JP2004004968A - Reflection type color display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a display color from varying depending on viewing angles and also prevent the color purity from being lowered, in a reflection type color display device provided with light control layers which reflect color light in a specific wavelength band depending on a periodical change in refractive index. <P>SOLUTION: The light control layers 51, 52, 53 are laminated in order from the external light incident side. The light control layers 51, 52, 53 are arranged so as to reflect the color light of blue, green, and red, respectively, when the incident angle of each external light is 0°. A color filter layer 82 for absorbing blue light and green light and transmitting red light is arranged between the light control layers 52, 53. Since the incident angles of the external light are large, the refection wavelength band of the light control layer 52 is shifted toward the wavelength band of blue, and even if the reflection wavelength band of the light control layer 53 is shifted toward the wavelength band of green, the blue light is reflected by the light control layer 52, and the green light and further the blue light are not reflected by the light control layer 53. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a reflective color display device including a dimming layer that reflects colored light in a specific wavelength band by periodically changing the refractive index according to the presence or absence or degree of an external stimulus such as an electric field.

Depending on the presence or absence or degree of external stimuli such as electric and magnetic fields, as a reflective display element that reflects or transmits color light in a specific wavelength band, an interference reflection method that uses the periodic change in the refractive index within the element is used. Things are considered.

The reflection type display element using this interference reflection method has features such as high use efficiency of external light, high contrast between light and dark, high color purity, and the like, and a plurality of display colors different due to different reflection wavelength bands. By stacking display elements, multicolor display can be performed.

Patent Document 1 (Japanese Unexamined Patent Application Publication No. 6-294952) discloses a reflection type display element based on an interference reflection method utilizing a periodic change in the refractive index. A light modulating layer using a molecular complex is shown.

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, multi-color 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 Patent Document 1 (Japanese Patent Laid-Open No. 6-294952), in which a display element 1 in which a dimming layer 51 is sandwiched between transparent substrates 11 and 12, a transparent substrate 13. , 14 and a display element 3 having a dimming layer 53 sandwiched between the transparent substrates 15 and 16 are laminated, and a black light absorbing layer is provided on the back side of the display element 3. A layer 25 is provided.

The light control layers 51, 52, and 53 are formed as the above liquid crystal polymer composites, and reflect blue (400 to 500 nm), green (500 to 600 nm), and red (600 to 700 nm) color lights, respectively. , Transparent electrodes 41, 42, 43, 44, 45, 46 are provided for each of them so that the reflectance can be controlled 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 FIGS. 0032 and 0033 show a surface of an optical element in which liquid crystals and polymers are alternately formed in layers, on the external light incident side of the element. It is disclosed that the viewing angle is widened by providing a light-scattering plate to the light-emitting device.

The prior art documents listed above are as follows.
JP-A-6-294952 JP-A-7-92483

However, in a reflective display element such as a liquid crystal polymer composite utilizing a periodic change in the refractive index, there is a problem that the reflection wavelength changes depending on the incident angle of external light. Referring to FIG. 13, the dependence of the reflection wavelength on the incident angle will be described. The reflection type display element shown in FIG. 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 °, since the optical path difference between the two lights that cause interference is the largest, the reflection wavelength band of the light control layer 53 is the longest wavelength side, but the input angle is The reflection wavelength band of the light control layer 53 shifts to the shorter wavelength side as the optical path difference decreases as θ increases. 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, in the reflective display element of FIG. 13A, when the incident angle θ of the external light 101 is 0 °, the original wavelength band of 600 to 700 nm becomes the reflection wavelength band, but as the input angle θ increases, the reflection wavelength band increases. When 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 becomes 50 ° or more, the original wavelength band of 600 to 700 nm is not reflected at all.

Therefore, in the conventional reflective color display device disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 6-294952) and shown in FIG. 12, external light is obliquely directed to the dimming layers 51, 52, and 53. Incident on the light control layer 52, which reflects green light, reflects blue light together with green light, or reflects only blue light, and the light control layer 53, which should reflect red light, emits green light together with red light. There is a drawback that the display color is largely changed from the original color by reflecting blue light, or reflecting only green light, and further reflecting blue light together with green light.

