JP2003096459A - Chiral nematic liquid-crystal composition and liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide chiral nematic liquid-crystal compositions for liquid-crystal display elements having high reliability capable of affording a good light reflectance over a long period and maintaining stablely display quality with suppressed burn-in (a residual image) and display unevenness over a long period, and to provide the liquid-crystal display elements. SOLUTION: The chiral nematic liquid-crystal compositions 21r, 21g and 21b comprise at least a nematic liquid-crystal composition and one or more kinds of chiral materials and are capable of selectively reflecting light at a specific wavelength. The moisture content in the liquid-crystal compositions is <=200 ppm. The liquid-crystal display elements A1 and A2 are obtained by sandwiching the chiral nematic liquid-crystal compositions 21r, 21g and 21b capable of selectively reflecting light at the specific wavelength between a pair of substrates 11 and 12. The element A1 has <=400 ppm moisture content in the liquid-crystal compositions 21r, 21g and 21b in the element and the element A2 has <=20 C/cm<2> ion concentration in the liquid-crystal compositions 21r, 21g and 21b.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a chiral nematic liquid crystal composition and a liquid crystal display device.

[0002]

2. Description of the Related Art A liquid crystal display element basically includes a pair of substrates and a liquid crystal layer sandwiched between these substrates. By applying a drive voltage to the liquid crystal layer, the alignment of the liquid crystal molecules is controlled, and the external light incident on the device is modulated to display a desired image.

Various liquid crystal display systems have been proposed.

In recent years, a liquid crystal display device using a chiral nematic liquid crystal composition which exhibits a cholesteric liquid crystal phase at room temperature by adding a chiral material to nematic liquid crystal has been studied.

It is known that this type of liquid crystal display element can be used as a reflection type liquid crystal display element which can be driven with low power consumption by utilizing the selective reflection ability of a chiral nematic liquid crystal composition.

In this reflection type liquid crystal display element, by applying high and low pulse voltages, the liquid crystal can be switched between a planar state (colored state) and a focal conic state (transparent state) for display.

Even after the application of the pulse voltage is stopped, the planar state, the focal conic state, or the mixed state thereof is maintained, that is, the so-called bistability or memory property is exhibited. It is possible to keep the display after stopping.

[0008]

However, in the reflection type liquid crystal display device using the conventional chiral nematic liquid crystal composition, in image display, a sufficiently stable light reflectance is maintained for a long period of time, and image sticking The fact is that a phenomenon having a sufficiently good display quality without a phenomenon called (a phenomenon that a display image remains like an afterimage) and display unevenness has not yet been obtained.

Therefore, it is an object of the present invention to provide a chiral nematic liquid crystal composition for obtaining a liquid crystal display device capable of obtaining a good light reflectance for a long period of time in image display and displaying an image with a large contrast.

Another object of the present invention is to provide a chiral nematic liquid crystal composition for obtaining a highly reliable liquid crystal display device capable of maintaining stable and high display quality in which burn-in and display unevenness are suppressed for a long period of time. And

Another object of the present invention is to provide a liquid crystal display device capable of obtaining a good light reflectance for a long period of time in image display and displaying an image with a large contrast.

Another object of the present invention is to provide a highly reliable liquid crystal display device capable of maintaining stable and high display quality in which burn-in and display unevenness are suppressed for a long period of time.

[0013]

Means for Solving the Problems The inventors of the present invention have made extensive studies to solve the above problems and found the following.

That is, in a liquid crystal display device in which a chiral nematic liquid crystal composition capable of selectively reflecting light of a specific wavelength at room temperature is sandwiched between a pair of substrates, at least one of which is transparent, an ionic substance is contained in the liquid crystal display device. If there is
Ions move with the application of voltage. When an image corresponding to the same information is displayed for a long time, uneven distribution of ions occurs. Therefore, image sticking or display unevenness may occur. The ion concentration in this element is 2
By reducing the value to 0 nC / cm ² or less, it is possible to prevent deterioration of display quality (image display such as image sticking and display unevenness).

If the chiral nematic liquid crystal composition contains water, the ionic substance is dissolved to generate ions. By reducing the amount of water in the chiral nematic liquid crystal composition to 200 ppm or less, it is possible to suppress the ion concentration in the liquid crystal display device when the liquid crystal display device is formed using the liquid crystal composition.

In particular, the water content of the liquid crystal display device itself (in other words, the water content in the liquid crystal composition in the liquid crystal display device when the liquid crystal composition is formed using the liquid crystal composition) is 400 ppm or less,
By setting the ion concentration in the liquid crystal display element to 20 nC / cm ² or less, stable display quality of the liquid crystal display element (image display with good light reflectance and large contrast) can be maintained for a long period of time.

In the production of a liquid crystal display device which constitutes a liquid crystal display device using a chiral nematic liquid crystal composition, water may be mixed into the liquid crystal composition in each step, and the water content of the liquid crystal composition may increase. . Therefore, the water content of the liquid crystal composition contained in the liquid crystal composition when the liquid crystal display element is formed by using the liquid crystal composition in consideration of the water content that will increase in the production of the liquid crystal display element Reduce the water content below.

According to the research conducted by the present inventor, when the amount of water in the chiral nematic liquid crystal composition is 200 ppm or less, the liquid crystal composition in the liquid crystal display device when the liquid crystal display device is formed by using the liquid crystal composition. The amount of water in it can be suppressed to a range where there is no practical problem.

Based on the above findings, the present invention provides the following chiral nematic liquid crystal composition and first and second liquid crystal display devices. (1) Chiral nematic liquid crystal composition A chiral nematic liquid crystal composition containing at least a nematic liquid crystal mixture and one or more chiral materials and capable of selectively reflecting light of a specific wavelength (at room temperature), wherein the water content in the liquid crystal composition is A chiral nematic liquid crystal composition having an amount of 200 ppm or less. (2) Liquid crystal display element (2-1) First liquid crystal display element Chiral nematic liquid crystal capable of selectively reflecting light of a specific wavelength (at room temperature) between a pair of substrates (usually at least one pair of transparent substrates). A liquid crystal display device sandwiching the composition, wherein the water content of the liquid crystal composition in the device is 400 ppm.
The following is a liquid crystal display device. (2-2) Second liquid crystal display device Liquid crystal in which a chiral nematic liquid crystal composition capable of selectively reflecting light of a specific wavelength (at room temperature) is sandwiched between a pair of substrates (usually a pair of substrates in which at least one is transparent). A liquid crystal display device, which is a display device and has an ion concentration of 20 nC / cm ² or less.

According to the chiral nematic liquid crystal composition of the present invention, the water content in the liquid crystal composition is 200 ppm.
Since it is below, when a liquid crystal display device is constructed using the liquid crystal composition, the amount of water in the liquid crystal composition in the device is suppressed low (for example, 400 ppm or less) to suppress the ion concentration in the device. be able to. For example, the ion concentration in the device can be suppressed to 20 nC / cm ² or less. In any case, in image display, a good light reflectance can be obtained for a long period of time, and an image can be displayed with a large contrast. When the ion concentration is 20 nC / cm ² or less, it is possible to maintain stable high display quality in which image sticking and display unevenness are further suppressed for a long period of time, and the liquid crystal display element has high reliability. The water content in the liquid crystal composition is 150 ppm
When the content is more preferably 100 ppm or less, the ion concentration in the liquid crystal display device can be further suppressed.

According to the first liquid crystal display element according to the present invention
And water in the chiral nematic liquid crystal composition in the device
Since the amount is 400 ppm or less, the ions in the element
The concentration can be suppressed. For example, the ions in the device
Concentration is 20 nC / cm²It can be suppressed to the following. In any case
However, in the image display, good light
It is possible to obtain the emissivity and display an image with a large contrast. Io
Concentration of 20 nC / cm ²If it is less than
For stable, high-quality display for a long time
It can be maintained for a long time and is reliable as a liquid crystal display element.
It is highly likely. In chiral nematic liquid crystal composition in device
Water content of 300ppm or less, more preferably 2
If the concentration is less than 00 ppm, the ion concentration in the device will be further increased.
It can be kept low.

