Patent Grant
9858865
This application claims priority to, and the benefit of, Korean Patent Application No. 10-2015-0084518, filed on Jun. 15, 2015 in the Korean Intellectual Property Office (KIPO), the contents of which are incorporated herein in its entirety by reference.
1. Field
Example embodiments relate to a display device. More particularly, embodiments of the present invention relate to a display device employing a dual scan technique, and a method of driving the display device.
2. Description of the Related Art
As a resolution of a display panel is increased, a driving time of a pixel (or, a pixel column) that is included in the display panel, and a compensation time for compensating a threshold voltage of the pixel, are reduced.
Recently, a display device that secures the driving time or the compensation time that is longer than that of the typical display device by employing a dual scan technique has been suggested. However, when the display device operates based on the dual scan technique, respective display regions of the display panel (e.g., an upper display region and a lower display region, which are divided with respect to a center line of the display panel) use different scan signals and have different line resistances. Thus, a current-resistance drop (which may be referred to as “IR drop,” or an ohmic drop) of a power voltage (or of a data signal) occurs differently in respective display regions, and a luminance difference (or, a brightness difference) may be seen at a border between the display regions.
Some example embodiments provide a display device that can control pixels to emit light with the same or substantially the same luminance, even when a power voltage supplied to each of the pixels is differently dropped (i.e., even when different current-resistance drops occur).
Some example embodiments provide a method of driving a display device that drives the display device.
According to example embodiments, a display device may include a power supply configured to generate a first power voltage, a display panel including a pixel that generates a sensing signal by sensing a local voltage level of the first power voltage using a storage capacitor, and a data driver configured to generate a data signal based on image data and the sensing signal.
In example embodiments, the display panel may further include a sensing data line that transfers the sensing signal to the data driver.
In example embodiments, the pixel may include a light emitting element, a driving transistor including a first electrode that receives the first power voltage, a second electrode that is electrically connected to the light emitting element, and a gate electrode that receives the data signal, and a sensing transistor including a first electrode that is electrically connected to the first electrode of the driving transistor, a second electrode that is electrically connected to the sensing data line, and a gate electrode that receives a sensing control signal, wherein the storage capacitor is electrically connected between the first electrode of the driving transistor and the gate electrode of the driving transistor.
In example embodiments, the pixel may sense a voltage at a terminal of the storage capacitor as the local voltage level when a supply of the first power voltage is stopped.
In example embodiments, the display device may further include a gate driver that generates a scan signal and a sensing control signal and to provide the display panel with the scan signal and the sensing control signal, where the gate driver controls the pixel to store the data signal in the storage capacitor based on the scan signal and controls the pixel to sense the local voltage level based on the sensing control signal.
In example embodiments, the display device may further include a timing controller that generates a power control signal and to control the power supply to stop a supply of the first power voltage based on the power control signal.
In example embodiments, the display panel may include a plurality of display regions, and the gate driver may provide mutually independent scan signals to the display regions.
In example embodiments, the data driver may calculate a voltage difference between the sensing signal and a voltage level of the first power voltage and may generate the data signal based on the image data and the voltage difference.
In example embodiments, the data driver may generate a first data signal based on the image data, may compensate the first data signal based on the voltage difference, and may output a compensated first data signal as the data signal.
In example embodiments, the data driver may reduce the first data signal by the voltage difference.
In example embodiments, the power supply may sense the supply voltage level of the first power voltage.
According to example embodiments, a display device may include a power supply configured to generate a first power voltage, a display panel configured to generate a sensing signal by sensing a local voltage level of the first power voltage, and a data driver configured to generate a data signal based on image data and the sensing signal, where the display panel may include a first pixel column including a first pixel that generates the sensing signal by sensing the local voltage level using a storage capacitor, and a second pixel column including a second pixel that emits light based on the data signal.
In example embodiments, the display panel includes a sensing data line that is electrically connected between the first pixel column and the data driver, the sensing data line transferring the sensing signal to the data driver.
