JPS62131234A - Liquid crystal display - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display to be stably operated without being influenced by temperature change by impressing a driving voltage pulse having pulse width and amplitude regulated dependently upon the temperature of a liquid crystal display. CONSTITUTION:A transistor 221 in a voltage level adjusting circuit 22 is arranged in the vicinity of a liquid crystal display part 4 so as to sense the temperature of the display part 4. A regulator IC circuit 227 generates a prescribed voltage based on a voltage difference between power sources VDD and VEE in response to the change of collector voltage and impresses a voltage-adjusted power supply voltage to the power supply terminal of an output driver circuit 21 through a resistor 228. A time constant circuit 23 consisting of R and C is arranged in the vicinity of the display part 4, the time constant is changed due to the temperature change of the display part 4 and a pulse width setting/ pulse shaping circuit 231 generates a shaped strobe signal STBy'. Consequently, the display part 4 can be operated under a stable status suppressing its temperature dependency at its minimum.

Description

[Detailed Description of the Invention] [1 Required] In order to stably operate a liquid crystal display device whose characteristics change depending on temperature, in addition to changing the voltage of the electrode driving pulse depending on the temperature, the pulse width is also changed. This is a liquid crystal display device.

[Industrial application field]

The present invention relates to an apparatus for driving and controlling a liquid crystal display device.

[Conventional technology]

Since the viscosity of liquid crystal in a liquid crystal display device changes depending on the temperature, the optical characteristics of the liquid crystal display device change if the same voltage pulse is applied to the electrodes of the liquid crystal display device. For this reason, it has conventionally been attempted to stabilize the display output of a liquid crystal display device by changing the amplitude of the electrode driving voltage pulse depending on the temperature.

[Problem that the invention seeks to solve]

The characteristics of a liquid crystal display device change depending on temperature as described above, but the change in characteristics cannot be sufficiently compensated for simply by adjusting the amplitude of the driving voltage pulse. For example, for devices with hysteresis in voltage and optical characteristics, such as phase roll type liquid crystal display devices made by mixing cholesteric liquid crystal and nematic liquid crystal, the voltage and optical characteristics curves will only shift to one side due to temperature changes. Rather, the shape of the hysteresis itself changes. Therefore, the problem has been encountered that stability cannot be ensured by voltage adjustment alone, or that display is virtually impossible when temperature changes are large.

[Means to solve the problem]

The present invention provides a liquid crystal display device and a display control means for applying driving voltage pulses to electrodes of the liquid crystal display device to obtain display content responsive to display data, the display control means being regulated depending on the temperature of the liquid crystal display device. A liquid crystal display device is provided, comprising: a drive voltage pulse having a pulse width and an amplitude of 0.1 to 1.0 and a driving voltage pulse having a pulse width and amplitude of 1.

[For production]

An electrode driving pulse having an optimum amplitude and pulse width determined by the temperature of the liquid crystal display device is applied to the electrode.

〔Example〕

FIG. 1 shows a configuration diagram of a liquid crystal display device as an embodiment of the present invention.

In FIG. 1, the opposite X side and Y side of the liquid crystal display section 4
Drive pulses are applied to the side electrodes (not shown) via the X-side driver circuit 3 and the Y-side driver circuit 2, respectively, in accordance with the display content, more precisely, the content that should transmit light or block light. Ru.

The control circuit 1, which is composed of, for example, a microprocessor and peripheral circuits, controls the X and Y side driver circuits so that drive pulses corresponding to the display contents are applied to the electrodes of the liquid crystal display section 4.

The Y-side driver circuit 2 includes an output driver 21 having a plurality of driving IC driver elements for applying necessary driving pulses to each of the plurality of Y-side electrodes of the liquid crystal display section 4, as well as a voltage level adjustment circuit 22. and pulse width adjustment circuit 23
has. The pulse width adjustment circuit 23 includes a time constant circuit 232 consisting of a resistance component R and a capacitor component C, and a pulse width setting and pulse shaping circuit 231.

The X side driver circuit 3 has a similar configuration, but 22 and 23
A configuration may be adopted in which one or both of these are shared with the Y-side driver, and the X-side driver circuit is omitted in this embodiment.

When the control circuit 1 receives display data from a host computer (not shown), it outputs data for driving the XyA electrodes, data for driving the T1 side electrodes DT, clock signals CLKx, CLKy, and strobe signals 5TBx, according to the display data. 5 TBy are output to the corresponding driver circuits 2 and 3, respectively. Strobe signal 5TBy (S
TBx) is for outputting an electrode driving application pulse having a reference pulse width from the output driver 21 at a reference temperature, for example, 25°C. However, the pulse width of this strobe signal STh is changed by the pulse width adjustment circuit 23, and the strobe signal STh is sent to the output driver 2 as a strobe signal 5tBy'.
1, which will be described later. Further, the amplitude of the applied pulse for electrode driving from the output driver 21 is changed by the voltage level adjustment circuit 22.

The liquid crystal display section 4 shows a cholesterin liquid crystal in which the directions of the molecules on each surface are aligned but the orientation order between the surfaces is arranged in a spiral manner, and a cholesterin liquid crystal in which the orientation order of the molecules is arranged in a spiral manner between the surfaces, and a cholesterin liquid crystal in which the center of gravity of the molecules is at random, but the direction of the molecules is FIG. 2 shows a characteristic diagram showing the relationship between voltage and passage rate when using a phase inversion type liquid crystal mixed with a nematic liquid crystal whose liquid crystals are uniaxially aligned. Curve C1 is temperature T
1, the broken line curve C2 is a characteristic diagram at temperature T2. As is clear from the curves C, , C, these characteristics have hysteresis and their shape changes depending on the temperature. At voltage 1, the transmittance is B, and B2, and the hysteresis margin is Δ■. On the other hand, the transmittance at voltage ■2 is B,',Bz, and the hysteresis margin is Δ■'. The difference in transmittance ΔB in curve C3 = B, -B is the difference in transmittance ΔB in curve C2
'=B, -B,' is larger than ', and a large contrast can be obtained. The hysteresis margin Δ■ is also larger than Δ■'.

