JP2003295225A - Liquid crystal display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display element capable of selectively reflecting light having comparatively long wavelength and having high respose speed, reduced driving voltage, brightness and excellent heat resistance stability and to provide a laminated liquid crystal display element. <P>SOLUTION: The liquid crystal display element is provided with a chiral nematic liquid crystal composition containing at least a nematic liquid crystal mixture and a chiral material, showing a cholesteric phase at room temperature, capable of selectively reflecting light having 580 to 690 nm peak wavelength and having 20 to 50 cP viscosity, dielectric anisotropy (Δε) of 10 to 30, refractive index anisotropy (Δn) of 0.13 to 0.20 and 75 to 100°C isotropic phase transition temperature and a pair of substrates with electrodes which sandwich the liquid crystal composition and at least one of which is transparent. The laminated liquid crystal display element is formed by using the liquid crystal display element. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using at least a nematic liquid crystal material and a chiral nematic liquid crystal composition composed of a chiral material, and a laminated liquid crystal display device using the liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, a reflective liquid crystal display device using a chiral nematic liquid crystal composition in which a chiral material is added to a nematic liquid crystal material to exhibit a cholesteric phase at room temperature has been studied. Such a liquid crystal display device basically comprises a chiral nematic liquid crystal composition sandwiched between a pair of substrates having transparent electrodes, and a liquid crystal is planarized by applying a high and low pulse voltage (driving voltage) between the electrodes. The display is switched by switching between the state and the focal conic state. In particular, in the planar state, the liquid crystal molecules are arranged so as to have a spiral structure in which the spiral axis is substantially perpendicular to the substrate surface, and light of a specific wavelength is selectively reflected based on the spiral pitch.

The peak wavelength of light selectively reflected by a liquid crystal display device (liquid crystal composition) is generally adjusted by controlling the helical pitch by the amount of chiral material added to the liquid crystal composition. That is, when the amount of the chiral material is increased, the force of twisting the liquid crystal molecules is increased, the helical pitch of the cholesteric phase is decreased, and the selective reflection wavelength is shifted to the short wavelength side. When the amount of chiral material is reduced, the force to twist the liquid crystal molecules is reduced, and the spiral pitch of the cholesteric phase is increased,
The selective reflection wavelength shifts to the long wavelength side.

On the other hand, the spiral pitch length and the homeotropic shape
Fall that indicates the speed of transition from the state to the planar state
An equation between the response time and; τ_d= (Η · P^Two) / (Π^Two・ K₂₂) (Where τ_dIs the fall response time, η is the viscosity of the liquid crystal composition.
Degree, P is the spiral pitch length, K ₂₂Is the twist elastic constant
It is generally known that there is a relationship.

Therefore, in the case of selectively reflecting light of a relatively long wavelength, as described above, the spiral pitch (P) becomes large and the fall response time (τ _d ) becomes long, that is, the fall response speed is Delay was a problem. That is, the liquid crystal display element (liquid crystal composition) that selectively reflects light having a relatively long wavelength, for example, red light, has a slow fall response speed.

Therefore, in order to increase the fall response speed, as apparent from the above formula, attempts have been made to reduce the viscosity (η) of the liquid crystal composition. In order to reduce the viscosity of the liquid crystal composition, the dielectric anisotropy of the liquid crystal composition is lowered, the refractive index anisotropy of the liquid crystal composition is lowered, and the isotropic phase transition temperature of the liquid crystal composition is lowered. Is known to be effective.

However, it has been found that when the dielectric anisotropy of the liquid crystal composition is lowered, the voltage (driving voltage) for driving the liquid crystal composition into the planar state or the focal conic state rises. Further, it has been found that when the refractive index anisotropy of the liquid crystal composition is lowered, the reflectance in the planar state is lowered, the display becomes dark, and it becomes difficult to achieve color balance when laminating. Further, when the isotropic phase transition temperature of the liquid crystal composition is lowered, the heat stability is deteriorated and the temperature tends to be deteriorated due to an increase in ambient temperature, or the upper limit of the temperature at which the liquid crystal display element can be used is approached. Was found to occur.

As described above, the liquid crystal display device using the conventional chiral nematic liquid crystal composition capable of selectively reflecting light having a relatively long wavelength can sufficiently satisfy the response speed, driving voltage, brightness and heat resistance stability. There was nothing.

Further, there has been a problem that the selective reflection wavelength of the liquid crystal composition, which is set at the time of preparation, shifts due to changes in the ambient environment, especially the ambient temperature.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances and is capable of selectively reflecting light of a relatively long wavelength, has a fast response speed, has a reduced driving voltage, is bright,
Another object of the present invention is to provide a liquid crystal display element and a multi-layer liquid crystal display element having excellent heat resistance stability.

The present invention is also capable of selectively reflecting light having a relatively long wavelength, suppressing the shift of the selective reflection wavelength due to a change in ambient temperature, and having excellent temperature compensation characteristics, high response speed, and a high driving voltage. It is an object of the present invention to provide a liquid crystal display element and a multi-layer liquid crystal display element that are reduced in brightness and are excellent in heat resistance stability.

[0012]

The present invention comprises at least a nematic liquid crystal mixture and a chiral material,
It shows a cholesteric phase at room temperature and has a peak wavelength of 580 nm to 690 nm.
Of which the viscosity is 20 to 50 cP, the dielectric anisotropy (Δε) is 10 to 30, and the refractive index anisotropy (Δn) is 0.13.
To 0.20, and a chiral nematic liquid crystal composition having an isotropic phase transition temperature of 75 ° C. to 100 ° C., and a pair of substrates with electrodes, at least one of which sandwiches the liquid crystal composition is transparent. Liquid crystal display device. The chiral material may include two or more kinds of chiral compounds. In addition, the viscosity of the chiral nematic liquid crystal composition
20-35cP, dielectric anisotropy (△ ε) 15-25, refractive index anisotropy (△ n) 0.16-0.19, isotropic phase transition temperature 80 ℃ ～ 90 ℃
May be The thickness of the liquid crystal layer sandwiched between the substrates is 3
It may be ˜15 μm. What is claimed is: 1. A multi-layer liquid crystal display device comprising a plurality of liquid crystal layers, each of which is sandwiched between a pair of substrates with electrodes, wherein at least one of the plurality of liquid crystal layers includes a pair of substrates sandwiching the liquid crystal layer. Term
It may constitute the liquid crystal display element described in any one of 1 to 4.