In example embodiments, the first pixel may include a light emitting element, a driving transistor including a first electrode that receives the first power voltage, a second electrode that is electrically connected to the light emitting element, and a gate electrode that receives the data signal, and a sensing transistor including a first electrode that is electrically connected to a first electrode of the driving transistor, a second electrode that is electrically connected to the sensing data line, and a gate electrode that receives a sensing control signal, wherein the storage capacitor is electrically connected between the first electrode of the driving transistor and the gate electrode of the driving transistor.
In example embodiments, the first pixel may sense a voltage at a terminal of the storage capacitor as the local voltage level when a supply of the first power voltage is stopped.
In example embodiments, the data driver may calculate a voltage difference between the sensing signal and a supply voltage level of the first power voltage and generates the data signal based on the image data and the voltage difference.
In example embodiments, the display device may further include a gate driver that generates a scan signal and a sensing control signal and to provide the display panel with the scan signal and the sensing control signal, where the gate driver controls the first pixel to store the data signal in the storage capacitor based on the scan signal and controls the first pixel to sense the local voltage level based on the sensing control signal.
According to example embodiments, a method of driving a display device including a pixel, where the pixel includes a light emitting element, a driving transistor that includes a first electrode receiving a first power voltage, a second electrode electrically connected to the light emitting element, and a gate electrode receiving a data signal, and a storage capacitor that is electrically connected between the first electrode of the driving transistor and the gate electrode of the driving transistor, the method may include supplying a second data signal to the pixel, generating a sensing signal by sensing a voltage at a terminal of the storage capacitor as a local voltage level of the first power voltage, and generating the data signal based on image data and the sensing signal.
In example embodiments, generating the sensing signal may include stopping a supply of the first power voltage, disconnecting the driving transistor and the light emitting element, and sensing the voltage at the terminal of the storage capacitor.
In example embodiments, generating the data signal may include calculating a voltage difference between the sensing signal and a supply voltage level of the first power voltage, and generating the data signal based on the image data and the voltage difference.
Therefore, a display device according to example embodiments may control pixels to emit light with the same or substantially the same luminance even when a current-resistance drop of a first power voltage is different at each pixel by sensing a local voltage level of a high power voltage using a storage capacitor of a pixel, which stores a data signal, and by generating the data signal based on the local voltage level. In addition, a method of driving a display panel according to example embodiments may efficiently drive the display panel
Illustrative, non-limiting example embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.
Hereinafter, the present invention will be explained in detail with reference to the accompanying drawings.
It will be understood that, although the terms “first”, “second”, “third”, etc., may be used herein to describe various elements, components, regions, layers, and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section, without departing from the spirit and scope of the present invention.
Spatially relative terms, such as “beneath”, “below”, “lower”, “under”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or in operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” or “under” other elements or features would then be oriented “above” the other elements or features. Thus, the example terms “below” and “under” can encompass both an orientation of above and below. The device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein should be interpreted accordingly.
Further, it will also be understood that when one element, component, region, layer and/or section is referred to as being “between” two elements, components, regions, layers, and/or sections, it can be the only element, component, region, layer and/or section between the two elements, components, regions, layers, and/or sections, or one or more intervening elements, components, regions, layers, and/or sections may also be present.
The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the present invention. As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise,” “comprises,” “comprising,” “includes,” “including,” and “include,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. Further, the use of “may” when describing embodiments of the present invention refers to “one or more embodiments of the present invention.” Also, the term “exemplary” is intended to refer to an example or illustration.
It will be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” “connected with,” “coupled with,” or “adjacent to” another element or layer, it can be “directly on,” “directly connected to,” “directly coupled to,” “directly connected with,” “directly coupled with,” or “directly adjacent to” the other element or layer, or one or more intervening elements or layers may be present. Further “connection,” “connected,” etc. may also refer to “electrical connection,” “electrically connect,” etc. depending on the context in which they are used as those skilled in the art would appreciate. When an element or layer is referred to as being “directly on,” “directly connected to,” “directly coupled to,” “directly connected with,” “directly coupled with,” or “immediately adjacent to” another element or layer, there are no intervening elements or layers present.
