JPS6041102B2 - electro-optical device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electro-optical devices such as optical modulators and optical deflectors using materials that exhibit large birefringence due to second-order electro-optic effects.

These electro-optical devices all have a cell filled with a liquid material having a secondary electro-optic effect between two electrodes as a common component.

Such an electro-optical device is known as a Kersel in the case of an optical modulator and is also known as a UWEKR-UG in the case of an optical deflector.
ER's report [Proc. lEEE. Vol. 61. N
o. 7. PP. 992-1007 (1973)]. Nitrobenzene is usually used as the liquid material used in these electro-optical devices, but optical modulators (Kersel) using nitrobenzene can be used, for example, with He-Ne laser light (wavelength: 633 nm).
), the voltage required for 100% modulation (
half-wave voltage) is approximately required V. The same applies to digital deflectors that utilize the Kerr effect of liquid. Such a high voltage has many disadvantages in the design and manufacture of drive circuits for these electro-optical devices, and is particularly unsuitable for practical blind pupils that require miniaturization. Examples of liquids having a secondary electro-optic effect other than nitrobenzene include the above-mentioned UWEKRUG.
The ERs listed a mixture of 7% methylacetamide by volume and 30% ethylacetamide by volume.

However, the Kerr coefficient of this liquid is about three times that of nitrobenzene, and the half-wavelength voltage is also reduced to only about 60% of that of nitrobenzene, which is still insufficient for practical use. On the other hand,
Recently, P-type nematic liquid crystal in an isotropic liquid state has attracted attention as a liquid having a secondary electro-optic effect. As a liquid that is generally expected to have a large secondary electro-optic effect (Kerr effect), it must have a high dipole efficiency, a large optical anisotropy, and the directions of the dipole efficiency and optical anisotropy match. However, p-type nematic liquid crystals, which have a temperature near the nematic isotropic phase transition temperature, have begun to attract attention because they meet these conditions. For example, p-
1:1 of [(p-butoxybenzylidene)amino]-benzonitrile, p-[(p-hexyloxybenzylidene)amino]-benzonitrile, and p-[(p-octyloxybenzylidene)amino]-penzonitrile
:1 mixture is known to exhibit a half-wave voltage of about 1'12 of nitrobenzene at 93.3 qo. The present invention is based on the discovery that a larger Kerr coefficient can be obtained by using a cyanobiphenyl liquid crystal than the above-mentioned cyanoschiff-based mixed liquid crystal. An object of the present invention is to provide electro-optical devices such as optical modulators and optical deflectors that use cyanobiphenyl-based p-type nematic liquid crystal, which has not been used so far, as a secondary electro-optic effect (Kerr effect) material. This is what I am trying to do.

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a perspective view showing an example of a cell included in the electro-optical device of the present invention.

In the figure, 11 is the main body of the cell 21, and inside thereof a pair of electrodes 12a and 12b with a length of 1 and a height of h are disposed facing each other with a gap d, and these electrodes constitute the main part of the present invention. It is filled with a compromising liquid 13 which has a secondary electro-optic effect. Since the front surface 14 and rear surface 15 of this cell 21 require passage of a modulated or deflected light beam, they are made of a material (for example, transparent glass) that has a high transmittance for this light beam. Although the side surfaces 16 and 17 are insulating materials in this embodiment, it is also possible to share the electrodes with the side surfaces. Further, in the illustrated example, for convenience of explanation, the top surface is a gate, but in actual use, it is sealed in an appropriate manner. FIG. 2 is a diagram showing an example of an optical modulator including the cell 21 of FIG. 1.

In the figure, a cell 21 receives power from a modulated power supply 22. 23 and 24 are polarizing plates (hereinafter, 24 will be referred to as an analyzer), and their polarization axes are perpendicular to each other, and are arranged at an angle of 45 degrees with respect to the electric field application direction of the cell 21. ing.

When no electric field is applied to the cell 21, the dielectric liquid 13 is isotropic, so the light beam 26 passes through the cell 21 without changing its polarization direction. 26 is not reached.

When an electric field is applied to the cell 21, the flexible liquid 13 exhibits birefringence, and since there is a difference in the refractive index in the direction of electric field application and in the direction perpendicular to it, the phase velocity of the electric field components in each direction is different. A phase difference occurs. Therefore, the light that has passed through the cell 21 is generally elliptical polarized light. Therefore, some components are allowed to pass through the analyzer 24,
The light beam reaches the detector 25. When the above phase difference becomes medium radian (corresponding to half a wavelength), cell 2
The light that has passed through the detector 1 changes into a linearly polarized light having the same polarization direction as the analyzer 24, and almost 100% of the light ray 26 reaches the detector 25. The voltage applied to the cell 21 at this time is called a half-wavelength voltage Vm. FIG. 3 is an example of a digital optical deflector including the cell 21 of FIG. In the same figure, 3
2 is a prism made of a material that exhibits natural birefringence, such as calcite, and its optical axis is perpendicular to the plane of the paper. cell 2
The direction of electric field application in No. 1 makes an angle of 45 degrees with the direction of the polarization plane of the incident deflected light beam. Now, when a linearly polarized light beam 33 having an electric field direction parallel to the plane of the paper is made to enter the cell 21, if no electric field is applied to the cell 21, the polarization direction will not change and it will pass through the cell 21 as it is.

