JPH10339881A - Reflection type liquid crystal display element and its driving method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a reflection type liquid crystal display element capable of multicolor display whose production cost is reduced, by which parallax is restrained and which can realize bright display. SOLUTION: Electrodes 3 and 4 are formed on the one-side surfaces of base plates 1 and 2, and display layers 5Y, 5M and 5C consisting of White-Taylor type guest host liquid crystal developing the colors of yellow, magenta and cyan are laminated between the electrodes 3 and 4 in a state where a separation base plate 6 intervenes between the display layers 5Y and 5M and a separation base plate 7 having solid ground electrodes 8 and 9 intervenes between the display layers 5M and 5C. The intensity of the phase change threshold electric field of the guest host liquid crystal forming the display layers 5Y and 5M is made a different value. Thus, eight colors such as black, white, yellow, magenta, cyan, red, green and blue are displayed in one picture element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a reflection type liquid crystal display device, a driving method thereof, and a driving device.

[0002]

2. Description of the Related Art A reflection type liquid crystal display element does not require a dedicated light source such as a backlight, consumes less power, and can be configured to be thin and lightweight. Attention has been paid.

As a reflection type liquid crystal display device capable of multicolor display, a type in which a polarizing plate and a reflection plate are combined with a TN (twisted nematic) liquid crystal cell and further a color filter is combined is known. . However, in this type of reflective liquid crystal display device, more than half of the incident light is lost by the polarizing plate and the color filter, so that a sufficient contrast is obtained as a reflective liquid crystal display device in which the amount of light cannot be amplified by the backlight. There are no drawbacks.

Therefore, a reflection type liquid crystal display device capable of multicolor display without using a polarizing plate or a color filter has been proposed.
Some have been proposed.

For example, JP-A-3-209425 discloses that
As shown in FIG. 10, the transparent electrode 19a is provided on one surface of the transparent substrate 15a, the transparent electrodes 20a and 19b are provided on one surface and the other surface of the transparent substrate 15b, and the transparent electrodes 20b and 19c are provided on one surface and the other surface of the transparent substrate 15c. A transparent electrode 20c is formed on one surface of the transparent substrate 15d, respectively.
9a, 20a, 19b, 20b, and 19c, 2
0c, the display layers 18a, 18b and 18c respectively
A selective reflection layer in which cholesteric liquid crystal is dispersed in a polymer and selectively reflects red, green, and blue light, respectively, is formed.
8b and 18c are connected to drive circuits 21a and 21b, respectively.
And 21c are driven separately to switch between a selective reflection state when an electric field is applied and a transmission state when no electric field is applied, thereby displaying an arbitrary color by the principle of additive color mixture.

In Japanese Patent Application Laid-Open No. 4-178623, two layers having different refractive indexes are alternately laminated as display layers 18a, 18b and 18c in FIG. 10, and at least one of the layers has a refractive index caused by an electric field. Are formed, the interference filters reflecting red, green and blue color lights, respectively, whose display layers 18a, 18b and 18 are changed.
1c are driven separately by drive circuits 21a, 21b and 21c, respectively, to display an arbitrary color according to the principle of additive color mixture.

Further, a Heilmeier type guest host cell or a White-Taylor type guest host cell containing dichroic dyes of yellow, magenta and cyan, respectively, is used as the display layers 18a, 18b and 18c in FIG. It is known that multicolor display can be realized by the principle of subtractive color mixture.

[0008]

However, such a conventional reflection type liquid crystal display device capable of multi-color display without using a polarizing plate or a color filter is patterned on each display layer. Since a driving electrode and a driving circuit are required, there is a disadvantage that the manufacturing cost is increased due to an increase in processes and a decrease in yield.

Further, since a thick transparent substrate for forming a patterned drive electrode between the respective display layers is required, the distance between the respective display layers is increased, and the distance between the display layers when viewed obliquely is increased. There is a disadvantage that the parallax increases. Further, in the case where opaque active elements such as TFTs and MIMs are provided for the respective drive electrodes, there is a disadvantage that the aperture ratio with respect to obliquely incident light is reduced and the display becomes dark.

Accordingly, the present invention is to provide a reflective liquid crystal display device capable of multicolor display, in which the manufacturing cost can be reduced, the parallax can be reduced, and a bright display can be realized.