According to the second liquid crystal display element of the present invention, since the ion concentration in the element is 20 nC / cm ² or less, it is possible to maintain stable and high display quality in which burn-in and display unevenness are suppressed for a long period of time. Therefore, the liquid crystal display device has high reliability. Ion concentration in the device is 10n
If it is C / cm ² or less, the reliability can be further improved. The amount of water in the chiral nematic liquid crystal composition in the second liquid crystal display device may be 400 ppm or less. In this case, in image display, good light reflectance can be obtained for a long period of time, and an image can be displayed with a large contrast.

The chiral nematic liquid crystal composition may be capable of selectively reflecting light having a specific wavelength in visible light. In any case, the chiral nematic liquid crystal composition has an advantage that the selective reflection wavelength can be controlled by changing the amount of the chiral material (chiral dopant) added. However, the chiral nematic liquid crystal composition may not be able to obtain sufficient reflection characteristics and memory properties when the amount of the chiral material added is less than 7% by weight, and when it is more than 50% by weight, it exhibits a cholesteric phase at room temperature. It may disappear or solidify. Therefore, the chiral nematic liquid crystal composition contains 7% by weight to the total amount of the chiral nematic liquid crystal composition.
It is desirable to contain 50% by weight of chiral material.

The chiral nematic liquid crystal composition of the present invention and the chiral nematic liquid crystal composition used in the first and second liquid crystal display devices of the present invention may contain two or more kinds of chiral materials in the nematic liquid crystal. By mixing two or more kinds of chiral materials, the shift amount of the selective reflection wavelength depending on the temperature can be adjusted, whereby the liquid crystal display element can exhibit stable temperature characteristics.

The chiral nematic liquid crystal composition for improving the contrast has a dielectric anisotropy (
It is preferable that Δε) is 5 to 45, more preferably 10 to 45. When the dielectric constant anisotropy is larger than 45, peripheral members such as a sealing material may melt into the liquid crystal and the reliability of the device may be lowered. If the dielectric anisotropy is less than 5, the driving voltage will be high.

Further, the refractive index anisotropy (Δn) is 0.10.
~ 0.30, more preferably about 0.15 to 0.30, and particularly preferably about 0.16 to 0.22. When the chiral nematic liquid crystal composition has a refractive index anisotropy of about 0.10 to 0.30, it is possible to increase the light reflectance in image display and display an image with high contrast. However, when it is lower than 0.10, the light scattering component decreases, the coloring (selective reflection) in the planar state becomes weak, and sufficient light reflectance cannot be obtained. Conversely, the refractive index anisotropy is 0.30
When it is larger, the scattering component becomes too large, the color purity is lowered, the decolored state in the focal conic state is deteriorated (transparency is difficult to be obtained), and the display performance is deteriorated. In any case, the chiral nematic liquid crystal,
If necessary, water or impurities may be removed by contacting with an ion exchange resin, an adsorbent or the like for purification.

In any case, a dye may be added to the chiral nematic liquid crystal composition. The color purity of the selective reflection peak waveform can be improved by adding a dye to the chiral nematic liquid crystal composition. In that case, as the dye to be added, various conventionally known dyes can be used, and those having good compatibility with the liquid crystal are preferable. For example, a dye composed of an azo compound, a quinone compound, an anthraquinone compound, or a dichroic dye can be used, and a plurality of these dyes may be used. The addition amount is preferably 3% by weight or less with respect to the total amount of the nematic liquid crystal and the chiral material. If the added amount is too large, the selective reflection amount of the liquid crystal becomes low, and the contrast is lowered.

A color filter may be used instead of adding a dye to the chiral nematic liquid crystal composition. In this case, for example, a filter layer can be provided on the liquid crystal display element. The material used for this filter layer may be, for example, a colorless and transparent substance to which a dye is added, or a material that is essentially in a colored state without the dye being added. For example, the filter layer may be a thin film made of a specific substance that acts like a dye. Similar effects can be obtained even if the substrate itself for forming the liquid crystal display element is formed of the above filter layer material.

The viscosity of the chiral nematic liquid crystal composition may be about 30 [cP] to 200 [cP]. The liquid crystal composition has a viscosity of 30 [cP] to 200 [c]
In the case of P], good characteristics such as color purity and light reflectance are obtained, the contrast is improved, the reliability of the device is good, and the driving voltage is low. The viscosity of the liquid crystal composition is 30
If it is lower than [cP], the memory property of the display state of the liquid crystal display element is deteriorated. On the other hand, if it is higher than 200 [cP], the driving voltage of the liquid crystal becomes high, and the time for driving the liquid crystal becomes long.

At least one of the pair of substrates in the first and second liquid crystal display elements may be a resin substrate. By using a resin substrate as the substrate, a lightweight and thin liquid crystal display element can be provided. Moreover, the liquid crystal display element formed of the resin substrate is difficult to break.

In any case, an alignment stabilizing film may be formed on at least one of the pair of substrates of the first and second liquid crystal display elements. By forming the alignment stabilizing film, the interaction between the liquid crystal and the alignment stabilizing film is strengthened, the liquid crystal molecules are uniformly aligned, the light reflectance in the planar state is increased, and the contrast as an element is improved.

In the first and second liquid crystal display devices, when the alignment stabilizing film is formed on at least one of the pair of substrates, the chiral nematic liquid crystal composition is used, and the nematic liquid crystal is mixed with a chiral material. weight%
˜50% by weight, the driving voltage is low by setting the film thickness of the alignment stabilizing film to 20 nm to 200 nm, and when a multi-layer liquid crystal display device is configured as described later, good full color display quality is obtained. Can be achieved.

In any case, a plurality of structures (resin structure, resin composition structure, etc.) mainly composed of a polymer material are provided between the pair of substrates of the first and second liquid crystal display elements. It may be. By providing a plurality of structures mainly composed of a polymer material between a pair of substrates, a large-area liquid crystal panel can be manufactured, and the accuracy and strength of the thickness between the substrates can be improved. Further, the memory property as a liquid crystal display element is improved.

A laminated liquid crystal display element may be formed by laminating a plurality of liquid crystal display elements, at least one of which is one of the first and second liquid crystal display elements according to the present invention. A liquid crystal having a liquid crystal composition capable of improving light reflectance by, for example, stacking a plurality of liquid crystal display elements including the first and second liquid crystal display elements and selectively reflecting the wavelength of red light. By laminating at least three liquid crystal display elements, a display element, a liquid crystal display element having a liquid crystal composition capable of selectively reflecting the wavelength of green light, and a liquid crystal display element having a liquid crystal composition capable of selectively reflecting the wavelength of blue light Full color display can be performed.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS (Structure and Display Operation of First Embodiment) FIG. 1 is a schematic view showing a cross-sectional structure of a reflective multi-layer liquid crystal display element according to a first embodiment of the present invention. A)
FIG. 1 shows a planar state (R (red) G (green) B (blue) colored state when a high voltage pulse is applied to FIG.
7B shows a focal conic state (transparent / black display state) when a low voltage pulse is applied. Note that this liquid crystal display element has a memory property, and the planar state and the focal conic state can be maintained even after the pulse voltage is applied.

The multi-layer liquid crystal display element shown in FIG. 1 includes an R liquid crystal layer r (red layer (red liquid crystal display element)) for displaying red color, which includes liquid crystal compositions 21r, 21g and 21b, respectively.
The three liquid crystal layers (liquid crystal display elements), G liquid crystal layer g (green layer (green liquid crystal display element)) for displaying green and B liquid crystal layer b (blue layer (blue liquid crystal display element)) for displaying blue color, are arranged in this order. It is the one that is laminated.

