JPH10221710A - Reflection type color display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multi-color displayable reflection type color display device capable of obtaining a high brightness display, remarkably improving particularly white display brightness, improving visibility and facilitating drive and manufacture of the device. SOLUTION: Light control elements 10G, 10R, 10B are laminated successively from an external light incident side. Respective light control elements 10G, 10R, 10B form transparent pixel electrodes 21, 22, and are constituted so that light control layers 23M, 23C, 23Y consisting of a chiral nematic liquid crystal containing a dichroic dystuff and dichroic mirrors 27G, 27R, 27B with a dielectric multilayer film are formed between transparent substrates 11, 12 performed with planar orientation processing. The dichroic dystuff in the light control layers 23M, 23C, 23Y are made the dichroic dystuff of respective magenta, cyan and yellow, the reflection wavelength regions of the dichroic mirrors 27G, 27R, 27B are made wavelength regions of respective green, red and blue.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflection type color display device capable of multicolor display.

[0002]

2. Description of the Related Art Notebook PCs and PDAs (Persons)
With the increase in demand for portable information devices such as al digital assistants, there is a need for flat panel displays that have low power consumption, are thin and lightweight, and have high display quality, especially flat panel displays capable of color display. The reflective color display device has been actively studied as a device for realizing it.

[0003] Various types of reflective color display devices have been proposed in the past, but a process that can realize a wide color reproduction range and can easily be made full-color has been proposed.
dings of SID'81 p22 1981,
And SID'96 Digest p103-106
Yellow, magenta, respectively, as shown in
There is a so-called guest-host three-layer system in which cells constituted by guest-host liquid crystals containing a dichroic dye of cyan are stacked, and a reflector is provided on the side opposite to the outside light incident side.

FIG. 4 shows an example of a reflection type color display device of the guest-host three-layer stack type, in which a planar alignment mode of a chiral nematic liquid crystal is used. The dimming elements 10G, 10R, and 10B are laminated, and a reflection plate 24 is provided on the side opposite to the side on which external light is incident.

The light control elements 10G, 10R, 10
B shows that transparent pixel electrodes 21 and 22 made of ITO or the like are formed on one surface of two transparent substrates 11 and 12 made of glass or the like, and are subjected to a planar alignment treatment.
2 are attached at intervals of about several μm to several tens of μm, and between the transparent substrates 11 and 12, the light control layers 23M, 23C and 23Y
As a nematic liquid crystal having a positive dielectric anisotropy,
A mixture consisting of a chiral agent and a dichroic dye is injected.

As a nematic liquid crystal having a positive dielectric anisotropy, a commercially available Merck E-8 is available.
And the like, and as a chiral agent, generally available ZLI-811, CB15 manufactured by Merck Ltd.
Etc. can be used. The mixture of the nematic liquid crystal and the chiral agent is mixed with an appropriate amount of dichroic dyes of magenta, cyan, and yellow, respectively, and the light modulating layer 2 is formed.
Three types of mixtures of 3M, 23C and 23Y are obtained.

The dichroic dyes of magenta, cyan, and yellow are generally 535 nm, 625 nm,
Those having a center value of the absorption wavelength near 445 nm are used, and M-618 and SI-49 manufactured by Mitsui Toatsu Co., Ltd. are used, respectively.
7, SI-486 or the like can be used.

After the respective mixtures are injected into the cells, the injection ports of the respective cells are sealed, and means for applying an electric field to the transparent pixel electrodes 21 and 22 are provided for the respective cells. Then, three cells, that is, the dimming element 10
G, 10R, and 10B are superimposed, and a reflection plate 24 made of an aluminum plate or the like is provided on the side opposite to the external light input side to obtain a reflection type color display device.

