JPH03502969A - Liquid crystal optical device with controlled surface order gradient - 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] M　　　　(′−・′　RO　　　−゛Ba) Regarding

The present invention is based on the Cendre Nacional de Recherche No. 040002. - Nanpa, a research institute affiliated with Siantifiq (National Institute of Science and Technology) It was completed at the Institute of Solid State Physics, University of Ri.

Much research has been conducted on liquid crystals for at least about 15 years.

Various research results conducted at the Institute of Solid State Physics at the University of South Paris were published on April 2, 1982. French patent application TH1 8207039 (publication number 2526177) filed on the 8th, French patent filed on October 23, 1984! 11th floor 8416192 (publication number No. 2572210), French painting patent application NCL8509 filed on June 18, 1985 224 (Publication number 2587916), and a French painting filed on May 14, 1986. Described in patent application Nt18606916 (publication number 2598827) .

Furthermore, research on liquid crystals has been published in many publications.

For example, the following documents may be mentioned.

1) Applied Physics Letters+vol, 25+ No,! L November 1974, pp. 479-481, Urbach et al. "Orientation of nematic and smectic liquid crystals on vapor deposited films", 2) Letters in Applied and Engineer ing 5 sciences + vol.

1, 1973, pp. 19-24, Guyon et al. ``On various boundary states of high-order nematic films'', and 3) Physical Review Letters, vol, 56+ No-19+ May 1986, pp. 2056-2059, Durand et al. , “Ordered electricity and surface alignment in nematic liquid crystals”.

Applied Physjcs Letters, vol. 25+ No, 9+ In November 1974, the thickness of the surface was about 50 to 1000 people. Plate (substrate) on which a vapor-deposited film of gold or SiO is pre-formed by oblique vapor deposition. Experimental results have been reported on a liquid crystal device constructed from. This document According to results published in (i.e., the liquid crystal molecules are oriented parallel to the plate), and oblique (i.e., the liquid crystal molecules are tilted with respect to the plate). Orientation) can be obtained.

According to the description on page 480, lines 43-46 of this document 1), the liquid on the plate is The oblique inclination of the crystal molecules is practically unrelated to the thickness of the first coating.

Reference 2) Letters in Applied and Engineer ing 5c4ences, vol, 1'+ 1973, pp. 19-24 proposed a model explanation of the experimental results reported in Reference 1). This model This explanation deals with the theoretical case where the thickness of the vapor-deposited film is 100 to 6,000 layers. Ru.

Reference 3) Physjcal Review Letters, vol, 56 + No. 19 + In May 1986, the nematic phase/isotropic phase liquid interface A theoretical analysis discussing the effects of fluctuations in the matic order is described.

From this analysis, the order fluctuation at the above interface is defined as cos”θ=173 The conclusion was that it involves energy twisting the molecules at an angle called the "magic angle". It will be done.

Here, the object of the present invention is to make the liquid crystal molecules oblique to the plate (substrate) of the device. By providing a new means of easily, reliably and economically defining slopes, be.

To this end, the present invention, based on many theoretical studies and experimental findings, On the plate of the liquid crystal device, there is a roughness (order) of the molecular dimensions of the liquid crystal used. It is proposed to form a roughness.

The thickness of the rough surface thus formed on the device plate is 20 to 40 mm thick. It is preferable that the degree of

The inventors have discovered that such a rough surface allows liquid crystals to be distributed along an oblique orientation with respect to the plate. to depolarizing fields that tend to twist the Order parameters that induce associated ordered electric (ordoelectrtc) polarization It was found that a gradient was generated.

Even more precisely, as a result of continued research, the inventors, for example, Defining the preferred direction of the rough surface by depositing a rough coating on the plate along the By this, the liquid crystal is obliquely aligned with respect to the plate. tation) and azimuthal orientation. We have found that it is possible to obtain both simultaneously in a controlled manner. even more Precisely, the orthographic alignment and azimuthal alignment of liquid crystals depend on the thickness of the rough surface and its preferred direction. i.e. in the case of vapor deposition, depending on the direction of incidence, in a plane oblique to the plate. It changes continuously.

This arrangement can provide many uses. In fact, the orthogonal alignment and azimuthal alignment of liquid crystals It is sufficient to control the thickness of the rough surface and its preferred direction to produce both directions simultaneously. be.