[0013]

FIG. 1 is a schematic view showing a cross-sectional structure of a liquid crystal display element which is an embodiment of the present invention, and when the voltage application is stopped after applying a high voltage pulse to FIG. 1 (A). 1B shows the planar state (colored state (red)), and FIG. 1 (B) shows the focal conic state (transparent / black display state) when the voltage application is stopped after the low voltage pulse is applied. The liquid crystal display element has a memory property, and the planar state and the focal conic state are maintained even after the pulse voltage application is stopped. That is, the planar state is maintained in the region that was in the planar state and the focal conic state is retained in the region that was in the focal conic state even after the application of the pulse voltage was stopped. 1 (A) and 1 (B) are similar except that the applied voltage is different.
When referring to any of the drawings in 1 (B), it shall be simply referred to as FIG.

The liquid crystal display element shown in FIG. 1 has a pair of substrates 11,
It has a structure in which a liquid crystal composition 21 is sandwiched between 12. In FIG. 1, reference numerals 11 and 12 denote transparent substrates having a light-transmitting property, and transparent electrodes 13 and 14 formed in a plurality of parallel strips are provided on the respective surfaces of the transparent substrates 11 and 12. These electrodes 13 and 14 are arranged so as to face each other so as to intersect each other. It is preferable that the electrodes 13 and 14 are coated with an insulating thin film. Here, only the electrode 13 is coated with the insulating thin film 15. A visible light absorbing layer 16 of black or the like is provided on the outer surface (back surface) of the substrate opposite to the side on which light is incident, if necessary. 20
Is a columnar structure as a spacer holding member, and 21 is a chiral nematic liquid crystal composition exhibiting a cholesteric phase at room temperature. 24 is a sealing material, the liquid crystal composition 21 to the substrate 11,
It is for sealing between 12 pieces. A pulse power source 25 applies a pulsed predetermined voltage to the electrodes 13 and 14.
Hereinafter, the main constituent members of the liquid crystal display member will be described in detail.

(Substrate) Although the substrates 11 and 12 in FIG. 1 are both transparent as described above, at least one substrate (a pair of substrates that can be used for the liquid crystal display element) It is sufficient that at least the substrate on which light is incident has a light-transmitting property. A glass substrate can be given as an example of the translucent substrate. In addition to glass substrates, for example, polycarbonate (PC), polyether sulfone (PE
Flexible substrates (resin substrates) such as S), polyarylate (PAr), and polyethylene terephthalate (PET) can be used. From the viewpoint of reducing the weight of the element, it is preferable to use a flexible substrate (resin substrate). When flexible substrates are 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) As the electrode, for example, Indium
Tin Oxide (ITO), Indium Zin
c Oxide (IZO: Indium Zinc Oxide) transparent conductive film, aluminum, silicon and other metal electrodes, amorphous silicon, BSO (Bismuth Silicon Oxide)
xide) or other photoconductive film can be used. In the liquid crystal display element shown in FIG. 1, as described above, the transparent substrate 1
Multiple strip-shaped transparent electrodes 13, 1 parallel to the surface of 1, 12
4 are formed, and the electrodes 13 and 14 are opposed to each other so as to intersect each other. To form the electrode in this way, for example, an ITO film may be mask-deposited on the substrate by 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) An insulating thin film may be formed in order to prevent a short circuit between electrodes or to improve the reliability of the liquid crystal display element with respect to gas barrier properties. As described above, the insulating thin film 15 is coated on the electrode 13 here. Examples of the insulating thin film include inorganic materials such as silicon oxide, titanium oxide, zirconium oxide and alkoxides thereof, and organic films such as polyimide resin, acrylic resin and urethane resin. These materials can be formed by a known method such as a vapor deposition method, a spin coating method or a roll coating method. Furthermore, the insulating thin film can be formed using the same material as the polymer resin used for the columnar structure.

(Alignment Film) The alignment film is preferably formed in order to effectively control and stabilize the alignment of the liquid crystal composition, but it may not be formed. When the alignment film is formed, it 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. Examples of the alignment film include organic films such as polyimide resin, polyamideimide resin, polyetherimide resin, polyvinyl butyral resin, and acrylic resin, and inorganic films such as silicon oxide and aluminum oxide. The alignment film formed using these materials may be subjected to rubbing treatment or the like.

(Spacer) A spacer may be provided between the pair of substrates to keep the gap between the substrates uniform. Examples of the spacer include spheres made of resin or inorganic oxide. Further, a fixed spacer whose surface is coated with a thermoplastic resin is also suitably used. Note that, as shown in FIG. 1, only the columnar structure 20 may be provided in order to uniformly maintain the gap between the substrates, but both the spacer and the columnar structure may be provided, and the columnar structure may be provided. Alternatively, only the spacer may be used as the space holding member. When forming a columnar structure, the diameter of the spacer is equal to or less than that height, preferably equal to the height. When the columnar structure is not formed, 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.

(Liquid Crystal Composition) The liquid crystal composition 21 contains at least a nematic liquid crystal material and a chiral material,
The liquid crystal composition for red display has the following physical properties. In the present specification, “red” is used as a concept including a red color close to yellow, and specifically, a peak wavelength of 580 nm to 6 nm.
It shall mean "reddish color" of 90 nm.

That is, the chiral nematic liquid crystal composition of the present embodiment (hereinafter sometimes simply referred to as “liquid crystal composition”) has a viscosity (η) of 20 to 50 cP, preferably 20 to 35 cP,
Dielectric anisotropy (Δε) is 10 to 30, preferably 15 to 25, and refractive index anisotropy (Δn) is 0.13 to 0.20, preferably 0.16 to 0.
19, and the isotropic phase transition temperature (Tc) is 75 ° C to 100 ° C, preferably 80 ° C to 90 ° C.

When the viscosity is within the above range, an excellent response speed can be achieved. That is, if the viscosity is too high, the response speed, especially the falling response speed from the homeotropic state to the planar state becomes slow.

In this specification, the viscosity is a value measured by an E-type viscometer (manufactured by Tokyo Keiki) at 20 ° C., but it does not have to be measured by the device. Any device may be used as long as it can be measured by the same principle as the above device.

By setting the dielectric anisotropy within the above range, both excellent response speed and reduced driving voltage can be achieved. That is, if the dielectric anisotropy is too large, the viscosity of the liquid crystal composition becomes high, and the response speed, particularly the falling response speed becomes slow. On the other hand, if the dielectric anisotropy of the liquid crystal composition is too low, the driving voltage of the liquid crystal element will increase.

