reduced and the width of a data line for applying a data voltage to the emitter 100 is narrowed. Increased data line resistance due to the narrowed data line width tends to cause a problem when a high resolution image is reproduced.
To solve the problem caused by the increased data line resistance, there has been proposed a method of exciting three subpixels by one emitter.
However, while this method can provide a data line width three times larger than that in the method shown in
[Technical Goal of the Invention]
The present invention provides a field emission display and a manufacturing method thereof, which can deflect an electron beam with a relatively-low voltage by providing a deflection electrode capable of adjusting the direction of the electron beam on a rear substrate, and can improve its reliability by providing a protective layer on an uppermost layer of the rear substrate.
[Structure and Operation of the Invention]
According to an aspect of the present invention, there is provided a field emission display including: a rear substrate; a cathode formed on the rear substrate, an emitter being formed on the cathode; a first dielectric layer formed on the cathode, a first through hole corresponding to the emitter being formed in the first dielectric layer; a gate electrode formed on the first dielectric layer, a gate hole corresponding to the emitter being formed in the gate electrode; a second dielectric layer formed on the gate electrode, a second through hole corresponding to the emitter being formed in the second dielectric layer; a deflection electrode formed on the second dielectric layer, the deflection electrode having at least two elements symmetrically arranged to face each other with the emitter therebetween, a deflection voltage of a predetermined waveform being applied to the deflection electrode; a third dielectric layer formed on the deflection electrode, a third through hole corresponding to the emitter being formed in the third dielectric layer; and a protective electrode formed on the third dielectric layer, the protective electrode having a hole corresponding to the emitter, a predetermined fixed voltage being applied to the protective electrode.
The emitter may be formed through the growth of a CNT or the coating of CNT paste. The deflection electrode may deflect an electron beam emitted from the emitter by a symmetrical or asymmetrical electric filed.
A predetermined low voltage may be applied to the protective electrode, whereby the electron beam can be focused without being dispersed and positively-charged particles can be prevented from being accumulated in a vacuum space of the field emission display.
According to another aspect of the present invention, there is provided a field emission display including: a rear substrate; a cathode formed on the rear substrate in parallel stripes, an emitter being formed on the cathode to be spaced apart from one another by a predetermined interval; a first dielectric layer formed on the cathode, a first through hole corresponding to the emitter being formed in the first dielectric layer; a gate electrode formed on the first dielectric layer in parallel stripes intersecting the parallel stripes of the cathode, a gate hole corresponding to the emitter being formed in the gate electrode; a second dielectric layer formed on the gate electrode, a second through hole corresponding to the emitter being formed in the second dielectric layer; a deflection electrode formed on the second dielectric layer in such a way to Intersect the gate electrode and correspond in parallel with the cathode, the deflection electrode having at least two elements symmetrically arranged to face each other with the emitter therebetween, a deflection voltage of a predetermined waveform being applied to the deflection electrode; a third dielectric layer formed on the deflection electrode, a third through hole corresponding to the emitter being formed in the third dielectric layer; and a protective electrode formed on the third dielectric layer, the protective electrode having a hole corresponding to the emitter, a predetermined fixed voltage being applied to the protective electrode.
Here, one emitter formed on the rear substrate may correspond to one pixel constituted by subpixels of various colored phosphor layers formed on a front substrate. The brightness of each pixel may be determined through combinations of a voltage applied to the cathode and a voltage applied to the gate electrode. That an electron beam will cause what color subpixel to emit light may be determined by a voltage applied to the deflection electrode.
The field emission display may include a deflection voltage controlling unit for adjusting a voltage applied across the deflection electrode, and a front substrate disposed to be spaced apart from the rear substrate by a predetermined distance. An anode may be formed on the front substrate's surface facing the rear substrate, and various colored parallel phosphor layers may be formed on the anode.
The deflection voltage controlling unit may apply voltages of several deflection modes to the deflection electrode. The direction of an electron beam emitted from the emitter may be adjusted through combination of voltages according to the respective deflection modes. Accordingly, an electron beam according to each deflection mode may be transferred to a corresponding colored phosphor layer formed on the anode of the front substrate.