For example, according to the present invention, a substance consisting of liquid crystal molecules is placed between two parallel transparent plates. Bistable display with very low energy consumption using a sandwich device spray). At least one of these two plates has a liquid crystal display. on its surface on the side adjacent to it, with a roughened surface of a thickness on the order of the molecular dimensions of the liquid crystal; The thickness and orientation of this rough surface are symmetrical to and relative to the preferred direction of the rough surface. such that two possible azimuthal orientations of liquid crystal molecules around 45° are formed.

Also, the external electric field applied to this device can change from one azimuth orientation to the other. Means are also provided for causing controlled switching of the liquid crystal molecules in the direction. It is growing.

U.S. Pat. No. 4,601,544 relates to liquid crystal devices exhibiting volumetric bistability effects. do.

Held October 24-26, 1978 in Cherry Hill, New Chassis, USA Report of the 1978 Biennial Display Research Conference, 56-58 Page; Japanese Journal of Applte d Physics), Vol. 19+ No. 3 (March 1980) ; and J. Appl, Phys, Vow, 50. No, 6.　 (June 1979), pp. 3975-3977. This study relates to observation of the tilt of liquid crystal molecules with respect to light. The above documents inter alia Although the effect of film thickness is briefly analyzed, the effect of rough surface thickness is Not analyzed.

Furthermore, the above-mentioned bistable effect has not been clarified.

French painting patent application publication no. Regarding micro-cutting of membranes using ion beams (icromachining) Ru.

Other features, objects and advantages of the invention will be apparent from the accompanying drawings, which are shown by way of illustration only. Please read the detailed explanation below (which is not intended to be limiting). In the accompanying drawings, it will become clear that: Figures 1 to 4 show the evaporator set up on the plate for four types of experiments, respectively. Changes in the azimuthal orientation φ and oblique orientation φ of liquid crystals depending on the deposition angle (evaporation angle) and thickness of the deposited layer Figure 5 shows the oblique and azimuthal orientations of liquid crystal molecules with respect to the deposition (evaporation) direction. Shown geometrically, Figure 6 shows the azimuthal orientation φ and oblique orientation depending on the thickness of the deposited layer for a specific deposition angle. Two curves showing changes in ψ are shown in Figures 7, 8, and 9A and 9. Figure 9B schematically illustrates three types of applications of the present invention for nematic liquid crystal devices. indicate, and Figure 10 shows the thickness of the SiO deposited layer on each side of the two plates of the device. A curve representing a change in the orthogonal alignment of a smectic liquid crystal is shown.

Two fork blood five traps A nematic liquid crystal is an oriented electric quadrupole in this liquid that can be expressed as It can be thought that.

5=-e3/25(Fu'r-Y/3) In the above formula, 1-e means the quadrupole charge density (-e~10-' cgs), -5 means the liquid crystal charge density The order parameter (S means between 0 and 1), and -) is a unit that indicates the orientation of the molecules. is a position vector.

In the presence of spatial changes, the electric polarization P expressed by the following equation is obtained76.2. -7.5 12-3/2e. , 5(FIFL-Y/3)S acts on i under certain conditions. Then, a flexographic (fluctuation) electric effect is obtained, and the polarization p is proportional to the curvature h (U・5) The second thing that comes to mind is ζ11.

On the other hand, under conditions where the talent is constant and S is variable, the ortho (order> Polarization is obtained.

P -3/2 e V S, [nn-1/3] D, Tomi 0 Midori 4 night Pz + t E.

(In the formula, 2 is the direction of S.) The associated energy has a charge density given by:

1/2 (d4+r) E,” m l/2 (4r/l) P, “This energy The gee is the oblique to 2 defined by P, 40, i.e. cos "θ-1/3" Take the minimum value for orientation θ.

of According to the results of the above general analysis, the gradient of the order parameter is The present inventors thought that stress would be applied to the liquid crystal along the oblique alignment, so the present inventors Small crystal grains with a particle size of about the size of the molecular size of the liquid crystal used, that is, about 20 to 40 By providing on the plate of the device, order parameters can be controlled on the surface of the liquid crystal device. The idea of controlling data S was proposed.

exhibits an orientation parallel to the plate plane but degenerates in the presence of the polishing plate, in other words If so, a nematic liquid crystal whose orientation varies in a plane parallel to the plate plane is used. , conducted an experiment. More precisely, the inventors investigated various combinations of deposited grain thickness and 1st angle. The alignment of the liquid crystal was controlled by

The present inventors have developed a method for forming a plate by forming a rough surface state by vapor deposition along a specific direction. Not only the orthogonal alignment of liquid crystal molecules, but also the controlled alignment that can be varied with respect to the deposition direction. It has been found that azimuthal orientation can also be obtained.

