JP2660895B2 - Liquid crystal element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal display device and a liquid crystal display.
The present invention relates to a liquid crystal element used for an optical shutter or the like, particularly to a liquid crystal element having a chiral smectic phase, and more particularly to a liquid crystal element having improved display characteristics by improving the alignment state of liquid crystal molecules.

[0002]

2. Description of the Related Art Conventionally, a display device of a type in which transmitted light is controlled in combination with a polarizing element utilizing the refractive index anisotropy of ferroelectric liquid crystal molecules has been proposed by Clark and Lagerwall. (JP-A-56-107216, U.S. Pat.
67,924).

The ferroelectric liquid crystal generally has a non-helical chiral smectic C phase (SmC ^* ) or H phase (SmH ^* ) in a specific temperature range, and responds to an applied electric field in this state. Takes a first optical stable state or a second optical stable state, and maintains the state when no electric field is applied, that is, it has bistability. It has a quick response and is expected to be widely used as a high-speed and storage type display element. In particular, its function is expected to be applied to a large screen and high definition display.

In order for an optical modulator using a liquid crystal having bistability to exhibit predetermined driving characteristics, the liquid crystal disposed between a pair of parallel substrates needs to be driven by the liquid crystal regardless of the state of application of an electric field. It is necessary to be in a state of molecular alignment in which conversion between the two stable states effectively takes place.

In the case of a liquid crystal element utilizing birefringence of liquid crystal, the transmittance under crossed Nicols is represented by the following equation.

[0006]

(Equation 1)

(Where I ₀ is the incident light intensity, I is the transmitted light intensity, θ is the tilt angle, Δn is the refractive index anisotropy, d is the thickness of the liquid crystal layer, and λ is the wavelength of the incident light. )

The tilt angle θ in the above-mentioned non-helical structure appears as an angle in the average molecular axis direction of the twisted liquid crystal molecules in the first and second alignment states. According to the above equation, the maximum transmittance is obtained when the tilt angle θ is an angle of 22.5 °, and the tilt angle θ in a non-helical structure that realizes bistability is as close as possible to 22.5 °. is necessary.

As a method of aligning a ferroelectric liquid crystal, a liquid crystal molecular layer organized by a plurality of molecules forming a smectic liquid crystal is uniaxially aligned along a normal line over a large area. It is desirable that the manufacturing process can be realized by a simple rubbing process.

As an alignment method for a ferroelectric liquid crystal, particularly a chiral smectic liquid crystal having a non-helical structure, for example, US Pat. No. 4,561,726 is known.

[0011]

However, the alignment method used so far, particularly the alignment method using a rubbed polyimide film, has been changed to a non-helical structure exhibiting bistability disclosed by Clark and Ragawall. When applied to a ferroelectric liquid crystal, it has the following problems.

That is, according to the experiments conducted by the present inventors, the tilt angle θ of a non-helical ferroelectric liquid crystal obtained by orientation using a conventional rubbed polyimide film is considered.
(The angle shown in FIG. 3 to be described later) is smaller than the tilt angle H (half the apex angle of the triangular pyramid shown in FIG. 2 to be described later) in the ferroelectric liquid crystal having a helical structure. There was found. In particular, the tilt angle θ of a non-helical structure ferroelectric liquid crystal obtained by orienting with a conventional rubbed polyimide film is generally about 3 ° to 8 °, and the transmittance at that time is about 3% to 5% at most. Met.

As described above, according to Clark and Ragawall, the tilt angle of a ferroelectric liquid crystal having a non-helical structure for realizing bistability has the same angle as the tilt angle of a ferroelectric liquid crystal having a helical structure. In fact, the tilt angle θ in the non-helical structure is smaller than the tilt angle H in the helical structure. Moreover, it has been found that the cause of the tilt angle θ in the non-helical structure being smaller than the tilt angle H in the helical structure is due to the twisted arrangement of the liquid crystal molecules in the non-helical structure.

The alignment state of the chiral smectic liquid crystal produced by the conventional rubbed polyimide alignment film depends on the presence of the polyimide alignment film as an insulator layer between the electrode and the liquid crystal layer. When one polarity voltage for switching from (for example, a white display state) to a second optically stable state (for example, a black display state) is applied, after the application of the one polarity voltage is canceled,
A reverse electric field V _rev of the other polarity was generated in the ferroelectric liquid crystal layer, and this reverse electric field V _rev caused an afterimage in a display. The above-mentioned reverse electric field generation phenomenon is clarified in, for example, "Switching Characteristics of SSFLC" by Akio Yoshida, October, 1987, "Transactions of Liquid Crystal Symposium", pp. 142-143.

On the other hand, for example, Japanese Patent Laid-Open No.
No. 27 proposes a method using an alignment film having a special structure. As a result, an image having a high contrast is displayed, and an alignment without causing an afterimage is achieved.

