JPH1082989A - Liquid crystal element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the image quality and to realize a smoothly animation image display by forming a liquid crystal orienting film with low polarization which has a property to relax polarization on the interface with a liquid crystal. SOLUTION: The liquid crystal oriented film is composed of an orienting film which has a property to relax polarization on the interface with a liquid crystal, especially an orienting film having high conductivity. In this case, it is preferable that the liquid crystal orienting film consists of a SiOX oblique vapor deposition film (wherein x is positive number <2) having <=103.3eV bonding energy of the Si2p orbit. The SiOX is more active than SiO2 and shows conductivity so that charges in the orienting film on the liquid crystal-orienting film interface are effectively released through the SiOX to decrease polarization. The polymer orienting film with low polarization consists of, for example, polyvinylalcohol, polyvinylacetate, polyacrylonitrile, polyethylene, and polyisoprene. Thereby, polarization such as electron polarization in the orienting film can be relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other at a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is arranged in the gap. (For example, liquid crystal display element or liquid crystal display)
It is about.

[0002]

2. Description of the Related Art A liquid crystal display (LCD) using a liquid crystal as a display has features of low power consumption, thinness and light weight, and taking advantage of this, from a clock and a calculator to a computer display and a television receiver. (T
Application to V) is progressing.

Research and development for using a ferroelectric liquid crystal (FLC) as a liquid crystal in such an LCD has been actively pursued. Regarding FLC, a ferroelectric liquid crystal was first synthesized by Meyer in 1975, and a surface-stabilized ferroelectric liquid crystal capable of domain inversion by an electric field was invented in 1980 by Clark and Lagaard. F
LC is a liquid crystal that has a permanent dipole moment in the molecule itself perpendicular to the long axis of the molecule, has spontaneous polarization, and can be switched by an electric field.
The display is an excellent display mainly having the following features (1) to (3).

(1) The switching speed is on the order of microseconds, the response is 1000 times faster than that of the TN liquid crystal display, and the high-speed response is excellent. (2) There is basically no twist structure in the molecular arrangement, and there is little viewing angle dependence. (3) Even if the power is turned off, the image is retained, the image has memory properties, and simple matrix driving is possible even for 1000 or more scanning lines that can support high definition.

Accordingly, the FLC display has a high definition,
It is a display that can pursue the performance of low cost and large screen.

Such an FLC display (ferroelectric liquid crystal display element) has a structure as schematically shown in FIGS. 15 and 16, for example. First, a transparent electrode (100 Ω / □ ITO: Indium tin oxide) is formed on a transparent glass substrate (Corning 7059, 0.7 mm thick) 1a, 1b.
2a and 2b are provided. These transparent electrodes are patterned in a striped shape by etching, and data electrodes (column electrodes) 2 which cross each other in a matrix shape.
a and the scanning electrode (row electrode) 2b.

On the transparent electrodes 2a, 2b, obliquely deposited SiO films 3a, 3b are formed as liquid crystal alignment films. In forming an obliquely deposited SiO film, a substrate is disposed vertically from a SiO deposition source in a vacuum deposition apparatus, and an angle between a vertical line and a substrate normal is set to 85 degrees. Si
After vacuum deposition of O at a substrate temperature of 170 ° C., baking is performed at 300 ° C. for 1 hour.

In the pair of substrates 1a and 1b provided with the alignment film thus manufactured, the alignment directions of the data electrode 2a and the scanning electrode 2b are antiparallel on opposite surfaces, and the data electrode 2a and the scanning electrode 2b are arranged so that the electrode arrangement is orthogonal. As the spacer, glass beads (straightening sphere: 0.8 to 3.0 μm in diameter (manufactured by Catalyst Chemical Industry Co., Ltd.)) 4 corresponding to the target gap length are used. Here, the alignment processing directions are set antiparallel, but they may be set parallel.

Depending on the size of the transparent substrates 1a and 1b, the spacer 4 has a sealing material (UV-curable adhesive (Photorec: manufactured by Sekisui Chemical Co., Ltd.)) 6 that adheres to the periphery when the area is small. By dispersing about 0.3 wt%, the gap between the substrates is controlled. When the substrate area is large, the above-mentioned straightening spheres have an average density of 100 pieces / ball on the substrate.
After spraying mm ² , a gap was formed, a liquid crystal injection hole was secured, and the periphery of the cell was bonded with a sealant 6.

A liquid crystal composition in which, for example, a ferroelectric liquid crystal (YS-C152 manufactured by Chisso Corporation) 5 is uniformly dispersed at an isotropic phase temperature using an ultrasonic homogenizer between a pair of substrates 1a-1b. Has been injected. This ferroelectric liquid crystal composition is injected under reduced pressure in a state showing fluidity such as an isotropic phase temperature or a chiral nematic phase temperature. After injecting the liquid crystal, the liquid crystal is slowly cooled, and the liquid crystal on the glass substrate around the injection hole is removed, and then sealed with an epoxy-based adhesive.
The display 11 is manufactured.

As a driving method of the FLC display 11, an XY matrix method is used. When the NTSC system is selected, 1H (one horizontal scanning time or one line selection time) is 63.5 μs, and the voltage is applied in bipolar in consideration of the electrical neutral condition. .5 / 2 μs width. Row side (electrode 2b)
, A select pulse as a threshold is applied, and a data pulse is applied from the column side (electrode 2a).