The orientation mode of the liquid crystal molecules in the liquid crystal cell of the guest-host liquid crystal containing a dichroic dye is not limited to the above-described planar orientation mode of the chiral nematic liquid crystal, but may be, for example, a homogeneous orientation mode of the nematic liquid crystal. You can also. However, in the case of homogeneous alignment, a polarizing plate is required. In addition, polymer dispersed liquid crystal (PDLC: Polymer Disperse) in which a nematic liquid crystal is dispersed in a polymer in a droplet shape.
A mode in which a dichroic dye is contained in rsed liquid crystals can also be used.

The above-described reflection type color display device of the guest-host three-layer lamination type can obtain a wide color reproduction range by a coloring principle similar to that of photography and printing.

However, in this method, each of the dimming elements 10G, 10R, and 10B is divided into pixel units,
Since a driving unit 25 including a switching element, a wiring, and the like for driving the pixel is provided for each pixel, light incident on each pixel is blocked by the driving unit 25. Further, generally, in order to improve the contrast, each of the light control elements 10G, 10R, and 10B
A black matrix 26 is provided on the transparent substrate 11 on the outside light incident side.

Therefore, in practice, the light utilization efficiency becomes about 70 to 80% each time the light passes through the light control element of one layer, and as shown in the example of FIG.
When the red light 1R and the blue light 1B are observed as reflected light by reciprocating through the three-layer light control elements 10G, 10R, and 10B, respectively, the light amount becomes six times of 80%, that is, about 30% or less. I will.

Therefore, the above-described conventional guest-host type reflection type color display device cannot display bright colors requiring brightness, and has a high reflectance particularly in white display where high brightness is required. And the lightness is not sufficient.

As a reflection type color display device which can solve such a problem, a device using a dimming element based on an interference reflection method has recently attracted attention. In principle, in the interference reflection method, a reflectance close to 100% can be obtained at a desired wavelength, so that a high-brightness color display is possible. As a dimming element using the interference reflection method and a method for manufacturing the same, Japanese Patent Application Laid-Open No. 4-355424 proposes the following.

That is, as shown in FIG. 5 (A), a pair of transparent substrates 71, 73 each having a transparent electrode 72, 74 formed on the inner surface thereof are opposed to a cell 70 at a predetermined interval. A mixture 80 containing a photopolymerizable compound in a nematic liquid crystal having anisotropy is injected, the cell 70 is irradiated with coherent light from both sides of the cell 70, and the interference between the two causes the photopolymerizable compound in the mixture 80 to be mixed. Is polymerized.

At this time, as shown in FIG. 5 (B), the polymerized compound forms a polymer layer 83 at a period determined by the wavelength and incident angle of the coherent light for hologram writing, and the nematic liquid crystal is The liquid crystal layer 85 is formed by depositing in a region other than the layer 83. Therefore, in the state where no voltage is applied between the transparent electrodes 72 and 74, the light control layer 8
1 can cause a periodic change in the refractive index,
A specific wavelength of reflection can be produced.

The refractive index no of the liquid crystal with respect to ordinary light
Is equal to the refractive index np of the polymer, the transparent electrode 7
In the state where a voltage is applied between 2, 74, the liquid crystal molecules are aligned in the direction of the electric field, so that the periodic change in the refractive index in the light control layer 81 disappears, and all the incident light passes through the cell 70. Become like Therefore, the amount of reflected light can be controlled according to the voltage applied between the transparent electrodes 72 and 74.

In this method, in principle, the reflection wavelength can be selected according to the wavelength or the incident angle of the coherent light for writing the hologram. Therefore, for example, by producing and superimposing three dimming elements each having a red, green, and blue wavelength region as a reflection wavelength region and providing a light absorbing layer on the side opposite to the external light incidence side, a wide color reproduction can be achieved. A range can be obtained, and full-color display can be performed.

According to this method, the light reflected by the dimming element closest to the external light is observed only by reciprocating the dimming element closest to the external light. 2
The light reflected by the intermediate dimming element is observed only by going back and forth between the dimming element closest to the external light and the intermediate dimming element.
The light is received only in batches, and only the light reflected by the light control element on the side opposite to the external light incident side is observed by reciprocating through all three light control elements.

