JPH1031210A - Reflection type color display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a display color from being changed as a viewing angle is changed and also to prevent color purity from being lowered, as to a reflection type color display device equipped with plural laminated light control layers for reflecting color light in a specified wavelength band by the periodical change of a refractive index. SOLUTION: The light control layers 51, 52 and 53 are laminated successively from the incident side of external light. In the case the external light is made incident on the light control layers 51, 52 and 53 at 0 deg., blue, green and red light are separately reflected by the light control layers 51, 52 and 53. A color filter layer 81 for absorbing the blue light and transmitting the green and red light is arranged between the light control layers 51 and 52. A color filter layer 82 for absorbing the blue and green light and transmitting the red light is arranged between the light control layers 52 and 53. Even in the case the reflection wavelength band of the layer 52 is shifted toward the blue wavelength band and also the reflection wavelength band of the layer 53 is shifted toward the green wavelength band because the incident angle of the external light becomes larger, the blue light is reflected by the layer 52, then, the green light is not reflected by the layer 53, and also, the blue light is not reflected by the layer 53.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflective color having a plurality of dimming layers that reflect colored light in a specific wavelength band by periodically changing the refractive index in accordance with the presence or absence or degree of an external stimulus such as an electric field. It relates to a display device.

[0002]

2. Description of the Related Art A reflective display element that reflects or transmits color light in a specific wavelength band according to the presence or absence or degree of an external stimulus such as an electric field or a magnetic field utilizes a periodic change in the refractive index in the element. An interference reflection method has been considered.

[0003] The reflection type display element based on the interference reflection method has features such as high use efficiency of external light, high contrast of light and dark, high color purity, and the like. By stacking a plurality of different display elements, multicolor display can be performed.

As a reflection type display element based on the interference reflection method utilizing the periodic change of the refractive index, Japanese Patent Laid-Open No. 6-29 is disclosed.
No. 4952 discloses a liquid crystal polymer composite in which a liquid crystal and a polymer are alternately formed in a layered form as a light control layer.

In this case, reflected light in a specific wavelength band is generated due to a periodic difference in refractive index between the liquid crystal layer and the polymer layer.
In addition, since the refractive index of the liquid crystal changes according to the voltage applied to the light control layer, the reflectance is controlled from the transmission state of 0% to the constant reflectance state by changing the voltage. can do. By stacking a plurality of dimming layers or display elements having different refractive index change periods, multicolor dimming becomes possible, and a reflective color display device capable of full-color display can be realized.

FIG. 12 shows a reflection type color display device disclosed in Japanese Patent Application Laid-Open No. 6-294952.
Display element 1, transparent substrate 1 with light control layer 51 sandwiched between two
The display element 2 having the light control layer 52 sandwiched between the display elements 3 and 14 and the display element 3 having the light control layer 53 sandwiched between the transparent substrates 15 and 16 are stacked. An absorption layer 25 is provided.

The light control layers 51, 52, and 53 are each formed as the above-described liquid crystal polymer composite, and each has a blue (40)
0-500 nm), green (500-600 nm), red (6
The transparent electrodes 41, 42, 43, 44, 45, and 46 are provided for each of them so as to reflect the color light of (00 to 700 nm) independently and to control each reflectance independently. Therefore, an arbitrary display color can be obtained by additive color mixture.

FIG. 8 of Japanese Patent Application Laid-Open No. 7-92483 and FIG. 8 show steps 0032 and 0033 of an optical element in which liquid crystals and polymers are alternately formed in layers. It is shown that the viewing angle is widened by providing a scattering plate.

[0009]

However, in a reflective display element such as a liquid crystal polymer composite utilizing a periodic change in the refractive index, the reflection wavelength changes depending on the incident angle of external light. There's a problem. Referring to FIG. 13, the reflection angle dependency of the reflection wavelength is shown. The reflection type display element shown in FIG. 13A has a black light absorption side on the opposite side of the dimming layer 53 to the outside light 101 incidence side. When the layer 25 is provided and the incident angle θ of the external light 101 is 0 °, the red light in the external light 101 is reflected by the light control layer 53, and after the other color light passes through the light control layer 53, It is formed so as to be absorbed by the light absorbing layer 25.

However, when the incident angle θ of the external light 101 is 0 °, the reflection wavelength band of the light control layer 53 becomes the longest wavelength side because the optical path difference between the two lights causing interference becomes the largest. As the input angle θ increases, the optical path difference decreases, so that the reflection wavelength band of the light control layer 53 shifts to the shorter wavelength side. Therefore, the relationship between the input angle θ of the external light 101 and the reflection wavelength band of the light control layer 53 is, for example, as shown in FIG.

That is, when the incident angle θ of the external light 101 is 0 °, the reflection type display element of FIG.
Although the wavelength band of 00 to 700 nm becomes the reflection wavelength band, as the input angle θ increases, the short wavelength end and the long wavelength end of the reflection wavelength band shift to the short wavelength side, and the input angle θ
Exceeds 50 °, the original wavelength band of 600 to 700 nm is not reflected at all.