A ferroelectric liquid crystal element (for example, a surface-stabilized ferroelectric liquid crystal element) has an externally applied electric field E (Ps is spontaneous polarization).
As shown in FIG.
And state 2 are switched. This change in molecular orientation appears as a change in transmittance by disposing a liquid crystal element between orthogonal polarizing plates, and the transmittance changes from 0% at a threshold voltage _Vth with respect to an applied electric field as shown in FIG. It changes sharply to 100%. The voltage width at which the transmittance changes is generally 1 V or less.

As described above, since the conventional ferroelectric liquid crystal display using the bistable mode is stable only in two states, it is difficult to provide a stable voltage range in the transmittance-applied voltage curve. In addition, gradation display by voltage control is difficult or impossible.

Therefore, the threshold voltage width for switching between the bistable states of the liquid crystal in one pixel is extended by giving a distribution to the effective electric field applied to the liquid crystal in one pixel. Can achieve analog gray scale display by the present applicant.
(This is hereinafter referred to as a prior invention).

According to the invention of the prior application, a method of adding and dispersing ultrafine particles such as titanium oxide in a ferroelectric liquid crystal in order to "extend the threshold voltage width" is employed.

By the addition of the ultrafine particles, fine regions (micro domains) having different threshold voltages (V _th ) are developed in one pixel, and the transmittance of the micro domains is changed according to the magnitude of the applied voltage. Is changed, the transmittance does not change sharply, but shows a relatively gradual change, and analog gray scale display becomes possible. And
In one domain, if the liquid crystal molecules are bistable, they have a memory function, and one pixel is formed from domains having a different threshold voltage on the order of μm, so that continuous gradation display is possible.

Therefore, as shown in FIG. 19, in the liquid crystal element obtained by the prior application, the transmittance does not change sharply as shown in FIG. 18 but changes relatively slowly according to the applied voltage. It is. This is, as mentioned above,
In particular, in one pixel, a fine region (micro domain) having a different threshold voltage (V _th ) _appears ,
This is because the number of microdomains changes according to the magnitude of the applied voltage, and thus the transmittance as a sum of one pixel changes. Then, in one domain, the liquid crystal molecules have a memory function of being bistable, and have different threshold voltages.
Since one pixel is formed from an m-order domain,
Continuous tone display becomes possible.

[0018]

The present inventors have concluded that the ferroelectric liquid crystal display element has the above-described excellent characteristics, but the dipole moment of the ferroelectric liquid crystal molecule itself, the dielectric constant, and the inside of the panel. The phenomenon that the transmittance cannot be determined to one value by the voltage applied in the previous frame due to impurity ions or the like (applied voltage-transmittance hysteresis),
It has been found that a phenomenon (burn-in phenomenon) that leaves the display color selected in the previous frame may occur.

This is because, in a normal black-and-white binary ferroelectric liquid crystal display, if the same image is continuously displayed for a long time, the next image cannot be displayed, or if the power consumption is increased, the driving method becomes complicated. And so on. In particular, in the above-mentioned ultrafine particle-containing ferroelectric liquid crystal display capable of analog gradation display, in addition to the above-described problems (hysteresis and burn-in phenomenon), instability of the number of gradation displays occurs, and The advantage of the tone display cannot be fully utilized.

One of the causes of the above-mentioned hysteresis and image sticking is that polarization (especially electronic polarization) in the alignment film at the liquid crystal-alignment film interface generated at the time of switching of spontaneous polarization which is a characteristic of ferroelectric liquid crystal. There was found. Hereinafter, the phenomenon will be described in detail.

As a method of evaluating the hysteresis, a transmittance curve in which the applied voltage is gradually increased and a transmittance curve in which the applied voltage is gradually decreased are measured, and a comparison can be made based on the voltage width of the deviation. For example, it corresponds to HΔV in FIG.
The value of the transmittance by random voltage application corresponding to the normal image quality display is between the curves, and the magnitude of the hysteresis (HΔV) causes the instability of the display color.

Therefore, this voltage width is set to zero (HΔV = 0)
By doing so, the effect of the applied voltage of the previous frame can be eliminated, that is, the transmittance can be selected to one value by the applied voltage value.

At the time of black-and-white binary display in a normal ferroelectric liquid crystal display, the next frame displaying black, even if it has a voltage value for displaying white (V1 shown in FIG. 21), is actually black. This is a phenomenon such as being displayed.
The opposite happens for the next frame in white. When viewed as a whole display, the image of the previous frame is distorted and appears as an afterimage.

In the case of an ultrafine particle-containing ferroelectric liquid crystal display capable of analog gradation display, this development is even more remarkable. That is, since this burn-in occurs even when gray is displayed, as shown in FIG. 22, not only does the curve have a deviation width such as HΔV, but also the curve shape (gamma) is deformed. Would be. For example, in FIG. 22, although a light color pattern is to be displayed in a dark color pattern as a display by the applied voltage V2, the color pattern may be reversed. In addition, unnaturalness occurs in moving image display. In addition, as a method of evaluating burn-in, the same measurement as described above is performed, and a comparison can be conveniently made using the value of YΔV in FIG.

