JP2002006307A - Reflection type liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a normally white mode reflection type liquid crystal display element with high reflectance and capable of displaying with excellent contrast. SOLUTION: In the normally white mode reflection type liquid crystal display element, a polarizing plate 1 and a reflection plate 4 are arranged opposite to each other sandwiching a liquid crystal cell 3 and an optically anisotropic body 2, a twist angle θ1 of liquid crystal substance molecules contained in a liquid crystal substance layer 3A seen from the polarizing plate side to the reflection plate side exists in (+200)-(+270) deg. range, a twist angle θ2 of a slow axis of the optically anisotropic body seen from the polarizing plate side to the reflection plate side exists in (-155)-(-420) deg. range, a product of birefringence Δn1 and thickness d1 of the liquid crystal substance layer (Δn1.d1) is included in 700-1,000 nm range and a product of birefringence Δn2 and thickness d2 of the optically anisotropic body (Δn2.d2) is included in 200-700 nm range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type liquid crystal display device having an optical anisotropic body and a polarizing plate and having good contrast.

[0002]

2. Description of the Related Art In recent years, display performance has been remarkably improved with the progress of liquid crystal display technology, and the use of liquid crystal display devices has been expanding. Since liquid crystal display devices are thin and lightweight, in the field of portable information processing equipment, liquid crystal display devices are used for almost all displays.
Since portable information processing equipment is usually driven by a battery, it is an important issue to reduce its power consumption. For this reason, a liquid crystal display device to be mounted on a portable information processing device does not need to use a backlight that consumes a large amount of power, so that it is possible to further reduce the thickness, weight, and power consumption. Special attention has been paid to a reflective liquid crystal display device. Conventionally, as a liquid crystal display device, TN
(Twisted nematic) type and STN (super twisted nematic) type have been mainly used. An STN type liquid crystal display device generally has a structure in which a liquid crystal cell is sandwiched between a pair of polarizing plates. In the case of a reflective liquid crystal display device, it is customary to arrange a reflecting plate outside the polarizing plate. It is. In the liquid crystal display device of the STN mode, the twist angle of the liquid crystal molecules in the liquid crystal cell is set to 90 ° or more, and the angle of the transmission axis of the polarizing plate with respect to the elliptically polarized light generated by the birefringence effect of the liquid crystal cell is optimally set. for that reason,
In this type of liquid crystal display device, it is possible to reflect abrupt molecular alignment deformation due to voltage application on a birefringence change of a liquid crystal,
An electro-optical characteristic accompanied by a sudden optical change at or above the threshold can be exhibited. In the STN type liquid crystal display device, yellow-green or dark blue may be generated as a display background color due to birefringence of liquid crystal. In order to improve this coloring phenomenon, in a reflection type display device, an optical compensation liquid crystal cell or a retardation plate formed of a polymer such as polycarbonate is superposed on the display side of the display STN liquid crystal cell in general. Is being done. In this way, color compensation is performed by means,
Reflective liquid crystal display device that performs display close to black and white display,
This is a so-called paper white type liquid crystal display device.

[0003] However, regardless of whether it is a reflection type or a transmission type, a polarizing plate used in a general liquid crystal display device adopting the STN method has a linearly polarized light whose light transmittance is parallel to a polarization axis. Is about 90% even when the light is incident, there is a problem that a sufficient brightness cannot be obtained with a conventional liquid crystal display device using two polarizing plates.
In particular, in the case of a reflection type liquid crystal display device that does not use a backlight, the incident light passes through the polarizing plate a total of four times before exiting, so that attenuation of the light amount becomes a problem. As a technique for solving this problem, JP-A-2-189519 and JP-A-6-11711 disclose a reflection plate having a configuration in which a polarizing plate, a retardation plate, a liquid crystal cell and a reflection plate are laminated in this order. Liquid crystal display devices have been proposed.
Since this display device does not have the polarizing plate on the side of the reflecting plate, which is provided in the above-described paper-white reflective liquid crystal display device, the light incident on the device is emitted only after passing through the polarizing plate twice. Therefore, as a matter of course, this display device can be expected to display white with high luminance and high reflectance. However, in a conventional reflection type liquid crystal display device using only one polarizing plate, a display with good contrast may be obtained due to insufficient study on optical parameters of a retardation plate and a liquid crystal cell used therefor. Difficult to obtain.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a normally white reflective liquid crystal display device having a high reflectance and a display with good contrast.

