JPH07140493A - Liquid crystal cell, liquid crystal light valve and instrument for measuring spiral pitch of antiferroelectric liquid crystal - Google Patents

Abstract

PURPOSE:To provide a liquid crystal light valve of high-speed response by low electric field driving by using a liquid crystal cell formed by perpendicularly orienting an antiferroelectric liquid crystal and impressing a low electric field between electrodes which are held in this cell and are disposed to face each other in parallel, thereby changing the direction in the molecule orientation of the antiferroelectric liquid crystal and generating a bright and dark contrast when the cell is placed between polarizing plates orthogonal with each other. CONSTITUTION:This liquid crystal cell is constituted by disposing transparent substrates 1, 2 having perpendicularly oriented layers 3, 4 opposite to each other in such a manner that the respective perpendicularly oriented layers 3, 4 exist on the inner side, inserting and arranging >=1 pairs of plus electrodes 5 and minus electrodes 6 therebetween in parallel and encapsulating the antiferroelectric liquid crystal 7 into the space enclosed between the plus electrodes 5 and the minus electrodes 6. This liquid crystal light valve is composed of such liquid crystal cell and the polarizing plates arranged on the outer sides of the upper and lower liquid crystal display substrates 1, 2 in such a relation that the respective polarization directions are not paralleled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal cell in which an antiferroelectric liquid crystal is sealed between electrodes facing in parallel sandwiched between transparent substrates having vertical alignment layers, or between transparent substrates having vertical alignment layers. A liquid crystal cell in which an antiferroelectric liquid crystal is sealed so that the spiral axis is perpendicular to the vertical alignment layer and parallel to the electrodes between electrodes facing each other sandwiched in parallel. The present invention relates to a liquid crystal light valve in which polarizing plates are sandwiched above and below and a spiral pitch measuring device.

[0002]

2. Description of the Related Art A conventional liquid crystal light valve uses a nematic liquid crystal, and the response speed of the nematic liquid crystal to an electric field is as slow as several milliseconds, so that the response speed is insufficient. Based on Japanese Patent Application Laid-Open No. 56-10726, attention has been paid to the fact that a ferroelectric liquid crystal has a faster response than a conventional nematic liquid crystal, and attempts have been made to develop a fast response type liquid crystal light valve. However, the orientation of the ferroelectric liquid crystal is more easily broken than the orientation of the nematic liquid crystal, and once it is broken, it does not recover. Further, there have been observed problems such as a higher threshold voltage than the TN mode of nematic liquid crystal.

Japanese Unexamined Patent Publication (Kokai) No. 2-153322 discloses an antiferroelectric liquid crystal display element that exhibits a third stable state when no electric field is applied. Using this liquid crystal, high-speed response and alignment are achieved. It should be possible to realize the durability.
However, the antiferroelectric liquid crystal is disclosed in JPN. J. APP
L. PHYS. VOL27, NO5, 1988, P72
9 to 732, the threshold electric field is high (2 MV / m or more), and when the light valve is driven by the alternating electric field, power consumption increases. The applicant has already applied for a liquid crystal electro-optical device in which an antiferroelectric liquid crystal having three stable states is enclosed between transparent substrates with transparent electrodes subjected to parallel alignment processing and a voltage is applied to the transparent substrates. It was filed as Japanese Patent Laid-Open No. 63-70212 and published as Japanese Patent Application Laid-Open No. 2-153322.

When sandwiched in a vertically aligned cell, the antiferroelectric liquid crystal has a double helix.
N. J. APPL. PHYS. VOL28, NO7, J
ULY, 1989, P1265-1268. Further, although the winding condition of the spiral, that is, the pitch of the spiral has a great influence on the orientation of the antiferroelectric liquid crystal when it is enclosed in the cell, it has not yet been accurately determined by the conventional method using the spectroscope. .

Further, an antiferroelectric liquid crystal compound is disclosed in Japanese Patent Application Laid-Open Nos. 1-331667 and 1-316372 of the present inventor.
JP-A-1-316339, JP-A-2-28128
And Japanese Patent Laid-Open No. 1-213390, such as Ichihashi,
Further, as a liquid crystal electro-optical device using an antiferroelectric liquid crystal, Japanese Patent Application Laid-Open No. 2-40625 and Japanese Patent Application Laid-Open No. 2-15 are filed by the applicant.
3322 and JP-A-2-173724. However, there is no description suggesting a liquid crystal light valve having the structure as in the present invention in these prior documents.

