JP3417450B2 - Reflective color liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective color liquid crystal display device.

[0002]

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

As a reflective liquid crystal display device capable of multicolor display, one using a color filter is known. However, when a color filter is used, light loss occurs, so that a sufficient contrast cannot be obtained for a reflective liquid crystal display device that cannot amplify the amount of light like a transmissive liquid crystal display device that uses a backlight. There is.

Therefore, there have been proposed some reflective liquid crystal display devices capable of multicolor display without using color filters.

For example, Japanese Patent Laid-Open No. 3-209425 discloses
As shown in FIG. 12, the transparent electrode 22a is provided on one surface of the transparent substrate 21a, the transparent electrodes 23a and 22b are provided on one surface and the other surface of the transparent substrate 21b, and the transparent electrodes 23b and 22c are provided on one surface and the other surface of the transparent substrate 21c. The transparent electrode 23c is formed on one surface of the transparent substrate 21d, and the transparent electrode 2c
2a and 23a, 22b and 23b, and 22c and 2
3c between the reflective layers 24a, 24b and 24c, respectively.
As the reflective layers 24a and 2b, cholesteric liquid crystals are dispersed in a polymer to form selective reflective layers that selectively reflect red, green and blue color lights, respectively.
4b and 24c are connected to drive circuits 25a and 25b, respectively.
And 25c are separately driven to display an arbitrary color by the principle of additive color mixture.

Further, in Japanese Patent Laid-Open No. 4-178623, two types of layers having different refractive indexes are alternately laminated as the reflection layers 24a, 24b and 24c of FIG. 12, and at least one layer has a refractive index depending on a voltage. Of the transparent substrate 21 on the side opposite to the incident side of external light, which forms an interference filter that reflects red, green, and blue color lights respectively.
A black film is formed on the back surface of d, and the reflection layers 24a, 24b and 24c are provided on the driving circuits 25a, 25b and 2 respectively.
It is shown that an arbitrary color is displayed according to the principle of additive color mixing by being driven separately by 5c.

[0007] Further, the Optical Engine
ring, 23 (1984), p247, multi-color display is achieved by using guest host cells containing dichroic dyes of yellow, cyan and magenta as the reflective layers 24a, 24b and 24c of FIG. 12, respectively. It has been shown to come true.

[0008]

However, it is possible to realize multicolor display without using a color filter as shown in FIG.
In the reflective liquid crystal display device shown in FIG. 2 and described above, driving electrodes and driving circuits for three colors are required, the manufacturing cost is high, and a transparent electrode and a transparent substrate are provided between the reflective layers 24a, 24b, 24c of each color. The reflective layer 24 of each color
Since the distance between a, 24b, and 24c becomes large, there is a drawback that the parallax becomes large.

Therefore, the inventor previously invented a reflection type liquid crystal display device capable of multicolor display, which can obtain a sufficient contrast, reduces parallax, and reduces manufacturing cost. It was proposed by Hira 8-353868 (filed on December 17, 1996).

In the invention of this prior application, as shown in FIG.
Cholesteric liquid crystal 7R having positive dielectric anisotropy, in which electrodes 3 and 4 are formed on one surface of substrates 1 and 2, and red, green, and blue color lights are selectively reflected between electrodes 3 and 4, respectively. , 7G, 7B are polymer 6R, 6
The selective reflection layers 5R, 5G and 5B dispersed in G and 6B are laminated, and the cholesteric liquid crystals 7R and 7R of the respective selective reflection layers 5R, 5G and 5B are laminated as described later.
The phase change threshold voltages of G and 7B are made different from each other.

The electrodes 3 and 4 are connected to the drive circuit 8, and for example, the substrates 1 and 2 are both transparent substrates, and the electrodes 3 and 4 are both transparent electrodes. Further, the substrate 2 on the side opposite to the incident side of external light has a selective reflection layer 5 on the back surface thereof.
The black film 9 for absorbing the visible light component transmitted through R, 5G and 5B is formed.

A cholesteric liquid crystal having a positive dielectric anisotropy in which liquid crystal molecules have a spiral structure separates light incident parallel to the spiral axis into right-handed light and left-handed light and matches the twist direction of the helix. Selective reflection is generated in which the circularly polarized light component is reflected and the remaining circularly polarized light component is transmitted. When the spiral pitch is p, the average refractive index in a plane orthogonal to the spiral axis is n, and the birefringence is Δn, the reflection center wavelength λ and the reflection wavelength width Δ
λ is represented by λ = n · p and Δλ = Δn · p, respectively, and the reflected light from the cholesteric liquid crystal exhibits a vivid color depending on the spiral pitch p.

