Patent Application
20070228930
This application claims priority of Korean Patent Application No. 2006-20256, filed Mar. 3, 2006, the entire disclosure of which is incorporated herein by reference.
This disclosure relates to making field emission backlights for display devices, such as liquid crystal displays (LCDs), and more particularly, to methods for making field emission backlights that substantially reduce their manufacturing costs.
Liquid crystal displays (LCDs) generally include an LCD panel that displays an image by using the optical transmittance of a layer of liquid crystal material disposed in the panel and the light produced by a backlight assembly disposed behind the panel.
Backlight assemblies can be classified according to the type of light sources used therein, e.g., cold cathode fluorescent lamp (CCFL) backlights, external electrode fluorescent lamp (EEFL) backlights, light emitting diode (LED) backlights, and so on.
A recent innovation in the field of backlights has been the development of field emission backlights. A field emission backlight generates light through an electric field applied between two substrates. A conventional field emission backlight includes upper and lower substrates. The upper substrate includes a transparent electrode and a fluorescent material. The lower substrate includes an electrode part and an electron-emitting part. When a high voltage is applied between the transparent electrode of the upper substrate and the electrode part of the lower substrate, an electric field is generated and electrons are emitted from the electron-emitting part. The emitted electrons excite the fluorescent material on the upper substrate and thereby produce light. However, one of the problems with conventional field emission backlights is that they consume a large amount of electrical power because of the high voltage that needs to be applied between the transparent electrode and the electrode part.
More recently, field emission backlights having a triode structure have been developed in an effort to resolve the above problem of conventional field emission backlights. The triode structured field emission backlight generates light using a relatively low voltage. The triode structured field emission backlight includes an anode, a cathode and a gate electrode. When a relatively low voltage is applied between the cathode and the gate electrode, and electrons are emitted from the cathode, the electrons advance toward the anode and collide with a fluorescent material so that light is generated.
Triode structured field emission backlights also have another structure that has been developed to improve the uniformity of brightness of the light they produce. The triode structured field emission backlight includes the above cathode and gate electrode that are arranged in an alternating in the same plane. However, the cost of the driving circuit in triode field emission backlights incorporating such a structure is increased because a relatively high voltage, e.g., 400V˜600V, must be applied between the cathode and the gate electrode to generate light of sufficient brightness.
In accordance with the exemplary embodiments thereof described herein, the present invention provides field emission backlights for display devices and methods for manufacturing them at a substantially reduced cost by enabling the voltage applied between the cathode and the gate electrode to be reduced, as well as to display devices incorporating the novel field emission backlights.
In one exemplary embodiment thereof, a field emission backlight includes upper and lower substrates. The upper substrate includes an upper transparent substrate, a transparent electrode formed on the upper transparent substrate, and a fluorescent part formed on the transparent electrode.
The lower substrate includes a lower transparent substrate having a receiving groove formed in an upper surface being disposed in facing opposition to the upper substrate, a first electrode part formed on the upper surface, a second electrode part formed on a bottom surface of the receiving groove, and an electron-emitting part formed on an upper surface of at least one of the first and second electrode parts. The upper surface of the lower substrate is disposed below and in facing opposition with the upper substrate. The first and second electrode parts are spaced apart from each other by a selected. The electron-emitting part emits electrons in response to an electric field generated between the first and second electrode parts.
An exemplary embodiment of a field emission display apparatus includes a field emission backlight producing light, and a display panel disposed above the field emission backlight. The display panel displays an image by means of the light produced by the backlight.
The field emission backlight of the display includes field emission backlight includes upper and lower substrates. The upper substrate includes an upper transparent substrate, a transparent electrode formed on the upper transparent substrate, and a fluorescent part formed on the transparent electrode. The lower substrate includes a lower transparent substrate having a receiving groove formed in an upper surface being disposed in facing opposition to the upper substrate, a first electrode part formed on the upper surface, a second electrode part formed on a bottom surface of the receiving groove, and an electron-emitting part formed on an upper surface of at least one of the first and second electrode parts. The upper surface of the lower substrate is disposed below and in facing opposition with the upper substrate. The first and second electrode parts are spaced apart from each other by a selected. The electron-emitting part emits electrons in response to an electric field generated between the first and second electrode parts.
An exemplary embodiment of method for manufacturing a field emission backlight includes forming a first metal layer on a upper surface of a lower transparent substrate, forming and patterning a first photoresist layer on the first metal layer, etching a portion of the first metal layer using the patterned first photoresist layer as a mask, forming a receiving groove by etching a portion of the lower transparent substrate using the etched first metal layer as a mask, forming a second metal layer on the patterned first photoresist layer and a bottom surface of the receiving groove, removing the patterned first photoresist layer, forming an electron-emitting part on the first and the second metal layers to form a lower substrate, forming an upper substrate, including an upper transparent substrate, a transparent electrode formed on the upper transparent substrate, and a fluorescent part formed on the transparent electrode, and combining the upper substrate and the lower substrate to form a field emission backlight.
