JP2006337626A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element that achieves sufficient excitation purity only by adding a relatively small amount of a self-assembling gelling agent and that can quickly perform rewriting display. <P>SOLUTION: The display element has a liquid crystal composition containing a cholesteric liquid crystal and a self-assembling gelling agent held between a pair of substrates, and the spectral distribution curve of the element in a planar state of the liquid crystal containing no gelling agent satisfies the following conditions (I) and (II). They are: (I) the curve shows two or more peaks in a wavelength range of 400 nm to 700 nm; and (II) a maximum reflectance R<SB>S</SB>in a wavelength range of 400 nm to less than 500 nm and a maximum reflectance R<SB>L</SB>in a wavelength of 500 nm to 700 nm satisfy a relation of R<SB>L</SB>×0.7≤R<SB>S</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display element.

  Conventionally, a liquid crystal display element using a chiral nematic liquid crystal composition that exhibits a cholesteric phase at room temperature by adding a chiral agent to a nematic liquid crystal is known. In such a liquid crystal display element, a chiral nematic liquid crystal composition is basically sandwiched between a pair of substrates having transparent electrodes, and a liquid crystal is produced by applying a high and low pulse voltage (driving voltage) between the electrodes. The display is switched to the planar (PL) state, the focal conic (FC) state, or the homeotropic (Homeo) state.

In such a display element, for the purpose of black and white display and wide viewing angle display, a polymer and a polymerization initiator are contained in cholesteric liquid crystal, and once the display element is produced, ultraviolet (UV) irradiation or the like is performed to form a polymer. A technique for polymerizing a polymer has been reported (for example, Non-Patent Document 1).
R. Q. Ma, 1 other person, “SID 97 DIGEST”, p.101-104

  However, even if the polymerization is sufficiently performed in the above technique, it is not possible to completely perform polymerization so that the unreacted monomer does not remain. As a result, there has been a problem that the display performance of the element changes. That is, the display color has changed, and the contrast between the PL state and the FC state or Homeo state has decreased. In particular, in the case of the black-and-white display method in which white is displayed in the PL state and black is displayed in the FC state or the Home state, the above problem is significant.

  As a means for improving the contrast, a method is known in which the reflectance in a relatively wide wavelength region in the PL state is increased to improve the whiteness during white display. However, in such a method, it is difficult to select a material for increasing the reflectance in a relatively wide wavelength region in the PL state, or in order to increase the reflectance in a wide wavelength region, it is necessary to increase the cell gap. It became a problem from the viewpoint of driving voltage.

  Therefore, as a result of various examinations, the present applicant has improved the stimulation purity (ie, the whiteness is improved) by adding a self-organizing gelling agent to a chiral nematic liquid crystal composition that exhibits a cholesteric liquid crystal phase at room temperature. It was found that display is possible.

  The present invention is a liquid crystal display element of the type in which such a cholesteric liquid crystal composition contains a self-organizing gelling agent. Further improvement is achieved, and the addition of a relatively small amount of the self-organizing gelling agent is sufficient. An object of the present invention is to provide a liquid crystal display element capable of achieving stimulation purity.

  Another object of the present invention is to provide a liquid crystal display element capable of promptly performing rewriting display.

In the present invention, a liquid crystal composition containing a cholesteric liquid crystal and a self-organizing gelling agent is sandwiched between a pair of substrates, and a spectral distribution curve at the time of planarization without containing the gelling agent has the following condition ( A liquid crystal display element satisfying I) and (II);
(I) It has two or more peaks in the wavelength range of 400 nm or more and 700 nm or less; and (II) The maximum reflectance in the wavelength range of 400 nm or more and less than 500 nm is R _S , and the maximum reflectance in the wavelength range of 500 nm or more and 700 nm or less. When R _L is satisfied, the relationship of R _L × 0.7 ≦ R _S is satisfied.

  The liquid crystal composition of the liquid crystal display element of the present invention is remarkably improved in stimulation purity by the addition of a self-organizing gelling agent. Therefore, the liquid crystal display element can achieve sufficient stimulation purity only by adding a relatively small amount of a self-organizing gelling agent, and as a result, rewriting display can be performed quickly.

FIG. 1 is a schematic view showing a cross-sectional structure of a liquid crystal display element according to an embodiment of the present invention. The liquid crystal display element shown in FIG. 1 has a structure in which a liquid crystal layer (liquid crystal composition) 11 is sandwiched between a pair of substrates 1 and 2. In FIG. 1, transparent electrodes 3 and 4 formed in a plurality of parallel strips are provided on the surfaces of substrates 1 and 2, respectively. The transparent electrode 3 and the transparent electrode 4 are arranged to face each other so as to cross each other. An insulating thin film 5 is coated on the electrodes 3 and 4. Further, an alignment film 7 is formed on the insulating thin film 5. Reference numeral 10 denotes a polymer structure that serves as a space holding member and an adhesive member for both substrates, and 13 denotes a spacer as a space holding member. Reference numeral 12 denotes a sealing material for sealing the liquid crystal composition 11 inside the cell. A black visible light absorbing layer 9 is provided on the outer surface (back surface) of the substrate 2 on the side opposite to the side on which light is incident, if necessary. Instead of providing the visible light absorbing layer 9, the substrate 2 itself having visible light absorptivity may be used.
Hereinafter, main components of the liquid crystal display element will be described in detail.

(Liquid crystal layer)
The liquid crystal layer 11 is made of a liquid crystal composition containing a cholesteric liquid crystal and a self-organizing gelling agent. In the present invention, such a liquid crystal composition is prepared so that a display element obtained without containing a gelling agent exhibits a specific spectral distribution curve (wavelength-reflectance curve) at the time of planarization. That is, the spectral distribution curve at the time of the planarization in the state containing no gelling agent satisfies the following conditions (I) and (II);

  (I) It has two or more, preferably two peaks in the wavelength range of 400 nm or more and 700 nm or less; more preferably one peak exists in the wavelength range of 400 nm or more and less than 500 nm, particularly 400 nm or more and 470 nm or less. The maximum peak is hereinafter referred to as peak A), and another peak is present in the wavelength range of 500 nm to 700 nm, particularly 520 nm to 650 nm (the maximum peak in the range is hereinafter referred to as peak B); and

(II) R _S (see FIG. 2), the maximum reflectance in the wavelength range from 400 nm to less than 500 nm, particularly in the wavelength range from 400 nm to 470 nm, the maximum in the wavelength range from 500 nm to 700 nm, particularly in the wavelength range from 520 nm to 650 nm. When the reflectance is R _L (see FIG. 2),
R _L × 0.7 ≦ R _S , preferably R _L × 0.8 ≦ R _S ≦ R _L × 1
Satisfy the relationship.

