JP4043848B2 - LIQUID CRYSTAL DISPLAY DEVICE, ITS MANUFACTURING METHOD, AND LIGHTING DEVICE DRIVE CONTROL METHOD - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid crystal display device, a manufacturing method thereof, and a driving control method of an illumination device, and more specifically, a field sequential type liquid crystal display device, a manufacturing method thereof, and driving of an illumination device used in the liquid crystal display device. It relates to a control method.
[0002]
[Prior art]
As a color display method of a liquid crystal display device, a field sequential method is known in which a plurality of different colors are sequentially emitted in a predetermined cycle, and color display is performed by controlling on / off of pixel electrodes in synchronization with this, For example, it is disclosed by Unexamined-Japanese-Patent No. 2000-28984.
[0003]
The liquid crystal display device described in this publication includes a liquid crystal display panel 50, a display drive control device 57, a backlight 63, and an illumination drive control device 64, as shown in an oblique projection view in FIG. .
[0004]
The liquid crystal display panel 50 is configured by laminating a polarizing film 51, a first glass substrate 52, a common electrode 53, a pixel electrode 54, a second glass substrate 55, and a polarizing film 56 in this order. An alignment film (not shown) is formed on each of the opposing surfaces of the common electrode 53 and the pixel electrode 54, and a liquid crystal 65 is sandwiched between these alignment films. A plurality of pixel electrodes 54 are provided corresponding to the TFTs 58 that are switching elements formed at the intersections of the plurality of gate lines 59 and the plurality of source lines 60.
The display drive control device 57 includes a gate driver, a source driver, and the like, and can selectively supply a voltage signal to each gate line 59 and each source line 60 from the gate driver and the source driver. By supplying a voltage signal to the gate line 59, the TFT 58 connected to the gate line 59 can be switched. By applying a voltage from the source line 60 to the pixel electrode 54 via the TFT 58 in the on state, The liquid crystal 65 can be driven. The common electrode 53 may be formed not on the second glass substrate 54 side but on the first glass substrate 52 side. Therefore, for example, a configuration similar to that of an IPS (In-Plane-Switching) mode liquid crystal display device may be used.
[0005]
The backlight 63 includes a light guide / light diffusing plate 631 and an LED array 632, and is disposed on the back side of the polarizing film 56 (lower side in the figure). The LED array 632 is a light emitting diode that emits light of R (red), G (green), and B (blue) on the surface facing the light guide and light diffusion plate 631, as shown in an oblique projection in FIG. (LED) are repeatedly arranged in this order, and light from each LED is diffused to the upper surface side of the light guide and light diffusion plate 631. The RGB LEDs are controlled by the illumination drive control device 64 so as to emit light in a time-sharing manner with a predetermined period.
[0006]
In the liquid crystal display device configured in this manner, each LED of the backlight 63 is sequentially emitted by the illumination drive control device 64, and the TFT 58 is switched by the display drive control device 57 in synchronization with this, thereby displaying a desired display. It can be carried out. An example of this operation will be described based on the timing chart shown in FIG.
[0007]
As shown in FIG. 15A, one field period is divided into three subfield periods, and each TFT is switched to apply a voltage to each pixel electrode. The liquid crystal sandwiched between them is driven (hereinafter, driving the liquid crystal in this way is referred to as “writing”). And as shown in FIG.15 (b), red LED is light-emitted after completion | finish of the writing of a 1st subfield period. Next, as shown in FIG. 15C, the green LED is caused to emit light after the end of writing in the second subfield period, and as shown in FIG. 15D, the blue LED is turned on after the end of writing in the third subfield period. Make the LED emit light. Thus, RGB light emission is repeated for each field period. This is time-division light emission. The field period is usually 16.7 ms (1/60 sec).
[0008]
According to such a field sequential method, the effective transmittance of the backlight is improved as compared with the conventional method using a color filter, and the power consumption of the backlight can be reduced to 1/3 to 1/4. . However, since the emission brightness of each color LED is different, it is necessary to adjust the chromaticity of the display color. Therefore, the above publication discloses a method for adjusting the chromaticity of the display color by changing the light emission time of each color.
[0009]
However, conventionally, since a method for adjusting the light emission time of each color has not been clarified, it has been necessary to rely solely on empirical rules and trial and error, and it has been difficult to obtain a good white display. For example, since it has been conventionally considered that the emission luminance of red LEDs is lower than the emission luminance of green and blue LEDs, the publication discloses red emission time (8.33 ms) as green and blue emission times ( It is shown that white display is performed by making it longer than 4.17 ms). However, it is difficult to adjust the desired chromaticity even if each color LED is actually made to emit light in such a light emission time, and there is room for further improvement in how to set the light emission time of each color LED.
[0010]
[Problems to be solved by the invention]
The present invention has been made to solve such a problem, and provides a liquid crystal display device capable of satisfactorily adjusting the chromaticity of a display color, a manufacturing method thereof, and a driving control method of an illumination device. The purpose is to do.
[0011]
[Means for Solving the Problems]
The above object of the present invention is to arrange a first substrate, a second substrate, a liquid crystal sandwiched between the first substrate and the second substrate, and a matrix on the second substrate. A liquid crystal display panel having a plurality of pixel electrodes, a counter electrode disposed on one of the first substrate and the second substrate, and a plurality of switching elements respectively connected to the pixel electrodes; Display driving control means for driving the liquid crystal sandwiched between each pixel electrode and the counter electrode by switching each switching element and applying a voltage to each pixel electrode, and red, green, and Each LED has a LED that emits light of each color of blue, and illumination means that irradiates each color light toward the liquid crystal display panel, and the LEDs of each color are time-sequentially emitted in synchronization with switching of the switching elements. And a lighting drive control means for, The illumination drive control means has storage means for storing the light emission time in one field period for each color light, and causes each LED of each color to emit light based on the light emission time, and is stored in the storage means. The light emission time for each color light is determined by causing the red, green and blue LEDs to emit light in a time-sharing manner at the maximum power for the same predetermined time, and determining the low-efficiency color with the lowest light emission efficiency based on the chromaticity at that time. The light emission time of the low efficiency color is determined as the predetermined time, and the light emission times of two colors other than the low efficiency color are determined so as to reduce the predetermined time. This is achieved by a liquid crystal display device.
[0012]
In this liquid crystal display device, the red light emission time is preferably about 1/3 or less of both the green and blue light emission times.
[0013]
Moreover, it is preferable that the said illumination drive control means has a memory | storage means to memorize | store the light emission time in 1 field period for every color light, It is preferable to light-emit each said LED of each color based on the said light emission time.
[0014]
The red LED is preferably made of a semiconductor material made of GaAlAs, and the green and blue LEDs are preferably made of a semiconductor material made of GaN.
[0015]
In each subfield period obtained by dividing the field period by the number of light of each color, it is preferable that at least one of the LEDs of each color starts to emit light after completion of writing to the pixel electrode.
[0016]
Further, the object of the present invention is to arrange a first substrate, a second substrate, a liquid crystal sandwiched between the first substrate and the second substrate, and a matrix on the second substrate. A liquid crystal display panel having a plurality of pixel electrodes, a counter electrode disposed on one of the first substrate and the second substrate, and a plurality of switching elements respectively connected to the pixel electrodes Display drive control means for driving the liquid crystal sandwiched between the pixel electrodes and the counter electrode by switching the switching elements and applying a voltage to the pixel electrodes, and red, The LED that emits light of each color of green and blue, and the illumination unit that irradiates the color light toward the liquid crystal display panel, and the LED of each color is synchronized with the switching of each switching element. Illumination drive control means for emitting light, and the illumination drive control means has storage means for storing a light emission time in one field period for each color light, and causes each LED of each color to emit light based on the light emission time. A method of manufacturing a liquid crystal display device in which the light emission time of an LED emitting red light is set to be shorter than any of the light emission times of LEDs emitting green light and blue light, the red, green and blue LEDs For each of the same predetermined time with maximum power, time division light emission, measuring the chromaticity by the time division light emission, and determining a low efficiency color having the lowest light emission efficiency based on the measured chromaticity And determining the predetermined time as the light emission time of the low-efficiency color and reducing the predetermined time for two colors other than the low-efficiency color A step of determining a light emission time, the achieved by a method of manufacturing a liquid crystal display device comprising the steps of: storing low efficiency color of the light emitting time and the 2-color light emission time in the storage means.
[0017]
In this method of manufacturing a liquid crystal display device, the step of determining the low-efficiency color includes each chromaticity when the LED of each color is caused to emit light alone and a combined chromaticity when the time-division emission is performed. In comparison, the method may include determining that the color corresponding to the chromaticity point of the single chromaticity having the longest distance from the chromaticity point of the composite chromaticity is a low-efficiency color on the chromaticity diagram. .
[0018]
Further, the step of determining the light emission time includes comparing the standard chromaticity for obtaining a good white display with the combined chromaticity when the time-division emission is performed, and calculating the standard chromaticity on the chromaticity diagram. A step of determining the light emission time for two colors other than the low-efficiency color from the positional relationship between the chromaticity point and the chromaticity point of the composite chromaticity can be included.
[0019]
The object of the present invention is also a method for controlling the driving of a lighting device including LEDs that emit red, green, and blue light, respectively, wherein the LEDs of each color are respectively operated at the maximum power for the same predetermined time. A step of emitting light in a time division manner, a step of measuring chromaticity by the time division light emission, a step of determining a low efficiency color having the lowest light emission efficiency based on the measured chromaticity, and the LED of the low efficiency color Is achieved by a drive control method for an illuminating device comprising: emitting light at maximum power, and reducing the power of two LEDs other than the low-efficiency color to emit light.
[0020]
In the drive control method of the lighting device, the step of causing the LED to emit light sets the predetermined time as the light emission time of the low efficiency color, and reduces the predetermined time for two colors other than the low efficiency color. Preferably, the method includes a step of determining the light emission times of the two colors and a step of causing the LEDs of the respective colors to emit light in a time-division manner for the light emission time in one field period.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings as appropriate.
[0034]
(First embodiment)
FIG. 1 is a circuit diagram of an illumination drive control device in a field sequential type liquid crystal display device according to a first embodiment of the present invention. In the present embodiment and the following embodiments, the configuration other than the illumination drive control device is the same as the conventional configuration described above, and a description thereof will be omitted.
[0035]
As shown in FIG. 1, the lighting drive control device includes a switching transistor 12 having a primary winding and a secondary winding on the primary side and the secondary side, respectively. On the primary side of the switching transformer 12, a pulse generator 2, an AND gate 4, an OR gate 6, a switching transistor 8 and a DC power source 10 are provided. On the secondary side of the switching transformer 12, rectifier diodes 14 and RGB colors are provided. LEDs 16a, 16b, 16c, light emission control transistors 18a, 18b, 18c and variable resistors 20a, 20b, 20c are provided.
[0036]
The pulse generator 2 inputs a pulse signal Psig having a frequency of about 30 kHz to 100 kHz to the AND gate 4. The AND gate 4 receives RGB light emission control signals Rsig, Gsig, and Bsig supplied from the signal supply device 5 through an OR gate 6 that takes these OR logic. The light emission control signals Rsig, Gsig, and Bsig are pulse signals, and light emission time information regarding each pulse width (that is, light emission time) is stored in advance in a storage device 7 such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). .
[0037]
The switching transistor 8 performs switching when a signal based on an AND logic result of any one of the light emission control signals Rsig, Gsig, and Bsig and the pulse signal Ps is input to the gate. In response to this switching, a current flows from the DC power supply 10 to the primary side of the switching transformer 12.
[0038]
The RGB color LEDs 16 a to 16 c of the backlight are connected in parallel to the end of the secondary winding on the secondary side of the switching transformer 12 via a rectifier diode 14. Between the rectifier diode 14 and the respective color LEDs 16a to 16c, light emission control transistors 18a to 18c and variable resistors 20a to 20c are arranged, respectively. Corresponding light emission control signals Rsig, Gsig, and Bsig are input to the gates of the light emission control transistors 18a to 18c, respectively. In FIG. 1, only one LED 16a to 16c is shown for each color, but a plurality of LEDs are actually installed.
[0039]
According to the illumination drive control device configured as described above, the corresponding color LEDs 16 a to 16 c emit light based on the input of the light emission control signals Rsig, Gsig, and Bsig from the signal supply device 5. Since the light emission control signals Rsig, Gsig, and Bsig are input not only to the gates of the light emission control transistors 18a to 18c but also to the AND gate 4 via the OR gate 6, only during the input period of the light emission control signals Rsig, Gsig, Bsig. The switching transistor 8 is turned on. Therefore, current can be prevented from flowing to the secondary side of the switching transformer 12 during the writing period to the pixel electrodes where the respective color LEDs 16a to 16c do not emit light, and power saving can be achieved. As shown in the timing chart of FIG. 2, the signal (Tr-Gate) input to the switching transistor 8 is a pulse signal in the present embodiment.
[0040]
The pulse widths of the light emission control signals Rsig, Gsig, and Bsig can be easily adjusted by changing the light emission time information stored in the storage device 7, thereby setting the light emission time of each color LED to a desired value. be able to.
[0041]
As described above, in the field sequential type liquid crystal display device, the chromaticity of the display color can be adjusted by changing the light emission time of each color. Conventionally, since it was thought that the luminous efficiency of the blue LED was the highest, a setting was made to shorten the emission time of the blue LED in order to adjust the chromaticity.
[0042]
However, the present inventors have found through experiments that a problem peculiar to the field sequential method occurs in setting the light emission time of each color LED of the backlight. That is, each color LED of the backlight does not always emit light, but emits light in pulses at a predetermined duty ratio for each subfield obtained by dividing one field by the number of each color LED. Therefore, it is necessary to investigate not only the absolute luminance of each color LED in a state where the duty ratio is 100% (always energized state) but also the influence of the duty ratio on the luminance of each color LED.
[0043]
Therefore, the relationship between the relative power and the relative luminance with the duty ratio as a parameter was measured for each color LED of R, G, and B. The results are shown in FIGS. 3 shows the measurement result of the red LED, FIG. 4 shows the measurement result of the green LED, and FIG. 5 shows the measurement result of the blue LED. Relative luminance and relative power are based on a state where the duty ratio is 100%. Moreover, as a semiconductor material, red LED used GaAlAs (gallium, aluminum, arsenic), and green and blue LED used GaN (gallium nitride).
[0044]
As shown in FIGS. 3 to 5, for the red LED, compared with the case where the duty ratio is 100%, a decrease in relative luminance is hardly seen even when the duty ratio is 10%. On the other hand, regarding the green LED and the blue LED, the present inventor has found that when the duty ratio is low (the duty ratio is 100% → the duty ratio is 10%), the relative luminance is significantly reduced. Found.
[0045]
Therefore, in the field sequential method in which each color LED of RGB is pulsed, even when the duty ratio is 50% or less, even when the duty ratio is low, the emission time of the red LED with little luminance decrease is shortened, so that high luminous efficiency is achieved. It became clear that
[0046]
The duty ratio is preferably 10% or more. This is because if the duty ratio is less than 10%, the light emission time of the LED is remarkably shortened, and it may be difficult to form an image. Therefore, the duty ratio suitable for the present invention is 10% or more and 50% or less.
[0047]
In the illumination drive control device shown in FIG. 1, when the number of LEDs 16a, 16b, 16c is the same and the current value per LED is 100 mA, the ratio of the pulse widths of the light emission control signals Rsig, Gsig, Bsig. When (= light emission time ratio) was about 1: 3: 3, the color temperature was about 6500 degrees, and a good white display could be realized. The optimum ratio of the pulse width varies depending on the brightness of each color LED 16a, 16b, 16c and the current value. When the brightness or the current value becomes higher, the green and blue light emission control with respect to the pulse width of the red light emission control signal Rsig. The ratio of the pulse widths of the signals Gsig and Bsig tended to be larger.
[0048]
Next, a method for concretely determining the light emission time of each of the RGB LEDs for good chromaticity adjustment will be described. According to the measurement by the present inventors, the brightness of the LED sometimes varies within a range of ± 40% even under the same color and current conditions. For this reason, it is difficult to uniformly determine the light emission time of each color LED, and it is necessary to efficiently determine for each product. This method will be described with reference to the flowchart shown in FIG.
[0049]
First, each color LED of RGB is caused to emit light in a time-sharing manner with the maximum power for the same predetermined time (step S1). The predetermined time can be, for example, the maximum time after completion of writing in each subfield period, and thereby each color LED can emit light with the maximum luminance.
[0050]
Next, the chromaticity due to the time-division emission is measured using a color meter (Step S2). Then, based on the measurement result, the low-efficiency color having the lowest light emission efficiency with respect to the power consumption is determined (step S3). That is, in the chromaticity diagram shown in FIG. 7, the combined chromaticity point C obtained by combining the RGB colors emitted at the maximum power, and the individual chromaticity points R and G when the RGB LEDs are individually emitted. , B, respectively, and the color corresponding to the single chromaticity point having the longest distance is determined to be a low-efficiency color. In FIG. 7, since the distance between the combined chromaticity point C and the single chromaticity point B is the longest, the low-efficiency color is blue.
[0051]
Next, the power of two colors other than the low efficiency color is reduced (step S4). That is, in FIG. 7, the movement distances of the red and green chromaticity points are respectively calculated based on the distance between the measured synthesized chromaticity point C and the standard chromaticity point S having a color temperature of 6500 degrees. The light emission times of the red and green LEDs are determined based on the relationship between the movement distance and the light emission time stored in the storage device. Generally, it is necessary to shorten the light emission time as the moving distance becomes longer. In determining the relationship between the movement distance and the light emission time, as described above, it is preferable to take into account that the relative luminance of the blue or green LED may be significantly reduced when the light emission time is shortened. . For the standard chromaticity point S, the color temperature may be a point other than 6500 degrees.
[0052]
Each color LED is caused to emit light again according to the determined RGB light emission times, and the chromaticity is measured (step S5). If the deviation between the newly measured composite chromaticity point and the standard chromaticity point S is not within the allowable range, the above-described steps S4 and after are repeated to finally determine the light emission time of each color LED, such as an EEPROM. (Step S6). By such a method, even when the light emission efficiency of the LED varies, it is possible to adjust the chromaticity satisfactorily while maintaining each color LED as bright as possible.
[0053]
(Second Embodiment)
FIG. 8 is a circuit diagram of the illumination drive control device in the field sequential type liquid crystal display device according to the second embodiment of the present invention. The illumination drive control device shown in the figure is the same as the illumination drive control device of the first embodiment shown in FIG. 1, but instead of providing the light emission control transistors 18a to 18c and the variable resistors 20a to 20c, the rectifier diode 14 and each color LED 16a. , 16b, 16c are provided with light emission control switches 24a, 24b, 24c, respectively. Since other components are the same as those in the first embodiment, the same components are denoted by the same reference numerals and description thereof is omitted.
[0054]
A detailed structure of the light emission control switches 24a to 24c is shown in FIG. Although FIG. 9 shows the light emission control switch 24a, the same applies to the light emission control switches 24b and 24c.
[0055]
As shown in FIG. 9, in the light emission control switch 24a, three transistors 241, 242, and 243 as resistance adjusting elements are connected in parallel, and the relative values of on-resistance are about 4: 2: 1, respectively. Is set to A voltage is applied to the control terminals T0, T1, T2 of the transistors 241, 242, 243 based on a control code stored in advance in a storage device such as an EEPROM.
[0056]
The control code is a code representing the control terminals T0, T1, and T2 to which the voltage is applied, and is individually determined for each of the light emission control switches 24a to 24c. Hereinafter, for ease of explanation, it is assumed that the LED having the highest light emission efficiency among the three LEDs 16a to 16c is 16a, and the LEDs 16b and 16c have lower light emission efficiency than the LED 16a. The light emission control switch 24a connected to the LED 16a having a high light emission efficiency is a control code that applies a voltage only to the control terminal T0, so that only the transistor 241 having the highest on-resistance is turned on, and the other transistors 242, 243 is left off. On the other hand, the light emission control switches 24b to 24c connected to the LEDs 16b to 16c having low light emission efficiency turn on all the transistors 241 to 243 by using a control code for applying a voltage to all the control terminals T0 to T2. .
[0057]
By such control, the resistance value can be changed according to the light emission efficiency of the LEDs 16a to 16c, and the current value of each of the LEDs 16a to 16c can be adjusted, so that the chromaticity can be adjusted well.
[0058]
Next, a description will be given of a method for specifically determining a control code in performing good chromaticity adjustment. Since the basic flow is the same as that of the first embodiment, description will be made according to the flowchart shown in FIG.
[0059]
First, the RGB color LEDs are caused to emit light in a time-sharing manner with the maximum power for the same predetermined time (step S1). That is, for all the light emission control switches 24a to 24c, the transistors 241 to 243 are turned on by applying a voltage to all of the control terminals T0 to T2. The predetermined time can be the maximum time after the end of writing in each subfield period, as in the first embodiment.
[0060]
Next, the chromaticity in this case is measured using a color meter (Step S2). Then, based on the measurement result, the low-efficiency color having the lowest light emission efficiency with respect to the power consumption is determined (step S3). This determination method is the same as that in the first embodiment. When the light emission efficiency of the blue LED 16c is the lowest as shown in FIG. 7, all the control terminals T0 for the light emission control switches 24c corresponding to the blue LED 16c are used. A control code for applying a voltage to T2.
[0061]
Next, the power of two colors other than the low efficiency color is reduced (step S4). That is, in FIG. 7, the movement distances of the red and green chromaticity points are respectively calculated based on the distance between the combined chromaticity point C and the standard chromaticity point S having a color temperature of 6500 degrees, and are previously stored in an EEPROM or the like Based on the relationship between the movement distance and the control code stored in the storage device, the control codes for red and green are determined. Generally, the control code may be determined so that the current value of the LED decreases as the moving distance increases.
[0062]
Each color LED is caused to emit light again based on the RGB control code thus determined, and the chromaticity is measured (step S5). If the deviation between the newly measured composite chromaticity point and the standard chromaticity point S is not within the allowable range, the above-described step S4 and subsequent steps are repeated, the control code is finally determined, and a storage device such as an EEPROM (Step S6). By such a method, even when the light emission efficiency of the LED varies, it is possible to adjust the chromaticity satisfactorily while maintaining each color LED as bright as possible.
[0063]
In this embodiment, the control code is stored in the storage means. Instead, the drain side or the source side of the transistors 241 to 243 that are turned off based on the control code is previously cut by laser cutting or the like. Then, all the control terminals T0 to T2 may be turned on. In this case, the same effect as in the present embodiment can be obtained without storing the control code.
[0064]
The number of transistors included in the light emission control switches 24a to 24c is three in the present embodiment, but is not particularly limited as long as it is plural. It is preferable that the relative value of the on-resistance of each transistor is a different value. For example, by setting the transistor size (generally gate width) so that the relative ratio with respect to the lowest resistance value is a power of 2, such as 1: 2: 4: 8:. Fine adjustments can be made.
[0065]
(Third embodiment)
FIG. 10 is a circuit diagram of the illumination drive control device in the field sequential type liquid crystal display device according to the third embodiment of the present invention. In the first embodiment shown in FIG. 1, the downstream side of the rectifier diode 14 connected to the secondary winding of the switching transformer 12 is branched and connected to the LEDs 16a, 16b and 16c. On the other hand, in this embodiment, instead of branching from the downstream side of the rectifier diode 14, the tap 121 is pulled out from the middle of the secondary winding of the switching transformer 12, and the light emitting control diode 18a and the variable resistor 20a are interposed. Connected to the red LED 16a. A rectifier diode 141 is newly provided between the tap 121 and the light emission control diode 18a. Since other components are the same as those in the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof is omitted.
[0066]
According to such a control circuit, the voltage applied to the red LED 16a is lower than the voltage applied to the green and blue LEDs 16b and 16c. As described in the first embodiment, in the field sequential method in which each color LED emits light in pulses, the luminance reduction of the red LED at a low duty ratio is less than the luminance reduction of the green and blue LEDs. A good white display can be obtained by reducing only the voltage to be applied. Adjustment of the voltage applied to the red LED 16a for adjusting the chromaticity of the display color can be performed by providing a plurality of taps 121 in advance and appropriately changing the position of the tap 121. Therefore, adjustment by the variable resistor 20a is performed. Is unnecessary. Therefore, the resistance value of the variable resistors 20a to 20c can be lowered to reduce the power loss.
[0067]
(Fourth embodiment)
FIG. 11 is a circuit diagram of the illumination drive control device in the field sequential type liquid crystal display device according to the fourth embodiment of the present invention. In the present embodiment, a pulse generator 21 whose pulse width can be adjusted is directly connected to the gate of the switching transistor 8. The pulse generator 21 is connected to storage means 7 for storing the duty ratio of the pulse signal. Since other components are the same as those in the first embodiment, the same components are denoted by the same reference numerals, and detailed description thereof is omitted.
[0068]
According to such a configuration, the duty ratio of the pulse signal generated by the pulse generator 21 is set for each of RGB and stored in advance in the storage device 7 such as an EEPROM connected to the pulse generator 21. By setting, the drive voltage of each color LED 16a-16c can be adjusted. For example, as shown in the timing chart of FIG. 12, when the red LED 16a emits light, the time on the positive side of the pulse signal is lengthened and the positive voltage generated on the secondary side of the switching transformer 12 is lowered. On the other hand, when the green LED 16b emits light, the time on the negative side of the pulse signal is lengthened, and the positive voltage generated on the secondary side of the switching transformer 12 is increased. Such control makes it possible to satisfactorily adjust the chromaticity of the display color. Needless to say, when the polarity of the switching transformer 12 changes, the relationship between the pulse signal and the generated voltage is reversed.
[0069]
(Other embodiments)
As mentioned above, although each embodiment of this invention was explained in full detail, the specific aspect of this invention is not limited to the said embodiment. For example, in each of the above-described embodiments, the backlight control circuit has been described. However, the same configuration can be applied to a front light control circuit combined with a reflective liquid crystal display device.
[0070]
The liquid crystal material is preferably a ferroelectric liquid crystal or an antiferroelectric liquid crystal, but is not particularly limited. Of these liquid crystal materials, the OCB (Optically Self-Compensated Birefringence) mode is particularly suitable. In the OCB mode, the liquid crystal molecules are aligned in the same direction on the upper and lower substrates (spray state), and the arrangement of the liquid crystal molecules in the center of the panel is bent by applying a DC voltage (bend state) to drive. And has high-speed response.
[0071]
Field sequential liquid crystal display devices are required to have a high response speed of liquid crystals. That is, since the writing period shown in FIG. 15A or the like is actually the sum of the actual writing time of the image data and the response time of the liquid crystal, if the response of the liquid crystal is slow, the light emission time is inevitably reduced. The brightness is lowered. For this reason, the response speed is preferably within 1 to 2 ms. However, in the OCB mode, such a high-speed response can be realized, which is extremely compatible with the field sequential method.
[0072]
【The invention's effect】
As is clear from the above description, according to the liquid crystal display device of the present invention, the manufacturing method thereof, and the drive control method of the illumination device, the chromaticity of the display color can be adjusted satisfactorily.
[Brief description of the drawings]
FIG. 1 is a circuit diagram of an illumination drive control device in a liquid crystal display device according to a first embodiment of the present invention.
FIG. 2 is a timing chart showing the operation of the illumination drive control device of FIG.
FIG. 3 is a diagram showing a relationship between relative power and relative luminance of a red LED.
FIG. 4 is a diagram showing a relationship between relative power and relative luminance of a green LED.
FIG. 5 is a diagram showing a relationship between relative power and relative luminance of a blue LED.
FIG. 6 is a flowchart showing a method for determining a light emission time of each color LED.
FIG. 7 is a chromaticity diagram for explaining display colors by respective color LEDs.
FIG. 8 is a circuit diagram of an illumination drive control device in a liquid crystal display device according to a second embodiment of the present invention.
9 is a diagram showing a detailed structure of a light emission control switch in the illumination drive control device of FIG.
FIG. 10 is a circuit diagram of an illumination drive control device in a liquid crystal display device according to a third embodiment of the present invention.
FIG. 11 is a circuit diagram of an illumination drive control device in a liquid crystal display device according to a fourth embodiment of the present invention.
12 is a timing chart showing the operation of the illumination drive control device of FIG. 11. FIG.
FIG. 13 is an oblique projection showing a configuration of a conventional liquid crystal display device.
14 is an oblique projection showing a configuration of an LED array in the liquid crystal display device of FIG.
15 is a timing chart showing the operation of the illumination drive control device of FIG.
[Explanation of symbols]
2,21 Pulse generator
4 AND gate
5 Signal supply device
6 OR gate
7 Storage device
8 Switching transistor
10 DC power supply
12 Switching transformer
121 taps
14,141 Rectifier diode
16a-16c LED
18a to 18c light emission control transistor
20a-20c variable resistor
24a-24c Light emission control switch
241, 242, 243 transistor
50 LCD panel
57 Display drive controller
63 Backlight

Claims (10)

A first substrate; a second substrate; a liquid crystal sandwiched between the first substrate and the second substrate; a plurality of pixel electrodes arranged in a matrix on the second substrate; A liquid crystal display panel having a counter electrode disposed on one of the first substrate and the second substrate, and a plurality of switching elements respectively connected to the pixel electrodes;
Display drive control means for driving the liquid crystal sandwiched between the pixel electrodes and the counter electrode by switching the switching elements and applying a voltage to the pixel electrodes;
Illuminating means having LEDs that emit red, green, and blue color lights, respectively, and irradiating the color lights toward the liquid crystal display panel;
Illumination drive control means for causing the LEDs of each color to emit light in a time-sharing manner in synchronization with the switching of each of the switching elements,
The illumination drive control means has storage means for storing the light emission time in one field period for each color light, and causes each LED of each color to emit light based on the light emission time,
The light emission time for each color light stored in the storage means causes the red, green and blue LEDs to emit light in a time-sharing manner at the maximum power for the same predetermined time, and has the lowest light emission efficiency based on the chromaticity at that time. A low-efficiency color is determined, the light emission time of the low-efficiency color is determined as the predetermined time, and the light emission time of two colors other than the low-efficiency color is determined so as to reduce the predetermined time. Display device.  The liquid crystal display device according to claim 1, wherein the red light emission time is about 1/3 or less of both the green light emission time and the blue light emission time.  The liquid crystal display device according to claim 1, wherein the illumination drive control unit includes a storage unit that stores a light emission time in one field period for each color light, and causes each LED of each color to emit light based on the light emission time. .  The liquid crystal display device according to claim 1, wherein the red LED is formed of a semiconductor material made of GaAlAs, and the green and blue LEDs are formed of a semiconductor material made of GaN.  2. The liquid crystal according to claim 1, wherein in each subfield period obtained by dividing the field period by the number of light of each color, at least one of the LEDs of each color starts to emit light after completion of writing to the pixel electrode. Display device. A first substrate; a second substrate; a liquid crystal sandwiched between the first substrate and the second substrate; a plurality of pixel electrodes arranged in a matrix on the second substrate; A liquid crystal display panel having a counter electrode disposed on one of the first substrate and the second substrate, and a plurality of switching elements respectively connected to the pixel electrodes;
Display drive control means for driving the liquid crystal sandwiched between the pixel electrodes and the counter electrode by switching the switching elements and applying a voltage to the pixel electrodes;
Illuminating means having LEDs that emit red, green, and blue color lights, respectively, and irradiating the color lights toward the liquid crystal display panel;
Illumination drive control means for causing the LEDs of each color to emit light in a time-sharing manner in synchronization with the switching of each of the switching elements,
The illumination drive control means has storage means for storing the light emission time in one field period for each color light, and causes each LED of each color to emit light based on the light emission time,
A method of manufacturing a liquid crystal display device in which the light emission time of an LED that emits red light is set to be shorter than any of the light emission times of LEDs that emit green and blue light,
Causing each of the red, green and blue LEDs to emit light in a time-sharing manner at a maximum power for the same predetermined time,
Measuring chromaticity by the time-division emission;
Determining a low efficiency color with the lowest luminous efficiency based on the measured chromaticity;
Determining the predetermined time as the light emission time of the low efficiency color, and determining the light emission time of the two colors so as to reduce the predetermined time for two colors other than the low efficiency color;
And a step of storing the light emission time of the low-efficiency color and the light emission time of the two colors in the storage means.  The step of determining the low-efficiency color is performed by comparing each chromaticity when the LED of each color is made to emit light alone with the combined chromaticity when the LED is made to emit light in a time division manner on the chromaticity diagram. The liquid crystal display device manufacturing method according to claim 6, further comprising: determining that a color corresponding to the chromaticity point of the single chromaticity having the longest distance from the chromaticity point of the composite chromaticity is a low-efficiency color. Method.  The step of determining the light emission time includes comparing a standard chromaticity for obtaining a good white display and a composite chromaticity when the time-division emission is performed, and a chromaticity of the standard chromaticity on the chromaticity diagram. The manufacturing method of the liquid crystal display device of Claim 6 including the step which determines the said light emission time about two colors other than the said low efficiency color from the positional relationship of a point and the chromaticity point of the said synthetic | combination chromaticity. A method for controlling the driving of a lighting device including LEDs that emit red, green, and blue light respectively.
Causing each of the LEDs of each color to emit light in a time-sharing manner at the maximum power for the same predetermined time;
Measuring chromaticity by the time-division emission;
Determining a low efficiency color with the lowest luminous efficiency based on the measured chromaticity;
A method for driving and controlling an illuminating device, comprising: causing the low-efficiency color LED to emit light with maximum power, and reducing the power of two color LEDs other than the low-efficiency color to emit light. The step of causing the LED to emit light is a step of determining the predetermined time as the light emission time of the low efficiency color and determining the light emission time of the two colors so as to reduce the predetermined time for two colors other than the low efficiency color. When the drive control method of the lighting device according to claim 9 including the step of the cell by respectively when the divided light-emitting light-emitting time at the LED one field period of each color.

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