[0006]

SUMMARY OF THE INVENTION Therefore, a first object of the present invention is to provide a liquid crystal cell in which an antiferroelectric liquid crystal is vertically aligned in order to deal with the above-mentioned problems, and this liquid crystal. By applying a low electric field between the electrodes sandwiched in the cell and facing each other in parallel, the direction of the molecular orientation of the antiferroelectric liquid crystal is changed, and it is preferable that the polarization directions are not parallel. The point is to provide a liquid crystal light valve capable of producing a high-speed response even when driven by a low electric field, by causing a contrast of light and dark when the liquid crystal cell is placed between polarizing plates having a relationship of being orthogonal to each other.

A second object of the present invention is to provide a liquid crystal cell in which a spiral axis of a spirally wound antiferroelectric liquid crystal is enclosed so as to be perpendicular to a vertical alignment layer in order to deal with the above-mentioned problems. And distort the spiral structure of the antiferroelectric liquid crystal by applying a low electric field perpendicularly to the spiral axis of the antiferroelectric liquid crystal between the electrodes sandwiched in the liquid crystal cell and facing each other in parallel. , Or the spiral pitch is changed so that the polarization directions are not parallel, preferably when they are placed between polarizing plates in such a relationship that the polarization directions are orthogonal to each other, a contrast of light and dark is generated, and high speed is achieved even by low electric field driving. The point is to provide a liquid crystal light valve capable of responding.

A third object of the present invention is to provide a device for accurately measuring the spiral pitch by accurately measuring the selective reflection wavelength of the antiferroelectric liquid crystal using the spirally wound cell. It is in.

[0009]

According to the first aspect of the present invention, transparent substrates having vertical alignment layers are made to face each other with the vertical alignment layers facing inward, and a pair of positive electrodes and negative electrodes are inserted in parallel therebetween. And a liquid crystal cell in which an antiferroelectric liquid crystal is enclosed in a space surrounded by the vertical alignment layer and the plus and minus electrodes.

In the second aspect of the present invention, the transparent substrates having the vertical alignment layers are made to face each other with the vertical alignment layers facing inside, and a pair of positive electrodes and negative electrodes are inserted in parallel between them to arrange the vertical alignment layers. An antiferroelectric liquid crystal wound in a space surrounded by the positive and negative electrodes is enclosed so that the spiral axis of the liquid crystal is perpendicular to the vertical alignment layer and parallel to both electrodes. Liquid crystal cell.

A third aspect of the present invention comprises a liquid crystal cell according to claim 1 and a polarizing plate arranged outside the upper and lower transparent substrates of the liquid crystal cell in such a relationship that their polarization directions are not parallel. The present invention relates to a liquid crystal light valve.

In the first to third inventions, the gap between the plus electrode and the minus electrode inserted and arranged in parallel is 100.
μm to 2 mm, preferably 100 μm to 200 μm. The distance between the transparent substrates facing each other is 50 to 200 μm.
Is preferred.

Further, in the third aspect of the present invention, it is preferable to arrange the polarizing plates outside the upper and lower transparent substrates in such a relationship that the respective polarization directions are orthogonal to each other (including a relationship close thereto).

In the liquid crystal light valve of the present invention thus constructed, the intensity of the light transmitted through the antiferroelectric liquid crystal is changed by the action of the polarizing plate whose polarization directions are orthogonal to each other with the applied electric field. By exhibiting the electric field-transmitted light intensity characteristic, the threshold electric field of the change of the transmitted light intensity with respect to the applied electric field was lowered, and the orientation could be made resistant to mechanical shock.