As shown in FIG. 6, the cholesteric liquid crystal 7 having a positive dielectric anisotropy loaded between the electrodes 3 and 4 is
As the electric field applied between the electrodes 3 and 4 increases, a planar phase in which the spiral axis is perpendicular to the cell surface as shown in FIG. 9A and selective reflection occurs, and a spiral phase as shown in FIG. There are three states, a focal conic phase in which the axes are randomly oriented, and a homeotropic phase in which the liquid crystal director is oriented in the electric field direction by unwinding the helical structure as shown in FIG. When there is no anchoring effect at the interface, the planar phase with the minimum free energy becomes the ground state in the absence of electric field.

However, the selective reflection layers 5R, 5G, 5
As in B, a cholesteric liquid crystal 7R, 7G, 7B is dispersed in a polymer 6R, 6G, 6B. A polymer dispersed cholesteric liquid crystal (PDCLC: Polymer Dispe
rsed Choresteric Liquid C
In the case of the liquid crystal, the phase transition from the focal conic phase to the planar phase due to thermal fluctuation does not occur due to the interaction with the polymer interface, and these two states exist stably without an electric field.

That is, the selective reflection layers 5R and 5R made of polymer-dispersed cholesteric liquid crystal having positive dielectric anisotropy.
Each of G and 5B changes from the planar phase to the focal conic phase and changes from the focal conic phase to the homeotropic phase as the voltage increases as described above during pulse application, but after voltage removal, As shown in the relationship between the voltage value of the applied pulse and the reflectance after the pulse is applied in FIG. 7, the homeotropic phase changes to the planar phase, and either the planar phase or the focal conic phase is held by the memory effect. It

Therefore, each selective reflection layer 5R,
The threshold voltage of the change from the planar phase to the focal conic phase of 5G and 5B is Vth1, and the threshold voltage of the change from the focal conic phase to the homeotropic phase is Vth.
If th2, the selective reflection layers 5R, 5G, 5
After voltage removal, B is in a selective reflection state due to the planar phase when the voltage before removal is Vth2 or higher, and Vth1
Between Vth2 and Vth2, the transmission state is the focal conic phase, and when Vth1 or less, the state before the voltage application is continued, that is, the selective reflection state by the planar phase or the transmission state by the focal conic phase.

In the invention of the prior application, by utilizing the bistable phenomenon of the polymer-dispersed cholesteric liquid crystal, each selective reflection layer 5R, 5G, 5B is selectively reflected by the planar phase as shown in FIG. 8A. Display is performed by switching between the state and the transmission state of the focal conic phase with small backscattering as shown in FIG.

Moreover, as shown in FIG. 10 by the relationship between the voltage value of the applied pulse and the reflectance after the pulse application, the cholesteric liquid crystal 7 of each selective reflection layer 5R, 5G, 5B.
R, 7G, 7B phase change threshold voltages Vth1 and V
th2 are different voltages Vr1, Vg1,
Let Vb1 and Vr2, Vg2, Vb2. In the example of FIG. 10, Vr1 <Vg1 <Vb1 and Vr2 <Vg2 <
This is the case where Vb2 is set.

As shown in FIG. 3, a signal between the electrodes 3 and 4 is composed of a refresh period and a select period of a pulse voltage of, for example, 1 kHz, and a non-voltage display period thereafter. Is applied, and the refresh voltage Vr and the select voltage Vs of the drive signal are changed between the voltages Va to Vg of seven stages shown in FIG. 10 based on the input data in a relationship of Vr> Vs.

FIG. 11 shows the refresh voltage V in this case.
It shows the state of the phase change of each selective reflection layer 5R, 5G, 5B depending on the combination of r and the select voltage Vs. The maximum value of the numerical value such as “0 ??” “00?” “000” “100” is shown. The upper (left) shows the phase state of the selective reflection layer 5R, the middle (center) shows the selective reflection layer 5G, and the lowermost (right side) shows the state of the selective reflection layer 5B. "1" indicates the selective reflection by the planar phase. The state, “0” indicates the transmissive state due to the focal conic phase, and “?” Indicates the undetermined state depending on the state before the application of the drive signal. However, V which is significant
Only the case of r> Vs is shown.

