JPH0229618A - Liquid crystal element and its operating method - 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 Industrial Application] The present invention relates to a liquid crystal element capable of displaying multiple colors and a method of operating the same.

[Prior art and problems to be solved by the invention] Typical display systems for liquid crystal display devices capable of multicolor display include twisted nematic ink type (hereinafter referred to as TN type) or guest host to which black pigment is added. Type (hereinafter referred to as G
There is a method that uses an H-type liquid crystal cell as a shutter to control the intensity of transmitted light through a color filter provided inside or outside the cell, and this method has been put to practical use. However, since this method uses color filters, its transmittance is low and requires illumination. Furthermore, those using TN type liquid crystal cells do not have sufficient time-division drive characteristics, making it difficult to display large capacity. Those using a GH type liquid crystal cell are inferior to those using a TN type liquid crystal cell in the steepness of voltage-transmittance characteristics. Therefore, in order to perform time-division driving, it is necessary to provide active elements such as thin film transistors, which increases the cost and also has the disadvantage of slow response. Furthermore, the above method has a problem in that the number of pixels increases because multicolor display is performed by additive color mixing of a plurality of pixels.

On the other hand, as a direct method using birefringence in contrast to the color mixing method described above, an electric field control birefringence method using nematic liquid crystal is known. Although this method allows multicolor display with one pixel, there are problems in that the viewing angle is highly dependent and the time-division drive characteristics are insufficient.

In view of the problems of the prior art, it is an object of the present invention to provide a liquid crystal element that can easily perform bright multicolor display, has high time division drive characteristics, and has improved viewing angle dependence. purpose.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a liquid crystal cell laminate having a structure in which a plurality of liquid crystal cells are stacked, each of which has a ferroelectric liquid crystal layer sandwiched between a pair of substrates having electrodes; It consists of a pair of polarizers arranged so as to sandwich the cell stack and their polarization axes are parallel or orthogonal to each other.

When a voltage is applied, one of the two alignment directions of liquid crystal molecules in each liquid crystal layer is parallel to or perpendicular to the polarization axis of the polarizer, and the other is at an angle of about 451 to the polarization axis of the polarizer. There is provided a liquid crystal element characterized in that it is configured to do the following.

Further, according to the present invention, by independently applying a voltage to each liquid crystal cell of the element, the liquid crystal molecules of each liquid crystal cell are switched between the two alignment directions, and the retardation is changed, thereby causing a plurality of dyes to be produced. A method of operating a liquid crystal device is provided.

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of the structure of a liquid crystal element of the present invention. In FIG.
12゜22 is a polarizer, 13.23 (23a, 23b),
33 is a transparent electrode.

14.24 (24a, 24b), 34 are alignment films, 15.
25 is a liquid crystal layer.

16.26 is a peripheral seal.

In the liquid crystal element of the present invention, the substrate 11 having the transparent electrode 13 on which the alignment film 14 is formed and subjected to the alignment treatment, and the substrate 21a on which the alignment film 24a and the transparent electrode 23a are similarly provided are spaced apart and facing each other. The open board 11.21
A ferroelectric liquid crystal is sealed in a space formed by a and an outer peripheral seal 16 to form a liquid crystal layer 15, thereby forming a first liquid crystal cell. Similarly, a substrate 21b is provided with an alignment film 24b and a transparent electrode 23b.

a substrate 31 provided with an alignment film 34 and a transparent substrate 33;

A ferroelectric liquid crystal is sealed in the space formed by the outer peripheral seal 26 to form a liquid crystal layer 25, thereby forming a second liquid crystal cell. The first liquid crystal cell and the second liquid crystal cell are stacked as shown in the figure, and polarizers 12 and 22 are disposed on both sides, respectively. The polarizers 12 and 22 are arranged so that their polarization axes (transmission axes) are parallel or orthogonal to each other. Note that the substrates 21a and 21b may be separate substrates,
It may be a single substrate.

The liquid crystal layer 15.25 is filled with a liquid crystal exhibiting a ferroelectric phase of chiral smectic C, chiral smectic G, chiral smectic H, chiral smectic E, chiral smectic J, chiral smectic K, or chiral smectic F. A smectic A phase exhibiting an electroclinic effect can also be used. The liquid crystal molecules of the liquid crystal layer 15.25 are alignment films 14.24a.

24b, 34 by substrate 11.21a, 21b, 31
These substrates 11.21
Transparent electrode 13.2 provided on the inner surface of a, 21b, 31
The orientation is deformed by the voltage applied to 3a, 23b, 33, and the direction of the applied electric field makes it bi-stabilized in the states A and B as shown in Figure 2. In Figure 6, P is a liquid crystal molecule, Q, Q '
is the substrate. The alignment treatment can be performed using a conventionally known rubbing method or oblique evaporation method.

