JPH1048635A - Liquid crystal element and display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease deterioration in a margin due to burning and to improve driving stability and durability by forming a polyimide layer having a specified structural unit on at least one substrate. SOLUTION: This liquid crystal element has a liquid crystal layer between a pair of substrates equipped with at least an electrode to apply voltage and an orientation controlling layer. Further, a polylmide layer having a structural unit expressed by formula is formed on at least one substrate. In formula, A is a quadrivalent aliphatic hydrocarbon group or aromatic hydrocarbon group, R is a straight chain alkylene group having 2 to 8 carbon atoms, and at least one hydrogen atom in the alkylene chain is replaced by a hydroxyl group. In this method, the polyimide layer having the structural unit expressed by formula is used as at least one orientation controlling layer on the substrate pair.

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a liquid crystal element used for a light valve used in a flat panel display, a projection display, a printer, and the like, and a display device using the same.

[0002]

2. Description of the Related Art Conventionally, as a liquid crystal display element widely used, for example, M. Schad
t) and W. Helfrich
h) "Applied Physics Let"
ters, Vol. 18, No. 4 (published on Feb. 15, 1971), pp. 127 to 128, using a twisted nematic liquid crystal is known.

[0003] A simple matrix type liquid crystal element is known as a typical liquid crystal element. This type has an advantage in that the element can be easily formed and the cost is low. However, when performing time-division driving using a matrix electrode structure with a high pixel density, there is a problem that crosstalk occurs, so that the number of pixels has been limited.
In addition, the response speed is as slow as 10 milliseconds or more, which limits the use as a display.

In recent years, a liquid crystal element called a TFT has been developed for such a simple matrix type element. Since this type creates a transistor for each pixel, the problems of crosstalk and response speed are solved, but as the area becomes larger, it is very difficult to create a liquid crystal element without defective pixels. Further, even if possible, a large cost is incurred.

In order to improve the disadvantages of the conventional liquid crystal device, a liquid crystal device having a bistable structure has been developed by Clark and Lagerwell.
1) (JP-A-56-107216).
No. 4,367,924). As the liquid crystal having the bistability, a ferroelectric liquid crystal having a chiral smectic C phase or a chiral smectic H phase is generally used. Since this ferroelectric liquid crystal performs inversion switching by spontaneous polarization, it has a very fast response speed and can exhibit a bistable state with memory properties. Further, since the viewing angle characteristics are also excellent, it is considered that they are suitable as a high-speed, high-definition, large-area display element or a light valve. Recently, a chiral smectic antiferroelectric liquid crystal device having three stable states has been proposed by Chandani, Takezoe et al. (Japanese Journal of Journal of Japan).
Applied Physics, Vol. 27, 1988
L729 page).

In such a chiral smectic liquid crystal element, for example, as described in "Structure and Physical Properties of Ferroelectric Liquid Crystal" (Corona Co., Atsuo Fukuda, Hideo Takezoe, 1990), a zigzag alignment defect is observed. This causes a problem that the contrast is remarkably reduced due to the occurrence of. This defect is attributable to the fact that the layered structure of the chiral smectic liquid crystal carried between the upper and lower substrates forms two types of chevron structures. Recently, there has been a movement to eliminate the chevron structure having such disadvantages and to realize a layered structure called a bookshelf or a structure similar thereto, thereby realizing a high-contrast good liquid crystal element (for example, “Next-generation liquid crystal display” And Liquid Crystal Materials ", edited by CMC, Atsuo Fukuda, 1992).

As a liquid crystal material exhibiting a book shelf or a structure similar thereto, a liquid crystal compound having a perfluoroether side chain (US Pat. No. 5,262,082,
International Patent Application WO 93/22396, 1993 4th International Conference on Ferroelectric Liquid Crystal P-46, Marc D. Radc
life et al.) are disclosed. This liquid crystal can exhibit a bookshelf or a structure with a small layer tilt angle close to the bookshelf without using an external field such as an electric field, and is suitable for high-speed, high-definition, large-area liquid crystal elements and display devices. However, further improvement is required in terms of driving stability of the liquid crystal element and the like.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such prior art. That is, the driving stability of the liquid crystal element is still insufficient.
In particular, the drive characteristics after writing in white or black are significantly reduced due to the afterimage phenomenon (burn-in). One of the causes of this phenomenon is that the liquid crystal molecules at the interface in contact with the alignment control layer anchor the state of continued writing for some reason, and symmetric switching cannot be performed.
It is considered that an afterimage phenomenon (burn-in) occurs as a result.

As one of the causes at this time, it is thought that the charge generated at the interface between the substrate and the liquid crystal interacts with the liquid crystal molecules at the interface, and as a result, the liquid crystal molecules at the interface are anchored.

Accordingly, the present inventors have alleviated the electrical interaction due to the charging of the liquid crystal molecules at the interface with the alignment control layer,
To provide the liquid crystal cell with an antistatic function, more specifically, to introduce a hydroxyl group into the polymer main chain in the alignment control layer, to increase the hydrophilicity of the alignment control layer to enhance the antistatic function, and to enhance the alignment control layer. It is considered that the memory property of the written state in the liquid crystal molecules near the interface and the anchoring of the liquid crystal molecules are suppressed, and as a result, it is possible to obtain a stable driving characteristic with less afterimage phenomenon (burn-in).

That is, the present invention has been made as a result of intensive studies in order to solve such problems of the prior art. By using a polyimide having a hydroxyl group in the main chain for an alignment control layer, a liquid crystal composition is obtained. In particular, an object of the present invention is to provide a liquid crystal element having excellent driving stability and durability performance and a display device using the same, by uniformly orienting a chiral smectic liquid crystal composition and reducing margin deterioration due to image sticking. Things.

