JP3416374B2 - Liquid crystal alignment treatment method, liquid crystal element manufacturing method, and liquid crystal element - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a terminal display for computers, various flat panel displays, word processors, typewriters, television sets, viewfinders for video cameras, light valves for projectors, light valves for liquid crystal printers, etc. The present invention relates to an alignment technique in a liquid crystal element used and the liquid crystal element.

[0002]

2. Description of the Related Art Conventionally, a CRT has been known as a display that has been most widely used, and is widely used as a moving image output of a television, a VTR or the like, or a monitor of a personal computer. However, due to the characteristics of the CRT, in a still image, flicker or scanning stripes due to insufficient resolution may reduce the visibility, or the phosphor may deteriorate due to burn-in. Also, recently CRT
It can be seen that the electromagnetic waves generated by the VDT have a bad effect on the human body, which may impair the health of the VDT worker. And
Due to the structure, it has a large volume behind the screen, so the office,
This is an obstacle to saving space in the home.

There is a liquid crystal display element as a means for solving such a drawback of the CRT. For example, M. Shut (M.
Schadt and W. Helfrich (W. He)
lfrich) "Applied Physics Letters"("Applied Physics Letter")
rs ") Vol. 18, No. 4 (published February 15, 1971), pages 127-128, twisted nematic: T
N) A liquid crystal is known.

As one of the liquid crystal elements using the TN liquid crystal, there is a simple matrix type liquid crystal element which is superior in cost. This liquid crystal element has a problem in that cross-talk occurs during time-divisional driving using a matrix electrode structure having a high image density, so that the number of pixels is limited.

In recent years, a liquid crystal element called TFT has been developed for such a simple matrix type liquid crystal element. This type creates a transistor in each pixel and controls the operation in each pixel, so that the problem of crosstalk and response speed is solved, but the larger the area, the more liquid crystal elements without defective pixels. Is very difficult to produce industrially, and even if it is possible, it costs a lot.

In order to improve the drawbacks of the conventional liquid crystal element, the display of the type in which the transmitted light rays are controlled by utilizing the anisotropy of the refractive index of the ferroelectric liquid crystal molecules in combination with the polarizing element. A device has been proposed by Clark and Lagerwall (JP 56-107216, U.S. Pat. No. 436).
7924). This ferroelectric liquid crystal generally has a chiral smectic C phase or a chiral smectic H phase in a specific temperature range, and in this state, in response to an applied electric field, the first optical stable state and the second optical stable state. Has one of two stable states, and has the property of maintaining that state when no electric field is applied, that is, bistability, and because it performs inverting switching by spontaneous polarization, it exhibits a very fast response speed. , A bistable state having a memory property can be expressed. Further, since it has excellent viewing angle characteristics, it is considered that it is particularly suitable as a high-speed, high-definition, large-area display element or light valve. Recently, Chandani and Takezoe have proposed a chiral smectic antiferroelectric liquid crystal device having three stable states (Japanese Journal of Applied Physics).
nal of Applied Physics) 27
Vol., 1988, p.729).

In such a chiral smectic liquid crystal element, for example, as described in "Structure and Physical Properties of Ferroelectric Liquid Crystal" (Corona Publishing Co., Atsuo Fukuda, Hideo Takezoe, 1990), a zigzag alignment defect is formed. There is a problem that the contrast may be deteriorated due to the occurrence of the phenomenon and twist of liquid crystal molecules between the upper and lower substrates (referred to as splay alignment). This defect is considered to be due to the fact that in the device structure, the layered structure of the chiral smectic liquid crystal sandwiched between the upper and lower substrates forms two types of chevron-shaped (mountain-shaped) structures.

As one method of solving this problem, by giving a pretilt angle optimally, the chevron layer structure is aligned in one direction, and the twisted state between the upper and lower substrates of liquid crystal molecules is uniform (called uniform orientation). There is a method of making the elastic energy unstable.

As another method, a chevron structure in which a liquid crystal layer structure is folded in a V shape is replaced with a layer structure called bookshelf which is a bookshelf structure in which each layer has a small inclination and is arranged substantially in parallel. Structure (hereinafter,
This structure is referred to as a bookshelf) to eliminate zigzag defects and at the same time realize uniform orientation and achieve high contrast (for example, "next-generation liquid crystal display and liquid crystal material" CMC, Fukuda). Atsuo, 1992). In order to realize a structure close to a bookshelf layer, one method is to adjust the material prescription and use a naphthalene-based liquid crystal material. In this case, the tilt angle is about 10 ° and the theoretical maximum transmission is obtained. Rate is obtained 22.
It is very small compared to 5 ° and has a problem of low transmittance. Another typical example is a method of inducing a bookshelf structure by externally applying an electric field to a liquid crystal element having a chevron structure, which is unstable to external stimuli such as temperature. Is a problem.

As a liquid crystal exhibiting a layer structure close to that of a bookshelf, a liquid crystal compound having a perfluoroether side chain (US Pat. No. 5,262,082), a liquid crystal composition (4th ferroelectric liquid crystal in 1993) International Conference P-46, M
arc D. Radcliffe et al.) Have been proposed. According to these liquid crystal materials, a bookshelf or a structure close to the bookshelf with a small layer tilt angle can be revealed with an optimum tilt angle without using an external field such as an electric field. However, the liquid crystal compound having the above-mentioned perfluoroether side chain generally does not have a cholesteric phase, and when it is used in a cell applied to a normal ferroelectric liquid crystal, a sufficiently good alignment state is finally obtained. Was difficult to obtain.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances.
It is to obtain a good alignment state in a liquid crystal device using a liquid crystal that does not take a cholesteric phase. In particular, a liquid crystal layer having a structure in which the layer inclination is small and which is substantially close to a bookshelf structure is stably taken, and a particularly excellent alignment state is obtained, and high contrast, fast response speed, high definition and high brightness are provided. Is to be realized.

