Patent Grant
9390673
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2012-212563, filed Sep. 26, 2012, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a liquid crystal display device and a method of driving the same.
Liquid crystal display devices are incorporated into various apparatuses such as a television receiver, automobile displays such as a car navigation apparatus, and mobile terminals such as a notebook computer and cellular phone.
For example, in a TN (Twisted Nematic)-mode or OCB (Optically Compensated Bend)-mode liquid crystal display device, the orientation direction of liquid crystal molecules contained in a liquid crystal layer held between upper and lower substrates is controlled by an electric field formed between a counterelectrode of the upper substrate and a pixel electrode of the lower substrate.
Also, in an IPS (In-Plane Switching)-mode or FFS (Fringe-Field Switching)-mode liquid crystal display device, both the counterelectrode (in this case, a COM electrode) and the pixel electrode are provided on one substrate, and the orientation direction of liquid crystal modules contained in a liquid crystal layer is controlled by an electric field (fringe electric field) formed between the two electrodes. The FFS-mode liquid crystal display device has a high luminance because a high aperture ratio can be secured, and also has a good viewing angle characteristic.
In general, according to one embodiment, there is provided a liquid crystal display device comprising: an array substrate comprising a pixel electrode forming a pixel, and a counterelectrode arranged opposite to the pixel electrode with an insulating layer being interposed between them, and forming the pixel, a counter substrate arranged opposite to the array substrate, a liquid crystal layer held between the array substrate and the counter substrate, and a driving unit configured to perform polarity inversion driving by applying, to the pixel electrode, positive and negative video signals corresponding to a gray level of an image to be displayed by the pixel, wherein when applying the video signals to the pixel electrode, the driving unit superposes a correction signal corresponding to a polarity inversion frequency and the gray level on the video signals in advance.
According to another embodiment, there is provided a method of driving a liquid crystal display device, the liquid crystal display device comprising an array substrate including a pixel electrode forming a pixel, and a counterelectrode arranged opposite to the pixel electrode with an insulating layer being interposed therebetween and forming the pixel, a counter substrate arranged opposite to the array substrate, a liquid crystal layer held between the array substrate and the counter substrate, and a driving unit, the method comprising performing polarity inversion driving by applying, to the pixel electrode, positive and negative video signals corresponding to a gray level of an image to be displayed by the pixel by the driving unit, and when applying the video signals to the pixel electrode, superposing a correction signal corresponding to a polarity inversion frequency and the gray level on the video signals in advance by the driving unit.
First, the idea of the embodiments of the present invention will be explained.
An image burn-in phenomenon sometimes occurs in an FFS-mode liquid crystal display device. Various factors cause this image burn-in. One known example is a state in which a DC operating point shifts due to the electric charge accumulation (charge-up) resulting from a display gray level in an interface between insulating film and alignment film in a pixel slit portion or an interface between alignment film and liquid crystal. Another known example is a state caused by an insufficient liquid crystal orientation anchoring strength.
As a means for suppressing this image burn-in phenomenon, a system including a correcting means for correcting a voltage to be applied to a pixel electrode in accordance with a gray level by applying a preset DC bias having a predetermined magnitude to the voltage has been proposed as disclosed in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 2011-112865. This system can provide a liquid crystal display device and a method of driving the same that improve the display quality by suppressing the image burn-in phenomenon.
It is necessary to reduce the circuit power consumption in a liquid crystal display device for a mobile terminal, particularly, a smartphone, and low-frequency driving and intermittent driving have been proposed as means for this purpose. The low-frequency driving is a method of reducing the circuit power by decreasing the driving frequency of a liquid crystal display device to, e.g., ½ or ¼ that of the standard conditions. The intermittent driving is a method of reducing the circuit power by inserting a circuit pause period having a few frames after write is performed in one display period (one frame) of a liquid crystal display device.
In either method, a side effect such as a moving image blur may occur because a video signal rewrite frequency decreases. However, each method is an effective circuit power reducing means when, e.g., displaying a still image for which the moving image visibility is not important. Note that in either method, a polarity inversion frequency necessarily decreases when the video signal rewrite frequency is decreased.
When the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2011-112865 was applied to the low-frequency driving and intermittent driving described above, it was impossible to obtain a desired image burn-in improving effect.