[0012]

That is, the present invention relates to a liquid crystal element having a liquid crystal layer between a pair of substrates having at least an electrode for applying a voltage and an alignment control layer, wherein at least one of the substrates has A liquid crystal element comprising a layer made of polyimide having a structural unit represented by the following general formula (I).

[0013]

Embedded image (In the formula, A represents a tetravalent aliphatic hydrocarbon group or an aromatic hydrocarbon group. R is a straight-chain alkylene chain having 2 to 8 carbon atoms, and R represents a hydrogen atom in the alkylene chain. At least one is substituted with a hydroxyl group.) Further, the present invention is a display device using the liquid crystal element.

In the present invention, it is preferable to use a layer made of polyimide having the structural unit represented by the general formula (I) as at least one of the orientation control layers of the pair of substrates. Further, it is preferable to use a polyimide having the structural unit represented by the general formula (I) as a component of at least one of the alignment control layers of the pair of substrates. Further, it is preferable that the liquid crystal layer is composed of a chiral smectic liquid crystal composition.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present inventors have at least electrodes for applying a voltage, an alignment control layer, and a liquid crystal layer on upper and lower substrates in a liquid crystal element.
Having a polyimide having a structural unit represented by
More specifically, by using a polyimide having a structural unit represented by the following general formula (I) as at least one of the alignment control layers of the upper and lower substrates, the interaction between the alignment control layer and the interfacial liquid crystal molecules is relaxed, and the writing state is reduced. It has been found that the memory performance of the liquid crystal device is suppressed, the afterimage phenomenon (burn-in) is reduced, and the driving stability of the liquid crystal element can be remarkably improved.

[0016]

Embedded image (In the formula, A represents a tetravalent aliphatic hydrocarbon group or an aromatic hydrocarbon group. R is a straight-chain alkylene chain having 2 to 8 carbon atoms, and R represents a hydrogen atom in the alkylene chain. At least one is substituted with a hydroxyl group.)

FIG. 1 is a schematic view showing an example of the chiral smectic liquid crystal device of the present invention. In the figure, 1 is a liquid crystal layer composed of a chiral smectic liquid crystal composition,
Usually, in order to realize bistability, the layer thickness is preferably 5 μm or less. Reference numeral 2 denotes a substrate made of glass, plastic, or the like. 3 is a transparent electrode such as ITO. Reference numeral 4 denotes an orientation control layer, which requires a uniaxial orientation control layer on at least one substrate. Preferably, a polyimide having a structural unit represented by the general formula (I) is used as at least one uniaxial orientation control layer. As a method of forming the orientation control layer, usually on a substrate, a film of a polyamic acid soluble in an organic solvent with a precursor of the above polyimide, formed by a solution coating, and then heated and dehydrated to form a polyimide film. . By rubbing the surface with a fibrous material such as velvet, cloth or paper, a polyimide orientation control layer is obtained.

In the present invention, another orientation control layer other than the above may be used for one substrate. Other methods for forming the orientation control layer include, for example, solution coating, evaporation, or sputtering on a substrate, such as silicon monoxide, silicon dioxide, aluminum oxide, zirconia, magnesium fluoride, cerium oxide, cerium fluoride, or silicon nitride. Substances, silicon carbide, inorganic substances such as boron nitride, polyvinyl alcohol, polyimide, polyimide amide, polyester, polyamide, polyester imide, polyparaxylene, polycarbonate, polyvinyl acetal, polyvinyl chloride, polystyrene, polysiloxane, cellulose resin, melamine resin, It is obtained by forming a film using an organic material such as a urea resin or an acrylic resin, and then rubbing the surface with a fibrous material such as velvet, cloth or paper. In addition, Si
An oblique vapor deposition method in which an oxide or a nitride such as O is vapor-deposited from the oblique direction of the substrate may be used.

The thickness of the orientation control layer is preferably 200 ° or less from the viewpoint of suppressing the reversal electric field generated with the switching of the spontaneous polarization Ps and maintaining good switching performance. Further, the angle is preferably 100 ° or less.

In addition to the orientation control layer, an insulating layer or another organic or inorganic layer may be formed as a short-circuit preventing layer for the upper and lower substrates. Reference numeral 5 denotes a gap control spacer, for example, silica beads or the like is used. 8 is a polarizing plate and 9 is a light source. Switching is performed according to a switching signal from a signal power supply (not shown), and functions as a light valve of a display element. Further, if the three transparent electrodes are arranged in a matrix with upper and lower crosses, pattern display and pattern exposure become possible, and they are used, for example, as displays for personal computers and workstations, and as light valves for printers.

According to the present invention, at least electrodes,
Having an alignment control layer and a liquid crystal layer, and having a polyimide having a structural unit represented by the above general formula (I) in the cell structure. More specifically, as the alignment control layer of at least one of the upper and lower substrates, It is intended to provide a liquid crystal element characterized by using a polyimide having a structural unit represented by (I).

As a specific structure of the polyimide in the present invention, repeating structural units are shown in Table 1 below, but the present invention is not limited to these.

[0023]

[Table 1]

In the present invention, a polyimide having the structural unit represented by the above general formula (I) and another polyimide can be used in combination in the orientation control layer. Specific examples of the method include a blended mixed film with another kind of polyimide and a hybrid film formed by copolymerization with another tetracarboxylic acid and diamine. A hydrocarbon polyimide is generally used as the polyimide other than the polyimide having the structural unit represented by the general formula (I), and its specific structure is represented by the following general formula (IV). Having a structure composed of repeating units.