Therefore, by providing the dimming element that reflects light of a color that requires particularly high brightness on the outside light incident side, it is possible to obtain a display with higher brightness as compared with the above-described conventional guest-host system. it can. For example, by stacking dimming elements from the external light incident side in the order of green, red, and blue, which are colors that are more sensitive to lightness, the reflectance of green and red is higher than that of the guest-host system. Is obtained.

[0021]

However, in the dimming device based on the interference reflection method, as shown in FIG.
6 are dispersed in the polymer 84 in the form of droplets, and the orientation direction of the liquid crystal droplets 86 becomes random.

Therefore, the effective refractive index of the liquid crystal layer 85 is greatly reduced by averaging by the refractive index of the polymer 84 contained therein and averaging by the random orientation of the liquid crystal droplet 86. The periodic change in the refractive index in the light control layer 81 is reduced. Therefore, the half width of the reflection spectrum is narrowed, and the brightness is low when used as a display element.

Although not yet known, Japanese Patent Application No. Hei 8-226046 (filed on Aug. 7, 1996) describes the first, second and third examples of the prior invention as follows. A dimming device as shown in the drawings has been proposed.

As shown in FIG. 6, the light control element of the first example of the invention of the prior application has a light control layer 50 sandwiched between transparent substrates 11 and 12, and the light control layer 50 is formed as described later. It is assumed that the dead layer 51 and the sensitive layer 52 are alternately formed in the Z-axis direction (the direction in which the transparent substrates 11 and 12 face each other).
Each of the pair of electrodes 43 and 4 is extended in a stripe shape in the X-axis direction (one direction perpendicular to the Z-axis direction) to face each other in the Y-axis direction (a direction perpendicular to the Z-axis direction and the X-axis direction).
4 is formed.

This dimming device is manufactured by the following method. First, the electrodes 43 and 44 are formed on the transparent substrate 12, and the transparent substrates 11 and 12 are each subjected to a homogeneous alignment treatment. A liquid crystal containing a small amount of such as is injected, the cell is irradiated with coherent light from both sides of the cell, and the photopolymerizable compound is periodically polymerized.
A dead layer 51 in which the alignment state of the liquid crystal molecules does not change by the voltage applied between the four layers is formed.

Further, after a certain exposure time, the entire cell is irradiated with ultraviolet light so that the electrodes 43 and 44 are interposed between the dead layers 51.
The sensitive layer 52 in which the alignment state of the liquid crystal molecules can be changed by the voltage applied therebetween is formed.

In this light control element, when no voltage is applied between the electrodes 43 and 44, as shown in FIG. 6A, the liquid crystal molecules in the light control layer 50 cause the light insensitive layer 51 and the sensitive layer 52 In each case, since they are uniformly oriented in the X-axis direction,
There is no difference in refractive index between the insensitive layer 51 and the sensitive layer 52, and no reflected light.

On the other hand, when a sufficient voltage is applied between the electrodes 43 and 44, an electric field is applied to the dimming layer 50 in the Y-axis direction, as shown in FIG.
The orientation direction of the liquid crystal molecules in the sensitive layer 52 changes in the Y-axis direction. Therefore, a refractive index difference occurs between the insensitive layer 51 and the sensitive layer 52, that is, a periodic change in the refractive index occurs in the Z-axis direction in the light control layer 50, and reflected light is generated.

According to this dimmer, in the reflection state shown in FIG. 6B, the liquid crystal in the insensitive layer 51 is oriented in the X-axis direction, whereas the liquid crystal in the sensitive layer 52 is in the Y-axis. Since the liquid crystal molecules are oriented in the same direction, the difference in the refractive index between the insensitive layer 51 and the sensitive layer 52 becomes very large, substantially equal to the birefringence of the liquid crystal, and a sufficiently wide half-width of the reflection spectrum can be obtained.