As is apparent from the above, when a drive signal that changes in the order of Vg → Va → 0V is applied between the electrodes 3 and 4, the selective reflection layers 5R, 5G and 5B are all in the selective reflection state, and white. Is displayed, and when a drive signal that changes in the order of Vg → Vd → 0V is applied, the selective reflection layer 5
All of R, 5G, and 5B are in the transmissive state, and the light transmitted through the selective reflection layers 5R, 5G, and 5B is absorbed by the black film 9, and black is displayed.

When a drive signal that changes in the order of Vg → Ve → 0V is applied, only the selective reflection layer 5R is in the selective reflection state, red is displayed, and Vf → Vb → 0.
When a drive signal that changes in the order of V is applied, only the selective reflection layer 5G is in the selective reflection state, green is displayed, and when a drive signal that changes in the order of Vg → Vc → 0V is applied, the selective reflection occurs. Only the layer 5B is in the selective reflection state, and blue is displayed.

Further, when applying a drive signal which changes in the order of Vg → Vf → 0V, the selective reflection layers 5R and 5R are provided.
G is in the selective reflection state, yellow is displayed, and Vg
When a drive signal that changes in the order of → Vb → 0V is applied, the selective reflection layers 5G and 5B enter the selective reflection state, and cyan is displayed.

Therefore, 7 pixels of white, black, red, green, blue, yellow, and cyan are included in one pixel.
Colors can be displayed, and multicolor display is possible.

The cholesteric liquid crystals 7R, 7G,
Since the reflectance of the selective reflection by 7B is 50% in principle, the contrast is high. Moreover, the selective reflection layer 5
Since R, 5G, and 5B are directly laminated without a transparent electrode and a transparent substrate interposed therebetween and have a common drive electrode and drive circuit, parallax is reduced and manufacturing cost is reduced.

In the above example, the colors displayed by the additive color mixture of the reflected light from the two selective reflection layers are yellow and cyan, but the phases of the cholesteric liquid crystals 7R, 7G and 7B are different. Change threshold voltage Vr1,
By changing the magnitude relationship between Vg1, Vb1 and Vr2, Vg2, Vb2 from the above example, the colors displayed by additive color mixing of the reflected light from the two selective reflection layers are cyan and magenta, or magenta and yellow. can do.

However, in the reflection type color liquid crystal display device of the invention of this earlier application, as described above, yellow, magenta among eight colors of white, black, red, green, blue, yellow, magenta and cyan are formed in one pixel. Alternatively, only 7 colors except cyan can be displayed.

Therefore, according to the present invention, sufficient contrast can be obtained, parallax is reduced, and manufacturing cost is reduced, and white, black, red, green, blue, yellow, magenta,
All the eight colors of cyan can be displayed.

[0029]

A reflective color liquid crystal display device of the present invention is a transparent substrate having a transparent electrode.
A substrate, a second substrate that is a substrate having electrodes and that is arranged so as to face the first substrate, a ground electrode that is arranged between the first substrate and the second substrate, and the first substrate And selectively reflects the light of the first color of red, green, and blue, which is laminated between one of the second substrates and the ground electrode without the other substrate and the electrode interposed therebetween. A first color selective reflection layer in which a cholesteric liquid crystal is dispersed in a polymer, and a second color selective reflection layer in which a cholesteric liquid crystal that selectively reflects light of a second color of red, green and blue is dispersed in a polymer A plurality of selective reflection layers each comprising a polymer-dispersed cholesteric liquid crystal layer, and red, green and blue formed between the other of the first substrate and the second substrate and the ground electrode. Cholesteric that selectively reflects the light of the third color inside A third color selective reflection layer in which crystals are dispersed in a polymer, and the plurality of selective reflection layers between the one substrate and the ground electrode have a phase change threshold voltage of each cholesteric liquid crystal. Are different from each other.

In this case, each of the first color selective reflection layer, the second color selective reflection layer and the third color selective reflection layer is formed by a cholesteric liquid crystal whose spiral direction is the right direction dispersed in a polymer. A reflective color liquid crystal display device comprising a spiral polymer dispersion-type cholesteric liquid crystal layer and a left-handed polymer dispersion cholesteric liquid crystal layer in which a cholesteric liquid crystal whose spiral direction is left is dispersed in a polymer. Can be a laminate of at least 6 polymer-dispersed cholesteric liquid crystal layers.