[0025]

Embedded image (Where K is tetravalent,

[0026]

Embedded image L ₄₁ and L ₄₂ are each independently:

[0027]

Embedded image Or, an alkyl group having 1 to 20 carbon atoms, P _41, P
₄₂ represents an imide bond. M represents a single bond or -O-, and a represents 0, 1, or 2. )

Further, in the liquid crystal element of the present invention, the liquid crystal layer
It is preferably composed of a chiral smectic liquid crystal composition. The chiral smectic liquid crystal composition used in the present invention preferably has a fluorocarbon terminal portion and a hydrocarbon terminal portion, and both terminal portions are bonded by a central nucleus, and has a smectic intermediate phase or a potential smectic intermediate phase. Those containing a liquid crystal compound are desirable.

Generally, the fluorine-containing liquid crystal compound used in the present invention comprises at least two aromatic rings, heteroaromatic rings, aliphatic rings, or substituted aromatic rings, substituted heteroaromatic rings or substituted aliphatic rings. And a central nucleus containing a ring selected from These rings are each other -COO-, -COS-,-
It may be bonded by a functional group selected from HC = N- and -COSe-. Even if these rings are fused,
It may not be condensed. Heteroatoms in the heteroaromatic ring include at least one atom selected from N, O or S. Non-adjacent methylene groups in the aliphatic ring may be replaced by O.

In the fluorine-containing liquid crystal compound, the terminal portion of the fluorocarbon is a group represented by -D ¹ -C _xa F _2xa -X (provided that xa is 1 to 20;
It represents -H or -F, D ¹ is, -CO-O- (C
_{H 2) ra -, - O-} (CH 2) ra -, - (CH 2) ra -,
_{-O-SO 2 -, - SO} 2 -, - SO 2 - (CH 2) ra -,
_{-O- (CH 2) ra -O- (} CH 2) rb -, - (CH 2)
_{ra -N (C pa H 2pa +} 1) -SO 2 -, or - (CH _{2) ra
-N (C pa H 2pa + 1} ) represents the -CO-. ra and r
b is independently 1 to 20; pa is 0 to 4; ), _{^{Or, -D 2 - (C xb F}} 2xb -O) za -C ya F
A group represented by _{2ya + 1} , wherein xb is independently 1 to 10 for each (C _xb F _2xb -O);
Is 1 to 10, za is 1 to 10, and D ² is-
_{CO-O-C rc H 2rc} -, - O-C rc H 2rc -, - C rc H
_{2rc -, - O- (C sa} H 2sa -O) ta -C rd H 2rd -, -
_{O-SO 2 -, - SO} 2 -, - SO 2 -C rc H 2rc -, - C
_rc H _2rc -N (C _pb H _{2pb + 1} ) -SO _2- , -C _rc H _{2rc-
Selected from} N (C _pb H _{2pb + 1} ) —CO— and a single bond;
And rd are independently 1 to 20, sa is independently 1 to 10 for each (C _sa H _2sa -O), and ta is 1
And pb is 0-4. ) Can be used.

Particularly preferably, the following general formula (II):
Alternatively, a fluorine-containing liquid crystal compound represented by (III) can be used.

[0032]

Embedded image In the formula, A ¹ , A ² and A ³ are each independently:

[0033]

Embedded image Represents

Ga, ha and ia each independently represent an integer of 0 to 3 (provided that ga + ha + ia is at least 2). L ¹ and L ² are each independently a single bond, —CO—O
-, -O-CO-, -COS-, -S-CO-, -CO
-Se-, -Se-CO-, -CO-Te-, -Te-
_{CO -, - CH 2 CH 2} -, - CH = CH -, - C≡C
-, - CH = N -, - N = CH -, - CH 2 -O -, -
O-CH ₂ -, - CO- or represent -O-.

Each of X ¹ , Y ¹ , and Z ¹ is a substituent of A ¹ , A ² , and A ³ and independently represents —H, —Cl, —F, —Br, —
_{I, -OH, -OCH 3, -CH} 3, -CN, or -NO
_And ja, ma and na each independently represent an integer of 0-4. J ¹ is —CO—O— (CH ₂ ) _ra —, —O
_{- (CH 2) ra -,} - (CH 2) ra -, - O-SO 2 -,
_{-SO 2 -, - SO 2 -} (CH 2) ra -, - O- (CH 2)
_{ra -O- (CH 2) rb -} , - (CH 2) ra -N (C pa H
_2pa + 1) -SO ₂ -, or _{- (CH 2) ra -N (} C pa H
_{2pa + 1} ) represents -CO-. ra and rb are independently 1
-20 and pa is 0-4.

R ¹ is _{-OC qa} H _{2qa -OC qb} H
_{2qb + 1, -C qa H 2qa} -O-C qb H 2qb + 1, -C qa H 2qa -
_{^{R 3, -O-C qa H}} 2qa -R 3, -CO-O-C qa H 2qa -
R ³ or —O—CO—C _qa H _2qa —R ³ , which may be linear or branched (where R ³ _{is-
O-CO-C qb H 2qb} + 1, -CO-O-C qb H 2qb + 1, -
_{H, -Cl, -F, -CF 3} , -NO 2, represents a -CN, qa and qb are 20 independently). R ² is C
_xa F _2xa -X (X represents -H or -F, x
a is an integer of 1 to 20).