The state not containing a gelling agent means a state of the same liquid crystal display element configuration as that of the liquid crystal display element of the present embodiment except that no gelling agent is contained.
The peak is the convex part when the tangential slope of the curve changes from positive to negative when the wavelength is increased from the short wavelength side in the spectral distribution curve, and the peak wavelength at the peak of the convex part is peaked. This is called wavelength.
The planar time means a state in which a pulse voltage is applied to the element when the element exhibits the maximum reflectance at the peak wavelength of selective reflection, and the wavelength-reflection measured from the element at this time. The rate curve is called the spectral distribution curve at the time of planarization.

In the liquid crystal display element exhibiting the spectral distribution curve as described above in the planar state in which no gelling agent is contained, the improvement in stimulation purity due to the addition of the gelling agent is remarkable. Therefore, such a liquid crystal display element can achieve sufficient stimulation purity only by adding a relatively small amount of a self-organizing gelling agent, and as a result, rewritten display can be performed quickly. Although the details of the mechanism by which the improvement of the stimulation purity by the addition of the gelling agent becomes remarkable when the spectral distribution curve is exhibited are not clear, it is considered to be based on the following mechanism. That is, when the above spectral distribution curve is exhibited at the time of planarization (when the scattering component is large), it is presumed that the helical axis of the liquid crystal in the vicinity of the alignment film is inclined moderately. It is considered that only a small amount of gelling agent is required because it is considered that it is only necessary to control the helical axis. On the other hand, when the above spectral distribution curve is not exhibited at the time of planarization (when the scattering component is small), it is presumed that the helical axis of the liquid crystal in the vicinity of the alignment film is perpendicular or nearly perpendicular to the alignment film. In this case, it is considered that the helical axis of the liquid crystal in the bulk and in the vicinity of the alignment film must be controlled, and a large amount of gelling agent needs to be added. In particular, in order to control the helical axis of the liquid crystal in the vicinity of the alignment film, the gelling agent required per molecule increases because the influence of the alignment film is strong. In addition to such alignment control of liquid crystal molecules, it is desirable to adjust the refractive index anisotropy of the liquid crystal composition in an appropriate range. For example, even in the slope of the helical axes are the same, as the refractive index anisotropy of the liquid crystal is large, the scattering component becomes larger R _{s /} R _L approaches 1.

In the case where the above spectral distribution curve is not exhibited in a state where no gelling agent is contained, for example, in the case of a spectral distribution curve at the time of planarization where no gelling agent is contained, R _L × 0.7> R _S is satisfied and 400 nm When there is only one peak in the wavelength range of 700 nm or less, the effect of improving the stimulation purity by adding the gelling agent is remarkably small. Therefore, in order to achieve a predetermined stimulation purity, a relatively large amount of gelling agent is used. It is necessary to contain. Therefore, the increase in viscosity of the liquid crystal composition due to the addition of the gelling agent becomes significant, and the device cannot be rewritten and displayed quickly.

In the present specification, the stimulus purity is one index representing the degree of whiteness and can be measured by the following method. That is, the chromaticity coordinates (x ₁ , y ₁ ) are obtained from the spectral distribution curve, and from the D65 standard (white: x ₀ = 0.3127, y ₀ = 0.329) on the chromaticity coordinates as shown in FIG. The distance (d ₁ ) is calculated. Further, the maximum distance (d ₂ ) in the coordinate (x ₁ , y ₁ ) direction is calculated from the D65 standard (x ₀ , y ₀ ) on the chromaticity coordinates. Next, the ratio (%) of the distance (d ₁ ) to the maximum distance (d ₂ ) is obtained, and this is used as the stimulation purity. A smaller stimulus purity indicates a whiter color.

  In this embodiment, since the improvement of the stimulation purity by the addition of the gelling agent is remarkable, the content of the gelling agent is relatively small. That is, it is 1% by weight or less, particularly 0.4 to 1.0% by weight, preferably 0.6 to 1.0% by weight based on the liquid crystal composition containing a cholesteric liquid crystal and a self-organizing gelling agent. Stimulus purity of 5% can be achieved simply by including the gelling agent in the amount as described above.

The gelling agent belongs to a self-organizing type. Specifically, without adding other means such as UV irradiation, the gelling agent can be self-organized and form a pseudo network structure simply by adding and mixing the gelling agent. is there. By adding a self-organizing type gelling agent, the maximum reflectance R _S can be increased and the stimulation purity can be effectively reduced. Although the detailed mechanism by which such an effect is obtained is not clear, the gelling agent molecules are easily dispersed uniformly at the molecular level in the liquid crystal composition, forming a pseudo network structure by hydrogen bonding, and the network structure is more It is considered to be based on the fact that the helical axis is appropriately tilted and the light is effectively irregularly reflected because it has fine precision and moderate flexibility. In addition, compared with a method of improving the reflectance over a wide wavelength range, it is not necessary to increase the cell gap, so that it can be driven with a low applied voltage and there are few restrictions on material selection.

  A self-organizing gelling agent is an organic compound capable of forming a hydrogen bond between self molecules, for example, an organic compound having at least an intermolecular hydrogen bonding group, preferably an organic compound having an intermolecular hydrogen bonding group and an alkylene group. Compounds. When an organic compound having an alkylene group together with an intermolecular hydrogen bonding group is used as a gelling agent, the formation of a pseudo-network structure is promoted by the intermolecular force between the alkylene groups.

The intermolecular hydrogen-bonding group is not particularly limited as long as it is a group that can form a hydrogen bond between molecules containing the group, and examples thereof include an amide bond group (—NHCO—).
It is desirable that one or more, preferably two or more intermolecular hydrogen bonding groups are contained in the molecule.

The alkylene group is a long-chain alkylene group (hereinafter sometimes referred to as Re), specifically a divalent saturated hydrocarbon group having 4 or more carbon atoms, preferably 6 to 20 carbon atoms, preferably a linear polymethylene group (- is _a) - _(CH 2) _n.
It is desirable that one or more, preferably two or more alkylene groups are contained in the molecule.

The structure of the gelling agent is not particularly limited as long as it is an organic compound having at least an intermolecular hydrogen-bonding group, preferably an intermolecular hydrogen-bonding group and an alkylene group.
Examples of such gelling agents include alicyclic amide compounds represented by the following general formula (I), aliphatic amide compounds represented by the following general formulas (II) to (IV), and And aliphatic urea compounds represented by the formula (V).

