JP2007304234A - Drive circuit and drive method for liquid crystal device, and liquid crystal device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drive circuit and drive method for a liquid crystal device, a liquid crystal device, and electronic equipment which can keep display quality constant and enable the power consumption thereof to be reduced irrespective of ambient temperature. <P>SOLUTION: A control circuit 400 is provided with a controller 401 as a calculating means, a variable oscillator circuit 402 as a drive frequency control means, and a temperature sensor 403 as a means for detecting temperature, and changes a frame frequency of a liquid crystal panel 100 according to temperature of liquid crystal detected by the temperature sensor 403, wherein the frame frequency of the liquid crystal panel 100 is set to be the higher, the higher the temperature of the liquid crystal is. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention includes a liquid crystal sandwiched between a pair of substrates, a plurality of scanning lines, a plurality of data lines,
The present invention relates to a liquid crystal device driving circuit and a driving method, a liquid crystal device, and an electronic apparatus, each including a plurality of pixels provided corresponding to intersections of the plurality of scanning lines and the plurality of data lines.

In recent years, a liquid crystal device as an electro-optical device for displaying an image has been widely used as a display device of a portable electronic device such as a mobile phone. In general, liquid crystal changes in physical properties such as viscosity and voltage holding ratio depending on environmental temperature.

For example, at low temperatures, the response of liquid crystal molecules slows due to increased viscosity,
There arises a problem that the image cannot be written in time and cannot be displayed. On the other hand, at a high temperature, the response of the liquid crystal molecules becomes faster due to the decrease in viscosity, and the voltage holding ratio further decreases, so that the liquid crystal molecules respond before the next image is written and flicker occurs. End up.

As a technique for making the image display quality by the liquid crystal device constant regardless of the environmental temperature, the application voltage or the application time of the drive signal for driving the liquid crystal is determined based on the environmental temperature information detected by the temperature detection unit. Liquid crystal device (electro-optical device) with temperature compensation element to change
Is disclosed in Japanese Patent Application Laid-Open No. 2004-219933.
JP 2004-219933 A

However, in the technique disclosed in Japanese Patent Application Laid-Open No. 2004-219933, the applied voltage of the drive signal for driving the liquid crystal must be increased or the application time must be increased as the temperature becomes lower, which increases the power consumption of the liquid crystal device. End up.

In order to reduce the power consumption of the liquid crystal device, it is conceivable to lower the image rewriting frequency (frame frequency) of the liquid crystal device, but in order to prevent flicker from occurring in a state where the environmental temperature is high, a frame is used. The frequency must be a relatively high value (for example, about 60 [Hz]), and it is difficult to reduce the power consumption while maintaining the display quality of the liquid crystal device regardless of the environmental temperature.

The present invention has been made in view of the above problems, and a liquid crystal device driving circuit, a driving method, a liquid crystal device, and a liquid crystal device capable of keeping display quality constant and reducing power consumption regardless of environmental temperature An object is to provide electronic equipment.

A driving circuit for a liquid crystal device according to the present invention includes a liquid crystal sandwiched between a pair of substrates, and intersects a plurality of scanning lines, a plurality of data lines, and the plurality of scanning lines and the plurality of data lines. A liquid crystal device driving circuit for a liquid crystal device comprising a plurality of pixels provided corresponding to the temperature detecting means for detecting the temperature of the liquid crystal or the ambient temperature of the liquid crystal device, and the temperature Calculation means for calculating a target frame frequency of the liquid crystal device based on the temperature detected by the detection means, and a drive signal for driving the liquid crystal device at the target frame frequency calculated by the calculation means are generated. Drive frequency control means.

The liquid crystal device driving method according to the present invention includes a liquid crystal sandwiched between a pair of substrates, a plurality of scanning lines, a plurality of data lines, the plurality of scanning lines, and the plurality of data lines. A liquid crystal device driving method for a liquid crystal device comprising a plurality of pixels provided corresponding to the intersection of the temperature, the temperature detecting step of detecting the temperature of the liquid crystal or the temperature of the environment around the liquid crystal device; A calculation step of calculating a target frame frequency of the liquid crystal device based on the temperature detected in the temperature detection step, and a drive signal for driving the liquid crystal device at the target frame frequency calculated in the calculation step And a drive frequency control step to be generated.

According to another aspect of the invention, an electro-optical device includes the electro-optical device driving circuit.

  According to another aspect of the invention, an electronic apparatus includes the electro-optical device.

According to such a configuration of the present invention, the frame frequency of the liquid crystal device can be made variable in accordance with the physical characteristics depending on the temperature of the liquid crystal, particularly the change in viscosity. As described above, by changing the frame frequency in accordance with the temperature of the liquid crystal, it is possible to keep the display quality of the image of the liquid crystal device constant regardless of the temperature and reduce the power consumption.