[0031]

In the reflection type color liquid crystal display device of the present invention constructed as described above, the phase change threshold voltage of each cholesteric liquid crystal is different between the electrode on one substrate and the ground electrode. A typical case in which the first reflective layer and the second reflective layer are formed and the third reflective layer is formed between the electrode on the other substrate and the ground electrode will be described. Depending on the voltage applied between the first and second reflective layers, either or both of the first reflective layer and the second reflective layer can be in the selective reflective state, or both can be in the transmissive state, and are independent of this. In addition, the third reflective layer can be brought into the selective reflection state or the transmission state according to the voltage applied between the electrode on the other substrate and the ground electrode.

Therefore, one of the three selective reflection layers is used.
By making the layer selectively reflect red color light, by making one layer of the remaining two layers selectively reflect green color light and by making the remaining one layer selectively reflect blue color light, (1) All three selective reflection layers are selected according to the voltage applied between the electrode on one substrate and the ground electrode, and the voltage applied between the electrode on the other substrate and the ground electrode. In the reflective state, white is displayed. (2) All the three selective reflection layers are in the transmissive state, and the light transmitted through the three selective reflection layers is provided on the side opposite to the incident side of external light. Absorbed by the black film, black is displayed, (3) Only one of the three selective reflection layers is in the selective reflection state, and red, green, or blue is displayed , (4) Any one of the three selective reflection layers Becomes a selective reflection state, and a state in which yellow, magenta, or cyan is displayed can be obtained, and all eight colors of white, black, red, green, blue, yellow, magenta, and cyan are displayed in one pixel. Can be displayed.

The three selective reflection layers include two of them.
Since only the ground electrode is interposed between the layer and the other layer, and the layers are laminated without the transparent substrate and the other transparent electrode being interposed, the parallax is reduced and the ground is provided between the three selective reflection layers. Since only the electrodes have to be formed and only two driving circuits are required, the manufacturing cost is reduced.

Furthermore, since the reflectance of selective reflection by the cholesteric liquid crystal is 50% in principle, the contrast is high. In particular, when the three selective reflection layers are composed of two types of cholesteric liquid crystals whose spiral directions are opposite to each other, the reflectance of the selective reflection is 100% in principle.
And the contrast is very high.

[0035]

FIG. 1 shows an embodiment of a reflective color liquid crystal display device of the present invention. In this embodiment,
Address electrodes 3 and 4 are formed on one surface of the substrates 1 and 2, and a polymer 6R,
Polymer dispersed cholesteric liquid crystal (PDCL) in which cholesteric liquid crystals 7R, 7G and 7B are dispersed in 6G and 6B.
The selective reflection layers 5R, 5G and 5B having the structure C) are laminated such that the interfaces of the selective reflection layers 5R and 5G are in contact with each other and the ground electrode 11 is formed between the selective reflection layers 5G and 5B.

The address electrode 3 and the ground electrode 11 are connected to the drive circuit 8a, and the address electrode 4 and the ground electrode 11 are connected to the drive circuit 8b.

The substrates 1 and 2 are made of a transparent insulating material such as glass or plastic, and the address electrodes 3 and 4 and the ground electrode 11 are made of a transparent conductive material such as ITO. Specifically, as the substrates 1 and 2 and the address electrodes 3 and 4, glass substrates with ITO electrodes, for example, 7059 manufactured by Corning Incorporated can be used, and the ground electrode 11 can be formed by a sputtering method.

A black film 9 for absorbing visible light components transmitted through the selective reflection layers 5R, 5G and 5B is formed on the back surface of the substrate 2 on the side opposite to the incident side of external light. Specifically, black resin such as BKR-10 manufactured by Nippon Kayaku Co., Ltd.
Apply 5.

The selective reflection layers 5R, 5G and 5B are, for example,
PIPS (Polymerization Induc)
ed Phase Separation) method.

That is, a photopolymerizable polymer precursor, such as NOA65 manufactured by Noland Co., which gives a refractive index almost the same as that of the liquid crystal after polymerization, is added to the cholesteric liquid crystal 7B,
It is applied on the substrate 2 on which the address electrode 4 is formed. By irradiating this with ultraviolet light having an intensity of, for example, 10 mW / cm ² , the skeleton of the polymer 6B is formed by the photopolymerization reaction, and the selective reflection layer 5B in which the cholesteric liquid crystal 7B is dispersed as minute droplets is obtained.

