JP2976202B2 - Liquid crystal element and display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal composition, a liquid crystal element and a display device using the same, and more particularly to a novel liquid crystal composition having improved response characteristics to an electric field and a liquid crystal display using the same. The present invention relates to a liquid crystal element used for an element or a liquid crystal-optical shutter, a method using the liquid crystal element for display, and a display device.

[0002]

2. Description of the Related Art Conventionally, liquid crystals have been applied in various fields as electro-optical elements. Most liquid crystal elements currently in practical use are, for example, M. Sch (M. Sch.
adt) and W. Helfrich
ch), “Applied Physics Letters”
("Applied Physics Letter
s ") Vo.18, No.4 (1971.2.15)
P. 127-128 "Voltage Depend
ent Optical Activity of a
Twisted Nematic Liquid Cr
ystal ”, the TN (Twisted Nem
(atic) type liquid crystal.

[0003] These are based on the dielectric alignment effect of liquid crystal, and use the effect that the average molecular axis direction is directed to a specific direction by an applied electric field due to the dielectric anisotropy of liquid crystal molecules. The limit on the optical response speed of these devices is said to be milliseconds, which is too slow for many applications.

On the other hand, in the application to a large flat display, driving by a simple matrix system is most effective in consideration of price, productivity, and the like. In the simple matrix system, an electrode configuration in which a scanning electrode group and a signal electrode group are configured in a matrix is employed. To drive the scanning electrode group, an address signal is sequentially and selectively applied to the scanning electrode group, and the signal electrode group is applied. Adopts a time-division driving method in which a predetermined information signal is selectively applied in parallel in synchronization with an address signal.

However, when the above-mentioned TN type liquid crystal is adopted as the element of such a driving system, the scanning electrode is selected and the signal electrode is not selected, or the scanning electrode is not selected and the signal electrode is selected. A finite electric field is also applied to the so-called “half-selected point”.

If the difference between the voltage applied to the selected point and the voltage applied to the half-selected point is sufficiently large and the voltage threshold required for aligning the liquid crystal molecules perpendicular to the electric field is set to an intermediate voltage value, The display element works normally,
When the number of scanning lines (N) is increased, the time (duty ratio) during which an effective electric field is applied to one selected point while scanning the entire screen (one frame) decreases at a rate of 1 / N. Resulting in.

For this reason, the voltage difference as the effective value between the selected point and the non-selected point when the repetitive scanning is performed becomes smaller as the number of the scanning lines increases, and as a result, the image contrast is reduced. Crosstalk is an inevitable drawback.

Such a phenomenon is caused by a liquid crystal having no bistability (a stable state in which liquid crystal molecules are horizontally aligned with respect to an electrode surface, and a vertical state only while an electric field is effectively applied. This is essentially an unavoidable problem that occurs when driving (ie, repeating scanning) using the time accumulation effect.

In order to improve this point, a voltage averaging method,
Although the two-frequency driving method and the multi-matrix method have already been proposed, any of these methods is insufficient, and the increase in the screen size and the density of the display element has ceased because the number of scanning lines cannot be sufficiently increased. It is the current situation.

[0010] As an improvement over the disadvantages of the conventional liquid crystal device, the use of a liquid crystal device having bistability has been improved by Clark and Lagerwell.
11) (JP-A-56-10721).
No. 6, US Pat. No. 4,367,924, etc.).

As a bistable liquid crystal, a chiral smectic C phase (SmC ^* phase) or an H phase (SmH ^* ) is generally used ^.
Phase) is used.

This ferroelectric liquid crystal has a bistable state consisting of a first optically stable state and a second optically stable state with respect to an electric field. Therefore, the optical modulation used in the above-mentioned TN type liquid crystal. Unlike the element, for example, the liquid crystal is oriented in a first optically stable state with respect to one electric field vector, and the liquid crystal is oriented in a second optically stable state with respect to the other electric field vector. In addition, this type of liquid crystal has a property (bistability) that takes one of the above two stable states in response to an applied electric field and maintains the state when no electric field is applied.

In addition to the characteristic having bistability as described above, the ferroelectric liquid crystal has an excellent characteristic of high-speed response. This is because the spontaneous polarization of the ferroelectric liquid crystal and the applied electric field act directly to induce a transition of the alignment state.
It is 3 to 4 orders of magnitude faster than the response speed due to the effects of dielectric anisotropy and electric field.

As described above, the ferroelectric liquid crystal potentially has extremely excellent properties. By utilizing such properties, it is possible to solve many of the problems of the conventional TN-type element described above. A fairly substantial improvement is obtained. In particular, applications to high-speed optical shutters and high-density, large-screen displays are expected. For this reason, liquid crystal materials with ferroelectricity have been widely studied, but the ferroelectric liquid crystal materials developed to date have sufficient characteristics to be used in liquid crystal devices, including low-temperature operation characteristics and high-speed response. It is hard to say that it has.

The following formula [II] τ = η / (Ps · E) [II] (where E is an applied electric field) is provided between the response time τ and the magnitude Ps of the spontaneous polarization and the viscosity η. A relationship exists. Therefore, to increase the response speed, there are (a) increasing the magnitude Ps of spontaneous polarization, (a) decreasing the viscosity η, and (c) increasing the applied electric field E. However, the applied electric field has an upper limit because it is driven by an IC or the like, and it is desirable that the applied electric field be as low as possible. Therefore, it is actually necessary to reduce the viscosity η or increase the value of the magnitude Ps of the spontaneous polarization.

In general, in a ferroelectric chiral smectic liquid crystal compound having a large spontaneous polarization, the internal electric field of the cell caused by the spontaneous polarization is large, and there is a tendency that restrictions on an element structure capable of taking a bistable state are increased. Further, even if the spontaneous polarization is increased unnecessarily, the viscosity tends to increase with the spontaneous polarization, and as a result, the response speed may not be so high.

In addition, when the operating temperature range of the actual display is, for example, about 10 to 40 ° C., the change in response speed is generally about 10 times, and the temperature compensation method using the driving voltage and frequency becomes complicated. I have.

In the case of a display device having a large surface screen,
Since the temperature of the display screen varies, it is necessary to provide a means for heating the display screen to a constant temperature.

As described above, in order to put a ferroelectric liquid crystal element into practical use, a chiral smectic phase having high spontaneous polarization and high viscosity due to low viscosity and having small temperature dependence of the response speed is required. A liquid crystal composition is required.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal composition which is effective for reducing the temperature dependence of the response speed in order to make the above-mentioned ferroelectric liquid crystal device practical, in particular, An object of the present invention is to provide a liquid crystal composition exhibiting a ferroelectric chiral smectic phase, a liquid crystal element using the liquid crystal composition, and a display device.

[0021]

SUMMARY OF THE INVENTION The present invention provides a first aspect.
A chiral smectic C phase having a pair of substrates and a cone angle Θ, and having at least two optically stable states in the absence of an electric field, and having a tilt angle θa which is の of the angle formed by these optical axes. In the liquid crystal device having the liquid crystal composition in which the liquid crystal composition has been generated, the liquid crystal molecules of the liquid crystal composition are oriented with a pretilt angle α with respect to the substrate, and the chiral smectic C
A) a chiral smectic C phase within a temperature range in which a plurality of layers organized by a plurality of liquid crystal molecules forming a phase are arranged with an inclination angle δ with respect to the normal of the substrate to generate a chiral smectic C phase. And b) in a temperature range lower than the first temperature range, the tilt angle δ in the chiral smectic C phase is shifted to a displacement point with a further temperature drop. And a second temperature range that decreases from
a, Θ, δ and α, c) Θ <α + δ, d) δ <α and e) Θ>θa> Θ / 2. And second, having a pair of substrates, a cone angle Θ, and at least two optically stable states in the absence of an electric field, having a tilt angle θa that is １ ／ of the angle between these optical axes. In a display device having a liquid crystal composition having a chiral smectic C phase and a voltage applying means for applying a voltage to the liquid crystal composition, liquid crystal molecules of the liquid crystal composition are aligned with a pretilt angle α with respect to a substrate. A) a plurality of layers organized by a plurality of liquid crystal molecules forming a chiral smectic C phase are arranged at an inclination angle δ with respect to the normal to the substrate, within a temperature range in which a chiral smectic C phase is generated; Inclination angle δ in chiral smectic C phase is temperature A first temperature range that increases with decreasing temperature; and b) a temperature range lower than the first temperature range, in which the tilt angle δ in the chiral smectic C phase decreases at the displacement point with a further temperature drop. And a temperature range of 2
a, Θ, δ and α, c) Θ <α + δ, d) δ <α and e) Θ>θa> Θ / 2. is there.

FIG. 1 is a schematic sectional view showing an example of a liquid crystal device having a chiral smectic liquid crystal layer of the present invention for explaining the structure of a liquid crystal device utilizing ferroelectricity.

In FIG. 1, reference numeral 1 denotes a chiral smectic liquid crystal layer, 2 denotes a glass substrate, 3 denotes a transparent electrode, 4 denotes an insulating alignment control layer, 5 denotes a spacer, 6 denotes a lead wire, 7 denotes a power source, 8 denotes a polarizing plate, Reference numeral 9 denotes a light source.

Each of the two glass substrates 2 has In ₂
O ₃ , SnO ₂ or ITO (indium tin
The transparent electrode 3 made of a thin film such as oxide (Indium-Tin Oxide) is covered. On top of that, a thin film of a polymer such as polyimide is rubbed with a gauze, an acetate flocking cloth or the like to form an insulating alignment control layer for arranging liquid crystals in the rubbing direction. Examples of the insulating material include silicon nitride, silicon carbide containing hydrogen, silicon oxide, boron nitride, boron nitride containing hydrogen, cerium oxide, aluminum oxide, zirconium oxide, and titanium oxide. Form an inorganic insulating layer such as magnesium fluoride, on which polyvinyl alcohol, polyimide, polyamide imide, polyester imide, polyparaxylene, polyester, polycarbonate, polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, Organic alignment materials such as cellulose resin, melamine resin, urea resin, acrylic resin and photoresist resin as the orientation control layer,
The insulating orientation control layer may be formed of two layers, or may be a single layer of an inorganic insulating orientation control layer or an organic insulating orientation control layer. If the insulating orientation control layer is inorganic, it can be formed by vapor deposition or the like, and if organic, it can be formed by dissolving an organic insulating material or its precursor solution (0.1 to 20% by weight, preferably 0 to 20% by weight in a solvent). .2 to 10% by weight) by spinner coating method, dip coating method, screen printing method, spray coating method, roll coating method and the like, and cured under predetermined curing conditions (for example, under heating) to form. be able to.

The thickness of the insulating orientation control layer is usually 30.degree.
μm, preferably 40 ° to 3000 °, more preferably 40 ° to 1000 °.

The two glass substrates 2 are kept at an arbitrary interval by a spacer 5. For example, there is a method in which silica beads or alumina beads having a predetermined diameter are sandwiched between two glass substrates as spacers, and the periphery is sealed with a sealing material, for example, an epoxy-based adhesive. Alternatively, a polymer film or glass fiber may be used as the spacer. A liquid crystal exhibiting ferroelectricity is sealed between the two glass substrates.

The chiral smectic liquid crystal layer 1 in which the chiral smectic liquid crystal is enclosed generally has a thickness of 0.5 to 20.
μm, preferably 1 to 5 μm.

The ferroelectric liquid crystal has an SmC ^* phase (chiral smectic C phase) in a wide temperature range including the room temperature (particularly at a low temperature side). A wide margin is desired.

In order to obtain a good uniform orientation and obtain a mono-domain state, particularly in the case of a device, the ferroelectric liquid crystal must have an isotropic phase to a Ch phase (cholesteric phase).
It is desirable to have a phase transition series of SmA (smectic A phase) -SmC ^* (chiral smectic C phase).

The transparent electrode 3 is connected to an external power supply 7 by a lead wire.

A polarizing plate 8 is attached to the outside of the glass substrate 2.

Since FIG. 1 is of a transmission type, a light source 9 is provided.

FIG. 2 schematically illustrates an example of a cell for explaining the operation of a liquid crystal element utilizing ferroelectricity.
Reference numerals 21a and 21b denote substrates (glass plates) each covered with a transparent electrode made of a thin film such as In ₂ O ₃ , SnO ₂ or ITO (Indium-Tin Oxide), between which the liquid crystal molecule layer 22 is perpendicular to the glass surface. The liquid crystal of the chiral smectic C phase which is oriented so as to be sealed is sealed. A bold line 23 represents a liquid crystal molecule, and the liquid crystal molecule 23 has a dipole moment (P⊥) 24 in a direction perpendicular to the molecule. When a voltage equal to or higher than a certain threshold is applied between the electrodes on the substrates 21a and 21b, the helical structure of the liquid crystal molecules 23 is released, and the dipole moment (P 分子) 24 is oriented in the direction of the electric field so that the liquid crystal molecules 23 are oriented in the orientation direction. Can be changed. Liquid crystal molecules 23
Has an elongated shape and exhibits refractive index anisotropy in the major axis direction and the minor axis direction.Therefore, for example, if crossed Nicol polarizers are placed above and below the glass surface, the optical characteristics will vary depending on the polarity of the applied voltage. To become a changing liquid crystal optical modulator,
It is easily understood.

The liquid crystal cell preferably used in the optical modulation element of the present invention can be made sufficiently thin (for example, 10 μm or less). As shown in FIG. 3, as the liquid crystal layer becomes thinner, the helical structure of the liquid crystal molecules is released even when no electric field is applied, and the dipole moment Pa or Pb thereof is directed upward (34a) or downward (34b). Take either of the states. When an electric field Ea or Eb having a different polarity or more than a certain threshold is applied to such a cell by the voltage applying means 31a and 31b as shown in FIG. 3, the dipole moment is directed upward corresponding to the electric field vector of the electric field Ea or Eb. The orientation is changed to 34a or downward 34b, and the liquid crystal molecules are accordingly oriented in either the first stable state 33a or the second stable state 33b.

As described above, there are two advantages of using such a ferroelectric property as an optical modulation element.

The first is that the response speed is extremely fast, and the second is that the orientation of the liquid crystal molecules has bistability. The second point will be further described with reference to FIG. 3, for example. When an electric field Ea is applied, the liquid crystal molecules are oriented to a first stable state 33a. This state is stable even when the electric field is turned off.
When an electric field Eb in the opposite direction is applied, the liquid crystal molecules are oriented to the second stable state 33b and change the direction of the molecules.
Again, this state remains even when the electric field is turned off. Also, as long as the applied electric field Ea or Eb does not exceed a certain threshold,
Each is also maintained in the previous alignment state.

By using the liquid crystal element of the present invention in a display panel section and employing a data synchronization format using image data and a SYNC signal having scanning line address information shown in FIG. 11 and FIG. To achieve.

In the figure, reference numerals are as follows. DESCRIPTION OF SYMBOLS 101 Ferroelectric liquid crystal display device 102 Graphic controller 103 Display panel 104 Scan line drive circuit 105 Information line drive circuit 106 Decoder 107 Scan signal generation circuit 108 Shift register 109 Line memory 110 Information signal generation circuit 111 Drive control circuit 112 GCPU 113 Host CPU 114 VRAM

The generation of image information is performed by the graphics controller 102 on the main unit side.
Display panel 103 according to the signal transfer means shown in FIG.
Is forwarded to The graphics controller 102
A CPU (Central Processing Unit, hereinafter abbreviated as GCPU 112) and a VRAM (memory for storing image information) 114 serve as a nucleus to manage and communicate image information between the host CPU 113 and the liquid crystal display device 101. The method is mainly realized on the graphics controller 102.

Note that a light source is arranged on the back surface of the display panel.

Although a smectic liquid crystal generally has a layer structure, a chiral smectic C composed of a smectic A phase is used.
When the phase changes to a phase, the layer interval is reduced, so that the liquid crystal layer denoted by 41 takes a structure (chevron structure) bent at the center between the upper and lower substrates 44a and 44b as shown in FIG. As shown in the figure, the direction of bending is the orientation state (C1 orientation state) 42 that appears immediately after the transition from the high temperature phase to the chiral smectic C phase, and the orientation state that appears in the C1 orientation state when the temperature is further lowered. There are two cases in the case of the portion 43 of (C2 alignment state). Thereafter, when a combination of a specific alignment film having a high pretilt α and a liquid crystal is used, the above C1 → C2 transition is unlikely to occur, and no C2 alignment state occurs depending on the liquid crystal material. In addition to two low-contrast stable states in which the director of the liquid crystal is twisted between the upper and lower substrates (hereinafter, referred to as a splay state), another two high-contrast stable states (hereinafter, referred to as a uniform state) ) Was found to appear.

These states transition with each other when electrolysis is applied. When a weak positive and negative pulse electric field is applied, a transition between the spray 2 states occurs, and when a strong positive and negative pulse electric field is applied, a transition between the uniform 2 states occurs.

When the uniform 2 state is used, a display device which is brighter and has a higher contrast than before can be realized.

Therefore, the entire screen as a display element is unified into the C1 alignment state, and the high contrast 2 within the C1 alignment is used.
If the states are used as two states of black and white display, it is expected that a display with higher quality than before can be realized.

As described above, the C1 alignment is not generated without the C2 alignment state.
In order to realize the orientation state, it is necessary to satisfy the following conditions.

That is, as shown in FIG.
The directors near the substrate in the orientation are on cone 51 in FIGS. 5 (a) and (b), respectively. As is well known, the rubbing causes the liquid crystal molecules at the interface of the substrate to form an angle called pretilt α with respect to the substrate, and the direction is shifted toward the rubbing direction (A direction in FIG. 4).
2 is the direction to raise the head (it looks like the tip is floating). From the above, the relationship of Θ + δ> α for C1 orientation and Θ−δ> α for C2 orientation must be established among the cone angle Θ, the pretilt angle α and the layer tilt angle δ of the liquid crystal.

Therefore, the condition for generating the C1 orientation without generating the C2 orientation is Θ−δ <α, that is, Θ <α + δ (I).

Further, from a simple consideration of the torque applied to the switching of the interface molecules from one position to the other position by the electric field, α> δ (II) is obtained as a condition under which the switching of the interface molecules is likely to occur.

Therefore, in order to form the C1 orientation state more stably, it is effective to satisfy the relationship of the formula (II) in addition to the relationship of the formula (I).