In the present invention, it is preferable that the calculation unit calculates the target frame frequency based on a linear expression using the temperature as a variable.

According to such a configuration, the circuit configuration of the calculation unit can be simplified, and the electro-optical device drive circuit can be configured inexpensively and easily.

In the present invention, the primary expression is preferably represented by the following expression.
F = 0.6T + 30
Where F is the target frame frequency [Hz] and T is the temperature [° C.].
According to such a configuration, since the frame frequency at room temperature (+ 25 ° C.) is 45 [Hz], power consumption at room temperature can be reduced as compared with the conventional case.

The present invention preferably further comprises signal voltage control means for controlling a voltage value of a voltage signal applied to the pixel based on the temperature detected by the temperature detection means.

According to such a configuration, the voltage value of the voltage signal applied to the pixel can be changed according to the temperature of the liquid crystal, and the liquid crystal device can be driven with lower power consumption.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing a configuration of a liquid crystal device 10 according to an embodiment of the present invention. FIG. 2 is a perspective view showing the overall configuration of the liquid crystal panel 100. FIG. 3 is a cross-sectional view showing a configuration when the liquid crystal panel 100 is broken along the X direction. FIG. 4 shows a pixel 116 in the liquid crystal panel 100.
It is explanatory drawing explaining the detailed structure of these.

As shown in FIG. 1, the liquid crystal device 10 includes a liquid crystal panel 100 and a control circuit 400. In this embodiment, the liquid crystal panel 100 as a display device is an electric field control birefringence mode liquid crystal device using homogeneously aligned liquid crystal, and is a two-terminal nonlinear device as a switching element for controlling a voltage applied to the liquid crystal. This is an active matrix transmissive liquid crystal panel using elements.

As shown in FIGS. 2 and 3, each of the liquid crystal panels 100 is translucent, and is disposed between a rectangular element substrate 200 and a counter substrate 300 that are spaced apart by a predetermined distance. A liquid crystal 160 which is an electro-optical material is sandwiched. The counter substrate 300 is formed to be slightly smaller than the element substrate 200, and the element substrate 200 and the counter substrate 300 are bonded together by a frame-shaped sealing material 110 disposed along the outer edge portion of the counter substrate 300. It has been. Seal material 11
0 is mixed with conductive particles 114, and the conductive particles 114 have a role of a spacer that keeps the separation distance between the element substrate 200 and the counter substrate 300 constant. Element substrate 200
The liquid crystal 160 sandwiched between the counter substrate 300 and the counter substrate 300 changes its alignment state according to the voltage applied between the two substrates, thereby changing the polarization state of the light transmitted through the liquid crystal 160. .

As shown in FIG. 1, the liquid crystal panel 100 includes a plurality of data lines (segment electrodes) 212 formed in the column (Y) direction on the element substrate 200 and rows (X) on the counter substrate 300. A plurality of scanning lines (common electrodes) 312 formed extending in the direction, and a plurality of pixels 116 provided corresponding to locations where the data lines 212 and the scanning lines 312 intersect and face each other. It has. The liquid crystal panel 100 includes a data line driving circuit 250 to which a plurality of data lines 212 are electrically connected, and a scanning line driving circuit 3 to which a plurality of scanning lines 312 are electrically connected.
50.

The pixel 116 includes a liquid crystal capacitor 118 and a TFD (Th
in film diode (220). As will be described later, the liquid crystal capacitor 118 has a configuration in which a liquid crystal 160 is sandwiched between a scanning line 312 that functions as a counter electrode and a rectangular pixel electrode 234. In the present embodiment, the liquid crystal panel 100
Although a transmissive TFD active matrix driving type liquid crystal panel is used, the liquid crystal panel 100 may be a transflective type or a reflective type. In addition, the liquid crystal panel 10
0 may use a TFT as an active element.

Hereinafter, a more specific configuration of the liquid crystal panel 10 will be described. In the following explanation,
For convenience of explanation, the total number of scanning lines 312 is 320, the total number of data lines 212 is 240, and the liquid crystal device 10 is described as a matrix type display device of 320 vertical rows × 240 horizontal columns. It is not limited to.

As shown in FIGS. 2 and 3, on the surface of the counter substrate 300 that faces the element substrate 200,
A plurality of scanning lines 312 are formed as band-like electrodes extending in the X direction (row direction), which is a predetermined direction. An alignment film 308 is formed on the scanning line 312, and the alignment film 308 is rubbed in a certain direction. Here, one end of each of the plurality of scanning lines 312 is extended to a region where the sealing material 110 is formed.

On the other hand, on the surface of the element substrate 200 facing the counter substrate 300, Y that is substantially orthogonal to the X direction.
A plurality of data lines 212 extending in the direction (column direction) and a plurality of rectangular pixel electrodes 234 adjacent to the data lines are formed. One end of the data line 212 is extended to the outside of the region where the sealing material 110 is formed. An alignment film 208 is formed over the data lines 212 and the pixel electrodes 234, and the alignment film 208 is rubbed in a direction substantially parallel to the direction applied to the alignment film 308 of the counter substrate 300. It has been subjected.