A ground electrode 11 is formed on the selective reflection layer 5B.
Then, the selective reflection layer 5G is formed on the ground electrode 11 by the same method, and the material to be the selective reflection layer 5R is applied on the selective reflection layer 5G to form the substrate 1 on which the address electrodes 3 are formed. The selective reflection layer 5R is formed by polymerizing with superposed light by ultraviolet light.

The cholesteric liquid crystals 7R, 7G and 7B are
In nematic liquid crystal having positive dielectric anisotropy,
It can be obtained by adding a liquid crystal having an optically active 2-methylbutyl group, 2-methylbutoxy group, 4-methylhexyl group or the like bonded as a terminal group called a chiral agent. Each spiral pitch pb,
pg and pr are determined by the amount of chiral agent added.

As an example, the cholesteric liquid crystals 7B, 7
G and 7R are cyanobiphenyl nematic liquid crystals,
For example, E8 manufactured by Merck Co., and a dextrorotatory chiral agent, for example, CB15 manufactured by Merck Co., Ltd. in a weight ratio of 50% and 42%, respectively.
%, 33%, the central wavelength λb of the selective reflection of the selective reflection layer 7B is 380 to 5 including the blue region.
The center wavelength λg of the selective reflection of the selective reflection layer 7G is 480 to 630 nm including the green region.
, And the central wavelength λ of the selective reflection of the selective reflection layer 7R.
Each of the spiral pitches pb, pg, and pr is adjusted so that r is in the range of 570 to 780 nm including the red region.

As shown in FIG. 6 and described above, the electrodes 3, 4
The cholesteric liquid crystal 7 having a positive dielectric anisotropy loaded between the electrodes has a helical axis perpendicular to the cell surface as shown in FIG. 3A as the electric field applied between the electrodes 3 and 4 increases. A planar phase which causes selective reflection, a focal conic phase in which the spiral axis faces a random direction as shown in FIG. 7B, and a liquid crystal director faces the electric field direction as the spiral structure unwinds as shown in FIG. The three states of the homeotropic phase are shown. When there is no anchoring effect at the interface, the planar phase with the minimum free energy becomes the ground state in the absence of electric field.

However, the selective reflection layers 5R, 5G, 5
In the polymer-dispersed cholesteric liquid crystal in which the cholesteric liquid crystals 7R, 7G, and 7B are dispersed in the polymers 6R, 6G, and 6B as in B, the interaction from the polymer interface causes a change from the focal conic phase to the planar phase due to thermal fluctuation. These two states exist stably without an electric field without causing a phase transition to.

That is, the selective reflection layers 5R, 5 made of polymer dispersed cholesteric liquid crystal having positive dielectric anisotropy.
Each of G and 5B changes from the planar phase to the focal conic phase and changes from the focal conic phase to the homeotropic phase as the voltage increases as described above during pulse application, but after voltage removal, As shown in the relationship between the voltage value of the applied pulse and the reflectance after the pulse is applied in FIG. 7, the homeotropic phase changes to the planar phase, and either the planar phase or the focal conic phase is retained by the memory effect. To be done.

Therefore, each selective reflection layer 5R,
The threshold voltage of the change from the planar phase to the focal conic phase of 5G and 5B is Vth1, and the threshold voltage of the change from the focal conic phase to the homeotropic phase is Vth.
If th2, the selective reflection layers 5R, 5G, 5
After voltage removal, B is in a selective reflection state due to the planar phase when the voltage before removal is Vth2 or higher, and Vth1
Between Vth2 and Vth2, the transmission state is the focal conic phase, and when Vth1 or less, the state before the voltage application is continued, that is, the selective reflection state by the planar phase or the transmission state by the focal conic phase.

In the reflective color liquid crystal display device of the embodiment shown in FIG. 1, the selective reflection layers 5R, 5G and 5B are utilized by utilizing the bistable phenomenon of the polymer dispersed cholesteric liquid crystal.
Therefore, by switching between the selective reflection state by the planar phase as shown in FIG. 8A and the transmission state by the focal conic phase with small backscattering as shown in FIG. 8B, the display is performed. To do.

Moreover, as shown in the relationship between the voltage value of the applied pulse and the reflectance after the application of the pulse in FIG. 2B, the phase change of the cholesteric liquid crystals 7R and 7G of the selective reflection layers 5R and 5G whose interfaces are in contact with each other. Threshold voltages Vth1 and Vt
Let h2 be different voltages Vr1, Vg1 and Vr2, Vg2, respectively. In the example of FIG. 2B, Vr1 <
This is the case where Vg1 and Vr2 <Vg2.