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

Patent Document 2 (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 that the viewing angle is widened, but the color purity of the display color is significantly reduced.

Therefore, the present invention provides a reflective color display device including a dimming layer that reflects color light in a specific wavelength band due to a periodic change in the refractive index, so that the display color does not change depending on the viewing angle and the color purity does not decrease. It was made.

The reflection type color display device of the first invention,
Multiple light control layers are stacked,
Each dimming layer reflects colored light in a specific wavelength band due to a periodic change in the refractive index, and mutually adjusts such that the specific wavelength band is on the short wavelength side as it is closer to the outside light incident side. The specific wavelength band of is changed,
A color filter layer is provided between adjacent light control layers of the plurality of light control layers,
The color filter layer is characterized in that it absorbs color light on a shorter wavelength side than a specific wavelength band of the light control layer that is away from the external light incident side of the adjacent light control layers.

The reflection type color display device of the second invention is
A dimming layer that reflects color light in a specific wavelength band by a periodic change in the refractive index,
A color filter layer provided on the outside light incident side of the light control layer and absorbing color light on a shorter wavelength side than the reflection wavelength band of the light control layer,
It is characterized by having.

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

For example, when three light modulating layers that reflect blue, green, and red light are laminated when the incident angle of the external light is 0 °, the light modulating of the first layer closest to the external light incident side is described. It is assumed that the layer reflects blue light, the intermediate second dimming layer reflects green light, and the third dimming layer opposite to the outside light incident side reflects red light. It is assumed that.

A color filter layer that absorbs blue light and transmits 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 a color filter that absorbs green light and transmits blue light and red light between the layer and the third light control layer A layer is 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 and the second light control layer can be used. Since the blue light does not enter the second light control layer due to the color filter layer between the light control layer and the light control layer, the blue light is not reflected by the second light control layer and A color filter layer between the second light control layer and the third light control layer even when the reflection wavelength bands of the three light control layers shift from the red wavelength band to the green wavelength band; The green light and the blue light do not enter the third light control layer due to the color filter layer between the first light control layer and the second light control layer. The layer does not reflect green light, or even blue light.

That is, even when the incident angle of the external light is large, each of the first, second, and third light control layers has a reflection wavelength band of the original blue, green, and red wavelength bands. In this case, only the wavelength shifts to the shorter wavelength side and becomes narrower, and does not shift to the shorter wavelength side than the original blue, green and red wavelength bands. Therefore, the display color does not change depending on the viewing angle, and the color purity does not decrease.

As described above, according to the present invention, in a reflective color display device including a dimming layer that reflects color light in a specific wavelength band due to a periodic change in refractive index, the display color does not change depending on the viewing angle, and The purity does not decrease.

[Example 1 ... FIGS. 1 and 2]
FIG. 1 shows a first example of a reflective color display device of 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. The light control layer 52 is sandwiched between the element 1, the transparent substrates 13 and 14 on which the transparent electrodes 43 and 44 are formed, and the display element 2 in which the color filter layer 82 is formed on the back surface side of the transparent substrate 14; The display element 3 in which the light control layer 53 is sandwiched between the transparent substrates 15 and 16 on which the 45 and 46 are formed, and the light absorbing layer 85 is formed on the back surface side of the transparent substrate 16, is exposed to external light as shown in the upper part of FIG. They are stacked in order from the side.

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 of blue. The light control layer 52 has a reflection wavelength band of a green wavelength band, and the light control 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, and 3 can be manufactured by the same method. That is, first, transparent electrodes 41 (43, 45) and 42 (44, 46) each made of an ITO film are formed on one surface of a transparent substrate 11 (13, 15), 12 (14, 16) made of a glass substrate, respectively, with a thickness of 100 nm. Formed to a thickness of

Next, the transparent substrates 11 (13, 15), 12 (14, 16) are placed with the surfaces on which the transparent electrodes 41 (43, 45), 42 (44, 46) are formed inside, as described later. The liquid crystal and the photo-curable polymer are mixed between them at predetermined intervals.

