JP2006267653A - Driving device for liquid crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase a response speed of a liquid crystal at a low temperature. <P>SOLUTION: Image data of images to be displayed in frames are input to a memory and a lookup table for every frame. A control signal indicating storage of the image data is input to the memory by a plurality of frames predetermined. Input image data are stored in the memory with respect to frames for which the control signal is input. The memory outputs stored image data to the lookup table fo every frame. That is, the memory outputs the same image data for a plurality of frames. The lookup table specifies a potential on the basis of a luminance difference between input image data for every frame and image data output from the memory. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal driving device for driving a liquid crystal display device.

As a method for driving the liquid crystal display device, there is a method called overdrive. Overdrive is a driving method in which a higher voltage or lower voltage is applied to the liquid crystal to promote a change in the state of the liquid crystal (that is, the response speed of the liquid crystal is increased). FIG. 6 is an explanatory diagram showing an example of overdrive. FIG. 6A shows a change in the transmittance of the liquid crystal accompanying a voltage application to the liquid crystal, and FIG. 6B shows a change in the applied voltage (V _LCD ) to the liquid crystal. Also, the horizontal axis in FIGS. 6A and 6B represents the passage of time. In this example, the case of normally white will be described as an example. Here, the case where the liquid crystal display device is driven so that the frame frequency is 60 Hz and one frame is about 16.7 msec is shown as an example. The frame is the time from when the first row common electrode is selected until the next first row common electrode is selected.

When the voltage applied to the liquid crystal is lowered to V ₁ as shown in FIG. 6B, the transmittance of the liquid crystal gradually increases as shown by the broken line in FIG. Further, as shown in FIG. 6B, when the voltage applied to the liquid crystal is reduced to V ₂ (V ₂ <V ₁ ), the transmittance of the liquid crystal is shown by a solid line in FIG. 6A. Thus, it rises more steeply than when V _{1 is} applied. The response time can be approximately the same as one frame. That is, in order to increase the transmittance of the liquid crystal faster in the case of normally white, a lower voltage may be applied. As described above, overdrive is a driving method in which a lower (or higher) voltage is applied to increase the response speed of the liquid crystal.

Further, FIG. 6 shows a change in transmittance at room temperature (room temperature). When the temperature is low, the response speed of the liquid crystal is lowered, and the method of changing the transmittance is different from that at room temperature. FIG. 7 is an explanatory diagram showing changes in the transmittance of the liquid crystal at low temperatures. FIG. 7A shows the change in the transmittance of the liquid crystal accompanying the voltage application to the liquid crystal, and FIG. 7B shows the change in the applied voltage to the liquid crystal. When the voltage applied to the liquid crystal is lowered to V ₁ as shown in FIG. 7B, the transmittance of the liquid crystal rises very slowly as shown by the broken line in FIG. 7A, and the response time is 1 It greatly exceeds the frame. Further, even when overdrive is performed with the voltage applied to the liquid crystal being V ₂ lower than V ₁ , the transmittance of the liquid crystal rises very slowly as shown by the solid line in FIG. The applied voltage when performing overdrive as V ₂ is that the response speed is quickened slightly than the case of applying a voltage V _1, the response time is greatly exceeds one frame, applying a voltage V ₂ at room temperature It is not possible to obtain a good response speed as when

  In order to obtain a good response speed at a low temperature, it is conceivable to apply a voltage that is lower (or higher) than a voltage applied by overdrive at room temperature.

  Note that the drive waveforms shown in FIGS. 6B and 7B may be taken as drive waveforms for the TFT liquid crystal display device. Alternatively, it may be understood as a drive waveform indicating the effective value of the applied voltage to the pixels of the STN liquid crystal display device. In either case, the change in the transmittance of the liquid crystal is as shown in FIGS. 6 (a) and 7 (a). That is, whether the overdrive is applied to the TFT liquid crystal display device or the overdrive is applied to the STN liquid crystal display device, the change in the transmittance of the liquid crystal is shown in FIG. ) And FIG. 7A.

  Further, when determining the voltage applied to the liquid crystal, a lookup table (hereinafter referred to as LUT) is used. Conventionally used LUTs determine the potential (the potential of the source electrode or source wiring) according to the difference in transmittance (luminance) between the image data one frame before and the image data to be displayed. . FIG. 8 is an explanatory diagram showing a situation in which image data is input to a conventional LUT.