[0012]

That is, the present invention is directed to a chiral smectic that undergoes a phase transition in the order of an isotropic phase and a smectic phase under a temperature decrease condition in which at least one is sandwiched between a pair of electrode substrates having an orientation control layer. A method for aligning liquid crystal, wherein the liquid crystal is subjected to a temperature cycle treatment between a temperature range in which an isotropic phase and a smectic phase are mixed and a temperature range in which the smectic phase is exhibited. It is in the orientation treatment method.

Further, according to the present invention, a chiral smectic liquid crystal is heat-sealed in a cell structure having at least one of a pair of electrode substrates having an orientation control layer facing each other, and then cooled to a smectic phase, As opposed to
Provided is a method for producing a liquid crystal element, which comprises a step of performing a temperature cycle treatment between a temperature range in which an isotropic phase and a smectic phase are mixed and a temperature range in which a smectic phase is exhibited.

Further, according to the present invention, there is provided a liquid crystal element in which a chiral smectic liquid crystal is sandwiched between a pair of electrode substrates, at least one of which has an orientation control layer, wherein the liquid crystal has an isotropic phase and a smectic phase. There is provided a liquid crystal element characterized by being subjected to a temperature cycle treatment between a mixed temperature range and a temperature range in which a smectic phase is exhibited.

The "temperature cycle treatment" in the present invention
The heating process up to the mixed temperature range region of the isotropic phase / smectic phase (specifically, for example, heating from the SmC ^* phase to the mixed temperature region of the I phase / SmA phase) and the mixed temperature region to the smectic phase. Cooling process (specifically, for example, from the mixed temperature region of I phase / SmA phase to SmC
^* Processing including cooling).

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION According to the method of the present invention, in a device having a structure in which a chiral smectic liquid crystal is sandwiched between a pair of electrode substrates, at least one of which has an orientation control layer, the chiral smectic liquid crystal has a smectic phase and a smectic liquid crystal. It is preferable because it reduces the alignment defects generated in the A phase, and is most preferable as the alignment treatment method for the liquid crystal that does not take the cholesteric phase during the temperature lowering process. Hereinafter, this point will be described in detail.

Bistability is exhibited in the chiral smectic liquid crystal element by the SmC ^* phase (chiral smectic C phase), and the orientation state is formed by slow cooling from the liquid phase (isotropic phase). Therefore, the phase series between the isotropic phase and the chiral smectic phase has a great influence on the alignment formation. From thermodynamic stability, as a phase series, 1) Iso-Ch-SmA-SmC ^* 2) Iso --- SmA-SmC ^* 3) Iso-Ch ----- SmC ^* 4) Iso --- There are four possible types of SmC ^* . Where Iso: liquid phase, C
h: cholesteric phase, SmA: smectic A phase.

FIG. 2 is a model of each of the above phases. The liquid crystal composition having the phase series of 1) has an Iso-Ch
In the transition, the long-axis order of the liquid crystal molecules is formed, for example, along the regulation of the uniaxial alignment treatment performed in the liquid crystal element, and C
In the h-SmA transition, a positional order (layer structure) of liquid crystal molecules is formed in accordance with, for example, regulation of uniaxial alignment treatment performed in the liquid crystal element, and tilt of the liquid crystal molecules is expressed by the SmA-SmC ^* transition. It is easy to obtain uniform orientation because the orientation is formed through However, 2), 3),
In the case of the liquid crystal composition having the phase sequence of 4), the long-axis order of the liquid crystal molecules and the layer formation are simultaneously 2), the layer formation and the tilt of the liquid crystal molecules are the same 3), and the long axis direction of the liquid crystal molecules is the same. There is a problem that it is difficult to obtain uniform alignment because a plurality of orders are formed at the same time, as in 4) in which layer formation and tilt are performed simultaneously. The present invention particularly preferably realizes uniform alignment of the liquid crystal composition having the phase sequence of 2) above.

As a result of observing the Iso-SmA phase transition process of the liquid crystal in the liquid crystal device using the substrate subjected to the uniaxial alignment treatment having the phase sequence of the above 2), the present inventor changed from the Iso state as shown in FIG. It was found that in the transition to the smectic A phase, islands of the SmA phase having an approximately elliptical shape (hereinafter referred to as “batones”) were generated, and the phase transition was completed by growing and joining them. It was also found that the orientation defects that appear at that time are due to the fact that the growth directions of the buttones are not aligned and are random. Although the reason for this is not clear, for example, in the liquid crystal element, the stretching degree of the polyimide alignment film that has been rubbed as a uniaxial orientation treatment has unevenness locally, and in the portion where the stretching degree is weak, the liquid crystal molecules are uniaxially treated (rubbing direction). It is considered that the regulation force for aligning the alignment film is weakened, or the uniaxial alignment regulation force of the alignment film is partially weakened due to unevenness of the underlying layer of the alignment film.