However, when the rubbing area is large, uneven alignment and threshold unevenness during switching are likely to occur depending on the location. This is because the rubbing treatment induces an angle (pretilt) between the liquid crystal molecules near the substrate interface and the substrate interface, and the nonuniformity of the pretilt value increases when the rubbing area increases. .

Accordingly, an object of the present invention is to provide a liquid crystal element which solves the above-mentioned problems, and in particular, a large tilt angle θ is generated by using a chiral smectic liquid crystal having a non-helical structure, and a high-contrast image can be obtained. It is an object of the present invention to provide a liquid crystal element which can be stably provided with a display having a large area and which does not cause an afterimage.

[0018]

That is, the present invention provides a liquid crystal device having an alignment film on at least one of a pair of parallel substrates provided with a transparent electrode, and interposing a ferroelectric liquid crystal between the substrates. In the above, the alignment film may be a diamine component represented by the following general formula (1), a tetracarboxylic acid represented by the following general formula (2), or a dicarboxylic acid represented by the following general formula (3). Composed of more than one acid component
It is a polyimide or polyimide amide, and at least one of the acid component is a liquid crystal element which is a naphthalene tetracarboxylic acid.

[0019]

Embedded image

(Wherein R ₁ and R ₂ have 1 to 1 carbon atoms)
And 10 alkyl groups or fluoroalkyl groups. However, R ₁ and R ₂ may be the same or different. )

[0021]

Embedded image (Where

[0022]

[Outside 7] Represents a tetravalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. )

[0023]

Embedded image (Where

[0024]

[Outside 8] Represents a divalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. Further, the present invention provides a liquid crystal device having an alignment film on at least one of a pair of parallel substrates provided with transparent electrodes, and a chiral smectic liquid crystal sandwiched between the substrates, wherein the alignment film has the following general formula: It is composed of a diamine component represented by (1) and two or more acid components selected from a tetracarboxylic acid represented by the following general formula (2) and a dicarboxylic acid represented by the following general formula (3).
That a polyimide or polyimide amide, and at least one of the acid component is a liquid crystal element which is a naphthalene tetracarboxylic acid.

Embedded image _(Wherein, R 1, _{R 2} represents an alkyl group or a fluoroalkyl group having 1 to 10 carbon atoms. However, _{R 1}
, R ₂ may be the same or different. )

Embedded image (Where

[Outside 9] Represents a tetravalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. )

Embedded image (Where

[Outside 10] Represents a divalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. Further, the present invention provides a layer structure in which a pair of substrates provided with an alignment film and a plurality of layers organized by a plurality of liquid crystal molecules are formed on at least one substrate, and an arrangement in which formation of a unique helical arrangement structure is suppressed. A chiral smectic liquid crystal in which the layer structure has a bent structure, and the direction of rotation of the bent structure with respect to the adjacent substrate is the same as the direction of lifting rotation of liquid crystal molecules adjacent to the adjacent substrate. A liquid crystal element having the alignment film, wherein the alignment film includes a diamine component represented by the following general formula (1), a tetracarboxylic acid represented by the following general formula (2), and a dicarboxylic acid represented by the following general formula (3): A polyimide or a poiy composed of two or more acid components selected from
The liquid crystal element is a imide, and at least one of the acid components is naphthalenetetracarboxylic acid.

Embedded image _(Wherein, R 1, _{R 2} represents an alkyl group or a fluoroalkyl group having 1 to 10 carbon atoms. However, _{R 1}
, R ₂ may be the same or different. )

Embedded image (Where

[Outside 11] Represents a tetravalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. )

Embedded image (Where

[Outside 12] Represents a divalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. )

Hereinafter, the present invention will be described in detail. FIG. 1 is a schematic view showing one example of the liquid crystal element of the present invention. In FIG. 1, reference numerals 11a and 11b denote In ₂ O ₃ and ITO (Indium Tin Oxide; Indium Tin O _2), respectively.
xide) and the like (glass substrate) covered with transparent electrodes 12a and 12b,
絶 縁 thick insulating films 13a and 13b (for example, SiO ₂ film, T
An iO ₂ film, a Ta ₂ O ₅ film, etc.) and alignment films 14a and 14b each formed of the polyimide and having a thickness of 50 to 1000 mm are laminated.

At this time, the alignment films 14a and 14b that have been rubbed (in the direction of the arrow) are arranged in parallel and in the same direction (the direction A in FIG. 1). Substrates 11a and 11
b, a ferroelectric smectic liquid crystal 15 is disposed, and the distance between the substrates 11a and 11b is small enough to suppress the formation of a helical array structure of the ferroelectric smectic liquid crystal 15 ( For example, 0.1 μm to 3 μm)
The ferroelectric smectic liquid crystal 15 has a bistable alignment state. Ferroelectric smectic liquid crystal 15
Are arranged, the distance between the liquid crystals is sufficiently small as described above.
It is held by a bead spacer 16 (for example, silica beads, alumina beads, etc.) disposed between the substrates 11a and 11b. Reference numerals 17a and 17b denote polarizing plates.

According to the experiments performed by the present inventors, as will be apparent from the examples described below, by using an alignment method using a specific alignment film subjected to a rubbing treatment, a large optical state can be obtained between a bright state and a dark state. It shows high contrast, and particularly produces a large contrast for non-selected pixels during multiplexing driving disclosed in U.S. Pat. No. 4,655,561, etc., and further causes switching during display (after multiplexing driving). (3) An alignment state which does not cause the optical response to be delayed was achieved.

The alignment film used in the present invention comprises a diamine component represented by the general formula (1), a tetracarboxylic acid represented by the general formula (2) and a dicarboxylic acid represented by the general formula (3). Polyimide or polyimide amide composite consisting of two or more acid components selected from
At least one of the acid components is composed of naphthalenetetracarboxylic acid.

Such a polyimide or polyimide amide coating used in the present invention is synthesized by a condensation reaction between a tetracarboxylic dianhydride and a diamine or a tetracarboxylic dianhydride, or a dicarboxylic acid and a diamine as shown below. The resulting polyamic acid is obtained by heat ring closure.

Specific examples of the naphthalenetetracarboxylic acid derivative include 1,4,5,8-naphthalenetetracarboxylic dianhydride 1,2,3,4-naphthalenetetracarboxylic dianhydride 1,2,2 5,6-naphthalenetetracarboxylic dianhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride, and more preferably 1,4,5,8-naphthalenetetracarboxylic dianhydride Anhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride is preferred.

In addition, in the general formula (2),

[0032]

[Outside 13] Specific examples of the tetravalent organic residue include pyromellitic dianhydride, 3,3 ′, 4,4′-tetracarboxybiphenyl dianhydride, 2,3,3 ′, 4′-tetra Examples thereof include carboxybiphenyl dianhydride, 2,3,6,7-tetracarboxyanthracene dianhydride, 3,3 ", 4,4" -tetracarboxyterphenyl dianhydride and the like.

In the general formula (3),

[0034]

[Outside 14] Specific examples of the divalent organic residue include 1,4-dicarboxybenzene, 1,3-dicarboxybenzene,
4,4'-dicarboxybiphenyl, 1,5-dicarboxynaphthalene, 2,3-dicarboxynaphthalene,
Examples thereof include 1,8-dicarboxynaphthalene, 2,6-dicarboxynaphthalene, and 4,4 ″ -dicarboxyterphenyl.

The content of naphthalenetetracarboxylic acid contained in the acid component represented by the general formula (2) is usually 9
0% by weight or less, preferably in the range of 10 to 80% by weight.

As the diamine represented by the general formula (1), a diamine in which R ₁ and R ₂ in the formula are an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group is used. However, R ₁ and R ₂ may be the same or different.

Specific examples of the diamine represented by the general formula (1) include 2,2-bis (4-amino-phenoxy-phenyl) propane, 3,3-bis (4-amino-phenoxy-phenyl) pentane, 4,4-bis (4-amino-phenoxy-phenyl) heptane, 5,5-bis (4
-Amino-phenoxy-phenyl) nonane, 2,2-bis (4-amino-phenoxy-phenyl) butane, 2,
2-bis (4-amino-phenoxy-phenyl) pentane, 2,2-bis (4-amino-phenoxy-phenyl) hexane, 3,3-bis (4-amino-phenoxy-phenyl) hexane, 3,3- Bis (4-amino-phenoxy-phenyl) heptane, 4,4-bis (4-amino-phenoxy-phenyl) octane, 2,2-bis (4-amino-phenoxy-phenyl) -3-methyl-
Butane, 2,2-bis (4-amino-phenoxy-phenyl) -4-methyl-pentane, 2,2-bis (4-amino-phenoxy-phenyl) -5-methyl-hexane and the like can be mentioned.

Other specific examples of the diamine represented by the general formula (1) include 2,2-bis (4-amino-phenoxyphenyl) hexafluoropropane and 2,2-bis (4-amino-phenoxy). Phenyl) decylfluoropentane and the like.

The alignment film in the present invention may be a mixture of polyimides, each of polyimide and polyamide, or a copolymer. In this case, the proportion of the polyimide composed of naphthalenetetracarboxylic acid in the total alignment film is usually 5 to 90% by weight, preferably 10 to 80% by weight. The proportion of the polyimide composed of the acid component represented by the general formula (2) in the total alignment film is generally 0 to 80% by weight, preferably 0 to 70% by weight. The proportion of the polyamide comprising the acid component represented by the general formula (3) in the pre-alignment film is usually 0 to 30% by weight, preferably 0 to 20% by weight.

