JP3402602B2 - Liquid crystal driving device and gradation display method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal driving device and a gradation display method, and more particularly to a liquid crystal driving device and a gradation display method of a new gradation display system.

[0002]

2. Description of the Related Art Conventionally, an active matrix type liquid crystal display device which performs multi-gradation display has been known. In this multi-gradation display, for example, one reference voltage corresponding to the gradation display data is selected by an analog switch from among the reference voltages corresponding to the number of display gradations, and the liquid crystal display device is driven by the selected reference voltage. Done.

FIG. 18 is a block diagram showing a conventional liquid crystal driving device for driving an active matrix type liquid crystal display device. In this liquid crystal drive device, the first latch 1 and the second latch
The latch 2 and the decoder 3 are provided for each vertical pixel line of the liquid crystal display device.

The first latch 1 reads 3-bit grayscale data D0 to D2 designating 8-step grayscale on each vertical pixel line in one horizontal scanning period. That is, the grayscale data D0 to D2 are latched by the first latch 1 and held for one horizontal scanning period.

The second latch 2 supplies the grayscale data D0 to D2 held in the first latch 1 to the decoder 3 in the next one horizontal scanning period. The decoder 3 decodes the grayscale data D0 to D2 from the second latch 2 and outputs the decoded signal S
0 to S7 are output to the control terminals of the analog switches A0 to A7, respectively.

The analog switches A0 to A7 selectively output the reference voltages V0 to V7 supplied to the input terminals in correspondence with the decoded signals S0 to S7. That is, one of the reference voltages V0 to V7 is selected by the decoded signals S0 to S7 and output as the liquid crystal drive voltage.

The reference voltages V0 to V7 correspond to gradation levels, as shown in FIG. Therefore, the reference voltage based on the grayscale data is selected, and the reference voltage is output to the liquid crystal panel as the applied voltage, so that the light transmission amount corresponding to the applied voltage is obtained, thereby enabling the grayscale display.

[0008]

However, the conventional liquid crystal driving device is not sufficient to drive the liquid crystal at high speed. As a result, it is necessary to increase the output of the LED in order to obtain sufficient brightness. However,
This increases power consumption and is not practical.

Particularly in recent years, with the spread of the Internet,
There is an increasing need for rapidly transmitting a large amount of data such as images, and it is also necessary to realize multi-gradation. In particular, in order to display a moving image, high-speed driving of liquid crystal and multi-gradation display are desired.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a novel liquid crystal driving device and a gradation display method capable of obtaining a desired brightness without increasing the output of the light emitting section. To do.

[0011]

A liquid crystal driving device of the present invention comprises a light emitting means for emitting light at a predetermined timing, a liquid crystal provided at a position for shielding the light emitting means, and a light emitting means.
ON / OFF cycle is short and equal to
Multiple on / off with different sequence depending on the number of on
Voltage application pattern setting that can set the applied voltage of the pattern
Method and the voltage application pattern setting procedure according to the gradation data.
Voltage of any on-off pattern set by the stage
And a voltage supply means for supplying the liquid crystal from a time point before the light emission start time of the light emitting means, in the unit light emission period.
Depending on the on / off pattern,
Variable control.

According to this structure, the voltage is applied to the liquid crystal from a time point a predetermined time before the light emitting means actually emits light, so that the desired transmittance is obtained from the light emitting means starting light emission. Will be able to get.
As a result, the brightness of the display screen can be increased without increasing the output of the light emitting means.

[0013]

[0014] According to this configuration, since it becomes possible to finely adjust the transmittance at the emission starting time of the light emitting means by the pattern of on-off pattern voltage, the first from the desired transmittance even when the unit light emitting period is short As a result, a desired amount of transmitted light can be obtained within the unit light emission period.

The liquid crystal driving device of the present invention is a liquid crystal driving device as described above.
As a field-sequential liquid crystal display device
Adopt the configuration used .

According to this configuration, LEs of R, G, and B colors are used.
In the field-sequential liquid crystal display device, in which the unit light emission period is very short because D blinks at a high speed, and a higher speed liquid crystal drive is required, to obtain a desired transmittance from the first point of each unit light emission period. As a result, a field-sequential type liquid crystal display device capable of displaying a desired gradation can be realized.