A fourth aspect of the present invention is: output light means for emitting light by continuously changing the wavelength of monochromatic light; transparent substrates having vertical alignment layers are made to face each other with the vertical alignment layers inside, and A pair of positive and negative electrodes are inserted in parallel with each other, and an antiferroelectric liquid crystal wound spirally in a space surrounded by the vertical alignment layer and the positive and negative electrodes is It consists of a liquid crystal cell enclosed perpendicularly to the alignment layer and parallel to both electrodes, a polarizer provided on one side and an analyzer provided on the other side. Are liquid crystal light valves arranged such that their respective polarization directions are not parallel, a temperature controller for controlling the operating temperature of the liquid crystal light valve, a polarizer from the output light means, the liquid crystal cell, and an analyzer. And a photodetector for detecting light passing through in this order, and a spiral pitch measuring device for an antiferroelectric liquid crystal.

The basic principle of the spiral pitch measuring device for antiferroelectric liquid crystal of the present invention will be described with reference to FIG. Monochromatic light is extracted from the light source with a monochromator, and while continuously changing the wavelength of this light, the light is polarized by a polarizer, a liquid crystal light valve,
An analyzer (the one on the light source side of the polarizing plate is called a polarizer and the one on the detector side is called an analyzer) is passed through, and the intensity of the transmitted light is measured by the detector. Then, by plotting this transmitted light intensity against the wavelength, the curve shown in FIG. 7 can be obtained. The conventional measuring device does not use a polarizer or an analyzer as shown in FIG. The relationship between the liquid crystal light valve and the polarizing plate (polarizer and analyzer) in the present invention is as shown in FIG. When the cell of the liquid crystal light valve is rotated as shown in the figure, the electrode surfaces facing each other in parallel are between the polarizer and the analyzer,
That is, the transmitted luminosity is measured while fixing them at an angle of 45 ° from both sides. The intensity of the transmitted light is strongest at this angle, so it is most effective. FIG. 3A shows
This fixed state is shown by emphasizing only the viewpoint of the cell, and FIG. 3B is a perspective view showing it.

When the liquid crystal is wound in a spiral, circularly polarized light in the same direction as the spiral is selectively reflected when its wavelength matches the spiral pitch (selective reflection). When linearly polarized light is incident on the liquid crystal phase having a spiral structure as in the present invention, the polarization direction is rotated due to the optical rotatory power. In the vicinity of the selective reflection wavelength, the rotation angle increases, the component of light parallel to the analyzer increases, and the light transmittance increases. The optical rotatory power changes as shown in FIG. 10, and it is considered that two transmittance peaks appear because the optical rotatory power is reversed by sandwiching the selective reflection wavelength. The portion where the transmittance drops corresponds to the selective reflection wavelength. For these reasons, it is possible to obtain the selective reflection wavelength by measuring the position of the valley between the peaks in FIG. 7, that is, the position of the minimum value between the two peaks. Once the selective reflection wavelength is obtained, the spiral pitch of the antiferroelectric liquid crystal can be calculated later by the following formula. If you want to measure with another liquid crystal, replace the liquid crystal in the liquid crystal light valve.

When the selective reflection wavelength is λ and the spiral pitch is P,

[ _Formula 1] λ = n _av · P / m (m = 1, 2, 3 ...
.. is a natural number such as. ) N _av = (n _e ² + n _o ² ) / 2 n _av : average refractive index n _o : ordinary light refractive index n _e : extraordinary light refractive index

Examples of the transparent substrate include a sheet or plate made of glass, quartz, synthetic resin or the like.

Examples of the vertical alignment layer include a chromium complex (eg, chromium perfluorononanoate complex), a silane coupling agent, and polyimide.

Examples of the counter electrode include a stainless plate and an aluminum plate. In order to make the applied voltage uniform, it is preferable to use a mirror-finished surface for holding the liquid crystal.

In the present invention, a combination of a pair of positive electrodes and negative electrodes can be used only, but a large number of pairs of positive electrodes and negative electrodes are inserted between large substrates and a large number of them are provided between a pair of substrates. The liquid crystal light valve can be formed. Alternatively, only one substrate may be a large substrate, and the other substrate may be provided with a large number of substrates each having a size corresponding to one light valve (see FIG. 5).