The number average molecular weight of the polyimide or polyimide amide forming the alignment film in the present invention is, for example, 1
A range of 10,000 to 100,000, preferably 30,000 to 80,000 is desirable.

When an alignment film used in the present invention is provided on a substrate, a polyamide acid or a polyamide acid which is a polyimide precursor or a polyamide acid which has been mixed in advance is mixed with dimethylformamide, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone. To a solution of 0.01 to 40% by weight, and the solution is applied on a substrate by a spinner coating method, a spray coating method, a roll coating method, or the like, and then 100 to 350 ° C., preferably 200 ° C.
The polyimide film can be formed by heating at a temperature of about 300 ° C. to effect dehydration and ring closure. This polyimide film is then rubbed with a cloth or the like.

The thickness of the polyimide film or polyimide amide film used in the present invention is set to about 30 to 1 μm, preferably 200 to 2000 μm. In this case, the use of 13a and 13b for the insulating film shown in FIG. 1 can be omitted. In the present invention, the insulating films 13a and
When a polyimide film is provided on 3b, the thickness of the polyimide film can be set to 200 ° or less, preferably 100 ° or less.

As the liquid crystal substance used in the present invention, a liquid crystal that generates a chiral smectic C phase through an isotropic phase, a cholesteric phase, and a smectic A phase in a temperature decreasing process is preferable. In particular, the pitch in the cholesteric phase is preferably 0.8 μm or more (however, the pitch in the cholesteric phase is measured at the central point in the temperature range of the cholesteric phase). Specific examples of the liquid crystal material include the following liquid crystal materials “A”, “B”, and “C”.
Is preferably used in the following ratio.

[0044]

Embedded image

Liquid crystal (1) [A] ₉₀ / [B] ₁₀ (2) [A] ₈₀ / [B] ₂₀ (3) [A] ₇₀ / [B] ₃₀ (4) [A] ₆₀ / [ B] ₄₀ (5) [C] (The above mixing ratios represent weight ratios, respectively.)

FIG. 2 schematically shows an example of a cell for explaining the operation of the ferroelectric liquid crystal. 21a and 2
Reference numeral 1b denotes a substrate (glass plate) coated with a transparent electrode made of a thin film of In ₂ O ₃ , SnO _2, ITO, or the like, between which a liquid crystal molecule layer 22 is oriented so as to be perpendicular to the glass substrate surface ^. Liquid crystal of (chiral smectic C) phase or SmH ^* (chiral smectic H) phase is enclosed. A bold line 23 represents a liquid crystal molecule, and the liquid crystal molecule 23 has a dipole moment (P⊥) 24 in a direction perpendicular to the molecule. At this time, 1/2 of the angle forming the apex angle of the triangular pyramid represents the tilt angle H in the chiral smectic phase having such a helical structure.

When a voltage equal to or higher than a predetermined threshold is applied between the electrodes on the substrates 21a and 21b, the helical structure of the liquid crystal molecules 23 is released, and the dipole moment (P⊥) 24 is directed in the direction of the electric field. Can change the orientation direction. The liquid crystal molecules 23 have an elongated shape,
It exhibits refractive index anisotropy in its major axis direction and minor axis direction. Therefore, for example, if crossed Nicol polarizers are placed above and below the glass substrate surface, it becomes a liquid crystal optical modulation element whose optical characteristics change depending on the polarity of voltage application. Is easily understood.

The surface stable ferroelectric liquid crystal cell in a bistable alignment state used in the liquid crystal element of the present invention can be made sufficiently thin (for example, 0.1 to 3 μm). As shown in FIG. 3, as the liquid crystal layer becomes thinner, the helical structure of the liquid crystal molecules is unwound and becomes a non-helical structure even when no electric field is applied, and the dipole moment Pa or Pb of the liquid crystal molecule is upward (34a). ) Or downward (34
Take either state of b). In such a cell, FIG.
When electric fields Ea or Eb having different polarities equal to or more than a certain threshold value are applied by the voltage applying means 31a and 31b as shown in FIG.
The dipole moment changes its direction to upward 34a or downward 34b in accordance with the electric field vector of the electric field Ea or Eb, and accordingly, the liquid crystal molecules are in one of the first stable state 33a and the second stable state 33b. Orientation.
At this time, 1/2 of the angle between the first and second stable states corresponds to the tilt angle θ.

