JP2013205726A - Display control circuit, display control method and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a reduction in display quality caused by application of a reset voltage to liquid crystal elements.SOLUTION: A display control circuit 10 controls a liquid crystal display device 1 that has a liquid crystal panel 100 including a plurality of pixels 110 individually having liquid crystal elements and drive circuits, a scan line drive circuit 130 and a data line drive circuit 140, for applying voltages to the liquid crystal elements corresponding to respective ones of the plurality of pixels 110. The display control circuit 10 comprises a control circuit 20 that, in a predetermined reset period, applies a first reset voltage for changing brightness of the pixels 110 in one-direction to the liquid crystal elements corresponding to the pixels 110 for at least a period until when the brightness corresponds to the first reset voltage, subsequently applies a second reset voltage for changing the brightness of the pixels 110 in an opposite direction in a remaining period and, subsequent to the reset period, controls the scan line drive circuit 130 and the data line drive circuit 140 so as to apply a voltage in response to a video signal specifying the brightness of each of the pixels 110 to the liquid crystal elements corresponding to the respective pixels 110.

Description

  The present invention relates to reset driving of a liquid crystal element.

  A display device provided with a liquid crystal or the like subdivides one field into a plurality of subfields, and performs gradation display by applying an on voltage or an off voltage to each pixel (liquid crystal element) in each subfield. (For example, Patent Document 1).

JP 2003-114661 A

  When the display image is rewritten for each field (for example, every frame) in the display device, the display image in the current field changes under the influence of the display image in the previous field, which may cause a deterioration in display quality. is there. In the case of subfield driving, the on-voltage on the high voltage side and the off-voltage on the low voltage side may be applied to the liquid crystal element, but the same in the current field depending on how the on-voltage and off-voltage are applied in the previous field. Even when a pixel is driven by a subfield code, the response state of the liquid crystal element is different. If the response state in the current field is different, the time integral value of the transmittance is also different, so that the subfield driving of the previous field affects the display image of the current field.

In order to suppress such influence of the previous field, reset driving for aligning the alignment state of the liquid crystal element in each field may be performed before rewriting the display image. However, when the so-called white reset driving is performed and the liquid crystal elements are aligned in the white state (transmittance or reflectance is 100%), the VA liquid crystal is white to black (transmittance or reflectivity is 0%). Since the response time for changing to a long time is long, black display is insufficient in the next field, and the display contrast may be lowered. On the other hand, when the so-called black reset driving is performed and the liquid crystal elements are aligned in the black state, the VA liquid crystal starts the response from the state in which the liquid crystal molecules are vertically aligned in the next field. The peak luminance may be lowered due to the decrease in the brightness. Such deterioration in display quality caused by reset driving is not limited to subfield driving, and may be a problem when a voltage is applied to a liquid crystal element according to a voltage modulation method or when a TN liquid crystal is used.
The present invention has been made in view of the above-described circumstances, and one of its purposes is to suppress display quality degradation caused by application of a reset voltage to a liquid crystal element.

To achieve the above object, a display control circuit according to the present invention includes a display unit including a plurality of pixels each having a liquid crystal element, and a drive circuit that applies a voltage to the liquid crystal element corresponding to each pixel of the plurality of pixels. A display control circuit that controls a display device having a first reset voltage that changes the brightness of the pixels in one direction in the liquid crystal elements corresponding to the plurality of pixels in a predetermined reset period. After applying at least a period until the brightness corresponding to the first reset voltage is reached, a second reset voltage is applied to change the brightness of the pixel in the opposite direction in the remaining period, and following the reset period, And a controller that controls the drive circuit so as to apply a voltage corresponding to a video signal designating brightness for each pixel to the liquid crystal element corresponding to each pixel. .
According to the present invention, in the reset period, the alignment state of the liquid crystal element is set according to the first reset voltage by applying the first reset voltage, and the alignment state of the liquid crystal element is controlled by applying the second reset voltage in the remaining period. Since display based on the video signal can be performed after that, it is possible to suppress deterioration in display quality caused by application of a reset voltage to the liquid crystal element.

In the present invention, the response time of the liquid crystal element when the second reset voltage is switched to the first reset voltage is the response time of the liquid crystal element when the first reset voltage is switched to the second reset voltage. May be shorter.
According to the present invention, even when a sufficiently long period cannot be secured as the reset period, the liquid crystal element can be aligned in accordance with the first reset voltage within the reset period.

In the present invention, the control unit is configured such that the response time of the liquid crystal element when the second reset voltage is switched to the first reset voltage, and the response time when the first reset voltage is switched to the second reset voltage. When any of the response times of the liquid crystal elements is shorter than the reset period, the second reset voltage is applied to change the pixel in the brightening direction after applying the first reset voltage to change the pixel in the darkening direction. May be applied.
According to the present invention, when either the first reset voltage or the second reset voltage can achieve the alignment state of the liquid crystal element according to the reset voltage within the reset period, the display contrast is preferentially reduced. Can be suppressed.

In the present invention, the control unit may make the application period of the second reset voltage shorter than the response time of the liquid crystal element when the first reset voltage is switched to the second reset voltage. .
According to the present invention, since the alignment state is closer to the application of the first reset voltage than the alignment state of the liquid crystal element according to the second reset voltage, it is possible to easily achieve the alignment state according to the video signal.

In the present invention, the control unit may apply a voltage corresponding to the video signal to each pixel according to a subfield driving method.
According to the present invention, it is possible to suppress deterioration in display quality caused by application of a reset voltage to a liquid crystal element while suppressing influence of subfield driving based on a video signal.