By setting these HΔV and YΔV to zero, in a normal ferroelectric liquid crystal display,
Data voltage value V input from a single matrix column
3 and a smooth moving image can be obtained, and a complete analog gradation can be completed in the ultrafine particle containing type.

[0026]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the above-mentioned hysteresis and image sticking in a liquid crystal element, to improve the image quality and to realize a smooth moving image display.

[0027]

The present inventors have found that in the liquid crystal device, the cause of the above-mentioned hysteresis and image sticking is electronic polarization in the alignment film at the interface between the liquid crystal and the alignment film which occurs during driving of the liquid crystal. The present inventors have found that the image quality can be improved and smooth moving image display can be realized by relaxing the mode, and the present invention has been achieved.

That is, the present invention provides a liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other with a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is disposed in the gap. The present invention relates to a liquid crystal element, wherein the liquid crystal alignment film is formed of an alignment film having a property of relaxing polarization at an interface with the liquid crystal, particularly an alignment film having high conductivity.

According to this liquid crystal element, polarization such as electronic polarization in the alignment film at the interface between the liquid crystal and the alignment film, which is considered to be the largest cause of hysteresis and image sticking, can be relaxed. HΔV) can be reduced, so that the image quality can be improved and a smooth moving image can be displayed regardless of the liquid crystal material or the like.

It is desirable that the above-mentioned liquid crystal alignment film is made of a SiO _x obliquely deposited film having a binding energy of Si _2p orbitals of 103.3 eV or less (where x is a positive number less than 2). Since such SiO _X is more active than SiO ₂ and exhibits conductivity, charges in the alignment film at the interface between the liquid crystal and the alignment film are effectively released through SiO _X to reduce the polarization phenomenon. Because you can do it.

The present invention also relates to a liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other with a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is disposed in the gap. There is also provided a liquid crystal element characterized in that a thin film of high conductivity or low polarization having a property of relaxing polarization in an alignment film at an interface between the liquid crystal alignment film and the liquid crystal is laminated on the liquid crystal alignment film. Is what you do.

In this liquid crystal device, a thin film having high conductivity for relaxing the polarization in the alignment film at the interface with the liquid crystal is laminated on the liquid crystal alignment film. Polarization such as electronic polarization can be alleviated, and image quality can be improved and smooth moving images can be displayed regardless of the liquid crystal material or the like. Further, when a low-polarization polymer thin film is laminated, the phenomenon of image sticking can be reduced from the beginning. Low-polarized polymer thin film, for example, polyvinyl alcohol, polyvinyl acetate, polyacrylonitrile,
It can be formed of polyethylene, polyisoprene, or the like.

In this case, the thin film having high conductivity is an organic or inorganic thin film having an electric conductivity (electric conductivity) of 2.0 S / cm or less, or the thin film having high electric conductivity has an electric conductivity of 1.2 S / cm. It is desirable to be an organic or inorganic thin film of at least 10 ^-8 S / cm.

The present invention further provides a liquid crystal device in which a plurality of substrates having a liquid crystal alignment film are opposed to each other with a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is arranged in the gap. A liquid crystal element characterized in that an organic complex having a degree of 1.2 × 10 ⁻⁸ S / cm or more is laminated on the liquid crystal alignment film.

In this liquid crystal element, an organic complex having a conductivity of 1.2 × 10 ⁻⁸ S / cm or more is laminated on the liquid crystal alignment film. The polarization can be alleviated, and the image quality can be improved and a smooth moving image can be displayed regardless of the liquid crystal material or the like.

Examples of such organic complexes include tetrathiafulvalene, dimethyltetrathiafulvalene, tetramethyltetrathiafulvalene, hexamethylenetetrathiafulvalene, tetraselenfulvalene, tetrathiotetracene, quinoline and the like, tetracyanoquinodimethane, Complex compounds with fluorotetracyanoquinodimethane, methyltetracyanoquinodimethane, dimethyltetracyanoquinodimethane, diethyltetracyanoquinodimethane, chlorotetracyanoquinodimethane, bromotetracyanoquinodimethane and the like can be mentioned.

As described above, according to the liquid crystal device of the present invention,
Hysteresis caused by polarization of the liquid crystal-alignment film interface can be eliminated, and in a normal ferroelectric liquid crystal display, the reduction of the data voltage value input from the column electrodes of a simple matrix and the smooth moving image can be obtained. Become. In the ultrafine particle-containing element as in the above-mentioned prior invention, a complete analog gradation can be realized.

In terms of gradation, it is desirable that regions having different threshold voltages for switching the ferroelectric liquid crystal are finely distributed, as in the above-mentioned prior application. In order to form such fine regions having different threshold voltages, fine particles are preferably added to the ferroelectric liquid crystal.

Here, the above-mentioned "regions having different threshold voltages are finely distributed" means that the transmittance due to the inversion domain (for example, the black domain in white or the opposite) is 2 or more.
When it is 5%, there are 300 or more (preferably 600 or more) domains (microdomains) having a size of 1 μmφ or more in a 1 mm ² field, and the threshold voltage width within the domain. Means 1 V or more, preferably 2 V or more in a transmittance range of 10 to 90%.