In general, a liquid crystal molecule alignment was formed by simply cooling a chiral smectic liquid crystal sample from an isotropic phase to a chiral smectic phase. However, in the case of a liquid crystal having an isotropic phase-smectic phase series, for example, the above-mentioned method is used. For some reason, liquid crystal molecule alignment defects in which the directions of the smectic liquid crystal layers are not aligned are formed as shown in FIG. 4, and leakage of transmitted light from the defective parts causes a marked deterioration of display element characteristics such as display contrast.

Therefore, the present inventor has made extensive studies as to the means for aligning the directions of the generation and growth of the buttones, and as a result, it was found that the temperature range between the mixed temperature range of the isotropic phase and the smectic phase and the temperature range of the smectic phase shown in FIG. It was confirmed that uniform liquid crystal molecule alignment can be obtained by performing a temperature cycle treatment of raising and lowering the temperature, and the present invention has been completed.

In the states shown in FIGS. 3 and 4, the liquid crystal cell, at least one of which has been subjected to the uniaxial alignment treatment, is arranged in crossed Nicols, and the polarization axis is aligned with the uniaxial alignment treatment direction. The dark state in can be observed as the bright state in the smectic A phase. The dimension of the observation surface in FIGS. 3 and 4 is about 100 μm □.

In the present invention, as the liquid crystal which does not take the cholesteric phase in the temperature decreasing process as described above, for example, a material which can be a liquid crystal layer having a bookshelf structure or a liquid crystal layer having a small layer tilt angle close to it is used. However, the method of the present invention is more preferable for improving the alignment state in such a liquid crystal layer structure.

FIG. 1 shows an example of the above-mentioned temperature cycle according to the present invention and the alignment state of liquid crystal molecules in the process.

As shown in FIG. 1, for example, in an element in which a liquid crystal is heated and sealed in a cell structure in which a pair of electrode substrates are opposed to each other, the liquid crystal heated to an isotropic phase is cooled to produce a smectic C phase. In the process of obtaining, a smectic phase buttone in which the directions of the liquid crystal molecules are not aligned is generated during the slow cooling process (alignment a), and by slow cooling as it is, it remains as an alignment defect in the chiral smectic C phase (alignment b). ). In order to remove this alignment defect, by performing a temperature cycle treatment as shown in FIG. 1 in which the upper limit temperature is in the temperature range in which the isotropic phase and the smectic phase coexist and the lower limit temperature is in the temperature range in which the smectic phase is exhibited. , Uniform c, and uniform d can be obtained. Here, one cycle of the temperature cycle process in FIG. 1 is: SmC ^* phase → (temperature increase) → I phase / Sm
Phase A → (cooling down) → SmC ^* phase. The temperature cycle process is one cycle or more.

The reason why a uniform liquid crystal molecule alignment is obtained by the above temperature cycle treatment, which is the greatest feature of the present invention, is as follows.
The present inventor thinks as follows based on the observation results.

Alignment defects formed by simple cooling have a smectic layer structure deviated from the uniaxial alignment treatment direction, especially from the rubbing direction, and are in a state of mismatching with the surrounding alignment state, which is energetically unstable. It is considered to be in a state. Therefore, in the temperature range in which the isotropic phase and the smectic phase coexist, the defect portion is transformed into the isotropic phase or is aligned in a good orientation state around it. By cooling again from this state, the defect portion is oriented in a state similar to that of the surroundings, and a uniform orientation in which the orientation defect is removed is formed. That is, only the alignment defects that once occurred in the smectic phase are selectively brought into an isotropic state in the temperature range in which the isotropic phase and the smectic phase coexist, and then the above-mentioned temperature cycle is performed in order to orient the good smectic phase in the surroundings. Are repeatedly performed to achieve uniform alignment in the smectic phase. Especially in the isotropic phase, the viscosity is low,
Orientation control can be performed quickly and without defects in the state of the SmA phase showing a good orientation state in the surroundings. From such a viewpoint, it becomes a problem which temperature in the temperature range in which the isotropic phase and the smectic phase coexist is optimal, but in the experiment of the present inventor, the temperature is determined to be the isotropic phase and the smectic phase. It is effective at a temperature where phases are mixed.
Preferably, when the temperature at which the phase transition from the isotropic phase to the smectic phase starts is T _PC , (T _PC −3)
℃ or more, more preferably (T _PC -1) ℃
The effect was more remarkable at the above temperatures. Further, regardless of the set upper limit temperature of the above-mentioned temperature cycle, the number of temperature cycles tends to be better, and it is preferable that the time of leaving the mixture at the mixed temperature of the isotropic phase and the smectic phase is longer. In addition, the rate of raising and lowering the temperature (℃ / min)
Alternatively, the set lower limit temperature can be appropriately set in order to adjust the alignment improvement depending on the liquid crystal material used and the characteristics of the film used for the alignment control layer in the cell structure. Further, the heater and the heating chamber are optimally designed to uniformly control the entire liquid crystal cell in a temperature range in which the isotropic phase and the smectic phase coexist.

A configuration example of a liquid crystal element to which the method of the present invention is applied will be described below in detail with reference to FIG.

FIG. 5 shows an example of the liquid crystal element of the present invention.
55 is a liquid crystal layer that is preferably composed of a chiral smectic liquid crystal composition, and preferably, in order to realize the bistability according to the Clark-Ragawell model described above,
The layer thickness (distance between substrates) is preferably 5 μm or less.

