JPS6015683A - 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 [Field of Application of the Invention] The present invention relates to a display panel using liquid crystal, and more particularly to a liquid crystal display panel that utilizes the thermo-electro-optical effects of smectic liquid crystal and the like.

[Background of the invention]

A display device using the thermo-electro-optical effect of liquid crystal is disclosed in U.S. Pat. No. 3,796,999 or No. 3,836,2.
It is described in detail in issue 43.゛These devices irradiate a cell filled with a liquid crystal material (for example, smectic liquid crystal) with laser light to locally heat any part of it, raising the temperature once above the phase transition temperature of the liquid crystal material. In the cooling process that follows, the optical properties of the liquid crystal layer after cooling are controlled by whether or not an electric field is applied, thereby achieving display.

FIG. 1 explains the thermal and electro-optic effects of smectic liquid crystal. In the initial state, liquid crystal molecules are arranged in an orderly manner and are in a transparent state. From this state, it is heated by V-za light or the like to raise the temperature until it becomes an isotropic liquid phase, and then cooled. At this time,
When an electric field Et is applied to the liquid crystal, it returns to its original transparent state, but the electric field E
If it is not added, it will be in a scattered state and cannot be written.

Figure 2 shows a liquid crystal display spring k(1) using the principle described above.
- FIG. [@The ]) directV
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2) ) Switch 3' (i- closed, current flows from the power supply 2 to the heat electrode l provided on the entire board 22 to generate Joule heat. This heat is applied to the portion of the liquid crystal layer 25 that is in contact with the heat electrode 1. The entire temperature of the liquid crystal is made to be an isotropic liquid. Next, switch 3 is opened to stop the current, and the liquid crystal is cooled. At this time, a voltage is selectively applied between electrode 1 and electrode 4 on the counter substrate 21. The liquid crystal in the area where the voltage is applied is in its original transparent state, and the liquid crystal in the area where no voltage is applied is in the scattering state, making it possible to display all optical information.

FIG. 3 is an enlarged plan view of a portion of the heat electrode 1 in FIG. 2. FIG.

In FIG. 3, lead wires are provided at both ends of the heat electrode 1 in the length direction (high resistance direction), and the other end is connected to the power source 2 via the switch 3, which is fully grounded. Therefore, current flows in the direction of arrow 119, and Joule heat is entirely generated due to the resistance of heat electrode 1.

If the device is large and the length of the heat electrode becomes long, the voltage (18) applied to both ends of the heat electrode 10 becomes proportionally very high.

When the voltage applied to the electrode becomes a high voltage, consideration must be given to the power supply and the peripheral circuits that control the power supply to withstand the high voltage. , with the disadvantage of high price.

Furthermore, insulation between adjacent heat electrodes had to be considered, making it difficult to produce a high-resolution display device.

[Purpose of the invention]

An object of the present invention is to improve the structure of the heat electrode, lower the voltage applied to the heat electrode, and provide a liquid crystal display panel that can be driven at a low voltage.

[Summary of the invention]

The present invention enables heating voltage metal processing and low voltage driving to be applied to both ends of the heat electrode by flowing the current necessary to generate Joule heat in the width direction (low resistance direction) of the heat electrode. It is.

[Embodiments of the invention]

The present invention will be described in detail below using the drawings.

FIG. 4 is a schematic diagram showing a liquid crystal display device using a liquid crystal display panel according to the first embodiment of the present invention, and FIG. 5 is a schematic cross-sectional view of the liquid crystal display panel in FIG. FIG. 6 is a schematic plan view.

In FIG. 4, 200 is a liquid crystal display panel, 120 is Y
The electrode drive circuit 121 is a row electrode drive circuit. 12
1 consists of three groups of two-channel switching elements for switching a heating power source 2 that generates a voltage Vmk for heating the X electrode. In addition, 122 indicates that the switch 121 is connected to the heating power supply 2.
This is a group of switch elements that turn on only when selected.

The liquid crystal display panel 200 has a plurality of heats (X) on opposing surfaces.
A gap of about 10 μm is created between a pair of substrates 21 and 22 arranged in parallel so that the electrode 100 and the plurality of X electrodes 4 intersect 9. A liquid crystal 25 having a smectic phase is placed between the substrates and a spacer 28 Seal with. Here, X electrode 1
00. The opposing portions of the X electrodes 4 serve as pixels, forming a matrix as a whole.

For the substrates 21 and 22, for example, a glass plate or a plastic plate is used, or an opaque substrate such as the 81 substrate is used for the substrate not to be observed, and a transparent substrate such as a glass plate or a plastic plate is used for the substrate to be observed.

(R is an alkyl group), it exhibits positive dielectric anisotropy, exhibits a smectic phase at room temperature, changes from a smectic phase to a nematic phase at 42C, and then from a nematic phase to an isotropic liquid phase at 45C. Use something that transfers to.

In addition, as other liquid crystals exhibiting smectic physiognomy, there are 4
．． A mixture of a 4'-alkoxybiphenylcarboxylic acid alkyl ester and a 4,4' alkylanotolane or a 4-alkoxyphenyl-4'-ylkylbenzoate ester! :P, P'-alkylcyanopiphenyl mixtures, etc.

Further, when a dichroic dye is added to the liquid crystal, the viewing angle characteristics of the display are improved, which is advantageous for a display device.