As the antiferroelectric liquid crystal used in the present invention, any of various antiferroelectric liquid crystals other than the antiferroelectric liquid crystal according to the invention filed by the present applicant can be used. it can.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 shows a cell structure. The surfaces of the glass substrates 1 and 2 are coated with a silane coupling agent, trade name TLI-3334 (manufactured by Merck Japan Ltd.) to form vertical alignment layers 3 and 4. A stainless plate is used for the two electrodes 5 and 6, and the distance between both electrodes is about 100 to 200 μm. These electrodes also serve as spacers and have a thickness of 50 μm.

FIG. 2 shows a system including an optical system for driving this cell. This is an improvement of the system often used in ordinary optical experiments, the filter and the monochromator are for arbitrarily changing the wavelength of the light source,
The lock-in amplifier is an amplifier that enables the amplitude of a signal whose frequency and phase are known to be measured with high sensitivity.
FIG. 3 shows a geometrical arrangement relationship between a polarizer, an analyzer and a cell. Rotate 45 degrees from crossed Nicols.

The antiferroelectric liquid crystal used in the experiment is the following compound,

[Chemical 1] The phase transition is shown in Table 1.

[Table 1]

FIG. 4 shows how the transmitted light intensity changes in response to changes in the applied voltage for this liquid crystal cell. In other words, the electric field dependence of the transmitted light intensity is shown in Fig. 4.
Shown in. The rise of the transmitted light intensity with respect to the increase of the electric field intensity is not steep, but the threshold value of this cell is less than that of the parallel-oriented antiferroelectric liquid crystal cell (2 MV / m or more). About 2 to 0.3 MV / m and about 1/1
It has dropped to zero. Also, the change in transmitted light intensity of this cell is due to the bulk property of the orientation distortion due to the electric field of the spirally wound antiferroelectric liquid crystal, and the dependence on the substrate interface is small, so the change process is reproducible, There is gradation.

Example 2 The same cell and antiferroelectric liquid crystal as in Example 1 were used. The optical system is the same as 3. The measuring device is shown in FIG. The monochromator and detector are synchronized by a microcomputer. The measurement is similar to the conventional selective reflection measurement, the spectral characteristic is measured in the Sm A phase, and the spectral characteristic is measured in the SmC * A phase with this as the background.
The transmittance is calculated by dividing. In the device of the present invention, the background is S which is made by putting the polarizer and the analyzer in parallel.
It was measured in the mA phase. The measurement in the SmC * A phase was performed with the polarizer and the analyzer orthogonal to each other, and the angle between the electrode and the polarizing plate was 45 °. At this time, the magnitude of the change in transmittance becomes the largest. FIG. 7 shows the measurement results of the transmittance. The position where the transmittance is minimized between the two peaks is the wavelength at which selective reflection occurs. From the selective reflection wavelength λ measured here (about 0.425 μm in FIG. 7), the spiral pitch P is obtained by the following formula.

[ _Formula 2] λ = n _av · P / m (m = 1, 2, 3 ...
(Natural number such as) n _av = (n _e ² + n _o ² ) / 2 (average refractive index) n _o : refractive index of ordinary light n _e : refractive index of extraordinary light For example, n _o = 1.46, n _e = 1.59, λ = 0.42
When it is 5 μm, m = 1 and P = 0.18 μm.

FIG. 8 shows the case where the device of the present invention is used and the applied voltage is 0V.
And the transmittance corresponding to each wavelength when the applied voltage is 40V. Even when a spiral is generated in the liquid crystal due to the applied voltage (40 V), the existing position of the valley (selective reflection wavelength) is clear. On the other hand, in the conventional case, as shown in FIG. 9, the more the applied voltage is applied, the more unclear the existing position of the valley (selective reflection wavelength). For example, 4 in FIG.
The selective reflection wavelength (the minimum value of the curve) when an electric field of 0 V is applied can be specified at one measurement point (0.4275 μm), but in the result of the conventional method when 60 V of FIG. It shows the same transmittance and is the minimum value of the curve, and it can be judged that the selective reflection wavelength is only about 0.400 to 0.402. As described above, the apparatus of the present invention can improve the measurement accuracy about three times or more as compared with the conventional method.

The embodiments of the present invention will be listed below. (1) The transparent substrates having the vertical alignment layers are made to face each other with the vertical alignment layers facing inward, and a pair of positive electrodes and negative electrodes are inserted in parallel between them to arrange them between the vertical alignment layers and the positive electrodes and negative electrodes. A liquid crystal cell that encloses an antiferroelectric liquid crystal in the enclosed space. (2) The transparent substrates having the vertical alignment layers are made to face each other with the vertical alignment layers facing inward, and a pair of positive electrodes and negative electrodes are inserted in parallel between them to arrange them between the vertical alignment layers and the positive electrodes and the negative electrodes. A liquid crystal cell in which an antiferroelectric liquid crystal wound in a spiral in an enclosed space is enclosed so that the spiral axis of the liquid crystal is perpendicular to the vertical alignment layer and parallel to both electrodes. (3) The gap between the plus electrode and the minus electrode inserted and arranged in parallel is 100 μm to 2 mm, preferably 10 μm.
The liquid crystal cell according to item (1) or (2), which has a thickness of 0 μm to 200 μm. (4) The interval between the transparent substrates facing each other is 50 to 200 μm.
The liquid crystal cell according to the above item (1), (2) or (3), wherein m is m. (5) Polarized light arranged on the liquid crystal cell according to (1), (2), (3) or (4) above and outside the upper and lower transparent substrates of the liquid crystal cell in such a relationship that their respective polarization directions are not parallel. A liquid crystal light valve that consists of a plate. (6) The liquid crystal light valve according to the above item (5), wherein the polarizing plates arranged outside the upper and lower transparent substrates are arranged in such a relationship that their polarization directions are orthogonal to each other. (7) Output light means for emitting light by continuously changing the wavelength of monochromatic light, transparent substrates having vertical alignment layers are made to face each other with the vertical alignment layers facing inside, and a pair of plus electrodes are provided between them. An antiferroelectric liquid crystal in which a negative electrode is inserted and arranged in parallel and a spiral is wound in a space surrounded by the vertical alignment layer and the positive electrode and the negative electrode, and the spiral axis of the liquid crystal is perpendicular to the vertical alignment layer. Consists of a liquid crystal cell enclosed so that it is parallel to both electrodes, a polarizer provided on one side and an analyzer provided on the other side, and both polarization directions are parallel. The liquid crystal light valve arranged in such a relationship that does not become a temperature controller, a temperature controller for controlling the operating temperature of the liquid crystal light valve, the light passing through the polarizer, the liquid crystal cell and the analyzer in this order from the output light means. An antiferroelectric liquid crystal spiral pitch measuring device comprising a photodetector for detecting. (8) The monochromator is used as a means for changing the wavelength of the artificial light continuously and the monochromator is used, and the monochromator and the detector are connected by a computer in order to synchronize the monochromator and the detector. )
An antiferroelectric liquid crystal spiral pitch measuring device as described. (9) The above item (7) or (8), wherein the polarizer and the analyzer arranged outside the upper and lower transparent substrates of the liquid crystal cell are arranged in such a relationship that their polarization directions are orthogonal to each other. Antiferroelectric Liquid Crystal Spiral Pitch Measuring Device. (10) The repulsive strength according to the above (7), (8) or (9), wherein the distance between the plus electrode and the minus electrode inserted in parallel in the liquid crystal cell is 100 μm to 2 mm, preferably 100 to 200 μm. Measuring device for spiral pitch of dielectric liquid crystal. (11) The preceding paragraphs (7), (8), wherein the distance between the transparent substrates facing each other in the liquid crystal cell is 50 to 200 μm.
(9) or the spiral pitch measuring device for an antiferroelectric liquid crystal according to (10).

[0032]

The liquid crystal cell of the present invention can provide a liquid crystal cell in which the axis of the antiferroelectric liquid crystal is vertically aligned or obliquely tilted by providing the vertical alignment layer. did it. The liquid crystal light valve of the present invention,
It operates with an extremely low electric field and can be driven with a high-speed response as compared with the conventional structure. It is also effective as a squeeze because it can continuously change the brightness. Since the liquid crystal light valve of the present invention is not easily broken in orientation, it can be used even in an environment susceptible to mechanical shock. Further, by using the measuring device of the present invention, the selective reflection wavelength of the antiferroelectric liquid crystal can be accurately measured, and the spiral pitch can be accurately obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a liquid crystal cell according to the present invention.