Substrates 51a and 51b are made of a highly transparent material such as glass or plastic. 52a,
52b is a transparent electrode such as ITO for applying a voltage to the liquid crystal layer 55. Reference numerals 53a and 53b are alignment control layers for controlling the alignment state of the liquid crystal, and at least one of the alignment control layers on the substrate side is uniaxially aligned. The method for forming the uniaxial orientation control layer is, for example, solution coating or vapor deposition or sputtering on the substrate, and silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, silicon nitride. , Inorganic substances such as silicon carbide and boron nitride, polyvinyl alcohol, polyimide, polyimide amide, polyester, polyamide, polyester imide, polyparaxylene, polycarbonate, polyvinyl acetal, polyvinyl chloride, polystyrene, polysiloxane, cellulose resin, melamine resin, urea Obtained by forming a film using an organic material such as resin, acrylic resin, or a polymer having a naphthalene skeleton, and then rubbing the surface with a fibrous material such as velvet, cloth or paper. That. Further, an oblique evaporation method or the like in which an oxide such as SiO or a nitride is evaporated from the oblique direction of the substrate can also be used. In the liquid crystal layer, when a liquid crystal having a phase transition sequence of isotropic phase → smectic phase (SmA phase / SmC ^* phase) without taking a cholesteric phase under cooling is used, uniaxial alignment treatment is preferably performed only on one substrate side, For example, it is preferable to provide an orientation control layer that has been subjected to a rubbing treatment.

Further, for example, ZnO, ZrO as a short-circuit preventing layer of the pair of substrates is provided between the transparent electrode and the orientation control layer,
An insulating layer such as TaO _x , another organic material layer, or an inorganic material layer may be formed. 54 is a gap control spacer, for example, silica beads or the like is used. 56a, 56
Reference numeral b is a polarizing plate, and a light source is provided on the back surface side of one of the substrates, if necessary. The liquid crystal element is switched according to a switching signal from a signal power source (not shown) and functions as a light valve of the display element. Also, 52a,
If the transparent electrodes 52b are arranged in a matrix in a vertical cross,
It enables pattern display and pattern exposure, and is used as a light valve for displays such as personal computers and workstations, and printers.

Further, by disposing a plurality of R, G, B, W (white) color filter films in a predetermined pattern on one substrate side, it can be applied to a color display.

Further, in the present invention, as the liquid crystal material to be used, the material of series 2) which does not exhibit the cholesteric phase as described above is used. In this case, in the isotropic phase-smectic phase transition of the liquid crystal material under the temperature decrease, the state that the buttone gradually starts to be generated from one substrate side and grows to the other substrate side, and the smectic C phase is generated. In order to obtain a better uniform alignment state, it is preferable to use an element configuration in which the one substrate side has an alignment control layer which is uniaxially oriented and the other substrate side is not uniaxially oriented. To do.

In the liquid crystal element of the present invention, the liquid crystal portion disposed between the pair of substrates (the liquid crystal layer 5 in the structure shown in FIG. 5).
As 5), a chiral smectic liquid crystal, particularly a liquid crystal which is preferably used as a ferroelectric liquid crystal, has the phase transition sequence of 2) described above, and preferably comprises a fluorocarbon terminal chain and a hydrocarbon chain, A chiral smectic liquid crystal composition containing at least one fluorine-containing liquid crystalline compound having both ends bound by a central nucleus and having a smectic mesophase or a latent smectic mesophase is used.

As the fluorine-containing liquid crystalline compound, a compound represented by the following general formula (1) or (2) is particularly preferable.

General formula (1)

[0037]

[Chemical 5] And a, b and c are each independently 0 or 1 to 3
Represents the integer. However, a + b + c is at least 2.

M ₁ and N ₁ are independently -COO-,
-COS -, - COSe -, - COTe -, - CH 2 C
_{H 2 -, - CH = CH} -, - CH = N -, - C≡C-,
_{-CH 2 -O -, - CO -} , - O-, a single bond, its orientation may be either.

X, Y and Z are substituents on B ₁ , D ₁ and E ₁ , which are independently --H, --Cl, --F and --B.
_{r, -I, -OH, -OCH 3} , -CN, representing the -NO _2. l, m, and n each independently represent an integer of 0 to 4.

G ₁ is --COO--C _e H _2e- , _--O --C _e H
_{2e -, - C e H 2e} -, - OSOO -, - OOSO -, -
_{SOO -, - SOOC e H 2e} -, - OC e H 2e -OC e 'H
_{2e '-, - C e H} 2e -N (C p H 2p + 1) -SOO -, - C e
_{H 2e -N (C p H 2p} + 1) -CO- (e, e ' represents an integer of from independently 1 to 20, p represents. An integer from 1 to 4) represents a.

[0041] A ₁ is _{-O-C f H 2f -O-} C g H 2g + 1, -
_{C f H 2f -O-C g} H 2g + 1, -C f H 2f -R ', - O-C f
_{H 2f -R ', - COO-} C f H 2f -R', - OCO-C f
H _2f -R '(R' is _{-Cl, -F, -CF 3, -NO} 2,
_{-CN, -H, -COO-C f} 'H 2f' + 1, -OCO-C
_{f ′} H _{2f ′ + 1} , f, f ′, and g each independently represent an integer of 1 to 20. ), A ₁ may be linear or branched.

R is -C _w F _{2w + 1} , w is 1 to 20
Represents an integer up to. ) General formula (2)

[0043]

[Chemical 6] And a, b and c are each independently 0 or 1 to 3
Represents the integer. However, a + b + c is at least 2.

