JP2008058782A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display a high-quality three-dimensional image by temperature-compensating a front liquid crystal panel and a rear liquid crystal panel. <P>SOLUTION: Temperature difference is produced between the front liquid crystal panel 10 and the rear liquid crystal panel 20 due to heat generated by a backlight. On the basis of an output from a temperature sensor 38 mounted on a circuit board 30, the most suited common voltage is generated from a common voltage generating circuit 36 for the front liquid crystal panel 10 and from a common voltage generating circuit 37 for the rear liquid crystal panel 20. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that displays a three-dimensional image by arranging two liquid crystal panels so as to overlap each other.

  In general, the three-dimensional image display apparatus recognizes different images using left and right eyes of an observer using special glasses or the like. On the other hand, there is a three-dimensional image display device in which a depth is expressed by overlapping a plurality of liquid crystal panels. Patent Documents 1 and 2 listed below are cited as documents disclosing display devices that perform three-dimensional display using a plurality of liquid crystal panels.

  The three-dimensional image display method described in Patent Literature 1 and Patent Literature 2 displays a display target object on a plurality of display screens at different depth positions as viewed from the observer.

  Patent Document 1 discloses that a three-dimensional image is displayed by assigning pixels that change greatly to a screen close to the observer and assigning pixels that change little to a screen far from the observer.

  Patent Document 2 discloses generating a three-dimensional stereoscopic image by changing the luminance of a two-dimensional image displayed on each display screen independently for each display surface. .

JP-T-2002-504964 JP 2002-214556 A

  In a conventional three-dimensional display device, temperature compensation of a common voltage applied to a plurality of liquid crystal panels is not considered. Also, consider that the temperature of the rear liquid crystal panel near the backlight rises above the temperature of the front liquid crystal panel due to the heat generated from the backlight in one of the two liquid crystal panels and the other rear liquid crystal panel. It has not been.

  That is, as shown in FIG. 7A, the front liquid crystal panel 10 is in contact with the outside air and is separated from the backlight 40, but the rear liquid crystal panel 20 is close to the backlight 40 and thus generates heat from the backlight 40. Thus, the temperature of the rear liquid crystal panel 20 is higher than the temperature of the front liquid crystal panel 10.

  This state is shown in FIG. FIG. 7B is a relationship diagram between the outside air temperature and the liquid crystal panel temperature. At the same outside air temperature, the temperature of the rear liquid crystal panel 20 is higher than the temperature of the front liquid crystal panel 10 by ΔT.

  In FIG. 7A, the circuit board 30 drives the front liquid crystal panel 10, the rear liquid crystal panel 20, and the backlight 40. The frame 50 supports and fixes them. A white arrow indicates backlight light from the backlight 40.

  As described above, the temperature difference ΔT is generated in the temperature change between the front liquid crystal panel 10 and the rear liquid crystal panel 20, so that flicker occurs on the three-dimensional display screen or the contrast decreases.

  Therefore, an object of the present invention is to provide a liquid crystal display device that performs temperature compensation of a front liquid crystal panel and a rear liquid crystal panel.

  The present invention is characterized in that an optimum common voltage is supplied to the front liquid crystal panel and the rear liquid crystal panel using one temperature sensor.

  Further, the present invention is characterized in that an optimum common voltage is supplied to the front liquid crystal panel and the rear liquid crystal panel in a transient state when the power is turned on / off.

  As described above, according to the present invention, temperature compensation of two liquid crystal panels can be performed in a steady state and a transient state, and a high-quality three-dimensional image can be displayed.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram of a liquid crystal display device according to the present invention. A front liquid crystal panel 10, a rear liquid crystal panel 20, a circuit board 30 and a backlight 40 (not shown) are arranged as shown in FIG. It has become.

  That is, the front liquid crystal panel 10, the rear liquid crystal panel 20, and the backlight 40 are arranged in this order from the observer side. Since the circuit board and each panel are connected by flexible wiring, the circuit board 30 can be arranged on the back side of the backlight. In this embodiment, the front liquid crystal panel 10, the rear liquid crystal panel 20, the backlight 40, and the circuit board 30 are arranged in this order, but the circuit board 30 may be arranged on the side surface of the liquid crystal panel.

  In FIG. 1, the front liquid crystal panel 10 includes a drain driver 12 and a gate driver 13 that drive a liquid crystal display unit 11. Similarly, the rear liquid crystal panel 20 includes a drain driver 22 and a gate driver 23 that drive the liquid crystal display unit 21.

  The circuit board 30 also receives a digital signal, a controller 31 that controls the front liquid crystal panel 10 and the rear liquid crystal panel 20, and a direct current voltage that is suitable for the front liquid crystal panel 10 and the rear liquid crystal panel 20. DC / DC converter 32 for converting to voltage, gradation voltage generation circuit 33 for front liquid crystal panel 10, gradation voltage generation circuit 34 for rear liquid crystal panel 20, and supply to front liquid crystal panel 10 and rear liquid crystal panel 20 And a common voltage generation circuit 35 for generating a common voltage.

  Further, the common voltage generation circuit 35 uses the common voltage generation circuit 36 for the front liquid crystal panel 10, the common voltage generation circuit 37 for the rear liquid crystal panel 20, and the common voltage generated by the common voltage generation circuits 36 and 37 as temperature. And a temperature sensor 38 for correcting accordingly.

  The controller 31 provided on the circuit board 30 controls the drain drivers 12 and 22 and the gate drivers 13 and 23 on the basis of the horizontal synchronization signal and the vertical synchronization signal included in the input digital signal. The liquid crystal display units 11 and 21 are scanned in the horizontal direction and the vertical direction. Further, the gradation voltages from the gradation voltage generation circuits 33 and 34 are supplied to the drain drivers 12 and 22 to control the luminance of the liquid crystal display units 11 and 21.

  Further, the luminance of the liquid crystal display units 11 and 21 also varies depending on the common voltage from the common voltage generation circuit 35. Further, it varies depending on the temperature of the front liquid crystal panel 10 and the rear liquid crystal panel 20. Therefore, the common voltage generation circuit 35 generates an optimal common voltage according to the temperatures of the front liquid crystal panel 10 and the rear liquid crystal panel 20.

  FIG. 2 is a relationship diagram between the liquid crystal panel temperature and the optimum common voltage, and it is necessary to increase the optimum common voltage as the liquid crystal panel temperature rises. For this purpose, as shown in FIG. 1, an optimum common voltage corresponding to the temperature is supplied from the common voltage generation circuit 35 to the front liquid crystal panel 10 and the rear liquid crystal panel 20.

  FIG. 3 is a circuit diagram of the common voltage generation circuit 35 shown in FIG. In FIG. 3, a temperature sensor 38 such as a thermistor is installed on the circuit board 30. Although temperature sensors may be installed in each of the front liquid crystal panel 10 and the rear liquid crystal panel 20, as already described with reference to FIG. 7, the temperature change between the front liquid crystal panel 10 and the rear liquid crystal panel 20 is related to the temperature difference ΔT. Therefore, one temperature sensor 38 is sufficient. The temperature sensor 38 is installed on the circuit board 30 that applies a common voltage to the front liquid crystal panel 10 and the rear liquid crystal panel 20.

  When the temperature rises, the resistance value of the temperature sensor 38 decreases, and when the temperature decreases, the resistance value increases. Therefore, when the temperature rises, the power supply voltage Vc is resistance-divided by the temperature sensor 38 and the resistor R0 connected in series thereto, and the operational amplifiers OP1 and OP2 connected to the connection point of the temperature sensor 38 and the resistor R0. The input voltage of the operational amplifier OP3 that applies the common voltage to the front liquid crystal panel and the output of the operational amplifier OP4 that applies the common voltage to the rear liquid crystal panel increase, and an optimum common voltage proportional to the temperature change is obtained as shown in FIG. It is done. When the temperature decreases, the output of the operational amplifier OP4 decreases contrary to the increase, and an optimum common voltage proportional to the temperature change is obtained as shown in FIG.

  The operational amplifier OP3 and the operational amplifier OP4 are set to the common voltage setting means (variable resistors) VR1 and VR2, and the reference common voltage is set by the outputs of the operational amplifiers OP1 and OP2. Generate common voltage. Note that the difference between the reference common voltages set in the operational amplifier OP3 and the operational amplifier OP4 corresponds to the temperature difference ΔT as shown in FIG.

  3 are input resistors of the operational amplifiers OP3 and OP4, and the resistors R3 and R5 are resistors that set the reference common voltage of the operational amplifier OP3 together with the variable resistor VR1. Similarly, the resistors R6 and R8 are resistors that set the reference common voltage of the operational amplifier OP4 together with the variable resistor VR2. Resistors R4 and R7 are input resistors of the operational amplifiers OP3 and OP4.

  In the first embodiment, steady state temperature compensation is performed by paying attention to the temperature difference ΔT between the front liquid crystal panel and the rear liquid crystal panel. However, in this embodiment, temperature compensation in the transient state when the power is turned on is performed. Is what you do.

  First, as shown in FIG. 4 (a), the temperature changes of the front and rear liquid crystal panels from when the power is turned on to the steady state are as follows. The temperature difference between the front LCD panel and the rear LCD panel is not constant until it reaches the steady state where the temperature change of the circuit board disappears from the start. ΔT.

  Therefore, when the power is turned on, as shown in FIG. 4A, the temperature of the rear liquid crystal panel is set lower by the temperature difference ΔT and is set to be the same as the temperature of the front liquid crystal panel. Next, the temperature difference ΔT is gradually reduced with the passage of time since the power is turned on, and the reduced temperature difference ΔT is made zero in a steady state.

  FIG. 5 is a block diagram for realizing the temperature change characteristics of the front liquid crystal panel and the rear liquid crystal panel shown in FIG. 5 is different from FIG. 1 in that a control means 39 incorporating a memory means such as a microcomputer is provided in the common voltage generation circuit 35, and the other points are the same as those in FIG.

  In FIG. 5, when detecting that the power supply is turned on, the control means 39 outputs a value for subtracting the common voltage corresponding to the temperature difference ΔT to the common voltage generating circuit 37 for the rear liquid crystal panel, and the passage of time. At the same time, the subtraction value is decreased, and when the change in the output voltage from the temperature sensor 38 becomes constant, the subtraction value is set to zero.

  FIG. 6 is a circuit diagram of the common voltage generation circuit 35 shown in FIG. 6 differs from FIG. 3 in that the control means 39 is provided, the output of the operational amplifier OP2 for the rear liquid crystal panel is connected to the A / D input of the control means 39, and the operational amplifier OP4 for the rear liquid crystal panel is controlled by the control means. The rest is the same as in FIG. 3 in that the control is performed with 39 D / A outputs.

  When the power is turned on, the control means 39 shown in FIG. 6 monitors the output of the temperature sensor 38 via the operational amplifier OP2 with the A / D input, and subtracts the value from the D / A output to the operational amplifier OP4 for the rear liquid crystal panel. give. This subtraction value is added to the reference common voltage of the operational amplifier OP4. After that, the subtraction value is decreased sequentially. In this way, the optimum common voltage during the power supply rising period is applied to the rear liquid crystal panel, and the temperature change characteristic shown in FIG.

  In this embodiment, temperature compensation is performed after the power is turned off after the power is turned on. FIG. 4B shows a temperature change of the front liquid crystal panel and the rear liquid crystal panel when the power is turned on / off. In order to realize this temperature change characteristic, the control means 39 shown in FIGS. In FIG. 4 (b), the slope of rising from power-on and the slope of falling from power-off differ from each other when the liquid crystal panel is rapidly overheated by the backlight from the time of power-on and from the time of power-off. This is due to natural heat dissipation from the LCD panel.

  First, in the storage means of the control means 39, the rise time from the power-on to the steady state shown in FIG. 4B and the common voltage difference corresponding to the temperature difference between the front liquid crystal panel and the rear liquid crystal panel during this period are shown. Store in advance. Similarly, the fall time from when the power is turned off to the outside air temperature without temperature change shown in FIG. 4B and the common voltage difference corresponding to the temperature difference between the front liquid crystal panel and the rear liquid crystal panel during this time are stored in advance. Let me.

  Note that the internal clock built in the control means 39 is backed up at the fall time. After the elapse of this time, the value of the internal clock becomes the reset value because the capacitor that backs up the power supply of the control means 39 is eliminated, so that the control means 39 can recognize that this time has elapsed.

  Here, at the rise time, the control means 39 sequentially reads out the common voltage difference at the rise time from the built-in storage means, and outputs it to the common voltage generation circuit 37 for the rear liquid crystal panel 20. As described above, the reference common voltage of the common voltage generation circuit 37 for the rear liquid crystal panel 20 is added over time by the D / A output of the control means 39.

  In this case, the reference common voltage for the rear liquid crystal panel set by the variable resistor VR2 shown in FIG. 6 is the same as the reference common voltage for the front liquid crystal panel set by the variable resistor VR1. It is.

  Next, at the fall time, the control means 39 sequentially reads out the common voltage difference at the fall time from the built-in storage means and outputs it to the common voltage generation circuit 37 for the rear liquid crystal panel 20. As described above, the reference common voltage of the common voltage generation circuit 37 for the rear liquid crystal panel 20 is added over time by the D / A output of the control means 39. In this case, the voltage to be added gradually decreases.

  Thus, the reason for sequentially reading the common voltage difference after the power is turned off is to perform temperature compensation of the liquid crystal panel when the power is turned on again at the fall time.

  For this purpose, the storage means of the control means 39 stores the elapsed time since the power was turned off. When the control means 39 recognizes that this elapsed time is less than the fall time, the control means 39 reads the common voltage difference when the power is turned on again from the storage means, and uses this common voltage difference, The same processing as the startup processing when the power is first turned on is performed.

  That is, when the power is turned on again during the fall processing, control is started from the middle of the rise processing when the power is first turned on.

  After the falling process, the internal clock becomes a reset value, and when the power is turned on thereafter, the rising process is performed from the beginning. Further, the same operation can be performed when the power is turned on, the power is turned off during the startup process, and the power is turned on again.

1 is a block diagram of a liquid crystal display device according to the present invention. The relationship between temperature and optimum common voltage. FIG. 2 is a circuit diagram of a common voltage generation circuit 35 shown in FIG. 1. Temperature change diagram when power is turned on / off. FIG. 6 is another block diagram of the liquid crystal display device according to the present invention. FIG. 6 is a circuit diagram of the common voltage generation circuit 35 shown in FIG. 5. FIG. 2 is a schematic diagram of a liquid crystal display device according to the present invention and a temperature change diagram of two liquid crystal panels.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Front liquid crystal panel, 11 ... Liquid crystal display part, 12 ... Drain driver, 13 ... Gate driver, 20 ... Rear liquid crystal panel, 21 ... Liquid crystal display part, 22 ... Drain driver, 23 ... Gate driver, 30 ... Circuit board, 31 ... Controller, 32 ... DC / DC converter, 33 ... Gradation voltage generation circuit for front liquid crystal panel 10, 34 ... Gradation voltage generation circuit for rear liquid crystal panel 20, 35 ... Common voltage generation circuit, 36 ... Front liquid crystal panel 10 ... Common voltage generation circuit for 10; 37 ... Common voltage generation circuit for rear liquid crystal panel 20; 38 ... Temperature sensor; 39 ... Control means; 40 ... Backlight; 50 ... Frame; Resistor).

Claims (5)

In a liquid crystal display device in which a front liquid crystal panel, a rear liquid crystal panel, a backlight, and a circuit board are sequentially arranged to perform three-dimensional display,
The circuit board is provided with a common voltage generation circuit including a temperature sensor,
The common voltage generation circuit generates a common voltage applied to a front liquid crystal panel and a common voltage applied to a rear liquid crystal panel based on an output from a temperature sensor.   The common voltage generation circuit is provided with common voltage setting means for applying a reference common voltage to the front liquid crystal panel and common voltage setting means for supplying a reference common voltage to the rear liquid crystal panel. The display device according to claim 1, wherein the display device corresponds to a temperature difference between the liquid crystal panel and the rear liquid crystal panel. In a liquid crystal display device in which a front liquid crystal panel, a rear liquid crystal panel, a backlight, and a circuit board are sequentially arranged to perform three-dimensional display,
The circuit board is provided with a common voltage generation circuit including a temperature sensor and a control means,
The common voltage generation circuit generates a common voltage to be applied to the front liquid crystal panel based on an output from the temperature sensor, and generates a common voltage to be applied to the rear liquid crystal panel based on an output from the control means. Liquid crystal display device.   4. The display device according to claim 3, wherein when the power is turned on, the control unit subtracts the common voltage applied to the front liquid crystal panel to generate the common voltage applied to the rear liquid crystal panel. The display device according to claim 3, wherein the control unit generates a common voltage to be applied to the rear liquid crystal panel based on an output from a built-in storage unit.

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