[0005]

A normally white reflective liquid crystal display device according to the present invention comprises a liquid crystal cell having a liquid crystal material layer interposed between a pair of transparent substrates having electrodes, a polarizing plate, and a reflective plate. And an optically anisotropic body, wherein two or more voltage values are selected and a driving voltage is applied to the liquid crystal material layer. (1) The polarizing plate and the reflecting plate Are disposed so as to face each other across the liquid crystal material layer and the optically anisotropic body. (2) Twisting of the liquid crystal material molecules included in the liquid crystal material layer from the polarizing plate side to the reflection plate side The angle θ1 is in the range of + 200 ° to + 270 °, the twist angle θ2 of the slow axis of the optically anisotropic body from the polarizing plate side to the reflecting plate side is in the range of -155 ° to -420 °, (3) Refractive index anisotropy of the liquid crystal material layer Δn
1 and the thickness d1 (△ n1 · d1) is 700 nm or more.
And the product of the refractive index anisotropy Δn2 of the optically anisotropic body and the thickness d2 of the optically anisotropic body (Δn2
-D2) is in the range of 200 nm to 700 nm. The optically anisotropic body used in the reflection type liquid crystal display device of the present invention is preferably a liquid crystal film,
In addition, at least one polarizing plate is provided between the polarizing plate and the reflecting plate.
A layer of light diffusing layer can be provided.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal cell (driving liquid crystal cell) used in a reflection type liquid crystal display device of the present invention comprises a pair of transparent substrates provided with electrodes, and a liquid crystal substance interposed between the two transparent substrates. And layers. In a liquid crystal cell, both sides of a liquid crystal material layer are usually adjacent to a transparent substrate, respectively.
If desired, a polarizing plate can be provided on one side between the liquid crystal material layer and the transparent substrate, and a reflecting plate can be provided on the other side. As the transparent substrate of the liquid crystal cell, a substrate capable of aligning molecules of a liquid crystal substance in a specific direction is used. Specifically, a transparent substrate having a property of orienting liquid crystal molecules or a transparent substrate having a property of orienting liquid crystal molecules on a transparent substrate having no alignment ability is used. Two transparent substrates capable of aligning liquid crystal molecules in a specific direction are opposed to each other so that the respective alignment directions are maintained in a twisted relationship, and a liquid crystal material layer is formed therebetween, thereby forming a liquid crystal material layer. A specific twist angle can be given. The electrodes of the liquid crystal cell are usually respectively provided on the surfaces of the two transparent substrates located on both sides of the liquid crystal material layer on the liquid crystal material layer side. When a transparent substrate having an alignment film is used, an electrode can be provided between the transparent substrate and the alignment film. The liquid crystal material used in the liquid crystal cell of the present invention is not particularly limited, and any of various liquid crystal materials used in a normal STN-type liquid crystal display device can be used.

[0007] The polarizing plate and the reflecting plate in the reflection type liquid crystal display element are arranged so as to face each other across the liquid crystal material layer of the liquid crystal cell. In general, a polarizing plate is provided on one surface of a liquid crystal cell in which a liquid crystal material layer is sandwiched between two transparent substrates with electrodes.
Usually, a reflection plate is provided on the other surface. And
However, as described above, the polarizing plate and / or the reflecting plate can be provided between the liquid crystal material layer and the transparent substrate, in other words, inside the liquid crystal cell, as desired. In this case, the polarizing plate and the reflecting plate must be in a positional relationship to face each other with the liquid crystal material layer interposed therebetween, but it is not always necessary that both are located in the liquid crystal cell. The polarizing plate used in the present invention is not particularly limited, and any general polarizing plate having an absorption axis can be used. However, in order to obtain a reflective liquid crystal display device having a high reflectance, a polarizing plate having a high transmittance is required. It is preferable to use More specifically, a uniaxially stretched polyvinyl alcohol film (PVA) is provided with a halogen polarizing film formed by arranging iodine molecules having a high degree of polarization in a certain direction, a polyvinyl alcohol film dyed with a direct dye, or the like. A polarizing plate sandwiched between films can be used. The reflection plate used in the present invention is not particularly limited, and aluminum foil, silver foil and the like can be used, and an aluminum layer or a silver layer is vacuum-deposited on a transparent glass substrate by a vacuum deposition method, and the reflection is performed. It can also be used for boards. When a reflector is provided in a liquid crystal cell, the reflector can also function as an electrode of the liquid crystal cell.

