Patent Application
20080036360
Embodiments of the present invention will now be described more fully with reference to the accompanying drawings
Referring to
Each of the first and second substrates 12 and 14 has an active area configured to emit visible light and an inactive area surrounding the active area. The inactive area does not emit light. The active area includes an electron emission unit 18 for emitting electrons located on the first substrate 12, and a light emission unit 20 for emitting the visible light located on the second substrate 14 as shown in
Referring to
When the electron emission regions 28 are formed on the first electrodes 22, the first electrodes 22 are cathode electrodes applying a current to the electron emission regions 28 and the second electrodes 26 are gate electrodes inducing the electron emission by forming the electric field around the electrode emission regions 28 corresponding to a voltage difference between the cathode and gate electrodes. On the contrary, when the electron emission regions 28 are formed on the second electrodes 26, the second electrodes 26 are the cathode electrodes and the first electrodes 22 are the gate electrodes.
Among the first and second electrodes 22 and 26, the electrodes arranged along the x-axis direction function as scan electrodes and the electrodes arranged along the y-axis direction function as data electrodes.
In
Openings 241 and 261 are formed through the insulating layer 24 and the second electrodes 26, respectively, to partly expose the surface of the first electrodes 22 as shown in
The electron emission regions 28 are formed of a material emitting electrons when an electric field is applied thereto under a vacuum atmosphere, such as a carbonaceous material or a nanometer-sized material. The electron emission regions 28 can be formed of carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbon, C60, silicon nanowires or a combination thereof. The electron emission regions 28 can be formed through a screen-printing process, a direct growth, a chemical vapor deposition, or a sputtering process.
Alternatively, the electron emission regions can be formed in a tip structure formed of a Mo-based or Si-based material.
One crossed region (one of the four electron emission groups shown in
In one embodiment, the light emission unit 20 includes a transparent anode electrode 30 formed on the second substrate 14, a phosphor layer 32 formed on the anode electrode 30, a plurality of first sub-electrodes 34 contacting the anode electrode 30 and covered by the phosphor layer 32, and a reflective layer 36 formed on the phosphor layer 32. In one embodiment, the first sub-electrodes 34 are arranged in a predetermined pattern and have a relatively lower resistance compared to that of the anode electrode 30.
The anode electrode 30 is formed of a transparent conductive layer such as an indium tin oxide (ITO) layer to transmit the visible light emitted from the phosphor layer 32. A portion of the anode electrode 30 extends out of the sealing member 16 to form an anode lead 38 (see
The phosphor layer 32 may be a white phosphor layer that is formed on the entire active area of the second substrate 14 or divided into a plurality of sections arranged in a predetermined pattern and spaced apart from each other. In both of these cases, the first sub-electrodes 34 may be covered by the phosphor layer 32 and formed in a line pattern or a lattice pattern (see
In one embodiment, the first sub-electrodes 34 are formed of a material having a resistance lower than that of the anode electrode 30. For example, the first sub-electrodes 34 may be formed of at least one of Mo, Al, a Mo alloy, and an Al alloy. The first sub-electrodes 34 may be formed on the anode electrode 30 before the phosphor layer 32 is formed. At this point, the thickness of the first sub-electrode 34 is about thousands Å. The thickness of the phosphor layer 32 may be several μm. The phosphor layer 32 is formed on the anode electrode 30 while covering the first sub-electrodes 34.
In one embodiment, the width of the first sub-electrode 34 is sized such that the first sub-electrodes 34 are invisible from the outer surface of the second substrate 14 and do not significantly block the path of the visible light emitted from the phosphor layer 32. In one embodiment, the width of the first sub-electrode 34 is substantially equal to or less than about 20 μm. If the width of the first sub-electrode 34 is too short, the line resistance of the first sub-electrode 34 increases and it is difficult to perform the patterning process for the first sub-electrodes 34. In another embodiment, the width of the first sub-electrode 34 is substantially equal to or greater than about 5 μm.
In one embodiment, the first sub-electrodes 34 reduce the line resistance of the anode electrode 30 when an anode voltage is applied to the anode electrode 30 through the anode lead 38 and thus minimize the voltage difference between a portion of the anode electrode 30 close to the anode lead 38 and a portion of the anode electrode 30 far from the anode lead 38. In another embodiment, first sub-electrodes 34 provide substantially uniform voltage distribution on the entire surface of the anode electrode 30.