[0037]

Embedded image Wherein A ⁴ , A ⁵ and A ⁶ are each independently

[0038]

Embedded image Represents

Gb, hb and ib are each independently 0 to 3
(Where gb + hb + ib is at least 2). Each of L ³ and L ⁴ is independently a single bond, -C
O-O-, -O-CO-, -CO-S-, -S-CO
-, -CO-Se-, -Se-CO-, -CO-Te
-, - Te-CO -, - (CH 2 CH 2) ka - (ka is 1
To 4), -CH = CH-, -C≡C-, -CH = N-,
_{-N = CH -, - CH 2} -O -, - O-CH 2 -, - CO
-Or -O-.

Each of X ² , Y ² and Z ² is a substituent of A ⁴ , A ⁵ and A ⁶ and independently represents —H, —Cl, —F, —Br,
_{I, -OH, -OCH 3, -CH} 3, -CF 3, -OC
F ₃ , —CN, or —NO ₂ , and each jb, m
b and nb each independently represent an integer of 0 to 4;

J ² is —CO—O—C _rc H _2rc —, —O—
_{C rc H 2rc -, - C} rc H 2rc -, - O- (C sa H 2sa -
O) _ta -C _rd H _2rd- , _-O -SO _2- , -SO ₂ -,-
_{SO 2 -C rc H 2rc -,} - C rc H 2rc -N (C pb H 2pb + 1)
_{-SO 2 -, - C rc H} 2rc -N (C pb H 2pb + 1) -CO-
_Where rc and rd are independently 1-20, sa is independently 1-10 for each (C _sa H _2sa -O), ta is 1-6, pb is 0-4. is there.

[0042] R ⁴ _{is, -O- (C qc H 2qc -O} ) wa -C qd
_{H 2qd + 1, - (C} qc H 2qc -O) wa -C qd H 2qd + 1, -C
_qc H _2qc -R ⁶ , _{-OC qc} H _2qc -R ⁶ , -CO- _OC
qc H _2qc -R ^6, or represents _{-O-CO-C qc H 2qc} -R 6, linear, may be either branched (Here, R
⁶ is _{-O-CO-C qd H 2qd} + 1, -CO-O-C qd H
_{2qd + 1, -Cl, -F,} -CF 3, -NO 2, represents -CN, or -H, qc and qd are independently an integer of 1 to 20, the wa is an integer of 1 to 10). R ⁵ is (C _xb F _2xb
-O) _za -C _ya F _{2ya + 1} (where xb is independently 1 to 10 for each (C _xb F _2xb -O)
And ya is 1 to 10, and za is 1 to 10.)

The compound represented by the general formula (II) is disclosed in Japanese Patent Application Laid-Open No. 2-127553, US Pat.
No. 82,587. Specific examples of such compounds are listed below.

[0044]

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[0045]

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[0046]

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[0047]

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[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

Embedded image

[0055]

Embedded image

The compound represented by the above general formula (III) is described in International Publication WO 93/22396, JP-T-Hei 7-506.
368 can be obtained.
Specific examples of such compounds are listed below.

[0057]

Embedded image

[0058]

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[0059]

Embedded image

[0060]

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[0061]

Embedded image

Further, the above general formulas (II) and (III)
The chiral smectic liquid crystal composition containing the compound represented by the formula (I) generally has a smectic A (S
mA) phase and a smectic C (SmC) phase, but many do not have a cholesteric (Ch) phase. In the case of using this, in order to obtain uniform uniaxial orientation, if the configuration of the orientation control layer on both substrates is different, It is preferable to use a closed element.

For example, a configuration is employed in which the orientation control layer of one substrate is subjected to a uniaxial orientation treatment, and the other substrate is not subjected to the uniaxial orientation treatment. In this case, the use of an orientation control layer made of polyimide having the structural unit represented by the general formula (I) on at least one of the substrates (preferably an orientation control layer that has been subjected to a uniaxial orientation treatment) is particularly problematic. It is preferable in terms of prevention.

Further, specific examples of the chiral compound include those having the following structures, but the present invention is not limited thereto.

[0065]

Embedded image

[0066]

Embedded image

D-1: n = 6, 2R, 5R D-2: n = 6, 2S, 5RD-3: n = 4, 2R, 5RD-4: n = 4, 2S, 5RD-5 : N = 3,2R, 5R D-6: n = 2,2S, 5R D-7: n = 2,2R, 5R D-8: n = 1,2S, 5R D-9: n = 1,2R , 5R

[0068]

Embedded image

D-10: n = 1 D-11: n = 2 D-12: n = 3 D-13: n = 4 D-14: n = 6 D-15: n = 10

[0070]

Embedded image

D-16: n = 8 D-17: n = 10

[0072]

Embedded image

[0073]

Embedded image

[0074]

Embedded image

The chiral smectic liquid crystal composition of the present invention contains other compounds such as dyes and pigments.
It is possible to contain additives such as antioxidants and ultraviolet absorbers.

The liquid crystal device of the present invention constitutes a liquid crystal device having various functions. The most suitable example is the use of the liquid crystal device in a display panel, and the scanning line address shown in FIG. 2 and FIG. A liquid crystal display device is realized by using a communication format using a data format including image information having information and a SYN signal. The reference numerals in the figure are as follows.

101 Chiral Smectic Liquid Crystal Display Device 102 Graphic Controller 103 Display Panel 104 Scan Line Drive Circuit 105 Information Line Drive Circuit 106 Decoder 107 Scan Line 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 image information is generated by the graphic controller 102 of the main unit, and is transferred to the display panel 103 according to the signal transmission means shown in FIGS. The graphic controller 102 includes a CPU (central processing unit, abbreviated as GCPU 112) and a VRAM.
(Image information storage memory) Host CPU 1 with 114 as a core
13 manages image information and communicates with the liquid crystal display device 101. Note that a light source is disposed on the back surface of the display panel.