Therefore, in the conventional reflection type color display device disclosed in Japanese Patent Application Laid-Open No. 6-294952 and shown in FIG. 12, when external light enters the dimming layers 51, 52 and 53 in an oblique direction. , A light control layer 52 that should reflect green light,
The dimming layer 53, which reflects blue light or green light together with green light and reflects red light, reflects green light together with red light, or reflects only green light and further green light In addition, there is a disadvantage that the display color is largely changed from the original color by reflecting blue light.

The visual dependence of the reflection wavelength becomes a problem particularly when the reflection type display element is placed under diffuse illumination and the reflected light can be observed from any direction.
It is not so problematic under strong straight-line lighting such as spotlights and sun rays. However, under strong straight-line lighting such as spotlights and sunlight, reflected light travels only in the specular direction, so it is not easy to observe from other directions, Conversely, it has a high specularity and is too dazzling to be suitable as a display device.

Japanese Patent Application Laid-Open No. 7-92483 discloses that in order to solve this problem, a light scattering plate is provided on the surface of the light control layer as described above to increase the viewing angle. However, this method has a disadvantage in that the viewing angle is widened, but the color purity of the display color is significantly reduced.

Therefore, the present invention provides a reflection type color display device in which a plurality of light control layers that reflect color light in a specific wavelength band due to a periodic change in the refractive index are stacked, the display color does not change depending on the viewing angle, and the color is not changed. The purity is not reduced.

[0016]

According to the present invention, a plurality of light control layers are stacked, and each of the light control layers reflects color light in a specific wavelength band by a periodic change in refractive index. The specific wavelength band is different from each other such that the specific wavelength band is closer to the incident side of the external light so that the specific wavelength band is on the shorter wavelength side, and between the dimming layers of adjacent layers, the incident side of the external light is included. Absorbs the color light of the specific wavelength band of the nearer light control layer, and the color light of the specific wavelength band of the light control layer farther from the incident side of the external light, and further external light than the light control layer. A color filter layer, which transmits the color light of the specific wavelength band in the light control layer remote from the incident side, is provided.

In this case, it is desirable to provide a light scattering means on an incident light path from the outside to each of the light control layers and on an outgoing light path from each of the light control layers to the outside.

In this specification, “color light” means visible light.

[0019]

In the reflection type color display device of the present invention configured as described above, for example, a plurality of dimming layers are formed so that blue, green and red color lights are respectively emitted when the incident angle of external light is 0 °. When three reflecting light control layers are used, the first light control layer closest to the outside light incident side reflects blue light, and the intermediate second light control layer reflects green light. The third light control layer on the side opposite to the incident side of external light reflects red light.

A color filter layer for absorbing blue light and transmitting green light and red light is provided between the first light control layer and the second light control layer. A color filter layer that absorbs blue light and green light and transmits red light, or that absorbs green light and transmits blue light and red light between the light control layer and the third light control layer. A color filter layer to be provided.

Therefore, even if the reflection wavelength band of the second light control layer shifts from the green wavelength band to the blue wavelength band due to the large incident angle of the external light, the first light control layer Since the blue light does not enter the second light control layer due to the color filter layer between the second light control layer and the second light control layer, the blue light is not reflected by the second light control layer. With the third
Even if the reflection wavelength band of the light control layer shifts from the red wavelength band to the green wavelength band, the color filter layer and the third light control layer between the second light control layer and the third light control layer can be adjusted. Due to the color filter layer between the one light control layer and the second light control layer, green light and blue light do not enter the third light control layer. Green light and even blue light are not reflected.

That is, the first, second, and third light control layers have respective reflection wavelength bands that are originally blue, green, and red even when the incident angle of external light is large. In the wavelength band of only shifting to the short wavelength side and narrowing, the original blue,
There is no shift to shorter wavelengths than the green and red wavelength bands. Therefore, the display color does not change depending on the viewing angle, and the color purity does not decrease.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIGS. 1 and 2 FIG. 1 shows a first embodiment of a reflective color display device according to the present invention. The reflective color display device of this example has a display in which a dimming layer 51 is sandwiched between transparent substrates 11 and 12 on which transparent electrodes 41 and 42 are formed, and a color filter layer 81 is formed on the back side of the transparent substrate 12. Element 1, transparent substrate 13, 1 on which transparent electrodes 43, 44 are formed
A display element 2 having a color filter layer 82 formed on the back surface side of the transparent substrate 14 and a transparent substrate 15, 1 having transparent electrodes 45 and 46 formed thereon.
The display element 3 in which the dimming layer 53 is sandwiched between 6 and the light absorbing layer 85 is formed on the rear surface side of the transparent substrate 16 is laminated in order from the outside light incidence side which is the upper side of the drawing.

The light control layers 51, 52, and 53 are each formed by alternately forming a liquid crystal 66 and a polymer 65 in a layer shape. As described later, the light control layer 51 has a reflection wavelength band. Is a blue wavelength band, the dimming layer 52 has a reflection wavelength band of a green wavelength band, and the dimming layer 53 has a reflection wavelength band of a red wavelength band. The color filter layer 81 absorbs blue light and transmits green light and red light, and the color filter layer 82 absorbs blue light and green light and transmits red light. .

The display elements 1, 2, 3 can be manufactured by a similar method. That is, first, the transparent substrates 11 (13, 15), 12 each made of a glass substrate are used.
On one surface of (14, 16), transparent electrodes 41 (43, 45) and 42 (44, 46) made of ITO
It is formed to a thickness of 0 nm.