The initial results obtained are reported in the accompanying Figures 1-4 and 6.

These results are shown for the geometric model shown in FIG.

This geometric model consists of a coordinate system with three mutually perpendicular axes, X, Y, and 2. Become.

The y-axis and the y-axis are parallel to the plate P.

The z-axis is perpendicular to this plane P and is in the direction of the volume of the liquid crystal.

The deposition direction is arbitrarily made to coincide with a plane (xz plane) defined by the y-axis and two axes. steaming The angle of incidence in the deposition direction, which corresponds to the inclination between the deposition direction and the two axes, is defined by the angle α .

The oblique alignment of liquid crystals, which corresponds to the tilt between the Z axis and the long axis of liquid crystal molecules, is shown in Figure 5. It is indicated by θ. The complementary angle of this angle θ is indicated by the symbol ψ.

Finally, the liquid crystal corresponding to the tilt between the y-axis and the projection of the long axis of the liquid crystal molecules onto the xy plane The azimuthal orientation of is represented by the angle shown as φ in FIG.

What is the attached Figure 1? For the case of IBBA liquid crystal, deposition of SiO on ordinary glass The change in azimuthal orientation φ due to the change in layer thickness and deposition angle α is shown.

For deposited layer thicknesses of less than 5 layers, the liquid crystal molecules are parallel to the plates but randomly oriented in the direction.

When the thickness of the deposited layer reaches 5 layers, degeneracy is eliminated. That is, the molecules are parallel to each other, It is oriented in a direction perpendicular to the xz plane including the deposition direction. At this stage, the azimuthal orientation of the molecules φ'' is equal to 90' and the oblique orientation θ'' is also equal to 90°.

The initial configuration of this molecule is shown schematically in FIG. It is.

As the thickness of the deposited layer increases further, the molecules move in a plane oblique to the plate P. azimuthal rotation is obtained as a function of the deposition angle α. In this case, the liquid crystal molecules position orientation φ.

is equal to 90° to an azimuthal domain in which φ can be 0° (i.e., if the molecule (domains oriented substantially parallel to the xz plane including the deposition direction) do. This azimuthal rotation is accompanied by the lifting of the molecule, and φ gradually changes from 90° to 0°. When changing, ψ changes from O" to 20 to 30 degrees.

The shaded area in Figure 1 shows that the azimuth orientation ψ gradually varies between 90° and 0°, and Deposition angle α and deposition where the orientation ψ gradually changes between 0° and about 20~30@ Corresponds to a range of layer thickness values. Orientation that can be controlled by the condition of the rough surface Such gradual variations in orientation φ and oblique orientation ψ result in φ=90@ or 0° and ψ = 0 or 20 to 30 degrees, which is new compared to conventional technology where only boundaries were known. , which forms an essential characteristic part of the present invention.

Comparable results are shown in the attached FIG. 2. This figure 2 was performed under the same test conditions. In other words, SiO was deposited on ordinary glass by varying the deposition angle and deposition layer thickness. In this test, 5C was used instead of MBBA as the liquid crystal, unlike in Figure 1. Regarding the test using B.

Similarly, in Figures 3 and 4, one uses MBBA as the liquid crystal, and the other uses MBBA. is the thickness of the SiO deposited layer on the ITO slide glass when using 5CB. Fig. 3 shows changes in the value of azimuthal orientation φ depending on the angle and the deposition angle α.

Similar to FIG. 1 described above, FIGS. 2, 3, and 4 also show that the azimuth orientation φ is 90°. The range of combinations of deposition angle α/deposition layer thickness when gradually changing from to Oo area (shaded area in the figure).

Figure 6 shows the case where a 5-channel liquid crystal is used, and the angle of incidence is 74°, and one screen is zero. Azimuthal orientation φ and orthorhombic as a function of the thickness of the Si0 layer deposited on the ride glass Simultaneous changes in orientation ψ are shown.

Consistent with the results shown in FIG. In this case, it is also recognized that the azimuthal orientation φ changes gradually from 90° to 0°. It will be done.

At the same time, the oblique orientation ψ also varies from 01 to 01 when the deposition thickness is within the range of 30 to 40 Gradual increase up to 20" is allowed.