Here, on the surface of the element substrate 200 facing the counter substrate 300, the plurality of scanning lines 3 described above are provided.
A plurality of wirings 342 having one end at a position facing each of the one ends of 12 are formed. A sealing material 110 is interposed between the scanning line 312 and the wiring 342. In the sealing material 110, a conductive material is provided at a location where the scanning line 312 and the wiring 342 face each other. The conductive particles 114 are dispersed in the sealing material 110 at such a ratio that at least one or more conductive particles 114 are interposed. Therefore, the scanning line 312 formed on the counter substrate 300 is electrically connected to the wiring 342 formed on the element substrate 200 through the conductive particles 114. Therefore, the scanning line 312 is electrically drawn out of the sealing material 110 formation region on the element substrate 200.

Further, polarizers 121 and 131 are attached to the surfaces of the element substrate 200 and the counter substrate 300 opposite to the liquid crystal 160, respectively.

Outside the display area of the liquid crystal panel 100, as shown in FIG. 2, a data line driving circuit 250 for driving the data lines 212 and scanning lines on two sides of the element substrate 200 protruding from the counter substrate 300. Each of the scanning line driving circuits 350 for driving 312 includes a COG
(Chip On Glass) technology. The data line driving circuit 250 is connected to the data line 2
12 is directly electrically connected to one end. On the other hand, the scanning line driving circuit 350 includes the wiring 3
42 and the conductive particles 114 are electrically connected to the scanning line 312.

The scanning line driving circuit 350 supplies scanning signals Y1, Y2, Y3,..., Y320 to the scanning lines 312 of the first row, the second row, the third row,. In detail,
The scanning line drive circuit 350 sequentially selects 320 scanning lines 312 one by one for each horizontal scanning period, and selects a selected voltage for the selected scanning line 312 and a non-selected voltage for the other scanning lines 312. The operations to be supplied are repeated every vertical scanning period.

The data line driving circuit 250 applies the data signals X1, X2, X3, and the like to the pixels 116 located on the scanning line 312 selected by the scanning line driving circuit 350 according to the display contents (gradation).
.., X240 are supplied via the data lines 212 in the first, second, third,..., 240th columns, respectively.

Further, in the vicinity of the outside of the area where the data line driving circuit 250 is mounted, an FPC (Flexible P
Rinted Circuit) One end of the substrate 150 is joined. The other end of the FPC board 150 is shown in FIG.
Although not shown, it is connected to the control circuit 400 in FIG. 1 and a power supply circuit (not shown).

Note that, unlike FIG. 2, the data line driving circuit 250 and the scanning line driving circuit 350 in FIG. 1 are located on the left side and the upper side of the liquid crystal panel 100, respectively, but this explains the electrical configuration. It is just a measure for convenience. Further, instead of COG mounting the data line driving circuit 250 and the scanning line driving circuit 350 on the element substrate 200, for example, TCP (Tape Automated Bonding) technology is used to mount each driver and power supply circuit TCP ( The tape carrier package may be electrically and mechanically connected by an anisotropic conductive film.

Next, a detailed configuration of the pixel 116 in the liquid crystal panel 100 will be described with reference to FIG. In FIG. 4, the alignment films 208 and 308 and the polarizers 121 and 131 are omitted for understanding.

As shown in FIG. 4, on the surface of the element substrate 200 facing the counter substrate 300, ITO (In
A rectangular pixel electrode 234 made of a transparent conductor such as dium tin oxide is arranged in a matrix (matrix) in the XY direction. Among the pixel electrodes 234 arranged in a matrix, the pixel electrodes 234 arranged in the same column are respectively connected to one common data line 212 with the TFD 220.
Are connected via a common connection.

The TFD 220 is formed from a tantalum simple substance or a tantalum alloy when viewed from the substrate side,
In addition, the first conductor 222 is branched from the data line 212 in a T shape, an insulator 224 obtained by anodizing the first conductor 222, and a second conductor 226 such as chromium. It has a conductor / insulator / conductor sandwich structure. For this reason, TFD
220 has a diode switching characteristic in which the current-voltage characteristic is nonlinear in both positive and negative directions.

On the other hand, on the surface of the counter substrate 300 facing the element substrate 200, a scanning line 312 made of a transparent conductor such as ITO and extending in a row direction (X direction) substantially orthogonal to the data line 212 is provided.
They are arranged at positions facing the pixel electrodes 234. Accordingly, the scanning line 312 functions as a counter electrode of the pixel electrode 234.