[0050] (I) and formula (II) conditions result of further advanced experiments under the tilt angle theta _a liquid crystal in the case of conventional liquid crystal elements which do not satisfy the (I) and formula (II) conditions from 3 ° to 8 ° approximately, (I) and increased to 8 ° approximately ~ 16 ° in the case of satisfying the present invention in formula (II), theta between the liquid crystal cone angle theta> theta _a It has been empirically obtained that the relational expression> Θ / 2 (III) holds.

As described above, (I), (II) and (I)
It has been clarified that a display capable of displaying a high-contrast image can be realized if the condition of the formula II) is satisfied.

In order to stably form the C1 alignment state and obtain good alignment, the rubbing directions of the upper and lower substrates are set to 2 ° to 25 °.
Cross rubbing shifted in the range of ° (intersection angle) is also extremely effective. Further, the rubbing directions shown in FIG. 4 can be set to be opposite to each other.

By the way, a display device using a chiral smectic liquid crystal element is a display device capable of realizing a larger screen and higher definition than a conventional CRT or TN type liquid crystal display. As the definition becomes higher, the frame frequency (single screen forming frequency) becomes lower. Therefore, the screen rewriting speed, smooth scrolling on character editing and graphics screens, and moving image display speed such as cursor movement are performed. However, there was a problem that the operation was slow. A solution to this problem is disclosed in JP-A-60-3
No. 1120, JP-A-1-140198 and the like.

That is, a display panel in which scanning electrodes and information electrodes are arranged in a matrix, a means for selecting all or a predetermined number of scanning electrodes (the case of selecting by this means is referred to as whole writing), and a method for selecting all or a predetermined number of scanning electrodes Means for partially selecting one of the above (a case of selecting by this means is referred to as partial writing). This enables high-speed display by performing partial moving image display by partial writing, and achieves both partial writing and full-surface writing.

As described above, the above (I) and (II)
It was also found that driving a liquid crystal element satisfying the conditions of the formula (III) with a display device capable of partial writing described above can realize a high-contrast image on a large screen and a high definition display at high speed.

In general, the cone angle Θ shows 0 ° at the phase transition point Tc of the smectic A phase and the chiral smectic C phase, shows a sharp change immediately below the phase transition point, and shows the phase transition point Tc
It is known that the distance increases from the distance. That is, the cone angle Θ shows a larger value as the temperature becomes lower.

On the other hand, the response speed tends to decrease as the cone angle 大 き い increases, and the temperature change of the response speed increases as the temperature change of the cone angle 大 き い increases.

According to the study of the present inventors, in the liquid crystal compound which is a component of the liquid crystal composition, almost similar liquid crystal compositions having only slightly different side chain lengths have different viscosity coefficients and spontaneous polarization. The temperature characteristics of the response speed (especially on the low-temperature side) may vary considerably even if the size of the angle does not change much, and it has been found that this phenomenon is largely derived from the temperature characteristics of the cone angle Θ. If the cone angle Θ shows a tendency to decrease with decreasing temperature on the low temperature side where the temperature dependence of the response speed is large, the temperature dependence of the response speed is much larger than that of the conventional monotonically increasing one. It can be improved.

The present inventors have found that the temperature dependence of the cone angle Θ can be reduced by selecting the type of the skeleton structure, the length of the side chain, the selection of the composition ratio, and the combination used in the constituent liquid crystal compound in the liquid crystal composition. It has been found that it is affected by the selection of the compound to be used, etc., but there is no particular regularity in reducing such dependence. By preparing a large number of blended liquid crystals and selecting from them, the chiral smectic C phase can be obtained. A first temperature range in which the cone angle 増 加 increases with a temperature drop within a temperature range of the first temperature range, and a second temperature range in which the cone angle 減少 decreases with a further temperature drop in a temperature range lower than the first temperature range. It has been found that the temperature dependence of the cone angle 低 減 is reduced by selecting a liquid crystal composition that produces a temperature range. In addition, the liquid crystal compositions that generate such first and second temperature ranges tend to be obtained by using a large number of liquid crystal compounds that tend to relatively widen the temperature range of the smectic A phase. .

In a preferred embodiment of the present invention, the phase transition point from the smectic A phase to the chiral smectic C phase is defined as T
Assuming that c, the temperature range is (Tc-10) ° C to 10 ° C, preferably (Tc-10) ° C to 20 ° C, particularly preferably (Tc-10) ° C to 30 ° C. By selecting a liquid crystal composition that produces the aforementioned displacement point,
The temperature dependency on the response speed when used as a liquid crystal element can be greatly reduced. Further, the above-mentioned Tc is a temperature of 60 ° C. or more, preferably a temperature of 65 ° C. or more.

In a preferred embodiment of the present invention, at least two optically stable states occur in the absence of an electric field, and a half of the angle between these optical axes is defined as a tilt angle θa. When a tilt angle of the liquid crystal molecules with respect to the substrate is a pretilt angle α, and a tilt angle at which a plurality of layers organized by a plurality of liquid crystal molecules forming a chiral smectic C phase is tilted with respect to a substrate normal is δ, Θ <α + δ , Δ <α and Θ>θa> Θ / 2, a display of a high-contrast image can be realized.

From 10 ° C. to 50 ° C., the cone angle を has a relationship of 7 ° <Θ <27 °, and the ratio of the maximum value Θ _max and the minimum value Θ _min of the cone angle Θ is Θ _max / It is preferable to have a relationship of Θ _min <1.5.

Further, according to the study of the present inventors, in the liquid crystal compound which is a component of the liquid crystal composition, almost similar liquid crystal compositions having only a slightly different side chain length have different viscosity coefficients and Even if the magnitude of the spontaneous polarization does not change much, the temperature characteristics of the response speed (especially on the low temperature side) may be quite different, and it has been found that this phenomenon is largely derived from the temperature characteristics of the inclination angle δ. If the inclination angle δ shows a tendency to decrease with decreasing temperature on the low temperature side where the temperature dependence of the response speed is large, the temperature dependence of the response speed will be much larger than that of the conventional monotonically increasing one. It can be improved.

The present inventors have found that the temperature dependence of the tilt angle δ can be reduced by selecting the type of the skeleton structure, the length of the side chain, the selection of the composition ratio, and the combination used in the constituent liquid crystal compound in the liquid crystal composition. It has been found that it is affected by the selection of the compound to be used, etc., but there is no particular regularity in reducing such dependence, and by preparing a large number of blended liquid crystals and selecting from among them, the chiral smectic C phase is obtained. A first temperature range in which the inclination angle δ increases with a temperature drop within a temperature range of the first temperature range, and a second temperature range in which the inclination angle δ decreases with a further temperature drop at a displacement point in a temperature range lower than the first temperature range. By selecting a liquid crystal composition that produces a temperature range, the tilt angle δ
Was found to have reduced temperature dependence. Further, the liquid crystal composition that generates such first and second temperature ranges is as follows:
The tendency was obtained by using a large amount of liquid crystal compounds which tend to broaden the temperature range of the smectic A phase relatively.

In a preferred embodiment of the present invention, by selecting a liquid crystal composition that produces the above-mentioned displacement point at a temperature of 10 ° C. or more, preferably 25 ° C. or more, the response speed when used as a liquid crystal element is selected. Temperature dependence can be greatly reduced.

Further, as a condition useful for increasing the screen rewriting speed (frame frequency) of the display element, δ _max is 2
0 ° or less, more preferably 15 ° or less.

As a more preferable characteristic of the liquid crystal composition with respect to the above-mentioned improvement of the temperature characteristic of the response speed, the magnitude (Ps) of spontaneous polarization increases with a decrease in temperature, and the above-mentioned δ
_Even when the temperature becomes equal to or lower than the _{maximum value} , no decrease tendency is shown.

FIG. 9 shows a substrate 8 having a rubbing axis A.
1a and 81b show an arrangement state of the molecular layer 82 in a chiral smectic C phase in which a chevron structure (tilt angle δ) in which a molecular layer 82 organized by a plurality of liquid crystal molecules 83 is bent non-planarly is formed. ing. FIG. 10 shows a molecular layer 8 organized by a plurality of liquid crystal molecules 85 forming a smectic A phase.
4 shows a state where the molecules 4 are arranged in an arrangement state different from that of the molecular layer 82. The degree of shape deformation between the molecular layer 82 and the molecular layer 84 generally changes according to the above-mentioned inclination angle δ.

As described above, if the liquid crystal element uses the C1 uniform orientation, a display capable of displaying a high-contrast image can be realized as described above. However, even in the liquid crystal element having the above-described relationship, when the display is performed by applying the electric field, the afterimage time is significantly long, and the image pattern displayed before is recognized for 10 seconds or more. It became clear that there was. This phenomenon was remarkable at a temperature lower than room temperature. Although the mechanism of this afterimage phenomenon is still largely unknown, it is presumed to be due to the behavior described below.

That is, when a liquid crystal element using a chiral smectic liquid crystal is actually used as a display panel, a polyimide alignment film as an insulator layer provided between electrodes arranged in a matrix on the upper and lower substrates and a liquid crystal layer, One polarity voltage for switching from the first optically stable state (for example, a white display state) to the second optically stable state (for example, a black display state) is applied due to the presence of the short prevention insulating film. In this case, after the application of the one-polarity voltage is cancelled, a reverse electric field V _rev of the other polarity is generated in the ferroelectric liquid crystal layer, and this reverse electric field V _rev leads to the following two phenomena which lead to an afterimage in a display. Was awake. (The above-mentioned reverse electric field phenomenon is clarified in, for example, “Switching Characteristics of SSFLC” on pages 142 to 143, “Preliminary Report on Liquid Crystal Symposium”, October 1987.)