In conclusion, according to the tests conducted by the inventors, the bare substrate before deposition has a planar orientation ( (i.e., parallel to the plate plane), but degeneracy can also be recognized. came. When the average deposition thickness (of SiO) reaches 5, the orientation degeneracy is resolved. However, the anchoring still remains flat.

When the average deposition thickness exceeds 10, lifting of the nematic liquid crystal is observed, from its initial planar position perpendicular to the deposition direction to a diagonal position toward the deposition direction. Rotate within the slope until the

By providing a rough surface condition on the plate according to the present invention, an order gradient can be generated. Therefore, the induced ordered electric polarization creates an orthorhombic configuration diagonal to the plate. Lifting of the liquid crystal can be caused according to the direction ψ. The formation of such a rough surface condition is , of course, other means than vapor deposition, such as chemical attack, atomization or ionic This can also be done by means such as impact.

The following describes various examples of applications of the invention, which are not intended to be limiting. stomach.

. Enables multiple use of up to 6 devices on the same smartphone , for the purpose of obtaining good contrast, a pre-preparation method is used, as shown diagrammatically in the accompanying Figure 7. at an angle β greater than 90", indicating an oblique orientation ψ with respect to at least one of the A nematic display (device) with oppositely inclined and fixed orientation on two plates. The development of display devices is being attempted today. If used, an oblique orientation ψ of 10-20° with respect to the plate and a controlled azimuthal orientation can be achieved. can be easily obtained.

h Mar, 1 to No. Furthermore, the present inventors discovered that liquid crystal molecules have two symmetrical structures with respect to the xz plane that includes the deposition direction. It was discovered that the azimuth orientation can be taken.

That is, FIG. 8 shows two azimuthal orientations that are symmetrical with respect to the XZ plane defined by the deposition direction. The Mtr angle α and the M deposition thickness shown schematically during vapor deposition on the plate are shown relative to the XZ plane. If the orientation φ is selected to be about ±45°, it is not possible to apply an external electric field. As a result, the liquid crystal molecules are controlled from one azimuth orientation to the other on this plate. This makes it easy to perform controlled switching. from one azimuth orientation to the other To perform controlled switching of liquid crystal molecules to azimuth orientation and vice versa , alternately in the cell, for example, if the liquid crystal has positive dielectric anisotropy, these If one of the orientations coincides with the other, or if the liquid crystal has negative dielectric anisotropy, each having at least an l component perpendicular to one of these azimuthal orientations. It is sufficient to apply an electric field parallel to the rate. 90゛ orientation of liquid crystal molecules The change in magnitude is thus obtained, and the maximum when the device is placed between polarizers It becomes possible to obtain a large contrast.

In the absence of an electric field, the resulting liquid crystal configuration remains stable.

When a rough surface condition is imparted to one electrode or plate, two types of domains [±φ] are created. is obtained.

When two electrodes or plates have a rough surface, four types of domains ( +φ1. +φb;+φ□−φb;−φ1. 10φb; -φ, -φ1) is possible . The symbols and mean upper and lower plates, respectively.

-Mar　・゛4-Vice・ Third possible scope of application of the invention to the design of nematic liquid crystal devices 9A, a plane fixation parallel to both plates of the device (a Anchor rings) are formed. However, on one side of this plate, the evaporated layer By controlling the angle α and the deposition thickness, the liquid crystal can be formed into the transition region shown by the shaded areas in Figures 1 to 4. be located near the area.

The liquid crystal is thus located near the unstable dark value, i.e. near the orientation switching dark value. Ru. This arrangement ensures that when an external electric field is applied, the uni, the liquid crystal switches to the direction of spiral formation (this switch itself is known) ) becomes easier.

Alternatively, it is possible to first form a spiral arrangement of liquid crystals close to the unstable dark value, and then This helical arrangement can also be converted to a parallel orientation of the molecules when an electric field is applied. It is possible.

Palpitation -C''-Su -・- of the day of Ferroelectric C* smectic display devices have a degenerate surface fixation when the smectic It is theoretically possible to have two positions of liquid crystal molecules that are symmetrical with respect to the liquid crystal layer. be. When an external electric field is applied, the electric dipole of the molecule changes to the position of the electrode at one of its positions. Theoretically, these two positions The positions should be equivalent and the formation of bistable display devices should be possible.

