JPH0455824A - Liquid crystal element and production thereof - Google Patents

Abstract

PURPOSE:To allow displaying with uniform medium contrasts by having coupling elements between main electrodes and auxiliary electrodes, by which the auxiliary electrodes are subordinately driven and the potential of the auxiliary electrodes kept lower than the potential of the main electrodes. CONSTITUTION:A liquid crystal panel 1 consists of a liquid crystal layer pinched by a upper substrate 2 and a lower substrate 3. The upper substrate 2 and lower substrate 3 having conductive thin films respectively formed with electrode patterns. The column electrodes 4a to 4d are provided on the upper substrate 2. The row main electrodes 5a to 5d and the line auxiliary electrodes 6a to 6d are similarly provided on the lower substrate 3. These main electrodes and auxiliary electrodes are electrically connected by the coupling elements 7a to 7d. The relatively smaller potential than the potential of the main electrodes is applied to the auxiliary electrodes in this way and if one picture element is taken like (a), (b), (c), the ternary displaying of on, gray and off is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a liquid crystal element used in display devices and the like, and a method for manufacturing the same.

Conventional technology A ferroelectric liquid crystal made into a thin film is stable in several limited states as shown in FIG. In the figure, 60 is a liquid crystal molecule, 61 is a cone, 62 is an upper substrate, and 63 is a lower substrate. In FIGS. 6(a) and 6(b), the directions of the liquid crystal molecules are almost aligned, and at this time, the spontaneous polarization of the molecules is directed upward or downward to the normal line of the substrate. FIG. 6(C) shows a state in which the liquid crystal molecules are twisted in the normal direction of the substrate, and there also exists a state in which the twisting direction is reversed. Although it may differ from FIG. 6 depending on the type of alignment film, the angle of inclination of the liquid crystal molecules on the substrate, and the way the liquid crystal layer is bent, this schematic diagram basically represents the stable state of the liquid crystal molecules. Figure 7(a),
(b) and (C) are respectively shown in Fig. 6 (a) and (b).
FIG. 2 is a plan view of the liquid crystal shown in FIG. In the figure, 70 is the direction of spontaneous polarization, 71 is a polarizer, 72 is an analyzer, 73 is a liquid crystal molecule near the upper substrate, and 74 is a liquid crystal molecule near the lower substrate. When a liquid crystal cell is sandwiched between polarizers 71 and 72 that are orthogonal to each other, brightness and darkness can be created using the --like state shown in FIG. 7(a). Figure 7 (
In a state where the liquid crystal molecules have a twisted structure as shown in C), the display becomes gray. A thin-film ferroelectric liquid crystal panel has such a stable state, and the transition between these states shows a steep threshold characteristic in terms of applied voltage and amount of transmitted light. A high-capacity, high-contrast display can be obtained using a simple matrix configuration consisting of only electrodes without providing a nonlinear element in each picture element.

However, since the ferroelectric liquid crystal can only stay in a stable state in a limited number of ways as shown in FIG. 7, it is extremely difficult to realize multiple gradations. The gray display state in Figure 7(C) is stable only in a small voltage range during the transition from Figure 7(a) to Figure 7(b), so the uniformity of the liquid crystal panel It is difficult to display uniform halftones unless the value is extremely high.

Therefore, normally, ferroelectric liquid crystal devices basically use a binary display, and produce gradations by using multiple picture elements or multiple scans (for example, T., Leroux, F., Baum et al.: 1988 International Display Research Conference Proceedings, pp. 111-113 (i, le
+r□(H,p,[lHH,ej,al,:19881
NTERNAT4ONAL DISPLAY RESEA
CHC0NFERENCE, pHl~113))
.

At this time, one driving circuit is required for each scanning electrode and signal electrode forming each pixel.

Additionally, several methods have been proposed for realizing gradation display without increasing the number of drive circuits. A method of varying the threshold of liquid crystal response by providing a region with a different thickness of the liquid crystal layer within one pixel (for example, Iwai et al., Proceedings of the 13th Liquid Crystal Symposium, pages 138 to 139), This method includes applying an intermediate voltage to the auxiliary electrode by dividing the voltage from the ground potential through a resistance element. In particular, the method of dividing the voltage from the ground potential through a resistance element involves coupling the main electrode and auxiliary electrode connected to the voltage source with a 5 (10 ohm) resistor, and connecting the auxiliary electrode and the ground potential with a 5 (10 ohm) resistor. An example of connection has been reported (Japanese Unexamined Patent Publication No. 63-316024), but this method has problems such as extremely high power consumption and poor stability of the liquid crystal on the auxiliary electrode. In most driving methods, a positive or negative potential is almost always applied to both the scanning signal side and the signal electrode side, and in this method, a considerable current is almost always applied through a resistor. It is caused by flowing.