In a conventional light emission device without sub-electrodes, since the anode electrode made of ITO has a relatively high resistance, there is a voltage difference between a portion close to the anode lead and a portion far from the anode lead. The luminance of the light emission device is proportional to the anode voltage. Therefore, the luminance of the light emission device is not uniform throughout the entire light emission surface thereof due to the voltage difference.
The reflective layer 36 is formed of metal such as Al to enhance the luminance of the screen by reflecting the visible light, which is emitted from the phosphor layer 32 to the first substrate 12, toward the second substrate 14.
Spacers (not shown) are disposed between the first and second substrates 12 and 14 in order to uniformly maintain a gap between the first and second substrates 12 and 14 against an external force.
As illustrated in
In one embodiment, the second sub-electrode 40 is formed of a material having a resistance lower than that of the anode electrode 30. The width of the second sub-electrode 40 is greater than that of the first sub-electrode 34. The second sub-electrode 40 may be formed of substantially the same conductive material as or a different conductive material from that of the first sub-electrodes 34. In the former case, the second sub-electrode 40 may be formed together with the first sub-electrodes using a single mask pattern.
In
A gap is formed between the reflective layer 36 and the phosphor layer 32 as follows. First, an interlayer (not shown) formed of a polymer material that can be decomposed at a high temperature is formed on the phosphor 32. Next, a material for forming the reflective layer 36 is deposited on the interlayer. Then, the interlayer is removed through a thermal process, thereby forming the fine gap. Since the phosphor layer 32 and the reflective layer 36 are supported by the spacer (not shown), the fine gap can be maintained. Therefore, the reflective layer 36 is not affected by a surface roughness of the phosphor layer 32 but is substantially planar.
The above-described light emission device 10 is driven by applying driving voltages to the first and second electrodes 22 and 26 and applying a positive DC voltage, for example thousands of volts, to the anode electrode 30. The reference number 42 in
Then, an electric field is formed around the electron emission regions 28 at pixel regions where a voltage difference between the first and second electrodes 22 and 26 is higher than a threshold value, thereby emitting electrons from the electron emission regions 28. The emitted electrons are accelerated by the high voltage applied to the anode electrode 30 to collide with a corresponding section of the phosphor layer 32, thereby exciting the corresponding section of the phosphor layer 32. A light emission intensity of the phosphor layer 34 at each pixel corresponds to an electron emission amount of the corresponding pixel.
In the above-described driving process, since the first and second sub-electrodes 34 and 40 lower the line resistance of the anode electrode 30, a voltage of a portion of the light emission unit 20, which is close to the anode lead 38, becomes substantially identical to that of a portion of the light emission unit 20, which is far from the anode lead 38. At this point, since the light emission intensity of the phosphor layer 32 is proportional to the anode voltage, the light emission device 10 of this embodiment can uniformly emit the light throughout the entire active area of the light emission unit 20.
Referring to
That is, in this embodiment, the first sub-electrodes 34′ is formed of a carbon-based material such as graphite through a thick filming process such as a screen-printing process to have the above-described height. The width of the first sub-electrode 34′ is designed to be substantially identical to that of the first sub-electrode 34 described in the foregoing embodiment.
In addition, when the phosphor layer 32′ is divided into a plurality of sections that are arranged in a predetermined pattern and spaced apart from each other, a second sub-electrode 40′ may be formed between the sections of the phosphor layer 32′. The second sub-electrode 40′ is formed of the same material as that of the first sub-electrodes 34′. Heights of the first and second sub-electrodes 34′ and 40′ may be similar or identical to each other.
In the above described at least one embodiment, the gap between the first and second substrates 12 and 14 may be, for example, about 5 mm to about 20 mm. The anode electrode 30 may receive a high voltage such as greater than about 10 kV, or about 10-15 kV, through the anode lead 38. Accordingly, in one embodiment, the light emission device 10 realizes a luminance above 10,000 cd/m2 at a central portion of the active area.
