JP3875039B2 - Liquid crystal display device and lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device that requires a lighting device and the lighting device.
[0002]
[Prior art]
In a liquid crystal display device used as a display screen of a conventional notebook type personal computer or word processor, when a high-speed moving image is displayed, the display quality is deteriorated such as a blurred image or blurring.
[0003]
Therefore, in JP-A-1-082019, JP-A-8-500915, and JP-A-11-202286, the illuminating unit of the liquid crystal display device is fixed every frame (one vertical synchronization period). It is disclosed that it is formed so as to have a light extinction period, thereby obtaining good display quality in high-speed moving images.
[0004]
[Problems to be solved by the invention]
However, in the above conventional technique, there are a lighting period and a light-off period of the illumination unit in one frame. At this time, paying attention to the temperature of the cold cathode tube, which is a light emitter of the illumination unit, the temperature starts to increase from the start of light emission, and when the light is extinguished, the temperature starts to decrease. Therefore, a cold cycle with one frame as one cycle is generated in the cold cathode tube.
[0005]
Such a cooling / heating cycle damages the cold cathode fluorescent lamp and causes a decrease in durability life. Also, with such a cold cycle, the temperature difference between the start of light emission when the temperature of the cold cathode tube is the lowest and the end of light emission when the temperature of the cold cathode tube is the highest is large, and the environmental temperature of the cold cathode tube is large. Is difficult to keep constant. If the ambient temperature of the cold cathode tube cannot be kept constant, the temperature itself decreases as a result, resulting in a decrease in light emission luminance.
[0006]
In the above description, the case where a cold cathode tube is used has been described. However, the same result can be obtained by using other light emitters such as a light emitting diode, an electroluminescence element, a hot cathode tube, a mercury lamp, a halogen lamp, and a laser.
[0007]
The present invention has been made in view of the above problems, and its purpose is to suppress a decrease in the durability life of the illuminator of the illuminating unit and to reduce a decrease in luminance of the illuminator, and is also favorable for high-speed moving images. An object of the present invention is to provide a liquid crystal display device capable of obtaining display quality.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problem, the liquid crystal display device of the present invention is a liquid crystal display device including a light emitter that irradiates a pixel with light according to a drive signal, and the luminance reduction period of the light emitter during one vertical synchronization period. And a light emission control means for controlling the drive signal so that the light emission luminance of the light emitter changes with one vertical synchronization period as one cycle. .
[0009]
According to the above invention, the light emitted from the light emitter is changed according to the drive signal, and is emitted to the pixels to display desired information. At this time, by applying a drive signal in which there is a luminance reduction period of the light emitter during one vertical synchronization period, only a moment with a high contrast ratio remains as an afterimage for the viewer, so that the contrast ratio is high. It looks like a simple screen. Thereby, especially the display quality of a high-speed moving image can be made very favorable.
[0010]
However, if there is a luminance reduction period and a lighting period of the light emitter during one vertical synchronization period, a cold cycle with one vertical synchronization period as one cycle occurs in the light emitter. The durable life of the tube is reduced. In addition, this cooling cycle increases the temperature difference between the start of light emission with the lowest light emitter temperature and the end of light emission with the highest light emitter temperature, making it difficult to keep the ambient temperature of the light emitter constant, As a result, the emission luminance is reduced.
[0011]
Therefore, according to the present invention, the drive signal is controlled by the light emission control means so that the luminance reduction period of the light emitter is divided into two or more during one vertical synchronization period. Thus, by dividing the luminance reduction period in one vertical synchronization period into at least two, the temperature decrease of the light emitter during the luminance reduction period can be reduced. When the temperature change of the light emitter during one vertical synchronization period is viewed as a whole, the temperature drop of the light emitter during the luminance reduction period can be reduced, so that the amplitude of the temperature change of the light emitter can be reduced. As a result, it becomes easy to keep the ambient temperature of the light emitter constant, and a decrease in light emission luminance can be reduced.
[0012]
By the way, even if the luminance reduction period of the illuminant is controlled to be divided into two or more in this way, if the change in the luminescence intensity of the illuminant does not change with one vertical synchronization period as one cycle, this time, It has been found that the effect of obtaining good display quality is lost in high-speed moving images due to the provision of a brightness reduction period.