In the formula (I), R ¹ is an alkyl group, an aryloxy group or an arylalkoxy group, and these groups optionally have a substituent such as a cyano group.
The alkyl group is an alkyl group having 1 to 3 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, and a sec-propyl group.
The aryloxy group is an aryloxy group having 6 to 14 carbon atoms, and examples thereof include a phenyloxy group, a biphenylyloxy group, and a naphthyloxy group.
The arylalkoxy group is a monovalent group in which 1 to 2 aryl groups having 6 to 14 carbon atoms are substituted with alkoxy groups having 1 to 3 carbon atoms, such as a phenylmethoxy group, a phenylethoxy group, and a phenylpropoxy group. Group, biphenylylmethoxy group, biphenylylethoxy group, biphenylylpropoxy group and the like.
Preferred R ¹ is an alkyl group or an aryloxy group.

Re is the same group as the long-chain alkylene group (Re), and a preferred group is the same as Re.
m is an integer of 1 to 3, preferably 2.
When there are a plurality of the same groups in one formula, these groups may be independently selected from a predetermined range (the same applies hereinafter).

Preferable specific examples of such alicyclic amide compounds (I) include the following compounds.

In formulas (II) to (IV), a common group means the same group.
R ² is the same group as R ¹ described above. Preferred R ² is an arylalkoxy group.
R ³ is a C 1-3 divalent alkylene group, and examples thereof include a methylene group, a dimethylene group, and a trimethylene group. R ³ may have a substituent, and examples of the substituent include the following groups, among which a branched alkyl group having 3 to 5 carbon atoms is preferable.

Re is the same group as the long-chain alkylene group (Re), and a preferred group is the same as Re.
R ⁴ is the same group as R ¹ described above. Preferred R ⁴ is an alkyl group.
R ⁵ is the same group as R ³ described above. Preferred R ⁵ is an alkylene group having no substituent.
n is an integer of 0 to 3, preferably 0 to 1.

Preferred specific examples of such aliphatic amide compounds (II) to (IV) include the following compounds.

In formula (V), R ⁶ is the same as R ⁴ described above, and preferred groups are also the same as R ⁴ described above.
Re is the same group as the long-chain alkylene group (Re), and a preferred group is the same as Re.
R ⁷ is the same as R ⁵ , and a preferred group is the same as R ⁵ .

Preferable specific examples of the aliphatic urea compound (V) include the following compounds.

These compounds can be synthesized according to a known synthesis method.
Of these, the preferred gelling agent is the alicyclic amide compound (I).

  A cholesteric liquid crystal exhibits a cholesteric phase at room temperature. For example, a chiral nematic liquid crystal composed of a nematic liquid crystal and a chiral agent can be used.

  The nematic liquid crystal is not particularly limited, and a nematic liquid crystal conventionally known in the field of liquid crystal display elements can be used. Examples of such nematic liquid crystal materials include liquid crystal ester compounds, liquid crystal pyrimidine compounds, liquid crystal cyanobiphenyl compounds, liquid crystal tolan compounds, liquid crystal phenyl cyclohexane compounds, liquid crystal terphenyl compounds, fluorine atoms, and fluoroalkyls. Other liquid crystalline compounds having a polar group such as a cyano group and a cyano group, and mixtures thereof.

As the chiral agent, various materials conventionally known in the field of liquid crystal display elements can be used. For example, a cholesteric compound having a cholesteric ring, a biphenyl compound having a biphenyl skeleton, a terphenyl compound having a terphenyl skeleton, an ester compound having a skeleton in which two benzene rings are connected by an ester bond, and a cyclohexane ring directly on the benzene ring A cyclohexane compound having a skeleton formed by linking a ring, a pyrimidine compound having a skeleton formed by directly linking a pyrimidine ring to a benzene ring, and an azoxy having a skeleton formed by linking two benzene rings by an azoxy bond or an azo bond Or an azo compound etc. are mentioned.
The content of the chiral agent is not particularly limited as long as the liquid crystal composition containing no gelling agent can exhibit the spectral distribution curve at the time of planarization, and is usually 3 to 40% by weight with respect to the cholesteric liquid crystal. .

A cholesteric liquid crystal has a refractive index anisotropy from the viewpoint of more effectively achieving the spectral distribution curve in a state in which it does not contain a gelling agent, particularly from the viewpoint of more effectively increasing R _S / _RL in the spectral distribution curve. It is preferable that it is 0.14 or more. However, it should not exceed 0.17 from the viewpoint of material stability.

An additive such as an ultraviolet absorber may be further added to the liquid crystal composition.
The ultraviolet absorber is intended to prevent ultraviolet deterioration of the liquid crystal composition, for example, fading or change in responsiveness with time. For example, materials such as a benzophenone compound, a benzotriazole compound, and a salicylate compound can be used. The addition amount is 5% by weight or less, preferably 3% by weight or less with respect to the cholesteric liquid crystal.

Such a liquid crystal composition can be obtained by mixing each material at a predetermined ratio.
If desired, the liquid crystal composition may be purified by contact with an ion exchange resin, an adsorbent or the like to remove moisture and impurities, and then used for manufacturing the device.

(substrate)
In FIG. 1, the substrates 1 and 2 are both translucent, but the pair of substrates that can be used in the above-described liquid crystal display element is at least one substrate (at least the substrate 1 on the light incident side). ) Should have translucency. As the light-transmitting substrate, a glass substrate and a flexible substrate made of a resin such as polycarbonate, polyethersulfone, polyarylate, and polyethylene terephthalate can be used. From the viewpoint of reducing the weight of the element, it is preferable to use a flexible substrate. When a flexible substrate is used as at least one of the pair of substrates, preferably both substrates, a lightweight and thin element can be manufactured and damage (cracking) can be suppressed.

(electrode)
Examples of the electrodes 3 and 4 include transparent conductive films such as ITO (Indium Tin Oxide) and IZO (Indium Zinc Oxide), metal electrodes such as aluminum and silicon, and amorphous silicon. A photoconductive film such as BSO (Bismuth Silicon Oxide) can be used. In the liquid crystal display device shown in FIG. 1, as described above, a plurality of strip-like transparent electrodes 3 and 4 parallel to each other are formed on the surfaces of the transparent substrates 1 and 2, and these electrodes 3 and 4 intersect each other. Are facing each other. In order to form the electrode in this manner, for example, an ITO film may be deposited on the substrate by a masking method using a sputtering method or the like, or an ITO film may be formed on the entire surface and then patterned by a photolithography method.

(Insulating thin film)
Although not essential in principle, an insulating thin film 5 is formed on at least one of the electrodes 3 and 4 in order to prevent a short circuit between the electrodes and to improve the reliability of the gas barrier property of the liquid crystal display element. It is preferable. Examples of the insulating thin film 5 include inorganic films made of silicon oxide, titanium oxide, zirconium oxide, alkoxides thereof, and the like, and organic films such as polyimide resin, epoxy resin, acrylic resin, and urethane resin. It can form by well-known methods, such as a vapor deposition method, a spin coat method, and a roll coat method, using such materials. Furthermore, the insulating thin film can be formed using the same material as the polymer resin used for the polymer structure.