Therefore, as illustrated in FIG. 19, in this liquid crystal element, the transmittance does not change sharply as shown in FIG. 18 but changes relatively slowly according to the applied voltage. This is because, as described above, in particular, in one pixel, micro-domains having different threshold voltages (V _th ) are developed, and the transmittance of the micro-domains is changed according to the magnitude of the applied voltage. Is changed. Then, within one domain, the liquid crystal molecules have a memory function when they are bistable, and have different threshold voltages.
Since one pixel is formed from an m-order domain,
Continuous tone display becomes possible.

In FIG. 19, of the threshold voltages at which the transmittance changes, V _th1 and transmittance 90% when the transmittance is 10%.
In the case where V _th2 is the time of (3), the variation width of the threshold voltage (△
(V _th = V _th2 −V _th1 ) is 1 V or more.

As for the micro domain, FIG.
As shown in the figure, when the transmittance is 25%, domains MD having a size of 1 μmφ or more are present at a rate of 300 / mm ² or more. Such a fine light-transmitting portion of the microdomain can realize a halftone screen (transmittance) as a whole, but since the structure of such a microdomain has a so-called starry sky,
Hereinafter, it is referred to as “starlight texture”.

According to the starlight texture, the light transmitting portion MD of the micro domain is enlarged (increased in transmittance) or reduced as shown by a dashed line in FIG. 6A according to the magnitude of the applied voltage. (Decrease in transmittance), and the transmittance can be arbitrarily changed by the applied voltage. On the other hand, in the devices of FIGS. 15 and 16, as shown in FIG. 6B, the threshold voltage width is extremely small, so that the light transmitting portion D due to the applied voltage sharply increases or disappears. And gray scale display is difficult.

In this method of manufacturing a liquid crystal element, fine particles (or ultrafine particles) can be dispersed in the liquid crystal 5 in a liquid crystal cell as a means for forming the above microdomain.

Here, the change in threshold voltage due to the ultrafine particles will be described in principle with reference to FIG. When the particle diameter of the ultrafine particles 10 is d ₂ , the dielectric constant is ε ₂ , the thickness of the liquid crystal 5 excluding the ultrafine particles 10 is d ₁ , and the dielectric constant is ε ₁ , the electric field Eeff applied to the ultrafine particles is expressed by the following equation (1). ). Eeff = (ε ₂ / (ε ₁ d ₂ + ε ₂ d ₁ )) × Vgap (1)

Therefore, when ultrafine particles having a dielectric constant smaller than that of the liquid crystal are added (ε ₂ <ε ₁ ), the total thickness dga of the liquid crystal layer is increased.
By introducing fine particles (d ₂ ) smaller than p (= d ₁ + d ₂ ), Eeff <Egap, and a small electric field Eeff acts on the liquid crystal as compared with the case where no fine particles are inserted (Egap).

On the contrary, by adding fine particles having a dielectric constant larger than that of the liquid crystal (ε ₂ > ε ₁ ), Eeff> Egap, and the liquid crystal is compared with the case where no fine particles are added (Egap). A large electric field Eeff acts.

The above is summarized as follows. When ε ₁ > ε ₂ → Eeff <{Vgap / (d ₁ + d ₂ )}
_{= Vgap / dgap = Egap ε 1} = ε 2 when → Eeff = Egap ε ₁ <when ε ₂ → Eeff> Egap

In any case, the addition of the ultrafine particles changes the effective electric field Eeff applied to the liquid crystal itself, and the effective electric field applied to the liquid crystal differs between a region where the ultrafine particles exist and a region where the ultrafine particles do not exist. . As a result, even when the same electric field Egap is applied, a region where an inversion domain occurs and a region where the inversion domain does not exist exist between these regions.
The starlight texture structure as shown in (A) can be expressed.

From this, the starlight texture structure is suitable for realizing continuous gradation, and the applied voltage (magnitude, pulse width, etc.) is controlled with the addition of ultrafine particles (that is, two or more types). , A variety of transmittances (that is, two or more types of gradation levels) can be obtained. On the other hand, only the presence of fine particles gives only the one shown in FIG. 6 (B). In particular, even if fine particles of 0.3 to 2 μm are present in a very small (about 2 μm) gap, the purpose can be improved. It is apparent that the display performance cannot be obtained, and even if the gap is not very small, color unevenness occurs due to the fine particle portion. In the starlight texture structure, the desired performance can be obtained without such a phenomenon.

In the liquid crystal device of the present invention, the fine particles to be added to the liquid crystal are distributed in the effective electric field intensity applied to the liquid crystal 5 existing between the opposed transparent electrode layers 2a and 2b shown in FIGS. Any fine particles can be used as long as the particles can have the following. For example, fine particles of a plurality of materials having different dielectric constants can be mixed and used. The presence of the fine particles having different dielectric constants as described above forms a distribution of the dielectric constant in each pixel.

As a result, as described above, even when an external electric field is applied uniformly between the transparent electrode layers 2a and 2b of a pixel, the effective electric field applied to the liquid crystal in the pixel has a distribution, and The distribution width of the threshold voltage for switching between bistable states (especially ferroelectric liquid crystal) can be widened, and analog gray scale display can be performed within one pixel.