However, in reality, in twisted tissues where contrast is low and multiplexing is not possible, Only a monostable representation can be obtained instead of a bistable representation between two types of symmetrical states. The present inventors believe that this phenomenon is due to the polarity of the electrode/liquid crystal interface. It was found that this was caused by This polarization is chemical (surface and molecular parts This seems to be due to the difference in affinity between the two.

According to the present invention, a nematic layer of appropriate sign and magnitude is formed in the smectink layer. Due to the ordered electric polarization induced by creating a magnetic order gradient, the above It becomes possible to cancel chemical polarization.

In order to achieve good cancellation of chemical polarity, nematic order must be present in the bulk (total) Highly polished interfaces with higher values or rougher interfaces with lower surface order You can take either.

FIG. 10 shows the 0.0. Formed by evaporation at an incident angle θ of 81@ on two ITO plates separated by 3 pm. This was done on each plate on the top and bottom of the device for different thickness values of the SiO75 deposit. The orientation θ of the liquid crystal obtained in this manner is shown below.

Needless to say, the present invention has been described above! ! Not limited to birch and use The present invention includes any modifications according to the technical idea of the present invention.

ξ Sign tightening rice 1□ nG-7 Nezhi-Nne7te*・775 night crystal to central circle/V stable threshold bridge r mie na two camellias 1 r mi solid (Fum outside)! 9ch6ppp・; Yoruman (goods T i positive sui 7 nan 2°.

international search report 1l1111′′6′″” = PCT/F’R88100623 International Investigation report FR8800623

Claims (12)

[Claims] 1. Molecules of the liquid crystal used on at least one of the plates that make up the liquid crystal device. a liquid, characterized in that it comprises a step consisting of forming a rough surface of the order of dimensions. A method for manufacturing a crystal device. 2. The rough surface formed on at least one of the plates of the device is in the range of 20 to 40 Å. 2. A method according to claim 1, characterized in that the thickness is within the range of . 3. At least one of the plates of the device is coated with the following methods: coating vapor deposition, coating spraying. Rough surface formation due to either fog formation, chemical attack, or ion bombardment A method according to any one of claims 1 and 2, characterized in that: 4. At least one of the plates of the device has a roughened surface, e.g. by controlling the deposition direction. A rough surface with a controlled preferred direction is formed and is inclined to at least one plate. At the same time, the orientation of the liquid crystal molecules with respect to the preferred direction of the rough surface is obtained. According to any one of claims 1 to 3, characterized in that the method also obtains a direction. the method of. 5. From two parallel plates and liquid crystal molecules arranged between these two plates A type of liquid crystal device consisting of a substance consisting of at least one of said plates. On the other hand, on its surface adjacent to the liquid crystal, there is a layer on the order of the molecular dimensions of the liquid crystal used. Any one of claims 1 to 4, characterized by having a rough surface. A liquid crystal device obtained by using the method described in . 6. The rough surface provided on at least one of the plates has a thickness within the range of 20 to 40 Å. Device according to claim 5, characterized in that it is a device. 7. characterized in that a roughened surface is provided on each of the two plates of the device. A device according to any one of claims 5 and 6. 8. Claims 5 to 5, wherein the liquid crystal is a nematic liquid crystal. The device according to any of clause 7. 9. The thickness and orientation of the roughened surface on at least one of the plates is such that the liquid against at least one of the plates to form a tick display device. Orthogonal crystal orientation φ and relative tilting at an angle β greater than 90° is characterized in that it defines the direction of fixation on the two plates that are A device according to any one of claims 5 to 7. 10. The rough surface has a preferred direction determined, for example, by the deposition direction, and The thickness and orientation of the roughened surface on at least one side of the plate are relative to the preferred direction of the roughened surface. two possible azimuthal orientations of liquid crystal molecules symmetrical to this direction and at an angle of 45° to this direction. It is like forming φ, and in order to achieve bistable nematic fixation, the device is The liquid crystal changes from one azimuth orientation to the other by an external electric field applied to the vice. equipped with means that allow controlled switching of molecules to occur The device according to any one of claims 5 to 8, characterized in that: . 11. The thickness and orientation of the roughened surface on at least one of the plates is such that it To make the orientation switching of the liquid crystal easier when Claim characterized in that the switching threshold is such as to be placed close to the switching threshold. The device according to any one of items 5 to 8. 12. The liquid crystal is a ferroelectric C* smectic liquid crystal, and at least The thickness and orientation of the rough surface on one side creates an ordered electrical polarization that cancels out the total polarization on the surface. The features of claims 5 to 7, characterized in that Any device listed in any of the above.