(Alignment film)
Although the alignment film 7 is not essential in principle, the viewpoint of more effectively achieving the spectral distribution curve without containing a gelling agent, in particular, increasing R _S / _RL more effectively in the spectral distribution curve. From the viewpoint, it is preferable to provide a vertical alignment film on at least one, preferably both substrate sides. By providing the vertical alignment film, the spiral axis of the liquid crystal molecules in the vicinity of the alignment film is inclined moderately during planarization, and light irregular reflection occurs, so that R _S / R _L can be increased more effectively.

  The vertical alignment film is a film for vertically aligning the axis of each liquid crystal molecule itself, and acts on the chiral nematic liquid crystal to tilt its helical axis. The degree of alignment of liquid crystal molecules varies depending on the film material.

  Examples of the constituent material of the alignment film include organic films such as polyamic acid, polyimide, modified polyimide, polyamideimide, polyetherimide, silicone resin, polyvinyl butyral, and acrylic resin, and inorganic films such as silicon oxide and aluminum oxide. .

A preferred alignment film is made of polyamic acid or modified polyimide. Such an alignment film contains a polyimide precursor. This precursor changes to polyimide by heat treatment, but since the imidation ratio does not reach 100% in the normal alignment film forming process, the polyimide precursor always remains. In the present embodiment, it is assumed that the remaining precursor appropriately aligns the liquid crystal molecules. If the alignment film is made of the polyamic acid or the modified polyimide, R _S / R _L in the spectral distribution curve. Is very effectively increased.

  Polyamic acid is a polyimide precursor formed from aromatic tetracarboxylic acids and aromatic diamines. Specifically, the aromatic tetracarboxylic acid is a compound having one or more aromatic rings and 4 carboxyl groups in the molecule, or an anhydride thereof.

で示される芳香族テトラカルボン酸二無水物からなる群から選択される少なくとも1種以上の化合物を使用することが好ましい。 Examples of such aromatic tetracarboxylic acids include, for example, the general formula (a);

It is preferable to use at least one compound selected from the group consisting of aromatic tetracarboxylic dianhydrides represented by

等である。式中、Zは2価の連結基であり、例えば、

等である。なお、「―」は両端の基を直接的に連結する単結合を意味する（以下、同様である）。 In the formula (a), R ¹¹ is a tetravalent organic residue having one or more aromatic rings, for example,

Etc. In the formula, Z is a divalent linking group, for example,

Etc. “-” Means a single bond directly connecting groups at both ends (hereinafter the same).

  Preferable specific examples of such aromatic tetracarboxylic dianhydrides include, for example, pyromellitic anhydride (chemical formula (a1)), 4,4′-oxydiphthalic anhydride (chemical formula (a2)), dianhydride 3, 3 ′, 4,4′-benzophenonetetracarboxylic acid (chemical formula (a3)), 4,4 ′-(hexafluoroisopropylidene) diphthalic anhydride (chemical formula (a4)), 3,4,3 ′, 4 ′ -Biphenyltetracarboxylic dianhydride (chemical formula (a5)) and the like. The structural formulas of these specific examples are shown below. The above chemical formula numbers correspond to the following structural formula numbers.

  Aromatic diamines that form polyamic acid are compounds having one or more aromatic rings and two amino groups in the molecule.

で示されるジアミン類からなる群から選択される少なくとも1種以上の化合物を使用することが好ましい。 Examples of such aromatic diamines include the general formula (b);

It is preferable to use at least one compound selected from the group consisting of diamines represented by the formula:

等である。
ｒおよびｓはそれぞれ独立して1または0である（ｒ≧ｓ）。 In formula (b), X is a divalent linking group, for example,

Etc.
r and s are each independently 1 or 0 (r ≧ s).

  The aminophenyl groups at both terminals are each independently a 4-aminophenyl group, a 3-aminophenyl group or a 2-aminophenyl group, preferably a 4-aminophenyl group or a 3-aminophenyl group.

  Preferable specific examples of such diamines include, for example, 4,4′-oxydianiline (chemical formula (b1)), 3,4′-oxydianiline (chemical formula (b2)), 4,4 ′-(1 , 3-phenylenedioxy) dianiline (chemical formula (b3)), diaminodiphenylsulfone (chemical formula (b4)), 3,3 ′-[sulfonylbis (4,1-phenyleneoxy)] dianiline (chemical formula (b5)), 2,2 ′-[sulfonylbis (4,1-phenyleneoxy)] dianiline (chemical formula (b6)), 4,4 ′-(1,1′-biphenyl-4,4′-diyldioxy) dianiline (chemical formula (b7 )), 2,2-bis [4- (4-aminophenoxy) phenyl] propene (chemical formula (b8)), (4 ″ -4 ′ ″-(hexafluoroisopropylidene) -bis (4 Phenoxyaniline) (chemical formula (b9)) and the like. The structural formula of these examples below. It should be noted that corresponding to the following structural formula numbers defined in Formula ID.

  The polyamic acid formed from the aromatic tetracarboxylic dianhydride and the diamine as described above is represented by the following general formula (c1), (c2) or (c3), and may be a mixed structure thereof.

Wherein ^{(c1) ~ (c3),} R 11, r and s are the same as ^{R 11,} r and s mentioned above, respectively. p is an arbitrary positive integer.

  The polyamic acid can be synthesized by dissolving aromatic tetracarboxylic acids and aromatic diamines in a suitable solvent in equimolar amounts to form a solution of, for example, about 20% by weight and polymerizing by heating. The polymerization conditions are not particularly limited as long as a polyamic acid is obtained, and may be sufficiently heated until the polymerization reaches saturation.

ｑは任意の正の整数である。
この種のポリイミドは、ポリイミドの原料となる酸無水物が非対称な化学構造を有するため、ポリイミド形成時の分子間相互作用が小さく溶剤に溶け易くなっている。なお、この可溶性ポリイミドにはポリイミドの前駆体は含まれていない。 The modified polyimide may be a mixture of the polyamic acid and the soluble polyimide or may be chemically bonded. A typical soluble polyimide is a polyimide obtained from a diamine and an acid anhydride having an asymmetric chemical structure, and examples thereof include a polyimide (d) obtained by the following chemical reaction formula.

q is an arbitrary positive integer.
In this type of polyimide, the acid anhydride used as a raw material for the polyimide has an asymmetric chemical structure, so that the intermolecular interaction at the time of polyimide formation is small and it is easy to dissolve in a solvent. This soluble polyimide does not contain a polyimide precursor.