  The liquid crystal driving device is provided with an LUT and a memory. Image data to be displayed in each frame is input to the LUT and the memory. In FIG. 8, this image data is shown as input data. When image data is input in each frame, the memory stores the image data and outputs the image data to the LUT in the next frame. In FIG. 8, this image data is shown as memory output data. Therefore, input data and memory output data (that is, image data one frame before) are input to the LUT for each frame. The LUT stores in advance a potential corresponding to the difference between the transmittance (luminance) indicated by the input data and the transmittance (luminance) indicated by the memory output data. Then, when input data and memory output data are input for each frame, the potential corresponding to the difference in transmittance indicated by both is specified, and the source driver is instructed to output the potential.

  Note that the types of voltages applied to the liquid crystal determined by the output potentials of the source driver and the common driver are predetermined such as 64 types. Accordingly, the type of potential that the LUT instructs the source driver to output is also predetermined.

  In the example shown in FIG. 8, for example, in a frame in which input data “N + 1” is input to the LUT, memory output data “N” is input from the memory to the LUT. This memory output data “N” is image data of the previous frame. The LUT specifies a potential corresponding to the difference in transmittance indicated by the two types of image data “N + 1” and “N”.

  In the LUT, a potential at which a good liquid crystal response speed can be obtained is stored in advance as a potential corresponding to the difference between the transmittance (luminance) indicated by the input data and the transmittance (luminance) indicated by the memory output data. Good.

  Also, in order to obtain a good response speed even at low temperatures, a plurality of LUTs corresponding to various temperatures are provided, and a method of switching LUTs according to temperatures, a high temperature LUT and a low temperature LUT are prepared, and a high temperature LUT A method has been proposed in which a potential corresponding to an intermediate temperature is determined by linearly interpolating with a low temperature LUT (see, for example, Patent Document 1).

JP 2004-4629 A (paragraphs 0011, 0057-0107)

  As described with reference to FIG. 7, at the low temperature, even if the same overdrive as that at the room temperature is applied, the response speed of the liquid crystal at the room temperature cannot be obtained. In that case, the response speed of the liquid crystal is improved by driving the liquid crystal display device using an LUT that is set to apply a voltage that is lower (or higher) than that applied by overdrive at room temperature. Can be made.

  However, the types of voltages applied to the liquid crystal are predetermined such as 64 types, and the maximum voltage and the minimum voltage that can be applied to the liquid crystal are also predetermined. Therefore, even if an attempt is made to apply a voltage lower or higher than the voltage applied by overdrive at room temperature, a voltage lower or higher than the applicable voltage range cannot be applied. Therefore, there is a limit to improving the response speed of the liquid crystal at low temperatures.

  Therefore, an object of the present invention is to provide a liquid crystal driving device that can further improve the response speed of liquid crystal at low temperatures.

  Aspect 1 according to the present invention is a liquid crystal drive device for driving a liquid crystal display device provided with a source electrode or a source wiring, wherein image data of an image to be displayed in the frame is input and stored for each frame. The image data to be displayed for each frame and the image data of the image to be displayed in the frame are input for each frame, and the image data and the image data output from the memory are respectively in accordance with the difference in luminance Specified by the lookup table, a memory control unit for outputting a control signal instructing to store the input image data to the memory every predetermined number of frames, and the lookup table. A liquid crystal driving device comprising: a source driver that sets a potential on the source electrode or source wiring To provide.

  Aspect 2 according to the present invention includes a temperature detection unit that outputs a signal corresponding to a temperature in the vicinity of the liquid crystal display device to the memory control unit in aspect 1, and the memory control unit is in the vicinity of the liquid crystal display device based on the signal. Whether or not the temperature of the liquid crystal display device is equal to or lower than a predetermined temperature. If the temperature in the vicinity of the liquid crystal display device is equal to or lower than the predetermined temperature, the input image Provided is a liquid crystal driving device that outputs a control signal instructing to store data.

  Aspect 3 according to the present invention includes, in aspect 1, a temperature detection unit that outputs a signal corresponding to a temperature in the vicinity of the liquid crystal display device to the memory control unit, and the memory control unit is in the vicinity of the liquid crystal display device based on the signal. It is determined which temperature range of a plurality of predetermined temperature ranges belongs, and the input image data is stored in the memory for each predetermined number of frames according to the determined temperature range Provided is a liquid crystal driving device that outputs a control signal instructing this.

  Aspect 4 according to the present invention includes an operation unit that is switched to a significant setting or an insignificant setting by the operator in Aspect 1, and the memory control unit is configured to perform a predetermined operation when the operation unit is set to a significant setting. There is provided a liquid crystal driving device that outputs a control signal instructing to store inputted image data to a memory for each of a plurality of frames.

