JPS61239296A - Liquid crystal input/output unit - 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] Industrial Application Field The present invention relates to an input/output device using a liquid crystal.
The present invention relates to a liquid crystal input/output device characterized in that display and data input by writing using a magnetic field can be performed in the same liquid crystal device.

2. Description of the Related Art Liquid crystal display devices having various characteristics depending on the materials used are already known. These liquid crystals are mainly used as display elements by changing the orientation of liquid crystal molecules by some external field and utilizing their optical properties. However, things that change due to external fields are accompanied by changes in not only optical properties but also electrical properties such as changes in capacitance.

An overview will be given of a finger touch sensing switch described in, for example, Japanese Unexamined Patent Publication No. 58-89737, which utilizes this change in electrical properties and has been applied as an input device.

FIG. 3 shows a sectional view of a conventional example.

The liquid crystal cell 31 has a thickness of 12 μm due to the spacer ring 34.
Two glass walls 2ff thick separated by 32.33
including. The electrodes 35, 36 are formed, for example, with a layer of tin oxide, on the inner surface of the glass walls 32, 33, and between the glass walls 32, 33 a layer 38 of nematic liquid crystal material is provided. The nematic liquid crystal material layer 38 contains a small amount of cholesteric material and □
Or it may contain a dye. Glass wall 3 before assembly
The inner surface of 233 is oriented by rubbing in a single direction, for example with a soft fabric, or by gradient deposition of MgF2. Two oriented glass walls 32 and 33 are arranged so as to be orthogonal to each other, and this is known as a twisted nematic liquid crystal. Polarizers 39 and 40 are arranged on both sides of the cell 31 in parallel in multiple directions.

When a voltage is applied to this, the orientation changes and display becomes possible. Also, when stress is applied to this cell, the capacitance between electrodes 35, 36 changes. This change is detected by the circuit shown in FIG. 4 and used as a switch. In FIG. 4, 4o is a liquid crystal cell (hereinafter referred to as cell) having electrodes 41, 42 and a liquid crystal material layer 43. A reference capacitor 44 is connected in series to the cell 4°. For example, frequency 1ooH
Two voltage sources 46 act on reference capacitor 44 and cell 4o. The voltage v0° appearing between the reference capacitor 44 and the cell 4o is supplied to a comparator 46. Comparator 46 also receives reference voltage vr8f.

The output of comparator 46 is provided to control logic 47.

Control logic section 47 supplies a predetermined voltage to liquid crystal display 48 .

Based on the principle described above, stress changes in the liquid crystal manifest as changes in capacitance, and by electrically detecting this change, the liquid crystal can be used as a touch switch and the liquid crystal can be used as an input device. It shows what can be done.

Problems to be Solved by the Invention However, in this method, since the liquid crystal cell is deformed, the deformation range is wide, and high resolution cannot be obtained as an input device for characters and graphics. The problem is that it is difficult to

Means for Solving the Problems In view of the above problems, the present invention provides a liquid crystal input/output device capable of displaying and inputting at -7V. The present invention focuses on the fact that the orientation of liquid crystal molecules is different when a magnetic field is applied and when it is not, and that the capacitance between the electrodes that sandwich the liquid crystal layer is also different, and detects changes in this capacitance. It is characterized by having an input function.

Effect In a liquid crystal consisting of elongated rod-shaped molecules, the magnetic susceptibility in the long axis direction of one molecule is “+”
1 and the magnetic susceptibility X□ in the direction perpendicular to it are different.

When a DC magnetic field IH is applied to a liquid crystal having such magnetic susceptibility anisotropy, a magnetic energy density fn expressed by the following equation is generated.

However, +h is a unit vector of molecular orientation, ΔX is magnetic susceptibility anisotropy (x, -xL), and IH is a magnetic field vector.

Here, the second term, which is unrelated to the direction of the director Ih, is a term that depends on the direction. When a magnetic field exceeding a certain strength ([>ll0) is applied to a nematic liquid crystal, its molecular axes are oriented parallel to the direction of the magnetic field. Therefore, when a magnetic field is applied perpendicular to the electrode, the molecular orientation changes from the direction along the electrode to the direction perpendicular to the electrode. Therefore, as the long axis of one molecule moves, the capacitance between the dielectric anisotropy and the spots of the liquid crystal also changes. Therefore, by detecting this change in capacitance, it is possible to determine whether a magnetic field has been applied or whether a multiple input has been made.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings. FIG. 1 shows the configuration of a liquid crystal input/output device according to an embodiment of the present invention. FIG. 1(b) is a perspective view of a liquid crystal panel of a liquid crystal input/output device showing a state in which input/output operations are performed using bar magnets. In FIG. 1(b), 1 is a bar magnet used for input, 2 is a liquid crystal panel having display and input functions, and 3 is a magnetic body for focusing the magnetic field applied to the liquid crystal panel 2.