The effects obtained by this ferroelectric liquid crystal cell are firstly that the response speed is extremely fast, and secondly that the orientation of liquid crystal molecules has bistability. The second point will be further described with reference to, for example, FIG.
When a is applied, the liquid crystal molecules are oriented to the first stable state 33a, which is stable even when the electric field is turned off. Also, when an electric field Eb in the opposite direction is applied, the liquid crystal molecules are oriented to the second stable state 33b and change the direction of the molecules, but remain in this state even after the electric field is turned off. As long as the applied electric field Ea does not exceed a certain threshold value, each orientation state is also maintained.

Next, FIG. 4 is a sectional view schematically showing an alignment state of liquid crystal molecules aligned by an alignment method using an alignment film in the liquid crystal element of the present invention, and FIG. 5 is a view showing the C-director thereof. .

Reference numerals 51a and 51b shown in FIG. 4 represent an upper substrate and a lower substrate, respectively. 50 is a liquid crystal molecule 52
The liquid crystal molecules 52 are arranged by changing the position along the bottom surface 54 (circle) of the cone 53. 56a and 56b each have a bent structure.
Adjacent substrate 51a having a bent structure of the bent molecular layer 50
And the rotation direction with respect to 51b. 55a and 55b
Is a liquid crystal adjacent to the adjacent substrates 51a and 51b, respectively.
This is the direction in which the molecule 52 rises and rotates.

FIG. 5 is a diagram showing a C-director.
In FIG. 5, U ₁ is the C-director 81 in one stable orientation state, and U ₂ is the C-director 81 in the other stable orientation state. The C-director 81 is a projection of the molecular long axis onto a virtual plane perpendicular to the normal of the liquid crystal molecular layer 50 shown in FIG.

On the other hand, the orientation state produced by the conventional rubbed polyimide film is shown by the C-director diagram in FIG. The orientation state shown in FIG.
Since the torsion of the molecular axis is large from a to the lower substrate 51b, the tilt angle θ is small.

Next, FIG. 7A shows a C-director 81.
Is an explanatory diagram showing the tilt angle θ in the state of FIG. 5 (referred to as a uniform alignment state), and FIG. 7B shows the tilt angle θ in the state where the C-director 81 is in the state of FIG. 6 (referred to as a splay alignment state). FIG. In the figure, reference numeral 60 denotes a rubbing axis applied to the above-mentioned specific polyimide film of the present invention, 61a denotes an average molecular axis in an alignment state U ₁ (one stable alignment state in a uniform), and 61b denotes an alignment state U _2.
The average molecular axis in the (uniform uniform orientation state), 62a is the average molecular axis in the orientation state S ₁ (one stable orientation state in the spray), and 62b is the orientation state S ₂ (the other in the spray state). 2 shows an average molecular axis in a stable alignment state).
The average molecular axes 61a and 61b can be converted by applying opposite polarity voltages exceeding the threshold voltage to each other. The same occurs between the average molecular axes 62a and 62b.

Next, the usefulness of the uniform alignment state with respect to the delay of optical response (afterimage) due to the reverse electric field V _rev will be described. The capacitance C _i of the insulating layer (alignment film) of the liquid crystal cell,
Assuming that the capacitance of the liquid crystal layer is C _LC and the spontaneous polarization of the liquid crystal is Ps, V _{rev which} causes an afterimage is represented by the following equation.

[0056]

(Equation 2)

FIG. 8 is a cross-sectional view schematically showing the charge distribution in the liquid crystal cell, the direction of the spontaneous polarization Ps, and the direction of the reverse electric field V _rev . FIG. 8A shows the distribution state of + and-charges under the memory state before the application of the pulse electric field. At this time, the direction of the spontaneous polarization Ps is from + charges to-charges.

FIG. 8B shows that the direction of the spontaneous polarization Ps immediately after the release of the pulse electric field is opposite to the direction of FIG. 8A (therefore, the liquid crystal molecules are shifted from one stable alignment state to the other). Although the orientation state is reversed), the distribution state of the + and-charges is the same as that in FIG. 8A, so that a reverse electric field V _rev is generated in the liquid crystal in the direction of arrow B. . After a while, the reverse electric field V _rev disappears as shown in FIG. 8C, and the distribution of the + and-charges changes.

FIG. 9 is an explanatory diagram showing a change in optical response in a splay alignment state caused by a conventional polyimide alignment film, in place of a change in tilt angle θ. As shown in FIG. 9, the pulse at the time of electric field application, the average molecular axis U under uniform alignment state of the maximum tilt angle around H average molecular axis S under splay alignment state along the direction of the arrow X ₁ (A) overshoot to _2, immediately after pulsed electric field cancellation is working action of the reverse electric field V _rev as shown in FIG. 8 (b), the average molecular axis S under splay alignment state in the direction of arrow X ₂
(B) the tilt angle θ is reduced to, and by the action of attenuation of the reverse electric field V _rev as shown in FIG. 8 (c), the up average molecular axis S under splay alignment state in the direction of arrow X ₃ (C) A stable alignment state in which the tilt angle θ is slightly increased can be obtained. FIG.
0 is a graph showing the state of the optical response at this time.