In accordance with the exemplary embodiments described herein, the gap between the first and second electrode parts of the lower substrate is substantially reduced relative to that in conventional field emission backlights because the first electrode part is formed at the upper surface of the lower transparent substrate and the second electrode part is formed at the bottom surface of the receiving groove. This enables the voltage applied between the first and the second electrode parts to reduced, thereby enabling the cost of the components of a driving circuit that produces the voltage to be reduced and resulting in an overall reduction in the manufacturing cost of the backlight.
A better understanding of the above and many other features and advantages of the field emission backlights and the methods for making them of the present invention may be obtained from a consideration of the detailed description of some exemplary embodiments thereof below, particularly if such consideration is made in conjunction with the appended drawings, wherein like reference numerals are used to identify like elements illustrated in one or more of the figures thereof.
Referring to
The upper substrate 100 includes an upper transparent substrate 110, a transparent electrode 120 and a fluorescent part 130. The upper transparent substrate 110 is plate shaped and comprises a transparent material, for example, glass, quartz or a transparent plastic. Preferably, the upper transparent substrate 110 comprises glass.
The transparent electrode 120 is formed, for example, by a vapor deposition process, on a lower surface of the upper transparent substrate 110. The transparent electrode 120 comprises a transparent conductive material, for example, indium tin oxide (ITO), indium zinc oxide (IZO), amorphous indium tin oxide (a-ITO), or the like. The transparent electrode 120 is electrically coupled with an external voltage supply that applies a direct current (DC) voltage V1 to it. The DC voltage V1 is, for example, in a range of from about 5 kilovolts (kV) to about 15 kV, and preferably, is in a range of from about 8 kV to about 10 kV.
The fluorescent part 130 is formed on the lower surface of the transparent electrode 120. The fluorescent part 130 generates light by means of electrons emitted from the lower substrate 200. The electrons emitted from the lower substrate 200 collide with the fluorescent part 130 to excite the fluorescent part 130, and when the excited fluorescent part 130 relaxes from the excitation, light radiates from it.
The lower substrate 200 is disposed with its upper surface facing upward toward the upper substrate 100. The lower substrate 200 includes a lower transparent substrate 210, a first electrode part 220, a second electrode part 230, an electron-emitting part 240 and a reflecting part 250.
The lower transparent substrate 210 is plate shaped and comprises a transparent material, for example, glass, quartz or a transparent plastic, and preferably, is glass.
As illustrated in
As illustrated in
As illustrated in
The second electrode part 230 includes an elongated second body electrode 232 and a plurality of elongated second branch electrodes 234. The second body electrode 232 is formed at the second side of the lower transparent substrate 210 and extends generally parallel to it and the first body electrode 222. The second branch electrodes 234 are electrically connected to the second body electrode, extend generally perpendicularly from it and toward the first side of the substrate, are arranged substantially parallel to each other, and are interleaved between the first branch electrodes 224. A gap is provided between the first and second branch electrodes 224 and 234 of from about 5 micrometers (μm) to about 15 μm, and preferably, of about 10 μm.
In the exemplary embodiment illustrated, the first electrode part 220 is formed on the protruding surface 214 of the lower transparent substrate 210, whereas, the second electrode part 230 is formed on the bottom surface of the receiving groove 212, and accordingly, the shape of the receiving groove 212 corresponds to that of the second electrode part 230.
A relatively low voltage is applied between the first and second electrode parts 220 and 230. The voltage applied is an alternating current (AC) voltage V2. For this purpose, an external voltage supply is electrically coupled to the first body electrode 222 of the first electrode part 220 and the second body electrode 232 of the second electrode part 230, and applies the alternating current voltage V2 to the first and the second electrodes 222 and 232. The alternating current voltage V2 may be, for example, in a range of from about 10 volts (V) to about 100 V, and preferably, is in a range of from about 40 V to about 60 V.
The electron-emitting part 240 is formed on at least one upper surface of either the first or the second electrode parts 220 and 230, and to increase brightness, may be formed on the upper surfaces of both the first and the second electrode parts 220 and 230. Accordingly, the electron-emitting part 240 may have elongated shapes corresponding to those of the underlying first and second electrode parts 220 and 230.
When an electric field is generated between the first and the second electrode parts 220 and 230, the electron-emitting part 240 emits electrons in response thereto. Thus, when the alternating current voltage V2 is applied to the first and second electrode parts 220 and 230, one electrode has a higher voltage and the other a lower voltage, and accordingly, an electric field is generated between them, resulting in the emission of electrons from the electron-emitting part 240. The intensity of the electric field may be in the range of from about 4 V/μm to about 6 V/μm.