Furthermore, the decrease in stability of the liquid crystal on the auxiliary electrode is thought to be because the auxiliary electrode is grounded through a low resistance and therefore responds sensitively to non-selection pulses, resulting in poor stability of the memory state.

Problems to be Solved by the Invention As described above, it is difficult to display stable halftones in ferroelectric liquid crystal devices, and it is also difficult to achieve uniform grayscale display over the entire surface of the device with low power consumption.The present invention solves the above problems. The object of the present invention is to provide a ferroelectric liquid crystal element that can provide stable halftone display with low power consumption and that can be easily formed.

Means for Solving the Problems In order to solve the above problems, the liquid crystal element of the present invention has a plurality of electrodes made of conductors on opposing surfaces, and a liquid crystal material is disposed between a pair of substrates forming a matrix-like picture element. The electrodes of at least one of the substrates are electrically connected to each other by a coupling element (n is an integer of 2 or more), and none of the electrodes is connected to a fixed potential. be.

A certain electrode (main electrode) Yl on the substrate is directly connected to the active scanning electrode circuit, and a group of electrodes X1 to Xn on the opposite substrate
It is assumed that is connected to the signal electrode circuit. It is known that the equivalent circuit between the main electrode and the signal electrode at this time is a parallel circuit of a capacitor and a resistor, but this resistance value is sufficiently large and can be ignored. That is, the equivalent circuit between the main electrode and the signal electrode is only the capacitor C1.

The main electrode Y1 and the electrode (auxiliary electrode) Y2 adjacent to the main electrode Y1 are connected by an electrical element, and this auxiliary electrode Y2
Assuming that is not directly connected to the scanning electrode circuit,
The equivalent circuit from the scanning electrode to the signal electrode via the auxiliary electrode is a series connection of a capacitor of the liquid crystal panel and a coupling element.

Let us now consider the case where the coupling element is a resistor. At this time, the equivalent circuit from the scanning electrode to the signal electrode via the auxiliary electrode Y2 is a series circuit of the resistor R1 and the capacitor CI. When the resistance value of the coupling element is R1 and a pulse voltage that changes stepwise is applied between the scanning electrode and the signal electrode, the potential applied to the auxiliary electrode is C determined by CI and R1.
It increases according to the charging waveform with R time constant. If this pulse value is sufficiently small, the capacitor is not sufficiently charged, and therefore a sufficiently small voltage is applied to the auxiliary electrode compared to the main voltage.

If the coupling element is a capacitor C2, the equivalent circuit from the scanning electrode to the signal 1ii8ii via the auxiliary electrode is a series connection of two capacitors C2 and CI.
The potential of the auxiliary electrode is the voltage between the scanning electrode and the signal electrode C2,
The voltage is divided by the reciprocal of the capacitance of CI, and a sufficiently smaller voltage is applied to the auxiliary electrode than to the main electrode.

As described above, by electrically connecting the main electrode and the auxiliary electrode with an appropriate coupling element, a relatively small potential is applied to the auxiliary electrode compared to the main electrode, allowing the signal pulse width and signal voltage to be changed appropriately. In this way, halftone display can be realized by combining the pixels on the main electrode and the pixels on the auxiliary electrode. Further, by increasing the number of auxiliary electrodes connected by the coupling element, it is possible to realize an even greater number of gradations.

EXAMPLE Hereinafter, a liquid crystal device and a manufacturing method thereof according to an example of the present invention will be explained with reference to the drawings.

Embodiment 1 FIG. 1 is a plan view of a liquid crystal element showing an embodiment of the present invention. The liquid crystal panel 1 consists of a liquid crystal layer sandwiched between an upper substrate 2 and a lower substrate 3. On this board 2. Each of the lower substrates 3 has a conductive thin film with an electrode pattern formed thereon, column electrodes 48 to 4d are provided on the upper substrate vi2, and similarly, event electrodes 5a to 5d and row auxiliary electrodes are provided on the lower substrate 3. 6a to 6d are provided. These main electrodes and auxiliary electrodes are electrically connected by coupling elements 7a to 7d. FIG. 2 is a cross-sectional view of the liquid crystal panel 1 shown in FIG. The formed alignment films 22 and 23 are provided. An ester-based ferroelectric liquid crystal 24 exhibiting a chiral smectic C phase is sandwiched between alignment films 22 and 23. The 0th row main electrode is connected to a scanning electrode output circuit, and the column electrodes are connected to a signal voltage output circuit.