M and N are independently -COO-,-
COS -, - COSe -, - COTe -, - (CH 2 C
H ₂ ) _d- (d represents an integer of 1 to 4), -C≡C-,
-CH = CH -, - CH = N -, - CH 2 -O -, - C
It represents O-, -O-, or a single bond, and its orientation may be any direction.

Each of X, Y and Z is independently -H and -C.
l, -F, -Br, -I, -OH, -OCH 3, -C
H _3, represents -CF _3, -OCF _3, -CN, and -NO _2. Each of l, m, and n independently represents an integer of 0 to 4.

[0046] G is _{-COO-C e H 2e -,} - O-C e H 2e
_{-, - O (C e "} H 2e" O) t -C e 'H 2e' -, - C e H
_{2e -, - OSOO -, -} SOO -, - SOOC e H
_{2e -, - C e H 2e} -N (C p H 2p + 1) -SOO -, - C e
_{H 2e -N (C p H 2p} + 1) -CO- (e, e ' represents an integer of from 1 independently to 20, p is an integer from 0 to 4 .e "is respectively ( C _{e "} H _2e" O) independently represents an integer of 1 to 10, and t represents an integer of 1 to 6).

[0047] A is _{-O- (C f H 2f -O)} u -C
_{h H 2h + 1, - (} C f H 2f -O) u -C h H 2h + 1, -C f H 2f
_{-W, -O-C f H 2f} -W, -COO-C f H 2f -W, -
_{OCO-C f H 2f -W (} W is -Cl, -F, -CF _3, -
_{NO 2, -CN, -H, -COO} -C h H 2h + 1, -OCO
-C _h H _{2h + 1} , where f and h are independently 1 to 2
Represents an integer of 0. u is an integer of 1 to 10. ), A may be linear or branched.

[0048] R 'is _{- (C x' F 2x '} O) z' is a _{C y 'F 2y' + 1} , x 1 'each (C _x' independently F _2x 'O) to 10 , Y'is an integer from 1 to 10, and z'is an integer from 1 to 10. )

In addition to these, various liquid crystal compounds other than the above structures and optically active compounds can be appropriately used.

In the present invention, specific examples of preferable liquid crystal compounds are listed below.

[0051]

[Chemical 7]

[0052]

EXAMPLES The following experiments were conducted in order to verify the effects of the present invention.

The liquid crystal compounds used in this experiment are shown below.

[0054]

[Chemical 8]

This composition (weight ratio; Compound A / Compound B =
The physical property parameters of 90/5) are shown below.

[0056]

[Chemical 9] Tilt angle (30 ° C.) Θ = 25.8 ° Spontaneous polarization (30 ° C.) Ps = −22.6 (nC / cm ² ) δ (layer tilt angle) = 0 ° (near 30 ° C.) First, the figure A liquid crystal cell as shown in No. 5 was prepared as follows.

An ITO film having a thickness of about 300 nm was formed as transparent electrodes 52a and 52b on glass substrates 51a and 51b having a thickness of 1.1 mm, and an orientation control film was further formed by spin coating.

Film formation was performed on each of the two substrates under different conditions. That is, for one of the substrates 51a, a 2/1 0.4 wt% solution of N-methylpyrrolidone / n-butylcellosolve of LP64 manufactured by Toray Industries, Inc. 2700r was used.
It was hung on a glass substrate rotating at a speed of pm and kept rotating for 20 seconds. After that, pre-drying was performed at 80 ° C. for 5 minutes, and then heat baking treatment was performed at 270 ° C. for 1 hour.
The thickness of the orientation control film 53a formed by this method was 3 nm. As the orientation treatment, a rubbing method using a nylon cloth was applied.

For the other substrate 51b, 2000r
Solution (silane coupling agent; 0.5% by weight of ethanol of ODS-E) on a glass substrate rotating at a speed of pm
The solution) was dropped, and the solution was rotated for 20 seconds. afterwards,
After drying at 80 ° C. for 5 minutes, heat drying treatment was performed at 180 ° C. for 1 hour.

Subsequently, the glass substrate 51 subjected to the orientation treatment
Silica beads having an average particle diameter of 2.0 μm were dispersed as spacers 54 on a, and the other glass substrate 51b was overlaid to prepare a cell.

After the above composition was vacuum-injected into this cell in the isotropic phase, in Experiment 1, liquid crystals were obtained by orienting by slowly cooling to room temperature at 4 ° C./min. As a result of measuring the contrast of the comparative liquid crystal element manufactured as described above, it was 60. In addition, with respect to this liquid crystal element, the isotropic phase-smectic A phase mixed temperature range was 4 ° C. (6
9 ° C to 65 ° C).

Here, the method of evaluating the alignment state and the contrast performed as the method of evaluating the orientation in the present invention will be described.

First, with respect to the alignment state, a liquid crystal element sandwiched in a polarizing plate arranged in crossed Nicols and not subjected to the temperature cycle treatment (Experiment 1) or (Experiment 2 to 7) as described below, Each is observed at a predetermined temperature near the lower limit of the temperature range of SmA in the final slow cooling process. At that time, if there is a region where light escapes at the observation temperature, it is an alignment defect. Then, the crossed Nicols are further rotated so that the light-exiting region (defect region) is brought to the darkest state. The angle formed by the two polarization axes before and after the rotation of the crossed Nicols is the angle at which the liquid crystal molecules of the Sm phase in the defect region deviate from the direction of the liquid crystal molecules in the normal region, that is, the layer normal of the smectic liquid crystal layer (layer method). The degree of the alignment defect is evaluated by this size as the deviation angle in the (line direction). The above observation is based on Sm
Continuously performed in the temperature range of phase A.