As the liquid crystal, a liquid crystal material composed of a rod-shaped low molecule having biphenyl, terphenyl, phenylbenzoate, azobenzene, phenylcyclohexyl, phenylpyrimidine, or the like in a liquid crystal skeleton can be used.

A 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 radically 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.

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

{Circle around (4)} The mixed liquid is irradiated from both sides of the transparent substrates 11 (13, 15) and 12 (14, 16) with laser light of the same phase at an angle as described later. As a result, interference fringes are formed in the mixed solution, and the photocurable polymer is polymerized along the interference fringes, thereby forming 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.

(4) The thickness of the light control layer 51 (52, 53) formed from the mixture 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 voltage applied between the transparent electrodes 41 (43, 45) and 42 (44, 46) for controlling the reflectance is extremely high. Must be done, which is not preferred. On the other hand, when the thickness of the light control layer 51 (52, 53) is 0.5 μm or less, the reflectance is undesirably low.

Actually, two laser beams of 488 nm from an argon ion laser were respectively introduced into the mixture from both sides of the transparent substrates 11 and 12 in order to obtain the light control layer 51 having a blue wavelength band as a reflection wavelength band. The light was incident on the transparent substrates 11 and 12 vertically, that is, at an intersection angle of 180 °. As a result, a light control layer 51 having a reflection spectrum peak at a position of 490 nm was obtained.

In addition, 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 were injected into the mixed solution from both sides of the transparent substrates 13 and 14 at 134 °. At an intersection angle of. 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 the 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 were injected into the mixed solution from both sides of the transparent substrates 15 and 16 at a wavelength of 99 °. At an intersection angle of. 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 a color filter that absorbs blue light and transmits green light and red light as described above. The layer 81 was formed. Further, 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 a color filter that absorbs blue light and green light and transmits red light as described above. Layer 82 was formed. Further, a polymer film containing a black dye was applied to the back surface of the transparent substrate 16 of the display element 3 similarly manufactured, to form a light absorbing layer 85 that absorbs all color light. Finally, these 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 preferably have high transparency, and dye-based dyes are preferable. 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 specular reflection of the light control layers 51, 52, and 53 when the reflective color display device of Example 1 manufactured as described above is illuminated with spot light from the direction where the incident angle θ is 10 °. FIG. 9 shows a light reflection spectrum and a transmission spectrum of the color filter layers 81 and 82, and the cutoff wavelength of the color filter layer 81 is set to 500 nm between the reflection wavelength band of the light control layer 51 and the reflection wavelength band of the light control layer 52. And the cutoff 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 this, according to the reflective 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, the color filter Since the blue light does not enter the light control layer 52 by the 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 to the green wavelength band side. Also, since green light and blue light do not enter the light control layer 53 due to the color filter layers 82 and 81, the light control layer 53 does not reflect green light and further blue light.

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 dimming layer 53 indicates that the dimming layers 51, 52, 53 As a result, each reflection wavelength band shifts to a shorter wavelength side within the original blue, green, and red wavelength bands and becomes narrower, but becomes shorter than the original blue, green, and red wavelength bands. There is no shift.

The reflection type color display device according to the first embodiment is placed under diffuse illumination by an illuminating body 7 using an integrating sphere 5 as shown by a reflection type color display device 10 in FIG. The detector 9 is arranged in the direction of the detection angle θo with respect to the normal direction of 10, and the CIE L ^* a ^* b ^* chromaticity coordinates of the reflected light from the reflective color display device 10 are measured, and the hue of the hue is measured. To find the detection angle dependence,
ΔC ^* = [｛a ^* (θo) -a ^* (0 ゜)｝ ²
+ {B ^* (θo) −b ^* (0 °)} ² ] ^1/2 (1)
ΔC ^* represented by 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 with black circles is the reflection type color display device of the first embodiment, and 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. 3 shows the change in ΔC ^* with respect to 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 first embodiment, the change in the hue is significantly suppressed at θo = 20 to 40 ° as compared with the 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, and the color purity hardly decreases.