Therefore, the liquid crystal capacitor 118 shown in FIG. 1 is constituted by the scanning line 312, the pixel electrode 234, and the liquid crystal 160 sandwiched between the data line 212 and the scanning line 312. The

In such a configuration, regardless of a data signal that is a voltage signal applied to the data line 212, when a scanning signal that is a voltage signal that forces the TFD 220 to be in a conductive state (on state) is applied to the scanning line 312, The TFD 220 corresponding to the intersection of the scanning line 312 and the data line 212 is turned on, and a charge corresponding to the voltage difference between the scanning signal and the data signal is charged in the liquid crystal capacitor 118 connected to the TFD 220 that is turned on. Accumulated. After the charge accumulation, even if the TFD 220 is turned off by applying a voltage as a non-selection signal to the scanning line 312, the charge accumulation in the liquid crystal capacitor 118 is maintained. That is, the liquid crystal 1
The voltage applied to 60 is held.

In the liquid crystal capacitor 118, the alignment state of the liquid crystal 160 changes according to the amount of accumulated charge, and thereby the amount of light passing through the pair of polarizers 121 and 131 changes. More specifically, according to the amount of charge accumulated in the liquid crystal capacitor 118, that is, the effective voltage value applied to the liquid crystal 160,
As the alignment state of the liquid crystal 160 changes and the polarization state of light transmitted through the liquid crystal 160 changes, the amount of light passing through the pair of polarizers 121 and 131 changes. Therefore, the liquid crystal capacitance 11
By controlling the charge accumulation amount at 8 for each pixel 116, a predetermined gradation display can be performed for each pixel 116 in the liquid crystal panel 100.

As described above, a data signal is supplied to each pixel 116 of the liquid crystal panel 100 every vertical scanning period. That is, the image display area constituted by each pixel 116 of the liquid crystal panel 100 is rewritten every one vertical scanning period. In general, this one vertical scanning period is also called one frame period, and its unit is expressed in seconds. The reciprocal of one vertical scanning period, which is the rewrite cycle of the image display area of the liquid crystal panel 100, is referred to as a frame frequency or a refresh rate, and the unit is expressed in hertz.

Since the liquid crystal panel 100 in the present embodiment is a transmissive liquid crystal panel, a backlight unit that irradiates uniform light to the area where the pixels 116 are formed is provided, but the illustration is omitted. is doing.

Next, the control circuit 400 connected to the liquid crystal panel 100 described above will be described with reference to FIG. FIG. 5 is an explanatory diagram illustrating a schematic configuration of the liquid crystal device drive circuit of the present embodiment.
The liquid crystal device drive circuit of the present embodiment includes a panel driver 410 including a data line drive circuit 250 and a scan line drive circuit 350 disposed in the liquid crystal panel 100, and a control circuit 400 described below. Is.

The control circuit 400 includes a controller 401, which is a calculation means including an MPU and a memory.
A variable oscillation circuit 402 which is a drive frequency control means, and a temperature sensor 40 which is a temperature detection means.
3 is configured. Note that the control circuit 400 is the liquid crystal panel 100 in this embodiment.
However, it may be configured integrally with the liquid crystal panel 100, for example.

The control circuit 400 is electrically connected to the external controller 600 through a signal line. Here, the external controller 600 is a circuit that generates moving image data Din to be displayed on the liquid crystal device 10 according to the present embodiment, and includes an MPU, a memory, and the like built in an electronic device including the liquid crystal device 10. The external controller 600 is, for example, MPEG (Moving Picture Exper
ts Group) standard, data stored in the flash memory is decoded, and the data is converted into moving image data Din that can be displayed by the liquid crystal device 10 and output to the control circuit 400. It has a decoder function.

The variable oscillation circuit 402 serving as drive frequency control means generates a drive signal CLK for controlling the drive timing of the panel driver 410 of the liquid crystal panel 100, and the panel driver 41.
This is a circuit for outputting to 0. That is, the liquid crystal panel 100 is driven by the variable oscillation circuit 4.
It is controlled by the drive signal CLK generated by 02. Here, the drive signal CLK is a signal that defines one horizontal scanning period and one vertical scanning period of the liquid crystal panel 100.

The variable oscillation circuit 402 is electrically connected to the controller 401, and can output the drive signal CLK by changing the frequency in accordance with a control signal from the controller 401. In the present embodiment, the variable oscillation circuit 402 includes the drive signal CLK so that the frame frequency Ff of the liquid crystal panel 100 becomes a predetermined value within the range of 10 Hz to 80 Hz.
Can be changed.

A temperature sensor 403 as temperature detecting means is a sensor circuit that measures the temperature of the environment around the liquid crystal panel 100 using a thermistor and detects the temperature T of the liquid crystal 160 from this value.
Similar to the panel driver 410, it is provided on the liquid crystal panel 100. Temperature sensor 40
3 is electrically connected to the controller 401 and outputs the temperature T of the liquid crystal 160 to the controller 401. The temperature sensor, which is a temperature detecting means, calculates the temperature of the liquid crystal 160 or the ambient environment from the change in the resistance value of the circuit element formed in the panel driver 410 or the liquid crystal panel 100, for example, the TFD 220. May be. The information measured by the temperature sensor 403 and output to the controller 401 may be the temperature of the environment around the liquid crystal panel 100.

The controller 401, which is a calculation means, calculates a target frame frequency F of the liquid crystal panel 100 corresponding to the temperature information of the liquid crystal 160 input from the temperature sensor 403 based on a predetermined function, and the target frame frequency F and the actual liquid crystal panel. A control signal for changing the drive signal CLK is output to the variable oscillation circuit 402 so that the frame frequency Ff of 100 becomes equal. Here, the controller 401 calculates the frame frequency F based on a pre-stored relational expression between the temperature T and the frame frequency F or a table of the frame frequency F determined according to the value of the temperature T. Is. At this time, the frame frequency F of the liquid crystal panel 100 calculated by the controller 401 is set so as to increase as the temperature T of the environment around the liquid crystal panel 100 increases.

FIG. 6 is a graph showing the relationship between the target frame frequency F [Hz] of the liquid crystal panel 100 and the liquid crystal temperature T [° C.] in the present embodiment. In FIG. 6, the horizontal axis represents the temperature T [
° C.], and the vertical axis represents the target frame frequency F [Hz] of the liquid crystal panel 100.

As shown in FIG. 6, the target frame frequency F is a linear function having a positive slope with the temperature T as a variable.
F = a · T + b (1)
(Where a is a positive constant and b is a constant)
It is represented by Specifically, in this embodiment, a = 0.6 and b = 30, and the controller 4
01 is the following linear expression using the temperature T of the liquid crystal 160.
F = 0.6T + 30 (2)
To calculate the target frame frequency F.

Further, the controller 401 generates frame data Df, which is an image signal to be written to each pixel 116 of the liquid crystal panel 100, from the input moving image data Din, and synchronizes the frame data Df with the drive signal CLK to generate the panel driver 410. Output to. Note that the controller 401 displays the panel driver 410 according to the frame frequency Ff of the liquid crystal panel 100.
The number of frames per second of the frame data Df to be output may be changed and output.

Although not shown, a power supply circuit is connected to each of the liquid crystal panel 100 and the control circuit 400.

As described above, the liquid crystal device drive circuit according to the present embodiment includes the temperature sensor 403 that detects the temperature T of the liquid crystal 160 and the controller that calculates the target frame frequency F of the liquid crystal panel 100 according to the temperature T of the liquid crystal 160. 401 and a variable oscillation circuit 402 that generates a drive signal CLK for driving the liquid crystal panel 100 at a target frame frequency F. Here, the target frame frequency F is set to be higher as the temperature T of the liquid crystal 160 is higher. In the liquid crystal device drive circuit of the present embodiment, the detection of the temperature T of the liquid crystal 160, the calculation of the target frame frequency F and the determination of the frequency of the drive signal CLK are repeated at a predetermined cycle. is there.

The liquid crystal device 10 including the liquid crystal device driving circuit according to the present embodiment is driven at a frame frequency Ff that varies depending on the value of the temperature T of the liquid crystal 160. The higher the temperature T of 160, the higher the value.

The above equation (2) is derived based on experiments, and the temperature T of the liquid crystal 160 is −30.
In the range of [° C.] to +70 [° C.], the frame frequency Ff in which no flicker occurs in the image display of the liquid crystal device 10 and the contrast does not decrease is approximated by a linear function. In particular, the frame frequency Ff of the liquid crystal panel 100 at normal temperature (25 [° C.] in the present embodiment).
45 [Hz], which can reduce power consumption while maintaining the display quality of images without flicker.
] Is set to be. As described above, by setting the frame frequency Ff of the liquid crystal panel 100 at a normal temperature (25 [° C.] in this embodiment) to a low value in a range where flicker does not occur, the liquid crystal device in the most frequently used temperature range. The power consumption of 10 can be suppressed.

The operation of the liquid crystal device 10 and the liquid crystal device drive circuit having the above-described configuration will be described below.
For example, when the temperature T of the liquid crystal 160 (or the temperature of the environment around the liquid crystal panel 100) detected by the temperature sensor 403 is +25 [° C.] (this is normal temperature in this embodiment), the controller 401 sets the target The frame frequency F is calculated as 45 [Hz]. If the current frame frequency Ff of the liquid crystal panel 100 is not 45 [Hz], the controller 401 controls the variable oscillation circuit 402 to generate a drive signal CLK that makes the frame frequency Ff equal to the target frame frequency F. Send a signal. The variable oscillation circuit 402 receives a drive signal CLK having a frequency corresponding to a control signal from the controller 401 as a panel driver 4.
10 is output. The drive signal CLK is also output to the controller 401, and the controller 4
01 outputs the frame data Df to the panel driver 410 in synchronization with the drive signal.
As described above, the liquid crystal device 10 is driven with the frame frequency Ff set to 45 [Hz], and an image corresponding to the frame data Df is displayed on the liquid crystal panel 100.

When the temperature of the environment around the liquid crystal panel 100 rises and the temperature T of the liquid crystal 160 detected by the temperature sensor 403 changes to +50 [° C.], the controller 401 sets the target frame frequency F to 60 [Hz]. And calculate. Here, the liquid crystal device 10 is driven at a frame frequency Ff of 60 [Hz] by the same operation as in the case of +25 [° C.], and an image corresponding to the frame data Df is displayed on the liquid crystal panel 100.

On the other hand, when the temperature of the environment around the liquid crystal panel 100 decreases and the temperature T of the liquid crystal 160 detected by the temperature sensor 403 changes to −20 [° C.], the controller 401 sets the target frame frequency F to 15 [Hz]. ] Is calculated. Here, the liquid crystal device 10 is driven at a frame frequency Ff of 15 [Hz] by the same operation as in the case of +25 [° C.], and an image corresponding to the frame data Df is displayed on the liquid crystal panel 100.

That is, when the environmental temperature is normal temperature (+25 [° C.]), the liquid crystal panel 100 is driven at a frame frequency Ff of 45 [Hz], and when the environmental temperature rises above normal temperature, the frame frequency Ff of the liquid crystal panel 100 is increased. If the ambient temperature drops below room temperature, the frame frequency Ff of the liquid crystal panel 100 decreases.

The effects of the liquid crystal device 10 and the drive circuit for the liquid crystal device of the present embodiment will be described below.
First, when the ambient temperature is normal, the frame frequency Ff of the liquid crystal panel 100 is 45 [H.
z], and the liquid crystal panel 100 is driven at a frame frequency lower than 60 [Hz], which is a frame frequency generally used conventionally. Also, when the ambient temperature is normal,
When the frame frequency Ff of the liquid crystal panel 100 is 45 [Hz], the liquid crystal panel 100
Flicker does not occur in the display of this image. Therefore, in the present embodiment, when the environmental temperature is normal, it is possible to reduce power consumption without degrading the display quality of the image of the liquid crystal panel 100 as compared with the conventional case.

Next, in a state where the environmental temperature is high (a state higher than normal temperature), the liquid crystal panel 100 is driven at a frame frequency Ff higher than 45 [Hz]. In this state, the liquid crystal 160
In the present embodiment, the frame frequency Ff of the liquid crystal panel 100 is such that flicker is likely to occur in the display of the liquid crystal panel 100. The value is increased to a value at which flicker does not occur. Therefore, in the present embodiment, even when the environmental temperature is high, the image display quality of the liquid crystal panel 100 is maintained in the same state as that at room temperature.

Next, in a state where the environmental temperature is low (a state lower than normal temperature), the liquid crystal panel 100 is driven at a frame frequency Ff lower than 45 [Hz]. In this state, the liquid crystal 160
However, in this embodiment, the frame frequency Ff of the liquid crystal panel 100 is a value that does not cause a response delay in image display. It is said that. Therefore, in the present embodiment, even when the environmental temperature is low, the image display quality of the liquid crystal panel 100 is maintained in the same state as the normal temperature state.
In addition, since the frame frequency Ff is low and the voltage holding ratio of the liquid crystal 160 does not decrease, the writing time of the voltage signal supplied to the pixel 116 can be extended. Therefore, the effective voltage applied to the liquid crystal 160 can be increased without increasing the voltage of the voltage signal supplied to the pixel 116, and the power consumption can be reduced as compared with the conventional case.

As described above, according to the present embodiment, the display quality of the image of the liquid crystal device 10 can be kept constant regardless of the environmental temperature, and the power consumption can be reduced.

In the present embodiment, the controller 401 serving as a calculation unit calculates the target frame frequency F based on a linear expression using the temperature T as a variable. By configuring the controller 401 in this way, the circuit configuration for calculating the target frame frequency F can be simplified, and the drive circuit for the liquid crystal device can be configured easily and inexpensively.

Note that the liquid crystal device of the above-described embodiment includes, for example, a liquid crystal panel that employs an operation mode such as a VA (vertical alignment) mode, a liquid crystal panel in which a pair of electrodes are formed on one substrate, for example, I
PS (In-Plane Switching) or the like may be used.

(Second Embodiment)
Hereinafter, a liquid crystal device according to a second embodiment of the present invention will be described with reference to FIGS. The liquid crystal device 10a of the present embodiment differs from the first embodiment only in the configuration of the liquid crystal device drive circuit. Therefore, only this difference is demonstrated, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and the description is abbreviate | omitted.

FIG. 7 is an explanatory diagram illustrating a schematic configuration of the liquid crystal device drive circuit of the present embodiment. In addition to the configuration of the liquid crystal device drive circuit of the first embodiment, the liquid crystal device drive circuit of the present embodiment further includes a signal voltage control circuit 404 that is a signal voltage control means. Signal voltage control circuit 404
Is electrically connected to the controller 401 and the panel driver 410, and the voltage value of the data signal, which is a voltage signal output from the controller 401 and applied to the pixel 116 in the frame data Df, is set as a command from the controller 401. The panel driver 41 is controlled accordingly.
Output to 0. Here, the data signal is a voltage signal applied to the data line 212 as described above, and is a signal that determines the effective voltage value applied to the liquid crystal 160.

In the present embodiment, the controller 401 outputs the frame data Df to the signal voltage control circuit 404 and, based on the information stored in advance, the liquid crystal panel 100 based on the temperature T of the liquid crystal 160 input from the temperature sensor 403. The optimum voltage value Vo of the data signal suitable for driving the signal is calculated, and a command is output to the signal voltage control circuit 404 so as to change the voltage value of the data signal to the optimum voltage value Vo.

That is, in the liquid crystal device 10a of the present embodiment, the frame frequency is changed similarly to the first embodiment according to the temperature of the liquid crystal 160 or the temperature of the surrounding environment, and the pixel 11
The voltage value of the voltage signal applied to 6 is also changed.

Here, the characteristic of the liquid crystal used for the liquid crystal panel 100 of this embodiment is demonstrated. FIG. 8 is a graph showing the relationship between the liquid crystal temperature and the threshold voltage when three different liquid crystal materials A to C are used. In FIG. 8, the horizontal axis is the temperature [° C.] of the liquid crystal, and the vertical axis is the threshold voltage [V] that is a voltage value at which the display gradation in the pixel starts to change when the voltage value applied to the liquid crystal is changed. is there. As shown in FIG. 8, the three types of liquid crystals all have a lower threshold voltage as the temperature rises, and this is generally common to other liquid crystals.
In the present embodiment, any one of the three types of liquid crystal materials shown in FIG.

The liquid crystal device 10a and the liquid crystal device drive circuit of the present embodiment have the same effects as those of the first embodiment, and further have the following effects.

First, when the ambient temperature is normal, the frame frequency Ff of the liquid crystal panel 100 is 45 [H.
z], and the liquid crystal panel 100 is driven at a frame frequency lower than 60 [Hz], which is a frame frequency generally used conventionally. Also, when the ambient temperature is normal,
When the frame frequency Ff of the liquid crystal panel 100 is 45 [Hz], the liquid crystal panel 100
Flicker does not occur in the display of this image. Therefore, in this embodiment, when the environmental temperature is room temperature, it is possible to reduce power consumption without degrading the image quality of the liquid crystal panel 100 as compared with the conventional case.

Next, in a state where the environmental temperature is high (a state higher than normal temperature), the liquid crystal panel 100 is driven at a frame frequency Ff higher than 45 [Hz]. In this state, the liquid crystal 160
In the present embodiment, the frame frequency Ff of the liquid crystal panel 100 is such that flicker is likely to occur in the display of the liquid crystal panel 100. The value does not cause flicker. In addition, the liquid crystal panel 100
The voltage value of the data signal applied to each pixel 116 is set lower than that at room temperature.
As shown in FIG. 8, the liquid crystal 160 has a tendency that the threshold voltage decreases as the temperature increases. Accordingly, in the present embodiment, the liquid crystal panel 100 is driven at a higher frame frequency in a high temperature state than in a normal temperature state. However, even if the voltage value of the data signal is lowered due to the low threshold voltage, the image quality is high. Display can be performed without lowering. Therefore, in the present embodiment, it is possible to display an image with lower power consumption than in the first embodiment.

Next, in a state where the environmental temperature is low (a state lower than normal temperature), the liquid crystal panel 100 is driven at a frame frequency Ff lower than 45 [Hz]. In this state, the liquid crystal 160
However, in this embodiment, the frame frequency Ff of the liquid crystal panel 100 is a value that does not cause a response delay in image display. It is said that. Therefore, in this embodiment, even when the environmental temperature is low, the image quality of the liquid crystal panel 100 is maintained in the same state as the normal temperature state. Also,
Since the frame frequency Ff is low and the voltage holding ratio of the liquid crystal 160 does not decrease, the pixel 11
The writing time of the voltage signal supplied to 6 can be extended. Accordingly, although the threshold voltage of the liquid crystal 160 increases at a low temperature, the effective value of the voltage applied to the liquid crystal 160 can be increased without increasing the voltage of the data signal supplied to the pixel 116. Power consumption can be further reduced as compared with the embodiment.