In the present invention, the liquid crystal layer 15.2 when voltage is applied is
Two alignment directions of liquid crystal molecules in No. 5 when voltage is applied (Fig. 2A)
, B) and the polarization axis of the polarizer 12.22 are defined to have the following relationship. That is, first, one of the bistable alignment directions A and B of the liquid crystal molecules is made parallel to or perpendicular to the polarization axis of the polarizer 12°22. Further, the other of the bistable orientation directions A and B, that is, the orientation direction that is not parallel or perpendicular to the polarization axis, is made to form an angle of about 45° with respect to the polarization axis. This angle corresponds to the apex angle of the cone in Figure 2,
The desired value can be easily set by selecting the liquid crystal material used. Further, the bistable alignment directions A and B can be easily controlled by the rubbing direction when a rubbing method is used for the alignment treatment, and by the vapor deposition direction when an oblique spotting method is used.

Next, an example of the orientation of liquid crystal molecules in the liquid crystal layer 15.25 when voltage is applied will be described with reference to FIG.

FIG. 3 is a schematic diagram of the alignment of liquid crystal molecules when viewed from above the liquid crystal cell. Here, the voltages applied to the liquid crystal layers 15.25 of the first liquid crystal cell and the second liquid crystal cell (potentials of the electrodes on the outer substrate with respect to the electrodes on the intermediate substrate) are respectively Vl and V2, and the threshold voltage Let the voltages exceeding the voltages be +V and -V, respectively.

FIG. 3(a) shows the orientation in the first liquid crystal cell when a voltage of v1=÷V is applied.

The orientation is shown when a voltage V□ such that V1=-V is applied. Figure 3(b) shows the orientation in the second liquid crystal cell, where the orientation is when a voltage of V, = +V is applied and when a voltage of V, = -V is applied. It is shown. Here, it is assumed that the polarization axes of the polarizers 12 and 22 are parallel to each other and are oriented in the left-right direction in the plane of the paper of FIG. That is, the polarization axis is perpendicular to the orientation direction of the liquid crystal molecules when a voltage of v1=+l/ and a voltage of v2=◆vI are applied.

Note that even if the polarization axis is made parallel to the orientation direction, the effect does not change at all.

FIG. 4 is a diagram showing the state of orientation of liquid crystal molecules when a voltage is applied independently to the first and second liquid crystal cells of the liquid crystal element of the present invention exhibiting the orientation shown in FIG. 3.

Figure 4(a) shows the orientation of liquid crystal molecules when V1 = V, = +V. In this case, the orientation directions of liquid crystal molecules in the first and second liquid crystal cells are the same, and the polarizer 12
．． It is perpendicular to the polarization axis of 22. Therefore, no birefringence occurs and white light is observed. On the other hand, let V, ,V, be v
z”vo=V2=-V,;VxkneeVP=vs”
◆V, ;V, =-V, .

When V, = -V, the orientations shown in FIGS. 4(b), (c), and (d) are obtained, and in these cases, birefringence occurs. Here, let Δn be the refractive index anisotropy of the liquid crystal, and d be the thickness of the liquid crystal layer.

The phase difference between the ordinary ray and the extraordinary ray is expressed as (Δnd/λ)·π. When Δnd is expressed by R, in the case of FIG. 4(b), the birefringence corresponding to R (=R2) due to the second liquid crystal cell is the same as that of the first liquid crystal cell in the case of FIG. 4(C). by R
In the case of FIG. 4(d), the birefringence corresponding to (=R) is R (=R1◆Ra
) is observed. By applying voltages to the two liquid crystal cells in this manner, display of white + three colors is possible.

FIG. 5 shows a different combination of orientation directions from that shown in FIG. 4, and the method of applying voltage in FIGS. 5(a) to (d) It is similar to

The relationship between the applied voltage and H is as shown in Table 1, and in this case as well, multicolor display corresponding to R=0, R1, R, and R□+R2 is possible.

Table 1 Figure 6 shows another combination of alignment directions from the above, and the method of applying voltage in Figures 6(a)-(d) is as shown in Figure 4(a)-(d). The combination shown in the diagram includes the case where the orientations of the liquid crystal molecules in the two liquid crystal cells are orthogonal to each other, and the relationship between the applied voltage and H is as shown in Table 2, R=O, Ryu, R2, Multicolor display corresponding to R□-R2 becomes possible.

Table 2 In the above example, the applied voltage was set to two values, ◆v0 and -v, but any voltage that exceeds the threshold voltage may be used, and the absolute value of the voltage applied to the two liquid crystal cells is Obviously, they can be different.

Further, the tilt angle of the liquid crystal (θ shown in FIG. 4(b)) is preferably in the range of 30''-60'' from the viewpoint of color purity.

Next, coloring due to birefringence will be explained with reference to FIGS. 7 and 8.

Figure 7 shows the retardation R (pa) of a liquid crystal cell in which the alignment direction of the liquid crystal sandwiched between a pair of polarizing plates whose polarization axes are orthogonal to each other is parallel to the substrate and forms an angle of 45° with the polarization axis. This figure shows the chromaticity change due to the XpV chromaticity coordinate. FIG. 8 is a diagram similar to FIG. 7 when polarizers whose polarization axes are parallel to each other are used. As can be seen from these figures, various color changes can be made by changing the retardation R in various ways.The liquid crystal element according to the present invention can change the retardation R by changing the liquid crystal orientation direction of the two liquid crystal cells. This is used to display multiple colors.

Specific examples of H values and color tones when the polarization axes of a pair of polarizers are parallel to each other are illustrated below.

Table 3 As described above, according to the liquid crystal element shown in FIG. 1, multicolor display of white + 3 colors is possible when the paired polarizers are parallel to each other, and black + 3 colors when they are perpendicular to each other.

Above, we have explained the case where the liquid crystal cell has a two-layer structure.
According to the present invention, the number of color reproductions can be increased by having a configuration of three or more layers. For example, a three-layer configuration allows multicolor display of white (or black) ÷ 6 colors.

Furthermore, for example, by alternately repeating color development by R1 and color development by R2 in a short period of time, mixed color display is also possible.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

A polyimide alignment film was formed on a glass substrate having a transparent electrode, and a rubbing treatment was performed. Another glass substrate subjected to similar treatment and the above glass substrate are pasted together with a spacer of 5 grain size 5 pa, and the rubbing directions are parallel to each other, and the outer periphery is fixed with an epoxy adhesive. Cell 1 was prepared by sealing Chisso's optical smectic liquid crystal C3lOII with Δn=0.13 in the cell. The retardation of this cell 1 was R=0.65IJs. Next, Cell 2 was produced in the same manner as Cell 1 except that a spacer with a particle size of 2.5- was used. The retardation of this cell 2 was R=0.32 μm. These cells 1 and 2 became bistable in the direction of 22° left and right with respect to the rubbing direction by voltage application (see FIG. 9).

Next, stack the two cells so that cell 1 is on top and the rubbing directions of the upper and lower substrates are parallel, and place polarizing plates on the top and bottom so that the transmission axes are parallel and the upper electrode of cell 1 is connected to the negative electrode. Orientation direction when voltage is applied (C in Fig. 9(a))
) were attached so that they were perpendicular to each other.

Assuming that the potentials of the outer electrodes with respect to the intermediate substrate electrodes in Cell 1 and Cell 2 are vl and v2, respectively, multicolor display as shown in Table 4 was possible by voltage application.

Table 4 [Effects of the Invention] As described above, according to the present invention, since birefringence is utilized, bright multicolor display can be easily performed, and since ferroelectric liquid crystal is used, High time division drive characteristics can be obtained. Furthermore, since the alignment of the liquid crystal occurs only in a plane parallel to the substrate, the viewing angle dependence seen in conventional birefringence mode is reduced, making it possible to perform high-quality multicolor display. Furthermore, since it is possible to perform multicolor display with one pixel,
There is no problem of an increase in the number of pixels as in conventional liquid crystal devices using the additive mixing method.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the structure of a liquid crystal element according to the present invention;
Figure 2 shows the bistable alignment direction of liquid crystal molecules, Figure 3 shows the liquid crystal alignment in two liquid crystal cells, and Figure 4 shows the alignment direction obtained by applying voltage independently to each liquid crystal cell. The diagrams showing the combinations, Figures 5 and 6, are respectively 4th
Figures 7 and 8, which show combinations of orientation directions different from those shown in the figure, show color changes due to retardation.
FIG. 9, which is a diagram shown on the tY chromaticity coordinate, is a diagram showing the bistable orientation direction of the liquid crystal of each liquid crystal cell in the example of the present invention. 11.21 (21a, 21b), 31-board 12.22
...Polarizer 13.23 (23a, 23b), 33-transparent electrode 14.
24 (24a, 24b), 31=alignment film 15.25...
・Liquid crystal layer 16.26...outer seal

Claims (2)

[Claims] (1) A liquid crystal cell laminate having a structure in which a plurality of liquid crystal cells are stacked, each having a liquid crystal layer exhibiting ferroelectricity sandwiched between a pair of substrates having electrodes, and a polarization axis arranged so as to sandwich the liquid crystal cell laminate. It consists of a pair of polarizers arranged parallel to each other or perpendicular to each other, and one of the two alignment directions of liquid crystal molecules in each liquid crystal layer when a voltage is applied is parallel to the polarization axis of the polarizer. 1. A liquid crystal element, characterized in that one of the polarizers is perpendicular to the polarization axis of the polarizer, and the other is configured to form an angle of about 45° with respect to the polarization axis of the polarizer. (2) By independently applying a voltage to each liquid crystal cell of the liquid crystal element according to claim 1, the liquid crystal molecules of each liquid crystal cell are
1. A method for operating a liquid crystal device, characterized by displaying a plurality of dyes by switching between two alignment directions and changing retardation.