As shown in FIG. 7, a dimming device according to a second embodiment of the invention of the prior application has a transparent substrate 11 on which a transparent electrode 41 is formed.
And the transparent substrate 12 on which the transparent electrode 42 is formed.
The light control layer 50 is sandwiched between the light control layers 50 and the liquid crystal molecules are
It is assumed that first layers 55 oriented in the axial direction and second layers 56 oriented in the Y-axis direction are alternately formed in the Z-axis direction.

This light control element is manufactured by the following method. First, the transparent electrodes 41, 4 are placed on the transparent substrates 11, 12, respectively.
2 to form a homogeneous alignment treatment,
A liquid crystal containing a small amount of a photopolymerizable compound or the like is injected into a cell in which the transparent substrates 11 and 12 are adhered at a desired interval, and the cell is irradiated with coherent light from both sides of the cell to remove the photopolymerizable compound. By periodically polymerizing, the first layer 55 in which the liquid crystal molecules are aligned in the X-axis direction and the alignment state is fixed is formed.

Further, while applying a sufficiently strong magnetic field in the Y-axis direction, the entire cell is irradiated with ultraviolet light, so that the liquid crystal molecules are aligned between the first layers 55 in the Y-axis direction and the alignment state is maintained. Is formed to form the second layer 56.

In this light control element, when no voltage is applied between the transparent electrodes 41 and 42, as shown in FIG. 7A, the liquid crystal molecules in the light control layer 50 and the X in the first layer 55 are reduced. The second layer 56 is oriented in the Y-axis direction while being oriented in the axial direction.
A difference in the refractive index between the light modulating layer 50 and the
In some cases, the refractive index is periodically changed in the Z-axis direction to generate reflected light.

On the other hand, when a voltage is applied between the transparent electrodes 41 and 42, an electric field is applied to the dimming layer 50 in the Z-axis direction, as shown in FIG. The alignment direction of the liquid crystal molecules in the first layer 55 and the alignment direction of the liquid crystal molecules in the second layer 56 change in the Z-axis direction. Therefore, the difference in the refractive index between the first layer 55 and the second layer 56 disappears, and the reflected light disappears.

According to this dimming device, in the reflection state shown in FIG. 7A, the refractive index difference between the first layer 55 and the second layer 56 is very equal to the birefringence of the liquid crystal. It becomes large, and a sufficiently wide half width of the reflection spectrum can be obtained.

As shown in FIG. 8, a light modulating device according to a third example of the invention of the prior application is a transparent substrate 11 on which a transparent electrode 41 is formed.
And the transparent substrate 12 on which the transparent electrode 42 is formed.
The light control layer 50 is sandwiched between the liquid crystal polymer composites in which liquid crystal droplets of nematic liquid crystal having positive dielectric anisotropy are dispersed in a polymer matrix. First layer 57 in which liquid crystal therein is oriented in the X-axis direction
And the second layer 58 oriented in the Y-axis direction are formed alternately in the Z-axis direction.

This light control element is manufactured by the following method. First, the transparent electrodes 41, 4 are placed on the transparent substrates 11, 12, respectively.
Form 2

Next, the transparent substrate 1 on which the transparent electrode 42 is formed
On steps 2, the following steps (1) to (4) are repeated, for example, ten times to form the light control layer 50. (1) A mixture of a nematic liquid crystal having a positive dielectric anisotropy, a photopolymerizable compound, and a solvent is spin-coated on the transparent substrate 12 to volatilize the solvent. (2) This is transferred into a chamber in a nitrogen atmosphere, and a transparent substrate 1 is applied while applying a magnetic field in the Y-axis direction using a superconducting magnet.
2 is irradiated with ultraviolet light to form a polymer dispersed liquid crystal layer constituting the second layer 58. (3) The above mixture is spin-coated on the transparent substrate 12,
Evaporate the solvent. (4) This is transferred into a chamber in a nitrogen atmosphere, and a transparent substrate 1 is applied while applying a magnetic field in the X-axis direction using a superconducting magnet.
2 is irradiated with ultraviolet light to form a polymer dispersed liquid crystal layer constituting the first layer 57.