The dielectric constant anisotropy (Δε) is a value (room temperature) obtained by subtracting the dielectric constant in the direction perpendicular to the axis of symmetry from the dielectric constant in the direction of the axis of symmetry in a liquid crystal sample having uniaxial symmetry.
In this specification, the dielectric anisotropy is a value measured at room temperature using an LCR meter 4192A (manufactured by HP), but it does not have to be measured by the above apparatus.
Any device may be used as long as the dielectric anisotropy can be measured.

By setting the refractive index anisotropy within the above range, both excellent response speed and bright display can be achieved. That is, when the refractive index anisotropy is too large, the viscosity of the liquid crystal composition becomes high, and the response speed, particularly the falling response speed becomes slow. On the other hand, if the refractive index anisotropy of the liquid crystal composition is too low, the peak reflectance is lowered in the planar state (colored state) and the display becomes dark.

The refractive index anisotropy (Δn) is calculated by the following equation from the refractive index n ₀ in the symmetric axis direction and the refractive index n _{e in the} direction perpendicular to the symmetric axis in a liquid crystal sample having uniaxial symmetry. Value (Δn) (25 ° C). ^{_{△ n = √ (2n 0 2}} -n e 2) in -n _e herein, optical anisotropy using the measured value at 25 ° C. using an Abbe refractometer type 1 (manufactured by Atago) However,
It does not have to be measured by the device. Any device may be used as long as the refractive index anisotropy can be measured.

By setting the isotropic phase transition temperature within the above range, both excellent response speed and excellent heat stability can be achieved. That is, if the isotropic phase transition temperature is too high, the viscosity of the liquid crystal composition becomes high, and the response speed, particularly the falling response speed becomes slow. On the other hand, if the isotropic phase transition temperature of the liquid crystal composition is too low, deterioration occurs due to an increase in ambient temperature, heat resistance stability deteriorates, and the liquid crystal composition becomes dark.

The isotropic phase transition temperature is a temperature at which the liquid crystal phase of the sample changes to an isotropic phase when the sample is heated. In the present specification, the isotropic phase transition temperature was measured by a liquid crystal evaluation device including a controller FP90 (manufactured by METTLER), a hot stage FP82HT (manufactured by METTLER), and a polarization microscope BX50 (manufactured by Olympus Optical Co., Ltd.). Values are used, but do not have to be measured by the device. Any device may be used as long as it can measure the isotropic phase transition temperature.

The type of nematic liquid crystal material is not particularly limited as long as it is a chiral nematic liquid crystal composition that exhibits a cholesteric phase at room temperature and can selectively reflect light of a red wavelength. In the present invention, a mixture obtained by blending nematic liquid crystal materials conventionally known in the field of liquid crystal display devices so as to exhibit the above physical properties is useful. Examples of nematic liquid crystal materials conventionally known in the field of liquid crystal display devices include liquid crystal ester compounds, liquid crystal pyrimidine compounds, liquid crystal cyanobiphenyl compounds, and polar groups such as fluorine atoms, fluoroalkyl groups and cyano groups. There are other liquid crystal compounds having, and mixtures thereof.

The chiral material is added to a nematic liquid crystal material to cause the liquid crystal material to exhibit a cholesteric phase at room temperature and to selectively reflect light having a red wavelength. Specifically, it is possible to form a layered helical structure (a molecular structure in which liquid crystal molecules are rotated 360 ° along a helical structure of liquid crystal molecules) in the molecules of a nematic liquid crystal material at room temperature. Such a chiral material may or may not exhibit liquid crystallinity by itself.

As such a chiral material, for example,
Cholesteric compound having cholesteric ring, biphenyl compound having biphenyl skeleton, terphenyl compound having terphenyl skeleton, ester compound having skeleton in which two benzene rings are connected by an ester bond, and cyclohexane ring directly to benzene ring A cyclohexane compound having a skeleton connected to each other, a pyrimidine compound having a skeleton where a pyrimidine ring is directly connected to a benzene ring, and an azoxy or azo having a skeleton where two benzene rings are connected by an azoxy bond or an azo bond. A compound etc. are mentioned.

Specific examples of the cholesteric compound include:
For example, the general formula;

[Chemical 1] Cholesteryl nonanoate represented by the compound represented by

Specific examples of the biphenyl compound include, for example, general formulas;

[Chemical 2] And a biphenyl compound represented by

Specific examples of the ester compound include, for example, general formulas;

[Chemical 3] And an ester compound represented by

Specific examples of the cyclohexane compound include
For example, the general formula;

[Chemical 4] And a cyclohexane compound represented by

From the viewpoint of ensuring excellent temperature compensation characteristics in which the selective reflection wavelength hardly shifts even when the ambient temperature changes, among the above chiral compounds, the structures are different.
It is preferable to use two or more kinds of chiral compounds.
More preferably, two or more kinds, preferably 2 to 4 kinds of chiral compounds having different structures and different “shift directions of selective reflection wavelength depending on temperature” are used. A chiral material, whether liquid crystalline or not, is mixed with a nematic liquid crystal material to raise the temperature of the mixture,
It has the property of shifting the selective reflection wavelength of the mixture in either the long wavelength direction or the short wavelength direction with reference to the selective reflection wavelength of the mixture before the temperature rise. In the present specification, such a shift direction in the long wavelength direction or the short wavelength direction is the “shift direction of the selective reflection wavelength due to temperature”.

The chiral compound has a characteristic peculiar to the compound that the helical direction of the helical structure is either right-handed or left-handed. When selecting the chiral material, it is not necessary to take such characteristics into consideration, but it is preferable to select only the chiral compound having the characteristics that the helical directions of the helical structure are the same direction in combination.

The chiral material is used in such an amount that the selective reflection wavelength of the obtained liquid crystal composition becomes a red wavelength (580 to 690 nm). Specifically, it is 7 to 45% by weight, preferably 10 to 45% by weight, particularly 1% by weight based on the total amount of the nematic liquid crystal material and the chiral material (all chiral compounds used).
It is 0 to 30% by weight. If the amount of the chiral material used is too small, sufficient memory properties may not be obtained, and if it is too large, the cholesteric phase may not be exhibited or solidified at room temperature. In addition, the viscosity of the liquid crystal composition becomes high, and the response speed, particularly the response speed of the falling edge, tends to be slow. Two or more kinds of chiral compounds may be used as the chiral material, and in that case, the total amount thereof may be within the above range.