Cholesteric liquid crystal 7B of selective reflection layer 5B
Of the phase change threshold voltages Vth1 and Vth2 of FIG.
As shown in (A) by the relationship between the voltage value of the applied pulse and the reflectance after the application of the pulse, the above threshold voltages Vr1 and Vg
1 and Vr2, Vg2, and a certain voltage V
Let b1 and Vb2. However, the example of FIG.
From the relationship between the spiral pitches pr, pg, and pb described later, Vb
This is the case where 1> Vg1 and Vb2> Vg2.

Let the dielectric anisotropy of cholesteric liquid crystal be Δε,
If the twist elastic modulus is K22 and the bend elastic modulus is K33, the threshold voltage Vth1 is p ⁻¹ , Δε ^−1/2 ,
It is represented by a function of K22 and K33 ^−1/2 , and the threshold voltage Vth2 is p ⁻¹ , Δε ^−1/2 and K22.
It is represented by a function of ^1/2 .

Therefore, as described above, the spiral pitches pr, pg, p of the cholesteric liquid crystals 7R, 7G, 7B.
b is a relation of pr>pg> pb, and reflection center wavelengths λr, λg, λb of the cholesteric liquid crystals 7R, 7G, 7B.
In the relationship of λr>λg> λb, and when the cholesteric liquid crystals 7R, 7G, and 7B are formed of the same nematic liquid crystal, Vr1 <Vg1 and Vr2 <Vg2 depending on the spiral pitches pr and pg. be able to.

However, in order to obtain a larger drive margin, the respective cholesteric liquid crystals 7R, 7G, 7
It is desirable that B is formed of nematic liquid crystal having different dielectric anisotropy Δε or twist elastic modulus K22 or bend elastic modulus K33.

The drive circuit 8b is provided between the address electrode 4 and the ground electrode 11 and the drive circuit 8a.
Between the address electrode 3 and the ground electrode 11,
As shown in FIG. 3, as the drive signals, signals composed of a refresh period and a select period of a pulse voltage of, for example, 1 kHz, and a non-voltage display period thereafter are applied.

Moreover, the address electrode 4 and the ground electrode 1
The drive signal applied between 1 and 1 is the refresh voltage Vr.
The select voltage Vs is changed between the three levels of voltages Va to Vc shown in FIG. 2 (A) based on the input data in a relationship of Vr> Vs, and the select voltage Vs is changed between the address electrode 3 and the ground electrode 11. The drive signal applied to
The refresh voltage Vr and the select voltage Vs are set to Vr
Based on the input data with the relation of> Vs, FIG.
The voltage is changed between the five levels of voltage Vd to Vh shown in (B).

FIG. 4A shows the state of the phase change of the selective reflection layer 5B due to the combination of the refresh voltage Vr and the select voltage Vs in this case, where "1" is the selective reflection state by the planar phase. “0” indicates the transmission state by the focal conic phase. However, only the case of significant Vr> Vs is shown.

FIG. 4B shows a combination of the refresh voltage Vr and the select voltage Vs in this case.
It shows the state of the phase change of the selective reflection layers 5R and 5G.
Numerical values such as “0?”, “00”, “10”, and “11” indicate the phase state of the upper (left side) of the selective reflection layer 5R, the lower (right side) of the selective reflection layer 5G, and “1” indicates the planar state. The selective reflection state by the phase, “0” indicates the transmission state by the focal conic phase, and “?” Indicates the undetermined state depending on the state before the application of the drive signal. However, only the case of significant Vr> Vs is shown.

As is apparent from this, for example, a drive signal that changes in the order of Vc → Vb → 0V is applied between the electrodes 4 and 11, and a drive signal that changes in the order of Vh → Vf → 0V is applied between the electrodes 3 and 11. When a signal is applied, the selective reflection layer 5R,
5G and 5B are all in a transmissive state, and the selective reflection layer 5
The light transmitted through R, 5G, and 5B is absorbed by the black film 9, and black is displayed.

A drive signal that changes in the order of Vc → Va → 0V is applied between the electrodes 4 and 11, and Vh → V is applied between the electrodes 3 and 11.
When applying a drive signal that changes in the order of d → 0V,
All the selective reflection layers 5R, 5G, and 5B are in the selective reflection state, and white is displayed.