When fine particles having the same dielectric constant are used as the fine particles to be used, the fine particles may have a distribution in size. As described above, the presence of fine particles having different dielectric constants but different sizes allows distribution of the thickness of the liquid crystal layer. As a result, even when an external electric field is applied uniformly between the transparent electrode layers 2a and 2b of one pixel, the effective electric field intensity applied to the liquid crystal in that pixel is distributed, and analog gradation display is performed in one pixel. Becomes possible. Regarding the distribution of the size of the fine particles, it is preferable that the spread of the distribution be large to some extent because excellent analog gradation display can be performed.

In the liquid crystal device of the present invention, it is desirable that the fine particles added to the liquid crystal have a surface of pH = 2.0 or more. This is because it is easily deteriorated.

The amount of the fine particles is not particularly limited and can be appropriately determined in consideration of desired analog gradation, etc., but is not more than 50% by weight and 0.0001% by weight.
It is desirable that the above ratio be added to the liquid crystal. If the added amount is too large, it is difficult to develop a starlite texture structure due to aggregation, and it is difficult to inject liquid crystal.

The fine particles that can be used may be composed of carbon black and / or titanium oxide. The carbon black is preferably carbon black produced by a furnace method, and the titanium oxide is preferably amorphous titanium oxide. Pyrolytic carbon black produced by the furnace method has a relatively wide particle size distribution of fine particles, and amorphous titanium oxide has good surface properties and excellent durability.

The usable fine particles, in the form of unagglomerated primary fine particles, preferably have a size of not more than half (0.4 μm or less, particularly 0.1 μm or less) of the liquid crystal cell gap.
The shape is preferably spherical for ease of control. Although the gradation display characteristics can be controlled by the particle size distribution, it is desirable that the standard deviation of the particle size distribution be 9.0 nm or more in that the change in transmittance (transmittance) can be moderated. The specific gravity of the fine particles is 0.1
It is preferably from 10 to 10 times from the viewpoint of preventing sedimentation when dispersed in the liquid crystal, and it is preferable that the fine particles are surface-treated with a silane coupling agent or the like so as to exhibit good dispersibility.

As described above, since the size of the fine particles is extremely small, the fine particles may be referred to as ultrafine particles.

In the present invention, the fine particles are desirably present in the liquid crystal between the opposing electrodes. In addition, the fine particles may be present in the liquid crystal alignment film or on the liquid crystal alignment film. The configuration other than the presence of the fine particles between the corresponding electrodes can be the same as that of the liquid crystal display device of FIG. 15 and FIG. 16 (particularly, the ferroelectric liquid crystal display device).

For example, a transparent glass plate is used as a substrate, ITO (indium tin oxide) is used as an electrode layer, and a rubbed polyimide film or SiO 2 is used as a liquid crystal alignment film.
An obliquely deposited film can be used. Although the driving method is performed based on the present invention, the gray level in the above-mentioned micro domain starlight texture is obtained by changing the voltage of the data pulse. Is in a state where a data pulse is applied.

The gradation can also be obtained by giving a distribution to the tilt angle of the liquid crystal layer. In other words, the existence of the above-mentioned ultrafine particles allows the distribution of the layer tilt angle of the liquid crystal represented by δ in FIG. 8 to be formed without being related to the characteristics thereof, that is, the effective spontaneous polarization Ps _eff (the ferroelectric liquid crystal The distribution of the characteristic values that determine the threshold values) results in a large number of domains having various threshold values within one pixel. Regarding the size of the domain, it has been found that ultrafine particles of the order of nanometers have a small particle size, break the continuity of the layer in the vicinity thereof, and have an effect of stopping domain expansion (pinning effect). In the case of large fine particles on the order of submicrons, this pinning effect is hardly observed, and even if it is observed, it becomes a large defect and has a large adverse effect on transmittance.

The ferroelectric liquid crystal usable in the present invention is actually a mixture of a chiral smectic C (SmC ^* ) liquid crystal and a non-chiral smectic C (SmC) liquid crystal. Each of these liquid crystals may be composed of only one kind, or may be a mixture of plural kinds.

Here, chiral smectic C (SmC
^* ) As the liquid crystal (ferroelectric liquid crystal), known pyrimidine-based, biphenyl-based, phenylbenzoate-based, etc. (however,
These ferroelectric liquid crystals may show a chiral nematic phase, a smectic phase or the like depending on a change in temperature. ) Is a chiral smectic C liquid crystal (ferroelectric liquid crystal).

Examples of usable non-chiral liquid crystals include non-chiral nematic C (SmC) liquid crystal ZLI-2008-000 manufactured by Merck (melting point -6 ° C., nematic phase temperature range -20 to 64 ° C.). Is mentioned. In addition to this liquid crystal, a known non-chiral smectic liquid crystal can be used. For example, biphenyl type, terphenyl type,
Tricyclic cyclohexyl, cyclohexylphenyl, biphenylcyclohexane, cyclohexylethane,
Ester, pyrimidine, pyridazine, ethane,
Dioxane type and the like.

[0065]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1 A 40 nm thick transparent ITO film (with a sheet resistance of 1
By heating (resistance heating) a tantalum boat (manufactured by Nippon Bax Metal Co., Ltd.) containing SiO powder (purity 99.99%, manufactured by Furuuchi Chemical Co., Ltd.) on a glass substrate provided with (00 Ω / cm ² ). Then, as shown in FIG. 5, a 50 nm thick SiO _x oblique deposition film 3 composed of SiO _x pillars 20 was vacuum deposited at a substrate temperature of 100 ° C. as a liquid crystal alignment film. At this time, the angle between the substrate normal and the vertical line of the evaporation source is 8
Deposition was performed at 5 °. After vapor deposition, firing was performed at 200 ° C. for 1 hour in the air in order to obtain good orientation.