In the display device of the present invention, since the liquid crystal element as a display medium has good switching characteristics as described above, excellent driving characteristics can be exhibited, and a high-definition, high-speed, large-area display image can be obtained. it can.

The driving method of the liquid crystal element of the present invention is described in, for example, JP-A-59-193426 and JP-A-59-1.
93427, JP-A-60-156046,
The driving method disclosed in Japanese Patent Application Laid-Open No. 60-156047 or the like can be applied.

FIG. 6 is a diagram showing an example of a waveform diagram of the driving method. FIG. 5 is a plan view showing an example of a ferroelectric liquid crystal panel in which matrix electrodes are arranged. The liquid crystal panel 51 shown in FIG.
And three data lines intersecting each other, and a ferroelectric liquid crystal is arranged between the scanning line and the data line at the intersection.

[0082] The S _S is selected scan waveform applied to the selected scanning line in FIG. 6 (A), the non-selection scanning waveform S _N is not selected, I _S is applied to the selected data line The selected information waveform (black), and _IN indicates a non-selected information signal (white) applied to an unselected data line. Also,
In Figure at _{(I S} -S S) and _(I N -S _S) is the voltage waveform applied to pixels on a selected scanning line, the voltage _(I S _-S S)
The pixel to which is applied a black display state, and the voltage ( _IN −
The pixel to which _{S s} ) is applied becomes a white display state.

FIG. 6B shows the driving waveform shown in FIG. 6A, which is a time-series waveform when the display shown in FIG. 4 is performed. In the driving example shown in FIG. 6, the minimum application time of a single polarity voltage Δt corresponds to the time the write phase t ₂ applied to a pixel on a selected scanning line, one line clearing phase t ₁ time 2
It is set to Δt. Now, the values of the parameters V _S , V _R , and Δt of the drive waveform shown in FIG. 6 are determined by the switching characteristics of the liquid crystal material used.

FIG. 7 shows the transmittance T when the drive voltage (V _S + V _I ) is changed while the bias ratio described later is kept constant.
, Ie, the VT characteristic. Here, Δt = 50 μsec, and the bias ratio V _I / (V _I + V
_S ) is fixed at 1/3. The positive side of Fig. 7 is shown in FIG. 6 _(I N _-S S), the negative side _{(I S} -S S) at the indicated waveform when applied _(V S + V _I) final transmission The relationship between the rates is shown. The positive side indicates a case where the previous state is black, the reset direction is white, and the negative side indicates a case where the previous state is white and the reset direction is white.

Here, V ₁ and V ₃ are called an actual drive threshold voltage and a crosstalk voltage, respectively. Also, V ₂ <V ₁ <
The ΔV ₌ V 3 -V ₁ becomes called matrix drivable voltage range and the voltage margin when V _3. V ₃ is a ferroelectric liquid crystal display element drive on, it may be said that generally present. Specifically a voltage value causing switching by _{V B} in the waveform of FIG. _{6 (A) (I N -S} S). Of course, by increasing the bias ratio, it is possible to increase the value of V _3, increasing the bias ratio corresponds to a large amplitude of the information signal, the increase in flickering in image quality, This leads to a decrease in contrast, which is not preferable.

The inventors of the present invention have studied that the bias ratio is 1/3 to
About 1/4 was appropriate. 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 the element configuration, and it goes without saying that an element having a large ΔV is very advantageous for matrix driving.

Similarly, the above-mentioned voltage is kept constant,
Driving can be performed by changing the voltage application time Δt. The above-described voltage may be used as the voltage application time as it is, and in this case, the voltage application time threshold is set to Δt ₁
, And the voltage application time crosstalk value is Δt2,
t ₂ −Δt ₁ ) = ΔT is referred to as a voltage application time margin.

At a certain constant temperature, two states of black and white can be written to the selected pixel according to the two directions of the information signal, and the non-selected pixels maintain the black or white state. The voltage margin or voltage application time margin that can be obtained differs depending on the liquid crystal material and the element configuration, and is unique. In addition, since the drive margins are different depending on the change in the environmental temperature, in the case of an actual display device, it is necessary to set optimal drive conditions for the liquid crystal material, the element configuration, and the environmental temperature.

In order to quantitatively evaluate the drive margin, the voltage application time threshold Δt ₁ and the voltage application time crosstalk value Δt ₂ are measured using a certain drive waveform which is fixed similarly. In many cases, a parameter “M ₂ ” representing the width of these values from the center value as a ratio is used.

[0090]

M ₂ = (Δt ₂ −Δt ₁ ) / (Δt ₂ + Δt ₁ )

[0091]

The present invention will be specifically described below with reference to examples and reference examples.

Reference Example 1 Synthesis of Exemplified Compounds of Polyimide I-1 to No. 1; All of the exemplary compounds of polyimide up to I-8 were polyimides obtained by heating and dehydrating polyamic acid, which is a polyimide precursor and soluble in an organic solvent.

Each of the polyamic acids can be prepared by a known method in the same manner as in the synthesis of a general hydrocarbon-based polyamic acid, and the corresponding diaminohydroxyalkylene and commercially available tetravalent tetracarboxylic dianhydride. Synthesized from the product. The synthesis example is shown below.

[0094]

Embedded image

Example 1 0.5% by weight of Exemplified Compound No. Polyamic acid which is a precursor of I-1 / [N-methylpyrrolidone (NMP) /
(N-butyl cellosolve (n-BC) = 8/2 (weight ratio)) A mixed solution was prepared, and then a pair of glass substrates on each of which a 700-mm-thick ITO film patterned by sputtering was formed as a transparent electrode. Was prepared.

On one of the substrates, the previously prepared polyamic acid solution was applied by a spinner so as to have a film thickness of 50 °, then 5 minutes in an 80 ° C. oven, and then 1 hour in a 200 ° C. oven. The compound was dehydrated and cyclized for 5 hours to give Exemplified Compound No. Film formation of I-1 was performed. This membrane is wrapped with a nylon cloth and has a diameter of 8c.
The film was rubbed with a roller of m to impart uniaxiality to the film.

Of the pair of substrates, 0.5 wt% of a vertical alignment agent and a silane coupling agent (ODS-E) was applied to the remaining substrates.
% Ethyl alcohol solution was applied by a spinner and then dried in an oven at 180 ° C. for 1 hour to form a film.

Of the two substrates, spacer beads were scattered toward the polyimide film, and a thermosetting sealant was printed on the vertically aligned substrate, and the two substrates were bonded together. Thereafter, the cells were thermally cured in a 150 ° C. oven for 1.5 hours to form cells.

A chiral smectic liquid crystal composition shown below was injected into this cell at an isotropic phase temperature to prepare a liquid crystal cell. The liquid crystal composition used here is a mixture of the following compounds in the following ratio.

[0100]

Embedded image

Weight ratio: A / B / C / D / E = 46.4 /
15.5 / 30.9 / 5.2 / 2.0 The physical property parameters of this composition are shown below.

[0102]

(Equation 2)

Using a polarizing microscope under crossed Nicols, the liquid crystal cell was evaluated for orientation and driving margin. Uniform uniform orientation was obtained over the entire surface.

In the evaluation of the driving margin, 30
The drive margin at 0.20 ° C. was 0.200, which was good drive characteristics. Writing was continued for 100 hours in two states of white and black in two adjacent pixels in the cell. When the drive margin of the adjacent two pixels after burning was measured, the margin at 30 ° C. was 0.190.

Example 2 Exemplified Compound No. A polyamic acid which is a precursor of I-1 and a known polyamic acid, LP-64 (manufactured by Toray Industries, Inc.) were mixed at a weight ratio of 1: 1.
% [N-methylpyrrolidone (NMP) / (n-butylcellosolve (n-BC) = 8/2 (weight ratio)] mixed solution was prepared.

Thereafter, in the same manner as in Example 1, the composition was applied to the ITO substrate with a spinner, and then
After that, dehydration and cyclization were performed in an oven at 200 ° C. for 1.5 hours to form a film having a thickness of 50 °. Thereafter, a liquid crystal cell was prepared and evaluated in the same steps as in Example 1. Uniform uniform orientation was obtained over the entire surface.

In the drive margin evaluation, 30
The driving margin at 0.2 ° C. was 0.208, indicating good driving characteristics. Writing was continued for 100 hours in each of the two pixels adjacent to each other in the cell in white and black, and the drive margin after burning of the two adjacent pixels was measured.
At 30 ° C., the margin was 0.188.

Comparative Example 1 A substrate having a patterned transparent electrode on a glass surface was diluted with NMP (N-methylpyrrolidone) by 0.5.
A polyamic acid of a polyimide having the following unit structure of wt% was applied by a spinner. The solvent NMP was heated and vaporized, and the polyamic acid was imidized to form a ring, thereby obtaining a substrate coated with a 50-mm-thick polyimide film. Thereafter, a liquid crystal cell was prepared and evaluated in the same steps as in Example 1.

[0109]

Embedded image

The uniform uniform orientation was obtained over almost the entire surface. In the drive margin evaluation, 30
The drive margin at 0.2 ° C. was 0.215, which was a good drive characteristic. Writing was continued for 100 hours in each of the two pixels adjacent to each other in the cell in white and black, and the drive margin after burning of the two adjacent pixels was measured.
At 30 ° C., the margin was 0.125.

Example 3 0.5% by weight of Exemplified Compound No. Polyamic acid which is a precursor of I-1 / [N-methylpyrrolidone (NMP) /
(N-butyl cellosolve (n-BC) = 8/2 (weight ratio)) A mixed solution was prepared.

Next, a pair of glass substrates on which a 700 ° -thick ITO film patterned by a sputtering method as a transparent electrode was prepared. On these two ITO substrates,
The mixed solution prepared above was applied with a spinner in the same manner as in Example 1, and thereafter, an oven at 80 ° C. for 5 minutes,
Dehydrate and cyclize in an oven at 0 ° C for 1.5 hours,
Exemplified Compound No. having a film thickness of 50 °. 1-1 was formed.

The two substrates were rubbed in the same manner as in Example 1 to impart uniaxiality, and spacer beads were sprayed, and a sealant was printed. After the two substrates were bonded so that the rubbing directions were parallel to each other, they were thermally cured in the same manner as in Example 1 to form a cell.

The following hydrocarbon-based chiral smectic liquid crystal composition was injected into the cell at an isotropic phase temperature under reduced pressure, and cooled to a smectic phase to prepare a liquid crystal element, which was evaluated.

The liquid crystal compounds were mixed with the following liquid crystal compounds in the following wt% to prepare chevron type liquid crystal compositions. In addition, the alphabet which shows the structure of each liquid crystalline compound means the cyclic skeleton shown below.

[0116]

Embedded image

[0117]

Embedded image

The liquid crystal composition had the following phase transition temperatures.