  According to the present invention, the response speed of the liquid crystal at a low temperature can be further improved.

  First, a liquid crystal display device driven by the liquid crystal driving device according to the present invention will be described. The liquid crystal display device may be a liquid crystal display device provided with a source electrode or source wiring connected to a source driver (see FIG. 1) described later. As an example of a liquid crystal display device provided with a source electrode, for example, a plurality of source electrodes are provided on one of a pair of transparent substrates, and a plurality of common electrodes are provided on the other transparent substrate so as to be orthogonal to the source electrodes. There is a liquid crystal display device in which a liquid crystal is disposed between a common electrode and a common electrode. In this liquid crystal display device, common electrodes are sequentially selected by a common driver. Then, a predetermined potential is set to the selected common electrode so that a voltage corresponding to the image data is applied to the pixel at the intersection of the selected common electrode and each source electrode, and each source electrode is set with a predetermined potential. The potential is set by the source driver based on the image data.

  An example of a liquid crystal display device provided with a source line is a TFT liquid crystal display device. In the TFT liquid crystal display device, a pixel electrode and a TFT are provided for each pixel. In addition, one common electrode is provided so as to face each pixel electrode, and a liquid crystal is disposed between the common electrode and each pixel electrode. The pixel electrode is connected to the drain of the TFT. The source of the TFT is connected to the source wiring, and the gate of the TFT is connected to the gate wiring. When the gate is set to the on potential through the gate wiring, the source and the drain are brought into conduction, and the pixel electrode is set to the same potential as the source wiring. When the gate potential is set to an off potential, the source and the drain are in a non-conductive state, and the source wiring and the pixel electrode are also switched to a non-conductive state. The on-potential is a predetermined potential of the gate for making a conductive state between the source and the drain. The off potential is a predetermined potential of the gate for making the source and drain nonconductive.

  Each pixel (pixel electrode and TFT) is arranged in a matrix, for example, and each gate wiring is connected to the gate of each TFT in one row for each row. Each source line is connected to the source of each TFT in one column for each column. When displaying an image, the common driver performs scanning while sequentially selecting gate lines, and sets the potential of the selected gate lines to an on potential. During the selection period of the selected row, the source driver sets the potential of each source wiring based on the image data of each pixel for one row corresponding to the selected gate wiring. As a result, a voltage corresponding to the image data is applied between each pixel electrode for one row corresponding to the selected gate wiring and the common electrode. Thereafter, by sequentially selecting the gate wiring in the same manner, an image for one screen is displayed.

  The liquid crystal driving device according to the present invention can be applied to a liquid crystal display device having a source electrode as exemplified above and a liquid crystal display device having a source wiring.

  Next, general characteristics of image data will be described. In the case of a moving image, the image data changes for each frame. When attention is focused on the luminance (transmittance) indicated by the image data for each pixel, in most cases, there is a characteristic of increasing (or decreasing) step by step for each frame. It is rare that the brightness repeats increasing and decreasing every frame. For example, the luminance indicated by the image data for a certain pixel increases stepwise such as 0, 0, 50, 60, 60, etc. for each frame. Or it descends in steps like 60, 60, 50, 0, 0, etc. It does not always rise or fall step by step from frame to frame, but in most cases it will change that way. And, it is rare to make a change such as 0, 50, 20, 60, 20 or the like that repeatedly rises and falls every frame. In addition, the numerical value shown here is an example of the numerical value which shows a brightness | luminance.

The best mode for carrying out the present invention will be described below with reference to the drawings.
FIG. 1 is a block diagram showing an example of a liquid crystal driving device according to the present invention. As shown in FIG. 1, the liquid crystal driving device includes a memory 1, a lookup table (hereinafter referred to as LUT) 2, a source driver 3, a memory control unit 4, and a temperature detection unit 5. The liquid crystal driving device also includes a common driver and a control unit that controls the common driver and the source driver. However, the common driver and the control unit are the same as a known common driver and a known control unit, and thus are not illustrated.

  The memory 1 receives image data of an image to be displayed for each frame. This image data is also input to the LUT2. Hereinafter, image data that is input to the memory 1 and the LUT 2 for each frame and is to be displayed in the frame is referred to as input data.