To determine the relationship between the conductivity at the liquid crystal-alignment film interface and the relaxation of the electron polarization, the firing temperature was changed by changing the value of x in SiO _X to change the conductivity. .
Fig. 1 shows the relationship between the firing temperature and the binding energy of the Si _2p orbit.
Shown in

The two glass substrates thus treated are
The deposition directions of the obliquely deposited SiO film are antiparallel to each other using a 1.6 μm-diameter spacer (warping sphere: manufactured by Sekisui Chemical Co., Ltd.) and an ultraviolet curable adhesive (Photorec: manufactured by Sekisui Fine Chemical Co., Ltd.). And assembled an empty liquid crystal cell. Into the cell gap, a ferroelectric liquid crystal (YS-C152: manufactured by Chisso Corporation) in which titanium oxide (IT-S: manufactured by Idemitsu Kosan Co., Ltd.) was uniformly dispersed at a ratio of 2% by weight was injected. A liquid crystal display device (liquid crystal panel) similar to the liquid crystal device of FIG. 16 was obtained. Since this device is configured in the same manner as the above-described prior invention, description other than the above is omitted.

The relationship between the applied voltage and the transmittance of this liquid crystal display device was examined. Under orthogonal Nicols, a drive waveform as shown in FIG. 2 was applied to the liquid crystal display element, and the light transmission intensity was monitored.

From the thus-obtained applied voltage-transmittance curves, the relationship between HΔV and the binding energy of the Si _2p orbital as shown in FIG. 20 is shown in FIG. 3, and YΔ as shown in FIG.
FIG. 4 shows the relationship between V and the binding energy of the Si _2p orbital.

From these results, when the above binding energy is 103.3 eV or less (especially 103.27 eV or less), H
ΔV and YΔV are both sufficiently reduced;
When the voltage exceeds 3.3 eV (especially 103.27 eV), HΔV
And YΔV rises sharply.

As described above, by reducing these HΔV and YΔV, in the ordinary ferroelectric liquid crystal display, a reduction in the data voltage value input from the columns of the simple matrix and a smooth moving image can be obtained. In an ultrafine particle (TiO ₂ ) -containing type as in the embodiment, a complete analog gradation can be completed.

Accordingly, the binding energy of the Si _2p orbit is 1
By using a SiO _x obliquely deposited film of 03.3 eV or less for the liquid crystal alignment film, electron polarization at the interface between the liquid crystal and the alignment film is relaxed. Such SiO _X oblique deposition film is a material of low polarization, the binding energy of 10
It is 3.3 eV or less, which is a state in which oxygen is deficient compared to SiO ₂ (the binding energy is 103.4 eV), and is more active. In addition, the electrical conductivity of SiO _X tends to increase as the firing temperature decreases in FIG. 1 (that is, as oxygen is further depleted).

Note that the binding energy of the Si _2p orbital can be determined by ESCA (XPS), which is a type of electron spectroscopy.

Example 2 In a liquid crystal panel manufactured in the same manner as in Example 1,
As shown in FIG. 10, the electric conductivity of 2.0 S / cm or less and 1.2 × 10 ⁻⁸ S / cm, which are considered to have lower polarization than the SiO oblique deposition film, are formed on the alignment film 3 of the SiO oblique deposition film. The above polymer film 21 is formed in the following manner, and the SiO oblique deposition film 3 is formed.
Laminated on top.

The polymer compound used was polyvinyl alcohol (molecular number: 13,000). Polyvinyl alcohol is an organic film for a rubbing alignment film that can obtain good alignment without depending on the type of liquid crystal. It has been reported that when such a rubbing film of polyvinyl alcohol is used for the alignment film, there is almost no hysteresis.However, due to stability problems such as unstable surface shape due to rubbing and inconsistent orientation, practical materials are not used. Can not be used as.

Therefore, it is expected that the polarization of the alignment film is small because there is no hysteresis.
It was diluted with water at a concentration of the seeds as a solvent, and laminated on a SiO oblique deposition film using a spinner. Spin coating conditions
500 rpm (after 4 seconds), 3500 rpm
pm (time: 10 seconds). After spin coating such an organic film, it was baked in a clean oven at 110 ° C. for 60 minutes to form a film.

The solution concentration of the polymer compound (polyvinyl alcohol) at the time of spin coating and the polymer compound film
FIG. 9 shows the relationship with the hysteresis (HΔV) during driving of the liquid crystal panel laminated on the iO alignment film. from this result,
When the concentration is 1% by weight, the thickness of the laminated film becomes large,
Since the orientation regulating force was weakened by flattening the surface of the O obliquely deposited film, the orientation was slightly degraded and the hysteresis was slightly increased. However, with a multilayer film having a concentration of 0.2% by weight,
It can be seen that the hysteresis can be improved to one-seventh as compared with the case without the laminated film (the data indicated by the white circles in FIG. 9). In order to keep the hysteresis low, the solution concentration is preferably 0.05 to 1.0% by weight, preferably 0.1 to 0.8% by weight, more preferably 0.15 to 0.6% by weight, and more preferably 0.1 to 0.6% by weight. 2
~ 0.3% by weight is more desirable.