When two or more kinds of chiral compounds having different "shift directions of selective reflection wavelength depending on temperature" are used as the chiral material, the chiral compound having "shift direction of selective reflection wavelength depending on temperature" is the long wavelength direction. The amount of the compound used (the total amount of two or more chiral compounds used) and the amount of the chiral compound whose “direction of selective reflection wavelength shift depending on temperature” is the short wavelength direction (two types of the chiral compound) When used above, the ratio to the total amount thereof is used in such a ratio that the shift to the long wavelength and the shift to the short wavelength are offset.

The chiral nematic liquid crystal composition contains a dye,
You may further add additives, such as an ultraviolet absorber. The dye is added for the purpose of improving color purity and contrast. As the dye to be added, various conventionally known reddish dyes can be used, and those having good compatibility with the liquid crystal are preferably used. For example, an azo compound, a quinone compound, an anthraquinone compound, or a dichroic dye can be used, and a plurality of types of these dyes may be used. The addition amount is 5% by weight or less, preferably 3% by weight or less, based on the total amount of the nematic liquid crystal material and the chiral material used.

The ultraviolet absorber prevents ultraviolet deterioration of the liquid crystal composition, for example, fading and change in responsiveness with time. For example, a material such as a benzophenone compound, a benzotriazole compound, or a salicylate compound can be used. The added amount is 5% by weight or less, preferably 3% by weight or less, based on the total amount of the nematic liquid crystal material and the chiral material used.

Such a chiral nematic liquid crystal composition is obtained by mixing each material in a predetermined ratio, and has an effect of improving response speed, driving voltage, brightness, and heat resistance stability. Furthermore, it preferably has excellent temperature compensation characteristics. If desired, the liquid crystal composition may be contacted with an ion exchange resin, an adsorbent or the like to be purified to remove water and impurities, and then used for the production of a device.

(Sealing material) The sealing material 24 is for sealing the liquid crystal composition 21 so as not to leak out between the substrates 11 and 12, and is a thermosetting resin such as epoxy resin or acrylic resin, or A photocurable adhesive or the like can be used.

(Columnar Structure) As shown in FIG. 1, the liquid crystal display device is provided with a strong self-holding property (strength).
The pair of substrates is preferably supported by the structure between them. The liquid crystal display element of this example includes a substrate 11,
A columnar structure 20 is provided between the columns 12. As the columnar structure, for example, a columnar body, a square columnar body, an elliptic columnar body, which are arranged at a constant interval in a predetermined pattern such as a lattice array,
Examples thereof include columnar structures such as trapezoidal columns. Further, it may be stripe-shaped ones arranged at predetermined intervals. This columnar structure is not a random array, but an array with an equal interval, an array with a gradually changing interval, an array in which a predetermined layout pattern is repeated at a constant cycle, and the like, can properly maintain the space between the substrates, and the image It is preferable that the arrangement is such that it does not interfere with the display. When the columnar structure has an area ratio of 1 to 40% in the display region of the liquid crystal display element, sufficient strength for practical use as a liquid crystal display element can be obtained.

The columnar structure 20 is made of, for example, a polymerizable monomer.
Formed by using a polymerizable composition containing a polymerization initiator
It Examples of the polymerizable composition include photocurable monomers.
Or a mixed solution of an oligomer and a photopolymerization initiator
Any commercially available photocurable resin material
It Light-curing resin material is irradiated with light to be polymerized to form a columnar structure.
Once the object is formed, the columnar structures are arranged with a predetermined shape and interval.
Easy to do. Specific examples of materials that make up the columnar structure
By way of example, particularly suitable are acrylic ester compounds
It is mainly composed of things. Acrylic ester is 2
Acrylate compound or meta having the above allyl group
It is a acrylate compound and has no
Structures such as incense rings may be included, and other structures on the main chain
Is CO, CO _Two, CH_Two, O and other divalent groups may be included
Yes. The acrylate compound is epoxy acrylate
Also included are compounds and urethane acrylate compounds.

A method of manufacturing the columnar structure 20 will be described in detail. First, an ultraviolet curable compound (columnar structure composition) is sandwiched between the substrate on which the ITO electrode is formed and a mask on which a predetermined pattern is formed, or the ultraviolet curable compound is applied on the electrode surface of the substrate. Then, a mask is covered, and ultraviolet rays are irradiated on this. Next, the mask is peeled off, the compound of the unexposed portion is washed with a predetermined solvent, dried and cured. Forming a columnar structure by sandwiching a mixture of liquid crystal material and photo-curable resin material between glass substrates in advance, placing a photomask on the glass substrate and irradiating with light to perform polymerization phase separation. Is also possible.

The columnar structure can also be formed by a screen printing method. The screen printing method covers the electrode surface of the substrate with a screen on which a predetermined pattern is formed,
A printing material (a composition for forming a columnar structure, such as a photocurable resin) is placed on the screen. Then, the squeegee is moved at a predetermined pressure, angle and speed. This transfers the printing material through the pattern of the screen onto the substrate. Next, the transferred material is cured by heating,
dry. When the columnar structure is formed by the screen printing method, the resin material is not limited to the photocurable resin, and a thermosetting resin such as an epoxy resin or an acrylic resin or a thermoplastic resin can also be used. As the thermoplastic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl acetate resin, polymethacrylic acid ester resin, polyacrylic acid ester resin, polystyrene resin, polyamide resin, polyethylene resin, polypropylene resin, fluororesin, polyurethane resin , Polyacrylonitrile resin, polyvinyl ether resin, polyvinyl ketone resin, polyether resin, polyvinylpyrrolidone resin, saturated polyester resin, polycarbonate resin, chlorinated polyether resin and the like. The resin material is preferably used in the form of paste by dissolving the resin in an appropriate solvent.

After the columnar structure and the like are formed on the substrate as described above, spacers are scattered on at least one of the substrates, if desired, and a pair of substrates are superposed with their electrode forming surfaces facing each other to form an empty cell. Form. By heating the pair of stacked substrates while applying pressure from both sides, the substrates are bonded together to obtain a liquid crystal display cell. In order to obtain a liquid crystal display element, a liquid crystal composition may be injected between the substrates by a vacuum injection method or the like. Alternatively, the liquid crystal composition may be dropped on one of the substrates when the substrates are bonded together, and the liquid crystal composition may be sealed at the same time as the bonding of the substrates.

The thickness of the cell gap in the liquid crystal display device, that is, the thickness of the liquid crystal layer composed of the liquid crystal composition is 3 to 15
μm, more preferably 3 to 10 μm is suitable.