Accordingly, the embodiments of the present invention have been made to solve this problem, and can provide a liquid crystal display device and a method of driving the same that improve the display quality by suppressing the image burn-in phenomenon even in a liquid crystal display device using the low-frequency driving or intermittent driving. A remarkable image burn-in reducing effect can be obtained especially when decreasing the frame inversion frequency in order to reduce the driving power. This makes it possible to achieve both a low power consumption and the image burn-in reducing effect. Means for embodying the above-mentioned idea in order for the embodiments of the present invention to solve the above problem will be explained below.
A liquid crystal display device and a method of driving the liquid crystal display device according to the first embodiment will be explained in detail below with reference to the accompanying drawing.
As shown in
As shown in
The other one of the pair of substrates is an array substrate 100 comprising a transparent insulating substrate SB1, a counterelectrode (first electrode) COM, and a plurality of pixel electrodes (second electrodes) PE arranged on an insulating layer L1 made of, e.g., silicon nitride (SiN) and face the counterelectrode COM. The pixel electrodes PE are arranged in one-to-one correspondence with the pixels PX, and slit-like holes SLT are formed in the pixel electrode PE. The counter electrode COM and pixel electrodes PE are transparent electrodes made of, e.g., ITO (Indium Tin Oxide).
In the display unit as shown in
The pixel switch SW comprises a TFT (Thin-Film Transistor). The gate electrode of the pixel switch SW is electrically connected to the corresponding scanning line GL, and faces the semiconductor layer. The source electrode of the pixel switch SW is electrically connected to the corresponding signal line SL, and is also electrically connected to the source region of the semiconductor layer. The drain electrode of the pixel switch SW is electrically connected to the corresponding pixel electrode PE, and is also electrically connected to the drain region of the semiconductor layer.
The array substrate 100 comprises a gate driver GD and source driver SD as driving means for driving the plurality of pixels PX. The plurality of scanning lines GL are electrically connected to the output terminals of the gate driver GD. The plurality of signal lines SL are electrically connected to the output terminals of the source driver SD.
The gate driver GD and source driver SD are arranged in the peripheral region of the display unit. The gate driver GD sequentially applies an ON voltage to the scanning lines SL, and applies the ON voltage to the gate electrodes of the pixel switches SW electrically connected to a selected scanning line GL. An electric current flows between the source electrode and drain electrode of a pixel switch to the gate electrode of which the ON voltage is applied. The source driver SD supplies corresponding output signals (video signals) to the signal lines SL. The signal supplied to each signal line SL is applied to the corresponding pixel electrode PE via the pixel switch SW in which an electric current flows between the source electrode and drain electrode.
A controller CTR arranged outside the liquid crystal display panel PNL controls the operations of the gate driver GD and source driver SD. The controller CTR applies a countervoltage Vcom to the counterelectrode COM. The gate driver GD, source driver SD, and controller CTR function as a driving unit.
The controller CTR has a function (low-frequency driving function) of changing the driving frequency in order to reduce the driving power. As an example, assume that the standard frame inversion frequency of the liquid crystal display device is 60 Hz (i.e., the polarity of a voltage to be applied to a liquid crystal inverts every ( 1/60) sec). When displaying a moving image, the display device operates at 60 Hz. When displaying, e.g., a still image for which the moving image visibility is not important, however, the driving speed of the controller CTR is decreased to, e.g., ½, ¼, ⅛, or 1/64, thereby setting the frame inversion frequency at 30, 15, 7.5, or 0.9375 Hz, respectively. By thus changing the driving speed in accordance with a display image, the power consumption for driving can be reduced. Note that in this driving, the scanning rate of the gate driver GD and source driver SD is also synchronously decreased to, e.g., ½, ¼, ⅛, or 1/64.
Alternatively, the controller CTR may also have an intermittent driving function. For example, although a 60-Hz operation (i.e., an operation of performing full-screen write for ( 1/60) sec) is the basic operation, a pause period equivalent to, e.g., 1 frame, 3 frames, 7 frames, or 63 frames is inserted after write (scanning from the upper end to the lower end of the screen) of 1 frame (=( 1/60) sec) is performed when, e.g., displaying a still image. When the operation of the controller CTR is stopped in this pause period, the circuit power consumption during this period is practically 0 (zero), and the circuit power consumption averaged by the time including the write time is reduced to ½, ¼, ⅛, or 1/64.