In the first embodiment, the coupling element is a resistor. This resistor element is made by applying a resistor by screen printing.
Similar results were obtained using a resistor formed by firing and a resistor formed by transferring the resistor from a film. Furthermore, since the conductive thin film that forms the electrode acts as a resistor when it is etched thinly, we also attempted to form the resistor at the same time using an etching method during the process of forming the electrode pattern; The results were obtained. Furthermore, similar results were obtained when the resistance element was formed on a flexible substrate and when it was formed on a printed circuit board. In this example, the resistance value was approximately 10Ω.

Figure 3 shows an example of the drive waveform used in this example. In this example, a 4-pulse method with a pause phase was used, but in addition to this, the normal 2-pulse method and 4-pulse method can also be used. In this embodiment, one auxiliary electrode is used for one main electrode, so the number of gray levels that can be realized is three. Therefore, the column electrodes 4a, 4b, and 4c are connected to each other as shown in FIG.
a), (b).

The signal waveform of 3 (!) in (C) was applied, and the scanning signal waveform of FIG. 3(d) was applied to the main electrode 5C.
The waveforms (b) and (C) are signal waveforms for writing on, gray, and off, respectively, and the gray signal waveform has a potential exactly between on and off. In addition, the scanning waveform applied to the main electrode is used to write the liquid crystal on the main electrode 5c and the row auxiliary electrode 6c on the electrode during the selection period shown in FIG. The voltage applied to the layer is the signal voltage FIG. 3(a).

Φ), (C) and the scanning voltage (d) in the same figure. This is shown in FIG. Main electrode 5c and column electrodes 4a, 4b, 4c
The waveforms of the voltage pulses applied between them are shown in Figure 4 (a).
), (b), (C), whereas the main electrode 5C
The auxiliary electrode 6c and the column electrode 4a are connected to each other by a resistor.

The waveforms of the voltage pulses applied between 4b and 4c are shown in Figure 4 (e) and (f), respectively.In the nine-drive method, the write pulse consists of four pulses, and the first two pulses are as shown in the picture. The latter two perform pixel writing, so when the height of the latter pulse exceeds the liquid crystal response threshold, the liquid crystal is written.The liquid crystal response threshold is the same. It is represented by the diagram Vt.

The voltage applied to the liquid crystal on the auxiliary electrode has a slow rise in the waveform because the capacitor formed by the liquid crystal layer is charged through the resistance, and the waveform is transmitted with a kind of delay, so if the pulse width is sufficiently short, The response of a ferroelectric liquid crystal has a steep threshold characteristic, and its value is indicated by Vt.
The liquid crystal is driven when the write pulse exceeds the threshold Vt. Therefore, between the column electrode 4a and the main electrode 5C and the second row auxiliary electrode 60, and between the column electrode 4b and the main electrode 50 are turned on. As shown in Figure 1, the l picture element is a.

When taken like 口 and ha, a three-value display of on, gray, and off was realized. Here, the shaded area is the area where the liquid crystal responds to the electric field and is in the on state.

Embodiment 2 A second embodiment of the present invention is shown below. The second embodiment also has the structure shown in FIG. This is the point.

The capacitor is a dielectric Tii film 20°2 to prevent dielectric breakdown.
1, formed by printing or transferring a conductive paste on top of 1, forming a ferroelectric material on an S electric thin film and forming a conductive layer on top of that, and forming a conductive layer on a circuit board. Both types were used, and similar results were obtained with both types. In this example, the capacitance of the capacitor is approximately 1 (10
It was set to 0 pF.

In this example, when the driving waveform shown in FIG. 3 is applied,
The voltage applied to the liquid crystal layer of each picture element was as shown in FIG. Main electrode 5C and column electrode 4a.

The waveforms of the voltage pulses applied between 4b and 4c are shown in FIGS. 5(a), 5(b), and 5(c), respectively. On the other hand, the waveforms of the voltage pulses applied between the auxiliary electrode 6c and the column electrodes 4a, 4b, and 4c are shown in FIGS. 5(d) and 5(e), respectively.
.

(f) Due to voltage division by the capacitor formed by the liquid crystal layer and the capacitor of the coupling element, the voltage applied to the auxiliary electrode is smaller than that to the main electrode.The response of ferroelectric liquid crystal has a steep threshold characteristic. and its value is Vt
is shown. When this threshold is exceeded, the liquid crystal molecules begin to move and switch from the off state to the on state. At this time, as shown in FIG. 1, three-value display of on-gray and off was realized for picture elements A, B, and C, respectively.