Example 3 In a liquid crystal panel manufactured in the same manner as in Example 1,
As shown in FIG. 13 (A), it is assumed that the conductivity is higher than that of the SiO obliquely deposited film on the alignment film 3 of the SiO obliquely evaporated film (the electric conductivity is 1.2 × 10 ⁻⁸ S / cm or more). A possible organic complex 22 was formed into a film in the following manner and laminated on the SiO oblique deposition film 3.

The organic complex used is a complex consisting of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) shown in FIG. 14: TTF-TCNQ. This TTF-TCNQ is a single crystal of 1 × 10 ² S /
It has been found that the electro-optical properties such as the response speed can be improved by laminating on a SiO obliquely deposited alignment film having a conductivity of at least 10 cm. ｛E. Matsui et al. “Enhanc
ement of FLC SwitchingProperties Using SiO Alignme
nt Layers Combined with Charge-Transfer Complexes
”, Ferroelectrics, Vol. 149, p97-107 (1993)｝.

The same amount of TTF and TCNQ were mixed in acetonitrile, filtered, and dried in a vacuum oven to obtain TTF-TCNQ. This TTF-TCNQ is put into a deposition boat, and the angle between the normal direction of the substrate and the deposition source is set to 0.
°, a distance of 30 cm, and a substrate temperature of room temperature, each of the following several film thicknesses was laminated. After lamination, 100
Firing was performed at 30 ° C. for 30 minutes.

The TTF-TCNQ organic complex 22 thus formed on the SiO obliquely deposited film 3 actually has the structure shown in FIG.
As shown in the enlarged view in (B), the film is formed not only on the upper surfaces of the SiO pillars 20 obliquely deposited on the electrodes 2a and 2b, but also between the particles. Thus S
When entering between the iO pillars, charges flow in the b-axis direction (length direction) due to the conductivity of the complex 22, and the electrodes 2a, 2a
Since the light is easily released to the b side, electron polarization that may occur at the interface with the liquid crystal can be reduced or eliminated.

The organic complex 22 between such pillars 20
Can be indicated by an infrared absorption spectrum.

As a result of measuring the electric conductivity (electric conductivity) of this organic complex film, as shown in FIG.
1.2 × 10 ⁻⁸ S / cm, and as the film thickness increases,
It can be seen that the conductivity is improved. Here, the “film thickness” means the height from the lower surface of the alignment film (electrode surface).

Further, by laminating the TTF-TCNQ complex, as shown in FIG. 12, the value of the hysteresis at the time of driving the liquid crystal panel is greatly improved. In particular, when the thickness is 5 to 50 nm, the hysteresis (HΔV) is about 2 V / Μm or less.

Although the embodiment of the present invention has been described above, the above-described embodiment can be further modified based on the technical idea of the present invention.

For example, the types and combinations of the above-described liquid crystal alignment film, organic or inorganic thin films and organic complexes laminated thereon, and the method of forming the film are not limited to those described above. Further, the material and physical properties of the fine particles may be changed.

Further, the above-mentioned transparent electrode includes the above-mentioned I
In addition to TO, known transparent electrodes such as tin oxide and indium oxide can be used, and conventionally known materials for the liquid crystal element such as a transparent substrate, a spacer, and a sealing material can also be used.

In addition to the display, the above-mentioned element can be used for an optical shutter, an optical switch, an optical blind, and the like. Further, when combined with an electro-optical element or the like, a liquid crystal prism, a liquid crystal lens, an optical path switch, It can also be used for optical modulators, phase diffraction gratings, A / D converters, optical logic circuits and the like.

[0090]

As described above, according to the present invention, a plurality of substrates having a liquid crystal alignment film face each other with a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is arranged in the gap. In a liquid crystal device, the liquid crystal alignment film is formed of a low polarization alignment film having a property of relaxing polarization at an interface with the liquid crystal, and is considered to be the largest cause of hysteresis and image sticking. Since the generated polarization such as electron polarization in the alignment film at the interface between the liquid crystal and the alignment film can be relaxed and the above-described hysteresis (HΔV) can be reduced, the image quality can be improved regardless of the liquid crystal material and the added fine particles. Improved and smooth moving image display can be realized.

Also, in a liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other with a predetermined gap on the liquid crystal alignment film side and liquid crystal is arranged in the gap, Low polarization thin film having the property of relaxing the polarization at the interface between
^Since the organic complex of ^-8 S / cm or more is laminated on the liquid crystal alignment film, the polarization such as the electron polarization in the alignment film at the interface can be relaxed as described above, and the liquid crystal material and the added fine particles can be reduced. Irrespective of this, improvement in image quality and smooth moving image display can be realized.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a baking temperature of a SiO obliquely deposited alignment film and a binding energy of a Si _2p orbit in a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a drive waveform diagram of the same liquid crystal display element.

FIG. 3 is a graph showing the relationship between the binding energy of the Si _2p orbit and the hysteresis of the SiO obliquely deposited alignment film.

FIG. 4 is a graph showing the relationship between the bond energy of the Si _2p orbit of the SiO obliquely deposited alignment film and the burn-in.