When a voltage corresponding to a half-wavelength voltage is applied to the cell 21,
As described above, the polarization direction of the incident light beam 33 is rotated by 90 degrees and becomes perpendicular to the plane of the paper. Therefore, when no voltage is applied, the ray is refracted in the direction 34 shown in FIG. 3 according to the ordinary ray refractive index, and when a voltage is applied, it is refracted in the direction 35 shown in FIG. 3 according to the extraordinary ray refractive index. Light deflection becomes possible. Cell 2 in the electro-optical device of the present invention described above
The dielectric liquid 13 contained in 1 has the general formula: [where,
R represents a saturated chain alkoxy group having up to about 10 carbon atoms.

] : It is an isomerial liquid consisting of the compounds represented by and mixtures thereof. Examples are shown below. Example 1 In the cell shown in FIG. 1, the electrode gap d is defined as 1 side, and the length 1 in the light beam passing direction is defined as 1 side.

The cell was filled with 4-n-propoxy-4'-cyanobiphenyl and maintained at about 6,400 and arranged as shown in FIG. When a He-Ne laser beam (63 background) was used as the modulated light beam 26 and voltage was applied to the cell, the output of the detector 25 reached its maximum at 650V. This value indicates that the optical phase difference has reached radians, and corresponds to a half-wavelength voltage V. In addition, the Kerr coefficient B is Bd2
/2 IV in 2, in this case 118×10-lo 伽′V
It is 2.

This value is a large value corresponding to 4 points of bitterness and weakness of nitrobenzene. Example 2 Using a method similar to Example 1, 4-n-poxy-4
'-cyanobiphenyl Kerr effect was observed (70.7q
0), half-wave voltage 460V, Kerr coefficient 236×10-1
Obtained 0 skin/V2.

Example 3 Using the same method as in Example 1, the Kerr effect of 4-n-bentyloxy-4-cyanobiphenyl was observed (66.
9qo), half-wave voltage 320V, Kerr coefficient 488×10
The arc/V2 was obtained.

Example 4 Using the same method as in Example 1, the Kerr effect of 4-n-hexyloxy-4'-cyanobiphenyl was observed (71
．． is 0), half-wave voltage 430V, Kerr coefficient 270×10
- Obtained 10 skins/V2.

Example 5 Using a method similar to Example 1, heptyloxy-4'
- observed the Kerr effect of cyanobiphenyl (68.0'
0), half-wave voltage 445V, Kerr coefficient 252×10-l
o skin/V2 was obtained.

Example 6 Using the same method as in Example 1, the Kerr effect of 4-n-octyloxy-4'-cyanobiphenyl was observed (78
．． is o), half-wave voltage 485V, Kerr coefficient 213×10
-10 arc/V2 was obtained.

Example 7 Using a method similar to Example 1, 4-n-propoxy-4'-cyanobiphenyl, 4-n-benthyloxy-4
The Kerr effect of a mixture of -cyanobiphenyl and 4-n-heptyloxy-4-cyanobiphenyl in a molar ratio of 1:1:1 was observed (65.500), and the half-wave voltage was 280 V.
, a Kerr coefficient of 638×10-lo skin'V2 was obtained.

This value is better than any single compound in the mixture. It is clear from the measurement results that the cells of the above embodiments respond to frequencies at least up to the IM ratio in all examples.

Furthermore, as described above, when nitrobenzene is used as the dielectric liquid in the same configuration as shown in Example 1, the half-wavelength voltage is 4100V. In Example 7, which is the most excellent, the half-wave voltage is 280 V, which corresponds to 1/14.6 of nitrobenzene, and it is clear that the practical effect is great.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of a cell for applying an electric field to an isomerotic liquid, which is included as a common element in the electro-optical device of the present invention, and FIG. 2 shows an example of a modulator including the cell shown in FIG. The figure shown in FIG. 3 is a diagram showing an example of a digital optical deflector including the cell of FIG. 1. 12a, 12b...electrode, 13...conductive liquid, 21... ···cell. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. Contains a dielectric liquid that causes birefringence due to a second-order electro-optic effect when an electric field is applied, and the dielectric liquid has a general formula: ▲ A mathematical formula, a chemical formula, a table, etc. ▼ [Here, R represents a saturated linear alkoxy group having up to about 10 carbon atoms. ]: An electro-optical device comprising a compound represented by and a mixture thereof, wherein the liquid is an isotropic liquid. 2 In claim 1, the mixture includes 4-n-propoxy-4'-cyanobiphenyl, 4-n-propoxy-4'-cyanobiphenyl,
An electro-optical device characterized in that it is an isotropic liquid comprising a mixture of n-pentyloxy-4'-cyanobiphenyl and 4-n-heptyloxy-4'-cyanobiphenyl in a molar ratio of 1:1:1.