As another embodiment of the liquid crystal display element of the present invention, a liquid crystal display element having no columnar structure is shown in FIG. The liquid crystal display element of FIG. 2 shows a planar state (colored state (red)) when a high voltage pulse is applied. The structure of this liquid crystal display element is basically the same as that of the liquid crystal display element shown in FIG. 1, and no columnar structure is provided in the display area. In FIG. 2, the same members as those in FIG. 1 are designated by the reference numerals, and therefore their explanations are omitted.

As another embodiment of the liquid crystal display element of the present invention, a liquid crystal display element in which the columnar structure does not extend so much is illustrated.
Shown in 3. The liquid crystal display element of FIG. 3 shows a planar state (colored state (red)) when a high voltage pulse is applied. The structure of this liquid crystal display element is basically the same as that of the liquid crystal display element of FIG. 1, and is provided with a columnar structure 20 ′ extending to an intermediate portion of the gap between the substrates 11 and 12. In FIG. 3, the same members as those in FIG. 1 are denoted by the reference numerals, and thus their description will be omitted.

(Display Method) In the liquid crystal display element having the above structure, display is performed by applying a pulse voltage from the power supply 25 to the electrodes 13 and 14. That is, by applying a pulse voltage of relatively high energy, the liquid crystal becomes a planar state and selectively reflects light having a wavelength mainly determined based on the pitch of the spiral of liquid crystal molecules. By applying a pulse voltage of relatively low energy, the liquid crystal becomes a focal conic state and becomes a transparent state. Such a liquid crystal display device has a memory property, and the planar state and the focal conic state are maintained even after the pulse voltage application is stopped. That is, the planar state is maintained in the region that was in the planar state and the focal conic state is retained in the region that was in the focal conic state even after the application of the pulse voltage was stopped.

Since the liquid crystal display device also has an intermediate state between the focal conic state and the planar state,
By applying a pulse voltage having an intermediate energy, it is possible to express a halftone. In the intermediate state, it is considered that the focal conic state and the planar state coexist, and this state can also be configured to be maintained when the voltage application is stopped. When the visible light absorption layer 16 is provided, black is displayed in the focal conic state.

In the present liquid crystal display element, the strip electrodes 13 and 14 are
Areas where and intersect are display pixels. Further, in the present liquid crystal display element, the region where the liquid crystal is composed of the pixels that perform the light modulation is the light modulation region and is the display region, and the other regions are outside the light modulation region where the light modulation is not performed and This is the display area.

Since the liquid crystal display element of the present invention as described above selectively reflects light having a relatively long wavelength, that is, red light, among visible light, it selectively reflects light having a peak wavelength shorter than that of the liquid crystal display element. In combination with one or more liquid crystal display elements,
A multi-layer liquid crystal display element for color display can be formed.

FIG. 4 shows a sectional structure of an example of such a multi-layer liquid crystal display element. This multi-layer liquid crystal display element is a reflection type for full color display in which three liquid crystal display elements (31, 32 and 33) hold liquid crystal compositions (21, 21 'and 21'') having different selective reflection wavelengths. It is a liquid crystal display element. Specifically, the liquid crystal display element 31 that is the lowest layered
Is for red display and is similar to the liquid crystal display element of FIG. The liquid crystal display element 32 and the liquid crystal display element 33 are the same as the liquid crystal display element of FIG. 1 except that the visible light absorption layer 16 is not formed and the selective reflection wavelength of the liquid crystal composition is different. Further, the substrates other than the substrate 12 of the lowermost liquid crystal display element 31 are required to have translucency. In Figure 4,
Since the same members as those in FIG. 1 are designated by the same reference numerals, the description thereof will be omitted.

In FIG. 4, each liquid crystal composition (21, 21 ′ and
The selective reflection wavelength of 21 '') is adjusted to the red wavelength (R), the green wavelength (G), and the blue wavelength (B), respectively. It is preferable that the response speeds of the liquid crystal display elements (21, 21 ′ and 21 ″) containing the liquid crystal compositions having different selective reflection wavelengths are similar to each other.

The lamination of the liquid crystal display elements (31, 32 and 33) is achieved by the adhesive layer 30. Such an adhesive layer 30
Is transparent and has liquid crystal display elements (31, 32, and
It may be formed of any material as long as 33) can be integrated, and for example, an adhesive material such as acrylic resin can be used.

In such a multi-layer liquid crystal display device, each liquid crystal display device is made into a planar state, a focal conic state, or an intermediate thereof based on the respective color image data obtained by separating the image data into R, G and B. By switching to the state, full color display can be performed well.

[0061]

【Example】

Example 1 As a chiral nematic liquid crystal composition sandwiched between substrates, chiral materials MLC-6247 and S811 were used.
A liquid crystal composition containing 20 wt% of a 2: 3 mixture (both manufactured by Merck) with respect to the total amount of the liquid crystal composition and exhibiting a cholesteric phase at room temperature and selectively reflecting light having a wavelength near 680 nm (refractive index anisotropic Property Δn: 0.131, dielectric anisotropy Δε: 10.
3, the transition temperature to the isotropic phase Tc: 79 ° C., the viscosity η: 23 cP) was used.

A silicon oxide thin film was applied as an insulating film on a glass substrate on which ITO electrodes were formed, and an alignment stabilizing film AL4552 (manufactured by JSR) was further formed thereon. The substrates were opposed to each other, a cell gap was adjusted between the substrates with a cell gap adjusted to 7 μm, and sealing was performed with a sealing material XN21S (manufactured by Mitsui Chemicals) except the liquid crystal injection part. Then, a predetermined amount of the chiral nematic composition was injected using a vacuum injection device. A black light absorbing film was provided on the back surface of the liquid crystal display element (the surface of the substrate opposite to the light incident side).

In the above liquid crystal element, 43 V · 5 m between the electrodes
After applying the pulse voltage of s for 2 seconds, the pulse voltage of 0V ・ 2ms-25V ・ 2ms was applied twice, it became transparent (focal conic state), and the Y value was 1.5. 50V ・ 5ms between electrodes
When the pulse voltage of 0V ・ 2ms-43V ・ 2ms was applied twice after the application of the pulse voltage of No.2, it became a colored state (planar state), and the Y value was 5.7. After leaving this liquid crystal element in an oven at 80 ° C for 24 hours, the Y value was measured in the same manner. The Y value in the focal conic state was 1.5, and the Y value in the planar state was Y.
The value was 5.7 and no deterioration occurred. When the response speed was measured, it was 0.38 ms.