FIG. 5 is a schematic cross-sectional view of a main part of the liquid crystal display element mainly showing a SiO obliquely deposited alignment film.

FIG. 6 is a schematic diagram for explaining a state of domain generation at the time of driving the liquid crystal display element in comparison with a conventional example.

FIG. 7 is a principle diagram for explaining a change in threshold voltage of the liquid crystal display element.

FIG. 8 is a schematic diagram showing a relationship between a layer tilt angle of a ferroelectric liquid crystal of a liquid crystal display element and an effective spontaneous polarization.

FIG. 9 illustrates a liquid crystal display device according to another embodiment of the present invention.
4 is a graph showing a relationship between a polyvinyl alcohol solution concentration and hysteresis at the time of forming a polyvinyl alcohol thin film laminated on an O oblique deposition alignment film.

FIG. 10 is a schematic sectional view of a main part of the liquid crystal display element.

FIG. 11 shows an organic complex composed of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ): T
It is a graph which shows the relationship between the film thickness of TF-TCNQ complex, and its electrical conductivity.

FIG. 12 is a graph showing the relationship between the thickness of a TTF-TCNQ complex and hysteresis.

FIG. 13 is a schematic cross-sectional view of a main part of the liquid crystal display element (A) and a partially enlarged view (B) thereof.

FIG. 14 is a diagram showing each structural formula of TTF and TCNQ.

FIG. 15 is a schematic plan view of a conventionally used liquid crystal display element viewed from a select electrode side.

FIG. 16 is a sectional view taken along lines XVI-XVI in FIG.

FIG. 17 is a model diagram of a ferroelectric liquid crystal.

FIG. 18 is a transmittance-applied voltage characteristic diagram showing a threshold voltage characteristic of a conventionally used liquid crystal display element.

FIG. 19 is a transmittance-applied voltage characteristic diagram showing a threshold voltage characteristic of the liquid crystal display element according to the invention of the prior application.

FIG. 20 is a general characteristic diagram (particularly, an explanatory diagram of hysteresis) showing a relationship between an applied voltage and transmittance in a liquid crystal display element.

FIG. 21 is a general characteristic diagram (particularly an explanatory diagram of burn-in) showing a relationship between an applied voltage and a transmittance in a liquid crystal display element.

FIG. 22 is a model diagram showing a change in an applied voltage-transmittance curve due to burn-in in a liquid crystal display element.

[Explanation of symbols]

1a, 1b: substrate, 2a, 2b: transparent electrode layer 3a, 3b: SiO oblique deposition layer, 5: liquid crystal (FLC),
10: fine particles, 11: FLC element, 20: SiO pillar, 21: thin film, 22: organic complex, HΔV: voltage width indicating hysteresis, YΔV: voltage width indicating burn-in

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hidehiko Takanashi 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Akio Yasuda 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (13)

[Claims] 1. A liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other with a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is disposed in the gap. A liquid crystal element characterized by comprising an alignment film having a property of relaxing polarization at an interface with the liquid crystal. 2. The liquid crystal alignment film according to claim 1, wherein the liquid crystal alignment film is formed of a SiO _x oblique deposition film having a binding energy of Si _2p orbitals of 103.3 eV or less (where x is a positive number less than 2). Liquid crystal element. 3. A liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other at a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is disposed in the gap. A liquid crystal element comprising a laminated film in which a thin film having a property of relaxing polarization at an interface with the liquid crystal is laminated on an alignment film. 4. A thin film for relaxing polarization has an electric conductivity of 2.0 S
4. The liquid crystal device according to claim 3, wherein the liquid crystal device is an organic or inorganic thin film having a thickness of not more than / cm. 5. The thin film for relaxing polarization has an electric conductivity of 1.2 ×
^{4. The} liquid crystal device according to claim 3, wherein the liquid crystal device is an organic or inorganic thin film of 10 ^-8 S / cm or more. 6. A liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other with a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is disposed in the gap. A liquid crystal element, wherein an organic complex of 2 × 10 ⁻⁸ S / cm or more is laminated on the liquid crystal alignment film. 7. The liquid crystal device according to claim 1, wherein regions having different threshold voltages for switching the ferroelectric liquid crystal are finely distributed. 8. The liquid crystal device according to claim 7, wherein fine particles are added to the ferroelectric liquid crystal to form fine regions having different threshold voltages. 9. A liquid crystal device in which a plurality of substrates having a liquid crystal alignment film face each other with a predetermined gap on the liquid crystal alignment film side, and a liquid crystal is disposed in the gap. , A liquid crystal element comprising a laminated film in which a thin film having a property of low polarization at the interface with the liquid crystal is laminated on an alignment film. 10. A plurality of substrates having a liquid crystal alignment film face each other at a predetermined gap on the liquid crystal alignment film side,
In a liquid crystal device in which liquid crystal is arranged in the gap, the liquid crystal alignment film is formed of a laminated film in which a polymer thin film is laminated on the alignment film. 11. The liquid crystal device according to claim 10, wherein the polymer thin film is a material having low polarization at an interface with the liquid crystal. 12. The liquid crystal element according to claim 9, wherein regions having different threshold voltages for switching the ferroelectric liquid crystal are finely distributed. 13. The liquid crystal device according to claim 12, wherein fine particles are added to the ferroelectric liquid crystal to form fine regions having different threshold voltages.