A signal written in each pixel must be held in it for a long time in the driving as described above, so it is desirable to use a TFT having a small off-leakage current and hence suited to low-frequency driving. An example of the TFT is a TFT including a semiconductor layer made of, e.g., IGZO (an oxide containing In (indium), Ga (gallium), and Zn (zinc)).
As shown in
As shown in
As shown in
An image burn-in phenomenon sometimes occurs in the FFS-mode liquid crystal display device as described above. The image burn-in phenomenon is a phenomenon by which when, for example, a gray image (halftone image) is displayed on the entire surface of the display unit after a black-and-white checker pattern is displayed on the screen for a while, an afterimage of the checker pattern remains, like a residual image.
The liquid crystal display device according to this embodiment comprises a correcting means (correction unit) SDA for correcting an output signal to be supplied to the signal line SL, in order to suppress this image burn-in phenomenon, as will be described later. Note that the controller CTR can determine whether the voltage signal (video signal) is burned into the pixel electrode PE, based on, e.g., the time during which the voltage signal is continuously applied to the pixel electrode PE. The liquid crystal display device can be configured so that if the voltage signal is continuously applied to the pixel electrode PE for a predetermined time or more, the controller CTR controls the correcting means SDA to output a corrected voltage signal (video signal) as an output signal to the signal line SL.
In the liquid crystal display device according to the embodiment, a correction signal is preset in the correcting means SDA. For example, in the testing stage after the liquid crystal display device is manufactured, an image burn-in test is conducted to measure a series of luminance-Vcom characteristic curves as will be explained later, an optimal correction signal is calculated based on the measurement results, and the correcting means SDA is so adjusted as to output the calculated correction signal. In this embodiment, therefore, the correcting means SDA is so configured as to perform correction by which a correction signal corresponding to the polarity inversion frequency and the gray level of an image to be displayed on the pixel PX is superposed on an electrical signal (video signal) in advance, regardless of whether the voltage signal (video signal) is burned into the pixel electrode PE.
The luminance-Vcom characteristic curve described above is an important concept when analyzing an image burn-in state. Details are disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2011-112865. Therefore, only the points of the luminance-Vcom characteristic curve will be explained below.
The luminance-Vcom characteristic curve is a graph plotting the luminance and the potential (Vcom) of the counterelectrode COM by changing the potential (Vcom) after a video signal having a specific display gray level (burn-in gray level) is burned into a pixel and the display gray level is switched to a gray level (measurement gray level) for evaluating the image burn-in. The abscissa represents a deviation (Vcom deviation) from a reference Vcom value corresponding to the burn-in. The luminance-Vcom characteristic curve generally has a parabola shape projecting downward. The apex coordinate along the abscissa (i.e., a point where the luminance is minimal) of the parabola is called a “minimal-luminance Vcom deviation”, and the apex coordinate along the ordinate (i.e., the minimal value of the luminance) is called a “luminance bottom level”.
The luminance-Vcom characteristic curve generally shifts in the horizontal or perpendicular direction when an image burn-in occurs. That is, even when the measurement gray level is constant, the minimal-luminance Vcom deviation and luminance bottom level take different values if the burn-in gray level changes. An image burn-in occurring due to the dependence of the minimal-luminance Vcom deviation on the burn-in gray level is called a “DC shift mode image burn-in”. An image burn-in occurring due to the dependence of the luminance bottom level on the burn-in gray level is called a “luminance bottom level fluctuation mode image burn-in”. Note that an actual visual image burn-in corresponds to a fluctuation width at the luminance (called an intercept luminance) at a point (Vcom deviation=0) where the luminance-Vcom characteristic curve corresponding to each burn-in gray level intersects the ordinate.