  The memory 1 stores image data and outputs the stored image data to the LUT 2 for each frame. Whether or not the memory 1 stores input data is controlled by the memory control unit 4. When the memory control unit 4 outputs to the memory 1 a control signal that instructs to store input data, the memory 1 stores the input data. In this case, the memory 1 outputs the image data to the LUT 2 in the next frame. When the memory control unit 4 does not output the control signal to the memory 1, the memory 1 discards the input data without storing it. In this case, the memory 1 outputs the image data stored before the discarded input data is input to the LUT 2 in the next frame.

  When the memory 1 stores input data input in a certain frame, the memory 1 outputs the input data to the LUT 2 after the next frame. Image data that the memory 1 outputs to the LUT 2 for each frame is referred to as memory output data.

  Similarly to the memory 1, the LUT 2 receives input data (image data of an image to be displayed in the frame) for each frame. Memory output data is input from the memory 1 for each frame. When the memory 1 stores input data input in a certain frame, the memory 1 outputs the stored image data to the LUT 2 as memory output data after the next frame. Therefore, the memory output data input to the LUT 2 is image data of an image displayed in a frame before the current time.

  The LUT 2 stores in advance a potential corresponding to the difference between the luminance indicated by the memory output data and the luminance indicated by the input data. Here, it is assumed that a potential at which a good liquid crystal response speed can be obtained at room temperature by overdrive is defined as a potential to be stored in the LUT 2 and that the potential is stored in advance. When the input data and the memory output data are input, the LUT 2 specifies a potential corresponding to the difference between the luminance indicated by the memory output data and the luminance indicated by the input data for each pixel. Then, the LUT 2 outputs information on each potential specified for each pixel to the source driver 3.

  The source driver 3 is connected to a plurality of source lines or a plurality of source electrodes provided in the liquid crystal display device. The source driver 3 sets the potential specified by the LUT 2 as the potential corresponding to each pixel existing in the selected row to each source wiring or each source electrode corresponding to each pixel.

  The temperature detector 5 is disposed in the vicinity of a liquid crystal display device (not shown) driven by the liquid crystal drive device according to the present invention. Then, the temperature detection unit 5 outputs a signal corresponding to the temperature in the vicinity of the liquid crystal display device to the memory control unit 4.

FIG. 2 is an explanatory diagram illustrating a configuration example of the temperature detection unit 5. The temperature detection unit 5 includes, for example, a thermistor 11, a resistor 12, and a power source 13. One end 11 _a of the thermistor 11 is grounded in the vicinity of the liquid crystal display device (not shown.). Further, the other end 11 _{b of the} thermistor 11 is connected to a power source 13 through a resistor 12. The thermistor 11 decreases the resistance value when the temperature increases, and increases the resistance value when the temperature decreases. Therefore, the potential of the other end 11 _b of the thermistor 11 varies with the ambient temperature. Temperature detection unit 5 outputs the potential of the other end 11 _b of the thermistor, as a signal corresponding to the temperature near the liquid crystal display device, the memory control unit 4.

When the memory control unit 4 receives a signal corresponding to the temperature in the vicinity of the liquid crystal display device from the temperature detection unit 5, the memory control unit 4 determines whether the temperature in the vicinity of the liquid crystal display device is equal to or lower than a predetermined temperature based on the signal. judge. For example, when the temperature in the vicinity of the liquid crystal display device is equal to or lower than a predetermined temperature, the memory control unit 4 exceeds the predetermined temperature range and the potential range of the other end 11 _b (see FIG. 2) of the thermistor 11. it may be stored and scope of the potential of the other end 11 _b of the thermistor 11 in. Then, based on the potential input as a signal from the temperature detection unit 5 and the information on the potential range stored in advance, it is determined whether or not the temperature in the vicinity of the crystal display device is equal to or lower than a predetermined temperature. Good.

  When the temperature in the vicinity of the liquid crystal display device is equal to or lower than the predetermined temperature, the memory control unit 4 stores the input data in the memory 1 every predetermined plural frames (here, every two frames). A control signal for instructing to store is output.

  In addition, when the temperature near the liquid crystal display device exceeds a predetermined temperature, the memory control unit 4 outputs a control signal instructing to store input data in the memory 1 for each frame.

  Next, the operation will be described. In the following description, it is assumed that the liquid crystal display device is normally white.

It is assumed that the temperature in the vicinity of the liquid crystal display device is room temperature (a state where the temperature exceeds a predetermined temperature). Then, the memory controller 4 signals the temperature detecting unit 5 outputs (e.g., the potential of the other end 11 _b of the thermistor 11 shown in FIG. 2) based on the temperature in the vicinity of the liquid crystal display device exceeds a predetermined temperature It is determined that In this case, the memory control unit 4 outputs a control signal for instructing the memory 1 to store the input data for each frame.