[0119]

(Equation 3) The phase transition temperature of the liquid crystal composition was measured by DSC7 manufactured by PerkinElmer and an alignment film applied to a glass plate and injected into a rubbed liquid crystal cell. The thermosystem FP-80 / FP-82 manufactured by Mettler was used. Was determined by observing with a polarizing microscope while controlling the temperature in a hot stage.

As for the orientation, uniform uniform orientation over the entire surface was obtained. In the drive margin evaluation, the drive margin at 30 ° C. was 0.188, indicating good drive characteristics.
Writing was continued for 100 hours in each of the two pixels adjacent to each other in the cell in white and black, and the drive margin of the adjacent two pixels after burning was measured.
At ° C, the margin was 0.172.

Comparative Example 2 A polyamic acid of 0.5 wt% of a polyimide having the following unit structure diluted with NMP (N-methylpyrrolidone) was applied to two substrates having patterned transparent electrodes on a glass surface by a spinner. Applied. The solvent NMP is heated and vaporized, and the polyamic acid is imidized and ring-closed,
Two substrates coated with a polyimide film having a thickness of 50 ° were obtained. Thereafter, a liquid crystal cell was prepared and evaluated in the same steps as in Example 3.

[0122]

Embedded image

The uniform uniform orientation was obtained over almost the entire surface. In the drive margin evaluation, 30
The driving margin at 0.1 ° C. was 0.194, which was good driving characteristics. Writing was continued for 100 hours in each of the two pixels adjacent to each other in the cell in white and black, and the drive margin after burning of the two adjacent pixels was measured.
At 30 ° C., the margin was 0.095.

[0124]

As described above, in the liquid crystal device of the present invention, by using a polyimide having a hydroxyl group in the main chain, the chiral smectic liquid crystal composition can be uniformly aligned and the margin deterioration due to image sticking can be reduced. This makes it possible to provide a display element having excellent driving stability and durability.

[Brief description of the drawings]

FIG. 1 is a schematic view showing one example of a liquid crystal element of the present invention.

FIG. 2 is a block diagram showing a connection state between a liquid crystal display device according to the present invention and a graphic controller.

FIG. 3 is a timing chart showing an image information communication state between the liquid crystal display device and the graphic controller according to the present invention.

FIG. 4 is a schematic diagram showing a display pattern when actual driving is performed with the time-series driving waveform shown in FIG.

FIG. 5 is a plan view of a liquid crystal panel on which matrix electrodes are arranged.

FIG. 6 is a waveform chart showing an example of a driving waveform used for driving the liquid crystal element of the present invention.

FIG. 7 is a diagram (VT characteristic diagram) showing a change in transmittance when a drive voltage is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Liquid crystal layer 2 Substrate 3 Transparent electrode 4 Alignment control layer 5 Spacer 8 Polarizing plate 9 Light source I ₀ Incident light I Transmitted light 51 Liquid crystal panel 52 Scanning electrode group 53 Information electrode group 101 Chiral smectic 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

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yasushi Shimizu 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (10)