FIG. 7 is an enlarged plan view and cross-sectional view of the portion of the heat electrode 100 in thermal contact with the liquid crystal in FIGS. 4 to 6.

Low resistance conductors 10 are provided at both ends of a heat electrode 100 provided on a substrate 22 in a low resistance direction (width direction). One end of this conductor 10 is grounded, and the other end is connected to the heating power source 2 via the switch 3.

Using extremely high heat, chromium, nickel, tin, lead, tungsten, manganese, molybdenum, iron, zinc, indium, platinum, or their alloys or oxides,
The conductor 10 is made of a highly electrically conductive metal such as gold, silver, or aluminum, or an alloy thereof. The sheet resistance value of the heat electrode 100 is desirably about 0.05 to 1.0Ω, and the sheet resistance value of the conductor 10 is desirably about 0.01 to 0.1Ω or more. As shown in FIG. 8, when the switch 3 is closed, current flows in the width direction of the heat electrode 100 (in the direction of the arrow 11) and generates Joule heat. Therefore, the heat electrode 100 has a low resistance as a whole.
It can be seen that the voltage vH applied to can be lowered. Now, if the heat electrode 100 is made of the same material and shape as the heat electrode 1 in the conventional example shown in FIG. 3, the heating voltage VHI applied to the heat electrode 100 in this embodiment and the conventional example shown in FIG. where t is the length of the heat electrode 1,100 and W is the width of the heat electrode 1,100. For example, if t = 20 cm and W = 250 pm, then V
Il should be 1/800 of Vil2.

In addition, the material of the heat electrode 1oO or the conductor 10
It is also possible to satisfy the above sheet resistance value by changing the total thickness of the material.

Further, as shown in FIG. 6, by connecting the external connection terminal portion 150 and the heat electrode 100 using a low resistance conductor 10, the resistance can be further reduced. In addition, connection terminal part 1
50 may be the same material as the low resistance conductor 1°,
Other materials may also be used.

Further, in FIGS. 4 to 6, the X electrode 4 is formed of a transparent conductive film made of a mixture of indium oxide and tin oxide, which is generally called a Nesa film.

FIG. 9 shows a second embodiment of the invention. A low resistance conductor 10 is provided at both ends of the upper part of the heat electrode 100 provided on the substrate 22 in the low resistance direction (width direction). Current flows in the direction of arrow 11. In this embodiment, the electrode width including the conductor portion can be narrowed, and a liquid crystal display panel with higher definition can be obtained.

FIG. 6 shows a third embodiment of the invention. A low resistance conductor 10 is provided between a substrate 22 and a heat electrode 100 provided on the substrate 22. Current flows in the direction of arrow 11. In this embodiment, the Joule heat generated by the heat electrode 100 is directly transferred to the liquid crystal, so thermal efficiency is good. Further, since there is only one type of electrode on the substrate 22, there is no difference in reflectance, and the display becomes clearer.

Next, the operation of the liquid crystal display device shown in FIG. 4 will be explained using the operating waveforms shown in FIG. 11.

In this embodiment, the X electrode 10 is
The left terminal part of 0 (Xl, Xs...X,) is
A voltage as shown in FIG. 11 is applied. That is, at time t1 + "2... river t, the switching element 3 selects the heating power source 2 side in the first half and the AC heavy pressure source 23 in the second half. First, at time t! when X + all selections,
In the first half of tll, corresponding to the selected X electrode,
One of the 122 switch element groups is turned on. Therefore, the X electrode generates heat, and the state of the liquid crystal transitions from a smectic phase to a nematic phase to an isotropic liquid phase. Next, t
At step 12, 121 is switched to the AC voltage source VB, and at the same time, the switch 122 is turned off. At the same time, from the Y electrode drive circuit side 120 side, ±1 according to the large sword data signal
All signals of Vow or Vsff having an amplitude of /2Vt and different phases from each other are applied.

This operation is repeated in the same way, and X2, Xs...
Xl is sequentially scanned. Therefore, the alternating current electric field applied to the liquid crystal becomes as shown in FIG. is determined. In this example, the unselected X electrode is always set to ±1.
An alternating current voltage of /2 Vt is applied, but since the unselected X electrodes are not heated, no change in the display state occurs.

〔Effect of the invention〕

According to the present invention, it is possible to generate Joule heat necessary for thermal writing at a low voltage in a liquid crystal display panel that utilizes thermo-electro-optic effects such as a smectic liquid crystal, and a power supply and peripheral circuit. It is easy to integrate the devices, which makes it possible to downsize and reduce costs.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the thermal and electro-optical effects of smectic liquid crystal, Figure 2 is a diagram showing an example of a conventional liquid crystal display panel, and Figure 3 is an enlarged plan view of the heat electrode 1 part in Figure 2. 4 to 8 are diagrams showing a first embodiment of the invention, FIG. 9 is a diagram showing a second embodiment of the invention, and FIG. 10 is a diagram showing a third embodiment of the invention. FIG. 11 is an operating waveform diagram of the liquid crystal display device of FIG. 4. 1.100...Heat electrode, 10...Conductor, 11.
・Electric notification

Claims (1)

[Claims] 1. In a liquid crystal display device having a liquid crystal having thermal and electro-optic effects held between a pair of substrates and at least one heat electrode in thermal contact with the liquid crystal, the heat electrode has low resistance. A liquid crystal display panel characterized in that low resistance conductors are provided at both ends of the heat electrode.