  Then, the memory 1 stores the input data in each frame, and outputs the image data to the LUT 2 in the next frame. Input data and memory output data output from the memory 1 are input to the LUT 2. That is, as in the case shown in FIG. 8, the image data of the image displayed in each frame and the image data of the image displayed in the previous frame are input to the LUT 2. The LUT 2 specifies, for each pixel, a potential corresponding to the difference from the luminance indicated by the two types of image data. Then, the LUT 2 outputs information on each potential specified for each pixel to the source driver 3. The source driver 3 sets the potential specified by the LUT 2 as the potential corresponding to each pixel existing in the selected row to each source wiring or each source electrode corresponding to each pixel. For example, the LUT 2 specifies a potential for each pixel based on the luminance difference indicated by the image data “N + 2” and the image data “N + 1” illustrated in FIG. This potential is a potential that is predetermined as a potential at which a good liquid crystal response speed can be obtained at room temperature by overdrive, and as a result, a voltage that increases the response speed by overdrive is applied to the liquid crystal, which is favorable. Response speed can be realized.

  It is assumed that the temperature in the vicinity of the liquid crystal display device is low (below a predetermined temperature), and the response speed of the liquid crystal is delayed compared to that at room temperature. Then, the memory control unit 4 determines that the temperature in the vicinity of the liquid crystal display device is equal to or lower than a predetermined temperature based on the signal output from the temperature detection unit 5. In this case, the memory control unit 4 outputs a control signal for instructing the memory 1 to store the input data every two frames.

  When the memory 1 receives this control signal from the memory control unit 4 in a certain frame, the memory 1 stores the input data input in that frame. In the next frame, the control signal instructing to newly store input data is not received from the memory control unit 4, so the memory 1 continues to store the same image data in the next frame. Further, in the frame next to the frame that has received the control signal from the memory control unit 4, the stored image data is output to the LUT 2 as memory output data. Further, in the next frame, the stored image data is again output to the LUT 2 as memory output data. In this frame, since the control signal is received again from the memory control unit 4, the stored image data is replaced.

  FIG. 3 is an explanatory diagram showing an input state of image data to the LUT 2 when a control signal instructing to store input data is output every two frames. In the example shown in FIG. 3, in each of the first, third, fifth,... Frames, the memory control unit 4 outputs a control signal instructing to store input data.

  In the first frame, the input data “N” is input to the LUT 2 and the memory 1. Further, since the memory control unit 4 outputs a control signal in the first frame, the memory 1 stores the image data “N”. In the next second frame, the memory 1 outputs the stored image data “N” to the LUT 2 as memory output data. Further, the input data “N + 1” is input to the LUT2. The LUT 2 specifies a potential corresponding to the difference between the luminance indicated by the memory output data “N” and the luminance indicated by the input data “N + 1” for each pixel. Then, the LUT 2 outputs information on each potential specified for each pixel to the source driver 3. The source driver 3 sets the potential specified by the LUT 2 as the potential corresponding to each pixel existing in the selected row to each source wiring or each source electrode corresponding to each pixel.

  Further, since the memory control unit 4 does not output a control signal in the second frame, the memory 1 does not store the input data “N + 1” in the second frame and continues to store the image data “N”. Accordingly, in the third frame, the memory 1 again outputs the image data “N” as memory output data to the LUT 2. In the third frame, the input data “N + 2” is input to the LUT 2. Accordingly, the LUT 2 specifies a potential corresponding to the difference between the luminance indicated by the memory output data “N” and the luminance indicated by the input data “N + 2” for each pixel. Then, the LUT 2 outputs information on each potential specified for each pixel to the source driver 3. The source driver 3 sets the potential specified by the LUT 2 as the potential corresponding to each pixel existing in the selected row to each source wiring or each source electrode corresponding to each pixel.

  The memory 1 and LUT 2 repeat the same operation thereafter. Since the memory control unit 4 outputs a control signal in the third frame, the memory 1 stores the input data “N + 2” in the third frame. Then, “N + 2” is output as memory output data in the fourth and fifth frames. The LUT 2 specifies a potential for each pixel according to the luminance difference indicated by the memory output data “N + 2” and the input data “N + 3” in the fourth frame. In the fifth frame, the potential is specified for each pixel in accordance with the luminance difference indicated by the memory output data “N + 2” and the input data “N + 4”. The subsequent operations are the same.