The thickness of one layer of the liquid crystal polymer composite after curing is set to be about 80 nm. Finally, the light control layer 5
The transparent substrate 11 on which the transparent electrode 41 is formed is bonded on the substrate 0.

In this light control device, when no voltage is applied between the transparent electrodes 41 and 42, as shown in FIG. In 57, while being oriented in the X-axis direction, the second layer 5
8, the first layer 5 is oriented in the Y-axis direction.
7 and the second layer 58, that is, a periodic change in the refractive index occurs in the dimming layer 50 in the Z-axis direction to generate reflected light.

On the other hand, when a voltage is applied between the transparent electrodes 41 and 42, an electric field is applied to the dimming layer 50 in the Z-axis direction, as shown in FIG. The orientation direction of the liquid crystal molecules in the droplet in the one layer 57, and
The orientation directions of the liquid crystal molecules in the droplets in the layer 58 are Z
It changes in the axial direction. Therefore, the first layer 57 and the second layer 58
And the reflected light disappears, and the reflected light disappears.

According to this dimming device, in the reflection state shown in FIG. 8A, the difference in the refractive index between the first layer 57 and the second layer 58 is very large, and the reflection spectrum is sufficiently wide. The price range is obtained.

As described above, the first, second, and third inventions of the prior application
The light modulating device of the third example reflects light in a specific wavelength region or transmits light in the entire wavelength region according to a voltage applied between the electrodes 43 and 44 or between the transparent electrodes 41 and 42.
Therefore, for example, by producing and superimposing three dimming elements each having a red, green, and blue wavelength region as a reflection wavelength region and providing a light absorbing layer on the side opposite to the external light incidence side, a wide color reproduction can be achieved. Can get a range,
Full color display becomes possible.

Moreover, as described above, the periodic change in the refractive index in the light control layer 50 in the reflection state becomes very large, and a sufficiently wide half-width of the reflection spectrum is obtained. In this case, the brightness becomes sufficiently high, and very good display characteristics can be obtained.

However, the dimming device of the first example of the invention of the prior application shown in FIG. 6 forms the electrodes 43 and 44 for applying an electric field in the plane direction of the substrates 11 and 12 in the pixel. The aperture ratio of the pixel is significantly reduced. Further, considering driving by the electric field in the plane direction, the threshold voltage Vt between the transmission state and the reflection state is as follows: Vt = (πL / d) × (k2 / εoΔε) ^1/2 (1) Here, L is the distance between the electrodes 43 and 44, d is the thickness of the light control layer 50, k2 is the twist elastic modulus of the liquid crystal, and Δε is the dielectric anisotropy of the liquid crystal.

Since d is equivalent to the thickness of each layer forming the periodic structure, d is a value corresponding to the wavelength of light, and is as small as several tens to 100 nm. Therefore, a very high voltage is required as the threshold voltage Vt,
Driving the element becomes difficult, and the power consumption increases.

The dimming elements of the second and third examples of the prior invention shown in FIGS. 7 and 8 control the alignment direction of the liquid crystal molecules by applying a magnetic field during the manufacturing process. A very strong magnetic field is required. Therefore, it is difficult to apply a magnetic field uniformly over a wide area,
There are difficulties in terms of device productivity and uniformity.

Therefore, according to the present invention, in a reflection type color display device capable of multicolor display, not only a wide color reproduction range can be realized, but also a high-brightness display can be obtained. This improves the visibility and facilitates the driving and manufacturing of the device.