As used herein, the term “substantially,” “about,” and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art.
As used herein, the terms “use,” “using,” and “used” may be considered synonymous with the terms “utilize,” “utilizing,” and “utilized,” respectively.
Referring to
The display device 100 may display an image based on externally supplied image data. For example, the display device 100 may be an organic light emitting display device. The display panel 110 may include scan lines S1 through S2j, data lines D1 through Di, and pixels 111 respectively arranged in crossing regions of the scan lines S1 through S2j and the data lines D1 through Di. The display panel 110 may include a light emission control line En, at least one sensing control line SSn, and at least one sensed data line.
Each of the pixels 111 may store a respective data signal supplied through the data lines D1 through Di in response to a scan signal supplied through the scan lines S1 through S2j. Each of the pixels 111 may emit light based on the stored data signal in response to the light emission control signal through the light emission control line En.
In example embodiments, at least one pixel 111 among pixels may generate a sensing signal by sensing/measuring/detecting a local voltage level of a first power voltage ELVDD (e.g., a first power voltage supplied to the display panel 110 for driving the pixel 111) by using a storage capacitor. Here, the storage capacitor may store the externally supplied data signal, and may be electrically connected between a data line Dn and a first line for transferring the first power voltage ELVDD.
For example, the pixel 111 may charge the storage capacitor based on the externally supplied data signal, and may sense a voltage at a terminal of the storage capacitor as the local voltage level corresponding to the first power voltage ELVDD when a supply of the first power voltage ELVDD is stopped (or, interrupted). A configuration of the pixel 111 to sense the local voltage level will be explained in detail with reference to
The display panel 110 may include display regions A and B. For example, the display panel 110 may include an upper display region A and a lower display region B that are divided based on an horizontal axis located at a center of the display panel 110 (e.g., the dashed line shown in
The gate driver 120 may receive a scan driving control signal from the timing controller 140, and may generate a scan signal SCAN[n], a light emission control signal EM, and a sensing control signal SENSING SCAN[n] (see
The gate driver 120 may control the pixel 111 to store the data signal in the storage capacitor based on the scan signal SCAN[n] and to sense the local voltage level of the first power voltage ELVDD supplied to the pixel 111.
In example embodiments, the gate driver 120 may include sub gate drivers 121 and 122 (e.g., gate driving units 121 and 122) for supplying at least one of the scan signal SCAN[n], the light emission control signal EM, and the sensing control signal SENSING SCAN[n] to the display regions A and B, respectively. For example, the gate driver 120 may include a first sub gate driver 121 for supplying the scan signal SCAN[n] to the upper display region A, and a second sub gate driver 122 for supplying the scan signal SCAN[n] to the lower display region B. Here, the first sub gate driver 121 and the second sub gate driver 122 may provide mutually independent scan signals to the display panel 110. For example, the first sub gate driver 121 may sequentially provide the scan signal SCAN[n] to the upper display region A through some scan lines (e.g., S1 through Sj), and the second sub gate driver 122 may sequentially provide the scan signal SCAN[n] to the lower display region B through remaining scan lines (e.g., Sj+1 through S2j). That is, the gate driver 120 may provide at least one selected from the scan signal SCAN[n], the light emission control signal EM, and the sensing control signal SENSING SCAN[n] by employing a multi scan technique (e.g., a dual scan technique).
The data driver 130 may provide the data signal to the display panel 110. The data driver 130 may generate the data signal based on image data supplied from the timing controller 140, and may provide the data signal to the display panel 110 (or to the pixels) through the data lines D1 through Di in response to a data driving control signal.
In example embodiments, the data driver 130 may generate the data signal based on image data and the sensing signal (e.g., SENSED DATA in
The timing controller 140 may control operations of the display panel 110, the gate driver 120, the data driver 130, and the power supplier 150. The timing controller 140 may generate a clock signal, the scan driving control signal, and the light emission control signal, and may provide them to the gate driver 120. The timing controller 140 may generate the data driving control signal, and may provide the driving control signal to the data driver 130. The timing controller 140 may generate a power control signal, and may control the power supplier 150 to stop a supply of the first power voltage ELVDD based on the power control signal.