In the present invention, the control unit includes a first display period for displaying a right-eye image in 3D video display on the display unit and a second display period for displaying a left-eye image in 3D video display on the display unit. And applying a voltage according to the video signal, and applying the first reset voltage and the second reset voltage in the reset period provided between the first display period and the second display period, respectively. You may do it.
According to the present invention, when a 3D image is displayed by alternately switching between a right-eye image and a left-eye image, the right-eye image enters the user's left eye or the left-eye image enters the user's right eye. The occurrence of crosstalk can be suppressed.

  The present invention can be conceptualized as a display control method and an electronic device in addition to a display control circuit.

1 is a block diagram showing an overall configuration of a liquid crystal display device according to a first embodiment. The figure which shows the equivalent circuit in a liquid crystal panel. The figure which shows the structure of the subfield in the case of displaying 3D image | video. Explanatory drawing of operation | movement of the scanning line drive circuit and data line drive circuit which concern on the embodiment. The flowchart which shows the flow of operation | movement of the control circuit which concerns on the same embodiment. Explanatory drawing of the reset drive which concerns on the same embodiment. Explanatory drawing of operation | movement of the scanning line drive circuit and data line drive circuit which concern on 2nd Embodiment. Explanatory drawing of the reset drive which concerns on the same embodiment. The figure which shows the projector to which the liquid crystal display device which concerns on each embodiment is applied. Explanatory drawing of reset drive including only white reset drive. Explanatory drawing of reset drive including only black reset drive.

Embodiments of the present invention will be described below with reference to the drawings.
<First Embodiment>
First, a first embodiment of the present invention will be described.
FIG. 1 is a block diagram showing the overall configuration of the liquid crystal display device according to the embodiment. The liquid crystal display device 1 is a display device that displays a 3D image that allows a user to perceive a 3D image with the 3D glasses 60 on. As shown in FIG. 1, the liquid crystal display device 1 includes a display control circuit 10, a transmission unit 50, and a liquid crystal panel 100. More specifically, the display control circuit 10 includes a control circuit 20, a memory 30, and a conversion unit 40.

The control circuit 20 is a control unit that controls each unit of the liquid crystal display device 1 in synchronization with a vertical scanning signal Vs, a horizontal scanning signal Hs, and a dot clock signal Clk supplied from a host device (not shown).
The memory 30 has a storage area corresponding to each of the pixels 110 arranged in vertical m rows × horizontal n columns, and each storage area stores a video signal Vid corresponding to each pixel 110. The video signal Vid is digital data that designates the brightness (that is, the gradation level) of the pixel 110 with 8 bits. Here, the video signal Vid specifies that the pixel 110 is brighter as the gradation level is higher, and that the pixel 110 is darker as the gradation level is lower.
The video signal Vid is stored in the storage area corresponding to the pixel by the control circuit 20, while data corresponding to the pixel to be scanned in the liquid crystal panel 100 is read from the memory 30 as display data Da.

The conversion unit 40 converts the display data Da read from the memory 30 into the pixel 110 according to the subfield defined by the gradation level specified by the display data Da and the data sfn supplied by the control circuit 20. It is converted into a display bit Db that designates whether (liquid crystal element) is turned on or off.
Note that when displaying 3D video, two video signals Vid corresponding to the left-eye image and the right-eye image with parallax are supplied in, for example, time division, so that the image displayed on the liquid crystal panel 100 is for the right eye. The storage / reading to / from the memory 30 and the conversion by the conversion unit 40 are controlled in accordance with whether it is for the left eye or the left eye.

  In addition, the conversion unit 40 outputs a display bit Db that specifies whether to turn on or off the pixel 110 in accordance with the reset signal RES supplied from the control circuit 20. The reset signal RES is a signal that is output when the liquid crystal element 120 is reset by the control circuit 20. When the conversion signal 40 is supplied with a reset signal REsw for instructing white reset driving for setting all the pixels 110 (liquid crystal elements 120) in the display area 101 to a white state (that is, setting them to the all white state), these pixels 110 are displayed. Is turned on, and all pixels 110 (liquid crystal element 120) in the display region 101 are set to a black state (that is, set to the all black state), and when a reset signal RESb instructing black reset driving is supplied, these pixels 110 are turned on. Turn off. Details of the reset driving will be described later.

  The liquid crystal panel 100 is a display unit in which a plurality of pixels 110 are arranged in a matrix in the display region 101. More specifically, in the display area 101, m rows of scanning lines 112 extend in the X (horizontal) direction in the figure, while n columns of data lines 114 are electrically insulated from the scanning lines 112, while FIG. 1 extends in the Y (vertical) direction (m and n are both natural numbers). Pixels 110 are provided so as to correspond to the intersections of the scanning lines 112 and the data lines 114. In the present embodiment, the pixels 110 are arranged in a matrix of vertical m rows × horizontal n columns.

FIG. 2 is a diagram showing an equivalent circuit in the liquid crystal panel 100.
As shown in FIG. 2, the liquid crystal panel 100 has a configuration in which liquid crystal elements 120 each having a liquid crystal 105 sandwiched between a pixel electrode 118 and a common electrode 108 are arranged corresponding to the intersection of a scanning line 112 and a data line 114. . In the equivalent circuit in the liquid crystal panel 100, as shown in FIG. 2, an auxiliary capacitor (storage capacitor) 125 is provided in parallel with the liquid crystal element 120. The auxiliary capacitor 125 has one end connected to the pixel electrode 118 and the other end commonly connected to the capacitor line 115. The capacitor line 115 is maintained at a constant voltage over time.
Here, when the scanning line 112 becomes H level, the TFT 116 having the gate electrode connected to the scanning line is turned on, and the pixel electrode 118 is connected to the data line 114. Therefore, when a data signal having a voltage corresponding to the gradation is supplied to the data line 114 when the scanning line 112 is at the H level, the data signal is applied to the pixel electrode 118 via the turned-on TFT 116. When the scanning line 112 becomes L level, the TFT 116 is turned off, but the voltage applied to the pixel electrode 118 is held by the capacitive element of the liquid crystal element 120 and the auxiliary capacitor 125.
In the liquid crystal element 120, the molecular alignment state of the liquid crystal 105 changes according to the electric field generated by the pixel electrode 118 and the common electrode 108. For this reason, if the liquid crystal element 120 is a transmission type, it has a transmittance corresponding to the applied / holding voltage. In the liquid crystal panel 100, since the transmittance varies for each liquid crystal element 120, the liquid crystal element 120 corresponds to a pixel.
Note that in this embodiment, the liquid crystal 105 is a VA liquid crystal, and a normally black mode in which the liquid crystal element 120 is in a black state when no voltage is applied.

Returning to FIG.
The scanning line driving circuit 130 sequentially shifts the start pulse Dy supplied from the control circuit 20 in accordance with the clock signal Cly, and supplies the scanning signal G1, G2, G3, G4,..., Gm are supplied.
The data line driving circuit 140 sequentially samples the display bit Db converted by the conversion unit 40 using the clock signal Clx and converts the display bit Db into a voltage having the polarity specified by the polarity specifying signal Pol. , Dn are supplied as data signals d 1, d 2, d 3, d 4, d 5,.

The polarity designation signal Pol supplied from the control circuit 20 is a signal that designates the writing polarity to the pixel (the liquid crystal element 120). For example, if it is H level, it designates positive writing, and if it is L level, it designates negative polarity. Specifies sex writing. Here, regarding the writing polarity, the case where the pixel electrode 118 is higher than the common electrode 108 is positive, and the case where the pixel electrode 118 is lower is negative.
A driving circuit in the liquid crystal display device 1 is realized by the cooperation of the scanning line driving circuit 130 and the data line driving circuit 140.

The transmission unit 50 transmits the control signal R (/ L) supplied from the control circuit 20 to the 3D glasses 60 by, for example, infrared communication. The control signal R (/ L) is a control signal indicating whether the display period of the right-eye image (first period) or the display period of the left-eye image (second period) is displayed when displaying the 3D video. . In the 3D glasses 60, the lens part of the right eye is a liquid crystal shutter 62R, and the lens part of the left eye is a liquid crystal shutter 62L. The liquid crystal shutters 62R and 62L are controlled to a transmission state or a non-transmission state, respectively, according to a control signal R (/ L) received by the reception unit 61. Specifically, during the display of 3D video, the liquid crystal shutter 62R is in a transmissive state, the liquid crystal shutter 62L is in a non-transmissive state during a right eye opening period, which will be described later, and the liquid crystal shutter 62R is in a non-transmissive state during a left eye opening period. Thus, the liquid crystal shutter 62L is in a transmissive state. During the other periods, the liquid crystal shutters 62R and 62L are both impermeable.
When the liquid crystal display device 1 displays a 2D video, both the liquid crystal shutters 62R and 62L are in a transmissive state regardless of the control signal R (/ L).

FIG. 3 is a diagram illustrating a configuration of subfields when 3D video is displayed in the present embodiment. FIG. 4 is a diagram for explaining the operation of the scanning line driving circuit 130 and the data line driving circuit 140 of this embodiment.
In the present embodiment, the frequency of the vertical scanning signal Vs is assumed to be 240 Hz, and the liquid crystal display device 1 divides one frame equally into four fields as shown in FIGS. The so-called quadruple speed driving for scanning the scanning lines is realized. The liquid crystal display device 1 displays an image of one frame corresponding to the video signal Vid supplied at a supply speed of 60 Hz from the host device by driving the liquid crystal panel 100 at a drive speed of 240 Hz. Here, one frame means a period during which the video signal Vid for one cut (frame) is supplied from the host device or a period required for the liquid crystal panel 100 to display an image for one cut. If the frequency of the scanning signal Vs is 60 Hz, it becomes 16.67 milliseconds for one period. Therefore, the period of one field corresponds to a ¼ frame period, which is approximately 4.16 milliseconds here.

  Here, assuming that four fields included in one frame are a first field, a second field, a third field, and a fourth field in chronological order, the liquid crystal panel 100 is used for the second field and the fourth field in 3D video display. This corresponds to a display period for displaying an image. More specifically, the second field is the left eye opening period assigned to display the left eye image, and the fourth field is the right eye opening period assigned to display the right eye image. Each of the second field and the fourth field is divided into a plurality of subfields (for example, 20 subfields having the same period length). When an image is displayed using the liquid crystal panel 100, on / off of each subfield is controlled according to the gradation level specified by the display data Da, and a voltage corresponding to the gradation level is applied to the liquid crystal element 120. .

  A well-known method can be adopted for gradation expression using subfields, for example, a method disclosed in Japanese Patent Laid-Open No. 2003-114661 (see Patent Document 1). The polarity designation signal Pol supplied from the control circuit 20 designates positive polarity writing in the first and second fields, and designates negative polarity writing in the third and fourth fields, for example. In this case, the liquid crystal panel 100 inverts the writing polarity every two fields and writes data to the pixels 110.

On the other hand, in the 3D video display, the first field and the third field correspond to a reset period for reset driving the pixel 110 (liquid crystal element 120). The reset period is provided between the left eye opening period and the right eye opening period, and the period is determined in advance. Specifically, the liquid crystal display device 1 displays an image based on the video signal Vid using the liquid crystal panel 100 in the left eye opening period and the right eye opening period provided after the reset period.
Here, an overall operation flow of the liquid crystal display device 1 will be described.