Next, the transparent substrates 11 (13, 15), 12
(14, 16) to the transparent electrodes 41 (43, 4), respectively.
5), 42 (44, 46) are formed with the surface side facing inward and facing at predetermined intervals as described later.
A liquid mixture of a liquid crystal and a photocurable polymer is loaded.

As the liquid crystal, a rod-like low-molecular material having biphenyl, terphenyl, phenylbenzoate, azobenzene, phenylcyclohexyl, phenylpyrimidine or the like as a liquid crystal skeleton can be used.

The photocurable polymer is a mixture of a monomer and a photopolymerization initiator, and is a polymer that polymerizes with visible light. As the monomer, for example, a radical polymerizable or ionic polymerizable compound such as acryl, acrylamide, and methacryl can be used.As the photopolymerization initiator, for example, benzoin, benzoin, which is a cleavage type photopolymerization initiator Ether, benzoin ketal and the like, hydrogen abstraction type photopolymerization initiators such as benzyl, benzophenone and Michler's ketone, and ion reaction type photopolymerization initiators such as allyldiazonium fluoroborate can be used.

In addition, a thermal polymerization inhibitor, a binder polymer, an oligomer, a chain transfer agent and the like may be appropriately added. In order to improve the light receiving sensitivity in the visible light region, a sensitizing dye such as rose bengal or methylene blue may be added to the photocurable polymer.

Next, the transparent substrates 11 (13, 15), 12
The mixed liquid is irradiated from both sides of (14, 16) with laser light having the same phase at an angle as described later. As a result, interference fringes are formed in the mixed liquid, and the photocurable polymer is polymerized along the interference fringes to form a structure in which the polymer and the liquid crystal are phase-separated in a layer. However, it is essential here that a layered periodic structure is formed, and the presence or absence of phase separation is not essential. A liquid crystal polymer gel in which a polymerized polymer chain swells in a gel state with liquid crystal may be used.

The light control layer 51 (52, 52) formed from the mixed solution
The thickness of 53) is selected in the range of 1 to 20 μm. When the thickness of the light control layer 51 (52, 53) is larger than this, the transparent electrode 41 (43, 4) is used to control the reflectance.
5), the voltage applied between 42 (44, 46) must be extremely high, which is not preferable. The light control layer 51
When the thickness of (52, 53) is 0.5 μm or less, the reflectance is undesirably low.

Actually, in order to obtain a light control layer 51 having a blue wavelength band as a reflection wavelength band, two laser beams of 488 nm from an argon ion laser are applied to the transparent substrates 11 and 12.
From the both sides of the transparent substrate 11, 12 at a crossing angle of 180 °. As a result, a light control layer 51 having a reflection spectrum peak at a position of 490 nm was obtained.

Further, in order to obtain the light control layer 52 having a green wavelength band as a reflection wavelength band, two laser beams of 488 nm from an argon ion laser are introduced into the mixture from both sides of the transparent substrates 13 and 14. , 134 °.
As a result, a light control layer 52 having a reflection spectrum peak at a position of 530 nm was obtained.

Further, in order to obtain a light control layer 53 having a red wavelength band as a reflection wavelength band, two laser beams of 488 nm from an argon ion laser are applied to the transparent substrates 15 and 16.
At a crossing angle of 99 °.
As a result, a light control layer 53 having a reflection spectrum peak at a position of 640 nm was obtained.

A polymer film containing a yellow dye is applied to the back surface of the transparent substrate 12 of the display element 1 thus manufactured, and absorbs blue light and transmits green light and red light as described above. The color filter layer 81 to be formed was formed. Also,
A polymer film containing a red dye is applied to the back surface of the transparent substrate 14 of the display element 2 similarly manufactured, and the color filter layer 82 that absorbs blue light and green light and transmits red light as described above. Was formed. Further, a polymer film containing a black dye is applied to the back surface of the transparent substrate 16 of the display element 3 similarly manufactured, and the light absorbing layer 85 absorbing all the color light is applied.
Was formed. Finally, the display elements 1, 2, and 3 were stacked to obtain a reflective color display device of Example 1.

The dyes forming the color filter layers 81 and 82 are desirably highly transparent, and are preferably dye-based dyes. As a black pigment for forming the light absorbing layer 85, carbon black or the like is preferable. In addition, as a binder polymer of each layer, polyimide, polyacryl, polyvinyl, polyester, or the like can be used.

FIG. 2 shows the dimming layers 51, 52, and 52 when the reflective color display device of the first embodiment manufactured as described above is illuminated with spot light from the direction where the incident angle θ is 10 °.
53 shows the reflection spectrum of the specular reflection light 53 and the transmission spectrum of the color filter layers 81 and 82. And the cut-off wavelength of the color filter layer 82 is set to 600 nm between the reflection wavelength band of the light control layer 52 and the reflection wavelength band of the light control layer 53.

As is clear from the above, according to the reflection type color display device of Example 1, even if the reflection wavelength band of the light control layer 52 shifts to the blue wavelength band side due to the large incident angle θ. Since blue light is not incident on the light control layer 52 by the color filter layer 81, the blue light is not reflected by the light control layer 52 and the reflection wavelength band of the light control layer 53 is shifted toward the green wavelength band. Even if the light is shifted, green light and blue light do not enter the light control layer 53 due to the color filter layers 82 and 81, so that the green light,
Further, blue light is not reflected.

