JPS61134736A - Smectic c* liquid crystal display apparatus - Google Patents

Abstract

PURPOSE:To obtain the titled apparatus having a good contrast rate and a rapid response and having a good switching effect by piling up two layers of a smectic C* liquid crystal cell contg. dichroism coloring matter so as to twist-rotate each molecular axes of the liquid crystals by 45 deg.. CONSTITUTION:The above described cells are piled up so as to dispose polarization aces 71, 72 of the upperward and the downward cells in either a vertical or a parallel position respectively. If the polarization axes 71, 72 are disposed in the vertical position, the axis 71 of the upperward cell and that 72 of the downward cell are disposed in a vertical direction under a condition that a voltage is not impressed, and a light does not penetrate. When the voltage is charged to the cell, the axes 71, 72 rotate 45 deg. in an opposite direction each other whereby the axes 71 and 72 coincide, and the light transmitts. If the voltage is charged to the cell, the axes 71 and 72 dispose in a vertical direction and the light does not transmit.

Description

[Detailed description of the invention] Technical fields> The present invention relates to a smectic c-to liquid crystal display device.

<Prior Art> Ferroelectric smectic zero-bundle liquid crystal cells are characterized by their high-speed response and memory performance, and are being developed and put into practical use as single display elements for printer mm optical heads. In that case, the cell configurations are the birefringence control type shown in Figure 4 and the 5th cell configuration.
There is a guest-host type with added dye as shown in the figure.

The birefringence control type has polarizing plates placed above and below, and the amount of transmitted light is adjusted by controlling the alignment direction of smectic C* phase liquid crystal molecules. FIG. 4(A) shows a cross section of the cell, where 21 is an upper polarizing plate, 1 is an upper substrate, 2 is a transparent electrode, 3 is an insulating film, and 4
is a smectic C* liquid crystal, 5 is a sealing part, 6 is an insulating film,
7 is a transparent electrode.

8 is a lower substrate, and 22 is a lower polarizing plate. FIG. 4(B) is a plan view of the cell, where 31 indicates the direction of the polarization axis of the upper polarizing plate 21, and 32 indicates the direction of the polarization axis of the lower polarizing plate 22. The change in the alignment direction 41.42 of the liquid crystal molecules is twice the tilt angle φ of the liquid crystal molecules with respect to the polarization axis direction, but since the tilt angle is usually 22.5 degrees, the change in the alignment direction is 45 degrees. It is.

In this case, the amount of transmitted light is given by the following equation.

δ Transmitted light amount 1=Ipsin'2φsin' -+ 1
0δ=2πdΔn/λ d: Cell gap Δn: Refractive index anisotropy λ: Wavelength Io: Amount of transmitted light when polarizer and analyzer are crossed If no voltage is applied here, the amount of transmitted light is 2φ-〇 ■1 is r+=r.

Also, when voltage is applied, Since 2φ = 45 degrees, the amount of transmitted light ■2 is δ Therefore, the contrast ratio is It is regulated by sin 2 δ/2.

Therefore, the larger d·Δn, the larger sin 'δ/2 and the larger the contrast ratio I 2 / 11 . On the other hand, since the response time is proportional to d2, there is a problem that increasing d slows down the response time.

Next, for the guest-host type, the cross section of the cell is shown in Figure 5 (A).
As shown in FIG. and when the long axis direction of the dye and the direction of the polarization axis 51 of the polarizing plate 22 match,
The contrast ratio is determined by the ratio of the amount of transmitted light in the case of tilting and the amount of transmitted light. However, in this case, the contrast is determined by the dichroic ratio of the guest dye material, but there is a problem in that the contrast ratio is not very high.

<Objective> An object of the present invention is to provide a smectic C* liquid crystal display device that eliminates the drawbacks of the above-mentioned prior art, realizes a good contrast ratio and high-speed response, and exhibits a good switching effect.

<Structure> The present invention consists of two layers of smectic Cx liquid crystal cells containing dichroic dyes, and the molecular axis direction of the upper and lower liquid crystals is
This is a smectic C* liquid crystal display device characterized in that the amount of transmitted light is adjusted by twisting each of the parts 1 and 1 by 45 degrees.

<Example> FIG. 1 is a sectional view of a smectic C* liquid crystal display device showing an example of the present invention. Codes 1 to 8 are the upper cells,
Cells 11 to 19 are lower cells. 1, 11 are upper substrates, 2, 12 are transparent electrodes, 3° 13 are insulating films, 4, 14
is smectic C1 liquid crystal, 5.15 is the seal part, 6.1
6 is an insulating film, 7.17 is a transparent electrode, 8.18 is a lower substrate,
19 is a reflecting plate. As described above, the present invention is characterized in that two smectic zero-bundle liquid crystal cells are stacked one on top of the other. The insulating films 3.6 and 13.16 are made of organic films such as polyimide and polyvinyl alcohol, and the surfaces thereof are subjected to a rubbing treatment. The rubbing directions of the insulating films 3 and 6 and the insulating films 13 and 16 are parallel. Also smectic 0 bundle liquid crystal 4
．． 14 is, for example, Chisso's C3-3a or C3-37.
As a dichroic black dye, for example, M-3 of Japan Photosensitive Dyes
78 etc. is used. With this configuration, the upper cell and the lower cell each have polarization performance. In this case, the molecular axis direction of the smectic C liquid crystal, ie, the absorption axis direction of the dichroic dye, becomes the polarization axis direction. The upper and lower cells are arranged so that the polarization axis direction is perpendicular to the upper and lower cells (FIG. 2(A)).

There is a case where it is arranged in parallel with (FIG. 3(A)).

When arranged vertically, the molecular axis direction 71 of the upper cell and the molecular axis direction 72 of the lower cell are perpendicular as shown in FIG. 2 (A) when no voltage is applied, and no light is transmitted. It is. When a voltage is applied to this, the molecular axes rotate 45 degrees in opposite directions, as shown in Figure 2 (B), and the molecular axis direction 7
1.72 match and light is transmitted. On the other hand, when the polarization axes of the upper and lower cells are arranged in parallel, the molecular axis direction 71 of the upper cell and the molecular axis direction 72 of the lower cell are aligned as shown in FIG. 3(A) with no voltage applied. Therefore, light is transmitted.

Then, when a voltage is applied, the molecular axes rotate 45 degrees in opposite directions as shown in Figure 3 (B), and the molecular axis direction is 71.7 degrees.
2 are orthogonal and light is not transmitted.

Effects> The present invention has the above-described configuration, and as with the normal twisted nematic liquid crystal mode, contrast can be obtained by the transmittance ratio of orthogonal and parallel polarization directions. Moreover, since it is a liquid crystal displaying smectic CI, high-speed response can be realized. Further, it is possible to obtain sufficiently good contrast compared to the birefringence mode and guest-host mode of smectic C*. Also, compared to the twisted nematic type, the twisted nematic type has three layers including the polarizing plate, but the structure of the present invention is only two layers, and is that much simpler. Furthermore, since the smectic C* mode has memory properties, multiplex driving and multi-scanning line driving are possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an apparatus for implementing the present invention, and FIGS.
) is a plan view of the implementation device, showing the case in which the upper and lower liquid crystal cells are arranged with their polarization axes perpendicular, where (A) shows a state in which no voltage is applied, and (B) shows a state in which a voltage is applied. Third
Figures (A) and (B) are plan views of the implementation device, showing the case where the polarization axes of the upper and lower liquid crystal cells are arranged in parallel, (A) shows the state where no voltage is applied, and (B) shows the case where the polarization axes of the upper and lower liquid crystal cells are arranged in parallel. Shows the state where voltage is applied. FIG. 4 shows a conventional device, with (A) being a sectional view and (B) being a plan view. FIG. 5 shows another conventional device, in which (A) is a sectional view and (B) is a plan view. 1.11--monogroup i 2,12-transparent electrode4.
14-11 Smectic C*Liquid crystal 5.15--Seal part 7.17-Transparent electrode 8.1
8-Lower substrate 71-Molecular axis direction of upper cell 72-Molecular axis direction of lower cell

Claims (1)

[Claims] A smectic C^* liquid crystal display characterized by stacking two layers of smectic C^* liquid crystal cells containing dichroic dyes and adjusting the amount of transmitted light by twisting and rotating the molecular axes of the upper and lower liquid crystals by 45 degrees. Device.