Further, Vc → Vb → 0V between the electrodes 4 and 11.
The driving signal that changes in the order of
When a drive signal that changes in the order of h → Vg → 0V is applied, only the selective reflection layer 5R is in the selective reflection state, and red is displayed.

A drive signal that changes in the order of Vc → Vb → 0V is applied between the electrodes 4 and 11, and Vh → V is applied between the electrodes 3 and 11.
When applying a drive signal that changes in the order of e → 0V,
Only the selective reflection layer 5G is in the selective reflection state, and green is displayed.

A drive signal that changes in the order of Vc → Va → 0V is applied between the electrodes 4 and 11, and Vh → V is applied between the electrodes 3 and 11.
When applying a drive signal that changes in the order of f → 0V,
Only the selective reflection layer 5B is in the selective reflection state, and blue is displayed.

Furthermore, Vc → Vb → 0 between the electrodes 4 and 11.
When a drive signal that changes in the order of V is applied and a drive signal that changes in the order of Vh → Vd → 0V is applied between the electrodes 3 and 11, the selective reflection layers 5R and 5G are in the selective reflection state, and yellow Is displayed.

A drive signal that changes in the order of Vc → Va → 0V is applied between the electrodes 4 and 11, and Vh → V is applied between the electrodes 3 and 11.
When applying a drive signal that changes in the order of g → 0V,
The selective reflection layers 5B and 5R are in the selective reflection state, and magenta is displayed.

A drive signal varying in the order of Vc → Va → 0V is applied between the electrodes 4 and 11, and Vh → V is applied between the electrodes 3 and 11.
When applying a drive signal that changes in the order of e → 0V,
The selective reflection layers 5B and 5G are in the selective reflection state, and cyan is displayed.

Therefore, within one pixel, white, black, red, green, blue, yellow, magenta,
All eight colors of cyan can be displayed.

The cholesteric liquid crystals 7R, 7G,
Since the reflectance of the selective reflection by 7B is 50% in principle, the contrast is high. Moreover, the selective reflection layer 5
Since R, 5G, and 5B are laminated only through the ground electrode 11 between the selective reflection layer 5G and the selective reflection layer 5B, without being interposed by the transparent substrate and other transparent electrodes, parallax is reduced and Since only the ground electrode 11 needs to be formed between the selective reflection layers 5R, 5G and 5B, and only two driving circuits are required, the manufacturing cost is reduced.

FIG. 5 shows another embodiment of the reflection type color liquid crystal display device of the present invention, in which the selective reflection layers 5R, 5G and 5B shown in the embodiment of FIG. Cholesteric liquid crystals 7Ra, 7Ga, 7Ba in which the spiral direction is changed to the right direction by the addition are added to the upper reflection layers 5Ra, 5Ga, 5Ba in which the polymer is dispersed, and the spiral direction is changed to the left direction by the addition of the levorotatory chiral agent. This is a case where the cholesteric liquid crystal 7Rb, 7Gb, 7Bb has a two-layer structure of lower reflection layers 5Rb, 5Gb, 5Bb dispersed in a polymer.

As described above, the cholesteric liquid crystal having the positive dielectric anisotropy reflects only the circularly polarized light in the same direction as the spiral direction out of the light having the wavelength determined by the spiral pitch, and therefore, the implementation of FIG. In the reflection type color liquid crystal display device of the embodiment, the reflectance of selective reflection is 50% in principle.

On the other hand, in the reflection type color liquid crystal display device of the embodiment shown in FIG. 5, the selective reflection layers 5R and 5R are provided.
G and 5B are cholesteric liquid crystals 7 whose spiral direction is the right direction.
Since it has Ra, 7Ga, 7Ba and cholesteric liquid crystals 7Rb, 7Gb, 7Bb whose spiral direction is the left direction, the reflectance of selective reflection is 100% in principle, and the contrast is very high.

The upper reflection layers 5Ra, 5Ga, 5Ba
The spiral direction of the cholesteric liquid crystals 7Ra, 7Ga, 7Ba may be leftward, and the spiral direction of the cholesteric liquid crystals 7Rb, 7Gb, 7Bb of the lower reflective layers 5Rb, 5Gb, 5Bb may be rightward.

In the embodiment shown in FIGS. 1 and 5, the selective reflection layers 5R and 5G for selectively reflecting red and green color lights, respectively, are provided.
A selective reflection layer 5B which is formed between the address electrode 3 on the outside light incident side and the ground electrode 11 and selectively reflects blue color light,
In the case of forming it between the ground electrode 11 and the other address electrode 4, any two layers of the three selective reflection layers may be used as the address electrode 3 on the outside light incident side and the ground electrode 1.
It may be formed between 1 and 1.

Any two layers of the three selective reflection layers are formed between the address electrode 4 and the ground electrode 11 on the side opposite to the external light incident side, and the remaining one layer is the ground electrode. It may be formed between 11 and the address electrode 3 on the incident side of external light.

[0074]

As described above, according to the present invention, sufficient contrast can be obtained, parallax is reduced, manufacturing cost is reduced, and white, black, red, and green are formed within one pixel. It is possible to display all eight colors of blue, yellow, magenta and cyan.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a reflective color liquid crystal display device of the present invention.

FIG. 2 is a diagram showing an example of a relationship of a phase change threshold voltage of cholesteric liquid crystal of each selective reflection layer in the reflective color liquid crystal display device of FIG.

FIG. 3 is a diagram showing an example of a mode of a drive signal applied between electrodes of the reflective color liquid crystal display device of FIG.

FIG. 4 is a diagram showing an example of a phase change state of each selective reflection layer due to a combination of a refresh voltage and a select voltage in the reflective color liquid crystal display device of FIG.

FIG. 5 is a diagram showing another embodiment of the reflective color liquid crystal display device of the present invention.

FIG. 6 is a diagram showing a phase change of a cholesteric liquid crystal having a positive dielectric anisotropy.

FIG. 7 is a diagram showing a switching operation of a cholesteric liquid crystal having a positive dielectric anisotropy.

8 is a diagram showing a bistable state of each selective reflection layer of the reflection type color liquid crystal display device of FIG. 1 or FIG.

FIG. 9 is a diagram showing an embodiment of a reflective color liquid crystal display device of the invention of the prior application.

10 is a diagram showing an example of the relationship between the phase change threshold voltages of the cholesteric liquid crystals of each selective reflection layer in the reflective color liquid crystal display device of FIG.

11 is a diagram showing an example of a phase change state of each selective reflection layer due to a combination of a refresh voltage and a select voltage in the reflective color liquid crystal display device of FIG.

FIG. 12 is a diagram showing an example of a conventional reflective color liquid crystal display device.

[Explanation of symbols]

1, 2 substrates 3,4 address electrodes 5R, 5G, 5B selective reflection layer 6R, 6G, 6B polymer 7R, 7G, 7B cholesteric liquid crystal 8a, 8b drive circuit 9 Black film 11 Ground electrode

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02F 1/1347 G02F 1/1334 G02F 1/133 G02F 1/137

Claims (2)

(57) [Claims] 1. A first substrate which is a transparent substrate having a transparent electrode, a second substrate which is a substrate having an electrode and which is arranged so as to face the first substrate, the first substrate and the second substrate. And a ground electrode disposed between the ground electrode and one of the first substrate and the second substrate and the ground electrode, which are laminated and formed on the way without interposing another substrate and an electrode on the red. , A first color selective reflection layer in which a cholesteric liquid crystal that selectively reflects the first color light in green, blue and blue is dispersed in a polymer, and a cholesteric that selectively reflects the second color light in red, green and blue. A plurality of selective reflection layers each comprising a polymer-dispersed cholesteric liquid crystal layer including a second color selective reflection layer in which liquid crystal is dispersed in a polymer; and the other one of the first substrate and the second substrate, and Red formed between the ground electrode and A third color selective reflection layer in which a cholesteric liquid crystal that selectively reflects light of a third color in green and blue is dispersed in a polymer, and the plurality of selections between the one substrate and the ground electrode In the reflective color liquid crystal display device, the reflective layer has different phase change threshold voltages of the cholesteric liquid crystals. 2. The reflection type color liquid crystal display device according to claim 1, wherein the first color selective reflection layer, the second color selective reflection layer and the third color selective reflection layer each have a spiral direction to the right. A right-handed polymer-dispersed cholesteric liquid crystal layer in which cholesteric liquid crystals are dispersed in a polymer, and a left-handed polymer-dispersed cholesteric liquid crystal layer in which cholesteric liquid crystals whose spiral direction is left are dispersed in the polymer. A reflective color liquid crystal display device comprising: