JPH05100227A - Liquid crystal element - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display element which can make image display of a high contrast and obviates the degradation in the contrast of written parts even if partial writing are frequency executed. CONSTITUTION:The chiral smectic liquid crystal of the liquid crystal element which is constituted by crimping the chiral smectic liquid crystal 15 between a pair of substrates 11a and 11b formed with electrodes 12a, 12b and orientation control films 14a, 14b has <=2X1010OMEGAcm specific resistance and has the orientation state expressed by THETA<alpha+delta and delta<alpha0 when the pretilt angle as the chiral smectic liquid crystal is designated as alpha, the cone angle as THETA, and the inclination angle of the liquid crystal layer as delta. Further, this liquid crystal exhibits at least two stable states in the oriented state. The apparent tilt angle thetaa which is half the angle formed by the optical axes thereof and the cone angle THETA of the chiral smectic liquid crystal are set to satisfy a relation THETA>gammaq>THETA/2o.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal element used in a liquid crystal display element, a liquid crystal optical shutter or the like, particularly a ferroelectric liquid crystal element. More specifically, the specific resistance value in a liquid crystal layer is set to a specific value or less. Therefore, the present invention relates to a liquid crystal element having improved display characteristics.

[0002]

2. Description of the Related Art A display device of the type in which transmitted light rays are controlled by using a refractive index anisotropy of ferroelectric liquid crystal molecules in combination with a polarizing device has been proposed by Clark and Lagerwall. (Unexamined-Japanese-Patent No. 56-107216, US Patent 43679.
No. 24, etc.). This ferroelectric liquid crystal generally has a non-helical chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) in a specific temperature range, and in this state, it has a first phase in response to an applied electric field. Has an optical stable state and a second optical stable state, and has the property of maintaining that state when no electric field is applied, that is, bistability, and responds quickly to changes in the electric field. Therefore, it is expected to be widely used for high-speed and memory type display elements, and in particular, its function is expected to be applied to a large-screen and high-definition display.

In general, in the case of a liquid crystal element utilizing the birefringence of liquid crystal, the transmittance under orthogonal Nicols is

[0004]

[Equation 1] It is represented by. The apparent tilt angle θ _a in the above-mentioned non-helical structure appears as an angle in the average molecular axis direction of the twisted liquid crystal molecules in the first and second alignment states. According to the above equation, the maximum transmittance is obtained when the apparent tilt angle θ _a is 22.5 °, and the apparent tilt angle θ _a in the non-helical structure that realizes the bistability is 22.5 °.
It is desirable to be as close as possible to 2.5 °.

However, the alignment method that has been used so far, in particular, the alignment method using a rubbing-treated polyimide film, is applied to the ferroelectric liquid crystal having a non-helical structure and exhibiting the bistability disclosed by Clark and Lagerwol. When applied, it had the following problems.

That is, according to an experiment by one of the present inventors, an apparent tilt angle θ _{a in a} ferroelectric liquid crystal having a non-helical structure obtained by aligning with a conventional rubbing-treated polyimide film. The (corner angle 1/2 forming the molecular axes of the two stable states) is the cone angle in the ferroelectric liquid crystal (see FIG.
It has been found that the angle is smaller than the angle Θ) which is 1/2 the apex angle of the triangular pyramid. In particular, the apparent tilt angle θ _a of a non-helical ferroelectric liquid crystal obtained by aligning with a conventional rubbing-treated polyimide film is generally 3
The transmittance was about 8 to 8 °, and the transmittance at that time was about 3 to 5% at most.

Therefore, one of the inventors of the present invention has produced _a large apparent tilt angle θ _a in the non-helical structure of the chiral smectic liquid crystal, and is sufficient to realize a display in which a high-contrast image is displayed. But first of all, I found the following, so I will explain it.

That is, a chiral smectic liquid crystal,
Electrodes for applying a voltage to the respective chiral smectic liquid crystals are formed on the opposing surfaces with the liquid crystal held therebetween, and the uniaxial alignment axes for aligning the liquid crystals are at a predetermined angle from each other. In a liquid crystal device including a pair of substrates subjected to crossed alignment treatment, if the pre-tilt angle of the smectic liquid crystal device is α, the cone angle is Θ, and the tilt angle of the liquid crystal layer is δ, the smectic liquid crystal is A liquid crystal element having an alignment state represented by <α + δ and δ <α, and the liquid crystal in the alignment state exhibits at least two stable states, and the apparent angle is 1/2 of the angle formed by the optical axes thereof. If the tilt angle θ _a and the cone angle Θ of the chiral smectic liquid crystal have a relationship of Θ> θ _a > Θ / 2, a high-contrast image is displayed. It has become clear that a display that can be realized can be realized. This will be sequentially described below.