Existence of Small Unreversed Region Generally, a chiral smectic liquid crystal display is
Various protrusions existing in the pixel (spacer beads for maintaining the cell gap, steps between pixels, or steps in the metal wiring portion for lowering wiring resistance, etc.) remain without complete inversion. There is a very small area
Further, a small area around the area is more stable than the area where no protrusions are present in the vicinity, which seems to be derived from the decay time of the generated reverse electric field when switching from white display to black display. There may be a time lag before reaching the state.

Existence of Apparent Tilt Angle θ _a Stabilization Time at the Time of Driving Compared to a pixel that was in one display state from the beginning, the pixel immediately after switching from another display state has an average position of liquid crystal molecules of liquid crystal. A slight shift to the layer normal direction side occurs. That is, the apparent tilt angle becomes slightly smaller. This is confirmed by monitoring the optical response by the time it takes to reach a stable optical level. This time is presumed to be derived from the reverse electric field decay time.

Due to the above two phenomena, for example, a pixel which has been in a white display state for a certain period of time compared to a pixel which has been in a black display state from the beginning, and has just been switched to a black display state, is not displayed. Have a slight difference in the brightness level of the image. In other words, black is recognized as an area that looks slightly pale, and a uniform display is obtained over time. In some cases, a few seconds to several tens of seconds may be seen as an afterimage.

Further, these phenomena appear more remarkably in a low temperature region where it takes a long time for the generated reverse electric field to attenuate.

In order to solve the above-mentioned problem of the after-image phenomenon on the low-temperature side in the liquid crystal element satisfying the conditions represented by the above formulas (I), (II) and (III), As a result of repeated investigations and experiments, we focused on the correlation with the tilt angle of the liquid crystal composition layer, and due to the difference in temperature characteristics, the afterimage does not deteriorate even at low temperatures, and furthermore, the liquid crystal element with small temperature dependence of driving conditions I found what I could do.

That is, in the case of a liquid crystal element using a liquid crystal composition having a displacement point in which the inclination angle δ of the layer in the smectic phase increases with a decrease in temperature and then decreases, such a temperature characteristic is obtained. Compared to an element using no element, afterimages in a low temperature range are small, and display characteristics can be significantly improved.

The inclination angle δ of the layer is generally SmA → Sm
It shows 0 at the C ^* phase transition point and increases with the temperature drop. As the inclination angle δ of the layer increases, the net magnitude of the spontaneous polarization director in the direction normal to the substrate decreases, and the effective action with the external electrode decreases, which adversely affects the switching speed. At the same time, the non-selection signal waveform during actual driving (such as a small-voltage AC signal equal to or smaller than a threshold) causes molecules to easily fluctuate on the cone, and the driving characteristics generally deteriorate. If the inclination angle δ of the layer shows a decreasing tendency with respect to the temperature drop on the low temperature side where the degree of the afterimage and the temperature dependence of the response speed become worse, the afterimage phenomenon in the low temperature region is lower than that of the conventional monotonically increasing one. And the temperature dependence of the response speed is remarkably improved.

FIG. 6 schematically shows another preferred example of the liquid crystal device of the present invention. In FIG. 6, 11a and 11b are:
In ₂ O ₃ and ITO (Indium Tin)
Oxide) is a substrate (glass plate) covered with transparent electrodes 12a and 12b, and 200-3000３
Thick insulating films 13a and 13b (SiO ₂ film, TiO ₂ film,
Or Ta ₂ O ₅ film).

[0079]

Embedded image (N is 3 or more, number average molecular weight 10,
000-1,000,000)
Polyimide orientation control films 14a and 14b each having a thickness of 000 mm are laminated. Alignment control films 14a and 14b
Indicates that the upper alignment film 1 has an alignment direction based on the lower alignment film 14a.
4b performs a uniaxial alignment process in a counterclockwise direction (or a clockwise direction) with a crossing angle of 0 to 20 ° as viewed from the upper alignment film 14a and in the same direction (the direction of arrow A in FIG. 6). It has been rubbed. In the following, the intersection angle is defined as described above.

A chiral smectic C liquid crystal 15 is disposed between the substrates 11a and 11b.
1b is the chiral smectic C liquid crystal 15
The distance is set to a distance (for example, 0.1 to 3 μm) that is small enough to suppress the formation of a spiral array structure, and the chiral smectic liquid crystal 15 has a bistable alignment state. The sufficiently small distance described above is maintained by a bead spacer 16 (such as silica beads or alumina beads) disposed between the substrates 11a and 11b. 17a and 17b are polarizing plates.

In the case where the above-described simple matrix display device is constituted by an element in which the ferroelectric liquid crystal layer is sandwiched between a pair of substrates, for example, JP-A-59-193426 and JP-A-59-193427. JP-A-60-1560
No. 46, Japanese Patent Application Laid-Open No. 60-156047 and the like can be applied.

FIG. 7 is an example of a waveform diagram of the driving method. FIG. 8 is a plan view of a ferroelectric liquid crystal panel on which the matrix electrodes used in the present invention are arranged. In the liquid crystal panel 71 of FIG. 8, the scanning lines of the scanning electrode group 72 and the data lines of the information electrode group 73 are wired so as to intersect each other, and a ferroelectric material is provided between the scanning line and the data line at the intersection. Liquid crystal is arranged.

In FIG. 22A, S _S applies a selected scanning waveform to be applied to a selected scanning line, S _N applies an unselected scanning waveform that is not selected, and I _S applies to a selected data line. A selected information waveform (black) and _IN indicates a non-selected information signal (white) applied to an unselected data line. In the drawing, (I _S -S _S ) and (I _N -S _S ) are voltage waveforms applied to the pixels on the selected scanning line, and the voltage (I _S -S S)
_S ) is applied to a pixel in a black display state, and the voltage (I)
_The pixels to which ( _N− S _S ) is applied take a white display state.

FIG. 22B shows the driving waveforms shown in FIG. 22A, which are time-series waveforms when the display shown in FIG. 23 is performed.

In the driving example shown in FIG. 22, the minimum application time Δ of the single polarity voltage applied to the pixels on the selected scanning line
t corresponds to the time of the writing phase t ₂ , and one line clear t
The time of _one phase is set to 2Δt.

The values of the parameters V _S , V ₁ and Δt of the drive waveform shown in FIG. 22 are determined by the switching characteristics of the liquid crystal material used.

[0087] Figure 24 shows the transmittance change T, then namely V-T characteristic when changing the driving voltage while maintaining constant the bias ratio to be described later (V _S + V _1). Here, Δt = 50 μsec, and the bias ratio V _I / (V _I +
V _S ) = 1/3. The positive side of FIG.
Shown in 2 (I _N -S _S), the negative side waveform shown by (I _S -S _S) is applied.

Here, V ₁ and V ₃ are called an actual drive threshold voltage and a crosstalk voltage, respectively. Also, V ₂ <V ₁ <V
_{In the case of 3} , ΔV = V ₃ −V ₁ is called a voltage margin, which is a voltage width in which matrix driving is possible. It can be said that V ₃ generally exists in driving the FLC display element. Specifically, a voltage value causing switching by V _B in the waveform of FIG. _{22 (A) (I N -S} S). Of course, it is possible to increase the value of V ₃ by increasing the bias ratio, increasing the bias ratio corresponds to a large amplitude of a data signal, an increase in flickering in image quality, contrast Is undesirably caused.

In our study, the bias ratio was 1/3 to 1/4.
The degree was practical. By the way, if the bias ratio is fixed, the voltage margin ΔV strongly depends on the switching characteristics of the liquid crystal material, and it goes without saying that a liquid crystal material having a large ΔV is very advantageous for matrix driving.

At such a certain temperature, two states of "black" and "white" can be written to the selected pixel depending on the two directions of the information signal, and the unselected pixel can be written in the "black" or "white" state. The value of the upper and lower limits of the applied voltage and its width (driving voltage margin Δ
V) is unique because there is a difference between liquid crystal materials. In addition, since the driving margin is deviated by the change in the environmental temperature, it is necessary to set the driving voltage to an optimum value for the liquid crystal material and the environmental temperature in an actual display device.

However, when the display area of such a matrix display device is expanded for practical use, the difference in the environment in which the liquid crystal exists in each pixel (specifically, the difference in the temperature and the cell gap between the electrodes) is naturally large. Therefore, a liquid crystal having a small drive voltage margin cannot obtain a good image over the entire display area.

The cone angle Θ, the apparent tilt angle θ _a , the tilt angle δ of the liquid crystal layer, and the pretilt angle α in the liquid crystal device according to the present invention can be measured as follows.

<Measurement of cone angle Θ> ± 30 to ± 50 V,
While applying an AC (alternating current) of 1 to 100 Hz between the upper and lower substrates of the liquid crystal element through electrodes, the liquid crystal element disposed therebetween is rotated in parallel with the polarizing plate under orthogonal crossed Nicols, and at the same time, a photomultiplier (Hamamatsu) is formed. The first extinction position (the position at which the transmittance becomes lowest) and the second extinction position are determined while detecting the optical response with Photonics Corporation. Then, the angle of the angle from the first extinction position to the second extinction position at this time is 1
/ 2 is the cone angle Θ.