[0013]
Therefore, according to the present invention, the luminance reduction period of the light emitter is divided into two or more during one vertical synchronization period, and the light emission luminance of the light emitter is equal to one vertical synchronization period. The drive signal is controlled by the light emission control means so as to change as a cycle. Thus, since the light emission luminance of the light emitter is controlled so as to change with one vertical synchronization period as one cycle, it is possible to obtain a good display quality in high-speed moving images.
[0014]
The light emission control means may insert a small pulse that divides the luminance reduction period into the drive signal of a constant luminance reduction period provided for each vertical synchronization period. That is, two or more off periods may be provided by inserting a small pulse that divides the off period into the off period of the drive signal that is the luminance reduction period of the light emitter.
[0015]
In the liquid crystal display device of the present invention, the light emission control unit may further control the drive signal so as to blunt rise and fall of the waveform of the drive signal applied to the light emitter. It is preferable that the rise and fall of the waveform of the drive signal are dulled so that the light emission of the light emitter is gradually increased near the rise and gradually decreased near the fall.
[0016]
When the drive signal has a rectangular waveform, high-frequency electromagnetic radiation is observed, which adversely affects the human body. In addition, when a rectangular wave driving signal is applied to the light emitter, a sudden current flows through the light emitter when light emission rises, and when the light emission falls, the current to the light emitter is suddenly interrupted and a reverse current is applied to the light emitter. Such current behavior may significantly reduce the durable life of the light emitter.
[0017]
Therefore, in the present invention described above, the drive signal is further controlled by the light emission control means so that the rise and fall of the waveform of the drive signal are dull. As a result, as described above, an abrupt current does not flow to the light emitter near the rise of light emission, and the current to the light emitter is not suddenly interrupted near the fall of light emission. It is also possible to avoid flowing to the light emitter.
[0018]
Therefore, it is possible to prolong the life of the light emitter by reliably and reliably avoiding a significant decrease in the life of the light emitter, and to reliably reduce the electromagnetic interference that the harmonic components pose a danger to the human body. -It will be possible to alleviate and overcome the problem of electromagnetic interference.
[0019]
Moreover, in order to solve the above-described problem, the illumination device of the present invention includes a light emitter that emits light according to a drive signal, and the light emission luminance of the light emitter is periodically changed in one cycle. And a light emission control means for controlling the drive signal so that the luminance reduction period of the light emitter is divided into two or more.
[0020]
In such an illuminating device, since the drive signal is controlled by the light emission control means so that the luminance reduction period of the light emitter is divided into two or more in one cycle, this one cycle is synchronized by one vertical synchronization. As a period, for example, by mounting in a liquid crystal display device, it is possible to obtain the same operation as already described as the liquid crystal display device of the present invention.
[0021]
As the light emitter, it is preferable to use a cold cathode tube, a light emitting diode element, an electroluminescence element, a hot cathode tube, a mercury lamp, a halogen lamp, or a laser.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
One embodiment of the present invention will be described below with reference to FIGS.
[0023]
As shown in FIG. 1, the liquid crystal display device according to the present embodiment (active matrix type liquid crystal display device) mainly includes an inverter control circuit 1, an inverter 2, a cold cathode tube (light emitter) 3, and a liquid crystal panel control circuit. 4 and the liquid crystal panel 5. The inverter control circuit 1, the inverter 2, the cold cathode tube (light emitter) 3, and the liquid crystal panel control circuit 4 constitute an illumination device.
[0024]
The inverter control circuit 1 receives the vertical synchronization signal output from the liquid crystal panel control circuit 4 and outputs an inverter drive signal for driving the inverter 2 to the inverter 2. A high voltage whose frequency changes according to the inverter drive signal is applied from the inverter 2 to the cold cathode tube (white cold cathode tube) 3. When a high voltage is applied to the cold cathode tube 3, light is emitted from the cold cathode tube 3 and applied to the liquid crystal panel 5. Here, the cold cathode tube 3 constitutes an illumination unit that irradiates light to the liquid crystal panel 5.
[0025]
When the video signal is input, the liquid crystal panel control circuit 4 separates the synchronization signal, and the vertical synchronization signal is sent to the inverter control circuit 1 as described above. Further, based on the video signal, a gate driver 5a and a source driver 5b that drive scanning lines and signal lines (both not shown) are driven to select desired pixels (not shown), and the cold cathode tube 3 The irradiated light is transmitted through the selected pixel, and an image corresponding to the video signal is displayed.
[0026]
Here, the case where the waveforms of the main signals (vertical synchronization signal, inverter input signal (inverter drive signal), inverter output signal) of the liquid crystal display device are as shown in FIG. 2 will be described.
[0027]
In this case, by providing an extinguishing period (luminance reduction period) for each frame, only the moment with a high contrast ratio remains as an afterimage for the viewer, so that it appears as a clear screen with a good contrast ratio, particularly for high-speed moving images. Display quality is improved.
[0028]
However, when driving as shown in FIG. 2, it was found that the temperature change of the cold cathode tube 3 occurred with one frame as one cycle, as shown in the cold cathode tube temperature change at the bottom of FIG. . Such a temperature change gives a cold cycle to the cold cathode tube 3 to reduce the durability life of the cold cathode tube 3, and also decreases the temperature stability of the cold cathode tube 3 at the time of light emission. As a result, the emission luminance is lowered.
[0029]
Therefore, according to the present embodiment, as shown in FIG. 4, the inverter control circuit 1 has a small pulse P during the OFF period of the inverter input signal (inverter drive signal) that is the extinguishing period of the cold cathode tube 3. Inserted. The time width H2 of the small pulse P is sufficiently shorter than the time width H1 of the ON period that is the lighting period of the cold cathode tube 3 (see the inverter input signal in FIG. 4). In response to this, a small pulse P is also inserted in the off period of the inverter output signal applied from the inverter 2 to the cold cathode tube 3 (see the inverter output signal in FIG. 4).
[0030]
In this way, when the high voltage with the small pulse P inserted in the off period is applied to the cold cathode tube 3, the cold cathode tube 3 emits light by the small pulse during the extinguishing period of FIG. The light extinction period is divided into two, and the time width of the light extinction period is shortened (see the light emission waveform in FIG. 4).
[0031]
Thereby, the temperature fall of the cold cathode tube 3 in a light extinction period can be reduced. When the temperature change of the cold cathode tube 3 in one frame is viewed in total, the temperature drop of the cold cathode tube 3 in the extinguishing period can be reduced, so that the amplitude of the temperature change of the cold cathode tube 3 in one frame is It can be made smaller than that shown in FIG. 2 (refer to the cold cathode tube temperature change in FIG. 4).
[0032]
As a result, it is possible to suppress a decrease in the durability due to the temperature change of the cold cathode tube 3 described above, and a decrease in light emission luminance due to a decrease in temperature stability of the cold cathode tube 3 during light emission and a decrease in temperature itself. it can.
[0033]
By the way, as shown in FIG. 3, the inverter control circuit 1 has an ON period that is a lighting period of the cold cathode tube 3 in an OFF period of the inverter input signal (inverter drive signal) that is a lighting period of the cold cathode tube 3. When a pulse PP having a time width similar to the time width H1 is inserted, the end of the light-off period is shortened and the time width is shortened, thereby reducing the durability of the cold cathode tube 3 and the light emission of the cold cathode tube 3. Although it was possible to suppress the decrease in luminance (refer to the cold-cathode tube temperature change in FIG. 3), the cycle of the emission luminance change became 1/2 frame instead of 1 frame (the emission waveform in FIG. Reference), high-speed moving image performance could not be improved as compared with the case of constant light emission.
[0034]
Therefore, in order to improve the high-speed moving image performance, it is necessary that the period of the light emission luminance change is one frame. In such a case, the high-speed moving image performance can be improved as compared with the case of always emitting light. .
[0035]
Therefore, in the present embodiment, as described above, the time width H2 of the small pulse P is set in the lighting period of the cold cathode tube 3 so that the emission luminance of the cold cathode tube 3 changes with one frame as one cycle. It is sufficiently shorter than the time width H1 of a certain ON period (see the inverter input signal and light emission waveform in FIG. 4). Thereby, the effect of obtaining a good display quality in high-speed moving images by providing a light-out period for each frame is not lost, and the high-speed moving image performance can be improved as compared with the case of always emitting light.
[0036]
(Embodiment 2)
The following will describe another embodiment according to the present invention with reference to FIG. For convenience of explanation, constituent elements having the same functions as those shown in the drawings of Embodiment 1 are given the same reference numerals, and descriptions thereof are omitted.
[0037]
According to this embodiment, in the liquid crystal display device of FIG. 1, as shown in FIG. 5, the inverter control circuit 1 has an off period of the inverter input signal (inverter drive signal) that is the extinguishing period of the cold cathode tube 3. Four small pulses P were evenly inserted. The time width H2 of the small pulse P is sufficiently shorter than the time width H1 of the on period that is the lighting period of the cold cathode tube 3. In response to this, four small pulses P are also inserted in the off period of the inverter output signal applied from the inverter 2 to the cold cathode tube 3.
[0038]
In this way, by applying a high voltage in which four small pulses P are inserted in the off period to the cold cathode tube 3, the cold cathode tube 3 emits light by the plurality of small pulses and the extinguishing period is 5 times. The time width of the extinguishing period is further shortened (see the light emission waveform in FIG. 5).
[0039]
Thereby, the temperature fall of the cold cathode tube 3 in a light extinction period can be reduced. When the temperature change of the cold cathode tube 3 in one frame is viewed in total, the temperature drop of the cold cathode tube 3 in the extinguishing period can be reduced, so that the amplitude of the temperature change of the cold cathode tube 3 in one frame is 2 can be made smaller than that in FIG. 2 (see the cold cathode tube temperature change in FIG. 5).
[0040]
As a result, it is possible to suppress a decrease in the durability due to the temperature change of the cold cathode tube 3 described above, and a decrease in light emission luminance due to a decrease in temperature stability of the cold cathode tube 3 during light emission and a decrease in temperature itself. it can.
[0041]
In this embodiment, four small pulses are inserted during the OFF period of the inverter input signal. However, the small pulse P is changed so that the light emission luminance of the cold cathode tube 3 changes with one frame as one period. Since the time width H2 is sufficiently shorter than the time width H1 that is the lighting period of the cold cathode tube 3 (see the inverter input signal and the light emission waveform in FIG. 5), the high-speed moving image by providing the light-off period for each frame In this case, the effect of obtaining good display quality is not lost, and the high-speed moving image performance can be improved as compared with the case of always emitting light.
[0042]
(Embodiment 3)
The following describes another embodiment according to the present invention with reference to FIG. For convenience of explanation, constituent elements having the same functions as those shown in the drawings of Embodiment 1 are given the same reference numerals, and descriptions thereof are omitted.
[0043]
According to this embodiment, in the liquid crystal display device of FIG. 1, as shown in FIG. 6, the inverter control circuit 1 has an off period of the inverter input signal (inverter drive signal) that is the extinguishing period of the cold cathode tubes 3. In addition, two small pulses P were inserted at the beginning and end of the extinguishing period. The time width H2 of the small pulse P is sufficiently shorter than the time width H1 of the on period that is the lighting period of the cold cathode tube 3. In response to this, two small pulses P are also inserted in the OFF period of the inverter output signal applied from the inverter 2 to the cold cathode tube 3.
[0044]
In this way, by applying a high voltage with two small pulses P inserted in the off period to the cold cathode tube 3, the cold cathode tube 3 emits light by the plurality of small pulses, and the extinguishing period is 3 times. The time duration of the extinguishing period is shortened (see the light emission waveform in FIG. 6).
[0045]
Thereby, the temperature fall of the cold cathode tube 3 in a light extinction period can be reduced. When the temperature change of the cold cathode tube 3 in one frame is viewed in total, the temperature drop of the cold cathode tube 3 in the extinguishing period can be reduced, so that the amplitude of the temperature change of the cold cathode tube 3 in one frame is It can be made smaller than that shown in FIG. 2 (refer to the cold cathode tube temperature change in FIG. 6).
[0046]
As a result, it is possible to suppress a decrease in the durability due to the temperature change of the cold cathode tube 3 described above, and a decrease in light emission luminance due to a decrease in temperature stability of the cold cathode tube 3 during light emission and a decrease in temperature itself. it can.
[0047]
In this embodiment, two small pulses are inserted during the OFF period of the inverter input signal. However, the small pulse P is changed so that the light emission luminance of the cold cathode tube 3 changes with one frame as one period. Since the time width H2 is sufficiently shorter than the time width H1 of the ON period that is the lighting period of the cold cathode tube 3 (see the inverter input signal and the light emission waveform in FIG. 6), a light extinction period is provided for each frame. The effect of obtaining a good display quality is not lost in the high-speed moving image by, and the high-speed moving image performance can be improved as compared with the case of always emitting light.
[0048]
(Embodiment 4)
Another embodiment according to the present invention will be described below with reference to FIGS. For convenience of explanation, constituent elements having the same functions as those shown in the drawings of Embodiment 1 are given the same reference numerals, and descriptions thereof are omitted.
[0049]
When the inverter output signal has a rectangular waveform as shown in FIG. 2 described above, high-frequency electromagnetic radiation is observed, which adversely affects the human body. In addition, when a rectangular wave driving signal is applied to the cold cathode tube 3, an abrupt current flows to the cold cathode tube 3 at the rising edge of light emission, and an electric current to the cold cathode tube 3 abruptly when the cold cathode tube 3 falls. The reverse current may flow to the cold cathode tube 3, and the behavior of such current significantly reduces the durability life of the cold cathode tube 3.
[0050]
Therefore, according to this embodiment, in the liquid crystal display device of FIG. 1, the inverter control circuit 1 has the inverter input signal (inverter drive signal) that is in the cold-out period of the cold cathode tube 3 as shown in FIG. During the off period, a small pulse P was inserted, and the rise and fall of the waveform of the inverter input signal were further blunted (see the inverter input signal in FIG. 8). The time width H2 of the small pulse P is sufficiently shorter than the time width H1 of the on period that is the lighting period of the cold cathode tube 3.
[0051]
In response to this, a small pulse P is also inserted in the OFF period of the inverter output signal applied from the inverter 2 to the cold cathode tube 3 (see the inverter output signal in FIG. 8), and the waveform of the lighting period is set. Rise and fall are dull (see inverter output signal in FIG. 8).
[0052]
As described above, when the high voltage with the small pulse P inserted in the off period is applied to the cold cathode tube 3, the cold cathode tube 3 emits light by the small pulse during the extinguishing period of FIG. The light extinction period is divided into two, and each time width is shortened. FIG. 7 shows the main part signal and the signal at that time when the inverter control circuit 1 in the liquid crystal display device of FIG. 1 merely blunts the rise and fall of the waveform of the inverter input signal (inverter drive signal). The light emission waveform and temperature conversion of the cold cathode tube 3 are shown.
[0053]
Thereby, the temperature fall of the cold cathode tube 3 in a light extinction period can be reduced. When the temperature change of the cold cathode tube 3 in one frame is viewed in total, the temperature drop of the cold cathode tube 3 in the extinguishing period can be reduced, so that the amplitude of the temperature change of the cold cathode tube 3 in one frame is It can be made smaller than that in FIG. 7 (see the cold cathode tube temperature change in FIG. 8).
[0054]
As a result, it is possible to suppress a decrease in the durability due to the temperature change of the cold cathode tube 3 described above, and a decrease in light emission luminance due to a decrease in temperature stability of the cold cathode tube 3 during light emission and a decrease in temperature itself. it can.
[0055]
Further, although a small pulse is inserted in the off period, the time width H2 of the small pulse P is set to the lighting period of the cold cathode tube 3 so that the light emission luminance of the cold cathode tube 3 changes with one frame as one period. (See the inverter input signal and the light emission waveform in FIG. 8) and providing an extinction period for each frame has the effect of obtaining good display quality in high-speed moving images. There is no loss, and high-speed video performance can be improved as compared to the case of constant light emission.
[0056]
Further, in the present embodiment, when a high voltage whose waveform rises and falls is applied to the cold cathode tube 3, an abrupt current flows through the cold cathode tube 3. Therefore, it is possible to prevent the reverse current from flowing through the cold cathode tube 3. As a result, it is possible to reliably and reliably prevent the durability of the cold cathode tube 3 from being significantly reduced.
[0057]
Further, since the rise and fall of the inverter output signal applied to the cold cathode tube 3 is dull, the harmonic components can be reduced / mitigated, thereby greatly reducing electromagnetic radiation that poses a danger to the human body, Can overcome the problem of electromagnetic interference.
[0058]
In addition to the waveform of the inverter input signal described in the above embodiments, the cold cathode tube 3 extinguishing period in one frame is divided into two or more, and the emission luminance of the cold cathode tube 3 is one frame. Needless to say, the above can be realized if the waveform changes in a period.
[0059]
Similarly, in the above description, the case where the lighting body 4 is repeatedly turned on and off in one frame has been described. However, it is not necessary to completely turn off the light emitting body 4; The same effect can be obtained even if light reduction is performed with the luminance of the light emitter 4 lowered.
[0060]
That is, the gist of the present invention is that a change in light emission luminance of a light emitter is controlled by one vertical synchronization in a conventional liquid crystal display device that is controlled to have a constant luminance decrease period every vertical synchronization period and flashes the light emitter. Within a range that satisfies the conditions for improving high-speed moving image performance such as changing the period as one cycle, the luminance reduction period is finely divided to suppress the temperature decrease in the luminance reduction period, to reduce the cooling cycle, The purpose is to reduce the durability life and the reduction in luminance.
[0061]
In each of the above embodiments, a liquid crystal display device having a single light emitter has been described. However, the present invention is not limited to this, and has a plurality of light emitting regions in the scanning direction. Applicable to the case where a plurality of light emitting areas are synchronized with the vertical synchronizing signal of the liquid crystal display device, and each light emitter is applied with a voltage waveform as in the above five embodiments to emit light sequentially. it can.
[0062]
In each of the above embodiments, the case where a cold cathode tube is used as a light emitter has been described. However, the present invention is not limited to this, and a light emitting diode, an electroluminescent element, a hot cathode tube, a mercury lamp. It can also be applied to the case of using a light emitter such as a halogen lamp or a laser.
[0063]
Finally, if the liquid crystal display device of the present invention described above uses different expressions, at least two or more off periods are given to the driving signal of the lighting device (backlight) during one vertical synchronization period (in one frame). The light emission luminance of the lighting device is converted with one vertical synchronization period as one cycle.
[0064]
【The invention's effect】
As described above, the liquid crystal display device of the present invention is a liquid crystal display device including a light emitter that irradiates a pixel with light according to a drive signal. The light emission control means for controlling the drive signal so that the light emission luminance of the light emitting body is divided as described above and changes with one vertical synchronization period as one cycle is provided.
[0065]
According to this, the luminance reduction period of the light emitter is divided into two or more during one vertical synchronization period, and the light emission luminance of the light emitter changes with one vertical synchronization period as one cycle. Since the drive signal is controlled by the light emission control means, the temperature drop of the light emitter during the luminance reduction period is reduced without reducing the high speed moving image performance, and the temperature change amplitude of the light emitter during one vertical synchronization period is reduced. It can be made small, and a decrease in the durability of the light emitter and a decrease in luminance of the light emitter can be suppressed.
[0066]
As a result, there is an effect that it is possible to provide a liquid crystal display device that can suppress a decrease in the durability life of the light emitter and reduce a decrease in luminance of the light emitter and obtain a good display quality even in a high-speed moving image.
[0067]
The light emission control means may insert a small pulse that divides the luminance reduction period into the drive signal of a constant luminance reduction period provided for each vertical synchronization period.
[0068]
In the above-described liquid crystal display device of the present invention, the light emission control means further controls the drive signal so as to blunt the rise and fall of the waveform of the drive signal applied to the light emitter. It is preferable that the rising and falling edges of the waveform of the drive signal are dulled so that the light emission of the light emitter is gradually increased near the rising edge and gradually decreased near the falling edge.
[0069]
According to this, since the drive signal is further controlled by the light emission control means so as to blunt the rise and fall of the waveform of the drive signal applied to the light emitter, an abrupt current may flow through the light emitter. In addition, the current to the light emitter is not suddenly interrupted near the falling edge of the light emission, and the reverse current can be avoided from flowing to the light emitter. Thereby, it can avoid reliably that the durable lifetime of a light-emitting body falls remarkably.
[0070]
Further, since the rise and fall of the waveform of the drive signal applied to the light emitter is controlled to be dull, the harmonic component can be reliably reduced / reduced. As a result, electromagnetic radiation that causes danger to the human body is greatly reduced, and the problem of electromagnetic interference can be overcome.
[0071]
As a result, there is an effect that it is possible to provide a liquid crystal display device capable of obtaining a good display quality even in a high-speed moving image while suppressing a decrease in the durability life of the light emitter and reducing luminance reduction and electromagnetic interference of the light emitter. Play.
[0072]
Further, as described above, the illumination device of the present invention includes a light emitter that emits light according to a drive signal, and the light emission luminance of the light emitter is periodically changed. In this configuration, the light emission control means for controlling the drive signal is provided so that the luminance reduction period of the body is divided into two or more.
[0073]
In such an illuminating device, the drive signal is controlled by the light emission control means so that the luminance reduction period of the light emitter is divided into two or more in one cycle. By mounting in the liquid crystal display device, for example, as the vertical synchronization period, the same effects as those already described for the liquid crystal display device of the present invention can be obtained.
[0074]
As the light emitter, it is preferable to use a cold cathode tube, a light emitting diode element, an electroluminescence element, a hot cathode tube, a mercury lamp, a halogen lamp, or a laser.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram illustrating a configuration example of a liquid crystal display device of the present invention.
FIG. 2 is a waveform diagram showing an example of an applied signal waveform for explaining the operation of the liquid crystal display device, and a light emission waveform and a temperature change of a light emitter in the case of the applied signal waveform.
FIG. 3 is a waveform diagram showing another example of an applied signal waveform for explaining the operation of the liquid crystal display device, and a light emission waveform of the light emitter and a temperature change in the case of the applied signal waveform.
4 is a waveform diagram showing an example of an applied signal waveform for overcoming the problems caused by the signal waveforms of FIGS. 2 and 3, and a light emission waveform and a temperature change of a light emitter in the case of the applied signal waveform. FIG. is there.
5 shows another example of an applied signal waveform for overcoming the problems caused by the signal waveforms of FIGS. 2 and 3, and a waveform showing a light emission waveform and a temperature change of a light emitter in the case of the applied signal waveform. FIG.
6 shows still another example of an applied signal waveform for overcoming the problems caused by the signal waveforms of FIGS. 2 and 3, and a light emission waveform of the light emitter and a temperature change in the case of the applied signal waveform. FIG. It is a waveform diagram.
FIG. 7 is a waveform diagram showing another example of an applied signal waveform for explaining the operation of the liquid crystal display device, and a light emission waveform of the light emitter and a temperature change in the case of the applied signal waveform.
8 is a waveform diagram showing an example of an applied signal waveform for overcoming the problems caused by the signal waveforms of FIGS. 7 and 3, and a light emission waveform and a temperature change of the light emitter in the case of the applied signal waveform. FIG. is there.
[Explanation of symbols]
1 Inverter control circuit (light emission control means)
2 Inverter
3 Cold cathode tube (light emitter)
4 LCD panel control circuit
5 LCD panel
5a Gate driver
5b Source driver

Claims (3)

In a liquid crystal display device including a cold cathode tube that irradiates pixels with light according to a drive signal,
1 controls the drive signals so that the light emission luminance of the cold-cathode tube is changed to one vertical synchronization period as one cycle with brightness reduction period of the vertical synchronization period said cold-cathode tube during the presence divided into two or more A light emission control means for
The light emission control means is a small pulse that divides the luminance reduction period into the drive signal of a constant luminance reduction period provided for each vertical synchronization period, and is intended to raise the temperature of the cold cathode tube. A liquid crystal display device, wherein a small pulse having a time width that does not change a period of light emission luminance of the cold cathode tube is inserted .   The liquid crystal display device according to claim 1, wherein the light emission control unit further dulls the rise and fall of the waveform of the drive signal. In a lighting device mounted on a liquid crystal display device, comprising a cold cathode tube that emits light according to a drive signal, and periodically changing the emission luminance of the cold cathode tube,
Varying one one vertical synchronizing period of the liquid crystal display device in which light intensity of the vertical luminance reduction period of the cold-cathode tube during the synchronization period exists divided into two or more Rutotomoni the cold-cathode tube is mounted as one cycle And a light emission control means for controlling the drive signal ,
The light emission control means is a small pulse that divides the luminance reduction period into the drive signal of a constant luminance reduction period provided for each vertical synchronization period, and is intended to raise the temperature of the cold cathode tube. A lighting device, wherein a small pulse having a time width that does not change a period of light emission luminance of the cold cathode tube is inserted .

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