Smectic liquid crystals generally have a layered structure, but when the S _A phase transitions to the S _C phase or the S _C ^* phase, the layer spacing shrinks, so that the layer represented by 31 in the center of the upper and lower substrates as shown in FIG. It has a bent structure (chevron structure). S _C from the high temperature phase as the direction shown in FIG bent
^* The present inventors have two possible that the appearing mixed in C1 alignment state when immediately after transition to the phase further reduce the temperature and appearing alignment state (C1 alignment state) alignment state (C2 alignment state) discovered. Furthermore, it was newly discovered that, when a specific combination of the alignment film and the liquid crystal is used, the above-mentioned transition from C1 to C2 is unlikely to occur, and depending on the liquid crystal material, the C2 alignment state does not occur at all. It was discovered that the contrast of the C1 orientation is very high and the contrast of the C2 orientation is low when the relationship of Θ <α + δ is satisfied by using a high pretilt alignment film. As a result, a high pretilt alignment film is used as a display element, and the entire screen is unified into a C1 alignment state.
If used as a state, it is expected that a display with higher quality than before can be made. The pretilt will be described below.

As described above, C1 is produced without producing the C2 orientation state.
It is concluded that the following conditions must be satisfied in order to realize the oriented state.

That is, as shown in FIG. 3, the directors near the substrate in the C1 orientation and the C2 orientation are respectively shown in FIG.
It is on the cone 41 of (a) and (b). As is well known, the liquid crystal molecules at the substrate interface by rubbing are
An angle called a pretilt is formed with respect to the substrate, and its direction is a direction in which liquid crystal molecules lift their heads (the ends become floating) in the rubbing direction (direction A in FIG. 3). From the above, the relationship of Θ + δ> α in the C1 orientation, Θ−δ> α in the C2 orientation, must be established among the cone angle Θ, the pretilt angle α and the layer tilt δ of the liquid crystal.

Therefore, the condition for producing the C1 orientation without producing the C2 orientation in the present invention is Θ-δ <α, that is, Θ <α + δ (1).

Furthermore, α> δ (2) is obtained as a condition under which switching of interface molecules is likely to occur from a simple consideration of the torque received when switching the molecules of the interface from one position to the other by the electric field.

Therefore, in order to form the C1 orientation state more stably, it is effective to satisfy the relationship of the expression (2) in addition to the relationship of the expression (1).

As a result of further experiments under the conditions of the equations (1) and (2), the apparent tilt angle θ _a of the liquid crystal is
From about 3 ° to 8 ° in the case of the conventional liquid crystal element that does not satisfy the conditions of the expressions (1) and (2), to 8 ° to 16 ° in the case of the present invention that satisfies the conditions of the expressions (1) and (2). It has been empirically obtained that the relational expression of Θ> θ _a > Θ / 2 (3) holds with the cone angle Θ of the liquid crystal.

As described above, it has been clarified that a display capable of displaying a high-contrast image can be realized if the conditions of the expressions (1), (2) and (3) are satisfied.

In order to stably form the C1 orientation state and obtain a good orientation, the rubbing directions of the upper and lower substrates are 2 ° to 25 °.
It was found that cross rubbing displaced in the range of ° (crossing angle) is also extremely effective in the present invention. The above is described in detail in Japanese Patent Application No. 2-49582.

By the way, a display device using a chiral smectic liquid crystal element is a display device capable of far larger screen and higher definition than conventional CRT or TN type liquid crystal displays. The frame frequency (one screen forming frequency) becomes low frequency with the high definition, and therefore the screen rewriting speed, the smooth scroll on the character editing and graphics screens, and the moving image display speed such as cursor movement. There was a problem that was slow. A solution to this problem is Japanese Patent Laid-Open No.
0-31120, JP-A-1-140198 and the like.

That is, a display panel in which scan electrodes and information electrodes are arranged in a matrix, a means for selecting all or a predetermined number of scan electrodes (selection by this means is called full surface writing), and a total or predetermined number of scan electrodes. It means that a display device having a means for partially selecting (a case of selecting by this means is called partial writing) is used. This enables high-speed display by performing partial moving image display by partial writing, and can achieve both partial writing and full writing.

As described above, when the liquid crystal element satisfying the above-described expressions (1), (2) and (3) is driven by the display device capable of partial writing, a high contrast is achieved in a large screen and a high definition display. It has become clear that various images can be displayed at high speed.

[0021]

However, when performing the above-described partial writing, for example, when a character font (16 lines × 16 lines configuration) is partially written on the scanning electrodes for 16 lines, the scanning for 16 lines is performed. The scanning signal is frequently applied only to the electrodes, and as a result, the contrast of the image on the scanning line in which the partial writing is performed is lowered, and black is particularly pale and the display quality is deteriorated. The present inventors have discovered that there is a problem.

The same phenomenon occurs when a moving image is continuously displayed by partial writing in a narrow area of scan electrodes (for example, 8 to 16 lines), or when partial writing is performed when moving a cursor or a mouse on the same scanning line. ..

Further, it was also found that the phenomenon of this contrast reduction becomes more remarkable as the number of scanning lines selected when performing partial writing is smaller.

An object of the present invention is to provide a liquid crystal display device capable of displaying a high-contrast image and in which the contrast of the portion is not deteriorated even if the partial writing is frequently performed.

[0025]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have solved the above problems by setting the specific resistance ρ of a chiral smectic liquid crystal to a specific value or less. Have found that the display characteristics of liquid crystal elements can be significantly improved.

That is, according to the present invention, the chiral smectic liquid crystal and the liquid crystal are opposed to each other with the liquid crystal held therebetween, and electrodes for applying a voltage to the chiral smectic liquid crystal are respectively formed on the opposed surfaces, and the liquid crystal is aligned. In a liquid crystal element comprising a pair of substrates subjected to an alignment treatment in which uniaxial alignment axes for intersect at a predetermined angle,
The specific resistance ρ of the chiral smectic liquid crystal is 2 × 10 ¹⁰
If the pretilt angle of the smectic liquid crystal element is α, the cone angle is Θ, and the tilt angle of the liquid crystal layer is δ, the smectic liquid crystal has an orientation state represented by Θ <α + δ and δ <α. An apparent tilt angle θ _a which is a liquid crystal element and in which the liquid crystal in the alignment state exhibits at least two stable states, and which is ½ of an angle forming the optical axes thereof, and a cone angle Θ of the chiral smectic liquid crystal. Is a liquid crystal element characterized by having a relationship of Θ> θ _a > Θ / 2.

[0027]

Next, the present invention will be described in detail.

In the case of a display element using a chiral smectic liquid crystal, it has been clarified that the ionic behavior in the liquid crystal layer has a significant influence on the characteristics of the element.
135352 for further details. That is, in the chiral smectic liquid crystal layer, there is an electric field generated by spontaneous polarization charges of liquid crystal molecules, and the electric field causes ionic impurities existing in the liquid crystal layer to migrate, resulting in uneven distribution of ions. Occurs. Due to this, the bistability is reduced, and the display characteristics of the liquid crystal element are significantly reduced.

The present inventors have already described (1),
In order to solve the problem that the contrast is lowered when a liquid crystal device satisfying the conditions of the expressions (2) and (3) is displayed at high speed with high contrast using the partial writing method, studies and experiments have been repeated. As a result, rather than decreasing the number of ions existing in the liquid crystal layer, by positively increasing the specific resistance value of the liquid crystal layer to reduce the uneven distribution of ions, good bistability and high contrast can be maintained. However, it has been discovered that the contrast of the display section in which partial writing is performed does not decrease even when high-speed display is performed by partial writing.

Although the mechanism of this behavior is not sufficiently clear, the low resistance of the liquid crystal eliminates the uneven distribution of ions in the liquid crystal layer, which causes the internal electric field due to spontaneous polarization of the liquid crystal molecules to relax. It is speculated that the improvement in switching characteristics led to a small change in contrast during partial writing.

As a method for controlling the specific resistance value ρ of liquid crystal to 2 × 10 ¹⁰ Ωcm or less, it is generally known to add a salt such as tetrabutylammonium bromide (TBAB) as an ionic substance. Such salts generally have poor solubility in liquid crystals and have a problem of precipitation particularly at low temperatures, so a compound having good solubility is required.

In the present invention, in order to lower the specific resistance of the liquid crystal layer stably and with good reproducibility, the compound of the structural formula shown below can be added to the chiral smectic liquid crystal and used.

[0033]

[Chemical 1]

[0034]

[Chemical 2]

[0035]

[Chemical 3]

[0036]

[Chemical 4]

[0037]

[Chemical 5]

[0038]

[Chemical 6]

[0039]

[Chemical 7]

[0040]

[Chemical 8]

[0041]

[Chemical 9]

[0042]

[Chemical 10]

[0043]

[Chemical 11]

[0044]

[Chemical 12]

[0045]

[Chemical 13]

[0046]

[Chemical 14]

[0047]

[Chemical 15]

[0048]

[Chemical 16]

[0049]

[Chemical 17]

[0050]

[Chemical 18]

[0051]

[Chemical 19]

[0052]

[Chemical 20]

[0053]

[Chemical 21]

[0054]

[Chemical formula 22]

[0055]

[Chemical formula 23]

[0056]

[Chemical formula 24]

[0057]

[Chemical 25]

[0058]

[Chemical formula 26]

[0059]

[Chemical 27]

[0060]

[Chemical 28]

[0061]

[Chemical 29]

[0062]

[Chemical 30]

[0063]

[Chemical 31]

[0064]

[Chemical 32]

The liquid crystal composition of the present invention can be obtained by mixing at least one additive represented by the above formula with another chiral smectic liquid crystal in an appropriate ratio.

However, when a large amount of the above-mentioned additives is added, there are drawbacks such as lowering of the temperature of the liquid crystal layer and precipitation at low temperature. Therefore, the optimum compounding ratio of the chiral smectic liquid crystal and the additive compound used in the present invention is 0.01% of the additive compound per 100 parts by weight of the liquid crystal material.
˜5 weight percent, more preferably 0.05 to 2 weight percent.

A preferred example of the liquid crystal device of the present invention is schematically shown in FIG. In FIG. 1, 11a and 11b are In ₂ O ₃ and ITO (Indium Tin Ox), respectively.
a substrate (glass plate) covered with transparent electrodes 12a and 12b such as an ide) on which insulating films 13a and 13b (SiO ₂ film, TiO ₂ film, Ta ₂ O ₅ film, etc.) having a thickness of 200 to 3000 Å are formed. ) And the general formula

[0068]

[Chemical 33] Alignment control films 14a and 14b having a thickness of 50 to 1000 Å formed of polyimide are laminated respectively. The orientation control films 14a and 14b have a lower orientation film 14a in the orientation direction.
The upper alignment film 14b is subjected to uniaxial alignment treatment with a crossing angle of 6 ° counterclockwise as viewed from the upper alignment film 14b, and is rubbed so that it is in the same direction (direction of arrow A in FIG. 1). It has been processed. In the following, the intersection angle is defined as described above.

A chiral smectic liquid crystal 15 is arranged between the substrates 11a and 11b, and the substrates 11a and 11b.
Is set to a distance (for example, 0.1 to 3 μm) that is sufficiently small to suppress the formation of the helical alignment structure of the chiral smectic liquid crystal 15, and the chiral smectic liquid crystal 15 has a bistable alignment state. . The sufficiently small distance described above is held by the bead spacers 16 (silica beads, alumina beads, or the like) arranged between the substrates 11a and 11b. 17a and 17b are polarizing plates.

In the above experiment, the cone angle Θ, the layer tilt angle δ, the pretilt angle α, the apparent tilt angle θ _a ,
And the specific resistance ρ were measured as follows.

Measurement of cone angle Θ An AC voltage of ± 30 V to ± 50 V, 100 Hz was applied between the upper and lower substrates of the FLC element under orthogonal crossed Nicols, and the FLC element arranged between them was rotated horizontally with the polarizing plate. The first extinction position (the position where the transmittance is lowest) and the second extinction position are searched for while detecting the optical response with Photomal (manufactured by Hamamatsu Photonics KK). At this time, 1/2 of the angle from the first extinction position to the second extinction position was defined as the cone angle Θ.

Measurement of apparent tilt angle θ _a After applying a single pulse having a threshold value of liquid crystal,
Then, the FLC element arranged between them under the orthogonal crossed Nicols is rotated horizontally with the polarizing plate to search for the first extinction position, and then the pulse of the opposite polarity to the above-mentioned single-shot pulse is applied. Find the extinction position of 2. The angle 1/2 from the first extinction position to the second extinction position at this time was defined as θ _a .

Measurement of Layer Inclination Angle δ was measured by X-ray analysis using an X-ray analyzer RAD-IIB (45 KV, 30 mA).

Measurement of pretilt angle α Jpn. J. Appl. Phys. ． vo119 (19
80) No. 10, Short Notes 2013
The method described in (Crystal rotation method)
Sought according to.

That is, parallel and oppositely rubbed substrates are bonded together to form a cell having a cell thickness of 20 μm.
The liquid crystal (A) having the SmA phase was enclosed in the range of 0 ° C to 60 ° C and the measurement was performed.

While rotating the liquid crystal cell in a plane perpendicular to the upper and lower substrates and including the alignment treatment axis, helium / neon laser light having a polarization plane forming an angle of 45 ° with the rotation axis is irradiated from a direction perpendicular to the rotation axis. The intensity of transmitted light was measured with a photodiode through a polarizing plate having a transmission axis parallel to the plane of incident polarization on the opposite side.

The angle formed by the center of the hyperbolic group of transmitted light intensity formed by interference and the line perpendicular to the liquid crystal cell is φ _X
Then, the pretilt angle α _O was calculated by substituting in the following equation.

[0078]

[Equation 2]

Measurement of Specific Resistance ρ The specific resistance ρ of the liquid crystal layer was measured by using the measuring device having the structure shown in FIG. In FIG. 4A, the cell 51 is an IT
An alignment film of polyimide ultra-thin film (<50Å) was applied on the O electrode. A Mylar capacitor 52 having a capacity of Ci is attached to the outside of this cell, and a rectangular wave is applied from a function generator 53. A schematic diagram of the voltage waveform of the cell 51 measured via the buffer amplifier 54 at this time is shown in FIG. 4B. With the polarity reversal of the rectangular wave, V _O / sec after the time τ (sec) from the maximum voltage V _O It is attenuated to e.

At this time, the resistance value R _LC of the liquid crystal layer is given by the following equation.

[0081]

[Equation 3] This value is further converted into a specific resistance value ρ by the following formula.

[0082]

[Equation 4]

[0083]

EXAMPLES Examples of the present invention will be described below. Examples 1 to 4 A thin film of tantalum oxide was formed on a glass substrate having a transparent electrode by a sputtering method, and 1% of polyamic acid LQ1802 manufactured by Hitachi Chemical Co., Ltd., represented by the structural formula of Chemical formula 33, was formed thereon.
The NMP solution was applied with a spinner and baked at 270 ° C. for 1 hour. Next, this substrate was rubbed, and another substrate that had been subjected to the same treatment had a crossing angle of 6 ° (according to the above definition) and the same direction as the rubbing direction.
A cell was created by bonding with a gap of about 1.2 to 1.3 μm maintained. The pretilt angle α of the cell was 17 ° by the crystal rotation method.

As shown in Comparative Example 2 of Table 1 as a comparative example, a mixed chiral smectic liquid crystal (B) containing phenylpyrimidine and an ester as a main component was injected into the cell to form a liquid crystal element. It was made. Further, as shown in Comparative Example 1 and Examples 1 to 4 in Table 1, the additive compounds shown in Chemical Formulas 7 and 10 are used alone or in order to reduce the specific resistance value of the chiral smectic liquid crystal (B). The liquid crystal composition was prepared by mixing and mixing 0.05 to 1% of the liquid crystal (B), and the liquid crystal composition was injected into the same cell as above to prepare a liquid crystal element. Table 1 shows ρ, Θ, δ, θ _a and P _S (spontaneous polarization values) of these liquid crystals and liquid crystal elements. Here, P _S was measured using the triangular wave method.

[0085]

[Table 1]

All the liquid crystal-filled cells shown in Table 1 clearly satisfy all the conditions of the above formulas (1), (2) and (3), and all have a high contrast C1 orientation state at 30 ° C. was gotten.

Next, the characteristics of contrast change during partial writing in the C1 orientation state were evaluated.

First, a matrix display cell was prepared with the same configuration as above except that stripe-shaped electrodes were attached to the upper and lower substrates and pixels were formed at the intersections thereof, and a drive waveform as shown in FIG. 5 was applied. ..

In FIG. 5, S _N , S _{N + 1} , S _{N + 2,} etc. are voltage waveforms applied to the scan electrodes, and I is a voltage waveform applied to the information electrodes. As a composite waveform of these, S _N − I,
S _{N + 1} −I and the like have a voltage waveform that is actually applied to the pixel. For example, white (W) is written on the negative side of the waveform shown by S _N -I in FIG. 5 and black (B) is written on the positive side of the waveform shown by S _{N + 1} -I. Black display is possible.

Now, assuming that the number of scanning electrodes is 1000, the scanning signal is applied to the target display pixel once every 1000 times, and only the information signal is continuously applied 999 times. become. The duty at this time is 1
It is defined as 000. This is the applied waveform in the case of full writing. On the other hand, when partial writing is continued, for example, when the number of partial writing scan electrodes is 16, the scanning signal is applied to the target display pixel once every 16 times. Therefore, the duty is 16.

Therefore, a waveform in which the duty was changed from 8 to 1000 was applied to the above-mentioned matrix display cell, and the change in contrast during partial writing was visually observed. Since the change in contrast can be more easily observed when black is written, the waveform of S _{N + 1} -I in FIG. 5 was used.

The results are summarized in the rightmost column of Table 1.

First, in Comparative Examples 1 and 2, as the duty was reduced to 1000, 64 and 16, black in the black writing state became lighter and there was a large contrast change. On the other hand, in the case of Examples 1, 2, 3 and 4, there was almost no change in contrast even when the duty was reduced, and even when the duty was set to 8, black did not become light.

From the above results, the specific resistance value ρ of the liquid crystal is 2
With the × 10 ¹⁰ [Omega] cm or lower resistance liquid, suppress the contrast variation in the partial writing, a high contrast, it is understood that the display of high-speed writing can be realized.

[0095]

As described above, the liquid crystal element of the present invention which utilizes the C1 orientation state for display and uses the low resistance liquid crystal,
The device can achieve high contrast and high speed writing.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a liquid crystal cell of the present invention.

FIG. 2 is an explanatory diagram showing a difference between two kinds of orientation states of C1 and C2.

FIG. 3 is an explanatory diagram showing a relationship among a cone angle, a pretilt angle, and a layer tilt angle in C1 and C2 orientations.

FIG. 4 is an explanatory diagram showing a method for measuring the specific resistance value of liquid crystal.

FIG. 5 is a timing chart showing drive waveforms applied to the liquid crystal element.

[Explanation of symbols]

11a and 11b: glass substrates, 12a and 12b: transparent electrodes, 13a and 13b: insulating films, 14a and 14b: alignment control films, 15: chiral smectic liquid crystals, 16: bead spacers, 17a and 17b: polarizing plates.

Front Page Continuation (72) Inventor Kenji Shinjo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (2)

[Claims] 1. A chiral smectic liquid crystal and a liquid crystal which are opposed to each other with the liquid crystal held therebetween, and an electrode for applying a voltage to the chiral smectic liquid crystal is formed on each of the facing surfaces, and the liquid crystal is aligned. In a liquid crystal device comprising a pair of substrates which are subjected to an alignment treatment in which uniaxial alignment axes intersect each other at a predetermined angle, the chiral smectic liquid crystal has a specific resistance ρ of 2 × 10 ¹⁰ Ωcm or less and the smectic The pretilt angle of the liquid crystal element is α,
If the cone angle is Θ and the tilt angle of the liquid crystal layer is δ, then there are orientation states represented by Θ <α + δ and δ <α, and at least two stable states are exhibited in the orientation state, and their optical axes are A liquid crystal device characterized in that an apparent tilt angle θ _a , which is ½ of the formed angle, and a cone angle Θ of the chiral smectic liquid crystal have a relationship of Θ> θ _a > Θ / 2. 2. The intersection angle of the uniaxial orientation axes is 2 ° to 25.
The chiral smectic liquid crystal element according to claim 1, wherein