  Thus, the memory 1 outputs the same memory output data in succession for two frames. Here, a case where memory output data “N” is output in succession for two frames will be described as an example. The LUT 2 specifies the potential according to the luminance difference indicated by the memory output data “N” and the input data “N + 1” in the first frame of the two frames from which the memory output data “N” is output. In the next frame, the potential is specified according to the luminance difference indicated by the memory output data “N” and the input data “N + 2”. As described above, in most cases, the luminance indicated by the image data increases (or decreases) step by step for each frame. Therefore, the luminance difference indicated by the memory output data “N” and the input data “N + 2” is equal to or larger than the luminance difference indicated by the memory output data “N” and the input data “N + 1”. The LUT 2 specifies a potential corresponding to the luminance difference over two frames, and the source driver 3 sets the potential to the source electrode or the source wiring. Therefore, the same overdrive is performed in the first frame between two frames in which the same memory output data is output, and the same overdrive is continued in the next frame. Therefore, the overdrive time is longer at low temperatures than at room temperature, and as a result, the response speed of the liquid crystal at low temperatures can be improved. In particular, if the luminance difference indicated by the memory output data “N” and the input data “N + 2” is larger than the luminance difference indicated by the memory output data “N” and the input data “N + 1”, the response speed is further improved.

  FIG. 4 is an explanatory diagram showing changes in the transmittance of the liquid crystal based on the operation of the liquid crystal driving device at a low temperature. FIG. 4A shows the change in the transmittance of the liquid crystal accompanying the voltage application to the liquid crystal, and FIG. 4B shows the change in the applied voltage to the liquid crystal. The broken line shown in FIG. 4B shows the drive waveform when overdrive is not performed, like the broken line shown in FIG. 7B. A solid line shown in FIG. 4B shows an example of a driving waveform of an applied voltage applied to the liquid crystal at a low temperature by the liquid crystal driving device according to the present invention. When overdrive is not performed, the transmittance of the liquid crystal increases very slowly as shown by the broken line in FIG. The response of the liquid crystal indicated by the broken line in FIG. 4A is the same as the response of the liquid crystal indicated by the broken line in FIG.

  As already explained, in the first frame between two frames in which the same memory output data is output, the same overdrive as at room temperature is performed, and the same overdrive is continued in the next frame. Become. Thus, overdrive is performed over a plurality of frames (here, two frames) at low temperatures. As a result, as shown by the solid line in FIG. 4A, the transmittance of the liquid crystal increases sharply. That is, the response speed of the liquid crystal is improved.

The memory output data "N" and the input data "N + 1" voltage is applied on the basis of the brightness difference indicated, and a V _a shown in Figure 4 (b). Then, it is assumed that the voltage applied based on the luminance difference indicated by the memory output data “N” and the input data “N + 2” is V _b shown in FIG. FIG. 4 shows a case where the luminance difference indicated by the memory output data “N” and the input data “N + 2” is equivalent to the luminance difference indicated by the memory output data “N” and the input data “N + 1”. If the luminance difference indicated by the memory output data “N” and the input data “N + 2” is larger than the luminance difference indicated by the memory output data “N” and the input data “N + 1”, the voltage V _b is as shown in FIG. Even lower than the case, the response speed is further improved.

  In the above description, when the temperature in the vicinity of the liquid crystal display device is equal to or lower than the predetermined temperature, the memory control unit 4 outputs a control signal for instructing to store input data every two frames. . The output of this control signal may not be performed every two frames. The memory control unit 4 may perform this control signal every three frames or may be performed every more frames.

  FIG. 5 is an explanatory diagram showing an input state of image data to the LUT 2 when a control signal instructing to store input data is output every three frames. When the control signal is output every 3 frames, the memory 1 outputs the same memory output data to the LUT 2 continuously for 3 frames. The LUT 2 specifies a potential for each pixel based on the same memory output data and input data in each frame during these three frames. For example, in the example illustrated in FIG. 5, the LUT 2 specifies a potential for each pixel according to the luminance difference indicated by the memory output data “N” and the input data “N + 1” in the second frame. In the third frame, the potential is specified for each pixel in accordance with the luminance difference indicated by the memory output data “N” and the input data “N + 2”. In the fourth frame, the potential is specified for each pixel in accordance with the luminance difference indicated by the memory output data “N” and the input data “N + 3”. As a result, overdrive is performed over three frames, and the response speed of the liquid crystal is further improved.