The pixel may be constituted by R/G/B parallel subpixels disposed on the anode. The deflection voltage controlling unit may cause electron beams of the same brightness signal to be sequentially transferred to the R/G/B subpixels, whereby a desired color image can be formed by the resulting afterimage.
According to a further aspect of the present invention, there is provided a method for manufacturing a field emission display, the method including: forming a cathode of a predetermined pattern on a rear substrate, sequentially depositing a resistor layer, a first dielectric layer and a first metal layer on the cathode, and then forming a gate electrode by patterning the first metal layer; sequentially depositing a second dielectric layer and a second metal layer on the gate electrode, and then forming a deflection electrode by patterning the second metal layer, forming an emitter hole through an etching process so that the cathode is exposed at a position where the emitter is to be formed; and forming an emitter in the emitter hole by using a carbon nanotube.
According to a still further aspect of the present invention, there is provided a method for manufacturing a field emission display, the method including: forming a cathode of a predetermined pattern on a rear substrate, sequentially depositing a resistor layer, a first dielectric layer and a first metal layer on the cathode, and then forming a gate electrode by patterning the first metal layer, sequentially depositing a second dielectric layer and a second metal layer on the gate electrode, and then forming a deflection electrode by patterning the second metal layer, sequentially depositing a third dielectric layer and a third metal layer on the deflection electrode, and then forming a protective electrode by patterning the third metal layer; forming an emitter hole through an etching process so that the cathode is exposed at a position where the emitter is to be formed; and forming an emitter in the emitter hole by using a carbon nanotube.
The present invention will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments of the invention are shown. Like reference numerals in the drawings denote like elements, and thus their description will be omitted.
The inventive field emission display further includes a cathode 20 formed on the rear substrate 10, an emitter 100 formed of a carbon nanotube, a gate electrode 45 formed on the cathode 20 in such a way to be isolated from the cathode 20, and a deflection electrode 55 formed on the gate electrode 45.
The deflection electrode 55 includes at least two elements facing each other with the emitter 100 between them. When one deflection axis is necessary for controlling the direction of an electron beam, the deflection electrode 55 may be constituted by first and second elements.
A voltage V1 and a voltage V2 are applied respectively to first element 551 and second element 552 of the deflection electrode. When V1 equals V2, a symmetrical electric field is formed in an emitter hole, whereby an electron beam emitted from the emitter 100 travels straight. On the contrary, when V1 differs from V2, an asymmetrical electric field is formed in the emitter hole, whereby the electron beam emitted from the emitter 100 is deflected to one side.
Meanwhile, an anode 85 is formed on the front substrate 80's surface facing the rear substrate 10, and parallel phosphor layers 90 of various colors are formed on the anode 85. Accordingly, to cause an electron beam (deflected by the deflection electrode 55) to reach one of the phosphor layer of an cause a phosphor layer of a desired color to emit light.
Here, the phosphor layers 90 may be constituted by R/G/B subpixels, and one pixel constituted by three subpixels may correspond to one emitter 100.
Referring to
Two elements of the deflection electrode 55 are symmetrically arranged to face each other with the emitter 100 between them. Here, first elements 551 of deflection electrodes passing by the left side of the emitter 100 are connected with one another, and second elements 552 of deflection electrodes passing by the right side of the emitter 100 are connected with one another. A voltage V1 and a voltage V2 are applied respectively to the first element 551 and the second element 552, and the direction of an electron beam can be adjusted as described above.
The deflection electrodes 55 have arc portions at their inner sides and arranged to surround the emitter 100 through the arc portions, whereby an average gap between the deflection electrodes 55 and the emitter 100 can be reduced. The magnitude of the voltages applied to the deflection electrodes 55 are set in consideration of signal voltages applied to the cathode 20 and the gate electrode 45 and a distance between it and an anode. When V1 and V2 are all minus, the deflection electrodes 55 can simultaneously function as focusing gates because they have the arc portions surrounding the emitter 100.
These features of the above embodiments can be applied to other embodiments of the present invention.
A predetermined low voltage Vc is applied to the protective electrode 65. Accordingly, an electron beam deflected by the deflection electrode 55 can reach a targeted subpixel without being dispersed. Voltages V3 and V4 applied to the deflection electrode 55 may be identical to or different from each other according to whether or not the electron beam has been deflected, and may be concretely determined according to the relationships among them and Vc and a gate electrode voltage.
Referring to
As described above, the protective electrode 65 to which a low voltage Vc is applied can function as a focusing gate. In addition, the protective electrode can prevent the accumulation of positively-charged particles generated at an vacuum space in the field emission display. Accordingly, the protective electrode 65 can protect the field emission display from various problems that may be caused by static electricity of high voltage.
In a general field emission display, a front substrate and a rear substrate are installed to be spaced apart from each other by a predetermined distance with a spacer, a circumference portion thereof is sealed, and an inner space thereof is maintained in a near vacuum state of about 10−6 through 10−5 mbar. However, since the inner space is not a perfect vacuum state, gas molecules exists in the inner space and the gas molecules is positively charged by the device's inner environment of high positive polarity. When these positively-charged particles are accumulated in a dielectric layer exposed upward and thus static charge of high voltage is formed, an arcing may be generated due to a breakdown between the accumulated charge and emitters or metal electrodes and the conductivity of a ballast resistor (that is, a semiconductor) may be changed.
In this embodiment, the protective electrode 65 is formed of a metal electrode of high conductivity, whereby the accumulation of the positive charge is prevented and thus the cold cathode device formed on the rear substrate 10 is protected.
Voltages +11V and −42V are supplied respectively to two voltage input ports 51 and 52, and three combinations of output port voltages, that is, R(−42V, +11V), G(−42V, −42V) and B(+11V, −42V) are obtained through a predetermined switching circuit.
Switches 563 and 564 provided respectively to input ports of the first and second elements 553 and 554 of the deflection electrodes are sequentially connected to the three output ports, whereby the three combinations of the output port voltages are applied to the deflection electrodes. Three switching operations for each of R/G/B colors are necessary for reproducing one color. Accordingly, when a frame frequency is 60 Hz, a switch 56 is switched at the rate of 180 Hz.
The magnitude of a voltage applied to the deflection electrode 55 is determined in consideration of the voltage relationship between the gate electrode and the protective electrode. However, since generally determined within a low voltage range of about −200V through +200V, the applied voltage does not cause a problem that may be generated due to a residual voltage, even when the switch 56 is switched at the rate of 180 Hz.
In addition, the deflection voltage controlling unit can increase/decrease a voltage of one of at least two elements of the deflection electrodes by the same magnitude with respect to all the deflection modes. Accordingly, arrival positions of electron beams for all the colors can be horizontally shifted. Therefore, a possible misallignemnt between the rear and front substrates can be compensated through an electrical adjustment.
A method for manufacturing the inventive field emission display will now be described in detail.
The ballast resistor 30 may be made of material having resistivity of about 100 Ωcm through 107 Ωcm, such as amorphous silicon and the like. The dielectric layer 40 is made mainly of silica (SiO2). A metal electrode such as the gate electrode 45 is formed by depositing chrome (Cr) and patterning the resulting layer. When the gate electrode 45 is patterned, a gate hole 45A corresponding to an emitter is formed in the gate electrode 45.
Referring to
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While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
[Effect of the Invention]
As stated above, the direction of the electron beam can be controlled with a relatively-low voltage by providing the deflection electrode capable of controlling the direction of the electron beam on the rear substrate. Also, a possible misalignment between the front substrate and the rear substrate during a packaging process can be corrected through a simple method of uniformly adjusting a voltage applied to the deflection electrode.
Further, a sufficient data line width can be obtained even in a high-resolution device because emitters are in 1:1 correspondence with pixels, and a sufficient luminance can be obtained by applying a high voltage because a voltage of the anode need not be switched.
Furthermore, the cold cathode device on the rear substrate can be protected from charged particles generated in the display through a high voltage by providing a protective electrode formed in a body with respect to a whole surface of an uppermost layer of the rear substrate, whereby the lifetime and reliability of the field emission display can be improved.