The primary factors of the DC shift mode image burn-in include, e.g., a factor (internal factor) caused by electric charge accumulation (chart-up) in an interface between the insulating film and alignment film in the pixel slit portion or an interface between alignment film and liquid crystal, and a factor (external factor) caused by the positive-negative asymmetry (DC offset) of the voltage to be applied to the liquid crystal. The minimal-luminance Vcom deviation (δV) can generally be represented by equation (1) below:
(δV)=(pixel potential positive-negative average
on measurement gray level)−(pixel
potential positive-negative average on
burn-in gray level)+(component resulting
from display unit internal factor) (1)
On the other hand, the insufficiency of the liquid crystal orientation regulating force (anchoring force) is well known as the primary factor of the luminance bottom level fluctuation mode image burn-in. Also, the luminance bottom level fluctuation mode image burn-in sometimes occurs in addition to the DC shift mode image burn-in when charge-up occurs in the liquid crystal cell slit portion or the interface between the overcoat layer and alignment film described above. The luminance bottom level fluctuation mode image burn-in is mainly caused by the internal factor, and is generally independent of the positive-negative asymmetry (DC offset) of a voltage to be applied to a liquid crystal. One of the DC shift mode image burn-in and luminance bottom level fluctuation mode image burn-in is dominant in some cases, and they sometimes occur together as well.
Since low-frequency driving or intermittent driving is performed in this embodiment, the polarity inversion frequency of the voltage to be applied to the liquid crystal layer LQ becomes lower than the standard frequency in some cases.
The present inventors, therefore, measured luminance-Vcom characteristic curves after a burn-in at three polarity inversion frequencies of 60, 15, and 0.9375 Hz. Assume that the standard polarity inversion frequency is 60 Hz. Also, 15 Hz (¼ of the standard frequency) and 0.9375 Hz ( 1/64 of the standard frequency) are taken as examples of a frequency decreased by performing low-frequency driving or intermittent driving.
As shown in
The measurement results reveal that as the polarity inversion frequency decreases, the dependence of the minimal-luminance Vcom deviation on the burn-in gray level increases. For example, the difference between the minimal-luminance Vcom deviations on burn-in gray levels of 0/63 and 63/63 is approximately 70 mV when the polarity inversion frequency is 60 Hz (
The phenomenon in which the difference between the minimal-luminance Vcom deviations changes in accordance with the polarity inversion frequency as described above is a novel fact found by the present inventors by experiments and the like. The degree of image burn-in is given by the fluctuation width (ΔL in the drawing) of the intercept luminance. The values of ΔL are ΔL=0.0118 when the polarity inversion frequency is 60 Hz (
Note that the dependence of the minimal-luminance Vcom deviation on the burn-in gray level increases as the polarity inversion frequency decreases perhaps because charge transfer in, e.g., an interface between the pixel electrode and alignment film has positive-negative asymmetry (rectification) like that of a diode, i.e., the period of polarity inversion becomes longer than the charge transfer time at low frequencies. This facilitates charge transfer, and increases the charge-up amount.
Based on the above-described results (
As shown in
In other words, the offset voltage (correction signal) is set such that the change amount of the countervoltage Vcom when the average luminance value of an image having a first gray level to be displayed by the pixel PX is minimal is equal to the change amount of the countervoltage Vcom when the average luminance value of an image having a second gray level to be displayed by the pixel PX is minimal, at each polarity inversion frequency.
This will be explained in detail below by taking a case in which the polarity inversion frequency is 0.9375 Hz as an example.
As shown in
Referring to
In equation (1) presented earlier, “the pixel potential positive-negative average on the measurement gray level” is “the offset voltage on the measurement gray level”, “the pixel potential positive-negative average on the burn-in gray level” is “the offset voltage on the burn-in gray level”, and “the component resulting from the display unit internal factor” is the minimal-luminance Vcom deviation shown in
From the foregoing, the corrected minimal-luminance Vcom deviation (δV) can be calculated for each burn-in gray level by using equation (1):
Burn-in gray level=0/63
δV=40 mV−0 mV+20 mV=60 mV
Burn-in gray level=31/63
δV=40 mV−40 mV+60 mV=60 mV
Burn-in gray level=63/63
δV=40 mV−150 mV+170 mV=60 mV
From the foregoing, the minimal-luminance Vcom deviations certainly match.
That is, the video signal is corrected such that the bottom position of each luminance-Vcom characteristic curve shown in
When signal correction (correction of superposing the correction signal on the video signal) of this embodiment is performed (
For comparison, a liquid crystal display device of a comparative example that does not take account of the dependence on the polarity inversion frequency will be explained below.