"Defect x" There is a defect region in which the normal direction of the smectic layer deviates largely (5 ° or more) from the uniaxial orientation treatment direction (if any, it is judged in this way). “Defect Δ” The normal direction of the smectic layer is a little (1-5
°) There is a defective area that is displaced (if there is even a small amount, it is judged in this way). "No defect" The state where the normal direction of the smectic layer deviates by 1 ° or more does not exist at all.

Liquid crystal elements that were not subjected to the temperature cycle treatment (Experiment 1) or were subjected (Experiment 2) as described later between the polarizing plates arranged in the crossed Nicols were the same at the temperature showing the SmC ^* phase. Drive waveform (20) shown in FIG.
V, 1/3 bias, 1000 duty) is applied. Next, the pulse width is changed, and the element is rotated to an angle at which the darkest transmitted light intensity during driving is obtained at the threshold pulse width of bistable inversion, and the transmitted light intensity at that time is as shown in FIG. 6B. Ib, the transmitted light intensity Iw when the liquid crystal molecules are inverted at that position is detected by a photodirector, and the ratio (I
w / Ib) was used as the evaluation value of contrast. When uniform orientation is not obtained, light leakage from the orientation defect causes I
The b value increases and the contrast decreases.

Next, as Experiments 2, 3 and 4, the above Experiment 1 was conducted.
The liquid crystal element of 4 ° C / mi up to 66 ° C, which is 3 ° C lower than the isotropic phase-smectic A phase transition temperature (69 ° C).
The temperature was raised at n, held for 10 minutes, and then gradually cooled again to room temperature (30 ° C.) at 4 ° C./min, repeated 1, 3 and 5 times (holding time at room temperature is 10 minutes). ,
The contrast is shown in Table 1 below.

Further, as Experiments 5, 6 and 7, the above Experiment 1
The liquid crystal element of 4 ° C / mi up to 68 ° C, which is 1 ° C lower than the isotropic phase-smectic A phase transition temperature (69 ° C).
The temperature was raised at n, held for 10 minutes, and then gradually cooled again to room temperature (30 ° C.) at 4 ° C./min, repeated 1, 3 and 5 times (holding time at room temperature is 10 minutes). ,
The contrast is shown in Table 1 below.

[0068]

[Table 1]

As shown in Table 1, by performing the temperature cycle treatment according to the present invention, even in the chiral smectic liquid crystal having a bookshelf structure having a layer tilt angle close to 0 ° C., a uniform alignment state can be obtained. It turns out that

[0070]

As described above, according to the present invention, in a device using a ferroelectric liquid crystal suitable for high speed, high definition, high brightness, and large area, a bookshelf structure or a layer inclination close to it It is possible to stably obtain a liquid crystal layer having a small structure and obtain a particularly excellent alignment state. As a result, a liquid crystal device having high contrast, high response speed, high definition, high brightness, and large area is realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a temperature cycle according to the present invention and an alignment state of liquid crystal molecules in the process.

FIG. 2 is a diagram modeling each phase of a chiral smectic liquid crystal.

FIG. 3 is a diagram schematically showing a result of observing a phase transition process of a chiral smectic liquid crystal.

FIG. 4 is a schematic diagram for explaining an alignment defect that appears in a liquid crystal molecule that has undergone a phase transition by conventional simple cooling.

FIG. 5 is a schematic view showing an example of a cell configuration according to the liquid crystal element of the present invention.

FIG. 6 is a diagram for explaining a method of measuring the contrast of the liquid crystal element shown in the example.

[Explanation of symbols]

51a, b glass substrate 52a, b transparent electrode 53a, b Alignment film 54 Spacer 55 Liquid crystal layer 56a, b Polarizing plate 57 Sealant

Continuation of the front page (56) Reference JP 63-121021 (JP, A) JP 63-77019 (JP, A) JP 62-30222 (JP, A) JP 60-118823 (JP , A) JP-A-6-186516 (JP, A) JP-A-5-203959 (JP, A) JP-A-4-119326 (JP, A) Actual Kai-hei 1-79019 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1337

Claims (22)