FIG. 2 is a diagram showing an optical system in a liquid crystal light valve.

3 is a diagram showing the positional relationship between the liquid crystal cell, the polarizer, and the analyzer when viewed in the direction of the arrow in FIG. 1, and FIG. 3A is a sectional view showing the positional relationship between the liquid crystal cell, the polarizer, and the analyzer. And (b) is a perspective view.

FIG. 4 is a diagram showing changes in an electric field applied to a liquid crystal light valve and a transmitted light intensity.

FIG. 5 is a diagram showing a structure of a liquid crystal light valve of a type in which a large transparent substrate is used on the lower side and a large number of small transparent substrates having a pair of + electrodes and − electrodes for each pixel are arranged on the upper side.

FIG. 6 is a diagram for explaining the basics of the spiral pitch measuring device for antiferroelectric liquid crystal of the present invention.

FIG. 7 is a graph plotting the results of measurement using the spiral pitch measuring device for antiferroelectric liquid crystal of the present invention in the relationship between wavelength and transmitted light intensity.

FIG. 8 is a relationship diagram of transmittance and wavelength for showing that the selective reflection wavelength clearly appears when a voltage is applied using the device of the present invention.

FIG. 9 is a relationship diagram between the transmittance and the wavelength, which shows the result of the conventional method corresponding to FIG.

FIG. 10 is a diagram for explaining that when linearly polarized light is incident on a liquid crystal phase having a spiral structure in the present invention, the polarization direction is rotated, that is, the rotation angle is changed according to the wavelength, and the vertical axis is the rotation angle. , The horizontal axis is the wavelength.

[Explanation of symbols]

 1 Glass Substrate 2 Glass Substrate 3 Vertical Alignment Layer 4 Vertical Alignment Layer 5 Electrode 6 Electrode 7 Antiferroelectric Liquid Crystal in a Helixed State 8 Lead Wire 9 Lead Wire

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G02F 1/1335 510 1/1337 510 G09G 3/36

Claims (5)

[Claims] 1. A vertical alignment layer, a plus electrode and a minus electrode, wherein transparent substrates having vertical alignment layers are opposed to each other with the vertical alignment layers facing inward, and a pair of positive electrodes and negative electrodes are inserted in parallel between them. A liquid crystal cell that encloses an antiferroelectric liquid crystal in the space surrounded by it. 2. A transparent substrate having a vertical alignment layer is made to face each other with the vertical alignment layer facing inward, and a pair of positive electrodes and negative electrodes are inserted in parallel between them to arrange the vertical alignment layer, the positive electrode and the negative electrode. A liquid crystal cell in which an antiferroelectric liquid crystal wound in a space surrounded by a spiral is enclosed so that the spiral axis of the liquid crystal is perpendicular to the vertical alignment layer and parallel to both electrodes. 3. A liquid crystal comprising the liquid crystal cell according to claim 1 or 2 and a polarizing plate arranged outside the upper and lower transparent substrates of the liquid crystal cell in such a relationship that their polarization directions are not parallel to each other. Light valve. 4. Output light means for continuously changing the wavelength of monochromatic light to emit light, and transparent substrates each having a vertical alignment layer face each other with the vertical alignment layer inside, and a pair of plus or more positive electrodes therebetween. An antiferroelectric liquid crystal in which an electrode and a negative electrode are inserted and arranged in parallel and a spiral is wound in a space surrounded by the vertical alignment layer and the plus electrode and the negative electrode, and the spiral axis of the liquid crystal is relative to the vertical alignment layer. Consists of a liquid crystal cell enclosed vertically, parallel to both electrodes, a polarizer provided on one side and an analyzer provided on the other side. Liquid crystal light valves arranged in such a way that they do not become parallel, a temperature controller for controlling the operating temperature of the liquid crystal light valve, a polarizer from the output light means, the liquid crystal cell, and an analyzer in this order. An antiferroelectric liquid crystal spiral pitch measuring device comprising a photodetector for detecting the emitted light. 5. A monochromator is used as a means for continuously changing the wavelength of the artificial light, and a monochromator and a detector are connected by a computer in order to synchronize the monochromator and the detector. Item 4. An antiferroelectric liquid crystal spiral pitch measuring device according to Item 4.