Referring to
The display panel 50 may be a liquid crystal display panel or any other non-self emissive display panel. In the following description, a liquid crystal display panel is exampled.
The display panel 50 includes a thin film transistor (TFT) substrate 52 comprised of a plurality of TFTs, a color filter substrate 54 disposed on the TFT substrate 52, and a liquid crystal layer (not shown) disposed between the TFT substrate 52 and the color filter substrate 54. Polarizer plates (not shown) are attached on a top surface of the color filter substrate 54 and a bottom surface of the TFT substrate 52 to polarize the light passing through the display panel 50.
The TFT substrate 52 is a glass substrate on which the TFTs are arranged in a matrix pattern. A data line is connected to a source terminal of one TFT and a gate line is connected to a gate terminal of the TFT. In addition, a pixel electrode is formed on a drain terminal of the TFT.
When electrical signals are input from circuit board assemblies 56 and 58 to the respective gate and data lines, electrical signals are input to the gate and source terminals of the TFT. Then, the TFT turns on or off according to the electrical signals input thereto, and outputs an electrical signal required for driving the pixel electrode to the drain terminal.
RGB color filters are formed on the color filter substrate 54 so as to emit predetermined colors as the light passes through the color filter substrate 54. A common electrode is deposited on an entire surface of the color filter substrate 54.
When electrical power is applied to the gate and source terminals of the TFTs to turn on the TFTs, an electric field is formed between the pixel electrode and the common electrode. Due to the electric field, the orientation of liquid crystal molecules of the liquid crystal layer disposed between the TFT substrate 52 and the color filter substrate 54 can be varied, and thus the light transmissivity of each pixel can be varied according to the orientation of the liquid crystal molecules.
The circuit board assemblies 56 and 58 of the display panel 50 are connected to drive IC packages 561 and 581, respectively. In order to drive the display panel 50, the gate circuit board assembly 56 transmits a gate drive signal and the data circuit board assembly 58 transmits a data drive signal.
The number of pixels of the light emission device 10 is less than that of the display panel 50 so that one pixel of the light emission device 10 corresponds to two or more pixels of the display panel 50. Each pixel of the light emission device 10 emits light in response to the highest gray value among the corresponding pixels of the display panel 50. The light emission device 10 can represent 2-8 bits gray value at each pixel.
For convenience, the pixels of the display panel 50 will be referred to as first pixels and the pixels of the light emission device 10 will be referred to as second pixels. In addition, a plurality of first pixels corresponding to one second pixel will be referred to as a first pixel group.
In order to drive the light emission device 10, a signal control unit (not shown) for controlling the display panel 50 detects a highest gray value among the first pixels of the first pixel group, calculates a gray value required for the light emission of the second pixel according to the detected gray value, converts the calculated gray value into digital data, and generates a driving signal of the light emission device 10 using the digital data. The drive signal of the light emission device 10 includes a scan drive signal and a data drive signal.
Circuit board assemblies (not shown), that is a scan circuit board assembly and a data circuit board assembly, of the light emission device 10 are connected to drive IC packages 441 and 461, respectively. In order to drive the light emission device 10, the scan circuit board assembly transmits a scan drive signal and the data circuit board assembly transmits a data drive signal. One of the first and second electrodes receives the scan drive signal and the other receives the data drive signal.
Therefore, when an image is to be displayed by the first pixel group, the corresponding second pixel of the light emission device 10 is synchronized with the first pixel group to emit light with a predetermined gray value. The light emission device 10 has pixels arranged in rows and columns. The number of pixels arranged in each row may be 2 through 99 and the number of pixels arranged in each column may be 2 through 99.
As described above, in the light emission device 10, the light emission intensities of the pixels of the light emission device 10 are independently controlled to emit a proper intensity of light to each first pixel group of the display panel 50. As a result, the display device 100 of the present invention can enhance the dynamic contrast and image quality of the screen.
While the above description has pointed out novel features of the invention as applied to various embodiments, the skilled person will understand that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made without departing from the scope of the invention. Therefore, the scope of the invention is defined by the appended claims rather than by the foregoing description. All variations coming within the meaning and range of equivalency of the claims are embraced within their scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2006-0076662 | Aug 2006 | KR | national |