  The alignment film made of polyamic acid or modified polyimide can be formed by the following method, for example. A solution obtained by dissolving polyamic acid or modified polyimide in a coating solvent (for example, a solution of about 4% by weight) is applied using a method such as spin coating or roll coating, and is baked by an oven or a hot plate. The alignment film is formed by baking. The solvent for coating is not particularly limited as long as it dissolves polyamic acid or modified polyimide. Examples thereof include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, and γ-butyrolactone. These solvents can be used alone or in combination of two or more. Furthermore, the coating solution includes butyrocellosolve, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-butoxy-2-propanol, propylene glycol monoacetate, propylene glycol-1-monoethyl ether-2-acetate, 2 -(2-Ethoxypropoxy) propanol, lactic acid n-butyl ester, lactic acid isoamyl ester and the like may be added.

  When polyamic acid is used, the firing conditions are not particularly limited. For example, the firing temperature may be 150 to 300 ° C., and the firing time may be 20 to 120 minutes.

  When the modified polyimide is used, the firing conditions are not particularly limited. For example, the firing temperature may be 150 to 300 ° C., preferably 180 ° C. or less, and the firing time may be 20 to 120 minutes.

The thickness of the alignment film is not particularly limited, and is usually preferably 400 to 800 Å.
The alignment film is formed on the insulating thin film when the insulating thin film is formed on the electrode, and on the electrode when the insulating thin film is not formed on the electrode.
The alignment film may be subjected to a rubbing process or the like.

(spacer)
A spacer 13 is provided between the pair of substrates to keep the gap between the substrates uniform. Examples of the spacer include a sphere made of resin or inorganic oxide. For example, ball-shaped glass, ceramic powder, or spherical particles made of an organic material can be used. Further, a fixed spacer having a surface coated with a thermoplastic resin is also preferably used. In order to keep the gap between the substrates more uniform, it is preferable to provide both the spacer 13 and the polymer structure 10 as shown in FIG. 1, but only one of them may be provided. . When the polymer structure is formed, the spacer has a diameter equal to or less than the height of the spacer, and when the device is completed, the spacer has the same height as the polymer structure. Regardless of the presence or absence of the polymer structure, the diameter of the spacer corresponds to the thickness of the cell gap, that is, the thickness of the liquid crystal layer made of the liquid crystal composition.

(Seal material)
The sealing material 12 is for sealing the liquid crystal composition 11 so that it does not leak from between the substrates 1 and 2, and includes a thermosetting resin such as an epoxy resin or an acrylic resin, or a photocurable adhesive. Can be used.

(Polymer structure)
The polymer structure 10 may have any shape such as a columnar body, an elliptical columnar body, a quadrangular columnar body, the arrangement thereof may be random, and has regularity such as a lattice shape. It may be a thing. By providing such a polymer structure, it becomes easy to keep the gap between the substrates constant, and the self-holding property of the liquid crystal display element itself can be improved. In particular, when dot-shaped polymer structures are arranged at regular intervals, the display performance is easily uniformed. The height of the polymer structure corresponds to the thickness of the cell gap, that is, the thickness of the liquid crystal layer made of the liquid crystal composition. It is particularly effective to provide a polymer structure when a flexible resin substrate is used as a substrate for sandwiching the liquid crystal layer. It is because it can prevent that the thickness of a liquid crystal layer becomes non-uniform | heterogenous because a board | substrate is flexible. It is particularly effective to make the thickness of the liquid crystal layer uniform when a spherical spacer and a polymer structure are used in combination and the polymer structure has a function as an adhesive member for adhering the upper and lower substrates.

To form a polymer structure, a photocurable resin material such as a photoresist material made of an ultraviolet curable monomer is used and applied to the outermost surface film (insulating thin film, alignment film) of the substrate with a desired thickness. A so-called photolithography method can be used in which pattern exposure is performed by irradiating ultraviolet rays through a mask to remove uncured portions.
Alternatively, a polymer structure made of a thermoplastic resin may be formed using a resin material in which a thermoplastic resin is dissolved in an appropriate solvent. In this case, the resin material is applied onto the substrate from the tip of the nozzle, such as a printing method in which printing is performed on the substrate by extruding the thermoplastic resin material with a squeegee using a screen plate or a metal mask, or a dispenser method or an inkjet method. The polymer structure can be arranged by a method of forming by discharging, or a transfer method in which a resin material is supplied onto a flat plate or a roller and then transferred to the substrate surface.

(Scattering layer)
A scattering layer (not shown) may be provided on the surface (upper surface in the figure) of the substrate 1 and / or between the substrate 2 and the visible light absorbing layer 9. By providing the scattering layer, the degree of scattering at the time of white display is increased, and the stimulation purity is improved. Examples of the scattering layer include product name FT-014 (manufactured by Polatechno).

(Cell gap)
As the thickness of the cell gap in the liquid crystal display element, that is, the thickness of the liquid crystal layer made of the liquid crystal composition increases, the reflectance during white display increases, but the reflectance during driving voltage and black display also increases. Therefore, the thickness of the cell gap may be 2 to 50 μm, but 3 to 15 μm is preferable.

  In the liquid crystal display element of the present embodiment as described above, the content of the self-organizing gelling agent in the liquid crystal composition is within the above-mentioned range, and the stimulation purity is 5% or less, particularly 5% and in the three-stage drive system. One line rewrite time is 1 ms or less, particularly 0.2 to 1 ms.

(Production method)
A method for manufacturing a liquid crystal display element according to a preferred embodiment of the present invention is characterized in that a liquid crystal layer is formed using the liquid crystal composition in an unheated state. In the present invention, the addition amount of the gelling agent is relatively small, and the liquid crystal composition exhibits fluidity at room temperature (for example, 25 ° C.). Therefore, the liquid crystal composition can be used at room temperature without heating. Therefore, the manufacturing process is further simplified, and the device can be easily manufactured.

For example, the following methods (1) and (2) can be employed.
(1) A liquid crystal composition is vacuum-injected into an empty cell of a liquid crystal display element at room temperature, and then the injection hole is closed. An empty cell of a liquid crystal display element is produced by heating or / and pressurizing two substrates on which the above-mentioned predetermined constituent members of the liquid crystal display element are formed so that their member formation surfaces face each other. Is possible.

  (2) Applying the liquid crystal composition at room temperature on one of the two substrates on which the above-mentioned predetermined constituent members of the liquid crystal display element are formed, using a coating device such as a spin coater, bar coater, roll coater, etc. Or just dripping. Thereafter, the other substrate is overlaid and sealed by pressing or / and heating.

(Display method)
In the liquid crystal display element having the above configuration, display is performed by applying a pulse voltage from the drive circuit 20 to the electrodes 3 and 4. For example, a PL-FC driving system that performs display by switching the liquid crystal layer between a planar state and a focal conic state may be employed, or the liquid crystal layer may be switched between a planar state and a homeotropic state. A PL-Home drive system that performs display may be adopted.