FIG. 1(C) is a block diagram of the system of the device. In FIG. 1(b), 2 is a liquid crystal panel which has both an input function and a display function. 4 is a host system that outputs display data and outputs control signals for the control device that takes in the input data. 6 is the control circuit,
It exchanges data with the refresh memory 7, and has the function of functioning as a circuit for detecting capacitance for electrodes that are not currently displayed. Reference numeral 7 denotes a refresh memory in which data for one side for display is stored, and a random access memory (RAM) or the like is used. Reference numeral 8 denotes a driving power source that supplies power to the liquid crystal panel 2.

Figure 1 (&) shows the changes in the capacitance of picture elements when a beam-shaped magnetic field is applied to the liquid crystal panel 2 formed by the X electrode 29 and the Y electrode 26 to obtain high resolution, and one display is made. This figure shows a circuit diagram of the main parts. In FIG. 1, the control circuit 6 assumes that if the refresh memory 7, E bit is "0", it is an undisplayed electrode, and switches the status switching electronic switch 19, 20 from the terminal 19 to 1.
9B.

The pixel capacitor 25 is changed by changing from 2 Ω to 2 OB.
The capacitance C8 is connected to the resistors 9, 11 . Capacitor 13.14.
Detection is performed using a bridge circuit formed with 22. Therefore, when a magnetic field is applied to the picture element capacitor 25 as shown in FIG. 1(b), the amount of electrostatic charge changes. Thereupon, the bridge is unbalanced, and the unbalanced portion is rectified by the diode 2), smoothed by the capacitor 15°16 and the resistor 1o, and then enters the comparator 23. And the unbalanced voltage is the reference voltage Vr, f27
When this happens, an output appears at the terminal 28 and is sent to the control circuit 5 in FIG. 1(C), allowing the refresh memory to be rewritten. FIG. 2 shows how a twisted nematic (TN) type liquid crystal of a 1D cell changes when a magnetic field is applied.

Effects of the Invention The present invention makes it possible to provide an input function to the liquid crystal panel by applying a magnetic field to the liquid crystal, detecting changes in capacitance, and rewriting display data with the refresh memory.

Therefore, by taking advantage of the good response of the twisted nematic liquid crystal, it is possible to create a device with input and display functions in the same device, and because the input section and display section are separate from each other as in the past, the inputter does not have to worry about where to input data. This eliminates the inconvenience of not knowing whether the person is present or not.

[Brief explanation of drawings]

FIG. 1 (1L) is a circuit diagram of a main part of a liquid crystal input/output device according to an embodiment of the present invention, and FIG. 1 (b) is a perspective view showing the input/output state of the liquid crystal panel and a bar magnet. (c) is the system block diagram, Figure 2 is a characteristic diagram showing the relationship between capacitance and magnetic field in this embodiment, Figure 3 is a cross-sectional view of the conventional liquid crystal panel, and Figure 4 is the conventional example. FIG. 1... Bar magnet, 2... Liquid crystal panel, 3
...Ferromagnetic material, 4 ... Host system, 5 ... Control circuit, 7 ... Refresh memory, 8 ... Drive power supply , 9-1
1...Resistance, 13-16, 22...
Capacitance, 19.20...Electronic switch. 23... Comparator, 25... Picture element capacitor, 26... τ electrode, 27... Reference voltage, 28... Output terminal , 29...
...X electrode. Name of agent: Patent attorney Toshio Nakao and 1 other person 2nd
Figure y also --- Figure 3 Figure 4

Claims (6)

[Claims] (1) A liquid crystal input/output device comprising a liquid crystal cell formed from two opposing electrodes and a layer of liquid crystal material sandwiched between them, and means for detecting changes in capacitance caused by applying a magnetic field to this cell. . (2) A magnetic plate is used on at least one side of the liquid crystal to apply a magnetic field, and a beam-shaped magnetic field is formed between it and a bar-shaped magnetic pole for input to change the orientation. LCD input/output device. (3) A write and read mode switch is provided, and when the write mode is set, the capacitance is detected only for the picture elements at the combination of positions where the drive memory becomes low level. LCD input/output device. (4) A patent claim in which capacitance corresponding to a picture element forms one side of an AC bridge, and detection is performed by utilizing the fact that the balance of the bridge is disrupted due to the capacitance that changes when a magnetic field is applied. The liquid crystal input/output device according to item 3. (5) The unbalanced portion of the bridge is rectified using a comparator, and if there is a change of more than the reference voltage, it is assumed that writing has been performed and the refresh memory is rewritten. LCD input/output device. (6) The liquid crystal input/output device according to claim 4, wherein the liquid crystal is a twisted nematic liquid crystal.