This comparative example adopts the offset voltage at 60 Hz (the standard polarity inversion frequency) regardless of the polarity inversion frequency. That is, the offset voltage as shown in
As shown in
As shown in
According to the liquid crystal display device and method of driving the liquid crystal display device according to the first embodiment configured as described above, the liquid crystal display device comprises the array substrate 100, counter substrate 200, liquid crystal layer LQ, and driving unit. The array substrate 100 includes the pixel electrodes PE forming the pixels PX, and the counterelectrode COM. The driving unit applies, to the pixel electrode PE, positive and negative video signals corresponding to the gray level of an image to be displayed by the pixel PX, thereby performing polarity inversion driving.
When applying the video signal to the pixel electrode PE, the driving unit performs correction of superposing a correction signal corresponding to the polarity inversion frequency and gray level on the video signal in advance.
The driving unit superposes a first correction signal corresponding to a first polarity inversion frequency and a gray level on the video signal in a first mode, and superposes a second correction signal corresponding to a second polarity inversion frequency and the gray level in a second mode. The second polarity inversion frequency differs from the first polarity inversion frequency, the first mode is a mode of performing driving at the first polarity inversion frequency, the second mode is a mode of performing driving at the second polarity inversion frequency, and the second correction signal differs from the first correction signal.
Assuming that the first polarity inversion frequency is higher than the second polarity inversion frequency, the voltage value of the first correction signal is not more than that of the second correction signal on each gray level.
In this embodiment, the correction signal is set such that the change amount of the countervoltage Vcom when the average luminance value of an image having a first gray level to be displayed by the pixel PX is minimal is equal to the change amount of the countervoltage Vcom when the average luminance value of an image having a second gray level to be displayed by the pixel PX is minimal, at each polarity inversion frequency. Note that the countervoltage Vcom is a constant voltage at the time of actual use (when displaying an image by performing polarity inversion driving). When setting the correction signal, e.g., when measuring the luminance-Vcom characteristic curve in the testing stage, the voltage value of the countervoltage Vcom is changed.
Consequently, a liquid crystal display device capable of suppressing the image burn-in phenomenon can be obtained even at a polarity inversion frequency different from the standard frequency. In addition, the image burn-in phenomenon can be suppressed even in a liquid crystal display device using low-frequency driving or intermittent driving. This makes it possible to reduce the circuit power, thereby achieving low power consumption.
From the foregoing, it is possible to obtain a liquid crystal display device and method of driving the liquid crystal display device that improve the display quality by suppressing the image burn-in phenomenon.
Next, a liquid crystal display device and a method of driving the liquid crystal display device according to the second embodiment will be explained. In this embodiment, the same reference numerals as in the above-described first embodiment denote the same functional parts, and a detailed explanation thereof will be omitted.
The correction of the video signal by the offset voltage (
In the above-mentioned first embodiment, the change width (ΔL) of the intercept luminance is decreased by shifting the luminance-Vcom characteristic curve in the horizontal direction in accordance with equation (1). The variable range of the intercept luminance has the following restrictions.
[1] The intercept luminance cannot be made lower than the luminance bottom level. (This is so because the luminance-Vcom characteristic curve is a parabola projecting downward.)
[2] The intercept luminance cannot be varied when the burn-in gray level matches the measurement gray level. (This is so because the first two terms in equation (1) become equal and cancel each other.)
In other words, it is impossible to make the upper limit of ΔL smaller than the maximum value of the luminance bottom level, and make the lower limit of ΔL larger than the intercept luminance.
As shown in
(i) At each polarity inversion frequency, the minimal-luminance Vcom deviation corresponding to a burn-in gray level of 63/63 (the condition under which the luminance bottom level is maximum) is nearly 0.
(ii) At each polarity inversion frequency, an intercept luminance corresponding to a burn-in gray level of 0/63 is nearly equal to an intercept luminance corresponding to a burn-in gray level of 31/63 (when the burn-in gray level is equal to the measurement gray level).
When adopting correction using the offset voltage shown in
As shown in
According to the liquid crystal display device and method of driving the liquid crystal display device according to the second embodiment configured as described above, the liquid crystal display device comprises the array substrate 100, counter substrate 200, liquid crystal layer LQ, and driving unit. In this embodiment, if a first minimal value as a minimum of the average luminance value of an image which is to be displayed by the pixel PX and has a first gray level is larger than a second minimal value as a minimum of the average luminance value of an image which is to be displayed by the pixel PX and has a second gray level having a luminance level lower than that of the first gray level, at each polarity inversion frequency, a correction signal corresponding to the polarity inversion frequency and first gray level is superposed on a video signal corresponding to the polarity inversion frequency and first gray level, such that the change amount of the countervoltage Vcom is zero when the luminance of the image having the first gray level takes the first minimal value.