  For example, in the PL-FC drive system, by applying a relatively high energy pulse voltage (a large voltage value, a large pulse width, etc.), the liquid crystal becomes a planar state, and the pitch and refractive index of the spiral of the liquid crystal molecules are changed. The light having a wavelength determined based on the light is selectively reflected. On the other hand, by applying a pulse voltage having a relatively low energy (a small voltage value, a small pulse width, etc.), the liquid crystal becomes a focal conic state and becomes a transparent state. Several drive waveforms have been proposed, for example, a drive waveform that changes the liquid crystal to the focal conic state by applying a relatively low voltage for a long time and then changes the desired part to the planar state, and a state in which a high voltage is applied After resetting the liquid crystal to the planar state by suddenly turning off the voltage from the drive waveform, applying the reset pulse to the drive waveform that changes only the desired part to the focal conic state, and finally bringing the liquid crystal to the homeotropic state It is possible to employ a driving waveform composed of three stages to which a selection pulse having a magnitude corresponding to the display state to be applied is applied and a pulse for establishing the last selected state is applied. In these driving systems, the display can be maintained even after the voltage application is stopped by utilizing the memory property of the liquid crystal display element. When the visible light absorption layer 9 is provided, black is displayed in the focal conic state.

  Further, for example, in the PL-Home drive system, a planar state is realized by rapidly turning off the voltage from a state where a high voltage is applied, and the liquid crystal is kept in a homeotropic state by continuing to apply a high voltage. The transparency in the homeotropic state is higher than that in the focal conic state, which is advantageous for improving the contrast (the visible light absorbing layer 9 is also black in the homeotropic state), but the voltage is required to maintain the display. Need to continue to be applied.

  In the present embodiment, when switching between the planar state and the focal conic state, a driving method for temporarily switching to the homeotropic state (for example, a reset period for resetting the liquid crystal to the homeotropic state, and a final state of the liquid crystal are determined. A driving method for driving using a driving waveform having three consecutive periods, a selection period for applying a selection pulse for the purpose and a sustaining period for applying a sustain pulse for establishing a state selected in the selection period (hereinafter referred to as a driving method) It is preferable to perform display by employing a three-stage driving method))). This is because it can be rewritten in a relatively short time.

(Drive circuit)
The liquid crystal display device includes the liquid crystal display element and a drive circuit.
The pixel configuration of the liquid crystal display element 100 is represented by a matrix of a plurality of scanning electrodes R1, R2 to Rm and signal electrodes C1, C2 to Cn (m and n are natural numbers), respectively, as shown in FIG. . The scan electrodes R1, R2 to Rm are connected to the output terminal of the scan drive IC 131, and the signal electrodes C1, C2 to Cn are connected to the output terminal of the signal drive IC 132.

  The scan driving IC 131 outputs a selection signal to a predetermined one of the scan electrodes R1, R2 to Rm to be in a selected state, while outputting a non-selection signal to the other electrodes to be in a non-selected state. The scan driver IC 131 sequentially applies selection signals to the scan electrodes R1, R2 to Rm while switching the electrodes at a predetermined time interval. On the other hand, the signal driving IC 132 simultaneously outputs signals corresponding to image data to the signal electrodes C1, C2 to Cn in order to rewrite each pixel on the scanning electrodes R1, R2 to Rm in the selected state. For example, when the scan electrode Ra is selected (a is a natural number satisfying a ≦ m), the pixels LRa-C1 to LRa-Cn at the intersections of the scan electrode Ra and the signal electrodes C1, C2 to Cn are simultaneously rewritten. It is done. Thereby, the voltage difference between the scan electrode and the signal electrode in each pixel becomes the rewrite voltage of the pixel, and each pixel is rewritten in accordance with this rewrite voltage.

  The drive circuit includes a central processing unit (CPU) 135, an LCD controller 136, an image processing device 137, an image memory 138, drive ICs (drivers) 131 and 132, and a nonvolatile memory 141. Power is supplied from the power source 140. Based on the image data stored in the image memory 138, the LCD controller 136 controls the drive ICs 131 and 132, and sequentially applies a voltage between the scanning electrodes and the signal electrodes of the liquid crystal display element 100, thereby displaying an image on the liquid crystal display element 100. Write. In addition, the CPU 135 acquires environmental temperature information from a temperature sensor 139 provided in the vicinity of the element 100. The nonvolatile memory 141 stores information for determining how to set the selection pulse application period Tsp and the selection period Ts described below according to the environmental temperature.

  The drive ICs 131 and 132 are preferably provided for each of the red, green, and blue display layers (that is, three systems are provided). However, either of the drive ICs 131 or 132 can be shared by the display layers. In the following, only one system of driving will be described as a representative, but it goes without saying that the same driving method is applied to each liquid crystal layer.

  Image rewriting is performed by sequentially selecting all scanning lines. In the case of partial rewriting, only specific scanning lines may be sequentially selected so as to include a portion to be rewritten. Thereby, only a necessary part can be rewritten in a short time.

(Driving principle and basic driving example)
The basic principle of the driving method of the liquid crystal display element 100 adopting the three-stage driving method will be described. Although a specific example using an alternating pulse waveform will be described here, it goes without saying that the driving method is not limited to this waveform.

  FIG. 5 shows basic drive waveforms output from the scan drive IC 131 to each scan electrode. This driving method is roughly composed of a reset period Trs, a selection period Ts, a sustain period Trt, and a display period Ti (also referred to as a crosstalk period). The selection period Ts further includes a selection pulse application period Tsp, a pre-selection period Tsz, and a post-selection period Tsz ′.

  FIG. 6 shows an example of basic drive in which basic drive waveforms are sequentially output from 28 scan electrodes (rows 1, 2, 3 to 28) and signal waveforms are output from one signal electrode (column). The signal waveform output from the column is shown as a pulse sequentially selecting transmission, halftone, and total reflection. The LCDs 1, 2, 3 to 28 are pixels where the scanning electrodes and the signal electrodes intersect.

  In the basic drive waveform, a reset pulse of ± V1 is applied in the reset period Trs. In the selection period Ts, a selection pulse of ± V2 is applied in the selection pulse application period Tsp. Further, in this period Tsp, a signal pulse of ± V4 is superimposed from the signal driving IC 132. The signal pulse ± V4 is a voltage set based on the image data. In the basic drive waveform, the pre-selection period Tsz and the post-selection period Tsz ′ are periods of zero voltage. Further, a sustain pulse of ± V3 is applied during the sustain period.

  The operation of the liquid crystal is as follows. First, when a reset pulse of ± V1 is applied in the reset period Trs, the liquid crystal is reset to the homeotropic state. Next, the selection pulse application period Tsp is reached through the previous selection period Tsz (the liquid crystal is slightly twisted back). The waveform of the selection pulse applied here differs between the pixel that finally selects the planar state and the pixel that selects the focal conic state.