According to the gradation display method of the present invention, from the time point before the light emitting section emits light, the number of times of ON is the same, but the mutual display is performed.
Application of multiple on / off patterns with different sequence
One of the on / off patterns depending on the gradation of the voltage
By selecting an applied voltage and supplying it to the liquid crystal , the liquid crystal is controlled so as to have a desired transmittance from the light emission start time of the light emitting unit, and a gradation corresponding to the gradation data is obtained.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a schematic configuration of a liquid crystal drive device according to Embodiment 1.
The liquid crystal drive device 10 according to the first embodiment includes an application time control unit 102 that controls a voltage application time according to grayscale data.
And a reference table 101 in which application times (ON times) corresponding to gradations are associated with each other, and a constant voltage generated by the constant voltage generation circuit 105 according to an ON time control signal output from the application time control unit 102. A switch 103 for outputting to the LCD panel 20 is provided.

As shown in FIG. 2, the reference table 101 is a table in which gradation levels are associated with application times for which the switches are turned on. Here, gradation display of the liquid crystal drive device according to the present invention will be described with reference to FIGS.

FIG. 3 is a diagram showing the relationship between light transmittance and time, FIG. 4 is a diagram showing the relationship between applied voltage and time, and FIG. 5 is a graph for each gradation. It is a figure which shows the relationship between an applied voltage and time.

When a voltage is applied to the liquid crystal so that the liquid crystal responds and transmits light, it exhibits a light transmittance as shown in FIG. In FIG. 3A, τ _ON is the time required for the light transmittance to change from 10% to 90%.

On the other hand, when the voltage application to the liquid crystal is stopped and the light is blocked, the light transmittance as shown in FIG. 3B is exhibited. In FIG. 3B, τ _OFF is the time taken for the light transmittance to change from 90% to 10%.

As is clear from FIGS. 3 (A) and 3 (B), τ _OFF is longer than τ _ON . This means that there is a difference between the time until the light is transmitted in response to the liquid crystal by applying the voltage and the time until the light is blocked after the voltage application is stopped.

In this case, the response speed τON of the liquid crystal
Is represented by kG ² / (V ² −V _th ² ), and the response speed τ _{OFF of the} liquid crystal is represented by k′G ² (k, k ′: constant, V: applied voltage, V _th : Threshold voltage, G: cell gap). As can be seen from this formula, the response speed of the liquid crystal is different between the voltage application (τ _ON ) and the voltage application stop (τ _OFF ). For this reason, the voltage application time and the voltage application stop time differ in the rate of change in voltage over time, that is, they are asymmetric.

Therefore, in the liquid crystal, the time (rising) to reach the applied voltage value is different as shown in FIG. 4, depending on whether the applied voltage is 2.5V or the applied voltage 5V. When 5V is applied, the time to reach the applied voltage value becomes shorter.

As described above, when a voltage is applied to the liquid crystal, the liquid crystal responds (opens) and transmits light. Therefore, if a voltage is continuously applied for a certain period of time, the liquid crystal continues to respond for that period of time and is in an open state, so that light continues to be transmitted. Therefore, the amount of transmitted light at that time can be considered as the integrated value of the applied voltage at that time. That is, it can be considered that the area of the hatched portion in FIG. 4 represents the amount of transmitted light. Specifically, the amount of transmitted light when the applied voltage is 5V is the area shown by the diagonal lines rising to the left in FIG. 4, and the amount of transmitted light when the applied voltage is 2.5V is the area shown by the diagonal lines rising to the right in FIG. Is.

In the conventional gradation display in liquid crystal driving, a reference voltage such as 2.5 V or 5 V shown in FIG. 4 is set in advance and the reference voltage is applied to the liquid crystal. As described above, when the amount of transmitted light is considered as the total amount of opening time, that is, the applied voltage × time (area of diagonal lines in FIG. 4),
As shown in FIG. 5, it is possible to control the application time (t0 to t7) by keeping the applied voltage constant. In other words, by changing the application time in FIG.
The waveform from the rising edge to the falling edge changes, and the area in the waveform (applied voltage × time) changes accordingly. As a result, the amount of transmitted light is different, and gradation display can be realized.