Each of the R, G, and B liquid crystal layers r, g, and b emits light of a specific wavelength in visible light at room temperature between a pair of substrates 11 and 12 in which at least one (here, both) is transparent. Chiral nematic liquid crystal composition 21 capable of selective reflection
r, 21g, 21b and a space holding material (here, the spacer 18 and the columnar structure 20) for holding the space between the substrates 11 and 12 are sandwiched.

In each of the liquid crystal layers r, g and b in FIG.
Reference numerals 1 and 12 denote transparent substrates having a light-transmitting property.
A plurality of transparent electrodes 13 and 14 formed in parallel with each other are provided on the respective surfaces of 1 and 12. These electrodes 13 and 14 are opposed to each other so as to intersect each other when viewed in a direction perpendicular to the substrate. The electrodes are preferably coated with an insulating thin film. Here, the electrodes 13 and 14 are each coated with an insulating thin film 15. An orientation stabilizing film 17 is provided on the insulating thin film 15. If necessary, on the outer surface (back surface) of the substrate opposite to the side on which light is incident,
A visible light absorbing layer is provided. Here, the visible light absorption layer 16 is provided on the back surface of the substrate 12 in the red layer r.

Reference numerals 18 and 20 denote spacers and columnar structures serving as space holding members, respectively.
Here, g and 21b are chiral nematic liquid crystal compositions that exhibit a cholesteric phase at room temperature. These materials and combinations thereof will be specifically described by the following experimental examples. 24 is a sealing material, and the liquid crystal composition 21
It is for enclosing r, 21g, and 21b between the substrates 11 and 12.

Reference numeral 25 is a pulse applying device for applying a pulsed predetermined voltage between the electrodes 13 and 14 of each liquid crystal layer.

This multi-layer liquid crystal display device is one of the following. That is, (a) each liquid crystal layer r, g, b
In the liquid crystal compositions 21r, 21g, and 21b, the water content is 4
A multi-layer liquid crystal display element A1 having a content of 00 ppm or less. (B)
Ion concentration in each liquid crystal layer r, g, b is 20 nC / cm
^2. A multi-layer liquid crystal display device A2 having ² or less. The amount of water in the liquid crystal composition 21r, 21g, 21b in each of the liquid crystal layers r, g, b may be 400 ppm or less. (Substrate) As described above, the substrates 11 and 12 each have a light-transmitting property, but the substrates 11 and 12 have a light-transmitting property that transmits at least visible light for image observation. It should be one. A glass substrate can be given as an example of the translucent substrate. Besides glass substrates, for example, polycarbonate (PC), polyether sulfone (PE
Flexible substrates such as S), polyarylate (PAr), and polyethylene terephthalate (PET) can be used. (Electrode) As the electrode, for example, Indium Tin
Oxide (ITO: Indium Tin Oxide), Ind
transparent conductive film such as ium zinc oxide (IZO: indium zinc oxide), metal electrode such as aluminum and silicon, or amorphous silicon, BSO
A photoconductive film such as (Bismuth Silicon Oxide) can be used.

In the liquid crystal display elements A1 and A2 shown in FIG. 1, a plurality of belt-shaped transparent electrodes 13 and 14 parallel to each other are formed on the surfaces of the transparent substrates 11 and 12, as described above. 13 and 14 are opposed to each other so as to intersect each other when viewed from the direction perpendicular to the substrate.

To form the electrodes in this way, for example, an ITO film may be mask-deposited on the transparent substrate by a sputtering method or the like, or the ITO film may be entirely formed and then patterned by a photolithography method. (Insulating thin film) In the liquid crystal display element, an insulating thin film having a function of preventing a short circuit between electrodes or having a function of improving reliability of the liquid crystal display element may be formed as a gas barrier layer. As described above, the insulating thin film 15 is coated on each of the electrodes 13 and 14 here.

The thickness of the insulating thin film is, for example, 20 n.
About m to 200 nm is desirable. Examples of the material of the insulating thin film include inorganic materials such as silicon oxide, titanium oxide, zirconium oxide and alkoxides thereof, and organic materials such as polyimide resin, acrylic resin and urethane resin.

The insulating thin film can be formed using these materials by a known method such as a spin coating method or a roll coating method.

The insulating thin film also functions as a color filter by adding a dye to the above material. (Alignment stabilizing film) As the alignment stabilizing film, a polyimide resin, a polyamideimide resin, a polyetherimide resin,
Examples thereof include organic films such as polyvinyl butyral resin and acrylic resin, and inorganic films such as silicon oxide and aluminum oxide.

By providing the orientation stabilizing film, the orientation of the liquid crystal is improved, the light reflectance at the time of coloring is improved, and the response of the liquid crystal is also accelerated.

The alignment stabilizing film is formed, for example, as follows. That is, first, the above resin or its precursor is dissolved in N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, γ-butyrolactone or the like to prepare a coating solution. This coating solution, like the insulating thin film,
It is applied onto the substrate by using a method such as a spin coating method or a roll coating method. At that time, it is dried in a hot oven or hot plate. Thus, the alignment stabilizing film can be obtained.

It is not necessary to perform rubbing treatment on the alignment stabilizing film formed by using these materials. But,
For example, the reflectance can be improved by weakly rubbing one surface of the alignment stabilizing film 17 formed on each of the substrates 11 and 12. However, if rubbing is performed on both substrates or if the rubbing density is too high, the viewing angle dependency may become too large, or the memory property may be lost.

(Spacer) In the liquid crystal display element, a spacer may be provided between a pair of substrates for maintaining a uniform gap between the substrates. In the liquid crystal display elements A1 and A2 of this example, a spacer 18 is arranged between the substrates 11 and 12.

Examples of this spacer include spheres made of resin or inorganic oxide. Inorganic oxide spheres have the advantage over the resin spheres in that the thickness accuracy of the cell is easier to obtain and the heat resistance is better. Note that the structure in which both the spacer and the columnar structure are provided as in this example can accurately and satisfactorily maintain the distance between the substrates, and when a flexible substrate such as a resin substrate is used, or the area of the display region. Although it is very preferable that the distance between the substrates can be accurately maintained even when is large, only the columnar structure may be used as the space holding member. (Liquid crystal composition) The liquid crystal composition contained in the liquid crystal layer is prepared so as to exhibit a cholesteric liquid crystal phase by adding a chiral material to nematic liquid crystal, and selectively reflects light of a specific wavelength. . As described above, the water content is 200 ppm or less. Water content 150p
pm or less, and more preferably 100 ppm or less. The chiral nematic liquid crystal composition has a refractive index anisotropy (Δn) of 0.10 to 0.30 and a dielectric anisotropy.
(Δε) is preferably 5 to 45, more preferably 10 to 45.

When the refractive index anisotropy is lower than 0.10, the color purity of reflected light is poor and the reflectance is poor. On the contrary, 0.30
If it is too high, the viewing angle dependency becomes large.

If the dielectric constant anisotropy is lower than 5, the driving voltage will be high, and if it is higher than 45, the stability and reliability of the device will be deteriorated, and image defects and image noises will easily occur. turn into. Chiral material is 7% by weight to 5
It is preferable to add 0% by weight. The addition amount of the chiral material is a value when the total amount of the nematic liquid crystal and the chiral material is 100% by weight.