As described above, the display device 100 according to example embodiments may control the pixels to emit light with the same or substantially the same luminance when the display device 100 has a current-resistance drop (“IR drop”) of the first power voltage ELVDD that is different for each pixel, because the display device 100 may generate the sensing signal by sensing the local voltage level of the first power voltage ELVDD using the storage capacitor of the pixel 111, and by generating the data signal based on the image data and the sensing signal.
Referring to
The switching transistor TR_SC may include a first electrode electrically connected to a first data line 210, a second electrode electrically connected to a gate electrode of the driving transistor TR_D, and a gate electrode for receiving the scan signal SCAN[n]. The switching transistor TR_SC may transfer a first data signal DATA1 supplied through the first data line 210 to a gate electrode of the driving transistor TR_D in response to the scan signal SCAN[n].
The storage capacitor Cst may be electrically connected between a first line for transferring the first power voltage ELVDD and the gate electrode of the driving transistor TR_D. The storage capacitor Cst may store the data signal supplied to a gate electrode of the driving transistor TR_D.
The driving transistor TR_D may include a first electrode for receiving the first power voltage ELVDD, a second electrode electrically connected to a first electrode of the light emitting transistor TR_E, and the gate electrode for receiving the data signal DATA1. The driving transistor TR_D may transfer a driving current based on the first data signal DATA1 stored in the storage capacitor Cst.
The light emitting transistor TR_E may include a first electrode electrically connected to the second electrode of the driving transistor TR_D, a second electrode electrically connected to the light emitting element EL, and a gate electrode for receiving the light emitting control signal EM. The light emitting transistor TR_E may couple (or, connect) the driving transistor TR_D and the light emitting element EL in response to the light emitting control signal EM.
The light emitting element EL may be electrically connected between the light emitting transistor TR_E and a second line for transferring the second power voltage ELVSS, and may emit light based on the driving current supplied according to an operation of the light emitting transistor TR_E. For example, the light emitting element EL may be an organic light emitting diode.
The sensing transistor TR_SEN may include a first electrode electrically connected to the first electrode of the driving transistor TR_D, a second electrode electrically connected to a second data line 220 (e.g., a sensed data line 220), and a gate electrode for receiving the sensing control signal SENSING SCAN[n]. The sensing transistor TR_SEN may sense a voltage Vs at a first node based on the sensing control signal SENSING SCAN[n], and may output a sensed voltage Vs (e.g., SENSED DATA) through the second data line 220 to the outside. Here, the first node may be electrically connected to the first power voltage ELVDD, the driving transistor TR_D, and the storage capacitor Cst.
In
In example embodiments, the pixel 111 may sense a local voltage level of the first power voltage ELVDD using the storage capacitor Cst, and may generate the sensing signal SENSED DATA.
Referring to
The second period T2 may be a data writing period. In the second period T2, the pixel 111 may store the first data signal DATA1, which is transferred through the first data line 210, in the storage capacitor Cst. For example, the first data signal DATA1 may be any value, and the scan signal SCAN[n] may have a turn-on level (i.e., a turn-on voltage level). Here, the pixel 111 may turn on the switching transistor TR_SC in response to the scan signal SCAN[n], may transfer the first data signal DATA1 to the gate electrode of the driving transistor TR_D, and may store the first data signal DATA1 in the storage capacitor Cst, where the first data signal DATA1 may be any voltage supplied to sense the local voltage level of the first power voltage ELVDD. When the light emitting control signal EM has a turn-off level (i.e., a turn-off voltage level), the pixel 111 may turn off the light emitting transistor TR_E, and may stop (or, interrupt) a flow of the driving current supplied to the light emitting element EL.
The storage capacitor Cst may be charged with a voltage difference between a third power voltage and the first data signal DATA1 (i.e., the third power voltage—the first data signal DATA1). Here, the third power voltage may have a local voltage level of the first power voltage ELVDD, where the first power voltage ELVDD has a voltage drop due to line resistances and is supplied to the pixel 111.