(57) [Claims] 1. A method for orienting a chiral smectic liquid crystal in which at least one is sandwiched between a pair of electrode substrates having an orientation control layer and undergoes a phase transition in the order of an isotropic phase and a smectic phase under a temperature decrease. A method for aligning a liquid crystal, which comprises subjecting the liquid crystal to a temperature cycle treatment between a temperature range in which an isotropic phase and a smectic phase are mixed and a temperature range in which the smectic phase is exhibited. 2. The upper limit temperature of the temperature cycle is (T _PC −3) ° C. or higher, where T _PC is the temperature at which the phase transition from the isotropic phase to the smectic phase begins. 1. The liquid crystal alignment treatment method according to 1. 3. The upper limit temperature of the temperature cycle is (T _PC −1) ° C. or higher, where T _PC is the temperature at which the phase transition from the isotropic phase to the smectic phase starts. 1. The liquid crystal alignment treatment method according to 1. 4. The liquid crystal alignment treatment method according to claim 1, wherein at least one of the substrates is provided with an alignment control layer subjected to uniaxial alignment treatment. 5. The liquid crystal alignment treatment method according to claim 1, wherein the alignment control layer subjected to the uniaxial alignment treatment is provided on only one of the substrates. 6. The method of aligning a liquid crystal according to claim 4, wherein the uniaxial alignment treatment is a rubbing treatment. 7. The liquid crystal alignment treatment method according to claim 5, wherein the uniaxial alignment treatment is a rubbing treatment. 8. The chiral smectic liquid crystal contains at least one compound represented by the following general formula (1) and / or at least one compound represented by the following general formula (2). Item 2. A method for aligning a liquid crystal according to item 1. General formula (1) And a, b, and c each independently represent 0 or an integer of 1 to 3. However, a + b + c is at least 2. M ₁ ,
N ₁ is each independently -COO-, -COS-, -C.
OSe -, - COTe -, - CH 2 CH 2 -, - CH = C
H -, - CH = N - , - C≡C -, - CH 2 -O -, -
It represents CO-, -O-, or a single bond, and its orientation may be any direction. X, Y, and Z are substituents on B ₁ , D ₁ , and E ₁ , and are independently -H, -Cl, -F, -Br,-.
_{I, -OH, -OCH 3, -CN} , represents a -NO _2. l,
m and n each independently represent an integer of 0 to 4. G ₁ is-
_{COO-C e H 2e -,} - O-C e H 2e -, - C e H 2e -,
-OSOO-, -OOSO-, -SOO-, -SOOC
_{e H 2e -, - OC e} H 2e -OC e 'H 2e' -, - C e H 2e -N
_{(C p H 2p + 1)} -SOO -, - C e H 2e -N (C
_{p H 2p + 1) -CO- (} e, e ' represents an integer of from independently 1 to 20, p represents represents.) an integer from 1 to 4. A ₁ is _{-O-C f H 2f -O-} C g H 2g + 1,
_{-C f H 2f -O-C g} H 2g + 1, -C f H 2f -R ', - O-
_{C f H 2f -R ', -} COO-C f H 2f -R', - OCO-
_{C f H 2f -R '(R} ' is -Cl, -F, -CF _3, -NO
_{2, -CN, -H, -COO-} C f 'H 2f' + 1, -OCO-
It represents _{C f 'H 2f' + 1} , f, f ', g each independently 1
Represents an integer from 20 to 20. ), A ₁ may be linear or branched. R is a -C _w F _{2w + 1, w} is from 1 to 20
Represents an integer up to. ) General formula (2) And a, b, and c each independently represent 0 or an integer of 1 to 3. However, a + b + c is at least 2. M, N
Are independently -COO-, -COS-, -COS
e -, - COTe -, - (CH 2 CH 2) d - (d is an integer of from 1 4), - C≡C -, - CH = CH -, -
_{CH = N -, - CH 2} -O -, - CO -, - O-, a single bond, its orientation may be either. Each X,
Y and Z are independently -H, -Cl, -F, -Br, -I,-.
_{OH, -OCH 3, -CH 3,} -CF 3, -OCF 3, -C
N, representing the -NO _2. Each l, m, n is 0 independently
Represents an integer of 4; G is _{-COO-C e H 2e -,} - O-
_{C e H 2e -, - O} (C e "H 2e" O) t -C e 'H 2e' -, - C
_{e H 2e -, - OSOO -} , - SOO -, - SOOC e H 2e
_{-, - C e H 2e -N} (C p H 2p + 1) -SOO -, - C e H
_{2e -N (C p H 2p +} 1) -CO- (e, e ' represents an integer of from independently 1 to 20, p is an integer from 0 to 4 .e "is each (C _e "H _2e" O) independently represents an integer of 1 to 10, t is .A representative of the representative.) an integer from 1 to _{6 -O- (C f H 2f -O} ) u -C h H
_{2h + 1, - (C f} H 2f -O) u -C h H 2h + 1, -C f H 2f -
_{W, -O-C f H 2f} -W, -COO-C f H 2f -W, -O
_{CO-C f H 2f -W (} W is -Cl, -F, -CF _3, -N
_{O 2, -CN, -H, -COO} -C h H 2h + 1, -OCO-
_Represents C _h H _{2h + 1} , and f and h are each independently 1 to 20
Represents the integer. u is an integer of 1 to 10. ), A may be linear or branched. R'is-(C _{x '} F
_{2x 'O) z'} is a _{C y 'F 2y' + 1} , x ' is each (C _x'
F _{2x ′} O) is independently an integer from 1 to 10 and y ′