If the content of the chiral material is less than 7% by weight, the desired selective reflection wavelength may not be obtained or sufficient memory property may not be obtained, and if it exceeds 50% by weight, the cholesteric phase may be formed at room temperature. May not show or may solidify. As a nematic liquid crystal,
Various conventionally known nematic liquid crystals can be used. For example, a mixture of various liquid crystal compounds such as a tolan compound, an ester compound and a phenylcyclohexane compound can be used. (Columnar Structure) In the liquid crystal display element, a pair of substrates may be supported by a structure in order to impart a strong self-holding property. The liquid crystal display elements A1 and A2 of this example include a substrate 11,
A columnar structure 20 is provided between the columns 12.

Regarding the columnar structure, the structural surface will be described first. Examples of the columnar structure include columnar structures such as a columnar body, a square columnar body, an elliptic columnar body, a trapezoidal columnar body, and a conical columnar body, which are arranged at a predetermined interval in a predetermined pattern such as a lattice arrangement. be able to. Further, it may be stripe-shaped ones arranged at predetermined intervals. The columnar structure is not a random array, but an array of even intervals, an array in which the intervals gradually change, 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 display an image. It is preferable that the arrangement is such that it does not interfere with The columnar structure has a practical strength as a liquid crystal display device while maintaining an appropriate strength.
The ratio of the area occupied by the display area of the liquid crystal display element is 1% to 4
It may be about 0%.

Examples of the material of the columnar structure include various resin materials such as thermoplastic resin material, thermosetting resin material and photocurable resin material. Specific examples thereof include epoxy resin, acrylic resin, polyester resin, polyether resin, polyethylene resin, and polyimide resin. The columnar structure can be formed by various methods such as a method of directly disposing the resin material by screen printing or the like, or a method of applying the resin material and then forming it by a photolithography process using a mask.

To form a liquid crystal display device after the columnar structure is formed, the liquid crystal composition may be injected between the substrates sandwiching the columnar structure by a vacuum injection method or the like. Alternatively, the liquid crystal composition may be dropped when the substrates are attached, and the liquid crystal composition may be sealed at the same time when the substrates are attached.

Further, in order to improve the accuracy of controlling the gap between the substrates, when forming the columnar structure, a spacer material having a size smaller than the film thickness of the columnar structure, for example, between the substrates is used.
Glass fibers, spherical glass or ceramic powder, or spherical particles made of an organic material are arranged so that the gap is not changed by heating or pressing. By doing so, the gap accuracy can be further improved, and the voltage application unevenness, the display unevenness, and the like can be reduced accordingly. (Structure of Second Embodiment) FIG. 2 shows a cross-sectional structure of reflective multilayer liquid crystal display elements B1 and B2 according to a second embodiment of the present invention. Note that FIG. 2A shows the planar state when a high voltage pulse is applied, and FIG. 2B shows the focal conic state when a low voltage pulse is applied.

The liquid crystal display elements B1 and B2 are the same as the liquid crystal display elements A1 and A2 of the first embodiment shown in FIG. 1 except that no columnar structure is provided in the liquid crystal display element display region. They are essentially the same. The device B1 is a device (device of the type described in (a) above) containing a chiral nematic liquid crystal composition of the same type as the device A1,
The element B2 is an element (element of the type described in (b) above) containing the same type of chiral nematic liquid crystal composition as the element A2. In addition, in FIG. 2, the same reference numerals are attached to the portions having basically the same configurations and functions as those of the element of FIG. (Structure of Third Embodiment) FIG. 3 shows a sectional structure of a reflective liquid crystal display device according to a third embodiment of the present invention. Note that FIG.
FIG. 3A shows a planar state when a high voltage pulse is applied, and FIG. 3B shows a focal conic state when a low voltage pulse is applied.

This liquid crystal display element uses each of the liquid crystal layers in the liquid crystal display elements A1 and A2 shown in FIG. 1 in a single layer structure, and has a structure substantially similar to that of each liquid crystal layer in FIG. It is one that can be used as a mono-color or monochrome display element (one that can perform two-color display by the selective reflection color of liquid crystal and the color of the visible light absorbing layer on the back surface).
Incidentally, in FIG. 3, basically the same configuration as the element of FIG.
The parts having the action are given the same reference numerals.

The liquid crystal display element shown in FIG. 3 has a pair of substrates 11, 12 of which at least one (here, both) is transparent.
In between, a chiral nematic liquid crystal composition 21y and substrates 11, 12 capable of selectively reflecting light of a specific wavelength in visible light at room temperature
The space holding members 18 and 20 for holding the space therebetween are sandwiched and are any of the following. That is, (a) a liquid crystal display element C1 in which the amount of water in the liquid crystal composition 21y in the element is 400 ppm or less. (B)
A liquid crystal display device C2 having an ion concentration of 20 nC / cm ² or less in the device. The amount of water in the liquid crystal composition in the liquid crystal display element C2 may be 400 ppm or less.

If necessary, the visible light absorbing layer 16 is provided on the outer surface (back surface) of the substrate opposite to the side on which light is incident.
Is provided. (Structure of Fourth Embodiment) FIG. 4 shows a sectional structure of a reflective liquid crystal display device according to a fourth embodiment of the present invention. Note that FIG.
FIG. 4A shows a planar state when a high voltage pulse is applied, and FIG. 4B shows a focal conic state when a low voltage pulse is applied.

The liquid crystal display elements D1 and D2 are the same as the liquid crystal display elements C1 and C2 of the third embodiment shown in FIG. 3 except that no columnar structure is provided in the liquid crystal display element display region. It has substantially the same structure and can be used as a mono-color or monochrome display element. The device D1 is a device containing the same type of chiral nematic liquid crystal composition as the device C1 (the above (a)).
The device of the type described above), and the device D2 is a device containing the same type of chiral nematic liquid crystal composition as the device C2 (device of the type described in (b)). Note that FIG.
In Fig. 3, the same reference numerals are given to the portions having basically the same configurations and functions as those of the element of Fig. 3.

According to the liquid crystal display devices A1 to D1 (devices of the above-mentioned (a) type) of the first to fourth embodiments described above, the chiral nematic liquid crystal composition 2 in the device is used.
Water content in 1r, 21g, 21b, 21y is 400pp
Since it is m or less, the ion concentration in the device can be suppressed. For example, if the ion concentration in the device is 20 nC /
It can be suppressed to cm ² or less. In any case, in image display, a good light reflectance can be obtained for a long period of time, and an image can be displayed with a large contrast. Ion concentration is 20 nC
When it is / cm ² or less, it is possible to maintain stable and high display quality in which image sticking and display unevenness are suppressed for a long period of time, and the reliability as a liquid crystal display device is high.

Further, according to the liquid crystal display elements A2 to D2 (elements of the above-mentioned (b) type), since the ion concentration in the element is 20 nC / cm ² or less, burn-in and display unevenness are suppressed and stable. High display quality can be maintained for a long period of time, and the liquid crystal display device has high reliability.
When the amount of water in the chiral nematic liquid crystal composition in the liquid crystal display elements A2 to D2 is 400 ppm or less, a good light reflectance can be obtained and an image can be displayed with a large contrast for a long time in image display.
In particular, in the liquid crystal display elements A1 to D1 and A2 to D2,
When the ion concentration of the chiral nematic liquid crystal composition in the device is 10 nC / cm ² or less and the water content is 200 ppm or less, more excellent properties are exhibited.

Next, a performance evaluation experiment of the liquid crystal display device according to the present invention was conducted, and it will be specifically described together with a comparative experiment. However, the present invention is not limited to those experimental examples.

In each of the following experimental examples and comparative experimental examples, the reflectance of the liquid crystal display device was measured by a reflection type spectrocolorimeter CM-3.
Luminous reflectance (Y value) using 700d (Minolta)
Was measured. The smaller the Y value when erasing, the better the transparency and black display, and the larger the Y value when coloring, the better the color display. Also, the contrast is [Y value in high reflectance state (colored) / Y value in low reflectance state (decolored)].
Given in. In the liquid crystal display element in each experimental example and comparative experimental example described below, the liquid crystal display element is in a high reflectance state when it is in a planar state and in a low reflectance state when it is in a focal conic state.