The third period T3 may be a sensing period. In the third period T3, the pixel 111 may sense a local voltage level of the first power voltage ELVDD based on the data signal stored in the storage capacitor Cst. The first power voltage ELVDD supplied to the pixel 111 may have a low voltage level. That is, a supply of the first power voltage ELVDD to the pixel 111 may be stopped (or, interrupted). The sensing control signal SENSING SCAN may have a logic low level. Here, the pixel 111 may turn on the sensing transistor TR_SEN and may output a stored voltage (i.e., a voltage Vs of the first node) through the second data line 220 to the outside. Therefore, the pixel 111 may sense the voltage Vs at the first node as the local voltage level of the first power voltage ELVDD, and may output the local voltage level as the sensing signal SENSED DATA to the outside (e.g., to a read-out apparatus or to the data driver 130) when a supply of the first power voltage ELVDD is stopped.
The pixel 111 may sense the local voltage level at a first driving of the display panel 110 (i.e., when the display panel 110 is driven for the first time), or at an initial driving of the display panel 110 (i.e., when the display panel 110 is initialized). That is, the gate driver 120 may provide the sensing control signal SENSING SCAN to the display panel 110 at a first driving point or at an initial driving point of the display panel 110, and the pixel 111 may sense the local voltage level in response to the sensing control signal SENSING SCAN.
As described above, the pixel 111 may store the first data signal DATA1 in the storage capacitor Cst in response to the scan signal SCAN[n], may sense a charged voltage of the storage capacitor Cst in response to the sensing control signal SENSING SCAN, and may generate the sensing signal SENSED DATA based on a sensed voltage.
Referring to
The voltage difference calculator 310 may calculate a voltage difference ΔV between the sensing signal SENSED DATA (i.e., the local voltage level of the first power voltage ELVDD) and the supply voltage level SENSED ELVDD. For example, the voltage difference calculator 310 may receive the sensing signal SENSED DATA from the pixel 111, and may receive the supply voltage level SENSED ELVDD from the power supplier 150. The voltage difference calculator 310 may calculate the voltage difference ΔV by differentially amplifying the sensing signal SENSED DATA and the supply voltage level SENSED ELVDD.
The voltage difference calculator 310 may calculate the voltage difference ΔV at a first driving point or at an initial driving point of the display panel 110, and may store a calculated voltage difference ΔV.
The data signal generator 320 may generate a data signal DATA based on externally supplied image data IMAGE and the calculated voltage difference ΔV.
In an example embodiment, the data driver 130 may generate the first data signal DATA1 based on the image data IMAGE, may compensate the first data signal DATA1 based on the calculated voltage difference ΔV, and may output a compensated first data signal DATA1 as the data signal DATA.
For example, the data driver 130 may generate the first data signal DATA1 corresponding to the image data IMAGE based on a gamma curve, where the gamma curve may represent a relation between a grayscale/gray level of the image data IMAGE and a gray level voltage. The data driver 130 may output the data signal DATA by increasing or decreasing the first data signal DATA1 by the voltage difference ΔV.
Referring to
The pixel 111 located (or, arranged) at the certain point may sense “V3−ΔV” as the local voltage level. The data driver 130 may calculate a voltage difference ΔV based on the local voltage level (i.e., V3−ΔV) and the supply voltage level (V3), and may generate the data signal DATA based on the voltage difference ΔV.
As describe in
In
Referring to
The display device 500 may be the same as, or similar to, the display device 100 described with reference to
Compared to the display panel 110 described in
As described in
The first pixel 511 included in the first pixel column may be the same as, or similar to, the pixel 111 of
The data driver 530 may generate a data signal supplied to the second pixel (or, the second pixel column) based on the sensing signal generated by the first pixel 511 (or by a pixel of the first pixel column). The first power voltage ELVDD supplied to pixels arranged in the same pixel column have the same or substantially the same current-resistance drop. Therefore, the data driver 130 may generate the data signal supplied to the second pixel (or to pixels arranged in the pixel column including the first pixel 511) based on the local voltage level of the first power voltage ELVDD sensed by the first pixel 511.
A configuration of the data driver 530 to generate the data signal may be the same as, or similar to, that of the data driver 130 described with reference to
As described above, the display device 500 may include a first pixel 511 (or a dummy pixel) for sensing the local voltage level of the power voltage ELVDD for each pixel column, and may generate the data signal supplied to other suitable pixels based on the local voltage level sensed by the first pixel 511 (or by the dummy pixel).
Referring to
The dummy pixels 511-n and 511-n+1 may store the first data signal DATA1 in the storage capacitor Cst in response to the scan signal SCAN[n] provided from the gate driver 120. Here, the scan signal SCAN[n] may be provided to pixel rows sequentially or simultaneously.
After a certain amount of time elapses, and when a supply of the first power voltage ELVDD is stopped or interrupted, the dummy pixels 511-n and 511-n+1 may output the sensing signal SENSED DATA by sensing the local voltage level of the first power voltage ELVDD in response to sensing control signals SENSING SCAN[n] and SENSING SCAN[n+1], respectively. Here, the sensing control signals SENSING SCAN[n] and SENSING SCAN[n+1] may be provided from the gate driver 120 to the pixel rows sequentially. For example, the first dummy pixel 511-n may output a first sensing signal by sensing a first local voltage level supplied to the first dummy pixel 511-n in response to an (n)th scan signal SENSING SCAN[n]. The second dummy pixel 511-n+1 may output a second sensing signal by sensing a second local voltage level supplied to the second dummy pixel 511-n+1 in response to an (n+1)th scan signal SENSING SCAN[n+1]. The sensing signal SENSED DATA may include the first sensing signal and the second sensing signal that are sequentially outputted from the dummy pixels 511-n and 511-n+1.
As described in
The data driver 530 may calculate a voltage difference ΔV between the sensing signal SENSED DATA and the local voltage level of the first power voltage ELVDD, and may generate an error signal that represents a magnitude of a current-resistance drop of the first power voltage ELVDD for each pixel row based on the voltage difference ΔV. Here, the error signal may be expressed as only a magnitude of the voltage difference ΔV between the supply voltage level and the local voltage level.
As described with reference to
As described above, the display device 500 may sense the local voltage level of the first power voltage ELVDD using the first dummy pixel 511, and may generate the second data signal supplied to pixels arranged in a pixel row including the dummy pixel 511 based on the local voltage level (or, the sensing signal). Therefore, the display device 500 may reduce a production cost as compared to a configuration generating a data signal by sensing the local voltage level at all of the pixels.
Referring to
The method of
After a certain amount of time elapsed (i.e., when a storage or a charging of the storage capacitor Cst is finished), the method of
When the supply of the first driving power is stopped, the method of
The method of
For example, the method of
The method of
The present invention may be applied to any display device (e.g., an organic light emitting display device, a liquid crystal display device, etc.). For example, the present invention may be applied to a television, a computer monitor, a laptop, a digital camera, a cellular phone, a smart phone, a personal digital assistant (PDA), a portable multimedia player (PMP), an MP3 player, a navigation system, a video phone, etc.
The foregoing is illustrative of example embodiments, and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and features of example embodiments. Accordingly, all such modifications are intended to be included within the scope of example embodiments as defined in the claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Therefore, it is to be understood that the foregoing is illustrative of example embodiments and is not to be construed as limited to the specific embodiments disclosed, and that modifications to the disclosed example embodiments, as well as other example embodiments, are intended to be included within the scope of the appended claims. The present invention is defined by the following claims, with equivalents of the claims to be included therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2015-0084518 | Jun 2015 | KR | national |
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| 20040252089 | Ono | Dec 2004 | A1 |
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| 1999-009765 | Feb 1999 | KR |
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| Number | Date | Country | |
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| 20160365037 A1 | Dec 2016 | US |