FIG. 5 is a flowchart showing an operation flow of the control circuit 20.
First, the control circuit 20 determines whether it is either the left eye opening period or the right eye opening period (step S1). When it is determined that the 3D video corresponding to the video signal Vin is displayed in the left eye opening period or the right eye opening period, the control circuit 20 determines “YES” in the process of step S1. If “YES” is determined in the process of step S1, the control circuit 20 applies a voltage corresponding to the gradation level specified by the video data Vid to the liquid crystal element 120 corresponding to each pixel 110, and 3D based on the video data Vid. The liquid crystal panel 100 is controlled to display an image (step S2). Here, the control circuit 20 reads the display data Da from the memory 30 in which the video signal Vid is stored, supplies the display data Da to the conversion unit 40, converts the display data Da into the display bit Db by the conversion unit 40, and the data line driving circuit. The display bit Db is supplied to 140. The data line driving circuit 140 applies an on voltage or an off voltage to the liquid crystal element 120 corresponding to each pixel 110 according to the supplied display bit Db.

On the other hand, when the control circuit 20 determines that it is neither the left eye opening period nor the right eye opening period (step S1; NO), the liquid crystal element 120 is reset in the reset period (step S3). The control circuit 20 supplies the reset signal RESw or RESb to the conversion unit 40 in the reset period, and sets the display area 101 in the all white state or the all black state by the display bit Db supplied from the conversion unit 40 to the data line driving circuit 140. A reset voltage is applied to the liquid crystal element 120.
For example, the control circuit 20 repeatedly executes the above processing steps in a period during which the liquid crystal display device 1 is powered on.
Next, reset driving performed in the liquid crystal display device 1 will be described.

FIG. 6 is a diagram for explaining reset driving according to the present embodiment, and shows a time-series change in the transmittance of the liquid crystal element 120 in one frame. In the following description, at time t = t0, it is assumed that the liquid crystal element 120 is in a black state with a transmittance of 0% due to the application of the off voltage in the immediately preceding subfield drive.
As shown in FIGS. 4 and 6, the control circuit 20 divides the reset period into two periods and applies a reset voltage dH (first reset voltage) for white reset driving to the liquid crystal element 120. Then, the liquid crystal panel 100 is controlled so that a reset voltage dL (second reset voltage) for performing black reset driving is applied to the liquid crystal element 120. The white reset driving is reset driving in which the display area 101 of the liquid crystal panel 100 is changed to the all white state, that is, the direction in which all the pixels 110 are brightened (one direction) to change the transmittance to 100%. The reset voltage dH is, for example, the highest voltage at which the pixel electrode 118 and the common voltage LCcom are used for gradation expression. On the other hand, the black reset drive is a reset drive in which the display area 101 of the liquid crystal panel 100 is changed to the all black state, that is, all the pixels 110 are darkened (opposite direction) to make the transmittance 0%. The reset voltage dL corresponds to, for example, an applied voltage in which the pixel electrode 118 and the common voltage LCcom have the same potential, and is the lowest voltage used for gradation expression.
Hereinafter, a specific procedure of reset driving will be described.

First, the control circuit 20 supplies the conversion unit 40 with a reset signal REsw instructing white reset driving at time t = t0. Then, the control circuit 20 supplies the conversion unit 40 with a reset signal RESb instructing black reset driving at time t = tb1 after the response of the liquid crystal element 120 to the white state is completed (that is, the white state is reached). To do. Then, the control circuit 20 instructs the conversion unit 40 to stop the black reset driving at t = t1, which is the end time of the reset period. As shown in FIG. 6, in the liquid crystal element 120, the response from the black state to the white state is completed by applying the reset voltage dH corresponding to the white reset drive, and the black reset drive is performed in the remaining period of the reset period. A reset voltage dL corresponding to is applied. On the other hand, at time t = t1 when the reset period ends, the liquid crystal element 120 is in the process of changing from the white state to the black state, and the response to the black state is not completed. It is assumed that the transmittance of the liquid crystal element 120 at time t = t1 is δ ₁ [%] (for example, 5%) which is slightly higher than 0% in the black state.

In the VA liquid crystal, the response time when changing from the black state to the white state is generally shorter than the response time when changing from the white state to the black state. Therefore, the longest response time of the liquid crystal element 120 when the reset voltage dH for turning the liquid crystal element 120 into the white state is applied is that of the liquid crystal element 120 when the reset voltage dL corresponding to the black reset driving is applied. It can be considered that it is shorter than the longest response time. Here, the longest response time of the liquid crystal element 120 when the reset voltage dH for applying the white state is applied is the response time T1 (here, T1 for changing the black state liquid crystal element 120 to the white state). = 2 milliseconds)). Further, the longest response time of the liquid crystal element 120 when the reset voltage dL for applying the black state is applied is the response time T2 for changing the white state liquid crystal element 120 to the black state (here, T2 = 5 ms)).
The control circuit 20 of the present embodiment satisfies the relationship of response time T1 <reset period (here, 4.16 milliseconds) <response time T2, and because the response time T1 is shorter than the reset period, , The white reset driving is performed first, and after the response of the liquid crystal element 120 to the white state is completed, the black reset driving is performed in the remaining period. Next, the basis for such reset driving will be described.

First, the white reset driving performed first in the reset period is performed so that the response of the liquid crystal element 120 to the white state is completed within the reset period. As a result, the display area 101 becomes an all white state within the reset period, and the alignment state of the liquid crystal element 120 is aligned with the white state. Therefore, the period during which the white reset driving is performed is the response time T1 or more, and is a period of time until the liquid crystal element 120 is at least in the white state. The period during which the white reset driving is performed may be, for example, 2 milliseconds corresponding to the response time T1, but may be longer than the response time T1, for example, 3 milliseconds.
Next, since the response time T2 is shorter than the remaining period of the reset period (or the reset period), the black reset drive performed following the white reset drive is terminated before the display area 101 becomes the all black state. . When this black reset driving is performed, the alignment state of the liquid crystal element 120 does not become a black state, but is aligned with an alignment state having a slightly higher transmittance δ ₁ [%] than the black state. Furthermore, since the alignment state of the liquid crystal element 120 is shifted to the next display period (that is, the left eye opening period) in a state where the transmittance is δ ₁ [%], the transmittance δ ₁ [%] is initially set in the left eye opening period. As a state, a voltage having a gradation level corresponding to the video signal Vid is applied to the liquid crystal element 120.

  As shown in FIG. 10, if white reset driving is performed in the entire reset period, the response of the liquid crystal element 120 to the white state may be completed within the reset period. In this case, even when a voltage corresponding to the transmittance in the black state or a state close to the black state is applied to the liquid crystal element 120 in the display period (that is, the left eye opening period) after the reset period, the target transmittance is higher than the target transmittance. May be high. This is because, as described above, it takes a certain amount of time for the liquid crystal element 120 in the white state to respond to the black state or a state close to the black state. In this case, even when black display or display close to black display is desired based on the video signal Vid, the transmittance becomes higher than the target transmittance, and so-called black floating may occur. This black float may cause a reduction in display quality such as a decrease in display contrast of the liquid crystal panel 100.

On the other hand, according to the reset driving of the present embodiment, the control circuit 20 performs black reset driving in the remaining period after performing white reset driving in the reset period, whereby the display period (left eye) next to the reset period is set. In the open period), the transmittance of the liquid crystal element 120 can be lowered to δ ₁ [%]. As a result, black floating is less likely to occur than when only black reset driving is performed (see hatched portions in FIGS. 6 and 10). Therefore, a reduction in display quality that the display contrast of the liquid crystal panel 100 is reduced by reset driving performed by the control circuit 20 can be suppressed.

The control circuit 20 performs the reset driving in the above-described procedure even in the reset period before the right eye opening period after displaying the image based on the video signal Vid in the left eye opening period. Also here, the control circuit 20 supplies the reset signal REsw for performing the white reset driving at the time t = t2, and the black reset is performed at the time t = tb2 after the response time T1 from the time t = t2. Switching to the reset signal RESb for driving, black reset driving is performed until time t = t3. Also in this case, the liquid crystal element 120 is aligned in the white state at time t = tb2, and the alignment state of the liquid crystal element 120 is substantially in the transmittance δ ₁ [%] state at t = t3, which is the end time of the reset period. As a result, for the same reason as the left eye opening period, it is possible to suppress a reduction in display quality such that the display contrast of the liquid crystal panel 100 is reduced during the right eye opening period from time t = t3 to t = t4.

  In the present embodiment, the control circuit 20 performs black reset driving in the remaining period after performing white reset driving, because this satisfies the relationship of response time T1 <response time T2. In this way, the control circuit 20 performs reset driving with a shorter response time first, so that it is sufficient as a reset period in order to avoid a decrease in the number of gradations that can be expressed by, for example, the subfield driving method (digital driving). Even when the length period cannot be secured, the liquid crystal element 120 can be aligned in accordance with the reset voltage within the reset period.

  Also, when 3D images are displayed by alternately switching between the right eye image and the left eye image, the right eye image enters the user's left eye or the left eye image enters the user's right eye. It is necessary to suppress the occurrence. In order to suppress the occurrence of the crosstalk, in the 3D display of the voltage modulation method (analog driving) in which an analog voltage corresponding to a target gradation is applied to the liquid crystal element 120, for example, two images are displayed in the first half of the display period. There are cases where writing is repeated repeatedly and the 3D glasses are opened in the second half period. On the other hand, in the sub-field driving method, the optical response speed changes according to the initial state of the liquid crystal element 120 in the display period. Therefore, the method of repeatedly writing the same image multiple times is affected by the previous field, It is not sufficient to suppress crosstalk. On the other hand, in the liquid crystal display device 1 of the present embodiment, by performing the reset driving described above, in the image display in the right eye opening period, it is possible to suppress the influence of the left eye opening period that precedes it, and in the next frame. In the image display in the left eye opening period, the influence of the right eye opening period preceding it can be suppressed. Therefore, according to the liquid crystal display device 1, it is possible to suppress the display of the right-eye image and the display of the left-eye image from affecting each other, so that it is possible to suppress the display quality from being degraded due to the occurrence of crosstalk.

Second Embodiment
Next, a second embodiment of the present invention will be described.
The liquid crystal display device 1 of the present embodiment performs a white reset for changing the pixel 110 in the direction of brightening (opposite direction) after performing the black reset driving for changing the pixel 110 in the direction of darkening (one direction) in the reset period. It differs from the configuration of the first embodiment described above in that it is driven. However, in this embodiment, the response time T1 for changing the black liquid crystal element 120 to the white state is set to 2 milliseconds, and the response time T2 for changing the white liquid crystal element 120 to the black state is 3 milliseconds. Seconds. That is, in this embodiment, it is assumed that the relationship of response time T1 <response time T2 <reset period (here 4.16 milliseconds) is satisfied.
Next, reset driving performed by the control circuit 20 of the present embodiment during the reset period will be described. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 7 is a diagram for explaining the driving operation of the scanning line driving circuit 130 and the data line driving circuit 140 of this embodiment. Also in this embodiment, when the 3D image is displayed, the liquid crystal display device 1 uses the second field as the left eye opening period assigned to display the left-eye image, and assigns the fourth field to display the right-eye image. The right eye opening period is set, and the first field and the third field are set as the reset period.

FIG. 8 is a diagram illustrating reset driving according to the present embodiment, and shows a time-series change in the transmittance of the liquid crystal element 120 in one frame. In the following description, at time t = t0, it is assumed that the liquid crystal element 120 is in a white state with a transmittance of 100% due to the application of the on-voltage in the immediately preceding subfield drive.
As shown in FIGS. 7 and 8, the control circuit 20 divides the reset period into two periods and applies a reset voltage dL (first reset voltage) for performing black reset driving to the liquid crystal element 120. Then, the reset signal RES is supplied to the conversion unit 40 so that the reset voltage dH (second reset voltage) for performing white reset driving is applied to the liquid crystal element 120. The reset voltages dL and dH may be the same voltages as those in the first embodiment described above.
Hereinafter, a specific procedure of reset driving will be described.

First, the control circuit 20 supplies the conversion unit 40 with a reset signal RESb instructing black reset driving at time t = t0. Then, at time t = tw1, which is after the response to the black state of the liquid crystal element 120 is completed (that is, after the black state), the control circuit 20 sends the reset signal REsw instructing the white reset driving to the conversion unit 40. Supply. Then, the control circuit 20 instructs the conversion unit 40 to stop the white reset driving at t = t1, which is the end time of the reset period. In the liquid crystal element 120, as shown in FIG. 8, the response from the white state to the black state is completed before time t = tw1 in accordance with the black reset driving, and then the reset voltage dH corresponding to the white reset driving is completed. Is applied. At time t = t2 when the reset period ends, the liquid crystal element 120 is in the process of changing from the black state to the white state, and the liquid crystal element 120 has not completed the response to the state. Therefore, the transmittance of the liquid crystal element 120 at time t = t1 is δ ₂ [%] (for example, 5%) which is slightly higher than 0% in the black state.

  As described above, in the VA mode liquid crystal, the response time when changing from the black state to the white state is generally shorter than the response time when changing from the white state to the black state. In some cases, the liquid crystal element 120 can be fully responded to a black state. Under this assumption, the control circuit 20 of the present embodiment performs black reset driving first in the reset period, and performs white reset driving in the remaining period after the response of the liquid crystal element 120 to the black state is completed. Next, the basis for such reset driving will be described.

First, the black reset driving performed in advance in the reset driving of the present embodiment is performed so that the response of the liquid crystal element 120 to the black state is completed. As a result, the display area 101 becomes an all-black state, and the alignment state of the liquid crystal element 120 is aligned with the black state. Therefore, the period during which the black reset driving is performed is a period of at least the response time T2 and the length until the liquid crystal element 120 becomes at least black. The period during which the black reset driving is performed may be, for example, 3 milliseconds corresponding to the response time T2, but may be longer than the response time T2, such as 3.5 milliseconds.
Next, since the response time T1 (= 2 milliseconds) is shorter than the remaining period of the reset period, the white reset drive performed following the black reset drive is terminated before the display area 101 becomes the all white state. . When this white reset driving is performed, the alignment state of the liquid crystal element 120 does not change until the white state, but the transmittance δ ₂ [%] is slightly higher than that of the black state. Furthermore, it means that the alignment state of the liquid crystal element 120 is changed to the next display period in transmittance δ _{2 [%]} (i.e. left open period), the initial state the transmittance [delta] _{2 [%]} is left open period A voltage having a gradation level corresponding to the video signal Vid is applied to the liquid crystal element 120.

  As shown in FIG. 11, if black reset driving is performed in the entire reset period, the response of the liquid crystal element 120 to the black state may be completed within the reset period. In this case, when the liquid crystal element 120 is to be changed to the transmittance in the white state or a state close to the white state in the display period (that is, the left eye opening period) after the reset period, the liquid crystal molecules are aligned vertically. It tries to respond from the transmittance of 0%, and the liquid crystal molecules hardly move. Therefore, in this display period, even when a voltage corresponding to the video signal Vid is applied to the liquid crystal element 120, the transmittance according to the voltage is not achieved, and the liquid crystal element 120 becomes lower than the target transmittance. In this case, even when a white display or a display close to a white display is desired based on the video signal Vid, the display quality is such that the transmittance of the liquid crystal element 120 is lower than the target transmittance and the peak luminance is reduced. A drop will occur.

On the other hand, according to the reset driving of this embodiment, the control circuit 20 performs white reset driving in the remaining period after the black reset driving in the reset period, so that transmission is performed at t = t1 that is the end time of the reset period. The rate can be increased to δ ₂ [%]. As a result, the liquid crystal molecules are more likely to start moving than when the transmittance is even lower, so that even if it is desired to display an image that is white or close to white in the next display period, the peak luminance is reduced. Degradation can be suppressed.

Note that δ ₂ [%] is a transmittance for facilitating the movement of the liquid crystal molecules, but is preferably a transmittance such that a change in transmittance is not perceived by the user. In addition, the control circuit 20 performs the reset driving in the above-described procedure in the reset period before the right eye opening period after performing the image display based on the display data Da in the left eye opening period. Also here, the control circuit 20 supplies the reset signal RESb for performing black reset driving at time t = t3, and at time t = tw2, which is further after response time T2 from time t = t3, Switching to the reset signal REsw for performing reset driving, white reset driving is performed until time t = t3. As a result, for the same reason as in the left eye opening period, it is possible to suppress a reduction in display quality such that the peak luminance is lowered in the right eye opening period from time t = t3 to t = t4.

The liquid crystal display device 1 according to the present embodiment executes the white reset drive after executing the black reset drive when the black reset drive and the white reset drive can be completed within the reset period. It was. One reason for this is that the display contrast is less likely to be a problem when the white state is set to the initial state of the display period.
In addition, according to the liquid crystal display device 1 of the present embodiment, there is an effect of suppressing the occurrence of crosstalk in 3D video display for the same reason as in the first embodiment described above. In the present embodiment, the case where both the black reset drive and the white reset drive are completed within the reset period has been described. On the other hand, when the relationship of response time T2 <reset period <response time T1 is satisfied and black reset driving can be completed within the reset period, white reset driving cannot be completed within the reset period. Alternatively, the liquid crystal display device 1 may perform white reset driving after black reset driving as in the present embodiment.

<Modification>
The present invention can be implemented in a form different from the above-described embodiment. Further, the following modifications may be combined as appropriate.
(Modification 1)
In each of the above-described embodiments, the display control circuit 10 applies a voltage corresponding to the video signal Vid to the liquid crystal element 120 in accordance with the subfield driving method. However, the display control circuit 10 aims at the liquid crystal element 120 via the data line 114. A voltage corresponding to the video signal Vid may be applied to the liquid crystal element 120 in accordance with a voltage modulation method (analog driving) that applies an analog voltage corresponding to the gradation level.

(Modification 2)
In the second embodiment described above, the liquid crystal display device 1 executes the black reset drive and then the white reset drive when the black reset drive and the white reset drive can be completed within the reset period. However, the black reset drive may be executed after the white reset drive is executed according to the procedure described in the first embodiment.

(Modification 3)
In each of the above-described embodiments, the longest response time of the liquid crystal element 120 when the reset voltage dH for setting the liquid crystal element 120 to the white state is applied is to change the black state liquid crystal element 120 to the white state. I thought it was response time. If the response time for changing from the transmittance corresponding to the intermediate gradation to the white state is longer due to the characteristics of the liquid crystal 105 or the like, either black reset driving or white reset driving is performed based on this response time. It may be decided whether to do it first. Similarly, the longest response time of the liquid crystal element 120 when the reset voltage dL for setting the liquid crystal element 120 to the black state is applied is considered as the response time for changing the white state liquid crystal element 120 to the black state. However, if the response time for changing from the transmittance corresponding to the intermediate gradation to the black state is longer, it is determined based on this response time whether the black reset driving or the white reset driving is performed first. May be.

(Modification 4)
Whether the black reset driving is performed after the white reset driving is performed as in the first embodiment described above, or the white reset driving is performed after the black reset driving is performed as in the second embodiment described above. The display device 1 may determine. For example, the control circuit 20 applies the reset voltage dH for applying a reset voltage dL to the liquid crystal element 120 that has been brought into the black state, and measures the response time T1 from the black state to the white state. Further, the control circuit 20 applies a reset voltage dL for applying a reset voltage dH to the liquid crystal element 120 that has been brought into a white state, and measures a response time T2 from the white state to the black state. Then, the control circuit 20 may perform reset driving with a shorter response time first. Further, in order to give priority to the suppression of the display contrast reduction, the control circuit 20 performs the black reset driving and then the white reset when the response time T2 is shorter than the reset period, as in the second embodiment described above. You may make it drive.
Further, as described in the modification example 3, the response time for changing from the transmittance corresponding to the intermediate gradation to the black state or the white state may be the longest response time. It may be determined whether to perform black reset driving or white reset driving first based on the longest response time.

(Modification 5)
The liquid crystal display device 1 of each embodiment described above performs the above-described reset driving in the reset period in 3D video display. For example, in the 2D video display, the reset period is provided before the display period. You may perform reset drive by the method of form.
Further, the reset voltage dH is not limited to the highest applied voltage used for gradation expression, but is a voltage lower than that to increase the transmittance of the liquid crystal element 120 (the direction in which the pixel 110 is brightened). The voltage may be changed to Further, the reset voltage dL is not limited to the voltage corresponding to the applied voltage at which the pixel electrode 118 and the common voltage LCcom are at the same potential, but is a voltage higher than that to reduce the transmittance of the liquid crystal element 120 (pixel 110). The voltage may be changed in the direction of darkening.

(Modification 6)
In each of the above-described embodiments, the example in which the VA method is used for the liquid crystal 105 has been described. However, the TN method may be used (that is, the liquid crystal element 120 is in the normally white mode). In this case, the white state in which the transmittance of the liquid crystal element is 100% corresponds to, for example, a low-voltage applied voltage in which the pixel electrode 118 and the common voltage LCcom have the same potential, and the transmittance of the liquid crystal element is 0%. The black state corresponds to the highest applied voltage at which the pixel electrode 118 and the common voltage LCcom are used for gradation expression, for example.
The reset driving performed in the liquid crystal display device 1 is not limited to all pixels 110 (the liquid crystal elements 120) in the display area 101, but is intended for some pixels 110 (the liquid crystal elements 120). It may be.

(Modification 7)
In addition, the display control circuit of the present invention is not limited to 4 × speed driving, and can be applied to a liquid crystal display device that employs double speed driving such as 2 × speed or 8 × speed driving. In addition, the display control circuit of the present invention may not be applied to a liquid crystal display device that employs double speed driving. For example, the display control circuit may provide a reset period before a display period (for example, a plurality of frame periods) corresponding to the video signal Vid for one frame.
In each of the above-described embodiments, the video signal Vid designates the gradation level of the pixel, but may designate the applied voltage of the liquid crystal element.
In each embodiment, the liquid crystal element 120 is not limited to a transmissive type, and may be a reflective type.
In addition, the 3D glasses 60 are not limited to the liquid crystal shutter 62L or 62R being opened during the entire period of the left eye opening period and the right eye opening period, and may be open during a part of the period.

<Electronic equipment>
Next, an electronic apparatus to which the liquid crystal display device 1 according to the above-described embodiment is applied will be described using a projector as an example.
FIG. 9 is a plan view showing the configuration of the projector.
As shown in this figure, a projector 2100 is provided with a lamp unit 2102 made of a white light source such as a halogen lamp. The projection light emitted from the lamp unit 2102 is provided with three primary colors of R (red), G (green), and B (blue) by three mirrors 2106 and two dichroic mirrors 2108 disposed therein. And led to the light valves 100R, 100G and 100B corresponding to the respective primary colors. Note that B light has a longer optical path than other R and G colors, and therefore, in order to prevent the loss, B light passes through a relay lens system 2121 including an incident lens 2122, a relay lens 2123, and an exit lens 2124. Led.

In this projector 2100, three sets of display devices according to the embodiment are provided corresponding to each of R color, G color, and B color. Then, video signals corresponding to each of R color, G color, and B color are supplied from the host device. The light valves 100R, 100G, and 100B are the same as the liquid crystal panel 100 described above, and are driven according to video signals corresponding to the R, G, and B colors.
The lights modulated by the light valves 100R, 100G, and 100B are incident on the dichroic prism 2112 from three directions. In the dichroic prism 2112, the R and B light beams are refracted at 90 degrees, while the G light beam travels straight. Therefore, after the images of the respective colors are combined, a color image is projected onto the screen 2120 by the projection lens 2114.

Since light corresponding to each of the R, G, and B colors is incident on the light valves 100R, 100G, and 100B by the dichroic mirror 2108, there is no need to provide a color filter. In addition, the transmission images of the light valves 100R and 100B are projected after being reflected by the dichroic prism 2112, whereas the transmission image of the light valve 100G is projected as it is, so the horizontal scanning direction by the light valves 100R and 100B is The image is reversed in the horizontal scanning direction by the light valve 100G and displayed in an inverted image.
If the image projected on the screen 2120 is viewed with the 3D glasses 60 described above, 3D video can be perceived.

  In addition to the projector described with reference to FIG. 9, examples of the electronic device include an electronic viewfinder, a rear projection type television, a head mounted display, and the like.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display device, 10 ... Display control circuit, 100 ... Liquid crystal panel, 101 ... Display area, 110 ... Pixel, 120 ... Liquid crystal element, 130 ... Scanning line drive circuit, 140 ... Data line drive circuit, 20 ... Control circuit, 30 ... Memory, 40 ... Conversion unit, 50 ... Transmission unit, 60 ... 3D glasses, 2100 ... Projector

Claims (8)

A display control circuit for controlling a display device including a display unit including a plurality of pixels each having a liquid crystal element and a drive circuit for applying a voltage to the liquid crystal element corresponding to each pixel of the plurality of pixels;
In a predetermined reset period, a first reset voltage that changes the brightness of the pixels in one direction is applied to the liquid crystal elements corresponding to the plurality of pixels until the brightness reaches at least the brightness corresponding to the first reset voltage. A second reset voltage for changing the brightness of the pixel in the opposite direction in the remaining period after applying the period;
A control unit that controls the drive circuit to apply a voltage corresponding to a video signal designating brightness for each pixel to the liquid crystal element corresponding to each pixel following the reset period. A display control circuit. The response time of the liquid crystal element when the second reset voltage is switched to the first reset voltage is shorter than the response time of the liquid crystal element when the first reset voltage is switched to the second reset voltage. The display control circuit according to claim 1. The controller is
Both of the response time of the liquid crystal element when the second reset voltage is switched to the first reset voltage and the response time of the liquid crystal element when the first reset voltage is switched to the second reset voltage. If shorter than the reset period,
The said 2nd reset voltage which changes the said pixel in the direction which makes the said pixel bright is applied after applying the said 1st reset voltage which changes the said pixel in the direction which makes the said pixel dark. Display control circuit. The controller is
The application period of the second reset voltage is shorter than a response time of the liquid crystal element when the first reset voltage is switched to the second reset voltage. The display control circuit according to claim 1. The controller is
5. The display control circuit according to claim 1, wherein a voltage corresponding to the video signal is applied to each of the pixels in accordance with a sub-field driving method. The controller is
A voltage corresponding to the video signal is displayed in each of a first display period in which an image for the right eye in 3D video display is displayed on the display unit and a second display period in which the image for the left eye in 3D video display is displayed on the display unit. Applied,
The display according to claim 5, wherein the first reset voltage and the second reset voltage are applied in the reset period provided between the first display period and the second display period. Control circuit. A display control method for controlling a display device having a display unit including a plurality of pixels each having a liquid crystal element,
In a predetermined reset period, a first reset voltage that changes the brightness of the pixels in one direction is applied to the liquid crystal elements corresponding to the plurality of pixels until the brightness reaches at least the brightness corresponding to the first reset voltage. A second reset voltage for changing the brightness of the pixel in the opposite direction in the remaining period after applying the period;
Subsequent to the reset period, a voltage corresponding to a video signal designating the brightness of each pixel is applied to the liquid crystal element corresponding to each pixel. The electronic device which has a display control circuit of any one of Claims 1-6.

Images