[0008] The term "optically anisotropic body" means an optically anisotropic body having a structure in which the optically anisotropic axis is twisted from one surface to the other surface. Therefore, the optically anisotropic material referred to here has the same characteristics as those obtained by laminating a plurality of optically anisotropic layers so that each optically anisotropic axis is continuously twisted. , Like a normal TN liquid crystal cell or the like. As the optically anisotropic body of the present invention, (a) a twist-aligned liquid crystal cell itself,
A laminate of (b) a liquid crystal film and (c) a retardation film can be exemplified, and among them, the liquid crystal film of (b) is preferable. As the twisted liquid crystal cell of (a), a liquid crystal cell in which a liquid crystal material layer inserted between two transparent substrates is oriented in a specific direction to give a twist angle as in the above-described driving liquid crystal cell. Can be exemplified. Further, the liquid crystal film of (b) means a film having a structure in which a layer having an optically anisotropic axis is continuously twisted in one film. This liquid crystal film is generally formed by forming a liquid crystal material having a twist characteristic into a film, and more specifically, a liquid crystal material having a twist characteristic has a twist alignment formed in a liquid crystal state, for example, photocrosslinking, thermal crosslinking. It can be obtained by immobilization by a method such as crosslinking or cooling. A liquid crystal substance having a twisting property includes a liquid crystal compound or a liquid crystal compound capable of exhibiting optically positive uniaxial property regardless of the shape of the liquid crystal molecule and regardless of whether the molecule is a low molecule or a polymer. The composition can be used. Specifically, a polymer liquid crystal having a unit that induces twisting, for example, a main-chain polymer liquid crystal such as polyester, polyamide, polycarbonate, or polyesterimide exhibiting liquid crystallinity, or polyacrylate, polymethacrylate, polymalonate, or polysiloxane And other side-chain polymer liquid crystals. Among them, polyester is preferred from the viewpoint of easiness of synthesis, orientation, and appropriateness such as glass transition point. As units for inducing twist, optically active 2-methyl-1,
4-butanediol, 2,4-pentanediol, 1,
2-propanediol, 2-chloro-1,4-butanediol, 2-fluoro-1,4-butanediol, 2-
Bromo-1,4-butanediol, 2-ethyl-1,4
A unit derived from -butanediol or 2-propyl-1,4-butanediol or a derivative thereof (for example, a derivative such as a diacetoxy compound) can be used. The unit that induces the above-mentioned torsion may be any of R-form and S-form, or may be a mixture of R-form and S-form. The liquid crystal film referred to in the present invention does not matter whether the film itself exhibits liquid crystallinity. Another example that can be used as the optically anisotropic material of the present invention is the retardation film (c). This retardation film is generally
Polycarbonate, a transparent plastic film represented by polymethacrylate is precisely uniaxially stretched, and a plurality of the obtained stretched films are formed by laminating each optically anisotropic axis by a small amount to have a twist angle. be able to. In any of the above (a) to (c) when using an optical anisotropic body, the optical anisotropic body is located between the polarizing plate and the reflecting plate, and is located outside the driving liquid crystal cell. , Or located inside. However, in general, the polarizing plate and the reflecting plate face each other with the driving liquid crystal cell interposed therebetween, and in this case, the driving liquid crystal cell and the polarizing plate or the reflecting plate are interposed. In addition, it is preferable to dispose an optical anisotropic body, and particularly to dispose an optical anisotropic body between the driving liquid crystal cell and the polarizing plate. The optically anisotropic material used in the present invention has a temperature compensation effect in which the product of the refractive index anisotropy Δn2 and the thickness d2 of the optically anisotropic material (Δn2 · d2) changes with temperature. Is preferred. This is because even if the ambient temperature changes, the color development does not fluctuate, and it is possible to provide a reflective liquid crystal display element capable of displaying good black and white. In this case, the change due to the temperature of Δn2 · d2 is caused by the temperature-dependent change in the product (Δn1 · d1) of the refractive index anisotropy Δn1 of the liquid crystal material layer included in the driving liquid crystal cell and the thickness d1. It is desirable that they are approximately equal. Further, the optically anisotropic material used in the present invention preferably has a different optical anisotropy dispersion depending on the wavelength. Thereby, it is possible to provide a reflective black-and-white display device in which an achromatic color is further improved.