The water content of the chiral nematic liquid crystal composition and the water content of the chiral nematic liquid crystal composition in the liquid crystal display device (liquid crystal cell) were measured using a Karl Fischer moisture meter CA-100 (manufactured by Mitsubishi Chemical Corporation). . Incidentally, the measurement of the water content of the liquid crystal composition in the liquid crystal cell is carried out by first preparing the liquid crystal cell, then extracting the liquid crystal composition from the liquid crystal cell with an injector in an autoclave, and extracting the water content of the liquid crystal composition. This was done by measuring the amount.

The ion concentration in the liquid crystal display element (liquid crystal cell) is measured by an ion concentration measuring device M manufactured by Toyo Technica.
Performed using RTI. (Experimental Example 1) 41 parts by weight of a chiral material CB15 (manufactured by Merck) was added to 59 parts by weight of a nematic liquid crystal mixture E31 (manufactured by Merck), and a liquid crystal composition was prepared so as to selectively reflect light having a wavelength of 570 nm. A was prepared, and then the liquid crystal composition was purified by the following procedure. First, the process of dissolving the liquid crystal composition in toluene, adding ultrapure water, shaking and separating water was repeated 3 times. After further adding silica gel to adsorb residual water and the like, the silica gel was removed and toluene was distilled off. Further, after drying the liquid crystal composition under heating and reduced pressure, the liquid crystal composition was transferred to a container, air in the container was degassed, and an inert gas was sealed. Thus, this liquid crystal composition was purified.

The water content of the liquid crystal composition A was measured and found to be 75 ppm. Further, the refractive index anisotropy Δn, the dielectric anisotropy Δε, and the viscosity η of the liquid crystal composition A are Δ, respectively.
The values were n: 0.18, Δε: 12, and η: 70 cP.

Next, two polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1 was formed on the transparent electrodes provided on the first PC film substrate.
001 (Nissan Chemical Co., Ltd.) is used to form an insulating film having a thickness of 1000 Å, and then an alignment film material AL4552 (J
SR-made) was used to form an alignment stabilizing film having a thickness of 450 Å, and spacers having a diameter of 6 μm were further scattered thereon.

On the transparent electrode on the second PC film substrate, an insulating film material OA-1001 (manufactured by Nissan Kagaku Co., Ltd.) was first used to form an insulating film having a thickness of 1000Å, and then an alignment film material was formed thereon. An alignment stabilizing film having a thickness of 450Å was formed using AL4552.

Then, the sealing material X is formed on the peripheral portion of the first substrate.
N21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed to form a wall having a predetermined height.

The two substrates were washed with isopropyl alcohol and dried.

After that, the liquid crystal composition A is applied on the first substrate in an amount calculated from the height of the sealing material and the area of the portion surrounded by the sealing material, and the first and second liquid crystal compositions are bonded using a bonding apparatus.
The substrates were attached so that their electrode-formed surfaces faced each other, and heated at 150 ° C. for 1 hour. Thus, a liquid crystal cell was obtained.

A black light absorbing film was provided on the back surface of this liquid crystal cell (the surface of the second substrate opposite to the light incident side).

The water content of the liquid crystal composition in the liquid crystal cell thus produced was 98 ppm. The ion concentration of this liquid crystal cell was measured and found to be 12 nC / cm ² .

Next, in order to bring this liquid crystal cell into a colored state, a pulse voltage under the following conditions was applied.

Reset pulse: ± 48 V, width 0.5 m
s, reset period 50 ms selection pulse: ± 28 V, width 0.1 ms, selection period 0.5
ms sustain pulse: ± 20V, width 0.5ms, sustain period 50m
As a result, the liquid crystal cell exhibited a green color, the Y value was 22.8, and the peak reflectance was 37%.

The reset pulse is a pulse which brings the liquid crystal into a homeotropic state, and the selection pulse is a reset pulse which is obtained by modulating a voltage value or a pulse width according to image data in order to set the liquid crystal in a desired state. The sustain pulse is a pulse applied after the selection pulse to establish a state to be selected by the selection pulse.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

Reset pulse: ± 48 V, width 0.5 m
s, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 10 V, width 0.5 ms, sustain period 50 m
s As a result, the liquid crystal cell exhibited a black color, the Y value was 2.5, the contrast (Y value ratio) was 9.1, which was very high, and a good display without the influence of the coloring state was obtained. (Experimental Example 2) 19 parts by weight and 15 parts by weight of chiral material CB15 (made by Merck) and chiral material R-811 (made by Merck) are added to 66 parts by weight of nematic liquid crystal mixture E44 (made by Merck). Then, a liquid crystal composition B was prepared so as to selectively reflect light having a wavelength of 558 nm, and this liquid crystal composition was purified by the same procedure as in Experimental Example 1.

The water content of the liquid crystal composition B was measured and found to be 68 ppm. The liquid crystal composition B has a refractive index anisotropy, a dielectric anisotropy, and a viscosity of Δn: 0.1, respectively.
7, Δε: 13, η: 68 cP.

Next, two polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1 was formed on the transparent electrodes provided on the first PC film substrate.
001 (Nissan Chemical Co., Ltd.) is used to form an insulating film having a thickness of 1000 Å, and then an alignment film material AL4552 (J
SR-made) was used to form an alignment stabilizing film having a thickness of 450 Å, and spacers having a diameter of 6 μm were further scattered thereon.

On the transparent electrode on the second PC film substrate, an insulating film material OA-1001 (manufactured by Nissan Kagaku Co., Ltd.) was first used to form an insulating film having a thickness of 1000 Å, and then an alignment film material was formed thereon. An alignment stabilizing film having a thickness of 450Å was formed using AL4552.

Then, the sealing material X is applied to the peripheral portion on the first substrate.
N21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed to form a wall having a predetermined height.

The two substrates were washed with pure water and dried.

After that, the liquid crystal composition B in an amount calculated from the height of the sealing material and the area of the portion surrounded by the sealing material is applied onto the first substrate, and the first and second layers are applied using a bonding apparatus.
The substrates were attached so that their electrode-formed surfaces faced each other, and heated at 150 ° C. for 1 hour. Thus, a liquid crystal cell was obtained.

A black light absorbing film was provided on the back surface of this liquid crystal cell (the surface of the second substrate opposite to the light incident side).

The water content of the liquid crystal composition in the liquid crystal cell thus produced was 120 ppm. The ion concentration of this liquid crystal cell was measured and found to be 10 nC / cm ² .

Next, in order to bring this liquid crystal cell into a colored state, a pulse voltage under the following conditions was applied.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms selection pulse: ± 30 V, width 0.1 ms, selection period 0.5
ms sustain pulse: ± 20V, width 0.5ms, sustain period 50m
s As a result, the liquid crystal cell exhibited a green color, the Y value was 24.0, and the peak reflectance was 36%.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 10 V, width 0.5 ms, sustain period 50 m
s As a result, the liquid crystal cell exhibited a black color, the Y value was 2.6, and the contrast (Y value ratio) was 9.2, which was very high, and a good display that was not affected by the coloring state was possible. (Experimental Example 3) 34 parts by weight of chiral material S-811 (manufactured by Merck & Co., Inc.) was added to 66 parts by weight of the nematic liquid crystal mixture a containing a liquid crystal ester compound and a liquid crystal tolan compound as main components, and 478 nm. A liquid crystal composition C was prepared so as to selectively reflect light of a wavelength, and this liquid crystal composition was purified by the same procedure as in Experimental Example 1.

The water content of the liquid crystal composition C was measured and found to be 43 ppm. The liquid crystal composition C has a refractive index anisotropy, a dielectric constant anisotropy, and a viscosity of Δn: 0.1, respectively.
8, Δε: 25, η: 75 cP.

Next, two polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1 was formed on the transparent electrodes provided on the first PC film substrate.
001 (Nissan Chemical Co., Ltd.) is used to form an insulating film having a thickness of 1000 Å, and then an alignment film material AL4552 (J
SR-made) was used to form an alignment stabilizing film having a thickness of 450 Å, and spacers having a diameter of 5 μm were scattered on the film.

On the transparent electrode on the second PC film substrate, an insulating film material OA-1001 (manufactured by Nissan Chemical Co., Ltd.) was first used to form an insulating film having a thickness of 1000 Å, and then an alignment film material was formed thereon. An alignment stabilizing film having a thickness of 450Å was formed using AL4552.

Then, the sealing material X is applied to the peripheral portion on the first substrate.
N21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed to form a wall having a predetermined height.

The two substrates were washed with a mixed solvent of pure water and ethanol and dried.

After that, the liquid crystal composition C is applied on the first substrate in an amount calculated from the height of the sealing material and the area of the portion surrounded by the sealing material, and the first and second liquid crystal compositions are bonded using a bonding apparatus.
The substrates were attached so that their electrode-formed surfaces faced each other, and heated at 150 ° C. for 1 hour. Thus, a liquid crystal cell was obtained.

A black light absorbing film was provided on the back surface of this liquid crystal cell (the surface of the second substrate opposite to the light incident side).

The water content of the liquid crystal composition in the liquid crystal cell thus produced was 75 ppm. The ion concentration of this liquid crystal cell was measured and found to be 8 nC / cm ² .

Next, in order to bring this liquid crystal cell into a colored state, a pulse voltage under the following conditions was applied.

Reset pulse: ± 45 V, width 0.5 m
s, reset period 50 ms selection pulse: ± 28 V, width 0.1 ms, selection period 0.5
ms sustain pulse: ± 20V, width 0.5ms, sustain period 50m
s As a result, the liquid crystal cell exhibited a blue color, the Y value was 25.5, and the peak reflectance was 37%.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

Reset pulse: ± 45 V, width 0.5 m
s, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 9 V, width 0.5 ms, sustain period 50 ms As a result, the liquid crystal cell exhibits a black color, the Y value shows 2.7, and the contrast ( The Y value ratio) was 9.4, which was very high, and a good display was obtained without being affected by the coloring state. (Experimental Example 4) Chiral material R-811 (manufactured by Merck) and chiral material CB15 (manufactured by Merck) were added to 74 parts by weight of a nematic liquid crystal mixture b containing a liquid crystal castel compound and a liquid crystal tolan compound as main components, respectively. 14 parts by weight,
12 parts by weight, and further the dye KAYASET Yellow GW
(Nippon Kayaku Co., Ltd.) was added in an amount of 0.6 part by weight to prepare a liquid crystal composition D so as to selectively reflect light having a wavelength of 690 nm.
This liquid crystal composition was purified by the same procedure as in Experimental Example 1.

The water content of the liquid crystal composition D was measured and found to be 35 ppm. The liquid crystal composition D has a refractive index anisotropy, a dielectric anisotropy, and a viscosity of Δn: 0.1, respectively.
7, Δε: 28.5, η: 65 cP.

Next, two polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1 was formed on the transparent electrodes provided on the first PC film substrate.
001 (Nissan Chemical Co., Ltd.) is used to form an insulating film having a thickness of 1000 Å, and then an alignment film material AL4552 (J
SR-made) was used to form an alignment stabilizing film having a thickness of 450 Å, and spacers having a diameter of 6 μm were further scattered thereon.

On the transparent electrode on the second PC film substrate, an insulating film material OA-1001 (manufactured by Nissan Chemical Co., Ltd.) was first used to form an insulating film having a thickness of 1000 Å, and then an alignment film material was formed thereon. An alignment stabilizing film having a thickness of 450Å was formed using AL4552.

Then, the sealing material X is applied to the peripheral portion on the first substrate.
N21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed to form a wall having a predetermined height.

The two substrates were washed with isopropyl alcohol and dried.

After that, an amount of the liquid crystal composition D calculated from the height of the sealing material and the area of the portion surrounded by the sealing material is applied onto the first substrate, and the first and second liquid crystal devices are bonded using a bonding apparatus.
The substrates were attached so that their electrode-formed surfaces faced each other, and heated at 150 ° C. for 1 hour. Thus, a liquid crystal cell was obtained.

A black light absorbing film was provided on the back surface of this liquid crystal cell (the surface of the second substrate opposite to the light incident side).

The water content of the liquid crystal composition in the liquid crystal cell thus produced was 68 ppm. The ion concentration of this liquid crystal cell was measured and found to be 5 nC / cm ² .

Next, in order to bring this liquid crystal cell into a colored state, a pulse voltage under the following conditions was applied.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms, selection pulse: ± 35 V, width 0.1 ms, selection period 0.5
ms sustain pulse: ± 18V, width 0.5ms, sustain period 50m
s As a result, the liquid crystal cell exhibited a red color, the Y value was 26.5, and the peak reflectance was 38%.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 12 V, width 0.5 ms, sustain period 50 m
s As a result, the liquid crystal cell exhibited a black color, the Y value was 3.1, and the contrast (Y value ratio) was 8.5, which was very high, and a good display unaffected by the coloring state was obtained. Experimental Example 5 To 76 parts by weight of a nematic liquid crystal mixture c containing a liquid crystal ester compound as a main component, 24 parts by weight of a chiral material S-811 (manufactured by Merck Ltd.) was added, and 690
Liquid crystal composition E was prepared so as to selectively reflect light having a wavelength of nm, and this liquid crystal composition was purified by the same procedure as in Experimental Example 1.

The water content of the liquid crystal composition E was measured and found to be 165 ppm. Further, the refractive index anisotropy, the dielectric anisotropy, and the viscosity of the liquid crystal composition E are Δn: 0.
16, Δε: 31, η: 110 cP.

Next, two polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1 was formed on the transparent electrodes provided on the first PC film substrate.
001 (Nissan Chemical Co., Ltd.) is used to form an insulating film having a thickness of 1000 Å, and then an alignment film material AL4552 (J
SR-made) was used to form an alignment stabilizing film having a thickness of 450 Å, and spacers having a diameter of 6 μm were further scattered thereon.

On the transparent electrode on the second PC film substrate, first, an insulating film material OA-1001 (manufactured by Nissan Chemical Industries, Ltd.) was used to form an insulating film having a thickness of 1000 Å, and then an alignment film material was formed thereon. An alignment stabilizing film having a thickness of 450Å was formed using AL4552.

Then, the sealing material X is applied to the peripheral portion on the first substrate.
N21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed to form a wall having a predetermined height.

The two substrates were washed with pure water and dried.

Then, the liquid crystal composition E is applied on the first substrate in an amount calculated from the height of the sealing material and the area of the portion surrounded by the sealing material, and the first and second liquid crystal compositions are bonded by using a bonding apparatus.
The substrates were attached so that their electrode-formed surfaces faced each other, and heated at 150 ° C. for 1 hour. Thus, a liquid crystal cell was obtained.

A black light absorbing film was provided on the back surface of this liquid crystal cell (the surface of the second substrate opposite to the light incident side).

The water content of the liquid crystal composition in the liquid crystal cell thus produced was 350 ppm. The ion concentration of this liquid crystal cell was measured and found to be 17 nC / cm ² .

Next, in order to bring this liquid crystal cell into a colored state, a pulse voltage under the following conditions was applied.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms, selection pulse: ± 35 V, width 0.1 ms, selection period 0.5
ms sustain pulse: ± 18V, width 0.5ms, sustain period 50m
s As a result, the liquid crystal cell exhibited a red color, the Y value was 26.5, and the peak reflectance was 38%.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 12 V, width 0.5 ms, sustain period 50 m
s As a result, the liquid crystal cell exhibited a black color, the Y value was 3.1, and the contrast (Y value ratio) was 8.5, which was very high. It was (Experimental Example 6) 36 parts by weight of the chiral material CB15 (manufactured by Merck) was added to 64 parts by weight of the nematic liquid crystal mixture E31 (manufactured by Merck), and a liquid crystal composition was prepared so as to selectively reflect light having a wavelength of 672 nm. f1 was prepared. Further, 42 parts by weight of the chiral material CB15 was added to 58 parts by weight of the nematic liquid crystal mixture E31, and a liquid crystal composition f2 was prepared so as to selectively reflect light having a wavelength of 562 nm. Furthermore, 47 parts by weight of the chiral material CB15 was added to 53 parts by weight of the nematic liquid crystal mixture E31,
A liquid crystal composition f3 was prepared so as to selectively reflect light having a wavelength of 476 nm. Then, the liquid crystal compositions f1, f2, and f3 were each purified in the same procedure as in Experimental Example 1.

The water content of each of the liquid crystal compositions f1, f2 and f3 was measured to be 86 ppm, 90 ppm and
It was 95 ppm. The liquid crystal composition f1 has a refractive index anisotropy, a dielectric anisotropy, and a viscosity of Δn: 0.1, respectively.
9, Δε: 14, η: 60 cP. Liquid crystal composition f
The refractive index anisotropy, the dielectric anisotropy, and the viscosity of 2 are Δ respectively.
The values were n: 0.18, Δε: 12, and η: 70 cP. The refractive index anisotropy, the dielectric anisotropy, and the viscosity of the liquid crystal composition f3 are
The values were Δn: 0.17, Δε: 10 and η: 78 cP, respectively.

Next, six polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1001 (Nissan Chemical Co., Ltd.) was placed on the transparent electrodes provided on the three first PC film substrates. 1) thickness using
After forming each 000 Å insulating film, an alignment film material AL4552 (manufactured by JSR) is used to form a thickness of 450
Å Alignment stabilization films are formed respectively, and 7
Spacers with a diameter of μm, 6 μm, and 5 μm were sprayed, respectively.

On the remaining three transparent electrodes on the second PC film substrate, first, the insulating film material OA-1001 was used.
(Nissan Chemical Co., Ltd.) was used to form an insulating film having a thickness of 1000 Å, and then an alignment stabilizing film having a thickness of 450 Å was formed thereon using the alignment film material AL4552.

Subsequently, the sealing material XN21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed on the peripheral portions of the three first substrates to form walls having predetermined heights.

The three first substrates and the three second substrates were washed with isopropyl alcohol and dried.

After that, the liquid crystal compositions f1, f2, and f3 in amounts calculated from the height of the sealing material and the area of the portion surrounded by the sealing material were applied onto the three first substrates, respectively, and the bonding device was applied. Then, the first and second substrates are attached to each other so that their electrode formation surfaces face each other.
Heated at 50 ° C. for 1 hour. Thus, the liquid crystal compositions f1 and f
2 and f3 filled with thickness of 7 μm, 6 μm, 5
Liquid crystal cells F1, F2, and F3 having a size of μm were obtained.

These three types of liquid crystal cells F1, F2, F3
With the cell F1 at the bottom, the cells F1, F2, and F3 are stacked in this order, and the back surface of the stack (the substrate surface opposite to the side on which light is incident: the outer surface (back surface) of the liquid crystal cell F1) is A black light absorbing film was provided.

The liquid crystal cells F1 and F2 thus manufactured are
The water content of the liquid crystal composition in F3 is 150 pp each
m, 180 ppm, and 200 ppm. When the ion concentrations in the liquid crystal cells F1, F2 and F3 were measured, they were 9 nC / cm ² , 10 nC / cm ² and 11 nC, respectively.
Was / cm ² .

Next, in order to bring the liquid crystal cells F1, F2 and F3 into a colored state, a pulse voltage under the following conditions was applied.

F1: Reset pulse: ± 52 V, width 0.5 ms, reset period 50 ms Selection pulse: ± 33 V, width 1 ms, selection period 0.5 ms Sustain pulse: ± 25 V, width 0.5 ms, sustain period 50 ms F2: Reset Pulse: ± 48V, width 0.5ms, reset period 50ms Selection pulse: ± 28V, width 0.1ms, selection period 0.5ms Sustain pulse: ± 20V, width 0.5ms, sustain period 50ms F3: Reset pulse: ± 50V , Width 0.5 ms, reset period 50 ms Selection pulse: ± 33 V, width 0.1 ms, selection period 0.5 ms Sustain pulse: ± 25 V, width 0.5 ms, sustain period 50 ms As a result, the liquid crystal cell appears white and Y The value was 32.5 and the peak reflectance was 39%.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

F1: reset pulse: ± 52 V, width 0.5 ms, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 12 V, width 0.5 ms, sustain period 50 ms F2: reset pulse: ± 48 V , Width 0.5 ms, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 10 V, width 0.5 ms, sustain period 50 ms F3: reset pulse: ± 50 V, width 0.5 ms, reset period 50 ms selection Pulse: 0 V, selection period 0.5 ms Sustain pulse: ± 13 V, width 0.5 ms, sustain period 50 ms As a result, the liquid crystal cell exhibited black, Y value was 3.6, and contrast (Y value ratio) was 9 It was very high at 0.0, and good display was obtained without being affected by the coloring state. (Comparative Example 1) 22 parts by weight of chiral material S-811 (manufactured by Merck & Co., Inc.) was added to 78 parts by weight of a nematic liquid crystal mixture d containing a liquid crystal tolan compound and a liquid crystal pyrimidine compound as main components, and 685 nm of A liquid crystal composition G1 was prepared so as to selectively reflect light having a wavelength. This liquid crystal composition has a Δ
The values were n: 0.17, Δε: 4, and η: 26 cP.

The water content of the liquid crystal composition G was measured and found to be 220 ppm.

Next, two polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1 was formed on the transparent electrodes provided on the first PC film substrate.
001 (Nissan Chemical Co., Ltd.) is used to form an insulating film having a thickness of 1000 Å, and then an alignment film material AL4552 (J
SR-made) was used to form an alignment stabilizing film having a thickness of 450 Å, and spacers having a diameter of 6 μm were further scattered thereon.

On the transparent electrode on the second PC film substrate, an insulating film material OA-1001 (manufactured by Nissan Chemical Co., Ltd.) was first used to form an insulating film having a thickness of 1000 Å, and then an alignment film material was formed thereon. An alignment stabilizing film having a thickness of 450Å was formed using AL4552.

Then, the sealing material X is applied to the peripheral portion on the first substrate.
N21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed to form a wall having a predetermined height.

After that, the liquid crystal composition G is applied on the first substrate in an amount calculated from the height of the sealing material and the area of the portion surrounded by the sealing material, and the first and second liquid crystal compositions are bonded using a bonding apparatus.
The substrates were attached so that their electrode-formed surfaces faced each other, and heated at 150 ° C. for 1 hour. Thus, a liquid crystal cell was obtained.

A black light absorbing film was provided on the back surface of this liquid crystal cell (the surface of the second substrate opposite to the light incident side).

The water content of the liquid crystal composition in the liquid crystal cell thus produced was 450 ppm. The ion concentration of this liquid crystal cell was measured and found to be 23 nC / cm ² .

Next, in order to bring this liquid crystal cell into a colored state, a pulse voltage under the following conditions was applied.