[0049]

According to the present invention, a plurality of dimming modes that can selectively take two states, a state of reflecting a specific wavelength region and a state of absorbing a specific wavelength region, and different from each other in the specific wavelength region. In the reflective color display device in which the elements are stacked, the plurality of dimming elements are each
A dichroic mirror for selectively reflecting the specific wavelength region; and a dichroic mirror provided on the external light incident side of the dichroic mirror and having dichroism for the specific wavelength region and substantially transmitting the other wavelength regions. And an optical layer.

In this case, the plurality of dimming elements can be three dimming elements each of which has the specific wavelength region of red, green, and blue wavelength regions.

In this case, it is preferable that the three dimming elements are stacked in such a manner that the green, red, and blue wavelength regions are set to the specific wavelength region in order from the external light incident side.

It is preferable that the dichroic mirror of each of the light control elements is formed by a dielectric multilayer film adjacent to the light control layer of the light control element.

[0053]

In a typical case where three light control elements are stacked, in the reflection type color display device of the present invention configured as described above, the light control element on the outside light incident side is the first layer. If the intermediate dimming element is the second layer and the dimming element most opposite to the external light incident side is the third layer, the light of the first color transmitted through the first dimming layer is the first layer. Is reflected by the dichroic mirror, and is observed as reflected light only by going back and forth through the dimming element of the first layer, and is affected only by the aperture ratio twice.

The light of the second color transmitted through the first light control layer and the dichroic mirror and the second light control layer is:
The light is reflected by the dichroic mirror of the second layer and is observed as reflected light only by going back and forth between the dimming elements of the first and second layers, and is only affected by the aperture ratio four times.

The first light control layer and the dichroic mirror and the second light control layer and the dichroic mirror and the third
Only the light of the third color transmitted through the light control layer of the layer is reflected by the dichroic mirror of the third layer, and is observed as reflected light by reciprocating through the light control elements of all three layers.

Therefore, a display with high brightness can be obtained by using, as the first layer, a dimming element that reflects light of a color required to be particularly bright by the dichroic mirror.

When the first, second, and third layers of the dimming elements reflect the green, red, and blue wavelength regions with a dichroic mirror, respectively, a person is sensitive to brightness. Since the light control elements are arranged in the order of colors from the observation side, a vivid color can be expressed, and the brightness of white display in particular is greatly improved.

When the dichroic mirror of each dimming element is formed by a dielectric multilayer film adjacent to the dimming layer of the dimming element, each dichroic mirror constitutes the dimming element. Since the influence of the aperture ratio of the dimming element on the reflected light is almost only one way, the reflectance is improved over the entire wavelength range.

[0059]

FIG. 1 shows an example of a reflection type color display device according to the present invention.
This is the case where R and 10B are stacked.

Each light control element 10G, 10R, 10
B denotes a black matrix 26, a driving unit 25 including switching elements such as thin film transistors, wiring, and the like on one surface of a transparent substrate 11 made of glass or the like;
An active matrix substrate is formed by forming a transparent pixel electrode 21 made of O or the like, and dichroic mirrors 27G, 27R, and 27B are formed by a dielectric multilayer film on one surface of a transparent substrate 12 made of glass or the like.
A transparent pixel electrode 22 made of ITO or the like is formed thereon, and a counter substrate is manufactured.
The surface on the 22 side is subjected to a planar alignment treatment. Then, the transparent substrates 11 and 12 are bonded together at intervals of about several μm to several tens μm such that the transparent pixel electrodes 21 and 22 are on the inner side to produce a cell.

The dichroic mirrors 27G, 27R, and 27B made of a dielectric multilayer film have a reflection wavelength range of 490 nm to 580 nm for the dichroic mirror 27G, 580 nm or more for the dichroic mirror 27R, and 490 nm or less for the dichroic mirror 27B. Specifically, ZrO ₂ or the like can be used as the high-refractive-index film, and MgF ₂ or the like can be used as the low-refractive-index film, and each film is formed by an electron beam evaporation method.