[Example 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 light control layers 51, 52 and 53 are made of cholesteric liquid crystal (chiral nematic liquid crystal). Different from 1.

The display elements 1, 2, and 3 can be manufactured by the same method. That is, first, transparent electrodes 41 (43, 45) and 42 (44, 46) each made of an ITO film are formed on one surface of a transparent substrate 11 (13, 15), 12 (14, 16) made of a glass substrate, respectively, with a thickness of 100 nm. Formed to a thickness of

Next, although not shown in the drawing, an alignment film made of polyimide is formed on each of the transparent electrodes 41 (43, 45) and 42 (44, 46), and the surface thereof is rubbed with a cloth in one direction. A rubbing process is performed.

Next, the transparent substrates 11 (13, 15) and 12 (14, 16) are placed at predetermined intervals with the side on which the transparent electrodes 41 (43, 45) and 42 (44, 46) are formed inside. A cholesteric liquid crystal prepared by adding a chiral agent to a nematic liquid crystal is loaded between them so as to form a dimming layer 51 (52, 53).

The cholesteric liquid crystal loaded between the transparent substrates 11 (13, 15), 12 (14, 16) has an alignment film formed on the transparent electrodes 41 (43, 45), 42 (44, 46) as described above. Accordingly, when no voltage is applied between the transparent electrodes 41 (43, 45) and 42 (44, 46), the helical axis is shifted to the transparent substrates 11 (13, 15), 12 (14, 16), the liquid crystal molecules are in a planar alignment state in which the liquid crystal molecules are arranged parallel to the transparent substrates 11 (13, 15) and 12 (14, 16).

Therefore, when no voltage is applied to the light control layers 51, 52, 53, the cholesteric liquid crystal helical light of the light of a specific wavelength determined by the helical pitch of the cholesteric liquid crystal forming the light control layers 51, 52, 53 is used. Selectively reflects circularly polarized light having the same optical rotation direction as the direction, and transmits circularly polarized light having an optical rotation direction opposite to the helical direction of the cholesteric liquid crystal of light of a specific wavelength, and light of a wavelength other than the specific wavelength. .

When a voltage equal to or higher than a certain threshold is applied to the light control layers 51, 52, and 53, the cholesteric liquid crystal forming the light control layers 51, 52, and 53 becomes a homeotropic liquid crystal molecule in which the liquid crystal molecules are arranged vertically. A phase transition to a tropic-like alignment state occurs, the helical structure disappears, and the light control layers 51, 52, 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.

In addition, the dimming 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 where the liquid crystal 66 and the polymer 65 are alternately formed in layers, the reflection wavelength changes depending on the incident angle of external light.

Actually, by using E44 manufactured by Merck as a nematic liquid crystal and CB15 manufactured by Merck as a chiral agent, and adding the chiral agent CB15 to 50, 42, and 35% by weight, respectively, the light control layer 51 is obtained. , 52, and 53, the reflection spectrum having the center wavelengths of 450 nm, 560 nm, and 640 nm, respectively, were obtained.

On the back surfaces of the transparent substrates 12 and 14 of the display elements 1 and 2 manufactured in this way, the same color filter layers 81 and 82 as those in the first embodiment of FIG. 1 are formed, and on the back surface of the transparent substrate 16 of the display element 3. Then, the same light absorbing layer 85 as in Example 1 was formed, and finally, the display elements 1, 2, and 3 were laminated to obtain a reflective color display device of Example 2.