Reset pulse: ± 49 V, width 0.5 m
s, reset period 50 ms, selection pulse: ± 32 V, width 0.1 ms, selection period 0.5
ms sustain pulse: ± 20V, width 0.5ms, sustain period 50m
s As a result, the liquid crystal cell exhibited a red color, the Y value was 26.0, and the peak reflectance was 34%.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

Reset pulse: ± 49 V, width 0.5 m
s, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 12 V, width 0.5 ms, sustain period 50 m
As a result, the liquid crystal cell exhibited an uneven black color, the Y value was 5.2, the contrast (Y value ratio) was 5.0, and the display was affected by the colored state. (Comparative Example 2) 74 of a nematic liquid crystal mixture e containing a liquid crystal tolan compound and a liquid crystal pyrimidine compound as main components.
Chiral material S-811 (manufactured by Merck) with respect to parts by weight
Was added to prepare a liquid crystal composition H so as to selectively reflect light having a wavelength of 575 nm. The liquid crystal composition had Δn: 0.16, Δε: 4, and η: 28 cP.

The water content of the liquid crystal composition H was measured and found to be 75 ppm.

Next, two polycarbonate (PC) film substrates having transparent electrodes were prepared, and the insulating film material OA-1 was formed on the transparent electrodes provided on the first PC film substrate.
001 (Nissan Chemical Co., Ltd.) is used to form an insulating film having a thickness of 1000 Å, and then an alignment film material AL4552 (J
SR-made) was used to form an alignment stabilizing film having a thickness of 450 Å, and spacers having a diameter of 4 μm were scattered on the film.

On the transparent electrode on the second PC film substrate, an insulating film material OA-1001 (manufactured by Nissan Kagaku Co., Ltd.) was first used to form an insulating film having a thickness of 1000 Å, and then an alignment film material was formed thereon. An alignment stabilizing film having a thickness of 450Å was formed using AL4552.

Then, the sealing material X is applied to the peripheral portion on the first substrate.
N21S (manufactured by Mitsui Chemicals, Inc.) was screen-printed to form a wall having a predetermined height.

Then, the liquid crystal composition E1 was applied on the first substrate in an amount calculated from the height of the sealing material and the area of the portion surrounded by the sealing material, and the first and second substrates were applied using a bonding apparatus. Were bonded so that their electrode forming surfaces face each other, and heated at 150 ° C. for 1 hour. Thus, a liquid crystal cell was obtained.

A black light absorbing film was provided on the back surface of the liquid crystal cell (the surface of the second substrate opposite to the light incident side).

The water content of the liquid crystal composition in the liquid crystal cell thus produced was 430 ppm. The ion concentration of this liquid crystal cell was measured and found to be 25 nC / cm ² .

Next, in order to bring this liquid crystal cell into a colored state, a pulse voltage under the following conditions was applied.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms, selection pulse: ± 33 V, width 0.1 ms, selection period 0.5
ms sustain pulse: ± 20V, width 0.5ms, sustain period 50m
s As a result, the liquid crystal cell exhibited a green color, the Y value was 24.0, and the peak reflectance was 32%.

The liquid crystal cell was left in a colored state for 10 minutes,
After that, a pulse voltage under the following conditions was applied in order to obtain a decolored state.

Reset pulse: ± 50 V, width 0.5 m
s, reset period 50 ms selection pulse: 0 V, selection period 0.5 ms sustain pulse: ± 10 V, width 0.5 ms, sustain period 50 m
As a result, the liquid crystal cell exhibited an uneven black color, the Y value was 5.5, the contrast (Y value ratio) was 4.4, and the display was affected by the colored state.

[0165]

As described above, according to the present invention, there is provided a chiral nematic liquid crystal composition for obtaining a liquid crystal display device capable of obtaining a good light reflectance for a long period in image display and displaying an image with a large contrast. can do.

Further, according to the present invention, it is possible to provide a chiral nematic liquid crystal composition for obtaining a highly reliable liquid crystal display device capable of maintaining stable and high display quality in which burn-in and display unevenness are suppressed for a long period of time. it can.

Further, according to the present invention, in image display,
It is possible to provide a liquid crystal display element that can obtain a good light reflectance and display an image with a large contrast over a long period of time.

Further, according to the present invention, it is possible to provide a highly reliable liquid crystal display element capable of maintaining stable and high display quality in which burn-in and display unevenness are suppressed for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of a liquid crystal display device according to a first embodiment of the present invention, and FIG. 1A is a planer state (R (red) G (green) when a high voltage pulse is applied. B
(Blue) colored state), and FIG. (B) shows a focal conic state (transparent / black display state) when a low-voltage pulse is applied.

FIG. 2 is a diagram showing a cross-sectional structure of a liquid crystal display device according to a second embodiment of the present invention, FIG. 2 (A) shows a planar state when a high voltage pulse is applied, and FIG. It shows a focal conic state when a voltage pulse is applied.

FIG. 3 is a diagram showing a cross-sectional structure of a liquid crystal display device according to a third embodiment of the present invention, FIG. 3 (A) shows a planar state when a high voltage pulse is applied, and FIG. It shows a focal conic state when a voltage pulse is applied.

FIG. 4 is a diagram showing a cross-sectional structure of a liquid crystal display element that is a fourth embodiment of the present invention. FIG. 7A shows a planar state when a high voltage pulse is applied, and FIG. 7B shows a focal conic state when a low voltage pulse is applied.

[Explanation of symbols]

11, 12 Transparent substrate 13, 14 Transparent electrode 15 Insulating thin film 16 Light absorption layer 17 Alignment stabilizing film 18 Spacer 20 Columnar structure 21b, 21g, 21r, 21y Liquid crystal composition 24 Seal material 25 pulse application device b B liquid crystal layer for blue display g G liquid crystal layer for green display r R liquid crystal layer for displaying red A1, A2 multi-layer liquid crystal display device B1, B2 Multi-layer liquid crystal display device C1, C2 liquid crystal display device D1, D2 Liquid crystal display element

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shoji Otani             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. (72) Inventor Hideaki Ueda             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. F-term (reference) 4H027 BA02 BD01 BD20 BD24 BE01                       BE07

Claims (10)

[Claims] 1. A chiral nematic liquid crystal composition containing at least a nematic liquid crystal mixture and one or more chiral materials, capable of selectively reflecting light of a specific wavelength, and having a water content of 200 ppm or less in the liquid crystal composition. A chiral nematic liquid crystal composition comprising: 2. The chiral nematic liquid crystal composition according to claim 1, which contains 7% by weight to 50% by weight of a chiral material. 3. The chiral nematic liquid crystal composition according to claim 1, which contains two or more chiral materials. 4. The chiral nematic liquid crystal composition according to claim 1, which contains a dye. 5. A liquid crystal display device in which a chiral nematic liquid crystal composition capable of selectively reflecting light of a specific wavelength is sandwiched between a pair of substrates, and the amount of water in the liquid crystal composition in the device is 40.
A liquid crystal display device characterized by being 0 ppm or less. 6. A liquid crystal display device in which a chiral nematic liquid crystal composition capable of selectively reflecting light of a specific wavelength is sandwiched between a pair of substrates, and the ion concentration in the device is 20 nC / cm.
A liquid crystal display device characterized by being ² or less. 7. The liquid crystal display element according to claim 6, wherein the amount of water in the liquid crystal composition in the liquid crystal display element is 400 ppm or less. 8. The chiral nematic liquid crystal composition is 7
The liquid crystal display device according to claim 5, 6 or 7, which contains a chiral material in an amount of 50% by weight to 50% by weight. 9. The chiral nematic liquid crystal composition is 2
9. The liquid crystal display device according to claim 5, which contains the above chiral material. 10. The liquid crystal display device according to claim 5, wherein the chiral nematic liquid crystal composition contains a dye.