JPH01121819A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To enable uniform and stable gradation control even with any picture elements by forming regular ruggedness and spacers by pressing so that distributions are provided to the spacings between picture element electrodes. CONSTITUTION:Regular grooves 3 and the pacers 2 are formed on at least one face of a pair of substrates 1, 4 consisting of glass or resin by pressing said surface with a heated casting mold. Since the spacers 2 are simultaneously formed by pressing, the positions of the spacers 2 can be confined and the specified distribution of the inter-substrate spacing is maintained in the cell. The cell provided with the specific distribution in the spacings between the opposed picture element electrodes is, therefore, easily formed by the simple method. Gradients are thereby given to the electric fields impressed thereto and the medium contrast is uniformly produced even with the many picture elements or the elements.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a liquid crystal element having a ferroelectric liquid crystal as a liquid crystal layer, which can control the gradation of the amount of transmitted light.

Conventional technology In recent years, reports have been made on ferroelectric liquid crystals with fast response speed and memory properties (for example, Hideo Takezoe, Atsuo Fukuda, Hideo Kuze; "Industrial Materials", Vol. 31, No. 1θ, 22 ).

An example of a conventional ferroelectric liquid crystal panel will be described below with reference to the drawings. FIG. 4 shows the structure of a conventional smectic liquid crystal panel. In FIG. 4, 21 is a glass substrate, 22 is a transparent electrode made of ITO (indium tin oxide), 24 is a ferroelectric liquid crystal layer, 25 is a C director of liquid crystal molecules, and 126 is a dipole moment.

Ferroelectric liquid crystals generally have a dipole moment in the direction perpendicular to the long axis of the molecules, and as they become thinner, they come to have spontaneous polarization. FIG. 5 shows how to describe ferroelectric liquid crystal using an example of a chiral smectic phase exhibiting ferroelectricity. Fifth
Figure fa) shows a state in which the long axis of the molecules is tilted by +θ degrees with respect to the normal 27 of the molecular layer, and FIG. 27 is the normal to the layer, 28 is the long axis direction of the molecule n129 is the dipole moment PS, and 30 is n x
The C director -C131 when projected onto the y-plane is an inclination angle of ±θ degrees with respect to the normal to the long axis of the molecule. The operating principle of the ferroelectric liquid crystal panel having the above structure will be explained below with reference to the drawings.

FIG. 6 shows a diagram of the principle of the display method of a conventional ferroelectric liquid crystal panel. 32 is a liquid crystal molecule whose long axis of the molecule is tilted by ±θ degrees with respect to the layer normal; 33 is a liquid crystal molecule whose molecular axis is tilted by 1θ degree; 34 is a dipole moment in the front direction of the paper, 35 is a dipole moment in the back direction of the paper, and 36 is the direction of the two polarizing plates. Now, Fig. 6 (a) shows a state in which no voltage is applied, Fig. 6 (b) shows a case in which a positive voltage is applied from the front to the back of the paper, and Fig. 6 (C) shows a state in which a positive voltage is applied from the back to the front of the paper. This is the operating principle when applying .

Depending on the voltage application method, the entire cell takes on two states tilted by ±θ degrees, and therefore brightness and darkness can be expressed by using birefringence or dichroism due to the electro-optic effect.

As mentioned above, ferroelectric liquid crystals can take only two states when viewed microscopically, so to create halftones, choose from Figure 6 (mountain) to Figure 6 (C), or Figure 6 (0) to Consideration has been given to using a mixed state of the two states as shown in Figure 6(a), which is obtained during the transition period to Figure 6(b), or to changing the ratio of the appearance times of the two states. (e.g. Clark, Lagabar, Wall Neurodisplay
84 Digest 1984, p. 73 (N, A, C1a
rk, S., T., Lagerwall and
J.

WahL: Eurodisplay '84
(1984) p. 73)).

Problems to be Solved by the Invention However, it is extremely difficult to uniformly cause a mixture of the above two states to appear in many picture elements on a normal planar electrode. Furthermore, regarding the method of changing the appearance time ratio of two states, no detailed study has been made regarding matrix driving suitable for large-scale devices.

In view of the above-mentioned problems, the present invention provides a liquid crystal element using ferroelectric liquid crystal that can control the gradation of light transmission.

Means for Solving the Problems In order to solve the above-mentioned problems, the liquid crystal element of the present invention is provided by pressing the surface of at least one of a pair of substrates made of glass or resin to form regular irregularities and spacers. Gradation control can be easily performed by sandwiching the ferroelectric liquid crystal between the electrodes.

Operation On a conventional uniform electrode, when a voltage equal to or higher than the threshold voltage is applied to a ferroelectric liquid crystal element, the liquid crystal molecules on the electrode almost simultaneously reverse their spontaneous polarization so that they are oriented in the direction of the electric field.