According to the present invention, since the alignment film made of the polyimide film having the above-mentioned specific chemical structure is used, in the alignment state, the average molecular axis S (in the splay state shown in FIG. 9) is obtained. A), S (B) and S (C)
, And therefore can be arranged on the average molecular axis that produces a tilt angle θ close to the maximum tilt angle H.
FIG. 11 is a graph showing the state of the optical response of the present invention at this time.

In other words, it can be said that the use of the alignment film of the present invention enables the uniform alignment state described above to be obtained.

[0062]

The present invention will be described more specifically with reference to the following examples. Example 1 A 1.1 mm thick ITO film was provided.
Prepare two thick glass plates, and on each glass plate,
1,4,5,8-naphthalenetetracarboxylic dianhydride 30% by weight, pyromellitic dianhydride 35% by weight,
Polyamide acid obtained by a condensation reaction of 100 parts by weight of an acid component composed of 35% by weight of 3 ', 4,4'-tetracarboxybiphenyl dianhydride and 100 parts by weight of a diamine represented by the following structural formula (4) N-methylpyrrolidone / n
A 3.0% by weight solution of -butyl cellosolve = 1/1 was applied for 30 seconds by a spinner having a rotation speed of 3000 rpm.

[0063]

Embedded image

After the film formation, a heating and baking treatment was performed at 250 ° C. for about 1 hour. The number average molecular weight of the obtained orientation control film is about 5
It was 10,000. The number average molecular weight indicates a value measured by gel permeation chromatography (GPC). At this time, the film thickness was 300 °. This coating film was subjected to a one-way rubbing treatment with a nylon flocking cloth.

Thereafter, alumina beads having an average particle size of about 1.5 μm were sprayed on one of the glass plates, and the two glass plates were overlapped so that the respective rubbing treatment axes were parallel to each other and in the same treatment direction. Together, a cell was produced.

Into this cell, "CS-1014" (trade name), a ferroelectric smectic liquid crystal manufactured by Chisso Corporation, was vacuum-injected under an isotropic phase, and then 0.5 cm from the isotropic phase.
Orientation could be achieved by gradually cooling to 30 ° C. at 30 ° C./h. The phase change in the cell of this example using this ferroelectric liquid crystal “CS-1014” was as follows.

[0067]

(Equation 3) (Iso. = Isotropic phase, Ch = cholesteric phase, SmA
= Smectic A phase, SmC ^* = Chiral smectic C phase)

The liquid crystal cell described above is sandwiched between a pair of 90 ° crossed Nicol polarizers, a 30 V pulse of 50 μsec is applied, and the 90 ° crossed Nicol is set to the extinction position (darkest state). Was measured with a photomultiplier. Subsequently, a -30 V pulse of 50 μsec was applied, and the transmittance (bright state) at this time was measured by the same method. The tilt angle θ was 15 °, and the transmittance in the darkest state was 1. 0%, bright state transmittance 50%
Met. Therefore, the contrast ratio was 50: 1.

The delay of the optical response that causes the afterimage is 0.
It was less than 2 seconds. When this liquid crystal cell was displayed by multiplexing drive using the drive waveform shown in FIG. 12, high-contrast, high-quality display was obtained. After displaying an image by inputting a predetermined character, the liquid crystal cell was completely erased to a white state. However, the occurrence of afterimages could not be read.

Further, the value of pretilt was examined for the uniformity of alignment in the liquid crystal element. At the time of measurement, an orientation film was formed and rubbing treatment was performed in the same manner as in the cell preparation in Example 1, and then two glass plates were overlapped so that the rubbing treatment axes were parallel to each other and in the opposite treatment directions to form a cell. Created.

The measurement was performed in the SmA phase by the crystal rotation method. Measurements were taken at nine locations on the liquid crystal cell. The maximum value α _max is 18 ° and the minimum value α _min is 17.5.
The value of Δα in ° was 0.5 °. In addition, when the unevenness of the threshold value at the time of switching in the actual multiplexing drive was observed, there was no difference even in a large area, and good results were obtained.

In FIG. 12, S _N , S _{N + 1} , and S _{N + 2} represent the voltage waveforms applied to the scanning lines, and I represents the voltage waveform applied to typical information lines. (IS
_N ) is a composite waveform applied to the intersection of the information line I and the scanning line _SN . In the present embodiment, V ₀ = 5 to 8 V,
The test was performed at ΔT = 20 to 70 μsec.

Examples 2 to 13 An orientation control film (number average molecular weight was about 50,000 in each example) obtained by using 100 parts by weight of the carboxylic acid component and 100 parts by weight of the diamine component shown in Tables 1 to 4 and A cell was obtained in the same manner as in Example 1 except that a liquid crystal material was used. The same test as in Example 1 was performed for each.

Tables 5 and 6 show the results of the contrast ratio and the delay time of the optical response, the uniformity of the alignment in the liquid crystal element, and the difference Δα between the maximum value and the minimum value of the pretilt. When the display was performed by the multiplexing drive in the same manner as in the first embodiment, the same results as in the first embodiment were obtained with respect to the contrast and the afterimage. In addition, the ratio of the acid component in a table | surface shows a weight%.

[0075]

[Table 1]

[0076]

[Table 2]

[0077]

[Table 3]

[0078]

[Table 4]

[0079]

[Table 6]

(Note) Evaluation of uniformity in the liquid crystal element A: Uniform alignment without threshold unevenness. ：: There is some threshold unevenness depending on the location during switching.

Comparative Examples 1 to 8 Cells were prepared in exactly the same manner as in Example 1 except that the alignment control films shown in Tables 7 and 8 or the acid component, the diamine component and the liquid crystal material were used. Table 9 shows the results of the contrast ratio and the delay of the optical response for each cell, and for Comparative Examples 1 to 4, the results of the uniformity of the orientation of the liquid crystal element and the difference Δα between the maximum and minimum values of the pretilt. Indicated.

When a display was performed by the same multiplexing drive as in the first embodiment, the contrasts of Comparative Examples 5 to 8 were smaller than those of the present embodiment.
Moreover, an afterimage occurred. Further, with respect to the uniformity of the orientation and the threshold value at the time of switching in Comparative Examples 1 to 4, when the area was large, the unevenness occurred slightly as compared with the present example.

[0083]

[Table 7]

[0084]

[Table 8]

[0085]

[Table 9]

[0086]

As described above, according to the liquid crystal device of the present invention, the contrast in the bright state and the dark state is high, especially the display contrast at the time of the multiplexing drive is very large, and the area is wider than the conventional one. In this case, a high-quality display was obtained in which non-uniformity of the threshold value during switching did not occur. In addition, an effect of preventing a remarkable afterimage phenomenon from occurring can be obtained.

[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 perspective view showing an alignment state of a chiral smectic liquid crystal having a helical structure.

FIG. 3 is a perspective view showing an orientation state of a chiral smectic liquid crystal having a non-helical molecular arrangement.

FIG. 4 is a cross-sectional view showing an alignment state of a chiral smectic liquid crystal aligned by an alignment method using an alignment film according to the present invention.

FIG. 5 is a C-director diagram of the chiral smectic liquid crystal of FIG. 4 in a uniform alignment state.

FIG. 6 is a C-director diagram in a splay alignment state.

FIG. 7A is an explanatory diagram showing a tilt angle θ in a uniform orientation state, and FIG. 7B is an explanatory diagram showing a tilt angle θ in a splay orientation state.

[8] The charge distribution of the ferroelectric in a liquid crystal, a cross-sectional view showing the orientation of the orientation and the reverse electric field V _rev of the spontaneous polarization P _s.

FIG. 9 is an explanatory diagram showing a change in a tilt angle θ at the time of applying an electric field and after the electric field is applied.

FIG. 10 is a graph showing optical response characteristics of a conventional liquid crystal element.

FIG. 11 is a graph showing optical response characteristics of the liquid crystal element of the present invention.

FIG. 12 is a waveform diagram of a driving voltage used in an example of the present invention.

[Explanation of symbols]

11a, 11b Glass substrate 12a, 12b Transparent electrode 13a, 13b Insulating film 14a, 14b Alignment film 15 Ferroelectric smectic liquid crystal 16 Bead spacer 17a, 17b Polarizing plate 21a, 21b Substrate 22 Liquid crystal molecular layer 23 Liquid crystal molecule 24 Dipole moment 31a , 31b Voltage applying means 32 Vertical layer 33a First stable state 33b Second stable state 34a Upward dipole moment 34b Downward dipole moment H Tilt angle in helical structure θ Tilt angle in non-helical structure Ea, Eb Electric field 50 the average molecular axis in the average molecular axis 62a orientation state S ₁ in the average molecular axis 61b oriented state U ₂ of the liquid crystal molecular layer 51a under the substrate 51b substrate 52 liquid crystal molecules 53 cone 54 bottom 60 rubbing axis 61a oriented state U ₁ the average molecular axis 8 at 62b orientation state S ₂ C- director

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Takeshi Kadoba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-3-6529 (JP, A)

Claims (10)

(57) [Claims] 1. A liquid crystal device having an alignment film on at least one of a pair of parallel substrates provided with a transparent electrode and a ferroelectric liquid crystal sandwiched between the substrates, wherein the alignment film has the following general formula ( and the diamine component represented by 1), a polyimide composed of two or more acid components selected from the dicarboxylic acid represented by the tetracarboxylic acid or the following general formula represented by the following general formula (2) (3) Or Polyimi
A liquid crystal device , which is doamide, and at least one of the acid components is naphthalenetetracarboxylic acid. Embedded image _(Wherein, R 1, _{R 2} represents an alkyl group or a fluoroalkyl group having 1 to 10 carbon atoms. However, _{R 1}
, R ₂ may be the same or different. ) (Where: Represents a tetravalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. ) (Where: Represents a divalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. ) 2. The method according to claim 1, wherein the tetracarboxylic acid component is 1,4,4.
5,8-naphthalenetetracarboxylic dianhydride, 1,
2,3,4-naphthalenetetracarboxylic dianhydride,
1,2,5,6-naphthalenetetracarboxylic dianhydride
And 2,3,6,7-naphthalenetetracarboxylic acid
Claims that are at least one member selected from the group consisting of water products
Item 2. The liquid crystal element according to item 1. 3. A liquid crystal device having an alignment film on at least one of a pair of parallel substrates provided with transparent electrodes and having a chiral smectic liquid crystal sandwiched between the substrates, wherein the alignment film has the following general formula (1). ) And a diamine component represented by:
Polyimide or a polyimide composed of two or more acid components selected from tetracarboxylic acids represented by the following general formula (2) and dicarboxylic acids represented by the following general formula (3)
A polyimide amide, and at least one of
A liquid crystal element, wherein the seed is naphthalenetetracarboxylic acid. Embedded image (In the formula, R ₁ and R ₂ represent an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group, provided that R ₁ and R ₂
May be the same or different. ) (Where: Represents a tetravalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. ) (Where: Represents a divalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. ) 4. The method according to claim 1, wherein the tetracarboxylic acid component is 1,4,4.
5,8-naphthalenetetracarboxylic dianhydride, 1,
2,3,4-naphthalenetetracarboxylic dianhydride,
1,2,5,6-naphthalenetetracarboxylic dianhydride
And 2,3,6,7-naphthalenetetracarboxylic acid
Claims that are at least one member selected from the group consisting of water products
Item 4. A liquid crystal device according to item 3. 5. A layer structure in which at least one substrate has a pair of substrates provided with an alignment film and a plurality of layers organized by a plurality of liquid crystal molecules, and an array structure in which formation of a unique helical array structure is suppressed. A liquid crystal comprising a chiral smectic liquid crystal, wherein the layer structure has a bent structure, and the direction of rotation of the bent structure with respect to an adjacent substrate is the same as the direction in which liquid crystal molecules adjacent to the adjacent substrate float. In the device, the alignment film is selected from a diamine component represented by the following general formula (1), a tetracarboxylic acid represented by the following general formula (2), and a dicarboxylic acid represented by the following general formula (3). Polyimide or polyimide amide composed of two or more different acid components
There, and a liquid crystal element in which at least one of the acid component is characterized in that it is a naphthalene tetracarboxylic acid. Embedded image (In the formula, R ₁ and R ₂ represent an alkyl group having 1 to 10 carbon atoms or a fluoroalkyl group, provided that R ₁ and R ₂
May be the same or different. ) (Where: Represents a tetravalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. ) (Where: Represents a divalent organic residue comprising an aromatic ring, an aromatic polycyclic ring or a condensed polycyclic ring. ) 6. The method according to claim 1, wherein the tetracarboxylic acid component is 1,4,4.
5,8-naphthalenetetracarboxylic dianhydride, 1,
2,3,4-naphthalenetetracarboxylic dianhydride,
1,2,5,6-naphthalenetetracarboxylic dianhydride
And 2,3,6,7-naphthalenetetracarboxylic acid
Claims that are at least one member selected from the group consisting of water products
Item 6. A liquid crystal device according to item 5. Wherein said alignment film is formed by rubbing in one direction according liquid crystal device in claim 5. Alignment film formed by rubbing a unidirectional parallel and the same directions to each other provided the wherein said pair of substrates
The liquid crystal device according to claim 5 . 9. The chiral smectic liquid crystal has a temperature range in which a smectic A phase is generated on a higher temperature side than a temperature range of the chiral smectic C phase, and is cooled to a chiral smectic C phase via the temperature range of the smectic A phase. 6. A liquid crystal device according to claim 5 , wherein the liquid crystal device comprises: 10. has a temperature range that yields smectic A phase and a cholesteric phase to the high temperature side than the temperature range of the chiral smectic liquid crystal is a chiral smectic C phase, said cholesteric phase, via the temperature range of smectic A phase Chiral 6. The liquid crystal device according to claim 5, which is a liquid crystal cooled to a smectic C phase.