In the reflection type liquid crystal display device of the present invention, a light diffusion layer can be provided at an arbitrary position between the polarizing plate and the reflecting plate. The reflection type liquid crystal display element having a natural viewing angle with a small viewing angle dependence can be suppressed by providing a light diffusion layer, particularly when the reflection plate is a specular reflection type, so that characteristic deterioration due to liquid crystal alignment disorder can be suppressed. Can be obtained. When the above-described optically anisotropic member is provided between the driving liquid crystal cell and the polarizing plate, the light diffusion layer is generally located between the optically anisotropic member and the driving liquid crystal cell. The light diffusion layer as referred to herein means a layer having a property of diffusing incident light isotropically or anisotropically, and its material is not limited.
The light diffusion layer may be formed from a plastic sheet, a plastic film, a plastic substrate, a substrate other than plastic, and the like, which exhibit light diffusion properties.
A non-self-supporting sheet or film in which particles having a refractive index different from that of the matrix are dispersed in an adhesive matrix may be used. Sheet,
The film, the substrate, and the like may have self-supporting properties or may have no self-supporting properties. When the film does not have self-supporting properties, it is only necessary that the film is held on a film or a transparent substrate having self-supporting properties by some means so that the light diffusing property is not impaired as a whole. Further, on the optically anisotropic body, a compound or a composition capable of forming a light diffusion layer is applied by means such as melt coating or solution application, and if necessary, an electric field, a magnetic field, and some treatment such as polarized light irradiation is performed. Alternatively, a light diffusion layer may be formed. However, it is necessary to perform the melt coating or the solution coating so that the film strength of the optically anisotropic body does not decrease.

The light-diffusing layer having an adhesive property includes an acrylic adhesive, a rubber adhesive, a silicone adhesive, an ethylene-vinyl acetate copolymer adhesive, a urethane adhesive, a vinyl ether adhesive, and a polyvinyl alcohol adhesive. Adhesives, polyacrylamide-based adhesives and a matrix composed of such a mixed adhesive, for example, an average particle size of 0.5 to
Organic fine particles such as polystyrene fine particles and polymethacrylic acid fine particles of 5 μm, silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide,
Examples thereof include dispersions of appropriate particles such as inorganic fine particles such as antimony oxide, hollow fine particles containing gas, and microcapsules containing liquid. Among them, acrylic pressure-sensitive adhesives are preferable as a matrix because they are excellent in transparency, weather resistance, heat resistance and the like. When the adhesive light diffusing layers are superposed, the individual adhesive light diffusing layers can be of the same type or different types in an appropriate combination. As the acrylic pressure-sensitive adhesive, any of known materials can be used. For example, methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, isobutyl, amyl, isoamyl, hexyl, heptyl, cyclohexyl, 2-ethylhexyl, octyl Acrylic acid having a linear or branched alkyl group having 1 to 18 carbon atoms such as a group, isooctyl group, nonyl group, isononyl group, decyl group, undecyl group, lauryl group, tridecyl group, tetradecyl group, stearyl group, octadecyl group And an adhesive mainly composed of an acrylic polymer using one or two or more acrylic acid alkyl esters composed of methacrylic acid esters.

The light-diffusing layer having an adhesive property includes, for example, a petroleum resin, a rosin resin, a terpene resin, a synthetic petroleum resin within a range not impairing the effects of the present invention.
Tackifiers such as phenolic resins, xylene resins, alicyclic petroleum resins, coumarone indene resins, styrene resins, dicyclopentadiene resins, phthalates, phosphates, paraffin chloride, polybutene,
An appropriate additive such as a softening agent such as polyisobutylene or other various fillers, an antioxidant, and a crosslinking agent can be compounded. As a light diffusion layer without adhesiveness,
For example, in a resin matrix, a plastic sheet in which particles having a different refractive index from the matrix are dispersed,
Examples include films and substrates. Specifically, polyimide, polyamide imide, polyamide, polyether imide, polyether ether ketone, polyether ketone, polyketone sulfide, polyether sulfone, polysulfone, polyphenylene sulfide, polyphenylene oxide, polyethylene terephthalate, polybutylene terephthalate, polyethylene na Phthalate, polyacetal, polycarbonate, polyarylate, acrylic resin, polyvinyl alcohol, polystyrene, polyurethane, polyethylene, polypropylene, cellulosic plastics, epoxy resin, phenolic resin, etc., the inorganic fine particles, organic fine particles, and gas as exemplified above. Plastic film substrate in which encapsulated hollow microparticles and liquid-encapsulated microcapsules are dispersed Etc. can be mentioned. Although the thickness of the light diffusion layer is not particularly limited, it is usually 10 μm or more and 500 μm or more.
μm or less. The total light transmittance of the light diffusion layer is 50.
% Or more, and particularly preferably 70% or more. Further, the diffusion transmittance of the light diffusion layer is usually 5 to 99%, preferably 50 to 99%.
In the reflection type liquid crystal display device of the present invention, light enters through a polarizing plate, passes through an optically anisotropic body and a liquid crystal material layer,
Further, the light is reflected by the reflecting plate, passes through the optically anisotropic body and the liquid crystal material layer in the opposite direction, and further passes through the polarizing plate to be emitted. The reflective liquid crystal display element of the present invention can be obtained by arranging the driving liquid crystal cell, the polarizing plate, the reflective plate, the optically anisotropic material, and the light diffusing layer as required, in the positional relationship described above. By applying a drive voltage of arbitrarily selected binary or more to the liquid crystal material layer of the driving liquid crystal cell, the liquid crystal material layer becomes active optics capable of displaying bright achromatic and dark achromatic colors. Functions as a layer.

In the reflection type liquid crystal display device of the present invention, the twist angle θ1 of the liquid crystal molecules contained in the liquid crystal material layer in the liquid crystal cell from the polarizing plate side to the reflecting plate side is in the range of + 200 ° to + 270 °. When the torsion angle is less than + 200 °, a change in liquid crystal state when time-division driving is performed at a high duty ratio that requires a steep change in transmittance is small. Also, +270
When the angle exceeds °, hysteresis easily occurs. In the present specification, the + direction and the − direction of the angle mean the rotation direction of the relative angle, and if the counterclockwise direction from the polarizing plate toward the reflecting plate is +, the clockwise direction is When the clockwise direction is set to +, the counterclockwise direction is set to-. However, the case where both are set to + is included in the scope of the present invention, and equivalent effects can be obtained. The product (Δn1 · d1) of the refractive index anisotropy Δn1 and the thickness d1 of the liquid crystal material layer is in the range of 700 nm to 1000 nm. If it is less than 700 nm, a change in the state of the liquid crystal when a voltage is applied is small.
Viewing angle characteristics and responsiveness deteriorate. On the other hand, the twist angle θ2 of the slow axis of the optically anisotropic body used in the reflection type liquid crystal display device of the present invention from the polarizing plate side to the reflecting plate side is −155 ° to −4 °.
In the range of 20 ° and the refractive index anisotropy of the optically anisotropic material Δn2
And the product of the thickness d2 of the optically anisotropic body (△ n2 · d2)
Is in the range of 200 nm to 700 nm. That is, favorable contrast can be realized by setting θ1 = + 200 ° to + 270 °, Δn1 · d1 = 700 nm to 1000 nm, θ2 = −155 ° to −420 °, and Δn2 · d2 = 200 nm to 700 nm. .

In the reflection type liquid crystal display device of the present invention, in addition to restricting the above-mentioned θ1, θ2, Δn1 · d1 and Δn2 · d2 to respective specific ranges, an optically anisotropic material is measured from the absorption axis of the polarizing plate. The angle θ3 to the slow axis on the surface of the polarizing plate and the angle θ4 from the absorption axis of the polarizing plate to the alignment direction of the liquid crystal material layer on the surface of the polarizing plate can be appropriately adjusted. It is preferable for realizing a small and good contrast. The relationship between the above angles will be specifically described with reference to FIG. 1. In FIG. 1, reference numeral 1 denotes a polarizing plate, 2 denotes an optically anisotropic body, and 3A denotes a liquid crystal material layer (a transparent substrate provided with electrodes is illustrated in FIG. 1). 4 is a reflector
(Layers) and 6 indicate external light, respectively. Liquid crystal material layer 3A
The orientation direction 31 on the surface on the polarizing plate 1 side and the orientation direction 32 on the surface on the reflection plate 4 side form an angle θ1. The direction 21 of the slow axis of the optically anisotropic body 2 on the surface on the side of the polarizing plate 1 and the direction 22 of the slow axis on the surface of the side of the reflecting plate 4 form an angle θ2. In addition, polarizing plate 1
And the direction 21 of the slow axis on the surface of the optically anisotropic body 2 on the side of the polarizing plate 1 form an angle θ3, and the absorption axis 11 of the polarizing plate 1 and the polarizing plate 1 of the liquid crystal material layer 3A are formed. An angle θ4 is formed with the orientation direction 31 on the side surface. FIG. 2 is a plan view showing the positional relationship when these are superimposed and viewed from the polarizing plate side toward the reflecting plate side using the same symbols. In FIGS. 1 and 2, θ1 to θ4 are all counterclockwise from the polarizing plate toward the reflecting plate for convenience of explanation.
That is, they are relatively rotated in the same direction. However, in the reflective liquid crystal display element of the present invention, the rotation direction of θ1 is always opposite to θ2. The reflection type liquid crystal display element of the present invention includes a liquid crystal cell, a polarizing plate, a reflection plate, and the optically anisotropic body as essential components, and further includes a light diffusion layer as necessary. In addition, other components may be provided. Specifically, for example, by further providing a color filter, a color reflection type liquid crystal display element capable of multicolor or full-color display with high color purity can be obtained.

[0014]

The reflection type liquid crystal display device of the present invention has a polarizing plate only on one surface side of a liquid crystal material layer (liquid crystal layer) and has a specific liquid crystal cell and an optically anisotropic body. It is possible to realize a display with high efficiency and good contrast, and to obtain a much higher display quality as compared with a conventional reflection type liquid crystal display device.

[0015]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In this example, an experiment was performed by creating an apparatus in which the counterclockwise direction was + and the clockwise direction was-from the polarizing plate side to the reflecting plate side. However,
When the clockwise direction from the polarizing plate side to the reflecting plate side is +, and the counterclockwise direction is-, the same result can be obtained by performing the same experiment. Example 1 An STN-type reflective liquid crystal display device schematically shown in FIG. 3 was produced. As shown in FIG. 3, the liquid crystal cell 3 includes a pair of opposing transparent substrates 3 </ b> C, electrodes 3 </ b> B provided on inner surfaces thereof, and an alignment film printed and formed thereon and subjected to an alignment process. 3E. A liquid crystal substance is sealed in a space defined by the alignment film 3E and a sealant 3D formed by printing and forming around the transparent substrate, thereby forming a liquid crystal layer 3A. Alignment film 3 using ZLI-2293 as a liquid crystal material
The liquid crystal layer 3A was aligned in a predetermined direction by adjusting the alignment treatment direction of E, and twisted at θ1 = + 240 °. Further, the refractive index anisotropy of the liquid crystal material in the liquid crystal cell 3 △ n
The product Δn1 · d1 of 1 and the thickness d1 of the liquid crystal layer 3A is approximately 85
It was set to 0 nm. The polarizing plate 1 was arranged on the display surface side (upper side in the figure) of the liquid crystal cell 3, while the reflector 4 was arranged on the back side (lower side in the figure) of the liquid crystal cell 3. An optically anisotropic body 2 is disposed between the polarizing plate 1 and the liquid crystal cell 3, and a light diffusion sheet IDS-21 manufactured by Dai Nippon Printing Co., Ltd. is provided between the optically anisotropic body 2 and the liquid crystal cell as a light diffusion layer 5. (Total light transmittance 91.1%, haze 5
1.6) was arranged. Refractive index anisotropy of optically anisotropic material 2 △ n
The product △ n2 · d2 of 2 and thickness d2 is approximately 400 nm,
θ2 = −270 °. The angle θ3 from the absorption axis of the polarizing plate 1 to the slow axis of the optically anisotropic body 2 on the polarizing plate side is + 140 °, and the angle θ3 from the absorption axis of the polarizing plate 1 to the polarizing plate side of the liquid crystal layer 3A. Θ4 = + 11 to the alignment direction at
0 °. To this liquid crystal display device, a driving voltage was applied from a driving circuit (not shown) to the transparent electrode 3B, and the relationship with the reflectance was obtained. FIG. 4 shows the results. FIG. 5 is a diagram illustrating spectral characteristics when the electric field is on and when the electric field is off. Also, 1/1
The contrast when driving at 00 duty and the optimum bias and the luminous reflectance (Y value) when the electric field was turned on were determined. Table 1 shows the results. From the results shown in FIG. 4, it can be seen that in this liquid crystal display device, the reflectance sharply changes near the driving voltage of 2.1 V. In addition, it can be seen from the results of FIG. 5 that this liquid crystal display device achieves good black-and-white display.

Embodiment 2 Δn1 · d1 is approximately 850 nm, Δn2 · d2 is approximately 400 nm, θ1 = + 240 °, θ2 = −300
A liquid crystal display device was prepared in the same manner as in Example 1 except that °, θ3 = + 140 °, and θ4 = + 110 °, and the relationship between the drive voltage and the reflectance, the spectral characteristics when the electric field was on and when the electric field was off, and 1 The contrast and the reflectance (Y value) at the time of driving with an optimal bias at / 100 duty were obtained.
The results are shown in FIGS. 6, 7 and Table 1, respectively. 6 and 7, it can be seen that a sharp change in the reflectance near the drive voltage of 2.1 V and excellent black and white display are achieved. Example 3 Δn1 · d1 was approximately 850 nm, Δn2 · d2 was approximately 500 nm, θ1 = + 240 °, θ2 = −360
A liquid crystal display device was prepared in the same manner as in Example 1 except that °, θ3 = + 20 °, and θ4 = + 110 °, and the relationship between the drive voltage and the reflectance, the spectral characteristics when the electric field was on and when the electric field was off, and 1 The contrast and the reflectance (Y value) at the time of driving with an optimal bias at / 100 duty were obtained. The results are shown in FIGS. 8 and 9 and Table 1, respectively. 8 and 9
It can be seen from the results that a sharp change in the reflectance near the driving voltage of 2.1 V and a good black-and-white display are achieved.

Comparative Example Δn1 · d1 was approximately 650 nm, Δn2 · d2 was approximately 400 nm, θ1 = + 240 °, θ2 = −360
A liquid crystal display device was prepared in the same manner as in Example 1 except that °, θ3 = + 110 °, and θ4 = + 110 °, and the relationship between the drive voltage and the reflectance, the spectral characteristics when the electric field was on and when the electric field was off, and 1 The contrast and the reflectance (Y value) at the time of driving with an optimal bias at / 100 duty were obtained.
The results are shown in FIGS. 10, 11 and Table 1, respectively. FIG.
From the results of FIG. 11 and FIG.
It can be seen that it changes slowly around 1 V, and good black-and-white display is not achieved.

[0018]

[Table 1]

By comparing the measurement results of the contrast and the reflectance (Y value) shown in Table 1, the reflection type liquid crystal display device of the present invention has higher contrast and brightness (compared to the device of the comparative example). It can be seen that black-and-white display with extremely high reflectance (reflectance) can be achieved. From the above results, it was confirmed that the reflection type liquid crystal display device of the present invention had significantly higher display quality than the device of the comparative example. Example 4 A reflective color liquid crystal display device including the color filter 7 schematically shown in FIG. 12 was produced. 12 that are the same as those of the apparatus shown in FIG. 2 are denoted by the same reference numerals. As shown in FIG. 12, between the transparent substrate 3C on the display surface side of the liquid crystal cell 3 and the transparent electrode 3B,
A color filter 7 including pixels of three colors of red, green and blue was inserted. By providing the color filter layer with such a configuration, a favorable multi-color or full-color display could be performed.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the position and angle relationship of each component in a liquid crystal display device of the present invention.

FIG. 2 is a plan view illustrating an angle relationship among an absorption axis of a polarizing plate, an alignment direction of a liquid crystal material layer, and a slow axis direction of an optically anisotropic body in the liquid crystal display device of the present invention.

FIG. 3 is an elevational sectional view schematically showing the device of Example 1.

FIG. 4 is a diagram showing a change in reflectance with respect to a change in drive voltage of the device of Example 1.

FIG. 5 is a diagram showing the device of Example 1 when an electric field is turned on and when an electric field is turned off.

FIG. 6 is a diagram showing a change in reflectance with respect to a change in drive voltage of the device of Example 2.

FIG. 7 is a diagram showing the device of Example 2 when the electric field is on and when the electric field is off.

FIG. 8 is a diagram showing a change in reflectance with respect to a change in drive voltage of the device of Example 3.

FIG. 9 is a diagram illustrating the device of Example 3 when the electric field is on and when the electric field is off.

FIG. 10 is a diagram showing a change in reflectance with respect to a change in drive voltage of the device of the comparative example.

FIG. 11 is a diagram showing the device of the comparative example when the electric field is on and when the electric field is off.

FIG. 12 is an elevational sectional view schematically showing the device of Example 4.

[Explanation of symbols]

Reference Signs List 1 polarizing plate 2 optical anisotropic body 3A liquid crystal layer 3B electrode 3C transparent substrate 3D sealant 3E alignment film 4 reflective layer (plate) 5 light diffusion layer 6 external light 7 color filter 11 absorption axis of polarizing plate 21 optical anisotropic body Slow axis on the surface on the polarizing plate side 22 Slow axis on the surface on the reflecting plate side of the optically anisotropic material 31 Orientation direction of molecules of the liquid crystal material on the surface on the polarizing plate side of the layer of the liquid crystal material 32 Orientation of liquid crystal molecules on the reflector side of the layer

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takehiro Toyooka 8 Chidori-cho, Naka-ku, Yokohama-shi, Kanagawa Nishiishi Mitsui Co., Ltd. Central Research Laboratory F-term (reference) 2H049 BA06 BA42 BB44 BC05 BC22 2H091 FA08X FA11Z FA14Z FA31X FA31Z FB02 KA02 KA03

Claims (3)

[Claims] 1. A liquid crystal cell having a liquid crystal material layer interposed between a pair of transparent substrates having electrodes, a polarizing plate, a reflecting plate, and an optically anisotropic body, and a voltage value of two or more values is selected. In the reflection type liquid crystal display element in which a driving voltage is applied to the liquid crystal material layer, (1) a positional relationship in which the polarizing plate and the reflection plate face each other with the liquid crystal material layer and the optically anisotropic material interposed therebetween. (2) the twist angle θ1 of the liquid crystal molecules contained in the liquid crystal material layer from the polarizing plate side to the reflection plate side is in the range of + 200 ° to + 270 °, and The twist angle θ2 of the slow axis from the polarizing plate side to the reflecting plate side is in the range of −155 ° to −420 °, and (3)
The product of the refractive index anisotropy Δn1 of the liquid crystal material layer and the thickness d1 (Δn1 · d1) is in the range of 700 nm to 1000 nm, and the refractive index anisotropy Δn2 of the optically anisotropic material and the optical The product of the thickness d2 of the anisotropic body (△ n2 · d2) is 200
a normally white reflective liquid crystal display device having a wavelength in the range of nm to 700 nm. 2. The reflection type liquid crystal display device according to claim 1, wherein the optically anisotropic member is formed of a liquid crystal film. 3. The reflection type liquid crystal display device according to claim 1, wherein at least one light diffusion layer is further disposed between the polarizing plate and the reflection plate.