In such gradation display, since the applied voltage can be made constant, the applied state and the non-applied state can be controlled at timing, that is, digital control can be performed. The digital control facilitates control. Further, since all the gradation levels are applied with a relatively high applied voltage with a high liquid crystal response speed, it is possible to shorten the liquid crystal drive time as a whole.

Next, the operation of the liquid crystal driving device having the above structure will be described.

Grayscale data representing a grayscale level in grayscale display is input to the application time control unit 102 of the liquid crystal drive device 10. The gradation data is represented by 3 bits for 8 gradations, for example, and gradation levels 0 to 7 are set.

Upon receiving the gradation data, the application time control unit 102 refers to the reference table 101 shown in FIG.
The application time (ON time) corresponding to the gradation data is set. Then, the application time control unit 102 outputs the ON time control signal to the switch 103 for the determined ON time. In this way, as shown in FIGS. 6A to 6C, gradation display is performed by digitally controlling the application time for a predetermined applied voltage.

The switch 103 is an application time control unit 102.
The switch is turned on in accordance with the ON time control signal from (1) to apply a voltage to the pixels of the LCD panel 20. That is, a signal voltage is supplied to the source electrode line according to the ON time control signal to drive the liquid crystal.

As described above, the liquid crystal driving device according to the present embodiment can perform multi-gradation display by digital control. This facilitates control in multi-gradation display. Further, in all gradation display, since the time control is performed with a comparatively high applied voltage which has a high response speed, it is possible to shorten the liquid crystal drive time as a whole.
Further, since the liquid crystal driving voltage is digitally applied by the time control with the constant value, the D / A (digital / analog) converter normally required in the liquid crystal driving device becomes unnecessary.

(Second Embodiment) FIG. 7 is a block diagram showing a schematic structure of a liquid crystal drive device according to the second embodiment.
The liquid crystal drive device according to the second embodiment includes an application time control unit 102 that controls a voltage application time according to gradation data.
A pattern table 104 in which application patterns (ON patterns) corresponding to gradations are associated with each other, and an application time control unit 102.
According to the ON pattern control signal output from the LCD, the constant voltage generated by the constant voltage generation circuit 105 is displayed on the LCD.
A switch 103 for outputting to the panel 20 is provided.

As shown in FIG. 8, the pattern table 104 is a table in which gradation levels are associated with application patterns for turning on the switches. As the application pattern, for example, a pattern in which a predetermined liquid crystal drive time as shown in FIG. 9 is divided into a plurality of blocks and voltage application / non-voltage application is switched can be considered.

When a voltage is applied to the liquid crystal, the rising and the falling are asymmetrical as shown in FIGS. 3 (A) and 3 (B). Therefore, if this is used, as shown in FIG. 9, even if the voltage application time is the same, the pattern is different, and therefore the applied voltage × (applied voltage) × The area of time will be different. As a result, the first embodiment
It is possible to perform finer gradation display.

For example, as in the conventional PWM control, the LED
The voltage application time is not changed during the unit light emission period, but in the embodiment, the voltage application pattern is changed within the unit light emission period. Here, the unit light emission period of the LED is the LE provided so as to correspond to each liquid crystal.
D (light emitting diode) is a period from the start of light emission to the stop thereof.

Incidentally, in the case of this embodiment, the display is carried out by using the field sequential method, and the LED array is used as a backlight so as to blink at high speed. That is, the unit light emission period is one lighting period of each LED array.

In this way, by changing the voltage application pattern within the unit light emission period of the LED, it is possible to display a much finer gradation as compared with the conventional PWM control, for example.

Next, the operation of the liquid crystal driving device having the above structure will be described.

Grayscale data representing a grayscale level in grayscale display is input to the application time control unit 102 of the liquid crystal drive device 10. The gradation data is represented by 4 bits for 16 gradations, for example, and gradation levels 0 to 15 are set.

Upon receiving the gradation data, the application time control unit 102 refers to the pattern table 104 shown in FIG. 8 to determine the application pattern (ON pattern) corresponding to the gradation data. Then, the application time control unit 102 outputs the ON pattern control signal to the switch 103 only for the determined ON pattern.