Therefore, by applying a pulse voltage that is slightly lower than the dark value voltage or has a short pulse width, it is possible to make a mottled state appear. The brightness distribution varies depending on the picture element or element because it is easily influenced by subtle factors that are difficult to control, such as orientation and orientation state. Therefore, in the liquid crystal element of the present invention, regular irregularities and spacers are formed by pressing to give a distribution in the gap between the picture element electrodes, and as a result, an electric field distribution is created within one picture element. Uniform and stable gradation control is possible even when the color is blank.

Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is an example of a configuration diagram of a liquid crystal element of the present invention. A glass substrate was pressed using a heated mold to form grooves as 1 in FIG. 1 and spacers as 2. The depth d of the groove is 0.6 μm, and the height of the spacer is 2.0 μm. Conventionally, spacers have been used in liquid crystal devices by scattering fine particles of glass or resin, but this method is not effective when the substrate surface has irregularities because the position of the spacer cannot be controlled. In the present invention, since the spacer is also molded in one press, the position of the spacer can be defined, the distribution of substrate spacing can be made constant within the cell, and the construction method is also simplified. By immersing a part of the spacer in polyvinyl alcohol, a film is formed only on a part of the spacer, and after indium tin oxide is deposited on the film, the polyvinyl alcohol is peeled off by washing with water, leaving a transparent electrode only on the inclined surface. A striped pattern of electrodes was formed. The substrate 2 in FIG. 1 has stripe electrodes provided on a flat glass substrate by the usual method.
It may have a similar shape. All electrodes had a pitch of 0.3 m. By applying an adhesive around the substrate 20 and bonding it to the substrate 1, the distance between the substrates is maintained at 2.0 μm to 2.6 μm. This spacing is ±0.0 for a 15cm square panel.
The error could be suppressed to 0.05 μm. After coating a polyimide film on a substrate and performing a rubbing treatment, a mixture of ester-based ferroelectric liquid crystals was heated to the isotokish phase and injected, and then slowly cooled, resulting in uniform orientation. I tried driving this panel with the waveform shown in Figure 3. Figure 3 fa)
represents the waveform applied to the scanning electrode and the signal electrode, and is shown in Figure 3 (
b) represents the voltage applied to the picture element at that time.

The pixel is reset to black by a negative pulse during the selection period, and the gradation is controlled by changing the pulse width Pw (0 to 400 μsec) of the on-voltage vo (17 volts) of the last pulse applied. , the brightness hardly changes during the non-selection period pulses. As a result of experiments, it was found that the liquid crystal element of the present invention can uniformly display four gradations for all picture elements. Conventional liquid crystal elements with flat electrodes could only display two levels uniformly using the same driving method, but the liquid crystal element of the present invention has the effect of uniformly displaying more gradations. I found out. As for the driving method, analog modulation that changes the signal voltage value depending on the gradation may be used.

In addition, in this example, a difference of 0.6 μm was made in the distance between the substrates, but this difference in the distance between the substrates can obtain the necessary gradation depending on the liquid crystal material, orientation, pixel size, driving method, etc. The optimal value for should be chosen.

Furthermore, it was also effective to provide step-shaped grooves as shown in FIG. 2 instead of grooves with slopes.

In the above embodiments, a glass substrate was pressed, but the same effect could be obtained by pressing a resin substrate or the surface of a substrate coated with resin on glass.

Effects of the Invention In the liquid crystal element of the present invention, by providing regular irregularities and spacers on at least one substrate by pressing, a cell with a specific distribution in the gap between opposing picture element electrodes can be created using a simple construction method. It can be made uniformly, and by applying a gradient to the applied electric field, it is possible to uniformly produce halftones in a large number of picture elements or elements.

[Brief explanation of the drawing]

1 and 2 are block diagrams of one embodiment of the liquid crystal element of the present invention, FIG. 3 is a waveform diagram showing matrix drive waveforms in the embodiment, and FIG. 4 is a cross section of a conventional ferroelectric liquid crystal panel. figure,
FIG. 5 is a schematic diagram showing the notation method of chiral smect C liquid crystal, and FIG. 6 is a plan view showing the principle of display of a conventional ferroelectric liquid crystal panel. 1...Lower board, 2...Part of spacer,
3...Groove portion, 4...Upper substrate, 5...
...Transparent electrode, 6...Alignment film, 7...
・Seal material. Name of agent: Patent attorney Toshio Nakao (1 name) Ken Eitaka (1)
Shih Shigawa El--Glass Kaede 22-ITOt Polar Figure 6

Claims (3)

[Claims] (1) A liquid crystal element characterized in that regular irregularities and spacers are provided by pressing the surface of at least one of a pair of substrates made of glass or resin, and a ferroelectric liquid crystal is sandwiched between the substrates. (2) Claim (1) characterized in that the regular unevenness is formed by forming grooves with a slope in a stripe shape.
The liquid crystal element described in . (3) A liquid crystal element according to claim (1), characterized in that step-like grooves are formed in a stripe shape as the regular irregularities.