  Further, in the above description, an example is described in which a potential at which a good liquid crystal response speed is obtained at room temperature by overdrive is defined as a potential to be stored in the LUT 2 and the potential is stored in the LUT 2 in advance. A potential at which a liquid crystal response speed as good as possible can be obtained at a low temperature by overdrive may be determined as a potential to be stored in the LUT 2, and the potential may be stored in the LUT 2 in advance. In this case, the effect of overdrive can be further obtained at both room temperature and low temperature, and the response speed of the liquid crystal can be further improved.

  Further, the LUT 2 stores both a potential at which a good liquid crystal response speed can be obtained at room temperature by overdrive and a potential at which a good liquid crystal response speed can be obtained at a low temperature by overdrive, in the vicinity of the liquid crystal display device. The specified potential may be changed depending on the temperature. In this case, the temperature detection unit 5 outputs a signal corresponding to the temperature in the vicinity of the liquid crystal display device not only to the memory control unit 4 but also to the LUT 2. Similar to the memory control unit 4, the LUT 2 determines whether or not the temperature near the liquid crystal display device is equal to or lower than a predetermined temperature based on the signal. The LUT 2 indicates the luminance indicated by the memory output data and the input data from among the potentials stored as “potential at which a good liquid crystal response speed can be obtained at room temperature” at room temperature (a state where the temperature exceeds a predetermined temperature). What is necessary is just to specify the electric potential according to the difference with a brightness | luminance. At this time, the memory control unit 4 outputs a control signal for instructing to store the input data to the memory 1 for each frame. Further, the LUT 2 has a luminance indicated by the memory output data and a luminance indicated by the input data from among the potentials stored as “a potential at which a liquid crystal response speed is as good as possible at a low temperature” at a low temperature (below a predetermined temperature). What is necessary is just to specify the electric potential according to a difference. At this time, the memory control unit 4 outputs to the memory 1 a control signal instructing to store the input data for each of a plurality of predetermined frames (for example, every two frames). With such a configuration, the effect of overdrive can be obtained more at low temperatures, and the response speed of the liquid crystal can be further improved.

  In the description so far, the case where the memory control unit 4 changes the interval of the frame for outputting the control signal according to the temperature in the vicinity of the liquid crystal display device has been shown. The interval between frames in which the memory control unit 4 outputs control signals may be switched manually. In this case, the liquid crystal driving device includes an operation unit (for example, a switch or the like, not shown) operated by an operator instead of the temperature detection unit 5 shown in FIG. The operation unit is switched to either an on state setting (significant setting) or an off state setting (insignificant setting). The memory control unit 4 outputs a control signal to the memory 1 for instructing to store the input data for each frame when the operation unit is set to the OFF state. In addition, when the operation unit is set to the on state, the memory control unit 4 sends a control signal instructing to store input data to the memory 1 every predetermined number of frames (for example, every two frames). Output. As a result, when the operation unit is set to the on state, the response speed of the liquid crystal can be improved. The operator himself / herself determines whether or not the temperature is low, and when the operator determines that the temperature is low, the operator may set the operation unit to the on state. Even in such a configuration, the LUT 2 stores both a potential at which a good liquid crystal response speed can be obtained at room temperature by overdrive and a potential at which a good liquid crystal response speed can be obtained at low temperature by overdrive. In addition, the specified potential may be changed according to the state of the operation unit.

Further, the frame interval at which the memory control unit 4 outputs the control signal is not changed in two steps depending on whether or not it is equal to or lower than a predetermined temperature, but depending on the temperature in the vicinity of the liquid crystal display device, 3 It may be changed in stages or more. For example, when the temperature in the vicinity of the liquid crystal display device exceeds 0 ° C., the memory control unit 4 outputs a control signal instructing to store the input data for each frame, and −10 ° C. to 0 ° C. If it is ° C., the control signal 2 may be output every 2 frames, and if it is less than −10 ° C., the control signal may be output every 3 frames. Note that the temperature ranges shown here (“when exceeding 0 ° C.”, “when it is −10 ° C. to 0 ° C.”, “when it is below −10 ° C.”) are examples, and the liquid crystal display device The method of dividing the temperature range in the vicinity of is not limited to this example. Such a plurality of types of temperature ranges are determined in advance. The memory control unit 4 stores, for example, the potential range of the other end 11 _b (see FIG. 2) of the thermistor 11 in each temperature range, and stores the potential input as a signal from the temperature detection unit 5 in advance. Based on the stored potential range information, the temperature range in the vicinity of the liquid crystal display device may be determined. Then, a control signal may be output every predetermined number of frames according to the determined temperature range. However, the predetermined number of values is set as a large value so that the interval between frames for outputting the control signal is increased as the temperature range is lower. Even in such a configuration, the LUT 2 stores, for each temperature range, a potential at which a liquid crystal response speed as good as possible is obtained in each temperature range, and the LUT 2 specifies according to the temperature. The potential may be switched. At this time, like the memory control unit 4, the LUT 2 may determine which range the temperature near the liquid crystal display device is.