Dichroic mirrors 27G, 27R, 2
The central wavelength and the bandwidth of the 7B reflection wavelength region can be easily controlled by the thickness of the periodic film, the ratio of the respective refractive indexes, and the ratio of the film thickness.

Then, each of the light control elements 10G, 10
A mixture composed of a nematic liquid crystal having a positive dielectric anisotropy, a chiral agent, a dichroic dye, and the like is injected into the cells of R and 10B as the dimming layers 23M, 23C, and 23Y, and the injection ports are sealed. .

As a nematic liquid crystal having a positive dielectric anisotropy, a commercially available Merck E-8
And the like, and as a chiral agent, generally available ZLI-811, CB15 manufactured by Merck Ltd.
Etc. can be used. The mixing ratio between the nematic liquid crystal and the chiral agent is adjusted so that the selective reflection wavelength of the chiral nematic liquid crystal does not fall in the visible light region.

In the mixture of the nematic liquid crystal and the chiral agent, the light control layer 23M is provided with a magenta dichroic dye having an absorption wavelength center value of about 535 nm, and the light control layer 23M.
For C, a cyan dichroic dye whose central value of the absorption wavelength is around 625 nm is mixed, and for the light control layer 23Y, a yellow dichroic dye whose central value of the absorption wavelength is around 445 nm is mixed. The magenta, cyan, and yellow dichroic dyes include M-Toshiatsu M-
618, SI-497, SI-486, and the like. The mixing ratio of the dichroic dye is determined based on a balance between the contrast and the maximum transmittance.
To within several%.

As is already clear from the above description, the combination of the dichroic mirror in the same dimming element and the dichroic dye in the dimming layer causes the dichroic mirror to reflect the dichroic mirror with respect to the reflected color of the dichroic mirror. Make the absorption color a complementary color. That is, for the dichroic mirror 27G that reflects the green light 1G, magenta 2
A dichroic dye is combined with the dichroic mirror 27R that reflects the red light 1R, and a dichroic dye with yellow is combined with the dichroic mirror 27B that reflects the blue light 1B.

The light control elements 10G, 10 thus manufactured
Liquid crystal driving means are connected to R and 10B, respectively, and three light control elements 10G, 10R and 10B are superposed and bonded in this order from the external light incident side to complete a reflection type color display device.

In the reflection type color display device of this example, the green light 1G in the incident light passes through the light control layer 23M, is reflected by the dichroic mirror 27G, transmits again through the light control layer 23M, and is reflected. Observed as light, the red light 1R passes through the dimming layer 23M and the dichroic mirror 27.
G, is transmitted through the dimming layer 23C, is reflected by the dichroic mirror 27R, is transmitted again through the dimming layer 23C, the dichroic mirror 27G, and the dimming layer 23M, is observed as reflected light, and the blue light 1B is dimmed. The light passes through the layer 23M, the dichroic mirror 27G, the dimming layer 23C, the dichroic mirror 27R, and the dimming layer 23Y, is reflected by the dichroic mirror 27B, and is returned again to the dimming layer 23Y, the dichroic mirror 27R, the dimming layer 23C, and the dichroic mirror 27G. The light passes through the light control layer 23M and is observed as reflected light.

FIG. 2A shows the color reproduction range of the reflective color display device of this example, and FIG. 4 shows the color reproduction range of the conventional guest-host three-layer reflective color display device shown in FIG. FIG. 2B shows the result of comparison between the two, and FIG. 3 shows the result. However, when viewed in CIE · L ^* a ^* b ^* space, the aperture ratio of a single-layer light control element is 80
%, The dichroic ratio of the dichroic dye is 10, and the reflection plate 24 in FIG. 4 is compared in a state where the gain is zero.

As is apparent from the above description, according to the reflection type color display device of the example shown in FIG. 1, the brightness of white display is greatly improved as compared with the conventional example shown in FIG. Further, the color gamut in the yellow, green, and cyan directions is expanded, and the lightness is improved.

This is, as described above, the green light 1
G is reflected by the dichroic mirror 27G, and is observed as reflected light only by reciprocating on a portion of the dimming mirror 27G of the dimming element 27 on the side of incident external light. The red light 1R is reflected by the dichroic mirror 27R.
This is because the reflected light is observed only by reciprocating between the dichroic mirror 27R and the portion of the dimmer element 27R on the outside light incident side and the dimmer element 10G.

Further, unlike the dimming element of the first example of the prior application shown in FIG. 6 and described above, a high voltage is not required for driving the element, and the element can be easily driven. It is not necessary to apply a strong magnetic field in the manufacturing process of the element as in the dimming elements of the second and third examples of the prior application shown in FIGS. 7 and 8 and described above. It can be easily manufactured.

FIG. 1 shows an example of the light control layer 2 of the guest-host liquid crystal.
As the 3M, 23C, and 23Y, a case where a chiral nematic liquid crystal having a planar orientation is used is not limited thereto, and a combination of a cell of a nematic liquid crystal having a homogeneous orientation and a polarizing plate, or a polymer dispersed liquid crystal (PDL) is used.
A method utilizing C) can be used, and the same effect can be obtained in such a case.

[0074]

As described above, according to the present invention, not only a wide color reproduction range can be realized but also a display with high brightness can be obtained in a reflection type color display device capable of multicolor display. Brightness of white display is greatly improved, visibility is improved, and driving and manufacturing of the device are facilitated.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a reflection type color display device of the present invention.

2 is a diagram showing a comparison between the color reproduction range of the reflective color display device of FIG. 1 and the color reproduction range of the reflective color display device of FIG. 4;

3 is a diagram showing a comparison between the color reproduction range of the reflection type color display device of FIG. 1 and the color reproduction range of the reflection type color display device of FIG. 4;

FIG. 4 is a diagram showing an example of a conventional reflective color display device.

FIG. 5 is a diagram illustrating an example of a conventional light control element.

FIG. 6 is a diagram showing a dimming element according to a first example of the invention of the prior application.

FIG. 7 is a diagram showing a dimming device according to a second example of the invention of the prior application.

FIG. 8 is a diagram showing a light modulating element according to a third example of the invention of the prior application.

[Explanation of symbols]

 10G, 10R, 10B Dimming element 11, 12 Transparent substrate 21, 22 Transparent pixel electrode 23M, 23C, 23Y Dimming layer 25 Driver 26 Black matrix 27G, 27R, 27B Dichroic mirror

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Seiichi Suzuki 430 Sakai, Nakai-cho, Ashigarakami-gun, Kanagawa Prefecture Green Tech Inside Fuji Xerox Co., Ltd.

Claims (4)

[Claims] The present invention can selectively take two states, a state of reflecting a specific wavelength region and a state of absorbing a specific wavelength region, respectively.
In a reflective color display device in which a plurality of dimming elements having different specific wavelength regions from each other are stacked, the plurality of dimming elements each include a dichroic mirror that selectively reflects the specific wavelength region. And a dimming layer provided on the external light incident side of the dichroic mirror and having dichroism with respect to the specific wavelength region, and substantially transmitting the other wavelength regions. apparatus. 2. The reflection type color display device according to claim 1, wherein the plurality of dimming elements are three dimming elements each of which has the specific wavelength region as a red, green, and blue wavelength region. A reflective color display device characterized by the above-mentioned. 3. The reflection type color display device according to claim 2, wherein the three dimming elements are green,
A reflection type color display device, wherein red and blue wavelength regions having the specific wavelength region are stacked. 4. The reflection type color display device according to claim 1, wherein the dichroic mirror of each of the light control elements is provided on the light control layer of the light control element by a dielectric multilayer film. A reflective color display device formed adjacently.