The Y value was measured using a spectrocolorimeter CM-3700d (manufactured by Minolta) having a white light source. The viscosity was measured using an E-type viscometer (manufactured by Tokyo Keiki). The response speed is shown by the fall response time. Specifically, a photodiode is installed in a stereoscopic microscope to apply a relatively high voltage (a voltage that can keep the liquid crystal phase in a homeotropic state), monitor the change in reflectance, and change the reflectance from when voltage application is stopped. The time until the end of the abrupt change was measured, and this time was taken as the fall response time. The measurement was performed at room temperature. It should be noted that the liquid crystal in the homeotropic state to which the voltage is applied will eventually be in the planar state when the voltage application is stopped. Two stages are usually observed in the change of the reflectance at that time, the first stage in which the reflectance rapidly increases from the homeotropic state and transits to the intermediate state, and then the reflectance gradually increases and becomes the planar state. The second that becomes calm and constant
There are stages and. Here, in the chart showing the change in reflectance with respect to the elapsed time from the stop of voltage application,
The elapsed time at the intersection of the tangent in the stage and the tangent in the second stage was regarded as the fall response time. Examples below,
The same applies to the comparative example.

Example 2 As a chiral nematic liquid crystal composition sandwiched between substrates, chiral materials CB-15, R811 and R
A liquid crystal composition containing a 5: 3: 2 mixture of 1011 (both manufactured by Merck & Co., Inc.) in an amount of 18 wt% relative to the total amount of the liquid crystal composition, exhibiting a cholesteric phase at room temperature, and selectively reflecting light having a wavelength near 670 nm (△ n: 0.152, Δε: 10.5, Tc: 85 ° C, η: 30c
P) was used.

Next, a polyimide-based orientation control film AL4552 (manufactured by JSR) having a thickness of 800 angstrom was formed on the transparent electrode formation surface of the PES film on which the patterned transparent electrode was formed, to obtain a first substrate. A predetermined amount of a gap control spacer having a diameter of 6 μm was sprayed on the orientation control film formation surface of the first substrate, and then a sealing material XN21S (manufactured by Mitsui Chemicals Inc.) was screen-printed on the peripheral portion in a continuous grid shape. At the same time, an insulating film HIM3000 (manufactured by Hitachi Chemical Co., Ltd.) is formed to a thickness of 2000 angstroms on another PES film (second substrate) on which a patterned transparent electrode is formed, and an alignment control film AL4552 is further formed thereon. Formed to a thickness of 800 Å. The rubbing treatment was not applied to the orientation control film on both substrates.

Subsequently, a resin material containing a thermoplastic resin as a main component is applied on the second substrate, and a large number of holes each having a diameter of about 100 μm are about 500.
It was placed on a metal mask formed at intervals of μm and screen-printed using a squeegee to form a polymer structure in a columnar shape having a height of about 6.5 μm. Then, the liquid crystal composition was applied onto the first substrate, the first and second substrates were bonded together using a bonding apparatus, and heated at 150 ° C. for 1 hour.

In the above liquid crystal element, 38V / 5m between the electrodes
After applying a pulse voltage of s, a pulse voltage of 0V · 2ms−23V · 2ms was applied twice, a transparent state was obtained (focal conic state), and the Y value was 1.8. Also, 38V ・ 5m between electrodes
After applying the pulse voltage of s for 2 seconds, the pulse voltage of 0V ・ 2ms-38V ・ 2ms was applied twice, it became a colored state (planar state), and the Y value was 8.0. After leaving this liquid crystal element in an oven at 80 ° C for 24 hours, the Y value was measured in the same manner. The Y value in the focal conic state was 1.9, and the Y value in the planar state was Y.
The value was 8.0 and there was no deterioration. When the response speed was measured, it was 0.46 ms.

(Example 3) As a chiral nematic liquid crystal composition sandwiched between substrates, a 1: 1 mixture of a chiral material CNL-611R (manufactured by Adeka) and MLC6247 (manufactured by Merck) was added to the total amount of the liquid crystal composition. Of the liquid crystal composition (Δn: 0.165, Δε: 14.8, Tc: 87 ° C, η: 2), which has a cholesteric phase at room temperature and selectively reflects light with a wavelength near 640 nm.
9cP) was used. Next, a liquid crystal element was produced in the same manner as in Example 2. However, the diameter of the gap control spacer was 6 μm, and the height of the cylindrical polymer structure was about 6 μm.

In such a liquid crystal element, between the electrodes
After applying the pulse voltage of 35V ・ 5ms and then applying the pulse voltage of 0V ・ 2ms-20V ・ 2ms twice, it became transparent (focal conic state) and the Y value was 2.3. Also, between the electrodes
After applying a pulse voltage of 35V ・ 5ms and then applying a pulse voltage of 0V ・ 2ms-35V ・ 2ms twice, it was colored (planar state) and the Y value was 14.5. After leaving this liquid crystal element in an oven at 80 ° C. for 24 hours, the Y value was similarly measured. As a result, the Y value in the focal conic state was 2.3, the Y value in the planar state was 14.7, and no deterioration occurred. When the response speed was measured, it was 0.43 ms.

Example 4 As a chiral nematic liquid crystal composition sandwiched between substrates, chiral materials MLC-6247 and S101 were used.
A liquid crystal composition containing a 2: 1 mixture of 1 (both manufactured by Merck & Co., Inc.) in an amount of 14 wt% with respect to the total amount of the liquid crystal composition, exhibiting a cholesteric phase at room temperature, and selectively reflecting light having a wavelength near 610 nm (Δn: 0.175, Δε: 20.8, Tc: 83 ° C, η: 41cP)
It was used. Next, a liquid crystal element was produced in the same manner as in Example 2. However, the diameter of the gap control spacer is 8
The height of the columnar polymer structure was about 8 μm.

In such a liquid crystal element, between the electrodes
After applying a pulse voltage of 40V ・ 5ms and then applying a pulse voltage of 0V ・ 2ms-25V ・ 2ms twice, it became transparent (focal conic state) and the Y value was 2.9. Also, between the electrodes
After applying a pulse voltage of 40V ・ 5ms and then applying a pulse voltage of 0V ・ 2ms-40V ・ 2ms twice, it became colored (planar state) and the Y value was 23.7. After leaving this liquid crystal device in an oven at 80 ° C. for 24 hours, the Y value was similarly measured. The Y value in the focal conic state was 3.0, the Y value in the planar state was 23.9, and no deterioration occurred. When the response speed was measured, it was 0.56 ms.

Example 5 As a chiral nematic liquid crystal composition sandwiched between substrates, chiral materials CB-15 and R811 were used.
A liquid crystal composition containing a 5: 3: 2 mixture of R1011 and R1011 (both manufactured by Merck & Co., Inc.) in an amount of 19 wt% relative to the total amount of the liquid crystal composition, exhibiting a cholesteric phase at room temperature, and selectively reflecting light having a wavelength near 650 nm ( Δn: 0.183, Δε: 16.5, Tc: 95 ° C, η: 3
3cP) was used.

Next, a polyimide-based orientation control film AL4552 (made by JSR) was formed to a thickness of 800 Å on the transparent electrode formation surface of the PES film on which the patterned transparent electrode was formed, and used as the first substrate. Then, a predetermined amount of a gap control spacer having a diameter of 7 μm was sprayed on the orientation control film formation surface of the first substrate, and then a sealing material XN21S (manufactured by Mitsui Chemicals Inc.) was screen-printed in a continuous grid pattern on the peripheral portion. At the same time, an insulating film HIM3000 (manufactured by Hitachi Chemical Co., Ltd.) is formed to a thickness of 2000 angstroms on another PES film (second substrate) on which a patterned transparent electrode is formed, and an alignment control film AL4552 is further formed thereon. Formed to a thickness of 800 Å. The orientation control film on one of the substrates was lightly rubbed.

Subsequently, a resin material containing a thermoplastic resin as a main component is applied on the second substrate, and a large number of holes each having a diameter of about 100 μm are about 500.
It was placed on a metal mask formed at intervals of μm and screen-printed using a squeegee to form a polymer structure in a columnar shape having a height of about 7 μm. Then, the liquid crystal composition was applied onto the first substrate, the first and second substrates were bonded together using a bonding apparatus, and heated at 150 ° C. for 1 hour.

In the above liquid crystal element, 38V / 5m between electrodes
After applying the pulse voltage of s for 2 seconds, the pulse voltage of 0V ・ 2ms-23V ・ 2ms was applied twice, it became transparent (focal conic state), and the Y value was 2.1. Also, 38V ・ 5m between electrodes
After applying the pulse voltage of s for 2 seconds, the pulse voltage of 0V ・ 2ms-38V ・ 2ms was applied twice, it became a colored state (planar state), and the Y value was 12.8. After leaving this liquid crystal element in an oven at 80 ° C for 24 hours, similarly measuring the Y value,
Focal conic Y value of 2.1, planar state
The Y value was 12.7 and there was no deterioration. When the response speed was measured, it was 0.46 ms.

(Example 6) As a first liquid crystal composition, a 2: 1 mixture of chiral materials S-811 and S-1011 (both manufactured by Merck & Co., Inc.) was added to the total amount of the liquid crystal composition in an amount of 20 wt% and yellow. Dye Kaya
liquid crystal composition (Δn: 0.192, Δε: 25.2, T) that contains 0.5 wt% of set Yellow GN (manufactured by Nippon Kayaku Co., Ltd.), exhibits a cholesteric phase at room temperature, and selectively reflects light having a wavelength near 580 nm.
c: 78 ° C., η: 48 cP) was used. As the second liquid crystal composition, a 2: 1 mixture of chiral materials S-811 and S-1011 (both manufactured by Merck & Co., Inc.) was used in an amount of 26 wt% based on the total amount of the liquid crystal composition.
%, A liquid crystal composition showing a cholesteric phase at room temperature and selectively reflecting light having a wavelength near 480 nm (Δn: 0.174, Δ
ε: 20.4, Tc: 76 ° C., η: 84 cP) was used.

Next, an insulating film HIM3000 (manufactured by Hitachi Chemical Co., Ltd.) having a thickness of 2000Å is formed on the transparent electrode provided on the PC film of the first substrate, and an alignment stabilizing film AL4552 (manufactured by JSR) is formed on the insulating film HIM3000.
Was formed to a thickness of 800Å, and spacers (made by Sekisui Fine Chemical) having a diameter of 5 μm were sprinkled thereon. On the transparent electrode on the PC film substrate of the second substrate, the thickness of 2000 Å
After forming the insulating film HIM3000 (manufactured by Hitachi Chemical Co., Ltd.), the alignment stabilization film AL4552 (manufactured by JSR) was formed on it with a thickness of 800 Å.

Then, the sealing material XN is applied to the peripheral portion on the first substrate.
21S (manufactured by Mitsui Chemicals Inc.) was screen-printed to form a wall having a predetermined height, and the first substrate and the second substrate were superposed and cured. In this way, two pairs of substrates were prepared. After that, a predetermined amount of each of the first and second liquid crystal compositions was injected using a vacuum injection device. These cells were laminated using an adhesive sheet to obtain a liquid crystal display element. In addition, a black light absorbing film was provided on the back surface of this liquid crystal display element (the surface of the substrate opposite to the side on which light is incident, the outer surface of the liquid crystal cell into which the first liquid crystal composition was injected).

In the above liquid crystal element, after applying a pulse voltage of 35 V · 5 ms between the electrodes of all cells, 0 V · 2 ms is applied.
When a pulse voltage of -25V ・ 2ms was applied twice, it became transparent (focal conic state) and the Y value was 3.3. Also, after applying a pulse voltage of 35V ・ 5ms between the electrodes, 0V ・ 2m
When a pulse voltage of s-35V ・ 2ms was applied twice, it became a colored state (planar state), and the Y value was 44.3. After leaving this liquid crystal element in an oven at 80 ° C for 24 hours,
When the value is measured, the Y value in the focal conic state is 3.5,
The Y value in the planar state was 44.5, indicating no deterioration. When the response speed was measured, it was 0.52 ms for both the liquid crystal cell injected with the first liquid crystal composition and the liquid crystal cell injected with the second liquid crystal composition. The response speed of the two laminated layers was high and the same, and the drive voltage was also uniform, so it showed desirable characteristics as a laminated element.

Comparative Example 1 As a chiral nematic liquid crystal composition sandwiched between substrates, chiral materials CB15 and R1011 were used.
A liquid crystal composition (Δn: 0.205) containing a 3: 1 mixture (all manufactured by Merck) in an amount of 16 wt% with respect to the total amount of the liquid crystal composition, exhibiting a cholesteric phase at room temperature, and selectively reflecting light having a wavelength near 680 nm. , Δε: 17.1, Tc: 85 ° C, η: 65cP)
It was used. Next, a liquid crystal element was produced in the same manner as in Example 1. However, the diameter of the gap control spacer is 7
It was μm.

After applying a pulse voltage of 38V ・ 5ms between the electrodes to the above liquid crystal element, a pulse voltage of 0V ・ 2ms-23V ・ 2ms was applied for 2 seconds.
When it was applied twice, it became transparent (focal conic state), and the Y value was 1.9. When a pulse voltage of 38V ・ 5ms is applied between the electrodes and then a pulse voltage of 0V ・ 2ms−38V ・ 2ms is applied twice, it becomes a colored state (planar state).
The value was 9.6. Place this liquid crystal element in an oven at 80 ° C.
When the Y value was measured in the same manner after standing for 4 hours, the Y value in the focal conic state was 1.9, and the Y value in the planar state was 9.8, indicating no deterioration. However, the response speed slowed down to 0.83 ms due to the high viscosity of the chiral nematic liquid crystal.

(Comparative Example 2) As a chiral nematic liquid crystal composition sandwiched between substrates, a chiral material R811 (manufactured by Merck & Co., Inc.) was contained in an amount of 22 wt% with respect to the total amount of the liquid crystal composition, and showed a cholesteric phase at room temperature and had a wavelength of about 670 nm. Liquid crystal composition (Δn: 0.163, Δε: 9.8, Tc: 69
C, η: 31 cP) was used. Next, a liquid crystal element was produced in the same manner as in Example 1. However, the diameter of the gap control spacer was 5 μm.

After applying a pulse voltage of 55V · 5ms between the electrodes to the above liquid crystal element, a pulse voltage of 0V · 2ms−25V · 2ms was applied for 2 seconds.
When it was applied twice, it became transparent (focal conic state), and the Y value was 1.9. After applying a pulse voltage of 55V ・ 5ms between the electrodes and then applying a pulse voltage of 0V ・ 2ms−55V ・ 2ms twice, it becomes colored (planar state), and Y
The value was 8.2. Place this liquid crystal element in an oven at 80 ° C.
When the Y value was measured in the same manner after standing for 4 hours, the Y value in the focal conic state was 2.7, and the Y value in the planar state was 7.8, indicating deterioration. This is because the transition temperature to the isotropic phase is low, and the liquid crystal composition was deteriorated and the characteristics were changed by leaving it at 80 ° C. for 24 hours. When the response speed was measured, it was 0.48 ms before the high temperature test and 0 after the high temperature test.
It was 56 ms.

Comparative Example 3 As a chiral nematic liquid crystal composition sandwiched between substrates, chiral materials CB15 and R1011 were used.
A liquid crystal composition (Δn: 0.151) that contains a 2: 3 mixture (both manufactured by Merck Co., Ltd.) of 24 wt% with respect to the total amount of the liquid crystal composition, exhibits a cholesteric phase at room temperature, and selectively reflects light having a wavelength near 650 nm. , Δε: 29.3, Tc: 98 ° C, η: 73cP)
It was used. Next, a liquid crystal element was produced in the same manner as in Example 1. However, the diameter of the gap control spacer is 9
It was μm.

After applying a pulse voltage of 45 V · 5 ms between the electrodes to the above liquid crystal element and then applying a pulse voltage of 0 V · 2 ms−28 V · 2 ms twice, it becomes transparent (focal conic state) and the Y value is It showed 2.1. Further, when a pulse voltage of 45V ・ 5ms was applied between the electrodes and then a pulse voltage of 0V ・ 2ms-45V ・ 2ms was applied twice, it became a colored state (planar state) and the Y value was 12.5. After leaving this liquid crystal element in an oven at 80 ° C for 24 hours, similarly measuring the Y value,
Y value of 3.5 in the focal conic state,
Y value was 11.3 and deterioration was recognized. The response speed was measured and found to be 0.80 ms before the high temperature test and 0.89 ms after the high temperature test.

The above evaluation results are shown in the table below.

[Table 1]

[0089]

The liquid crystal display device containing the chiral nematic liquid crystal composition for red display of the present invention has a relatively high response speed, a reduced driving voltage, is bright, and is excellent in heat resistance stability.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a liquid crystal display element of the present invention.

FIG. 2 is a schematic cross-sectional view of another example of the liquid crystal display element of the present invention.

FIG. 3 is a schematic cross-sectional view of another example of the liquid crystal display element of the present invention.

FIG. 4 is a schematic cross-sectional view of a multi-layer liquid crystal display element.

[Explanation of symbols]

11, 12: substrate, 13, 14: electrode, 15: insulating thin film, 16: visible light absorbing layer, 20: columnar structure, 21: liquid crystal composition, 24: sealing material, 30: adhesive layer, 31: red Liquid crystal display device for display, 3
2: Liquid crystal display element for green display, 33: Liquid crystal display element for blue display.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Noboru Ueda             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture             Osaka International Building Minolta Co., Ltd. F term (reference) 2H088 GA03 GA17 HA21 JA15 MA10                       MA20                 2H089 HA21 RA11 SA09 TA17                 4H027 BA02 BD01 BD04 BD08 BE02                       BE03

Claims (5)

[Claims] 1. At least a nematic liquid crystal mixture and a chiral material are contained, which exhibits a cholesteric phase at room temperature and can selectively reflect light having a peak wavelength of 580 nm to 690 nm, a viscosity of 20 to 50 cP, and a dielectric anisotropy ( Δε) is 10 to 30,
A chiral nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.13 to 0.20 and an isotropic phase transition temperature of 75 ° C to 100 ° C, and a pair of electrodes in which at least one of the electrodes sandwiching the liquid crystal composition is transparent. A liquid crystal display device, comprising: 2. The liquid crystal display device according to claim 1, wherein the chiral material contains two or more kinds of chiral compounds. 3. The viscosity of the chiral nematic liquid crystal composition is
20-35 cP, dielectric anisotropy (△ ε) 15-25, refractive index anisotropy (△ n) 0.16-0.19, isotropic phase transition temperature 80 ℃ ～ 90 ℃
3. The liquid crystal display element according to claim 1 or 2. 4. The thickness of the liquid crystal layer sandwiched between the substrates is 3 to 1
The liquid crystal display device according to claim 1, which has a thickness of 5 μm. 5. A multi-layer liquid crystal display device comprising a plurality of liquid crystal layers, each sandwiched between a pair of substrates with electrodes, wherein at least one of the plurality of liquid crystal layers sandwiches the liquid crystal layer. 5. A multi-layer liquid crystal display device comprising the liquid crystal display device according to claim 1 together with a pair of substrates.