[Claims] 1. A liquid crystal element having a liquid crystal layer between a pair of substrates having at least an electrode for applying a voltage and an alignment control layer, wherein at least one of the substrates is represented by the following general formula (I). A liquid crystal element comprising a layer made of polyimide having a structural unit. Embedded image (In the formula, A represents a tetravalent aliphatic hydrocarbon group or an aromatic hydrocarbon group. R is a straight-chain alkylene chain having 2 to 8 carbon atoms, and R represents a hydrogen atom in the alkylene chain. At least one is substituted with a hydroxyl group.) 2. The liquid crystal device according to claim 1, wherein a layer made of polyimide having a structural unit represented by the general formula (I) is used as at least one alignment control layer of the pair of substrates. 3. The liquid crystal device according to claim 1, wherein a polyimide having a structural unit represented by the general formula (I) is used as a component of at least one alignment control layer of the pair of substrates. 4. The liquid crystal device according to claim 1, wherein the liquid crystal layer is composed of a chiral smectic liquid crystal composition. 5. The fluorine-containing liquid crystal having a chiral smectic liquid crystal composition having a fluorocarbon terminal portion and a hydrocarbon terminal portion, both terminal portions being linked by a central nucleus, and having a smectic intermediate phase or a potential smectic intermediate phase. The liquid crystal device according to claim 4, comprising a compound. 6. The liquid crystal device according to claim 5, wherein the terminal portion of the fluorocarbon in the fluorine-containing liquid crystal compound is a group represented by -D ¹ -C _xa F _2xa -X. (However, the formula xa is 1 to 20, X represents -H or -F, D ¹ _{is, -CO-O- (CH 2)} ra -, - O- (CH
_{2) ra -, - (CH} 2) ra -, - O-SO 2 -, - SO
_{2 -, - SO 2 - (} CH 2) ra -, - O- (CH 2) ra -O
_{- (CH 2) rb -,} - (CH 2) ra -N (C pa H 2pa + 1)
-SO _{2- or-} (CH ₂ ) _ra -N (C _pa H _{2pa + 1} )-
Represents CO-. ra and rb are independently 1 to 20, and pa is 0 to 4. ) 7. A fluorocarbon terminal portion in the fluorine-containing liquid crystal _{^{compounds, -D 2 - (C xb F}} 2xb -O) za
-C _ya F _{2ya + 1} liquid crystal device according to claim 5, wherein the group represented by. (However, in the above formula, xb is the respective (C _xb F
_2xb -O) independently is 1 to 10, ya is 1 to 10, za is 1 to 10, D ² are, -CO-O-C
_rc H _2rc- , _{-OC rc} H _2rc- , -C _rc H _2rc- , _-O
-(C _sa H _2sa -O) _ta -C _rd H _2rd- , -O-SO
_{2 -, - SO 2 -,} - SO 2 -C rc H 2rc -, - C rc H 2rc
_{-N (C pb H 2pb + 1} ) -SO 2 -, - C rc H 2rc -N (C
_pb H _2pb + 1) -CO-, selected from a single bond, rc and r
d is independently 1 to 20, and sa is the respective (C _sa H
_2sa- O) is independently 1 to 10, ta is 1 to 6, and pb is 0 to 4. ) 8. The liquid crystal device according to claim 5, wherein the fluorine-containing liquid crystal compound is a compound represented by the following general formula (II). Embedded image Wherein A ¹ , A ² and A ³ are each independently: Represents ga, ha, and ia each independently represent an integer of 0 to 3 (provided that ga + ha + ia is at least 2). Each L ¹ and L ² is independently a single bond, —CO—O—,
-O-CO-, -COS-, -S-CO-, -CO-S
e-, -Se-CO-, -CO-Te-, -Te-CO
_{-, - CH 2 CH 2 -} , - CH = CH -, - C≡C -, -
CH = N -, - N = CH -, - CH 2 -O -, - O-C
Represents H ₂ —, —CO— or —O—. Each X ¹ ,
Y ¹ and Z ¹ are substituents of A ¹ , A ² and A ³ , and independently
H, -Cl, -F, -Br, -I, -OH, -OC
H ₃ , —CH ₃ , —CN, or —NO ₂ , each representing j
a, ma and na each independently represent an integer of 0 to 4; J
_{^1, -CO-O- (CH 2)} ra -, - O- (CH 2) ra
_{-, - (CH 2) ra} -, - O-SO 2 -, - SO 2 -, -
_{SO 2 - (CH 2) ra} -, - O- (CH 2) ra -O- (C
_{H 2) rb -, - (} CH 2) ra -N (C pa H 2pa + 1) -SO 2
-, or _{- (CH 2) ra -N (} C pa H 2pa + 1) represents the -CO-. ra and rb are independently 1 to 20, pa
Is 0-4. R ¹ is _{-OC qa} H _{2qa -OC qb} H
_{2qb + 1, -C qa H 2qa} -O-C qb H 2qb + 1, -C qa H 2qa -
_{^{R 3, -O-C qa H}} 2qa -R 3, -CO-O-C qa H 2qa -
R ³ or —O—CO—C _qa H _2qa —R ³ , which may be linear or branched (where R ³ _{is-
O-CO-C qb H 2qb} + 1, -CO-O-C qb H 2qb + 1, -
_{H, -Cl, -F, -CF 3} , -NO 2, represents a -CN, qa and qb are 20 independently). R ² is C
_xa F _2xa -X (X represents -H or -F, x
a is an integer of 1 to 20). ] 9. The liquid crystal device according to claim 5, wherein the fluorine-containing liquid crystal compound is a compound represented by the following general formula (III). Embedded image Wherein A ⁴ , A ⁵ , and A ⁶ are each independently: Represents gb, hb, and ib are each independently an integer of 0 to 3 (however, gb + hb + ib is at least 2)
Represents L ³ and L ⁴ are each independently a single bond, -CO-
O-, -O-CO-, -CO-S-, -S-CO-,-
CO-Se-, -Se-CO-, -CO-Te-, -T
e-CO -, - (CH 2 CH 2) ka - (ka is 1 to 4),
-CH = CH-, -C≡C-, -CH = N-, -N = C
_{H -, - CH 2 -O -} , - O-CH 2 -, - CO- or -
Represents O-. Each of X ² , Y ² , and Z ² is a substituent of A ⁴ , A ⁵ , and A ⁶ and independently represents —H, —Cl, —F, —Br, —
_{I, -OH, -OCH 3, -CH} 3, -CF 3, -OC
F ₃ , —CN, or —NO ₂ , and each jb, m
b and nb each independently represent an integer of 0 to 4; J ² is, -C
_{O-O-C rc H 2rc} -, - O-C rc H 2rc -, - C rc H
_{2rc -, - O- (C sa} H 2sa -O) ta -C rd H 2rd -, -
_{O-SO 2 -, - SO} 2 -, - SO 2 -C rc H 2rc -, - C
_rc H _2rc -N (C _pb H _{2pb + 1} ) -SO _2- , -C _rc H _2rc-
N (C _pb H _{2pb + 1} ) —CO—, rc and rd are independently 1 to 20, and sa is the respective (C _sa H _2sa −).
O) independently from 1 to 10, ta from 1 to 6, p
b is 0-4. R ⁴ _{is, -O- (C qc H 2qc -O} ) wa
_{-C qd H 2qd + 1, -} (C qc H 2qc -O) wa -C
_qd H _{2qd + 1} , -C _qc H _2qc -R ⁶ , _{-OC qc} H _2qc-
R ⁶ , -CO- _{OC qc} H _2qc -R ⁶ , or -O-CO-
_{C qc} H 2qc -R ⁶ represents a linear, it may be either branched (wherein, R ⁶ is _{-O-CO-C qd H 2qd} + 1, -
_{CO-O-C qd H 2qd} + 1, -Cl, -F, -CF 3, -N
Represents O ₂ , —CN, or —H, qc and qd are each independently an integer of 1 to 20, and wa is an integer of 1 to 10). R
^5, (C _xb F _2xb -O) represented by _za -C _ya F _{2ya + 1} (where the above formula xb is each (C _xb F _2xb -O)
Is independently 1 to 10, ya is 1 to 10, za
Is 1 to 10.) ] 10. A display device using the liquid crystal element according to claim 1.