[0011]

According to the present invention, each of the electrodes has an electrode, and at least one of the electrodes is provided between a pair of transparent substrates.
Three or more display layers in which dichroic dyes that absorb light of different wavelengths are added to cholesteric liquid crystal, and a ground electrode is interposed between two or more display layers and another display layer. The phase change threshold electric field strength of each cholesteric liquid crystal is set to a different value between a plurality of display layers stacked in a state and not via the ground electrode.

In this case, each display layer can contain a polymer.

[0013]

The guest host cell changes the alignment direction of the dichroic dye by adding a dye having anisotropy in light absorption ability, that is, a dichroic dye to the liquid crystal and reorienting the liquid crystal molecules by applying an electric field. The display is performed by switching between the colored state and the non-colored state. As a guest host cell not using a polarizing plate, there is a White-Taylor type guest host cell utilizing a phase transition of a cholesteric liquid crystal (including a chiral nematic liquid crystal) having a helical structure.

A cholesteric liquid crystal having a positive dielectric anisotropy has a planar phase in which the helical axis is perpendicular to the cell surface as shown in FIG. 7A with an increase in the applied electric field, and as shown in FIG. 3 shows a focal conic phase in which the helical axis is substantially parallel to the cell surface, and a homeotropic phase in which the helical structure is released and the liquid crystal director faces the electric field direction as shown in FIG. In FIG. 7, reference numeral 5 denotes a cholesteric liquid crystal, reference numerals 3 and 4 denote a pair of electrodes of a cell, and reference numeral 11 denotes a drive circuit.

When a p-type dichroic dye having a high absorption coefficient in the major axis direction of a dye molecule is added to such a cholesteric liquid crystal having a positive dielectric anisotropy, a dichroic dye along the liquid crystal molecule is obtained. As shown in FIG. 8, the absorbance decreases in the order of the planar phase, the focal conic phase, and the homeotropic phase, and the colored state can be changed.

As described above, a cholesteric liquid crystal having a positive dielectric anisotropy has three phase structures depending on the applied electric field strength, but the phase change is not unique to the electric field strength. In the absence of an electric field, the liquid crystal exhibits either a planar phase or a focal conic phase. In particular, in a cholesteric liquid crystal to which a polymer is added, the memory effect becomes more stable due to interference with a polymer interface.
Furthermore, when a signal is applied such that the electric field suddenly becomes zero, the homeotropic phase changes to the planar phase.
The absorbance of the Taylor-type guest host cell changes as shown in FIG. 9 with respect to the electric field intensity of the pulse signal.

Therefore, if the threshold electric field intensity of the change between the planar phase and the focal conic phase is Eth1, and the threshold electric field intensity of the change between the focal conic phase and the homeotropic phase is Eth2, the electric field before the electric field is removed after the electric field is removed. When Eth2 or more, a high light absorption state is caused by the planar phase, and when between Eth1 and Eth2, a low light absorption state is caused by the focal conic phase.
When the value is 1 or less, the state before application of the electric field is continued, that is, a high light absorption state due to the planar phase or a low light absorption state due to the focal conic phase.

In the present invention, by utilizing the bistability phenomenon of the cholesteric liquid crystal to which the dichroic dye is added, (A) the absorbance of (A) is measured for three or more display layers each composed of a White-Taylor type guest-host liquid crystal. It switches between a colored state due to a high planar phase and (B) a transmission state due to a focal conic phase having a low absorbance, and the three or more display layers are cholesteric with a dichroic dye that absorbs light of different wavelengths. While being added to the liquid crystal, and laminated with a ground electrode interposed between two or more of the display layers and another display layer, between a plurality of display layers not via the ground electrode,
The two phase-change threshold electric field strengths Eth1 and Eth2 of each cholesteric liquid crystal are set to different values.

Therefore, for example, yellow,
When three guest host display layers that emit magenta and cyan colors are stacked, a refresh period and a select period are provided between an electrode on one substrate and a ground electrode sandwiching the two guest host display layers. And a subsequent display period of no electric field, and the electric field strengths Er and E in the refresh period and the select period.
A drive signal is applied in which s has an electric field strength selected from five levels of electric field intensities having a relation of Er> Es and a boundary between electric field intensities of phase change of cholesteric liquid crystal of the two guest host display layers. A refresh period, a select period, and a non-electric field display period between the electrode on the other substrate and the ground electrode sandwiching the remaining one guest host display layer. The electric field strengths Er and Es at
By applying a drive signal having an electric field intensity selected from three-stage electric field intensity having a boundary of a phase change threshold electric field intensity of the cholesteric liquid crystal of the one guest host display layer in a relation of Er> Es, (1) All three guest host display layers are in the planar phase, (2) All three guest host display layers are in the focal conic phase, (3) Any of the three guest host display layers. One layer is in the planar phase, the remaining two layers are in the focal conic phase, and (4) one of the three guest host display layers is in the planar phase and the remaining one is in the focal conic phase. , Are obtained.