FIG. 4 shows the specular reflection of the light control layers 51, 52, and 53 when the reflective color display device of Example 2 manufactured as described above is illuminated with spot light from the direction where the incident angle θ is 10 °. FIG. 9 shows a light reflection spectrum and a transmission spectrum of the color filter layers 81 and 82, and the cutoff wavelength of the color filter layer 81 is set to 500 nm between the reflection wavelength band of the light control layer 51 and the reflection wavelength band of the light control layer 52. And the cutoff 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 reflective color display device according to the second embodiment is placed under diffuse illumination by an illuminator 7 using an integrating sphere 5 as shown by a reflective color display device 10 in FIG. The detector 9 is arranged in the direction of the detection angle θo with respect to the normal direction of 10, and the CIE L ^* a ^* b ^* chromaticity coordinates of the reflected light from the reflective color display device 10 are measured, and the hue of the hue is measured. In order to determine the detection angle dependency, ΔC ^* represented by the above equation (1) was defined.

In FIG. 11 (B), what is plotted with black squares is the reflection type color display device of Example 2, which is the detection when 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. 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, the change in the hue is remarkably suppressed at θo = 20 to 40 ° as compared with the comparative example described later.

As described above, according to the second embodiment in FIG. 3, the display color hardly changes depending on the viewing angle, and 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. Although only circularly polarized light having the same optical rotation direction is reflected and the reflection spectrum peak does not exceed 50%, 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 from the reflective color display device of the second embodiment.

The reflection type color display device of the comparative example is placed under diffuse illumination by the illuminating body 7 using the integrating sphere 5 as shown in the reflection type color display device 10 of FIG. The detector 9 is arranged in the direction of the detection angle θo with respect to the normal direction of C, and the CIE L ^* a ^* b ^* chromaticity coordinates of the reflected light from the reflective color display device 10 are measured to detect the hue. In order to determine the angle dependency, 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, 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. The change in ΔC ^* 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.

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

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. Then, a liquid mixture of a liquid crystal and a photocurable polymer is applied to a thickness of 1 to 20 μm, then the transparent substrate 11 coated with the liquid mixture is placed in a chamber, and air is replaced with nitrogen. A laser beam having the same phase is irradiated into the mixed liquid from both sides of the liquid at an angle as described later to form a dimming layer 51 having a structure in which the liquid crystal and the polymer are separated into layers. A transparent electrode 42 made of an ITO film is formed on the optical 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 inhibited by the presence of air, but the curing reaction is not inhibited even in the presence of air as the photocurable polymer. When using a gas, it is not always necessary to replace air with nitrogen.

Similarly, a transparent electrode 44 is formed on one surface of the transparent substrate 14, a liquid mixture of a liquid crystal and a photocurable polymer is applied on the transparent electrode 44, and the mixed liquid is irradiated with laser light to form a light control layer. A transparent electrode 43 is formed on the dimming layer 52, a transparent electrode 46 is formed on one surface of the transparent substrate 16, and a liquid mixture of a liquid crystal and a photocurable polymer is formed on the transparent electrode 46. The liquid mixture is applied, and the mixed liquid is irradiated with laser light to form a light control layer 53, and a transparent electrode 45 is formed on the light control layer 53.

Actually, as in the first embodiment, two laser beams of 488 nm from an argon ion laser are made to enter each mixed solution at intersection angles of 180 °, 134 °, and 99 °, respectively. Light modulating layers 51, 52, and 53 having reflection spectrum peaks at positions of 490 nm, 530 nm, and 640 nm, respectively, were 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 bonded with an adhesive 83 containing a yellow dye. The transparent electrode 45 on the light modulating layer 53 on the transparent substrate 16 is adhered to the rear surface of the transparent substrate 14 with an adhesive 84 containing a red dye, and the light absorbing layer 85 is formed on the rear surface of the transparent substrate 16. 3 is obtained.

The adhesives 83 and 84 constitute the above-described color filter layers 81 and 82 by containing yellow and red dyes, respectively, and may be one-pack type or two-pack type, and may be acrylic, epoxy, etc. Any material may be used. The curing form may be any of a thermosetting type, an ultraviolet curing type, and the like.

According to the third embodiment, as in the first embodiment of 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. As compared with Example 1, there is an advantage that parallax when viewed from an oblique direction is reduced.

Example 4 FIGS. 6 to 9
According to the first, second, and third embodiments shown in FIGS. 1, 3, and 5, the display color hardly changes depending on the viewing angle, and the color purity hardly decreases. However, as shown in the reflection region of FIG. 10 and as described above with reference to FIG. 11B, when the incident angle θ or the detection angle θo becomes a certain value or more, specifically, when it becomes 50 ° or more, the light control layer 51, Since the reflectances of 52 and 53 become 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 of the present invention. In consideration of the above points, the reflection type color display device of the second embodiment shown in FIG. This is a case where a light scattering layer 90 is provided between the transparent substrate 11 and the transparent electrode 41 of the color display device.

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 center values of the reflection spectra of the light control layers 51, 52, and 53 were actually set to 510 nm, 570 nm, and 700 nm, respectively, for the reason described later.

As the light scattering layer 90,
A. A system containing fine particles having different refractive indices, for example, (A1) a white inorganic pigment such as titanium oxide, lead oxide, barium sulfate, an organic fine particle such as a resin or an organic low molecular material, a fiber, or the like as a binder such as a resin. Dispersed dye, (A2) resin containing bubbles, (A3) ceramic plate, (A4) crystalline polymer containing microcrystals, (A5) glass containing microcrystals,
B. A system in which a plurality of materials having different refractive indices are intertwined, for example, (B1) a composite resin material obtained by uniformly mixing a plurality of resins or their monomers once and then performing phase separation; (B2) a chalcogen Glass that can be phase separated, such as glass,
C. Birefringent multi-domain material, for example, (C1) liquid crystalline polymer, (C2) composite phase separation material of liquid crystalline polymer and crystalline polymer or amorphous polymer, (C3) liquid crystalline polymer A composite material in which an inorganic pigment, organic fine particles, and fibers are dispersed in a polymer; a composite material in which a low-molecular liquid crystal is dispersed in a polymer matrix (C4);
D. Microlens arrays, optical fiber plates,
Etc. can be used.

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

(4) In order to reduce blurring of a displayed image due to light scattering, it is desirable that the light scattering layer 90 and the light control layers 51, 52, 53 are provided close to each other. From that viewpoint, the light scattering layer 90 is preferably provided between the transparent substrate 11 and the transparent electrode 41 as shown in FIG. 6, and the thickness of the transparent substrates 11 to 15 is desirably as small as possible. Also, 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 a multi-domain is preferable.

作用 The operation of the light scattering layer 90 will be described with reference to FIG. FIG. 7 shows a case where incident light 101 of blue, green, and red is obliquely incident on the light control layers 51, 52, and 53. FIG. 7A shows a light scattering layer as in the second embodiment of FIG. FIG. 6B shows the case where the light scattering layer 90 is provided as in the case of Example 4 in FIG. The light control layers 51, 52, and 53 have a structure in which a liquid crystal and a polymer are separated in layers for the sake of convenience, but the same applies to a layer formed of a cholesteric liquid crystal.

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

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. The blue, green, and red incident lights 101 obliquely incident on the light control layers 51, 52, 53, respectively, do not become blue, green, and red reflected lights on the light control layers 51, 52, 53, respectively. The light is transmitted through the layers 51, 52 and 53 and is absorbed by the color filter layers 81 and 82 and the light absorbing layer 85. Therefore, blue, green, and red reflected lights are not observed.

On the other hand, when the light scattering layer 90 is provided as shown in FIG. 7B, the blue incident light 101 incident on the light control layer 51 is incident on the light scattering layer 90 before being incident on the light control layer 51. As a result, the scattered incident light 102 is scattered by the light scattering layer 90, and the scattered incident light 102 has an angle of incidence with respect to the dimming layer 51 such that blue reflected light is generated by the dimming layer 51. The light enters the optical layer 51. Therefore, blue reflected light 104 is generated in the light control layer 51. 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 lights 101 incident on the light control layers 52 and 53.

That is, in the fourth embodiment of FIG. 6 in which the light scattering layer 90 is provided, the reflected light is not reflected even at an incident angle where no reflected light is generated without the light scattering layer 90 as in the second embodiment of FIG. And 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 light incident on the light control layers 51, 52, and 53 from the outside into an angular distribution B having a spread by performing scattering average. 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 the angle distribution A. No dependence at all. Therefore, the above effects can be obtained widely without depending on the angular distribution A of light incident on the light control layers 51, 52, 53 from the outside.

In the display device disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 7-92483), a light scattering plate is provided on the surface of the dimming layer to increase the viewing angle. Since the dependence is not taken into account, 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, the color filters 81 and 82 are provided and the light scattering layer 90 is provided, so that the display color hardly changes depending on the viewing angle and the color purity is almost lowered. In this state, the display can be viewed even from an oblique direction.

FIG. 8 shows the 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, the curve 201 is the case where the light scattering layer 90 is not provided, and thus the structure is the same as that of the embodiment 2 of FIG. 3, but the center wavelength of the reflection spectrum of the light control layer 53 is 700 nm as described above. The curve 202 is the case where the light scattering layer 90 is provided.

In the case of the curve 201 where the light scattering layer 90 is not provided, the interface between the transparent substrate 11 and the transparent electrode 41 becomes a mirror surface. The light intensity increases about two orders of magnitude. Therefore, the scale of the vertical axis with respect to the curve 202 is actually 1/100 of the figure.

As is clear 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 width is wide due to the widening of the incident angle range by the light scattering layer 90. At the same time, the reflection spectrum peak shifts to the shorter wavelength side due to the average incident angle on the light control layer 53 becoming larger. 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 constituting the light control layers 51, 52, and 53 is determined as shown in FIG. Is set on the 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 layers 81 and 52 when the reflective color display device of the fourth embodiment is illuminated with spot light from the direction where the incident angle θ is 10 °. 82 shows a transmission spectrum of 82. In the first, second, and third embodiments, the reflection spectra of the light control layers 51, 52, and 53 are set so that they do not overlap. However, as in the fourth embodiment, the reflection spectra may overlap.

The reflection type color display device according to the fourth embodiment is placed under diffuse illumination by an illuminating body 7 using an integrating sphere 5 as shown by a reflection type color display device 10 in FIG. The detector 9 is arranged in the direction of the detection angle θo with respect to the normal direction of 10, and the CIE L ^* a ^* b ^* chromaticity coordinates of the reflected light from the reflective color display device 10 are measured, and the hue of the hue is measured. In order to determine the detection angle dependency, ΔC ^* represented by the above equation (1) was defined.

In FIG. 11 (B), what is plotted with black triangles is the reflection type color display device of the fourth embodiment, which is the detection when 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, according to the fourth embodiment, the reflected light can be observed in the range of θo = 0 to 90 °, and the change in hue is significantly suppressed in a wide incident angle range as compared with the comparative example described above. Is done. Further, 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-described examples, since blue light is absorbed by the color filter layer 81, the color filter layer 82 absorbs only green light by applying a polymer film containing a magenta dye, and It may be formed to transmit light and red light.

The embodiment 4 in FIG. 6 is a case where the light-adjusting layers 51, 52 and 53 are made of cholesteric liquid crystal and the light scattering layer 90 is provided as in the embodiment 2 in FIG. The light control layer 51, 52, 53 has a multilayer structure of the liquid crystal 66 and the polymer 65 as in the first embodiment, or the light control layer 51, 52, 53 has a reduced parallax as in the third embodiment in FIG. A scattering layer can be provided, and in this case, the same effect as that of the fourth embodiment in FIG. 6 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 stacked so that full-color display can be performed. The present invention can be applied, for example, to a case in which two dimming layers each having blue, green, or green, red, or a blue or red wavelength band as a reflection wavelength band are laminated.

FIG. 1 is a sectional view showing a first example of a reflective color display device of the present invention. FIG. 2 is a diagram illustrating 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. 1. FIG. 5 is a sectional view showing a second example of the reflective color display device of the present invention. FIG. 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. 9 is a sectional view showing a third example of the reflective color display device of the present invention. FIG. 14 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 in FIG. 6. FIG. 7 is a diagram comparing the reflection spectra of one light control layer with and without the light scattering layer in the reflection type color display device of FIG. 6. FIG. 7 is a diagram illustrating 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. 6. It is a figure which shows the change of the reflection wavelength with respect to the external light incident angle of one light control layer of the reflection type color display of each example. FIG. 9 is a diagram for explaining aspects of a hue change with respect to an incident angle of external light of the reflective color display device of each example and the reflective color display device of the comparative example. FIG. 11 is a cross-sectional view illustrating an example of a conventional reflective color display device. FIG. 13 is a diagram for explaining 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 FIG. 12.

Explanation of reference numerals

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 (8)

Multiple light control layers are stacked,
Each dimming layer reflects colored light in a specific wavelength band due to a periodic change in the refractive index, and mutually adjusts such that the specific wavelength band is on the short wavelength side as it is closer to the outside light incident side. The specific wavelength band of is changed,
A color filter layer is provided between adjacent light control layers of the plurality of light control layers,
A reflection type color display device, characterized in that the color filter layer absorbs color light on a shorter wavelength side than a specific wavelength band of the light control layer remote from the external light incident side of the adjacent light control layers. . Multiple light control layers are stacked,
Each dimming layer reflects colored light in a specific wavelength band due to a periodic change in the refractive index, and mutually adjusts such that the specific wavelength band is on the short wavelength side as it is closer to the outside light incident side. The specific wavelength band of is changed,
A color filter layer is provided between adjacent light control layers of the plurality of light control layers,
The color filter layer absorbs color light on a shorter wavelength side than the specific wavelength band of the light control layer of the adjacent light control layer that is remote from the external light incident side, and transmits other color light. Characteristic reflective color display device. Multiple light control layers are stacked,
Each dimming layer reflects colored light in a specific wavelength band due to a periodic change in the refractive index, and mutually adjusts such that the specific wavelength band is on the short wavelength side as it is closer to the outside light incident side. The specific wavelength band of is changed,
A color filter layer is provided between adjacent light control layers of the plurality of light control layers,
The color filter layer includes a specific wavelength band of the light control layer closer to the external light incident side of the adjacent light control layers and a light control layer of the adjacent light control layer that is away from the external light incident side of the adjacent light control layers. A reflection type color display device characterized by absorbing color light on a shorter wavelength side than a cutoff wavelength set between a specific wavelength band of an optical layer and the light layer. Multiple light control layers are stacked,
Each dimming layer reflects colored light in a specific wavelength band due to a periodic change in the refractive index, and mutually adjusts such that the specific wavelength band is on the short wavelength side as it is closer to the outside light incident side. The specific wavelength band of is changed,
A color filter layer is provided between adjacent light control layers of the plurality of light control layers,
The color filter layer includes a specific wavelength band of the light control layer closer to the external light incident side of the adjacent light control layers and a light control layer of the adjacent light control layer that is away from the external light incident side of the adjacent light control layers. A reflective color display device, which absorbs color light on a shorter wavelength side than a cutoff wavelength set between a specific wavelength band of an optical layer and transmits other color light. The reflective color display device according to claim 1,
A reflection type color display device comprising light scattering means 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 dimming layer that reflects color light in a specific wavelength band by a periodic change in the refractive index,
A color filter layer provided on the outside light incident side of the light control layer and absorbing color light on a shorter wavelength side than the reflection wavelength band of the light control layer,
A reflective color display device comprising: A dimming layer that reflects color light in a specific wavelength band by a periodic change in the refractive index,
A color filter layer provided on the external light incident side of the light control layer and absorbing color light on a shorter wavelength side than a cutoff wavelength set on a shorter wavelength side than the reflection wavelength band of the light control layer,
A reflective color display device comprising: The reflective color display device according to claim 6 or 7,
A reflection type color display device comprising light scattering means on an optical path incident on the light control layer from the outside and on an optical path output from the light control layer to the outside.

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