The electrons emitted from the electron-emitting part 240 move toward the upper substrate 100 in response to the electric field generated between the upper substrate 100 and the lower substrate 200 by the direct current voltage V1.
As illustrated in
Because the reflecting part 250 includes metal and the ground voltage is applied to it, the reflecting part 250 prevents external electromagnetic fields from penetrating into the field emission backlight 300, and accordingly, enables the stability of the electric fields inside the field emission backlight 300 to be preserved.
The first and second electrode parts 220 and 230 and the electron-emitting part 240 are described in more detail in connection with
The electron emitting protrusions 242 protrude substantially perpendicular to the first and second electrode parts 220 and 230, and comprise, for example, carbon nanotubes. The conductive balls 244 are disposed at an end portion of the electron emitting protrusions 242, and comprise, for example, nickel (Ni). Because of the presence of the electron emitting protrusions 242 and the conductive balls 244 on the electron-emitting part 240, the electron-emitting part 240 readily emits electrons as a result of the electric field formed between the first and second electrode parts 220 and 230.
Of importance, in the exemplary embodiment illustrated, the gap between the first and the second electrode parts 220 and 230 can be shortened because the first electrode part 220 is formed on the protruding surface 214 of the lower transparent substrate 210 and the second electrode part 230 is formed on the bottom surface of the receiving groove 212. As a result, the voltage applied between the first and second electrode parts 220 and 230 to generate the electrons can be correspondingly reduced.
In a conventional field emission backlight, electrodes corresponding to the first and second electrode parts 220 and 230 above are formed in the same layer, and hence, at the same level, and accordingly, are separated from each other by about 100 μm, due to limitations of the photo processes used to form them. However, the gap between the first and the second electrode parts 220 and 230 of the embodiment illustrated and described above can be reduced substantially below this because the first electrode part 220 is formed on and at the same level as the protruding surface 214 of the lower transparent substrate 210, whereas, the second electrode part 230 is formed on and at the same level as the bottom surface of the receiving groove 212.
When the gap between the first and the second electrode parts 220 and 230 is reduced, this enables the voltage that needs to be applied between the first and second electrode parts 220 and 230 to generate the electrons to be correspondingly reduced relative to that required in the conventional field emission backlight. This in turn, enables the cost of the components of a driving circuit that produces the voltage to be reduced, thereby resulting in a reduction in the manufacturing cost of the backlight.
Referring to
The display panel 400 is disposed over the field emission backlight 300 and displays images by using the light provided by the field emission backlight 300. The display panel 400 includes a first substrate 410, a second substrate 420 and a liquid crystal layer 430.
The first substrate 410 includes a plurality of pixel electrodes arranged in a rectangular matrix form, a plurality of thin film transistors (TFTs) that respectively applying a driving voltage to each of the pixel electrodes, and a plurality of signal lines that drive the TFTs.
The second substrate 420 is disposed in facing opposition to the first substrate 410, and includes a transparent conductive common electrode and a plurality of color filters, each disposed in facing opposition to a corresponding one of the pixel electrodes. In one exemplary embodiment, the color filters include transparent red, green and blue color filters.
A layer of a liquid crystal material 430 is interposed between the first and second substrates 410 and 420. The orientation of the molecules of the liquid crystal layer 430 is rearranged when an electric field is generated between the pixel electrodes and the common electrode. The rearranged molecules of the liquid crystal layer 430 adjust the optical transmittance of the panel to external light passing through it. The light, with an adjusted intensity, passes through respective ones of the color filters, so that images are displayed by the panel.
Hereinafter, a “second metal pattern 50b” is defined as the first metal layer 50 after being further etched, as above, and a “protruding surface 214” of the lower transparent substrate 210 is defined as that portion of the upper surface of the lower transparent substrate 210 remaining after the above etching processes are complete, i.e., the portion of the protruding surface 214 in which the receiving groove 212 is not formed. By this definition, it may be seen that the second metal pattern 50b is disposed only on the protruding surface 214 of the lower transparent substrate 210.
The second metal layer 70 may also incorporate a triplex layer structure that is the same as that of the first metal layer 50. Thus, for example, the bottom layer 72 of the second metal layer 70 may include molybdenum-tungsten (MoW), the middle layer 74 may include titanium (Ti), and the top layer 76 may include nickel (Ni).
Hereinafter, a “third metal pattern 70a” is defined as that portion of the second metal layer 70 that is formed on the bottom surface of the receiving groove 212.
In one exemplary embodiment, the nickel (Ni) layers are partially etched to form conductive balls thereon that are spaced apart from each other, and then grown in a direction substantially perpendicular to the upper surface of the lower transparent substrate 210 by using the conductive balls as seed, so that the grown nickel (Ni) layers form electron emitting protrusions (not illustrated in
In one possible exemplary embodiment, the growth of the Nickel (Ni) layers may be omitted from respective portions of the molybdenum-tungsten (MoW) and titanium (Ti) layers of the second and third metal patterns 50b and 70a, and these portions may form the first and second electrode parts 220 and 230, respectively, as described above. A lower substrate 200 of a field emission display may thus be manufactured in accordance with the process described above.
Next, and referring again to
In accordance with the exemplary embodiments of the field emission backlight described above, the gap between the first and the second electrode parts 220 and 230 can be substantially reduced relative to that required in a conventional field emission backlight because the receiving groove 212 is formed by etching a portion of the lower transparent substrate 210, and the second electrode part 230 is formed on the bottom surface of the receiving groove 212, thus providing a vertical separation between the two electrode parts that enables the horizontal separation between them to be reduced while maintaining the requisite minimum separation therebetween.
After the metal layer 50 is etched to form the first metal pattern 50a, a portion of the lower transparent substrate 210 is etched using the first metal pattern 50a as a mask, so that a receiving groove 212 having a selected depth and tapering sidewalls is formed in the lower substrate. A hydrofluoric acid (HF) diluted with distilled water may be used as the etching solution in etching the lower transparent substrate. As above, when a “protruding surface 214” of the substrate is defined to be the portion of the upper surface of the lower transparent substrate 210 in which the receiving groove 212 is not formed, the first metal pattern 50a is formed on only the protruding surface 214 of the lower transparent substrate 210.
An electron-emitting part 240 is then formed on the first and second metal patterns 50a and 70a. In the exemplary embodiment illustrated, each of the nickel (Ni) layers of the first and second metal patterns 50a and 70a is grown in a direction substantially perpendicular to the upper surface of the lower transparent substrate 210, so that the grown nickel (Ni) layers form the electron-emitting part 240.
As in the first embodiment above, the growth of the electron emitting nickel layers may be omitted from respective portions of the molybdenum-tungsten (MoW) and titanium (Ti) layers of the second and third metal patterns 50b and 70a, and these portions may form the first and second electrode parts 220 and 230, respectively, as described above. A lower substrate 200 of a field emission display may thus be manufactured in accordance with the process described above. Then, the lower substrate 200 manufactured by the above-described process and an upper substrate 100 manufactured through other processes are combined to form a field emission backlight 300.
First, referring back to
A portion of the first metal layer 50 is then etched using the patterned first photoresist layer 60 as a mask so that a first metal pattern 50a is formed. In this etching process, the first metal layer 50 is etched in a direction substantially perpendicular to the upper surface of the lower transparent substrate 210. Accordingly, the etched first metal layer 50 has vertical side-walls and substantially the same shape as the patterned first photoresist layer 60 when viewed in a plan view.
An electron-emitting part 240 is then formed on the first and second metal patterns 50a and 70a. For example, as described above, each of the nickel (Ni) layers of the first metal pattern 50a and the second metal pattern 70a are grown in a direction substantially perpendicular to the upper surface of the lower transparent substrate 210, so that the grown nickel (Ni) layers form the electron-emitting part 240.
As in the above embodiments, the growth of the electron emitting nickel layers may be omitted from respective portions of the molybdenum-tungsten (MoW) and titanium (Ti) layers of the second and third metal patterns 50b and 70a, and these portions may form the first and second electrode parts 220 and 230, respectively, as described above. The lower substrate 200 manufactured in accordance with the process described above is then combined with an upper substrate 100 manufactured through other processes to form a field emission backlight 300.
In accordance with the exemplary embodiments of the present invention described above, the gap between the first and second electrode parts can be substantially reduced relative to that required in a conventional field emission backlight because a receiving groove is formed by etching a portion of the lower transparent substrate and the second electrode part 230 is formed at the bottom surface of the receiving groove, thereby providing a vertical separation between the two electrode parts that enables the horizontal separation between them to be reduced, relative to that of conventional field emission backlights, while maintaining the requisite minimum separation between them. This, in turn, enables the level of the voltage applied between the first and the second electrode parts to be reduced, thereby enabling the cost of the components of a driving circuit to be reduced and resulting in an overall reduction in the manufacturing cost of a field emission backlight.
By now, those of skill in this art will appreciate that many modifications, substitutions and variations can be made in and to the field emission backlights and the methods for making them of the present invention without departing from its spirit and scope. In light of this, the scope of the present invention should not be limited to that of the particular embodiments illustrated and described herein, as they are only exemplary in nature, but instead, should be fully commensurate with that of the claims appended hereafter and their functional equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-20256 | Mar 2006 | KR | national |