As described above, in the present embodiment, the display quality of the image of the liquid crystal device 10a is changed regardless of the environmental temperature by changing the voltage value of the voltage signal supplied to each pixel according to the liquid crystal or the ambient environmental temperature. This makes it possible to keep the power consumption lower than in the first embodiment.

In the present embodiment, any voltage signal may be used as long as the voltage value applied to the pixel 116 is changed according to the temperature of the liquid crystal 160 or the ambient environmental temperature, and the voltage signal is controlled by the signal voltage control circuit 404. Is not limited to a data signal, and may be a scanning signal, or may be both a data signal and a scanning signal.

Next, specific examples of electronic devices to which the liquid crystal device according to the invention can be applied will be described with reference to FIG.
An example in which the liquid crystal device according to the present invention is applied to a display unit of a mobile phone will be described. FIG. 9 is a perspective view showing the configuration of the mobile phone. As shown in FIG. 7, the cellular phone 1200 includes a plurality of operation buttons 1201, a receiver 1202, a transmitter 1203, and a display unit 1204 to which the liquid crystal device according to the present invention is applied.

According to the mobile phone 1200 which is an electronic device as described above, a high-quality image can be provided on the display unit 1204 without being affected by the temperature of the environment in which the mobile phone 1200 is used. Since the power consumption of the display unit 1204 is low, it is possible to operate for a long time with a rechargeable battery having the same capacity.

Note that, as an electronic device to which the liquid crystal device according to the present invention is applied, in addition to the mobile phone shown in FIG. 7, a media player, a digital still camera, a notebook computer, a liquid crystal television, a viewfinder type (or a monitor direct view type) ) Video recorders, car navigation devices, pagers, electronic notebooks, PDAs, calculators, word processors, workstations, videophones, POS terminals, devices equipped with touch panels, and the like.

The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and the liquid crystal device drive accompanying such a change is possible. Circuits, driving methods, liquid crystal devices, and electronic devices are also included in the technical scope of the present invention.

1 is a block diagram illustrating a configuration of a liquid crystal device according to a first embodiment. It is a perspective view which shows the structure of the liquid crystal device. It is sectional drawing which shows the structure of the liquid crystal panel in the liquid crystal device. It is a partially broken perspective view which shows the structure of the pixel in the liquid crystal device. It is explanatory drawing explaining schematic structure of the drive circuit for liquid crystal devices. It is a graph which shows the relationship between the target frame frequency F of a liquid crystal panel, and the temperature T of a liquid crystal. It is a block diagram which shows the structure of the liquid crystal device which concerns on 2nd Embodiment. It is a graph which shows the relationship between the temperature of a liquid crystal, and threshold voltage. It is a perspective view which shows the structure of a mobile telephone.

Explanation of symbols

10 liquid crystal device, 100 liquid crystal panel, 400 control circuit, 401 controller, 402 variable oscillation circuit, 403 temperature sensor, 410 panel driver, 6
00 External controller

Claims (7)

A plurality of scanning lines, a plurality of data lines, and a plurality of pixels provided corresponding to intersections of the plurality of scanning lines and the plurality of data lines, each having a liquid crystal sandwiched between a pair of substrates. A driving circuit for a liquid crystal device of a liquid crystal device comprising:
Temperature detecting means for detecting the temperature of the liquid crystal or the temperature of the environment around the liquid crystal device;
Calculating means for calculating a target frame frequency of the liquid crystal device based on the temperature detected by the temperature detecting means;
A drive circuit for a liquid crystal device, comprising: drive frequency control means for generating a drive signal for driving the liquid crystal device at the target frame frequency calculated by the calculation means. 2. The driving circuit for a liquid crystal device according to claim 1, wherein the calculating means calculates the target frame frequency based on a linear expression using the temperature as a variable. The drive circuit for a liquid crystal device according to claim 2, wherein the linear expression is expressed by the following expression.
F = 0.6T + 30
Where F is the target frame frequency [Hz] and T is the temperature [° C.]. 4. A signal voltage control means for controlling a voltage value of a voltage signal applied to the pixel based on the temperature detected by the temperature detection means.
The driving circuit for a liquid crystal device according to any one of the above. A liquid crystal device comprising the drive circuit for a liquid crystal device according to claim 1.   An electronic apparatus comprising the liquid crystal device according to claim 5. A plurality of scanning lines, a plurality of data lines, and a plurality of pixels provided corresponding to intersections of the plurality of scanning lines and the plurality of data lines, each having a liquid crystal sandwiched between a pair of substrates. A liquid crystal device driving method for a liquid crystal device comprising:
A temperature detection step of detecting the temperature of the liquid crystal or the temperature of the environment around the liquid crystal device;
A calculation step of calculating a target frame frequency of the liquid crystal device based on the temperature detected in the temperature detection step;
A driving frequency control step for generating a driving signal for driving the liquid crystal device at the target frame frequency calculated in the calculating step.

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