Therefore, (1) a state in which all three guest host display layers are in a colored state and black is displayed, and (2) a state in which all three guest host display layers are in a transmissive state. The light transmitted through the guest host display layer is scattered by the reflection layer provided on the side opposite to the incident side of the external light, and white is displayed. (3) Of the three guest host display layers, A state in which only one of the layers is colored and yellow, magenta or cyan is displayed,
(4) Any two of the three guest host display layers
The layer becomes a colored state, and a state in which red, green, or blue is displayed can be obtained. In one pixel, the total of black, white, yellow, magenta, cyan, red, green, and blue can be obtained. Eight colors can be displayed.

Therefore, according to the present invention, the drive electrodes on the upper and lower substrates and the drive electrodes on the upper and lower substrates are provided without providing drive electrodes or drive circuits patterned for each of the three display layers to be laminated. With this ground electrode, multicolor display of eight colors can be performed by the subtractive color mixture method, and the manufacturing cost can be reduced by reducing the process and improving the yield.

Further, only by providing a thin transparent substrate for forming a solid ground electrode between two of the three display layers and another one, patterning is performed between the respective display layers. It is not necessary to provide a thick transparent substrate or an opaque active element for forming the formed driving electrodes, so that the distance between the respective display layers can be reduced, the aperture ratio can be increased, and the parallax can be increased. Can be reduced, and a bright display can be realized.

[0023]

FIG. 1 shows an embodiment of the reflection type liquid crystal display device of the present invention. In this embodiment, electrodes 3 and 4 are formed on one surface of substrates 1 and 2, respectively, and a display layer 5 </ b> Y made of a White-Taylor type guest-host liquid crystal that emits yellow, magenta, and cyan is formed between the electrodes 3 and 4. , 5M, 5C, and the display layers 5Y, 5M,
5C, spacers 10Y, 10M, and 10C are inserted, respectively, and between the display layers 5Y and 5M, a separation substrate 6 is interposed.
Between the display layers 5M and 5C, via a separation substrate 7 having solid ground electrodes 8 and 9 on both sides, the electrodes are stacked.
4 and the ground electrodes 8 and 9 are connected to the drive circuit 11.

The substrates 1 and 2 are formed of an insulating material such as glass or silicon, and the substrate 1 at least on the display surface side is formed of a material having a light transmitting property such as glass.

The electrode 3 is formed of a conductive and light-transmissive material such as ITO or SnO ₂ on the substrate 1 on the display surface side by an evaporation method, a sputtering method, or the like. Electrode 4
Is preferably made of a material having light reflectivity such as aluminum or silver, and is formed on the substrate 2 on the non-display surface side by a vapor deposition method, a sputtering method, or the like, and has a scattering property by roughening the surface.

When the electrode 4 is formed of a material having a light transmitting property, a layer of a conductive and light reflecting material is formed on the electrode 4 or between the substrate 2 and the electrode 4. When the substrate 2 has light transmittance, a layer of a material having light reflectivity may be formed on the back surface of the substrate 2.

The separation substrates 6 and 7 are formed of an insulating and light-transmitting polymer film such as polyethylene, polystyrene and polyethylene terephthalate. The separation substrate 6 has a thickness of several μm, and the separation substrate 7 has a ground electrode 8. ,
It is desirable to have a film thickness of several tens of μm capable of forming 9. The ground electrodes 8 and 9 are formed of a conductive and light-transmissive material such as ITO and SnO ₂ .

The spacers 10Y, 10M, and 10C are made of glass or plastic, and the thickness of the display layers 5Y, 5M, and 5C is controlled to about several μm to 10 μm.

The guest-host liquid crystal constituting the display layers 5Y, 5M, and 5C is a cholesteric liquid crystal obtained by adding a chiral agent to a nematic liquid crystal.
It is formed by adding a trace amount of a dichroic dye. The nematic liquid crystal is not particularly limited as long as it has a positive dielectric anisotropy, such as a biphenyl type, a terphenyl type, a Schiff base type, and the like.