That is, as shown in FIG. 10, the relationship between the incident angle θ of the external light and the reflection wavelength band of the light control layer 53 is large, and the light control layers 51, 52, and 53 have a large incident angle θ of the external light. Sometimes, as a result, each reflection wavelength band becomes the original blue,
In the green and red wavelength bands, only the wavelength shifts to the short wavelength side and narrows, but there is no shift to the shorter wavelength side than the original blue, green and red wavelength bands.

The reflection type color display device of Embodiment 1 is shown in FIG.
As shown in the reflection type color display device 10 of FIG.
The detector 9 is arranged in the direction of
ΔC ^* = [｛a ^* (θo) -a ^* (0 ゜)｝ ^{2 in} order to measure the CIE · L ^* a ^* b ^* chromaticity coordinates of the reflected light from, and to determine the detection angle dependence of the hue. + {B ^* (θo) −b ^* (0 °)} ² ] ^1/2 (1) ΔC ^* is defined. The larger the ΔC ^* , the larger the change in hue, and therefore, the smaller the ΔC ^* , the better.

In FIG. 11 (B), what is plotted by black circles is the reflective color display device of Example 1, where the light control layer 53 is in the reflection state and the light control layers 51 and 52 are in the transmission state. The change of ΔC ^* with respect to the detection angle θo is shown.
However, since the reflectance was almost 0% when θo ≧ 50 °, the range of θo ≦ 40 ° was plotted. As is clear from this, according to Example 1, a change in hue is significantly suppressed at θo = 20 to 40 ° as compared with a comparative example described later.

As described above, according to the first embodiment of FIG. 1, the display color hardly changes depending on the viewing angle.
The color purity hardly decreases.

Embodiment 2 FIGS. 3 and 4 FIG. 3 shows a second embodiment of the reflection type color display device of the present invention. The overall structure of the reflective color display device of this embodiment is the same as that of the first embodiment shown in FIG. 1 except that the dimming layers 51, 52 and 53 are made of cholesteric liquid crystal (chiral nematic liquid crystal). Different from 1.

The display elements 1, 2, 3 can be manufactured by a similar method. That is, first, the transparent substrates 11 (13, 15), 12 each made of a glass substrate are used.
On one surface of (14, 16), transparent electrodes 41 (43, 45) and 42 (44, 46) made of ITO
It is formed to a thickness of 0 nm.

Next, although omitted in the figure, the transparent electrode 4
An alignment film made of polyimide is formed on each of 1 (43, 45) and 42 (44, 46), and the surface thereof is rubbed in one direction with a cloth, so-called rubbing treatment.

Next, the transparent substrates 11 (13, 15), 12
(14, 16) to the transparent electrodes 41 (43, 4), respectively.
5), the cholesteric liquid crystal prepared by adding a chiral agent to a nematic liquid crystal is loaded between the two, with the surface side on which the 42 (44, 46) is formed facing inward, and a dimming control. The layer 51 (52, 53) is formed.

The transparent substrates 11 (13, 15) and 12 (1
The cholesteric liquid crystal loaded between 4, 4 and 16) has the transparent electrodes 41 (43, 45) and 42 (44, 4) as described above.
6) By forming an alignment film on the transparent electrode 41
When no voltage is applied between (43, 45) and 42 (44, 46), the helical axis is perpendicular to the transparent substrates 11 (13, 15), 12 (14, 16) as shown in FIG. The liquid crystal molecules are transparent substrates 11 (13, 15),
12 (14, 16) are arranged in a planar alignment state.

Therefore, the light control layers 51, 52, 53
When no voltage is applied to this, the light control layers 51, 5
2, 53 of the light of a specific wavelength determined by the helical pitch of the cholesteric liquid crystal, circularly polarized light having the same optical rotation direction as the helical direction of the cholesteric liquid crystal is selectively reflected. It transmits circularly polarized light having an optical rotation direction opposite to the helical direction of the liquid crystal and light having a wavelength other than the specific wavelength.

When a voltage higher than a certain threshold is applied to the light control layers 51, 52, 53, the light control layers 51, 52, 53
Of the cholesteric liquid crystal, the liquid crystal molecules undergo a phase transition to a homeotropic alignment state in which the liquid crystal molecules are arranged perpendicular to the substrate, and the helical structure disappears.
2 and 53 are in a state of transmitting all color light.

The helical pitch of the cholesteric liquid crystal is determined by the type and amount of the chiral agent. Therefore, by adjusting the amount of the chiral agent added and adjusting the helical pitch of the cholesteric liquid crystal, the wavelength of the selective reflection by the light control layers 51, 52, 53 can be set.

Further, the light control layers 51, 52 and 53 have a structure in which the refractive index changes periodically with the helical pitch of the cholesteric liquid crystal as one cycle in the selective reflection state. As in the case of the liquid crystal 66 and the polymer 65 alternately formed in layers in Example 1, the reflection wavelength changes depending on the incident angle of external light.

Actually, E44 manufactured by Merck as a nematic liquid crystal, CB15 manufactured by Merck as a chiral agent,
The light control layers 51, 52, and 53 having a central wavelength of 450 nm, 560 nm, and 640 nm, respectively, as the light control layers 51, 52, and 53 by using the chiral agent CB15 in amounts of 50, 42, and 35% by weight, respectively. I got

On the back surfaces of the transparent substrates 12 and 14 of the display elements 1 and 2 thus produced, the same color filter layers 81 and 82 as those of the first embodiment shown in FIG. A light absorbing layer 85 similar to that of Example 1 was formed on the back surface of the device, and finally, these display elements 1, 2, and 3 were stacked to obtain a reflective color display device of Example 2.

FIG. 4 shows the dimming layers 51, 52, and 52 when the reflective color display device of the second embodiment manufactured as described above is illuminated with spot light from the direction where the incident angle θ is 10 °.
53 shows the reflection spectrum of the specular reflection light 53 and the transmission spectrum of the color filter layers 81 and 82. The cut-off wavelength of the color filter layer 81 is set to the reflection wavelength band of the light control layer 51 and the reflection wavelength band of the light control layer 52. And the cut-off wavelength of the color filter layer 82 is set to 600 nm between the reflection wavelength band of the light control layer 52 and the reflection wavelength band of the light control layer 53.

The reflection type color display device of Embodiment 2 is shown in FIG.
As shown in the reflection type color display device 10 of FIG.
The detector 9 is arranged in the direction of
In order to measure the CIE L ^* a ^* b ^* chromaticity coordinates of the reflected light from, and to determine the detection angle dependence of the hue, ΔC ^* represented by the above equation (1) was defined.

In FIG. 11B, what is plotted by black squares is the reflective color display device of the second embodiment.
The change of ΔC ^* with respect to the detection angle θo when the light control layer 53 is in the reflection state and the light control layers 51 and 52 are in the transmission state is shown. However, since the reflectance was almost 0% when θo ≧ 50 °, the range of θo ≦ 40 ° was plotted. As is clear from this, according to the second embodiment,
Compared with a comparative example described later, a change in hue is significantly suppressed at θo = 20 to 40 °.

As described above, according to the second embodiment shown in FIG. 3, the display color hardly changes depending on the viewing angle.
The color purity hardly decreases. Further, according to the second embodiment, since the cholesteric liquid crystal is used as the light control layers 51, 52, and 53, the light control layers 51, 52, and 53 have the helical direction of the cholesteric liquid crystal of the light of the specific wavelength as described above. It reflects only circularly polarized light having the same optical rotation direction, and the reflection spectrum peak does not exceed 50%. However, a wide reflection wavelength bandwidth can be easily obtained, and a bright display can be achieved.

In the comparative example, the color filter layers 81 and 82 are omitted in the reflection type color display device of the second embodiment.

The reflection type color display device of the comparative example is shown in FIG.
(A) As shown in the reflection type color display device 10, it is placed under diffuse illumination by the illuminating body 7 using the integrating sphere 5, and the direction of the detection angle θo with respect to the normal direction of the reflection type color display device 10 , A CIE L ^* a ^* b ^* chromaticity coordinate of the reflected light from the reflective color display device 10 is measured,
In order to determine the detection angle dependence of hue, ΔC ^* represented by the above equation (1) was defined.

In FIG. 11 (B), what is plotted by white circles is a reflection type color display device of a comparative example, in which the light control layer 53 is in the reflection state and the light control layers 51 and 52 are in the transmission state. The change of ΔC ^* with respect to the angle θo is shown. As is clear from this, in the reflective color display device of the comparative example, the display color greatly changes depending on the viewing angle.

Embodiment 3 FIG. 5 FIG. 5 shows a third embodiment of the reflection type color display device of the present invention. The reflective color display of this example omits the transparent substrates 12, 13, and 15 of the reflective color display of Example 1 of FIG.
This is the case where the light control layers 51, 52, 53 are brought close to each other by forming the color filter layers 81, 82 with the adhesives 83, 84.

In order to manufacture the reflection type color display device of this example, first, a transparent electrode 41 made of an ITO film is formed to a thickness of 100 nm on one surface of a transparent substrate 11 made of a glass substrate. On 41, a liquid mixture of a liquid crystal and a photocurable polymer is applied to a thickness of 1 to 20 μm,
After placing the transparent substrate 11 coated with the mixed solution in a chamber and replacing the air with nitrogen, the mixed solution was irradiated with laser light having the same phase from both sides of the mixed solution at an angle as described later. Light control layer 5 having a structure in which liquid crystal and polymer are separated into layers.
Then, a transparent electrode 42 made of an ITO film is formed on the light control layer 51 to a thickness of 100 nm.

The purpose of replacing air with nitrogen is to prevent the curing reaction of the photocurable polymer from being hindered by the presence of air. However, the curing reaction is performed even in the presence of air as the photocurable polymer. It is not always necessary to replace the air with nitrogen when using a material that does not hinder the reaction.

Similarly, the transparent electrode 4 is formed on one surface of the transparent substrate 14.
4, a liquid mixture of a liquid crystal and a photocurable polymer is applied on the transparent electrode 44, and a laser beam is irradiated into the mixture to form a light control layer 52. Transparent electrode 43
And a transparent electrode 4 is formed on one surface of the transparent substrate 16.
6, a liquid mixture of a liquid crystal and a photocurable polymer is applied on the transparent electrode 46, and a laser light is irradiated into the liquid mixture to form a light control layer 53. Transparent electrode 45
To form

Actually, as in the first embodiment, two laser beams of 488 nm from an argon ion laser are made to enter the respective mixed liquids at intersection angles of 180 °, 134 °, and 99 °, respectively. Thereby, the light control layers 51, 5
490 nm, 530 nm, 6
One having a reflection spectrum peak at a position of 40 nm was obtained.

Next, the transparent electrode 42 on the light control layer 51 on the transparent substrate 11 and the transparent electrode 43 on the light control layer 52 on the transparent substrate 14 are adhered by an adhesive 83 containing a yellow dye. The transparent electrode 45 on the light control layer 53 on the transparent substrate 16 is
An adhesive 84 containing a red dye is adhered to the back surface of the transparent substrate 14 and a light absorbing layer 85 is formed on the back surface of the transparent substrate 16 to obtain a reflective color display device of the third embodiment.

The adhesives 83 and 84 constitute the above-mentioned color filter layers 81 and 82 by containing yellow and red dyes, respectively. Any material such as an epoxy-based material may be used. The curing mode may be any of a thermosetting type, an ultraviolet curing type, and the like.

According to the third embodiment, similarly to the first embodiment in FIG. 1, the display color hardly changes depending on the viewing angle, and the color purity hardly decreases. Further, according to the third embodiment, there is no transparent substrate between the dimming layers 51 and 52 and only one transparent substrate 14 exists between the dimming layers 52 and 53. Compared to Example 1, there is an advantage that parallax when viewed from an oblique direction is reduced.

Embodiment 4 FIGS. 6 to 9 According to Embodiments 1, 2 and 3 shown in FIGS. 1, 3 and 5, the display color hardly changes depending on the viewing angle, and the color purity also hardly decreases. do not do. However, as shown in the reflection area of FIG.
As described above in 1 (B), when the incident angle θ or the detection angle θo is equal to or larger than a certain value, specifically, when the incident angle θ is equal to or larger than 50 °, the reflectance of the dimming layers 51, 52, and 53 becomes zero. There is a disadvantage that the display cannot be seen from an oblique direction.

FIG. 6 shows a fourth embodiment of the reflection type color display device according to the present invention. In view of the above points, the second embodiment shown in FIG. Transparent substrate 11 and transparent electrode 41 of the reflective color display device
This is the case where the light scattering layer 90 is provided between.

That is, in this example, the light scattering layer 90 is formed on one surface of the transparent substrate 11, and the transparent electrode 41 is formed on the light scattering layer 90. Other configurations and manufacturing methods are the same as those of the second embodiment. However, the light control layers 51 and 5
The center values of the reflection spectra of 2,53 are actually 510 nm, 570 nm, and 70 nm, respectively, for the reason described later.
It was set to 0 nm.

The light scattering layer 90 includes: A system containing fine particles having different refractive indices, for example, titanium oxide, lead oxide, white inorganic pigments such as barium sulfate, organic fine particles such as a resin or an organic low-molecular material, fibers and the like,
Dye dispersed in a binder such as resin, resin containing air bubbles, ceramic plate, crystalline polymer containing microcrystals,
A glass containing microcrystals; A system in which multiple materials with different refractive indices are intertwined,
For example, a phase-separable glass such as a composite resin material or chalcogen glass obtained by uniformly mixing a plurality of resins or their monomers once and then performing phase separation; Birefringent multi-domain material, for example,
Liquid crystal polymer, composite phase separation material of liquid crystal polymer and crystalline polymer or amorphous polymer, composite material in which inorganic pigments, organic fine particles, fibers are dispersed in liquid crystal polymer,
D. a composite material in which a low-molecular liquid crystal is dispersed in a polymer matrix; A microlens array, an optical fiber plate, or the like can be used.

However, in order to reduce the contrast of the display, the light scattering layer 90 is preferably formed of a material having large forward scattering and small back scattering. From that viewpoint, among the above-mentioned materials, a liquid crystalline polymer having a multi-domain is particularly suitable. In fact, poly-4- (6-Acryloxyhexyloxy) -4'-cyano-biphenyl as a liquid crystalline polymer
This was dissolved in cyclohexanone, and applied to one surface of the transparent substrate 11 to obtain a light scattering layer 90 composed of a liquid crystal polymer film having a multi-domain. The thickness was 5 μm.

In order to reduce the blur of the displayed image due to the scattering of light, the light scattering layer 90 and the light control layers 51 and 5 are used.
It is desirable that the reference numerals 2 and 53 be provided close to each other. From that viewpoint, the light scattering layer 90 is, as shown in FIG.
1 and the transparent electrode 41 are preferably provided.
It is desirable that the thickness of the transparent substrates 11 to 15 be as small as possible. In addition, from the same viewpoint, the smaller the thickness of the light scattering layer 90 is, the better. From this viewpoint, a liquid crystal polymer film having multiple domains is preferable.

The operation of the light scattering layer 90 will be described with reference to FIG. FIG. 7 shows that the incident light 101 of blue, green, and red has the dimming layer 51,
FIG. 5A shows a case where light is obliquely incident on 52 and 53.
In the case where the light scattering layer 90 is not provided as in Example 2 in FIG.
FIG. 9B shows a case where the light scattering layer 90 is provided as in the fourth embodiment in FIG. The light control layers 51, 52, 53 are, for convenience,
Although the structure is such that the liquid crystal and the polymer are separated in layers, the same applies to the case of a cholesteric liquid crystal.

In this case, the light scattering layer 90 is composed of light scattering means placed on the light path incident on the light control layers 51, 52, 53 from the outside, and light emitted from the light control layers 51, 52, 53 to the outside. It also serves as light scattering means placed on the road.

As described above, as the incident angle θ increases, the reflection wavelength band of the light control layers 51, 52, and 53 shifts to the shorter wavelength side. Therefore, as shown in FIG.
If there is no 0, the blue, green, and red incident lights 101 obliquely incident on the light control layers 51, 52, and 53 respectively become blue, green, and red reflected lights at the light control layers 51, 52, and 53, respectively. Without passing through the light control layers 51, 52, 53 and the color filter layer 8.
1, 82, are absorbed by the light absorbing layer 85. Therefore,
No reflected blue, green or red light is observed.

On the other hand, when the light scattering layer 90 is provided as shown in FIG. 7B, the blue incident light 1
01 is scattered by the light scattering layer 90 by being incident on the light scattering layer 90 before being incident on the light modulation layer 51, and
The scattered incident light 102 has an angle of incidence such that blue light is reflected by the light control layer 51 at an incident angle with respect to the scattered incident light 1.
02 enters the light control layer 51. Therefore, the light control layer 51
Produces blue reflected light 104. Moreover, the blue reflected light 104 is scattered by the light scattering layer 90, and scattered light 105 is generated from the light scattering layer 90. The scattered incident light 103 whose incident angle with respect to the light control layer 51 is such that blue reflected light does not occur in the light control layer 51 passes through the light control layer 51 and is absorbed by the color filter layer 81. The same applies to the green and red incident light 101 incident on the light control layers 52 and 53.

That is, FIG. 6 in which the light scattering layer 90 is provided.
In the fourth embodiment, as in the second embodiment in FIG.
When there is no reflected light, reflected light is generated even for an incident angle at which no reflected light is generated, and the reflected light can be observed from a wide angle range.

As described above, the light scattering layer 90 has a function of converting the angular distribution A of the light incident on the light control layers 51, 52, 53 from the outside into an angular distribution B having a spread by performing scattering average. I do. If the degree of scattering is larger than a certain degree, the angle distribution B does not depend so much on the angle distribution A. For example, when the light scattering layer 90 is a perfect diffusion transmission surface,
The angle distribution B becomes completely independent of the angle distribution A. Therefore, the above-mentioned effects are obtained from the light control layers 51, 52, 53 from outside.
Can be widely obtained without depending on the angular distribution A of the light incident on the light source.

In the display device disclosed in JP-A-7-92483, a light scattering plate is provided on the surface of the light control layer to increase the viewing angle. Since no consideration is given to this, the color purity of the display color is significantly reduced as described above.

On the other hand, in the fourth embodiment shown in FIG. 6, since the color filter layers 81 and 82 are provided and the light scattering layer 90 is provided, the display color hardly changes depending on the viewing angle, and the color purity is not changed. The display can be viewed even from an oblique direction with almost no decrease.

FIG. 8 shows a reflection spectrum of the light control layer 53 when the reflection type color display device of Example 4 is illuminated with spot light from the direction where the incident angle θ is 10 °. However,
Curve 201 is the same as Example 2 of FIG. 3 in the case where light scattering layer 90 is not provided, but the center wavelength of the reflection spectrum of light control layer 53 is 700 n as described above.
m, and the curve 202 is the case where the light scattering layer 90 is provided.

The curve 201 without the light scattering layer 90 was used.
In the case of (1), the interface between the transparent substrate 11 and the transparent electrode 41 becomes mirror-like, so that the intensity of the reflected light is about two orders of magnitude higher than in the case of the curve 202 in which the light scattering layer 90 is provided. Therefore, the scale of the vertical axis with respect to the curve 202 is actually 1/100 of the figure.

As is apparent from the curve 202 in FIG. 8, by providing the light scattering layer 90 as in the fourth embodiment in FIG. 6, the reflection spectrum is increased due to the widening of the incident angle range by the light scattering layer 90. As the width increases, the light control layer 53
The peak of the reflection spectrum shifts to the shorter wavelength side due to the average increase in the incident angle to the light. In consideration of the shift of the reflection spectrum peak to the short wavelength side, as described above, the central value of the selective reflection wavelength of the cholesteric liquid crystal forming the light control layers 51, 52, and 53 is determined as shown in FIG. Is set to a longer wavelength side than in the case of.

FIG. 9 shows the reflection spectra of the light control layers 51, 52, and 53 and the color filter when the reflection type color display device of the fourth embodiment is illuminated with spot light from the direction where the incident angle θ is 10 °. 9 shows transmission spectra of layers 81 and 82. Embodiments 1, 2, and 3 are cases where the reflection spectra of the light control layers 51, 52, and 53 are set so as not to overlap.
There may be an overlap as in the fourth embodiment.

The reflection type color display device of Example 4 is shown in FIG.
As shown in the reflection type color display device 10 of FIG.
The detector 9 is arranged in the direction of
In order to measure the CIE L ^* a ^* b ^* chromaticity coordinates of the reflected light from, and to determine the detection angle dependence of the hue, ΔC ^* represented by the above equation (1) was defined.

In FIG. 11B, what is plotted with black triangles is the reflective color display device of the fourth embodiment.
The change of ΔC ^* with respect to the detection angle θo when the light control layer 53 is in the reflection state and the light control layers 51 and 52 are in the transmission state is shown. As is clear from this, according to the fourth embodiment, θ
The reflected light can be observed in the range of o = 0 to 90 °,
Compared with the comparative example described above, a change in hue is significantly suppressed in a wide incident angle range. Also, it was recognized that the display color hardly changed even by the angle of illumination by the illumination body 7.

[Other Embodiments] Although common to each of the above-mentioned embodiments, since blue light is absorbed by the color filter layer 81,
The color filter layer 82 may be formed to absorb only green light and transmit blue light and red light by, for example, applying a polymer film containing a magenta dye.

The fourth embodiment shown in FIG. 6 is different from the second embodiment shown in FIG.
This is the case where the light scattering layers 90 are provided on the light control layers 51, 52, 53 made of cholesteric liquid crystal as described in FIG. 1, but, of course, the light control layers 51, 52, 5 as in the first embodiment of FIG.
A light-scattering layer can be provided on the element 3 having a multilayer structure of the liquid crystal 66 and the polymer 65, or on the element having reduced parallax as in the embodiment 3 in FIG.
The same effect as that of the fourth embodiment can be obtained.

Each of the illustrated examples is a case in which three light control layers 51, 52, and 53 each having a blue, green, and red wavelength band as a reflection wavelength band are laminated so that full-color display is possible. However, the present invention provides, for example, blue, green,
Alternatively, the present invention can also be applied to a case where two dimming layers having green, red, blue, and red wavelength bands as reflection wavelength bands are laminated.

[0092]

As described above, according to the first aspect of the present invention, a reflection type color display device in which a plurality of dimming layers that reflect color light of a specific wavelength band due to a periodic change in refractive index is stacked. The display color does not change depending on the angle, and the color purity does not decrease. According to the second aspect of the present invention, the display can be viewed even from an oblique direction.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first example of a reflection type color display device of the present invention.

FIG. 2 is a diagram showing a reflection spectrum of each light control layer and a transmission spectrum of each color filter layer of the reflection type color display device of FIG.

FIG. 3 is a sectional view showing a second example of the reflection type color display device of the present invention.

4 is a diagram showing a reflection spectrum of each light control layer and a transmission spectrum of each color filter layer of the reflection type color display device of FIG. 3;

FIG. 5 is a sectional view showing a third example of the reflection type color display device of the present invention.

FIG. 6 is a sectional view showing a fourth example of the reflective color display device of the present invention.

FIG. 7 is a diagram provided for describing an operation of a light scattering layer of the reflective color display device of FIG. 6;

8 is a diagram showing a comparison of the reflection spectrum of one light control layer between the case where there is no light scattering layer and the case where there is a light scattering layer in the reflection type color display device of FIG. 6;

9 is a diagram showing a reflection spectrum of each light control layer and a transmission spectrum of each color filter layer of the reflection type color display device of FIG.

FIG. 10 is a diagram illustrating a change in a reflection wavelength with respect to an external light incident angle of one light control layer of the reflection type color display device of each example.

FIG. 11 is a diagram for explaining aspects of hue change with respect to an incident angle of external light in the reflective color display device of each example and the reflective color display device of the comparative example.

FIG. 12 is a cross-sectional view illustrating an example of a conventional reflective color display device.

13 is a diagram for explaining a change in a reflection wavelength with respect to an incident angle of external light of one light control layer of the reflection type color display device of FIG. 12;

[Explanation of symbols]

 1,2,3 Display element 11,12,13,14,15,16 Transparent substrate 41,42,43,44,45,46 Transparent electrode 51,52,53 Dimming layer 65 Polymer 66 Liquid crystal 81,82 Color Filter layer 83, 84 Adhesive 85 Light absorbing layer 90 Light scattering layer

Claims (2)

[Claims] 1. A light control device according to claim 1, wherein a plurality of light control layers are laminated, and each of the light control layers reflects color light in a specific wavelength band by a periodic change in refractive index, and is provided on an incident side of external light. The specific wavelength bands are changed so that the closer the specific wavelength band is to the shorter wavelength side, the closer the dimming layers of the adjacent layers are the dimming layers closer to the incident side of external light. Absorbs the color light of the specific wavelength band, and the color light of the specific wavelength band of the light control layer remote from the incident side of the external light, and the light control further away from the incident side of the external light than the light control layer. A reflective color display device, comprising a color filter layer that transmits color light of the specific wavelength band of the layer. 2. The reflection type color display device according to claim 1, wherein light scattering means is provided on an incident light path from outside to each of the light control layers and on an output light path from each of the light control layers to the outside. A reflective color display device, comprising: