JPS6159496A - Driving of heat mode type liquid crystal display panel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Description of the field to which the invention pertains The present invention relates to a method for driving a heat-mode liquid crystal display panel, and particularly a heat-mode liquid crystal display panel that can perform high-quality display at high speed and memorize the display. The present invention relates to a display panel driving method.

(2) Description of the Prior Art A thermal writing type liquid crystal panel is considered to be a promising planar device with a high display density and a large display capacity. The operating principle of the thermal writing type liquid crystal is shown below.

A cyanobiphenyl-based liquid crystal material is used as a liquid crystal material, and this liquid crystal material exhibits the following phase transition as the temperature rises.

Furthermore, this liquid crystal has high positive dielectric anisotropy in the nematic state. A liquid crystal panel is made by sandwiching two glass substrates with electrode wires on their inner surfaces at right angles, in the same way as in the conventional method. Note that silane treatment is applied in advance to vertically align the liquid crystal.

Note that a resistance wire made of N1-C wire or the like is installed as the heat electrode of the liquid crystal panel, and a transparent electrode made of L203 or the like is used as the signal electrode. Therefore, a heat pulse can be supplied to the liquid crystal by driving the heat electrode, and an electric field pulse can be supplied to the liquid crystal by driving the signal electrode. The liquid crystal at the intersection of the two electrodes then instantaneously rises from a smectic state to an isotropic liquid. Next, when the heat pulse is removed, the temperature of the liquid crystal drops rapidly and returns to the smectic state. However, depending on the presence or absence of a signal pulse, a difference in force occurs when passing through the nematic state, resulting in two cases. That is, when the signal pulse is turned on, it becomes a normal well-oriented smectic state (homeotropic structure) and is transparent. On the other hand, when the signal pulse is off, the state force at high temperature is quenched, resulting in an irregular state (focal conic domain), which strongly scatters light. The above situation is schematically shown in FIG. The representation is therefore given as a transparent pattern in a scattered state,
It is controlled by whether or not the scanning electrode (heat electrode) and signal electrode are driven. This is summarized in the first
It is a table.

As described above, since the heat mode liquid crystal has a memory property, it does not cause flicker due to an increase in the number of scanning lines, and has the advantage that there is essentially no crosstalk.

However, since it is necessary to raise the temperature of the liquid crystal to display a pattern, when writing at high speed, the temperature of the liquid crystal does not rise sufficiently, resulting in low contrast and deterioration in display quality. Furthermore, when repeatedly displaying on a liquid crystal, the heat applied to the liquid crystal accumulates in the liquid crystal or the glass substrate forming the heat electrode, resulting in a disadvantage that the contrast becomes low and the display quality deteriorates.

(3) Purpose of the Invention In order to eliminate these drawbacks, the present invention applies heat only when erasing the display on the liquid crystal, and displays the display on the liquid crystal only using an electric field. Explain.

(4) Explanation of the structure and operation of the invention FIG. 2 is a circuit diagram in an embodiment of the invention, and is an IC
-1f is a heat electrode, 2α~2g is a signal electrode, 3α~3
f and 4α~4f are heat electrode changeover switches, 5a~
5g is a signal electrode changeover switch, 6 is a heat electrode heating power source, 7 is a heat electrode signal writing auxiliary power source, and 8 is a signal electrode signal writing power source. The liquid crystal material is heat electrode 1.
It is filled between a to 1f and the signal electrodes 2α to 2g, and the signal electrodes 28 to 2g are formed of an optically transparent material.

FIG. 3 is a time chart for operating the liquid crystal display device. In the figure, 9 indicates the voltage waveform applied to the heat electrode 1a, similarly, 10 indicates the heat electrode 1b, 11 indicates the heat electrode 1i+, 12 indicates the heat electrode ld, 13 indicates the heat electrode 16, and 14 indicates the heat electrode 1f. This is the voltage waveform to be applied. 15 is a voltage waveform applied to the signal electrodes 2a to 2g.

The method of operation will be explained below. First, in Fig. 2, the signal electrode 2a
-2σ changeover switches are all set to the ground side, the changeover switches 4α to 4f of the heat electrodes 1a to 1f are turned on to ground them, the changeover switches 36 to 3f are connected to the heating power source 6, and the liquid crystal is connected to the heat electrode. A current is applied until it is heated to 1α to 1f and becomes a liquid. Next, the changeover switches 3a to 3f of the heat electrodes 1a to 1f are opened, and the changeover switches 4a to 4f are opened to cut off the current.

The liquid crystal cools down after a certain period of time and changes from a liquid state to a nematic state and then a smectic state. Since the potentials of the heat electrodes 1α to 1f and signal electrodes 2α to 2g are grounded, the liquid crystal is fixed in the 1 scattering state. The entire surface is erased and becomes blank. To write a signal, when displaying a pixel where the heat electrode 15 and the signal electrodes 26 to 2g intersect, the changeover switch 3eL of the heat electrode 1cL is connected to the signal writing auxiliary power source 7, and at the same time, the changeover switch 4a is connected to the changeover switch 3eL of the heat electrode 1cL.
is opened, and the potential of the heater μ electrode 1cL is set to the potential of the signal writing auxiliary power source 7 -EB. Other heat electrode 1b
~1f open selector switches 3b~3o, 4b~4
Turn on f and set the potential to ground.

And changeover switches 5a to 5g for signal electrodes 2a to 2g.
When displaying on a pixel that intersects with the heat electrode 1α, it is connected to the signal writing power source 8 to set the potential to Er, and when not displaying, it is connected to the ground.

Here, pixels where the signal electrodes 2α, 2b 126 and the heat electrode intersect are displayed, and the signal electrodes 2d, 2m, 2f, 2g
Assuming that there is no display in pixels where the and heat electrodes intersect, the heat electrode IIS and the signal electrodes 2α, 2b,
There is a potential difference of Ede + E8 in the pixel that intersects with 2a,
Heat electrode 1a and signal electrodes 2d, 2#, which are not displayed on the other hand,
There is a potential difference of EB at the pixel where 2/ and 2g intersect.

In addition, at this time, the potential difference is Er in the pixels where the unselected heat electrode /b-// and the signal electrodes 2a, 2b, and 2C intersect, and the potential difference is Er in the pixels where the signal electrodes 2d, 2g, 2/, and 2g intersect. There isn't. The liquid crystal used in this device has the characteristic that even in a cooled state, when a voltage equal to or higher than the critical voltage EtA is applied, the phase changes from a scattering state to a transparent state and maintains that state.

Therefore, if the potential difference Er + Ea applied to the pixel to be displayed and the potential difference E8 or ET applied to the pixel not to be displayed are set within a range that satisfies the following conditions, the pixel to be displayed will be in a transparent state, Pixels that are not displayed can be maintained in a scattered state.

Similarly, information can be written on one screen by sequentially selecting the heat electrodes 1b to 1f and setting the potentials of the signal electrodes 2α to 2g using the changeover switches 5cL to 5σ.

An example of a liquid crystal used in this device is a cyanobiphenyl type liquid crystal, and if the thickness of the liquid crystal layer is 10 m, the critical voltage is about 70 V. Therefore, the voltages -EB and Er of the signal write auxiliary power supply 7 and the signal write power supply 8 may be set to -35V and 35V, respectively.

(5) Description of Effects As explained above, according to the present invention, since the device applies heat when erasing the liquid crystal display and controls the signal display using the applied voltage, it is possible to maintain the contrast. Signals can be written and displayed at high speed with good quality. Furthermore, even if writing is performed repeatedly, the accumulation of heat can be reduced, resulting in high quality display.

INDUSTRIAL APPLICATION This invention is applied to the recording of the received facsimile image, the display apparatus of the search data of an image database, etc.

[Brief explanation of the drawing]

FIG. 1 is a phase transition diagram of a liquid crystal, FIG. 2 is a circuit diagram of an embodiment of the present invention, and FIG. 3 is a time chart for driving the circuit of FIG. 2. lα~lf...Heat electrode, 2a~2g...
- Signal electrodes, 3α to 3f1. ... Selector switch, 4a
~4f...Choice switch, 5a~5 Q...
, selector switch, 6... power supply for heating the heat electrode, 7.1
．． ... Heat electrode signal writing auxiliary power supply, 89. , signal write power.

Claims (1)

[Claims] A transparent front substrate on which a plurality of strip-shaped transparent electrodes are arranged in one direction, a rear substrate on which a plurality of strip-shaped resistance heating electrodes are arranged in a direction perpendicular to the strip-shaped transparent electrodes, and a transparent substrate sandwiched between these substrates. In a heat mode liquid crystal display panel having a liquid crystal layer, the band-shaped resistance heating electrode is temporarily energized and
The liquid crystal layer is heated to bring it into a front scattering state, and the liquid crystal layer is heated at room temperature at the intersection of any one of the plurality of band-shaped transparent electrodes and any one of the plurality of band-shaped resistance heating electrodes. By applying an electric field to the sandwiched liquid crystal layers,
A method for driving a heat mode liquid crystal display panel, characterized in that information is written by selectively making the liquid crystal layer transparent.