The helical pitch of the cholesteric liquid crystal is adjusted by the amount of the chiral agent added, and the central wavelength of selective reflection by the helical structure is desirably outside the visible region. Further, as generally performed to compensate for the temperature dependence of the helical pitch, it is preferable to add a plurality of types of chiral agents having different twist directions or exhibiting opposite temperature dependence.

The dichroic dyes of the display layers 5Y, 5M, and 5C absorb the spectra of blue, green, and red, which are complementary colors of yellow, magenta, and cyan, respectively.
An azo-based or anthraquinone-based dye having a high absorption coefficient in the major axis direction of the dye molecule is used.

The display layers 5Y, 5M, and 5C for each color include:
In addition to the structure consisting of only the guest-host liquid crystal described above,
P containing network polymer in continuous layer of guest-host liquid crystal
NLC (Polymer Network Liquid)
d Crystal) structure or PDLC (P
oligomer Dispersed Liquid C
(rystal) structure can also be used.

The PNLC structure and the PDLC structure are prepared by an emulsion method, PIPS (Polymerization I).
nduced Phase Separation)
Method, TIPS (Thermally Induced)
Phase Separation) method, SIPS (S
solvent Induced Phase Sepa
The liquid crystal layer can be formed by a method of phase-separating a polymer and a liquid crystal, such as a ratio method.

By using the PNLC structure or the PDLC structure, an anchoring effect is generated at the interface between the liquid crystal and the polymer, and the holding state of the planar phase or the focal conic phase in the absence of an electric field becomes more stable. When the PDLC structure is used, the display layers 5Y, 5M, and 5C of the respective colors can be directly stacked.

FIG. 6 shows an embodiment in that case, and the display layers 5Y, 5M, and 5C are each provided with Whi in a polymer skeleton.
A te-Taylor-type guest-host liquid crystal is dispersed in the form of droplets. No spacer is inserted between the display layers 5Y, 5M, and 5C, and a separation substrate is provided between the display layers 5Y and 5M and between the display layers 5M and 5C. The display layers 5Y, 5M, and 5C are stacked and formed only by sandwiching one layer of the ground electrode 8 between the display layers 5M and 5C without any intervening layers.

FIG. 1 or FIG. 6 shows how to form two display layers 5Y and 5M between the electrode 3 and the ground electrode 8.
The phase change threshold electric field strengths of the e-Taylor type guest-host liquid crystal are set to different values.

Examples of the method include a method in which the helical pitch of the cholesteric liquid crystal in each layer is different, a method in which a nematic liquid crystal having a different dielectric anisotropy or elastic modulus is used for the cholesteric liquid crystal in each layer, a PNLC structure or a PDL.
In the case of using the C structure, a method using a polymer having a different anchoring effect at the interface in each layer, a method in which liquid crystal droplets dispersed in the polymer have different sizes in each layer, and the like can be considered. However, it is not particularly limited to these.

White-Tayl forming another display layer 5C between the electrode 4 and the ground electrode 9 or 8
The phase-change threshold electric field intensity of the or-type guest-host liquid crystal can be arbitrarily set with respect to those of the two display layers 5Y and 5M.

Therefore, of the display layers 5Y and 5M,
The layer having a large phase change threshold electric field strength is H layer,
When the display layer 5C is an L layer, the absorbance of the H layer and the M layer changes as shown in FIG. 2A with respect to the intensity of the pulse electric field applied between the electrodes 3 and 8. , L change with the intensity of the pulse electric field applied between the electrodes 4, 9 or 4, 8 as shown in FIG.

Here, the boundary between the electric field strength Ea and the electric field strength Eb and the boundary between the electric field strength Eb and the electric field strength Ec are as follows:
The threshold electric field strength Eth1 of the change of the planar phase and the focal conic phase of the M layer and the H layer, respectively, the boundary between the electric field strength Ec and the electric field strength Ed, and the electric field strength Eth
The boundary between d and the electric field intensity Ee is the threshold electric field intensity Eth2 of the change of the focal conic phase and the homeotropic phase of the M layer and the H layer, respectively, the boundary between the electric field intensity Ef and the electric field intensity Eg, and the electric field intensity. Eg and electric field strength Eh
Are the threshold electric field strength Eth1 of the change in the planar layer and the focal conic phase and the threshold electric field strength Eth2 of the change in the focal conic phase and the homeotropic phase of the L layer.