[0094] After applying the single pulse of <tilt angle θ measured in _a> liquid crystal threshold, no electric field under and under orthogonal cross-nicol to rotate the liquid crystal element disposed therebetween in parallel with the polarizing plate , The first extinction position is determined. Next, after applying a pulse having a polarity opposite to that of the above-mentioned single pulse, a second extinction position is obtained without an electric field. The first tilt angle theta _a apparent half angle from the extinction position to a second extinction position at this time.

<Measurement of tilt angle δ of liquid crystal layer> A method basically performed by Clark or Lager Wall (Japan)
n Display '86, Sep. 30 to Oct.
2, 1986.456 to 458) or the method of Ouchi et al. (JJAP, 27 (5) (1988) 725).
To 728). As a measuring device, a rotating cathode type X-ray diffractometer (manufactured by MAC Science) was used. In order to reduce the absorption of X-rays into the glass substrate of the liquid crystal cell, a microsheet (80 μm, manufactured by Corning) was used as the substrate.
m thickness).

<Measurement of Pretilt Angle α> J. A.
P. 19 (1980) NO. 10 Short Note
s 2013 was determined according to the method described above (crystal rotation method).

That is, the rubbed substrates were bonded in parallel and in opposite directions to form a cell having a thickness of 20 μm, and a compound represented by the following structural formula was added to a ferroelectric liquid crystal CS-1014 manufactured by Chisso Corporation. A mixture mixed at a ratio of 20% was injected as a standard liquid crystal and measured.

[0098]

Embedded image

Note that this mixed liquid crystal composition was
Shows the SmA phase at 55 ° C.

The measurement method is as follows. While rotating the liquid crystal cell on a plane perpendicular to the upper and lower substrates and including the alignment processing axis, the rotation axis is set to 45 degrees.
A helium-neon laser beam with a polarization plane at an angle of ° is irradiated from the direction perpendicular to the rotation axis, and the opposite side is used to reduce the transmitted light intensity with a photodiode through a polarizing plate with a transmission axis parallel to the incident polarization plane. It was measured.

The pretilt angle α was measured by substituting the angle between the center of the hyperbolic group of the intensity of the transmitted light formed by the interference and the line perpendicular to the liquid crystal cell into the following _equation as φx.

[0102]

(Equation 1) n _o: ordinary refractive index n _e: extraordinary refractive index

[0103]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following examples, all “parts” indicate “parts by weight”.

Reference Example 1 Liquid crystal compositions 1-B and 1-A having the following compositions were prepared.

[0105]

Embedded image

[0106]

Embedded image

Table 1 below shows the phase transition temperatures of the liquid crystal compositions 1-A and 1-B.

[0108]

[Table 1]

The temperature characteristics of the value of the cone angle Θ (DEG) according to the method for measuring the cone angle Θ are shown below.
It is shown in FIG.

[0110]

[Table 2]

Next, two glass plates having a thickness of 0.7 mm were prepared, an ITO film was formed on each of the glass plates, a voltage application electrode was prepared, and SiO ₂ was deposited thereon to form an insulating layer. And A 0.2% isopropyl alcohol solution of a silane coupling agent [KBM-602 manufactured by Shin-Etsu Chemical Co., Ltd.] was applied on a glass plate for 15 seconds with a spinner having a rotation speed of 2,000 rpm for surface treatment. After this, 120 ° C
For 20 minutes.

Further, a polyimide resin precursor [Toray Co., Ltd. SP-5] was placed on a glass plate with an ITO film which had been subjected to a surface treatment.
10] 1.5% dimethylacetamide solution at 20 rpm
The coating was performed with a spinner of 00 rpm for 15 seconds. After film formation,
A heat condensation baking treatment at 300 ° C. was performed for 60 minutes. At this time, the thickness of the coating film was about 250 °.

The baked film is subjected to a rubbing treatment with an acetate flocking cloth, then washed with an isopropyl alcohol solution, and dispersed with silica beads having an average particle size of 2 μm on one glass plate. The glass plates were bonded together using an adhesive sealant [Rixson Bond (Chisso Corporation)] so that the axes were parallel to each other, and heated and dried at 100 ° C. for 60 minutes to prepare a cell. The cell thickness of this cell was about 2 μm when measured with a Berek phase plate.

The liquid crystal compositions 1-A and 1-B were injected into this cell in an isotropic liquid state, and the liquid crystal compositions 1-A and 1-B were added at 20 ° C./h at 25 ° C.
The ferroelectric liquid crystal device was produced by gradually cooling the liquid crystal.

Using this ferroelectric liquid crystal element, the time t ^{e / ec} (corresponding to the current response speed and the optical response speed) to the peak position of the reversal current by applying a peak-to-peak voltage Vpp = 20 V is applied. ) (Hereinafter referred to as response speed).

The results are shown below.

[0117]

[Table 3]

As is clear from Reference Example 1, the liquid crystal composition 1-A using the liquid crystal composition effective for the cone angle Θ to have a maximum value has a higher response than the base liquid crystal composition 1-B. The temperature dependence of speed is reduced.

The liquid crystal compositions 2-A, 2-B, 3-A, 3-B, 3-C, 3-C used in Reference Examples 2 and 3 and Comparative Examples below.
D and 3-E were as shown in Table 4 below.

[0120]

[Table 4]

R _{1 to} R ₁₂ in the above table are normal alkyl, and the numbers in the table indicate the carbon numbers of the normal alkyl as R ₁ / R ₂ , R ₃ / R ₄ , R ₅ / R ₆ , R ₇ / R
₈ , R ₉ / R ₁₀ , R ₁₁ / R ₁₂ .

Reference Example 2 A liquid crystal composition 2-A was prepared as described above.

This liquid crystal composition 2-A has a phase transition temperature of 30 ° C.
Table 5 below shows the magnitude Ps of the spontaneous polarization in

[0124]

[Table 5]

The temperature characteristics of the value (DEG) of the cone angle Θ by the above-described method of measuring the cone angle Θ are shown below.
Table 6 and FIG. 14 show the results of the cone angle Θ.

[0126]

[Table 6]

Further, the liquid crystal composition 1 used in Reference Example 1
A ferroelectric liquid crystal device was prepared in the same manner as in Reference Example 1 except that -A and 1-B were injected into the cell, and the optical response speed was measured.

The results are shown in Table 7 below.

[0129]

[Table 7]

Comparative Example 1 The above-mentioned liquid crystal composition 2-B was prepared.

The liquid crystal composition 2-B has a phase transition temperature of 30 ° C.
Table 8 below shows the magnitude Ps of the spontaneous polarization in

[0132]

[Table 8]

The value of the temperature characteristic of the value (DEG) of the cone angle Θ by the above-described method of measuring the cone angle 示 す is shown below.
Table 9 and FIG. 14 show the results of the cone angle Θ.

[0134]

[Table 9]

Further, the liquid crystal composition 1 used in Reference Example 1
A ferroelectric liquid crystal device was prepared in the same manner as in Reference Example 1 except that -A and 1-B were injected into the cell, and the optical response speed was measured.

The results are shown in Table 10 below.

[0137]

[Table 10]

As is clear from Reference Example 2 and Comparative Example 1, the liquid crystal composition 2-A using the liquid crystal composition effective for changing the temperature characteristic of the cone angle Θ was the liquid crystal composition of Comparative Example 1. 2
The temperature dependency of the response speed is reduced as compared with -B.

Reference Example 3 The above-mentioned liquid crystal compositions 3-A, 3-B and 3-C were prepared.

The magnitude Ps of spontaneous polarization of the liquid crystal compositions 3-A, 3-B and 3-C at a phase transition temperature of 30 ° C. is shown in Table 11 below.

[0141]

[Table 11]

Further, the value of the temperature characteristic of the value of the cone angle に よ り (DEG) according to the above-described method of measuring the cone angle Θ is shown below.
Table 12 and FIG. 15 show the results of the cone angle Θ.

[0143]

[Table 12]

Further, the liquid crystal composition 1 used in Reference Example 1
A ferroelectric liquid crystal device was prepared in the same manner as in Reference Example 1 except that -A and 1-B were injected into the cell, and the optical response speed was measured.

The results are shown in Table 13 below.

[0146]

[Table 13]

Comparative Example 2 The above-mentioned liquid crystal compositions 3-D and 3-E were prepared.

Table 14 below shows the magnitude Ps of spontaneous polarization of the liquid crystal compositions 3-D and 3-E at a phase transition temperature of 30 ° C.

[0149]

[Table 14]

The temperature characteristics of the value (DEG) of the cone angle Θ by the above-described method of measuring the cone angle Θ are shown below.
Table 15 and FIG. 16 show the results of the cone angle Θ.

[0151]

[Table 15]

Further, the liquid crystal composition 1 used in Reference Example 1
A ferroelectric liquid crystal device was prepared in the same manner as in Reference Example 1 except that -A and 1-B were injected into the cell, and the optical response speed was measured.

The results are shown in Table 16 below.

[0154]

[Table 16]

As is apparent from Reference Example 3 and Comparative Example 2, liquid crystal compositions 3-A, 3-B, and 3-C using liquid crystal compositions effective for changing the temperature characteristics of cone angle Θ. In Comparative Example 2, the temperature dependence of the response speed was reduced as compared with the liquid crystal compositions 3-D and 3-E of Comparative Example 2.

Further, in Reference Example 3, the liquid crystal compositions 3-A and 3-B in which the temperature showing the cone angle max is on the high temperature side are:
The temperature dependence of the response speed is further reduced as compared with the liquid crystal composition 3-C on the low temperature side.

Reference Example 4 The maximum value of the cone angle = a liquid crystal composition 2-A having a cone angle max of about 35 ° C. and a liquid crystal composition 2-B having a tilt angle max of 10 ° C. or less were used. A and 2-B are shown in Table 1 below.
7 and the liquid crystal compositions 4-AB-1,4-
AB-2 was produced.

[0158]

[Table 17]

This liquid crystal composition 4-AB-1,4-AB-
Table 18 below shows the magnitude Ps of the spontaneous polarization at a phase transition temperature of 30 ° C of No. 2.

[0160]

[Table 18]

The value of the temperature characteristic of the value of the cone angle Ｄ (DEG) according to the method of measuring the cone angle Θ is shown below.
Table 19 and FIG. 17 show the results of the cone angle Θ.

[0162]

[Table 19]

Further, the liquid crystal composition 1 used in Reference Example 1
A ferroelectric liquid crystal device was prepared in the same manner as in Reference Example 1 except that -A and 1-B were injected into the cell, and the optical response speed was measured.

The results are shown in Table 20 below.

[0165]

[Table 20]

As is apparent from the above results, the temperature characteristic of the cone angle has the maximum value in the liquid crystal composition 2-B in which the temperature characteristic of the cone angle does not have the maximum value (increases as the temperature decreases). By adding the liquid crystal composition 2-A, a liquid crystal composition having a maximum cone angle is obtained. Then, the temperature dependence of the response speed at this time is 4.10 → 3.73 → 3.10 →
It can be seen that it is reduced as in 2.57.

The temperature indicating the cone angle max is about 20
C. liquid crystal composition 4-AB-1 and a liquid crystal composition 2 at about 35.degree.
Comparing -A, it can be seen that 2-A, which has a cone angle max on the higher temperature side, has reduced the temperature dependence of the response speed.

Example 1 Temperature characteristics of the inclination angle δ of the layer are generally (continuously increasing with the temperature drop) CS-1 manufactured by Chisso Corporation
Using 017, the following liquid crystal composition 11-A was produced.

[0169]

Embedded image

The phase transition temperatures of CS-1017 and 11-A and the magnitude Ps of spontaneous polarization at 30 ° C. are shown in Table 21 below.
Shown in

[0171]

[Table 21]

Table 22 shows the temperature characteristics of the value of δ (°) measured by the above-mentioned X-ray diffraction method.

[0173]

[Table 22]

Next, two glass plates having a thickness of 0.7 mm were prepared, an ITO film was formed on each of the glass plates, a voltage application electrode was formed, and SiO ₂ was deposited thereon to form an insulating layer. And A 0.2% isopropyl alcohol solution of a silane coupling agent [KBM-602 manufactured by Shin-Etsu Chemical Co., Ltd.] was applied on a glass plate for 15 seconds with a spinner having a rotation speed of 2,000 rpm for surface treatment. After this, 120 ° C
For 20 minutes.

Further, a polyimide resin precursor [Toray Co., Ltd. SP-5] was placed on a glass plate with an ITO film which had been subjected to a surface treatment.
10] 1.5% dimethylacetamide solution at 20 rpm
The coating was performed with a spinner of 00 rpm for 15 seconds. After film formation,
A heat condensation baking treatment at 300 ° C. was performed for 60 minutes. At this time, the thickness of the coating film was about 250 °.

The baked film is subjected to a rubbing treatment with an acetate flocking cloth, then washed with an isopropyl alcohol solution, and silica beads having an average particle size of 2 μm are sprayed on one of the glass plates. The glass plates were bonded together using an adhesive sealant [Rixson Bond (Chisso Corporation)] so that the axes were parallel to each other, and heated and dried at 100 ° C. for 60 minutes to prepare a cell. The cell thickness of this cell was about 2 μm when measured with a Berek phase plate.

The liquid crystal compositions CS-1017 and 11-A were injected into this cell in an isotropic liquid state.
By slowly cooling to 25 ° C. at 0 ° C./h, a ferroelectric liquid crystal device was produced.

Using this ferroelectric liquid crystal element, an optical response (a change in transmitted light amount of 0 to 90%) under orthogonal Nicols is detected by applying a peak-to-peak voltage Vpp = 20 V, and the response speed ( (Hereinafter referred to as the optical response speed).

The results are shown in Table 23.

[0180]

[Table 23] * () Indicates temperature characteristics (f ^0/10 , f
^10/20 , f ^20/30 and f ^30/40 ).

From the above results, in the liquid crystal composition 11-A in which the temperature characteristic of the inclination angle δ of the layer takes a maximum value with respect to the temperature drop, and thereafter shows a tendency to decrease, the original δ increases with the temperature drop. The temperature dependence of the response speed is less than that of the continuously increasing liquid crystal composition CS-1017. In particular, a large difference is observed in the temperature characteristic f ^0/10 in a temperature range of 10 ° C. or lower where the value of δ tends to decrease. Thus, the temperature characteristics of the response speed have been improved.

Example 2 The temperature characteristic of the inclination angle δ of the layer is a general liquid crystal material (which continues to increase with the temperature drop). ZLI-323 manufactured by Merck Ltd.
Using No.3, a liquid crystal composition 12-A shown below was produced.

[0183]

Embedded image

ZLI-3233 and composition 12-A have a spontaneous polarization Ps (nc / cm) at a phase transition temperature (° C.) of 30 ° C.
² ) is shown in Table 24 below.

[0185]

[Table 24]

Table 25 shows the temperature characteristics of the value of δ (°) measured by the aforementioned X-ray diffraction method.

[0187]

[Table 25]

Next, the liquid crystal composition 11- used in Example 1
A ferroelectric liquid crystal device was produced in the same manner as in Example 1 except that ZLI-3233 and 12-A were used instead of A, and the optical response speed was measured in the same manner as in Example 1.

The results are shown in Table 26.

[0190]

[Table 26] * () Indicates temperature characteristics (f ^0/10 , f
^10/20 , f ^20/30 and f ^30/40 ).

From the above results, in the liquid crystal composition 12-A in which the temperature characteristic of the inclination angle δ of the layer takes a maximum value with respect to the temperature drop and thereafter shows a decreasing tendency, the original δ becomes smaller with the temperature drop. The temperature dependence of the response speed is less than that of the continuously increasing liquid crystal composition ZLI-3233, and the temperature characteristic f particularly in a temperature range of 10 ° C. to 0 ° C. where the value of δ tends to decrease.
^A large difference was observed at ^0/10, and the temperature characteristics of the response speed were improved.

Example 3 Temperature characteristics of the inclination angle δ of the layer are generally (continuously increasing with the temperature drop) CS-1 manufactured by Chisso Corporation
Using No. 031, a liquid crystal composition 13-A shown below was produced.

[0193]

Embedded image

Table 27 shows the phase transition temperature of CS-1031 and 13-A and the magnitude Ps of spontaneous polarization at 30 ° C.
Shown in

[0195]

[Table 27]

Table 28 shows the temperature characteristics of the value of δ (°) measured by the above-mentioned X-ray diffraction method.

[0197]

[Table 28]

Next, the liquid crystal composition 11- used in Example 1
A ferroelectric liquid crystal device was produced in the same manner as in Example 1 except that CS-1031 and 13-A were used instead of A, and the optical response speed was measured in the same manner as in Example 1.

The results are shown in Table 29.

[0200]

[Table 29] * () ^Indicates temperature characteristics at 10 ° C (f ^10/0 , f
^20/10, shows the f ^30/20).

From the above results, the liquid crystal composition 13-A in which the temperature characteristic of the inclination angle δ of the layer takes a maximum value with respect to the temperature drop and thereafter tends to decrease, has the original δ with the temperature drop. The temperature dependence of the response speed is less than that of the continuously increasing liquid crystal composition CS-1031. In particular, the temperature characteristic f in the temperature range of 0 ° C. to 20 ° C. or lower where the value of δ tends to decrease.
There is a large difference between ^0/10 and f ^10/20, and the temperature characteristics of the response speed are improved.

Example 4 A liquid crystal composition 14-A having a maximum value δ _MAX of the inclination angle δ of the layer of about 35 ° C. and a liquid crystal composition 14- having a maximum δ _MAX of about 10 ° C.
B was prepared. Next, 14-A and 14-B were mixed at the ratio shown below to obtain compositions 14-AB-11 and 14-AB-1.
2 was produced.

The phase transition temperatures of these liquid crystal compositions and 1
Table 30 below shows the magnitude Ps of the spontaneous polarization at 0 ° C., 30 ° C., and 50 ° C.

[0204]

[Table 30]

Next, Table 31 and FIG. 18 show the temperature characteristics of the value of δ (°) measured by the aforementioned X-ray diffraction method.

[0206]

[Table 31]

Next, the liquid crystal composition 11 used in Example 1 was used.
14-A, 14-B, 14-AB-1 instead of -A
Except for using 1,14-AB-12, a ferroelectric liquid crystal element was produced in the same manner as in Example 1, and the optical response speed was measured in the same manner as in Example 1.

Table 32 shows the results.

[0209]

[Table 32] * () Indicates temperature characteristics at 10 ° C (f ^10/20 , f
^20/30, f ^30/40, shows the f ^40/50).