Is an integer from 1 to 10, and z ′ is an integer from 1 to 10. ) 9. A step of heating and enclosing a chiral smectic liquid crystal in a cell structure in which a pair of electrode substrates each having an orientation control layer are opposed to each other, and an isotropic phase and a smectic phase are mixed with the liquid crystal. And a step of performing a temperature cycle treatment between the temperature range in which the smectic phase is exhibited and the temperature range in which the smectic phase is exhibited. 10. The method for producing a liquid crystal element according to claim 9, wherein the chiral smectic liquid crystal is heat-sealed at a temperature at which it becomes an isotropic phase. 11. The upper limit temperature of the temperature cycle is (T _PC −3) ° C. or higher, where T _PC is the temperature at which the phase transition from the isotropic phase to the smectic phase starts. 9. The method for manufacturing a liquid crystal device according to item 9. 12. The upper limit temperature of the temperature cycle is (T _PC −1) ° C. or more, where T _PC is a temperature at which a phase transition from an isotropic phase to a smectic phase starts. 9. The method for manufacturing a liquid crystal device according to item 9. 13. The method of manufacturing a liquid crystal device according to claim 9, wherein at least one of the substrates is provided with an alignment control layer which has been subjected to a uniaxial alignment treatment. 14. The method of manufacturing a liquid crystal device according to claim 9, wherein the uniaxial alignment control layer is provided on only one of the substrates. 15. The method of manufacturing a liquid crystal device according to claim 13, wherein the uniaxial alignment treatment is a rubbing treatment. 16. The method for manufacturing a liquid crystal device according to claim 14, wherein the uniaxial alignment treatment is a rubbing treatment. 17. The chiral smectic liquid crystal contains at least one compound represented by the following general formula (1) and / or at least one compound represented by the following general formula (2). Item 10. A method for manufacturing a liquid crystal device according to item 9. General formula (1) And a, b, and c each independently represent 0 or an integer of 1 to 3. However, a + b + c is at least 2. M ₁ ,
N ₁ is each independently -COO-, -COS-, -C.
OSe -, - COTe -, - CH 2 CH 2 -, - CH = C
H -, - CH = N - , - CH 2 -O -, - CO -, - O
-, -C≡C-, represents a single bond, and its orientation may be any. X, Y, and Z are substituents on B ₁ , D ₁ , and E ₁ , and are independently -H, -Cl, -F, -Br,-.
_{I, -OH, -OCH 3, -CN} , represents a -NO _2. l,
m and n each independently represent an integer of 0 to 4. G ₁ is-
_{COO-C e H 2e -,} - O-C e H 2e -, - C e H 2e -,
-OSOO-, -OOSO-, -SOO-, -SOOC
_{e H 2e -, - OC e} H 2e -OC e 'H 2e' -, - C e H 2e -N
_{(C p H 2p + 1)} -SOO -, - C e H 2e -N (C
_{p H 2p + 1) -CO- (} e, e ' represents an integer of from independently 1 to 20, p represents represents.) an integer from 1 to 4. A ₁ is _{-O-C f H 2f -O-} C g H 2g + 1,
_{-C f H 2f -O-C g} H 2g + 1, -C f H 2f -R ', - O-
_{C f H 2f -R ', -} COO-C f H 2f -R', - OCO-
_{C f H 2f -R '(R} ' is -Cl, -F, -CF _3, -NO
_{2, -CN, -H, -COO-} C f 'H 2f' + 1, -OCO-
It represents _{C f 'H 2f' + 1} , f, f ', g each independently 1
Represents an integer from 20 to 20. ), A ₁ may be linear or branched. R is a -C _w F _{2w + 1, w} is from 1 to 20
Represents an integer up to. ) General formula (2) And a, b, and c each independently represent 0 or an integer of 1 to 3. However, a + b + c is at least 2. M, N
Are independently -COO-, -COS-, -COS
e -, - COTe -, - (CH 2 CH 2) d - (d is an integer of from 1 4), - C≡C -, - CH = CH -, -
_{CH = N -, - CH 2} -O -, - CO -, - O-, a single bond, its orientation may be either. Each X,
Y and Z are independently -H, -Cl, -F, -Br, -I,-.
_{OH, -OCH 3, -CH 3,} -CF 3, -OCF 3, -C
N, representing the -NO _2. Each l, m, n is 0 independently
Represents an integer of 4; G is _{-COO-C e H 2e -,} - O-
_{C e H 2e -, - O} (C e "H 2e" O) t -C e 'H 2e' -, - C
_{e H 2e -, - OSOO -} , - SOO -, - SOOC e H 2e
_{-, - C e H 2e -N} (C p H 2p + 1) -SOO -, - C e H
_{2e -N (C p H 2p +} 1) -CO- (e, e ' represents an integer of from independently 1 to 20, p is an integer from 0 to 4 .e "is each (C _e "H _2e" O) independently represents an integer of 1 to 10, t is .A representative of the representative.) an integer from 1 to _{6 -O- (C f H 2f -O} ) u -C h H
_{2h + 1, - (C f} H 2f -O) u -C h H 2h + 1, -C f H 2f -
_{W, -O-C f H 2f} -W, -COO-C f H 2f -W, -O
_{CO-C f H 2f -W (} W is -Cl, -F, -CF _3, -N
_{O 2, -CN, -H, -COO} -C h H 2h + 1, -OCO-
_Represents C _h H _{2h + 1} , and f and h are each independently 1 to 20
Represents the integer. u is an integer of 1 to 10. ), A may be linear or branched. R'is-(C _{x '} F
_{2x 'O) z'} is a _{C y 'F 2y' + 1} , x ' is each (C _x'
F _{2x ′} O) is independently an integer from 1 to 10 and y ′
Is an integer from 1 to 10, and z ′ is an integer from 1 to 10. ) 18. A liquid crystal device comprising a pair of electrode substrates, at least one of which has an orientation control layer, between which a chiral smectic liquid crystal is sandwiched, wherein a temperature range in which an isotropic phase and a smectic phase are mixed with the liquid crystal. , A liquid crystal element characterized by being subjected to a temperature cycle between a temperature range exhibiting a smectic phase. 19. The liquid crystal device according to claim 18, wherein at least one of the substrates is provided with an alignment control layer which has been subjected to a uniaxial alignment treatment. 20. The liquid crystal element according to claim 18, wherein an alignment control layer subjected to a uniaxial alignment treatment is provided on only one of the substrates. 21. The liquid crystal device according to claim 19, wherein the uniaxial alignment treatment is a rubbing treatment. 22. The liquid crystal element according to claim 20, wherein the uniaxial alignment treatment is a rubbing treatment.