  First, the case where the planar state is selected will be described. In this case, a selection pulse of ± (V2 + V4) is applied in the selection pulse application period Tsp, and the liquid crystal is again brought into a homeotropic state. Thereafter, in the post-selection period Tsz ′, the liquid crystal is in a state where the twist is slightly returned. After that, when a sustain pulse is applied in the sustain period Trt, the liquid crystal in which the twist is slightly returned in the previous post-selection period Tsz ′ is untwisted again by the sustain pulse and is brought into a homeotropic state. Become.

  Here, the liquid crystal in the homeotropic state becomes a planar state by setting the voltage to zero, and is fixed in the planar state. In the display period Ti, a crosstalk pulse of ± V4 is applied to the liquid crystal. However, since the crosstalk pulse is set to be smaller than a threshold value for changing the display state of the liquid crystal in the display period Ti, The display state is not affected.

  On the other hand, when the focal conic state is finally selected, a selection pulse of ± (V2-V4) is applied in the selection pulse application period Tsp. Then, in the post-selection period Tsz ′, the liquid crystal returns to the twist and the helical pitch is expanded about twice.

  Thereafter, a sustain pulse is applied in the sustain period Trt. The liquid crystal whose twist has returned in the post-selection period Tsz ′ transitions to the focal conic state by applying this sustain pulse. Here, the liquid crystal in the focal conic state is fixed in the focal conic state even if the voltage is zero. In the display period Ti, as in the case of selecting the planar state, a ± V4 crosstalk pulse is applied to the liquid crystal, but the display state is not substantially affected.

  As described above, the final display state of the liquid crystal can be selected by the selection pulse applied in the selection pulse application period Tsp. Further, by adjusting the voltage value and pulse width of the selection pulse, specifically, by changing the waveform of the pulse applied to the signal electrode according to the image data, halftone display can be performed.

  In the basic driving example shown in FIG. 6, the scanning of each scanning electrode is performed based on the length of the selection pulse application period Tsp, and the selection of the next scanning electrode is performed when the selection pulse application period in the previous scanning electrode ends. The pulse application period begins.

Hereinafter, “parts” means “parts by weight”.
Example 1
62 parts of nematic liquid crystal (BL006; manufactured by Merck, refractive index anisotropy: 0.286, dielectric anisotropy: 17.3), 38 parts of chiral agent (CB15; manufactured by Merck), and the chemical formula (2) A chiral nematic liquid crystal composition was obtained by mixing a gelling agent represented by the formula: The refractive index anisotropy of the cholesteric liquid crystal composed of the nematic liquid crystal and the chiral agent was 0.14.

Using the obtained liquid crystal composition and the following materials, the display element shown in FIG. 1 (however, the polymer structure and the insulating thin film were omitted) was produced. The measurement temperature for each value was 25 ° C.
-Substrate: glass 0.7mm thickness-ITO sheet resistance: 10Ω / □
・ Spacer: Micropearl 5.5μm by Sekisui Fine Chemical Co., Ltd.
-Seal material: Sumitomo Bakelite Co., Ltd. Sumilite ERS-2400 (main agent), ERS-2840 (curing agent)
-Light absorption layer: Black paint containing carbon black-Orientation film: A layer made of polyamic acid (manufactured by JSR; AL60101) is printed on the electrode by flexographic printing, dried at 80 ° C for 5 minutes by a hot plate, and then in an oven The vertical alignment film was formed by baking for 90 minutes at the temperature shown in Table 2.
・ Alignment film thickness: 60 nm (printing)

  The amount of the gelling agent used was adjusted as appropriate so that the purity of the resulting liquid crystal display element during the planarization was 5%.

(Examples 2-5 and Comparative Examples 1-6)
As a nematic liquid crystal, in Comparative Example 5, BL032 (refractive index anisotropy 0.286, dielectric anisotropy 17.3) manufactured by Merck Ltd. is used. In Comparative Example 6, BL004 (refractive index anisotropy 0) is manufactured. 2240, dielectric anisotropy 15.6), and as an alignment film, in Examples 3 to 5 and Comparative Examples 1, 2, 5, and 6, modified polyimide (AL60601 manufactured by JSR) was used as Comparative Example 3. In No. 4, a soluble polyimide (ALS682 manufactured by JSR) was used, and a liquid crystal display device was produced in the same manner as in Example 1 except that an alignment film was formed at the firing temperature shown in Table 1.

(Evaluation)
Table 2 shows the amount of gelling agent added so that the stimulation purity of the liquid crystal display device during planarization is 5%, and the one-line rewriting time of the liquid crystal display device manufactured with such gelling agent addition amount was measured.
Further, in the above examples and comparative examples, a liquid crystal display element was produced by the same method as described in the above examples and comparative examples, except that no gelling agent was added. Was measured, and R _S / R _L was calculated. Moreover, the stimulus purity at the time of the planar of the liquid crystal display element produced without adding a gelatinizer was measured.
Regarding the peak wavelength of selective reflection before the addition of the gelling agent in each Example / Comparative Example, except for Comparative Example 4, there are all two peaks near 440 nm and 610 nm, and Comparative Example 4 is 1 near 610 nm. There were two peaks.

・ Measurement method of 1 line rewrite time (3-stage drive system)
The pulse voltage shown in FIG. 5 is applied between the upper and lower electrodes of the liquid crystal display element manufactured in each example and each comparative example with various changes in V2, and the application of the sustain pulse is completed after the reset pulse application is started. After a lapse of time (here, 3 seconds after the application of the reset pulse), the Y value of the panel is measured. Here, the pulse voltage applied to the liquid crystal during the reset period is set to a voltage value and length sufficient for the liquid crystal to be in a homeotropic state, and the pulse voltage applied to the liquid crystal during the sustain period is not applied during the selection period. In some cases, the voltage value and the length were such that a substantially minimum Y value was obtained. From the “voltage (V2) −Y value” curve obtained by this measurement, the Y value is 95% when the minimum Y value (Y0) is 0% and the maximum Y value (Y100) is 100%. A difference (hereinafter referred to as “gamma”) between the minimum V2 value indicating (Y95) and the maximum V2 value indicating 5% Y value (Y05) is obtained. Then, the range of Tsp is determined so that the above gamma, Y95, and Y05 are optimal by the following procedure, and finally the rewrite time for one line is determined. That is, while maintaining the relationship of Tsp × 3 = Ts, Tsp and Ts in FIG. 5 are changed, and changes in gamma, Y95, and Y05 with respect to Tsp are measured. Then, a value of Tsp that maximizes Y95 is obtained when gamma is in the range of 6.0 to 9.0 and Y05 is 10 or less. The value of Tsp × 3 (= Ts) is defined as one line rewrite time.
The rewriting time for one line is within a range where 1 ms or less can be recognized as “rapid”, preferably 0.9 ms or less, and more preferably 0.7 ms or less.

R _S / R _L and stimulation purity The pulse shown in FIG. 7 is applied to the liquid crystal display element (in this drive waveform, the liquid crystal is once reset to the planar state by the preceding pulse), and the voltage-Y value curve ( Hereinafter, this is referred to as a VY curve). Specifically, the spectral distribution curve (wavelength-reflectance curve) and Y value of the element at the measurement point shown in the figure while changing the voltage (V) of the section (X) in the pulse of FIG. 7 from ± 20 to ± 50 V. Y) is repeatedly measured several times with a spectrocolorimeter (CM3700d; manufactured by Konica Minolta Sensing Co., Ltd.), and a V (absolute value of voltage) -Y (Y value) curve is created. An example of the VY curve is shown in FIG. A state showing the maximum Y value (Ymax) in the VY curve is a planar state (PL), and a state showing the minimum Y value (Ymin) is a focal conic state (FC).
R _S / R _L and stimulation purity were determined from the spectral distribution curve when such a planar state was exhibited.

The obtained results are shown in a graph. That is, FIG. 9 shows the relationship between R _S / _RL and the stimulation purity when no gelling agent is added. FIG. 10 shows the relationship between R _S / _RL when no gelling agent is added and the amount of gelling agent necessary to achieve a stimulation purity of 5%. FIG. 11 shows the relationship between R _S / _RL when no gelling agent is added and one line rewriting time when the gelling agent is added.

In FIG. 10, when a characteristic curve is drawn based on each plot, it can be read that the change in the slope has three regions as R _S / R _L decreases. This is presumably due to the following mechanism. That is, in the region where R _S / R _L is relatively large (R _S / R _L = 1 vicinity), as shown in FIG. 12, the influence that the vertical alignment film tries to make the helical axis of the liquid crystal molecules appropriately random. Is expected to be large. Therefore, when viewed from the bulk side of the liquid crystal, it can be presumed that when the helical axis of the liquid crystal molecules in the second layer is tilted by the gelling agent from the interface, it can be tilted relatively easily (with a low addition amount). In the region where R _S / R _L is a little small (R _S / R _L = 0.8 vicinity), the action as a vertical alignment film is becoming smaller as shown in FIG. Although it is becoming difficult to tilt due to the agent, the amount of the gelling agent is not so much increased. When R _S / R _L is further reduced and becomes a region below R _S / R _L = 0.7, the function as a vertical alignment film is hardly received as shown in FIG. Are thought to be almost complete. In this case, even if the addition amount of the gelling agent is increased, the liquid crystal molecules cannot be tilted, and it is presumed that the addition amount of the gelling agent greatly changes with respect to the change of R _S / _RL . If the amount of gelling agent added is further increased, the orientation of the liquid crystal molecules closest to the alignment film changes by increasing the orientation of the gelling agent, or the network density of the gelling agent increases and scattering increases. For the reason, it is presumed that the stimulation purity can be reduced to 5% or less by increasing the addition amount again. However, in this case, the required amount of gelling agent is more than 2% by weight.

It is a schematic sectional drawing of the liquid crystal display element which is one Embodiment of this invention. It is an example of the spectral distribution curve which the liquid crystal display element which is embodiment of this invention can have when it is a state which does not contain a gelatinizer. It is the schematic of the chromaticity coordinate for demonstrating the calculation method of stimulus purity. It is a block diagram which shows the control circuit of the liquid crystal display element which is embodiment of this invention. It is a chart figure showing the basic drive waveform in the drive method suitable for the liquid crystal display element which is an embodiment of the present invention. It is a chart figure which shows the drive waveform applied to each pixel in the example of basic drive of the liquid crystal display element which is embodiment of this invention. It is a figure which shows the example of the drive waveform used by the experiment example. An example of the VY curve for setting a planar state and a focal conic state is shown. It is a graph which shows the relationship between _RS / _RL and stimulation purity at the time of a gelling agent additionless about the liquid crystal display element produced by the Example and the comparative example. It is a graph which shows the relationship between _RS / _RL when gelling agent addition is not added, and the gelling agent addition amount required in order to make stimulation purity 5% about the liquid crystal display element produced in the Example and the comparative example. It is a graph which shows the relationship between _RS / _RL when the gelling agent is not added and the one-line rewriting time when the gelling agent is added for the liquid crystal display devices manufactured in Examples and Comparative Examples. FIG. 11 is a schematic diagram for explaining a relationship between an alignment film and a helical axis of liquid crystal molecules when R _S / R _L is near 1 in the graph shown in FIG. 10. FIG. 11 is a schematic diagram for explaining a relationship between an alignment film and a helical axis of liquid crystal molecules when R _S / R _L is around 0.8 in the graph shown in FIG. 10. FIG. 11 is a schematic diagram for explaining a relationship between an alignment film and a helical axis of liquid crystal molecules when R _S / R _L is less than 0.7 in the graph shown in FIG. 10.

Explanation of symbols

1: 2: substrate, 3: 4: electrode, 5: insulating thin film, 7: alignment film, 9: visible light absorption layer, 10: polymer structure, 11: liquid crystal layer (liquid crystal composition), 12: seal Wood.

Claims (6)

A planar distribution spectrum obtained by sandwiching a liquid crystal composition containing a cholesteric liquid crystal and a self-organizing gelling agent between a pair of substrates and containing no gelling agent has the following conditions (I) and ( A liquid crystal display device characterized by satisfying II);
(I) It has two or more peaks in the wavelength range of 400 nm or more and 700 nm or less; and (II) The maximum reflectance in the wavelength range of 400 nm or more and less than 500 nm is R _S , and the maximum reflectance in the wavelength range of 500 nm or more and 700 nm or less. When R _L is satisfied, the relationship of R _L × 0.7 ≦ R _S is satisfied.   The liquid crystal display element according to claim 1, further comprising a vertical alignment film on at least one substrate side.   The liquid crystal display element according to claim 2, wherein the refractive index anisotropy of the cholesteric liquid crystal is 0.14 or more, and the vertical alignment film is a polyamic acid.   The liquid crystal display element according to claim 2, wherein the refractive index anisotropy of the cholesteric liquid crystal is 0.14 or more, and the vertical alignment film is a modified polyimide baked at a baking temperature of 180 ° C or lower.   The content of the self-organizing gelling agent is 1% by weight or less based on the liquid crystal composition containing the cholesteric liquid crystal and the self-organizing gelling agent. Liquid crystal display element. 6. The liquid crystal display element according to claim 1, wherein when switching between the planar state and the focal conic state, display is performed by adopting a three-stage driving method in which the homeotropic state is once switched.

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