From the above results, the liquid crystal compositions 14-A, 14-B, and 14-AB show that the temperature characteristics of the inclination angle δ of the layer increase with the temperature drop, reach a maximum value, and then decrease. -1
1,14-AB-12 is a general liquid crystal composition ZL shown in Examples 1 and 2 in which δ continuously increases with a temperature drop.
Temperature dependence of response speed is reduced as compared with I-3233 or CS-1017. Further, the temperature at which the maximum value δ _{MAX of} δ is on the higher temperature side is reduced in the temperature dependence of the response speed near the temperature, so that the temperature characteristics in the total temperature range can be further improved. The temperature characteristic of the response speed of a normal liquid crystal composition largely depends on the viscosity coefficient, and therefore often becomes sharper at a lower temperature side in an Arrhenius plot. (For example, f ^10/20 > f
^20/30 > f ^30/40 ). However, in the liquid crystal composition shown in this example, even if the temperature characteristic of the response speed in the temperature range where
^10/20 can be a smaller value.

[0211]

[Outside 1]

Examples 5 to 10 and Comparative Examples 3 to 6 Two 1.1 mm-thick glass plates were prepared for a pair of substrates, and ITO (indium oxide) with side metal (molybdenum) was provided on each of the glass plates. Tin oxide)
Was formed, and a tantalum oxide film was formed thereon as a transparent dielectric film by sputtering at a thickness of 1500 °.

On the tantalum oxide film, NMP of LQ1802 (manufactured by Hitachi Chemical Co., Ltd.)
The solution was applied by a printing method and baked at 270 ° C. to form a polyimide alignment control film having a thickness of 300 °.
The baked film was subjected to a rubbing treatment with an acetate flocking cloth. Thereafter, epoxy resin adhesive particles having an average particle size of 5.5 μm (trade name: Trepearl; manufactured by Toray Industries, Inc.) were sprayed onto one substrate by a Nordson electrostatic spraying method so as to have a distribution density of 30 particles / mm ^2. did. On another substrate, silica microbeads having an average particle size of 1.5 μm were sprayed at a distribution density of 300 / mm ² by a Nordson electrostatic spraying method. Next, 6 liquid adhesives (trade name: Structbond; manufactured by Mitsui Toatsu Co., Ltd.) are used as the sealing member 115.
Print coating was performed with a film thickness of μm. Then, the two glass plates are bonded counterclockwise at a crossing angle of 6 to 10 ° and in the same direction, and pressed at 70 ° C. by applying a pressure of 2.8 kg / cm ² for 5 minutes, Further, while applying a pressure of 0.63 kg / cm ² at a temperature of 150 ° C., the two types of adhesives were cured for 4 hours to produce a cell.

Thereafter, the pressure inside the liquid crystal cell was reduced to 10 ^-4, and the liquid crystal composition A having the characteristics shown in Tables 33 and 34 below was obtained.
~ G was injected.

[0215]

[Table 33]

[0216]

[Table 34] Cry; crystalline phase or higher smectic phase SmC ^* ; chiral smectic C phase SmA; smectic A phase Ch; cholesteric phase Iso;

Thereafter, a chiral smectic C phase is formed through the cholesteric phase and the smectic A phase.
Cooled to 5 ° C.

The liquid crystal element thus manufactured was used for a display panel, and a liquid crystal having a screen size of about 280 mm in width (information line side), 220 mm in length (scanning line side), and 1280 × 1024 pixels shown in FIG. A display device was manufactured. This liquid crystal display was scanned on the scanning side using the driving waveform shown in FIG.
The display was performed at 10.5 V (4.5 V in part) and ± 4.5 V on the information side. The measurement of the afterimage time was performed by writing an 80 × 80 white / black checker pattern for 3 minutes, then turning the entire display area black, and visually observing the time until the entire surface became a uniform black state. The environmental temperature was controlled in a thermostat, and the temperature of the panel surface was directly monitored using a thermocouple. The results are shown in Table 35.

[0219]

[Table 35]

In the table, 1H is the writing time for one scanning line (shown in FIG. 7), which is adjusted to a state in which good display can be performed on the entire surface of the panel. Incidentally, these liquid crystal elements clearly satisfied all the conditions of the above formulas (I), (II) and (III), and exhibited a high contrast of 20 or more.

In the liquid crystal displays of Examples 5 to 10, the afterimage time does not increase divergently as the environmental temperature decreases, but decreases again at the low temperature side, and the display quality does not significantly deteriorate. Absent. On the other hand, in the liquid crystal displays of Comparative Examples 3 to 6, the degree of the afterimage on the low temperature side is significantly long, and the display quality is degraded.

Except for the liquid crystal composition A having a low transition temperature of SmA → SmC ^*, the ratio f of the driving 1H of each of Examples 6 to 10 at 10 ° C. to 40 ° C. was 1.8 to 2.0.
9 times, which is much better than 3.5 to 4.3 times of Comparative Examples 3 to 6.

As is apparent from the above results, the liquid crystal element using the liquid crystal composition having a temperature characteristic in which the inclination angle δ of the layer takes a maximum value and then decreases as the temperature decreases. In this device, a remarkable afterimage at a low temperature can be suppressed, and the temperature dependence of driving characteristics can be reduced.

Reference Example 5 The optical response of the liquid crystal composition 2-A used in Reference Example 2 and the liquid crystal composition 2-B used in Comparative Example 1 were observed using a cell manufactured according to the following procedure.

A thin film of tantalum oxide is formed on a glass substrate provided with a transparent electrode by a sputtering method, and a polyamic acid LQ1 manufactured by Hitachi Chemical Co., Ltd.
1% NMP solution of 802 is applied with a spinner, 270 ° C.
For 1 hour to produce a polyimide film.

Next, this substrate was rubbed, and another substrate which had been subjected to the same treatment had a crossing angle of 10 ° (described above), and a gap of about 1.2 to 1.3 μm was formed so as to be in the same direction. The cell was prepared by holding and bonding. The pretilt angle α of the cell was 17 ° by a crystal rotation method.

The liquid crystal compositions 2-A and 2-B were injected into this cell in an isotropic liquid state, and the liquid crystal composition was discharged from the isotropic phase at 20 ° C./h at 25 ° C.
The ferroelectric liquid crystal device was produced by gradually cooling the liquid crystal.

Using this ferroelectric liquid crystal element, a driving margin ΔV (V) with a driving waveform (1/3 bias ratio) shown in FIG.
₂ -V ₁₎ was measured. The results are shown in Tables 36 and 37. (Note that Δt was set so that V ₁ ≒ 15 V.)

[0229]

[Table 36]

[0230]

[Table 37]

Further, when the voltage is set to the center value of the driving voltage margin at 30 ° C. and the measured temperature is changed,
The driveable temperature difference (hereinafter referred to as a drive temperature margin) is as follows.

[0232]

Further, Table 38 shows the transmitted light amounts and contrast ratios of white and black.

[0234]

[Table 38]

At this time, the contrast change rate was 1.27 for 2-A and 2.97 for 2-B. (Contrast change rate = maximum contrast value / minimum contrast value)

As is evident from Reference Example 5, the liquid crystal device containing the liquid crystal composition 2-A having a maximum cone angle according to the present invention did not exhibit a low contrast at low temperatures, and did not exhibit a low contrast due to temperature change. Composition 2.
It can be seen that this is greatly improved as compared with the liquid crystal element containing -B.

Further, it can be seen that the drive voltage margin and the drive temperature margin are also widened.

Reference Example 6 The liquid crystal compositions 3-A, 3-B and 3-C used in Reference Example 3 were used.

Next, the liquid crystal composition 2 used in Reference Example 5
Instead of using A and 2-B, liquid crystal compositions 3-A and 3-A
A ferroelectric liquid crystal element was manufactured in the same manner as in Reference Example 5 except that B and 3-C were injected into the cell, and the driving voltage margin ΔV was measured.

[0240]

[Table 39]

[0241]

[Table 40]

[0242]

[Table 41]

The driving temperature margin at 30 ° C. is as follows.

[0244]

Further, the transmitted light amount and contrast of white and black are shown below.

[0246]

[Table 42]

At this time, the contrast change ratio was 1.32 for 3-A, 1.50 for 3-B, and 2.62 for 3-C.

The above results are shown in FIGS. FIG.
20 shows the transmitted light amount and contrast ratio of 3-A, FIG. 20 shows 3-B, and FIG. 21 shows 3-C, respectively.

As is apparent from Reference Example 6, the liquid crystal device according to the present invention containing the liquid crystal compositions 3-A and 3-B having a maximum cone angle has a low contrast at low temperatures without a change in temperature. The accompanying change rate of the contrast is 1.32, 1..
It can be seen that this is greatly improved as compared with the liquid crystal device containing 50 and the composition 3-C.

Further, it can be seen that the drive voltage margin and the drive temperature margin are also widened.

The liquid crystal composition 5- used in Reference Examples 7 and 8
A, 5-B, 6-A and 6-B were as follows.

[0252]

[Table 43]

R _{1 to} R ₁₂ in the above table are normal alkyl, and the numbers in the table indicate the carbon number of the normal alkyl as R ₁ / R ₂ , R ₃ / R ₄ , R ₅ / R ₆ , R ₇ / R
₈ , R ₉ / R ₁₀ , R ₁₁ / R ₁₂ .