In the above-mentioned case, a correction signal corresponding to the polarity inversion frequency and second gray level is further superposed on a video signal corresponding to the polarity inversion frequency and second gray level, so that the luminance of the image having the second gray level takes a predetermined value. This predetermined value is a value deviated from the second minimal value. Note that the countervoltage Vcom is a constant voltage in an actual use (when displaying an image by performing polarity inversion driving).
Consequently, it is possible to obtain a liquid crystal display device capable of further suppressing the image burn-in phenomenon, and capable of suppressing the burn-in phenomenon even at a polarity inversion frequency different from the standard frequency. In addition, the image burn-in phenomenon can be suppressed even in a liquid crystal display device using low-frequency driving or intermittent driving. This can achieve a low power consumption.
From the foregoing, it is possible to obtain the liquid crystal display device and method of driving the liquid crystal display device that improve the display quality by suppressing the image burn-in phenomenon.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
For example, when giving a liquid crystal display device the function of low-frequency driving or intermittent driving, it is necessary to determine whether to perform low-frequency driving or intermittent driving, and select a polarity inversion frequency when performing low-frequency driving or intermittent driving, in accordance with conditions such as user's mode selection (e.g., a power-saving mode) and a display image (e.g., a still image or moving image). It is possible to perform this determination by a control circuit (e.g., a CPU) of an apparatus main body (e.g., the main body of a smartphone or tablet PC), and send a control signal to the controller (driving unit) of the liquid crystal display device. It is also possible to cause the control circuit itself of the liquid crystal display device to perform the determination. In either case, the control circuit of the liquid crystal display device recognizes the polarity inversion frequency in real time. Therefore, when offset voltage (correction signal) information is prestored as a table in a memory of the control circuit, an optimal offset correction voltage can be selected in accordance with the real-time polarity inversion frequency.
The polarity inversion frequency can be selected from several conditions (e.g., selected from the three conditions, i.e., 60, 15, and 0.9375 Hz in the previously described embodiments), and can also be continuously set (e.g., continuously varied between 60 and 0.1 Hz). In the latter case, it is possible to store, in a memory, offset voltages for some discrete conditions within a frequency interval, and obtain an optimal offset voltage by an interpolating calculation (line graph approximation) as needed.
Note that the above-described embodiments have been explained by assuming that the countervoltage Vcom is a constant voltage in an actual use (when displaying an image by performing polarity inversion driving). However, even when the positive and negative values of the countervoltage Vcom are different, such as when performing common-line inversion driving (driving in which even- and odd-numbered lines have opposite signal polarities, and the signal polarity is inverted for each frame), video signal correction is applicable as in the above-described embodiments. When measuring the luminance-Vcom characteristic curve in this case, the values of the countervoltages Vcom having the positive and negative polarities are changed while maintaining a given difference between them.
Furthermore, the embodiments of the present invention are not limited to the above-mentioned liquid crystal display device and method of driving the liquid crystal display device, and are applicable to various kinds of liquid crystal display devices and methods of driving the liquid crystal display devices.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-212563 | Sep 2012 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 20030132903 | Ueda | Jul 2003 | A1 |
| 20030156086 | Maeda | Aug 2003 | A1 |
| 20040223006 | Nakayama | Nov 2004 | A1 |
| 20080170025 | Song et al. | Jul 2008 | A1 |
| 20120050147 | Iwasa | Mar 2012 | A1 |
| Number | Date | Country |
|---|---|---|
| 1637544 | Jul 2005 | CN |
| 101071213 | Nov 2007 | CN |
| 2002-14363 | Jan 2002 | JP |
| 2007-298801 | Nov 2007 | JP |
| 2010-281981 | Dec 2010 | JP |
| 2011-112865 | Jun 2011 | JP |
| Entry |
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| Japanese Office Action issued Nov. 4, 2015 in Patent Application No. 2012-212563 (with English translation). |
| Combined Chinese Office Action and Search Report issued Sep. 1, 2015 in Patent Application No. 201310445585.3 (with English language translation). |
| Number | Date | Country | |
|---|---|---|---|
| 20140085356 A1 | Mar 2014 | US |