Then, the driving circuit 11 causes the electrodes 3,
As shown in FIG. 3, as one of the drive signals,
Each is constituted by a refresh period and a select period of an AC pulse, and a subsequent display period of no electric field, and the electric field strengths Er and Es in the refresh period and the select period are based on input data in a relationship of Er> Es. , The electric field intensity E in five stages in FIG.
a) applying a signal having an electric field strength selected from a to Ee,
Similarly, between the electrodes 4, 9 or 4, 8 are formed a refresh period, a select period, and a non-electric field display period as the other drive signal, and the electric field strengths Er and Es in the refresh period and the select period are set. ,
Based on the input data, a signal having an electric field strength selected from the three-step electric field strengths Ef to Eh of FIG. 2B is applied in a relationship of Er> Es.

FIG. 4A shows a state of the phase change of the H layer and the M layer by the combination of the refresh electric field Er (a) and the select electric field Es (a) in this case, and FIG. It shows a state of a phase change of the L layer due to a combination of the refresh electric field Er (b) and the select electric field Es (b), where “p” is a colored state by the planar phase,
“F” indicates a decolored state (transmission state) due to the focal conic phase, and “?” Indicates an undetermined state depending on the state before the application of the driving signal. In FIG. The layers are shown in order.

As is apparent from the above, according to the above-described display element and driving method, (1) all three layers of the H layer, the M layer and the L layer are in a planar phase, and (2) the H layer, the M layer and the All three layers of the L layer are in a focal conic phase,
(3) H layer is a planar phase, M layer and L layer are in a focal conic phase, (4) M layer is a planar phase,
H layer and L layer are in a focal conic phase, (5)
L layer is a planar phase, H layer and M layer are in a focal conic phase, (6) H layer and M layer are in a planar phase, L layer is in a focal conic phase, (7) M layer and L layer are in a In the planar phase, the H layer is in a focal conic phase, and (8) the H layer and the L layer are in the planar phase and M
Eight types of phase change states, that is, the layer is in a focal conic phase, are obtained.

Accordingly, for example, the display layer 5Y for emitting magenta is used as the H layer for the display layer 5Y for emitting yellow.
Is an M layer, and the display layer 5C that emits cyan is an L layer, as shown in FIG. 5 (“T” in FIG. 5 indicates that the corresponding layer is in a transmission state by the focal conic phase). (1) Er (a) = Ee, Es (a) = E
a, Er (b) = Eh, Es (b) = Ef, a state where black (Bk) is displayed by a drive signal, (2) For example, Er (a) = Ee, Es (a) = Ec, Er
By the drive signal of (b) = Eh, Es (b) = Eg,
A state in which white (W) is displayed, (3) for example, Er
(A) = Ee, Es (a) = Ed, Er (b) = Eh,
With the drive signal of Es (b) = Eg, yellow (Y)
(4) For example, Er (a) = Ee,
Es (a) = Eb, Er (b) = Eh, Es (b) = E
state in which magenta (M) is displayed by the drive signal g, (5) for example, Er (a) = Ee, Es (a) = E
A state in which cyan (C) is displayed by a drive signal of c, Er (b) = Eh, Es (b) = Ef, (6) For example, Er (a) = Ee, Es (a) = Ea, Er (B)
= Eh, Es (b) = Eg, a state where red (R) is displayed by the drive signal, and (7) Er (a) = Ee, E
s (a) = Eb, Er (b) = Eh, Es (b) = Ef
State where blue (B) is displayed by the drive signal of
(8) For example, Er (a) = Ee, Es (a) = Ed,
With the drive signals of Er (b) = Eh and Es (b) = Ef, eight display states, that is, a state in which green (G) is displayed, can be obtained. In one pixel, black, white, and yellow can be obtained. , Magenta, cyan, red, blue and green.

Further, at least black, white,
A full-color display can be performed by performing an area gradation method such as a dither method using five colors of yellow, magenta, and cyan.

In the above example, the phase-change threshold electric field of the display layer 5Y between the display layer 5Y that emits yellow and the display layer 5M that emits magenta is sandwiched between the electrode 3 and the ground electrode 8. In the case where the intensity is increased, the electric field intensity at the phase change threshold of the display layer 5M may be increased.

The stacking order of the display layers 5Y, 5M, and 5C that respectively emit yellow, magenta, and cyan colors is not limited to the stacking order shown in FIG. 1 or FIG.

Example 1 The reflection type liquid crystal display device of the embodiment shown in FIG. 1 was manufactured by the following method.

As the yellow guest-host liquid crystal forming the display layer 5Y, a nematic liquid crystal ZL having a positive dielectric anisotropy is used.
An azo-based p-type dichroic dye SI-486 (manufactured by Mitsui Toatsu Chemicals) was added to a homogeneous solution of 84 wt% of I-1840 (manufactured by Merck) and 16 wt% of a dextrorotatory chiral agent CB15 (manufactured by Merck). 1 wt% was added.

As the magenta guest-host liquid crystal forming the display layer 5M, the above nematic liquid crystal ZLI-18 is used.
40 (manufactured by Merck) and 89% by weight of the above chiral agent CB
An azo p-type dichroic dye M-618 (manufactured by Mitsui Toatsu Chemicals) 1 wt.
% Was added.

As the cyan guest-host liquid crystal forming the display layer 5C, the above nematic liquid crystal ZLI-184 is used.
0 (manufactured by Merck) and the above-mentioned chiral agent CB1
To a homogeneous solution of 5 wt.% (Merck) and 1 wt% of anthraquinone-based p-type dichroic dye SI-497 (Mitsui Toatsu Chemicals) was added.

Cyan guest-host liquid crystal mixed with a 5 μm adhesive spacer on a first transparent glass substrate 7059 (manufactured by Corning) constituting the substrate 2 on which an aluminum reflective electrode is formed by sputtering as the electrode 4 And a 25-μm-thick first PET film (manufactured by Toray Co., Ltd.) forming a separation substrate 7 on which ITO transparent electrodes are sputter-deposited on both sides as ground electrodes 8 and 9 while applying heat and pressure. And a cyan display layer 5C.

Next, on the first PET film, 5 μm
Magenta guest-host liquid crystal mixed with a spacer with an adhesive is dropped, and a 2.5-μm-thick second PET film forming the separation substrate 6 is laminated while applying heat and pressure to form a magenta display layer 5M. Was formed.

Further, 5 μm was placed on the second PET film.
m, a yellow guest-host liquid crystal mixed with a spacer with an adhesive is dropped, and while applying heat and pressure, an ITO transparent electrode is deposited as the electrode 3 to form the second substrate 1.
Was laminated to form a yellow display layer 5Y, thereby completing a cell of the display element.

(Example 2) In Example 1, the thiol-based polymer precursor N was added to the guest-host liquid crystal of each color.
After adding 15 wt% of OA65 (manufactured by Norland Corp.) and forming a guest-host liquid crystal of each color, 4 mW /
Irradiation with ultraviolet light having an intensity of cm ² was performed for 10 minutes to form display layers 5C, 5M, and 5Y each having a PNLC structure.

Example 3 A reflection type liquid crystal display device of the embodiment shown in FIG. 6 was manufactured by the following method.

The guest-host liquid crystal of each color used in Example 1 was mixed with a 10% aqueous solution of PVA (manufactured by Wako Pure Chemical Industries, Ltd.) at a weight ratio of 5 to 2 and stirred with a homogenizer at 7000 rpm. Then, emulsions of each color were prepared.

On a first transparent glass substrate 7059 (manufactured by Corning Incorporated) constituting a substrate 2 on which an aluminum reflective electrode was formed by sputtering as an electrode 4, a cyan emulsion diluted twice with water was used with a doctor blade. Apply,
After drying, a cyan display layer 5C having a PDLC structure with a thickness of 5 μm was formed.

Next, on the obtained cyan display layer 5C,
As a ground electrode 8, an ITO transparent electrode was sputter-deposited. Next, a ground electrode 8 made of the ITO transparent electrode is used.
A magenta emulsion diluted twice with water is applied on the top with a doctor blade, dried, and a 5 μm-thick PD
A magenta display layer 5M having an LC structure was laminated.

Further, a yellow emulsion diluted twice with water was applied on a second transparent glass substrate constituting the substrate 1 on which an ITO transparent electrode was deposited as the electrode 3 by a doctor blade and dried. , 5μm thick PDL
A yellow display layer 5Y having a C structure was formed.

Then, the magenta display layer 5M on the first transparent glass substrate and the yellow display layer 5Y on the second transparent glass substrate were pressure-bonded to complete the display element cell.

[0062]

As described above, according to the present invention, the drive electrodes and the drive electrodes on the upper and lower substrates can be connected without providing a drive electrode or a drive circuit patterned for each of the three display layers to be laminated. The multi-color display of eight colors can be performed by the subtractive color mixture method using the ground electrode in the display layer, and the manufacturing cost can be reduced by reducing the process and improving the yield.

Further, only by providing a thin transparent substrate for forming a solid ground electrode between two of the three display layers and another one, patterning is performed between the respective display layers. It is not necessary to provide a thick transparent substrate or an opaque active element for forming the formed driving electrodes, so that the distance between the respective display layers can be reduced, the aperture ratio can be increased, and the parallax can be increased. Can be reduced, and a bright display can be realized.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a reflection type liquid crystal display device of the present invention.

FIG. 2 is a diagram illustrating an example of a relationship between a phase change threshold electric field intensity of a cholesteric liquid crystal of each display layer.

FIG. 3 is a diagram illustrating an example of a mode of a drive signal applied between a pair of electrodes.

FIG. 4 is a diagram showing an example of a state of a phase change of each display layer due to a combination of a refresh electric field and a select electric field.

FIG. 5 is a diagram illustrating an example of a display state of each color.

FIG. 6 is a diagram showing another embodiment of the reflection type liquid crystal display device of the present invention.

FIG. 7 is a diagram showing a phase change of a cholesteric liquid crystal having a positive dielectric anisotropy.

FIG. 8: White-Tayl having positive dielectric anisotropy
FIG. 4 is a diagram showing switching behavior of an or-type guest-host liquid crystal when a constant electric field is applied.

FIG. 9: White-Tayl having positive dielectric anisotropy
FIG. 4 is a diagram illustrating a switching behavior of an or-type guest host liquid crystal when a pulsed electric field is applied.

FIG. 10 is a diagram showing an example of a conventional reflective liquid crystal display device capable of multicolor display.

[Explanation of symbols]

 1, 2 substrate 3, 4 electrode 5Y, 5M, 5C display layer 6, 7 separation substrate 8, 9 ground electrode 10Y, 10M, 10C spacer 11 drive circuit

Claims (4)

[Claims] 1. A cholesteric liquid crystal display comprising three or more display layers each having an electrode and at least one of a pair of transparent substrates and a cholesteric liquid crystal to which a dichroic dye absorbing light of a different wavelength is added. Are stacked with a ground electrode interposed between two or more display layers and another display layer, and between a plurality of display layers not via the ground electrode,
A reflection type liquid crystal display device characterized in that each cholesteric liquid crystal has a different phase change threshold electric field strength. 2. The reflective liquid crystal display device according to claim 1, wherein each of said display layers contains a polymer. 3. The method for driving a reflective liquid crystal display element according to claim 1, wherein a refresh period and a select period are provided between an electrode on one of the substrates sandwiching the plurality of display layers and the ground electrode. , Followed by a field-free display period,
The electric field strengths Er and Es in the refresh period and the select period are selected from a plurality of electric field intensities having a boundary of a phase change threshold electric field intensity of the cholesteric liquid crystal of the plurality of display layers, with a relation of Er> Es. A drive signal for applying an electric field intensity is applied, and a refresh period and a select period are formed between the electrode on the other substrate sandwiching the other display layer and the ground electrode, and a display period without an electric field thereafter. , The electric field intensity E in the refresh period and the select period.
Applying a drive signal in which r and Es have an electric field strength selected from a plurality of electric field intensities having a relation of Er> Es and having a boundary with a phase-change threshold electric field strength of the cholesteric liquid crystal of the another display layer. A display element driving method comprising: 4. A device for driving a reflective liquid crystal display device according to claim 1, wherein a refresh period and a select period are provided between an electrode on one of the substrates sandwiching the plurality of display layers and the ground electrode. , Followed by a field-free display period,
The electric field strengths Er and Es in the refresh period and the select period are selected from a plurality of electric field intensities having a boundary of a phase change threshold electric field intensity of the cholesteric liquid crystal of the plurality of display layers, with a relation of Er> Es. A drive signal for applying an electric field intensity is applied, and a refresh period and a select period are formed between the electrode on the other substrate sandwiching the other display layer and the ground electrode, and a display period without an electric field thereafter. , The electric field intensity E in the refresh period and the select period.
Applying a drive signal in which r and Es have an electric field strength selected from a plurality of electric field intensities having a relation of Er> Es and a boundary between electric field intensities of a phase change threshold of the cholesteric liquid crystal of the other display layer. A display element driving device characterized by the following.