Reference Example 7 Liquid crystal compositions 5-A and 5-B were prepared as described above.

The phase transition temperatures, spontaneous polarization magnitude Ps at 30 ° C., and cone angle magnitudes of the liquid crystal compositions 5-A and 5-B are shown below.

[0256]

[Table 44]

[0257]

[Table 45]

Next, the liquid crystal composition 2 used in Reference Example 5
Instead of using A and 2-B, liquid crystal compositions 5-A and 5-
A ferroelectric liquid crystal device was fabricated in the same manner as in Reference Example 5 except that B was injected into the cell, and the drive voltage margin ΔV was measured.

[0259]

[Table 46]

[0260]

[Table 47]

The driving temperature margin at 30 ° C. is as follows.

5-A ± 8.0 ° C. 5-B ± 7.5 ° C.

Further, the transmitted light amounts and contrasts of white and black are shown below.

[0264]

[Table 48]

At this time, the contrast change rate was 1.45 for 5-A and 1.76 for 5-B.

As is apparent from Reference Example 7, in the liquid crystal element containing the liquid crystal compositions 5-A and 5-B having the maximum cone angles, Δmax / Δmin is changed to Δmax / Δmi.
An element containing 5-A where n <1.5 (Θmax / Θmin =
1.42) has a smaller contrast fluctuation width due to a temperature change than an element containing 5-B satisfying Θmax / Θmin ≧ 1.5 (Θmax / Θmin = 1.76).

Reference Example 8 Liquid crystal compositions 6-A and 6-B were prepared as described above.

Next, the liquid crystal composition 2 used in Reference Example 5
Liquid crystal compositions 6-A, 6-B instead of using A, 2-B
The ferroelectric liquid crystal device was manufactured in exactly the same manner as in Reference Example 5 except that the liquid crystal was injected into the cell, and an attempt was made to measure the drive voltage margin ΔV. And the drive voltage margin and the amount of transmitted light could not be measured.

[0269]

As described above, the liquid crystal composition in which the inclination angle δ of the layer of the present invention increases with the temperature drop and decreases after the maximum value δ _max is obtained, and the device using the liquid crystal composition, A liquid crystal composition and a device in which the temperature dependence of the response speed was reduced were obtained.

Further, by controlling the temperature at which δ _max is obtained, it is possible to control the temperature range in which the temperature characteristics of the response speed are good. Also, the response speed could be improved by controlling the magnitude of δ.

Further, a display device using the liquid crystal element of the present invention as a display element in combination with a light source, a driving circuit, and the like was a good device.

Further, the liquid crystal device of the present invention is a device having a high contrast, an afterimage on the low temperature side is improved, and the temperature dependence of driving conditions is reduced, and a liquid crystal display device using the same has a very excellent display. Was able to do.

Further, in the element structure according to the present invention, the liquid crystal element containing the liquid crystal composition having the maximum cone angle does not decrease the contrast at a low temperature, and can reduce the contrast fluctuation due to the temperature change. did it.

Further, a liquid crystal element with small contrast fluctuation can be obtained by setting the ratio (Θmax / Θmin) of the maximum value and the minimum value of the cone angle to 1.5 or less.

Further, a liquid crystal element having a large driving temperature margin and a large driving temperature margin capable of satisfactorily driving the matrix in all the pixels was obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of an example of the liquid crystal element of the present invention.

FIG. 2 is a perspective view schematically showing an example of a liquid crystal cell using a ferroelectric liquid crystal.

FIG. 3 is a perspective view schematically showing an example of a liquid crystal cell using a ferroelectric liquid crystal.

FIG. 4 is an explanatory diagram of C1 and C2.

FIG. 5 is an explanatory diagram showing a relationship among a tilt angle, a pretilt angle, and a layer tilt angle in C1 and C2 orientations.

FIG. 6 is a schematic sectional view of another example of the liquid crystal element of the present invention.

FIG. 7 is a timing chart of a driving waveform used in the present invention.

FIG. 8 is a plan view of a matrix electrode.

FIG. 9 is a schematic cross-sectional view of a chevron structure in a chiral smectic C phase.

FIG. 10 is a schematic sectional view of a molecular layer in a smectic A phase.

FIG. 11 is a block diagram showing a liquid crystal display device and a graphics controller of the present invention.

FIG. 12 is a timing chart of image information communication between the liquid crystal display device of the present invention and a graphics controller.

FIG. 13 is a characteristic diagram of temperature and cone angle Θ.

FIG. 14 is a characteristic diagram of temperature and cone angle Θ.

FIG. 15 is a characteristic diagram of temperature and cone angle Θ.

FIG. 16 is a characteristic diagram of temperature and cone angle Θ.

FIG. 17 is a characteristic diagram of temperature and cone angle Θ.

FIG. 18 is a characteristic diagram of temperature and inclination angle δ.

FIG. 19 is a characteristic diagram of temperature and transmitted light amount.

FIG. 20 is a characteristic diagram of temperature and transmitted light amount.

FIG. 21 is a characteristic diagram of temperature and transmitted light amount.

FIG. 22 is a waveform diagram of a driving method used in the conventional technique.

FIG. 23 is a schematic diagram of a display pattern when actual driving is performed using the time-series driving waveform shown in FIG.

FIG. 24 is a graph (VT characteristic diagram) showing a change in transmittance when a drive voltage is changed.

──────────────────────────────────────────────────続 き Continuation of the front page (31) Priority claim number Japanese Patent Application No. 4-38392 (32) Priority date Hei 4 (1992) January 30 (33) Priority claim country Japan (JP) (72) Inventor Shosei Mori 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Masataka Yamashita 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Kazuharu Katagiri 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-3-17074 (JP, A) JP-A-3-83971 (JP, A) JP-A-2-279681 ( JP, A) JP-A-3-220183 (JP, A) JP-A-4-46991 (JP, A) JP-A-4-13667 (JP, A) JP-A-4-193872 (JP, A) Hei 3-252624 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C09K 19/02

Claims (13)

(57) [Claims] A pair of substrates, a cone angle Θ, and at least two optically stable states in the absence of an electric field;
The tilt angle θa which is の of the angle between these optical axes
In a liquid crystal device having a liquid crystal composition having a chiral smectic C phase having the following characteristics, the liquid crystal molecules of the liquid crystal composition are oriented with a pretilt angle α with respect to the substrate to form a chiral smectic C phase. A plurality of organized layers are arranged at an inclination angle δ with respect to the normal line of the substrate, and within a temperature range in which a chiral smectic C phase is generated: a) The inclination angle δ in the chiral smectic C phase causes a temperature drop. A first temperature range that increases with the increase of the temperature, and b) a second temperature range in which the tilt angle δ in the chiral smectic C phase decreases at a temperature drop with a further temperature drop in a temperature range lower than the first temperature range. Temperature range, and θa, Θ, δ and α, c) Θ <α + δ, d) δ <α and e) Θ>θa> Θ / 2. Liquid crystal element. 2. The liquid crystal device according to claim 1 , wherein at least one of the pair of substrates is subjected to a uniaxial alignment treatment. 3. The liquid crystal device according to claim 2 , wherein the uniaxial alignment treatment is a rubbing treatment. 4. The liquid crystal device according to claim 1 , wherein both of the pair of substrates are subjected to uniaxial alignment processing in parallel and in the same direction or in the opposite direction. 5. The liquid crystal device according to claim 4 , wherein the uniaxial alignment treatment is a rubbing treatment. 6. The liquid crystal device according to claim 1 , wherein both of the pair of substrates are subjected to a uniaxial alignment process crossing each other. 7. The liquid crystal device according to claim 6 , wherein the crossing angle of the crossed uniaxial alignment treatment is 2 ° to 15 °. 8. The liquid crystal device according to claim 7 , wherein the uniaxial alignment treatment is a rubbing treatment. 9. The liquid crystal device according to claim 1 , wherein the displacement point appears at a temperature of 10 ° C. or higher, and a chiral smectic C phase is generated by lowering the temperature from the smectic A phase. 10. The liquid crystal device according to claim 1 , wherein the displacement point appears at a temperature of 25 ° C. or higher, and a chiral smectic C phase is generated by lowering the temperature from the smectic A phase. 11. The liquid crystal device according to claim 1 , wherein a chiral smectic C phase is generated by lowering the temperature from the cholesteric phase and the smectic A phase. 12. A pair of substrates, having a cone angle Θ and producing at least two optically stable states in the absence of an electric field,
The tilt angle θa which is の of the angle between these optical axes
A liquid crystal composition having a chiral smectic C phase having the formula: and a display device having a voltage applying means for applying a voltage to the liquid crystal composition, wherein the liquid crystal molecules of the liquid crystal composition generate a pretilt angle α with respect to the substrate. In a temperature range in which a plurality of layers organized by a plurality of liquid crystal molecules forming a chiral smectic C phase are arranged at an inclination angle δ with respect to the normal to the substrate, and a chiral smectic C phase is generated, a) a first temperature range in which the tilt angle δ in the chiral smectic C phase increases with a temperature drop; and b) a tilt angle δ in the chiral smectic C phase in a temperature range lower than the first temperature range. A second temperature range that decreases at the displacement point with the temperature drop, and between θa, Θ, δ and α, c) Θ <α + δ, d) δ <α and e) Θ>θa> Θ / 2 A display device, comprising: 13. The display device according to claim 12 , further comprising control means for controlling the voltage application means.