As is clear from Figure 2, when the temperature is T2 and the amplitude of the electrode drive voltage pulse is ■, the liquid crystal display device does not operate; conversely, when the temperature is T and the amplitude is ■2, the liquid crystal display device still operates. do not. Even between these temperatures,
This shows that in order to increase the contrast, it is necessary to adjust the amplitude of the electrode driving pulse voltage.

An example of a voltage level adjustment circuit is shown in FIG. The voltage level adjustment circuit 22 includes resistors 223 to 226 and a transistor 221 connected as shown, and the output of the voltage level adjustment circuit 22 is connected to each circuit of the output driver 21 shown in FIG. In FIG. 3, a regulator IC circuit 227 and resistors 228 and 229 are connected as shown.

The 1-transistor 221 is provided near the liquid crystal display section 4 and is designed to be sensitive to the temperature of the liquid crystal display section 4.

That is, the state of the PN junction of the transistor 221 changes depending on the temperature of the liquid crystal display section 4, and the current flowing through the transistor 221 changes depending on the temperature. This allows transistor 2
The collector voltage of 21 changes. Regulator IC circuit 227 responds to changes in collector voltage by increasing power supply v. ,V
A predetermined voltage is generated from the voltage difference between EE and EE. Resistor 2
28 is an output resistor, and the power supply voltage adjusted as described above is applied to the power supply terminal of the output dryer circuit 21 via the resistor. Resistor 229 is a variable resistor for adjusting output voltage.

As shown in Figure 2, hysteresis margins ΔV, Δ■
' changes depending on the temperature. Next, the relationship between the write pulse width PW and the hysteresis margin Δ■ is shown in FIG. Curves CII, CIZ, and C10 show the characteristics when the temperature of the liquid crystal display section is T, T2, and T3, respectively. The temperature is T + < T z < T3, e.g. T,
=10℃, Tz=30℃, T.

-50°C. As is clear from Fig. 4, the optimum hysteresis margin and write pulse width are determined by temperature, and it is not preferable to have a pulse width that is too narrow or too wide, and as the temperature decreases, the pulse width PW tends to become wider. shows.

As mentioned above, the pulse width PWo of the strobe signal 5TBV
is defined based on a reference temperature, for example, 25° C. (FIG. 5(a)). A time constant circuit 23 consisting of R and C shown in FIG. Since a capacitor using a depletion layer or a variable capacitance diode type capacitor is used in the device, the time constant changes depending on the temperature change of the liquid crystal display section 4. Further, the resistance component R can also be one whose resistance changes greatly with temperature changes, and one or more of R and C of the circuit 232 can be used which has temperature dependence. Due to such a change in the time constant, the rise and fall characteristics of the strobe signal 5TBy change (FIG. 5(b)). The strobe signal passed through the time constant circuit 232 changes as shown in widths W, W2, respectively, based on the threshold value vl (as shown in FIG. 5(b)).
A solid line indicates a case where the temperature of the liquid crystal display section is low, and a broken line indicates a case where the temperature is high. The pulse width setting and pulse shaping circuit 231 is configured to set pulse widths PW, , P that are defined according to the widths W, , W2 in FIG.
A shaped strobe signal STh' having W2 is generated (FIG. 5(C)). A drive pulse having a pulse width based on the thus adjusted strobe signal 5TBy' and whose amplitude has been adjusted as described above is applied to the electrodes of the liquid crystal display section 4. As a result, the liquid crystal display section 4
can operate in a stable state with minimal temperature dependence. As a means for changing the amplitude and pulse width of the pulse voltage in response to temperature, the above-mentioned extrapolation means can be considered. For example, the pulse width can be changed using a transistor as a temperature sensitive element. Also, the pulse width can be changed using a thermistor. The same applies to the amplitude adjustment of the pulse voltage.

〔Effect of the invention〕

As described above, according to the present invention, by applying the optimum electrode driving pulse determined by the temperature of the liquid crystal display device to the liquid crystal display device electrode, the liquid crystal display can operate stably without depending on temperature changes. A display device is provided.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a liquid crystal display device according to an embodiment of the present invention, FIG. 2 is a characteristic diagram of the liquid crystal display section of FIG. 1, and FIG. 4 is a characteristic diagram showing the relationship between the write pulse width and hysteresis margin of the liquid crystal display section in FIG. 1, and FIGS. 5(a) to (c) are pulse waveform diagrams in the pulse width adjuster of FIG. 1. It is. (Explanation of symbols) ■...Control circuit, 2...Y side driver circuit, 3...X side driver circuit, 4...Liquid crystal display section, 2I...Output driver゛, 22... Voltage level adjustment circuit, 23...Pulse width adjustment circuit.

Claims (1)

[Claims] 1. A liquid crystal display device, and a display control means for applying a driving voltage pulse to an electrode of the liquid crystal display device so as to obtain a display content responsive to display data, the display control means being dependent on the temperature of the liquid crystal display device. 1. A liquid crystal display device, comprising: a drive voltage pulse having a pulse width and amplitude defined by: 2. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a phase change type liquid crystal display device having hysteresis in voltage and optical characteristics.