  The inventor of the present invention conducted the following experiment and confirmed the effect of the present invention. First, a liquid crystal driving device shown in FIG. 1 was manufactured using an LUT 2 in which a potential at which a good liquid crystal response speed can be obtained at room temperature was stored by overdrive. In addition, the memory control unit 4 outputs a control signal instructing to store input data to the memory 1 every three frames when the temperature is low (when the temperature in the vicinity of the liquid crystal display device is equal to or lower than a predetermined temperature). I did it. In a low temperature environment, the liquid crystal display device was driven by the liquid crystal drive device to display a moving image, and the image quality was confirmed. Then, in a low temperature environment, a control signal instructing to store input data was compared with the image quality of a moving image when the memory control unit outputs each frame. As a result, better image quality was obtained when the control signal instructing to store the input data was output to the memory 1 every three frames. That is, the response speed of the liquid crystal could be increased.

  Further, the liquid crystal driving device shown in FIG. 1 was manufactured by using the LUT 2 in which the potential at which a liquid crystal response speed as good as possible was obtained at a low temperature by overdrive was stored. In addition, the memory control unit 4 outputs a control signal instructing to store input data to the memory 1 every two frames at a low temperature. In a low temperature environment, the liquid crystal display device was driven by the liquid crystal drive device to display a moving image, and the image quality was confirmed. Then, in a low temperature environment, a control signal instructing to store input data was compared with the image quality of a moving image when the memory control unit outputs each frame. As a result, better image quality was obtained when the control signal instructing to store the input data was output to the memory 1 every two frames. That is, the response speed of the liquid crystal could be increased.

The block diagram which shows the example of the liquid-crystal drive device by this invention. Explanatory drawing which shows the structural example of a temperature detection part. FIG. 4 is an explanatory diagram showing an input state of image data to the LUT 2 when a control signal instructing to store input data is output every two frames. Explanatory drawing which shows the change of the transmittance | permeability of the liquid crystal based on operation | movement of the liquid crystal drive device at the time of low temperature. Explanatory drawing which shows the input condition of the image data to LUT in case the control signal which instruct | indicates storing input data is output for every 3 frames. Explanatory drawing which shows the example of overdrive. Explanatory drawing which shows the change of the transmittance | permeability of the liquid crystal at the time of low temperature. Explanatory drawing which shows the condition where image data is input into the conventional LUT

Explanation of symbols

1 Memory 2 Look-up table (LUT)
3 Source driver 4 Memory controller 5 Temperature detector

Claims (4)

A liquid crystal driving device for driving a liquid crystal display device provided with a source electrode or source wiring,
A memory for inputting image data of an image to be displayed in each frame for each frame and outputting stored image data for each frame;
Image data of an image to be displayed for each frame is input for each frame, and a lookup table that specifies a potential corresponding to a difference in luminance between the image data and the image data output from the memory,
A memory control unit that outputs a control signal instructing to store input image data to the memory every predetermined number of frames;
And a source driver that sets a potential specified by the lookup table to the source electrode or the source wiring. A temperature detection unit that outputs a signal corresponding to the temperature in the vicinity of the liquid crystal display device to the memory control unit;
The memory control unit determines whether the temperature in the vicinity of the liquid crystal display device is equal to or lower than a predetermined temperature based on the signal. If the temperature in the vicinity of the liquid crystal display device is equal to or lower than the predetermined temperature, the memory control unit The liquid crystal driving device according to claim 1, wherein a control signal instructing to store the input image data is output to the memory for each of the plurality of frames. A temperature detection unit that outputs a signal corresponding to the temperature in the vicinity of the liquid crystal display device to the memory control unit;
The memory control unit determines whether the temperature in the vicinity of the liquid crystal display device belongs to a predetermined temperature range based on the signal, and a predetermined number corresponding to the determined temperature range. The liquid crystal driving device according to claim 1, wherein a control signal instructing to store the input image data is output to the memory for each frame. It has an operation unit that can be switched between significant and insignificant settings by the operator,
The memory control unit outputs a control signal instructing to store the input image data to the memory for each of a plurality of predetermined frames when the operation unit is set to be significant. Item 2. A liquid crystal driving device according to item 1.

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