Note that similar halftone display was also possible when the coupling element used a switching element such as a transistor, FET, or diode. Furthermore, in this embodiment, an auxiliary electrode coupled and connected to the scanning electrode side was formed, but the same effect can be obtained when such an auxiliary electrode is used on the signal side, or when used on both the scanning side and the signal side. It was possible to display halftones. Also,
In the above embodiments, the number of auxiliary electrodes was the same as the number of main electrodes, but it was possible to increase the number of gradations by increasing the number of auxiliary electrodes. Further, in this embodiment, an example using ferroelectric liquid crystal was given, but the present invention is not limited to ferroelectric liquid crystal.

Effects of the Invention The liquid crystal element of the present invention has a coupling element between the electrodes in a liquid crystal element having a ferroelectric liquid crystal in the liquid crystal layer, so that the auxiliary electrode is driven in a subordinate manner, and the potential of the auxiliary electrode is changed to that of the main electrode. By setting the potential lower than the potential, a uniform halftone display can be realized, and manufacturing is also relatively easy.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a liquid crystal element according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of the same in elevation, FIG. 3 is a driving waveform diagram of a liquid crystal element according to an embodiment of the present invention, and FIG. 4 5 is a voltage waveform diagram applied to the liquid crystal layer of the liquid crystal element showing the first embodiment of the present invention.
The figure is a voltage waveform diagram applied to the liquid crystal layer of a liquid crystal element showing a second embodiment of the present invention, Figure 6 is a schematic diagram of ferroelectric liquid crystal molecules, and Figure 7 is a diagram of the ferroelectric liquid crystal shown in Figure 6. FIG. 2 is a plan view of liquid crystal molecules. 1...Liquid crystal panel, 2...Upper substrate, 3
...Lower substrate, 4a to 4d...Column electrodes,
5a to 5d... Main electrode, 6a to 6d...
...Row auxiliary electrode, 7a to 7d...Coupling element, 2
0.21...Dielectric thin film, 22゜23...
...Alignment film, 24...Ferroelectric liquid crystal. Name of agent: Patent attorney Shigetaka Awano, 1 person, 41-1-11 companies, 5-ff! , - Gyosu (7 to 6 ~C4--OtereriHvTakaetakafake1TlL~'lt
--Gunai Kamishi tJS3 Figure 1 '5-, i Ji-tatsurikyo]-ノ1 ■ Sei Fi cane (C-at-bun-nl'lkiden-9-te+4! ahead) kJHin#Lrisemi1 -Imashio' ki arrived at the rainbow (6 lines → 3- (C)

Claims (14)

[Claims] (1) A liquid crystal material is sandwiched between a pair of substrates that have a plurality of electrodes made of a conductor on opposing surfaces and form picture elements in a matrix, and the electrodes of at least one of the substrates are
A liquid crystal element characterized in that each electrode (n is an integer of 2 or more) is electrically connected by a coupling element, and none of the electrodes is connected to a fixed potential. (2) The liquid crystal device according to claim (1), wherein the coupling element functions as a signal delaying means. (3) The liquid crystal element according to claim (1), wherein the coupling element is a resistor. (4) The liquid crystal element according to claim (1), wherein the coupling element is a capacitor. (5) The liquid crystal element according to claim (1), wherein the coupling element is formed on a substrate. (6) The liquid crystal element according to claim (5), wherein the whole or a part of the coupling element is made of the same material as the electrode. (7) The liquid crystal element according to claim (1), wherein the coupling element is formed on a circuit board connected to the substrate. (8) The liquid crystal element according to claim (1), wherein the coupling element is formed on a flexible substrate connected to the substrate. (9) The liquid crystal element according to claim (1), wherein every n electrodes provided with coupling elements are connected to a scanning voltage output circuit. (10) The method for manufacturing a liquid crystal element according to any one of claims (5), (7), and (8), characterized in that the coupling element is formed using printing. (11) The method for manufacturing a liquid crystal device according to any one of claims (5), (7), and (8), characterized in that the coupling element is formed using transfer. (12) The method for manufacturing a liquid crystal device according to claim (6), wherein all or part of the coupling element is formed at the same time as etching the electrode pattern. (13) The method for manufacturing a liquid crystal element according to claim (4), wherein a capacitor is formed by forming an insulator on the electrode and forming a conductor on the insulator. (14) The method for manufacturing a liquid crystal element according to claim (4), wherein a capacitor is formed by forming a dielectric on the electrode and forming a conductor on the insulator.