The switch 103 is an application time control unit 102.
Switch ON according to the ON pattern control signal from
A voltage is applied to the pixels of the LCD panel 20 when set to N. That is, a signal voltage is supplied to the source electrode line according to the ON pattern control signal to drive the liquid crystal.

As described above, the liquid crystal driving device according to the present embodiment can perform multi-gradation display by digital control. This facilitates control in multi-gradation display. Further, in all gradation display, since the time control is performed with a comparatively high applied voltage which has a high response speed, it is possible to shorten the liquid crystal drive time as a whole.
Further, since the liquid crystal driving voltage is digitally applied by the time control with the constant value, the D / A (digital / analog) converter normally required in the liquid crystal driving device becomes unnecessary.

Further, in the liquid crystal drive device according to the embodiment,
By utilizing the asymmetry of rising and falling in voltage application to express gradation by combining voltage application units, it is possible to realize more gradation display.

Further, by changing the voltage application pattern within the unit light emission period of the LED, fine gradation display can be performed.

(Embodiment 3) In this embodiment, when the maximum voltage of the rated voltage of the liquid crystal is applied, the area obtained by integrating the transmitted light amount at each time point of the liquid crystal in the LED emission period is taken into consideration. , Voltage application time (or voltage application pattern) corresponding to each gradation data is set. Specifically, FIG.
As shown in, the area (area of the shaded portion in the figure) obtained by integrating the transmitted light amount waveform that passes through the liquid crystal when the drive voltage is applied during the LED emission period is associated with each gradation.

That is, the liquid crystal is driven so that the shaded area in FIG. 10 becomes larger as the inputted gray scale data indicates a higher gray scale. In practice, the applied voltage is kept constant at the maximum voltage of the rated voltage of the liquid crystal, so by changing the voltage application time (or voltage application pattern), the area of the shaded area is changed according to the gradation. . Incidentally, FIG. 10 (A) shows a state of change in the amount of transmitted light of the liquid crystal over time when the applied voltage is turned on during the period from time t0 to time ta, and FIG. 10 (B) shows the liquid crystal having a predetermined pattern. 7 shows how the amount of transmitted light of the liquid crystal changes with the application of the voltage. Specifically, FIG. 10B shows a case where the voltage of the application pattern # 3 in FIG. 9 is applied, and the period is from time t0 to time t2, and from time t3 to time t.
4 shows a case where the ON voltage is applied during the period 4 and the period from time t5 to time t6.

As described above, in the liquid crystal drive device according to this embodiment, the voltage application time to the liquid crystal is set by associating the area obtained by integrating the transmitted light amount in the LED light emission period with the gradation and setting a constant applied voltage. Thus, even when the liquid crystal is driven, it is possible to perform delicate gradation display as if the liquid crystal is driven by an analog voltage.

Further, by applying the voltage of the on / off pattern in consideration of the area of the amount of transmitted light in the LED light emission period to the liquid crystal, it becomes possible to perform more delicate gradation display according to the gradation data. That is, as is clear from comparison between FIG. 10A and FIG. 10B, when the voltage of the on / off pattern is applied (FIG. 10B), the area of the transmitted light amount during the LED light emission period is made finer. Since it becomes possible to select, more delicate gradation expression is possible. Eg 1
R, G, B can be set by setting a 0-bit on / off pattern.
It is possible to express 1024 gradations for each.

Further, in this embodiment, the LED is actually used.
The voltage of the on-off pattern is applied to the liquid crystal from a time point a predetermined time before the time point when the light is emitted. As a result, the desired transmittance can be obtained from the time when the LED starts to emit light, so that the brightness of the display screen can be increased without increasing the output of the LED.

Such a liquid crystal driving device is the first embodiment.
The reference table 10 of the liquid crystal drive device 10 described above in
It can be realized by creating 1 as described below. Figure 11
Indicates an apparatus for creating the reference table 101, and the voltage application time (or voltage application pattern) associated with each gradation data is stored in the reference table 101.

The reference table creating device inputs the gradation data to the application time setting circuit 201. Application time setting circuit 2
01 sets a plurality of application times (or a plurality of application patterns) for each gradation indicated by the gradation data. That is, a plurality of application times are sequentially set to one gradation data from a short application time to a long application time. The application time (or application pattern) set in this way is determined by the switch 2
02 is used as an ON / OFF control signal.

The switch 202 has a constant voltage generating circuit 203.
A constant voltage (maximum rated voltage 5 [v] in this embodiment) is always input from the LCD panel 2 for the time set by the application time setting circuit 201.
0 is applied as a drive voltage to the liquid crystal.

The LCD panel 20 is provided with a brightness sensor 204, and the amount of transmitted light of the liquid crystal obtained from the brightness sensor 204 is sent to the integrating circuit 205. Integrating circuit 20
Reference numeral 5 obtains the area shown by the shaded area in FIG. 10 by integrating the amount of transmitted light during the LED emission period, and sends this area to the gradation determination circuit 206. Grayscale data is also input to the grayscale determination circuit 206. The gradation determination circuit 206 compares each gradation with the integrated area, and when the area corresponding to the gradation is input, sends a write control signal for permitting writing to the reference table 101.

The reference table 101 has gradation data and application time information (or application pattern information) as write information.
When the writing is permitted by the gradation determination circuit 206, the gradation data and the application time (or the application pattern) are written in association with each other. In this way, the reference table 101 stores the voltage application time (or voltage application pattern) corresponding to each gradation, in which the area of the shaded portion in FIG. 10 is considered.

Incidentally, when displaying an actual image, it is ideal to select a point such that the relationship between gradation and luminance lies on a gamma curve as shown in FIG. At this time, as in this embodiment, the LEDs of each color are used for the liquid crystal.
By applying voltages with different application patterns within the light emission period of, it is possible to create a great number of gradations by the application pattern, so that it becomes possible to easily select points on the gamma curve, and high accuracy is achieved. Gamma correction of can be performed.

Next, the operation of the liquid crystal driving device of this embodiment will be described with reference to FIG. FIG. 13A shows a drive voltage waveform applied to the liquid crystal. FIG. 13B is the same as FIG.
It is a waveform diagram which shows the transmitted light amount of a liquid crystal when the voltage of the pattern of (A) is applied. Further, in the figure, the portions indicated by R, G, and B represent the light emission periods of the LEDs of the respective colors.

That is, when the drive voltage is applied at time t1, the amount of transmitted light starts to increase at time t1. Then, at time t2, the R (red) LED emits light. Next, when the drive voltage is no longer applied at time t2, this time t
From 2, the amount of transmitted light begins to fall. Next, when the ON voltage is applied from time t2a to time t3, the amount of transmitted light increases during this period. Next, when the drive voltage is no longer applied at time t3, the amount of transmitted light starts to decrease at time t3, and
At 4, the amount of light becomes 0. By the way, during the period from the time point t1 to the time point t2, the transmitted light amount increases but the LED does not emit light, so that the LCD display is not performed.

Similarly, when the drive voltage is applied at time t6, the amount of transmitted light starts to increase at time t6. Time t
When the G (green) LED starts to emit light at 7, this time t7
The LCD display is started from. Next, when the drive voltage is no longer applied at time t7a, the amount of transmitted light starts to decrease at time t7a. Next, when the ON voltage is applied during the period from time t7b to time 8, the amount of transmitted light increases. Next, when the drive voltage is no longer applied at time t8, the amount of transmitted light starts to drop from this time t8, and the amount of transmitted light becomes 0 at time t9, and the display ends.

Similarly, when a drive voltage is applied at time t10, the amount of transmitted light starts increasing at time t10, and when the B (blue) LED starts emitting light at time t11, the LCD display starts at time t11. Be started. Next, at time t12, the drive voltage is not applied and the LED emission stops, so the display ends. By the way, in this B (blue) display, the area surrounded by the amount of transmitted light and the light emission period is the maximum, which means that the maximum gradation in this liquid crystal is displayed.

Similarly, when a driving voltage is applied at time t13, the amount of transmitted light starts to increase at time t13, and when the R (red) LED starts to emit light at time t14, this time t
LCD display is started from 14. Next, when the drive voltage is not applied at time t15, the amount of transmitted light starts to decrease from this time t15, and the amount of transmitted light becomes 0 at time t16, and the display ends.

As described above, since the liquid crystal drive device according to this embodiment drives the liquid crystal at the maximum rated voltage, the rise and fall of the transmitted light amount waveform shown in FIG. 13B is sharp. Therefore, the response speed of the liquid crystal can be increased. Thereby, for example, the frame frequency can be increased.

Further, since the voltage application time is set in consideration of the area obtained by integrating the amount of transmitted light in the LED light emission period, it is possible to perform delicate gradation display suitable for gradation.

Further, by applying the voltage of the on / off pattern in consideration of the area of the amount of transmitted light in the LED light emission period, it becomes possible to perform more delicate gradation display according to the gradation data.

Here, as a comparative example with the liquid crystal drive device of this embodiment, FIG. 14 shows a waveform diagram when the liquid crystal is driven by the conventional applied voltage variable system. In this liquid crystal driving method, the applied voltage value is increased as the designated gradation becomes higher.

That is, when a medium drive voltage is applied during the period from the time point t1 to the time point t3, the transmitted light amount corresponding to this voltage value is obtained from the liquid crystal. Similarly,
When a relatively large drive voltage is applied during the period from time t4 to time t6, a relatively large amount of transmitted light corresponding to this voltage value is obtained from the liquid crystal.

When the maximum drive voltage is applied during the period from time t7 to time t9, the maximum amount of transmitted light corresponding to this voltage value is obtained from the liquid crystal. Furthermore, time point t10
When a small drive voltage is applied in the period from to t12, a small amount of transmitted light corresponding to this voltage is obtained from the liquid crystal. By the way, the LCD is actually displayed in the period from time t2 to time t3 when the RGB LEDs are emitting light, from time t5 to time t6, from time t8 to time t9, and from time t11 to time t12. Is the period.

In the liquid crystal drive of the applied voltage variable system, the drive voltage value is set by paying attention to the average height of the transmitted light amount waveform in each display period. For example, from time t2 to time t3
The drive voltage is set such that the average height of the amount of transmitted light in the period of 3 satisfies the specified gradation.

On the other hand, in the liquid crystal driving of the transmitted light amount integration method of the embodiment, since the liquid crystal driving is performed in consideration of the integrated area of the transmitted light amount, it is more visual than the conventional liquid crystal driving method. It is possible to perform suitable delicate gradation expression.

As described above, according to the liquid crystal drive device of this embodiment, the drive voltage is controlled with reference to the integrated value of the amount of transmitted light from the liquid crystal, so that the drive voltage applied to the liquid crystal is eventually changed. The response time (ON / OFF) is changed earlier in time. This makes it possible to obtain the desired brightness by controlling the opening degree of the liquid crystal at an optimal timing with respect to time.

(Fourth Embodiment) FIG. 15 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals and shows a structure of a liquid crystal drive device according to a fourth embodiment. This liquid crystal driving device has an LCD panel 2
A temperature sensor 301 is provided near 0. When the temperature sensor 301 detects the ambient temperature of the liquid crystal, it sends the detection result to the correction circuit 302 as temperature information.

The correction circuit 302, based on the temperature information,
The ON time control signal output from the application time control unit 102 is corrected. Here, as shown in FIG. 16, the liquid crystal has a temperature characteristic that the response speed of the liquid crystal becomes slower and the amount of transmitted light becomes lower as the temperature becomes lower. In this embodiment, in consideration of this point, the ON time control signal is corrected such that the ON time becomes longer as the ambient temperature of the liquid crystal becomes lower.

Thus, according to the above configuration, in addition to the effects obtained by the above-described first to third embodiments, a liquid crystal driving device having further improved gradation display accuracy in consideration of the temperature characteristics of the liquid crystal is provided. The effect that it can be realized can be obtained.

(Fifth Embodiment) FIG. 17 in which parts corresponding to those in FIG. 1 are assigned the same reference numerals and shows a structure of a liquid crystal drive device according to the fifth embodiment. In this liquid crystal drive device, the brightness detection section 401 is provided at a position inconspicuous on the periphery of the LCD panel 20. In the case of this embodiment, the brightness detection unit 401
Is composed of a detection cell arranged in the liquid crystal cell array and a photo sensor for detecting the brightness of the detection cell. Then, the brightness detection result detected by the photo sensor is sent to the correction circuit 402 as brightness information.

To the correction circuit 402, in addition to the brightness information from the brightness detection unit 401, gradation data is also input,
The brightness information and the gradation data are compared. When the brightness information is different from the gradation data, the ON time control signal output from the application time control unit 102 is corrected according to the difference. Specifically, when the brightness indicated by the brightness information is smaller than the gradation indicated by the gradation data, the ON time control signal is corrected so that the ON time becomes longer.

Here, when the LED is used for many years, the brightness tends to decrease due to aging. B among RGB
The brightness of the (blue) LED may decrease significantly due to aging. In this embodiment, in consideration of this point, the ON time control signal is corrected such that the ON time becomes longer as the brightness of the transmitted light of the liquid crystal becomes lower. In addition to this, the white balance is corrected again by changing the current value of each color according to the luminance information. As a result, a liquid crystal display device having a good luminance balance can be obtained.

Thus, according to the above configuration, in addition to the effects obtained by the above-described first to third embodiments, the gradation display accuracy is further improved in consideration of the decrease in brightness due to the aging of the LED. It is possible to obtain the effect of realizing a liquid crystal driving device.

(Other Embodiments) The operation modes of the liquid crystal molecules of the LCD panel in this embodiment are as follows.
TN (Twisted Nematic) mode, STN (Super Twist)
ed Nematic) mode, ferroelectric liquid crystal mode, birefringence mode, guest-host mode, dynamic scattering mode, phase transition mode, etc.

Further, the present invention is not limited to the above-mentioned embodiments, but can be implemented with various modifications. For example,
In the above embodiment, the case where the applied voltage is 5V has been described, but the present invention is not limited to this and can be applied to the case where the applied voltage is other than 5V.

Further, in the above-described third embodiment, the reference table 101 of the first embodiment stores the data by the transmitted light amount integration method, so that the voltage in which the area obtained by integrating the transmitted light amount of the liquid crystal in the LED emission period is taken into consideration. Although the case of setting the application time has been mainly described, the present invention is not limited to this, and the pattern table 104 according to the second embodiment may store data by the transmitted light amount integration method. In this case, the amount of transmitted light of the liquid crystal when a voltage of a certain pattern is applied to the liquid crystal is detected, and the voltage application pattern suitable for each gradation is set by considering the area obtained by integrating the amount of the transmitted light during the LED emission period. Good.

In particular, the pattern voltage application method of the present invention, as described in the second embodiment, applies the pattern voltage according to the gradation data within one LED light emission period as compared with the conventional PWM control. Thus, delicate LCD display can be performed according to the gradation data. In addition to this, by determining this application pattern according to the above-mentioned integrated area, it is possible to obtain a more delicate L according to the gradation data.
CD can be displayed.

In the above-described fourth embodiment, the case where the voltage application time is corrected according to the temperature detection result has been described, but the present invention is not limited to this, and the voltage application pattern may be corrected according to the temperature detection result. Good.

Similarly, in the above-described fifth embodiment, the case where the voltage application time is corrected according to the brightness detection result has been described, but the present invention is not limited to this, and the voltage application pattern may be corrected according to the brightness detection result. May be.

In the above embodiment, the pulse pattern control method considering the integrated value of the transmitted light quantity is applied to the control without using the D / A converter. However, the present invention is not limited to this. It can also be applied to control using a D / A converter. For example, a D / A converter capable of expressing a specific gradation (for example, 4 gradations) (which can be considered as a 2 gradation D / A converter in the case of digital control as in the embodiment), and the present invention When combined with the driving method (for example, a four-valued voltage application pattern), it is possible to express gray scales with even more gradations.

Further, in the above-described embodiments, the case where the liquid crystal driving device and the liquid crystal driving method according to the present invention are applied to the field sequential type liquid crystal display device has been described. However, the present invention is not limited to this and, for example, a color filter is used. Even when it is applied to another liquid crystal display device such as a display system or a projector system, it is possible to obtain the same effect as that of the above-described embodiment.

[0088]

As described above, according to the present invention,
By supplying a voltage to the liquid crystal from a time point before the light emitting section emits light, the liquid crystal is controlled so as to have a desired transmittance from the light emission starting point of the light emitting section. It becomes possible to obtain a desired transmittance from the time point when the light emission is started, and it is possible to increase the brightness of the display screen without increasing the output of the light emitting section.

[Brief description of drawings]

FIG. 1 is a block diagram showing a schematic configuration of a liquid crystal drive device according to a first embodiment.

FIG. 2 is a diagram showing a reference table in the liquid crystal drive device shown in FIG.

FIG. 3 is a diagram showing a relationship between light transmittance and time.

FIG. 4 is a diagram showing the relationship between applied voltage and time.

FIG. 5 is a diagram showing a relationship between applied voltage and time for each gradation.

FIG. 6 is a diagram showing timing of voltage application.

FIG. 7 is a block diagram showing a schematic configuration of a liquid crystal drive device according to a second embodiment.

8 is a diagram showing a pattern table in the liquid crystal drive device shown in FIG.

FIG. 9 is a diagram showing a voltage application pattern.

FIG. 10 is a diagram showing the relationship between the amount of transmitted light and time used for explaining the method of integrating the amount of transmitted light according to the third embodiment.

FIG. 11 is a block diagram used for explaining the creation of a reference table used in the liquid crystal drive device according to the third embodiment.

FIG. 12 is a characteristic curve diagram for explaining gamma correction.

FIG. 13 is a waveform diagram for explaining the operation of the transmitted light amount integration method according to the third embodiment.

FIG. 14 is a waveform diagram for explaining an applied voltage variable system used for comparison with the third embodiment.

FIG. 15 is a block diagram showing a schematic configuration of a liquid crystal drive device according to a fourth embodiment.

FIG. 16 is a diagram showing temperature characteristics of liquid crystal.

FIG. 17 is a block diagram showing a schematic configuration of a liquid crystal drive device according to a fifth embodiment.

FIG. 18 is a block diagram showing a schematic configuration of a conventional liquid crystal drive device.

FIG. 19 is a diagram showing the relationship between light transmittance and applied voltage.

[Explanation of symbols]

10 LCD drive 20 LCD panel 101 reference table 102 Application time control unit 103 switch 104 pattern table 105, 203 constant voltage generation circuit 201 Application time setting circuit 204 brightness sensor 205 integrating circuit 301 Temperature sensor 302, 402 correction circuit 401 brightness detection unit

─────────────────────────────────────────────────── ─── Continued Front Page (51) Int.Cl. ⁷ Identification Code FI G09G 3/20 642 G09G 3/20 642D 642J 642P 3/34 3/34 J 3/36 3/36 H04N 5/66 102 H04N 5 / 66 102B (58) Fields surveyed (Int.Cl. ⁷ , DB name) G09G 3/00-3/38 G02F 1/133 H04N 5/66 H04N 9/30

Claims (3)

(57) [Claims] 1. A light emitting means for emitting light at a predetermined timing, and a liquid crystal provided at a position to shield the light emitting means.
On / off cycle shorter than the unit light emitting period of the light emitting means
And the sequences are different from each other with the same number of times of ON.
Voltage that can set the applied voltage of multiple on-off patterns
Depending on the application pattern setting means and the gradation data,
Any of the options set by the pressure application pattern setting means
And a voltage supply means for supplying a voltage of an on-off pattern to the liquid crystal from a time point before the light emission start time of the light emitting means, and an amount of transmitted light of the liquid crystal in a unit light emission period.
Is variably controlled according to the on / off pattern . 2. The liquid crystal drive device according to claim 1,
A liquid crystal drive device , which is used for a field sequential liquid crystal display device. 3. From the point in time before the light emitting section emits light,
Same number of times of ON, but different sequences
Depending on the gradation of the applied voltage of multiple on-off patterns
Select the applied voltage of either on-off pattern and the liquid crystal
By controlling the liquid crystal so that the liquid crystal has a desired transmittance from the time when the light emitting section starts emitting light, and a gradation according to the gradation data is obtained. Method.