JP2009042681A - Liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display, wherein satisfactory viewing is attained by suppressing instantaneous and sudden variation in overall light emission luminance generated when overall light emission luminance of the liquid crustal display is switched. <P>SOLUTION: Light emission luminance of a backlight is gradually changed up to target overall light emission luminance when overall light emission luminance of a liquid crystal display indicator 2 is switched. Thereby, a variation width of overall light emission luminance in a delay time Td after a drawing circuit 6 receives a second signal until drawing output is switched to the target overall light emission luminance and a variation width of the overall light emission luminance in a switch time Tg to be a time required for the overall light emission luminance to be finally switched can be suppressed. As a result, the liquid crystal display with satisfactory viewing can be provided by eliminating deficiencies generated when switching of overall light emission luminance of a liquid crystal display indicator of a conventional liquid crystal display is controlled, that is, by relaxing instantaneous and sudden variation in target overall light emission luminance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and is particularly suitable for use in automobiles and the like.

As a conventional liquid crystal display device, a backlight disposed behind the liquid crystal display is provided, and the liquid crystal display is transmitted and illuminated by light from the backlight, and is externally input to the control means. By simultaneously adjusting both the backlight emission brightness and the gradation of the display data itself displayed on the liquid crystal display, for example, the RGB output and other drawing outputs in response to changes in the display, the overall display of the liquid crystal display There is one that can adjust the luminance (see Patent Document 1).
Japanese Patent Laid-Open No. 11-194736

  A conventional liquid crystal display device includes a drawing circuit that performs a drawing operation on a liquid crystal display, a drive circuit that performs a light emission operation on a backlight, and a drawing circuit and a drive circuit corresponding to a change in a detection signal input from the outside. The control means which actuates is provided. When the detection signal is input, the control means determines a target total light emission luminance, a target light emission luminance and a target drawing output based on the detection signal, and outputs a first signal to the drive circuit, and a liquid crystal display And a second control unit that performs display image control and receives a signal related to the target drawing output from the first control unit and outputs a second signal to the drawing circuit.

  A first signal is simultaneously transmitted from the first controller to the drive circuit, and a target drawing output information signal is simultaneously transmitted to the second controller. The drive circuit receives the first signal to drive the backlight, and the light emission luminance of the backlight is switched to the target light emission luminance in steps. On the other hand, the drawing output of the liquid crystal display is switched to the target drawing output later than the time when the light emission luminance of the backlight is switched to the target light emission luminance.

  This is because when the first signal is received, the driving circuit immediately drives the backlight, so that the backlight switches to the target light emission luminance almost simultaneously with the first signal being transmitted, whereas the second control unit sets the target light emission luminance. Since it takes a little time to output the second signal to the drawing circuit after receiving the drawing output information signal, the image display on the liquid crystal display by the drawing circuit is executed at a predetermined time interval. This is because it takes time until the image display of the liquid crystal display is switched to the one based on the second signal after the circuit receives the second signal.

  A switching operation of the total light emission luminance in the conventional liquid crystal display device will be described.

  Here, the liquid crystal display device is applied to a combination meter mounted on an automobile. In this case, the detection signal input from the outside is a position signal of the light control switch.

  The total light emission brightness of the liquid crystal display device is low during the daytime, that is, when the light control switch is in the off position, and is controlled to be high at night, that is, when the light control switch is in the vehicle width lamp position or the headlamp position. In the daytime, the light emission luminance of the backlight is driven to a high level, and the drawing output of the liquid crystal display is driven to a low level. On the other hand, at night, the light emission luminance of the backlight is driven to a low level, and the drawing output of the liquid crystal display is driven to a high level.

  First, the case where the light control switch is switched from the off position to the vehicle width lamp position from daytime to nighttime will be described. The light emission brightness of the backlight switches from a high daytime level to a low level in a stepwise manner. On the other hand, the drawing output of the liquid crystal display is switched from a low level in the daytime to a high level after a certain time delay from the light emission luminance switching time of the backlight. That is, during the delay time described above, the light emission luminance of the backlight is low, the drawing output of the liquid crystal display is also low, and the total light emission luminance of the liquid crystal display device is considerably low. .

  Next, the case where the light control switch is switched from the vehicle width lamp position to the off position from night to daytime will be described. The light emission luminance of the backlight switches from a low level at night to a high level in a stepwise manner. On the other hand, the drawing output of the liquid crystal display is switched from a high level at night to a low level after a certain time delay from the light emission luminance switching time of the backlight. That is, during the delay time described above, the light emission luminance of the backlight is high, the drawing output of the liquid crystal display is also high, and the total light emission luminance of the liquid crystal display device is considerably high. .

  Next, how the liquid crystal display device looks during the switching operation described above, that is, how it looks to the driver will be described.

  First, when the light control switch is switched from the off position to the vehicle width lamp position from daytime to nighttime, the total light emission brightness of the liquid crystal display device is considerably low for the delay time described above, and then the normal total light emission brightness. become. When the driver sees this, the liquid crystal display appears to be dark for a moment for the delay time described above.

  On the other hand, when the light control switch is switched from the vehicle width lamp position to the off position from night to daytime, the total light emission brightness of the liquid crystal display device is considerably high for the delay time described above, and then the normal total light emission brightness. become. When this is seen by the driver, it appears that the liquid crystal display flashes briefly for the delay time described above.

  In general, the intensity of the stimulus for the visual perception of the viewer is weak when the screen of the liquid crystal display becomes dark for a moment, but is strong when the screen of the liquid crystal display becomes bright for a moment, that is, when it flashes. Accordingly, the driver reacts sensitively to a phenomenon in which the screen of the liquid crystal display flashes for a moment, and there is a risk that the merchantability of the liquid crystal display device is lowered.

  The present invention has been made in view of the above-described problems, and suppresses a sudden change in the total light emission luminance at the time of switching the total light emission luminance of the liquid crystal display device. The purpose is to provide.

  In order to achieve the above object, the present invention employs the following technical means.

  According to a first aspect of the present invention, there is provided a liquid crystal display device, a backlight for transmitting and illuminating the liquid crystal display disposed on the back side of the liquid crystal display, and causing the liquid crystal display to perform a drawing operation. A liquid crystal display by changing the drawing circuit for driving the liquid crystal display, the driving circuit for driving the backlight so that the backlight performs light emission, and the light emission luminance of the backlight and the drawing output of the liquid crystal display Control means for adjusting the total light emission luminance that is the light emission luminance to the outside of the device, the control means corresponding to the change of the detection signal input from the outside, the target total light emission luminance that is the total light emission luminance to be realized The target backlight emission luminance, which is the backlight emission luminance to achieve the target overall emission luminance, and the target drawing output, which is the drawing output of the liquid crystal display The control means outputs a first signal for switching the light emission luminance of the backlight to the target backlight light emission luminance to the drive circuit, and the control means for switching the drawing output of the liquid crystal display to the target drawing output. A driving circuit that outputs a second signal to a drawing circuit, a driving circuit that receives the first signal and changes backlight emission luminance, and a drawing circuit that receives the second signal and changes a drawing output. Is characterized by gradually changing the backlight emission luminance to the target backlight emission luminance when receiving the first signal.

  The drawing circuit that controls the drawing output of the liquid crystal display switches the drawing output every predetermined time period. For this reason, when the second signal is input to the drawing circuit, the drawing output is switched only at the timing synchronized with the above-described time period. Therefore, there is a delay time from when the second signal is input to the drawing circuit until when the drawing output of the liquid crystal display is actually switched to the target drawing output. On the other hand, the light emission luminance of the backlight is immediately switched to the target backlight light emission luminance when the first signal is input to the drive circuit. In other words, the light emission luminance of the backlight is switched to the target backlight light emission luminance almost simultaneously with the input of the second signal to the drawing circuit. That is, within the above-described delay time, the backlight output luminance has already been switched to the target backlight emission luminance, but the drawing output of the liquid crystal display is still in the state before switching. For example, the backlight emission brightness immediately decreases and the drawing output does not increase, or the backlight emission brightness immediately increases but the drawing output does not decrease. For this reason, in the conventional liquid crystal display device, the total light emission brightness seems to be very low and disappears for a moment within the above-mentioned delay time, or the total light emission brightness is very high and seems to flash for a moment. This has caused a problem that the merchantability of the liquid crystal display device may be reduced.

  On the other hand, in the liquid crystal display device according to claim 1 of the present invention, when performing control to switch the target total light emission luminance, the control means gradually changes the backlight light emission luminance to the target backlight light emission luminance. ing. According to this configuration, within the delay time described above, the backlight emission luminance is at a level that is changing from the emission luminance before the control toward the target emission luminance. Therefore, the method of changing the total light emission luminance within the delay time described above changes from a step shape to a slope shape. A brilliant liquid crystal display device can be provided.

  In this case, as in the liquid crystal display device according to claim 2 of the present invention, if the drawing circuit is configured to gradually change the drawing output to the target drawing output when receiving the second signal, the drawing circuit starts to receive the second signal. Since the sudden change width of the change in the total light emission luminance within the delay time can be reduced until the drawing output is switched to the target drawing output, the sudden change in the total light emission luminance that occurs when the total light emission luminance is switched. The effect of relaxing can be enhanced.

  Since the total issue luminance of the present invention reaches the target total light emission luminance, the liquid crystal display device described in the above, a liquid crystal display, a backlight that transmits and illuminates the liquid crystal display disposed on the back side of the liquid crystal display, A drawing circuit that drives the liquid crystal display to perform a drawing operation on the liquid crystal display, a drive circuit that drives the backlight to perform a light emitting operation, the light emission luminance of the backlight, and the drawing output of the liquid crystal display And controlling means for adjusting the total light emission brightness, which is the light emission brightness with respect to the outside of the liquid crystal display, by changing the brightness of the liquid crystal display, the control means corresponding to the change of the detection signal input from the outside, In addition to determining the target overall emission brightness, which is the brightness, the target backlight emission brightness, which is the backlight emission brightness to achieve the target overall emission brightness, and the LCD display The target drawing output as an output is determined, the control means outputs a first signal for switching the backlight emission luminance to the target backlight emission luminance to the drive circuit, and the control means outputs the drawing output of the liquid crystal display. A second signal for switching to the target drawing output is output to the drawing circuit, the drive circuit receives the first signal and changes the backlight emission luminance, and the drawing circuit receives the second signal and changes the drawing output. The control means outputs the first signal after a predetermined time has elapsed after outputting the second signal, and the drawing circuit gradually changes the drawing output to the target drawing output upon receiving the second signal. It is characterized by that.

  The above-described configuration is the first for changing the control target to be gradually changed from the backlight emission luminance to the drawing output and switching the backlight emission luminance with respect to the liquid crystal display device according to claim 1 of the present invention. The signal is transmitted with a delay from the second signal for switching the drawing output.

  According to such a configuration, the change in the total light emission luminance within the delay time from when the second signal is received until the drawing output is switched to the target drawing output is reduced, and the drawing output is gradually increased even after the backlight emission luminance is switched. Since the total issue luminance reaches the target total emission luminance while changing, it is possible to reduce the degree of fluctuation in the total issue luminance from when the second signal is transmitted until the total issue luminance reaches the target total emission luminance. it can. Thereby, it is possible to provide a liquid crystal display device with a good appearance by alleviating a sudden change in the total light emission luminance that occurs when the total light emission luminance of the liquid crystal display device is switched.

  In the liquid crystal display device according to claim 4 of the present invention, when the detection signal is input, the control means determines a target total light emission luminance, a target light emission luminance, and a target drawing output based on the detection signal, and outputs the first signal to the drive circuit. And a second control unit that performs display image control of the liquid crystal display and outputs a second signal to the drawing circuit based on the target drawing output determined by the first control unit. It is characterized by.

  In the above-described configuration, the control unit includes two control units, that is, a control unit that processes a signal input from the outside to the control unit and a control unit that controls the display operation of the liquid crystal display. As a result, it is possible to easily respond to requests for increase / decrease in the types of signals input from outside and requests for increase / decrease in display information. The liquid crystal display device with good appearance can be provided by relaxing.

  The liquid crystal display device according to claim 5 of the present invention is characterized in that the detection signal is a light control switch of a vehicle.

  Usually, the driver of the vehicle switches the selected position by operating the light control switch according to the brightness around the vehicle. That is, the brightness around the vehicle can be determined by detecting the selected position of the light control switch.

  As a result, even if the brightness around the liquid crystal display device changes, the visibility of the liquid crystal display device is maintained at a satisfactory level while the total light emission luminance of the liquid crystal display device is changed suddenly. Therefore, a liquid crystal display device with good appearance can be provided.

  In this case, as in the liquid crystal display device according to claim 6 of the present invention, when the light control switch is switched from the off position to the vehicle width lamp position, the control device changes the total light emission luminance from the daytime total light emission luminance to the night total light emission. If the control device is configured to switch the total light emission luminance from the night total light emission luminance to the daytime total light emission luminance when the light control switch is switched from the vehicle width lamp position to the off position, the brightness around the liquid crystal display device Responding to changes in height, the visibility of the liquid crystal display is reliably maintained in an optimal state, and the sudden change in the total light emission brightness that occurs when switching the total light emission brightness of the liquid crystal display device is alleviated. Can be provided.

  The liquid crystal display device according to claim 7 of the present invention is characterized in that the detection signal is an output signal from an illuminance detection device that is installed in a vehicle and detects the illuminance outside the passenger compartment.

  According to the above configuration, the brightness around the vehicle can be accurately detected. As a result, even if the brightness around the liquid crystal display device changes, the visibility of the liquid crystal display device is maintained at a satisfactory level while the total light emission luminance of the liquid crystal display device is changed suddenly. Therefore, a liquid crystal display device with good appearance can be provided.

  In this case, as in the liquid crystal display device according to claim 8 of the present invention, when the illuminance calculated by the control device based on the output signal is less than the threshold illuminance that is a predetermined illuminance, If the total light emission at night is selected as the total light emission luminance, and the illuminance calculated by the control device based on the output signal is equal to or greater than the threshold illuminance, the control device should be configured to select the daytime total light emission luminance as the total light emission luminance. For example, while maintaining the visibility of the liquid crystal display in an optimum state in response to changes in the brightness around the liquid crystal display device, the momentary total light emission luminance that occurs when switching the total light emission luminance of the liquid crystal display device It is possible to provide a liquid crystal display device with good appearance by mitigating rapid changes.

  Hereinafter, embodiments of a liquid crystal display device according to the present invention will be described with reference to FIGS. 1 to 5 by taking as an example a case where the liquid crystal display device is applied to a combination meter 1 mounted in an automobile.

(First embodiment)
The combination meter 1 is arranged in an instrument panel in front of a driver's seat in a vehicle interior, and displays information necessary for driving the vehicle and information on operating states of various parts of the vehicle for the driver. The combination meter 1 includes a liquid crystal display 2 and displays all of the various information described above as an image formed on the liquid crystal display 2. In other words, the combination meter 1 includes only the liquid crystal display 2 as display means for displaying information.

  On the display screen of the liquid crystal display 2, as shown in FIG. 1, a speedometer S for instructing the traveling speed of the automobile, a tachometer T for instructing the rotational speed of the engine, a water temperature meter W for instructing the engine coolant temperature, A fuel meter F or the like that indicates the amount of remaining fuel in the fuel tank is formed.

  As the liquid crystal display 2, for example, a TFT (Thin Film Transistor) type dot matrix type liquid crystal panel is used. The liquid crystal display 2 is illuminated and displayed by a backlight 3 which is a light source disposed behind (right side in FIG. 2). More specifically, the backlight 3 is a liquid crystal display that emits light emitted from the light emitting diode (not shown) that converts supplied power into light and light emitted from the light emitting diode over the entire area of the liquid crystal display 2 with uniform brightness. And a light guide (not shown) led to the back of the device 2. The light guide is formed in a flat plate shape from a translucent material such as a colorless and transparent acrylic resin or polycarbonate resin. The planar shape of the light guide is substantially the same as the planar shape of the liquid crystal display 1, and the entire display screen of the liquid crystal display 2 is obtained by emitting light with uniform brightness over the entire surface of the light guide. Transmitted illumination with uniform brightness. The total light emission luminance that is the light emission luminance of the liquid crystal display 2 is formed as a combined output of both the backlight light emission luminance that is the light emission luminance of the backlight 3 and the drawing output of the liquid crystal display 2.

  Next, the electrical circuit configuration of the combination meter 1 according to the first embodiment of the present invention will be described based on the electrical circuit configuration diagram shown in FIG.

  As shown in FIG. 3, the combination meter 1 causes the backlight 3 to have a desired light emission luminance based on the first signal output from the liquid crystal display 2, the backlight 3, the controller 4, and the controller 4. The driving circuit 5 to be turned on, the drawing circuit 6 for driving the liquid crystal display 2 based on the second signal output from the controller 4, and the drawing for the driver to adjust the drawing output of the liquid crystal display 2 according to his / her preference The output adjuster 7, the brightness adjuster 8 for the driver to adjust the light emission brightness of the backlight 3 according to his / her preference, and the light control switch 9 for switching the lighting state of the automobile light. As shown in FIG. 3, the controller 4 is always supplied with power from the battery 11. In addition, as shown in FIG. 3, an ignition switch 10 is connected to the controller 4. When the ignition switch 10 is turned on and the vehicle is in an operating state, the controller 4 detects this via the ignition switch 10 and starts the display operation of the combination meter 1. In addition to the above-described components, the combination meter 1 includes a number of elements (not shown), such as a vehicle speed sensor that detects the traveling speed of an automobile, a rotation sensor that detects the engine rotation speed, and a water temperature sensor that detects the engine coolant temperature. A liquid level sensor for detecting the amount of remaining fuel in a fuel tank (not shown) is provided, and these elements are connected to the controller 4. However, since it is not directly related to the total light emission luminance control of the liquid crystal display 2 which is a feature of the present invention, the description is omitted.

  The controller 4 is composed of, for example, a microcomputer. The controller 4 is functionally composed of a first control unit 41 and a second control unit 42 as shown in FIG. A position signal as a detection signal is input from the light control switch 9 to the first control unit 41. The first control unit 41 determines a target total light emission luminance that is a total light emission luminance to be controlled by the liquid crystal display 2 based on the position signal, and also sets a target backlight light emission luminance and a target drawing corresponding to the target total light emission luminance. Determine the output. Then, the first control unit 41 outputs a first signal for setting the light emission luminance of the backlight to the target backlight light emission luminance to the drive circuit 5. The first control unit 41 outputs the determined target drawing output to the second control unit 42. When the target drawing output information is input from the first control unit, the second control unit 42 outputs a second signal for setting the drawing output of the liquid crystal display 2 as the target drawing output to the drawing circuit 6 based on the target drawing output information. To do.

  The drawing output adjuster 7 is operated by the driver in the daytime, that is, the drawing output when the light control switch 9 to be described later is selected in the off position, and at the night time, that is, the width of the light control switch 9 or the headlamp. The drawing output when selecting a position is set individually. As shown in FIG. 3, the selection signal from the drawing output adjuster 7 is input to the second control unit 42, and the second control unit 42 receives the selection signal and the target drawing output input from the first control unit 41. The second signal is output to the drawing circuit 6 based on the information.

  The brightness adjuster 8 is operated by the driver to operate the backlight emission brightness at daytime, that is, when the light control switch 9 described later is selected, and at night, that is, the position of the width of the light control switch 9 or the headlight. The backlight emission brightness when the lamp position is selected is set individually. As shown in FIG. 3, the selection signal from the brightness adjuster 8 is input to the first control unit 41, and the first control unit 41 receives the first signal based on the selection signal and the position signal from the light control switch 9. 1 signal is output to the drive circuit 5.

  The light control switch 9 has, for example, three positions of an off position, a vehicle width lamp position, and a headlight position, and one of the three types of signals corresponding to each position, that is, the detection signal is the controller 4. Thus, the controller 4 can recognize which position is selected in the light control switch 9.

  Next, the operation of the combination meter 1 according to the first embodiment of the present invention, particularly the total light emission luminance control operation of the liquid crystal display 2 will be described.

  As a premise for the explanation of the operation, the drawing output controller 7 is set to the daytime and nighttime drawing outputs, and the luminance controller 8 is set to the daytime and nighttime emission luminances at the values shown in the table of FIG. . As a result, the total light emission luminance of the liquid crystal display 2 during the daytime and at night is also set to the values shown in the table of FIG. Here, the daytime is when the light control switch 9 is in the off position, and the nighttime is when the light control switch 9 is in the vehicle width lamp position or the headlamp position. Therefore, when the light control switch 9 is switched between the off position and the vehicle width lamp position, the controller 4 performs control to switch the total light emission luminance of the liquid crystal display 2, but the light control switch 9 controls the vehicle width light position and When switched between the headlight positions, the controller 4 keeps the total light emission luminance of the liquid crystal display 2 in the night state. As described above, the controller 4 controls the total light emission luminance of the liquid crystal display 2 in accordance with the selected position of the light control switch 9. Therefore, even when it is daytime, the light control switch 9 is set to the vehicle width lamp position or the headlamp position when traveling in a tunnel or when it is raining and the clouds are thick and dark. Then, the total light emission luminance of the liquid crystal display 2 is set to the “night” state.

  Next, the overall light emission luminance control operation of the liquid crystal display 2 executed by the controller 4 will be described with reference to FIG. FIG. 5 shows a case where a vehicle passes through a tunnel during daytime. 5A shows the time transition of the selected position of the light control switch 9, FIG. 5B shows the time transition of the light emission luminance of the backlight 3, and FIG. 5C shows the time transition of the drawing output of the liquid crystal display 2. (D) is a timing chart showing the time transition of the total light emission luminance of the liquid crystal display 2 respectively.

  Hereinafter, the total light emission luminance control operation of the liquid crystal display 2 by the controller 4 of the combination meter 1 will be described with time. Since the surroundings are bright at daytime, the light control switch 9 is in the off position. Thereby, the controller 4 controls the total light emission luminance of the liquid crystal display 2 to the daytime mode. That is, as shown in FIGS. 5B and 5C, the backlight emission luminance is set to 100%, the drawing output is set to 10%, and the total emission luminance is 10% as shown in FIG. 5D. It has become.

  The car approached the tunnel entrance, and at time t10, the driver switched the light control switch 9 from the off position to the headlight position. Normally, the light control switch 9 is configured as a rotary rotary switch, and is arranged in the order of the off position, the vehicle width lamp position, and the headlamp position in the rotational operation direction. Therefore, when the driver operates the light control switch 9 from the off position to the headlamp position, the driver is always switched to the vehicle width lamp position. Accordingly, when the switching from the off position to the vehicle width lamp position is detected, the first control unit 41 of the controller 4 determines the target total light emission luminance, the target backlight light emission luminance, and the target drawing output of the liquid crystal display 2. Simultaneously output the first signal to the drive circuit 5 and the target drawing output information to the second control unit 42. The second control unit 42 receives the target drawing output information transmitted from the first control unit 41 and outputs a second signal to the drawing circuit 6. The first signal and the second signal are output simultaneously. When the driving circuit 5 receives the first signal, the backlight emission luminance is changed to 25% luminance as the nighttime backlight emission luminance which is the target backlight emission luminance, as shown in FIG. Over time. The switching of the backlight emission luminance ends at time t12 as shown in FIG. On the other hand, since the image display on the liquid crystal display 2 by the drawing circuit 6 is executed at a predetermined time interval, a delay time Td from when the drawing circuit 6 receives the second signal until the drawing output of the liquid crystal display 2 is switched. The drawing output of the liquid crystal display 2 is actually switched at time t11 as shown in FIG. 5C. Here, the switching time Tg> the delay time Td. During this delay time Td, the backlight emission luminance is decreasing, and thus the emission luminance is intermediate between 100% and 25%. The drawing output remains at 10%. Therefore, during the delay time Td, the total light emission luminance of the liquid crystal display 2 gradually decreases from the daytime total light emission luminance as shown in FIG. At time t11, the drawing output of the liquid crystal display 2 is switched to 100%, but the backlight emission luminance is still decreasing, and is an intermediate emission luminance between 100% and 25%. For this reason, at time t11, as shown in FIG. 5 (d), the total light emission luminance becomes a value slightly higher than 25%, which is the night total light emission luminance, and then gradually decreases, at time t12, that is, When the switching of the backlight emission luminance is completed, the normal night total emission luminance is 25%.

  After traveling through the tunnel in this state, the car approached the tunnel exit, and at time t12, the driver switched the light control switch 9 from the headlight position to the off position. Even in this operation, the headlight position, the vehicle width lamp position, and the off position are actually switched in this order. That is, the vehicle width lamp position is switched to the off position. In response to this, the first control unit 41 of the controller 4 determines the target total light emission luminance, the target backlight light emission luminance, and the target drawing output of the liquid crystal display 2, and sends the first signal to the drive circuit 5 and the second control. The target drawing output information is simultaneously output to the unit 42. The second control unit 42 receives the target drawing output information transmitted from the first control unit 41 and outputs a second signal to the drawing circuit 6. The first signal and the second signal are output simultaneously. When the drive circuit 5 receives the first signal, the backlight emission luminance is changed to 100% luminance as the daytime backlight emission luminance, which is the target backlight emission luminance, as shown in FIG. Over time. The switching of the backlight emission luminance ends at time t15 as shown in FIG. On the other hand, since the image display on the liquid crystal display 2 by the drawing circuit 6 is executed at a predetermined time interval, a delay time Td from when the drawing circuit 6 receives the second signal until the drawing output of the liquid crystal display 2 is switched. The drawing output of the liquid crystal display 2 is actually switched at time t14 as shown in FIG. Here, the switching time Tg> the delay time Td. During this delay time Td, the backlight emission luminance is increasing, and thus the intermediate emission luminance is between 25% and 100%. The drawing output remains at 100%. Therefore, during the delay time Td, the total light emission luminance of the liquid crystal display 2 gradually increases from the night total light emission luminance as shown in FIG. At time t14, the drawing output of the liquid crystal display 2 is switched to 10%, but the backlight emission luminance is still increasing and is an intermediate luminance between 100% and 25%. Therefore, at time t14, as shown in FIG. 5 (d), the total light emission luminance becomes a value slightly lower than 10%, which is the daytime total light emission luminance, and then gradually increases, at time t15, that is, When the switching of the backlight emission luminance is completed, the normal night total emission luminance is 10%.

  As described above, when the controller 4 switches the total light emission luminance of the liquid crystal display 2, that is, when switching from the daytime total light emission luminance to the night total light emission luminance and from the night total light emission luminance to the daytime total light emission luminance, the backlight emission is performed. The brightness is gradually changed to the target total light emission brightness. That is, as shown in FIG. 5B, it is gradually changed over the switching time Tg. As a result, the fluctuation range of the total light emission luminance in the delay time Td when the drawing circuit 6 receives the second signal and the drawing output switches to the target drawing output, and the switching that is the time required for the total light emission luminance to switch finally. The fluctuation range of the total light emission luminance at time Tg can be suppressed small. Therefore, it is possible to provide a liquid crystal display device having a good appearance by alleviating a problem that has occurred during the overall light emission brightness switching control of the liquid crystal display of the conventional liquid crystal display device, that is, a sudden change in the target overall light emission brightness. Can do.

  In the liquid crystal display device 1 according to the first embodiment of the present invention described above, the manner in which the backlight emission luminance changes during the overall emission luminance switching control is linear. That is, although the rate of change in backlight emission luminance is constant, it is not necessary to limit it to a constant value. For example, the change rate of the short time immediately after the start of switching and the short time immediately before the end of the switching may be set small, and the change rate of the time in the middle may be set large. Alternatively, the change rate may be changed in a curved line for a short time immediately after the start of switching and a short time immediately before the end of the switching, and may be changed linearly in the middle of the time.

(Second Embodiment)
In the liquid crystal display device 1 according to the first embodiment of the present invention described above, the first signal for switching the backlight emission luminance and the second signal for switching the drawing output are simultaneously transmitted and gradually changed. The control target is the backlight emission luminance. On the other hand, in the liquid crystal display device 1 according to the second embodiment of the present invention, the transmission timing of the first signal and the transmission timing of the second signal are not simultaneous, and after the delay time Tc elapses after the second signal transmission. While the first signal is transmitted, the controlled object to be gradually changed is set as a drawing output.

  The configuration of the liquid crystal display device 1 according to the second embodiment of the present invention is the same as that of the liquid crystal display device 1 according to the first embodiment of the present invention except for the above points. Below, the total light emission luminance control operation of the liquid crystal display 2 executed by the controller 4 will be described with reference to FIG. FIG. 6 shows a case where a vehicle passes through a tunnel during daytime. 6A shows the time transition of the selected position of the light control switch 9, FIG. 6B shows the time transition of the light emission luminance of the backlight 3, and FIG. 6C shows the time transition of the drawing output of the liquid crystal display 2. (D) is a timing chart showing the time transition of the total light emission luminance of the liquid crystal display 2 respectively.

  In the liquid crystal display device 1 according to the second embodiment of the present invention, the timing when the first control unit 41 transmits the first signal and the timing after the delay time Tc has elapsed since the second control unit 42 transmitted the second signal. It is said. In this embodiment, as shown in FIG. 6B, the delay time Tc is set equal to the delay time Td until the drawing output is switched. Further, the drawing output is switched to the target drawing output over a switching time Tf as shown in FIG. That is, the drawing circuit 6 starts to change after the delay time Td after receiving the second signal, and then reaches the target drawing output after the switching time Tf.

  The car approached the tunnel entrance, and at time t10, the driver switched the light control switch 9 from the off position to the headlight position. In this case, as in the case of the liquid crystal display device 1 according to the first embodiment described above, in actuality, switching is performed in the order of the off position → the vehicle width lamp position → the headlight position, and from the off position to the vehicle width lamp position. A switch has occurred. In response to this, the first control unit 41 of the controller 4 determines the target total light emission luminance, the target backlight light emission luminance, and the target drawing output of the liquid crystal display 2, and simultaneously outputs the target drawing output information to the second control unit 42. Output. The second control unit 42 receives the target drawing output information transmitted from the first control unit 41 and outputs a second signal to the drawing circuit 6. Further, the first control unit 41 outputs the first signal to the drive circuit 5 after the delay time Tc elapses after the second signal is output, that is, at time t11. Upon receiving the first signal, the drive circuit 5 switches the backlight emission luminance to 25% luminance as the nighttime backlight emission luminance which is the target backlight emission luminance. On the other hand, the drawing circuit 6 starts control at time t10, the drawing output gradually increases from time t11 after the delay time Td, and the drawing output is output at the target drawing output at time t12 after the switching time Tf from time t11. To reach.

  From the viewpoint of the driver, when the light control switch 9 is operated, it seems that the total light emission luminance of the liquid crystal display 2 gradually increases and stabilizes at a certain light emission luminance after a slight delay time Td after the operation. That is, there is no abrupt fluctuation of the total light emission luminance when the light control switch is operated in the conventional liquid crystal display device, and an extremely natural and good appearance is obtained.

  After traveling through the tunnel in this state, the car approached the tunnel exit, and at time t13, the driver switched the light control switch 9 from the headlight position to the off position. In response to this, the first control unit 41 of the controller 4 determines the target total light emission luminance, the target backlight light emission luminance, and the target drawing output of the liquid crystal display 2, and simultaneously outputs the target drawing output information to the second control unit 42. Output. The second control unit 42 receives the target drawing output information transmitted from the first control unit 41 and outputs a second signal to the drawing circuit 6. The first control unit 41 outputs the first signal to the drive circuit 5 after the delay time Tc has elapsed since the second signal was output, that is, at time t14. Upon receiving the first signal, the drive circuit 5 switches the backlight emission luminance to 100% luminance as the daytime backlight emission luminance, which is the target backlight emission luminance. On the other hand, the drawing circuit 6 starts control at time t13, and the drawing output gradually decreases from time t14 after the delay time Td, and the drawing output is output at the target drawing output at time t15 after the switching time Tf from time t14. To reach.

  From the viewpoint of the driver, when the light control switch 9 is operated, the total light emission luminance of the liquid crystal display 2 gradually decreases and stabilizes at a certain light emission luminance after a slight delay time Td after the operation. That is, there is no abrupt fluctuation of the total light emission luminance when the light control switch is operated in the conventional liquid crystal display device, and an extremely natural and good appearance is obtained.

  As described above, even with the liquid crystal display device 1 according to the second embodiment of the present invention, the instantaneous change of the target total light emission luminance that occurred during the total light emission luminance switching control of the liquid crystal display of the conventional liquid crystal display device can be detected. It can suppress and can provide the liquid crystal display device 1 of favorable appearance.

In addition, in the liquid crystal display device 1 according to the second embodiment of the present invention described above, the first signal for switching the backlight emission luminance has passed the delay time Tc after the second signal transmission for switching the drawing output. Instead of outputting, it may be configured to transmit simultaneously with the second signal and gradually change. That is, both the backlight emission luminance and the drawing output may be gradually changed.


As described above, when the controller 4 switches the total light emission luminance of the liquid crystal display 2, that is, when switching from the daytime total light emission luminance to the night total light emission luminance and from the night total light emission luminance to the daytime total light emission luminance, the backlight emission is performed. The brightness is gradually changed to the target total light emission brightness. That is, as shown in FIG. 5B, it is gradually changed over the switching time Tg. As a result, the fluctuation range of the total light emission luminance in the delay time Td when the drawing circuit 6 receives the second signal and the drawing output switches to the target drawing output, and the switching that is the time required for the total light emission luminance to switch finally. The fluctuation range of the total light emission luminance at time Tg can be suppressed small. Therefore, it is possible to provide a liquid crystal display device having a good appearance by alleviating a problem that has occurred during the overall light emission brightness switching control of the liquid crystal display of the conventional liquid crystal display device, that is, a sudden change in the target overall light emission brightness. Can do.

  In the combination meter 1 according to the first embodiment and the second embodiment of the present invention described above, the detection signal for the controller 4 to perform control for switching the total light emission luminance of the liquid crystal display 2 is used as the light control switch 9. However, instead of this, the output signal of an illuminance detector (not shown) for detecting the illuminance outside the vehicle may be used. In this case, the controller 4 calculates the illuminance outside the vehicle based on the output signal of the illuminance detector (not shown), and when the calculated illuminance is less than the threshold illuminance that is a predetermined illuminance, the controller 4 The night total light emission luminance may be selected as the target total light emission luminance, and the controller 4 may be configured to select the daytime total light emission luminance as the target total light emission luminance when the calculated illuminance is equal to or greater than the threshold illuminance.

It is a front view of the combination meter 1 by 1st Embodiment of this invention. It is the II-II sectional view taken on the line in FIG. 2 is a schematic diagram for explaining an electric circuit configuration of the combination meter 1. FIG. It is a list explaining the setting conditions of various parameters related to the total light emission luminance control of the liquid crystal display 2 of the combination meter 1. (A) shows the time transition of the selected position of the light control switch 9, (b) shows the time transition of the light emission luminance of the backlight 3, and (c) shows the time transition of the drawing output of the liquid crystal display 2. (D) is a timing chart which shows the time transition of the total light emission luminance of the liquid crystal display 2 respectively. (A) shows the time transition of the selected position of the light control switch 9, (b) shows the time transition of the light emission luminance of the backlight 3, and (c) shows the time transition of the drawing output of the liquid crystal display 2. (D) is a timing chart which shows the time transition of the total light emission luminance of the liquid crystal display 2 respectively.

Explanation of symbols

1 Combination meter (liquid crystal display)
2 Liquid crystal display 3 Backlight (light source)
4 Controller (control means)
41 1st control part 42 2nd control part 5 Drive circuit 6 Drawing circuit 7 Drawing output controller 8 Brightness controller 9 Light control switch 10 Ignition switch 11 Battery F Fuel meter S Speedometer T Tachometer Tc Delay time Td Delay time Tg Switching Time Tf Switching time t10 to t15 Time W Water temperature gauge

Claims (8)

A liquid crystal display,
A backlight for transmitting and illuminating the liquid crystal display disposed on the back side of the liquid crystal display;
A drawing circuit that drives the liquid crystal display to cause the liquid crystal display to perform a drawing operation;
A driving circuit for driving the backlight so that the backlight performs a light emitting operation;
Control means for adjusting a total light emission luminance that is a light emission luminance with respect to the outside of the liquid crystal display by changing a light emission luminance of the backlight and a drawing output of the liquid crystal display;
The control means determines a target total light emission luminance that is a total light emission luminance to be realized in response to a change in a detection signal inputted from the outside, and emits the backlight for realizing the target total light emission luminance. Determining a target backlight emission luminance as a luminance and a target drawing output as a drawing output of the liquid crystal display;
The control means outputs a first signal for switching the emission luminance of the backlight to the target backlight emission luminance to the drive circuit,
The control means outputs a second signal for switching the drawing output of the liquid crystal display to the target drawing output to the drawing circuit,
The drive circuit receives the first signal and changes the backlight emission luminance, and the drawing circuit receives the second signal and changes the drawing output,
The liquid crystal display device, wherein the driving circuit gradually changes the backlight emission luminance to the target backlight emission luminance when receiving the first signal.   The liquid crystal display device according to claim 1, wherein the drawing circuit gradually changes the drawing output to the target drawing output when receiving the second signal. A liquid crystal display,
A backlight for transmitting and illuminating the liquid crystal display disposed on the back side of the liquid crystal display;
A drawing circuit that drives the liquid crystal display to cause the liquid crystal display to perform a drawing operation;
A drive circuit for driving the backlight to perform a light emission operation;
Control means for adjusting a total light emission luminance that is a light emission luminance with respect to the outside of the liquid crystal display by changing a light emission luminance of the backlight and a drawing output of the liquid crystal display;
The control means determines a target total light emission luminance that is a total light emission luminance to be realized in response to a change in a detection signal inputted from the outside, and emits the backlight for realizing the target total light emission luminance. Determining a target backlight emission luminance as a luminance and a target drawing output as a drawing output of the liquid crystal display;
The control means outputs a first signal for switching the emission luminance of the backlight to the target backlight emission luminance to the drive circuit,
The control means outputs a second signal for switching the drawing output of the liquid crystal display to the target drawing output to the drawing circuit,
The drive circuit receives the first signal and changes the backlight emission luminance, and the drawing circuit receives the second signal and changes the drawing output,
The control means outputs the first signal after a predetermined time has elapsed after outputting the second signal,
The drawing circuit, when receiving the second signal, gradually changes the drawing output to the target drawing output.   When the detection signal is input, the control unit determines the target total light emission luminance, the target light emission luminance, and the target drawing output based on the detection signal, and outputs the first signal to the drive circuit. And a second control unit that performs display image control of the liquid crystal display and outputs the second signal to the drawing circuit based on the target drawing output determined by the first control unit. The liquid crystal display device according to any one of claims 1 to 3.   The liquid crystal display device according to claim 1, wherein the detection signal is a light control switch of a vehicle. When the light control switch is switched from the off position to the vehicle width lamp position, the control device switches the total light emission luminance from the daytime total light emission luminance to the night total light emission luminance,
6. The control device according to claim 5, wherein when the light control switch is switched from a vehicle width lamp position to an off position, the control device switches the total light emission luminance from the night total light emission luminance to the daytime total light emission luminance. Liquid crystal display device.   The liquid crystal display device according to any one of claims 1 to 4, wherein the detection signal is an output signal from an illuminance detection device that is installed in a vehicle and detects illuminance outside the passenger compartment. When the illuminance calculated by the control device based on the output signal is less than a threshold illuminance that is a predetermined illuminance, the control device selects the night total light emission luminance as the total light emission luminance,
The control device selects the daytime total light emission luminance as the total light emission luminance when the illuminance calculated by the control device based on the output signal is equal to or greater than the threshold illuminance. The liquid crystal display device described.

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